Thermal,FT-IR and SHG efficiency studies of L-arginine doped KDP crystals

Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material with different applications. Since most of the amino acids exhibit NLO property, it is of interest to dope them in KDP. In the present study, amino acid L-arginine was doped in KDP. The doping of L-arginine was confirmed by FT-IR and paper chromatography. Thermogravimetry suggested that as the amount of doping increases the thermal stability decreases as well as the value of thermodynamic and kinetic parameters decreases. The second harmonic generation (SHG) efficiency of L-arginine doped KDP crystals was found to be increasing with doping concentration of L-arginine. The results are discussed here.     

Comparative study of the electronic structure of natural and synthetic rubies using XAFS and EDAX analyses

We have studied the Cr-K-edge XANES and EXAFS in natural Indian rubies from two sources and a synthetic ruby at ESRF. Weight % of various constituents in them is determined using EDAX measurements. Taking the results from the three techniques together we are able to demonstrate their feasibility in quantitative study of precious stones.     

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.<>     

The prediction of critical mass flux by the use of fanno lines

Fanno lines have been used extensively for the prediction of the critical flow in homogeneous single phase fluids. This paper attempts to apply this method for the prediction of critical flow in a two-phase evaporative fluid. Homogeneous and slip conditions are examined for water-steam flow. The criterion of critical flow is set as the turning point of the constant mass flow rate line in the entropy-enthalpy diagram. The proposed criterion gives very good agreement of the critical mass flux with experimental data, and with previous models on critical flows.     

Assessment of solar applications for transfer of technology a case of solar pump

For the large and increasing rural population in the developming countries, decentralized solar applications could be relevant. However, new solar technologies being developed in the laboratories presently have to ultimately be acceptable in the field conditions. The conditions which have to be satisfied before the solar applications could be acceptable are discussed. The solar pump is examined in detail in particular due to the interest expressed by many developing countries in this specific application. A comparative techno-economic analysis is carried out for solar pumps and diesel pumps which considered escalation of the diesel price and factors related to climate, geography, locale, social and institutional environment for two types of uses namely for drinking water and for irrigation. It seems unlikely that a solar pump could compete with the diesel engine before the costs are brought down by a factor of 20–50 for irrigation purposes. However, for obtaining the drinking water the cost reduction required is by a factor less than 10 than currently charged for the prototypes. Although specific example of India is taken the matters are relevant to most developing countries. The issues discussed for the case of a solar pump are also relevant to other solar applications used only for seasonal purposes since the capital costs are high and operating diesel pumps during the season would be cheaper for several decades.     

Performance and hot-carrier reliability of 100 nm channel lengthjet vapor deposited Si3N4 MNSFETs

Metal-nitride-semiconductor FETs (MNSFETs) having channel lengths down to 100 mm and a novel jet vapor deposited (JVD) Si₃N₄ gate dielectric have been fabricated and characterized. When compared with MOSFETs having a thermal SiO₂ gate insulator, the MNSFETs show a comparable drain current drive, transconductance, subthreshold slope and pre-stress interface quality. A novel charge pumping technique is employed to characterize the hot-carrier induced interface-trap generation in MNSFETs and MOSFETs. Under identical substrate current during stress, MNSFETs show less interface-state generation and drain current degradation, for various channel lengths, stress times and supply voltages, despite the fact that the Si-Si₃N₄ barrier (2.1 eV) is lower than the Si-SiO₂ barrier (3.1 eV). The time and voltage dependence of hot-carrier degradation has been found to be distinctly different for MNSFETs compared to SiO₂ MOSFETs     

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     

Formulation and evaluation of clotrimazole transdermal spray

Context: Transdermal spray (TS) of clotrimazole (CTZ) was formulated to improve the drug transport through the skin up to 12?h to achieve the antifungal efficacy.

Objective: The aim of present study was to formulate and evaluate antifungal transdermal spray to improve the permeation of clotrimazole across the skin and to decrease the dosing frequency in fungal infection.

Materials and methods: Different ratios of ethanol and acetone and various grades of eudragit and ethyl cellulose were evaluated according to six criteria: viscosity, drying time, stickiness, appearance and integrity on skin and water washability. Propylene glycol (PG) and polyethylene glycol 400 (PEG 400) were used in the study as plasticizer and solubilizer. The TS was evaluated for in vitro drug release, spray angle, spray pattern, average weight per dose, pH, drug content, evaporation time, leak test and antifungal efficacy study.

Results and discussion: Eudragit E100 and blend of ethanol and acetone (80:20) satisfied the desired criteria. The selection of optimized batch was based on the results of in vitro drug release, spray pattern and spray angle. The optimized batch showed the spray angle <85° and uniform spray pattern. The formulation containing PG showed higher drug release than PEG 400. The inclusion of eutectic mixture consisting of camphor and menthol (1:1) showed improved drug transport through the rat skin and larger mean zone of inhibition indicating the improved antifungal efficacy.

Conclusion: The TS of CTZ can be an innovative and promising approach for the topical administration in the fungal diseases.     

Application of in-line viscometer for in-process monitoring of microcrystalline cellulose-carboxymethylcellulose hydrogel formation during batch manufacturing

Physical stability and consistent dose delivery of pharmaceutical suspension formulations comprised of microcrystalline cellulose (MCC) and sodium carboxymethylcellulose (NaCMC) hydrogels is dependent on their rheological properties. To obtain the desired rheological characteristics, good control of the hydrogel dispersion in water is required. The goal of this study was to evaluate whether the XL7-100 Process Viscometer could be employed as a process analytical technology (PAT) tool to monitor the dispersion process in real time during batch manufacturing. Using this instrument, viscosity profiles were measured during the hydrogel processing for a range of operating conditions. It was confirmed that viscosity obtained by the XL7-100 Process Viscometer in the off-line mode, could be linearly correlated to that of the conventional Brookfield viscometer. In addition, the XL7-100 Process Viscometer was able to detect variations in the hydrogel concentrations as well as process conditions in real time. Under fixed operating conditions, the dynamic viscosity profile showed low variability and good inter-batch reproducibility for a properly dispersed hydrogel. For a well-validated mixing process, an off-trend in-line viscosity reading may be indicative of batch failure or poor dispersion homogeneity. Therefore, the in-line viscometer can be used in manufacturing to monitor the batch to batch consistency. However, it is not proven to be able to characterize the real-time structure formation of the hydrogel. It is recommended that the in-line viscometer be used as a complimentary tool along with the off-line rheometer for both efficient and effective in-process quality control of the MCC & NaCMC hydrogel dispersion.