22,663 research outputs found

    Magnetically-controlled impurities in quantum wires with strong Rashba coupling

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    We investigate the effect of strong spin-orbit interaction on the electronic transport through non-magnetic impurities in one-dimensional systems. When a perpendicular magnetic field is applied, the electron spin polarization becomes momentum-dependent and spin-flip scattering appears, to first order in the applied field, in addition to the usual potential scattering. We analyze a situation in which, by tuning the Fermi level and the Rashba coupling, the magnetic field can suppress the potential scattering. This mechanism should give rise to a significant negative magnetoresistance in the limit of large barriers.Comment: 4 pages, 2 figure

    Effect of Electrolyte Balance in Low-Protein Diets on Broiler Performance and Tibial Dyschondroplasia Incidence

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    A proper dietary electrolyte balance (DEB) is essential to ensure an optimum acid-base equilibrium and broiler performance. In low-CP diets, this balance can be affected by reduction of soybean meal and inclusion of high levels of synthetic amino acids. Although, some studies have related low-protein diets supplemented with amino acids and DEB, these relations are not well explained, because some research demonstrates confusion about the deficiency and balance of nutrients. The objective of these experiments was to evaluate the DEB effects of diets with low levels of protein supplemented with amino acids on broiler performance and bone development. Results indicated that DEB and CP content influenced broiler chick performance in the starter and growing periods. There was no significant effect due to the interaction between DEB and CP content for tibial dyschondroplasia incidence (TD) or in bone breaking resistance during the growing period of either experiment. The incidence of TD was reduced with 253 mEq/kg DEB in the starter period

    Dynamic structure factor of Luttinger liquids with quadratic energy dispersion and long-range interactions

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    We calculate the dynamic structure factor S (omega, q) of spinless fermions in one dimension with quadratic energy dispersion k^2/2m and long range density-density interaction whose Fourier transform f_q is dominated by small momentum-transfers q << q_0 << k_F. Here q_0 is a momentum-transfer cutoff and k_F is the Fermi momentum. Using functional bosonization and the known properties of symmetrized closed fermion loops, we obtain an expansion of the inverse irreducible polarization to second order in the small parameter q_0 / k_F. In contrast to perturbation theory based on conventional bosonization, our functional bosonization approach is not plagued by mass-shell singularities. For interactions which can be expanded as f_q = f_0 + f_0^{2} q^2/2 + O (q^4) with finite f_0^{2} we show that the momentum scale q_c = 1/ | m f_0^{2} | separates two regimes characterized by a different q-dependence of the width gamma_q of the collective zero sound mode and other features of S (omega, q). For q_c << q << k_F we find that the line-shape in this regime is non-Lorentzian with an overall width gamma_q of order q^3/(m q_c) and a threshold singularity at the lower edge.Comment: 33 Revtex pages, 17 figure

    In welfare we trust? Political trust in Portugal and Spain, 2008-2014

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    info:eu-repo/semantics/publishedVersio

    Runoff at the micro-plot and slope scale following wildfire, central Portugal

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    Through their effects on soil properties and vegetation/litter cover, wildfires can strongly enhance overland flow generation and accelerate soil erosion [1] and, thereby, negatively affect land-use sustainability as well as downstream aquatic and flood zones. Wildfires are a common phenomenon in present-day Portugal, devastating in an average year some 100.000 ha of forest and woodlands and in an exceptional year like 2003 over 400.000 ha. There therefore exists a clear need in Portugal for a tool that can provide guidance to post-fire land management by predicting soil erosion risk, on the one hand, and, on the other, the mitigation effectiveness of soil conservation measures. Such a tool has recently been developed for the Western U.S.A. [3: ERMiT] but its suitability for Portuguese forests will need to be corroborated by field observations. Testing the suitability of existing erosion models in recently burned forest areas in Portugal is, in a nutshell, the aim of the EROSFIRE projects. In the first EROSFIRE project the emphasis was on the prediction of erosion at the scale of individual hill slopes. In the ongoing EROSFIRE-II project the spatial scope is extended to include the catchment scale, so that also the connectivity between hill slopes as well as channel and road processes are being addressed. Besides ERMiT, the principal models under evaluation for slope-scale erosion prediction are: (i) the variant of USLE [4] applied by the Portuguese Water Institute after the wildfires of 2003; (ii) the Morgan–Morgan–Finney model (MMF) [5]; (iii) MEFIDIS [6]. From these models, MEFIDIS and perhaps MMF will, after successful calibration at the slope scale, also be applied for predicting catchment-scale sediment yields of extreme events

    The Framework “Iberian Massif Landscape and Fluvial Network” in the scope of the Portuguese Geological Heritage Inventory

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    A diversidade de aspectos do relevo e da drenagem fluvial no Maciço Ibérico justificaram a definição de 5 temas dominantes, agrupados numa categoria temática, com vista ao processo de inventariação de geossítios de valor científico e relevância internacional ou nacional, no âmbito da inventariação do património geológico português em curso. Os temas sucintamente caracterizados são: Macro-geoformas residuais, Geoformas graníticas, Geoformas tectónicas, Sedimentos cenozóicos e Geoformas fluviais. Para cada tema foram definidos alguns subtemas e áreas-chave para a selecção dos geossítios.Five themes were defined taking into account the diversity of geomorphological elements in the Portuguese Iberian Massif. These themes are grouped under a geological framework established to help the selection of geosites with scientific value of national or international significance, under the scope of the ongoing inventory of the Portuguese geological heritage. These themes are: Residual macro-landforms, Granite landforms, Tectonic landforms, Cenozoic sediments, and Fluvial landforms. For each theme, some sub-themes were defined as well as key-areas for the selection of geosites.Este trabalho é apoiado pela Fundação para a Ciência e a Tecnologia, através do financiamento plurianual do CGUP e do projecto de investigação “Identificação, caracterização e conservação do património geológico: uma estratégia de geoconservação para Portugal” (PTDC/CTE-GEX/64966/2006).info:eu-repo/semantics/publishedVersio

    First Trimester Aneuploidy Screening Program for Preeclampsia Prediction in a Portuguese Obstetric Population

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    Objective. To evaluate the performance of a first trimester aneuploidy screening program for preeclampsia (PE) prediction in a Portuguese obstetric population, when performed under routine clinical conditions. Materials and Methods. Retrospective cohort study of 5672 pregnant women who underwent routine first trimester aneuploidy screening in a Portuguese university hospital from January 2009 to June 2013. Logistic regression-based predictive models were developed for prediction of PE based on maternal characteristics, crown-rump length (CRL), nuchal translucency thickness (NT), and maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) and free beta-subunit of human chorionic gonadotropin (free β-hCG). Results. At a false-positive rate of 5/10%, the detection rate for early-onset (EO-PE) and late-onset (LO-PE) PE was 31.4/45.7% and 29.5/35.2%, respectively. Although both forms of PE were associated with decreased PAPP-A, logistic regression analysis revealed significant contributions from maternal factors, free β-hCG, CRL, and NT, but not PAPP-A, for prediction of PE. Conclusion. Our findings support that both clinical forms of EO-PE and LO-PE can be predicted using a combination of maternal history and biomarkers assessed at first trimester aneuploidy screening. However, detection rates were modest, suggesting that models need to be improved with additional markers not included in the current aneuploidy screening programs

    Runoff and erosion at the micro-plot and slope scale in a small burnt catchment, central Portugal

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    Wildfires can have important impacts on hydrological processes and soil erosion in forest catchments, due to the destruction of vegetation cover and changes to soil properties. However, the processes involved are non-linear and not fully understood. This has severely limited the understanding on the impacts of wildfires, especially in the up-scaling from hillslopes to catchments; in consequence, current models are poorly adapted for burnt forest conditions. The objective of this presentation is to give an overview of the hydrological response and sediment yield from the micro-plot to slope scale, in the first year following a wildfire (2008/2009) that burnt an entire catchment nearby the Colmeal village, central Portugal. The overview will focus on three slopes inside the catchment, with samples including: • Runoff at micro-plot scale (12 bounded plots) and slope scale (12 open plots); • Sediments and Organic Matter loss at micro-plot scale (12 bounded plots) and slope scale (12 open plots plus 3 Sediment fences); • Rainfall and Soil moisture data; • Soil Water Repellency and Ground Cover data. The analysis of the first year following the wildfire clearly shows the complexity of runoff generation and the associated sediment transport in recently burnt areas, with pronounced differences between hillslopes and across spatial scales as well as with marked variations through time. This work was performed in the framework of the EROSFIRE-II project (PTDC/AGR-CFL/70968/2006) which has as overall aim to predict soil erosion risk in recently burnt forest areas, including common post-fire forest management practices; the project focuses on the simultaneous measurement of runoff and soil erosion at multiple spatial scales.The results to be presented in this session are expected to show how sediment is generated, transported and exported in the Colmeal watershed; and contribute to understand and simulate erosion processes in burnt catchments, including for model development and evaluation

    Healthcare Services and Formal Caregiver’s Psychosocial Risk Factors: An Observational Study

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    The prevention and management of chronic disease primarily requires risk reduction measures, through strategic coordination across various government areas. Recognizing that health workers and the public health workforce are integral to building strong and resilient health, the present study analyses the relation between Psychosocial Risk Factors (PRFs, to which formal caregivers are exposed in the healthcare settings), and the work system related elements of the Systems Engineering Initiative for Patient Safety (SEIPS 3.0) framework. An empirical study was carried out, involving 333 formal caregivers of healthcare services. A total of 31 PRFs were assessed (using the COPSOQ III), making it possible to find a relationship between the PRFs analyzed with three elements of the work system, namely Task (5 PRFs), Organizational factors (17 PRFs), and Individual (9 PRFs). The present work contributes not only in terms of outcomes that allow the development of mental illness prevention and mental health promotion actions for healthcare formal caregivers, but also in terms of the relevance that these factors can have on the quality of health services, as well as their users (patients), in line with SEIPS 3.0 model

    Shannon Meets Carnot: Generalized Second Thermodynamic Law

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    The classical thermodynamic laws fail to capture the behavior of systems with energy Hamiltonian which is an explicit function of the temperature. Such Hamiltonian arises, for example, in modeling information processing systems, like communication channels, as thermal systems. Here we generalize the second thermodynamic law to encompass systems with temperature-dependent energy levels, dQ=TdS+dTdQ=TdS+dT, where denotes averaging over the Boltzmann distribution and reveal a new definition to the basic notion of temperature. This generalization enables to express, for instance, the mutual information of the Gaussian channel as a consequence of the fundamental laws of nature - the laws of thermodynamics
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