Posts by Jai Ganesh

Jai Ganesh · Exercises

Hi,

Unit Conversion Method

and

Measurement Index

The links in the website MathsIsFun website my be of help!

Also, Proportions.

Jai Ganesh · This is Cool

Tobacco

Gist

Within 10 seconds of your first puff, the toxic chemicals in tobacco smoke reach your brain, heart and other organs. Smoking harms almost every part of your body and increases your risk of many diseases. Smoking also affects how you look and feel, your finances and the people close to you.

Tobacco in cigarettes is made from dried, cured tobacco leaves that are processed and often mixed with additives for flavor. These leaves are wrapped in paper and contain a highly addictive drug called nicotine. When a cigarette is burned, it releases a mixture of thousands of chemicals, at least 69 of which are known to cause cancer.

Summary

Tobacco is the common name of several plants in the genus Nicotiana of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. Seventy-nine species of tobacco are known, but the chief commercial crop is N. tabacum. The more potent variant N. rustica is also used in some countries.

Dried tobacco leaves are mainly used for smoking in cigarettes and cigars, as well as pipes and shishas. They can also be consumed as snuff, chewing tobacco, dipping tobacco, and snus.

Tobacco contains the highly addictive stimulant alkaloid nicotine as well as harmala alkaloids. Due to the widespread availability and legality of tobacco, nicotine is one of the most widely used recreational drugs. Tobacco use is a cause or risk factor for many deadly diseases, especially those affecting the heart, liver, and lungs, as well as many cancers. In 2008, the World Health Organization named tobacco use as the world's single greatest preventable cause of death.

Details:

Key facts

* Tobacco kills up to half of its users who don’t quit.
* Tobacco kills more than 7 million people each year, including an estimated 1.6 million non-smokers who are exposed to second-hand smoke.
* Around 80% of the world's 1.3 billion tobacco users live in low- and middle-income countries.
* To address the tobacco epidemic, WHO Member States adopted the WHO Framework Convention on Tobacco Control (WHO FCTC) in 2003. Currently 183 countries are Parties to this treaty.
* The WHO MPOWER measures are in line with the WHO FCTC and have been shown to save lives and reduce costs from averted healthcare expenditure.

Overview

The tobacco epidemic is one of the biggest public health threats the world has ever faced, responsible for over 7million deaths annually as well as disability and long-term suffering from tobacco-related diseases.

All forms of tobacco use are harmful, and there is no safe level of exposure to tobacco. Cigarette smoking is the most common form of tobacco use worldwide. Other tobacco products include waterpipe tobacco, cigars, cigarillos, heated tobacco, roll-your-own tobacco, pipe tobacco, bidis and kreteks, and smokeless tobacco products.

Around 80% of the 1.3 billion tobacco users worldwide live in low- and middle-income countries, where the burden of tobacco-related illness and death is heaviest. Tobacco use contributes to poverty by diverting household spending from basic needs such as food and shelter to tobacco. This spending behaviour is difficult to curb because tobacco is so addictive.

The economic costs of tobacco use are substantial and include significant health care costs for treating the diseases caused by tobacco use as well as the lost human capital that results from tobacco-attributable morbidity and mortality.

Key measures to reduce the demand for tobacco:

Surveillance is key

Good monitoring tracks the extent and character of the tobacco epidemic and indicates how best to tailor policies. Almost half of the world's population are regularly asked about their tobacco use in nationally representative surveys among adults and adolescents.

Second-hand smoke kills

Second-hand smoke is the smoke that fills restaurants, offices, homes, or other enclosed spaces when people smoke tobacco products. There is no safe level of exposure to second-hand tobacco smoke. Second-hand smoke causes serious cardiovascular and respiratory diseases, including coronary heart disease and lung cancer, and kills around 1.6 million people prematurely every year.

Over third of the world's population living in 79 countries are protected by comprehensive national smoke-free laws.

Tobacco users need help to quit

Among smokers who are aware of the dangers of tobacco, most want to quit. Counselling and medication can more than double a tobacco user’s chance of successful quitting.

National comprehensive cessation services with full or partial cost-coverage are available to assist tobacco users to quit in only 31 countries, representing a third of the world's population.

Hard-hitting anti-tobacco mass media campaigns and pictorial health warnings prevent children and other vulnerable groups from taking up tobacco use, and increase the number of tobacco users who quit.

Today 62% of the world’s population live in the 110 countries that meet best practice for graphic health warnings, which includes among other criteria, large (50% or more of the main areas of the package) pictorial health warnings displayed in the national language and rotating regularly.

2.9 billion people live in the 36 countries that have aired at least one strong anti-tobacco mass media campaign within the last 2 years.

Bans on tobacco advertising lower consumption

Tobacco advertising promotion and sponsorship (TAPS) increases and sustains tobacco use by effectively recruiting new tobacco users and discouraging tobacco users from quitting.

More than one third of countries (68), representing over a quarter of the world’s population, have completely banned all forms of TAPS.

Taxes are effective in reducing tobacco use

Tobacco taxes are the most cost-effective way to reduce tobacco use, especially among youth and low-income groups. A tax increase that increases tobacco prices by 10% decreases tobacco consumption by about 4% in high-income countries and about 5% in low- and middle-income countries.

Even so, high tobacco taxes are rarely implemented. Only 41 countries, with 12% of the world's population, have introduced taxes on tobacco products so that at least 75% of the retail price is tax.

Illicit trade of tobacco products must be stopped

The illicit trade in tobacco products poses major health, economic and security concerns around the world. It is estimated that 1 in every 10 cigarettes and tobacco products consumed globally is illicit.

Experience from many countries demonstrates that illicit trade can be successfully addressed even when tobacco taxes and prices are raised, resulting in increased tax revenues and reduced tobacco use.

The WHO FCTC Protocol to Eliminate the Illicit Trade of Tobacco Products (ITP) is the key supply side policy to reduce tobacco use and its health and economic consequences.

Newer nicotine and tobacco products

Heated tobacco products (HTPs) are tobacco products that produce aerosols containing nicotine and toxic chemicals upon heating of the tobacco, or activation of a device containing the tobacco. They contain the highly addictive substance nicotine, non-tobacco additives and are often flavoured.

Despite claims of “risk reduction”, there is no evidence to demonstrate that HTPs are less harmful than conventional tobacco products. Many toxicants found in tobacco smoke are at significantly lower levels in HTP aerosol but HTP aerosol contains other toxicants found sometimes at higher levels than in tobacco smoke, such as glycidol, pyridine, dimethyl trisulfide, acetoin and methylglyoxal.

Further, some toxicants found in HTP aerosols are not found in conventional cigarette smoke and may have associated health effects. Additionally, these products are highly variable and some of the toxicants found in the emissions of these products are carcinogens.

Electronic cigarettes (or e-cigarettes) are the most common form of electronic nicotine delivery systems (ENDS) and electronic non-nicotine delivery systems (ENNDS) but there are others, such as e-cigars and e-pipes. ENDS contain varying amounts of nicotine and harmful emissions. Use of ENDS/ENNDS products is colloquially referred to as ‘vaping’. However this does not mean that they are harmless or emit water vapour.

E-cigarette emissions typically contain nicotine and other toxic substances that are harmful to users and non-users who are exposed to the aerosols second-hand. Some products claiming to be nicotine-free have been found to contain nicotine.

Evidence reveals that these products are harmful to health and are not safe. However, it is too early to provide a clear answer on the long-term impacts of using them or being exposed to them. Some recent studies suggest that ENDS use can increase the risk of heart disease and lung disorders. Nicotine exposure in pregnant women can have negative health consequences on the fetus, and nicotine, which is a highly addictive substance is damaging for brain development.

Nicotine pouches are pre-portioned pouches that contain nicotine and are similar to traditional smokeless tobacco products such as snus in some respects including appearance, inclusion of nicotine and manner of use (placing them between the gum and lip). They are often promoted, as “tobacco-free”, which can be used anywhere and in some jurisdictions, such as the USA, they are referred to as “white pouches”.

Additional Information

Tobacco is common name of the plant Nicotiana tabacum and, to a limited extent, Aztec tobacco (N. rustica) and the cured leaf that is used, usually after aging and processing in various ways, for smoking, chewing, snuffing, and extraction of nicotine. Various other species in the genus Nicotiana are grown as ornamentals, known collectively as flowering tobaccos. This article deals with the farming of commercial tobacco from cultivation to curing and grading.

Cultivation

Though tobacco is tropical in origin, it is grown throughout the world. Cultivated tobacco (N. tabacum) requires a frost-free period of 100 to 130 days from date of transplanting to maturity in the field. Aztec tobacco (N. rustica), which is grown to some extent in India, Vietnam, and certain Transcaucasian countries, matures more quickly and is more potent than cultivated tobacco.

The prime requisite for successful tobacco culture is a supply of well-developed healthy seedlings that is available at the proper time for transplanting. Soil for a plant bed should be fertile and of good tilth and drainage; it must be protected from chilling winds and exposed to the sun. The soil is usually partially sterilized by burning or using chemicals such as methyl bromide (now illegal in many countries) to control plant diseases, weeds, insect pests, and nematodes. The soil must be finely pulverized and level so that the seed can be lightly covered with soil by rolling or trampling. Uniform distribution of seeds is important. In warm regions of the world, the germinating seedlings are produced outdoors in cold frames covered with thin cotton cloth or a thin mulch, such as chopped grass (used in particular in Zimbabwe), straw, or pine needles. Glass or plastic is used in colder regions, and close attention is given to watering and ventilation. After 8 to 10 weeks the seedlings are 10 to 18 cm (4 to 7 inches) in length and are ready for transplanting in the field. Transplanting machines are used extensively in some areas, but much of the world’s tobacco is planted by hand.

Spacing of plants in the field varies widely according to the type of tobacco. Orinoco strains, used for flue curing, are grown in rows 1.2 metres (4 feet) apart, with plants 50 to 60 cm (20 to 24 inches) apart in the row. Varieties in the Pryor group are grown to produce the dark air-cured and fire-cured types and are often planted in hills 1 metre (3.5 feet) apart. Burley and Maryland strains, used for the production of light air-cured tobaccos, may be planted 81 to 91 cm (32 to 36 inches) apart or closer. Broadleaf and seed-leaf strains, including the Havana seed, Cuban, and Sumatra varieties, are used for the production of cigars; they are grown in rows spaced 1 metre (3 feet) apart, with individual plants placed at a distance of 38 to 68 cm (15 to 27 inches) from each other. The variety grown for production of Perique is spaced the widest, with rows 1.5 metres (5 feet) apart and 91 to 107 cm (36 to 42 inches) between plants. Aromatic tobaccos, also used for cigars, are spaced in rows 38 to 60 cm (15 to 24 inches) apart with 8 to 20 cm (3 to 8 inches) between plants in the row.

Soil requirements vary widely with the type of tobacco grown, though well-drained soil with good aeration is generally desirable. Flue-cured, Maryland, cigar-binder, and wrapper types of tobacco are produced on sandy and sandy loam soil. Burley, dark air-cured, fire-cured, and cigar-filler types are grown on silt loam and clay loam soils, with clay subsoils. The need for fertilizer is determined by the type of tobacco, soil, and climate; nitrogen, phosphorus, and potassium are commonly applied as necessary to prevent symptoms of nutritional deficiency.

Large-leaf tobaccos are often topped—that is, the terminal growth is removed—when the plant has reached the desired size, usually at or shortly after flowering. The number of leaves remaining varies widely. Dark air-cured and fire-cured tobaccos may have 10 to 16 leaves, while Burley, flue-cured, Maryland, and cigar types may have 16 to 20 leaves. After topping, the suckers, or lateral shoots, are removed to increase leaf development, providing increased yields. The work may be done by hand, in which case it must be repeated regularly, or by application of sucker-suppressing chemicals. Aromatic tobacco culture differs from that of most of the large-leafed tobaccos in that the plants are rarely topped and preferably are grown on soils of low productivity.

Diseases and pests

Common diseases and pests are black root rot, Fusarium wilt, tobacco mosaic virus (TMV), bacterial leaf spot, downy mildew, black shank, broomrape, and witchweed. These may be controlled by sanitation, crop rotation, the use of fungicide and herbicide sprays and fumigants, and breeding of disease-resistant strains. Some resistant varieties of tobacco have been produced by blending desired characteristics from longflower tobacco (N. longiflora) and N. glutinosa, among others, with strains of commercial tobacco.

Common insect pests are green June beetle larvae, cutworms, and flea beetles in the plant bed and hornworms, grasshoppers, flea beetles, cutworms, budworms, and aphids in the field. The cigarette, or tobacco, beetle damages the stored leaf and sometimes the manufactured product. Insect pests are controlled on the growing crop by using pesticide sprays and dusts, on the stored product by fumigating and trapping. Biological control often is effective. Fumigation controls nematodes in the field.

Harvest

Tobacco is harvested 70 to 130 days after transplanting by one of two methods: (1) the entire plant is cut and the stalk split or speared and hung on a tobacco stick or lath, or (2) the leaves are removed at intervals as they mature. The leaves of cigar-wrapper and aromatic tobaccos are strung using a needle, and leaves to be flue-cured are looped, using a string tied to a lath or stick that is hung in a curing barn. To prevent breakage and bruising during the handling necessary in curing, it is desirable for the leaf to wilt without sunburning. Tobacco may be left in the field from a few hours to two days to wilt.

Curing

The three most common methods of curing are by air, fire, and flue. A fourth method, sun curing, is practiced with aromatic types and to a limited extent with air-cured types. Curing entails four essential steps: wilting, yellowing, colouring, and drying. These involve physical and chemical changes in the leaf and are regulated to develop the desired properties. Air curing is accomplished mainly by mechanical ventilation inside buildings. Coke, charcoal, or petroleum gas may be burned to provide heat when conditions warrant. Air curing, which requires from one to two months’ time, is used for many tobaccos, including dark air-cured types, cigar, Maryland, and Burley.

The fire-curing process resembles air curing except that open wood fires are kindled on the floor of the curing barn after the tobacco has been hanging for two to six days. The smoke imparts to the tobacco a characteristic aroma of creosote. The firing process may be continuous or intermittent, extending from three weeks to as long as 10 weeks until curing is complete and the leaf has been cured to the desired finish.

The barns for flue curing are usually small and tightly constructed with ventilators and metal pipes, or flues, extending from furnaces around or under the floor of the barn. Fuels used are wood, coal, oil, and liquid petroleum gas. If oil or gas heaters are used, flues are not needed. Heat is applied carefully, and the leaves are observed closely for changes in their chemical and physical composition. Flue curing requires from four to eight days’ time and is used for Virginia, or bright, tobacco. In the process called bulk curing, the leaves are loaded evenly in racks arranged in a curing chamber.

Grading

After curing, the leaf may be piled in bulk to condition for a time before it is prepared for sale. The preparation consists usually of grading the leaf and putting it in a bale or package of convenient size and weight for inspection and removal by the buyer. Except during humid periods, the leaf must be conditioned in moistening cellars or humidified rooms before it can be handled without breakage. Type of leaf and local custom determine the fineness of grading. At its most elaborate, grading may be by position of the leaf on the plant, colour, size, maturity, soundness, and other recognizable qualities; flue-cured tobacco in the United States is graded that way, and each grade is bulked or baled separately. Much simpler grading is usual in developing countries, where the buyer is as much concerned with the proportions of each grade as with the quality of the entire lot; aromatic tobaccos are an example of this. Most tobaccos entering world trade, except the aromatic, are assembled before sale into bundles, or hands, of 15 to 30 leaves and tied with one leaf wrapped securely around the butts.

Most tobaccos, except aromatic and cigar, are regraded if necessary and usually redried after purchase; then the exact amount of moisture needed for aging is added and the tobacco is securely packed in cases or hogsheads. Exported tobacco is shipped in this form. The trend is for the packing factories to stem the leaf—that is, remove most of the stem leaving the lamina (leaf blade)—usually by threshing machines but sometimes by hand, before redrying it. The aging process, particularly with cigar tobaccos, is sometimes hastened by forced fermentation procedures. After purchase, aromatic tobaccos are manipulated; that is, they are factory-graded, baled, and subjected to an elaborate in-the-bale fermentation process before going to the ultimate manufacturer.

Jai Ganesh · Science HQ

Freezing Point

Gist

The freezing point is the temperature at which a liquid becomes a solid, or when the liquid and solid states of a substance exist in equilibrium. For pure water, this temperature is 0 degrees Celsius (32 degrees Fahrenheit), but it can be lowered by adding a solute, a phenomenon known as freezing point depression.

The freezing point is the temperature at which a liquid becomes a solid. At this specific temperature, the liquid and solid phases of a substance can coexist in equilibrium. For example, pure water freezes at 0 degrees Celsius) (32 degrees Fahrenheit).

Summary

Freezing point is the temperature at which a liquid becomes a solid. As with the melting point, increased pressure usually raises the freezing point. The freezing point is lower than the melting point in the case of mixtures and for certain organic compounds such as fats. As a mixture freezes, the solid that forms first usually has a composition different from that of the liquid, and formation of the solid changes the composition of the remaining liquid, usually in a way that steadily lowers the freezing point. This principle is used in purifying mixtures, successive melting and freezing gradually separating the components. The heat of fusion, the heat that must be applied to melt a solid, must be removed from the liquid to freeze it. Some liquids can be supercooled—i.e., cooled below the freezing point—without solid crystals forming. Putting a seed crystal into a supercooled liquid triggers freezing, whereupon the release of the heat of fusion raises the temperature rapidly to the freezing point.

The addition of one mole (molecular weight in grams) of any nonionic (does not form ions) solute to 1,000 grams of water lowers the freezing point of the water by 1.885 °C, and this has been used as an accurate method for determining molecular weights.

Details

The freezing point is the temperature at which the solid begins to form from the liquid in the presence of atmospheric pressure. The freezing point of water (which defines 0 °C), for instance, is approximately 0.01 °C lower than the triple point, primarily because the melting temperature of water is depressed by the application of pressure, although it also is affected by dissolved gases and other impurities. The uncontrollable impurity effects make the freezing point of water less satisfactory as a fixed point than the triple point. To prevent ambiguities, standards thermometry is referred exclusively to the triple point of water, which is defined to be exactly −0.01 °C. Melting temperatures generally increase with applied pressure, so the freezing points for most materials are higher than the triple points. Since metals tend to oxidize at high temperatures when exposed to air, atmospheric pressure may be transmitted by an inert gas, but the effect is the same. Again, as for triple points, impurities can destroy the sharpness with which the freezing point can be defined.

Additional Information

The freezing point is defined as the temperature at which a liquid transitions into a solid state under atmospheric pressure. The most commonly recognized freezing point is that of water, which is 32°F (0°C), although water can be supercooled to temperatures as low as -55°F (-48.3°C) without freezing. Freezing, also referred to as solidification or crystallization, is a first-order thermodynamic phase transition, and the process is influenced by molecular interactions; stronger forces between molecules lead to higher freezing points.

Additionally, the freezing point can be altered by the introduction of substances, such as salt in water, which lowers its freezing point and prevents ice formation in cold conditions. This principle of freezing-point depression is widely applied, including in the automotive industry with antifreeze solutions.

Interestingly, the phenomenon known as the Mpemba effect suggests that warmer water can sometimes freeze faster than cooler water due to differences in energy release. The freezing point varies among different substances, with milk and soda having lower freezing points than water due to additional solutes, while metals like silver have significantly higher freezing points. In more extreme cases, some substances, like low-temperature helium, do not freeze under normal atmospheric conditions. In food preservation, techniques like flash freezing are utilized to rapidly lower temperatures and maintain quality.

Freezing point

The temperature at which a liquid freezes or changes from a liquid to a solid state at atmospheric pressure is known as the freezing point. The most well-known freezing point is that of water at 32°F or 0°C.

In scientific terms, freezing, also known as solidification or crystallization, is a first-order thermodynamic phase transition in which liquids become solids when their temperature drops below their freezing point. A strongly related measure is the melting point, the temperature at which a solid changes from solid to liquid state at atmospheric pressure.

The melting and freezing temperature for most substances is approximately standard and unique to that substance. However, certain substances have variant solid-to-liquid transition temperatures, and some substances have the ability to supercool, which means they remain a liquid even when the temperature is lowered to below their freezing point. For this reason, the melting point rather than the freezing point is considered the characteristic property of a substance.

Background

Water's normal freezing point is 32°F or 0°C; however, water can be supercooled or undercooled to form a new thermodynamic phase at -55 F or -48.3 C. Cooled at an even faster rate, water can become a non-crystalline solid or what is known as glass. Scientists estimate water's glass transition temperature to be approximately -215 F or -137 C.

Other instances of lowering the temperature of a liquid below its freezing point without it forming a solid include freezing rain (which unlike hail and ice pellets is made up of solely liquid droplets), cumulous clouds, and supercooled water droplets in the stratosphere that sometimes form ice on aircraft wings and interfere with avionic instruments.

While it is possible to cool a liquid below its normal freezing point via supercooling, there are no liquids that do not freeze. For the property of "never freezing" to occur, a liquid's freezing point would have to be the lowest temperature matter is capable of reaching, which is absolute zero and measures 0 degrees Kelvin or -459.67 degrees Fahrenheit. To date, all known liquids freeze when sufficiently cooled.

In addition to temperature, freezing and melting points are affected by the amount of atmospheric pressure. To facilitate comparison testing of chemical and physical processes in different locations, scientists have established standard sets of conditions. The International Union of Pure and Applied Chemistry (IUPAC) has established the standard temperature and pressure (STP), and the National Institute of Standards and Technology (NIST) has established the normal temperature and pressure (NTP).

The STP, which is defined as 0°C and 1 atmosphere of pressure, is used in many industrial, commercial, and chemical settings to compute thermodynamic tabulations where properties of matter such as density and viscosity vary with changes in temperature and pressure. In the field of aeronautics, the International Standard Atmosphere (ISA) is utilized, specifying temperature, pressure, density, and sound speeds at various altitudes up to 65,000 feet above sea level.

Overview

Much of what determines the freezing point of a liquid is the interaction among its molecules. Liquids with a strong force between molecules possess a high freezing point while liquids with a weak force between molecules possess a low freezing point. In what is called the Mpemba effect, warmer water freezes more quickly than cooler water because of the faster rate at which its molecules store and release energy.

Practical applications of these principles include sprinkling salt on icy roads and walkways during the winter, which lowers the freezing point of water and thus prevents new ice from forming or melted snow from refreezing. The freezing point of water is also affected by combining it with other liquids, such as adding antifreeze to a car's cooling system, which lowers the freezing point and makes it safe to drive in below-freezing temperatures.

Freezing is also referred to as an exothermic process, wherein heat and pressure are released as a liquid changes into a solid. Although no rise in temperature is noticeable in the substance, heat is continually being released throughout the freezing process. The process is known as the enthalpy of fusion, and the energy released, called latent heat, is the same energy required to melt the same amount of the solid substance.

In a related process, freezing-point depression occurs when a solute is added to a solvent in order to decrease the freezing point of the solvent. Practical technical applications include adding salt to water, adding ethylene glycol to water, and mixing two solids in a powdered drug. Freezing point depression also causes sea water to remain liquid at below-freezing temperatures (in the case of pure water, 0 C/32 F).

Liquids such as milk and soda have freezing points that are slightly lower than the freezing point of water, which is 32 degrees Fahrenheit. In the case of milk, the presence of water-soluble substances brings down the freezing point to below that of water (approximately 31.06 degrees Fahrenheit). In the case of soda, the addition of carbon dioxide lowers the freezing point of water, while the further addition of sugar lowers the freezing point even more (down to approximately 28 degrees Fahrenheit). Following these same principles, the freezing point of wines and champagne is also lower than that of water (between 15 and 22 degrees Fahrenheit) because of the liquid composition of water and alcohol. Therefore, experts recommend storing champagne bottles at temperatures of 40 to 60 degrees Fahrenheit and not chilling the bottles for more than fifteen minutes in the freezer prior to serving.

On the other end of the spectrum, the temperature at which silver changes from a liquid to a solid state (the freezing point of silver) is approximately 1,762 degrees. Silver's equally high melting point is why it remains a solid at room temperature.

Tungsten is the chemical element with the highest melting point, making it ideal for use as a filament in light bulbs. Low-temperature helium, on the other end of the spectrum, does not freeze at all under normal pressure but only at pressures twenty times greater than normal atmospheric pressure.

Finally, the food industry uses a process called flash freezing to protect perishable foods by purposely subjecting them to temperatures below water's freezing point. Placed in direct contact with liquid nitrogen or subjected to extremely low temperatures, the rapid freezing speed directly affects the crystallization process. In addition to food preservation, flash freezing is also used to freeze biological samples via submergence in liquid nitrogen or in an ethanol and dry ice mixture.

Jai Ganesh · Dark Discussions at Cafe Infinity

2387) George Wald

Gist:

Work

Our vision functions because light from the surrounding world is captured by many light-sensitive cells in the retina at the back of the eye. George Wald found that vitamin A is an important component in rhodopsin, a light-sensitive substance in the retina, and explained in a series of studies from the 1930s to the 1960s how light causes rhodopsin to change form and be converted. This conversion gives rise to signals in a complicated network of nerve cells by which a number of reconnections and transformations occur before the signals eventually are transformed into visual impressions in the brain.

Summary

George Wald (born Nov. 18, 1906, New York, N.Y., U.S.—died April 12, 1997, Cambridge, Mass.) was an American biochemist who received (with Haldan K. Hartline of the United States and Ragnar Granit of Sweden) the Nobel Prize for Physiology or Medicine in 1967 for his work on the chemistry of vision.

While studying in Berlin as a National Research Council fellow (1932–33), Wald discovered that vitamin A is a vital ingredient of the pigments in the retina and, hence, important in maintaining vision. After further research in Heidelberg and at the universities of Zürich and Chicago, he joined the faculty of Harvard University in 1934.

By the early 1950s Wald had succeeded in elucidating the chemical reactions involved in the vision process of the rods (receptors on the retina used for night vision). In the late 1950s, with Paul K. Brown, he identified the pigments in the retina that are sensitive to yellow-green light and red light and in the early 1960s the pigment sensitive to blue light. Wald and Brown also discovered the role of vitamin A in forming the three colour pigments and showed that colour blindness is caused simply by the absence of one of them. Wald became professor emeritus at Harvard in 1977.

Details

George Wald (November 18, 1906 – April 12, 1997) was an American scientist and activist who studied pigments in the retina. He won a share of the 1967 Nobel Prize in Physiology or Medicine with Haldan Keffer Hartline and Ragnar Granit.

In 1970, Wald predicted that “civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.”

Biography

George Wald was born in New York City, the son of Ernestine (Rosenmann) and Isaac Wald, Jewish immigrant parents. He was a member of the first graduating class of the Brooklyn Technical High School in New York in 1923. He received his Bachelor of Science degree from New York University in 1927 and his PhD in zoology from Columbia University in 1932. After graduating, he received a travel grant from the US National Research Council. Wald used this grant to work in Germany with Otto Heinrich Warburg where he identified vitamin A in the retina. Wald then went on to work in Zürich, Switzerland, with the discoverer of vitamin A, Paul Karrer. Wald then worked briefly with Otto Fritz Meyerhof in Heidelberg, Germany, but left Europe for the University of Chicago in 1933 when Adolf Hitler came to power and life in Europe became more dangerous for Jews. In 1934, Wald went to Harvard University where he became an instructor, then a professor.

Wald was elected to the American Academy of Arts and Sciences in 1948. He was elected to the National Academy of Sciences in 1950, the American Philosophical Society in 1958, and in 1967 was awarded the Nobel Prize for Physiology or Medicine for his discoveries in vision. In 1966 he was awarded the Frederic Ives Medal by the OSA and in 1967 the Paul Karrer Gold Medal of the University of Zurich. In 1992, he was elected an Honorary Member of OSA.

Wald spoke out on many political and social issues and his fame as a Nobel laureate brought national and international attention to his views. He was a pacifist and vocal opponent of the Vietnam War and the nuclear arms race. Speaking at MIT in 1969 Wald said, "Our government has become preoccupied with death, with the business of killing and being killed." In 1980, he served as part of Ramsey Clark's delegation to Iran during the Iran hostage crisis.

With a small number of other Nobel laureates, he was invited in 1986 to fly to Moscow to advise Mikhail Gorbachev on a number of environmental questions. While there, he questioned Gorbachev about the arrest, detention and exile of Yelena Bonner and her husband, fellow Nobel laureate Andrei Sakharov (Peace prize, 1975). Wald reported that Gorbachev said he knew nothing about it. Bonner and Sakharov were released shortly thereafter, in December 1986.

A member of the Circumcision Resource Center in Boston, he was one of the first scientists committed against circumcision but his article "Circumcision", rejected by The New York Times in 1975, was published in 2012 only by an English magazine.

Wald died in Cambridge, Massachusetts. He was married twice: in 1931 to Frances Kingsley (1906–1980) and in 1958 to the biochemist Ruth Hubbard. He had two sons with Kingsley—Michael and David; he and Hubbard had a son—musicologist and musician Elijah Wald—and a daughter, Deborah, a family law attorney. He was an atheist.

Scientific career

As a postdoctoral researcher, Wald discovered that vitamin A was a component of the retina. His further experiments showed that when the pigment rhodopsin was exposed to light, it yielded the protein opsin and a compound containing vitamin A. This suggested that vitamin A was essential in retinal function.

In the 1950s, Wald and his colleagues used chemical methods to extract pigments from the retina. Then, using a spectrophotometer, they were able to measure the light absorbance of the pigments. Since the absorbance of light by retina pigments corresponds to the wavelengths that best activate photoreceptor cells, this experiment showed the wavelengths that the eye could best detect. However, since rod cells make up most of the retina, what Wald and his colleagues were specifically measuring was the absorbance of rhodopsin, the main photopigment in rods. Later, with a technique called microspectrophotometry, he was able to measure the absorbance directly from cells, rather than from an extract of the pigments. This allowed Wald to determine the absorbance of pigments in the cone cells.

Jai Ganesh · This is Cool

2439) Coal mine

Gist

A coal mine is a site where coal is extracted from the earth through either underground or surface (strip mining) methods. Coal mining has historically been crucial for energy, particularly for fueling the industrial revolution, and modern operations are highly mechanized, though the practice has shifted towards surface mining for efficiency and cost.

A coal mine is a site where coal is extracted from the ground through either surface or underground methods. It is a process that involves digging deep holes or long, narrow openings to remove the coal, which is then used for energy generation, steel production, and making cement.

Summary

Coal mining is the process of extracting coal from the ground or from a mine. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. The Steel industry uses coal as a fuel for extraction of iron from iron ore and the and cement industry for cement production. In the United Kingdom and South Africa, a coal mine and its structures are a colliery, a coal mine is called a "pit", and above-ground mining structures are referred to as a "pit head". In Australia, "colliery" generally refers to an underground coal mine.

Coal mining has had many developments in recent years, from the early days of tunneling, digging, and manually extracting the coal on carts to large open-cut and longwall mines. Mining at this scale requires the use of draglines, trucks, conveyors, hydraulic jacks, and shearers.

The coal mining industry has a long history of significant negative environmental impacts on local ecosystems, health impacts on local communities and workers, and contributes heavily to the global environmental crises, such as poor air quality and climate change. For these reasons, coal has been one of the first fossil fuels to be phased out of various parts of the global energy economy. The major coal producing countries, though, such as China, Indonesia, India and Australia, have not reached peak production, with production increases replacing falls in Europe and the United States and proposed mines under development.

As of 2023 the coal mining industry employed over 2.7 million workers, 2.2 million of them in Asia, but declines in global coal production were predicted to greatly decrease the number of coal jobs in coming decades.

Details

Coal mining is extraction of coal deposits from the surface of Earth and from underground.

Coal is the most abundant fossil fuel on Earth. Its predominant use has always been for producing heat energy. It was the basic energy source that fueled the Industrial Revolution of the 18th and 19th centuries, and the industrial growth of that era in turn supported the large-scale exploitation of coal deposits. Since the mid-20th century, coal has yielded its place to petroleum and natural gas as the principal energy supplier of the world. The mining of coal from surface and underground deposits today is a highly productive, mechanized operation.

History:

Ancient use of outcropping coal

There is archaeological evidence that coal was burned in funeral pyres during the Bronze Age, 3,000 to 4,000 years ago, in Wales. Aristotle mentions coal (“combustible bodies”) in his Meteorologica, and his pupil Theophrastus also records its use. The Romans in Britain burned coal before 400ce; cinders have been found among the ruins of Roman villas and towns and along the Roman wall, especially in Northumberland, near the outcrop of coal seams. The Hopi Indians of what is now the southwestern United States mined coal by picking and scraping and used it for heating, cooking, and in ceremonial chambers as early as the 12th century ce; in the 14th century they used it industrially in pottery making. Marco Polo reports its use as widespread in 13th-century China. The Domesday Book (1086), which recorded everything of economic value in England, does not mention coal. London’s first coal arrived by sea in 1228, from the areas of Fife and Northumberland, where lumps broken from submarine outcroppings and washed ashore by wave action were gathered by women and children. Thereafter, the name sea coal was applied to all bituminous coal in England. Later in the century, monks began to mine outcroppings in the north of England.

Developments in mine entry:

Shafts

Except for the Chinese, who may have mined coal underground, all the early coal seams were worked from the surface, in fully exposed outcroppings. In the later Middle Ages, however, exhaustion of outcrop coal in many places forced a change from surface to underground, or shaft, mining. Early shaft mines were little more than wells widened as much as miners dared in the face of danger of collapse. Shafts were sunk on high ground, with adits—near-horizontal tunnels—for drainage driven into the side of the hill. In England some shallow mine shafts were exhausted as early as the 14th century, making it necessary to go deeper and expand mining at the shaft bottoms. These remained small operations; a record of 1684 shows 70 mines near Bristol, employing 123 workers. Greater depth created many problems. First, water could no longer simply be drained away. Crude methods were devised to lift it to the surface. A bucket-and-chain device was first powered by men and later by horses; a continuous belt of circular plates was drawn up through a pipe. Windmills were used for pumps. But shafts had to be restricted to depths of 90 to 105 metres (300 to 350 feet) and a mining radius of 180 metres. It was not until 1710 that the water problem was eased by Thomas Newcomen’s steam atmospheric engine, which supplied a cheap and reliable power source for a vertical reciprocating lift pump.

Hoisting

Raising the coal itself was another problem. Manpower, operating a windlass, was replaced by horsepower; and, as the shafts went deeper, more horses were added. At Whitehaven in 1801, coal was hoisted 180 metres by four horses at the rate of 42–44 metric tons (46–48 tons) in nine hours. The introduction of the steam engine to hoist coal was a major turning point for the industry. Small steam-powered windlasses were successfully tried out about 1770. About 1840 the first cage was used to hoist the loaded car; and from 1840 onward advances in coal-mining techniques were rapid.

Ventilation

The presence of noxious and flammable gases caused miners to recognize the critical importance of ventilation in coal mines from the earliest days. Natural ventilation was afforded by level drainage tunnels driven from the sloping surface to connect with the shaft. Surface stacks above the shaft increased the efficiency of ventilation; their use continued in small mines until the early 20th century. The most reliable method, before the introduction of fans, was the use of a furnace at the shaft bottom or on the surface. Despite the hazard of fire and explosion, there were still a large number of furnaces operating, at least in nongassy mines, in the early 20th century.

Open-flame illumination, however, was a much more common cause of explosions until the introduction of the Davy safety lamp (about 1815), in which the flame is enclosed in a double layer of wire gauze that prevents ignition of flammable gases in the air of the mine. Presence of strong air currents, however, made even the Davy lamp unsafe.

Rotary ventilating fans were introduced in mines in the 18th century. Originally of wood and powered by steam, they were improved throughout the 19th and 20th centuries by the introduction of steel blades, electric power, and aerodynamically efficient shapes for the blades.

From manual to mechanized extraction:

Conventional mining

Early European miners wedged coal out of the seam or broke it loose with a pick. After explosives were introduced, it was still necessary to undercut the coal seam with hand tools. The advent of steam, compressed air, and electricity brought relief from this hard, dangerous work. In 1868, after almost 100 years of trial and error, a commercially successful revolving-wheel cutter for undercutting the coal seam was introduced in England. This first powered cutting tool was soon improved by introduction of compressed air as a power source in place of steam. Later, electricity was used. The longwall cutter was introduced in 1891. Originally driven by compressed air and later electrified, it could begin at one end of a long face (the vertical, exposed cross section of a seam of coal) and cut continuously to the other.

Development of continuous mining

The conventional mining techniques described above, made up of the cyclic operations of cutting, drilling, blasting, and loading, developed in association with room-and-pillar mining. The oldest of the basic underground methods, room-and-pillar mining grew naturally out of the need to recover more coal as mining operations became deeper and more expensive. During the late 1940s, conventional techniques began to be replaced by single machines, known as continuous miners, that broke off the coal from the seam and transferred it back to the haulage system. The Joy Ripper (1948) was the first continuous miner applicable to the room-and-pillar method.

Origins of longwall mining

The other principal method of modern mining, longwall mining, had been introduced as early as the 17th century and had found general use by the 19th century, but it had long been less productive than room-and-pillar mining. This began to change in the 1940s, when a continuous system involving the “plow” was developed by Wilhelm Loebbe of Germany. Pulled across the face of the coal and guided by a pipe on the face side of a segmented conveyor, the plow carved a gash off the bottom of the seam. The conveyor snaked against the face behind the advancing plow to catch the coal that chipped off from above the gash. Substantially reducing the labour required at the coal face (except that needed to install roof support), the Loebbe system quickly became popular in Germany, France, and the Low Countries.

The plow itself had limited application in British mines, but the power-advanced segmented conveyor became a fundamental part of equipment there, and in 1952 a simple continuous machine called the shearer was introduced. Pulled along the face astride the conveyor, the shearer bore a series of disks fitted with picks on their perimeters and mounted on a shaft perpendicular to the face. The revolving disks cut a slice from the coal face as the machine was pulled along, and a plow behind the machine cleaned up any coal that dropped between the face and the conveyor.

Roof support

The technique of supporting the roof by rock bolting became common in the late 1940s and did much to provide an unobstructed working area for room-and-pillar mining, but it was a laborious and slow operation that prevented longwall mining from realizing its potential. In the late 1950s, however, powered, self-advancing roof supports were introduced by the British. Individually or in groups, these supports, attached to the conveyor, could be hydraulically lowered, advanced, and reset against the roof, thus providing a prop-free area for equipment (between the coal face and the first row of jacks) and a canopied pathway for miners (between the first and second rows of jacks).

Haulage:

Manual labour to electric power

In the first shaft mines, coal was loaded into baskets that were carried on the backs of men or women or loaded on wooden sledges or trams that were then pushed or hauled through the main haulage roadway to the shaft bottom to be hung on hoisting ropes or chains. In drift and slope mines, the coal was brought directly to the surface by these and similar methods. Sledges were pulled first by men and later by animals, including mules, horses, oxen, and even dogs and goats.

Steam locomotives designed by Richard Trevithick were used in the fields of South Wales and Tyne and later in Pennsylvania and West Virginia, but they created too much smoke. Compressed-air locomotives, which appeared in the 1880s, proved expensive to operate. Electric locomotives, introduced in 1887, rapidly became popular, but mules and horses were still working in some mines as late as the 1940s.

Mechanized loading

The loading by hand of broken coal into railcars was made obsolete early in the 20th century by mobile loaders. The Stanley Header, the first coal-loading machine used in the United States, was developed in England and tested in Colorado in 1888. Others were developed, but few progressed beyond the prototype stage until the Joy machine was introduced in 1914. Employing the gathering-arm principle, the Joy machine provided the pattern for future successful mobile loaders. After the introduction in 1938 of electric-powered, rubber-tired shuttle cars designed to carry coal from the loading machine to the elevator, mobile loading and haulage rapidly supplanted track haulage at the face of room-and-pillar mines.

Conveyors

In 1924 a conveyor belt was successfully used in an anthracite mine in central Pennsylvania to carry coal from a group of room conveyors to a string of cars at the mine entry. By the 1960s belts had almost completely replaced railcars for intermediate haulage.

Preparation

The history of coal preparation begins in the 19th century, with the adaptation of mineral-processing methods used for enriching metallic ores from their associated impurities. In the early years, larger pieces of coal were simply handpicked from pieces composed predominantly of mineral matter. Washing with mechanical devices to separate the coal from associated rocks on the basis of their density differences began during the 1840s.

At first, coal preparation was necessitated by the demand for higher heating values; another demand was for such special purposes as metallurgical coke for steelmaking. In recent years, as concern has grown over the emission of sulfur dioxide in the flue gases of power plants, coal preparation has taken on greater importance as a measure to remove atmospheric pollutants.

Jai Ganesh · Dark Discussions at Cafe Infinity

Codes Quotes

1. The issues a president faces are not black and white, and cannot be boiled down into 140 characters. Because when you have the nuclear codes at your fingertips and the military at your command, you can't make snap decisions. You can't have a thin skin or the tendency to lash out. - Michelle Obama

2. Moral codes adjust themselves to environmental conditions. - Will Durant

3. I cannot help thinking that the menace of Hell makes as many devils as the severe penal codes of inhuman humanity make villains. - Lord Byron

4. Many British people of different faiths follow religious codes and practices and benefit a great deal from the guidance they offer. - Theresa May

5. I knew that the most important thing a man has is in his head, and from a young age, I often studied the head structure of each person, hoping to crack his codes. I considered a high forehead a gift from God. - Shimon Peres.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#10653. What does the term in Geography Chott mean?

#10654. What does the term in Geography Cinder cone mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#5849. What does the adjective delinquent mean?

#5450. What does the adjective delirious mean?

Jai Ganesh · Jokes

Q: What did one water bottle say to another?
A: Water you doing today?
* * *
Q: How do you make holy water?
A: Boil the hell out of it.
* * *
Q: When does it rain money?
A: When there is "change" in the weather.
* * *
Q: If H2O is the formula for water, what is the formula for ice?
A: H2O cubed.
* * *
Q: What did the bottle of water say to the spy?
A: The names Bond.... Hydrogen bond.
* * *

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#2519. What does the medical term Neurilemma mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#9798.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#6293.

Jai Ganesh · Exercises

Hi,

2641.

Jai Ganesh · This is Cool

Iodized Salt

Gist

Iodized salt is regular table salt with added iodine to prevent iodine deficiency disorders. The human body cannot produce iodine, a vital mineral needed for thyroid hormone production, which regulates metabolism and is critical for brain development. Adding iodine to salt is a global public health measure to ensure people get enough of this essential nutrient.

Is iodized salt good for you?

Yes, iodized salt is good for you because it provides essential iodine, which is crucial for brain development and the production of thyroid hormones that regulate metabolism. It is an effective public health strategy to prevent iodine deficiency disorders, which can lead to goiter, mental retardation, and other developmental issues. However, salt should be consumed in moderation, as excess sodium can cause health problems like high blood pressure.

Summary

Iodised salt (also spelled iodized salt) is table salt mixed with a minuscule amount of various iodine salts. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of intellectual and developmental disabilities. Deficiency also causes thyroid gland problems, including endemic goitre. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the sodium chloride salt.

Iodine is a micronutrient and dietary mineral that is naturally present in the food supply in some regions (especially near sea coasts) but is generally quite rare in the Earth's crust. Where natural levels of iodine in the soil are low and vegetables do not take up the iodine, iodine added to salt provides the small but essential amount of iodine needed by humans.

An opened package of table salt with iodide may rapidly lose its iodine content in high temperature and high relative humidity conditions through the process of oxidation and iodine sublimation. Poor manufacturing techniques and storage processes can also lead to insufficient amounts of iodine in table salt.

Chemistry, biochemistry, and nutritional aspects

Four inorganic compounds are used as iodide sources, depending on the producer: potassium iodate, potassium iodide, sodium iodate, and sodium iodide. Any of these compounds supplies the body with the iodine required for the biosynthesis of thyroxine (T4) and triiodothyronine (T3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the hydrogen iodide derivative of ethylenediamine is the main supplement to livestock feed.

Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed in more predictable amounts than most other commodities. For example, the concentration of iodine in salt has gradually increased in Switzerland: 3.75 mg/kg in 1922, 7.5 mg/kg in 1962, 15 mg/kg in 1980, 20 mg/kg in 1998, and 25 mg/kg since 2014. These increases were found to improve iodine status in the general Swiss population.

Salt that is iodized with iodide may slowly lose its iodine content by exposure to excess air over long periods. Salts fortified with iodate are relatively stable to storage and heat; the main concern is reducing impurities in the salt itself, which can be removed relatively easily. Moisture accelerates the decomposition of iodate, but ceases to do so once reducing impurities are removed.

Contrary to popular belief, iodised salt cannot be used as a substitute for potassium iodide (KI) to protect a person's thyroid gland in the event of a nuclear emergency. There is not enough iodine in iodised salt to block the uptake of radioactive iodine by the thyroid.

Details

Salt iodization is an effective, safe and economical strategy to increase iodine intake in populations and ensure adequate iodine intakes. It is considered to be the most appropriate strategy for iodine fortification. Salt iodization has several advantages. Table salt is usually consumed in similar quantities throughout the year and is easily distributed. Its low cost means all socio-economic classes use it. In many countries, salt is produced in a few locations, which allows for easier quality control of iodization.

Salt is iodized using iodate or iodide, but iodate is a better choice in humid tropical areas because it is more stable and less soluble. Salt with 15–40 mg of iodine per kg is considered adequately iodized. This is based on a daily per capita consumption of 10 g of salt. When salt iodization is initiated in iodine-deficient regions, there is a rapid shift of the urine iodine concentration curve to the right indicating increased iodine intake. Successful implementation of a salt iodization program is defined as ≥ 90% of households consuming adequately iodized salt. In countries that monitor use of iodized salt, coverage ranges from less than 35% to ≥ 90%.

The efficacy of salt iodization programs depend on a number of factors including household economic status, education level and quality control efforts during preparation. At present, policies and regulations on salt iodization vary among countries. For example, in Canada iodization of table salt is mandatory, whereas in the United States salt iodization is voluntary. Regulations or recommendations on levels of iodine fortification of salt also differ among countries. Rapid test kits, despite limitations, are predominantly used to measure use of iodized salt in households and assess coverage of salt iodization programs. However, in many high-income countries including Canada, United States and Australia use of iodized salt is not regularly monitored.

Additional Information

Iodized salt is table salt with small amounts of iodine added, usually as potassium iodide, to ensure against dietary deficiency of iodine. Where iodized salt is used, particularly in Switzerland and the United States, endemic goitre has disappeared.

In the United States, iodized salt contains 1 part in 10,000 iodide; in Switzerland, 1 part in 200,000. The World Health Organization recommends 1 part in 100,000.

Iodine is a micronutrient which has a very crucial part to play in the development and functioning of our body. Although needed in a small quantity, it can have grave ramifications if not consumed in the recommended dose. Iodine deficiency causes serious health issues in pregnant women and in children. Iodine insufficiency may adversely affect mental development in children.

The Significance of iodine

Iodine is naturally found in seafood, dairy products, eggs and grains. Most countries iodize their salt to prevent iodine deficiency and its awful consequences. Iodine deficiency triggers a horde of symptoms ranging from mildly discomforting to severe to even perilous.

Here are the essential uses of the mineral in our body:

* Principally, the thyroid gland needs iodine to synthesize thyroid hormones, which are pivotal for the physical and mental growth and development, tissue repair and to regulate metabolism.

* Thyroid hormones, and indirectly iodine, have a part to play in the monitoring of body temperature, blood pressure, and heart rate.

* Iodine also has a huge bearing on the functioning of the immune system.

The Relation Between Iodine and Mental Health

When the body’s iodine requirement is not met, the thyroid gland fails to manufacture adequate amounts of the thyroid hormones. Consequently, the amount of the thyroid hormones in the blood is low and it causes grave functional and developmental anomalies.

Iodine deficit is a major cause of poor mental developmental in children, causing a low IQ in school- going kids. The consequence of iodine deficiency during pregnancy is - an inadequate manufacture of the thyroid hormones by the mother and the foetus. As a result, there can be mental retardation in the child. In fact, impairment to the brain and irreversible mental retardation are the most severe disorders linked to a lack of iodine.

Experts state that a daily intake of salt that has been fortified with iodine is an efficient stratagem to prevent iodine deficiency. Consumption of iodized salt is sufficient to meet your everyday iodine requirement.

Iodized Salt – Vitally Important For Health

In India, iodine deficiency disorders comprise of an important causative factor of avoidable brain damage. The ramifications of iodine deficiency disorders are invisible and irreversible; but - preventable. We are prone to iodine deficiency disorders because of an iodine deficit in the soil of the subcontinent and accordingly in the food derived from it. Statistics reveal that about 350 million people do not consume iodized salt and are prone to iodine deficiency disorders. To circumvent the risk, our salt is reinforced with iodine. Iodized salt is a very efficient way to increase iodine intake in the population. As of today, iodized salt coverage in our country is 91% with only 71% people consuming sufficiently iodized salt. The National Iodine Deficiency Disorders Control Program’s (NIDDCP) goal in India is to decrease the prevalence of iodine deficiency disorders below 10%.

Tata Salt ensures purity as well as the right amount of iodine. In fact, if you are wondering which is the best salt for your health requirements Tata Salt offers a whole range to choose from– Tata salt, Tata Salt Lite (Iodized and Low Sodium), Tata Salt Plus (Double Fortified Salt: Iron & Iodine), Tata Rock Salt and Tata Black Salt. Consult your physician and choose the right alternative from this range.

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Jai Ganesh · Dark Discussions at Cafe Infinity

2386) Haldan Keffer Hartline

Gist:

Work

Our vision functions because light from the surrounding world is captured by many light-sensitive cells in the retina at the back of the eye. A series of reconnections and transformations of chemical and electrical signals finally result in visual impressions. In studies of the horseshoe crab around 1950, Keffer Hartline analyzed how the primary signals from visual cells are processed in a network of nerve cells. Among other things, he showed that when a cell is stimulated, signals from surrounding cells are suppressed. This makes it easier to understand the concept of contrasts.

Summary

Haldan Keffer Hartline (born Dec. 22, 1903, Bloomsburg, Pa., U.S.—died March 17, 1983, Fallston, Md.) was an American physiologist who was a co-winner (with George Wald and Ragnar Granit) of the 1967 Nobel Prize for Physiology or Medicine for his work in analyzing the neurophysiological mechanisms of vision.

Hartline began his study of retinal electrophysiology as a National Research Council Fellow at Johns Hopkins University, Baltimore, receiving his M.D. in 1927. After attending the universities of Leipzig and Munich as an Eldridge Johnson traveling research scholar, he became professor of biophysics and chairman of the department at Johns Hopkins in 1949. He joined the staff of Rockefeller University, New York City, in 1953 as professor of neurophysiology.

Hartline investigated the electrical responses of the retinas of certain arthropods, vertebrates, and mollusks because their visual systems are much simpler than those of humans and are thus easier to study. He concentrated his studies on the eye of the horseshoe crab (Limulus polyphemus). Using minute electrodes in his experiments, he obtained the first record of the electrical impulses sent by a single optic nerve fibre when the receptors connected to it are stimulated by light. He found that the receptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus enhancing the contrast in light patterns and sharpening the perception of shapes. Hartline thus built up a detailed understanding of the workings of individual photoreceptors and nerve fibres in the retina, and he showed how simple retinal mechanisms constitute vital steps in the integration of visual information.

Details

Haldan Keffer Hartline (December 22, 1903 – March 17, 1983) was an American physiologist who was a co-recipient (with George Wald and Ragnar Granit) of the 1967 Nobel Prize in Physiology or Medicine for his work in analyzing the neurophysiological mechanisms of vision.

Biography

Haldan Hartline did his undergraduate studies at Lafayette College in Easton, Pennsylvania, graduating in 1923. He began his study of retinal electrophysiology as a National Research Council Fellow at Johns Hopkins School of Medicine, receiving his medical degree in 1927.

Scientific career

After attending the universities of Leipzig and Munich as an Eldridge Johnson traveling research scholar from the University of Pennsylvania, he returned to the US to take a position in the Eldridge Reeves Johnson Foundation for Medical Physics at Penn, which was under the directorship of Detlev W. Bronk at that time. In 1940–1941, he was Associate Professor of Physiology at Cornell Medical College in New York City but returned to Penn and stayed until 1949. Then he became professor of biophysics and chairman of the Jenkins Department of Biophysics at Johns Hopkins University in 1949. One of Hartline's graduate students at Johns Hopkins, Paul Greengard, also won the Nobel Prize. Hartline joined the staff of Rockefeller University, New York City, in 1953 as professor of neurophysiology.

Hartline investigated the electrical responses of the retinas of certain arthropods, vertebrates, and mollusks, because their visual systems are much simpler than those of humans and thus easier to study. He concentrated his studies on the eye of the horseshoe crab (Limulus polyphemus). Using minute electrodes, he obtained the first record of the electrical impulses sent by a single optic nerve fibre when the receptors connected to it are stimulated by light. He found that the photoreceptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus enhancing the contrast in light patterns and sharpening the perception of shapes. Hartline thus built up a detailed understanding of the workings of individual photoreceptors and nerve fibres in the retina, and he showed how simple retinal mechanisms constitute vital steps in the integration of visual information.

Awards and honors

In 1948, Hartline was elected to the United States National Academy of Sciences. He was elected to the American Philosophical Society in 1952 and the American Academy of Arts and Sciences in 1957. He was elected to the inaugural class of Fellows of the Optical Society (OSA) of America in 1959. Later, OSA elected him an Honorary Member in 1980. Hartline was elected a Foreign Member of the Royal Society in 1966. He was awarded the Nobel Prize in Physiology or Medicine in 1967.

Personal life

Hartline married Elizabeth Kraus Hartline in 1936. They had three children: Daniel, Peter, and Frederick Hartline.

Jai Ganesh · This is Cool

2438) Compressed Natural Gas

Gist

Compressed Natural Gas (CNG) is a fuel derived from natural gas, primarily methane, that has been compressed to less than 1% of its volume for storage and transport. It is used as a cleaner-burning alternative to gasoline and diesel, especially in vehicles, and offers environmental and economic benefits like lower emissions and cost savings.

Compressed Natural Gas (CNG) is a fossil fuel that is mainly composed of methane, which has been compressed to a high pressure to store it in a smaller volume, making it a viable alternative to petrol and diesel for vehicles. It is considered a cleaner-burning fuel because it emits significantly lower levels of harmful pollutants like carbon monoxide, sulfur dioxide, and nitrogen oxides, and contains no lead or benzene.

Summary

Compressed natural gas (or simply shortened as CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 20–25 megapascals (2,900–3,600 psi; 200–250 bar), usually in cylindrical or spherical shapes.

CNG is used in traditional petrol/internal combustion engine vehicles that have been modified, or in vehicles specifically manufactured for CNG use: either alone (dedicated), with a segregated liquid fuel system to extend range (dual fuel), or in conjunction with another fuel (bi-fuel). It can be used in place of petrol, diesel fuel, and liquefied petroleum gas (LPG). CNG combustion produces fewer undesirable gases than the aforementioned fuels. In comparison to other fuels, natural gas poses less of a threat in the event of a spill, because it is lighter than air and disperses quickly when released. Biomethane, biogas from anaerobic digestion or landfill, can be used.

In response to high fuel prices and environmental concerns, CNG has been used in auto rickshaws, pickup trucks, transit and school buses, and trains.

The cost and placement of fuel storage containers is the major barrier to wider/quicker adoption of CNG as a fuel. It is also why municipal government, public transportation vehicles were the most visible early adopters of it, as they can more quickly amortize the money invested in the new (and usually cheaper) fuel. In spite of these circumstances, the number of vehicles in the world using CNG has grown steadily (30 percent per year). Now, as a result of the industry's steady growth, the cost of such fuel storage cylinders has been brought down to a much more acceptable level. Especially, for the CNG Type 1 and Type 2 cylinders, many countries are able to make reliable and cost effective cylinders for conversion need.

Details

Compressed natural gas or CNG is simply natural gas mainly comprised of methane that is stored under high pressures (while remaining in its gaseous form), mainly as a means to transport it, or as storage for later use as vehicle fuel. In this form it remains clear, odourless, and non-corrosive. CNG is used widely as an alternative fuel for vehicles as it has a fairly high octane rating. CNG is not to be confused with liquefied natural gas, which has been turned into a liquid—and must be at very low temperatures. Although it's still in its gaseous form, compressed natural gas is under more pressure and thus takes up a smaller volume than ordinary natural gas (but more volume than LNG : Liquefied Natural Gas).

Storage and Transport

After being extracted from wells and treated, the gas travels through pipelines to a distributor. These distributors then send this fuel out to customers in pressurized tanks or sent out to fueling stations. At smaller fueling stations and in vehicles, the compressed gas is stored in thick-walled tanks made of aluminum, steel, or some composite. These high pressure tanks are kept at pressures around 20-25 MPa, 200-250 bar, or 3000-3600 psi. This high pressure reduces the volume of the natural gas to less than 1% of its volume at standard atmospheric pressure.

Use as an Alternative Fuel

CNG can be used as a gasoline alternative in a number of different vehicles and many commercial vehicles have recently become CNG fueled. Vehicles of any size from sedans to heavy-duty transit vehicles like buses and street sweepers can be fueled by CNG. Currently, natural gas powers more than 12 million vehicles on the road with about 250,000 of these located in the United States.

There are several benefits to using natural gas as an alternative fuel for transportation. For example, 99% of the natural gas the US produces comes from somewhere in North America. Moving to CNG would reduce their reliance on oil from overseas. It burns more cleanly than gasoline or diesel fuel—showing an average reduction in emissions of 80% as compared to gasoline vehicles. Additionally, current estimates say that compressed natural gas costs about 40% less than gasoline.

Safety

Natural gas is flammable, however a leak is not always extraordinarily dangerous. Because natural gas is lighter than air, it quickly dissipates when it leaks out of a tank and it is only flammable when the air/natural gas mixture is 5-15% natural gas. Additionally, a sulfur-based mercaptan—an odourant—is added to make leaks more simple to detect. This narrow flammability range makes it a safe fuel to use, but strict safety standards exist to make CNG powered vehicles as safe as those powered by gasoline. There are some safety concerns with large buses fueled by CNG compared to diesel buses. One of these is a longer breaking distance due to the added weight of the fuel storage system. Finally, the composition of natural gas itself can be an issue. CNG is mainly methane —a greenhouse gas—which could contribute to climate change if a leak existed.

Additional Information:

Introducing CNG

Have you ever wondered what makes Compressed Natural Gas (CNG) a more environmentally friendly alternative to traditional fuel?

CNG is natural gas under pressure which remains clear, odourless, and non-corrosive. This means CNG is not just friendlier on our naturally lush landscape, but it can be used as an economical alternative as well.

Compressed Natural Gas (CNG), is natural gas under pressure which remains clear, odourless, and non-corrosive. It is also a cheaper, greener, and more efficient alternative to the traditional petrol and diesel fuels for vehicles.

CNG is comprised of:

• Mostly methane gas which, like gasoline, produces engine power when mixed with air and fed into your engine’s combustion chamber.

• When CNG reaches the combustion chamber, it mixes with air, is ignited by a spark and the and the energy from the explosion moves the vehicle.

• CNG is compressed so that enough fuel can be stored in your vehicle to extend driving range, much like the gasoline tank in vehicle.

• Although vehicles can use natural gas as either a liquid or a gas, most vehicles use the gaseous form compressed to 3,000 psi.

CNG vs Liquid Fuels

Still wondering why CNG is better than traditional petrol?

We break it down for you here:

• CNG is one of the most viable alternatives to traditional liquid fuels for vehicles here in Trinidad and Tobago.

• CNG is one fifth the price of super gasoline, resulting in substantial savings in fuel costs.

• CNG reduces maintenance costs since it contains no additives and burns cleanly leaving no by-products of combustion to contaminate your spark plugs and engine oil.

• The combustion chamber parts function at peak output for longer periods before requiring service. The engine oil also remains clean which minimizes engine wear and requires less frequent changes.

• CNG is more environment friendly and CNG engines are much quieter due to the higher octane rating of CNG over gasoline.

• CNG produces less exhaust emissions and as a result, harmful emissions such as carbon monoxide (CO), carbon dioxide (CO2 and nitrous oxide (N2O) are generally reduced by as much as 95% when compared to gasoline powered vehicles.

• CNG is the safe bet as its components are designed and made to international standards and are monitored to ensure safe operation.

• CNG fuel systems are also sealed, which prevents any spill or evaporation losses.

Jai Ganesh · Dark Discussions at Cafe Infinity

Code Quotes - IV

1. We have a rule that if you check in code, you have to maintain it. So I mostly code on the side. I don't check in code anymore. - Mark Zuckerberg

2. Roy Rogers, Gene Autry, John Wayne - these men had the code of the West. - Chuck Norris

3. Frequent elections not only entail more burden on human resources, imposition of model code also impedes the development process. - Ram Nath Kovind

4. Simply put, when you have very large pieces of software, most of the tools look at the individual lines of code as text. It is often extremely powerful to look not at individual pieces of code but at a system as a whole. - James Gosling.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#10651. What does the term in Biology/Chemistry Electron acceptor mean?

#10652. What does the term in Biology in Biology/Chemistry Electron transport chain mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#5847. What does the noun functionary mean?

#5848. What does the adjective fungible mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#2518. What does the medical term Pre-eclampsia mean?

Jai Ganesh · Jokes

Q: What do you call blueberries playing the guitar?
A: A jam session.
* * *
Q: What do you call a sad strawberry?
A: A blueberry.
* * *
Q: What did one blueberry say to the other blueberry?
A: If you weren't so sweet, we wouldn't be in this jam!
* * *
Patient: Doctor, there is a berry growing out of my head.
Doctor: Oh, that's easy. Just put some cream on it!
* * *
Q: What do you call a blueberry that uses foul language?
A: Berry Rude.
* * *
Q: How many grams of protein are in a blueberry pi?
A: 3.14159265...
* * *

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#9797.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#6292.

Jai Ganesh · Exercises

Hi,

2640.

Jai Ganesh · Science HQ

Melting Point

Gist

The melting point is the temperature at which a solid substance changes into a liquid under normal atmospheric pressure. At this temperature, the solid and liquid phases of the substance exist together in equilibrium. Melting occurs when added heat provides enough energy for the particles in the solid to break free from the rigid structure and move more freely as a liquid. For example, ice melts at 0 degrees Celsius (32 degrees Fahrenheit), which is also the freezing point for water.

Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached. More heat then will convert the solid into a liquid with no temperature change.

Summary

Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached. More heat then will convert the solid into a liquid with no temperature change. When all the solid has melted, additional heat will raise the temperature of the liquid. The melting temperature of crystalline solids is a characteristic figure and is used to identify pure compounds and elements. Most mixtures and amorphous solids melt over a range of temperatures.

The melting temperature of a solid is generally considered to be the same as the freezing point of the corresponding liquid; because a liquid may freeze in different crystal systems and because impurities lower the freezing point, however, the actual freezing point may not be the same as the melting point. Thus, for characterizing a substance, the melting point is preferred.

Details

The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.

When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact, the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point."

Examples

For most substances, melting and freezing points are approximately equal. For example, the melting and freezing points of mercury is 234.32 kelvins (−38.83 °C; −37.89 °F). However, certain substances possess differing solid-liquid transition temperatures. For example, agar melts at 85 °C (185 °F; 358 K) and solidifies from 31 °C (88 °F; 304 K); such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is very close to 0 °C (32 °F; 273 K); this is also known as the ice point. In the presence of nucleating substances, the freezing point of water is not always the same as the melting point. In the absence of nucleators water can exist as a supercooled liquid down to −48.3 °C (−54.9 °F; 224.8 K) before freezing.

The metal with the highest melting point is tungsten, at 3,414 °C (6,177 °F; 3,687 K); this property makes tungsten excellent for use as electrical filaments in incandescent lamps. The often-cited carbon does not melt at ambient pressure but sublimes at about 3,700 °C (6,700 °F; 4,000 K); a liquid phase only exists above pressures of 10 MPa (99 atm) and estimated 4,030–4,430 °C (7,290–8,010 °F; 4,300–4,700 K). Hafnium carbonitride (HfCN) is a refractory compound with the highest known melting point of any substance to date and the only one confirmed to have a melting point above 4,273 K (4,000 °C; 7,232 °F) at ambient pressure. Quantum mechanical computer simulations predicted that this alloy (HfN0.38C0.51) would have a melting point of about 4,400 K. This prediction was later confirmed by experiment, though a precise measurement of its exact melting point has yet to be confirmed. At the other end of the scale, helium does not freeze at all at normal pressure even at temperatures arbitrarily close to absolute zero; a pressure of more than twenty times normal atmospheric pressure is necessary.

Melting point measurements

Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient (range from room temperature to 300 °C). Any substance can be placed on a section of the strip, revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.

A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window (most basic design: a Thiele tube) and a simple magnifier. Several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated (and stirred) and with the aid of the magnifier (and external light source) melting of the individual crystals at a certain temperature can be observed. A metal block might be used instead of an oil bath. Some modern instruments have automatic optical detection.

The measurement can also be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel "online", meaning that the sample is taken from the process and measured automatically. This allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory.[citation needed]

Techniques for refractory materials

For refractory materials (e.g. platinum, tungsten, tantalum, some carbides and nitrides, etc.) the extremely high melting point (typically considered to be above, say, 1,800 °C) may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees. The spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature. In this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer. For temperatures above the calibration range of the source, an extrapolation technique must be employed. This extrapolation is accomplished by using Planck's law of radiation. The constants in this equation are not known with sufficient accuracy, causing errors in the extrapolation to become larger at higher temperatures. However, standard techniques have been developed to perform this extrapolation.

Consider the case of using gold as the source (mp = 1,063 °C). In this technique, the current through the filament of the pyrometer is adjusted until the light intensity of the filament matches that of a black-body at the melting point of gold. This establishes the primary calibration temperature and can be expressed in terms of current through the pyrometer lamp. With the same current setting, the pyrometer is sighted on another black-body at a higher temperature. An absorbing medium of known transmission is inserted between the pyrometer and this black-body. The temperature of the black-body is then adjusted until a match exists between its intensity and that of the pyrometer filament. The true higher temperature of the black-body is then determined from Planck's Law. The absorbing medium is then removed and the current through the filament is adjusted to match the filament intensity to that of the black-body. This establishes a second calibration point for the pyrometer. This step is repeated to carry the calibration to higher temperatures. Now, temperatures and their corresponding pyrometer filament currents are known and a curve of temperature versus current can be drawn. This curve can then be extrapolated to very high temperatures.

In determining melting points of a refractory substance by this method, it is necessary to either have black body conditions or to know the emissivity of the material being measured. The containment of the high melting material in the liquid state may introduce experimental difficulties. Melting temperatures of some refractory metals have thus been measured by observing the radiation from a black body cavity in solid metal specimens that were much longer than they were wide. To form such a cavity, a hole is drilled perpendicular to the long axis at the center of a rod of the material. These rods are then heated by passing a very large current through them, and the radiation emitted from the hole is observed with an optical pyrometer. The point of melting is indicated by the darkening of the hole when the liquid phase appears, destroying the black body conditions. Today, containerless laser heating techniques, combined with fast pyrometers and spectro-pyrometers, are employed to allow for precise control of the time for which the sample is kept at extreme temperatures. Such experiments of sub-second duration address several of the challenges associated with more traditional melting point measurements made at very high temperatures, such as sample vaporization and reaction with the container.

Additional Information

1. What Is Melting Point?

Melting point is a characteristic property of solid crystalline substances. It is the temperature at which the solid phase changes to the liquid phase. Melting point determination is the thermal analysis most frequently used to characterize solid crystalline materials. It is used in research and development as well as in quality control in various industry segments to identify solid crystalline substances and to check their purity.

Melting point is a characteristic property of solid crystalline substance. It is the temperature at which the solid phase changes to the liquid phase. This phenomenon occurs when the substance is heated. During the melting process, all of the energy added to the substance is consumed as heat of fusion, and the temperature remains constant (see diagram below). During the phase transition, the two physical phases of the material exist side-by-side.

Crystalline materials consist of fine particles that for a regular, 3-dimensional arrangement – a crystalline lattice. The particles within the lattice are held together by lattice forces. When the solid crystalline material is heated, the particles become more energetic and start to move more strongly, until finally the forces of attraction between them are no longer strong enough to hold them together. The crystalline structure is destroyed and the solid material melts.

The stronger the forces of attraction between the particles, the more energy is needed to overcome them. The more energy is needed, the higher the melting point. The melting temperature of a crystalline solid is thus an indicator for the stability of its lattice.

At the melting point not only the aggregate state changes; quite a lot of other physical characteristics also change significantly. Amongst these are the thermodynamic values, specific heat capacity, enthalpy, and rheological properties such as volume or viscosity. Last but not least, the optical properties birefringence reflection and light transmission change. Compared to other physical values the change in light transmission can easily be determined and can therefore be used for melting point detection.

2. Why Measure Melting Points?

Melting points are often used to characterize organic and inorganic crystalline compounds and to ascertain their purity. Pure substances melt at a sharp, highly-defined temperature (very small temperature range of 0.5 – 1 °C) whereas impure, contaminated substances generally exhibit a large melting interval. The temperature at which all material of a contaminated substance is molten is usually lower than that of a pure substance. This behavior is known as melting point depression and can be used to obtain qualitative information about the purity of a substance.

In general, melting point determination is used in the lab in research and development as well as in quality control in various industry segments to identify and check the purity of different substances.

3. Melting Point Determination Principle

At the melting point, there is a change in light transmission. Compared to other physical values the change in light transmission can easily be determined and can therefore be used for melting point detection. Powdered crystalline materials are opaque in the crystalline state and transparent in the liquid state. This distinct difference in optical properties can be measured in order to determine the melting point by recording the percentage of light intensity shining through the substance in the capillary, the transmittance, in relation to the measured furnace temperature.

There are different stages of the melting point process of a solid crystalline substance: At the collapse point, the substance is mostly solid and comprises only a small amount of molten material. At the meniscus point, most of the substance has melted but some solid material is still present. At the clear point, the substance has completely melted.

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