Synthesis of C-9 oxidised N-acetylneuraminic acid derivatives as biological probes

Sialic acids are 9-carbon acidic sugars involved in a number of important biological processes and human diseases. As part of our ongoing interest in the development of novel sialic acids as biological probes, we have developed an efficient and simple synthesis of C-9 oxidised sialic acid derivatives. The key oxidative step involves the use of TEMPO under carefully controlled aqueous pH conditions.     

Study of electronic and optical properties of pure and metal decorated boron nitride nanoribbons (B15N14H14-X): first principle calculations

Density functional theory (DFT)/time dependent density functional theory (TDDFT) based calculations were performed for basis sets 6-31G for DFT and 6-31G (d), 6-31G (d,p) and 6-31+G (d,p) for TDDFT calculations on pure boron nitride nanoribbon (BNNR) B₁₅N₁₅H₁₄ and metal decorated B₁₅N₁₄H₁₄-X BNNRs, where X = Ni⁺, Fe⁺, Co, Cr⁺, Cu and Al. The metal doping ratio = 3.45% and the doping site (nitrogen atom), were fixed for all the BNNRs. Electronic properties dipole moment, binding energy and bandgap were determined. Absorption properties in the wavelength range (100–600 nm) were studied, and optical gaps, absorption wavelengths, oscillator strengths and dominant transitions were calculated. The effect of metal doping on the electronic and optical properties was investigated. Single metal doping shifts the electronic gap of pure BNNR from insulating to semiconducting nature. Red shift in the absorption wavelengths from ultraviolet to visible in all the BNNRs was noticed.     

The partition problem

In this paper we describe several forms of thek-partition problem and give integer programming formulations of each case. The dimension of the associated polytopes and some basic facets are identified. We also give several valid and facet defining inequalities for each of the polytopes.Partial Support from NSF Grants DMS 8606188 and ECS 8800281 is gratefully acknowledged.     

Synthesis and structural characterisation of new Re(III) complexes using aldimines of α-amino acids as coligands

Complexes of the general formula [Re^III(L)Cl(PPh₃)₂] have been synthesised by reacting H₂L and [ReOCl₃(PPh₃)₂] in ethanol. Here H₂L represents imines of α-amino acids (glycine, l-alanine, l-valine, l-phenylalanine) derived from salicylaldehyde and naphthaldehyde. The crystal structure of one complex has been determined. The complexes are mononuclear, paramagnetic and display paramagnetic ¹H NMR in CDCl₃ solution. Their spectral and redox properties are scrutinised.     

Design of a Hybrid Fiber-Optic Network Using 3-D Optical Code Sequences

We present the design of a 3-dimensional (3-D) noncoherent optical hybrid network. We also report the design of a new family of 3-D codes for fiber optic hybrid networks. We show that the hybrid network allows for shorter bit times and a higher number of users, given a set chip rate, compared to previously conceived networks. These newly designed hybrid single-pulse-per-row (HSPR) codes have very low autocorrelation side-lobes and very small cross-correlation peaks. We compare the performance of our hybrid model using our codes with the Optical Orthogonal Codes (OOCs) and Temporal/Spatial (T/S) codes and show that the new network can support a greater number of users and higher data rates than those using OOCs and T/S codes.     

Sorption of some isomeric monohydric alcohols on egg albumin

Summary Sorption of iso-propyl, iso-butyl, sec-butyl, tert-butyl and iso-amyl alcohols on egg albumin has been studied at 35 °C by using quartz fiber spring technique. Sorption is related inversely to the molar volume of the sorbate. The specific surface area of egg albumin has been calculated by the BET method. The thermodynamic functions have also been evaluated.With 3 figures and 2 tables     

Soft X-ray appearance-potential spectroscopy studies of DyFe2 and ErFe2 intermetallics

The soft X-ray appearance-potential spectra (SXAPS) of the M_4,5 levels of Dy and Er and the L_2,3 levels of Fe in pure metals and their intermetallics DyFe₂ and ErFe₂ have been obtained in the energy range of 700–1500 eV. SXAPS probes the binding energies of the core levels and the distribution of local unfilled conduction-band states. Both the constituents of DyFe₂ show negative shifts with respect to the pure metals while those of ErFe₂ show a negative shift for Er and a positive shift for Fe. The widths of the Dy and Er peaks increase and that of the Fe decreases on alloying. The results are interpreted in terms of the Fermi level changes and the charge transfer from the rare earth to Fe. The discrepancy in Fe chemical shifts has been correlated to the electronic specific heat capacity coefficient reported for these intermetallics.     

Core excitation in79Br and81Br

TheE2 andM1 reduced transition probabilities between the low lying levels, in the case of⁷⁹Br and⁸¹Br, have been calculated on the core-excitation model. To account for the observed M1 transition probabilities admixture among the like spin states is considered. In addition, the ground state static moments have been computed. For the same amount of admixture among the like spin states, a good agreement with the experimental results is obtained, for both⁷⁹Br and⁸¹Br. The results are compared with other existing theoretical calculations. From our analysis, we obtain, the quadrupole moment of the first excited 2⁺ state in the neighbouring even-even nuclei. It is in good agreement with the value calculated on the basis of the anharmonic vibrational model.     

Surface studies of absorbing thin solid films

We report some experimental results concerning the surface roughness studies of a variety of absorbing thin solid films using a Digital Photon Correlator designed and fabricated by us. We determine the mean square (m.s.) deviation of thickness about the average value as determined by gravimetric techniques. The corresponding electron micrographs are presented for comparison.