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Topic Review
Holeum
Holeums are hypothetical stable, quantized gravitational bound states of primordial or micro black holes. Holeums were proposed by L. K. Chavda and Abhijit Chavda in 2002. They have all the properties associated with cold dark matter. Holeums are not black holes, even though they are made up of black holes.
  • 1.2K
  • 28 Sep 2022
Biography
Christopher Slowe
Christopher Brian Slowe (born November 8, 1978, Boston, MA) is an American businessman. He gained his PhD in Physics from Harvard, went on to co-found reddit, with Aaron Swartz, Alexis Ohanian and Steve Huffman. He later departed reddit and began work for Hipmunk, where he has been Chief Scientist since 2010. Slowe was awarded his Ph.D. in Physics from Harvard for his thesis "Experiments and
  • 1.2K
  • 13 Dec 2022
Topic Review
Nanoflares
A nanoflare is a very small episodic heating event which happens in the corona, the external atmosphere of the Sun. The hypothesis of small impulsive heating events as a possible explanation of the coronal heating was first suggested by Thomas Gold and then later developed and dubbed "nanoflares" by Eugene Parker. According to Parker a nanoflare arises from an event of magnetic reconnection which converts the energy stored in the solar magnetic field into the motion of the plasma. The plasma motion (thought as fluid motion) occurs at length-scales so small that it is soon damped by the turbulence and then by the viscosity. In such a way the energy is quickly converted into heat, and conducted by the free electrons along the magnetic field lines closer to the place where the nanoflare switches on. In order to heat a region of very high X-ray emission, over an area 1" x 1", a nanoflare of 1017 J should happen every 20 seconds, and 1000 nanoflares per second should occur in a large active region of 105 x 105 km2. On the basis of this theory, the emission coming from a big flare could be caused by a series of nanoflares, not observable individually. The nanoflare model has long suffered from a lack of observational evidence. Simulations predict that nanoflares produce a faint, hot (~10 MK) component of the emission measure. Unfortunately, current instruments, such as the Extreme-Ultraviolet Imaging Spectrometer on board Hinode, are not adequately sensitive to the range in which this faint emission occurs, making a confident detection impossible. Recent evidence from the EUNIS sounding rocket has provided some spectral evidence for non-flaring plasma at temperatures near 9 MK in active region cores.
  • 1.2K
  • 30 Nov 2022
Biography
Gregory Jaczko
Gregory B. Jaczko (/ˈjɑːskoʊ/; born October 29, 1970, Norristown, Pennsylvania) was a Chairman of the U.S. Nuclear Regulatory Commission (NRC). A physicist with public policy experience in academia and serving on Congressional staffs, he has been deeply interested in the development of nuclear power and its relation to the American public. On May 21, 2012, he announced his resignation pend
  • 1.1K
  • 29 Nov 2022
Topic Review
International Course-based Undergraduate Research Experiences
Course-based Undergraduate Research Experiences (CUREs) are a proven methodology for transforming short-term study abroad to yield higher impact and quality student outcomes, especially as they relate to teaching environmental sustainability.
  • 1.1K
  • 30 Dec 2020
Topic Review
Nanotechnology in Agriculture
Research has shown nanoparticles to be a groundbreaking tool for tackling many arising global issues, the agricultural industry being no exception. In general, a nanoparticle is defined as any particle where one characteristic dimension is 100nm or less. Because of their unique size, these particles begin to exhibit properties that their larger counterparts may not. Due to their scale, quantum mechanical interactions become more important than classic mechanical forces, allowing for the prevalence of unique physical and chemical properties due to their extremely high surface-to-body ratio. Properties such as cation exchange capacity, enhanced diffusion, ion adsorption, and complexation are enhanced when operating at nanoscale. This is primarily the consequence of a high proportion of atoms being present on the surface, with an increased proportion of sites operating at higher reactivities with respect to processes such as adsorption processes and electrochemical interactions. Nanoparticles are promising candidates for implementation in agriculture. Because many organic functions such as ion exchange and plant gene expression operate on small scales, nanomaterials offer a toolset that works at just the right scale to provide efficient, targeted delivery to living cells. Current areas of focus of nanotechnology development in the agricultural industry include development of environmentally conscious nanofertilizers to provide efficient ion, nutrient delivery into plant cells, and plant gene transformations to produce plants with desirable genes such as drought resistance and accelerated growth cycles. With the global population on the rise, it is necessary to make advancements in sustainable farming methods that generate higher yields in order to meet the rising food demand. However, it must be done without generating long-term consequences such as depletion of arable land or water sources, toxic runoff, or bioaccumulative toxicity. In order to meet these demands, research is being done into the incorporation of nanotechnology agriculture.
  • 1.1K
  • 08 Nov 2022
Topic Review
Operator
In physics, an operator is a function over a space of physical states onto another space of physical states. The simplest example of the utility of operators is the study of symmetry (which makes the concept of a group useful in this context). Because of this, they are very useful tools in classical mechanics. Operators are even more important in quantum mechanics, where they form an intrinsic part of the formulation of the theory.
  • 1.1K
  • 24 Nov 2022
Topic Review
ZnO Nanostructures
Zinc oxide (ZnO) nanostructures are structures with at least one dimension on the nanometre scale, composed predominantly of zinc oxide. They may be combined with other composite substances to change the chemistry, structure or function of the nanostructures in order to be used in various technologies. Many different nanostructures can be synthesised from ZnO using relatively inexpensive and simple procedures. ZnO is a semiconductor material with a wide band gap energy of 3.3eV and has the potential to be widely used on the nanoscale. ZnO nanostructures have found uses in environmental, technological and biomedical purposes including ultrafast optical functions, dye-sensitised solar cells, lithium-ion batteries, biosensors, nanolasers and supercapacitors. Research is ongoing to synthesise more productive and successful nanostructures from ZnO and other composites. ZnO nanostructures is a rapidly growing research field, with over 5000 papers published during 2014-2019.
  • 1.1K
  • 07 Nov 2022
Topic Review
Lattice Gauge Theory
In physics, lattice gauge theory is the study of gauge theories on a spacetime that has been discretized into a lattice. Gauge theories are important in particle physics, and include the prevailing theories of elementary particles: quantum electrodynamics, quantum chromodynamics (QCD) and particle physics' Standard Model. Non-perturbative gauge theory calculations in continuous spacetime formally involve evaluating an infinite-dimensional path integral, which is computationally intractable. By working on a discrete spacetime, the path integral becomes finite-dimensional, and can be evaluated by stochastic simulation techniques such as the Monte Carlo method. When the size of the lattice is taken infinitely large and its sites infinitesimally close to each other, the continuum gauge theory is recovered.
  • 1.1K
  • 25 Nov 2022
Biography
Heinrich Rubens
Heinrich Rubens (30 March 1865, Wiesbaden, Nassau, Germany – 17 July 1922, Berlin, Germany) was a German physicist. He is known for his measurements of the energy of black-body radiation which led Max Planck to the discovery of his radiation law. This was the genesis of quantum theory. After having attended realgymnasium Wöhlerschule in Frankfurt am Main, he started in 1884 to study electric
  • 1.1K
  • 09 Dec 2022
Biography
Geoffrey G. Eichholz
Geoffrey Gunther Eichholz, (June 29, 1920 – January 8, 2018) an educational leader in health physics at the Georgia Institute of Technology. Dr. Eichholz played a key role in the successful establishment of the Department of Nuclear Engineering and Health Physics. The Department has been a constant source of well-educated and well trained graduates in the field of nuclear engineering, health p
  • 1.1K
  • 27 Dec 2022
Biography
Moritz Ludwig Frankenheim
Moritz Ludwig Frankenheim (June 29, 1801 – January 14, 1869) was a German physicist, geographer, and crystallographer. Moritz Ludwig Frankenheim was born in 1801 in Brunswick. His family was Jewish.[1] He attended the Gymnasium (high school) there and in Wolfenbüttel. Afterwards he went to Berlin to attend the Alma Mater Berolinensis (today Humboldt University of Berlin) to study physics.
  • 1.1K
  • 26 Dec 2022
Topic Review
Mean Field Particle Methods
Mean field particle methods are a broad class of interacting type Monte Carlo algorithms for simulating from a sequence of probability distributions satisfying a nonlinear evolution equation. These flows of probability measures can always be interpreted as the distributions of the random states of a Markov process whose transition probabilities depends on the distributions of the current random states. A natural way to simulate these sophisticated nonlinear Markov processes is to sample a large number of copies of the process, replacing in the evolution equation the unknown distributions of the random states by the sampled empirical measures. In contrast with traditional Monte Carlo and Markov chain Monte Carlo methods these mean field particle techniques rely on sequential interacting samples. The terminology mean field reflects the fact that each of the samples (a.k.a. particles, individuals, walkers, agents, creatures, or phenotypes) interacts with the empirical measures of the process. When the size of the system tends to infinity, these random empirical measures converge to the deterministic distribution of the random states of the nonlinear Markov chain, so that the statistical interaction between particles vanishes. In other words, starting with a chaotic configuration based on independent copies of initial state of the nonlinear Markov chain model, the chaos propagates at any time horizon as the size the system tends to infinity; that is, finite blocks of particles reduces to independent copies of the nonlinear Markov process. This result is called the propagation of chaos property. The terminology "propagation of chaos" originated with the work of Mark Kac in 1976 on a colliding mean field kinetic gas model
  • 1.1K
  • 26 Oct 2022
Topic Review
Main-belt Comet
User:RMCD bot/subject notice Main-belt comets (MBCs) are bodies orbiting within the asteroid belt that have shown comet-like activity during part of their orbit. The Jet Propulsion Laboratory defines a main-belt asteroid as an asteroid with a semi-major axis (average distance from the Sun) of more than 2 AU but less than 3.2 AU, and a perihelion (closest approach distance to the Sun) of no less than 1.6 AU. David Jewitt from UCLA points out that these objects are most likely not comets with sublimating ice, but asteroids that exhibit dust activity, and hence he and others started calling these class of objects active asteroids. The first main-belt comet discovered is 7968 Elst–Pizarro. It was discovered in 1979 and was found to have a tail by Eric Elst and Guido Pizarro in 1996 and given the cometary designation 133P/Elst-Pizarro.
  • 1.1K
  • 19 Oct 2022
Topic Review
Mir EO-28
Soyuz TM-30 (Russian: Союз ТМ-30, Union TM-30), also known as Mir EO-28, was a Soyuz mission, the 39th and final human spaceflight to the Mir space station. The crew of the mission was sent by MirCorp, a privately funded company, to reactivate and repair the station. The crew also resupplied the station and boosted the station to an orbit with a low point (perigee) of 360 and a high point (apogee) of 378 kilometers (223 and 235 miles, respectively); the boost in the station's orbit was done by utilizing the engines of the Progress M1-1 and M1-2 spacecraft. At that time a transit between Mir and the International Space Station was already impossible - such a transfer was deemed undesired by NASA - and the orbital plane of ISS had been chosen some time before to be around 120 degrees away from that of Mir. The mission was the first privately funded mission to a space station. The mission was part of an effort by MirCorp to refurbish and privatize the aging Mir space station, which was nearing the end of its operational life. Further commercially funded missions beyond Soyuz TM-30 were originally planned to continue the restoration efforts of the then 14-year-old space station, but insufficient funding and investment ultimately led to the de-orbit of the station in early 2001.
  • 1.1K
  • 25 Nov 2022
Topic Review
VSOP (Planets)
The semi-analytic planetary theory VSOP (French: Variations Séculaires des Orbites Planétaires) is a mathematical model describing long-term changes (secular variation) in the orbits of the planets Mercury to Neptune. The earliest modern scientific model considered only the gravitational attraction between the Sun and each planet, with the resulting orbits being unvarying Keplerian ellipses. In reality, all the planets exert slight forces on each other, causing slow changes in the shape and orientation of these ellipses. Increasingly complex analytical models have been made of these deviations, as well as efficient and accurate numerical approximation methods. VSOP was developed and is maintained (updated with the latest data) by the scientists at the Bureau des Longitudes in Paris. The first version, VSOP82, computed only the orbital elements at any moment. An updated version, VSOP87, computed the positions of the planets directly at any moment, as well as their orbital elements with improved accuracy. At present, the difference between computational predictions and observations is so small that the model seems essentially complete in its physical principles. Such hypothetical deviations are often referred to as post-Keplerian effects.
  • 1.1K
  • 28 Nov 2022
Biography
John Boardman
Jack Melton Boardman, commonly known as John Boardman, (born September 8, 1932) is an American physicist. He is a former professor of physics at Brooklyn College; a noted science fiction fan, author and fanzine publisher; and a gaming authority. Boardman earned his B.A. at the University of Chicago in 1952 and his M.S. from Iowa State University in 1956. He then attended Florida State Univers
  • 1.1K
  • 26 Dec 2022
Biography
Richard Dronskowski
Richard Dronskowski (born 11 November 1961, in Brilon) is a German chemist and physicist. He is a full professor at the RWTH Aachen University. Dronskowski studied chemistry and physics at the University of Münster from 1981 to 1986.[1] He completed his chemistry diploma with Bernt Krebs and Arndt Simon in 1987.[1] He finished his physics diploma with Ole Krogh Andersen and Johannes Pollmann
  • 1.1K
  • 12 Dec 2022
Topic Review
Minimal Models
In theoretical physics, a minimal model or Virasoro minimal model is a two-dimensional conformal field theory whose spectrum is built from finitely many irreducible representations of the Virasoro algebra. Minimal models have been classified and solved, and found to obey an ADE classification. The term minimal model can also refer to a rational CFT based on an algebra that is larger than the Virasoro algebra, such as a W-algebra.
  • 1.1K
  • 07 Nov 2022
Topic Review
Photoacoustic Imaging Techniques
2D materials can be used as carriers for delivering therapeutic agents into a lesion, leading to phototherapy. Various optical imaging techniques have been used for the monitoring of the treatment process. 
  • 1.0K
  • 21 Feb 2021
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