Gauging the impact of fishing mortality on non-target species   总被引：4，自引：4，他引：0  

Pope  John G.; Macdonald  Dave S.; Daan  Niels; Reynolds  John D.; Jennings  Simon 《ICES Journal of Marine Science》2000,57(3):689-696

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George Housner: A Personal Remembrance (1910–2008)     

Paul C. Jennings 《地震工程与结构动力学》2009,38(3):269-284

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The C/C isotopic ratio in Titan hydrocarbons from Cassini/CIRS infrared spectra     

C.A. Nixon  R.K. Achterberg  B. Bézard  P.G.J. Irwin  R. de Kok  D.E. Jennings  F.M. Flasar 《Icarus》2008,195(2):778-791

We have analyzed infrared spectra of Titan recorded by the Cassini Composite Infrared Spectrometer (CIRS) to measure the isotopic ratio ¹²C/¹³C in each of three chemical species in Titan's stratosphere: CH₄, C₂H₂ and C₂H₆. This is the first measurement of ¹²C/¹³C in any C₂ molecule on Titan, and the first measurement of ¹²CH₄/¹³CH₄ (non-deuterated) on Titan by remote sensing. Our spectra cover five widely-spaced latitudes, 65° S to 71° N and we have searched for both latitude variability of ¹²C/¹³C within a given species, and also for differences between the ¹²C/¹³C in the three gases. For CH₄ alone, we find (1-σ), essentially in agreement with the ¹²CH₄/¹³CH₄ measured by the Huygens Gas Chromatograph/Mass Spectrometer instrument (GCMS) [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784]: 82.3±1.0, and also with measured values in H¹³CN and ¹³CH₃D by CIRS at lower precision [Bézard, B., Nixon, C., Kleiner, I., Jennings, D., 2007. Icarus 191, 397-400; Vinatier, S., Bézard, B., Nixon, C., 2007. Icarus 191, 712-721]. For the C₂ species, we find in C₂H₂ and 89.8±7.3 in C₂H₆, a possible trend of increasingly value with molecular mass, although these values are both compatible with the Huygens GCMS value to within error bars. There are no convincing trends in latitude. Combining all fifteen measurements, we obtain a value of , also compatible with GCMS. Therefore, the evidence is mounting that ¹²C/¹³C is some 8% lower on Titan than on the Earth (88.9, inorganic standard), and lower than typical for the outer planets (88±7 [Sada, P.V., McCabe, G.H., Bjoraker, G.L., Jennings, D.E., Reuter, D.C., 1996. Astrophys. J. 472, 903-907]). There is no current model for this enrichment, and we discuss several mechanisms that may be at work.  相似文献   

Ice flow‐unit influence on glacier structure,debris entrainment and transport          下载免费PDF全文

Stephen J.A. Jennings  Michael J. Hambrey  Neil F. Glasser 《地球表面变化过程与地形》2014,39(10):1279-1292

The links between structural glaciology, glacial debris entrainment and transport have been established in a number of different glacier settings. Here we document the structural evolution of a temperate Alpine valley glacier (Vadrec del Forno, Switzerland) and demonstrate that individual flow units within the glacier have very different structural and debris characteristics. The glacier consists of a broad accumulation area with multiple basins feeding a relatively narrow tongue and is formed from six distinct flow units. Each flow unit has its own characteristic structural assemblage. Flow units that narrow rapidly down‐glacier are dominated by primary stratification that has evolved into longitudinal foliation. In contrast, wider flow units preferentially develop an axial planar foliation. Glacier structure plays a limited role in the entrainment of debris, which is more strongly influenced by ice‐marginal rockfall and avalanche inputs onto the glacier surface. However, once entrained, glacier structure controls the reorientation and redistribution of debris within the ice mass. By taking a whole‐glacier approach to describing glacier structure and debris transport, we conclude that individual flow units are unique with regard to structure and debris transfer. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

ON CONFIDENCE INTERVALS FOR THE PRODUCT OF THREE MEANS OF THREE NORMALEY DISTRIBUTED POPULATIONS     

E.A.YFANTIS Computer Science Department  University of Neva  Las Vegas  NV  U.S.A.G.T.FLATMAN U.S.Environmental Protection Agency  E.Harmon  Las Vegas  NV  U.S.A. 《地理学报(英文版)》1991,(3)

In many environmental applications,such as exposure assessment and risk modelling,the desiredestimate is a random variable computed as the product of three independently distributed randomvariables.These variables may not necessarily have the same mean and variance.The method for findingthe 100(1-α)% confidence interval for the mean of the product random variable has been proposed bysome practitioners as the product of the 100(1-α)% confidence interval of the three means.In this paperwe show that the distribution of the product of three independent normal random variables is not normal.We find the mean and variance of the product distribution.Further,we show that although the meanof the product is equal to the product of the means,the product of the three confidence intervals is nota good approximation of the confidence intervals for the mean of the product variable.The confidenceinterval of the mean of the product variable may be estimated by computer simulation.An algorithmfor estimating the confidence interval for the mean of the product random variable is given.The programimplementing this algorithm is given as an appendix.  相似文献   

Calculation of selected ordinates of fourier spectra     

Paul C. Jennings 《地震工程与结构动力学》1973,2(3):281-293

A method is presented for calculating single or, by repeated use, selected ordinates of Fourier spectra rapidly and efficiently. The approach differs from standard methods in that any frequency consistent with the interval of digitization may be chosen and records of arbitrary length may be analysed. The method is based on the relation between Fourier spectra of an accelerogram and the final response of an undamped oscillator to the same accelerogram. This relation is reviewed and extended to aid the development of the computing method and to assist in the interpretation of Fourier spectrum techniques in earthquake engineering. Because only the terminal values of the response of an undamped oscillator are required to define the Fourier spectra, repeated application of superposition is used to form equivalent excitations with durations of only one-quarter of the period of the oscillator.  相似文献   

The response of veterans hospital building 41 in the San Fernando earthquake     

Avigdor Rutenberg  Paul C. Jennings  George W. Housner 《地震工程与结构动力学》1982,10(3):359-379

During the 9 February, 1971 San Fernando earthquake, Building 41 of the Veterans Administration Hospital was in an area of very strong snaking; being directly over a portion of the causative fault; it is estimated that the building experienced a maximum base shear of 60 to 130 per cent of the weight of the structure. It survived with very minor structural damage, although designed with a lateral force coefficient of only 10 per cent. The study attempts to reconcile these facts by analysis of the transverse response of the building. A code-oriented, lateral force analysis is only partially successful in this reconciliation in that it indicates first yield at lateral loads of 15–20 per cent of the weight of the structure, with a capacity of 35–45 per cent if redistribution of loads among the walls is permitted. The capacity against static overturning is 45–50 per cent. A dynamic analysis of a fixed-base three-dimensional linear model of the structure gives essentially the same results. A third study of a two-dimensional, dynamic model incorporating partial uplift and soil yielding indicates that the successful response of the building is attributable to the large strength built into the structure and the beneficial effects of non-linear soil-structure interaction.  相似文献