Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Valley Network
Valley networks are branching networks of valleys on Mars that superficially resemble terrestrial river drainage basins. They are found mainly incised into the terrain of the martian southern highlands, and are typically - though not always - of Noachian age (approximately four billion years old). The individual valleys are typically less than 5 kilometers wide, though they may extend for up to hundreds or even thousands of kilometers across the martian surface. The form, distribution, and implied evolution of the valley networks are of great importance for what they may tell us about the history of liquid water on the martian surface, and hence Mars' climate history. Some authors have argued that the properties of the networks demand that a hydrological cycle must have been active on ancient Mars, though this remains contentious. Objections chiefly arise from repeated results from models of martian paleoclimate suggesting high enough temperatures and pressures to sustain liquid water on the surface have not ever been possible on Mars. The advent of very high resolution images of the surface from the HiRISE, THEMIS and Context (CTX) satellite cameras as well as the Mars Orbital Laser Altimeter (MOLA) digital terrain models have drastically improved our understanding of the networks in the last decade.
  • 366
  • 25 Oct 2022
Topic Review
Wireless USB
Wireless USB (Universal Serial Bus) was a short-range, high-bandwidth wireless radio communication protocol created by the Wireless USB Promoter Group which intended to increase the availability of general USB-based technologies. It was unrelated to Wi-Fi, and different from the Cypress WirelessUSB offerings. It was maintained by the WiMedia Alliance which ceased operations in 2009. Wireless USB is sometimes abbreviated as "WUSB", although the USB Implementers Forum discouraged this practice and instead prefers to call the technology Certified Wireless USB to distinguish it from the competing UWB standard. Wireless USB was based on the (now defunct) WiMedia Alliance's Ultra-WideBand (UWB) common radio platform, which is capable of sending 480 Mbit/s at distances up to 3 metres (9.8 ft) and 110 Mbit/s at up to 10 metres (33 ft). It was designed to operate in the 3.1 to 10.6 GHz frequency range, although local regulatory policies may restrict the legal operating range in some countries. The standard is now obsolete, and no new hardware has been produced for many years. Support for the standard was deprecated in Linux 5.4 and removed in Linux 5.7
  • 366
  • 28 Oct 2022
Topic Review
Osmium-194
Osmium (76Os) has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotopes, 184Os, and 186Os, have extremely long half-life (1.12×1013 years and 2×1015 years, respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago. There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of six years; all others have half-lives under 94 days. There are also nine known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
  • 365
  • 01 Dec 2022
Biography
Juan Gualterio Roederer
Juan G. Roederer is a professor of physics emeritus at the University of Alaska Fairbanks (UAF). His research fields are space physics, psychoacoustics, science policy and information theory. He conducted pioneering research on solar cosmic rays, on the theory of earth’s radiation belts, neural networks for pitch processing, and currently on the foundations of information theory. He is also an
  • 364
  • 06 Dec 2022
Topic Review
Thermodynamics and an Introduction to Thermostatistics
Thermodynamics and an Introduction to Thermostatistics is a textbook written by Herbert Callen that explains the basics of classical thermodynamics and discusses advanced topics in both classical and quantum frameworks. The textbook contains three parts, each building upon the previous. The first edition was published in 1960 and a second followed in 1985.
  • 363
  • 22 Nov 2022
Topic Review
Lunar Regolith Penetrating Radar
An extraordinary component of this mission is the “Lunar Regolith Penetrating Radar” (LRPR) housed within its lander, which currently stands as the most advanced payload in terms of vertical resolution among all penetrating radars employed in lunar exploration.
  • 362
  • 10 Nov 2023
Topic Review
Mechanism of Surface-Enhanced Raman Spectroscopy
Raman spectroscopy is an analytical technique discovered by the Indian scientist C.V. Raman. It can be applied to analyze the molecular structure based on the molecular vibration and rotation information of scattering spectra. Benefiting from the recent advancements in material science, nanotechnology and optical technology, surface-enhanced Raman scattering (SERS) was developed and widely used in bioanalysis, clinical diagnosis and biomedical research. In SERS, Raman signals of molecules can be enhanced by six to ten orders of magnitude, owing to the electromagnetic field enhancement and chemical enhancement effects generated by nanostructures. The detection limit of SERS is even as low as the single-molecule level, so SERS is regarded as an ultrasensitive technique.
  • 362
  • 21 Mar 2023
Topic Review
Transient Reactor Test Facility (TREAT)
Coordinates: 43°41′11″N 112°45′36″W / 43.68647°N 112.75998°W / 43.68647; -112.75998 Lua error in Module:Location_map at line 522: Unable to find the specified location map definition: "Module:Location map/data/Idaho" does not exist. The Transient Reactor Test Facility (TREAT) is an air-cooled, graphite moderated, thermal spectrum test nuclear reactor designed to test reactor fuels and structural materials. Constructed in 1958, and operated from 1959 until 1994, TREAT was built to conduct transient reactor tests where the test material is subjected to neutron pulses that can simulate conditions ranging from mild transients to reactor accidents. TREAT was designed by Argonne National Laboratory, and is located at the Idaho National Laboratory. Since original construction, the facility had additions or systems upgrades in 1963, 1972, 1982, and 1988. The 1988 addition was extensive, and included upgrades of most of the instrumentation and control systems. The U.S. Department of Energy (DOE) has decided to resume a program of transient testing, and plans to invest about $75 million to restart the TREAT facility by 2018. The renewed interest in TREAT was sparked by the 2011 Fukushima Daiichi nuclear disaster, which prompted the shutdown of Japan's and Germany's nuclear plants. One use for TREAT is planned to be testing of new accident tolerant fuel for nuclear reactors. TREAT was successfully restarted in November 2017.
  • 362
  • 13 Oct 2022
Topic Review
Osmium-196
Osmium (76Os) has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotopes, 184Os, and 186Os, have extremely long half-life (1.12×1013 years and 2×1015 years, respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago. There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of six years; all others have half-lives under 94 days. There are also nine known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
  • 361
  • 10 Oct 2022
Topic Review
Mensa
Mensa is a faint constellation in the southern celestial hemisphere, first introduced by the French astronomer Nicolas Louis de Lacaille in the 18th century. It is named after the Table Mountain in South Africa.
  • 358
  • 15 Mar 2024
  • Page
  • of
  • 131
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback