1,552 research outputs found

    Improved Method for Detecting Local Discontinuities in CMB data by Finite Differencing

    Full text link
    An unexpected distribution of temperatures in the CMB could be a sign of new physics. In particular, the existence of cosmic defects could be indicated by temperature discontinuities via the Kaiser-Stebbins effect. In this paper, we show how performing finite differences on a CMB map, with the noise regularized in harmonic space, may expose such discontinuities, and we report the results of this process on the 7-year Wilkinson Microwave Anisotropy Probe data.Comment: 5 pages, 6 figures; Text has been edited, in line with the PRD articl

    The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs

    Get PDF
    The performance and cost of four 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States was studied. Each region has different insolation characteristics which result in varying collector field areas, plant performance, capital costs and energy costs. The regional variation in solar plant performance was assessed in relation to the expected rise in the future cost of residential and commercial electricity supplied by conventional utility power systems in the same regions. A discussion of the regional insolation data base is presented along with a description of the solar systems performance and costs. A range for the forecast cost of conventional electricity by region and nationally over the next several decades is given

    The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs

    Get PDF
    The performance and cost of the 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States were determined. The regional insolation data base is discussed. A range for the forecast cost of conventional electricity by region and nationally over the next several cades are presented

    Pretreatment of citrus by-products affects polyphenol recovery:a review

    Get PDF
    A large amount of citrus waste is generated annually. This waste is of great economic worth, since it contains high levels of polyphenols, which have attracted scientific interest due to their potent antimicrobial and antiradical activities. Pretreatment is a crucial step that precedes the extraction process and influences the yields and quality of polyphenols. This review emphasizes the effect of different drying processes, such as freeze drying, hot-air drying, vacuum drying, microwave drying, infrared drying, and high-speed drying, on the polyphenol retention in citrus by-products. Further treatments of the dried citrus by-products for assisting the liberation of bound polyphenols are also provided and comprehensively discussed

    ORFEUS-II Far-Ultraviolet Observations of 3C273: 1. Interstellar and Intergalactic Absorption Lines

    Get PDF
    We present the first intermediate-resolution (lambda / 3000) spectrum of the bright quasi-stellar object 3C273 at wavelengths between 900 and 1200 A. Observations were performed with the Berkeley spectrograph aboard the ORFEUS-SPAS II mission. We detect Lyman beta counterparts to previously-identified intergalactic Lyman-alpha features at cz = 19900, 1600, and 1000 km/s; counterparts to other putative Lyman-alpha clouds along the sight line are below our detection limit. The strengths of the two very low redshift Lyman-beta features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations, suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H I column density of 4 E14/cm^2 for the 1600 km/s cloud. We find marginally significant evidence for Galactic H_2 along the sight line, with a total column density of about 1 E15/cm^2. We detect the stronger interstellar O VI doublet member unambiguously; the weaker member is blended with other features. If the Doppler b value for O VI is comparable to that determined for N V then the O VI column density is 7 +/- 2 E14/cm^2, significantly above the only previous estimate. The O VI / N V ratio is about 10, consistent with the low end of the range observed in the disk. Additional interstellar species detected for the first time toward 3C273 (at modest statistical significance) include P II, Fe III, Ar I, and S III.Comment: LaTeX file, 11 pages, 4 encapsulated PostScript figures. Uses aaspp4.sty and astrobib.sty. (Astrobib is available from http://www.stsci.edu/software/TeX.html .) The ORFEUS telescope is described at http://sag-www.ssl.berkeley.edu/orfeus/ . To appear in ApJ (Letters

    Implications of a Nonthermal Origin of the Excess EUV Emission from the Coma Cluster of Galaxies

    Full text link
    The inverse Compton (IC) interpretation of the excess EUV emission, that was recently reported from several clusters of galaxies, suggests that the amount of relativistic electrons in the intracluster medium is highly significant, W_e>10^{61} erg. Considering Coma as the prototype galaxy cluster of nonthermal radiation, we discuss implications of the inverse Compton origin of the excess EUV fluxes in the case of low intracluster magnetic fields of order 0.1 muG, as required for the IC interpretation of the observed excess hard X-ray flux, and in the case of high fields of order 1 muG as suggested by Faraday rotation measurements. Although for such high intracluster fields the excess hard X-rays will require an explanation other than by the IC effect, we show that the excess EUV flux can be explained by the IC emission of a `relic' population of electrons driven into the incipient intracluster medium at the epoch of starburst activity by galactic winds, and later on reenergized by adiabatic compression and/or large-scale shocks transmitted through the cluster as the consequence of more recent merger events. For high magnetic fields B > 1 muG the interpretation of the radio fluxes of Coma requires a second population of electrons injected recently. They can be explained as secondaries produced by a population of relativistic protons. We calculate the fluxes of gamma-rays to be expected in both the low and high magnetic field scenarios, and discuss possibilities to distinguish between these two principal options by future gamma-ray observations.Comment: LaTeX, 6 figures; accepted for publication in Ap

    X-ray Signatures of an Ionized Reprocessor in the Seyfert galaxy Ton S 180

    Full text link
    We discuss the hard X-ray properties of the Seyfert galaxy Ton S 180, based upon the analysis of ASCA data. We find the X-ray flux varied by a factor ~2 on a time scale of a few thousand seconds. The source showed significantly higher amplitude of variability in the 0.5-2 keV band than in the 2-10 keV band. The continuum is adequately parameterized as a Gamma ~ 2.5 power-law across the 0.6--10 keV band . We confirm the recent discovery of an emission line of high equivalent width, due to Fe K-shell emission from highly-ionized material. These ASCA data show the Fe line profile to be broad and asymmetric and tentatively suggest it is stronger during the X-ray flares, consistent with an origin from the inner parts of an accretion disk. The X-ray spectrum is complex below 2 keV, possibly due to emission from a blend of soft X-ray lines, which would support the existence of an ionized reprocessor, most likely due to a relatively high accretion rate in this source.Comment: 24 pages, 8 figures. LaTeX with encapsulated postscript. To appear in the Astrophysical Journa

    Towards Autopoietic Computing

    Full text link
    A key challenge in modern computing is to develop systems that address complex, dynamic problems in a scalable and efficient way, because the increasing complexity of software makes designing and maintaining efficient and flexible systems increasingly difficult. Biological systems are thought to possess robust, scalable processing paradigms that can automatically manage complex, dynamic problem spaces, possessing several properties that may be useful in computer systems. The biological properties of self-organisation, self-replication, self-management, and scalability are addressed in an interesting way by autopoiesis, a descriptive theory of the cell founded on the concept of a system's circular organisation to define its boundary with its environment. In this paper, therefore, we review the main concepts of autopoiesis and then discuss how they could be related to fundamental concepts and theories of computation. The paper is conceptual in nature and the emphasis is on the review of other people's work in this area as part of a longer-term strategy to develop a formal theory of autopoietic computing.Comment: 10 Pages, 3 figure
    corecore