Hydrogen bonds and van der Waals forces in ice at ambient and high pressures

The first principles approaches, density functional theory (DFT) and quantum Monte Carlo, have been used to examine the balance between van der Waals (vdW) forces and hydrogen (H) bonding in ambient and high pressure phases of ice. At higher pressure, the contribution to the lattice energy from vdW increases and that from H bonding decreases, leading vdW to have a substantial effect on the transition pressures between the crystalline ice phases. An important consequence, likely to be of relevance to molecular crystals in general, is that transition pressures obtained from DFT functionals which neglect vdW forces are greatly overestimated.Comment: Submitted to Phys. Rev. Lett., 5 pages, 3 figure

On the Accuracy of van der Waals Inclusive Density-Functional Theory Exchange-Correlation Functionals for Ice at Ambient and High Pressures

Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.Comment: 13 pages, 5 figures, 4 table

Desenvolvimento e validação de um questionário de avaliação da atividade física para adolescentes

OBJETIVO: Desenvolver um questionário de atividade física para adolescentes brasileiros e verificar sua validade e reprodutibilidade. MÉTODOS: Participaram do estudo 94 adolescentes (30 meninos e 64 meninas) com idade entre 11 a 16 anos, em 2004. O questionário foi composto por 17 questões sobre atividades habituais exercidas nos últimos 12 meses (exercícios físicos/esportes e atividades de locomoção) e foi padronizado para gerar escores semanal e anual. Como método de referência utilizou-se o teste de corrida vai-e-vem de 20 metros com as variáveis tempo em minutos, velocidade máxima em km/h, consumo máximo de oxigênio e freqüência cardíaca máxima. Para a análise de validação, foram utilizados o coeficiente de Spearman e correlação ajustada por idade. Para a análise da reprodutibilidade, utilizou-se medida repetida com intervalo de 15 dias e coeficiente de correlação intraclasse. RESULTADOS: Para o escore semanal de atividade física, os maiores coeficientes de correlação foram obtidos com o tempo total para a análise em conjunto (r=0,19), velocidade total para os meninos (r=0,20), e consumo máximo de oxigênio e tempo total para as meninas (r=0,17). Para o escore anual de atividade física, os maiores coeficientes de correlação foram obtidos com o tempo total para a análise em conjunto (r=0,30), freqüência cardíaca final após o ajuste pela idade para os meninos (r=0,22) e tempo total para as meninas (r=0,23). Nas análises de reprodutibilidade, a correlação do escore semanal foi de 0,61 e a do escore anual foi de 0,68. CONCLUSÕES: O questionário apresentou evidências de validade e reprodutibilidade. Recomenda-se sua utilização para avaliação da atividade física habitual em estudos epidemiológicos com adolescentes

A highly diastereoselective chloride-mediated dynamic kinetic resolution at phosphorus on-route to a key intermediate in the synthesis of GSK2248761A

A highly diastereoselective chloride-mediated dynamic kinetic resolution at phosphorus has been developed to access a key intermediate in the synthesis of GSK2248761A. This procedure utilises a soluble chloride source and a cheap readily available chiral auxiliary. The practicality of this transformation is demonstrated on a multi-gram scale

Validade e confiabilidade das medidas referidas de peso e estatura para o diagnóstico do estado nutricional de adolescentes

PURPOSE: To assess the validity and reliability of self-reported height, weight, and Body Mass Index (BMI) to diagnose the nutritional status of adolescents. METHODS: The study included 360 public school students of both genders, with ages ranging from 10 to 15 years. Adolescents self-reported their weight and height, and these values were later obtained directly by interviewers. The validity of BMI based on self-reported measures was calculated using sensitivity and specificity indexes, and positive predictive value (PPV). Agreement between self-reported and measured BMI was evaluated using Kappa's weight coefficient, the Lin correlation coefficient, and Bland-Altman and Lin's plots. RESULTS: Both girls and boys underestimated their weight (-1.0 girls and boys) and height (girls - 1.2 and boys - 0.8) (p < 0.001). BMI presented moderate agreement between measured and self-reported values. Sensitivity of estimated BMI based on reported measures to classify obese subjects was higher for boys (87.5%) than it was for girls (60.9%), whereas specificity was higher for girls (92.7%) than it was for boys (80.6%). PPV was high only for classification of normal-weight adolescents. CONCLUSIONS: Self-reported measures of weight and height in adolescents do not present valid measures; therefore, they should not be used to replace measured values. Additionally, we observed that 10% of obese boys and 40% of obese girls could have remained unidentified if we had used only self-reported measures, emphasizing the effects of the low reliability of self-reporting. __________________________________________________________________________________________________________________ RESUMO:OBJETIVO: Avaliar a validade do peso, estatura e Índice de Massa Corporal (IMC) referidos e sua confiabilidade para o diagnóstico do estado nutricional de adolescentes de Piracicaba. MÉTODOS: Participaram do estudo 360 adolescentes de ambos os sexos, de escolas públicas de Piracicaba, com idade entre 10 e 15 anos. Os adolescentes auto-relataram seu peso e estatura, sendo esses valores obtidos por medidas diretas, logo em seguida, pelos entrevistadores. A validade do IMC referido foi calculada segundo índices de sensibilidade, especificidade e valor preditivo positivo (VPP). Avaliou-se a concordância entre as categorias de IMC obtido por meio das medidas referidas e aferidas a partir do coeficiente kappa ponderado, coeficiente de correlação de Lin. e gráficos de Bland e Altman e Lin. RESULTADOS: Verificou-se que tanto os meninos quanto as meninas subestimaram o peso (-1,0 meninas e meninos) e a estatura (meninas -1,2 e meninos -0,8) (p < 0,001). Os valores de IMC aferidos e referidos apresentaram uma concordância moderada. A sensibilidade do IMC referido para classificar os indivíduos obesos foi maior para os meninos (87,5%), enquanto a especificidade foi maior para as meninas (92,7%). O VPP foi elevado somente para a classificação da eutrofia. CONCLUSÕES: As medidas referidas de peso e estatura de adolescentes não representam medidas válidas e, portanto, não devem ser usadas em substituição aos valores mensurados. Além disso, verificou-se que 10% dos meninos obesos e 40% das meninas obesas poderiam permanecer não identificados utilizando-se as medidas auto-referidas, confirmando a baixa validade das medidas auto-referidas

Determining of body mass index in adolescents from public schools in Piracicaba, São Paulo State

O objetivo do presente estudo foi verificar os fatores determinantes do índice de massa corporal (IMC) de adolescentes matriculados nas escolas públicas de Piracicaba, São Paulo. A amostra foi constituída por 328 adolescentes de ambos os sexos, com idade mínima de dez anos. Verificou-se peso, estatura, maturação sexual, atividade física e consumo alimentar. Foi usado um modelo de regressão linear múltipla para verificar a associação entre as variáveis independentes e o IMC. Enquanto as meninas consideradas fisicamente ativas apresentaram maior média de IMC do que as insuficientemente ativas, a média do IMC dos meninos não apresentou diferença estatística quando comparada entre meninos ativos e insuficientemente ativos. A maturação sexual foi determinante do IMC, para ambos os sexos, reforçando a ideia de que é fundamental levar em consideração essa variável em estudos que avaliam o estado nutricional em adolescentes. Acredita-se que os métodos utilizados no presente estudo, os quais são normalmente utilizados em pesquisas semelhantes, apresentaram importantes limitações para avaliar a influência do nível de atividade física e do consumo alimentar sobre o IMC dos adolescentes. Dessa forma, ressalta-se a necessidade de aprimoramento desses métodos para adoção em futuros estudos.The objective of this study was to assess determining factors of body mass index (BMI) in adolescents enrolled in public schools in Piracicaba, São Paulo. The sample had 328 adolescents from both genders; minimum age was 10 years old. We have assessed weight, height, sexual maturity, physical activity, and diet. A multiple linear regression model was used to assess the association between independent variables and BMI. While girls considered physically active presented greater mean BMI than those insufficiently active, boys did not present statistical difference between mean BMI among those active and those insufficiently active. Sexual maturity was a determinant for BMI, for both genders, reinforcing the idea that it is essential to take this variable into account in studies that assess the nutritional situation in adolescents. We believe that the methods used in the present study, which are normally used in similar surveys, have important limitations to assess the influence of variables such as the level of physical activity and food intake on the BMI of adolescents. Thus, it is important to improve these methods and adopt them in further studies

A microstructured fiber source of photon pairs at widely separated wavelengths

We demonstrate a source of photon pairs with widely separated wavelengths, 810 nm and 1548 nm, generated through spontaneous four-wave mixing in a microstructured fiber. The second-order auto-correlation function g^{(2)}(0) was measured to confirm the non-classical nature of a heralded single photon source constructed from the fiber. The microstructured fiber presented herein has the interesting property of generating photon pairs with wavelengths suitable for a quantum repeater able to link free-space channels with fiber channels, as well as for a high quality telecommunication wavelength heralded single photon source. It also has the advantage of straightforward coupling into optical fiber. These reasons make this photon pair source particularly interesting for long distance quantum communication.Comment: 3 pages, 3 figures. Published versio

Estimate of corrected values and the effect of correction for measurement error in dietary data obtained by the Food Frequency Questionnaire for Adolescents (AFFQ)

The scope of this study was to estimate calibrated values for dietary data obtained by the Food Frequency Questionnaire for Adolescents (FFQA) and illustrate the effect of this approach on food consumption data. The adolescents were assessed on two occasions, with an average interval of twelve months. In 2004, 393 adolescents participated, and 289 were then reassessed in 2005. Dietary data obtained by the FFQA were calibrated using the regression coefficients estimated from the average of two 24-hour recalls (24HR) of the subsample. The calibrated values were similar to the the 24HR reference measurement in the subsample. In 2004 and 2005 a significant difference was observed between the average consumption levels of the FFQA before and after calibration for all nutrients. With the use of calibrated data the proportion of schoolchildren who had fiber intake below the recommended level increased. Therefore, it is seen that calibrated data can be used to obtain adjusted associations due to reclassification of subjects within the predetermined categories

Optimised insert design for improved single-molecule imaging and quantification through CRISPR-Cas9 mediated knock-in

© 2019, The Author(s). The use of CRISPR-Cas9 genome editing to introduce endogenously expressed tags has the potential to address a number of the classical limitations of single molecule localisation microscopy. In this work we present the first systematic comparison of inserts introduced through CRISPR-knock in, with the aim of optimising this approach for single molecule imaging. We show that more highly monomeric and codon optimised variants of mEos result in improved expression at the TubA1B locus, despite the use of identical guides, homology templates, and selection strategies. We apply this approach to target the G protein-coupled receptor (GPCR) CXCR4 and show a further insert dependent effect on expression and protein function. Finally, we show that compared to over-expressed CXCR4, endogenously labelled samples allow for accurate single molecule quantification on ligand treatment. This suggests that despite the complications evident in CRISPR mediated labelling, the development of CRISPR-PALM has substantial quantitative benefits