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981.
982.
The determination of doxazosin by high-performance liquid chromatography with fluorescence detection is described. Propanolol was used as the internal standard. Plasma samples were treated with methanol to precipitate the proteins. Doxazosin was isolated with C18 reversed-phase extraction columns. The determination limit is 1 ng/ml of plasma, while the extraction columns can be reused frequently. The method is applied to clinical trial samples. 相似文献
983.
Karl F. Canter 《Hyperfine Interactions》1992,73(1-2):159-171
The present status of low energy positron diffraction (LEPD) and positron reemission microscopy (PRM) is reviewed in the context
of unanswered questions regarding the elastic scattering of positrons in the 1–300 eV energy range from atoms in solids and
at solid surfaces. Recent LEPD studies yield an agreement between theoretical and experimental diffraction intensities for
semiconductors that has never been equalled in electron diffraction studies. This situation is discussed in terms of the repulsive
interaction between the positron and the embedded atomic potential and the lack of exchange with the nonspherically distributed
valence electrons. The scattering of re-emitted positrons in PRM from atoms chemisorbed or physisorbed on the re-emitting
surface has not yet received the same theoretical attention as scattering from embedded atoms in LEPD. Possible ways in which
positron scattering from overlying atomic structures manifests itself in PRM as well as positron re-emission holography are
discussed, both from the practical viewpoint of observing these structures and in the context of fundamental questions regarding
the positron re-emission process itself. 相似文献
984.
985.
Electron energy distribution functions (eedf) in CO2 laser discharge (He—CO2—N2—CO mixture) have been calculated by solving the Boltzmann equation in the presence of given concentrations of excited (vibrational and electronic) states. The results show a well structured eedf as a result of second kind collisions coming from metastable electronic states of N2 and He as well as a strong dependence of rate coefficients for CO2 dissociation and for the ionization of the different species. 相似文献
986.
M. F. Gorodnii 《Mathematical Notes》1992,51(4):338-341
Translated from Matematicheskie Zametki, Vol. 51, No. 4, pp. 17–22, April, 1992. 相似文献
987.
F. F. Éfendiev 《Mathematical Notes》1992,51(2):204-207
Translated from Matematicheskie Zametki, Vol. 51, No. 2, pp. 139–143, February, 1992. 相似文献
988.
The influence of spatio-temporal external multiplicative fluctuations on a single kink in a bistable distributed system is studied. For this purpose we derive a stochastic dynamic equation for the position of the shifted kink. An analytical estimate for spatio-temporally uncorrelated fluctuations is represented and discussed. We draw the conclusion that multiplicative noise induces a propagation of the most probable kink into the region of larger noise. This effect is demonstrated in numerical simulations. 相似文献
989.
Principles and recent developments in ultrasound contrast agents 总被引:6,自引:1,他引:5
The behaviour of gas bubbles and gas encapsulated spheres as echographic contrast agents is reviewed. Compared with rigid spheres, gas bubbles are superior scattering agents and they offer a number of useful properties which can be exploited in a variety of ways. The analysis of their velocity of sound, back-scatter intensity, second harmonic emission and resonant frequency opens up new perspectives in the development of contrast agents for echocardiographic research with potential clinical applications. 相似文献
990.
Polymer lightguides of PMMA doped with the azo dyes methyl-red and N, N-dihexyl-4-amino-4'-nitro-azobenzene (DHANA) are investigated with respect to their opto-optical properties. The trans-cis photoisomerisation of the dyes leads to reversible polarization-dependent optically induced refractive index changes. The index changes are anisotropic. Birefringence is measured using index matched lightguides. The changes with respect to each polarization are determined by leaky mode spectroscopy and by using a half-integrated interferometer. These changes are intensity dependent and, with a suitable geometry, bistability at low intensities (3 mW/mm3) can be obtained. 相似文献