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61.
This paper is an attempt to construct simple analytic models to study the internal structure of main sequence stars. Explicit closed form expressions, which are computable, are given for a number of quantities such as nuclear reaction rate, luminosity, and the number of two particle reactions when the radial matter density of the stellar model is a nonlinear function decreasing from the center to the surface. All analytic results are obtained by taking advantage of the integration theory of generalized hypergeometric functions. 相似文献
62.
It is the aim of our letter to embedd the presently well understood scale of stellar mass into a simple cosmological scenario for the origin of Population III objects. The result of our consideration will be that if the first bound objects with typical stellar mass of the order of 30 M⊙ could evolve as ordinary stars ending up exploding (Type II supernovae) the problem of the pregalactic enrichment of a primordial gas cloud be solved. 相似文献
63.
HJ. Mellin 《Acta Mathematica》1887,9(1):137-166
Ohne Zusammenfassung 相似文献
64.
Background
Many systems in nature are characterized by complex behaviour where large cascades of events, or avalanches, unpredictably alternate with periods of little activity. Snow avalanches are an example. Often the size distribution f(s) of a system's avalanches follows a power law, and the branching parameter sigma, the average number of events triggered by a single preceding event, is unity. A power law for f(s), and sigma = 1, are hallmark features of self-organized critical (SOC) systems, and both have been found for neuronal activity in vitro. Therefore, and since SOC systems and neuronal activity both show large variability, long-term stability and memory capabilities, SOC has been proposed to govern neuronal dynamics in vivo. Testing this hypothesis is difficult because neuronal activity is spatially or temporally subsampled, while theories of SOC systems assume full sampling. To close this gap, we investigated how subsampling affects f(s) and sigma by imposing subsampling on three different SOC models. We then compared f(s) and sigma of the subsampled models with those of multielectrode local field potential (LFP) activity recorded in three macaque monkeys performing a short term memory task. 相似文献65.
66.
Toman Rudolf Garidel Patrick Andrä Jörg Slaba Katarina Hussein Ahmed Koch Michel HJ Brandenburg Klaus 《BMC biochemistry》2004,5(1):1-14
Background
Coxiella burnetiiis the etiological agent of Q fever found worldwide. The microorganism has like other Gram-negative bacteria a lipopolysaccharide (LPS, endotoxin) in its outer membrane, which is important for the pathogenicity of the bacteria. In order to understand the biological activity of LPS, a detailed physico-chemical analysis of LPS is of utmost importace. 相似文献67.
68.
69.
This paper is concerned with the hydrostatic equilibrium of a purely gaseous star generating energy at a rate . By the common technique of integration theory of special functions the total net rate of nuclear energy generation is evaluated analytically for a linear density distribution function assumed for a simple stellar model. 相似文献
70.
Diboron Heterocyclic Compounds: Oxadiborolane – Oxadiborinane – Diazadiborinane The diboryl compounds R(Cl)B(CH2)nB(Cl)R (R ? Cl or CH3; n = 2, 3) and the silylated or stannylated starting materials [(CH3)3Y]2X (Y ? Si or Sn; X ? S, NCH3, O, NCH3? NCH3) were used for (5+1)- and (4+2)-cyclocondensation reactions. Dimethylether was an additional starting molecule. While no thiadiborinanes could be isolated, the nitrogen or oxygen containing heterocycles were formed in varying yields. Synthesis and properties of these compounds are described. 相似文献