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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 133 (1990), S. 149-165 
    ISSN: 1420-9136
    Keywords: Volcanic seismicity ; volcanic gravity anomaly ; volcanic tectonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Subduction induced compressional stress, lateral displacement faults probably linked to the NW extension of the Polochic-Motagua fault system, and local magma emplacement create a complex geological setting for the El Chichon volcano. Gravity analysis reveals that the principal structures in the area correspond to synclines and anticlines. Downward continuation of the gravity field suggests the presence of magma emplacement SE of the volcano. This magmatic emplacement appears to be the principal cause of the truncation of the syncline in which the volcano lies. Analyses of earthquakes occurring after eruptions show that the vertical distribution of events is confined to a roughly cylindrical zone which correlates well with the region of magmatic emplacement inferred from the gravity analysis. Even though more than 350 km separate the volcano from the Middle American trench, the compressional stress regime reported for the area may correlate with subduction stress (N30°E). However, the strike direction for the principal faults in the zone, N60°W, permits us to postulate that the NW extension of the Polochic-Motagua fault system is implicated in the local tectonics of the El Chichon area.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A series of pooled gamete matings was carried out employing eggs and milt from mature male and female rainbow trout selected for a consistently high- or low-responsiveness to stress, as indicated by post-stress plasma cortisol elevation. Development of the progeny was closely monitored and the responsiveness to stress of the progeny of high-responding parents and the progeny of low-responding parents was assessed by two methods. For a period of 14 months, at approximately monthly intervals, the plasma cortisol elevation evoked by a standardized confinement stress was determined in fish from each group, and secondly, on one occasion, the time-course of the plasma cortisol response to a 24-h period of confinement was monitored. Progeny of high-responding parents snowed a significantly greater cortisol response to stress than the progeny of low-responding parents during both testing procedures. However, when the effect of a 14-day confinement stress was examined, high-responding progeny showed a more rapid recovery of plasma cortisol levels, while levels in the low-responding progeny, although initially lower, showed a more sustained elevation. To assess the possible functional implications of these observations, circulating lymphocyte numbers, an immunologically important cortisol-sensitive component of the blood cell complement, were determined. The duration of the lymphocytopenia observed following the onset of confinement was found to be related to the initial, not the sustained, cortisol response. These data suggest that manipulation of the sensitivity to stress of fish is feasible by selective breeding, but that careful.choice of the indices employed to identify traits considered desirable is necessary.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 43 (1993), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plasma levels of cortisone, a steroid hormone of potential physiological significance in fish, have rarely been measured. This study examines the interrelationship between circulating levels of cortisone and the major teleost corticosteroid, cortisol, in the blood of two strains of rainbow trout subject to confinement stress, a condition know to stimulate corticosteroidogenic activity. In unstressed fish from both strains, mean plasma cortisol levels were within the range 0.4–7.5 ng ml−1. Mean plasma cortisone levels were within the range 7.1–15.9 ng ml−1. Plasma cortisol levels were elevated within 5 min of the onset of strees and reached peak values within 45 min, although there was a marked difference betweed the maxima observed in the two strains (strain 1:70 ng ml−1; strain 2:150 ng ml−1). The rate of increase of plasma cortisone levels during strees was more rapid than that of cortisol, maximum values (strain 1:100ng ml−1; strain 2:160 ng ml−1) being reached within 10 to 20 min of the onset of stress. This rapid stress-induced elevation of plasme cortisone has not previously been reported in fish. We suggest that rapid conversion of cortisol to cortisone during the initial response to stress accounts for the appearance of large amounts of cortisone in the blood, indicating that circulating for the appearance of large amounts of cortisone in the blood, indicating that circulating levels of cortisol alone do not fully reflect the secretory activity of the interregnal during the initial of cortisol alone do not fully the secretory activity of the interregnal during the initial phase of the stress response. The results also indicate that the rate of clearance of cortisone from the circulation may be a major factor in determining stress-stimulated levels of plasma cortisol.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 10042-10047 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1276-1278 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have prepared Gd1−xPrxBa2Cu3O7−δ phase spread alloy thin films with well-defined variations in the concentration of Pr across a single substrate. Their Pr concentrations were independently determined from electrical resistivity and Auger electron spectroscopy measurements. The results from both methods are in good agreement with each other. Using this technique several high-temperature superconducting thin-film alloys may be grown under virtually identical conditions. As an example of an important application of this technique, we measured the changes in the films' resistivities and critical temperatures (Tc) induced by decreasing their oxygen concentration. The observed shifts in Tc of the oxygen-deficient samples appear to be slightly dependent on their Pr concentrations.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2590-2592 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ni/Co multilayers grown by molecular beam epitaxy are found to exhibit a magnetoresistance ΔR/R at liquid helium temperature as large as 8.2%, with saturation fields ΔH≈22 Oe and a sensitivity (ΔR/R)/(2ΔH)≈0.19% Oe−1. The highest room temperature sensitivity obtained to date in this system is 0.18% Oe−1 and at 4.2 K is 0.29% Oe−1. This demonstrates that high values of the sensitivity can be achieved in multilayers in which both components are ferromagnetic. The magnetoresistance and saturation field can be tuned by the superlattice and growth parameters.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 70 (1994), S. 373-377 
    ISSN: 1572-9672
    Keywords: Solar corona ; Coronal holes ; Solar wind ; UV spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Profiles of the visible Fe X (6374 Å) coronal emission line as a function of height above the limb were obtained out to 1.16 solar radii in a coronal hole using the NSO/Sacramento Peak Observatory Coronagraph, Universal Spectrograph and a CCD camera. These are the first coronal line profiles obtained as a function of height in a coronal hole from the ground. Analysis of the line widths suggests a large component of nonthermal broadening which increases with height ranging from 40 to 60 km/s, depending upon the assumed temperature or thermal component of the profile.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 142 (1992), S. 35-46 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate further the interpretation of dark magnetic faculae observed in previous imaging of the solar photosphere at 1.63 μm. We show that their contrast at 1.63 μm increases with magnetic flux beyond a threshold value of Φ ∼ 2 × 1018 Mx and blends smoothly with the contrast vs flux relation measured at this wavelength for larger structures of sunspot size. Not all facular structures that are bright in Ca K are dark at 1.63 μm, apparently because their magnetic flux is not large enough. After correction for blurring, the contrast of the dark faculae observed near the disc center at 1.63 μm is approximately 4%. But our observations at 1.23 μm, which probe slightly higher photospheric levels, do not show these dark faculae. These results indicate that magnetic flux tubes of diameter as small as 500 km significantly inhibit convective heat flow to the photosphere, much as do sunspot flux tubes of much larger diameter. They also suggest that, in even smaller flux tubes, the inhibition becomes rapidly less significant. Finally, we show that the sunspot-size dependence of umbral infrared contrast versus wavelength that we observe can probably be explained in terms of instrumental blurring. Observations with lower scattered light will be required to determine whether a real decrease of contrast with diameter also plays a role.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 135 (1991), S. 179-191 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe an ‘electrograph’ instrument designed for measurement of macroscopic electric fields in solar plasmas, using the polarization dependence of line width in Stark-broadened hydrogen Paschen emission lines. Observations of quiescent prominences and limb chromosphere with our electrograph at the NSO/Sac Peak Evans Coronal Facility provide upper limits of 5–10 V cm−1 for transverse macroscopic electric fields in these structures, averaged over an area of about 5 × 7 arc sec. Random thermal motions of hydrogen ions across magnetic field lines generate a quasi-static electric field, which should be distinguishable from pressure broadening in the intensely magnetized chromosphere over a sunspot, given an electrograph sensitivity a factor 2–3 better than that achieved here. Future electrograph measurements of limb flares, post-flare loops and eruptive prominences, even at 5 V cm−1 sensitivity, could provide a useful new test of reconnection and discharge effects in such dynamic structures.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Fish physiology and biochemistry 10 (1992), S. 55-66 
    ISSN: 1573-5168
    Keywords: stress ; rainbow trout ; corticosteroids ; steroid conjugates ; GC/MS ; biliary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The accumulation of immunoreactive corticosteroids in the bile of rainbow trout during stress was monitored by radioimmunoassay and GUMS. Although plasma cortisol levels were elevated by confinement for 1 hour, biliary levels of free and conjugated steroids in the bile were unaffected. However, after 24 hours confinement, in addition to elevated plasma cortisol levels, free and conjugated steroids in the bile were also significantly higher than in control, unstressed fish. The time-course of change in plasma and biliary corticosteroid levels was determined in rainbow trout subject to 96 hours confinement stress. Free steroid levels in the bile of stressed fish were elevated within 2 hours of the onset of stress, while levels of conjugated steroids were significantly elevated within 4 hours of the onset of confinement. Analysis of bile from stressed fish, by GC/MS, established the major conjugated steroids present to be tetrahydrocortisone (230 μg ml−1 bile), tetrahydrocortisol (75 μg ml−1), cortisone (33.5 μg ml−1), cortisol (25 μg ml−1) and β-cortolone (5 μg ml−1). The data are discussed with reference to the role of cortisone and conjugating enzymes in the clearance of cortisol, and further data are presented to suggest that the analysis of biliary steroid content may provide a suitable means of identifying stressed fish under conditions in which an additional sampling stress is unavoidable.
    Type of Medium: Electronic Resource
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