Transmission planning for Indian power grid: a mixed integer programming approach

The paper presents a modeling framework to analyze some important issues associated with operation planning of a power system. Major activities involved in operations planning of large integrated power systems are considered simultaneously to ensure optimal utilization of generation and transmission capacity. The model also examines optimal transmission expansion plans vis-à-vis fuel supply issues. A mixed integer programming model is developed for this purpose and the Indian power system considered. Specific emphasis is on spatial transmission expansion plan for the existing Indian inter-state transmission grid and new transmission links, coordinated operation of the isolated regional grids and system benefits accruing from transmission expansion, enhanced fuel production and supply rescheduling to ensure efficient operation of various generating stations.     

Photoluminescence spectroscopy measurement of elastic strain in heteroepitaxial GaAs films

GaAs films have been grown on silicon and various insulating substrates. These include silicon-on-sapphire, silicon with a buried implanted oxide, and single crystal sapphire. Quantitative comparison of the respective measured shifts in the dominant photoluminescence peaks (7 K) indicates that the GaAs layers deposited on silicon-on-sapphire substrates that have been microstructurally upgraded by the double solid-phase epitaxy process are strain-free.<>     

Device scaling effects on hot-carrier induced interface andoxide-trapped charge distributions in MOSFETs

The influence of channel length and oxide thickness on the hot-carrier induced interface (N_it) and oxide (N_ot) trap profiles is studied in n-channel LDD MOSFET's using a novel charge pumping (CP) technique. The technique directly provides separate N_it and N_ot profiles without using simulation, iteration or neutralization, and has better immunity from measurement noise by avoiding numerical differentiation of data. The N_it and N_ot profiles obtained under a variety of stress conditions show well-defined trends with the variation in device dimensions. The N_it generation has been found to be the dominant damage mode for devices having thinner oxides and shorter channel lengths. Both the peak and spread of the N_it profiles have been found to affect the transconductance degradation, observed over different channel lengths and oxide thicknesses. Results are presented which provide useful insight into the effect of device scaling on the hot-carrier degradation process     

n-Hexane Hydroisomerization over Nano-Crystalline Zeolite Beta

Abstract

Nano-crystalline (about 44 nm in size) zeolite beta was hydrothermally synthesized. Effects of reaction temperature, pressure, hydrogen/n-hexane molar ratio, platinum content of the catalyst, and contact time on n-hexane conversion and selectivity to desired branched-paraffins were studied. At conditions affording the highest yields of branched paraffins, the catalyst did not show any sign of deactivation for 20 h onstream. Performance of Pt, Pd, Ni and Pt + Pd impregnated zeolites was compared. It could be concluded that higher conversions and selectivities may be attributable to the size of the crystals of zeolite beta employed.     

SALT EFFECT IN LIQUID-LIQUID EQUILIBRIA OF ACETIC ACID-WATER-BENZENE SYSTEM

The effect of sodium sulphate, potassium-sulphate and potassium chloride on the distribution of acetic acid between benzene and water at 35°C is reported. Distribution data of the three quaternaries have been determined at salt saturation and unsaturation in each case, as well as the basic ternary in the absence of salt at that temperature. The simple method of Setschenov is used to correlate the distribution data for the salt effect. All the three salts studied are found to have salting out effect for acetic acid in varying degrees.     

Preparation, characterization and in vivo studies of proliposomes containing Cyclosporine A

The present study was undertaken to prepare proliposomes of Cyclosporine A (CsA) to increase its oral bioavailability. The proliposomes were prepared by spraying a solution of CsA, egg lecithin and cremophor EL in methanol-chloroform mixture onto directly compressible lactose (carrier) in a rotary evaporator. A dry free flowing powder of proliposomes was obtained. The dry proliposomal powder was characterized for surface morphology by scanning electron microscopy (SEM). Then the proliposomes were hydrated with distilled water to produce liposomes, which were characterized for particle size distribution, % drug entrapment, and morphological characteristics by transmission electron microscopy (TEM). The liposomes exhibited good entrapment of about 99%. The entrapment of CsA in liposomes was found to be dependent mainly on the drug:lipid ratio. Bioavailability studies were carried out for three different formulations of CsA i.e., free drug suspension; proliposomes derived liposomes and marketed formulation (Pannimun Bioral, Microemulsion) on male SD rats. The results of bioavailability studies indicated that the difference in the mean drug concentration of the free drug and the liposomes was found to be statistically significant (p < 0.05, p value is 0.032). The absorption constant for liposomal product was much greater (10.26 h(-1)) than for free drug solution (1.2 h(-1)) or the marketed sample of microemulsion (2.51 h(-1)) and the volume of distribution was found to be less for liposomes (7629.88 ml/kg) than that of the free drug solution (10971.92 ml/kg) and marketed microemulsion (9012.07 ml/kg). The results of these studies have shown that a stable proliposomal formulation of CsA for oral administration can be prepared which can be easily hydrated into liposomes from which CsA can exert its clinical effects with a better oral bioavailability.     

Twenty years of biochemistry of human P450s: purification, expression, mechanism, and relevance to drugs

Today cytochrome P450 (P450) research is accepted as an integral part of drug development and discovery. Work leading to this point included biochemical studies on P450 in experimental animal models and application to human systems. The development of recombinant expression systems has been an important part of the progress, and in this article we describe some recently developed bacterial systems that can be used for the production of metabolites, genotoxicity testing, and screening in random mutagenesis work. Rate-limiting aspects of P450 reactions vary with particular systems, and further investigations are in order. Non-ionic detergents have been utilized widely in P450 purification work; these compounds are now shown to be substrates for P450s. These oxidations are not only of fundamental interest in expanding the repertoire of P450 substrates but have significance in light of human exposure to these compounds.     

MutY catalytic core, mutant and bound adenine structures define specificity for DNA repair enzyme superfamily

The DNA glycosylase MutY, which is a member of the Helix-hairpin-Helix (HhH) DNA glycosylase superfamily, excises adenine from mispairs with 8-oxoguanine and guanine. High-resolution crystal structures of the MutY catalytic core (cMutY), the complex with bound adenine, and designed mutants reveal the basis for adenine specificity and glycosyl bond cleavage chemistry. The two cMutY helical domains form a positively-charged groove with the adenine-specific pocket at their interface. The Watson-Crick hydrogen bond partners of the bound adenine are substituted by protein atoms, confirming a nucleotide flipping mechanism, and supporting a specific DNA binding orientation by MutY and structurally related DNA glycosylases.     

Role of the B cell antigen receptor in antigen processing and presentation. Involvement of the transmembrane region in intracellular trafficking of receptor/ligand complexes

To study the role of the B cell Ag receptor (membrane-bound Ig [mIg]) in Ag processing and presentation, we have generated several Ig transfectants that express transfected TEPC-15 idiotype (T15-Id) mIgM with phosphorylcholine (PC)-binding specificity. The wild-type Ig transfectant is able to present a specific Ag (e.g., PC-conjugated hen egg-white lysozyme [PC-HEL]) more efficiently than a nonspecific Ag (HEL) to a T cell hybridoma recognizing an epitope on the HEL molecule. A substitution in the entire spacer, transmembrane, and cytoplasmic region of mIg with an equivalent region of I-A alpha chain completely abolishes this mIg-enhanced Ag presentation. Experiments with the wild-type and substituted variant Ig transfectants suggest that this substitution may interfere with normal intracellular trafficking of mIg after cross-linking with specific Ag or antibodies specific for the mIg (anti-T15-Id mAb). Prolonged treatment of the wild-type Ig transfectants with specific Ag or anti-T15-Id mAb reduces the surface expression of T15-Id mIgM and leads to an accumulation of T15-Id mIgM inside the cells. The reduced surface expression and the elevated cytoplasmic accumulation of T15-Id mIgM are not observed in the variant Ig transfectant. Despite the ability of the variant to endocytose ligands similarly to the wild-type Ig transfectant, this variant displays a higher rate of recycling of the mIg/ligand complexes back to the cell surface and a lower rate of degradation of the ligands. These abnormalities may be responsible for the deficiency in mIg-mediated enhancement of Ag presentation in the variant Ig transfectant. Therefore, our results suggest that the transmembrane region of mIg is involved in intracellular trafficking of receptor/ligand complexes and that proper delivery and handling of internalized Ag are required for the enhanced presentation of specific Ag by B cells.