Squeeze flow of a power-law fluid between non-parallel plates

Squeeze flow in the gap between non-parallel circular plates of radius R is discussed. The test material is assumed to be a power-law fluid, with a no-slip boundary condition at the plates. If the mean separation between the plates is h, and the angle of inclination between the plates is ? ? h/R, the force on the plates is perturbed only at O(?²) and is increased by less than 10% if ? < 0.35h/R. A torque O(?) tends to return the plates to a parallel configuration.     

Photoelectron spectroscopic studies of the formation of hydroxyapatite films on titanium pretreated with etidronic acid

X‐ray photoelectron spectroscopy in the core and valence band region was used to study the formation of hydroxyapatite films on the surface of titanium. The approach used achieves the adhesion of hydroxyapatite by the initial formation of a thin, mainly oxide‐free, etidronate film on the metal. In this approach, it was not possible to prepare hydroxyapatite films of any reasonable thickness on the titanium surface without prior treatment with etidronic acid. Because hydroxyapatite is a principal component of teeth and bones, it is likely that the coated metals will have desirable biocompatible properties. The hydroxyapatite film showed no changes when the film was exposed to air, water, and 1 m sodium chloride solution as representative components of the environment of the film in the human body. These films formed on titanium may find application in medical implants. The thin hydroxyapatite and etidronate film on the metal show differential charging effects that caused a doubling of some of the spectral features. Copyright © 2012 John Wiley & Sons, Ltd.     

A comparative investigation into the effect of chronic alcohol feeding on the myocardium of normotensive and hypertensive rats: an electrophoretic and biochemical study

We investigated whether the imposition of chronic alcohol in hypertension leads to greater biochemical and cellular abnormalities of the myocardium than those arising in normotension. Fifteen-week-old spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were fed ethanol-containing diets for six weeks. Particular attention was focused on the composition of contractile proteins identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), fractional rate of protein synthesis, and synthesis rates relative to RNA (RNA activity) or DNA (cellular efficiency). In addition, myocardial enzymes and adenine nucleotides were measured. In both SHR and WKY rats chronic ethanol caused a general decrease in the contents of all nine contractile proteins with myosin heavy chain predominantly affected. Fractional rates of mixed (i.e., total) and myofibrillary proteins remained unaltered in both WKY rats and SHR, as were cellular efficiencies. The RNA activity was significantly reduced in ethanol-treated SHR but not in WKY rats. In ethanol-treated SHR, cardiac creatine kinase (CK) and malate dehydrogenase (MDH) activities were increased, AMP levels were elevated, whilst ATP levels and the energy charge were reduced. In WKY rats, the only significant change related to increased aspartate aminotransferase activities in response to alcohol feeding. Although there were only subtle differences between the response of the normotensive and hypertensive rats due to ethanol dosage, the reduced ATP levels and increased CK and MDH activities in SHR may reflect a greater susceptibility to ischaemic damage. Reduced contractile protein content, particularly myosin heavy chain, may contribute to contractile defects, a common feature of subclinical and clinical alcoholic cardiomyopathy.     

Structure, optical properties and defects in nitride (III-V) nanoscale cage clusters

Density Functional Theory calculations are reported on cage structured BN, AlN, GaN and InN sub- and low nanosize stoichiometric clusters, including two octahedral families of T(d) and T(h) symmetry. The structures and energetics are determined, and we observe that BN clusters in particular show high stability with respect to the bulk phase. The cluster formation energy is demonstrated to include a constant term that we attribute to the curvature energy and the formation of six tetragonal defects. The (BN)(60) onion double-bubble structure was found to be particularly unstable. In contrast, similar or greater stability was found for double and single shell cages for the other nitrides. The optical absorption spectra have been first characterised by the one-electron Kohn-Sham orbital energies for all compounds, after which we concentrated on BN where we employed a recently developed Time Dependent Density Functional Theory approach. The one-electron band gaps do not show a strong and consistent size dependency, in disagreement with the predictions of quantum confinement theory. The density of excited bound states and absorption spectrum have been calculated for four smallest BN clusters within the first ionisation potential cut-off energy. The relative stability of different BN clusters has been further explored by studying principal point defects and their complexes including topological B-N bond rotational defects, vacancies, antisites and interstititials. The latter have the lowest energy of formation.     

The use of holding coils to facilitate long incubation times in unsegmented flow analysis : Determination of serum prostatic acid phosphatase

Conventional unsegmented flow analysis is best suited to determinations involving rapid chemical reactions. Analyses requiring relatively long reaction times necessitate stopping the flow to allow sufficient reaction product to accumulate, which significantly decreases sampling frequency. An automated distribution valve is described which directs samples into one of four holding coils where they remain for a predetermined time. Because one parallel coil may be filled with a sample while the others hold other samples for reaction, thoroughput is increased fourfold compared with a comparable single tube system. This technique is applied to the determination of prostatic acid phosphatase in human blood sera. The method is compared with a manual procedure.