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Electron nuclear double resonance (ENDOR) spectroscopy was used to measure the 1H hyperfine tensors of the non-heme-type catalase enzyme dimanganese(III,IV) oxidation state from Thermus thermophilus at pH 6.5-9. Two classes of anisotropic tensors associated with two D2O-exchangeable protons were found. A displaceable water molecule located in the active site was suggested as the origin of all ligand hyperfine couplings. These couplings were studied using a novel theoretical model suitable for multispin clusters. The angle-selected ENDOR spectrum was then simulated to determine the potential locations of 1H nuclei.

The hyperfine ligand coupling constants for two classes of nitrogen atoms in the manganese cluster were investigated. Experiments were performed wherein the S2 multiline EPR signal of the PSII membranes from the thermophilic cyanobacterium Synechococcus elongatus were analyzed by ENDOR spectroscopy. Results reveal the presence of a dry environment with weak H-bonds that bind coordinated ligands to the manganese cluster.

Studies on the water molecule coordination structure around paramagnetic Mn2+ ions in frozen solutions using classical metal ion solvation molecular dynamics simulations reveal that the data supports the symmetrization of the first two solvation shells. A three point flexible water model validates the distances to both shells. The proposed model suggests that Mn2+ ligand field second shell solvent fluctuation splitting causes the electron spin relaxation.

The homogeneous and substantial dispersion of nanoparticles into base fluids is vital since the final properties of any nanolubricant are estimated by their quality of stability. This paper addresses the effect of NiO nanoparticles dispersion into SN500 lubricant oil and its nonisothermal thermo stability. The dispersion of NiO nanoparticles is achieved by ultrasonication method. The thermo stability is estimated by Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The result shows that the thermo stability of base fluid enhances up to 0.3 wt.% particle concentration then it decreases due to agglomeration of dispersed nanoparticles. The findings recommend that 0.1 wt.% and 0.3 wt.% of NiO-nanolubricant can be used for the temperature-dependent applications up to 200∘C. [ABSTRACT FROM AUTHOR]

Byline: M. Sivaraja, S. Kandasamy Interest in natural fibres – both as natural and waste materials – for improving structural resistance as reinforcement arose mostly because of their lower cost and better availability. So far the work on concrete and other composites has been mainly concentrated on aero and automobile applications and a very few have been attempted in civil infrastructural activities. Those studies are mostly concentrated on mechanical strength, not on its usage in infrastructural systems. So here in this study, an attempt to reuse locally available waste fibrous natural materials in concrete as fibre composites, is made so that its resistance to cracking and unanticipated loadings like seismic effects is improved particularly in structural systems. In this paper rice husk, coconut coir and sugarcane waste fibres are taken and randomly distributed in reinforced concrete beams. Performance of the composite beams are ascertained under monotonic loading and compared with conventional concrete beams.

Seismic resistance calls for energy absorption in critical location of building/structural systems. Energy dissipation through moment-rotation-flexibility and load-deflection-ductility is aimed at in the development of composites. The present constructions are mostly in brick, mud and concrete and these materials are notoriously weak in tension and have meager energy absorbing capabilities. Hence the focus of the present study is to characterize the structure related and durability properties of locally available organic and inorganic waste composites like plastics, rubber, corn, rice husk, coir etc., for achieving reasonable energy absorbing capacity. In this characterization stress-strain, moment-rotation and load-deflection will be identified and the energy enhancement over conventional concrete will be characterized. [ABSTRACT FROM AUTHOR]

Describes the chemical identification of the amino acid free-radical site, one of two oxidizing equivalents stored in compound ES of the enzyme cytochrome c peroxidase (CcP). Trytophan, specifically Trp191, was identified by electron nuclear double resonance (ENDOR) spectroscopy.