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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 157 (2000), S. 505-521 
    ISSN: 1420-9136
    Keywords: Key Words: Cataclasis, particle size distribution, fractal, microfault, chromite.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Chromitite from seams in the early Proterozoic Great Dyke, Zimbabwe, has three types of microstructure. Grains in intact samples have an average of just over five slightly curved grain boundaries around each polygonal grain, and triangular-shaped triple grain junctions, some with grain boundaries intersecting at 120°. These features show adjustment to a minimum surface energy configuration. Samples with extension microcracks have smaller particles on average, which are more inequant and have a stronger preferred orientation than particles in the intact samples, due to fragmentation by impingement microcracking. Microfaults have still smaller average particle sizes, but more equant and less well orientated angular fragments, formed by sliding and rotation of particles after linkage between extension microcracks. Intact samples have a curved relationship on a log-log plot between cumulative numbers of particles and grain size. This particle size distribution evolves with strain to a linear, fractal relationship in the microfaults, with a fractal dimension of 2.8. The changes in particle size distribution are consistent with constrained comminution, and an additional process of selective fracture of larger particles. The degree of cataclasis is an important factor in determining chromite ore quality.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of applied ichthyology 16 (2000), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: There is a current need to establish scientific guidelines for Best Environmental Practice for the regulation and monitoring of marine aquaculture throughout the European Union. This paper will demonstrate how the ‘MARAQUA’ Concerted Action will address this need using several methods including a comprehensive literature review and production of a computerized bibliography, establishment of a ‘Register of Experts’ and a worldwide website, circulation of a newsletter and a series of workshops. A brief comparison of the regulations and monitoring programmes associated with marine aquaculture in European countries is briefly outlined. These issues are described in depth in the individual country reviews presented in this special edition of the Journal.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 5 (1980), S. 27-35 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The resonating group method is used to study the effective potential between two nucleons, due to the confining potential between quarks taken together with the Pauli principle for quarks. The potential used has harmonic form, unitary spin factor λ(1)·λ(2), and both ordinary and spin-spin components. Its parameters are determined by appeal to experimental data, and phase shifts are calculated for the1 S 0 and3 S 1 states of the nuncleon-nucleon (NN) system. The results indicate that the repulsive core in theNN potential may arise from quark antisymmetrization required if nucleons are composed of quarks.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The widespread presence of cellulose-binding domains in cellulases from aerobic bacteria and fungi suggests the existence of a strong selective pressure for the retention of these non-catalytic modules. The complete nucleotide sequence of the cellulase gene, celA, from the aerobic soil bacterium Cellvibrio mixtus, was determined. It revealed an open reading frame of 1089 bp that encoded a polypeptide, defined as cellulase A (CelA), of M r 41 548. CelA displayed features characteristic of an endo-β-1,4-glucanase, rapidly decreasing the viscosity of the substrate while releasing only moderate amounts of reducing sugar. Deletion studies in celA revealed that removal of 78 nucleotides from the 5′ end or 75 from the 3′ end of the gene led to the complete loss of cellulase activity of the encoded polypeptides. The deduced primary structure of CelA revealed an N-terminal signal peptide followed by a region that exhibited significant identity with the catalytic domains of cellulases belonging to glycosyl hydrolase family 5. These data suggest that CelA is a single-domain endoglucanase with no distinct non-catalytic cellulose-binding domain. Analysis of the biochemical properties of CelA revealed that the enzyme hydrolyses a range of soluble cellulosic substrates, but was inactive against Avicel, xylan or any other hemicellulose. CelA was resistant to proteolytic inactivation by pancreatic proteinases and surprisingly, in view of its mesophylic origin, was shown to be thermostable. The significance of these findings in relation to the role of single-domain cellulases in plant cell wall hydrolysis by aerobic microorganisms is discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose-binding domains (CBD) play a pivotal role during plant cell wall hydrolysis by cellulases and xylanases from aerobic soil bacteria. Recently we␣have reported the molecular characterisation of a single-domain endoglucanase from Cellvibrio mixtus, suggesting that some cellulases produced by this aerobic bacterium preferentially hydrolyse soluble cellulosic substrates. Here we describe the complete nucleotide sequence of a second cellulase gene, celB, from the soil bacterium C. mixtus. It revealed an open reading frame of 1863 bp that encoded a polypeptide, defined as cellulase B (CelB), with a predicted M r of 66 039. CelB contained a glycosyl hydrolase family 5 catalytic domain at its N terminus followed by two repeated domains, which exhibited sequence identity with type VI CBD previously found in xylanases. Full-length CelB bound to cellulose while catalytically active truncated cellulase derivatives were unable to bind the polysaccharide, confirming that CelB is a modular enzyme and that the type VI CBD homologues were functional. Analysis of the biochemical properties of CelB revealed that the enzyme hydrolyses a range of cellulosic substrates, although it was unable to depolymerise Avicel. We propose that type VI CBD, usually found in xylanases, provide an additional mechanism by which cellulases can accumulate on the surface of the plant cell wall, although they do not potentiate cellulase activity directly. These results demonstrate that C. mixtus, in common with other aerobic bacteria, is able to produce cellulases that are directed to the hydrolysis of cellulose in its natural environment, the plant cell wall.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5125
    Keywords: estuarine management ; coastal zone management ; Tagus ; Humber ; England ; Portugal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper describes the local, national, European and wider-area framework, statutes, and formal and voluntary mechanisms for managing European estuaries. These aspects are discussed in relation to two large and representative estuarine systems, the Tagus, Portugal, and the Humber, on the English North Sea coast As estuaries are sites of many activities and uses, most of which are encouraged or at least condoned, management has the role of preventing and resolving conflicts between those uses and users. Accepted uses of estuaries include the discharge and dumping of waste materials, fin and shell-fisheries, conservation, land reclamation, natural usage, abstraction by industry, and recreation. Estuarine management is now being carried out within the constraints of local and regional government planning, planning and activities of water pollution control bodies, fisheries control bodies, and navigation and port authorities The Tagus and Humber estuaries support all of the above activities and uses, and have controls within a European legislative framework but have differing histories of management and planning in order to resolve conflicts. In addition the Humber is subject to controls placed on North Sea areas. The paper discusses the relevant national and European legislation (Directives) and accepted practices for management. Furthermore, the paper discusses the formulation and practice of estuarine management plans as used by various bodies (nature conservation, water quality and regional authority). It is of particular note that the lessons from these two estuaries are relevant to many other European estuaries.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2016-04-05
    Description: The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector’s response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP’s density measurement is likely due to simplifications in the SPIS model geometry.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
    Publication Date: 1992-08-15
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2012-12-26
    Description: The kallikrein ( KLK ) gene family comprises the largest uninterrupted locus of serine proteases in the human genome and represents a notable case for studying the evolutionary fate of duplicated genes. In primates, a recent duplication event gave rise to KLK2 and KLK3 , both encoding essential proteins for the cascade of seminal plasma liquefaction. We reconstructed the evolutionary history of KLK2 and KLK3 by comparative analysis of the orthologous sequences from 22 primate species, calculated d N / d S ratios, and addressed the hypothesis of coevolution with their substrates, the semenogelins (SEMG1 and SEMG2). Our findings support the placement of the KLK2–KLK3 duplication in the Catarrhini ancestor and unveil the frequent loss of KLK2 throughout primate evolution by different genomic mechanisms, including unequal crossing-over, deletions, and pseudogenization. We provide evidences for an adaptive evolution of KLK3 toward an expanded enzymatic spectrum, with an effect on the hydrolysis of semen coagulum. Furthermore, we found associations between mating system, the number of SEMG repeat units, and the number of functional KLK2 and KLK3 , suggesting complex evolutionary dynamics shaped by reproductive biology.
    Electronic ISSN: 1759-6653
    Topics: Biology
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  • 10
    Publication Date: 2011-10-20
    Description: Author(s): E. K. Lenzi, P. R. G. Fernandes, T. Petrucci, H. Mukai, and H. V. Ribeiro [Phys. Rev. E 84, 041128] Published Wed Oct 19, 2011
    Keywords: Statistical physics
    Print ISSN: 1539-3755
    Electronic ISSN: 1550-2376
    Topics: Physics
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