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221.
It is shown that using position-sensitive detectors in μSR experiments to determine the muon stopping site in a target permits
one to study correlation effects in μSR time histograms produced by the decay of muons stopping in the same domain, i.e. to
obtain time correlators of μSR histograms of decays from a small region. These correlators contain information on the spatial
correlation of magnetic fields in the sample under study. The proposed method (μSR2-technique) allows measuring correlation radii (r
c
) down to 10−5 cm in a bulk sample. Among interesting physical phenomena occuring overr
c≥3×10−6 cm are, for instance, long wavelength fluctuations of the order parameter near the phase transition point in ferromagnets
and antiferromagnets and magnetic field correlations in magnet domains and spin glasses. One may use this method also on heavy-current
accelerators producing pulsed muon beams to investigate the variation in time of spatial correlations in magnets, spin glasses
and superconductors. 相似文献
222.
A method of identifying low-energy nuclei from the readings of an ionizational mass spectrometer is considered. The identification principles for particles recorded by a multilayer detector are discussed, together with the fundamentals of a probabilistic approach to the solution of this problem. The method permits correct analysis of the experimental data obtained. The determination of the charge and isotopic composition of radiation consisting of a mixture of different nuclei is considered. The results of calculations by the given method which permit the determination of the optimal detector parameters for the solution of the specific physical problem are outlined. This approach is also applicable for the analysis of data from other types of measuring apparatus.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 84–88, July, 1991. 相似文献
223.
N. Gass 《The Journal of the Operational Research Society》1994,45(2):133-142
A methodology is developed to analyse present and future crisis and conflict potentials of small or large geopolitical regions. A set of criteria is used to describe the present economic, social, political and military conditions of a country and the future criteria trends. A multi-criteria decision analysis model is invoked to compute the crisis and conflict potentials under simultaneous consideration of all other countries in that region. The methodology is demonstrated in the crisis and conflict potentials analysis of the former Soviet republics including bordering countries. 相似文献
224.
Rate constants have been measured by pulse radiolysis for the reactions of the carbonate radical, CO3·?, with a number of organic and inorganic reactants as a function of temperature, generally over the range 5 to 80°C. The reactants include the substitution-inert cyano complexes of FeII, MoIV, and WIV, the simple inorganic anions SO32?, ClO2?, NO2?, I?, and SCN?, several phenolates, ascorbate, tryptophan, cysteine, cystine, methionine, triethylamine, and allyl alcohol. The measured rate constants ranged from less than 105 to 3 × 109 M?1 s?1, the activation energies ranged from ?11.4 to 18.8 kJ mol?1, and the pre-exponential factors ranged from log A = 6.4 to 10.7. The activation energies for the metal complexes and inorganic anions generally decrease with increasing driving force for the reaction, as expected for an outer sphere electron transfer. For highly exothermic reactions, however, the activation energy appears to increase, probably reflecting the temperature dependence of diffusion. For many of the organic reactants, the activation energies were low and independent of driving force, suggesting that the oxidation is via an inner sphere mechanism. 相似文献
225.
A potential of mean torque is derived for a solute at infinite dilution in a uniaxial liquid crystal solvent, which contains terms originating from the dispersion interaction, and the electrostatic interaction between quadrupole moments on both molecules. It is shown that the electrostatic term is non-zero only if the solute-solvent vectors are distributed with lower than spherical symmetry. If this distribution has cylindrical symmetry then both the electrostatic and dispersion terms in the potential of mean torque are shown to depend on order parameters for the orientational distribution of the solute-solvent vectors, as well as on the order parameters of the solvent molecules. 相似文献
226.
A nonuniform electron density distribution is observed in La1−x− y
NdySrxCuO4 and La1−x−y
EuySrxCuO4, and long-lived magnetic fluctuations in these compounds are studied. The dynamics of the magnetic fluctuations depends strongly
on the magnetic properties of the rare-earth ions, which stabilize the low-temperature tetragonal phase.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 344–349 (10 March 1998) 相似文献
227.
P. I. H. Bastiaens S. G. Mayhew E. M. O'Naulláin A. van Hoek A. J. W. G. Visser 《Journal of fluorescence》1991,1(2):95-103
Both a mode-locked argon-ion laser and synchrotron radiation were used as excitation sources to obtain time-resolved polarized fluorescence of the two FAD cofactors in electron transferring flavoprotein fromMegasphaera elsdenii. Red-edge excited and blue-edge detected fluorescence anisotropy decay curves did not contain a fast relaxation process which was observed upon mainband excitation and detection. This relaxation was assigned to homo-energy transfer between the two FAD cofactors. Failure of energy transfer as observed with edge spectroscopy on this protein excludes restricted reorientational motion of the flavins as a possible mechanism of depolarization. From the global analysis of the fluorescence anisotropy decay surface obtained at multiple excitation and detection wavelengths, the distance between and the relative orientation of the flavins could be estimated. The methodology described has general applicability in other multichromophoric biopolymers and has the potential to acquire accurate geometrical parameters in these systems. 相似文献
228.
A. S. Il'inskii S. V. Trubnikov N. A. Fedoseeva 《Computational Mathematics and Modeling》1994,5(3):195-202
Translated from Matematicheskie Modeli i Optimizatsiya Vychislitel'nykh Algoritmov, pp. 131–143, 1993. 相似文献
229.
A. K. Shahani N. Korve K. P. Jones D. J. Paynton 《The Journal of the Operational Research Society》1994,45(8):916-926
Asthma is one of the major chronic diseases in many countries. At present there is no cure for asthma, but medical advances can help to reduce the chances of attacks of the condition. Efficient care for asthma involves complexity, uncertainty, variability and the use of scarce resources, and these are the same conditions that indicate a possible use for the modelling approach of operational research. This paper is concerned with a pilot model that was developed through joint work by medical professionals and operational researchers. The development of the model is explained and illustrative results indicate the potential value of the modelling approach for the care of asthma in the community. 相似文献
230.
We investigate the possibility of approximating a function on a compact setK of the complex plane in such a way that the rate of approximation is almost optimal onK, and the rate inside the interior ofK is faster than on the whole ofK. We show that ifK has an external angle smaller than π at some point zo∈δK, then geometric convergence insideK is possible only for functions that are analytic at zo. We also consider the possibility of approximation rates of the form exp(?cn β), for approximation insideK, where β is related to the largest external angle ofK. It is also shown that no matter how slowly the sequence {γ n } tends to zero, there is aK and a Lip β, β<1, functionf such that approximation insideK cannot have order {γ n }. 相似文献