The field-induced states at the surfaces of the nearly-free-electron metals

We have studied theoretically the energy spectra of the field-induced electronic states, generated by the positive external electric field applied to the Au(001) and Au(111) surfaces. The aim of this paper was to investigate the influence of the Schockley-inverted energy gap in the metal band structure on the energies of these states. The investigations have been performed for different intensitiesF of the applied electric field (0<F}<10⁸ V/cm). Our results indicate that the crystal potential influences considerably the energy spectra of the field-induced states. This effect is especially important in the case where these states appear near the energy gap.     

Extended convergence to continuous in probability processes with independent increments

Summary A special (extended) kind of convergence in distribution of processes with filtration is considered. Recent theorems on the functional convergence of semimartingales are improved by showing that their assumptions imply the extended convergence of semimartingales to continuous in probability processes with independent increments.     

Catalytic activity of Pd/CN systems in hydrogenation of styrene

Hydrogenation of styrene was applied as a test reaction to study the catalytic activity of Pd deposited on the surface of carbonaceous materials enriched with nitrogen (C_N). The nitrogen content in the support material was found to have a great influence on the degree of styrene conversion to ethylbenzene. In addition, the reaction was carried out in the presence of modified carbonaceous materials acting as catalysts.     

Conformational flexibility, UV-induced decarbonylation, and FTIR spectra of 1-phenyl-1,2 propanedione in solid xenon and in the low temperature amorphous phase

1-Phenyl-1,2-propanedione has been isolated in low-temperature xenon matrixes and studied by FTIR spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. In good agreement with previous electron diffraction data [Shen, Q.; Hagen, K. J. Phys. Chem. 1993, 97, 985], the calculations predicted the existence of only one stable conformation for the compound, in which the O=C-C=O dihedral angle is 135.6 degrees. On the other hand, the experimental data clearly reveals that, in the as-deposited xenon matrixes (T = 20 K), there is a distribution of molecules with different O=C-C=O dihedral angles around the equilibrium value. This distribution results from the efficient trapping of the conformational distribution existing in the gas phase, prior to deposition, which is determined by the low frequency, large amplitude torsional vibration around the C-C central bond. Upon annealing to higher temperatures (T approximately 45 K), the initially trapped conformational distribution can be modified in a certain degree, favoring more polar structures (corresponding to smaller O=C-C=O dihedral angles), as a result of the interactions with the matrix media. Irradiation of the matrix with UV light (lambda > 235 nm) led to decarbonylation of the compound, with generation of acetophenone and carbon monoxide, with an almost complete consumption of the reagent after 1100 min of irradiation (k = 2.8 x 10(-2) min.(-1)). Aggregation of the compound resulting from the matrix warming was also investigated, providing useful information for interpretation of the spectroscopic data obtained for the low-temperature amorphous state of the neat compound.     

Ligand.Info small-molecule Meta-Database

Ligand.Info is a compilation of various publicly available databases of small molecules. The total size of the Meta-Database is over 1 million entries. The compound records contain calculated three-dimensional coordinates and sometimes information about biological activity. Some molecules have information about FDA drug approving status or about anti-HIV activity. Meta-Database can be downloaded from the http://Ligand.Info web page. The database can also be screened using a Java-based tool. The tool can interactively cluster sets of molecules on the user side and automatically download similar molecules from the server. The application requires the Java Runtime Environment 1.4 or higher, which can be automatically downloaded from Sun Microsystems or Apple Computer and installed during the first use of Ligand.Info on desktop systems, which support Java (Ms Windows, Mac OS, Solaris, and Linux). The Ligand.Info Meta-Database can be used for virtual high-throughput screening of new potential drugs. Presented examples showed that using a known antiviral drug as query the system was able to find others antiviral drugs and inhibitors.     

Molecular tight-binding method. II. One- and many-electron method for excess electron bands of molecular crystals

An ab initio method for calculating the energies of excess-electron bands in a molecular crystal is developed. These energies represent the electron affinities of a crystal. The present method employs a tight-binding approximation to describe the molecules in a crystal and a set of local functions to describe the excess electron. One- and many-electron formulations of the method are given, the latter takes into account the effect of polarization of all the molecules in the crystal by the excess electron. A scheme for approximate determination of the electronic-correlation corrections to the one-electron bands is developed and applied to calculation of the excess-electron bands in the HCP helium crystal.     

The Photophysics of β-Tyrosine and Its Simple Derivatives

Synthesis and photophysical studies of (O-methyl)--tyrosine (-tyrosine; an analogue of tyrosine, in which the amino group is moved from the - to the -carbon, closer to the phenol ring) and its derivatives with a blocked amino and/or carboxyl group were performed to explain the nature of the fluorescence of tyrosine derived analogues. All -tyrosine derivatives, except Ac-Tyr(Me), displayed the monoexponential fluorescence decay. The biexponential fluorescence decay observed for Ac-Tyr(Me) is assumed to be the result of the presence of two low-energy conformations (extended and with an intramolecular hydrogen bond). Higher quenching of the fluorescence of -tyrosine derivatives by the N-acetyl group than by the N-methylamide group moved farther was found, contrary to the data found for the respective derivatives of natural tyrosine. The obtained photophysical data are discussed with theoretical calculations (AMBER, AM1) on the basis of the rotamer model.     

Surface electronic structure of zinc-blende-type GaN(111)

The electronic structure (layer resolved density of states) has been calculated for the gallium nitride (111) oriented slab, using the linear combination of atomic orbitals procedure. The existence of surface states on both Ga- and N-terminated surfaces has been shown. The origin and localization properties of these states have also been analysed.