7,802 research outputs found

    Accomplishments of the NASA Johnson Space Center portion of the soil moisture project in fiscal year 1981

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    The NASA/JSC ground scatterometer system was used in a row structure and row direction effects experiment to understand these effects on radar remote sensing of soil moisture. Also, a modification of the scatterometer system was begun and is continuing, to allow cross-polarization experiments to be conducted in fiscal years 1982 and 1983. Preprocessing of the 1978 agricultural soil moisture experiment (ASME) data was completed. Preparations for analysis of the ASME data is fiscal year 1982 were completed. A radar image simulation procedure developed by the University of Kansas is being improved. Profile soil moisture model outputs were compared quantitatively for the same soil and climate conditions. A new model was developed and tested to predict the soil moisture characteristic (water tension versus volumetric soil moisture content) from particle-size distribution and bulk density data. Relationships between surface-zone soil moisture, surface flux, and subsurface moisture conditions are being studied as well as the ways in which measured soil moisture (as obtained from remote sensing) can be used for agricultural applications

    Surface Topographical and Compositional Characterization Using Backscattered Electron Methods

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    Two pairs of diametrically opposed Schottky surface barrier diodes in a modified scanning electron microscope (SEM) are used to reconstruct surface elevations and composition differences. An empirically determined function of difference of signals from opposing diodes is used to calculate slopes, which are then integrated to elevations by an efficient 2-dimensional Fast Fourier Transform. Composition differences are distinguished by variations in the overall backscattered electron (BSE) intensity estimated by the sum of the four diode signals. Arithmetic average roughness measurements from the BSE device are within 10% of stylus surface tracer measurements when surface slopes average less than 6 degrees and maximum slopes are less than 45°; shadowing effects for rough surfaces, aliasing, and averaging effects from Fourier integration are apparent. Composition measurements show distinction of high contrast phases; phase boundary-slope interactions are noted

    High Resolution Hybrid Pixel Sensors for the e+e- TESLA Linear Collider Vertex Tracker

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    In order to fully exploit the physics potential of a future high energy e+e- linear collider, a Vertex Tracker, providing high resolution track reconstruction, is required. Hybrid Silicon pixel sensors are an attractive option, for the sensor technology, due to their read-out speed and radiation hardness, favoured in the high rate environment of the TESLA e+e- linear collider design but have been so far limited by the achievable single point space resolution. In this paper, a conceptual design of the TESLA Vertex Tracker, based on a novel layout of hybrid pixel sensors with interleaved cells to improve their spatial resolution, is presented.Comment: 12 pages, 5 figures, to appear in the Proceedings of the Vertex99 Workshop, Texel (The Netherlands), June 199

    Understanding the Basis for Down Syndrome Phenotypes

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    Down syndrome is a collection of features that are caused by trisomy for human Chromosome 21. While elevated transcript levels of the more than 350 genes on the chromosome are primarily responsible, it is likely that multiple genetic mechanisms underlie the numerous ways in which development and function diverge in individuals with trisomy 21 compared to euploid individuals. We consider genotype–phenotype interactions with the goal of producing working concepts that will be useful for approaches to ameliorate the effects of trisomy

    Swimming against the tide: a study of a neighbourhood trying to rediscover its ‘reason for being’– the case of South Bank, Redcar and Cleveland.

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    Many of the programmes and initiatives to regenerate deprived neighbourhoods appear to have had limited lasting impact. It has been argued that one reason for this is that we still have little real understanding of the nature and scale of the problems some communities face (Bernt, 2009). This article attempts to add to our knowledge through close study of an area with multiple problems and a history of failed regeneration attempts. An in-depth case study, undertaken to explore the current situation and future prospects of South Bank, a small neighbourhood in the North East of England, highlights transferable knowledge which may be applied to other regeneration areas. The analysis considers the nature and consequences of industrial decline; entrenched deprivation; the stigmatization of communities; the value of community consultation and the potential impact of retail-led regeneration. We question whether negative stigma attached to places can be changed and we ask what the future may hold for deprived communities now that public sector funding has largely dried up, and we consider an alternative approach: the potential impacts of private sector retail-led regeneration in the absence of public sector funding

    A Path Algorithm for Constrained Estimation

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    Many least squares problems involve affine equality and inequality constraints. Although there are variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current paper proposes a new path following algorithm for quadratic programming based on exact penalization. Similar penalties arise in l1l_1 regularization in model selection. Classical penalty methods solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to \infty, one recovers the constrained solution. In the exact penalty method, squared penalties are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the lasso and generalized lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well chosen examples illustrate the mechanics and potential of path following.Comment: 26 pages, 5 figure

    Book Reviews

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    Testing the Higgs boson gluonic couplings at LHC

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    We study Higgs + jet production at hadron colliders in order to look for new physics residual effects possibly described by the dim=6dim=6 operators {\O}_{GG} and {\widetilde\O}_{GG} which induce anomalous HggHgg and HgggHggg couplings. Two ways for constraining these operators at LHC may be ~useful. The first is based on the total Higgs boson production rate induced by gluon-gluon fusion, in which the main cause of limitations are due to theoretical uncertainties leading to sensitivities of dG3.×104|d_G|\simeq 3.\times 10^{-4} and d~G1.4×103|\widetilde{d}_G|\simeq 1.4\times 10^{-3} for the corresponding anomalous couplings, in the mass range 100 GeV \lsim \mh \lsim 2~00 GeV. These results imply sensitivity to new physics scales of 51 and 24 TeV respectively. The second way investigated here concerns the shape of the Higgs transverse momentum; for which the theoretical uncertainties are less severe and the limitations are mainly induced by statistics. A simple analysis, based on the ratio of the number of events at large and low pTp_T at LHC, leads to similar sensitivities, if only the HγγH\to \gamma \gamma decay mode is used. But the sensitivities can now be improved by a factor 2 to 10, depending on the Higgs mass, if the Higgs decay modes to WWWW^*, ZZZZ^*, WWWW, ZZZZ are also used.Comment: 23 pages and 7 figures, version to appear in Phys.ReV.D. e-mail: [email protected]
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