Polymerization Kinetics of Water-Soluble N-Vinyl Monomers in Aqueous and Organic Solution

Summary: Free-radical batch polymerization (FRP) of N-vinyl pyrrolidone (NVP) and N-vinyl formamide (NVF) monomers in aqueous solution as well as NVP polymerization in organic (n-butanol) solution has been studied. The differences found in rate of monomer conversion with monomer and solvent choice correlates well with the differences in values of the propagation rate coefficients (k_p) and their variation with monomer concentration measured in independent pulsed-laser polymerization studies, a result demonstrating that a generalized understanding of water-soluble vinyl monomers can be obtained once their k_p differences have been accounted for. A reasonable representation of polymer molecular mass averages and the complete molecular mass distributions for the three systems was obtained by assuming that the rate coefficient for transfer to monomer, polymer, and organic solvent also vary as a function of monomer concentration.     

Fluorophilicity of alkyl and polyfluoroalkyl nicotinic acid ester prodrugs

The fluorophilicity of a series of hydrocarbon and fluorocarbon-functionalized nicotinic acid esters (nicotinates) is measured from their partitioning behavior (log K_p) in the biphasic solvent system of perfluoro(methylcyclohexane) (PFMC) and toluene. The chain length of the hydrocarbon or fluorocarbon alkyl group of the ester ranges from one to twelve carbon atoms. Knowledge of the fluorophilicity of these solutes is relevant to the design of these prodrugs for fluorocarbon-based drug delivery. The experimental log K_p values range from −1.72 to −3.40 for the hydrocarbon nicotinates and −1.64 to 0.13 for the fluorinated nicotinates, where only the prodrug with the longest fluorinated chain (2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl nicotinic acid ester) partitions preferentially into the fluorinated phase (log K_p = 0.13). Predictions of the partition coefficients using solubility parameters calculated from group contribution techniques or molecular dynamics simulation are in reasonable agreement for the perhydrocarbon nicotinates and short chained perfluorinated nicotinates (≈0.3-39% deviation). Significant deviations from experimental partition coefficients (greater than 100%) are observed for the longest chain perfluoroalkyl nicotinates.     

Aerobic Biodegradation Pathway for Remazol Orange by Pseudomonas aeruginosa

Removal of azo dyes from effluent generated by textile industries is rather difficult. Azo dyes represent a major class of synthetic colorants that are mutagenic and carcinogenic. Pseudomonas aeruginosa grew well in the presence of Remazol Orange (RO) and was able to decolorize and degrade it. In the present study, the decolorization and degradation efficiency using single culture P. aeruginosa with RO and textile wastewaters is studied. The elucidation of decolorization pathway for P. aeruginosa is of special interest. The degradation pathway and the metabolic products formed during the degradation were also predicted with the help of high performance liquid chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy analysis. The data show the cleavage of the azo dye RO to form both methyl metanilic acid and 4-aminobenzoic acid after decolorization and finally to oxidation forms benzoic acid, alkenes, aldehydes, and alkynes. The organism was able to decolorize the dye RO and wastewater effectively to the maximum of 82.4% and 62%, respectively.     

Zn(II) based colorimetric sensor for ATP and its use as a viable staining agent in pure aqueous media of pH 7.2

Selective colorimetric detection of ATP in physiological conditions by a Zn(II)-based receptor is reported. This reagent was found to be non-toxic to the living cells and could be used for studying the growth of the yeast cells.     

Magnetic and transport studies on nanocrystalline Fe73.5Si13.5B8CuNb2VAl ribbon

The magnetic and the transport properties of the Fe_73.5Si_13.5B₈CuNb₂VAl nanocrystalline ribbon have been presented. The coercive field was found to increase from 0.24 to 1 Oe on lowering the temperature from 300 to 5 K. The irreversibility in the FC-ZFC was observed and the magnetization was found to follow T^3/2 law. Magnetoresistance measurements were done along the length of the ribbon and the MR of −0.07% was observed at 300 K. Cluster glass behavior was predicted by the power law.     

Development of underwater laser cutting technique for steel and zircaloy for nuclear applications

In nuclear field, underwater cutting and welding technique is required for post-irradiation examination, maintenance, decommissioning and to reduce storage space of irradiated materials like used zircaloy pressure tubes etc., of nuclear power plants. We have developed underwater cutting technique for 4.2 mm thick zircaloy pressure tubes and up to 6 mm thick steel using fibre-coupled 250 W average power pulsed Nd:YAG laser. This underwater cutting technique will be highly useful in various nuclear applications as well as in dismantling/repair of ship and pipe lines in water.     

Contact and non-contact magnetoimpedance in amorphous and nanocrystalline Fe73.5Si13.5B8CuV3Al ribbons

The giant magnetoimpedance (GMI) effect in amorphous and nanocrystalline Fe_73.5Si_13.5B₈CuV₃Al ribbons has been studied as a function of a dc magnetic field, by contact and non-contact methods. In the contact method, an MI of 19% was obtained in the nanocrystalline ribbon while it is of the order of 10⁴ in the non-contact method. The huge sensitivity of the non-contact method is promising with regard to the increase of the sensitivity of the MI sensors. Field dependence of MI has shown double peak behavior in contact method and single peak profile in non-contact method. The domains were found to lie normal to the plane of the ribbon, through MFM studies. All the experimental results were discussed using the Polivanov model.     

Assessment of surface relief and short cracks under cyclic creep in a type 316LN austenitic stainless steel

Formation of surface relief and short cracks under cyclic creep (stress-controlled fatigue) in type 316LN stainless steel was studied at temperatures ranging from ambient to 923 K using scanning electron microscopy technique. The surface topography and crack distribution behaviour under cyclic creep were found to be strong functions of testing temperature due to the difference in strain accumulation. At 823 K, surface relief mainly consisted of fine slip markings due to negligible accumulation of strain as a consequence of dynamic strain ageing (DSA) which led to an increase in the cyclic life. Persistent slip markings (PSM) with distinct extrusions containing minute cracks were seen to prevail in the temperature range 873–923 K, indicating a higher slip activity causing higher strain accumulation in the absence of DSA. Besides, a large number of secondary cracks (both transgranular and intergranular) which were partially accentuated by severe oxidation, were observed. Extensive cavitation-induced grain boundary cracking took place at 923 K, which coalesced with PSM-induced transgranular cracks resulting in failure dominated by creep that in turn led to a drastic reduction in cyclic life. Investigations on the influence of stress rate were also carried out which underlined the presence of DSA at 823 K. At 923 K, lowering the stress rate caused further strengthening of the contribution from creep damage marked by a shift in the damage mechanism from cyclic slip to diffusion.     

A novel and facile synthesis of 3,5-Disubstituted isothiozoles under metal free conditions using acetophenones and dithioesters

Abstract

A facile and conveniently simple new protocol is devised for the synthesis of 3,5-disubstituted and annulated isothiozoles under transition metal and catalyst free conditions utilizing easily available acetophenones, dithioesters and NH₄OAc. This strategy involves C=O and C=S functionalization via sequential imine formation followed by intra molecular cyclization and aerial oxidation forming consecutive C?N and S?N bonds respectively in one pot. This protocol offers a low cost, user friendly, straight forward and widely applicable approach to 3,5-disubstituted isothiazoles.     

Transient Repetitive Exposure to Low Level Light Therapy Enhances Collateral Blood Vessel Growth in The Ischemic Hindlimb of The Tight Skin Mouse

The tight skin mouse (Tsk^?/+) is a model of scleroderma characterized by impaired vasoreactivity, increased oxidative stress, attenuated angiogenic response to VEGF and production of the angiogenesis inhibitor angiostatin. Low‐level light therapy (LLLT) stimulates angiogenesis in myocardial infarction and chemotherapy‐induced mucositis. We hypothesize that repetitive LLLT restores vessel growth in the ischemic hindlimb of Tsk^?/+ mice by attenuating angiostatin and enhancing angiomotin effects in vivo. C57Bl/6J and Tsk^?/+ mice underwent ligation of the femoral artery. Relative blood flow to the foot was measured using a laser Doppler imager. Tsk^?/+ mice received LLLT (670 nm, 50 mW cm^?2, 30 J cm^?2) for 10 min per day for 14 days. Vascular density was determined using lycopersicom lectin staining. Immunofluorescent labeling, Western blot analysis and immunoprecipitation were used to determine angiostatin and angiomotin expression. Recovery of blood flow to the ischemic limb was reduced in Tsk^?/+ compared with C57Bl/6 mice 2 weeks after surgery. LLLT treatment of Tsk^?/+ mice restored blood flow to levels observed in C57Bl/6 mice. Vascular density was decreased, angiostatin expression was enhanced and angiomotin depressed in the ischemic hindlimb of Tsk^?/+ mice. LLLT treatment reversed these abnormalities. LLLT stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb of Tsk^?/+ mice.