Structural Origins of Conductance Fluctuations in Gold-Thiolate Molecular Transport Junctions

We report detailed atomistic simulations combined with high-fidelity conductance calculations to probe the structural origins of conductance fluctuations in thermally evolving Au-benzene-1,4-dithiolate-Au junctions. We compare the behavior of structurally ideal junctions (electrodes with flat surfaces) to structurally realistic, experimentally representative junctions resulting from break junction simulations. The enhanced mobility of metal atoms in structurally realistic junctions results in significant changes to the magnitude and origin of the conductance fluctuations. Fluctuations are larger by a factor of 2-3 in realistic junctions compared to ideal junctions. Moreover, in junctions with highly deformed electrodes, the conductance fluctuations arise primarily from changes in the Au geometry, in contrast to results for junctions with non-deformed electrodes, where the conductance fluctuations are dominated by changes in the molecule geometry. These results provide important guidance to experimentalists developing strategies to control molecular conductance for device applications, and also to theoreticians invoking simplified structural models of junctions to predict their behavior.Comment: 15 pages, 4 figures, to appear in Journal of Physical Chemistry Letter

Atomistic Simulations of Highly Conductive Molecular Transport Junctions Under Realistic Conditions

We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate(BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nature Nanotech., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices.Comment: To appear in Nanoscale; 5 pages, 4 figure

Induction of systemic resistance by rhizobacteria in hydroponic system

Rizobactérias do grupo fluorescente de Pseudomonas spp. foram selecionadas quanto a sua capacidade na promoção de crescimento em plântulas de alface (Lactuca sativa L.) e atividade antagônica contra Pythium aphanidermatum a partir de teste in vitro. Em seguida, em sistema hidropônico, foi avaliada a aplicação prévia dos isolados visando reduzir os danos provocados por P. aphanidermatum em pepino (Cucumis sativus) por resistência sistêmica induzida (RSI), pela adoção da técnica "raízes subdivididas". As variáveis massa da matéria seca (parte aérea e raízes) e comprimento radicular foram utilizadas na avaliação. A produção de compostos antagônicos e/ou promotores de crescimento pelos isolados de Pseudomonas spp. fluorescente foi verificada de modo a associar sua atividade com os resultados obtidos nos testes in vitro e em hidroponia. No experimento in vitro os isolados Ps 140B e Ps 140C proporcionaram maior crescimento das plantas (raiz e hipocótilo) de alface nos tratamentos com e sem patógeno. Alguns dos isolados avaliados no experimento hidropônico demonstraram uma possível expressão da RSI. Não houve correspondência entre os compostos produzidos e a promoção de crescimento vegetal ou controle da doença.Rhizobacteria of the fluorescent group of Pseudomonas spp. were selected for both their capacity in the growth promotion of lettuce seedlings (Lactuca sativa L.) and antagonistic activity against Pythium aphanidermatum from test in vitro. Then, in hydroponic system was assayed the previous application of the Pseudomonas strains in order to reduce damages caused by P. aphanidermatum in cucumber (Cucumis sativus) for induced systemic resistance (ISR), using a technical split-root. The variables shoots and roots dry weight and root length were used in evaluation. The production of antagonistic and/or growth promoters compounds by rhizobacteria strains was observed to associate its activity with the results obtained in the tests under hydroponic system and in vitro conditions. In the in vitro experiment, strains Ps 140B and Ps 140C provided the largest development of plants (root and hypocotyls) in the treatments with and without pathogen. Some strains tested indicating a possible expression of ISR in in vivo experiments. No correspondence among the compounds produced by rhizobacteria, plant growth promotion and bioprotection was detected

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport properties calculations, that this assumption can not be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy levels positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrodes separation.Comment: 14 pages, 13 figures, to appear in Nanoscal

O futuro da democracia: cenários político-institucionais até 2022

THIS article reports the results of a political scenario-building exercise carried out by the Institute of Advanced Studies within the framework of a larger project sponsored by the federal government. The authors first draw a positive scenario, characterized by political stability, improvement of the party system and of the legislative machinery, and better social policies. Next they turn to two negative scenarios, under which the above-mentioned goals seem unlikely to be reached. The positive scenario is unlikely to come about without substantial political reforms. An effort is therefore made to analyze reform proposals debated in the country over the last two decades, with special reference to those aiming to strengthen the party system, improve Executive versus Legislative relations and increase accountability in the political system as a whole.O PRESENTE artigo relata os resultados de um exercício de cenários políticos realizado pelo Instituto de Estudos Avançados (IEA-USP) no quadro de um projeto mais amplo patrocinado pelo Executivo federal. Os autores traçam inicialmente um cenário positivo, caracterizado por estabilidade política, aperfeiçoamento do sistema de partidos e do Legislativo, e melhores políticas sociais. Passam, em seguida, a dois cenários negativos, nos quais aqueles objetivos dificilmente serão atingidos. Dado que a ocorrência do cenário positivo provavelmente exigirá reformas políticas substanciais, os autores analisam algumas das propostas debatidas ao longo das últimas duas décadas, notadamente as que objetivam fortalecer o sistema partidário, melhorar as relações Executivo versus Legislativo e tornar o sistema como um todo mais representativo (accountable)

ASSOCIATION BETWEEN AEROSOLS AND HOSPITALIZATIONS FOR RESPIRATORY DISEASES

The fires in Campo Grande have been a serious environmental problem. The objective is to study the trend of respiratory diseases (DAR), and correlates them with precipitation, wind speed, relative humidity, temperature, concentration of surface ozone, optical depth, number of outbreaks of fires and carbon monoxide. The records were obtained from the DAR Datasus; the outbreaks of fires and optical depth were obtained from the National Institute for Space Research and the concentration of ozone and carbon monoxide at the Institute of Physics of the UFMS. The mathematical correlation between the number of admissions for respiratory diseases and climatic indicators , indicated that the main source in order of significance are ozone, carbon monoxide, optical depth , fire outbreaks , wind speed , relative humidity , minimum temperature , rainfall . had two first principal components explained 91.48 % of the variance in the data studied, with a positive correlation between respiratory diseases, ozone, carbon monoxide, wind speed, optical depth and focus of fire and a negative correlation between rainfall, humidity and minimum air temperature, and the equation was determined with an error between the observed and estimated values of 2.29% and R- Sq = 89.1%

Análises Multivariadas, análises de Componente Principal (ACP) e de Agrupamento (AA), para identificar futuros sítios de geração de energia eólica.

Apresenta-se neste estudo a avaliação da metodologia de Analises Multivariadas, Analise em Componentes Principal ACP e Analises de Agrupamento AA aos dados de velocidade médias diárias dos ventos de 19 estações meteorológicas no estado de Mato Grosso do Sul. Todas as Estações estão bem distribuídas espacialmente e o período de dados diários entre 2008 e 2010. Os resultados da Analises de Componentes Principal (ACP) identificou as regiões R1 e R3 como as mais favoráveis para a geração de energia eólica, em especial Campo Grande e Ivinhema. A analise de agrupamento (AA) pelo método de Ward, permitiu o agrupamento das estações em  três regiões homogêneas

Predictors of in-hospital mortality in patients with ST-segment elevation myocardial infarction undergoing pharmacoinvasive treatment

OBJECTIVES: To identify predictors of in-hospital mortality in patients with acute myocardial infarction undergoing pharmacoinvasive treatment. METHODS: This was an observational, prospective study that included 398 patients admitted to a tertiary center for percutaneous coronary intervention within 3 to 24 hours after thrombolysis with tenecteplase. ClinicalTrials.gov: NCT01791764 RESULTS: The overall in-hospital mortality rate was 5.8%. Compared with patients who survived, patients who died were more likely to be older, have higher rates of diabetes and chronic renal failure, have a lower left ventricular ejection fraction, and demonstrate more evidence of heart failure (Killip class III or IV). Patients who died had significantly lower rates of successful thrombolysis (39% vs. 68%; p = 0.005) and final myocardial blush grade 3 (13.0% vs. 61.9%; p<0.0001). Based on the multivariate analysis, the Global Registry of Acute Coronary Events score (odds ratio 1.05, 95% confidence interval (CI) 1.02-1.09; p = 0.001), left ventricular ejection fraction (odds ratio 0.9, 95% CI 0.89-0.97; p = 0.001), and final myocardial blush grade of 0-2 (odds ratio 8.85, 95% CI 1.34-58.57; p = 0.02) were independent predictors of mortality. CONCLUSIONS: In this prospective study that evaluated patients with ST-segment elevation myocardial infarction treated by a pharmacoinvasive strategy, the in-hospital mortality rate was 5.8%. The Global Registry of Acute Coronary Events score, left ventricular ejection fraction, and myocardial blush were independent predictors of mortality in this high-risk group of acute coronary syndrome patients.Universidade Federal de São Paulo (UNIFESP) Department of CardiologySecretaria de Saude do Municipio de São PauloHospital Municipal TatuapeUNIFESP, Department of CardiologySciEL