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  • 1
    Electronic Resource
    Electronic Resource
    OPTIMIZED RECEIVER ARRAY SIMULATION BASED UPON RESOLUTION CONSTRAINTS (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 37 (1989), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The use of cables with a large number of closely spaced receivers has become increasingly common in marine seismic acquisition; this gives geophysicists the opportunity to improve data quality in processing centres. In particular, arrays need not be fixed in the field, but instead can be flexibly simulated in the computer.The paper defines a strategy to optimize the application of receiver-array simulation, based on the requirement that signal resolution should not be compromised. The approach consists in the design of k-domain filters through the use of Chebyshev polynomials that define the spatial response of the desired array, with array length that varies with time according to spatial and vertical resolution constraints set by the interpreter.An example, taken from a marine 240-channel seismic line, ties the underlying ideas to practical application and shows that appropriate array processes can contribute to improving the quality of seismic data, especially in areas with complex geology and strong coherent noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1989.tb02225.x
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  • 2
    Electronic Resource
    Electronic Resource
    LIMITS OF STRUCTURAL INVERSION OF SEISMIC HORIZONS (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 32 (1984), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Time horizons can be depth-migrated when interval velocities are known; on the other hand, the velocity distribution can be found when traveltimes and NMO velocities at zero offset are known (wavefront curvatures; Shah 1973).Using these concepts, exact recursive inversion formulae for the calculation of interval velocities are given. The assumption of rectilinear raypath propagation within each layer is made; interval velocities and curvatures of the interfaces between layers can be found if traveltimes together with their gradients and curvatures and very precise VNMO velocities at zero offset are known.However, the available stacking velocity is a numerical quantity which has no direct physical significance; its deviation from zero offset NMO velocity is examined in terms of horizon curvatures, cable length and lateral velocity inhomogeneities.A method has been derived to estimate the geological depth model by searching, iteratively, for the best solution that minimizes the difference between stacking velocities from the real data and from the structural model.Results show the limits and capabilities of the approach; perhaps, owing to the low resolution of conventional velocity analyses, a simplified version of the given formulae would be more robust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1984.tb01708.x
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  • 3
    Electronic Resource
    Electronic Resource
    NON-LINEAR ESTIMATION OF REFLECTION COEFFICIENTS FROM SEISMIC DATA (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 29 (1981), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: For years, reflection coefficients have been the main aim of traditional deconvolution methods for their significant informational content.A method to estimate seismic reflection coefficients has been derived by searching for their amplitude and their time positions without any other limitating assumption. The input data have to satisfy certain quality constraints like amplitude and almost zero phase noise—ghosts, reverberations, long period multiples, and diffracted waves should be rejected by traditional processing. The proposed algorithm minimizes a functional of the difference between the spectra of trace and reflectivity in the frequency domain. The estimation of reflection coefficients together with the consistent “wavelet’ is reached iteratively with a multidimensional Newton-Raphson technique. The residual error trace shows the behavior of the process. Several advantages are then obtainable from these reflection coefficients, like conversion to interval velocities with an optimum calibration either to the well logs or to the velocity analysis curves. The procedure can be applied for detailed stratigraphic interpretations or to improve the resolution of a conventional velocity analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1981.tb00702.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stabilizing the gravitational action and Coleman's solution to the cosmological constant problem
    Amsterdam : Elsevier
    Physics Letters B 276 (1992), S. 36-40 
    Details
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0370-2693(92)90538-F
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  • 5
    Electronic Resource
    Electronic Resource
    The vacuum polarization around an axionic stringy black hole
    Amsterdam : Elsevier
    Physics Letters B 297 (1992), S. 63-66 
    Details
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0370-2693(92)91070-P
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  • 6
    Electronic Resource
    Electronic Resource
    On the stability of a stringy black hole
    Amsterdam : Elsevier
    Physics Letters B 289 (1992), S. 35-44 
    Details
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0370-2693(92)91358-G
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  • 7
    Electronic Resource
    Electronic Resource
    Mass transfer from mothers to pups and mass recovery by mothers during the post-breeding foraging period in southern elephant seals (Mirounga leonina) at King George Island (1997)
    Springer
    Polar biology 18 (1997), S. 305-310 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mass transfer from mother to pup during the lactation period, and mass recovery for the same females during the foraging period were measured in the southern elephant seal at King George Island, Antarctica. During the 19.2 ± 0.9-day lactation period measured (which represented 87% of the entire nursing), females lost a mean mass of 10.56 ± 1.76 kg/day (n = 27), while their pups gained a mean mass of 5.27 ± 1.1 kg/day. There was a correlation between daily body weight gain in pups and daily weight loss by their mothers. Pup weaning mass was positively related to maternal post-partum mass. Serial samples showed that weight losses by females and gains by their pups were not linear over lactation, but showed lower values at the beginning and at the end of lactation. During the 60.5 ± 6.2-day foraging phase between the end of lactation and molt, females gained 2.21 ± 0.65 kg/day (n = 12), or 54% of the mass lost during nursing. Growth rates reported here are higher than those reported in other breeding sites. However, the ratio of body mass loss by females to gain by their pups was similar, suggesting that higher growth rates and greater weaning mass at South Shetland are due to a higher mean weight of females on arrival at this breeding site. The foraging period was shorter and the mass gained greater than those measured at South Georgia; this could be related to relatively shorter distances to foraging areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050192
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  • 8
    Electronic Resource
    Electronic Resource
    The diet of the Antarctic fur seal Arctocephalus gazella at Harmony Point, Nelson Island, South Shetland Islands (1998)
    Springer
    Polar biology 20 (1998), S. 424-428 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diet of non-breeding male Antarctic fur seals (Arctocephalus gazella) was investigated at Harmony Point, Nelson Island, South Shetland Islands, by the analysis of 18 and 33 scats collected during February 1996 and 1997 respectively. Overall, fish were the most frequent prey (74.5%) and predominated by mass (54.4%), whereas krill predominated by number (94.2%). This coincides well with the pattern observed in 1997, but in 1996 krill was the most important prey by number and mass (50.2%). The importance of the remaining taxa represented in the samples (octopods, hyperiids and bivalves) was negligible. Among fish, myctophids represented 85.2% of the fish mass, with Gymnoscopelus nicholsi and Electrona antarctica being the main prey. These two species predominated in 1997, whereas the channichthyid Cryodraco antarcticus and the nototheniid Gobionotothen gibberifrons were dominant in 1996. The importance of the myctophids as prey of the Antarctic fur seal is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050324
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  • 9
    Electronic Resource
    Electronic Resource
    Southern elephant seals: IgM concentration in milk of cows and serum of their pups (2000)
    Springer
    Polar biology 23 (2000), S. 671-674 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Serum and milk Immunoglobulin M (IgM) concentrations in 11 mother-pup pairs were measured in southern elephant seals (Mirounga leonina) throughout lactation during 2 breeding seasons at King George Island. Samples were obtained sequentially throughout the suckling period (approximately 23 days). The IgM concentration was measured by single radial immunodiffusion on agarose plates. Milk IgM concentrations showed significant differences throughout lactation, with the highest concentrations on the 1st day (x=989.7 mg/dL skimmed milk; SD=433.2) followed by a sharp fall during the next 3–6 days of the suckling period. The ratio of milk IgM/serum IgM concentrations from mothers ranged from 0.21 to 21.92, with highest values in the 1st day of lactation (x=8.25, SD=5.4) and a decrease in concentration as lactation progressed. This was due to the fact that, throughout lactation, milk IgM concentrations fell while serum IgM values showed an increasing trend. Pups showed the lowest serum IgM values in the 1st day of the suckling period (x=13.0 mg/dL, SD=4.3) with an increasing trend as lactation progressed. Despite the high IgM concentrations of milk at day 1 of lactation, by 1 week of age pups had serum IgM concentrations only slightly greater than at birth. This suggests that much of this Ig was newly formed and little or no milk IgM was absorbed during the 1st week. Possibly, the function of ingested IgM is to provide local immunity in the pup's gut, during the first few days of postnatal life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000000136
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  • 10
    Electronic Resource
    Electronic Resource
    Southern elephant seal, Mirounga leonina: composition of milk during lactation (1994)
    Springer
    Polar biology 14 (1994), S. 37-42 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An analysis of milk constituents during various stages of lactation in the southern elephant seal Mirounga leonina was carried out. Forty-six milk samples were taken from 30 females throughout lactation during 1985, 1987, 1990 and 1991 on Stranger Point, King George Island, South Shetland Islands. Total nitrogen (TN), non-protein nitrogen (NPN), sugar, fat, ash and water were measured, and from some of these data true protein and energy content were calculated. The results showed a high degree of variation in water and fat concentrations among samples at different stages of lactation. During the first 20 days the fat content of milk increased from about 12 to approximately 52%, while water content fell from 70 to 33%. The composition of milk changes rapidly during the first days post-partum. Protein, minerals and sugar appear to remain stable after the fourth day of lactation. Milk samples contain significant levels of sugars; thin layer chromatography indicates the presence of lactose and glucose together with other unidentified components. There is evidence of a striking change in composition of the milk in the later part of lactation; the progressive increase in the fat:water ratio is abruptly reversed just prior to weaning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240270
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