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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 200-204 
    ISSN: 0044-2313
    Keywords: Alkaline Earth ; Praseodym ; Iron Oxide ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Ba6Pr2Fe4O15, Ba5SrPr2Fe4O15 and Ba5CaPr2Fe4O15Ba6Pr2Fe4O15 (I), Ba5SrPr2Fe4O15 (II), and Ba5CaPr2Fe4O15 (III) have been prepared by high temperature CO2-LASER techniques. (I)-(III) crystallize isotypic to the Ba6Ln2Al4O15 type, space group C6v4-P63mc, (I): a = 11.808(2), c = 6.894(5), Z = 2. Typical features of the crystal structure are face shared MO6 octahedra (M = Ba or Ba/Sr, Ba/Ca) and a statistical distribution of Ba and Pr in a ratio of 1 : 2 within double capped trigonal prisms of oxygen. Fe shows tetrahedral as well as octahedral coordination by oxygen. Calculation of coulomb terms of lattice energy indicate the stabilization of Pr3+ beside Fe3+ by the Ba6Ln2Al4O15 type.
    Notes: Ba6Pr2Fe4O15 (I), Ba5SrPr2Fe4O15 (II) und Ba5CaPr2Fe4O15 (III) wurden mit Hochtemperatur-CO2-LASER-Technik dargestellt. (I)-(III) kristallisieren mit hexagonaler Symmetrie, Raumgruppe C6V4-P63mc, (I): a = 11.808(2), c = 7,036(4) Å; (II): a = 11.689(2), c = 6.954(2) Å; (III): a = 11.602(6), c = 6.894(5) Å, Z = 2. Charakteristische Eigenschaften dieser Kristallstruktur sind flächenverknüpfte MO6-Oktaeder (M = Ba oder Ba/Sr, Ba/Ca) und eine statistische Verteilung von Ba und Pr im Verhältnis 1 : 2 in einem zweifach überkappten trigonalen Sauerstoffprisma. Fe zeigt sowohl tetraedrische als auch oktaedrische Sauerstoffkoordination. Berechnungen der Coulomb-Terme zur Gitterenergie deuten an, daß durch den Ba6Ln2A4O15-Typ Pr3+ neben Fe3+ stabilisiert wird.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1693-1698 
    ISSN: 0044-2313
    Keywords: Barium ; Copper ; Vanadyl Phosphate ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cu4O12 Groups Built of Square Planar CuO4 Polygones in the Barium Vanadyl Oxocuprate(II) Phosphate Ba(VO)Cu4(PO4)4Single crystals of Ba(VO)Cu4(PO4)4 have been prepared by solid state reactions just below the melting points of the reaction mixtures of BaP2O6, Cu3(PO4)2, CuO, V2O5 and V2O3 in evacuated closed quartz glas tubes. The compound crystallizes with tetragonal symmetry, Space group D42—P4212, a = 9.560(2), c = 7.160(2) Å, Z = 2. Special and new features of the crystal structure are to each other isolated Cu4O12 and (VO)(PO4)4 groups. The crystal chemistry of the Cu4O12 groups is discussed with respect to other compounds containing out of plane connected square planar MO4 polygones.
    Notes: Einkristalle von Ba(VO)Cu4(PO4)4 wurden mit Festkörperreaktionen dicht unterhalb des Schmelzpunktes des Reaktionsgemenges aus BaP2O6, Cu3(PO4)2, CuO, V2O5 und V2O3 in geschlossenen, evakuierten Quarzglasampullen dargestellt. Diese Verbindung kristallisiert tetragonal, Raumgruppe D42—P4212, mit a = 9,560(2), c = 7,160(2) Å, Z = 2. Besondere und neue Eigenschaften der Kristallstruktur sind zueinander isolierte Cu4O12- und (VO)(PO4)4-Gruppen. Die Kristallchemie der Cu4O12-Baugruppen wird mit Blick auf andere Verbindungen, die nicht in Ebenen verknüpfte MO4-Polygone aufweisen, diskutiert.
    Additional Material: 5 Ill.
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  • 3
    Publication Date: 2011-08-24
    Description: The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) has determined the dipole spectrum of the cosmic microwave background radiation (CMBR) from 2 to 20/cm. For each frequency the signal is decomposed by fitting to a monopole, a dipole, and a Galactic template for approximately 60% of the sky. The overall dipole spectrum fits the derivative of a Planck function with an amplitude of 3.343 +/- 0.016 mK (95% confidence level), a temperature of 2.714 +/- 0.022 K (95% confidence level), and an rms deviation of 6 x 10(exp -9) ergs/sq cm/s/sr cm limited by a detector and cosmic-ray noise. The monopole temperature is consistent with that determined by direct measurement in the accompanying article by Mather et al.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 2; p. 445-449
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  • 4
    Publication Date: 2011-08-24
    Description: The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 2; p. 439-444
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  • 5
    Publication Date: 2011-08-24
    Description: The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite was designed to accurately measure the spectrum of the cosmic microwave background radiation (CMBR) in the frequency range 1-95/cm with an angular resolution of 7 deg. We describe the calibration of this instrument, including the method of obtaining calibration data, reduction of data, the instrument model, fitting the model to the calibration data, and application of the resulting model solution to sky observations. The instrument model fits well for calibration data that resemble sky condition. The method of propagating detector noise through the calibration process to yield a covariance matrix of the calibrated sky data is described. The final uncertainties are variable both in frequency and position, but for a typical calibrated sky 2.6 deg square pixel and 0.7/cm spectral element the random detector noise limit is of order of a few times 10(exp -7) ergs/sq cm/s/sr cm for 2-20/cm, and the difference between the sky and the best-fit cosmic blackbody can be measured with a gain uncertainty of less than 3%.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 2; p. 457-473
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  • 6
    Publication Date: 2019-07-13
    Description: Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM) are analyzed to place limits on Gaussian fluctuations in the cosmic microwave background radiation (CMBR). This instrument chops a 30 min beam in a three-position pattern with a throw of +/- 40 min; the resulting data is analyzed in statistically independent single- and double-difference sets. We observe in four spectral channels at 5.6, 9.0, 16.5, and 22.5/cm, allowing the separation of interstellar dust emission from CMBR fluctuations. The dust component is correlated with the IRAS 100 micron map. The CMBR component has two regions where the signature of an unresolved source is seen. Rejecting these two source regions, we obtain a detection of fluctuations which match CMBR in our spectral bands of 0.6 x 10(exp -5) is less than Delta (T)/T is less than 2.2 x 10(exp -5) (90% CL interval) for total rms Gaussian fluctuations with correlation angle 0.5 deg, using the single-difference demodulation. Fore the double difference demodulation, the result is 1.1 x 10(exp -5) is less than Delta(T)/T is less than 3.1 x 10(exp -5) (90% CL interval) at a correlation angle of 0.3 deg.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 422; 2; p. L37-L40
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