Use of the liquid-liquid interface for generating ultrathin nanocrystalline films of metals,chalcogenides,and oxides

The air-water interface has traditionally been employed to prepare particle assemblies and films of metals and semiconductors. The interface between water and an organic liquid, however, has not been investigated sufficiently for possible use in preparing nanocrystals and thin films of materials. In this article, we demonstrate the use of the liquid-liquid interface as a medium for preparing ultrathin films of metals, chalcogenides and oxides. The method involves the reaction at the interface between a metal-organic compound in the organic layer and an appropriate reagent for reduction, sulfidation, etc. in the aqueous layer. Some of the materials discussed are nanocrystalline films of gold, CuS, CuSe, CuO, and Cu(OH)(2) formed at the liquid-liquid interface. The results reported in this article should demonstrate the versatility and potential of the liquid-liquid interface for preparing nanomaterials and ultrathin films and encourage further research in this area.

Some experimental observations on the use of activated sludge as fertilizer for fish culture

Experiments were conducted in cement cisterns to find out the effect of adding different dosages of activated sludge on fish growth and plankton production. Three dosages of sludge,viz., 62·5 gm., 125 gm. and 250 gm. per 240 litres of water were used. Fingerlings ofCyprinus carpio, Cirrhina mrigala andCatla catla responded positively,C. mrigala showing maximum growth. The results indicate that the sludge has a direct influence on increasing growth of fish and production of plankton due to the release of nutrients into the water. The increase in plankton content stops after about 30 days. When greater quantities of sludge were added in the cisterns, fish mortality took place.

Road kills of amphibians in different land use areas from Sharavathi river basin, central Western Ghats, India

A survey of amphibian mortality on roads was carried out in the Sharavathi river basin in the central Western Ghats. Road kills in three different land use areas: agricultural fields, water bodies and forests were recorded for four days along three 100m stretches in each type of area. One-hundred-and-forty-four individuals belonging to two orders, eight families, 11 genera and 13 species were recorded in the survey. Kills/km observed were: in forest 55, agricultural fields 38 and water bodies 27, for an overall average of 40 kills/km. Kill species compositions varied significantly between land use areas, but not overall kill rates.

Experimental evidence of the cavity theory of sorption-desorption hysteresis by a study of the effect of electric discharge on entrapped water in silica gel

With the use of the quartz fiber spring balance, sorptions and desorptions of water on silica gel at 30°C were studied and the permanent and reproducible hysteresis loop was obtained. At different points on the desorption curve forming the loop, the gel was subjected to high tension glow electric discharge. As a result of the electric discharge, the gel at any point on the desorption curve shifts to a corresponding point on the sorption curve. This is due to the release from the cavities of gel of the entrapped water held in a metastable state. The electric discharge has no effect on the gel at different points on portions of the desorption curve which coincide with the sorption curve and also on the sorption curve itself, indicating the absence of entrapped water in the gel in these regions. The results afford direct experimental evidence of the reality of the cavity theory of sorption-desorption hysteresis.

Single-File Diffusion of Water Inside Narrow Carbon Nanorings

We use atomistic molecular dynamics (MD) simulations to study the diffusion of water molecules confined inside narrow (6,6) carbon nanorings. The water molecules form two oppositely polarized chains. It is shown that the effective interaction between these two chains is repulsive in nature. The computed mean-squared displacement (MSD) clearly shows a scaling with time similar to t(1/2), which is consistent with single-file diffusion (SFD). The time up to which the water molecules undergo SFD is shown to be the lifetime of the water molecules inside these chains. Simulations of "uncharged" water molecules inside the nanoring show the formation of several water chains and yield SFD. These observations conclusively prove that the diffusion is Fickian when there is a single chain of water and SFD is observed only when two or more chains are present.

COMMON-Sense net:Improved water management for resource-poor farmers via sensor networks

We describe the on-going design and implementation of a sensor network for agricultural management targeted at resource-poor farmers in India. Our focus on semi-arid regions led us to concentrate on water-related issues. Throughout 2004, we carried out a survey on the information needs of the population living in a cluster of villages in our study area. The results highlighted the potential that environment-related information has for the improvement of farming strategies in the face of highly variable conditions, in particular for risk management strategies (choice of crop varieties, sowing and harvest periods, prevention of pests and diseases, efficient use of irrigation water etc.). This leads us to advocate an original use of Information and Communication Technologies (ICT). We believe our demand-driven approach for the design of appropriate ICT tools that are targeted at the resource-poor to be relatively new. In order to go beyond a pure technocratic approach, we adopted an iterative, participatory methodology.

Systems Analysis of Tank Irrigation: II. Delayed Start and Water Deficit

Tank irrigation systems in the semiarid regions of India are discussed in this paper. To optimize the grain yield of rice, it is essential to start the agricultural operations in the second week of July so that favorable climatic conditions will prevail during flowering and yield formation stages. Because of low inflow during the initial few weeks of the crop season, often farmers are forced to delay planting until sufficient sowing rain and inflow have occurred or to adopt deficit irrigation during this period. The delayed start affects the grain yield, but will lead to an improved irrigation efficiency. A delayed start of agricultural operations with increased irrigation efficiency leads to the energy resources becoming critical during the peak requirement week, particularly those of female labor and animal power. This necessitates augmenting these resources during weeks of their peak use, either by reorganizing the traditional methods of cultivation or by importing from outside the system.

Performance evaluation of an integrated solar water heater as an option for building energy conservation

Since a majority of residential and industrial building hot water needs are around 50 degrees C, an integrated solar water heater could provide a bulk source that blends collection and storage into one unit. This paper describes the design, construction and performance test results of one such water-heating device. The test unit has an absorber area of 1.3 m(2) and can hold 1701 of water, of which extractable volume per day is 1001. Its performance was evaluated under various typical operating conditions. Every morning at about 7:00 a.m., 1001 of hot water were drawn from the sump and replaced with cold water from the mains. Although, during most of the days, the peak temperatures of water obtained are between 50 and 60 degrees C, the next morning temperatures were lower at 45-50 degrees C. Daytime collection efficiencies of about 60% and overall efficiencies of about 40% were obtained. Tests were conducted with and without stratification. Night radiation losses were reduced by use of a screen insulation.

Use of Polyazaheterocycles in the Assembly of New Cadmium Sulfate Frameworks: Synthesis, Structure, and Properties

The reaction of cadmium sulfate in the presence of polyazaheterocyclic organic molecules gave rise to a variety of new cadmium sulfate phases in water containing solvothermal reaction. The compounds have two- (I) and three-dimensionally (II-VI) extended structures. All the compounds have structures built up by the connectivity involving the cadmium octahedra and the sulfate tetrahedra in which the heterocyclic organic molecules act as the ligand. The linkages between the Cd2+ and (SO4)2- ions form one- (II), two- (I, III, and IV), and three- (V and VI) dimensionally extended cadmium sulfate phases. The connectivity between Cd2+ ion and the heterocyclic ligand also gives rise to one- and two-dimensional structures. The inter-connectivity between the two units gives rise to the observed structures. The presence of Cd-O-Cd chains and Cd-O-Cd layers in some of the structures is noteworthy. The adsorption/desorption studies suggest that the cadmium sulfate phases adsorb/desorb anionic dyes selectively in the presence of water/ethanol, respectively. The photocatalytic degradation studies on cationic dyes under UV-irradiation indicate modest activity. The cyanosilylation of imines using the present compounds as heterogeneous catalyst indicate good catalytic behavior. The various properties exhibited by the cadmium sulfate phases suggest that these compounds are versatile. All the compounds were characterized by powder X-ray diffraction, thermogravimetric analysis, infrared (IR) and UV-visible studies.

Solution of a Boundary-Value Problem associated with Diffraction of Water Waves by a Nearly Vertical Barrier

An exact solution is derived for a boundary-value problem for Laplace's equation which is a generalization of the one occurring in the course of solution of the problem of diffraction of surface water waves by a nearly vertical submerged barrier. The method of solution involves the use of complex function theory, the Schwarz reflection principle, and reduction to a system of two uncoupled Riemann-Hilbert problems. Known results, representing the reflection and transmission coefficients of the water wave problem involving a nearly vertical barrier, are derived in terms of the shape function.

Analysis of an Aquifer-water table aquitard system

The problem of pumping an aquifer in an aquifer-water table aquitard system is considered, accounting for the elastic properties of both the aquifer and the aquitard, the gravity drainage in the aquitard and treating the water table as an unknown boundary. The coupled partial differential equations are nondimensionalised, yielding three principal parameters governing the problem. The numerical solution of these equations is obtained for a wide range of parameter values. Type curves are generated and their use is illustrated through a field application.

Thermodynamics of water entry in hydrophobic channels of carbon nanotubes

Experiments and computer simulations demonstrate that water spontaneously fills the hydrophobic cavity of a carbon nanotube. To gain a quantitative thermodynamic understanding of this phenomenon, we use the recently developed two phase thermodynamics method to compute translational and rotational entropies of confined water molecules inside single-walled carbon nanotubes and show that the increase in energy of a water molecule inside the nanotube is compensated by the gain in its rotational entropy. The confined water is in equilibrium with the bulk water and the Helmholtz free energy per water molecule of confined water is the same as that in the bulk within the accuracy of the simulation results. A comparison of translational and rotational spectra of water molecules confined in carbon nanotubes with that of bulk water shows significant shifts in the positions of the spectral peaks that are directly related to the tube radius. (C) 2011 American Institute of Physics.

Leak Detection In Pressure Tubes Of A Pressurized Heavy-Water Reactor By Acoustic-Emission Technique

Leak detection in the fuel channels is one of the challenging problems during the in-service inspection (ISI) of Pressurised Heavy Water Reactors (PHWRs). In this paper, the use of an acoustic emission (AE) technique together with AE signal analysis is described, to detect a leak that was ncountered in one (or more) of the 306 fuel channels of the Madras Atomic Power Station (PHWR), Unit I. The paper describes the problems encountered during the ISI, the experimental methods adopted and the results obtained. Results obtained using acoustic emission signal analysis are compared with those obtained from other leak detection methods used in such cases.

Sequential Assembly of an Active RNA Polymerase Molecule at the Air-Water Interface

At the heart of understanding cellular processes lies our ability to explore the specific nature of communication between sequential information carrying biopolymers. However, the data extracted from conventional solution phase studies may not reflect the dynamics of communication between recognized partners as they occur in the crowded cellular milieu. We use the principle of immobilization of histidine-tagged biopolymers at a Ni(II)-encoded Langmuir monolayer to study sequence-specific protein-protein interactions in an artificially crowded environment The advantage of this technique lies in increasing the surface density of one of the interacting partners that allows us to study macromolecular interactions in a controlled crowded environment, but without compromising the speed of the reactions. We have taken advantage of this technique to follow the sequential assembly process of the multiprotein complex Escherichia coil RNA polymerase at the interface and also deciphered the role of one of the proteins, omega (omega), in the assembly pathway. Our reconstitution studies indicate that in the absence of molecular chaperones or other cofactors, omega (omega) plays a decisive role in refolding the largest protein beta prime (beta') and its recruitment into the multimeric assembly to reconstitute an active RNA polymerase. It was also observed that the monolayer had the ability to distinguish between sequence-specific and -nonspecific interactions despite the immobilization of one of the biomacromolecules. The technique provides a universal two-dimensional template for studying protein-ligand interactions while mimicking molecular crowding.

Potential-distance relationships of clay-water systems considering the Stern theory

This paper deals with the use of Stem theory as applied to a clay-water electrolyte system, which is more realistic to understand the force system at micro level man the Gouy-Chapman theory. The influence of the Stern layer on potential-distance relationship has been presented quantitatively for certain specified clay-water systems and the results are compared with the Gouy-Chapman model. A detailed parametric study concerning the number of adsorption spots on the clay platelet, the thickness of the Stern layer, specific adsorption potential and the value of dielectric constant of the pore fluid in the Stern layer, was carried out. This study investigates that the potential obtained at any distance using the Stern theory is higher than that obtained by the Gouy-Chapman theory. The hydrated size of the ion is found to have a significant influence on the potential-distance relationship for a given clay, pore fluid characteristics and valence of the exchangeable ion.