615 research outputs found
Null-Wave Giant Gravitons from Thermal Spinning Brane Probes
We construct and analyze thermal spinning giant gravitons in type II/M-theory
based on spherically wrapped black branes, using the method of thermal probe
branes originating from the blackfold approach. These solutions generalize in
different directions recent work in which the case of thermal (non-spinning)
D3-brane giant gravitons was considered, and reveal a rich phase structure with
various new properties. First of all, we extend the construction to M-theory,
by constructing thermal giant graviton solutions using spherically wrapped M2-
and M5-branes. More importantly, we switch on new quantum numbers, namely
internal spins on the sphere, which are not present in the usual extremal limit
for which the brane world volume stress tensor is Lorentz invariant. We examine
the effect of this new type of excitation and in particular analyze the
physical quantities in various regimes, including that of small temperatures as
well as low/high spin. As a byproduct we find new stationary dipole-charged
black hole solutions in AdS_m X S^n backgrounds of type II/M-theory. We finally
show, via a double scaling extremal limit, that our spinning thermal giant
graviton solutions lead to a novel null-wave zero-temperature giant graviton
solution with a BPS spectrum, which does not have an analogue in terms of the
conventional weakly coupled world volume theory.Comment: v1: 31p
Long time scale simulation of a grain boundary in copper
doi:10.1088/1367-2630/11/7/073034 Abstract. A general, twisted and tilted, grain boundary in copper has been simulated using the adaptive kinetic Monte Carlo method to study the atomistic structure of the non-crystalline region and the mechanism of annealing events that occur at low temperature. The simulated time interval spanned 67µs at 135 K. Similar final configurations were obtained starting from different initial structures: (i) by bringing the two grains into contact without any intermediate layer, and (ii) by inserting an amorphous region between the grains. The results obtained were analyzed with a radial distribution function and a common neighbor analysis. Annealing events leading to lowering of the energy typically involved concerted displacement of several atoms—even as many as 10 atoms displaced by more than half an Ångström. Increased local icosahedral ordering is observed in the boundary layer, but local HCP coordination was also observed. In the final low-energy configurations, the thickness of the region separating the crystalline grains corresponds to just one atomic layer, in good agreemen
Coherent Transport through an interacting double quantum dot: Beyond sequential tunneling
Various causes for negative differential conductance in transport through an
interacting double quantum dot are investigated. Particular focus is given to
the interplay between the renormalization of the energy levels due to the
coupling to the leads and the decoherence of the states. The calculations are
performed within a basis of many-particle eigenstates and we consider the
dynamics given by the von Neumann-equation taking into account also processes
beyond sequential tunneling. A systematic comparison between the levels of
approximation and also with different formalisms is performed. It is found that
the current is qualitatively well described by sequential processes as long as
the temperature is larger than the level broadening induced by the contacts.Comment: 11 pages, 5 figures included in tex
Tunneling through nanosystems: Combining broadening with many-particle states
We suggest a new approach for transport through finite systems based on the
Liouville equation. By working in a basis of many-particle states for the
finite system, Coulomb interactions are taken fully into account and correlated
transitions by up to two different contact states are included. This latter
extends standard rate equation models by including level-broadening effects.
The main result of the paper is a general expression for the elements of the
density matrix of the finite size system, which can be applied whenever the
eigenstates and the couplings to the leads are known. The approach works for
arbitrary bias and for temperatures above the Kondo temperature. We apply the
approach to standard models and good agreement with other methods in their
respective regime of validity is found.Comment: 9 pages, 5 figures included to tex
Surface and Bulk Relaxation of Vapour-Deposited Polystyrene Glasses
We have studied the liquid-like response of the surface of vapour-deposited
glassy films of polystyrene to the introduction of gold nanoparticles on the
surface. The build-up of polymer material was measured as a function of time
and temperature for both as-deposited films, as well as films that have been
rejuvenated to become normal glasses cooled from the equilibrium liquid. The
temporal evolution of the surface profile is well described by the
characteristic power law of capillary-driven surface flows. In all cases, the
surface evolution of the as-deposited films and the rejuvenated films are
enhanced compared to bulk and are not easily distinguishable from each other.
The temperature dependence of the measured relaxation times determined from the
surface evolution is found to be quantitatively comparable to similar studies
for high molecular weight spincast polystyrene. Comparisons to numerical
solutions of the glassy thin film equation provide quantitative estimates of
the surface mobility. For temperatures sufficiently close to the
glass-transition temperature, particle embedding is also measured and used as a
probe of bulk dynamics, and in particular bulk viscosity
Identification of the first surrogate agonists for the G protein-coupled receptor GPR132
This is the accepted manuscript. The final version is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/RA/c5ra04804d#!divAbstract.GPR132 is an orphan Class A G protein-coupled receptor. It has been proposed to be activated by protons\ud
and to regulate apoptosis, atherosclerosis and inflammation, but these results are still preliminary. In the\ud
current work, we now designed and screened a focused compound library using a ?-arrestin recruitment\ud
assay, and thereby identified the first disclosed surrogate GPR132 agonist 1 with a potency of 3.4 ?M.\ud
This constitutes the first available pharmacological tool for the in vitro characterization of the orphan\ud
receptor GPR132. The testing of 32 analogs furthermore identified a number of compounds with lower\ud
activity - of which six were agonists and two were antagonists - that were used to construct preliminary\ud
structure-activity relationships. Docking followed by molecular dynamics simulation of compound 1 in a\ud
structural model of GPR132 displayed the putative interactions for the key ligand functionalities.M.A.S. was supported by a research scholarship from the\ud
Drug Research Academy and Novo Nordisk A/S. D.E.G.\ud
and H.B.-O. gratefully acknowledge financial support by\ud
the Carlsberg Foundation. D.E.G. and D.S.P. gratefully\ud
acknowledges financial support by the Lundbeck\ud
Foundation. Nils Nyberg is acknowledged for help with\ud
NMR spectroscopy. NMR equipment used in this work\ud
was purchased via a grant from The Lundbeck\ud
Foundation (R77-A6742)
Gene Expression in Peripheral Blood Leukocytes in Monozygotic Twins Discordant for Chronic Fatigue: No Evidence of a Biomarker
Background: Chronic fatiguing illness remains a poorly understood syndrome of unknown pathogenesis. We attempted to identify biomarkers for chronic fatiguing illness using microarrays to query the transcriptome in peripheral blood leukocytes. Methods: Cases were 44 individuals who were clinically evaluated and found to meet standard international criteria for chronic fatigue syndrome or idiopathic chronic fatigue, and controls were their monozygotic co-twins who were clinically evaluated and never had even one month of impairing fatigue. Biological sampling conditions were standardized and RNA stabilizing media were used. These methodological features provide rigorous control for bias resulting from case-control mismatched ancestry and experimental error. Individual gene expression profiles were assessed using Affymetrix Human Genome U133 Plus 2.0 arrays. Findings: There were no significant differences in gene expression for any transcript. Conclusions: Contrary to our expectations, we were unable to identify a biomarker for chronic fatiguing illness in the transcriptome of peripheral blood leukocytes suggesting that positive findings in prior studies may have resulted fro
Thermal Giant Gravitons
We study the giant graviton solution as the AdS_5 X S^5 background is heated
up to finite temperature. The analysis employs the thermal brane probe
technique based on the blackfold approach. We focus mainly on the thermal giant
graviton corresponding to a thermal D3-brane probe wrapped on an S^3 moving on
the S^5 of the background at finite temperature. We find several interesting
new effects, including that the thermal giant graviton has a minimal possible
value for the angular momentum and correspondingly also a minimal possible
radius of the S^3. We compute the free energy of the thermal giant graviton in
the low temperature regime, which potentially could be compared to that of a
thermal state on the gauge theory side. Moreover, we analyze the space of
solutions and stability of the thermal giant graviton and find that, in
parallel with the extremal case, there are two available solutions for a given
temperature and angular momentum, one stable and one unstable. In order to
write down the equations of motion, action and conserved charges for the
thermal giant graviton we present a slight generalization of the blackfold
formalism for charged black branes. Finally, we also briefly consider the
thermal giant graviton moving in the AdS_5 part.Comment: v1: 32 pages + 11 pages appendices, 13 figures, v2: typos fixed in
Sec.2 and other misprints, references adde
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