Zinc and Cadmium Complexes of a Plant Metallothionein under Radical Stress: Desulfurisation Reactions Associated with the Formation of trans‐Lipids in Model Membranes

Biomimetic tandem protein/lipid damage : The reactions of reductive reactive species, produced by γ irradiation of water, with Zn and Cd complexes of a metallothionein from a plant afford diffusible sulfur‐centred radicals generated from methionine residues and sulfide ligands. These species migrate from the aqueous phase to the lipid bilayer and transform the cis double bond of the oleate moiety to trans isomer (see scheme).

     

Extraction and partial characterisation of antioxidant pigment produced by Chryseobacterium sp. kr6

Pigments synthesised by Chryseobacterium sp. kr6 growing on feather waste were extracted and characterised. The pigment extract was characterised by KOH test, UV–vis, CIELAB colour system, HPLC-DAD-MS, FTIR and its antioxidant capacity was evaluated. A positive bathochromic shift was observed when kr6 colonies or pigment extracts were subjected to alkaline solution (20% KOH) and a λ_max at 450 nm was detected for acetone extracts, although no typical fine structure of carotenoids was detected in the electomagnetic spectra. The HPLC profile of the extracted pigment showed that the compound has three different peaks with λ_max near 450 nm. The FTIR analysis shows some principal functional groups from a flexirubin-like molecule. The pigmented compound also presents antioxidant activity evaluated by the scavenging of the ABTS radical.     

Topological insight into the non-arrhenius mode hopping of semiconductor ring lasers

We investigate both theoretically and experimentally the stochastic switching between two counterpropagating lasing modes of a semiconductor ring laser. Experimentally, the residence time distribution cannot be described by a simple one-parameter Arrhenius exponential law and reveals the presence of two different mode-hop scenarios with distinct time scales. In order to elucidate the origin of these two time scales, we propose a topological approach based on a two-dimensional dynamical system.     

Adiabatic dynamics in open quantum critical many-body systems

The purpose of this work is to understand the effect of an external environment on the adiabatic dynamics of a quantum critical system. By means of scaling arguments we derive a general expression for the density of excitations produced in the quench as a function of its velocity and of the temperature of the bath. We corroborate the scaling analysis by explicitly solving the case of a one-dimensional quantum Ising model coupled to an Ohmic bath.     

Novel twist grain boundary smectic-C phases

Several new kinds of smectic-C twist grain boundary phases (TGBC) have been observed during the last few years. These pure compounds or mixtures exhibit unusual textures with polygonal lattices (square or hexagonal grids) in the plane normal to the TGB helix. The structure of these new phases seems to be complex and different from reported and predicted TGBC phases. In this article, we review the main results obtained on these different new phases, and we propose new TGBC structures based on the well-known splayed polarization --twisted director structures adopted by chiral smectic-C's in planar aligned (bookshelf) cells. The observed square or hexagonal lattices are made of superimposed pairs of unwinding lines due to the suppression of the helix within smectic-C blocks by the grain boundaries (unwinding walls). A lattice-free TGBC occurs if the helix within smectic-C blocks is suppressed completely. Received 15 March 2001     

Semigroups of length increasing transformations

The semigroup of all operators T such that (Tx,Tx)?(x,x), for all elements of x of a finite-dimensional complex vector space with ( , ) a given, possibly indefinite Hermitian form on that space, is the object under study. It is shown that this semigroup is closed under the operation of taking adjoints with respect to the given form and that every semigroup element may be written as a product of a unitary and a self-adjoint operator (polar form), with the unitarity and self-adjointness defined with respect to the given form. It is further shown that the semigroup is generated by the group of isometries of the given form and the union of a finite family of semigroups, each of which is of an elementary nature. The intersection of the above semigroup with the complex symplectic group is also considered; all the above results have analogues in this case.     

Optical and electrical energy gaps of the n-type impure silicon at 300 K

The band-gap narrowing ΔE_{g, opt} and ΔE_{g, elec} (or ΔE_{g, eff}) for optical and electrical energy gaps of the n-type impure silicon at 300 K, are investigated based on simplified models of heavily doped semiconductors. It is suggested that, for $\text{4 × 10}{}^{19}\text{cm}{}^{-3}\text{? n}{}_0\text{? 3 × 10}{}^{20}\text{cm-3}\text{, ΔE}{}_{\mathrm{g,\; elec}}\text{(or ΔE}{}_{\mathrm{g,\; eff}}\text{)}$ is significantly larger than ΔE_{g, opt}, in good agreement with observed results. This difference is caused especially by the effect of the polaron.