Features of modern coinage

The milled, or reeded, edges still found on many coins (always those that were once made of gold or silver, even if not so now) were originally designed to show that none of the valuable metal had been shaved off the coin. Prior to the use of milled edges, circulating coins commonly suffered from "shaving", by which unscrupulous persons would shave a small amount of precious metal from the edge. Unmilled British sterling silver coins were known to be shaved to almost half of their minted weight. This form of debasement in Tudor England was commented on by Sir Thomas Gresham, whose name was later attached to Gresham's Law. The monarch would have to periodically recall circulating coins, paying only bullion value of the silver, and reminting them. Traditionally, the side of a coin carrying a bust of a monarch or other authority, or a national emblem, is called the obverse, or colloquially, heads. The other side is called the reverse, or colloquially, tails. However, the rule is violated in some cases.[13] Another rule is that the side carrying the year of minting is the obverse, although some Chinese coins, most Canadian coins, the pre-2008 British 20p coin, and all Japanese coins, are exceptions. In cases where a correctly oriented coin is flipped vertically to show the other side correctly oriented, the coin is said to have coin orientation. In cases where a coin is flipped horizontally to show the other side, it is said to have medallic orientation. The latter is found in British coins. Bi-metallic coins are sometimes used for higher values and for commemorative purposes. In the 1990s, France used a tri-metallic coin. Common circulating examples include the €1, €2, British £2 and Canadian $2. The exergue is the space on a coin beneath the main design, often used to show the coin's date, although it is sometimes left blank or containing a mint mark, privy mark, or some other decorative or informative design feature. Many coins do not have an exergue at all, especially those with few or no legends, such as the Victorian bun penny. Not all coins are round. The Australian 50 cent coin, for example, has twelve flat sides. A twist on it is wavy edges, found in the two dollar and the twenty cent coins of Hong Kong and the 10 cent coins of Bahamas. Some other coins, like the British Fifty Pence coin, have an odd number of sides, with the edges rounded off. This way the coin has a constant diameter, recosgnisable by vending machines whichever direction it is inserted. The triangular coin (produced to commemorate the 2007/2008 Tutankhamun exhibition at the The O2 Arena) was commissioned by the Isle of Man, became legal tender on 6 December 2007.[14] and has a value of 25p (a crown). Other triangular coins issued earlier include: Cabinda coin, Bermuda coin, 2 Dollar Cook Islands 1992 triangular coin, Uganda Millennium Coin and Polish Sterling-Silver 10-Zloty Coin.[15] Guitar-shaped coins were once issued in Somalia, Poland once issued a fan-shaped 10 złoty coin, but perhaps the oddest coin ever was the 2002 $10 coin from Nauru, a Europe-shaped coin.[16] Some coins, called bracteates, are so thin they can be struck on only one side. The Royal Canadian Mint is now able to produce holographic-effect gold and silver coinage. For a list of many pure metallic elements and their alloys which have used in actual circulation coins and for trial experiments, see coinage metals.[17] Coins are popularly used as a sort of two-sided die; in order to choose between two options with a random possibility, one choice will be labeled "heads" and the other "tails", and a coin will be flipped or "tossed" to see whether the heads or tails side comes up on top. See Bernoulli trial; a fair coin is defined to have the probability of heads (in the parlance of Bernoulli trials, a "success") of exactly 0.5. A widely publicized example of an asymmetrical coin which will not produce "fair" results in a flip is the Belgian one euro coin[18]. See also coin flipping. Coins are sometimes falsified to make one side weigh more, in order to simulate a fair type of coin which is actually not fair. Such a coin is said to be "weighted".

Genetics and biochemistry of hair color

There are two types of pigments that give hair its color: eumelanin and phaeomelanin. Phaeomelanin colors hair red. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color. A low concentration of brown eumelanin in the hair results in blonde hair, whereas a higher concentration of brown eumelanin will color the hair brown. High amounts of black eumelanin results in black hair, while low concentrations of black eumelanin in the hair results in gray hair color. Although most noticeable in red-heads, all humans have varying concentrations of phaeomelanin in their hair.

Phaeomelanin is more chemically stable than black eumelanin, but less chemically stable than brown eumelanin, so it breaks down more slowly when oxidized. This is the reason bleach will cause darker hair to turn reddish-brown during the artificial coloring process. As the phaeomelanin continues to break down, the hair will gradually become orange, later yellow, and then white.

The genetics of hair colors are not yet firmly established. According to one theory, at least two gene pairs control human hair color. One gene, which is a brown/blonde pair, has a dominant brown allele and a recessive blonde allele. A person with a brown allele will have brown hair; a person with no brown alleles will be blonde. This also explains why two brown-haired parents can produce a blonde-haired child. The other gene pair is a not-red/red pair, where the not-red allele (which suppresses production of pheomelanin) is dominant and the allele for red hair is recessive. Since the two gene pairs both govern hair color, a person with two copies of the red-haired allele will have red hair, but it will be either auburn or bright reddish orange depending upon whether the first gene pair gives brown or blonde hair, respectively.

The two-gene model does not account for all possible shades of brown, blonde, or red (for example, platinum blonde versus dark blonde/light brown), nor does it explain why hair color sometimes darkens as a person ages. Several gene pairs control the light versus dark hair color in a cumulative effect. A person's genotype for a multifactorial trait can interact with environment to produce varying phenotypes (see quantitative trait locus).

Grean Tea

Green tea is a type of tea made solely with the leaves of Camellia sinensis, that has undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures in Asia from Japan to the Middle East. Recently, it has become more widespread in the West, where black tea is traditionally consumed. Many varieties of green tea have been created in countries where it is grown. These varieties can differ substantially due to variable growing conditions, processing and harvesting time.

Over the last few decades green tea has been subjected to many scientific and medical studies to determine the extent of its long-purported health benefits, with some evidence suggesting regular green tea drinkers may have lower chances of heart disease and developing certain types of cancer^[1]. Green tea has also been claimed useful for weight loss management.