Effect of sintering on microstructure and mechanical properties of nano-TiO2 dispersed Al65Cu20Ti15 amorphous/nanocrystalline matrix composite

Mechanically alloyed Al₆₅Cu₂₀Ti₁₅ amorphous alloy powder with or without 10 wt% nano-TiO₂ dispersion was consolidated by isothermal spark plasma sintering in the range 200–500 °C with pressure up to 50 MPa. Selected samples were separately cold compacted with 50 MPa pressure and sintered at 500 °C using controlled atmosphere resistance and microwave heating furnaces. Phase and microstructural evolution at appropriate stages of mechanical alloying/blending and sintering was monitored by X-ray diffraction and scanning and transmission electron microscopy. Measurement and comparison of relevant properties (density/porosity, microhardness and yield strength) of the sintered compacts suggest that spark plasma sintering is the most appropriate technique for developing nano-TiO₂ dispersed amorphous/nanocrystalline Al₆₅Cu₂₀Ti₁₅ matrix composite for structural application.     

Temperature-dependent refractive index of semiconductors

A single-oscillator Lorentz model is applied to four different semiconductors having diamond-like crystal structure to describe the temperature dependence of their refractive index between 300 and 600 K. Theoretical results are compared to previous experiments and to experiments carried out in this study for Si, Ge, GaAs, and InP. An efficient experimental method is also presented, enabling fast measurements of the refractive index of materials. Using the Yu-Brooks formalism and the energy bandgap at the X-point of the Brillouin zone, the temperature-dependent refractive indices are calculated and they agree well with experiments, particularly, considering the simplicity of the Lorentz model. However, there are discrepancies between the theory and experiment at high temperatures (near 600 K) in certain cases. This discrepancy may be due to the single-oscillator approximation. Additionally the effect of “self-energy” on the temperature dependence of the energy bandgap, such as the temperature-dependent damping of the oscillation of electrons, can be significant at higher temperatures.     

Effect of clay on vulcanization,network structure,and technical properties of natural rubber in the presence of silane coupling agents

The presence of silane coupling agents do not cause a change in network structure in clay-filled natural rubber vulcanizates, both in sulfur vulcanization and peroxide vulcanization systems. However, the improvement in technical properties in the presence of silane coupling agents is more in the peroxide vulcanization system and is accompanied by enhanced polymer—filler interactions. Scanning electron microscopy (SEM) studies have been made in order to understand the failure behavior.     

Incorporating Events into Cross-Organizational Business Processes

Because Web-scale processes are inherently cross-organizational, they require the robust enactment of interactions among autonomous parties. However, specifying the processes involved is difficult. To overcome this obstacle, the authors use a business protocol that lets the applicable events and responses vary based on where the process is deployed and the infrastructure and IT applications installed therein. Treating events and business logic as separate concerns also yields clearer models and improves reusability. The authors describe the architecture and tools and outline a methodology by which each participant in a process can define, detect, and respond to events.     

Multivariate statistical techniques for the evaluation of spatial and temporal variations in water quality of Gomti River (India)--a case study

This case study reports different multivariate statistical techniques applied for evaluation of temporal/spatial variations and interpretation of a large complex water-quality data set obtained during monitoring of Gomti River in Northern part of India. Water quality of the Gomti River, a major tributary of the Ganga River was monitored at eight different sites selected in relatively low, moderate and high pollution regions, regularly over a period of 5 years (1994-1998) for 24 parameters. The complex data matrix (17,790 observations) was treated with different multivariate techniques such as cluster analysis, factor analysis/principal component analysis (FA/PCA) and discriminant analysis (DA). Cluster analysis (CA) showed good results rendering three different groups of similarity between the sampling sites reflecting the different water-quality parameters of the river system. FA/PCA identified six factors, which are responsible for the data structure explaining 71% of the total variance of the data set and allowed to group the selected parameters according to common features as well as to evaluate the incidence of each group on the overall variation in water quality. However, significant data reduction was not achieved, as it needed 14 parameters to explain 71% of both the temporal and spatial changes in water quality. Discriminant analysis showed the best results for data reduction and pattern recognition during both temporal and spatial analysis. Discriminant analysis showed five parameters (pH, temperature, conductivity, total alkalinity and magnesium) affording more than 88% right assignations in temporal analysis, while nine parameters (pH, temperature, alkalinity, Ca-hardness, DO, BOD, chloride, sulfate and TKN) to afford 91% right assignations in spatial analysis of three different regions in the basin. Thus, DA allowed reduction in dimensionality of the large data set, delineating a few indicator parameters responsible for large variations in water quality. This study presents necessity and usefulness of multivariate statistical techniques for evaluation and interpretation of large complex data sets with a view to get better information about the water quality and design of monitoring network for effective management of water resources.     

Effect of pH on the extra cellular synthesis of gold and silver nanoparticles by Saccharomyces cerevisae

In the present study, the synthesis of gold and silver nanoparticles was investigated using the culture supernatant broth of the yeast Saccharomyces cerevisae. Gold nanoparticles were formed within 24 hours of gold ion coming in contact with the culture supernatant broth. In case of silver the reduction process took 48 hours. The synthesized nanoparticles were investigated by UV-Visible spectroscopy. Distinct surface plasmon peaks were observed at 540 nm and 415 nm for gold and silver nanoparticles respectively. Bio-TEM micrographs of the synthesized nanoparticles indicated that the particles were well dispersed and near spherical in shape. The size range of the gold and silver nanoparticles was around 20-100 nm and 5-20 nm respectively. XRD patterns showed the presence of three distinct peaks corresponding to gold and silver nanoparticles respectively. A pH range of 4 to 6 and 8 to 10 favored optimum synthesis of gold and silver nanoparticles respectively. The process of reduction being extra cellular could be used in future for downstream processing in an eco friendly manner.     

Comparative study of porphyrin derivatives in monolayers at the air-water interface and in Langmuir-Blodgett films

The orientation and aggregation of various porphyrin derivatives at the air-water interface and in Langmuir-Blodgett films were investigated. Monolayer properties of these molecules, where long alkyl chain(s) were covalently bound through different functionality of varying hydrophilicity were studied by measuring surface pressure area isotherms. Such derivatives, where ether functionality (functionalities) was (were) used for linking long alkyl chain(s), did not form uniform monolayer; instead they were found to form multilayer clusters or aggregates on the water surface. On the other hand, porphyrin derivative functionalized at the four peripheral phenyl rings with eight hexadecyl ether chains formed stable spherical vesicles when deposited on mica. Tetra N-alkyl pyridinium porphyrins with long alkyl chain were found to form various phases on the water surface. Evidence of transition from horizontal orientation to vertical orientation of porphyrin rings of porphyrin molecules having C₁₄ chains was observed. This type of transition was lost with the porphyrin molecule with a relatively smaller chain (C₈).