Summary of Results in N=1 Supersymmetric SU(2) Gauge Theories

We summarize some results in 4d, N=1 supersymmetric SU(2) gauge theories: the exact effective superpotentials, the vacuum structure, and the exact effective Abelian couplings for arbitrary bare masses and Yukawa couplings.Comment: 13 page

Two-Species Reaction-Diffusion System with Equal Diffusion Constants: Anomalous Density Decay at Large Times

We study a two-species reaction-diffusion model where A+A->0, A+B->0 and B+B->0, with annihilation rates lambda0, delta0 > lambda0 and lambda0, respectively. The initial particle configuration is taken to be randomly mixed with mean densities nA(0) > nB(0), and with the two species A and B diffusing with the same diffusion constant. A field-theoretic renormalization group analysis suggests that, contrary to expectation, the large-time density of the minority species decays at the same rate as the majority when d<=2. Monte Carlo data supports the field theory prediction in d=1, while in d=2 the logarithmically slow convergence to the large-time asymptotics makes a numerical test difficult.Comment: revised version (more figures, claim on exactnes of d=2 treatment removed), 5 pages, 3 figures, RevTex, see related paper Phys. Rev. E, R3787, (1999) or cond-mat/9901147, to appear in Phys. Rev.

Effective Potentials and Vacuum Structure in N=1 Supersymmetric Gauge Theories

We derive the exact effective superpotential in 4d, N=1 supersymmetric SU(2) gauge theories with $N_A$ triplets and $2N_f$ doublets of matter superfields. We find the quantum vacua of these theories; the equations of motion (for $N_A=1$) can be reorganized into the singularity conditions of an elliptic curve. From the phase transition points to the Coulomb branch, we find the exact Abelian gauge couplings, $\tau$, for arbitrary bare masses and Yukawa couplings. We thus {\em derive} the result that $\tau$ is a section of an $SL(2,\Z)$ bundle over the moduli space and over the parameters space of bare masses and Yukawa couplings. For $N_c>2$, we derive the exact effective superpotential in branches of supersymmetric $SU(N_c)$ gauge theories with one supermultiplet in the adjoint representation ($N_A=1$) and zero or one flavor ($N_f=0,1$). We find the quantum vacua of these theories; the equations of motion can be reorganized into the singularity conditions of a genus $N_c-1$ hyperelliptic curve. Finally, we present the effective superpotential in the $N_A$, $N_f<N_c$ cases.Comment: 62 page

Emergency department point-of-care ultrasonography improves time to pericardiocentesis for clinically significant effusions

Objective Our objective was to determine the utility of point-of-care ultrasound (POCUS) to identify and guide treatment of tamponade or clinically significant pericardial effusions in the emergency department (ED). Methods This was a retrospective cohort study of non-trauma patients who were diagnosed with large pericardial effusions or tamponade by the ED physician using POCUS. The control group was composed of those patients later diagnosed on the medical wards or incidentally in the ED by other means such as a computed tomography. The following data were abstracted from the patient’s file: demographics, medical background, electrocardiogram results, chest radiograph readings, echocardiogram results, and patient outcomes. Results There were 18 patients in the POCUS arm and 55 in the control group. The POCUS arm had a decreased time to pericardiocentesis (11.3 vs. 70.2 hours, P=0.055) as well as a shorter length of stay (5.1 vs. 7.0 days, P=0.222). A decreased volume of pericardial fluid was drained (661 vs. 826 mL, P=0.139) in the group diagnosed by POCUS. Conclusion This study suggests that POCUS may effectively identify pericardial effusions and guide appropriate treatment, leading to a decreased time to pericardiocentesis and decreased length of hospital stay. Pericardial tamponade or a large pericardial effusion should be considered in all patients presenting to the ED with clinical, radiographic, or electrocardiographic signs of cardiovascular compromise

A renormalization group study of a class of reaction-diffusion model, with particles input

We study a class of reaction-diffusion model extrapolating continuously between the pure coagulation-diffusion case ($A+A\to A$) and the pure annihilation-diffusion one ($A+A\to\emptyset$) with particles input ($\emptyset\to A$) at a rate $J$. For dimension $d\leq 2$, the dynamics strongly depends on the fluctuations while, for $d >2$, the behaviour is mean-field like. The models are mapped onto a field theory which properties are studied in a renormalization group approach. Simple relations are found between the time-dependent correlation functions of the different models of the class. For the pure coagulation-diffusion model the time-dependent density is found to be of the form $c(t,J,D) = (J/D)^{1/\delta}{\cal F}[(J/D)^{\Delta} Dt]$, where $D$ is the diffusion constant. The critical exponent $\delta$ and $\Delta$ are computed to all orders in $\epsilon=2-d$, where $d$ is the dimension of the system, while the scaling function $\cal F$ is computed to second order in $\epsilon$. For the one-dimensional case an exact analytical solution is provided which predictions are compared with the results of the renormalization group approach for $\epsilon=1$.Comment: Ten pages, using Latex and IOP macro. Two latex figures. Submitted to Journal of Physics A. Also available at http://mykonos.unige.ch/~rey/publi.htm

Equilibrium statistical mechanics on correlated random graphs

Biological and social networks have recently attracted enormous attention between physicists. Among several, two main aspects may be stressed: A non trivial topology of the graph describing the mutual interactions between agents exists and/or, typically, such interactions are essentially (weighted) imitative. Despite such aspects are widely accepted and empirically confirmed, the schemes currently exploited in order to generate the expected topology are based on a-priori assumptions and in most cases still implement constant intensities for links. Here we propose a simple shift in the definition of patterns in an Hopfield model to convert frustration into dilution: By varying the bias of the pattern distribution, the network topology -which is generated by the reciprocal affinities among agents - crosses various well known regimes (fully connected, linearly diverging connectivity, extreme dilution scenario, no network), coupled with small world properties, which, in this context, are emergent and no longer imposed a-priori. The model is investigated at first focusing on these topological properties of the emergent network, then its thermodynamics is analytically solved (at a replica symmetric level) by extending the double stochastic stability technique, and presented together with its fluctuation theory for a picture of criticality. At least at equilibrium, dilution simply decreases the strength of the coupling felt by the spins, but leaves the paramagnetic/ferromagnetic flavors unchanged. The main difference with respect to previous investigations and a naive picture is that within our approach replicas do not appear: instead of (multi)-overlaps as order parameters, we introduce a class of magnetizations on all the possible sub-graphs belonging to the main one investigated: As a consequence, for these objects a closure for a self-consistent relation is achieved.Comment: 30 pages, 4 figure

Magnetic character of a large continental transform : an aeromagnetic survey of the Dead Sea Fault

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q07005, doi:10.1029/2007GC001582.New high-resolution airborne magnetic (HRAM) data along a 120-km-long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate boundary. Despite infrequent seismic activity and only intermittent surface exposure, the fault is delineated clearly on a map of the first vertical derivative of the magnetic intensity, indicating that the source of the magnetic anomaly is shallow. The fault is manifested by a 10–20 nT negative anomaly in areas where the fault cuts through magnetic basement and by a <5 nT positive anomaly in other areas. Modeling suggests that the shallow fault is several hundred meters wide, in agreement with other geophysical and geological observations. A magnetic expression is observed only along the active trace of the fault and may reflect alteration of magnetic minerals due to fault zone processes or groundwater flow. The general lack of surface expression of the fault may reflect the absence of surface rupture during earthquakes. The magnetic data also indicate that unlike the San Andreas Fault, the location of this part of the plate boundary was stable throughout its history. Magnetic anomalies also support a total left-lateral offset of 105–110 km along the plate boundary, as suggested by others. Finally, despite previous suggestions of transtensional motion along the Dead Sea Transform, we did not identify any igneous intrusions related to the activity of this fault segment.The project was funded by U.S.-AID Middle Eastern Regional Cooperation grant TA-MOU-01-M21-012

Visualization of both proximal M2-MCA segments in patients (the Tilted-V Sign) with acute M1-MCA occlusion stroke is associated with better procedural and prognostic outcomes

IntroductionWe aimed to assess the clinical significance of M1-MCA occlusion with visualization of both MCA-M2 segments [“Tilted-V sign” (TVS)] on initial CT angiography (CTA) in patients with acute ischemic stroke (AIS) undergoing endovascular thrombectomy (EVT).MethodsData for patients with consecutive AIS undergoing EVT for large vessel occlusion (LVO) in two academic centers are recorded in ongoing databases. Patients who underwent EVT for M1-MCA occlusions ≤ 6 h from symptom onset were included in this retrospective analysis.ResultsA total of 346 patients met the inclusion criteria; 189 (55%) had positive TVS. Patients with positive TVS were younger (68 ± 14 vs. 71 ± 14 years, P = 0.028), with similar rates of vascular risk factors and baseline modified Rankin scores (mRS) 0–2. The rates of achieving thrombolysis in cerebral ischemia (TICI) 2b-3 were similar to the two groups (79%), although successful first-pass recanalization was more common with TVS (64 vs. 36%, p = 0.01). On multivariate analysis, higher collateral score [odds ratio (OR) 1.38 per unit increase, p = 0.008] and lower age (OR 0.98 per year increase, p = 0.046) were significant predictors of TVS. Patients with positive TVS had higher post-procedural Alberta Stroke Program Early CT Score (ASPECTS; 6.9 ± 2.2 vs. 5.2 ± 2.3, p = 0.001), were discharged with lower National Institutes of Health Stroke Score (NIHSS; 6±6 vs. 9±7, p = 0.003) and higher rates of mRS 0–2 (29.5 vs. 12%, p = 0.001), and had lower rates of 90-day mortality (13.2 vs. 21.6%, p = 0.038). However, TVS was not an independent predictor of functional independence (OR 2.51; 95% CI 0.7–8.3).ConclusionTilted-V Sign, an easily identifiable radiological marker, is associated with fewer recanalization attempts, better functional outcomes, and reduced mortality

Epigenetic Regulation of Virulence Gene Expression in Parasitic Protozoa

Protozoan parasites colonize numerous metazoan hosts and insect vectors through their life cycles, with the need to respond quickly and reversibly while encountering diverse and often hostile ecological niches. To succeed, parasites must also persist within individuals until transmission between hosts is achieved. Several parasitic protozoa cause a huge burden of disease in humans and livestock, and here we focus on the parasites that cause malaria and African trypanosomiasis. Efforts to understand how these pathogens adapt to survive in varied host environments, cause disease, and transmit between hosts have revealed a wealth of epigenetic phenomena. Epigenetic switching mechanisms appear to be ideally suited for the regulation of clonal antigenic variation underlying successful parasitism. We review the molecular players and complex mechanistic layers that mediate the epigenetic regulation of virulence gene expression. Understanding epigenetic processes will aid the development of antiparasitic therapeutics