Algebraic approach in unifying quantum integrable models

A novel algebra underlying integrable systems is shown to generate and unify a large class of quantum integrable models with given $R$-matrix, through reductions of an ancestor Lax operator and its different realizations. Along with known discrete and field models a new class of inhomogeneous and impurity models are obtained.Comment: Revtex, 6 pages, no figure, revised version to be published in Phys. Rev. Lett., 199

Theoretical study of the electronic spectra of small molecules that incorporate analogues of the copper-cysteine bond

The copper-sulphur bond which binds cysteinate to the metal centre is a key factor in the spectroscopy of blue copper proteins. We present theoretical calculations describing the electronically excited states of small molecules, including CuSH, CuSCH_3, (CH_3)_2SCuSH, (imidazole)-CuSH and (imidazole)_2-CuSH, derived from the active site of blue copper proteins that contain the copper-sulphur bond in order to identify small molecular systems that have electronic structure that is analogous to the active site of the proteins. Both neutral and cationic forms are studied, since these represent the reduced and oxidised forms of the protein, respectively. For CuSH and CuSH^+, excitation energies from time-dependent density functional theory with the B97-1 exchange-correlation functional agree well with the available experimental data and multireference configuration interaction calculations. For the positive ions, the singly occupied molecular orbital is formed from an antibonding combination of a 3d orbital on copper and a 3pπ orbital on sulphur, which is analogous to the protein. This leads several of the molecules to have qualitatively similar electronic spectra to the proteins. For the neutral molecules, changes in the nature of the low lying virtual orbitals leads the predicted electronic spectra to vary substantially between the different molecules. In particular, addition of a ligand bonded directly to copper results in the low-lying excited states observed in CuSH and CuSCH_33 to be absent or shifted to higher energies

Sensitivity analysis of a dispersed clad mode to surrounding refractive index

The sensitivity of a specific dispersed clad mode and a normal clad mode of a Long Period Grating (LPG) near Turn Around Point (TAP) to surrounding refractive index in the range of 1.3332 - 1.3348 has been studied experimentally. We could attain a sensitivity of ∼2413 nm/RIU using LP0, 11 dispersed clad mode of a TAP-LPG with ∼3dB attenuation at resonance

Copper binding to the Alzheimer’s disease amyloid precursor protein

Alzheimer’s disease is the fourth biggest killer in developed countries. Amyloid precursor protein (APP) plays a central role in the development of the disease, through the generation of a peptide called Aβ by proteolysis of the precursor protein. APP can function as a metalloprotein and modulate copper transport via its extracellular copper binding domain (CuBD). Copper binding to this domain has been shown to reduce Aβ levels and hence a molecular understanding of the interaction between metal and protein could lead to the development of novel therapeutics to treat the disease. We have recently determined the three-dimensional structures of apo and copper bound forms of CuBD. The structures provide a mechanism by which CuBD could readily transfer copper ions to other proteins. Importantly, the lack of significant conformational changes to CuBD on copper binding suggests a model in which copper binding affects the dimerisation state of APP leading to reduction in Aβ production. We thus predict that disruption of APP dimers may be a novel therapeutic approach to treat Alzheimer’s disease

Preparation of nano-sized CoFe2O4 particles from a non-aqueous precursor

Nano-sized particles of CoFe2O4 were prepared from a non-aqueous precursor by thermolysis. The precursor medium comprise of calculated amount of stearic acid, Fe(NO3)3.9HP and Co(N°3)3.6H2O. Thermolysis of the precursor at 125°C causes precipitation of CoFe2O4 in the stearic acid medium which gradually turns viscous as a function of thermolysis time. Heat treatment of precipitates obtained by centrifugation of tetrahydrofuran (THF) treated thermolysed precursor at 350, 450 and 550°C for one hour yields 15, 20 and 27 nm sized particles of CoFe2O4. The chemical and thermal characteristics of the powder precipitates were studied with the aid of Fourier transform infrared (FTIR) spectroscopy and Differential scanning calorimetry (DSC). X-ray Diffraction (XRD) studies carried out on the heat treated precipitates reveal the presence of CoFe2o4 in the samples