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  • 1
    Electronic Resource
    Electronic Resource
    Two- and three-dimensional inversions of magnetic anomalies in the MARK area (Mid-Atlantic Ridge 23° N) (1988)
    Springer
    Marine geophysical researches 10 (1988), S. 41-57 
    Details
    ISSN: 1573-0581
    Keywords: Mid-Atlantic Ridge ; seafloor spreading ; magnetic anomalies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Magnetic data collected in conjunction with a Sea Beam bathymetric survey of the Mid-Atlantic Ridge south of the Kane Fracture Zone are used to constrain the spreading history of this area over the past 3 Ma. Two-dimensional forward modeling and inversion techniques are carried out, as well as a full three-dimensional inversion of the anomaly field along a 90-km-long section of the rift valley. Our results indicate that this portion of the Mid-Atlantic Ridge, known as the MARK area, consists of two distinct spreading cells separated by a small, zero-offset transform or discordant zone near 23°10′ N, The youngest crust in the median valley is characterized by a series of distinct magnetization highs which coalesce to form two NNE-trending bands of high magnetization, one on the northern ridge segment which coincides with a large constructional volcanic ridge, and one along the southern ridge segment that is associated with a string of small axial volcanos. These two magnetization highs overlap between 23° N and 23°10° N forming a non-transform offset that may be a slow spreading ridge analogue of the small ridge axis discontinuities found on the East Pacific Rise. The crustal magnetizations in this overlap zone are generally low, although an anomalous, ESE-trending magnetization high of unknown origin is also present in this area. The present-day segmentation of spreading in the MARK area was inherited from an earlier ridge-transform-ridge geometry through a series of small (∼ 10 km) eastward ridge jumps. These small ridge jumps were caused by a relocation of the neovolcanic zone within the median valley and have resulted in an overall pattern of asymmetric spreading with faster rates to the west (14 mm yr−1) than to the east (11 mm yr−1). Although the detailed magnetic survey described in this paper extends out to only 3 Ma old crust, a regional compilation of magnetic data from this area by Schoutenet al. (1985) indicates that the relative positions and dimensions of the spreading cells, and the pattern of asymmetric spreading seen in the MARK area during the past 3 Ma, have characterized this part of the Mid-Atlantic Ridge for at least the past 36 Ma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02424660
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  • 2
    Electronic Resource
    Electronic Resource
    The morphology and tectonics of the Mark area from Sea Beam and Sea MARC I observations (Mid-Atlantic Ridge 23° N) (1988)
    Springer
    Marine geophysical researches 10 (1988), S. 59-90 
    Details
    ISSN: 1573-0581
    Keywords: Mid-Atlantic Ridge ; seafloor spreading ; rift valley ; oceanic crust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract High-resolution Sea Beam bathymetry and Sea MARC I side scan sonar data have been obtained in the MARK area, a 100-km-long portion of the Mid-Atlantic Ridge rift valley south of the Kane Fracture Zone. These data reveal a surprisingly complex rift valley structure that is composed of two distinct spreading cells which overlap to create a small, zero-offset transform or discordant zone. The northern spreading cell consists of a magmatically robust, active ridge segment 40–50 km in length that extends from the eastern Kane ridge-transform intersection south to about 23°12′ N. The rift valley in this area is dominated by a large constructional volcanic ridge that creates 200–500 m of relief and is associated with high-temperature hydrothermal activity. The southern spreading cell is characterized by a NNE-trending band of small (50–200 m high), conical volcanos that are built upon relatively old, fissured and sediment-covered lavas, and which in some cases are themselves fissured and faulted. This cell appears to be in a predominantly extensional phase with only small, isolated eruptions. These two spreading cells overlap in an anomalous zone between 23°05′ N and 23°17′ N that lacks a well-developed rift valley or neovolcanic zone, and may represent a slow-spreading ridge analogue to the overlapping spreading centers found at the East Pacific Rise. Despite the complexity of the MARK area, volcanic and tectonic activity appears to be confined to the 10–17 km wide rift valley floor. Block faulting along near-vertical, small-offset normal faults, accompanied by minor amounts of back-tilting (generally less than 5°), begins within a few km of the ridge axis and is largely completed by the time the crust is transported up into the rift valley walls. Features that appear to be constructional volcanic ridges formed in the median valley are preserved largely intact in the rift mountains. Mass-wasting and gullying of scarp faces, and sedimentation which buries low-relief seafloor features, are the major geological processes occurring outside of the rift valley. The morphological and structural heterogeneity within the MARK rift valley and in the flanking rift mountains documented in this study are largely the product of two spreading cells that evolve independently to the interplay between extensional tectonism and episodic variations in magma production rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02424661
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusion and solid dissolution/precipitation in permeable media (1989)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1057-1072 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed an analytical solution which describes mineral zonation caused by diffusion in permeable media. For a semiinfinite domain, the species conservation equations transform into ordinary differential equations that yield a closed-form solution. The solution exhibits shock dissolution/precipitation fronts and gradual (nonshock) precipitation fronts. The solution can exhibit regions (gaps) containing no reactive solids which separate moving dissolution and precipitation fronts. The analysis is, in principle, extendable to include intraaqueous reactions, although the mathematics quickly becomes intractable.Numerical simulation exhibits all of the features of the more restricted analytical solution and is in good agreement with the data on hydroxyapatite dissolution taken by Kim and Cussler (1987).
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690350702
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  • 4
    Electronic Resource
    Electronic Resource
    Rule-based mineral sequences in geochemical flow processes (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1607-1614 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The infiltration of an aqueous solution into a permeable medium generally results in the dissolution of some of the minerals initially present and the possible precipitation of others. When the infiltration velocities are small, as is the case for many natural processes, conditions of local equilibrium apply and the dissolution and precipitation processes exhibit a wave-type behavior reminiscent of chromatogrphic fronts. Zones of constant composition (state) will be separated by narrow regions within which the aqueous and solid phase concentrations exhibit sharp changes. Because of this wave-like structure, an algebraic solution of the coupled material balance equations exists, but in a form that involves a trial and error solution procedure which has heretofore discouraged its application. This paper describes the essence of a scheme which uses a combination of graph theory and heuristics to minimize trials and thereby render the algebraic solution practical. The scheme offers an alternative to time-sequencing solutions (e.g., finite difference) of the set of partial differential equations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690341004
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular thermodynamics of aqueous two-phase systems for bioseparations (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1585-1594 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aqueous polymer-polymer two-phase systems provide a powerful method for separating biomolecules by extraction. When a complex mixture of biomolecules (e.g., a fermentation broth or a solution of lysed cells) is added to such a system, biomolecules partition uniquely between the two phases, achieving separation.A thermodynamic framework is presented for optimizing extraction performance in biological separations. First, a molecular-thermodynamic model, based on the osmotic virial equation, is proposed to describe phase equilibria for dilute aqueous mixtures containing polymers and protein. Second, experimental phase-equilibrium data (protein partition coefficients) are reported for a number of model proteins including albumin, lysozyme, and α-chymotrypsin. To interpret and correlate the experimental data, Low-Angle Laser-Light Scattering (LALLS) measurements were made to determine osmotic second virial coefficients for aqueous mixtures containing polymers, proteins, salts (KCl, KH2PO4 and K2SO4 at concentrations of 50 and 100 mM) and several combinations of polymer-polymer and polymer-protein pairs. Combined with electrochemical measurements (differences in potential between the two phases and protein net charge), these data provide parameters for the model to calculate the desired phase equilibria. A comparison of calculated and experimental results indicates that the virial-equation model provides good prediction of binodals and a reliable basis for estimating infinite-dilution protein partition coefficients for biotechnical process design.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690341002
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  • 6
    Electronic Resource
    Electronic Resource
    PVC thermoplastic elastomers (1988)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 10 (1988), S. 33-36 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The paper describes the development and properties of a new family of thermoplastic elastomers based on polyvinyl chloride.Comparisons of the new products with traditional flexible PVC's will be presented, pointing up differences in specific gravity, low temperature properties, heat resistance, melt viscosity, and general physical properties such as tensile modulus and elongation.The elastomeric properties of the new materials are explored and compared to some typical cured elastomers - chloroprene, chlorosulphonated polyethylene. The common thermoplastic elastomers based on block copolymers and polyurethanes are also considered in relation to the new compositions. Such properties as compression-set, flex and fatigue resistance, oil and chemical resistance, weatherability, and performance at elevated temperatures are detailed.The unique feature of this technology that allows one to tailor the surface characteristics from typically high PVC gloss to the fine dull satin finish of cured elastomers is discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730100108
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  • 7
    Electronic Resource
    Electronic Resource
    Notes (1987)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 9 (1987), S. 140-141 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730090312
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