Corporate governance effects on market volatility:empirical evidence from portuguese listed firms

Purpose This study examines the relationship between internal corporate governance mechanisms and firm risk-taking. Design/methodology/approach This research comprises a sample of 38 non-financial Portuguese firms listed on Euronext Lisbon, over the period from 2007 to 2017. To test the formulated hypotheses we use panel-corrected standard errors (PCSE) models. Findings Our results provide evidence that, in the Portuguese context, bigger and younger firms, with larger boards of directors and a greater number of independent directors, present higher levels of systematic risk. Our results are consistent across the robustness checks. Originality/value To the best of our knowledge, this is the first time that a robust incremental effect of board size on firm systematic risk is reported. This result contradicts the prevailing literature and opens up a new debate, from a financial markets viewpoint, on the benefits of larger boards of directors in terms of mitigating market volatility.info:eu-repo/semantics/publishedVersio

El ajuste de las escuelas primarias a la disminución de la población: un enfoque de modelado espacial

The adjustment of services of general interest to ageing and shrinking populations is a significant challenge in many European regions. This article analyses the response in the number of primary schools to changes in the student population in the municipalities of mainland Portugal between 2007 and 2016. It focuses on the time lag of this adjustment, the territorial factors that influence it and the role of spatial spill-over effects. The main finding is that the relationship between the number of schools and the number of students is not straightforward and can only be understood considering the broader geographic contexts and spatial dependence structures.La adaptación de los servicios de interés general al envejecimiento y la disminución de la población es un reto importante en muchas regiones europeas. Este artículo analiza la respuesta del número de escuelas primarias a los cambios en la población estudiantil en los municipios de Portugal continental para el período de 2007-2016. Se centra en el desfase temporal de este ajuste, los factores territoriales que influyen en él y el papel de efectos de contagio espaciales. El principal hallazgo es que la relación entre el número de escuelas y el número de estudiantes no es directa y solo puede entenderse considerando los contextos geográficos más amplios y las estructuras de dependencia espacial

Navegação baseada no terreno com dados de sonar de varrimento lateral

Mestrado em Engenharia Electrónica e TelecomunicaçõesO presente trabalho propõe uma técnica de matching de imagens de sonar de varrimento lateral, baseada nos conceitos de entropia de Shannon e informação mútua, com aplicação à navegação de veículos robóticos subaquáticos. Para tal, recorre-se não só à informação fornecida pela escala de cinzentos, como também à informação fornecida por um conjunto de features texturais (Haralick Features), extraídas dos dados de sonar. Uma parte significativa do trabalho incide sobre o estudo e a implementação dos algoritmos de estimação de entropia, para cálculo da informação mútua. É feita também uma contextualização do problema proposto, onde, para além da apresentação dos conceitos teóricos envolvidos, são definidos os objectivos gerais, assim como uma revisão às tecnologias de navegação subaquática existentes. Os métodos propostos são validados experimentalmente com dados obtidos de distribuições probabilísticas conhecidas e que permitem a validação dos mesmos analiticamente. São realizados testes adicionais com imagens fotográficas e com dados de SSS para validação daqueles métodos. Para a aplicação de navegação em vista, o cálculo da entropia das imagens baseia-se nos dados originais de SSS, representados em níveis de cinzento, complementados com a informação extraída desses dados segundo os métodos propostos originalmente por Haralick. A selecção das features texturais a usar é feita tendo em conta a natureza dos dados, as limitações associadas à aquisição dos mesmos em ambiente submarino e os objectivos da sua aplicação em termos de navegação. Para tal apresenta-se uma proposta de classificação e escolha das Haralick Features mais adequadas a imagens de sonar de varrimento lateral. Os testes finais aplicam a metodologia proposta a dados reais de sonar de varrimento lateral para demonstrar o potencial da sua utilização no âmbito da navegação de veículos robóticos subaquáticos.The the work presented here proposes a technique for matching of Sidescan Sonar images, based on Shannon’s Entropy and Mutual Information concepts, applied to the naviagtion of underwater robotic vehicles. For such, it is used not only the information given by the grey-scale levels, but also by a set of textural features (Haralick features), which are extracted from the sonar data. A significant parto f this work was spent studying and implementing algorithms for entropy estimation and mutual information calculation. The theoretical concepts involved are presented, the objectives are defined as well as a revision of underwater navigation technologies in existence. All this is done in order to contextualize the proposed problem. The proposed methods are validated experimentally through data acquired from known probability distributions which allow for na analytical validation.Aditional tests with both photographic images and sidescan sonar data are performed in order to validate such methods. For the intended navigational application, the images’ entropy estimation is based on the original sidescan sonar data. This data is represented by grey-scale levels complemented by the information extracted in accordance to the method proposed by Haralick. The selection of the textural features is done by taking into account the data’s nature, limitations associated with data acquisition in submarine environments and the objectives of its application in terms of navigation. It is therefore proposed a more adequate classification and selection of the Haralick features. The final tests are done by applying the proposed methodology to real sidescan sonar data in order to demonstrate its potential for use in assisting robotic underwater vehicles’ navigation

Transporte de informação directamente sobre sistemas de comunicação ópticos

Mestrado em Engenharia ElectrónicaNum futuro próximo, a informação transmitida entre vários utilizadores, seja áudio, vídeo ou dados, poderá ser transportada directamente sobre redes ópticas. Neste sentido, têm sido estudadas e analisadas várias tecnologias emergentes de redes ópticas, que culminaram com o aparecimento de soluções que permitem a integração de redes IP (Internet Protocol) sobre redes ópticas. Tendo em vista este cenário, o objectivo deste trabalho foi o estudo dos mecanismos de transporte de informação sobre sistemas de comunicação ópticos. Foi dada especial relevância a tecnologias ópticas multicanal utilizadas actualmente, o Wavelength Division Multiplexing (WDM) e o Multiprotocol Label Switching (MPLS). Uma vez que uma das formas usuais de avaliar o impacto da camada física nos sistemas de comunicação é através das taxa de erro binários, foi efectuada a caracterização da camada física em termos de taxas de erros binários e da probabilidade de erros na transmissão de pacotes de informação. Este estudo englobou várias fases, nomeadamente a caracterização do meio de transmissão, a fibra (através da taxa de erros binários e do factor Q), e a análise do impacto dos erros binários nas camadas de ligação de dados, de rede e de transporte, traduzida na probabilidade de erros em sequências de bits. Foi também abordado o impacto dos esquemas de detecção e/ou de correcção de erros utilizados nas várias camadas protocolares. Finalmente, foi analisado e caracterizado o comportamento da rede em função das características físicas do canal de transmissão.In a near future, information (audio, video and data) may be transmitted between several users directly over optical networks. Several emerging technologies on optical networks, which allow the IP (Internet Protocol) integration in the optical domain, have already been widely studied and analyzed. Keeping in mind this scenario, the goal of this work was the study of the information transport mechanisms over optical communication systems. Special attention was given to technologies currently used, the Wavelength Division Multiplexing (WDM) and the Multiprotocol Label Switching (MPLS). The Bit Error Rate (BER) is used as a measure of the negative effects of all physical impairments on the fibre, being usually a comprehensive criterion for the evaluation of the signal transmission quality. This way, the physical layer characterization was made in terms of BER and/or packet error rate (PER). This study concerned several stages: the fibre characterization in terms of BER and Q-factor, the study of the impact of the binary errors in the network behaviour, and the study and analysis of the error detection and correction schemes used in the several layers. Finally, the network behaviour was analysed and characterized as a function of the channel physical characteristics and constraints

Polymyositis and the Spectrum of Scleroderma Disorders

Polymyositis (PM) is usually associated to other autoimmune or connective tissue diseases. The authors report the case of a 59-year-old man with pulmonary fibrosis, who presented with constitutional symptoms and gradually developed proximal muscle weakness, Raynaud phenomenon, and dysphagia. Besides creatine kinase (CK) elevation, he had positive anti-Polymyositis-Scleromyositis (PM-Scl) and anti-Sjögren's-syndrome A (SSA) antibodies. Nailfold capillaroscopy showed a scleroderma pattern and muscle biopsy revealed necrosis, regeneration of muscle fibers, and inflammatory infiltrate. Prednisolone was started, with great improvement. Taking into account the overlap features between PM and systemic sclerosis sine scleroderma, it is important to closely monitor the patient for signs of pulmonary and cardiac decompensation

Different locations but common associations in subcortical hypodensities of presumed vascular origin: cross-sectional study on clinical and neurosonologic correlates

BACKGROUND: Subcortical hypodensities of presumed vascular etiology (SHPVO) are a clinical, radiological and neuropathological syndrome with a still largely unexplained pathophysiology. Parallel to the clinical heterogeneity, there is also recognised cerebral topographical diversity with undetermined etiological implications. Our aim is to assess clinical and neurosonological predictors of SHPVO according to their location. METHODS: Cross sectional analysis of consecutive patients that underwent neurosonologic evaluation and head CT within one month, during a one year period. We excluded patients with absent temporal sonographic window, any pathology with a possible confounding effect on cerebral arterial pulsatility, atrial fibrillation and other etiologies of white matter diseases. The mean pulsatility index (PI) of both middle cerebral arteries was measured in the middle third of the M1 segment; intima media thickness was evaluated in the far wall of both common carotid arteries. SHPVO were rated by analysis of head CT in deep white matter (DWMH), periventricular white matter (PVWMH) and basal ganglia (BGH). We conducted a multivariate ordinal logistic regression model including all clinical, demographic and ultrasonographic characteristics to determine independent associations with SHPVO. RESULTS: We included 439 patients, mean age 63.47 (SD: 14.94) years, 294 (67.0%) male. The independent predictors of SHPVO were age (OR = 1.067, 95% CI: 1.047-1.088, p < 0.001 for DWMH; OR = 1.068, 95% CI: 1.049-1.088, p < 0.001 for PVWMH; OR = 1.05, 95% CI: 1.03-1.071, p < 0.001 for BGH), hypertension (OR = 1.909, 95% CI: 1.222-2.981, p = 0.004 for DWMH; OR = 1.907, 95% CI: 1.238-2.938, p = 0.003 for PVWMH; OR = 1.775, 95% CI: 1.109-2.843, p = 0.017 for BGH) and PI (OR = 17.994, 95% CI: 6.875-47.1, p < 0.001 for DWMH; OR = 5.739, 95%CI: 2.288-14.397, p < 0.001 for PVWMH; OR = 11.844, 95% CI: 4.486-31.268, p < 0.001 for BGH) for all locations of SHPVO. CONCLUSIONS: Age, hypertension and intracranial pulsatility are the main independent predictors of SHPVO across different topographic involvement and irrespective of extracranial atherosclerotic involvement

Tratamento endovascular de doença oclusiva aorto-ilíaca: estudo retrospectivo

Objetivos: Avaliar os resultados técnicos do tratamento endovascular em lesões oclusivas do sector aorto-ilíaco.Material e métodos: Foi efectuada uma análise retrospectiva entre Janeiro de 2008 e Janeiro de 2016 de todos os procedimentos endovasculares realizados num único centro para tratamento de lesões ateroscleróticas aorto-ilíacas. Foram avaliados os tipos de lesões existentes, os procedimentos endovasculares utilizados, as taxas de sucesso técnico e de complicações.Resultados: Foram estudados retrospectivamente 194 doentes (idade média 67,44 anos, DP=10,29; 91% sexo masculino). O tipo de lesão mais frequente foi estenose das artérias ilíacas comuns. A colocação de kissing stents foi a técnica mais utilizada (n=96; 49,5%), seguida da colocação de stent ilíaco único (n=85; 43,8%) e angioplastia com balão isolada (n=8; 4,1%). Em cinco casos (2,6%) não foi possível ultrapassar a lesão oclusiva. Verificaram-se complicações imediatas em 5,2% (n=10), sendo a ocorrência de laceração arterial a complicação mais comum, tendo-se registado casos isolados de migração do stent, hematoma e embolização para a artéria femoral superficial. A taxa de sucesso técnico imediato foi de 96,9%.Conclusões: O tratamento endovascular de lesões estenosantes/oclusivas do sector aorto-ilíaco é tecnicamente eficaz na esmagadora maioria dos doentes, com baixas taxas de complicações associadas

Hepatic safety and efficacy of immunomodulatory drugs used in patients with autoimmune hepatitis.

BACKGROUND AND AIMS There is little data on the hepatic efficacy and safety of immunomodulatory drugs used in patients with autoimmune hepatitis (AIH), despite their established use in dermatology, rheumatology and inflammatory bowel diseases (IBD). Our aim was to collect real-life data on the experience of expert centres in treating AIH patients with these drugs, considered unconventional for AIH management. METHODS Online survey among hepatology centres being part of the European Reference Network on Hepatological Diseases (ERN RARE-LIVER). RESULTS 25 AIH patients have been reported. Ten were female, median age at diagnosis was 28 years; median follow-up was 17 months. All had initially received AIH-standard treatment. AIH-unconventional treatment was initiated for concomitant autoimmune diseases in 15 cases: nine for IBD (five vedolizumab and four ustekinumab), and one each for following diseases: autoinflammatory syndrome (tocilizumab), chronic urticaria (omalizumab), rheumatoid arthritis (abatacept), psoriasis (guselkumab), psoriatric arthritis (secukinumab, followed by ustekinumab) and alopecia (ruxolitinib). Three patients were treated with immunomodulatory drugs for side effects of previous treatments, including two patients with IBD treated with vedolizumab and ustekinumab, respectively, and one treated with belimumab. At the end of follow-up, 13 patients were in complete biochemical response, the patient on omalizumab had a relapse, and four patients with concomitant IBD had insufficient response. Seven patients were treated for lack of biochemical remission, of whom six with belimumab, all initially reaching complete biochemical response, but five relapsing during follow-up; and one with secukinumab, having concomitant rheumatoid arthritis and ankylosing spondylitis, reaching complete biochemical response. Only the patient on abatacept received unconventional treatment as monotherapy. Side effects were reported in two patients on belimumab: one recurrent soft tissue infections, one fatigue and arthralgia. CONCLUSION Among 25 AIH patients who were treated with immunomodulatory drugs for different reasons, the majority had a fovorable course, relapse was frequent in difficult-to-treat patients who received belimumab, and four with concomitant IBD had insufficient response

Livro de resumos da Conferência do Projeto de Investigação Científica “Fatores de Transformação Urbana (DRIVIT-UP)” em conjunto com I Conferência sobre Ciência de Dados para Ciências Sociais e VI Conferência de Planeamento Regional e Urbano

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