Zinc Titanate Nanofibers for the Detoxification of Chemical Warfare Simulants

Fabrication of a novel ceramic nanofiber system viz. zinc titanate using the well-known electrospinning technology with polyvinylpyrrolidone as a binder is reported. Use of zinc titanates as reactive sorbents to detoxify chemical warfare agents is hypothesized and proved. The zinc titanate nanofibers are tested against simulants of nerve and mustard agents and show satisfactory destructive activity. The extent of detoxification is measured using GC-MS analysis. The products of reaction of zinc titanate against the simulants are identified and are found to be relatively harmless. The possibility of replacement of conventional-activated carbon by electrospun ceramic nanofibers for face masks and protective clothing is proposed.     

Odd-even oscillations of SHG efficiencies in twin NLO chromophores

Twin NLO chromophores having two azobenzene units linked by a flexible polymethylene spacer of varying lengths are shown to exhibit odd-even oscillations in their second harmonic generation (SHG) efficiencies, when measured in the powder form. These twin systems were designed to also exhibit liquid crystallinity, and indeed most of them do exhibit a nematic mesophase. The anticipated odd-even oscillations, in both their isotropization transition temperatures (Ti) and isotropization entropies (ΔSi), were also observed. The odd-even oscillation of the SHG efficiencies has been ascribed to a more effective cancellation of mesogenic dipoles in the even twins as compared to their odd counterparts, due to a preferred centrosymmetric packing in the former case. Based on the behaviour of these twin chromophoric molecules, it may be anticipated that such odd-even oscillations will also be observed in the analogous main chain NLO polymers. Received: 20 June 1997/Accepted: 22 August 1997     

Role of microorganisms in improving nutritional status of the poor

The intestinal microflora as well as bacteria involved in fermentation of foods ordinarily consumed in India may contribute substantially for the improvement of nutritional status of poor Indians.     

Diffusion bonding of SU 263

Using a specially constructed apparatus, diffusion bonding of SU 263 alloy was studied in the temperature range of 1123–1323 K and compressive stress of 90% of its yield strength at the corresponding temperatures to determine the relative importance of the process parameters, the mechanism(s) responsible for bonding and the joint characteristics. Bond quality was assessed by optical metallography and lap shear testing. The mechanism of bonding was evaluated by grain growth equation. The experimental results were compared with a model developed by Pilling [Pilling, J., 1988. The kinetics of isostatic diffusion bonding in superplastic materials. Mater. Sci. Eng. 100, 137–144] in which the void closure by creep flow and diffusion are considered. Quantified EPMA line scan analysis was carried out to confirm the bonding mechanism and to determine the composition at the interface.     

Microfibres

Microfibres denote synthetic fibres that are finer than any fibre in nature. Microfibres are usually made of polyester, polyamide, acrylic, modal, lyocell and viscose in the range of 0.5-1.2 dtex. The progress starts with direct spinning and post-spinning developments for manufacturing microfibres. Researches on conjugate spinning techniques are reported along with the development in bicomponent spinning. Interesting developments in manufacturing techniques like the change of cross section without altering the spinneret, radial quenching system, etc., have been discussed. Recent developments like electrospinning have also been taken up. The mechanical processing section commences with the properties of microfibres affecting the downstream process and then discusses the processing of microfibres in blow room, carding, draw frame, speed frame and ring frame. Alternative spinning technologies like open-end, air-jet and compact spinning are dealt with. In the fabric forming systems, weaving and knitting with microfibres are discussed in depth highlighting research on such fabrics. High-speed weaving of microfibres is discussed with reference to three major technologies of projectile, rapier and air-jet weaving. The reactions of microfibres to different hydrolysis environments like alkaline, acidic and enzymatic are taken up. Dyeing of microfibres and the specific problems in dyeing of microfibres are discussed. The study of fibre structure by critical dissolution time is addressed. Different uses of microfibres in terms of industrial, medical, apparel and miscellaneous applications are presented. The economics of production along with the limitations and precautions of the fibre are subsequently discussed followed by suggestions for future work.     

Recognition of heterospecific alarm vocalization by Bonnet Macaques (Macaca radiata).

Recognition of heterospecific alarm vocalizations is an essential component of antipredator behavior in several prey species. The authors examined the role of learning in the discrimination of heterospecific vocalizations by wild bonnet macaques (Macaca radiata) in southern India. The bonnet macaques' flight and scanning responses to playbacks of their own alarm vocalizations were compared with their responses to playbacks of vocalizations of Nilgiri langurs (Trachypithecus johnii), Hanuman langurs (Semnopithecus entellus), and sambar deer (Cervus unicolor). The study was conducted in 3 regions that differed in the frequency with which bonnet macaques encountered these species and included an urban setting. Call recognition was highest in adults and in regions where individuals were frequently exposed to the calling species; calls were not recognized by urban monkeys. Thus, age and experience are important factors in heterospecific call recognition by bonnet macaques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis of boron/nitrogen substituted carbons for aqueous asymmetric capacitors

Boron/nitrogen substituted carbons were synthesized by co-pyrolysis of polyborazylene/coal tar pitch blends to yield a carbon with a boron and nitrogen content of 14 at% and 10 at%, respectively. The presence of heteroatoms in these carbons shifted the hydrogen evolution overpotential to −1.4 V vs Ag/AgCl in aqueous electrolytes, providing a large electrochemical potential window (∼2.4 V) as well as a specific capacitance of 0.6 F/m². An asymmetric capacitor was fabricated using the as-prepared low surface area carbon as the negative electrode along with a redox active manganese dioxide as the positive electrode. The energy density of the capacitor exceeded 10 Wh/kg at a power density of 1 kW/kg and had a cycle life greater than 1000 cycles.     

Globally optimal transmitter placement for indoor wireless communication systems

A global optimization technique is applied to solve the optimal transmitter placement problem for indoor wireless systems. An efficient pattern search algorithm - DIviding RECTangles (DIRECT) of Jones et al.- has been connected to a parallel three-dimensional radio propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations. Surrogate functions for a parallel wideband code-division multiple-access (WCDMA) simulator were used to estimate the system performance for the global optimization algorithm. Power coverage and bit-error rate are considered as two different criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. This paper briefly describes the underlying radio propagation and WCDMA simulations and focuses on the design issues of the optimization loop.     

ECG coding by wavelet-based linear prediction

Presents a novel coding scheme for the electrocardiogram (ECG). Following beat delineation, the periods of the beats are normalized by multirate processing. After amplitude normalization, a discrete wavelet transform is applied to each beat. Due to the period and amplitude normalization, the wavelet transform coefficients bear a high correlation across beats at identical locations. To increase the compression ratio, the residual sequence obtained after linear prediction of the significant wavelet coefficients is transmitted to the decoder. The difference between the actual period and the mean beat period, and that between the actual scale factor and the average amplitude scale factor are also transmitted for each beat. At the decoder, the inverse wavelet transform is computed from the reconstructed wavelet transform coefficients. The original amplitude and period of each beat are then recovered. The approximation achieved, at an average rate of 180 b/s, is of high quality. The authors have evaluated the normalized maximum amplitude error and its position in each cycle, in addition to the normalized root mean square error. The significant feature of the proposed technique is that, while the error is nearly uniform throughout the cycle, the diagnostically crucial QRS region is kept free of maximal reconstruction error