Analysis of the neural hypercolumn in parallel PCSIM simulations

AbstractLarge and sudden changes in pitch or loudness occur statistically less frequently than gradual fluctuations, which means that natural sounds typically exhibit 1/f spectra. Experiments conducted on human subjects showed that listeners indeed prefer 1/f distributed melodies to melodies with faster or slower dynamics. It was recently demonstrated by using animal models, that neurons in primary auditory cortex of anesthetized ferrets exhibit a pronounced preference to stimuli that exhibit 1/f statistics. In the visual modality, it was shown that neurons in primary visual cortex of macaque monkeys exhibit tuning to sinusoidal gratings featuring 1/f dynamics.One might therefore suspect that neurons in mammalian cortex exhibit Self-Organizing Criticality. Indeed, we have found SOC-like phenomena in neurophysiological data collected in rat primary somatosensory cortex. In this paper we concentrated on investigation of the dynamics of cortical hypercolumn consisting of about 128 thousand simulated neurons. The set of 128 Liquid State Machines, each consisting 1024 neurons, was simulated on a simple cluster built of two double quad-core machines (16 cores).PCSIM was designed as a tool for simulating artificial biological-like neural networks composed of different models of neurons and different types of synapses. The simulator was written in C++ with a primary interface dedicated for the Python programming language. As its authors ensure it is intended to simulate networks containing up to millions of neurons and on the order of billions of synapses. This is achieved by distributing the network over different nodes of a computing cluster by using Message Passing Interface.The results obtained for Leaky Integrate-and-Fire model of neurons used for the construction of the hypercolumn and varying density of inter-column connections will be discussed. Benchmarking results for using the PCSIM on the cluster and predictions for grid computing will be presented to some extent. Research presented herein makes a good starting point for the simulations of very large parts of mammalian brain cortex and in some way leading to better understanding of the functionality of human brain

Effect Of High-optical Excitation On The Ultrafast Electron Dynamics In Stacked-monolayer Graphene Samples

We report on transient absorption experiments performed at high optical excitation fluences and used to study the ultrafast dynamics in graphene. We employed a degenerated scheme of pump and probe at 800 nm (1.55 eV). The time resolution of our measurements was limited by the pulse duration similar to 100 fs. The samples were prepared by chemical vapor deposition (CVD) as single-layers on silica and, then staked layer-by-layer in order to make a stack of up to 5 graphene monolayers. We observed saturable absorption (SA) and fluence-dependent relaxation times. We see that the ultrafast carrier dynamics is composed by two decay mechanisms, one with response time of about 200 fs and a slower process of about 1 ps. The fast decay, due to both carrier-carrier and carrier-optical phonon scattering, becomes slower when the density of excited carrier was increased. We implemented a theoretical model and found that both the optical phonon rate emission and the optical phonon lifetime are affect by the pump fluence.9835Conference on Ultrafast Bandgap PhotonicsAPR 18-20, 2016Baltimore, M

Análisis de Formatos Coherentes de Modulación Avanzados para Redes Ópticas Metropolitanas y de Acceso

Las Redes Ópticas Flexibles (FON) requieren una asignación dinámica de recursos a los usuarios. Para ello se han probado diversos binomios Confromado-Formato de modulación, los de mayor interes permiten obtener un canal de 1Tbps y 4Tbps mediante la combinación dinámica para un espectro óptico de 12nm de ancho

Subsystems for future access networks

Current evolution and tendencies of Telecom Networks in general and more specifically optical Metro and Access Networks and their convergence are reported. Based on this evolution, a set of research lines are foreseen regarding subsystems and devices as: high speed optical sources, modulators and receivers, for the next generation of Passive Optical Networks. The ICT project EURO-FOS is achieving European level cooperative research among academia and industry, enabling future telecommunication networks

Analysis of thermal fields generated by natural fires on the structural elements of tall buildings

The Windsor Tower in Madrid was involved in a major fire, on 12-13 February 2005, which caused extensive structural damage to the upper floors of the building. This fire has provoked intense interest amongst researchers hoping to better understand the performance of concrete structures in fire. A research team integrated for Group GIDAI (University of Cantabria –Spain) and BRE Centre for Fire Safety Engineering (The Edinburgh University – UK) has begun a study with the purpose of properly characterising the fire and the performance of the structure. The objectives of the study are (1) to analyze the fire growth conditions in order to understand the fire propagation mechanisms between floors of the building, using computational fire modelling, and (2) to evaluate the response of the structure to the fire. The research undertaken on the fire propagation on the 21st floor, the origin of the fire, has allowed assessment of the severity conditions reached as consequence of the fully-developed fire, due the combustion of the present flammable materials. Starting from these results, characteristic curves of heat release rate representative of the real fire have been determined, to facilitate study of the thermal attack (temperatures, heat flux, etc.) on the structural elements. The tools used for this purpose were the Fire Dynamics Simulator (FDS) LES code, developed at the National Institute of Standards and Technology (NIST), and the SOFIE RANS code. These results will allow, in the next stages, to make use of finite element methods to obtain the corresponding thermal and mechanical state (stress and strain) of each element due to these conditions

Análise e avaliação de riscos na actividade de manutenção de juntas de dilatação em obras de arte rodoviárias

Relatório de Estágio para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de EdificaçõesO presente relatório é o resultado de um estágio realizado num ambiente real de trabalho, promovido pelo Instituto Superior de Engenharia de Lisboa (ISEL), em consonânciacom a empresa Freyssinet – Terra Armada, Pré-esforço, Estudos e Construções, S.A., no contexto do Mestrado em Engenharia Civil, perfil de Edificações. O estudo em questão compreende a identificação de riscos profissionais e respectiva Análise dos Riscos associada à actividade de manutenção de Juntas de Dilatação em obras de arte rodoviárias, com o objectivo de realizar uma Avaliação de Riscos e posteriormente, apresentar Instruções Técnicas de Segurança que contribuam para melhorar as condições de Segurança na actividade acima referida. A metodologia utilizada para a identificação dos perigos foi o Método das Energias. Os acidentes de trabalho foram classificados com base no EEAT (EUROSTAT 2001), sendo o “contacto – modalidade da lesão” o que define a natureza do risco. A Avaliação dos Riscos e o Nível de Risco foi determinado com base na matriz e nos critérios da norma OHSAS –British Standard 8800:2004. Através desta Avaliação de Riscos foi possível concluir sobre quais os principais riscos inerentes à actividade da manutenção de Juntas de Dilatação, e também entender sobre quais existe maior exposição. Com base neste estudo foram propostas medidas de segurança específicas para a totalidade dos riscos identificados, e posteriormente, foram elaborados procedimentos e instruções de segurança, com o intuito de virem a ser implementados na empresa em trabalhos futuros da mesma natureza.Abstract: The present report is the result of a post-graduate training performed in a real work environment, promoted by the Instituto Superior de Engenharia de Lisboa (ISEL), in consonance with the company Freyssinet – Terra Armada, Pre-stress, Studies and Constructions, S.A., in the context of the Master's degree in Civil Engineering, profile of Edifications This study includes the identification of occupational risks and respective Risk Analysis associated to the maintenance activity of Expansion Joints on road bridges, in order to accomplish a risk assessment and thereafter, the presentation of Technical Safety Instructionswhich contributes to improve the Safety conditions on the activity referred to above. The methodology used for the dangers identification was the Energies Method. The occupational accidents were classified based in the EEAT (EUROSTAT 2001), being the "contact - modality of the injury" what defines the nature of the risk. The Risk Assessment and Risk Level was determined based on the matrix and the criteria of the norm OHSAS –British Standard 8800:2004. Through this Risk Assessment was possible to conclude about which the principal risks inherent to the maintenance activity of Expansion Joints, and also understand about which exists greater exposure. Based on this study were proposed specific security measures for all the risks identified, and thereafter, were developed safety procedures and instructions, with the intention that they will be implemented in the company in future works of the same nature

Emergence of Tuning to Natural Stimulus Statistics along the Central Auditory Pathway

We have previously shown that neurons in primary auditory cortex (A1) of anaesthetized (ketamine/medetomidine) ferrets respond more strongly and reliably to dynamic stimuli whose statistics follow "natural" 1/f dynamics than to stimuli exhibiting pitch and amplitude modulations that are faster (1/f(0.5)) or slower (1/f(2)) than 1/f. To investigate where along the central auditory pathway this 1/f-modulation tuning arises, we have now characterized responses of neurons in the central nucleus of the inferior colliculus (ICC) and the ventral division of the mediate geniculate nucleus of the thalamus (MGV) to 1/f(gamma) distributed stimuli with gamma varying between 0.5 and 2.8. We found that, while the great majority of neurons recorded from the ICC showed a strong preference for the most rapidly varying (1/f(0.5) distributed) stimuli, responses from MGV neurons did not exhibit marked or systematic preferences for any particular gamma exponent. Only in A1 did a majority of neurons respond with higher firing rates to stimuli in which gamma takes values near 1. These results indicate that 1/f tuning emerges at forebrain levels of the ascending auditory pathway

A Priori Modelling of Fire Test One

Chapter 10 in the book: The Dalmarnock Fire Tests: Experiments and Modelling, Edited by G. Rein, C. Abecassis Empis and R. Carvel, Published by the School of Engineering and Electronics, University of Edinburgh, 2007. ISBN 978-0-9557497-0-4An international round-robin study of fire modelling was conducted prior to the Dalmarnock Fire Tests in order to assess the state-of-the-art of fire modelling in real scenarios. The philosophy behind the Dalmarnock Fire Tests was to provide instrumentation density suitable for comparison to field models and designed the scenario for maximum test reproducibility. Each participating team independently simulated a priori the test using a common detailed description of the compartment geometry, fuel packages, ignition source and ventilation conditions. The aim of the exercise was to forecast the test results as accurately as possible, and not to provide an engineering analysis with adequate conservative assumptions or safety factors. The modelling results and experimental measurements are compared among themselves, allowing for conclusions on the robustness, reliability and accuracy of current modelling practices. The results indicate large scatter and considerable disparity among predicted fires and also differing from the experimental data. The Dalmarnock Fire Test One was benchmarked against a second test to establish the potential experimental variability. The scatter of the simulations is much larger than the experimental error and the experimental variability. The study emphasises on the inherent difficulty of predicting fire dynamics and demonstrates that the main source of scatter is originated in the many degrees of freedom and the uncertainty in the input parameters. The conclusions from the study are made public to encourage debate and exchange of views on the topic of fire modelling

Correction to: First COVID-19 infections in the Philippines: a case report.

[This corrects the article DOI: 10.1186/s41182-020-00203-0.]