On the recombination in high-order harmonic generation in molecules

We show that the dependence of high-order harmonic generation (HHG) on the molecular orientation can be understood within a theoretical treatment that does not involve the strong field of the laser. The results for H_2 show excellent agreement with time-dependent strong field calculations for model molecules, and this motivates a prediction for the orientation dependence of HHG from the N_2 3s_g valence orbital. For both molecules, we find that the polarization of recombination photons is influenced by the molecular orientation. The variations are particularly pronounced for the N_2 valence orbital, which can be explained by the presence of atomic p-orbitals.Comment: 6 pages 7 figure

The gravitational wave spectrum of non-axisymmetric, freely precessing neutron stars

Evidence for free precession has been observed in the radio signature of several pulsars. Freely precessing pulsars radiate gravitationally at frequencies near the rotation rate and twice the rotation rate, which for rotation frequencies greater than $\sim 10$ Hz is in the LIGO band. In older work, the gravitational wave spectrum of a precessing neutron star has been evaluated to first order in a small precession angle. Here we calculate the contributions to second order in the wobble angle, and we find that a new spectral line emerges. We show that for reasonable wobble angles, the second-order line may well be observable with the proposed advanced LIGO detector for precessing neutron stars as far away as the galactic center. Observation of the full second-order spectrum permits a direct measurement of the star's wobble angle, oblateness, and deviation from axisymmetry, with the potential to significantly increase our understanding of neutron star structure.Comment: 22 pages, 1 figure. Minor changes in the text, typos correcte

Anomalous Phase Transition in Strained SrTiO3_3 Thin Films

We have studied the cubic to tetragonal phase transition in epitaxial SrTiO$_3$ films under various biaxial strain conditions using synchrotron X-ray diffraction. Measuring the superlattice peak associated with TiO$_6$ octahedra rotation in the low temperature tetragonal phase indicates the presence of a phase transition whose critical temperature is a strong function of strain, with T$_C$ as much as 50K above the corresponding bulk temperature. Surprisingly, the lattice constants evolve smoothly through the transition with no indication of a phase change. This signals an important change in the nature of the phase transition due to the epitaxy strain and substrate clamping effect. The internal degrees of freedom (TiO$_6$ rotations) have become uncoupled from the overall lattice shape.Comment: 4 pages, 3 figures, REVTeX

Evaluation of non-intrusive flow measurement techniques for a re-entry flight experiment

This study evaluates various non-intrusive techniques for the measurement of the flow field on the windward side of the Space Shuttle orbiter or a similar reentry vehicle. Included are linear (Rayleigh, Raman, Mie, Laser Doppler Velocimetry, Resonant Doppler Velocimetry) and nonlinear (Coherent Anti-Stokes Raman, Laser-Induced Fluorescence) light scattering, electron-beam fluorescence, thermal emission, and mass spectroscopy. Flow-field properties were taken from a nonequilibrium flow model by Shinn, Moss, and Simmonds at the NASA Langley Research Center. Conclusions are, when possible, based on quantitative scaling of known laboratory results to the conditions projected. Detailed discussion with researchers in the field contributed further to these conclusions and provided valuable insights regarding the experimental feasibility of each of the techniques

Schoolchildren in the Principality of Liechtenstein are mildly iodine deficient

Abstract Objective To investigate the iodine status of schoolchildren in the Principality of Liechtenstein. Design A representative, cross-sectional principality-wide screening of iodine level in household salt and urinary iodine concentrations (UIC) in primary-school children. Data were compared with the WHO criteria and with 2009 iodine survey data from Switzerland, a neighbouring country that supplies most of the salt used in Liechtenstein. Settings Principality of Liechtenstein. Subjects Schoolchildren (n 228) aged 6-12 years from five different primary schools representing 11·4 % of the children at this age. Results The median UIC was 96 (range: 10-446) μg/l; 11 %, 56 % and 1 % of children had a UIC 300 μg/l, respectively. In all, 79 % of households were using adequately iodised salt (≥15 ppm). The median UIC was 20 % lower than that in children at comparable age in Switzerland (120 μg/l; P < 0·05). Conclusions According to the WHO criteria, schoolchildren in Liechtenstein are mildly iodine deficient and household iodised salt coverage is inadequate. Public health measures to increase iodine intakes in the Principality should be considere

Preferential antiferromagnetic coupling of vacancies in graphene on SiO_2: Electron spin resonance and scanning tunneling spectroscopy

Monolayer graphene grown by chemical vapor deposition and transferred to SiO_2 is used to introduce vacancies by Ar^+ ion bombardment at a kinetic energy of 50 eV. The density of defects visible in scanning tunneling microscopy (STM) is considerably lower than the ion fluence implying that most of the defects are single vacancies. The vacancies are characterized by scanning tunneling spectroscopy (STS) on graphene and HOPG exhibiting a peak close to the Fermi level. The peak persists after air exposure up to 180 min, albeit getting broader. After air exposure for less than 60 min, electron spin resonance (ESR) at 9.6 GHz is performed. For an ion flux of 10/nm^2, we find a signal corresponding to a g-factor of 2.001-2.003 and a spin density of 1-2 spins/nm^2. The ESR signal consists of a mixture of a Gaussian and a Lorentzian of equal weight exhibiting a width down to 0.17 mT, which, however, depends on details of the sample preparation. The g-factor anisotropy is about 0.02%. Temperature dependent measurements reveal antiferromagnetic correlations with a Curie-Weiss temperature of -10 K. Albeit the electrical conductivity of graphene is significantly reduced by ion bombardment, the spin resonance induced change in conductivity is below 10^{-5}.Comment: 10 pages, 5 figures, discussion on STM images in the literature of defects in graphene adde