1,295 research outputs found
Eleutherodactylus augusti
Number of Pages: 4Integrative BiologyGeological Science
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Lampropeltis zonata
Number of Pages: 4Integrative BiologyGeological Science
Relationships among Generalized PhaseâSpace Distributions
The generalized phaseâspace distributions, including the Wigner distribution, are presented in terms of expected values of generating operators. A generalization of the Weyl correspondence is obtained to provide expressions for generalized Wigner equivalents. Finally, rather simple relationships are obtained connecting the generalized phaseâspace distributions to the Wigner distribution; and similar relationships are obtained for the generalized Wigner equivalents. In particular, it appears that, among the class considered, there is no reason to use any distribution other than the Wigner for performing any calculations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69967/2/JMAPAQ-10-2-233-1.pd
Systematics of Microhylid Frogs, Genus Oreophryne, from the North Coast Region of New Guinea
Fig. 4. Regression of internarial span on snoutÂvent length in two samples of Oreophryne biroi from Papua New Guinea. Squares, specimens from Madang Prov.; crosses, specimens from East Sepik Prov.Published as part of <i>ZWEIFEL, RICHARD G., MENZIES, JAMES I. & PRICE, DAVID, 2003, Systematics of Microhylid Frogs, Genus Oreophryne, from the North Coast Region of New Guinea, pp. 1-32 in American Museum Novitates 3415</i> on page 10, DOI: 10.1206/0003-0082(2003)415<0001:SOMFGO>2.0.CO;2, <a href="http://zenodo.org/record/10111440">http://zenodo.org/record/10111440</a>
Quantum Statistics and Slow Neutron Scattering by Gases
A surprisingly simple expression in ``closed form'' for the cross section d2Ï/dΩdÏ” for the scattering of thermal neutrons (including polarized neutrons) from an ideal quantum gas is derived. This result extends the work of Van Hove on the quantum gas. An expansion is obtained for dÏ/dÏ”. The case of elastic scattering is treated separately. From these expressions is obtained a criterion for ignoring the statistics of the scatterer in favor of classical (Boltzmann) statistics. This criterion should have some validity for weakly interacting systems. It is shown that the effects of statistics on the neutron cross section for a heliumâ4 gas range from 5% or less for the noninteracting gas up to as much as 40% for the interacting system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70882/2/JCPSA6-47-12-4923-1.pd
The [4+2]âCycloaddition of αâNitrosoalkenes with Thiochalcones as a Prototype of Periselective HeteroâDielsâAlder ReactionsâExperimental and Computational Studies
The [4+2]âcycloadditions of αânitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styrylâsubstituted 4Hâ1,5,2âoxathiazines in moderate to good yields. Of the eight conceivable heteroâDielsâAlder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the αânitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bisâheterocyclic [4+2]âcycloadducts. The experiments are supported by highâlevel DFT calculations that were also extended to related heteroâDielsâAlder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2âdithiin and 2Hâthiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process
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