Results 1 - 10 of 63044
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[en] A method is presented of producing boron compounds by thermal decomposition of boron-containing raw material at 1350-2000 deg C in the flow of fuel gases. To intensify the process and increase the product yield, decomposition is performed in a reducing atmosphere with a carbon oxide in the gases of 2.5-20%
[en] The solvolysis mechanism of 4-methylthiobenzoyl chloride (1) was studied by kinetic methods, and these results were compared with 4-methoxy (2) and 3,4,5-trimethoxybenzoyl chlorides (3) reported previously. The analysis of kinetic data was carried out using both the simple and extended Grunwald-Winstein(G-W) equations, thermodynamic parameters, and kinetic solvent isotope effects (KSIE). In fact, 4-methylthiobenzoyl chloride (1) has a sulfur atom which is bigger in size and has more electrons than oxygen in the para-position. The results were obtained and showed typical dispersed plots from the simple (R = 0.939) and extended G-W equations (l/m = 0.33, R = 0.952) for all data, and when the data from some of the most dispersed points were removed, the correlation coefficients were improved remarkably. Thermodynamic parameters revealed that the change of enthalpies were 16.2 ⁓ 17.6 kJ/mol and the change of entropies were -16.5 ⁓ -8.6 J/K-mol. The KSIE of MeOH/MeOD was 1.42. The above results for 4-methylthiobenzoyl chloride supported a unimolecular pathway, or more precisely, a dissociated S_N2 mechanism classified by l/m ratio.
[en] In order to predict thermal hazards of high-energy materials, accurate kinetics constants must be determined. Predictions of thermal hazards for mixtures of high-energy materials require measurements on the mixtures, because interactions among components are common. A differential-scanning calorimeter (DSC) can be used to observe rate processes directly, and isothermal methods enable detection of mechanism changes. Rate-controlling processes will change as components of a mixture are depleted, and the correct depletion function must be identified for each specific stage of a complex process. A method for kinetics measurements on mixed explosives can be demonstrated with Composition B is an approximately 60/40 mixture of RDX and TNT, and is an important military explosive. Kinetics results indicate that the mator process is the decomposition of RDX in solution in TNT with a perturbation caused by interaction between the two components. It is concluded that a combination of chemical kinetics and experimental self-heating procedures provides a good approach to the production of predictive models for thermal hazards of high-energy materials. Systems involving more than one energy-contributing component can be studied. Invalid and dangerous predictive models can be detected by a failure of agreement between prediction and experiment at a specific size, shape, and density. Rates of thermal decomposition for Composition B appear to be modeled adequately for critical-temperature predictions with the following kinetics constants: E = 180.2 kJ mole-1 and Z = 4.62 X 1016 s-1
[en] A one-dimensional biofilm-based reactive transport model is developed to simulate biologically mediated substrate metabolism and contaminant destruction in saturated porous media. The resulting equations are solved by a finite-difference based, three-level, operator-split approach. The numerical solution procedure is stable, easy-to-code, and computationally efficient. As an example problem, biological denitrification and fortuitous CT destruction processes in one-dimensional porous media is studied. The simulation results of the example problem show that the present model can be successfully used to predict biological processes and nutrient/contaminant transport in saturated porous media
[en] Transport of bentazone, isoproturon, linuron, metamitron and metalaxyl were studied under three different flows in macrocosms. The aim was to verify the observations from Part I of the accompanying paper, with an increase in column volume and decrease in chemical and hydraulic load. Very limited breakthrough occurred in the macrocosms for all pesticides, except bentazone, at all flows. From batch degradation experiments, it was observed that the lag time of metamitron and linuron decreased drastically in time for all flows, indicating a growth in the pesticide degrading population. This in contrast to isoproturon and metalaxyl, where an increase in lag time could be observed in time for all flows. From the batch degradation experiments, it could be concluded that the influence of flow on the lag time was minimal and that the inoculation of the pesticide-primed soil had a little surplus value on degradation. - Retention and degradation of pesticides in macrocosms liable to different fluxes.
[en] Tongkat Ali (Eurycoma longifolia) and Ginseng (Panax ginseng) are well known herbs among Asians and have been sought after by Europeans and others for the benefits to health, especially as aphrodisiac and nourishing stimulants. They have high antioxidant level and were reported to be used in the treatment of type II diabetes, as well as for sexual dysfunction in men. Since Tongkat Ali and Ginseng are difficult to cultivate and have a long cultivation period, the bioreactor technology is the alternative method to produce huge amount of raw materials for the herbal industry and continuous supply of standardized raw materials that is not affected by geographical and environmental factors, soil less and free from pesticides and other contaminants. Tongkat Ali and Ginseng extracts from mass propagated roots derived from bioreactor technology have similar profiles as extracts derived from normal cultivation. Liquid Chromatography-Mass Spectrometer (LC-MS) profiles showed presence of active compounds in the Tongkat Ali and Ginseng extracts from the mass propagated roots. Cytotoxicity test using the brine shrimp (Artemia salina Leach) lethality assay, revealed that higher concentration of Tongkat Ali and Ginseng extracts from mass propagated roots did not kill or affect the brine shrimps, implying that the extracts were safe for consumption. Incorporation of combination of Tongkat Ali and Ginseng total extracts from mass propagated roots derived from bioreactor technology energy chocolate confectionery was accepted by the panelists in sensory evaluation and showed that the chocolate product has good potential as a carrier besides beverages and capsules. (author)
[en] Effective Microorganisms solution is being used in various parts of Sindh as fertilizer substitute in the agriculture fields since years. Soils of two locations at Bozdar Wada Khairpur Mir's and Nawazabad farm Mirpurkhas were surveyed. Soil samples were collected at a depth of 0.6 and 6-12 inches. Using analytical methods, given in the Laboratory manual for Soil Analysis, carried out the Physico-chemical analysis. The comparative study of 20-Acre land area of both soils, the one treated with EM (Effective Microorganisms) technology and the other without treatment was carried out. The soil color, soil texture/Particle size analysis, soil moisture, bulk density, soil pH, Electric conductivity, and organic matter were determined. The analysis showed positive results, and it is observed that the quality of the soil was improved by using EM technology. (author)