A direct comparison of high-speed methods for the numerical Abel transform

The Abel transform is a mathematical operation that transforms a cylindrically symmetric three-dimensional (3D) object into its two-dimensional (2D) projection. The inverse Abel transform reconstructs the 3D object from the 2D projection. Abel transforms have wide application across numerous fields of science, especially chemical physics, astronomy, and the study of laser-plasma plumes. Consequently, many numerical methods for the Abel transform have been developed, which makes it challenging to select the ideal method for a specific application. In this work eight transform methods have been incorporated into a single, open-source Python software package (PyAbel) to provide a direct comparison of the capabilities, advantages, and relative computational efficiency of each transform method. Most of the tested methods provide similar, high-quality results. However, the computational efficiency varies across several orders of magnitude. By optimizing the algorithms, we find that some transform methods are sufficiently fast to transform 1-megapixel images at more than 100 frames per second on a desktop personal computer. In addition, we demonstrate the transform of gigapixel images.Comment: 9 pages, 5 figure

Tomographic readout of an opto-mechanical interferometer

The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. The complete tomographic reconstruction of the state of light requires the ability to readout arbitrary quadratures. Here we demonstrate such a readout by applying a balanced homodyne detector to an interferometric position measurement of a thermally excited high-Q silicon nitride membrane in a Michelson-Sagnac interferometer. A readout noise of \unit{1.9 \cdot 10^{-16}}{\metre/\sqrt{\hertz}} around the membrane's fundamental oscillation mode at \unit{133}{\kilo\hertz} has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.Comment: 7 pages, 5 figure

Proprioceptive localization for a quadrupedal robot on known terrain

We present a novel method for the localization of a legged robot on known terrain using only proprioceptive sensors such as joint encoders and an inertial measurement unit. In contrast to other proprioceptive pose estimation techniques, this method allows for global localization (i.e., localization with large initial uncertainty) without the use of exteroceptive sensors. This is made possible by establishing a measurement model based on the feasibility of putative poses on known terrain given observed joint angles and attitude measurements. Results are shown that demonstrate that the method performs better than dead-reckoning, and is also able to perform global localization from large initial uncertainty

Applications of graphics to support a testbed for autonomous space vehicle operations

Researchers describe their experience using graphics tools and utilities while building an application, AUTOPS, that uses a graphical Machintosh (TM)-like interface for the input and display of data, and animation graphics to enhance the presentation of results of autonomous space vehicle operations simulations. AUTOPS is a test bed for evaluating decisions for intelligent control systems for autonomous vehicles. Decisions made by an intelligent control system, e.g., a revised mission plan, might be displayed to the user in textual format or he can witness the effects of those decisions via out of window graphics animations. Although a textual description conveys essentials, a graphics animation conveys the replanning results in a more convincing way. Similarily, iconic and menu-driven screen interfaces provide the user with more meaningful options and displays. Presented here are experiences with the SunView and TAE Plus graphics tools used for interface design, and the Johnson Space Center Interactive Graphics Laboratory animation graphics tools used for generating out out of the window graphics

Open Doors College Preparation Program

Originally published as the Bilingual College Preparation Program for Latino/a Youth (2016)

Spatially Resolving a Starburst Galaxy at Hard X-ray Energies: NuSTAR, Chandra, AND VLBA Observations of NGC 253

Prior to the launch of NuSTAR, it was not feasible to spatially resolve the hard (E > 10 keV) emission from galaxies beyond the Local Group. The combined NuSTAR dataset, comprised of three ~165 ks observations, allows spatial characterization of the hard X-ray emission in the galaxy NGC 253 for the first time. As a follow up to our initial study of its nuclear region, we present the first results concerning the full galaxy from simultaneous NuSTAR, Chandra, and VLBA monitoring of the local starburst galaxy NGC 253. Above ~10 keV, nearly all the emission is concentrated within 100" of the galactic center, produced almost exclusively by three nuclear sources, an off-nuclear ultraluminous X-ray source (ULX), and a pulsar candidate that we identify for the first time in these observations. We detect 21 distinct sources in energy bands up to 25 keV, mostly consisting of intermediate state black hole X-ray binaries. The global X-ray emission of the galaxy - dominated by the off-nuclear ULX and nuclear sources, which are also likely ULXs - falls steeply (photon index >~ 3) above 10 keV, consistent with other NuSTAR-observed ULXs, and no significant excess above the background is detected at E > 40 keV. We report upper limits on diffuse inverse Compton emission for a range of spatial models. For the most extended morphologies considered, these hard X-ray constraints disfavor a dominant inverse Compton component to explain the {\gamma}-ray emission detected with Fermi and H.E.S.S. If NGC 253 is typical of starburst galaxies at higher redshift, their contribution to the E > 10 keV cosmic X-ray background is < 1%.Comment: 20 pages, 14 figures, accepted for publication in Ap

Accaparement de terres et droits de l'homme: rôle des sociétés et des entités financières européennes dans l'accaparement de terres en dehors de l'Union européenne

Dans les travaux de recherche antérieurs sur l'accaparement de terres, les auteurs se sont initialement intéressés aux sociétés étrangères investissant dans d'autres pays et ont mis notamment l'accent sur les sociétés implantées dans des pays tels que la Chine, les États du Golfe, la Corée du Sud et l'Inde. Ces dernières années, il est devenu évident que la palette des pays d'origine des investisseurs fonciers est bien plus large et comprend des acteurs implantés en Atlantique Nord et dans l'Union européenne. Dans la présente étude, nous fournissons des données qualitatives et quantitatives pour illustrer le rôle des entités financières et des sociétés établies dans l'Union européenne dans les transactions foncières opérées en dehors de l'Union. Cette étude analyse également le phénomène international de "ruée vers la terre" avec les droits de l'homme en arrière-plan, en examinant les répercussions de certaines transactions foncières auxquelles des investisseurs basés dans l'Union européenne participent, ainsi que leurs effets sur les populations qui vivent dans les secteurs visés par les investissements. Ces recherches s'appuient en partie sur l'étude réalisée en 2014 par Cotula sur les facteurs favorisant l'accaparement de terres et les répercussions de ce phénomène sur les droits de l'homme, mais s'en écartent également par la façon dont l'accent est mis expressément sur certains cas d'abus et de violations, potentielles ou effectives des droits de l'homme dans le cadre d'activités dans lesquelles des sociétés et des entités financières européennes sont impliquées. Dans nos conclusions, nous proposons une série de recommandations sur la façon dont l'Union européenne peut s'attaquer de façon efficace à ces problèmes

Land Grabbing and Human Rights: the Involvement of European Corporate and Financial Entities in Land Grabbing outside the European Union

In early research on land grabbing, the initial focus was on foreign companies investing abroad, with a particular focus on those based in countries such as China, Gulf States, South Korea, and India. In recent years, it has become evident that the range of countries land investors originate in is far broader, and includes both North Atlantic - and EU-based actors. In this study, we offer both quantitative and qualitative data illustrating the involvement of EU-based corporate and financial entities in land deals occurring outside of the EU. This study also analyses the global land rush within a human rights framework, examining the implications of particular land deals involving EU-based investors and their impact on communities living in areas where the investments are taking place. The research presented here builds partly on Cotula’s 2014 study on the drivers and human rights implications of land grabbing, but differs in that it focuses explicitly on particular cases of possible, actual or potential human rights abuses and violations, in the context of activities involving European corporate and financial entities. In our conclusions, we offer a series of recommendations on how the EU can more effectively address these issues

The non-equilibrium steady state of sparse systems with nontrivial topology

We study the steady state of a multiply-connected system that is driven out of equilibrium by a sparse perturbation. The prototype example is an $N$-site ring coupled to a thermal bath, driven by a stationary source that induces transitions with log-wide distributed rates. An induced current arises, which is controlled by the strength of the driving, and an associated topological term appears in the expression for the energy absorption rate. Due to the sparsity, the crossover from linear response to saturation is mediated by an intermediate regime, where the current is exponentially small in $\sqrt{N}$, which is related to the work of Sinai on "random walk in a random environment".Comment: 6 pages, 4 figure