Inviscid Flow Field Effects: Experimental results

The aero-optical distortions due to invisid flow effects over airborne laser turrets is investigated. Optical path differences across laser turret apertures are estimated from two data sources. The first is a theoretical study of main flow effects for a spherical turret assembly for a Mach number (M) of 0.6. The second source is an actual wind tunnel density field measurement on a 0.3 scale laser turret/fairing assembly, with M = 0.75. A range of azimuthal angles from 0 to 90 deg was considered, while the elevation angle was always 0 deg (i.e., in the plane of the flow). The calculated optical path differences for these two markedly different geometries are of the same order. Scaling of results to sea level conditions and an aperture diameter of 50 cm indicated up to 0.0007 cm of phase variation across the aperture for certain forward look angles and a focal length of F = -11.1 km. These values are second order for a 10.6 micron system

Na I and Hα\alpha absorption features in the atmosphere of MASCARA-2b/KELT-20b

We have used the HARPS-North high resolution spectrograph ($\mathcal{R}$=115 000) at TNG to observe one transit of the highly irradiated planet MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly resolve the spectral features of the atomic sodium (Na I) doublet and the H$\alpha$ line in its atmosphere, measuring absorption depths of 0.17$\pm$0.03$\%$ and 0.59$\pm$0.08$\%$ for a 0.75 $\AA$ passband, respectively. These absorptions are corroborated with the transmission measured from their respective transmission light curves, which show a large Rossiter-McLaughlin effect. In case of H$\alpha$, this absorption corresponds to an effective radius of $R_{\lambda}/R_P$=1.20$\pm$0.04. While the S/N of the final transmission spectrum is not sufficient to adjust different temperature profiles to the lines, we find that higher temperatures than the equilibrium are needed to explain the lines contrast. Particularly, we find that the Na I lines core require a temperature of T=4210$\pm$180K and that H$\alpha$ requires T=4330$\pm$520K. MASCARA-2b, like other planets orbiting A-type stars, receives a large amount of UV energy from its host star. This energy excites the atomic hydrogen and produces H$\alpha$ absorption, leading to the expansion and abrasion of the atmosphere. The study of other Balmer lines in the transmission spectrum would allow the determination of the atmospheric temperature profile and the calculation of the lifetime of the atmosphere. In the case of MASCARA-2b, residual features are observed in the H$\beta$ and H$\gamma$ lines, but they are not statistically significant. More transit observations are needed to confirm our findings in Na I and H$\alpha$, and to build up enough S/N to explore the presence of H$\beta$ and H$\gamma$ planetary absorptions.Comment: 14 pages, 12 figure

Nuclear effects in atomic transitions

Atomic electrons are sensitive to the properties of the nucleus they are bound to, such as nuclear mass, charge distribution, spin, magnetization distribution, or even excited level scheme. These nuclear parameters are reflected in the atomic transition energies. A very precise determination of atomic spectra may thus reveal information about the nucleus, otherwise hardly accessible via nuclear physics experiments. This work reviews theoretical and experimental aspects of the nuclear effects that can be identified in atomic structure data. An introduction to the theory of isotope shifts and hyperfine splitting of atomic spectra is given, together with an overview of the typical experimental techniques used in high-precision atomic spectroscopy. More exotic effects at the borderline between atomic and nuclear physics, such as parity violation in atomic transitions due to the weak interaction, or nuclear polarization and nuclear excitation by electron capture, are also addressed.Comment: review article, 53 pages, 14 figure

MASCARA-2 b: A hot Jupiter transiting the mV=7.6m_V=7.6 A-star HD185603

In this paper we present MASCARA-2 b, a hot Jupiter transiting the $m_V=7.6$ A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million flux measurements of the star, corresponding to a total of almost 3000 hours of observations, revealing a periodic dimming in the flux with a depth of $1.3\%$. Photometric follow-up observations were performed with the NITES and IAC80 telescopes and spectroscopic measurements were obtained with the Hertzsprung SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of $3.474119^{+0.000005}_{-0.000006}~\rm{days}$ at a distance of $0.057 \pm 0.006~\rm{AU}$, has a radius of $1.83 \pm 0.07~\rm{R}_{\rm{J}}$ and place a $99\%$ upper limit on the mass of $< 17~\rm{M}_{\rm{J}}$. HD 185603 is a rapidly rotating early-type star with an effective temperature of $8980^{+90}_{-130}~\rm{K}$ and a mass and radius of $1.89^{+0.06}_{-0.05}~M_\odot$, $1.60 \pm 0.06~R_\odot$, respectively. Contrary to most other hot Jupiters transiting early-type stars, the projected planet orbital axis and stellar spin axis are found to be aligned with $\lambda=0.6 \pm 4^\circ$. The brightness of the host star and the high equilibrium temperature, $2260 \pm 50~\rm{K}$, of MASCARA-2 b make it a suitable target for atmospheric studies from the ground and space. Of particular interest is the detection of TiO, which has recently been detected in the similarly hot planets WASP-33 b and WASP-19 b.Comment: 8 pages, 4 figures, Accepted for publication in A&

ENIGMA: Efficient Learning-based Inference Guiding Machine

ENIGMA is a learning-based method for guiding given clause selection in saturation-based theorem provers. Clauses from many proof searches are classified as positive and negative based on their participation in the proofs. An efficient classification model is trained on this data, using fast feature-based characterization of the clauses . The learned model is then tightly linked with the core prover and used as a basis of a new parameterized evaluation heuristic that provides fast ranking of all generated clauses. The approach is evaluated on the E prover and the CASC 2016 AIM benchmark, showing a large increase of E's performance.Comment: Submitted to LPAR 201

Research Activities for the DORIS Contribution to the Next International Terrestrial Reference Frame

For the preparation of ITRF2008, the IDS processed data from 1993 to 2008, including data from TOPEX/Poseidon, the SPOT satellites and Envisat in the weekly solutions. Since the development of ITRF2008, the IDS has been engaged in a number of efforts to try and improve the reference frame solutions. These efforts include (i) assessing the contribution of the new DORIS satellites, Jason-2 and Cryosat2 (2008-2011), (ii) individually analyzing the DORIS satellite contributions to geocenter and scale, and (iii) improving orbit dynamics (atmospheric loading effects, satellite surface force modeling. . . ). We report on the preliminary results from these research activities, review the status of the IDS combination which is now routinely generated from the contributions of the IDS analysis centers, and discuss the prospects for continued improvement in the DORIS contribution to the next international reference frame

Search for Rayleigh scattering in the atmosphere of GJ1214b

We investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the spectrum. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Most observations favor a water-dominated atmosphere with a small scale-height, however, some observations indicate that GJ1214b could have an extended atmosphere with a cloud layer muting the molecular features. In an atmosphere with a large scale-height, Rayleigh scattering at blue wavelengths is likely to cause a measurable increase in the apparent size of the planet towards the blue. We observed the transit of GJ1214b in the B-band with the FOcal Reducing Spectrograph (FORS) at the Very Large Telescope (VLT) and in the g-band with both ACAM on the William Hershel Telescope (WHT) and the Wide Field Camera (WFC) at the Isaac Newton Telescope (INT). We find a planet-to-star radius ratio in the B-band of 0.1162+/-0.0017, and in the g-band 0.1180+/-0.0009 and 0.1174+/-0.0017 for the WHT & INT observations respectively. These optical data do not show significant deviations from previous measurements at longer wavelengths. In fact, a flat transmission spectrum across all wavelengths best describes the combined observations. When atmospheric models are considered a small scale-height water-dominated model fits the data best.Comment: Accepted for publication in Ap

Uphill and downhill walking in unilateral lower limb amputees

Objective: To study adjustment strategies in unilateral amputees in uphill and downhill walking. Design: observational cohort study. Subjects: Seven transfemoral, 12 transtibial unilateral amputees and 10 able-bodied subjects. Methods: In a motion analysis laboratory the subjects walked over a level surface and an uphill and downhill slope. Gait velocity and lower limb joint angles were measured. Results: In uphill walking hip and knee flexion at initial contact and hip flexion in swing were increased in the prosthetic limb of transtibial amputees. In downhill walking transtibial amputees showed more knee flexion on the prosthetic side in late stance and swing. Transfemoral amputees were not able to increase prosthetic knee flexion in uphill and downhill walking. An important adjustment strategy in both amputee Groups was a smaller hip extension in late stance in uphill and downhill walking, probably related with a shorter step length. In addition, amputees increased knee flexion in early stance in the non-affected limb in uphill walking to compensate for the shorter prosthetic limb length. In downhill walking fewer adjustments were necessary, since the shorter prosthetic limb already resulted in lowering of the body. Conclusion: Uphill and downhill walking can be trained in rehabilitation, which may improve safety and confidence of amputees. Prosthetic design should focus on better control of prosthetic knee flexion abilities without reducing stability. (c) 2007 Elsevier B.V. All fights reserved

Bilayer Button Graft for Endoscopic Repair of High-Flow Cranial Base Defects

Closure of dural defects in trans-nasal, extended, endoscopic techniques remains a challenge, and published cerebrospinal fluid (CSF) leak rates are higher than rates for trans-cranial approaches. Development of a technique that used a vascularized, nasoseptal flap (NSF) significantly reduced the rate of CSF leak, and several groups have developed ways to buttress the NSF. A closure technique developed at our institution uses a bilayer “button” of fascia lata. The initial series of twenty patients repaired with this method from 2007 to July 1, 2009 were presented, with a CSF leak rate of 10% (Luginbuhl et al 2010)