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Articles 1 - 6 of 6
Full-Text Articles in Physical Sciences and Mathematics
Evidence For Microbial Enhanced Electrical Conductivity In Hydrocarbon-Contaminated Sediments, Estella A. Atekwana, Eliot A. Atekwana, D. Dale Werkema, Jonathan P. Allen, Laura A. Smart, Joseph W. Duris, Daniel P. Cassidy, William A. Sauck, Silvia Rossbach
Evidence For Microbial Enhanced Electrical Conductivity In Hydrocarbon-Contaminated Sediments, Estella A. Atekwana, Eliot A. Atekwana, D. Dale Werkema, Jonathan P. Allen, Laura A. Smart, Joseph W. Duris, Daniel P. Cassidy, William A. Sauck, Silvia Rossbach
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Bulk electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale laboratory experiment consisting of biotic contaminated and uncontaminated columns. Population numbers of oil degrading microorganisms increased with a clear pattern of depth zonation within the contaminated column not observed in the uncontaminated column. Microbial community structure determined from ribosomal DNA intergenic spacer analysis showed a highly specialized microbial community in the contaminated column. The contaminated column showed temporal increases in bulk conductivity, dissolved inorganic carbon, and calcium, suggesting that the high bulk conductivity is due to enhanced mineral weathering from microbial activity. The greatest change …
Field Evidence For Geophysical Detection Of Subsurface Zones Of Enhanced Microbial Activity, Eliot A. Atekwana, Estella A. Atekwana, Franklyn D. Legall, R. V. Krishnamurthy
Field Evidence For Geophysical Detection Of Subsurface Zones Of Enhanced Microbial Activity, Eliot A. Atekwana, Estella A. Atekwana, Franklyn D. Legall, R. V. Krishnamurthy
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Geochemical data from closely spaced vertical intervals in a hydrocarbon-impacted aquifer were used to assess the relationship between bulk conductivity and zones of enhanced microbial activity. The bulk conductivity was measured using in situ vertical resistivity probes. Microbial activity was verified using terminal electron acceptors (nitrate, sulfate, iron, and manganese), dissolved inorganic carbon (DIC), and major ion chemistry. Peaks in bulk conductivity in the aquifer overlapped with zones where nitrates and sulfates were depleted, total petroleum hydrocarbon, iron, manganese, dissolved ions, and DIC were elevated, suggesting a link between higher electrical conductivity and zones of enhanced microbial activity stimulated by …
Hopping Versus Bulk Conductivity In Transparent Oxides: 12cao - 7al₂O₃, Julia E. Medvedeva, Arthur J. Freeman
Hopping Versus Bulk Conductivity In Transparent Oxides: 12cao - 7al₂O₃, Julia E. Medvedeva, Arthur J. Freeman
Physics Faculty Research & Creative Works
First-principles calculations of the mayenite-based oxide, [Ca12Al14O32]2+(2e-), reveal the mechanism responsible for its high conductivity. A detailed comparison of the electronic and optical properties of this material with those of the recently discovered transparent conducting oxide, H-doped UV-activated Ca12Al14O33, allowed us to conclude that the enhanced conductivity in [Ca12Al14O32]2+(2e-) is achieved by elimination of the Coulomb blockade of the charge carriers. This results in a transition from variable range-hopping behavior with a Coulomb gap in H-doped UV-irradiated Ca …
Electronic Structure And Light-Induced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Electronic Structure And Light-Induced Conductivity Of A Transparent Refractory Oxide, Julia E. Medvedeva, Arthur J. Freeman, Mariana I. Bertoni, Thomas O. Mason
Physics Faculty Research & Creative Works
Combined first-principles and experimental investigations reveal the underlying mechanism responsible for a drastic change of the conductivity (by 10 orders of magnitude) following hydrogen annealing and UV irradiation in a transparent oxide, 12CaO · 7Al2O3, found by Hayashi et al. [Nature (London) 419, 462 (2002).] The charge transport associated with photoexcitation of an electron from H- occurs by electron hopping.We identify the atoms participating in the hops, determine the exact paths for the carrier migration, estimate the temperature behavior of the hopping transport, and predict a way to enhance the conductivity by specific doping.
Effects Of Microbial Processes On Electrolytic And Interfacial Electrical Properties Of Unconsolidated Sediments, Gamal Z. Abdal Aal, Estella A. Atekwana, Lee D. Slater, Eliot A. Atekwana
Effects Of Microbial Processes On Electrolytic And Interfacial Electrical Properties Of Unconsolidated Sediments, Gamal Z. Abdal Aal, Estella A. Atekwana, Lee D. Slater, Eliot A. Atekwana
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The effect of microbial processes on electrical properties of unconsolidated sediments was investigated in a laboratory experiment consisting of biotic and abiotic sand columns. The biotic column (nutrient, diesel and bacteria) showed (a) temporal increase in the real, imaginary, and surface conductivity, and (b) temporal decrease in the formation factor. The abiotic columns (nutrient; and nutrient and diesel) showed no significant changes. Increase in microbial population numbers, decrease in organic carbon source, nitrate, and sulfate and increase in dissolved inorganic carbon and fluid conductivity were indicative of microbial activity in the biotic column. We also measure relative increase in the …
In-Situ Apparent Conductivity Measurements And Microbial Population Distribution At A Hydrocarbon-Contaminated Site, Estella A. Atekwana, D. Dale Werkema, Joseph W. Duris, Silvia Rossbach, Eliot A. Atekwana, William A. Sauck, Daniel P. Cassidy, Jay Means, Franklyn D. Legall
In-Situ Apparent Conductivity Measurements And Microbial Population Distribution At A Hydrocarbon-Contaminated Site, Estella A. Atekwana, D. Dale Werkema, Joseph W. Duris, Silvia Rossbach, Eliot A. Atekwana, William A. Sauck, Daniel P. Cassidy, Jay Means, Franklyn D. Legall
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light nonaqueous-phase liquid (LNAPL). The bulk conductivity was measured using in-situ vertical resistivity probes; the most probable number method was used to characterize the spatial distribution of aerobic heterotrophic and oil-degrading microbial populations. The purpose of this study was to assess if high conductivity observed at aged LNAPL-impacted sites may be related to microbial degradation of LNAPL. The results show higher bulk conductivity coincident with LNAPL-impacted zones, in contrast to geoelectrical models that predict lower conductivity in such zones. The highest bulk conductivity …