Radiation effects on styrene–butadiene–ethylene–propylene diene monomer‐multiple walled carbon nanotube nanocomposites: vulcanization and characterization

Varying compositions of styrene–butadiene rubber (SBR) and ethylene–propylene diene monomer (EPDM) 50:50 blend containing multiple walled carbon nanotube (MWNT) as nanoparticulate filler (0.5–5%) were prepared and their efficacy for radiation vulcanization was analyzed by gel‐content, Charlesby‐Pinner parameter, and crosslinking density measurements. Radiation sensitivity of the nanocomposites increased with increase in the MWNT fraction and radiation dose in the dose range studied. The elastic modulus, tensile strength increased with the radiation dose, while elongation at break exhibited downward trend. The extent of reinforcement as assessed using Kraus equation suggested high reinforcement of blend on MWNT addition. The reinforcing mechanism of nanocomposites was studied by various micromechanics models which predicted higher modulus than the experimentally observed results, indicating agglomeration in the nanocomposites. The thermal stability of the composites increased with increase in MWNT loading has been attributed to the antioxidancy induced by nanotubes and higher crosslinking extent of the nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and X-ray structural studies of pyrimidin-2,4-dione and 2-thioxo-1H-pyrimidin-4-one bearing chloroethyl moiety

The present work is aimed to investigate non-covalent bonding capabilities of uracil derivative bearing hydrophobic side chain in solid crystalline state. The synthesis and crystal structure of 5-(2-chloro-ethyl)-6-methyl-uracil 3 and 5-(2-chloro-ethyl)-6-methyl-2-thiouracil 4 are described, which revealed sulfur-π interaction including resonance-induced intermolecular H-bonding in 4 whereas compound 3 showed only strong H-bonding and formed a dimer. Thus the analysis of such moieties in solid state provides useful structural information on the binding characteristics of functional groups and has implications for the de novo design of drugs and enzyme's inhibitors.     

Grafting Vinyl Monomers onto Nylon 6 Fiber. III. Graft Copolymerization of Vinyl Monomers onto Nylon 6 Fiber in Water Medium in the Presence of Fructose

Nylon 6 fiber was grafted with various vinyl monomers e.g., methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA), in water in the presence of fructose using a carbon arc lamp as the source of photoirradiation at 70°C and a liquor ratio of 1:26. The effects of various parameters, e.g., monomer concentration, time of grafting, and fructose concentration on grafting reactions, were studied individually for each monomer. The graft yield is greatly enhanced by increasing the monomer concentration and the time of grafting. However, the optimum fructose concentration is required for maximum grafting efficiency. The accelerating action of photopolymerization by fructose was attributed to the sensitizing action of fructose involving an energy transfer.     

A mathematical model of measurement uncertainty of single substrate enzyme assays

Clinical laboratory tests provide critical information at every stage of the medical decision‐making process, and measurement of the activity levels of enzymes such as alkaline phosphatase, lactate dehydrogenase, etc. provide information regarding various body functions such as the liver and gastrointestinal tract. The uncertainty associated with these enzyme measurement processes describes the quality of the measurement process, and therefore methods to improve the quality of the measurement process require minimizing the measurement uncertainty of the enzyme assay. In this study, we develop a mathematical model of the lactate dehydrogenase measurement process, with uncertainty introduced into its parameters that represent the sources of variation in the different components and stages of the measurement process. The Monte Carlo method is then utilized to estimate the uncertainty associated with the model, and therefore the measurement process. An empirical function used to generate estimates of uncertainty for patient samples with unknown activity levels is constructed using the model. The model is then used to quantify the contributions of the individual sources of uncertainty to the net measurement uncertainty and also quantify the effect of uncertainty within the calibration process on the distribution of the measurement result. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation of cesium trimolybdate by the thermal decomposition of a new oxomolybdenum(VI) oxalato complex

A new molybdenum(VI) complex Cs₂(NH₄)2[Mo₃O₈(C₂O₄)₃] (CAMO) has been prepared and characterized by chemical analysis and IR spectral studies. Thermal decomposition studies have been made using TG, DTA and DTG techniques. The compound is anhydrous and stable up to 160°C. Thereafter it decomposes in three stages. The first and the second stages occur in the temperature ranges 160–220°C and 220–280°C to give the intermediate compounds having the tentative compositions Cs₄(NH₄)₂[Mo₆O₁₆(C₂O₄)₃(CO₃)₂] and Cs₄[Mo₆O₁₆(C₂O₄)₂(CO₃)₂] respectively, the later then decomposing to give the end product Cs₂Mo₃O₁₀ at 370°C. The end product was characterized by chemical analysis, IR spectral and X-ray studies.     

Bispidine as a β-strand nucleator: from a β-arch to self-assembled cages and vesicles

The development of synthetic scaffolds that nucleate well-folded secondary structures is highly challenging. Herein, we designed and synthesized a series of core-modified peptides (F1, F2, F3, and F4) that fold into β-strand structures. These bispidine-scaffolded peptides were studied by CD, IR, NMR, single crystal XRD, and Molecular Dynamics (MD) simulations to investigate their conformational preferences. Solid-state and solution studies revealed that bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating the β-strand structure. Scaffolds that nucleate an isolated β-strand conformation are rare. Bispidine placed at the C-terminus of the peptide chain could nucleate a β-strand conformation, while bispidine placed at the middle resulted in a β-arch conformation. This nucleation activity stems from the ability to restrict the psi torsion angle (ψ) through intramolecular C5 hydrogen bonding between the equatorial hydrogen(s) of bispidine and the carbonyl oxygen(s) of the amino acid close to the scaffold. Furthermore, the bispidine peptidomimetic with a super secondary structure, namely β-arch, assembled into single-hole submicron cages and spherical vesicles as evident from microscopic studies. The design logic defined here will be a significant strategy for the development of β-strand mimetics and super secondary structures.

Bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating β-strand structures. These β-strand mimetics self-assemble to single hole submicron cages and vesicles.     

N-Bridged Acyclic Trimeric Poly-Cyclodiphosphazanes: Highly Tuneable Cyclodiphosphazane Building Blocks

We have synthesized a completely new family of acyclic trimeric cyclodiphosphazane compounds comprising NH, NⁱPr, N^tBu and NPh bridging groups. In addition, the first NH-bridged acyclic dimeric cyclophosphazane has been produced. The trimeric species display highly tuneable characteristics so that the distance between the terminal N(H)R moieties can be readily modulated by the steric bulk present in the bridging groups (ranging from ≈6 to ≈10 Å). Moreover, these species exhibit pronounced topological changes when a weak non-bonding NH⋅⋅⋅π aryl interaction is introduced. Finally, the NH-bridged chloride binding affinities have been calculated and benchmarked along with the existing experimental data available for monomeric cyclodiphosphazanes. Our results underscore these species as promising hydrogen bond donors for supramolecular host–guest applications.     

EPR evidence for a single electron transfer mechanism in reactions of aromatic ketones with lithium amides

Direct spectroscopic evidence (EPR) supporting a single electron transfer mechanism in the reaction of lithium amides with aromatic ketones is presented.