Genetic Differentiation Among Three Species of \u3ci\u3eParadosa\u3c/i\u3e (Arachnida: Lycosidae)

Allozymic variation in nine protein producing loci was examined in three species of Pardosa using starch gel electrophoresis. Allozyme frequencies showed a high degree of geographic uniformity among conspecific populations. Estimated heterozygosities for the three species ranged from 0.05 to 0.15. Rogers\u27 coefficients of genetic similarity based on allozyme frequencies averaged over conspecific populations ranged from 0.16 to 0.37 fo rthe three species

The strength and timing of the mitochondrial bottleneck in salmon suggests a conserved mechanism in vertebrates

In most species mitochondrial DNA (mtDNA) is inherited maternally in an apparently clonal fashion, although how this is achieved remains uncertain. Population genetic studies show not only that individuals can harbor more than one type of mtDNA (heteroplasmy) but that heteroplasmy is common and widespread across a diversity of taxa. Females harboring a mixture of mtDNAs may transmit varying proportions of each mtDNA type (haplotype) to their offspring. However, mtDNA variants are also observed to segregate rapidly between generations despite the high mtDNA copy number in the oocyte, which suggests a genetic bottleneck acts during mtDNA transmission. Understanding the size and timing of this bottleneck is important for interpreting population genetic relationships and for predicting the inheritance of mtDNA based disease, but despite its importance the underlying mechanisms remain unclear. Empirical studies, restricted to mice, have shown that the mtDNA bottleneck could act either at embryogenesis, oogenesis or both. To investigate whether the size and timing of the mitochondrial bottleneck is conserved between distant vertebrates, we measured the genetic variance in mtDNA heteroplasmy at three developmental stages (female, ova and fry) in chinook salmon and applied a new mathematical model to estimate the number of segregating units (N(e)) of the mitochondrial bottleneck between each stage. Using these data we estimate values for mtDNA Ne of 88.3 for oogenesis, and 80.3 for embryogenesis. Our results confirm the presence of a mitochondrial bottleneck in fish, and show that segregation of mtDNA variation is effectively complete by the end of oogenesis. Considering the extensive differences in reproductive physiology between fish and mammals, our results suggest the mechanism underlying the mtDNA bottleneck is conserved in these distant vertebrates both in terms of it magnitude and timing. This finding may lead to improvements in our understanding of mitochondrial disorders and population interpretations using mtDNA data

Estimates of in situ Larval Development Time for the Lobster, Homarus Americanus

Larval development time is a critical factor in assessing the potential for larval transport, mortality. and subsequently, the connectivity of marine populations through larval exchange. Most estimates of larval duration are based on laboratory studies and may not reflect development times in nature. For larvae of the American lobster (Homarus americanus), temperature-dependent development times have been established in previous laboratory studies. Here, we used the timing of seasonal abundance curves for newly hatched larvae (stage 1) and the final plankonic instar (postlarva), coupled with a model of temperature-dependent development to assess development time in the field. We were unable to reproduce the timing of the seasonal abundance curves using laboratory development rates in our model. Our results suggest that larval development in situ may be twice as fast as reported laboratory rates. This will result in reduced estimates of larval transport potential, and increased estimates of instantaneous mortality rate and production

Probing the Crust of the Neutron Star in EXO 0748-676

X-ray observations of quiescent X-ray binaries have the potential to provide insight into the structure and the composition of neutron stars. EXO 0748-676 had been actively accreting for over 24 yr before its outburst ceased in late 2008. Subsequent X-ray monitoring revealed a gradual decay of the quiescent thermal emission that can be attributed to cooling of the accretion-heated neutron star crust. In this work, we report on new Chandra and Swift observations that extend the quiescent monitoring to ~5 yr post-outburst. We find that the neutron star temperature remained at ~117 eV between 2009 and 2011, but had decreased to ~110 eV in 2013. This suggests that the crust has not fully cooled yet, which is supported by the lower temperature of ~95 eV that was measured ~4 yr prior to the accretion phase in 1980. Comparing the data to thermal evolution simulations reveals that the apparent lack of cooling between 2009 and 2011 could possibly be a signature of convection driven by phase separation of light and heavy nuclei in the outer layers of the neutron star.Comment: 9 pages, 4 tables, 3 figures. Minor revisions according to referee report. Accepted to Ap

The 2-dimensional non-linear sigma-model on a random latice

The O(n) non-linear $\sigma$-model is simulated on 2-dimensional regular and random lattices. We use two different levels of randomness in the construction of the random lattices and give a detailed explanation of the geometry of such lattices. In the simulations, we calculate the mass gap for $n=3, 4$ and 8, analysing the asymptotic scaling of the data and computing the ratio of Lambda parameters $\Lambda_{\rm random}/\Lambda_{\rm regular}$. These ratios are in agreement with previous semi-analytical calculations. We also numerically calculate the topological susceptibility by using the cooling method.Comment: REVTeX file, 23 pages. 13 postscript figures in a separate compressed tar fil

Disk Diffusion Propagation Model for the Outburst of XTE J1118+480

We present a linear diffusion model for the evolution of the double-peaked outburst in the transient source XTEJ1118+480. The model treats the two outbursts as episodic mass deposition at the outer radius of the disk followed by evolution of disk structure according to a diffusion process. We demonstrate that light curves with fast-rise, exponential decay profile are a general consequence of the diffusion process. Deconvolution of the light curve proves to be feasible and gives an input function specifying mass deposition at the outer disk edge as well as the total mass of the disk, both as functions of time. The derived evolution of total disk mass can be correlated with the observed evolution of the ~0.1 Hz QPO in the source reported in Wood et al. (2000).Comment: 26 pages, 6 figures, accepted for publication in Ap

Finite-size scaling of the helicity modulus of the two-dimensional O(3) model

Using Monte Carlo methods, we compute the finite-size scaling function of the helicity modulus $\Upsilon$ of the two-dimensional O(3) model and compare it to the low temperature expansion prediction. From this, we estimate the range of validity for the leading terms of the low temperature expansion of the finite-size scaling function and for the low temperature expansion of the correlation length. Our results strongly suggest that a Kosterlitz-Thouless transition at a temperature $T > 0$ is extremely unlikely in this model.Comment: 4 pages, 3 Postscript figures, to appear in Phys. Rev. B Jan. 1997 as a Brief Repor

Asymptotic behavior in the scalar field theory

An asymptotic solution of the system of Schwinger-Dyson equations for four-dimensional Euclidean scalar field theory with interaction $\frac{\lambda}{2}(\phi^*\phi)^2$ is obtained. For $\lambda>\lambda_{cr}=16\pi^2$ the two-particle amplitude has the pathology-free asymptotic behavior at large momenta. For $\lambda<\lambda_{cr}$ the amplitude possesses Landau-type singularity.Comment: 16 pages; journal version; references adde

Fluctuations of Spatial Patterns as a Measure of Classical Chaos

In problems where the temporal evolution of a nonlinear system cannot be followed, a method for studying the fluctuations of spatial patterns has been developed. That method is applied to well-known problems in deterministic chaos (the logistic map and the Lorenz model) to check its effectiveness in characterizing the dynamical behaviors. It is found that the indices $\mu _q$ are as useful as the Lyapunov exponents in providing a quantitative measure of chaos.Comment: 10 pages + 7 figures (in ps file), LaTex, Submitted to Phys. Rev.