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    In:  Geological Society Special Publication 240: 25-36.
    Publication Date: 2007-10-08
    Description: This investigation of naturally occurring fractures in the mafic rocks of the Palisades dolerite sill characterizes the porosity of this crystalline rock sequence, and yields a method of determining the in situ porosity when complete down-hole information is not available. Two holes, 229 m and 305 m deep, were drilled 450 m apart through the sill and into the underlying Triassic sediments of the Newark Basin. Both holes were logged with geophysical tools, including the acoustic borehole televiewer (BHTV), to identify intervals of high porosity, fracturing, and potential zones of active fluid flow. Using the BHTV data, 96 and 203 fractures were digitally mapped within the sill in Well 2 and Well 3, respectively. Most fractures dip steeply (76-78{degrees}). There is a shift in fracture orientation between Well 2 and Well 3, although the lithology of the sill is continuous. The dolerite penetrated in both holes is fresh and unaltered, and intersects a 7-m thick olivine-rich layer about 15 m above the bottom of the sill. Several fractures identified in the sill have large apparent aperture (>6 cm) that correspond to high-porosity zones (6-14%), measured from both resistivity and neutron logs in Well 2. We use a relationship between porosity and apparent fracture aperture in Well 2 to infer the porosity in Well 3. This correlative method for estimating porosity may be applicable between holes in other crystalline rock environments where down-hole log data are incomplete. Changes in the temperature gradient log also indicate active fluid flow, although flow appears to be most active in fractured and high-porosity zones in the sediments.
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  • 3
    Publication Date: 2007-10-08
    Description: The deployment of a down-hole dipole shear sonic tool in Hole 395A and Hole 735B marked the first two opportunities to measure high-resolution shear-wave velocity and VS anisotropy profiles in oceanic crustal rocks. In Hole 395A near the Kane Fracture Zone, dipole sonic logs were recorded from 100-600 mbsf, and allow azimuthal anisotropy to be determined as a function of depth in the crust. The magnitude of VS anisotropy varies with depth, from less than 3.2% in low-porosity flows at the bottom of the hole, to approximately 15.5% in highly fractured pillow basalts and breccias. The orientation of the fast VS direction also varies over depth, with a mean value between 75{degrees}N and 80{degrees}E, and aligns with the strike of steeply dipping structures observed by down-hole electrical and acoustic images. This fast VS angle orientation is locally oblique to the plate-spreading direction and to the Mid-Atlantic Ridge axis. In Hole 735B, drilled near the Atlantis Fracture Zone, dipole sonic logs from 23 to 596 mbsf indicate that VS anisotropy varies with depth, with averages of 5.3% in the foliated and deformed gabbros recovered at the bottom of the hole; 4.5% in undeformed olivine and oxide-rich gabbros around 300 mbsf; and 6.8% in highly deformed mylonitic zones at shallow depths. The fast VS angle also varies with depth, giving a mean orientation of approximately S45{degrees}E for well-resolved estimates in the upper interval of the hole. This direction aligns with the strike of steeply dipping fractures observed by down-hole imaging, and is locally oblique to the Southwest Indian ridge axis. Although the effects of regional stresses and local deformation of these holes may introduce anisotropy in the dipole sonic data, we conclude that crustal morphology in the vicinity of the holes contributes significantly to the magnitude and orientation of VS anisotropy.
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  • 4
    Publication Date: 2007-10-08
    Description: A newly developed logging-while-coring system was deployed during Ocean Drilling Program legs 204 and 209 off the coast of Oregon and near the Mid-Atlantic Ridge. The system consists of two existing devices modified to be used together -- a Schlumberger Resistivity-at-the-Bit* tool, and a Texas A&M University wireline-retrieved core barrel and latching tool. The combination allows for precise core-log depth calibration and core orientation within a single borehole, and without a pipe trip. These tests, conducted in clay-bearing sediments (Leg 204) and in crustal peridotite and gabbroic rocks (Leg 209), mark the first simultaneous use of coring and logging-while-drilling technologies. Sediment cores were recovered with 33% recovery, on average, and as high as 68% to 75 m depth below the sea floor. Core recovery in crustal rocks was only 1-2%, however, penetrating to 21 m depth below sea floor, which is attributed to a problem with the core catcher. High-resolution logs were recorded in the downhole tool memory over the entire drilled intervals at both test sites. It is anticipated that logging-while-coring systems will be utilized more routinely where rig time constraints may otherwise preclude coring in difficult drilling environments.
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  • 5
    ISSN: 1573-5036
    Keywords: Grumusol ; O.D.R. ; Oxygen flux ; Root extension ; Soil aeration ; Soil model ; Trickle irrigation ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A two-dimensional trickle-irrigated soil model was examined in order to determine its aeration regime. Oxygen diffusion rate (O.D.R.) was used as an index of the soil aeration regime, and its influence on the development of root systems was determined. Volumetric soil air content was calculated from soil water tension data, using a retention curve. The root system was markedly concentrated at the periphery of the trickle-irrigated soil volume, while in the center there were few roots. An exponential correlation was found between root distribution and O.D.R., in which 20×10−8g O2×cm−2×min−1 was the critical value for root growth. There was a linear correlation between O.D.R. and volumetric air content which was affected by diffusion distance.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-9591
    Keywords: neutral beam injection ; negative ion beam line ; laser photodetachment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We present a design for a 200 keV, 1 MW negative-ion-based beam line which is intended to serve as a proof-of-principle demonstration for the LBL surface-conversion negative ion source. The design is straightforward and conservative, and uses existing technology for all major components. An alternate beam line design is also presented, to demonstrate the advantages of reduced size and gas load and increased neutral beam power accruing from the introduction of a laser photo-detachment neutralizes This design is less conservative, but requires only reasonable extrapolations from existing technology.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Atomic and electronic structures, magnetic properties of intermetallic compound NiAl with Fe additions (up to IO at .% for different types of alloying) were studied using NMR and magnetic susceptibility measurements. The effect of these parameters on the probability of occurence of phase transformation B2-LIo was explored. Experimental results were compared with those obtained by computer calculations of the electronic structure for atomic arrangement of Fe impurity in both sublattices by means of the cluster variant of TBA-LCAO method. The responsibility of the density of 3d-states at the Fermi level increasing effects (Fe−Ni substitution) and corresponding contributions, associated with orbital interactions (Fe−Al substitution), for observed behaviour of measured parameters were determined. Appearance of B2-LIo phase transition with increasing of antistructural Fe atoms (ASA) concentration was observed experimentally by means of transmission electron microscopy and X-ray diffraction analysis.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-8900
    Keywords: Poly(caprolactone) (PCL) ; biodegradability ; utility ; extrusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Since the early 1970s, it has been known that exposure of poly(caprolactone) (PCL) to a variety of microorganisms results in biodegradation of this polymer. Besides the ability of PCL to be utilized as a carbon source for microorganisms, it has been demonstrated that, during degradation, carbon dioxide is generated. Soil burial and compost experiments have shown that chain scission of the PCL backbone occurs, mechanical properties of articles prepared from PCL are reduced rapidly, and significant weight loss occurs in a short time period. This inherent biodegradability of PCL, in combination with its ability to be converted by conventional extrusion equipment, allows for the preparation of biodegradable articles that have utility.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two kinds of errors are found in protein models made with the tool of Rubin and Richardson. Global errors result from the accumulation of many errors too small to localize, while local errors are assignable to particular bends in the model. We here locate the sources of local errors, and show how to minimize both kinds of errors.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2019-07-17
    Description: Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (〈500m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of 〈5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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