The hydrogenation of α-methylstyrene by tricarbonyl(cyclopentadienyl)hydride compounds of tungsten and molybdenum; support for a radical mechanism

Rates of reaction of the hydrides of tungsten and molybdenum of the form HM(η5-C₅H₅(CO)₃, with β-methylstyrene have been determined. The rate law is first order in olefin and in hydride. A mechanism involving a rate limiting step of hydrogen atom transfer to the olefin is consistent with the rate law, isotope effect and the absence of CO inhibition. The activation enthalpy for the reactions of HW(η5-C₅H₅)(CO)₃ and HMo(η5-C₅H₅)(CO)₃ are 97.5 ± 4.2 and 89.1 ± 3.3 kJ/mol, respectively. The rate constant for the reaction of styrene and HW(β5-C₅H₅)(CO)₃ is approximately that of β-methylstyrene, while β-methylstyrene was not observed to react under the conditions of the previous determinations. This suggests that attack by the hydride occurs at the β-carbon and this process is inhibited by substituents at that location.     

A generalized cluster theory of disordered alloys extended to include random off-diagonal elements

The generalized cluster expansion of the coherent potential approximation as applied to the case of a disordered binary alloy is discussed and extended to include the case of random off-diagonal elements of the Hamiltonian. Numerical results are presented.     

A combinatorial approach to the discovery of biocidal six-residue cyclic D,L-alpha-peptides against the bacteria methicillin-resistant Staphylococcus aureus (MRSA) and E. coli and the biofouling algae Ulva linza and Navicula perminuta

A combinatorial approach has been used to rapidly identify cyclic d,l-alpha-peptide hexamer sequences that exert biocidal activity towards both methicillin-resistant Staphylococcus aureus (MRSA) and E. coli bacteria, as well as the marine algae Ulva linza and Navicula perminuta. Evaluation of the effects against marine algae was facilitated by the development of a reliable, automated assay for toxicity, which should be of general utility for biofouling investigations. While the selective toxicity of cyclic D,L-alpha-peptides towards bacteria has been proven to be highly sensitive to minor changes in amino acid composition, this study demonstrates that this phenomenon extends to eukaryotic species as well, despite their significant structural differences. In performing toxicity assays on both prokaryotic and eukaryotic organisms in parallel, we have discovered examples of six-residue cyclic D,L-alpha-peptide sequences with either broad-spectrum or highly selective biocidal activities. Sequence [KWFFFH] (underlined amino acid abbreviations represent D-amino acid residues) was found to display 100-fold selectivity towards U. linza, demonstrating that the approach described herein may help lead to the development of new biofouling tools which are not generally toxic to all organisms, but rather specifically target microbial agents of interest.     

A novel metal-organic ternary topology constructed from triangular, square and tetrahedral molecular building blocks

A novel metal-organic network [Cu(4)(5-NH(2)-1,3-bdc)(4)(pyridine)(2)(H(2)O)(2)](n), displaying an unprecedented topology has been constructed utilizing the different coordinating functional groups of 5-NH(2)-1,3-bdc to generate a ternary network based upon vertex-linked triangular, square and tetrahedral molecular building blocks (MBBs).     

A kinetic investigation of styrene/ethyl acrylate copolymerization

An experimental study of the bulk-free radical copolymerization of styrene (STY)/ethyl acrylate (EA) initiated by 2,2′-azobisisobutyronitrile was conducted. Reactivity ratios were evaluated using both nonlinear least-squares (NLLS) and error-in-variables model (EVM) techniques. A thorough study of the kinetics over the full conversion range was subsequently carried out at a variety of feed compositions, initiator concentrations, and temperatures, with and without added chain transfer agent (CTA). © 1996 John Wiley & Sons, Inc.     

Primary decompositions and morita contexts

As shown by Mueller, a Morita context (R,M,N,S) yields a one-to-one order preserving correspondence between certain torsion theories on R^Mand S^MIn addition, Goldman has defined the notions of prime kernei functors and primary modules for arbitrary associative rings. These notions lead to a type of primary decomposition for kernel functors. In this paper we show that under the above correspondence prime kernel functors correspond to prime kernel functors and primary modules correspond to primary modules. Finally we show that the above correspondence preserves the primary decomposition of kernel functors.     

Bis-phenanthroline copper(II) phthalate complexes are potent in vitro antitumour agents with 'self-activating' metallo-nuclease and DNA binding properties

Three, structurally characterised, bis-phen Cu(II) complexes of the phthalate isomers display rapid, low micromolar in vitro cytotoxicity against a range of epithelial tumour cells. The complexes induce relaxation of supercoiled plasmid DNA in the absence of external reducing agents and display efficient CT-DNA, Poly[d(A-T)](2) and Poly[d(G-C)](2) binding.     

Mechanical properties of liquid-filled shellac composite capsules

This paper describes the mechanical properties of thin-walled, liquid-filled composite capsules consisting of calcium pectinate and shellac. In a series of experiments we measured the deformation of these particles in a spinning drop apparatus. For different pH-values we studied the elastic properties of these particles and compared the obtained results with the mechanical response measured by squeezing capsule experiments. In analogy to these experiments, we also investigated liquid-filled unloaded calcium pectinate capsules without the addition of shellac. The deformation properties of these experiments and the surface Young moduli were in good agreement. Furthermore we investigated the liquid-filled calcium pectinate and the composite capsules by NMR microscopy. These experiments allowed investigations of the membrane thickness and the kinetics of membrane growing. Additional characterizations by stress controlled small amplitude surface shear experiments of similar composed gel layers provided coherent results for the surface Young modulus.     

Biological activity and coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands

The coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands, which had previously shown good anti-Candida activity, were investigated by pH-potentiometric and UV-Vis spectroscopic methods. These studies confirmed the coordination mode of the ligands to be through the N of the imine and deprotonated phenol of the coumarin-derived ligand in solution. In addition, the more active complexes and their corresponding ligands were investigated in the presence of copper(II) in liquid and frozen solution by ESR spectroscopic methods. A series of secondary amine derivatives of the Schiff base ligands, were isolated with good solubility characteristics but showed little anti-Candida activity. However, cytotoxicity studies of the secondary amines, together with the copper complexes and their corresponding ligands, against human colon cancer and human breast cancer cells identified the chemotherapeutic potential of these new ligands.