A study on the bond strength of tension lap splices in self compacting concrete

The primary objective of the research reported in this paper was to evaluate the effect of using self compacting concrete on the bond strength and mode of bond failure of tension lap splices anchored in normal strength concrete (NSC). Studies on the effect of transverse reinforcement on anchored reinforcement in self compacting concrete to prevent brittle mode of failure is limited. To meet this objective, full-scale NSC beam specimens were tested. Each beam was designed with bars spliced in a constant moment region at mid-span with various levels of stirrup confinement. The slip of the reinforcement with respect to concrete is also measured by providing notches at the end of the splices. Test results indicated that there is an increase in the bond strength when self compacting concrete is used in place of vibrated concrete. Ductility and splice strength increased as the confinement increased. When the stirrup spacing is less than 150 mm, the failure in the splice region was by yielding of steel. The influence of confinement on the crack formation of the beams is also reported.     

The kinetics of the polymerization reaction of toluene diisocyanate with HTPB prepolymer

The uncatalysed and catalysed polymerization of a hydroxyl-terminated polybutadiene with toluene diisocyanate has been studied in toluene solution at four different temperatures. The rate constants (k₁, k₂) and the activation parameters (Ea₁, Ea₂, ΔS₁^?, ΔS₂^?) for the isocyanate groups in the 4 and 2 positions were calculated. It was found that the catalysts enhance the reactivity of the 2 position isocyanate group rather than the 4 position isocyanate group. It was also found that diethylcyclohexylamine has higher selectivity than dibutyltin dilaurate to enhance the reactivity of the isocyanate group in the 2 position. The effect of solvent has also been studied. The reactivity decreased in the following order; benzene = toluene > chlorobenzene > dioxane > nitrobenzene. © 1993 John Wiley & Sons, Inc.     

Grafting of glycidyl methacrylate onto gelatin

Gelatin was graft copolymerized with poly(glycidyl methacrylate) using potassium peroxydisulfate in aqueous medium. Effect of temperature, time, initiator, monomer, and backbone concentrations were studied. The percent grafting was found to increase initially and then decrease in all the cases except with variation of monomer concentration. The rate of grafting, grafting efficiency, and percent of grafting were calculated. The grafting results have been discussed in the light of the rate of grafting. Mechanical properties, FT IR spectra, percent swelling, and percent dye uptake were carried out on the graft copolymerization and the results discussed.     

Ovarian cancer proteomics: Many technologies one goal

The last decade has seen major changes in the technologies used to identify markers for diagnosing cancer. This review focuses on recent developments on the evolving field of biomarker discovery, and validation techniques using proteomics platforms for ovarian cancer. It is possible now to diagnose various disease conditions using microliter quantities of body fluids. Currently the major developments were made in three distinct areas: (i) protein profiling, (ii) high-throughput validation techniques, and (iii) solid and liquid phase protein microarray platforms for analyzing candidate markers across subclasses and stages of cancers. The recent addition to the long list of technologies is metabolomics using metabolite profiling and informatics-based filtering of information for biomarker discovery of ovarian cancer. Emerging technologies need to address ways to eliminate the limitations posed by the complex dynamic nature of body fluids as well as ways to enrich low-abundance tumor markers if they were to become a successful biomarker discovery tool. These new technologies hold significant promise in identifying more robust markers for ovarian cancer. Since the prevalence of this disease in the population is low, the test must have a high specificity.     

S,N co-doped graphene quantum dots decorated TiO2 and supported with carbon for oxygen reduction reaction catalysis

Sluggish kinetics and catalyst instability in oxygen reduction reaction are the central issues in fuel cell and metal-air battery technologies. For that, highly active, stable, and low-cost non-platinum based electrocatalysts for oxygen reduction reaction are an immediate requirement in fuel cell and metal-air battery technologies. A new composite (S,N-GQD/TiO₂/C-800) is synthesized, made of sulfur (S) and nitrogen (N) co-doped graphene quantum dot (GQD) with TiO₂. This composite is supported on carbon on heating at 800 °C under N₂ atmosphere and is explored for oxygen reduction reaction (ORR) catalyst. The synthesized composite S,N-GQD/TiO₂/C-800, shows outstanding catalytic activity with an onset potential of 0.91 V and a half-wave potential of 0.82 V vs. RHE, an alkaline medium. The Tafel slope of the catalyst is 61 mV dec^?1. The catalyst is an excellent methanol tolerant and shows good stability in an alkaline medium. The excellent ORR activity of S,N-GQD/TiO₂/C-800 is ascribed to well-built interactivity between the S,N-GQD/TiO₂, and the carbon support. The unique structure offers advantages, with outstanding electrical conductivity, high surface area, and excellent charge transfer kinetics between the doped GQD and TiO₂ interface and subsequently from the carbon surface to the S,N-GQD/TiO_2.     

Metal-containing polyurethanes

Summary Metal-containing polyurethanes were prepared from cobalt and copper mono(hydroxyethyl) phthalate with hexamethylene diisocyanate and tolylenediisocyanate and characterized. The presence of ionic links in the polymers was shown by IR spectra, solution viscosity and conductance measurements.     

Studies of the thermal properties of poly (2,3-dibromo-but-2-ene-1,4-diol adipate)

Poly(2,3-dibromo-but-2-ene-1,4-diol adipate) (PDBD), molecular weight 1 900, was prepared. 1ts i.r. and n.m.r. spectra are discussed. Its thermal properties were extensively studied by d.s.c. The polymer melted at 366 K and decomposed at 577 K. On first heating, it did not show any T_g or T_c; but after a single heat treatment, it exhibited T_g at 250K and two cold crystallization exotherms at 310K and 342K. The effect of cooling rate on ΔH_f, ΔS_f, ΔH_c and crystallinity was studied. The polymer was annealed at 320K and 342K for various time intervals. It was found that ΔH_f exhibited a maximum at 320K, and reached an asymptotic value at 342K. The multiple endotherms observed at 342K are discussed in terms of the different crystal morphologies of the polymer.