Moisture Sorption Studies on Garlic Powder

The moisture sorption isotherms of two samples of garlic powder, one containing corn starch (CS) and the other without starch, were deter-mined using saturated salt solutions. Monolayer values were calculated from the isotherms using the Brunauer, Emmett and Teller (BET) equation. The addition of CS at 5% slightly increased the monolayer value of the garlic powder, but it had little effect on the caking behavior of the powder. Equilibrium relative humidity (ERH) of garlic powder corresponding to the monolayer value was found to be 14%.     

Effect of refrigerated storage temperature on the viability of probiotic micro-organisms in yogurt

The effect of refrigerated storage temperature was studied at 2, 5 and 8°C on the viability of probiotics in ABY ( Lactobacillus acidophilus, Bifidobacterium lactis BB-12 and yogurt bacteria. Bulgaricus , i.e. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus ) probiotic yogurt. The study was carried out during a 20-day refrigerated storage period to identify the best storage temperature(s). Also, the viability change of the probiotic micro-organisms was analysed at 5-day intervals throughout the refrigerated storage period. After 20 days, storage at 2°C resulted in the highest viability of L. acidophilus , whereas for Bifidobacterium lactis the highest viability was obtained when yogurt was stored at 8°C.     

ULTRAFILTRATION METHOD OF STUDYING BINDING OF LIGANDS TO MACROMOLECULES

The principles and procedures for studying binding of low molecular weight ligands to macromolecules using ultrafiltration are reviewed. Ultrafiltration methods are much faster and theoretically equivalent to equilibrium dialysis, which is the most commonly used subtractive method. An entire binding isotherm and the effect of free species concentration on the binding equilibrium can be determined with a single run of a few hours duration. The calculations and data analysis, which are normally quite complicated, can be easily performed using popular spread-sheet programs such as Lotus 1-2-3® on a personal computer. The experimental protocol, the control experiments to account for nonspecific binding and the calculation procedures are given in detail using a case study of a typical ligand-protein interaction.     

Phototransients in anodic tantalum oxide thin films

Phototransients under radiation of 274 nm have been studied in anodic tantalum oxide thin films. The area under the phototransient curves, the relaxation time end the decay time are found U> decrease with the applied field. For short times ΔI αexp ( ? t/r) with τ decreasing with field, while for longer times thore is a departure from exponential behaviour. These photo transients may be due to the drift of photoexcited electrons under the action of an applied field end their subsequent retrapping.     

The effect of circular bridge piers with different inclination angles toward downstream on scour

A fundamental principle in the safe design of bridge piers is to estimate maximum scour depth. As such, many researchers devoted their efforts to study the phenomenon of scour around bridge piers and to present relationships to estimate maximum scour depth. In the current research, scour around circular bridge piers with two different diameters and different inclination angles toward downstream has been investigated experimentally under clear water and different discharges. The obtained results revealed that increase in the inclination angle leads to a significant decrease in the scour depth, dimensions of sediment ridge and scour hole. Moreover, by comparing the data obtained from vertical bridge pier and well-known relationships, a relationship having the most agreement with the results was selected and modified to estimate equilibrium scour depth around inclined piers.     

Synthesis and properties of new polyimide/clay nanocomposite films

A series of polymer–clay nanocomposite (PCN) materials consisting of polyimide and typical clay were prepared by solution dispersion. Quaternary alkylammonium modified montmorillonite, Cloisite 20A, was used as organoclay. Poly(amic acid) solution was prepared from the reaction of benzophenone-4,4′,3,3′-tetracarboxylic dianhydride and 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl) pyridine in dimethylacetamide. Thermal imidization was performed on poly(amic acid)/organoclay dispersion in a regular temperature-programmed circulation oven. The study of interlayer d-spacing with X-ray diffraction pattern indicates that an exfoliated structure may be present in the nanocomposite 1%. Intercalated structures were obtained at higher organoclay loadings. Nanocomposites were studied using thermogravimertic analysis and differential scanning calorimetry. Nanocomposites exhibit higher glass transition temperature and improved thermal properties compared to neat polyimide due to the interaction between polymer matrix and organoclay particles. The results are also compared with data of a similar work. Morphology study with scanning electron microscopy showed that the surface roughness in nanocomposite 1% increased with respect to pristine polyimide. Solvent uptake measurements were also carried out for the prepared materials. Maximum solvent adsorption was observed for dimethyl sulfoxide (DMSO). It was found that the solvent uptake capacity decreased with increasing clay content.     

Stability of a Hurwitz polynomial under coefficient perturbations: necessary and sufficient conditions

Necessary and sufficient conditions for a perturbed polynomial to remain Hurwitz are given. The conditions allow considerable freedom in allocating different weights to various coefficients to reflect different levels of uncertainty in the coefficients. The new conditions are an extension of a previous result of the author in which sufficient conditions for the same problem were obtained.     

Effect of chemical composition and alumina content on structure and properties of ceramic insulators

In the present work, six electrical porcelain compositions with different amount of alumina and silica have been prepared and fired in an industrial furnace at 1300 °C. Density, porosity, bending strength and electrical strength were measured in the samples. In order to find a relationship between properties and sample microstructures, samples were analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD) techniques. The results showed that, with chemical composition of 53·5 wt.% SiO₂ and 37·5 wt.% alumina, highest electrical strength of 21·97 kV/mm was achieved in fabricated electrical porcelains. Increasing amount of alumina up to 30 wt.% decreases quartz and cristobalite phases, but increases corundum phase 3 to 5 times. SEM observation revealed that dense particles and uniform distribution of long and thin needle shaped mullite are predominant in sample microstructures with highest electrical strength.     

Nanohydroxyapatite synthesis using optimized process parameters for load-bearing implant

In this study, nanohydroxyapatite (NHA) was synthesized using calcium nitrate tetrahydrate and diammonium hydrogen phosphate via the precipitation method assisted with ultrasonication. Three independent process parameters: temperature (T) (70, 80 and 90°C), ultrasonication time (t) (20, 25 and 30 min), and amplitude (A) (60, 65 and 70%) were studied and optimized using response surface methodology based on 3 factors and 5 level central composite design. The responses of the model were analysed with the help of the particle size measured from field-emission scanning electron microscopy and Brunauer–Emmett–Teller (BET). The surface area of particle was measured with BET and the thermal stability of the powder was measured using thermogravimetric analysis. Finally, with the optimized process parameters obtained from the model, the NHA powder was synthesised and validated against the predicted value. The results show a good agreement with an average error 8% between the actual and predicted values. Moreover, the thermal stability and porosity of synthesized NHA was further improved after calcination. This improvement could be due to the removal of impurities from the NHA powder after calcination as indicated by the Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy.