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  • Polymer and Materials Science  (184)
  • Astronomy  (101)
  • 2020-2023
  • 2010-2014  (101)
  • 1970-1974  (184)
  • 1965-1969
  • 1935-1939
  • 2011  (101)
  • 1972  (184)
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  • 2020-2023
  • 2010-2014  (101)
  • 1970-1974  (184)
  • 1965-1969
  • 1935-1939
Year
  • 1
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-07-13
    Description: We present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the active galactic nuclei (AGNs) detected by Fermi during its first year of operation, with the largest data sets ever used for this purpose.We use both archival interferometric 8.4 GHz data (from the Very Large Array and ATCA, for the full sample of 599 sources) and concurrent single-dish 15 GHz measurements from the OwensValley RadioObservatory (OVRO, for a sub sample of 199 objects). Our unprecedentedly large sample permits us to assess with high accuracy the statistical significance of the correlation, using a surrogate data method designed to simultaneously account for common-distance bias and the effect of a limited dynamical range in the observed quantities. We find that the statistical significance of a positive correlation between the centimeter radio and the broadband (E 〉 100 MeV) gamma-ray energy flux is very high for the whole AGN sample, with a probability of 〈10(exp -7) for the correlation appearing by chance. Using the OVRO data, we find that concurrent data improve the significance of the correlation from 1.6 10(exp -6) to 9.0 10(exp -8). Our large sample size allows us to study the dependence of correlation strength and significance on specific source types and gamma-ray energy band. We find that the correlation is very significant (chance probability 〈 10(exp -7)) for both flat spectrum radio quasars and BL Lac objects separately; a dependence of the correlation strength on the considered gamma-ray energy band is also present, but additional data will be necessary to constrain its significance.
    Keywords: Astronomy
    Type: GSFC.JA.5653.2011 , The Astrophysical Journal; 741; 30
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  • 3
    Publication Date: 2019-08-26
    Description: Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(exp -26) cm(exp 3) / s at 5 GeV to about 5 X 10(exp -23) cm(exp 3)/ s at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (approx 3 X 10(exp -26) cm(exp 3)/s for a purely s-wave cross section), without assuming additional boost factors.
    Keywords: Astronomy
    Type: GSFC.JA.5867.2012
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 3353-3360 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two independently derived distribution function methods validate both the calibration curve and the dispersion correction of the “effective linear calibration” method used in gel permeation chromatography (GPC). Experimental conditions are specified for making the method more useful by permitting linear extrapolation of the calibration line, \documentclass{article}\pagestyle{empty}\begin{document}$ V_R = C_1 + C_2 \log M, $\end{document} and for using a minimum number of standards. The independent methods quantitatively relate known differential of integral distribution functions for standard samples to their respective chromatograms. As such, they are useful calibration methods also, but are limited in scope and range.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The presence of the antiparallel-β-pleated sheet coformation io isolated human amyloid protein fibrils has been confirmed by infrared spectroscopy. In most amyloid samples, this conformation was enhanced by acidic solution conditions. Infrared spectroscopy (Amide I and Amide V absorption bands) and x-ray diffraction methods were also used to examine the immunoglobulin molecule for solid state-β-structure. It was found that both heavy chains and Bence Jones proteins exhibited some β-pleated sheet content upon acid and/or heat treatment. Furthermore, pepsin digests comprising either the variable-rich region (Fd′) of the immunloglobulin heavy chain or in particular, filamentous variable segments of κ and λ Bence Jones proteins were, as isolated, very similar to amyloid in β-structure content. Data from other immunoglobulin-derived sample did not exhibit extensive β-pleated sheet content. On the other hand, most amyliod and immunoglobulin-derived samples did display some β-structure when cast from 50% HCOOH solution. Under these conditions, however, filamentous light chain-variable segments exhibited well-defined infrared patterns rich in antiparallel-β-pleated sheet structure and gave a “cross-β” x-ray diffraction pattern.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 3267-3277 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electroinitiated preparation of equimolar copolymers of styrene and diethyl fumarate is described. The reaction medium consisted of these monomers dissolved in a methanol-zinc bromide solution. Rates of polymerization increased with increasing applied current and the copolymer yield increased linearly with the total number of Faradays transferred. The copolymer composition is 1:1 and is essentially invariant with the degree of conversion (〈15%), electroinitiation rate, and monomer feed ratios. A reaction mechanism involving donor-acceptor complexes and electroinitiated excitation of these complexes at the electrode is postulated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 3253-3265 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparative analysis of photoinitiation and electroinitiation can help elucidate initiation processes in donor-acceptor charge-transfer copolymerization. The technique has been applied to the zinc bromide-catalyzed copolymerization of styrene and diethyl fumarate in methanol. The photocopolymer product was analyzed by GPC, NMR, and elemental analysis. The results showed that 1:1 copolymers were formed initially, but changes occurred in both the kinetics and products after the early stages of the reaction. Significant correlations found between the two initiation methods included the initial kinetic order with respect to the initiating process and the effect on product yield of equivalent increases in total initiation energy. The limiting value of zinc bromide for both initiation methods was found to be the same. The data obtained support the contention that the copolymerization proceeds through a donor-acceptor process and that photoactivation of the preformed complex, inducing electron transfer, is a likely initiation process.
    Additional Material: 9 Ill.
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  • 8
    Publication Date: 2019-07-13
    Description: Upcoming experiments aim to produce high fidelity polarization maps of the cosmic microwave background. To achieve the required sensitivity, we are developing monolithic, feedhorn-coupled transition edge sensor polarimeter arrays operating at 150 GHz. We describe this focal plane architecture and the current status of this technology, focusing on single-pixel polarimeters being deployed on the Atacama B-mode Search (ABS) and an 84-pixel demonstration feedhorn array backed by four 10-pixel polarimeter arrays. The feedhorn array exhibits symmetric beams, cross-polar response less than -23 dB and excellent uniformity across the array. Monolithic polarimeter arrays, including arrays of silicon feedhorns, will be used in the Atacama Cosmology Telescope Polarimeter (ACTPol) and the South Pole Telescope Polarimeter (SPTpol) and have been proposed for upcoming balloon-borne instruments.
    Keywords: Astronomy
    Type: GSFC.JA.7384.2012 , Journal of Low Temperature Physics; 167; 6-May; 904-910
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  • 9
    Publication Date: 2019-07-12
    Description: We investigate the potential of submm-mm and submm-mm-radio photometric red-shifts using a sample of mm-selected sources as seen at 250, 350 and 500 micrometers by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm-sources with reliable radio identifications in the GOODS-N and Lockman Hole North fields 46 (73 per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm-sources are adequately described by a modified blackbody with constant optical depth Tau = (nu/nu(0))beta where beta = +1.8 and nu(0) = c/100 micrometers. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation we derive photometric redshift estimates for the 46 SPIRE detected mm-sources. Testing against the 22 sources with known spectroscopic, or good quality optical/near-IR photometric, redshifts we find submm/mm photometric redshifts offer a redshift accuracy of |delta z|/(1+z) = 0.16 (less than |delta z| greater than = 0.51). Including constraints from the radio-far IR correlation the accuracy is improved to |delta z|/(1 + z) = 0.15 (less than |delta z| greater than = 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z greater than 3 when compared to 850 micrometer selected samples.
    Keywords: Astronomy
    Type: GSFC.JA.5683.2011
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  • 10
    Publication Date: 2019-07-12
    Description: We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and -ray bands, and we compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set has allowed us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by Fermi Large Area Telescope (LAT), whereas 30 to 40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-millimetre spectral slope of blazars is quite flat, with [alpha] approximately 0 up to about 70 GHz, above which it steepens to [alpha] approximately -0.65. BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (v(sup IC) (sub (PEAK)), ranges from 10(sup 21) to 10(sup 22) HZ. The distribution of the rest-frame synchrotron peak frequency (v(sup s)(sub peak)) in the spectral energy distribution (SED) of FSRQs is the same in all the blazar samples with (v(sup s)(sub peak) = 10(sup 13:1 plus or minus 0.1) Hz, while the mean inverse-Compton peak frequency,(v(sup IC)(sub peak) ranges from 10(sup 21) to 10(sup 22) Hz. The distributions of v(sup S)(sub peak) and of v(sup IC)(sub peak) of BL Lacs are much broader and are shifted to higher energies than those of FSRQs; their shapes strongly depend on the selection method. The Compton dominance of blazars ranges from less than 0.2 to nearly 100, with only FSRQs reaching values larger than about 3. Its distribution is broad and depends strongly on the selection method, with gamma-ray selected blazars peaking at approximately 7 or more, and radio-selected blazars at values close to 1, thus implying that the common assumption that the blazar power budget is largely dominated by high-energy emission is a selection effect. A comparison of our multi-frequency data with theoretical predictions shows that simple homogeneous SSC models cannot explain the simultaneous SEDs of most of the gamma-ray detected blazars in all samples. The SED of the blazars that were not detected by Fermi-LAT may instead be consistent with SSC emission. Our data challenge the correlation between bolometric luminosity and v(sup S)(sub peak) predicted by the blazar sequence.
    Keywords: Astronomy
    Type: GSFC.JA.5665.2011
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