[B]MFI membrane: Synthesis, physico-chemical properties and catalytic behavior in the double-bond isomerization of 1-butene

An MFI type borosilicate, [B]MFI (Si/B=56), membrane was synthesized on the external surface of tubular -alumina support. The structure, morphology and acidity of the synthesized membrane were characterized by X-ray diffraction, SEM and FT-IR spectroscopy. A flow-through membrane reactor was constructed and the simultaneous catalytic and separation selectivity of the membrane was tested in the double-bond isomerization of 1-butene in the temperature range of 120-250°C and at 1-butene partial pressure of 18 and 50 kPa. No product of skeletal isomerization was formed under these conditions. The catalytic selectivity is attributed to the low acid strength of the Brønsted sites generated by the framework boron. Equilibrium trans/cis-2-butenes ratio was obtained in the retentate stream (1.4-1.5), whereas, that ratio at the permeate stream was up to ~2.2 at 250 oC. The high trans/cis ratio was attributed to the permeation selectivity of the MFI membrane for trans-2-butene

Precipitation of calcium phosphate from simulated milk ultrafiltrate solutions

The present work deals with the influence of pH and temperature on the spontaneous precipitation of calcium phosphate from simulated milk ultrafiltrate (SMUF) solutions. The pH range investigated is 5.7-7.0, and the temperature varied from 55 to 75 degrees C. It was found that the precipitates were prisms of hydroxyapatite (HAP) with low crystallinity preceded by amorphous calcium phosphate (ACP). Crystallinity improved with solution aging. Microscopic particles in the range of 200 nm were obtained at relatively high supersaturation (pH = 6.8), whereas at relatively low supersaturation (pH = 6.0), aggregates in the range of 1 mu m were formed. Moreover, it was found that although the SMUF solution is also supersaturated with respect to magnesium phosphate, no magnesium salt was identified in the precipitates, thus precluding the coprecipitation of magnesium phosphate. At the same temperature, the supersaturation was regulated by adjusting the solution pH. Kinetics study of precipitation showed a parabolic dependence of the (initial) rates on the solution supersaturation, suggesting a surface diffusion-controlled mechanism with activation energy equal to 96 kJ mol(-1). The rates of precipitation were significantly reduced in the presence of citrate ions due to the decrease of the solution supersaturation caused by complexation of citrates with Ca2+ ions. Additionally, a decreasing effect of citrates on the precipitation rate resulted from the adsorption of these species on the formed crystals, blocking some active sites of crystal growth and diminishing the constant of precipitation rate

Fatores associados ao sofrimento psíquico de policiais militares da cidade do Rio de Janeiro, Brasil Factors associated with psychological distress among military police in Rio de Janeiro, Brazil

Nesse artigo, foram investigados fatores associados ao sofrimento psíquico dos policiais militares da cidade do Rio de Janeiro, Brasil, a partir de estudo transversal com 1.120 policiais, sendo caracterizados o perfil socioeconômico e demográfico, a qualidade de vida, as suas condições de saúde e de trabalho. Para mensurar o sofrimento psíquico, utilizou-se o Self-Reported Questionnaire. Na análise de associações, usou-se o modelo de regressão logística, considerando-se variáveis relacionadas ao sofrimento psíquico. Os resultados indicaram associação entre sofrimento psíquico e fatores como: capacidade de reagir a situações difíceis e grau de satisfação com a vida; problemas de saúde, sobretudo, digestivos, nervosos, musculares e ósseos; e condições adversas de trabalho, como carga excessiva, constante exposição ao estresse e à vitimização. Conclui-se apontando a necessidade de intervenções que visem à promoção da saúde desses profissionais, sobretudo da sua saúde mental.<br>This study investigates factors associated with psychological distress among military police (n = 1,120) in Rio de Janeiro, Brazil. The article describes their social, economic, and demographic characteristics, quality of life, mental health, and work conditions. Measurement of psychological distress used the Self-Reported Questionnaire. Analysis of associations used logistic regression, considering factors associated with psychological distress. The results indicate an association between psychological distress and factors such as ability to react to difficult situations, dissatisfaction with life, health problems (especially digestive, nervous, and musculoskeletal symptoms), and adverse work conditions such as excessive workload, constant stress, and victimization. The article concludes by highlighting the need for health promotion interventions for the military police, focusing especially on their mental health