377 research outputs found
Onthophagus species (Coleoptera: Scarabaeidae) associated with the Hungarian lesser blind mole-rat (Nannospalax hungaricus) (Mammalia: Spalacidae)
Two rare species of Onthophagus Latreille, 1802 associated with subterranean rodents were found in a nature protection area where the Hungarian lesser blind mole-rat, Nannospalax
hungaricus (Nehring, 1898) is also present. Onthophagus parmatus Reitter, 1892 is reported as new to the fauna of Hungary. Occurrence of Onthophagus kindermanni Harold, 1877 is confi rmed in Hungary. With 2 fi gures and one table
Rediscovery of Parazuphium chevrolatii praepannonicum in Hungary (Coleoptera: Carabidae)
Parazuphium (Parazuphium) chevrolatii praepannonicum (Endrődy-Younga, 1958) was found in 2014, 61 years aft er its discovery (1953) in Hungary. Three specimens were collected in
the Pilis Mts under a large boulder embedded in loessy soil above andesite bedrock. Zuphium hungaricum J. Frivaldszky, 1877 is deleted from the list of Carabidae of present-day Hungary. With 2 figures
ATLAS Monitored Drift Tube Chambers in E = 11 MeV Neutron Background
The influence of fast neutrons on the occupancy and the single tube
resolution of ATLAS muon drift detectors was investigated by exposing a chamber
built out of 3 layers of 3 short standard drift tubes to neutron flux-densities
of up to 16 kHz/cm2 at a neutron energy of E=11 MeV. Pulse shape capable NE213
scintillaton detectors and a calibrated BF3 neutron detector provided
monitoring of the neutron flux-density and energy. The sensitivity of the drift
chamber to the neutrons was measured to be 4*10-4 by comparing data sets with
and without neutron background. For the investigation of tracks of cosmic muons
two silicon-strip detectors above and underneath the chamber allow to compare
measured drift-radii with reference tracks. Alternatively, the single tube
resolution was determined using the triple-sum method. The comparison between
data with and without neutron irradiation shows only a marginal effect on the
resolution and little influence on the muon track reconstruction.Comment: 4 pages, 11 figures, conferenc
Temperature Studies for ATLAS MDT BOS Chambers
Data sets with high statistics taken at the cosmic ray facility, equipped
with 3 ATLAS BOS MDT chambers, in Garching (Munich) have been used to study
temperature and pressure effects on gas gain and drifttime. The deformation of
a thermally expanded chamber was reconstructed using the internal RasNik
alignment monitoring system and the tracks from cosmic data. For these studies
a heating system was designed to increase the temperature of the middle chamber
by up to 20 Kelvins over room temperature. For comparison the temperature
effects on gas properties have been simulated with Garfield. The maximum
drifttime decreased under temperature raise by -2.21 +- 0.08 ns/K, in agreement
with the results of pressure variations and the Garfield simulation. The
increased temperatures led to a linear increase of the gas gain of about 2.1%
1/K. The chamber deformation has been analyzed with the help of reconstructed
tracks. By the comparison of the tracks through the reference chambers with
these through the test chamber the thermal expansion has been reconstructed and
the result shows agreement with the theoretical expansion coefficient. As the
wires are fixed at the end of the chamber, the wire position calculation can
not provide a conclusion for the chamber middle. The complete deformation has
been identified with the analysis of the monitoring system RasNik, whose
measured values have shown a homogeneous expansion of the whole chamber,
overlayed by a shift and a rotation of the chamber middle with respect to the
outer part of the chamber. The established results of both methods are in
agreement. We present as well a model for the position-drifttime correction as
function of temperature.Comment: 4 pages, 12 figures, conferenc
Relativistic quantum mechanics with trapped ions
We consider the quantum simulation of relativistic quantum mechanics, as
described by the Dirac equation and classical potentials, in trapped-ion
systems. We concentrate on three problems of growing complexity. First, we
study the bidimensional relativistic scattering of single Dirac particles by a
linear potential. Furthermore, we explore the case of a Dirac particle in a
magnetic field and its topological properties. Finally, we analyze the problem
of two Dirac particles that are coupled by a controllable and confining
potential. The latter interaction may be useful to study important phenomena as
the confinement and asymptotic freedom of quarks.Comment: 17 pages, 4 figure
Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Quantum simulation is a powerful tool to study a variety of problems in
physics, ranging from high-energy physics to condensed-matter physics. In this
article, we review the recent theoretical and experimental progress in quantum
simulation of Dirac equation with tunable parameters by using ultracold neutral
atoms trapped in optical lattices or subject to light-induced synthetic gauge
fields. The effective theories for the quasiparticles become relativistic under
certain conditions in these systems, making them ideal platforms for studying
the exotic relativistic effects. We focus on the realization of one, two, and
three dimensional Dirac equations as well as the detection of some relativistic
effects, including particularly the well-known Zitterbewegung effect and Klein
tunneling. The realization of quantum anomalous Hall effects is also briefly
discussed.Comment: 22 pages, review article in Frontiers of Physics: Proceedings on
Quantum Dynamics of Ultracold Atom
H2r: Identification of evolutionary important residues by means of an entropy based analysis of multiple sequence alignments
BACKGROUND: A multiple sequence alignment (MSA) generated for a protein can be used to characterise residues by means of a statistical analysis of single columns. In addition to the examination of individual positions, the investigation of co-variation of amino acid frequencies offers insights into function and evolution of the protein and residues. RESULTS: We introduce conn(k), a novel parameter for the characterisation of individual residues. For each residue k, conn(k) is the number of most extreme signals of co-evolution. These signals were deduced from a normalised mutual information (MI) value U(k, l) computed for all pairs of residues k, l. We demonstrate that conn(k) is a more robust indicator than an individual MI-value for the prediction of residues most plausibly important for the evolution of a protein. This proposition was inferred by means of statistical methods. It was further confirmed by the analysis of several proteins. A server, which computes conn(k)-values is available at http://www-bioinf.uni-regensburg.de. CONCLUSION: The algorithms H2r, which analyses MSAs and computes conn(k)-values, characterises a specific class of residues. In contrast to strictly conserved ones, these residues possess some flexibility in the composition of side chains. However, their allocation is sensibly balanced with several other positions, as indicated by conn(k)
Solitary waves in the Nonlinear Dirac Equation
In the present work, we consider the existence, stability, and dynamics of
solitary waves in the nonlinear Dirac equation. We start by introducing the
Soler model of self-interacting spinors, and discuss its localized waveforms in
one, two, and three spatial dimensions and the equations they satisfy. We
present the associated explicit solutions in one dimension and numerically
obtain their analogues in higher dimensions. The stability is subsequently
discussed from a theoretical perspective and then complemented with numerical
computations. Finally, the dynamics of the solutions is explored and compared
to its non-relativistic analogue, which is the nonlinear Schr{\"o}dinger
equation. A few special topics are also explored, including the discrete
variant of the nonlinear Dirac equation and its solitary wave properties, as
well as the PT-symmetric variant of the model
Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of s√=7TeV proton-proton collisions
Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb−1 of pp collision data at s√=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV
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