Direct vs. indirect optical recombination in Ge films grown on Si substrates

The optical emission spectra from Ge films on Si are markedly different from their bulk Ge counterparts. Whereas bulk Ge emission is dominated by the material's indirect gap, the photoluminescence signal from Ge films is mainly associated with its direct band gap. Using a new class of Ge-on-Si films grown by a recently introduced CVD approach, we study the direct and indirect photoluminescence from intrinsic and doped samples and we conclude that the origin of the discrepancy is the lack of self-absorption in thin Ge films combined with a deviation from quasi-equilibrium conditions in the conduction band. The latter is confirmed by a simple model suggesting that the deviation from quasi-equilibrium is caused by the much shorter recombination lifetime in the films relative to bulk Ge

Rural health service planning: the need for a comprehensive approach to costing

The precipitous closure of rural maternity services in industrialized countries over the past two decades is underscored in part by assumptions of efficiencies of scale leading to cost-effectiveness. However, there is scant evidence to support this and the costing evidence that exists lacks comprehensiveness. To clearly understand the cost-effectiveness of rural services we must take the broadest societal perspective to include not only health system costs, but also those costs incurred at the family and community levels. We must consider manifest costs (hard, easily quantifiable costs, both direct and indirect) and latent costs (understood as what is sacrificed or lost), and take into account cost shifting (reallocating costs to different parts of the system) and cost downloading (passing costs on to women and families). Further, we must compare the costs of having a rural maternity service to those incurred by not having a service, a comparison that is seldom made. This approach will require determining a methodological framework for weighing all costs, one which will likely involve attention to the rich descriptions of those experiencing loss

Reconceptualising risk: Perceptions of risk in rural and remote maternity service planning.

OBJECTIVE: to explore perceptions and examples of risk related to pregnancy and childbirth in rural and remote Australia and how these influence the planning of maternity services. DESIGN: data collection in this qualitative component of a mixed methods study included 88 semi-structured individual and group interviews (n=102), three focus groups (n=22) and one group information session (n=17). Researchers identified two categories of risk for exploration: health services risk (including clinical and corporate risks) and social risk (including cultural, emotional and financial risks). Data were aggregated and thematically analysed to identify perceptions and examples of risk related to each category. SETTING: fieldwork was conducted in four jurisdictions at nine sites in rural (n=3) and remote (n=6) Australia. PARTICIPANTS: 117 health service employees and 24 consumers. MEASUREMENTS AND FINDINGS: examples and perceptions relating to each category of risk were identified from the data. Most medical practitioners and health service managers perceived clinical risks related to rural birthing services without access to caesarean section. Consumer participants were more likely to emphasise social risks arising from a lack of local birthing services. KEY CONCLUSIONS: our analysis demonstrated that the closure of services adds social risk, which exacerbates clinical risk. Analysis also highlighted that perceptions of clinical risk are privileged over social risk in decisions about rural and remote maternity service planning. IMPLICATIONS FOR PRACTICE: a comprehensive analysis of risk that identifies how social and other forms of risk contribute to adverse clinical outcomes would benefit rural and remote people and their health services. Formal risk analyses should consider the risks associated with failure to provide birthing services in rural and remote communities as well as the risks of maintaining services

Effective interactions between inclusions in complex fluids driven out of equilibrium

The concept of fluctuation-induced effective interactions is extended to systems driven out of equilibrium. We compute the forces experienced by macroscopic objects immersed in a soft material driven by external shaking sources. We show that, in contrast with equilibrium Casimir forces induced by thermal fluctuations, their sign, range and amplitude depends on specifics of the shaking and can thus be tuned. We also comment upon the dispersion of these shaking-induced forces, and discuss their potential application to phase ordering in soft-materials.Comment: 10 pages, 8 figures, to appear in PR

Peptide-based microcapsules obtained by self-assembly and microfluidics as controlled environments for cell culture

Funding for this study was provided by the Portuguese Foundation for Science and Technology (FCT, grant PTDC/EBB-BIO/ 114523/2009). D. S. Ferreira gratefully acknowledges FCT for the PhD scholarship (SFRH/BD/44977/2008)

Swarming in shallow waters

A swarm is a collection of separate objects that move autonomously in the same direction in a concerted fashion. This type of behavior is observed in ensembles of various organisms but has proven inherently difficult to realize in artificial chemical systems, where the components have to self-assemble dynamically and, at the same time, propel themselves. This paper describes a class of systems in which millimeter-sized components interact hydrodynamically and organize into dissipative structures that swarm in thin fluid layers. Depending on the geometry of the particles, various types of swarms can be engineered, including ensembles that rotate, follow a "leader", or are pushed in front of a larger particle

Sementes de louro-pardo: produção e qualidade.

Louro-pardo (Cordia trichotoma (Vell.) Arráb. ex Steud.) é uma espécie florestal nativa, da família Boraginaceae, com ampla distribuição geográfica no Brasil (Figura 1), sendo de ocorrência natural desde o Ceará até o Rio Grande do Sul, principalmente nos biomas Caatinga, Cerrado e Mata Atlântica (Carvalho, 2002). Com crescimento moderado, sua madeira possui valor comercial pelas propriedades físicas e mecânicas (Mantovani et al., 2001), atingindo altura comercial de fuste (até a inserção da copa viva) equivalente a outras espécies nativas, com uma média de aproveitamento de 2 toras/fuste, indicando seu potencial para reflorestamento (Roman et al., 2009). Sua madeira é considerada nobre, sendo indicada para a produção de laminados e móveis requintados (Grings; Brack, 2011). Como possui madeira nobre, a espécie tem sido empregada em sistemas de produção integrados, cuja prática vem ganhando espaço no País (Antonelli et al., 2015). Além disso, as árvores apresentam valor ornamental e paisagístico, podendo ser utilizadas na arborização urbana. Outra aptidão da espécie é para a recuperação de áreas degradadas (Grings; Brack, 2011), estando presente na lista de espécies recomendadas para recuperação de ecossistemas florestais degradados, segundo as regiões Bioclimáticas do Paraná (IAT, 2020)

Current polarity-dependent manipulation of antiferromagnetic domains

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching

Impacts of biomass production at civil airports on grassland bird conservation and aviation strike risk

Growing concerns about climate change, foreign oil dependency, and environmental quality have fostered interest in perennial native grasses (e.g., switchgrass [Panicum virgatum]) for bioenergy production while also maintaining biodiversity and ecosystem function. However, biomass cultivation in marginal landscapes such as airport grasslands may have detrimental effects on aviation safety as well as conservation efforts for grassland birds. In 2011–2013, we investigated effects of vegetation composition and harvest frequency on seasonal species richness and habitat use of grassland birds and modeled relative abundance, aviation risk, and conservation value of birds associated with biomass crops. Avian relative abundance was greater in switchgrass monoculture plots during the winter months, whereas Native Warm-Season Grass (NWSG) mixed species plantings were favored by species during the breeding season. Conversely, treatment differences in aviation risk and conservation value were not biologically significant. Only 2.6% of observations included avian species of high hazard to aircraft, providing support for semi-natural grasslands as a feasible landcover option at civil airports. Additionally, varied harvest frequencies across a mosaic of switchgrass monocultures and NWSG plots allows for biomass production with multiple vegetation structure options for grassland birds to increase seasonal avian biodiversity and habitat use