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The promotion of organic farming involves curtailing extensive use of mineral fertilizers. The present study was aimed to compare the effects of vermicompost (10 Mg ha -1 ), commercial mineral fertilizer (NPK-100:80:80), and their combination on (1) the growth of a major cash crop "onion" (Allium cepa L.) and (2) the changes that may have occurred in the amended soil. The experiment was a randomized complete block design with four replications during the crop-growing season of 2008/09. Results showed significantly higher plant growth in the combined/mix treatment of vermicompost and NPK, as measured by the vegetative growth of bulbs, number and length of tillers per bulb, and fresh weight of bulbs and by the biochemical characteristics of the onion tillers/leaves (total chlorophyll, caretenoids, protein, and total sugar contents). Comparison of the mixed treatment as compared to the control showed increases in bulb size (54%), total number of bulbs per bed (52%), and fresh weight of all bulbs (198%). The chemical properties and enzyme activity of the amended soil also improved significantly in the combined treatment as compared to the application of vermicompost or the mineral fertilizer alone. Total organic C, microbial biomass C, and sulfate content were significantly higher in the mix treatment, with increases of 60%, 127%, and 126%, respectively, as compared to those of the chemical-fertilizer-alone treatment. Similarly, b-glucosidase, alkaline phosphatase, and dehydrogenase were significantly higher by 145%, 91%, 71%, respectively, in the mix treatment as compared to those of fertilizer-alone application. This study indicates that application of a combination of mineral fertilizer and vermicompost in the field can positively influence the biological properties and fertility of soils, and support better plant growth, when compared to the application of mineral fertilizer or vermicompost alone. The study suggests that this combined application can reduce the quantity and cost of mineral-fertilizers application for bulbous-crop cultivation by 50%, while also sustaining soil biological activity of tropical and subtropical soils.

Coagulation of concentrated aqueous alumina slurries prepared using an ammonium poly(acrylate) dispersant by MgO has been studied for direct coagulation casting (DCC). A small amount of MgO (0.2 wt% of alumina) increased the viscosity of the concentrated alumina slurry with time and finally transformed it into a stiff gel. The mechanism of coagulation is proposed such that the time‐delayed in situ generation of Mg2+ ions from the sparingly soluble MgO forms Mg–poly(acrylate) with the unadsorbed ammonium poly(acrylate) molecules in solution that shift the poly(acrylate) adsorption equilibrium toward the left by depleting the poly(acrylate) molecules adsorbed on the alumina particle surface. This leads to insufficient dispersant coverage on the particle surface and coagulation of the slurry. DCC using MgO is possible only if the slurry is prepared at a dispersant concentration higher than that required for optimum dispersion as the slurries prepared at the optimum dispersant concentration underwent premature coagulation. The gelation time could be tailored within 20 min to a few hours by maintaining the temperature in the range of 70°–30°C. The wet coagulated bodies prepared from 50 vol% alumina slurry showed a compressive strength of nearly 0.05 MPa.

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Through computer simulations and surface plasmon resonance (SPR) measurements, we establish optimum parameters for the design and fabrication of SPR sensors of high sensitivity, resolution, stability, and long decay-length evanescent fields. We present simulations and experimental SPR data for variety of sensors fabricated by using bimetal (Ag/Au) and multilayer waveguide-coupled Ag/Si3N4/Au structures. The simulations were carried out by using the transfer matrix method in MATLAB environment. Results are presented as functions of the thickness of the metal (Ag or Au) and the waveguide dielectric used in Ag/Si3N4/Au structures. Excellent agreement is observed between the simulations and experiments. For optimized thickness of the Si3N4 waveguide (150 nm), the sensor exhibits very high sensitivity to changes in the refractive index of analytes, Sn≈52°/RIU, extremely high resolution (FWHM≤0.28°), and long penetration depth of evanescent fields (δ≥305nm).

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Coagulation of aqueous alumina slurries prepared using various concentrations (0.43–1.04 wt% based on alumina) of ammonium poly(acrylate) dispersant by MgO has been studied for direct coagulation casting (DCC) of alumina. The slurries prepared at dispersant concentration below 0.84 wt% are not suitable for DCC at room temperature (∼30°C) as they undergo premature coagulation. Mixing the slurry with MgO at a low temperature of nearly 5°C slows down the reactions leading to coagulation and keeps the slurry viscosity low for a sufficient period of time. Coagulation of slurries prepared at a dispersant concentration of 0.92 wt% and above at room temperature requires MgO concentrations much higher than the equivalent amount required for reaction with the dispersant. This anomalous behavior at higher dispersant concentration is explained such that the Mg‐poly(acrylate) formed by the reaction between ammonium poly(acrylate) and MgO formed a sheath over the remaining MgO particles and prevented them from further dissolution at room temperature. Faster coagulation could be achieved by heating the slurries after casting in closed molds. The Mg‐poly(acrylate) acts as a binder and stabilizes the coagulated bodies as their strength and stability against oscillatory stresses increase with an increase in dispersant concentration.

We utilized Raman spectroscopy to investigate H 2 O adsorption in and desorption from single-walled carbon nanotubes (SWCNTs). SWCNT tips were opened by known chemical methods and H 2 O was inserted into the tubes via capillary action over periods up to 136 h. The wavenumbers in the OH bending region of H 2 O increase almost exponentially with H 2 O treatment time. Following H 2 O adsorption for 136 h, Raman spectra were also measured as a function of heat-treatment temperature. These data lead to 0.07 eV for the H 2 O desorption energy from SWCNTs.