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51.
Douglas K. Lilly Gene Bassett Kelvin Droegemeier Peter Bartello 《Theoretical and Computational Fluid Dynamics》1998,11(3-4):139-153
The first author proposed earlier that the atmospheric energy spectrum in the mesoscale range is controlled by upscale energy
transport in stratified and geostrophic turbulence, with the source of the energy probably convective clouds and storms. This
hypothesis is reviewed in the light of a variety of theoretical and mechanistic tests, mostly involving numerical simulation.
Some conflicting results are noted, with fluid dynamics simulations mostly negative and meteorological simulations positive,
including one new set presented here. The rapid increase in larger-scale energy shown in our simulations should, however,
be ascribed in part to a different mechanism, involving the rapid growth of the unconstrained outflow and its further spreading
by mean shear.
Received 23 May 1997 and accepted 21 February 1998 相似文献
52.
The first asymmetric synthesis of (+)-crocacin C (3) is described which served to confirm the absolute configuration of this compound. The key step in the sequence was the stereoselective assembly of the (E,E)-diene amide side chain by a Stille cross-coupling between the stannane 5 and vinyl iodide 6. 相似文献
53.
Cayzer TN Lilly MJ Williamson RM Paddon-Row MN Sherburn MS 《Organic & biomolecular chemistry》2005,3(7):1302-1307
Reactions between conjugated dienols and maleic anhydride provide either cis-fused or trans-fused bicyclic products as major products, depending upon how the reaction is carried out. Simply mixing the two reactants together generally leads to cis-fused lactone acids in thermal reactions which proceed viaintermolecular Diels-Alder reaction followed by intramolecular esterification. Pre-forming the maleate half ester derivative followed by heating affords predominantly trans-fused lactone acids in good yields by way of an intramolecular Diels-Alder (IMDA) reaction. Sorbyl citraconate half esters undergo a rapid thermolytic fragmentation in refluxing toluene to form the dienol and citraconic anhydride. The resulting diene-dienophile pair undergo an intermolecular cycloaddition followed by a rapid intramolecular esterification to give cis-fused bicyclic lactone acids as major products. The IMDA reaction of citraconic half esters is sufficiently rapid in DMSO to dominate over fragmentation: the exo-cycloadduct is formed almost exclusively. Nine literature reports of endo-selective IMDA reactions of triene acids are erroneous; the cycloadditions proceed in an intermolecular manner. 相似文献
54.
[structure: see text] The first asymmetric synthesis of (+)-crocacin D (4) is described. The key steps in the sequence are the stereoselective assembly of the stereotetrad via a substrate-controlled aldol reaction and anti-selective reduction, formation of the (E,E)-diene by a Stille cross-coupling between the stannane 8 and vinyl iodide 9, and the acylation of (Z)-enecarbamate 6 with the acid chloride derived from polyketide fragment 16 which introduced the (Z)-enamide functionality. 相似文献
55.
Lilly Sanathanan Elizabeth Danaher Ki-Hwan Kim Yvonne Martin 《Journal of computational chemistry》1987,8(8):1075-1083
The computer program PRODIS is used to find low energy conformations of flexible molecules by searching the potential energy surface(s) of one or more torsion angles via rigid rotation. The n-dimensional grid of energy versus torsion angles is then converted to a Boltzman probability distribution, with the probability being represented not as a function of torsion angle, but rather a distance between two atoms. These atoms are chosen by comparison with a known, active analogue in which certain atoms have previously been determined as requirements for drug activity. PRODIS produces a list of low energy conformations, their corresponding interatomic distances and the Boltzman probability for each distance ±0.125, as well as the total probability for each conformation. The user also specifies a target interatomic distance and range (usually derived from a more rigid analogue) for which PRODIS lists all conformations and their Boltzman probability that meet this distance. 相似文献
56.
57.
58.
A. Pratap T. Lilly Shanker Rao K. N. Lad Heena D. Dhurandhar 《Journal of Thermal Analysis and Calorimetry》2007,89(2):399-405
The crystallization of metallic glasses has been studied quite extensively using differential scanning calorimetry (DSC) technique.
Most methods rely on isokinetic hypothesis for the kinetic analysis of crystallization for which the choice of a reliable
model is very important. Due to inherent uncertainty in the determination of kinetic parameters, the model-free isoconversional
analytical techniques were proposed. However, these isoconversional methods are scarcely used for metallic glasses. In the
present work, the crystallization kinetics of Fe67Co18B14Si1 metallic glass through both isoconversional and isokinetic methods has been investigated and attention has been focused on
the relative applicability of the two methods. 相似文献
59.
We have measured the surface acoustic wave velocity shift in a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES) in a low-density regime (<1010 cm−2) at zero magnetic field. The interaction of the surface acoustic wave with the 2DES is not well described by a simple model using low-frequency conductivity measurements. We speculate that this conflict is a result of inhomogeneities in the 2DES, which become very important at low density. This has implications for the putative metal-insulator transition in two dimensions. 相似文献
60.
A recently developed rf echo planar imaging method has been modified to rapidly generate spectroscopic information along one in-plane axis and spatial information along the other. The method allows the production of one-dimensional chemical shift images (1D CSIs) in acquisition times of 18 sec or less. A specific phase-encode-reordering algorithm provides convenient manipulation of T2 weighting, yielding partial suppression of short T2 species like muscle water. The method is demonstrated in phantoms and in vivo with 1D CSIs of human brain and limbs. Abnormal fat distribution is demonstrated in the calf of a patient with aggressive fibromatosis. The advantages of short acquisition times obtainable with SIRFEN are offset by limited spectral resolution, suggesting that primary applications will be confined to rapid spatial mapping of major spectral components. 相似文献