Effect of powder metallurgy synthesis parameters for pure aluminium on resultant mechanical properties

In this work, pure aluminium powders of different average particle size were compacted, sintered into discs and tested for mechanical strength at different strain rates. The effects of average particle size (15, 19, and 35 μm), sintering rate (5 and 20 °C/min) and sample indentation test speed (0.5, 0.7, and 1.0 mm/min) were examined. A compaction pressure of 332 MPa with a holding time of six minutes was used to produce the green compacted discs. The consolidated green specimens were sintered with a holding time of 4 h, a temperature of 600 °C in an argon atmosphere. The resulting sintered samples contained higher than 85% density. The mechanical properties and microstructure were characterized using indentation strength measurement tests and SEM analysis respectively. After sintering, the aluminium grain structure was observed to be of uniform size within the fractured samples. The indentation test measurements showed that for the same sintering rate, the 35 μm powder particle size provided the highest radial and tangential strength while the 15 μm powder provided the lowest strengths. Another important finding from this work was the increase in sintered sample strength which was achieved using the lower sinter heating rate, 5 °C/min. This resulted in a tangential stress value of 365 MPa which was significantly higher than achieved, 244 MPa, using the faster sintering heating rate, 20 °C/min

Maternal smoking during pregnancy and subcutaneous fat mass in early childhood. The Generation R Study

Maternal smoking during pregnancy increases the risk of obesity in the offspring. Not much is known about the associations with other measures of body composition. We assessed the associations of maternal smoking during pregnancy with the development of subcutaneous fat mass measured as peripheral and central skinfold thickness measurements in early childhood, in a population-based prospective cohort study from early fetal life onward in the city of Rotterdam, The Netherlands. The study was performed in 907 mothers and their children at the ages of 1.5, 6 and 24 months. As compared to non-smoking mothers, mothers who continued smoking during pregnancy were more likely to have a younger age and a lower educational level. Their children had a lower birth weight, higher risk of small size for gestational age and were breastfed for a shorter duration (P-values <0.01). We did not observe differences in peripheral, central and total subcutaneous fat mass between the offspring of non-smoking mothers, mothers who smoked in first trimester only and mothers who continued smoking during pregnancy (P > 0.05). Also, the reported number of cigarettes smoked by mothers in both first and third trimester of pregnancy were not associated with peripheral, central and total subcutaneous fat mass in the offspring at the ages of 1.5, 6 and 24 months. Our findings suggest that fetal exposure to cigarette smoke during pregnancy does not influence subcutaneous fat mass in early childhood. Follow-up studies are needed in children at older ages and to identify associations of maternal smoking during pregnancy with other measures of body composition

Bruno Touschek: particle physicist and father of the electron-positron collider

This article gives a brief outline of the life and works of the Austrian physicist Bruno Touschek, who conceived, proposed and, 50 years ago, brought to completion the construction of AdA, the first electron-positron storage ring. The events which led to the approval of the AdA pro ject and the Franco-Italian collaboration which con- firmed the feasibility of electron-positron storage rings will be recalled. We shall illustrate Bruno Touschek's formation both as a theoretical physicist and as an expert in particle accelerators during the period be- tween the time he had to leave the Vienna Staat Gymnasium in 1938, because of his Jewish origin from the maternal side, until he arrived in Italy in the early 1950s and, in 1960, proposed to build AdA, in Frascati. The events which led to Touschek's collaboration with Rolf Wideroe in the construction of the first European betatron will be de- scribed. The article will make use of a number of unpublished as well as previously unknown documents, which include an early correspon- dence with Arnold Sommerfeld and Bruno Touschek's letters to his family in Vienna from Italy, Germany and Great Britain. The impact of Touschek's work on students and collaborators from University of Rome will be illustrated through his work on QED infrared radiative corrections to high energy e+e- experiments and the book Meccanica Statistica.Comment: To be published in EPJ

Maternal smoking during pregnancy and offspring overweight : is there a dose–response relationship? An individual patient data meta-analysis

We want to thank the funders of the individual studies: the UK Medical Research Council and the Wellcome Trust (Grant ref: 102215/2/13/2) and the University of Bristol, the Danish National Research Foundation, Pharmacy Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health Foundation, the US NICHD (contracts no. 1-HD-4-2803 and no. 1-HD-1-3127, R01 HD HD034568), the NHMRC, the CNPq (Portuguese acronym for the National Research Council—grant 523474/96-2) and FAPESP (Portuguese acronym for the São Paulo State Research Council—grant 00/0908-7). We would like to thank the participating families of all studies for the use of data. For the ASPAC study, we want to thank the midwives for their help in recruiting families, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses. This work was supported by the Deutschen Forschungsgesellschaft (German Research Foundation, DFG) [KR 1926/9-1, KU1443/4-1]. Dr. Gilman’s contribution was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.Peer reviewedPostprin

Proton and apparent hydride ion conduction in Al-substituted SrTiO3

Hydrogen ion conductivity in 2% and 10% Al-substituted SrTiO3 has been investigated by transport number measurements using the concentration cell/emf method in wet atmospheres as a function of pO(2) (10 (- 20) -1 atm) and temperature (350 - 1000 degreesC). Earlier indications of apparent negative charge transport by hydrogen under reducing conditions and high temperatures have been confirmed. By the present measurements, possible artefacts from the type of acceptor-dopant, gas buffer, electrode material, and porosity of the sample appear to have been ruled out. Electrochemical pumping experiments with gas chromatography were inconclusive with respect to hydride ion transport. Thermogravimetry as a function of hydrogen activity did not show evidence of hydride ion incorporation, but indicated uptake of neutral hydrogen under reducing conditions and high temperatures. Quantum molecular dynamics simulations indicate the existence of defect species or clusters that may be reminiscent of interstitial hydrogen with a tendency to associate with effective negative charge, e.g., on neighbouring titanium ions, under simulated reducing conditions. (C) 2002 Elsevier Science B.V. All rights reserved

Preconditioning Triggered by Carbon Monoxide (CO) Provides Neuronal Protection Following Perinatal Hypoxia-Ischemia

Perinatal hypoxia-ischemia is a major cause of acute mortality in newborns and cognitive and motor impairments in children. Cerebral hypoxia-ischemia leads to excitotoxicity and necrotic and apoptotic cell death, in which mitochondria play a major role. Increased resistance against major damage can be achieved by preconditioning triggered by subtle insults. CO, a toxic molecule that is also generated endogenously, may have a role in preconditioning as low doses can protect against inflammation and apoptosis. In this study, the role of CO-induced preconditioning on neurons was addressed in vitro and in vivo. The effect of 1 h of CO treatment on neuronal death (plasmatic membrane permeabilization and chromatin condensation) and bcl-2 expression was studied in cerebellar granule cells undergoing to glutamate-induced apoptosis. CO's role was studied in vivo in the Rice-Vannucci model of neonatal hypoxia-ischemia (common carotid artery ligature +75 min at 8% oxygen). Apoptotic cells, assessed by Nissl staining were counted with a stereological approach and cleaved caspase 3-positive profiles in the hippocampus were assessed. Apoptotic hallmarks were analyzed in hippocampal extracts by Western Blot. CO inhibited excitotoxicity-induced cell death and increased Bcl-2 mRNA in primary cultures of neurons. In vivo, CO prevented hypoxia-ischemia induced apoptosis in the hippocampus, limited cytochrome c released from mitochondria and reduced activation of caspase-3. Still, Bcl-2 protein levels were higher in hippocampus of CO pre-treated rat pups. Our results show that CO preconditioning elicits a molecular cascade that limits neuronal apoptosis. This could represent an innovative therapeutic strategy for high-risk cerebral hypoxia-ischemia patients, in particular neonates

Carbon monoxide effect in hippocampus after perinatal hypoxia-ischemia – apoptotic profiles.

<p>Whereas contralateral hippocampus displayed a preserved morphology (<b>A</b>) following HI, diffuse tissue disruption was detected in the hippocampus ipsilateral to the occlusion (<b>B</b>). C–E are representative pictures of ischemic hippocampus, where diffuse apoptosis was documented; with peculiar morphological features including pyknotic nuclei (<b>C</b>), indicating early stage of apoptosis, progressive nuclear fragmentation (<b>D</b>) and karyorrhexis as confirmed by detectable apoptotic bodies (<b>E</b>). Compared to HI group, the number of apoptotic profiles was significantly lower when animals were exposed to CO prior to HI (<b>F</b>). All values are mean ± SD (error bars); *<i>p</i><0.05 compared to Control group for the corresponding side and **<i>p</i><0.05 compared to HI group ischemic hippocampus. (<b>G</b>) For each group there is no significant difference in cytotoxic edema volume (mm³) between the ipsi- and the contralateral hippocampus.</p

Effect of carbon monoxide treatment on neuronal apoptosis.

<p>(<b>A</b>) Representative micrographs of neurons treated or not with 20 µM of glutamate and 10 µM of CO. Apoptotic hallmarks were analyzed by fluorescent microscopy. <i>Upper panel</i>, for the photos taken with the filter for phase contrast, <i>middle panel</i>, for Hoechst (white arrows for nuclei with condensed chromatin) and <i>lower panel</i>, for propidium iodide (white arrows for cells which membrane integrity was lost). (<b>B</b>) Primary cultures of neuronal cells were pre-treated with 10 µM CO, followed by 24 h of glutamate (10–30 µM) treatment. Cell viability was assessed by counting cells containing normal nuclei and plasmatic membrane integrity. For each coverslip, at least 1500 cells were counted. All values are mean ± SD (error bars), n = 5; *<i>p</i><0.05 compared to control. (<b>C</b>) The effect of 10 µM CO treatment on Bcl-2 expression was assessed by its mRNA quantification.</p

Carbon monoxide effect in hippocampus after perinatal hypoxia-ischemia – cleaved caspase 3 expression.

<p>Low (scale bar = 100 µm) magnification CLSM photographs of the hippocampus of HI (A, B), CO-HI (C, D) and CO sham operated (E, F) rat pups. In blue, DAPI-stained nuclei; in red, cleaved caspase 3-positive cells. Caspase 3-positive profiles following HI were particularly frequent in CA1–2 and in the dentate gyrus, and were decreased in number following CO preconditioning. CO preconditioning alone did not induce caspase 3 activation in sham operated animals.</p