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Eurypterus
Eurypterus (/jʊəˈrɪptərəs/ yoo-RIP-tər-əs) is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens. There are fifteen species belonging to the genus Eurypterus, the most common of which is E. remipes, the first eurypterid fossil discovered and the state fossil of New York. Members of Eurypterus averaged at about 13 to 23 cm (5 to 9 in) in length, but the largest individual discovered was estimated to be 60 cm (24 in) long. They all possessed spine-bearing appendages and a large paddle they used for swimming. They were generalist species, equally likely to engage in predation or scavenging.
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  • 09 Nov 2022
Topic Review
Radio Advertisement
In the United States, commercial radio stations make most of their revenue by selling airtime to be used for running radio advertisements. These advertisements are the result of a business or a service providing a valuable consideration, usually money, in exchange for the station airing their commercial or mentioning them on air. The most common advertisements are "spot commercials", which normally last for no more than one minute, and longer programs, commonly running up to one hour, known as "informercials". The United States Federal Communications Commission (FCC), established under the Communications Act of 1934, regulates commercial broadcasting, and the laws regarding radio advertisements remain relatively unchanged from the Radio Act of 1927. In 2015, radio accounted for 7.8% of total U.S. media expenditures.
  • 1.2K
  • 09 Nov 2022
Topic Review
Thin Layers (Oceanography)
Thin layers are concentrated aggregations of phytoplankton and zooplankton in coastal and offshore waters that are vertically compressed to thicknesses ranging from several centimeters up to a few meters and are horizontally extensive, sometimes for kilometers. Generally, thin layers have three basic criteria: 1) they must be horizontally and temporally persistent; 2) they must not exceed a critical threshold of vertical thickness; and 3) they must exceed a critical threshold of maximum concentration. The precise values for critical thresholds of thin layers has been debated for a long time due to the vast diversity of plankton, instrumentation, and environmental conditions. Thin layers have distinct biological, chemical, optical, and acoustical signatures which are difficult to measure with traditional sampling techniques such as nets and bottles. However, there has been a surge in studies of thin layers within the past two decades due to major advances in technology and instrumentation. Phytoplankton are often measured by optical instruments that can detect fluorescence such as LIDAR, and zooplankton are often measured by acoustic instruments that can detect acoustic backscattering such as ABS. These extraordinary concentrations of plankton have important implications for many aspects of marine ecology (e.g., phytoplankton growth dynamics, zooplankton grazing, behaviour, environmental effects, harmful algal blooms), as well as for ocean optics and acoustics. Zooplankton thin layers are often found slightly under phytoplankton layers because many feed on them. Thin layers occur in a wide variety of ocean environments, including estuaries, coastal shelves, fjords, bays, and the open ocean, and they are often associated with some form of vertical structure in the water column, such as pycnoclines, and in zones of reduced flow.
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  • 09 Nov 2022
Topic Review
Calyptranthes
Calyptranthes is a genus of flowering plants in the family Myrtaceae. They are known commonly as lidflowers, spicewoods, and mountainbays. There are about 100 species. They are evergreen shrubs or small trees, growing to 5 meters tall. They have simple, opposite, evergreen leaves and clusters of small flowers lacking petals. The sepals are capped in bud by a lidlike cover, which is shed later. The fruit is a dry, berry-like, reddish brown. The bark is smooth to scaly and pale-white in color. The genus is widely distributed across the warmer parts of the Western Hemisphere, from Florida, Mexico and the Bahamas south to Uruguay. Fourteen species occur within the United States , (in Florida, Puerto Rico and the Virgin Islands).
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  • 09 Nov 2022
Topic Review
Kikuchi Lines
Kikuchi lines are patterns of electrons formed by scattering. They pair up to form bands in electron diffraction from single crystal specimens, there to serve as "roads in orientation-space" for microscopists uncertain of what they are looking at. In transmission electron microscopes, they are easily seen in diffraction from regions of the specimen thick enough for multiple scattering. Unlike diffraction spots, which blink on and off as one tilts the crystal, Kikuchi bands mark orientation space with well-defined intersections (called zones or poles) as well as paths connecting one intersection to the next. Experimental and theoretical maps of Kikuchi band geometry, as well as their direct-space analogs e.g. bend contours, electron channeling patterns, and fringe visibility maps are increasingly useful tools in electron microscopy of crystalline and nanocrystalline materials. Because each Kikuchi line is associated with Bragg diffraction from one side of a single set of lattice planes, these lines can be labeled with the same Miller or reciprocal-lattice indices that are used to identify individual diffraction spots. Kikuchi band intersections, or zones, on the other hand are indexed with direct-lattice indices i.e. indices which represent integer multiples of the lattice basis vectors a, b and c. Kikuchi lines are formed in diffraction patterns by diffusely scattered electrons, e.g. as a result of thermal atom vibrations. The main features of their geometry can be deduced from a simple elastic mechanism proposed in 1928 by Seishi Kikuchi, although the dynamical theory of diffuse inelastic scattering is needed to understand them quantitatively. In x-ray scattering, these lines are referred to as Kossel lines (named after Walther Kossel).
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  • 09 Nov 2022
Topic Review
Seaplane
A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water. Seaplanes are usually divided into two categories based on their technological characteristics: floatplanes and flying boats; the latter are generally far larger and can carry far more. Seaplanes that can also take off and land on airfields are in a subclass called amphibious aircraft, or amphibians. Seaplanes were sometimes called hydroplanes, but currently this term applies instead to motor-powered watercraft that use the technique of hydrodynamic lift to skim the surface of water when running at speed. The use of seaplanes gradually tapered off after World War II, partially because of the investments in airports during the war. In the 21st century, seaplanes maintain a few niche uses, such as for aerial firefighting, air transport around archipelagos, and access to undeveloped or roadless areas, some of which have numerous lakes.
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  • 09 Nov 2022
Topic Review
Jungle Warfare
Jungle warfare is a term used to cover the special techniques needed for military units to survive and fight in jungle terrain. It has been the topic of extensive study by military strategists, and was an important part of the planning for both sides in many conflicts, including World War II and the Vietnam War. The jungle has a variety of effects on military operations. Dense vegetation can limit lines of sight and arcs of fire, but can also provide ample opportunity for camouflage and plenty of material with which to build fortifications. Jungle terrain, often without good roads, can be inaccessible to vehicles and so makes logistical supply and transport difficult, which in turn places a premium on air mobility. The problems of transport make engineering resources important as they are needed to improve roads, build bridges and airfields, and improve water supplies. Jungle environments can also be inherently unhealthy, with various tropical diseases that have to be prevented or treated by medical services. Likewise the terrain can make it difficult to deploy armoured forces, or any other kind of forces on any large scale. Successful jungle fighting emphasises effective small unit tactics and leadership.
  • 4.4K
  • 09 Nov 2022
Topic Review
Carcharodontosaurus
Carcharodontosaurus (/ˌkɑːrkəroʊˌdɒntoʊˈsɔːrəs/; lit. sharp-toothed lizard) is a genus of large carcharodontosaurid theropod dinosaur that existed during the Cenomanian age of the Late Cretaceous in Northern Africa. The genus Carcharodontosaurus is named after the shark genus Carcharodon, itself composed of the Greek karchar[os] (κάρχαρος, meaning "jagged" or "sharp") and odōn (ὀδών, "teeth"), and the suffix -saurus ("lizard"). It is currently known to have two species: C. saharicus and C. iguidensis.
  • 5.6K
  • 09 Nov 2022
Topic Review
Climate Change and Indigenous Peoples
Climate change disproportionately impacts indigenous people around the world, especially in terms of their health, environments, and communities. Indigenous people found in Africa, the Arctic, Asia, Australia, the Caribbean, Latin America, North America and the Pacific have strategies and traditional knowledge to adapt to climate change. These knowledge systems can be beneficial for their own adaptation to climate change as well as applicable to non-indigenous people.   The majority of the world’s biological, ecological, and cultural diversity is located within Indigenous territories. There are over 370 million indigenous peoples found across 90+ countries. Approximately 22% of the planet's land is comprised of indigenous territories, varying slightly depending on how indigeneity and land usage is determined. Indigenous people have the important role of the main knowledge keepers within their communities, including knowledge relating to the maintenance of social-ecological systems. The United Nations Declaration on the Rights of Indigenous People recognizes that Indigenous people have specific knowledge, traditional practices, and cultural customs that can contribute to the proper and sustainable management of ecological resources. Indigenous Peoples have a myriad of experiences with the effects of climate change because of the varying geographical areas they inhabit across the globe and because of the differences in cultures and livelihoods. Indigenous Peoples have a wide variety of experiences that Western science is beginning to include in its research of climate change and its potential solutions. The concepts of ancestral knowledge and traditional practices are increasingly respected and considered in Western scientific research.
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  • 09 Nov 2022
Topic Review
Macchi C.202
The Macchi C.202 Folgore (Italian "thunderbolt") was an Italian fighter aircraft developed and manufactured by Macchi Aeronautica. It was operated mainly by the Regia Aeronautica (RA; Royal (Italian) Air Force) in and around the Second World War. According to aviation author David Mondey, the Folgore has been considered to be one of the best wartime fighters to serve in large numbers with the Regia Aeronautica. The C.202 was designed by a team headed by the company's chief of design, Italian aeronautics engineer Mario Castoldi. As per company tradition, Macchi aircraft designed by Mario Castoldi received the "C" letter in their model designation, hence the Folgore is commonly referred to as the C.202 or MC.202. The C.202 was a development of the earlier C.200 Saetta, powered by an Italian-built version of the German Daimler-Benz DB 601Aa engine and featuring a redesigned fuselage for greater streamlining. During July 1941, the Folgore went into service with the Regia Aeronautica. In combat, it very quickly proved itself to be an effective and deadly dogfighter against its contemporaries. During its service life, the C.202 was deployed on all fronts in which Italy was involved. During late 1941, it commenced offensive operations over Malta and in North Africa, where Italian and German forces were engaged in heavy combat against British and later United States operations. The C.202 continued to be used in North Africa as late as mid-1943, by which point the type was withdrawn to support defensive efforts in Sicily and the Italian mainland following their invasion by Allied forces. It also saw limited use on the Eastern Front. Following the 1943 Armistice with Italy, the type was mostly used as a trainer aircraft. The type was also operated by Croatia. The Australian ace Clive Caldwell, who fought a wide variety of German, Italian and Japanese fighters during 1941–45, later stated that the C.202 was "one of the best and most undervalued of fighters". The C.202 also had its defects: like its predecessor, the C.200, it could enter a dangerous spin. The radios were unreliable, routinely forcing pilots to communicate by waggling their wings and Western historians regard the C.202 as insufficiently armed, being furnished with just a pair of machine guns that had a tendency for jamming. Still in mid-Summer 1942, in North Africa, the Folgore achieved a ratio kill/loss better than that of the Messerschmitt Bf 109s.
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  • 10 Nov 2022
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