Study of metal poisoning in natural rubber–based tire‐tread compound

In the present study the effect of metal poisoning was studied in a natural rubber (NR)–based tire‐tread compound. The experimental compound contained 1000 ppm copper metal as an additional ingredient. A detailed study was carried out and the results of the experimental compound were compared against a control compound having no metal ion. The effect of metal poisoning was not significant in the case of the green experimental compound, even after prolonged storage of 150 days. However, the cured experimental compound deteriorated substantially after ageing in aerobic‐, anaerobic‐, oil‐, and outdoor‐ageing conditions. The ozone resistance property of the experimental compound also proved to be inferior. The degradation kinetic of metal poisoning was found to be a first‐order reaction and the service life (as expressed by the half‐life period) was drastically reduced for the poisoned compound. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1492–1499, 2005     

Morphology and properties of stearate‐intercalated layered double hydroxide nanoplatelet‐reinforced thermoplastic polyurethane

In the past few years, layered double hydroxides (LDHs) with monolayer structure have been much studied for the development of polymer nanocomposites. LDHs with intercalated stearate anions form a bilayer structure with increased interlayer spacing and are expected to be better nanofillers in polymers. In the work reported, thermoplastic polyurethane (PU)/stearate‐intercalated LDH nanocomposites were prepared by solution intercalation and characterized. X‐ray diffraction and transmission electron microscopy confirmed the exfoliation at lower filler loading followed by intercalation at higher filler loading in PU matrix. As regards mechanical properties, these nanocomposites showed maximum improvements in tensile strength (45%) and elongation at break (53%) at 1 and 3 wt% loadings. Maximum improvements in storage and loss moduli (20%) with a shift of glass transition temperature (15 °C) and an increase in thermal stability (32 °C) at 50% weight loss were observed at 8 wt% loading in PU. Differential scanning calorimetry showed a shift of melting temperature of the soft segment in the nanocomposites compared to neat PU, possibly due to the nucleating effect of stearate‐intercalated LDH on the crystal structure of PU. All these findings are promising for the development of mechanically improved, thermally stable novel PU nanocomposites. Copyright © 2011 Society of Chemical Industry     

An electroamalgamation approach to separate 47Sc from neutron-activated 46Ca target for use in cancer theranostics

Scandium-47 [T_½ = 3.35 d, E_β-(max.) = 600 keV, Eγ = 159 keV] is a relatively new radioisotope that holds tremendous potential for use in cancer theranostics. The radioisotope was produced by thermal neutron irradiation of enriched ⁴⁶Ca producing ⁴⁷Ca, which decays by β^? emission to ⁴⁷Sc. A viable method based on the selective electroamalgamation of Ca²⁺ ions has been developed for the clinical-scale separation of ⁴⁷Sc from ⁴⁷Ca. The overall yield of ⁴⁷Sc after the separation process was >80% and it was obtained with >99.9% radionuclidic purity in a form suitable for radiopharmaceutical preparation. This strategy holds promise for future clinical translation of this radioisotope.     

Microstructure and Thermal Characterization of Plasma-Sprayed Nanostructured La2Ce2O7-Doped YSZ Coatings

Nanostructured La₂Ce₂O₇-doped YSZ coatings were developed using atmospheric plasma-spraying technique by optimizing various process parameters. To ensure the retention of nanostructure, the molten state of nanoagglomerates was monitored using plasma and particle diagnostic tools. It was observed that the morphology of the coating exhibits a bimodal microstructure consisting of nanozones reinforced in a matrix of fully-molten particles. The thermal diffusivity of nano-LaCeYSZ coatings is lower than that of nano and bulk YSZ. The reason for this change in thermal diffusivity may be attributed to scattering of phonons at grain boundaries, point defect scattering and higher inter-splat porosity. Also, the thermal conductivity of the nanocomposite coatings was lower than those of nanostructured and bulk YSZ coatings. XRD results show cubic zirconia with a small amount of tetragonal zirconia. The average grain size of the as-sprayed La₂Ce₂O₇-YSZ nanocomposite coatings is ~150-200 nm. The improved thermal behavior is mainly due to a dense, packed, and more compact structure of the coatings.     

Microstructural evolution and mechanical properties of misch metal added Mg-Si alloys

Effect of misch metal additions (0.3, 0.6, 0.9 and 1.2 wt%) on the refinement of Mg₂Si phase in Mg-1.15Si alloy has been studied and compared with the base alloy. MM addition effectively refines the microstructure by breaking the α-Mg halos and lamellar eutectic phase and the maximum refinement is obtained for 0.6 MM addition. For higher MM additions (0.9 and 1.2 wt%), the refinement effect gets reduced and the formation of RE-Si compound is dominated. Improved tensile properties are obtained with the addition of MM and are attributed to the refinement of microstructure and the presence RE-Si compound. The tensile properties obtained are correlated with the microstructure and mirofractomechnisms.     

Engineering 2-oxoglutarate dehydrogenase to a 2-oxo aliphatic dehydrogenase complex by optimizing consecutive components

Multienzyme complexes have the potential for green catalysis of sequential reactions. The Escherichia coli 2-oxoglutarate dehydrogenase complex (OGDHc) was converted from a 2-oxoglutarate dehydrogenase to a 2-oxo aliphatic dehydrogenase complex by engineering consecutive components. OGDHc catalyzes succinyl-CoA synthesis in the Krebs cycle. OGDHc is composed of three components: E1o, 2-oxoglutarate dehydrogenase; E2o, dihydrolipoylsuccinyl transferase; E3, dihydrolipoyl dehydrogenase. There are three substrate checkpoints. One is in E1o and two in E2o. OGDHc was reprogrammed to accept alternative substrates by evolving the E1o and E2o components. Wt-ODGHc does not accept aliphatic substrates. E1o was previously engineered to accept a non-natural aliphatic substrate, 2-oxovalerate (2-OV). E2o also required engineering to accept 2-OV in the overall reaction. Hence, saturation mutagenesis libraries of E2o were screened for 2-OV activity. E2o-S333M, E2o-H348F, E2o-H348Q, and E2o-H348Y were identified to show activity for 2-OV in the reconstituted complex. Variants also displayed activity for larger aliphatic substrates.     

Vitiligo, psoralen, and melanogenesis: some observations and understanding

Since the etiology of vitiligo is still unknown, we searched for some abnormal biochemical parameters, if any, in subjects with vitiligo. Higher urinary excretion of indole metabolites in vitiliginous patients have been noted, in association with higher dioxygenase, superoxide dismutase, and tyrosine aminotransferase activity in their serum. Similar results have also been found in an animal model, Bufo melanostictus, during induced tyrosinase inhibition. Treatment with psoralen can reverse the parameters, except tyrosine aminotransferase, to a normal level. Although psoralens are not the magic bullet for the therapy of vitiligo, they are still being used as a chemotherapeutic agent against vitiligo on a major scale to date. Tryptophan was found to participate in the pathway of melanogenesis, as a precursor as well as a positive regulator of tyrosinase. Its behavior in this regard is much more similar to the conventional substrates tyrosine and dopa (dihydroxyphenylalanine). In consideration of combined participation of tyrosine and tryptophan in the synthesis of melanin and its breakdown, the possible influence of different enzymatic reactions, like mono-oxygenase, dioxygenase, and deamination, has been suggested.     

Detection of cross-reactive antigens shared by Fusarium oxysporum and Glycine max by indirect ELISA and their cellular location in root tissues

Pathogenicity test of Fusarium oxysporum on ten cultivars of soybean revealed Soymax and Punjab-1 to be most resistant while JS-2 and UPSM-19 were most susceptible. Antigens were prepared from the roots of all the ten varieties of soybean and the mycelium of F. oxysporum. Polyclonal antisera were raised against the mycelial suspension of F. oxysporum and the root antigen of the susceptible cultivar UPSM-19. Cross reactive antigens shared by the host and the pathogen were detected first by immunodiffusion. The immunoglobulin fraction of the antiserum was purified by ammonium sulfate precipitation and DEAE-Sephadex column chromatography. The immunoglobulin fractions were used for detection of cross-reactive antigens by enzyme-linked immunosorbent assay. In enzyme-linked immunosorbent assay, antigens of susceptible cultivars showed higher absorbance values when tested against the purified anti-F. oxysporum antiserum. Antiserum produced against UPSM-19 showed cross-reactivity with the antigens of other cultivars. Indirect staining of antibodies using fluorescein isothiocyanate indicated that in cross-sections of roots of susceptible cultivar (UPSM-19) cross-reactive antigens were concentrated around xylem elements, endodermis and epidermal cells, while in the resistant variety, fluorescence was concentrated mainly around epidermal cells and distributed in the cortical tissues. CRAs were also present in microconidia, macroconidia and chlamydospores of the fungus.     

Neutralizing monoclonal antibodies against listeriolysin: mapping of epitopes involved in pore formation

Six different mouse monoclonal antibodies (MAbs) and a specific rabbit polygonal antibody were raised against listeriolysin. Four of the MAbs also recognized seeligeriolysin, and five cross-reacted with ivanolysin. The hemolytic activity could be neutralized by the polygonal antibody as well as by five of the MAbs. None of the neutralizing antibodies interfered with the binding of listeriolysin to the cellular membrane. The epitopes recognized by the MAbs were localized by using overlapping synthetic peptides between positions 59 and 279, a region hitherto not implicated in mediating hemolytic activity.