Chemical modification of viscose rayon by dimethyl and methylvinyl diacetoxysilanes

Crosslinking of viscose rayon filament with dimethyl and methylvinyl diacetoxysilanes in benzene has been studied. The extent of crosslinking appears to depend on the nature of the reactant, material-to-reactant ratio, time, and temperature of the reaction. An increase in the breaking stress, initial modulus, and recovery properties was observed with increase in the crosslink density. Birefringence values as well as orientation index decrease in the treated samples. Thermal behavior of the crosslinked viscose was also studied by TGA and DTA, and it was found that IPDT (integral procedural decomposition temperature) and D_max (maximum decomposition temperature) values of the crosslinked samples are higher than those of the untreated viscose.     

Distributed and collaborative visualization

Visualization typically involves large computational tasks, often performed on supercomputers. The results of these tasks are usually analyzed by a design team consisting of several members. Our goal is to depart from traditional single-user systems and build a low-cost scientific visualization environment that enables computer-supported cooperative work in the distributed setting. A synchronously conferenced collaborative visualization environment would let multiple users on a network of workstations and supercomputers share large data sets, simultaneously view visualizations of the data, and interact with multiple views while varying parameters. Such an environment would support collaboration in both the problem-solving phase and the review phase of design tasks. In this article we describe two distributed visualization algorithms and the facilities that enable collaborative visualization. These are all implemented on top of the distribution and collaboration mechanisms of an environment called Shastra, executing on a set of low-cost networked workstations     

Generation of configuration space obstacles: The case of moving algebraic curves

We present algebraic algorithms to generate the boundary of planar configuration space obstacles arising from the translatory motion of objects among obstacles. Both the boundaries of the objects and obstacles are given by segments of algebraic plane curves.     

The Indian PHWR

The nuclear power program in India at present is based mainly on a series of Pressurized Heavy Water Reactors (PHWRs). Starting from Rajasthan Atomic Power Station comprising two units of 200 MW_e Canadian designed PHWRs in 1973, the program has come a long way with 12 PHWR units in operation and 6 units under construction which includes 2 units of 540 MW_e PHWRs. Narora Atomic Power Station commissioned in 1991 marked major indigenization and standardization of PHWR designs. The choice of PHWRs in the current stage of India's Nuclear Power Plants program is based on long-term objectives in the right available resources and infrastructure. These reactors use natural uranium as fuel and heavy water as moderator and coolant. The nuclear power stations in India are generally planned as twin-unit modules, sharing common facilities such as service building, spent fuel bay, etc.This paper brings out the key features of the design of Indian PHWR, highlighting the areas of evolution in successive project. Also covered are highlights of the operating experience with these reactors.     

Hazardous concentrations of selenium in soil and groundwater in North-West India

Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 μg L(-1)) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg(-1)) and Barwa (3.1 mg kg(-1)). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO(2) (40-62 wt.%), Al(2)O(3) (9-21 wt.%) and K(2)O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.     

Beauty is skin deep: a surface monolayer perspective on nanoparticle interactions with cells and bio-macromolecules

Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed.     

Deposition and optoelectronic properties of ITO (In<Subscript>2</Subscript>O<Subscript>3</Subscript>:Sn) thin films by Jet nebulizer spray (JNS) pyrolysis technique

Nanocrystalline ITO thin films were deposited on glass substrates by a new spray pyrolysis route, Jet nebulizer spray (JNS) pyrolysis technique, for the first time at different substrate temperatures varying from 350 to 450 °C using a precursor containing indium and tin solution with 90:10 at% concentration. The structural, optical and electrical properties have been investigated as a function of temperature. X-ray diffraction analysis showed that the deposited films were well crystallized and polycrystalline with cubic structure having (222) preferred orientation. The optical band gap values calculated from the transmittance spectra of all the ITO films showed a blue shift of the absorbance edge from 3.60 to 3.76 eV revealing the presence of nanocrystalline particles. AFM analysis showed uniform surface morphology with very low surface roughness values. XPS results showed the formation of ITO films with In³⁺ and Sn⁴⁺ states. TEM results showed the nanocrystalline nature with grain size about 12-15 nm and SAED pattern confirmed cubic structure of the ITO films. The electrical parameters like the resistivity, mobility and carrier concentration are found as 1.82 × 10⁻³ Ω cm, 8.94 cm²/Vs and 4.72 × 10²⁰ cm⁻³, respectively for ITO film deposited at 400 °C. These results show that the ITO films, prepared using the new JNS pyrolysis technique, have the device quality optoelectronic properties when deposited under the proposed conditions at 400 °C.     

Configurational sequence lengths in polyacrylonitrile and poly(acrylonitrile-CO-haloalkyl acrylate/methacrylate)s determined by 13C n.m.r.

The tacticity and number average sequence length of like ($\text{n}\text{?}{}_{\mathrm{<mtext>o</mtext>}}$), meso ($\text{n}\text{?}{}_{\mathrm{<mtext>m</mtext>}}$) and racemic ($\text{n}\text{?}{}_{\mathrm{<mtext>r</mtext>}}$) acrylonitrile (AN) triad units in polyacrylonitrile (PAN) prepared in both water and water—acetone (2:1 v/v) media and AN-3-chloro, 2-hydroxypropyl acrylate/methacrylate, AN-2-bromoethyl methacrylate and AN-2-chloroethyl acrylate copolymers have been calculated using ¹³C n.m.r. spectra of the polymer solutions concerned at a field strength of 24.99 MHz. The spectra reveal that PAN prepared in water medium has a greater percentage (33.4%) of isotactic units than PAN prepared in water-acetone (2:1 v/v) medium (28.3%). The tacticity distribution of AN sequences in PAN and the copolymers is found to be random ($\text{n}\text{?}{}_{\mathrm{<mtext>m</mtext>}}\text{?}\text{n}\text{?}{}_{\mathrm{<mtext>r</mtext>}}\text{?2.0}$) and the number average sequence length of AN sequences in a copolymer containing 14.8 mole% of 3-chloro, 2-hydroxypropyl methacrylate was 15.2.