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#1526 2022-10-08 14:10:48

ganesh
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Registered: 2005-06-28
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Re: Miscellany

1499) Actinism

Summary

That property of ultraviolet light, X-rays, or other radiations, by which chemical changes are produced.

Details

Actinism is the property of solar radiation that leads to the production of photochemical and photobiological effects. Actinism is derived from the Ancient Greek ("ray, beam"). The word actinism is found, for example, in the terminology of imaging technology (esp. photography), medicine (concerning sunburn), and chemistry (concerning containers that protect from photo-degradation), and the concept of actinism is applied, for example, in chemical photography and X-ray imaging.

Actinic chemicals include silver salts used in photography and other light sensitive chemicals.

In chemistry

In chemical terms, actinism is the property of radiation that lets it be absorbed by a molecule and cause a photochemical reaction as a result. Albert Einstein was the first to correctly theorize that each photon would be able to cause only one molecular reaction. This distinction separates photochemical reactions from exothermic reduction reactions triggered by radiation.

For general purposes, photochemistry is the commonly used vernacular rather than actinic or actino-chemistry, which are again more commonly seen used for photography or imaging.

In medicine

In medicine, actinic effects are generally described in terms of the dermis or outer layers of the body, such as eyes and upper tissues that the sun would normally affect, rather than deeper tissues that higher-energy shorter-wavelength radiation such as x-ray and gamma might affect. Actinic is also used to describe medical conditions that are triggered by exposure to light, especially UV light.

The term actinic rays is used to refer to this phenomenon.

In biology

In biology, "actinic light" denotes light from solar or other sources that can cause photochemical reactions such as photosynthesis in a species.

In photography

Actinic light was first commonly used in early photography to distinguish light that would expose the monochrome films from light that would not. A non-actinic safe-light (e.g., red or amber) could be used in a darkroom without risk of exposing (fogging) light-sensitive films, plates or papers.

Early "non colour-sensitive" (NCS) films, plates and papers were only sensitive to the high-energy end of the visible spectrum from green to UV (shorter-wavelength light). This would render a print of the red areas as a very dark tone because the red light was not actinic. Typically, light from xenon flash lamps is highly actinic, as is daylight as both contain significant green-to-UV light.

In the first half of the 20th century, developments in film technology produced films sensitive to red and yellow light, known as orthochromatic and panchromatic, and extended that through to near infra-red light. These gave a truer reproduction of human perception of lightness across the color spectrum. In photography, therefore, actinic light must now be referenced to the photographic material in question.

In manufacturing

Actinic inspection of masks in computer chip manufacture refers to inspecting the mask with the same wavelength of light that the lithography system will use.

In aquaculture

Actinic lights are also common in the reef aquarium industry. They are used to promote coral and invertebrate growth. They are also used to accentuate the fluorescence of fluorescent fish.

Actinic lighting is also used to limit algae growth in the aquarium. Since algae (like many other plants), flourish in shallower warm water, algae cannot effectively photosynthesize from blue and violet light, thus actinic light minimizes its photosynthetic benefit.

Actinic lighting is also a great alternative to black lights as it provides a "night environment" for the fish, while still allowing enough light for coral and other marine life to grow. Aesthetically, they make fluorescent coral "pop" to the eye, but in some cases also to promote the growth of deeper-water coral adapted to photosynthesis in regions of the ocean dominated by blue light.

In artificial lighting

"Actinic" lights are a high-color-temperature blue light. They are also used in electric fly killers to attract flies.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1527 2022-10-09 14:45:50

ganesh
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Posts: 40,614

Re: Miscellany

1500) Goldsmith

A goldsmith is a metalworker who specializes in working with gold and other precious metals. Nowadays they mainly specialize in jewelry-making but historically, goldsmiths have also made silverware, platters, goblets, decorative and serviceable utensils, and ceremonial or religious items.

Goldsmiths must be skilled in forming metal through filing, soldering, sawing, forging, casting, and polishing. The trade has very often included jewelry-making skills, as well as the very similar skills of the silversmith. Traditionally, these skills had been passed along through apprenticeships; however, more recently jewelry arts schools, specializing in teaching goldsmithing and a multitude of skills falling under the jewelry arts umbrella, are available. Many universities and junior colleges also offer goldsmithing, silversmithing, and metal arts fabrication as a part of their fine arts curriculum.

Gold

Compared to other metals, gold is malleable, ductile, rare, and it is the only solid metallic element with a yellow color. It may easily be melted, fused, and cast without the problems of oxides and gas that are problematic with other metals such as bronzes, for example. It is fairly easy to "pressure weld", wherein, similarly to clay, two small pieces may be pounded together to make one larger piece. Gold is classified as a noble metal—because it does not react with most elements. It usually is found in its native form, lasting indefinitely without oxidization and tarnishing.

History

Gold has been worked by humans in all cultures where the metal is available, either indigenously or imported, and the history of these activities is extensive. Superbly made objects from the ancient cultures of Africa, Asia, Europe, India, North America, Mesoamerica, and South America grace museums and collections throughout the world. The Copper Age Varna culture (Bulgaria) from the 5th millennium BC is credited with inventing goldsmith (gold metallurgy). The associated Varna Necropolis treasure contains the oldest golden jewellery in the world with an approximate age of over 6,000 years.

Some pieces date back thousands of years and were made using many techniques that still are used by modern goldsmiths. Techniques developed by some of those goldsmiths achieved a skill level that was lost and remained beyond the skills of those who followed, even to modern times. Researchers attempting to uncover the chemical techniques used by ancient artisans have remarked that their findings confirm that "the high level of competence reached by the artists and craftsmen of these ancient periods who produced objects of an artistic quality that could not be bettered in ancient times and has not yet been reached in modern ones."

In medieval Europe goldsmiths were organized into guilds and usually were one of the most important and wealthiest of the guilds in a city. The guild kept records of members and the marks they used on their products. These records, when they survive, are very useful to historians. Goldsmiths often acted as bankers, since they dealt in gold and had sufficient security for the safe storage of valuable items, though they were usually restrained from lending at interest, which was regarded as usury. In the Middle Ages, goldsmithing normally included silversmithing as well, but the brass workers and workers in other base metals normally were members of a separate guild, since the trades were not allowed to overlap. Many jewelers also were goldsmiths.

The Sunar caste is one of the oldest communities in goldsmithing in India, whose superb gold artworks were displayed at The Great Exhibition of 1851 in London. In India, 'Daivadnya Brahmins',viswakarma (Viswabrahmins,Achari cast )'Kshatriya Sunar' are the goldsmith castes.

The printmaking technique of engraving developed among goldsmiths in Germany around 1430, who had long used the technique on their metal pieces. The notable engravers of the fifteenth century were either goldsmiths, such as Master E. S., or the sons of goldsmiths, such as Martin Schongauer and Albrecht Dürer.

Contemporary goldsmithing

A goldsmith might have a wide array of skills and knowledge at their disposal. Gold, being the most malleable metal of all, offers unique opportunities for the worker. In today's world a wide variety of other metals, especially platinum alloys, also may be used frequently. 24 karat is pure gold and historically, was known as fine gold.

Because it is so soft, however, 24 karat gold is rarely used. It is usually alloyed to make it stronger and to create different colors. Depending on the metals used to create the alloy, the color can change.

This alloyed gold is then stamped with the 725 mark, representing the percentage of gold present in the alloy for commercially used gold. The majority of the jewellery is made with this alloy, while a smaller part uses lower gold-density alloys to keep jewelry cheaper. The gold may be cast into some item then, usually with the lost wax casting process, or it may be used to fabricate the work directly in metal.

In the latter case, the goldsmith will use a variety of tools and machinery, including the rolling mill, the drawplate, and perhaps, swage blocks and other forming tools to make the metal into shapes needed to build the intended piece. Then parts are fabricated through a wide variety of processes and assembled by soldering. It is a testament to the history and evolution of the trade that those skills have reached an extremely high level of attainment and skill over time. A fine goldsmith can and will work to a tolerance approaching that of precision machinery, but largely using only his eyes and hand tools. Quite often the goldsmith's job involves the making of mountings for gemstones, in which case they often are referred to as jewelers.

'Jeweller', however, is a term mostly reserved for a person who deals in jewellery (buys and sells) and not to be confused with a goldsmith, silversmith, gemologist, diamond cutter, and diamond setters. A 'jobbing jeweller' is the term for a jeweller who undertakes a small basic amount of jewellery repair and alteration.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1528 2022-10-10 14:48:08

ganesh
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Posts: 40,614

Re: Miscellany

1501) Gold leaf

Gold leaf is gold that has been hammered into thin sheets (usually around 0.1 micrometer thick) by goldbeating and is often used for gilding. Gold leaf is available in a wide variety of karats and shades. The most commonly used gold is 22-karat yellow gold.

Gold leaf is a type of metal leaf, but the term is rarely used when referring to gold leaf. The term metal leaf is normally used for thin sheets of metal of any color that do not contain any real gold. Pure gold is 24 karat. Real, yellow gold leaf is approximately 91.7% pure (i.e. 22-karat) gold. Silver-colored white gold is about 50% pure gold.

Layering gold leaf over a surface is called gold leafing or gilding. Traditional water gilding is the most difficult and highly regarded form of gold leafing. It has remained virtually unchanged for hundreds of years and is still done by hand.

In art

Gold leaf is sometimes used in art in a "raw" state, without a gilding process. In cultures including the European Bronze Age it was used to wrap objects such as bullae simply by folding it tightly over, and the Classical group of gold lunulae are so thin, especially in the centre, that they might be classed as gold leaf. It has been used in jewellery in various periods, often as small pieces hanging freely.

Since the decline of gold ground painting at the end of the Middle Ages, gold leaf has been most popular and most common in its use as gilding material for decoration of art (including statues and Eastern Christian icons) or the picture frames that are often used to hold or decorate paintings, mixed media, small objects (including jewelry) and paper art. Gold glass is gold leaf held between two pieces of glass, and was used to decorate Ancient Roman vessels, where some of the gold was scraped off to form an image, as well as tesserae gold mosaics. Gold-ground paintings, where the background of the figures was all in gold, was introduced in mosaics in later Early Christian art, and then used in icons and Western panel paintings until the late Middle Ages; all techniques use gold leaf. Gold leaf is also used in Buddhist art to decorate statues and symbols. Gold leafing can also be seen on domes in religious and public architecture. "Gold" frames made without leafing are also available for a considerably lower price, but traditionally some form of gold or metal leaf was preferred when possible and gold leafed (or silver leafed) moulding is still commonly available from many of the companies that produce commercially available moulding for use as picture frames.

Gold leaf is the basis of the gold ink used in Islamic calligraphy and Islamic manuscript illumination. The leaves are crushed in honey or gum arabic, then suspended in gelatinous water. Because the gold is not pulverized as in industrially produced metal inks, the resulting surface looks very much like solid gold.

In architecture

Gold leaf has long been an integral component of architecture to designate important structures, both for aesthetics and because gold's non-reactive nature provides a protective finish.

Gold in architecture became an integral component of Byzantine and Roman churches and basilicas in 400 AD, most notably Basilica di Santa Maria Maggiore in Rome. The church was built by Pope Sixtus III and is one of the earliest examples of gold mosaics. The mosaics were made of stone, tile or glass backed on gold leaf walls, giving the church a beautifully intricate backdrop. The Athenian marble columns supporting the nave are even older, and either come from the first basilica, or from another antique Roman building; thirty-six are marble and four granite, pared down, or shortened to make them identical by Ferdinando Fuga, who provided them with identical gilt-bronze capitals. The 14th century campanile, or bell tower, is the highest in Rome, at 240 feet, (about 75 m.). The basilica's 16th-century coffered ceiling, designed by Giuliano da Sangallo, is said to be gilded with gold that Christopher Columbus presented to Ferdinand and Isabella, before being passed on to the Spanish pope, Alexander VI. The apse mosaic, the Coronation of the Virgin, is from 1295, signed by the Franciscan friar, Jacopo Torriti.

In Ottawa, Ontario, the Centre Block is the main building of the Canadian parliamentary complex on Parliament Hill, containing the House of Commons and Senate chambers, as well as the offices of a number of members of parliament, senators, and senior administration for both legislative houses. It is also the location of several ceremonial spaces, such as the Hall of Honour, the Memorial Chamber, and Confederation Hall. In the east wing of the Centre Block is the Senate chamber, in which are the thrones for the Canadian monarch and her consort, or for the federal viceroy and their consort, and from which either the sovereign or the governor general gives the Speech from the Throne and grants Royal Assent to bills passed by parliament. The overall color in the Senate chamber is red, seen in the upholstery, carpeting, and draperies, and reflecting the color scheme of the House of Lords in the United Kingdom; red was a royal color, associated with the Crown and hereditary peers. Capping the room is a gilt ceiling with deep octagonal coffers, each filled with heraldic symbols, including maple leaves, fleur-de-lis, lions rampant, clàrsach, Welsh Dragons, and lions passant. This plane rests on six pairs and four single pilasters, each of which is capped by a caryatid, and between which are clerestory windows. Below the windows is a continuous architrave, broken only by baldachins at the base of each of the above pilasters.

On the east and west walls of the chamber are eight murals depicting scenes from the First World War; painted in between 1916 and 1920, they were originally part of the more than 1,000 piece Canadian War Memorials Fund, founded by the Lord Beaverbrook, and were intended to hang in a specific memorial structure. However, the project never eventuated, and the works were stored at the National Gallery of Canada until 1921, when the Parliament requested a loan for some of the collection's oil paintings to display in the Centre Block. The murals have remained in the Senate chamber ever since.

In London, the Criterion Restaurant is an opulent building facing Piccadilly Circus in the heart of London. It was built by architect Thomas Verity in Neo-Byzantine style for the partnership Spiers and Pond who opened it in 1873. One of the restaurant’s most famous features is the 'glistering' ceiling of gold mosaic, coved at the sides and patterned all over with lines and ornaments in blue and white tesserae. The wall decoration accords well with the real yellow gold leaf ceiling, incorporating semi-precious stones such as jade, mother of pearl, turquoise being lined with warm marble and formed into blind arcades with semi-elliptical arches resting on slender octagonal columns, their unmolded capitals and the impost being encrusted with goldground mosaic.

Gold leaf adorns the wrought iron gates surrounding the Palace of Versailles in France, when refinishing the gates nearly 200 years after they were torn down during the French Revolution, it required hundreds of kilograms of gold leaf to complete the process.

Culinary uses

Gold leaf (as well as other metal leaf such as vark) is sometimes used to decorate food or drink, typically to promote a perception of luxury and high value; however, it is flavorless. It is occasionally found in desserts and confectionery, including chocolates, honey and mithai. In India it may be used effectively as a garnish, with thin sheets placed on a main dish, especially on festive occasions. When used as an additive to food, gold has the E-number E175. A centuries-old traditional artisan variety of green tea contains pieces of gold leaf; 99% of this kind of tea is produced in Kanazawa, Japan, a historic city for samurai craftsmanship. The city is also home to a gold leaf museum, Kanazawa Yasue Gold Leaf Museum.

In Continental Europe liquors with tiny floating pieces of gold leaf are known of since the late 16th century; originally the practice was regarded as medicinal. Well-known examples are Danziger Goldwasser, originally from Gdańsk, Poland, which has been produced since at least 1598, Goldstrike from Amsterdam, Goldwasser from Schwabach in Germany, and the Swiss Goldschläger, which is perhaps the best known in both Canada and the United States.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1529 2022-10-11 13:40:45

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1502) Caustic Soda

Summary

Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na+ and hydroxide anions OH−.

Sodium hydroxide is a highly caustic base and alkali that decomposes proteins at ordinary ambient temperatures and may cause severe chemical burns. It is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air. It forms a series of hydrates NaOH·nH2O. The monohydrate NaOH·H2O crystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound.

As one of the simplest hydroxides, sodium hydroxide is frequently used alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students.

Sodium hydroxide is used in many industries: in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents, and as a drain cleaner.

Details

Sodium hydroxide (NaOH), also known as caustic soda or lye, is a highly versatile substance used in a variety of manufacturing processes. Sodium hydroxide is a co-product of chlorine production.

Uses & Benefits

Sodium hydroxide is used to manufacture many everyday products, such as paper, aluminum, commercial drain and oven cleaners, and soap and detergents.

Sodium Hydroxide in Cleaning & Disinfectant Products

Sodium hydroxide is used to manufacture soaps and a variety of detergents used in homes and commercial applications. Chlorine bleach is produced by combining chlorine and sodium hydroxide. Drain cleaners that contain sodium hydroxide convert fats and grease that can clog pipes into soap, which dissolves in water.

Sodium Hydroxide in Pharmaceuticals & Medicine

Sodium hydroxide is used to help manufacture a variety of medicines and pharmaceutical products, from common pain relievers like aspirin, to anticoagulants that can help to prevent blood clots, to cholesterol-reducing medications.

Sodium Hydroxide in Energy

In the energy sector, sodium hydroxide is used in fuel cell production. Fuel cells work like batteries to cleanly and efficiently produce electricity for a range of applications, including transportation; materials handling; and stationary, portable and emergency backup power applications. Epoxy resins, manufactured with sodium hydroxide, are used in wind turbines.

Sodium Hydroxide in Water Treatment

Municipal water treatment facilities use sodium hydroxide to control water acidity and to help remove heavy metals from water. Sodium hydroxide is also used to produce sodium hypochlorite, a water disinfectant.

Sodium Hydroxide in Food Production

Sodium hydroxide is used in several food processing applications, such as curing foods like olives or helping to brown Bavarian-style pretzels, giving them their characteristic crunch. Sodium hydroxide is used to remove skins from tomatoes, potatoes and other fruits and vegetables for canning and also as an ingredient in food preservatives that help prevent mold and bacteria from growing in food.

Sodium Hydroxide in Wood & Paper Products

In many paper making processes, wood is treated with a solution containing sodium sulfide and sodium hydroxide.  This helps dissolve most of the unwanted material in the wood, leaving relatively pure cellulose, which forms the basis of paper. In the paper recycling process, sodium hydroxide is used to separate the ink from the paper fibers allowing the paper fibers to be reused again.

Sodium hydroxide is also used to refine raw materials for wood products such as cabinets and furniture and in wood bleaching and cleaning.

Sodium Hydroxide in Aluminum Ore Processing

Sodium hydroxide is used to extract alumina from naturally occurring minerals. Alumina is used to make aluminum and a variety of products including foil, cans, kitchen utensils, beer kegs and airplane parts. In building and construction, aluminum is used in materials that enable building facades and window frames.

Sodium Hydroxide in Other Industrial Manufacturing Uses

Sodium hydroxide is used in many other industrial and manufacturing processes. It is used to manufacture rayon, spandex, explosives, epoxy resins, paints, glass and ceramics. It is also used in the textile industry to make dyes, process cotton fabric and in laundering and bleaching, as well as in metal cleaning and processing, oxide coating, electroplating and electrolytic extracting.

Additional Information

Caustic soda or lye, a corrosive white crystalline solid that contains the Na+ (sodium) cation and the OH− (hydroxide) anion. It readily absorbs moisture until it dissolves. Sodium hydroxide is the most widely used industrial alkali and is often used in drain and oven cleaners. It is highly corrosive to animal and vegetable tissue. The alkaline solutions it forms when dissolved in water neutralize acids in various commercial processes. In petroleum refining, it removes sulfuric and organic acids. In soapmaking, it acts on natural fats or oils, such as tallow or vegetable oil, to produce sodium fatty acid salt (soap) and glycerin (or glycerol); this saponification reaction is the basis for all soapmaking. In papermaking, sodium hydroxide is used to break down wood into pulp. Solutions of NaOH are used in the treatment of cellulose and in the manufacture of many chemicals.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1530 2022-10-12 13:38:34

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1503) Bleach

Summary

Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to a dilute solution of sodium hypochlorite, also called "liquid bleach".

Many bleaches have broad spectrum bactericidal properties, making them useful for disinfecting and sterilizing. They are used in swimming pool sanitation to control bacteria, viruses, and algae, and in many places where sterile conditions are required. They are also used in many industrial processes, notably in the bleaching of wood pulp. Bleaches also have other minor uses like removing mildew, killing weeds, and increasing the longevity of cut flowers.

Bleaches work by reacting with many colored organic compounds, such as natural pigments, and turning them into colorless ones. While most bleaches are oxidizing agents (chemicals that can remove electrons from other molecules), some are reducing agents (that donate electrons).

Chlorine, a powerful oxidizer, is the active agent in many household bleaches. Since pure chlorine is a toxic corrosive gas, these products usually contain hypochlorite, which releases chlorine. "Bleaching powder" usually means a formulation containing calcium hypochlorite.

Oxidizing bleaching agents that do not contain chlorine are usually based on peroxides such as hydrogen peroxide, sodium percarbonate, and sodium perborate. These bleaches are called 'non-chlorine bleach,' 'oxygen bleach' or 'color-safe bleach.'

Reducing bleaches have niche uses, such as sulfur dioxide used to bleach wool, either as gas or from solutions of sodium dithionite; and sodium borohydride.

Bleaches generally react with many other organic substances besides the intended colored pigments, so they can weaken or damage natural materials like fibers, cloth, and leather, and intentionally applied dyes such as the indigo of denim. For the same reason, ingestion of the products, breathing of the fumes, or contact with skin or eyes can cause health damage.

Details

Bleach is a solid or liquid chemical used to whiten or remove the natural colour of fibres, yarns, other textiles, and paper. In textile finishing, the bleaching process is used to produce white cloth, to prepare fabrics for other finishes, or to remove discoloration that has occurred in other processes. Bleach is also used as a disinfectant because of its microbicidal properties. Chlorine, sodium hypochlorite, calcium hypochlorite, and hydrogen peroxide are commonly used as bleaches.

Sunlight was the chief bleaching agent up to the discovery of chlorine in 1774 by Swedish chemist Karl Wilhelm Scheele and the demonstration of its bleaching properties in 1785 by French chemist Claude Berthollet. Bleaching powder, a solid combination of chlorine and slaked lime, introduced in 1799 by Scottish chemist Charles Tennant, was thereafter produced in large quantity to bleach cloth and paper. It had the same effect as chlorine and could be more easily handled and shipped, but it was unstable and contained a large proportion of inert material. It remained the standard bleaching agent until the 1920s, but then it was gradually replaced by liquefied chlorine and solutions of sodium hypochlorite.

In the production of bleaching powder, slaked lime spread on the floors of large rectangular chambers of lead or concrete is exposed to chlorine gas; or lime is propelled through horizontal tubes that are fed with the gas.

Hydrogen peroxide is commonly used to bleach cotton cloth, with sodium chlorite and sodium hypochlorite as alternatives. Wood and animal fibres are bleached by acidic reducing agents such as sulfur dioxide. In the pulp and paper industry chlorine dioxide, hydrogen peroxide, sodium peroxide, sulfur dioxide, sodium bisulfite, and sodium hydrosulfite are commonly used. Synthetic fibres are bleached with either oxidizing or reducing agents, depending on their chemical composition. Optical bleaches, fluorescent white chemicals giving off a bluish-white light, are not true bleaches.

Various bleach solutions are used as disinfectants. For example, dilute (about 5 percent) sodium hypochlorite solutions are used to sanitize food-processing equipment. Stronger solutions, ranging from about 10 to 20 percent bleach, may be used in hospitals, laboratories, and other settings where sanitization against potentially infectious microorganisms is critical.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1531 2022-10-13 14:00:58

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1504) Cupboard

Summary

A cupboard is a piece of furniture for enclosing dishware or grocery items that are stored in a home. The term gradually evolved from its original meaning: an open-shelved side table for displaying dishware, more specifically plates, cups and saucers. These open cupboards typically had between one and three display tiers, and at the time, a drawer or multiple drawers fitted to them.

Types of cupboards:

Airing cupboard

An airing cupboard (or hot press) is a built-in storage space, sometimes of walk-in dimensions, containing a water heater, either an immersion heater for hot running water or a boiler for central heating water (hence, also "boiler cupboard"), or a hot water storage tank. Shelves, usually slatted to allow for circulation of heat, are positioned above or around the heater to provide room for clothing. The purpose is to allow air to circulate around the stored fabrics to prevent damp forming.

Some variants of airing cupboards also serve as the linen cupboard, the storing area of the household's clean sheets and towels.

In another version, the airing cupboard serves as a temporary drying space, either for laundry or for wet outdoor clothes and shoes. Its shelves can be used to fully remove traces of damp from dried clothing before the items are put away elsewhere in drawers and wardrobes. A moveable electrical version of this is a drying cabinet.

Built-in cupboard

A built-in cupboard is a storage space that forms part of the design of the room and is not free-standing or moving. It is not the same as a cabinet. In the United Kingdom houses often have a built-in cupboard under the stairs.

Linen cupboard

A linen cupboard is an enclosed recess of a room used for storing household linen (e.g. sheets, towels, tablecloths) and other things for storage, usually with shelves, or a free-standing piece of furniture for this purpose.

Stationery cupboard

Most offices have a lockable repository for valuables. The heart of this is usually the supply of stationery.

Details

Cupboard is a type of furniture that originated in the Middle Ages as a board or table for cups. The word also may have been used for a stepped sideboard and later for open shelves, both to display plate. Since the 16th century the name has referred to a case fitted with doors.

Byzantine and Romanesque cupboards were of simple board construction, though they were sometimes decorated with elaborate painted designs. A fine example of about 1200, painted inside and out with pictures of saints on a gesso ground, survives in the cathedral at Halberstadt, Ger. Such freestanding cupboards were made for churches long before they were in common use in domestic interiors. The latter stage was reached only in the 14th century, when portable furniture began to be preferred to fixed objects that stood as permanent parts of a building. Many of the finest medieval cupboards were finely carved with Gothic designs closely following architectural motifs and forms.

Late 15th-century cupboards for food storage, such as the English livery cupboard, had ventilating holes, often taking the form of carved open tracery. Another variety was the hall, or parlour, cupboard, an enclosed version of the cupboard for display. The court cupboard, for example, was important in Tudor and Stuart times in England but lost fashion after the Restoration.

By the 17th century the cupboard was taking over the role of the chest as the principal piece of storage furniture. In certain parts of Europe, such as southern Germany, the cupboard may have developed from a chest placed on another chest, each opening at the front rather than at the top. For a long time cupboards were divided in two, horizontally, with handles sometimes attached to the sides of each section to facilitate moving.

With the increasing importance of the cupboard, decoration became more lavish, taking the form of panelling, carving, and intarsia (mosaic of wood). Italy led the way in the 16th century with some of the finest intarsia panels. Panels were rectangular and sometimes contained finely carved scenes, or motifs, accompanied by carved friezes (horizontal bands). In the 17th century the Low Countries popularized a heavy form of cupboard, called in Dutch a kast (or, in the United States, kas), in which the panels were raised and three evenly spaced twisted columns supported a heavy cornice, the whole resting on squat bun (or ball) feet. Northern Germany was particularly noted for its massive cupboards, which were the most important pieces of furniture in the house.

The press was a tall cupboard that held bed linen, curtains, and clothes as international trade provided for a greater number of luxury goods in the well-to-do household. In the early 18th century a press composed of a cupboard above a chest of drawers became popular in England, and its use spread to the Continent. Until modern times no major advances in cupboard design were made after the 18th century.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1532 2022-10-14 14:07:14

ganesh
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Posts: 40,614

Re: Miscellany

1505) Lock and key

Summary

A lock is a mechanical or electronic fastening device that is released by a physical object (such as a key, keycard, fingerprint, RFID card, security token or coin), by supplying secret information (such as a number or letter permutation or password), by a combination thereof, or it may only be able to be opened from one side, such as a door chain.

A key is a device that is used to operate a lock (to lock or unlock it). A typical key is a small piece of metal consisting of two parts: the bit or blade, which slides into the keyway of the lock and distinguishes between different keys, and the bow, which is left protruding so that torque can be applied by the user. In its simplest implementation, a key operates one lock or set of locks that are keyed alike, a lock/key system where each similarly keyed lock requires the same, unique key.

The key serves as a security token for access to the locked area; locks are meant to only allow persons having the correct key to open it and gain access. In more complex mechanical lock/key systems, two different keys, one of which is known as the master key, serve to open the lock. Common metals include brass, plated brass, nickel silver, and steel.

Details

A key is nothing more than the solution to a mechanical puzzle, the lock. As with most puzzles there is potentially more than one solution. Substitute solutions range from lock picks to unauthorized duplicate keys. To create the puzzle, four basic methods of keying are used in the construction of mechanical-type locks—warded, lever tumbler, pin tumbler, and wafer, or disc tumbler. The construction of some locks combines more than one of these methods.

Bit key

A lock that incorporates more than a single keying method is the bit key, or “skeleton key,” lock popular in America at the turn of the 20th century. It has lever tumblers that require a key with a bit, or projecting part, of proper depth and position cut on the top to cause a lever to rise as the key is rotated. Wards, or protrusions cast into the lock case on either side, require the key to have corresponding cuts on the side of the bit before it can be rotated to engage the lever tumblers. Many such locks also had entering wards cast in the lock case that required a cut running diagonally across the face of the key’s bit. Without this cut the key could not enter the keyhole. The bit key lock lost its popularity because of the large cavity that had to be created in the door to hold the lock body and the limited number of possible key changes, or combinations, available.

Lever tumbler

An example of the lever lock in popular use today is that for the safe-deposit box. Perhaps the most dominant use of lever-type locks is on lockers that are found in schools and industry.

Pin Tumbler

The keying method used most often on door locks, and in many padlocks, is the pin tumbler lock. This type was invented in the 1860s by Linus Yale, Jr., and is still used extensively on the North American continent. It is not nearly so popular, however, in most other parts of the world. The pin tumbler lock provides almost unlimited quantities of possible combinations and is readily master keyed, a system that allows a single master key to open a number of individually keyed locks. The configuration, or shape, of the keyway is also almost unlimited. This shape is broached, or cut, into the lock cylinder plug and a corresponding shape milled into the blank brass stock that constitutes a key.

In a pin tumbler lock a key with cuts of a proper depth is inserted into a lock cylinder, causing the tumblers in the lock to rise to a “shear line.” This line is at the outside diameter of the plug and allows the key to turn. A cam attached to the rear of the plug engages the locking, or retracting, mechanism and moves as the key is rotated.

As lock technology improved in the 1960s, this pin tumbler lock with single action became susceptible to alternative methods of operation such as the use of lock picks and unauthorized duplicate keys. In 1970 a United States patent was issued to Roy Oliver, E.C. Flora, Roy Spain, and Paul Powell for a pin tumbler type with double action known as the Medeco High Security Lock Cylinder. This was the first major variation to improve security and control in the pin tumbler lock. The construction of the Medeco lock requires not only proper depth cuts on the key but also proper angles of the cuts. These angles vary, causing the tumblers to rotate to a particular position, which then allows a side bar to operate. Another variation is the Norman High Security Lock Cylinder, patented in 1976 by Norman Epstein. Pins are replaced by balls, and the cylinder has a curved keyhole with a computer-designed key.

Wafer, Or Disc Tumbler, Locks

They came into popular use around the late 1940s. This method of keying requires flat tumblers stamped out of sheet brass. The tumblers are usually incorporated into a die metal cylinder, which results in low-cost manufacture. Wafer tumbler locks are used extensively in desks, cabinets, padlocks, and in some door locks. The possible combinations available in this type are comparatively limited as is the ability to master key.

Combination, Or Dial, Locks

They are operated by a pattern of movements of a knob or handle over a predetermined set of numbers. A more recent adaptation has a set of push buttons. Such locks are used where extreme precautions are needed. Since they have no keyholes, the lock mechanisms are inaccessible.

Time Locks

They are equipped with clockwork devices that make it impossible to open the lock except at the hour for which the timepiece is set. They are often used on bank vaults.

History

Locks in varying configurations have been employed by mankind since a large stone was first rolled in front of a cave entrance to assure privacy and control over entry. There is evidence that ancient Egyptians used intricate locks 4,000 years ago. The ancient Greeks developed several refinements of bar-and-bolt locks that permitted a door to be unbarred from the outside as well as from the inside. One improvement consisted of a rope attached to a pivoted bar and passed through a hole in the door. A tug on the rope lifted the bar from its cleats.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1533 2022-10-15 13:29:55

ganesh
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Re: Miscellany

1506) Algeria

Summary

Algeria, officially the People's Democratic Republic of Algeria, is a country in North Africa. Algeria is bordered to the northeast by Tunisia; to the east by Libya; to the southeast by Niger; to the southwest by Mali, Mauritania, and Western Sahara; to the west by Morocco; and to the north by the Mediterranean Sea. It is considered to be a part of the Maghreb region of North Africa. It has a semi-arid geography, with most of the population living in the fertile north and the Sahara dominating the geography of the south. Algeria covers an area of 2,381,741 square kilometres (919,595 sq mi), making it the world's tenth largest nation by area, and the largest nation in Africa, being more than 200 times as large as the smallest country in the continent, The Gambia. With a population of 44 million, Algeria is the ninth-most populous country in Africa, and the 32nd-most populous country in the world. The capital and largest city is Algiers, located in the far north on the Mediterranean coast.

Algeria produced and is linked to many civilizations, empires and dynasties, including ancient Numidians, Phoenicians, Carthaginians, Romans, Vandals, Byzantines, Umayyads, Abbasids, Rustamids, Idrisids, Aghlabids, Fatimids, Zirids, Hammadids, Almoravids, Almohads, Zayyanids, Spaniards, Ottomans and the French colonial empire. The vast majority of Algeria's population is Arab-Berber, practicing Islam, and using the official languages of Arabic and Berber. However, French serves as an administrative and educational language in some contexts. The main spoken language is Algerian Arabic.

Algeria is a semi-presidential republic, with local constituencies consisting of 58 provinces and 1,541 communes. Algeria is a regional power in North Africa, and a middle power in global affairs. It has the highest Human Development Index of all non-island African countries and one of the largest economies on the continent, based largely on energy exports. Algeria has the world's sixteenth-largest oil reserves and the ninth-largest reserves of natural gas. Sonatrach, the national oil company, is the largest company in Africa, supplying large amounts of natural gas to Europe. Algeria's military is one of the largest in Africa, and has the largest defence budget on the continent. It is a member of the African Union, the Arab League, the OIC, OPEC, the United Nations, and the Arab Maghreb Union, of which it is a founding member.

Details

Algeria is a large, predominantly Muslim country of North Africa. From the Mediterranean coast, along which most of its people live, Algeria extends southward deep into the heart of the Sahara, a forbidding desert where Earth’s hottest surface temperatures have been recorded and which constitutes more than four-fifths of the country’s area. The Sahara and its extreme climate dominate the country. The contemporary Algerian novelist Assia Djebar has highlighted the environs, calling her country “a dream of sand.”

History, language, customs, and an Islamic heritage make Algeria an integral part of the Maghreb and the larger Arab world, but the country also has a sizable Amazigh (Berber) population, with links to that cultural tradition. Once the breadbasket of the Roman Empire, the territory now comprising Algeria was ruled by various Arab-Amazigh dynasties from the 8th through the 16th century, when it became part of the Ottoman Empire. The decline of the Ottomans was followed by a brief period of independence that ended when France launched a war of conquest in 1830.

By 1847 the French had largely suppressed Algerian resistance to the invasion and the following year made Algeria a département of France. French colonists modernized Algeria’s agricultural and commercial economy but lived apart from the Algerian majority, enjoying social and economic privileges extended to few non-Europeans. Ethnic resentment, fueled by revolutionary politics introduced by Algerians who had lived and studied in France, led to a widespread nationalist movement in the mid-20th century. A war of independence ensued (1954–62) that was so fierce.

Negotiations ended the conflict and led to Algerian independence, and most Europeans left the country. Although the influence of the French language and culture in Algeria remained strong, since independence the country consistently has sought to regain its Arab and Islamic heritage. At the same time, the development of oil and natural gas and other mineral deposits in the Algerian interior brought new wealth to the country and prompted a modest rise in the standard of living. In the early 21st century Algeria’s economy was among the largest in Africa.

The capital is Algiers, a crowded bustling seaside metropolis whose historic core, or medina, is ringed by tall skyscrapers and apartment blocks. Algeria’s second city is Oran, a port on the Mediterranean Sea near the border with Morocco. Less hectic than Algiers, Oran has emerged as an important centre of music, art, and education.

Land

Algeria is bounded to the east by Tunisia and Libya; to the south by Niger, Mali, and Mauritania; to the west by Morocco and Western Sahara (which has been virtually incorporated by the former); and to the north by the Mediterranean Sea. It is a vast country—the largest in Africa and the 10th largest in the world—that may be divided into two distinct geographic regions. The northernmost, generally known as the Tell, is subject to the moderating influences of the Mediterranean and consists largely of the Atlas Mountains, which separate the coastal plains from the second region in the south. This southern region, almost entirely desert, forms the majority of the country’s territory and is situated in the western portion of the Sahara, which stretches across North Africa.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1534 2022-10-16 14:30:14

ganesh
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Re: Miscellany

1507) Nigeria

Summary

Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea to the south in the Atlantic Ocean. It covers an area of 923,769 square kilometres (356,669 sq mi), and with a population of over 218 million, it is the most populous country in Africa, and the world's sixth-most populous country. Nigeria borders Niger in the north, Chad in the northeast, Cameroon in the east, and Benin in the west. Nigeria is a federal republic comprising 36 states and the Federal Capital Territory, where the capital, Abuja, is located. The largest city in Nigeria is Lagos, one of the largest metropolitan areas in the world and the second-largest in Africa.

Nigeria has been home to several indigenous pre-colonial states and kingdoms since the second millennium BC, with the Nok civilization in the 15th century BC, marking the first internal unification in the country. The modern state originated with British colonialization in the 19th century, taking its present territorial shape with the merging of the Southern Nigeria Protectorate and Northern Nigeria Protectorate in 1914 by Lord Lugard. The British set up administrative and legal structures while practising indirect rule through traditional chiefdoms in the Nigeria region. Nigeria became a formally independent federation on 1 October 1960. It experienced a civil war from 1967 to 1970, followed by a succession of military dictatorships and democratically elected civilian governments until achieving a stable democracy in the 1999 presidential election. The 2015 general election was the first time an incumbent president would lose re-election.

Nigeria is a multinational state inhabited by more than 250 ethnic groups speaking 500 distinct languages, all identifying with a wide variety of cultures. The three largest ethnic groups are the Hausa in the north, Yoruba in the west, and Igbo in the east, together comprising over 60% of the total population. The official language is English, chosen to facilitate linguistic unity at the national level. Nigeria's constitution ensures freedom of religion and it is home to some of the world's largest Muslim and Christian populations, simultaneously. Nigeria is divided roughly in half between Muslims, who live mostly in the north, and Christians, who live mostly in the south; indigenous religions, such as those native to the Igbo and Yoruba ethnicities, are in the minority.

Nigeria is a regional power in Africa, a middle power in international affairs, and is an emerging global power. Nigeria's economy is the largest in Africa, the 31st-largest in the world by nominal GDP, and 26th-largest by PPP. Nigeria is often referred to as the Giant of Africa owing to its large population and economy and is considered to be an emerging market by the World Bank. However, the country ranks very low in the Human Development Index and remains one of the most corrupt nations in the world. Nigeria is a founding member of the African Union and a member of many international organizations, including the United Nations, the Commonwealth of Nations, NAM, the Economic Community of West African States, and OPEC. It is also a member of the informal MINT group of countries and is one of the Next Eleven economies.

Details

Nigeriais a country located on the western coast of Africa. Nigeria has a diverse geography, with climates ranging from arid to humid equatorial. However, Nigeria’s most diverse feature is its people. Hundreds of languages are spoken in the country, including Yoruba, Igbo, Fula, Hausa, Edo, Ibibio, Tiv, and English. The country has abundant natural resources, notably large deposits of petroleum and natural gas.

The national capital is Abuja, in the Federal Capital Territory, which was created by decree in 1976. Lagos, the former capital, retains its standing as the country’s leading commercial and industrial city.

Modern Nigeria dates from 1914, when the British Protectorates of Northern and Southern Nigeria were joined. The country became independent on October 1, 1960, and in 1963 adopted a republican constitution but elected to stay a member of the Commonwealth.

Land

Nigeria is bordered to the north by Niger, to the east by Chad and Cameroon, to the south by the Gulf of Guinea of the Atlantic Ocean, and to the west by Benin. Nigeria is not only large in area—larger than the U.S. state of Texas—but also Africa’s most populous country.

Relief
In general, the topography of Nigeria consists of plains in the north and south interrupted by plateaus and hills in the centre of the country. The Sokoto Plains lie in the northwestern corner of the country, while the Borno Plains in the northeastern corner extend as far as the Lake Chad basin. The Lake Chad basin and the coastal areas, including the Niger River delta and the western parts of the Sokoto region in the far northwest, are underlain by soft, geologically young sedimentary rocks. Gently undulating plains, which become waterlogged during the rainy season, are found in these areas. The characteristic landforms of the plateaus are high plains with broad, shallow valleys dotted with numerous hills or isolated mountains, called inselbergs; the underlying rocks are crystalline, although sandstones appear in river areas. The Jos Plateau rises almost in the centre of the country; it consists of extensive lava surfaces dotted with numerous extinct volcanoes. Other eroded surfaces, such as the Udi-Nsukka escarpment (see Udi-Nsukka Plateau), rise abruptly above the plains at elevations of at least 1,000 feet (300 metres). The most mountainous area is along the southeastern border with Cameroon, where the Cameroon Highlands rise to the highest points in the country, Chappal Waddi (7,936 feet [2,419 metres]) in the Gotel Mountains and Mount Dimlang (6,699 feet [2,042 metres]) in the Shebshi Mountains.

Drainage

The major drainage areas in Nigeria are the Niger-Benue basin, the Lake Chad basin, and the Gulf of Guinea basin. The Niger River, for which the country is named, and the Benue, its largest tributary, are the principal rivers. The Niger has many rapids and waterfalls, but the Benue is not interrupted by either and is navigable throughout its length, except during the dry season. Rivers draining the area north of the Niger-Benue trough include the Sokoto, the Kaduna, the Gongola, and the rivers draining into Lake Chad. The coastal areas are drained by short rivers that flow into the Gulf of Guinea. River basin development projects have created many large man-made lakes, including Lake Kainji on the Niger and Lake Bakolori on the Rima River.

The Niger delta is a vast low-lying region through which the waters of the Niger River drain into the Gulf of Guinea. Characteristic landforms in this region include oxbow lakes, river meander belts (see meander), and prominent levees. Large freshwater swamps give way to brackish mangrove thickets near the seacoast.

Soils

Soils in Nigeria, and in Africa generally, are usually of a poorer quality than those in other regions of the world. However, over the centuries Nigerians have utilized agricultural techniques such as slash and burn, intercropping, and the use of shallow planting implements to cope with the shortcomings of the soil. In the precolonial period the country normally produced enough agricultural commodities to feed its population, and it even maintained a surplus for export.

Nigeria’s major soil zones conform to geographic location. Loose sandy soils consisting of wind-borne deposits and riverine sands are found in the northern regions, although, in areas where there is a marked dry season, a dense surface layer of laterite develops, making these soils difficult to cultivate. The soils in the northern states of Kano and Sokoto, however, are not subject to leaching and are therefore easily farmed. South of Kano the mixed soils contain locally derived granite and loess (wind-borne deposits). The middle two-thirds of the country, the savanna regions, contain reddish, laterite soils; they are somewhat less fertile than those of the north because they are not subject to as much seasonal drying, nor do they receive the greater rainfall that occurs in the more southerly regions. The forest soils represent the third zone. There the vegetation provides humus and protects it from erosion by heavy rainfall. Although these soils can readily be leached and lose their fertility, they are the most productive agriculturally. Hydromorphic and organic soils, confined largely to areas underlain by sedimentary rocks along the coast and river floodplains, are the youngest soil types.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1535 2022-10-17 14:49:33

ganesh
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Re: Miscellany

1508) Ethiopia

Summary

Ethiopia is a country on the Horn of Africa. The country lies completely within the tropical latitudes and is relatively compact, with similar north-south and east-west dimensions. The capital is Addis Ababa (“New Flower”), located almost at the centre of the country. Ethiopia is the largest and most populated country in the Horn of Africa. With the 1993 secession of Eritrea, its former province along the Red Sea, Ethiopia became landlocked.

Ethiopia is one of the world’s oldest countries, its territorial extent having varied over the millennia of its existence. In ancient times it remained centred on Aksum, an imperial capital located in the northern part of the modern state, about 100 miles (160 km) from the Red Sea coast. The present territory was consolidated during the 19th and 20th centuries as European powers encroached into Ethiopia’s historical domain. Ethiopia became prominent in modern world affairs first in 1896, when it defeated colonial Italy in the Battle of Adwa, and again in 1935–36, when it was invaded and occupied by fascist Italy. Liberation during World War II by the Allied powers set the stage for Ethiopia to play a more prominent role in world affairs. Ethiopia was among the first independent nations to sign the Charter of the United Nations, and it gave moral and material support to the decolonization of Africa and to the growth of Pan-African cooperation. These efforts culminated in the establishment of the Organization of African Unity (since 2002, the African Union) and the United Nations Economic Commission for Africa, both of which have their headquarters in Addis Ababa.

Details

Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east and northeast, Kenya to the south, South Sudan to the west, and Sudan to the northwest. Ethiopia has a total area of 1,100,000 square kilometres (420,000 sq mi). As of 2022, it is home to around 113.5 million inhabitants, making it the 12th-most populous country in the world and the 2nd-most populous in Africa after Nigeria. The national capital and largest city, Addis Ababa, lies several kilometres west of the East African Rift that splits the country into the African and Somali tectonic plates.

Anatomically modern humans emerged from modern-day Ethiopia and set out to the Near East and elsewhere in the Middle Paleolithic period. Southwestern Ethiopia has been proposed as a possible homeland of the Afroasiatic language family. In 980 BCE, the Kingdom of D'mt extended its realm over Eritrea and the northern region of Ethiopia, while the Kingdom of Aksum maintained a unified civilization in the region for 900 years. Christianity was embraced by the kingdom in 330, and Islam arrived by the first Hijra in 615. After the collapse of Aksum in 960, a variety of kingdoms, largely tribal confederations, existed in the land of Ethiopia. The Zagwe dynasty ruled the north-central parts until being overthrown by Yekuno Amlak in 1270, inaugurating the Ethiopian Empire and the Solomonic dynasty, claimed descent from the biblical Solomon and Queen of Sheba under their son Menelik I. By the 14th century, the empire grew in prestige through territorial expansion and fighting against adjacent territories; most notably, the Ethiopian–Adal War (1529–1543) contributed to fragmentation of the empire, which ultimately fell under a decentralization known as Zemene Mesafint in mid-18th century. Emperor Tewodros II ended Zemene Mesafint at the beginning of his reign in 1855, marking the reunification and modernization of Ethiopia.

From 1878 onwards, Emperor Menelik II launched a series of conquests known as Menelik's Expansions, which resulted in the formation of Ethiopia's current border. Externally, during the late 19th century, Ethiopia defended itself against foreign invasions, including from Egypt and Italy; as a result, Ethiopia and Liberia preserved their sovereignty during the Scramble for Africa. In 1935, Ethiopia was occupied by Fascist Italy and annexed with Italian-possessed Eritrea and Somaliland, later forming Italian East Africa. In 1941, during World War II, it was occupied by the British Army, and its full sovereignty was restored in 1944 after a period of military administration. The Derg, a Soviet-backed military junta, took power in 1974 after deposing Emperor Haile Selassie and the Solomonic dynasty and ruled the country for nearly 17 years amidst the Ethiopian Civil War. Following the dissolution of the Derg in 1991, the Ethiopian People's Revolutionary Democratic Front (EPRDF) dominated the country with a new constitution and ethnic-based federalism. Since then, Ethiopia has suffered from prolonged and unsolved inter-ethnic clashes and political instability marked by democratic backsliding. From 2018, regional and ethnically based factions carried out armed attacks in multiple ongoing wars throughout Ethiopia.

Ethiopia is a multi-ethnic state with over 80 different ethnic groups. Christianity is the most widely professed faith in the country, with significant minorities of the adherents of Islam and a small percentage to traditional faiths. This sovereign state is a founding member of the UN, the Group of 24, the Non-Aligned Movement, the Group of 77, and the Organisation of African Unity. Addis Ababa is the headquarters of the African Union, the Pan African Chamber of Commerce and Industry, the United Nations Economic Commission for Africa, the African Standby Force and many of the global non-governmental organizations focused on Africa. Ethiopia is considered an emerging power and developing country, having the fastest economic growth in Sub-Saharan African countries because of foreign direct investment in expansion of agricultural and manufacturing industries. However, in terms of per capita income and the Human Development Index,[32] the country is regarded as poor with high rates of poverty, poor respect for human rights, and a literacy rate of only 49%. Agriculture is the largest economic sector in Ethiopia, accounting for 36% of the country's gross domestic product as of 2020. 

(The Horn of Africa (HoA), also known as the Somali Peninsula, is a large peninsula and geopolitical region in East Africa. Located on the easternmost part of the African mainland, it is the fourth largest peninsula in the world. It is composed of Ethiopia, Eritrea, Somalia and Djibouti; broader definitions also include parts or all of Kenya, Sudan, South Sudan, and Uganda. The term Greater Horn Region (GHR) can additionally include Burundi , Rwanda, and Tanzania. It lies along the southern boundary of the Red Sea and extends hundreds of kilometres into the Guardafui Channel, Gulf of Aden, and Indian Ocean and shares a maritime border with the Arabian Peninsula of Western Asia.)

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1536 2022-10-18 14:12:17

ganesh
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Re: Miscellany

1509) Pinball

Summary

Pinball is an arcade game in which a ball rolls and is propelled inside a specially designed cabinet known as a pinball machine, hitting various lights, bumpers, ramps, and other targets depending on its design. The game's object is generally to score as many points as possible by hitting these targets and making various shots with flippers before the ball is lost. Most pinball machines use one ball per turn (except during special multi-ball phases), and the game ends when the ball(s) from the last turn are lost. The biggest pinball manufacturers historically include Bally Manufacturing, Gottlieb, Williams Electronics and Stern Pinball.

Details

Pinball

Pinball machine, also called Pinball Game, is earliest of the coin-activated popular electromechanical games, usually found in candy stores, pool halls, drinking establishments, and amusement arcades, some of which, at the height of the game’s popularity, were exclusively devoted to pinball. Pinball originated in its modern form in about 1930. Earlier machines had been purely mechanical. The earliest machines with coin slots used marbles and cost a penny to play. Steel balls replaced the marbles, and the single-coin price to play rose with inflation.

The pinball player inserts a coin, which unlocks a spring plunger with which the player may propel a ball up an alley on the side of the glass-topped, inclined playing area. From the top, the ball descends through gates, between posts, and off bumpers, whose electrical contact points produce a cumulative score recorded on a lighted panel at the top of the machine. The scoring is accompanied by the ringing of bells and the flashing of lights. Finally, the ball drops into one of several holes, scoring variously. As the game grew in popularity, added features allowed the player control of choices by use of levers or buttons. A rollover slot acted to multiply scores, so that they rose from tens of thousands to hundreds of thousands and finally to millions. The player could apply physical torque or impetus to the machine (called “body English”), the amount of such force allowable being controlled by cut-off switches, which could be set so that an excess of force would flash on a “Tilt” sign, ending the game automatically.

For decades almost all pinball machines were manufactured in the United States, but the game came to be played worldwide. After World War II, the Japanese developed a similar vertical machine, onomatopoeically named pachinko, that hung on the wall and had an automatic payoff receptacle like that of a slot machine.

In the late 20th century, electronic games displaced pinball games in popularity in most countries except Japan, where pachinko remained popular.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1537 2022-10-19 14:45:07

ganesh
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Re: Miscellany

1510) Tea bag

A tea bag, or the compound teabag, is a small, porous, sealed bag or packet, typically containing tea leaves or the leaves of other herbs, which is immersed in water to steep and make an infusion. Originally used only for tea (Camellia sinensis), they are now made with other tisanes ("herbal teas") as well.

Tea bags are commonly made of filter paper or food-grade plastic, or occasionally of silk cotton or silk. The tea bag performs the same function as a tea infuser. Tea bags can be used multiple times until there is no extraction left. Some tea bags have an attached piece of string with a paper label at the top that assists in removing the bag, while also displaying the brand or variety of tea.

History

Tea bag patents date from 1903, and the first modern tea bags were hand-sewn fabric bags. Appearing commercially around 1904, tea bags were successfully marketed in about 1908 by Thomas Sullivan, a tea and coffee importer from New York, who shipped his silk tea bags around the world. A popular legend states that this was accidental; the loose tea was intended to be removed from the bags by customers, but they found it easier to brew the tea with the tea leaves still enclosed in the porous bags. The first tea bag packing machine was invented in 1929 by Adolf Rambold for the German company Teekanne.

The heat-sealed paper fiber tea bag was patented in 1930 by William Hermanson. The now-common rectangular tea bag was not invented until 1944. Prior to that, tea bags resembled small sacks.

Production:

Teas

A broad variety of teas as well as other infusions like herbal teas, are available in tea bags. Typically, tea bags use fannings, the left-overs after larger leaf pieces are gathered for sale as loose tea, but some companies sell teabags containing whole-leaf tea.

Shapes and material:

Circular tea bags

Traditionally, tea bags have been square or rectangular in shape. They are usually made of filter paper, a blend of wood and vegetable fibers related to paper found in milk and coffee filters. The latter is bleached pulp abaca hemp, a plantation banana plant grown for its fiber, mostly in the Philippines and Colombia. Some bags have a heat-sealable thermoplastic such as PVC or polypropylene as a component fiber on the inner tea bag surface, making them not fully biodegradable. Some newer paper tea bags are made in a circular shape.

Tetrahedral tea bags were introduced by the PG Tips brand in 1997. They are typically made of nylon, soilon (PLA mesh made from corn starch), or silk. Nylon is non-biodegradable, so silk is preferred by environmentalists. PLA on the other hand is biodegradable, but is not compostable.

Empty tea bags are also available for consumers to fill with tea leaves themselves. These are typically open-ended pouches with long flaps. The pouch is filled with an appropriate quantity of leaf tea and the flap is closed into the pouch to retain the tea. Such tea bags combine the ease of use of a commercially produced tea bag with the wider tea choice and better quality control of loose leaf tea.

Plastics

In 2017, Mike Armitage, a gardener in Wrexham, UK, found that tea bags left a plastic residue after being composted. He started a petition urging Unilever to remove plastic from bag production. In January 2018, Co-op Food announced that they were removing plastic from their own brand 99 tea bags in conjunction with their supplier Typhoo. In February 2018, PG Tips announced that their pyramid bags would now use corn starch adhesive in place of polypropylene.

Microplastics may be found in the tea meant for human consumption. A 2019 study showed that "steeping a single plastic teabag at brewing temperature (95 °C) releases approximately 11.6 billion microplastics and 3.1 billion nanoplastics into a single cup of the beverage". A 2021 study analyzed purportedly cellulose tea bags and found that 15 of the 22 bags tested also contained polyester, polyethylene or polypropylene, which are known to shed microplastic fibers. Although cellulose is considered to be biodegradable, the plastic components are not and release microplastics to the environment when composted.

Tea bag-related activities

Decorative tea bags have become the basis for large collections and many collectors collect tea bags from around the world. Tea bag collector clubs are widely spread around the world and members consist of people interested in items related to teas. Online collector clubs often include catalogs of tea bags, as well as collection tracking tools. In addition, tea bag collectors often collect other tea-related items such as labels. These websites also provide forums for discussions and trade arrangements between collectors.

Teabag folding began in the Netherlands and is often credited to Tiny van der Plas. It is a form of origami in which identical squares of patterned paper (cut from the front of tea bag wrappers) are folded, and then arranged in rosettes. These rosettes are usually used to decorate gift cards and it has become a popular craft in both the US and UK since 2000.

Soil scientists used standardized tea bags to measure the decomposition rate of organic materials in different soils.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1538 2022-10-20 14:24:36

ganesh
Administrator
Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1511) Doll

Summary

A dollis a child’s toy modeled in human or animal form. It is perhaps the oldest plaything.

No dolls have been found in prehistoric graves, probably because they were made of such perishable materials as wood and fur or cloth, but a fragment of a Babylonian alabaster doll with movable arms has been recovered. Dolls dating from 3000–2000 BC, carved of flat pieces of wood, geometrically painted, with long, flowing hair made of strings of clay or wood beads, have been found in some Egyptian graves.

Some ancient dolls may have had religious meaning, and some authorities often argue that the religious doll preceded the toy. In ancient Greece and Rome, marriageable girls consecrated their discarded dolls to goddesses. Dolls were buried in children’s graves in Egypt, Greece, and Rome and in early Christian catacombs. Ancient rag, or stuffed, dolls have been found, as well as dolls crocheted of bright wool and others with woolen heads, clothed in coloured wool frocks.

As early as 1413 there were Dochenmacher, or doll makers, in Nürnberg, Germany, which, from the 16th to the 18th century, was the leading manufacturer of dolls and toys. Paris was another early mass-producer of dolls, making chiefly fashion dolls. Doll’s houses were also popular in Europe from the 16th century.

Doll heads were made of wood, terra-cotta, alabaster, and wax—the last a technique perfected in England by Augusta Montanari and her son Richard (c. 1850–87), who popularized infant dolls. About 1820, glazed porcelain (Dresden) doll heads and unglazed bisque (ceramic) heads became popular. A French bisque doll made by the Jumeau family in the 1860s had a swivel neck; the body was made of kid-covered wood or wire or of kid stuffed with sawdust, a type of manufacture that remained common until it was supplanted by molded plastics in the 20th century. Socket joints, movable eyes, dolls with voices, and walking dolls were introduced in the 19th century, as were paper-doll books and dolls of India rubber or gutta-percha. The period from 1860 to 1890 was the golden age of the elaborately dressed Parisian bisque fashion dolls and the smaller “milliner’s models.”

The oldest American dolls may be those found in Inca and Aztec graves, such as those near the pyramids of Teotihuacán. Colonial dolls mostly followed European models. Among American Indian dolls, the kachina doll of the Pueblo Indians is noteworthy.

In Japan, dolls are more often festival figures than playthings. At the girls’ festival held in March, dolls representing the emperor, empress, and their court are displayed; girls from 7 to 17 visit each other’s collections, and refreshments are offered: first, to their majesties, then to the guests, in a ritual more than 900 years old. Japanese boys also have an annual doll festival, from the first May after they are born until they are about 15 years old. Warrior dolls, weapons, banners, and legendary-figure groups are displayed to encourage chivalrous virtues.

In India, elaborately dressed dolls were given to child brides by both Hindus and Muslims. In Syria, girls of marriageable age hang dolls in their windows. In South Africa, among the Mfengu people, every grown girl is given a doll to keep for her first child; on its birth, the mother receives a second doll to keep for the second child.

In the 20th century, notably popular dolls included the teddy bear (1903); the Kewpie Doll (1903); the Bye-lo Baby, who closed her eyes in sleep (1922); the Dydee and Wetsy Betsy dolls (1937); the Barbie doll (1959); Cabbage Patch Kids (1983); and the American Girls Collection (1986).

Details

A doll is a model typically of a human or humanoid character, often used as a toy for children, especially little girls. Dolls have also been used in traditional religious rituals throughout the world. Traditional dolls made of materials such as clay and wood are found in the Americas, Asia, Africa and Europe. The earliest documented dolls go back to the ancient civilizations of Egypt, Greece, and Rome. They have been made as crude, rudimentary playthings as well as elaborate art. Modern doll manufacturing has its roots in Germany, from the 15th century. With industrialization and new materials such as porcelain and plastic, dolls were increasingly mass-produced. During the 20th century, dolls became increasingly popular as collectibles.

Early history and traditional dolls

The earliest dolls were made from available materials such as clay, stone, wood, bone, ivory, leather, or wax. Archaeological evidence places dolls as the foremost candidate for the oldest known toy. Wooden paddle dolls have been found in Egyptian tombs dating to as early as the 21st century BC. Dolls with movable limbs and removable clothing date back to at least 200 BC. Archaeologists have discovered Greek dolls made of clay and articulated at the hips and shoulders. Rag dolls and stuffed animals were probably also popular, but no known examples of these have survived to the present day. Stories from ancient Greece around 100 AD show that dolls were used by little girls as playthings. In ancient Rome, dolls were made of clay, wood or ivory. Dolls have been found in the graves of Roman children. Like children today, the younger members of Roman civilization would have dressed their dolls according to the latest fashions. In Greece and Rome, it was customary for boys to dedicate their toys to the gods when they reached puberty and for girls to dedicate their toys to the goddesses when they married. Rag dolls are traditionally home-made from spare scraps of cloth material. Roman rag dolls have been found dating back to 300 BC.

Traditional dolls are sometimes used as children's playthings, but they may also have spiritual, magical and ritual value. There is no defined line between spiritual dolls and toys. In some cultures dolls that had been used in rituals were given to children. They were also used in children's education and as carriers of cultural heritage. In other cultures dolls were considered too laden with magical powers to allow children to play with them.

African dolls are used to teach and entertain; they are supernatural intermediaries, and they are manipulated for ritual purposes. Their shape and costume vary according to region and custom. Dolls are frequently handed down from mother to daughter. Akuaba are wooden ritual fertility dolls from Ghana and nearby areas. The best known akuaba are those of the Ashanti people, whose akuaba have large, disc-like heads. Other tribes in the region have their own distinctive style of akuaba.

There is a rich history of Japanese dolls dating back to the Dogū figures (8000–200 BCE). and Haniwa funerary figures (300–600 AD). By the eleventh century, dolls were used as playthings as well as for protection and in religious ceremonies. During Hinamatsuri, the doll festival, hina dolls are displayed. These are made of straw and wood, painted, and dressed in elaborate, many-layered textiles. Daruma dolls are spherical dolls with red bodies and white faces without pupils. They represent Bodhidharma, the East Indian who founded Zen, and are used as good luck charms. Wooden Kokeshi dolls have no arms or legs, but a large head and cylindrical body, representing little girls.

The use of an effigy to perform a spell on someone is documented in African, Native American, and European cultures. Examples of such magical devices include the European poppet and the nkisi or bocio of West and Central Africa. In European folk magic and witchcraft, poppet dolls are used to represent a person for casting spells on that person. The intention is that whatever actions are performed upon the effigy will be transferred to the subject through sympathetic magic. The practice of sticking pins in voodoo dolls have been associated with African-American Hoodoo folk magic. Voodoo dolls are not a feature of Haitian Vodou religion, but have been portrayed as such in popular culture, and stereotypical voodoo dolls are sold to tourists in Haiti. Likely the voodoo doll concept in popular culture is influenced by the European poppet. A kitchen witch is a poppet originating in Northern Europe. It resembles a stereotypical witch or crone and is displayed in residential kitchens as a means to provide good luck and ward off bad spirits.

Hopi Kachina dolls are effigies made of cottonwood that embody the characteristics of the ceremonial Kachina, the masked spirits of the Hopi Native American tribe. Kachina dolls are objects meant to be treasured and studied in order to learn the characteristics of each Kachina. Inuit dolls are made out of soapstone and bone, materials common to the Inuit. Many are clothed with animal fur or skin. Their clothing articulates the traditional style of dress necessary to survive cold winters, wind, and snow. The tea dolls of the Innu people were filled with tea for young girls to carry on long journeys. Apple dolls are traditional North American dolls with a head made from dried apples. In Inca mythology, Sara Mama was the goddess of grain. She was associated with maize that grew in multiples or was similarly strange. These strange plants were sometimes dressed as dolls of Sara Mama. Corn husk dolls are traditional Native American dolls made out of the dried leaves or husk of a corncob. Traditionally, they do not have a face. The making of corn husk dolls was adopted by early European settlers in the United States. Early settlers also made rag dolls and carved wooden dolls, called Pennywoods. La última muñeca, or "the last doll", is a tradition of the Quinceañera, the celebration of a girl's fifteenth birthday in parts of Latin America. During this ritual the quinceañera relinquishes a doll from her childhood to signify that she is no longer in need of such a toy. In the United States, dollmaking became an industry in the 1860s, after the Civil War.

Matryoshka dolls are traditional Russian dolls, consisting of a set of hollow wooden figures that open up and nest inside each other. They typically portray traditional peasants and the first set was carved and painted in 1890. In Germany, clay dolls have been documented as far back as the 13th century, and wooden doll making from the 15th century. Beginning about the 15th century, increasingly elaborate dolls were made for Nativity scene displays, chiefly in Italy. Dolls with detailed, fashionable clothes were sold in France in the 16th century, though their bodies were often crudely constructed. The German and Dutch peg wooden dolls were cheap and simply made and were popular toys for poorer children in Europe from the 16th century. Wood continued to be the dominant material for dolls in Europe until the 19th century. Through the 18th and 19th centuries, wood was increasingly combined with other materials, such as leather, wax and porcelain and the bodies made more articulate. It is unknown when dolls' glass eyes first appeared, but brown was the dominant eye color for dolls up until the Victorian era when blue eyes became more popular, inspired by Queen Victoria.

Dolls, puppets and masks allow ordinary people to state what is impossible in the real situation; In Iran for example during Qajar era, people criticised the politics and social conditions of Ahmad-Shah's reign via puppetry without any fear of punishment. According to the Islamic rules, the act of dancing in public especially for women, is a taboo. But dolls or puppets have free and independent identities and are able to do what is not feasible for the real person. Layli is a hinged dancing doll, which is popular among the Lur people of Iran. The name Layli is originated from the Middle East folklore and love story, Layla and Majnun. Layli is the symbol of the beloved who is spiritually beautiful. Layli also represents and maintains a cultural tradition, which is gradually vanishing in urban life.

Industrial era

During the 19th century, dolls' heads were often made of porcelain and combined with a body of leather, cloth, wood, or composite materials, such as papier-mâché or composition, a mix of pulp, sawdust, glue and similar materials. With the advent of polymer and plastic materials in the 20th century, doll making largely shifted to these materials. The low cost, ease of manufacture, and durability of plastic materials meant new types of dolls could be mass-produced at a lower price. The earliest materials were rubber and celluloid. From the mid-20th century, soft vinyl became the dominant material, in particular for children's dolls. Beginning in the 20th century, both porcelain and plastic dolls are made directly for the adult collectors market. Synthetic resins such as polyurethane resemble porcelain in texture and are used for collectible dolls.

Colloquially the terms porcelain doll, bisque doll and china doll are sometimes used interchangeably. But collectors make a distinction between china dolls, made of glazed porcelain, and bisque dolls, made of unglazed bisque or biscuit porcelain. A typical antique china doll has a white glazed porcelain head with painted molded hair and a body made of cloth or leather. The name comes from china being used to refer to the material porcelain. They were mass-produced in Germany, peaking in popularity between 1840 and 1890 and selling in the millions. Parian dolls were also made in Germany, from around 1860 to 1880. They are made of white porcelain similar to china dolls but the head is not dipped in glaze and has a matte finish. Bisque dolls are characterized by their realistic, skin-like matte finish. They had their peak of popularity between 1860 and 1900 with French and German dolls. Antique German and French bisque dolls from the 19th century were often made as children's playthings, but contemporary bisque dolls are predominantly made directly for the collectors market. Realistic, lifelike wax dolls were popular in Victorian England.

Up through the middle of the 19th century, European dolls were predominantly made to represent grown-ups. Childlike dolls and the later ubiquitous baby doll did not appear until around 1850. But, by the late 19th century, baby and childlike dolls had overtaken the market. By about 1920 baby dolls typically were made of composition with a cloth body. The hair, eyes, and mouth were painted. A voice box was sewn into the body that cried ma-ma when the doll was tilted, giving them the name Mama dolls. During 1923, 80% of all dolls sold to children in the United States were Mama dolls.

Paper dolls are cut out of paper, with separate clothes that are usually held onto the dolls by folding tabs. They often reflect contemporary styles, and 19th century ballerina paper dolls were among the earliest celebrity dolls. The 1930s Shirley Temple doll sold millions and was one of the most successful celebrity dolls. Small celluloid Kewpie dolls, based on illustrations by Rose O'Neill, were popular in the early 20th century. Madame Alexander created the first collectible doll based on a licensed character – Scarlett O'Hara from Gone with the Wind.

Contemporary dollhouses have their roots in European baby house display cases from the 17th century. Early dollhouses were all handmade, but, following the Industrial Revolution and World War II, they were increasingly mass-produced and became more affordable. Children's dollhouses during the 20th century have been made of tin litho, plastic, and wood. Contemporary houses for adult collectors are typically made of wood.

The earliest modern stuffed toys were made in 1880. They differ from earlier rag dolls in that they are made of plush furlike fabric and commonly portray animals rather than humans. Teddy bears first appeared in 1902–1903.

Black dolls have been designed to resemble dark-skinned persons varying from stereotypical to more accurate portrayals. Rag dolls made by American slaves served as playthings for slave children. Golliwogg was a children's book rag doll character in the late 19th century that was widely reproduced as a toy. The doll has very black skin, eyes rimmed in white, clown lips, and frizzy hair, and has been described as an anti-black caricature.[40] Early mass-produced black dolls were typically dark versions of their white counterparts. The earliest American black dolls with realistic African facial features were made in the 1960s.

Fashion dolls are primarily designed to be dressed to reflect fashion trends and are usually modeled after teen girls or adult women. The earliest fashion dolls were French bisque dolls from the mid-19th century. Contemporary fashion dolls are typically made of vinyl. Barbie, from the American toy company Mattel, dominated the market from her inception in 1959. Bratz was the first doll to challenge Barbie's dominance, reaching forty percent of the market in 2006.

Plastic action figures, often representing superheroes, are primarily marketed to boys. Fashion dolls and action figures are often part of a media franchise that may include films, TV, video games and other related merchandise. Bobblehead dolls are collectible plastic dolls with heads connected to the body by a spring or hook in such a way that the head bobbles. They often portray baseball players or other athletes.

With the introduction of computers and the Internet, virtual and online dolls appeared. These are often similar to traditional paper dolls and enable users to design virtual dolls and drag and drop clothes onto dolls or images of actual people to play dress up. These include KiSS, Stardoll and Dollz.

Also with the advent of the Internet, collectible dolls are customized and sold or displayed online. Reborn dolls are vinyl dolls that have been customized to resemble a human baby with as much realism as possible. They are often sold online through sites such as eBay. Asian ball-jointed dolls (BJDs) are cast in synthetic resin in a style that has been described as both realistic and influenced by anime. Asian BJDs and Asian fashion dolls such as Pullip and Blythe are often customized and photographed. The photos are shared in online communities.

Uses, appearances and issues

Since ancient times, dolls have played a central role in magic and religious rituals and have been used as representations of deities. Dolls have also traditionally been toys for children. Dolls are also collected by adults, for their nostalgic value, beauty, historical importance or financial value. Antique dolls originally made as children's playthings have become collector's items. Nineteenth-century bisque dolls made by French manufacturers such as Bru and Jumeau may be worth almost $22,000 today.

Dolls have traditionally been made as crude, rudimentary playthings as well as with elaborate, artful design. They have been created as folk art in cultures around the globe, and, in the 20th century, art dolls began to be seen as high art. Artist Hans Bellmer made surrealistic dolls that had interchangeable limbs in 1930s and 1940s Germany as opposition to the Nazi party's idolization of a perfect Aryan body. East Village artist Greer Lankton became famous in the 1980s for her theatrical window displays of drug addicted, anorexic and mutant dolls.

Lifelike or anatomically correct dolls are used by health professionals, medical schools and social workers to train doctors and nurses in various health procedures or investigate cases of all sexual abuse of children. Artists sometimes use jointed wooden mannequins in drawing the human figure. Many ordinary doll brands are also anatomically correct, although most types of dolls are degenitalized.

Egli-Figuren are a type of doll that originated in Switzerland in 1964 for telling Bible stories.

In Western society, a gender difference in the selection of toys has been observed and studied. Action figures that represent traditional masculine traits are popular with boys, who are more likely to choose toys that have some link to tools, transportation, garages, machines and military equipment. Dolls for girls tend to represent feminine traits and come with such accessories as clothing, kitchen appliances, utensils, furniture and jewelry.

Pediophobia is a fear of dolls or similar objects. Psychologist Ernst Jentsch theorized that uncanny feelings arise when there is an intellectual uncertainty about whether an object is alive or not. Sigmund Freud further developed on these theories. Japanese roboticist Masahiro Mori expanded on these theories to develop the uncanny valley hypothesis: if an object is obviously enough non-human, its human characteristics will stand out and be endearing; however, if that object reaches a certain threshold of human-like appearance, its non-human characteristics will stand out, and be disturbing.

Doll hospitals

A doll hospital is a workshop that specializes in the restoration or repair of dolls. Doll hospitals can be found in countries around the world. One of the oldest doll hospitals was established in Lisbon, Portugal in 1830, and another in Melbourne, reputedly the first such establishment in Australia, was founded in 1888. There is a Doll Doctors Association in the United States. Henri Launay, who has been repairing dolls at his shop in northeast Paris for 43 years, says he has restored over 30,000 dolls in the course of his career. Most of the clients are not children, but adults in their 50s and 60s. Some doll brands, such as American Girl and Madame Alexander, also offer doll hospital services for their own dolls.

Dolls and children's tales

Many books deal with dolls tales, including Wilhelmina. The Adventures of a Dutch Doll, by Nora Pitt-Taylor, pictured by Gladys Hall. Rag dolls have featured in a number of children's stories, such as the 19th century character Golliwogg in The Adventures of Two Dutch Dolls and a Golliwogg by Bertha Upton and Florence K. Upton and Raggedy Ann in the books by Johnny Gruelle, first published in 1918. The Lonely Doll is a 1957 children's book by Canadian author Dare Wright. The story, told through text and photographs, is about a doll named Edith and two teddy bears.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1539 2022-10-21 13:21:28

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1512) Oasis

Summary

An oasis is a fertile tract of land that occurs in a desert wherever a perennial supply of fresh water is available. Oases vary in size, ranging from about 1 hectare (2.5 acres) around small springs to vast areas of naturally watered or irrigated land. Underground water sources account for most oases; their springs and wells, some of them artesian, are supplied from sandstone aquifers whose intake areas may be more than 800 km (500 miles) away, as at Al-Khārijah Oasis (Kharga) and Al-Dākhilah Oasis (Dakhla) in the Libyan Desert. Two-thirds of the total population of the Sahara are sedentary peoples living in oases and depending on irrigation; these areas have temperatures conducive to rapid vegetative growth. In all Saharan oases the date palm constitutes the main source of food, while in its shade are grown citrus fruits, figs, peaches, apricots, vegetables, and cereals such as wheat, barley, and millet.

Details

In geography, an oasis is a fertile land in a desert or semi-desert environment. Oases also provide habitats for animals and plants. Surface water may be present, or water may only be accessible from wells or underground channels created by humans.

Description

Typically, an oasis has a “central pool of open water surrounded by a ring of water-dependent shrubs and trees…which are in turn encircled by an outlying transition zone to desert plants.” Oases in the Middle East and North Africa cover about 1,000,000 hectares (10,000 sq km), however, they support the livelihood of about 10 million inhabitants. The stark ratio of oasis to desert land in the world means that the oasis ecosystem is “relatively minute, rare and precious.”

Oases are made when sources of freshwater, such as underground rivers or aquifers, irrigate the surface naturally or via man-made wells. The presence of water on the surface or underground is necessary and the local or regional management of this essential resource is strategic, but not sufficient to create such areas: continuous human work and know-how (a technical and social culture) are essential to maintain such ecosystems.

Rain showers provide subterranean water to sustain natural oases, such as the Tuat. Substrata of impermeable rock and stone can trap water and retain it in pockets, or on long faulting subsurface ridges or volcanic dikes water can collect and percolate to the surface. Any incidence of water is then used by migrating birds, which also pass seeds with their droppings which will grow at the water's edge forming an oasis. It can also be used to plant crops.

There are 90 “major oases” within the Sahara Desert. Some of their fertility may derive from irrigation systems called foggaras, khettaras, lkhttarts, or a variety of other regional names.

In some oases systems, there is “a geometrical system of raised channels that release controlled amounts of the water into individual plots, soaking the soil.”

Oases often have human histories that are measured in millennia. Archeological digs at Ein Gedi in the Dead Sea Valley have found evidence of settlement dating to 6,000 BP. Al-Ahsa on the Arabian Peninsula shows evidence of human residence dating to the Neolithic.

Anthropologically, the oasis is “an area of sedentary life, which associates the city [medina] or village [ksar] with its surrounding feeding source, the palm grove, within a relational and circulatory nomadic system.”

The location of oases has been of critical importance for trade and transportation routes in desert areas; caravans must travel via oases so that supplies of water and food can be replenished. Thus, political or military control of an oasis has in many cases meant control of trade on a particular route. For example, the oases of Awjila, Ghadames and Kufra, situated in modern-day Libya, have at various times been vital to both north–south and east–west trade in the Sahara Desert. The location of oases also informed the Darb el-Arba camel route through Egypt to Sudan, as well as the caravan route from the Niger River to Tangier, Morocco. The Silk Road “traced its course from water hole to water hole, relying on oasis communities such as Turpan in China and Samarkand in Uzbekistan.”

According to the United Nations, “Oases are at the very heart of the overall development of peri-Saharan countries due to their geographical location and the fact they are preferred migration routes in times of famine or insecurity in the region.”

Oases in Oman, on the Arabian Peninsula near the Persian Gulf, vary somewhat from the Saharan form. While still located in an arid or semi-arid zone with a date palm overstory, these oases are usually located below plateaus and “watered either by springs or by aflaj, tunnel systems dug into the ground or carved into the rock to tap underground aquifers.” This rainwater harvesting system “never developed a serious salinity problem.”

In the drylands of southwestern North America, there is a habitat form called Palm Oasis (alternately Palm Series or Oasis Scrub Woodland) that has the native California fan palm as the overstory species. These Palm Oases can be found in California, Arizona, Baja California, and Sonora.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1540 2022-10-22 13:42:58

ganesh
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Posts: 40,614

Re: Miscellany

1513) Charcoal

Summary

Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, called charcoal burning, often by forming a charcoal kiln, the heat is supplied by burning part of the starting material itself, with a limited supply of oxygen. The material can also be heated in a closed retort. Modern "charcoal" briquettes used for outdoor cooking may contain many other additives, e.g. coal.

This process happens naturally when combustion is incomplete, and is sometimes used in radiocarbon dating. It also happens inadvertently while burning wood, as in a fireplace or wood stove. The visible flame in these is due to combustion of the volatile gases exuded as the wood turns into charcoal. The soot and smoke commonly given off by wood fires result from incomplete combustion of those volatiles. Charcoal burns at a higher temperature than wood, with hardly a visible flame, and releases almost nothing except heat and carbon dioxide (One kilogram of charcoal contains 680 to 820 grams of carbon, which when combined with oxygen from the atmosphere form 2.5 to 3 kg of carbon dioxide).

Details

Charcoal is a impure form of graphitic carbon, obtained as a residue when carbonaceous material is partially burned, or heated with limited access of air. Coke, carbon black, and soot may be regarded as forms of charcoal; other forms often are designated by the name of the materials, such as wood, blood, bone, and so on, from which they are derived. Charcoal has been replaced by coke for reducing metal ores in blast furnaces and by natural gas as a source of carbon in making certain chemicals, but it is still employed in making black gunpowder and in case-hardening metals. Formerly, charcoal production from wood was an important source of acetone, methyl alcohol, and acetic acid, all of which are now produced from other raw materials.

The use of special manufacturing techniques results in highly porous charcoals that have surface areas of 300–2,000 square metres per gram. These so-called active, or activated, charcoals are widely used to adsorb odorous or coloured substances from gases or liquids, as in the purification of drinking water, sugar, and many other products, in the recovery of solvents and other volatile materials, and in gas masks for the removal of toxic compounds from the air. They also are used as catalysts in making certain chemicals (e.g., phosgene, sulfuryl chloride) or as supports for other catalytic agents.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1541 2022-10-23 13:55:10

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1514) Monopoly

Summary

Monopoly is a multi-player economics-themed board game. In the game, players roll two dice to move around the game board, buying and trading properties and developing them with houses and hotels. Players collect rent from their opponents, aiming to drive them into bankruptcy. Money can also be gained or lost through Chance and Community Chest cards and tax squares. Players receive a stipend every time they pass "Go" and can end up in jail, from which they cannot move until they have met one of three conditions. House rules, hundreds of different editions, many spin-offs, and related media exist. Monopoly has become a part of international popular culture, having been licensed locally in more than 103 countries and printed in more than 37 languages. As of 2015, it was estimated that the game had sold 275 million copies worldwide.

Monopoly is derived from The Landlord's Game, created by Lizzie Magie in the United States in 1903 as a way to demonstrate that an economy that rewards individuals is better than one where monopolies hold all the wealth and to promote the economic theories of Henry George—in particular, his ideas about taxation. The Landlord's Game originally had two sets of rules, one with tax and another on which the current rules are mainly based. When Parker Brothers first published Monopoly in 1935, the game did not include the less capitalistic taxation rule, resulting in a more aggressive game. Parker Brothers were eventually absorbed into Hasbro in 1991. The game is named after the economic concept of a monopoly—the domination of a market by a single entity.

Details

Monopoly is a real-estate board game for two to eight players, in which the player’s goal is to remain financially solvent while forcing opponents into bankruptcy by buying and developing pieces of property.

Each side of the square board is divided into 10 small rectangles representing specific properties, railroads, utilities, a jail, and various other places and events. At the start of the game, each player is given a fixed amount of play money; the players then move around the board according to the throw of a pair of dice. Any player who lands on an unowned property may buy it, but, if he or she lands on a property owned by another player, rent must be paid to that player. Certain nonproperty squares require the player landing on them to draw a card that may be favourable or unfavourable. If a player acquires a monopoly—that is, all of a particular group of properties—that player may purchase improvements for those properties; improvements add substantially to a property’s rental fee. A player continues to travel around the board until he or she is bankrupt. Bankruptcy results in elimination from the game. The last player remaining on the board is the winner.

Monopoly, which is the best-selling privately patented board game in history, gained popularity in the United States during the Great Depression when Charles B. Darrow, an unemployed heating engineer, sold the concept to Parker Brothers in 1935. Before then, homemade versions of a similar game had circulated in many parts of the United States. Most were based on the Landlord’s Game, a board game designed and patented by Lizzie G. Magie in 1904. She revised and renewed the patent on her game in 1924. Notably, the version Magie originated did not involve the concept of a monopoly; for her, the point of the game was to illustrate the potential exploitation of tenants by greedy landlords. Magie used the Landlord’s Game to promote a remedy for such exploitation—namely, the single tax on property owners, a leading social issue among those who criticized land speculation as a cause of economic injustice.

The Landlord’s Game was still circulating in the early 1900s as a handmade board game, and other variations emerged that incorporated the monopolization of properties. Among those promoting this version were the brothers Louis and Fred Thun, who abandoned their patent attempt in 1931 when records of Magie’s 1904 patent came to light, and Dan Layman, who named his game Finance but, like the Thuns, did not patent it. Darrow drew upon the earlier models, successfully marketing his version of Monopoly to retailers in the northeastern United States between 1933 and 1934. Demand soon overwhelmed his ability to mass-produce the game sets, but it took repeated efforts to convince Parker Brothers of the game’s merit. Once the company acquired the game from Darrow, Parker Brothers promoted Monopoly as the brainchild of an out-of-work engineer seeking an affordable means of entertainment during a time of economic hardship. Lawsuits from others claiming to have invented Monopoly were settled by Parker Brothers.

Monopoly became popular in many other parts of the world. In the original North American sets, the properties were named for streets in Atlantic City, New Jersey. Notable among these is Marvin Gardens, which is a misspelling of the real Marven Gardens in Atlantic City. Sets marketed in other countries may be modified to represent a local city; for example, London streets are used in the British version. Monopoly games also have been licensed with other North American cities as the subject (e.g., Chicago); prominent local landmarks and points of interest usually replace street names as properties.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1542 2022-10-24 14:14:11

ganesh
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Posts: 40,614

Re: Miscellany

1515) Marble (Toy)

Summary

A marble is a small spherical object often made from glass, clay, steel, plastic, or agate. They vary in size, and most commonly are about 13 mm (1⁄2 in) in diameter. These toys can be used for a variety of games called marbles, as well being placed in marble runs or races, or created as a form of art. They are often collected, both for nostalgia and for their aesthetic colors.

Sizes may range from less than 1 mm (1⁄30 in)[citation needed] to over 8 cm (3 in), while some art glass marbles for display purposes are over 30 cm (12 in) wide.

In the North of England the objects and the game are called "taws", with larger taws being called "bottle washers" after the use of a marble in Codd-neck bottles, which were often collected for play.

Details

Marble is a small, hard ball that is used in a variety of children’s games and is named after the 18th-century practice of making the toy from marble chips. The object of marble games is to roll, throw, drop, or knuckle marbles against an opponent’s marbles, often to knock them out of a prescribed area and so win them. (Knuckling is the act of placing a marble on the forefinger, balancing that finger or the bottom of the hand against the ground, and shooting the marble outward with the thumb.)

Marble games date from antiquity, and ancient games were played with sea-rounded pebbles, nuts, or fruit pits. The young Octavian (later the emperor Augustus), like other Roman children, played games with nut marbles, and engraved marbles have been dug up from the earthen mounds built by some early North American Indian tribes. Jewish children use filberts as marbles at Passover. Marbles have been made of a variety of other materials as well: baked clay, glass, steel, plastic, onyx, agate. Particular marbles may be known for their use (e.g., shooters), their original material (“alleys” were once made of alabaster), or their appearance (e.g., “flints,” “cloudies”).

The names and rules of marble games are as varied as the localities and countries where they are played, but a few may be mentioned. In taw, ringtaw, or ringer, players attempt to shoot marbles, sometimes arranged in a cross, out of a ring as much as 6 to 10 feet (about 2 to 3 metres) in diameter. In hit and span, players try to shoot or roll marbles either against an opponent’s marbles or a hand’s span from them. In various pot games (a pot is a small hole in the ground), including moshie, the player tries to pitch his own marbles or knock his opponents’ marbles into a hole. In bridgeboard, or nineholes, a board with several numbered arches is set up, and players try to shoot their marbles through the arches. A Chinese marble game consists of kicking a marble against an opponent’s to make the latter rebound in a specified direction. Local, regional, and national tournaments are held in many countries.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1543 2022-10-25 15:08:04

ganesh
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Re: Miscellany

1516) Lemonade

Summary

Lemonade is a sweetened lemon-flavored beverage.

There are varieties of lemonade found throughout the world. In North America and South Asia, cloudy still lemonade is the most common variety. There it is traditionally a homemade drink using lemon juice, water, and a sweetener such as cane sugar, simple syrup or honey. In the United Kingdom, Ireland, Central Europe, Australia, and New Zealand, a carbonated lemonade soft drink is more common. Despite the differences between the drinks, each is known simply as "lemonade" in countries where it is dominant.

The suffix "-ade" may also be applied to other similar drinks made with different fruits, such as limeade, orangeade, or cherryade.

Details:

History

A drink made with lemons, dates, and honey was consumed in 13th and 14th century Egypt, including a lemon juice drink with sugar, known as qatarmizat. In 1676, a company known as Compagnie de Limonadiers sold lemonade in Paris. Vendors carried tanks of lemonade on their backs and dispensed cups of the soft drink to Parisians.

While carbonated water was invented by Joseph Priestley in 1767, the first reference found to carbonated lemonade was in 1833 when the drink was sold in British refreshment stalls. R. White's Lemonade has been sold in the UK since 1845.

Varieties:

Cloudy lemonade

The predominant form of lemonade found in the US, Canada, and India, cloudy lemonade, also known as traditional or old fashioned lemonade in the UK and Australia, is non-carbonated and made with fresh lemon juice; however, commercially produced varieties are also available. Generally served cold, cloudy lemonade may also be served hot as a remedy for congestion and sore throats, frozen, or used as a mixer.

Traditionally, children in US and Canadian neighborhoods start lemonade stands to make money during the summer months. The concept has become iconic of youthful summertime Americana to the degree that parodies and variations on the concept exist across media. References can be found in comics and cartoons such as Peanuts, and the 1979 computer game Lemonade Stand.

This is Hibiscus Iced Tea and Lemonade. The pink Hibiscus Ice Tea is poured on top of the yellow Lemonade to create a color contrast. The glass is resting outside on the sidewalk and the sun is creating a long shadow from the glass toward the viewer.

Pink lemonade

A popular variation of traditional lemonade, pink lemonade, is created by adding additional fruit juices, flavors, or food coloring to the recipe. Most store-bought pink lemonade is simply colored with concentrated grape juice or dyes.

A 1912 obituary credited the invention of pink lemonade to circus worker Henry E. "Sanchez" Allott, saying he had dropped in red cinnamon candies by mistake.

Another origin story credits another circus worker, Pete Conklin, in 1857. His brother George Conklin tells the story in his 1921 memoir. According to the story, Conklin's lemonade was a mixture of water, sugar and tartaric acid, with the tub garnished with a single lemon that he repeatedly used for the season. One day, he ran out of water. Searching desperately, he found a tub of water a bareback rider had recently used to rinse her pink tights. Adding in the sugar, acid and remaining bits of lemon, he offered the resulting mixture as "strawberry lemonade" and saw his sales double.

Clear lemonade

The predominant form of lemonade in the UK, Ireland, South Africa, and Australia is a clear, lemon-flavoured carbonated beverage. Schweppes, R. White's Lemonade and C&C are common brands, and shops usually carry a store-branded lemonade as well. Schweppes uses a blend of lemon and lime oils. Other fizzy drinks, soft-drinks (or pop) which are both lemon and lime flavoured may also sometimes be referred to as lemonade, such as Sprite and 7 Up. There are also speciality flavours, such as Fentimans Rose Lemonade, which is sold in the UK, the US, and Canada. Shandy, a mixture of beer and clear lemonade, is often sold pre-bottled, or ordered in pubs.

Brown lemonade

There are various drinks called brown lemonade. In Ulster, the northern province in Ireland, brown lemonade is flavoured with brown sugar. A variant from Venezuela has cane sugar and lime.

Other varieties

In India and Pakistan, where it is commonly known as nimbu paani, and in Bangladesh, lemonades may also contain salt and/or ginger juice. Shikanjvi is a traditional lemonade from this region, and can also be flavored with saffron, cumin and other spices.

Limonana, a type of lemonade made from freshly squeezed lemon juice and mint leaves, is a common summer drink in the Middle East. In Northern Africa, a drink called cherbat is made of lemon, mint, and rose water.

Switcha is a version of the drink made in the Bahamas and Turks & Caicos that can also be made with limes instead of lemons.

Citron pressé

In France, it is common for restaurants to offer citron pressé, an unmixed version of lemonade in which the customer is given lemon juice, syrup and water separately to be mixed in their preferred proportions.

Health effects

The high concentration of citric acid in lemon juice is the basis for popular culture recommendations of consumption of lemonade to prevent calcium-based kidney stones. Studies have not demonstrated that lemonade causes a sustained improvement of urine pH, increased citric acid concentration in urine, reduction in supersaturation by stone-forming salts, or prevention of recurrent stones.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1544 2022-10-26 00:07:44

ganesh
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Posts: 40,614

Re: Miscellany

1517) Ceiling

Summary

A ceiling is an overhead interior surface that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings can be decorated to taste, and there are many fine examples of frescoes and artwork on ceilings especially in religious buildings. A ceiling can also be the upper limit of a tunnel.

The most common type of ceiling is the dropped ceiling, which is suspended from structural elements above. Panels of drywall are fastened either directly to the ceiling joists or to a few layers of moisture-proof plywood which are then attached to the joists. Pipework or ducts can be run in the gap above the ceiling, and insulation and fireproofing material can be placed here. Alternatively, ceilings may be spray painted instead, leaving the pipework and ducts exposed but painted, and using spray foam.

A subset of the dropped ceiling is the suspended ceiling, wherein a network of aluminum struts, as opposed to drywall, are attached to the joists, forming a series of rectangular spaces. Individual pieces of cardboard are then placed inside the bottom of those spaces so that the outer side of the cardboard, interspersed with aluminum rails, is seen as the ceiling from below. This makes it relatively easy to repair the pipes and insulation behind the ceiling, since all that is necessary is to lift off the cardboard, rather than digging through the drywall and then replacing it.

Other types of ceiling include the cathedral ceiling, the concave or barrel-shaped ceiling, the stretched ceiling and the coffered ceiling. Coving often links the ceiling to the surrounding walls. Ceilings can play a part in reducing fire hazard, and a system is available for rating the fire resistance of dropped ceilings.

Details

Ceiling is the overhead surface or surfaces covering a room, and the underside of a floor or a roof. Ceilings are often used to hide floor and roof construction. They have been favourite places for decoration from the earliest times: either by painting the flat surface, by emphasizing the structural members of roof or floor, or by treating it as a field for an overall pattern of relief.

Little is known of ancient Greek ceilings, but Roman ceilings were rich with relief and painting, as is evidenced by the vault soffits of Pompeian baths. During the Gothic period, the general tendency to use structural elements decoratively led to the development of the beamed ceiling, in which large cross-girders support smaller floor beams at right angles to them, beams and girders being richly chamfered and molded and often painted in bright colours.

In the Renaissance, ceiling design was developed to its highest pitch of originality and variety. Three types were elaborated. The first was the coffered ceiling, in the complex design of which the Italian Renaissance architects far outdid their Roman prototypes. Circular, square, octagonal, and L-shaped coffers abounded, with their edges richly carved and the field of each coffer decorated with a rosette. The second type consisted of ceilings wholly or partially vaulted, often with arched intersections, with painted bands emphasizing the architectural design and with pictures filling the remainder of the space. The loggia of the Farnesina villa in Rome, decorated by Raphael and Giulio Romano, is a good example of this. In the Baroque period, fantastic figures in heavy relief, scrolls, cartouches, and garlands were also used to decorate ceilings of this type. The Pitti Palace in Florence and many French ceilings in the Louis XIV style illustrate this. In the third type, which was particularly characteristic of Venice, the ceiling became one large framed picture, as in the Doges’ Palace.

In modern architecture ceilings may be divided into two major classes—the suspended (or hung) ceiling and the exposed ceiling. With ceilings hung at some distance below the structural members, some architects have sought to conceal great amounts of mechanical and electrical equipment, such as electrical conduits, air-conditioning ducts, water pipes, sewage lines, and lighting fixtures. Most suspended ceilings use a lightweight metal grid suspended from the structure by wires or rods to support plasterboard sheets or acoustical tiles. Other architects, emphasizing the aesthetic of the exposed structural system, delight in revealing the mechanical and electrical equipment. In response to this desire, many structural systems have been developed that have an expressive power in themselves and make admirable ceilings—e.g., Frank Lloyd Wright’s Johnson Wax offices in Racine, Wis., and Pier Luigi Nervi’s Exposition Hall in Turin, Italy.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1545 2022-10-27 00:02:08

ganesh
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Re: Miscellany

1518) Science, technology, engineering, and mathematics

Summary

Science, technology, engineering, and mathematics (STEM) is a broad term used to group together these academic disciplines. This term is typically used to address an education policy or curriculum choices in schools. It has implications for workforce development, national security concerns (as a shortage of STEM-educated citizens can reduce effectiveness in this area) and immigration policy.

There is no universal agreement on which disciplines are included in STEM; in particular whether or not the science in STEM includes social sciences, such as psychology, sociology, economics, and political science. In the United States, these are typically included by organizations such as the National Science Foundation (NSF). The National Science Foundation deals with all matters concerning science and new discoveries in science as it affects development, research, and innovations, the Department of Labor's O*Net online database for job seekers, and the Department of Homeland Security. In the United Kingdom, the social sciences are categorized separately and are instead grouped together with humanities and arts to form another counterpart acronym HASS (Humanities, Arts, and Social Sciences), rebranded in 2020 as SHAPE (Social Sciences, Humanities and the Arts for People and the Economy).

Details

STEM, it's one of the most talked about topics in education. But what exactly is STEM? STEM stands for Science, Technology Engineering, and Mathematics. But it's more than that.

STEM has grown to represent a unique approach to teaching and learning, one that centers around individual students' learning styles and interests. This means STEM education has something to offer every student. Unlike traditional education experiences in which subject areas are concentrated on separately, STEM education emphasizes technology and integrates subjects in ways that connect disciplines and relate them to each other.

So why is STEM getting so much attention? STEM moves beyond simple test performance and focuses on developing higher level thinking skills by connecting classroom learning to the real world. STEM emphasizes collaboration, communication, research, problem solving, critical thinking, and creativity, skills that students need to be successful in today's world regardless of specific interests or career goals. STEM is a direct response to the realization that our future will be built on our capacity for innovation, invention, and creative problem solving.

What is STEM Education?

STEM education, now also know as STEAM, is a multi-discipline approach to teaching.

STEM education is a teaching approach that combines science, technology, engineering and math. Its recent successor, STEAM, also incorporates the arts, which have the "ability to expand the limits of STEM education and application," according to Stem Education Guide. STEAM is designed to encourage discussions and problem-solving among students, developing both practical skills and appreciation for collaborations, according to the Institution for Art Integration and STEAM.

Rather than teach the five disciplines as separate and discrete subjects, STEAM integrates them into a cohesive learning paradigm based on real-world applications.

According to the U.S. Department of Education "In an ever-changing, increasingly complex world, it's more important than ever that our nation's youth are prepared to bring knowledge and skills to solve problems, make sense of information, and know how to gather and evaluate evidence to make decisions."

In 2009, the Obama administration announced the "Educate to Innovate" campaign to motivate and inspire students to excel in STEAM subjects. This campaign also addresses the inadequate number of teachers skilled to educate in these subjects.

The Department of Education now offers a number of STEM-based programs, including research programs with a STEAM emphasis, STEAM grant selection programs and general programs that support STEAM education.

In 2020, the U.S. Department of Education awarded $141 million in new grants and $437 million to continue existing STEAM projects a breakdown of grants can be seen in their investment report. 

STEAM education is crucial to meet the needs of a changing world. According to an article from iD Tech, millions of STEAM jobs remain unfilled in the U.S., therefore efforts to fill this skill gap are of great importance. According to a report from the U.S. Bureau of Labor Statistics there is a projected growth of STEAM-related occupations of 10.5% between 2020 and 2030 compared to 7.5% in non-STEAM-related occupations. The median wage in 2020 was also higher in STEAM occupations ($89,780) compared to non-STEAM occupations ($40,020).

Between 2014 and 2024, employment in computer occupations is projected to increase by 12.5 percent between 2014 and 2024, according to a STEAM occupation report. With projected increases in STEAM-related occupations, there needs to be an equal increase in STEAM education efforts to encourage students into these fields otherwise the skill gap will continue to grow.

STEAM jobs do not all require higher education or even a college degree. Less than half of entry-level STEAM jobs require a bachelor's degree or higher, according to skills gap website Burning Glass Technologies. However, a four-year degree is incredibly helpful with salary — the average advertised starting salary for entry-level STEAM jobs with a bachelor's requirement was 26 percent higher than jobs in the non-STEAM fields.. For every job posting for a bachelor's degree recipient in a non-STEAM field, there were 2.5 entry-level job postings for a bachelor's degree recipient in a STEAM field.

What separates STEAM from traditional science and math education is the blended learning environment and showing students how the scientific method can be applied to everyday life. It teaches students computational thinking and focuses on the real-world applications of problem-solving. As mentioned before, STEAM education begins while students are very young:

Elementary school — STEAM education focuses on the introductory level STEAM courses, as well as awareness of the STEAM fields and occupations. This initial step provides standards-based structured inquiry-based and real-world problem-based learning, connecting all four of the STEAM subjects. The goal is to pique students' interest into them wanting to pursue the courses, not because they have to. There is also an emphasis placed on bridging in-school and out-of-school STEAM learning opportunities.

Middle school — At this stage, the courses become more rigorous and challenging. Student awareness of STEAM fields and occupations is still pursued, as well as the academic requirements of such fields. Student exploration of STEAM-related careers begins at this level, particularly for underrepresented populations.

High school — The program of study focuses on the application of the subjects in a challenging and rigorous manner. Courses and pathways are now available in STEAM fields and occupations, as well as preparation for post-secondary education and employment. More emphasis is placed on bridging in-school and out-of-school STEAM opportunities.

Much of the STEAM curriculum is aimed toward attracting underrepresented populations. There is a significant disparity in the female to male ratio when it comes to those employed in STEAM fields, according to Stem Women. Approximately 1 in 4 STEAM graduates is female. 

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1546 2022-10-28 16:33:50

ganesh
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Posts: 40,614

Re: Miscellany

1519) Electronics

Summary

Electronics is a branch of physics and electrical engineering that deals with the emission, behaviour, and effects of electrons and with electronic devices.

Electronics encompasses an exceptionally broad range of technology. The term originally was applied to the study of electron behaviour and movement, particularly as observed in the first electron tubes. It came to be used in its broader sense with advances in knowledge about the fundamental nature of electrons and about the way in which the motion of these particles could be utilized. Today many scientific and technical disciplines deal with different aspects of electronics. Research in these fields has led to the development of such key devices as transistors, integrated circuits, lasers, and optical fibres. These in turn have made it possible to manufacture a wide array of electronic consumer, industrial, and military products. Indeed, it can be said that the world is in the midst of an electronic revolution at least as significant as the industrial revolution of the 19th century.

Details

The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification and rectification, which distinguishes it from classical electrical engineering, which only uses passive effects such as resistance, capacitance and inductance to control electric current flow.

History and development

Electronics has hugely influenced the development of modern society. The identification of the electron in 1897, along with the subsequent invention of the vacuum tube which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age. Practical applications started with the invention of the diode by Ambrose Fleming and the triode by Lee De Forest in the early 1900s, which made the detection of small electrical voltages such as radio signals from a radio antenna possible with a non-mechanical device.

Vacuum tubes (Thermionic valves) were the first active electronic components which controlled current flow by influencing the flow of individual electrons, They were responsible for the electronics revolution of the first half of the twentieth century, They enabled the construction of equipment that used current amplification and rectification to give us radio, television, radar, long-distance telephony and much more. The early growth of electronics was rapid, and by the 1920s, commercial radio broadcasting and communications were becoming widespread and electronic amplifiers were being used in such diverse applications as long-distance telephony and the music recording industry.

The next big technological step took several decades to appear, when the first working point-contact transistor was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947. However, vacuum tubes played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since then, solid-state devices have all but completely taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices.

In April 1955, the IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. The 608 contained more than 3,000 germanium transistors. Thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic and peripherals. However, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis, which limited them to a number of specialised applications.

The MOSFET (MOS transistor) was invented by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959. The MOSFET was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses. Its advantages include high scalability, affordability, low power consumption, and high density. It revolutionized the electronics industry, becoming the most widely used electronic device in the world. The MOSFET is the basic element in most modern electronic equipment.

As the complexity of circuits grew, problems arose. One problem was the size of the circuit. A complex circuit like a computer was dependent on speed. If the components were large, the wires interconnecting them must be long. The electric signals took time to go through the circuit, thus slowing the computer. The invention of the integrated circuit by Jack Kilby and Robert Noyce solved this problem by making all the components and the chip out of the same block (monolith) of semiconductor material. The circuits could be made smaller, and the manufacturing process could be automated. This led to the idea of integrating all components on a single-crystal silicon wafer, which led to small-scale integration (SSI) in the early 1960s, and then medium-scale integration (MSI) in the late 1960s, followed by VLSI. In 2008, billion-transistor processors became commercially available.

(The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. A metal-insulator-semiconductor field-effect transistor (MISFET) is a term almost synonymous with MOSFET. Another synonym is IGFET for insulated-gate field-effect transistor.

The basic principle of the field-effect transistor was first patented by Julius Edgar Lilienfeld in 1925.

Two power MOSFETs in D2PAK surface-mount packages. Operating as switches, each of these components can sustain a blocking voltage of 120 V in the off state, and can conduct a con­ti­nuous current of 30 A in the on state, dissipating up to about 100 W and controlling a load of over 2000 W.

The main advantage of a MOSFET is that it requires almost no input current to control the load current, when compared with bipolar transistors (bipolar junction transistors/BJTs). In an enhancement mode MOSFET, voltage applied to the gate terminal increases the conductivity of the device. In depletion mode transistors, voltage applied at the gate reduces the conductivity.

The "metal" in the name MOSFET is sometimes a misnomer, because the gate material can be a layer of polysilicon (polycrystalline silicon). Similarly, "oxide" in the name can also be a misnomer, as different dielectric materials are used with the aim of obtaining strong channels with smaller applied voltages.

The MOSFET is by far the most common transistor in digital circuits, as billions may be included in a memory chip or microprocessor. Since MOSFETs can be made with either p-type or n-type semiconductors, complementary pairs of MOS transistors can be used to make switching circuits with very low power consumption, in the form of CMOS logic.)

Devices and components:

Various electronic components.

An electronic component is any component in an electronic system either active or passive. Components are connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits. Passive electronic components are capacitors, inductors, resistors, whilst active components are such as semiconductor devices; transistors and thyristors, which control current flow at electron level.

Types of circuits

Electronic circuit functions can be divided into two function groups: analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types. Analog circuits are becoming less common, as many of their functions are being digitised.

Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage or current as opposed to discrete levels as in digital circuits.

The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.

Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.

One rarely finds modern circuits that are entirely analog - these days analog circuitry may use digital or even microprocessor techniques to improve performance. This type of circuit is usually called "mixed signal" rather than analog or digital.

Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output. In fact, many digital circuits are actually implemented as variations of analog circuits similar to this example – after all, all aspects of the real physical world are essentially analog, so digital effects are only realized by constraining analog behaviour.

Digital circuits

Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. Most digital circuits use a binary system with two voltage levels labelled "0" and "1". Often logic "0" will be a lower voltage and referred to as "Low" while logic "1" is referred to as "High". However, some systems use the reverse definition ("0" is "High") or are current based. Quite often the logic designer may reverse these definitions from one circuit to the next as they see fit to facilitate their design. The definition of the levels as "0" or "1" is arbitrary.

Ternary (with three states) logic has been studied, and some prototype computers made. Mass-produced binary systems have caused lower significance for using ternary logic. Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital signal processors, which measure, filter or compress continuous real-world analog signals, are another example. Transistors such as MOSFET are used to control binary states.

Design

Electronic systems design deals with the multi-disciplinary design issues of complex electronic devices and systems, such as mobile phones and computers. The subject covers a broad spectrum, from the design and development of an electronic system (new product development) to assuring its proper function, service life and disposal. Electronic systems design is therefore the process of defining and developing complex electronic devices to satisfy specified requirements of the user.

Due to the complex nature of electronics theory, laboratory experimentation is an important part of the development of electronic devices. These experiments are used to test or verify the engineer's design and detect errors. Historically, electronics labs have consisted of electronics devices and equipment located in a physical space, although in more recent years the trend has been towards electronics lab simulation software, such as CircuitLogix, Multisim, and PSpice.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1547 2022-10-29 13:38:16

ganesh
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Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1520) Tessellation

Summary

A tessellation or tiling is the covering of a surface, often a plane, using one or more geometric shapes, called tiles, with no overlaps and no gaps. In mathematics, tessellation can be generalized to higher dimensions and a variety of geometries.

A periodic tiling has a repeating pattern. Some special kinds include regular tilings with regular polygonal tiles all of the same shape, and semiregular tilings with regular tiles of more than one shape and with every corner identically arranged. The patterns formed by periodic tilings can be categorized into 17 wallpaper groups. A tiling that lacks a repeating pattern is called "non-periodic". An aperiodic tiling uses a small set of tile shapes that cannot form a repeating pattern. A tessellation of space, also known as a space filling or honeycomb, can be defined in the geometry of higher dimensions.

A real physical tessellation is a tiling made of materials such as cemented ceramic squares or hexagons. Such tilings may be decorative patterns, or may have functions such as providing durable and water-resistant pavement, floor or wall coverings. Historically, tessellations were used in Ancient Rome and in Islamic art such as in the Moroccan architecture and decorative geometric tiling of the Alhambra palace. In the twentieth century, the work of M. C. Escher often made use of tessellations, both in ordinary Euclidean geometry and in hyperbolic geometry, for artistic effect. Tessellations are sometimes employed for decorative effect in quilting. Tessellations form a class of patterns in nature, for example in the arrays of hexagonal cells found in honeycombs.

Details

What is Tessellation?

A tessellation can be accurately described as tiling. Tessellations consist of a repeating pattern of one or more shapes. There are a few qualifications for a pattern to be a tessellation. These include:

* Shapes cannot overlap.
* Shapes cannot have space between them.
* The patterns are created by rotating, translating, or reflecting the shapes.

Tessellations are used in art and architecture around the world because they are visually appealing. The most prominent tessellation artist is M.C. Escher, famous for creating uniquely shaped tessellations like the lizard tessellation.

Types of Tessellations

There are four types of tessellations: regular, semi-regular, wallpaper, and aperiodic tilings. Both regular and semi-regular tessellations are made from polygon shapes, but they have some distinct differences in the included polygons. Tessellation patterns can also be named by what kind of symmetry they have, as is the case with wallpaper designs.

Regular Tessellations

The regular tessellation only has one repeating polygon shape within its image. A regular polygon is a shape that has equal side lengths and angle measurements. The shapes that are commonly used include squares, triangles, or hexagons. The pattern of a regular tessellation is identical at each of its vertices. Regular and semi- tessellations are named using a number system based on the vertex within the pattern. It does not matter which vertex is picked, as they will all lead to the same naming based on the number system. The name of the tessellation coincides with the number of sides a polygon has that meets with the vertex. When looking at a regular triangle tessellation, six triangles meet at one vertex. Each triangle has three sides. This leads the name of the simple tessellation to be 3.3.3.3.3.3. Each three within the name represents a triangle that meets at the vertex. Another example of a regular tessellation is one created using one repeating square.

Semi-Regular Tessellations

A semi-regular tessellation is made up of two or more regular polygons. There are eight types of semi-regular tessellations, but it is a requirement of all types that each vertex must be the same. This allows for the names based on the numbering system to work. The eight semi-regular tessellations incorporate different squares, hexagons, octagons, equilateral triangles, and dodecagons. An example of a semi-regular tessellation is a combination of triangles and dodecagons. When looking at any given vertex, the tessellation can be named 3.12.12 because one triangle with three sides and two dodecagons with 12 sides meet at each vertex. Several semi-regular tessellations have reflective symmetry, which is where one side is a mirror image of the other. Semi regular tessellations 4.6.12 and 4.8.8 are two examples of reflection tessellations.

Tessellations can be made from non-geometric shapes, such as the tessellations in M.C. Eschers work. The number system used to name regular and semi-regular tessellation groups does not work with these sorts of tessellations. The naming system only works if a tessellation is made up of regular polygons, not other shapes.

Wallpaper Groups

A wallpaper pattern is a plane figure that has more than one direction of translation symmetry.

Wallpaper groups of tessellations are made up of wallpaper patterns with a plane figure that has more than one direction of transitional symmetry. This is so that they can hang vertically on a wall. The wallpaper groups are based on the types of symmetries that are incorporated in them. There are a total of 17 tessellation types within the wallpaper group.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1548 2022-10-30 14:18:49

ganesh
Administrator
Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1521) Microsoft Solitaire

Solitaire is a computer game included with Microsoft Windows, based on a card game of the same name, also known as Klondike. Its original version was programmed by Wes Cherry, and the cards were designed by Susan Kare.

History

Microsoft has included the game as part of its Windows product line since Windows 3.0, starting from 1990. The game was developed during the summer of 1988 by the intern Wes Cherry. The card deck itself was designed by Macintosh pioneer Susan Kare. Cherry's version was to include a boss key that would have switched the game to a fake Microsoft Excel spreadsheet, but he was asked to remove this from the final release.

Microsoft intended Solitaire "to soothe people intimidated by the operating system," and at a time where many users were still unfamiliar with graphical user interfaces, it proved useful in familiarizing them with the use of a mouse, such as the drag-an-drop technique required for moving cards.

According to Microsoft telemetry, Solitaire was among the three most-used Windows programs and FreeCell was seventh, ahead of Word and Microsoft Excel. Lost business productivity by employees playing Solitaire has become a common concern since it became standard on Microsoft Windows.

In October 2012, along with the release of the Windows 8 operating system, Microsoft released a new version of Solitaire called Microsoft Solitaire Collection. This version, game designed by Microsoft Studios, with visual design led by William Bredbeck, and developed by Arkadium, is advertisement supported and introduced many new features to the game. As with the original release of the game, William Bredbeck is quoted as saying "One of the intentions of the redesign was to introduce users to the novel changes incorporated in the new Windows 8 operating system". This design is still in use through Windows 11.

Microsoft Solitaire celebrated its 25th anniversary on May 18, 2015. To celebrate this event, Microsoft hosted a Solitaire tournament on the Microsoft campus and broadcast the main event on Twitch.

In 2019, The Strong National Museum of Play inducted Microsoft Solitaire to its World Video Game Hall of Fame.

By its 30th anniversary in 2020, it was estimated that the game still had 35 million active monthly players and more than 100 million games played daily, according to Microsoft.

Features

When a game is won, the cards appear to fall off each stack and bounce off the screen. This "victory" screen is considered a prototypical element that would become popular in casual games, compared to the use of "Ode to Joy" on winning a level of Peggle, and makes Solitaire one of the first such casual video games.

Since Windows 3.0, Solitaire allows selecting the design on the back of the cards, choosing whether one or three cards are drawn from the deck at a time, switching between Vegas scoring and Standard scoring, and disabling scoring entirely. The game can also be timed for additional points if the game is won. There is a cheat that will allow drawing one card at a time when 'draw three' is set.

In Windows 2000 and later versions of Solitaire, right-clicking on open spaces automatically moves available cards to the four foundations in the upper right-hand corner, as in FreeCell. If the mouse pointer is on a card, a right click will move only that card to its foundation, provided that it is a possible move. Left double-clicking will also move the card to the proper foundation.

Until the Windows XP version, the card backs were the original works designed by Susan Kare, and many were animated.

The Windows Vista and Windows 7 versions of the game save statistics on the number and percentage of games won, and allow users to save incomplete games and to choose cards with different face styles.

On Windows 8, Windows 10, Windows 11, Windows Phone, Android and iOS, the game is issued as Microsoft Solitaire Collection, where in addition to Klondike four other game modes were featured, Spider, FreeCell (both of which had been previously featured in versions of Windows as Microsoft Spider Solitaire and Microsoft FreeCell), Pyramid, and TriPeaks (both of which were previously part of the Microsoft Entertainment Pack series, the former under the name Tut's Tomb).

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1549 2022-10-31 14:03:31

ganesh
Administrator
Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1522) Sieve

Summary

A sieve is a kitchen tool that has many small holes and that is used to separate smaller particles from larger ones or solids from liquids.

Details

A sieve, fine mesh strainer, or sift, is a device for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet material. The word sift derives from sieve.

In cooking, a sifter is used to separate and break up clumps in dry ingredients such as flour, as well as to aerate and combine them. A strainer, meanwhile, is a form of sieve used to separate suspended solids from a liquid by filtration.

Industrial strainer

Some industrial strainers available are simplex basket strainers, duplex basket strainers, T-strainers and Y-strainers. Simple basket strainers are used to protect valuable or sensitive equipment in systems that are meant to be shut down temporarily. Some commonly used strainers are bell mouth strainers, foot valve strainers, basket strainers. Most processing industries (mainly pharmaceutical, coatings and liquid food industries) will opt for a self-cleaning strainer instead of a basket strainer or a simplex strainer due to limitations of simple filtration systems. The self-cleaning strainers or filters are more efficient and provide an automatic filtration solution.

Sieving

Sieving is a simple technique for separating particles of different sizes. A sieve such as used for sifting flour has very small holes. Coarse particles are separated or broken up by grinding against one another and the screen openings. Depending upon the types of particles to be separated, sieves with different types of holes are used. Sieves are also used to separate stones from sand. Sieving plays an important role in food industries where sieves (often vibrating) are used to prevent the contamination of the product by foreign bodies. The design of the industrial sieve is of primary importance here.

Triage sieving refers to grouping people according to their severity of injury.

Wooden sieves

Wooden sieves

The mesh in a wooden sieve might be made from wood or wicker. Use of wood to avoid contamination is important when the sieve is used for sampling. Henry Stephens, in his Book of the Farm, advised that the withes of a wooden riddle or sieve be made from fir or willow with American elm being best. The rims would be made of fir, oak or, especially, beech.

US standard test sieve series

A sieve analysis (or gradation test) is a practice or procedure used (commonly used in civil engineering or sedimentology) to assess the particle size distribution (also called gradation) of a granular material. Sieve sizes used in combinations of four to eight sieves.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#1550 2022-11-01 14:18:02

ganesh
Administrator
Registered: 2005-06-28
Posts: 40,614

Re: Miscellany

1523) Physiotherapy

Summary

Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient education, physical intervention, rehabilitation, disease prevention, and health promotion. Physical therapists are known as physiotherapists in many countries.

In addition to clinical practice, other aspects of physical therapist practice include research, education, consultation, and health administration. Physical therapy is provided as a primary care treatment or alongside, or in conjunction with, other medical services. In some jurisdictions, such as the United Kingdom, physical therapists have the authority to prescribe medication.

Details

Physical therapy, also called physiotherapy, is a health profession that aims to improve movement and mobility in persons with compromised physical functioning. Professionals in the field are known as physical therapists.

History of physical therapy

Although the use of exercise as part of a healthy lifestyle is ancient in its origins, modern physical therapy appears to have originated in the 19th century with the promotion of massage and manual muscle therapy in Europe. In the early 20th century, approaches in physical therapy were used in the United States to evaluate muscle function in those affected by polio. Physical therapists developed programs to strengthen muscles when possible and helped polio patients learn how to use their remaining musculature to accomplish functional mobility activities. About the same time, physical therapists in the United States were also trained to work with soldiers returning from World War I; these therapists were known as “reconstruction aides.” Some worked in hospitals close to the battlefields in France to begin early rehabilitation of wounded soldiers. Typical patients were those with amputated limbs, head injuries, and spinal cord injuries. Physical therapists later practiced in a wide variety of settings, including private practices, hospitals, rehabilitation centres, nursing homes, public schools, and home health agencies. In each of those settings, therapists work with other members of the health care team toward common goals for the patient.

Patients of physical therapy

Often, persons who undergo physical therapy have experienced a decrease in quality of life as a result of physical impairments or functional limitations caused by disease or injury. Individuals who often are in need of physical therapy include those with back pain, elderly persons with arthritis or balance problems, injured athletes, infants with developmental disabilities, and persons who have had severe burns, strokes, or spinal cord injuries. Persons whose endurance for movement is affected by heart or lung problems or other illnesses are also helped by exercise and education to build activity tolerance and improve muscle strength and efficiency of movement during functional activities. Individuals with limb deficiencies are taught to use prosthetic replacement devices.

Patient management

Physical therapists complete an examination of the individual and work with him or her to determine goals that can be achieved primarily through exercise prescription and functional training to improve movement. Education is a key component of patient management. Adults with impairments and functional limitations can be taught to recover or improve movements impaired by disease and injury and to prevent injury and disability caused by abnormal posture and movement. Infants born with developmental disabilities are helped to learn movements they have never done before, with an emphasis on functional mobility for satisfying participation in family and community activities. Some problems, such as pain, may be addressed with treatments, including mobilization of soft tissues and joints, electrotherapy, and other physical agents.

Progress in physical therapy

New areas of practice are continually developing in the field of physical therapy. The scope of practice of a growing specialty in women’s health, for example, includes concerns such as incontinence, pelvic/vaginal pain, prenatal and postpartum musculosketelal pain, osteoporosis, rehabilitation following breast surgery, and lymphedema (accumulation of fluids in soft tissues). Females across the life span, from the young athlete to the childbearing, menopausal, or elderly woman, can benefit from physical therapy. Education for prevention, wellness, and exercise is another important area in addressing physical health for both men and women.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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