Stochastic cycle selection in active flow networks

Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such nonequilibrium networks. Here we connect concepts from lattice field theory, graph theory, and transition rate theory to understand how topology controls dynamics in a generic model for actively driven flow on a network. Our combined theoretical and numerical analysis identifies symmetry-based rules that make it possible to classify and predict the selection statistics of complex flow cycles from the network topology. The conceptual framework developed here is applicable to a broad class of biological and nonbiological far-from-equilibrium networks, including actively controlled information flows, and establishes a correspondence between active flow networks and generalized ice-type models. Keywords: networks; active transport; stochastic dynamics; topologyNational Science Foundation (U.S.) (Award CBET-1510768

A torque-based method demonstrates increased rigidity in Parkinson’s disease during low-frequency stimulation

Low-frequency oscillations in the basal ganglia are prominent in patients with Parkinson's disease off medication. Correlative and more recent interventional studies potentially implicate these rhythms in the pathophysiology of Parkinson's disease. However, effect sizes have generally been small and limited to bradykinesia. In this study, we investigate whether these effects extend to rigidity and are maintained in the on-medication state. We studied 24 sides in 12 patients on levodopa during bilateral stimulation of the STN at 5, 10, 20, 50, 130 Hz and in the off-stimulation state. Passive rigidity at the wrist was assessed clinically and with a torque-based mechanical device. Low-frequency stimulation at ≤20 Hz increased rigidity by 24 % overall (p = 0.035), whereas high-frequency stimulation (130 Hz) reduced rigidity by 18 % (p = 0.033). The effects of low-frequency stimulation (5, 10 and 20 Hz) were well correlated with each other for both flexion and extension (r = 0.725 ± SEM 0.016 and 0.568 ± 0.009, respectively). Clinical assessments were unable to show an effect of low-frequency stimulation but did show a significant effect at 130 Hz (p = 0.002). This study provides evidence consistent with a mechanistic link between oscillatory activity at low frequency and Parkinsonian rigidity and, in addition, validates a new method for rigidity quantification at the wrist

Clinical review: Influenza pandemic – physicians and their obligations

An influenza pandemic threatens to be the most lethal public health crisis to confront the world. Physicians will have critical roles in diagnosis, containment and treatment of influenza, and their commitment to treat despite increased personal risks is essential for a successful public health response. The obligations of the medical profession stem from the unique skills of its practitioners, who are able to provide more effective aid than the general public in a medical emergency. The free choice of profession and the societal contract from which doctors derive substantial benefits affirm this commitment. In hospitals, the duty will fall upon specialties that are most qualified to deal with an influenza pandemic, such as critical care, pulmonology, anesthesiology and emergency medicine. It is unrealistic to expect that this obligation to treat should be burdened with unlimited risks. Instead, risks should be minimized and justified against the effectiveness of interventions. Institutional and public cooperation in logistics, remuneration and psychological/legal support may help remove the barriers to the ability to treat. By stepping forward in duty during such a pandemic, physicians will be able to reaffirm the ethical center of the profession and lead the rest of the healthcare team in overcoming the medical crisis

A Doctor’s First, and Last, Responsibility is to Care Comment on “Denial of Treatment to Obese Patients—the Wrong Policy on Personal Responsibility for Health”

The obesity epidemic raises important and complex issues for clinicians and policy-makers, such as what clinical and public health measures will be most effective and most ethically-sound. While Nir Eyal’s analysis of these issues is very helpful and while he correctly concludes that “conditioning the very aid that patients need in order to become healthier on success in becoming healthier” is wrong, further discussions of these issues must include unequivocal support for safeguarding the fundamental moral basis of the doctor-patient relationship. Regardless of any patients’ failures to demonstrate effective responsibility for their own health, each patient needs and deserves a physician whose caring is never in doubt. Policy- makers need to ensure that our health systems always make this a top priority