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#3305. What does the adjective disoriented mean?

#3306. What does the verb (used with object) disown mean?

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The solution #4633 is correct. Good work, Monox D. I-Fly!

#4634. Solve:

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#4633. Solve:

391) Firefly

Firefly, (family Lampyridae), also called lightning bug, any of some 2,000 species of beetles (insect order Coleoptera) found in most tropical and temperate regions that have special light-producing organs on the underside of the abdomen. Most fireflies are nocturnal, although some species are diurnal. They are soft-bodied beetles that range from 5 to 25 mm (up to 1 inch) in length. The flattened, dark brown or black body is often marked with orange or yellow.

Some adult fireflies do not eat, whereas many feed on pollen and nectar. In a few species females are predatory on males of other firefly species. Both sexes are usually winged and luminous, although in some species only one gender has the light-producing organ. Females lacking wings and resembling the long, flat larvae are commonly referred to as glowworms. The larvae are sometimes luminescent before they hatch. Larvae live on the ground and feed on snails and slugs by injecting a fluid into their prey and then withdrawing the partly digested matter through hollow mouthparts. The common glowworm (Lampyris noctiluca) is a member of this family.

Most fireflies produce short, rhythmic flashes in a pattern characteristic of the species. The rhythmic flash pattern is part of a signal system that brings the sexes together. Both the rate of flashing and the amount of time before the female’s response to the male are important. Some authorities feel that the flashing is also a protective mechanism, reminding predators of the firefly’s bitter taste. However, some frogs eat such large numbers of fireflies that they themselves glow.

Firefly light is produced under nervous control within special cells (photocytes) richly supplied with air tubes (tracheae). Firefly light is a cold light with approximately 100 percent of the energy given off as light and only a minute amount of heat. Only light in the visible spectrum is emitted. Some tropical members of the coleopteran family Elateridae are also called fireflies.

About Fireflies

Fireflies are familiar, but few realize that these insects are actually beetles, nocturnal members of the family Lampyridae. Most fireflies are winged, which distinguishes them from other luminescent insects of the same family, commonly known as glowworms.

Habitat

There are about 2,000 firefly species. These insects live in a variety of warm environments, as well as in more temperate regions, and are a familiar sight on summer evenings. Fireflies love moisture and often live in humid regions of Asia and the Americas. In drier areas, they are found around wet or damp areas that retain moisture.

Bioluminescence

Everyone knows how fireflies got their name, but many people don't know how the insects produce their signature glow. Fireflies have dedicated light organs that are located under their abdomens. The insects take in oxygen and, inside special cells, combine it with a substance called luciferin to produce light with almost no heat.
Firefly light is usually intermittent, and flashes in patterns that are unique to each species. Each blinking pattern is an optical signal that helps fireflies find potential mates. Scientists are not sure how the insects regulate this process to turn their lights on and off.

Firefly light may also serve as a defense mechanism that flashes a clear warning of the insect's unappetizing taste. The fact that even larvae are luminescent lends support to this theory.

Reproduction and Diet

Females deposit their eggs in the ground, which is where larvae develop to adulthood. Underground larvae feed on worms and slugs by injecting them with a numbing fluid.

Adults eschew such prey and typically feed on nectar or pollen, though some adults do not eat at all.

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#1354. What is 'Retinoschisis'?

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#7315. When did the 'World War I' last?

#7316. When did the 'World War II' last?

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649. Find the radius of a circle whose center is (-5, 4) and which passes through the point (-7, 1).

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#4632. Find the value of

390) Rubber

Think of rubber and you probably think of elastic bands, car tires, or pencil erasers. But this super-stretchy material actually finds its way into tens of thousands of different products—everything from rubber stamps and waterproof shoes to surfing wetsuits, swimming caps, and dishwasher hoses. Rubber, which has been commonly used for over 1000 years, once came entirely from natural sources; now rubber products are just as likely to be made artificially in chemical plants. That's largely because we can't produce enough natural rubber to meet all our needs. And that, in turn, is because rubber is so fantastically useful. Let's take a closer look at one of the world's most amazing materials!

What is rubber?

When people talk about "rubber", they don't usually specify what kind. There are many different kinds of rubber, but they all fall into two broad types: natural rubber (latex—grown from plants) and synthetic rubber (made artificially in a chemical plant or laboratory). Commercially, the most important synthetic rubbers are styrene butadiene (SBR), polyacrylics, and polyvinyl acetate (PVA); other kinds include polyvinyl chloride (PVC), polychloroprene (better known as neoprene), and various types of polyurethane. Although natural rubber and synthetic rubbers are similar in some ways, they're made by entirely different processes and chemically quite different.

Natural rubber

Natural rubber is made from a runny, milky white liquid called latex that oozes from certain plants when you cut into them. (Common dandelions, for example, produce latex; if you snap off their stems, you can see the latex dripping out from them. In theory, there's no reason why we couldn't make rubber by growing dandelions, though we'd need an awful lot of them.) Although there are something like 200 plants in the world that produce latex, over 99 percent of the world's natural rubber is made from the latex that comes from a tree species called Hevea brasiliensis, widely known as the rubber tree.

This latex is about one third water and one third rubber particles held in a form known as a colloidal suspension. Natural rubber is a polymer of isoprene (also known as 2-methylbuta-1,3-diene) with the chemical formula (C5H8)n. To put it more simply, it's made of many thousands of basic C5H8 units (the monomer of isoprene) loosely joined to make long, tangled chains. These chains of molecules can be pulled apart and untangled fairly easily, but they spring straight back together if you release them—and that's what makes rubber elastic.

Synthetic rubbers

Synthetic rubbers are made in chemical plants using petrochemicals as their starting point. One of the first (and still one of the best known) is neoprene (the brand name for polychloroprene), made by reacting together acetylene and hydrochloric acid. Emulsion styrene-butadiene rubber (E-SBR), another synthetic rubber, is widely used for making vehicle tires.

For the rest of this article, we'll concentrate mostly on natural rubber.

How is rubber made?

It takes several quite distinct steps to make a product out of natural rubber. First, you have to gather your latex from the rubber trees using a traditional process called rubber tapping. That involves making a wide, V-shaped cut in the tree's bark. As the latex drips out, it's collected in a cup. The latex from many trees is then filtered, washed, and reacted with acid to make the particles of rubber coagulate (stick together). The rubber made this way is pressed into slabs or sheets and then dried, ready for the next stages of production.

By itself, unprocessed rubber is not all that useful. It tends to be brittle when cold and smelly and sticky when it warms up. Further processes are used to turn it into a much more versatile material. The first one is known as mastication (a word we typically use to describe how animals chew food). Masticating machines "chew up" raw rubber using mechanical rollers and presses to make it softer, easier to work, and more sticky. After the rubber has been masticated, extra chemical ingredients are mixed in to improve its properties (for example, to make it more hardwearing). Next, the rubber is squashed into shape by rollers (a process called calendering) or squeezed through specially shaped holes to make hollow tubes (a process known as extrusion). Finally, the rubber is vulcanized (cooked): sulfur is added and the rubber is heated to about 140°C (280°F) in an autoclave (a kind of industrial pressure cooker).

Where does rubber come from?

As its name suggests, the rubber tree Hevea brasiliensis originally came from Brazil, from where it was introduced to such countries of the Far East as Malaysia, Indonesia, Burma, Cambodia, China, and Vietnam. During World War II, supplies of natural rubber from these nations were cut off just when there was a huge demand from the military—and that accelerated the development of synthetic rubbers, notably in Germany and the United States. Today, most natural rubber still comes from the Far East, while Russia and its former republics, France, Germany, and the United States are among the world's leading producers of synthetic rubber. The world's largest single source of latex rubber is the Harbel Rubber Plantation near Monrovia in Liberia, established in the 1920s and 1930s by the Firestone tire company.

Rubber—the kind you get from a tree—starts off as white and runny latex. Even when it's set into a product, this latex-based, natural rubber is very squashy, pretty smelly, and not very useful. The kind of rubber you see in the world around you, in things like car and bicycle tires, is vulcanized: cooked with sulfur (and often other additives) to make it harder, stronger, and longer lasting.

So what's the difference between raw, latex rubber and cooked, vulcanized rubber? In its natural state, the molecules in rubber are long chains that are tangled up and only weakly linked together. It's relatively easy to pull them apart—and that's why latex rubber is so stretchy and elastic. When latex is vulcanized, the added sulfur atoms help to form extra bonds between the rubber molecules, which are known as cross-links. These work a bit like the trusses you see on a bridge, tying the molecules together and making them much harder to pull apart.

What do we use rubber for?

The physical and chemical properties of a material dictate what we use it for. Even if you know absolutely nothing about the real-world uses of rubber, you can probably make some very good guesses. For example, everyone knows rubber is strong, stretchy, flexible (elastic), durable, and waterproof, so it's no surprise to find it used in things like waterproof clothes and wellington boots, sticking plasters, and adhesives.

The most important use of rubber is in vehicle tires; about half of all the world's rubber ends up wrapped around the wheels of cars, bicycles, and trucks! You'll find rubber in the hard, black vulcanized outsides of tires and (where they have them) in their inner tubes and liners. The inner parts of tires are usually made from a slightly different, very flexible butyl rubber, which is highly impermeable to gases (traps them very effectively), so tires (generally) stay inflated for long periods of time.

The fact that rubber can be made either soft or hard greatly increases the range of things we can use it for. Soft and stretchy latex is used in all kinds of everyday things, from pencil erasers, birthday balloons, and condoms to protective gloves, adhesives (such as sticky white PVA), and paints. Harder rubbers are needed for tougher applications like roofing membranes, waterproof butyl liners in garden ponds, and those rigid inflatable boats (RIBs) used by scuba divers. Because rubber is strong, flexible, and a very poor conductor of heat and electricity, it's often used as a strong, thin, jacketing material for electrical cables, fiber-optic cables, and heat pipes. But the range of applications is truly vast: you'll find it in everything from artificial hearts (in the rubber diaphragms that pump blood) to the waterproof gaskets that seal the doors on washing machines!

Neoprene (polychloroprene) is best known as the heat-insulating, outer covering of wetsuits—but it has far more applications than most people are aware of. Medical supports of various kind use it because, tightly fitted, it compresses and warms injured bits of your body, promoting faster healing. Since it's flexible and waterproof, it's also widely used as a building material, for example, as a roof and floor sealant, and as a spongy absorber of sound and vibration in door and window linings.

Although the world has a vast appetite for new rubber, we also produce a huge quantity of rubber waste, especially from discarded vehicle tires—and that's becoming an important raw material in its own right. According to the Rubber Manufacturers Association, the United States alone produced almost 270 million waste rubber vehicle tires in 2011, which is about a third of all the tires used worldwide. While some of these are retreaded and others are ground up to make a low-grade aggregate that can be used for the floors in things like children's playgrounds, over half of them are wasted (either burned as a fuel or buried in landfills). Rubber manufacturers have recently turned their attention to recycling tires in all kinds of new ways, making everything from mouse mats and sports bags to shoe soles and car components.

A brief history of rubber

*1000CE: Indians living in Central and South America have learned how to made waterproof clothes and shoes using latex from rubber trees. They call rubber trees "cahuchu" (crying wood), which is why the French still call rubber caoutchouc (pronounced "cow-chew") today.
*1731: During an expedition to South America, French explorer Charles Marie de La Condamine (1701–74) sends back samples of rubber to Europe, prompting intense scientific interest.
*1770: The discoverer of oxygen, English scientist Joseph Priestley (1733–1804), finds he can use pieces of rubber to erase the marks made by pencil on paper. In England, erasers are still widely called "rubbers" today.
*1791: Englishman Samuel Peal develops a method of waterproofing cloth with a rubber solution.
*1818: Scottish medical student James Syme (1799–1870) uses rubber-coated cloth to make raincoats.
*1823: Scotsman Charles Macintosh learns of Syme's discovery, refines it, and patents it, earning fame and fortune as the inventor of the rubberized, waterproof coat. Waterproof coats have been known as "Mackintoshes" (with a slight variation of spelling) ever since.
*1829: English chemist and physicist Michael Faraday (1791–1867) analyzes samples of Hevea and works out that the chemical formula for isoprene-type rubber is C5H8.
*1839: American inventor Charles Goodyear (1800–1860) accidentally discovers how to vulcanize rubber after dropping a piece of the material (which has been treated with sulfur) onto a hot stove.
*1830s~1840s: Botanist Thomas Lobb discovers a rubbery substance called Gutta-percha (Palaquium gutta) in Malaysia; Dr William Montgomerie, a surgeon working in the same region, sends samples back to Britain in 1843. According to a contemporary account by William Dalton, it has "remarkable properties, vast utility, and application to scientific and ornamental purposes" in everything from "boots and shoes" to "prevention of toothache."
*1876: Intrepid English explorer Sir Henry Wickham (1846–1928) smuggles thousands of seeds from the rubber tree Hevea brasiliensis out of Brazil and back to England. The English grow the seeds at Kew Gardens just outside London and export them to various Asian countries, establishing the giant plantations that now supply much of the world's rubber.
*1877: US rubber manufacturer Chapman Mitchell develops the first commercial process for recycling rubber from scratch.
*1882: John Boyd Dunlop (1840–1921) invents the pneumatic (air-filled) rubber tire. The development of gasoline-powered cars with rubber tires leads to a huge increase in the need for rubber.
*1883: US chemist George Oenslager (1873–1956) develops a much faster way of vulcanizing rubber using chemicals called organic (carbon-based) accelerators.
*1906–12: Bayer, a German chemical company, develops methyl rubber (a polymer of methylisoprene). It becomes critically important to Germany during World War I when supplies of natural rubber are cut off, but falls out of fashion when better alternatives are eventually developed.
*1910: English Chemist S.S. Pickles becomes the first person to propose (correctly) that rubber consists of long chains of isoprene. Technically, Hevea has the chemical name cis-1,4-polyisoprene, while Gutta-Percha is a variation known as trans-1,4-polyisoprene.
*1930: German chemical company IG Farben develops a type of general-purpose, synthetic rubber named Buna-S ("bu" from butadiene, "na" from the chemical symbol for sodium, and "S" for styrene). Technically, it's a copolymer of butadiene (75 percent) and styrene (25 percent), which is why it's now more generally known as styrene-butadiene or styrene-butadiene-rubber (SBR); it's also sold under tradenames such as Goodyear's Neolite®. Today, styrene-butadiene remains by far the world's most important synthetic rubber.
*1930: A team of US chemists at the DuPont company, led by Wallace Carothers (1896–1937), develop a revolutionary synthetic rubber called polychloroprene and sold as neoprene. (Shortly afterward, the same group developed an even more revolutionary material: nylon.)
*1940s: Synthetic rubbers are produced in the United States for the first time by companies such as Firestone, Goodyear, and Goodrich.

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#3301. What does the adjective dismal mean?

#3302. What does the noun dismay mean?

562) Irving Langmuir

Irving Langmuir, (born Jan. 31, 1881, Brooklyn, N.Y., U.S.—died Aug. 16, 1957, Falmouth, Mass.), American physical chemist who was awarded the 1932 Nobel Prize for Chemistry “for his discoveries and investigations in surface chemistry.” He was the second American and the first industrial chemist to receive this honour. Besides surface chemistry, his scientific research, spanning more than 50 years, included chemical reactions, thermal effects, and electrical discharges in gases; atomic structure; surface phenomena in a vacuum; and atmospheric science.

Early Life And Education

Langmuir was the third of four sons of Charles Langmuir, an insurance executive, and Sadie Comings. Both of his parents were inveterate record keepers, and he developed this habit himself while still young. He attended schools in Brooklyn and Philadelphia, as well as Paris during his father’s three-year company assignment in Europe. Interested in chemistry, physics, and mathematics from his youth, Langmuir chose a major in metallurgical engineering at Columbia University in New York City because that curriculum, as he later said, “was strong in chemistry…had more physics than the chemical course, and more mathematics than the course in physics—and I wanted all three.”

After graduating from Columbia’s School of Mines in 1903, Langmuir studied with physical chemist Walther Nernst at the University of Göttingenin Germany. His dissertation focused on the dissociation of gases near a hot platinum wire, for which he received a doctorate in 1906. As a student, he was influenced not only by Nernst, who often sought practical applications of his fundamental research, but also by the mathematician Felix Klein, who advocated the use of mathematics as a tool and promoted the interaction between theoretical science and its practical applications. During his years in Germany, Langmuir frequented the mountains for skiing in the winter and for climbing in the summer. Such outdoor activities remained lifelong interests for him.

Finding A Career

After returning to the United States, Langmuir became an instructor at the Stevens Institute of Technology in Hoboken, N.J., but he did not find his three years there particularly satisfying. His teaching duties left him little time for research, and he was not paid what he thought he was worth. He quickly realized that this was not the avenue to the scientific reputation and financial security that he sought.

In the summer of 1909, instead of a mountain climbing vacation, Langmuir worked at the General Electric Company’s research laboratory in Schenectady, N.Y. Enticed by the company’s commitment to fundamental research, the latitude given to the scientists working there, and the availability of equipment, Langmuir accepted an invitation to remain. At first he apparently intended to find another academic position, but he stayed at General Electric for the rest of his career, retiring in 1950 but continuing as a consultant until his death.

Major Research

Improving the early tungsten-filament incandescent light bulbs was one of the ongoing projects at the research lab in 1909. These high-vacuum bulbs had several drawbacks: their glass envelopes blackened over time, thus reducing their illumination, and the tungsten filaments were relatively short-lived. While other workers at the laboratory believed that a better vacuum would lengthen the bulbs’ lives, Langmuir began to investigate the behaviour of gases near a hot tungsten filament. The blackening of the bulbs, he discovered, resulted from the deposition of tungsten that evaporated from the hot filament, and an atmosphere of inert gas within the bulb—a mixture of nitrogen and argon worked best—reduced the problem. This, along with Langmuir’s development of an improved design for the tungsten filament, led to a much-improved and commercially successful incandescent bulb.

Among the gases that Langmuir studied was hydrogen. A hot tungsten filament rapidly cools in the presence of this gas, and he postulated the cause to be the dissociation of hydrogen molecules into atoms. When he later read about the heating caused by the recombination of hydrogen atoms into molecules at solid surfaces, he combined this with his earlier work to develop an atomic hydrogen welding torch, which generates high temperatures through the dissociation and subsequent recombination of hydrogen.

Langmuir’s study of gases near hot metal surfaces also led him to investigate thermionic emission—the ejection of electrons from a heated surface—and the behaviour of surfaces in a vacuum. These investigations resulted in theoretical advances in describing the spatial distribution of charge between a pair of electrodes and practical improvements to vacuum tubes, as well as the invention of a fast and efficient vacuum pump.

The largest body of Langmuir’s work involved the behaviour of molecules at solid and liquid surfaces. He laid the groundwork for his prize-winning work on surface chemistry as early as 1916–17 with important publications on the adsorption, condensation, and evaporation of gas molecules at solid surfaces and on the arrangements of molecules in the surface layers of liquids. These studies, like most of his investigations, showed his penchant for simple experimental designs coupled with extensive mathematical analysis. After 1932 Langmuir returned to his earlier interest in liquid surfaces and, together with his collaborators Katherine Blodgett and Vincent Schaefer, examined the monomolecular layers of various organic compounds on the surface of water. Blodgett developed a method for transferring such a monolayer to a solid surface, and the successive buildup of monolayers became known as a Langmuir-Blodgett film. This technique proved significant in later biophysical studies of the membranes of living cells.

Working independently of the American atomic chemist Gilbert N. Lewis, Langmuir formulated theories of atomic structure and chemical bond formation, known as the Lewis-Langmuir theory of molecular structure, and introduced the term covalence.

Meteorology Research

During World War II, Langmuir worked on the problem of airplane deicing at a station on the summit of Mount Washington, N.H. With Schaefer, he also investigated the production of particles of various sizes and their behaviour in the atmosphere and in filters. These studies led to improved methods for generating smokescreens by the military, as well as to his subsequent interest in weather modification by seeding clouds with small particles. Some of his experiments in seeding clouds preceded a heavy snowfall in Schenectady in the winter of 1946 and heavy rainfall near Albuquerque, N.M., on a day in July 1949 when no substantial rain was predicted. Whether there was any connection between the seeding and the subsequent precipitation, however, remained controversial.

Avocations And Awards

This excursion into experimental meteorology was part of Langmuir’s interest in “science out-of-doors,” which involved his close observation and explanation of many natural everyday phenomena. An avid outdoorsman, he enjoyed hiking, mountain climbing, skiing, swimming, and boating throughout much of his life. He learned to pilot a plane at age 49 and was a personal friend of Charles Lindbergh. He was also a friend of the musical conductor Leopold Stokowski, with whom he worked to improve the quality of radio broadcasts of orchestral music.

Langmuir was an ardent conservationist and an advocate for the control of atomic energy, as well as an unsuccessful candidate to Schenectady’s city council and an organizer of the Boy Scouts in that city. In 1912 he married Marion Mersereau of South Orange, N.J., and they adopted two children. He involved his family in many of his hobbies and outdoor activities. He died of a heart attack while vacationing at Cape Cod, Mass.

In addition to the Nobel Prize, Langmuir was the recipient of numerous awards and more than a dozen honorary degrees. He served as president of both the American Chemical Society (1929) and the American Association for the Advancement of Science (1941). Since his death, a mountain in Alaska, a residential college of the State University of New York at Stony Brook, and the surface chemistry journal published by the American Chemical Society have been named for him. Described as the quintessential industrial researcher, Langmuir himself claimed that his accomplishments came from his working “for the fun of it.”