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101.
Philip L. Wylie Richard J. Phillips Kenneth J. Klein Michael Q. Thompson Bruce W. Hermann 《Journal of separation science》1991,14(10):649-655
An experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment. 相似文献
102.
Tarek M. El-Gogary Mostafa A. Diab Shreen F. El-Tantawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(8):1027-1042
Summary. Equilibrium constants and molar extinction coefficients for 1:1 charge-transfer complexes between 2-hydroxyaniline (HA), 5-chloro-2-hydroxyaniline (CHA), and 4-bromo-2,6-dimethylaniline (BMA) as donors and iodine, as a typical σ-acceptor were determined spectrophotometrically in chloroform, dichloromethane, and
carbontetrachloride solutions. Spectral characteristics and formation constants are discussed in terms of donor molecular
structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data
were subjected to the form of the Rose-Drago equation for 1:1 equilibria. Electronic absorption spectra of the studied anilines were measured in different solvents. Spectral
data were reported and band maxima were assigned to the appropriate molecular orbital transitions (π–π* and n–π* electronic transition). Solvent effects on the electronic transitions were discussed. Optimized geometry of the studied anilines
was obtained at B3LYP/6-31 + G(d). The effect of the electronic factors of the substituents on the geometrical parameters
of the ring has been explored. Geometrical values of the ring deviate from the regular hexagonal ring. Intramolecular H-bonds
in HA and CHA have been computed at B3LYP/6-31 + G(d) and MP2/6-31 + G(d) levels. The H-bonding distance was calculated to be 2.105 ? in
HA and 2.127 ? in CHA.
Abstracted from her M.Sc. thesis 相似文献
103.
利用双光束电子散斑干涉法(ESPI)对试件受热变形进行了实时观测,针对一次实验过程中得到的图片较多(300~500幅)的特点,在图像处理时摒弃了以往的手动识别等位移线的办法,用MATLAB语言编写了批处理程序,能够在采集的大量散斑图片中自动快速准确地标定等位移线,得到相应的位移和应变,并结合实时测量的温度值,获得了45钢和LY12铝合金在不同温升率下的热膨胀系数及其随温度的变化。实验结果表明,在涉及的温升率范围内,温升率的改变对材料热膨胀系数的影响不明显,材料的热膨胀系数随温度的升高略有上升。 相似文献
104.
Dispersion-corrected density functional theory method was performed to report on a high-performance adsorbent for removal of CO2 from the precombustion and natural gases. At first, the effect of Al atom impurity on the structural and electronic properties of B80 fullerene is studied. Then, the adsorption geometries and energies of gases (H2, CH4, or CO2) on the B80 and AlB79 (amphoteric adsorbents) are explored. The Al atom enhances reactivity of the cage toward the gases and the adsorption processes are more exothermic with low and high energy barriers for chemisorption of H2 and CO2, respectively. Stable chemisorption of CO2 on the AlB79 is validated by the high adsorption energy and large charge transfer, while the CH4 is just physically adsorbed on the AlB79. Further, the physisorbed gases can enhance field emission current of the AlB79 and in the continuous capturing of the gases, the magnetic moment of the cage is quenched. Furthermore, dependency of the electronic structure of the adsorbent on the gas adsorption is intensively studied. We suggest that the AlB79 could be a promising material for capture, storage, and separation of the gases and as a novel material for sustainable energy and sweetening process in the petroleum industry. 相似文献
105.
V.I. Val'kov А.V. Golovchan D.V. Varyukhin V.I. Mitsiuk V.M. Ryzhkovskii 《Journal of magnetism and magnetic materials》2012
An analysis is presented of experimental and theoretical results of the MnFeAsyP1−y (0.15≤y≤0.66) and Mn2−xFexAs0.5P0.5 (0.5≤x≤1.0) systems to identify main traits that underlie the mechanism of formation of different antiferromagnetic (AF) phases in the two systems. The discrepancy between the calculated from first principles and experimental values of the magnetic moment in the ferromagnetic phase with cation substitution in the system Mn2−xFexAs0.5P0.5 is due to the appearance of a canted magnetic structure. In this case, the emergence of an AF phase with decreasing iron concentration precedes a significant change in the electronic d-band filling. In the model of the spiral structure in the system of itinerant electrons it is shown that the stabilization of the AF phase with decreasing arsenic concentration, while maintaining the number of d-electrons, is a consequence of changes in the shape of the density of electronic states that occur with a decrease in unit-cell volume. 相似文献
106.
H. DagistanliR.H. Mutlu 《Radiation Physics and Chemistry》2012,81(3):240-241
The occupation numbers of the 3d transition metals are calculated as a function of pressure by means of the linear muffin-tin-orbital method. This data is used with the multiconfiguration Dirac-Fock (MCDF) X-ray intensity ratios (R) to estimate the variation of the intensity ratios of 3d metals with pressure. It is found that R decreases with pressure for the early 3d metals whereas it increases for the heavier 3d transition metals. 相似文献
107.
Spectra of 107Ag18O and 107Ag16O molecules have been obtained in a low-pressure arc in oxygen atmosphere, and recorded with medium dispersion. Vibrational assignments for the bands of B 2π —X2π system were verified by the study of the oxygen isotope effect, and the vibrational constants were obtained for the states involved in transitions. 相似文献
108.
The interpretation of electrical resistivity measurement results of Al base alloys is critically discussed. Correct numerical data evaluation with respect to the atomistic properties rc/rp, rt and Pft/Pf is yet impossible for Al and its alloys because of the overlapping of Ic and Id recovery for those electron irradiations for which damage rate measurements exist and because of the unexplained scatter of initial damage rate data. 相似文献
109.
《Current Applied Physics》2018,18(2):200-208
The electronic structure and optical properties of La0.75Sr0.25MnO3-σ (LSMO3-σ) materials with 1 × 1 × 4 orthorhombic perovskite structure were performed by first-principles calculation. The structural changing of LSMO3 (ideal structure, σ = 0) was not obvious under generalized gradient approximation (GGA) and GGA + U arithmetic. On the contrary, the structural changing of LSMO3-σ (σ = 0.25, with oxygen vacancies defects in the z = 0, c/8, c/6, c/4, and c/2) with GGA + U were more obvious than the result of ideal. This structural distortion induced distinct changing in density of states (DOS) for LSMO3-σ materials. Oxygen vacancy defects caused a shift of the total density of states (TDOS) features toward low binding energies and LSMO3-σ keep half-metal properties as well as LSMO3 ideal structure. In addition, the hybridization between the Mn-eg and O-2p orbital was weakened and the partial density of states (PDOS) of Mn indicated a strong d-d orbital interaction. By the result of oxygen vacancy formation energy, oxygen vacancy defects can be more easily formed in La-O layers (z = 0 and c/6) to compare with other layers (z = c/8, c/4 and c/2). The calculation result of optical properties suggested that the ideal LSMO could be produced strong absorption in the range of ultraviolet and visible light, while the LSMO3-σ with oxygen vacancies defects were presented weak absorption in the range of visible light. 相似文献
110.
H. O. Di Rocco 《光谱学快报》2013,46(9):1573-1582
Screening parameters to be used in Slater Type Orbitals were obtained in analytic form. The values compared well with the numerical results given by Clementi and Roetti (after a laborious process of optimization) and with the phenomenological values of Jung and Gould. The analytic formulation is based on the splitting of the two-body operator 1/rst as the sum of effective one-body operators. 相似文献