Rheological and thermal characteristics of a two phase hydrogel system for potential wound healing applications

Hydrogels fabricated from single polymers have been extensively investigated for wound healing applications. However, in many cases a single polymer cannot meet divergent demands in terms of both properties and performance. In this work, a two phase hydrogel was prepared by physically imbedding a xerogel in the core of a freeze thawed hydrogel. The outer hydrogel was prepared by freeze thawing poly (vinyl alcohol) (PVA) and poly (acrylic acid) (PAA) while the xerogels were prepared by UV polymerisation of 1-vinyl-2-pyrrolidinone (NVP). The rheological results indicated that the two phase hydrogels over a period of 2 weeks formed a strong interface and demonstrated greater physical strength. This suggested that the inner gel containing PVP diffused into the PVA/PAA hydrogel, which in turn increased hydrogen bonding, resulting in the overall increase in the stiffness of the gel. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirmed hydrogen bonding had occurred between the constituents of the two phase hydrogels. Thermal analysis suggested that T _g of each of the samples was above 80 °C, which indicated no impact on the behaviour of the gel at body temperature, but did however, give an indication of the stiffness of the dry polymer.     

Study on parasitic and channel resistance of poly‐Si thin‐film transistors by metal‐induced crystallization

Abstract— The channel‐length‐dependent transfer characteristics of TFTs using poly‐Si by metal‐induced crystallization through a cap (MICC) of a‐Si to evaluate the parasitic and channel resistances have been studied. The MICC p‐channel TFTs studied in the present work showed a maximum field‐effect mobility, threshold voltage, and gate swing of 53 cm²/V‐sec, −4.4 V, and 0.8 V/dec for W/L = 12 μm/6 μm, 71 cm²/V‐sec, −5.3 V, and 0.9 V/dec for W/L = 12 μm/12 μm, and 113 cm²/V‐sec, −7 V, and 1 V/dec for W/L = 12 μm/24 μm, respectively. It is found that the parasitic resistance is higher than the channel resistance, and both decrease with increasing temperature.     

Chaotic Oscillators Derived from Sinusoidal Oscillators Based on the Current Feedback Op Amp

A collection of novel chaotic oscillators displaying behavior similar to that of the chaotic Colpitts oscillator and requiring the same number and type of energy storage elements is proposed. The oscillators use as an active element the current feedback op amp (CFOA) mostly employed as a current negative impedance converter (INIC). Nonlinearity is introduced through a two-terminal voltage-controlled nonlinear device with an antisymmetric driving-point characteristic. The chaos generators are designed based on sinusoidal oscillators that have been modified for chaos in a semi-systematic manner. By using CFOAs, several attractive features are attained, in particular suitability for high frequency operation. Systems of third- and fourth-order ordinary differential equations describing the chaotic behaviors are derived. Experimental results, PSpice circuit simulations and numerical simulations of the derived mathematical models are included.     

Overexpression of rice phytochrome A partially complements phytochrome B deficiency in Arabidopsis

The red/far-red reversible phytochromes play a central role in regulating the development of plants in relation to their light environment. Studies on the roles of different members of the phytochrome family have mainly focused on light-labile, phytochrome A and light-stable, phytochrome B. Although these two phytochromes often regulate identical responses, they appear to have discrete photosensory functions. Thus, phytochrome A predominantly mediates responses to prolonged far-red light, as well as acting in a non-red/far-red-reversible manner in controlling responses to light pulses. In contrast, phytochrome B mediates responses to prolonged red light and acts photoreversibly under light-pulse conditions. However, it has been reported that rice (Oryza sativa L.) phytochrome A operates in a classical red/far-red reversible fashion following its expression in transgenic tobacco plants. Thus, it was of interest to determine whether transgenic rice phytochrome A could substitute for loss of phytochrome B in phyB mutants of Arabidopsis thaliana (L.) Heynh. We have observed that ectopic expression of rice phytochrome A can correct the reduced sensitivity of phyB hypocotyls to red light and restore their response to end-of-day far-red treatments. The latter is widely regarded as a hallmark of phytochrome B action. However, although transgenic rice phytochrome A can correct other aspects of elongation growth in the phyB mutant it does not restore other responses to end-of-day far-red treatments nor does it restore responses to low red:far-red ratio. Furthermore, transgenic rice phytochrome A does not correct the early-flowering phenotype of phyB seedlings.     

Reduced immunotoxicity and preservation of antibacterial activity in a releasable side-chain carbapenem antibiotic

A carbapenem antibiotic, L-786,392, was designed so that the side chain that provides high-affinity binding to the penicillin-binding proteins responsible for bacterial resistance was also the structural basis for ameliorating immunopathology. Expulsion of the side chain upon opening of the beta-lactam ring retained antibacterial activity while safely expelling the immunodominant epitope. L-786,392 was well tolerated in animal safety studies and had significant in vitro and in vivo activities against methicillin- and vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci.     

Flux-assisted infiltration of liquid Al-6063 into TiC beds in air

This study details trials to produce aluminium metal matrix composites reinforced with TiC particles by means of a flux-assisted infiltration technique. Whilst no infiltration of TiC beds occurred, by using a K-Al-F flux infiltration was successful at temperatures as low as 680°C. Some reaction of TiC with the Al matrix, forming TiAl_2.3Si_0.1 and Al₄C₃, was observed in the microstructure along with flux trapped within the Al-6063 matrix. DSC showed exothermic oxidation of TiC to occur, until the flux melts at 545°C arresting and preventing further oxidation by spreading over, coating and cleaning the particle surfaces. As soon as the flux melts, it also starts dissolving the oxide layer on the Al alloy and prevents any re-oxidation by isolating the surface from the surrounding atmosphere. Sessile drop experiments suggest that when the alloy melts and the oxide layer has been dissolved by the flux, intimate contact occurs between the liquid and the particles. The low tensions for the solid/flux and liquid metal/flux interfaces facilitates spreading and wetting of liquid Al on the TiC particles, followed by infiltration of the bed and the displacement of the flux to the outer surfaces of the sample.     

Bacteriocins: Recent Trends and Potential Applications

In the modern era, there is great need for food preservation in both developing and developed countries due to increasing demand for extending shelf life and prevention of spoilage of food material. With the emergence of new pathogens and ability of micro-organisms to undergo changes, exploration of new avenues for the food preservation has gained importance. Moreover, awareness among consumers regarding harmful effects of chemical preservatives has been increased. Globally, altogether there is increasing demand by consumers for chemical-free and minimal processed food products. Potential of bacteriocin and its application in reducing the microbiological spoilages and in the preservation of food is long been recognized. Bacteriocins are normally specific to closely related species without disrupting the growth of other microbial populations. A number of applications of bacteriocin have been reported for humans, live stock, aquaculture etc. This review is focused on recent trends and applications of bacteriocins in different areas in addition to their biopreservative potential.     

Covalent immobilization of naringinase for the transformation of a flavonoid

Naringinase (EC 3.2.1.40) from Penicillium sp was immobilized by covalent binding to woodchips to improve its catalytic activity. The immobilization of naringinase on glutaraldehyde‐coated woodchips (600 mg woodchips, 10 U naringinase, 45 °C, pH 4.0 and 12h) through 1% glutaraldehyde cross‐linking was optimized. The pH–activity curve of the immobilized enzyme shifted toward a lower pH compared with that of the soluble enzyme. The immobilization caused a marked increase in thermal stability of the enzyme. The immobilized naringinase was stable during storage at 4 °C. No loss of activity was observed when the immobilized enzyme was used for seven consecutive cycles of operations. The efficiency of immobilization was 120%, while soluble naringinase afforded 82% efficacy for the hydrolysis of standard naringin under optimal conditions. Its applicability for debittering kinnow mandarin juice afforded 76% debittering efficiency. Copyright © 2005 Society of Chemical Industry