Effect of membrane action on the plastic collapse load of circular orthotropic slabs with fixed edges

In the case of reinforced concrete slabs fixed at the boundaries, considerable enhancement in the load carrying capacity takes place due to compressive membrane action. In this paper a method is presented to analyse the effects of membrane action in fixed orthotropic circular slabs, carrying uniformly distributed loads. Depending on the radial moment capacity being greater or less than the circumferential moment capacity, two cases of orthotropy have been considered. Numerical results are worked out for certain assumed physical parameters and for different coefficients of orthotropy. Variations of load and bending moments with the central deflection are presented.     

Method of moments solution for a printed patch/slot antenna on a thin finite dielectric substrate using the volume Integral equation

In this paper, a volume integral equation (VIE)-based modeling method suitable for a patch or slot antenna on a thin finite dielectric substrate is developed and tested. Two new key features of the method are the use of proper dielectric basis functions and proper VIE conditioning, close to the metal surface, where the surface boundary condition of the zero tangential E -component must be extended into adjacent tetrahedra. The extended boundary condition is the exact result for the piecewise-constant dielectric basis functions. The latter operation allows one to achieve a good accuracy with one layer of tetrahedra for a thin dielectric substrate and thereby greatly reduces computational cost. The use of low-order basis functions also implies the use of low-order integration schemes and faster filling of the impedance matrix. For some common patch/slot antennas, the VIE-based modeling approach is found to give an error of about 1% or less in the resonant frequency for one-layer tetrahedral meshes with a relatively small number of unknowns. This error is obtained by comparison with fine finite-element method (FEM) simulations, or with measurements, or with the analytical mode matching approach. Hence it is competitive with both the method of moments surface integral equation approach and with the FEM approach for the printed antennas on thin dielectric substrates.     

Microstructure and compressive properties of carbon microballoons

Carbon microballoons (CMBs) with tap densities of 0.143, 0.161, and 0.177 g/cm³, as measured per ASTM B 527-93, were characterized in terms of individual balloon diameter, wall thickness, and mechanical behavior in compression through a novel uniaxial compression test technique. This compression test, performed on an MTS Nanoindenter XP II, utilized a flat-ended cylindrical tip rather than the common Berkovich indenter. Quantitative microscopy techniques were used to obtain diameter and wall thickness measurements on the polished cross-sections of individual CMBs that had been cold mounted in epoxy resin. Though there was significant overlap in the three populations, a trend toward increasing average wall thickness—from 1.32 to 2.16 μm—with increasing tap density was observed. Compressive property data including failure load, failure strain, fracture energy, and stiffness were obtained for individual microballoons. Comparison of these data, both inter- and intra-tap density, has yielded some viable trends. CMB failure strain exhibited a dependence upon the inverse square root of the CMB diameter, and CMB failure load depended linearly upon CMB stiffness. Averages for each tap density’s failure load, pseudo-stiffness, and fracture energy were also calculated and observed to increase with tap density.     

Optimizing growth conditions for electroless deposition of Au films on Si(111) substrates

Electroless deposition of Au films on Si(111) substrates from fluorinated-aurate plating solutions has been carried out at varying concentrations, deposition durations as well as bath temperatures, and the resulting films were characterized by X-ray diffraction, optical profilometry, atomic force microscopy and scanning electron microscopy. Depositions carried out with dilute plating solutions (< 0.1 mM) at 28°C for 30 min produce epitaxial films exhibiting a prominent Au(111) peak in the diffraction patterns, while higher concentrations or temperatures, or longer durations yield polycrystalline films. In both epitaxial and polycrystalline growth regimes, the film thickness increases linearly with time, however, in the latter case, at a rate an order of magnitude higher. Interestingly, the surface roughness measured using atomic force microscopy shows a similar trend. On subjecting to annealing at 250°C, the roughness of the film decreases gradually. Addition of poly (vinylpyrrolidone) to the plating solution is shown to produce a X-ray amorphous film with nanoparticulates capped with the polymer as evidenced by the core-level photoelectron spectrum. Nanoindentation using AFM has shown the hardness of the films to be much higher (∼ 2.19 GPa) than the bulk value.     

Isolation of ceramide-monomethylaminoethylphosphonate from the lipids of Tetrahymena pyriformis W

Ceramide-monomethylaminoethylphosphonate has been isolated for the first time from the lipids of Tetrahymena pyriformis W and characterized on the basis of its chromatographic mobility, chemical analysis, and infrared and nuclear magnetic resonance properties.     

Effect of dietary fat level on growth and lipogenesis in the colostrum deprived neonatal pig

Thirty male neonatal pigs were obtained by cesarean section and randomly allotted from littermate groups to three diets containing 2%, 17%, and 32% fat on a dry matter basis. Butterfat was used to replace glucose in the isoenergetic liquid, semipurified diets. Each pig was placed in a sterile isolator and fed ad libitum five times daily. After 14 days, pigs were weighed, killed, and samples of liver and backfat were obtained. The carcass of each pig was ground and samples obtained for determination of total body fat and protein. An increase in the level of dietary fat resulted in a significant increase in 14 day weight gain and a tendency for improved feed efficiency. These results demonstrate not only that the neonatal pig can utilize semipurified liquid diets high in butterfat content, but also that energy from butterfat appears to be used as efficiently as energy from glucose from growth purposes. Increasing dietary fat level decreased the activity of fatty acid synthetase and citrate cleavage enzyme in adipose tissue and liver, and decreased the activity of malic enzyme in adipose tissue. The specific activities of these three enzymes were higher in adipose tissue than in liver.     

On the role of penetrant structure in diffusion in structured polymers

Marked differences between the diffusional behaviour of linear and non-linear penetrant molecules in structured polymers exist, which remain hitherto unexplained. The existing theories of transport in polymers have been re-examined with a view to explain such differences. Direct and indirect experimental evidence has been analysed to support the view-point that linear molecules diffuse by a segmental motion. A diagnostic method in the context of a modified Maxwell model has been proposed to differentiate between different diffusive phenomena. The role of co-operative segmental motion for the polymer matrix has been quantitatively examined. Possible technological implications of the findings of the work have been elaborated on.