Asymmetry of temporal cross-correlations in turbulent shear flows

We investigate spatial and temporal cross-correlations between streamwise and normal velocity components in three shear flows: a low-dimensional model for vortex-streak interactions, direct numerical simulations for a nearly homogeneous shear flow and experimental data for a turbulent boundary layer. A driving of streamwise streaks by streamwise vortices gives rise to a temporal asymmetry in the short time correlation. Close to the wall or the bounding surface in the free-slip situations, this asymmetry is identified. Further away from the boundaries the asymmetry becomes weaker and changes character, indicating the prevalence of other processes. The systematic variation of the asymmetry measure may be used as a complementary indicator to separate different layers in turbulent shear flows. The location of the extrema at different streamwise displacements can be used to read off the mean advection speed; it differs from the mean streamwise velocity because of asymmetries in the normal extension of the structures.Comment: 10 pages, 7 Postscript figures (low quality due to downsizing

Fabrication of alignment structures for a fiber resonator by use of deep-ultraviolet lithography

We present a novel method to mount and align an optical-fiber-based resonator on the flat surface of an atom chip with ultrahigh precision. The structures for mounting a pair of fibers, which constitute the fiber resonator, are produced by a spin-coated SU-8 photoresist technique by use of deep-UV lithography. The design and production of the SU-8 structures are discussed. From the measured finesses we calculate the coupling loss of the SU-8 structures acting as a kind of fiber splice to be smaller than 0.013 dB.Comment: 4 pages, 3 figure

Fully-Coupled Fluid/Structure Vibration Analysis Using MSC/NASTRAN

MSC/NASTRAN's performance in the solution of fully-coupled fluid/structure problems is evaluated. NASTRAN is used to perform normal modes (SOL 103) and forced-response analyses (SOL 108, 111) on cylindrical and cubic fluid/structure models. Bulk data file cards unique to the specification of a fluid element are discussed and analytic partially-coupled solutions are derived for each type of problem. These solutions are used to evaluate NASTRAN's solutions for accuracy. Appendices to this work include NASTRAN data presented in fringe plot form, FORTRAN source code listings written in support of this work, and NASTRAN data file usage requirements for each analysis

The Influences of Lamination Angles on the Interior Noise Levels of an Aircraft

The feasibility of reducing the interior noise levels of an aircraft passenger cabin through optimization of the composite lay up of the fuselage is investigated. MSC/NASTRAN, a commercially available finite element code, is used to perform the dynamic analysis and subsequent optimization of the fuselage. The numerical calculation of sensitivity of acoustic pressure to lamination angle is verified using a simple thin, cylindrical shell with point force excitations as noise sources. The thin shell used represents a geometry similar to the fuselage and analytic solutions are available for the cylindrical thin shell equations of motion. Optimization of lamination angle for the reduction of interior noise is performed using a finite element model of an actual aircraft fuselage. The aircraft modeled for this study is the Beech Starship. Point forces simulate the structure borne noise produced by the engines and are applied to the fuselage at the wing mounting locations. These forces are the noise source for the optimization problem. The acoustic pressure response is reduced at a number of points in the fuselage and over a number of frequencies. The objective function is minimized with the constraint that it be larger than the maximum sound pressure level at the response points in the passenger cabin for all excitation frequencies in the range of interest. Results from the study of the fuselage model indicate that a reduction in interior noise levels is possible over a finite frequency range through optimal configuration of the lamination angles in the fuselage. Noise reductions of roughly 4 dB were attained. For frequencies outside the optimization range, the acoustic pressure response may increase after optimization. The effects of changing lamination angle on the overall structural integrity of the airframe are not considered in this study

Deterministic quantum teleportation between distant atomic objects

Quantum teleportation is a key ingredient of quantum networks and a building block for quantum computation. Teleportation between distant material objects using light as the quantum information carrier has been a particularly exciting goal. Here we demonstrate a new element of the quantum teleportation landscape, the deterministic continuous variable (cv) teleportation between distant material objects. The objects are macroscopic atomic ensembles at room temperature. Entanglement required for teleportation is distributed by light propagating from one ensemble to the other. Quantum states encoded in a collective spin state of one ensemble are teleported onto another ensemble using this entanglement and homodyne measurements on light. By implementing process tomography, we demonstrate that the experimental fidelity of the quantum teleportation is higher than that achievable by any classical process. Furthermore, we demonstrate the benefits of deterministic teleportation by teleporting a dynamically changing sequence of spin states from one distant object onto another

A lattice of microtraps for ultracold atoms based on patterned magnetic films

We have realized a two dimensional permanent magnetic lattice of Ioffe-Pritchard microtraps for ultracold atoms. The lattice is formed by a single 300 nm magnetized layer of FePt, patterned using optical lithography. Our magnetic lattice consists of more than 15000 tightly confining microtraps with a density of 1250 traps/mm$^2$. Simple analytical approximations for the magnetic fields produced by the lattice are used to derive relevant trap parameters. We load ultracold atoms into at least 30 lattice sites at a distance of approximately 10 $\mu$m from the film surface. The present result is an important first step towards quantum information processing with neutral atoms in magnetic lattice potentials.Comment: 7 pages, 7 figure

Characterization of infectious and defective cloned avian hepadnavirus genomes

The infectivity in vivo, replication competence in vitro, and expression of viral genes of several molecularly cloned duck hepatitis B virus (DHBV) genomes were investigated. In addition, replication competence, core protein expression, and secretion of viral proteins were investigated for a grey heron hepatitis B virus genome. Except two, all DHBV isolates tested induced a systemic infection in Pekin ducks when injected as cloned viral DNA into the liver. After transfection of chicken hepatoma cells, both defective DHBV genomes expressed intracellular nucleocapsid and pre-S envelope proteins and secreted DHBs/pre-S particles into the medium. One of the defective DHBV genomes and HHBV produced within the cells replicative intermediates encapsidated in core particles and secreted virions, whereas the other defective DHBV genome did not and was unable to efficiently encapsidate the RNA pregenome. Comparative sequence analysis was performed to identify potential amino acid changes in viral proteins of both defective DHBV genomes. The data obtained demonstrate that most cloned avian hepadnaviruses are infectious or replication competent and suggest defects in envelope, polymerase or encapsidation function, respectively, in two cloned DHBV genomes

Three-dimensional character of atom-chip-based rf-dressed potentials

We experimentally investigate the properties of radio-frequency-dressed potentials for Bose-Einstein condensates on atom chips. The three-dimensional potential forms a connected pair of parallel waveguides. We show that rf-dressed potentials are robust against the effect of small magnetic-field variations on the trap potential. Long-lived dipole oscillations of condensates induced in the rf-dressed potentials can be tuned to a remarkably low damping rate. We study a beam-splitter for Bose-Einstein condensates and show that a propagating condensate can be dynamically split in two vertically separated parts and guided along two paths. The effect of gravity on the potential can be tuned and compensated for using a rf-field gradient.Comment: 9 pages, 7 figure

Electrical and Structural Properties of \u3ci\u3ep-n\u3c/i\u3e Junctions in cw Laser Annealed Silicon

Depth profiles of the electrical quality of ion implanted and cw laser annealed p-n junctions in silicon are obtained for the first time by secondary ion mass spectroscopy. A comparison with the crystallographic properties of the surface and the junction as observed by Nomarski optical microscopy as well as cross-sectional and plan view transmission electron microscopy is made. Samples containing slip dislocations show better insulation and a lower reverse bias current across the p-n junction as compared to samples with a perfect surface in agreement with current-voltage characteristics. Small dislocation loops located at the junction are found to degrade the junction quality

High quality anti-relaxation coating material for alkali atom vapor cells

We present an experimental investigation of alkali atom vapor cells coated with a high quality anti-relaxation coating material based on alkenes. The prepared cells with single compound alkene based coating showed the longest spin relaxation times which have been measured up to now with room temperature vapor cells. Suggestions are made that chemical binding of a cesium atom and an alkene molecule by attack to the C=C bond plays a crucial role in such improvement of anti-relaxation coating quality