Multiple classical limits in relativistic and nonrelativistic quantum mechanics

The existence of a classical limit describing interacting particles in a second-quantized theory of identical particles with bosonic symmetry is proved. This limit exists in addition to a previously established classical limit with a classical field behavior, showing that the limit $\hbar \to 0$ of the theory is not unique. An analogous result is valid for a free massive scalar field: two distinct classical limits are proved to exist, describing a system of particles or a classical field. The introduction of local operators in order to represent kinematical properties of interest is shown to break the permutation symmetry under some localizability conditions, allowing the study of individual particle properties.Comment: 13 page

Practical computational toolkits for dendrimers and dendrons structure design

Dendrimers and dendrons offer an excellent platform for developing novel drug delivery systems and medicines. The rational design and further development of these repetitively branched systems are restricted by difficulties in scalable synthesis and structural determination, which can be overcome by judicious use of molecular modelling and molecular simulations. A major difficulty to utilise in silico studies to design dendrimers lies in the laborious generation of their structures. Current modelling tools utilise automated assembly of simpler dendrimers or the inefficient manual assembly of monomer precursors to generate more complicated dendrimer structures. Herein we describe two novel graphical user interface (GUI) toolkits written in Python that provide an improved degree of automation for rapid assembly of dendrimers and generation of their 2D and 3D structures. Our first toolkit uses the RDkit library, SMILES nomenclature of monomers and SMARTS reaction nomenclature to generate SMILES and mol files of dendrimers without 3D coordinates. These files are used for simple graphical representations and storing their structures in databases. The second toolkit assembles complex topology dendrimers from monomers to construct 3D dendrimer structures to be used as starting points for simulation using existing and widely available software and force fields. Both tools were validated for ease-of-use to prototype dendrimer structure and the second toolkit was especially relevant for dendrimers of high complexity and size.Peer reviewe

Coordinate representation of particle dynamics in AdS and in generic static spacetimes

We discuss the quantum dynamics of a particle in static curved spacetimes in a coordinate representation. The scheme is based on the analysis of the squared energy operator E^2, which is quadratic in momenta and contains a scalar curvature term. Our main emphasis is on AdS spaces, where this term is fixed by the isometry group. As a byproduct the isometry generators are constructed and the energy spectrum is reproduced. In the massless case the conformal symmetry is realized as well. We show the equivalence between this quantization and the covariant quantization, based on the Klein-Gordon type equation in AdS. We further demonstrate that the two quantization methods in an arbitrary (N+1)-dimensional static spacetime are equivalent to each other if the scalar curvature terms both in the operator E^2 and in the Klein-Gordon type equation have the same coefficient equal to (N-1)/(4N).Comment: 14 pages, no figures, typos correcte

Estudo entre a maturação das vertebras cervicais e a idade cronológica

Poster apresentado na SPODF2015 - XXVII Reunião Científica Anual da Sociedade Portuguesa de Ortopedia Dento-Facial, 23-25 Abril de 2015, Figueira da Foz, Portugal

Central Venous Catheterisation in Pediatric Intensive Care - Five Years Experiense

Objectivo: Avaliar a incidência de complicações relacionadas com o cateterismo venoso central e a existência de eventuais factores de risco para a sua ocorrência. Material e métodos: Estudo retrospectivo de 305 catéteres venosos centrais colocados pelos médicos da Unidade de Cuidados Intensivos Pediátricos (UCIP) do Hospital Dona Estefânia, durante 5 anos. As variáveis estudadas foram: idade, peso, instituição de ventilação mecânica, alteração da coagulação, local de inserção, número de lúmens e tempo de utilização do catéter, número e tipo de complicações. Na análise estatística foram utilizados o teste do Quiquadrado, o teste exacto de Fisher e o t-teste de Student, considerando-se haver diferenças estatisticamente significativas para valores de p< 0,05. Resultados: Foram submetidos a cateterismo 296 crianças, com idades compreendidas entre 0.08 e 16.00 anos (média=3,6 anos) e pesos entre 2 e 85 Kg (média=16,2 Kg). Os locais de inserção foram, por ordem decrescente de utilização, a veia subclávia (63,3%), a veia femural (29,8%) e veia jugular (6,9%). Os catéteres de duplo lúmen foram os mais utilizados (61,9%), seguidos dos de mono (32,5%) e de triplo lúmen (5,6%). Ocorreram 46 (15,1%) complicações, mas não se verificaram óbitos directamente relacionados com o cateterismo. A remoção do catéter foi electiva em 98 (32,1%) casos, por óbito em 97 (31,8%), por complicações em 39 (12,8%) e por outras causas em 71 (23,2%). O tempo de utilização dos catéteres foi em média de 7,6 dias. Os catéteres com e sem sépsis tiveram uma duração média de utilização de 6,9 dias e 17,0 dias, respectivamente. Conclusões: Este estudo revelou um padrão de complicações do cateterismo venoso central semelhante ao descrito por outros autores, sendo que nenhuma das variáveis analisadas se revelou, por si só, como factor de risco de complicações, excepto o tempo de utilização do catéter na ocorrência de sépsis

The History of the Portuguese Aviation - A Summary

This article is intended as a summary of a new area of study on the History of the Portuguese Aeronautics and Aerospace and addresses issues such as: the forthcoming of the aircraft at Portugal, its military and civilian use; the scope of early days concerning Portuguese intercontinental flights and their authors; the development of air navigation devices by Portuguese inventors in the 1920s and 30s; the Aeronautics industry and the need to develop expertise in Aeronautical/Aerospace Engineering in Portugal during the centuries XX and XXI.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

First Aerial South Atlantic Night Crossing

The history of the transatlantic flights began in 1919 when Albert C. Read’s team flew between Newfoundland and Lisbon, with a stopover at Azores, for fuel and repairs. The flight was made following a chain of 60 U.S. warships in order to guide it along its route and to provide assistance if needed. Two weeks later, John Alcock and Sir Arthur Whitten Brown made the first nonstop transatlantic flight from Newfoundland to County Galway, Ireland, covering more than 3000 km in just 16 hours of flight. In 1922, Gago Coutinho and Sacadura Cabral crossed the South Atlantic Ocean by air, for the first time using only internal means of navigation: a modified sextant and a course corrector; both devices proved its effectiveness. The Portuguese Aeronautics rejoiced auspicious days that time, with its aviation pioneers trying consecutively to reach more distant places along intercontinental flights. Several Around-the-World Flight Attempts were made in 1924: United States, England, France, Portugal, Argentina and Italy. However the circumnavigation purpose was only officially confirmed before the general public, when a considerable flying progress was achieved. In 1923, Gago Coutinho and Sacadura Cabral were contemplating to perform an Around the World Flight, a dream pursued also by Sarmento de Beires in 1924 and 1927. In 1927 and by following the knowledge obtained by Coutinho and Cabral, four Portuguese Airmen started an Around the World Flight Attempt in a mission that ended with seaplane sunk at the Ocean; however this mission was renamed after the seaplane loss and became known in the World as the First Aerial South Atlantic Night Crossing. For the first time in history, during the night of 16 to 17 March 1927, a Portuguese crew flew 2595 km over the Atlantic Ocean from Guinea, Africa to Fernando de Noronha Island, Brazil. The flight was made only by astronomical processes navigation resources that proved again to be absolutely feasible and trustworthy, regardless day or night lighting conditions.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio