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Biography
Chih-Kung Jen
Chih-Kung Jen (Chinese: 任之恭; pinyin: Rén Zhīgōng; August 15 or October 2, 1906 – November 19, 1995) was a Chinese physicist who emigrated to the U.S. and participated in some of the 20th century's major scientific, political and social developments in both the United States and China. Born in a mud house in a remote and largely illiterate village in China, he was awarded a scholarshi
  • 471
  • 09 Dec 2022
Topic Review
Chemiluminescence Measurements of Premixed Flames Applying Abel Transform
The temperature field and chemiluminescence measurements of axisymmetric flame are obtained simultaneously in only one image. Digital Laser Speckle Displacement measures temperature fields, and direct image flame determines chemiluminescence values. Applying the Abel transform of axisymmetric objects for volume visualization requires smooth intensity profiles. Due to the nature of the experimental setup, direct image flame is corrupted with speckle noise and a crosstalk effect. These undesirable effects deteriorate the measurement results. Then, experimental data need crosstalk correction and speckle noise reduction to improve the measurements. 
  • 313
  • 29 Dec 2023
Topic Review
Chemical Reaction Rate
The reaction rate for a reactant or product in a particular reaction is defined as the amount of the chemical that is formed or removed (in moles or mass units) per unit time per unit volume. Knowledge of these rates is essential in, among other disciplines, chemical engineering and environmental engineering. Chemical kinetics is the part of physical chemistry which studies reaction rates.
  • 616
  • 28 Nov 2022
Topic Review
Chemical Ionization
Chemical ionization (CI) is a soft ionization technique used in mass spectrometry. This was first introduced by Burnaby Munson and Frank H. Field in 1966. This technique is a branch of gaseous ion-molecule chemistry. Reagent gas molecules (often methane or ammonia) are ionized by electron ionization to form reagent ions, which subsequently react with analyte molecules in the gas phase to create analyte ions for analysis by mass spectrometry. Negative chemical ionization (NCI), charge-exchange chemical ionization, atmospheric-pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) are some of the common variants of the technique. CI mass spectrometry finds general application in the identification, structure elucidation and quantitation of organic compounds as well as some utility in biochemical analysis. Samples to be analyzed must be in vapour form, or else (in the case of liquids or solids), must be vapourized before introduction into the source.
  • 742
  • 28 Nov 2022
Topic Review
Chemical Force Microscopy
In materials science, chemical force microscopy (CFM) is a variation of atomic force microscopy (AFM) which has become a versatile tool for characterization of materials surfaces. With AFM, structural morphology is probed using simple tapping or contact modes that utilize van der Waals interactions between tip and sample to maintain a constant probe deflection amplitude (constant force mode) or maintain height while measuring tip deflection (constant height mode). CFM, on the other hand, uses chemical interactions between functionalized probe tip and sample. Choice chemistry is typically gold-coated tip and surface with R–SH thiols attached, R being the functional groups of interest. CFM enables the ability to determine the chemical nature of surfaces, irrespective of their specific morphology, and facilitates studies of basic chemical bonding enthalpy and surface energy. Typically, CFM is limited by thermal vibrations within the cantilever holding the probe. This limits force measurement resolution to ~1 pN which is still very suitable considering weak COOH/CH3 interactions are ~20 pN per pair. Hydrophobicity is used as the primary example throughout this consideration of CFM, but certainly any type of bonding can be probed with this method.
  • 331
  • 23 Nov 2022
Topic Review
Chemical Beam Epitaxy
Chemical beam epitaxy (CBE) forms an important class of deposition techniques for semiconductor layer systems, especially III-V semiconductor systems. This form of epitaxial growth is performed in an ultrahigh vacuum system. The reactants are in the form of molecular beams of reactive gases, typically as the hydride or a metalorganic. The term CBE is often used interchangeably with metal-organic molecular beam epitaxy (MOMBE). The nomenclature does differentiate between the two (slightly different) processes, however. When used in the strictest sense, CBE refers to the technique in which both components are obtained from gaseous sources, while MOMBE refers to the technique in which the group III component is obtained from a gaseous source and the group V component from a solid source.
  • 643
  • 30 Nov 2022
Biography
Charles V. Shank
Charles Vernon (Chuck) Shank (born July 12, 1943) is an American physicist, best known as the director of the Lawrence Berkeley National Laboratory from 1989 to 2004. Charles Vernon (Chuck) Shank was born in Mount Holly, New Jersey, on July 12, 1943.[1][2][3] He entered the University of California, Berkeley, where he earned his Bachelor of Science (B.S.) degree in 1965, his Master of Science
  • 636
  • 29 Dec 2022
Topic Review
Charles Hard Townes Medal
The Charles Hard Townes Medal of The Optical Society is a prize for Quantum Electronics — that is to say, the physics of lasers. Awarded annually since 1981, it is named after the Nobel Prize-winning laser pioneer Charles H. Townes. Former winners include Nobel Prize laureates John L. Hall, Claude Cohen-Tannoudji, Serge Haroche, Arthur Ashkin, and Gérard Mourou.
  • 449
  • 25 Oct 2022
Topic Review
Charge
In physics, a charge is any of many different quantities, such as the electric charge in electromagnetism or the color charge in quantum chromodynamics. Charges correspond to the time-invariant generators of a symmetry group, and specifically, to the generators that commute with the Hamiltonian. Charges are often denoted by the letter Q, and so the invariance of the charge corresponds to the vanishing commutator [math]\displaystyle{ [Q,H]=0 }[/math], where H is the Hamiltonian. Thus, charges are associated with conserved quantum numbers; these are the eigenvalues q of the generator Q.
  • 596
  • 14 Oct 2022
Topic Review
Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy
The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. 
  • 647
  • 26 Jan 2022
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