Angular Momentum of the BTZ Black Hole in the Teleparallel Geometry

We carry out the Hamiltonian formulation of the three- dimensional gravitational teleparallelism without imposing the time gauge condition, by rigorously performing the Legendre transform. Definition of the gravitational angular momentum arises by suitably interpreting the integral form of the constraint equation Gama^ik=0 as an angular momentum equation. The gravitational angular momentum is evaluated for the gravitational field of a rotating BTZ black hole.Comment: 17 pages, no figures, v2: some misprints corrected, Ref.s added, Eq.s revised, submitted to General Relativity and Gravitatio

A computationally efficient method for calculating the maximum conductance of disordered networks: Application to 1-dimensional conductors

Random networks of carbon nanotubes and metallic nanowires have shown to be very useful in the production of transparent, conducting films. The electronic transport on the film depends considerably on the network properties, and on the inter-wire coupling. Here we present a simple, computationally efficient method for the calculation of conductance on random nanostructured networks. The method is implemented on metallic nanowire networks, which are described within a single-orbital tight binding Hamiltonian, and the conductance is calculated with the Kubo formula. We show how the network conductance depends on the average number of connections per wire, and on the number of wires connected to the electrodes. We also show the effect of the inter-/intra-wire hopping ratio on the conductance through the network. Furthermore, we argue that this type of calculation is easily extendable to account for the upper conductivity of realistic films spanned by tunneling networks. When compared to experimental measurements, this quantity provides a clear indication of how much room is available for improving the film conductivity.Comment: 7 pages, 5 figure

Upper bound for the conductivity of nanotube networks

Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. By considering ideal ballistic-like contacts between nanotubes we use the Kubo formalism to calculate the upper bound for the conductivity of such films and show how it depends on the nanotube concentration as well as on their aspect ratio. Highest measured conductivities reported so far are approaching this limiting value, suggesting that further progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied Physics Letter

Traumatismo Crânio-Encefálico em Portugal: Tendências em Doentes Internados de 2000 a 2010

Introduction: Traumatic brain injury has a considerable socio-economic impact, being a major cause of morbi-mortality, often with permanent disability. We sought to characterize health resource utilization of adult traumatic brain injury patients in Portugal between 2000 and 2010. Material and Methods: Retrospective study of medical records of adult patients with ICD9 diagnostic code of traumatic brain injury included in the National Diagnosis Related Groups Database from 2000-2010. Descriptive statistical analysis was performed and trends during the decade were evaluated. Results: We analysed 72 865 admissions to 111 hospitals, 64.1% males, mean age 57.9 ± 21.8 years (18-107). We found a decrease in number of traumatic brain injury in younger patients and an increase in older ones. The number of traffic accidents decreased and the number of falls increased. There was an increase of moderate to severe traumatic brain injury admissions: 47.2% in 2000 / 80% in 2010. Patients admitted in Intensive Care have nearly doubled (15.8% vs 29.5%) as well as the number submitted to neurosurgical procedures (8.2% vs 15.2%). Total mortality increased from 7.1% to 10.6%. Discussion: The decrease of traumatic brain injury may be associated with the trauma prevention campaigns, road network improvement and health politics. The increase in mortality may be related to better pre-hospital care, enabling more severe cases to arrive in hospital alive, and although treated more frequently in Intensive Care and requiring more neurosurgical procedures, they end up having higher mortality. Also this may be due to an increase in patients' age and worse pre-morbid status. Conclusion: Traumatic brain injury in Portugal is changing. Although hospital admissions due to global traumatic brain injury have decreased, mortality rate has increased

Cancro do colo do útero: que rastreio?

O cancro do colo do útero é um dos cancros evitáveis mais frequente nas mulheres, Ferlay (2004) e Parkin(2005). O padrão epidemiológico da doença, caracterizado por um período longo entre a detecção das primeiras lesões e a instalação da doença, favorece a sua inclusão em programas de rastreio organizado, por serem custo-eficientes e terem ganhos de saúde associados, ver Anttila (2004), Castellsague (2006) e Koutsky (1998). O presente estudo teve como objectivo auxiliar os elementos da Comissão de Rastreio do Cancro do Colo do Útero na Região Norte na tomada de decisões relativas aos aspectos mais controversos dos rastreios ao cancro do colo do útero: limite de idade das mulheres rastreadas, intervalo entre exames e método utilizado. Assim, construiu-se um modelo matemático, com o intuito de simular os impactos económicos e de saúde, das combinações das várias alternativas de rastreio. Por fim, foi feita uma análise custo-benefício das soluções encontradas e determinou-se a solução, i.e. a opção de rastreio, mais vantajosa.Cervical cancer is one of the most frequent avoidable cancers in women, Ferlay (2004) and Parkin(2005). The natural history of the disease, characterized for a long period between the detection of the rst injuries and invasive cancer, favours its inclusion in organized screening programs, since they are cost-e ective and have clear advantages for the health of the population, see Anttila (2004), Castellsague (2006) and Koutsky (1998). The aim of this study is to construct a mathematical model that can help the elements of the Commission delegated for planning the screening program, to decide about the most controversial aspects: target population, interval between examinations and method to be used. The mathematical model allows to simulate the economical and health impact of all the possible solutions. Finally, a cost-bene t analysis of the combined screening alternatives was done to determine the solution, i.e, the more advantageous screening program

Application of a statistic tool for on-line characterization of bubble population complexity in a multiphase reactor

Este resumo faz parte de: Book of abstracts of the Meeting of the Institute for Biotechnology and Bioengineering, 2, Braga, Portugal, 2010. A versão completa do livro de atas está disponível em: http://hdl.handle.net/1822/1096

Fluorinated beta-sheet breaker peptides

The aggregation of amyloid-beta peptide (Ab) has been linked to the formation of neuritic plaques, which are pathological hallmarks of Alzheimer's disease. We synthesized peptides containing fluorinated amino acids and studied their effect on the Ab aggregation. The peptides were based on the sequence LVFFD, in which valine was substituted by either 4,4,4-trifluorovaline or 4-fluoroproline, or the phenylalanine at position 3 was replaced by 3,4,5-trifluorophenylalanine. Our results demonstrate that fluorination of the hydrophobic residue valine or phenylalanine is effective in preventing the Ab aggregation. This study opens up the possibility of using new sequences based on fluorinated amino acids to inhibit the amyloid- fibril formation