Structure of a five-coordinate mononuclear cobalt(II) complex: chlorobis([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine)cobalt(II) bromide

A penta-coordinate mononuclear cobalt(II) complex, [Co(BP)₂(Cl⁻)](Br⁻), 1 with a novel, biphenyl-appended N,N-bidentate ligand, BP ([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine) was synthesized and characterized by elemental analysis, UV-Vis, electro-spray ionization mass spectrum and single crystal XRD. The title complex crystallizes in the monoclinic space group C2/c with cell dimensions a = 11.389(2), b = 25.627(3), c = 12.276(3) Å, β = 100.419(18)° and Z = 2. The cobalt atom has a distorted trigonal bipyramidal (tbp) geometry and is surrounded by 4Ns of two BP, and a Cl⁻/Br⁻ at the 5th coordination site. This is the first report of a mononuclear tbp cobalt complex with biphenyl appended bidentate ligand containing amino-pyridyl moiety.     

PHOTOCYCLOADDITION OF ACETONE TO URACIL AND CYTOSINE

Abstract— Ultraviolet irradiation (Λ > 280 nm) of uracil in aqueous acetone (1:1) produces cyclobutane uracil dimer and uracil-acetone addition product. The addition product is identified as an oxetane. The same product is also obtained from cytosine irradiated under the same conditions. The cytosine-acetone oxetane apparently undergoes deamination readily. Irradiation (Λ= 265 nm) of the oxetane in aqueous solution produces acetone and uracil with a quantum efficiency of 0–16.     

T-duality simplifies bulk–boundary correspondence: the noncommutative case

We state and prove a general result establishing that T-duality, or the Connes–Thom isomorphism, simplifies the bulk–boundary correspondence, given by a boundary map in K-theory, in the sense of converting it to a simple geometric restriction map. This settles in the affirmative several earlier conjectures of the authors and provides a clear geometric picture of the correspondence. In particular, our result holds in arbitrary spatial dimension, in both the real and complex cases, and also in the presence of disorder, magnetic fields, and H-flux. These special cases are relevant both to string theory and to the study of the quantum Hall effect and topological insulators with defects in condensed matter physics.     

Influence of quenching on the structural and conduction characteristics of lithium sulfate

Lithium sulfate quenched from the high-temperature melt using conventional quenching as well as rapid quenching techniques has been investigated using X-ray diffraction, scanning electron microscope, differential scanning calorimetry (DSC), vibrational spectroscopy techniques, and electrical conductivity measurements. Crystal structure of the quenched samples studied using X-ray diffraction shows a less ordered β-Li₂SO₄ phase. This is accompanied by a decrease in phase transition temperature in DSC measurements along with a decrease in the molar enthalpy associated with the transition. Raman and FT-IR spectroscopy studies reveal the disorder in the quenched samples by a significant broadening of the bands associated with the fundamental vibrational modes of SO₄ ^2? ion. Temperature variation of conductivity shows an enhancement in ionic conductivity by one order of magnitude with a slight decrease in phase transition point for quenched samples over unquenched Li₂SO₄.     

D-Branes,RR-Fields and Duality on Noncommutative Manifolds

We develop some of the ingredients needed for string theory on noncommutative spacetimes, proposing an axiomatic formulation of T-duality as well as establishing a very general formula for D-brane charges. This formula is closely related to a noncommutative Grothendieck-Riemann-Roch theorem that is proved here. Our approach relies on a very general form of Poincaré duality, which is studied here in detail. Among the technical tools employed are calculations with iterated products in bivariant -theory and cyclic theory, which are simplified using a novel diagram calculus reminiscent of Feynman diagrams.     

Correlation analysis of reactivity in the addition of substituted benzylamines to benzylidenemalononitrile

The kinetics of addition of a number of ortho‐, meta‐, and para‐substituted benzylamines to benzylidenemalononitrile (BMN) in acetonitrile have been studied. The reaction is first‐order with respect to BMN. The order with respect to the amine is more than one. It has been shown that the reaction followed two mechanistic pathways, uncatalyzed and catalyzed by the amine. The enthalpy of activation for the catalyzed path is negative indicating the presence of a preequilibrium (k₁, k₋₁) leading to the formation of a zwitterion. The values of rate constant, k₁, for the nucleophilic attack have been determined for twenty‐eight benzylamines. The rate constant, k₁ was subjected to correlation analyses using various single‐ and multi‐parametric equations. The best correlation is obtained in terms of Charton's LDR and LDRS equations. The polar regression coefficients are negative indicating the formation of a cationic species in the transition state. The reaction is subject to steric hindrance by ortho‐substituents. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 245–252, 1999     

Electron donor properties and catalytic activity of manganese ferrospinels

The electron donating properties of manganese ferrospinels of various compositions (MnFe₂O₄, Mn_1.2Fe_1.8O₄, Mn₂FeO₄ and Mn_2.5Fe_0.5O₄) were studied from the adsorption of electron acceptors of various electron affinity values from acetonitrile as solvent. The limit of electron transfer from the oxide surface is from 1.77 to 2.40 eV in terms of the electron affinity of the electron acceptor. The data have been correlated with the catalytic activity of these oxides towards autoxidation of sulfites. Both weak and strong electron donor sites catalyze the reaction.     

An Unexpected Role of Hyaluronic Acid in Trafficking siRNA Across the Cellular Barrier: The First Biomimetic,Anionic, Non‐Viral Transfection Method

Circulating nucleic acids, such as short interfering RNA (siRNA), regulate many biological processes; however, the mechanism by which these molecules enter the cell is poorly understood. The role of extracellular‐matrix‐derived polymers in binding siRNAs and trafficking them across the plasma membrane is reported. Thermal melting, dynamic light scattering, scanning electron microscopy, and computational analysis indicate that hyaluronic acid can stabilize siRNA via hydrogen bonding and Van der Waals interactions. This stabilization facilitated HA size‐ and concentration‐dependent gene silencing in a CD44‐positive human osteosarcoma cell line (MG‐63) and in human mesenchymal stromal cells (hMSCs). This native HA‐based siRNA transfection represents the first report on an anionic, non‐viral delivery method that resulted in approximately 60 % gene knockdown in both cell types tested, which correlated with a reduction in translation levels.     

Titanium Nanorods Loaded PCL Meshes with Enhanced Blood Vessel Formation and Cell Migration for Wound Dressing Applications

Proper management of nonhealing wounds is an imperative clinical challenge. For the effective healing of chronic wounds, suitable wound coverage materials with the capability to accelerate cell migration, cell proliferation, angiogenesis, and wound healing are required to protect the healing wound bed. Biodegradable polymeric meshes are utilized as effective wound coverage materials to protect the wounds from the external environment and prevent infections. Among them, electrospun biopolymeric meshes have got much attention due to their extracellular matrix mimicking morphology, ability to support cell adhesion, and cell proliferation. Herein, electrospun nanocomposite meshes based on polycaprolactone (PCL) and titanium dioxide nanorods (TNR) are developed. TNR incorporated PCL meshes are fabricated by electrospinning technique and characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) analysis, and X‐Ray diffraction (XRD) analysis. In vitro cell culture studies, in ovo angiogenesis assay, in vivo implantation study, and in vivo wound healing study are performed. Interestingly, obtained in vitro and in vivo results demonstrated that the presence of TNR in the PCL meshes greatly improved the cell migration, proliferation, angiogenesis, and wound healing. Owing to the above superior properties, they can be used as excellent biomaterials in wound healing and tissue regeneration applications.     

Fractional quantum numbers via complex orbifolds

This paper studies both the conductance and charge transport on 2D orbifolds in a strong magnetic field. We consider a family of Landau Hamiltonians on a complex, compact 2D orbifold Y that are parametrised by the Jacobian torus J(Y) of Y. We calculate the degree of the associated stable holomorphic spectral orbibundles when the magnetic field B is large and obtain fractional quantum numbers as the conductance and a refined analysis also gives the charge transport. A key tool studied here is a nontrivial generalisation of the Nahm transform to 2D orbifolds.