13,459 research outputs found

    Теорія систем мобільних інфокомунікацій. Системна архітектура

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    Навчальний посібник містить опис логічних та фізичних структур, процедур, алгоритмів, протоколів, принципів побудови і функціонування мереж стільникового мобільного зв’язку (до 3G) і мобільних інфокомунікацій (4G і вище), приділяючи увагу розгляду загальних архітектур мереж операторів мобільного зв’язку, їх управління і координування, неперервності еволюції розвитку засобів функціонування і способів надання послуг таких мереж. Посібник структурно має сім розділів і побудований так, що складність матеріалу зростає з кожним наступним розділом. Навчальний посібник призначено для здобувачів ступеня бакалавра за спеціальністю 172 «Телекомунікації та радіотехніка», буде також корисним для аспірантів, наукових та інженерно-технічних працівників за напрямом інформаційно-телекомунікаційних систем та технологій.The manual contains a description of the logical and physical structures, procedures, algorithms, protocols, principles of construction and operation of cellular networks for mobile communications (up to 3G) and mobile infocommunications (4G and higher), paying attention to the consideration of general architectures of mobile operators' networks, their management, and coordination, the continuous evolution of the development of the means of operation and methods of providing services of such networks. The manual has seven structural sections and is structured in such a way that the complexity of the material increases with each subsequent chapter. The textbook is intended for applicants for a bachelor's degree in specialty 172 "Telecommunications and Radio Engineering", and will also be useful to graduate students, and scientific and engineering workers in the direction of information and telecommunication systems and technologies

    Complement mediated synapse elimination in schizophrenia

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    Schizophrenia (SCZ) is a devastating psychiatric disorder with a typically age of onset in late adolescence. The heritability is estimated to be in between 60-80% and large-scale genome-wide studies have revealed a prominent polygenic component to SCZ risk and identified more than three-hundred common risk variants. Despite a better understanding of which genetic risk variants that increases SCZ risk, it has been challenging to map out the pathophysiology of the disorder. This has stalled the development of target drugs and current treatment options display moderate efficacy and are prone to produce side-effects. SCZ is generally considered a neurodevelopmental disorder and it was proposed more than forty years ago that physiological removal of less active synapses in adolescence, i.e., synaptic pruning, is increased in SCZ and hereby causes the core symptoms of the disorder. This theory has then been supported by post-mortem brain tissue and imaging studies displaying decreased synapse density in SCZ. More recently, it was then shown that the most strongly associated risk loci can largely be explained by copy numbers of a gene coding for the complement factor 4A (C4A). As microglia prune synapses with the help of complement signalling, we therefore decided to use a recently developed human 2D in vitro assay to assess microglial uptake of synaptic structures in models based on cells from individuals with SCZ and healthy controls (study I). We observed excessive uptake of synaptic structures in SCZ models and by mixing synapses from healthy controls with microglia from SCZ patients, and vice versa, we showed the contribution of microglial and neuronal factors contributing to this excessive uptake of synaptic structures. We then developed an in vitro assay to study neuronal complement deposition dependent on copy numbers of C4A in the neuronal lines. Complement 3 (C3) deposition increased by C4A copy numbers but was independent of C4B copy numbers (also unrelated to SCZ risk). Similar C4A copy numbers correlated with the extent of microglial uptake of synapses. Microglial uptake of synaptic structures could also be inhibited by the tetracycline minocycline that also decreased risk of developing SCZ in an electronic health record cohort. In study II, we cerebrospinal fluid (CSF) from first-episode psychosis patients to measure protein levels of C4A. In two independent cohorts, we observed elevated C4A levels (although not C4B levels) in first-episode patients that later were to develop SCZ and could show correlations with markers of synapse density. However, elevated C4A levels could not fully be explained by more copy numbers of C4A in individuals with SCZ and in vitro experiments revealed that SCZ-associated cytokines can induce C4A mRNA expression while also correlating with C4A in patient-derived CSF. In study III, we set-up a 3D brain organoid models to more fully comprehensively capture processes in the developing human brain and then also included innately developing microglia. We display synaptic pruning within these models and use single cell RNA sequencing to validate them. In conclusion, this thesis uses patient-derived cellular modelling to uncover a disease mechanism in SCZ that link genetic risk variants with bona fide protein changes in living patients

    Examples of works to practice staccato technique in clarinet instrument

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    Klarnetin staccato tekniğini güçlendirme aşamaları eser çalışmalarıyla uygulanmıştır. Staccato geçişlerini hızlandıracak ritim ve nüans çalışmalarına yer verilmiştir. Çalışmanın en önemli amacı sadece staccato çalışması değil parmak-dilin eş zamanlı uyumunun hassasiyeti üzerinde de durulmasıdır. Staccato çalışmalarını daha verimli hale getirmek için eser çalışmasının içinde etüt çalışmasına da yer verilmiştir. Çalışmaların üzerinde titizlikle durulması staccato çalışmasının ilham verici etkisi ile müzikal kimliğe yeni bir boyut kazandırmıştır. Sekiz özgün eser çalışmasının her aşaması anlatılmıştır. Her aşamanın bir sonraki performans ve tekniği güçlendirmesi esas alınmıştır. Bu çalışmada staccato tekniğinin hangi alanlarda kullanıldığı, nasıl sonuçlar elde edildiği bilgisine yer verilmiştir. Notaların parmak ve dil uyumu ile nasıl şekilleneceği ve nasıl bir çalışma disiplini içinde gerçekleşeceği planlanmıştır. Kamış-nota-diyafram-parmak-dil-nüans ve disiplin kavramlarının staccato tekniğinde ayrılmaz bir bütün olduğu saptanmıştır. Araştırmada literatür taraması yapılarak staccato ile ilgili çalışmalar taranmıştır. Tarama sonucunda klarnet tekniğin de kullanılan staccato eser çalışmasının az olduğu tespit edilmiştir. Metot taramasında da etüt çalışmasının daha çok olduğu saptanmıştır. Böylelikle klarnetin staccato tekniğini hızlandırma ve güçlendirme çalışmaları sunulmuştur. Staccato etüt çalışmaları yapılırken, araya eser çalışmasının girmesi beyni rahatlattığı ve istekliliği daha arttırdığı gözlemlenmiştir. Staccato çalışmasını yaparken doğru bir kamış seçimi üzerinde de durulmuştur. Staccato tekniğini doğru çalışmak için doğru bir kamışın dil hızını arttırdığı saptanmıştır. Doğru bir kamış seçimi kamıştan rahat ses çıkmasına bağlıdır. Kamış, dil atma gücünü vermiyorsa daha doğru bir kamış seçiminin yapılması gerekliliği vurgulanmıştır. Staccato çalışmalarında baştan sona bir eseri yorumlamak zor olabilir. Bu açıdan çalışma, verilen müzikal nüanslara uymanın, dil atış performansını rahatlattığını ortaya koymuştur. Gelecek nesillere edinilen bilgi ve birikimlerin aktarılması ve geliştirici olması teşvik edilmiştir. Çıkacak eserlerin nasıl çözüleceği, staccato tekniğinin nasıl üstesinden gelinebileceği anlatılmıştır. Staccato tekniğinin daha kısa sürede çözüme kavuşturulması amaç edinilmiştir. Parmakların yerlerini öğrettiğimiz kadar belleğimize de çalışmaların kaydedilmesi önemlidir. Gösterilen azmin ve sabrın sonucu olarak ortaya çıkan yapıt başarıyı daha da yukarı seviyelere çıkaracaktır

    Toward Optimization of Medical Therapies with a Little Help from Knowledge Management

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    This chapter emphasizes the importance of identifying and managing knowledge from Informally Structured Domains, especially in the medical field, where very short and repeated serial measurements are often present. This information is made up of attributes of both patients and their treatments that influence their state of health and usually includes measurements of various parameters taken at different times during the duration of treatment and usually after the application of the therapeutic resource. The chapter communicates the use of the KDSM methodology through a case study and the importance of paying attention to the characteristics of the domain to perform appropriate knowledge management in the domain

    Design and development of a traction motor emulator using a three-phase bidirectional buck-boost AC-DC converter

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    An industrial drive testing, with a ???real-machine??? can pave way, for some serious issues to test-bench, motor, and the operator. A slight disturbance in control logic amid testing, can damage the physical machine or drive. Such dangerous testing conditions can be avoided by supplanting real motor with a power electronic converter based ???Motor Emulator??? (ME) test-bench system. The conventional ME comprises of two-stage three-phase AC-DC-AC conversion with first-stage AC-DC as emulator and second-stage DC-AC as regenerating unit. This two-stage power conversion, require independent control algorithm, burdening control complexity as well as the number of power electronic switches are quite significant. Therefore, to economize and downsize conventional multistage ME system, this research work experimentally validates a common-DC-bus-configured ME system with only the AC-DC regenerative emulator stage. A bidirectional three-phase AC-DC converter is proposed as the regenerative emulator converter in a common-DC-Bus-configured ME system. The Proposed converter???s operating principle along with mathematical design and control strategy are also presented. To validate the operation of the proposed converter as a common DC-bus-configured emulator, two permanent magnet synchronous motors (PMSM) of 7.5 kW and 2.0 kW are emulated and their simulation and experimental results are presented here. The proposed bi-directional converter inspired from classical buck-boost operation, requires just ten unidirectional IGBT switches preventing any circulating current in the system. The proposed converter also eliminates the regenerative converter stage in classical ME system. Also, the proposed common-DC-bus-configured ME system requires a single stage control unlike independent control in existing ME system. The proposed converter provides four-quadrant operation and emulation of motor under study. The dynamic model of PMSM motor is simulated on the MATLAB simulation platform and the Simulation results are compared with experimental results. From the simulation and experimental results, it is concluded that, with the presented control scheme, the proposed ME converter can be made to draw the same current as a real machine would have drawn, had it been driven by the same DUT. Since, the output current of proposed converter is fed back to DC bus, the input power source requirement is reduced, making the overall ME system more energy efficient

    Brain simulation as a cloud service: The Virtual Brain on EBRAINS

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    open access articleThe Virtual Brain (TVB) is now available as open-source services on the cloud research platform EBRAINS (ebrains.eu). It offers software for constructing, simulating and analysing brain network models including the TVB simulator; magnetic resonance imaging (MRI) processing pipelines to extract structural and functional brain networks; combined simulation of large-scale brain networks with small-scale spiking networks; automatic con- version of user-specified model equations into fast simulation code; simulation-ready brain models of patients and healthy volunteers; Bayesian parameter optimization in epilepsy patient models; data and software for mouse brain simulation; and extensive educational material. TVB cloud services facilitate reproducible online collabo- ration and discovery of data assets, models, and software embedded in scalable and secure workflows, a precondition for research on large cohort data sets, better generalizability, and clinical translation

    Developing automated meta-research approaches in the preclinical Alzheimer's disease literature

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    Alzheimer’s disease is a devastating neurodegenerative disorder for which there is no cure. A crucial part of the drug development pipeline involves testing therapeutic interventions in animal disease models. However, promising findings in preclinical experiments have not translated into clinical trial success. Reproducibility has often been cited as a major issue affecting biomedical research, where experimental results in one laboratory cannot be replicated in another. By using meta-research (research on research) approaches such as systematic reviews, researchers aim to identify and summarise all available evidence relating to a specific research question. By conducting a meta-analysis, researchers can also combine the results from different experiments statistically to understand the overall effect of an intervention and to explore reasons for variations seen across different publications. Systematic reviews of the preclinical Alzheimer’s disease literature could inform decision making, encourage research improvement, and identify gaps in the literature to guide future research. However, due to the vast amount of potentially useful evidence from animal models of Alzheimer’s disease, it remains difficult to make sense of and utilise this data effectively. Systematic reviews are common practice within evidence based medicine, yet their application to preclinical research is often limited by the time and resources required. In this thesis, I develop, build-upon, and implement automated meta-research approaches to collect, curate, and evaluate the preclinical Alzheimer’s literature. I searched several biomedical databases to obtain all research relevant to Alzheimer’s disease. I developed a novel deduplication tool to automatically identify and remove duplicate publications identified across different databases with minimal human effort. I trained a crowd of reviewers to annotate a subset of the publications identified and used this data to train a machine learning algorithm to screen through the remaining publications for relevance. I developed text-mining tools to extract model, intervention, and treatment information from publications and I improved existing automated tools to extract reported measures to reduce the risk of bias. Using these tools, I created a categorised database of research in transgenic Alzheimer’s disease animal models and created a visual summary of this dataset on an interactive, openly accessible online platform. Using the techniques described, I also identified relevant publications within the categorised dataset to perform systematic reviews of two key outcomes of interest in transgenic Alzheimer’s disease models: (1) synaptic plasticity and transmission in hippocampal slices and (2) motor activity in the open field test. Over 400,000 publications were identified across biomedical research databases, with 230,203 unique publications. In a performance evaluation across different preclinical datasets, the automated deduplication tool I developed could identify over 97% of duplicate citations and a had an error rate similar to that of human performance. When evaluated on a test set of publications, the machine learning classifier trained to identify relevant research in transgenic models performed was highly sensitive (captured 96.5% of relevant publications) and excluded 87.8% of irrelevant publications. Tools to identify the model(s) and outcome measure(s) within the full-text of publications may reduce the burden on reviewers and were found to be more sensitive than searching only the title and abstract of citations. Automated tools to assess risk of bias reporting were highly sensitive and could have the potential to monitor research improvement over time. The final dataset of categorised Alzheimer’s disease research contained 22,375 publications which were then visualised in the interactive web application. Within the application, users can see how many publications report measures to reduce the risk of bias and how many have been classified as using each transgenic model, testing each intervention, and measuring each outcome. Users can also filter to obtain curated lists of relevant research, allowing them to perform systematic reviews at an accelerated pace with reduced effort required to search across databases, and a reduced number of publications to screen for relevance. Both systematic reviews and meta-analyses highlighted failures to report key methodological information within publications. Poor transparency of reporting limited the statistical power I had to understand the sources of between-study variation. However, some variables were found to explain a significant proportion of the heterogeneity. Transgenic animal model had a significant impact on results in both reviews. For certain open field test outcomes, wall colour of the open field arena and the reporting of measures to reduce the risk of bias were found to impact results. For in vitro electrophysiology experiments measuring synaptic plasticity, several electrophysiology parameters, including magnesium concentration of the recording solution, were found to explain a significant proportion of the heterogeneity. Automated meta-research approaches and curated web platforms summarising preclinical research could have the potential to accelerate the conduct of systematic reviews and maximise the potential of existing evidence to inform translation

    Secure authentication and key agreement via abstract multi-agent interaction

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    Authentication and key agreement are the foundation for secure communication over the Internet. Authenticated Key Exchange (AKE) protocols provide methods for communicating parties to authenticate each other, and establish a shared session key by which they can encrypt messages in the session. Within the category of AKE protocols, symmetric AKE protocols rely on pre-shared master keys for both services. These master keys can be transformed after each session in a key-evolving scheme to provide the property of forward secrecy, whereby the compromise of master keys does not allow for the compromise of past session keys. This thesis contributes a symmetric AKE protocol named AMI (Authentication via Multi-Agent Interaction). The AMI protocol is a novel formulation of authentication and key agreement as a multi-agent system, where communicating parties are treated as autonomous agents whose behavior within the protocol is governed by private agent models used as the master keys. Parties interact repeatedly using their behavioral models for authentication and for agreeing upon a unique session key per communication session. These models are evolved after each session to provide forward secrecy. The security of the multi-agent interaction process rests upon the difficulty of modeling an agent's decisions from limited observations about its behavior, a long-standing problem in AI research known as opponent modeling. We conjecture that it is difficult to efficiently solve even by a quantum computer, since the problem is fundamentally one of missing information rather than computational hardness. We show empirically that the AMI protocol achieves high accuracy in correctly identifying legitimate agents while rejecting different adversarial strategies from the security literature. We demonstrate the protocol's resistance to adversarial agents which utilize random, replay, and maximum-likelihood estimation (MLE) strategies to bypass the authentication test. The random strategy chooses actions randomly without attempting to mimic a legitimate agent. The replay strategy replays actions previously observed by a legitimate client. The MLE strategy estimates a legitimate agent model using previously observed interactions, as an attempt to solve the opponent modeling problem. This thesis also introduces a reinforcement learning approach for efficient multi-agent interaction and authentication. This method trains an authenticating server agent's decision model to take effective probing actions which decrease the number of interactions in a single session required to successfully reject adversarial agents. We empirically evaluate the number of interactions required for a trained server agent to reject an adversarial agent, and show that using the optimized server leads to a much more sample-efficient interaction process than a server agent selecting actions by a uniform-random behavioral policy. Towards further research on and adoption of the AMI protocol for authenticated key-exchange, this thesis also contributes an open-source application written in Python, PyAMI. PyAMI consists of a multi-agent system where agents run on separate virtual machines, and communicate over low-level network sockets using TCP. The application supports extending the basic client-server setting to a larger multi-agent system for group authentication and key agreement, providing two such architectures for different deployment scenarios

    Monitoring Adsorption Dynamics on the Rutile TiO2(110)-(1×1) Surface with WFS and XPS: Surface Defects, Water and Oxygen Adsorption

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    In the crystal form of rutile or anatase, the TiO2 surface is one of the most studied metallic oxide surfaces, due to its potential applications in the catalysis field, in addition to other technological uses. The reactivity of the TiO2 surface is governed in part by its concentration of defects, such as oxygen vacancies, with its catalytic activity also being affected by the adsorption of atmospheric gases such as water or oxygen. In the preceding work performed by the Applied Surface Science group of CEFITEC, the kinetics of water adsorption on the TiO2(110)-(1×1) surface were studied by monitoring the time-dependence of the work function change during the adsorption process, by measuring the cut-off position of the secondary electron energy spectra (onset method). This technique has proven to be a very useful tool for the analysis of adsorption dynamics, due to its high sensitivity to adsorbates which modify the surface dipole layer, and short acquisition time requirement. In the work here presented, this study is extended, and the onset method is used as a primary tool, together with XPS, for performing an analysis of the adsorption dynamics of water and oxygen on the rutile TiO2(110)-(1×1) surface, and how this process is affected by the surface temperature, and the presence of surface defects or contaminants. First, the physical model behind the onset method was revised, as some of the previous results obtained with this technique could not be explained under the present interpretation of the measurement. In this revision, the electric field between surface regions with different local work functions is considered, and its effect on the onset position is calculated as a function of the surface morphology and external fields. The TiO2 related experiments presented in this thesis were performed on a Kratos XSAM 800 system. Before initiating the experimental campaign, the Kratos system was upgraded to the needs of this work. Its control and acquisition hardware system and software was replaced, so that both control and data acquisition tasks could be performed with a modern PC. The spectrometer was recalibrated by measuring its transmission function with two methods, the standard first principles method, and a newly introduced biasing method, which presents clear advantages with respect to the first. Lastly, a method was introduced for the optimization of the transmission function, by a applying the differential evolution search algorithm to the voltages of the spectrometer’s electrodes, resulting in an increase of the system’s sensitivity in the whole energy range. Finally, the onset method was used to study the presence of surface defects and the adsorption of water and oxygen on the rutile TiO2(110)-(1×1) surface. A water adsorption model was introduced which was capable of explaining the results that were previously obtained. The adsorption of hydrocarbon contaminants, accumulated in the UHV system over time, was found to be of substantial importance. It was possible with this model to calculate the constants of the adsorption kinetics and estimate the concentration of water molecules adsorbed on Ti rows and dissociated on bridging oxygen vacancies. The oxygen adsorption process was monitored both by work function and XPS measurements. The adsorption kinetics were determined for surfaces prepared with different reduction levels. Oxygen adsorption was also associated with a decrease of the Ti3+ contribution in the XPS Ti 3p peak, and the magnitude of this decrease was linearly correlated with the increase of the work function following oxygen adsorption. The process of oxygen adsorption were found to be influenced by the presence of both bridging oxygen vacancies and Ti interstitial species. The onset method was also used as a tool to study the electron stimulated desorption of oxygen and hydrogen species from the TiO2(110)-(1×1) surface. A Monte-Carlo simulation was used to estimate how the cross-section of oxygen species is affected by the local the presence of oxygen vacancies, and its value was determined for bombardment energies of 40 and 80 eV. The ESD cross-section of hydrogen species for a bombardment energy of 30 eV was measured by first exposing the surface to water, thus introducing surface OH groups, and then initiating the electron bombardment.Nas formas cristalinas de rutilo e anatase, a superfície do TiO2 é uma das mais estudadas entre as superfícies de óxidos metálicos, devido à sua potencial aplicação no campo da catálise, entre outras aplicações tecnológicas. A reactividade da superfície do TiO2 é ditada em parte pela sua concentração de defeitos, tais como lacunas de oxigénio, sendo a sua actividade catalítica afectada pela adsorção de gases atmosféricos, tais como água ou oxigénio. Em trabalhos realizados anteriormente pelo grupo de ciência de superfícies do CEFITEC, as dinâmicas da adsorção de água na superfície TiO2(110)-(1×1) de rutilo foram estudadas através da monitorização da função trabalho durante o processo de adsorção, através da medição da posição do limiar do espectro de energia de electrões secundários (método onset). Esta técnica revelou-se bastante útil para a analise das dinâmicas de adsorção, devido à sua extrema sensibilidade a modificação da camada de dipolo da superfície provocada por gases adsorvidos, e ao curto intervalo de tempo necessário para a aquisição de dados. No trabalho aqui apresentado, este estudo foi aprofundado, e o método onset foi usado como ferramenta principal, juntamente com XPS, para a realização de uma análise detalhada das dinâmicas de adsorção água e oxigénio na superfície TiO2(110)-(1×1), e como este processo é afectado pela temperatura da superfície, e pela presença de defeitos ou contaminantes. Inicialmente, o modelo físico que descreve o método onset foi revisto, uma vez que alguns dos resultados previamente obtidos com esta técnica não se enquadravam com a sua interpretação corrente. Nesta revisão, foi considerado o campo eléctrico presente entre regiões de uma superfície com funções trabalho locais diferentes, e o seu efeito na posição do onset foi calculado em função da morfologia da superfície, e da aplicação de campos eléctricos externos. As experiências relacionadas com o TiO2 apresentadas neste trabalho foram realizadas num sistema Kratos XSAM 800. Antes da campanha experimental ser iniciada, este sistema foi actualizado de acordo com as necessidades previstas. O sistema de controlo e aquisição foi substituído, de forma a que tanto as tarefas de controlo como de aquisição de dados pudessem ser realizadas por um PC actual. O espectrómetro foi recalibrado, através da medição da sua função de transmissão, com dois métodos distintos, o habitual método dos primeiros princípios, e um novo método aqui introduzido, que revelou apresentar claras vantagens em relação ao primeiro. Por último, introduziu-se também um método de optimização da função de transmissão do espectrómetro, através da aplicação de um algoritmo de evolução diferencial para procura de uma melhor combinação de tensões dos seus eléctrodos, resultando no aumento da sensibilidade do sistema, em toda a sua gama de energias. O método onset foi depois usado para o estudo da presença de defeitos e adsorção de água e oxigénio na superfície de rutilo TiO2(110)-(1×1). Introduziu-se um modelo para descrever o processo de adsorção de água, capaz de descrever e explicar os resultados previamente obtidos. A adsorção de hidrocarbonetos, contaminantes que se acumulam no sistema de UHV com o tempo e uso, revelou ter uma influência considerável neste processo. Com a introdução deste modelo, foi possível calcular as constantes relacionadas com a cinética de adsorção, e estimar a concentração de moléculas de água adsorvidas nas linhas de Ti, ou dissociadas em lacunas de oxigénio. O processo de adsorção de oxigénio foi monitorizado pela medição da função trabalho e XPS. A cinética de adsorção foi determinada para superfícies preparadas com diferentes níveis de redução. A adsorção de oxigénio foi associada a um decréscimo da contribuição de Ti3+ no pico Ti 3p obtido por XPS, e obteve-se uma relação linear entre a amplitude deste decréscimo e o aumento da função trabalho causada pela adsorção de oxigénio. Concluiu-se ainda que o processo de adsorção do oxigénio é influenciado tanto pela presença de lacunas de oxigénio, como por iões de Ti intersticiais. Por último, o método onset foi também usado como ferramenta de estudo do processo de desorção estimulada por electrões, de oxigénio e hidrogénio, da superfície TiO2(110)-(1×1). O método de Monte-Carlo foi usado para estimar a alteração da secção eficaz de ESD do oxigénio é afectada pela presença local de lacunas de oxigénio, e o seu valor foi determinado para energias de bombardeamento de 40 e 80 eV. A secção eficaz de ESD do hidrogénio para energias de bombardeamento de 30 eV foi também medida, através da exposição prévia da superfície a vapor de água, introduzindo assim grupos OH na superfície, seguida pelo bombardeamento por electrões
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