Methane capture at room temperature: adsorption on cubic d-MoC and orthorhombic b-Mo2C molybdenum carbide (001) surfaces

Based on periodic Density Functional Theory (DFT) calculations, carried out using a standard generalized gradient approximation type exchange-correlation functional including or not a van der Waals dispersive forces, the ability of the cubic δ-MoC(001) surface to capture methane at room temperature is suggested. Adsorption on the orthorhombic β-Mo2C(001) surfaces, with two possible terminations, has been also considered and, in each case, several molecular orientations have been tested with one, two, or three hydrogen atoms pointing towards the surface on all high-symmetry adsorption sites. The DFT results indicate that the δ-MoC(001) surface shows a better affinity towards CH4 than β-Mo2C(001). The calculated adsorption energy values on δ-MoC(001) surface are larger, and hence better, than on other methane capturing materials such as metal organic frameworks. Besides, the theoretical desorption temperature values estimated from the Redhead equation indicate that methane would desorbs at 330 K when adsorbed on the δ-MoC(001) surface, whereas this temperature is lower than 150 K when the adsorption involves β-Mo2C(001). Despite of this, adsorbed methane presents a very similar structure compared to the isolated molecule, due to a weak molecular interaction between the adsorbate and the surface. Therefore, the activation of methane molecule is not observed, so these surfaces are, in principle, not recommended as possible methane dry reforming catalysts

Optimization of cutoff parameters using DFT periodic calculations for (110) rutile and (101) anatase TiO2 surfaces

O uso do TiO2 como catalisador na conversão de Compostos Orgânicos Voláteis em substâncias menos tóxicas é uma importante aplicação para a melhoria da qualidade de vida do ser humano. Nesse trabalho, foram estudadas as superfícies (110) rutilo e (101) anatase do TiO2. Estas superfícies foram utilizadas para estudos de adsorção de moléculas de benzeno, tolueno, etilbenzeno, o-xileno, m-xileno e p-xileno (BTEX). A Teoria do Funcional de Densidade (DFT) com condições de contorno periódicas e conjunto de funções de base de ondas planas e o funcional de troca e correlação PW91 foram usados. Os resultados mostraram que o uso de 300 eV e 3x3x3 para a energia de corte das ondas planas e a malha de pontos k, respectivamente, foram considerados apropriados para os cálculos da adsorção do BTEX. As supercélulas com quatro camadas (3x2) para a superfície (110) do TiO2 rutilo e (3x1) para a superfície (101) do TiO2 anatase foram usadas para a modelagem da superfície. _______________________________________________________________________________________________ ABSTRACTTiO2 used as a catalyst in the conversion of Volatile Organic Compounds into less toxic substances is an important application for improving the quality of human life. In this work, TiO2 (110) rutile and (101) anatase surfaces were studied. These surfaces were used for benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX) molecules adsorption studies. The Density Functional Theory (DFT) with periodic boundary conditions and plane wave basis set with the PW91 exchange-correlation functional were used. The results showed that 300 eV for the cutoff energy of the plane waves and 3x3x3 k points mesh were appropriate for the BTEX adsorption calculation. A supercell with four layers (3x2) for the (110) rutile TiO2, and (3x1) for the (101) anatase TiO2 were considered for the surface modeling

Mineração de dados meteorológicos para previsão de eventos severos Meteorological data mining for the prediction of severe convective events

O objetivo do trabalho proposto é detectar antecipadamente possíveis ocorrências de eventos convectivos severos, por meio do monitoramento das saídas do modelo de previsão numérica de tempo Eta, para cada intervalo de previsão e para um conjunto de variáveis selecionadas. O período de estudo estende-se de janeiro a fevereiro de 2007. Classificadores foram desenvolvidos pela abordagem de similaridade de vetores e de conjuntos aproximativos, de forma a identificar saídas do modelo Eta que possam ser associados a esses eventos. Assumiu-se como premissa que os eventos convectivos severos possam ser correlacionados com grande número de ocorrências de descargas elétricas atmosféricas. Os classificadores agruparam as saídas do modelo Eta, compostas por essas variáveis, com base na densidade de ocorrência de descargas elétricas atmosféricas nuvem-solo. Ambos os classificadores apresentaram bom desempenho para os testes realizados para um período de dois meses escolhido para três mini-regiões selecionadas do território brasileiro.<br>This work aims the early detection of possible occurrences of severe convective events in Central and Southeast Brazil by means of monitoring the output of the Eta numerical weather prediction model for each forecasted time interval and for a selected set of variables. The studied period ranges from January to February 2007. Classifiers were developed by two approaches, vector similarity and rough sets, in order to identify Eta outputs that can be associated to such events. It was assumed that severe convective events can be correlated to a large number of atmospheric electric discharges. The classifiers grouped the Eta meteorological model outputs for these selected variables based on the density of occurrences of cloud-to-ground atmospheric electrical discharges. Both classifiers show good performance for the chosen 2-month period at the three selected mini-regions of the Brazilian territory

Effect of general anaesthesia on functional outcome in patients with anterior circulation ischaemic stroke having endovascular thrombectomy versus standard care: a meta-analysis of individual patient data

Background: General anaesthesia (GA) during endovascular thrombectomy has been associated with worse patient outcomes in observational studies compared with patients treated without GA. We assessed functional outcome in ischaemic stroke patients with large vessel anterior circulation occlusion undergoing endovascular thrombectomy under GA, versus thrombectomy not under GA (with or without sedation) versus standard care (ie, no thrombectomy), stratified by the use of GA versus standard care. Methods: For this meta-analysis, patient-level data were pooled from all patients included in randomised trials in PuMed published between Jan 1, 2010, and May 31, 2017, that compared endovascular thrombectomy predominantly done with stent retrievers with standard care in anterior circulation ischaemic stroke patients (HERMES Collaboration). The primary outcome was functional outcome assessed by ordinal analysis of the modified Rankin scale (mRS) at 90 days in the GA and non-GA subgroups of patients treated with endovascular therapy versus those patients treated with standard care, adjusted for baseline prognostic variables. To account for between-trial variance we used mixed-effects modelling with a random effect for trials incorporated in all models. Bias was assessed using the Cochrane method. The meta-analysis was prospectively designed, but not registered. Findings: Seven trials were identified by our search; of 1764 patients included in these trials, 871 were allocated to endovascular thrombectomy and 893 were assigned standard care. After exclusion of 74 patients (72 did not undergo the procedure and two had missing data on anaesthetic strategy), 236 (30%) of 797 patients who had endovascular procedures were treated under GA. At baseline, patients receiving GA were younger and had a shorter delay between stroke onset and randomisation but they had similar pre-treatment clinical severity compared with patients who did not have GA. Endovascular thrombectomy improved functional outcome at 3 months both in patients who had GA (adjusted common odds ratio (cOR) 1·52, 95% CI 1·09–2·11, p=0·014) and in those who did not have GA (adjusted cOR 2·33, 95% CI 1·75–3·10, p&lt;0·0001) versus standard care. However, outcomes were significantly better for patients who did not receive GA versus those who received GA (covariate-adjusted cOR 1·53, 95% CI 1·14–2·04, p=0·0044). The risk of bias and variability between studies was assessed to be low. Interpretation: Worse outcomes after endovascular thrombectomy were associated with GA, after adjustment for baseline prognostic variables. These data support avoidance of GA whenever possible. The procedure did, however, remain effective versus standard care in patients treated under GA, indicating that treatment should not be withheld in those who require anaesthesia for medical reasons

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity