Dynamic networks and directed percolation

We introduce a model for dynamic networks, where the links or the strengths of the links change over time. We solve the model by mapping dynamic networks to the problem of directed percolation, where the direction corresponds to the evolution of the network in time. We show that the dynamic network undergoes a percolation phase transition at a critical concentration $p_c$, which decreases with the rate $r$ at which the network links are changed. The behavior near criticality is universal and independent of $r$. We find fundamental network laws are changed. (i) For Erd\H{o}s-R\'{e}nyi networks we find that the size of the giant component at criticality scales with the network size $N$ for all values of $r$, rather than as $N^{2/3}$. (ii) In the presence of a broad distribution of disorder, the optimal path length between two nodes in a dynamic network scales as $N^{1/2}$, compared to $N^{1/3}$ in a static network.Comment: 10 pages 5 figures; corrected metadata onl

A Large-scale Dataset for Argument Quality Ranking: Construction and Analysis

Identifying the quality of free-text arguments has become an important task in the rapidly expanding field of computational argumentation. In this work, we explore the challenging task of argument quality ranking. To this end, we created a corpus of 30,497 arguments carefully annotated for point-wise quality, released as part of this work. To the best of our knowledge, this is the largest dataset annotated for point-wise argument quality, larger by a factor of five than previously released datasets. Moreover, we address the core issue of inducing a labeled score from crowd annotations by performing a comprehensive evaluation of different approaches to this problem. In addition, we analyze the quality dimensions that characterize this dataset. Finally, we present a neural method for argument quality ranking, which outperforms several baselines on our own dataset, as well as previous methods published for another dataset.Comment: Accepted to AAAI 202

Limited path percolation in complex networks

We study the stability of network communication after removal of $q=1-p$ links under the assumption that communication is effective only if the shortest path between nodes $i$ and $j$ after removal is shorter than $a\ell_{ij} (a\geq1)$ where $\ell_{ij}$ is the shortest path before removal. For a large class of networks, we find a new percolation transition at $\tilde{p}_c=(\kappa_o-1)^{(1-a)/a}$, where $\kappa_o\equiv /$ and $k$ is the node degree. Below $\tilde{p}_c$, only a fraction $N^{\delta}$ of the network nodes can communicate, where $\delta\equiv a(1-|\log p|/\log{(\kappa_o-1)}) < 1$, while above $\tilde{p}_c$, order $N$ nodes can communicate within the limited path length $a\ell_{ij}$. Our analytical results are supported by simulations on Erd\H{o}s-R\'{e}nyi and scale-free network models. We expect our results to influence the design of networks, routing algorithms, and immunization strategies, where short paths are most relevant.Comment: 11 pages, 3 figures, 1 tabl

Significant levels of extracellular reactive oxygen species produced by brown rot basidiomycetes on cellulose

AbstractIt is often proposed that brown rot basidiomycetes use extracellular reactive oxygen species (ROS) to accomplish the initial depolymerization of cellulose in wood, but little evidence has been presented to show that the fungi produce these oxidants in physiologically relevant quantities. We used [14C]phenethyl polyacrylate as a radical trap to estimate extracellular ROS production by two brown rot fungi, Gloeophyllum trabeum and Postia placenta, that were degrading cellulose. Both fungi oxidized aromatic rings on the trap to give monohydroxylated and more polar products in significant yields. All of the cultures contained 2,5-dimethoxyhydroquinone, a fungal metabolite that has been shown to drive Fenton chemistry in vitro. These results show that extracellular ROS occur at significant levels in cellulose colonized by brown rot fungi, and suggest that hydroquinone-driven ROS production may contribute to decay by diverse brown rot species

Burnout in Israeli medical students:a national survey

INTRODUCTION: Professional burnout is characterized by loss of enthusiasm for work, cynicism, and a low sense of personal efficacy. Burnout may adversely affect medical professionalism. Burnout is common in clinicians and varying rates have been reported in medical students. No data exist regarding the prevalence of burnout among Israeli medical students. The aims of this study were to assess the rate of burnout in Israeli medical students and to identify students who were particularly susceptible to burnout. METHODS: A cross-sectional questionnaire design was employed, gathering data from medical students in all years of study across three medical schools. Burnout was measured using the Maslach Burnout Inventory Student Survey (MBI-SS), translated into Hebrew. RESULTS: Of the 2160 students in the participating medical schools, 966 (44.7%) completed MBI-SS and demographic questionnaires. The overall burnout rate was 50.6%. Multivariate logistic regression analysis yielded that female gender, age under 25, advanced year of study, studying at a specific medical school and not being a parent are all significantly correlated with higher levels of burnout. CONCLUSIONS: A high rate of burnout was found. The identification of young women who are not parents during advanced years of studies as being at-risk is important, in order to guide the development of burnout prevention interventions

Genetic Manipulation of Iron Biomineralization Enhances MR Relaxivity in a Ferritin-M6A Chimeric Complex

Ferritin has gained significant attention as a potential reporter gene for in vivo imaging by magnetic resonance imaging (MRI). However, due to the ferritin ferrihydrite core, the relaxivity and sensitivity for detection of native ferritin is relatively low. We report here on a novel chimeric magneto-ferritin reporter gene – ferritin-M6A – in which the magnetite binding peptide from the magnetotactic bacteria magnetosome-associated Mms6 protein was fused to the C-terminal of murine h-ferritin. Biophysical experiments showed that purified ferritin-M6A assembled into a stable protein cage with the M6A protruding into the cage core, enabling magnetite biomineralisation. Ferritin-M6A-expressing C6-glioma cells showed enhanced (per iron) r2 relaxivity. MRI in vivo studies of ferritin-M6A-expressing tumour xenografts showed enhanced R2 relaxation rate in the central hypoxic region of the tumours. Such enhanced relaxivity would increase the sensitivity of ferritin as a reporter gene for non-invasive in vivo MRI-monitoring of cell delivery and differentiation in cellular or gene-based therapies

Estratégias de neuromodulação para o tratamento da depressão maior: desafios e recomendações de uma força-tarefa

The use of neuromodulation as a treatment for major depressive disorder (MDD) has recently attracted renewed interest due to development of other non-pharmacological therapies besides electroconvulsive therapy (ECT) such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and vagus nerve stimulation (VNS). METHOD: We convened a working group of researchers to discuss the updates and key challenges of neuromodulation use for the treatment of MDD. RESULTS: The state-of-art of neuromodulation techniques was reviewed and discussed in four sections: [1] epidemiology and pathophysiology of MDD; [2] a comprehensive overview of the neuromodulation techniques; [3] using neuromodulation techniques in MDD associated with non-psychiatric conditions; [4] the main challenges of neuromodulation research and alternatives to overcome them. DISCUSSION: ECT is the first-line treatment for severe depression. TMS and tDCS are strategies with a relative benign profile of side effects; however, while TMS effects are comparable to antidepressant drugs for treating MDD; further research is needed to establish the role of tDCS. DBS and VNS are invasive strategies with a possible role in treatment-resistant depression. In summary, MDD is a chronic and incapacitating condition with a high prevalence; therefore clinicians should consider all the treatment options including invasive and non-invasive neuromodulation approaches.O uso de técnicas de neuromodulação para o tratamento do transtorno depressivo maior (TDM) tem despertado um renovado interesse nos últimos anos com o desenvolvimento de outras intervenções não-farmacólogicas além da eletroconvulsoterapia (ECT), como a estimulação magnética transcraniana (EMT), a estimulação transcraniana por corrente continua (ETCC), a estimulação cerebral profunda (DBS) e a estimulação de nervo vago (VNS). MÉTODO: Nós organizamos um grupo de trabalho com vários pesquisadores para discutir os avanços recentes e os principais desafios para o uso da neuromodulação no tratamento do TDM. RESULTADOS: O estado-da-arte da neuromodulação foi revisado e discutido em quatro seções: [1] epidemiologia e fisiopatologia do TDM; [2] uma revisão das técnicas de neuromodulação; [3] o uso das técnicas de neuromodulação na depressão que ocorre associada ou em virtude de condições não-psiquiátricas; [4] os principais desafios da pesquisa na neuromodulação e alternativas para superá-los. DISCUSSÃO: ECT é o tratamento de primeira linha para depressão grave. EMT e ETCC são estratégias com um perfil benigno de efeitos adversos; contudo, enquanto os efeitos da EMT são comparáveis ao das drogas antidepressivas para o tratamento da TDM, a eficácia da ETCC ainda precisa ser estabelecida por mais pesquisas clínicas. DBS e VNS são intervenções invasivas com um papel possível para a depressão refratária. Em resumo, TDM é uma condição crônica, incapacitante e de alta prevalência; portanto na prática clínica todas as opções de tratamento possíveis, incluindo as farmacológicas e não-farmacológicas, devem ser consideradas.University of São Paulo Department and Institute of PsychiatryHospital 9 de Julho Pain Center and Functional NeurosurgeryUniversity of Paulo Department of Physical Medicine and RehabilitationUniversity of Brasília Laboratory of Neurosciences and BehaviorColumbia UniversityFederal University of Minas Gerais Faculty of Medicine Department of Internal Medicine (Neurology Unit)Centro Brasileiro de Estimulação MagnéticaFederal University of São Paulo Department of PsychiatryUniversity MackenzieSpaulding Rehabilitation Hospital Laboratory of NeuromodulationHarvard Medical SchoolBerenson-Allen Center for Noninvasive Brain StimulationHarvard Medical School Beth Israel Deaconess Medical CenterUNIFESP, Department of PsychiatrySciEL

Unanesthetized Rodents Demonstrate Insensitivity of QT Interval and Ventricular Refractory Period to Pacing Cycle Length

Aim: The cardiac electrophysiology of mice and rats has been analyzed extensively, often in the context of pathological manipulations. However, the effects of beating rate on the basic electrical properties of the rodent heart remain unclear. Due to technical challenges, reported electrophysiological studies in rodents are mainly from ex vivo preparations or under deep anesthesia, conditions that might be quite far from the normal physiological state. The aim of the current study was to characterize the ventricular rate-adaptation properties of unanesthetized rats and mice.Methods: An implanted device was chronically implanted in rodents for atrial or ventricular pacing studies. Following recovery from surgery, QT interval was evaluated in rodents exposed to atrial pacing at various frequencies. In addition, the frequency dependence of ventricular refractoriness was tested by conventional ventricular programmed stimulation protocols.Results: Our findings indicate total absence of conventional rate-adaptation properties for both QT interval and ventricular refractoriness. Using monophasic action potential recordings in isolated mice hearts we could confirm the previously reported shortening of the action potential duration at fast pacing rates. However, we found that this mild shortening did not result in similar decrease of ventricular refractory period.Conclusion: Our findings indicate that unanesthetized rodents exhibit flat QT interval and ventricular refractory period rate-dependence. This data argue against empirical use of QT interval correction methods in rodent studies. Our new methodology allowing atrial and ventricular pacing of unanesthetized freely moving rodents may facilitate more appropriate utility of these important animal models in the context of cardiac electrophysiology studies