Atmospheric Turbulence Compensation of Point Source Images Using Asynchronous Stochastic Parallel Gradient Descent Technique on AMOS 3.6 m Telescope

The Stochastic Parallel Gradient Descent Technique-based Adaptive Optics (SPGD-AO) system described in this presentation does not use a conventional wavefront sensor. It uses a metric signal collected by a single pixel detector placed behind a pinhole in the image plane to drive three deformable mirrors (DMs). The system is designed to compensate the image for turbulence effects. The theory behind this method is described in detail in [1]. However this technique, while widely simulated and tested in the laboratory, was not yet verified in astronomical field site experiments. During the month of May 2007, a series of experiments with SPGD-AO compensation on stars at several elevation angles and turbulence levels were conducted successfully at the US Air Force Maui Optical and Supercomputing Site (AMOS) using the 3.6 m telescope. Some of the results of these experiments are described in this paper. This is the first time SPGD-AO systems have been tested and verified in astronomical field site experiments

Transport through correlated quantum dots: An investigation using the functional renormalization group

Calculations using the (exact) fermionic functional renormalization group are usually truncated at the second order of the corresponding hierarchy of coupled ordinary differential equations. We present a method for the systematic determination of higher order vertex functions. This method is applied to a study of transport properties of various correlated quantum dot systems. It is shown that for large Coulomb correlations higher order vertex functions cannot be neglected, and a static approximation is insufficient.Comment: 10 figures, accepted by Phys. Rev.

Theoretical study of the dynamic structure factor of superfluid 4He

We study the dynamic structure factor $S(\vec{q},\omega)$ of superfluid 4He at zero temperature in the roton momentum region and beyond using field-theoretical Green's function techniques. We start from the Gavoret-Nozi\`{e}res two-particle propagator and introduce the concept of quasiparticles. We treat the residual (weak) interaction between quasiparticles as being local in coordinate space and weakly energy dependent. Our quasiparticle model explicitly incorporates the Bose-Einstein condensate. A complete formula for the dynamic susceptibility, which is related to $S (\vec{q},\omega)$, is derived. The structure factor is numerically calculated in a self-consistent way in the special case of a momentum independent interaction between quasiparticles. Results are compared with experiment and other theoretical approaches.Comment: 17 pages, 16 figure

Characterization of Atmospheric Turbulence Effects Over 149 km Propagation Path Using Multi-Wavelength Laser Beacons

We describe preliminary results of a set of laser beam propagation experiments performed over a long (149 km) near-horizontal propagation path between Mauna Loa (Hawaii Island) and Haleakala (Island of Maui) mountains in February 2010. The distinctive feature of the experimental campaign referred to here as the Coherent Multi-Beam Atmospheric Transceiver (COMBAT) experiments is that the measurements of the atmospheric-turbulence induced laser beam intensity scintillations at the receiver telescope aperture were obtained simultaneously using three laser sources (laser beacons) with different wavelengths (λ1 = 0.53 μm, λ2 = 1.06 μm, and λ3 = 1.55 μm). The presented experimental results on intensity scintillation characteristics reveal complexity of the observed phenomena that cannot be fully explained based on the existing atmospheric turbulence models

Comparison of Turbulence-Induced Scintillations for Multi-Wavelength Laser Beacons Over Tactical (7 km) and Long (149 km) Atmospheric Propagation Paths

We report results of the experimental analysis of atmospheric effects on laser beam propagation over two distinctive propagation paths: a long-range (149 km) propagation path between Mauna Loa (Island of Hawaii) and Haleakala (Island of Maui) mountains, and a tactical-range (7 km) propagation path between the roof of the Dayton Veterans Administration Medical Center (VAMC) and the Intelligent Optics Laboratory (IOL/UD) located on the 5th floor of the University of Dayton College Park Center building. Both testbeds include three laser beacons operating at wavelengths 532 nm, 1064 nm, and 1550 nm and a set of identical optical receiver systems with fast-framing IR cameras for simultaneous measurements of pupil and focal plane intensity distributions. The results reported here are focused on analysis of intensity scintillations that were simultaneously measured at three wavelengths. Comparison of experimental results shows significant differences in the physics of atmospheric turbulence impact on laser beam propagation over the long- and tactical-range distances

Comment on “Unique Translation between Hamiltonian Operators and Functional Integrals”

A comment on the letter by Tim Gollisch and Christof Wetterich, Phys. Rev. Lett. 86, 1 (2001).Michael Weyrauch, and Andreas W. Schreibe

Radiative decays of decuplet hyperons

We calculate the radiative decay widths of decuplet hyperons in a chiral constituent quark model including electromagnetic exchange currents between quarks. Exchange currents contribute significantly to the E2 transition amplitude, while they largely cancel for the M1 transition amplitude. Strangeness suppression of the radiative hyperon decays is found to be weakened by exchange currents. Differences and similarities between our results and other recent model predictions are discussed.Comment: 11 pages, 1 eps figure, revtex, accepted for publication in Phys. Rev.

Nucleon Spin-Polarisabilities from Polarisation Observables in Low-Energy Deuteron Compton Scattering

We investigate the dependence of polarisation observables in elastic deuteron Compton scattering below the pion production threshold on the spin-independent and spin-dependent iso-scalar dipole polarisabilities of the nucleon. The calculation uses Chiral Effective Field Theory with dynamical Delta(1232) degrees of freedom in the Small Scale Expansion at next-to-leading order. Resummation of the NN intermediate rescattering states and including the Delta induces sizeable effects. The analysis considers cross-sections and the analysing power of linearly polarised photons on an unpolarised target, and cross-section differences and asymmetries of linearly and circularly polarised beams on a vector-polarised deuteron. An intuitive argument helps one to identify kinematics in which one or several polarisabilities do not contribute. Some double-polarised observables are only sensitive to linear combinations of two of the spin-polarisabilities, simplifying a multipole-analysis of the data. Spin-polarisabilities can be extracted at photon energies \gtrsim 100 MeV, after measurements at lower energies of \lesssim 70 MeV provide high-accuracy determinations of the spin-independent ones. An interactive Mathematica 7.0 notebook of our findings is available from [email protected]: 30 pages LaTeX2e, including 22 figures as 66 .eps file embedded with includegraphicx; three errors in initial submission corrected. This submission includes ot the erratum to be published in EPJA (2012) and the corrections in the tex

Non-perturbative Gluons and Pseudoscalar Mesons in Baryon Spectroscopy

We study baryon spectroscopy including the effects of pseudoscalar meson exchange and one gluon exchange potentials between quarks, governed by $\alpha_s$. The non-perturbative, hyperspherical method calculations show that one can obtain a good description of the data by using a quark-meson coupling constant that is compatible with the measured pion-nucleon coupling constant, and a reasonably small value of $\alpha_s$.Comment: 12 pages; Submitted to Phys. Rev. C. Rapid Communication

Muscle-specific ablation of glucose transporter 1 (GLUT1) does not impair basal or overload-stimulated skeletal muscle glucose uptake

Glucose transporter 1 (GLUT1) is believed to solely mediate basal (insulin-independent) glucose uptake in skeletal muscle; yet recent work has demonstrated that mechanical overload, a model of resistance exercise training, increases muscle GLUT1 levels. The primary objective of this study was to determine if GLUT1 is necessary for basal or overload-stimulated muscle glucose uptake. Muscle-specific GLUT1 knockout (mGLUT1KO) mice were generated and examined for changes in body weight, body composition, metabolism, systemic glucose regulation, muscle glucose transporters, and muscle