The Navier–Stokes approach for thermal EHL line contact solutions

The complicated nature of the EHL-problem has so far forced researchers to develop their own computer codes. These codes are ultimately based on the Reynolds equation, and if thermal EHL-simulations are required, a simultaneous solution of the equation of energy also has to be performed. To date only a few attempts to solve the full equations of momentum and continuity as well as equations of energy have been performed. However, such an approach will give extended possibilities of simulating EHL-contacts; i.e. the computational domain can be expanded and it will be possible to simulate the flow, not only in the contact but also around the contact. Another possibility is to investigate how the altering length scales of the surface roughness influence the behaviour of the flow in the contact. However, the aim of the work presented in this paper is to investigate the possibilities of using a commercial CFD-code (computational fluid dynamics code) based on the above-mentioned equations for simulating thermal EHL. The rheology is assumed to be Newtonian and the equations of momentum and continuity are then commonly referred to as the Navier–Stokes equations (N–S equations). The geometry chosen for the simulations is a smooth line contact geometry, for which the results from the simulations show that it is possible to use the N–S equations for thermal EHL for contact pressures up to approximately 0.7 GPa. The code used in this work is the commercial CFD software (CFX 4.3 user guide). There is a limitation in the N–S approach due to a singularity that can occur in the equation of momentum when the principal shear stresses in the film become too high. However, a thermal approach makes it possible to simulate EHL-contacts at higher loads compared with an isothermal approach, due to the reduction of the viscosity in the former approach. The singularity is not present in the Reynolds approach.     

Ischemia-induced transplant arteriosclerosis in the rat. Induction of peptide growth factor expression

A 3-wk feeding trial with 240 sexed, day-old broiler chickens was conducted to determine the efficacy of microbial phytase at different levels of dietary Ca on performance and utilization of minerals in broiler chickens fed a low-P corn-soybean diet. The experimental design was a 3 x 2 factorial arrangement of treatments; Ca at 0.6, 1.0, and 1.25% and phytase at 0 and 600 phytase U/kg diet. Phytase supplementation, regardless of Ca level, increased (P < or = 0.005) feed intake, (P < or = 0.0001) body weight, and (P < or = 0.025) feed efficiency at 21 d; the optimum levels of body weight, feed intake, and feed efficiency were obtained with low (0.6%) dietary Ca plus phytase. Retentions of P, Ca, and N were increased (P < or = 0.05) by phytase supplementation. Although maximum retentions of P and N were obtained at the 1.0 and 1.25% Ca levels, respectively, they were not significantly different from the values obtained at 0.6% Ca. The increasing level of dietary Ca decreased plasma P ( P < or = 0.05) and Cu (P < or = 0.06). Phytase supplementation had the opposite effect; i.e., increased plasma P (P < or = 0.03) and Cu (P < or = 0.02). The maximum level of plasma P was obtained with phytase at the 1.0% Ca level, but this value was not significantly different from the value obtained with phytase at the 0.6% Ca level. Phytase supplementation increased (P < 0.04) the ash content of both tibia head and shaft but had no effect on mineral contents in the ash. The optimum level of ash content was observed with the 0.06% Ca diet plus phytase. The results show that microbial phytase supplementation to a low P diet improved growth performance and mineral utilization in broiler chickens. Dietary Ca levels had a significant effect on the response to phytase; the optimum growth performance and mineral utilization were achieved at the low (0.6%) level of dietary Ca supplemented with phytase.     

Effects of removal of weight-bearing function on contractility and myosin isoform composition in single human skeletal muscle cells

The purpose of this study was to investigate the effects of a 6-week period without weight bearing, achieved by bed rest, on the contractile behaviour, myosin isoform expression and myofibrillar protein content of single human muscle fibres. Percutaneous biopsied specimens of the quadriceps muscle were taken from three healthy male volunteers before and at the end of the experimental period. Maximum force normalised to cross-sectional area (specific tension), maximum velocity of unloaded shortening (V0), and myosin heavy chain (MyHC) and light chain (MyLC) isoform composition were measured in single membrane-permeabilised muscle cells obtained from these specimens. At the end of the experimental period, specific tension was reduced (P < 0.001) by 40% and there was a parallel decline in myofibrillar protein content per muscle cell volume. V0 did not change significantly in response to bed rest when data from all muscle cells were pooled. In two of the subjects, however, V0 decreased (P < 0.01-0.001) in muscle cells expressing the beta/slow (type I) MyHC isoform, but there was no change in fibres expressing type IIA or a combination of type IIA and IIB MyHCs. The slowing in type I MyHC fibres was associated with a change in the isoform composition of the regulatory MyLC.     

Kinetics of coal desulphurization by Acidianus brierleyi

Acidianus brierleyi was demonstrated to remove pyritic sulphur from coal. A. brierleyi was also found capable of catalyzing the removal of what is normally reported as organic sulphur from coal 171US34. A kinetic analysis was performed by assuming a first order reaction. The first order kinetics allowed a comparison with literature data for Thiobacillus ferrooxidans. Also, formation of jarosite was taken into account in the analysis. The simple first order kinetics was observed to fit the data on removal of sulphur satisfactorily.     

Elderly patients'' experiences of pain and distress in intensive care: a grounded theory study

Plasma membrane vesicles prepared from the bag region of the somatic muscle cell of the parasite Ascaris suum contain a large conductance, voltage-sensitive, calcium-activated chloride channel. The ability of this channel to conduct a variety of carboxylic acids, a number of which are products of anaerobic respiration, was investigated using the patch-clamp technique and isolated inside-out patches of muscle membrane. The channel has a conductance of 140 pS in symmetrical 140 mM chloride. Replacement of internal chloride with various carboxylic acids (140 mM) caused large hyperpolarizing shifts in the reversal potential. Permeability ratios, relative to chloride, were calculated for each acid. The relationship between permeability ratio and ionic size is inverse and linear predicting a pore diameter of 6.55 A. This simple relationship was not observed between ionic size and conductance. Calculation of the transition state energy required to transfer a single methyl group from aqueous phase to the binding site afforded a value that was low but favorable, indicating a cationic binding site of low field strength. As the channel is able to open fully at the resting membrane potential of Ascaris and is permeable to fatty acids produced by anaerobic respiration, the possible role of this channel in the removal of metabolic products across the muscle membrane is discussed.     

On dynamic effects at folding of coated papers

Folding of coated papers is examined numerically using the finite element method. The analysis is focused on the influence from dynamic effects on the folding process. In particular, the behaviour of field variables relevant for cracking of the coating layers are studied in some detail. The results presented indicate that dynamic effects are of little importance as regards maximum strain levels in the coating but will influence the stress and strain distributions. Accordingly, a quasi-static analysis of the problem will be sufficient in order to describe many of the important features related to cracking.     

Contractile studies of single human skeletal muscle fibers: a comparison of different muscles, permeabilization procedures, and storage techniques

The study of single muscle fibers has improved our understanding of muscle physiology and pathology. To compare three techniques for fiber preparation and storage, biopsies were obtained from the tibialis anterior and vastus lateralis muscles of a hemiparetic patient and a control subject. Single fibers were prepared with: (1) chemical skinning (CS) and storage at -20 degrees C; (2) chemical skinning followed by sucrose (SU) incubation and storage at -80 degrees C; or (3) freeze-drying (FD) and -80 degrees C storage. Cross-sectional area (CSA), resting, maximal (P0), and specific tension (P0/CSA), and maximum shortening velocity (V0) were determined in 189 cells. CSA was similar in all groups. Resting tension was higher and P0 and P0/CSA lower after FD. In general, V0 was the same in all groups. Our data suggest that CS and SU preserve the properties of single muscle fibers better than FD. SU may allow longer storage of fibers.     

Efficient collision detection for models deformed by morphing

Published online: 5 February 2003