bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Approach for Automated Analysis of Cell Attachment and Spreading Based on Backscattered Electron Imaging by Scanning Electron Microscopy
Authors: Katsen-Globa Alisa , Peter Leonora , Zöllner Susan , Dörge Thomas , Daffertshofer Martin , Preckel Hartwig , Schmitt Daniel , Zimmermann Heiko
Published: September 2009

The development of new materials for biological application requires in vitro testing of cell/surface interactions. Cell adhesion and spreading are difficult to quantify as most materials are non-transparent and transmission microscopy cannot be used. Contrast in reflection microscopy is rather poor. We propose an alternative method for the automated screening of cell attachment and spreading using backscattered electron imaging of scanning electron microscopy. The enhanced cell contrast permits study of cell/material interactions by little differences between cells and material.
Single‐layer axisymmetric model for a Hadley circulation with parameterized eddy momentum forcing
Authors: Sobel Adam H , Schneider Tapio
Published: September 2009

An axisymmetric single‐layer model is used to study interactions of the Hadley circulation with extratropical eddies. Eddy momentum fluxes are parameterized using a simple closure motivated by calculations with an idealized dry general circulation model (GCM). Calculations are performed in which the heating is parameterized as Newtonian relaxation of temperatures toward a prescribed radiative‐convective equilibrium (RCE) state. The latitude at which the maximum RCE temperature occurs is varied to represent seasonal variations. In the axisymmetric model, as in the GCM, qualitative changes in the zonal momentum budget occur as the RCE temperature maximum moves away from the equator past a threshold latitude. For RCE temperature maxima closer to the equator, eddy momentum fluxes play a dominant role in the zonal momentum budget, nonlinearity is weak, and the meridional circulation is a weak function of the degree of asymmetry about the equator. For RCE temperature maxima sufficiently far from the equator, the zonal momentum budget becomes more nonlinear, angular momentum is more nearly conserved, and the circulation is a stronger function of the degree of asymmetry about the equator. Since the axisymmetric model can capture this behavior while being much simpler than the GCM, it may be a useful step towards a more comprehensive theory of the zonal‐mean general circulation.
Biventricular Pulsus Alternans
Authors: Vidwan Param , Stouffer George A.
Published: September 2009

Pulsus alternans is a rare hemodynamic condition characterized by beat-to-beat variability in systolic pressure. It is attributed to variations in stroke volume with alternate cardiac cycles and is typically seen in patients with advanced myopathic conditions. Left ventricular pulsus alternans is rare, and right ventricular pulsus alternans is even less common. There are only a few reports of biventricular pulsus alternans. We report the case of a 62-year-old female with a recent anterior wall myocardial infarction who had biventricular pulsus alternans at the time of cardiac catheterization.
First-Arrival Alignment Static Corrections Applied to Shallow Seismic Reflection Data
Authors: Pugin André , Pullan Susan E.
Published: September 2009

The proper handling of static corrections is an issue that is of critical importance to shallow seismic reflection surveys because of the high frequencies used, and the significant velocity and thickness variations that frequently exist in the very-near surface. The application of standard conventional methods of determining static corrections must be very carefully considered, as these are sometimes inadequate for shallow seismic reflection data. This paper addresses the problem of static corrections for shallow reflection data in terms of long-, medium-, and short-wavelength statics related to topography and variations in the very-low-velocity, near-surface layer, and presents a first-arrival alignment method of static corrections which is an adaptation of refraction and common offset methods. First-break picking is completed on the entire data set, and a refraction analysis of first-arrival data at selected intervals along the survey line is used to estimate a laterally-interpolated, layered, near-surface velocity structure. The first arrivals on all shot gathers are then aligned to the determined velocity function. This process corrects for medium- (i.e., within spread length), and long-wavelength ([Formula: see text] length), near-surface velocity variations, as well as most of the static contributions related to individual geophone locations and elevations (i.e., short-wavelength corrections). Residual statics are used to correct any remaining short-wavelength errors. Finally, topographic variations (long-wavelength) are corrected post-stack. Both model results and application of this method to actual shallow seismic reflection data show this to be a robust and effective method of correcting for statics related to a very-low-velocity near-surface layer, though the method (based on refraction analyses) cannot account for near-surface velocity inversions, if these exist.
Aquifer Characterization in the Blue Ridge Physiographic Province Using Resistivity Profiling and Borehole Geophysics: Geologic Analysis
Authors: Seaton William J. , Burbey Thomas J.
Published: September 2009

Existing hydrogeological models used to describe the recharge and movement of groundwater in the Blue Ridge Province in the eastern United States generally rely on a simplified two-layer system consisting of regolith overlying a fractured bedrock aquifer. The regolith in these models is assumed to be relatively homogeneous and contains a water table aquifer that supplies water to the underlying variably fractured homogeneous crystalline bedrock. The interconnected fractures in the bedrock serve as conduits for predominantly downward vertical and limited horizontal flow. Recent acquisition of two-dimensional surface resistivity profiles and borehole geophysical logs has revealed new insights into this geologically complex province. The shallow regolith contains large unsaturated areas and also localized sand and clay prone facies with water table and confined aquifer conditions residing locally. Within the crystalline bedrock are anomalous lower resistivity intervals that are associated with ancient fault shear zones. These shear zones intercept the regolith-bedrock interface at high angles and become more horizontal with depth. Brecciated rock adjacent to the shear zones, as well as the shear zones themselves, can be hydraulically conductive and serve as pathways for vertical and horizontal groundwater movement from source-recharge areas to distant wellbores. Regolith and aquifer-property characterization from geophysical and hydrological data acquired in this investigation has allowed reasonable conclusions to be drawn about groundwater movement in the Blue Ridge Province for water supply, contaminant transport, and watershed∕wellhead protection delineation.
Difference Inversion of ERT Data: a Fast Inversion Method for 3-D In Situ Monitoring
Authors: LaBrecque Douglas J. , Yang Xianjin
Published: September 2009

A three-dimensional (3-D) Occam’s inversion algorithm for electrical resistivity tomography is modified to allow for inversion on the differences between the background and subsequent data sets. The algorithm is optimized for in situ monitoring applications. The resistivity obtained by the inversion of background data serves as the a priori model in the difference inversion. There are several advantages to this method. First, convergence is fast since the inverse routine needs only to find small perturbations about a good initial guess. Second, systematic errors such as those due to errors in field configuration and discretization errors in the forward modeling algorithm tend to cancel. The result is that we can fit the difference data far more closely than the individual potentials. Better data fits often equate to better resolution with fewer inversion artifacts. The difference inversion technique was applied to monitoring in-situ steam remediation in Portsmouth, Ohio and monitoring of flow in fluid fractures at the Box Canyon site near the Idaho National Engineering Laboratory. Small changes of conductivity were better resolved using the difference inversion method. Difference inversion produced high-quality images with fewer artifacts, and only took 25% to 50% run time of standard Occam’s inversion in the Box Canyon case.
A Discrimination Algorithm for UXO Using Time Domain Electromagnetics
Authors: Pasion Leonard R. , Oldenburg Douglas W.
Published: September 2009

An assumption is made that the Time Domain Electromagnetic (TEM) response of a buried axisymmetric metallic object can be modelled as the sum of two dipoles centered at the midpoint of the body. The strength of the dipoles depends upon the relative orientation between the object and the source field, and also upon the shape and physical properties of the body. Upon termination of the source field, each dipole is assumed to decay as [Formula: see text]. The parameters [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] depend upon the conductivity, permeability, size and shape of the object, and these can be extracted from the measurements by using a nonlinear parametric inversion algorithm. Investigations carried out using an analytic solution for a sphere and laboratory measurements of steel and aluminum rectangular prisms, suggest the following two-step methodology: (1) The value of [Formula: see text] is first used as a diagnostic to assess whether the metallic object is non-magnetic or magnetic, (2) the ratios of [Formula: see text] and [Formula: see text] are then diagnostic indicators as to whether the geometry is plate-like (uninteresting) or rod-like (a high candidate for being a UXO). Results from the application of this algorithm to a TEM field data set acquired at the United States Army Corps of Engineers Research and Development Centre (ERDC) UXO Test Site have successfully identified a UXO to be magnetic and rod-like.
Dispersive and Non-Dispersive Noise Removal by Local, Slant-Sum, Adaptive Filtering
Authors: Liu Zhi-Ming , Young Roger Adams
Published: September 2009

This paper presents a new interactive procedure, Local Slant-Sum Adaptive Noise Removal (LSSANR), for attenuating linear, coherent, noise modes in the time-space domain. The procedure uses either a fixed or a sliding window to estimate noise wavelets and then subtracts the noise wavelets from the seismic traces on shot records. The procedure can adapt to dispersive noise in local, time-space windows, thereby minimizing smearing associated with filtering. Because the algorithm can attenuate ground roll and refraction first-arrivals, it may be especially useful in geotechnical and environmental seismic reflection surveys in which low fold, weak reflections are commonly obscured by these other two events. Synthetic examples and a field data case show that the algorithm is also successful in attenuating multiple noise events.
Geophysical Monitoring Through a Tidal Cycle at Crescent Beach State Park, Maine
Authors: Sandberg Stewart K. , Slater Lee D.
Published: September 2009

This paper presents results of an experiment in which data from a combination of geophysical methods (resistivity, induced polarization, electromagnetic profiling, and magnetic profiling) were used to identify shallow geologic and hydrogeologic structure, and to enhance understanding of groundwater flow in a dynamic beach environment. Based on this study, well sorted beach sand is underlain by laterally variable glacial till, which overlies bedrock. An extensive patch of glacial till was mapped toward the ocean side of the beach. Bedrock has lithologic variability, as evidenced by a non-uniform magnetic response. In particular, a northeast-southwest trending magnetic body, believed to be a basalt dyke, was detected by its magnetic signature. During the transgressive phase of the tidal cycle, saline groundwater flow appeared to be quite rapid, extending ahead of the surfical water by at least [Formula: see text], as evidenced by the electromagnetic response. During the regressive phase, a slug of saline water remained up beach from the high tide mark for several hours prior to draining. Also during this regression, electromagnetic evidence for preferential groundwater flow pathways, probably bedrock fracture zones, was observed. These fracture zones appear to contain a relatively constant concentration of saltwater, while surficial sediments above and to the side are flushed with fresh groundwater during tidal regression.
Use of Principal Component Analysis to Determine Down-hole Tool Orientation and Enhance SH-Waves
Authors: Michaels P.
Published: September 2009

A common problem in down-hole shear wave surveys is the determination of the tool rotation relative to the seismic source polarization direction. This paper reports an algorithm which has been developed to solve for this angle in the horizontal plane. The method employs Principal Component Analysis (PCA) to determine the angle from the large motion of the SH-wave (not first motion). Once the angle is known, the horizontal component data may be rotated so that one component is aligned with the source polarization, and the other orthogonal to it. Significant findings include the following. First, subtraction of oppositely polarized source efforts improves the PCA formulation by enhancing the S-waves. Second, the Swave enhancement is improved by scaling the oppositely polarized source efforts by the vertical (not horizontal) component data, as this provides a better attenuation of non-Swave energy. Third, observation of the tool orientation as it exits the borehole is helpful in resolving the [Formula: see text] azimuthal ambiguity in the PCA approach. Finally, the polarization of the source radiation may drift relative to the axis of the source during a survey, and should not be assumed invariant.
The Use of 3D Electrical Resistivity Tomography to Characterise Waste and Leachate Distribution within a Closed Landfill, Thriplow, UK
Authors: Ogilvy Richard , Meldrum Philip , Chambers Jon , Williams Geoffrey
Published: September 2009

Electrical Resistivity Tomography (ERT) has been used to map the 3D spatial distribution of waste and leachate concentrations within a closed and unconfined landfill. Borehole sampling and a 2D ERT survey down-gradient of the landfill boundary had failed to detect a pollution plume. Accordingly, a 3D survey was undertaken to determine the pattern of leachate drainage within the waste so that a more refined contaminant transport model could be developed. A full 3D survey was undertaken by sub-dividing the landfill into a number of discrete rectangular blocks and acquiring data on multiple parallel lines. The line data were merged into a single x-y matrix file and then inverted using a 3D finite element algorithm. The results are presented as 3D volumetric tomograms to show the inferred waste distribution and leachate flow-paths. The resistivity models indicate that leachate has accumulated at several discrete localities within the landfill. The controlling mechanism appears to be the depth and geometry of the original Chalk quarries used for waste disposal. The deepest leachate infiltration of the underlying Chalk bedrock invariably occurs below these drainage sinks. A narrow leachate plume is indicated in one part of the landfill, migrating down-gradient to the north-west. The inferred leachate concentrations in the Chalk were subsequently confirmed by drilling and hydrochemical sampling which showed elevated solute levels coincident with distinct resistivity lows of [Formula: see text].
Investigation of Potential Saltwater Intrusion Pathways in a Fractured Aquifer using an Integrated Geophysical, Geological and Geochemical Approach
Authors: Allen D. M. , Abbey D. G. , Mackie D. C. , Luzitano R. D. , Cleary M.
Published: September 2009

Borehole geophysics and horizontal loop electromagnetic profiling (Max-Min) were integrated with regional and site-scale geological and geochemical data to investigate the occurrence of, and possible pathways for, saltwater intrusion near fracture zones on a small island in British Columbia, Canada. An island-wide geochemical study identified a number of coastal wells that are contaminated by seawater; however, the occurrence of high salinity groundwater is spatially irregular due to variable fracturing of the bedrock. To investigate the influence of fracturing on the presence of high salinity groundwaters, geophysical investigations were undertaken at several sites. The nature of the bedrock permeability at these sites, with respect to lithology and fracture zone proximity, is described from geologic and hydrogeologic investigations and supported using surface EM profiling. Fractures and bedding contacts within boreholes, which were suspected to dominate bedrock permeability on the basis of outcrop studies, were identified using borehole video camera in conjunction with normal resistivity, spontaneous potential and natural gamma logs. Flow meter logs, acquired under a variety of aquifer stress conditions including static, tidal and pumping are used to identify potential water transmitting fractures and the locations of entry points for fresh and saline groundwater. The low flow rates measured under the various stress conditions confirm that groundwater flow is minimal and is restricted to mudstone units and single, generally sub-vertical fractures. The low natural groundwater discharge rates near the coast, even at close distances to fracture zones, may be key to the occurrence of saltwater intrusion on many parts of the island.
The Accuracy of Water Table Elevation Estimates Determined from Ground Penetrating Radar Data
Authors: Bentley L. R. , Trenholm N. M.
Published: September 2009

Water table elevations measured at sparsely distributed monitoring wells are used to interpolate the water table surface. Ground-penetrating radar (GPR) is a non-invasive technique that has been used to estimate water table elevations between monitoring wells. GPR can be used to estimate the elevation of the top of the capillary fringe. The water table elevation is obtained by subtracting an estimate of the height of the capillary fringe from the capillary fringe elevation. The accuracy of these estimates is affected by numerous sources of error including surface elevation, GPR wave velocity, spatial velocity variations, capillary rise estimates and the time sampling interval. The main sources of uncertainty are due to GPR velocity estimates and predicting the height above the water table of the capillary fringe reflection. Theoretical analysis and field experiments indicate that, under favorable circumstances, the elevation of shallow water tables can be estimated with an accuracy on the order of [Formula: see text].
Geophysical Investigation of Vadose Zone Conductivity Anomalies at a Hydrocarbon Contaminated Site: Implications for the Assessment of Intrinsic Bioremediation
Authors: Atekwana Estella A. , Sauck William A. , Abdel Aal Gamal Zidan , Werkema D. Dale
Published: September 2009

Electromagnetic (EM-31), dc resistivity, and ground penetrating radar (GPR) methods were used to investigate part of a former refinery site in Kalamazoo, Michigan, USA. The study area is underlain by about [Formula: see text] of heterogeneous glacial drift deposits overlying a sandy outwash unit. Three large above ground storage tanks (ASTs) formerly occupied the study area and were removed by the U.S. Environmental Protection Agency (USEPA) in 1997. EM-31 surveys revealed eight remnants of buried pipe ranging from [Formula: see text] to more than [Formula: see text] in length. Emanating from some of these abandoned pipe segments are extensive near surface conductivity anomalies, with values ranging from [Formula: see text] to greater than [Formula: see text] vs. background values of less than [Formula: see text]. GPR and dipole-dipole resistivity surveys performed along selected profiles with anomalous conductive zones revealed a channel form within the shallow subsurface. Shallow hand augured soil borings into these conductive zones encountered hydrocarbons perched on thin clay lenses, or trapped in low permeability sandy-silt layers, while borings in background conductivity areas showed only clean sand and silt. We also observed that areas underlain by clays in association with perched hydrocarbons exhibited a higher conductivity (greater than [Formula: see text] and up to [Formula: see text]) when compared to areas underlain by uncontaminated clays. Based on these observations and results of our prior work in similar settings, we infer that the conductivity anomalies may be due to the occurrence of intrinsic biodegradation of the hydrocarbons. Thus, the previous conductive model originally proposed by our research group for ‘aged’ hydrocarbon spills at the water table can be extended upward to include vadose zone occurrences of biodegradation of these contaminants. The findings from this study have significant implications for the use of geophysical techniques in the assessment of vadose zone biodegradation.
Magnetometric Resistivity (MMR) Imaging of Subsurface Solute Flow: Inversion Framework and Laboratory Tests
Authors: Kulessa Bernd , Jaekel Uwe , Kemna Andreas , Vereecken Harry
Published: September 2009

In support of the development of the magneto-electrical resistivity imaging technique (MERIT), a framework is presented for forward and inverse modeling of near-surface magnetometric resistivity (MMR) data, and results are reported from initial laboratory tests. Application of MMR involves injection of a low-frequency current into the ground, and measurement of the resulting magnetic field using state-of-the-art lock-in technology to suppress magnetic noise around the centre frequency. Forward and inverse calculations are both two-step procedures, involving intermittent computation of current density. The validity of this framework is demonstrated using synthetic numerical tests. The laboratory experiment reported considers a saturated sand sample placed in a non-conducting container furnished with electrodes. Migration of a conductive salt tracer was monitored over three days using a fluxgate magnetometer mounted on a device that allowed repeat scans of the sample. Data inversion uses any two of the three measured magnetic field components, and is unique in two spatial dimensions. Combination of inverted data for different electrode arrangements allows visualization of temporal and spatial tracer migration, consistent with preferential tracer movement along pathways located near the container walls.
Cavity Detection in the Southwestern Hilly Portion of Mexico City by Resistivity Imaging
Authors: Tejero A. , Chávez R. E. , Urbieta J. , Flores-Márquez E. L.
Published: September 2009

Resistivity imaging (electric tomography) is a methodology for defining lateral variations of resistivity associated with structural anomalies such as caves, water contamination, and fractured zones among others. Important urban areas in Mexico City are currently at high risk of collapse. Cavities and shallow fractures have been created as a result of mining in hilly regions beneath several of today’s urbanized neighborhoods located in the southwestern portion of Mexico City. Selected areas have been investigated. Caves and tunnels were found for depths ranging between [Formula: see text] up to [Formula: see text]. Diameters of such features were between [Formula: see text] up to [Formula: see text]. Some of these structures are across paved roads and beneath buildings and houses, running for several tens of meters in length. Topographic effects were also studied in one profile. It showed important inaccuracies in resolving the geometry of the cave, mainly in terms of depth to the top, where differences of [Formula: see text] were encountered. GPR (Ground Penetrating Radar) was also used to confirm the results obtained in a resistivity profile surveyed on a test site. Results are very encouraging, demonstrating that the resistivity imaging helped to locate and characterize mined areas, jointly with other geophysical methods. Unfortunately, true resistivity is not well resolved, because of inherent ambiguity of the inverse method used.
Studies of a Riverbed Scour Monitor System Using a Pier-Interior Cased Borehole
Authors: Davies E. B. , Mercado E. J. , O’Neill M. W. , McDonald J. A.
Published: September 2009

One approach to seismic-based riverbed scour measurement utilizes a seismic source together with detectors deployed in a cased borehole adjacent to the bridge pier (the Parallel Seismic System). This approach can have disadvantages as, during river floods, cased boreholes near a pier could be damaged by the action of floodwaters. Detectors deployed in a cased borehole located within the pier would, however, be protected from the action of floodwaters. This paper describes simulated field experiments designed to determine if detectors deployed within a pier-interior cased borehole could record useful seismic data. If so, then the same data analysis will be applicable that successfully identifies the depth of scour around a bridge pier from seismic data obtained in a cased borehole adjacent to the pier. The test site contained a replica of a bridge in a water-filled pond. A cased borehole was located within one of the bridge piers. Tests were carried out with the detectors located in the pier-interior cased boreholes. Both hammer strikes applied to the top of the pier and an air gun located in the water layer were used as seismic sources. Comparative tests were carried out where the detectors were deployed in a cased borehole exterior to the pier. Analysis of the test results indicated that valid seismic events could be detected within the pier and that data derived from these could be used to provide information about scour conditions adjacent to the pier. Thus, a pier-interior cased borehole could be a useful component of a seismic based scour measurement system.
Multi-Channel Filtering Approach for Unsupervised Segmentation of Subsurface Radar Images
Authors: Al-Nuaimy W. , Huang Y. , Shihab S. , Eriksen A.
Published: September 2009

The volume of image data generated in ground-penetrating radar surveys can severely restrict the practicality of this site investigation technique. This is particularly true in situations where automatic analysis or interpretation is required, as segmentation and classification tasks that utilise multivariate data are critically affected by the volume and dimensionality of the data. A general-purpose unsupervised image segmentation system is presented here for the automatic detection of image regions exhibiting different visual texture properties. A bank of Gabor filters is used to achieve multi-channel filtering analogous to the processing of information in the visual cortex. A suboptimal feature-selection procedure is proposed to automatically select the set of texture features best suited for the particular application. The reduction in the size of the feature set both reduces the computation time and improves the accuracy of the final classification. Unsupervised neural networks are employed to segment and classify the image data into categories. Results presented for two typical radargrams match closely the interpretation of a human expert, in the fraction of the time. Applications of this technique can be found in disciplines as diverse as medical image analysis and ultrasonic non-destructive testing.
Assessment of Soil Moisture Content Measured by Borehole GPR and TDR Under Transient Irrigation and Drainage
Authors: Galagedara L. W. , Parkin G. W. , Redman J. D. , Endres A. L.
Published: September 2009

Borehole ground penetrating radar (GPR) was assessed as a method to measure the temporal and spatial variability of soil moisture under uniform wetting and drying conditions on a sandy loam soil. Zero Offset Gather (ZOG) and Multiple Offset Gather (MOG) surveys were conducted before and during the uniform irrigation and the subsequent drainage experiments using the PulseEKKO 100 borehole system with [Formula: see text] antennas in horizontal access tubes. Time domain reflectometry (TDR) data were collected from 10 vertical probes installed at [Formula: see text] increments from [Formula: see text] below the ground surface. The TDR data were used as standard measures of soil moisture to compare with the GPR estimated soil moisture. Electromagnetic wave velocity along the survey profile at about [Formula: see text] below the ground surface was estimated using ZOG and MOG data by picking the arrival time of the first event. Volumetric soil moisture was calculated using a standard empirical relationship between velocity and water content for each ZOG location. MOG data were used to develop horizontal soil moisture distribution maps at about [Formula: see text] below the soil surface by performing borehole tomogram analyses. Velocity tomograms were developed assuming straight ray paths between the source and receiver antennas and the velocity tomograms were converted to soil moisture maps. High repeatability of soil moisture measurement was found with borehole GPR method since the observed high moisture zones were consistent with time throughout both irrigation and drainage. The radius of influence of the borehole GPR measurements was about [Formula: see text] as determined theoretically and by comparing the GPR and TDR soil moisture contents.
Sparse Borehole Radar Array Imaging of Orebodies in Three Dimensions
Authors: Osman Naomi , Mason Iain , Turner Greg , Wedepohl Eric
Published: September 2009

Broadband very high frequency (VHF) borehole radars (BHR) can be used as tactical tools to map orebodies, faults and marker horizons; to identify hazards well in advance of mining and to optimize mine development. In principle, radar profiles and cross-hole scans from fanned arrays of boreholes can be used to synthesize three-dimensional images interferometrically if: borehole trajectories are accurately known; signal-to-noise ratios are adequate; the spatial sampling rate is sufficient; target echoes are well correlated, and if the target space is sufficiently uncluttered to limit the formation of mirages during reconstruction. However, automatic methods of projecting data into three-dimensional image space make stringent demands upon rock homogeneity, translucence and the accuracy of borehole trajectories. These demands can be relaxed by reconstructing objects from parts of geologically plausible 3D primitives such as cylinders, planes and spheres. In this paper we show that a number of useful primitives derive from a common element—a hoop (with semi-circular shell cross-section) of finite radius, centered on the borehole. The parameters defining the hoop’s plane, radius and thickness can be recovered sequentially from borehole radar data to determine the shape of curved 3D reflectors. We show how kinematic mapping can be applied in practice by using data acquired in a Western Australian mine. This survey was shot using [Formula: see text] borehole radars from a fanned array of [Formula: see text] long boreholes. The holes were drilled from a single station at relative angles of [Formula: see text]. Both cross-hole transmission and single-hole reflection surveys were performed. Reflection ranges of [Formula: see text] were achieved in the rocks hosting the deposit. Echo patterns correlated by using kinematic primitives were used to establish the geometry of an arched interface that was located approximately [Formula: see text] above the uppermost edge of the borehole array.
Two-Dimensional Electrical Resistivity Study of the Basement Aquifers of the Moshupa Wellfield Area, Botswana
Authors: Shemang E. M. , Chaoka T. R.
Published: September 2009

In the Moshupa Wellfield area of Botswana, fractured and weathered parts of the basement granitic rocks constitute the dominant local aquifers. Investigation of these aquifers was achieved using 2-D electrical resistivity imaging. The 2-D continuous vertical electrical sounding (CVES) techniques proved a significant advantage over the conventional vertical electrical sounding (VES) technique in that mapping of the subsurface was continuous along a profile. Three 2-D CVES profiles were undertaken in the area of study and the interpretations were used to identify areas with good prospects of finding groundwater in sufficient quantities for small-scale water supply development. Boreholes drilled in the area yielded groundwater in sufficient quantities [Formula: see text] to support small-scale domestic water supply and∕or livestock and vegetable farming in the area. The results of this study indicate that the 2-D CVES is very useful in selecting borehole sites and if properly employed could greatly assist in choosing productive borehole locations, thus reducing financial losses associated with a poorer choice of boreholes location outside fractured regions.
Electrical Conductivity in Soils: Underlying Phenomena
Authors: Klein Katherine A. , Santamarina J. Carlos
Published: September 2009

Electrical conductivity can be accurately and readily measured in the laboratory and in the field, with minimal electrode effects even in high specific surface soils and∕or high ionic concentration pore fluids. Electrical conductivity combines the contributions of particle conduction, surface conduction and pore fluid conduction, and the effects of particle shape and fabric. The interplay between participating soil parameters is often obscured in typical empirical equations, such as Archie’s law. New experimental results show that surface conduction is an important contributor to global soil conduction in high specific surface soils that are saturated with low-ionic concentration pore fluids; the relevance of surface conduction increases with decreasing porosity. On the other hand, pore fluid conduction prevails as the conductivity of the electrolyte and the porosity of the soil increase. Furthermore, low frequency conductivity anisotropy increases with increasing ionic concentration. Simple yet robust microscale analytical models properly capture the observed interplay between the most relevant soil parameters.
Electrical Properties of Sand–Clay Mixtures Containing Trichloroethylene and Ethanol
Authors: Roberts Jeffery J. , Wildenschild Dorthe
Published: September 2009

A series of laboratory experiments that measured electrical properties and permeability was performed on carefully characterized sand–clay mixtures. Different mixtures and configurations of quartz sand and 10% Na-montmorillonite clay were investigated using solutions of NaCl, [Formula: see text], and deionized water. A sample containing 10% dispersed clay was also studied using fluids containing 20- and [Formula: see text] trichloroethylene (TCE). Each sample’s electrical properties after fluid saturation were measured at frequencies between [Formula: see text] and [Formula: see text] by using the four-electrode method with Ag–AgCl inner electrodes at room temperature and [Formula: see text] confining pressure, which corresponds to a soil depth of [Formula: see text]. Our results show that adding TCE had a small effect on electrical resistivity: resistivity was greater at higher concentrations of TCE. The influence of TCE on electrical properties was most prominent in plots of loss tangent as a function of frequency. These plots showed that loss-tangent peaks occurred at [Formula: see text] and that peak and peak frequency were smaller at higher concentrations of TCE. Additional experiments were performed on a sample that contained a distinct clay layer parallel to the current flow. The electrical properties of the sample were measured as it was saturated with deionized water and [Formula: see text] solutions, and as an ethanol–water mixture (80:20) was flowed through the sample. Resistivity increased by about a factor of 4 as the ethanol mixture replaced the water solution. Nondestructive x-ray imaging of the sample at various stages of dewatering indicated a decrease in the thickness of the clay layer as more pore volumes of ethanol–water were flowed. Our results show that electrical measurements are useful tools for characterizing porous rocks and soils and that it is feasible to remotely detect the presence and follow the transport of contaminants such as TCE in the subsurface.
Discovery of a 1st Century AD Roman Amphitheater and Other Structures at the Forum Novum by GPR
Authors: Goodman Dean , Piro Salvatore , Nishimura Yasushi , Patterson Helen , Gaffney Vince
Published: September 2009

A Roman marketplace and town called the Forum Novum, initially began construction in the [Formula: see text] century BC and flourished well into the [Formula: see text] century AD. At present most of the town remains is below ground. The site is situated next to a completely restored [Formula: see text] century AD church and a partially reconstructed marketplace. Ground penetrating radar surveys have been conducted at the Forum Novum during 1998 through 2001 field seasons to remotely detect buildings of this ancient town. Using 300 and [Formula: see text] radar antennas and closely spaced radar profiles, time slice and 3-D volume analysis of the reflection data were computed. GPR surveys in the area detected a large oval-shaped structure [Formula: see text] along its major axis. This structure is from a [Formula: see text] century AD Roman amphitheater. Subsequent excavations from one of the eight entrances reveal that the internal amphitheater oval is nearly a meter thick and is composed of a cemented stone wall buried [Formula: see text] below the ground surface. The time slices revealed completely different top layer reflections from structures associated with a destroyed mausoleum, which could also be seen by the naked eye as crop marks. Archaeologists often reconstruct subsurface archaeology based on crop marks. In this case however, radar was able to detect structures near the surface—and a much different set of structures lying deeper using time slice analysis. Other structures detected in the GPR surveys include a large building complex found next to a reconstructed marketplace, and believed to be living quarters adjacent to the central market area. A large Roman villa was also imaged in one area and later excavated to reveal internal walls that include a garden atrium.
Calibration of a Low Induction Number Electromagnetic Instrument for Sea Ice Thickness Measurements
Authors: Reid J. E. , Kimber B. A. , Worby A. P.
Published: September 2009

Sea ice thickness measurements using low induction number electromagnetic instruments require accurate electromagnetic data. Calibration of EM sea ice thickness data acquired using a shipborne low induction number electromagnetic sensor can be performed by making measurements at a range of heights over level sea ice of known thickness, and by comparing the observed data with the expected layered-earth response. Calibration corrections can be derived using least-squares inversion to minimise the misfit between the observed data and the theoretical response, and can be applied to ship-borne sea ice thickness data during post-processing. This paper presents a case history illustrating identification and correction of calibration errors in low induction number electromagnetic data for shipborne Antarctic sea ice thickness measurements. The method described could also be applied to calibration of low induction number electromagnetic instruments for conventional environmental and engineering geophysical surveys.
A Radar Survey at a Granite Quarry to Delineate Fractures and Estimate Fracture Density
Authors: Seol Soon Jee , Kim Jung-Ho , Cho Seong-Jun , Chung Seung-Hwan
Published: September 2009

Borehole radar, both reflection and tomography methods, and GPR surveys were conducted at a granite quarry to delineate rock inhomogeneities, including major fractures, and to estimate the fracture density. The borehole reflection survey used a directional antenna to get the spatial orientations of the reflectors. The center frequency was [Formula: see text] for the borehole radar reflection and tomography surveys and [Formula: see text] for GPR. Through the interpretation of borehole reflection data using dipole and directional antennas, as well as surface GPR images, we could determine the orientation of the major fractures in three dimensions. Portions of the tomography travel time curves exhibited velocity anisotropy, which is uncommon in granite. Comparing the tomography data with Televiewer images showed that the anisotropy effect in this area is closely related to the alignment of fine fissures. From the borehole radar, tomography, and GPR images as well as the distribution of anisotropy, we conclude that the area bounded by the two fractures, MF2 and MF5, has the freshest granite in the surveyed area. This case study demonstrates that a combination of surface, borehole reflection, and tomographic radar surveys can provide the three-dimensional distribution of major fractures and an estimate of fracture density.
GPR Application for Mapping Toluene Infiltration in a Heterogeneous Sand Model
Authors: Hagrey Said Attia al
Published: September 2009

The high resolution radar technique is applied for monitoring infiltrated hydrocarbon liquids in a partially saturated heterogeneous sand medium as a function of time. Here I used a frequent LNAPL (light non-aqueous phase liquid) contaminant of toluene, which is electrically insulating and has a low relative dielectric constant [Formula: see text] of 2.2. In a laboratory experiment, a thin model box of [Formula: see text] was filled with a medium sand (for sand grains [Formula: see text], [Formula: see text]). The sand was saturated with water in the lowermost [Formula: see text] thick zone, and dry to partially-saturated in the overlying layer. Five small prismatic objects of fine sand (objects 1, 4) and coarse sand (objects 2, 3, 5) were embedded at different positions within the sand model. For a total time of [Formula: see text], less than [Formula: see text] toluene was infiltrated from a drip-source at the center of the upper surface of the model. Radar measurements from one side of the model using [Formula: see text] antenna showed that mapping toluene is in principle possible in the fully and partially saturated zones of objects 1, 2 and 4 and but failed in the other parts. The weak reflections within the low-saturation region may be related to the weak electromagnetic impedance contrast at the interface between the toluene, which replaced the pore water, and air.
High-Frequency and Very-High-Frequency (HF & VHF) Above-Ground Electromagnetic Impedance Measurements
Authors: Frangos William , Becker Alex , Lee K. H.
Published: September 2009

We have field-tested an apparatus for measuring the electromagnetic impedance above the ground at several frequencies in the [Formula: see text] range. This window in the frequency spectrum, which lies between frequencies used for GPR and those used for conventional loop-loop EM soundings, has not been used because of difficulties in fielding equipment for making absolute and accurate measurements. Model and physical parameter studies however confirm that data in this frequency band can be used to construct high-resolution maps of electrical conductivity and permittivity of near-surface material. Our equipment was assembled using commercial electric and magnetic antennas. The magnetic loop source is excited by a conventional signal generator—power amplifier assembly. Signal detection is accomplished using RF lock-in amplifiers. All system elements are appropriately isolated by optical fiber links. We estimate a measurement accuracy of about [Formula: see text] for an [Formula: see text] separation between source and detector. Field tests were done at the University of California Richmond Field Station where the near surface electrical structure is well known. The experimental data at this site are mainly a function of electrical conductivity. In this context, we have obtained good agreement with the known local variations in resistivity both with depth and with position along a [Formula: see text] traverse. Additional tests in more resistive regimes where dielectric permittivity is not negligible yield spectral data compatible with the less well known near-surface electrical properties.
Analysis of Correlated Noise in Airborne Magnetic Gradients for Unexploded Ordnance Detection
Authors: Gamey T. Jeffrey , Doll William E. , Beard Les P. , Bell David T.
Published: September 2009

In this paper, we examine several field tests of correlated helicopter noise and demonstrate that measured vertical gradients can offer signal-to-noise improvements of 4:1 in rotor noise and 6:1 in maneuver noise over comparable total field measurements for unexploded ordnance (UXO) applications. This translates into an additional [Formula: see text] in acceptable survey height or ordnance depth. Horizontal gradients, both transverse and longitudinal to the helicopter flight path, are also examined. These offer smaller signal-to-noise improvements over the total field (approximately 1.5:1) and have other disadvantages not found in the vertical gradient.
Exploring a taxonomy for aggression against women: can it aid conceptual clarity?
Authors: Cook Sarah , Parrott Dominic
Published: September 2009

The assessment of aggression against women is demanding primarily because assessment strategies do not share a common language to describe reliably the wide range of forms of aggression women experience. The lack of a common language impairs efforts to describe these experiences, understand causes and consequences of aggression against women, and develop effective intervention and prevention efforts. This review accomplishes two goals. First, it applies a theoretically and empirically based taxonomy to behaviors assessed by existing measurement instruments. Second, it evaluates whether the taxonomy provides a common language for the field. Strengths of the taxonomy include its ability to describe and categorize all forms of aggression found in existing quantitative measures. The taxonomy also classifies numerous examples of aggression discussed in the literature but notably absent from quantitative measures. Although we use existing quantitative measures as a starting place to evaluate the taxonomy, its use is not limited to quantitative methods. Implications for theory, research, and practice are discussed. Aggr. Behav. 35:462–476, 2009. © 2009 Wiley‐Liss, Inc.
Do aggression and rule‐breaking have different interpersonal correlates? A study of antisocial behavior subtypes, negative affect, and hostile perceptions of others
Authors: Burt S. Alexandra , Mikolajewski Amy J. , Larson Christine L.
Published: September 2009

There is mounting evidence that physical aggression and nonaggressive, rule‐breaking delinquency constitute two separable though correlated subtypes of antisocial behavior. Even so, it remains unclear whether these behavioral subtypes have meaningfully different interpersonal correlates, particularly as they are subsumed within the same broad domain of antisocial behavior. To evaluate this, we examined whether hostile perceptions of others (assessed via exposure to a series of neutral unknown faces) were linked to level and type of antisocial behavior aggression vs. rule‐breaking, and moreover, whether this association persisted even when also considering the common association with negative affect (as manipulated via written recollection of one's best and worst life experiences). Analyses revealed that aggression, but not rule‐breaking, was uniquely tied to hostile perceptions of others. Furthermore, this association persisted over and above the common association of both hostile perceptions and aggression with negative affect (at both trait and state levels). Such results provide additional support for clinically meaningful differences between the behavioral subtypes of aggression and nonaggressive rule‐breaking and for the independent role of hostile perceptions in aggressive behavior. Aggr. Behav. 35:453–461, 2009. © 2009 Wiley‐Liss, Inc.