A Renormalization Group Approach to Spontaneous Stochasticity

We develop a theoretical approach to ``spontaneous stochasticity'' in classical dynamical systems that are nearly singular and weakly perturbed by noise. This phenomenon is associated to a breakdown in uniqueness of solutions for fixed initial data and underlies many fundamental effects of turbulence (unpredictability, anomalous dissipation, enhanced mixing). Based upon analogy with statistical-mechanical critical points at zero temperature, we elaborate a renormalization group (RG) theory that determines the universal statistics obtained for sufficiently long times after the precise initial data are ``forgotten''. We apply our RG method to solve exactly the ``minimal model'' of spontaneous stochasticity given by a 1D singular ODE. Generalizing prior results for the infinite-Reynolds limit of our model, we obtain the RG fixed points that characterize the spontaneous statistics in the near-singular, weak-noise limit, determine the exact domain of attraction of each fixed point, and derive the universal approach to the fixed points as a singular large-deviations scaling, distinct from that obtained by the standard saddle-point approximation to stochastic path-integrals in the zero-noise limit. We present also numerical simulation results that verify our analytical predictions, propose possible experimental realizations of the ``minimal model'', and discuss more generally current empirical evidence for ubiquitous spontaneous stochasticity in Nature. Our RG method can be applied to more complex, realistic systems and some future applications are briefly outlined.Comment: 25 pages, 8 figures. Version 2 has reordered some of the exposition in version 1, for improved readabilit

Jon Bialecki: A Diagram for Fire. Miracles and Variation in an American Charismatic Movement

Anmeldes af Andreas Bandak.&nbsp

Rituximab for the treatment of refractory simultaneous anti-glomerular basement membrane (anti-GBM) and membranous nephropathy

Antibody-mediated anti-glomerular basement membrane (anti-GBM) disease occurs rarely in the presence of another B-cell disorder, membranous nephropathy. The coexistence of these two autoimmune disorders would be anticipated to require differing, specific therapies targeted to each disease process. We describe a case of concomitant membranous nephropathy and anti-GBM disease in which conventional therapy, including steroids, plasmapheresis and cyclophosphamide, failed to attenuate the anti-GBM disease, yet responded to an alternative treatment of rituximab. This B-cell directed, monoclonal, chimeric antibody treatment substantially reduced anti-GBM antibody titers and led to discontinuation of plasmapheresis, while maintaining the remission of membranous nephropathy and anti-GBM disease. © 2014 © The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For permissions, please email: [email protected]

BØN: Antropologiske åbninger i arbejdet med religiøs praksis

Foror

Bilateral Pulmonary Embolism associated with Varicella Zoster Meningoencephalitis in an Immunocompetent Adult: A case report and literature review

Association of Varicella Zoster Virus (VZV) with a considerable variety of complications has been well documented throughout literature. Primary infection, most often seen in children, is generally characterized by mild symptoms, as opposed to the more severe presentations in adult and immunocompromised populations. Manifestations of disseminated VZV include dermatologic, pulmonary, neurologic, and ocular involvement. Vascular and hematologic complications are also reported and sometimes pose serious health threat. We present an interesting case of disseminated VZV infection, complicated by meningitis, encephalitis, and bilateral pulmonary embolism in an otherwise immunocompetent 52-year-old man with no prior chicken pox exposure

Quantification of indirect pathway inhibition by the adenosine A 2a antagonist SYN115 in Parkinson disease

Adenosine A(2a) receptor antagonists reduce symptom severity in Parkinson disease (PD) and animal models. Rodent studies support the hypothesis that A(2a) antagonists produce this benefit by reducing the inhibitory output of the basal ganglia indirect pathway. One way to test this hypothesis in humans is to quantify regional pharmacodynamic responses with cerebral blood flow (CBF) imaging. That approach has also been proposed as a tool to accelerate pharmaceutical dose-finding, but has not yet been applied in humans to drugs in development. We successfully addressed both these aims with a perfusion MRI study of the novel adenosine A(2a) antagonist SYN115. During a randomized, double-blind, placebo-controlled, crossover study in 21 PD patients on levodopa but no agonists, we acquired pulsed arterial spin labeling MRI at the end of each treatment period. SYN115 produced a highly significant decrease in thalamic CBF, consistent with reduced pallidothalamic inhibition via the indirect pathway. Similar decreases occurred in cortical regions whose activity decreases with increased alertness and externally-focused attention, consistent with decreased self-reported sleepiness on SYN115. Remarkably, we also derived quantitative pharmacodynamic parameters from the CBF responses to SYN115. These results suggested that the doses tested were on the low end of the effective dose range, consistent with clinical data reported separately. We conclude that (1) SYN115 enters the brain and exerts dose-dependent regional effects, (2) the most prominent of these effects is consistent with deactivation of the indirect pathway as predicted by preclinical studies; and (3) perfusion MRI can provide rapid, quantitative, clinically relevant dose-finding information for pharmaceutical development