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991.
992.
993.
994.
The interaction of 3,5-diamino-4-nitropyrazole with such electrophilic reagents as acetic anhydride, dimethylformamide acetal, orthoformic ester, and ketones has been studied. Derivatives of pyrazolol[1,5-a]pyrimidines were formed on reaction with 1,3-diketones and some of their properties have been studied.Center for Drug Chemistry, All-Russian Chemical and Pharmaceutical Research Institute (VNIKhFI), Moscow 119815. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 329–335, March, 1997. 相似文献
995.
Basic equations of linear computer tomography are considered; a connection of the mathermatical formulation of problems of
computer tomography with problems of integral geometry is indicated; the properties of the Radon transform for even- and odd-dimensional
spaces are analyzed, and applications of Radon inversion to problems of diffraction tomography are presented. Bibliography:
5 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 230, 1995, pp. 264–277.
Translated by V. N. Troyan. 相似文献
996.
T. Engel M. Würtz S. Borneis St. Becker I. Klaft A. Kohl T. Kühl F. Laeri D. Marx K. Meier R. Neumann F. Schmitt P. Seelig L. Völker 《Hyperfine Interactions》1997,108(1-3):251-258
Laser spectroscopy at storage rings often suffers from a limited resolution due to Doppler-broadened resonances. Broadening
is caused by the velocity spread of the ions stored in the beam. In the following, the present status of our work on laser
systems specialized on the specific needs of laser spectroscopy at storage rings is reported.
Two pulsed laser systems were developed. One is a dye laser whose spectral bandwidth can be switched by inserting different
Littrow-prisms into the resonator. An increase in bandwidth up to a factor of 45 was achieved. This laser was used for fast
qualitative scans and high resolution measurements. The other laser system is a Nd : YAG laser pumped optical parametric oscillator.
It is a tunable laser system covering the spectral range from 410 to 4000 nm. Furthermore, a continuous wave laser with a
frequency shifted feedback cavity is described. It shows broadband emission with an adjustable bandwidth of up to 4.5 GHz.
This laser can be advantageous for laser cooling of ion beams.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
997.
L.-Q. Han S.-Y. Zhao Y.-D. Zhou P.-L. Zhang 《Applied physics. B, Lasers and optics》1997,65(3):399-402
Received: 18 June 1996/Revised version: 3 January 1997 相似文献
998.
For fields above a critical value the expansion of the conductivity in powers of the field ceases to be valid and the weak-nonlinearity
approximation no longer works. The density behavior of the critical fields in strongly inhomogeneous media near the percolation
threshold is found on the basis of two criteria—an average criterion and a local criterion. The parameter values of the medium
for which crossover—a change of the critical behavior—occurs are determined. Similar calculations are performed for the critical
currents.
Zh. Tekh. Fiz. 68, 5–8 (June 1998) 相似文献
999.
V. A. Lyubetsky 《Algebra and Logic》1997,36(3):169-181
A set theory ZFI′ which does not employ the Law of the Excluded Middle φ ∀ ⊥ φ, for all φ, retians the stock of expressive
capacities of the classical set theory ZF, on the one hand, and has many of the features of an effective theory on the other.
In the article, a broad class of formulas σ is constructed for which ZF ⊥ σ implies ZFI′ ⊥ σ. This result provides a generalization
of Friedman's theorem on AE-arithmetic formulas. Besides, we prove transfer theorems of classical logic for the case of rings;
in particular, Hilbert's theorem on zeros and Artin's theorem on ordered fields are extended to the case of regular f-rings,
and we bring in appropriate upper bounds for them.
Supported by RFFR grant No. 93-012-1027.
Translated fromAlgebra i Logika, Vol. 36, No. 3, pp. 282–303, May–June, 1997. 相似文献
1000.
A. Sánchez-Lavega A. Salazar A. Ocariz L. Pottier E. Gomez L.M. Villar E. Macho 《Applied Physics A: Materials Science & Processing》1997,65(1):15-22
Received: 16 September 1996/Accepted: 6 January 1997 相似文献