Nonperturbative approach to interfacial spin-orbit torques induced by Rashba effect

Current-induced spin-orbit torque (SOT) in normal metal/ferromagnet (NM/FM) bilayers bears great promise for technological applications, but the microscopic origin of purely interfacial SOTs in ultra-thin systems is not yet fully understood. Here, we show that a linear response theory with a nonperturbative treatment of spin-dependent interactions and impurity scattering potential predicts damping-like SOTs that are strictly absent in perturbative approaches. The technique is applied to a two-dimensional Rashba-coupled ferromagnet (the paradigmatic model of a NM/FM interface), where higher-order scattering processes encoding skew scattering from nonmagnetic impurities allow for current-induced spin polarization with nonzero components along all spatial directions. This is in stark contrast to previous results of perturbative methods (neglecting skew scattering), which predict a coplanar spin-polarization locked perpendicular to the charge current as a result of conventional Rashba-Edelstein effect. Furthermore, the angular dependence of ensuing SOTs and their dependence upon the scattering potential strength is analysed numerically. Simple analytic expressions for the spin-density--charge-current response function, and related SOT efficiencies, are obtained in the weak scattering limit. We find that the extrinsic damping-like torques driven by impurity scattering reaches efficiencies of up to 7% of the field-like (Rashba-Edelstein) torque. Our microscopic theory shows that bulk phenomena, such as the spin Hall effect, are not a necessity in the generation of the damping-like SOTs of the type observed in experiments on ultra-thin systems.Comment: 9 Pages, 4 figure

Efficient graphene-based photodetector with two cavities

We present an efficient graphene-based photodetector with two Fabri-P\'erot cavities. It is shown that the absorption can reach almost 100% around a given frequency, which is determined by the two-cavity lengths. It is also shown that hysteresis in the absorbance is possible, with the transmittance amplitude of the mirrors working as an external driving field. The role of non-linear contributions to the optical susceptibility of graphene is discussed.Comment: 10 pages, 8 figures. published version: minor revisio

Production of enzymatic extracts for aquafeeds by solid-state fermentation with Aspergillus ibericus of winery and olive mill wastes

[Excerpt] Introduction The replacement of fishmeal by plant ingredients in aquafeeds imposed new formulation strategies to overcome some nutritional restrictions associated with these alternative ingredients. Thus, supplementation of plant-based diets with feed additives, as exogenous enzymes and antioxidants compounds, has recently attracted increasing interest to improve feed utilization and to promote animal health. Solid state fermentation (SSF) of agro-industrial wastes has a high potential for the production of these additives, being a practical, economical, and environmentally-friendly process. Olive mill and winery wastes have valuable compounds that may be valorized thought SSF and that may be used as additives for aquafeeds. This study was conducted to optimize the production of non-starch carbohydrases through the SSF of the olive mill and winery wastes and to test its efficacy to improve the release of pentoses during digestion of a plant-based diet in European seabass.[...]Work supported by FCT PhD grant SFRH/BD/131219/2017, SFRH/BDP/114942/2016, IJFCT-POCI 01-0145-FEDER-030377 and MAR-02.01.01-FEAMP-0111info:eu-repo/semantics/publishedVersio

Cross-cultural adaptation and psychometric properties of the Brazilian-Portuguese version of the VSP-A (Vécu et Santé Perçue de l'Adolescent), a health-related quality of life (HRQoL) instrument for adolescents, in a healthy Brazilian population

<p>Abstract</p> <p>Background</p> <p>Health-related quality of life (HRQoL) assessment, encompassing the adolescents' perceptions of their mental, physical, and social health and well-being is increasingly considered an important outcome to be used to identify population health needs and to provide targeted medical care. Although validated instruments are essential for accurately assessing HRQoL outcomes, there are few cross-culturally adapted tools for use in Brazil, and none designed exclusively for use among adolescents. The Vécu et Santé Perçue de l'Adolescent (VSP-A) is a generic, multidimensional self-reported instrument originally developed and validated in France that evaluates HRQoL of ill and healthy adolescents.</p> <p>Purpose</p> <p>To cross-culturally adapt and validate the Brazilian-Portuguese version of the VSP-A, a generic HRQoL measure for adolescents originally developed in France.</p> <p>Methods</p> <p>The VSP-A was translated following a well-validated forward-backward process leading to the Brazilian version. The psychometric evaluation was conducted in a sample of 446 adolescents (14-18 years) attending 2 public high schools of São Gonçalo City. The adolescents self-reported the Brazilian VSP-A, the validated Psychosomatic Symptom Checklist and socio-demographic information. A retest evaluation was carried out on a sub-sample (n = 195) at a two-week interval.</p> <p>The internal construct validity was assessed through confirmatory factor analysis (CFA), multi-trait scaling analyses, Rasch analysis evaluating unidimensionality of each scale and Cronbach's alpha coefficients. The reproducibility was evaluated by intra-class correlation coefficients (ICC). Zumbo's ordinal logistic regression analysis was used to detect differential item functioning (DIF) between the Brazilian and the French items. External construct validity was investigated testing expected differences between groups using one-way analysis of variance (ANOVA), Mann-Whitney tests and the univariate general regression linear model.</p> <p>Results</p> <p>CFA showed an acceptable fit (RMSEA=0.05; CFI=0.93); 94% of scaling success was found for item-internal consistency and 98% for item discriminant validity. The items showed good fit to the Rasch model except 3 items with an INFIT at the upper threshold. Cronbach's Alpha ranged from 0.60 to 0.85. Test-retest reliability was moderate to good (ICC=0.55-0.82). DIF was evidenced in 4 out of 36 items. Expected patterns of differences were confirmed with significantly lower physical, psychological well being and vitality reported by symptomatic adolescents.</p> <p>Conclusions</p> <p>Although DIF in few items and responsiveness must be further explored, the Brazilian version of VSP-A demonstrated an acceptable validity and reliability in adolescents attending school and might serve as a starting point for more specific clinical investigations.</p

Staphylococcus aureus in former Portuguese colonies from Africa and the Far East: missing data to help fill the world map

AbstractThe aim of the present study was to determine the prevalence and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage among patients and healthcare workers in Angola (ANG), São Tomé and Príncipe (STP), Cape Verde (CV) and East Timor (ET), and to characterize the antimicrobial susceptibility, virulence content and population structure of all S. aureus. Despite the importance of MRSA as a major human pathogen, data from these former Portuguese colonies in Africa and Asia are scarce. A total of 2065 nasal swabs recovered between 2010–14 were included in the study. Antimicrobial susceptibility testing and molecular characterization of S. aureus showed: (i) a very high MRSA prevalence in ANG (61.6%), moderate in STP (25.5%), low in CV (5.6%) and null in ET; (ii) a high prevalence of Panton–Valentine leukocidin in STP (36.8%), ET (29.2%) and CV (28.3%) contrasting with ANG (7.9%); (iii) ST5-SCCmecIVa, ST8-IV/V and ST5-VI were the major MRSA clones in ANG (65.2%), STP (44.8%) and CV (50%), respectively; (iv) a high resistance to trimethoprim-sulfamethoxazole in ANG (66.5%) and STP (50.9%), to rifampin in ANG (77.3%), and to tetracycline in STP (26.3%) and ET (20.8%); (v) three major methicillin-susceptible S. aureus clones (ST15, ST508, ST152) were present in all four countries. Age <18 years (OR 2.03, 95% CI 1.24–3.31), previous surgery (OR 2.45, 95% CI 1.24–4.83), no smoking (OR 4.04, 95% CI 1.05–15.50), and longer hospitalization (OR 2.53, 95% CI 1.49–4.28) were risk factors for MRSA carriage. This study provided the first comprehensive overview on MRSA in former Portuguese colonies in Africa and Asia, missing data in the world map