Strained graphene structures: from valleytronics to pressure sensing

Due to its strong bonds graphene can stretch up to 25% of its original size without breaking. Furthermore, mechanical deformations lead to the generation of pseudo-magnetic fields (PMF) that can exceed 300 T. The generated PMF has opposite direction for electrons originating from different valleys. We show that valley-polarized currents can be generated by local straining of multi-terminal graphene devices. The pseudo-magnetic field created by a Gaussian-like deformation allows electrons from only one valley to transmit and a current of electrons from a single valley is generated at the opposite side of the locally strained region. Furthermore, applying a pressure difference between the two sides of a graphene membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing.Comment: to appear in proceedings of the NATO Advanced Research Worksho

Nut production in Bertholletia excelsa across a logged forest mosaic: implications for multiple forest use

Although many examples of multiple-use forest management may be found in tropical smallholder systems, few studies provide empirical support for the integration of selective timber harvesting with non-timber forest product (NTFP) extraction. Brazil nut (Bertholletia excelsa, Lecythidaceae) is one of the world’s most economically-important NTFP species extracted almost entirely from natural forests across the Amazon Basin. An obligate out-crosser, Brazil nut flowers are pollinated by large-bodied bees, a process resulting in a hard round fruit that takes up to 14 months to mature. As many smallholders turn to the financial security provided by timber, Brazil nut fruits are increasingly being harvested in logged forests. We tested the influence of tree and stand-level covariates (distance to nearest cut stump and local logging intensity) on total nut production at the individual tree level in five recently logged Brazil nut concessions covering about 4000 ha of forest in Madre de Dios, Peru. Our field team accompanied Brazil nut harvesters during the traditional harvest period (January-April 2012 and January-April 2013) in order to collect data on fruit production. Three hundred and ninety-nine (approximately 80%) of the 499 trees included in this study were at least 100 m from the nearest cut stump, suggesting that concessionaires avoid logging near adult Brazil nut trees. Yet even for those trees on the edge of logging gaps, distance to nearest cut stump and local logging intensity did not have a statistically significant influence on Brazil nut production at the applied logging intensities (typically 1–2 timber trees removed per ha). In one concession where at least 4 trees ha-1 were removed, however, the logging intensity covariate resulted in a marginally significant (0.09) P value, highlighting a potential risk for a drop in nut production at higher intensities. While we do not suggest that logging activities should be completely avoided in Brazil nut rich forests, when a buffer zone cannot be observed, low logging intensities should be implemented. The sustainability of this integrated management system will ultimately depend on a complex series of socioeconomic and ecological interactions. Yet we submit that our study provides an important initial step in understanding the compatibility of timber harvesting with a high value NTFP, potentially allowing for diversification of forest use strategies in Amazonian Perù

Antioxidant pathways are up-regulated during biological nitrogen fixation to prevent ROS-induced nitrogenase inhibition in Gluconacetobacter diazotrophicus

Gluconacetobacter diazotrophicus, an endophyte isolated from sugarcane, is a strict aerobe that fixates N2. This process is catalyzed by nitrogenase and requires copious amounts of ATP. Nitrogenase activity is extremely sensitive to inhibition by oxygen and reactive oxygen species (ROS). However, the elevated oxidative metabolic rates required to sustain biological nitrogen fixation (BNF) may favor an increased production of ROS. Here, we explored this paradox and observed that ROS levels are, in fact, decreased in nitrogen-fixing cells due to the up-regulation of transcript levels of six ROS-detoxifying genes. A cluster analyses based on common expression patterns revealed the existence of a stable cluster with 99.8% similarity made up of the genes encoding the α-subunit of nitrogenase Mo–Fe protein (nifD), superoxide dismutase (sodA) and catalase type E (katE). Finally, nitrogenase activity was inhibited in a dose-dependent manner by paraquat, a redox cycler that increases cellular ROS levels. Our data revealed that ROS can strongly inhibit nitrogenase activity, and G. diazotrophicus alters its redox metabolism during BNF by increasing antioxidant transcript levels resulting in a lower ROS generation. We suggest that careful controlled ROS production during this critical phase is an adaptive mechanism to allow nitrogen fixation

Markers of Myocardial Damage Predict Mortality in Patients With Aortic Stenosis

Background: Cardiovascular magnetic resonance (CMR) is increasingly used for risk stratification in aortic stenosis (AS). However, the relative prognostic power of CMR markers and their respective thresholds remains undefined. Objectives: Using machine learning, the study aimed to identify prognostically important CMR markers in AS and their thresholds of mortality. Methods: Patients with severe AS undergoing AVR (n = 440, derivation; n = 359, validation cohort) were prospectively enrolled across 13 international sites (median 3.8 years’ follow-up). CMR was performed shortly before surgical or transcatheter AVR. A random survival forest model was built using 29 variables (13 CMR) with post-AVR death as the outcome. Results: There were 52 deaths in the derivation cohort and 51 deaths in the validation cohort. The 4 most predictive CMR markers were extracellular volume fraction, late gadolinium enhancement, indexed left ventricular end-diastolic volume (LVEDVi), and right ventricular ejection fraction. Across the whole cohort and in asymptomatic patients, risk-adjusted predicted mortality increased strongly once extracellular volume fraction exceeded 27%, while late gadolinium enhancement >2% showed persistent high risk. Increased mortality was also observed with both large (LVEDVi >80 mL/m2) and small (LVEDVi ≤55 mL/m2) ventricles, and with high (>80%) and low (≤50%) right ventricular ejection fraction. The predictability was improved when these 4 markers were added to clinical factors (3-year C-index: 0.778 vs 0.739). The prognostic thresholds and risk stratification by CMR variables were reproduced in the validation cohort. Conclusions: Machine learning identified myocardial fibrosis and biventricular remodeling markers as the top predictors of survival in AS and highlighted their nonlinear association with mortality. These markers may have potential in optimizing the decision of AVR

Construction and validation of indicators and respective definitions for the nursing outcome Swallowing Status

;;OBJETIVO:;; construir e validar por especialistas e clinicamente os indicadores para o resultado de enfermagem Estado da deglutição e suas definições conceituais e operacionais em pacientes após acidente vascular cerebral.;;;;MÉTODO:;; estudo metodológico, com análise de conceito e validações de conteúdo e clínica. Verificou-se o Índice de Validade de Conteúdo para as notas atribuídas por 11 especialistas aos indicadores revisados. Na validação clínica, examinaram-se 81 pacientes por duas duplas de enfermeiros, uma usando instrumento com as definições construídas e outra com instrumento sem definições. As avaliações foram comparadas pelo Coeficiente de Correlação Intraclasse, teste de Friedman e Diferença Mínima Significante.;;;;RESULTADOS:;; exceto o indicador Captura do alimento, todos apresentaram Índice de Validade de Conteúdo superior a 0,80. A dupla de enfermeiros com instrumento contendo as definições construídas apresentou Coeficiente de Correlação Intraclasse superior a 0,80 para todos os indicadores e pelo cálculo da Diferença Mínima Significante houve similaridade entre todas as avaliações. Na dupla que estava sem as definições elaboradas, o coeficiente foi baixo (ρ;;;;CONCLUSÃO:;; os dados evidenciaram aumento na uniformidade e acurácia entre as avaliações dos enfermeiros ao utilizar as definições conceituais e operacionais para os indicadores do resultado de enfermagem Estado da deglutição.;;;;OBJECTIVE:;; to develop indicators for the nursing outcome Swallowing Status and the respective conceptual and operational definitions validated by experts and in a clinical setting among patients after having experienced a stroke.;;;;METHOD:;; methodological study with concept analysis and content and clinical validations. The Content Validation Index was verified for the scores assigned by 11 experts to indicators. Two pairs of nurses assessed 81 patients during the clinical validation: one pair used an instrument with definitions and the other used an instrument without definitions. The resulting assessments were compared using Intraclass Correlation Coefficient, Friedman's test, and Minimal Important Difference calculation.;;;;RESULTS:;; All the indicators, with the exception of the indicator Ability to bring food to mouth, presented Content Validation Index above 0.80. The pair using the instrument with definitions presented an Intraclass Correlation Coefficient above 0.80 for all the indicators and similarity was found in all the assessments, according to the Minimal Important Difference calculation. The pair using the instrument without definitions presented a low coefficient (ρ;;OBJETIVO:;; construir y validar por especialistas y clínicamente los indicadores para el resultado de enfermería Estado de la deglución y sus definiciones conceptuales y operacionales en pacientes después de accidente vascular cerebral.;;;;MÉTODO:;; estudio metodológico, con análisis de concepto y validaciones de contenido y clínicas. Se verificó el Índice de Validez de Contenido para las notas atribuidas por 11 especialistas a los indicadores revisados. En la validación clínica, fueron examinados 81 pacientes por dos parejas de enfermeros, una usando instrumento con las definiciones construidas y la otra con instrumento sin definiciones. Las evaluaciones fueron comparadas por el Coeficiente de Correlación Intraclase, test de Friedman y Diferencia Mínima Significativa.;;;;RESULTADOS:;; exceptuando el indicador Captura del alimento, todos presentaron Índice de Validez de Contenido superior a 0,80. La pareja de enfermeros con instrumento conteniendo las definiciones construidas presentó Coeficiente de Correlación Intraclase superior a 0,80 para todos los indicadores y por el cálculo de la Diferencia Mínima Significativa hubo semejanza entre todas las evaluaciones. En la pareja que estaba sin las definiciones elaboradas, el coeficiente fue bajo (

Impaired gas exchange: accuracy of defining characteristics in children with acute respiratory infection

OBJECTIVE: to analyze the accuracy of the defining characteristics of the Impaired gas exchange nursing diagnosis in children with acute respiratory infection.METHOD: open prospective cohort study conducted with 136 children monitored for a consecutive period of at least six days and not more than ten days. An instrument based on the defining characteristics of the Impaired gas exchange diagnosis and on literature addressing pulmonary assessment was used to collect data. The accuracy means of all the defining characteristics under study were computed.RESULTS: the Impaired gas exchange diagnosis was present in 42.6% of the children in the first assessment. Hypoxemia was the characteristic that presented the best measures of accuracy. Abnormal breathing presented high sensitivity, while restlessness, cyanosis, and abnormal skin color showed high specificity. All the characteristics presented negative predictive values of 70% and cyanosis stood out by its high positive predictive value.CONCLUSION: hypoxemia was the defining characteristic that presented the best predictive ability to determine Impaired gas exchange. Studies of this nature enable nurses to minimize variability in clinical situations presented by the patient and to identify more precisely the nursing diagnosis that represents the patient's true clinical condition