Restricted geographic distribution and low genetic distinctiveness of steppic Crioceris quinquepunctata (Coleoptera: Chrysomelidae) populations in Central East Europe

Crioceris quinquepunctata is a European leafbeetle, rare and strictly associated with steppe-like habitats in Central and Eastern Europe. We sampled suitable localities in Central East Europe to determine the current distribution and to verify whether populations isolated by the Carpathian Mountains (within Pannonian and Pontic area) show genetic differentiation. Sequences from the beetle COI and ITSl were amplified and compared. Furthermore, ftsZ and hcpA genes of the endosymbiont Wolbachia were analysed as additional genetic markers. We found only two populations of C. quinquepunctata (in Moravia and Podolian Upland). Unusually low genetic differences between these populations were revealed, which is in contrast to previous studies on other steppe beetles. The reasons for such low diversity are speculative and probably related to recent natural expansion or man-made translocation of C. quinquepunctata

Finite volume effects using lattice chiral perturbation theory

Lattice regularization is used to perform chiral perturbation theory calculations in finite volume. The lattice spacing is chosen small enough to be irrelevant, and numerical results are obtained from simple summations.Comment: Lattice2004(spectrum), 3 page

Evidence of Strong-Coupled Superconductivity in CaC6 from Tunneling Spectroscopy

Point-contact tunneling on CaC$_6$ crystals reproducibly reveals superconducting gaps, $\Delta$, of 2.3$\pm$0.2 meV which are $\sim$~40% larger than earlier reports. That puts CaC$_6$ into the class of very strong-coupled superconductors since 2$\Delta$/kT$_c\sim$~4.6. Thus soft Ca phonons will be primarily involved in the superconductivity, a conclusion that explains the large Ca isotope effect found recently for CaC$_6$. Consistency among superconductor-insulator-normal metal (SIN), SIS and Andreev reflection (SN) junctions reinforces the intrinsic nature of this result.Comment: 2nd version, 4 pages, 4 figures, re-submitted to Physical Review Letter

ELECTRON TUNNELING STUDY OF SURFACE AND CORRELATION EFFECTS IN BI-LAYERED LANTHANUM-STRONTIUM MANGANITES

Katedra fyziky povrchů a plazmatuDepartment of Surface and Plasma ScienceFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Large Energy Gaps in CaC₆ from Tunneling Spectroscopy: Possible Evidence of Strong-Coupling Superconductivity

Tunneling in CaC6 crystals reproducibly reveals superconducting gaps Δ of 2.3±0.2 meV that are ~40% larger than reported earlier. In an isotropic s -wave scenario, that puts CaC6 into the class of very strongly coupled superconductors, since 2Δ k Tc ~4.6, implying that soft Ca phonons are primarily involved in the superconductivity. This conclusion explains the relatively large Ca isotope effect found recently for CaC6, but it could also signal a strong anisotropy in the electron-phonon interaction

Reconstructing nonlinear dynamic models of gene regulation using stochastic sampling

<p>Abstract</p> <p>Background</p> <p>The reconstruction of gene regulatory networks from time series gene expression data is one of the most difficult problems in systems biology. This is due to several reasons, among them the combinatorial explosion of possible network topologies, limited information content of the experimental data with high levels of noise, and the complexity of gene regulation at the transcriptional, translational and post-translational levels. At the same time, quantitative, dynamic models, ideally with probability distributions over model topologies and parameters, are highly desirable.</p> <p>Results</p> <p>We present a novel approach to infer such models from data, based on nonlinear differential equations, which we embed into a stochastic Bayesian framework. We thus address both the stochasticity of experimental data and the need for quantitative dynamic models. Furthermore, the Bayesian framework allows it to easily integrate prior knowledge into the inference process. Using stochastic sampling from the Bayes' posterior distribution, our approach can infer different likely network topologies and model parameters along with their respective probabilities from given data. We evaluate our approach on simulated data and the challenge #3 data from the DREAM 2 initiative. On the simulated data, we study effects of different levels of noise and dataset sizes. Results on real data show that the dynamics and main regulatory interactions are correctly reconstructed.</p> <p>Conclusions</p> <p>Our approach combines dynamic modeling using differential equations with a stochastic learning framework, thus bridging the gap between biophysical modeling and stochastic inference approaches. Results show that the method can reap the advantages of both worlds, and allows the reconstruction of biophysically accurate dynamic models from noisy data. In addition, the stochastic learning framework used permits the computation of probability distributions over models and model parameters, which holds interesting prospects for experimental design purposes.</p

Conservation genetics of endangered leaf-beetle Cheilotoma musciformis populations in Poland

Steppe-like habitats in Europe are seriously threatened as a result of fragmentation and anthropogenic degradation, at least in western and central parts. Considering the dramatic loss of steppe-like habitats, the evaluation of genetic variation in populations of steppe species is of immediate importance if appropriate conservation measures are to be undertaken. In this paper, we examine the genetic diversity of the highly endangered populations of the leaf-beetle Cheilotoma musciformis, which inhabits only a limited area in south-central Poland, which is geographically isolated from the continuous range of this species. Both mitochondrial and nuclear markers show that the Polish populations are distinct from Slovakian and Ukrainian ones. These regional populations should be considered independent conservation units. On the other hand, very little (mtDNA) or no (nuclear DNA) diversity has been found among the Polish subpopulations. This leads to the conclusion that this species has gone through a strong bottleneck leading to a drastic reduction in its genetic diversity prior to the establishment of present-day populations. Host plants have been identified for this species using barcodes, and the only hosts for the Polish and Ukrainian samples are sainfoins Onobrychis spp. while for the Slovakian sample it is either Dorycnium pentaphyllum or Lotus spp. (all Fabaceae). All of these data can be very valuable for the conservation of C. musciformis populations (e.g. for reintroductions)

Characteristic Energy of the Coulomb Interactions and the Pileup of States

Tunneling data on $\mathrm{La_{1.28}Sr_{1.72}Mn_2O_7}$ crystals confirm Coulomb interaction effects through the $\sqrt{\mathrm{E}}$ dependence of the density of states. Importantly, the data and analysis at high energy, E, show a pileup of states: most of the states removed from near the Fermi level are found between ~40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR