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31.
E. de A. Gonçalves V. M. de Oliveira A. Rosas P. R.A. Campos 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):127-132
Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective
advantage
to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a
long history
in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces
affecting the strength of natural selection in the populations.
In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations
(demes)
can exchange migrants
among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We
have observed that the migration rate
drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on
the
migration rate, accordingly to
Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when
clonal interference
becomes effective. 相似文献
32.
Aït Hmaïdouch L. Mançour Billah S. El Hadek M. 《Journal of Thermal Analysis and Calorimetry》2002,69(2):659-667
The solid—liquid equilibria of the ternary system H2O—Al(NO3)3—Mg(NO3)2 were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO3)3·9H2O, Mg(NO3)2·9H2O and Mg(NO3)2·6H2O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
33.
Within the framework of a simple electrostatic model, as compared to recent experimental results, we here discuss the stability
of very weakly bound molecular negative ions. In contrast with the case of conventional valence anions, the excess electron
is then located in a very diffuse orbital and is mainly bound by electrostatic dipolar, quadrupolar, and polarization forces,
at large distances from the neutral molecular core. By fitting a single repulsion parameter of the model to the available
experimental data, it is possible to make quantitative predictions of the excess-electron binding energies in these species.
Critical values of the dipole moment, quadrupole moment or polarizability required for the observation of stable multipole-bound
negative ions are predicted and compared to available experimental data and ab initio calculations.
Received October 24, 2001; accepted for publication November 16, 2001 相似文献
34.
The HERA - B Collaboration I. Abt et al. 《The European Physical Journal C - Particles and Fields》2003,26(3):345-355
Using the HERA - B detector, the production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The production was tagged via inclusive bottom quark decays into by exploiting the longitudinal separation of decay vertices from the primary proton-nucleus interaction. Both e
+
e
-
and channels have been reconstructed and the combined analysis yields the cross section .
Received: 6 June 2002 / Revised version: 2 September 2002 / Published online: 8 November 2002 相似文献
35.
François Loiseau Jean-Mary Simone David Carcache Pavel Bobal Reinhard Neier 《Monatshefte für Chemie / Chemical Monthly》2007,138(2):121-129
Summary. Free radical couplings from furan, as cheap starting material, were studied in view of developing a rapid strategy en route to the synthesis of derivatives of nonactin. The chain containing the alcohol function was introduced in one or two steps
in 86% yield. For the introduction of the second chain with the ester function two different coupling methods were tested.
Starting from the advanced intermediates obtained nonactin derivatives can be prepared by catalytic hydrogenation of the furan
ring. 相似文献
36.
A palladium‐TPPTS catalyst heterogenized on KF/alumina has been shown to be effective and recyclable for the selective formation of monooctadienylxylopyranosides via the telomerization of butadiene with D ‐xylose. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
37.
Hisao Fujita Yashima et Saliha Hamdous 《Rendiconti del Circolo Matematico di Palermo》2007,56(1):79-89
On considére l’équation stochastique decrivant un systéme den espéces avec une perturbation stochastique du type environnemental et une diffusion dans un territoire de chaque espéce.
On suppose la compétition avec un effet limité entre le espéces différentes, tandis que l’effet logistique pour chaque espéce
est supposé quadratique. Sous une condition convenable pour les coefficients, on démontre l’existence d’une mesure invariante
pour cette équation stochastique, oú la densité de population de chaque espéce est presque surement positive.
相似文献
38.
François Métayer 《Archive for Mathematical Logic》1994,33(3):169-188
This work defines homology groups for proof-structures in multiplicative linear logic (see [Gir1], [Gir2], [Dan]). We will show that these groups characterize proof-nets among arbitrary proof-structures, thus obtaining a new correctness criterion and of course a new polynomial algorithm for testing correctness. This homology also bears information on sequentialization. An unexpected geometrical interpretation of the linear connectives is given in the last section. This paper exclusively focuses onabstract proof-structures, i.e. paired-graphs. The relation with actual proofs is investigated in [Gir1], [Gir2], [Dan], [Ret] and [Tro]. 相似文献
39.
振动谱学研究中的光谱线型函数 总被引:3,自引:1,他引:2
本文讨论了在振动谱带计算拟合处理中的光谱线型函数问题,推导出适用于单道及多道拉曼光谱仪及色散型红外谱仪谱带线型公式。通过实验及拟合计算证实了它们的适用性并讨论了可能的误差源。理论计算和实验验证结果说明:在振动谱的谱带拟合计算中,应使用根据测谱条件计算求得的谱带线型函数,以保证拟合结果的可靠性。 相似文献
40.
François Bolley Arnaud Guillin Cédric Villani 《Probability Theory and Related Fields》2007,137(3-4):541-593
We establish quantitative concentration estimates for the empirical measure of many independent variables, in transportation
distances. As an application, we provide some error bounds for particle simulations in a model mean field problem. The tools
include coupling arguments, as well as regularity and moment estimates for solutions of certain diffusive partial differential
equations. 相似文献