Atomic and electronic structure of the corundum (0001) surface: comparison with surface spectroscopies

The electronic structure and geometry of the Al-terminated corundum (0001) surface were studied using a slab model within the ab-initio Hartree-Fock technique. The distance between the top Al plane and the next O basal plane is found to be considerably reduced on relaxation (by 0.57 Å, i.e. by 68% of the corresponding interlayer distance in the bulk). An interpretation of experimental photoelectron spectra (UPS He I) and metastable impact electron spectra (MIES) is given using the calculated total density of states of the slab and the projections to the atoms, atomic orbitals, and He 1s floating atomic orbital at different positions above the surface. Calculated projected densities of states exhibit a strong dependence on the relaxation of surface atoms. The good agreement of simulated and experimental UPS and MIES spectra supports the correctness of calculated surface relaxation.     

Use of IR spectroscopy for studying the cross-linking of peroxide melamine-formaldehyde oligomer

Translated from Zhurnal Prikladnoi Spektroskoppi, Vol. 48, No. 3, pp. 449–453, March, 1988.     

Localization of electron group functions

The requirements of variational freedom of electron group functions and their spatial separation are basic statements of the group functions method as they are necessary for taking into account the intragroup electron correlation while neglecting the intergroup one. But these requirements seem to be inconsistent with one another. This contradiction can be removed using the notion of antisymmetrical annulment of many-electron functions introduced in the present work. The transformation of group functions (GF ) by means of functions antisymmetrically annulling (ASA ) other GF 's is proposed that does not affect the whole system's wave function but can be used for localizing GF 's. The problem of construction of a function $ \tilde \Phi $ ASA a given Φ can be reduced to solving a system of linear algebraic equations. A sufficient condition of existing of nontrivial $ \tilde \Phi $ is obtained.     

Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.     

Effect of the deletion of the C region on the structure and hydration of insulin-like growth factor 1: a molecular dynamics investigation

The structure and hydration of insulin-like growth factor 1 and an inactive mutant lacking the C region have been investigated in aqueous solution by molecular dynamics simulation. The overall structures of the two polypeptide resemble those determined by NMR spectroscopy. The deletion of the C region in the wild polypeptide introduces structural stability in the mutant, leading to a better definition of the secondary structure elements. A detailed hydration analysis was performed using the radial distribution functions and energy distributions. The backbone of the mutant is in general more solvent accessible than the wild polypeptide backbone. The structural rearrangements induced in the mutant led to changes in the solvent exposition of Tyr24 and Tyr60, which are residues important for ligand—receptor complex formation. Tyr24 exhibited a similar degree of solvent exposition in both IGF-I and in the mutant; however, its hydroxyl group in the wild polypeptide is better solvated than in the mutant. Tyr60 was found to be solvent exposed in the wild protein, while in the mutant the involvement of its hydroxyl group in intramolecular hydrogen bonds led to it being buried away from the solvent.