Collinear versus non-collinear magnetic order in Pd atomic clusters: ab-initio calculations

We present a thorough theoretical assessment of the stability of non-collinear spin arrangements in small palladium clusters. We generally find that ferromagnetic order is always preferred, but that antiferromagnetic and non-collinear configurations of different sorts exist and compete for the first excited isomers. We also show that the ground state is insensitive to the choice of atomic configuration for the pseudopotential used and to the approximation taken for the exchange and correlation potential. Moreover, the existence and relative stability of the different excited configurations also depends weakly on the approximations employed. These results provide strong evidence on the transferability of pseudopotential and exchange and correlation functionals for palladium clusters as opposed to the situation found for the bulk phases of palladium.Comment: 5 pages, 4 figure

Topology of Almost Complex Structures on Six-Manifolds

We study the space of (orthogonal) almost complex structures on closed six-dimensional manifolds as the space of sections of the twistor space for a given metric. For a connected six-manifold with vanishing first Betti number, we express the space of almost complex structures as a quotient of the space of sections of a seven-sphere bundle over the manifold by a circle action, and then use this description to compute the rational homotopy theoretic minimal model of the components that satisfy a certain Chern number condition. We further obtain a formula for the homological intersection number of two sections of the twistor space in terms of the Chern classes of the corresponding almost complex structures

Estudio comparativo entre el proyecto educativo del programa (PEP) de Licenciatura en Informática de la Universidad de Nariño y proyectos educativos de otros programas de licenciatura afines en universidades públicas a nivel nacional.

La investigación compara las propuestas educativas que estas universidades presentan en esta área de estudio, desde los componentes fundamentales que conforman el programa y que están escritos en los documentos legales que debe tener cada una. Se busca similitudes, diferencias, ventajas, desventajas, etc., en aras de alcanzar la mejora de la calidad educativa ofrecida para los profesionales en este campo. Para tal fin, se utilizó el método comparativo de Hilker y Bereday (1972), organizado en cuatro fases: descripción, interpretación, yuxtaposición y comparación que dio lugar a dos tipos de resultados: los componentes coincidentes entre los programas, y por tanto las oportunidades de transferencias, traslados e intercambios que se abren; y los componentes que se diferencian, lo que causa que algunos programas tengan desventajas a la hora de ofrecerlos a la comunidad, pero a la vez abre la oportunidad de mejora en la calidad de su propuesta, inherente a la cultura de autoevaluación que cada uno debe tener

Índices de qualidade de serviço em sistemas de drenagem e tratamento de águas residuais

O abastecimento de água, o saneamento de águas residuais urbanas e a gestão integrada de resíduos sólidos urbanos constituem serviços públicos de carácter estrutural, essenciais ao bem-estar geral, à saúde pública e à segurança colectiva das populações, às actividades económicas e à protecção do ambiente. A Entidade Reguladora dos Serviços de Águas e Resíduos (ERSAR) implementou um sistema de avaliação de desempenho das entidades gestoras (EG) baseado em indicadores de desempenho (ID). Estes indicadores incidem sobre aspectos parcelares do desempenho duma dada EG, tendo por objectivo o aumento dos padrões de eficiência e de eficácia dos serviços prestados. Este trabalho tem como principal objectivo contribuir para a melhoria do modelo de avaliação de desempenho existente, através da definição e cálculo de índices (sectoriais e global) de qualidade de serviço em sistemas de drenagem e tratamento de águas residuais, com base numa metodologia de análise multicritério. O seu valor resulta duma criteriosa combinação das pontuações normalizadas de cada ID. Além de facilitarem a aplicação de estratégias de benchmarking, a integração destes índices em sistemas de suporte à decisão, associados à gestão patrimonial de infra-estruturas de saneamento básico poderá ser um instrumento muito útil para as EG na definição das suas prioridades de investimento e de planos operacionais de reabilitação

Characterization of Thin p-on-p Radiation Detectors with Active Edges

Active edge p-on-p silicon pixel detectors with thickness of 100 $\mu$m were fabricated on 150 mm Float zone silicon wafers at VTT. By combining measured results and TCAD simulations, a detailed study of electric field distributions and charge collection performances as a function of applied voltage in a p-on-p detector was carried out. A comparison with the results of a more conventional active edge p-on-n pixel sensor is presented. The results from 3D spatial mapping show that at pixel-to-edge distances less than 100 $\mu$m the sensitive volume is extended to the physical edge of the detector when the applied voltage is above full depletion. The results from a spectroscopic measurement demonstrate a good functionality of the edge pixels. The interpixel isolation above full depletion and the breakdown voltage were found to be equal to the p-on-n sensor while lower charge collection was observed in the p-on-p pixel sensor below 80 V. Simulations indicated this to be partly a result of a more favourable weighting field in the p-on-n sensor and partly of lower hole lifetimes in the p-bulk.Comment: 23 pages, 16 figures, 1 tabl

Morphodynamic modelling of a gravel beach at the NW Portuguese coast

Besides exhibiting an erosion trend for decades, the NW coastal zone of Portugal, since the end of 20th century, was the stage of a new phenomenon. Between Lima and Cávado rivers, previously dissipative, sandy beaches transformed in mixed sand-gravel beaches with gravelly beach cusps (by the end of 80?s) and progressively convert in entire reflective gravel beaches (since 2000), though maintaining the inherited dune systems on their backshore. This beach is being monitored since 2013 using DGPS, aerophotogrametic surveys and expedite gravel size characterization. Based on these monitoring results a modeling work was carried out to simulate the beach morphodynamics, applying XBeach-G software. The model was able to simulate the beach morphodynamics

Attachment of Staphylococcus epidermidis RP62A to chemically modified cellulose derivatives

Coagulase negative staphylococci, most notably Staphylococcus epidermidis, have been identified as a predominant cause of cardiovascular implant infection, which begins with the colonization of the device by the bacteria. One possible approach to reduce this event is to understand how the physicochemical properties of bacterial surface influence attachment to biomaterials. In the present study, the attachment of coagulase negative Staphylococcus epidermidis expressing capsular polysaccharide/adhesin (PS/A), the most common etiological agent of colonization of implantable medical devices, was assessed in vitro to cellulose diacetate (CDA), to CDA chemically modified by de-acetylation (CDA-D) and by phosphorylation (CDA-P), as well as to reference Low Density Polyethylene (LDPE). The quantification of S. epidermidis attached to cellulose diacetate (CDA) in phosphate buffer saline (PBS) elicited information regarding the interaction between the bacterial strain and the polymeric biomaterial. There was a significant difference in the adhesion of RP62A to CDA, compared to LDPE. Chemical modifications of CDA by de-acetylation and by phosphorylation were effective in lowering bacterial attachment. These chemical treatments increased the acidic parameter of the surface energy and decreased the acid-base interactions with acidic sites of the capsular PS/A. In other terms, these treatments also promoted a decrease in hydrophobicity that linearly correlates with a decrease in the number of attached cells

Abrupt field-induced transition triggered by magnetocaloric effect in phase-separated manganites

The occurrence at low temperatures of an ultrasharp field-induced transition in phase separated manganites is analyzed. Experimental results show that magnetization and specific heat step-like transitions below 5 K are correlated with an abrupt change of the sample temperature, which happens at a certain critical field. This temperature rise, a magnetocaloric effect, is interpreted as produced by the released energy at the transition point, and is the key to understand the existence of the abrupt field-induced transition. A qualitative analysis of the results suggests the existence of a critical growing rate of the ferromagnetic phase, beyond which an avalanche effect is triggered.Comment: 6 pages, 4 figures included. Acepted for publication in Phys. Rev.