Upscaling microbial chemotaxis in porous media     

Francisco J. Valds-Parada  Mark L. Porter  Karthik Narayanaswamy  Roseanne M. Ford  Brian D. Wood 《Advances in water resources》2009,32(9):1413-1428

Biodegradation is an important mechanism for contaminant reduction in groundwater environments; in fact, in situ bioremediation and bioaugmentation methods represent alternatives to traditional methods such as pump-and-treat. Microbial chemotaxis has been shown to significantly increase contaminant degradation in subsurface environments. In this work, the method of volume averaging is used to upscale the microscale chemotactic microbial transport equations in order to obtain the corresponding effective medium models for the mass balance of bacteria and the chemical attractant to which they respond. As a first approach, cellular growth/death and consumption of the attractant by chemical reaction are assumed to be negligible with respect to convective and diffusive transport mechanisms. For microorganisms, two effective coefficients are introduced, namely a total motility tensor and a total velocity vector. Our results show that, under certain conditions, these coefficients can differ considerably from the values corresponding to non-chemotactic transport. These transport coefficients show strong dependence of the microstructure of the porous medium, the fluid flow fields and the distribution of the attractant.  相似文献   

Quantification of seismic potential failure modes in concrete dams          下载免费PDF全文

Mohammad Amin Hariri‐Ardebili  Victor. E. Saouma  Keith A. Porter 《地震工程与结构动力学》2016,45(6):979-997

A comprehensive framework for potential failure modes (PFM) identification and quantification of concrete dams subjected to seismic excitation is presented. A quantifiable indicator of PFM is presented in the context of both linear and nonlinear analyses. As an illustrative example, a thin arch dam subjected to a set of ground motions at different seismic intensity levels is investigated and corresponding PFM quantified. An outcome of this analysis is the probabilistic‐based correlation between linear and nonlinear analyses and identification of the optimal intensity measure parameter. This study, is an adaptation and extension of well‐accepted procedures defined by the performance‐based earthquake engineering paradigm in buildings. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Compositions of four unusual CM or CM-related Antarctic chondrites     

Gina M. Moriarty  Douglas Rumble III 《Chemie der Erde / Geochemistry》2009,69(2):161-2323

To identify chemical group affinities and infer the occurrence of thermal metamorphism or aqueous alteration in their histories, we quantified 43 trace elements in the CM or CM-related Antarctic carbonaceous chondrites EET 96010, LAP 02277, MET 01070, and WIS 91600. We also analyzed LAP 02206, a CV chondrite, to add to our comparison database. We present whole-rock oxygen isotope data for LAP 02206, LAP 02277, and MET 01070 to complement our trace element results. With these data, we confirm the CV classification of LAP 02206 and CM or CM-like classification for the other four chondrites in this study. On the basis of moderately volatile element content, our results show that EET 96010 experienced open-system heating, while any heating LAP 02277 and MET 01070 may have experienced was in a chemically closed-system. WIS 91600, on a trace element basis, appears to be CM-like material. Our analyses support the idea that CM material has experienced a wide variety of post-accretionary processing.  相似文献   

Real Time Analysis and Display of Scanning Lidar Scattering Data     

B. R. Lienert  J. N. Porter  S. K. Sharma 《Marine Geodesy》1999,22(4):259-265

We describe software for an IBM compatible personal computer (PC) that we have developed and used to collect and analyze backscatter data from a multi-wavelength Mie-Rayleigh scanning lidar system. Both one and two-dimensional distributions of optical scattering coefficients are calculated from the lidar return signals and displayed in real time. Although we are using the software for analyzing marine aerosols, the modular nature of the software and data acquisition drivers make it straightforward to adapt the software to different systems, such as differential absorption lidar (DIAL) and oceanic lidars. We show examples of both horizontal and vertical Mie-Rayleigh lidar scans collected at the Makai Pier and Bellows Beach on the northeast side of the island of Oahu.  相似文献   

Defining and estimating global marine fisheries bycatch     

R.W.D. Davies  S.J. Cripps  A. Nickson  G. Porter 《Marine Policy》2009

Unselective fishing catches non-target organisms as ‘bycatch’—an issue of critical ocean conservation and resource management concern. However, the situation is confused because perceptions of target and non-target catch vary widely, impeding efforts to estimate bycatch globally. To remedy this, the term needs to be redefined as a consistent definition that establishes what should be considered bycatch. A new definition is put forward as: ‘bycatch is catch that is either unused or unmanaged’. Applying this definition to global marine fisheries data conservatively indicates that bycatch represents 40.4 percent of global marine catches, exposing systemic gaps in fisheries policy and management.  相似文献   

Ocean-bottom seismograph observations on the Mid-Atlantic Ridge near 45° N     

R. C. Ldwall  T. J. G. Francis  I. T. Porter 《Geophysical Journal International》1977,51(2):357-370

Summary. Rayleigh-wave phase velocities at very long periods (185–290 s) are investigated and regionalized, taking into account the lateral heterogeneities within ocean plates revealed by earlier studies at shorter periods. The two-station method is applied to a few 'pure-age' oceanic paths, and is shown to be compatible with the average Earth model C2 (Anderson & Hart 1976) below depths of 180 km. Under this assumed oceanic model, regionalized for age above 180 km, continental velocities are then derived from a set of experimental great-circle values, both new or taken from previously published studies. The results basically agree with earlier studies (Dziewonski 1970; Kanamori 1970), although they exhibit less scatter than Kanamori's model. Results are successfully checked against a set of values derived by the two-station method from a pure continental path.
Although the shield velocities are substantially different from the mean oceanic ones, they still fall within the range of variation of oceanic velocities with the age of the plate. This makes velocities derived theoretically from Jordan's (1975a, b) models of deep continent—ocean lateral heterogeneities, inconsistent with the present set of experimental data. Finally, we show that Dziewonski's (1971) model S2 reconciles all experimental seismic data relative to shields, without being significantly different from oceanic models below 240 km.  相似文献   

ERRORS IN PARALLAX MEASUREMENTS AND THEIR ASSESSMENT IN STUDENT EXERCISES     

R. F. D. Porter  Goff 《The Photogrammetric Record》1975,8(46):528-534

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Laboratory Tests on Thin Spray-On Liner Penetrated Rock Joints in Direct Shear     

Qiuqiu Qiao  Jan Nemcik  Ian Porter  Ernest Baafi 《Rock Mechanics and Rock Engineering》2015,48(5):2173-2177

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Improvements to Shellfish Harvest Area Closure Decision Making Using GIS,Remote Sensing,and Predictive Models     

Rense Heath Kelsey  Geoffrey I. Scott  Dwayne E. Porter  Thomas C. Siewicki  Donald G. Edwards 《Estuaries and Coasts》2010,33(3):712-722

Currently, many states use precipitation information to regulate periodic closures of shellfish harvest areas based on a presumptive relationship between rainfall and bacteria concentration. We evaluate this relationship in four South Carolina estuaries and suggest new predictive models that integrate remote sensing precipitation data with additional environmental and climatic data. Model comparisons using Akaike’s information criterion, tenfold cross-validation, and model r ² values show substantial and consistent improvements using integrated precipitation, salinity, and water temperature data as predictors. These models may be useful for shellfish area closure regulation support. The model development approaches used here may also be useful in estimating bacteria concentration at beaches and can serve as the basis for developing near-real-time estimates and forecast predictions of bacteria levels for closure decision-making tools.  相似文献   

Evolutionary models for two hyper-iron-poor low-mass stars     

Gregory J. Harris  Rachael Porter  A. E. Lynas-Gray  Jonathan Tennyson 《Monthly notices of the Royal Astronomical Society》2007,377(4):1520-1530

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