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Analysis of Injection-Induced Micro-Earthquakes in a Geothermal Steam Reservoir, The Geysers Geothermal Field, California

Description: In this study we analyze relative contributions to the cause and mechanism of injection-induced micro-earthquakes (MEQs) at The Geysers geothermal field, California. We estimated the potential for inducing seismicity by coupled thermal-hydrological-mechanical analysis of the geothermal steam production and cold water injection to calculate changes in stress (in time and space) and investigated if those changes could induce a rock mechanical failure and associated MEQs. An important aspect of th… more
Date: May 15, 2008
Creator: Rutqvist, Jonny; Rutqvist, J. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department
open access

Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems

Description: Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic con… more
Date: March 15, 2008
Creator: Seol, Yongkoo & Javandel, Iraj
Partner: UNT Libraries Government Documents Department
open access

Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

Description: Where Martian rocks have been exposed to liquid water, chemistry versus depth profiles could elucidate both Martian climate history and potential for life. The persistence of primary minerals in weathered profiles constrains the exposure time to liquid water: on Earth, mineral persistence times range from {approx}10 ka (olivine) to {approx}250 ka (glass) to {approx}1Ma (pyroxene) to {approx}5Ma (plagioclase). Such persistence times suggest mineral persistence minima on Mars. However, Martian so… more
Date: March 15, 2008
Creator: Steefel, Carl; Hausrath, E. M.; Navarre-Sitchler, A. K.; Sak, P. B.; Steefel, C. & Brantley, S. L.
Partner: UNT Libraries Government Documents Department
open access

Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis

Description: Starch branching enzyme (SBE) activity in the cassava storage root exhibited a diurnal fluctuation, dictated by a transcriptional oscillation of the corresponding SBE genes. The peak of SBE activity coincided with the onset of sucrose accumulation in the storage, and we conclude that the oscillatory mechanism keeps the starch synthetic apparatus in the storage root sink in tune with the flux of sucrose from the photosynthetic source. When storage roots were uncoupled from the source, SBE expres… more
Date: January 15, 2008
Creator: Jansson, Christer; Baguma, Yona; Sun, Chuanxin; Boren, Mats; Olsson, Helena; Rosenqvist, Sara et al.
Partner: UNT Libraries Government Documents Department
open access

Ground Penetrating Radar in Hydrogeophysics

Description: To meet the needs of a growing population and to provide us with a higher quality of life, increasing pressures are being placed on our environment through the development of agriculture, industry, and infrastructures. Soil erosion, groundwater depletion, salinization, and pollution have been recognized for decades as major threats to ecosystems and human health. More recently, the progressive substitution of fossil fuels by biofuels for energy production and climate change have been recognized… more
Date: January 15, 2008
Creator: Hubbard, Susan; Lambot, S.; Binley, A.; Slob, E. & Hubbard, S.
Partner: UNT Libraries Government Documents Department
open access

The continental margin is a key source of iron to the HNLC North Pacific Ocean

Description: Here we show that labile particulate iron and manganese concentrations in the upper 500m of the Western Subarctic Pacific, an iron-limited High Nutrient Low Chlorophyll (HNLC) region, have prominent subsurface maxima between 100-200 m, reaching 3 nM and 600 pM, respectively. The subsurface concentration maxima in particulate Fe are characterized by a more reduced oxidation state, suggesting a source from primary volcagenic minerals such as from the Kuril/Kamchatka margin. The systematics of the… more
Date: January 15, 2008
Creator: Lam, P. J. & Bishop, J. K. B
Partner: UNT Libraries Government Documents Department
open access

Gravity monitoring of CO2 movement during sequestration: Model studies

Description: We examine the relative merits of gravity measurements as a monitoring tool for geological CO{sub 2} sequestration in three different modeling scenarios. The first is a combined CO{sub 2} enhanced oil recovery (EOR) and sequestration in a producing oil field, the second is sequestration in a brine formation, and the third is for a coalbed methane formation. EOR/sequestration petroleum reservoirs have relatively thin injection intervals with multiple fluid components (oil, hydrocarbon gas, brine… more
Date: July 15, 2008
Creator: Gasperikova, E. & Hoversten, G.M.
Partner: UNT Libraries Government Documents Department
open access

Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations

Description: The interactions between two plant growth promoting rhizobacteria (PGPR), Pseudomonas fluorescens SBW25 and Paenibacillus brasilensis PB177, two arbuscular mycorrhizal (AM) fungi (Glomus mosseae and G. intraradices) and one pathogenic fungus (Microdochium nivale) were investigated on winter wheat (Triticum aestivum cultivar Tarso) in a greenhouse trial. PB177, but not SBW25, had strong inhibitory effects on M. nivale in dual culture plate assays. The results from the greenhouse experiment show … more
Date: May 15, 2008
Creator: Jaderlund, Lotta; Arthurson, Veronica; Granhall, Ulf & Jansson, Janet K.
Partner: UNT Libraries Government Documents Department
open access

UXO detection and identification based on intrinsic target polarizabilities: A case history

Description: Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the obje… more
Date: July 15, 2008
Creator: Gasperikova, E.; Smith, J.T.; Morrison, H.F.; Becker, A. & Kappler, K.
Partner: UNT Libraries Government Documents Department
open access

Poroelastic modeling of fracture-seismic wave interaction

Description: Rock containing a compliant, fluid-filled fracture can be viewed as one case of heterogeneous poroelastic media. When this fracture is subjected to seismic waves, a strong contrast in the elastic stiffness between the fracture itself and the background can result in enhanced grain-scale local fluid flow. Because this flow--relaxing the pressure building up within the fracture--can increase the dynamic compliance of the fracture and change energy dissipation (attenuation), the scattering of seis… more
Date: August 15, 2008
Creator: Nakagawa, Seiji
Partner: UNT Libraries Government Documents Department
open access

Joint inversion of crosshole radar and seismic traveltimes acquired at the South Oyster BacterialTransport Site

Description: The structural approach to joint inversion, entailing common boundaries or gradients, offers a flexible way to invert diverse types of surface-based and/or crosshole geophysical data. The cross-gradients function has been introduced as a means to construct models in which spatial changes in two models are parallel or anti-parallel. Inversion methods that use such structural constraints also provide estimates of non-linear and non-unique field-scale relationships between model parameters. Here, … more
Date: April 15, 2008
Creator: Linde, Niklas; Tryggvason, Ari; Peterson, John & Hubbard, Susan
Partner: UNT Libraries Government Documents Department
open access

Spectral induced polarization and electrodic potential monitoring of microbially mediated iron sulfide transformations

Description: Stimulated sulfate-reduction is a bioremediation technique utilized for the sequestration of heavy metals in the subsurface.We performed laboratory column experiments to investigate the geoelectrical response of iron sulfide transformations by Desulfo vibriovulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential measurements, were investigated. Aqueous geochemistry (sulfate, lactate, sulfide, and acetate), observations of precipitates (identifi… more
Date: February 15, 2008
Creator: Hubbard, Susan; Personna, Y.R.; Ntarlagiannis, D.; Slater, L.; Yee, N.; O'Brien, M. et al.
Partner: UNT Libraries Government Documents Department
open access

A comparison between Gauss-Newton and Markov chain Monte Carlo basedmethods for inverting spectral induced polarization data for Cole-Coleparameters

Description: We develop a Bayesian model to invert spectral induced polarization (SIP) data for Cole-Cole parameters using Markov chain Monte Carlo (MCMC) sampling methods. We compare the performance of the MCMC based stochastic method with an iterative Gauss-Newton based deterministic method for Cole-Cole parameter estimation through inversion of synthetic and laboratory SIP data. The Gauss-Newton based method can provide an optimal solution for given objective functions under constraints, but the obtained… more
Date: May 15, 2008
Creator: Chen, Jinsong; Kemna, Andreas & Hubbard, Susan S.
Partner: UNT Libraries Government Documents Department
open access

A Semi-Analytical Solution for Large-Scale Injection-Induced PressurePerturbation and Leakage in a Laterally Bounded Aquifer-AquitardSystem

Description: A number of (semi-)analytical solutions are available to drawdown analysis and leakage estimation of shallow aquifer-aquitard systems. These solutions assume that the systems are laterally infinite. When a large-scale pumping from (or injection into) an aquifer-aquitard system of lower specific storativity occurs, induced pressure perturbation (or hydraulic head drawdown/rise) may reach the lateral boundary of the aquifer. We developed semi-analytical solutions to address the induced pressure p… more
Date: July 15, 2008
Creator: Zhou, Quanlin; Birkholzer, Jens T. & Tsang, Chin-Fu
Partner: UNT Libraries Government Documents Department
open access

Antisense oligodeoxynucleotide inhibition as a potent diagnostic tool for gene function in plant biology

Description: Antisense oligodeoxynucleotide (ODN) inhibition emerges as an effective means for probing gene function in plant cells. Employing this method we have established the importance of the SUSIBA2 transcription factor for regulation of starch synthesis in barley endosperm, and arrived at a model for the role of the SUSIBAs in sugar signaling and source-sink commutation during cereal endosperm development. In this addendum we provide additional data demonstrating the suitability of the antisense ODN … more
Date: January 15, 2008
Creator: Jansson, Christer; Sun, Chuanxin; Ghebramedhin, Haile; Hoglund, Anna-Stina & Jansson, Christer
Partner: UNT Libraries Government Documents Department
open access

Reservoir permeability from seismic attribute analysis

Description: In case of porous fluid-saturated medium the Biot's poroelasticity theory predicts a movement of the pore fluid relative to the skeleton on seismic wave propagation through the medium. This phenomenon opens an opportunity for investigation of the flow properties of the hydrocarbon-saturated reservoirs. It is well known that relative fluid movement becomes negligible at seismic frequencies if porous material is homogeneous and well cemented. In this case the theory predicts an underestimated sei… more
Date: February 15, 2008
Creator: Silin, Dmitriy; Goloshubin, G.; Silin, D.; Vingalov, V.; Takkand, G. & Latfullin, M.
Partner: UNT Libraries Government Documents Department
open access

Exact Averaging of Stochastic Equations for Flow in Porous Media

Description: It is well known that at present, exact averaging of the equations for flow and transport in random porous media have been proposed for limited special fields. Moreover, approximate averaging methods--for example, the convergence behavior and the accuracy of truncated perturbation series--are not well studied, and in addition, calculation of high-order perturbations is very complicated. These problems have for a long time stimulated attempts to find the answer to the question: Are there in exis… more
Date: March 15, 2008
Creator: Karasaki, Kenzi; Shvidler, Mark & Karasaki, Kenzi
Partner: UNT Libraries Government Documents Department
open access

Mesoscale Characterization of Coupled Hydromechanical Behavior of a Fractured Porous Slope in Response to Free Water-Surface Movement

Description: To better understand the role of groundwater-level changes on rock-slope deformation and damage, a carbonate rock slope (30 m x 30 m x 15 m) was extensively instrumented for mesoscale hydraulic and mechanical measurements during water-level changes. The slope is naturally drained by a spring that can be artificially closed or opened by a water gate. In this study, a 2-hour slope-dewatering experiment was analyzed. Changes in fluid pressure and deformation were simultaneously monitored, both at … more
Date: May 15, 2008
Creator: Rutqvist, Jonny; Guglielmi, Y.; Cappa, F.; Rutqvist, J.; Tsang, C.-F. & Thoraval, A.
Partner: UNT Libraries Government Documents Department
open access

The Use of Horizontal Wells in Gas Production from Hydrate Accumulations

Description: The amounts of hydrocarbon gases trapped in natural hydrate accumulations are enormous, leading to a recent interest in the evaluation of their potential as an energy source. Earlier studies have demonstrated that large volumes of gas can be readily produced at high rates for long times from gas hydrate accumulations by means of depressurization-induced dissociation, using conventional technology and vertical wells. The results of this numerical study indicate that the use of horizontal wells d… more
Date: April 15, 2008
Creator: Reagan, Matthew; Moridis, George J.; Reagan, Matthew T. & Zhang, Keni
Partner: UNT Libraries Government Documents Department
open access

Special Issue on geophysics applied to detection and discrimination of unexploded ordnance

Description: Unexploded ordnance (UXO) presents serious problems in Europe, Asia, as well as in the United States. Explosives and mines from World War I and World War II still turn up at European and Asian construction sites, backyard gardens, beaches, wildlife preserves and former military training grounds. The high rate of failure among munitions from 60-90 years ago is cited as one of the main reasons for such a high level of contamination. Apart from war activities, military training has resulted in man… more
Date: January 15, 2007
Creator: Gasperikova, Erika; Gasperikova, Erika & Beard, Les P.
Partner: UNT Libraries Government Documents Department
open access

Shotgun Metaproteomics of the Human Distal Gut Microbiota

Description: The human gut contains a dense, complex and diverse microbial community, comprising the gut microbiome. Metagenomics has recently revealed the composition of genes in the gut microbiome, but provides no direct information about which genes are expressed or functioning. Therefore, our goal was to develop a novel approach to directly identify microbial proteins in fecal samples to gain information about the genes expressed and about key microbial functions in the human gut. We used a non-targeted… more
Date: October 15, 2008
Creator: VerBerkmoes, N. C.; Russell, A. L.; Shah, M.; Godzik, A.; Rosenquist, M.; Halfvarsson, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Modeling of Oceanic Gas Hydrate Instability and Methane Release in Response to Climate Change

Description: Paleooceanographic evidence has been used to postulate that methane from oceanic hydrates may have had a significant role in regulating global climate, implicating global oceanic deposits of methane gas hydrate as the main culprit in instances of rapid climate change that have occurred in the past. However, the behavior of contemporary oceanic methane hydrate deposits subjected to rapid temperature changes, like those predicted under future climate change scenarios, is poorly understood. To det… more
Date: April 15, 2008
Creator: Reagan, Matthew; Reagan, Matthew T. & Moridis, George J.
Partner: UNT Libraries Government Documents Department
open access

Six-week time series of eddy covariance CO2 flux at Mammoth Mountain, California: performance evaluation and role of meteorological forcing

Description: CO{sub 2} and heat fluxes were measured over a six-week period (09/08/2006 to 10/24/2006) by the eddy covariance (EC) technique at the Horseshoe Lake tree kill (HLTK), Mammoth Mountain, CA, a site with complex terrain and high, spatially heterogeneous CO{sub 2} emission rates. EC CO{sub 2} fluxes ranged from 218 to 3500 g m{sup -2} d{sup -1} (mean = 1346 g m{sup -2} d{sup -1}). Using footprint modeling, EC CO{sub 2} fluxes were compared to CO{sub 2} fluxes measured by the chamber method on a gr… more
Date: October 15, 2007
Creator: Lewicki, Jennifer; Lewicki, J. L.; Fischer, M. L. & Hilley, G. E.
Partner: UNT Libraries Government Documents Department
open access

Effects of organic carbon supply rates on mobility of previously bioreduced uranium in a contaminated sediment

Description: Bioreduction-based strategies for remediating uranium (U)-contaminated sediments face the challenge of maintaining the reduced status of U for long times. Because groundwater influxes continuously bring in oxidizing terminal electron acceptors (O{sub 2}, NO{sub 3}{sup -}), it is necessary to continue supplying organic carbon (OC) to maintain the reducing environment after U bioreduction is achieved. We tested the influence of OC supply rates on mobility of previously microbial reduced uranium U… more
Date: May 15, 2008
Creator: Wan, J.; Tokunaga, T.K.; Kim, Y.; Brodie, E.; Daly, R.; Hazen, T.C. et al.
Partner: UNT Libraries Government Documents Department
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