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141.
Summary A new method of evaluating the Tolman cone angle from X-ray structural data available from the Cambridge Crystallographic Data Base has been developed and a statistical analysis of the cone angles of the phosphines PPh3, PMe2Ph, PMePh2, PMe3, PEt3 and PCy3 (Cy = cyclohexyl) in transition metal complexes has been completed. 相似文献
142.
We give estimates of quark masses from a comparison of two methods of regularizing the coefficient of the Schwinger term. The masses of the first radial excited states of ?, ω, and ? would have to be slightly higher than indicated by the new Orsay data for this method to yield real solutions for the masses of theu, d, ands quarks. 相似文献
143.
144.
It is shown, using a Born-Oppenheimer model, that the four-body Efimov effect may occur in a system consisting of three identical heavy particles and one light particle, if the light-heavy interaction leads to a zeroenergy two-heavy-one-light bound state. 相似文献
145.
We give an almost complete classification of ergodicity and transience conditions for a general multi-queue system with the
following features: arrivals form Poisson streams and there are various routing schemes for allocating arrivals to queues;
the servers can be configured in a variety of ways; completed jobs can feed back into the system; the exponential service
times and feedback probabilities depend upon the configuration of the servers (this model includes some types of multi-class
queueing system); switching between service regimes is instantaneous. Several different levels of control of the service regimes
are considered. Our results for the N-queue system require randomisation of service configurations but we have studied the two queue system in situations where
there is less control. We use the semi-martingale methods described in Fayolle, Malyshev and Menshikov [3] and our results
generalise Kurkova [8] and complement Foley and McDonald [4] and [5].
AMS 2000 subject classification: Primary: 90B22; Secondary: 60J10 90B15 相似文献
146.
147.
148.
V. Shatokhin T. Wellens C. A. Müller A. Buchleitner 《The European physical journal. Special topics》2007,151(1):51-57
We survey recent progress achieved in understanding the
impact of inelastic processes on coherent backscattering of light
from cold atoms that are saturated by a powerful laser field. 相似文献
149.
150.
H. W. Wenz W. J. Lichtenberg H. Katterwe 《Fresenius' Journal of Analytical Chemistry》1991,341(3-4):155-165
Summary When a shot is fired, the projectile and the cartridge case are released from the weapon, as well as components of the priming charge and propellant, the so-called powder-gunshot residues. In order to solve firearm offences, it is therefore very important to determine the topography of trace-bearing areas on the bullet and the cartridge case, as well as the chemical composition of gunshot residue particles. Gunshot residue particles are made visible with the scanning electron microscope (SEM) and are analysed by means of energy-dispersive X-ray spectroscopy (EDXS) and lately also by means of wavelength-dispersive X-ray spectroscopy (WDXS). In addition to this, analyses of these particles are displayed by means of Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) and depth profiles are prepared. To determine the local distributions of gunshot residue elements with regard to their quantity, the direct Zeeman atomic absorption spectroscopy (DZ-AAS) is employed. Besides the determination of the chemical composition, the topography of the trace-bearing areas on the bullet and cartridge case plays an important part. For the detection of these surfaces, light optical and electron-optical methods are employed. Moreover, the use of opto-electronical testing systems has been attracting more and more attention recently. 相似文献