Adsorptive stripping differential pulse voltammetric determination of venlafaxine and desvenlafaxine employing Nafion–carbon nanotube composite glassy carbon electrode

A Nafion-carbon nanotube-modified glassy carbon electrode (NAF-CNT-GCE) was developed for the determination of venlafaxine (VF) and desvenlafaxine (DVF). The electrochemical behavior of both these molecules was investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and adsorptive stripping differential pulse voltammetry (AdSDPV). The surface morphology of the electrodes has been studied by means of scanning electron microscopy (SEM). These studies revealed that the oxidation of VF and DVF is facilitated at NAF-CNT-GCE. After optimization of analytical conditions employing this electrode at pH 7.0 in Britton–Robinson buffer (0.05 M) for VF and pH 5.0 in acetate buffer (0.1 M) for DVF, the peak currents for both the molecules were found to vary linearly with their concentrations in the range of 3.81 × 10⁻⁸–6.22 × 10⁻⁵ M for VF and 5.33 × 10⁻⁸–3.58 × 10⁻⁵ M for DVF. The detection limits (S/N = 3) of 1.24 × 10⁻⁸ and 2.11 × 10⁻⁸ M were obtained for VF and DVF, respectively, using AdSDPV. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. The proposed method was employed for the determination of VF and DVF in pharmaceutical formulations, urine and blood serum samples.     

Study of electrochemically grown copper indium diselenide (CIS) thin films for photovoltaic applications

CIS thin films have been grown electrochemically from an aqueous electrolyte at room temperature on fluorine doped tin oxide coated glass substrate at different deposition potentials ranging from ?0.7 to ?1.0 V versus Ag/AgCl reference electrode. Cyclic voltammetry was studied at slow scan rate to optimize the deposition potential. The thin film samples were selenized in a tubular furnace at 400 °C for 20 min. X-ray diffraction and Raman analysis was used to study the structural properties. Optical absorption, scanning electron microscopy and energy dispersive X-ray analysis (EDAX) have been used to investigate the band-gap, surface morphology and compositional analysis. Electrical properties were studied with the help of current–voltage measurements. Conductivity type for CIS thin films was studied by using photo-electrochemical study. The prominent reflections (112), (204/220) and (312/116) of tetragonal chalcopyrite CIS have been revealed for all as-grown and selenized samples. The energy band gap of the selenized CIS thin film deposited at various deposition potentials was found to be ~1.03 to 1.24 eV. Granular, uniform and void free surface was observed in as-prepared sample, while large clusters were noticed in selenized samples. EDAX results reveal that the stoichiometric CIS thin film are deposited ?0.8 V, however, Cu-rich and In-rich CIS layers were grown at lower and higher cathodic deposition potentials, deviated from ?0.8 V. The values ideality factor (η) calculated from I–V measurements were found to be decreased upon selenization. The Raman spectra of stoichiometric CIS thin film shows dominant A1 mode with spectral features sensitive to the microcrystalline quality of the layers. A ordered defect compound layer and secondary phases of CuSe are observed in In-rich and Cu-rich CIS layers, respectively.     

Synergism of microwave irradiation and enzyme catalysis in synthesis of isoniazid

Isoniazid is a useful antitubercular drug widely employed in combination therapy with rifampicin. The synthesis of isoniazid from ethyl isonicotinate and hydrazine hydrate was studied in non‐aqueous media via lipase‐catalyzed hydrazinolysis under both conventional heating and microwave irradiation by using different supported lipases. Among three different commercial lipases used, namely Novozym 435 (Candida antarctica lipase), Lipozyme RM IM (Rhizomucor miehei lipase) and Lipozyme TL IM (Thermomyces lanuginosus lipase), Novozym 435 was found to be the most effective, with conversion of 54% for equimolar concentrations at 50 °C in 4 h. The rate of reaction as well as final conversion increased synergistically under microwave irradiation in comparison with conventional heating, which showed 36.4% conversion, even after 24 h, for the control experiment. Effects of various process parameters such as speed of agitation, catalyst loading, substrate concentration, product concentration and temperature were studied. A kinetic model is also described. Copyright © 2007 Society of Chemical Industry     

Determinants of metabolic acidosis among hemodialysis patients

Metabolic acidosis is frequently present, poorly controlled, and associated with adverse effects among hemodialysis patients. Potential determinants of metabolic acidosis include endogenous acid production, administration of alkali, neutralization of acid by buffers, dilution of serum bicarbonate by interdialytic fluid gain, and loss of bicarbonate in stool. Understanding the relative importance of these determinants may help guide efforts to manage metabolic acidosis. We used chart abstraction, patient interviews, and laboratory testing to assess variables related to acid production (protein breakdown), alkali administration (dialysis dose, missed treatments, dialysate bicarbonate concentration, oral bicarbonate supplements), acid buffering (phosphorus binders), dilution of bicarbonate (interdialytic weight gain), and loss of bicarbonate in stool (diarrhea) for 190 randomly selected patients from 44 hemodialysis facilities. We used multivariate analyses to determine which potential determinants were independently associated with predialysis serum bicarbonate levels. Of all patients, 30% had metabolic acidosis (serum bicarbonate level <22 mEq/L). On multivariate analysis, metabolic acidosis was more likely with increased protein nitrogen appearance (odds ratio [OR] 1.60 per 0.2 g/kg/day, p=0.001) and less likely with increased Kt/V (OR 0.61 per 0.20 increase in Kt/V, p<0.001) and with increased calcium carbonate use (OR 0.38 per 2 g/day, p=0.003). Key determinants of metabolic acidosis among hemodialysis patients are protein breakdown, dialysis dose, and specific phosphorus binders. Further work is needed to develop interventions to address these determinants.     

Solid lipid nanoparticles of ondansetron HCl for intranasal delivery: development, optimization and evaluation

The present investigation deals with the development and statistical optimization of solid lipid nanoparticles (SLNs) of ondansetron HCl (OND) for intranasal (i.n.) delivery. SLNs were prepared using the solvent diffusion technique and a 2(3) factorial design. The concentrations of lipid, surfactant and cosurfactant were independent variables in this design, whereas, particle size and entrapment efficiency (EE) were dependent variables. The particle size of the SLNs was found to be 320-498?nm, and the EE was between 32.89 and 56.56?%. The influence of the lipid, surfactant and cosurfactant on the particle size and EE was studied. A histological study revealed no adverse response of SLNs on sheep nasal mucosa. Transmission electron microscopic analysis showed spherical shape particles. Differential scanning calorimetry and X-ray diffraction studies indicated that the drug was completely encapsulated in a lipid matrix. In vitro drug release studies carried out in phosphate buffer (pH 6.6) indicated that the drug transport was of Fickian type. Gamma scintigraphic imaging in rabbits after i.n. administration showed rapid localization of the drug in the brain. Hence, OND SLNs is a promising nasal delivery system for rapid and direct nose-to-brain delivery.     

Zirconium based bulk metallic glass / tungsten fibre composite — fabrication and characterization

The aim of the present work was to fabricate and characterize a composite consisting of Zr based bulk metallic glass as the matrix and W fibres as the reinforcement. This kind of composite because of its very high impact toughness has got widespread applications including in some strategic areas. The glass forming Zr₅₂Ti₆Al₁₀Cu₁₈Ni₁₄ (at%) alloy was selected for this purpose because of its high glass forming ability and tungsten was selected as the reinforcing medium because of its high melting point, non reactivity with the liquid phase and high strength. The composite was fabricated in a unique way where a preform of W wires was made and the glass forming alloy was vitrified with this preform as reinforcement using the copper mold casting technique The composite produced was characterized using optical microscopy and EPMA studies. Compression testing was done to evaluate the mechanical properties of the composite.     

Effect of complexing agent on the chemically deposited ZnS thin film

Zinc sulfide (ZnS) thin films have been deposited onto fluorine doped tin oxide and microscopic glass substrates from an aqueous alkaline reaction by chemical bath deposition. The effect of concentrations of hydrazine hydrate (HyH) (complexing agent) on the deposit is studied. X-ray analysis confirm the growth of nanocrystalline ZnS thin films with reflections (111), (220) and (311) correspond to cubic crystalline phase. TEM results support the growth of cubic ZnS layers. The energy band gap was successfully tailored from 2.77 to 3.80 eV. Photoluminescence study indicates a strong band-edge emission with some defect like vacancies. It was also noticed that HyH plays an important role on the nucleation. The remarkable improvement in the growth rate of ZnS thin films have been observed upon increasing the contents of HyH. Nearly stoichiometric ZnS layer was obtained upon annealing prepared with 2.5 M HyH. The crystallinity was found to be increased upon annealing the layers. The ideality factor for the ZnS layers prepared with 0 and 1.0 M HyH were obtained?~1.71 and 1.24, respectively. The capacitance–voltage plots behave according to Schottky–Mott theory. The doping concentrations?~10¹⁷ and 10¹⁸ cm^?3 were calculated for the layers deposited with 0 and 1.0 M HyH, respectively.     

The Misprediction Recovery Cache

In modern processors, deep pipelines couple with superscalar techniques to allow each pipe stage to process multiple instructions. When such a pipe must be flushed and refilled, as when predicted program flow beyond a branch is subsequently recognized as wrong, the temporary performance loss is significant. While modern branch target buffer (BTB) technology makes this flush/refill penalty fairly rare, the penalty that accrues from the remaining branch mispredictions is a serious impediment to even higher processor performance. Advanced mechanisms that can reduce this residual misprediction penalty can be of enormous value in future microprocessor designs. In this paper we describe the design and performance of a promising new mechanism called the Misprediction Recovery Cache (MRC). The key results of our study are. (1) Small, finite sized MRCs (16 to 256 entry) can effectively reduce branch penalty in deeply pipelined processors. (2) Commercial Benchmarks such as the Winstone benchmarks make better use of larger M RCs due to large number of unique branch instructions unlike the predominantly technical SPECint benchmarks. (3) The MRC hit rates increase with increasing BTB prediction accuracy (5-200% depending on MRC size) due to fewer residual mispredictions associated with better prediction. (4) For the processor architecture we studied, the M RC resulted in up to 20% improvement in cpi(cycles per instruction). (5) The incremental performance gain achievable by adding an MRC to a modern CISC processor (which uses a BTB with a two-level predictor) is two to three times of what was achievable by going from a one-level predictor to a two-level predictor.     

Enhancement of luminescence intensity and spectroscopic analysis of Eu3+ activated and Li+ charge-compensated Bi2O3 nanophosphors for solid-state lighting

The present work reports the synthesis, characterization, photoluminescence and photocatalytic activity of Eu~(3+)(1 mol%-11 mol%) doped and Li~+(0.5 mol%-5 mol%) co-doped Bi_2 O_3 nanophosphors(NPs) by sonochemical method. The average particle size was estimated using powder X-ray diffraction(PXRD)and transmission electron microscopy(TEM) and is found to be in the range of 30-35 nm. The scanning electron microscopy(SEM) images were highly dependent on sonication time and concentration of epigallocatechin gallate(EGCG) bio-surfactant. The energy gap of doped and co-doped Bi_2 O_3 nanophosphors was estimated using Kubelka-Munk(K-M) function and is found to be in the range of2.9-3.08 eV. The effect of Li+ co-doping on luminescence of optimized Bi_2 O_3:Eu~(3+) was studied and is found about more than 3 fold enhancement of emission intensity. Judd-Ofelt parameters(Ω_2, Ω_4 and Ω_6).transition probabilities(A_T), quantum efficiency(η), luminescence lifetime(τ_(rad)), color chromaticity coordinates(CIE) and correlated color temperature(CCT) values were estimated from the emission spectra and are discussed in detail. The estimated CIE chromaticity co-ordinates are very close to the NTSC(National Television Standard Committee) standard value of red emission. The synthesized NPs show excellent photocatalytic activity of acid red-88 under UV-light irradiation, which can degrade 98.1% in60 min. The decreasing electron-hole pair recombination rate with quick electron transfer ability is predominantly ascribed to the balance between crystallite size, morphology, band gap, defects, surface area, etc. These results show a light for the use of sonochemical route of Bi_2 O_3:Eu~(3+):Li~+ in solid state display and photocatalytic applications.     

Particle size distribution control in emulsion polymerization

Effects of the operating policies—the initial initiator amount; the initial emulsifier amount; the monomer addition mode: batch or semibatch; and the monomer addition rate under “monomer‐starved conditions” for the control of particle size distribution (PSD)—were studied through a model that simulates batch and semibatch reactor operations in conventional emulsion polymerization. The population balance model incorporates both the nucleation stage and the growth stage. The full PSDs were reported, which have normally been omitted in earlier studies. It was shown through simulations that the broadness of the distributions, both initial (obtained after the end of nucleation) and final (after complete conversion of monomer), can be controlled by the initial initiator amount and the emulsifier amount. The higher initiator amounts and the lower emulsifier amounts favor narrower initial and final distributions. The shape of the initial PSDs and the trends in the average size and range were preserved with subsequent addition of monomer in the batch or in the semibatch mode, although the final PSD was always considerably narrower than that of the initial PSD. The addition of monomer in the semibatch mode gave narrower distribution compared to that of the batch mode, and also, lower monomer addition rates gave narrower distributions (larger average sizes), which was a new result. It was further shown through simulations that, under monomer‐starved conditions, the reaction rate closely matched the monomer feed rate. These conclusions are explained (1) qualitatively—the shorter the length of the nucleation stage and the larger the length of the growth stage (provided the number of particles remains the same), the narrower is the distribution; and (2) mathematically—in terms of the “self‐sharpening” effect. Experimental evidence in favor of the self‐sharpening effect was given by analyzing the experimental particle size distributions in detail. The practical significance of this work was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2884–2902, 2004