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991.
E.R. Berger M. Diehl B. Pire 《The European Physical Journal C - Particles and Fields》2002,23(4):675-689
We investigate the exclusive photoproduction of a heavy timelike photon which decays into a lepton pair, . This can be seen as the analog of deeply virtual Compton scattering, and we argue that the two processes are complementary
for studying generalized parton distributions in the nucleon. In an unpolarized experiment the angular distribution of the
leptons readily provides access to the real part of the Compton amplitude. We estimate the possible size of this effect in
kinematics where the Compton process should be dominated by quark exchange.
Received: 9 October 2001 / Published online: 5 April 2002 相似文献
992.
Nowadays much attention is being paid to the determination of trace amounts of noble metals in geological, industrial, biological and environmental samples. The most promising techniques, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS) are characterized by high sensitivity. However, the accurate determination of trace noble metals has been limited by numerous interferences generated from the presence of matrix elements. To decrease, or eliminate, these interferences, the sorption preconcentration of noble metals is often used prior to their instrumental detection. A great number of hyphenated methods of noble metal determination using sorption preconcentration have been developed. This review describes the basic types of available sorbents, preconcentration procedures and preparations of the sorbent to the subsequent determination of noble metals. The specific features of instrumental techniques and examples of ETAAS, FAAS, ICP-AES, ICP-MS determinations after the sorption preconcentration of noble metals are considered. The references cited here were selected mostly from the period 1996 - 2006. 相似文献
993.
994.
The coupling of visible nanosecond laser pulses to metallic targets irradiated in vacuum is studied. The expressions of the vapour and plasma ignition times are obtained. Two cases for vapour breakdown in the plasma ignition process are considered. The first case is that 40 generations of new electrons are born in vapour generation time before plasma formation as assumed in the literature. The second case is that 10 generations of new electrons are born in vapour generation time. Molybdenum (Mo), niobium (Nb) and aluminium (Al) targets are considered for illustrations of our results. The expression of the plasma ignition time for the Al target is substantially different from that reported in the literature. The vapour and plasma ignition threshold laser intensities are calculated and compared with those reported in the literature. Reasons for disagreement are discussed. The plasma ignition threshold estimated in the second case is noted to be in good agreement with the reported experimental result. 相似文献
995.
The supersymetric path integrals in solving the problem of relativistic spinning particle interacting with pseudoscalar potentials
is examined. The relative propagator is presented by means of path integral, where the spin degrees of freedom are described
by odd Grassmannian variables and the gauge invariant part of the effective action has a form similar to the standard pseudoclassical
action given by Berezin and Marinov. After integrating over fermionic variables (Grassmannian variables), the problem is reduced
to a nonrelativistic one with an effective supersymetric potential. Some explicit examples are considered, where we have extracted
the energy spectrum of the electron and the wave functions.
PACS numbers: 03.65. Ca-Formalism, 03.65. Db-Functional analytical methods, 03.65. Pm-Relativistic wave equations. 相似文献
996.
997.
We consider some regression relations for record values X(n), n > 0, generated by a sequence of independent random variables
X1, X2, X3,... with a common continuous cumulative distribution function F(x). New characterizations of distributions based on regression
properties of record values are obtained. Bibliography: 7 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 339, 2006, pp. 5–14. 相似文献
998.
999.
L. S. Pul’kina 《Journal of Mathematical Sciences》2007,144(1):3832-3840
The author proves the existence and uniqueness of a generalized solution of a nonlocal problem with an integral condition
for a hyperbolic equation with n spatial variables.
This work is a continuation of the studies started in [3–5], where the solvability problem of nonlocal problems with an integral
condition was studied for hyperbolic equations on the plane.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 33, Suzdal
Conference-2004, Part 1, 2005. 相似文献
1000.
V. E. Bening V. Yu. Korolev S. Koksharov V. N. Kolokoltsov 《Journal of Mathematical Sciences》2007,146(4):5950-5958