Optimization of Nb-substitution and Cs+/Sr+2 ion exchange in crystalline silicotitanates (CST)

Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is a candidate material for remediation of aqueous nuclear waste streams. Niobium substituted crystalline silicotitanates (Nb-CST) with varying concentrations of Nb (2, 4, 8, 12 and 24 mmol) and with constant concentrations of Ti-12 mmol, Si-16 mmol, Na-165 mmol were prepared hydrothermally and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA, surface area respectively. Batch experiments were carried out to study the kinetics of uptake of Cs¹³⁷ and Sr⁹⁰, to estimate the decontamination factor (DF) values and distribution coefficients (K _d) for the above synthesized Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs and Sr by Nb-CST for the optimized Nb-concentration of 4 mmol after 24 h of equilibration was 355 and 136 respectively. The K _d values for uptake of Cs and Sr for Nb-CST (Nb-4 mmol) after 24 h of equilibration was found to be 35,490 and 13,500 ml/g respectively. The ion exchange capacity of Nb-CST (Nb-4 mmol) towards Sr ⁹⁰ and Cs¹³⁷ was estimated to be 11.8 and 3.2 meq/g respectively.     

1‐Alkyl‐2‐{(O‐Thioalkyl)Phenylazo}Imidazole Complexes of PbII and Their Photochromic Property

Pb^II complexes of 1‐alkyl‐2‐{(o‐thioalkyl)phenylazo}imidazole (SRaaiNR'), [Pb(SRaaiNR')₂X₂] were characterized by spectroscopic studies. The single‐crystal X‐ray structure of [Pb(SEtaaiNEt)₂Cl₂] (SEtaaiNEt = 1‐ethyl‐2‐{(o‐thioalkyl)phenylazo}imidazole) proved imidazolyl‐N and –SEt coordination forming unusual puckered eight member chelate rings. UV light irradiation of the complexes in DMF solution shows E‐to‐Z (E and Z refer to trans and cis‐configuration about –N=N–, respectively) photoisomerization of the coordinated azoimidazole. The rate of isomerization follows the sequence: [Pb(SRaaiNR')₂Cl₂] < [Pb(SRaaiNR')₂Br₂] < [Pb(SRaaiNR')₂I₂]. Quantum yields (φ_E→Z) and the activation energy (E_a) of the isomerization of the complexes are lower than observed for the free ligand. This can be explained by considering the molecular assembly and the thus observed increase in mass and rotor volume of the complexes. DFT and TDDFT calculations of optimized geometry could explained the spectral properties and photochromic activity.     

Microtribological study of perfluoropolyether with different functional groups coated on hydrogen terminated Si

Friction and wear properties of different perfluoropolyether (PFPE) films with and without hydrogen termination on Si (Si-H) were studied using a ball-on-disk tribometer. The physical and chemical properties of the films were evaluated using contact angle measurement, atomic force microscopy and X-ray photoelectron spectroscopy. Coating of PFPEs onto bare Si has lowered the coefficient of friction (from 0.6 for Si to ∼0.05 with PFPE) and enhanced the wear durability (20,000 times) in comparison with those for bare Si which failed immediately. The introduction of hydrogen termination onto Si prior to PFPE coating has further increased the wear durability of PFPE with different functional groups several times (>5 times) under a normal load of 30 mN and a sliding speed of 0.052 m/s.     

Brownian bridge in quantum probability

The Classical Brownian Bridge is constructed in Symmetric Fock space over an appropriate base Hilbert space. While the representation of the classical Ito-Wiener integral with respect to the increments of the Brownian bridge implements the unitary isomorphism between the Fock space and the (classical) L² space of the Brownian bridge (as is the case with the standard Brownian motion (SBM)), the quantum Ito-integrals with respect to the associated creation and annihilation bridge processes give different left-and right-integrals. This essentially displays the feature that the Brownian Bridge is not a process of independent increments.     

Design,synthesis and MAO inhibitory activity of 2-(arylmethylidene)-2,3-dihydro-1-benzofuran-3-one derivatives

A series of 2-(arylmethylidene)-2,3-dihydro-1-benzofuran-3-one derivatives(aurones, 1–20) were synthesized and screened for their inhibitory activity against h MAO. Seventeen compounds(1–5, 7–17,19) were found to be selective towards h MAO-B, while two were non-selective(6 and 20) and one(18)selective towards h MAO-A. Compound 17(Ki = 0.10 0.01 mmol/L) was found to be equally potent and selective towards h MAO-B, when compared with the standard drug Selegiline(Ki = 0.12 0.01 mmol/L).Nature and position of substitution in aryl ring at 2nd position of benzofuranone influences h MAO-B inhibitory potency, while their structural bulkiness influences selectivity between h MAO-A and h MAO-B.Molecular docking simulation was also carried out to understand the interaction of inhibitor with the enzyme at molecular level, and we found the docking results were in good agreement with the experimental values. Comparison of the activity profile of the aurones with their corresponding flavones reported earlier by our group revealed that there exists no difference in potency as well as selectivity.     

SURFACE PROPERTIES OF SOME LOW MOLECULAR WEIGHT PROTEINS

Surface properties of four proteins having molecular weights less than 5,000 are reported at air/water and alumina/water interface at pH 7.0. Reversibility in the adsorption of these proteins at the alumina/water interface is tested. The adsorption on alumina/water interface has been found to be controlled by electrostatic interaction. Positive adsorption was obtained when protein and alumina surface had opposite charges and negative adsorption was obtained when both protein and surface had same charges. Of the four proteins reversibility in adsorption was observed with the one having the lowest molecular weight of 3100. The adsorption behavior apparently had no correlation with their surface hydrophobic!ty. Time dependent changes in air/water interfacial tension was observed for all the four proteins indicating time dependent loosening of compact protein structure and surface unfolding.