Interferometric investigation of an early stage of plasma expansion with the high-power laser system PALS

The results of interferometric investigation of early stage of plasma expansion carried out in the high-power laser system PALS are presented. The plasma was generated on planar solid Al and Mo targets, irradiated by iodine laser pulses with energies of 100 and 600 J in 0.4 ns at a wavelength of 1.315 μm. The interferometric investigation allowed to determine electron density distributions at chosen moments of the plasma expansion. On the basis of these distributions, information about dynamics and properties of expanding plasma was obtained. The effects of laser-target interaction, i.e., the diameter and the depth of craters as well as the crater shape, were investigated. This research was carried out within the framework of the project PALS/013 (reg. no. HPRI-CT-1999-00053).     

Rotational Spectrum of Hydrazine in the Submillimeter Range

In the submillimeter range, from 345 to 410 GHz, 472 new rotational transitions in the vibrational ground state of hydrazine have been measured. The majority of recorded lines form eight K=2←1 Q-branches with J≤30, each branch being split due to internal rotation in hydrazine. New rotational transitions together with 443 known earlier have been fitted to an effective group-theoretical Hamiltonian originally developed by Hougen (J. T. Hougen, J. Mol. Spectrosc.89, 296-327 (1981)). A reasonable fit was obtained using several ΔK=0, ±1, ±2, and ±4 matrix elements. For all 915 rotational transitions an overall standard deviation of the fit of 0.59 MHz was obtained using 32 parameters. These were 14 asymmetric rotor constants, 16 NH₂ inversion parameters, and 2 internal rotation parameters.     

Pulling monatomic gold wires with single molecules: an Ab initio simulation

Car-Parrinello molecular dynamics simulations demonstrate that pulling a single thiolate molecule anchored on a stepped gold surface does not preferentially break the sulfur-gold chemical bond. Instead, it is found that this process leads to the formation of a monoatomic gold nanowire, followed by breaking a gold-gold bond with a rupture force of about 1.2 nN. The simulations also indicate that previous single-molecule thiolate-gold and gold-gold rupture experiments both probe the same phenomenon, namely, the breaking of a gold-gold bond within a gold nanowire.     

Photoexcitation of a dipole-forbidden resonance in helium

We have observed photoexcitation of the dipole-forbidden 1s(2) 1S0-->2p(2) 1D2 resonance in helium by measuring the nondipolar forward-backward asymmetry of photoelectron angular distributions in the 2l2l(') autoionizing region. By exploiting the electric dipole-quadrupole interference in the excitation of both the 2s2p 1P1 and 2p(2) 1D2 levels, we have observed the quadrupole resonance in photoabsorption and extracted its Fano line shape parameters and the relative phase of the 1sEp and 1sEd continua. We find the quadrupole line profile index q(2) to be markedly different from theoretical expectations.     

Electric polarization of heteropolar nanotubes as a geometric phase

The threefold symmetry of planar boron nitride (BN), the III-V analog to graphene, prohibits an electric polarization in its ground state, but this symmetry is broken when the sheet is wrapped to form a BN nanotube. We show that this leads to an electric polarization along the nanotube axis which is controlled by the quantum mechanical boundary conditions on its electronic states around the tube circumference. Thus the macroscopic dipole moment has an intrinsically nonlocal quantum mechanical origin from the wrapped dimension. We formulate this novel phenomenon using the Berry's phase approach and discuss its experimental consequences.     

Highly extended image states around nanotubes

We predict that freely suspended, linear molecular conductors or dielectrics, such as carbon nanotubes, can support electronic states that are localized far from the surface. These "tubular image states" are formed in extended potential wells resulting from the tug of war between the external electron's attraction to its image charge in the nanotube, and its repulsion from the tube due to its transverse angular momentum. The displacement of these states (>10 nm) away from the surface prevents their wave functions from collapsing, resulting in long lifetimes at low temperatures. We predict that tubular image states with binding energies of 1-10 meV can be formed via radiative recombination.     

Proteome analysis of Corynebacterium glutamicum.

By the use of different Corynebacterium glutamicum strains more than 1.4 million tons of amino acids, mainly L-glutamate and L-lysine, are produced per year. A project was started recently to elucidate the complete DNA sequence of this bacterium. In this communication we describe an approach to analyze the C. glutamicum proteome, based on this genetic information, by a combination of two-dimensional (2-D) gel electrophoresis and protein identification via microsequencing or mass spectrometry. We used these techniques to resolve proteins of C. glutamicum with the aim to establish 2-D protein maps as a tool for basic microbiology and for strain improvement. In order to analyze the C. glutamicum proteome, methods were established to fractionate the C. glutamicum proteins according to functional entities, i.e., cytoplasm, membranes, and cell wall. Protein spots of the cytoplasmic and membrane fraction were identified by N-terminal sequencing, immunodetection, matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and electrospray ionization-mass spectrometry (ESI-MS). Additionally, a protocol to analyze proteins secreted by C. glutamicum was established. Approximately 40 protein spots were observed on silver-stained 2-D gels, 12 of which were identified.     

The Plancherel Theorem for invariant Hilbert spaces

We calculate explicitly the Plancherel measure for certain Hilbert spaces of holomorphic functions naturally associated to affine symmetric spaces with holomorphic discrete series. Received April 6, 1999; in final form September 17, 1999 / Published online February 5, 2001     

Boundary element methods for potential problems with nonlinear boundary conditions

Galerkin boundary element methods for the solution of novel first kind Steklov-Poincaré and hypersingular operator boundary integral equations with nonlinear perturbations are investigated to solve potential type problems in two- and three-dimensional Lipschitz domains with nonlinear boundary conditions. For the numerical solution of the resulting Newton iterate linear boundary integral equations, we propose practical variants of the Galerkin scheme and give corresponding error estimates. We also discuss the actual implementation process with suitable preconditioners and propose an optimal hybrid solution strategy.