Crab
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) (Greek: βραχύς / brachys = short,οὐρά / οura = tail), usually entirely hidden under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton and have a single pair of claws. Many other animals with similar names – such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice – are not true crabs.
Evolution
Crabs are generally covered with a thick exoskeleton, composed primarily of calcium carbonate, and armed with a single pair of chelae (claws). Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 metres (13 ft).
About 850 species of crab are freshwater, terrestrial or semi-terrestrial species; they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be a monophyletic group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World.
Crab (unit)
A Crab is a standard astrophotometrical unit for measurement of the intensity of Astrophysical X-ray sources. One Crab is defined as the intensity of the Crab Nebula at the corresponding X-ray photon energy.
The Crab Nebula, and the Crab Pulsar within it, is an intense space X-ray source. It is used as a standard candle in the calibration procedure of X-ray instruments in space. However, because of the Crab Nebula's variable intensity at different X-ray energies, conversion of the Crab to another units depends on the X-ray energy range of interest.
In the photon energy range from 2 to 10 keV, 1 Crab equals 2.4 · 10−8erg cm−2s−1 = 15 keV cm−2 s−1 = 2.4 · 10−11W m−2. For energies greater than ~30 keV, the Crab Nebula becomes unsuitable for calibration purposes, as its flux can no longer be characterized by a single coherent model.
The unit mCrab, or milliCrab, is sometimes used instead of the Crab.
References
Crab (cipher)
In cryptography, Crab is a block cipher proposed by Burt Kaliski and Matt Robshaw at the first Fast Software Encryption workshop in 1993. Not really intended for use, Crab was developed to demonstrate how ideas from hash functions could be used to create a fast cipher.
Crab has an unusually large block size of 8192 bits. Its creators suggested using an 80-bit key, but the cipher could use any key size. The authors didn't specify an actual key schedule, only that the key is used to generate two large sets of subkeys: a permutation of the numbers 0 through 255, and an array of 2048 32-bit numbers. The block is divided into 256 32-bit subblocks, which are permuted at the beginning. Then the algorithm makes four passes over the data, each time applying one of four transformations adapted from MD5.
A brief note on the cryptanalysis of Crab is included in Markku-Juhani Saarinen's paper on block ciphers based on SHA-1 and MD5, published at FSE 2003. The author demonstrates a weakness in Crab that permits a distinguisher using no more than a dozen chosen plaintexts, and speculates that this can be converted into a full key-recovery attack using no more than 216 chosen plaintexts. Such an attack would depend on the key schedule used.
Crab (posture)
The Crab is the name given to a body position sometimes seen in basic gymnastics, yoga, and breakdancing. The body is supinated so that the back turns to the ground, the legs are bent like sitting in a chair, and the arms extend straight backward. Only the feet and hands touch the ground, and the torso is held parallel with the ground. The position's name originates from that of a crab.
The position is said to strengthen the arms, legs and back.
References
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See also
Crab (scratch)
A crab is a type of scratch used by turntablists. It is made from a combination of moving the record on the turntable by hand and quick movement of the crossfader.
Creation
The crab scratch was invented by DJ Qbert as a variation on DJ Excel's "twiddle." The two met up in Japan for the Vestax DJ competition in 1995 and Excel was asking Qbert how to flare. When he showed Qbert how he thought the flare was performed, he was actually doing the twiddle instead (using his thumb as a spring and "twiddling" the fader with 2 fingers). After this meeting, Qbert took the idea back to San Francisco and after showing the scratch to DJ Disk, he created a move that used 3 or 4 fingers: the crab. Later in 1995, while the DMC USA finals were being held in San Francisco, a group of DJs and judges which included The Beat Junkies, The X-Men (now called the X-ecutioners), and the rest of ISP among others got together for what would later be known as the "Famous Warehouse Session" at Yoga Frog's old mobile DJ warehouse. It was at this session that Qbert publicized the new scratch.
List of Pokémon (52–101)
The Pokémon (ポケモン, Pokemon) franchise has 721 (as of the release of Pokémon Omega Ruby and Alpha Sapphire) distinctive fictional species classified as the titular Pokémon. This is a selected listing of 50 of the Pokémon species, originally found in the Red and Green versions, arranged as they are in the main game series' National Pokédex.
Meowth
Meowth (ニャース, Nyāsu, Nyarth), known as the Scratch Cat Pokémon, has a distinctly feline appearance, resembling a small housecat. It has cream-colored fur, which turns brown at its paws and tail tip. Its oval-shaped head features prominent whiskers, black-and-brown ears, and a koban, a gold oval coin (also known as "charm") embedded in its forehead. Meowth are valued for their ability to collect coins using their signature move, "Pay Day", as it is the only Pokémon that learns it. Meowth's coloration, its love of coins, and its charm indicate that Meowth is based on the Japanese Maneki Neko, a cat-shaped figurine that is said to bring good luck and money to its owner. Aspects of Meowth were drawn from a Japanese myth dealing with the true value of money, in which a cat has money on its head but does not realize it.
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