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21.
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1-Piperidino-1-trimethylsilyloxycyclopropane and the corresponding 1-hydroxy-1-piperidinocyclopropane are conveniently perpared from the piperidide of 3-chloropropionic acid. Reactions of these cyclopropanone equivalents with various nucleophiles are described. 相似文献
23.
Linear response time-dependent density functional theory is used to study low-lying electronic continuum states of targets that can bind an extra electron. Exact formulas to extract scattering amplitudes from the susceptibility are derived in one dimension. A single-pole approximation for scattering phase shifts in three dimensions is shown to be more accurate than static exchange for singlet electron-He(+) scattering. 相似文献
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25.
Y. Wasserman 《Journal of sound and vibration》1978,59(2):181-194
In this work, exact formulae have been obtained for determining the lowest natural frequencies and critical loads of elastic circular arches with flexibly supported ends for symmetrical vibration in the direction perpendicular to the initial curvature of the arch. This investigation is concerned with three cases of load behaviour during the process of deformation. The values of the frequencies and critical loads are shown to be dependent on the opening angle of the arch, on the stiffness of the flexibly supported ends and on the ratio of the flexural rigidity to the torsional rigidity of the arch cross-section. 相似文献
26.
The de Haas-van Alphen (dHvA) effect, or Landau quantum oscillatory magnetization of metals, has been widely used to explore the single-particle aspects of electrons in metals with the aim of determining their Fermi surfaces. Its role in studying many-body effects in metals is less familiar, even though the influence of such interactions is well known. We present a general field-theoretic approach to this problem which shows that the paradigm for understanding the influence of many-body interactions in the dHvA effect should be shifted from the intuitively reasonable but potentially misleading arguments based on the electron self-energy on the real energy axis to an analysis of the self-energy along the imaginary energy axis. When viewed in this way, the dHvA effect assumes the role of a many-body self-energy filter in which the real part of the self-energy renormalizes the dHvA frequency while the imaginary part renormalizes independently the dHvA amplitude. We obtain a general theory for the dHvA effect in an interacting system which preserves the structure of the original non-interacting theory of Lifshitz and Kosevich. We then apply this extended Lifshitz-Kosevich theory to the analysis of several problems of interest, including electron-electron and electron-phonon interactions, heavy fermions and type II superconductors. 相似文献
27.
Abstract Introduction to Graphical Modelling by David Edwards, New York: Springer-Verlag, 1995, 274 pp. Reviewed by Garry Robins Introduction to Graphical Modelling by David Edwards, New York: Springer-Verlag, 1995, 274 pp. Reviewed by Garry Robins Graphical Models by Steffen L. Lauritzen, Oxford, U.K.: Clarendon Press, 1996, 298 pp. Reviewed by Garry Robins 相似文献
28.
Stanley Wasserman Column Editor 《CHANCE》2013,26(2):44-46
Abstract An Introduction to Categorical Data Analysis : Alan Agresti, New York: Wiley, 1996, 312 pp. Reviewed by Carolyn J. Anderson 相似文献
29.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献30.