78 research outputs found
Revisiting Absorbing Phase Transition in Energy Exchange Models
A recent study of conserved Manna model, with both discrete and continuous
variable, indicates that absorbing phase transitions therein belong to the
directed percolation (DP) universality class. In this context we revisit
critical behaviour in energy exchange models with a threshold. Contrary to the
previous claims [PRE 83, 061130 (2011), arXiv:1102.1631], our results indicate
that both the maximal and minimal versions of this model belong to the DP
class.Comment: 8 pages, 7 eps figure
Comparison of coherent and weakly incoherent transport models for the interlayer magnetoresistance of layered Fermi liquids
The interlayer magnetoresistance of layered metals in a tilted magnetic field
is calculated for two distinct models for the interlayer transport. The first
model involves coherent interlayer transport and makes use of results of
semi-classical or Bloch-Boltzmann transport theory. The second model involves
weakly incoherent interlayer transport where the electron is scattered many
times within a layer before tunneling into the next layer. The results are
relevant to the interpretation of experiments on angular-dependent
magnetoresistance oscillations (AMRO) in quasi-one- and quasi-two-dimensional
metals. We find that the dependence of the magnetoresistance on the direction
of the magnetic field is identical for both models except when the field is
almost parallel to the layers. An important implication of this result is that
a three-dimensional Fermi surface is not necessary for the observation of the
Yamaji and Danner oscillations seen in quasi-two- and quasi-one-dimensional
metals, respectively. A universal expression is given for the dependence of the
resistance at AMRO maxima and minima on the magnetic field and scattering time
(and thus the temperature). We point out three distinctive features of coherent
interlayer transport: (i) a beat frequency in the magnetic oscillations of
quasi-two-dimensional systems, (ii) a peak in the angular-dependent
magnetoresistance when the field is sufficiently large and parallel to the
layers, and (iii) a crossover from a linear to a quadratic field dependence for
the magnetoresistance when the field is parallel to the layers. Properties (i)
and (ii) are compared with published experimental data for a range of
quasi-two-dimensional organic metals and for Sr2RuO4.Comment: 21 pages, RevTeX + epsf, 4 figures. Published version. Subsection
added. References update
Recommended from our members
Cause of Death and Predictors of All-Cause Mortality in Anticoagulated Patients With Nonvalvular Atrial Fibrillation : Data From ROCKET AF
M. Kaste on työryhmän ROCKET AF Steering Comm jäsen.Background-Atrial fibrillation is associated with higher mortality. Identification of causes of death and contemporary risk factors for all-cause mortality may guide interventions. Methods and Results-In the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF) study, patients with nonvalvular atrial fibrillation were randomized to rivaroxaban or dose-adjusted warfarin. Cox proportional hazards regression with backward elimination identified factors at randomization that were independently associated with all-cause mortality in the 14 171 participants in the intention-to-treat population. The median age was 73 years, and the mean CHADS(2) score was 3.5. Over 1.9 years of median follow-up, 1214 (8.6%) patients died. Kaplan-Meier mortality rates were 4.2% at 1 year and 8.9% at 2 years. The majority of classified deaths (1081) were cardiovascular (72%), whereas only 6% were nonhemorrhagic stroke or systemic embolism. No significant difference in all-cause mortality was observed between the rivaroxaban and warfarin arms (P=0.15). Heart failure (hazard ratio 1.51, 95% CI 1.33-1.70, P= 75 years (hazard ratio 1.69, 95% CI 1.51-1.90, P Conclusions-In a large population of patients anticoagulated for nonvalvular atrial fibrillation, approximate to 7 in 10 deaths were cardiovascular, whereasPeer reviewe
Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management
Atrioventricular block is classified as congeni-
tal if diagnosed in utero, at birth, or within the first
month of life. The pathophysiological process is believed
to be due to immune-mediated injury of the conduction
system, which occurs as a result of transplacental pas-
sage of maternal anti-SSA/Ro-SSB/La antibodies.
Childhood atrioventricular block is therefore diagnosed
between the first month and the 18th year of life.
Genetic variants in multiple genes have been described
to date in the pathogenesis of inherited progressive car-
diac conduction disorders. Indications and techniques of
cardiac pacing have also evolved to allow safe perma-
nent cardiac pacing in almost all patients, including
those with structural heart abnormalities
Contagion Shocks in One Dimension
We consider an agent-based model of emotional contagion coupled with motion in one dimension that has recently been studied in the computer science community. The model involves movement with a speed proportional to a “fear” variable that undergoes a temporal consensus averaging based on distance to other agents. We study the effect of Riemann initial data for this problem, leading to shock dynamics that are studied both within the agent-based model as well as in a continuum limit. We examine the behavior of the model under distinguished limits as the characteristic contagion interaction distance and the interaction timescale both approach zero. The limiting behavior is related to a classical model for pressureless gas dynamics with “sticky” particles. In comparison, we observe a threshold for the interaction distance vs. interaction timescale that produce qualitatively different behavior for the system - in one case particle paths do not cross and there is a natural Eulerian limit involving nonlocal interactions and in the other case particle paths can cross and one may consider only a kinetic model in the continuum limit
Thromboembolic risk after knee endoprosthesis
Thromboembolic complications are the most frequent associated pathologies after knee replacement. The secondary deep vein thrombosis in the knee arthroplasty is often low symptomatic or asymptomatic and, sometime, it could lead to fatal pulmonary embolism. This is the main purpose recommending an antithrombotic prophylaxis. In this study 214 patients operated for knee arthroplasty and receiving low molecular heparin therapy were enrolled. They were clinically and echo/radiologically monitored for thromboembolic and/or hemorrhagic complications on the 2nd, 7 th, 14th and 45th day from surgery. Results showed that only 45% of the cases developed DVT (deep vein thrombosis) out of which 17% could be objectively verified by ultrasonography and phlebography. In only one case massive pulmonary embolism with fatal evolution was discovered. It was not found any major bleeding except in four cases in which local haematomas were discovered (most probably related to anticoagulant treatment). This study concluded that the administration of low molecular weight heparin after knee arthroplasty significantly reduces the risks of thromboembolism in conditions where the increase of hemorrhagic complications doesn't result statistically significant
Our experience in Helicobacter pylori infection and gastric MALTomas
OBJECTIVE: A number of recent studies have expanded our understanding of
Helicobacter pylori (Hp) infection and of the pathogenesis of MALT lymphoma. The
purpose of this paper is to perform a retrospective analysis of the clinical
characteristics of gastric MALT lymphoma and its relationship with H. pylori
infection in authors' experience.
MATERIALS AND METHODS: We report nineteen patients observed during 10 years,
presenting with gastric MALTomas at any stage. The staging classification and the
presence of H. pylori infection have been assessed, and the chosen therapy also.
RESULTS: The most part of our patients underwent surgery, still now resulting the
most effective therapy. None of the patients had eradicating therapy due to their
poor compliance and because the most part of cases were observed before the time
of clinical validation of such treatment.
CONCLUSIONS: In our series, surgery was effective for treatment of gastric MALT
lymphomas. Surgery and chemotherapy remain, in accord with literature data, the
best treatment for gastric MALTomas. Hence, because Hp may play a role in the
development of such pathology in certain patients, antibiotic treatment for Hp
eradication should not be discouraged in these patients, especially in them with
low grade gastric MALT lymphomas. In fact, the failure of this therapy will not modify either survival or later recourse to surgical and/or radio- and
chemotherapy
- …