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11.
David J. Rousell Sucharita M. Dutta Mark W. Little Kermit K. Murray 《Journal of mass spectrometry : JMS》2004,39(10):1182-1189
Infrared soft laser desorption/ionization was performed using a 2.94 µm Er : YAG laser and a commercial reflectron time-of-flight mass spectrometer. The instrument was modified so that a 337 nm nitrogen laser could be used concurrently with the IR laser to interrogate samples. Matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization and desorption/ionization on silicon with UV and IR lasers were compared. Various target materials were tested for IR soft desorption ionization, including stainless steel, aluminum, copper, silicon, porous silicon and polyethylene. Silicon surfaces gave the best performance in terms of signal level and low-mass interference. The internal energy resultant of the desorption/ionization was assessed using the easily fragmented vitamin B12 molecule. IR ionization produced more analyte fragmentation than UV-MALDI analysis. Fragmentation from matrix-free IR desorption from silicon was comparable to that from IR-MALDI. The results are interpreted as soft laser desorption and ionization resulting from the absorption of the IR laser energy by the analyte and associated solvent molecules. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Photonic crystals fabricated from the colloidal spheres of polymethyl methacrylate (PMMA) using the inward-growing self-assembly
technique were subsequently in-filled with zinc oxide (ZnO) prepared by the sol-gel process. The polymer template was removed
by heat treatment and chemical method to get ZnO-inverse photonic crystal. The structural quality of the inverse photonic
crystal obtained by the chemical method was found to be superior to that obtained by heat treatment. The ZnO-inverse photonic
crystal obtained by the chemical method was further treated at an elevated temperature to ensure the crystalline nature of
ZnO. Laser-induced emission studies on ZnO-inverse photonic crystals were carried out at an excitation wavelength of 325 nm.
The emission spectra showing UV and visible bands at collection angle of 45° from the direction of excitation helped to establish
the role of crystalline ZnO. 相似文献
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Govindaswami Ragupathi Susan F. Slovin Sucharita Adluri Dalibor Sames In Jong Kim Hyunjin M. Kim Maria Spassova William G. Bornmann Kenneth O. Lloyd Howard I. Scher Philip O. Livingston Samuel J. Danishefsky 《Angewandte Chemie (International ed. in English)》1999,38(4):563-566
Human trials on the globo H carbohydrate vaccine (see picture, KLH=the carrier protein keyhole limpet hemocyanin) show that it produces strong IgM, and in some cases IgG, responses in patients with progressive and recurrent prostate cancer. Furthermore, these antibodies not only recognize synthetic antigens, but also globo H‐positive tumors in biopsy extracts and tumor tissues. 相似文献
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Sucharita Banerjee Jonathan A. Groeper Jean M. Standard Shawn R. Hitchcock 《Tetrahedron: Asymmetry》2009,20(18):2154-2161
N-Pyridylmethyl-substituted Ephedra derivatives were synthesized by either direct alkylation or reductive alkylation of (1R,2S)-norephedrine, (1S,2S)-pseudo norephedrine, and (1R,2S)-ephedrine. These derivatives were then employed in asymmetric addition reactions with diethylzinc and aldehydes and diphenylphosphinoylimines. The use of the diastereomers from the Ephedra family allowed for a systematic evaluation of the contribution of the N-pyridylmethyl. 相似文献
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This paper reports the imaging characteristics of an optical system consisting of a lens made of a uniaxial birefringent crystal sandwiched between two linear polarizers under polychromatic input illumination. The optic axis of the birefringent crystal is perpendicular to the lens axis and for an initial investigation, the spectral profile of the input beam is considered to be uniform for all wavelengths. The study reveals that if the variation of the birefringence parameters of the device with the wavelength is less, a larger bandwidth may be used without considerably deviating from the imaging characteristics under strictly monochromatic illumination. The nonlinear variation of birefringence with wavelength results in an asymmetric axial irradiance distribution. This obviates an optimal operating wavelength as well as a proper choice of the lens material. It is found that no appreciable change in image quality under diffraction-limited condition results for an input beam having 632 nm operating wavelength and 60 nm bandwidth. Therefore, it may be feasible to use this system with a white light source in conjunction with a wavelength-selective filter. 相似文献
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The oxorhenium(V) complexes [Re (V)O(L A)Cl 2] bearing the (N-2-pyridylmethyl) of l-valine (HL A (1)), l-leucine (HL A (2)), and l-phenylalanine (HL A (3)) and [Re (V)O(L B)Cl] containing the {(N-2pyridylmethyl)-(N-(5-nitro-2-hydroxybenzyl)} of l-valine (H 2L B (1)), l-leucine (H 2L B (2)), and l-phenylalanine (H 2L B (3)) are presented in this article. The complexes are isolated in enantiomeric pure form examined from X-ray structure determination. The complexes are characterized by spectroscopic and electrochemical methods. The molecular structures observed in the solid state are grossly preserved in solution ( (1)H, (13)C, and circular dichroism spectra). Gas-phase geometry optimization and the electronic structures of [Re (V)O(L A (1))Cl 2], [Re (V)O(L A (2))Cl 2], and [Re (V)O(L B (2))Cl] have been investigated with the framework of density functional theory. The absorption and circular dichroism spectra of the complexes were also calculated applying time-dependent density functional theory (TDDFT) using the conductor-like polarizable continuum solvent model to understand the origin of the electronic excitations. The chemical shift ( (1)H and (13)C) as well as (1)H- (1)H spin-spin coupling constant were also computed by the gauge-independent atomic orbital method, and the computed values are consistent with the experimental data. 相似文献
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An asymmetric synthesis of the calcimimetic agent NPS R‐568 using a (1R,2S)‐N‐benzylephedrine‐promoted addition of dimethylzinc to a diphenylphosphinoylimine derived from 3‐methoxybenzaldehyde is described. The enantiomeric ratio of the key amine fragment was determined to be 93:7 (86% ee), favoring the (R)‐enantiomer by derivatization and chiral stationary phase HPLC analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A flexible class of anisotropic stationary lattice processes with long memory can be defined in terms of a two-way fractional ARIMA (FARIMA) representation. We consider parameter estimation based on minimizing an approximate residual sum of squares. The method can be applied to sampling areas that are not necessarily rectangular. A central limit theorem is derived under general conditions. The method is illustrated by an analysis of satellite data consisting of total column ozone amounts in Europe and the Atlantic respectively. 相似文献