3,045 research outputs found
Influence of polydispersity on micromechanics of granular materials
We study the effect of polydispersity on the macroscopic physical properties
of granular packings in two and three dimensions. A mean-field approach is
developed to approximate the macroscale quantities as functions of the
microscopic ones. We show that the trace of the fabric and stress tensors are
proportional to the mean packing properties (e.g. packing fraction, average
coordination number, and average normal force) and dimensionless correction
factors, which depend only on the moments of the particle-size distribution.
Similar results are obtained for the elements of the stiffness tensor of
isotropic packings in the linear affine response regime. Our theoretical
predictions are in good agreement with the simulation results.Comment: 13 pages, 13 figures, 2 table
SUSY QCD one-loop effects in (un)polarized top-pair production at hadron colliders
We study the effects of O(alpha_s) supersymmetric QCD (SQCD) corrections on
the total production rate and kinematic distributions of polarized and
unpolarized top-pair production in pp and p anti-p collisions. At the Fermilab
Tevatron p anti-p collider, top-quark pairs are mainly produced via
quark-antiquark annihilation, q anti-q -> t anti-t, while at the CERN LHC pp
collider gluon-gluon scattering, g g -> t anti-t, dominates. We compute the
complete set of O(alpha_s) SQCD corrections to both production channels and
study their dependence on the parameters of the Minimal Supersymmetric Standard
Model. In particular, we discuss the prospects for observing strong,
loop-induced SUSY effects in top-pair production at the Tevatron Run II and the
LHC.Comment: 56 pages, 29 figures, RevTeX
Die Welt jenseits der Oszillografen : ein StreitgesprÀch zwischen dem Hirnforscher Wolf Singer und dem Philosophen Marcus Willaschek
Neurowissenschaftler fordern einen illusionslosen Umgang mit Begriffen wie Willensfreiheit und Bewusstsein. Philosophen kritisieren offen die Thesen von Hirnforschern. Stehen sich diese Positionen unversöhnlich gegenĂŒber? Wo gibt es Möglichkeiten einer AnnĂ€herung, gar einer Kooperation? Der Religionsphilosoph Prof. Dr. Thomas M. Schmidt und der Biologe Stefan KieĂ loten die Situation in Frankfurt aus; ihre GesprĂ€chspartner sind der Hirnforscher Prof. Dr. Wolf Singer (links), Direktor am Max-Planck-Institut fĂŒr Hirnforschung, und Prof. Dr. Marcus Willaschek (rechts), Philosoph an der UniversitĂ€t Frankfurt
Non-perturbative effects in semi-leptonic B_c decays
We discuss the impact of the soft degrees of freedom inside the B_c meson on
its rate in the semi-leptonic decay B_c -> X l nu_l where X denotes light
hadrons below the D^0 threshold. In particular we identify contributions
involving soft hadrons which are non-vanishing in the limit of massless
leptons. These contributions become relevant for a measurement of the purely
leptonic B_c decay rate, which due to helicity suppression involves a factor
m_l^2 and thus is much smaller than the contributions involving soft hadrons.Comment: LaTeX, 22 pages, 1 figur
Particle-Particle, Particle-Scaling function (P3S) algorithm for electrostatic problems in free boundary conditions
An algorithm for fast calculation of the Coulombic forces and energies of
point particles with free boundary conditions is proposed. Its calculation time
scales as N log N for N particles. This novel method has lower crossover point
with the full O(N^2) direct summation than the Fast Multipole Method. The
forces obtained by our algorithm are analytical derivatives of the energy which
guarantees energy conservation during a molecular dynamics simulation. Our
algorithm is very simple. An MPI parallelised version of the code can be
downloaded under the GNU General Public License from the website of our group.Comment: 19 pages, 11 figures, submitted to: Journal of Chemical Physic
Inhibitor of Apoptosis Proteins as Novel Targets in Inflammatory Processes
Objective: Inhibitor of apoptosis proteins (IAPs), such as X-linked or cellular IAP 1/2 (XIAP, cIAP1/2), are important regulators of apoptosis. IAP antagonists are currently under clinical investigation as anticancer agents. Interestingly, IAPs participate in the inflammation-associated TNF receptor signaling complex and regulate NFÎșB signaling. This raises the question about the role of IAPs in inflammation. Here, we investigated the anti-inflammatory potential of IAP inhibitors and the role of IAPs in inflammatory processes of endothelial cells.
Methods and Results: In mice, the small molecule IAP antagonist A-4.10099.1 (ABT) suppressed antigen-induced arthritis, leukocyte infiltration in concanavalin A-evoked liver injury, and leukocyte transmigration in the TNFα-activated cremaster muscle. In vitro, we observed an attenuation of leukocyteâ endothelial cell interaction by downregulation of the intercellular adhesion molecule-1. ABT did not impair NFÎșB signaling but decreased the TNFα-induced activation of the TGF-ÎČâactivated kinase 1, p38, and c-Jun N-terminal kinase. These effects are based on the proteasomal degradation of cIAP1/2 accompanied by an altered ratio of the levels of membrane-localized TNF receptor-associated factors 2 and 5.
Conclusion: Our results reveal IAP antagonism as a profound anti-inflammatory principle in vivo and highlight IAPs as important regulators of inflammatory processes in endothelial cells
Moduli-Space Dynamics of Noncommutative Abelian Sigma-Model Solitons
In the noncommutative (Moyal) plane, we relate exact U(1) sigma-model
solitons to generic scalar-field solitons for an infinitely stiff potential.
The static k-lump moduli space C^k/S_k features a natural K"ahler metric
induced from an embedding Grassmannian. The moduli-space dynamics is blind
against adding a WZW-like term to the sigma-model action and thus also applies
to the integrable U(1) Ward model. For the latter's two-soliton motion we
compare the exact field configurations with their supposed moduli-space
approximations. Surprisingly, the two do not match, which questions the
adiabatic method for noncommutative solitons.Comment: 1+15 pages, 2 figures; v2: reference added, to appear in JHE
An online programme to reduce depression in patients with multiple sclerosis: a randomised controlled trial
Summary
Background With a lifetime risk for major depressive disorder of up to 50%, depression is a common comorbidity in
multiple sclerosis but remains widely underdiagnosed and untreated. We investigated the potential of a fully
automated, internet-based, cognitive behavioural therapy programme, Deprexis, to reduce depressive symptoms in
patients with multiple sclerosis.
Methods For this randomised controlled trial, we recruited patients from an outpatient clinic in Hamburg, Germany.
Patients aged 18â65 years were eligible for inclusion if they had multiple sclerosis and self-reported depressive
symptoms. By use of a computer-generated randomisation sequence, we allocated 90 patients (1:1; no blocking or
stratification) to either the intervention group or a waitlist control group for 9 weeks. The primary endpoint was the
Beck Depression Inventory (BDI), as assessed by an intention-to-treat analysis. This trial is registered with
ClinicalTrials.gov, number NCT01663649.
Findings 71 patients completed the trial: 35 patients in the intervention group and 36 patients in the control group.
During the intervention, BDI scores decreased in the Deprexis group and increased in the control group, yielding a
positive effect of Deprexis relative to the waitlist group (mean group difference â4·02 points [95% CI â7·26 to â0·79],
p=0·015, effect size d=0·53). Worsening of depressive symptoms from below to above the clinical cutoff (BDI >13)
occurred in three (7%) of 45 patients in the control group and no patients in the Deprexis group. We noted no adverse
events with respect to new occurrence of suicidal ideation during the trial.
Interpretation Psychological online-intervention programmes could be suitable for patients with multiple sclerosis
who are unable to regularly attend therapeutic sessions because of mobility impairments.
Funding European Union and the Deutsche Forschungsgemeinschaft
Effect of amoxicillinâclavulanic acid on clinical scores, intestinal microbiome, and amoxicillinâresistant Escherichia coli in dogs with uncomplicated acute diarrhea
Background
Despite limited evidence of efficacy, antibiotic treatment is still frequently prescribed in dogs with uncomplicated acute diarrhea (AD).
Objective
To assess whether amoxicillinâclavulanic acid has a clinical benefit, an effect on the fecal microbiome, and the proportion of amoxicillinâresistant Escherichia coli in dogs with AD.
Animals
Sixteen dogs with AD of <3âdays duration.
Methods
Prospective, placeboâcontrolled, doubleâblinded study. Clinical scores were compared between clientâowned dogs randomly assigned to an antibiotic (AG) or a placebo (PG) group. The intestinal microbiome was analyzed using quantitative PCR assays. Amoxicillinâresistant fecal E. coli were assessed semiquantitatively with microbiological methods.
Results
There was no difference in clinical recovery between treated dogs or controls (CADS index day 10: AG group median: 2 (range: 1â3; CI [1.4; 2.6]); PG group median: 1.6 (range: 1â3; CI [1.1; 2.4]); P >â.99). All dogs gained normal clinical scores (CADS index â€3) after 1 to 6âdays (median 2âdays) after presentation. There was no significant difference in the fecal dysbiosis index (during treatment: AG mean â2.6 (SD 3.0; CI [â5.1; 0.0]); PG mean â0.8 (SD 4.0; CI [â4.2; 2.5]; P >â.99) or its bacterial taxa. The proportion of resistant fecal E. coli increased (to median: 100%; range: 35%â100%) during treatment with amoxicillinâclavulanic acid and was still increased (median: 10%; range 2%â67%) 3âweeks after treatment, both of which were significantly higher proportions than in the placebo group for both time points (during treatment AG median 100% versus PG median 0.2% (P <â.001); after treatment AG median 10% versus PG median 0.0% (P =â.002)).
Conclusions and Clinical Importance
Our study suggests that treatment with amoxicillinâclavulanic acid confers no clinical benefit to dogs with AD, but predisposes the development of amoxicillinâresistant E. coli , which persist for as long as 3âweeks after treatment. These findings support international guideline recommendations that dogs with diarrhea should not be treated with antimicrobials unless there are signs of sepsis
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