Direct observation of large strain through van der Waals gaps on epitaxial B i2 T e3 /graphite : Pseudomorphic relaxation and the role of B i2 layers on the B ix T ey topological insulator series

Layered materials can usually grow without strain on top of distinct substrates if the only interaction between them is due to van der Waals forces. In such a scenario it would be expected that the heterointerface made up of weak bounds would not affect the overlayed material significantly for several large lattice-mismatched systems. Here we have studied the first stages of the heteroepitaxial growth of layered bismuth telluride topological insulator on top of highly oriented pyrolitic graphite (HOPG) by molecular beam epitaxy. Samples were investigated by atomic force microscopy (AFM), synchrotron x-ray diffraction (XRD), and micro-Raman spectroscopy. AFM images show hexagonal/triangular flat islands with exposed HOPG areas for the low coverage regime, and the lattice parameter of these Bi2Te3 structures were measured by XRD. The existence of pseudomorphic strain at the initial Bi2Te3 layers was retrieved by both XRD and Raman spectroscopy. We have found evidence that Bi2Te3 layers near the interface are subject to an in-plane compressive strain, leading to a pseudomorphic out-of-plane lattice expansion. Furthermore, the presence of Bi2Te3 islands locally distorts the topmost layer of HOPG, resulting in tensile strain which was measured by Raman spectroscopy. The observed relaxation of 0.1-0.2% for each van der Waals gap is used to calculate elastic constants of Bi2 bilayers, which are crucial building blocks for the formation of other BixTey topological insulator compounds. Finally, the impact of such a strain in Bi2Te3 electronic structure was investigated by density functional theory calculations. The results show that the band structure of this strained material remains unchanged at the center of the Brillouin zone, confirming the robustness of surface states, but it is consistently affected at the M and K zone edges

Schistosomiasis mansoni in an area of low transmission: II. Risk factors for infection Esquistossomose mansônica em área de baixa transmissão: II. Fatores de risco para infecção

Risk factors for Schistosoma mansoni infection were identified using a 1:1 matched case-control design. The work was conducted in the municipality of Pedro de Toledo, São Paulo State, Brazil, an area where the snail host is Biomphalaria tenagophila. Information on water contact patterns, knowledge, attitudes and pratices (kap), socioeconomic and sanitary conditions were obtained by mean of questionnaires. The crude odds ratio estimates and the adjusted odds ratio estimates using the logistic regression model are presented. Most of the examined individuals admitted recent water contacts (90.6% of the cases). The most frequent reason for contact was swimming, playing and fishing and the preferential site of contact was the river. According to the logistic regression technique, the main risk factors for infection were: a) water contact through swimming, playing and fishing; b) fording; c) bad hygiene. We concluded that recreational activities are the main reasons for schistosomiasis transmission in Pedro de Toledo and leisure alternatives should be offered to the local population.<br>A partir de um estudo de caso-controle por pareamento (1:1) foram determinados os fatores de risco para infecção por Schistosoma mansoni. O trabalho foi desenvolvido no município de Pedro de Toledo, São Paulo, Brasil, área onde Biomphalaria tenagophila é o hospedeiro intermediário. Por meio de questionários foram obtidas informações sobre o padrão de contato com águas naturais; percepção da doença e condições sanitárias e socio-econômicas. Os fatores de risco foram estimados individualmente e através de modelo logístico. A maioria dos pesquisados admitiu contatos recentes com águas naturais (90,6% dos casos). O motivo mais freqüente para estes contatos foi nadar, brincar e pescar. O rio representou o principal local de contato com águas naturais. De acordo com a técnica de regressão logística, os principais fatores de risco foram: a) contato com água para nadar, brincar, pescar; b) vadear; c) más condições de higiene. Concluímos que as atividades recreativas são as principais responsáveis pela transmissão da esquistossomose em Pedro de Toledo e alternativas de lazer devem ser oferecidas a esta população

Efeitos da temperatura e da umidade relativa sobre o desempenho e o rendimento de cortes nobres de frangos de corte de 1 a 49 dias de idade Effects of temperature and relative humidity on performance and yield of noble cuts of broilers from 1 to 49 days old

Foram utilizados 180 pintos machos de 1 dia de idade, da linhagem Ross (peso inicial 43,0 &plusmn; 0,2 g) para avaliação dos efeitos de diferentes ambientes sobre o desempenho e as características de carcaça. As aves foram criadas no período de 1 a 49 dias de idade em um delineamento experimental inteiramente casualizado, com três ambientes (conforto térmico, calor seco e calor úmido), seis repetições por tratamento e dez aves por unidade experimental. As rações e a água foram fornecidas à vontade. O monitoramento da temperatura e da umidade relativa do ar de cada ambiente foi feito por meio de termômetros de bulbo seco e de globo negro. Os valores obtidos foram convertidos em valor único - Índice de Temperatura de Globo e Umidade (ITGU), para caracterização do ambiente. As temperaturas que caracterizaram os ambientes de conforto, de calor seco e de calor úmido foram, respectivamente, 25,1 &plusmn; 2,99; 35,0 &plusmn; 0,14 e 31,2 &plusmn; 1,82ºC e as umidades relativas registradas nos ambientes de calor seco e calor úmido foram, respectivamente, de 40 e 75%. Foram avaliados o consumo de ração, o ganho de peso e a conversão alimentar nos períodos de 1 a 21, 1 a 41 e 1 a 49 dias de idade. Ao final do experimento, as aves foram abatidas para avaliação dos pesos absolutos e do rendimento de carcaça e de cortes nobres (coxa, sobrecoxa e peito). O ambiente de calor influenciou negativamente o consumo de ração e o ganho de peso das aves em todos os períodos estudados, mas esse efeito foi mais acentuado nas aves mantidas em ambiente de calor úmido. O calor também influenciou negativamente os pesos absolutos de coxa, sobrecoxa e peito. Altas temperaturas prejudicam o desempenho e o rendimento de cortes nobres de frangos de corte de 1 a 49 dias de idade, de modo que esses efeitos são mais acentuados pelo aumento da umidade relativa do ar.<br>One hundred and eighty male Ross 1-d chicks averaging initial weight of 43.0 &plusmn; 0.2 g were used to evaluate the effects of different environments on performance and carcass characteristics. The experiment was analyzed as a completely randomized design with three environments (thermal comfort, dry heat and wet heat), six replicates of ten birds per experimental unity reared from 1 to 49 days old. Diets and water were fed ad libitum. The temperature and relative humidity control in each environment were measured by dry bulb and black globe thermometers. The values obtained were converted in a single value Black Globe Humidity and Temperature Index (BGHI) to characterize the environment. The temperatures that characterize the comfort, dry heat and wet heat were respectively: 25.1 &plusmn; 2.99, 35.0 &plusmn; 0.14, 31.2 &plusmn; 1.82ºC. The relative humidity recorded in dry and wet heat environments were respectively 40 and 75%. Feed intake, weight gain, feed:gain ratio in the periods from 1 to 21, 1 to 41 and 1 to 49 days of old were evaluated. In the end of the experiment, the birds were slaughtered for evaluation of absolute weights of noble cuts (thigh, drumstick and breast) and carcass yield. It was observed negative effect of heat environment on feed intake and weight gain in all periods and it was higher in birds on wet heat environment. Heat also influenced negatively absolute weights of thigh, drumstick and breast of birds. It was concluded that high temperatures impair the performance and yield of noble cuts of birds from 1 to 49 days old; in fact, these effects were higher with the greatest air relative humidity