Picosecond pulse generator using delay lines

A passive circuit built with either high-quality coaxial cable of microstrip delay lines can convert a step signal with 25 ps rise time, from a conventional time-domain reflectometer, into a rectangular pulse of duration in the 50 ps-500 ns range, a separate delay line circuit being required for each pulse duration, The system provides an excellent probing signal for single rectangular pulse testing of analog pulse-shaping circuitry built to operate in the 2 Mb/s to 20 Gb/s range     

Evaluation of the nutritive value of plant protein concentrates

The nutritive value of acid and steam precipitated plant proteins extracted at pH 11 and acid precipitated plant proteins extracted at pH 8–11 were estimated. Acid precipitation was found to result in a higher true protein digestibility, biological value, net protein utilisation and protein efficiency ratio in rats and to be more completely hydrolysed in vitro than steam precipitated proteins. Proteins extracted from leaves at pH 11 were superior, for the same nutritive characteristics, to proteins extracted at lower pH (8–10) values. These differences are discussed in terms of differences in the quantities of certain amino acids present in the proteins, structural changes in the proteins and protein-carbohydrate interactions.     

The Update Complexity of Selection and Related Problems

We present a framework for computing with input data specified by intervals, representing uncertainty in the values of the input parameters. To compute a solution, the algorithm can query the input parameters that yield more refined estimates in the form of sub-intervals and the objective is to minimize the number of queries. The previous approaches address the scenario where every query returns an exact value. Our framework is more general as it can deal with a wider variety of inputs and query responses and we establish interesting relationships between them that have not been investigated previously. Although some of the approaches of the previous restricted models can be adapted to the more general model, we require more sophisticated techniques for the analysis and we also obtain improved algorithms for the previous model. We address selection problems in the generalized model and show that there exist 2-update competitive algorithms that do not depend on the lengths or distribution of the sub-intervals and hold against the worst case adversary. We also obtain similar bounds on the competitive ratio for the MST problem in graphs.     

X-ray absorption spectroscopy of PbMoO<Subscript>4</Subscript> single crystals

X-ray absorption spectra of PbMoO₄ (LMO) crystals have been investigated for the first time in literature. The measurements have been carried out at Mo absorption edge at the dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The optics of the beamline was set to obtain a band of 2000 eV at 20,000 eV and the channels of the CCD detector were calibrated by recording the absorption edges of standard Mo and Nb foils in the same setting. The absorption spectra have been measured for three LMO samples prepared under different conditions viz. (i) grown in air from stoichiometric starting charge, (ii) grown in argon from stoichiometric starting charge and (iii) grown in air from PbO-rich starting charge. The results have been explained on the basis of the defect structure analysed in LMO crystals prepared under different conditions. The Mo absorption edge is significantly influenced by the deviations in crystal stoichiometry.     

Evidences of solvent‐induced miscibility in polychloroprene‐co‐ethylene‐propene diene terpolymer blends

Solvent dependent changes in the compatibility behavior of Polychloroprene/Ethylene–propylene–diene terpolymer blends (CR/EPDM) have been investigated using dilute solution viscometry and solvent permeability analysis. To predict the compatibility of rubber blends of different compositions in solvents of different cohesive energy densities, Huggins interaction parameter (ΔB), hydrodynamic interaction (Δη) and Sun's parameter (α) were evaluated from the analysis of the specific and reduced viscosity data of two and three‐component polymer solutions. Miscibility criteria were not satisfied for CR/EPDM blends over the entire composition range in toluene, xylene, and carbon tetrachloride (CCl₄), however, a narrow miscibility domain was observed in chloroform (CHCl₃) for CR/EPDM/CHCl₃ system. These results were further corroborated with the analysis of heat of mixing (ΔH_m) and polymer–polymer interaction parameter (χ₁₂), for all rubber blend compositions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polychloroprene rubber/ethylene-propylene diene monomer/multiple walled carbon nanotube nanocomposites: synergistic effects of radiation crosslinking and MWNT addition

Synergistic effect of MWNT induced reinforcement and high energy radiation induced crosslinking on the physico-mechanical and thermal characteristics of polychloroprene rubber (PCR)/ethylene-propylene diene rubber (EPDM)/MWNT elastomeric nanocomposites was investigated. The extent of reinforcement, as assessed using the Kraus equation suggested high reinforcement of the blend on MWNT addition; though, the thermal stability and glass transition of the PCR and EPDM components were not significantly affected by MWNTs. The elastic modulus increased with the radiation dose as well as with the increase in MWNT content. The reinforcing mechanism of the nano-composites was studied by various micromechanics models all of which predicted higher moduli than the experimentally observed results, indicating agglomeration in the nano-composites. Nevertheless, in all the composites synergistic effect of radiation crosslinking and MWNT induced reinforcement were seen, suggesting radiation induced crosslinking between polymer and MWNT interface.     

Use of chitosan derivatives as solid phase extractors for metal ions

This paper shows a comparative study between the two radiation grafted chitosan derivatives viz. cross-linked chitosan (CRC) and cross-linked chitosan after hydrolysis (CRCH). These chitosan derivatives were used as solid phase extractors for several radionuclides. The uptake of ¹³⁷Cs, ^85,89Sr, ¹⁵²Eu, ²⁴¹Am, ²³⁴Th and ²³³U by CRCH and CRC was studied using batch and column methods. The K_d, exchange capacity, breakthrough capacity for different metal ions with the functionalized polymers were determined. The uptake followed the following trend: UO₂²⁺>Th⁴⁺>Cs⁺>Eu³⁺>Am³⁺>Sr²⁺ for both sorbents. It was seen that CRCH has a greater uptake of metal ions compated to CRC but CRC was more selective of the two.     

Influence of silica and electron beam radiation on the properties of a high vinyl styrene-butadiene-styrene block copolymer

Radiation crosslinking of polymers has gained importance over conventional crosslinking because the system is fast, pollution free and relatively simple. In high energy electron beam curing, which is one of the radiation curing methods, the material to be cured is bombarded with electrons of specified energy to produce free radials. These radicals unite to give rise to chemical crosslinks. In the process, some unwanted chain scission may also occur. The mechanical properties of such electron beam crosslinked systems can further be improved by the incorporation of nanosilica. In this work, a high vinyl (~50%) S-B-S block copolymer incorporated with varying doses of specific hydrophilic nanosilica was irradiated with electron beam at 25 and 50 kGy. Mechanical properties were studied and compared with that of the unirradiated system. The influence of a silane coupling agent was also investigated. Morphological studies were done to understand the dispersion of nanosilica in the polymer matrix. Relatively moderate amounts of nanosilica along with an optimum dose of the coupling agent were found to be effective in improving the properties. Rheological properties were also studied in details to understand the possibility of recycling the polymer.     

Shrinkage studies in electron beam curable polyurethane pressure-sensitive adhesive

Polyurethane (PU)-based pressure-sensitive adhesive (PSA) has been manufactured by electron beam (e-beam) irradiation using urethane-acrylate. The effect of variation of e-beam dose and crosslinkers viz. triallyl cyanurate (TAC), triallyl isocyanurate, polymeric methylene diphenyl diisocyanate, carbodiimide-modified methylene diphenyl di-isocyanate, methylene diphenyl di-isocyanate, and isophorone di-isocyanate (IPDI) has been studied concerning the shrinkage, adhesion properties, and gel content of the PU-PSA. It was found that with increasing e-beam dose the shrinkage is increased up to 25?kGy, but remained constant thereafter with further increasing the dose up to 60?kGy. Similarly, with increasing concentration of crosslinkers from 2 to 6%, shrinkage is increased but beyond that there is no appreciable change. A comparative study of the effect of different crosslinkers on shrinkage, adhesion properties, and gel content of PU-PSA was carried out, and it was found that TAC leads to the maximum, while IPDI to the lowest shrinkage. However, the opposite was observed for the adhesion properties, i.e. the use of IPDI ensures the maximum and of TAC, the minimum adhesive performance characteristics.     

Deep facial recognition after medical alterations

Multimedia Tools and Applications - Medical alterations on the facial region introduce skin consistency deviations amongst images of the same individual, thus making face recognition after medical...