Anticipating the response of excitable systems driven by random forcing

We study the regime of anticipated synchronization in unidirectionally coupled model neurons subject to a common external aperiodic forcing that makes their behavior unpredictable. We show numerically and by implementation in analog hardware electronic circuits that, under appropriate coupling conditions, the pulses fired by the slave neuron anticipate (i.e. predict) the pulses fired by the master neuron. This anticipated synchronization occurs even when the common external forcing is white noise.Comment: 12 pages (RevTex format

Directed cycles and related structures in random graphs: II--Dynamic properties

We study directed random graphs (random graphs whose edges are directed) as they evolve in discrete time by the addition of nodes and edges. For two distinct evolution strategies, one that forces the graph to a condition of near acyclicity at all times and another that allows the appearance of nontrivial directed cycles, we provide analytic and simulation results related to the distributions of degrees. Within the latter strategy, in particular, we investigate the appearance and behavior of the strong components that were our subject in the first part of this study.Comment: submitted to Physica

Early appraisal of the fixation probability in directed networks

In evolutionary dynamics, the probability that a mutation spreads through the whole population, having arisen in a single individual, is known as the fixation probability. In general, it is not possible to find the fixation probability analytically given the mutant's fitness and the topological constraints that govern the spread of the mutation, so one resorts to simulations instead. Depending on the topology in use, a great number of evolutionary steps may be needed in each of the simulation events, particularly in those that end with the population containing mutants only. We introduce two techniques to accelerate the determination of the fixation probability. The first one skips all evolutionary steps in which the number of mutants does not change and thereby reduces the number of steps per simulation event considerably. This technique is computationally advantageous for some of the so-called layered networks. The second technique, which is not restricted to layered networks, consists of aborting any simulation event in which the number of mutants has grown beyond a certain threshold value, and counting that event as having led to a total spread of the mutation. For large populations, and regardless of the network's topology, we demonstrate, both analytically and by means of simulations, that using a threshold of about 100 mutants leads to an estimate of the fixation probability that deviates in no significant way from that obtained from the full-fledged simulations. We have observed speedups of two orders of magnitude for layered networks with 10000 nodes

Splenic Rupture in a COVID-19 Patient – A Case Report

Background: It is well known that the Coronavirus disease 2019 (COVID-19) causes coagulation changes, requiring frequent monitoring for potential sequelae such as myocardial infarction and stroke. Non-traumatic splenic rupture is a rare and poorly understood occurrence in the clinical setting. Possible causes of nontraumatic splenic rupture include neoplasm, infection, inflammatory disease, iatrogenic and mechanical causes. Furthermore, increased intrasplenic tension, increased abdominal pressure, and thrombotic vascular occlusion are possible mechanisms. The Case: We report a case of splenic rupture in a COVID-19 patient. Our patient was a 52-year-old black man, presenting with diarrhea and moderate dyspnea, who was found to be COVID-19 positive. He had a past medical history significant for end-stage renal disease, chronic anemia, and aortic valve replacement. In an otherwise uneventful, 7-day hospital course, the patient’s stay abruptly resulted in a nontraumatic splenic rupture and demise. In this report, we have evaluated the likelihood of COVID-19 causing splenic rupture in a patient with no prior splenic disease. Conclusion: This case highlights the possibility of splenic rupture in otherwise normally recovering COVID-19 patients, particularly in the presence of comorbid conditions of renal failure and anticoagulation, with increased abdominal pressure during routine defecation. This information may assist in furthering the pathophysiology of COVID-19 and its life-threatening complications. In patients with COVID-19, non-traumatic splenic rupture should be considered as one of the differential diagnoses in patients who present with abdominal pain and early recognition of the same, owing to a high index of suspicion, can be lifesaving

Reduction of atherosclerotic lesions in rabbits treated with etoposide associated with cholesterol-rich nanoemulsions

Elaine R Tavares1, Fatima R Freitas1, Jayme Diament1, Raul C Maranhão1,21Heart Institute of the Medical School Hospital (InCor), University of São Paulo, São Paulo, Brazil; 2Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, BrazilObjectives: Cholesterol-rich nanoemulsions (LDE) bind to low-density lipoprotein (LDL) receptors and after injection into the bloodstream concentrate in aortas of atherosclerotic rabbits. Association of paclitaxel with LDE markedly reduces the lesions. In previous studies, treatment of refractory cancer patients with etoposide associated with LDE had been shown devoid of toxicity. In this study, the ability of etoposide to reduce lesions and inflammatory factors in atherosclerotic rabbits was investigated.Methods: Eighteen New Zealand rabbits were fed a 1% cholesterol diet for 60 days. Starting from day 30, nine animals were treated with four weekly intravenous injections of etoposide oleate (6 mg/kg) associated with LDE, and nine control animals were treated with saline solution injections.Results: LDE-etoposide reduced the lesion areas of cholesterol-fed animals by 85% and intima width by 50% and impaired macrophage and smooth muscle cell invasion of the intima. Treatment also markedly reduced the protein expression of lipoprotein receptors (LDL receptor, LDL-related protein-1, cluster of differentiation 36, and scavenger receptor class B member 1), inflammatory cytokines (interleukin-1β and tumor necrosis factor-α), matrix metallopeptidase-9, and cell proliferation markers (topoisomerase IIα and tubulin).Conclusion: The ability of LDE-etoposide to strongly reduce the lesion area and the inflammatory process warrants the great therapeutic potential of this novel preparation to target the inflammatory-proliferative basic mechanisms of the disease.Keywords: atherosclerosis treatment, drug delivery, LDL-receptor

Electrodynamic Radiation Reaction and General Relativity

We argue that the well-known problem of the instabilities associated with the self-forces (radiation reaction forces) in classical electrodynamics are possibly stabilized by the introduction of gravitational forces via general relativity