312 research outputs found
Prozess- und Ergebnisqualität der chirurgischen Therapie von Ösophagusperforationen
Die Arbeit untersucht den stationären und postoperativen Langzeitverlauf von 58 Patienten, die aufgrund einer Ösophagusperforation operativ behandelt wurden. Zur Diagnosestellung eignete sich eine Kombination aus Ösophagographie und ÖGD/Röntgenaufnahme des Thorax. OP-Verfahren der Wahl war unabhängig vom Ausmaß der Läsion oder vom OP-Zeitpunkt die Übernähung (74%). Bei gegebener Indikation erfolgte eine Ösophagusresektion (17%), eine alleinige Drainagenversorgung (7%) oder Exploration (2%). Zur Reduktion der Nahtinsuffizienz nach Übernähung sollte bei Achalasiepatienten zusätzlich eine Myotomie erfolgen. Die postoperative Letalität (14%) war mit Komplikationen infektiöser Genese (v.a. Mediastinitis, Sepsis) korreliert. Ein verspäteter Therapiebeginn, das Perforationsausmaß oder OP-Verfahren hatten keinen signifikanten Einfluss. Eine postoperative Versorgung durch eine Magensonde erwies sich als Vorteil, da diese Patienten im Langzeitverlauf signifikant häufiger beschwerdefrei waren
Dynamic Approach to the Fully Frustrated XY Model
Using Monte Carlo simulations, we systematically investigate the
non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional
fully frustrated XY model. The critical initial increase of the staggered
chiral magnetization is observed. By means of the short-time dynamics approach,
we estimate the second order phase transition temperature and all the
dynamic and static critical exponents , z, and .Comment: 5 pages with 6 figures include
Multiplet ligand-field theory using Wannier orbitals
We demonstrate how ab initio cluster calculations including the full Coulomb
vertex can be done in the basis of the localized, generalized Wannier orbitals
which describe the low-energy density functional (LDA) band structure of the
infinite crystal, e.g. the transition metal 3d and oxygen 2p orbitals. The
spatial extend of our 3d Wannier orbitals (orthonormalized Nth order muffin-tin
orbitals) is close to that found for atomic Hartree-Fock orbitals. We define
Ligand orbitals as those linear combinations of the O 2p Wannier orbitals which
couple to the 3d orbitals for the chosen cluster. The use of ligand orbitals
allows for a minimal Hilbert space in multiplet ligand-field theory
calculations, thus reducing the computational costs substantially. The result
is a fast and simple ab initio theory, which can provide useful information
about local properties of correlated insulators. We compare results for NiO,
MnO and SrTiO3 with x-ray absorption, inelastic x-ray scattering, and
photoemission experiments. The multiplet ligand field theory parameters found
by our ab initio method agree within ~10% to known experimental values
Critical exponents of the two-layer Ising model
The symmetric two-layer Ising model (TLIM) is studied by the corner transfer
matrix renormalisation group method. The critical points and critical exponents
are calculated. It is found that the TLIM belongs to the same universality
class as the Ising model. The shift exponent is calculated to be 1.773, which
is consistent with the theoretical prediction 1.75 with 1.3% deviation.Comment: 7 pages, with 10 figures include
Dynamic Simulations of the Kosterlitz-Thouless Phase Transition
Based on the short-time dynamic scaling form, a novel dynamic approach is
proposed to tackle numerically the Kosterlitz-Thouless phase transition. Taking
the two-dimensional XY model as an example, the exponential divergence of the
spatial correlation length, the transition temperature and all
critical exponents are computed. Compared with Monte Carlo simulations in
equilibrium, we obtain data at temperatures nearer to .Comment: to appear in Phys. Rev. E in Rapid Communicatio
Finite Size Scaling and Critical Exponents in Critical Relaxation
We simulate the critical relaxation process of the two-dimensional Ising
model with the initial state both completely disordered or completely ordered.
Results of a new method to measure both the dynamic and static critical
exponents are reported, based on the finite size scaling for the dynamics at
the early time. From the time-dependent Binder cumulant, the dynamical exponent
is extracted independently, while the static exponents and
are obtained from the time evolution of the magnetization and its higher
moments.Comment: 24 pages, LaTeX, 10 figure
The stress-inducible protein DRR1 exerts distinct effects on actin dynamics
Cytoskeletal dynamics are pivotal to memory, learning, and stress physiology, and thus psychiatric diseases. Downregulated in renal cell carcinoma 1 (DRR1) protein was characterized as the link between stress, actin dynamics, neuronal function, and cognition. To elucidate the underlying molecular mechanisms, we undertook a domain analysis of DRR1 and probed the effects on actin binding, polymerization, and bundling, as well as on actin-dependent cellular processes. METHODS: DRR1 domains were cloned and expressed as recombinant proteins to perform in vitro analysis of actin dynamics (binding, bundling, polymerization, and nucleation). Cellular actin-dependent processes were analyzed in transfected HeLa cells with fluorescence recovery after photobleaching (FRAP) and confocal microscopy. RESULTS: DRR1 features an actin binding site at each terminus, separated by a coiled coil domain. DRR1 enhances actin bundling, the cellular F-actin content, and serum response factor (SRF)-dependent transcription, while it diminishes actin filament elongation, cell spreading, and actin treadmilling. We also provide evidence for a nucleation effect of DRR1. Blocking of pointed end elongation by addition of profilin indicates DRR1 as a novel barbed end capping factor. CONCLUSIONS: DRR1 impacts actin dynamics in several ways with implications for cytoskeletal dynamics in stress physiology and pathophysiology
Inelastic X-ray Scattering by Electronic Excitations in Solids at High Pressure
Investigating electronic structure and excitations under extreme conditions
gives access to a rich variety of phenomena. High pressure typically induces
behavior such as magnetic collapse and the insulator-metal transition in 3d
transition metals compounds, valence fluctuations or Kondo-like characteristics
in -electron systems, and coordination and bonding changes in molecular
solids and glasses. This article reviews research concerning electronic
excitations in materials under extreme conditions using inelastic x-ray
scattering (IXS). IXS is a spectroscopic probe of choice for this study because
of its chemical and orbital selectivity and the richness of information it
provides. Being an all-photon technique, IXS has a penetration depth compatible
with high pressure requirements. Electronic transitions under pressure in 3d
transition metals compounds and -electron systems, most of them strongly
correlated, are reviewed. Implications for geophysics are mentioned. Since the
incident X-ray energy can easily be tuned to absorption edges, resonant IXS,
often employed, is discussed at length. Finally studies involving local
structure changes and electronic transitions under pressure in materials
containing light elements are briefly reviewed.Comment: submitted to Rev. Mod. Phy
Dynamic Monte Carlo Measurement of Critical Exponents
Based on the scaling relation for the dynamics at the early time, a new
method is proposed to measure both the static and dynamic critical exponents.
The method is applied to the two dimensional Ising model. The results are in
good agreement with the existing results. Since the measurement is carried out
in the initial stage of the relaxation process starting from independent
initial configurations, our method is efficient.Comment: (5 pages, 1 figure) Siegen Si-94-1
Lindhard and RPA susceptibility computations in extended momentum space in electron doped cuprates
We present an approximation for efficient calculation of the Lindhard
susceptibility in a periodic system through the use of
simple products of real space functions and the fast Fourier transform (FFT).
The method is illustrated by providing results for the
electron doped cuprate NdCeCuO extended over several
Brillouin zones. These results are relevant for interpreting inelastic X-ray
scattering spectra from cuprates.Comment: 6 pages, 6 figures, accepted in Physical Review
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