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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 18 (1986), S. 93-96 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 116 (1985), S. 89-96 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spherical accretion onto black holes at high accretion rates leads to temperatures and optical depths for which Comptonization of the emerging radiation plays an important role, altering both the plasma temperature and the emergent spectrum. In this paper the nonlocal effects of Comptonization are accounted for by numerically modeling the scattering process with Monte Carlo techniques. Calculations are performed for black hole masses ranging from 101–109 M ⊙ and are compared with the local scattering model of Ipser and Price (1983). It is found that the local scattering approximation underestimates the energy in the X-ray portion of the spectrum. Monte Carlo calculations shows that the spectrum flattens and the spectral index decreases to values about 20% below those obtained by using the local scattering approximation.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 35 (1974), S. 83-103 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two hundred and eighty-five hours of solar data obtained from the University of Iowa 2 cm radiometer during 1968–1969 were analyzed for evidence of periodic structure related to the 5 min periodic chromospheric oscillations detected in optical line emissions. A power spectral analysis of the data failed to show any statistically significant (〉 96 % confidence) periodic activity in the frequency range 1–15 mHz (periods of 1–16 min) for data organized according to solar activity in Hα, soft solar X-rays (2–12 Å), and several microwave frequencies (3–15 GHz). A small shift in power from low to higher frequencies in the power spectrum of the 2 cm data was found to be correlated with Hα and X-ray activity. This power shift is attributed to a relative increase in chromospheric turbulence at altitudes common to Hα, X-ray, and 2 cm emission. Consistent statistical analyses of previous works reporting evidence for oscillations at microwave and extreme-ultraviolet frequencies indicate that confidence in these previous results is marginal. A model for chromospheric oscillation bursts in quiescent supergranules is incorporated into a statistical analysis of the power spectrum detectability of the oscillations to understand the negative results obtained.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root formation and in vivo nitrate reductase (NR) activity were determined in leafy spurge cell suspensions. Cells grown in B5 media with 1 mg L−1 2,4-D were transferred to B5 media without 2,4-D, but containing either high (92:8) or low (15:85) ratios of nitrogen as NO 3 − -N:NH 4 + -N. In older cell lines root formation occurred only in the low NO 3 − medium with =〈30 roots per flask. In younger cell lines root numbers were greatest in the high NO 3 − medium (1000 to 3000 per flask). Cells grown in low NO 3 − medium were about one-third the final dry weight as those in high NO 3 − medium. Root length was consistently greater for cell lines of all ages in the low NO 3 − medium. Developmental profiles of NR activity were similar in cell lines of all ages, whether or not roots were formed. NR activity was lower, however, in cultures grown in low NO 3 − medium compared to high NO 3 − medium. There was no consistent relationship between NR activity and root initiation. Therefore, nitrate reductase does not appear to be a primary target for regulation of leafy spurge growth by chemical application.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 115 (1994), S. 427-437 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract U-Pb geochronology of igneous zircon from rhyolitic host rocks to the Archean Kidd Creek, Geco and Winston Lake massive sulfide deposits, in the Superior Province of Ontario, shows that volcanism, which accompanied mineralization, occupied a narrow time span (2717±2 Ma, 2720±2 Ma and 2723±2 Ma, respectively). Precise ages of hydrothermal monazite, allanite and rutile from alteration zones surrounding the above deposits indicate that these minerals crystallized 40–70 million years after volcanism. Monazite from Kidd Creek mine is 2659±3 Ma old, in agreement with spatially associated 2664±25 Ma old rutile. Monazite from a biotite schist at Geoco mine gives a similar age of 2661±1 Ma. However, monazite from a sericite schist, which hosts the ore at Geco mine, is 2675±2 Ma old. Abraded large monazite grains from three units in the Winston Lake deposit are coeval with biotite crystallization and record an age of 2677±2 Ma, approximately the same as monazite in the sericite schist at Geco. Data points from allanite fractions from both the Winston Lake and Geco deposits fall on a Pb-Pb isochron that gives an age of 2672±5 Ma. Rutile from Winston Lake gives a younger age of 2651±6/-2 Ma and may date retrograde alteration of biotite to chlorite. The ca. 2676 Ma age of monazite from Winston Lake and in the sericite schist at Geco mine probably dates a regional metamorphic event that affected most of the southern Superior Province. The ca. 2660 Ma old monazite in the biotite schist at Geco mine and in the chlorite-sericite alteration at Kidd Creek may date later K-metasomatism caused by metamorphically derived fluids that were focussed along old fault structures. Such fluids were also responsible for local sulfide remobilization. Monazite and rutile are spatially associated with chlorite and sericite alterations at Kidd Creek. Their young ages indicate that these originally syngenetic mineral assemblages may have been significantly affected by regional metamorphism. Formation of monazite at all three deposits studied was a result of significant REE remobilization during metamorphism. The discrete character of syn-metamorphic hydrothermal activity in different units of the same deposit, as well as its synchroneity among different, widely separated deposits, requires a mechanism for episodic injection of heat and fluid into the crust on a regional scale. These activities are broadly coeval with, and probably related to, plutonism within adjacent metasedimentary subprovinces and middle to lower crustal metamorphism in the Superior Province.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 44 (1973), S. 309-318 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract LSD was found to induce chromosomal aberrations in root tip cells of Allium cepa, Hordeum vulgare and Secale cereale. Aberrations occurred in the form of chromatid and isochromatid breaks with most of these breaks failing to rejoin. The distribution of chromosome breaks was not uniform over the length of chromosomes, and a majority of the breaks were localized at the centromeric regions. For a given dose of LSD (30 μg/ml), onion appeared to be more susceptible than barley or rye. The diploid and tetraploid rye used in the study showed no appreciable difference in sensitivity to LSD treatment. — A preliminary study on meiotic chromosomes in LSD-treated diploid rye revealed the presence of univalents, chromosome breaks and fragments, suggesting that LSD can induce meiotic abnormalities in plant material.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Environmental management 5 (1981), S. 191-205 
    ISSN: 1432-1009
    Keywords: Pollutant toxicity ; Water Quality Criteria ; Microbemediated ecological processes ; Ecological dosage 50% (EcD50) ; Cadmium ; Phenol ; Physicochemical environmental factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The physicochemical characteristics of the recipient environment into which chemical contaminants are deposited may influence their chemical speciation, mobility, bioavailability, and toxicity. In formulating Water Quality Criteria, the Environmental Protection Agency of the United States (EPA) considered the modifying effect of abiotic environmental factors on pollutant toxicity in an innovative regulatory approach. Scientific knowledge of the interactions and correlations between pollutant toxicity and abiotic factors remains limited. Recognition of the influence of the physicochemical characteristics of the recipient environment on pollutant toxicity has implications for the eventual formulation of regional, rather than uniform and national, criteria. In addition, in developing Water Quality Criteria that incorporate the effects of pollutants on “aquatic life,” EPA primarily focused on toxicity to aquatic animals and plants (including unicellular algae). The effects of pollutants on microbe-mediated ecological processes that are necessary for maintaining the state and quality of the ecosphere (such as biogeochemical cyclings, litter decomposition, and mineralization) were not included in the formulation of the Water Quality Criteria. To facilitate the recognition and quantification of adverse effects of pollutants on these ecological processes, the development of a computation, termed the “ecological dosage 50%” (EcD50) is recommended. Such a formulation could also be applied to setting environmental quality criteria for terrestrial ecosystems.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 62 (1992), S. 269-277 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As part of a larger 3-yr study, container-grown seedlings of black cherry (Prunus serotina) red maple (Acer rubrum), red oak (Ouercus rubra), sweetgum (Liquidambar styraciflua), white ash (Fraxinus americana), white oak (Ouercus alba), yellow-poplar (Liriodendron tulipifera), and yellow birch (Betula allegheniensis) were exposed to 0,0.075, or 0.15 μL L-1 O3 in laboratory controlled-environment chambers for 6 hr d−1 on 2 consecutive days for 12 weeks. On the third consecutive day of each week, plants were treated for 45 min with precipitation at pH 3.0 or 4.2. The only significant foliar symptoms were induced by the O3 treatments, and the severity of symptoms was not influenced by precipitation pH. The most common symptom was a dark, adaxial stipple which was most severe on the oldest leaves. Equations were developed to express the influence of leaf position on percent leaf injury following 4, 8, and 12 weeks of treatment. Based on percent leaf tissue showing stipple and defoliation following exposure to 0.15 μL L−1 O3, the most sensitive species to O3 was black cherry, followed by sweetgum, yellow-poplar, white ash, red maple and yellow birch. Red oak and white oak foliage did not exhibit stipple.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 2 (1982), S. 287-299 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Regulatory agencies commonly set standards for a myriad of chemical and physical hazards, with a special focus on carcinogens. This focus can obscure the need to update previously set standards for non-carcinogenic hazards in response to new scientific data. This paper considers n-hexane as a representative chemical hazard: the occupational standard of 500 ppm over an 8 hr time weighted average for a 40 hr week as set in 1948. In the last 12 yr, n-hexane has been shown to cause adverse effects on the peripheral and central nervous systems, the eye, and the respiratory tract. Yet, these new data have not, as yet, been incorporated into a revised standard for n-hexane. The lack of scientific data on the carcinogenicity of n-hexane may be an underlying reason explaining the failure of regulatory agencies to revise their standards. Perhaps, the most troubling problem to regulatory agencies is the sheer magnitude of the chemical regulatory burden. Research should proceed on developing meaningful categories or groupings both for the initial setting of standards and for revising existing standards.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 22 (1987), S. 3508-3516 
    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 Particulate-filled resins, or dental composites, are being increasingly used to restore the load-bearing surfaces of teeth. If these restorations are not to fracture in service, and if improvements are to be made, an understanding of the fracture behaviour of these materials is essential. The fracture parameter used is the stress intensity factor at crack instability (K IC). This has been calculated using the double torsion test in an Instron universal testing machine. The fracture behaviour was studied by varying the amount of filler (7, 15, 26 and 41 vol %); the surface treatment of the filler (coated or uncoated); the environment (air or water); and the crosshead rate (0.05, 0.5, 5 and 50 mm min−1). Fracture was found to occur in either a continuous or stick-slip manner. The stick-slip behaviour was due to blunting of the crack tip, which was controlled by the yield behaviour. If there was no significant blunting, continuous crack growth occurred. A unique fracture criterion was shown to apply, which was that a critical stress of approximately three and a half times the yield stress must be obtained at a critical distance ahead of the crack tip.[/p]
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