175 research outputs found
Dissociative electron attachment and vibrational excitation of : Effect of two vibrational modes revisited
We present a study of dissociative electron attachment and vibrational
excitation processes in electron collisions with the CFCl molecule. The
calculations are based on the two-dimensional nuclear dynamics including the
C-Cl symmetric stretch coordinate and the CF symmetric deformation
(umbrella) coordinate. The complex potential energy surfaces are calculated
using the ab initio R-matrix method. The results for dissociative attachment
and vibrational excitation of the umbrella mode agree quite well with
experiment while the cross section for excitation of the C-Cl symmetric stretch
vibrations is about a factor of three low as compared to experimental data.Comment: 24 pages, 7 figures, submitted to Physical Review
Full scale static loading and fire resistance tests of LSF mezzanine systems
The subject of the article is an experimental investigation of the actual behavior of thin-walled cold-formed C profiles used in the mezzanine systems as floor beams under the effects of static load and under the effects of fire. The aim is to determine the improved design characteristics of floor beams derived from the results of experiments, which will lead to their more economical and efficient design compared to design performed based on the rules and calculation procedures specified in the relevant European standards (Eurocodes). In total 16 static loading tests were performed on a section of the floor structure in real scale using the vacuum test method, which allows apply the uniform load. The results of static loading tests are statistically evaluated and the characteristic values of bending resistances for primary beams are derived based on the Annex D of EN 1990. Generally, the number of fire resistance tests carried out in the past on full-scale sections of load- bearing thin-walled steel structures is very limited. Therefore, standard full-scale fire resistance tests were performed on light gauge steel frame floor structures of two different configurations. First configuration includes one internal (middle) doubled primary beam and two single outer primary beams, a second configuration includes only two single outer primary beams. The fire resistance tests were performed according to EN 1365-2 „Fire resistance tests for loadbearing elements - Part 2: Floors and roofs”. Both tested configurations are classified based on the EN 13501-2 „Fire classification of construction products and building elements - Part 2: Classification using data from fire resistance tests, excluding ventilation services” and compared with the predicted fire resistance calculated according to EN 1993-1-2 „Eurocode 3: Design of steel structures - Part 1-2: General rules - Structural fire design”.The authors gratefully acknowledge to the Technology Agency of the Czech Republic – TACR (www.tacr.cz) for its support under the framework of research project FW01010206
Increasing Incidence of Geomyces destructans Fungus in Bats from the Czech Republic and Slovakia
BACKGROUND: White-nose syndrome is a disease of hibernating insectivorous bats associated with the fungus Geomyces destructans. It first appeared in North America in 2006, where over a million bats died since then. In Europe, G. destructans was first identified in France in 2009. Its distribution, infection dynamics, and effects on hibernating bats in Europe are largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: We screened hibernacula in the Czech Republic and Slovakia for the presence of the fungus during the winter seasons of 2008/2009 and 2009/2010. In winter 2009/2010, we found infected bats in 76 out of 98 surveyed sites, in which the majority had been previously negative. A photographic record of over 6000 hibernating bats, taken since 1994, revealed bats with fungal growths since 1995; however, the incidence of such bats increased in Myotis myotis from 2% in 2007 to 14% by 2010. Microscopic, cultivation and molecular genetic evaluations confirmed the identity of the recently sampled fungus as G. destructans, and demonstrated its continuous distribution in the studied area. At the end of the hibernation season we recorded pathologic changes in the skin of the affected bats, from which the fungus was isolated. We registered no mass mortality caused by the fungus, and the recorded population decline in the last two years of the most affected species, M. myotis, is within the population trend prediction interval. CONCLUSIONS/SIGNIFICANCE: G. destructans was found to be widespread in the Czech Republic and Slovakia, with an epizootic incidence in bats during the most recent years. Further development of the situation urgently requires a detailed pan-European monitoring scheme
Correlation Between the Deuteron Characteristics and the Low-energy Triplet np Scattering Parameters
The correlation relationship between the deuteron asymptotic normalization
constant, , and the triplet np scattering length, , is
investigated. It is found that 99.7% of the asymptotic constant is
determined by the scattering length . It is shown that the linear
correlation relationship between the quantities and
provides a good test of correctness of various models of nucleon-nucleon
interaction. It is revealed that, for the normalization constant and
for the root-mean-square deuteron radius , the results obtained with the
experimental value recommended at present for the triplet scattering length
are exaggerated with respect to their experimental counterparts. By
using the latest experimental phase shifts of Arndt et al., we obtain, for the
low-energy scattering parameters (, , ) and for the
deuteron characteristics (, ), results that comply well with
experimental data.Comment: 19 pages, 1 figure, To be published in Physics of Atomic Nucle
Conservation genetics of the pond bat (Myotis dasycneme) with special focus on the populations in northwestern Germany and in Jutland, Denmark
Conservation genetics is important in the management of endangered species, helping to understand their connectivity and long‐term viability, thus identifying populations of importance for conservation. The pond bat (Myotis dasycneme) is a rare species classified as “Near Threatened” with a wide but patchy Palearctic distribution. A total of 277 samples representing populations in Denmark, Germany, Latvia, Hungary, and Russia were used in the genetic analyses; 224 samples representing Denmark, Germany, and Russia were analyzed at 10 microsatellite loci; 241 samples representing all areas were analyzed using mitochondrial D‐loop and cytochrome B sequences. A Bayesian clustering approach revealed two poorly resolved clusters, one representing the Danish and German groups and the other the Russian group. However, significantly different pairwise FST and DEST estimates were observed between the Danish and German groups and between the Danish and Russian groups suggesting a recent population structure. These conflicting results might be attributed to the effect of migration or low resolution due to the number of microsatellite markers used. After concatenating the two mitochondrial sequences, analysis detected significant genetic differentiation between all populations, probably due to genetic drift combined with a founder event. The phylogenetic tree suggested a closer relationship between the Russian and Northern European populations compared to the Hungarian population, implying that the latter belongs to an older ancestral population. This was supported by the observed haplotype network and higher nucleotide diversity in this population. The genetic structuring observed in the Danish/German pond bat stresses the need for a cross‐border management between the two countries. Further, the pronounced mtDNA structuring, together with the indicated migration between nearby populations suggest philopatric female behavior but male migration, emphasizes the importance of protecting suitable habitat mosaics to maintain a continuum of patches with dense pond bat populations across the species' distribution range
The dynamical Green's function and an exact optical potential for electron-molecule scattering including nuclear dynamics
We derive a rigorous optical potential for electron-molecule scattering
including the effects of nuclear dynamics by extending the common many-body
Green's function approach to optical potentials beyond the fixed-nuclei limit
for molecular targets. Our formalism treats the projectile electron and the
nuclear motion of the target molecule on the same footing whereby the dynamical
optical potential rigorously accounts for the complex many-body nature of the
scattering target. One central result of the present work is that the common
fixed-nuclei optical potential is a valid adiabatic approximation to the
dynamical optical potential even when projectile and nuclear motion are
(nonadiabatically) coupled as long as the scattering energy is well below the
electronic excitation thresholds of the target. For extremely low projectile
velocities, however, when the cross sections are most sensitive to the
scattering potential, we expect the influences of the nuclear dynamics on the
optical potential to become relevant. For these cases, a systematic way to
improve the adiabatic approximation to the dynamical optical potential is
presented that yields non-local operators with respect to the nuclear
coordinates.Comment: 22 pages, no figures, accepted for publ., Phys. Rev.
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