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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 190 (1961), S. 650-651 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We find that interferon is produced most easily by a method suggested by Wagner4; this involves the intra-allantoic inoculation of chick embryos with small amounts of infective virus and prolonged (65-72 hr.) incubation before harvesting allantoic fluid. After dialysis of allantoic fluid at pK 2-0, ...
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  • 2
    Publication Date: 2008-01-02
    Description: Mechanical stratigraphy exerts a first-order control on deformation at a range of scales from oilfield-scale structural style to deformation (e.g. fracturing) within an individual reservoir stratum. This paper explores an outcrop example where mechanical stratigraphy in a limestone and shale sequence directly influenced the structural style and distribution of deformation related to the propagation of a seismic-scale' normal fault that has maximum displacement on the order of 100500 m and extends for more than 10 km. A monocline developed in Cretaceous Buda Limestone above tectonically thinned Del Rio Clay and faulted Santa Elena Limestone is here interpreted as an extensional fault propagation fold. Monocline limb dips reach 59{degrees}. The Del Rio Clay is thinned from approximately 36 m to 1.5 m, whereas the underlying Santa Elena Limestone is offset vertically by approximately 74 m along a steep (approximately 80{degrees}) normal fault. This large fault displacement of the Santa Elena Limestone is not transferred upward to the Buda Limestone because of ductile flow within the intervening Del Rio Clay. Although upward fault propagation has been inhibited, thinning of the Del Rio Clay and the resultant extreme displacement gradient at the tip of the fault have forced the Buda Limestone into a monoclinal fold. Two competent packstone and grainstone beds, 6 m and 2.7 m thick and separated by 10.5 m of less competent calcareous shale, comprise the Buda Limestone at this location. Deformation features within the competent Buda beds include bed-perpendicular veins that accommodate bed-parallel extension, and bedding plane slip surfaces with an up-dip sense of shear that offset the veins. Deformation is concentrated in the monoclinal limb and not in the monoclinal hinge regions. Consequently, bed-parallel extension and shear strain are associated with monoclinal dip, not with curvature. These results show that for this structure, bed dip is a better proxy for bed-parallel extension and related fracture dilation than is curvature.
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  • 3
    Publication Date: 2015-12-15
    Description: Characterizing natural fracture systems involves understanding fracture types (faults, joints, and veins), patterns (orientations, sets, and spacing within sets), size distributions (penetration across layering, aperture, and trace length), and timing relationships. Traditionally, observation-based relationships to lithology, mechanical stratigraphy, bed thickness, structural position, failure mode, and stress history have been proposed for predicting fracture spacing along with the relative abundance of opening-mode fracture versus faults in fractured rocks. Developing a conceptual fracture model from these relationships can be a useful process to help predict deformation in a fractured reservoir or other fractured rock systems. A major pitfall when developing these models is using assumptions based on general relationships that are often site specific rather than universal. In this paper, we examine a mixed carbonate-shale sequence that is cut by a seismic-scale normal fault where fracture attributes do not follow commonly reported fracture relationships. Specifically, we find (1) no clear relationship between frequency (or spacing) of opening-mode fractures (joints and veins) and proximity to the main fault trace and (2) no detectable relationship between fracture spacing and bed thickness. However, we did find that (1) the frequency of small-displacement faults is strongly and positively correlated with proximity to the main fault trace, (2) fracture networks change pattern and failure mode (extension versus shear fracture) from pavement to pavement through the mechanically layered stratigraphic section, and (3) faults are more abundant than opening-mode fractures in many areas within the fracture network. We interpret that the major fracturing initiated near maximum burial under relatively high-differential stress conditions where shear failure dominated and that mode-1 extension fracturing occurred later under lower differential stress conditions, filling in between earlier formed shear fractures. We conclude that whenever possible, site-specific observations need to be carefully analyzed prior to developing fracture models and perhaps a different set of fracture network rules apply in rocks where shear failure dominates and mechanical stratigraphy influences deformation.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
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  • 4
    Publication Date: 2011-09-25
    Description: Peatlands are important carbon stores and many have natural pipes (tunnels) that transport water and carbon. Pipes are often viewed as passive and slowly changing features of peatland landscapes, particularly for sites that are relatively undisturbed by land management. However, there is a lack of data on pipe morphology change over time. This paper presents the first survey of natural pipe outlets in a peatland in which morphological changes in pipe outlets through time were measured. Three surveys of natural pipe outlets between 2007–2010 were conducted in a 17.4 hectare, relatively undisturbed, blanket-peat-covered catchment in northern England. 27 of the 91 pipe outlets mapped in the first survey had perennial discharge and these outlets were significantly larger and shallower than those from ephemerally-flowing pipes. The cross-sectional area of 85 % of pipe outlets changed (increased or decreased) during the study, with 20 % of pipe outlet areas changing by more than 50 cm 2 (equivalent to a median 207 % change in area for this upper fifth of pipes) up to a maximum of 312 cm 2 for one pipe outlet. During the study, 18 pipe outlets completely infilled, while four new ones appeared. Mean pipe outlet area increased between August 2007 and July 2009 but decreased from July 2009 to April 2010. The largest changes in pipe morphology occurred between July 2009 and April 2010, which spanned the coldest winter for 31 years in the UK. During this period there was a significant increase in the proportion of vertically-elongated pipes and a decrease in the proportion of circular pipes. Pipe outlet morphology in blanket peat catchments is shown to be dynamic and may respond relatively quickly to changes in flow or extreme events, linked to short-term changes in weather and hence potentially to longer-term changes in climate or land management. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 5
    Publication Date: 2014-10-28
    Description: Outcrops of the middle Eagle Ford Formation in south-central Texas reveal well-developed joint networks in subhorizontal competent carbonate (chalk) beds and less well developed networks in interlayered incompetent calcareous mudrock beds. Northeast-striking bed-perpendicular joints in competent beds have the longest trace lengths and are abutted by northwest-striking joints. All observed joints terminate vertically in incompetent beds. Normal faults are common but less abundant than joints; dominantly dip north, northwest, or southeast; and are abutted by the joint sets and, thus, predated jointing. The faults cut multiple competent and incompetent beds, providing vertical connectivity across mechanical layering. Products of hybrid and shear failure, the dip of these faults is steep through competent beds and moderate through incompetent beds, resulting in refracted fault profiles with dilation and calcite precipitation along steep segments. Fluid inclusions in fault zone calcite commonly contain liquid hydrocarbons. Rare two-phase fluid inclusions homogenized between about (1) 40 and 58°C, and (2) 90 and 100°C, suggesting trapping of aqueous fluids at elevated temperatures and depths on the order of 2 km (6562 ft). Fluid inclusion and stable isotope geochemistry analyses suggest that faults transmitted externally derived fluids. These faults likely formed at depths equivalent to portions of the present-day oil and gas production from the Eagle Ford play in south Texas. Faults connect across layering and provide pathways for vertical fluid movement within the Eagle Ford Formation, in contrast to vertically restricted joints that produce bed-parallel fracture permeability. These observations elucidate natural fractures and induced hydraulic fracturing within the Eagle Ford Formation.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
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  • 6
    Publication Date: 2014-10-28
    Description: The increasing exploration and production in unconventional resource plays in the past decade has been accompanied by a greater need for understanding the effectiveness of multistage hydraulic fracturing programs, particularly in long (〉1500 m or 5000 ft) subhorizontal boreholes (laterals). Traditional (analytical) analysis techniques for estimating the size and orientation of fractures induced by fluid injection typically result in predictions of relatively long and planar extension (mode I) bi-wing fractures, which may not be representative of natural systems. Although these traditional approaches offer the advantage of rapid analysis, neglect of key features of the natural system (e.g., realistic mechanical stratigraphy, pre-existing natural faults and fractures, and heterogeneity of in situ stresses) may render results unrealistic for planning, executing, and interpreting multimillion-dollar hydraulic stimulation programs. Numerical geomechanical modeling provides a means of including key aspects of natural complexity in simulations of hydraulic fracturing. In this study, we present the results of two-dimensional finite element modeling of fluid-injection-induced rock deformation that combines a coupled stress–pore pressure analysis with a continuum damage-mechanics-based constitutive relationship. The models include both the natural mechanical stratigraphic variability as well as the in situ stress-state anisotropy, and permit tracking of the temporal and spatial development of shear and tensile permanent strains that develop in response to fluid injection. Our results show that simple, long planar fractures are unlikely to be induced in most mechanically layered natural systems under typical in situ stress conditions. Analyses that assume this type of fracture geometry may significantly overestimate the reach of hydraulically induced fractures and/or effectively stimulated rock volume.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
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  • 7
    Publication Date: 2016-05-26
    Description: Mapping of normal faults cutting the Bishop Tuff in the Volcanic Tableland, northern Owens Valley, California, using side-looking airborne radar data, low-altitude aerial photographs, airborne light detection and ranging (LiDAR) data, and standard field mapping yields insights into fault scarp development, fault system evolution, and timing. Fault zones are characterized by multiple linked fault segments, tilting of the welded ignimbrite surface, dilation of polygonal cooling joints, and toppling of joint-bounded blocks. Maximum fault zone width is governed by ( i ) lateral spacing of cooperating fault segments and ( ii ) widths of fault tip monoclines. Large-displacement faults interact over larger rock volumes than small-displacement faults and generate larger relay ramps, which, when breached, form the widest portions of fault zones. Locally intense faulting within a breached relay ramp results from a combination of distributed east-west extension, and within-ramp bending and stretching to accommodate displacement gradients on bounding faults. One prominent fluvial channel is offset by both east- and west-dipping normal faults such that the channel is no longer in an active flowing configuration, indicating that channel incision began before development of significant fault-related geomorphic features. The channel thalweg is "hanging" with respect to modern (Q1) and previous (Q2) Owens River terraces, is incised through the pre-Tahoe age terrace level (Q4, 131–463 ka), and is at grade with the Tahoe age (Q3, 53–119 ka) terrace. Differential incision across fault scarps implies that the channel remained active during some of the faulting history, but it was abandoned between Q2 and Q3 time, while faulting continues to the present day.
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
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  • 8
    Publication Date: 2016-04-01
    Description: Analyses of normal faults in mechanically layered strata reveal that material properties of rock layers strongly influence fault nucleation points, fault extent (trace length), failure mode (shear v. hybrid), fault geometry (e.g. refraction through mechanical layers), displacement gradient (and potential for fault tip folding), displacement partitioning (e.g. synthetic dip, synthetic faulting, fault core displacement), fault core and damage zone width, and fault zone deformation processes. These detailed investigations are progressively dispelling some common myths about normal faulting held by industry geologists, for example: (i) that faults tend to be linear in dip profile; (ii) that imbricate normal faults initiate due to sliding on low-angle detachments; (iii) that friction causes fault-related folds (so-called normal drag); (iv) that self-similar fault zone widening is a direct function of fault displacement; and (v) that faults are not dilational features and/or important sources of permeability.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 9
    Publication Date: 2012-08-15
    Description: Natural soil pipes, which have been widely reported in peatlands, have been shown to contribute significantly to total stream flow. Here, using measurements from eight pipe outlets, we consider the role of natural pipes in the transport of fluvial carbon within a 17.4-ha blanket-peat-covered catchment. Concentrations of dissolved and particulate organic carbon (DOC and POC) from pipe waters varied greatly between pipes and over time, ranging between 5.3 and 180.6 mg L −1 for DOC and 0.08 and 220 mg L −1 for POC. Pipes were important pathways for peatland fluvial carbon export, with fluxes varying between 0.6 and 67.8 kg yr −1 (DOC) and 0.1 and 14.4 kg yr −1 (POC) for individual pipes. Pipe DOC flux was equivalent to 20% of the annual DOC flux from the stream outlet while the POC flux from pipes was equivalent to 56% of the annual stream POC flux. The proportion of different forms of aquatic carbon to total aquatic carbon flux varied between pipes, with DOC ranging between 80.0 and 91.2%, POC from 3.6 to 17.1%, dissolved CO 2 -C from 2.4 to 11.1% and dissolved CH 4 -C from 0.004 to 1.3%. The total flux of dissolved CO 2 -C and CH 4 -C scaled up to all pipe outlets in the study catchment was estimated to be 89.4 and 3.6 kg yr −1 respectively. Overall, pipe outlets produced discharge equivalent to 14% of the discharge in the stream but delivered an amount of aquatic carbon equivalent to 22% of the aquatic carbon flux at the catchment outlet. Pipe densities in blanket peatlands are known to increase when peat is affected by drainage or drying. Hence, environmental change in many peatlands may lead to an increase in aquatic carbon fluxes from natural pipes, thereby influencing the peatland carbon balance and downstream ecological processes. © 2012 Blackwell Publishing Ltd
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 10
    Publication Date: 2013-06-14
    Description: A high-resolution version of the WRF (Weather Research and Forecasting) model has been used to study the fine structure of a cloud head and its associated cold conveyor belt jet (CJ) and sting jet (SJ) in an intense extratropical cyclone that produced damaging surface winds in northern Ireland and central Scotland on 3 January 2012. The model was run with many different initialisation times and physical parametrisations, and a run was selected that verified well against a variety of observations. New methods have been devised to visualise the 3D structure of the CJ and SJ and to attribute strong surface winds to one or other of them, and the validity of regarding the SJ as a semi-Lagrangian feature has been assessed. The model suggests that, whereas the CJ remained mainly below the 850 hPa level as it circulated around the bent-back front, the SJ consisted of a stream or streams of air within the bent-back frontal zone that first ascended from close to the surface into the middle and upper-level parts of the cloud head before descending from evaporating cloud filaments at the tip of the cloud head and reaching the top of the boundary layer slightly ahead of the CJ. The simulations did not support the idea that either the evaporation or conditional symmetric instability (CSI) played a major role in the development of these jets. The strong gusts (up to 47 m s −1 ) which were recorded on the north coast of Ireland appear to have been due mainly to the CJ, which by then was undercutting the SJ. The SJ was responsible for stronger surface winds than the CJ several hours earlier during the initial stage of frontal fracture, but only for a limited period.
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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