734 research outputs found
Improvements of the Variable Thermal Resistance
A flat mounting unit with electronically variable thermal resistance [1] has
been presented in the last year [2]. The design was based on a Peltier cell and
the appropriate control electronics and software. The device is devoted
especially to the thermal characterization of packages, e.g. in dual cold plate
arrangements. Although this design meets the requirements of the static
measurement we are intended to improve its parameters as the settling time and
dynamic thermal impedance and the range of realized thermal resistance. The new
design applies the heat flux sensor developed by our team as well [3], making
easier the control of the device. This development allows even the realization
of negative thermal resistances.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Holonomy groups of stable vector bundles
We define the notion of holonomy group for a stable vector bundle F on a variety in terms of the Narasimhan-Seshadri unitary representation of its restriction to curves. Next we relate the holonomy group to the minimal structure group and to the decomposition of tensor powers of F. Finally we illustrate the principle that either the holonomy is large or there is a clear geometric reason why it should be small
Autocompensative System for Measurement of the Capacitances
A simple and successful design of an autocompensative system with flip-flop sensor for measurement of capacitances is presented. The analysis of the sensor is based on the state description with the vertical rise segments of the control pulse. The theoretical results are compared with measured data and good agreement is reported
Measuring correlated electron dynamics with time-resolved photoemission spectroscopy
Time-resolved photoemission experiments can reveal fascinating quantum
dynamics of correlated electrons. However, the thermalization of the electronic
system is typically so fast that very short probe pulses are necessary to
resolve the time evolution of the quantum state, and this leads to poor energy
resolution due to the energy-time uncertainty relation. Although the
photoemission intensity can be calculated from the nonequilibrium electronic
Green functions, the converse procedure is therefore difficult. We analyze a
hypothetical time-resolved photoemission experiment on a correlated electronic
system, described by the Falicov-Kimball model in dynamical mean-field theory,
which relaxes between metallic and insulating phases. We find that the
real-time Green function which describes the transient behavior during the
buildup of the metallic state cannot be determined directly from the
photoemission signal. On the other hand, the characteristic
collapse-and-revival oscillations of an excited Mott insulator can be observed
as oscillating weight in the center of the Mott gap in the time-dependent
photoemission spectrum.Comment: 12 pages, 5 figure
Cardiotoxicity of mitoxantrone treatment in a german cohort of 639 multiple sclerosis patients
Background and Purpose: The aim of this study was to elucidate the role of therapy-related cardiotoxicity in multiple sclerosis (MS) patients treated with mitoxantrone and to identify potential predictors for individual risk assessment. Methods: Within a multicenter retrospective cohort design, cardiac side effects attributed to mitoxantrone were analyzed in 639 MS patients at 2 MS centers in Germany. Demographic, disease, treatment, and follow-up data were collected from hospital records. Patients regularly received cardiac monitoring during the treatment phase. Results: None of the patients developed symptomatic congestive heart failure. However, the frequency of patients experiencing cardiac dysfunction of milder forms after mitoxantrone therapy was 4.1% (26 patients) among all patients. Analyses of the risk for cardiotoxicity revealed that cumulative dose exposure was the only statistically relevant risk factor associated with cardiac dysfunction. Conclusions: The number of patients developing subclinical cardiac dysfunction below the maximum recommended cumulative dose is higher than was initially assumed. Interestingly, a subgroup of patients was identified who experienced cardiac dysfunction shortly after initiation of mitoxantrone and who received a low cumulative dose. Therefore, each administration of mitoxantrone should include monitoring of cardiac function to enhance the treatment safety for patients and to allow for early detection of any side effects, especially in potential high-risk subgroups (as determined genetically)
Hydrogen Sulfide as a Toxic Product in the Small-Large Intestine Axis and its Role in IBD Development
The small-large intestine axis in hydrogen sulfide accumulation and testing of sulfate and lactate in the gut-gut axis of the intestinal environment has not been well described. Sulfate reducing bacteria (SRB) of the Desulfovibrio genus reduce sulfate to hydrogen sulfide and can be involved in ulcerative colitis development. The background of the research was to find correlations between hydrogen sulfide production under the effect of an electron acceptor (sulfate) and donor (lactate) at different concentrations and Desulfovibrio piger Vib-7 growth, as well as their dissimilatory sulfate reduction in the intestinal small-large intestinal environment. METHODS: Microbiological, biochemical, and biophysical methods, and statistical processing of the results (principal component and cross-correlation analyses) were used. RESULTS: D. piger Vib-7 showed increased intensity of bacterial growth and hydrogen sulfide production under the following concentrations of sulfate and lactate: 17.4 mM and 35.6 mM, respectively. The study showed in what kind of intestinal environment D. piger Vib-7 grows at the highest level and produces the highest amount of hydrogen sulfide. CONCLUSIONS: The optimum intestinal environment of D. piger Vib-7 can serve as a good indicator of the occurrence of inflammatory bowel diseases; meaning that these findings can be broadly used in medicine practice dealing with the monitoring and diagnosis of intestinal ailments
Laterally coupled and field-induced quantum Hall systems
A quantum Hall system which is divided into two laterally coupled subsystems
by means of a tunneling barrier exhibits a complex Landau level dispersion.
Magnetotunneling spectroscopy is employed to investigate the small energy gaps
which separate subsequent Landau bands. The control on the Fermi level permits
to trace the anticrossings for varying magnetic fields. The band structure
calculation predicts a magnetic shift of the band gaps on the scale of the
cyclotron energy. This effect is confirmed experimentally by a displacement of
the conductance peaks on the axis of the filling factor. Tunneling centers
within the barrier are responsible for quantum interferences between opposite
edge channels. Due to the disorder potential, the corresponding Aharonov-Bohm
interferometers generate additional long-period and irregular conductance
features. In the regime of strong localization, conductance fluctuations occur
at small magnetic fields before the onset of the regular Landau oscillations.
The Landau dispersion is obtained by a dedicated algorithm which solves the
Schroedinger equation exactly for a single electron residing in a quantum Hall
system with an arbitrary unidirectional, threefold staircase potential.Comment: 20 pages, 11 figures, 1 table; v2: explanation added in section 2,
some minor change
Generalized Gibbs ensemble prediction of prethermalization plateaus and their relation to nonthermal steady states in integrable systems
A quantum many-body system which is prepared in the ground state of an
integrable Hamiltonian does not directly thermalize after a sudden small
parameter quench away from integrability. Rather, it will be trapped in a
prethermalized state and can thermalize only at a later stage. We discuss
several examples for which this prethermalized state shares some properties
with the nonthermal steady state that emerges in the corresponding integrable
system. These examples support the notion that nonthermal steady states in
integrable systems may be viewed as prethermalized states that never decay
further. Furthermore we show that prethermalization plateaus are under certain
conditions correctly predicted by generalized Gibbs ensembles, which are the
appropriate extension of standard statistical mechanics in the presence of many
constants of motion. This establishes that the relaxation behaviors of
integrable and nearly integrable systems are continuously connected and
described by the same statistical theory.Comment: 11 pages, 2 figure
Momentum-resolved spectral functions of SrVO calculated by LDA+DMFT
LDA+DMFT, the merger of density functional theory in the local density
approximation and dynamical mean-field theory, has been mostly employed to
calculate k-integrated spectra accessible by photoemission spectroscopy. In
this paper, we calculate k-resolved spectral functions by LDA+DMFT. To this
end, we employ the Nth order muffin-tin (NMTO) downfolding to set up an
effective low-energy Hamiltonian with three t_2g orbitals. This downfolded
Hamiltonian is solved by DMFT yielding k-dependent spectra. Our results show
renormalized quasiparticle bands over a broad energy range from -0.7 eV to +0.9
eV with small ``kinks'', discernible in the dispersion below the Fermi energy.Comment: 21 pages, 8 figure
Mega2: validated data-reformatting for linkage and association analyses.
BACKGROUND: In a typical study of the genetics of a complex human disease, many different analysis programs are used, to test for linkage and association. This requires extensive and careful data reformatting, as many of these analysis programs use differing input formats. Writing scripts to facilitate this can be tedious, time-consuming, and error-prone. To address these issues, the open source Mega2 data reformatting program provides validated and tested data conversions from several commonly-used input formats to many output formats. RESULTS: Mega2, the Manipulation Environment for Genetic Analysis, facilitates the creation of analysis-ready datasets from data gathered as part of a genetic study. It transparently allows users to process genetic data for family-based or case/control studies accurately and efficiently. In addition to data validation checks, Mega2 provides analysis setup capabilities for a broad choice of commonly-used genetic analysis programs. First released in 2000, Mega2 has recently been significantly improved in a number of ways. We have rewritten it in C++ and have reduced its memory requirements. Mega2 now can read input files in LINKAGE, PLINK, and VCF/BCF formats, as well as its own specialized annotated format. It supports conversion to many commonly-used formats including SOLAR, PLINK, Merlin, Mendel, SimWalk2, Cranefoot, IQLS, FBAT, MORGAN, BEAGLE, Eigenstrat, Structure, and PLINK/SEQ. When controlled by a batch file, Mega2 can be used non-interactively in data reformatting pipelines. Support for genetic data from several other species besides humans has been added. CONCLUSIONS: By providing tested and validated data reformatting, Mega2 facilitates more accurate and extensive analyses of genetic data, avoiding the need to write, debug, and maintain one's own custom data reformatting scripts. Mega2 is freely available at https://watson.hgen.pitt.edu/register/
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