Distributional approach to point interactions in one-dimensional quantum mechanics

We consider the one-dimensional quantum mechanical problem of defining interactions concentrated at a single point in the framework of the theory of distributions. The often ill-defined product which describes the interaction term in the Schr\"odinger and Dirac equations is replaced by a well-defined distribution satisfying some simple mathematical conditions and, in addition, the physical requirement of probability current conservation is imposed. A four-parameter family of interactions thus emerges as the most general point interaction both in the non-relativistic and in the relativistic theories (in agreement with results obtained by self-adjoint extensions). Since the interaction is given explicitly, the distributional method allows one to carry out symmetry investigations in a simple way, and it proves to be useful to clarify some ambiguities related to the so-called $\delta^\prime$ interaction.Comment: Open Access link: http://journal.frontiersin.org/Journal/10.3389/fphy.2014.00023/abstrac

Postproduction of potted miniature rose: flower respiration and single flower longevity

Research was conducted to investigate the relationship between flower respiration and flower longevity as well as to assess the possibility of using miniature rose (Rosa hybrida L.) flower respiration as an indicator of potential flower longevity. Using several miniature rose cultivars as a source of variation, four experiments were conducted throughout the year to study flower respiration and flower longevity under interior conditions. For plants under greenhouse as well as interior conditions, flower respiration was assessed on one flower per plant, from end-of-production (sepals beginning to separate) up to 8 days after anthesis. Interior conditions were 21 ± 1 °C and 50 ± 5% relative humidity with a 12-hour photoperiod of 12 μmol.m–2.s–1 (photosynthetically active radiation). Flower respiration was higher if the plants were produced during spring/summer as compared to fall/winter. ‘Meidanclar’, ‘Schobitet’, and ‘Meilarco’ miniature roses had higher flower respiration rates than ‘Meijikatar’ and ‘Meirutral’. These two cultivars with the lowest respiration rates showed much greater flower longevity if grown during spring/summer as compared to fall/winter. The three cultivars with the higher respiration rates did not show differences in flower longevity between seasons. For plants under greenhouse or interior conditions, flower respiration was negatively correlated with longevity in spring/summer but a positive correlation between these parameters was found in fall/winter. During spring/summer, flower respiration rate appears to be a good indicator of potential metabolic rate, and flowers with low respiration rates last longer.American Floral Endowment and Junta de Investigação Científica e Tecnológica (Programa Ciência, Portugal). Yodder Brothers (Parrish, Florida, U.S.A.) ofereceu as plantas

Exogenous sucrose effects on carbohydrate level, flower respiration and longevity of potted miniature rose (Rosa hybrida) flowers during postproduction.

The effect of continuous injection of exogenous sucrose on single flower postproduction longevity of attached flowers of potted ‘Meijikatar’ miniature roses was studied. At bud showing color, with sepals starting to unfold, plants were moved to interior conditions and started being continuously injected with a solution of 3% sucrose or distilled water. Carbohydrate levels, flower respiration and single flower longevity were assessed. The method presented some variability in the amounts of solution supplied to the plants. Infusion of exogenous sucrose increased attached miniature rose flower longevity by 1.5 days and also increased flower respiration rate. The higher the uptake rate of sucrose solution the longer the flowers lasted. Exogenously supplied sucrose was consumed by increased respiration and consequently, at day 6 after anthesis, no differences were found in nonstructural carbohydrate levels between water and sucrose treatments. However, stem percent of soluble sugars was higher in the sucrose infused plants, suggesting that exogenous sucrose supply not only served as an extra source of respirable carbohydrates but also released stored carbohydrates to flower respiration. At flower death, leaf soluble sugars and total non-structural carbohydrates were higher in the sucrose infusion treatment and, independently of infusion treatment flower soluble sugars and total non-structural carbohydrates positively correlated with flower longevity.American Floral Endowment, Junta de Investigação Científica e Tecnológica (Programa Ciência, Portugal). Yodder Brothers (Parrish, Florida, U.S.A.) forneceu as plantas. Dr. Rebecca Darnell (Univ. of Florida) colocou o laboratório à disposição para os trabalhos com 14C-sacarose

High production temperature increases postproduction flower longevity and reduces bud drop of potted, miniature roses ‘Meirutral’ and ‘Meidanclar’

The effect of two temperature regimes (29 °C day/24 °C night and 24 °C day/18 °C night) and of a 4-hour night interruption, during production, was studied on postproduction flower longevity and bud drop of ‘Meirutral’ and ‘Meidanclar’ potted, miniature roses (Rosa L. sp.). High production temperatures increased postproduction flower longevity and decreased postproduction bud drop. In ‘Meidanclar’, the high production temperature increased incidence of malformed flowers. No effects of night interruption could be shown on either postproduction flower longevity or bud drop.Esta trabalho foi financiado em parte pela American Flower Endowment and Junta de Investigação Científica e Tecnológica Programa Ciência, Portugal). Yoder Brothers (Parrish, Fla., USA) ofereceu as plantas

A Fast Monte Carlo algorithm for evaluating matrix functions with application in complex networks

We propose a novel stochastic algorithm that randomly samples entire rows and columns of the matrix as a way to approximate an arbitrary matrix function. This contrasts with the "classical" Monte Carlo method which only works with one entry at a time, resulting in a significant better convergence rate than the "classical" approach. To assess the applicability of our method, we compute the subgraph centrality and total communicability of several large networks. In all benchmarks analyzed so far, the performance of our method was significantly superior to the competition, being able to scale up to 64 CPU cores with a remarkable efficiency.Comment: Submitted to the Journal of Scientific Computin

A SEGURANÇA DO PACIENTE CIRÚRGICO, O PAPEL DOS PROFISSIONAIS E O IMPACTO SÓCIOECONÓMICO NUMA UNIDADE LOCAL DE SAÚDE

Os eventos adversos são uma realidade nos cuidados de saúde, com particular interesse para o paciente cirúrgico, pelo que é determinante que se conheça a sua dimensão, no sentido de os evitar, sempre que possível. A interiorização de uma cultura de segurança, como uma prioridade, por parte dos profissionais, pode contribuir para o desenvolvimento de sistemas que conduzam a cuidados mais seguros. Deste modo, pode reduzir-se a ocorrência dos eventos e os seus impactos negativos, principalmente nos dias de internamento e nos custos adicionais associados. Nesta perspectiva, foi desenvolvido um estudo exploratório numa Unidade Local de Saúde, com o objectivo de conhecer a cultura de segurança existente nos serviços cirúrgicos, referente ao ano de 2008, e se esta é influenciada por três dimensões: a liderança, o trabalho de equipa e a comunicação. Associado a este estudo, foi desenvolvido um outro para conhecer os impactos socioeconómicos de determinados eventos adversos relacionados com a cirurgia, também relativamente ao ano de 2008. Os resultados obtidos demonstram que a cultura de segurança é influenciada por qualquer das três dimensões referidas, constatando-se que a cultura existente nestes serviços se situa num nível intermédio, classificado como aceitável. Ao nível dos resultados socioeconómicos, verificou-se que para os 40 casos identificados, em que ocorreram eventos adversos, houve um adicional de 753,4 dias de internamento, correspondendo a 553,412€ de custos adicionais, com uma taxa de mortalidade associada de 17,5% e a necessidade de voltar ao bloco operatório em 55% dos casos