Elasticity studies of aluminium-substituted highT c superconducting materials

Longitudinal and shear wave velocities of Al-substituted Bi-Sr-Ca-Cu-O superconducting materials prepared by the ceramic technique were measured by the pulse transmission technique. Using the data, several elasticity parameters like Young’s modulus, rigidity modulus, Poisson’s ratio, Debye temperature etc were evaluated. Variation of elasticity parameters with composition has been explained in terms of binding forces between various atoms of the superconducting materials. Temperature variation of longitudinal wave velocity has also been measured and attempts have been made to explain the anomalies at 200 K.     

Quantification of two basic proteins related to a thymic hormone (LSH) and their occurrence in serum of normal and cancerous adults

A quantitative assay for a thymic hormone (LSHr) was developed and utilized for biologic materials. The protein was isolated from tissue extracts or biologic fluids by precipitation with 20% (NH4)2SO4 and reprecipitation with 75% methanol with subsequent disc-electrophoresis on polyacrylamide gel. The proteins on the gel were stained with amido black. One of the two protein bands was readily identified with LSHr by its electrophoretic mobility and agar immunodiffusion tests. Comparison of the intensity of the protein bands obtained from biologic tissues with those of graded amounts of the pure LSHr allowed quantitative estimation. Another basic protein of the serum is found along with LSHr by the above fractionation procedure; it was tentatively named GEM 126 on the basis of its electrophoretic mobility. The total quantity of each of these serum basic proteins and their ratios to each other showed no correlation to any of 20 clinical and laboratory parameters in either healthy or cancerous adults. The lack of correlation between the quantity of serum protein presumed to be LSHr and cancer susceptibility suggests this thymic hormone is not deficient in patients with cancer. Treatment of female cancer patients with radiation and chemotherapy caused a decrease in serum GEM 126 when compared to healthy adults, and untreated or surgically treated cancer patients.     

A 2-D DNS investigation of extinction and reignition dynamics in nonpremixed flame–vortex interactions

Two-dimensional (2-D) DNS investigations of extinction and reignition dynamics during interactions of laminar nonpremixed flames with counterrotating vortex pairs are performed. The length and velocity scales chosen for the vortices are representative of those in the near fields of high-Reynolds-number jets such as those occurring in Diesel engines. The governing equations are solved with sixth-order spatial discretization and fourth-order time integration. Chemistry is modeled as an irreversible single-step reaction. Local extinction along the symmetry axis, followed by reignition, is observed. The extinction is characterized by strong unsteady effects, which are captured well by 1-D transient diffusion flamelet libraries, provided the time-history of the instantaneous scalar dissipation rate is taken into account. On the other hand, reignition is essentially a 2-D phenomenon involving flame–flame interactions, which are favored for smaller vortices and increasing flame curvature. The effects of unsteadiness and curvature on extinction and reignition are carefully assessed through parametric studies involving a range of vortex and flame characteristics. The interaction outcomes are summarized on Reynolds–Damköhler number (Re–Da) diagrams, which show the combined effects of unsteadiness and curvature on extinction and reignition. The implications of the observed interaction outcomes for turbulent combustion modeling in the near fields of jet diffusion flames are discussed.     

Neuroscience instrumentation and distributed analysis of brain activity data: a case for eScience on global Grids

The distribution of knowledge (by scientists) and data sources (advanced scientific instruments), and the need for large‐scale computational resources for analyzing massive scientific data are two major problems commonly observed in scientific disciplines. Two popular scientific disciplines of this nature are brain science and high‐energy physics. The analysis of brain‐activity data gathered from the MEG (magnetoencephalography) instrument is an important research topic in medical science since it helps doctors in identifying symptoms of diseases. The data needs to be analyzed exhaustively to efficiently diagnose and analyze brain functions and requires access to large‐scale computational resources. The potential platform for solving such resource intensive applications is the Grid. This paper presents the design and development of MEG data analysis system by leveraging Grid technologies, primarily Nimrod‐G, Gridbus, and Globus. It describes the composition of the neuroscience (brain‐activity analysis) application as parameter‐sweep application and its on‐demand deployment on global Grids for distributed execution. The results of economic‐based scheduling of analysis jobs for three different optimizations scenarios on the world‐wide Grid testbed resources are presented along with their graphical visualization. Copyright © 2005 John Wiley & Sons, Ltd.     

Phosphorus implantation into 4H-silicon carbide

Sheet resistances in nitrogen- and phosphorus-implanted 4H-SiC are measured to assess the time and temperature dependencies of this variable. In 4H-SiC implanted with 3 × 10¹⁵ cm^?2 nitrogen ions to a depth of 2800 Å, the minimum sheet resistance observed is 534 Ω/□. The minimum sheet resistance in 4H-SiC implanted with 4 × 10¹⁵ cm^?2 phosphorus ions to a depth of 4000 Å is 51 Ω/□, a record low value for any implanted element into any polytype of SiC. Time-independent sheet resistances are observed following anneals at 1700°C for nitrogen and phosphorus samples. Lower temperature anneals produce sheet resistances which decrease monotonically with increasing time of anneal. Overall, sheet resistances from phosphorus-implanted 4H-SiC are an order of magnitude below those measured from nitrogen implanted samples. The response of phosphorus to low-temperature annealing is significant, and sheet resistances below 500 Ω/□ are achieved at 1200°C. Activation of phosphorus is attempted in an oxidizing atmosphere with and without prior argon annealing. A three-hour gate oxidation in wet O₂ at 1150°C, followed by a 30 min argon anneal, produced a sheet resistance of 1081 Ω/□. Oxidation after argon annealing caused sheet resistances to increase by about 20% compared to samples subjected solely to argon annealing. It is also found that oxide growth rates are much higher over phosphorus implanted than over unimplanted 4H-SiC. Reasons for the disparity in sheet resistances between nitrogen and phosphorus implants, and for the difference in oxide growth rates are suggested.     

Microstructural Characterization and Mechanical Properties of Powder Metallurgy Dual Phase Steel Preforms

In order to improve the mechanical properties of powder metallurgy (P/M) ferrite-pearlite steel, a dual phase (DP) ferrite-martensite steel was produced through intercritical annealing of sintered P/M preforms. Mi-crostructures of the sintered and DP steels were examined with optical, scanning and transmission electron microscopes. Mechanical properties were evaluated through hardness measurements and compression tests. Microstructural studies revealed that sintered steel contained polygonal ferrite-pearlite while the DP steel contained polygonal, lath and acicular ferrite along with lath-type martensite as microstructural constituents. In DP steels, with increasing mean preform density, the microstructure contained fine and continuous network of martensite colonies with minimum porosity. The work hardening rate vs plastic strain plots (Jaoul-Crussard analysis) of both the steels revealed typical three stage deformation behaviour for low and high mean preform densities. Compression tests revealed that, DP P/M steel displayed higher strength-plasticity combination than the sintered steel.     

Vapor phase synthesis of methylpyrazine using aqueous glycerol and ethylenediamine over ZnCr2O4 catalyst: Elucidation of reaction mechanism

A novel method has been developed for the synthesis of methylpyrazine (MP) by using aqueous glycerol and ethylenediamine (EDA) over Zn–Cr catalyst derived from hydrotalcite precursors. The X-ray diffraction analysis of the oven-dried Zn–Cr samples synthesized at various pH ranging from 7 to 11 showed hydrotalcite phase whereas the calcined catalysts displayed ZnO and ZnCr₂O₄ phases. The cyclisation activity of Zn–Cr catalyst prepared at pH ~ 9 demonstrated 99.4% conversion of EDA and 94% of glycerol with ~ 72% selectivity to MP at a reaction temperature of 400 °C. This process demonstrates direct utilization of bio-glycerol for the synthesis of MP.