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  • 1
    Electronic Resource
    Electronic Resource
    Stoichiometry, kinetics, and mechanisms of the chromium(VI) oxidation of L-cysteine at neutral pH (1984)
    s.l. : American Chemical Society
    Inorganic chemistry 23 (1984), S. 2528-2532 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00184a030
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  • 2
    Electronic Resource
    Electronic Resource
    Physical and biological controls on the formation of carbonate and siliciclastic bedforms on the north-east Brazilian shelf (1999)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 46 (1999), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The continental shelf of the State of Rio Grande do Norte, Brazil, is an open shelf area located 5°S and 35°W. It is influenced by strong oceanic and wind-driven currents, fair weather, 1·5-m-high waves and a mesotidal regime. This work focuses on the character and the controls on the development of suites of carbonate and siliciclastic bedforms, based on Landsat TM image analysis and extensive ground-truth (diving) investigations. Large-scale bedforms consist of: (i) bioclastic (mainly coralline algae and Halimeda) sand ribbons (5–10 km long, 50–600 m wide) parallel to the shoreline; and (ii) very large transverse siliciclastic dunes (3·4 km long on average, 840 m spacing and 3–8 m high), with troughs that grade rapidly into carbonate sands and gravels. Wave ripples are superposed on all large-scale bedforms, and indicate an onshore shelf sediment transport normal to the main sediment transport direction. The occurrence of these large-scale bedforms is primarily determined by the north-westerly flowing residual oceanic and tidal currents, resulting mainly in coast-parallel transport. Models of shelf bedform formation predict sand ribbons to occur in higher energy settings rather than in large dunes. However, in the study area, sand ribbons occur in an area of coarse, low-density and easily transportable bioclastic sands and gravels compared with the very large transverse dunes in an offshore area that is composed of denser medium-grained siliciclastic sands. It suggests that the availability of different sediment types is likely to exert an influence on the nature of the bedforms generated. The offshore sand supply is time limited and originates from sea floor erosion of sandstones of former sea-level lowstands. The trough areas of both sand ribbons and very large transverse dunes comprise coarse calcareous algal gravels that support benthic communities of variable maturity. Diverse mature communities result in sediment stabilization through branching algal growth and binding that is thought to modify the morphology of dunes and sand ribbons. The occurrence and the nature of the bedforms is controlled by their hydrodynamic setting, by grain composition that reflects the geological history of the area and by the carbonate-producing benthic marine communities that inhabit the trough areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.1999.00213.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sedimentology and budget of a Recent carbonate mound, Florida Keys (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 32 (1985), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The sedimentology of a Recent carbonate mound is investigated to further our understanding of mound building communities, surface and subsurface mound sediments, and the overall sediment budget of mounds. Nine sedimentary facies of the surface of Tavernier mound, Florida Keys are described. These sediments are composed of Neogoniolithon, Halimeda, Porites, mollusc and foraminiferal grains, and lime mud. Muds rich in aragonite and high magnesian calcite show little mineralogical variation over the mound surface. Geochemical evidence suggests that the mud is mainly formed from breakdown of codiacean algae and Thalassia blade epibionts. Production rates of the facies are established from in situ growth rate experiments and standing-crop surveys. Annual calcium carbonate production is c. 500gm-2, intermediate between reef and other bay and lagoonal environment production rates in the Caribbean. The internal structure of the mound, studied from piston cores and sediment probes, indicates that seven facies can be identified. Five of these can be related to the present-day facies, and occur in the upper part of the mound (gravel-mound stage). The remaining two facies, characterized by molluscs and aragonite-rich muds, occur in the lower part of the mound (mud-mound stage), and are most similar to facies from typical Florida Bay mud mounds. Mangrove peats within the mound indicate former intertidal areas and C14 dates from these peats provide a time framework for mound sedimentation. The mound appears to have formed because of an initial valley in the Pleistocene surface which accumulated mud in a shallow embayment during the Holocene transgression.A sediment budget for the mound is presented which compares production rates from present-day facies with subsurface sediment masses. During the mud mound stage production rates were similar to accumulation rates and the mound was similar to the present-day mounds of Florida Bay. During the gravel mound stage (3400 yr BP-present day), conditions were more normal marine and the establishment of Porites and Neogoniolithon on the mound increased production rates 10% over accumulation rates. This excess sediment is thought to be transported off the mound to the surrounding seabed. Models are proposed which divide carbonate mounds on the basis of internal versus external sediment supply. Comparisons are made with other Recent and ancient mounds. Similarities exist between the roles of the biotic components of late Palaeozoic mounds but major differences are found when structures and early diagenesis are compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1985.tb00515.x
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  • 4
    Electronic Resource
    Electronic Resource
    Dolomitization by penesaline sea water in Early Jurassic peritidal platform carbonates, Gibraltar, western Mediterranean (2001)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 48 (2001), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Peritidal carbonates of the Lower Jurassic (Liassic) Gibraltar Limestone Formation, which form the main mass of the Rock of Gibraltar, are replaced by fine and medium crystalline dolomites. Replacement occurs as massive bedded or laminated dolomites in the lower 100 m of an ≈460-m-thick platform succession. The fine crystalline dolomite has δ18Ο values either similar to, or slightly higher than, those expected from Early Jurassic marine dolomite, and δ13C values together with 87Sr/86Sr ratios that overlap with sea-water values for that time, indicating that the dolomitizing fluid was Early Jurassic sea water. Absence of massive evaporitic minerals and/or evaporite solution-collapse breccias in these carbonate rocks indicates that the salinity of sea water during dolomitization was below that of gypsum precipitation. The occurrence of peritidal facies, a restricted microbiota and rare gypsum pseudomorphs are also consistent with penesaline conditions (salinity 72–199‰). The medium crystalline dolomite has some δ18Ο and δ13C values and 87Sr/86Sr ratios similar to those of Early Jurassic marine dolomites, which indicates that ambient sea water was again a likely dolomitizing fluid. However, the spread of δ18Ο, δ13C and 87Sr/86Sr values indicates that dolomitization occurred at slightly increased temperatures as a result of shallow (≈500 m) burial or that dolomitization was multistage. These data support the hypothesis that penesaline sea water can produce massive dolomitization in thick peritidal carbonates in the absence of evaporite precipitation. Taking earlier models into consideration, it appears that replacement dolomites can be produced by sea water or modified sea water with a wide range of salinities (normal, penesaline to hypersaline), provided that there is a driving mechanism for fluid migration. The Gibraltar dolomites confirm other reports of significant Early Jurassic dolomitization in the western Tethys carbonate platforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2001.00361.x
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  • 5
    Electronic Resource
    Electronic Resource
    The subcycled Newmark algorithm (1997)
    Springer
    Computational mechanics 20 (1997), S. 272-281 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The popular Newmark algorithm, used for implicit direct integration of structural dynamics, is extended by means of a nodal partition to permit use of different timesteps in different regions of a structural model. The algorithm developed has as a special case an explicit-explicit subcycling algorithm previously reported by Belytschko, Yen and Mullen. That algorithm has been shown, in the absence of damping or other energy dissipation, to exhibit instability over narrow timestep ranges that become narrower as the number of degrees of freedom increases, making them unlikely to be encountered in practice. The present algorithm avoids such instabilities in the case of a one to two timestep ratio (two subcycles), achieving unconditional stability in an exponential sense for a linear problem. However, with three or more subcycles, the trapezoidal rule exhibits stability that becomes conditional, falling towards that of the central difference method as the number of subcycles increases. Instabilities over narrow timestep ranges, that become narrower as the model size increases, also appear with three or more subcycles. However by moving the partition between timesteps one row of elements into the region suitable for integration with the larger timestep these the unstable timestep ranges become extremely narrow, even in simple systems with a few degrees of freedom. As well, accuracy is improved. Use of a version of the Newmark algorithm that dissipates high frequencies minimises or eliminates these narrow bands of instability. Viscous damping is also shown to remove these instabilities, at the expense of having more effect on the low frequency response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050248
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and Chemistry of Dithiadiazole Free Radicals [4-(4′-C5H4N)CN2S2] and [4-(3′-C5H4N)CN2S2]; X-ray Crystal Structures of [Pd3{μ-SNC(Ar′)NS-S,S′}2(PPh3)4] (Ar′ = 4′-C5H4N, 4′-C5H4NBEt3 and 3′-C5H4NBEt3) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 1045-1054 
    Details
    ISSN: 1434-1948
    Keywords: Palladium ; Dithiadiazole ; Radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new 1,2,3,5-dithiadiazoles, [4-(4′-C5H4N)CN2S2] (L1) and [4-(3′-C5H4N)CN2S2] (L2), with different pyridyl groups at the 4-position were prepared. As Lewis bases, the dithiadiazoles reacted with Lewis acids via their pyridyl groups to form acid-base adducts with retention of the five-membered dithiadiazole ring. Ligands L1 and L2 reacted with excess triethylborane to give L1BEt3 and L2BEt3 (1a and 1b) and with Mn(CO)5Br to give the fac-Mn(CO)3Br(L1)2 (2a) and fac-Mn(CO)3Br(L2)2 (2b) complexes. When reacted with Pd0 complexes, namely, Pd(PPh3)4 and a mixture of [Pd2(dba)3] and dppf, the dithiadiazoles underwent ring-opening reaction by reductive cleavage of the S-S bond of the dithiadiazole ring. The resulting formation of Pd-S bonds gave the corresponding trinuclear complexes [Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(PPh3)4] (3a), [Pd3{μ-SNC(3′-C5H4N)NS-S,S′}2(PPh3)4] (3b), and [Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(dppf)2] (4) [dba = dibenzylideneacetone, dppf = 1,1′-bis(diphenylphosphanyl)ferrocene]. Complexes 3a and 3b reacted with excess triethylborane to give the corresponding acid-base adducts [Pd3{μ-SNC(4′-C5H4NBEt3)NS-S,S′}2(PPh3)4] (5a) and [Pd3{μ-SNC(3′-C5H4NBEt3)NS-S,S′}2(PPh3)4] (5b.) Complex 3a reacted with Mn(CO)5Br to give {[Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(PPh3)4][MnBr(CO)3]}n (6). The structures of 3a, 5a, and 5b were established by X-ray crystallography.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Performance of reduction methods for fluid-structure and acoustic eigenvalue problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1585-1594 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A methodology is presented for measuring the effectiveness of a finite element approach when compared with a reference finite element approach with respect to accuracy and computation. The effectiveness measure is applied to the Hughes reduction method for structural eigenvalue problems and three proposed analogous methods for fluid or fluid-structure problems. Comparisons of the three methods with consistent interpolation solutions indicate that improved effectiveness can be obtained.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620151102
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  • 8
    Electronic Resource
    Electronic Resource
    Modal methods in finite element fluid-structure eigenvalue problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1161-1175 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The technique of fixed-interface modal synthesis used to solve large structural eigenvalue problems is extended to fluid-structure eigenvalue problems with a view to efficient solution of problems involving localized modifications. Three cases are considered: namely, those fluid or fluid-structure vibration problems directly analogous to the structural case; the modification of the fluid model of a structure enclosing a compressible fluid; and the modification of fluid and structural models of a structure enclosing an incompressible fluid. Examples of the three cases are given, as are estimates of the computation that can be saved when using the methods to avoid resolving modified eigenvalue problems. It is also shown that the hard-walled modes of a fluid enclosure can be used to modify the incompressible-fluid modes of the fluid-structure system to account for a degree of compressibility in the fluid. An example and computation estimates are given.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150805
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  • 9
    Electronic Resource
    Electronic Resource
    Subcycling first- and second-order generalizations of the trapezoidal rule (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 42 (1998), S. 1091-1119 
    Details
    ISSN: 0029-5981
    Keywords: transient dynamics ; direct integration ; subcycling ; diffusion problems ; structural dynamics ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Subcycling algorithms which employ multiple timesteps have been previously proposed for explicit direct integration of first- and second-order systems of equations arising in finite element analysis, as well as for integration using explicit/implicit partitions of a model. The author has recently extended this work to implicit/implicit multi-timestep partitions of both first- and second-order systems. In this paper, improved algorithms for multi-timestep implicit integration are introduced, that overcome some weaknesses of those proposed previously. In particular, in the second-order case, improved stability is obtained. Some of the energy conservation properties of the Newmark family of algorithms are shown to be preserved in the new multi-timestep extensions of the Newmark method. In the first-order case, the generalized trapezoidal rule is extended to multiple timesteps, in a simple way that permits an implicit/implicit partition. Explicit special cases of the present algorithms exist. These are compared to algorithms proposed previously. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 19 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis and implementation of a new constant acceleration subcycling algorithm (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 2841-2855 
    Details
    ISSN: 0029-5981
    Keywords: transient ; structural dynamics ; explicit integration ; subcycling ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm for explicit integration of structural dynamics problems with multiple time steps is proposed that averages accelerations to obtain subcycle states at a nodal interface between regions integrated with different time steps. With integer time step ratios, the resulting subcycle updates at the interface sum to give the same effect as a central difference update over a major cycle. The algorithm is shown to have good accuracy, and stability properties in linear elastic analysis similar to those of constant velocity subcycling algorithms. The implementation of a generalised form of the algorithm with non-integer time step ratios is presented. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
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