2,185 research outputs found
Separability for lattice systems at high temperature
Equilibrium states of infinite extended lattice systems at high temperature
are studied with respect to their entanglement. Two notions of separability are
offered. They coincide for finite systems but differ for infinitely extended
ones. It is shown that for lattice systems with localized interaction for high
enough temperature there exists no local entanglement. Even more quasifree
states at high temperature are also not distillably entangled for all local
regions of arbitrary size. For continuous systems entanglement survives for all
temperatures. In mean field theories it is possible, that local regions are not
entangled but the entanglement is hidden in the fluctuation algebra
Enhancement of the Deuteron-Fusion Reactions in Metals and its Experimental Implications
Recent measurements of the reaction d(d,p)t in metallic environments at very
low energies performed by different experimental groups point to an enhanced
electron screening effect. However, the resulting screening energies differ
strongly for divers host metals and different experiments. Here, we present new
experimental results and investigations of interfering processes in the
irradiated targets. These measurements inside metals set special challenges and
pitfalls which make them and the data analysis particularly error-prone. There
are multi-parameter collateral effects which are crucial for the correct
interpretation of the observed experimental yields. They mainly originate from
target surface contaminations due to residual gases in the vacuum as well as
from inhomogeneities and instabilities in the deuteron density distribution in
the targets. In order to address these problems an improved differential
analysis method beyond the standard procedures has been implemented. Profound
scrutiny of the other experiments demonstrates that the observed unusual
changes in the reaction yields are mainly due to deuteron density dynamics
simulating the alleged screening energy values. The experimental results are
compared with different theoretical models of the electron screening in metals.
The Debye-H\"{u}ckel model that has been previously proposed to explain the
influence of the electron screening on both nuclear reactions and radioactive
decays could be clearly excluded.Comment: 22 pages, 12 figures, REVTeX4, 2-column format. Submitted to Phys.
Rev. C; accepte
Dynamic shipments of inventories in shared warehouse and transportation networks
In shared warehouse and transportation networks, dynamic shipments of inventories are carried out based on up-to-date inventory information. This paper studies the effect of network structures on optimal decision-making. We propose a discrete time modeling framework with stochastic demand, capturing a wide variety of network structures. Using Markov decision processes, we obtain optimal order and dynamic shipment decisions for small networks. We compare optimal solutions of different four-node network structures. Results indicate product characteristics significantly influence the effectiveness of network structures. Surprisingly, two-echelon networks are occasionally costlier than any other network. Moreover, dynamic shipments yield considerable gains over static shipments
Hot Nuclear Matter in the Quark Meson Coupling Model with Dilatons
We study hot nuclear matter in an explicit quark model based on a mean field
description of nonoverlapping nucleon bags bound by the self-consistent
exchange of scalar and vector mesons as well as the glueball field. The
glueball exchange as well as a realization of the broken scale invariance of
quantum chromodynamics is achieved through the introduction of a dilaton field.
The calculations also take into account the medium-dependence of the bag
constant. The effective potential with dilatons is applied to nuclear matter.
The nucleon properties at finite temperature as calculated here are found to be
appreciably different from cold nuclear matter. The introduction of the dilaton
potential improves the shape of the saturation curve at T=0 and is found to
affect hot nuclear matter significantly.Comment: LaTeX/TeX 12 pages (zak2), 13 figures in TeX forma
Electromagnetic vertex function of the pion at T > 0
The matrix element of the electromagnetic current between pion states is
calculated in quenched lattice QCD at a temperature of . The
nonperturbatively improved Sheikholeslami-Wohlert action is used together with
the corresponding improved vector current. The electromagnetic
vertex function is extracted for pion masses down to and
momentum transfers .Comment: 17 pages, 8 figure
Pion structure from improved lattice QCD: form factor and charge radius at low masses
The charge form factor of the pion is calculated in lattice QCD. The
non-perturbatively improved Sheikholeslami-Wohlert action is used together with
the improved vector current. Other choices for the current are
examined. The form factor is extracted for pion masses from 970 MeV down to 360
MeV and for momentum transfers . The mean square
charge radius is extracted, compared to previous determinations and its
extrapolation to lower masses discussed.Comment: 12 pages REVTeX, 15 figures. Designation of currents clarified.
Details concerning extraction of parameters added. Version accepted by Phys.
Rev.
Finite Nuclei in a Relativistic Mean-Field Model with Derivative Couplings
We study finite nuclei, at the mean-field level, using the Zimanyi-Moskowski
model and one of its variations (the ZM3 model). We calculate energy levels and
ground-state properties in nuclei where the mean-field approach is reliable.
The role played by the spin-orbit potential in sorting out mean-field model
descriptions is emphasized.Comment: 17 pages, 9 figures, 30 kbytes. Uses EPSF.TEX. To appear in Zeit. f.
Phys. A (Hadrons and Nuclei
Design, Development and Optimization of a Functional Mammalian Cell-Free Protein Synthesis Platform
In Vivo Time- Resolved Microtomography Reveals the Mechanics of the Blowfly Flight Motor
Dipteran flies are amongst the smallest and most agile of flying animals. Their wings are driven indirectly by large power muscles, which cause cyclical deformations of the thorax that are amplified through the intricate wing hinge. Asymmetric flight manoeuvres are controlled by 13 pairs of steering muscles acting directly on the wing articulations. Collectively the steering muscles account for <3% of total flight muscle mass, raising the question of how they can modulate the vastly greater output of the power muscles during manoeuvres. Here we present the results of a synchrotron-based study performing micrometre-resolution, time-resolved microtomography on the 145 Hz wingbeat of blowflies. These data represent the first four-dimensional visualizations of an organism's internal movements on sub-millisecond and micrometre scales. This technique allows us to visualize and measure the three-dimensional movements of five of the largest steering muscles, and to place these in the context of the deforming thoracic mechanism that the muscles actuate. Our visualizations show that the steering muscles operate through a diverse range of nonlinear mechanisms, revealing several unexpected features that could not have been identified using any other technique. The tendons of some steering muscles buckle on every wingbeat to accommodate high amplitude movements of the wing hinge. Other steering muscles absorb kinetic energy from an oscillating control linkage, which rotates at low wingbeat amplitude but translates at high wingbeat amplitude. Kinetic energy is distributed differently in these two modes of oscillation, which may play a role in asymmetric power management during flight control. Structural flexibility is known to be important to the aerodynamic efficiency of insect wings, and to the function of their indirect power muscles. We show that it is integral also to the operation of the steering muscles, and so to the functional flexibility of the insect flight motor
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