Rapid low temperature synthesis of a titanate pyrochlore by molten salt mediated reaction

Ytterbium titanate pyrochlore, Yb₂Ti₂O₇, was prepared by molten salt mediated synthesis (MSS) from titanium oxide (TiO₂) and ytterbium oxide (Yb₂O₃) reagents. Potassium and sodium chloride mixtures were used as the molten salt medium and the effects of salt to reagent ratio, salt composition, synthesis temperature, reaction time, and TiO₂ particle size were explored. Synthesis temperatures and times required for formation of single phase Yb₂Ti₂O₇ were found to be lower than those required for solid state synthesis (SSS). Whereas MSS synthesis of single phase Yb₂Ti₂O₇ was achieved with micron-sized powders after a single reaction at 1200 °C for 1 h, SSS with micron-sized powders required an extended reaction time of 36 h at 1350 °C. Yb₂Ti₂O₇ micron-sized powder prepared by MSS showed similar particle size and morphology to that of the TiO₂ precursor demonstrating a template growth mechanism. However, the use of TiO₂ nano-sized powder changed the dominant synthesis mechanism from template growth to dissolution–precipitation and facilitated synthesis of near single phase Yb₂Ti₂O₇ at the remarkably low temperature of 700 °C in only 1 h. The potential application for lanthanide and actinide immobilisation from molten salt reprocessing wastes was demonstrated by preparation of Yb₂Ti₂O₇ by molten salt mediated synthesis from TiO₂ and ytterbium chloride (YbCl₃) reagents.     

Esophageal elastance in awake and anesthetized recumbent dogs

Esophageal elastance was measured in trained dogs placed in the prone, supine, and left lateral postures before and during sodium thiopental anesthesia. Esophageal elastance was measured from static pressure-volume curves and during spontaneous breathing at functional residual capacity. There was a significant decrease in esophageal elastance, estimated from the pressure-volume curves, during anesthesia in both prone and lateral positions but not in the supine posture. Changes in vagal tone produced by stimulation of the vagal nerves did not alter esophageal elastance. Therefore, underlying mechanisms for these changes in esophageal elastance are not fully understood. There was an increase in esophageal elastance when lung volumes increased from 55 to 80% total lung capacity. However, we did not find a significant change in esophageal elastance between awake and anesthetized conditions or between positions during spontaneous breathing at functional residual capacity.     

Glass Properties in the Yttria-Alumina-Silica System

The glass formation region in the yttria-alumina-silica system was investigated. Properties of glasses containing 25 to 55 wt% yttria were measured and the effect of the composition was determined. The density, refractive index, thermal-expansion coefficient, and microhardness increased with increasing yttria content. The dissolution rate in IN HCl increased with increasing yttria content and temperature. These glasses were also found to have high electrical resistivity.     

Determinants of fertility in urban and rural Kenya: estimates and a simulation of the impact of education policy

Fertility behavior and population growth and its impact on economics in Kenya are a concern because of recent trends. The aim of this research study was to examine the impact of multiple factors on fertility in urban and rural areas based on the 1984 Kenya contraceptive Prevalence Survey. Simulation models were used to project the number of births expected with the current educational program. The expectation was that increasing female education in rural areas would have an impact on birth probabilities. Policy implications are discussed in terms of increasing educational expenditures, particularly for rural women. The empirical model selected was based on theories on proximate determinants, demographic effects, and neoclassical models. A probit model was used to estimate whether or not a woman had a child in the year preceding the survey. Explanatory variables were economic (female employment and years of schooling), biological (mother's age and child mortality), and cultural (marital state, number of live births, and religion). The sample included 6405 women aged 15-49 years. Married urban women were 37% more likely than unmarried urban women to have given birth. Married rural women in monogamous marriages were 23% more likely to have given birth than their unmarried counterparts. The number in a marital union of wives did not affect the probability of birth in urban areas; the effect was quite small in rural areas. Probability of birth increased until age 25 in urban areas and to age 28 in rural areas. Previous live births had a small impact, and the inhibiting effect of an additional child is 2.7 times larger in urban than in rural areas. Only in urban areas did employment reduce the probability of a birth (by 7.4%). In rural areas, increases in education after the primary level were related to a decline in the probability of a birth (for a 26-year old woman there is a reduction in the probability of .18). The fertility rate of a woman completing secondary school was 3.5 and 7.8 for a woman completing primary school. There were no differences in urban Nairobi and Mombasa. The total fertility rate should decline by 25% between 1984 and 2014, and should fall further based on educational increases which affect family planning use, employment, and infant mortality. By 2014, the savings in education and related expenses for reduction in births of 5.8 million will be considerable.     

Ontogeny and nutritional programming of mitochondrial proteins in the ovine kidney, liver and lung

This study investigated the developmental and nutritional programming of two important mitochondrial proteins, namely voltage-dependent anion channel (VDAC) and cytochrome c, in the sheep kidney, liver and lung. The effect of maternal nutrient restriction between early and mid-gestation (i.e. 28- to 80-day gestation, the period of maximal placental growth) on the abundance of these proteins was also examined in fetal and juvenile offspring. Fetuses were sampled at 80 and 140 days of gestation (term approximately 147 days), and postnatal animals at 1 and 30 days and 6 months of age. The abundance of VDAC peaked at 140 days of gestation in the lung, compared with 1 day after birth in the kidney and liver, whereas cytochrome c abundance was greatest at 140 days of gestation in the liver, 1 day after birth in the kidney and 6 months of age in lungs. This differential ontogeny in mitochondrial protein abundance between tissues was accompanied with very different tissue-specific responses to changes in maternal food intake. In the liver, maternal nutrient restriction only increased mitochondrial protein abundance at 80 days of gestation, compared with no effect in the kidney. In contrast, in the lung mitochondrial protein, abundance was raised near to term, whereas VDAC abundance was decreased by 6 months of age. These findings demonstrate the tissue-specific nature of mitochondrial protein development that reflects differences in functional adaptation after birth. The divergence in mitochondrial response between tissues to maternal nutrient restriction early in pregnancy further reflects these differential ontogenies.     

Microstructure characterization of the non-modulated martensite in Ni–Mn–Ga alloy

The microstructure of the non-modulated martensite in a Ni–Mn–Ga alloy has been characterized in detail by conventional transmission electron microscopy. Bright field images show that the martensite exhibits an internal substructure consisting of a high density of narrow twins. Using electron diffraction, it is found that the martensite has a tetragonal crystal structure. The lattice correspondence between the parent phase and the non-modulated martensite is investigated. Furthermore, the four twinning elements describing the microtwinning have been graphically and quantitatively determined. The results indicate that the microtwinning within the non-modulated martensite belongs to the compound type.     

Effects of maternal cold exposure and nutrient restriction on the ghrelin receptor, the GH-IGF axis, and metabolic regulation in the postnatal ovine liver

Maternal cold exposure of pregnant sheep promotes fetal growth, whereas nutrient restriction (NR) can reverse this effect. The present study was designed to establish whether cold exposure induced by winter shearing of the mother at 70 days gestation (term=147 days), with or without NR (induced by a 50% reduction in maternal food intake from 110 days gestation), has specific effects on mRNA abundance of hepatic genes related to growth and liver energy metabolism that could regulate postnatal body and liver growth. Measurements of hepatic gene expression for the GH secretagog receptor-1a (GHSR-1A), peroxisome proliferator-activated receptor (PPAR)alpha, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase activity together with glycogen content were made in the livers of offspring at 1 and 30 days of age. Maternal NR reduced liver mass at day 1, whereas offspring of cold-exposed mothers had larger livers at day 30 irrespective of maternal diet. Cold exposure resulted in the up-regulation of GHSR-1A mRNA abundance and reduced glucose-6-phosphatase activity at 1, but not 30 days of age, whereas IGF-II mRNA was decreased at 1 and 30 days. PPARalpha mRNA abundance was enhanced, while PEPCK was reduced in 30-day old offspring of cold-exposed mothers. NR caused reductions in IGF-I mRNA and, at 1-day postnatal age, down-regulated GHR, while, at 30 days, reduced GHSR-1A gene expression and hepatic glycogen content. In conclusion, we have shown that maternal cold exposure and NR have different effects on the hepatic GH-IGF and metabolic axis that may contribute to changes in liver growth over the first month of life.     

Initiation of vertebrate left-right axis formation by maternal Vg1

In the development of the three-dimensional vertebrate body plan, the left-right axis is linked to the dorsoventral and anterioposterior axes. In humans, altered left-right development results in severe cardiovascular and visceral abnormalities in individuals and in conjoined twins. Although zygotically transcribed genes that are asymmetrically expressed have been identified, the mechanism by which left-right asymmetries are established during embryogenesis is unknown. Here we show that the Xenopus maternal gene Vg1, a member of the TGF-beta family of cell-signalling molecules which are implicated in dorsoanterior development, initiates left-right axis formation. Altered expression of Vg1 on the right side of 16-cell embryos or disruption of endogenous Vg1 signalling on the left side randomizes cardiac and visceral left-right orientation and alters expression of Xnr-1, a nodal-related molecular marker for left-right development. Furthermore, the orientation of the left-right axis in conjoined twins is dependent upon which cell-signalling molecule initiated twin formation and on whether the secondary axis is on the left or right side of the primary embryonic axis, implicating a molecular pathway leading to the formation of conjoined twins.     

Genesis of methicillin-resistant Staphylococcus aureus (MRSA), how treatment of MRSA infections has selected for vancomycin-resistant Enterococcus faecium, and the importance of antibiotic management and infection control

We extensively studied the epidemiology and time course of endemic methicillin-resistant Staphylococcus aureus (MRSA) in the Millard Fillmore Hospital, a 600-bed teaching hospital in Buffalo. The changeover from methicillin-susceptible S. aureus to MRSA begins on the first hospital day, when patients are given cefazolin as presurgical prophylaxis. Under selective antibiotic pressure, colonizing flora change within 24 to 48 hours. For patients remaining hospitalized, subsequent courses of third-generation cephalosporins further select and amplify the colonizing MRSA population. Therefore, managing antibiotic selective pressure might be essential. Other strategies include attention to dosing, so that serum concentrations of drug exceed the minimum inhibitory concentration, and antibiotic cycling. Although there are some promising new antibiotics on the horizon, it is necessary to deal with many resistance patterns by using the combined strategies of infection control and antibiotic management.