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  • 1
    Electronic Resource
    Electronic Resource
    ACOUSTIC MODELING OF THE SEAFLOOR (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 34 (1986), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Data from routine seismic surveys contain considerable information about the geo-acoustic properties of the seafloor. Waves are reflected at a wide range of angles of incidence from near-vertical reflections (higher multiples) to supercritical reflections (primary and lower multiples). The reflection coefficient is approximately constant for small angles of incidence (〈 10°) but varies greatly for larger angles of incidence. Near-vertical reflections are used to determine the seafloor density. The P-velocity in the seafloor is determined in advance from the critical distance using the amplitude variation of the primary as well as the multiples. The Vp/VS ratio is determined by modeling the amplitude variation with the angle of incidence. The primary reflection from the seafloor and the first three multiples are included in the modeling.Seismic data obtained with both conventional and superlong airgun arrays have been modeled. Data collected from the Barents Sea show that even if the P-velocity is the same at different sites, the Vp/Vs ratio, density and Poisson's ratio vary significantly. The most extreme example shows that for a P-velocity of 2.80 km/s the Vp/Vs ratio varies between 1.9 and 6.0. The corresponding densities vary from 2.36 g/cm3 to 1.80 g/cm3 and the Poisson's ratio varies from 0.31 to 0.49.The acoustic modeling offers a method of assessing the mean geotechnical or mechanical properties of larger volumes of marine sediments in terms of incompressibility, shear modulus and Poisson's ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1986.tb00450.x
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  • 2
    Electronic Resource
    Electronic Resource
    A METHOD TO DETERMINE THE VELOCITIES OF THE SEAFLOOR AND NEAR-SURFACE SEDIMENTS (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 33 (1985), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Shotpoint gathers from conventional reflection seismic surveys contain both reflected and refracted waves. In this study shot records were processed and analyzed, and the data were modeled with reflected, refracted, and reflected-refracted waves to fit the recorded data. The result is a detailed velocity model. The inverse problem for refracted waves was solved by using the Wiechert-Herglotz inversion.A 500-km-long 26-fold reflection seismic line from the Barents Sea, north of Norway, has been investigated. The data show high velocities, multiple reflections, and various types of noise. To test the method a total of 34 shot gathers were analyzed along this line. The aim of the interpretation was to determine the velocity in the seafloor and the near-surface sediments. It is possible to map the vertical as well as the lateral velocity distribution in detail. Depending on the length of the streamer and the velocity gradient in the sediments, the calculated depth varies between 300 and 500 m below the seafloor. These velocities were also compared to the stacking velocities obtained from the reflection seismic data to see how the velocities determined by different methods were related.The velocity distribution in the sediments is one of the key factors in seismic interpretation. The technique discussed in this paper can contribute to velocity information both in the processing and interpretation of seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1985.tb00442.x
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  • 3
    Electronic Resource
    Electronic Resource
    Genes for the fermentation of maltose and α-methylglucoside in Saccharomyces carlsbergensis (1972)
    Springer
    Molecular genetics and genomics 115 (1972), S. 80-88 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Saccharomyces carlsbergensis N.C.Y.C.74 was shown to be diploid and heterothallic. On acetate medium four spored asci were produced with a spore viability of no more than 2%. However diploid hybrids from the viable spores yielded asci with a spore viability of 75%, thus making tetrad analysis and consequently a genetical study of sugar fermentation in this strain feasible. 2. Auxotrophic mutants in a haploid derivative of this strain were obtained, some of which could be classified as ade 1, ade 2, ade 4, ade 5, ade 6, ade 7, ura 2, ura 3, lys 1, trp 2, trp 5, his 4 and his 5. 3. 150 Random spores all fermented glucose, sucrose, mannose, galactose, melibiose, raffinose, and maltose, but only 28% fermented α-methylglucoside. The same fermentation pattern was found in petites of these 150 spores, except that 40% grew poorly on galactose; this gal phenotype could not be ascribed to a single gene. 4. In crosses with mal strains the maltose fermenting ability of the spores from S. carlsbergensis appeared to be dependent upon 1 single gene, which could be identified as MAL 6, one of the 7 known polymeric genes for maltose fermentation in Saccharomyces. 5. Our strain was found to be heterozygous for 2 unlinked MGL genes, in this paper indicated as MGL a, and MGL b, both indispensable for the fermentation of α-methylglucoside. 6. After mutagenesis of a haploid strain with genotype MGL aMGLb, one mgl mutant was found, which complemented a strain with genotype mgl amglb. This third indispensable MGL gene, preliminarily called MGL c, is homozygously present in our strain and is not linked to either MGL a or MGL b.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272220
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of maltose fermentation in Saccharomyces carlsbergensis (1973)
    Springer
    Molecular genetics and genomics 125 (1973), S. 139-146 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The isolation in S. carlsbergensis of a mutant (C 2), constitutive for maltase and for maltose transport is described. This mutant, in crosses behaving as closely linked or allelic to MAL 6, is different from the constitutive MAL 4-mutant, described by other authors, in four respects: C 2 is recessive to the wild type; the mutant is sensitive to catabolite repression; the level of maltase is not superinducible by maltose; and maltase produced in response to C 2 is not different from wild type maltase. 2. Hybrids made by crossing C 2 with a number of mal 6-mutants grow on maltose and maltase is induced by maltose as in the wild type MAL 6-strain. 3. The properties of C 2 are discussed and compared with litterature data on positive enzyme regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268867
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic fine structure and function of mutants at the ilv1-gene locus of Saccharomyces cerevisiae (1971)
    Springer
    Molecular genetics and genomics 112 (1971), S. 60-72 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 27 point-mutations at the ilv1 locus of Saccharomyces cerevisiae were subjected to genetical analysis, including fine-structure mapping, interallelic complementation and selection of nonsense supersuppressors. The following information was obtained: 1. A genetic map of the locus was established on the basis of mitotic gene conversion induced with gamma rays. It has a length of about 16 units and fails to show any expansion, contrary to what is generally observed in fungal intragenic maps based on meiotic allelic recombination. 2. A circular complementation map is obtained, the shape of which strongly depends on temperature. 3. Non-complementing alleles are distributed over the entire locus, thus showing that it consists of one cistron. 4. Several complementing and temperature sensitive mutant alleles were found to be suppressible by nonsense-suppressors. These alleles were clustered at one end of the map, thus indicating the direction of translation in respect to the gene. The sense of translation relative to the entire chromosome could be derived because the sequence of two mutant alleles included in the present study had been previously determined in relation to outside markers by Kakar (1963a).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266933
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  • 6
    Electronic Resource
    Electronic Resource
    Regulation of maltose fermentation in Saccharomyces carlsbergensis (1973)
    Springer
    Molecular genetics and genomics 123 (1973), S. 233-246 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. In S. carlsbergensis 25 recessive mal 6-mutants were isolated, which did not complement each other in any combination. Maltose induces maltase and a maltose transport system in the wild type but not in the mutants. The derepression, however, of these activities on galactose is the same for the wild type and the mutants. We could not detect significant differences between some kinetic properties of partially purified maltase from the wild type and from one of the mutants (mal 6-13). 2. From mutant mal 6-6 (ϱ−) a number of temperature sensitive revertants was obtained, which grew on maltose at 26°, but not at 36°. Diploids made by crossing these temperature sensitive revertants with the mal 6-mutants (ϱ+) either did not grow on maltose at the restrictive temperature, or only weakly, and therefore the ts-revertants were considered to be mal 6-alleles. A biochemical study of some of the mal 6-ts-mutants indicated that the temperature sensitivity could not be explained by an inactivation or breakdown of maltase or of the maltose transport system at the restrictive temperature. From these results we concluded that the mal 6-ts-alleles and, consequently, all mal 6-alleles are alleles of a regulator gene rather than of a structural gene for maltase or maltose permease. 3. Maltose negative segregants from crosses between strains, carrying one of the polymeric genes MAL 3, MAL 4 or MAL 6, were shown to contain a basal activity of maltase and of maltose transport. Partially purified maltase from two of those mal-segregants had comparable properties to wild type maltase (MAL 6), indicating the presence of maltase cistrons in the parent strains, not linked to the MAL-gene. 4. Indications that the mal 6-mutants are regulatory mutants in a positive regulation system are discussed as well as possible explanations for the fact that no structural mutants for maltase could be detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271242
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  • 7
    Electronic Resource
    Electronic Resource
    Regulation of maltose fermentation in Saccharomyces carlsbergensis (1974)
    Springer
    Molecular genetics and genomics 131 (1974), S. 113-121 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 0405 02 1) In addition to the mutant C2, described previously, 9 other constitutive MLA 6-mutants have been isolated. These, like C2, are sensitive to catabolite repression and not super-inducible by maltose. One of these mutants (C19) is dominant relative to the wild type strain and to mal 6-mutants. The others, like C2, are recessive to the wild type, and their hybrids with mal 6-mutants show a partial or complete loss of the constitutivity and a partial or complete restoration of the inducibility, depending on the particular mutant combination used, which indicates that these recessive constitutive MAL 6-mutations are allelic to the mal 6-mutations. The mutation MAL 6 c19 is possiblynot allelic to the mal 6-mutations. 2) A maltose negative mutation (mal x ) of a type different from the mal 6-mutations was isolated. This mutation, unlinked to MAL 6, is not expressed in combination with the wild type MAL 6-gene, but only in the presence of constitutive MAL 6 c -alleles by changing the constitutive phenotype (not the genotype) into a mal 6-phenotype. Similarly, another mutation (mal y ) was found that is linked neither to MAL 6 nor to mal x and that changes the phenotype of the constitutive allele MAL 6 c14 into a mal 6-phenotype. In contrast with mal x , mutation mal y is specific for the allele MAL 6 c14 . 3) The properties of the new constitutive mutants and the nature of the suppressors mal x and mal y and their importance for mapping constitutive MAL 6 c -alleles are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266147
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  • 8
    Electronic Resource
    Electronic Resource
    Dominance and recessiveness at the protein level in mutant x wildtype crosses in Saccharomyces cerevisiae (1969)
    Springer
    Molecular genetics and genomics 104 (1969), S. 321-330 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The is 1-locus of the yeast Saccharomyces cerevisiae is the structural gene for threonine dehydratase. is 1-mutants require isoleucine for growth and do not have active threonine dehydratase. Interallelic complementation is frequent among is 1-mutants. This is indicative for an aggregate or multimeric structure of yeast threonine dehydratase. Complementing and non-complementing mutants were crossed to wildtype. Properties of threonine dehydratase were assayed in crude extracts of the resulting heterozygotes. Specific activities varied considerably between full wildtype activity and a level about 10% of that. The apparent Michaelis constants were increased in many heterozygotes. This effect was probably due to the aggregation of both mutant and wildtype subunits to form a hybrid threonine dehydratase with reduced substrate affinity in addition to pure wildtype enzyme. This notion is supported by the observation in one heterozygote of two enzyme fractions with increased Michaelis constants in addition to a wildtype-like fraction. The possible formation of hybrid enzymes with normal, reduced or no activity is considered to blur gene dosage relations. A given pair of alleles in a heterozygous cell can generate a new type of enzyme with properties not encountered in the corresponding two homozygous cells. This situation is not accounted for by the classical concepts of dominant-recessive or intermediate behaviour, because the difference between the heterozygotes and the homozygotes is not necessarily only quantitativ but also qualitative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334231
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  • 9
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    Crustal structure in the northern North Sea: an integrated geophysical study (2000)
    Geological Society of London
    Details
    Publication Date: 2000-01-01
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
    Published by Geological Society of London
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  • 10
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    ACOUSTIC MODELING OF THE SEAFLOOR* (1986)
    Wiley
    Details
    Publication Date: 1986-02-01
    Print ISSN: 0016-8025
    Electronic ISSN: 1365-2478
    Topics: Geosciences , Physics
    Published by Wiley
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