1,026 research outputs found
Carbon doped symmetric GaAs/AlGaAs quantum wells with hole mobilities beyond 10^6 cm^2/Vs
Utilizing a novel carbon doping source, we prepared two-dimensional hole
gases in a symmetric quantum well structure in the GaAs/AlGaAs heterosystem.
Low temperature hole mobilities up to 1.2 x 10^6 cm^2/Vs at a density of 2.3 x
10^11 cm^-2 were achieved on GaAs (001) substrates. In contrast to electron
systems, the hole mobility sensitively depends on variations of the quantum
well width and the spacer thickness. In particular an increase of the quantum
well width from an optimal value of 15 nm to 18 nm is accompanied by a 35 %
reduction of the hole mobility. The quality of ultrahigh-mobility electron
systems is not affected by the employed carbon doping source
Binocular function to increase visual outcome in patients implanted with a diffractive trifocal intraocular lens
Background: To evaluate binocular visual outcome for near, intermediate and distance compared to monocular visual outcome at the same distances in patients implanted with a diffractive trifocal intraocular lens (IOL). Methods: The study comprised of 100 eyes of 50 patients that underwent bilateral refractive lens exchange or cataract surgery with implantation of a multifocal diffractive IOL (AT LISA tri 839MP, Carl Zeiss Meditech, Germany). A complete ophthalmological examination was performed preoperatively and 3 month postoperatively. The main outcome measures were monocular and binocular uncorrected distance (UDVA), corrected distance (CDVA), uncorrected intermediate (UIVA), and uncorrected near visual acuities (UNVA), keratometry, and manifest refraction. Results: The mean age was 59.28 years ± 9.6 [SD] (range 44â79 years), repectively. There was significant improvement in UDVA, UIVA, UNVA and CDVA. Comparing the monocular results to the binocular results there was a statistical significant better binocular outcome in all distances (UDVA pâ=â0.036; UIVA p <â0.0001; UNVA pâ=â0.001). The postoperative manifest refraction was in 86 % of patients within ± 0.50 [D]. Conclusions: The trifocal IOL improved near, intermediate, and distance vision compared to preoperatively. In addition a statistical significant increase for binocular visual function in all distances could be found. Trial registration German Clinical Trials Register (DRKS) DRKS0000783
Collision of One-Dimensional Nonlinear Chains
We investigate one-dimensional collisions of unharmonic chains and a rigid
wall. We find that the coefficient of restitution (COR) is strongly dependent
on the velocity of colliding chains and has a minimum value at a certain
velocity. The relationship between COR and collision velocity is derived for
low-velocity collisions using perturbation methods. We found that the velocity
dependence is characterized by the exponent of the lowest unharmonic term of
interparticle potential energy
Langzeituntersuchung der Kohlenstoff- und StickstoffkreislĂ€ufe eines intensiven ökologischen Betriebssystems â am Beispiel des Versuchsgutes Scheyern
Carbon, nitrogen and energy flows are considered as an appropriate basis to characterize farming systems and to evaluate the environmental effects. Using the model REPRO the carbon and nitrogen flows of the experimental farm âKlostergut Scheyernâ have been evaluated since 1991 on the basis of complete cultivation data as well as with the help of detailed site and weather data. Thus âScheyernâ is characterised as an intensive organic farming system with a high turnover of C and N
Fission half-lives of super-heavy nuclei in a microscopic approach
A systematic study of 160 heavy and super-heavy nuclei is performed in the
Hartree-Fock-Bogoliubov approach with the finite range and density dependent
Gogny force with the D1S parameter set. We show calculations in several
approximations: with axially symmetric and reflexion symmetric wave functions,
with axially symmetric and non-reflexion symmetric wave functions and finally
some representative examples with triaxial wave functions are also discussed.
Relevant properties of the ground state and along the fission path are
thoroughly analyzed. Fission barriers, Q-factors and lifetimes with
respect to fission and -decay as well as other observables are
discussed. Larger configuration spaces and more general HFB wave functions as
compared to previous studies provide a very good agreement with the
experimental data.Comment: 26 pages, 15 figure
Performance of HPGe Detectors in High Magnetic Fields
A new generation of high-resolution hypernuclear gamma$-spectroscopy
experiments with high-purity germanium detectors (HPGe) are presently designed
at the FINUDA spectrometer at DAPhiNE, the Frascati phi-factory, and at PANDA,
the antiproton proton hadron spectrometer at the future FAIR facility. Both,
the FINUDA and PANDA spectrometers are built around the target region covering
a large solid angle. To maximise the detection efficiency the HPGe detectors
have to be located near the target, and therefore they have to be operated in
strong magnetic fields B ~ 1 T. The performance of HPGe detectors in such an
environment has not been well investigated so far. In the present work VEGA and
EUROBALL Cluster HPGe detectors were tested in the field provided by the ALADiN
magnet at GSI. No significant degradation of the energy resolution was found,
and a change in the rise time distribution of the pulses from preamplifiers was
observed. A correlation between rise time and pulse height was observed and is
used to correct the measured energy, recovering the energy resolution almost
completely. Moreover, no problems in the electronics due to the magnetic field
were observed.Comment: submitted to Nucl. Instrum. Meth. Phys. Res. A, LaTeX, 19 pages, 9
figure
Hydrodynamics of driven granular gases
Hydrodynamic equations for granular gases driven by the Fokker-Planck
operator are derived. Transport coefficients appeared in Navier-Stokes order
change from the values of a free cooling state to those of a steady state.Comment: 5 pages, 3 figure
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