Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

This is a study on the kinetics of the liquid-phase hydrogenation of styrene to ethylbenzene over a catalyst of palladium supported on an inorganic–organic composite. This support has a better mechanical resistance than other commercial supports, e.g. alumina, and yields catalysts with egg-shell structure and a very thin active Pd layer. Catalytic tests were carried out in a batch reactor by varying temperature, total pressure and styrene initial concentration between 353–393 K, 10–30 bar, and 0.26–0.60 mol L−1. Kinetic models were developed on the assumptions of dissociative hydrogen chemisorption and non-negligible adsorption of hydrogen and styrene. Final chemical reaction expressions useful for reactor design were obtained. The models that best fitted the experimental data were those ones that considered the surface reaction as the limiting step. In this sense, a two-step Horiuti–Polanyi working mechanism with half hydrogenation intermediates gave the best fit of the experimental data. The heats of adsorption of styrene and ethylbenzene were also estimated.The authors are gratefully indebted to CONICET, ANPCyT and Universidad Nacional del Litoral for financially sponsoring this research work

Pre-eclampsia: evidence of altered ventricular repolarization by standard ECG parameters and QT dispersion.

Pre-eclampsia complicates approximately 6-8\% of all pregnancies. Epidemiologic studies have demonstrated a relationship between pre-eclampsia and cardiac morbidity and mortality later in life, but the effect of pre-eclampsia on electrical cardiac activity during the acute phase has not yet been understood. The aim of this study was to investigate ECG alterations during pre-eclampsia. Prepartum ECGs of 76 consecutive pre-eclamptic women were compared with those of 76 healthy pregnant women. All of the routine ECG parameters were considered, and ventricular repolarization was assessed by QT interval and QT dispersion (QTd). Pregnancies complicated by pre-eclampsia showed a significant alteration of ventricular repolarization compared with the control group. Among ECG parameters, QT and QTc intervals and QTd were more prolonged in pre-eclamptic women. Multivariate analysis also showed that pre-eclampsia was the only independent determinant of QTd. In conclusion, pre-eclampsia has a significant effect on ventricular repolarization. This alteration could, in part, explain the increased cardiovascular risk of women with a history of pre-eclampsia. Further studies are necessary to confirm the relationship between ventricular repolarization abnormalities and increased cardiovascular risk later in life

Sex Differences in the Cerebellum and Frontal Cortex: Roles of Estrogen Receptor Alpha and Sex Chromosome Genes

Most neurobehavioral diseases are sexually dimorphic in their incidence, and sex differences in the brain may be key for understanding and treating these diseases. Calbindin (Calb) D28K is used as a biomarker for the well-studied sexually dimorphic nucleus, a hypothalamic structure that is larger in males than in females. In the current study weanling C56BL/6J mice were used to examine sex differences in the Calb protein and message focusing on regions outside of the hypothalamus. A robust sex difference was found in Calb in the frontal cortex (FC) and cerebellum (CB; specifically in Purkinje cells); mRNA and protein were higher in females than in males. Using 2 mouse lines, i.e. one with a complete deletion of estrogen receptor alpha (ERα) and the other with uncoupled gonads and sex chromosomes, we probed the mechanisms that underlie sexual dimorphisms. In the FC, deletion of ERα reduced Calb1 mRNA in females compared to males. In addition, females with XY sex chromosomes had levels of Calb1 equal to those of males. Thus, both ERα and the sex chromosome complement regulate Calb1 in the FC. In the CB, ERα knockout mice of both sexes had reduced Calb1 mRNA, yet sex differences were retained. However, the sex chromosome complement, regardless of gonadal sex, dictated Calb1 mRNA levels. Mice with XX chromosomes had significantly greater Calb1 than did XY mice. This is the first study demonstrating that sex chromosome genes are a driving force producing sex differences in the CB and FC, which are neuoranatomical regions involved in many normal functions and in neurobehavioral diseases