bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of a Solution Cavity Adjacent to a Highway in Southwest Jordan Using Electrical Resistivity Methods
Authors: Batayneh Awni T. , Al-Zoubi Abdallah S.
Published: September 2009

A DC resistivity profiling experiment was conducted over a buried cavity using a SYSCAL-R2 resistivity instrument at the location of a proposed highway at the Ras en Naqab escarpment, Aqaba Province, southwest Jordan. The objective of the study was to evaluate the resolution of the resistivity technique in detecting and locating significant anomalies (high resistivity) over underground cavities. Resistivity profiling measurements were carried out utilizing the following arrays: (1) Alpha-Wenner; (2) Beta-Wenner; (3) Gamma-Wenner; (4) Pole-Pole; (5) Combined Head-on. Results of the survey demonstrated a strong correlation between resistivity anomalies and a subsurface void. An open and air-filled cavity exhibits markedly high-resistivity anomalies. In addition, the survey indicated that caverns with diameters as small as [Formula: see text] can be detected at shallow depths below surface and can be positioned using the resistivity profiling method. Correlations between field results obtained from different resistivity profiling arrays show that the head-on resistivity technique was found to be the most reliable since it showed details over the buried cavity. Results using other arrays were inconclusive.
Conductivity and Susceptibility Mapping Using Broadband Electromagnetic Sensors
Authors: Huang Haoping , Won I. J.
Published: September 2009

The apparent conductivity and apparent magnetic permeability are derived from broadband electromagnetic data using a conductive and magnetic half-space model. The apparent permeability is first estimated from the inphase and quadrature (or amplitude and phase) data at a low frequency. This is followed by the computation of the apparent conductivity at each frequency, using the precomputed apparent permeability. The apparent conductivity may be computed from broadband data using five different algorithms. In general, three of the five methods yield a unique solution; the three yielding a unique solution are the apparent conductivity defined from inphase, phase, or phase-amplitude. A suite of synthetic data based on two-layer models is presented and it is concluded that the phase-amplitude approach is the preferred method. The apparent permeability is virtually independent of the conductivity contrast at low induction numbers. However, the permeability contrast affects the apparent conductivity, especially when a resistive layer overlays a conductive basement. The field data examples show the usefulness of the broadband electromagnetic data and the resultant frequency-dependent conductivity-permeability maps for characterizing complex environmental sites.
Pushing the Limits of High-Resolution in Marine Seismic Profiling
Authors: McGee Thomas M.
Published: September 2009

It has become commonplace to record high-resolution marine seismic profiles in digital format and to base the choice of sampling rate on the traditional assumption that seismic signals are of limited bandwidth. The truth is that seismic signals are causal and the Heisenberg uncertainty principle prohibits causal signals being bandlimited. Since only signals with finite bandwidth can be digitized without loss of information, the implication is that at least some resolution is always lost when seismic signals are digitized. A research program to improve seismic resolution, begun in 1987 at the University of Utrecht and now continuing at the University of Mississippi, has investigated ways to minimize that loss and to recover from seismograms as much geologic information as possible. This paper addresses theoretical considerations encountered by the program and presents experimental results which demonstrate the seismic resolution it is currently possible to achieve in shallow and deep water using commercially available systems.
Petrophysical Parameters Affecting NMR Relaxation Times and Cementation Factor: Artificial Neural Network Analysis
Authors: Boadu Fred Kofi
Published: September 2009

The feasibility of using artificial neural networks (ANN) to model complex relationships between petrophysical parameters, porosity [Formula: see text], permeability [Formula: see text], volume-to-surface ratio [Formula: see text] and the exchange cation molarity [Formula: see text] and measurable geophysical properties, cementation factor [Formula: see text] and NMR relaxation times [Formula: see text] is investigated. Existing laboratory measurements of petrophysical and geophysical properties are used in modeling the relationships. The relative importance of the petrophysical parameters in influencing the geophysical measurements is assessed using the weights of the trained neural network. The results of the analyses indicate that the most influential parameter affecting NMR relaxation time is porosity followed by cation exchange molarity. The least affected parameter is permeability. The most important parameter influencing measurements of [Formula: see text] is the porosity followed closely by permeability. The percentage of clay, which is quantified by the cation exchange molarity, has significant influence on both [Formula: see text] and [Formula: see text]. We compared the predictions of [Formula: see text] and [Formula: see text] using ANN with those using conventional multivariate regression models. In both cases of prediction, ANN does a better job.
Detection of Buried Steel Drums from Magnetic Anomaly Data using a Supervised Neural Network
Authors: Salem Ahmed , Ravat Dhananjay , Johnson Ross , Ushijima Keisuke
Published: September 2009

This paper investigates the ability of a supervised artificial neural network to estimate the location of buried steel drums from magnetic anomaly data. The neural network was trained using magnetic signatures of a magnetic dipole source, which experience shows to be equivalent to the field from a buried drum. It is demonstrated that for sources buried at depths less than [Formula: see text], the supervised neural network estimates the source locations from theoretical magnetic data with errors not exceeding [Formula: see text] for depth and [Formula: see text] for horizontal location. The network also showed a potential to locate the sources in the presence of noise. The technique was also tested on field data collected at a Stanford University test site. The estimated horizontal locations and depths from field data collected over buried steel drums are close to the ground truth, with average errors of [Formula: see text] for depths and [Formula: see text] for horizontal locations. These estimated depths are better than those given by the commonly used Euler method, whereas the horizontal locations are comparable. Using the trained network, the solutions could be derived in a few milliseconds. The time required for training is significant, but could be reduced with faster computers.
Recovering Soil Distributions from Seismic Data using Laboratory Velocity Measurements
Authors: Bertete-Aguirre Hugo , Berge Patricia A.
Published: September 2009

Imaging the shallow subsurface is a problem central to many environmental and engineering applications. Recent advances in laboratory measurement techniques have provided high quality compressional velocity (Vp) and shear velocity (Vs) data for soils at low pressures that can be used to improve interpretation of field data. This paper presents a new approach for constraining interpretation of seismic velocity data in terms of subsurface soil distribution, intended for application to environmental and engineering problems. An inversion code has been developed to obtain the soil distribution in the shallow sub-surface from Vp and Vs data. The code minimizes the misfit between the observed (simulated field) Vp, Vs pairs of data in the region of interest and velocities for known soil composition as determined by second-order curve fits to laboratory velocity-pressure data for soils. The paper shows how laboratory data can be used to infer lithology from simulated field data for two near-surface examples. The laboratory data used for this purpose are ultrasonic velocity measurements from artificial soils made by combining various amounts of sand, clay, and peat moss. The availability of laboratory data for Vp and Vs at low pressures allows quantification of the improvement in resolution that may be possible if Vp and Vs seismic data are used together to image the shallow subsurface. It is shown that using the two datasets together provides better estimates of subsurface structure than either Vp or Vs alone can provide.
Geophysical Mapping of a Shallow Contaminant Plume in Thin Glacial Till, Northeast Newfoundland: Part II Interpretation of New Data
Authors: Miller Hugh G. , McCallum David S. , Guzzwell G. Keith
Published: September 2009

Geophysical techniques have been used to detect the presence and map the lateral extent of a groundwater contaminant plume in a region of thin glacial till overburden at a domestic waste disposal site in Newfoundland. This site is typified by waste cells which have significant quantities of material above the water table. An earlier investigation documented the use of various electromagnetic methods to detect the presence of a contaminant plume in the groundwater and to determine the bedrock topography which constrains the flow of the plume. The earlier study demonstrated the correlation of the electromagnetic signatures of the plume with the presence of chloride ions in the groundwater as detected at water monitoring wells in the study area. The present study provides additional information on geophysical techniques which work in this environment. The geophysical methods presented are (i) the inversion of terrain conductivity data acquired using four different coil positions relative to the ground at two elevations and two coil orientations, (ii) the results from DC resistivity sounding and profiling, and (iii) imaging of selected profiles using Ground Probing Radar. The results corroborate the depth to bedrock derived from the previous investigation. In addition, the water table depth and the location and intensity of the contaminant concentration in the subsurface have been resolved and mapped. This enables the plume configuration to be understood, and suggests a strategy for easy monitoring of the advance of the plume front.
SH-Wave Seismic Reflection Images of Anomalous Foundation Conditions at the Mississinewa Dam, Indiana
Authors: Woolery Edward W.
Published: September 2009

Geologic features (i.e., solution cavities, active∕inactive faults, fractures, and filled∕open joints) often go undetected by traditional geotechnical exploration methods, but can have long-term adverse affects on the foundation conditions of large engineered structures. These geologic features can be relatively small and nevertheless have significant consequences for foundation integrity when high hydraulic heads are present. A noninvasive, horizontally polarized shear-wave, seismic reflection survey was performed at a large flood-control facility in northern Indiana, U.S.A., in order to identify a possible geologic cause for irregular settlement along the crest of a compacted earth-filled dam. The objectives included acquisition of a high-resolution bedrock surface image beneath the structure for remedial design considerations, as well as a search for signal anomalies that may be indicative of unfavorable geologic foundation conditions. The resultant SH-wave reflection profile collected coincident with die dam’s centerline successfully imaged a coherent, relatively continuous signal consistent with known points of top-of-rock elevation. Depth to bedrock along the profile varied from [Formula: see text] near the right abutment, to [Formula: see text] near the outlet works at the survey’s western terminus. A distinct, isolated amplitude anomaly in the bedrock reflector directly below the crest settlement area was imaged and interpreted as an enlarged (open) joint or collapsed karst feature. Subsequent geotechnical drilling of the anomaly found a [Formula: see text] discrepancy in the expected top-of-rock elevation, as well as soft foundation fill, thus confirming the geophysical interpretation.
Investigation of Hazardous Waste Sites and their Environment Using the BGR Helicopter-Borne Geophysical System
Authors: Siemon Bernhard , Stuntebeck Christiane , Sengpiel Klaus-Peter , Röttger Bernd , Rehli Hans-Joachim , Eberle Detlef G.
Published: September 2009

The Federal Institute for Geosciences and Natural Resources of Germany (BGR) completed a research and development project aiming at optimizing its helicopter-borne geophysical system for high resolution site characterization. The overall objective was to adapt the existing helicopter-borne geophysical system used for groundwater and mineral exploration to survey conditions where the anomalies to be recorded are much smaller. The BGR helicopter-borne system permits simultaneous electromagnetic (AEM), magnetic (AMAG), and gamma-ray surveying. At the suggestion of the BGR, the AEM system manufactured by Geoterrex-Dighem, Toronto, Canada, was improved compared with the Dighem III system formerly used. The new system operates at five frequencies and the transmitter and receiver dipole moments are increased up to 25%. In addition, the system is now calibrated during flight. The sensitivity to waste objects was augmented by reducing the sensor heights from more than [Formula: see text] (AEM) and [Formula: see text] (AMAG), respectively, to less than [Formula: see text] about ground level by means of installing a magnetic sensor and a laser altimeter in the AEM bird. Enhanced spatial resolution was achieved by decreasing the sampling distance along line from about [Formula: see text] and by reducing the line separation from about a hundred meters to less than [Formula: see text] due to better navigational and positioning instruments. The modified system was tested over two former military training areas south of Berlin, Germany. Special surveys to locate steel drums, scrap metal, steel pipes, petrol tanks, ordnance, buried at depths from [Formula: see text] were carried out with nominal bird heights of [Formula: see text] and flight-line spacings of [Formula: see text]. Due to the extremely weak AEM and magnetic anomalies produced by these materials, suitable detection algorithms were developed to recognize and to identify these weak anomalies. They were tested using an airborne data set collected over an area where thousands of anomalies had been found. Many of them were subsequently verified on the ground. More than 90% of the anomalies selected for verification could be confirmed either by visual inspection of the ground surface or ground geophysical surveying or excavation. The modified AEM system not only allows better detection of waste but also better investigation of the environment. The AEM data could be reliably inverted to resistivity vs. depth sections using multi-layer inversion procedures. These resistivity data provide information about the hydrogeology and lithology, e.g., the depth of the groundwater table or the distribution of clay and silt. Thus, AEM can be successfully used for the hydrogeological and geological mapping of the near surface.
A Method for Using Laboratory Measurements of Electrical and Mechanical Properties to Assist in the Interpretation of Field Data from Shallow Geophysical Measurements
Authors: Bertete-Aguirre Hugo , Berge Patricia A. , Roberts Jeffery J.
Published: September 2009

In this study, simulations were done to study the interpretation of synthetic field data generated from laboratory measurements for seismic and electrical properties. Synthetic seismic and electrical properties were used to investigate whether using two independent data sets would improve underground imaging of the shallow subsurface. Laboratory measurements consisted of (1) compressional-wave travel times measured at pressures appropriate for the shallow subsurface and (2) electrical impedance with fluid salinities analogous to groundwater. The key elements of this approach were the availability of laboratory measurements for ultrasonic velocities at low pressures in unconsolidated materials and for electrical impedance in similar samples. An inversion code was developed to reconstruct the soil distribution in the shallow subsurface from compressional-wave velocity [Formula: see text] and conductivity [Formula: see text] data. This code minimized the misfit between the observed (simulated field data) [Formula: see text], [Formula: see text] pairs of data, and [Formula: see text] and [Formula: see text] for known soil compositions in the region of interest. Shallow soil distributions reconstructed from seismic and electrical data provided reliable reconstructions of the subsurface. The results showed that the availability of both types of data (seismic and electric) for this work reduced the ambiguity when compared to results using only one data set.
A Case Study of Dipole-Dipole Resistivity for Geotechnical Engineering from the Ras en Naqab Area, South Jordan
Authors: Batayneh Awni T. , Barjous Majdi O.
Published: September 2009

A data set utilizing the dipole-dipole resistivity technique covering an area of 5 excavation levels at a proposed highway site at the Ras en Naqab escarpment, south Jordan has been collected and interpreted to provide additional stratigraphic and subsurface structural information at the site. The interpretations obtained from 2D-modelling of the field data demonstrated a strong correlation between resistivity anomalies and mapped subsurface geology. Based upon the lateral and vertical resistivity changes with depth, the thickness and slope of the subsurface members was outlined. Analysis of the exposed section showed that estimated member thicknesses and quantitative assessment of resistivity inferred from dipole-dipole resistivity data were in good agreement with the thickness and lithology found in the section.
Numerical Simulation of the Wave-Guide Effect of the Near-Surface Thin Layer on Radar Wave Propagation
Authors: Liu Lanbo , Arcone Steve A.
Published: September 2009

This paper assesses ground-penetrating radar (GPR) moveout survey performance in different near-surface geological stratigraphy and different antenna orientations using two-dimensional (2D) finite difference time domain (FDTD) numerical simulations of field data. We first treat the simple cases of radar pulses propagating along (a) the interface between two half-spaces (air∕ice); and (b) an ice thin-layer wave-guide (air∕ice∕water) between two half-spaces. We then simulate four more complex cases combining two radiation polarizations (TM and TE), and two geological settings: a sandy∕gravelly half-space overlain by a silty∕clayey layer, and a silty∕clayey half-space overlain by a sandy∕gravelly layer. Both cases are represented through different dielectric constants. The results show that, first, more EM energy is radiated as an air wave for the TM mode, and more EM energy will be sent into the ground when the TE mode is used, regardless of stratigraphic sequence. Second, where a gravelly sandy half-space overlain by a silty∕clayey layer, more EM energy will be trapped in the silty∕clayey layer as the guided ground wave. Third, when the TE mode is used there is much less air radiation for the case of silt overlying gravel than that of silty∕clayey half-space overlain by a gravel∕sand layer. Fourth, for the stratigraphic sequence of a sandy∕gravelly half-space overlain by a silty∕clayey layer, the TE mode fundamentally contains only a ground wave, and the TM mode essentially contains only air wave energy. This implies that for this case a far more complete separation of the air wave and the ground wave can be reached. Fifth, dispersion of phase and group velocities of the guided ground wave will be well developed for the TE mode. These simulations imply that antenna polarization mode is an important factor when using moveout surveys to study subsurface electromagnetic properties.
Magnetic and Electromagnetic Induction Studies at Archaeological Sites in Southwestern Jordan
Authors: Witten Alan , Calvert Greg , Witten Benjamin , Levy Thomas
Published: September 2009

In support of ongoing archaeological excavations in southwestern Jordan, a number of geophysical studies have been performed in this region. The work reported was executed in three different years and, in the first year, electromagnetic induction, magnetometry, and ground penetrating radar studies were performed at three sites in the region known to have buried stone walls. While integrated geophysical methods were planned, this first field experience revealed that electromagnetic induction provided, by far, the most useful results and this became the mainstay of subsequent geophysical investigations. To date, five large sites and numerous smaller sites have been surveyed ranging in dates of occupation from the Pre-Pottery Neolithic to the Iron Age. Results from three of the larger sites are reported here. These sites are sufficiently large that they cannot be completely excavated in a single field season and the results of the geophysics are used to identify the most interesting areas at a particular site for subsequent excavation. At the oldest site, the Pre-Pottery Neolithic, the three-dimensional structure of buried stone walls are characterized. At an Iron Age site, walls and magnetic artifacts within a fortress are revealed and a possible tomb containing metal artifacts was discovered immediately outside of the fortress. A third site surveyed, a Biblical copper mine, was exploited by cultures spanning several millennia.
The Performance of Electrical Methods for Assessing the Integrity of Geomembrane Liners in Landfill Caps and Waste Storage Ponds
Authors: Binley Andrew , Daily William
Published: September 2009

Geomembrane leak location methods have been established based on injecting electrical current through the liner into the surrounding soil and then, using pairs of electrodes above the liner, high potential gradients associated with current leakage may be identified. Recently, permanent electrode arrays have been installed at a number of sites as a means of long term monitoring of the integrity of a landfill liner. There has, however, been no scientific study to date which addresses the performance of such systems. Here, we utilise a physical scale model of a landfill liner∕cap and investigate the usefulness of grid based and boundary electrode arrays for detecting multiple leaks in a landfill liner or cap. We compare the two electrode geometries under a series of controlled electrical leak experiments and demonstrate how both these arrangements can detect and locate leaks in a geomembrane. We also demonstrate some of the limitations of the method. For example, present data processing schemes can give misleading results when there are multiple leaks. The influence of variation in resistivity of the soil above or below the liner and also boundary current leakage on the performance of the technique is also studied. The results suggest that these two factors, unless they are accounted for, can have a significant impact on the results and subsequently affect the practical value of electrical leak detection systems.
Triaxial Modeling and Target Classification of Multichannel, Multicomponent EM Data for UXO Discrimination
Authors: Grimm Robert E.
Published: September 2009

Time-domain electromagnetic data collected for discrimination of unexploded ordnance (UXO) span one spatial component in one time gate to three spatial components and multiple time channels. The relative merits of additional temporal and spatial-component information were assessed by analyzing decimated data from the Geonics EM61-3D. The responses of 25 unique ordnance- and scrap-like objects buried in 45 depth-orientation states were modeled as triaxial time-dependent dipoles and were classified using the properties of the inferred model parameters. Performance was measured by the fraction of false positives for ordnance-like objects at 91% true positives. The best false-positive rate for the full multicomponent, multichannel data was 5%, which was achieved using the power-law slope of the time decay of the secondary-field EMF: ordnance-like items remain in “intermediate” time longer and display a characteristic [Formula: see text] slope, whereas scrap-like items (even those made of steel) transition to “late” time and the recovered power-law indices vary widely. However, this excellent performance is largely due to the fact that the ordnance-like objects are often larger than the scrap-like objects in this data set. Better generalization may be obtained with discriminants based solely on shape—ordnance-like objects are usually axisymmetric about a long axis—which yielded 32% false positives, again in the power-law slope. In contrast, the best false-positive rate for single-component, single-channel data was 68%. Other instrument configurations (single-component, multichannel or multicomponent, single channel) were generally ranked intermediately between these extremes. Additional experiments with intermediate numbers and positions of time gates revealed that the best discrimination is achieved when recording a broad time range for the secondary-field decay [Formula: see text]; the number or density of time gates has a smaller impact. These results demonstrate in an internally consistent way the significant performance improvement in UXO discrimination that can be achieved with multicomponent, multichannel electromagnetic sensors.
Combined Electrical and Magnetic Resistivity Tomography: Synthetic Model Study and Inverse Modeling
Authors: LaBrecque Douglas , Sharpe Roger , Casale Dan , Heath Gail , Svoboda John
Published: September 2009

Electrical Resistivity Tomography (ERT), which has seen increasingly wide use for environmental monitoring, uses the measurement of electrical potentials induced by a low-frequency electric current source. An alternative technique, magnetometric resistivity (MMR), measures the magnetic fields created by the same type of low-frequency electric current source used for ERT. Combining these two methods and thus the two types of data, provides an opportunity for producing improved subsurface images in a wider range of environments. This paper discusses the use of a fully three-dimensional inverse routine that combines magnetic and electric field measurements. The algorithm is based on a 3-D finite difference forward algorithm. The magnetic fields are modeled by applying the reciprocity theorem to model the electric fields induced by a coil of unit moment at a frequency of one radian per second. Using this method, allows for an adjoint formulation for calculating sensitivities of both magnetic and electric fields with respect to changes in the conductivities of individual cells within the finite-difference mesh. In initial model studies, combined MMR∕ERT surveys were better able to resolve 3-D structures than ERT alone. The paper also considers design issues and choices of arrays for MMR surveys over a simple 3-D model. In this case, an integral-equation modeling algorithm is used to calculate the expected magnetic fields over a simple 3-D model. Several horizontal and buried vertical electric sources with surface magnetic receivers are employed. This work suggests that in-well horizontal arrays produce the strongest anomalous signals, while vertical dipoles provide the best sensitivity to target location.
Object-Based Inversion of Crosswell Radar Tomography Data to Monitor Vegetable Oil Injection Experiments
Authors: Lane John W. , Day-Lewis Frederick D. , Versteeg Roelof J. , Casey Clifton C.
Published: September 2009

Crosswell radar methods can be used to dynamically image ground-water flow and mass transport associated with tracer tests, hydraulic tests, and natural physical processes, for improved characterization of preferential flow paths and complex aquifer heterogeneity. Unfortunately, because the raypath coverage of the interwell region is limited by the borehole geometry, the tomographic inverse problem is typically underdetermined, and tomograms may contain artifacts such as spurious blurring or streaking that confuse interpretation. We implement object-based inversion (using a constrained, non-linear, least-squares algorithm) to improve results from pixel-based inversion approaches that utilize regularization criteria, such as damping or smoothness. Our approach requires pre- and post-injection travel-time data. Parameterization of the image plane comprises a small number of objects rather than a large number of pixels, resulting in an overdetermined problem that reduces the need for prior information. The nature and geometry of the objects are based on hydrologic insight into aquifer characteristics, the nature of the experiment, and the planned use of the geophysical results. The object-based inversion is demonstrated using synthetic and crosswell radar field data acquired during vegetable-oil injection experiments at a site in Fridley, Minnesota. The region where oil has displaced ground water is discretized as a stack of rectangles of variable horizontal extents. The inversion provides the geometry of the affected region and an estimate of the radar slowness change for each rectangle. Applying petrophysical models to these results and porosity from neutron logs, we estimate the vegetable-oil emulsion saturation in various layers. Using synthetic- and field-data examples, object-based inversion is shown to be an effective strategy for inverting crosswell radar tomography data acquired to monitor the emplacement of vegetable-oil emulsions. A principal advantage of object-based inversion is that it yields images that hydrologists and engineers can easily interpret and use for model calibration.
Assessing the Precision of GPR Velocity and Vertical Two-way Travel Time Estimates
Authors: Jacob Robert W. , Hermance John F.
Published: September 2009

Accurate estimates of ground penetrating radar (GPR) traveltimes and velocities are essential to a number of civil engineering, agricultural and watershed management activities. This paper reports on a study to assess confidence limits on radar parameters using a sequence of high quality common midpoint (CMP) soundings collected on eight different days over the course of a year at a single location for a range of soil moisture conditions. On each day, a “repeat” CMP was acquired leading to a total of 16 independent CMP soundings. Two prominent reflections, present in all 16 independent CMP soundings, were analyzed to provide NMO velocities and vertical two-way traveltimes along with their associated 95% confidence limits estimated using Student’s t-test, accounting for both the appropriate number of observations and estimated parameters. Interval properties were then determined using the Dix relation. The radar velocity of the [Formula: see text] interval has the largest variation observed, from [Formula: see text] for wet and dry soil moisture conditions, respectively. However, over this same time period, the estimated thickness of each interval, 0.9 [Formula: see text] and 2.9 [Formula: see text], remains constant within the respective 95% confidence limits on the 16 independent estimates and their composite average. The latter result provides a useful check on the quality of our interpretation. Analysis of the ground refraction phases also confirmed the interval velocity and thickness inferred from the reflection data. The global results of this study suggest that NMO radar velocities and vertical two-way traveltimes may be optimally resolved at the 95% confidence level with precisions of [Formula: see text] and [Formula: see text], respectively. The deviation between measurements from repeat CMPs on a given day typically fall well within the 95% confidence limit. Thus, while repeat CMP data provide a valuable check on quality control, we note that a posteriori estimates of confidence limits might provide an acceptable alternative for many applications. Regardless of the field procedure selected, this study emphasizes that an assessment of data quality is only possible by a clear statement of confidence limits and by carefully defining the basis for their estimation.
Tracing Groundwater Flow by Mise-à-la-masse Measurement of Injected Saltwater
Authors: Pant Surendra Raj
Published: September 2009

Conventional use of the mise-à-la-masse method is limited to the study of the conductive mineralized deposits but can also be applied to engineering and environmental studies. This paper deals with an experiment that was carried out in the dam site of Middle Marsyangdi Hydroelectric Project to study the flow direction and velocity of groundwater around two boreholes. Concentrated salt solution was injected continuously at the rate of [Formula: see text] into the boreholes below the water table. The potential field of the current electrode at the borehole was monitored on the surface. For both boreholes, analyses were carried out by the equipotential line method, which uses the time and the distance traversed by the equipotential lines to determine velocity of the groundwater. This experiment demonstrates that the mise-à-la-masse method is useful to find the velocity and flow direction of the groundwater. The experiment can also be conducted in a metal-cased borehole. The experiment also shows that the placement of the remote current electrode has effects on the calculated velocity. The method provides reliable results if the monitoring is carried out for injection at shallow depths, most likely less than [Formula: see text].
Monitoring Yearly Changes and Their Influence on Electrical Properties of the Shallow Subsurface at Two Sites Near the Rio Grande, West Texas
Authors: Doser Diane I. , Dena-Ornelas Oscar S. , Langford Richard P. , Baker Mark R.
Published: September 2009

We present the results of a case study that monitored changes in the electrical properties of soils on a bi-monthly basis between August 1999 and November 2000 at two sites located along the banks of the Rio Grande, west Texas. One site was located within an abandoned channel of the Rio Grande and showed relatively homogeneous layering, while the second site exhibited complex interfingerings of crevasse splay (sands and silts) and floodplain muds. Repeated EM-31 ground conductivity measurements at both sites showed that conductivities within the upper [Formula: see text] of soil could change by up to a factor of 2 within a year’s time. DC resistivity studies suggested up to a factor of 5 change in resistivity values within the upper [Formula: see text] of soil. These changes appear to be related to remobilization of salt in the soil following rainfall or irrigation events. These dramatic fluctuations make it difficult to image deeper ([Formula: see text] depth) conductivity changes in the subsurface.
Permittivity Measurements of High Conductivity Specimens using an Open-Ended Coaxial Probe—Measurement Limitations
Authors: Klein Katherine
Published: September 2009

Non-destructive electromagnetic wave-based techniques have been used for over a century to gain insight into the behaviour of geomaterials. The technique used in this study is a high frequency [Formula: see text] open-ended coaxial probe measurement system. This study highlights the importance of knowing the limitations of the measurement system. The specimens that are tested are aqueous solutions of NaCl, [Formula: see text], and [Formula: see text] with conductivities ranging from approximately [Formula: see text]. Real permittivity data of the high conductivity specimens show a relaxation phenomena at MHz frequencies where none exists, indicating that electrode polarization is occurring. The frequency at which electrode polarization begins to manifest (e.g., limiting frequency) increases as the specimen conductivity increases. An empirical relationship between the limiting frequency and specimen conductivity is presented and is applied to three kaolinite-NaCl slurries. Additional problems associated with measuring high conductivity specimens using this equipment may arise since the model for the aperture admittance was optimized using low conductivity materials. Previous studies have shown that measurement errors at low frequencies are reduced if the system is calibrated using a material of similar electrical properties to the test specimen.
Effects of Signal Processing and Antenna Frequency on the Geostatistical Structure of Ground-Penetrating Radar Data
Authors: Oldenborger Greg A. , Knoll Michael D. , Barrash Warren
Published: September 2009

Recent research has suggested that the geostatistical structure of ground-penetrating radar data may be representative of the spatial structure of hydraulic properties. However, radar images of the subsurface can change drastically with application of signal processing or by changing the signal frequency. We perform geostatistical analyses of surface radar reflection profiles in order to investigate the effects of data processing and antenna frequency on the semivariogram structure of radar reflection amplitudes. Surface radar reflection data collected at the Boise Hydrogeophysical Research Site illustrate the processing- and antenna-dependence of radar semivariograms for a fluvial, cobble-and-sand aquifer. Compensating for signal attenuation and spreading using a gain function removes a non-stationary trend from the data and a trace-specific gain function reduces fluctuation of semivariogram values at large lags. Otherwise, geostatistical structures of surface reflection data are quite robust to the effects of data gains. Migration is observed to reduce the strength of diffraction features in the semivariogram fields and to increase the principal exponential range. Principal exponential range increases only slightly after application of migration with a realistic velocity but over-migration results in a significant artificial increase of exponential range. The geostatistical structures of radar reflection data exhibit marked dependence on antenna frequency, thus highlighting the critical importance of the scale of measurement. Specifically, the exponential ranges of radar reflection amplitudes decrease in proportion to the increased signal frequency for the [Formula: see text], [Formula: see text] and [Formula: see text] range of antennas. Results demonstrate that processing and antenna frequency must be considered before the application of radar reflection data in a geostatistical context.
Borehole Corrections for a Thick Resistivity Probe
Authors: Thunehed Hans , Olsson Olle
Published: September 2009

The electrical resistivity contrast between the borehole fluid and the surrounding rock can be very large during borehole logging in crystalline rock. In resistivity logging we are in general interested in acquiring information about the true resistivity of the rock. The fluid will cause an unwanted deflection of the measured apparent resistivity from the sought rock resistivity. The nonconducting probe and its finite dimensions will also affect the measurements. By assuming homogeneous rock and concentric geometry, the Laplace equation has been solved for a thick resistivity probe with normal electrode configuration. The resulting cosine-integral can be calculated numerically with the digital filter method. The corresponding solution for other types of electrode configurations can be found by superposition of results for the normal configuration. The inverse solution that is needed to correct the data is found by fitting calculated values in a least-squares sense to a low-order polynomial. The correction method has been tested on data from a deep hole in granitic rock in south-eastern Sweden. Significant variations in both borehole diameter and fluid resistivity are present in the hole. The assumptions of homogeneous rock and concentric geometry were not valid for the data. In spite of this it was possible to correct the data in a proper way. The resulting estimates of the rock resistivity were about the same for both the normal and the lateral logs. Also, no significant level shifts appeared in the corrected data where there was an abrupt change in borehole diameter. The large volume bulk resistivity of the rock mass was estimated from the corrected data and was found to be in accordance with estimates from ground-based geophysics. By supporting the logging data with petrophysical measurements on core samples it was possible to get reasonable estimates of the rock porosity along the borehole.
Effect of surface modifying macromolecules stoichiometric ratio on composite hydrophobic/hydrophilic membranes characteristics and performance in direct contact membrane distillation
Authors: Qtaishat M. , Rana D. , Matsuura T. , Khayet M.
Published: September 2009

The stoichiometric ratio for the synthesis components of hydrophobic new surface modifying macromolecules (nSMM) was altered systematically to produce three different types of nSMMs, which are called hereafter nSMM1, nSMM2, and nSMM3. The newly synthesized SMMs were characterized for fluorine content, average molecular weight, and glass transition temperature. The results showed that fluorine content decreased with increasing the ratio of α,ω‐aminopropyl poly(dimethyl siloxane) to 4,4′‐methylene bis(phenyl isocyanate). The synthesized nSMMs were blended into hydrophilic polyetherimide (PEI) host polymer to form porous hydrophobic/hydrophilic composite membranes by the phase inversion method. The prepared membranes were characterized by the contact angle measurement, X‐ray photoelectron spectroscopy, gas permeation test, measurement of liquid entry pressure of water, and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation and the results were compared with those of commercial polytetraflouroethylene membrane. The effects of the nSMM type on the membrane morphology were identified, which enabled us to link the membrane morphology to the membrane performance. It was found that the nSMM2/PEI membrane yielded the best performance among the tested membranes. In particular, it should be emphasized that the above membrane was superior to the commercial one. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Two‐phase flow behavior in microtube reactors during biodiesel production from waste cooking oil
Authors: Guan Guoqing , Teshima Marion , Sato Chie , Mo Son Sung , Faisal Irfan Muhammad , Kusakabe Katsuki , Ikeda Norihiro , Lin Tsao‐Jin
Published: September 2009

Flow patterns in the course of transesterification of waste cooking oil (WCO), sunflower oil (SFO) with water and/or oleic acid as a model of WCO, and pure SFO in the presence of a KOH catalyst in microtubes were investigated. FAME yield for the transesterification of WCO reached more than 89% in the microtube reactors with a residence time of 252 s at 333 K. The flow patterns when using WCO were changed from a liquid–liquid slug flow at the inlet region to a parallel flow at the middle region, and then to a homogeneous liquid flow at the outlet region as the reaction proceeded at 333 K. Fine droplets containing glycerol and methanol generally formed in oil slugs when using pure SFO, but were almost unobservable when using WCO. The soap produced from free fatty acids was considered to be the main factor affecting the flow patterns of WCO and SFO. © 2009 American Institute of Chemical Engineers AIChE J, 2010
Graphen, das neue zweidimensionale Nanomaterial
Authors: Rao C. N. R. , Sood A. K. , Subrahmanyam K. S. , Govindaraj A.
Published: September 2009

Alle paar Jahre werden neue Stoffklassen mit einzigartigen und faszinierenden Eigenschaften entdeckt. Beispiele aus der jüngeren Vergangenheit sind Hochtemperatur‐Supraleiter und Nanoröhren aus Kohlenstoff. Die jüngste dieser spektakulären Entdeckungen ist Graphen. Graphen weist ungewöhnliche Eigenschaften wie einen halbzahligen Quanten‐Hall‐Effekt und eine ballistische Elektronenbewegung auf. Graphen ist ein zweidimensionaler Stoff und die Stammverbindung aller graphitischen Kohlenstoff‐Formen. Graphen besteht in Reinform nur aus Monoschichten, es gibt aber auch beträchtliches Interesse an Graphen‐Doppel‐ und ‐Mehrfachschichten. Die Synthese und Charakterisierung von Graphenen ist schwierig, in jüngster Zeit sind hier aber große Fortschritte erzielt worden. Wir berichten hier über den aktuellen Stand der Graphenforschung einschließlich Synthese, Charakterisierung, Struktur und Eigenschaften.
Recombinant shrimp (Litopenaeus vannamei) trypsinogen production in Pichia pastoris
Authors: Guerrero‐Olazarán Martha , Escamilla‐Treviño Luis L. , Castillo‐Galván Mauricio , Gallegos‐López Juan A. , Viader‐Salvadó José M.
Published: September 2009

Shrimp (Litopenaeus vannamei) trypsinogen has never been isolated from its natural source. To assess the production of L. vannamei trypsinogen, we engineered Pichia pastoris strains and evaluated two culture approaches with three induction culture media, to produce recombinant shrimp trypsinogen for the first time. The trypsinogen II cDNA was fused to the signal sequence of the Saccharomyces cerevisiae alpha mating factor, placed under the control of the P. pastoris AOX1 promoter, and integrated into the genome of P. pastoris host strain GS115. Using standard culture conditions for heterologous gene induction of a GS115 strain in shake flasks, recombinant shrimp trypsinogen was not detected by SDS‐PAGE and Western blot analysis. Growth kinetics revealed a toxicity of recombinant shrimp trypsinogen or its activated form over the cell host. Thus, a different culture approach was tested for the induction step, involving the use of high cell density cultures, a higher frequency of methanol feeding (every 12 h), and a buffered minimal methanol medium supplemented with sorbitol or alanine; alanine supplemented medium was found to be more efficient. After 96 h of induction with alanine supplemented medium, a 29‐kDa band from the cell‐free culture medium was clearly observed by SDS‐PAGE, and confirmed by Western blot to be shrimp trypsinogen, at a concentration of 14 μg/mL. Our results demonstrate that high density cell cultures with alanine in the induction medium allow the production of recombinant shrimp trypsinogen using the P. pastoris expression system, because of improved cell viability and greater stability of the recombinant trypsinogen. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Association of cholesteryl ester transfer protein −629C > A polymorphism with high‐density lipoprotein cholesterol levels in coronary artery disease patients
Authors: Tanrikulu Sevda , Ademoglu Evin , Gurdol Figen , Mutlu‐Turkoglu Umit , Bilge Ahmet Kaya , Nisanci Yilmaz
Published: September 2009

In Turkish population, plasma HDL‐C levels were found to be lower than in any other country and it is suggested that this is associated with genetic origin. The cholesteryl ester transfer protein (CETP) −629C > A polymorphism is associated with lower plasma CETP concentration, with increased HDL‐C level. In the present study, the frequency of −629C > A polymorphism in patients with coronary artery disease (CAD) was investigated and the effect of genotype on HDL‐C was evaluated in a Turkish population. For this aim CETP −629C > A polymorphism was studied in angiographically documented CAD patients and healthy controls.

There was no statistical significance in the distribution of genotypes between patients and controls. Although A allele carriers with CAD had significantly lower HDL‐C levels than controls, plasma lipid levels showed no difference according to the genotypes. Adjustment by a logistic regression model predicting CAD status through HDL‐C and including some risk factors as covariate indicated that the HDL‐C doesn't have a significant association with CAD risk in CA and AA genotype carriers. Smoking, gender and hypertension were the common predictors for the HDL‐C levels in CA and AA carriers. Although HDL‐C appeared to be the only significant predictor of CAD in our study groups, the contribution of CETP −629C > A polymorphism to the alterations in HDL‐C level appears to be weak to mention a protective effect of this polymorphism for CAD. In conclusion, the findings of the present study indicate that the CETP −629C > A polymorphism is not among the determinants of the coronary artery disease in Turks. Copyright © 2009 John Wiley & Sons, Ltd.