Effect of grain boundary phase on the thermal conductivity of aluminium nitride ceramics

AIN with high thermal conductivity was fabricated by pressureless sintering with Y₂O₃ as the sintering aid. The thermal conductivity was observed to increase with sintering time (up to 8 h) at 1810 °C. The distribution of the sintering aid was identified as one of the major factors influencing the thermal conductivity in AIN. Non-uniform distribution of the grain boundary phase was found to be associated with a significant amount of porosity, resulting in the enhancement of phonon scattering and thereby lowering the thermal conductivity.     

Hearing loss after spinal anesthesia. An audiological controlled trial

Audiological tests were conducted on 34 patients before and after undergoing an operation in spinal anaesthesia. One of these patients developed a considerable unilateral hearing loss in the low-frequency range, which persisted until an epidural blood-patch was given. Unexpectedly, we also found a general small but significant threshold shift at 500 Hz, which has never before been described in the literature. The biological mechanism is discussed, and the results suggest that the explanation of the hearing loss could be a condition similar to endolymphatic hydrops, resulting from perilymphatic hypotension due to loss of liquor during and after the spinal anaesthesia.     

Nanomechanics and Raman spectroscopy of fibrillin 2 knock-out mouse bones

Absence of fibrillin 2 (Fbn2), a non-collagenous bone protein, causes a connective tissue disorder called congenital contractural arachnodactyly (CCA) and has been associated with decreased bone mineral density. Nanoindentation and Raman microspectroscopy have been used to compare the mechanical and chemical properties of cortical bone from femora of Fbn2−/− deficient mice and their wild-type controls (Fbn2+/+). It was found that Fbn2−/− bones have significantly lower hardness and elastic modulus compared to Fbn2+/+ bones, especially in the mid-cortical section. The Raman analysis showed little difference with genotype except for a decrease in type-B carbonate substitution in the endosteal region of Fbn2−/− bones. The results indicate that Fbn2 plays a direct role in determining the mechanical properties of bone.     

3D Micro-PIXE at atmospheric pressure: A new tool for the investigation of art and archaeological objects

The paper describes a novel experiment characterized by the development of a confocal geometry in an external Micro-PIXE set-up. The position of X-ray optics in front of the X-ray detector and its proper alignment with respect to the proton micro-beam focus provided the possibility of carrying out 3D Micro-PIXE analysis. As a first application, depth intensity profiles of the major elements that compose the patina layer of a quaternary bronze alloy were measured. A simulation approach of the 3D Micro-PIXE data deduced elemental concentration profiles in rather good agreement with corresponding results obtained by electron probe micro-analysis from a cross-sectioned patina sample. With its non-destructive and depth-resolving properties, as well as its feasibility in atmospheric pressure, 3D Micro-PIXE seems especially suited for investigations in the field of cultural heritage.     

Sucrose and fructose have qualitatively different flavors to rats

Previous studies suggest that rats might be able to discriminate between sucrose and fructose, but no previous study has examined this possibility in much detail. Rats were conditioned to avoid either sucrose or fructose by injecting them with lithium chloride when they drank these substances. Control rats were given the same injections but were not exposed to either sugar during training. After training, the rats were given a choice of fructose vs. sucrose. Data from control rats provided information about the relative taste intensity of the sugars. If the sugars possess only a single gustatory quality, control rats should prefer the sweeter sugar; under this assumption, sucrose appears to be two-four times sweeter than fructose. The two sugars share a common taste because rats trained to avoid sucrose avoided fructose when the fructose concentration was much greater than the sucrose concentration. Nevertheless, the two sugars are discriminable because, when the apparent sweetness of the sugars was matched, rats showed a greater aversion to the sugar they were trained to avoid. Aversions to sucrose and fructose also generalized to maltodextrins, but sucrose may have a somewhat greater maltodextrin flavor than does fructose. It is proposed that the biological function of maltodextrin taste is to allow animals to sense the ratio of glucose to fructose in foods.     

Effect of MoS2 morphology on the HDS activity of hydrotreating catalysts

We have applied near-edge X-ray absorption fine structure (NEXAFS) to characterize the surface and bulk properties of Li_xNi_1–xO catalysts. In our experimental set-up, NEXAFS spectra of powder materials could be obtained by measuring the intensity of either electron-yield or fluorescence-yield. While the electron-yield method is sensitive only to the top few atomic layers, the fluorescence-yield method can detect species up to a few thousands angstroms deep into the bulk structure. The ability to distinguish surface and bulk compositions is demonstrated in studies of a number of Li_0.5Ni_0.5O samples, of which the surface compositions vary as a function of preparation procedures. In addition, NEXAFS investigations following the reaction of Li_xNi_1–xO with CH₄ have also been carried out and the results indicate that the initial surface reaction intermediates are Li₂CO₃.     

Different thermal behavior of neonatal hepatic and cerebral 3-hydroxy-3-methylglutaryl-CoA reductase

The Arrhenius plots of hepatic and cerebral 3-hydroxy-3-methylglutaryl-CoA reductase activity were studied in neonatal chicks fed with a standard diet. Supplementation of the diet with 2% cholesterol from hatching has no effect on the thermal characteristics of the brain enzyme. The Arrhenius plot of brain reductase was practically similar to that found in control chicks. However, hepatic reductase was inhibited by cholesterol feeding. Dietary cholesterol increased the cholesterol/lipidic phosphorus molar ratio in liver microsomes, whereas no significant differences were observed in brain microsomes. These results are in agreement with the hypothesis that activity of hepatic reductase is regulated by the fluidity of microsomal membrane and show that cholesterol feeding does not alter the fluidity of microsomal membranes in neonatal chick brain having, thus, no effect on the thermal behavior of cerebral reductase.     

A single phase model of mechanisms effecting miscible surfactant oil recovery

The concept of volume averaging is used to theoretically study the mechanisms of mass dispersion, adsorption, and dead-space volume. These mechanisms are important to the understanding of miscible surfactant flooding. After simpiffication based on order-of-magnitude scaling, a linear core model is solved using state variable finite-difference techniques. Mass dispersion and adsorption are shown to be important model parameters while dead-space volume is a rather insensitive model parameter.