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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.
  • 1.8K
  • 18 Oct 2022
Topic Review
Verneuil Process
The Verneuil process, also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1800s by the French chemist Auguste Verneuil. It is primarily used to produce the ruby, sapphire and padparadscha varieties of corundum, as well as the diamond simulants rutile and strontium titanate. The principle of the process involves melting a finely powdered substance using an oxyhydrogen flame, and crystallising the melted droplets into a boule. The process is considered to be the founding step of modern industrial crystal growth technology, and remains in wide use to this day.
  • 1.6K
  • 18 Oct 2022
Topic Review
Taupo Volcano
Lake Taupo, in the centre of New Zealand’s North Island, is the caldera of a large rhyolitic supervolcano called the Taupo Volcano. This huge volcano has produced two of the world’s most violent eruptions in geologically recent times. The Taupo Volcano forms part of the Taupo Volcanic Zone, a region of volcanic activity that extends from Ruapehu in the South, through the Taupo and Rotorua districts, to White Island, in the Bay of Plenty region. Taupo began erupting about 300,000 years ago, but the main eruptions that still affect the surrounding landscape are the Oruanui eruption, about 26,500 years ago, which is responsible for the shape of the modern caldera, and the Hatepe eruption, dated 232 ± 5 CE. However, there have been many more eruptions, with major ones every thousand years or so (see timeline of last 10,000 years of eruptions). Considering recent history alone, the volcano has been inactive for an unusually long period of time, but considering its long-term activity, it was inactive for much longer between 8100 and 5100 BCE (3,000 year inactivity, compared to the current 1,800 years). Some volcanoes within the Taupo Volcanic Zone have erupted far more recently, however, notably a violent VEI-5 eruption of Mount Tarawera in 1886, and frequent activity of Whakaari/White Island, which erupted most recently in December 2019.
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  • 18 Oct 2022
Topic Review
Devil's Garden (Grand Staircase-Escalante National Monument)
The Devil's Garden of the Grand Staircase-Escalante National Monument (GSENM) in south central Utah, the United States, is a protected area featuring hoodoos, natural arches and other sandstone formations. The United States Geological Survey (USGS) designated the name Devils Garden—without an apostrophe according to USGS naming conventions—on December 31, 1979. The area is also known as the Devils Garden Outstanding Natural Area within the National Landscape Conservation System. The formations in the Devils Garden were created, and continue to be shaped, by various weathering and erosional processes. These natural processes have been shaping sandstone layers formed more than 166 million years ago during the Jurassic period's Middle epoch. The Bureau of Land Management (BLM) administers the Devils Garden and the entire GSENM which is the first national monument assigned to the BLM.
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  • 18 Oct 2022
Topic Review
Dilophosaurus
Dilophosaurus (/daɪˌloʊfəˈsɔːrəs, -foʊ-/ dy-LOH-fə-SOR-əs, -⁠foh-) is a genus of theropod dinosaurs that lived in what is now North America during the Early Jurassic, about 193 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserved were collected in 1942. The most complete specimen became the holotype of a new species in the genus Megalosaurus, named M. wetherilli by Samuel P. Welles in 1954. Welles found a larger skeleton belonging to the same species in 1964. Realizing it bore crests on its skull, he assigned the species to the new genus Dilophosaurus in 1970, as Dilophosaurus wetherilli. The genus name means "two-crested lizard", and the species name honors John Wetherill, a Navajo councilor. Further specimens have since been found, including an infant. Footprints have also been attributed to the animal, including resting traces. Another species, Dilophosaurus sinensis from China, was named in 1993, but was later found to belong to the genus Sinosaurus. At about 7 m (23 ft) in length, with a weight of about 400 kg (880 lb), Dilophosaurus was one of the earliest large predatory dinosaurs and the largest known land-animal in North America at the time. It was slender and lightly built, and the skull was proportionally large, but delicate. The snout was narrow, and the upper jaw had a gap or kink below the nostril. It had a pair of longitudinal, arched crests on its skull; their complete shape is unknown, but they were probably enlarged by keratin. The mandible was slender and delicate at the front, but deep at the back. The teeth were long, curved, thin, and compressed sideways. Those in the lower jaw were much smaller than those of the upper jaw. Most of the teeth had serrations at their front and back edges. The neck was long, and its vertebrae were hollow, and very light. The arms were powerful, with a long and slender upper arm bone. The hands had four fingers; the first was short but strong and bore a large claw, the two following fingers were longer and slenderer with smaller claws; the fourth was vestigial. The thigh bone was massive, the feet were stout, and the toes bore large claws. Dilophosaurus is a member of the family Dilophosauridae along with Dracovenator, a group placed between the Coelophysidae and later theropods. Dilophosaurus would have been active and bipedal, and may have hunted large animals; it could also have fed on smaller animals and fish. Due to the limited range of movement and shortness of the forelimbs, the mouth may instead have made first contact with prey. The function of the crests is unknown; they were too weak for battle, but may have been used in visual display, such as species recognition and sexual selection. It may have grown rapidly, attaining a growth rate of 30 to 35 kg (66 to 77 lb) per year early in life. The holotype specimen had multiple paleopathologies, including healed injuries and signs of a developmental anomaly. Dilophosaurus is known from the Kayenta Formation, and lived alongside dinosaurs such as Megapnosaurus and Sarahsaurus. Dilophosaurus was featured in the novel Jurassic Park and its movie adaptation, wherein it was given the fictional abilities to spit venom and expand a neck frill, as well as being smaller than the real animal. It was designated as the state dinosaur of Connecticut based on tracks found there.
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  • 18 Oct 2022
Topic Review
Clathrate Gun Hypothesis
The clathrate gun hypothesis refers to a proposed explanation for the periods of rapid warming during the Quaternary. The idea is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes, these events would have caused the Bond Cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials. The hypothesis was supported for the Bølling-Allerød and Preboreal period, but not for Dansgaard–Oeschger interstadials, although there are still debates on the topic.
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  • 18 Oct 2022
Topic Review
Countries Dependent on the Bay of Bengal
The countries dependent on the Bay of Bengal include littoral and landlocked countries that depend on the Bay of Bengal for maritime usage. Historically, the Bay of Bengal has been a highway of transport, trade and cultural exchange between diverse peoples encompassing South Asia and Southeast Asia. Today, the Bay of Bengal region is the convergence of two major geopolitical blocs- the Association of Southeast Asian Nations (ASEAN) and the South Asian Association for Regional Cooperation (SAARC). The Bay of Bengal Initiative for Multisectoral Technical and Economic Cooperation (BIMSTEC) promotes regional engagement in the area. The Bay of Bengal countries are often categorized into a maritime subregion. The bay hosts vital shipping routes linking its littoral and landlocked hinterland with the Indian Ocean. Its sea bed is being explored and exploited for hydrocarbon reserves.
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Topic Review
Precambrian Supereon
The Precambrian (or Pre-Cambrian, sometimes abbreviated pЄ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian (colored green in the timeline figure) is an informal unit of geologic time, subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about 541 million years ago (Ma), when hard-shelled creatures first appeared in abundance.
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  • 18 Oct 2022
Topic Review
Carbon Diet
A carbon diet refers to reducing the impact on climate change by reducing greenhouse gas production specifically, CO2 production. In today’s society, humans produce CO2 in every day activities such as driving, heating, deforestation and the burning of fossil fuels such as coal, oil and gas. It has been found that carbon dioxide from the burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions. For years, governments and corporations have been attempting to balance out their emissions by participating in carbon-offsetting — the practice in which they invest in renewable energy to compensate for the global-warming pollution that they produce. Despite these efforts the results are still far off and we continue to see growth in CO2 concentration. Now, a growing number of individuals are trying to make a reduction in the amount of CO2 that is being produced by participating in low carbon dieting. This small adjustment in household CO2 production has the potential to reduce emissions much more quickly than other kinds of changes and it deserves explicit consideration as part of climate policy. It can potentially help avoid “overshoot” of greenhouse gas concentration targets; provide a demonstration effect; reduce emissions at low cost; and buy time to develop new technologies, policies, and institutions to reach long-term greenhouse gas emission targets and to develop adaptation strategies.
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  • 18 Oct 2022
Topic Review
List of Peaks by Prominence
This is a list of mountain peaks ordered by their topographic prominence.
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  • 18 Oct 2022
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