Magnetic monopole and string excitations in a two-dimensional spin ice

We study the magnetic excitations of a square lattice spin-ice recently produced in an artificial form, as an array of nanoscale magnets. Our analysis, based upon the dipolar interaction between the nanomagnetic islands, correctly reproduces the ground-state observed experimentally. In addition, we find magnetic monopole-like excitations effectively interacting by means of the usual Coulombic plus a linear confining potential, the latter being related to a string-like excitation binding the monopoles pairs, what indicates that the fractionalization of magnetic dipoles may not be so easy in two dimensions. These findings contrast this material with the three-dimensional analogue, where such monopoles experience only the Coulombic interaction. We discuss, however, two entropic effects that affect the monopole interactions: firstly, the string configurational entropy may loose the string tension and then, free magnetic monopoles should also be found in lower dimensional spin ices; secondly, in contrast to the string configurational entropy, an entropically driven Coulomb force, which increases with temperature, has the opposite effect of confining the magnetic defects.Comment: 8 pages. Accepted by Journal of Applied Physics (2009

Evaluation of influenza vaccination services and users’ perception about its utility: a study in a community pharmacy in Lisbon, Portugal

Poster presented at the 25th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID). Copenhagen, Denmark, 25–28 April 201

Efeito da radiação ultravioleta-B sobre a germinação de conídios de Botrytis cinerea e colonização em discos de morango.

RESUMO: O ultravioleta é um fator de grande impacto na agricultura e está intimamente relacionado à camada de ozônio, a qual vem sendo reduzida paulatinamente, em consequência das atividades antrópicas. A camada de ozônio está sendo degradada, principalmente, por ação dos clorofluorcarbonos (CFC) utilizados pelo homem alterando assim a intensidade de radiação ultravioleta na superfície terrestre em especial no comprimento de onda da radiação ultravioleta B (UV-B). O objetivo do trabalho foi avaliar a resistência de conídios de Botrytis cinerea à radiação UV-B. Foram testados 13 isolados do patógeno, onde uma suspensão contendo 105 conídios mL-1 de cada isolado foi preparada e uma alíquota de 20 ?L foi colocada no centro de uma placa de Petri contendo BDA. Os conídios foram expostos à radiação UV-B 5,6 kJ m-2 a uma irradiância de 823 mW m-2. Também foi avaliada a esporulação de B. cinerea em discos de folha de morangueiro em meio de cultura paraquat-clorofenicolágar (PCA). Os isolados apresentaram germinação relativa entre 15% e 90%, sendo que os isolados com maior resistência à radiação UV-B foram o LQC 162, LQC 150 e LQC 159. No teste da esporulação foi observado maior diferenças entre os isolados quanto a formação de conidióforos do patógeno sendo os isolados LQC 150 e LQC 157 superiores aos outros isolados. Foi selecionado o isolado LQC 150 para ensaios posteriores onde será comparada a tolerância desse isolado com isolados de agentes de controle biológico deste patógeno quanto a tolerância a radiação UV-B

Long-snouted seahorse, Hippocampus guttulatus, under global warming

The earth’s climate system and the global ocean have been warming up, since the mid-twentieth century and it is expected that the global and ocean´s temperature will rise in the next years even more [1,2,13,25,28]. For ectotherms, such as fish, temperature is a determinant cue for several behavioural [29], physiological [24], and metabolic processes [6]. Seahorses’ particular life history makes them vulnerable to human or natural disturbances [17]. The long snout seahorse, Hippocampus guttulatus, is one of the two species that inhabit the coastal areas of Portugal [23]. The present study aims to assess the effects of ocean warming on growth, feed intake and behavior patterns of adult H. guttulatus. Results provide clear evidence of detrimental effects of exposure to warming on this species. Under extreme temperatures (24ºC), the increased food ingestion was not enough for fish to support growth (weighted less), which suggests that fish were spending energy to counterbalance the thermal stress they were exposed to. Fish under both elevated temperature treatments (20 and 24ºC) were also spending more energy in active behaviours. Altogether, these data may indicate that ocean warming will have a drastic effect on seahorse populations currently inhabiting the Sado estuary.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio