A solid state sensor for mapping and profiling stimulated bioluminescence in the marine environment     

J. Aiken  J. Kelly 《Continental Shelf Research》1984,3(4):455-464

This paper describes the design and development of a solid state sensor for the measurement, in situ, of stimulable bioluminescence of marine organisms. It can be towed in the Undulating Oceanographic Recorder or used in vertical profiling mode from a stationary research vessel. The sensor can detect signals from 10⁹ quanta s⁻¹, from a single dinoflagellate flash, up to 10¹³ quanta s⁻¹, at cell densities of 10⁶ to 10⁸ m⁻³. Measurements of bioluminescence and associated environmental conditions are presented from a variety of deployments of the sensor in the Undulating Oceanographic Recorder.  相似文献   

Additive versus multiplicative models in ecologic regression     

W. Douglas Thompson  Daniel Wartenberg 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(5):635-646

Much research in environmental epidemiology relies on aggregate-level information on exposure to potentially toxic substances and on relevant covariates. We compare the use of additive (linear) and multiplicative (log-linear) regression models for the analysis of such data. We illustrate how both additive and multiplicative models can be fit to aggregate-level data sets in which disease incidence is the dependent variable, and contrast these results with similar models fitted to individual-level data. We find (1) that for aggregate-level data, multiplicative models are more likely than additive models to introduce bias into the estimation of rates, an effect not found with individual-level data; and (2) that under many circumstances multiplicative models reduce the precision of the estimates, an effect also not found in individual-level models. For both additive and multiplicative models of aggregate-level data, we find that, in the presence of covariates, narrow confidence interval are obtained only when two or more antecedent factors are strongly related to the measured covariate and/or the exposure of primary substantive interest. We conclude that the equivalency of fitting additive versus multiplicative models in studies with individual-level binary data does not carry over to studies that analyze aggregate-level information. For aggregate data, we strongly recommend use of additive models. Supported by Grant #1 U19 EH000102 from the National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA.  相似文献   

Relation Between Anisotropic Transmissivity and Azimuthal Resistivity Surveys in Shallow, Fractured, Carbonate Flow Systems   总被引：2，自引：0，他引：2  

Robert William Ritzi  Jr.  Robert Henry Andolsek 《Ground water》1992,30(5):774-780

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Revising the paradigm of tidal analysis – the uses of non-stationary data     

David A.?JayEmail author  Tobias?Kukulka 《Ocean Dynamics》2003,53(3):110-125

Surface elevation and current records contain non-tidal variance, often dismissed as noise. The processes responsible for the non-tidal component may also modulate the tidal signal, altering its strength and frequency structure. Because of their manner of generation and propagation, internal tides are inherently irregular. The non-stationary character of these and other tidal processes provides an integral and useful property of tidal records, because it provides an opportunity to obtain insights into tidal dynamics and the interaction of tidal and non-tidal processes. It is, moreover, productive to use multiple approaches in analyzing coastal and estuarine tidal processes so that both the time-varying and average frequency content are determined. Only by confronting the causes of non-stationary behaviour in this way can some of the remaining challenges in tidal analysis and prediction be overcome, e.g. shelf and estuarine currents, river tides, internal tides, tide-surge interactions and tidally influenced ecological processes. Several examples illustrate the utility of non-stationary tidal analysis methods.Responsible Editor: Jens Kappenberg  相似文献   

Observations of the Polar Magnetic Fields During the Polarity Reversals of Cycle 22     

Snodgrass  H.B.  Kress  J.M.  Wilson  P.R. 《Solar physics》2000,191(1):1-19

The Mount Wilson synoptic magnetic data for the period September 1987 through March 1996 are completely revised and used to provide polar plots of the solar magnetic fields for both hemispheres. This period, from Carrington rotations 1793 to 1906, covers the reversals of the polar magnetic fields in cycle 22. Comparison of our plots with the presently available H filtergrams for this period shows that the polarity boundaries are consistent in these two data sets where they overlap. The Mount Wilson plots show that the polar field reversals involve a complex sequence of events. Although the details differ slightly, the basic patterns are similar in each hemisphere. First the old polarity becomes isolated at the pole, then shortly thereafter, the isolation is broken, and the polar field includes unipolar regions of both polarities. The old polarity then reclaims the polar region, but when the isolation of this field is established for a second time, it declines in both area and strength. We take the reversal to be complete when the old polarity field is no longer observed in the Mount Wilson plots. With this criterion we find that the polar field reversal is completed in the north by CR 1836, i.e., by December 1990, and in the south by CR 1853, i.e., March 1992.  相似文献   

Aggregate production: Fines generation during rock crushing     

M.S. Guimaraes  J.R. Valdes  A.M. Palomino  J.C. Santamarina 《International Journal of Mineral Processing》2007

The energy required to crush rocks is proportional to the amount of new surface area that is created; hence, a very important percentage of the energy consumed to produce construction aggregates is spent in producing non-commercial fines. Data gathered during visits to quarries, an extensive survey and laboratory experiments are used to explore the role of mineralogy and fracture mode in fines production during the crushing of single aggregates and aggregates within granular packs. Results show that particle-level loading conditions determine the failure mode, resulting particle shape and fines generation. Point loading (both single particles and grains in loose packings) produces clean fractures and a small percentage of fines. In choked operations, high inter-particle coordination controls particle-level loading conditions, causes micro-fractures on new aggregate faces and generates a large amount of fines. The generation of fines increases when shear is imposed during crushing. Aggregates produced in current crushing operations show the effects of multiple loading conditions and fracture modes. Results support the producers' empirical observations that the desired cubicity of aggregates is obtained at the expense of increased fines generation when standard equipment is used.  相似文献   

Particle trapping in stratified estuaries: consequences of mass conservation     

David A. Jay  Philip M. Orton  Thomas Chisholm  Douglas J. Wilson  Annika M. V. Fain 《Estuaries and Coasts》2007,30(6):1095-1105

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Solubility of KFe(CrO₄)₂·2H₂O at 4–75°C     

Dirk Baron  Carl D. Palmer 《Applied Geochemistry》1998,13(8):961-973

The solubility of KFe(CrO₄)₂·2H₂O, a precipitate recently identified in a Cr(VI)-contaminated soil, was studied in dissolution and precipitation experiments. Ten dissolution experiments were conducted at 4–75°C and initial pH values between 0.8 and 1.2 using synthetic KFe(CrO₄)₂·2H₂O. Four precipitation experiments were conducted at 25°C with final pH values between 0.16 and 1.39. The log K_SP for the reaction