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  • 1
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    In:  Geophys. Pros, Kunming, China, D. Reidel Publishing Company, vol. 22, no. 30, pp. 627-651, pp. L09303, (ISSN: 1340-4202)
    Publication Date: 1974
    Keywords: Inversion
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 21 (1973), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: A seismic trace recorded with suitable gain control can be treated as a stationary time series. Each trace, χj(t), from a set of traces, can be broken down into two stationary components: a signal sequence, αj(t) *s(t—τj), which correlates from trace to trace, and an incoherent noise sequence, nj(t), which does not correlate from trace to trace. The model for a seismic trace used in this paper is thus χj(t) =αj(t) * s(t—τj) +nj(t) where the signal wavelet αj(t), the lag (moveout) of the signal τj, and the noise sequence nj(t) can vary in any manner from trace to trace. Given this model, a method for estimating the power spectra of the signal and incoherent noise components on each trace is presented.The method requires the calculation of the multiple coherence function γj(f) of each trace. γj(f) is the fraction of the power on traced at frequency f that can be predicted in a least-square error sense from all other traces. It is related to the signal-to-noise power ratio ρj(f) by 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR660:GPR_660_mu1"/〉 where Kj(f) can be computed and is in general close to 1.0. The theory leading to this relation is given in an Appendix.Particular attention is paid to the statistical distributions of all estimated quantities. The statistical behaviour of cross-spectral and coherence estimates is complicated by the presence of bias as well as random deviations. Straightforward methods for removing this bias and setting up confidence limits, based on the principle of maximum likelihood and the Goodman distribution for the sample multiple coherence, are described.Actual field records differ from the assumed model mainly in having more than one correctable component, components other than the required sequence of reflections being lumped together as correlated noise. When more than one correlatable component is present, the estimate for the signal power spectrum obtained by the multiple coherence method is approximately the sum of the power spectra of the correlatable components. A further practical drawback to estimating spectra from seismic data is the limited number of degrees of freedom available. Usually at least one second of stationary data on each trace is needed to estimate the signal spectrum with an accuracy of about 10%. Examples using synthetic data are presented to illustrate the method.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: A seismic trace after application of suitable amplitude recovery may be treated as a stationary time-series. Such a trace, or a portion of it, is modelled by the expression 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR627:GPR_627_mu1"/〉 where j represents trace number on the record, t is time, αj is a time delay, α (t) is the seismic wavelet, s(t) is the reflection impulse response of the ground and nj is uncorrelated noise. With the common assumption that s(t) is white, random, and stationary, estimates of the energy spectrum (or auto-correlation function) of the pulse α(t) are obtained by statistical analysis of the multitrace record. The time-domain pulse itself is then reconstituted under the assumption of minimum-phase. Three techniques for obtaining the phase spectrum have been evaluated: (A) use of the Hilbert transform, (B) Use of the z-transform, (C) a fast method based on inverting the least-squares inverse of the wavelets, i.e. inverting the normal time-domain deconvolution operator. Problems associated with these three methods are most acute when the z-transform of α(t) has zeroes on or near the unit circle. Such zeroes result from oversampling or from highly resonant wavelets. The behaviour of the three methods when the energy spectra are perturbed by measurement errors is studied. It is concluded that method (A) is the best of the three. Examples of reconstituted pulses are given which illustrate the variability from trace-to-trace, from shot-to-shot, and from one shot-point medium to another. There is reasonable agreement between the minimum-phase pulses obtained by this statistical analysis of operational records and those estimated from measurements close to the source. However, this comparison incorporates a “fudge-factor” since an allowance for absorption has to be made in order to attenuate the high frequencies present in the pulse measured close to the shot.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 225 (1970), S. 1156-1158 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our object here is briefly to summarize some interesting new findings with gannets (Sula bassana); a full account is in the press3. The interesting features are that the usual frequency-time parameters were of little use in analysing individual vocal features; instead, changes in the amplitude ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 36 (1972), S. 427-447 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relative yield response and phosphate uptake ofS. humilis, P. atropurpureus andD. intortum, grown on a very deficient soil, enriched with phosphate, were measured at four successive harvests during 42 days growth under controlled environmental conditions. Except at the first harvest (19–21 days), the relative yields ofS. humilis andP. atropurpureus at P0 were identical, and slightly greater than that ofD. intortum; the relative response to applied phosphate was similar for the three species, up to the maximum yield attained. The higher relative yield ofD. intortum, at harvest 1, reflected the influence of a higher initial phosphate concentration in the small Desmodium seedling, compared toS. humilis andP. atropurpureus. The mean absorption rate for phosphate $$\overline {\left( {AR} \right)} $$ ofD. intortum, and to a lesser degreeS. humilis andP. atropurpureus, showed two distinct maxima: an initial peak at low soil activities (0.3 — 3µM P), and a second at higher soil activities (37–43µM P) when maximum yield had been attained, and luxury accumulation of phosphate appear to occur. The initial peak in $$\overline {AR} $$ was followed by a decline (significant (P=0.05) forD. intortum) at soil phosphate activities corresponding to maximum yield, suggesting that the rate of absorption by the roots was influenced by the demand for phosphate created within the growing plant. Mean absorption rates and relative growth rates $$\overline {\left( {RGR} \right)} $$ , averaged over all phosphate levels, fell in the orderD. intortum 〉S. humilis 〉P. atropurpureus. Conversely, the efficiency of phosphate utilization by the plant, which may be expected to be greater in plants of low RGR, fell in the orderP. atropurpureus 〉S. humilis 〉D. intortum, and so counteracted the lower $$\overline {AR} $$ ofP. atropurpureus, and to a lesser extent,S. humilis. However,S. humilis had the advantage of a lower retention of phosphate in the root system, compared toP. atropurpureus, due to a relatively greater shortage of nitrogen in the tops when grown on symbiotically-fixed nitrogen.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 36 (1972), S. 427-447 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relative yield response and phosphate uptake ofS. humilis, P. atropurpureus andD. intortum, grown on a very deficient soil, enriched with phosphate, were measured at four successive harvests during 42 days growth under controlled environmental conditions. Except at the first harvest (19–21 days), the relative yields ofS. humilis andP. atropurpureus at P0 were identical, and slightly greater than that ofD. intortum; the relative response to applied phosphate was similar for the three species, up to the maximum yield attained. The higher relative yield ofD. intortum, at harvest 1, reflected the influence of a higher initial phosphate concentration in the small Desmodium seedling, compared toS. humilis andP. atropurpureus. The mean absorption rate for phosphate $$\overline {\left( {AR} \right)} $$ ofD. intortum, and to a lesser degreeS. humilis andP. atropurpureus, showed two distinct maxima: an initial peak at low soil activities (0.3 — 3µM P), and a second at higher soil activities (37–43µM P) when maximum yield had been attained, and luxury accumulation of phosphate appear to occur. The initial peak in $$\overline {AR} $$ was followed by a decline (significant (P=0.05) forD. intortum) at soil phosphate activities corresponding to maximum yield, suggesting that the rate of absorption by the roots was influenced by the demand for phosphate created within the growing plant. Mean absorption rates and relative growth rates $$\overline {\left( {RGR} \right)} $$ , averaged over all phosphate levels, fell in the orderD. intortum 〉S. humilis 〉P. atropurpureus. Conversely, the efficiency of phosphate utilization by the plant, which may be expected to be greater in plants of low RGR, fell in the orderP. atropurpureus 〉S. humilis 〉D. intortum, and so counteracted the lower $$\overline {AR} $$ ofP. atropurpureus, and to a lesser extent,S. humilis. However,S. humilis had the advantage of a lower retention of phosphate in the root system, compared toP. atropurpureus, due to a relatively greater shortage of nitrogen in the tops when grown on symbiotically-fixed nitrogen.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 38 (1973), S. 509-523 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rate of accumulation of phosphorus in the roots, and its transport to the shoots, of whole plants grown in very dilute nutrient solutions, did not conform to the kinetic models derived from studies with excised roots or tissue slices. The demand for phosphorus associated with the rate of plant growth, or the level of metabolic activity within the tissues, appeared to have a marked influence on the rate of phosphorus uptake at deficient to optimum (1 to 10 μM P) levels of supply. A hypothesis is presented whereby the rate of influx of orthophosphate into the root cortical cells is regulated by the turn-over rate of the pool of inorganic phosphate in the cytoplasm, and by the rate of transport of inorganic phosphate to the shoot. The turn-over rate of this labile pool depends on inherent factors, such as the relative growth rate of the species, and on environmental factors, including the supply of essential nutrients such as nitrogen. re]19720502
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 1419-1426 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of polycarbonates with pendent ester groups have been synthesized. These ester groups have been converted to hydroxyl functionalities by reduction with diborane in tetrahydrofuran. The number of methylene groups in the pendent chain has a large effect on the reducibility of the ester.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 1971-10-01
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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  • 10
    Publication Date: 1973-06-01
    Print ISSN: 0032-079X
    Electronic ISSN: 1573-5036
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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