1,376 research outputs found

    Conodonts from isolated Devonian outcrops

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    Shales, sandy shales, and sandstones were sampled from isolated outcrops at Sulphur Springs and at Coal Hollow in Ste. Genevieve County. An attempt was made to find the answers to the following questions: (1) Can the boundary between the Devonian and the Mississippian be located at these localities by determining the distribution of conodonts? (2) Are there faunal difference between the concodonts in the Devonian part of the section? (3) Are there differences between the conodonts of the sandstones and the sandy shales that may be interpreted as environmental responses? (4) What other formation or formations do the conodonts of these two Devonian sections or parts of these sections suggest as time equivalents? It was concluded the boundary can be located in each of these localities. It was also concluded that there are no faunal differences in the Devonian part of the Ste. Genevieve County section or between the sandstones and shales that could not be interpreted as the result of factors which could not be controlled in the present study. Other formations or sections suggested as time equivalents to the Ste. Genevieve County section are the sandstone facies of the Eureka shale, the Sees Creek section, and the "Grassy Creek" group, as defined in this paper. Owing to the lack of conodonts in the Sulpur Springs samples, no similar conclusions were drawn concerning this locality

    The Planck Surveyor mission: astrophysical prospects

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    Although the Planck Surveyor mission is optimized to map the cosmic microwave background anisotropies, it will also provide extremely valuable information on astrophysical phenomena. We review our present understanding of Galactic and extragalactic foregrounds relevant to the mission and discuss on one side, Planck's impact on the study of their properties and, on the other side, to what extent foreground contamination may affect Planck's ability to accurately determine cosmological parameters. Planck's multifrequency surveys will be unique in their coverage of large areas of the sky (actually, of the full sky); this will extend by two or more orders of magnitude the flux density interval over which mm/sub-mm counts of extragalactic sources can be determined by instruments already available (like SCUBA) or planned for the next decade (like the LSA-MMA or the space mission FIRST), which go much deeper but over very limited areas. Planck will thus provide essential complementary information on the epoch-dependent luminosity functions. Bright radio sources will be studied over a poorly explored frequency range where spectral signatures, essential to understand the physical processes that are going on, show up. The Sunyaev-Zeldovich effect, with its extremely rich information content, will be observed in the direction of a large number of rich clusters of Galaxies. Thanks again to its all sky coverage, Planck will provide unique information on the structure and on the emission properties of the interstellar medium in the Galaxy. At the same time, the foregrounds are unlikely to substantially limit Planck's ability to measure the cosmological signals. Even measurements of polarization of the primordial Cosmic Microwave background fluctuations appear to be feasible.Comment: 20 pages, Latex (use aipproc2.sty, aipproc2.cls, epsfig.sty), 10 PostScript figures; invited review talk, Proc. of the Conference: "3 K Cosmology", Roma, Italy, 5-10 October 1998, AIP Conference Proc, in press Note: Figures 6 and 7 have been replaced by new and correct version

    Angular Power Spectrum of the Microwave Background Anisotropy seen by the COBE Differential Microwave Radiometer

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    The angular power spectrum estimator developed by Peebles (1973) and Hauser & Peebles (1973) has been modified and applied to the 4 year maps produced by the COBE DMR. The power spectrum of the observed sky has been compared to the power spectra of a large number of simulated random skies produced with noise equal to the observed noise and primordial density fluctuation power spectra of power law form, with P(k)∝knP(k) \propto k^n. The best fitting value of the spectral index in the range of spatial scales corresponding to spherical harmonic indices 3≀ℓâ‰Č303 \leq \ell \lesssim 30 is an apparent spectral index nappn_{app} = 1.13 (+0.3) (-0.4) which is consistent with the Harrison-Zel'dovich primordial spectral index npri=1n_{pri} = 1 The best fitting amplitude for napp=1n_{app} = 1 is ⟹QRMS2⟩0.5\langle Q_{RMS}^2\rangle^{0.5} = 18 uK.Comment: 17 pages including 3 PostScript figures. Submitted to The Astrophysical Journal (Letters

    Power Spectrum Analysis of Far-IR Background Fluctuations in 160 Micron Maps From the Multiband Imaging Photometer for Spitzer

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    We describe data reduction and analysis of fluctuations in the cosmic far-IR background (CFIB) in observations with the Multiband Imaging Photometer for Spitzer (MIPS) instrument 160 micron detectors. We analyzed observations of an 8.5 square degree region in the Lockman Hole, part of the largest low-cirrus mapping observation with this instrument. We measured the power spectrum of the CFIB in these observations by fitting a power law to the IR cirrus component, the dominant foreground contaminant, and subtracting this cirrus signal. The CFIB power spectrum in the range 0.2 arc min^{-1} <k< 0.5 arc min^{-1} is consistent with previous measurements of a relatively flat component. However, we find a large power excess at low k, which falls steeply to the flat component in the range 0.03 arc min^{-1} <k< 0.1 arc min^{-1}. This low-k power spectrum excess is consistent with predictions of a source clustering "signature". This is the first report of such a detection in the far-IR.Comment: This is the version of the paper accepted by A&A, which includes various changes and new material. The superior-quality PDF with integrated figures may be downloaded at http://www-astro.lbl.gov/~bruce/spitzerpaper1/cfibaa_pub.pdf 15 pages, figures integrated with text. This paper supersedes astro-ph/050416

    Investigation into Cloud Computing for More Robust Automated Bulk Image Geoprocessing

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    Geospatial resource assessments frequently require timely geospatial data processing that involves large multivariate remote sensing data sets. In particular, for disasters, response requires rapid access to large data volumes, substantial storage space and high performance processing capability. The processing and distribution of this data into usable information products requires a processing pipeline that can efficiently manage the required storage, computing utilities, and data handling requirements. In recent years, with the availability of cloud computing technology, cloud processing platforms have made available a powerful new computing infrastructure resource that can meet this need. To assess the utility of this resource, this project investigates cloud computing platforms for bulk, automated geoprocessing capabilities with respect to data handling and application development requirements. This presentation is of work being conducted by Applied Sciences Program Office at NASA-Stennis Space Center. A prototypical set of image manipulation and transformation processes that incorporate sample Unmanned Airborne System data were developed to create value-added products and tested for implementation on the "cloud". This project outlines the steps involved in creating and testing of open source software developed process code on a local prototype platform, and then transitioning this code with associated environment requirements into an analogous, but memory and processor enhanced cloud platform. A data processing cloud was used to store both standard digital camera panchromatic and multi-band image data, which were subsequently subjected to standard image processing functions such as NDVI (Normalized Difference Vegetation Index), NDMI (Normalized Difference Moisture Index), band stacking, reprojection, and other similar type data processes. Cloud infrastructure service providers were evaluated by taking these locally tested processing functions, and then applying them to a given cloud-enabled infrastructure to assesses and compare environment setup options and enabled technologies. This project reviews findings that were observed when cloud platforms were evaluated for bulk geoprocessing capabilities based on data handling and application development requirements

    Large Angular Scale CMB Anisotropy Induced by Cosmic Strings

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    We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy maps. Based on 192192 maps, we compute the anisotropy power spectrum for multipole moments ℓ≀20\ell \le 20. By comparing with the observed temperature anisotropy, we set the normalization for the cosmic string mass-per-unit-length ÎŒ\mu, obtaining GÎŒ/c2=1.05−0.20+0.35×10−6G\mu/c^2=1.05 {}^{+0.35}_{-0.20} \times10^{-6}, which is consistent with all other observational constraints on cosmic strings. We demonstrate that the anisotropy pattern is consistent with a Gaussian random field on large angular scales.Comment: 4 pages, RevTeX, two postscript files, also available at http://www.damtp.cam.ac.uk/user/defects/ to appear in Physical Review Letters, 23 September 199

    Feasibility of a Small, Rapid Optical-to-IR Response, Next Generation Gamma Ray Burst Mission

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    We present motivations for and study feasibility of a small, rapid optical to IR response gamma ray burst (GRB) space observatory. By analyzing existing GRB data, we give realistic detection rates for X-ray and optical/IR instruments of modest size under actual flight conditions. Given new capabilities of fast optical/IR response (about 1 s to target) and simultaneous multi-band imaging, such an observatory can have a reasonable event rate, likely leading to new science. Requiring a Swift-like orbit, duty cycle, and observing constraints, a Swift-BAT scaled down to 190 square cm of detector area would still detect and locate about 27 GRB per yr. for a trigger threshold of 6.5 sigma. About 23 percent of X-ray located GRB would be detected optically for a 10 cm diameter instrument (about 6 per yr. for the 6.5 sigma X-ray trigger).Comment: Elaborated text version of a poster presented at 2012 Malaga/Marbella symposiu

    Two Dimensional Topology of Large Scale Structure in the Las Campanas Redshift Survey

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    We have measured the topology (genus) of the density distribution of large-scale structure observed in the Las Campanas Redshift Survey (LCRS). The LCRS is complete to magnitude 17.5, and contains nearly 24000 galaxies with median redshift of 30000 km/s. The large volume and large number of galaxies allows sampling of nearly 100 independent structures with which to compute the genus topology, a vast improvement over previous studies. We find that the genus is consistent with a random-phase Gaussian distribution of initial density fluctuations, as would be produced naturally in inflationary models. When we combine these results with the genus measurements of the COBE microwave background fluctuations, we find that two orthogonal projections of the three-dimensional distribution of initial density fluctuations are consistent with Gaussian random-phase behavior, in agreement with standard inflationary models. Particular attention is given to statistical significance of the genus test.Comment: AASTeX, v4, preprint, 11 pages including 2 PS figure

    Detecting a stochastic background of gravitational radiation: Signal processing strategies and sensitivities

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    We analyze the signal processing required for the optimal detection of a stochastic background of gravitational radiation using laser interferometric detectors. Starting with basic assumptions about the statistical properties of a stochastic gravity-wave background, we derive expressions for the optimal filter function and signal-to-noise ratio for the cross-correlation of the outputs of two gravity-wave detectors. Sensitivity levels required for detection are then calculated. Issues related to: (i) calculating the signal-to-noise ratio for arbitrarily large stochastic backgrounds, (ii) performing the data analysis in the presence of nonstationary detector noise, (iii) combining data from multiple detector pairs to increase the sensitivity of a stochastic background search, (iv) correlating the outputs of 4 or more detectors, and (v) allowing for the possibility of correlated noise in the outputs of two detectors are discussed. We briefly describe a computer simulation which mimics the generation and detection of a simulated stochastic gravity-wave signal in the presence of simulated detector noise. Numerous graphs and tables of numerical data for the five major interferometers (LIGO-WA, LIGO-LA, VIRGO, GEO-600, and TAMA-300) are also given. The treatment given in this paper should be accessible to both theorists involved in data analysis and experimentalists involved in detector design and data acquisition.Comment: 81 pages, 30 postscript figures, REVTE
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