Bregman Proximal Gradient Algorithm with Extrapolation for a class of Nonconvex Nonsmooth Minimization Problems

In this paper, we consider an accelerated method for solving nonconvex and nonsmooth minimization problems. We propose a Bregman Proximal Gradient algorithm with extrapolation(BPGe). This algorithm extends and accelerates the Bregman Proximal Gradient algorithm (BPG), which circumvents the restrictive global Lipschitz gradient continuity assumption needed in Proximal Gradient algorithms (PG). The BPGe algorithm has higher generality than the recently introduced Proximal Gradient algorithm with extrapolation(PGe), and besides, due to the extrapolation step, BPGe converges faster than BPG algorithm. Analyzing the convergence, we prove that any limit point of the sequence generated by BPGe is a stationary point of the problem by choosing parameters properly. Besides, assuming Kurdyka-{\'L}ojasiewicz property, we prove the whole sequences generated by BPGe converges to a stationary point. Finally, to illustrate the potential of the new method BPGe, we apply it to two important practical problems that arise in many fundamental applications (and that not satisfy global Lipschitz gradient continuity assumption): Poisson linear inverse problems and quadratic inverse problems. In the tests the accelerated BPGe algorithm shows faster convergence results, giving an interesting new algorithm.Comment: Preprint submitted for publication, February 14, 201

Bifurcations and Slow-Fast Analysis in a Cardiac Cell Model for Investigation of Early Afterdepolarizations

In this study, we teased out the dynamical mechanisms underlying the generation of arrhythmogenic early afterdepolarizations (EADs) in a three-variable model of a mammalian ventricular cell. Based on recently published studies, we consider a 1-fast, 2-slow variable decomposition of the system describing the cellular action potential. We use sweeping techniques, such as the spike-counting method, and bifurcation and continuation methods to identify parametric regions with EADs. We show the existence of isolas of periodic orbits organizing the different EAD patterns and we provide a preliminary classification of our fast-slow decomposition according to the involved dynamical phenomena. This investigation represents a basis for further studies into the organization of EAD patterns in the parameter space and the involved bifurcations

Promoción de talentos deportivos y representación deportiva para impulsar la sostenibilidad de procesos de desarrollo comunitario en África del Este

Editorial en el que se describe un plan ético de promoción de talentos deportivos y representación deportiva para impulsar la sostenibilidad de procesos de desarrollo comunitario que se está intentando desarrollar en Etiopía

Dynamical analysis of early afterdepolarization patterns in a biophysically detailed cardiac model

Arrhythmogenic early afterdepolarizations (EADs) are investigated in a biophysically detailed mathematical model of a rabbit ventricular myocyte, providing their location in the parameter phase space and describing their dynamical mechanisms. Simulations using the Sato model, defined by 27 state variables and 177 parameters, are conducted to generate electrical action potentials (APs) for different values of the pacing cycle length and other parameters related to sodium and calcium concentrations. A detailed study of the different AP patterns with or without EADs is carried out, showing the presence of a high variety of temporal AP configurations with chaotic and quasiperiodic behaviors. Regions of bistability are identified and, importantly, linked to transitions between different behaviors. Using sweeping techniques, one-, two-, and three-parameter phase spaces are provided, allowing ascertainment of the role of the selected parameters as well as location of the transition regions. A Devil’s staircase, with symbolic sequence analysis, is proposed to describe transitions in the ratio between the number of voltage (EAD and AP) peaks and the number of APs. To conclude, the obtained results are linked to recent studies for low-dimensional models and a conjecture is made for the internal dynamical structure of the transition region from non-EAD to EAD behavior using fold and cusp bifurcations and maximal canards. In a healthy heart, the sinoatrial node sends out an electrical impulse that spreads throughout the heart activating all cardiac myocytes to produce an electrical response called the action potential (AP). The AP follows a sequence of AP phases corresponding to the inflow and outflow of ions through the membrane of cardiac myocytes. Under some circumstances, that sequence of AP phases can be disrupted by the presence of the so-called early afterdepolarizations (EADs), which are secondary voltage depolarizations that can appear during phase 2 or 3 of the AP. Side effects of drugs, ion channel dysfunction, or oxidative stress, among others, can lead to the genesis of EADs.1–3 In heart failure, long QT syndrome, and other pathological conditions, EADs have been reported to be a relevant cause of fatal ventricular arrhythmias,4–6 but more knowledge is required to understand the theoretical mechanisms underlying their generation. During the last few decades, computational models of cardiac electrical activity have been instrumental in shedding light on various cardiac phenomena, including EADs. Biophysically detailed models of high dimension, i.e., with a large number of state variables, allow more faithful reproduction of experimental observations and facilitate biophysical interpretation. Here, we use the high-dimensional electrophysiological model of a rabbit ventricular myocyte developed by Sato et al.6 with 27 state variables and 177 model parameters. By combining different techniques for dynamical system analysis, we investigate the parameter phase space using three parameters reported to highly influence model dynamics.7 We identify regions in the phase space showing transitions from absence to presence of EADs through different temporal sequences of EADs. In these processes, dynamical phenomena are present, including bistability, chaos, fold, and cusp bifurcations. Putting all this information together and taking into account recent findings using low-dimensional models, we provide a conjecture about the internal dynamical structure of the transition region from absence to presence of EADs in the parameter phase space studied for the Sato model

Dangerous women of Hong Kong? Media construction of stigma in female sex workers

This study used a cultural model analysis to examine the Hong Kong print media’s social construction of stigma in respect to female sex workers. An analysis was conducted on captions and main headlines of two newspaper (Chinese and English) median in Hong Kong, 2003-2006. A total of 591 articles on sex workers were recruited in the analysis with 422 located from the Ming Pao and 169 articles the SCMP. A total of Sixty seven articles on health issues were identified. In Hong Kong, as in elsewhere, sex workers were commonly labeled as the sources of sexually transmitted diseases and as women who endangered the public safety through socially unacceptable occupations. They were also portrayed as “ugly”, “weak” and “powerless” in the articles identified. We conclude the Hong Kong print media plays a significant role in contributing to the stigmatization of sex workers, heightening health risk and vulnerability. Such social construction of public stigma then in turn, can be argued to contribute to a lessened propensity for female sex workers both seek and engage with formal health services.published_or_final_versio

100 GHz Multiple Colliding Pulse Generation From Cleaved Facet-Free Multi-Section Semiconductor Laser Diode

We present a monolithically integrated mode-locked laser (MLL) with 25 GHz fundamental repetition rate frequency, which has been designed to operate in a fourth-order colliding regime, to generate 100 GHz. This device has been fabricated within a multi-project wafer (MPW) run in an InP-based active-passive generic foundry. The Fabry-Perot laser resonator, of around 1.66 mm length, is defined by two on-chip reflectors, eliminating the need of cleaved facet. Three saturable absorber sections are symmetrically located by spacing them a quarter of this total length, dividing the cavity into four gain segments. We show that this structure can generate an electrical beat note at 25 GHz as well as 100 GHz, with a linewidth of 350 kHz and 150 kHz, respectively, operating in passive operation regime

Prevalence, Risk Factors and Impact of Nutrition Interruptions in Critically Ill Children

Enteral nutrition; Interruptions; Nutrition barriersNutrició enteral; Interrupcions; Barreres nutricionalsNutrición enteral; Interrupciones; Barreras nutricionalesBackground: Enteral nutrition interruptions (ENI) are prevalent in the pediatric intensive care unit (PICU), but there is little evidence of their characteristics. Methods: This is a cross-sectional multicenter study including critically ill children on enteral nutrition. ENIs were classified as PICU procedures, procedures performed outside the PICU (PPOP), feeding intolerance and other criteria. The number and features of ENIs were collected. Results: A total of 75 children were enrolled. There were 41 interruptions affecting 37.3% of the patients with a median duration of 5 ± 9.4 h. The most common reason for ENI was PPOP (41.5%), followed by other criteria. Interruptions were considered preventable in 24.4% of the cases, but only eight were compensated. ENIs were more prevalent among children with cardiac disease (p = 0.047), higher PRISM (p = 0.047) and longer PICU stay (p = 0.035). There was association between PRISM and total interruption time (p = 0.02) and lower caloric intake (p = 0.035). Patients with respiratory illness (p = 0.022) and on noninvasive ventilation (p = 0,028) had fewer ENIs. ENI total time was associated with lower caloric (p = 0.001) and protein (p = 0.02) intake. Conclusions: ENIs are prevalent in PICU, especially in children with higher PRISM, longer PICU stays and cardiac disease, and result in lower caloric and protein intake.This research was funded by the Primary Care Interventions to Prevent Maternal and Child Chronic Diseases of Perinatal and Development Origin Network (RICORS) RD21/0012/0011, Instituto de Salud Carlos III, Madrid, Spain Developmental Origin Network (RICORS), RD21/0012/0011, Instituto de Salud Carlos III, Madrid, Spain

Repensando la enseñanza de los números negativos en la escuela secundaria

Este trabajo se enmarca en un proyecto de investigación-dependiente de la Universidad Nacional del Comahue, Argentina- que pretende construir conjuntamente, investigadores y profesores, un modo posible donde la didáctica de la matemática se convierta en un marco posible para que los docentes puedan pensar sus clases de matemática. A partir de encuentros periódicos pretendemos crear un ambiente de estudio y producción de conocimiento matemático-didáctico para hacer más visible el complejo marco de decisiones del docente en su tarea diaria. Estamos convencidos que los investigadores necesitamos conocer más sobre las necesidades y desafíos que enfrentan los docentes en su trabajo, intentando encontrar posibles nexos entre la didáctica de la matemática y el quehacer docente. Autores como Bednarz (1999), Desgagné (2001) y Anadón (2001, 2008), destacan la importancia de incorporar a los docentes de las escuelas medias a los grupos de estudio para realizar investigaciones “con” ellos más que “sobre” ellos

Screening for an ivermectin slow-release formulation suitable for malaria vector control

BACKGROUND: The prospect of eliminating malaria is challenged by emerging insecticide resistance and vectors with outdoor and/or crepuscular activity. Ivermectin can simultaneously tackle these issues by killing mosquitoes feeding on treated animals and humans. A single oral dose, however, confers only short-lived mosquitocidal plasma levels. METHODS: Three different slow-release formulations of ivermectin were screened for their capacity to sustain mosquito-killing levels of ivermectin for months. Thirty rabbits received a dose of one, two or three silicone implants containing different proportions of ivermectin, deoxycholate and sucrose. Animals were checked for toxicity and ivermectin was quantified periodically in blood. Potential impact of corresponding long-lasting formulation was mathematically modelled. RESULTS: All combinations of formulation and dose released ivermectin for more than 12 weeks; four combinations sustained plasma levels capable of killing 50% of Anopheles gambiae feeding on a treated subject for up to 24 weeks. No major adverse effects attributable to the drug were found. Modelling predicts a 98% reduction in infectious vector density by using an ivermectin formulation with a 12-week duration. CONCLUSIONS: These results indicate that relatively stable mosquitocidal plasma levels of ivermectin can be safely sustained in rabbits for up to six months using a silicone-based subcutaneous formulation. Modifying the formulation of ivermectin promises to be a suitable strategy for malaria vector control

EVALLER: a web server for in silico assessment of potential protein allergenicity

Bioinformatics testing approaches for protein allergenicity, involving amino acid sequence comparisons, have evolved appreciably over the last several years to increased sophistication and performance. EVALLER, the web server presented in this article is based on our recently published ‘Detection based on Filtered Length-adjusted Allergen Peptides’ (DFLAP) algorithm, which affords in silico determination of potential protein allergenicity of high sensitivity and excellent specificity. To strengthen bioinformatics risk assessment in allergology EVALLER provides a comprehensive outline of its judgment on a query protein's potential allergenicity. Each such textual output incorporates a scoring figure, a confidence numeral of the assignment and information on high- or low-scoring matches to identified allergen-related motifs, including their respective location in accordingly derived allergens. The interface, built on a modified Perl Open Source package, enables dynamic and color-coded graphic representation of key parts of the output. Moreover, pertinent details can be examined in great detail through zoomed views. The server can be accessed at http://bioinformatics.bmc.uu.se/evaller.html