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  • Liquid chromatography  (6)
  • Gas-solid chromatography  (4)
  • Chemistry  (2)
  • Quantum optics, physics of lasers, nonlinear optics, classical optics  (2)
  • Surface physics, nanoscale physics, low-dimensional systems
  • binary mixtures
  • equation of state
  • 2010-2014  (2)
  • 1980-1984  (12)
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  • 1
    Publication Date: 2014-04-03
    Description: Author(s): Alexei D. Kiselev and Dmytro O. Plutenko We study Mie scattering of Laguerre-Gaussian (LG) light beams remodelled using the method of far-field matching. The theoretical results are used to analyze the optical field in the near-field region for purely azimuthal LG beams characterized by a nonzero azimuthal mode number mLG. The morphology o... [Phys. Rev. A 89, 043803] Published Wed Apr 02, 2014
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 2
    Publication Date: 2012-04-21
    Description: Author(s): A. P. Kiselev, A. B. Plachenov, and P. Chamorro-Posada We present exact solutions of the wave equation involving an arbitrary wave form with a phase closely similar to the general astigmatic phase of paraxial wave optics. Special choices of the wave form allow general astigmatic beamlike and pulselike waves with a Gaussian-type unrestricted localization... [Phys. Rev. A 85, 043835] Published Fri Apr 20, 2012
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 3
    ISSN: 1612-1112
    Keywords: Chemical modification of silica ; Liquid chromatography ; Cardiac glycosides ; Chromatographic investigation of adsorption from solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chemical modification of silica surface using dichlorosilanes with methyl and phenyl groups and triethylamine as donor in the liquid phase was investigated. This modification leads to a dense coverage of the silica surface by the organic functional groups. Liquid chromatography permits the determination of the thermodinamic characteristics of intermolecular interactions of different molecules during adsorption from solutions on the modified surface of the silica. Silica gels modified with dichlorosilanes containing phenyl groups, possess high selectivity (α) and capacity (k′) for the cardiac glycosides G-strophanthin, K-strophanthoside, K-strophanthin-β and cymarin using water-alcohol mixture as the mobile phase, and the selectivity and capacity is much higher than observed on silica gels modified with methyl groups only.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Aromatic hydrocarbons ; Molecular structure ; Influence on retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The regularities of the retention of polymethyl- and monoalkylbenzenes on a nonpolar adsorbent (silanized silica gel) with a polar eluent (2∶3 isopropanol-water) have been studied. In contrast to the retention of the same compounds on a polar adsorbent (silica gel with hydroxylated surface) and with a nonpolar eluent (hexane) polymethylbenzenes are retained on silanized silica gel for a shorter time than the corresponding monoalkylbenzene isomers. The retention order of tert.-, sec.- and n-butylbenzenes is the reverse of that observed on silica gel having a hydroxylated surface. The retention order of xylenes, trimethyl- and tetramethylbenzenes is also the reverse of their retention order on silica gel having a hydroxylated surface. All the mixtures of the corresponding homologues and isomers have been separated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Graphitized thermal carbon black ; Thermodynamics of adsorption ; Nitrogen compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary To study the role of the nitrogen atom in various valence states in the adsorption of nitrogen-containing molecules on the surface of hydrogen-treated graphitized thermal carbon black (HGTCB) gas chromatography was applied to determine the thermodynamic characteristics of adsorption: Henry's constants and heats of adsorption at zero surface coverage of nitriles, amines and indols on HGTCB. Adsorption characteristics of nitrogen-containing organic compounds and corresponding hydrocarbons are compared. It is shown that the logarithm of the retention volume and the heat of adsorption of n-alkylamines and n-alkylnitriles linearly depend on the number of carbon atoms in the molecule and on the average polarisability of the molecule. Relationship has been established between the Henry's constant as well as the heat of adsorption and the geometry of the molecule's disposition on HGTCB surface. Examples are given for the separation of a number of amines on the basis of the geometry of their molecules.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Graphitized carbon black ; Aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper defines values of retention volumes for zero surface coverage (Henry's constant) at different temperatures, retention indices and variations of the internal energy (differential heats of adsorption) of diphenyl and its alkyl derivatives, terphenyls, diphenylmethane, triphenylmethane, diphenylethanes and fluorene on graphitized thermal carbon black (GTCB). Adsorption on GTCB takes place in accordance with the geometry of these molecules, the strongest adsorption being observed for para-terphenyl with least inhibited internal rotation of the molecule, while the weakest adsorption occurs for 2,6,2′,6′-tetramethyldiphenyl with the most inhibited internal rotation of the molecules. The flat molecules of fluorene are adsorbed on GTCB more readily than the nonflat molecules of diphenylmethane.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 143-148 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Intermolecular interactions ; Adsorption from solutions ; Chemically modified layers in LC ; Conformation of bonded chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the investigation of intermolecular interactions in adsorption from solution, which are the basis of selectivity in molecular liquid chromatography (LC), it is convenient to use the LC method itself. Using this method the Henry's constants, K1, and other thermodynamic adsorption characteristics of hydrocarbons and of a series of polar substances on hydroxylated silica surface were determined from aqueous solutions. On the basis of the adsorption of hydrocarbons from water solutions the structure of the chemically modifying layers formed by different hydrocarbon groups on the silica surface is considered. The role of conformation ability of straight-chain bonded phases is demonstrated. Hydrocarbons are adsorbed on the hydroxylated silica surface more strongly from aqueous solutions than from solutions in saturated hydrocarbons and their retention increases with the increase in the number of carbon atoms in the molecule. The retention in LC is determined by the intermolecular interaction of the solute and solvent molecules with the adsorbent, as well by the contribution of the intermolecular interaction, between the solute and the solvent. The thermodynamic characteristics of adsorption of cymarin from water-ethanol solutions on hydroxylated silica gel and on silica gel surface modified by diphenylsilyl groups is compared. The solubility of silica gel modified by diphenylsilyl groups at different composition of water-ethanol eluent at different temperatures is investigated.
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  • 8
    ISSN: 1612-1112
    Keywords: Adsorption from solutions ; Liquid chromatography ; Cardiac glycosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the cardiac glycoside cymarin as the example the application of liquid chromatography for the study of adsorption from solutions and the determination of the corresponding thermodynamic characteristics was investigated. The adsorption isotherm of cymarin at small concentrations from a water-ethanol solvent on silica gel modified by dimethyldichlorosilane was measured under static conditions using analytical LC to determine the concentrations of solutions after adsorption. The values of the Henry constants were obtained by extrapolating the slope of the adsorption isotherm down to zero concentration. The specific retention volumes for different but small sample sizes of cymarin in the chromatographic column were measured, the adsorbent and the water-ethanol eluent being the same as in the static conditions. The specific retention volume for a small (zero) sample size determined by liquid chromatography experiment coincides with the Henry constant of cymarin adsorption determined in static conditions. In favourable cases liquid chromatography can be used to determine the equilibrium constants for adsorption from solution. The dependence of the Henry constants on temperature was investigated for several cardiac glycosides. The influence of the modification of the adsorbent surface on the separation of the cardiac glycosides was also studied.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Geometric isomers ; Gas-solid chromatography ; Graphitized carbon black ; Packed capillaries ; Polycyclic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the example of perhydrophenanthrene, perhydroanthracene and cyclopentanodecalin isomers a possibility is shown to use packed capillary columns containing graphitized thermal carbon black for a complete separation of high-boiling mixtures of polycyclic saturated hydrocarbon isomers in accordance with the geometric structure of their molecules.
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  • 10
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Retention on graphitized carbon black ; Phenylcyclanes, phenyl- and biphenylalkenes and ; alkines, bicyclohexyl, bicyclohexylmethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention volume values for zero cample size (Henry's constants) at different temperatures, retention indices and differential adsorption heats of phenylethylene, phenylacetylene, C9–C12 phenylcyclanes, biphenylethylenes, biphenylacetylene, bicyclohexyl and bicyclohexylmethane have been determined on graphitized thermal carbon black (GTCB). The molecules of all these hydrocarbons are capable of internal rotation. The values of the thermodynamic adsorption characteristics of phenylcyclanes increase with increasing number of carbon atoms in the cycle. Bicyclohexyl is retained on GTCB considerably weaker than biphenyl while bicyclohexylmethane is retained stronger than biphenylmethane. Symmetric and nonsymmetric biphenylethylenes are retained much stronger than the corresponding biphenylethanes. Phenylethylene (styrene) and trans-biphenylethylene (trans-stilbene) are stronger retained on GTCB than phenylacetylene and biphenylacetylene (tolane), respectively. The relationship between the structure of these molecules and their retention on GTCB is discussed.
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