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Vishnu Vardhan Krishnamachari Eric Olaf Potma 《Journal of Raman spectroscopy : JRS》2008,39(5):593-598
Focus‐engineered coherent anti‐Stokes Raman scattering (FE‐CARS) microscopy is used to highlight the lateral interfaces between chemically distinct media. Interface highlighting is achieved by using a HG10 mode for the Stokes laser beam and a HG00 mode for the pump laser beam in the forward detection scheme. The spectral and the orientation dependence of FE‐CARS are found to be in agreement with theoretical predictions. A brief discussion on the relevance of this technique for imaging third‐order nonlinear susceptibility interfaces in thin samples of biological or chemical importance is presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The N2 laser excited fluorescence spectrum and the intensity of fluorescence of oxalyl chloride C2O2Cl2) condensed at 77°K either alone, or, diluted with a non-hydrocarbon or a hydrocarbon with dilution ratios ranging from 10 to 100 were studied. A slow condensation of the hydrocarbon matrix diluted sample showed a considerable reduction in the fluorescence intensity as compared to a fast condensation of the same sample. 相似文献
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The low pressure method of determination of carbon in metals and alloys was modified to include certain new techniques. An isopentane slush bath dispensed with the use of liquid oxygen and the usual McLeod gauge was replaced by a differential oil manometer, which increased the sensitivity. As little as 5 μg of carbon in CaCO3-quartz standards could be determined with a coefficient of variation of 16.0% which improved to 3.3% at the 100-μg level. The apparatus was used for the determination of carbon in metals such as uranium, zirconium and iron and in steels and cupronickel alloy. 相似文献
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A. K. Nayak S. K. Sarkar R. S. Karve V. Parthasarathy K. V. S. Rama Rao J. P. Mittal S. L. N. G. Krishnamachari T. V. Venkitachalam 《Applied physics. B, Lasers and optics》1989,48(5):437-443
Infrared laser multiple photon excitation/dissociation of Thiophene (Th) was studied as a function of Th pressure, laser pulse energy, pulse duration and added buffer gas. While the excitation process was probed via optoacoustic technique, the stable reaction products were analyzed by IR spectroscopy and mass spectrometry. Although C2H2 and CH3CCH were the major hydrocarbon products under all experimental conditions, the distribution of these, as well as higher hydrocarbons of lower yield, was found to be very much dependent upon the experimental conditions. The laser induced reaction under dielectric breakdown conditions with either high substrate pressure or laser energy produced significant amount of CS2 and unidentified polymer as well. We propose a mechanism involving breakage of the C–S bond in Th to form an unstable 1,5-diradical which further decomposed via different channels. However, at higher substrate pressures, radical-Th reactions complicated the overall chemistry of the system. Evidences for collisional energy-pooling and rotational hole-filling were also obtained. 相似文献
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The complex, multi-level super molecular architecture of cellulose has been the subject of interest for several decades. The mechanical, physical, and environmental properties of cellulose depend on the molecular, supramolecular and morphological structure of the cellulose. This paper gives a brief overview to micro structural analysis of cellulose, as studied using transmission electron microscopy and scanning electron microscopy. The application of these techniques to study the diverse morphology of cellulose and its composites is illustrated using several examples. 相似文献
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Zubair M. Abdulla Radhakrishnan P. Iyer Krishnamachari G. Akamanchi Mariam S. Degani Evans C. Coutinho 《Journal of heterocyclic chemistry》2011,48(1):38-49
Open‐chain bis‐Reissert compounds 1 were converted to the corresponding bis‐oxazolium intermediates via acid‐catalyzed intramolecular cyclization. These oxazolium compounds exist in a variety of tautomeric structures in which the meso‐ionic form can be intercepted by reaction with dipolarophiles in a 1,3‐dipolar‐cycloaddition reaction to produce a variety of highly functionalized bis‐pyrrole esters 2 . In turn, the bis‐pyrrole esters could be converted to the corresponding bis‐pyrrole tetrols 3 in high yields. J. Heterocyclic Chem., 2011. 相似文献
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S. L. N. G. Krishnamachari 《Photochemistry and photobiology》1974,20(1):33-35
Abstract —From flash photolyses of methyl formate (HCOOCH3 ), d -methyl formate (DCOOCH3 ), methyl formate- d 3 (HCOOCD3 ) and fully ***deuterated methyl formate (DCOOCD3 ) in the vapour phase at room temperature, the relative efficiencies of the formyl and methoxyl radicals in producing formaldehyde have been determined. 相似文献
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In the flash photolyses of isoxazole and oxazole, a new band system has been observed in the region 2500 - 3050 Å. Based on the considerations of the method of production, long radiative life time and the vibrational frequencies, these bands are attributed to the triplet-triplet transition of HCN. 相似文献