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Topic Review
Udwadia–Kalaba Equation
In theoretical physics, the Udwadia–Kalaba equation is a method for deriving the equations of motion of a constrained mechanical system. The equation was first described by Firdaus E. Udwadia and Robert E. Kalaba in 1992. The approach is based on Gauss's principle of least constraint. The Udwadia–Kalaba equation applies to both holonomic constraints and nonholonomic constraints, as long as they are linear with respect to the accelerations. The equation generalizes to constraint forces that do not obey D'Alembert's principle.
  • 561
  • 14 Oct 2022
Topic Review
Plasmonic Photothermal Therapy
The laser application for hyperthermia makes it possible to obtain managed thermal damage of tumor tissue. However, the small spatial selectivity of tumor tissue heating remains a problem of laser hyperthermia. The development of innovative nanoparticle-based technologies to improve the selectivity of laser heating is intensively pursued, and various types of plasmon resonance nanoparticles are used for this purpose, as follows: nanospheres nanoshells, nanorods, nanocages. Plasmonic photothermal therapy is referred to by the acronym PPT.
  • 559
  • 11 Mar 2022
Topic Review
High-Precision Trace Hydrogen Sensing
Despite its growing importance in the energy generation and storage industry, the detection of hydrogen in trace concentrations remains challenging, as established optical absorption methods are ineffective in probing homonuclear diatomics. Besides indirect detection approaches using, e.g., chemically sensitized microdevices, Raman scattering has shown promise as an alternative direct method of unambiguous hydrogen chemical fingerprinting. 
  • 559
  • 13 Jun 2023
Topic Review
X-ray Absorption Near Edge Structure
X-ray absorption near edge structure (XANES), also known as near edge X-ray absorption fine structure (NEXAFS), is a type of absorption spectroscopy that indicates the features in the X-ray absorption spectra (XAS) of condensed matter due to the photoabsorption cross section for electronic transitions from an atomic core level to final states in the energy region of 50–100 eV above the selected atomic core level ionization energy, where the wavelength of the photoelectron is larger than the interatomic distance between the absorbing atom and its first neighbour atoms.
  • 559
  • 18 Oct 2022
Topic Review
Metasurface Photodetectors
Photodetectors are the essential building blocks of a wide range of optical systems. Typical photodetectors only convert the intensity of light electrical output signals, leaving other electromagnetic parameters, such as the frequencies, phases, and polarization states unresolved. 
  • 559
  • 26 Jan 2022
Topic Review
Coronagraph
A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view the corona of the Sun, but a new class of conceptually similar instruments (called stellar coronagraphs to distinguish them from solar coronagraphs) are being used to find extrasolar planets and circumstellar disks around nearby stars as well as host galaxies in quasars and other similar objects with active galactic nuclei (AGN).
  • 558
  • 23 Nov 2022
Biography
David Carroll
David Carroll (born January 13, 1963) is a U.S. physicist, materials scientist and nanotechnologist, Fellow of the American Physical Society, and director of the Center for Nanotechnology and Molecular Materials at Wake Forest University.[1] He has contributed to the field of nanoscience and nanotechnology through his work in nanoengineered cancer therapeutics, nanocomposite-based display and li
  • 557
  • 29 Dec 2022
Topic Review
Stress Measures
The most commonly used measure of stress is the Cauchy stress tensor, often called simply the stress tensor or "true stress". However, several other measures of stress can be defined. Some such stress measures that are widely used in continuum mechanics, particularly in the computational context, are: The Kirchhoff stress (τ). The Nominal stress (N). The first Piola-Kirchhoff stress (P). This stress tensor is the transpose of the nominal stress (P=NT). The second Piola-Kirchhoff stress or PK2 stress (S). The Biot stress (T).
  • 556
  • 06 Dec 2022
Topic Review
Intermetallic Quasicrystals
A quasicrystal is the natural extension of the notion of a crystal to structures with quasiperiodic, rather than periodic, translational order. Intermetallic quasicrystals are a class of quasiperiodically ordered solids made of typical metallic atoms, though they do not exhibit the physical properties that usually signal the presence of metallic bonding, and their electrical and thermal transport properties resemble a more semiconductor-like than metallic character. The distribution of atoms throughout the space in these compounds exhibits a characteristic self-similar, scale invariant symmetry, based on a hierarchy of nested atomic clusters.
  • 554
  • 10 Jan 2022
Topic Review
Standard Electrode Potential
In electrochemistry, standard electrode potential [math]\displaystyle{ E^\ominus }[/math], or [math]\displaystyle{ E^\ominus_{red} }[/math], is a measure of the reducing power of any element or compound. The IUPAC "Gold Book" defines it as: "the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode".
  • 554
  • 06 Oct 2022
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