Modulador de amplitude para amplificadores de rádio frequência

Mestrado em Engenharia Electrónica e TelecomunicaçõesEste trabalho enquadra-se na área de Electrónica para Telecomunicações. A alteração dinâmica da fonte de alimentação do amplificador de potência é uma das actuais soluções para ultrapassar o compromisso linearidade rendimento. A construção do modulador para gerar a alimentação dinâmica é crucial para a obtenção de um conjunto que cumpra os requisitos de linearidade e rendimento. Os requisitos chave deste bloco são a largura de banda e rendimento. Neste trabalho foi feito o estudo das diversas abordagens e técnicas para melhoramento da eficiência num amplificador de potência para rádio frequência em particular as que recorrem a modelação da amplitude da fonte de Alimentação (Seguidor de envolvente (SE), eliminação e restauro de envolvente (EER) e modulação polar). Efectuou-se o estudo dos moduladores de amplitude, seus requisitos chave e técnicas de construção. Foi implementado um modulador de amplitude capaz de fornecer 12W, uma largura de banda para sinal fraco de 6MHz e um rendimento médio para um sinal de CDMA2000FW de 57%. Este modulador permite a sua utilização em outros standards tais como o EDGE e CDMA2000RV com rendimento respectivamente de 73% e 67% respectivamente.This work is included in the area of electronics for telecommunications. The dynamic shifting of the supply source of the power amplifier is one of the nowadays solutions to overcome the efficiency linearity compromise. The modulator construction to generate the dynamic supply is crucial to obtain a set that meets the linearity and efficiency requirements. A study of several approaches and techniques for improvement of efficiency in a radio frequency power amplifier, particularly the ones that use the power supply amplitude modulation (envelope tracking (ET), envelope elimination and restoration (EER) e Polar modulation) was made. The study of the amplitude Modulators, its key requirements and construction techniques was be made. An amplitude modulator able to supply 12W, a small signal bandwidth of 6MHz and a 57% average efficiency for a CDMA2000RV signal was implemented. This modulator allows it application in other standards like EDGE and CDMA2000RV with respectably efficiency of 73% e 67%

Inibição do catabolismo de citrato in vitro pelos ácidos DL-2-hidroxibutírico e 4-hidroxibutírico em córtex cerebral de ratos jovens

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a detailed view of the methodology

Rheumatic and musculoskeletal diseases (RMD) are prevalent and leading causes of disability and consumption of healthcare and social resources. EpiReumaPt is a national population-based survey developed by the Portuguese Society of Rheumatology that aimed to estimate the prevalence of RMDs and determine their impact on function, quality of life, mental health and use of healthcare resources. This article describes in detail the design, methodology and planned analyses of EpiReumaPt. Recruitment started in September 2011 and finished in December 2013. This study involved a three-stage approach. The first step was a face-to-face survey performed by trained interviewers at the household of 10,661 subjects who where randomly selected by a stratified multistage sampling. A highly sensitive screening questionnaire for RMDs was used. Secondly, participants who screened positive (64%) for at least one RMD as well as 20% of individuals with a negative screening were invited for assessment by a rheumatologist. In total, 3,877 subjects participated in this second phase, where they were also invited to donate a blood sample to be stored at the Biobanco-IMM. History and physical examination, followed by appropriate laboratory and imaging tests were performed. At the end of the visit, the rheumatologist established a diagnosis. Finally, a team of three experienced rheumatologists reviewed all the clinical data and defined the diagnoses according to previously validated criteria. The EpiReumaPt dataset, containing data from several questionnaires, various clinical measurements and information from laboratory and imaging tests, comprises an invaluable asset for research. The large amount of information collected from each participant and the large number of participants, with a wide age range covering and being representative of the adults from the entire country, makes EpiReumaPt the largest study of RMDs performed in Portugal.publishersversionpublishe

O que as revisões sistemáticas dizem sobre o impacto da cirurgia robótica na neurocirurgia?

Introduction: Neurosurgery, with its intricate complexities and demands for extreme precision, has been shaped and transformed over the years by the constant evolution of medical technology. Methodology: The methodology adopted for this work involved a systematic literature review focused on specific MESH descriptors, conducted in the PUBMED database. The period considered for article searches spanned from 2017 to 2023, aiming to capture the latest contributions to the topic. The selected MESH descriptors to outline the research were "Robotic Surgical Procedures," "Neurosurgery," and "Minimally Invasive Surgical Procedures." Results: Systematic reviews present a comprehensive overview of recent advances in robotic surgery and its applications in various areas. The promising landscape outlined by these analyses not only validates the progress made but also underscores the ongoing need for research and development to further enhance surgical practices. Conclusion: The learning curve, the need for specialized training, and economic considerations are crucial aspects shaping the practical implementation of robotic surgery in the neurosurgical scenario.Introdução: A neurocirurgia, com suas complexidades intricadas e demandas por precisão extrema, tem sido moldada e transformada ao longo dos anos pela constante evolução da tecnologia médica. Metodologia: A metodologia adotada para este trabalho compreendeu uma revisão sistemática de literatura, focada em descritores MESH específicos, realizada no banco de dados PUBMED. O período considerado para a busca de artigos abrangeu de 2017 a 2023, visando capturar as mais recentes contribuições à temática. Os descritores MESH selecionados para delinear a pesquisa foram "Robotic Surgical Procedures", "Neurosurgery" e "Minimally Invasive Surgical Procedures". Resultado: As revisões sistemáticas apresentam um panorama abrangente dos avanços recentes na cirurgia robótica e suas aplicações em diversas áreas. O cenário promissor delineado por essas análises não apenas valida os progressos alcançados, mas também ressalta a necessidade contínua de pesquisa e desenvolvimento para aprimorar ainda mais as práticas cirúrgicas. Conclusão: A curva de aprendizado, a necessidade de treinamento especializado e as considerações econômicas são aspectos cruciais que moldam a implementação prática da cirurgia robótica no cenário neurocirúrgico

A list of land plants of Parque Nacional do Caparaó, Brazil, highlights the presence of sampling gaps within this protected area

Brazilian protected areas are essential for plant conservation in the Atlantic Forest domain, one of the 36 global biodiversity hotspots. A major challenge for improving conservation actions is to know the plant richness, protected by these areas. Online databases offer an accessible way to build plant species lists and to provide relevant information about biodiversity. A list of land plants of “Parque Nacional do Caparaó” (PNC) was previously built using online databases and published on the website "Catálogo de Plantas das Unidades de Conservação do Brasil." Here, we provide and discuss additional information about plant species richness, endemism and conservation in the PNC that could not be included in the List. We documented 1,791 species of land plants as occurring in PNC, of which 63 are cited as threatened (CR, EN or VU) by the Brazilian National Red List, seven as data deficient (DD) and five as priorities for conservation. Fifity-one species were possible new ocurrences for ES and MG states

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Práticas artísticas no ensino básico e secundário

A mediação entre os conteúdos culturais e a Educação Artística formal tem emergido como uma distinta área de inovação e de intervenção, como o mostram os 18 artigos selecionados nesta nona edição da revista Matéria-Prima.Entre a identidade, fundada nos focos de conhecimento local, e uma inserção integrada nos problemas e conteúdos globais joga-se a problematização da Educação Artística. As propostas articulam quer discursos curatoriais (museu, bienal, exposição), como ações de mediação visando uma expansão das atividades, a que se juntam as reflexões sobre a realidade da formação de professores, nas suas diversas modalidades, em diversas realidades sociais.Propiciam-se oportunidades de ações de intervenção, concertadas ou não, entre os agentes artísticos e os educadores. O resultado pode ser potenciado se se conseguir uma perspetiva informada e integrada das realidades artísticas: pede-se a todos os intervenientes mais integração e disponibilidade para um conhecimento mútuo consequente.info:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016