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Topic Review
Materials for Chemical Sensing
The ability to measure and monitor the concentration of specific chemical and/or gaseous species (i.e., “analytes”) is the main requirement in many fields, including industrial processes, medical applications, and workplace safety management. As a consequence, several kinds of sensors have been developed in the modern era according to some practical guidelines that regard the characteristics of the active (sensing) materials on which the sensor devices are based. These characteristics include the cost-effectiveness of the materials’ manufacturing, the sensitivity to analytes, the material stability, and the possibility of exploiting them for low-cost and portable devices. Consequently, many gas sensors employ well-defined transduction methods, the most popular being the oxidation (or reduction) of the analyte in an electrochemical reactor, optical techniques, and chemiresistive responses to gas adsorption. Many of the efforts devoted to improving these methods have been directed towards the use of certain classes of specific materials.
  • 564
  • 26 Aug 2022
Topic Review
Materials Science, Glasses
Glasses are solid amorphous materials which transform into liquids upon heating through the glass transition. The International Commission on Glass defines glass as a state of matter, usually produced when a viscous molten material is cooled rapidly to below its glass transition temperature, with insufficient time for a regular crystal lattice to form. The solid-like behaviour of glasses is separated from the liquid-like behaviour at higher temperatures by the glass transition temperature, Tg. The IUPAC Compendium on Chemical Terminology defines glass transition as a second order transition in which a supercooled melt yields, on cooling, a glassy structure. It states that below the glass-transition temperature the physical properties of glasses vary in a manner similar to those of the crystalline phase. Moreover, it is deemed that the bonding structure of glasses has the same symmetry signature in terms of Hausdorff-Besikovitch dimensionality of chemical bonds as for the crystalline materials. 
  • 3.3K
  • 09 May 2024
Topic Review
Mathematical and Logical Realism
According to Balaguer, only two views of the metaphysics of mathematics manage to adequately answer all objections: these are Platonic set theory (as a form of realism) and fictionalism (as a form of anti-realism). Balaguer takes a relatively reserved stance towards the dilemma that one of these two perspectives is correct through three epistemic conclusions: (a) there is no reason to believe or not believe in abstract mathematical objects, (b) it can never in principle have a reason to believe or not believe in abstract mathematical objects, or (c) there is no material fact that could determine between Platonic set theory and fictionalism, although both adequately answer all objections (except, in a way, the question of proving the existence of abstract mathematical objects). The first key question that divides the metaphysics of mathematics into two domains, is the question of whether mathematical theories represent truthful descriptions of some real part of the world. Realistic theories answer affirmatively, while anti-realistic theories answer negatively, claiming that mathematics has no ontology, or that its concepts are objectively empty. The question further divides the realist camp into two groups and is “are mathematical objects spatiotemporal?”. Platonic set theory answers negatively, while anti-Platonism answers affirmatively. The question further divides anti-Platonism into psychologism and physicalism and reads: “what is the nature of mathematical spatiotemporal objects?”. According to psychologism, the objects in question are mental objects, or mathematical statements represent truthful descriptions of mental objects, while according to physicalism, the subject of mathematical statements is non-mental parts of physical reality.
  • 213
  • 17 Nov 2023
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
  • 369
  • 26 Oct 2022
Topic Review
Mean Field Theory
In physics and probability theory, mean-field theory (aka MFT or rarely self-consistent field theory) studies the behavior of high-dimensional random (stochastic) models by studying a simpler model that approximates the original by averaging over degrees of freedom. Such models consider many individual components that interact with each other. In MFT, the effect of all the other individuals on any given individual is approximated by a single averaged effect, thus reducing a many-body problem to a one-body problem. The main idea of MFT is to replace all interactions to any one body with an average or effective interaction, sometimes called a molecular field. This reduces any multi-body problem into an effective one-body problem. The ease of solving MFT problems means that some insight into the behavior of the system can be obtained at a lower computational cost. MFT has since been applied to a wide range of fields outside of physics, including statistical inference, graphical models, neuroscience, artificial intelligence, epidemic models, queueing theory, computer network performance and game theory, as in the Quantal response equilibrium.
  • 3.1K
  • 03 Nov 2022
Topic Review
Meanings of Minor Planet Names: 1–1000
As minor planet discoveries are confirmed, they are given a permanent number by the IAU's Minor Planet Center (MPC), and the discoverers can then submit names for them, following the IAU's naming conventions. The list below concerns those minor planets in the specified number-range that have received names, and explains the meanings of those names. Official naming citations of newly named small Solar System bodies are published in MPC's Minor Planet Circulars several times a year. Recent citations can also be found on the JPL Small-Body Database (SBDB). Until his death in 2016, German astronomer Lutz D. Schmadel compiled these citations into the Dictionary of Minor Planet Names (DMP) and regularly updated the collection. Based on Paul Herget's The Names of the Minor Planets, Schmadel also researched the unclear origin of numerous asteroids, most of which had been named prior to World War II.  This article incorporates public domain material from the United States Government document "SBDB". New namings may only be added after official publication as the preannouncement of names is condemned by the Committee on Small Body Nomenclature.
  • 1.4K
  • 25 Oct 2022
Topic Review
Measurement of Compact Muon Solenoid Magnetic Field
The Compact Muon Solenoid (CMS) is a general-purpose detector at the Large Hadron Collider. The goal of CMS experiment is to investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter. The CMS magnetic field is provided by a wide-aperture superconducting thin solenoid with a diameter of 6 m and a length of 12.5 m, where a central magnetic flux density of 3.8 T is created by an operational direct current of 18.164 kA.
  • 998
  • 15 Feb 2022
Topic Review
Mechanical Properties of BCC-Structured High-Entropy Alloys
A new metallurgical strategy was introduced to develop advanced materials with outstanding performance—high-entropy alloys (HEAs). Today, HEAs contain five or more multiple principle metallic elements in equal or near-equal atomic percentages. HEAs’ four core effects—high configurational entropy, sluggish diffusion, severe lattice distortion, and the cock-tail effect—are mainly responsible for their various physical and mechanical properties. HEAs present promising properties, such as high strength and fracture toughness at room temperature and high temperatures and have excellent wear resistance, and corrosion resistance, along with high-temperature oxidation.
  • 2.0K
  • 28 Mar 2022
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.
  • 318
  • 21 Mar 2023
Topic Review
Mechanisms of Co-Evolution of Wheat and Rust Pathogens
Wheat (Triticum spp.) is a cereal crop domesticated >8000 years ago and the second-most-consumed food crop nowadays. Ever since mankind has written records, cereal rust diseases have been a painful awareness in antiquity documented in the Old Testament (about 750 B.C.). The pathogen causing the wheat stem rust disease is among the first identified plant pathogens in the 1700s, suggesting that wheat and rust pathogens have co-existed for thousands of years. With advanced molecular technologies, wheat and rust genomes have been sequenced, and interactions between the host and the rust pathogens have been extensively studied at molecular levels.
  • 330
  • 08 Jun 2023
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