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41.
Atmospheric aerosols exhibit a high degree of variability in their properties and their spatial and temporal distribution. Mapping atmospheric aerosols is of great importance for monitoring the effects of anthropogenic activities and natural processes upon local air quality, as well as for producing accurate input for radiative transfer models. To help enhance our understanding of radiative, physical, chemical, and dynamic processes in the atmosphere, laser radar is used to provide systematic monitoring of the temporal evolution of the aerosol rich boundary layer. The Micro Pulse Lidar (Light Detection and Ranging) System is capable of long-term autonomous mapping of vertical aerosol structure. We present a new automated method for tracking boundary layer height from Micro Pulse Lidar data and show the results of this method for a continuous 16 h study conducted on the east coast of the United States. 相似文献
42.
A technique introducing pairing correlations in the Projected Hartree-Fock model is described for a few f-p shell nuclei. It provides a good example of Marumori and Eichler's considerations on the importance of pairing in producing nuclear deformation. 相似文献
43.
The extent to which the Hartree-Fock (HF) procedure converts a two-body interaction into an effective one-body operator has been studied. For this purpose, the nuclear Hamiltonian is classified according to its tensor properties under the unitary group U(N) and its direct-sum subgroup U(m) + U(N ? m) generated by the Hartree-Fock procedure. Here N is the total number of HF single particle states of which m are occupied. The sizes of different tensor parts in m-particle spaces have been determined for both U(N) and U(m) + U(N ? m). In terms of these sizes a ratio is defined which provides a measure of the conversion efficiency of HF and a global measure of the goodness of HF s.p. basis. This ratio is evaluated for N = Z even-even nuclei in 0d-1s shell and 0f-1p shell using realistic Hamiltonian operators. 相似文献
44.
Jyoti K Parikh 《Pramana》1976,6(1):42-58
The energy levels of21, 23Na,22, 23Ne,24, 28Mg and25, 29Al are obtained by mixing various bands using the projected deformed Hartree-Fock (DHF) method. Solutions having minimum energies
are found to be prolate for all the nuclei considered here. Higher bands are obtained either by considering particle-hole
excitations or oblate solutions. These various bands are mixed using the projection method and care has been taken to orthogonalize
the bands. The interactions used in this study are those given by Kuo, Preedom-Wildenthal (PW) and WHMK interactions. The
last one seems to give good results for most of the nuclei considered here. Not only are the lowest bands well-reproduced
but the second lowest bands agree reasonably well in most nuclei. The third lowest ones obtained in some nuclei are not yet
observed as complete bands. However, K obtained for the third band seems to be correct. A comparison with shell model calculations—which
are numerically exhausting—shows similar results for the lowest band. However, the agreement of the second band varies from
nucleus to nucleus. A comparison between matrix elements of the interactions is made to analyze the results. 相似文献
45.
Jigisha Parikh Jitendra Rathore Darshak Bhatt Meghal Desai 《Journal of Dispersion Science and Technology》2013,34(10):1392-1398
The present study investigates the effect of different additives on the cloud point (CP) of nonionic surfactants Triton X-100 (TX-100) and Triton X-114 (TX-114) in aqueous solutions. The thermodynamic parameters of these mixtures were calculated at different additive concentrations. The cloud point of nonionic surfactants TX-100 and TX-114 decreased with the increment of electrolyte concentrations and increased with alcohol concentrations. The standard Gibbs free energy was found to be positive for both the surfactants, whereas the enthalpy and the entropy of the clouding phenomenon were found to be positive with alcohols and negative with electrolytes. The overall clouding process was endothermic for alcohols and exothermic for electrolytes. 相似文献
46.
Soluble complexes of group (IV) metallocenes anchored on a substituted polyhedral oligomeric silsesquioxane trisilanol support were prepared and characterized. These catalyst precursors formulated as [M(O^O^O)X] are found to be active in polymerization of ethylene at high temperature in combination with ethylaluminum sesquichloride (Et3Al2Cl3, EASC) as co‐catalyst. The polyethylene obtained by these catalysts is linear, crystalline and displays narrow dispersity. The unique low molecular weight PE formed in this reaction exhibits properties comparable to commercial micronized PE waxes that have potential industrial applications in surface coating and ink formulations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
47.
T. S. Stein W. E. Kauppila C. K. Kwan S. P. Parikh S. Zhou 《Hyperfine Interactions》1992,73(1-2):53-63
We have made preliminary measurements of positronium (Ps) formation cross sections for 9 to 452 eV positrons scattered from
Ar atoms and for 1 to 20 eV positrons scattered from K atoms. Our experimental approach involves setting lower and upper limits
on Ps formation cross sections using a combination of (1) the detection of the coincidences of 511 keV annihilation gamma
rays produced by the decay of para-Ps and by the interaction of ortho-Ps with the wall of the scattering cell in which the
Ps is formed, and (2) the determination of scattering cross sections associated with the measured transmission of the positron
beam through the gas in our scattering cell with the angular discrimination of our apparatus deliberately made as poor as
possible. The constraints placed by these lower and upper limits are used to check for consistency with prior experimental
and theoretical results for Ar and to provide the first measurements of Ps formation cross sections for K, which are compared
with available theoretical results. 相似文献
48.
Manab Chakraborty V.K.Brahmam Kota Jitendra C. Parikh 《Physics letters. [Part B]》1981,100(3):201-204
The number of bosons deduced from variational calculations of spectra and intrinsic mass quadrupole moments of heavy deformed nuclei are compared with predictions of IBA in the SU(3) limit. The differenct between the two suggest the need for including l > 2 bosons in IBA. 相似文献
49.
Electron beam damage is a problem for low-energy electron diffraction, Auger electron spectroscopy, and electron microscopy. We have used tunneling spectroscopy to study the damage caused by 30 keV incident electrons on chemisorbed monolayer films of hexanoic acid, 2,4-hexadienoic acid, and benzoic acid. Our results on monolayer films are compared to existing work on bulk samples. Damage cross sections are similar to bulk values; molecules with more delocalized electrons are more resistant to damage. In contrast to bulk results, however, we find little if any conjugation or cross linking after irradiation. 相似文献
50.
Vinchurkar MS Bricarello DA Lagerstedt JO Buban JP Stahlberg H Oda MN Voss JC Parikh AN 《Journal of the American Chemical Society》2008,130(33):11164-11169
We show that a two-step process, involving spontaneous self-assembly of lipids and apolipoproteins and surface patterning, produces single, supported lipid bilayers over two discrete and independently adjustable length scales. Specifically, an aqueous phase incubation of DMPC vesicles with purified apolipoprotein A-I results in the reconstitution of high density lipoprotein (rHDL), wherein nanoscale clusters of single lipid bilayers are corralled by the protein. Adsorption of these discoidal particles to clean hydrophilic glass (or silicon) followed by direct exposure to a spatial pattern of short-wavelength UV radiation directly produces microscopic patterns of nanostructured bilayers. Alternatively, simple incubation of aqueous phase rHDL with a chemically patterned hydrophilic/hydrophobic surface produces a novel compositional pattern, caused by an increased affinity for adsorption onto hydrophilic regions relative to the surrounding hydrophobic regions. Further, by simple chemical denaturation of the boundary protein, nanoscale compartmentalization can be selectively erased, thus producing patterns of laterally fluid, lipid bilayers structured solely at the mesoscopic length scale. Since these aqueous phase microarrays of nanostructured lipid bilayers allow for membrane proteins to be embedded within single nanoscale bilayer compartments, they present a viable means of generating high-density membrane protein arrays. Such a system would permit in-depth elucidation of membrane protein structure-function relationships and the consequences of membrane compartmentalization on lipid dynamics. 相似文献