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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of COMPTEL gamma-ray burst locations and spectra (1995)
    Springer
    Astrophysics and space science 231 (1995), S. 231-234 
    Details
    ISSN: 1572-946X
    Keywords: gamma-ray bursts: observations ; locations ; spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In its first three years of operation, the COMPTEL instrument on theCompton Gamma-Ray Observatory has measured the locations (mean accuracy ∼1°) and spectra (0.75-30 MeV) of 18 gamma-ray bursts and continues to observe new events at a rate of ∼1/month. With good angular resolution and sensitivity at MeV energies, the growing COMPTEL burst catalog is an important new piece of evidence in the on-going GRB mystery. The COMPTEL burst locations are consistent with an isotropic distribution of sources, yet the spatial coincidence of two of the bursts indicates the possibility of repetition. The COMPTEL burst spectra are in most cases consistent with a single power law model with spectral index in the range 2–3. However, two bursts show evidence of a spectral break in the MeV range. Measurement of rapid variability at MeV energies in the stronger bursts provides evidence that either the sources are nearby (within the Galaxy) or the gamma-ray emission is relativistically beamed. We present an overview of analysis results obtained from the COMPTEL burst catalog concentrating on the search for burst repetition and the implications of highly variable MeV emission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658622
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  • 2
    Electronic Resource
    Electronic Resource
    Oxidation behavior of the aligned lamellar eutectic alloy Ni3Al-Ni3Nb (1974)
    Springer
    Oxidation of metals 8 (1974), S. 309-341 
    Details
    ISSN: 1573-4889
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the directionally aligned Ni3Al-Ni3Nb lamellar eutectic alloy has been examined as a function of lamellar spacing for two interlamellar spacings (1.7 and 3.3μ) in the temperature range from 600 to 1155°C. At the low and high temperatures examined, 600 and 1155°C, no dependency of the oxidation behavior on the interlamellar spacing is observed. However, in the intermediate temperature regime, 800 and 990°C, such a dependency is seen, with the finer spacing structure oxidizing more rapidly at 800°C and more slowly at 990°C. The oxide scale formed on these alloys is very complex and varies markedly as a function of oxidation temperature. The structure of the oxidized aligned samples and their thermogravimetric behavior during oxidation differ from the behavior reported for the cast alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609947
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  • 3
    Electronic Resource
    Electronic Resource
    Dry sliding wear of hard materials against a diamond composite (1985)
    Springer
    Journal of materials science 20 (1985), S. 1222-1236 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Pin-on-disc wear tests using ceramic and metal pins running against diamond composite discs were conducted in air at room temperature. Pin wear rate and the coefficient of friction were measured. The pin wear rate did not consistently increase with decreasing hardness, and the lowest wear rate was obtained with a cemented tungsten carbide pin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026318
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  • 4
    Electronic Resource
    Electronic Resource
    CATSAT - a very low cost burst distance measuring mission (1995)
    Springer
    Astrophysics and space science 231 (1995), S. 459-462 
    Details
    ISSN: 1572-946X
    Keywords: gamma-ray bursts ; experimental - distance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract CATSAT is a small, fast and cheap space mission currently funded for Phase A studies under the Student Explorer Demonstration Initiative (STEDI) by University Space Research Association. Its prime scientific objective is to determine burst distances by measuring their spectra at energies from 〈 500 eV to several MeV. Soft X-ray spectral measurements will be made with 2 cm2 Si Avalanche Photodiodes (APD). The spectrometer will consist of seven collimated arrays, each containing 14 APDs and covering ∼ 1 steradians. CATSAT also contains three other context instruments. The Directional Gamma Spectrometer is a NaI-PMT array which will provide burst triggering as well as spectra and directional information from 〉 200 keV observations. The Hard X-Ray spectrometer consists of CaF2(Eu)-PMT detectors which are optimized in the cyclotron absorption energy band. The X-ray Albedo Polarimeter consists of nine collimated NaI-PMT detectors observing the earth reflected emission. Results from the XAP will be used to determine the burst direction and to place constraints on X-ray polarization. CATSAT was designed at three universities to be built with student help in two years for a cost of $3.5M.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658670
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  • 5
    Electronic Resource
    Electronic Resource
    The use of Y2O3 coatings in preventing solid-state Si-base ceramic/metal reaction (1983)
    Springer
    Journal of materials science 18 (1983), S. 3195-3205 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The use of Y2O3 sputtered coatings on the order of 0.1 μm thick have been found to greatly reduce the degree of reaction between metals and Si-base ceramics. Even though the Y2O3 coating tends to become detached from the sputtered ceramic after one heating cycle, modifications in the surface chemistry of the ceramic continues to provide protection from further attack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544143
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  • 6
    Electronic Resource
    Electronic Resource
    The solid-state reaction of silicon nitride with an Ni-base alloy (1983)
    Springer
    Journal of materials science 18 (1983), S. 508-514 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The nature of the solid-state reaction between hot-pressed Si3N4 and a model Ni-based superalloy was examined and compared to that previously found with SiC. The Si3N4 reacted with the metal to a significantly lesser extent than SiC, presumably because of the dependence of the Si3N4/metal reaction on the partial pressure of N2. Products of the reaction in both metal and ceramic were AIN, Ni2Si, other Ni and Cr silicides, and probably a chromium nitride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00560640
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  • 7
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    The use of Y2O3 coatings in preventing solid-state Si-base ceramic/metal reaction (1983)
    Springer
    Details
    Publication Date: 1983-11-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 8
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    Dry sliding wear of hard materials against a diamond composite (1985)
    Springer
    Details
    Publication Date: 1985-04-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 9
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    Constraining recent lead pollution sources in the North Pacific using ice core stable lead isotopes (2012)
    Wiley
    Details
    Publication Date: 2012-08-22
    Description: Trends and sources of lead (Pb) aerosol pollution in the North Pacific rim of North America from 1850 to 2001 are investigated using a high-resolution (subannual to annual) ice core record recovered from Eclipse Icefield (3017 masl; St. Elias Mountains, Canada). Beginning in the early 1940s, increasing Pb concentration at Eclipse Icefield occurs coevally with anthropogenic Pb deposition in central Greenland, suggesting that North American Pb pollution may have been in part or wholly responsible in both regions. Isotopic ratios (208Pb/207Pb and 206Pb/207Pb) from 1970 to 2001 confirm that a portion of the Pb deposited at Eclipse Icefield is anthropogenic, and that it represents a variable mixture of East Asian (Chinese and Japanese) emissions transported eastward across the Pacific Ocean and a North American component resulting from transient meridional atmospheric flow. Based on comparison with source material Pb isotope ratios, Chinese and North American coal combustion have likely been the primary sources of Eclipse Icefield Pb over the 1970–2001 time period. The Eclipse Icefield Pb isotope composition also implies that the North Pacific mid-troposphere is not directly impacted by transpolar atmospheric flow from Europe. Annually averaged Pb concentrations in the Eclipse Icefield ice core record show no long-term trend during 1970–2001; however, increasing 208Pb/207Pb and decreasing 206Pb/207Pb ratios reflect the progressive East Asian industrialization and increase in Asian pollutant outflow. The post-1970 decrease in North American Pb emissions is likely necessary to explain the Eclipse Icefield Pb concentration time series. When compared with low (lichen) and high (Mt. Logan ice core) elevation Pb data, the Eclipse ice core record suggests a gradual increase in pollutant deposition and stronger trans-Pacific Asian contribution with rising elevation in the mountains of the North Pacific rim.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Water Isotope Diffusion in the WAIS Divide Ice Core During the Holocene and Last Glacial (2016)
    Wiley
    Details
    Publication Date: 2016-12-17
    Description: We use a high-resolution water isotope record from the West Antarctic Ice Sheet (WAIS) Divide ice core (WDC) to evaluate the effects of water isotope diffusion for the last 29 ka BP. Using spectral analysis of the data, we determine diffusion lengths in depth and time domains. The diffusion length quantifies the mean cumulative diffusive displacement of water molecules relative to their original location at time of deposition. We simulate the observed signal with models, and find that our understanding of processes and conditions in the ice sheet is incomplete. With the effects of ice-deformational thinning removed, portions of the Holocene record show total diffusion lengths smaller than predicted for a lower-limit case of diffusion through a single ice-crystal. Such reduced diffusion is probably due to structural features such as crusts and tortuous porosity that inhibit vapor transport in the firn. In the Late Glacial portion of the record, diffusion lengths double between ~19.5 and 17 ka BP. Known dependencies of diffusion on climatic variables do not account for this enhancement in models, and we hypothesize that it could arise from thermal gradients in the firn column, impurity-driven enhancement of solid ice diffusion, or changes in firn grain properties that alter vapor access to open pores. Despite model uncertainties, the WDC diffusion length chronology will be an essential input to future studies of high-frequency variability in the water isotope climate record, as it allows for the effects of diffusion to be removed.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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