Wastewater treatment using photo-impinging streams cyclone reactor: Computational fluid dynamics and kinetics modeling

A photo impinging streams cyclone reactor has been used as a novel apparatus in photocatalytic degradation of organic compounds using titanium dioxide nanoparticles in wastewater. The operating parameters, including catalyst loading, pH, initial phenol concentration and light intensity have been optimized to increase the efficiency of the photocatalytic degradation process within this photoreactor. The results have demonstrated a higher efficiency and an increased performance capability of the present reactor in comparison with the conventional processes. In the next step, residence time distribution (RTD) of the slurry phase within the reactor was measured using the impulse tracer method. A CFD-based model for predicting the RTD was also developed which compared well with the experimental results. The RTD data was finally applied in conjunction with the phenol degradation kinetic model to predict the apparent rate coefficient for such a reaction.     

Dynamic Mechanical Thermal Analysis and Rheological Properties of Synthesized Polypropylene Reactor Blends Using Homogeneous Binary Metallocene Catalyst

A homogenous binary metallocene catalytic system comprising of isospecific rac-Me₂Si(2-Me-4-Ph In)₂ZrCl₂(I) producing high molecular weight isotactic polypropylene and oscillating (2-Ph In)₂ZrCl₂(II) precursor producing low isotactic elastomer polypropylene at three varying molar ratios of two types of catalysts was used to synthesize polypropylene reactor blends. Dynamic mechanical thermal analysis and rheological properties along with molecular weight of synthesized polypropylene reactor blends were studied and correlations among these properties were established. It was found that molar ratio of catalysts is a significant factor in determination of molecular weight and its distribution. The produced polymers with unimodal molecular weight distribution showed intermediate modulus during dynamic mechanical thermal experiment, while the ones with bimodal molecular weight distribution exhibited a kind of phase separation at low temperature. Depending on strength of the developed structures, determined by the presence of interfacial connectors, the modulus could be adjusted. Origins of other types of relaxations and their differences for each type of the developed products were discussed in detail. From rheological results and particularly the relaxation curves, the characteristics of the chain structure of the synthesized reactor blends could be resolved. It was revealed that one of the synthesized polymers had long chain branches unlike the rest of the samples having linear chain structure.     

TiC-Maraging stainless steel composite： microstructure, mechanical and wear properties

Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy （P/M）. TiC-maraging stainless steel composites with theoretical density 〉97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of （core-rim structure） spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was at- tributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.     

Rehabilitating acid soils for increasing crop productivity through low-cost liming material

Productivity of red and lateritic soils is low because of their acidity and deficiencies in few essential nutrients viz., nitrogen, phosphorus, calcium, zinc, boron, molybdenum etc. We compared the effectiveness of basic slag, a low-cost liming material, with that of calcite as an ameliorant for these soils using mustard followed by rice as test crops. Experiments were conducted with three levels of each of basic slag and calcite along with a control on farmers' fields at 14 different locations. Influence of farmyard manure (FYM) and poultry manure (PM) on the effectiveness of the slag was also tested. On an average, basic slag performed better than calcite in increasing yields of both mustard and rice and left over higher amounts of available Ca, Si and Zn in residual soils. The slag also improved N, P, K and Ca nutrition of mustard and Si and Zn nutrition of rice with a favorable benefit:cost (B:C) ratio over the calcite (4.82 vs. 1.44). Effectiveness of the basic slag improved when it was applied in combination with FYM or PM (B:C, 5.83 and 6.27). Basic slag can, therefore, be advocated for use in the acidic red and lateritic soils for economically improving their productivity.     

Molecular Dynamics Study of Surface Anisotropy in $$\hbox {Ag}_{60}\; \hbox {Cu}_{40}$$ Alloy at Nanoscale

In the present study, molecular dynamics simulation has been performed to investigate the anisotropic behavior of free standing \(\hbox {Ag}_{60}\; \hbox {Cu}_{40}\) nanorods. We choose different orientations with various cross sections to study the dynamics of thermal behavior of \(\hbox {Ag}_{60}\; \hbox {Cu}_{40}\) nanorods. The system is modeled using embedded atom method potentials. The radial distribution functions are analyzed to reveal the dynamic evolution of the structural behavior of nanorods with different orientations and sample sizes. The total energy and mean square displacement is also calculated to characterize the melting phenomenon of various samples. The melting temperature of the nanorods is found to be significantly size and orientation dependent, and it increases with the increase in cross-sectional area. The nanorods with low-index crystallographic surfaces such as (110) exhibit lowest melting temperature as compared to compact surfaces (111).     

Heterosynaptic long-term facilitation of sensory-evoked responses in the auditory cortex by stimulation of the magnocellular medial geniculate body in guinea pigs.

The magnocellular nucleus of the medial geniculate body (MGm) develops physiological plasticity during classical conditioning and may be involved in learning-induced receptive field plasticity in the auditory cortex. To determine the ability of the MGm to produce long-term modification of evoked activity in the auditory cortex, the experimenters paired electrical stimulation of the MGm with preceding clicks in adult guinea pigs under barbiturate anesthesia. The amplitudes of average click-evoked potentials were significantly facilitated in all Ss. Facilitation endured for 2 hrs, the maximum duration of recording. Sham-stimulated control guinea pigs did not develop facilitation. Thus, a nonlemniscal thalamic sensory nucleus can produce enduring facilitation of sensory-evoked activity in primary sensory cortex, suggesting that long-term physiological plasticity in the sensory cortex during learning may involve nonlemniscal thalamic mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)