Structural and antibacterial properties of a γ‐radiation‐assisted,in situ prepared silver–polycarbonate matrix

A silver–polycarbonate (Ag–PC) matrix was prepared by a γ‐radiation‐assisted diffusion method, and its antibacterial properties were studied. Rutherford backscattering spectroscopy, X‐ray diffraction, and transmission electron microscopy results showed the diffusion of good, crystalline‐structured (face‐centered cubic) silver nanoparticles (AgNPs) inside polycarbonate (PC) after irradiation. Ultraviolet–visible spectroscopic results indicated a blueshift in the surface plasmon resonance of the AgNPs; this revealed a particle size decrease with increasing γ‐radiation dose. This was also supported by the scanning electron microscopy results. The microstructure of the pristine PC and silver‐doped PC was monitored with positron annihilation spectroscopy, and it showed decreases in the free‐volume hole size and fractional free‐volume for Ag–PC and γ‐ray‐irradiated PC. This corroborated the Doppler broadening spectroscopy results. The thermal degradation temperature of PC was increased because of the diffusion of AgNPs in PC. The antibacterial activity of the synthesized Ag–PC matrix was evaluated by the zone of inhibition, and the results demonstrated its bacterial growth inhibition ability. The results indicate the potential to produce an Ag–PC matrix for various applications in medical and food industries. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43729.     

Stimuli Responsive Self-Assembly of 3-(Octyloxy)-3-Oxopropyl Acrylate-Co-Acrylic Acid Polymer in Aqueous Media

A novel copolymer based on 3-(alkyloxy)-3-oxopropyl acrylate and acrylic acid was synthesized and characterized. Surface tension and fluorescence probe techniques (using N-phenyl-1-naphthylamine as a probe) were employed to evaluate the surface properties of the amphiphilic copolymer. The copolymer was found to reduce the surface tension of water to 40–46 mN/m depending on the pH of the medium. The critical aggregation concentration of the copolymer determined by surface tension measurements was found to be 0.28 mg/ml at pH 4, 1.13 mg/ml at pH 8, and 1.44 mg/ml at pH 10, very close to those obtained by steady state fluorescence probe techniques (0.21, 1.13 and 1.48 mg/ml, respectively, at pH 4, 8, and 10). The pH-induced structural transitions of the copolymer were also studied using steady state fluorescence with pyrene and 1,6-diphenyl-1,3,5-hexatriene as probes, dynamic light scattering and transmission electron microscopy. The protonation of pendant carboxylate groups at acidic pH makes the aggregate compact and rigid. Conversely, ionization of the carboxylate groups under alkaline conditions resulted in larger aggregates.     

Superconductivity and cryogenics for linear accelerator programme at IUAC, New Delhi

The Inter-University Accelerator Center, New Delhi is involved in commissioning a superconducting linear accelerator (LINAC) as a booster to its existing 15 UD Pelletron accelerator. The booster consists of three LINAC modules, each containing eight superconducting Nb quarter wave resonators and a superconducting solenoid magnet. The first LINAC module preceded by a superbuncher with one cavity and followed by a rebuncher cryostat with two cavities was installed in 0° beam line of Pelletron and has been under operation for some time at the Center. The module is integrated with a liquid helium (LHe) refrigerator through a cryogen valve box and the distribution line. The performance tests of each component like the RF cavity, the cryomodule and the liquid helium distribution line were carried out independently prior to the beam acceleration test. After having many trial runs on this integrated cryonetwork system, beam acceleration tests were performed during 2007. The energy of silicon beam with charge state of +10 has been enhanced approximately from 130 MeV to 158 MeV using the first module with seven effective cavities and the accelerated beam was delivered at user’s scattering chamber. The present paper highlights the performance of the first module producing an accelerating beam duly bunched in the rebuncher. The performance of first LINAC cryomodule along with problems and the solution associated with the cryogenic system and the cavities encountered during the beam runs are presented in this paper.     

Photoluminescence of Tris-(8-hydroxyquinoline)aluminum Thin Films and Influence of Swift Heavy Ion Irradiation

The effect of swift heavy ion (SHI) irradiation on the optical properties of Tris-(8-hydraxyquinoline) aluminum (Alq₃) thin films has been studied. It is confirmed that PL and lifetime of SHI irradiated Alq₃ thin films irradiated both at room temperature and low temperature decrease for increasing ion fluences indicating the transfer of excitons energy to unstable cationic Alq₃ species. It is also confirmed that PL and lifetime of Alq₃ thin films irradiated at low temperature decrease largely compared to that of at the room temperature indicating that a large number of unstable cationic Alq₃ species are generated by SHI irradiation.     

Chemo‐enzymatic synthesis of lipophilic ferulates and their evaluation for antioxidant and antimicrobial activities

An efficient chemo‐enzymatic synthesis of ferulic acid‐based structured lipids mimicking triacylglycerol with a pendant phenolic moiety was carried out for the first time. Initially, ferulic acid was reduced to coniferyl alcohol, followed by its esterification with fatty acids. The key step in the synthesis was dihydroxylation of the olefinic side chain of coniferyl ester, which was eventually esterified with fatty acids to generate phenolic structured lipids. Two such compounds of varying fatty acid chain lengths were synthesized in good yield. Structural confirmation of both compounds is based on IR, ¹H and ¹³C NMR, and MS techniques. The synthesized compounds were tested for in vitro antioxidant and antimicrobial activities. Both compounds exhibited moderate to good antioxidant activity. The phenolic structured lipid with only shorter‐chain fatty acids showed antibacterial activity. Both compounds did not show any antifungal activity.     

Hypocholesterolemic effects of low calorie structured lipids on rats and rabbits fed on normal and atherogenic diet

The hypocholesterolemic effects of two low calorie structured lipids (SL1 and SL2) containing essential fatty acids, prepared by lipase catalysed interesterification of ethyl behenate respectively with sunflower and soybean oils were studied in rats and rabbits. The feeding experiment conducted on rats as well as rabbits, fed on normal and atherogenic diet containing 10% of SL1 and SL2 (experimental) and sunflower oil (control) indicated no adverse effects on growth and food intake. However, the structured lipids beneficially lowered serum and liver lipids, particularly cholesterol, LDL cholesterol, triglycerides and also maintains the essential fatty acid status in serum and liver. The lipid deposition observed in the arteries of rabbits fed on atherogenic diets was significantly reduced when structured lipids were included in the diet. These observations coincided with reduced levels of serum cholesterol particularly LDL cholesterol observed in experimental groups. Therefore the structured lipids, designed to have low calorific value also beneficially lower serum lipids and lipid deposition in animals fed on atherogenic diets.     

Nanotwinning and structural phase transition in CdS quantum dots

Nanotwin structures are observed in high-resolution transmission electron microscopy studies of cubic phase CdS quantum dots in powder form by chemical co-precipitation method. The deposition of thin films of nanocrystalline CdS is carried out on silicon, glass, and TEM grids keeping the substrates at room temperature (RT) and 200°C by pulsed laser ablation. These films are then subjected to thermal annealing at different temperatures. Glancing angle X-ray diffraction results confirm structural phase transitions after thermal annealing of films deposited at RT and 200°C. The variation of average particle size and ratio of intensities in Raman peaks I_2LO/I_1LO with annealing temperature are studied. It is found that electron-phonon interaction is a function of temperature and particle size and is independent of the structure. Besides Raman modes LO, 2LO and 3LO of CdS at approximately 302, 603, and 903 cm⁻¹ respectively, two extra Raman modes at approximately 390 and 690 cm⁻¹ are studied for the first time. The green and orange emissions observed in photoluminescence are correlated with phase transition.     

Investigations of structural, dielectric and optical properties on silicon ion irradiated glycine monophosphate single crystals

The 50 MeV silicon ion irradiation induced modifications on structural, optical and dielectric properties of solution grown glycine monophosphate (GMP) crystals were studied. The high-resolution X-ray diffraction study shows the unaltered value of integrated intensity on irradiation. The dielectric constant as a function of frequency and temperature was studied. UV-visible studies reveal the decrease in bandgap values on irradiation and presence of F-centers. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The scanning electron micrographs reveal the defects formed on irradiation.     

Enrichment of γ-linolenic acid in the lipid extracted from Mucor zychae MTCC 5420

The aim of this work was to study the enrichment of the Gamma linolenic acid (GLA) content of lipid extracted from Mucor zychae by employing a low-temperature urea crystallization process. GLA, a polyunsaturated fatty acid has been reported to have many health benefits and has potential implications in food and pharmaceutical industry. Lipids extracted from the mycelia of fermented broth were transesterfied and analysed by gas chromatography. Results showed that the fungal oil contained (%) myristic acid (1.2), palmitic acid (35.3), palmitoleic acid (3.7), stearic acid (2.7), oleic acid (39.2), linoleic acid (6.4) and gamma linolenic acid (8.7). After the first step of crystallization, the percentage of GLA enriched in the total lipid was increased to 63.5. The concentration of GLA further increased when the enriched lipid sample was subjected to urea crystallization for the second time. GLA percentage increased from 63.5 to 92.7, and recovery of GLA was 63%. By altering the ratio of fatty acid ethyl ester:urea, the concentration characteristics and the recovery of GLA also varied; highest recovery of GLA (69%) was obtained when, the above ratio was 1:3. Furthermore, GLA recovery was in considerable amounts at 0 °C crystallization.