Hydrostatic pressure effect on Tc of new BiS2‐based Bi4O4S3 and NdO0.5F0.5BiS2 layered superconductors

We investigate the external hydrostatic pressure effect on the superconducting transition temperature (T_c) of new layered superconductors Bi₄O₄S₃ and NdO_0.5F_0.5BiS₂. Though the T_c is found to have a moderate decrease from 4.8 K to 4.3 K (dT_c^onset/dP = –0.28 K/GPa) for Bi₄O₄S₃ superconductor, the same increases from 4.6 K to 5 K (dT_c^onset/dP = 0.44 K/GPa) up to 1.31 GPa followed by a sudden decrease from 5 K to 4.7 K up to 1.75 GPa for NdO_0.5F_0.5BiS₂ superconductor. The variation of T_c in these systems may be correlated to an increase or decrease of the charge carriers in the density of states under externally applied pressure. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The morphology of fibrillar polyethylene crystals

A comparison has been made of the morphology of fibrillar polyethylene crystals prepared by shear-induced crystallization and heterogeneous Ziegler-Natta catalysis under similar solvent and temperature conditions. Both specimens had a shish-kebab superstructure consisting of lamellar overgrowths on a filamentary backbone. For polyethylenes stirrer-crystallized at small supercoolings, the overgrown lamallae were removed by nitric acid oxidation followed by selective dissolution, leaving naked filamentary ribbons. Thermal analysis of these specimens suggested a dual molecular conformation of both folded and extended chains. The fact that these fibrils did not deform easily under uniaxial stress conforms with a core of extended chains. Thermal and oxidative behavior of polyethylenes prepared at lower crystallization temperatures suggested a greater content of chain folds in the central thread as the degree of supercooling increased. The Ziegler-Natta fibrils were degraded into lamellar fragments on oxidation and their thermal behavior suggested a predominantly folded-chain conformation. Uniaxial deformation occurred on stretching the Ziegler-Natta specimens in harmony with a core of folded chains. Molecular models have been proposed to account for the observed phenomena.     

Loop thermosiphon thermal collector for waste heat recovery power generation

A loop thermosiphon thermal collector was developed for the waste heat recovery power generation with electric capacity of 500 W. The heat collector with heat transfer area of 0.159 m² (500 mm width and 300 mm depth) was connected to the condenser with a shrunken heat transfer area by a loop. The thermal performance of the apparatus was declined when increasing the water filling rate to 90% as the working fluid occupied the internal volume. In the range of water filling rate between 30% and 60%, the effective thermal conductivity was around100 times of the conductivity of copper.     

Molecular docking approach on the molecular interactions involving beta-lactoglobulin (βLG)-4-Dicyanomethylene2,6-Dimethyl-4-Hpyran (DDP) dye in the presence of an antibiotic,norfloxacin

Molecular docking (MD) techniques were employed in the determination of binding stability of Beta-lactoglobulin (βLG) with 4-Dicyanomethylene2,6-Dimethyl-4-Hpyran (DDP) dye in the presence of quinolone-based antibiotic, norfloxacin (NOR). βLG acts as the host and drug/dye is employed as the guest molecule. The energetics and molecular interaction parameters of βLG-DDP were found to be stable than βLG-NOR. DDP resides in three distinguishably different binding sites of βLG, however the binding energies does not differ considerably. Interestingly, the energetics of βLG-NOR conformers differs significantly and reveals the existence of two distinguishable conformers. NOR acts as a hydrogen-bonding (HB) acceptor and the amino acid (AA) residues of βLG as the donor. The extent of HB interactions predominates over hydrophobic interactions in βLG-NOR than βLG-DDP complex. MD studies authenticates no direct binding of dye-drug inside the domains of βLG, when docked simultaneously. On the contrary, docking of dye to βLG-NOR complex enhances the binding stability. Several molecular interactions govern the stability of the complex and play a major role on the binding affinity of the host-guest complex in the presence of two competitive ligands. MD techniques authenticate that DDP/NOR is bound to several AA residues through conventional and non-conventional HB interactions accompanied with hydrophobic, pi-pi, pi-alkyl and van der Waals forces of interactions. Further, MD methods is employed as an efficient tool and a non-evasive technique in establishing the stability of 1:1complex of drug/dye with βLG in the present study.     

A rare earth metallocene containing a 2,2′-azopyridyl radical anion

Introducing spin onto organic ligands that are coordinated to rare earth metal ions allows direct exchange with metal spin centres. This is particularly relevant for the deeply buried 4f-orbitals of the lanthanide ions that can give rise to unparalleled magnetic properties. For efficacy of exchange coupling, the donor atoms of the radical ligand require high-spin density. Such molecules are extremely rare owing to their reactive nature that renders isolation and purification difficult. Here, we demonstrate that a 2,2′-azopyridyl (abpy) radical (S = 1/2) bound to the rare earth metal yttrium can be realized. This molecule represents the first rare earth metal complex containing an abpy radical and is unambigously characterized by X-ray crystallography, NMR, UV-Vis-NIR, and IR spectroscopy. In addition, the most stable isotope ⁸⁹Y with a natural abundance of 100% and a nuclear spin of ½ allows an in-depth analysis of the yttrium–radical complex via EPR and HYSCORE spectroscopy. Further insight into the electronic ground state of the radical azobispyridine-coordinated metal complex was realized through unrestricted DFT calculations, which suggests that the unpaired spin density of the SOMO is heavily localized on the azo and pyridyl nitrogen atoms. The experimental results are supported by NBO calculations and give a comprehensive picture of the spin density of the azopyridyl ancillary ligand. This unexplored azopyridyl radical anion in heavy element chemistry bears crucial implications for the design of molecule-based magnets particularly comprising anisotropic lanthanide ions.

Unambiguous characterization of the first 2,2′-azobispyridine radical-containing rare earth metal complex through X-ray crystallography, DFT computations, EPR and HYSCORE spectroscopy.     

Mineralization of gold in block copolymer micelles

Ultrasmall gold particles have been prepared inside the micelles of polystyrene-block-poly(ethylene oxide) and polystyrene-block-poly(2-vinylpyridine) in toluene. Starting point was the formation of a thermodynamically stable dispersion of HAuCl₄ or LiAuCl₄ in the inverse micelles of the block copolymer which were treated with hydrazine or pyrrole. Analysis of the effect of the reduction agent on the stability of the micelles yielded a simple model for the transformation process involving coagulation of the swelling micelles. Kinetic control of the different steps, i.e., reduction, mineralization, coagulation, film formation, allowed to prepare thin films in which highly uniform gold particles were arranged in yet unknown order. When pyrrole was employed for the reduction, the gold monocrystals got embedded in a shell of polypyrrole.