Influence of surface modification by 2-aminothiophenol on optoelectronics properties of ZnO nanoparticles

In this study, a precipitation method was used to synthesise ZnO nanoparticles using suitable precursors. An efficient surface modification method was proposed in order to reduce the agglomeration among synthesised small sized ZnO nanoparticles using 2-aminothiophenol as a capping agent. This article briefly investigated the effects of capping agent like 2-aminothiophenol on the optoelectronic properties of ZnO nanoparticles. The modified effectivity of 2-aminothiophenol has been examined on the nanosized ZnO nanoparticle for fluorescence and UV–visible (UV–vis) studies. The mechanism was studied for ZnO nanoparticles light emitting capability under different conditions. By facilitating the capping of ZnO with 2-aminothiophenol, fluorescence emission of the surface defects vanishes and ultraviolet (UV) emission increases. Surface capping by 2-aminothiophenol effectively covers most of the surface defects of ZnO and results in quenching of the visible region. The UV–vis absorption spectra of modified ZnO nanoparticles has been influenced by modified ZnO nanoparticles as a result of surface modification; where marked blue shift in absorption edge results. By surface modification of ZnO nanoparticles, change in optoelectronics properties has opened the new scope and possibilities to explore and fine tune the optical character of the modified ZnO for various optoelectronics applications such as UV laser.     

Determination of Main Parameters Affecting Ozone Bleaching of Wheat Straw Pulp Using Plackett–Burman Design

Laboratory-scale studies were carried out on ozone bleaching of wheat straw soda pulp. Effects of five variables—pH, consistency, time, temperature, and ozone dose—on three pulp parameters— kappa number, brightness, and viscosity–were determined using Plackett–Burman experimental design. Results showed that for the parameter kappa number of pulp, ozone dose is the most important factor followed by pH and consistency. Pulp parameter viscosity is affected by factor pH, followed by consistency and ozone dose. Brightness of the wheat straw pulp mostly depends on factor ozone dose, followed by pH.     

Maternal care receptivity and its relation to perinatal and neonatal mortality. A rural study

A longitudinal study was conducted on 212 pregnant women from May 1987 to April 1988. Maternal Care Receptivity (MCR) "an innovative approach" was adopted for the assessment of maternal care services provided to pregnant mothers at their door steps. During follow-up, scores were allotted to each of the services rendered and antenatal status of pregnant women. Depending on the score--MCR was classified as high (11 to 8), moderate (7 to 4) or poor (3 to 0). Perinatal and neonatal deaths were recorded and an inverse relationship between MCR and perinatal and mortalities was observed (z = 5.46, p < 0.0001). Significantly, no perinatal or neonatal deaths occurred in women with high MCR. One of the most important cause of high PNMR and neonatal mortality rate in developing countries is poor MCR, i.e., under utilization of even the existing maternal health services. The main reasons for this under utilization appear to be poverty, illiteracy, ignorance and lack of faith in modern medicine.     

The future 700 MWe pressurized heavy water reactor

The design of a 700 MWe pressurized heavy water reactor has been developed. The design is based on the twin 540 MWe reactors at Tarapur of which the first unit has been made critical in less than 5 years from construction commencement. In the 700 MWe design boiling of the coolant, to a limited extent, has been allowed near the channel exit. While making the plant layout more compact, emphasis has been on constructability. Saving in capital cost of about 15%, over the present units, is expected. The paper describes salient design features of 700 MWe pressurized heavy water reactor.     

Swelling behavior of radiation‐polymerized polyampholytic two‐component gels: Dynamic and equilibrium swelling kinetics

Polyampholytic hydrogels, with varying degrees of crosslinking and ionic content, were prepared by radiation polymerization of p‐sodium styrene sulfonate (SSS) and vinyl benzyl trimethylammoniumchloride (VBT). These gels were investigated for their dynamic and equilibrium swelling kinetics. Dynamic swelling of these gels established that the gels containing equal amounts of SSS and VBT strictly follow Fickian diffusion. The hydrogels containing excess of SSS followed the case II type of diffusion, whereas those containing excess of VBT followed anomalous diffusion. Equilibrium swelling kinetics of these gels in aqueous system, ethanol–water mixture, at different pHs, and in the presence of solutions of biological interest was studied. It was seen that gels containing equal amounts of SSS and VBT show the lowest equilibrium swelling. Swelling of the polyampholytic gel decreased with an increase in the radiation dose imparted and the amount of crosslinking agent incorporated in the gel. The gels having an excess of VBT showed higher equilibrium swelling in comparison to those having an excess of SSS. Differential scanning calorimetry (DSC) studies showed that crosslinking of the gels decreases equilibrium swelling but increases the bonded nonfreezable water content of the gels. The organic solvents like ethanol cause abrupt collapse of the polyampholyte gels containing excess of SSS and those containing equal amounts of both the monomers at some critical ratio of water and ethanol in swelling medium. However, the deswelling in the water–ethanol mixture was gradual for gels containing an excess of VBT and the extent of deswelling was also low for these gels in comparison to other gels. The swelled gels of all compositions deswelled when they were transferred to solutions at pH in the range 2–12. Biologically important solutes like urea, glucose, and surfactants like Triton‐X tend to further swell the polymer matrices, whereas NaCl causes their deswelling. The additive effect is more prominent for polyampholyte gels containing excess of either of the monomers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 730–742, 2003     

Fast switching characteristics of a widely tunable laser transmitter

We demonstrate a widely tunable laser transmitter that accesses 32 ITU channels with 100-GHz spacing and switches between all channel combinations in less than 45 ns. The compact module uses commercially available electronic components. We investigate the electrical and thermal properties of the laser and the tuning section driver. The experiments show that a low output impedance driver circuit produces faster switching times. Also, temperature variation of the laser limits the wavelength accuracy of the switching. Finally, we present the correlation between switching times and the laser tuning currents.     

Development of anodic stripping voltammetry for determination of gallium in U–Ga alloy

Deposition potential, deposition time, square-wave frequency, rotation speed of the rotating disc electrode and gallium concentration have been studied in detail, for trace concentration level determination of gallium metal in U–Ga alloy by square-wave voltammetry anodic stripping analysis, in 1 M NaClO₄ + 0.5 M NaSCN at mercury film electrode (MFE). Optimum conditions have been found for Ga(III) determination by obtaining calibration graphs for the range 1–10 × 10⁻⁷ M gallium. Error and standard deviation less than 1% were assessed of this method with all gallium standard solutions. The developed methodology was applied successfully as a subsidiary method for the determination of gallium content in synthetic U–Ga samples with very good precision and accuracy (under 1% error and std. dev.).