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  • 1
    Electronic Resource
    Electronic Resource
    Velocity anomalies: An alternative explanation based on data from laboratory experiments (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 765-772 
    Details
    ISSN: 1420-9136
    Keywords: Velocity anomalies ; Microfractures ; Stick-slip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Locations and velocities were calculated for microseisms occurring in samples of rock subjected to triaxial loading and injection of pore fluid. This was accomplished by analyzing arrival times of acoustic emission using an automatic first arrival picker. Apparent velocity anomalies were observed prior to both failure of intact samples and violent slip in samples containing saw cuts. Further analysis revealed that these fluctuations in calculated velocity were not due to changes in the true seismie velocity. Instead, variations in calculated velocity are shown to be related to sampling errors in picking first arrivals. The systematic picking of late first arrivals for small magnitude events was found to be a persistent bias resulting in low calculated velocities. This has encouraged the reexamination of earthquake records to determine how important sampling biases are in contributing to reported velocity anomalies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876537
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  • 2
    Electronic Resource
    Electronic Resource
    A two-stage model of fracture of rocks (1996)
    Springer
    Pure and applied geophysics 146 (1996), S. 253-263 
    Details
    ISSN: 1420-9136
    Keywords: Fracture ; fault nucleation ; critical crack density ; hierarchic failure ; earthquakes ; thermal activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In this paper we propose a two-stage model of rock fracture. In the first stage, cracks or local regions of failure are uncorrelated and occur randomly throughout the rock in response to loading of pre-existing flaws. As damage accumulates in the rock, there is a gradual increase in the probability that large clusters of closely spaced cracks or local failure sites will develop. Based on statistical arguments, a critical density of damage will occur where clusters of flaws become large enough to lead to larger-scale failure of the rock (stage two). While crack interaction and cooperative failure is expected to occur within clusters of closely spaced cracks, the initial development of clusters is predicted based on the random variation in pre-existing flaw populations. Thus the onset of the unstable second stage in the model can be computed from the generation of random, uncorrelated damage. The proposed model incorporates notions of the kinetic (and therefore time-dependent) nature of the strength of solids as well as the discrete hierarchic structure of rocks and the flaw populations that lead to damage accumulation. The advantage offered by this model is that its salient features are valid for fracture processes occurring over a wide range of scales including earthquake processes. A notion of the rank of fracture (fracture size) is introduced, and criteria are presented for both fracture nucleation and the transition of the failure process from one scale to another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876492
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  • 3
    Electronic Resource
    Electronic Resource
    Shear and tension hydraulic fractures in low permeability rocks (1977)
    Springer
    Pure and applied geophysics 115 (1977), S. 191-198 
    Details
    ISSN: 1420-9136
    Keywords: Stress hydrofracture ; Hydrofracture technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Laboratory hydrofracture experiments were performed on triaxially stressed specimens of oil shale and low-permeability granite. The results show that either shear or tension fractures could develop depending on the level of differentials stress, even in specimens containing preexisting fractures. With 1 kb of confining pressure and differential stress greater than 2kb, hydraulic fluid diffusion into the specimens reduced the effective confining pressure until failure occurred by shear fracture. Below 2kb of differential stress, tension fractures occurred. These results suggest that hydraulic fracturing in regions of significant tectonic stress may produce shear rather than tension fractures. In this casein situ stress determinations based on presumed tension fractures would lead to erroneous results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01637103
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of temperature and sliding rate on frictional strength of granite (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 445-469 
    Details
    ISSN: 1420-9136
    Keywords: Shear strength ; temperature ; deformation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Layers of artificial granite gouge have been deformed on saw-cut granite surfaces inclined 30° to the sample axes. Samples were deformed at a constant confining pressure of 250 MPa and temperatures of 22 to 845°C. The velocity dependence of the steady-state coefficient of friction (μss) was determined by comparing sliding strengths at different sliding rates. The results of these measurements are consistent with those reported bySolberg andByerlee (1984) at room temperature andStesky (1975) between 300 and 400°C. Stesky found that the slip-rate dependence of (μss) increased above 400°C. In the present study, however, the velocity dependence of (μss) was nearly independent of temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877211
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  • 5
    Electronic Resource
    Electronic Resource
    Stick slip, charge separation and decay (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 601-608 
    Details
    ISSN: 1420-9136
    Keywords: Induced polarization ; earthquake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Measurements of charge separation in rock during stable and unstable deformation give unexpectedly large decay times of 50 sec. Time-domain induced polarization experiments on wet and dry rocks give similar decay times and suggest that the same decay mechanisms operate in the induced polarization response as in the relaxation of charge generated by mechanical deformation. These large decay times are attributed to electrochemical processes in the rocks, and they require low-frequency relative permittivity to be very large, in excess of 105. One consequence of large permittivity, and therefore long decay times, is that a significant portion of any electrical charge generated during an earthquake can persist for tens or hundreds of seconds. As a result, electrical disturbances associated with earthquakes should be observable for these lengths of time rather than for the milliseconds previously suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877218
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitation of Erythropoiesis (1963)
    [s.l.] : Nature Publishing Group
    Nature 199 (1963), S. 390-391 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Five hsematologically healthy subjects were examined and their PIT measured3. Inactive iron as iron-dextrin (Ferrigen, kindly supplied by Astra, Sodertalje) was slowly injected intravenously, in 100-mg doses, at the indicated intervals. Radioiron incorporation into the erythrocytes was followed for ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/199390a0
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  • 7
    Electronic Resource
    Electronic Resource
    Sites of the Physiological Breakdown of the Red Blood Corpuscles (1958)
    [s.l.] : Nature Publishing Group
    Nature 181 (1958), S. 911-911 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Since the plasma contains no radioiron, the only source of iron-59 present in the depot iron fractions is radioiron liberated from the transfused labelled red corpuscles. This line of thought induced us to replace red corpuscles contained in 20 ml. of rabbit blood with the corresponding amount of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/181911a0
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical impedance and erythrocyte sedimentation rate (ESR) of blood
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 1153 (1993), S. 243-248 
    Details
    ISSN: 0005-2736
    Keywords: Blood ; Electric conductivity ; Erythrocyte sedimentation rate ; Membrane ; Sedimentation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(93)90411-R
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  • 9
    Electronic Resource
    Electronic Resource
    George de Hevesy-80 years
    Amsterdam : Elsevier
    The @International Journal Of Applied Radiation And Isotopes 16 (1965), S. 513-516 
    Details
    ISSN: 0020-708X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-708X(65)90134-1
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  • 10
    Electronic Resource
    Electronic Resource
    Quasi-static fault growth and shear fracture energy in granite (1991)
    [s.l.] : Nature Publishing Group
    Nature 350 (1991), S. 39-42 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The failure process in a brittle granite sample can be stabilized by controlling axial stress to maintain a constant rate of acoustic emission. As a result, the post-failure stress curve can be followed quasi-statically, extending to hours the fault growth process which normally would occur ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/350039a0
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