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81.
Dempsey LP Murray C Cleary PA Lester MI 《Physical chemistry chemical physics : PCCP》2008,10(10):1424-1432
A pump-probe laser-induced fluorescence technique has been used to examine the nascent OH X (2)Pi product state distribution arising from non-reactive quenching of electronically excited OH A (2)Sigma(+) by molecular hydrogen and deuterium under single-collision conditions. The OH X (2)Pi products were detected in v'=0, 1 and 2; the distribution peaks in v'=0 and decreases monotonically with increasing vibrational excitation. In all vibrational levels probed, the OH X (2)Pi products are found to be highly rotationally excited, the distribution peaking at N'=15 when H(2) was used as the collision partner and N'=17 for D(2). A marked propensity for production of Pi(A') Lambda-doublet levels was observed, while both OH X (2)Pi spin-orbit manifolds were equally populated. These observations are interpreted as dynamical signatures of the nonadiabatic passage of the OH + H(2)/D(2) system through the seams of conical intersection that couple the excited state (2 (2)A') and ground state (1 (2)A') surfaces. 相似文献
82.
Calculations based on the Mie theory are performed to determine the locally enhanced electric fields due to whispering-gallery mode resonances for dielectric microspheres, with emphasis on electromagnetic "hot spots" that are located along the wavevector direction on the surface of the sphere. The local electric field enhancement associated with these hot spots is used to determine the surface enhanced Raman scattering enhancement factors for a molecule, here treated as a classical dipole, located near the surface of the sphere. Both incident and Raman emission enhancements are calculated accurately using an extension of the Mie theory that includes interaction of the Raman dipole field with the sphere. The enhancement factors are calculated for dielectric spheres in vacuum with a refractive index of 1.9 and radii of 5, 10, and 20 microm and for wavelengths that span the visible spectrum. Maximum Raman scattering enhancement factors on the order of 10(3)-10(4) are found at locations slightly off the propagation axis when the incident excitation but not the Stokes-shifted radiation is coincident with a whispering-gallery mode resonance. The enhancement factors are found to vary inversely with the resonance width, and this determines the influence of the mode number and order on the results. Additional calculations are performed for the case where the Stokes-shifted radiation is also on-resonance and Raman enhancement factors as large as 10(8) are found. These enhancement factors are typically a factor of 10(2) smaller than would be obtained from /E/4 enhancement estimates, as enhancement of the Raman dipole emission is significantly reduced compared to the local field enhancement for micron size particles or larger. Conditions under which single-molecule or few-molecule measurements are feasible are identified. 相似文献
83.
Renfrow MB Mackay CL Chalmers MJ Julian BA Mestecky J Kilian M Poulsen K Emmett MR Marshall AG Novak J 《Analytical and bioanalytical chemistry》2007,389(5):1397-1407
IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis. In IgAN, IgA1 molecules with incompletely galactosylated
O-linked glycans in the hinge region (HR) are present in mesangial immunodeposits and in circulating immune complexes. It is
not known whether the galactose deficiency in IgA1 proteins occurs randomly or preferentially at specific sites. We have previously
demonstrated the first direct localization of multiple O-glycosylation sites on a single IgA1 myeloma protein by use of activated ion-electron capture dissociation (AI-ECD) Fourier
transform ion cyclotron resonance (FT-ICR) tandem mass spectrometry. Here, we report the analysis of IgA1 O-glycan heterogeneity by use of FT-ICR MS and liquid chromatography FT-ICR MS to obtain unbiased accurate mass profiles of
IgA1 HR glycopeptides from three different IgA1 myeloma proteins. Additionally, we report the first AI-ECD fragmentation on
an individual IgA1 O-glycopeptide from an IgA1 HR preparation that is reproducible for each IgA1 myeloma protein. These results suggest that future
analysis of IgA1 HR from IgAN patients and normal healthy controls should be feasible. 相似文献
84.
Dana Bartošová Klaas Pieter Hart Logan C. Hoehn 《Topology and its Applications》2011,158(18):2479-2484
We show that Lelek?s problem on the chainability of continua with span zero is not a metric problem: from a non-metric counterexample one can construct a metric one. 相似文献
85.
We propose a complementary interpretation of the mechanism responsible for the strong enhancement observed in surface enhanced raman scattering (SERS). The effect of a strong static local electric field due to the Schottky barrier at the metal-molecule junction on SERS is systematically investigated. The study provides a viable explanation to the low repeatability of SERS experiments as well as the Raman peak shifts as observed in SERS and raw Raman spectra. It was found that a strong electrostatic built-in field at the metal-molecule junction along specific orientations can result in 2-4 more orders of enhancement in SERS. 相似文献
86.
Zhida Xu Manas R. Gartia Charles J. Choi Jing Jiang Yi Chen Brian T. Cunningham Gang Logan Liu 《Journal of Raman spectroscopy : JRS》2011,42(11):1939-1944
Anomalous surface‐enhanced Raman scattering (SERS) peaks were identified for liquid sample stored in polypropylene (PP) centrifuge tubes for months. We observed unexpected Raman peaks during experiments with thiamine hydrochloride aqueous solutions stored in PP tubes for 2 months. In order to identify the contaminants, we have performed SERS experiments on deionized (DI) water stored in PP centrifuge tubes for 2 months and compared them with those from fresh DI water sample. We have also carried out ultraviolet (UV) absorption spectra for both fresh and contaminated water. We believe that the water is contaminated because of chemicals leaching from the PP tube. From the gas chromatography‐mass spectrometry data, the main contaminants were found to be phthalic acid (PA) and its derivatives. Further SERS and UV absorption experiment for PA correlated well with the anomalous peaks identified earlier. We qualitatively confirmed the identification and quantitatively estimated the concentration of the suspect contaminants as between 1 and 10 µM with both SERS and UV absorption spectroscopy. With UV absorption spectroscopy, we precisely estimated the concentration as 2.1 µM . We have shown that the sample in PP tube can be contaminated by the leaching chemicals upon long‐term storage, and suggest SERS and UV absorption spectroscopy as two quick and simple techniques to detect the contamination. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
87.
We consider the non-Fermi-liquid quantum critical state of the spin-S two-impurity Kondo model and its potential realization in a quantum dot device. Using conformal field theory and the numerical renormalization group, we show the critical point to be identical to that of the two-channel Kondo model with additional potential scattering, for any spin S. Distinct conductance signatures are shown to arise as a function of device asymmetry, with the square-root behavior commonly believed to arise at low-energies dominant only in certain regimes. 相似文献
88.
Hyperpolarization of Nitrogen‐15 Schiff Bases by Reversible Exchange Catalysis with para‐Hydrogen
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Dr. Angus W. J. Logan Prof. Thomas Theis Dr. Johannes F. P. Colell Prof. Warren S. Warren Prof. Steven J. Malcolmson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10777-10781
NMR with thermal polarization requires relatively concentrated samples, particularly for nuclei with low abundance and low gyromagnetic ratios, such as 15N. We expand the substrate scope of SABRE, a recently introduced hyperpolarization method, to allow access to 15N‐enriched Schiff bases. These substrates show fractional 15N polarization levels of up to 2 % while having only minimal 1H enhancements. 相似文献
89.
Zhang Chuanlun Liu Shi Logan John Mazumder Raja Phelps Tommy J. 《Applied biochemistry and biotechnology》1996,57(1):923-932
Applied Biochemistry and Biotechnology - An unusual thermophilic bacterium has been isolated from deep subsurface sediments and tested for its ability to enhance Fe(III), Co(III), and Cr(VI)... 相似文献
90.