Physicochemical and antimicrobial properties of sodium alginate/gelatin-based silver nanoformulations

In the present investigation, synthesis of silver nanoparticles (AgNPs) has been successfully carried out in a very simple and cost-effective manner by reducing Ag⁺ ions in sodium alginate solution and further stabilizing the colloidal mixture with gelatin solution. The ultraviolet–visible (UV–vis) spectra were in excellent agreement with the nanostructure morphology obtained from dynamic light scattering transmission electron microscopy and their size distributions. Increase in precursor concentration was found to promote agglomeration of AgNPs. Antibacterial assays revealed that the nanoformulations were more active against Gram-negative bacteria. Swelling studies of the hydrogel films demonstrated a rapid increase in water uptake. However, an increase in swelling % was observed with decreasing AgNP content. The use of biocompatible materials such as sodium alginate and gelatin not only provides green and economic attributes to this piece of research work but, at the same time, also opens up possibilities of using the nanoformulations in wound dressings, active packaging and several other biomedical applications.     

Titanium carbide derived nanoporous carbon for energy-related applications

High surface area nanoporous carbon has been prepared by thermo-chemical etching of titanium carbide TiC in chlorine in the temperature range 200-1200 °C. Structural analysis showed that this carbide-derived carbon (CDC) was highly disordered at all synthesis temperatures. Higher temperature resulted in increasing ordering and formation of bent graphene sheets or thin graphitic ribbons. Soft X-ray absorption near-edge structure spectroscopy demonstrated that CDC consisted mostly of sp² bonded carbon. Small-angle X-ray scattering and argon sorption measurements showed that the uniform carbon-carbon distance in cubic TiC resulted in the formation of small pores with a narrow size distribution at low synthesis temperatures; synthesis temperatures above 800 °C resulted in larger pores. CDC produced at 600-800 °C show great potential for energy-related applications. Hydrogen sorption experiments at −195.8 °C and atmospheric pressure showed a maximum gravimetric capacity of ∼330 cm³/g (3.0 wt.%). Methane sorption at 25 °C demonstrated a maximum capacity above 46 cm³/g (45 vol/vol or 3.1 wt.%) at atmospheric pressure. When tested as electrodes for supercapacitors with an organic electrolyte, the hydrogen-treated CDC showed specific capacitance up to 130 F/g with no degradation after 10 000 cycles.     

Molecular motions within the pore of voltage-dependent sodium channels

The pores of ion channel proteins are often modeled as static structures. In this view, selectivity reflects rigidly constrained backbone orientations. Such a picture is at variance with the generalization that biological proteins are flexible, capable of major internal motions on biologically relevant time scales. We tested for motions in the sodium channel pore by systematically introducing pairs of cysteine residues throughout the pore-lining segments. Two distinct pairs of residues spontaneously formed disulfide bonds bridging domains I and II. Nine other permutations, involving all four domains, were capable of disulfide bonding in the presence of a redox catalyst. The results are inconsistent with a single fixed backbone structure for the pore; instead, the segments that line the permeation pathway appear capable of sizable motions.     

Curing kinetics of epoxy-anhydride systems using quaternary ammonium guar and hydroxyethyl guar as catalysts

The kinetic parameters for the curing reactions of initially uncured and partly cured samples of the diglycidyl ether of bisphenol-A (DGEBA) with phthalic anhydride and quaternary ammonium compounds of guar gum or quaternary ammonium compounds of hydroxyethyl guar gum as catalyst, with or without n-butanol as diluent, were determined using the differential scanning calorimetry technique with a dynamic scan. To evaluate the kinetic parameters, four different computational methods were applied. The reaction was found to be first-order, with activation energy in the range 65-96 kJ mol^?1.     

Influence of the cropping pattern on aflatoxin contamination in preharvest Kharif (monsoon) maize crop (Zea mays)

Aflatoxin contamination in three varieties of maize (Zea mays L), viz Diara composite, M₉ and Suwan composite, under various cultivation rates and planting densities was examined during the 1987 and 1989 Kharif (monsoon) crops. Cultivation rates comprising single line weeding (SLW) with one spading, SLW with two spadings and SLW with three spadings did not have significant effects on aflatoxin production in the preharvest standing crop. Of the three planting populations, the toxin level was highest under 56000 plants ha^?1 followed by 83000 plants ha^?1, and 67000 plants ha^?1 in Aspergillus flavus inoculated plots (I₁) and uninoculated plots (I₀), respectively. The variety M₉ was most susceptible to A flavus infection and supported higher aflatoxin production under I₁ condition. Aflatoxin concentration was lowest in Diara composite. Correlation analysis showed a positive and highly significant relation between A flavus incidence and aflatoxin contamination (r = +0.73, P < 0.01).     

On the complexity of or-parallelism

We formalize the implementation mechanisms required to support or-parallel execution of logic programs in terms of operations on dynamic data structures. Upper and lower bounds are derived, in terms of the number of operationsn performed on the data structure, for the problem of guaranteeing correct semantics during or-parallel execution. The lower bound Ω(lgn) formally proves the impossibility of achieving an ideal implementation (i.e., parallel implementation with constant time overhead per operation). We also derive an upper bound of $\tilde O\left( {\sqrt[3]{n}} \right)$ per operation for or-parallel execution. This upper bound is far better than what has been achieved in the existing or-parallel systems and indicates that faster implementations may be feasible.     

Solution‐Processed Lead Iodide for Ultrafast All‐Optical Switching of Terahertz Photonic Devices

Solution‐processed lead iodide (PbI₂) governs the charge transport characteristics in the hybrid metal halide perovskites. Besides being a precursor in enhancing the performance of perovskite solar cells, PbI₂ alone offers remarkable optical and ultrasensitive photoresponsive properties that remain largely unexplored. Here, the photophysics and the ultrafast carrier dynamics of the solution processed PbI₂ thin film is probed experimentally. A PbI₂ integrated metamaterial photonic device with switchable picosecond time response at extremely low photoexcitation fluences is demonstrated. Further, findings show strongly confined terahertz field induced tailoring of sensitivity and switching time of the metamaterial resonances for different thicknesses of PbI₂ thin film. The approach has two far reaching consequences: the first lead‐iodide‐based ultrafast photonic device and resonantly confined electromagnetic field tailored transient nonequilibrium dynamics of PbI₂ which could also be applied to a broad range of semiconductors for designing on‐chip, ultrafast, all‐optical switchable photonic devices.