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Topic Review
Jet (Gemstone)
Jet is a type of lignite, the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid. It is derived from wood that has changed under extreme pressure. The English noun jet derives from the French word for the same material, jaiet (modern French jais), ultimately referring to the ancient town of Gagae. Jet is either black or dark brown, but may contain pyrite inclusions which are of brassy colour and metallic lustre. The adjective "jet-black", meaning as dark a black as possible, derives from this material.
  • 2.7K
  • 27 Oct 2022
Topic Review
List of Selected Stars for Navigation
Fifty-eight selected navigational stars are given a special status in the field of celestial navigation. Of the approximately 6,000 stars visible to the naked eye under optimal conditions, the selected stars are among the brightest and span 38 constellations of the celestial sphere from the declination of −70° to +89°. Many of the selected stars were named in antiquity by the Babylonians, Greeks, Romans, and Arabs. The star Polaris, often called the "North Star", is treated specially due to its proximity to the north celestial pole. When navigating in the Northern Hemisphere, special techniques can be used with Polaris to determine latitude or gyrocompass error. The other 57 selected stars have daily positions given in nautical almanacs, aiding the navigator in efficiently performing observations on them. A second group of 115 "tabulated stars" can also be used for celestial navigation, but are often less familiar to the navigator and require extra calculations. For purposes of identification, the positions of navigational stars — expressed as declination and sidereal hour angle — are often rounded to the nearest degree. In addition to tables, star charts provide an aid to the navigator in identifying the navigational stars, showing constellations, relative positions, and brightness.
  • 2.7K
  • 26 Oct 2022
Topic Review
Western European Colonialism and Colonization
File:SierraLeoneHofstra3.1.tiff European colonialism and colonization was the policy or practice of acquiring full or partial political control over other societies and territories, creating a colony, occupying it with settlers, and exploiting it economically. Research suggests, the current conditions of postcolonial countries have roots in colonial actions and policies. For example, colonial policies, such as the type of rule implemented, the nature of investments, and identity of the colonizers, are cited as impacting postcolonial states. Examination of the state-building process, economic development, and cultural norms and mores shows the direct and indirect consequences of colonialism on the postcolonial states.
  • 2.7K
  • 04 Nov 2022
Topic Review
Stone Mountain
Stone Mountain is a quartz monzonite dome monadnock and the site of Stone Mountain Park near Stone Mountain, Georgia. At its summit, the elevation is 1,686 feet (514 m) above sea level and 825 feet (251 m) above the surrounding area. Stone Mountain is well known for not only its geology, but also the enormous rock relief on its north face, the largest bas-relief in the world. The carving depicts three Confederate figures, Jefferson Davis, Robert E. Lee and Stonewall Jackson, and has been the subject of widespread controversy. Stone Mountain was once owned by the Venable Brothers. It was purchased by the State of Georgia in 1958 "as a memorial to the Confederacy." Stone Mountain Park officially opened on April 14, 1965 – 100 years to the day after Lincoln's assassination, although the park had been in use for a few years. It is the most visited destination in the state of Georgia. Stone Mountain is more than 5 miles (8 km) in circumference at its base. The summit of the mountain can be reached by a walk-up trail on the west side of the mountain or by the Skyride aerial tram.
  • 2.7K
  • 04 Nov 2022
Topic Review
Platinum Group Minerals
Russia and South Africa are the world’s leading producers of platinum group elements (PGEs). This places them in a unique position regarding the supply of these two key industrial commodities. The purpose of this paper is to provide a comparative high-level overview of aspects of the geological occurrence, mineralogy, and processing by flotation of the platinum group minerals (PGMs) found in each country. A summary of some of the major challenges faced in each country in terms of the concentration of the ores by flotation is presented alongside the opportunities that exist to increase the production of the respective metals. These include the more efficient recovery of minerals such as arsenides and tellurides, the management of siliceous gangue and chromite in the processing of these ores, and, especially in Russia, the development of novel processing routes to recover PGEs from relatively low grade ores occurring in dunites, black shale ores and in vanadium-iron-titanium-sulphide oxide formations.
  • 2.5K
  • 26 Jan 2021
Topic Review
Amazon Basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 6,300,000 km2 (2,400,000 sq mi), or about 35.5 percent that of the South American continent. It is located in the countries of Bolivia, Brazil , Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela. Most of the basin is covered by the Amazon Rainforest, also known as Amazonia. With a 5.5 million km2 (2.1 million sq mi) area of dense tropical forest, this is the largest rainforest in the world.
  • 2.5K
  • 03 Nov 2022
Topic Review
French Geodesic Mission
The French Geodesic Mission (also called the Geodesic Mission to Peru, Geodesic Mission to the Equator and the Spanish-French Geodesic Mission) was an 18th-century expedition to what is now Ecuador carried out for the purpose of measuring the roundness of the Earth and measuring the length of a degree of latitude at the Equator. The mission was one of the first geodesic (or geodetic) missions carried out under modern scientific principles, and the first major international scientific expedition.
  • 2.5K
  • 19 Oct 2022
Topic Review
New Guinea Highlands
The New Guinea Highlands, also known as the Central Range or Central Cordillera, is a long chain of mountain ranges on the island of New Guinea, including the island's tallest peak, Puncak Jaya 16,024 ft (4,884 m), the highest mountain in Oceania. The range is home to many intermountain river valleys, many of which support thriving agricultural communities. The highlands run generally east-west the length of the island, which is divided politically between Indonesia in the west and Papua New Guinea in the east.
  • 2.4K
  • 09 Nov 2022
Topic Review
List of Minerals (Complete)
Mineralogy is an active science in which minerals are discovered or recognised on a regular basis. Use of old mineral names is also discontinued, for example when a name is no longer considered valid. Therefore, a list of recognised mineral species is never complete. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species. Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety. The International Mineralogical Association (IMA) is the international group that recognises new minerals and new mineral names. However, minerals discovered before 1959 did not go through the official naming procedure. Some minerals published previously have been either confirmed or discredited since that date. This list contains a mixture of mineral names that have been approved since 1959 and those mineral names believed to still refer to valid mineral species (these are called "grandfathered" species). Presently, each year about 90-110 new mineral species (the sum of all mutations c. 120/year) are officially approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association. The IMA/CNMNC administrates c. 6,500 names, and (As of January 2018), the Handbook of Mineralogy lists 4,507 species. (As of March 2018), the IMA Database of Mineral Properties/ Rruff Project lists 5,312 valid species (IMA/CNMNC) of a total of 5,525 minerals. There are 1,289 Pre-IMA minerals. (As of April 2011), the Webmineral.com website lists 2,722 published and approved (IMA/CNMNC) minerals, 81 discredited minerals (IMA/CNMNC status; Michael Fleischer discredited around thousand species in his lifetime), 2,691 synonyms and 123 "not approved" names. (As of November 2018), the IMA - CNMNC Master List of Minerals lists 5,413 valid minerals, including c. 1,166 pre-IMA minerals (grandfathered), c. 272 approved minerals but without a published description yet and c. 99 questionable minerals. Due to the length of this list, it is divided into alphabetical groups. The minerals are sorted by name.
  • 2.4K
  • 02 Nov 2022
Topic Review
Indoor Air Pollution in Developing Nations
Indoor air pollution in developing nations is a significant form of indoor air pollution (IAP) that is little known to those in the developed world. Three billion people in developing countries across the globe rely on biomass, in the form of wood, charcoal, dung, and crop residue, as their domestic cooking fuel. Since much of the cooking is carried out indoors in environments that lack proper ventilation, millions of people, primarily poor women and children face serious health risks. The major sources of indoor air pollution include combustion and building materials. Globally, 4.3 million deaths were attributed to exposure to IAP in developing countries in 2012, almost all in low and middle-income countries. The South East Asian and Western Pacific regions bear most of the burden with 1.69 and 1.62 million deaths, respectively. Almost 600,000 deaths occur in Africa, 200,000 in the Eastern Mediterranean region, 99,000 in Europe and 81,000 in the Americas. The remaining 19,000 deaths occur in high-income countries. Even though the rate of dependence on biomass fuel is declining, this dwindling resource will not keep up with population growth which could ultimately put environments at even greater risk. Over the past several decades, there have been numerous studies investigating the air pollution generated by traditional household solid fuel combustion for space heating, lighting, and cooking in developing countries. It is now well established that, throughout much of the developing world, indoor burning of solid fuels (biomass, coal, etc.) by inefficient, often insufficiently vented, combustion devices results in elevated exposure to household air pollutants. This is due to the poor combustion efficiency of the combustion devices and the elevated nature of the emissions. In addition, they are often released directly into living areas. Smoke from traditional household solid fuel combustion commonly contains a range of incomplete combustion products, including both fine and coarse particulate matter (e.g., PM2.5, PM10), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and a variety of organic air pollutants (e.g., formaldehyde, 1,3-butadiene, benzene, acetaldehyde, acrolein, phenols, pyrene, benzopyrene, benzo(a)pyrene, dibenzopyrenes, dibenzocarbazoles, and cresols). In a typical solid fuel stove, about 6–20% of the solid fuel is converted into toxic emissions (by mass). The exact quantity and relative composition is determined by factors such as the fuel type and moisture content, stove type and operation influencing the amount. While many pollutants can evolve, most measurements have been focused on breathing-zone exposure levels of particulate matter (PM) and carbon monoxide (CO), which are the main products of incomplete combustion and are considered to pose the greatest health risks. Indoor PM2.5 exposure levels have been consistently reported to be in the range of hundreds to thousands of micrograms per cubic meter (μg/m3). Similarly, CO exposure levels have been measured to be as high as hundreds to greater than 1000 milligrams per cubic meter (mg/m3). A recent study of 163 households in two rural Chinese counties reported geometric mean indoor PM2.5 concentrations of 276 μg/m3 (combinations of different plant materials, including wood, tobacco stems, and corncobs), 327 μg/m3 (wood), 144 μg/m3 (smoky coal), and 96 μg/m3 (smokeless coal) for homes using a variety of different fuel types and stove configurations (e.g., vented, unvented, portable, fire pit, mixed ventilation stove).
  • 2.4K
  • 22 Nov 2022
Topic Review
Dome C
Dome C, also known as Dome Circe, Dome Charlie or Dome Concordia, located at Antarctica at an elevation of 3,233 metres (10,607 ft) above sea level, is one of several summits or "domes" of the Antarctic Ice Sheet. Dome C is located on the Antarctic Plateau, 1,100 kilometres (680 mi) inland from the French research station at Dumont D'Urville, 1,100 kilometres (680 mi) inland from the Australian Casey Station and 1,200 kilometres (750 mi) inland from the Italian Zucchelli station at Terra Nova Bay. Russia's Vostok Station is 560 kilometres (350 mi) away. Dome C is the site of the Concordia Research Station, jointly operated by France and Italy.
  • 2.3K
  • 04 Nov 2022
Topic Review
List of Minerals N (Complete)
This list includes those recognised minerals beginning with the letter N. The International Mineralogical Association is the international group that recognises new minerals and new mineral names, however minerals discovered before 1959 did not go through the official naming procedure, although some minerals published previously have been either confirmed or discredited since that date. This list contains a mixture of mineral names that have been approved since 1959 and those mineral names believed to still refer to valid mineral species (these are called "grandfathered" species). The list is divided into groups: The data was exported from mindat.org on 29 April 2005; updated up to 'IMA2018'. The minerals are sorted by name, followed by the structural group (rruff.info/ima and ima-cnmnc by mineralienatlas.de, mainly) or chemical class (mindat.org and basics), the year of publication (if it's before of an IMA approval procedure), the IMA approval and the Nickel–Strunz code.
  • 2.3K
  • 10 Oct 2022
Topic Review
Inner Core
The Earth's inner core is the Earth's innermost part. It is primarily a solid ball with a radius of about 1,220 kilometres (760 miles), which is about 70% of the Moon's radius. It is composed of an iron–nickel alloy and some other elements. The temperature at the inner core's surface is approximately 5,700 K (5,430 °C) or 9806 °F, which is about the temperature at the surface of the Sun.
  • 2.3K
  • 10 Nov 2022
Topic Review
The Bruun Rule
The Bruun Rule is a formula for estimating the magnitude of the retreat of the shoreline of a sandy shore in response to changes in sea level. Originally published in 1962 by Per Bruun, the Bruun Rule was the first to give a relationship between sea level rise and shoreline recession. The rule is a simple, two dimensional mass conversion, and remains in common use to estimate shoreline recession in response to sea level rise, despite criticism and modification, and the availability more complex alternate models.
  • 2.3K
  • 28 Oct 2022
Topic Review
Detecting Lithium Mineralizations from Space
Optical and thermal remote sensing data have been an important tool in geological exploration for certain deposit types. However, the present economic and technological advances demand the adaptation of the remote sensing data and image processing techniques to the exploration of other raw materials like lithium (Li). A review of the application studies and developments in this field was also made. The addressed topics include: (i) achievements made in Li exploration using remote sensing methods; (ii) the main weaknesses of the approaches; (iii) how to overcome these difficulties; and (iv) the expected research perspectives. We expect that the number of studies concerning this topic will increase in the near future and that remote sensing will become an integrated and fundamental tool in Li exploration.
  • 2.2K
  • 30 Oct 2020
Topic Review
Classical Plant Breeding
Classical plant breeding uses deliberate interbreeding (crossing) of closely or distantly related species to produce new crops with desirable properties. Plants are crossed to introduce traits/genes from a particular variety into a new genetic background. For example, a mildew resistant pea may be crossed with a high-yielding but susceptible pea, the goal of the cross being to introduce mildew resistance without losing the high-yield characteristics. Progeny from the cross would then be crossed with the high-yielding parent to ensure that the progeny were most like the high-yielding parent, (backcrossing), the progeny from that cross would be tested for yield and mildew resistance and high-yielding resistant plants would be further developed. Plants may also be crossed with themselves to produce inbred varieties for breeding. Germplasm resources from genebanks have invaluable for classical breeding. Classical breeding relies heavily on the naturally occuring plant life-cycle and homologous recombination to generate genetic diversity and to eliminate undesirable traits. It may also makes use of a variety of artificial laboratory procedures to overcome obstacles to introduction of useful traits from wild species that do not usually exchange genes with the domesticated line. These approaches include in vitro techniques such as protoplast fusion, embryo rescue or mutagenisis (see below) to generate genetic alterations and produce transgenic plants that would not exist in nature. Traits that breeders' have tried to incorporate into crop plants in the last 100 years include: Intraspecific hybridization within a plant species was demonstrated by Charles Darwin and Gregor Mendel, and was further developed by geneticists and plant breeders. In the early 20th century, plant breeders realized that Mendel's findings on the non-random nature of inheritance could be applied to seedling populations produced through deliberate pollinations to predict the frequencies of different types. In 1908, George Harrison Shull described heterosis, also known as hybrid vigor. Heterosis describes the tendency of the progeny of a specific cross to outperform both parents. The detection of the usefulness of heterosis for plant breeding has lead to the development of inbred lines that reveal a heterotic yield advantage when they are crossed. Maize was the first species where heterosis was widely used to produce hybrids. Heterosis made breeders aware of the broad practical value of many genes carried in plant chromosomes even when the identity and trait specified by the paticular genes is unknown - that is that diverse plant Germplasm is generally valuable to the breeder. By the 1920s, statistical methods were developed to analyze gene action and distinguish heritable variation from variation caused by environment. In 1933, another important breeding technique, cytoplasmic male sterility (CMS), developed in maize, was described by Marcus Morton Rhoades. CMS is a maternally inherited trait that makes the plant produce sterile pollen, enabling the production of hybrids and removing the need for detasseling maize plants. The scientific use of Transgenic plants in farming gained impetus in the 1930s when a transgenic wheat variety named Hope bred by E. S. McFadden with a transgene originating in a wild grass saved American wheat growers from devastating stem rust outbreaks. These early breeding techniques resulted in large yield increase in the United States in the early 20th century. Similar yield increases were not produced elsewhere until after World War II, the Green Revolution increased crop production in the developing world in the 1960s. Success stories like Hope and hybrid-vigor made it clear that genetic divesity present in wild-species was of great potential value to plant breeders, and eventially lead to the establisment of Germplasm collections consisting of seed-banks devoted to preservation of potentially useful uncharacterised traits for posterity. Following World War II a number of techniques were developed that allowed plant breeders to hybridize distantly related species, and artificially induce genetic diversity. When distantly related species are crossed, plant breeders make use of a number of plant tissue culture techniques to produce progeny from other wise fruitless mating. Interspecific and intergeneric hybrids are produced from a cross of related species or genera that do not normally sexually reproduce with each other. These crosses are referred to as Wide crosses. The cereal triticale is a wheat and rye hybrid. The first generation created from the cross was sterile, so the cell division inhibitor colchicine was used to double the number of chromosomes in the cell. Cells with an uneven number of chromosomes are sterile. Failure to produce a hybrid may be due to pre- or post-fertilization incompatibility. If fertilization is possible between two species or genera, the hybrid embryo may abort before maturation. If this does occur the embryo resulting from an interspecific or intergeneric cross can sometimes be rescued and cultured to produce a whole plant. Such a method is referred to as Embryo Rescue. This technique has been used to produce new rice for Africa, an interspecific cross of Asian rice (Oryza sativa) and African rice (Oryza glaberrima). Hybrids may also be produced by a technique called protoplast fusion. In this case protoplasts are fused, usually in an electric field. Viable recombinants can be regenerated in culture. Chemical mutagens like EMS and DMSO, radiation and transposons are used to generate mutants with desirable traits to be bred with other cultivars. Classical plant breeders also generate genetic diversity within a species by exploiting a process called somaclonal variation, which occurs in plants produced from tissue culture, particularly plants derived from callus. Induced polyploidy, and the addition or removal of chromosomes using a technique called chromosome engineering also found uses. When a desirable trait has been bred into a species, a number of crosses to the favoured parent are made to make the new plant as similar as the parent as possible. Returning to the example of the mildew resistant pea being crossed with a high-yielding but susceptible pea, to make the mildew resistant progeny of the cross most like the high-yielding parent, the progeny will be crossed back to that parent for several generations (See backcrossing ). This process removes most of the genetic contribution of the mildew resistant parent. Classical breeding is therefore a cyclical process. It should be noted that with classical breeding techniques, the breeder does not know exactly what genes have been introduced to the new cultivars. Some scientists therefore argue that plants produced by classical breeding methods should undergo the same safety testing regime as genetically modified plants. There have been instances where plants bred using classical techniques have been unsuitable for human consumption, for example the poison solanine was accidentally re-introduced into varieties of potato through plant breeding.
  • 2.2K
  • 14 Oct 2022
Topic Review
Fossil Fuels Lobby
"Fossil fuels lobby" is a term used to label the paid representatives of large fossil fuel (oil, gas, coal) and electric utilities corporations who attempt to influence governmental policy. So-called Big Oil companies such as ExxonMobil, Royal Dutch Shell, BP, Total S.A., Chevron Corporation, and ConocoPhillips are amongst the largest corporations associated with the fossil fuels lobby. General Electric, Southern Company, First Energy, and the Edison Electric Institute are also among the most influential electric utilities corporations. By sector, "Energy/Nat Resource" comes fifth, behind "Misc Business", "Finance/Insur/RealEst", Health and "Communic/Electronics".
  • 2.1K
  • 27 Oct 2022
Topic Review
Aerial Photography
Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other flying object. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs or "drones"), balloons, blimps and dirigibles, rockets, pigeons, kites, parachutes, stand-alone telescoping and vehicle-mounted poles. Mounted cameras may be triggered remotely or automatically; hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that "chase" and photograph other aircraft in flight.
  • 2.1K
  • 30 Nov 2022
Topic Review
List of Traffic Separation Schemes
A Traffic Separation Scheme is an area in the sea where navigation of ships is highly regulated. It is meant to create lanes in the water and ships in a specific lane are all going in (roughly) the same direction. A TSS is created in locations with dense shipping where ships can go in different directions and where there is a high risk of collisions. In the overview below the regulating authority is always the IMO unless stated differently) If below TSS or Routing Scheme is not governed by the IMO the governing body will be mentioned between ' (brackets). 
  • 2.1K
  • 29 Sep 2022
Topic Review
Biochemical Oxygen Demand
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic pollution of water. BOD reduction is used as a gauge of the effectiveness of wastewater treatment plants. BOD of wastewater effluents is used to indicate the short-term impact on the oxygen levels of the receiving water. BOD analysis is similar in function to chemical oxygen demand (COD) analysis, in that both measure the amount of organic compounds in water. However, COD analysis is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically oxidized organic matter.
  • 2.1K
  • 18 Oct 2022
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