排序方式: 共有40条查询结果,搜索用时 31 毫秒
21.
Teague M. McGinitie Bryan R. KarolatCurtis Whale James J. Harynuk 《Journal of chromatography. A》2011,1218(21):3241-3246
We present an investigation into the influence of carrier gas on the thermodynamics governing a capillary gas chromatographic separation. Thermodynamic parameters are estimated for a series of alkanes and alcohols on three common stationary phases using helium, hydrogen, and nitrogen carrier gases. It is shown that the substitution of carrier gases for one another results in a change in the thermodynamic parameters governing the separation. The effect of the carrier gas on the thermodynamic parameters is large enough to compromise the accuracy of the retention time calculations based on thermodynamic parameters collected in a carrier gas other than the one actually in use in a specific gas chromatographic system. A possible kinetic explanation for these observations is also investigated. 相似文献
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Teague ML Drayna GK Lockhart GP Cheng P Shen B Wen HH Yeh NC 《Physical review letters》2011,106(8):087004
Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering. 相似文献
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Jing Zhang King-Wai Chu Ella B. Teague Randall E. Newmark Monte S. Buchsbaum 《Magnetic resonance imaging》2013
Functional magnetic resonance imaging (fMRI) studies have shown dysfunction in key areas associated with the thalamocortical circuit in patients with schizophrenia. This study examined the functional connectivity involving the frontal-thalamic circuitry during a spatial focusing-of-attention task in 18 unmedicated patients with schizophrenia and 38 healthy controls. Functional connectivity was analyzed by assigning seed regions (in the thalamic nuclei (mediodorsal nucleus (MDN), pulvinar, anterior nucleus (AN)), the dorsolateral prefrontal cortex (Brodmann areas 9 and 46), and the caudate), and correlating their respective activity with that in the non-seed regions voxel-wise. Functional connectivity analysis demonstrated that functional connectivity was significantly impaired in patients, e.g., between the right pulvinar and regions such as the prefrontal and temporal cortices and the cerebellum. On the other hand, enhanced functional connectivity was found in patients e.g., between the AN and regions such as the prefrontal and temporal cortices. In addition, the patients had significantly lower task performance and less (but non-significant) brain activation than those of controls. These results revealed disturbed functional integration in schizophrenia, and suggested that the functional connectivity abnormalities in the thalamocortical circuitry, especially the frontal-thalamic circuitry, may underlie the attention deficits in schizophrenia patients. Further, this study suggested that functional connectivity analysis might be more sensitive than brain activation analysis in detecting the functional abnormalities in schizophrenia. 相似文献
24.
B.-L. Yu J.C.F. Wang A.D. Beyer M.L. Teague G.P. Lockhart J.S.A. Horng S.-P. Lee N.-C. Yeh 《Solid State Communications》2009,149(7-8):261-265
We investigate the scenario of competing order (CO) induced Fermi arcs and pseudogap in cuprate superconductors. For hole-type cuprates, both phenomena as functions of temperature and doping level can be accounted for if the CO vanishes at above the superconducting transition and the CO wave-vector Q is parallel to the antinodal direction. In contrast, the absence of these phenomena and the non-monotonic -wave gap in electron-type cuprates may be attributed to and a CO wave-vector Q parallel to the nodal direction. 相似文献
25.
Frank S. Pullen George L. Perkins Keith I. Burton Richard S. Ware Mathew S. Teague Jeffrey P. Kiplinger 《Journal of the American Society for Mass Spectrometry》1995,6(5):394-399
The ease of use of the newer liquid chromatography-mass spectrometry interfaces has made possible the automated acquisition of spectra from large batch queues of samples. This fact, combined with the realization that unit molecular mass determination was the only datum desired by a majority of drug discovery synthetic chemists, led us to develop open access mass spectrometry in the early 1990s. Open access spectrometers now scan over 100,000 samples per year from synthesis laboratories at Pfizer. Our experiences with this novel use of mass spectrometry in a large research facility are discussed and we detail some of the pitfalls we believe to be common to this approach. In addition, we offer some reflection on the cultural changes we have observed in our research environment since this experiment began. 相似文献
26.
The efficient self-assembly and functional characterization of arrays containing multiple types of chromophores will provide a basis for the design and applications of functional photonic materials that are unobtainable using only one type of molecule. The design, synthesis, and characterization of supramolecular systems bearing two different types of porphyrinic chromophores, porphyrins and porphyrazines, are reported. Because the porphyrins and porphyrazines bear different exocyclic ligands for self-assembly by metal ion coordination, these systems require new supramolecular synthetic strategies wherein reactants are added in a specific order. These arrays display unique photophysical properties derived from the component chromophores, the metal geometry, and the supramolecular nanoarchitecture. 相似文献
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An asymptotic solution for large spacing is obtained in the problem of diffraction by an aperture between two conducting wedges. The variation of the wedge angles is shown to have significant effect on the far field amplitude of the transmitted field in certain ranges of angle forE-polarization. The wedge angles are seen to have a greater effect than interaction corrections in some cases but a lesser effect in others. Numerical comparisons are carried out. 相似文献
30.
A total synthesis of (11), the 8-epimer of Δ9(12)-capnellene-8β,10α-diol (1,RH) found in the soft coral is described. 相似文献