bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagenesis of the shallow marine Fulmar Formation in the Central North Sea
Authors: Stewart D. J.
Published: November 2006

The diagenetic history of the Upper Jurassic Fulmar Formation of the Central North Sea is described with emphasis on the Fulmar Field. The Fulmar Formation was deposited on a variably subsiding shallow-marine shelf under the influence of halokinetic and fault movements. The sediments are extensively bio-destratified although large-scale cross-bedding is locally preserved. The dominant mechanism of deposition is thought to have been storm-generated currents. Soft-sediment deformation structures are common and are attributed to syn- and post-depositional dewatering of the sandstones. The dewatering was associated with fractures and shear zones which reflect tectonic instability resulting from periodic salt withdrawal and/or graben fault movements. The dewatering may have been initiated by repacking of the sediments during earth movements or by the gradual build-up and sudden release of overpressures due to compaction and/or clay mineral dehydration during rapid burial at the end of the Cretaceous. The formation is composed of arkosic sandstone of similar composition to Triassic sandstones from which it was probably derived. The sandstones also contain limited amounts of marine biogenic debris including sponge solenasters, bivalve shells, rare ammonites and belemnites. Initial diagenesis began with an environment-related phase during which quartz and feldspar overgrowths and chalcedony and calcite cements were precipitated. These cements appear to form concretions adjacent to local concentrations of sponge debris and shell debris, respectively, and were disturbed after their formation by fracturing and dewatering. This was followed by an early burial stage of diagenesis which resulted in extensive dolomite cementation and minor clay mineral authigenesis (illite and chlorite). The last phase of mineral growth was probably pyrite. During early burial diagenesis, secondary porosity after feldspar and/or carbonate was produced, although the exact timing is not clear. The lack of both stylolitic developments and extensive illitization indicates that the late burial diagenesis stage was never reached, although sufficient clay diagenesis occurred to destroy all traces of mixed-layer illite-smectite (present in some shallower wells). The main control on reservoir behaviour is primary depositional fabric. Diagenesis only overprints these controls. Locally-cemented fracture sets act as baffles to fluid flow, but they are not extensive and the reservoir acts as one unit.
An SEM study of phyllosilicate diagenesis in sandstones and mudstones in the Westphalian Coal Measures using back-scattered electron microscopy
Authors: Huggett J. M.
Published: November 2006

Back-scattered electron imaging was used in conjunction with energy-dispersive spectral analysis to study phyllosilicate minerals in polished thin-sections of Carboniferous (Westphalian) sandstones and associated mudstones from the East Midlands and from the diagenetically higher grade area of Abernant in the South Wales coalfield. Chemical diagenesis proceeded more rapidly in the sandstones than in the mudstones. In the East Midlands, greater flow of freshwater through the sandstones than the mudstones produced a higher degree of alteration of muscovite to kaolinite in the sandstones. Chlorite is present in the Well 1 and Well 2 East Midlands sandstones but not the mudstones nor any Well 3 samples. The chlorite may be an early diagenetic replacement of biotite. Much chlorite has been replaced by kaolinite. In the Abernant samples chlorite is present in both the sandstones and mudstones. In the former it appears to have replaced detrital biotite. In the latter the chlorite is too fine-grained to discern whether it is detrital or authigenic. The chlorite may have formed during the Hercynian orogeny. Much of the mica and chlorite in the Abernant sandstones has been replaced by illite, possibly in the post-orogenic period. The scarcity of kaolinite in the Abernant samples reflects the lack of freshwater leaching.
Sandstone reservoir description: an overview of the role of geology and mineralogy
Authors: Hurst A. , Archer J. S.
Published: November 2006

Reservoir description is achieved by the integration of geological, petrophysical and engineering data. Modelling of reservoir performance is made by creating a three-dimensional model of the reservoir volume, where the reservoir is built of cells and layered zones which are defined geologically. Although the scale of cell size is coarse compared to the scale of geological data, it is important that the geological input to define cells is as precise as possible. The texture of clay minerals and their composition are requisite for understanding their influence on reservoir characteristics. Wireline logs probably do not provide sufficient information about clay mineralogy to evaluate reservoir characteristics, but do allow the extrapolation of ‘point’ mineralogical data into a continuous reservoir description. Evaluation of porosity, permeability and saturation are described, and the possible influence of clay mineralogy on evaluation of these characteristics is discussed.
Moisture damage and childhood asthma: a population-based incident case–control study
Authors: Pekkanen J. , Hyvärinen A. , Haverinen-Shaughnessy U. , Korppi M. , Putus T. , Nevalainen A.
Published: November 2006

Most previous studies on the association between moisture damage and asthma have been cross-sectional and relied on self-reported exposure and health. The present authors studied the association by carrying out careful home inspections among new, clinically determined cases of asthma and controls.

New cases of asthma aged 12–84 months (n = 121) were recruited prospectively and matched for year of birth, sex and living area with two randomly selected population controls (n = 241). Trained engineers visited all homes. Both cases and controls had lived ≥75% of their lifetime or the past 2 yrs in their current home.

Risk of asthma increased with severity of moisture damage and presence of visible mould in the main living quarters but not in other areas of the house. Cases more often had damage in their bedroom. Associations were comparable for atopic and nonatopic asthma and for children aged >30 months or ≤30 months.

The present results, using standardised assessment of exposure and asthma, suggest that moisture damage and mould growth in the main living quarters are associated with the development of asthma in early childhood.
Prehistory of the Notion of Circulating Nucleic Acids in Plasma/Serum (CNAPS)
Authors: STROUN MAURICE , ANKER PHILIPPE
Published: November 2006

Abstract:  In the late 50s and early 60s of the last century, a theoretical fight was taking place between Western and Russian scientists about the theory explaining the mechanism of evolution. According to neo‐Darwinism, evolution was the result of hazard and necessity, that is, mutations arriving by chance favoring the survival of the fittest. For the Russian geneticists, acquired characteristics were the basis of evolution, that is, the environment modified the characteristics of the gene. One of the main experiments on which the Russian geneticists based their theory was the transmission of hereditary characteristics by a special technique of grafting between two varieties of plants—a mentor plant and a pupil plant. The pupil variety being entirely dependent on the development of the mentor plant its hereditary characteristics were modified accordingly. In the Western world these experiments were regarded with doubt. We were among the few who tried to repeat this kind of experiment. After three generations of grafting between two varieties of eggplant, we succeeded in obtaining hereditary modifications of the pupil plants, which acquired some of the characteristics of the mentor variety. The linkage between some hereditary characteristics of the mentor plant were broken, the segregation of the offspring was abnormal, dominant characteristics appearing in the offspring of a recessive plant. Rather than adopting the views of the Russian scientists about acquired characteristics, we suggested that DNA was circulating between the mentor and pupil plants and assumed that some nucleic acid molecules bearing genetic information could enter the somatic and reproductive cells of the pupil plant at a propitious moment and remain active.
Occurrence of Neutrophil Extracellular DNA Traps (NETs) in Pre‐Eclampsia
Authors: GUPTA ANURAG , HASLER PAUL , GEBHARDT STEPHAN , HOLZGREVE WOLFGANG , HAHN SINUHE
Published: November 2006

Abstract:  Manifest pre‐eclampsia is associated with activation of peripheral neutrophils as well as elevations in maternal cell‐free DNA. For this reason, we were very intrigued by recent reports indicating that activated circulatory neutrophils secrete nuclear DNA to generate extracellular DNA lattices, termed NETs (neutrophil extracellular traps). Our preliminary data indicate that placental syncytiotrophoblast microparticles, which are released in elevated amounts in pre‐eclampsia, can induce NETs in isolated neutrophils. Furthermore, we found evidence for the increased presence of NETs directly in the intervillous space of pre‐eclamptic placentae. Therefore, these newly discovered entities may be implicated in the underlying etiology of this disorder.
Quantification of Total Plasma Cell‐Free DNA in Ovarian Cancer Using Real‐Time PCR
Authors: KAMAT APARNA A. , SOOD ANIL K. , DANG DIANNE , GERSHENSON DAVID M. , SIMPSON JOE L. , BISCHOFF FARIDEH Z.
Published: November 2006

Abstract:  Our objective was to compare the levels of total circulating plasma cell‐free DNA (CfDNA) using real‐time PCR in patients with late‐stage ovarian cancer with those in unaffected controls. Following IRB consent, DNA was extracted from archived frozen plasma of 19 patients with primary ovarian carcinoma and 12 age‐matched controls using Qiagen DNA Isolation Kits. Quantification of total CfDNA was performed using real‐time PCR with the TaqMan Assay for GAPDH, β‐actin and β‐globin and the number of genome equivalents (GE/mL) were determined from a standard curve. CfDNA levels of these loci were compared between the groups with Student's t‐test, with P < 0.05 being statistically significant. The mean age of the patients was 61.6 years (±9.6) and of the controls was 54 years (±12.2). All patients had high‐grade, advanced stage (III or IV) serous ovarian carcinomas. Preoperative CA‐125 levels ranged from 43 to 15,626 IU/mL (mean 2487.2 ± 3686 IU/mL). Total CfDNA in ovarian cancer was higher among patients with ovarian cancer as compared to controls at all three loci: GAPDH (P= 0.022), β‐actin (P= 0.025), and β‐globin (P= 0.0089). CfDNA is elevated in advanced stage disease compared to controls. These preliminary results suggest that total CfDNA in the plasma of patients with ovarian cancer may be useful for noninvasive screening and disease surveillance.
Cell‐free DNA and RNA in Plasma as a New Molecular Marker for Prostate and Breast Cancer
Authors: PAPADOPOULOU EIRINI , DAVILAS ELIAS , SOTIRIOU VASILIOS , GEORGAKOPOULOS ELEFTHERIOS , GEORGAKOPOULOU STAVROULA , KOLIOPANOS ALEXANDER , AGGELAKIS FILIPOS , DARDOUFAS KONSTANTINOS , AGNANTI NIKI J. , KARYDAS IRINI , NASIOULAS GEORGIOS
Published: November 2006

Abstract:  In this study, we examined several molecular markers in prostate and breast cancer patients and in normal individuals. The markers tested were: variations in the quantity of plasma DNA, glutathione‐S‐transferase P1 gene (GSTP1), Ras association domain family 1A (RASSF1A), and ataxia telangiectasia mutated (ATM) methylation status in plasma, carcinoembryonic antigen (CEA) and prostate‐specific membrane antigen (PSMA) mRNA in peripheral blood mononuclear cells (PBMC) and plasma samples from prostate cancer patients. DNA quantification in plasma was performed using real‐time PCR (RT‐PCR). We assessed the methylation status of GSTP1 in plasma DNA using methylation‐specific PCR (MSP) assay, while the methylation status of RASSF1A and ATM genes was examined by the MethyLight technology. RT‐PCR analysis was used for the detection of mRNA, PSMA, and CEA. In 58.3% of newly diagnosed prostate cancer patients and 26.7% of prostate cancer patients under therapy, plasma DNA levels were increased. Additionally, 48.5% of breast cancer patients showed plasma DNA levels above the cutoff limit. GSTP1 Promotor hypermethylation was detectable in 75% of plasma samples obtained from patients with newly diagnosed prostate cancer and in 36.8% of patients under therapy, whereas 26% and 14% of the breast cancer patients tested were positive for RASSF1A and ATM methylation, respectively. The combination of DNA load and promotor methylation status identified 88% of prostate cancer patients and 54% of breast cancer patients. This study shows that free‐circulating DNA can be detected in cancer patients compared with disease‐free individuals, and suggests a new, noninvasive approach for early detection of cancer.
The Importance of Careful Blood Processing in Isolation of Cell‐Free DNA
Authors: PAGE KAREN , POWLES TOM , SLADE MARTIN J. , DE BELLA MANUELA TAMBURO , WALKER ROSEMARY A. , COOMBES R. CHARLES , SHAW JACQUELINE A.
Published: November 2006

Abstract:  In healthy individuals, the source of cell‐free plasma DNA is predominantly apoptotic, whereas, increased plasma DNA integrity is seen in cancer patients. Therefore, it is important to carefully isolate absolutely “cell‐free” plasma DNA. Plasma DNA from 30 healthy females was analyzed using 4 PCR amplicons of increasing size, comparing standard blood processing with additional centrifugation steps prior to DNA extraction. Cellular DNA contamination, indicated by positive amplicons >300 bp was eliminated only after the extra centrifugation step. This highlights the importance of careful processing in preparation of cell‐free plasma DNA as a tool for cancer detection and we recommend the use of a microcentrifuge spin, prior to DNA extraction.
A Limited Access Compartment between the Pore Domain and Cytosolic Domain of the BK Channel
Authors: Zhang Zhe , Zhou Yu , Ding Jiu-Ping , Xia Xiao-Ming , Lingle Christopher J.
Published: November 2006

Cytosolic N-terminal segments of many K+channel subunits mediate rapid blockade of ion permeation by physical occlusion of the ion-conducting pore. For some channels with large cytosolic structures, access to the channel pore by inactivation domains may occur through lateral entry pathways or “side portals” that separate the pore domain and associated cytosolic structures covering the axis of the permeation pathway. However, the extent to which side portals control access of molecules to the channel or influence channel gating is unknown. Here we use removal of inactivation by trypsin as a tool to examine basic residue accessibility in both the N terminus of the native auxiliary β2 subunit of Ca2+-activated, BK-type K+channels and β2 subunits with artificial inactivating N termini. The results show that, for BK channels, side portals define a protected space that precedes the channel permeation pathway and excludes small proteins such as trypsin but allows inactivation domains to enter. When channels are closed, inactivation domains readily pass through side portals, with a central antechamber preceding the permeation pathway occupied by an inactivation domain approximately half of the time under resting conditions. The restricted volume of the pathway through side portals is likely to influence kinetic properties of inactivation mechanisms, blockade by large pharmacological probes, and accessibility of modulatory factors to surfaces of the channel within the protected space.
Hydrogeophysical Investigation at Luxor, Southern Egypt
Authors: Ismail Ahmed , Anderson Neil L. , Rogers J. David
Published: November 2006

Over the past [Formula: see text], the exposed stone foundations of the ancient Egyptian monuments at Luxor have deteriorated at an alarmingly accelerated rate. Accelerated deterioration is attributable to three principal factors: 1) excavation and exposure of foundation stone; 2) construction of the Aswan High Dam; and 3) changes in the regional groundwater regime. In an effort to better elucidate the hydrostratigraphy in the Luxor study area that extends from the River Nile to the boundaries of the Nile Valley and covers about [Formula: see text], a geophysical∕hydrological investigation was conducted. Forty Schlumberger vertical electrical soundings (VES), two approximately [Formula: see text] long seismic refraction profiles and a total number of 39 groundwater and surface water samples were acquired. Based on the integrated interpretation of the acquired geophysical∕hydrological data, the main contributions of this study were the geophysical definition of the hydrostratigraphy using resistivity (seven distinct geologic∕ hydrologic units were mapped), the mapping of the water table using seismic refraction and the mapping of groundwater salinity trends through geochemical sampling. The factors contributing to the rise of groundwater and its accompanying increase in salinity were identified and documented. This characterization establishes a model for evaluating various plans to lower groundwater levels and salinities in the areas of archeological monuments.
Applications of Love Wave Dispersion for Improved Shear-wave Velocity Imaging
Authors: Safani Jamhir , O’Neill Adam , Matsuoka Toshifumi , Sanada Yoshinori
Published: November 2006

Love wave dispersion and associated analytic partial derivatives are theoretically derived using the reflection∕transmission (R∕T) method. The numerical implementation is then applied to linearised inversion of synthetic and field data. For simple cases dominated by the fundamental mode, Love wave sensitivity and inversion stability is higher than the Rayleigh wave dispersion. However, in general, Rayleigh wave inversion converges more rapidly than Love waves, although similar low misfits can be achieved. When assumed interfaces are used, the inversion of fundamental-mode Love wave dispersion of the normally dispersive profile provides a more accurate result, because the Love wave dispersion is independent of the Poisson’s ratio. In more realistic, irregularly dispersive profiles, deep structure is only interpreted using higher-mode Love and Rayleigh wave dispersion. A field test over a shallow geologic fault with coincident Love and Rayleigh wavefields shows the fundamental—mode Love wave dispersion above [Formula: see text] to have at least 10% higher phase velocities than Rayleigh waves. However, at lower frequencies, Love wave dispersion is at least 10% slower. The resulting inverted models show up to 25% difference in shear-wave velocity. This is attributed to transverse isotropy of [Formula: see text] and [Formula: see text] in shallow fluvial sediments and allows improved geological horizon interpretation and soil discrimination over conventional, single-component surface wave inversion. A second test at a seismograph station site shows the Love wavefield less scattered and mode identification is simple, unlike Rayleigh waves over the same line, and the inversion results correlate well to downhole shear-wave velocity logs.
Surface-wave Inversion Limitations from Laser-Doppler Physical Modeling
Authors: Bodet Ludovic , van Wijk Kasper , Bitri Adnand , Abraham Odile , Côte Philippe , Grandjean Gilles , Leparoux Donatienne
Published: November 2006

Surface-wave dispersion inversion is growing in popularity for geotechnical applications, due to its noninvasive character, relative straightforward field procedures and interpretation, especially when the subsurface structure is locally assumed to be one-dimensional (1D). Here, laser-Doppler physical modeling of surface-wave propagation is used to address issues of surface-wave depth penetration, the presence of dipping layers, and the associated limitations and systematic errors propagated in conventional 1D surface-wave inversion. Flat-layered models show that, with an active source and linear spread, the maximum resolvable wavelength of the Rayleigh-wave fundamental mode is on the order of 40% of the spread length. Linearised inversions confirm the rule of thumb that the depth penetration is 20–25% of the spread length, and that correct a priori layer interface depths from refraction analysis allow more accurate results. However, even under optimal conditions, failing to account for a dominant higher mode at low frequency when a stiff shallow layer is present, causes an overestimate of deeper layer shear-wave velocity. Moreover, a layer dip of only a few degrees can significantly bias the surface-wave inversion. If the incorrect a priori information from a single-shot refraction analysis is incorporated in the inverse problem, estimated interface depth depends on the shot position and deeper layer shear-wave velocity is underestimated. Even if correct a priori constraints are used, an underestimate of half-space shear-wave velocity of up to 25% remains.
Joint Analysis of a Surface-wave Method and Micro-gravity Survey
Authors: Hayashi Koichi , Matsuoka Toshifumi , Hatakeyama Hideki
Published: November 2006

We propose a joint analysis of a surface-wave and a micro-gravity survey for estimating both S-wave velocity and density of the subsurface. The surface-wave method and micro-gravity surveys were performed to delineate a buried channel filled with soft alluvium sediments. A CMP crosscorrelation analysis of surface-waves was applied to multi-shot and multi-channel surface-wave data and an S-wave velocity model was estimated. A micro-gravity survey was performed on the same survey line and a clear Bouguer anomaly low was detected. The S-wave velocity model was converted into a density model by a transform developed by combining density from laboratory soil tests and the S-wave model. The theoretical gravity anomaly was calculated, and compared well with the observed data, supporting the accuracy of the assumed transform. This density model was used as the initial model in a least squares inversion and a clear low-density area was obtained, which agrees with a low S-wave velocity area obtained from the surface-wave method. The two images are combined to estimate the shear modulus, and the lateral extent of the buried channel is clearly delineated.
Comparison of Shear-velocity Profiles of Unconsolidated Sediments Near the Coyote Borehole (CCOC) Measured with Fourteen Invasive and Non-invasive Methods Editorial
Authors: Asten Michael , Boore David
Published: November 2006

A set of fourteen invasive and non-invasive geophysical methods are compared for the measurement of the shear-velocity (Vs) profile at or near a borehole at the Coyote Creek outdoor Classroom, Santa Clara Valley, California. The borehole with geophysical logs provided opportunity for a series of blind trials of methods for measurement of the Vs profile in thick, soft sediments. The various methods are important in the task of establishing shear-velocity profiles for purposes of earthquake hazard site classification in California. Results of the trials were presented at a one-day workshop at the US Geological Survey in May 2004; this paper summarizes results, relative depths of penetration and differences between the fourteen methods.
Characteristics of Surface Waves in Media with Significant Vertical Variations in Elasto-Dynamic Properties
Authors: De Nil Denise
Published: November 2006

In media with strong vertical variations in elasto-dynamic properties, the characteristics of surface waves may deviate significantly from their typical appearance in media with small contrasts. Different numerical examples suggest that ignoring this behavior may lead to poor results in surface wave analysis. The cases analysed are: (1) Neighboring surface wave modes which exchange their major characteristics at osculation points of their dispersion curves; (2) Quasi-channel waves propagating inside a buried low velocity channel; (3) Surface waves in the presence of a low-velocity layer at the very surface; and (4) Rayleigh surface waves in the presence of a very high velocity contrast allowing normal quasi-compressional pseudo-modes. Amplitude-depth functions are used to analyze the physical cause of the unusual characteristics. One important result is a vanishing vertical displacement of the fundamental mode and dominance of the first higher Rayleigh mode at low frequency for cases with a large elastic contrast at shallow depth (increase in Vs approaching 300% at [Formula: see text]). If the displacement is treated as the fundamental mode, a systematic overestimate of deeper shear wave velocity will arise in the inversion, since higher modes have higher phase velocity. A second result is from a profile with a very thin, surficial low-velocity layer, where higher modes dominating the response might prevent fundamental mode detection and inversion. Finally, if shear wave velocity of the half-space exceeds the compressional wave velocity of an overlying layer, quasi-compressional waves (or guided P-waves) come into the velocity range of normal modes. This may lead to surface wave mode-misidentification.
An Unsupervised Wavelet Transform Method for Simultaneous Inversion of Multimode Surface Waves
Authors: Tillmann Axel
Published: November 2006

Dispersive surface waves are sensitive to the geometry of layered structures and the compressional and shear wave velocities within each layer. Therefore they can be used to estimate the structure and lithology of shallow soils. It is common practice to use the low frequency fundamental mode for inversion; thus, it is necessary to separate the single modes contained in the data interactively, which is time consuming and a source of error. The fast algorithm presented in this paper interprets all excited modes of a surface wave simultaneously and avoids the need to identify individual mode-numbers. The inversion is based on the group travel time of a Rayleigh wave, estimated from a single seismic trace by application of the Continuous Wavelet Transform (CWT). The resulting CWT distribution is fitted by a composition of wavelets determined from theoretical group-velocity dispersion relations of possible models, in connection with appropriate boundary conditions. A feasibility test on a synthetic dispersion dataset with dominant higher modes shows that the systematic inversion error associated with a fundamental-mode assumption does not arise, and both layer thicknesses and elastic properties can converge rapidly to the true values. However, two possible problems with the proposed method are the imperfect reconstruction (in this case especially at low frequencies), owing to the limited number of wavelets and theoretical modal dispersion curves used for approximation, and possible convergence to local minima, due to the increased nonlinearity of the misfit function.
Nonlinear Complex-Resistivity Survey for DNAPL at the Savannah River Site A-014 Outfall
Authors: Grimm Robert E. , Olhoeft Gary R. , McKinley Kate , Rossabi Joseph , Riha Brian
Published: November 2006

Nonlinear complex-resistivity (NLCR) cross-hole imaging of the vadose zone was performed at the A-014 Outfall at the Savannah River Site, Aiken, SC. The purpose of this experiment was to field-test the ability of this method to detect dense nonaqueous phase liquids (DNAPLs), specifically tetrachloroethene (PCE), known to contaminate the area. Five vertical electrode arrays (VEAs) were installed with [Formula: see text] [Formula: see text] separations in and around the suspected source zone to depths of [Formula: see text] [Formula: see text], and measurements were carried out at seven nearest-neighbor panels. Amplitude and phase data were edited for quality and then inverted to form three-dimensional (3D) images. The comparatively small magnitude of the nonlinear resistivity Hilbert distortion allowed approximate linearized imaging of the 3D distribution of this quantity as well. Laboratory analysis of nearby soil contaminated in situ indicated that the NLCR response to the PCE-clay reaction is maximized near [Formula: see text], leading to the development of a metric involving the phase and resistivity Hilbert distortion to infer the 3D distribution of PCE. Variations in PCE content were independently detailed at three drilling locations within the NLCR survey area using direct penetration-based soil-collection tools. Approximately 400 soil samples were collected and analyzed for chlorinated solvent mass composition at [Formula: see text] [Formula: see text] vertical intervals to compare with the NLCR-predicted distribution of DNAPL. The optimum performance for [Formula: see text] PCE was [Formula: see text] detection (true positives) with [Formula: see text] false alarms (false positives) at an effective resolution of [Formula: see text] [Formula: see text], or [Formula: see text] of the interwell separation. When smoothed to [Formula: see text] [Formula: see text] resolution (comparable to well spacing), detection was 100% with just 12% false alarms. NLCR successfully predicted the general distribution of PCE at parts-per-thousand soil-mass fractions, specifically widespread near-surface contamination and a zone of discontinuous stringers and pods below the source.
Injection Electrode Overprinting
Authors: Merriam J. B.
Published: November 2006

Polarization of the injection electrodes in resistivity and induced polarization may in some cases result in an anomalous response at the receiving electrodes. This is referred to here as injection electrode overprinting. Overprinting may occur in resistivity measurements when an electrode is used as a receiving electrode immediately following duty as an injection electrode, such as in multi-electrode systems with automatic switching. The circumstances that produce overprinting are demonstrated here and recommendations are made to limit its occurrence and effect. It is found that the overvoltage on injection electrodes is unlikely to exceed a few volts and that the period of rapid, nonlinear, decay is over in a few seconds. Most modern resistivity equipment can easily accommodate potentials with these characteristics as part of spontaneous potential rejection. A simple procedure is recommended to test if overprinting is occuring. Injection sequences with short and long delays between injector-receiver duty should be executed. Any difference in apparent resistivity indicates a possible problem with overprinting. Situations where one of an injection pair has a large surface area and the other a small surface area, as is often the case in pole-pole or pole-dipole surveys, are more likely to be problematic in that the polarization and circuit impedance may depend on the polarity of the pulse.
A Comparison of Self-Potential Tomography with Electrical Resistivity Tomography for the Detection of Abandoned Mineshafts
Authors: Wilkinson Paul B. , Chambers Jonathan E. , Meldrum Philip I. , Ogilvy Richard D. , Mellor Chris J. , Caunt Simon
Published: November 2006

We present a comparison of the abilities of Electrical Resistivity Tomography (ERT) and Self-Potential Tomography (SPT) to detect and characterize buried mineshafts at the site of a former colliery. Surface electrical resistivity and self-potential (SP) surveys were carried out at two test sites, each containing a hidden shaft. The ERT survey results indicate that both sites had a highly heterogeneous subsurface resistivity distribution, which we attribute to colliery spoil and former infrastructure. ERT managed to distinguish an air-filled, highly resistive mineshaft from this background, but failed to detect the second shaft, which was backfilled and therefore had a much lower resistivity contrast with the surrounding formation. However, SPT located both shafts, gave an indication of their size, shape and depth of burial, and was able to distinguish the open-from the backfilled mineshaft due to the strength of the associated SP anomalies. We argue that these SP anomalies are likely to be due to changes in the streaming potential caused by preferential drainage into the shafts.
Design and Application of an Electromagnetic Vibrator Seismic Source
Authors: Haines Seth S.
Published: November 2006

Vibrational seismic sources frequently provide a higher-frequency seismic wavelet (and therefore better resolution) than other sources, and can provide a superior signal-to-noise ratio in many settings. However, they are often prohibitively expensive for lower-budget shallow surveys. In order to address this problem, I designed and built a simple but effective vibrator source for about one thousand dollars. The ‘‘EMvibe’’ is an inexpensive electromagnetic vibrator that can be built with easy-to-machine parts and off-the-shelf electronics. It can repeatably produce pulse and frequency-sweep signals in the range of [Formula: see text], and provides sufficient energy for recording at offsets up to [Formula: see text]. Analysis of frequency spectra show that the EMvibe provides a broader frequency range than the sledgehammer at offsets up to [Formula: see text] in data collected at a site with soft sediments in the upper several meters. The EMvibe offers a high-resolution alternative to the sledgehammer for shallow surveys. It is well-suited to teaching applications, and to surveys requiring a precisely-repeatable source signature.
Investigation of Fractures Using Seismic Computerized Crosshole Tomography
Authors: Gu Hanming , Cai Chengguo , Wang Yunsheng
Published: November 2006

Geological features such as fractures and voids pose potential hazards to the safe construction and operation of tunnels. The high resolution of seismic computerized tomography has been successfully applied to the detection of such features prior to the construction of a railway tunnel through Qiyue Mountain in central China. Data were acquired using three boreholes drilled to [Formula: see text] in Triassic carbonates and interpreted using seismic computerized tomography (CT) based on ray theory. We used a sparker source in one borehole and an array of hydrophones in a second borehole as receivers. First arrival times were picked automatically, and we applied the algorithm SIRT to reconstruct the variation of seismic velocity between the boreholes. Combining the results with information from engineering drilling, we were able to map precisely the distribution of fractures, rock fragmentation and small voids in the plane defined by the three wells. The results show that there are four linear low-velocity features, which are interpreted as fracture zones. Discrete low-velocity anomalies along these fracture zones are interpreted as small voids. These are consistent with the drilling results. The results provide an excellent example of the applicability of seismic elastic CT in mapping geological hazards such as voids and fractures.
Neural Network Based Interpretation Algorithm for Combined Induced Polarization and Vertical Electrical Soundings of Coastal Zones
Authors: Sastry Rambhatla G. , Tesfakiros Haile G.
Published: November 2006

The problem of fresh water availability in coastal aquifers is a reality. For in-situ and dynamic characterization of seawater encroachment into coastal aquifers, electrical geophysical methods are better suited. Vertical Electrical sounding (VES) when combined with induced polarization soundings (IPS) can resolve saline sands from moist clays. Our feed forward back-propagation neural network (BPNN) based approach automates the analysis of combined vertical electrical and induced polarization soundings to suit practical needs. Our method is initially tested on synthetic data computed from available geo-electric sections and geological information concerning coastal aquifers of the East Coast of India. The synthetic data comprised 18 combined Schlumberger IPS and VES soundings (504 apparent resistivity and chargeability samples) spread over five profiles in the study region. Fictitious apparent resistivity (product of apparent resistivity and apparent chargeability) soundings are derived from them. We used 118 carefully selected discrete fictitious apparent resistivity values from 210 sample sets gathered from 15 (420 samples) combined soundings to train the BPNN, while 33 samples from 3 separate combined soundings, and 26 random samples from 92 unused training samples of 15 soundings were used for testing. Our trained BPNN involved one input node and one bias-unit at the input layer stage, one node in the output layer, and 18 nodes and one bias-unit in hidden layer. The trained neural net showed an overall success rate of 83% in testing phase for distinguishing clays from saline sands in the synthetic example. Our method is also tested on real data concerning a shaly groundwater aquifer in Bahia, Brazil yielding an overall accuracy of 85%, quite comparable to that of synthetic case. Thus, both synthetic and field data analysis validate our neural network based algorithm.
Prediction of cloth wetting times from diffusion constants of alcohol ethoxylate mixtures
Authors: Smith Dewey L.
Published: November 2006

Commercial alcohol ethoxylates are composed of a distribution of ethoxymers, and the width of the distribution can affect some performance properties such as cloth wetting. For example, if the distribution is peaked at the fastest wetting ethoxymer, wetting time decreases. One can predict if further peaking will significantly improve wetting performance if the relationship between ethoxymer distribution peaking and wetting can be determined. As a first step in predicting how cloth wetting time changes with peaking of the ethoxymer distribution, the cloth wetting time of a binary mixture of octaethylene glycol monododecyl ether (C12−8) and hexaethylene glycol monotetradecyl ether (C14−6) was studied. Wetting time was inversely dependent on the average diffusion constant of the mixture, which is predicted from the diffusion constants of the ethoxymers in the mixture and the mixture composition. Diffusion constants of the ethoxymers are derived from dynamic surface tension measurements. Therefore, it is possible to predict the relative cloth wetting time for any alcohol ethoxylate distribution by knowing the diffusion constant of each ethoxymer in the distribution and the distribution composition.
Conductance behavior of lithium soaps in aqueous methanol
Authors: Varma R. P. , Goel H.
Published: November 2006

Conductance behavior of lithium soaps (abietate, oleate, and myristate) has been used to evaluate the true dissociation constant, limiting molar conductance, and thermodynamic parameters (viz., enthalpy, free energy, and entropy changes) for dissociation. The soaps behave as week electrolytes in mixtures, and the Debye‐Huckel‐Onsagar equation is not applicable for these soap solutions.
Use of certain alcohol ethoxylates to maintain protease stability in the presence of anionic surfactants
Authors: Russell Geoffrey L. , Britton Larry N.
Published: November 2006

Anionic surfactants, including linear alkylbenzene sulfonate (LAS), are known to decrease the stability of detergent proteases, possibly by hastening autoproteolytic processes. Thus, protease shelf life in enzyme‐containing, heavy‐duty liquid laundry detergents (HDL) is typically maintained by adding stabilizers, by limiting the level of interfering anionics, or by utilizing more compatible anionics, such as alcohol ethoxysulfates (AES). This study examines the stability of Savinase® detergent protease in HDL formulations based on LAS and containing different alcohol ethoxylates (AE) for protection against protease inactivation. Dose response curves demonstrated that all commonly used anionic surfactants except AES promote loss of protease activity. In HDL formulations with equal percentage compositions of LAS and AE, the structure of the selected AE was found to have a profound influence on protease stability. Inclusion of AE with chain length ≥C14 and ethoxylate levels >70% resulted in greater protease stability. HDL containing LAS and these protective AE could be formulated to achieve protease stability matching those of simulated commercial products. Unlike polyhydric stabilizers, the AE by themselves confer no additional stability to the protease. It is more likely that the stabilizing effect of the “protective” AE is due to decreased availability of LAS to the protease.
Critical micelle concentrations of different classes of surfactants: A quantitative structure property relationship study
Authors: Anoune Naoual , Nouiri Moustapha , Berrah Yacine , Gauvrit Jean‐Yves , Lanteri Pierre
Published: November 2006

The critical micelle concentration (CMC) values of a 49‐surfactant dataset, among them 30 derived from α‐hydroxy acids or from gluconolactone synthesized and characterized in our laboratory, were subjected to Quantitative Structure Property Relationship (QSPR) studies. In this study, a principal component analysis (PCA) was used to compare the behavior of the synthesized surfactants to commercial ones that are used as detergents. The PCA shows the importance of the molecular structure of a surfactant in determining its activity (application field). We found that gluconolactone derivatives exhibited the same activity as those observed for glucopyranoside derivatives. A partial least squares regression was used to build a model that describes the CMC of diverse surfactants as a function of molecular descriptors.
Micellar association in simultaneous presence of organic salts/additives
Authors: Kumar Sanjeev , Khan Ziya Ahmad , Kabir‐ud‐Din
Published: November 2006

Viscosity measurements under Newtonian flow conditions had been performed on cetyltrimethylammonium bromide (CTAB) aqueous solutions in the combined presence of sodium salts of aromatic acids (sodium salicylate, NaSal; sodium benzoate, NaBen; sodium anthranilate, NaAn) and organic additives (1‐hexanol, C6OH; n‐hexylamine, C6NH2) at 30°C. On addition of C6OH or C6NH2, the viscosity of 25 mM CTAB solution remained nearly constant without salt as well as with a lower salt concentration. This is due to low CTAB concentration which is not sufficient to produce structural changes in this concentration range of salts. However, as the salt concentration was increased further, the effect of C6OH/C6NH2 addition was different with different salts: The viscosity first increased; then a decrease was observed with the former while with C6NH2 a decrease followed by constancy appeared in plots of relative viscosities (ηr) vs. organic additive concentrations. At further higher salt concentration, the magnitude of ηr was much higher. The viscosity increase is explained in terms of micellar growth and the decrease in terms of swollen micelle formation (due to interior solubilization of organic additive) or micellar disintegration (due to formation of water + additive pseudophase).
Effect of nutrients on optimal production of biosurfactants by Pseudomonas putida—A gujarat oil field isolate
Authors: Pruthi V. , Cameotra S. S.
Published: November 2006

Nutritional requirements for maximal production of biosurfactant by an oil field bacterium Pseudomonas putida were determined. The optimal concentrations of nitrogen, phosphate, sulfur, magnesium, iron, potassium, sodium, calcium, and trace elements for maximal production of biosurfactants were ascertained, and a new “Pruthi and Cameotra” salt medium was formulated. Data show that maximal biomass (2.4 g L−1) and biosurfactant production (6.28 g L−1) takes place after 72 h of growth on 2% hexadecane. The biosurfactant was produced optimally over pH and temperature ranges of 6.4–7.2 and 30–40°C, respectively. That the highest biosurfactant yield was obtained during late log phase of growth indicates that the biosurfactant is a secondary metabolite.
Additive‐induced association in unconventional systems: A case of the hydrotrope
Authors: Kumar Sanjeev , Parveen Nahid , Kabir‐ud‐Din
Published: November 2006

It is well known that hydrotropes have a very high minimum hydrotrope concentration (MHC), posing a question on their applications. We have found that MHC (obtained by conductivity and surface tension measurements) can be reduced by the addition of foreign materials. The association tendency can be improved by the addition of salts, n‐alkanols, and ureas. Urea decreases or increases the MHC depending on whether the urea content is lower or higher (e.g., the increased solubility of sparingly soluble riboflavin corroborates the increase in the hydrotropic properties of the system). In the present work, the association tendencies of sodium salicylate (a well‐known hydrotrope), sodium dodecyl sulfate, and sodium bromide were compared. The results have direct implications in the mechanism of protein denaturation and may provide insight into the role of urea in supramolecular assemblies.
Contact angle of surfactant solutions on precipitated surfactant surfaces. III. Effects of subsaturated anionic and nonionic surfactants and NaCl
Authors: Luepakdeesakoon Bungon , Saiwan Chintana , Scamehorn John F.
Published: November 2006

The contact angles of saturated calcium dodecanoate (CaC12) solutions containing a second subsaturated surfactant on a precipitated CaC12 surface were measured by using the drop shape analysis technique. The subsaturated surfactants used were anionic sodium dodecylsulfate (NaDS), anionic sodium octanoate (NaC8), and nonionic nonylphenol polyethoxylate (NPE). Comparing at the critical micelle concentration (CMC) for each surfactant, NaC8 was the best wetting agent, followed by NaDS, with NPE as the poorest wetter (contact angles of 320, 420, and 620, respectively). Surface tension at the CMC increased in the order NaC8<NPE<NaDS, and subsaturated surfactant adsorption increased in the order NPE≪NaDS (1.4 vs. 84 μmole/g); adsorption of the NaC8 was not measurable. Interfacial tension (IFT) reduction at the solid‐liquid interface due to subsaturated surfactant adsorption is an important contribution to contact angle reduction, in addition to surface tension reduction at the air‐water interface. Surfactant adsorption onto the soap scum solid is crucial to solid‐liquid IFT reduction and to good wetting. The fatty acid was the best wetting agent of the three surfactants studied, probably because calcium bridging with the carboxylate group synergizes surfactant adsorption onto the solid of the higher molecular weight soap. NaCl added to NaDS surfactant results in depressed CMC, lower surface tension at the CMC, decreased NaDS adsorption onto the solid, and decreased reduction in solid‐liquid IFT. The contact angle is not dependent on the NaCl concentration for NaDS. The NaCl causes an increased tendency to form monolayers, which decrease air‐water surface tension, but a decreased tendency to form adsorbed aggregates on the solid; the two trends offset each other, so wettability is not affected by added salt. The Zisman equation does not describe the wetting data for these systems well except for NaDS, further emphasizing the danger of ignoring solid‐liquid IFT reduction in interpreting wetting data in these systems.