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By
Oeschler, Helmut
Summary
<p>A review of strange particle production in heavy ion collisions at incident energies from SIS up to 40 <i>A</i>·GeV is presented. A statistical model assuming chemical equilibrium and local strangeness conservation (i.e. strangeness conservation per collision) describes most of the observed features.</p> <p>It is demonstrated that the K^{} production at SIS energies occurs predominantly via strangeness exchange and that this channel is approaching chemical equilibrium. The observed maximum in the K^{+}/π^{+} excitation function is also seen in the ratio of strange to nonstrange particle production. The appearance of this maximum around 30 <i>A</i>·GeV is due to the energy dependence of the chemical freezeout parameters temperature <i>T</i> and baryochemical potential μ_{B}.
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By
Hofmann, W.; Rahim, H.; Grobovschek, M.; Mandl, H.
Show all (4)
The dose distribution and the integral dose for CTexaminations of the skull can be obtained experimentally from a threedimensional array of TLdosimeters in a tissueequivalent phantom. In this paper we propose a new method which is based on two measured dose profiles for a single scan: f(z) along the central body axis z, and f(x,y) in the xy plane perpendicular to z and parallel to the single phantom slices. Both dose profiles were measured with Harshaw TLD 100 rods and ribbons in an Alderson phantom in supine position. The computer — aided superposition of both dose profiles allows us then to reconstruct the spatial dose distribution and to compute the integral dose for any combination of scans. The application of this method is illustrated for a standard brain examination consisting of 14 scans adjacent to each other with a FWHM of the beam profile of 9 mm. The validity of this procedure was checked by comparing the theoretical reconstruction with TLmeasurements revealing excellent agreement between calculation and experiment.
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By
Lukács, B.; Zimányi, J.; Balazs, N. L.
It has been shown that strange and nonstrange quarks generally possess different hadronization rates in a quarknucleon phase transition. Since the main process driving the rehadronization is the expansion and cooling of the fireball of quarks, this complicated phase transition is intimately connected with relativistic hydrodynamics. Here the consistent hydro+thermodynamical description of the transition is presented.
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By
Softley, T. P.
Spectroscopic and theoretical studies concerning thea^{3}II state of CH^{+} are reviewed, with particular consideration given to the infrared predissociation spectrum of the ion. This spectrum is primarily due to vibrationrotation transitions of thea^{3}II state involvingv=5 to 12 andJ=20 to 35. Some results of a spectral simulation, making use of a rotationallyadiabatic model, are presented to justify the proposed assignment. The nuclearhyperfine structure of the observed transitions is studied in detail, with a new calculation of splittings presented. Some semiquantitative conclusions can be drawn with reference to the variation of the Fermi Contact parameter,b, as a function of internuclear distance.
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By
Lavrov, B. P.; Ustimov, V. I.
The theory of electronicvibrorotational radiative transitions is considered within the framework of the perturbation theory. For the case of regular (monotonic) perturbations caused by relatively far lying terms of the molecule the simple analytical expressions for the line strengths of the^{2s+1}A′→^{2s+1}A″ transitions are derived in the second order of the perturbation theory. Most distributed schemes of angular momenta coupling — Hund’s cases “a” and “b” — are considered. It is shown that the line strengths can be expressed in terms of a finite number (usually small) of the parameters (certain combinations of matrix elements describing the effects of perturbations and vibrationrotation interaction) which may be determined either from the experimental data in a semiempirical approach or from numerical calculations of adiabatic electronic and vibrational wave functions.
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By
Kapuy, E.; Kozmutza, C.; Ozoróczy, Zs.
The possibility of the calculation of molecular properties on ab initio level for extended systems is investigated in a series of papers.
In the first Part the effect of the magnitude of basis function exponents as well as that of the threshold on the number of vanishing twoelectron integrals is studied.
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By
Baruah, S.; Bhuyan, P. K.
An empirical model based on a harmonic analysis approach for calculating the peak density of ionospheric F layer over Chungli (24.95° N, 121.23° E) for all levels of solar activity is proposed. The harmonic coefficients were obtained by normalizing the NmF2 data collected during the period 1976 to 1983 to a common level of solar activity. The coefficients exhibit expected seasonal variations. A set of 49 coefficients comprising the mean, first, second and third harmonics was found to be sufficient to recreate monthly mean NmF2 under any level of solar activity. The proposed model requires only the precalculated set of coefficients as input and enables one to use the NmF2 values so calculated as single station input to IRI or other similar models.
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By
Marx, G.
The relic microwave radiation indicates that the universe was in the state of thermal equilibrium (heat death) in the past. The question arises how could it happen that the universe departed from the thermal equilibrium? According to the models presented here this was the outcome of an interplay among dynamic instability, matter differentiation and weakening of some interactions.
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