222 research outputs found
Beleuchtung und Mikro-KohĂ€renz fĂŒr die Mikroskopie
Die Themen der Arbeit sind die partielle KohĂ€renz im Mikrometerbereich sowie eine interferenzoptische Beleuchtung und beider Anwendung in der optischen Mikroskopie. Dazu wird eine Chip-Anordnung zum Vermessen der rĂ€umlichen KohĂ€renzeigenschaften von LED-Lichtquellen, Halogen- und Quecksilberdampflampen erarbeitet. Beispielhaft werden die Vorteile einer Mikro-KohĂ€renz fĂŒr die digitale in-line holografische Mikroskopie und die Anwendbarkeit eines Beleuchtungs-Chips in der strukturierten Beleuchtung fĂŒr die Mikroskopie gezeigt
Time-dependent energy absorption changes during ultrafast lattice deformation
The ultrafast time-dependence of the energy absorption of covalent solids
upon excitation with femtosecond laser pulses is theoretically analyzed. We use
a microscopic theory to describe laser induced structural changes and their
influence on the electronic properties. We show that from the time evolution of
the energy absorbed by the system important information on the electronic and
atomic structure during ultrafast phase transitions can be gained. Our results
reflect how structural changes affect the capability of the system to absorb
external energy.Comment: 7 pages RevTeX, 8 ps figures, submitted to Journal of Appl. Physic
Single therapeutic and supratherapeutic doses of sacubitril/valsartan (LCZ696) do not affect cardiac repolarization
Purpose: Sacubitril/valsartan (LCZ696) is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) indicated to reduce the risk of cardiovascular death and hospitalization for heart failure in patients with chronic heart failure (NYHA class IIâIV) and reduced ejection fraction. This study was aimed to evaluate the effect of single oral therapeutic (400Â mg) and supratherapeutic (1200Â mg) doses of LCZ696 on cardiac repolarization. Method: This randomized double-blind crossover study in healthy male subjects compared the effect of therapeutic and supratherapeutic doses of LCZ696 with placebo and moxifloxacin 400Â mg (open-label treatment) as positive control. The primary assessment was mean baseline- and placebo-corrected QTcF (ââQTcF; Fridericia correction). Additional assessments included the ââQTcB (Bazettâs correction), PR interval, QRS duration, heart rate (HR), LCZ696 pharmacokinetics, pharmacokinetic/pharmacodynamic relationships, and safety. Results: Of the 84 subjects enrolled, 81 completed the study. The maximum upper bound of the two-sided 90Â % confidence interval for ââQTcF for LCZ696 400Â mg and 1200Â mg were <10Â ms, and assay sensitivity was confirmed with moxifloxacin. No relevant treatment-emergent changes were observed in any of the ECG-derived parameters with LCZ696 or placebo, and the incidence of adverse events was comparable among the treatment groups. Conclusion: Single therapeutic and supratherapeutic doses of LCZ696 did not affect cardiac repolarization as defined by the E14 ICH guidelines
Dynamical ionization ignition of clusters in intense and short laser pulses
The electron dynamics of rare gas clusters in laser fields is investigated
quantum mechanically by means of time-dependent density functional theory. The
mechanism of early inner and outer ionization is revealed. The formation of an
electron wave packet inside the cluster shortly after the first removal of a
small amount of electron density is observed. By collisions with the cluster
boundary the wave packet oscillation is driven into resonance with the laser
field, hence leading to higher absorption of laser energy. Inner ionization is
increased because the electric field of the bouncing electron wave packet adds
up constructively to the laser field. The fastest electrons in the wave packet
escape from the cluster as a whole so that outer ionization is increased as
well.Comment: 8 pages, revtex4, PDF-file with high resolution figures is available
from http://mitarbeiter.mbi-berlin.de/bauer/publist.html, publication no. 24.
Accepted for publication in Phys. Rev.
Characterization of doping levels in heteronuclear, gas-phase, van der Waals clusters and their energy absorption from an intense optical field
A simple mass spectrometric method has been developed to quantify dopant
levels in heteronuclear clusters in the gas phase. The method is demonstrated
with reference to quantification of the water content in supersonic beams of
water-doped argon clusters. Such doped clusters have assumed much importance in
the context of recently-reported doping-induced enhancement in the emission of
energetic charged particles and photons upon their interaction with intense
laser pulses. We have also measured the energy that a doped cluster absorbs
from the optical field; we find that energy absorption increases with
increasing level of doping. The oft-used linear model of energy absorption is
found to be quantitatively inadequate.Comment: To appear in Chemical Physics Letter
Enhanced ionization in small rare gas clusters
A detailed theoretical investigation of rare gas atom clusters under intense
short laser pulses reveals that the mechanism of energy absorption is akin to
{\it enhanced ionization} first discovered for diatomic molecules. The
phenomenon is robust under changes of the atomic element (neon, argon, krypton,
xenon), the number of atoms in the cluster (16 to 30 atoms have been studied)
and the fluency of the laser pulse. In contrast to molecules it does not
dissappear for circular polarization. We develop an analytical model relating
the pulse length for maximum ionization to characteristic parameters of the
cluster
Probing impulsive strain propagation with x-ray pulses
Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden
reflections in InSb is used to follow the propagation of a coherent acoustic
pulse generated by ultrafast laser-excitation. The surface and bulk components
of the strain could be simultaneously measured due to the large x-ray
penetration depth. Comparison of the experimental data with dynamical
diffraction simulations suggests that the conventional model for impulsively
generated strain underestimates the partitioning of energy into coherent modes.Comment: 4 pages, 2 figures, LaTeX, eps. Accepted for publication in Phys.
Rev. Lett. http://prl.aps.or
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