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Bomb Pulse
The bomb pulse is the sudden increase of carbon-14 (14C) in the Earth's atmosphere due to the hundreds of aboveground nuclear bombs tests that started in 1945 and intensified after 1950 until 1963, when the Limited Test Ban Treaty was signed by the United States, the Soviet Union and the United Kingdom. These hundreds of blasts were followed by a doubling of the relative concentration of 14C in the atmosphere. We discuss “relative concentration”, because measurements of 14C levels by mass spectrometers are most accurately made by comparison to another carbon isotope, often the common isotope 12C. Isotope abundance ratios are not only more easily measured, they are what 14C carbon daters want, since it is the fraction of carbon in a sample that is 14C, not the absolute concentration, that is of interest in dating measurements. The figure shows how the fraction of carbon in the atmosphere that is 14C, of order only a part per trillion, has changed over the past several decades ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934. There are three naturally occurring isotopes of carbon on Earth: carbon-12 (), which makes up 99% of all carbon on Earth; carbon-13 (), which makes up 1%; and carbon-14 (), which occurs in trace amounts, making up about 1 or 1.5 atoms per 1012 atoms of carbon in the atmosphere. Carbon-12 and carbon-13 are both stable, while carbon-14 is unstable and has a half-life of 5,730 ± 40 years. Carbon-14 decays into nitrogen-14 () through beta decay. A gra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-chase Analysis
In biochemistry and molecular biology, a pulse-chase analysis is a method for examining a cellular process occurring over time by successively exposing the cells to a labeled compound (pulse) and then to the same compound in an unlabeled form (chase). Mechanism A selected cell or a group of cells is first exposed to a labeled compound (the pulse) that is to be incorporated into a molecule or system that is studied (also see pulse labeling). The compound then goes through the metabolic pathways and is used in the synthesis of the product studied. For example, a radioactively labeled form of leucine (3H-leucine) can be supplied to a group of pancreatic beta cells, which then uses this amino acid in insulin synthesis. Shortly after introduction of the labeled compound (usually about 5 minutes, but the actual time needed is dependent on the object studied), excess of the same, but unlabeled, substance (the chase) is introduced into the environment. Following the previous example, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-chase Analysis
In biochemistry and molecular biology, a pulse-chase analysis is a method for examining a cellular process occurring over time by successively exposing the cells to a labeled compound (pulse) and then to the same compound in an unlabeled form (chase). Mechanism A selected cell or a group of cells is first exposed to a labeled compound (the pulse) that is to be incorporated into a molecule or system that is studied (also see pulse labeling). The compound then goes through the metabolic pathways and is used in the synthesis of the product studied. For example, a radioactively labeled form of leucine (3H-leucine) can be supplied to a group of pancreatic beta cells, which then uses this amino acid in insulin synthesis. Shortly after introduction of the labeled compound (usually about 5 minutes, but the actual time needed is dependent on the object studied), excess of the same, but unlabeled, substance (the chase) is introduced into the environment. Following the previous example, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effects Of Nuclear Explosions
The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories: *the blast itself: 50% of total energy *thermal radiation: 30–50% of total energy * ionizing radiation: 5% of total energy (more in a neutron bomb) * residual radiation: 5–10% of total energy with the mass of the explosion. Depending on the design of the weapon and the location in which it is detonated, the energy distributed to any one of these categories may be significantly higher or lower. The physical blast effect is created by the coupling of immense amounts of energy, spanning the electromagnetic spectrum, with the surroundings. The environment of the explosion (e.g. submarine, ground burst, air burst, or exo-atmospheric) determines how much energy is distrib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenland Shark
The Greenland shark (''Somniosus microcephalus''), also known as the gurry shark, grey shark, or by the Kalaallisut name ''eqalussuaq'', is a large shark of the family Somniosidae ("sleeper sharks"), closely related to the Pacific and southern sleeper sharks. The distribution of this species is mostly restricted to the waters of the North Atlantic Ocean and Arctic Ocean; however, more recent evidence indicates that at great depths it may range as far south as the Caribbean. The Greenland shark has the longest known lifespan of all vertebrate species (estimated to be between 250 and 500 years), and is among the largest extant species of shark. It is a generalist feeder, consuming a variety of available foods. As an adaptation to living at depth, it has a high concentration of trimethylamine ''N''-oxide in its tissues, which causes the meat to be toxic. Greenland shark flesh, treated to reduce toxin levels, is eaten in Iceland as a delicacy known as '' kæstur hákarl''. As ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pristipomoides Filamentosus
''Pristipomoides filamentosus'', the crimson jobfish, rosy snapper, bluespot jobfish, crimson snapper, king emperor, king snapper or rosy jobfish, is a species of ray-finned fish, a snapper belonging to the family Lutjanidae. It is found in the Indian Ocean and in the Pacific Ocean as far east as Hawaii and Tahiti. This species is very important to local commercial fisheries and is sought out as a game fish--one of the Deep Seven species of Hawai'i. Taxonomy ''Pristipomoides filamentosus'' was first formally described as ''Serranus filamentosus'' in 1830 by the French zoologist Achille Valenciennes with the type locality given as Saint-Denis on Réunion. The specific name ''filamentosus'' means "filamentous" and refers to the filament-like last soft rays in the dorsal and anal fins. Description ''Pristipomoides filamentosus'' has an elongated, robust body with a depth of roughly a third of its standard length. The space between the eyes is flat, and has a slightly protrudin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salmonidae
Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefishes, graylings, taimens and lenoks, which are collectively known as the salmonids ("salmon-like fish"). The Atlantic salmon (''Salmo salar''), whose Latin name became that of its genus '' Salmo'', is also the source of the family and order names. Salmonids have a relatively primitive appearance among the teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back. They have slender bodies, with rounded scales and forked tails, and their mouths contain a single row of sharp teeth. Although the smallest species is just long as an adult, most are much larger, with the largest reaching . All salmonids spawn in fresh water of upper reaches of rivers and creeks, but in many cases, the fish spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bigmouth Buffalo
Bigmouth may refer to: * "Bigmouth", a song by Underworld The underworld, also known as the netherworld or hell, is the supernatural world of the dead in various religious traditions and myths, located below the world of the living. Chthonic is the technical adjective for things of the underwor ... * Bigmouth, an ogre in ''The Smurfs'' comics and animated cartoon series Marine life * Bigmouth buffalo, fish * Bigmouth goby, fish * Bigmouth skate, fish * Bigmouth rocksnail, snail See also * * * " Bigmouth Strikes Again", a 1986 alternative rock song by The Smiths * Big Mouth (other) {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pallid Sturgeon
The pallid sturgeon (''Scaphirhynchus albus'') is an endangered species of ray-finned fish, endemic to the waters of the Missouri and lower Mississippi river basins of the United States. It may have even reached the St. Croix River before colonization. Named for its pale coloration, it is closely related to the relatively common shovelnose sturgeon (''Scaphirhynchus platorynchus''), but is much larger, averaging between in length and in weight at maturity. This species takes 15 years to mature and spawns infrequently, but can live up to a century. A member of the sturgeon family, Acipenseridae, which originated during the Cretaceous period 70 million years ago, the pallid sturgeon has changed little since then. In 1990, the U.S. Fish and Wildlife Service placed the pallid sturgeon on its endangered species list because few young individuals had been observed in the preceding decade and sightings had greatly diminished; the species is now rarely seen in the wil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Sturgeon
The lake sturgeon (''Acipenser fulvescens''), also known as the rock sturgeon, is a North American temperate freshwater fish, one of about 25 species of sturgeon. Like other sturgeons, this species is a bottom feeder with evolutionarily basal traits among fish, reflecting its early divergence from the shark lineage. These traits include a partly cartilaginous skeleton, an overall streamlined shape, and skin bearing rows of bony plates on the sides and back. The lake sturgeon uses its elongated, spade-like snout to stir up the substrate and sediments on the beds of rivers and lakes to feed. Four sensory organs ( barbels) hang near its mouth to help the sturgeon locate bottom-dwelling prey. Lake sturgeons can grow to a large size for freshwater fish, topping 7.25 ft (2.2 m) long and 240 lb (108 kg). Description The lake sturgeon has taste buds on and around its barbels near its rubbery, prehensile lips. It extends its lips to vacuum up soft live food, which it sw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Freshwater Drum
The freshwater drum, ''Aplodinotus grunniens'', is a fish endemic to North and Central America. It is the only species in the genus ''Aplodinotus'', and is a member of the family Sciaenidae. It is the only North American member of the group that inhabits freshwater for its entire life.Fish of the Great Lakes: Wisconsin Sea Grant. Freshwater Drum Aplodinotus grunniens. Wisconsin Sea Grant 2002.http://seagrant.wisc.edu/greatlakesfish/drum.html. Its generic name, ''Aplodinotus'', comes from Greek meaning "single back", and the specific epithet, ''grunniens'', comes from a Latin word meaning "grunting". It is given to it because of the grunting noise that mature males make. This noise comes from a special set of muscles within the body cavity that vibrate against the swim bladder. The purpose of the grunting is unknown, but due to it being present in only mature males and during the spawning season, it is assumed to be linked to spawning. The drum typically weighs . The world record ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuroregeneration
Neuroregeneration refers to the regrowth or repair of nervous tissues, cells or cell products. Such mechanisms may include generation of new neurons, glia, axons, myelin, or synapses. Neuroregeneration differs between the peripheral nervous system (PNS) and the central nervous system (CNS) by the functional mechanisms involved, especially in the extent and speed of repair. When an axon is damaged, the distal segment undergoes Wallerian degeneration, losing its myelin sheath. The proximal segment can either die by apoptosis or undergo the chromatolytic reaction, which is an attempt at repair. In the CNS, synaptic stripping occurs as glial foot processes invade the dead synapse. Nervous system injuries affect over 90,000 people every year. It is estimated that spinal cord injuries alone affect 10,000 each year. As a result of this high incidence of neurological injuries, nerve regeneration and repair, a subfield of neural tissue engineering, is becoming a rapidly growing field de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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