Consideration of viscosity variation in determining the performance characteristics of circular bearings in the laminar and turbulent regimes

The effect of viscosity variation with hydrodynamic pressure on the performance characteristics of hydrodynamic circular journal bearings was studied. Weibull's exponential relation for the pressure-dependent viscosity and the linearized turbulence theory of Ng and Pan were used to obtain the static and dynamic performance characteristics of journal bearings for a wide range of operating eccentricity ratios. The results are compared for the different values of the normalized pressure-viscosity coefficients.     

Investigation of the wear mechanism of carbon-fiberreinforced acetal

The friction and wear characteristics of acetal reinforced with 25 wt.% of randomly dispersed carbon fibers were investigated and compared with those of the base resin. The addition of carbon fibers to the polymer decreased the coefficient of friction and wear rate for the composite material sliding against a hardened and ground steel disk for extended periods of time. A number of surface topography parameters pertinent to the wear process, i.e. arithmetic average roughness, autocorrelation function, asperity density, tip radius of curvature, distribution of the radii of curvature and heights of asperity peaks, and ordinale heights, were calculated and evaluated for the sliding surface of the disk. The worn surfaces of filled and unfilled polymer pins were examined by scanning electron microscopy to investigate the probable wear mechanism for these materials. It was found that the wear of reinforced polymers proceeds by the pulling-out of the broken and worn fibers.     

Allergenic responses of red kidney bean (Phaseolus vulgaris cv chitra) polypeptides in BALB/c mice recognized by bronchial asthma and allergic rhinitis patients

Allergenicity potential of red kidney beans (Phaseolus vulgaris cv chitra) was assessed and attempts were made to identify the responsible proteins by pepsin digestibility assay and IgE immunoblotting. To evaluate allergenic potential, BALB/c mice were sensitized with red kidney bean proteins and levels of specific immunoglobulin, histamine, mast cell protease-1, cytokines and CCL-2 were measured. To confirm our findings in BALB/c, the studies were also extended to human subjects. Human sera collected from control subjects and allergic patients after skin prick test were used for IgE immunoblotting, measuring the levels of total and specific IgE and determining cross reactivity of red kidney bean with other legumes. Red kidney bean allergenic potential was evident by significant increase in specific IgE, IgG1, histamine, mast cell protease-1 and Th2 cytokine levels in comparison to control. Enhanced level of eosinophils in jejunum, prominent anaphylactic symptoms, and eruptive histopathological changes give indication towards red kidney beans allergenicity. IgE immunoblotting detected five protein components with molecular weights of approximately 170, 100, 43, 34 and 20 kDa. Red kidney bean proteins showed cross reactivity with peanut, soybean, chickpea and black gram. Finally, this work demonstrated that red kidney beans may induce allergic response in mice similar to human subjects, with identification of five clinically relevant allergenic protein components.     

Effects of diet on rumen proliferation and fecal shedding of Escherichia coil O157:H7 in calves

Calves inoculated with Escherichia coli O157:H7 and fed either a high-roughage or high-concentrate diet were evaluated for rumen proliferation and fecal shedding of E. coli O157:H7. Calves fed the high-roughage diet had lower mean rumen volatile fatty acid concentrations and higher rumen pH values than did calves fed the high-concentrate diet. Despite these differences in rumen conditions, the calves fed the high-roughage diet did not have greater rumen populations of E. coli O157: H7 and did not exhibit increased or longer fecal shedding compared with the calves fed the high-concentrate diet. Two calves shedding the highest mean concentrations of E. coli O157:H7 were both fed the high-concentrate diet. There was a significant (P < 0.05) positive correlation between fecal shedding and rumen volatile fatty acid concentration in calves fed a high-concentrate diet. The effects of diet on E. coli O157:H7 proliferation and acid resistance were investigated using an in vitro rumen fermentation system. Rumen fluid collected from steers fed a high-roughage diet, but not from steers fed a high-concentrate diet, supported the proliferation of E. coli O157:H7. Rumen fluid from steers fed a high-concentrate diet rapidly induced acid resistance in E. coli O157:H7. The impact of diet on fecal shedding of E. coli O157:H7 is still unclear and may depend on dietary effects on fermentation in the colon and on diet-induced changes in the resident microflora. However, rapid development of acid tolerance by E. coli O157:H7 in the rumens of calves fed high-concentrate diets, allowing larger populations to survive passage through the acidic abomasum to proliferate in the colon, may be one factor that influences fecal shedding in cattle on feed.     

Sterile keratitis after corneal collagen crosslinking in a child

Corneal collagen crosslinking (CXL) is a non invasive technique used in halting the progression of keratoconus. Complications with this modality are rare. We report a case of an 8-year-old child who developed sterile infiltrates in the immediate postoperative period after uneventful corneal collagen crosslinking for keratoconus. The infiltrates resolved with topical steroid therapy. There was also present coexisting vernal keratoconjunctivitis (VKC) which was controlled with topical 2% cyclosporine A eye drops prior to crosslinking treatment. This case highlights importance of controlling VKC prior to CXL in keratoconus as it adds to the risk of developing post operative sterile keratitis.     

Propellant Gas Phase Chemical Kinetics

An adiabatic constant pressure chemical kinetic study of the AP gas phase is conducted. The objective is to examine the importance of chemical kinetic studies for propellant deflagration modelling in general and for AP in particular. A reaction mechanism consisting of ninety five elementary reactions involving twenty one chemical species is developed to represent the AP gas phase. An important parameter that can be obtained from the kinetics is the time rate of change of temperature of the gas phase at the condensed phase-gas phase boundary (dT/dt at t = 0). This is directly related to the heat feedback from the gas phase to the condensed phase. Comparison with earlier work indicates that the use of a one-step overall reaction could lead to underestimates of heat feedback from the gas phase by a factor of about four. In addition it is found that the rate of decrease of dT/dt at t = 0, with pressure is much larger at lower pressures, suggesting a possible gas phase role in the low pressure deflagration limit. Further, the kinetic study does not support the conclusion of a constant fraction of AP reacting in the condensed phase in the pressure range 20–100 atmospheres. These results are at variance with what is obtained by use of a one-step overall reaction. Thus, the one-step overall reaction cannot represent even qualitatively several gas phase characteristics important for deflagration studies, and its use leads to erroneous results. It is concluded that a full reaction mechanism representation of gas phase chemical kinetics is essential to AP deflagration modelling. The same conclusion is probably valid for propellant deflagration modelling in general.     

Energetics of Propellants,Fuels and Explosives; a chemical valence approach

A simple approach involving the chemical valences of the fuel and the oxidizer elements present in a combustible mixture is described to evaluate the energetics related parameters of propellants, fuels and explosives. It simplifies the stoichiometric balancing of complex combustion equations, and provides an easy method of calculating the elemental stoichiometric coefficient. The method correctly predicts whether a mixture is fuel-lean, fuel-rich or stoichiometrically balanced. The calorimetric value of various stoichiometrically balanced combustible systems has been shown to be linearly dependent upon their total oxidizing (or reducing) valences. This relationship has been used successfully to evaluate the calorific value of fossil fuels. For fuel-rich explosives, a new valence dependent parameter has been derived which is found to be related with properties such as detonation velocity, heat of explosion and impact sensitivity.