Treating some solid state problems with the Dirac equation

The ambiguity involved in the definition of effective-mass Hamiltonians for nonrelativistic models is resolved using the Dirac equation. The multistep approximation is extended for relativistic cases allowing the treatment of arbitrary potential and effective-mass profiles without ordering problems. On the other hand, if the Schrodinger equation is supposed to be used, our relativistic approach demonstrate that both results are coincidents if the BenDaniel and Duke prescription for the kinetic-energy operator is implemented. Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure

Avaliação de quatro alternativas de análise de experimentos em látice quadrado, quanto a estimação de componentes de variância.

Estudou-se, no presente trabalho, a eficiencia das seguintes alternativas de analise de experimentos realizados em latice quanto a precisao na estimacao de componentes de variancia, atraves da simulacao computacional de dados. i) analise intrablocos do latice com tratamentos ajustados (primeira analise); ii) analise de latice em blocos casualizados completos (segunda analise); iii) analise intrablocos do latice com tratamentos nao-ajustados (terceira analise); iv) analise do latice como blocos casualizados completos, utilizando as medias ajustadas dos tratamentos, obtidos a partir da analise com recuperacao da informacao interblocos, tendo como quadrado medio do residuo a variancia efetiva media dessa analise do latice (quatro analise). Os resultados obtidos mostram que se deve utilizar o modelo de analise intra blocos de experimentos em latos para se estimar em componentes de variancia sempre que a eficiencia relativa do delineamento em latice, em relacao ao delineamento em Blocos Completos Casualizados, for superior a 100% e, em caso contrario, deve-se optar pelo modelo de analise em Blocos Casualizados Completos. A quarta alternativa de analise nao deve ser recomendada em qualquer das duas situacoes

Emergy evaluation of tillage systems in maize production in the agreste of sergipe state.

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Integrating psychosocial and WASH school interventions to build disaster resilience

This paper reviews the key disaster risk management (DRM) frameworks used for protecting children's wellbeing in disaster settings and identifies a lack of consideration for (1) psychosocial and (2) water, sanitation and hygiene (WASH) needs. It also demonstrates that these two domains are meaningfully linked, as access to adequate WASH provision may protect psychosocial wellbeing and promote community resilience. As support in both domains is vitally important to children's wellbeing, these gaps warrant immediate attention. Schools are uniquely situated to support these needs as part of disaster risk management and resilience building. Therefore, we consider the ASEAN Common Framework for Comprehensive School Safety (ACFCSS), which is an adaptation of the Comprehensive School Safety Framework (CSS) implemented in schools across the ASEAN region. While the CSS explicitly considers WASH, it only briefly considers psychosocial support; the ACFCCS lacks consideration of both domains. We argue revisions of the ACFCSS should prioritise the inclusion of psychosocial and WASH support and consider the role of schools beyond their capacity as educational institutions. We present an adaptation of ACFCSS with an additional framework pillar to guide this revision. Overall, we advocate for an integrated approach to DRM in schools based on an evidence-based, interdisciplinary perspective. We provide a series of evidence-based recommendations for DRM frameworks to consider, especially for those that intend to safeguard the wellbeing of children

Development of an injectable PHBV microparticles-GG hydrogel hybrid system for regenerative medicine

Uncontrollable displacements that greatly affect the concentration of active agents at the target tissues are among a major limitation of the use of microparticulate drug delivery systems (DDS). Under this context a biphasic injectable DDS combining poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microparticles (MPs) and a gellan gum (GG) injectable hydrogel is herein proposed for the localized delivery and long-term retention of MPs carrying hydrophilic and hydrophobic model active agents. A double emulsion-solvent evaporation method was adopted to develop the PHBV MPs, carrying bovine serum albumin (BSA) or dexamethasone (Dex) as hydrophilic and hydrophobic active agents’ models, respectively. Moreover, this method was modified, together with the properties of the hydrogel to tailor the delivery profile of the active agents. Variations of the composition of the organic phase during the process allowed tuning surface topography, particle size distribution and core porosity of the PHBV MPs and, thus, the in vitro release profile of Dex but not of BSA. Besides, after embedding hydrogels of higher GG concentration led to a slower and more sustained release of both active agents, independently of the processing conditions of the microparticulate system.The authors would like to acknowledge the Project RL1 - ABMR - NORTE-01-0124-FEDER-000016 co-financed by North Portugal Regional Operational Programme (ON.2 - O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). This work was partially supported by European Research Council grant agreement ERC-2012-ADG 20120216-321266 for project ComplexiTE

Neutrinos from Accreting Neutron Stars

The magnetospheres of accreting neutron stars develop electrostatic gaps with huge potential drops. Protons and ions, accelerated in these gaps along the dipolar magnetic field lines to energies greater than 100 TeV, can impact onto a surrounding accretion disc. A proton-induced cascade so develops, and $\nu$-emission is produced from charged pion decays. Using GEANT4, a computer code that tracks particles produced in high energy collisions, we have calculated the resulting $\nu$-spectrum with extensive disc shower simulations. We show that the $\nu$-spectrum produced out of the proton beam is a power law. We use this result to propose accretion-powered X-ray binaries (with highly magnetized neutron stars) as a new population of point-like $\nu$-sources for km-scale detectors, such as ICECUBE. As a particular example we discuss the case of A0535+26. We show that ICECUBE should find A0535+26 to be a periodic $\nu$-source: one for which the formation and loss of its accretion disc can be fully detected. Finally, we briefly comment on the possibility that smaller telescopes, like AMANDA, could also detect A0535+26 by folding observations with the orbital period.Comment: 7 pages, 5 figures. Updates to match accepted version in Astrophys.