Effect of exchanging PbO with NiO on the structure and optical parameters action of some lanthanum borate oxide glasses

Journal of Materials Science: Materials in Electronics - This work is an attempt to estimate the effect of the exchanging of PbO with NiO on the optical and structural parameters for some...     

Preparation and Catalytic Performance of Al2O3, TiO2 and SiO2 Supported Vanadium Based-Catalysts for C–H Activation

A series of Al₂O₃, SiO₂ and TiO₂-supported vanadium oxide catalysts with different vanadium loadings has been prepared by two different methods: wet impregnation using ammonium metavanadate as a vanadium precursor and grafting using VOCl₃. Characterization of these catalysts by XRD, FTIR, TEM, SEM, EDX, DR and TGA techniques revealed that the structure of vanadium oxide VO _x species depends on the preparation method, the type of the support and loadings of vanadium on the oxides surfaces. Monomeric vanadium oxide species are predominant at low vanadium loadings while polymeric vanadium oxide species increase with higher loadings. The catalytic activity of the prepared catalysts was evaluated for the liquid-phase oxidation of cyclohexane as a model reaction to obtain cyclohexylhydroperoxide, cyclohexanol and cyclohexanone with PCA as co-catalyst. The results show that the catalysts exhibit good cyclohexane conversion and remarkable selectivity to the target products and high turnover numbers (TON).     

The design and calibration of a simulation model of a star computer network

A simulation model of the CERN (European Organization for Nuclear Research) SPS star computer network is described. The model concentrates on simulating the message handling computer, through which all messages in the network pass. The paper describes the main features of the model, the transfer time parameters in the model and how performance measurements were used to assist in the calibration of the model.     

Analysis of alkaloid mixtures by charge-transfer complexation

Binary mixtures of weak and strong UV-absorbing alkaloids were analyzed by a charge-transfer spectrophotometric method, utilizing iodine in ethylene dichloride as the acceptor. In the uncomplexed form, the strong absorbing alkaloid (papaverine, quinine, ergotamine, or reserpine) was measured at a wavelength where there was no interference from weak absorbers (at 335, 332, 315, or 300 nm, respectively). The weak absorbing alkaloid (ephedrine, codeine, atropine, or homatropine methylbromide) was determined by computing its contribution to the total charge-transfer band at 295 nm where absorbance was linearly additive for mixtures. The greater increase in the original epsilon-values of the weak absorbers upon complexation with iodine relative to the corresponding increase in the epsilon-values of the strong absorbers led to good recoveries even at the low dose ratios of the weakly absorbing, and often more potent, alkaloids.     

Forecasting compensatory control (FCC) of machining flatness

Forecasting Compensatory Control (FCC) was implemented to improve the flatness of three dimensional prismatic workpieces in an end-milling operation. The basic logic of the strategy is based on inprocess error measurement, stochastic modelling, and prediction and compensation of the cutting errors.The proposed FCC system consisted of a newly developed laser-based in-process flatness error measurement system, a hydraulic positioning servo system, and a digital microcomputer control system. Through the application of the FCC system to on-line cutting experiments, the workpiece flatness error was reduced by up to 80% during machining.     

Metal-insulator-semiconductor solar cell under gamma irradiation

The performance of a home made MIS–p-Si solar cell was experimentally studied under various gamma irradiation doses (up to 500 Mrad). The effect of radiation dose on the I−V and C−V characteristics was investigated in this work. The obtained results showed that all the output parameters of the cells under investigation were degraded with gamma radiation exposure. In addition, the effects of fabrication conditions (metal thickness and adding of antireflection coating) on the cell output parameters were also investigated.     

Inhibition of heterocyclic aromatic amine formation in fried ground beef patties by garlic and selected garlic-related sulfur compounds

The effects of garlic and selected organosulfur compounds (diallyl disulfide, dipropyl disulfide, diallyl sulfide, allyl methyl sulfide, allyl mercaptan, cysteine, and cystine) on the formation of heterocyclic aromatic amines (HAAs) in fried ground beef patties were evaluated. Minced garlic cloves (ca. 4.8 to 16.7%, wt/wt) or organosulfur compounds (0.67 mmol) were added directly to ground beef. Patties (100 g) were fried at 225 degrees C (surface temperature) for 10 min per side. Two patties were fried for each replication, and five replicates were analyzed for each treatment. For each replicate, four subsamples were analyzed (two unspiked subsamples for concentration and two spiked subsamples for the recovery of HAA standards). The volatile sulfur compounds significantly (P < 0.05) reduced concentrations of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine by reductions of 46 to 81%, while average reductions of 35, 22, and 71%, were achieved with cystine, cysteine, and whole garlic, respectively. The volatile sulfur compounds reduced concentrations of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline by 34 to 67%, while reductions of 25, 19, and 63% (P < 0.05) were achieved with cystine, cysteine, and whole garlic, respectively. These studies confirm that garlic and some organosulfur compounds have the potential to reduce HAA formation incooked beef patties.     

Three-dimensional generalized thermoelastic diffusion and application for a thermoelastic half-space subjected to rectangular thermal pulse

In this article, a model of three-dimensional generalized thermo-diffusion in a half-space thermoelastic medium subjected to permeating gas and the rectangular thermal pulse has been constructed. The half-space is considered to be made of an isotropic homogeneous thermoelastic material. The chemical potential is also assumed to be known on the bounding plane. Laplace transform techniques have been applied, and the solution is obtained in the Laplace transform domain using a direct approach. The solution of the problem in the physical domain is obtained numerically using a numerical method based on a Riemann-sum approximation for the inversion of Laplace transform. The temperature increment, stress, strain, diffusion concentration, and chemical potential distributions are represented graphically. The nonzero value of the relaxation time parameter predicts the finite speed of thermal, mechanical, diffusion waves.     

Flavor Release from a Banana Soft Drink Complex Model System: Evaluation of the Efficiency of Different Adsorbents for Trapping the Released Volatiles During Storage

The main objective of the present study was to evaluate the release of aroma compounds from a banana soft drink complex model system in comparison with their release from simple model systems, each contains individual food ingredients. The effect of different food ingredients (sweeteners and thickeners at different concentrations), used in formulation of the soft drinks, on flavor release from simple model systems containing banana flavor was evaluated separately. The optimum release of isoamyl acetate (the most potent odorant of banana aroma) was observed at a concentration of 10% of each investigated sweetener (sucrose, glucose, and corn syrup). Pectin and xanthane showed the highest release at a concentration of 2.5 and 0.8% w/w, respectively. The level of each ingredient that showed the optimum release of isoamyl acetate was selected and used in formulation of a banana soft drink complex model system. The released volatiles were trapped by tenax and activated carbon. The gas chromatographic-mass spectrometric analysis revealed a gradual decrease (p < 0.05) in the volatile compounds release from the complex banana soft drink model system during storage for 90 days. However, the total content of the volatiles adsorbed by activated carbon trap was higher than that trapped by tenax. The percentage of isoamyl acetate to total volatiles (isoamyl acetate/total volatiles %) was calculated for each sample during storage. A distinct linear correlation was found between the calculated values and storage time (r = 0.97 and 0.92 for volatiles trapped by tenax and activated carbon, respectively). Sample stored for 60 days showed the highest value. These findings confirmed the results of aroma sensory evaluation.