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151.
Digrazia Philip M. Blackburn James W. Bienkowski Paul R. Hilton Barry Reed Gregory D. King J. M. Henry Sayler Gary S. 《Applied biochemistry and biotechnology》1990,(1):237-252
An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading
mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis
tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating
the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables
and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow
differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to
system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the
two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure
of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption,
and biodegradation of napththalene. 相似文献
152.
We measured FT-IR spectra of intact Acholeplasma laidlawii cells grown at 37 °C on palmitic acid (C16:0) or on binary palmitic acid-d31/oleic acid (C16:0-d31/C18:1(9)) at an initial mole ratio of 2:3, which have been previously reported to produce significant fluctuations in CH2 symmetric stretching (νsCH2) and CD2 asymmetric stretching (νaCD2) frequencies (Biochim. Biophys. Acta 1279 (1996) 49). Time courses for acyl chain νsCH2 and νaCD2 frequencies determined from fourth derivative spectra are presented. Fluctuations were detected with the C16:0 enriched cells at temperatures above 40 °C as well as with the cells enriched in 2:3 C16:0-d31/C18:1(9). These observations at temperatures above 40 °C for the C16:0 enriched cells were not in agreement with the conclusion in the previous work by Moore et al. Our results have suggested that the 2850 cm−1 νsCH2 band comprises two components arising from trans and gauche conformations, and that the fluctuations in νsCH2 frequency are caused by random temporal changes in the relative intensities of these two components. 相似文献
153.
The field constant of the NQR frequency of a chlorine atom (35Cl) in a series of arsenic derivatives [R1R2R3AsCl]+M− was estimated from correlations. The field frequency is ∼41.5±3.5 Hz cm kV−1, which is nearly twice as much as that in analogous phosphorus compounds.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1758–1760, August, 2005. 相似文献
154.
Denis J. Evans 《Journal of statistical physics》1980,22(1):81-90
Nonequilibrium molecular dynamics is used to calculate the spectrum of shear viscosity for a Lennard-Jones fluid. The calculated zero-frequency shear viscosity agrees well with experimental argon results for the two state points considered. The low-frequency behavior of shear viscosity is dominated by an
1/2 cusp. Analysis of the form of this cusp reveals that the stress-stress time correlation function exhibits at
–3/2 long-time tail. It is shown that for the state points studied, the amplitude of this long-time tail is between 12 and 150 times larger than what has been predicted theoretically. If the low-frequency results are truly asymptotic, they imply that the cross and potential contributions to the Kubo-Green integrand for shear viscosity exhibit at
–3/2 long-time tail. This result contradicts the established theory of such processes. 相似文献
155.
Garth J Simpson 《Chemphyschem》2004,5(9):1301-1310
Recent observations of remarkably large chiroptical effects in second-harmonic generation (SHG) and sum-frequency generation (SFG) measurements suggest exciting possibilities for the development of new chiral-specific spectroscopies and novel chiral materials for nonlinear optics. Several fundamental studies designed to elucidate the molecular and macromolecular origins of the chiral responses are reviewed to provide a framework for development of this emerging field. In general, the chiral activity in SHG and SFG has the potential to arise from complex interactions between hosts of different competing effects. Fortunately, relatively simple electric dipole-allowed mechanisms routinely dominate the nonlinear optical chiral activities of most practical systemsexpressions can often be generated to link the. This substantial reduction in complexity allows for the development of simple models connecting the macroscopic nonlinear optical response to intuitive molecular and supramolecular properties. 相似文献
156.
超拉伸聚乙烯的弹性模量和导热性能 总被引:8,自引:0,他引:8
为了揭示聚合物分子链伸展、取向的本征特性,发展了两个新的测量方法和实验装置,用于研究拉伸比高达200的超拉伸聚乙烯凝胶的弹性性能、传热性能和聚合物结构的关系.应用激光脉冲热致超声法给出材料拉伸方向和横向杨氏模量,应用激光脉冲光热辐射法给出拉伸方向,横向和厚度方向的导热系数.随拉伸比λ的增加,轴向杨氏模量急剧的增加,而横向的仅有少许减小.导热系数具有相似的特性.本文发现当λ=200时,这种拉伸取向聚乙烯的轴向模量可达钢的80%,而导热系数甚至可达2倍,直至成为热的良导体,这是由于在高拉伸比时形成了相当数量的伸展分子链构成的针状晶体———晶桥.本文提出晶桥作为短纤维分散相的取向聚合物的结构模型,对于超拉伸聚乙烯的上述特性可以进行统一描述和定量化分析,和实验结果很好符合. 相似文献
157.
Ab initio calculations ofp-dichlorobenzene molecule were carried out using the Hartree-Fock method in the 6–31 G* valence-split basis set. The molecule was also calculated by the MNDO method in the valence sp-basis set for comparison. The populations of the valent p-orbitals of the C and CI atoms were analyzed. The optimized geometry of the molecule as well as its35Cl NQR frequency and the asymmetry parameter of the electric field gradient at the35CI nuclei calculated using the populations of the less diffuse components of the valent p-orbitals of the Cl atoms are in agreement with the corresponding experimental values for the -modification of 1,4-Cl2C6H4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2177–2179, September, 1996. 相似文献
158.
J. Franzke R.W. Fox L. Hollberg 《Spectrochimica Acta Part B: Atomic Spectroscopy》1998,53(14):1951-1955
High resolution atomic absorption measurements of lead at 283 nm in a vapor cell were performed by frequency doubling an 850 nm laser diode to obtain 425 nm light, followed by sum frequency generation of the harmonic radiation with a second 850 nm laser diode. 相似文献
159.
Sh. Sh. Nabiev I. I. Ostroukhova N. V. Revina L. P. Sukhanov 《Russian Chemical Bulletin》1998,47(3):417-422
The Raman spectra of ClOF2
+ cation in solutions of anhydrous HF were studied. In the ClOF2
+HF2
− and ClOF2
+BF4
−−HF systems, this cation exists as a pyramidal structure (C
s
symmetry), while in the ClOF2
+AuF6
−−HF system, it exists as a planar structure (C
2v
symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the
structure of the ClOF2
+ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and
rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution
to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998. 相似文献
160.
采用从头计算HF, MP2方法和密度泛函理论, 对Au(II)系列化合物[Au(CH2)2PH2]2X2 (X=F, Cl, Br, I)的几何结构、电子结构和振动频率进行了研究. 研究表明Au的5d和6s电子参与Au—Au以及Au—X之间的成键. Au—Au, Au—X键强烈的电子相关作用使HF方法不适于该体系的研究, BP86和B3LYP两种泛函给出较大的Au—Au和Au—X键长, 而MP2方法和局域的密度泛函方法则给出了合理的结构参数. 局域密度泛函方法计算得到的Au—Au键和
Au—X键振动频率也与实验数据符合较好. 还运用含时密度泛函理论计算了[Au(CH2)2PH2]2X2的电子激发能, 对分子在紫外-可见光谱范围内的电子跃迁进行了分析, 考察了卤素配体对激发能的影响, 并结合分子轨道能级的变化对此给予了解释. 相似文献