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  • 1990-1994  (6)
  • 1960-1964  (1)
  • 1940-1944
  • 1935-1939
  • 1905-1909
  • 1900-1904
  • Life and Medical Sciences  (5)
  • permeability  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 8 (1992), S. 93-97 
    ISSN: 1573-1634
    Schlagwort(e): Porous rock ; permeability ; porosity ; fractal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract Effective permeability for porous rocks is calculated using mean field theory. We make two simplifying assumptions about the internal conductances in a network representation of the porous rock: (i) Pore space is characterized by a uniform fractal scaling; (ii) the internal conductances depend only on the characteristic pore sizes. Within these approximations, it is possible to derive a simple probability density for the internal conductances which is used for calculating effective permeability. Good agreement between calculations and experimental data of permeability vs. porosity is achieved.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 8 (1992), S. 133-147 
    ISSN: 1573-1634
    Schlagwort(e): Fractal ; multifractal ; sedimentary rocks ; permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf(α) spectrum, which can be modelled by a simple two-scale Cantor set.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0730-2312
    Schlagwort(e): DNA/protein interaction ; simple repetitive DNA ; binding domain ; conformation changes ; intron 2 ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Electrophoretic mobility shift assays reveal that HeLa neuclear proteins bind fast and with measurable affinity to target DNAs containing mixed simple repetitive (gt)n(ga)m stretches. Preincubation of the proteins at elevated temperature prevents the formation of the major DNA/protein complex in favour of several distinct assemblies. A similar pattern of retarded bands was observed employing higher salt concentrations in binding reaction. Thus conformational changes of different proteins appear to influence the complex rather than alternating DNA structures. Separation of the total nuclear extract into a water soluble and an insoluble protein fraction leads to a complete loss of target DNA bindinlg capability of the fractions. The binding capacity is restored by combining the two fractions suggesting that at least two protein components are necessary to form a complex with the target sequence. The proteins can be differentiated into head sensitive, water soluble and temporary stable, water insoluble, respectively. Furthermore, specifically binding polypeptides are not detectable by Southwestern analyses, probably because the essential components are separated during electrophoresis. DNase 1 footpoint analyses yield four different protein binding regions only on the (gt)n(ga)m harbouring strand. The footprints cover larger portions of the mixed simple repeat in addition to a portion 5′ of the (gt)n part. Hence at lealst two nuclear protein components of unknown biological function have to be present simultaneously to protect preferentially the (gt)n(ga)m-containing strand intron 2 in HLA-DRB genes
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 38 (1994), S. 440-452 
    ISSN: 1040-452X
    Schlagwort(e): Spermiogenesis ; Nuclear condensation ; Chromatin ; Protamines ; Protein-precursors ; Neogastropod mollusc ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: During the process of chromatin cndensation in the spermiogenesis of the neogastropod mollusc Murex brandaris, the nuclear protein complement undergoes a complex series of changes. These changes lead to the appearance of three small protamines in the ripe sperm nuclei. We have characterized this system electrophoretically and at the compositions with antibodies elicited against a specific spermatozoan protamine. Our results indicate that the complex pattern of chromatin condensation during spermiogenesis in this species (M. brandaris) may be modulated by a series of post-translational (and intranuclear) modifications of DNA-interacting proteins, such as precursors to the sperm protamines. The amino acid composition of each sperm protamine is remarkably simple (lys + arg + gly ≥96 mol%). This system of spermiogenic/spermatozoal proteins in the neogastropod M. brandaris clearly differs from that in patellogastropods and archaeogastropods, and it may be helpful in understanding evolutionary changes in the chromatin condensation pattern during the spermiogenesis of gastropod molluscs. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1059-910X
    Schlagwort(e): Ultrastructure ; Immunocytochemistry ; Chromatin structure ; Nuclear proteins ; Testis ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Allgemeine Naturwissenschaft
    Notizen: We have followed the fine structural distribution of two nucleosomal core histones, H2B and H3, and of protamines in the course of mouse spermiogenesis by means of specific antibodies and ultrastructural immunocytochemistry.Our results demonstrate that the nuclear labeling density of histone H2B decreases during steps 6-8 and then increases again in step 9-10 spermatids, while the labeling for histone H3 is constant throughout this period. In step 12 spermatids, the anti-H2B antibody labels mainly the central area of the nucleus. The first signs of protamine labeling are present in step 12 spermatids, where the gold grains can be found over the periphery of the nucleus. Later on, protamine labeling constantly increases and, by the end of spermiogenesis, the whole nucleus is labeled.We suggest that the morphological and structural differences between the central area and the periphery of mouse spermatids are, at least partly, due to a difference in the protein moiety associated with DNA. The central area, which is peculiar to the mouse and has been previously considered as a focus of chromatin condensation, represents, however, the last nuclear region containing histones and consequently the last area where the substitution of histones by protamines takes place.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 63 (1964), S. 77-84 
    ISSN: 0095-9898
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 8 (1992), S. 117-120 
    ISSN: 0749-503X
    Schlagwort(e): Thioredoxin ; TRX1 ; TRX2 ; genetic map location ; Life and Medical Sciences ; Genetics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The two genes encoding thioredoxims in Saccharomyces cerevisiae, TRX1 and TRX2, map to chromosome XII and VII, respectively. From the DNA sequence of the intragenic region TRX1 is 500 bp downstream of PDC1. Tetrad analysis places TRX21·1 cM from ADE3, while a physical map of this region positions TRX2 4·5 kb downstreams of ADE3. The mapping of TRX1 adjacent to PDC1 clarifies previous results (Muller, E. G. D. J. Biol. Chem. 266, 9194-9202, 1991) that suggested a third thioredoxims gene.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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