434 research outputs found
Ruling factors in cinnamaldehyde hydrogenation: Activity and selectivity of pt-mo catalysts
To obtain selective hydrogenation catalysts with low noble metal content, two carbon-supported Mo-Pt bimetallic catalysts have been synthesized from two different molybdenum precursors, i.e., Na2MoO4 and (NH4)6Mo7O24. The results obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) combined with the presence and strength of acid sites clarified the different catalytic behavior toward cinnamaldehyde hydrogenation. After impregnating the carbon support with Mo precursors, each sample was used either as is or treated at 400 °C in N2 flow, as support for Pt nanoparticles (NPs). The heating treatment before Pt deposition had a positive effect on the catalytic performance. Indeed, TEM analyses showed very homogeneously dispersed Pt NPs only when they were deposited on the heat-treated Mo/C supports, and XPS analyses revealed an increase in both the exposure and reduction of Pt, which was probably tuned by different MoO3/MoO2 ratios. Moreover, the different acid properties of the catalysts resulted in different selectivity
Daylight saving time and acute myocardial infarction: a meta-analysis
Background
The current evidence on the effects of daylight saving time (DST) transitions on major cardiovascular diseases is limited, and available results are conflicting. We carried out the first meta-analysis aimed at evaluating the risk of acute myocardial infarction (AMI) following DST transitions.
Methods
We searched MedLine and Scopus up to December 31, 2018, with no language restriction, to retrieve cohort or case-control studies evaluating AMI incidence among adults (â„18y) in the week following spring and/or autumn DST shifts versus control periods. A summary relative risk of AMI was computed after: (1) spring, (2) autumn, (3) both transitions considered together versus control weeks. Stratified analyses were performed by gender and age. Data were combined using a generic inverse-variance approach.
Results
Seven studies (>115,000 subjects) were included in the analyses. A significantly higher risk of AMI (Odds Ratio: 1.03; 95% CI: 1.01-1.06) was observed in the two weeks following spring or winter DST transitions. The risk increase was however significant only after the spring shift (OR: 1.05; 1.02-1.07), while AMI incidence in the week after winter DST transition was comparable to control periods (OR 1.01; 0.98-1.04). No substantial differences by age or gender emerged.
Conclusions
The risk of AMI increases modestly but significantly following DST transitions, supporting the proposal of DST shifts discontinuation. Additional studies fully adjusting for potential confounders are required to confirm the present findings
Weight discordance and perinatal mortality in twin pregnancy: systematic review and metaâanalysis
Objectives
The primary aim of this systematic review was to explore the strength of association between birthâweight (BW) discordance and perinatal mortality in twin pregnancy. The secondary aim was to ascertain the contribution of gestational age and growth restriction in predicting mortality in growthâdiscordant twins.
Methods
MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases were searched. Only studies reporting on the risk of mortality in twin pregnancies affected compared with those not affected by BW discordance were included. The primary outcomes explored were incidence of intrauterine death (IUD), neonatal death (NND) and perinatal death. Outcome was assessed separately for monochorionic (MC) and dichorionic (DC) twin pregnancies. Analyses were stratified according to BW discordance cutâoff (â„ 15%, â„ 20%, â„ 25% and â„ 30%) and selected gestational characteristics, including incidence of IUD or NND before and after 34 weeks' gestation, presence of at least one smallâforâgestational age (SGA) fetus in the twin pair and both twins being appropriateâforâgestational age. Risk of mortality in the larger vs smaller twin was also assessed. Metaâanalyses using individual data randomâeffects logistic regression and metaâanalyses of proportion were used to analyze the data.
Results
Twentyâtwo studies (10 877 twin pregnancies) were included in the analysis. In DC pregnancies, a higher risk of IUD, but not of NND, was observed in twins with BW discordance â„ 15% (odds ratio (OR) 9.8, 95% CI, 3.9â29.4), â„ 20% (OR 7.0, 95% CI, 4.15â11.8), â„ 25% (OR 17.4, 95% CI, 8.3â36.7) and â„ 30% (OR 22.9, 95% CI, 10.2â51.6) compared with those without weight discordance. For each cutâoff of BW discordance explored in DC pregnancies, the smaller twin was at higher risk of mortality compared with the larger one. In MC twin pregnancies, excluding cases affected by twinâtwin transfusion syndrome, twins with BW discordance â„ 20% (OR 2.8, 95% CI, 1.3â5.8) or â„ 25% (OR 3.2, 95% CI, 1.5â6.7) were at higher risk of IUD, compared with controls. MC pregnancies with â„ 25% weight discordance were also at increased risk of NND (OR 4.66, 95% CI, 1.8â12.4) compared with those with concordant weight. The risk of IUD was higher when considering discordant pregnancies involving at least one SGA fetus. The overall risk of mortality in MC pregnancies was similar between the smaller and larger twin, except in those with BW discordance â„ 20%.
Conclusion
DC and MC twin pregnancies discordant for fetal growth are at higher risk of IUD but not of NND compared with pregnancies with concordant BW. The risk of IUD in BWâdiscordant DC and MC twins is higher when at least one fetus is SGA
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