Uni-axial stress–strain response and thermal conductivity degradation of ceramic matrix composite fibre tows

A physical model, previously developed by one of the authors, has been extended to cover thermal conductivity degradation owing to the uni-axial stress–strain response of aligned groups of fibres or tows found in ceramic matrix composites. Both the stress–strain and thermal models, together with their coupling, have been shown to predict known composite behaviour qualitatively. The degradation of longitudinal thermal properties is shown to be driven by strain-controlled fibre failure; while the degradation of transverse thermal properties is because of the growth of fibre–matrix interface wake-debonded cracks, coupled with strain-driven fibre failure.

The effect of nitrogen form on rhizosphere soil pH and zinc phytoextraction by Thlaspi caerulescens

The phytoextraction of Zn may be improved by applying N fertilizers to increase the biomass and Zn content of shoots. Rhizosphere-pH change from uptake of different N forms will affect Zn phyto-availability in the rhizosphere and Zn phytoextraction. This glasshouse study examined the effect of N form on Zn phytoextraction by Thlaspi caerulescens (Prayon). The plants were grown in a Zn-contaminated soil (total Zn 250 mg kg-1 soil; pHwater 5.7) and supplied with (NH4)2SO4, Ca(NO3)2 or urea [(NH2)2CO]. The form was maintained by applying the nitrification inhibitor dicyandiamide. A biodegradable chelator ethylenediaminedisuccinic acid (EDDS) was included for comparison. The addition of N doubled the shoot biomass. The highest shoot Zn content occurred in the Ca(NO3)2 treatment and was associated with the highest rhizosphere pH. The lowest shoot dry weight occurred in the EDDS treatment. The Zn concentration in the shoots increased as the rhizosphere pH increased. A significant correlation occurred between Ca and Zn concentrations in the shoots. This study demonstrated that Ca(NO3)2 is a more effective treatment than , urea or EDDS for enhancing Zn phytoextraction in a mildly acidic soil.

Delayed signal detection by diffusion-weighted imaging in brainstem infarction

Diffusion-weighted magnetic resonance imaging (DW MRI) is a sensitive and specific technique for imaging acute hemispheric infarction. Its utility in the diagnosis of acute brainstem infarction has not been well studied. We present 3 cases of brainstem infarction in which DW MRI performed 5 to 15 hours after symptom onset failed to reveal any abnormality. Repeat diffusion-weighted imaging (DWI) 2 to 5 days later did demonstrate an abnormality in the clinically appropriate region in each instance. This suggests that the time course to the development of abnormalities detectable by DWI may be longer in brainstem than in hemispheric infarctions. Therefore, repeat studies after initially negative DWI might be useful in the diagnosis of brainstem infarctions.

Thalamic metabolism and symptom onset in preclinical Huntington's disease

The neural basis for the transition from preclinical to symptomatic Huntington's disease (HD) is unknown. We used serial positron emission tomography (PET) imaging in preclinical HD gene carriers (p-HD) to assess the metabolic changes that occur during this period. Twelve p-HD subjects were followed longitudinally with [11C]-raclopride and [18F]-fluorodeoxyglucose PET imaging, with scans at baseline, 18 and 44 months. Progressive declines in striatal D2-receptor binding were correlated with concurrent changes in regional metabolism and in the activity of an HD-related metabolic network. We found that striatal D2 binding declined over time (P < 0.005). The activity of a reproducible HD-related metabolic covariance pattern increased between baseline and 18 months (P < 0.003) but declined at 44 months (P < 0.04). These network changes coincided with progressive declines in striatal and thalamic metabolic activity (P < 0.01). Striatal metabolism was abnormally low at all time points (P < 0.005). By contrast, thalamic metabolism was elevated at baseline (P < 0.01), but fell to subnormal levels in the p-HD subjects who developed symptoms. These findings were confirmed with an MRI-based atrophy correction for each individual PET scan. Increases in network expression and thalamic glucose metabolism may be compensatory for early neuronal losses in p-HD. Declines in these measures may herald the onset of symptoms in gene carriers.

[Thelohanellus njinei sp nov and T lagdoensis sp nov, Myxosporidia (Myxozoa: Myxosporea) parasites of Schilbeidae and Citharinidae fishes in Cameroon (central Africa)]

The study of Myxosporidia infecting Schilbe mystus (Linné, 1758) (Schilbeidae) and Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) from the Sanaga and Bénoué basins revealed the presence of two new species of the genus Thelohanellus kudo, 1993. These species are Thelohanellus njinei sp. nov. and Thelohanellus lagdoensis sp. nov., found in the gut of Schilbe mystus and Citharinus citharus respectively. New data are also given on the diagnosis of Thelohanellus citharini, a species previously described in Chad.

Tibial geometry is associated with failure load ex vivo: a MRI, pQCT and DXA study

We studied the relations between bone geometry and density and the mechanical properties of human cadaveric tibiae. Bone geometry, assessed by MRI and pQCT, and bone density, assessed by DXA, were significantly associated with bone's mechanical properties. However, cortical density assessed by pQCT was not associated with mechanical properties.

INTRODUCTION

The primary objective of this study was to determine the contribution of cross-sectional geometry (by MRI and pQCT) and density (by pQCT and DXA) to mechanical properties of the human cadaveric tibia.

METHODS

We assessed 20 human cadaveric tibiae. Bone cross-sectional geometry variables (total area, cortical area, and section modulus) were measured with MRI and pQCT. Cortical density and areal BMD were measured with pQCT and DXA, respectively. The specimens were tested to failure in a four-point bending apparatus. Coefficients of determination between imaging variables of interest and mechanical properties were determined.

RESULTS

Cross-sectional geometry measurements from MRI and pQCT were strongly correlated with bone mechanical properties (r(2) range from 0.55 to 0.85). Bone cross-sectional geometry measured by MRI explained a proportion of variance in mechanical properties similar to that explained by pQCT bone cross-sectional geometry measurements and DXA measurements.

CONCLUSIONS

We found that there was a close association between geometry and mechanical properties regardless of the imaging modality (MRI or pQCT) used.

Irreversible pressure-induced transformation of boron nitride nanotubes

We have used Raman spectroscopy to study the behavior of multi-walled boron nitride nanotubes and hexagonal boron nitride crystals under high pressure. While boron nitride nanotubes show an irreversible transformation at about 12 GPa, hexagonal boron nitride exhibits a reversible phase transition at 13 GPa. We also present molecular dynamics simulations which suggest that the irreversibility of the pressure-induced transformation in boron nitride nanotubes is due to the polar nature of the bonds between boron and nitrogen.

Hepatic Metabolism of MK-0457, a Potent Aurora Kinase Inhibitor: Interspecies Comparison and Role of Human Cytochrome P450 and Flavin-Containing Monooxygenase

MK-0457 (N-[4([4-(4-methylpiperazin-1-yl)-6-[(3-methyl-1H-pyrazol-5 -yl)amino]pyrimidin-2-yl]thio)phenyl]cyclopropanecarboxamide), an Aurora kinase inhibitor in development for the treatment of cancer, was evaluated for its in vitro metabolism in different species. This compound primarily underwent N-oxidation and N-demethylation in human, monkey, dog, and rat liver preparations. However, N-demethylation was less significant in dogs. The formation of minor metabolites varied with species, but all metabolites generated in human hepatocytes were observed in animals. Results of immunoinhibition, selective chemical inhibition, thermal inactivation, and metabolism by recombinant cytochromes P450 and flavin-containing monoogygenases (FMOs) strongly suggest that CYP3A4 and FMO3 comparably contributed to MK-0457 N-oxidation in human liver microsomes, where the reaction conformed to Michaelis-Menten kinetics. These studies indicate a major role of CYP2C8 in the N-demethylation reaction, whereas CYP3A4 only made a minor contribution. However, significant substrate inhibition was observed with MK-0457 N-demethylation at high substrate concentrations (>10 microM) in human liver microsomes relative to the anticipated therapeutic exposure. A multienzyme metabolic pathway such as this may mitigate the potential of drug interactions in clinical treatment with MK-0457.

[Effects of surfactants on adsorption of methyl parathion by neutral alumina]

The sorption of methyl parathion by neutral alumina which was modified by ionic surfactants such as SDS, SDBS and CTMAB was studied. It showed that the adsorbability of alumina to methyl parathion were related to the type and concentration of surfactant and pH of the system. The adsorbabilities of alumina on three kinds of surfactants were different. When pH = 7, the adsorbance of SDS was the largest, but the adsorbance of CTMAB was the smallest. When pH = 4, the adsorbance of SDS or SDBS was increased, while the adsorbance of CTMAB was decreased. The adsorbability of alumina was strengthened, not weakened, by the cooperation of pollutant and anionic surfactant, while the sorption of methyl parathion by alumina with cationic surfactant was weakened. These features had the practical value when neutral alumina is used to remove more than one contaminants from wastewater.

Genotypic variation in phosphorus utilisation of soybean [Glycine max (L.) Murr.] grown in various sparingly soluble P sources

This study compared the utilisation of sparingly soluble P among soybean genotypes selected from 3 geographical regions with contrasting soil pH. Plants of 5 genotypes from each region were grown for 72 days in soil columns supplied with hydroxyapetite (Ca-P), AlPO4 (Al-P), or FePO4 (Fe-P) at a rate of 25 mg P/kg soil. NaH2PO4 (Na-P) was used as control at the same rate. Shoot weights ranged from 2.4 to 5.9 g/plant. On average, the genotypes selected from calcareous soils of north-west China produced the highest shoot biomass whereas those from neutral soils of the north-east region the least. Root biomass and root surface area followed the same trend. In contrast, the root-to-shoot weight ratio was highest in Fe-P and lowest in Na-P while root length in Na-P and Fe-P was greater than in the other P forms. The genotypes from the north-east region had higher P concentration in the shoot than those from the other 2 regions. Total P uptake ranged from 9.0 to 15.9 mg/plant for Na-P, and from 6.3 to 12.4 for the sparingly soluble P. Average total P uptake was the highest for the genotypes from the north-west region, and was greatest in Na-P and lowest in Fe-P. The genotypes from the north-east region displayed the greatest ability to use sparingly soluble P, and those from the north-west the least relative to Na-P. Total P uptake from the sparingly soluble P correlated highly with plant biomass production, N2 fixation and nodulation, and seed P, while the relative P uptake correlated highly with P concentration in shoots but neither correlated with root carboxylate release nor leachate pH. The results suggest that there is a substantial genotypic variation in utilisation of sparingly soluble P, which is related to early vigour, nodulation, and seed P reserve but not to origin site pH or root exudation.

Repellent and insecticidal activities of essential oils from Artemisia princeps and Cinnamomum camphora and their effect on seed germination of wheat and broad bean

Repellent and insecticidal activities of essential oils extracted from leaves of Artemisia princeps Pamp and seeds of Cinnamomum camphora (L.) Presl. against storage pests Sitophillus oryzae L. and Bruchus rugimanus Bohem were investigated. Results showed that the two individual oils displayed good, but their mixture (1:1) exhibited much better repellent activities at concentrations from 250 to 1000 microg g(-1) and insecticidal actions at concentrations 1000 microg g(-1) against the test beetles S. oryzae and B. rugimanus. Oils from A. princeps and C. camphora applied individually were significantly toxic to seed germination of wheat at 500 microg ml(-1). However, no toxic effects were found when the two oils were mixed (1:1 w/w) at the same concentration. These observations indicated that the mixture of the two plant-derived oils had a synergic effect and could be used in the control of storage pests.