Mode visibilities in radial velocity and intensity Sun-as-a-star helioseismic measurements

We analyze more than 5000 days of Sun-as-a-star radial velocity GOLF and intensity VIRGO observations to measure the visibilities of the l=0, 1, 2, and 3 modes and the m-amplitude ratios of the l=2 and 3 modes in the solar acoustic spectrum. We provide observational values that we compare to theoretical predictions.Comment: SOHO 24 / GONG 2010 conference, to be published in JPC

Learning Ground Traversability from Simulations

Mobile ground robots operating on unstructured terrain must predict which areas of the environment they are able to pass in order to plan feasible paths. We address traversability estimation as a heightmap classification problem: we build a convolutional neural network that, given an image representing the heightmap of a terrain patch, predicts whether the robot will be able to traverse such patch from left to right. The classifier is trained for a specific robot model (wheeled, tracked, legged, snake-like) using simulation data on procedurally generated training terrains; the trained classifier can be applied to unseen large heightmaps to yield oriented traversability maps, and then plan traversable paths. We extensively evaluate the approach in simulation on six real-world elevation datasets, and run a real-robot validation in one indoor and one outdoor environment.Comment: Webpage: http://romarcg.xyz/traversability_estimation

CoRoT reveals a magnetic activity cycle in a Sun-like star

The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solar-like oscillations in the star HD49933, for signatures of stellar magnetic activity. Asteroseismic measurements of global changes in the oscillation frequencies and mode amplitudes reveal a modulation of at least 120 days, with the minimum frequency shift corresponding to maximum amplitude as in the Sun. These observations are evidence of a stellar magnetic activity cycle taking place beneath the surface of HD49933 and provide constraints for stellar dynamo models under conditions different from those of the Sun.Comment: Brevia text and supporting online material, published in Scienc

Evaluating forest Growth Models

Effective model evaluation is not a single, simple procedure, but comprises several interrelated steps that cannot be separated from each other or from the purpose and process of model construction. We draw attention to several statistical and graphical procedures that may be used both with data used for model calibration and with data used in the evaluation of the model. We emphasize that the validity of conclusions depends on the validity of assumptions. These principles should be kept in mind throughout model construction and evaluation

Immigration Legislation and Issues in the 114th Congress

The House and the Senate have considered immigration measures on a variety of issues in the 114th Congress. The Consolidated Appropriations Act, 2016 (P.L. 114-113) extends four immigration programs through September 30, 2016: the EB-5 immigrant investor Regional Center Pilot Program, the E-Verify employment eligibility verification system, the Conrad State program for foreign medical graduates, and the special immigrant religious worker program. P.L. 114-113 also contains provisions on the Visa Waiver Program and certain nonimmigrant visa categories. Other enacted immigration-related measures include the Border Jobs for Veterans Act of 2015 (P.L. 114-68) on border security personnel, the Adoptive Family Relief Act (P.L. 114-70) on intercountry adoption, and the National Defense Authorization Act for Fiscal Year 2016 (P.L. 114-92) on the Afghan special immigrant visa program. The House has passed several other immigration-related bills. Among them are the Northern Border Security Review Act (H.R. 455), the Preclearance Authorization Act of 2015 (H.R. 998), the Border Security Technology Accountability Act of 2015 (H.R. 1634), the Enforce the Law for Sanctuary Cities Act (H.R. 3009), and the American SAFE Act of 2015 (H.R. 4038). H.R. 998 has also been reported by the Senate Homeland Security and Governmental Affairs Committee with an amendment in the nature of a substitute. In addition, various bills on border security, interior enforcement, visa security, and asylum, among other issues, have been considered by a House or Senate committee. Border security- related measures have been reported or ordered to be reported by the House Homeland Security Committee (H.R. 399, H.R. 3583, H.R. 3586), or the Senate Homeland Security and Governmental Affairs Committee (S. 750, S. 1808, S. 1864,S. 1873). Interior enforcement provisions are included in bills ordered to be reported by the House Judiciary Committee (H.R. 1147, H.R. 1148, H.R. 1153) or reported by the House Appropriations Committee (H.R. 3128). S. 1635, as reported by the Senate Foreign Relations Committee, also contains interior enforcement- related provisions. Several of these interior enforcement bills also contain key provisions on other immigration issues. Among the other issues addressed in these bills are employment eligibility verification (H.R. 1147); visa security and naturalization (H.R. 1148); and expedited removal, asylum, parole, and unaccompanied alien children (H.R. 1153). H.R. 1149, as ordered to be reported by the House Judiciary Committee, also addresses unaccompanied alien children. This report discusses these and other immigration-related issues that have received legislative action or are of significant congressional interest in the 114th Congress. Department of Homeland Security appropriations are addressed in CRS Report R44053, Department of Homeland Security Appropriations: FY2016, and, for the most part, are not covered here

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

We theoretically investigate the process of coupling cold atoms into the core of a hollow-core photonic-crystal optical fiber using a blue-detuned Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam to couple the atoms, the blue-detuned hollow-beam can confine cold atoms to the darkest regions of the beam thereby minimizing shifts in the internal states and making the guide highly robust to heating effects. This single optical beam is used as both a funnel and guide to maximize the number of atoms into the fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical trap (MOT) above a vertically-oriented optical fiber. We observe a gravito-optical trapping effect for atoms with high orbital momentum around the trap axis, which prevents atoms from coupling to the fiber: these atoms lack the kinetic energy to escape the potential and are thus trapped in the laser funnel indefinitely. We find that by reducing the dipolar force to the point at which the trapping effect just vanishes, it is possible to optimize the coupling of atoms into the fiber. Our simulations predict that by using a low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a 20-{\mu}m radius core hollow-fiber it is possible to couple 11% of the atoms from a MOT 9 mm away from the fiber. When MOT is positioned further away, coupling efficiencies over 50% can be achieved with larger core fibers.Comment: 11 pages, 12 figures, 1 tabl

Roll Calibration for CryoSat-2: a comprehensive approach

International audienceCryoSat-2 is the first satellite mission carrying a high pulse repetition frequency radar altimeter with interferometric capability on board. Across track interferometry allows the angle to the point of closest approach to be determined by combining echoes received by two antennas and knowledge of their orientation. Accurate information of the platform mispointing angles, in particular of the roll, is crucial to determine the angle of arrival in the across-track direction with sufficient accuracy. As a consequence, different methods were designed in the CryoSat-2 calibration plan in order to estimate interferometer performance along with the mission and to assess the roll’s contribution to the accuracy of the angle of arrival. In this paper, we present the comprehensive approach used in the CryoSat-2 Mission to calibrate the roll mispointing angle, combining analysis from external calibration of both man-made targets, i.e., transponder and natural targets. The roll calibration approach for CryoSat-2 is proven to guarantee that the interferometric measurements are exceeding the expected performance

Non-Parametric Extraction of Implied Asset Price Distributions

Extracting the risk neutral density (RND) function from option prices is well defined in principle, but is very sensitive to errors in practice. For risk management, knowledge of the entire RND provides more information for Value-at-Risk (VaR) calculations than implied volatility alone [1]. Typically, RNDs are deduced from option prices by making a distributional assumption, or relying on implied volatility [2]. We present a fully non-parametric method for extracting RNDs from observed option prices. The aim is to obtain a continuous, smooth, monotonic, and convex pricing function that is twice differentiable. Thus, irregularities such as negative probabilities that afflict many existing RND estimation techniques are reduced. Our method employs neural networks to obtain a smoothed pricing function, and a central finite difference approximation to the second derivative to extract the required gradients. This novel technique was successfully applied to a large set of FTSE 100 daily European exercise (ESX) put options data and as an Ansatz to the corresponding set of American exercise (SEI) put options. The results of paired t-tests showed significant differences between RNDs extracted from ESX and SEI option data, reflecting the distorting impact of early exercise possibility for the latter. In particular, the results for skewness and kurtosis suggested different shapes for the RNDs implied by the two types of put options. However, both ESX and SEI data gave an unbiased estimate of the realised FTSE 100 closing prices on the options' expiration date. We confirmed that estimates of volatility from the RNDs of both types of option were biased estimates of the realised volatility at expiration, but less so than the LIFFE tabulated at-the-money implied volatility.Comment: Paper based on Application of Physics in Financial Analysis,APFA5, Conference Presentation, Torino, Italy. 11.5 Page

The PdBI Arcsecond Whirlpool Survey (PAWS): Environmental Dependence of Giant Molecular Cloud Properties in M51

Using data from the PdBI Arcsecond Whirlpool Survey (PAWS), we have generated the largest extragalactic Giant Molecular Cloud (GMC) catalog to date, containing 1,507 individual objects. GMCs in the inner M51 disk account for only 54% of the total 12CO(1-0) luminosity of the survey, but on average they exhibit physical properties similar to Galactic GMCs. We do not find a strong correlation between the GMC size and velocity dispersion, and a simple virial analysis suggests that 30% of GMCs in M51 are unbound. We have analyzed the GMC properties within seven dynamically-motivated galactic environments, finding that GMCs in the spiral arms and in the central region are brighter and have higher velocity dispersions than inter-arm clouds. Globally, the GMC mass distribution does not follow a simple power law shape. Instead, we find that the shape of the mass distribution varies with galactic environment: the distribution is steeper in inter-arm region than in the spiral arms, and exhibits a sharp truncation at high masses for the nuclear bar region. We propose that the observed environmental variations in the GMC properties and mass distributions are a consequence of the combined action of large-scale dynamical processes and feedback from high mass star formation. We describe some challenges of using existing GMC identification techniques for decomposing the 12CO(1-0) emission in molecule-rich environments, such as M51's inner disk.Comment: 73 pages, 18 figures, 14 tables, accepted for publication in Ap

The PdBI Arcsecond Whirlpool Survey (PAWS): Multi-phase cold gas kinematic of M51

The kinematic complexity and the favorable position of M51 on the sky make this galaxy an ideal target to test different theories of spiral arm dynamics. Taking advantage of the new high resolution PdBI Arcsecond Whirlpool Survey (PAWS) data, we undertake a detailed kinematic study of M51 to characterize and quantify the origin and nature of the non-circular motions. Using a tilted-ring analysis supported by several other archival datasets we update the estimation of M51's position angle (PA=(173 +/- 3) deg) and inclination (i=(22 +/- 5) deg). Harmonic decomposition of the high resolution (40 pc) CO velocity field shows the first kinematic evidence of an m=3 wave in the inner disk of M51 with a corotation at R(CR,m=3)=1.1 +/- 0.1 kpc and a pattern speed of Omega_p(m=3) = 140 km/(s kpc). This mode seems to be excited by the nuclear bar, while the beat frequencies generated by the coupling between the m=3 mode and the main spiral structure confirm its density-wave nature. We observe also a signature of an m=1 mode that is likely responsible for the lopsidedness of M51 at small and large radii. We provide a simple method to estimate the radial variation of the amplitude of the spiral perturbation (Vsp) attributed to the different modes. The main spiral arm structure has =50-70 km/s, while the streaming velocity associated with the m=1 and m=3 modes is, in general, 2 times lower. Our joint analysis of HI and CO velocity fields at low and high spatial resolution reveals that the atomic and molecular gas phases respond differently to the spiral perturbation due to their different vertical distribution and emission morphology.Comment: 42 pages, 12 figures, accepted for publication in Ap