Rocking stiffness of mounting arrangements in electrical cabinets and control panels

Several studies have shown that the consideration of a rigid body-rocking mode in a cabinet is necessary to evaluate accurate incabinet spectra. Observations from finite element analyses are used to study cabinet rocking behavior and to show that accurate representation of the boundary conditions at the cabinet base is essential in the evaluation of correct rocking mode. Simple formulations for evaluating the rocking stiffness are developed by conducting detailed analytical studies for three different types of cabinet mounting arrangements. Availability of these formulations enables incorporation of a cabinet rocking mode in the Ritz vector approach [Nucl. Eng. Des. 190 (1990) 225] for evaluating the cabinet dynamic properties in significant mode and for generating the incabinet response spectra.     

CVD growth and characterization of 3C-SiC thin films

Cubic silicon carbide (3C-SiC) thin films were grown on (100) and (111) Si substrates by CVD technique using hexamethyldisilane (HMDS) as the source material in a resistance heated furnace. HMDS was used as the single source for both Si and C though propane was available for the preliminary carbonization. For selective epitaxial growth, patterned Si (100) substrates were used. The effect of different growth parameters such as substrate orientation, growth temperature, precursor concentration, etc on growth was examined to improve the film quality. The surface morphology, microstructure and crystallinity of grown films were studied using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS).     

CtpB Facilitates Mycobacterium tuberculosis Growth in Copper-Limited Niches

Copper is required for aerobic respiration by Mycobacterium tuberculosis and its human host, but this essential element is toxic in abundance. Copper nutritional immunity refers to host processes that modulate levels of free copper to alternately starve and intoxicate invading microbes. Bacteria engulfed by macrophages are initially contained within copper-limited phagosomes, which fuse with ATP7A vesicles that pump in toxic levels of copper. In this report, we examine how CtpB, a P-type ATPase in M. tuberculosis, aids in response to nutritional immunity. In vitro, the induced expression of ctpB in copper-replete medium inhibited mycobacterial growth, while deletion of the gene impaired growth only in copper-starved medium and within copper-limited host cells, suggesting a role for CtpB in copper acquisition or export to the copper-dependent respiration supercomplex. Unexpectedly, the absence of ctpB resulted in hypervirulence in the DBA/2 mouse infection model. As ctpB null strains exhibit diminished growth only in copper-starved conditions, reduced copper transport may have enabled the mutant to acquire a “Goldilocks” amount of the metal during transit through copper-intoxicating environments within this model system. This work reveals CtpB as a component of the M. tuberculosis toolkit to counter host nutritional immunity and underscores the importance of elucidating copper-uptake mechanisms in pathogenic mycobacteria.     

Broad line proton magnetic resonance investigations on solid L-alanine: Crystal structure and molecular reorientations

Broad line NMR investigations on solid L -alanine have been carried out over the temperature range 77°K to 493°K. A comparison between the observed and theoretical values of the second moment has been made, to provide check on the crystal structure and to study the molecular motions. Investigations reveal the presence of NH₃ group motion at about 230°K. The activation energy for NH₃ group rotation has been computed to be 7.19 ± 1.0 kcal/mole. The crystal lattice remains rigid below 230°K. There is a possibility of torsional oscillation of the CH₃ group at about 352°K.     

Preparation of Trimethylsilyl Derivatives of Polysaccharides

Trimethylsilyl derivatives of starch, amylose, amylopectin, and glycogen have been prepared by using hexamethyldisilazane as the silylating reagent and formamide as solvent. The degree of silylation ranged from 0.9 to 2.2 and is believed to be dependent on the structure and solubility of the polysaccharide. An important property of these trimethylsilyl derivatives is their complete solubility in common organic solvents like benzene, toluene, chloroform, etc.     

Stem Cell Models for Cancer Therapy

Metastatic progression of female breast and colon cancer represents a major cause of mortality in women. Spontaneous/acquired resistance to conventional and targeted chemo-endocrine therapy is associated with the emergence of drug-resistant tumor-initiating cancer stem cell populations. The cancer-initiating premalignant stem cells exhibit activation of select cancer cell signaling pathways and undergo epithelial–mesenchymal transition, leading to the evolution of a metastatic phenotype. The development of reliable cancer stem cell models provides valuable experimental approaches to identify novel testable therapeutic alternatives for therapy-resistant cancer. Drug-resistant stem cell models for molecular subtypes of clinical breast cancer and for genetically predisposed colon cancer are developed by selecting epithelial cells that survive in the presence of cytostatic concentrations of relevant therapeutic agents. These putative stem cells are characterized by the expression status of select cellular and molecular stem cell markers. The stem cell models are utilized as experimental approaches to examine the stem-cell-targeted growth inhibitory efficacy of naturally occurring dietary phytochemicals. The present review provides a systematic discussion on (i) conceptual and experimental aspects relevant to the chemo-endocrine therapy of breast and colon cancer, (ii) molecular/cellular aspects of cancer stem cells and (iii) potential stem-cell-targeting lead compounds as testable alternatives against the progression of therapy-resistant breast and colon cancer.     

A new extrinsic dc model for high speed lattice matched InAlAs/InGaAs/InP HEMT with a predicted 135 GHz cut-off frequency

Extrinsic lattice matched InAlAs/InGaAs/InP HEMT model, incorporating the parasitic source and drain resistance, for very high frequency application is developed. The current voltage characteristics and the transconductance have been evaluated and the influence of carrier concentration dependent mobility on frequency has also been analyzed. A cut-off frequency of 135 GHz is obtained.     

Oxidation of Starch by Hydrogen Peroxide in the Presence of UV Light-Part II

Various reaction variables in the hydrogen peroxide oxidation of starch in the presence of UV light have been investigated. Higher carboxyl and carbonyl contents of oxystarches were obtained under acidic than under alkaline conditions. Extent of oxidation was found to increase with time. Increasing the concentration of hydrogen peroxide results in an increase in the carboxyl and carbonyl contents. Apparently, air has no effect on the degree of oxidation whereas, oxygen seems to accelerate it.     

Hybrid system for handling premature convergence in GA – Case of grammar induction

Grammar induction (also known as grammar inference or language learning) is the process of learning grammar from training data. This paper presents hybrid genetic algorithm (GA) Tool for handling premature convergence for the case of grammar induction. The tool is developed in Java and the results are tested for the set of 20 languages. It is an effort towards introduction of a hybrid GA system where the collection of more than one type of reproduction methods is used for the grammar induction. Paper also includes the discussion on the various approaches used by author for handling the premature convergence problem in using GA.     

Teaching to Facilitate the Transfer of Learning [Educator's Corner]

An amusing anecdote that is old (having appeared in Esquire and Reader's Digest over half a century ago) concerns a man who experienced severe motion sickness during train travel whenever he would ride backwards, i.e., sat facing the rear of the train; so he learned to exchange such a seat by requesting the passenger sitting opposite to him. When he got off the train very sick and nauseated one day, his friend receiving him at the train station asked what was wrong. He replied that he had been riding the train backwards. Why didn't you ask the person sitting across from you to change seats with you? asked his friend. How could I, said the traveler, There wasn't anybody in that seat.