Water‐Resistant Poly(vinyl alcohol)‐Silica Hybrids through Sol‐Gel Processing

Poly(vinyl alcohol) (PVA)‐silica hybrids with exceptionally reduced solubility in water were synthesized. The hybrid xerogels were fabricated through sol‐gel processing of a mixture of PVA and the acid‐catalyzed silica precursor tetraethoxysilane. The effects of varying ratios of PVA and silica precursor on the surface structure, thermal properties, crystallinity, and solubility of the hybrids were investigated. Unlike the highly water‐soluble nature of PVA, all the hybrids displayed considerably reduced solubility in water. This anomalous behavior of PVA in the hybrids can be attributed to the unavailability of its pendant –OH groups. Water‐resistant PVA‐silica hybrids can find applications in various technologies requiring biocompatible systems that are stable in aqueous environments.     

Utilisation of fruit and vegetable wastes in layers' diet

Improvement in egg production and egg size was noted when dietary rice polishing was replaced by carrot residue at 80 g kg^?1 diet. The layers fed on a diet containing orange waste or mango peels showed results comparable with the control. Egg production and egg size were adversely affected when mango stone was added to the layers' diet.     

An online resource allocation algorithm to minimize system interference for inband underlay D2D communications

This paper addresses the research question of total system interference minimization while maintaining a target system sum rate gain in an inband underlay device‐to‐device (D2D) communication. To the best of our knowledge, most of the state of the art research works exploit offline resource allocation algorithms to address the research problem. However, in Long‐Term Evolution (LTE) and beyond systems (4G, 5G, or 5G+), offline resource allocation algorithms do not comply with the fast scheduling requirements because of the high data rate demand. In this paper, we propose a bi‐phase online resource allocation algorithm to minimize the total system interference for inband underlay D2D communication. Our proposed algorithm assumes D2D pairs as a set of variable elements whereas takes the cellular user equipment (UEs) as a set of constant elements. The novelty of our proposed online resource allocation algorithm is that it incurs a minimum number of changes in radio resource assignment between two successive allocations among the cellular UEs and the D2D pairs. Graphical representation of the simulation results suggests that our proposed algorithm outperforms the existing offline algorithm considering number of changes in successive allocation for a certain percentage of sum rate gain maintaining the total system interference and total system sum rate very similar.     

Superconducting ceramics: preparation,XRD, SEM and EPR measurements to study the influence of compositional variations on superconductivity of La-(Ba/Sr/Ca)-CuO ceramic systems

A systematic substitution of strontium ions by barium and/or calcium ions in the 21-structure ternary oxide La_1.85Sr_0.15CuO_4–y , considered as the host system in this study, was carried out to produce four- and five-component metal oxides of the type La_1.85(Sr_0.15–x R _x ) CuO_4–y , where R=Ba and/or Ca and x<0.15. A series of samples was prepared using an oxalate coprecipitation procedure where high-purity starting materials, usually required in solid-state pyrolysis reactions, were not required. The experimental conditions for co-precipitation, annealing and pulverization processes were optimized. The X-ray powder diffraction patterns were used to indicate when the materials would become superconducting after annealing. The transition temperatures, T _c, were measured from resistance versus temperature data which confirm that strontium is the best alkaline-earth metal among calcium, barium and strontium. Substitution or partial doping of strontium by calcium and/or barium in the host system decreased the T _c of these ceramics. SEM measurements were carried out to determine the grain size of these materials and characteristic electron paramagnetic resonance spectra for these materials at different temperatures are reported.     

Interaction of Azo Dye with Cationic Surfactant Under Different pH Conditions

The aggregation induced by Alizarin Yellow R (AYR) in the cationic surfactant, cetyltrimethylammonium bromide (CTAB), was investigated by measuring their UV–visible absorption spectra. Conductance measurements as a function of surfactant concentration below and above the critical micelle concentration (CMC) were studied. CTAB aggregation takes place at the concentration far below its normal CMC in the presence of AYR. Both hydrophobic and electrostatic interactions affect the aggregation process in aqueous solution. The dye effect on the CMC of CTAB was noted by a specific conductivity method as well. AYR–CTAB binding constant (K_s) and water–micelle partition co-efficient (K_x) were quantified with the help of mathematical models employed to determine the partitioning of organic additives in the micellar phase. The number of dye molecules per micelle was estimated at particular CTAB concentrations above CMC, during this study.     

X-ray photoelectron spectroscopy and Fourier transform-infrared studies of transition metal phosphate glasses

X-ray photoelectron spectroscopy and Fourier transform-infrared studies were carried out on phosphate glasses containing oxides of iron, cobalt, nickel, copper and zinc. The results suggest that the glasses containing iron and zinc may have structures in which both the phosphorus and the iron (or zinc) atoms are tetrahedrally coordinated by oxygen into three-dimensional structures which resemble the polymorphic forms of silica, whereas the glasses containing cobalt, nickel and copper may consist of polymeric chains of PO₄ tetrahedra bonded to adjacent tetrahedra via bridging oxygens. These polyphosphate chains are linked together by the interaction between the metal cation and the oxygens of the network former. In addition, the core level 2p shake-up satellites of the 3d-transition metal ions in these glasses were studied. The results support a suggestion that the satellites in the glass are most likely due to the electron transfer from ligand to metal 3d orbitals.     

Antibacterial activity of chitosan-based matrices on oral pathogens

Chitosan is a well sought-after polysaccharide in biomedical applications due to its biocompatibility, biodegradability to non-toxic substances, and ease of fabrication into various configurations. However, alterations in the anti-bacterial properties of chitosan in various forms is not completely understood. The objective of this study was to evaluate the anti-bacterial properties of chitosan matrices in different configurations against two pathogens—Gram-positive Streptococcus mutans and Gram-negative Actinobacillus actinomycetemcomitans. Two-dimensional (2-D) membranes and three-dimensional (3-D) porous scaffolds were synthesized by air drying and controlled-rate freeze drying. Matrices were suspended in bacterial broths with or without lysozyme (enzyme that degrades chitosan). Influences of pore size, blending with Polycaprolactone (PCL, a synthetic polymer), and neutralization process on bacterial proliferation were studied. Transient changes in optical density of the broth, adhesion characteristics, viability, and contact-dependent bacterial activity were assessed. 3-D porous scaffolds were more effective in reducing the proliferation of S. mutans in suspension than 2-D membranes. However, no significant differences were observed on the proliferation of A. actinomycetemcomitans. Presence of lysozyme significantly increased the antibacterial activity of chitosan against A. actinomycetemcomitans. Pore size did not affect the proliferation kinetics of either species, with or without lysozyme. NaOH neutralization of chitosan increased bacterial adhesion whereas ethanol neutralization inhibited adhesion without lowering proliferation. Mat culture tests indicated that chitosan does not allow proliferation on its surface and it loses antibacterial activity upon blending with PCL. Results suggest that the chemical and structural characteristics of chitosan-based matrices can be manipulated to influence the interaction of different bacterial species. Aparna R. Sarasam and Phoebe Brown contributed equally