Science.gov

Sample records for electrical resistivity profiling

  1. Measurement of the electrical resistivity profile in the Madison Symmetric Torus

    NASA Astrophysics Data System (ADS)

    Anderson, Jay K.

    A two dimensional, toroidal equilibrium reconstruction code has been developed for the reversed field pinch. The parallel current density profile has been measured by incorporating several diagnostics into the code. A new fitting technique of derivatives of magnetic signals has been developed to determine the inductive electric field profile. During periods of low MHD activity, Ohm's law obeys its simplest form and the ratio of measured E and J profiles determines the plasma electrical resistivity profile. Presented is an upper bound of Zeff through spectroscopic measurements of bremsstrahlung and several pollutants in the near infrared wavelength region. This enables a comparison of the measured resistivity with Spitzer and neoclassical models. The computed resistivity profile is consistent with the Spitzer model and there is no need to invoke an anomaly factor when describing the resistivity in the reversed field pinch. The second primary result is that a bremsstrahlung measurement in MST is not feasible over the majority of MST operating conditions. An overwhelming emission continuum due to neutral particles and wall recycling complicates extraction of the relatively dim bremsstrahlung contribution. The standard definition of Zeff = SsnsZ 2sne is not sufficient to describe collisionality in the edge of MST due to the effects of non-fully stripped impurity ions.

  2. Acidic Barren Slope Profiling using Electrical Resistivity Imaging (ERI) at Ayer Hitam area Johor, Malaysia

    NASA Astrophysics Data System (ADS)

    Azhar, A. T. S.; Hazreek, Z. A. M.; Aziman, M.; Haimi, D. S.; Hafiz, Z. M.

    2016-04-01

    Recently, non-destructive method such as the electrical resistivity technique has become increasingly popular in engineering, environmental, mining and archeological studies nowadays. This method was popular in subsurface profiling due to its ability to replicate the images of the subsurface indirectly. The soil slope found in Batu Pahat, specifically in Ayer Hitam, is known to be problematic due to its barren condition. This location is believed to contain futile soil due to its difficulty in supporting the growth of vegetations. In the past, acidic barren slope assessment using non-destructive method was rarely being used due to several reasons related to the equipment and knowledge constraints. Hence, this study performed an electrical resistivity imaging using ABEM Terrameter LS in order to investigate the acidic barren slope conditions. Field data acquisition was based on Schlumberger and Wenner arrays while RES2DINV software was used to analyze and generate a 2-D model of the problematic subsurface profile. Based on electrical resistivity results, it was found that the acidic barren slope studied consists of two main zones representing residual soil (electrical resistivity value = 10 - 600 Ωm) and shale (electrical resistivity value = 20 - 2000 Ωm). The results of resistivity value were correlated with the physical mapping and the in situ mackintosh probe test for verification purposes. It was found that the maximum depth of the mackintosh probe test was 1.8 m due to its ground penetration limitation. However, the results of the resistivity section managed to achieve greater depth up to 40 m. Hence, the correlation between electrical resistivity and mackintosh probe results can only be performed at certain depth of the acidic barren slope profile in contrast with the physical mapping which able to define the whole section of the barren soil slope structure. Finally, a good match of electrical resistivity results calibrated with mackintosh and physical

  3. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption

    NASA Astrophysics Data System (ADS)

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-06-01

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity.

  4. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption.

    PubMed

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-06-21

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity. PMID:27223656

  5. On the computation of a retina resistivity profile for applications in multi-scale modeling of electrical stimulation and absorption

    PubMed Central

    Loizos, Kyle; RamRakhyani, Anil Kumar; Anderson, James; Marc, Robert; Lazzi, Gianluca

    2016-01-01

    This study proposes a methodology for computationally estimating resistive properties of tissue in multi-scale computational models, used for studying the interaction of electromagnetic fields with neural tissue, with applications to both dosimetry and neuroprosthetics. Traditionally, models at bulk tissue- and cellular-level scales are solved independently, linking resulting voltage from existing resistive tissue-scale models as extracellular sources to cellular models. This allows for solving the effects that external electric fields have on cellular activity. There are two major limitations to this approach: first, the resistive properties of the tissue need to be chosen, of which there are contradicting measurements in literature; second, the measurements of resistivity themselves may be inaccurate, leading to the mentioned contradicting results found across different studies. Our proposed methodology allows for constructing computed resistivity profiles using knowledge of only the neural morphology within the multi-scale model, resulting in a practical implementation of the effective medium theory; this bypasses concerns regarding the choice of resistive properties and accuracy of measurement setups. A multi-scale model of retina is constructed with an external electrode to serve as a test bench for analyzing existing and resulting resistivity profiles, and validation is presented through the reconstruction of a published resistivity profile of retina tissue. Results include a computed resistivity profile of retina tissue for use with a retina multi-scale model used to analyze effects of external electric fields on neural activity. PMID:27223656

  6. Use of vertical electrical resistivity profiles to characterize the riverbed of losing-disconnected rivers

    NASA Astrophysics Data System (ADS)

    Lamontagne, Sebastien; Davis, Aaron; Crosbie, Russell; Taylor, Andrew; Munday, Tim

    2014-05-01

    There are few field techniques available to estimate infiltration rates from losing-disconnected rivers, where infiltration rates are often constrained by the presence of clay layers with a low hydraulic conductivity. It is hypothesized that, in this environment, the bulk of the infiltration would occur in 'hotspots' where the clay layer is thin or absent. Infiltration was estimated over a 2 km section of Billabong Creek (Murray-Darling Basin, Australia) using vertical electrical sounding (VES) resistivity to characterize the continuity and thickness of the riverbed clay layer. Both a towed in-river survey over the whole study reach and three fixed array measurements at the shoreline at selected areas were used. Using locations with measured high and low resistivity, the resistivity profiles were constrained by coring the riverbed to measure vertical variations in riverbed texture, porewater content and porewater salinity. The VES showed that the clay layer was continuous along the study reach and varied in thickness between 1 m and >4 m. Using a simple steady-state model, infiltration rates along the study reach were estimated to vary between 1700 and 7800 m3 km-1 year-1, with an average of 3400 m3 km-1 year-1. This methodology can provide independent estimates of infiltration rates at a scale suitable for the calibration of regional groundwater models.

  7. Anatomy of the southern Cordilleran hingeline, Utah and Nevada, from deep electrical resistivity profiling

    SciTech Connect

    Wannamaker, P.E.; Stodt, J.A.; Johnston, J.M.; Booker, J.R.

    1997-07-01

    To address outstanding questions in Mesozoic-Cenozoic structure and present-day deep physicochemical state in the region of the southern Cordilleran hingeline, a detailed, east-west profile of magnetotelluric (MT) soundings 155 km in length was acquired. From these soundings, a resistivity interpretation was produced using an inversion algorithm based on a structural parameterization. In the upper ten kilometers of the transect, the interpretation shows two segments of low resistivity lying beneath allochthonous rocks of the Late Mesozoic, Sevier thrust sheet. Subsequent industry drilling motivated in part by this surveying confirms the existence and position of the eastern subthrust conductor and, more spectacularly, identifies the presence of yet deeper, autochthonous Mesozoic rocks. A simple structural interpretation is offered where one underthrust segment of low-resistivity sediments was created originally, but this segment was broken later into two major ones during higher-angle Tertiary extension. For the middle and lower crust, the MT data imply a nearly 1-D resistivity structure of remarkable uniformity across the entire transect. Pre-existing structural fabrics have had no measurable influence on localizing regions of high temperature fluids and melting in the lower crust, at least averaged over the scale of tens of kilometers. Given its uniformity over a distance of 155 km or more, the depth to the regional deep conductor does not appear related to the distribution of high-temperature geothermal resources.

  8. Simultaneous depth-profiling of electrical and elemental properties of ion-implanted arsenic in silicon by combining secondary-ion mass spectrometry with resistivity measurements

    NASA Astrophysics Data System (ADS)

    Bennett, N. S.; Wong, C. S.; McNally, P. J.

    2016-07-01

    A method is proposed to extract the electrical data for surface doping profiles of semiconductors in unison with the chemical profile acquired by secondary-ion mass spectrometry (SIMS)—a method we call SIMSAR (secondary-ion mass spectrometry and resistivity). The SIMSAR approach utilizes the inherent sputtering process of SIMS, combined with sequential four-point van der Pauw resistivity measurements, to surmise the active doping profile as a function of depth. The technique is demonstrated for the case of ion-implanted arsenic doping profiles in silicon. Complications of the method are identified, explained, and corrections for these are given. While several techniques already exist for chemical dopant profiling and numerous for electrical profiling, since there is no technique which can measure both electrical and chemical profiles in parallel, SIMSAR has significant promise as an extension of the conventional dynamic SIMS technique, particularly for applications in the semiconductor industry.

  9. Mapping refuse profile in Singapore old dumping ground through electrical resistivity, S-wave velocity and geotechnical monitoring.

    PubMed

    Yin, Ke; Tong, Huan Huan; Noh, Omar; Wang, Jing-Yuan; Giannis, Apostolos

    2015-03-01

    The purpose of this study was to track the refuse profile in Lorong Halus Dumping Ground, the largest landfill in Singapore, by electrical resistivity and surface wave velocity after 25 years of closure. Data were analyzed using an orthogonal set of plots by spreading 24 lines in two perpendicular geophone-orientation directions. Both geophysical techniques determined that refuse boundary depth was 13 ± 2 m. The refuse boundary revealed a certain degree of variance, mainly ascribed to the different principle of measurements, as well as the high heterogeneity of the subsurface. Discrepancy was higher in spots with greater heterogeneity. 3D analysis was further conducted detecting refuse pockets, leachate mounding and gas channels. Geotechnical monitoring (borehole) confirmed geophysical outcomes tracing different layers such as soil capping, decomposed refuse materials and inorganic wastes. Combining the geophysical methods with borehole monitoring, a comprehensive layout of the dumping site was presented showing the hot spots of interests. PMID:25427774

  10. Matching high-resolution seismic and electrical resistivity profiling to infer the shallow structure of Solfatara Volcano (Italy)

    NASA Astrophysics Data System (ADS)

    Bruno, Pier Paolo; Gresse, Marceau; Maraio, Stefano; Vandemeulebrouck, Jean; Di Fiore, Vincenzo

    2016-04-01

    Two coincident high-resolution seismic reflection and electrical resistivity profiles were acquired in the Solfatara tuff cone in May and November 2014, along with CO2 flux and surface temperature measurements. The acquired data are a subset of the MedSuV - RICEN dataset, which also includes a wider series of time-lapse geophysical and geochemical experiments carried out within Solfatara volcano, with the aim of studying changes in the properties of the medium at small scales through repeated high-resolution multi-parameter observations over time. Seismic reflection data were processed using the Common-Reflection-Surface stack, a fast and cost-effective alternative to standard reflection processing which allows to greatly improve signal-to-noise ratio in settings where structural complexity and high levels of ambient noise make it challenging to obtain a reliable seismic image. The reflection profiles provide the first high-resolution seismic images of Solfatara crater, depicting an asymmetrical structure filled by volcanoclastic sediments and whose bottom is found at about 400 ms TWT. Seismic data also display several narrow zones with distinctive anomalous of very low amplitude located in several areas within the crater, which were interpreted as gas chimneys created by intersection of NE- and NW-trending sets of sub-vertical fault and fractures and filled by fluids (both in gas and liquid phases) escaping from the deeper hydrothermal source. The imaged degassing pathways terminate against a strong horizontal reflector at about 100 ms TWT. Just above those structural pathways, electric data show the presence of a dome-shaped electrically conductive structure, buried in the centre of the volcano at a minimum depth of 50 m and interpreted as the upper end of the hydrothermal plume. The plume projection at the surface of the crater matches with high CO2 flux and soil temperature anomalies. Our results provide a solid framework to constrain the near

  11. Electrical Resistivity Imaging

    EPA Science Inventory

    Electrical resistivity imaging (ERI) is a geophysical method originally developed within the mining industry where it has been used for decades to explore for and characterize subsurface mineral deposits. It is one of the oldest geophysical methods with the first documented usag...

  12. Electrical resistivity probes

    DOEpatents

    Lee, Ki Ha; Becker, Alex; Faybishenko, Boris A.; Solbau, Ray D.

    2003-10-21

    A miniaturized electrical resistivity (ER) probe based on a known current-voltage (I-V) electrode structure, the Wenner array, is designed for local (point) measurement. A pair of voltage measuring electrodes are positioned between a pair of current carrying electrodes. The electrodes are typically about 1 cm long, separated by 1 cm, so the probe is only about 1 inch long. The electrodes are mounted to a rigid tube with electrical wires in the tube and a sand bag may be placed around the electrodes to protect the electrodes. The probes can be positioned in a borehole or on the surface. The electrodes make contact with the surrounding medium. In a dual mode system, individual probes of a plurality of spaced probes can be used to measure local resistance, i.e. point measurements, but the system can select different probes to make interval measurements between probes and between boreholes.

  13. [Nosocomial bacteria: profiles of resistance].

    PubMed

    Sow, A I

    2005-01-01

    Nosocomial infections may be parasitic, mycosal or viral, but bacterial infections are more frequent. They are transmitted by hands or by oral route. This paper describes the main bacteria responsive of nosocomial infections, dominated by Staphylococcus, enterobacteria and Pseudomonas aeruginosa. The author relates natural and savage profiles of these bacterias, characterized by multiresistance due to large use of antibiotics. Knowledge of natural resistance and verification of aquired resistance permit to well lead probabilist antibiotherapy. PMID:16190117

  14. Electrically Variable Resistive Memory Devices

    NASA Technical Reports Server (NTRS)

    Liu, Shangqing; Wu, Nai-Juan; Ignatiev, Alex; Charlson, E. J.

    2010-01-01

    Nonvolatile electronic memory devices that store data in the form of electrical- resistance values, and memory circuits based on such devices, have been invented. These devices and circuits exploit an electrically-variable-resistance phenomenon that occurs in thin films of certain oxides that exhibit the colossal magnetoresistive (CMR) effect. It is worth emphasizing that, as stated in the immediately preceding article, these devices function at room temperature and do not depend on externally applied magnetic fields. A device of this type is basically a thin film resistor: it consists of a thin film of a CMR material located between, and in contact with, two electrical conductors. The application of a short-duration, low-voltage current pulse via the terminals changes the electrical resistance of the film. The amount of the change in resistance depends on the size of the pulse. The direction of change (increase or decrease of resistance) depends on the polarity of the pulse. Hence, a datum can be written (or a prior datum overwritten) in the memory device by applying a pulse of size and polarity tailored to set the resistance at a value that represents a specific numerical value. To read the datum, one applies a smaller pulse - one that is large enough to enable accurate measurement of resistance, but small enough so as not to change the resistance. In writing, the resistance can be set to any value within the dynamic range of the CMR film. Typically, the value would be one of several discrete resistance values that represent logic levels or digits. Because the number of levels can exceed 2, a memory device of this type is not limited to binary data. Like other memory devices, devices of this type can be incorporated into a memory integrated circuit by laying them out on a substrate in rows and columns, along with row and column conductors for electrically addressing them individually or collectively.

  15. State electricity profiles, March 1999

    SciTech Connect

    1999-03-01

    Due to the role electricity plays in the Nation`s economic and social well-being, interested parties have been following the electric power industry`s transition by keeping abreast of the restructuring and deregulation events that are taking place almost daily. Much of the attention centers around the States and how they are restructuring the business of electricity supply within their respective jurisdictions. This report is designed to profile each State and the District of Columbia regarding not only their current restructuring activities, but also their electricity generation and concomitant statistics from 1986 through 1996. Included are data on a number of subject areas including generating capability, generation, revenues, fuel use, capacity factor for nuclear plants, retail sales, and pollutant emissions. Although the Energy Information Administration (EIA) publishes this type of information, there is a lack of a uniform overview for each individual State. This report is intended to help fill that gap and also to serve as a framework for more detailed studies. In addition to basic statistics in tables and graphs, a textual section is provided for each State, discussing some of the points relative to electricity production that are noteworthy in, or unique to, that particular State. Also, each State is ranked according to the place it holds, as compared to the rest of the states, in various relevant areas, such as its average price of electricity per kilowatthour, its population, and its emissions of certain atmospheric pollutants. The final chapter covers the Nation as a whole. 451 figs., 520 tabs.

  16. Electrical resistivity of composite superconductors

    NASA Technical Reports Server (NTRS)

    Davis, J. H.; Lee, J. A.

    1983-01-01

    In addition to its superconducting properties, a superconductor is usually characterized by poor thermal conductivity and relatively high electrical resistivity in the normal state. To remedy this situation a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted. Some of the specimens were prepared by melting, directional solidification and diffusing in Tin. A total of 12 wire specimens was tested. Each specimen was analyzed by plotting experimental data into the following curves: the graph of the residual resistivity as a function of the specimen current at 4.3 K; and the graph of the electrical resistivity as a function of the temperature at a constant current.

  17. Delineation of graves using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Nero, Callistus; Aning, Akwasi Acheampong; Danuor, Sylvester K.; Noye, Reginald M.

    2016-03-01

    A suspected old royal cemetery has been surveyed at the Kwame Nkrumah University of Science and Technology (KNUST) campus, Kumasi, Ghana using Electrical Resistivity Tomography (ERT) with the objective of detecting graves in order to make informed decisions with regard to the future use of the area. The survey was conducted on a 10,000 m2 area. Continuous Vertical Electrical Sounding (CVES) was combined with the roll along technique for 51 profiles with 1 m probe separation separated by 2 m. Inverted data results indicated wide resistivity variations ranging between 9.34 Ωm and 600 Ωm in the near surface. Such heterogeneity suggests a disturbance of the soil at this level. Both high (≥ 600 Ωm) and low resistivity (≤ 74.7 Ωm) anomalies, relative to background levels, were identified within the first 4 m of the subsurface. These were suspected to be burial tombs because of their rectangular geometries and resistivity contrasts. The results were validated with forward numerical modeling results. The study area is therefore an old cemetery and should be preserved as a cultural heritage site.

  18. Discontinuities detection using transmission electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Cabrera, Justo; Boyle, Alistair; Grychtol, Bartłomiej; Adler, Andy

    2015-04-01

    In the context of nuclear waste storage, low permeability clays are investigated as potential geological barrier. Discontinuities in such formations might facilitate the radionuclide transport to the environment. The underground platform of Tournemire (Aveyron, France) presents the opportunity to perform in-situ experiments to evaluate the potential of geophysical methods to detect and characterize the presence of discontinuities in the sub-surface. In this work, we apply transmission electrical resistivity tomography to image the medium surrounding a regional fault. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault. The objective of a such geometry is to acquire data in transmission across the massif in addition to classical protocol such as Schlumberger or dipole-dipole in order to better cover the sounded medium. 3D models considering the gallery geometry, the topography and the injection of current in transmission through the massif were developed for the analysis of such particular data sets. For the reconstruction of the medium electrical resistivity, the parametrization of the inverse problem was adapted to the geometry of the experience in a scope to reduce the inversion under-determination. The resulting image obtained with classical protocols and transmission current injection is compared to an image obtained using only classical protocols to better highlight the interest of a transmission experiment in terms of resolution and penetration depth. The addition of protocols in transmission allows a better coverage of the sounded medium so the resulting image presents a better resolution at higher depths than the image resulting from a single profile of electrodes. The proposed configuration of electrical resistivity measurements in transmission is then promising for hydrogeophysical studies, in particular for

  19. Resist profile simulation with fast lithography model

    NASA Astrophysics Data System (ADS)

    He, Yan-Ying; Chou, Chih-Shiang; Tang, Yu-Po; Huang, Wen-Chun; Liu, Ru-Gun; Gau, Tsai-Sheng

    2014-03-01

    A traditional approach to construct a fast lithographic model is to match wafer top-down SEM images, contours and/or gauge CDs with a TCC model plus some simple resist representation. This modeling method has been proven and is extensively used for OPC modeling. As the technology moves forward, this traditional approach has become insufficient in regard to lithography weak point detection, etching bias prediction, etc. The drawback of this approach is from metrology and simulation. First, top-down SEM is only good for acquiring planar CD information. Some 3D metrology such as cross-section SEM or AFM is necessary to obtain the true resist profile. Second, the TCC modeling approach is only suitable for planar image simulation. In order to model the resist profile, full 3D image simulation is needed. Even though there are many rigorous simulators capable of catching the resist profile very well, none of them is feasible for full-chip application due to the tremendous consumption of computational resource. The authors have proposed a quasi-3D image simulation method in the previous study [1], which is suitable for full-chip simulation with the consideration of sidewall angles, to improve the model accuracy of planar models. In this paper, the quasi-3D image simulation is extended to directly model the resist profile with AFM and/or cross-section SEM data. Resist weak points detected by the model generated with this 3D approach are verified on the wafer.

  20. Integration of Electric Resistivity Profile and Infiltrometer Measurements to Calibrate a Numerical Model of Vertical Flow in Fractured and Karstic Limestone.

    NASA Astrophysics Data System (ADS)

    Caputo, M. C.; de Carlo, L.; Masciopinto, C.; Nimmo, J. R.

    2007-12-01

    Karstic and fractured aquifers are among the most important drinking water resources. At the same time, they are particularly vulnerable to contamination. A detailed scientific knowledge of the behavior of these aquifers is essential for the development of sustainable groundwater management concepts. Due to their special characteristics of extreme anisotropy and heterogeneity, research aimed at a better understanding of flow, solute transport, and biological processes in these hydrogeologic systems is an important scientific challenge. This study integrates a geophysical technique with an infiltrometer test to better calibrate a mathematical model that quantifies the vertical flow in karstic and fractured limestone overlying the deep aquifer of Alta Murgia (Southern Italy). Knowledge of the rate of unsaturated zone percolation is needed to investigate the vertical migration of pollutants and the vulnerability of the aquifer. Sludge waste deposits in the study area have caused soil-subsoil contamination with toxics. The experimental test consisted of infiltrometer flow measurements, more commonly utilized for unconsolidated granular porous media, during which subsoil electric resistivity data were collected. A ring infiltrometer 2 m in diameter and 0.3 m high was sealed to the ground with gypsum. This large diameter yielded infiltration data representative of the anisotropic and heterogeneous rock, which could not be sampled adequately with a small ring. The subsurface resistivity was measured using a Wenner-Schlumberger electrode array. Vertical movement of water in a fracture plane under unsaturated conditions has been investigated by means of a numerical model. The finite difference method was used to solve the flow equations. An internal iteration method was used at every time step to evaluate the nodal value of the pressure head, in agreement with the mass- balance equation and the characteristic functional relationships of the coefficients.

  1. Electrical resistivity measurements in the Neillsville area, Wisconsin

    USGS Publications Warehouse

    Spicer, H. Cecil; Edwards, George J.

    1955-01-01

    Sixty-eight electrical depth profiles were completed in the vicinity of Neillsville, Wis. to obtain information on the water-bearing beds in the glacial moraine and consolidated sedimentary rocks in the area. No productive aquifers were found but the best areas for test drilling are described. The basic theory and interpretation procedures, together with a short description of field methods on electrical resistivity measurements are also presented.

  2. TUTORIAL: Electrical resistance: an atomistic view

    NASA Astrophysics Data System (ADS)

    Datta, Supriyo

    2004-07-01

    This tutorial article presents a 'bottom-up' view of electrical resistance starting from something really small, like a molecule, and then discussing the issues that arise as we move to bigger conductors. Remarkably, no serious quantum mechanics is needed to understand electrical conduction through something really small, except for unusual things like the Kondo effect that are seen only for a special range of parameters. This article starts with energy level diagrams (section 2), shows that the broadening that accompanies coupling limits the conductance to a maximum of q2/h per level (sections 3, 4), describes how a change in the shape of the self-consistent potential profile can turn a symmetric current-voltage characteristic into a rectifying one (sections 5, 6), shows that many interesting effects in molecular electronics can be understood in terms of a simple model (section 7), introduces the non-equilibrium Green function (NEGF) formalism as a sophisticated version of this simple model with ordinary numbers replaced by appropriate matrices (section 8) and ends with a personal view of unsolved problems in the field of nanoscale electron transport (section 9). Appendix A discusses the Coulomb blockade regime of transport, while appendix B presents a formal derivation of the NEGF equations. MATLAB codes for numerical examples are listed in appendix C. (The appendices are available in the online version only.)

  3. [Resistance profile and genetic barrier of dolutegravir].

    PubMed

    Llibre, Josep M; Clotet, Bonaventura

    2015-03-01

    The resistance profile of dolutegravir differs significantly from those of earlier integrase inhibitors (INI). Dolutegravir displays in vitro activity against mutant HIV-1 harboring any isolated resistance mutations selected during failures to raltegravir or elvitegravir (Y143C/H/, N155H, Q148H/K/R, E92G/Q, T66A/I/K, T97A, E138A/K, G140A/S). Its activity is only compromised by Q148X mutations combined with other mutations, particularly > 1 mutation. The drug has pharmacokinetic/pharmacodynamic properties (plasmatic t1/2 15.3 h, inhibitory quotient 19, dissociative t1/2 from the IN-DNA complex 71 h) that favor a high genetic barrier to resistance. In vitro the selection of HIV-1 resistance to dolutegravir is extremely difficult to achieve. The mutations eventually selected (R263K, H51Y and E138K) do not confer significant resistance, and induce a fitness cost that prevents HIV-1 from evading drug pressure. Suprisingly, HIV-1 is not able to compensate, leading the virus to a previously unnoticed evolutionary pathway with very low chances of developing resistance to INI or the backbone. No treatment-naïve patients starting dolutegravir therapy (+TDF/FTC o ABC/3TC) have selected resistance in IN or against the backbone. No INI- naïve patients with prior virologic failure selected phenotypic dolutegravir resistance. Only 4 out of 354 patients selected resistance mutations in IN, and rates of selection of mutations in IN or against the backbone were significantly lower than with raltegravir. In multitreated patients with widespread resistance including IN resistance, the high efficacy of dolutegravir was confirmed, irrespective of the previous pattern of IN mutations, provided that Q148X associated with other mutations was absent. PMID:25858608

  4. Vertical soil profiling using a galvanic contact resistivity scanning approach.

    PubMed

    Pan, Luan; Adamchuk, Viacheslav I; Prasher, Shiv; Gebbers, Robin; Taylor, Richard S; Dabas, Michel

    2014-01-01

    Proximal sensing of soil electromagnetic properties is widely used to map spatial land heterogeneity. The mapping instruments use galvanic contact, capacitive coupling or electromagnetic induction. Regardless of the type of instrument, the geometrical configuration between signal transmitting and receiving elements typically defines the shape of the depth response function. To assess vertical soil profiles, many modern instruments use multiple transmitter-receiver pairs. Alternatively, vertical electrical sounding can be used to measure changes in apparent soil electrical conductivity with depth at a specific location. This paper examines the possibility for the assessment of soil profiles using a dynamic surface galvanic contact resistivity scanning approach, with transmitting and receiving electrodes configured in an equatorial dipole-dipole array. An automated scanner system was developed and tested in agricultural fields with different soil profiles. While operating in the field, the distance between current injecting and measuring pairs of rolling electrodes was varied continuously from 40 to 190 cm. The preliminary evaluation included a comparison of scan results from 20 locations to shallow (less than 1.2 m deep) soil profiles and to a two-layer soil profile model defined using an electromagnetic induction instrument. PMID:25057135

  5. Vertical Soil Profiling Using a Galvanic Contact Resistivity Scanning Approach

    PubMed Central

    Pan, Luan; Adamchuk, Viacheslav I.; Prasher, Shiv; Gebbers, Robin; Taylor, Richard S.; Dabas, Michel

    2014-01-01

    Proximal sensing of soil electromagnetic properties is widely used to map spatial land heterogeneity. The mapping instruments use galvanic contact, capacitive coupling or electromagnetic induction. Regardless of the type of instrument, the geometrical configuration between signal transmitting and receiving elements typically defines the shape of the depth response function. To assess vertical soil profiles, many modern instruments use multiple transmitter-receiver pairs. Alternatively, vertical electrical sounding can be used to measure changes in apparent soil electrical conductivity with depth at a specific location. This paper examines the possibility for the assessment of soil profiles using a dynamic surface galvanic contact resistivity scanning approach, with transmitting and receiving electrodes configured in an equatorial dipole-dipole array. An automated scanner system was developed and tested in agricultural fields with different soil profiles. While operating in the field, the distance between current injecting and measuring pairs of rolling electrodes was varied continuously from 40 to 190 cm. The preliminary evaluation included a comparison of scan results from 20 locations to shallow (less than 1.2 m deep) soil profiles and to a two-layer soil profile model defined using an electromagnetic induction instrument. PMID:25057135

  6. Electric field profiles in obstructed helium discharge

    NASA Astrophysics Data System (ADS)

    Fendel, Peter; Ganguly, Biswa; Bletzinger, Peter

    2014-10-01

    Axial and radial variations of electric field have been measured in dielectric shielded 25 mm diameter parallel plate electrode for 2 mA, 2250 V helium dc discharge at 1.75 Torr with 6.5 mm gap. The axial and radial electric field profiles have been measured from the polarization dependent Stark splitting of 21S --> 11 1P transition through collision induced fluorescence from 43D --> 23P. The electric field values showed a strong radial variation peaking up to 5 kV/cm near the cathode radial boundary, and decreasing to about 1 kV/cm near the anode, suggesting the formation of an obstructed discharge for this low Pd condition. Also, the on-axis electric field was nearly constant across the gap indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with COMSOL finite element modeling program. The model discharge dimensions were selected to match the experimental dimensions. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) =ρ0 (r/r0)3 , where ρ(r) is the local space charge density, ρ0 is the maximum space-charge density, r the local radial value and r0 the radius of the electrode.

  7. Electrical Resistive Heaters for Magnetically Sensitive Instruments

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael

    2014-05-01

    US Patent 8,138,760 ``Temperature System with Magnetic Field Suppression'' describes design concepts and examples for development of electrical resistive heaters and temperature detectors suitable for temperature control of the alkali vapor cells of magnetically sensitive atomic instruments such as spin-exchange relaxation free (SERF) magnetometers. This is achieved through careful manipulation of electromagnetic multi-pole moments in the design of these resistive heaters for substantial self-cancellation of electrically generated magnetic fields. The magnetic performance of electrical resistive heaters produced according to these design principles and directly attached to a rubidium vapor cell has been demonstrated to cause no measurable degradation of the performance of a SERF magnetometer exhibiting noise below 2 femto-Tesla per square root Hz.

  8. Resistance after firing protected electric match

    DOEpatents

    Montoya, Arsenio P.

    1981-11-10

    An electric match having electrical leads embedded in flame-producing compound is protected against an accidental resistance across the leads after firing by a length of heat-shrinkable tubing encircling the match body and having a skirt portion extending beyond the leads. The heat of the burning match and an adjacent thermal battery causes the tubing to fold over the end of the match body, covering the ends of the leads and protecting them from molten pieces of the battery.

  9. Pedotransfer functions in soil electrical resistivity estimation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface electrical resistivity tomography (ERT) is recognized as a powerful non-invasive soil survey and monitoring method. Relationships between ER and soil water contents that are needed to infer the spatial distribution of soil moisture from the ERT results, are known to reflect soil properties. ...

  10. Temperature dependent electrical resistivity of liquid Sn

    NASA Astrophysics Data System (ADS)

    Prajapati, A. V.; Sonvane, Y. A.; Patel, H. P.; Thakor, P. B.

    2016-05-01

    The present paper deals with the effect of temperature variation on the electrical resistivity (ρ) of liquid Sn(Tin). We have used a new parameter free pseudopotential along with screening Taylor et al and Farid et al local field correction functions. The Percus-Yevick Hard Sphere (PYHS) reference system is used to describe structural information. Zeeman formula has been used for finding resistivity with the variation of temperature. The balanced harmonies between present data and experimental data have been achieved with a minimal deviation. So, we concluded that our newly constructed model potential is an effective one to produce the data of electrical resistivity of liquid Sn(Tin) as a function of temperature.

  11. Release Resistant Electrical Interconnections For Mems Devices

    DOEpatents

    Peterson, Kenneth A.; Garrett, Stephen E.; Reber, Cathleen A.

    2005-02-22

    A release resistant electrical interconnection comprising a gold-based electrical conductor compression bonded directly to a highly-doped polysilicon bonding pad in a MEMS, IMEMS, or MOEMS device, without using any intermediate layers of aluminum, titanium, solder, or conductive adhesive disposed in-between the conductor and polysilicon pad. After the initial compression bond has been formed, subsequent heat treatment of the joint above 363 C creates a liquid eutectic phase at the bondline comprising gold plus approximately 3 wt % silicon, which, upon re-solidification, significantly improves the bond strength by reforming and enhancing the initial bond. This type of electrical interconnection is resistant to chemical attack from acids used for releasing MEMS elements (HF, HCL), thereby enabling the use of a "package-first, release-second" sequence for fabricating MEMS devices. Likewise, the bond strength of an Au--Ge compression bond may be increased by forming a transient liquid eutectic phase comprising Au-12 wt % Ge.

  12. On equivalent resistance of electrical circuits

    NASA Astrophysics Data System (ADS)

    Kagan, Mikhail

    2015-01-01

    While the standard (introductory physics) way of computing the equivalent resistance of nontrivial electrical circuits is based on Kirchhoff's rules, there is a mathematically and conceptually simpler approach, called the method of nodal potentials, whose basic variables are the values of the electric potential at the circuit's nodes. In this paper, we review the method of nodal potentials and illustrate it using the Wheatstone bridge as an example. We then derive a closed-form expression for the equivalent resistance of a generic circuit, which we apply to a few sample circuits. The result unveils a curious interplay between electrical circuits, matrix algebra, and graph theory and its applications to computer science. The paper is written at a level accessible by undergraduate students who are familiar with matrix arithmetic. Additional proofs and technical details are provided in appendices.

  13. Electrical resistance tomography for imaging concrete structures

    SciTech Connect

    Buettner, M.; Ramirez, A.; Daily, W.

    1995-11-08

    Electrical Resistance Tomography (ERT) has been used to non-destructively examine the interior of reinforced concrete pillars in the laboratory during a water infiltration experiment. ERT is a technique for determining the electrical resistivity distribution within a volume from measurement of injected currents and the resulting electrical potential distribution on the surface. The transfer resistance (ratio of potential to injected current) data are inverted using an algorithm based on a finite element forward solution which is iteratively adjusted in a least squares sense until the measured and calculated transfer resistances agree to within some predetermined value. Laboratory specimens of concrete pillars, 61.0 cm (24 in) in length and 20.3 cm (8 in) on a side, were prepared with various combinations of steel reinforcing bars and voids (1.27 cm diameter) which ran along the length of the pillars. An array of electrodes was placed around the pillar to allow for injecting current and measuring the resulting potentials. After the baseline resistivity distribution was determined, water was added to a void near one comer of the pillar. ERT was used to determine the resistivity distribution of the pillar at regular time intervals as water was added. The ERT images show very clearly that the water was gradually imbibed into the concrete pillar during the course of the experiment. The resistivity decreased by nearly an order of magnitude near the point of water addition in the first hour, and by nearly two orders of magnitude by the end of the experiment. Other applications for this technology include monitoring of curing in concrete structures, detecting cracks in concrete structures, detecting rebar location and corrosion state, monitoring slope stability and the stability of footings, detecting and monitoring leaks from storage tanks, monitoring thermal processes during environmental remediation, and for detecting and monitoring contaminants in soil and groundwater.

  14. Results of Electrical Resistivity Data Collected near the Town of Guernsey, Platte County, Wyoming

    USGS Publications Warehouse

    McDougal, Robert R.; Abraham, Jared D.; Bisdorf, Robert J.

    2004-01-01

    As part of a study to investigate subsurface geologic conditions as they relate to ground-water flow in an abandoned landfill near the town of Guernsey, Wyoming, geophysical direct current (DC) resistivity data were collected. Eight vertical resistivity soundings and eight horizontal resistivity profiles were made using single channel and multi-channel DC instruments. Data collected in the field were converted from apparent resistivity to inverted resistivity with depth using a numerical inversion of the data. Results of the inverted resistivity data are presented as horizontal profiles and as profiles derived from the combined horizontal profile and vertical sounding data. The data sets collected using the single-channel and multi-channel DC systems provided for the resistivity investigation to extend to greater depth. Similarity of the electrical properties of the bedrock formations made interpretation of the resistivity profiles more difficult. High resistivity anomalies seen in the profiles are interpreted as quartzite lenses and as limestone or metadolomite structures in the eastern part of the study area. Terrace gravels were mapped as resistive where dry and less resistive in the saturated zone. The DC resistivity methods used in this study illustrate that multi-electrode DC resistivity surveying and more traditional methodologies can be merged and used to efficiently map anomalies of hydrologic interest in geologically complex terrain.

  15. Electrical Resistivity Imaging and Depression Focused Recharge

    NASA Astrophysics Data System (ADS)

    Bentley, L. R.; Hayashi, M.; Berthold, S.

    2003-12-01

    Seasonal wetlands and small depressions play a fundamental role in recharging regional aquifers in the northern glaciated planes. Water from snowmelt collects in the depressions in the spring and infiltrates into the ground after the soil unfreezes. Infiltrating water leaches salts from the soil beneath depressions. The majority of the infiltrating water moves to the local uplands where it leaves the ground through ET leaving behind zones of evaporitically concentrated salts. A small percentage infiltrates down to the regional aquifer. Leaching and concentrating salts effect the electrical resistivity distribution of the subsurface. Three-dimensional electrical resistivity imaging (ERI) was combined with groundwater and soil measurements to generate a conceptual model of three dimensional fluid flow at San Denis, Saskatchewan. Water chemistry was used to generate a conceptual model of different geochemical zones which could be distinguished by the electrical conductivity of pore water. The Waxman-Smits equation was used to link groundwater electrical conductivity to in situ bulk resistivity. Electrical resisistivity from ERI was then used to map geochemical zones in the subsurface. ERI and chemistry show that infiltrating water reaches a regional aquifer at 20 meters depth. Seasonal wetlands have large zones of high resistivity that reach to the regional water table indicating that salts have been leached out of the tills to the depth of the regional aquifer. Small local depressions also have zones of leached soil beneath them indicating that they contribute to regional groundwater recharge. Since there are millions of small depressions, they may play a fundamental role in groundwater recharge and must be considered in land management. The images show a complex distribution of salts. Most of the salt is located in the upper weathered zone in the glacial tills and the horizontal distribution is controled by the locations of wetlands, steepness of slopes and the

  16. Electrical resistance tomography of concrete structures

    SciTech Connect

    Daily, W.; Ramirez, A.; Binley, A.; Henry-Poulter, S.

    1993-10-01

    The purpose of this work is to determine the feasibility of using Electrical resistance tomography (ERT) to nondestructively examine the interior of concrete structures such as bridge pillars and roadways. We report the results of experiments wherein ERT is used to image the two concrete specimens in the laboratory. Each specimen is 5 inches square and 12 inches long and contained steel reinforcing rods along its length. Twenty electrodes were placed on each sample and an-image of electrical resistivity distribution was generated from current and voltage measurements. We found that the images show the general location of the reinforcing steel and, what`s more important, delineate the absence of the steel. The method may therefore be useful for determining if such steel has been destroyed by corrosion, however to make it useful, the technique must have better resolution so that individual reinforcing steel units are resolved.

  17. Soil Identification using Field Electrical Resistivity Method

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.

    2015-06-01

    Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 Ωm & 285 Ωm) was slightly higher than SiltySAND (223 Ωm & 199 Ωm) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.

  18. Rational Experimental Design for Electrical Resistivity Imaging

    NASA Astrophysics Data System (ADS)

    Mitchell, V.; Pidlisecky, A.; Knight, R.

    2008-12-01

    Over the past several decades advances in the acquisition and processing of electrical resistivity data, through multi-channel acquisition systems and new inversion algorithms, have greatly increased the value of these data to near-surface environmental and hydrological problems. There has, however, been relatively little advancement in the design of actual surveys. Data acquisition still typically involves using a small number of traditional arrays (e.g. Wenner, Schlumberger) despite a demonstrated improvement in data quality from the use of non-standard arrays. While optimized experimental design has been widely studied in applied mathematics and the physical and biological sciences, it is rarely implemented for non-linear problems, such as electrical resistivity imaging (ERI). We focus specifically on using ERI in the field for monitoring changes in the subsurface electrical resistivity structure. For this application we seek an experimental design method that can be used in the field to modify the data acquisition scheme (spatial and temporal sampling) based on prior knowledge of the site and/or knowledge gained during the imaging experiment. Some recent studies have investigated optimized design of electrical resistivity surveys by linearizing the problem or with computationally-intensive search algorithms. We propose a method for rational experimental design based on the concept of informed imaging, the use of prior information regarding subsurface properties and processes to develop problem-specific data acquisition and inversion schemes. Specifically, we use realistic subsurface resistivity models to aid in choosing source configurations that maximize the information content of our data. Our approach is based on first assessing the current density within a region of interest, in order to provide sufficient energy to the region of interest to overcome a noise threshold, and then evaluating the direction of current vectors, in order to maximize the

  19. Electrical resistance tomography from measurements inside a steel cased borehole

    DOEpatents

    Daily, William D.; Schenkel, Clifford; Ramirez, Abelardo L.

    2000-01-01

    Electrical resistance tomography (ERT) produced from measurements taken inside a steel cased borehole. A tomographic inversion of electrical resistance measurements made within a steel casing was then made for the purpose of imaging the electrical resistivity distribution in the formation remotely from the borehole. The ERT method involves combining electrical resistance measurements made inside a steel casing of a borehole to determine the electrical resistivity in the formation adjacent to the borehole; and the inversion of electrical resistance measurements made from a borehole not cased with an electrically conducting casing to determine the electrical resistivity distribution remotely from a borehole. It has been demonstrated that by using these combined techniques, highly accurate current injection and voltage measurements, made at appropriate points within the casing, can be tomographically inverted to yield useful information outside the borehole casing.

  20. Complex Electrical Resistivity for Monitoring DNAPL Contamination

    SciTech Connect

    Stephen R. Brown; David Lesmes; John Fourkas

    2003-09-12

    Nearly all Department of Energy (DOE) facilities have landfills and buried waste areas. Of the various contaminants present at these sites, dense non-aqueous phase liquids (DNAPL) are particularly hard to locate and remove. There is an increasing need for external or non-invasive sensing techniques to locate DNAPLs in the subsurface and to track their spread and monitor their breakdown or removal by natural or engineered means. G. Olhoeft and colleagues have published several reports based on laboratory studies using the complex resistivity method which indicate that organic solvents, notably toluene, PCE, and TCE, residing in clay-bearing soils have distinctive electrical signatures. These results have suggested to many researchers the basis of an ideal new measurement technique for geophysical characterization of DNAPL pollution. Encouraged by these results we proposed to bring the field measurement of complex resistivity as a means of pollution characterization from the conceptual stage to practice. We planned to document the detectability of clay-organic solvent interactions with geophysical measurements in the laboratory, develop further understanding of the underlying physical and chemical mechanisms, and then apply these observations to develop field techniques. As with any new research endeavor we note the extreme importance of trying to reproduce the work of previous researchers to ensure that any effects observed are due to the physical phenomena occurring in the specimen and not due to the particular experimental apparatus or method used. To this end, we independently designed and built a laboratory system, including a sample holder, electrodes, electronics, and data analysis software, for the measurement of the complex electrical resistivity properties of soil contaminated with organic solvents. The capabilities and reliability of this technique were documented. Using various standards we performed measurement accuracy, repeatability, and noise immunity

  1. Continuous resistivity profiling data from the Corsica River Estuary, Maryland

    USGS Publications Warehouse

    Cross, V.A.; Bratton, J.F.; Worley, C.R.; Crusius, J.; Kroeger, K.D.

    2011-01-01

    Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine its importance in nutrient delivery to the Chesapeake Bay. The Corsica River Estuary represents a coastal lowland setting typical of much of the eastern bay. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the lower estuary in April and May 2007. Resource managers are concerned about nutrients that are entering the estuary via SGD that may be contributing to eutrophication, harmful algal blooms, and fish kills. Techniques employed in the study included continuous resistivity profiling (CRP), piezometer sampling of submarine groundwater, and collection of a time series of radon tracer activity in surface water. A CRP system measures electrical resistivity of saturated subestuarine sediments to distinguish those bearing fresh water (high resistivity) from those with saline or brackish pore water (low resistivity). This report describes the collection and processing of CRP data and summarizes the results. Based on a grid of 67.6 kilometers of CRP data, low-salinity (high-resistivity) groundwater extended approximately 50-400 meters offshore from estuary shorelines at depths of 5 to >12 meters below the sediment surface, likely beneath a confining unit. A band of low-resistivity sediment detected along the axis of the estuary indicated the presence of a filled paleochannel containing brackish groundwater. The meandering paleochannel likely incised through the confining unit during periods of lower sea level, allowing the low-salinity groundwater plumes originating from land to mix with brackish subestuarine groundwater along the channel margins and to discharge. A better understanding of the spatial variability and geological controls of submarine groundwater flow beneath the Corsica River Estuary could lead to improved models and mitigation strategies for nutrient over-enrichment in the

  2. Cone-based electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Pidlisecky, Adam

    Determining the 3-D spatial distribution of subsurface properties is a critical part of managing the clean-up of contaminated sites. Most standard hydrologic methods sample small regions immediately adjacent to wells or testing devices. This provides data which are not representative of the entire region of interest. Furthermore, at many contaminated sites invasive methods are not acceptable, due to the risks associated with contacting and spreading the contaminants. To address these issues, I have developed a minimally invasive technology that provides information about the 3-D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), integrates the existing technologies of resistivity cone penetration testing (RCPT) with electrical resistivity tomography. Development of this tool included the creation of new software and modeling algorithms, the design of field equipment, field testing, and processing and interpretation of the resulting data. I present a 2.5-D forward modeling algorithm that incorporates an effective correction for the errors caused by boundary effects and source singularities. The algorithm includes an optimization technique for acquiring the Fourier coefficients required for the solution. A 3-D inversion algorithm is presented that has two major improvements over existing algorithms. First, it includes a 3-D version of the boundary correction/source singularity correction developed for the 2.5-D problem. Second, the algorithm can handle any type of acquisition geometry; this was a requirement for the development of C-bert. C-bert involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer and at the surface to measure the resultant potential field. In addition to these measurements, we obtain the standard suite of RCPT data, including high resolution resistivity logs. The RCPT data can be used to generate a realistic

  3. Electrical Resistance Tomography imaging of concrete

    SciTech Connect

    Karhunen, Kimmo; Seppaenen, Aku; Lehikoinen, Anssi; Monteiro, Paulo J.M.; Kaipio, Jari P.

    2010-01-15

    We apply Electrical Resistance Tomography (ERT) for three dimensional imaging of concrete. In ERT, alternating currents are injected into the target using an array of electrodes attached to the target surface, and the resulting voltages are measured using the same electrodes. These boundary measurements are used for reconstructing the internal (3D) conductivity distribution of the target. In reinforced concrete, the metallic phases (reinforcing bars and fibers), cracks and air voids, moisture gradients, and the chloride distribution in the matrix carry contrast with respect to conductivity. While electrical measurements have been widely used to characterize the properties of concrete, only preliminary results of applying ERT to concrete imaging have been published so far. The aim of this paper is to carry out a feasibility evaluation with specifically cast samples. The results indicate that ERT may be a feasible modality for non-destructive evaluation of concrete.

  4. Tank leak detection using electrical resistance methods

    SciTech Connect

    Ramirez, A.; Daily, W.; Binley, A.; LaBrecque, D.

    1996-01-01

    Large volumes of hazardous liquids and high-level radioactive wastes are stored worldwide in surface and underground tanks. Frequently these tanks are found to leak, thereby resulting in not only a loss of stored inventory, but in contamination to soils and groundwater. It is important to develop a reliable method of detecting leaks before large quantities are emitted into the environment surround the tanks. Two field experiments were performed to evaluate the performance of electrical resistance tomography (ERT) as a leak detection method under metal underground storage tanks (UST). This paper provides a summary of the field experiments performed under a 15 m diameter steel tank mockup located at the Hanford Reservation.

  5. Integrating Shear-Wave Reflection and Resistivity Profiling to Improve Subsurface Characterization of Glacial Sediments

    NASA Astrophysics Data System (ADS)

    Larson, T. H.; Ismail, A. M.; Thomason, J.; Curry, B.; Stumpf, A.; Dey, W.

    2012-12-01

    In Illinois, both high resolution seismic reflection and 2-D resistivity profiling have become fairly common tools for mapping glacial sediments. Over the past several years we have been using the two methods in combination to improve the characterization of these sediments and to refine geologic and hydrogeologic models. We demonstrate our approach with several case studies where high-resolution shear (S)-wave reflection and electrical resistivity profiling surveys were acquired at the same locations in northern and central Illinois. The two geophysical methods measure the mechanical and the electrical properties of these sediments in the subsurface which together improve our understanding of the sedimentary sequences and the underlying bedrock surface. We present results from measurements made along co-located geophysical lines which vary in length from 400 m to greater than 2300 m. Typically, the S-wave reflection profiles have greater vertical resolution and provide better imaging of depositional surfaces than the corresponding resistivity profiles. On the other hand, the resistivity profiles better express the horizontal variability within individual units compared to the reflection profiles. The reflection profiles more reliably image the bedrock surface, whereas the resistivity profiles are more sensitive to variations in moisture content, mineral content and cementation within the glacial sediments. Together, the overall geometry of depositional packages can be inferred from reflection surfaces, while compositional variations within those packages can be inferred from variations primarily in the resistivity data and secondarily in the seismic data. Geophysical and geological interpretations are constrained by core data and downhole geophysical data from boreholes located on or near the geophysical profiles.

  6. Determination of electrical resistivity of dry coke beds

    SciTech Connect

    Eidem, P.A.; Tangstad, M.; Bakken, J.A.

    2008-02-15

    The electrical resistivity of the coke bed is of great importance when producing FeMn, SiMn, and FeCr in a submerged arc furnace. In these processes, a coke bed is situated below and around the electrode tip and consists of metallurgical coke, slag, gas, and metal droplets. Since the basic mechanisms determining the electrical resistivity of a coke bed is not yet fully understood, this investigation is focused on the resistivity of dry coke beds consisting of different carbonaceous materials, i.e., coke beds containing no slag or metal. A method that reliably compares the electrical bulk resistivity of different metallurgical cokes at 1500{sup o} C to 1600{sup o}C is developed. The apparatus is dimensioned for industrial sized materials, and the electrical resistivity of anthracite, charcoal, petroleum coke, and metallurgical coke has been measured. The resistivity at high temperatures of the Magnitogorsk coke, which has the highest resistivity of the metallurgical cokes investigated, is twice the resistivity of the Corus coke, which has the lowest electrical resistivity. Zdzieszowice and SSAB coke sort in between with decreasing resistivities in the respective order. The electrical resistivity of anthracite, charcoal, and petroleum coke is generally higher than the resistivity of the metallurgical cokes, ranging from about two to about eight times the resistivity of the Corus coke at 1450{sup o}C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.

  7. Antimicrobial resistance profiles in pathogens isolated from chickens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antimicrobial resistance profiles are frequently studied from the perspective of epidemiology and not so often from the perspective of population genetics. The population geneticist assumes that gene flow, vertically (generation to generation), horizontally (individual to individual) or migratory (...

  8. The electrical resistivity method in cased boreholes

    SciTech Connect

    Schenkel, C.J.

    1991-05-01

    The use of downhole current sources in resistivity mapping can greatly enhance the detection and delineation of subsurface features. The purpose of this work is to examine the resistivity method for current sources in wells cased with steel. The resistivity method in cased boreholes with downhole current sources is investigated using the integral equation (IE) technique. The casing and other bodies are characterized as conductivity inhomogeneities in a half-space. For sources located along the casing axis, an axially symmetric Green's function is used to formulate the surface potential and electric field (E-field) volume integral equations. The situations involving off-axis current sources and three-dimensional (3-D) bodies is formulated using the surface potential IE method. The solution of the 3-D Green's function is presented in cylindrical and Cartesian coordinate systems. The methods of moments is used to solve the Fredholm integral equation of the second kind for the response due to the casing and other bodies. The numerical analysis revealed that the current in the casing can be approximated by its vertical component except near the source and the axial symmetric approximation of the casing is valid even for the 3-D problem. The E-field volume IE method is an effective and efficient technique to simulate the response of the casing in a half-space, whereas the surface potential approach is computationally better when multiple bodies are involved. Analyzing several configurations of the current source indicated that the casing response is influenced by four characteristic factors: conduction length, current source depth,casing depth, and casing length. 85 refs., 133 figs., 11 tabs.

  9. Electrical Resistivity Imaging to Quantify Spatial Soil Heterogeneit

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electrical resistivity (ER) sounding is increasingly being used as non-invasive technique to reveal and map soil heterogeneity. The objective of this work was to evaluate effects of soil properties on the electric resistivity and to observe these effects in spatial context in coarse-textured soil. T...

  10. Soil spatial heterogeneity effect on soil electrical resistivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electrical resistivity (ER) is growing in popularity due to its ease of use and because of its non-invasive techniques, which are used to reveal and map soil heterogeneity. The objective of this work was to evaluate how differing soil properties affect the electric resistivity and to observe these e...

  11. Resistance profiles in surgical-site infection.

    PubMed

    Lenz, Andreas M; Fairweather, Mark; Cheadle, William G

    2008-08-01

    Surgical-site infections (SSIs) remain a common complication, affecting some 5% of patients undergoing surgical procedures and can sometimes present a major challenge after surgery with life-threatening septic illness. The appearance of organisms that are often resistant to common antibiotic treatment is of great concern. Staphylococcus aureus is the organism most commonly recovered from infected surgical wounds, and usually contaminates wounds from the patients own skin. SSIs occur despite appropriate skin disinfection, sterilization of instruments, use of gown and gloves, appropriate sterile technique and prophylactic antimicrobials. In fact, it is difficult to maintain a sterile field over time, and most wounds become contaminated throughout the course of surgery. Methicillin-resistant S. aureus (MRSA) first arose in the hospital setting, but have more recently evolved in the community. Such community-acquired MRSA are genetically different and seem to be even more virulent owing to genes that encode virulence factors, such as staphylococcal cassette chromosome mec type IV and Panton-Valentine leukocidin. The purpose of this review is to summarize characteristics of frequently isolated bacterial strains from SSIs. The focus will be on Gram-positive organisms because of their increasing prevalence in SSIs and their high potential to develop resistance against several antibiotic agents, including vancomycin. PMID:18651816

  12. Assessment of groundwater vulnerability to leachate infiltration using electrical resistivity method

    NASA Astrophysics Data System (ADS)

    Mosuro, G. O.; Omosanya, K. O.; Bayewu, O. O.; Oloruntola, M. O.; Laniyan, T. A.; Atobi, O.; Okubena, M.; Popoola, E.; Adekoya, F.

    2016-02-01

    This aim of this work is to assess the degree of leachate infiltration at a dumpsite in Agbara industrial estate, Southwestern Nigeria using electrical resistivity techniques. Around the dumpsite were 45 vertical electrical sounding (VES) stations and 3 electrical resistivity tomography profiles. Current electrode spread varied from 300 to 600 m for the electrical sounding. Electrode configuration includes Schlumberger and Wenner array for sounding and profiling. The state of leachate contamination was tested using parameters such as aquifer vulnerability index, overburden protective capacity and longitudinal unit conductance (Si) derived from the apparent resistivity values. Four principal geoelectric layers inferred from the VES data include the topsoil, sand, clayey sand, and clay/shale. Resistivity values for these layers vary from 3 to 1688, 203 to 3642 123 to 388, and 67 to 2201 Ω m with corresponding thickness of 0.8-2.4, 2.5-140, 3-26 m and infinity, respectively. The leachate plume occurs at a maximum depth of 10 m on the 2-D inverse models of real electrical resistivity with an average depth of infiltration being 6 m in the study area. The correlation between longitudinal conductance and overburden protective capacity show that aquifers around the dumpsite have poor protective capacity and are vulnerable to leachate contamination. Leachate infiltration is favored by the absence of lithological barriers such as clay which in the study area are either mixed with sand or positioned away from the aquifer.

  13. Transcriptome Profiling of Antimicrobial Resistance in Pseudomonas aeruginosa.

    PubMed

    Khaledi, Ariane; Schniederjans, Monika; Pohl, Sarah; Rainer, Roman; Bodenhofer, Ulrich; Xia, Boyang; Klawonn, Frank; Bruchmann, Sebastian; Preusse, Matthias; Eckweiler, Denitsa; Dötsch, Andreas; Häussler, Susanne

    2016-08-01

    Emerging resistance to antimicrobials and the lack of new antibiotic drug candidates underscore the need for optimization of current diagnostics and therapies to diminish the evolution and spread of multidrug resistance. As the antibiotic resistance status of a bacterial pathogen is defined by its genome, resistance profiling by applying next-generation sequencing (NGS) technologies may in the future accomplish pathogen identification, prompt initiation of targeted individualized treatment, and the implementation of optimized infection control measures. In this study, qualitative RNA sequencing was used to identify key genetic determinants of antibiotic resistance in 135 clinical Pseudomonas aeruginosa isolates from diverse geographic and infection site origins. By applying transcriptome-wide association studies, adaptive variations associated with resistance to the antibiotic classes fluoroquinolones, aminoglycosides, and β-lactams were identified. Besides potential novel biomarkers with a direct correlation to resistance, global patterns of phenotype-associated gene expression and sequence variations were identified by predictive machine learning approaches. Our research serves to establish genotype-based molecular diagnostic tools for the identification of the current resistance profiles of bacterial pathogens and paves the way for faster diagnostics for more efficient, targeted treatment strategies to also mitigate the future potential for resistance evolution. PMID:27216077

  14. Iron aluminide useful as electrical resistance heating elements

    SciTech Connect

    Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

    1999-11-02

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {le}1% Cr and either {ge}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {ge}0.1% oxide dispersoid particles. The alloy can contain 14--32% Al, {le}2% Ti, {le}2% Mo, {le}1% Zr, {le}1% C, {le}0.1% B, {le}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {le}1% rare earth metal, {le}1% oxygen, {le}3% Cu, balance Fe.

  15. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2001-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  16. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1997-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  17. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, V.K.; Deevi, S.C.; Fleischhauer, G.S.; Hajaligol, M.R.; Lilly, A.C. Jr.

    1997-04-15

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, {<=}1% Cr and either {>=}0.05% Zr or ZrO{sub 2} stringers extending perpendicular to an exposed surface of the heating element or {>=}0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, {<=}2% Ti, {<=}2% Mo, {<=}1% Zr, {<=}1% C, {<=}0.1% B, {<=}30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, {<=}1% rare earth metal, {<=}1% oxygen, {<=}3% Cu, balance Fe. 64 figs.

  18. Iron aluminide useful as electrical resistance heating elements

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    1999-01-01

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  19. Theoretical relationship between elastic wave velocity and electrical resistivity

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Sub; Yoon, Hyung-Koo

    2015-05-01

    Elastic wave velocity and electrical resistivity have been commonly applied to estimate stratum structures and obtain subsurface soil design parameters. Both elastic wave velocity and electrical resistivity are related to the void ratio; the objective of this study is therefore to suggest a theoretical relationship between the two physical parameters. Gassmann theory and Archie's equation are applied to propose a new theoretical equation, which relates the compressional wave velocity to shear wave velocity and electrical resistivity. The piezo disk element (PDE) and bender element (BE) are used to measure the compressional and shear wave velocities, respectively. In addition, the electrical resistivity is obtained by using the electrical resistivity probe (ERP). The elastic wave velocity and electrical resistivity are recorded in several types of soils including sand, silty sand, silty clay, silt, and clay-sand mixture. The appropriate input parameters are determined based on the error norm in order to increase the reliability of the proposed relationship. The predicted compressional wave velocities from the shear wave velocity and electrical resistivity are similar to the measured compressional velocities. This study demonstrates that the new theoretical relationship may be effectively used to predict the unknown geophysical property from the measured values.

  20. Mapping Contaminant Remediation with Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Gerhard, J.; Power, C.; Tsourlos, P.; Karaoulis, M.; Giannopoulos, A.; Soupios, P. M.; Simyrdanis, K.

    2014-12-01

    The remediation of sites contaminated with industrial chemicals - specifically dense non-aqueous phase liquids (DNAPLs) like coal tar and chlorinated solvents - represents a major geoenvironmental challenge. Remediation activities would benefit from a non-destructive technique to map the evolution of DNAPL mass in space and time. Electrical resistivity tomography (ERT) has long-standing potential in this context but has not yet become a common tool at DNAPL sites. This work evaluated the potential of time-lapse ERT for mapping DNAPL mass reduction in real time during remediation. Initially, a coupled DNAPL-ERT numerical model was developed for exploring this potential at the field scale, generating realistic DNAPL scenarios and predicting the response of an ERT survey. Also, new four-dimensional (4D) inversion algorithms were integrated for tracking DNAPL removal over time. 4D ERT applied at the surface for mapping an evolving DNAPL distribution was first demonstrated in a laboratory experiment. Independent simulation of the experiment demonstrated the reliability of the DNAPL-ERT model for simulating real systems. The model was then used to explore the 4D ERT approach at the field scale for a range of realistic DNAPL remediation scenarios. The approach showed excellent potential for mapping shallow DNAPL changes. However, remediation at depth was not as well resolved. To overcome this limitation, a new surface-to-horizontal borehole (S2HB) ERT configuration is proposed. A second laboratory experiment was conducted that demonstrated that S2HB ERT does better resolve changes in DNAPL distribution relative to surface ERT, particularly at depth. The DNAPL-ERT model was also used to demonstrate the improved mapping of S2HB ERT for field scale DNAPL scenarios. Overall, this work demonstrates that, with these innovations, ERT exhibits significant potential as a real time, non-destructive geoenvironmental remediation site monitoring tool.

  1. Sinkhole detection using electrical resistivity tomography in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Youssef, Ahmed M.; El-Kaliouby, Hesham; Zabramawi, Yasser A.

    2012-12-01

    Karst phenomena exist in different areas in the Kingdom of Saudi Arabia, causing serious environmental problems that affect urban development and infrastructure (buildings, roads and highways). One of the most important problems are sinkholes, which most of the time consist of unfilled voids. These sinkholes are formed as a result of the chemical leaching of carbonate and evaporite formations by percolating water. Field investigations show that there are many surface expressions of sinkholes in the area; some appear on the ground surface and others are hidden in the subsurface. Geophysical data were collected at the study area using two-dimensional electrical resistivity tomography (ERT) with different electrode spacings to delineate buried sinkholes and associated subsurface cavities. Our findings indicated that the dipole-dipole method using an electrode spacing of 1 m was successful in detecting a known subsurface sinkhole. According to the ERT method the detected sinkhole depth ranges from 2 to 4 m, its height ranges from 2 to 4 m, and its width ranges from 5 to 7 m. Field observation has verified the geophysical data, especially along the profile A-A\\. Finally, closely spaced ERT profiles were successful in determining the three-dimensional volume of the subsurface sinkhole.

  2. Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes

    SciTech Connect

    Lan, Chun; Amama, Placidus B.; Fisher, Timothy S.; Reifenberger, Ronald G.

    2007-08-27

    A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes (MWNTs) has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition (PECVD) at 800, 900, and 950 deg. C. The lowest resistances were obtained mainly from MWNTs grown at 900 deg. C. The MWNT resistance is larger on average at lower (800 deg. C) and higher (950 deg. C) growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.

  3. Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lan, Chun; Amama, Placidus B.; Fisher, Timothy S.; Reifenberger, Ronald G.

    2007-08-01

    A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes (MWNTs) has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition (PECVD) at 800, 900, and 950°C. The lowest resistances were obtained mainly from MWNTs grown at 900°C. The MWNT resistance is larger on average at lower (800°C) and higher (950°C) growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.

  4. State Waste Discharge Permit Application: Electric resistance tomography testing

    SciTech Connect

    Not Available

    1994-04-01

    This permit application documentation is for a State Waste Discharge Permit issued in accordance with requirements of Washington Administrative Code 173-216. The activity being permitted is a technology test using electrical resistance tomography. The electrical resistance tomography technology was developed at Lawrence Livermore National Laboratory and has been used at other waste sites to track underground contamination plumes. The electrical resistance tomography technology measures soil electrical resistance between two electrodes. If a fluid contaminated with electrolytes is introduced into the soil, the soil resistance is expected to drop. By using an array of measurement electrodes in several boreholes, the areal extent of contamination can be estimated. At the Hanford Site, the purpose of the testing is to determine if the electrical resistance tomography technology can be used in the vicinity of large underground metal tanks without the metal tank interfering with the test. It is anticipated that the electrical resistance tomography technology will provide a method for accurately detecting leaks from the bottom of underground tanks, such as the Hanford Site single-shell tanks.

  5. Electro-dewatering of activated sludge: Electrical resistance analysis.

    PubMed

    Conrardy, Jean-Baptiste; Vaxelaire, Jean; Olivier, Jérémy

    2016-09-01

    The significant risk of ohmic heating and the high electric energy consumption at terminal stages of the dewatering are two problems that hamper the development of the electro-dewatering (EDW) technology. In the future prospect of studying these two issues, it is important to provide and analyse quantitative data relative to the behavior of the electric resistance in EDW. It was the main goal of this study. It showed that the electric resistance of the complete system (cake + filter cloth) depended on the cake dryness. It increased sharply when the solids content exceeded around 45%.The solids loading also influenced the apparent resistance at the beginning of the process. The electric resistance of the filter cloth represented about 20% of the total resistance. It remained relatively constant over the process except at the terminal stage where it generally increased sharply. The use of conductive filter, such as metallic cloth, enabled to decrease the electric resistance and reduce the energy consumption of the process. The electric resistance decreased across the cake from the anode to the cathode. This behavior may be explained by several phenomena such as the ions migration and their interaction with the solid, the decrease of dry solids content from the anode to the cathode and the gas presence at the anode (due to electrolysis reaction). PMID:27192354

  6. Electrical Resistivity Imaging to Quantify Spatial Soil Heterogeneity

    NASA Astrophysics Data System (ADS)

    Guber, A. K.; Hadzick, Z. L.; Garzio, A.; Pachepsky, Y. A.; Hill, R. L.; Rowland, R. A.; Golovko, L. A.

    2008-12-01

    Electrical resistivity (ER) sounding is increasingly being used as non-invasive technique to reveal and map soil heterogeneity. The objective of this work was to evaluate effects of soil properties on the electric resistivity and to observe these effects in spatial context in coarse-textured soil. The studied soil had the sandy loam texture. The 20x20-m study plot was located at the ARS Beltsville OPE3 site. Relationship between ER, bulk density, and soil water contents was first studied in disturbed 80-cm3 soil samples taken at 10 depths with 20 cm increment. Soil water contents were brought to 6 predefined levels in each sample and were in the range from air dry to 0.27g g-1. Soil bulk density varied in the range from 1.28 to 1.45 g cm-3. The ER in soil samples decreased as the gravimetric water content increased. The ER decrease became more pronounced as bulk density decreased. Next, soil samples were taken at field water contents from 10 depths at 12 locations. Particle size distributions, pH, water content and ER were measured in each sample. Bulk density values in part of the soil profiles below 80 cm ranged from 1.5 to 1.8 g cm- 3 and no dependence between ER and water content could be established in this soil layer where the lowest values of ER were recorded. The increased conductivity of the soil solid phase could be a possible reason for that since soil in this part of the profile had pH values two or more units less than in the upper part. The lowest sand contents corresponded to highest ER values in this soil layer. Finally, the vertical electrical sounding (LandMapper ERM-02) was used to infer spatial distribution of soil resistivity along a 9-m transect for different dates when soil was dry and when it was relatively uniformly wetted with long low- intensity rain. The Wenner-Shlumberger array with 31-electrodes spaced 30-cm apart was used. Soil temperature and water content with multisensor capacitance probes (SENTEC) were monitored at 10 depths down

  7. Electrical resistance tomography using steel cased boreholes as electrodes

    DOEpatents

    Daily, W.D.; Ramirez, A.L.

    1999-06-22

    An electrical resistance tomography method is described which uses steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constrain the models. 2 figs.

  8. Electrical resistance tomography using steel cased boreholes as electrodes

    DOEpatents

    Daily, William D.; Ramirez, Abelardo L.

    1999-01-01

    An electrical resistance tomography method using steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constain the models.

  9. Marine permafrost detection using galvanic electrical resistivity methods

    SciTech Connect

    Corwin, R.F.

    1983-05-01

    Because of the high electrical resistivity contrast between ice-bonded sediments (permafrost) and the same sediments in an unfrozen state, galvanic (direct-current) electrical resistivity measurements are capable of determining the depth below the sea floor of marine permafrost layers. Unlike the seismic refraction method usually used for offshore permafrost surveying, resistivity measurements can determine the thickness as well as the depth of a permafrost layer. Also, the resistivity method is usable in acoustic anomaly areas where seismic data cannot be obtained and in shallow water where air gun sources are not effective. Marine resistivity measurements may be made through the sea ice in the winter or from a stationary or moving boat in the summer. The results of field trials conducted in the Prudhoe Bay area indicated that marine permafrost depths and thicknesses determined from resistivity measurements agreed well with those obtained from borehole data.

  10. COMPLEX ELECTRICAL RESISTIVITY FOR MONITORING DNAPL CONTAMINATION

    EPA Science Inventory

    We propose to develop new practical complex resistivity field measurement techniques for pollution characterization and monitoring. For this purpose we will document the detectability of clay-organic interactions with geophysical measurements in the laboratory, develop further un...

  11. INORGANIC PLUME DELINEATION USING SURFACE HIGH RESOLUTION ELECTRICAL RESISTIVITY AT THE BC CRIBS & TRENCHES SITE HANFORD

    SciTech Connect

    BENECKE, M.W.

    2007-05-29

    A surface resistivity survey was conducted on the Hanford Site over a waste disposal trench that received a large volume of liquid inorganic waste. The objective of the survey was to map the extent of the plume that resulted from the disposal activities approximately 50 years earlier. The survey included six resistivity transects of at least 200m, where each transect provided two-dimensional profile information of subsurface electrical properties. The results of the survey indicated that a low resistivity plume resides at a depth of approximately 25-44 m below ground surface. The target depth was calibrated with borehole data of pore-water electrical conductivity. Due to the high correlation of the pore-water electrical conductivity to nitrate concentration and the high correlation of measured apparent resistivity to pore-water electrical conductivity, inferences were made that proposed the spatial distribution of the apparent resistivity was due to the distribution of nitrate. Therefore, apparent resistivities were related to nitrate, which was subsequently rendered in three dimensions to show that the nitrate likely did not reach the water table and the bounds of the highest concentrations are directly beneath the collection of waste sites.

  12. Pseudomonas aeruginosa: arsenal of resistance mechanisms, decades of changing resistance profiles, and future antimicrobial therapies.

    PubMed

    El Zowalaty, Mohamed E; Al Thani, Asmaa A; Webster, Thomas J; El Zowalaty, Ahmed E; Schweizer, Herbert P; Nasrallah, Gheyath K; Marei, Hany E; Ashour, Hossam M

    2015-01-01

    Antimicrobial resistance is one of the most serious public health issues facing humans since the discovery of antimicrobial agents. The frequent, prolonged, and uncontrolled use of antimicrobial agents are major factors in the emergence of antimicrobial-resistant bacterial strains, including multidrug-resistant variants. Pseudomonas aeruginosa is a leading cause of nosocomial infections. The abundant data on the increased resistance to antipseudomonal agents support the need for global action. There is a paucity of new classes of antibiotics active against P. aeruginosa. Here, we discuss recent antibacterial resistance profiles and mechanisms of resistance by P. aeruginosa. We also review future potential methods for controlling antibiotic-resistant bacteria, such as phage therapy, nanotechnology and antipseudomonal vaccines. PMID:26439366

  13. Slime thickness evaluation of bored piles by electrical resistivity probe

    NASA Astrophysics Data System (ADS)

    Chun, Ok-Hyun; Yoon, Hyung-Koo; Park, Min-Chul; Lee, Jong-Sub

    2014-09-01

    The bottoms of bored piles are generally stacked with soil particles, both while boreholes are being drilled, and afterward. The stacked soils are called slime, and when loads are applied on the pile, increase the pile settlement. Thus to guarantee the end bearing capacity of bored piles, the slime thickness should be precisely detected. The objective of this study is to suggest a new method for evaluating the slime thickness, using temperature compensated electrical resistivity. Laboratory studies are performed in advance, to estimate and compare the resolution of the electrical resistivity probe (ERP) and time domain reflectometry (TDR). The electrical properties of the ERP and TDR are measured using coaxial type electrodes and parallel type two-wire electrodes, respectively. Penetration tests, conducted in the fully saturated sand-clay mixtures, demonstrate that the ERP produces a better resolution of layer detection than TDR. Thus, field application tests using the ERP with a diameter of 35.7 mm are conducted for the investigation of slime thickness in large diameter bored piles. Field tests show that the slime layers are clearly identified by the ERP: the electrical resistivity dramatically increases at the interface between the slurry and slime layer. The electrical resistivity in the slurry layer inversely correlates with the amount of circulated water. This study suggests that the new electrical resistivity method may be a useful method for the investigation of the slime thickness in bored piles.

  14. Electrical resistivity of coal-bearing rocks under high temperature and the detection of coal fires using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Shao, Zhenlu; Wang, Deming; Wang, Yanming; Zhong, Xiaoxing; Tang, Xiaofei; Xi, Dongdong

    2016-02-01

    Coal fires are severe hazards to environment, health and safety throughout the world. Efficient and economical extinguishing of these fires requires that the extent of the subsurface coal fires should be delineated. Electrical and electromagnetic methods have been used to detect coal fires in recent years. However, the resistivity change of coal-bearing rocks at high temperature is rarely investigated. The resistivity characteristics of coal fires at different temperatures and depths are seldomly researched as well. In this paper, we present the results of measurements of several coal-bearing rocks' resistivity and permeability under high temperature. Two major causes for the change in resistivity with increasing temperature are recognized, there are the increase of charge carriers and thermal fracturing, of which the first one is probably the dominant cause. A set of 2-D simulations is carried out to compare the relation of resolution and efficiency of coal fires detection to temperature and depth when adopting the electrical resistance tomography. The simulation results show that the resolution and efficiency decrease with the decrease of temperature and the increase of depth. Finally, the electrical resistance tomography is used to delineate coal fires in the Anjialing Open Pit Mine. Most low-resistivity regions are verified as coal-fire areas according to the long-term monitoring of borehole temperature. The results indicate that the electrical resistance tomography can be used as a tool for the detection of coal fires.

  15. Control of the Electric Field Profile in the Hall Thruster

    SciTech Connect

    A. Fruchtman; N. J. Fisch; Y. Raitses

    2000-10-05

    Control of the electric field profile in the Hall Thruster through the positioning of an additional electrode along the channel is shown theoretically to enhance the efficiency. The reduction of the potential drop near the anode by use of the additional electrode increases the plasma density there, through the increase of the electron and ion transit times, causing the ionization in the vicinity of the anode to increase. The resulting separation of the ionization and acceleration regions increases the propellant and energy utilizations. An abrupt sonic transition is forced to occur at the axial location of the additional electrode, accompanied by the generation of a large (theoretically infinite) electric field. This ability to generate a large electric field at a specific location along the channel, in addition to the ability to specify the electric potential there, allows one further control of the electric field profile in the thruster. In particular, when the electron temperature is high, a large abrupt voltage drop is induced at the vicinity of the additional electrode, a voltage drop that can comprise a significant part of the applied voltage.

  16. Resistance mutations generate divergent antibiotic susceptibility profiles against translation inhibitors

    PubMed Central

    Cocozaki, Alexis I.; Altman, Roger B.; Huang, Jian; Buurman, Ed T.; Kazmirski, Steven L.; Doig, Peter; Prince, D. Bryan; Blanchard, Scott C.; Cate, Jamie H. D.; Ferguson, Andrew D.

    2016-01-01

    Mutations conferring resistance to translation inhibitors often alter the structure of rRNA. Reduced susceptibility to distinct structural antibiotic classes may, therefore, emerge when a common ribosomal binding site is perturbed, which significantly reduces the clinical utility of these agents. The translation inhibitors negamycin and tetracycline interfere with tRNA binding to the aminoacyl-tRNA site on the small 30S ribosomal subunit. However, two negamycin resistance mutations display unexpected differential antibiotic susceptibility profiles. Mutant U1060A in 16S Escherichia coli rRNA is resistant to both antibiotics, whereas mutant U1052G is simultaneously resistant to negamycin and hypersusceptible to tetracycline. Using a combination of microbiological, biochemical, single-molecule fluorescence transfer experiments, and X-ray crystallography, we define the specific structural defects in the U1052G mutant 70S E. coli ribosome that explain its divergent negamycin and tetracycline susceptibility profiles. Unexpectedly, the U1052G mutant ribosome possesses a second tetracycline binding site that correlates with its hypersusceptibility. The creation of a previously unidentified antibiotic binding site raises the prospect of identifying similar phenomena in antibiotic-resistant pathogens in the future. PMID:27382179

  17. Resistance mutations generate divergent antibiotic susceptibility profiles against translation inhibitors.

    PubMed

    Cocozaki, Alexis I; Altman, Roger B; Huang, Jian; Buurman, Ed T; Kazmirski, Steven L; Doig, Peter; Prince, D Bryan; Blanchard, Scott C; Cate, Jamie H D; Ferguson, Andrew D

    2016-07-19

    Mutations conferring resistance to translation inhibitors often alter the structure of rRNA. Reduced susceptibility to distinct structural antibiotic classes may, therefore, emerge when a common ribosomal binding site is perturbed, which significantly reduces the clinical utility of these agents. The translation inhibitors negamycin and tetracycline interfere with tRNA binding to the aminoacyl-tRNA site on the small 30S ribosomal subunit. However, two negamycin resistance mutations display unexpected differential antibiotic susceptibility profiles. Mutant U1060A in 16S Escherichia coli rRNA is resistant to both antibiotics, whereas mutant U1052G is simultaneously resistant to negamycin and hypersusceptible to tetracycline. Using a combination of microbiological, biochemical, single-molecule fluorescence transfer experiments, and X-ray crystallography, we define the specific structural defects in the U1052G mutant 70S E. coli ribosome that explain its divergent negamycin and tetracycline susceptibility profiles. Unexpectedly, the U1052G mutant ribosome possesses a second tetracycline binding site that correlates with its hypersusceptibility. The creation of a previously unidentified antibiotic binding site raises the prospect of identifying similar phenomena in antibiotic-resistant pathogens in the future. PMID:27382179

  18. Electrical resistivity image of the South Atlantic continental margin derived from onshore and offshore magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Kapinos, G.; Weckmann, U.; Jegen-Kulcsar, M.; Meqbel, N.; Neska, A.; Katjiuongua, T. T.; Hoelz, S.; Ritter, O.

    2016-01-01

    We present a deep electrical resistivity image from the passive continental margin in Namibia. The approximately 700 km long magnetotelluric profile follows the Walvis Ridge offshore, continues onshore across the Kaoko Mobile Belt and reaches onto the Congo Craton. Two-dimensional inversion reveals moderately resistive material offshore, atypically low for oceanic lithosphere, reaching depths of 15-20 km. Such moderate resistivities are consistent with seismic P wave velocity models, which suggest up to 35 km thick crust. The Neoproterozoic rocks of the Kaoko Mobile Belt are resistive, but NNW-striking major shear-zones are imaged as subvertical, conductive structures in the upper and middle crust. Since the geophysical imprint of the shear zones is intact, opening of the South Atlantic in the Cretaceous did not alter the middle crust. The transition into the cratonic region coincides with a deepening of the high-resistive material to depths of more than 60 km.

  19. Electrical Resistivity of Liquid Alkali Na-based Binary Alloys

    NASA Astrophysics Data System (ADS)

    Vora, Aditya M.

    2007-11-01

    The study of the electrical resistivity rL of alkali Na-based binary alloys Na1-xLix, Na1-xKx, Na1-xRbx and Na1-xCsx have been made by well-recognized model potential of Gajjar et al. The most recent exchange and correlation functions due to Farid et al (F) and Sarkar et al (S) are used for the first time in the study of electrical resistivity of liquid binary mixtures and found suitable for such study. The results, due to the inclusion of Sarkar et al's local field correction function, are found superior to those obtained due to Farid et al's local field correction function. Electrical resistivity of Na-based binary alloys compare well with the experimental data available in the literature.

  20. Electrical resistivity study of Magnetite under high pressure

    NASA Astrophysics Data System (ADS)

    Muramatsu, Takaki; Struzhkin, Viktor; Gasparov, Lev

    2014-03-01

    Magnetite is known as one of the oldest magnetic materials and crystallizes in the inversed spinel structure. At about 120 K magnetite undergoes a structural phase transition called Verway transition where electrical resistivity abruptly increases with decreasing temperature. Pressure effects of Verway transition studied by magnetic susceptibility and electrical resistivity by several groups revealed Verway transition decreased with pressure and the precise pressure effects depend on the pressure condition i.e., pressure transmitting media. In this work, electrical resistivity measurements were made to revisit the property of magnetite under pressure. Both metallization observed in precedent work using cubic anvil press and the higher pressure properties beyond metallization are examined by diamond anvil cell.

  1. Electrical resistivity borehole measurements: application to an urban tunnel site

    NASA Astrophysics Data System (ADS)

    Denis, A.; Marache, A.; Obellianne, T.; Breysse, D.

    2002-06-01

    This paper shows how it is possible to use wells drilled during geotechnical pre-investigation of a tunneling site to obtain a 2-D image of the resistivity close to a tunnel boring machine. An experimental apparatus is presented which makes it possible to perform single and borehole-to-borehole electrical measurements independent of the geological and hydrogeological context, which can be activated at any moment during the building of the tunnel. This apparatus is first demonstrated through its use on a test site. Numerical simulations and data inversion are used to analyse the experimental results. Finally, electrical resistivity tomography and single-borehole measurements on a tunneling site are presented. Experimental results show the viability of the apparatus and the efficiency of the inverse algorithm, and also highlight the limitations of the electrical resistivity tomography as a tool for geotechnical investigation in urban areas.

  2. Delineating the Groundwater Recharge Zone in the Pingtung Plan , Taiwan with Electrical Resistivity Surveys

    NASA Astrophysics Data System (ADS)

    Wu, C.; Chang, P.; Chang, L.; Chen, J.; Huang, C.

    2012-12-01

    In this study we used the two-dimensional electrical resistivity imaging (ERI) method, as well as the core records of monitoring wells to help determine the groundwater recharge zone in Pingtung plain in southwestern Taiwan. Pingtung fluvial plain is one of the major groundwater resources in Taiwan which is composed of several alluvial fans deriving from the uplifted mountain area to the east and north of the plain. The thick gravel layer constitutes the main recharge area of the upper alluvial fans and the conductive clay sediments dominate most of the lower fans. With the core records, we found that, the gravel layers have higher resistivity (mostly over 200 Ohm-m) and the resistivities of the clayey layers are low (about 1~10 Ohm-m). Therefore with the resistivity surveys we can have more confidences for determining the boundary of the groundwater recharge area in the area in-between the monitoring wells. In the past two years, we have finished 24 two-dimensional electrical resistivity imaging profile lines from Meinong to Fangliao, the lines are oriented in the east-west direction, and each line was about 400 meters long. With the inverted results, we are able to characterize two major alluvial systems and their recharge zones in the Pingtung fluvial plain. The resistivities we measured almost are consistent to the core records of monitoring wells except for the Wanluan site, which shows thick gravel layer in the drilling records but has low resistivity in the nearby resistivity survey. A reasonable explanation is that the electrical resistivity is sensitive to clayey materials with lower resistivities. The intercalated clay within the gravel layers is not shown in the churn drilling records.

  3. High electrical resistivity carbon/graphite fibers

    NASA Technical Reports Server (NTRS)

    Vogel, F. L.; Forsman, W. C.

    1980-01-01

    Carbon/graphite fibers were chemically oxidized in the liquid phase to fibers of graphite oxide. Resistivity increases as high as 10,000 times were obtained, the oxidized fiber decomposed on exposure to atmosphere. A factor of 1,000 remained as a stable increment. The largest change observed was 1,000,000 times. Best results were obtained on the most highly graphitized fibers. Electrochemical oxidation yielded a lower increase--about 10 times, but provided a controllable method of synthesis and insight to the mechanism of reaction. Tensile tests indicated that the strength of the fiber on oxidation was decreased by no more than 25 percent.

  4. Bacteriological and Resistance Profile in Isolates from Diabetic Patients

    PubMed Central

    Rawat, Vinita; Singhai, Monil; Kumar, Ashok; Jha, Pawan Kumar; Goyal, Rajeev

    2012-01-01

    Background: Diabetes mellitus has become a global epidemic illness and poses a threat for development of resistant bacterial infections. Aim: This study was aimed to know the bacteriological and resistance profile of isolates obtained from diabetic patients. Materials and Methods: The bacterial isolates obtained from various samples of diabetic patients admitted in medicine department in 6-month period were identified and tested for antibiotic susceptibility. The extended spectrum beta-lactamases (ESβL), AmpC, and metallo-beta-lactamases (MβL) enzymes were detected in gram-negative bacilli. Methicillin, macrolide-lincosamide-streptogramin (MLS), and linezolid resistance in Staphylococcus spp. were detected. High-level aminoglycoside resistance (HLAR) in Enterococcus spp. was also tested. Results: In all, 38 of 125 diabetic patients (30.4%) had bacterial infection, 18 patients had wound infections, 18 had urinary tract infections (UTIs), and 2 had respiratory tract infections. Escherichia coli among gram-negative bacteria and Staphylococcus aureus among gram-positive bacteria were the predominant pathogens. 32.5% gram-negative bacilli were AmpC producers, 37.5% were MβL producers, and 40% were ESβL producers. Methicillin and MLS resistance was found in 50% and 33.3% isolates of Staphylococcus spp., respectively. HLAR resistance was alarming in Enterococcus spp. Polymyxin among gram-negative bacteria and vancomycin for gram-positive bacteria were the last resort with highest susceptibility rates to treat infections among diabetic patients. Conclusion: Resistant bacterial infections in diabetic patients are common. The presence of various resistance mechanisms in isolates of our study shows that therapeutic failure can occur if empirical prescription is unsubstantiated. PMID:23181227

  5. Influence of Electrical Resistivity and Machining Parameters on Electrical Discharge Machining Performance of Engineering Ceramics

    PubMed Central

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  6. Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.

    PubMed

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  7. Resistivity of flame plasma in an electric field

    NASA Astrophysics Data System (ADS)

    Ikuta, Kazunari

    1989-03-01

    A generalized Ohm's law is obtained for a flame plasma in an electric field for the study of arc resistivity in an electromagnetic launcher (EML). The resistivity of flame plasma is reduced by the particle source, which suggests the injection of premixed combustible fuel into the arc plasma as the particle source in order to reduce the arc voltage. Reduction of the voltage in the arc is desirable to reduce the damage of electrodes in EML since the electric field in the arc plasma energizes charged particles which can bombard the electrodes.

  8. Electrical resistivity of Au-ZnO nanocomposite films

    SciTech Connect

    Argibay, N.; Goeke, R. S.; Dugger, M. T.; Rodriguez, M. A.; Michael, J. R.; Prasad, S. V.

    2013-04-14

    The electrical resistivity of electron beam codeposited gold and zinc oxide (Au-ZnO) films was investigated over the full composition range. The electrical resistivity was shown to increase monotonically with increasing ZnO content, with three characteristic regimes of behavior associated primarily with (1) grain boundary electron scattering due to grain refinement at ZnO volume fractions below 0.3, (2) percolation theory for ZnO volume fractions at and above the percolation threshold (f{sub c} = 0.85), and (3) a transition region between these where it was proposed that resistivity was influenced by the formation of Au-Zn complexes due to an oxygen deficiency in the deposited ZnO. The electrical resistivity of the composite films remained below 100 {mu}{Omega} cm for ZnO volume fractions below 0.5. A model combining the general effective media equation and Mayadas-Shatzkes grain boundary electron scattering model was shown to generally describe the composition dependence of electrical resistivity for the investigated oxide dispersion hardened metal-matrix composite thin films.

  9. Using electrical resistance tomography to map subsurface temperatures

    DOEpatents

    Ramirez, A.L.; Chesnut, D.A.; Daily, W.D.

    1994-09-13

    A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations. 1 fig.

  10. Using electrical resistance tomography to map subsurface temperatures

    DOEpatents

    Ramirez, Abelardo L.; Chesnut, Dwayne A.; Daily, William D.

    1994-01-01

    A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations.

  11. Modeling the Electrical Contact Resistance at Steel-Carbon Interfaces

    NASA Astrophysics Data System (ADS)

    Brimmo, Ayoola T.; Hassan, Mohamed I.

    2016-01-01

    In the aluminum smelting industry, electrical contact resistance at the stub-carbon (steel-carbon) interface has been recurrently reported to be of magnitudes that legitimately necessitate concern. Mitigating this via finite element modeling has been the focus of a number of investigations, with the pressure- and temperature-dependent contact resistance relation frequently cited as a factor that limits the accuracy of such models. In this study, pressure- and temperature-dependent relations are derived from the most extensively cited works that have experimentally characterized the electrical contact resistance at these contacts. These relations are applied in a validated thermo-electro-mechanical finite element model used to estimate the voltage drop across a steel-carbon laboratory setup. By comparing the models' estimate of the contact electrical resistance with experimental measurements, we deduce the applicability of the different relations over a range of temperatures. The ultimate goal of this study is to apply mathematical modeling in providing pressure- and temperature-dependent relations that best describe the steel-carbon electrical contact resistance and identify the best fit relation at specific thermodynamic conditions.

  12. Resistivity of flame plasma in an electric field

    NASA Astrophysics Data System (ADS)

    Ikuta, Kazunari

    1989-01-01

    A generalized Ohm's law is obtained for a flame plasma in an electric field for the study of arc resistivity in an electromagnetic launcher (EML). The effective resistivity of flame plasma is reduced by the source, which suggests the injection of premixed combustible fuel into the arc plasma in EML in order to reduce the electron energy of the arc. The reduction of electron energy in the arc is desirable to minimize the damage of electrodes in EML.

  13. Resistance after firing protected electric match. [Patent application

    DOEpatents

    Montoya, A.P.

    1980-03-20

    An electric match having electrical leads embedded in flame-producing compound is protected against an accidental resistance across the leads after firing by a length of heat-shrinkable tubing encircling the match body and having a skirt portion extending beyond the leads. The heat of the burning match and an adjacent thermal battery causes the tubing to fold over the end of the match body, covering the ends of the leads and protecting them from molten pieces of the battery.

  14. Equivalent Electrical Circuit Representations of AC Quantized Hall Resistance Standards

    PubMed Central

    Cage, M. E.; Jeffery, A.; Matthews, J.

    1999-01-01

    We use equivalent electrical circuits to analyze the effects of large parasitic impedances existing in all sample probes on four-terminal-pair measurements of the ac quantized Hall resistance RH. The circuit components include the externally measurable parasitic capacitances, inductances, lead resistances, and leakage resistances of ac quantized Hall resistance standards, as well as components that represent the electrical characteristics of the quantum Hall effect device (QHE). Two kinds of electrical circuit connections to the QHE are described and considered: single-series “offset” and quadruple-series. (We eliminated other connections in earlier analyses because they did not provide the desired accuracy with all sample probe leads attached at the device.) Exact, but complicated, algebraic equations are derived for the currents and measured quantized Hall voltages for these two circuits. Only the quadruple-series connection circuit meets our desired goal of measuring RH for both ac and dc currents with a one-standard-deviation uncertainty of 10−8 RH or less during the same cool-down with all leads attached at the device. The single-series “offset” connection circuit meets our other desired goal of also measuring the longitudinal resistance Rx for both ac and dc currents during that same cool-down. We will use these predictions to apply small measurable corrections, and uncertainties of the corrections, to ac measurements of RH in order to realize an intrinsic ac quantized Hall resistance standard of 10−8 RH uncertainty or less.

  15. Young men's condom use resistance tactics: a latent profile analysis.

    PubMed

    Davis, Kelly Cue; Stappenbeck, Cynthia A; Norris, Jeanette; George, William H; Jacques-Tiura, Angela J; Schraufnagel, Trevor J; Kajumulo, Kelly F

    2014-01-01

    Research suggests that many men have used a variety of tactics to avoid using condoms when having sex with women. Guided by previous work demonstrating that men's use of coercive condom resistance tactics was predicted by negative attitudes toward women, inconsistent condom use, multiple partners, and sexual sensation seeking, the current study used latent profile analysis (LPA) to determine whether similar constructs were associated with a variety of resistance tactics. A community sample of 313 moderate-drinking men participated, of whom 80% reported employing at least one condom use resistance tactic since adolescence. The LPA revealed three classes of men. In general, men with the least negative beliefs about women, low levels of sexual sensation seeking and impulsivity, and positive beliefs about condoms (Condom Positive/Low Hostility) reported less use of resistance tactics than men with moderate sexual sensation seeking and impulsivity, negative beliefs about condoms, and moderate (Condom Negative/Moderate Hostility) or high (Condom Negative/High Hostility) negative attitudes about women. The classes also differed in terms of their sexual behaviors. This study demonstrated that sexual risk behavior interventions should not only address the tactics through which men resist using condoms but also tailor these efforts to men's individual characteristics. PMID:23548069

  16. Application of electrical resistivity tomography technique for investigation of landslides: a case from Turkey

    NASA Astrophysics Data System (ADS)

    Drahor, Mahmut G.; Göktürkler, Gökhan; Berge, Meriç A.; Kurtulmuş, T. Özgür

    2006-05-01

    Electrical resistivity imaging is a widely used tool in near surface geophysical surveys for investigation of various geological, environmental and engineering problems including landslide. In this study, an electrical resistivity tomography (ERT) survey was conducted in a landslide area, located in the Söke district of Aydın, Turkey. In 2003, the Neogene-aged units on the slope next to a newly built school building became unstable due to an excavation work and moved after a heavy rainfall. The resulting landslide partly covered the school. The authors carried out a 2-D resistivity survey along three profiles over the landslide mass using a Wenner configuration. It yielded useful information about the geometry and characteristics of the landslide. In addition, a 2-D synthetic resistivity modelling study was carried out to understand the response of the resistivity method to a landslide problem before the field surveys. Eight boreholes were also drilled in the landslide area. Both the drilling and resistivity results indicated the presence of a fault in the site. Also, the resistivity data from the line measured along the axis of the landslide revealed the surface of rupture.

  17. Nondestructive evaluation of composite materials by electrical resistance measurement

    NASA Astrophysics Data System (ADS)

    Mei, Zhen

    This dissertation investigates electrical resistance measurement for nondestructive evaluation of carbon fiber (CF) reinforced polymer matrix composites. The method involves measuring the DC electrical resistance in either the longitudinal or through thickness direction. The thermal history and thermal properties of thermoplastic/CF composites were studied by longitudinal and through-thickness resistance measurements. The resistance results were consistent with differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) results. The resistance measurements gave more information on the melting of the polymer matrix than TMA. They were more sensitive to the glass transition of the polymer matrix than DSC. The through-thickness resistance decreased as autohesion progressed. The activation energy of autohesion was 21.2 kJ/mol for both nylon-6 and polyphenylene sulfide (PPS)/CF composites. Adhesive bonding and debonding were monitored in real-time by measurement of the through-thickness resistance between the adherends in an adhesive joint during heating and subsequent cooling. Debonding occurred during cooling when the pressure or temperature during prior bonding was not sufficiently high. A long heating time below the melting temperature (T m) was found to be detrimental to subsequent PPS adhesive joint development above Tm, due to curing reactions below Tm and consequent reduced mass flow response above Tm. A high heating rate (small heating time) enhanced the bonding more than a high pressure. The longitudinal resistance measurement was used to investigate the effects of temperature and stress on the interface between a concrete substrate and its epoxy/CF composite retrofit. The resistance of the retrofit was increased by bond degradation, whether the degradation was due to heat or stress. The degradation was reversible. Irreversible disturbance in the fiber arrangement occurred slightly as thermal or load cycling occurred, as indicated by the

  18. Aerobic exercise augments muscle transcriptome profile of resistance exercise.

    PubMed

    Lundberg, Tommy R; Fernandez-Gonzalo, Rodrigo; Tesch, Per A; Rullman, Eric; Gustafsson, Thomas

    2016-06-01

    Recent reports suggest that aerobic exercise may boost the hypertrophic response to short-term resistance training. This study explored the effects of an acute aerobic exercise bout on the transcriptional response to subsequent resistance exercise. Ten moderately trained men performed ∼45 min cycling on one leg followed by 4 × 7 maximal knee extensions for each leg, 15 min later. Thus, one limb performed aerobic and resistance exercise (AE + RE) while the opposing leg did resistance exercise only (RE). Biopsies were obtained from the vastus lateralis muscle of each leg 3 h after the resistance exercise bout. Using DNA microarray, we analyzed differences [≥1.5-fold, false discovery rate (FDR) ≤10%] in gene expression profiles for the two modes of exercise. There were 176 genes up (127)- or downregulated (49) by AE + RE compared with RE. Among the most significant differentially expressed genes were established markers for muscle growth and oxidative capacity, novel cytokines, transcription factors, and micro-RNAs (miRNAs). The most enriched functional categories were those linked to carbohydrate metabolism and transcriptional regulation. Upstream analysis revealed that vascular endothelial growth factor, cAMP-response element-binding protein, Tet methylcytosine dioxygenase, and mammalian target of rapamycin were regulators highly activated by AE + RE, whereas JnK, NF-κβ, MAPK, and several miRNAs were inhibited. Thus, aerobic exercise alters the skeletal muscle transcriptional signature of resistance exercise to initiate important gene programs promoting both myofiber growth and improved oxidative capacity. These results provide novel insight into human muscle adaptations to diverse exercise modes and offer the very first genomic basis explaining how aerobic exercise may augment, rather than compromise, muscle growth induced by resistance exercise. PMID:27101291

  19. Electrical resistivity structure of the Great Slave Lake shear zone, northwest Canada: implications for tectonic history

    NASA Astrophysics Data System (ADS)

    Yin, Yaotian; Unsworth, Martyn; Liddell, Mitch; Pana, Dinu; Craven, James A.

    2014-10-01

    Three magnetotelluric (MT) profiles in northwestern Canada cross the central and western segments of Great Slave Lake shear zone (GSLsz), a continental scale strike-slip structure active during the Slave-Rae collision in the Proterozoic. Dimensionality analysis indicates that (i) the resistivity structure is approximately 2-D with a geoelectric strike direction close to the dominant geological strike of N45°E and that (ii) electrical anisotropy may be present in the crust beneath the two southernmost profiles. Isotropic and anisotropic 2-D inversion and isotropic 3-D inversions show different resistivity structures on different segments of the shear zone. The GSLsz is imaged as a high resistivity zone (>5000 Ω m) that is at least 20 km wide and extends to a depth of at least 50 km on the northern profile. On the southern two profiles, the resistive zone is confined to the upper crust and pierces an east-dipping crustal conductor. Inversions show that this dipping conductor may be anisotropic, likely caused by conductive materials filling a network of fractures with a preferred spatial orientation. These conductive regions would have been disrupted by strike-slip, ductile deformation on the GSLsz that formed granulite to greenschist facies mylonite belts. The pre-dominantly granulite facies mylonites are resistive and explain why the GSLsz appears as a resistive structure piercing the east-dipping anisotropic layer. The absence of a dipping anisotropic/conductive layer on the northern MT profile, located on the central segment of the GSLsz, is consistent with the lack of subduction at this location as predicted by geological and tectonic models.

  20. Resistance of a pulsed electrical breakdown channel in ionic crystals

    NASA Astrophysics Data System (ADS)

    Punanov, I. F.; Emlin, R. V.; Kulikov, V. D.; Cholakh, S. O.

    2014-04-01

    A technique for estimating the resistance of the electrical breakdown channel in ionic crystals is proposed. This technique is based on measuring the channel velocity in a sample when a ballast resistor is connected to the circuit of a needle anode and on using the theoretical dependence of the channel velocity on the channel conductivity. The breakdown channel resistance at a voltage of 140 kV is about 6.5 kΩ in KCl and about 6.1 kΩ in KBr. These resistances are shown to characterize a gas phase. The gas-phase resistance is found to be nonuniform along the breakdown channel. The head part ˜1 mm long has the maximum resistance. This head region is concluded to contain dielectric substance clusters, which then decompose into metal and halogen ions. The cluster lifetime is ˜10-9 s.

  1. Time lapse electrical resistivity and induced polarization monitoring of near-surface CO2 injection

    NASA Astrophysics Data System (ADS)

    Allègre, V.; Kremer, T.; Williard, E.; Schmutz, M.; Maineult, A. J.

    2013-12-01

    Field experiments were carried out to investigate the efficiency and the reliability of electrical geophysical methods to detect and monitor CO2 leakages at field scale. Each test consisted of injecting CO2 for approximately four hours at five meters depth, corresponding to a cumulative mass of gas of around six kilograms. Electrical resistivity tomography and temporal induced polarization were acquired at the surface before, during and after injections along profiles centered to the injection well. Time lapse measurements were compared to a reference acquisition performed before the injection. We observe that both methods are sensitive to variations in terms of gas saturation, the chargeability measurements being more sensitive to the presence of CO2 than electrical resistivity. During the injection, an increase of chargeability and a decrease of the measured resistivity are observed at depth in the vinicity of the injection well. Afterwards, the medium equilibrates and retrieves its original state, corresponding to the reference acquisition. The temporal variations of electrical resistivity and induced polarization responses are interpreted in terms of gas dissolution and water/gas saturation.

  2. Evaluation of physico-mechanical properties of clayey soils using electrical resistivity imaging technique

    NASA Astrophysics Data System (ADS)

    Kibria, Golam

    Resistivity imaging (RI) is a promising approach to obtaining continuous profile of soil subsurface. This method offers simple technique to identify moisture variation and heterogeneity of the investigated area. However, at present, only qualitative information of subsurface can be obtained using RI. A study on the quantification of geotechnical properties has become important for rigorous use of this method in the evaluation of geohazard potential and construction quality control of landfill liner system. Several studies have been performed to describe electrical resistivity of soil as a function of pore fluid conductivity and surface conductance. However, characterization tests on pore water and surface charge are not typically performed in a conventional geotechnical investigation. The overall objective of this study is to develop correlations between geotechnical parameters and electrical resistivity of soil, which would provide a mean to estimate geotechnical properties from RI. As a part of the study, multiple regression analyses were conducted to develop practically applicable models correlating resistivity with influential geotechnical parameters. The soil samples considered in this study were classified as highly plastic clay (CH) and low plasticity clay (CL) according to Unified Soil Classification System (USCS). Based on the physical tests, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) analysis, kaolinite was identified as the dominant mineral with some traces of magnesium, calcium, potassium, and iron. Electrical resistivity tests were conducted on compacted clays and undisturbed samples under varied geotechnical conditions. The experimental results indicated that the degree of saturation substantially influenced electrical resistivity. Electrical resistivity decreased as much as 11 times from initial value for the increase of degree of saturation from 23 to 100% in the laboratory tests on compacted clays. In case of

  3. Image-guided inversion of electrical resistivity data

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Revil, A.; Karaoulis, M.; Hale, D.; Doetsch, J.; Cuttler, S.

    2014-04-01

    Electrical resistivity tomography (ERT) is based on solving a Poisson equation for the electrical potential and is characterized by a good sensitivity only in the vicinity of the electrodes used to gather the data. To provide more information to ERT, we propose an image-guided or structure-constrained inversion of the apparent resistivity data. This approach uses structural information obtained directly from a guiding image. This guiding image can be drawn from a high resolution geophysical method based on the propagation equation (e.g. migrated seismic or ground penetrating radar images) or possibly from a geological cross-section of the subsurface based on some prior geological expertise. The locations and orientations of the structural features can be extracted by image processing methods to determine the structure tensor and the semblances of the guiding image at a set of pixel. Then, we introduce these structural constraints into the inversion of the apparent resistivity data by weighting the four-direction smoothing matrix to smooth along, but not across, structural features. This approach allows preserving both discontinuities and coherences in the inversion of the resistivity data. The image-guided inversion is also combined with an image-guided interpolation approach used to focus a smooth resistivity image. This yields structurally-appealing resistivity tomograms, while the whole process remains computationally efficient. Such a procedure generates a more realistic resistivity distribution (closer to the true ones), which can be, in turn, used quantitatively using appropriate petrophysical transforms, to obtain parameters of interest such as porosity and saturation. We check the validity of this approach using two synthetic case studies as well as two real datasets. For the field data, the image used to guide the inversion of the electrical resistivity data is a GPR section in the first case and a combination of seismic and structural information in the

  4. Electrical resistance sensors for soil water tension estimates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter, in a book to be published by the International Atomic Energy Agency/FAO Joint Division, provides detailed information on how to sense soil water tension with electrical resistance sensors. It provides insight into problems commonly encountered in using these sensors. Guidance on data r...

  5. Electrical Resistivity Changes in Saturated Rock under Stress.

    PubMed

    Brace, W F; Orange, A S

    1966-09-23

    Electrical resistivity of water-saturated crystalline rock such as granite, diabase, dunite, or quartzite changes by an order of magnitude prior to fracture of the rock in compression. The effect observed even under high confining pressure is due to formation of open cracks which first appear at one-third to two-thirds the fracture stress. PMID:17749731

  6. Using electrical resistance probes for moisture determination in switchgrass windrows

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determining moisture levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using the standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies need...

  7. Rolling resistance of electric-vehicle tires from track tests

    SciTech Connect

    Dustin, M.O.; Slavik, R.J.

    1982-06-01

    Two sets of low-rolling-resistance tires were track tested to obtain realistic tire characteristics for use in programming the Road Load Simulator, a special dynamometer facility located at the NASA Lewis Research Center. One set was specially made by Goodyear Tire and Rubber Company for DOE's ETV-1 electric vehicle, and the other was a set of standard commercial automotive tires. The tests were conducted over an ambient temperature range of 15/sup 0/ to 32/sup 0/C (59/sup 0/ to 89/sup 0/F) and with tire pressures of 207 and 276 kPa (30 and 40 psi). Both sets of tires had very low rolling resistance. The commercial tires, which were manufactured approximately 3 years after the electric vehicle tires, exhibited lower rolling resistance than the electric vehicle tires. This is a result of the continuing effort by the tire manufacturers to reduce rolling resistance in order to improve fuel economy. At a contained-air temperature of 38/sup 0/C (100/sup 0/F) and a pressure of 207 kPa (30 psi), the resistance of the electric vehicle tires was 0.0102 kilogram per kilogram of vehicle weight and the resistance of the commercial tires was 0.0088 kilogram per kilogram of vehicle weight. At a contained-air temperature of 38/sup 0/C (100/sup 0/F) and a pressure of 276 kPa (40 psi), the resistance of the electric vehicle tires was 0.009 kilogram per kilogram of vehicle weight and the resistance of the commercial tires was 0.0074 kilogram per kilogram of vehicle weight. The average time for the tires to reach an equilibrium temperature after startup was 20 minutes for the constant-speed tests regardless of vehicle speed and 27 minutes for the SAE J227a Schedule D driving cycle tests. The average change in rolling resistance from startup to final equilibrium value was 5% for all tests. There was very little heating of the tires from velocity-dependent losses. The predominant heating source for these tires was radiation heating from the Sun.

  8. Altering glucosinolate profiles modulates disease resistance in plants.

    PubMed

    Brader, Günter; Mikkelsen, Michael Dalgaard; Halkier, Barbara Ann; Tapio Palva, E

    2006-06-01

    Plant diseases are major contributing factors for crop loss in agriculture. Here, we show that Arabidopsis plants with high levels of novel glucosinolates (GSs) as a result of the introduction of single CYP79 genes exhibit altered disease resistance. Arabidopsis expressing CYP79D2 from cassava accumulated aliphatic isopropyl and methylpropyl GS, and showed enhanced resistance against the bacterial soft-rot pathogen Erwinia carotovora, whereas Arabidopsis expressing the sorghum CYP79A1 or over-expressing the endogenous CYP79A2 accumulated p-hydroxybenzyl or benzyl GS, respectively, and showed increased resistance towards the bacterial pathogen Pseudomonas syringae. In addition to the direct toxic effects of GS breakdown products, increased accumulation of aromatic GSs was shown to stimulate salicylic acid-mediated defenses while suppressing jasmonate-dependent defenses, as manifested in enhanced susceptibility to the fungus Alternaria brassicicola. Arabidopsis with modified GS profiles provide important tools for evaluating the biological effects of individual GSs and thereby show potential as biotechnological tools for the generation of plants with tailor-made disease resistance. PMID:16709192

  9. Using electrical resistivity imaging to understand surface coal mine hydrogeology

    NASA Astrophysics Data System (ADS)

    Hester, E. T.; Greer, B. M.; Burbey, T. J.; Zipper, C. E.

    2015-12-01

    Understanding the hydrology of disturbed lands is important given the increasing human footprint on earth. Surface coal mining has caused significant land-use change in central Appalachia in the past few decades. The mining process breaks up overburden rock above coal seams, and then replaces that material at the mine location and in adjacent unmined valleys (valley fills). The freshly exposed rock surfaces undergo weathering which often alters water quality and ultimately aquatic communities in effluent streams. One of the most common water quality effects is increased total dissolved solids (TDS), which is usually measured via its surrogate, specific conductance (SC). The SC of valley fill effluent is a function of fill construction methods, materials, and age. Yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of implementing traditional hydrologic measurements in fill material. We tested the effectiveness of electrical resistivity imaging (ERI) to monitor subsurface geologic patterns and hydrologic flow paths in a test-case valley fill. We paired ERI with artificial rainfall experiments to track infiltrated water as it moved through the valley fill material. Results indicate that ERI can be used to identify the subsurface geologic structure and track advancing wetting fronts or preferential flow paths. We observed that the upper portion of the fill profile contains significant fines, while the deeper profile is primarily composed of large rocks and void spaces. The artificial rainfall experiments revealed that water ponded on the surface of compacted areas until it reached preferential flow paths, where it infiltrated quickly and deeply. We observed water moving from the surface down to >10 m depth within 75 minutes. In sum, vertical and lateral preferential flow paths were evident at both shallow (through compacted layers) and deep (among boulders) locations. Such extensive preferential flow suggests that a

  10. Electrical resistivity imaging for unknown bridge foundation depth determination

    NASA Astrophysics Data System (ADS)

    Arjwech, Rungroj

    Unknown bridge foundations pose a significant safety risk due to stream scour and erosion. Records from older structures may be non-existent, incomplete, or incorrect. Nondestructive and inexpensive geophysical methods have been identified as suitable to investigate unknown bridge foundations. The objective of the present study is to apply advanced 2D electrical resistivity imaging (ERI) in order to identify depth of unknown bridge foundations. A survey procedure is carried out in mixed terrain water and land environments with rough topography. A conventional resistivity survey procedure is used with the electrodes installed on the stream banks. However, some electrodes must be adapted for underwater use. Tests were conducted in one laboratory experimentation and at five field experimentations located at three roadway bridges, a geotechnical test site, and a railway bridge. The first experimentation was at the bridges with the smallest foundations, later working up in size to larger drilled shafts and spread footings. Both known to unknown foundations were investigated. The geotechnical test site is used as an experimental site for 2D and 3D ERI. The data acquisition is carried out along 2D profile with a linear array in the dipole-dipole configuration. The data collections have been carried out using electrodes deployed directly across smaller foundations. Electrodes are deployed in proximity to larger foundations to image them from the side. The 2D ERI can detect the presence of a bridge foundation but is unable to resolve its precise shape and depth. Increasing the spatial extent of the foundation permits better image of its shape and depth. Using electrode < 1 m to detect a slender foundation < 1 m in diameter is not feasible. The 2D ERI method that has been widely used for land surface surveys presently can be adapted effectively in water-covered environments. The method is the most appropriate geophysical method for determination of unknown bridge foundations

  11. Characterizing a shallow groundwater system beneath irrigated sugarcane with electrical resistivity and radon (Rn-222), Puunene, Hawaii

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we use a combination of electrical resistivity profiling and radon (222Rn) measurements to characterize a shallow groundwater system beneath the last remaining, large-scale sugarcane plantation on Maui, Hawaii. Hawaiian Commercial & Sugar Company has continuously operated a sugarcane...

  12. Mantle electrical conductivity profile of Niger delta region

    NASA Astrophysics Data System (ADS)

    Obiora, Daniel N.; Okeke, Francisca N.; Yumoto, K.; Agha, Stan O.

    2014-06-01

    The mantle electrical conductivity-depth profile of the Niger delta region in Nigeria has been determined using solar quiet day ionospheric current (Sq). The magnetometer data obtained in 2010 from geomagnetic stations installed in Lagos by magnetic dataset (MAGDAS) in 2008 and data from magnetometers installed in some parts of Niger delta by Center for Basic Space Science, University of Nigeria, Nsukka, were employed in this study. Gauss spherical harmonic analysis (SHA) method was used to separate the internal and external field contributions to Sq current system. The result depicted that the conductivity profile rose steadily from about 0.032 S/m at a depth of 89 km to 0.041 S/m at 100 km and 0.09 S/m at 221 km. This high conductivity region agreed with the global seismic low velocity region, the asthenosphere. The conductivity profile continued increasing downward until it got to 0.157 S/m at a depth of about 373 km (close to the base of upper mantle), 0.201 S/m at 784 km and reached 0.243 S/m at a depth of 1179 km at the lower mantle.

  13. Recent Advances in Electrical Resistance Preheating of Aluminum Reduction Cells

    NASA Astrophysics Data System (ADS)

    Ali, Mohamed Mahmoud; Kvande, Halvor

    2016-06-01

    ABSTRACT There are two mainpreheating methods that are used nowadays for aluminum reduction cells. One is based on electrical resistance preheating with a thin bed of small coke and/or graphite particles between the anodes and the cathode carbon blocks. The other is flame preheating, where two or more gas or oil burners are used. Electrical resistance preheating is the oldest method, but is still frequently used by different aluminum producers. Many improvements have been made to this method by different companies over the last decade. In this paper, important points pertaining to the preparation and preheating of these cells, as well as measurements made during the preheating process and evaluation of the performance of the preheating, are illustrated. The preheating times of these cells were found to be between 36 h and 96 h for cell currents between 176 kA and 406 kA, while the resistance bed thickness was between 13 mm and 60 mm. The average cathode surface temperature at the end of the preheating was usually between 800°C and 950°C. The effect of the preheating methods on cell life is unclear and no quantifiable conclusions can be drawn. Some works carried out in the mathematical modeling area are also discussed. It is concluded that there is a need for more studies with real situations for preheated cells on the basis of actual measurements. The expected development in electrical resistance preheating of aluminum reduction cells is also summarized.

  14. Electrical Resistance Technique to Monitor SiC Composite Detection

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory; Xia, Zhenhai

    2008-01-01

    Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. The effect of matrix cracking on electrical resistivity for several composite systems will be presented and some initial measurements performed at elevated temperatures under stress-rupture conditions. The implications towards electrical resistance as a technique applied to composite processing, damage detection (health monitoring), and life-modeling will be discussed.

  15. Electrical conductivity of the Fennoscandian Shield margin from recent magnetotelluric profiles

    NASA Astrophysics Data System (ADS)

    Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.

    2009-04-01

    central part of the TESZ in the Polish Trough at mid-crustal depths is well resolved. The upper mantle of the Precambrian Craton is more resistive than the younger Paleozoic lithosphere by at least one order of magnitude. We can summarize the results from these profiles in the following conclusions. Magnetotelluric data revealed remarkable features at the crustal level along each profile. Some of them were not clearly identified before by other geophysical methods. Conductors like alum shales are very well indicated in the final models. Electrical lithosphere is thick beneath the Fennoscandian Shield and significantly thinner beneath younger domains. The resulting models shows the conductivity contrast at a depth of about 150 km across the cratonic margin to be at least one order of magnitude.

  16. Assist feature printability prediction by 3-D resist profile reconstruction

    NASA Astrophysics Data System (ADS)

    Zheng, Xin; Huang, Jensheng; Chin, Fook; Kazarian, Aram; Kuo, Chun-Chieh

    2012-06-01

    properties may then be used to optimize the printability vs. efficacy of an SRAF either prior to or during an Optical Proximity Correction (OPC) run. The process models that are used during OPC have never been able to reliably predict which SRAFs will print. This appears to be due to the fact that OPC process models are generally created using data that does not include printed subresolution patterns. An enhancement to compact modeling capability to predict Assist Features (AF) printability is developed and discussed. A hypsometric map representing 3-D resist profile was built by applying a first principle approximation to estimate the "energy loss" from the resist top to bottom. Such a 3-D resist profile is an extrapolation of a well calibrated traditional OPC model without any additional information. Assist features are detected at either top of resist (dark field) or bottom of resist (bright field). Such detection can be done by just extracting top or bottom resist models from our 3-D resist model. There is no measurement of assist features needed when we build AF but it can be included if interested but focusing on resist calibration to account for both exposure dosage and focus change sensitivities. This approach significantly increases resist model's capability for predicting printed SRAF accuracy. And we don't need to calibrate an SRAF model in addition to the OPC model. Without increase in computation time, this compact model can draw assist feature contour with real placement and size at any vertical plane. The result is compared and validated with 3-D rigorous modeling as well as SEM images. Since this method does not change any form of compact modeling, it can be integrated into current MBAF solutions without any additional work.

  17. Temperature and volumetric water content petrophysical relationships in municipal solid waste for the interpretation of bulk electrical resistivity data

    NASA Astrophysics Data System (ADS)

    Pilawski, Tamara; Dumont, Gaël; Nguyen, Frédéric

    2015-04-01

    Landfills pose major environmental issues including long-term methane emissions, and local pollution of soil and aquifers but can also be seen as potential energy resources and mining opportunities. Water content in landfills determine whether solid fractions can be separated and recycled, and controls the existence and efficiency of natural or enhanced biodegradation. Geophysical techniques, such as electrical and electromagnetic methods have proven successful in the detection and qualitative investigation of sanitary landfills. However, their interpretation in terms of quantitative water content estimates makes it more challenging due to the influence of parameters such as temperature, compaction, waste composition or pore fluid. To improve the confidence given to bulk electrical resistivity data and to their interpretation, we established temperature and volumetric water content petrophysical relationships that we tested on field and laboratory electrical resistivity measurements. We carried out two laboratory experiments on leachates and waste samples from a landfill located in Mont-Saint-Guibert, Belgium. We determined a first relationship between temperature and electrical resistivity with pure and diluted leachates by progressively increasing the temperature from 5°C to 65°C, and then cooling down to 5°C. The second relationship was obtained by measuring electrical resistivity on waste samples of different volumetric water contents. First, we used the correlations obtained from the experiments to compare electrical resistivity measurements performed in a landfill borehole and on reworked waste samples excavated at different depths. Electrical resistivities were measured every 20cm with an electromagnetic logging device (EM39) while a temperature profile was acquired with optic fibres. Waste samples were excavated every 2m in the same borehole. We filled experimental columns with these samples and measured electrical resistivities at laboratory temperature

  18. Electrical resistivity response due to elastic-plastic deformations

    SciTech Connect

    Stout, R.B.

    1987-01-01

    The electrical resistivity of many materials is sensitive to changes in the electronic band configurations surrounding the atoms, changes in the electron-phonon interaction cross-sections, and changes in the density of intrinsic defect structures. These changes are most directly dependent on interatomic measures of relative deformation. For this reason, a model for resistivity response is developed in terms of interatomic measures of relative deformation. The relative deformation consists of two terms, a continuous function to describe the recoverable displacement between two atoms in the atomic lattice structure and a functional to describe the nonrecoverable displacement between two atoms as a result of interatomic discontinuities from dislocation kinetics. This model for resistivity extends the classical piezoresistance representation and relates electric resistance change directly to physical mechanisms. An analysis for the resistivity change of a thin foil ideally embedded in a material that undergoes elastic-plastic deformation is presented. For the case of elastic deformations, stress information in the material surrounding the thin foil is inferred for the cases of pure strain coupling boundary conditions, pure stress coupling boundary conditions, and a combination of stress-strain coupling boundary conditions. 42 refs., 4 figs.

  19. Electrical Resistivity Monitoring of Voids: Results of Dynamic Modeling Experiments

    NASA Astrophysics Data System (ADS)

    Lane, J. W.; Day-Lewis, F. D.; Singha, K.

    2006-05-01

    Remote, non-invasive detection of voids is a challenging problem for environmental and engineering investigations in karst terrain. Many geophysical methods including gravity, electrical, electromagnetic, magnetic, and seismic have potential to detect voids in the subsurface; lithologic heterogeneity and method- specific sources of noise, however, can mask the geophysical signatures of voids. New developments in automated, autonomous geophysical monitoring technology now allow for void detection using differential geophysics. We propose automated collection of electrical resistivity measurements over time. This dynamic approach exploits changes in subsurface electrical properties related to void growth or water-table fluctuation in order to detect voids that would be difficult or impossible to detect using static imaging approaches. We use a series of synthetic modeling experiments to demonstrate the potential of difference electrical resistivity tomography for finding (1) voids that develop vertically upward under a survey line (e.g., an incipient sinkhole); (2) voids that develop horizontally toward a survey line (e.g., a tunnel); and (3) voids that are influenced by changing hydrologic conditions (e.g., void saturation and draining). Synthetic datasets are simulated with a 3D finite-element model, but the inversion assumes a 2D forward model to mimic conventional practice. The results of the synthetic modeling experiments provide insights useful for planning and implementing field-scale monitoring experiments using electrical methods.

  20. Electrical resistivity characterization of anisotropy in the Biscayne Aquifer.

    PubMed

    Yeboah-Forson, Albert; Whitman, Dean

    2014-01-01

    Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28-electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E-W/SE-NW beneath the ridge and E-W/SW-NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo-groundwater flow in the Biscayne Aquifer. PMID:24033332

  1. Using an Automatic Resistivity Profiler Soil Sensor On-The-Go in Precision Viticulture

    PubMed Central

    Rossi, Roberta; Pollice, Alessio; Diago, Maria-Paz; Oliveira, Manuel; Millan, Borja; Bitella, Giovanni; Amato, Mariana; Tardaguila, Javier

    2013-01-01

    Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial variability patterns of vegetative growth and yield of a commercial vineyard (Vitis vinifera L. cv. Tempranillo) located in the wine-producing region of La Rioja, Spain. High resolution continuous geoelectrical mapping was accomplished by an Automatic Resistivity Profiler (ARP) on-the-go sensor with an on-board GPS system; rolling electrodes enabled ER to be measured for a depth of investigation approximately up to 0.5, 1 and 2 m. Regression analysis and cluster analysis algorithm were used to jointly process soil resistivity data, landscape attributes and grapevine variables. ER showed a structured variability that matched well with trunk circumference spatial pattern and yield. Based on resistivity and a simple terrain attribute uniform management units were delineated. Once a spatial relationship to target variables is found, the integration of point measurement with continuous soil resistivity mapping is a useful technique to identify within-plots areas of vineyard with similar status. PMID:23325171

  2. Using an automatic resistivity profiler soil sensor on-the-go in precision viticulture.

    PubMed

    Rossi, Roberta; Pollice, Alessio; Diago, Maria-Paz; Oliveira, Manuel; Millan, Borja; Bitella, Giovanni; Amato, Mariana; Tardaguila, Javier

    2013-01-01

    Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial variability patterns of vegetative growth and yield of a commercial vineyard (Vitis vinifera L. cv. Tempranillo) located in the wine-producing region of La Rioja, Spain. High resolution continuous geoelectrical mapping was accomplished by an Automatic Resistivity Profiler (ARP) on-the-go sensor with an on-board GPS system; rolling electrodes enabled ER to be measured for a depth of investigation approximately up to 0.5, 1 and 2 m. Regression analysis and cluster analysis algorithm were used to jointly process soil resistivity data, landscape attributes and grapevine variables. ER showed a structured variability that matched well with trunk circumference spatial pattern and yield. Based on resistivity and a simple terrain attribute uniform management units were delineated. Once a spatial relationship to target variables is found, the integration of point measurement with continuous soil resistivity mapping is a useful technique to identify within-plots areas of vineyard with similar status. PMID:23325171

  3. Development of a Landslide Monitoring System using Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Hen-Jones, R. M.; Hughes, P. N.; Glendinning, S.; Gunn, D.; Chambers, J.; Stirling, R.

    2015-12-01

    Current assessments of slope stability rely on the use of point sensors, the results of which are often difficult to interpret, have relatively high associated installation and maintenance costs, and do not provide large-area coverage. A new system is currently under development, based on the use of integrated geophysical - geotechnical sensors to monitor ground water conditions via electrical resistivity tomography. This study presents the results of an in-situ electrical resistivity tomography survey, gathered over a two year investigation period at a full-scale clay test embankment in Northumberland, UK. The 3D resistivity array comprised 288 electrodes, at 0.7m grid spacing, covering an area of approximately 90 m2. The first year of investigation involved baseline data collection, followed by a second year which saw a series of deliberate interventions targeted at weakening the slope, to determine whether corresponding geotechnical property changes would be reflected in resistivity images derived from ERT. These interventions included the manual extension of four tension cracks already present in the slope, and the installation of a sprinkler system, eight months later. Laboratory methods were employed to derive a system of equations for relating resistivity to geotechnical parameters more directly relevant to slope stability, including moisture content, suction and shear strength. These equations were then applied to resistivity data gathered over the baseline and intervention periods, yielding geotechnical images of the subsurface which compared well with in-situ geotechnical point sensors. During the intervention period, no slope movement was recorded, however, tensiometers at 0.5 m and 1.0 m depths showed elevated pore pressures, with positive pressures being recorded at depths less than 0.5 m. Resistivity images were successful in capturing the extension of the tension cracks, and in identifying the development of a potential shear failure plane as water

  4. Modeling and analysis of direct-current electrical resistivity in the Durham Triassic basin, North Carolina

    USGS Publications Warehouse

    Brown, C. Erwin

    1987-01-01

    Sixty-two Schlumberger electrical soundings were made in the Durham Triassic basin in an effort to determine basin structural geometry, depth of the sedimentary layers, and spatial distribution of individual rock facies. A digital computer program was used to invert the sounding curves of apparent resistivity versus distance to apparent resistivity versus depth. The apparent-resistivity-versus-depth data from the computer-modeling program were used to construct a geoelectric model of the basin that is believed to accurately represent the subsurface geology of the basin. The largest depth to basement in the basin along a resistivity profile (geoelectric section) was determined to be 1,800 m. A resistivity decrease was observed on certain soundings from depths of 100 to 1,000 m; below a 1,000-m depth, apparent resistivity increased to the bottom of the basin. Resistivity values for basement rocks were greater than 1,000 ohm-m and less than 350 ohm-m for the sedimentary layers in the basin. The data suggest that the basin contains a system of step faults near its eastern boundary. ?? 1987.

  5. Electrical resistivity of K-based liquid binaries

    NASA Astrophysics Data System (ADS)

    Vora, A. M.

    2006-08-01

    The study of the electrical resistivity of alkali K-based liquid binaries, viz, K 1-x Na x, K 1-x Rb x, and K 1-x Cs x have been made by well recognized model potential. The most recent local field correction functions due to Farid et al. (F) and Sarkar et al. (S) are used for the first time in the study of electrical resistivity of liquid binary mixtures and found suitable for such study. The results due to the inclusion of Sarkar et al.’s local field correction function are found superior to those obtained due to Farid et al.’s local field correction function. The present results compare well the experimental data.

  6. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Fortini, A.

    1971-01-01

    Thermal conductivity and electrical resistivity of porous materials, including 304L stainless steel Rigimesh, 304L stainless steel sintered spherical powders, and OFHC sintered spherical powders at different porosities and temperatures are reported and correlated. It was found that the thermal conductivity and electrical resistivity can be related to the solid material properties and the porosity of the porous matrix regardless of the matrix structure. It was also found that the Wiedermann-Franz-Lorenz relationship is valid for the porous materials under consideration. For high conductivity materials, the Lorenz constant and the lattice component of conductivity depend on the material and are independent of the porosity. For low conductivity, the lattice component depends on the porosity as well.

  7. Determination of anisotropic karst features in the Biscayne Aquifer using multi electrical resistivity imaging techniques

    NASA Astrophysics Data System (ADS)

    Yeboah-Forson, A.; Whitman, D.

    2012-12-01

    The Biscayne Aquifer of Southeast Florida is characterized by limestone cavities and solution hole features that are often beneath the surface and are difficult to detect and quantify accurately. Electrical resistivity imaging (ERI) is often used to image the subsurface for detection of cavities and other karst features. A recent regional study of electrical anisotropy derived from rotated square array measurements measured coefficients of anisotropy of 1.12 or less. At one particular site however, the coefficient of anisotropy was found to be as high as 1.36 with the average minimum resistivity direction trending 105°. The highest values of anisotropy are found at squares array sizes equivalent to effective depths of 4-9m. The cause of this higher anisotropy and its associated orientation was investigated using a combination of azimuthal 2-D profiles and a 3-D tomography survey using a mixed dipole gradient array. Results indicate a low resistivity zone at a depth of 5-10 m in the saturated zone (10-40Ωm) trending 109° in the 2-D profiles and the presence of low resistivity zone (14-43Ωm) trending 90-105° in the 3-D model. This observed lower resistivity zone is at least 50% lower than the surrounding resistivity. Although further geophysical studies are planned at the site, the primary analysis from these three contrasting ERI techniques indicates that the cause of higher anisotropy might be due to the presence of a solution cavity oriented in the E-SE direction.

  8. Electrical resistivity surveys in Prospect Gulch, San Juan County, Colorado

    USGS Publications Warehouse

    McDougal, Robert R.

    2006-01-01

    Prospect Gulch is a major source of naturally occurring and mining related metals to Cement Creek, a tributary of the upper Animas River in southwestern Colorado. Efforts to improve water quality in the watershed have focused on Prospect Gulch because many of its abandoned mines and are located on federal lands. Information on sources and pathways of metals, and related ground-water flow, will be useful to help prioritize and develop remediation strategies. It has been shown that the occurrence of sulfate, aluminum, iron, zinc and other metals associated with historical mining and the natural weathering of pyritic rock is substantial. In this study, direct current resistivity surveys were conducted to determine the subsurface resistivity distribution and to identify faults and fractures that may act as ground-water conduits or barriers to flow. Five lines of resistivity data were collected in the vicinity of Prospect Gulch, and cross-section profiles were constructed from the field data using a two-dimensional inversion algorithm. The conductive anomalies in the profiles are most likely caused by wet or saturated rocks and sediments, clay rich deposits, or high TDS ground water. Resistive anomalies are likely bedrock, dry surficial and sub-surface deposits, or deposits of ferricrete.

  9. Electrical resistivity of V-Cr-Ti alloys

    SciTech Connect

    Zinkle, S.J.; Gubbi, A.N.; Eatherly, W.S.

    1997-04-01

    Room temperature electrical resistivity measurements have been performed on vanadium alloys containing 3-6%Cr and 3-6%Ti in order to evaluate the microstructural stability of these alloys. A nonlinear dependence on Cr and Ti concentration was observed, which suggests that either short range ordering or solute precipitation (perhaps in concert with interstitial solute clustering) has occurred in V-6Cr-6Ti.

  10. Negative differential electrical resistance of a rotational organic nanomotor

    PubMed Central

    Sadeghi, Hatef; Sangtarash, Sara; Al-Galiby, Qusiy; Sparks, Rachel

    2015-01-01

    Summary A robust, nanoelectromechanical switch is proposed based upon an asymmetric pendant moiety anchored to an organic backbone between two C60 fullerenes, which in turn are connected to gold electrodes. Ab initio density functional calculations are used to demonstrate that an electric field induces rotation of the pendant group, leading to a nonlinear current–voltage relation. The nonlinearity is strong enough to lead to negative differential resistance at modest source–drain voltages. PMID:26734524

  11. Calcium Activation Profile In Electrically Stimulated Intact Rat Heart Cells

    NASA Astrophysics Data System (ADS)

    Geerts, Hugo; Nuydens, Rony; Ver Donck, Luc; Nuyens, Roger; De Brabander, Marc; Borgers, Marcel

    1988-06-01

    Recent advances in fluorescent probe technology and image processing equipment have made available the measurement of calcium in living systems on a real-time basis. We present the use of the calcium indicator Fura-2 in intact normally stimulated rat heart cells for the spatial and dynamic measurement of the calcium excitation profile. After electric stimulation (1 Hz), the activation proceeds from the center of the myocyte toward the periphery. Within two frame times (80 ms), the whole cell is activated. The activation is slightly faster in the center of the cell than in the periphery. The mean recovery time is 200-400 ms. There is no difference along the cell's long axis. The effect of a beta-agonist and of a calcium antagonist is described.

  12. Uncertainty analysis for common Seebeck and electrical resistivity measurement systems.

    PubMed

    Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp

    2014-08-01

    This work establishes the level of uncertainty for electrical measurements commonly made on thermoelectric samples. The analysis targets measurement systems based on the four probe method. Sources of uncertainty for both electrical resistivity and Seebeck coefficient were identified and evaluated. Included are reasonable estimates on the magnitude of each source, and cumulative propagation of error. Uncertainty for the Seebeck coefficient includes the cold-finger effect which has been quantified with thermal finite element analysis. The cold-finger effect, which is a result of parasitic heat transfer down the thermocouple probes, leads to an asymmetric over-estimation of the Seebeck coefficient. A silicon germanium thermoelectric sample has been characterized to provide an understanding of the total measurement uncertainty. The electrical resistivity was determined to contain uncertainty of ±7.0% across any measurement temperature. The Seebeck coefficient of the system is +1.0%/-13.1% at high temperature and ±1.0% near room temperature. The power factor has a combined uncertainty of +7.3%/-27.0% at high temperature and ±7.5% near room temperature. These ranges are calculated to be typical values for a general four probe Seebeck and resistivity measurement configuration. PMID:25173324

  13. Complex electrical resistance tomography of a subsurface PCE plume

    SciTech Connect

    Ramirez, A.; Daily, W,; LeBrecque, D.

    1996-01-01

    A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE were released at a rate of 2 liters per hour from a point 0.5 m below ground surface. The spill was conducted within a double walled tank where saturated layers of sand, bentonite and a sand/bentonite mixture were installed. Complex electrical resistance measurements were performed. Data were taken before the release, several times during, and then after the PCE was released. Magnitude and phase were measured at 1 and 64 Hz. Data from before the release were compared with those during the release for the purpose of imaging the changes in conductivity resulting from the plume. Conductivity difference tomographs showed a decrease in electrical conductivity as the DNAPL penetrated the soil. A pancake-shaped anomaly developed on the top of a bentonite layer at 2 m depth. The anomaly grew in magnitude and extent during the release and borehole television surveys data confirmed the anomaly to be free-product PCE whose downward migration was stopped by the low permeability clay. The tomographs clearly delineated the plume as a resistive anomaly.

  14. Detecting Damage in Ceramic Matrix Composites Using Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Gyekenyesi, Andrew

    2011-01-01

    The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90 deg fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

  15. Detecting Cracks in Ceramic Matrix Composites by Electrical Resistance

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Gyekenyesi, Andrew

    2011-01-01

    The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90o fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

  16. Electrical resistivity tomography investigations on a paleoseismological trenching study

    NASA Astrophysics Data System (ADS)

    Berge, Meriç Aziz

    2014-10-01

    Two-dimensional electrical resistivity tomography (ERT) investigation was performed in a paleoseismological trenching study. Data acquisition strategies such as the selection of electrode configuration and electrode intervals of ERT application were investigated in this paper. The ERT results showed that the Wenner and Wenner-Schlumberger arrays yielded similar results for subsurface characteristics whereas the DD array provided slightly different results. The combined usage of these arrays produced satisfactory images of the subsurface resistivity distribution. In addition, the electrode spacing tests revealed that a suitable interpretation of subsurface geology can be obtained from a 5 m electrode interval. However, a suitable trenching location defined by successful 2D resistivity models was obtained for 1 m electrode spacing. Therefore, the comparison of the trench and ERT results was also possible. The results of trenching and ERT studies substantially support each other.

  17. Rolling resistance of electric vehicle tires from track tests

    NASA Technical Reports Server (NTRS)

    Dustin, M. O.; Slavik, R. J.

    1982-01-01

    Special low-rolling-resistance tires were made for DOE's ETV-1 electric vehicle. Tests were conducted on these tires and on a set of standard commercial automotive tires to determine the rolling resistance as a function of time during both constant-speed tires and SAE J227a driving cycle tests. The tests were conducted on a test track at ambient temperatures that ranged from 15 to 32 C (59 to 89 F) and with tire pressures of 207 to 276 kPa (30 to 40 psi). At a contained-air temperature of 38 C (100 F) and a pressure of 207 kPa (30 psi) the rolling resistances of the electric vehicle tires and the standard commercial tires, respectively, were 0.0102 and 0.0088 kilogram per kilogram of vehicle weight. At a contained-air temperature of 38 C (100 F) and a pressure of 276 kPa (40 psi) the rolling resistances were 0.009 and 0.0074 kilogram per kilogram of vehicle weight, respectively.

  18. Temporal Variabilities in Genetic Patterns and Antibiotic Resistance Profiles of Enterococci Isolated from Human Feces

    PubMed Central

    Nishiyama, Masateru; Shimauchi, Hidetaka; Suzuki, Yoshihiro

    2016-01-01

    Temporal variabilities in the genetic patterns and antibiotic resistance profiles of enterococci were monitored over a 7-month period. Enterococcus faecalis isolates (103 strains) collected from feces showed only one genetic pattern and antibiotic resistance profile within 0 d and 30 d. In contrast, after 60 d and 90 d, the genetic patterns and antibiotic resistance profiles of all E. faecalis isolates (8 strains) clearly differed within 30 d. These results indicate that the genetic patterns and antibiotic resistance profiles of E. faecalis in human feces changed to completely dissimilar patterns between 1 and 2 months. PMID:27265342

  19. Characterization of subsurface stratigraphy along the lower American River floodplain using electrical resistivity, Sacramento, California, 2011

    USGS Publications Warehouse

    Burton, Bethany L.; Powers, Michael H.; Ball, Lyndsay B.

    2014-01-01

    In July 2011, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, completed a geophysical survey using electrical resistivity along an approximately 6-mile reach of the lower American River in Sacramento, California, to map near-surface lithological variations. This survey is a part of a manifold and comprehensive study of river-flow dynamics and geologic boundary-property knowledge necessary to estimate scour potential and levee erosion risk. Data were acquired on the left (south or west) bank between river mile 5 and 10.7 as well as a short section on the right bank from river mile 5.4 to 6. Thirteen direct-current resistivity profiles and approximately 8.3 miles of capacitively coupled resisistivity data were acquired along accessible areas of the floodplain between the levee and river bank. Capacitively coupled resistivity was used as a reconnaissance tool, because it allowed for greater spatial coverage of data but with lower resolution and depth of investigation than the DC resistivity method. The study area contains Pleistocene-age alluvial deposits, dominated by gravels, sands, silts, and clays, that vary in both lateral extent and depth. Several generations of lithologic logs were used to help interpret resistivity variations observed in the resistivity models.

  20. Electrical resistivity tomography, VES and magnetic surveys for dam site characterization, Wukro, Northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Haile, Tigistu; Atsbaha, Solomun

    2014-09-01

    Geophysical surveys involving the techniques of electrical resistivity imaging, electrical sounding and magnetics were employed to characterize the ground conditions at a proposed dam site at Hizaeti-Afras, Wukro, North Ethiopia. The techniques were utilized to map the depth to the competent formations, their relative suitability for foundation work and the presence and extent of weak zones in the subsurface. The work has mapped the different lithologic units of the subsurface and determined the depth to the basement rocks in the area. Through correlation of the inverse model resistivity sections of the imaging surveys, the geoelectric section of the sounding survey and the magnetic profile plots with available borehole lithologic logs, it is shown that the results very well supplement the geotechnical point data in addition to providing a wider coverage in mapping areas of weak ground that could otherwise be missed with widely spaced borehole information. The combined results of the survey show the proposed dam axis to be unsuitable. The power of the electrical resistivity imaging technique and its potential to map the shallow subsurface with adequate resolution are illustrated. The result is a strong suggestion that geophysical techniques can be used to assist and extrapolate borehole geotechnical data especially when large area is to be used for development of large infrastructure.

  1. Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches

    SciTech Connect

    Wang, Langning Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu

    2014-04-15

    Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated. The differences between on-state resistances are small for various partial illuminations of the switching gap. Semiconductor modeling is used to simulate the electric field and current profiles for different partial illuminations. The simulation results show poor on-state switch performance when partially illuminated. Based on these results, a more revealing circuit model for the switch matches well with experimental results for partial illuminations.

  2. Electrical Resistivity Imaging for Studying Dynamics of Vadose Zone Processes

    NASA Astrophysics Data System (ADS)

    Mitchell, V.; Pidlisecky, A.; Knight, R. J.

    2010-12-01

    Determining the spatial distribution of subsurface hydrologic properties is critical to developing efficient groundwater management strategies. Electrical resistivity imaging (ERI) provides continuous maps of the subsurface electrical conductivity, which can be related to water content, making it particularly useful to groundwater studies. We present an application of ERI to monitoring infiltration in the top 20 m of the subsurface at the Harkins Slough Recharge Pond, located in an agricultural region on the northern California coast. The purpose of the recharge pond is two-fold: to store diverted storm-flow run-off to meet groundwater delivery demands and to replenish underlying aquifers, which have been overdrawn for several decades, allowing saltwater intrusion. Operators of the pond have rights to divert 2.5e6 m3 of surface water to the pond each year, but decreasing infiltration rates during diversion reduces the operational efficiency, only allowing infiltration of ~1e6 m3 each year. It is hypothesized that deposition of fine-sediments from diverted water, run-off from adjacent fields, and/or microbial activity reduce the hydraulic conductivity over time by clogging pore spaces. As part of an effort to better understand the hydrologic processes controlling infiltration to improve operational efficiency of the recharge pond we conducted time-lapse ERI experiments to monitor infiltration processes beneath the pond during the winters of 2008-2009 and 2009-2010. Each year measurements were made using four 3-m long permanent probes installed in the base of the pond in a T-shape configuration, with 20 m between each probe. The probes allow for monitoring of the conductivity profile to a depth of 2 m; the top meter of each probe monitors bulk conductivity of the pond water. In addition, a number of surface electrodes were laid out in lines between the four probes. In 2008-2009, 20-m lines were used. In 2009-2010, three lines of lengths 10 m, 65 m, and 75 m were

  3. Electrical Resistivity Tomography (ERT) Applied to Karst Carbonate Aquifers: Case Study from Amdoun, Northwestern Tunisia

    NASA Astrophysics Data System (ADS)

    Redhaounia, Belgacem; Ilondo, Batobo Ountsche; Gabtni, Hakim; Sami, Khomsi; Bédir, Mourad

    2016-04-01

    The Amdoun region is characterized by a high degree of karstification due to the climate impact (±1500 mm year-1) and the development of fracture network. Survey using electrical resistivity tomography (ERT) is deployed to provide a cost-effective characterization of the subsurface karst environments. A total of seven ERT profiles with lengths of 315 m were evaluated at the Béja governorate (NW Tunisia). The area represents a small syncline of Boudabbous limestone rocks (Lower Eocene), which is covered by a thin layer of clay. In this study, an ERT survey was conducted to examine the spatial distribution and shape of underground cavities in the karst area in Jebel Sabah anticline and Aïn Sallem-Zahret Medien syncline. In this study, geological, hydro-geological and electrical resistivity tomography (ERT) methods were applied to determine the geometry of the perched aquifer in the Amdoun region (NW Tunisia). The area is characterized by fractured and karstic limestone aquifer of Late Cretaceous (Abiod Fm.) and Lower Eocene (Boudabbous Fm.). The aquifers have a karstic functioning and drain aquifers of economical interest, despite some wells exploiting them. Seven resistivity profiles were conducted along the survey area at three sites. The orientation, extension and the degree of inclination of those profiles are shown in the location map. The correct resistivity data were interpreted using Earth Imager 2D software. The results of the interpreted geo-electrical sections showed that the resistivity of the carbonate aquifer varied between 2.5 to over 5794 Ωm. The thickness of the perched aquifer ranged from 15 to 50 m, while its depth from the surface lies between 10 and 60 m. The ERT not only provided precise near surface information, but was also very useful for establishing the 3D geometry and the position of several potential cavities and karts. The results show the presence of small to large isolated cavities at various depths. The low resistivity of cavities

  4. Electrical Resistivity Imaging of Subterranean Void Space for Assessment of Endangered Species Habitat

    NASA Astrophysics Data System (ADS)

    Weissling, B. P.; White, K.

    2007-12-01

    The challenge of identifying and delineating subterranean habitat for endangered species in karst environments has been addressed through the application of near-surface geophysical techniques. Electrical resistivity imaging (ERI) in both galvanic DC and capacitance-coupled modes has been applied to the problem of imaging subsurface voids, potentially conducive to karst invertebrate habitat, in two distinctly different geologic, geophysical, and environmental settings. Surveys were conducted in extrusive volcanic terrain on the south shore of Kauai, Hawaii, a site known for lava tube formation, and in limestone karst terrain in central Texas. The two study sites were distinctly different in their geophysical settings in terms of surface layer and subsurface background resistivities, values at the Kauai site ranging from 1000 - 5000 ohm-meters and at the Texas site 100 - 800 ohm-meters, values reflecting differing lithology, porosity, and pore fluid content. An Advanced Geosciences Inc. (AGI) Supersting R8 DC resistivity system was the primary instrumentation utilized for both surveys, with a capacitance-coupled Geometrics Inc. OhmMapper TR-2 system utilized on the Kauai site for reconnaissance profiles. Opportunities existed for direct comparisons of Supersting and OhmMapper pseudo- section profiles. Supersting lines were acquired with a mixed array combining the horizontal resolution sensitivity of the dipole-dipole array with the vertical resolution sensitivity of the Inverse Schlumberger array. At both sites, surveys were conducted over known and mapped cave passage for validation of the techniques. Forward simulation modeling was conducted to verify resistivity anomaly signatures of known void spaces. Results were highly encouraging and serve to reinforce the karst-imaging capabilities of electrical resistivity, especially when mixed array types are utilized.

  5. Electrical resistivity tomography to delineate greenhouse soil variability

    NASA Astrophysics Data System (ADS)

    Rossi, R.; Amato, M.; Bitella, G.; Bochicchio, R.

    2013-03-01

    Appropriate management of soil spatial variability is an important tool for optimizing farming inputs, with the result of yield increase and reduction of the environmental impact in field crops. Under greenhouses, several factors such as non-uniform irrigation and localized soil compaction can severely affect yield and quality. Additionally, if soil spatial variability is not taken into account, yield deficiencies are often compensated by extra-volumes of crop inputs; as a result, over-irrigation and overfertilization in some parts of the field may occur. Technology for spatially sound management of greenhouse crops is therefore needed to increase yield and quality and to address sustainability. In this experiment, 2D-electrical resistivity tomography was used as an exploratory tool to characterize greenhouse soil variability and its relations to wild rocket yield. Soil resistivity well matched biomass variation (R2=0.70), and was linked to differences in soil bulk density (R2=0.90), and clay content (R2=0.77). Electrical resistivity tomography shows a great potential in horticulture where there is a growing demand of sustainability coupled with the necessity of stabilizing yield and product quality.

  6. Connection equation and shaly-sand correction for electrical resistivity

    USGS Publications Warehouse

    Lee, Myung W.

    2011-01-01

    Estimating the amount of conductive and nonconductive constituents in the pore space of sediments by using electrical resistivity logs generally loses accuracy where clays are present in the reservoir. Many different methods and clay models have been proposed to account for the conductivity of clay (termed the shaly-sand correction). In this study, the connectivity equation (CE), which is a new approach to model non-Archie rocks, is used to correct for the clay effect and is compared with results using the Waxman and Smits method. The CE presented here requires no parameters other than an adjustable constant, which can be derived from the resistivity of water-saturated sediments. The new approach was applied to estimate water saturation of laboratory data and to estimate gas hydrate saturations at the Mount Elbert well on the Alaska North Slope. Although not as accurate as the Waxman and Smits method to estimate water saturations for the laboratory measurements, gas hydrate saturations estimated at the Mount Elbert well using the proposed CE are comparable to estimates from the Waxman and Smits method. Considering its simplicity, it has high potential to be used to account for the clay effect on electrical resistivity measurement in other systems.

  7. The `L' Array, a method to model 3D Electrical Resistivity Tomography (ERT) data

    NASA Astrophysics Data System (ADS)

    Chavez Segura, R. E.; Chavez-Hernandez, G.; Delgado, C.; Tejero-Andrade, A.

    2010-12-01

    The electrical resistivity tomography (ERT) is a method designed to calculate the distribution of apparent electrical resistivities in the subsoil by means of a great number of observations with the aim of determining an electrical image displaying the distribution of true resistivities in the subsoil. Such process can be carried out to define 2D or 3D models of the subsurface. For a 3D ERT, usually, the electrodes are placed in a squared grid keeping the distance between adjacent electrodes constant in the x and y directions. Another design employed, consists of a series of parallel lines whose space inter-lines must be smaller or equal to four times the electrode separation. The most common electrode arrays frequently employed for this type of studies are the pole-pole, pole-dipole and dipole-dipole. Unfortunately, ERT surface sampling schemes are limited by physical conditions or obstacles, like buildings, highly populated urban zones, and geologic/topographic features, where the lines of electrodes cannot be set. However, it is always necessary to characterize the subsoil beneath such anthropogenic or natural features. The ‘L’ shaped array has the main purpose to overcome such difficulties by surrounding the study area with a square of electrode lines. The measurements are obtained by switching automatically current and potential electrodes from one line to the other. Each observation adds a level of information, from one profile to the other. Once the total levels of data are completed, the opposite ‘L’ array can be measured following the same process. The complete square is computed after the parallel profiles are observed as well. At the end, the computed resistivities are combined to form a 3D matrix of observations. Such set of data can be inverted to obtain the true resistivity distribution at depth in the form of a working cube, which can be interpreted. The method was tested with theoretical models, which included a set of two resistive cubes

  8. Reservoir characterization combining elastic velocities and electrical resistivity measurements

    NASA Astrophysics Data System (ADS)

    Gomez, Carmen Teresa

    2009-12-01

    The elastic and electric parameters of rocks that can be obtained from seismic and electromagnetic data depend on porosity, texture, mineralogy, and fluid. However, seismic data seldom allow us to accurately quantify hydrocarbon saturation. On the other hand, in the case of common reservoir rocks (i.e., sandstones and carbonates), resistivity strongly depends on porosity and saturation. Therefore, the recent progress of controlled-source-electromagnetic (CSEM) methods opens new possibilities in identifying and quantifying potential hydrocarbon reservoirs, although its resolution is much lower than that of seismic data. Hence, a combination of seismic and CSEM data arguably offers a powerful means of finally resolving the problem of remote sensing of saturation. The question is how to combine the two data sources (elastic data and electrical resistivity data) to better characterize a reservoir. To address this question, we introduce the concept of P-wave impedance and resistivity templates as a tool to estimate porosity and saturation from well log data. Adequate elastic and resistivity models, according to the lithology, cementation, fluid properties must be chosen to construct these templates. These templates can be upscaled to seismic and CSEM scale using Backus average for seismic data, and total resistance for CSEM data. We also measured velocity and resistivity in Fontainebleau samples in the laboratory. Fontainebleau formation corresponds to clean sandstones (i.e., low clay content). We derived an empirical relation between these P-wave velocity and resistivity at 40MPa effective pressure, which is around 3 km depth at normal pressure gradients. We were not able to test if this relation could be used at well or field data scales (once appropriate upscaling was applied), since we did not have a field dataset over a stiff sandstone reservoir. A relationship between velocity and resistivity laboratory data was also found for a set of carbonates. This expression

  9. Using electrical resistance probes for moisture determination in switchgrass windrows

    SciTech Connect

    Chesser Jr., G. D.; Davis, J. D.; Purswell, J. L.; Lemus, R.

    2011-08-01

    Determining moisture levels in windrowed biomass is important for both forage producers and researchers. Energy crops such as switchgrass have been troublesome when using the standard methods set for electrical resistance meters. The objectives of this study were to i) develop the methodologies needed to measure MC in switchgrass using electrical resistance meters, ii) to determine the effects of pressure and probe orientation on MC measurement and iii) to generate MC calibration equations for electrical resistance meters using switchgrass in the senescence growth stage. Two meters (Meter 1, Farmex HT-PRO; Meter 2, Delmhorst F-2000) were selected based on commercial availability. A forage compression apparatus was designed and constructed with on-farm materials and methods to provide a simple system of applying pressure achievable by any forage producer or researcher in the field. Two trials were performed to test four levels of moisture contents (10, 20, 30, and 40%), five pressures (0, 1.68, 3.11, 4.55, 6.22 kN/m 2; 0, 35, 65, 95, 130 lb/ft 2), and two probe orientations (axial and transverse) in a 4x5x2 factorial design. Results indicated that meter accuracy increased as pressure increased. Regression models accounted for 91% and 81% of the variation for Meter 1 and Meter 2 at a pressure of 4.55 kN/m 2 (95 lb/ft 2) and a transverse probe orientation. Calibration equations were developed for both meters to improve moisture measurement accuracy for farmers and researchers in the field.

  10. A fully automated precise electrical resistance measurement system

    SciTech Connect

    Marhas, M.K.; Balakrishnan, K.; Ganesan, V.; Srinivasan, R.

    1996-08-01

    A fully automated precise electrical resistance measurement system for more than one sample has been constructed. Conventional four-probe measurements with van der Pauw and Montgomery configurations are possible with this system. Resistance measurements in the range of a few {mu}{Omega} to a few G{Omega} are possible for six samples at a time from room temperature down to liquid-helium or liquid-nitrogen temperatures with a temperature control accuracy of better than 10 mK. The design features of the system with special reference to the low-noise switching methods of currents and voltages are described in detail. Precision of the results thus obtained using this system are highlighted for a few superconducting and semiconducting samples. {copyright} {ital 1996 American Institute of Physics.}

  11. Optical device with low electrical and thermal resistance Bragg reflectors

    SciTech Connect

    Lear, K.L.

    1996-10-22

    A compound-semiconductor optical device and method are disclosed. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors. 16 figs.

  12. Optical device with low electrical and thermal resistance bragg reflectors

    SciTech Connect

    Lear, Kevin L.

    1996-01-01

    A compound-semiconductor optical device and method. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors.

  13. Electrical Resistivity and Negative Magnetoresistance in (SNBry)x Crystal

    NASA Astrophysics Data System (ADS)

    Kaneto, Keiichi; Sasa, Shigehiko; Yoshino, Katsumi; Inuishi, Yoshio

    1980-11-01

    Electrical resistivity, magnetoresistance and their temperature dependences in (SNBry)x are measured for various quantity of y. By bromination, negative magnetoresistance is enhanced at 4.2 K and also appears even at 77 K, at which temperature negative magnetoresistance is not observed in undoped (SN)x. These features are remarkable for the samples heavily doped and just after doping, and are abated by pumping bromine from (SNBry)x for a few days. The possible origins for the anomalous negative magnetoresistance are discussed taking the surface state of fiber bundles or crystal due to adsorped bromine into consideration.

  14. Building Better Electrodes for Electrical Resistivity and Induced Polarization Data

    NASA Astrophysics Data System (ADS)

    Adkins, P. L.; La Brecque, D. J.

    2007-12-01

    In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles" heal of the resistivity method. Even stainless steel, a commonly used electrode material because of its durability, showed only average results in laboratory tests for electrode noise. Better results have been found with non-polarizing metal-metal salt electrodes, which are widely used as surface electrodes and in IP surveys. But although they produce small measurement errors, they are not durable enough for in-situ borehole resistivity surveys, and often contain compounds that are toxic to the environment. They are also very seldom used as transmitters. In laboratory studies, we are exploring other materials and configurations for low-noise compound electrodes that will be nontoxic, inexpensive, and durable and can be used as both transmitters and receivers. Testing of the electrical noise levels of electrodes is an arduous task involving repeated measurements under varying conditions at field scales. Thus it is important to find methods of sorting out likely candidates from the mass of possible electrode configurations and construction methods. Testing of electrode impedance versus current density appears to provide simple criteria for predicting the suitability of electrodes. The best electrodes show relatively low overall contact impedance, relatively small changes in impedance with increased current density, and relatively small changes in impedance with time. Furthermore it can be shown that resistivity and induced polarization performance of electrodes is strongly correlated, so that methods of finding electrodes with low impedance and good direct current performance usually provide better quality induced

  15. Electrical resistivity imaging in transmission between surface and underground tunnel for fault characterization

    NASA Astrophysics Data System (ADS)

    Lesparre, N.; Boyle, A.; Grychtol, B.; Cabrera, J.; Marteau, J.; Adler, A.

    2016-05-01

    Electrical resistivity images supply information on sub-surface structures and are classically performed to characterize faults geometry. Here we use the presence of a tunnel intersecting a regional fault to inject electrical currents between surface and the tunnel to improve the image resolution at depth. We apply an original methodology for defining the inversion parametrization based on pilot points to better deal with the heterogeneous sounding of the medium. An increased region of high spatial resolution is shown by analysis of point spread functions as well as inversion of synthetics. Such evaluations highlight the advantages of using transmission measurements by transferring a few electrodes from the main profile to increase the sounding depth. Based on the resulting image we propose a revised structure for the medium surrounding the Cernon fault supported by geological observations and muon flux measurements.

  16. Multilayer Resist Profile Control in Oxygen Reactive Ion Etching Using Ethanol Gas Mixture

    NASA Astrophysics Data System (ADS)

    Kimura, Yasuki; Aoyama, Ryouichi; Suzuki, Seki

    1994-07-01

    By adding ethanol gas to oxygen-based chemistry, the controllability of resist profile and the overetch characteristic, under the condition with nearly no areas of material to be etched (etchable area), are improved. A model for resist profile control in which the resist profile is determined by the ratio of the sum of the isotropic etching component and the isotropic deposition component to the anisotropic etching component, is examined by evaluating the dependence of the resist profile and the etching rate on gas composition, the product of ion energy and ion current density (ion impact), and line and space (L & S) width. Both the gas composition and L & S width affect the sum of isotropic components. Ion impact affects the anisotropic etching component. When the isotropic components are balanced, resist profile is independent of ion impact and L & S width.

  17. Electrical resistivity and geotechnical assessment of subgrade soils in southwestern part of Nigeria

    NASA Astrophysics Data System (ADS)

    Adebisi, N. O.; Ariyo, S. O.; Sotikare, P. B.

    2016-07-01

    The subgrade soils in areas underlain by the slightly Migmatized to Non-migmatized Metasedimentary and Metaigneous rocks of Southwestern Nigeria have been considerably investigated. However, a serious research which employs electrical resistivity method for insight into the profile development, as well as estimation of resistance to deformation for predicting the stability of flexible highway pavements is yet to be carried out. In this study, Vertical Electrical Sounding (VES) were carried out after a reconnaissance survey based on stable and unstable locations on the road. Index and strength tests related to road construction were also carried out on bulk samples obtained from stable and failed (unstable) locations of the Ago-Iwoye/Ishara highway. Results show mostly three (3) layers in the profiles with H, HK, and HKH curve types. The subgrade soils below the stable locations have better vertical and interval variations in the resistivities (89-1095 Ωm) to a depth of 3.4 m as against those from the failed portions. Those from the stable locations also have higher specific gravity (2.72), low-medium plasticity and A-2-6 kaolinitic clayey soils with higher compacted density (2090 kg/m3) compared to subgrade soils from the failed locations. On the basis of Califonia Bearing Ratio (CBR), subgrade soils at stable locations have greater strength than those obtained from failed locations. Estimated resistance to deformation (R-value) and resilient modulus (MR) proved to be the overriding parameters for predicting the stability of the flexible highway pavements.

  18. Continuous resistivity profiling data from Great South Bay, Long Island, New York

    USGS Publications Warehouse

    Cross, V.A.; Bratton, J.F.; Kroeger, K.D.; Crusius, John; Worley, C.R.

    2013-01-01

    An investigation of submarine aquifers adjacent to the Fire Island National Seashore and Long Island, New York was conducted to assess the importance of submarine groundwater discharge as a potential nonpoint source of nitrogen delivery to Great South Bay. Over 200 kilometers of continuous resistivity profiling data were collected to image the fresh-saline groundwater interface in sediments beneath the bay. In addition, groundwater sampling was performed at sites (1) along the north shore of Great South Bay, particularly in Patchogue Bay, that were representative of the developed Long Island shoreline, and (2) at sites on and adjacent to Fire Island, a 50-kilometer-long barrier island on the south side of Great South Bay. Other field activities included sediment coring, stationary electrical resistivity profiling, and surveys of in situ pore water conductivity. Results of continuous resistivity profiling surveys are described in this report. The onshore and offshore shallow hydrostratigraphy of the Great South Bay shorelines, particularly the presence and nature of submarine confining units, appears to exert primary control on the dimensions and chemistry of the submarine groundwater flow and discharge zones. Sediment coring has shown that the confining units commonly consist of drowned and buried peat layers likely deposited in salt marshes. Low-salinity groundwater extends from 10 to 100 meters offshore along much of the north and south shores of Great South Bay based on continuous resistivity profiling data, especially off the mouths of tidal creeks and beneath shallow flats to the north of Fire Island adjacent to modern salt marshes. Human modifications of much of the shoreline and nearshore areas along the north shore of the bay, including filling of salt marshes, construction of bulkheads and piers, and dredging of navigation channels, has substantially altered the natural hydrogeology of the bay's shorelines by truncating confining units and increasing

  19. Electric-field-driven resistive switching in dissipative Hubbard model

    NASA Astrophysics Data System (ADS)

    Li, Jiajun; Aron, Camille; Kotliar, Gabriel; Han, Jong

    Understanding of solids driven out of equilibrium by external fields has been one of the central goals in condensed matter physics for the past century and is relevant to nanotechnology applications such as resistive transitions. We study how strongly correlated electrons on a dissipative lattice evolve from equilibrium when driven by a constant electric field, focusing on the extent of the linear regime and hysteretic non-linear effects at higher fields. We access the non-equilibrium steady states, non-perturbatively in both the field and the electronic interactions, by means of a non-equilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime is limited by Joule heating effects and breaks down at fields orders of magnitude smaller than the quasi-particle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. Hysteretic I- V curves suggest that the non-equilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state.

  20. Electrical Resistivity of natural Marcasite at High-pressures

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Gopalakrishnarao

    2013-06-01

    Marcasite is considered to be a common iron sulfide in reducing Martian sediments and may enclose microbial remains during growth and hence study of marcasite may have significance in the search for fossil life on Mars. The high-pressure phase stability investigations of marcasite are useful in understanding the sulfide mineralogy of Martian surface, affected by meteorite impacts. The sulfides were characterized by electron microprobe micro analyses (EPMA), powder X-ray diffraction, DTA, and FTIR spectroscopic measurements. The samples were powdered using a porcelain mortar and pestle. The chemical composition of the sample was determined by an electron probe micro-analyzer (EPMA). High-pressure electrical resistivity measurements were carried out on natural marcasite, and marcasite rich samples (Marcasite 95 mol % pyrite 5 mol %) up to 7 GPa. Marcasite sample shows a discontinuous decrease in the electrical resistivity at 5. 2 (+/- 0.5) GPa indicating a first order phase transition. The Differential thermal analyses and the Fourier transform infrared spectroscopic measurements on the pressure quenched sample shows the characteristics of pyrite, indicating the pressure induced marcasite-to -pyrite transition of the natural marcasite at 5. 2 (+/- 0.5) GPa. The observation of marcasite to pyrite phase transition may be useful in estimating the pressure experienced by shock events on the Martian surface as well as the meteorites where marcasite- pyrite phases coexist. Financial support from CSIR-SHORE-PSC0205.

  1. An analytical model and parametric study of electrical contact resistance in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Wu, Zhiliang; Wang, Shuxin; Zhang, Lianhong; Hu, S. Jack

    This paper presents an analytical model of the electrical contact resistance between the carbon paper gas diffusion layers (GDLs) and the graphite bipolar plates (BPPs) in a proton exchange membrane (PEM) fuel cell. The model is developed based on the classical statistical contact theory for a PEM fuel cell, using the same probability distributions of the GDL structure and BPP surface profile as previously described in Wu et al. [Z. Wu, Y. Zhou, G. Lin, S. Wang, S.J. Hu, J. Power Sources 182 (2008) 265-269] and Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Results show that estimates of the contact resistance compare favorably with experimental data by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Factors affecting the contact behavior are systematically studied using the analytical model, including the material properties of the two contact bodies and factors arising from the manufacturing processes. The transverse Young's modulus of chopped carbon fibers in the GDL and the surface profile of the BPP are found to be significant to the contact resistance. The factor study also sheds light on the manufacturing requirements of carbon fiber GDLs for a better contact performance in PEM fuel cells.

  2. Identification of Karstic Caves by Utilizing Two-Dimensional Electrical Resistivity Imaging (ERI) Method

    NASA Astrophysics Data System (ADS)

    Uçar, Fatih; Aktürk, Özgür

    2015-04-01

    The region consisting of easily soluble rocks is generally defined as karstic terrain and it is characterized by surface collapse and small or large scale dissolution voids on rock surface. Formation and expansion of these voids may cause dangerous situation during surface/subsurface construction works. Therefore, it is important to determine the location, size and dimension of karstic caves. Geophysical investigations are very helpful in determining the boundaries of geological subsurface structures. In order to determine subsurface profile and characteristic of soil, surface geophysical methods can be successfully applied. Electrical Resistivity Imaging (ERI) is the most important methods among the convenient and commonly used methods to determine subsurface profile. By using this method, cavernous and weathered zones can be determined easily. Within the scope of this study, near surface profiles were determined by utilizing ERI at Akdeniz University Campus and Masa Dağı region located in the city of Antalya, Turkey. The results obtained from four different locations in the Akdeniz University campus compared only with Vertical Electrical Sounding (VES) analyses. Since topographic cross-section is clearly seen in two different locations around Masa Dağı location, ERI results were superimposed with topography and also compared with VES. As a result, presences of subsurface cavities were determined and illustrated using 2D colorful images. Keywords: ERI, VES, Karstic terrain, Cave, Antalya

  3. THE VARIATION OF ELECTRICAL RESISTANCE WITH APPLIED POTENTIAL

    PubMed Central

    Blinks, L. R.

    1930-01-01

    Electrical resistance and polarization were measured during the passage of direct current across a single layer of protoplasm in the cells of Valonia ventricosa impaled upon capillaries. These were correlated with five stages of the P.D. existing naturally across the protoplasm, as follows: 1. A stage of shock after impalement, when the P.D. drops from 5 mv. to zero and then slowly recovers. There is very little effective resistance in the protoplasm, and polarization is slight. 2. The stage of recovery and normal P.D., with values from 8 to 25 mv. (inside positive). The average is 15 mv. At first there is little or no polarization when small potentials are applied in either direction across the protoplasm, nor when very large currents pass outward (from sap to sea water). But when the positive current passes inward there is a sudden response at a critical applied potential ranging from 0.5 to 2.0 volts. The resistance then apparently rises as much as 10,000 ohms in some cases, and the rise occurs more quickly in succeeding applications after the first. When the potential is removed there is a back E.M.F. displayed. Later there is also an effect of such inward currents which persists into the first succeeding outward flow, causing a brief polarization at the first application of the reverse potential. Still later this polarization occurs at every exposure, and at increasingly lower values of applied potentials. Finally there is a "constant" state reached in which the polarization occurs with currents of either direction, and the apparent resistance is nearly uniform over a considerable range of applied potential. 3. A state of increased P.D.; to 100 mv. (inside positive) in artificial sap; and to 35 or 40 mv. in dilute sea water or 0.6 M MgSO4. The polarization response and apparent resistance are at first about as in sea water, but later decrease. 4. A reversed P.D., to 50 mv. (outside positive) produced by a variety of causes, especially by dilute sea water, and

  4. Investigating Root Zone Soil Moisture Using Electrical Resistivity and Crop Modeling

    NASA Astrophysics Data System (ADS)

    Diker, K.; Van Dam, R. L.; Hyndman, D. W.; Kendall, A. D.; Bhardwaj, A. K.; Hamilton, S. K.; Basso, B.

    2011-12-01

    An accurate understanding of soil moisture variability is critical for agroecological modeling and for understanding the implications of climate change for agriculture. In recent years, electrical resistivity (ER) methods have successfully been used to characterize soil moisture in a range of environments, but there remains a need to better link these data to climate variability, soil textural properties, and vegetation and root dynamics. We present results for a novel ER measurement system at the Great Lakes Bioenergy Research Center (GLBRC) in southwest Michigan. Permanent multi-electrode arrays were installed beneath a range of annual and perennial biofuel crop types including corn, soybean, various grasses, and poplars. The ER arrays provide both high spatial resolution 2D and high temporal resolution 1D apparent resistivity data (4 week and 2 hour intervals, respectively). These data, along with a forward simulation of electrical resistivity in the soil column, are used to calibrate and refine root growth dynamics modules within the crop growth and soil hydrologic model SALUS (System Approach to Land Use Sustainability). Simulations are compared to 1D TDR-inferred soil moisture data. Variability in root zone dynamics among different biofuel cropping systems is explored. Total water use and efficiency, along with profile root water extraction, vary considerably among the crops.

  5. Imaging pathways in fractured rock using three-dimensional electrical resistivity tomography

    USGS Publications Warehouse

    Robinson, Judith; Slater, Lee; Johnson, Timothy B.; Shapiro, Allen M.; Tiedeman, Claire; Ntlargiannis, Dimitrios; Johnson, Carole D.; Day-Lewis, Frederick D.; Lacombe, Pierre; Imbrigiotta, Thomas; Lane, Jr., John W.

    2016-01-01

    Major challenges exist in delineating bedrock fracture zones because these cause abrupt changes in geological and hydrogeological properties over small distances. Borehole observations cannot sufficiently capture heterogeneity in these systems. Geophysical techniques offer the potential to image properties and processes in between boreholes. We used three-dimensional cross borehole electrical resistivity tomography (ERT) in a 9 m (diameter) × 15 m well field to capture high-resolution flow and transport processes in a fractured mudstone contaminated by chlorinated solvents, primarily trichloroethylene. Conductive (sodium bromide) and resistive (deionized water) injections were monitored in seven boreholes. Electrode arrays with isolation packers and fluid sampling ports were designed to enable acquisition of ERT measurements during pulsed tracer injections. Fracture zone locations and hydraulic pathways inferred from hydraulic head drawdown data were compared with electrical conductivity distributions from ERT measurements. Static ERT imaging has limited resolution to decipher individual fractures; however, these images showed alternating conductive and resistive zones, consistent with alternating laminated and massive mudstone units at the site. Tracer evolution and migration was clearly revealed in time-lapse ERT images and supported by in situ borehole vertical apparent conductivity profiles collected during the pulsed tracer test. While water samples provided important local information at the extraction borehole, ERT delineated tracer migration over spatial scales capturing the primary hydrogeological heterogeneity controlling flow and transport. The fate of these tracer injections at this scale could not have been quantified using borehole logging and/or borehole sampling methods alone.

  6. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  7. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  8. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  9. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  10. 30 CFR 7.407 - Test for flame resistance of electric cables and cable splices.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) at an ambient temperature of 104 °F (40 °C). (8) Monitor the electric current through the power... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Test for flame resistance of electric cables... Electric Cables, Signaling Cables, and Cable Splice Kits § 7.407 Test for flame resistance of...

  11. Electrical resistivity imaging study of near-surface infiltration

    NASA Astrophysics Data System (ADS)

    Lampousis, Angelos

    High resolution electrical resistivity images (ERI method) were obtained during vadose zone infiltration experiments on agricultural soils in cooperation with Cornell University's Agricultural Stewardship Program, Cooperative Extension of Suffolk County, Extension Education Center, Riverhead, New York [ as well as Cornell University's Long Island Horticultural Research & Extension Center (LIHREC) in Riverhead, New York]. One natural soil was also studied. Infiltration was monitored by means of image analysis of two-dimensional array resistivity generated by a Syscal Kid Switch resistivity system (Griffiths et al., 1990). The data was inverted with the computer program RES2DINV (Loke, 2004). The agricultural soils considered were Riverhead sandy loam (RdA), Haven loam (HaA), and Bridgehampton silt loam (BgA). The natural site was located in the Catskill Mountains of New York State. The soils there are classified as Schoharie silty clay loam. The electrical images of the three sites were compared against established soil properties, including particle size distribution, available water capacity, and soluble salts (from the literature), as well as against site-specific soil samples and penetrometer data, which were collected along with the geophysical measurements. This research evaluates the potential of acquiring high resolution, non-destructive measurements of infiltration in the uppermost 1.5 meter of the vadose zone. The results demonstrate that resistivity differences can detect infiltration in soils typical of the north-eastern United States. Temporal and spatial variations of soil water content in the upper 1.5 meters (relevant to agriculture) of the subsurface can be monitored successfully and non-destructively with ERI. The sensitivity of the method is higher in subsurface environments that demonstrate high overall apparent resistivity values (e.g. high sand content). Under conditions of increased soil heterogeneity, instead of the formation of a continuous

  12. Monitoring Damage Accumulation in Ceramic Matrix Composites Using Electrical Resistivity

    NASA Technical Reports Server (NTRS)

    Smith, Craig E.; Morscher, Gregory N.; Xia, Zhenhai H.

    2008-01-01

    The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection and accurate life prediction for high-temperature ceramic matrix composites. Woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMC) possess unique properties such as high thermal conductivity, excellent creep resistance, improved toughness, and good environmental stability (oxidation resistance), making them particularly suitable for hot structure applications. In specific, CMCs could be applied to hot section components of gas turbines [1], aerojet engines [2], thermal protection systems [3], and hot control surfaces [4]. The benefits of implementing these materials include reduced cooling air requirements, lower weight, simpler component design, longer service life, and higher thrust [5]. It has been identified in NASA High Speed Research (HSR) program that the SiC/SiC CMC has the most promise for high temperature, high oxidation applications [6]. One of the critical issues in the successful application of CMCs is on-board or insitu assessment of the damage state and an accurate prediction of the remaining service life of a particular component. This is of great concern, since most CMC components envisioned for aerospace applications will be exposed to harsh environments and play a key role in the vehicle s safety. On-line health monitoring can enable prediction of remaining life; thus resulting in improved safety and reliability of structural components. Monitoring can also allow for appropriate corrections to be made in real time, therefore leading to the prevention of catastrophic failures. Most conventional nondestructive

  13. Fabrication of an Electrically-Resistive, Varistor-Polymer Composite

    PubMed Central

    Ahmad, Mansor Bin; Fatehi, Asma; Zakaria, Azmi; Mahmud, Shahrom; Mohammadi, Sanaz A.

    2012-01-01

    This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spectroscopy (EDAX). The XRD pattern revealed the crystallinity of the composite. The XRD study also showed the presence of secondary phases due to the substitution of zinc by other cations, such as bismuth and manganese. The TEM picture of the sample revealed the distribution of the spherical, nano-sized, filler particles throughout the matrix, which were in the 10–50 nm range with an average of approximately 11 nm. The presence of a bismuth-rich phase and a ZnO matrix phase in the ZnO-based varistor powder was confirmed by FeSEM images and EDX spectra. From the current-voltage curves, the non-linear coefficient of the varistor polymer composite with 70 wt% of nano filler was 3.57, and its electrical resistivity after the onset point was 861 KΩ. The non-linear coefficient was 1.11 in the sample with 100 wt% polymer content. Thus, it was concluded that the composites established a better electrical non-linearity at higher filler amounts due to the nano-metric structure and closer particle linkages. PMID:23443085

  14. Rainfall infiltration process in mountain headwater region using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Ono, M.; Yamamiya, K.; Shimada, J.

    2008-12-01

    Many researchers have studied about the hydrological process, especially rainfall-runoff process, in the headwater region using multi hydrometric methods. Since the possibility has been recognized that bedrock groundwater has important role to play in the rainfall-runoff process, it is important to comprehend the rainfall infiltration process within fluctuations of bedrock groundwater. However, we would need many hydrological instruments to understand this process precisely. So we have applied electrical resistivity tomography (ERT) method to understand rainfall infiltration process in the area that is estimated the contribution of bedrock groundwater for rainfall-runoff processes. Resistivity changes with the saturation rate of the pore fluid in the subsurface material. So it is possible to estimate spatial and temporal distribution of subsurface water by using ERT. In this study, we will estimate rainfall infiltration process in mountain headwater region using resistivity method. The study area is the Mamushi-dani watershed in Shiranui, Kumamoto, Japan. We described the bedrock groundwater storage systems using resistivity method in this watershed previously. Resistivity has been observed at 2 measurement lines in slope areas of this watershed. Both measurement lines have 47m in length, 1m electrode spacing and 48 electrodes. We used the multi-electrode system, NEXT-400(Kowa Co. Ltd., Japan) for measuring apparent resistivity and the application software, E-tomo (Diaconsultant Co. Ltd., Japan) for inversion of apparent resistivity data. The observed resistivity data were compared with water head observed at borehole and specific discharge observed at foot of the watershed. Inverted resistivity profiles and observed hydrological data showed the interface between saturated and unsaturated zone. During rainfall occurs, resistivity in surface area gets lower than that before the rainfall and resistivity in some part of unsaturated area shows increasing tendency. Both

  15. Electrical resistivity mapping of the buried stream channel of the Canopic branch in the western Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    El-Gamili, M. M.; Shaaban, F. F.; El-Morsi, O. A.

    1994-08-01

    Buried stream channels, which can often be mapped accurately by resistivity, are favoured targets for exploration. Horizontal profiling, electrical soundings, or both, are generally used. In the western Nile Delta, the electrical sounding method was applied using a Schlumberger electrode array with the maximum AB distance being 200 m. The field survey was conducted along profiles extending NE-SW, perpendicular to the expected historical Canopic buried stream channel. About 107 vertical electrical soundings (VES) were measured along eleven profiles. The (VES) field curves were interpreted using the automatic interpretation method of Zohdy and Bisdorf (1989) in which a layered model is obtained directly from a digitized sounding curve. The interpreted results were correlated with borehole data to delineate the main lithological units and to help construct geoelectrical cross-sections based on layer thicknesses and their corresponding ranges in litho-resistivity. The lithological information from borehole data, surface geology and the present layer resistivities indicate three major lithofacies: Holocene clay and silt at the top, Pleistocene sands, and then gravelly sands and gravels (El-Tahrir gravels) at the bottom. From the thickness of the riverine topmost clay-silt facies and the paleotopograph of the Pleistocene sands, the buried stream channels can be delineated. It is evident that two streams existed for the defunct Canopic branch. These defunct streams are discussed and correlated with the historical records.

  16. Observation of infiltration experiments with time lapse electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Noell, Ursula; Ganz, Christina; Altfelder, Sven; Günther, Thomas; Duijnisveld, Wilhelmus; Grissemann, Christoph

    2010-05-01

    analysed quantitatively. For the first experiment this calculation shows one day after the infiltration about 40% of the infiltrated water being lost to the groundwater. For the second experiment the quantitative interpretation takes into account the increased conductivity of the infiltrating tracer solution compared to the pore water of the vadose zone before infiltration. Another infiltration experiment is done on Loess. Due to the low infiltration rate only about 9l of water could be infiltrated within about 3 h (38mm/h). The time lapse ERT clearly reveals the water remaining close to surface and no sign of resistivity change due to the infiltration is observed to penetrate deeper than 30cm. At this depth the plough pan seems to inhibit the infiltration. The analysis shows the high sensitivity of the ERT method. Although the original water content is quite high and therefore the resistivity changes due to water content changes are small (the flat part of the Archie function) the time lapse ERT inversion depicts the changes of resistivity quite clearly. The experiments show the advantages of ERT measurements to observe the infiltration process in real time. However, the interpretation of such measurements still poses difficulties mainly due to the limited resolution and the ill posedness of the inversion problem of electrical resistivity tomography (ERT). These problems are investigated further in order to advance the applicability of the method to infiltration problems showing signs of preferential flow.

  17. Electrical resistivity tomography applied to a complex lava dome: 2D and 3D models comparison

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2015-04-01

    The study of volcanic domes growth (e.g. St. Helens, Unzen, Montserrat) shows that it is often characterized by a succession of extrusion phases, dome explosions and collapse events. Lava dome eruptive activity may last from days to decades. Therefore, their internal structure, at the end of the eruption, is complex and includes massive extrusions and lava lobes, talus and pyroclastic deposits as well as hydrothermal alteration. The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for volcano structure imaging. Because a large range of resistivity values is often observed in volcanic environments, the method is well suited to study the internal structure of volcanic edifices. We performed an ERT survey on an 11ka years old trachytic lava dome, the Puy de Dôme volcano (French Massif Central). The analysis of a recent high resolution DEM (LiDAR 0.5 m), as well as other geophysical data, strongly suggest that the Puy de Dôme is a composite dome. 11 ERT profiles have been carried out, both at the scale of the entire dome (base diameter of ~2 km and height of 400 m) on the one hand, and at a smaller scale on the summit part on the other hand. Each profile is composed of 64 electrodes. Three different electrode spacing have been used depending on the study area (35 m for the entire dome, 10 m and 5 m for its summit part). Some profiles were performed with half-length roll-along acquisitions, in order to keep a good trade-off between depth of investigation and resolution. Both Wenner-alpha and Wenner-Schlumberger protocols were used. 2-D models of the electrical resistivity distribution were computed using RES2DINV software. In order to constrain inversion models interpretation, the depth of investigation (DOI) method was applied to those results. It aims to compute a sensitivity index on inversion results, illustrating how the data influence the model and constraining models

  18. Temperature and mixing effects on electrical resistivity of carbon fiber enhanced concrete

    NASA Astrophysics Data System (ADS)

    Chang, Christiana; Song, Gangbing; Gao, Di; Mo, Y. L.

    2013-03-01

    In this paper, the effect of temperature and mixing procedure on the electrical resistivity of carbon fiber enhanced concrete is investigated. Different compositions of concrete containing varying concentrations of carbon fiber into normal and self-consolidating concrete (SCC) were tested under DC electrical loading over the temperature range -10 to 20 °C. The electrical resistivity of the bulk samples was calculated and compared against temperature. It was observed that there is an inverse exponential relationship between resistivity and temperature which follows the Arrhenius relationship. The bulk resistivity decreased with increasing fiber concentration, though data from SCC indicates a saturation limit beyond which electrical resistivity begins to drop. The activation energy of the bulk electrically conductive concrete was calculated and compared. While SCC exhibited the lowest observed electrical resistance, the activation energy was similar amongst SCC and surfactant enhanced concrete, both of which were lower than fiber dispersed in normal concrete.

  19. Resistive graphene humidity sensors with rapid and direct electrical readout

    NASA Astrophysics Data System (ADS)

    Smith, Anderson D.; Elgammal, Karim; Niklaus, Frank; Delin, Anna; Fischer, Andreas C.; Vaziri, Sam; Forsberg, Fredrik; Råsander, Mikael; Hugosson, Håkan; Bergqvist, Lars; Schröder, Stephan; Kataria, Satender; Östling, Mikael; Lemme, Max C.

    2015-11-01

    We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. The interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO2 substrate leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical readout and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further

  20. Utilizing Continuous Resistivity Profiling for Assessment and Characterization of Canal Seepage in El Paso's Lower Valley Irrigation Network System

    NASA Astrophysics Data System (ADS)

    Brown, W. A.; Sheng, Z.

    2009-12-01

    Annually, billions of gallons of water are lost through seepage along sections of the irrigation network. To conserve water, El Paso County Water Improvement District has been assessing seepage losses and investigating measures for reducing such losses. Resistivity techniques were used to identify areas of high seepage and provide information on locations along canals that need to be structurally modified in an effort to curb water lost through seepage. Several half mile sections were selected along canals with varying seepage rates to conduct electric resistivity surveys in order generate soil profiles during the non-irrigation and irrigation seasons. Two different multiple channel resistivity meters (The“OhmMapper and the Super Sting R8”) were used, which both allow a vertical resistivity profile to be collected using a single current transmission. The results presented are preliminary and we believe that upon completion findings will serve multiple purposes. Firstly, a better understanding of seepage patterns, seepage rate and its spatial variation can be obtained. Secondly, our findings could be used to produce geological profiles associated with seepage areas which will enable the irrigation district to develop guidelines for improving delivery efficiency, especially during drought. And thirdly, our results will be transferable to other areas of the state and will have a positive impact on the environment and the overall quality of life.

  1. Prediction of antibiotic resistance by gene expression profiles

    PubMed Central

    Suzuki, Shingo; Horinouchi, Takaaki; Furusawa, Chikara

    2014-01-01

    Although many mutations contributing to antibiotic resistance have been identified, the relationship between the mutations and the related phenotypic changes responsible for the resistance has yet to be fully elucidated. To better characterize phenotype–genotype mapping for drug resistance, here we analyse phenotypic and genotypic changes of antibiotic-resistant Escherichia coli strains obtained by laboratory evolution. We demonstrate that the resistances can be quantitatively predicted by the expression changes of a small number of genes. Several candidate mutations contributing to the resistances are identified, while phenotype–genotype mapping is suggested to be complex and includes various mutations that cause similar phenotypic changes. The integration of transcriptome and genome data enables us to extract essential phenotypic changes for drug resistances. PMID:25517437

  2. Electrically resistive coating for remediation (regeneration) of a diesel particulate filter and method

    DOEpatents

    Phelps, Amanda C.; Kirby, Kevin K.; Gregoire, Daniel J.

    2012-02-14

    A resistively heated diesel particulate filter (DPF). The resistively heated DPF includes a DPF having an inlet surface and at least one resistive coating on the inlet surface. The at least one resistive coating is configured to substantially maintain its resistance in an operating range of the DPF. The at least one resistive coating has a first terminal and a second terminal for applying electrical power to resistively heat up the at least one resistive coating in order to increase the temperature of the DPF to a regeneration temperature. The at least one resistive coating includes metal and semiconductor constituents.

  3. Can we quantify local groundwater recharge using electrical resistivity tomography?

    NASA Astrophysics Data System (ADS)

    Noell, U.; Günther, T.; Ganz, C.; Lamparter, A.

    2012-04-01

    Electrical resistivity tomography (ERT) has become a common tool to observe flow processes within the saturated/unsaturated zones. While it is still doubtful whether the method can reliably yield quantitative results the qualitative success has been shown in "numerous" examples. To quantify the rate of rainfall which reaches the groundwater table is still a problematic venture due to a sad combination of several physical and mathematical obstacles that may lead to huge errors. In 2007 an infiltration experiment was performed and observed using 3D array ERT. The site is located close to Hannover, Germany, on a well studied sandy soil. The groundwater table at this site was at a depth of about 1.3 m. The inversion results of the ERT data yield reliably looking pictures of the infiltration process. Later experiments nearby using tracer fluid and combined TDR and resistivity measurements in the subsurface strongly supported the assumption that the resistivity pictures indeed depict the water distributions during infiltration reliably. The quantitative interpretation shows that two days after infiltration about 40% of the water has reached the groundwater. However, the question remains how reliable this quantitative interpretation actually is. The first obstacle: The inversion of the ERT data gives one possible resistivity distribution within the subsurface that can explain the data. It is not necessarily the right one and the result depends on the error model and the inversion parameters and method. For these measurements we assume the same error for every single quadrupole (3%), applied the Gauss-Newton method and minimum length constraints in order to reduce the smoothing to a minimum (very small lambda). Numerical experiments showed little smoothing using this approach, and smoothing must be suppressed if preferential flow is to be seen. The inversion showed artefacts of minor amplitude compared with other inversion parameter settings. The second obstacle: The

  4. Material morphology and electrical resistivity differences in EPDM rubbers.

    SciTech Connect

    Yang, Nancy Y. C.; Domeier, Linda A.

    2008-03-01

    Electrical resistance anomalies noted in EPDM gaskets have been attributed to zinc-enriched surface sublayers, about 10-{micro}m thick, in the sulfur cured rubber material. Gasket over-compression provided the necessary connector pin contact and was also found to cause surprising morphological changes on the gasket surfaces. These included distributions of zinc oxide whiskers in high pressure gasket areas and cone-shaped features rich in zinc, oxygen, and sulfur primarily in low pressure protruding gasket areas. Such whiskers and cones were only found on the pin side of the gaskets in contact with a molded plastic surface and not on the back side in contact with an aluminum surface. The mechanisms by which such features are formed have not yet been defined.

  5. Infiltration front monitoring using 3D Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Oxarango, Laurent; Audebert, Marine; Guyard, Helene; Clement, Remi

    2016-04-01

    The electrical resistivity tomography (ERT) geophysical method is commonly used to identify the spatial distribution of electrical resisitivity in the soil at the field scale. Recent progress in commercial acquisition systems allows repeating fast acquisitions (10 min) in order to monitor a 3D dynamic phenomenon. Since the ERT method is sensitive to moisture content variations, it can thus be used to delineate the infiltration shape during water infiltration. In heterogeneous conditions, the 3D infiltration shape is a crucial information because it could differ significantly from the homogeneous behavior. In a first step, the ERT method is validated at small scale (<1m) studying a suction infiltrometer test. The experiment is carried out in a pit filled with a homogenous silty-sandy soil. It is instrumented by 17 resistivity probes and 3 commercial capacitive moisture content probes to provide local measurements of the moisture content variation. The Multiple Inversion and Clustering Strategy (MICS) (Audebert et al 2014) is used to delineate the infiltration patern. A satisfying agreement between infiltration delineation and sensor measurements is obtained with a few centimeter accuracy on the moisture front location. In a second step, the same methodology is applied at a larger scale (> 10m). Two examples of leachate injection monitoring in municipal solid waste landfills are used to put forward benefits and limitations of the ERT-MICS method. Effective infiltration porosities in a range between 3% and 8% support the assumption of a flow in heterogeneous media. Audebert, M., R. Clément, N. Touze-Foltz, T. Günther, S. Moreau, and C. Duquennoi (2014), Time-lapse ERT interpretation methodology for leachate injection monitoring based on multiple inversions and a clustering strategy (MICS), Journal of Applied Geophysics, 111, 320-333. Keywords: ERT, infiltration front, field survey

  6. Functional Classification of Cellular Proteome Profiles Support the Identification of Drug Resistance Signatures in Melanoma Cells

    PubMed Central

    2013-01-01

    Drug resistance is a major obstacle in melanoma treatment. Recognition of specific resistance patterns, the understanding of the patho-physiology of drug resistance, and identification of remaining options for individual melanoma treatment would greatly improve therapeutic success. We performed mass spectrometry-based proteome profiling of A375 melanoma cells and HeLa cells characterized as sensitive to cisplatin in comparison to cisplatin resistant M24met and TMFI melanoma cells. Cells were fractionated into cytoplasm, nuclei and secretome and the proteome profiles classified according to Gene Ontology. The cisplatin resistant cells displayed increased expression of lysosomal as well as Ca2+ ion binding and cell adherence proteins. These findings were confirmed using Lysotracker Red staining and cell adhesion assays with a panel of extracellular matrix proteins. To discriminate specific survival proteins, we selected constitutively expressed proteins of resistant M24met cells which were found expressed upon challenging the sensitive A375 cells. Using the CPL/MUW proteome database, the selected lysosomal, cell adherence and survival proteins apparently specifying resistant cells were narrowed down to 47 proteins representing a potential resistance signature. These were tested against our proteomics database comprising more than 200 different cell types/cell states for its predictive power. We provide evidence that this signature enables the automated assignment of resistance features as readout from proteome profiles of any human cell type. Proteome profiling and bioinformatic processing may thus support the understanding of drug resistance mechanism, eventually guiding patient tailored therapy. PMID:23713901

  7. Low-thermal-resistance, high-electrical-isolation heat intercept connection

    SciTech Connect

    Niemann, R.C.; Gonczy, J.D.; Nicol, T.H.

    1993-07-01

    A method for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection is presented. Electrical conductors often require the removal of heat produced from their normal operation. The heat can be removed by mechanical connection to a refrigeration source. Such connections require both effective heat removal (low thermal resistance) and effective electrical isolation (high electrical resistance and high dielectric strength). Such connections should be straightforward to fabricate and provide reliable performance that is independent of operating temperature. The connection method described here involves clamping, by thermal interference fit, an electrically insulating cylinder between an outer metallic ring and an inner metallic disk.

  8. Low-thermal-resistance, high-electrical-isolation heat intercept connection

    SciTech Connect

    Niemann, R.C.; Gonczy, J.D. ); Nicol, T.H. )

    1993-01-01

    A method for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection is presented. Electrical conductors often require the removal of heat produced from their normal operation. The heat can be removed by mechanical connection to a refrigeration source. Such connections require both effective heat removal (low thermal resistance) and effective electrical isolation (high electrical resistance and high dielectric strength). Such connections should be straightforward to fabricate and provide reliable performance that is independent of operating temperature. The connection method described here involves clamping, by thermal interference fit, an electrically insulating cylinder between an outer metallic ring and an inner metallic disk.

  9. Monitoring Permeable Reactive Barriers using Electrical Resistance Tomography

    SciTech Connect

    Ramirez, A; Bratton, W; Maresca, J; Daily, W; Dickerson, W

    2003-12-08

    An electrical resistivity tomography (ERT) method is being evaluated as a measurement tool to determine the integrity of permeable reactive barriers (PRBs) during and after construction of the barrier and as a monitoring tool to determine the long-term operational health of the barrier. The method is novel because it inserts the electrodes directly into the barrier itself. Numerical modeling calculations indicate that the ERT method can detect flaws (voids) in the barrier as small as 0.11 m{sup 2} (0.33 m x 0.33 m) when the aspect ratio of the electrodes are 2:1. Laboratory measurements indicate that the change in resistance over time of the iron-filling mixture used to create the PRB is sufficient for ERT to monitor the long-term health of the barrier. The use of this ERT method allows for the cost-effective installation of the barrier, especially when the vadose zone is large, because borehole installation methods, rather than trenching methods, can be used.

  10. Electrical resistivity tomography study of Taal volcano hydrothermal system, Philippines

    NASA Astrophysics Data System (ADS)

    Fikos, I.; Vargemezis, G.; Zlotnicki, J.; Puertollano, J. R.; Alanis, P. B.; Pigtain, R. C.; Villacorte, E. U.; Malipot, G. A.; Sasai, Y.

    2012-10-01

    Taal volcano (311 m in altitude) is located in The Philippines (14°N, 121°E) and since 1572 has erupted 33 times, causing more than 2,000 casualties during the most violent eruptions. In March 2010, the shallow structures in areas where present-day surface activity takes place were investigated by DC resistivity surveys. Electrical resistivity tomography (ERT) lines were performed above the two identified hydrothermal areas located on the northern flank of the volcano and in the Main Crater, respectively. Due to rough topography, deep valleys, and dense vegetation, most measurements were collected using a remote method based on a laboratory-made equipment. This allowed retrieval of information down to a depth of 250 m. ERTs results detail the outlines of the two geothermal fields defined by previous self-potential, CO2 soil degassing, ground temperature, and magnetic mapping (Harada et al. Japan Acad Sci 81:261-266, 2005; Zlotnicki et al. Bull Volcanol 71:29-49, 2009a, Phys Chem Earth 34:294-408, 2009b). Hydrothermal fluids originate mainly from inside the northern part of the Main Crater at a depth greater than the bottom of the Crater Lake, and flow upward to the ground surface. Furthermore, water from the Main Crater Lake infiltrates inside the surrounding geological formations. The hydrothermal fluids, outlined by gas releases and high temperatures, cross the crater rim and interact with the northern geothermal field located outside the Main Crater.

  11. Investigations of discontinuous permafrost using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Lewkowicz, Antoni

    2016-04-01

    We have used electrical resistivity tomography (ERT) extensively over the past five years to examine frozen ground characteristics at natural and disturbed sites within the discontinuous permafrost zones of northern Canada. Examples of pure research include investigations to delimit permafrost patch size, to examine changes in permafrost conditions at altitudinal treeline, and to assess permafrost thickness in palsa bogs. Applied research has included hazard mapping where ERT, in association with boreholes, has been used to characterize permafrost conditions in different terrain units at Yukon communities as part of planning for climate change adaptation. ERT has also been used to examine temporal change through repeated surveys at sites equipped with permanent arrays. Rapid change is occurring at sites which were subject to recent forest fire in the Northwest Territories. Gradual reductions in average resistivity at sites along the Alaska Highway in Yukon and northern British Columbia indicate progressive increases in unfrozen moisture while ground temperatures at the same sites have increased only very slightly. We conclude that ERT should become a standard technique for the investigation of discontinuous permafrost sites and should be incorporated as a monitoring technique within international programs such as the Global Terrestrial Network for Permafrost.

  12. Applications of electrical resistance tomography to subsurface environmental restoration

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1994-11-15

    We are developing a new imaging technique, Electrical Resistance Tomography (ERT), to map subsurface liquids as flow occurs during natural or clean-up processes and to map geologic structure. Natural processes (such as surface water infiltrating the vadose zone) and man-induced processes (such as tank leaks and clean-up processes such as steam injection), can create changes in a soil`s electrical properties that are readily measured. We have conducted laboratory and a variety of field experiments to investigate the capabilities and limitations of ERT for imaging underground structures and processes. In the last four years we have used ERT to successfully monitor several field processes including: a subsurface steam injection process (for VOC removal), an air injection process (below the water table) for VOC removal, water infiltration through the vadose zone, radio-frequency heating, ohmic heating, and tank and pond leaks. The information derived from ERT can be used by remediation projects to: detect and locate leaks, determine the effectiveness of clean-up processes, select appropriate clean-up alternatives, and to verify the installation and performance of subsurface barriers.

  13. Estimation of tree root distribution using electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Schmaltz, Elmar; Uhlemann, Sebastian

    2016-04-01

    Trees influence soil-mantled slopes mechanically by anchoring in the soil with coarse roots. Forest-stands play an important role in mechanical reinforcement to reduce the susceptibility to slope failures. However, the effect of stabilisation of roots is connected with the distribution of roots in the ground. The architecture and distribution of tree roots is diverse and strongly dependent on species, plant age, stand density, relief, nutrient supply as well as climatic and pedologic conditions. Particularly trees growing on inclined slopes show shape-shifting root systems. Geophysical techniques are commonly used to non-invasively study hydrological and geomorphological subsurface properties, by imaging contrasting physical properties of the ground. This also poses the challenge for geophysical imaging of root systems, as properties, such as electrical resistivity, of dry and wet roots fall within the range of soils. The objective of this study is whether electrical resistivity tomography (ERT) allows a reliable reproduction of root systems of alone-standing trees on diverse inclined slopes. In this regard, we set the focus on the branching of secondary roots of two common walnut trees (Juglans regia L.) that were not disturbed in the adjacencies and thus expected to develop their root systems unhindered. Walnuts show a taproot-cordate root system with a strong tap-root in juvenile age and a rising cordate rooting with increasing age. Hence, mature walnuts can exhibit a root system that appears to be deformed or shifted respectively when growing at hillslope locations. We employed 3D ERT centred on the tree stem, comprising dipole-dipole measurements on a 12-by-41 electrode grid with 0.5 m and 1.0m electrode spacing in x- and y-direction respectively. Data were inverted using a 3D smoothness constrained non-linear least-squares algorithm. First results show that the general root distribution can be estimated from the resistivity models and that shape

  14. Advances in the application of in situ electrical resistance heating

    SciTech Connect

    Smith, Gregory J.; Beyke, Gregory

    2007-07-01

    Electrical Resistance Heating (ERH) is an aggressive in situ thermal remediation technology that was developed by the U.S. Department of Energy from the original oil production technology to enhance vapor extraction remediation technologies in low permeability soils. Soil and groundwater are heated by the passage of electrical current through saturated and unsaturated soil between electrodes, not by the electrodes themselves. It is the resistance to the flow of electrical current that results in increased subsurface temperatures, and this is typically applied to the boiling point of water. It is estimated that more than 75 ERH applications have been performed. Capacity to perform these projects has increased over the years, and as many as 15 to 20 of these applications now being performed at any given time, mainly in North America, with some European applications. While the main focus has been to vaporize volatile organic compounds, as one would expect other semi-volatile and non-volatile organic compounds have also been encountered, resulting in observations of chemical and physical reactions that have not been normally incorporated into environmental restoration projects. One such reaction is hydrolysis, which is slow under normal groundwater temperatures, becomes very rapid under temperatures that can easily be achieved using ERH. As a result, these chemical and physical reactions are increasing the applicability of ERH in environmental restoration projects, treating a wider variety of compounds and utilizing biotic and abiotic mechanisms to reduce energy costs. For the treatment of oil and coal tar residues from manufactured gas plants, a process TRS has called steam bubble floatation is used to physically remove the coal and oil tar from the soils for collection using conventional multi-phase collection methods. Heat-enhanced hydrolysis has been used to remediate dichloromethane from soils and groundwater at a site in Illinois, while heat-enhanced biotic and

  15. Electrical Resistance Tomography Field Trials to Image CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Newmark, R.

    2003-12-01

    , telluric noise can be comparable to the signal levels during periods of geomagnetic activity. Finally, instrumentation stability over long periods is necessary to follow trends in reservoir behavior for several years. Solutions to these and other problems will be presented along with results from the first two years of work at a producing field undergoing CO2 flood. If electrical resistance tomography (ERT) imaging can be performed using existing well casings as long electrodes, it will substantially reduce the cost to monitor CO2 sequestration. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  16. Direct-Current Resistivity Profiling at the Pecos River Ecosystem Project Study Site near Mentone, Texas, 2006

    USGS Publications Warehouse

    Teeple, Andrew P.; McDonald, Alyson K.; Payne, Jason D.; Kress, Wade H.

    2009-01-01

    The U.S. Geological Survey, in cooperation with Texas A&M University AgriLife, did a surface geophysical investigation at the Pecos River Ecosystem Project study site near Mentone in West Texas intended to determine shallow (to about 14 meters below the water [river] surface) subsurface composition (lithology) in and near treated (eradicated of all saltcedar) and control (untreated) riparian zone sites during June-August 2006. Land-based direct-current resistivity profiling was applied in a 240-meter section of the riverbank at the control site, and waterborne direct-current continuous resistivity profiling (CRP) was applied along a 2.279-kilometer reach of the river adjacent to both sites to collect shallow subsurface resistivity data. Inverse modeling was used to obtain a nonunique estimate of the true subsurface resistivity from apparent resistivity calculated from the field measurements. The land-based survey showed that the sub-surface at the control site generally is of relatively low resis-tivity down to about 4 meters below the water surface. Most of the section from about 4 to 10 meters below the water surface is of relatively high resistivity. The waterborne CRP surveys convey essentially the same electrical representation of the lithology at the control site to 10 meters below the water surface; but the CRP surveys show considerably lower resistivity than the land-based survey in the subsection from about 4 to 10 meters below the water surface. The CRP surveys along the 2.279-kilometer reach of the river adjacent to both the treated and control sites show the same relatively low resistivity zone from the riverbed to about 4 meters below the water surface evident at the control site. A slightly higher resistivity zone is observed from about 4 to 14 meters below the water surface along the upstream approximately one-half of the profile than along the downstream one-half. The variations in resistivity could not be matched to variations in lithology because

  17. Direct-current resistivity profiling at the Pecos River Ecosystem Project study site near Mentone, Texas, 2006

    USGS Publications Warehouse

    Teeple, Andrew P.; McDonald, Alyson K.; Payne, Jason D.; Kress, Wade H.

    2009-01-01

    The U.S. Geological Survey, in cooperation with Texas A&M University AgriLife, did a surface geophysical investigation at the Pecos River Ecosystem Project study site near Mentone in West Texas intended to determine shallow (to about 14 meters below the water [river] surface) subsurface composition (lithology) in and near treated (eradicated of all saltcedar) and control (untreated) riparian zone sites during June-August 2006. Land-based direct-current resistivity profiling was applied in a 240-meter section of the riverbank at the control site, and waterborne direct-current continuous resistivity profiling (CRP) was applied along a 2.279-kilometer reach of the river adjacent to both sites to collect shallow subsurface resistivity data. Inverse modeling was used to obtain a nonunique estimate of the true subsurface resistivity from apparent resistivity calculated from the field measurements. The land-based survey showed that the sub-surface at the control site generally is of relatively low resis-tivity down to about 4 meters below the water surface. Most of the section from about 4 to 10 meters below the water surface is of relatively high resistivity. The waterborne CRP surveys convey essentially the same electrical representation of the lithology at the control site to 10 meters below the water surface; but the CRP surveys show considerably lower resistivity than the land-based survey in the subsection from about 4 to 10 meters below the water surface. The CRP surveys along the 2.279-kilometer reach of the river adjacent to both the treated and control sites show the same relatively low resistivity zone from the riverbed to about 4 meters below the water surface evident at the control site. A slightly higher resistivity zone is observed from about 4 to 14 meters below the water surface along the upstream approximately one-half of the profile than along the downstream one-half. The variations in resistivity could not be matched to variations in lithology because

  18. Investigating fluvial features with electrical resistivity imaging and ground-penetrating radar: The Guadalquivir River terrace (Jaen, Southern Spain)

    NASA Astrophysics Data System (ADS)

    Rey, J.; Martínez, J.; Hidalgo, M. C.

    2013-09-01

    A geophysical survey has been conducted on the lowest terrace levels and the present day floodplain of the current course of the Guadalquivir River, passing through the province of Jaen (Spain), using two techniques: electrical resistivity imaging (ERI) and ground-penetrating radar (GPR). Three areas have been selected. In one of these sectors (Los Barrios) there is an old quarry where there are excellent outcrops that allow for the calibration of the survey techniques. Facies associations on these outcrops are typical of meandering rivers with sequences of channel fills, lateral accretion of point-bars and floodplain facies. The usefulness of the two methods is analysed and compared as a support for stratigraphic and sedimentological studies. The geometry and lithofacies of subsurface deposits were characterised using ERI and compared with field observations. A total of 5 electrical resistivity imaging profiles were obtained. The changes in electric resistivity highlight granulometric differences in terrace sediments. This technique can thus be used to identify the morphology of these bodies, the lithofacies (silt, sand or gravel) and buried channel pattern. In addition, 16 GPR profiles using 100 and 250 MHz antennas were acquired, indicating terrace morphology and the filling of the sedimentary bodies in a more detailed manner than in ERI. The study thus allows for inferring the existence of channel migration, the lateral accretion of point bars and the presence of vertical accretion deposits attributable to the floodplains.

  19. Global Gene Expression Profiles of Resistant and Susceptible Genotypes of Glycine tomentella During Phakopsora pachyrhizi Infection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean rust, caused by Phakopsora pachyrhizi, is a destructive foliar disease that occurs in many soybean-producing countries. Towards the goal of identifying genes controlling resistance to soybean rust, transcriptome profiling was conducted in resistant and susceptible Glycine tomentella genotype...

  20. Characterization of Antibiotic Resistance Profiles of Ocular Enterobacteriaceae Isolates.

    PubMed

    Paul-Satyaseela, Maneesh; Murali, Sowmiya; Thirunavukkarasu, Bharani; Naraharirao, Madhavan Hajib; Jambulingam, Malathi

    2016-03-01

    Emergence of extended-spectrum β-lactamase (ESBL) and fluoroquinolone resistance among ocular Enterobacteriaceae is increasing in higher frequency. Therefore, studies are being carried out to understand their multidrug resistance pattern. A total of 101 Enterobacteriaceae isolates recovered from various ocular diseases in a tertiary eye care center at Chennai, India during the period of January 2011 to June 2014 were studied. Forty one randomly chosen isolates were subjected to antibiotic susceptibility by minimum inhibitory concentration (MIC) and genotypic analysis. Of them, 16 were ESBL producers, one was carbapenemase producer and four were resistant to ertapenem which could be due to porin loss associated with AmpC production, and 17 were resistant to fluoroquinolones. Sixteen isolates harbored ESBL genes in which 14 had more than one gene and none of them were positive for blaNDM-1 gene. QNR genes were detected in 18 isolates. ESBL producers were predominantly isolated from conjunctiva. A high degree of ESBL production and fluoroquinolone resistance is seen among the genus Klebsiella sp. Hence, monitoring the rate of ESBL prevalence plays a vital role in the administration of appropriate intravitreal antibiotics to save the vision and also to reduce the development of drug resistance in ocular pathogens. PMID:27141313

  1. Characterization of Antibiotic Resistance Profiles of Ocular Enterobacteriaceae Isolates

    PubMed Central

    Paul-Satyaseela, Maneesh; Murali, Sowmiya; Thirunavukkarasu, Bharani; Naraharirao, Madhavan Hajib; Jambulingam, Malathi

    2016-01-01

    Emergence of extended-spectrum β-lactamase (ESBL) and fluoroquinolone resistance among ocular Enterobacteriaceae is increasing in higher frequency. Therefore, studies are being carried out to understand their multidrug resistance pattern. A total of 101 Enterobacteriaceae isolates recovered from various ocular diseases in a tertiary eye care center at Chennai, India during the period of January 2011 to June 2014 were studied. Forty one randomly chosen isolates were subjected to antibiotic susceptibility by minimum inhibitory concentration (MIC) and genotypic analysis. Of them, 16 were ESBL producers, one was carbapenemase producer and four were resistant to ertapenem which could be due to porin loss associated with AmpC production, and 17 were resistant to fluoroquinolones. Sixteen isolates harbored ESBL genes in which 14 had more than one gene and none of them were positive for blaNDM-1 gene. QNR genes were detected in 18 isolates. ESBL producers were predominantly isolated from conjunctiva. A high degree of ESBL production and fluoroquinolone resistance is seen among the genus Klebsiella sp. Hence, monitoring the rate of ESBL prevalence plays a vital role in the administration of appropriate intravitreal antibiotics to save the vision and also to reduce the development of drug resistance in ocular pathogens. PMID:27141313

  2. Predicting and tracking spatiotemporal moments in electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Ward, W. O. C.; Wilkinson, P. B.; Chambers, J.; Bai, L.

    2015-12-01

    Visualisation is an invaluable tool in the study of near sub-surface processes, whether by mathematical modelling or by geophysical imaging. Quantitative analysis can further assist interpretation of the ongoing physical processes, and it is clear that any reliable model should take direct observations into account. Using electrical resistivity tomography (ERT), localised areas can be surveyed to produce 2-D and 3-D time-lapse images. This study investigates combining quantitative results obtained via ERT with spatio-temporal motion models in tracer experiments to interpret and predict fluid flow. As with any indirect imaging technique, ERT suffers specific issues with resolution and smoothness as a result of its inversion process. In addition, artefacts are typical in the resulting volumes. Mathematical models are also a source of uncertainty - and in combining these with ERT images, a trade-off must be made between the theoretical and the observed. Using computational imaging, distinct regions of stable resistivity can be directly extracted from a time-slice of an ERT volume. The automated nature, as well the potential for more than one region-of-interest, means that multiple regions can be detected. Using Kalman filters, it is possible to convert the detections into a process state, taking into account pre-defined models and predicting progression. In consecutive time-steps, newly detected features are assigned, where possible, to existing predictions to create tracks that match the tracer model. Preliminary studies looked at a simple motion model, tracking the centre of mass of a tracer plume with assumed constant velocity and mean resistivity. Extending the model to factor in spatial distribution of the plume, an oriented semi-axis is used to represent the centralised second-order moment, with an increasing factor of magnitude to represent the plume dispersion. Initial results demonstrate the efficacy of the approach, significantly improving reliability as the

  3. Electric-field-modulated nonvolatile resistance switching in VO₂/PMN-PT(111) heterostructures.

    PubMed

    Zhi, Bowen; Gao, Guanyin; Xu, Haoran; Chen, Feng; Tan, Xuelian; Chen, Pingfan; Wang, Lingfei; Wu, Wenbin

    2014-04-01

    The electric-field-modulated resistance switching in VO2 thin films grown on piezoelectric (111)-0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-PT) substrates has been investigated. Large relative change in resistance (10.7%) was observed in VO2/PMN-PT(111) hererostructures at room temperature. For a substrate with a given polarization direction, stable resistive states of VO2 films can be realized even when the applied electric fields are removed from the heterostructures. By sweeping electric fields across the heterostructure appropriately, multiple resistive states can be achieved. These stable resistive states result from the different stable remnant strain states of substrate, which is related to the rearrangements of ferroelectric domain structures in PMN-PT(111) substrate. The resistance switching tuned by electric field in our work may have potential applications for novel electronic devices. PMID:24634978

  4. Application of electrical resistivity tomography to map lithological differences and subsurface structures (Eastern Sudetes, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Stan, Dominika; Stan-Kłeczek, Iwona

    2014-09-01

    The aim of this study is to determine the subsurface lithological variability and thickness of each metamorphic rocks unit by means of geophysical methods, which were presented within the framework of SEDIBUD. Research was performed on the ridge and the steep eastern slope of the Orlik massif (1204 m) in the Hrubý Jesenik range of the Eastern Sudetes, the Czech Republic. To obtain a spatial image of a geological rock mass, the non-invasive and relatively rapid method of electrical resistivity tomography (ERT) was used, which resulted in the creation of six profiles using the Dipole-Dipole and Wenner-Schlumberger arrays. As complementary methods, vertical electrical sounding (VES) and seismic refraction tomography were chosen. Fifteen measuring points along two profiles obtained by vertical electrical sounding allowed the determination of the following in the vertical section layers of different resistivity and thickness at direct points in contact primarily with Devonian quartzite rocks and weathered covers. In a series of field studies, a four-layered rock mass was examined in which the first layer is of fine-grained materials with medium- and large-size clasts, the second layer is quartzite, the third is gneiss and the fourth is phyllite. The five profiles measured by seismic refraction tomography made it possible to draw the boundary between the studied phyllites, gneisses and quartzites. In addition, geophysical surveys and the results of mineralogical composition analysis allowed us to determine the nature and thickness of the weathered layers present on the massif area, which, in the upper sections, are predominantly a clayey loam partially covered with blocks. The inclination of the slope is associated with an increase in the fraction of coarse material. The majority of the thickness of these layers is related to the local flattened surfaces and the presence of numerous streams, which contributed to the accumulation of the sediments that were also

  5. Determination of surface electric charge profile in pyroelectric crystals

    SciTech Connect

    Ghaderi, R.; Davani, F. Abbasi

    2014-12-08

    Pyroelectric crystals are used to produce high energy self-focused electron beams. Here, an experimental analysis in combination with simulation studies will be reported to investigate possible sources of this effect. In the experiments, the surface of crystal was divided into six separated parts and the rate of surface electric charge production was measured accordingly. A non-steady and spatially non-uniform distribution of the surface charge generation was observed, in which it tends to a uniform distribution in the course of experiment. The obtained surface electric charges from the experiments were used to simulate the electric field and potential around the crystal by COMSOL Multiphysics. It was observed that emitted electrons from the crystal surface were focused, and the non-uniformity in spatial charge is responsible for this phenomenon.

  6. Research on nonlinear feature of electrical resistance of acupuncture points.

    PubMed

    Wei, Jianzi; Mao, Huijuan; Zhou, Yu; Wang, Lina; Liu, Sheng; Shen, Xueyong

    2012-01-01

    A highly sensitive volt-ampere characteristics detecting system was applied to measure the volt-ampere curves of nine acupuncture points, LU9, HT7, LI4, PC6, ST36, SP6, KI3, LR3, and SP3, and corresponding nonacupuncture points bilaterally from 42 healthy volunteers. Electric currents intensity was increased from 0 μA to 20 μA and then returned to 0 μA again. The results showed that the volt-ampere curves of acupuncture points had nonlinear property and magnetic hysteresis-like feature. On all acupuncture point spots, the volt-ampere areas of the increasing phase were significantly larger than that of the decreasing phase (P < 0.01). The volt-ampere areas of ten acupuncture point spots were significantly smaller than those of the corresponding nonacupuncture point spots when intensity was increase (P < 0.05 ~ P < 0.001). And when intensity was decrease, eleven acupuncture point spots showed the same property as above (P < 0.05 ~ P < 0.001), while two acupuncture point spots showed opposite phenomenon in which the areas of two acupuncture point spots were larger than those of the corresponding nonacupuncture point spots (P < 0.05 ~ P < 0.01). These results show that the phenomenon of low skin resistance does not exist to all acupuncture points. PMID:23346191

  7. Measuring turbulence in a flotation cell using electrical resistance tomography

    NASA Astrophysics Data System (ADS)

    Meng, Jun; Xie, Weiguo; Runge, Kym; Bradshaw, Dee

    2015-11-01

    Measuring turbulence in an industrial flotation environment has long been problematic due to the opaque, aggressive, and abrasive three-phase environment in a flotation cell. One of the promising measurement techniques is electrical resistance tomography (ERT). By measuring the conductivity distribution across a measurement area, ERT has been adopted by many researchers to monitor and investigate many processes involving multiphase flows. In the research outlined in this paper, a compact ERT probe was built and then used to measure the conductivity distribution within a 60 l flotation cell operated with water and air. Two approaches were then developed to process the ERT data and estimate turbulence-related parameters. One is a conductivity variance method and the other is based on the Green-Kubo relations. Both rely on and use the fluctuation in the ERT measurement caused by bubbles moving through the measurement area changing the density of the fluid. The results from both approaches were validated by comparing the results produced by the ERT probe in a 60l flotation cell operated at different air rates and impeller speeds to that measured using an alternative turbulence measurement device. The second approach is considered superior to the first as the first requires the development of auxiliary information which would not usually be known for a new system.

  8. Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona

    USGS Publications Warehouse

    Adams, E.A.; Monroe, S.A.; Springer, A.E.; Blasch, K.W.; Bills, D.J.

    2006-01-01

    Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.

  9. Visualizing Moisture Storage in Basin Lysimeters Using Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Schnabel, W.; Munk, J.; Lee, W.

    2010-12-01

    Electrical resistivity tomography (ERT) was utilized to evaluate soil moisture in two large (10m x 20m x 2m) basin lysimeters over a four-year period in Anchorage, Alaska. The lysimeters were intended to test the efficacy of two competing landfill cover designs, thus water balance information was collected over the entire experimental period. The first lysimeter contained a thin (0.5m) layer of compacted soil within its 2m depth and was planted with local grasses. The second lysimeter contained no compacted soil layer and was planted with deep-rooting woody vegetation to maximize moisture removal via evapotranspiration. After four years of observation, 291mm of moisture percolated through the compacted soil lysimeter compared to 201mm in the evapotranspiration lysimeter. This presentation describes the observed water balance results, discusses efficacy of utilizing compacted soils versus evapotranspiration as the primary means of minimizing infiltration into engineered soil systems, and demonstrates the use of ERT as a technique for visualizing soil moisture storage.

  10. Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona.

    PubMed

    Adams, Eric A; Monroe, Stephen A; Springer, Abraham E; Blasch, Kyle W; Bills, Donald J

    2006-01-01

    Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration. PMID:16961484

  11. On the Intensity Profile of Electric Lamps and Light Bulbs

    ERIC Educational Resources Information Center

    Bacalla, Xavier; Salumbides, Edcel John

    2013-01-01

    We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light…

  12. Time-Lapse Electrical Resistivity Surveys of the Intertidal Zone: Implications for Submarine Groundwater Discharge

    NASA Astrophysics Data System (ADS)

    Durand, J. M.; Wong, T.

    2013-12-01

    Submarine groundwater discharge (SGD) is now widely recognized as a crucial contributor to surface water as it provides a pathway for nutrients and contaminants that can significantly impact coastal ecosystems. Field measurements in the vicinity of the freshwater/seawater interface (FSI) have shown that the spatio-temporal distribution of SGD can be highly heterogeneous. Some numerical models have identified 3 regions (a density-driven circulation cell offshore, an upper saline plume and a freshwater tube in the intertidal zone) which seem to persist over time, such that the distinct regions can be recognized in simulations that average the numerically predicted salinity profiles over the tidal phases. The size and shape of each region are influenced by factors such as the tidal and wave loading, inland hydraulic gradient, beach geometry and aquifer properties. There is a paucity of field data at the FSI on the evolution of the salinity profile during a tidal cycle. To characterize the spatio-temporal heterogeneities of the FSI and compare with numerical predictions, we used electrical resistivity as a proxy for salinity. Electrical resistivity surveys were acquired during a 12-hour cycle in a tidally dominated environment. On September 12 2012, at West Neck Bay (Shelter Island, NY), a 33.4 m long stationary cable with 56 electrodes was extended over land and sea to image the intertidal zone. Hourly measurements were conducted over a full tidal cycle. Our measurements indicate fundamentally different scenarios during high and low tide. At low tide, our resistivity data suggest a strong influx of freshwater from land, forming a plume that rises up and contributes significantly to SGD in the intertidal zone. We also observed the occurrence of 3 regions somewhat analogous to the numerical predictions. However, at high tide, instead of these distinct regions, we observed a diffuse mixing zone that extended along the water/sediment interface and overlaid the freshwater

  13. Electrical Resistivity Tomography of the Karstic Aquifer of Bittit spring (Middle Atlas, Morocco)

    NASA Astrophysics Data System (ADS)

    Qarqori, Kh.; Rouai, M.; Moreau, F.; Saracco, G.; Hermitte, D.; Boualoul, M.; Dauteuil, O.; Biessy, G.; Sahbi, H.

    2009-04-01

    3D picture of the fracture system has been drawn showing a mini-graben structure. Geophysical scans and interpreted fractures were displayed with Gocad software leading to geometric construction of aquifer units and to 3D modelling of subsurface architecture. Several horizontal electrical resistivity profiles and electromagnetic VLF profiles were also performed in order to discriminate between dry and favourable hydrological fractures. ERT appears to be an appropriate geophysical method in this issue, especially by improving understanding of fracture geometry. This study initiates a hydrogeophysical research in the Middle Atlas karst in order to improve water resources management and reducing aquifer vulnerability in the region.

  14. Imaging Pathways in Fractured Rock Using Three-Dimensional Electrical Resistivity Tomography.

    PubMed

    Robinson, Judith; Slater, Lee; Johnson, Timothy; Shapiro, Allen; Tiedeman, Claire; Ntarlagiannis, Dimitrios; Johnson, Carole; Day-Lewis, Frederick; Lacombe, Pierre; Imbrigiotta, Thomas; Lane, John

    2016-03-01

    Major challenges exist in delineating bedrock fracture zones because these cause abrupt changes in geological and hydrogeological properties over small distances. Borehole observations cannot sufficiently capture heterogeneity in these systems. Geophysical techniques offer the potential to image properties and processes in between boreholes. We used three-dimensional cross borehole electrical resistivity tomography (ERT) in a 9 m (diameter) × 15 m well field to capture high-resolution flow and transport processes in a fractured mudstone contaminated by chlorinated solvents, primarily trichloroethylene. Conductive (sodium bromide) and resistive (deionized water) injections were monitored in seven boreholes. Electrode arrays with isolation packers and fluid sampling ports were designed to enable acquisition of ERT measurements during pulsed tracer injections. Fracture zone locations and hydraulic pathways inferred from hydraulic head drawdown data were compared with electrical conductivity distributions from ERT measurements. Static ERT imaging has limited resolution to decipher individual fractures; however, these images showed alternating conductive and resistive zones, consistent with alternating laminated and massive mudstone units at the site. Tracer evolution and migration was clearly revealed in time-lapse ERT images and supported by in situ borehole vertical apparent conductivity profiles collected during the pulsed tracer test. While water samples provided important local information at the extraction borehole, ERT delineated tracer migration over spatial scales capturing the primary hydrogeological heterogeneity controlling flow and transport. The fate of these tracer injections at this scale could not have been quantified using borehole logging and/or borehole sampling methods alone. PMID:26172032

  15. Incidence and Diversity of Antimicrobial Multidrug Resistance Profiles of Uropathogenic Bacteria

    PubMed Central

    Linhares, Inês; Raposo, Teresa; Rodrigues, António

    2015-01-01

    The aim of this study was to assess the most frequent multidrug resistant (MDR) profiles of the main bacteria implicated in community-acquired urinary tract infections (UTI). Only the MDR profiles observed in, at least, 5% of the MDR isolates were considered. A quarter of the bacteria were MDR and the most common MDR profile, including resistance to penicillins, quinolones, and sulfonamides (antibiotics with different mechanisms of action, all mainly recommended by the European Association of Urology for empirical therapy of uncomplicated UTI), was observed, alone or in association with resistance to other antimicrobial classes, in the main bacteria implicated in UTI. The penicillin class was included in all the frequent MDR profiles observed in the ten main bacteria and was the antibiotic with the highest prescription during the study period. The sulfonamides class, included in five of the six more frequent MDR profiles, was avoided between 2000 and 2009. The results suggest that the high MDR percentage and the high diversity of MDR profiles result from a high prescription of antibiotics but also from antibiotic-resistant genes transmitted with other resistance determinants on mobile genetic elements and that the UTI standard treatment guidelines must be adjusted for the community of Aveiro District. PMID:25834814

  16. Incidence and diversity of antimicrobial multidrug resistance profiles of uropathogenic bacteria.

    PubMed

    Linhares, Inês; Raposo, Teresa; Rodrigues, António; Almeida, Adelaide

    2015-01-01

    The aim of this study was to assess the most frequent multidrug resistant (MDR) profiles of the main bacteria implicated in community-acquired urinary tract infections (UTI). Only the MDR profiles observed in, at least, 5% of the MDR isolates were considered. A quarter of the bacteria were MDR and the most common MDR profile, including resistance to penicillins, quinolones, and sulfonamides (antibiotics with different mechanisms of action, all mainly recommended by the European Association of Urology for empirical therapy of uncomplicated UTI), was observed, alone or in association with resistance to other antimicrobial classes, in the main bacteria implicated in UTI. The penicillin class was included in all the frequent MDR profiles observed in the ten main bacteria and was the antibiotic with the highest prescription during the study period. The sulfonamides class, included in five of the six more frequent MDR profiles, was avoided between 2000 and 2009. The results suggest that the high MDR percentage and the high diversity of MDR profiles result from a high prescription of antibiotics but also from antibiotic-resistant genes transmitted with other resistance determinants on mobile genetic elements and that the UTI standard treatment guidelines must be adjusted for the community of Aveiro District. PMID:25834814

  17. Latent profiles among sexual assault survivors: implications for defensive coping and resistance.

    PubMed

    Macy, Rebecca J; Nurius, Paula S; Norris, Jeanette

    2007-05-01

    Rape resistance trainings need to prepare women to recognize and resist sexual assault across a range of experiences and contexts. To help address this need, this research used an investigation of 415 college women who completed a survey about their situational responding to an experience of acquaintance sexual assault. A previously established person-centered analysis model of four distinct risk and protective factor profiles was used to investigate the variability in women's responding. The profiling factors included women's prior victimization, alcohol consumption, relationship expectancies of the assailant, and assertive precautionary habits. Multivariate ANOVA was used to test for differences among the four profile groups on their cognitive, emotional, and behavioral responding. Results showed that the profile groups significantly differed in their assault responses. The findings highlight the utility of holistic, multivariate analyses for understanding women's sexual assault responses and help inform tailored resistance and empowerment trainings. PMID:17429022

  18. Antibiotic resistant bacterial profiles of anaerobic swine lagoon effluent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although land application of swine manure lagoon effluent is a common and effective method of disposal, the presence of antibiotic-resistant bacteria, both pathogenic and commensal can complicate already understood issues associated with its safe disposal. To better understand this, more data is ne...

  19. Antibiotic Resistant Bacterial Profiles of Anaerobic Swine Lagoon Effluent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although land application of swine manure lagoon effluent is a common and effective method of disposal, the presence of antibiotic-resistant bacteria, both pathogenic and commensal can complicate already understood issues associated with its safe disposal. The aim of this study was to assess antibi...

  20. Three-dimensional electrical resistivity model of a nuclear waste disposal site

    SciTech Connect

    Rucker, Dale F.; Levitt, Marc T.; Greenwood, William J.

    2009-12-11

    A three-dimensional (3D) modeling study was completed on a very large electrical resistivity survey conducted at a nuclear waste site in eastern Washington. The acquisition included 47 pole-pole two dimensional (2D) resistivity profiles collected along parallel and orthogonal lines over an area of 850 m×570 m. The data were geo-referenced and inverted using EarthImager3D (EI3D). EI3D runs on a Microsoft 32-bit operating system (e.g. WIN-2K, XP) with a maximum usable memory of 2 GB. The memory limits the size of the domain for the inversion model to 200 m×200 m, based on the survey electrode density. Therefore, a series of increasing overlapping models were run to evaluate the effectiveness of dividing the survey area into smaller subdomains. The results of the smaller subdomains were compared to the inversion results of a single domain over a larger area using an upgraded form of EI3D that incorporates multi-processing capabilities and 32 GB of RAM memory. The contours from the smaller subdomains showed discontinuity at the boundaries between the adjacent models, which do not match the hydrogeologic expectations given the nature of disposal at the site. At several boundaries, the contours of the low resistivity areas close, leaving the appearance of disconnected plumes or open contours at boundaries are not met with a continuance of the low resistivity plume into the adjacent subdomain. The model results of the single large domain show a continuous monolithic plume within the central and western portion of the site, directly beneath the elongated trenches. It is recommended that where possible, the domain not be subdivided, but instead include as much of the domain as possible given the memory of available computing resources.

  1. Comparative Genomics of Environmental and Clinical Stenotrophomonas maltophilia Strains with Different Antibiotic Resistance Profiles.

    PubMed

    Youenou, Benjamin; Favre-Bonté, Sabine; Bodilis, Josselin; Brothier, Elisabeth; Dubost, Audrey; Muller, Daniel; Nazaret, Sylvie

    2015-09-01

    Stenotrophomonas maltophilia, a ubiquitous Gram-negative γ-proteobacterium, has emerged as an important opportunistic pathogen responsible for nosocomial infections. A major characteristic of clinical isolates is their high intrinsic or acquired antibiotic resistance level. The aim of this study was to decipher the genetic determinism of antibiotic resistance among strains from different origins (i.e., natural environment and clinical origin) showing various antibiotic resistance profiles. To this purpose, we selected three strains isolated from soil collected in France or Burkina Faso that showed contrasting antibiotic resistance profiles. After whole-genome sequencing, the phylogenetic relationships of these 3 strains and 11 strains with available genome sequences were determined. Results showed that a strain's phylogeny did not match their origin or antibiotic resistance profiles. Numerous antibiotic resistance coding genes and efflux pump operons were revealed by the genome analysis, with 57% of the identified genes not previously described. No major variation in the antibiotic resistance gene content was observed between strains irrespective of their origin and antibiotic resistance profiles. Although environmental strains generally carry as many multidrug resistant (MDR) efflux pumps as clinical strains, the absence of resistance-nodulation-division (RND) pumps (i.e., SmeABC) previously described to be specific to S. maltophilia was revealed in two environmental strains (BurA1 and PierC1). Furthermore the genome analysis of the environmental MDR strain BurA1 showed the absence of SmeABC but the presence of another putative MDR RND efflux pump, named EbyCAB on a genomic island probably acquired through horizontal gene transfer. PMID:26276674

  2. Mapping a Pristine Glaciofluvial Aquifer on the Canadian Shield Using Ground-Penetrating Radar and Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Graves, L. W.; Shirokova, V.; Bank, C.

    2013-12-01

    Our study aims to construct a 3D structural model of an unconfined pristine aquifer in Laurentian Hills, Ontario, Canada. The stratigraphy of the study site, which covers about 5400 square meters, features reworked glaciofluvial sands and glacial till on top of Canadian Shield bedrock. A network of 25 existing piezometers provides ground-truth. We used two types of geophysical surveys to map the water table and the aquifer basin. Ground-penetrating radar (GPR) collected 40 profiles over distances up to 140 meters using 200MHz and 400MHz antennas with a survey wheel. The collected radargrams show a distinct reflective layer, which can be mapped to outcrops of glacial till within the area. This impermeable interface forms the aquitard. Depths of the subsurface features were calculated using hyperbolic fits on the radargrams in Matlab by determining wave velocity then converting measured two-way-time to depth. Electrical resistivity was used to determine the water table elevations because the unconfined water table did not reflect the radar waves. 20 resistivity profiles were collected in the same area using Wenner-Alpha and dipole-dipole arrays with both 24 and 48 electrodes and for 0.5, 0.75, 1.0 and 2.0 meter spacing. The inverted resistivity models show low resistivity values (<1000 Ohm.m) below 2 to 5 meter depths and higher resistivity values (2000-6000 Ohm.m) above 1 to 2 meter depths. These contrasting resistivity values correspond to saturated and wet sand (lower resistivity) to dry sand (higher resistivity); a correlation we could verify with several bore-hole logs. The water table is marked on the resistivity profiles as a steep resistivity gradient, and the depth can be added to the comprehensive 3D model. This model also incorporates hydrogeological characteristics and geochemical anomalies found within the aquifer. Ongoing seasonal and annual monitoring of the aquifer using geophysical methods will bring a fourth dimension to our understanding of this

  3. A one-dimensional model of solid-earth electrical resistivity beneath Florida

    USGS Publications Warehouse

    Blum, Cletus; Love, Jeffrey J.; Pedrie, Kolby; Bedrosian, Paul A.; Rigler, E. Joshua

    2015-01-01

    An estimated one-dimensional layered model of electrical resistivity beneath Florida was developed from published geological and geophysical information. The resistivity of each layer is represented by plausible upper and lower bounds as well as a geometric mean resistivity. Corresponding impedance transfer functions, Schmucker-Weidelt transfer functions, apparent resistivity, and phase responses are calculated for inducing geomagnetic frequencies ranging from 10−5 to 100 hertz. The resulting one-dimensional model and response functions can be used to make general estimates of time-varying electric fields associated with geomagnetic storms such as might represent induction hazards for electric-power grid operation. The plausible upper- and lower-bound resistivity structures show the uncertainty, giving a wide range of plausible time-varying electric fields.

  4. The use of electrical resistivity techniques to detect an underground conduit in the karst regions of the Inner Bluegrass

    SciTech Connect

    Bonita, J.; Sendlein, L.V.A. . Dept. of Geological Sciences)

    1993-03-01

    Electrical resistivity studies conducted within the Inner Bluegrass Karst Region have been employed to map the presence of a fracture controlled solution that drains the royal Spring Basin. Exist theories by authors such as Thrailkill (1982) suggest that the Inner Bluegrass Karst Region is divided into basin and interbasin areas, with the zone of active meteoric water circulation at deep depths below the surface in basin areas and flow within a few meters of the surface in interbasin areas. Initial resistivity soundings were performed along various traverses to access information on the underlying lexington Limestone. Sounding curves calculated form the modeling program RESIX indicate that low resistivity zones occur at two distinctly different depth intervals, denoting the boundary between the basin and interbasin areas. Information from electric resistivity profiles within this now defined basin area indicate resistivity anomalies trending in linear segments of N45W and N40E. Fracture and joint orientation measurements at roadcuts and on topographic maps and air photographs also indicate a preferential orientation parallel to the orientation of the linear segments of the conduit.

  5. Thermal Expansion and Electrical Resistivity Studies of Nickel and ARMCO Iron at High Temperatures

    NASA Astrophysics Data System (ADS)

    Palchaev, D. K.; Murlieva, Zh. Kh.; Gadzhimagomedov, S. H.; Iskhakov, M. E.; Rabadanov, M. Kh.; Abdulagatov, I. M.

    2015-11-01

    The electrical resistance, ρ (T), and thermal expansion coefficient, β (T), of nickel and ARMCO iron have been simultaneously measured over a wide temperature range from (300 to 1100) K. The well-known standard four-probe potentiometric method was used for measurements of the electrical resistance. The thermal expansion coefficient was measured using the quartz dilatometer technique. Both techniques were combined in the same apparatus for simultaneous measurements of the electrical resistance and TEC for the same specimen. The combined expanded uncertainty of the electrical resistance and thermal expansion coefficient measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 0.5 % and (1.5 to 4.0) %, respectively. The distinct ρ (T) scattering contribution (phonon ρ _{ph}, magnetic ρ m, and residual ρ S) terms were separated and extracted from the measured total resistivity. The physical nature and details of the temperature dependence of the electrical resistance of solid materials and correct estimations of the contributions of various scattering mechanisms to the measured total resistivity were discussed in terms of the anharmonic effect. We experimentally found simple, universal, physically based, semiempirical linear correlations between the kinetic coefficient (electrical resistance) and a thermodynamic (equilibrium) property, the thermal expansion coefficient, of solid materials. The developed, physically based, correlation model has been successfully applied for nanoscale materials (ferromagnetic nickel nanowire). A new s-d-exchange interaction energy determination technique has been proposed.

  6. Electrical Properties of Materials for Elevated Temperature Resistance Strain Gage Application. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1987-01-01

    The objective was to study the electrical resistances of materials that are potentially useful as resistance strain gages at 1000 C. Transition metal carbides and nitrides, boron carbide and silicon carbide were selected for the experimental phase of this research. Due to their low temperature coefficient of resistance and good stability, TiC, ZrC, B sub 4 C and beta-SiC are suggested as good candidates for high temperature resistance strain gage applications.

  7. Corrosion-resistant, electrically-conductive plate for use in a fuel cell stack

    DOEpatents

    Carter, J. David; Mawdsley, Jennifer R.; Niyogi, Suhas; Wang, Xiaoping; Cruse, Terry; Santos, Lilia

    2010-04-20

    A corrosion resistant, electrically-conductive, durable plate at least partially coated with an anchor coating and a corrosion resistant coating. The corrosion resistant coating made of at least a polymer and a plurality of corrosion resistant particles each having a surface area between about 1-20 m.sup.2/g and a diameter less than about 10 microns. Preferably, the plate is used as a bipolar plate in a proton exchange membrane (PEMFC) fuel cell stack.

  8. Electrical resistivity of some Zintl phase and the precursors

    SciTech Connect

    Wolfe, L.

    1990-09-21

    Resistivity measurements have been performed for electric characterization of the compounds Ba{sub 5}Sb{sub 3} and Ba{sub 5}Sb{sub 3}Cl, both with the Mn{sub 5}Si{sub 3} structure type, along with Ca{sub 5}Bi{sub 3} and Ca{sub 5}Bi{sub 3}F, both with the {beta}-Yb{sub 5}Sb{sub 3} structure type. These measurements were taken as a function of temperature using the four probe method on pressed polycrystalline pellets of the compounds. A sealed apparatus was developed for containing these air-sensitive compounds throughout the experiments. By a simple electron count, one extra electron in both Ba{sub 5}Sb{sub 3} and Ca{sub 5}Bi{sub 3} should occupy a conduction band, giving these compounds a metallic character. In the cases of Ba{sub 5}Sb{sub 3}Cl and Ca{sub 5}Bi{sub 3}F, the extra electron should bond to the halide, both filling the valence band and giving rise to semiconducting character. Ca{sub 5}Bi{sub 3}, Ca{sub 5}Bi{sub 3}F, and Ba{sub 5}Sb{sub 3}Cl were found to comply with the electron count prediction. Ba{sub 5}Sb{sub 3}, however, was found to be a semiconductor (E{sub g} = 0.30 eV) with a larger band gap than its corresponding chloride (E{sub g} = 0.09 eV).

  9. On the Intensity Profile of Electric Lamps and Light Bulbs

    NASA Astrophysics Data System (ADS)

    Bacalla, Xavier; Salumbides, Edcel John

    2013-11-01

    We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light intensity of these sources displays modulation at twice the ac power supply frequency. The familiarity of ac line power supply, commonplace light sources, and simplicity of the setup encourage student confidence, allowing them to think deeper and continually reassess their notions, and if managed can lead to a satisfactory explanation of the observations.

  10. Measurement and modelling of moisture-electrical resistivity relationship of fine-grained unsaturated soils and electrical anisotropy

    NASA Astrophysics Data System (ADS)

    Merritt, A. J.; Chambers, J. E.; Wilkinson, P. B.; West, L. J.; Murphy, W.; Gunn, D.; Uhlemann, S.

    2016-01-01

    A methodology for developing resistivity-moisture content relationships of materials associated with a clayey landslide is presented. Key elements of the methodology include sample selection and preparation, laboratory measurement of resistivity with changing moisture content, and the derivation of models describing the relationship between resistivity and moisture content. Laboratory resistivity measurements show that the techniques utilised (samples and square array) have considerable potential as a means of electropetrophysical calibration of engineering soils and weak rock. Experimental electrical resistivity results show a hierarchy of values dependent on sample lithology, with silty clay exhibiting the lowest resistivities, followed by siltstones and sands, which return the highest resistivities. In addition, finer grained samples show a greater degree of anisotropy between measurement orientations than coarser grained samples. However, suitability of results in light of issues such as sample cracking and electrical conduction must be identified and accounted for if the results are to be accurately up-scaled to inverted model resistivity results. The existence of directional anisotropy makes model calibration curve selection more difficult due to variability in the range of measured laboratory resistances. The use of larger measurement array size means that experimental data will be more representative of bulk lithological properties. In addition, use of electrodes with a relatively high surface area (wide diameter) help maintain low contact resistances and repeat measurement error, relative to narrow electrodes. Variation exists between the fit of experimental data and petrophysical models. Model fit is best for clay-dominated samples but fits less well for sand-dominated samples. Waxman-Smits equation is appropriately applied in this investigation as all samples have considerable clay mineral content, as is shown in non-negligible CEC results. The

  11. Novel applications of motif-directed profiling to identify disease resistance genes in plants

    PubMed Central

    2013-01-01

    Background Molecular profiling of gene families is a versatile tool to study diversity between individual genomes in sexual crosses and germplasm. Nucleotide binding site (NBS) profiling, in particular, targets conserved nucleotide binding site-encoding sequences of resistance gene analogs (RGAs), and is widely used to identify molecular markers for disease resistance (R) genes. Results In this study, we used NBS profiling to identify genome-wide locations of RGA clusters in the genome of potato clone RH. Positions of RGAs in the potato RH and DM genomes that were generated using profiling and genome sequencing, respectively, were compared. Largely overlapping results, but also interesting discrepancies, were found. Due to the clustering of RGAs, several parts of the genome are overexposed while others remain underexposed using NBS profiling. It is shown how the profiling of other gene families, i.e. protein kinases and different protein domain-coding sequences (i.e., TIR), can be used to achieve a better marker distribution. The power of profiling techniques is further illustrated using RGA cluster-directed profiling in a population of Solanum berthaultii. Multiple different paralogous RGAs within the Rpi-ber cluster could be genetically distinguished. Finally, an adaptation of the profiling protocol was made that allowed the parallel sequencing of profiling fragments using next generation sequencing. The types of RGAs that were tagged in this next-generation profiling approach largely overlapped with classical gel-based profiling. As a potential application of next-generation profiling, we showed how the R gene family associated with late blight resistance in the SH*RH population could be identified using a bulked segregant approach. Conclusions In this study, we provide a comprehensive overview of previously described and novel profiling primers and their genomic targets in potato through genetic mapping and comparative genomics. Furthermore, it is shown how

  12. Resolving Large Pre-glacial Valleys Buried by Glacial Sediment Using Electric Resistivity Imaging (ERI)

    NASA Astrophysics Data System (ADS)

    Schmitt, D. R.; Welz, M.; Rokosh, C. D.; Pontbriand, M.-C.; Smith, D. G.

    2004-05-01

    Two-dimensional electric resistivity imaging (ERI) is the most exciting and promising geological tool in geomorphology and stratigraphy since development of ground-penetrating radar. Recent innovations in 2-D ERI provides a non-intrusive mean of efficiently resolving complex shallow subsurface structures under a number of different geological scenarios. In this paper, we test the capacity of ERI to image two large pre-late Wisconsinan-aged valley-fills in central Alberta and north-central Montana. Valley-fills record the history of pre-glacial and glacial sedimentary deposits. These fills are of considerable economical value as groundwater aquifers, aggregate resources (sand and gravel), placers (gold, diamond) and sometime gas reservoirs in Alberta. Although the approximate locations of pre-glacial valley-fills have been mapped, the scarcity of borehole (well log) information and sediment exposures make accurate reconstruction of their stratigraphy and cross-section profiles difficult. When coupled with borehole information, ERI successfully imaged three large pre-glacial valley-fills representing three contrasting geological settings. The Sand Coulee segment of the ancestral Missouri River, which has never been glaciated, is filled by electrically conductive pro-glacial lacustrine deposits over resistive sandstone bedrock. By comparison, the Big Sandy segment of the ancestral Missouri River valley has a complex valley-fill composed of till units interbedded with glaciofluvial gravel and varved clays over conductive shale. The fill is capped by floodplain, paludal and low alluvial fan deposits. The pre-glacial Onoway Valley (the ancestral North Saskatchewan River valley) is filled with thick, resistive fluvial gravel over conductive shale and capped with conductive till. The cross-sectional profile of each surveyed pre-glacial valley exhibits discrete benches (terraces) connected by steep drops, features that are hard to map using only boreholes. Best quality ERI

  13. Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.-H.; Cho, W.D.

    1996-11-01

    Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  14. Resistive memory effects in BiFeO3 single crystals controlled by transverse electric fields

    NASA Astrophysics Data System (ADS)

    Kawachi, S.; Kuroe, H.; Ito, T.; Miyake, A.; Tokunaga, M.

    2016-04-01

    The effects of electric fields perpendicular to the c-axis of the trigonal cell in single crystals of BiFeO3 are investigated through magnetization and resistance measurements. Magnetization and resistance exhibit hysteretic changes under applied electric fields, which can be ascribed to the reorientation of the magnetoelectric domains. Samples are repetitively switched between high- and low-resistance states by changing the polarity of the applied electric fields over 20 000 cycles at room temperature. These results demonstrate the potential of BiFeO3 for use in non-volatile memory devices.

  15. Comparative Genomics of Environmental and Clinical Stenotrophomonas maltophilia Strains with Different Antibiotic Resistance Profiles

    PubMed Central

    Youenou, Benjamin; Favre-Bonté, Sabine; Bodilis, Josselin; Brothier, Elisabeth; Dubost, Audrey; Muller, Daniel; Nazaret, Sylvie

    2015-01-01

    Stenotrophomonas maltophilia, a ubiquitous Gram-negative γ-proteobacterium, has emerged as an important opportunistic pathogen responsible for nosocomial infections. A major characteristic of clinical isolates is their high intrinsic or acquired antibiotic resistance level. The aim of this study was to decipher the genetic determinism of antibiotic resistance among strains from different origins (i.e., natural environment and clinical origin) showing various antibiotic resistance profiles. To this purpose, we selected three strains isolated from soil collected in France or Burkina Faso that showed contrasting antibiotic resistance profiles. After whole-genome sequencing, the phylogenetic relationships of these 3 strains and 11 strains with available genome sequences were determined. Results showed that a strain’s phylogeny did not match their origin or antibiotic resistance profiles. Numerous antibiotic resistance coding genes and efflux pump operons were revealed by the genome analysis, with 57% of the identified genes not previously described. No major variation in the antibiotic resistance gene content was observed between strains irrespective of their origin and antibiotic resistance profiles. Although environmental strains generally carry as many multidrug resistant (MDR) efflux pumps as clinical strains, the absence of resistance–nodulation–division (RND) pumps (i.e., SmeABC) previously described to be specific to S. maltophilia was revealed in two environmental strains (BurA1 and PierC1). Furthermore the genome analysis of the environmental MDR strain BurA1 showed the absence of SmeABC but the presence of another putative MDR RND efflux pump, named EbyCAB on a genomic island probably acquired through horizontal gene transfer. PMID:26276674

  16. An Ultra-Precise System for Electrical Resistivity Tomography Measurements

    SciTech Connect

    LaBrecque, Douglas J; Adkins, Paula L

    2008-12-09

    The objective of this research was to determine the feasibility of building and operating an ERT system that will allow measurement precision that is an order of magnitude better than existing systems on the market today and in particular if this can be done without significantly greater manufacturing or operating costs than existing commercial systems. Under this proposal, we performed an estimation of measurement errors in galvanic resistivity data that arise as a consequence of the type of electrode material used to make the measurements. In our laboratory, measurement errors for both magnitude and induced polarization (IP) were estimated using the reciprocity of data from an array of electrodes as might be used for electrical resistance tomography using 14 different metals as well as one non-metal - carbon. In a second phase of this study, using archival data from two long-term ERT surveys, we examined long-term survivability of electrodes over periods of several years. The survey sites were: the Drift Scale Test at Yucca Mountain, Nevada (which was sponsored by the U. S. Department of Energy as part of the civilian radioactive waste management program), and a water infiltration test at a site adjacent to the New Mexico Institute of Mines and Technology in Socorro, New Mexico (sponsored by the Sandia/Tech vadose program). This enabled us to compare recent values with historical values and determine electrode performance over the long-term as well as the percentage of electrodes that have failed entirely. We have constructed a prototype receiver system, made modifications and revised the receiver design. The revised prototype uses a new 24 bit analog to digital converter from Linear Technologies with amplifier chips from Texas Instruments. The input impedance of the system will be increased from 107 Ohms to approximately 1010 Ohms. The input noise level of the system has been decreased to approximately 10 Nanovolts and system resolution to about 1 Nanovolt at

  17. Challenges of using electrical resistivity method to locate karst conduits-A field case in the Inner Bluegrass Region, Kentucky

    USGS Publications Warehouse

    Zhu, J.; Currens, J.C.; Dinger, J.S.

    2011-01-01

    Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. ?? 2011 Elsevier B.V.

  18. Antimicrobial resistance profiles and mechanisms of resistance in Campylobacter jejuni isolates from pets.

    PubMed

    Acke, Els; McGill, Kevina; Quinn, Teresa; Jones, Boyd R; Fanning, Seamus; Whyte, Paul

    2009-01-01

    The presence of antimicrobial resistance in 51 Campylobacter jejuni isolates obtained from cats and dogs was determined by E-testing. Resistance to nalidixic acid (37.3% of isolates), ciprofloxacin (19.6%), tetracycline (13.7%), ampicillin (13.7%), erythromycin (11.8%), and chloramphenicol (5.9%) was detected. Resistance to two antimicrobials or more was present in 31.4% of isolates, and one isolate was resistant to all six antimicrobials. Of the isolates with ciprofloxacin and/or nalidixic acid resistance, 54.5% had the gyrA substitution Thr-86-Ile on sequencing. The tet o gene was detected in 75.0% isolates with high-level resistance to tetracycline. With the observed antimicrobial resistance in C. jejuni isolates from pets in this study, and the detection of identical mechanisms for quinolone and tetracycline resistance in pets and humans, pets should be considered a potential source of (multi)resistant C. jejuni infections in humans. PMID:19580444

  19. Analysis Clustering of Electricity Usage Profile Using K-Means Algorithm

    NASA Astrophysics Data System (ADS)

    Amri, Yasirli; Lailatul Fadhilah, Amanda; Fatmawati; Setiani, Novi; Rani, Septia

    2016-01-01

    Electricity is one of the most important needs for human life in many sectors. Demand for electricity will increase in line with population and economic growth. Adjustment of the amount of electricity production in specified time is important because the cost of storing electricity is expensive. For handling this problem, we need knowledge about the electricity usage pattern of clients. This pattern can be obtained by using clustering techniques. In this paper, clustering is used to obtain the similarity of electricity usage patterns in a specified time. We use K-Means algorithm to employ clustering on the dataset of electricity consumption from 370 clients that collected in a year. Result of this study, we obtained an interesting pattern that there is a big group of clients consume the lowest electric load in spring season, but in another group, the lowest electricity consumption occurred in winter season. From this result, electricity provider can make production planning in specified season based on pattern of electricity usage profile.

  20. Electrical resistivity imaging (ERI) and ground-penetrating radar (GPR) survey at the Giribaile site (upper Guadalquivir valley; southern Spain)

    NASA Astrophysics Data System (ADS)

    Martínez, J.; Rey, J.; Gutiérrez, L. M.; Novo, A.; Ortiz, A. J.; Alejo, M.; Galdón, J. M.

    2015-12-01

    The Giribaile archaeological site is one of the most important Iberian enclaves of the Alto Guadalquivir (Southern Spain). However, to date, only minimal excavation work has been performed at the site. Evaluation requires a preliminary, non-destructive general analysis to determine high-interest areas. This stage required a geophysical survey. Specifically, a 100 m2 grid was selected, where an initial campaign of nine electrical resistivity imaging (ERI) profiles was performed, where each profile was 111 m in length; these profiles were previously located using a detailed topographical survey. A total of 112 electrodes were used for each profile, spaced at 1 m apart with a Wenner-Schlumberger configuration. Secondly, 201 GPR profiles were created using a 500 MHz antenna. The 100 m long profiles were spaced 0.5 m apart and parallel to one another. The present research analyses the efficiency of each of these geophysical tools in supporting archaeological research. Using these methodologies, the position, morphology, and depth of different buried structures can be determined. 3D interpretation of the geophysical survey in 100 × 100 m grid allowed to differentiate structures square and rectangular, interesting buildings in a semicircle (interpreted as ovens) plus delineate different streets. From the geophysical survey follows the Carthaginian presence inside this ancient Iberian enclave.

  1. AF printability check with a full-chip 3D resist profile model

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-En R.; Chang, Jason; Song, Hua; Shiely, James

    2013-09-01

    A single compact resist model capable of predicting 3D resist profile is strongly demanded for the advanced technology nodes to avoid the potential hotspots due to imperfect resist pattern shape and its lack of resistance in the subsequent etch process. In this work, we propose a resist 3D (R3D) compact model that takes acidz-diffusion effect into account. The chemical reaction between acid and base along z-direction is treated as second order effect that is absorbed into the anisotropic diffusion length as a fitting parameter. Meanwhile, the resist model in the x-y wafer plane is still kept in general by applying the compact solution of 2D reaction-diffusion equation. In order to have the 2D contour predictability at arbitrary resist height, calibration from entire 3D data (CDs at several heights) areconducted simultaneously witha single cost function so that the R3D compact model is described by a common set of resist free parameters and threshold for all resist heights. With the low energy approximation, the acid z-diffusion effect is equivalent to a z-diffused TCC that takes the form of linear combination of pure optical TCCs sampled at discrete image-depth which can be pre-calculated. With this benefit, the R3D compact model offers a more physical approach but adds no runtime concern on the OPC and verification applications. The predicted resist cross-section profiles from our test patterns are compared those computed with rigorous lithography simulator SLITHO and show very good matching results between them. The demonstration of the AF printability check from the predicted cross-section profile at AF indicates the success of our R3D compact model.

  2. The influence of electric field and mobility profile on GaAs MESFET characteristics

    NASA Astrophysics Data System (ADS)

    Chen, Chung-Hsu; Arch, David K.

    1989-11-01

    Analytical approximations for the drain I-V relationship, including the mobility profile and field distribution in the channel from the drain to the source, of GaAs MESFETs are derived. The model includes the extended depletion from the gate to the drain for nonself-aligned devices. The calculation of the electric field along the channel is in very good agreement with existing analytical models and a two-dimensional numerical simulation. Experimentally, the authors fabricated and tested tilted angle lightly doped drain (LDD) GaAs MESFETs. It was found that the LLD MESFET structure suppresses the peak electric field under the gate near the drain region. A lower output conductance and higher drain-to-source breakdown were observed as expected. In addition to the electric field, the mobility profile is another factor that influences the performance of the devices. The accuracy of describing the low-field transconductance is strongly dependent on the mobility profile. Moreover, the mobility profile modifies the electric field along the channel and also influences the shape of the drain I-V curves. It is found that more accurate I-V curves can be obtained once the mobility profile is taken into account.

  3. Contrast in the Antibiotic Resistance Profiles of Campylobacter Isolates Originating from Different Poultry Production Facilities (Broiler Breeder Hens, Broilers, and Leghorn Hens) in the Same Geographical Region

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction: Antimicrobial resistance of foodborne pathogens is of major concern from both human and animal health perspectives and resistance profiles of Campylobacter spp. from individual poultry facilities have been extensively studied. However, a comparison of antimicrobial resistance profile...

  4. Fracture network characterisation of a landslide by electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Szalai, S.; Szokoli, K.; Novák, A.; Tóth, Á.; Metwaly, M.; Prácser, E.

    2014-06-01

    In contrary to most of the landslide studies which concentrate to the sliding surface in this paper the fracture system of a loess landslide is investigated. The continuity and geometry, orientation and dip of the major fractures are crucial parameters for assessing rock stability and landslide evolution. Rain infiltrating moreover easily into the rock mass through fractures providing lubrication for the material to slide, and increases the self-mass of the material increasing the slumping rate. Fracture maps enable beside of the characterisation of the fractured area the delineation of the endangered area of slow-moving landslides in due time and getting information about its inner structure. For constructing such maps Electrical Resistivity Tomography (ERT) measurements have been carried out using different geoelectric configurations. In spite of the high density of the fractures and their changing physical parameters in function of their water content - which make the interpretation rather difficult - a number of fractures have been detected and more or less well localised. On the basis of the present research the application of the Schlumberger and the Pole-Dipole arrays is recommended to fulfil the aim of the study. The optimised Stummer array is at the same time the only array which presents conductive anomalies (supposedly water filled fractures), as well, and indicates that fractures elongate deep downwards. Because these features seem to be realistic based on field observations or theoretical considerations the Stummer array may be a very good tool for completing e.g. P-Dp measurements. The study area could have been divided by all arrays into differently fractured zones, which assists a lot in understanding the landslide structure and evolution. It was shown, moreover, that in the still passive area there are thick fractures, too, verifying its dangerousness, as well. The ERT results enabled localising the rupture surfaces of future slumps which proved to

  5. Analysis of antimicrobial resistance and plasmid profiles in Salmonella serovars associated with tropical seafood of India.

    PubMed

    Kumar, Rakesh; Surendran, P K; Thampuran, Nirmala

    2009-06-01

    A total of 256 Salmonella strains consisting of 29 Salmonella serovars isolated from seafood of Cochin (India) were analyzed for resistance to antimicrobials commonly used in human and veterinary medicines as therapeutic agents. The 10 most predominant Salmonella serovars in seafood were also characterized for presence of plasmids using the alkaline lysis method. Antimicrobial susceptibility studies highlighted a comparatively high resistance in Salmonella isolates to sulfamethizol and carbenicillin, and moderate resistance to nalidixic acid and oxytetracycline. Nevertheless, antimicrobial resistance was not observed against ampicillin, ciprofloxacin, chloramphenicol, gentamicin, and kanamycin in different Salmonella serovars. Fifty percent of the Salmonella isolates, comprising 16 Salmonella serovars, were resistant to sulfamethizol followed by 39% resistant to carbenicillin and 14% resistant to oxytetracycline. Multidrug resistance was detected in 39.4%, 14.4%, 12.1%, and 1.5% of Salmonella isolates towards two drugs (sulfamethizol and carbenicillin), three drugs (sulfamethizol, carbenicillin, and oxytetracycline), four drugs (sulfamethizol, carbenicillin, oxytetracycline, and nalidixic acid), and five drugs (sulfamethizol, carbenicillin, oxytetracycline, nalidixic acid, and streptomycin), respectively. Plasmid profiling highlighted the presence of nine plasmid profiles in Salmonella serovars and plasmids that were not detected in Salmonella enterica subsp. enterica Weltevreden, Salmonella Rissen, Salmonella Bareilly, Salmonella Irumu, Salmonella Ohio, Salmonella Oslo, and Salmonella Typhi isolated from seafood. PMID:19422307

  6. Composite Materials with Distinctive Behaviors under High Electric Fields: I - Material Switches to 'High Resistive' State

    NASA Technical Reports Server (NTRS)

    Javadi, H.

    1994-01-01

    Electrically conductive silver filled epoxy ECF-563 preform, sandwiched between gold contact pads exhibits intermittent current-voltage characteristics with switching to 'high resistive' state under applied bias voltage.

  7. Distribution and drug resistance profile of methicillin-resistant Staphylococcus aureus after orthopaedic surgery.

    PubMed

    Song, Wen Chao; Zhang, Si Sen; Gong, Yu Hong

    2015-05-01

    This paper is aimed to comprehend clinical distribution and drug-resistance situation of methicillin-resistant Staphylococcus aureus. This study applied automatic microbe instrument Microscan W/A 96 for strain identification and drug susceptibility screening on the isolated strains. It was found that 312 MRSA strains were isolated in three years, which account for 58.1% of Staphylococcus aureus. MRSA were mainly focused in wound secretion, purulent sputum and prostatic fluid and a few of them were isolated from blood specimens; Endemic area distribution was mainly located in intensive care unit, neurosurgery, respiratory department, dermatology, orthopaedic burns and orthopaedics. MRSA strains showed high drug resistance of 82.37%~100% to most of the antibiotics including vancomycin, cotrimoxazole and rifampicin. Strain was 100% resistance towards ampicillin, amoxicillin/acid, cefalotin, cefazolin, tienam, benzylpenicillin, penicillin and tetracycline and 90% strains resisted clindamycin, cefotaxime, clarithromycin and gentamicin. PMID:26051737

  8. Temperature dependence of electrical resistivity measurements: A useful infiltration tracer?

    NASA Astrophysics Data System (ADS)

    Pidlisecky, A.; Knight, R.

    2008-12-01

    As part of an ongoing monitoring project, three resistivity probes were installed to a depth of 2m below a seasonal infiltration pond on the central coast of California. The probes were instrumented with 35 resistivity electrodes and 5 temperature loggers. They were designed to monitor the change in bulk resistivity beneath the pond during infiltration. The pond was filled in January 2008 and resistivity measurements were made on each probe every hour for a period of 4 months. In addition to changes in bulk resistivity, we observed diurnal fluctuations in the apparent resistivity signal due to the temperature dependence of in-situ resistivity. By processing the resistivity data, using a band pass filter, we can recover a time-depth section of pseudo- temperature data. We refer to these data as pseudo-temperature because they can be treated as a surrogate for temperature in terms of phase but not amplitude. These pseudo-temperature sections can be used as a tracer to calculate 1D infiltration rates. When compared with in-situ temperature loggers, we see good agreement. Moreover, we note that the resistivity fluctuations correspond to temperature variations that are less than one degree Celsius. The use of the temperature dependence of measured resistivity is a promising field technique. The pseudo-temperature data may prove more robust than using traditional temperature probes given that the larger sampling volume of the resistivity measurement will limit the influence local flow path perturbations caused by probe installation. Future research will involve extending this approach to 2D tomography in hopes of providing us with a technique for obtaining spatially exhaustive estimates of near-surface infiltration rates.

  9. The effects of electrical stimulation on body composition and metabolic profile after spinal cord injury – Part II

    PubMed Central

    Gorgey, Ashraf S.; Dolbow, David R.; Dolbow, James D.; Khalil, Refka K.; Gater, David R.

    2015-01-01

    Diet and exercise are cornerstones in the management of obesity and associated metabolic complications, including insulin resistance, type 2 diabetes, and disturbances in the lipid profile. However, the role of exercise in managing body composition adaptations and metabolic disorders after spinal cord injury (SCI) is not well established. The current review summarizes evidence about the efficacy of using neuromuscular electrical stimulation or functional electrical stimulation in exercising the paralytic lower extremities to improve body composition and metabolic profile after SCI. There are a number of trials that investigated the effects on muscle cross-sectional area, fat-free mass, and glucose/lipid metabolism. The duration of the intervention in these trials varied from 6 weeks to 24 months. Training frequency ranged from 2 to 5 days/week. Most studies documented significant increases in muscle size but no noticeable changes in adipose tissue. While increases in skeletal muscle size after twice weekly training were greater than those trials that used 3 or 5 days/week, other factors such as differences in the training mode, i.e. resistance versus cycling exercise and pattern of muscle activation may be responsible for this observation. Loading to evoke muscle hypertrophy is a key component in neuromuscular training after SCI. The overall effects on lean mass were modest and did not exceed 10% and the effects of training on trunk or pelvic muscles remain unestablished. Most studies reported improvement in glucose metabolism with the enhancement of insulin sensitivity being the major factor following training. The effect on lipid profile is unclear and warrants further investigation. PMID:25001669

  10. Total Protein Profile and Drug Resistance in Candida albicans Isolated from Clinical Samples

    PubMed Central

    Thawani, Vijay; Mehra, Arti

    2016-01-01

    This study was done to assess the antifungal susceptibility of clinical isolates of Candida albicans and to evaluate its total protein profile based on morphological difference on drug resistance. Hundred and twenty clinical isolates of C. albicans from various clinical specimens were tested for susceptibility against four antifungal agents, namely, fluconazole, itraconazole, amphotericin B, and ketoconazole. A significant increase of drug resistance in clinical isolates of C. albicans was observed. The study showed 50% fluconazole and itraconazole resistance at 32 μg mL−1 with a MIC50 and MIC90 values at 34 and 47 and 36 and 49 μg mL−1, respectively. All isolates were sensitive to amphotericin B and ketoconazole. The SDS-PAGE protein profile showed a prevalent band of ~52.5 kDa, indicating overexpression of gene in 72% strains with fluconazole resistance. Since the opportunistic infections of Candida spp. are increasing along with drug resistance, the total protein profile will help in understanding the evolutionary changes in drug resistance and also to characterize them. PMID:27478638

  11. Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials

    SciTech Connect

    Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

    2012-04-17

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700°C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 Ω-cm2 at RT, decreasing continuously to ~1-10 Ω-cm2 at 700°C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.

  12. Modeling the electrical resistivity of deformation processed metal-metal composites

    SciTech Connect

    Tian, Liang; Anderson, Iver; Riedemann, Trevor; Russell, Alan

    2014-09-01

    Deformation processed metal–metal (matrix–reinforcement) composites (DMMCs) are high-strength, high-conductivity in situ composites produced by severe plastic deformation. The electrical resistivity of DMMCs is rarely investigated mechanistically and tends to be slightly higher than the rule-of-mixtures prediction. In this paper, we analyze several possible physical mechanisms (i.e. phonons, interfaces, mutual solution, grain boundaries, dislocations) responsible for the electrical resistivity of DMMC systems and how these mechanisms could be affected by processing conditions (i.e. temperature, deformation processing). As an innovation, we identified and assembled the major scattering mechanisms for specific DMMC systems and modeled their electrical resistivity in combination. From this analysis, it appears that filament coarsening rather than dislocation annihilation is primarily responsible for the resistivity drop observed in these materials after annealing and that grain boundary scattering contributes to the resistivity at least at the same magnitude as does interface scattering.

  13. Time-lapse Measurements of Electrical Resistivities to Characterise Snowmelt Infiltration Patterns

    NASA Astrophysics Data System (ADS)

    French, H. K.; Du Saire, M.; Binley, A.; Baker, J.

    2006-12-01

    During snowmelt Oslo airport has on repeated occations experienced the formation of large meltwater ponds due to impermeable ice forming below the snowcover. The airport is situated on a large glacial outwash plane with coarse sandy gravely sediments, hence the area normaly has a high infiltration capacity. Focussed infiltration can cause fast transport of contaminants to the groundwater, hence improved understanding of the processes determining where and how the focussed infiltration takes place is important. Previously the melting process has been monitored successfully on a small scale (4 m2) using a two dimensional grid of permanently installed electrodes (French and Binley, 2004). In the present work snowmelt infiltration was monitored by time-lapse measurements of electrical resistivity using grounded electrodes on 4 and 20 m2 plots and a capacitively coupled resistivity system (Ohmmapper, Geometrics) on a larger scale. While the smaller scale systems provide 3D images the capacitively coupled system was used to monitor changes in two dimensional vertical sections in a retention pond adjacent to one of the runways. The area covered by 4 lines was 170 m by 340 m. The initial data were collected late in the spring (2006) during the final stages of the snowmelt. The lines were repeated later in the year when the soil profile was dryer. The lines show good consistency in the description of the general geology of the subsurface and the time-lapse changes describe the infiltration pattern that occurred during snowmelt and subsequent drainage. The surveys provide useful information about the differences in spatial distribution of snowmelt infiltration at different scales. And there are good indications that capacitively coupled resistivity surveys can be used to describe infiltration processes at relatively large spacio-temporal scales. References French, H. and A. Binley, 2004, Snowmelt infiltration: monitoring temporal and spatial variability using time- lapse

  14. Comparing spatial series of soil bulk electrical conductivity as obtained by Time Domain Reflectometry and Electrical Resistivity Tomography

    NASA Astrophysics Data System (ADS)

    Saeed, Ali; Dragonetti, Giovanna; Comegna, Allessandro; Garre, Sarah; Lamaddalena, Nicola; Coppola, Antonio

    2016-04-01

    Conventional ground survey of soil root zone salinity by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity, σb, in the field. This approach is faster and cheaper, and allows a more intensive surveying. Measurements of σb can be made either in situ or with remote devices. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on the Electrical Resistivity Tomography (ERT) techniques represent an alternative in respect to those traditional for soil salinity characterization. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from ERT sensors. The latter, in turn, depends on the specific depth distribution of the σb, as well as on the electrical configuration of the sensor used. With these premises, the main aim of this study is to estimate the vertical σb distribution starting from resistivity data series measured using the ERT method under different salinity conditions and using TDR data as ground-truth data for calibration and validation of the ERT sensor. This way, limited measured TDR data may be used for translating extensive ERT apparent electrical conductivity, σa, measurements to estimate depth

  15. Characterisation of Phenotypic and Genotypic Antibiotic Resistance Profile of Enterococci from Cheeses in Turkey.

    PubMed

    Kürekci, Cemil; Önen, Sevda Pehlivanlar; Yipel, Mustafa; Aslantaş, Özkan; Gündoğdu, Aycan

    2016-01-01

    The aim of this study was to determine the prevalence of enterococci in cheese samples and to characterize their antimicrobial resistance profiles as well as the associated resistance genes. A total of 139 enterococci were isolated from 99 cheese samples, the isolates were identified as E. faecalis (61.2%), E. faecium (15.1%), E. gallinarum (12.9%), E. durans (5.0%), E. casseliflavis (2.9%) and E. avium (2.9%). The most frequent antimicrobial resistance observed in enterococci isolates was to lincomycin (88.5%), followed by kanamycin (84.2%), gentamycin (low level, 51.1%), rifampin (46.8%) and tetracycline (33.8%). Among the isolates, the frequencies of high level gentamycin and streptomycin resistant enterococci strains were 2.2% and 5.8%, respectively. Apart from the mentioned antibiotics, low levels of resistance to ciprofloxacin, erythromycin and chloramphenicol were found. Moreover no resistance was observed against penicillin and ampicillin. The antimicrobial resistance genes including tetM, tetL, ermB, cat, aph(3')-IIIa, ant(6)-Ia and aac(6')-Ieaph(2")-Ia were found in enterococci from Turkish cheese samples. In the current study, we provided data for antibiotic resistance and the occurrence of resistance genes among enterococci. Regulatory and quality control programs for milk and other dairy products from farms to retail outlets has to be established and strengthened to monitor trends in antimicrobial resistance among emerging food borne pathogens in Turkey. PMID:27433106

  16. Characterisation of Phenotypic and Genotypic Antibiotic Resistance Profile of Enterococci from Cheeses in Turkey

    PubMed Central

    Yipel, Mustafa; Aslantaş, Özkan; Gündoğdu, Aycan

    2016-01-01

    The aim of this study was to determine the prevalence of enterococci in cheese samples and to characterize their antimicrobial resistance profiles as well as the associated resistance genes. A total of 139 enterococci were isolated from 99 cheese samples, the isolates were identified as E. faecalis (61.2%), E. faecium (15.1%), E. gallinarum (12.9%), E. durans (5.0%), E. casseliflavis (2.9%) and E. avium (2.9%). The most frequent antimicrobial resistance observed in enterococci isolates was to lincomycin (88.5%), followed by kanamycin (84.2%), gentamycin (low level, 51.1%), rifampin (46.8%) and tetracycline (33.8%). Among the isolates, the frequencies of high level gentamycin and streptomycin resistant enterococci strains were 2.2% and 5.8%, respectively. Apart from the mentioned antibiotics, low levels of resistance to ciprofloxacin, erythromycin and chloramphenicol were found. Moreover no resistance was observed against penicillin and ampicillin. The antimicrobial resistance genes including tetM, tetL, ermB, cat, aph(3’)-IIIa, ant(6)-Ia and aac(6’)-Ieaph(2”)-Ia were found in enterococci from Turkish cheese samples. In the current study, we provided data for antibiotic resistance and the occurrence of resistance genes among enterococci. Regulatory and quality control programs for milk and other dairy products from farms to retail outlets has to be established and strengthened to monitor trends in antimicrobial resistance among emerging food borne pathogens in Turkey. PMID:27433106

  17. An insight into the drug resistance profile & mechanism of drug resistance in Neisseria gonorrhoeae.

    PubMed

    Patel, Achchhe Lal; Chaudhry, Uma; Sachdev, Divya; Sachdeva, Poonam Nagpal; Bala, Manju; Saluja, Daman

    2011-10-01

    Among the aetiological agents of treatable sexually transmitted diseases (STDs), Neissseria gonorrhoeae is considered to be most important because of emerging antibiotic resistant strains that compromise the effectiveness of treatment of the disease - gonorrhoea. In most of the developing countries, treatment of gonorrhoea relies mainly on syndromic management rather than the aetiological based therapy. Gonococcal infections are usually treated with single-dose therapy with an agent found to cure > 95 per cent of cases. Unfortunately during the last few decades, N. gonorrhoeae has developed resistance not only to less expensive antimicrobials such as sulphonamides, penicillin and tetracyclines but also to fluoroquinolones. The resistance trend of N. gonorrhoeae towards these antimicrobials can be categorised into pre-quinolone, quinolone and post-quinolone era. Among the antimicrobials available so far, only the third-generation cephalosporins could be safely recommended as first-line therapy for gonorrhoea globally. However, resistance to oral third-generation cephalosporins has also started emerging in some countries. Therefore, it has become imperative to initiate sustained national and international efforts to reduce infection and misuse of antibiotics so as to prevent further emergence and spread of antimicrobial resistance. It is necessary not only to monitor drug resistance and optimise treatment regimens, but also to gain insight into how gonococcus develops drug resistance. Knowledge of mechanism of resistance would help us to devise methods to prevent the occurrence of drug resistance against existing and new drugs. Such studies could also help in finding out new drug targets in N. gonorrhoeae and also a possibility of identification of new drugs for treating gonorrhoea. PMID:22089602

  18. An insight into the drug resistance profile & mechanism of drug resistance in Neisseria gonorrhoeae

    PubMed Central

    Patel, Achchhe Lal; Chaudhry, Uma; Sachdev, Divya; Sachdeva, Poonam Nagpal; Bala, Manju; Saluja, Daman

    2011-01-01

    Among the aetiological agents of treatable sexually transmitted diseases (STDs), Neissseria gonorrhoeae is considered to be most important because of emerging antibiotic resistant strains that compromise the effectiveness of treatment of the disease - gonorrhoea. In most of the developing countries, treatment of gonorrhoea relies mainly on syndromic management rather than the aetiological based therapy. Gonococcal infections are usually treated with single-dose therapy with an agent found to cure > 95 per cent of cases. Unfortunately during the last few decades, N. gonorrhoeae has developed resistance not only to less expensive antimicrobials such as sulphonamides, penicillin and tetracyclines but also to fluoroquinolones. The resistance trend of N. gonorrhoeae towards these antimicrobials can be categorised into pre-quinolone, quinolone and post-quinolone era. Among the antimicrobials available so far, only the third-generation cephalosporins could be safely recommended as first-line therapy for gonorrhoea globally. However, resistance to oral third-generation cephalosporins has also started emerging in some countries. Therefore, it has become imperative to initiate sustained national and international efforts to reduce infection and misuse of antibiotics so as to prevent further emergence and spread of antimicrobial resistance. It is necessary not only to monitor drug resistance and optimise treatment regimens, but also to gain insight into how gonococcus develops drug resistance. Knowledge of mechanism of resistance would help us to devise methods to prevent the occurrence of drug resistance against existing and new drugs. Such studies could also help in finding out new drug targets in N. gonorrhoeae and also a possibility of identification of new drugs for treating gonorrhoea. PMID:22089602

  19. Numerical investigation of the flow profiles in the electrically enhanced cyclone.

    PubMed

    Shi, Liming; Bayless, David J; Kremer, Greg; Stuart, Ben

    2007-04-01

    A numerical model for simulation of the electrohydrodynamic flow in an electrically enhanced cyclone is presented. A finite element approach was applied to solve the coupled equations for the positive corona-induced electric field. Three-dimensional simulations of gas flow were carried using Reynolds-Averaged Navier-Stokes equations including the Reynolds stress model and the electrohydrodynamic effect. Numerical results show that the change in the flow profile because of the influence of the corona-induced electric field is apparent when the inlet flow rate is low but is negligible at higher flow rates. PMID:17458468

  20. An efficient, low profile, electrically small, three-dimensional, very high frequency magnetic EZ antenna

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Ching; Ziolkowski, Richard W.; Nielsen, Jean A.; Tanielian, Minas H.; Holloway, Christopher L.

    2010-03-01

    A very high frequency version of the electrically small, coax-fed, three-dimensional magnetic EZ antenna was designed and tested. The fabricated antenna was formed by integrating a capacitively loaded loop element with a coaxially-fed, electrically small, semicircular loop antenna. This low profile antenna (height ˜λ/25) had an electrical size that was ka ˜0.46 at 105.2 MHz (where a is the radius of the minimum enclosing hemisphere). Nearly complete matching to the 50 Ω source and a high overall efficiency (nearly 95%) were achieved. The numerically predicted and the measured results were in good agreement.

  1. Change Of Electrical Resistivity Depending On Water Saturation Of The Concrete Samples

    NASA Astrophysics Data System (ADS)

    Sabbaǧ, Nevbahar; Uyanık, Osman

    2016-04-01

    In this study, the changes of electrical apparent resistivity values depending on the water saturation of cubic concrete samples which designed according to different strength were investigated. For this purpose, 3 different concrete design as poor, middle and good strength 150x150x150mm dimensions 9 for each design cubic samples were prepared. After measuring the weight of the prepared samples, in oven were dried at 105 ° C for 24 hours and then the dry weights were measured. Then the samples were placed into the curing pool and saturated weight of the samples were measured in specific time periods during the 90 day take out from the curing pool and the water content were calculated at each stage of these processes. The water content of the samples were obtained during 90 days specific points in time and as well as electrical apparent resistivity method of the different surfaces of the samples the potential difference measurements made by electrical resistivity method and electrical apparent resistivity values of the samples were calculated. Depending on time obtained from this study with respect to time curves of the water content and the apparent resistivity values were constructed. Results showed that the electrical apparent resistivity values increased depends on the water content. This study was supported with OYP05277-DR-14 Project No. by SDU and State Hydraulic Works 13th Regional/2012-01 Project No. Keywords: Concrete, cubic sample, Resistivity, water content, time

  2. Plume and lithologic profiling with surface resistivity and seismic tomography.

    PubMed

    Watson, David B; Doll, William E; Gamey, T Jeffrey; Sheehan, Jacob R; Jardine, Philip M

    2005-01-01

    Improved surface-based geophysical technologies that are commercially available provide a new level of detail that can be used to guide ground water remediation. Surface-based multielectrode resistivity methods and tomographic seismic refraction techniques were used to image to a depth of approximately 30 m below the surface at the Natural and Accelerated Bioremediation Research Field Research Center. The U.S. Department of Energy (DOE) established the research center on the DOE Oak Ridge Reservation in Oak Ridge, Tennessee, to conduct in situ field-scale studies on bioremediation of metals and radionuclides. Bioremediation studies are being conducted on the saprolite, shale bedrock, and ground water at the site that have been contaminated with nitrate, uranium, technetium, tetrachloroethylene, and other contaminants (U.S. DOE 1997). Geophysical methods were effective in imaging the high-ionic strength plume and in defining the transition zone between saprolite and bedrock zones that appears to have a significant influence on contaminant transport. The geophysical data were used to help select the location and depth of investigation for field research plots. Drilling, borehole geophysics, and ground water sampling were used to verify the surface geophysical studies. PMID:15819938

  3. Plume and lithologic profiling with surface resistivity and seismic tomography

    SciTech Connect

    Watson, David B; Doll, William E.; Gamey, Jeff; Sheehan, Jacob R; Jardine, Philip M

    2005-03-01

    Improved surface-based geophysical technologies that are commercially available provide a new level of detail that can be used to guide ground water remediation. Surface-based multielectrode resistivity methods and tomographic seismic refraction techniques were used to image to a depth of approximately 30 m below the surface at the Natural and Accelerated Bioremediation Research Field Research Center. The U.S. Department of Energy (DOE) established the research center on the DOE Oak Ridge Reservation in Oak Ridge, Tennessee, to conduct in situ field-scale studies on bioremediation of metals and radionuclides. Bioremediation studies are being conducted on the saprolite, shale bedrock, and ground water at the site that have been contaminated with nitrate, uranium, technetium, tetrachloroethylene, and other contaminants (U.S. DOE 1997). Geophysical methods were effective in imaging the high-ionic strength plume and in defining the transition zone between saprolite and bedrock zones that appears to have a significant influence on contaminant transport. The geophysical data were used to help select the location and depth of investigation for field research plots. Drilling, borehole geophysics, and ground water sampling were used to verify the surface geophysical studies.

  4. Electrical contact resistance degradation of a hot-switched simulated metal MEMS contact.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2005-03-01

    Electrical contact resistance testing was performed by hot-switching a simulated gold-platinum metal microelectromechanical systems contact. The experimental objective was to determine the sensitivity of the contact resistance degradation to current level and environment. The contact resistance increased sharply after 100 hot-switched cycles in air. Hot-switching at a reduced current and in nitrogen atmosphere curtailed contact resistance degradation by several orders of magnitude. The mechanism responsible for the resistance degradation was found to be arc-induced decomposition of adsorbed surface contaminants.

  5. Electrical Resistivity of Natural Diamond and Diamond Films Between Room Temperature and 1200 C: Status Update

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W.; Zoltan, L. D.

    1993-01-01

    The electrical resistivity of diamond films has been measured between room temperature and 1200 C. The films were grown by either microwave Plasma CVD or combustion flame at three different places. The resistivities of the current films are compared to those measured for both natural IIa diamond and films grown only one to two years ago.

  6. Antibiotic resistance and plasmid profiling of Vibrio spp. in tropical waters of Peninsular Malaysia.

    PubMed

    You, K G; Bong, C W; Lee, C W

    2016-03-01

    Vibrio species isolated from four different sampling stations in the west coast of Peninsular Malaysia were screened for their antimicrobial resistance and plasmid profiles. A total of 138 isolates belonging to 15 different species were identified. Vibrio campbellii, V. parahaemolyticus, V. harveyi, and V. tubiashii were found to predominance species at all stations. High incidence of erythromycin, ampicillin, and mecillinam resistance was observed among the Vibrio isolates. In contrast, resistance against aztreonam, cefepime, streptomycin, sulfamethoxazole, and sulfonamides was low. All the Vibrio isolates in this study were found to be susceptible to imipenem, norfloxacin, ofloxacin, chloramphenicol, trimethoprim/sulfamethoxazole, and oxytetracycline. Ninety-five percent of the Vibrio isolates were resistant to one or more different classes of antibiotic, and 20 different resistance antibiograms were identified. Thirty-two distinct plasmid profiles with molecular weight ranging from 2.2 to 24.8 kb were detected among the resistance isolates. This study showed that multidrug-resistant Vibrio spp. were common in the aquatic environments of west coast of Peninsular Malaysia. PMID:26884358

  7. PREDOMINANT PROPERTIES AFFECTING PROFILE SOIL ELECTRICAL CONDUCTIVITY IN THE US MIDWEST

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercially available sensors for measuring apparent profile soil electrical conductivity (ECa) can provide an indirect indication of a number of soil physical and chemical properties helpful in characterizing within-field variability for precision agriculture. The objective of this research was to...

  8. Development of an angular scanning system for sensing vertical profiles of soil electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (EC**a**) is typically mapped to define soil spatial variability within an agricultural field. Knowledge of the vertical variability of EC**a** is desired to define site-specific behavior of the soil profile. A Pneumatic Angular Scanning System (PASS) was develo...

  9. Silicone oil contamination and electrical contact resistance degradation of low-force gold contacts.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2006-02-01

    Hot-switched low-force gold electrical contact testing was performed using a nanomechanical test apparatus to ascertain the sensitivity of simulated microelectromechanical systems (MEMS) contact to silicone oil contamination. The observed cyclic contact resistance degradation was dependent on both closure rate and noncontact applied voltage. The decomposition of silicone oil from electrical arcing was hypothesized as the degradation mechanism.

  10. Profiling cognitive impairment in treatment-resistant schizophrenia patients.

    PubMed

    Frydecka, Dorota; Beszłej, Jan Aleksander; Gościmski, Piotr; Kiejna, Andrzej; Misiak, Błażej

    2016-01-30

    The aim of this study was to compare cognitive performance between schizophrenia patients with and without treatment resistance (TRS and non-TRS patients) taking into account psychopathological symptoms and antipsychotic treatment. The following cognitive tests were administered to 53 TRS patients and 32 non-TRS subjects: Rey Auditory Verbal Learning Test (RAVLT), Trail Making Tests (TMT-A and TMT-B), verbal fluency tests (FAS test and Supermarket), as well as selected Wechsler Adults Intelligence Scale (WAIS-R-PI) subtests: Digit Symbol Coding Test, Digit Span Forward and Backward and Similarities. TRS patients performed significantly worse in comparison with non-TRS patients on the measures of processing speed (TMT-A, Stroop test, FAS test, Supermarket test, Digit Symbol Coding test), verbal fluency (FAS test, Supermarket test), cognitive flexibility and executive functions (Stroop test) after controlling for age, illness duration, clinical symptoms severity, the number of years of completed education and antipsychotics' dose. Cognitive performance was associated with negative and general symptomatology. Anticholinergic activity of antipsychotics had debilitating effect on cognitive functioning in non-TRS patients (FAS test) and in TRS patients (TMT-B test, Stroop test, RAVLT subtests, Digit Coding test and Similarities test), while low anticholinergic activity of antipsychotics was associated with better cognitive performance in non-TRS patients (Backward Digit Span test) and in TRS patients (Similarities test). Results of this study indicate that cognitive deficits are more robust in TRS patients than in non-TRS subjects, and are associated with clinical symptoms as well as the treatment with antipsychotics that exert high anticholinergic activity. PMID:26706131

  11. Gene Expression Profiling Analysis of Castration-Resistant Prostate Cancer

    PubMed Central

    Wang, Xuelei; Wen, Jiling; Li, Rongbing; Qiu, Guangming; Zhou, Lan; Wen, Xiaofei

    2015-01-01

    Background Prostate cancer is a global health issue. Usually, men with metastatic disease will progress to castration-resistant prostate cancer (CRPC). We aimed to identify the differentially expressed genes (DEGs) in tumor samples from non-castrated and castrated men from LNCaP Orthotopic xenograft models of prostate cancer and to study the mechanisms of CRPC. Material/Methods In this work, GSE46218 containing 4 samples from non-castrated men and 4 samples from castrated men was downloaded from Gene Expression Omnibus. We identified DEGs using limma Geoquery in R, the Robust Multi-array Average (RMA) method in Bioconductor, and Bias methods, followed by constructing an integrated regulatory network involving DEGs, miRNAs, and TFs using Cytoscape. Then, we analyzed network motifs of the integrated gene regulatory network using FANMOD. We selected regulatory modules corresponding to network motifs from the integrated regulatory network by Perl script. We preformed gene ontology (GO) and pathway enrichment analysis of DEGs in the regulatory modules using DAVID. Results We identified total 443 DEGs. We built an integrated regulatory network, found three motifs (motif 1, motif 2 and motif 3), and got two function modules (module 1 corresponded to motif 1, and module 2 corresponded to motif 2). Several GO terms (such as regulation of cell proliferation, positive regulation of macromolecule metabolic process, phosphorylation, and phosphorus metabolic process) and two pathways (pathway in cancer and Melanoma) were enriched. Furthermore, some significant DEGs (such as CAV1, LYN, FGFR3 and FGFR3) were related to CPRC development. Conclusions These genes might play important roles in the development and progression of CRPC. PMID:25592164

  12. Insecticide resistance profiles and synergism in field populations of the German cockroach (Dictyoptera: Blattellidae) from Singapore.

    PubMed

    Chai, Ru-Yuan; Lee, Chow-Yang

    2010-04-01

    The resistance profiles of 22 field-collected populations of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), from various localities in Singapore were determined by topical bioassay against novel and conventional insecticides from six classes: (1) pyrethroid (beta-cyfluthrin, deltamethrin), (2) carbamate (propoxur), (3) organophosphate (chlorpyrifos), (4) phenyl pyrazole (fipronil), (5) neonicotinoid (imidacloprid), and (6) oxadiazine (indoxacarb). Compared with a laboratory susceptible strain, resistance levels ranged from 3.0 to 468.0x for the pyrethroids, from 3.9 to 21.5x for the carbamate, from 1.5 to 22.8X for the organophosphate, from 1.0 to 10.0X for phenyl pyrazole, and were absent or low for the neonicotinoid (0.8-3.8x) and the oxadiazine (1.4-5.3x). One strain demonstrated broad-spectrum resistance to most of the insecticides. Synergism studies using piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) in combination with a discriminating dose (LD99) of selected insecticides were conducted to test for possible resistance mechanisms. Resistance to pyrethroid was reduced with PBO and DEF, suggesting the involvement of P450 monooxygenase and esterases in conferring resistance. Propoxur resistance also was suppressed with PBO and DEF, and coadministration of both synergists resulted in complete negation of the resistance, indicating the involvement of both P450 monooxygenase and esterase. In six B. germanica field strains evaluated, esterases were found to play a role in chlorpyrifos resistance, whereas the P450 monoxygenase involvement was registered in three strains. Additional resistance mechanisms such as kdr-type and Rdl mutation contributing toward pyrethroid and fipronil resistance, respectively, also may be involved in some strains in which the resistance levels were not affected by the synergists. We conclude that insecticide resistance is prevalent in field German cockroach populations in Singapore. PMID

  13. Electrical resistance of human soft tissue sarcomas: an ex vivo study on surgical specimens.

    PubMed

    Campana, L G; Cesari, M; Dughiero, F; Forzan, M; Rastrelli, M; Rossi, C R; Sieni, E; Tosi, A L

    2016-05-01

    This paper presents a study about electrical resistance, which using fixed electrode geometry could be correlated to the tissue resistivity, of different histological types of human soft tissue sarcomas measured during electroporation. The same voltage pulse sequence was applied to the tumor mass shortly after surgical resection by means of a voltage pulse generator currently used in clinical practice for electrochemotherapy that uses reversible electroporation. The voltage pulses were applied by means of a standard hexagonal electrode composed by seven, 20-mm-long equispaced needles. Irrespective of tumor size, the electrode applies electric pulses to the same volume of tissue. The resistance value was computed from the voltage and current recorded by the pulse generator, and it was correlated with the histological characteristics of the tumor tissue which was assessed by a dedicated pathologist. Some differences in resistance values, which could be correlated to a difference in tissue resistivity, were noticed according to sarcoma histotype. Lipomatous tumors (i.e., those rich in adipose tissue) displayed the highest resistance values (up to 1700 Ω), whereas in the other soft tissue sarcomas, such as those originating from muscle, nerve sheath, or fibrous tissue, the electrical resistance measured was between 40 and 110 Ω. A variability in resistance was found also within the same histotype. Among lipomatous tumors, the presence of myxoid tissue between adipocytes reduced the electrical resistance (e.g., 50-100 Ω). This work represents the first step in order to explore the difference in tissue electrical properties of STS. These results may be used to verify whether tuning electric field intensity according to the specific STS histotype could improve tissue electroporation and ultimately treatment efficacy. PMID:26324245

  14. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, W.D.; Laine, D.L.; Laine, E.F.

    1997-08-26

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution. 6 figs.

  15. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, William D.; Laine, Daren L.; Laine, Edwin F.

    2001-01-01

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner or between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid through the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.

  16. Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques

    DOEpatents

    Daily, William D.; Laine, Daren L.; Laine, Edwin F.

    1997-01-01

    Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.

  17. Heavy metal resistance and virulence profile in Pseudomonas aeruginosa isolated from Brazilian soils.

    PubMed

    Pitondo-Silva, André; Gonçalves, Guilherme Bartolomeu; Stehling, Eliana Guedes

    2016-08-01

    Pseudomonas aeruginosa is an opportunistic pathogen, which can have several virulence factors that confer on it the ability to cause severe, acute and chronic infections. Thus, the simultaneous occurrence of resistance to antibiotics and heavy metals associated with the presence of virulence genes is a potential threat to human health and environmental balance. This study aimed to investigate the resistance profile to heavy metals and the correlation of this phenotype of resistance to antimicrobials and to investigate the pathogenic potential of 46 P. aeruginosa isolates obtained from the soil of five Brazilian regions. The bacteria were evaluating for antimicrobial and heavy metal resistance, as well as the presence of plasmids and virulence genes. The isolates showed resistance to four different antibiotics and the majority (n = 44) had resistance to aztreonam or ticarcillin, furthermore, 32 isolates showed concomitant resistance to both of these antibiotics. A high prevalence of virulence genes was found, which highlights the pathogenic potential of the studied environmental isolates. Moreover, a high frequency of heavy metal resistance genes was also detected, however, the phenotypic results indicated that other genes and/or mechanisms should be related to heavy metal resistance. PMID:27197940

  18. Contribution of 3D inversion of Electrical Resistivity Tomography data applied to volcanic structures

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2016-04-01

    The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out

  19. Modeling the electrical resistance of gold film conductors on uniaxially stretched elastomeric substrates

    NASA Astrophysics Data System (ADS)

    Cao, Wenzhe; Görrn, Patrick; Wagner, Sigurd

    2011-05-01

    The electrical resistance of gold film conductors on polydimethyl siloxane substrates at stages of uniaxial stretching is measured and modeled. The surface area of a gold conductor is assumed constant during stretching so that the exposed substrate takes up all strain. Sheet resistances are calculated from frames of scanning electron micrographs by numerically solving for the electrical potentials of all pixels in a frame. These sheet resistances agree sufficiently well with values measured on the same conductors to give credence to the model of a stretchable network of gold links defined by microcracks.

  20. Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

    SciTech Connect

    Faraby, H.; DiBattista, M.; Bandaru, P. R.

    2014-04-28

    Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

  1. Electrical Resistance of Ceramic Matrix Composites for Damage Detection and Life-Prediction

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

    2008-01-01

    The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection or inspection of a component during "down time". The correlation of damage with appropriate failure mechanism can then be applied to accurate life prediction for high-temperature ceramic matrix composites.

  2. Polyphenolic Profile of Pear Leaves with Different Resistance to Pear Psylla (Cacopsylla pyri).

    PubMed

    Fotirić Akšić, Milica M; Dabić, Dragana Č; Gašić, Uroš M; Zec, Gordan N; Vulić, Todor B; Tešić, Živoslav Lj; Natić, Maja M

    2015-09-01

    The European pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the most serious arthropod pests of pear. Since proper control of this pest is essential, better understanding of the complex plant-pest relationship is mandatory. This research deals with constitutive polyphenolic profiles in leaves of 22 pear cultivars of diverse origin (P. communis, P. pyrifolia, and P. pyrifolia × P. communis) and different resistance to psylla. The study was designed to show which differences in the polyphenolic profile of leaves from resistant and susceptible pear cultivars could be utilized as information in subsequent breeding programs. The results demonstrated that the leaves of Oriental pear cultivars contained much higher amounts of p-hydroxybenzoic acid, ferulic acid, aesculin, and naringin, that, together with detected 3-O-(6″-O-p-coumaroyl)-hexoside, apigenin, apigenin 7-O-rutinoside, and hispidulin, indicated a clear difference between the species and might represent phenolics responsible for psylla resistance. PMID:26278376

  3. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites.

    PubMed

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-12-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.It is established that the changes of the relative intensities of the bands in FTIR spectra indicate the destruction of the carboxyl group -COOH and group -OH. Electrical conductivity of composites has percolation character and graphite nanoplatelets (ultraviolet ozone treatment for 20 min) addition which leads to a decrease of percolation threshold 0.005 volume fraction and increase values of electrical conductivity (by 2-3 orders of magnitude) above the percolation threshold in comparison with composite materials-graphite nanoplatelets/epoxy resin. The changes of the value and behavior of temperature dependences of the electrical resistivity of epoxy composites with ultraviolet/ozone-treated graphite nanoparticles have been analyzed within the model of effective electrical conductivity. The model takes into account the own electrical conductivity of the filler and the value of contact electric resistance between the filler particles of the formation of continuous conductive pathways. PMID:27550050

  4. Resistance profile and risk factors of drug resistant tuberculosis in the Baltic countries.

    PubMed

    Ignatyeva, Olga; Balabanova, Yanina; Nikolayevskyy, Vladyslav; Koshkarova, Ekaterina; Radiulyte, Birute; Davidaviciene, Edita; Riekstina, Vija; Jaama, Kadri; Danilovits, Manfred; Popa, Cristina M; Drobniewski, Francis A

    2015-09-01

    The rates of multi- and extensively drug-resistant tuberculosis (X/MDRTB) in the Baltic countries are the highest within the European Union hampering recent achievements of national TB control programmes. We included all consecutive culture-confirmed X/MDRTB patients registered for treatment in 2009 in Latvia, Lithuania and Estonia into this multicenter case-control study. Cases were compared with randomly selected controls with non-MDRTB registered for treatment in the same year across these sites. Of 495 MDRTB patients, 243 (49.7%) showed resistance to at least one second-line drug, 206 (42.1%) had pre-XDRTB (i.e. MDRTB with additional resistance to a second-line injectable or fluoroquinolones) and 64 (13.1%) had XDRTB. Younger age, male gender and known contact with an MDRTB case were associated with increased risk of primary infection with X/MDRTB strains. Previous treatment and alcohol abuse were strong predictors for MDRTB acquisition; defaults and failures in the past triggered XDRTB development. All patients received appropriate therapy; less than half of the patients were fully adherent. An erroneous treatment strategy is unlikely to drive resistance development. Increasing patients' compliance, addressing issues of social support, rapid detection of drug resistance and improving infection control is crucial for prevention of further spread of X/MDRTB and achieving higher cure rates. PMID:26164355

  5. Resistance and internal electric field in cloud-to-ground lightning channel

    SciTech Connect

    Cen, Jianyong; Yuan, Ping Xue, Simin; Wang, Xuejuan

    2015-02-02

    Cloud-to-ground lightning with six return strokes has been recorded by slitless spectrograph and the system of fast antenna and slow antenna. The physical parameters of the discharge channel have been obtained based on the combination of spectra and synchronous radiated electric field. The resistance and internal electric field of the channel are studied as the focus in this paper. The results show that the resistances per unit length of the lightning channel are in the order of 10{sup −2}–10{sup −1 }Ω/m and the internal electric field strengths are in the order of 10{sup 3 }V/m.

  6. Electrical resistance of CNT-PEEK composites under compression at different temperatures

    PubMed Central

    2011-01-01

    Electrically conductive polymers reinforced with carbon nanotubes (CNTs) have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10%) of multiwalled CNTs and polyether ether ketone (PEEK) were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure. PMID:21711952

  7. Relating permeability and electrical resistivity in fractures using random resistor network models

    NASA Astrophysics Data System (ADS)

    Kirkby, Alison; Heinson, Graham; Krieger, Lars

    2016-03-01

    We use random resistor network models to explore the relationship between electrical resistivity and permeability in a fracture filled with an electrically conductive fluid. Fluid flow and current are controlled by both the distribution and the volume of pore space. Therefore, the aperture distribution of fractures must be accurately modeled in order to realistically represent their hydraulic and electrical properties. We have constructed fracture surface pairs based on characteristics measured on rock samples. We use these to construct resistor networks with variable hydraulic and electrical resistance in order to investigate the changes in both properties as a fault is opened. At small apertures, electrical conductivity and permeability increase moderately with aperture until the fault reaches its percolation threshold. Above this point, the permeability increases by 4 orders of magnitude over a change in mean aperture of less than 0.1 mm, while the resistivity decreases by up to a factor of 10 over this aperture change. Because permeability increases at a greater rate than matrix to fracture resistivity ratio, the percolation threshold can also be defined in terms of the matrix to fracture resistivity ratio, M. The value of M at the percolation threshold, MPT, varies with the ratio of rock to fluid resistivity, the fault spacing, and the fault offset. However, MPT is almost always less than 10. Greater M values are associated with fractures above their percolation threshold. Therefore, if such M values are observed over fluid-filled fractures, it is likely that they are open for fluid flow.

  8. Cross-section electrical resistance tomography of La Soufrière of Guadeloupe lava dome

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Grychtol, Bartłomiej; Gibert, Dominique; Komorowski, Jean-Christophe; Adler, Andy

    2014-06-01

    The electrical resistivity distribution at the base of La Soufrière of Guadeloupe lava dome is reconstructed by using transmission electrical resistivity data obtained by injecting an electrical current between two electrodes located on opposite sides of the volcano. Several pairs of injection electrodes are used in order to constitute a data set spanning the whole range of azimuths, and the electrical potential is measured along a cable covering an angular sector of ≈120° along the basis of the dome. The data are inverted to perform a slice electrical resistivity tomography (SERT) with specific functions implemented in the EIDORS open source package dedicated to electrical impedance tomography applied to medicine and geophysics. The resulting image shows the presence of highly conductive regions separated by resistive ridges. The conductive regions correspond to unconsolidated material saturated by hydrothermal fluids. Two of them are associated with partial flank collapses and may represent large reservoirs that could have played an important role during past eruptive events. The resistive ridges may represent massive andesite and are expected to constitute hydraulic barriers.

  9. Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia.

    NASA Astrophysics Data System (ADS)

    Kvon, Dina; Vladimir, Shevnin; Boris, Nikulin; Albert, Ryjov; Alexey, Skobelev

    2013-04-01

    Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia. Kvon D. A.(1)*, Shevnin V.A.(1), Nikulin B. A.(1), Ryjov A. A.(2), Skobelev A. O.(1) (1)Geophysical dept., Faculty of Geology, Moscow state university; (2)VSEGINGEO Due to acute shortage of fresh drinking water near Anapa town (not far from the Black Sea), geophysical investigations were performed for searching and mapping aquifers in the area, where, according to rare wells exist probability to find fresh underground water. Geophysical explorations were carried out by Electrical resistivity tomography (ERT) method and water resistivity measurements. The resistivity of fresh groundwater is 15 Ohm.m, its salinity is 0.4 g/l. The structure of the area has been obtained by previous geological and hydrogeological studies and boreholes drilling. Geological structure of the area consists of two parts: the upper part of cross-section presented by loose lacustrine-alluvial sediments of Upper Pleistocene - Holocene, the lower part presented by hard rocs of carbonate-flysch formation of Upper Cretaceous age consisted of marl and limestone. Prospective areas to find underground water are: water-bearing horizon of upper Pleistocene-Holocene sediments, which is presented by gravel layer (base layer of modern lacustrine-alluvial sediments), and fractured zones in hard rocks of the carbonate-flysch formation of Maastricht age (Supseh formation). Analysis of rocks' resistivity obtained from Electrical resistivity tomography followed by calculation of rock resistivity on known petrophysical parameters (in Petrowin program created by A. A. Ryjov) [Shevnin et al., 2007]. The calculation showed that there is low clay content in carbonate rocks of the studied area, and the rock is limestone, not marl. Measurement of rock samples with X-ray radiometric method showed high calcium content (30-35%) or 75-87.5% limestone. This fact shows that flysch formation of the area is mainly

  10. Design and performance of low-thermal-resistance, high-electrical-isolation heat intercept connections

    NASA Astrophysics Data System (ADS)

    Niemann, R. C.; Gonczy, J. D.; Phelan, P. E.; Nicol, T. H.

    Electrical conductors often require the removal of heat produced by normal operation. The heat can be removed by mechanical connection of the conductor to a refrigeration source. Such connections require both effective heat removal (low thermal resistance) and effective electrical isolation (high electrical resistance and high dielectric strength). Fabrication of these connections should be straightforward, and performance must be reliable and independent of operating temperature. The connection method described here involves clamping (by thermal interference fit) an electrically insulating cylinder between an outer metallic ring and an inner metallic disc. Material candidates for insulating cylinders include composites, e.g. epoxy/fibreglass, and ceramics, e.g. alumina. Design factors, including geometry, materials and thermal contact resistance are discussed. The design, construction experience and performance measurements of a heat intercept connection in a high-temperature superconducting lead assembly is presented.

  11. Negative resist profiles in 248 nm photolithography: experiment, modelling and simulation

    NASA Astrophysics Data System (ADS)

    Karafyllidis, I.; Hagouel, P. I.; Neureuther, A. R.

    1998-06-01

    We consider the effects both of exposure energy dose and of developer temperature on the developed negative resist profiles. The spin-formatted resist film tends to have macromolecules oriented parallel to the substrate surface. The orientation of the resist macromolecules introduces an anisotropic component to the etch rate: higher in the direction parallel to the substrate surface and lower in the perpendicular one. We performed a series of experiments for 400 nm pitch periodic and isolated lines on Shipley SNR-248 negative resist coated Si wafers using a stepper and a deep UV source at 248 nm. We obtained scanning electron micrographs for various developer temperatures and exposure doses. The variation of the lateral etch rate manifested itself in sidewall profile slopes. We used Dill's ABC parameter model to model and quantify the exposure, and cellular automata to model the resist cross-linking during post-exposure bake and the resist etching. Simulation using an algorithm based on this model validated the experimental results.

  12. High definition cross-well electrical resistivity imaging using seismoelectric focusing and image-guided inversion

    NASA Astrophysics Data System (ADS)

    Sava, P.; Revil, A.; Karaoulis, M.

    2014-08-01

    We propose a new, simple and efficient method to image electrical resistivity between a set of wells. Our procedure consists of two steps: first, we map the interfaces between various subsurface formations using seismoelectric conversions; second, we derive the formation resistivity using image-guided cross-well electric tomography. In the first step, we focus seismic energy at a set of points located on a regular grid between wells, which enables us to map the geological formations in terms of heterogeneities in electrical, hydraulic and/or seismic properties. The density of the scanning points (i.e. the seismoelectric image resolution) is related to the wavelength of the seismic impulse used to scan the formations. Each time the seismic energy is focused at a point, the resulting electrical potential burst (equivalent to the one generated by a volumetric seismic source) is recorded remotely at a set of electrodes positioned in wells (the reference electrode can be located on the ground surface or far enough to be considered at infinity). We construct a high-resolution `seismoelectric' image by assigning the electrical potential simulated at these fixed electrodes to the location of the seismic focus. In a follow-up step, the structure of this image is used in image-guided inversion to improve electrical resistivity tomography between the two wells. The structural information from the seismoelectric image is used to impose constraints on the model covariance matrix used in the inversion of the electrical resistivity data. This approach offers new perspectives in recovering fine structure of resistivity (high definition resistivity tomography) between the wells, which cannot be resolved through conventional cross-well resistivity or from seismic tomography alone.

  13. Thermal treatment of low permeability soils using electrical resistance heating

    SciTech Connect

    Udell, K.S.

    1996-08-01

    The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground water temperature. Electrical heating with AC current is one method of increasing the soil and groundwater temperature and has particular applicability to low permeability soils. Several mechanisms have been identified that account for the enhanced removal of the contaminants during electrical heating. These are vaporization of liquid contaminants with low boiling points, temperature-enhanced evaporation rates of semi-volatile components, and removal of residual contaminants by the boiling of residual water. Field scale studies of electrical heating and fluid extraction show the effectiveness of this technique and its applicability to contaminants found both above and below the water table and within low permeability soils. 10 refs., 8 figs.

  14. Unconventional drop in the electrical resistance of chromium metal thin films at low temperature

    NASA Astrophysics Data System (ADS)

    Ohashi, M.; Ohashi, K.; Sawabu, M.; Miyagawa, M.; Kubota, T.; Takanashi, K.

    2016-09-01

    We studied the electrical resistance of single-crystal and polycrystalline chromium films. The ρ (T) curve of single-crystal films decrease with decreasing temperature and show humps at around 300 K consistent with the bulk chromium being an itinerant antiferromagnet. In the polycrystalline films, on the other hand, the ρ (T) curves deviate from those of the bulk chromium. Moreover, we observed sudden decrease in the resistance around 1.5 K. Although previous studies suggested that chromium films become superconductive (Schmidt et al. (1972) [12]), it is difficult to conclude whether a superconducting transition occurs because the electrical resistivity is not zero in all films. No anomaly was detected by resistance measurements around room temperature, and the sudden decrease in the resistance at low temperature may be attributed to the suppression of antiferromagnetic interaction by thinning down the chromium element.

  15. Three-dimensional electrical resistivity image of the South-Central Chilean subduction zone

    NASA Astrophysics Data System (ADS)

    Kapinos, Gerhard; Montahaei, Mansoureh; Meqbel, Naser; Brasse, Heinrich

    2016-01-01

    Based on isotropic 3-D inversion, we re-interpret long-period magnetotelluric data collected across the geotectonic structures of the South-Central Chilean continental margin at latitudes 38°-41°S and summarize results of long-period magnetotelluric (MT) investigations performed between 2000 and 2005. The new 3-D conductivity image of the South-Central Chilean subduction zone basically confirms former 2-D inversion models along three profiles and complete the previous results. The models show good electrical conductors in the tip of the continental crustal beneath the Pacific Ocean, the frequently observed forearc conductor at mid-crustal levels, a highly-conductive zone at similar levels slightly offset from the volcanic arc and a - not well-resolved - conductor in the Argentinian backarc. The subducted Nazca Plate generally appears as a resistive but discontinuous feature. Unlike before, we are now able to resolve upper crustal conductors (interpreted as magma reservoirs) beneath active Lonquimay, Villarrica, and Llaima volcanoes which were obscured in 2-D inversion. Data fit is rather satisfactory but not perfect; we attribute this to large-scale crustal anisotropy particularly beneath the Coastal Cordillera, which we cannot include into our solution for the time being.

  16. Identifying the changes of geo-engineering properties of dunites due to weathering utilizing electrical resistivity tomography (ERT)

    NASA Astrophysics Data System (ADS)

    Ündül, Ömer; Tuğrul, Atiye; Özyalın, Şenol; Halil Zarif, İ.

    2015-04-01

    Weathering phenomena have an important role in many construction facilities with varying depths and grades. Due to the anisotropic and heterogeneous nature of weathering profiles of some rocks, uncertainities exist in determining the geo-engineering properties. Geo-electrical studies have been utilized to overcome such uncertainities for various subsurface conditions including the determination of boundaries between weathered and unweathered parts of different rock types. In this study, the electrical resistivity tomography (ERT) results were correlated with conventional methods in determining the effects of weathering on the geo-engineering properties of dunites. During the research, weathering grades were determined by field studies including discontinuity spacings, aperture and properties of fill materials. The detailed petrographical studies, determination of petrophysical properties (e.g. water absorption and effective porosity) and mechanical properties (e.g. unconfined compressive strength (UCS)) constitute the laboratory studies. ERT studies were carried out in a row of sixty electrodes with electrode spacings of 0.5 m utilizing a Wenner-Schlumberger configuration. According to the comparison of the inversion model sections with the weathering profiles obtained by field and laboratory studies it is concluded that the use of ERT with a Wenner-Schlumberger configuration supplies comparable data for wider subsurface areas from the view of weathering and its effect on geo-engineering properties of dunites. In addition, ERT techniques are very useful where conventional techniques are inadequate in determining the full weathering profile.

  17. Electrical resistivity cross-section across the Garhwal Himalaya: Proxy to fluid-seismicity linkage

    NASA Astrophysics Data System (ADS)

    Rawat, Gautam; Arora, B. R.; Gupta, P. K.

    2014-12-01

    Magnetotelluric (MT) measurements along a profile cutting across the Garhwal Himalaya of India are inverted to obtain 2-D electrical resistivity structures of the Himalayan wedge and of the underthrusting Indian plate. The imaged resistivity cross-section is dominated by a low-angle north-east dipping intra-crustal high conducting layer (IC-HCL) with an average thickness of 5 km. At transition from the Lesser Himalaya to the Higher Himalaya, the IC-HCL is marked by a ramp structure across which its top jumps from a depth of 8 km to 13 km. High conductivity of the layer is caused by pounding of upward propagating metamorphic fluids trapped by tectonically induced neutral buoyancy. In compression regime of the Himalaya, the mechanical weakening effects of the fluids counteract the fault-normal stresses, thereby facilitating thrust-type earthquakes on a plane imaged as the top of the IC-HCL. It is suggested that in the Himalaya collision belt, like the active subduction zone, the active seismic plane forming seat of large and great earthquakes is located a few kilometers above the top of the down-going plate. In this tectonic setting, the high conductance ramp symbolizes a block of low shear strength and high strain, which under the deviatoric stresses release accentuated stresses into the brittle crust, thereby generating small but more frequent earthquakes in the narrow Himalayan Seismic Belt. In response to either the co-seismic pumping or the stress transfer during inter-seismic period, the upward infiltration of fluid fluxes into the over pressurized zones sufficiently reduces the shear strength of local thrusts and shear zones, turning these into locales of concentrated seismicity.

  18. The combined effect of electrical stimulation and resistance isometric contraction on muscle atrophy in rat tibialis anterior muscle.

    PubMed

    Fujita, Naoto; Murakami, Shinichiro; Arakawa, Takamitsu; Miki, Akinori; Fujino, Hidemi

    2011-05-01

    Electrical stimulation has been used to prevent muscle atrophy, but this method is different in many previous studies, appropriate stimulation protocol is still not decided. Although resistance exercise has also been shown to be an effective countermeasure on muscle atrophy, almost previous studies carried out an electrical stimulation without resistance. It was hypothesized that electrical stimulation without resistance is insufficient to contract skeletal muscle forcefully, and the combination of electrical stimulation and forceful resistance contraction is more effective than electrical stimulation without resistance to attenuate muscle atrophy. This study investigated the combined effects of electrical stimulation and resistance isometric contraction on muscle atrophy in the rat tibialis anterior muscle. The animals were divided into control, hindlimb unloading (HU), hindlimb unloading plus electrical stimulation (ES), and hindlimb unloading plus the combination of electrical stimulation and resistance isometric contraction (ES+IC). Electrical stimulation was applied to the tibialis anterior muscle percutaneously for total 240 sec per day. In the ES+IC group, the ankle joint was fixed to produce resistance isometric contraction during electrical stimulation. After 7 days, the cross-sectional areas of each muscle fiber type in the HU group decreased. Those were prevented in the ES+IC group rather than the ES group. The expression of heat shock protein 72 was enhanced in the ES and ES+IC groups. These results indicated that although electrical stimulation is effective to prevent muscle atrophy, the combination of electrical stimulation and isometric contraction have further effect. PMID:21619551

  19. Simultaneous electrical resistivity and mass uptake measurements in bromine intercalated fibers

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.

    1986-01-01

    Changes in mass and electrical resistivity of several types of pitch-based and vapor-grown graphite fibers were monitored during reaction with bromine. The observed threshold pressure dependent reaction suggested that the fibers were intercalated. In the fully brominated compound, the mass was increased by 44 percent and the resistivity was improved by a factor of 17. In the residue compound, the mass was increased by 22 percent and the resistivity was improved by a factor of 5. Fibers possessing different degrees of graphitization had surprisingly similar changes in both mass and resistivity.

  20. Electrical resistivity imaging survey to detect uncharted mine galleries in the mining district of Linares, Jaén, Spain

    NASA Astrophysics Data System (ADS)

    Martínez-López, J.; Rey, J.; Dueñas, J.; Hidalgo, C.; Benavente, J.

    2012-02-01

    The scarcity of information about the existence of old mining shafts and galleries in urban areas is an important issue for future urban development. Electrical resistivity tomography is a non-destructive geophysical technique that can detect and characterize such subsurface cavities based on differences in the behaviour of electrical current in the void and in the embedding rock. Here we present a study in which this technique was used to determine the location of old engineered structures around the city of Linares, southern Spain, and to relate these structures to the abandoned deep mines present in the area. Eight electrical resistivity imaging profiles were performed, with a total of 22 808 measurements. Correlations between geoelectrical anomalies allow detection of the depth and the direction of several galleries, as well as the voids that result from mining extraction. Given the depth at which these structures are located (in some cases less than 5 m), they pose an important risk for future construction projects in areas of urban expansion. This technique is shown to be a useful tool for locating areas that pose important urban risks and, by extension, for the decision-making process in territorial planning, especially in areas with a history of deep mining.

  1. Electrical resistivity tomography as monitoring tool for unsaturated zone transport: an example of preferential transport of deicing chemicals.

    PubMed

    Wehrer, Markus; Lissner, Heidi; Bloem, Esther; French, Helen; Totsche, Kai Uwe

    2014-01-01

    Non-invasive spatially resolved monitoring techniques may hold the key to observe heterogeneous flow and transport behavior of contaminants in soils. In this study, time-lapse electrical resistivity tomography (ERT) was employed during an infiltration experiment with deicing chemical in a small field lysimeter. Deicing chemicals like potassium formate, which frequently impact soils on airport sites, were infiltrated during snow melt. Chemical composition of seepage water and the electrical response was recorded over the spring period 2010. Time-lapse electrical resistivity tomographs are able to show the infiltration of the melt water loaded with ionic constituents of deicing chemicals and their degradation product hydrogen carbonate. The tomographs indicate early breakthrough behavior in parts of the profile. Groundtruthing with pore fluid conductivity and water content variations shows disagreement between expected and observed bulk conductivity. This was attributed to the different sampling volume of traditional methods and ERT due to a considerable fraction of immobile water in the soil. The results show that ERT can be used as a soil monitoring tool on airport sites if assisted by common soil monitoring techniques. PMID:24194415

  2. Time-lapse electrical resistivity tomography: a powerful tool for landslide monitoring?

    NASA Astrophysics Data System (ADS)

    Perrone, A.

    2011-12-01

    multichannel cable, 48 steel electrodes buried in the soil at a depth of about 0.5 m at a distance of 1 or 5 m; a TDR system linked to 4 probes 20 cm length, buried at different depths along the same profile of the geoelectrical one; while a weather station consists of a rain gauge to quantify the amount of rain falling on that area, one sensor to measure the temperature and another to determine the speed and direction of the wind. At the beginning the time-lapse ERT were analysed to verify the functionality and stability of the system and to decide the measurement time intervals. After that, the statistical analysis of the results obtained was performed with the aim to define the water content variation in the first layers of the subsoil, in particular in the vadose zone. The results were compared with the TDR ones and the piezometric measurements were performed in the area thanks to the presence of equipped boreholes. The correlation between the variation of the parameters measured (electrical resistivity, water content and piezometric level) and the rain-gauge measurements was also considered. The preliminary results seem to be encouraged also if the analysis of the data acquired on a longer period could better highlight the capability of the system.

  3. Experimental determination of the electrical resistivity of iron at Earth’s core conditions

    NASA Astrophysics Data System (ADS)

    Ohta, Kenji; Kuwayama, Yasuhiro; Hirose, Kei; Shimizu, Katsuya; Ohishi, Yasuo

    2016-06-01

    Earth continuously generates a dipole magnetic field in its convecting liquid outer core by a self-sustained dynamo action. Metallic iron is a dominant component of the outer core, so its electrical and thermal conductivity controls the dynamics and thermal evolution of Earth’s core. However, in spite of extensive research, the transport properties of iron under core conditions are still controversial. Since free electrons are a primary carrier of both electric current and heat, the electron scattering mechanism in iron under high pressure and temperature holds the key to understanding the transport properties of planetary cores. Here we measure the electrical resistivity (the reciprocal of electrical conductivity) of iron at the high temperatures (up to 4,500 kelvin) and pressures (megabars) of Earth’s core in a laser-heated diamond-anvil cell. The value measured for the resistivity of iron is even lower than the value extrapolated from high-pressure, low-temperature data using the Bloch–Grüneisen law, which considers only the electron–phonon scattering. This shows that the iron resistivity is strongly suppressed by the resistivity saturation effect at high temperatures. The low electrical resistivity of iron indicates the high thermal conductivity of Earth’s core, suggesting rapid core cooling and a young inner core less than 0.7 billion years old. Therefore, an abrupt increase in palaeomagnetic field intensity around 1.3 billion years ago may not be related to the birth of the inner core.

  4. Experimental determination of the electrical resistivity of iron at Earth's core conditions.

    PubMed

    Ohta, Kenji; Kuwayama, Yasuhiro; Hirose, Kei; Shimizu, Katsuya; Ohishi, Yasuo

    2016-06-01

    Earth continuously generates a dipole magnetic field in its convecting liquid outer core by a self-sustained dynamo action. Metallic iron is a dominant component of the outer core, so its electrical and thermal conductivity controls the dynamics and thermal evolution of Earth's core. However, in spite of extensive research, the transport properties of iron under core conditions are still controversial. Since free electrons are a primary carrier of both electric current and heat, the electron scattering mechanism in iron under high pressure and temperature holds the key to understanding the transport properties of planetary cores. Here we measure the electrical resistivity (the reciprocal of electrical conductivity) of iron at the high temperatures (up to 4,500 kelvin) and pressures (megabars) of Earth's core in a laser-heated diamond-anvil cell. The value measured for the resistivity of iron is even lower than the value extrapolated from high-pressure, low-temperature data using the Bloch-Grüneisen law, which considers only the electron-phonon scattering. This shows that the iron resistivity is strongly suppressed by the resistivity saturation effect at high temperatures. The low electrical resistivity of iron indicates the high thermal conductivity of Earth's core, suggesting rapid core cooling and a young inner core less than 0.7 billion years old. Therefore, an abrupt increase in palaeomagnetic field intensity around 1.3 billion years ago may not be related to the birth of the inner core. PMID:27251282

  5. Physical Modelling on Detecting Buried Object Using Electrical Resistivity Imaging (ERI)

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Nizam, Z. M.; Azhar, A. T. S.; Aziman, M.; Shaylinda, M. Z. N.

    2016-07-01

    This study focused on the evaluation of electrical resistivity method (ERM) for buried object detection and its relationship due to the different stiffness of material. In the past, the conventional method to detect the buried structure was face some limitation due to the time and cost. For example, previous approach related to the trial and error excavation has always expose to some risky outcome due to the uncertainties of the buried object location. Hence, this study introduced an alternative technique with particular reference to resistivity method to detect and evaluate the buried object with different strength of stiffness. The experiment was performed based on field miniature model (small scale study) using soil trial embankment made by lateritic soil and various concrete cube strengths (grade 20, 25 and 30) representing buried object with different conditions. 2D electrical resistivity test (electrical resistivity imaging) was perform using ABEM Terrameter SAS4000 during the data acquisition while the raw data was process using RES2DINV software. It was found that the electrical resistivity method was able to detect the buried concrete structures targeted based on the contrast of the electrical resistivity image produced. Moreover, three different strength of concrete cube were able to be differentiated based on the electrical resistivity values (ERV) obtained. This study found that the ERV of concrete cube for grade 20, 25 and 30 were 170 Ωm, 227 Ωm and 503 Ωm, respectively. Hence, this study shows that the ERV has a strong relationship with different stiffness of material thus applicable to be a useful alternative tool in underground structure detection.

  6. Molecular Characterization and Antimicrobial Resistance Profile of Methicillin-Resistant Staphylococcus aureus in Retail Chicken.

    PubMed

    Sallam, Khalid Ibrahim; Abd-Elghany, Samir Mohammed; Elhadidy, Mohamed; Tamura, Tomohiro

    2015-10-01

    The emergence of livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) in food-producing animals is of increasing interest, raising questions about the presence of MRSA in food of animal origin and potential sources of transmission to humans via the food chain. In this study, the prevalence, molecular characterization, virulence factors, and antimicrobial susceptibility patterns of MRSA isolates from 200 retail raw chicken samples in Egypt were determined. MRSA was detected by positive amplification of the mecA gene in 38% (76 of 200) of chicken samples analyzed. This represents a potential public health threat in Egypt, as this contamination rate seems to be the highest among other studies reported worldwide. Furthermore, genes encoding α-hemolysin (hla) and staphylococcal enterotoxins (sea, seb, and sec) were detected in all of the 288 MRSA isolates. Nonetheless, none of the strains tested carried tst, the gene encoding toxic shock syndrome toxin 1. Antimicrobial resistance of MRSA isolates was most frequently detected against penicillin (93.4%), ampicillin (88.9%), and cloxacillin (83.3%). These results suggest that retail chicken might be a significant potential source for transmission of multidrug-resistant and toxigenic S. aureus in Egypt. This underlines the need for stricter hygienic measures in chicken production in Egypt to minimize the risk of transmission of these strains to consumers. To the best of our knowledge, this is the first study that reports the isolation and molecular characterization of MRSA in retail chicken samples in Egypt. PMID:26408138

  7. PCR-based identification of methicillin-resistant Staphylococcus aureus strains and their antibiotic resistance profiles

    PubMed Central

    Pournajaf, Abazar; Ardebili, Abdollah; Goudarzi, Leyla; Khodabandeh, Mahmoud; Narimani, Tahmineh; Abbaszadeh, Hassan

    2014-01-01

    Objective To evaluated the PCR for mecA gene compared with the conventional oxacillin disk diffusion method for methicillin-resistant Staphylococcus aureus (S. aureus) identification. Methods A total of 292 S. aureus strains were isolated from various clinical specimens obtained from hospitalized patients. Susceptibility test to several antimicrobial agents was performed by disk diffusion agar according to Clinical and Laboratory Standards Institute guidelines. The PCR amplification of the mecA gene was carried out in all the clinical isolates. Results Among antibiotics used in our study, penicillin showed the least anti-staphylococcal activity and vancomycin was the most effective. The rate of methicillin-resistant S. aureus prevalence determined by oxacillin disk diffusion method was 47.6%; whereas, 45.1% of S. aureus isolates were mecA- positive in the PCR assay. Conclusions This study is suggestive that the PCR for detection of mecA gene is a fast, accurate and valuable diagnostic tool, particularly in hospitals in areas where methicillin-resistant S. aureus is endemic. PMID:25183100

  8. Permanent electrical resistivity measurements for monitoring water circulation in clayey landslides

    NASA Astrophysics Data System (ADS)

    Gance, J.; Malet, J.-P.; Supper, R.; Sailhac, P.; Ottowitz, D.; Jochum, B.

    2016-03-01

    Landslides developed on clay-rich slopes are controlled by the soil water regime and the groundwater circulation. Spatially-distributed and high frequency observations of these hydrological processes are important for improving our understanding and prediction of landslide triggering. This work presents observed changes in electrical resistivity monitored at the Super-Sauze clayey landslide with the GEOMON 4D resistivity instrument installed permanently on-site for a period of one year. A methodological framework for processing the raw measurement is proposed. It includes the filtering of the resistivity dataset, the correction of the effects of non-hydrological factors (sensitivity of the device, sensitivity to soil temperature and fluid conductivity, presence of fissures in the topsoil) on the filtered resistivity values. The interpretation is based on a statistical analysis to define possible relationships between the rainfall characteristics, the soil hydrological observations and the soil electrical resistivity response. During the monitoring period, no significant relationships between the electrical response and the measured hydrological parameters are evidenced. We discuss the limitations of the method due to the effect of heat exchange between the groundwater, the vadose zone water and the rainwater that hides the variations of resistivity due to variations of the soil water content. We demonstrate that despite the absence of hydrogeophysical information for the vadose zone, the sensitivity of electrical resistivity monitoring to temperature variations allows imaging water fluxes in the saturated zone and highlighting the existence of matrix and preferential flows that does not occur at the same time and for the same duration. We conclude on the necessity to combine electrical resistivity measurements with distributed soil temperature measurements.

  9. Studies on the drug resistance profile of Enterococcus faecium distributed from poultry retailers to hospitals.

    PubMed

    Limayem, Alya; Donofrio, Robert Scott; Zhang, Chao; Haller, Edward; Johnson, Michael G

    2015-01-01

    The multidrug resistant Enterococcus faecium (MEF) strains originating from farm animals are proliferating at a substantial pace to impact downstream food chains and could reach hospitals. This study was conducted to elucidate the drug susceptibility profile of MEF strains collected from poultry products in Ann Arbor, MI area and clinical settings from Michigan State Lab and Moffitt Cancer Center (MCC) in Florida. Presumptive positive Enterococcus isolates at species level were identified by Matrix Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) analysis. The antibiotic susceptibility profile for both poultry and clinical strains was determined by the Thermo Scientific's Sensititre conform to the National Committee for Clinical Laboratory Standards (NCCLS) and validated via quantitative real-time PCR (qPCR) methods. Out of 50 poultry samples (Turkey: n = 30; Chicken: n = 20), 36 samples were positive for Enterococcus species from which 20.83% were identified as E. faecium. All the E. faecium isolates were multidrug resistant and displayed resistance to the last alternative drug, quinupristin/dalfopristin (QD) used to treat vancomycin resistant E. faecium (VRE) in hospitals. Results indicate the presence of MEF strains in food animals and clinical settings that are also resistant to QD. PMID:26357893

  10. Extraction of semiconductor dopant profiles from spreading resistance data: An inverse problem

    NASA Astrophysics Data System (ADS)

    Choo, S. C.; Leong, M. S.; Liem, Chandra B. T.; Kong, K. C.

    1990-06-01

    The traditional method of solving, on a layer-by-layer basis, the inverse problem of extracting resistivity values from spreading resistance measurements is found to produce wildly oscillatory, physically unacceptable resistivity profiles in the case of p-type silicon structures, where a resistivity-dependent probe contact radius is used in conjunction with the probe calibration data. These oscillations are manifestations of the fact that the inverse problem has non-unique solutions; they occur because the problem is inherently ill-posed. The well-known Tikhonov regularisation technique, which converts the present set of highly non-linear integral equations to an equivalent variational problem, is applied to stabilise the solution. Tests are performed on a variety of simulated profiles, and they reveal the existence of an optimum value for the regularisation parameter that is to be used with a second difference expression for the stabiliser of the cost function. When applied to measured spreading resistance data, the technique is found to produce results of reconstruction that are stable and physically reasonable.

  11. River terrace sand and gravel deposit reserve estimation using three-dimensional electrical resistivity tomography for bedrock surface detection

    NASA Astrophysics Data System (ADS)

    Chambers, J. E.; Wilkinson, P. B.; Penn, S.; Meldrum, P. I.; Kuras, O.; Loke, M. H.; Gunn, D. A.

    2013-06-01

    We describe the application of 3D electrical resistivity tomography (ERT) to the characterisation and reserve estimation of an economic fluvial sand and gravel deposit. Due to the smoothness constraints used to regularise the inversion, it can be difficult to accurately determine the geometry of sharp interfaces. We have therefore considered two approaches to interface detection that we have applied to the 3D ERT results in an attempt to provide an accurate and objective assessment of the bedrock surface elevation. The first is a gradient-based approach, in which the steepest gradient of the vertical resistivity profile is assumed to correspond to the elevation of the mineral/bedrock interface. The second method uses an intrusive sample point to identify the interface resistivity at a location within the model, from which an iso-resistivity surface is identified that is assumed to define the interface. Validation of these methods has been achieved through direct comparison with observed bedrock surface elevations that were measured using real-time-kinematic GPS subsequent to the 3D ERT survey when quarrying exposed the bedrock surface. The gradient-based edge detector severely underestimated the depth to bedrock in this case, whereas the interface resistivity method produced bedrock surface elevations that were in close agreement with the GPS-derived surface. The failure of the gradient-based method is attributed to insufficient model sensitivity in the region of the bedrock surface, whereas the success of the interface resistivity method is a consequence of the homogeneity of the mineral and bedrock, resulting in a consistent interface resistivity. These results highlight the need for some intrusive data for model validation and for edge detection approaches to be chosen on the basis of local geological conditions.

  12. Changing antimicrobial resistance profiles among Neisseria gonorrhoeae isolates in Italy, 2003 to 2012.

    PubMed

    Carannante, Anna; Renna, Giovanna; Dal Conte, Ivano; Ghisetti, Valeria; Matteelli, Alberto; Prignano, Grazia; Impara, Giampaolo; Cusini, Marco; D'Antuono, Antonietta; Vocale, Caterina; Antonetti, Raffaele; Gaino, Marina; Busetti, Marina; Latino, Maria Agnese; Mencacci, Antonella; Bonanno, Carmen; Cava, Maria Carmela; Giraldi, Cristina; Stefanelli, Paola

    2014-10-01

    The emergence of Neisseria gonorrhoeae isolates displaying resistance to antimicrobial agents is a major public health concern and a serious issue related to the occurrence of further untreatable gonorrhea infections. A retrospective analysis on 1,430 N. gonorrhoeae isolates, collected from 2003 through 2012, for antimicrobial susceptibility by Etest and molecular characterization by Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) was carried out in Italy. Azithromycin-resistant gonococci decreased from 14% in 2007 to 2.2% in 2012. Similarly, isolates with high MICs to cefixime (>0.125 mg/liter) decreased from 11% in 2008 to 3.3% in 2012. The ciprofloxacin resistance rate remains quite stable, following an increasing trend up to 64% in 2012. The percentage of penicillinase-producing N. gonorrhoeae (PPNG) significantly declined from 77% in 2003 to 7% in 2012. A total of 81 multidrug-resistant (MDR) gonococci were identified, showing 11 different antimicrobial resistance patterns. These were isolated from men who have sex with men (MSM) and from heterosexual patients. Two sequence types (STs), ST661 and ST1407, were the most common. Genogroup 1407, which included cefixime-, ciprofloxacin-, and azithromycin-resistant isolates, was found. In conclusion, a change in the antimicrobial resistance profiles among gonococci was identified in Italy together with a percentage of MDR isolates. PMID:25070110

  13. Antimicrobial Resistance and Neisseria gonorrhoeae Multiantigen Sequence Typing Profile of Neisseria gonorrhoeae in New Delhi, India.

    PubMed

    Mahajan, Neeraj; Sood, Seema; Singh, Rajendra; Kapil, Arti; Das, Bimal Kumar; Sreenivas, Vishnubhatla; Kar, Hemanta Kumar; Sharma, Vinod Kumar

    2016-08-01

    Molecular epidemiology of 100 consecutive gonococcal isolates collected between April 2010 and October 2013 from New Delhi was investigated using Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) along with its association with antimicrobial resistance profiles. Neisseria gonorrhoeae isolates were assigned into 60 different sequence types and 43 (71.6%) were novel. Sole representation was seen in 76.6% sequence types. There was significant association between ST6058 and resistance to penicillin (P = 0.00) and tetracycline (P = 0.002). PMID:27414684

  14. The summit part of Mount Etna revealed by High Resolution DC Electrical Resistivity Tomography coupled with complementary geophysical and soil gas techniques

    NASA Astrophysics Data System (ADS)

    Finizola, Anthony; Ricci, Tullio; Antoine, Raphael; Delcher, Eric; Peltier, Aline; Bernard, Julien; Brothelande, Elodie; Fargier, Yannick; Fauchard, Cyrille; Foucart, Brice; Gailler, Lydie; Gusset, Rachel; Lazarte, Ivonne; Martin, Erwan; Mézon, Cécile; Portal, Angélie; Poret, Matthieu; Rossi, Matteo

    2016-04-01

    In the framework of the EC FP7 project "MEDiterranean SUpersite Volcanoes", one profile coupling DC electrical resistivity tomography (Pole-Dipole configuration with a remote electrode located between 8-10 km from the middle of the different acquisitions, 64 electrodes and 40 m spacing between the electrodes), self-potential, soil CO2 degassing, Radon measurements and sub-surface (30cm depth) temperature have been performed between June 25th and July 13th 2015. This profile, NE-SW direction, crossed the summit part of Mount Etna. A total 5720m of profile was performed, with a roll along protocol of 1/4 of the dispositive, for each new acquisitions. A total of 6 acquisitions was made to complete the entire profile. For the first time in the world, a multi-electrodes DC ERT profile, of high resolution (40 m of spacing between the electrodes) reached, thanks to a pole-dipole configuration, 900m for the depth of investigation. The ERT profile clearly evidences the hydrothermal system of Mount Etna: the lowest resistivity values are associated with a large scale positive self-potential anomaly, and smaller wavelength anomalies for temperature, CO2 concentration and Radon, in the area where the electrical conductor reach the surface. Structural discontinuities such as the Elliptic crater, was clearly evidenced by a sharp decrease of the self-potential values in the inner part of this crater. The striking result of this profile is the presence of a resistive body located just below the NE crater. This structure displays the highest degassing values of the entire profile. We interpret this resistive body as a consequence of the thermic over-heated plume rising from the top of the shallow feeding system. Indeed, above several hundred of degrees Celsuis, it is impossible to consider rain water infiltration and the presence of a wet hydrothermal system. The consequence would be therefore to obtain this resistive body, centred on the area of main heat transfer. Above this

  15. Fabrication of intermetallic coatings for electrical and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.H.; Cho, W.D.

    1994-10-01

    Several intermetallic films were fabricated to high-temperature alloys (V-alloys and 304 and 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain-growth behavior at 1000{degrees}C for the V-5Cr-5Ti was investigated to determine the stability of alloy substrate during coating formation by chemical vapor deposition (CVD) or metallic vapor processes at 800-850{degrees}C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and X-ray diffraction analysis and tested for electrical resistivity and corrosion resistance. The results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  16. Understanding Electrical Conduction States in WO3 Thin Films Applied for Resistive Random-Access Memory

    NASA Astrophysics Data System (ADS)

    Ta, Thi Kieu Hanh; Pham, Kim Ngoc; Dao, Thi Bang Tam; Tran, Dai Lam; Phan, Bach Thang

    2016-05-01

    The electrical conduction and associated resistance switching mechanism of top electrode/WO3/bottom electrode devices [top electrode (TE): Ag, Ti; bottom electrode (BE): Pt, fluorine-doped tin oxide] have been investigated. The direction of switching and switching ability depended on both the top and bottom electrode material. Multiple electrical conduction mechanisms control the leakage current of such switching devices, including trap-controlled space-charge, ballistic, Ohmic, and Fowler-Nordheim tunneling effects. The transition between electrical conduction states is also linked to the switching (SET-RESET) process. This is the first report of ballistic conduction in research into resistive random-access memory. The associated resistive switching mechanisms are also discussed.

  17. Comparing Spreading Resistance Profiling and C-V characterisation to identify defects in silicon sensors

    NASA Astrophysics Data System (ADS)

    Dragicevic, M.; Bergauer, T.; Hrubec, J.; Krammer, M.; Treberspurg, W.; Valentan, M.

    2013-02-01

    The quality and functionality of a silicon sensor strongly depends on the effective doping concentration of the active silicon bulk. The creation of additional defects, by certain steps in the production or through irradiation in a particle beam, can heavily influence its performance. Several methods exist to characterise the bulk material for a silicon sensor. C-V characterisation is a widely implemented, non-destructive method to extract the depth profile of Neff. A technique which is rarely used at laboratories developing silicon sensors is Spreading Resistance Profiling (SRP) which directly measures the resistivity of the silicon. We will show, that a comparison of measurements from these two methods can yield important information on the defect concentration in the bulk of the silicon. To demonstrate the technique, we investigated a sensor material where the active region was reduced using a deep diffusion process which is assumed to create additional defects in the bulk.

  18. Electrical resistivity investigations at Memphis, and Bolivar, Tennessee

    USGS Publications Warehouse

    Spicer, H. Cecil

    1948-01-01

    This geophysical investigation was undertaken upon request of Elliott M. Cushing of the Ground Water Division Office at Memphis, Tennessee. The field work was performed during the period March 13 to 28, 1947; the apparent resistivity curves were interpreted during November and December; and the report was written subsequent to the interpretation of the curves. The writer is grateful to Elliott M. Cushing and his staff for the splendid cooperation and generous assistance extended to him in obtaining the measurements. It is also a pleasure to acknowledge the assistance of George J. Edwards in obtaining the field measurements.

  19. Fracture Surface Area Effects on Fluid Extraction and the Electrical Resistivity of Geothermal Reservoir Rocks

    SciTech Connect

    Roberts, J J; Detwiler, R L; Ralph, W; Bonner, B

    2002-05-09

    Laboratory measurements of the electrical resistivity of fractured analogue geothermal reservoir rocks were performed to investigate the resistivity contrast caused by active boiling and to determine the effects of variable fracture dimensions and surface area on water extraction. Experiments were performed at confining pressures up to 10 h4Pa (100 bars) and temperatures to 170 C. Fractured samples show a larger resistivity change at the onset of boiling than intact samples. Monitoring the resistivity of fractured samples as they equilibrate to imposed pressure and temperature conditions provides an estimate of fluid migration into and out of the matrix. Measurements presented are an important step toward using field electrical methods to quantitatively search for fractures, infer saturation, and track fluid migration in geothermal reservoirs.

  20. An electrically resistive sheet of glial cells for amplifying signals of neuronal extracellular recordings

    NASA Astrophysics Data System (ADS)

    Matsumura, R.; Yamamoto, H.; Niwano, M.; Hirano-Iwata, A.

    2016-01-01

    Electrical signals of neuronal cells can be recorded non-invasively and with a high degree of temporal resolution using multielectrode arrays (MEAs). However, signals that are recorded with these devices are small, usually 0.01%-0.1% of intracellular recordings. Here, we show that the amplitude of neuronal signals recorded with MEA devices can be amplified by covering neuronal networks with an electrically resistive sheet. The resistive sheet used in this study is a monolayer of glial cells, supportive cells in the brain. The glial cells were grown on a collagen-gel film that is permeable to oxygen and other nutrients. The impedance of the glial sheet was measured by electrochemical impedance spectroscopy, and equivalent circuit simulations were performed to theoretically investigate the effect of covering the neurons with such a resistive sheet. Finally, the effect of the resistive glial sheet was confirmed experimentally, showing a 6-fold increase in neuronal signals. This technique feasibly amplifies signals of MEA recordings.

  1. Stochastic Inversion of Electrical Resistivity Changes Using a Markov Chain, Monte Carlo Approach

    SciTech Connect

    Ramirez, A; Nitao, J; Hanley, W; Aines, R; Glaser, R; Sengupta, S; Dyer, K; Hickling, T; Daily, W

    2004-09-21

    We describe a stochastic inversion method for mapping subsurface regions where the electrical resistivity is changing. The technique combines prior information, electrical resistance data and forward models to produce subsurface resistivity models that are most consistent with all available data. Bayesian inference and a Metropolis simulation algorithm form the basis for this approach. Attractive features include its ability to: (1) provide quantitative measures of the uncertainty of a generated estimate and, (2) allow alternative model estimates to be identified, compared and ranked. Methods that monitor convergence and summarize important trends of the posterior distribution are introduced. Results from a physical model test and a field experiment were used to assess performance. The stochastic inversions presented provide useful estimates of the most probable location, shape, and volume of the changing region, and the most likely resistivity change. The proposed method is computationally expensive, requiring the use of extensive computational resources to make its application practical.

  2. Strategies of ARP application (Automatic Resistivity Profiling) for viticultural precision farming

    NASA Astrophysics Data System (ADS)

    Costantini, E. A. C.; Andrenelli, M. C.; Bucelli, P.; Magini, S.; Natarelli, L.; Pellegrini, S.; Perria, R.; Storchi, P.; Vignozzi, N.

    2009-04-01

    Introduction Viticultural precision farming needs detailed soil information, which can be obtained by means of remote as well as proximal sensors, besides traditional invasive soil survey. Nevertheless, the use of the new technologies is still in its infancy, because of their costs and the lack of knowledge about the detail actually needed for the viticultural husbandry. The main aim of this work was to test the sensitivity of the ARP methodology (Automatic Resistivity Profiling) in supporting soil survey for viticultural precision farming. In addition, we tried to optimize the detail of geoelectrical measurements and soil sampling to reduce the cost of the integrated survey, maintaining a significant information accuracy for viticulture. Materials and methods Two vineyards in coastal Tuscany (central Italy), about 3.5 ha each, were selected. Vineyard 1 was cultivated with Cabernet Sauvignon and Cabernet Franc, while vineyard 2 only had Cabernet Sauvignon. Soil survey and geoelectrical investigation were conducted in may 2007. The ARP methodology consists in the injection in soil of electric current through one pair of electrodes mounted on teeth wheels and measuring the resulting potential with other three pairs of electrodes, placed of the same mobile equipment. The electrical resistance of the soil (ER) is expressed as ohm per m. The depth of investigation is a function of the geometry of the electrodes and the soil being probed. Increasing the distance between electrodes will increase the depth while decreasing the measured potential. The innovative character of the ARP technique is represented by the passage of a mobile machinery, able to perform 30,000 measurements per hectare, with a measurement every 0.2 m. The ARP system, equipped with a digital encoder and DGPS system, is transported by a four-wheeled vehicle. It is fitted with three sensors that contemporaneously analyse three distinct levels of the soil, the values of which are represented by maps of

  3. Determining concentration depth profiles in fluorinated networks by means of electric force microscopy

    SciTech Connect

    Miccio, Luis A.; Schwartz, Gustavo A.

    2011-08-14

    By means of electric force microscopy, composition depth profiles were measured with nanometric resolution for a series of fluorinated networks. By mapping the dielectric permittivity along a line going from the surface to the bulk, we were able to experimentally access to the fluorine concentration profile. Obtained data show composition gradient lengths ranging from 30 nm to 80 nm in the near surface area for samples containing from 0.5 to 5 wt. % F, respectively. In contrast, no gradients of concentration were detected in bulk. This method has several advantages over other techniques because it allows profiling directly on a sectional cut of the sample. By combining the obtained results with x-ray photoelectron spectroscopy measurements, we were also able to quantify F/C ratio as a function of depth with nanoscale resolution.

  4. Gene expression profiling in the thiamethoxam resistant and susceptible B-biotype sweetpotato whitefly, Bemisia tabaci.

    PubMed

    Xie, Wen; Yang, Xin; Wang, Shao-Ii; Wu, Qing-jun; Yang, Ni-na; Li, Ru-mei; Jiao, Xiao-guo; Pan, Hui-peng; Liu, Bai-ming; Feng, Yun-tao; Xu, Bao-yun; Zhou, Xu-guo; Zhang, You-jun

    2012-01-01

    Thiamethoxam has been used as a major insecticide to control the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Due to its excessive use, a high level of resistance to thiamethoxam has developed worldwide over the past several years. To better understand the molecular mechanisms underlying this resistance in B. tabaci, gene profiles between the thiamethoxam-resistant and thiamethoxam-susceptible strains were investigated using the suppression subtractive hybridization (SSH) library approach. A total of 72 and 52 upand down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These expressed sequence tags (ESTs) belong to several functional categories based on their gene ontology annotation. Some categories such as cell communication, response to abiotic stimulus, lipid particle, and nuclear envelope were identified only in the forward library of thiamethoxam-resistant strains. In contrast, categories such as behavior, cell proliferation, nutrient reservoir activity, sequence-specific DNA binding transcription factor activity, and signal transducer activity were identified solely in the reverse library. To study the validity of the SSH method, 16 differentially expressed genes from both forward and reverse SSH libraries were selected randomly for further analyses using quantitative realtime PCR (qRT-PCR). The qRT-PCR results were fairly consistent with the SSH results; however, only 50% of the genes showed significantly different expression profiles between the thiamethoxam-resistant and thiamethoxam-susceptible whiteflies. Among these genes, a putative NAD-dependent methanol dehydrogenase was substantially over-expressed in the thiamethoxamresistant adults compared to their susceptible counterparts. The distributed profiles show that it was highly expressed during the egg stage, and was most abundant in the abdomen of adult females. PMID:22957505

  5. Gene Expression Profiling in the Thiamethoxam Resistant and Susceptible B-biotype Sweetpotato Whitefly, Bemisia tabaci

    PubMed Central

    Xie, Wen; Yang, Xin; Wang, Shao-Ii; Wu, Qing-jun; Yang, Ni-na; Li, Ru-mei; Jiao, Xiaoguo; Pan, Hui-peng; Liu, Bai-ming; Feng, Yun-tao; Xu, Bao-yun; Zhou, Xu-guo; Zhang, You-jun

    2012-01-01

    Thiamethoxam has been used as a major insecticide to control the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Due to its excessive use, a high level of resistance to thiamethoxam has developed worldwide over the past several years. To better understand the molecular mechanisms underlying this resistance in B. tabaci, gene profiles between the thiamethoxam-resistant and thiamethoxam-susceptible strains were investigated using the suppression subtractive hybridization (SSH) library approach. A total of 72 and 52 upand down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These expressed sequence tags (ESTs) belong to several functional categories based on their gene ontology annotation. Some categories such as cell communication, response to abiotic stimulus, lipid particle, and nuclear envelope were identified only in the forward library of thiamethoxam-resistant strains. In contrast, categories such as behavior, cell proliferation, nutrient reservoir activity, sequence-specific DNA binding transcription factor activity, and signal transducer activity were identified solely in the reverse library. To study the validity of the SSH method, 16 differentially expressed genes from both forward and reverse SSH libraries were selected randomly for further analyses using quantitative realtime PCR (qRT-PCR). The qRT-PCR results were fairly consistent with the SSH results; however, only 50% of the genes showed significantly different expression profiles between the thiamethoxam-resistant and thiamethoxam-susceptible whiteflies. Among these genes, a putative NAD-dependent methanol dehydrogenase was substantially over-expressed in the thiamethoxamresistant adults compared to their susceptible counterparts. The distributed profiles show that it was highly expressed during the egg stage, and was most abundant in the abdomen of adult females. PMID:22957505

  6. Investigations of temperature dependences of electrical resistivity and specific heat capacity of metals

    NASA Astrophysics Data System (ADS)

    Eser, Erhan; Koç, Hüseyin

    2016-07-01

    In this study, we calculated the electrical resistivity and heat capacities of some ideal metals (Cu, Pt, and Pd) using a method that it employs the statistical model and Debye functions. The method is used to provide a simple and reliable analytical procedure for wide temperature range. The results obtained for the electrical resistivity and heat capacity have been compared with the results in literature. The results obtained at low temperature are in excellent agreement with experimental and theoretical results. Finally the used approximation and analytical method are a useful approach to calculate thermophysical properties of metals.

  7. Temperature dependent electrical resistivity of gallium and antimony in a liquid form

    NASA Astrophysics Data System (ADS)

    Prajapati, A. V.; Sonvane, Y. A.; Thakor, P. B.

    2016-05-01

    Present paper deals with the effects of temperature variation on the electrical resistivity (Ω) of liquid Gallium (Ga), and Antimony (Sb). We have used a new parameter free pseudopotential with a Zeeman formula for finding it. To see the effects of screening Farid et al local field correction function is used with the Charged Hard Sphere (CHS) reference system. Analysis and comparison between the plotted graphs, based on present computed data and other experimental data defines and conclude that our newly constructed model potential is an effective one to produce the data for the temperature dependent electrical resistivity of some liquid semiconductors.

  8. Electrical resistivity well-logging system with solid-state electronic circuitry

    USGS Publications Warehouse

    Scott, James Henry; Farstad, Arnold J.

    1977-01-01

    An improved 4-channel electrical resistivity well-logging system for use with a passive probe with electrodes arranged in the 'normal' configuration has been designed and fabricated by Westinghouse Electric Corporation to meet technical specifications developed by the U.S. Geological Survey. Salient features of the system include solid-state switching and current regulation in the transmitter circuit to produce a constant-current source square wave, and synchronous solid-state switching and sampling of the potential waveform in the receiver circuit to provide an analog dc voltage proportions to the measured resistivity. Technical specifications and design details are included in this report.

  9. Thermo-Electromotive Force and Electrical Resistivity of Hydrogenated VT1-0 Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Lider, A.; Larionov, V.; Kroening, M.; Kudiiarov, V.

    2016-06-01

    The method for measuring the structure transition of hydrogenated titanium from one state to another is suggested. The method is based on the comparison of thermo-electromotive force (thermo-emf), DC electrical resistance and the results of X-ray diffraction analysis. X-ray diffraction analysis is applied for identifying the quantity of defects in titanium structure. The authors have also identified the identical dependence of thermo-electromotive force and electrical resistivity on hydrogen concentration in titanium. The effect can be used for hydrogenated titanium structure control.

  10. Electrical resistivity and specific heat of La 2-XSr XNiO 4+δ

    NASA Astrophysics Data System (ADS)

    Matsushita, Akiyuki; Matsumoto, Takehiko; Takayanagi, Shigeru; Mōri, Nobuo

    1990-08-01

    Specific heat and electrical resistivity were measured on La 2-XSr XNiO 4+δ with various Sr concentrations as a function of temerature. The behaviors of electrical resistivity and lattice constants show a marked change at X⋃0.5 (Xc). The specific heat shows a hump at about 6K in C/T vs. T 2 plot for all of samples annealed in air. For the samples annealed in hydrogen no hump is observed. The relationship between Xc and interstitial oxygen defect is discussed.

  11. Thermal conductivity, electrical resistivity, and thermopower of aerospace alloys from 4 to 300 K.

    NASA Technical Reports Server (NTRS)

    Hust, J. G.; Weitzel, D. H.; Powell, R. L.

    1971-01-01

    Measurement of thermal conductivity, electrical resistivity, and thermopower for several aerospace alloys: titanium alloy A110-AT, aluminum alloy 7039, Inconel 718, and Hastelloy X. Tables and graphs of the measured properties and Lorenz ratio are presented over the range from 4 to 300 K. Comparisons to other measurements and theoretical analysis of the data are included. The uncertainties of the property data are estimated as 0.7 to 2.5% for thermal conductivity, 0.25% in electrical resistivity, and about 0.1 microvolt/K in thermopower.

  12. High pressure and temperature electrical resistivity of iron and implications for planetary cores (Invited)

    NASA Astrophysics Data System (ADS)

    Deng, L.; Seagle, C. T.; Fei, Y.; Shahar, A.

    2013-12-01

    Electrical resistivity measurements of polycrystalline iron have been performed at 5, 7 and 15 GPa and in the temperature range 293-2200 K by employing a four-wired method. The kinks in electrical resistivity associated with solid iron phase transitions and the solid to liquid transition were clearly observed upon increasing temperature. Geometry corrections due to volume variations with pressure and temperature were applied to the entire data set. High pressure and temperature thermal conductivity were calculated by fitting resistivity data through the Wiedemann-Franz law. The temperature dependences of electrical resistivity and thermal conductivity for α, γ and ɛ solid iron have been determined at high pressure conditions. Our study provides the first experimental constraint on the heat flux conducted at Mercury's outmost core, estimated to be 0.29-0.36 TW, assuming an adiabatic core. Extrapolations of our data to Martian outer core conditions yield a series of heat transport parameters (eg. electrical resistivity, thermal conductivity and heat flux), which are in reasonable comparison with various geophysical estimates.

  13. Electrical Resistivity Study of a Pleistocene Riverbed in Saltville, VA

    NASA Astrophysics Data System (ADS)

    Herman, R. B.; Whisonant, R. C.

    2008-05-01

    A shallow capacitively coupled resistivity survey was performed in Saltville, VA, in an area of suspected buried Pleistocene river deposits. Previous excavations in the sediments beneath the Saltville valley floor had been performed to recover late Pleistocene megafaunal remains and possible Clovis-age human artifacts. These digs encountered a zone, one to two meters deep, of gravel-sized rock fragments, including some boulders up to 75 cm. in diameter. These large clasts are rounded, show some imbrication (shingle-like overlapping indicative of current flow), and have been interpreted as river channel deposits. Carbon 14 dates from the megafaunal bones within and just above the gravel bed yielded dates of 14,500 years BP. Resistivity signals in a number of locations were consistent with cobbles and boulders deposited in a river channel. These signals are generally bowl- shaped areas with large circular (2-d scans) anomalies near the center, and smaller circular anomalies tapering out towards both sides. The bowl-shaped anomalies are within 3 meters of the surface. With several lines imaged in this survey a rough path of the riverbed, along with a number of branchings is traceable in the survey area. An exploratory hole confirmed the presence of a layer of rounded cobbles and boulders 1.3 meters deep beneath one of the survey lines.

  14. Degree of dispersion of latex particles in cement paste, as assessed by electrical resistivity measurement

    SciTech Connect

    Fu, X.; Chung, D.D.L.

    1996-12-31

    The degree of dispersion of latex particles in latex-modified cement paste was assessed by measurement of the volume electrical resistivity and modeling this resistivity in terms of latex and cement phases that are partly in series and partly in parallel. The assessment was best at low values of the latex-cement ratio; it underestimated the degree of latex dispersion when the latex/cement ratio was high, especially > 0.2.

  15. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2016-08-01

    We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.

  16. Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

    SciTech Connect

    Cousineau, J. Emily; Bennion, Kevin; DeVoto, Doug; Mihalic, Mark; Narumanchi, Sreekant

    2015-06-30

    The ability to remove heat from an electric machine depends on the passive stack thermal resistances within the machine and the convective cooling performance of the selected cooling technology. This report focuses on the passive thermal design, specifically properties of the stator and rotor lamination stacks. Orthotropic thermal conductivity, specific heat, and density are reported. Four materials commonly used in electric machines were tested, including M19 (29 and 26 gauge), HF10, and Arnon 7 materials.

  17. On the Modeling of Electrical Effects Experienced by Space Explorers During Extra Vehicular Activities: Intracorporal Currents, Resistances, and Electric Fields

    NASA Technical Reports Server (NTRS)

    Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.

    2011-01-01

    Recent research has shown that space explorers engaged in Extra Vehicular Activities (EVAs) may be exposed, under certain conditions, to undesired electrical currents. This work focuses on determining whether these undesired induced electrical currents could be responsible for involuntary neuromuscular activity in the subjects, possibly caused by either large diameter peripheral nerve activation or reflex activity from cutaneous afferent stimulation. An efficient multiresolution variant of the admittance method along with a millimeter-resolution model of a male human body were used to calculate induced electric fields, resistance between contact electrodes used to simulate the potential exposure condition, and currents induced in the human body model. Results show that, under realistic exposure conditions using a 15V source, current density magnitudes and total current injected are well above previously reported startle reaction thresholds. This indicates that, under the considered conditions, the subjects could experience involuntary motor response.

  18. Lipid profiling identifies a triacylglycerol signature of insulin resistance and improves diabetes prediction in humans

    PubMed Central

    Rhee, Eugene P.; Cheng, Susan; Larson, Martin G.; Walford, Geoffrey A.; Lewis, Gregory D.; McCabe, Elizabeth; Yang, Elaine; Farrell, Laurie; Fox, Caroline S.; O’Donnell, Christopher J.; Carr, Steven A.; Vasan, Ramachandran S.; Florez, Jose C.; Clish, Clary B.; Wang, Thomas J.; Gerszten, Robert E.

    2011-01-01

    Dyslipidemia is an independent risk factor for type 2 diabetes, although exactly which of the many plasma lipids contribute to this remains unclear. We therefore investigated whether lipid profiling can inform diabetes prediction by performing liquid chromatography/mass spectrometry–based lipid profiling in 189 individuals who developed type 2 diabetes and 189 matched disease-free individuals, with over 12 years of follow up in the Framingham Heart Study. We found that lipids of lower carbon number and double bond content were associated with an increased risk of diabetes, whereas lipids of higher carbon number and double bond content were associated with decreased risk. This pattern was strongest for triacylglycerols (TAGs) and persisted after multivariable adjustment for age, sex, BMI, fasting glucose, fasting insulin, total triglycerides, and HDL cholesterol. A combination of 2 TAGs further improved diabetes prediction. To explore potential mechanisms that modulate the distribution of plasma lipids, we performed lipid profiling during oral glucose tolerance testing, pharmacologic interventions, and acute exercise testing. Levels of TAGs associated with increased risk for diabetes decreased in response to insulin action and were elevated in the setting of insulin resistance. Conversely, levels of TAGs associated with decreased diabetes risk rose in response to insulin and were poorly correlated with insulin resistance. These studies identify a relationship between lipid acyl chain content and diabetes risk and demonstrate how lipid profiling could aid in clinical risk assessment. PMID:21403394

  19. Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging

    PubMed Central

    Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin

    2008-01-01

    Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head. PMID:18799394

  20. Comparative metabolite profiling of Solanum tuberosum against six wild Solanum species with Colorado potato beetle resistance.

    PubMed

    Tai, Helen H; Worrall, Kraig; Pelletier, Yvan; De Koeyer, David; Calhoun, Larry A

    2014-09-10

    The Colorado potato beetle Leptinotarsa decemlineata (Say) (CPB) is a coleopteran herbivore that feeds on the foliage on Solanum species, in particular, potato. Six resistant wild Solanum species were identified, and two of these species had low levels of glycoalkaloids. Comparative analysis of the untargeted metabolite profiles of the foliage using UPLC-qTOF-MS was done to find metabolites shared between the wild species but not with Solanum tuberosum (L.) to identify resistance-related metabolites. It was found that only S. tuberosum produced the triose glycoalkaloids solanine and chaconine. Instead, the six wild species produced glycoalkaloids that shared in common tetrose sugar side chains. Additionally, there were non-glycoalkaloid metabolites associated with resistance including hydroxycoumarin and a phenylpropanoid, which were produced in all wild species but not in S. tuberosum. PMID:25144460

  1. Mechanical flexible and electric fatigue resistant behavior of relaxor ferroelectric terpolymer

    NASA Astrophysics Data System (ADS)

    Fang, Fei; Yang, Wei; Yang, Wen

    2009-08-01

    Uniaxial tension and polarization evolution under cyclic electric field are investigated for poly(vinylidene fluoride-trifluorethylene-chlorofluoroethylene) terpolymer films prepared by different annealing conditions. The stress-strain behavior of the terpolymer film exhibits that of polymeric elastomers, with its fracture strain reaching 680%. Structure analysis demonstrates that the polymer chains undergo reorientation, and conformational change from nonpolar to polar phase takes place during uniaxial tension. Under cyclic electric field, the terpolymer film exhibits a narrow polarization loop typical of a ferroelectric relaxor. Conformational change from nonpolar to polar phase also occurs upon the electric field, and it reverses to the nonpolar phase when the field is removed. As the cycle number accumulates, the terpolymer film demonstrates excellent resistance to electric fatigue. Compared to the film annealed at 115 °C, the terpolymer film annealed at 100 °C has a larger volume fraction of crystallite/amorphous interfaces and shows better mechanical flexibility as well as electric fatigue resistance. The mechanical flexible and electric fatigue resistant terpolymer films hold promises for many applications, ranging from embedded sensors and actuators to flexible memory devices.

  2. A theoretical study of electrical and thermal response in resistance spot welding

    SciTech Connect

    Na, S.J.; Park, S.W.

    1996-08-01

    The effect of contact resistance including constriction and contamination resistance has been a major hurdle for the thermoelectrical analysis of the resistance spot welding process. In this paper, a simple model was suggested and used for calculating the electrical and thermal response of the resistance spot welding process to investigate the influence of contacting forces on the formation of weld nuggets. The electrode surface of the contact interface was assumed to be axisymmetric and its microasperities to have a trapezoidal cross-section. These microasperities were considered as the one-dimensional contact resistance elements in the finite element formulation. The contamination film was assumed to be a nonconducting oxide layer, which is very brittle, so that it is broken to some number of pieces when a contacting pressure is being applied. The crushed films were assumed to be distributed at regular intervals and to conserve their size and number during the welding process. The simulation results revealed that the proposed model can be successfully used to predict the effect of the contact resistance on the electrical and thermal response of the resistance spot welding process.

  3. Electrical Resistivity Tomography in the characterisation of wetting patterns of historical masonry

    NASA Astrophysics Data System (ADS)

    López-González, Laura; Gomez-Heras, Miguel; Ortiz de Cosca, Raquel Otero; García-Morales, Soledad

    2016-04-01

    Electrical Resistivity Tomography (ERT) is a geophysical technique widely used to identify subsurface structures based on electrical resistivity measurements made at the surface. In recent years this technique has been used for surveying historic buildings and characterise the subsurface of walls by using non-invasive EKG electrodes. This methods is used to locate wet areas based on the lower electrical resistivity wet materials have in relation to dry ones. A good knowledge of the wetting patterns of historic buildings during, for example, rainfalls is crucial to understand the decay processes that take place in the building and plan interventions. This paper presents results of transects of Electric Resistivity Tomography of walls of the Monastery of Santa Maria de Mave (Palencia, Spain), a 9th century Romanesque building, during rainfall. ERT transects were performed with a GeoTom device (Geolog2000) in areas with and without buttresses to understand how this architectural detail affected the wetting dynamics of the building. The ERT results were integrated with other resistivity-based techniques and Thermohygrometric survey in a GIS and showed how lower resistivity surface measurements ERT correspond with areas of higher humidity. Resistivity-based techniques measured and evaporation focal points take in the interior of the building mark the outer ground level. The highest moisture content measurements do not always correspond to the visibly most damaged areas of the wall. The consecutive ERT transects show the wall getting wetter as rainfall progresses. The comparison of the measurements obtained of a wall affected by water obtained with GIS mapping, allowed to quickly studying the development of moisture in the wall over time, which is essential for a correct diagnosis of the building. Research funded by Madrid's Regional Government project Geomateriales 2 S2013/MIT-2914

  4. Scientific evidence of three different insecticide-resistant profiles in Triatoma infestans (Hemiptera: Reduviidae) populations from Argentina and Bolivia.

    PubMed

    Germano, M D; Santo-Orihuela, P; Roca-Acevedo, G; Toloza, A C; Vassena, C; Picollo, M I; Mougabure-Cueto, G

    2012-11-01

    Triatoma infestans (Klug, 1834) (Hemiptera, Reduviidae) is the main vector of Chagas disease in the southern cone South America. Chemical control to the vectors appears to be the best option to reduce the incidence of the disease. However, since 2002, high resistance to insecticides that correlated with field control failures was detected in T. infestans from Argentina and Bolivia. In this paper, we analyzed three T. infestans populations whose pyrethroid-resistance had been recently detected, and we defined at least three resistant profiles according to the toxicological and biochemical characteristics of the studied resistant populations. The resistance profiles were identified as Ti-R1, Ti-R2, and Ti-R3, corresponding to the Argentinean Acambuco, and the Bolivians Entre Ríos and Mataral. Ti-R1 exhibited nymphs and eggs with medium resistance level to deltamethrin (RR = 32.5 and 28.6; respectively). Pyrethroid-esterases played a relevant role in deltamethrin resistance. Ti-R2 exhibited nymphs with high resistance to deltamethrin (RR = 173.8) and low resistance to fipronil (RR = 12.4). Pyrethroid-esterases were involved in resistance. Moreover, eggs showed medium resistance level to deltamethrin (RR = 39.1). Ti-R3 had nymphs with low resistance to deltamethrin (RR = 17.4), and medium resistance to fipronil (RR = 66.8). Pyrethroid-esterases showed increased activity, and eggs possessed low resistance to deltamethrin (RR = 8.4). The characterization of the resistance to pyrethroid in these T. infestans populations from Argentina and Bolivia do not permit the generalization of three forms of resistance profile. So far as we appear to know, the forms of mechanisms and their frequencies reported here are selected independently, so additional sites might well show additional combinations of resistance mechanisms and their frequencies. PMID:23270163

  5. Clinical Features and Drug-Resistance Profile of Urinary Tuberculosis in South-Western China

    PubMed Central

    Ye, Yuanxin; Hu, Xuejiao; Shi, Yunying; Zhou, Juan; Zhou, Yi; Song, Xingbo; Xie, Yi; Lu, Xiaojun; Wang, Lanlan; Ying, Binwu; Chen, Xuerong

    2016-01-01

    Abstract To investigate the epidemiology, clinical features, and drug-resistance profile of urinary tuberculosis (UTB) in south-western China to improve UTB diagnostics. After the screening of 1036 cases of suspected UTB, 193 patients with UTB were enrolled during 2009 to 2014. Urine samples were collected for routine urinalysis, smear, tuberculosis DNA (TB-DNA) detection, and drug-resistant analysis, whereas blood samples were collected for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and renal function evaluation. Clinical features (such as symptoms and outcome) and imageology results (such as B ultrasonic, computerized tomography, intravenous pyelography, and renography) were also collected and analyzed to investigate the epidemiology, clinical features, and drug-resistance profile. The most common presenting symptoms were urinary irritation (61.1%) and lumbago (49.2%). High proportions of microscopic hematuria (63.2%) and microscopic proteinuria (45.6%) were also observed. The positive rate for TB-DNA was 66.3%. The positive rate for culture was 13.1% and for smear it was 9.8%. The abnormal outcome rates of the computerized tomography, ultrasonography, intravenous pyelography, and the nephrogram were 76.9%, 70.1%, 29.8%, and 37.0%, respectively. The total rate of drug-resistant TB (resistant to at least 1 drug) was 39.7%, of which 20.7% was multidrug-resistance TB. The most prevalent mutation sites were katG S315T1, rpoB S531L, and gyrA D94G. We observed a serious epidemic of drug-resistant UTB and a substantial number of new UTB cases with multidrug resistance TB. Molecular diagnostics is crucial in the definite diagnosis of UTB, and our finding is a supplement and further confirmation of polymerase chain reaction usage for TB diagnosis. We recommend real-time polymerase chain reaction for TB-DNA identification instead of culture, and GenoType tests (MTBDRplus and MTBDRsl assay) for drug resistance as routine assays for patients with

  6. A study of the deposition of carbide coatings on graphite fibers. [to increase electrical resistance

    NASA Technical Reports Server (NTRS)

    Suplinskas, R. J.; Henze, T. W.

    1979-01-01

    The chemical vapor deposition of boron carbide and silicon carbide on graphite fibers to increase their electrical resistance was studied. Silicon carbide coatings were applied without degradation of the mechanical properties of the filaments. These coatings typically added 1000 ohms to the resistance of a filament as measured between two mercury pools. When SiC-coated filaments were oxidized by refluxing in boiling phosphoric acid, average resistance increased by an additional 1000 ohms; in addition resistance increases as high as 150 K ohms and breakdown voltages as high as 17 volts were noted. Data on boron carbide coatings indicated that such coatings would not be effective in increasing resistance, and would degrade the mechanical properties.

  7. Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag

    PubMed Central

    Kim, Ji Young; Oh, Min-Wook; Lee, Seunghun; Cho, Yong Chan; Yoon, Jang-Hee; Lee, Geun Woo; Cho, Chae-Ryong; Park, Chul Hong; Jeong, Se-Young

    2014-01-01

    Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35 μΩ·cm at room temperature after 3 mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior. PMID:24965478

  8. Aerodynamic resistance reduction of electric and hybrid vehicles

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The generation of an EHV aerodynamic data base was initiated by conducting full-scale wind tunnel tests on 16 vehicles. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current 4-passenger prototype automobile which was designed with aerodynamics as an integrated parameter. Characteristic effects of aspect ratio or fineness ratio which might appear if electric vehicle shape proportions were to vary significantly from current automobiles were identified. Some preliminary results indicate a 5 to 10% variation in drag over the range of interest. Effective drag coefficient wind-weighting factors over J227a driving cycles in the presence of annual mean wind fields were identified. Such coefficients, when properly weighted, were found to be from 5 to 65% greater than the zero-yaw drag coefficient in the cases presented. A vehicle aerodynamics bibliography of over 160 entries, in six general categories is included.

  9. Evolution of low-profile and lightweight electrical connectors for soldier-worn applications

    NASA Astrophysics Data System (ADS)

    Gans, Eric; Lee, Kang; Jannson, Tomasz; Walter, Kevin

    2011-06-01

    In addition to military radios, modern warfighters carry cell phones, GPS devices, computers, and night-vision aids, all of which require electrical cables and connectors for data and power transmission. Currently each electrical device operates via independent cables using conventional cable and connector technology. Conventional cables are stiff and difficult to integrate into a soldier-worn garment. Conventional connectors are tall and heavy, as they were designed to ensure secure connections to bulkhead-type panels, and being tall, represent significant snag-hazards in soldier-worn applications. Physical Optics Corporation has designed a new, lightweight and low-profile electrical connector that is more suitable for body-worn applications and operates much like a standard garment snap. When these connectors are mated, the combined height is <0.3 in. - a significant reduction from the 2.5 in. average height of conventional connectors. Electrical connections can be made with one hand (gloved or bare) and blindly (without looking). Furthermore, POC's connectors are integrated into systems that distribute data or power from a central location on the soldier's vest, reducing the length and weight of the cables necessary to interconnect various mission-critical electronic systems. The result is a lightweight power/data distribution system offering significant advantages over conventional electrical connectors in soldier-worn applications.

  10. Electrical resistivity characterization and defect detection on a geosynthetic clay liner (GCL) on an experimental site

    NASA Astrophysics Data System (ADS)

    Sirieix, C.; Fernández Martínez, J. L.; Riss, J.; Genelle, F.

    2013-03-01

    In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7 mm thick) and resistive layer (from 100,000 to 2,000,000 Ω·m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole-dipole DD and Wenner-Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole-dipole array provides a better resistivity resolution of the defects than the Wenner-Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 105 to 1.106 Ω·m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.104-9.104 Ω·m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects.

  11. Ion Permeability of Artificial Membranes Evaluated by Diffusion Potential and Electrical Resistance Measurements

    ERIC Educational Resources Information Center

    Shlyonsky, Vadim

    2013-01-01

    In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and "n"-decane. The electrical resistance and potential…

  12. High School Students' Understanding of Resistance in Simple Series Electric Circuits.

    ERIC Educational Resources Information Center

    Liegeois, Laurent; Mullet, Etienne

    2002-01-01

    Studies the understanding that 8-12 grade high school students were able to develop with regard to the interrelationships between resistance, potential difference, and current concepts (Ohm's law). Explores the immediate effects of exposure to electricity courses on the intuitive mastery of these relationships. (Contains 32 references.)…

  13. Electrical resistance determination of actual contact area of cold welded metal joints

    NASA Technical Reports Server (NTRS)

    Hordon, M. J.

    1970-01-01

    Method measures the area of the bonded zone of a compression weld by observing the electrical resistance of the weld zone while the load changes from full compression until the joint ruptures under tension. The ratio of bonding force to maximum tensile load varies considerably.

  14. Electrical resistivity sounding to study water content distribution in heterogeneous soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electrical resistivity (ER) sounding is increasingly being used as non-invasive technique to reveal and map soil heterogeneity. The objective of this work was to assess ER sounding applicability to study soil water distribution in spatially heterogeneous soils. The 30x30-m study plot was located at ...

  15. Concerning Proposed Superconducting Fluctuations in the Electrical Resistivity of Bulk Aluminum

    NASA Astrophysics Data System (ADS)

    Barnard, B. R.; Bass, J.; Caplin, A. D.; Dalimin, M. N. B.

    1980-03-01

    Bulk superconducting fluctuation contributions to rounding of the electrical resistivity of Al just above Tc are demonstrated to be at least 5 to 10 times smaller than claimed recently by Sinvani, Levy, and Greenfield. Metallurgical artifacts provide a more plausible explanation for all of the measured rounding.

  16. 3D Electrical resistivity tomography monitoring of an artificial tracer injected within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Houzé, Clémence; Pessel, Marc; Durand, Veronique

    2016-04-01

    Due to the high complexity level of hyporheic flow paths, hydrological and biogeochemical processes which occur in this mixing place are not fully understood yet. Some previous studies made in flumes show that hyporheic flow is strongly connected to the streambed morphology and sediment heterogeneity . There is still a lack of practical field experiment considering a natural environment and representation of natural streambed heterogeneities will be always limited in laboratories. The purpose of this project is to propose an innovative method using 3D Electrical Resistivity Tomography (ERT) monitoring of an artificial tracer injection directly within the streambed sediments in order to visualize the water pathways within the hyporheic zone. Field experiment on a small stream was conducted using a plastic tube as an injection piezometer and home-made electrodes strips arranged in a rectangular form made of 180 electrodes (15 strips of 12 electrodes each). The injection of tracer (NaCl) lasted approximatively 90 minutes, and 24h monitoring with increasing step times was performed. The physical properties of the water are controlled by CTD probes installed upstream and downstream within the river. Inverse time-lapse tomographs show development and persistence of a conductive water plume around the injection point. Due to the low hydraulic conductivity of streambed sediments (clay and overlying loess), the tracer movement is barely visible, as it dilutes gradually in the pore water. Impact of boundary conditions on inversion results can lead to significant differences on images, especially in the shallow part of the profiles. Preferential paths of transport are not highlighted here, but this experiment allows to follow spatially and temporarily the evolution of the tracer in a complex natural environment .

  17. Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M

    SciTech Connect

    Kaye, S.M.; Levinton, F.M.; Hatcher, R.; Kaita, R.; Kessel, C.; LeBlanc, B.; McCune, D.C.; Paul, S. )

    1992-03-01

    Direct measurements of the radial profile of the magnetic field line pitch on PBX-M (Phys. Fluids B {bold 2}, 1271 (1990)), coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by motional Stark effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the model profiles were distinguishable from each other in only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner-half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.

  18. Salmonella serovars and antimicrobial resistance profiles in beef cattle, slaughterhouse personnel and slaughterhouse environment in ethiopia.

    PubMed

    Sibhat, B; Molla Zewde, B; Zerihun, A; Muckle, A; Cole, L; Boerlin, P; Wilkie, E; Perets, A; Mistry, K; Gebreyes, W A

    2011-03-01

    The present study was undertaken to determine the occurrence, distribution and antimicrobial resistance profiles of Salmonella serovars in slaughter beef cattle, slaughterhouse environment and personnel engaged in flaying and evisceration during slaughtering process. A total of 800 samples (each sample type, n = 100) consisting of swabs from hides, slaughterhouse personnel hands at flaying and evisceration, rumen and caecal contents, mesenteric lymph nodes, carcasses and holding pens were collected. Of the total 100 beef cattle examined, 14% were Salmonella positive in caecal content and/or mesenteric lymph nodes. Of the various samples analysed, Salmonella was detected in 31% of hides, 19% of rumen contents, 8% of mesenteric lymph nodes, 6% of caecal contents, 2% of carcass swabs, 9% of palm swabs taken from the hands of personnel in the slaughterhouse during flaying (7%) and evisceration (2%), and in 12% of holding pen swabs. The Salmonella isolates (n = 87) belonged to eight different serovars of which S. Anatum (n = 54) and S. Newport (19) were the major serovars and both serovars were detected in all sample sources except in carcass swabs. Eighteen of the 87 (20.7%) Salmonella serovars consisting of Newport (n = 14), Anatum (n = 3) and Eastbourne (n = 1) were resistant to one or more antimicrobials. Among the antimicrobial resistant Salmonella serovars, S. Newport was multidrug resistant (15.6%) and exhibited resistance to streptomycin, sulphisoxazole and tetracycline. PMID:20042064

  19. Metagenomic profiles of antibiotic resistance genes in paddy soils from South China.

    PubMed

    Xiao, Ke-Qing; Li, Bing; Ma, Liping; Bao, Peng; Zhou, Xue; Zhang, Tong; Zhu, Yong-Guan

    2016-03-01

    Overuse and arbitrary discarding of antibiotics have expanded antibiotic resistance reservoirs, from gut, waste water and activated sludge, to soil, freshwater and even the ocean. Based on the structured Antibiotic Resistance Genes Database and next generation sequencing, metagenomic analysis was used for the first time to detect and quantify antibiotic resistance genes (ARGs) in paddy soils from South China. A total of 16 types of ARGs were identified, corresponding to 110 ARG subtypes. The abundances and distribution pattern of ARGs in paddy soil were distinctively different from those in activated sludge and pristine deep ocean sediment, but close to those of sediment from human-impacted estuaries. Multidrug resistance genes were the most dominant type (38-47.5%) in all samples, and the ARGs detected encompassed the three major resistance mechanisms, among which extrusion by efflux pumps was predominant. Redundancy analysis (RDA) showed that pH was significantly correlated with the distribution of ARG subtypes (P < 0.05). Our results provided a broad spectrum profile of ARGs in paddy soil, indicating that ARGs are widespread in paddy soils of South China. PMID:26850156

  20. Young Men’s Condom Use Resistance Tactics: A Latent Profile Analysis

    PubMed Central

    Davis, Kelly Cue; Stappenbeck, Cynthia A.; Norris, Jeanette; George, William H.; Jacques-Tiura, Angela J.; Schraufnagel, Trevor J.; Kajumulo, Kelly F.

    2013-01-01

    Research suggests that many men have used a variety of tactics to avoid using a condom when having sex with a woman. Guided by previous work demonstrating that men’s use of coercive condom resistance tactics was predicted by negative attitudes toward women, inconsistent condom use, multiple partners, and sexual sensation seeking, the current study used latent profile analysis (LPA) to determine whether similar constructs were associated with a variety of resistance tactics. A community sample of 313 moderate drinking men participated, of whom 80% reported employing at least one condom use resistance tactic since adolescence. The LPA revealed three classes of men. In general, men with the least negative beliefs about women, low levels of sexual sensation seeking and impulsivity, and positive beliefs about condoms (Condom Positive/Low Hostility) reported less use of resistance tactics than men with moderate sexual sensation seeking and impulsivity, negative beliefs about condoms, and moderate (Condom Negative/Moderate Hostility) or high (Condom Negative/High Hostility) negative attitudes about women. The classes also differed in terms of their sexual behaviors. This study demonstrated that sexual risk behavior interventions should not only address the tactics through which men resist using condoms but also tailor these efforts to men’s individual characteristics. PMID:23548069

  1. Species distribution and resistance profiles of coagulase-negative staphylococci isolated from bovine mastitis in Switzerland.

    PubMed

    Moser, A; Stephan, R; Ziegler, D; Johler, S

    2013-06-01

    Coagulase-negative staphylococci (CNS) are the predominant cause of bovine intra-mammary infections. They can lead to chronic infections and were reported to significantly increase milk somatic cell counts. The goal of our study was to determine the species distribution and antimicrobial susceptibility profiles of CNS in bovine mastitis milk samples in Switzerland. Between March 2011 and February 2012, a total of 120 CNS were isolated from mastitis milk samples from 117 different animals at 77 farms. The isolates were identified by matrix-assisted laser desorption ionization - time of flight mass spectrometry (MALDI-TOF MS) and subsequently tested for sensitivity to various antibiotic agents by disk diffusion. Antimicrobial agents were selected mainly based on their relevance to the treatment of bovine mastitis in Switzerland. MALDI-TOF MS assigned the 120 isolates to 12 different staphylococcal species - S. chromogenes (33 %), S. xylosus (28 %), S. sciuri (13 %), S. haemolyticus (9 %), S. epidermidis (4 %), S. simulans (4 %), S. warneri (3 %), S. equorum (2 %), S. hyicus (2 %), S. cohnii (1 %), S. succinus (1 %), and S. fleuretti (1 %). Resistance rates in CNS were high, with 39% of isolates exhibiting resistance to ampicillin and penicillin, 6% of isolates being resistant to amoxicillin with clavulanic acid, ceftiofur, cephalothin, and cefoxitin, and 5 % being resistant to erythromycin. In rare cases resistance to gentamicin (2 %), kanamycin (2 %), and kanamycin-cefalexin (1 %) was detected. PMID:23732379

  2. Characterization and monitoring of subsurface processes using parallel computing and electrical resistivity imaging

    SciTech Connect

    Johnson, Timothy C.; Truex, Michael J.; Wellman, Dawn M.; Marble, Justin

    2011-12-01

    This newsletter discusses recent advancement in subsurface resistivity characterization and monitoring capabilities. The BC Cribs field desiccation treatability test resistivity monitoring data is use an example to demonstrate near-real time 3D subsurface imaging capabilities. Electrical resistivity tomography (ERT) is a method of imaging the electrical resistivity distribution of the subsurface. An ERT data collection system consists of an array of electrodes, deployed on the ground surface or within boreholes, that are connected to a control unit which can access each electrode independently (Figure 1). A single measurement is collected by injecting current across a pair of current injection electrodes (source and sink), and measuring the resulting potential generated across a pair of potential measurement electrodes (positive and negative). An ERT data set is generated by collecting many such measurements using strategically selected current and potential electrode pairs. This data set is then processed using an inversion algorithm, which reconstructs an estimate (or image) of the electrical conductivity (i.e. the inverse of resistivity) distribution that gave rise to the measured data.

  3. An experimentally validated contactless acoustic energy transfer model with resistive-reactive electrical loading

    NASA Astrophysics Data System (ADS)

    Shahab, S.; Gray, M.; Erturk, A.

    2015-04-01

    This paper investigates analytical modeling and experimental validation of Ultrasonic Acoustic Energy Transfer (UAET) for low-power electricity transfer to exploit in wireless applications ranging from medical implants to underwater sensor systems. A piezoelectric receiver bar is excited by incident acoustic waves originating from a source of known strength located at a specific distance from the receiver. The receiver is a free-free piezoelectric cylinder operating in the 33- mode of piezoelectricity with a fundamental resonance frequency above the audible frequency range. In order to extract the electrical power output, the piezoelectric receiver bar is shunted to a generalized resistive-reactive circuit. The goal is to quantify the electrical power delivered to the load (connected to the receiver) in terms of the source strength. Experimental validations are presented along with parameter optimization studies. Sensitivity of the electrical power output to the excitation frequency in the neighborhood of the receiver's underwater resonance frequency, source-to-receiver distance, and source-strength level are reported. Resistive and resistive-reactive electrical loading cases are discussed for performance enhancement and frequency-wise robustness. Simulations and experiments reveal that the presented multiphysics analytical model for UAET can be used to predict the coupled system dynamics with very good accuracy.

  4. Transcriptome Profiling of Resistance to Fusarium oxysporum f. sp. conglutinans in Cabbage (Brassica oleracea) Roots

    PubMed Central

    Xing, Miaomiao; Lv, Honghao; Ma, Jian; Xu, Donghui; Li, Hailong; Yang, Limei; Kang, Jungen; Wang, Xiaowu; Fang, Zhiyuan

    2016-01-01

    Fusarium wilt caused by Fusarium oxysporum f. sp. conglutinans (FOC) is a destructive disease of Brassica crops, which results in severe yield losses. There is little information available about the mechanism of disease resistance. To obtain an overview of the transcriptome profiles in roots of R4P1, a Brassica oleracea variety that is highly resistant to fusarium wilt, we compared the transcriptomes of samples inoculated with FOC and samples inoculated with distilled water. RNA-seq analysis generated more than 136 million 100-bp clean reads, which were assembled into 62,506 unigenes (mean size = 741 bp). Among them, 49,959 (79.92%) genes were identified based on sequence similarity searches, including SwissProt (29,050, 46.47%), Gene Ontology (GO) (33,767, 54.02%), Clusters of Orthologous Groups (KOG) (14,721, 23.55%) and Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) (12,974, 20.76%) searches; digital gene expression analysis revealed 885 differentially expressed genes (DEGs) between infected and control samples at 4, 12, 24 and 48 hours after inoculation. The DEGs were assigned to 31 KEGG pathways. Early defense systems, including the MAPK signaling pathway, calcium signaling and salicylic acid-mediated hypersensitive response (SA-mediated HR) were activated after pathogen infection. SA-dependent systemic acquired resistance (SAR), ethylene (ET)- and jasmonic (JA)-mediated pathways and the lignin biosynthesis pathway play important roles in plant resistance. We also analyzed the expression of defense-related genes, such as genes encoding pathogenesis-related (PR) proteins, UDP-glycosyltransferase (UDPG), pleiotropic drug resistance, ATP-binding cassette transporters (PDR-ABC transporters), myrosinase, transcription factors and kinases, which were differentially expressed. The results of this study may contribute to efforts to identify and clone candidate genes associated with disease resistance and to uncover the molecular mechanism underlying

  5. Transcriptome Profiling of Resistance to Fusarium oxysporum f. sp. conglutinans in Cabbage (Brassica oleracea) Roots.

    PubMed

    Xing, Miaomiao; Lv, Honghao; Ma, Jian; Xu, Donghui; Li, Hailong; Yang, Limei; Kang, Jungen; Wang, Xiaowu; Fang, Zhiyuan

    2016-01-01

    Fusarium wilt caused by Fusarium oxysporum f. sp. conglutinans (FOC) is a destructive disease of Brassica crops, which results in severe yield losses. There is little information available about the mechanism of disease resistance. To obtain an overview of the transcriptome profiles in roots of R4P1, a Brassica oleracea variety that is highly resistant to fusarium wilt, we compared the transcriptomes of samples inoculated with FOC and samples inoculated with distilled water. RNA-seq analysis generated more than 136 million 100-bp clean reads, which were assembled into 62,506 unigenes (mean size = 741 bp). Among them, 49,959 (79.92%) genes were identified based on sequence similarity searches, including SwissProt (29,050, 46.47%), Gene Ontology (GO) (33,767, 54.02%), Clusters of Orthologous Groups (KOG) (14,721, 23.55%) and Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) (12,974, 20.76%) searches; digital gene expression analysis revealed 885 differentially expressed genes (DEGs) between infected and control samples at 4, 12, 24 and 48 hours after inoculation. The DEGs were assigned to 31 KEGG pathways. Early defense systems, including the MAPK signaling pathway, calcium signaling and salicylic acid-mediated hypersensitive response (SA-mediated HR) were activated after pathogen infection. SA-dependent systemic acquired resistance (SAR), ethylene (ET)- and jasmonic (JA)-mediated pathways and the lignin biosynthesis pathway play important roles in plant resistance. We also analyzed the expression of defense-related genes, such as genes encoding pathogenesis-related (PR) proteins, UDP-glycosyltransferase (UDPG), pleiotropic drug resistance, ATP-binding cassette transporters (PDR-ABC transporters), myrosinase, transcription factors and kinases, which were differentially expressed. The results of this study may contribute to efforts to identify and clone candidate genes associated with disease resistance and to uncover the molecular mechanism underlying

  6. Electrical resistance and transport numbers of ion-exchange membranes used in electrodialytic soil remediation

    SciTech Connect

    Hansen, H.K.; Ottosen, L.M.; Villumsen, A.

    1999-08-01

    Electrodialytic soil remediation is a recently developed method to decontaminate heavy metal polluted soil using ion-exchange membranes. In this method one side of the ion-exchange membrane is in direct contact with the polluted soil. It is of great importance to known if this contact with the soil causes damage to the membrane. This work presents the result of transport number and electrical resistance measurements done on four sets of ion-exchange membranes (Ionics, Inc CR67 HMR412 cation-exchange membranes and Ionics, Inc AR204 SXZR anion-exchange membranes), which have been used in four different electrodialytic soil remediation experiments. The experiments showed that after the use in electrodialytic soil remediation, the ion-exchange membranes had transport numbers in the same magnitude as new membranes. The electrical resistance for six membranes did not differ from that of new membranes, whereas two membranes showed a slightly increased resistance.

  7. Post-remediation evaluation of a LNAPL site using electrical resistivity imaging.

    PubMed

    Halihan, Todd; Paxton, Stanley; Graham, Ivy; Fenstemaker, Thomas; Riley, Matt

    2005-04-01

    Present understanding of the earth's subsurface is most often derived from samples at discrete points (wells) and interpolations or models that interpret the space between these points. Electrical resistivity imaging techniques have produced an improved capability to map contaminants (especially NAPLs--NonAqueous Phase Liquids) away from traditional wells using actual field data. Electrical resistivity image data, confirmed by drilling, have demonstrated that LNAPL (Light NAPL--less dense than water, such as gasoline) contaminants exist outside of a delineated and remediated area in Golden, Oklahoma. The data also demonstrate that LNAPL exists between monitoring and remediation wells which indicate low contaminant levels when sampled. Additionally, the electrical images provided the drilling location with the highest concentration of hydrocarbon ever found on the site, even after two phases of remediation work had been performed, although the sampling protocols varied. The results indicate that current methods of post-remediation site characterization are inadequate for complete site characterization. PMID:15798793

  8. Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements

    SciTech Connect

    Whelchel, R.; Gerhardt, Dr. Rosario; Littrell, Ken

    2010-01-01

    The mechanical properties in superalloys are controlled by the distribution of the {gamma}{prime} precipitate phase. Electrical measurements have been shown to be sensitive to certain aspects of the precipitation process and show promise for predicting the evolving microstructural state in superalloys. Aging experiments were conducted on Waspaloy samples for temperatures between 600 and 950 C for times ranging from 2min to 500h. Particle size distributions were obtained by modeling of small angle scattering (SAS) data, whereas, small precipitate size information, strain, and lattice mismatch data were obtained from X-ray diffraction. The microstructural information was then used to create a figure of merit of electron scattering intended to correlate electrical properties to the precipitate microstructure. The proposed figure of merit shows an empirical correlation with the electrical resistivity data, demonstrating the sensitivity of the resistivity measurements to the precipitation process and coarsening behavior.

  9. Shift in antibiotic resistance gene profiles associated with nanosilver during wastewater treatment.

    PubMed

    Ma, Yanjun; Metch, Jacob W; Yang, Ying; Pruden, Amy; Zhang, Tong

    2016-03-01

    This study investigated the response of antibiotic resistance genes (ARGs) to nanosilver (Ag) in lab-scale nitrifying sequencing batch reactors (SBRs), compared to Ag(+)-dosed and undosed controls. Quantitative polymerase chain reaction (q-PCR) targeting sul1, tet(O), ermB and the class I integron gene intI1 and corresponding RNA expression did not indicate measureable effects of nanoAg or Ag(+) on abundance or expression of these genes. However, high-throughput sequencing based metagenomic analysis provided a much broader profile of gene responses and revealed a greater abundance of aminoglycoside resistance genes (mainly strA) in reactors dosed with nanoAg. In contrast, bacitracin and macrolide-lincosamide-streptogramin (MLS) resistance genes were more abundant in the SBRs dosed with Ag(+). The distinct ARG profiles associated with nanoAg and Ag(+) were correlated with the taxonomic composition of the microbial communities. This study indicates that nanoAg may interact with bacteria differently from Ag(+) during biological wastewater treatment. Therefore, it cannot necessarily be assumed that nanosilver behaves identically as Ag(+) when conducting a risk assessment for release into the environment. PMID:26850160

  10. Characterization and calibration of seawater intrusion models using electrical resistivity tomography (Invited)

    NASA Astrophysics Data System (ADS)

    Nguyen, F. H.; Kemna, A.; Antonsson, A.; Engesgaard, P. K.; Beaujean, J.

    2009-12-01

    The urban development of coastal regions create seawater intrusion (SWI) problems which threatens groundwater quality and coastal ecosystems. To study SWI, one needs both robust measuring technologies, and reliable predictions. A key aspect in the calibration of SWI models involves reproducing measured groundwater chloride concentrations. Drilling such multi-screen wells to obtain a whole concentration profile is a risky task if reliable information about the position of the salt wedge is not available. Electrical resistivity tomography (ERT) is increasingly being used to characterize seawater intrusion and constrain corresponding models, given its high sensitivity to ion concentration in groundwater and its relatively high spatial resolution. We have investigated the potential of ERT using field data from a site in Almeria, SE Spain and synthetic data. Simulations have been run for several scenarios, with a simple hydrogeological model reflecting the local site conditions. The simulations showed that only the lower salt concentrations of the seawater-freshwater transition zone could be recovered, due to the loss of resolution with depth. We quantified this capability in terms of image appraisal indicators (cumulative sensitivity) associated with the measurement setup and showed that the mismatch between the targeted and imaged parameter values occurs from a certain threshold. Similarly, heterogeneity may only be determined accurately if located in an adequately sensitive area. Inversion of the synthetic data was performed by coupling an inversion code (PEST) with a finite-difference density-dependent flow and transport modeling code (HTS). The numerical results demonstrate the capacity of sensitivity-filtered ERT images to constrain transverse hydraulic dispersivity and longitudinal hydraulic conductivity of homogeneous seawater intrusion models. At the field site, we identified SWI at the scale of a few kilometers down to a hundred meters. Borehole logs show a

  11. Combined Seismic Refraction Inversion, Reflection, and Electrical Resistivity Tomography Imaging of a Glacially Buried Valley

    NASA Astrophysics Data System (ADS)

    Ahmad, J.; Ogunsuyi, O.; Schmitt, D. R.; Rokosh, C. D.; Pawlowicz, J. G.

    2008-12-01

    Buried valleys are common in the regions of the Northern Hemisphere covered by ice sheets during the last glaciation. The valleys are filled by a variety of glacio-lacustrine and glacio-fluvial sedimentation. These valleys are important sources of fresh water, aggregates, and even shallow methane deposits. The surface expressions of the buried valleys, however, are often not apparent and they are often only serendipitously found during drilling for water or petroleum. Geophysical investigations of one deep (~ 350 m) buried valley in northern Alberta that had been located on the basis of geophysical logs were carried out. This buried valley was somewhat unique in that shallow (~ 30 m) methane deposits, providing a significant hazard to drilling, exist. A 10 km high resolution seismic profile (vibrator sweep 14 Hz to 250 Hz, 40 Hz geophone singles at 4 m spacing) was obtained. Significant differences in the raw shot records were apparent across the array due to the lateral differences in compressional wave velocity between the untouched bedrock and the valley fill sediments. Travel time inversion of first arrivals and deeper reflections further quantifies this lateral variation showing that the valley fill and bedrock velocities differ by more than 50% ranging from about 1700 m/s to nearly 3000 m/s, respectively. The reflection seismic image agrees well with the refraction inversion. The gross structure of the steep-sided valley is apparent. The internal architecture, however, shows a variety of clino-form dipping reflectors at the edge of the valley that are possibly related to subglacial sedimentation, a strong dipping reflector that is unconformable with the others and may be representative of recurrent discharge events, and numerous flat lying reflectors that are likely related to lacustrine sedimentation. Co-incident electrical resistivity tomography, too, is largely in agreement with the gross structure. The clay rich bedrock shales are substantially more

  12. Subsurface electrical resistivity structure around the Noubi fault system, central Japan, by MT survey

    NASA Astrophysics Data System (ADS)

    Omura, K.; Matsuda, T.; Yamada, R.

    2009-12-01

    Subsurface electrical resistivity around active faults is an important property to investigate the position and the geometry of the faults, the scale of the fracture zones related to the fault activity, and the amount of water and/or clay minerals in fault zones. We performed MT (magnetotelluric) surveys with remote reference method across the Noubi active fault system, central Japan, in order to image the electrical resistivity structure in and around the faults, and to obtain fundamental information on the earthquake generation mechanism. The Noubi fault system, about 80 km long, activated at 1891 Noubi Earthquake, consisting of the Nukumi, the Neodani, and the Umehara faults, which slipped left laterally by 1 - 7 m at the 1891 earthquake. Seismological and geomorphologic studies revealed different features between these three faults; the amount of lateral slip of the Neodani fault was larger than those of the Nukumi and the Umehara fault at 1891 Noubi earthquake (Matsuda, 1974; Mikumo and Ando, 1976); the average recurrence intervals of activation of the Nukumi and the Neodani fault were shorter than that of the Umehara fault (The Headquarters for Earthquake Research Promotion, 2005). Survey areas are mainly covered by the Mino sedimentary complex formed in the Jurassic - Cretaceous period that consists of mudstone, sandstone, limestone, basalt, chart, and siliceous mudstone. But the Hida belt that consists of metamorphic and granitic rocks covers northeast area of the Nukumi fault. Three survey lines of about 20 km length were set crossing normal to the surface fault traces of the Nukumi, Neodani and Umehara faults. And 10 - 12 MT measurement sites were arranged with the same interval on the survey lines. We measured two components of electric field and three components of magnetic field by a 'MTU-5' system made by Phoenix Geophysics Ltd. at three different sampling frequencies to cover frequency bands of 0.0003 - 317 Hz of electric and magnetic field. Applying

  13. Electrical resistance response of polyaniline films to water, ethanol, and nitric acid solution

    NASA Astrophysics Data System (ADS)

    Yin, Hong-Xing; Li, Meng-Meng; Yang, H.; Long, Yun-Ze; Sun, Xin

    2010-08-01

    This paper reports on electrical resistance vs. aging time for the response of polyaniline films under exposure to water, ethanol and nitric acid (HNO3) solution. Camphor sulfonic acid-doped polyaniline films were prepared by a “doping-dedoping-redoping" method, the morphology and microstructures of the films were characterized by a scanning electron microscope and an x-ray diffractometer, the electrical resistance was measured by a four-probe method. It was found that a lower amount of water molecules infiltrating the film can decrease the film's resistance possibly due to an enhancement of charge carrier transfer between polyaniline chains, whereas excessive water molecules can swell inter-chain distances and result in a quick increase of resistance. The resistance of the film under exposure to ethanol increases and becomes much larger than the original value. However, HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid. These results can help to understand the conduction mechanism in polyaniline films, and also indicate that the films have potential application in chemical sensors.

  14. Monitoring six-phase ohmic heating of contaminated soils using electrical resistance tomography

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1994-09-01

    Electrical resistance tomography (ERT) was used to monitor six-phase ohmic heating used for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. The changes in electrical conductivity caused by six-phase ohmic-heating in a clay layer located in the vadose zone were monitored during a period of approximately 2 months, before, during and after heating. From an array of electrodes located in 4 boreholes, we collected electrical resistivity data between five pairs of adjacent holes pairs. This data was used to calculate tomographs which showed the electrical conductivity changes along five vertical planes. The difference tomographs show the combined effects of moisture redistribution and heating caused by six-phase heating and vapor extraction. The tomographs show that most of the clay layer increased in electrical conductivity during the first 3 weeks of the 4 week long heating phase. At this time, the electrical conductivities near the center of the heating array were twice as large as the pre-heat conductivities. Then the electrical conductivity started to decrease for portions of the clay layer closest to the vapor extraction well. We propose that the conductivity decreases are due to the removal of moisture by the heating and vacuum extraction. Parts of the clay layer near the extraction well reached electrical conductivities as low as 40% of the pre-heating values. We propose that these regions of lower than ambient electrical conductivities are indicators of regions where the vapor removal by vacuum extraction was most effective. At the end of the heating phase, our estimates suggest that the clay saturation may have dropped to as low as 10% based on the observed conductivity changes.

  15. Relationships among low frequency (2 Hz) electrical resistivity, porosity, clay content and permeability in reservoir sandstones

    NASA Astrophysics Data System (ADS)

    Han, Tongcheng; Best, Angus I.; Sothcott, Jeremy; North, Laurence J.; MacGregor, Lucy M.

    2015-01-01

    The improved interpretation of marine controlled source electromagnetic (CSEM) data requires knowledge of the inter-relationships between reservoir parameters and low frequency electrical resistivity. Hence, the electrical resistivities of 67 brine (35 g/l) saturated sandstone samples with a range of petrophysical properties (porosity from 2% to 29%, permeability from 0.0001 mD to 997.49 mD and volumetric clay content from 0 to 28%) were measured in the laboratory at a frequency of 2 Hz using a four-electrode circumferential resistivity method with an accuracy of ± 2%. The results show that sandstones with porosity higher than 9% and volumetric clay content up to 22% behave like clean sandstones and follow Archie's law for a brine concentration of 35 g/l. By contrast, at this brine salinity, sandstones with porosity less than 9% and volumetric clay content above 10% behave like shaly sandstones with non-negligible grain surface conductivity. A negative, linear correlation was found between electrical resistivity and hydraulic permeability on a logarithmic scale. We also found good agreement between our experimental results and a clay pore blocking model based on pore-filling and load-bearing clay in a sand/clay mixture, variable (non-clay) cement fraction and a shaly sandstone resistivity model. The model results indicate a general transition in shaly sandstones from clay-controlled resistivity to sand-controlled resistivity at about 9% porosity. At such high brine concentrations, no discernible clay conduction effect was observed above 9% porosity.

  16. Velocity profiles of electric-field-induced backflows in liquid crystals confined between parallel plates

    NASA Astrophysics Data System (ADS)

    Tsuji, Tomohiro; Chono, Shigeomi; Matsumi, Takanori

    2015-02-01

    For the purpose of developing liquid crystalline microactuators, we visualize backflows induced between two parallel plates for various parameters such as the twist angle, cell gap, applied voltage, and molecular configuration mode. We use 4-cyano-4'-pentyl biphenyl, a typical low-molar-mass nematic liquid crystal. By increasing the twist angle from 0° to 180°, the velocity component parallel to the anchoring direction of the lower plate changes from an S-shaped profile to a distorted S-shaped profile before finally becoming unidirectional. In contrast, the velocity component perpendicular to the anchoring direction evolves from a flat profile at 0° into an S-shaped profile at 180°. Because both an increase in the applied voltage and a decrease in the cell gap increase the electric field intensity, the backflow becomes large. The hybrid molecular configuration mode induces a larger backflow than that for the planar aligned mode. The backflow develops in two stages: an early stage with a microsecond time scale and a later stage with a millisecond time scale. The numerical predictions are in qualitative agreement with the measurements, but not quantitative agreement because our computation ignores the plate edge effect of surface tension.

  17. Stark Profiles In Plasmas Interacting With A Strong Oscillatory Quasi-Monochromatic Electric Field

    SciTech Connect

    Sauvan, P.; Oks, E.; Renner, O.; Weber, S.

    2010-10-29

    This paper presents an advanced analysis of the spectroscopic signatures of the interaction of a strong oscillating Quasi-monochromatic Electric Field (QEF), generated by a high-power short-pulse laser, with a preformed laser-produced plasma. The computation of a synthetic spectrum emitted by such plasmas requires the calculation of the Stark line shape in the presence of a QEF and the evaluation of the QEF intensity profile throughout the line of sight in the plasma. As for the Stark profiles in hot dense plasmas submitted to a strong QEF, they are calculated using the so-called Floquet-Liouville formalism. In this formalism, the Liouville space, usually used for the calculation of Stark profiles in dense plasmas, and the Floquet theory, developed to solve time-periodic problems, have been joined together to solve the time-dependent Liouville equation. A second kind of simulations involving Particle-In-Cell PIC kinetic simulations is required for the calculation of the QEF inhomogeneous intensity and the exotic features exhibited in the spectroscopic diagnostic. The global synthetic profile is obtained integrating all individual contributions for every time and location in the plasma. Finally, a spectroscopic analysis of the experimental Al He {beta} line is performed using the tools presented in this work. The spectroscopic signatures of the QEF show up as prominent satellites, non symmetrical with respect to the unperturbed line and distinguishable from the di-electronic satellites.

  18. Effects of borehole design on complex electrical resistivity measurements: laboratory validation and numerical experiments

    NASA Astrophysics Data System (ADS)

    Treichel, A.; Huisman, J. A.; Zhao, Y.; Zimmermann, E.; Esser, O.; Kemna, A.; Vereecken, H.

    2012-12-01

    Geophysical measurements within a borehole are typically affected by the presence of the borehole. The focus of the current study is to quantify the effect of borehole design on broadband electrical impedance tomography (EIT) measurements within boreholes. Previous studies have shown that effects on the real part of the electrical resistivity are largest for boreholes with large diameters and for materials with a large formation factor. However, these studies have not considered the effect of the well casing and the filter gravel on the measurement of the real part of the electrical resistivity. In addition, the effect of borehole design on the imaginary part of the electrical resistivity has not been investigated yet. Therefore, the aim of this study is to investigate the effect of borehole design on the complex electrical resistivity using laboratory measurements and numerical simulations. In order to do so, we developed a high resolution two dimensional axisymmetric finite element model (FE) that enables us to simulate the effects of several key borehole design parameters (e.g. borehole diameter, thickness of PVC well casing) on the measurement process. For the material surrounding the borehole, realistic values for complex resistivity were obtained from a database of laboratory measurements of complex resistivity from the test site Krauthausen (Germany). The slotted PVC well casing is represented by an effective resistivity calculated from the water-filled slot volume and the PVC volume. Measurements with and without PVC well casing were made with a four-electrode EIT logging tool in a water-filled rain barrel. The initial comparison for the case that the logging tool was inserted in the PVC well casing showed a considerable mismatch between measured and modeled values. It was required to consider a complete electrode model instead of point electrodes to remove this mismatch. This validated model was used to investigate in detail how complex resistivity

  19. Electrical resistivity and porosity structure of the upper Biscayne Aquifer in Miami-Dade County, Florida

    NASA Astrophysics Data System (ADS)

    Whitman, Dean; Yeboah-Forson, Albert

    2015-12-01

    Square array electrical soundings were made at 13 sites in the Biscayne Aquifer distributed between 1 and 20 km from the shoreline. These soundings were modeled to investigate how resistivity varies spatially and with depth in the upper 15 m of the aquifer. Porosity was estimated from the modeled formation resistivity and observed pore fluid resistivity with Archie's Law. The models were used to interpolate resistivity and porosity surfaces at -2, -5, -8, and -15 m elevations. Modeled resistivity in the unsaturated zone is generally higher than 300 Ω m with the resistivity at sites with thick unsaturated zones greater than 1000 Ω m. Resistivity in the saturated zone ranges from 30 to 320 Ω m. At many sites in the western portions of the study area, resistivity is constant or increases with depth whereas sites in the center of the Atlantic Coastal Ridge exhibit a distinct low resistivity zone (ρ < 45 Ω m) at elevations ranging between -5 and -10 m. At one site near the shore of Biscayne Bay, the resistivity is less than 10 Ω m at -5 m elevation reflecting the presence of salt water in the aquifer. The estimated porosity ranges between 14% and 71% with modal values near 25%. The porosity structure varies both with depth and spatially. Western sites exhibit a high porosity zone at shallow depths best expressed in a NE-SW trending zone of 40-50% porosity situated near the western margin of the Atlantic Coastal Ridge. This zone roughly corresponds in depth with the Q5 chronostratigraphic unit of the Miami Fm. which constitutes the upper flow unit of the Biscayne Aquifer. The highest porosity (>50%) is seen at elevations below -5 m at sites in the center of the Atlantic Coastal Ridge and likely corresponds to solution features. The general NE-SW trend of the resistivity and porosity structure suggests a causal connection with the Pleistocene paleogeography and sedimentary environments.

  20. Antimicrobial Resistance Profile of Planktonic and Biofilm Cells of Staphylococcus aureus and Coagulase-Negative Staphylococci.

    PubMed

    de Oliveira, Adilson; Cataneli Pereira, Valéria; Pinheiro, Luiza; Moraes Riboli, Danilo Flávio; Benini Martins, Katheryne; Ribeiro de Souza da Cunha, Maria de Lourdes

    2016-01-01

    The objective of the present study was to determine the antimicrobial resistance profile of planktonic and biofilm cells of Staphylococcus aureus and coagulase-negative staphylococci (CoNS). Two hundred Staphylococcus spp. strains were studied, including 50 S. aureus and 150 CoNS strains (50 S. epidermidis, 20 S. haemolyticus, 20 S. warneri, 20 S. hominis, 20 S. lugdunensis, and 20 S. saprophyticus). Biofilm formation was investigated by adherence to polystyrene plates. Positive strains were submitted to the broth microdilution method to determine the minimum inhibitory concentration (MIC) for planktonic and biofilm cells and the minimal bactericidal concentration for biofilm cells (MBCB). Forty-nine Staphylococcus spp. strains (14 S. aureus, 13 S. epidermidis, 13 S. saprophyticus, 3 S. haemolyticus, 1 S. hominis, 3 S. warneri, and 2 S. lugdunensis) were biofilm producers. These isolates were evaluated regarding their resistance profile. Determination of planktonic cell MIC identified three (21.4%) S. aureus strains that were resistant to oxacillin and six (42.8%) that were resistant to erythromycin. Among the CoNS, 31 (88.6%) strains were resistant to oxacillin, 14 (40%) to erythromycin, 18 (51.4%) to gentamicin, and 8 (22.8%) to sulfamethoxazole/trimethoprim. None of the planktonic isolates were resistant to vancomycin or linezolid. MICs were 2-, 4-, 8-, and up to 16-fold higher for biofilm cells than for planktonic cells. This observation was more common for vancomycin and erythromycin. The MBCB ranged from 8 to >256 µg/mL for oxacillin, 128 to >128 µg/mL for vancomycin, 256 to >256 µg/mL for erythromycin and gentamicin, >64 µg/mL for linezolid, and 32/608 to >32/608 µg/mL for sulfamethoxazole/trimethoprim. The results showed considerably higher MICs for S. aureus and CoNS biofilm cells compared to planktonic cells. Analysis of MBCM confirmed that even high concentrations of vancomycin were unable to eliminate the biofilms of S. aureus and CoNS species

  1. The Electrical Resistivity Structure of the Eastern Anatolian Collision Zone, Northeastern Anatolia

    NASA Astrophysics Data System (ADS)

    Cengiz, Özlem; Tuǧrul Başokur, Ahmet; Tolak Çiftçi, Elif

    2016-04-01

    The Northeastern Anatolia is located at the intensely deformed Eastern Anatolian Collision Zone (EACZ), and its tectonic framework is characterized by the collision of the Arabian plate with Eurasian. Although extensive attention is given to understand the crustal and upper mantle processes at this convergent boundary, there is still an ongoing debate over the geodynamic processes of the region. In this study, we were specifically interested in the geoelectric properties and thus geodynamics of the crust beneath the EACZ. Magnetotelluric (MT) measurements were made on two profiles across the north of the EACZ in 1998 as part of a national project undertaken by the Turkish Petroleum Corporation (TPAO). MT data in the frequency range of 300-0.001 Hz were collected from 168 stations located along 78 km north to south and 47 km west to east profiles where direct convergence occurs between Arabian and Eurasian plates. Two and three-dimensional inversion algorithms were used to obtain resistivity models of the study area. According to these models, the upper crust consists of low resistivity sedimentary rocks (<30 Ωm) that are underlain by highly resistive (~500-1000 Ωm) crystalline basement rocks of the Eastern Anatolian Accretionary Complex and Pontides. While the upper and lower crustal resistivity at the northern part of the study area shows a layered structure, significant horizontal and vertical variations for the rest of the EACZ exists on resistivity models. The broad low resistivity zones (<50 Ωm) observed at mid and lower crustal levels throughout the EACZ. These fluid-rich regions along with high temperatures could indicate weak zones representing the locations of active deformation induced by continent-continent collision and correlate with volcanic centers in the region. The variation in the resistivity structure supports the southward subduction model with the resistive continental block and the deep conductive zones presumably corresponding to the

  2. Some considerations on electrical resistivity imaging for characterization of waterbed sediments

    NASA Astrophysics Data System (ADS)

    Orlando, Luciana

    2013-08-01

    The paper focuses on defining the performance and limits of ERI in the detection and sedimentary characterization of near-bottom thin layers. The analysis of the resolution of floating and submerged cables, and the effect of the accuracy of a priori information (resistivity and thickness) in the data inversion, is based on theory, models and actual data. Theoretical models show that the actual reconstruction of the near water-bottom sediments, in terms of geometry and resistivity, can be obtained only with the submerged cable, however, the data, unlike that acquired with the floating cable, require a priori information on water resistivity and thickness for the data inversion. Theoretical forward models based on wrong a priori water thickness and resistivity information influence the inverted model in different ways, depending on the under- and over-estimation of water resistivity and thickness, and the resistivity contrast of the water-solid layer; however a water-solid resistivity contrast of less than 2 and within 10% of error in water resistivity has no effect. Overestimating water resistivity depicts a ground similar to the actual ground in terms of resistivity, more so than the underestimation of water resistivity. Moreover, the data inversion is less influenced by water parameter error in the case of low resistivity contrast in the water-solid layer, than it is for high resistivity contrast. Wenner and Schlumberger arrays give comparable results, while a dipole-dipole array seems to be more sensitive to the accuracy of apparent resistivity measurements and a priori information on water. The theoretical considerations were validated by actual data acquired with a submerged cable on the Tiber River. The study has shown that if highly accurate measurements are made of water thickness and resistivity, then electrical resistivity imaging from the submerged cable can be used in addition to, or even to substitute, seismic data for the reconstruction of the features

  3. Gene expression profiling of Naïve sheep genetically resistant and susceptible to gastrointestinal nematodes

    PubMed Central

    Keane, Orla M; Zadissa, Amonida; Wilson, Theresa; Hyndman, Dianne L; Greer, Gordon J; Baird, David B; McCulloch, Alan F; Crawford, Allan M; McEwan, John C

    2006-01-01

    Background Gastrointestinal nematodes constitute a major cause of morbidity and mortality in grazing ruminants. Individual animals or breeds, however, are known to differ in their resistance to infection. Gene expression profiling allows us to examine large numbers of transcripts simultaneously in order to identify those transcripts that contribute to an animal's susceptibility or resistance. Results With the goal of identifying genes with a differential pattern of expression between sheep genetically resistant and susceptible to gastrointestinal nematodes, a 20,000 spot ovine cDNA microarray was constructed. This array was used to interrogate the expression of 9,238 known genes in duodenum tissue of four resistant and four susceptible female lambs. Naïve animals were used in order to look at genes that were differentially expressed in the absence of infection with gastrointestinal nematodes. Forty one unique known genes were identified that were differentially expressed between the resistant and susceptible animals. Northern blotting of a selection of the genes confirmed differential expression. The differentially expressed genes had a variety of functions, although many genes relating to the stress response and response to stimulus were more highly expressed in the susceptible animals. Conclusion We have constructed the first reported ovine microarray and used this array to examine gene expression in lambs genetically resistant and susceptible to gastrointestinal nematode infection. This study indicates that susceptible animals appear to be generating a hyper-sensitive immune response to non-nematode challenges. The gastrointestinal tract of susceptible animals is therefore under stress and compromised even in the absence of gastrointestinal nematodes. These factors may contribute to the genetic susceptibility of these animals. PMID:16515715

  4. Antimicrobial Resistance Profiles in Escherichia coli O157 Isolates from Northern Colorado Dairies.

    PubMed

    McConnel, Craig S; Stenkamp-Strahm, Chloe M; Rao, Sangeeta; Linke, Lyndsey M; Magnuson, Roberta J; Hyatt, Doreene R

    2016-03-01

    Escherichia coli O157 (EcO157) infections can lead to serious disease and death in humans. Although the ecology of EcO157 is complex, ruminant animals serve as an important reservoir for human infection. Dairy cattle are unique because they may be a source of contamination for milk, meat, and manure-fertilized crops. Foodborne dairy pathogens such as EcO157 are of primary importance to public health. Antimicrobial resistance (AMR) is a complex phenomenon that complicates the treatment of serious bacterial infections and is of increasing concern. In the face of recommended use restrictions for antimicrobial agents in livestock operations, current AMR patterns in known foodborne pathogens should be documented. The objective of this study was to document AMR patterns in EcO157 isolates from dairies in northern Colorado using antimicrobial agents commonly found on dairies and representative of medically important antimicrobial drug classes. Seventy-five EcO157 isolates were recovered from three dairies. Six isolates were resistant to at least 1 of the 10 tested antimicrobial agents: four were resistant to streptomycin, sulfisoxazole, and tetracycline; one was resistant to streptomycin and tetracycline; and one was resistant to only tetracycline. All resistant isolates were from a single dairy. Overall, a low prevalence (8%) of AMR was observed among the 75 EcO157 isolates. No significant effects on AMR profiles due to virulence genes, parity, or previous antimicrobial treatments within the current lactation period were detected. The results of this study provide background information for future comparative studies investigating AMR trends. Future studies should include more participating farms and more samples and should control for potential confounding factors of AMR that may underlie individual farm variation. PMID:26939660

  5. Vaginal versus Obstetric Infection Escherichia coli Isolates among Pregnant Women: Antimicrobial Resistance and Genetic Virulence Profile

    PubMed Central

    Sáez-López, Emma; Guiral, Elisabet; Fernández-Orth, Dietmar; Villanueva, Sonia; Goncé, Anna; López, Marta; Teixidó, Irene; Pericot, Anna; Figueras, Francesc; Palacio, Montse; Cobo, Teresa; Bosch, Jordi; Soto, Sara M.

    2016-01-01

    Vaginal Escherichia coli colonization is related to obstetric infections and the consequent development of infections in newborns. Ampicillin resistance among E. coli strains is increasing, which is the main choice for treating empirically many obstetric and neonatal infections. Vaginal E. coli strains are very similar to extraintestinal pathogenic E. coli with regards to the virulence factors and the belonging to phylogroup B2. We studied the antimicrobial resistance and the genetic virulence profile of 82 E. coli isolates from 638 vaginal samples and 63 isolated from endometrial aspirate, placental and amniotic fluid samples from pregnant women with obstetric infections. The prevalence of E. coli in the vaginal samples was 13%, which was significant among women with associated risk factors during pregnancy, especially premature preterm rupture of membranes (p<0.0001). Sixty-five percent of the strains were ampicillin-resistant. The E. coli isolates causing obstetric infections showed higher resistance levels than vaginal isolates, particularly for gentamicin (p = 0.001). The most prevalent virulence factor genes were those related to the iron uptake systems revealing clear targets for interventions. More than 50% of the isolates belonged to the virulent B2 group possessing the highest number of virulence factor genes. The ampicillin-resistant isolates had high number of virulence factors primarily related to pathogenicity islands, and the remarkable gentamicin resistance in E. coli isolates from women presenting obstetric infections, the choice of the most appropriate empiric treatment and clinical management of pregnant women and neonates should be carefully made. Taking into account host-susceptibility, the heterogeneity of E. coli due to evolution over time and the geographical area, characterization of E. coli isolates colonizing the vagina and causing obstetric infections in different regions may help to develop interventions and avoid the aetiological link

  6. Antibiotic resistance profiles and quorum sensing-dependent virulence factors in clinical isolates of pseudomonas aeruginosa.

    PubMed

    Wang, Huafu; Tu, Faping; Gui, Zhihong; Lu, Xianghong; Chu, Weihua

    2013-06-01

    Pseudomonas aeruginosa produces multiple virulence factors that have been associated with quorum sensing. The aim of this study was to evaluate the prevalence of drug resistant profiles and quorum sensing related virulence factors. Pseudomonas aeruginosa were collected from different patients hospitalized in China, the isolates were tested for their susceptibility to different common antimicrobial drugs and detected QS-related virulence factors. We identified 170 isolates displaying impaired phenotypic activity, approximately 80 % of the isolates were found to exhibit the QS-dependent phenotypes, among them, 12 isolates were defective in AHLs production, and therefore considered QS-deficient strains. Resistance was most often observed to Cefazolin (81.2 %), followed by trimethoprim-sulfamethoxazole (73.5 %), ceftriaxone (62.4 %) and Cefotaxime, Levofloxacin, Ciprofloxacin (58.8 %), and to a lesser extent Meropenem (20.0 %), Cefepime (18.8 %), and Cefoperazone/sulbactam (2.4 %) The QS-deficient isolates that were negative for virulence factor production were generally less susceptible to the antimicrobials. The results showed a high incidences of antibiotic resistance and virulence properties in P. aeruginosa, and indicate that the clinical use of QS-inhibitory drugs that appear superior to conventional antimicrobials by not exerting any selective pressure on resistant strains. PMID:24426103

  7. Integrative Molecular Profiling Reveals Asparagine Synthetase Is a Target in Castration-Resistant Prostate Cancer

    PubMed Central

    Sircar, Kanishka; Huang, Heng; Hu, Limei; Cogdell, David; Dhillon, Jasreman; Tzelepi, Vassiliki; Efstathiou, Eleni; Koumakpayi, Ismaël H.; Saad, Fred; Luo, Dijun; Bismar, Tarek A.; Aparicio, Ana; Troncoso, Patricia; Navone, Nora; Zhang, Wei

    2013-01-01

    The identification of new and effective therapeutic targets for the lethal, castration-resistant stage of prostate cancer (CRPC) has been challenging because of both the paucity of adequate frozen tissues and a lack of integrated molecular analysis. Therefore, in this study, we performed a genome-wide analysis of DNA copy number alterations from 34 unique surgical CRPC specimens and 5 xenografts, with matched transcriptomic profiling of 25 specimens. An integrated analysis of these data revealed that the asparagine synthetase (ASNS) gene showed a gain in copy number and was overexpressed at the transcript level. The overexpression of ASNS was validated by analyzing other public CRPC data sets. ASNS protein expression, as detected by reverse-phase protein lysate array, was tightly correlated with gene copy number. In addition, ASNS protein expression, as determined by IHC analysis, was associated with progression to a therapy-resistant disease state in TMAs that included 77 castration-resistant and 40 untreated prostate cancer patient samples. Knockdown of ASNS by small-interfering RNAs in asparagine-deprived media led to growth inhibition in both androgen-responsive (ie, LNCaP) and castration-resistant (ie, C4-2B) prostate cancer cell lines and in cells isolated from a CRPC xenograft (ie, MDA PCa 180-30). Together, our results suggest that ASNS is up-regulated in cases of CRPC and that depletion of asparagine using ASNS inhibitors will be a novel strategy for targeting CRPC cells. PMID:22245216

  8. Metagenomic Profiling of Microbial Composition and Antibiotic Resistance Determinants in Puget Sound

    PubMed Central

    Port, Jesse A.; Wallace, James C.; Griffith, William C.; Faustman, Elaine M.

    2012-01-01

    Human-health relevant impacts on marine ecosystems are increasing on both spatial and temporal scales. Traditional indicators for environmental health monitoring and microbial risk assessment have relied primarily on single species analyses and have provided only limited spatial and temporal information. More high-throughput, broad-scale approaches to evaluate these impacts are therefore needed to provide a platform for informing public health. This study uses shotgun metagenomics to survey the taxonomic composition and antibiotic resistance determinant content of surface water bacterial communities in the Puget Sound estuary. Metagenomic DNA was collected at six sites in Puget Sound in addition to one wastewater treatment plant (WWTP) that discharges into the Sound and pyrosequenced. A total of ∼550 Mbp (1.4 million reads) were obtained, 22 Mbp of which could be assembled into contigs. While the taxonomic and resistance determinant profiles across the open Sound samples were similar, unique signatures were identified when comparing these profiles across the open Sound, a nearshore marina and WWTP effluent. The open Sound was dominated by α-Proteobacteria (in particular Rhodobacterales sp.), γ-Proteobacteria and Bacteroidetes while the marina and effluent had increased abundances of Actinobacteria, β-Proteobacteria and Firmicutes. There was a significant increase in the antibiotic resistance gene signal from the open Sound to marina to WWTP effluent, suggestive of a potential link to human impacts. Mobile genetic elements associated with environmental and pathogenic bacteria were also differentially abundant across the samples. This study is the first comparative metagenomic survey of Puget Sound and provides baseline data for further assessments of community composition and antibiotic resistance determinants in the environment using next generation sequencing technologies. In addition, these genomic signals of potential human impact can be used to guide

  9. Effects of contact resistance on electrical conductivity measurements of SiC-based materials

    SciTech Connect

    Youngblood, G. E.; Thomsen, E. C.; Henager, C. H.

    2013-11-01

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ~973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ~1000 Ω cm2 at RT, decreasing continuously to ~1–10 Ω cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. Finally, for the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.

  10. Long-term electrical resistivity monitoring of recharge-induced contaminant plume behavior

    NASA Astrophysics Data System (ADS)

    Gasperikova, Erika; Hubbard, Susan S.; Watson, David B.; Baker, Gregory S.; Peterson, John E.; Kowalsky, Michael B.; Smith, Meagan; Brooks, Scott

    2012-11-01

    Geophysical measurements, and electrical resistivity tomography (ERT) data in particular, are sensitive to properties that are related (directly or indirectly) to hydrological processes. The challenge is in extracting information from geophysical data at a relevant scale that can be used to gain insight about subsurface behavior and to parameterize or validate flow and transport models. Here, we consider the use of ERT data for examining the impact of recharge on subsurface contamination at the S-3 ponds of the Oak Ridge Integrated Field Research Challenge (IFRC) site in Tennessee. A large dataset of time-lapse cross-well and surface ERT data, collected at the site over a period of 12 months, is used to study time variations in resistivity due to changes in total dissolved solids (primarily nitrate). The electrical resistivity distributions recovered from cross-well and surface ERT data agrees well, and both of these datasets can be used to interpret spatiotemporal variations in subsurface nitrate concentrations due to rainfall, although the sensitivity of the electrical resistivity response to dilution varies with nitrate concentration. Using the time-lapse surface ERT data interpreted in terms of nitrate concentrations, we find that the subsurface nitrate concentration at this site varies as a function of spatial position, episodic heavy rainstorms (versus seasonal and annual fluctuations), and antecedent rainfall history. These results suggest that the surface ERT monitoring approach is potentially useful for examining subsurface plume responses to recharge over field-relevant scales.

  11. Rough surface electrical contact resistance considering scale dependent properties and quantum effects

    SciTech Connect

    Jackson, Robert L.; Crandall, Erika R.; Bozack, Michael J.

    2015-05-21

    The objective of this work is to evaluate the effect of scale dependent mechanical and electrical properties on electrical contact resistance (ECR) between rough surfaces. This work attempts to build on existing ECR models that neglect potentially important quantum- and size-dependent contact and electrical conduction mechanisms present due to the asperity sizes on typical surfaces. The electrical conductance at small scales can quantize or show a stepping trend as the contact area is varied in the range of the free electron Fermi wavelength squared. This work then evaluates if these effects remain important for the interface between rough surfaces, which may include many small scale contacts of varying sizes. The results suggest that these effects may be significant in some cases, while insignificant for others. It depends on the load and the multiscale structure of the surface roughness.

  12. Aging Effect on Oxygen-Sensitive Electrical Resistance of SrTiO3 Thin Films

    NASA Astrophysics Data System (ADS)

    Hara, Toru; Ishiguro, Takashi; Shinozaki, Kazuo

    2011-06-01

    Our previous studies showed that SrTiO3-based thin films can be used to detect trace amounts of oxygen. The sensitivity to oxygen of the films was attributed to the polaronic nature of SrTiO3. In this study, it was observed that the application of an electric field resulted in a decrease in electrical resistance (hereafter, the aging effect) possibly in the same way as a dc electrical degradation in ceramic capacitors, which is due to the demixing of the oxygen vacancies (the electrical migration of oxygen vacancies leading to their pileup at the interface between SrTiO3 and electrodes). The sensitivity to oxygen of the films was maintained even after aging.

  13. Temperature dependence of the electrical resistance of sound and carious teeth.

    PubMed

    Huysmans, M C; Longbottom, C; Christie, A M; Bruce, P G; Shellis, R P

    2000-07-01

    Temperature variations are expected to influence measurement error in electrical resistance of teeth. It was the aim of this study to determine the changes in electrical behavior of extracted human teeth due to temperature changes in the range of room temperature to intra-oral temperature. Nine extracted teeth were selected, and the occlusal or an approximal surface was chosen for measurement. Carious involvement of the surfaces ranged from sound to cavitated. Electrical impedance spectroscopy sweeps in a frequency range of about 100 kHz to 10 Hz were completed at selected temperatures between 22 degrees C and 40 degrees C. After fitting the data to equivalent circuits that yielded parameter values for components of the equivalent circuit, we calculated the dc bulk resistance (Rh). The temperature dependence of Rb of the surfaces with different carious involvement was very similar, and the mean drop of Rb from 20 to 35 degrees C was 45% (SD 2%). It was concluded that the electrical resistance of sound and carious tooth surfaces is inversely related to temperature. PMID:11005729

  14. Monitoring radio-frequency heating of contaminated soils using electrical resistance tomography

    SciTech Connect

    Ramirez, A.L.; Daily, W.D.

    1993-09-01

    Electrical resistance tomography (ERT) was used to monitor a radio-frequency heating process for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. A dipole antenna located in a horizontal well in the unsaturated zone was used to heat a contaminated clay layer. The heat-induced changes were tomographically imaged by their effects on the formation electrical resistivity. The resistivity changes observed appear to be related to heating and vaporization of the pore water, formation of steam condensate, and infiltration of rainwater through the heated zones and adjacent areas. There is a clear asymmetry downward in the resistivity decreases associated with the heating process. The resistivity decreases observed in the vicinity of the heating well are believed to be caused by the heating and downward migration of warm water originally located within a radius of a few feet around the heating well; the magnitude of the change is between 10--20%. The decreasing resistivity implies an increasing rate of radio wave attenuation as heating progressed; therefore, the rate of energy deposition around the heating well increased while the penetration distance of the radio waves decreased. Saturation changes in the clay near the antenna during heating were estimated to be 50--55% based on the observed resistivity decreases. Resistivity changes observed at distances greater than 3 meters to one side of the antenna appear to be related to rainwater infiltration. We propose that gaps in near surface clay layers allow rainwater to migrate downward and reach the top of clay rich zone penetrated by the antenna borehole. The water may then accumulate along the top of the clay.

  15. Implications for the lithospheric geometry of the Iapetus suture beneath Ireland based on electrical resistivity models from deep-probing magnetotellurics

    NASA Astrophysics Data System (ADS)

    Rao, C. K.; Jones, Alan G.; Moorkamp, Max; Weckmann, Ute

    2014-08-01

    Broad-band and long period magnetotelluric (MT) data were acquired at 39 stations along five NNW-SSE profiles crossing the Iapetus Suture Zone (ISZ) in Ireland. Regional strike analyses indicate that the vast majority of the MT data is consistent with an assumption of a 2-D geo-electric strike direction. Strike is N52°E for the three easternmost profiles and N75°E for the two westernmost profiles; these directions correlate well with the observed predominant geological strike of the study region. 2-D inversions of the galvanic distortion-corrected TE and TM mode data from each profile are shown and discussed. As mapped geological variations between the neighbouring profiles suggest a heterogeneous subsurface, it is important to verify the robustness of the presence and geometries of prominent conductivity anomalies by employing 3-D forward and inverse modelling. A high conductivity layer (resistivity of 1-10 Ωm), found at middle to lower crustal depths and presumed to be indicative of metamorphosed graphitic sediments rich in sulphides deposited during the convergence of the Laurentian and Avalonian continents, essentially constitutes the electrical signature of the ISZ. Shallow conductors observed are probably due to black shales that were widely deposited within the sedimentary accretionary wedge during Ordovician time. We interpret the moderately low resistivity at shallow depths from west to east across Ireland as indicative of an increase in maturity of the black shales in the easterly direction. From our conductivity models the southern extent of the ISZ is inferred to lie between the Navan Silvermines Fault and the Navan Tipperary Line, and shows clear resistivity contrast along all the profiles at the southern MT stations. The change in resistivity deduced from the 2-D models is spatially related to the composition of Lower Palaeozoic Ordovician, Silurian, Devonian and Carboniferous rocks. At upper mantle depths of about 60 km, a high conductivity block

  16. Using Electrical Resistivity Tomography for Constraining a Hydrogeological Model in a Data Sparse Region

    NASA Astrophysics Data System (ADS)

    Foster, S.; Allen, D. M.

    2013-12-01

    Geological and hydrogeological data are often spatially limited in mountainous regions. In these settings, geophysical techniques can be used to constrain hydrogeological models by providing insight into the hydrostratigraphy and the continuity of units in the subsurface. This study we used electrical resistivity tomography coupled with a priori geological data from residential water wells to improve the accuracy and confidence of a hydrogeological model. The study area is situated within the mountainous Cowichan watershed in British Columbia, Canada. Throughout the watershed, unconsolidated deposits of variable thickness overlie bedrock. Based on available water well information, at high elevation, sediment thickness is on the order of a few metres, but within the valley bottom, sediment thickness can be up to 300 m. The unconsolidated deposits are heterogeneous due to a complex depositional environment that was controlled by glacial advances and recessions, most notably during the Fraser Glaciation. Six electrical resistivity transects of various lengths spanning 135 to 830 metres were conducted in an area of the watershed that is particularly data poor. The electrical resistivity transects were strategically placed, first, to make use of available lithology information from existing water wells in order to constrain the geophysical interpretation, and second, to contribute data to areas that lack subsurface lithological records. Electrical resistivity was measured using a AGI SuperSting R1 system, and data were processed using robust inversion software to identify stark geophysical contacts. The technique successfully delineated zones of conductive and resistive units that have been interpreted as aquitards (clay and till formations), aquifers (water bearing sand and gravel lenses), and bedrock based on dielectric contrast. Available surficial geology and bedrock geology maps, coupled with residential well drilling records, further assisted in mapping the

  17. ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY

    SciTech Connect

    MYERS DA; RUCKER DF; FINK JB; LOKE MH

    2009-12-16

    Highly industrialized areas pose challenges for surface electrical resistivity characterization due to metallic infrastructure. The infrastructure is typically more conductive than the desired targets and will mask the deeper subsurface information. These challenges may be minimized if steel-cased wells are used as long electrodes in the area near the target. We demonstrate a method of using long electrodes to electrically monitor a simulated leak from an underground storage tank with both synthetic examples and a field demonstration. The synthetic examples place a simple target of varying electrical properties beneath a very low resistivity layer. The layer is meant to replicate the effects of infrastructure. Both surface and long electrodes are tested on the synthetic domain. The leak demonstration for the field experiment is simulated by injecting a high conductivity fluid in a perforated well within the S tank farm at Hanford, and the resistivity measurements are made before and after the leak test. All data are processed in four dimensions, where a regularization procedure is applied in both the time and space domains. The synthetic test case shows that the long electrode ERM could detect relative changes in resistivity that are commensurate with the differing target properties. The surface electrodes, on the other hand, had a more difficult time matching the original target's footprint. The field results shows a lowered resistivity feature develop south of the injection site after cessation of the injections. The time lapsed regularization parameter has a strong influence on the differences in inverted resistivity between the pre and post injection datasets, but the interpretation of the target is consistent across all values of the parameter. The long electrode ERM method may provide a tool for near real-time monitoring of leaking underground storage tanks.

  18. Monitoring of olive oil mills' wastes using electrical resistivity tomography techniques

    NASA Astrophysics Data System (ADS)

    Simyrdanis, Kleanthis; Papadopoulos, Nikos; Kirkou, Stella; Sarris, Apostolos; Tsourlos, Panagiotis

    2014-08-01

    Olive oil mills' wastes (OOMW) are one of the byproducts of the oil production that can lead to serious environmental pollution when they are deposited in ponds dug on the ground surface. Electrical Resistivity Tomography (ERT) method can provide a valuable tool in order to monitor through time the physical flow of the wastes into the subsurface. ERT could potentially locate the electrical signature due to lower resistivity values resulting from the leakage of OOMW to the subsurface. For this purpose, two vertical boreholes were installed (12m depth, 9 m apart) in the vicinity of an existing pond which is filled with OOMW during the oil production period. The test site is situated in Saint Andreas village about 15km south of the city of Rethymno (Crete, Greece). Surface ERT measurements were collected along multiple lines in order to reconstruct the subsurface resistivity models. Data acquisition was performed with standard and optimized electrode configuration protocols. The monitoring survey includes the ERT data collection for a period of time. The study was initiated before the OOMW were deposited in the pond, so resistivity fluctuations are expected due to the flow of OOMW in the porous subsurface media through time. Preliminary results show the good correlation of the ERT images with the drilled geological formations and the identification of low resistivity subsurface zone that could be attributed to the flow of the wastes within the porous layers.

  19. Influence of plant roots on electrical resistivity measurements of cultivated soil columns

    NASA Astrophysics Data System (ADS)

    Maloteau, Sophie; Blanchy, Guillaume; Javaux, Mathieu; Garré, Sarah

    2016-04-01

    Electrical resistivity methods have been widely used for the last 40 years in many fields: groundwater investigation, soil and water pollution, engineering application for subsurface surveys, etc. Many factors can influence the electrical resistivity of a media, and thus influence the ERT measurements. Among those factors, it is known that plant roots affect bulk electrical resistivity. However, this impact is not yet well understood. The goals of this experiment are to quantify the effect of plant roots on electrical resistivity of the soil subsurface and to map a plant roots system in space and time with ERT technique in a soil column. For this research, it is assumed that roots system affect the electrical properties of the rhizosphere. Indeed the root activity (by transporting ions, releasing exudates, changing the soil structure,…) will modify the rhizosphere electrical conductivity (Lobet G. et al, 2013). This experiment is included in a bigger research project about the influence of roots system on geophysics measurements. Measurements are made on cylinders of 45 cm high and a diameter of 20 cm, filled with saturated loam on which seeds of Brachypodium distachyon (L.) Beauv. are sowed. Columns are equipped with electrodes, TDR probes and temperature sensors. Experiments are conducted at Gembloux Agro-Bio Tech, in a growing chamber with controlled conditions: temperature of the air is fixed to 20° C, photoperiod is equal to 14 hours, photosynthetically active radiation is equal to 200 μmol m‑2s‑1, and air relative humidity is fixed to 80 %. Columns are fully saturated the first day of the measurements duration then no more irrigation is done till the end of the experiment. The poster will report the first results analysis of the electrical resistivity distribution in the soil columns through space and time. These results will be discussed according to the plant development and other controlled factors. Water content of the soil will also be detailed

  20. Application of 4D resistivity image profiling to detect DNAPLs plume.

    NASA Astrophysics Data System (ADS)

    Liu, H.; Yang, C.; Tsai, Y.

    2008-12-01

    In July 1993, the soil and groundwater of the factory of Taiwan , Miaoli was found to be contaminated by dichloroethane, chlorobenzene and other hazardous solvents. The contaminants were termed to be dense non-aqueous phase liquids (DNAPLs). The contaminated site was neglected for the following years until May 1998, the Environment Protection Agency of Miaoli ordered the company immediately take an action for treatment of the contaminated site. Excavating and exposing the contaminated soil was done at the previous waste DNAPL dumped area. In addition, more than 53 wells were drilled around the pool with a maximum depth of 12 m where a clayey layer was found. Continuous pumping the groundwater and monitoring the concentration of residual DNAPL contained in the well water samples have done in different stages of remediation. However, it is suspected that the DNAPL has existed for a long time, therefore the contaminants might dilute but remnants of a DNAPL plume that are toxic to humans still remain in the soil and migrate to deeper aquifers. A former contaminated site was investigated using the 2D, 3D and 4D resisitivity image technique, with aims of determining buried contaminant geometry. This paper emphasizes the use of resistivity image profiling (RIP) method to map the limit of this DNAPL waste disposal site where the records of operations are not variations. A significant change in resistivity values was detected between known polluted and non-polluted subsurface; a high resistivity value implies that the subsurface was contaminated by DNAPL plume. The results of the survey serve to provide insight into the sensitivity of RIP method for detecting DNAPL plumes within the shallow subsurface, and help to provide valuable information related to monitoring the possible migration path of DNAPL plume in the past. According to the formerly studies in this site, affiliation by excavates with pumps water remediation had very long time, Therefore this research was used

  1. Exploring electrical resistance: a novel kinesthetic model helps to resolve some misconceptions

    NASA Astrophysics Data System (ADS)

    Cottle, Dan; Marshall, Rick

    2016-09-01

    A simple ‘hands on’ physical model is described which displays analogous behaviour to some aspects of the free electron theory of metals. Using it students can get a real feel for what is going on inside a metallic conductor. Ohms Law, the temperature dependence of resistivity, the dependence of resistance on geometry, how the conduction electrons respond to a potential difference and the concepts of mean free path and drift speed of the conduction electrons can all be explored. Some quantitative results obtained by using the model are compared with the predictions of Drude’s free electron theory of electrical conduction.

  2. Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

    SciTech Connect

    Cousineau, Emily; Bennion, Kevin; Devoto, Douglas; Naramanchi, Sreekant

    2015-07-06

    Thermal management for electric motors is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric-drive systems. Thermal constraints place significant limitations on how electric motors ultimately perform. As thermal management improves, there will be a direct trade-off among motor performance, efficiency, cost, and the sizing of electric motors to operate within the thermal constraints. During the development of thermal finite element analysis models and computational fluid dynamics models for electric motors, it was found that there was a lack of open literature detailing the thermal properties of key materials common in electric motors that are significant in terms of heat removal. The lack of available literature, coupled with the strong interest from industry in the passive-stack thermal measurement results, led to experiments to characterize the thermal contact resistance between motor laminations. We examined four lamination materials, including the commonly used 26 gauge and 29 gauge M19 materials, the HF10 and Arnon 7 materials. These latter two materials are thinner and reduce eddy currents responsible for core losses. We measured the thermal conductivity of the lamination materials and the thermal contact resistance between laminations in a stack, as well as investigated factors affecting contact resistance between laminations such as the contact pressure and surface finish. Lamination property data will be provided and we also develop a model to estimate the through-stack thermal conductivity for materials beyond those that were directly tested in this work. For example, at a clamping pressure of 138 kPa, the 29 gauge M19 material has a through-stack thermal conductivity of 1.68 W/m-K, and the contact resistance between laminations was measured to be 193 mm^2-K/W. The measured bulk

  3. Assessment of Continuous Resistivity Profiling for the Characterization of Paved Roads

    NASA Astrophysics Data System (ADS)

    Chouteau, M.; Vallieres, S.; Miralles, M.

    2004-05-01

    We have assessed the continuous resistivity profiling method using towed arrays as a diagnostic NDT method for the evaluation of pavements. Whether the pavement consists of a sequence of asphalt, concrete slab and subgrade layer (rigid pavement) or a layer of asphalt overlying a subgrade and grade base layers (flexible pavement) defects within those different layers can cause pavement deterioration that must be identified. We first examine the response of the method to the various problems using numerical modeling. It is shown that with an optimally designed system the method allows the determination of the thickness and the location of cracks in the asphalt cover. It is also sensitive to the presence of cracks, internal defects and chloride ions (de-icing salt) within the concrete slab below. For reinforced concrete it is possible to estimate the concrete resistivity related directly to its composition (quality) and the thickness of the top coating over the level of rebars. A low resistivity of concrete will usually be diagnostic of advanced stage of rebar corrosion and delamination could occur. However it is shown that the rebars cause current channeling and the depth of investigation is limited then to the depth of the first row of rebars. Finally heterogeneities within the foundation reflecting subsidence, bad drainage, frost-defrost cycles or cavities can be mapped. The optimal design is based on a system with 10 to 20 receiver dipoles and one transmitter dipole (first or last of the array) with a dipole length typically of 10 cm that can be used in equatorial or in-line mode. Static resistivity measurements have been carried out at the laboratory scale over concrete slabs built to verify results obtained from the numerical modeling. Observed data fit very well the modeled data and validate the overall conclusions. Tests have been performed in December 2003 in some selected streets (6 visited, 3 re-visited) of Montreal using a CORIM system (Iris Instruments

  4. Protein profiling of mefloquine resistant Plasmodium falciparum using mass spectrometry-based proteomics

    PubMed Central

    Reamtong, Onrapak; Srimuang, Krongkan; Saralamba, Naowarat; Sangvanich, Polkit; Day, Nicholas P.J.; White, Nicholas J.; Imwong, Mallika

    2015-01-01

    Malaria is a mosquito borne infectious disease caused by protozoa of genus Plasmodium. There are five species of Plasmodium that are found to infect humans. Plasmodium falciparum can cause severe malaria leading to higher morbidity and mortality of malaria than the other four species. Antimalarial resistance is the major obstacle to control malaria. Mefloquine was used in combination with Artesunate for uncomplicated P. falciparum in South East Asia and it has developed and established mefloquine resistance in this region. Here, gel-enhanced liquid chromatography/tandem mass spectrometry (GeLC–MS/MS)-based proteomics and label-free quantification were used to explore the protein profiles of mefloquine-sensitive and -induced resistant P. falciparum. A Thai P. falciparum isolate (S066) was used as a model in this research. Our data revealed for the first time that 69 proteins exhibited at least 2-fold differences in their expression levels between the two parasite lines. Of these, 36 were up-regulated and 33 were down-regulated in the mefloquine-resistant line compared with the mefloquine-sensitive line. These findings are consistent with those of past studies, where the multidrug resistance protein Pgh1 showed an up-regulation pattern consistent with that expected from its average 3-copy pfmdr1 gene number. Pgh1 and eight other up-regulated proteins (i.e., histo-aspartyl protease protein, exportin 1, eukaryotic translation initiation factor 3 subunit 8, peptidyl-prolyl cis-trans isomerase, serine rich protein homologue, exported protein 1, ATP synthase beta chain and phospholipid scramblase 1) were further validated for their expression levels using reverse transcriptase quantitative real-time PCR. The data support the up-regulation status in the mefloquine-resistant parasite line of all the candidate genes referred to above. Therefore, GeLC–MS/MS-based proteomics combined with label-free quantification is a reliable approach for exploring mefloquine resistance

  5. Petrologically-based Electrical Profiles vs. Geophysical Observations through the Upper Mantle (Invited)

    NASA Astrophysics Data System (ADS)

    Gaillard, F.; Massuyeau, M.; Sifre, D.; Tarits, P.

    2013-12-01

    Mineralogical transformations in the up-welling mantle play a critical role on the dynamics of mass and heat transfers at mid-ocean-ridgeS. The melting event producing ridge basalts occur at 60 km depth below the ridge axis, but because of small amounts of H2O and CO2 in the source region of MOR-basalts, incipient melting can initiate at much greater depth. Such incipient melts concentrate incompatible elements, and are particularly rich in volatile species. These juices evolve from carbonatites, carbonated basalts, to CO2-H2O-rich basalts as recently exposed by petrological surveys; the passage from carbonate to silicate melts is a complex pathway that is strongly non-linear. This picture has recently been complicated further by studies showing that oxygen increasingly partitions into garnet as pressure increases; this implies that incipient melting may be prevented at depth exceeding 200 km because not enough oxygen is available in the system to stabilize carbonate melts. The aim of this work is twofold: - We modelled the complex pathway of mantle melting in presence of C-O-H volatiles by adjusting the thermodynamic properties of mixing in the multi-component C-O-H-melt system. This allows us to calculate the change in melt composition vs. depth following any sortS of adiabat. - We modelled the continuous change in electrical properties from carbonatites, carbonated basalts, to CO2-H2O-rich basalts. We then successfully converted this petrological evolution along a ridge adiabat into electrical conductivity vs. depth signal. The discussion that follows is about comparison of this petrologically-based conductivity profile with the recent profiles obtained by inversion of the long-period electromagnetic signals from the East-Pacific-Rise. These geophysically-based profiles reveal the electrical conductivity structure down to 400 km depth and they show some intriguing highly conductive sections. We will discuss heterogeneity in electrical conductivity of the upper

  6. Antimicrobial resistance and virulence gene profiles in P. multocida strains isolated from cats

    PubMed Central

    Ferreira, Thais Sebastiana Porfida; Felizardo, Maria Roberta; de Gobbi, Debora Dirani Sena; Moreno, Marina; Moreno, Andrea Micke

    2015-01-01

    Cats are often described as carriers of Pasteurella multocida in their oral microbiota. This agent is thought to cause pneumonia, conjunctivitis, rhinitis, gingivostomatitis, abscess and osteonecrosis in cats. Human infection with P. multocida has been described in several cases affecting cat owners or after cat bites. In Brazil, the cat population is approximately 21 million animals and is increasing, but there are no studies of the presence of P. multocida in the feline population or of human cases of infection associated with cats. In this study, one hundred and ninety-one healthy cats from owners and shelters in São Paulo State, Brazil, were evaluated for the presence of P. multocida in their oral cavities. Twenty animals were positive for P. multocida , and forty-one strains were selected and characterized by means of biochemical tests and PCR. The P. multocida strains were tested for capsular type, virulence genes and resistance profile. A total of 75.6% (31/41) of isolates belonged to capsular type A, and 24.4% (10/41) of the isolates were untypeable. None of the strains harboured toxA, tbpA or pfhA genes. The frequencies of the other genes tested were variable, and the data generated were used to build a dendrogram showing the relatedness of strains, which were clustered according to origin. The most common resistance profile observed was against sulfizoxazole and trimethoprim-sulphamethoxazole. PMID:26221117

  7. Association between insulin resistance and plasma amino acid profile in non-diabetic Japanese subjects

    PubMed Central

    Yamada, Chizumi; Kondo, Masumi; Kishimoto, Noriaki; Shibata, Takeo; Nagai, Yoko; Imanishi, Tadashi; Oroguchi, Takashige; Ishii, Naoaki; Nishizaki, Yasuhiro

    2015-01-01

    Aims/Introduction Elevation of the branched-chain amino acids (BCAAs), valine, leucine and isoleucine; and the aromatic amino acids, tyrosine and phenylalanine, has been observed in obesity-related insulin resistance. However, there have been few studies on Asians, who are generally less obese and less insulin-resistant than Caucasian or African-Americans. In the present study, we investigated the relationship between homeostasis model assessment of insulin resistance (HOMA-IR) and plasma amino acid concentration in non-diabetic Japanese participants. Materials and Methods A total of 94 healthy men and women were enrolled, and plasma amino acid concentration was measured by liquid chromatography/mass spectrometry after overnight fasting. The associations between HOMA-IR and 20 amino acid concentrations, and anthropometric and clinical parameters of lifestyle-related diseases were evaluated. Results The mean age and body mass index were 40.1 ± 9.6 years and 22.7 ± 3.9, respectively. Significantly positive correlations were observed between HOMA-IR and valine, isoleucine, leucine, tyrosine, phenylalanine and total BCAA concentration. Compared with the HOMA-IR ≤ 1.6 group, the HOMA-IR > 1.6 group showed significantly exacerbated anthropometric and clinical parameters, and significantly elevated levels of valine, isoleucine, leucine, tyrosine, phenylalanine and BCAA. Conclusions The present study shows that the insulin resistance-related change in amino acid profile is also observed in non-diabetic Japanese subjects. These amino acids include BCAAs (valine, isoleucine and leucine) and aromatic amino acids (tyrosine and phenylalanine), in agreement with previous studies carried out using different ethnic groups with different degrees of obesity and insulin resistance. PMID:26221519

  8. Direct-push hydrostratigraphic profiling: Coupling electrical logging and slug tests

    USGS Publications Warehouse

    Sellwood, S.M.; Healey, J.M.; Birk, S.; Butler, J.J., Jr.

    2005-01-01

    Spatial variations in hydraulic conductivity (K) can significantly affect the transport of contaminants in ground water. Conventional field methods, however, rarely provide a description of these variations at the level of detail necessary for reliable transport predictions and effective remediation designs. A direct-push (DP) method, hydrostratigraphic profiling, has been developed to characterize the spatial variability of both electrical conductivity (EC) and hydraulic conductivity in unconsolidated formations in a cost-effective manner. This method couples a dual-rod approach for performing slug tests in DP equipment with high-resolution EC logging. The method was evaluated at an extensively studied site in the Kansas River floodplain. A series of profiles was performed on a surface grid, resulting in a detailed depiction of the three-dimensional distribution of EC and K. Good agreement was found between K estimates obtained from this approach and those obtained using other methods. The results of the field evaluation indicate that DP hydrostratigraphic profiling is a promising method for obtaining detailed information about spatial variations in subsurface properties without the need for permanent wells.

  9. Evaluation of changes in microstructure and mechanical performance of metals via electrical resistivity measurements

    NASA Astrophysics Data System (ADS)

    Omari, Mohammad Ahmad

    This work focuses on experimental study of cross-property connections that link up effective linear elastic and electrical conductive properties of heterogeneous materials. Such connections are especially useful when one property (electrical conductivity) is easier to measure than the other (elastic constants). Also, take advantages from the easy of measure electrical resistance to study the microstructural changes, and then compare results with different methods like microscopy and other published methods. Mechanical and electrical properties of different specimens under both fatigue and quasi-static loading were investigated, combined with the analysis of microstructural changes produced by such loading. Two different types of metals (stainless steel 304 and Titanium CP-2) have been cut from sheets and then subjected to two different type of loading: cyclic loading (up to 80000 cycles) at several values of maximal stress sigmamax and then quasi-static loading. At low values of sigmamax as well as at the low number of cycles no significant changes in mechanical properties and mild decrease in electrical conductivity (approximately uniform over the specimen) have been observed. The latter can be explained by generation cluster of new dislocations that can be seen in photo images in the form of black dots. As the number of cycles and sigmamax grow up, reduction in Young's modulus and in ultimate strength of the specimens take place. This reduction is accompanied by local decrease in electrical conductivity due to formation of the microcracks. Changes in Young's modulus and electrical conductivity at high values of sigma max. (higher than the yield limit) follow the theoretically predicted cross-property connection for microcracked materials. Qualitative correlation between strength reduction and maximum value of local resistivity across the specimen has been observed at qualitative level.

  10. Laboratory measurements of basalts electrical resistivity under deep oceanic crustal conditions

    NASA Astrophysics Data System (ADS)

    Violay, M. E.; Gibert, B.; Azais, P.; Pezard, P. A.; Flovenz, O. G.; Asmundsson, R.

    2009-12-01

    For sixty years, electrical resistivity soundings have been used to explore geothermal resources in Iceland. They have generally revealed two zones of high electrical conductivity, one at shallow depths (Flovenz et al., 1985) and another at 10-30 km depth (Beblo and Björnsson, 1978). The interpretation of these conductive zones in terms of composition and in-situ physical conditions is often ambiguous, as various parameters can explain these observations like temperature, partial melting, change in minerals and type of pore fluid. Accurate interpretations of resistivity data needed for geothermal exploration require laboratory measurements of electrical conductivities performed on rock samples at different conditions. We present here a method to measure electrical conductivity of rocks under deep crustal conditions for oceanic crustal rock, i.e. at temperatures up to 600°C, confining pressures up to 200 MPa and pore fluid pressures up to 50 MPa. The method has been developed in a internally heated, gas pressure apparatus (Paterson press). Electrical conductivity is measured on large cylindrical samples (15 to 22 mm in diameter and 10 to 15 mm in length) in a two parallel electrodes geometry. Such experiments require that the fluid saturated sample is sleeved in an impermeable and deformable jacket serving to separate the confining pressure medium (high pressure argon) from the pore fluid saturated sample. At temperature above 200°C a metal sleeve must be used, although it induces high leakage currents that could affect electrical measurements. The leakage currents are reduced using addition of 2 guard-ring parallel electrodes (Glover, 1995). The electrical impedance of basalt has been measured over a frequency range from 10 -1 to 106 Hertz. Five different types of low porosity basalts were selected to cover a range in alteration grade, from albitic to granulite facies. Application of this method will provide data on electrical conductivity of fresh and altered

  11. Electrical resistivity measurements of the chalcogenide spinel, CuIr2S4, under extreme conditions

    NASA Astrophysics Data System (ADS)

    Hanni, Mark

    2006-10-01

    Electrical resistivity as a function of pressure will be investigated for the thiospinel compound, CuIr2S4, which exhibits a metal to insulator transition at high pressures. This study will corroborate existing experimental and theoretical work and is the first of its kind to perform high pressure electrical conductivity and insulating phase optical studies in the range of room temperature to liquid nitrogen temperature. In addition, the transport properties of adamantine semiconductors will be studied at high pressure. The resistivity measurements will be made using a pseudo four-wire probing technique, using an AC constant current source, to eliminate thermal noise in the connections, and a nanovoltmeter. The study is currently ongoing and results are still pending. Improvements made to a stepper motor control program and changes to the system used for optical studies will be presented.

  12. Electron scattering characteristics of polycrystalline metal transition films by in-situ electrical resistance measurements

    NASA Astrophysics Data System (ADS)

    Trindade, I. G.; Leitão, D.; Fermento, R.; Pogorelev, Y.; Sousa, J. B.

    2009-08-01

    In-situ electrical resistance measurements were performed to obtain the scattering characteristics of very thin polycrystalline metal transition magnetic alloys grown by ion beam deposition (IBD) on specific underlayers. The experimental curves show size effects at small film thicknesses and important differences between Co 85Fe 15 and Ni 81Fe 19 thin layers grown on identical underlayers of Ta70 Å/Ru13 Å. The largest difference was observed in Ni 81Fe 19 films grown on underlayers of amorphous Ta70 Å. The experimental curves of electrical resistivity/conductivity variation with layer thickness were well fit within the Mayadas and Shatzkes (M-S) model, assuming specific formulations for grain growth with layer thickness.

  13. Resistance oscillations of two-dimensional electrons in crossed electric and tilted magnetic fields

    NASA Astrophysics Data System (ADS)

    Mayer, William; Vitkalov, Sergey; Bykov, A. A.

    2016-06-01

    The effect of dc electric field on transport of highly mobile two-dimensional electrons is studied in wide GaAs single quantum wells placed in titled magnetic fields. The study shows that in perpendicular magnetic field resistance oscillates due to electric-field induced Landau-Zener transitions between quantum levels that correspond to geometric resonances between cyclotron orbits and periodic modulation of electron density of states. Magnetic field tilt inverts these oscillations. Surprisingly the strongest inverted oscillations are observed at a tilt corresponding to nearly absent modulation of the electron density of states in regime of magnetic breakdown of semiclassical electron orbits. This phenomenon establishes an example of quantum resistance oscillations due to Landau quantization, which occur in electron systems with a constant density of states.

  14. Specific heat and electrical resistivity of niobium measured by subsecond calorimetric technique

    NASA Astrophysics Data System (ADS)

    Maglić, K. D.; Perović, N. Lj.; Vuković, G. S.; Zeković, Lj. P.

    1994-09-01

    This paper presents results of measurements of specific heat and electrical resistivity of niobium from ambient temperature to the experimental limit of the equipment which is close to 2500 K. The study used a contact thermometry variant of the millisecond resolution pulse calorimetry developed at the Institute of Nuclear Sciences VINČA. In the experiments exceeding 1000 K, thermocouple thermometry was supplemented with parallel pyrometric temperature measurements. This, together with application of tungsten; rhenium thermocouple thermometry, increased the temperature range of measurements to 2500 K. In the range where two thermometries overlap, data on the specimen emittance were also generated. Novelties in the method, the results on electrical resistivity. specific heat, hemispherical total emittance and normal spectral emittance of niobium, and accuracies attained in different property measurements are discussed.

  15. Structural insight into selectivity and resistance profiles of ROS1 tyrosine kinase inhibitors

    PubMed Central

    Davare, Monika A.; Vellore, Nadeem A.; Wagner, Jacob P.; Eide, Christopher A.; Goodman, James R.; Drilon, Alexander; Deininger, Michael W.; O’Hare, Thomas; Druker, Brian J.

    2015-01-01

    Oncogenic ROS1 fusion proteins are molecular drivers in multiple malignancies, including a subset of non-small cell lung cancer (NSCLC). The phylogenetic proximity of the ROS1 and anaplastic lymphoma kinase (ALK) catalytic domains led to the clinical repurposing of the Food and Drug Administration (FDA)-approved ALK inhibitor crizotinib as a ROS1 inhibitor. Despite the antitumor activity of crizotinib observed in both ROS1- and ALK-rearranged NSCLC patients, resistance due to acquisition of ROS1 or ALK kinase domain mutations has been observed clinically, spurring the development of second-generation inhibitors. Here, we profile the sensitivity and selectivity of seven ROS1 and/or ALK inhibitors at various levels of clinical development. In contrast to crizotinib’s dual ROS1/ALK activity, cabozantinib (XL-184) and its structural analog foretinib (XL-880) demonstrate a striking selectivity for ROS1 over ALK. Molecular dynamics simulation studies reveal structural features that distinguish the ROS1 and ALK kinase domains and contribute to differences in binding site and kinase selectivity of the inhibitors tested. Cell-based resistance profiling studies demonstrate that the ROS1-selective inhibitors retain efficacy against the recently reported CD74-ROS1G2032R mutant whereas the dual ROS1/ALK inhibitors are ineffective. Taken together, inhibitor profiling and stringent characterization of the structure–function differences between the ROS1 and ALK kinase domains will facilitate future rational drug design for ROS1- and ALK-driven NSCLC and other malignancies. PMID:26372962

  16. Metabolic Profiling for Detection of Staphylococcus aureus Infection and Antibiotic Resistance

    PubMed Central

    Näsström, Elin; Kouremenos, Konstantinos; Sundén-Cullberg, Jonas; Guo, YongZhi; Moritz, Thomas; Wolf-Watz, Hans; Johansson, Anders; Fallman, Maria

    2013-01-01

    Due to slow diagnostics, physicians must optimize antibiotic therapies based on clinical evaluation of patients without specific information on causative bacteria. We have investigated metabolomic analysis of blood for the detection of acute bacterial infection and early differentiation between ineffective and effective antibiotic treatment. A vital and timely therapeutic difficulty was thereby addressed: the ability to rapidly detect treatment failures because of antibiotic-resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) were used in vitro and for infecting mice, while natural MSSA infection was studied in humans. Samples of bacterial growth media, the blood of infected mice and of humans were analyzed with combined Gas Chromatography/Mass Spectrometry. Multivariate data analysis was used to reveal the metabolic profiles of infection and the responses to different antibiotic treatments. In vitro experiments resulted in the detection of 256 putative metabolites and mice infection experiments resulted in the detection of 474 putative metabolites. Importantly, ineffective and effective antibiotic treatments were differentiated already two hours after treatment start in both experimental systems. That is, the ineffective treatment of MRSA using cloxacillin and untreated controls produced one metabolic profile while all effective treatment combinations using cloxacillin or vancomycin for MSSA or MRSA produced another profile. For further evaluation of the concept, blood samples of humans admitted to intensive care with severe sepsis were analyzed. One hundred thirty-three putative metabolites differentiated severe MSSA sepsis (n = 6) from severe Escherichia coli sepsis (n = 10) and identified treatment responses over time. Combined analysis of human, in vitro, and mice samples identified 25 metabolites indicative of effective treatment of S. aureus sepsis. Taken together, this study provides a

  17. Direct Mapping of Magnetic and Structural Profiles of Electric Field Moderated Oxygen Migration

    NASA Astrophysics Data System (ADS)

    Gilbert, Dustin A.; Grutter, Alexander J.; Kirby, Brian J.; Borchers, Julie A.; Maranville, Brian B.; Arenholz, Elke; Liu, Kai

    Recent studies on metal/oxide heterostructures have demonstrated control of interfacial magnetic anisotropy and saturation magnetization in ultrathin (5 ML) Co films through electric-field controlled oxygen migration. This approach presents a promising route to realizing next-generation, ultralow power sensor and data-storage technologies. Here we demonstrate magnetoelectric coupling moderated by electrically-driven oxygen migration in much thicker AlOx(1 um)/GdOx(2 nm)/Co (15 nm) heterostructures. Using polarized neutron reflectometry, we present direct, quantitative depth profiling of the magnetization and oxygen concentration in these systems. Electro-thermal conditioning moves oxygen from AlOx and GdOx base-layers throughout the entire thickness of the 15 nm Co layer, resulting in a suppressed magnetization. Switching the electric field polarity semi-reversibly ejects oxygen preferentially from the GdOX/Co interface, partially recovering the magnetization and establishing a practical limit to this approach. First order reversal curve diagrams show that the conditioned samples exhibit two distinct magnetic phases, while the as-grown samples are single phase, suggesting that the treatments alters the Co film microstructure. X-ray spectroscopy confirms the oxidation states of the Co and Gd, and suggest that the GdOX acts to transmit oxygen but does not source or sink it.

  18. Direct current resistivity profiling to study distribution of water in the unsaturated zone near the Amargosa Desert Research Site, Nevada

    USGS Publications Warehouse

    Abraham, Jared D.; Lucius, Jeffrey E.

    2004-01-01

    In order to study the distribution of water in the unsaturated zone and potential for ground-water recharge near the Amargosa Desert Research Site south of Beatty, Nevada, the U.S. Geological Survey collected direct-current resistivity measurements along three profiles in May 2003 using an eight-channel resistivity imaging system. Resistivity data were collected along profiles across the ADRS, across a poorly incised (distributary) channel system of the Amargosa River southwest of the ADRS, and across a well-incised flood plain of the Amargosa River northwest of the ADRS. This report describes results of an initial investigation to estimate the distribution of water in the unsaturated zone and to evaluate the shallow subsurface stratigraphy near the ADRS. The geophysical method of dc resistivity was employed by using automated data collection with numerous electrodes. 'Cross sections' of resistivity, produced by using an inversion algorithm on the field data, at the three field sites are presented and interpreted.

  19. Clonal profile, virulence and resistance of Staphylococcus aureus isolated from sheep milk

    PubMed Central

    Martins, Katheryne Benini; Faccioli-Martins, Patricia Yoshida; Riboli, Danilo Flávio Moraes; Pereira, Valéria Cataneli; Fernandes, Simone; Oliveira, Aline A.; Dantas, Ariane; Zafalon, Luiz Francisco; da Cunha, Maria de Lourdes Ribeiro de Souza

    2015-01-01

    The objective of this study was to characterize the clonal profile, virulence factors and antimicrobial resistance, particularly oxacillin resistance, of Staphylococcus aureus isolated from sheep milk. Milk samples were collected from all teats for the California Mastitis Test (CMT), somatic cell count, identification of S. aureus, investigation in these strains of genes encoding toxins (sea, seb, sec, sed, tst), biofilm (icaA, icaC, icaD, bap), leukocidin (luk-PV) oxacillin resistance by mecA gene detection and susceptibility testing (12 antibiotics). Messenger RNA expression was evaluated by RT-PCR in isolates carrying toxin and biofilm genes. Biofilm formation was also evaluated phenotypically by adherence to polystyrene plates. The clonal profile of S. aureus was investigated by pulsed-field gel electrophoresis. A total of 473 milk samples were collected from 242 animals on three farms and 20 S. aureus strains were isolated and none carried the mecA gene. The two sec gene-positive isolates and the isolates carrying the tst and luk-PV genes were positive by RT-PCR. Staphylococcus aureus isolated from the three flocks studied showed high susceptibility to the drugs tested and none was biofilm producer, indicating that biofilm formation was not a virulence factor causing infection by these strains. The typing of 17 S. aureus isolates revealed the presence of a common clone on the three farms studied, and the presence and expression of the sec and tst genes in one strain of this clone suggest the possible acquisition of virulence genes by this clone, a fact that is important for animal health and food hygiene. PMID:26273271

  20. Clonal profile, virulence and resistance of Staphylococcus aureus isolated from sheep milk.

    PubMed

    Martins, Katheryne Benini; Faccioli-Martins, Patricia Yoshida; Riboli, Danilo Flávio Moraes; Pereira, Valéria Cataneli; Fernandes, Simone; Oliveira, Aline A; Dantas, Ariane; Zafalon, Luiz Francisco; da Cunha, Maria de Lourdes Ribeiro de Souza

    2015-06-01

    The objective of this study was to characterize the clonal profile, virulence factors and antimicrobial resistance, particularly oxacillin resistance, of Staphylococcus aureus isolated from sheep milk. Milk samples were collected from all teats for the California Mastitis Test (CMT), somatic cell count, identification of S. aureus, investigation in these strains of genes encoding toxins (sea, seb, sec, sed, tst), biofilm (icaA, icaC, icaD, bap), leukocidin (luk-PV) oxacillin resistance by mecA gene detection and susceptibility testing (12 antibiotics). Messenger RNA expression was evaluated by RT-PCR in isolates carrying toxin and biofilm genes. Biofilm formation was also evaluated phenotypically by adherence to polystyrene plates. The clonal profile of S. aureus was investigated by pulsed-field gel electrophoresis. A total of 473 milk samples were collected from 242 animals on three farms and 20 S. aureus strains were isolated and none carried the mecA gene. The two sec gene-positive isolates and the isolates carrying the tst and luk-PV genes were positive by RT-PCR. Staphylococcus aureus isolated from the three flocks studied showed high susceptibility to the drugs tested and none was biofilm producer, indicating that biofilm formation was not a virulence factor causing infection by these strains. The typing of 17 S. aureus isolates revealed the presence of a common clone on the three farms studied, and the presence and expression of the sec and tst genes in one strain of this clone suggest the possible acquisition of virulence genes by this clone, a fact that is important for animal health and food hygiene. PMID:26273271

  1. Electrical Resistivity Investigations of the Kurşunlu (Manisa/Turkey) Geothermal Area

    NASA Astrophysics Data System (ADS)

    Sarı, Coşkun; Timur, Emre

    2016-04-01

    It is of considerable importance to explore the geological structure around active faults, especially near-surface unconsolidated layers, to estimate the faults' activity. There are numerous case studies to investigate geothermal reservoirs and surrounding active faults using geophysical exploration methods; however, only a few cases have been verified in detail by comparison with other geological information. Electrical resistivity data provide a substantial contribution to the geophysical mapping and monitoring of geothermal reservoirs. We applied electrical methods, which can be effective for exploring to several hundred meters depth, to reveal geological structures covered by thick Quaternary alluvium formations. Geothermal activity around city of Manisa in Gediz Graben (Western Turkey) has been investigated by many researchers and many geothermal boreholes were drilled in order to produce electricity and for heating purposes. The Kurşunlu geothermal area is with the southern side of the Gediz Graben in 2 km west of Salihli, Manisa, Turkey. According to rising demand on thermal water around Salihli, geophysical studies were performed using the Vertical Electrical Sounding (VES) measurements at 16 stations around the area of Kurşunlu hot springs, and they were interpreted using both one and two-dimensional modelling. Vertical and horizontal resistivity sections were mapped, and it was determined that two low-resistivity layers exist both in the North (stations 1,2 and 4) and the South (stations 6 and 10) part of the survey area. As a result of the studies, the boundaries of the low-resistivity layer were mapped and test drilling locations were recommended.

  2. Electrical resistivity variations associated with earthquakes on the san andreas fault.

    PubMed

    Mazzella, A; Morrison, H F

    1974-09-01

    A 24 percent precursory change in apparent electrical resistivity was observed before a magnitude 3.9 earthquake of strike-slip nature on the San Andreas fault in central California. The experimental configuration and numerical calculations suggest that the change is associated with a volume at depth rather than some near-surface phenomenon. The character and duration of the precursor period agree well with those of other earthquake studies and support a dilatant earthquake mechanism model. PMID:17833697

  3. [Testing the electric resistance as an objective diagnostic test in dental pulp diseases].

    PubMed

    Constantin, I; Severineanu, V; Tudose, N

    1976-01-01

    The authors test by means of a measuring device of high precision the resistence of health or sick human pulpa, comparing it to them of gums, excluding in the same time the sensibility of the patient in question. The authors corroborate the obtained dates with clinical symptomatology and the histopathological photos, discussing the possibility of objective electrical test as an expedient in the diagnosis of pulpa-affections. PMID:137616

  4. MicroRNA expression profiles of drug-resistance breast cancer cells and their exosomes

    PubMed Central

    Zhong, Shanliang; Chen, Xiu; Wang, Dandan; Zhang, Xiaohui; Shen, Hongyu; Yang, Sujin; Lv, Mengmeng; Tang, Jinhai; Zhao, Jianhua

    2016-01-01

    Exosomes have been shown to transmit drug resistance through delivering miRNAs. We aimed to explore their roles in breast cancer. Three resistant sublines were established by exposing parental MDA-MB-231 cell line to docetaxel, epirubicin and vinorelbine, respectively. Preneoadjuvant chemotherapy biopsies and paired surgically-resected specimens embedded in paraffin from 23 breast cancer patients were collected. MiRNA expression profiles of the cell lines and their exosomes were evaluated using microarray. The result showed that most miRNAs in exosomes had a lower expression level than that in cells, however, some miRNAs expressed higher in exosomes than in cells, suggesting a number of miRNAs is concentrated in exosomes. Among the dysregulated miRNAs, 22 miRNAs were consistently up-regulated in exosomes and their cells of origin. We further found that 12 of the 22 miRNAs were significantly up-regulated after preneoadjuvant chemotherapy. Further study of the role of these 12 miRNAs in acquisition of drug resistance is needed to clarify their contribution to chemoresistance. PMID:26910922

  5. A longitudinal, integrated, clinical, histological and mRNA profiling study of resistance exercise in myositis.

    PubMed

    Nader, Gustavo A; Dastmalchi, Maryam; Alexanderson, Helene; Grundtman, Cecilia; Gernapudi, Ramkishore; Esbjörnsson, Mona; Wang, Zuyi; Rönnelid, Johan; Hoffman, Eric P; Nagaraju, Kanneboyina; Lundberg, Ingrid E

    2010-01-01

    Polymyositis and dermatomyositis are orphan, chronic skeletal muscle disorders characterized by weakness, infiltrations by mononuclear inflammatory cells, and fibrosis. Until recently, patients were advised to refrain from physical activity because of fears of exacerbation of muscle inflammation. However, recent studies have shown that moderate exercise training in combination with immunosuppressive drugs can improve muscle performance. Despite the positive effects of exercise training, the molecular mechanisms underlying the exercise-associated clinical improvements remain poorly understood. The present study was designed to define, at the molecular level, the effects of resistance exercise training on muscle performance and disease progression in myositis patients. We evaluated changes in muscle strength, histology and genome-wide mRNA profiles to determine the beneficial effects of exercise and determine the possible molecular changes associated with improved muscle performance. A total of 8 myositis patients underwent a 7-wk resistance exercise training program that resulted in improved muscle strength and increased maximal oxygen uptake (VO(2max)). Training also resulted in marked reductions in gene expression, reflecting reductions in proinflammatory and profibrotic gene networks, changes that were also accompanied by a reduction in tissue fibrosis. Consistent with the exercise-associated increase in VO(2max), a subset of transcripts was associated with a shift toward oxidative metabolism. The changes in gene expression reported in the present study are in agreement with the performance improvements induced by exercise and suggest that resistance exercise training can induce a reduction in inflammation and fibrosis in skeletal muscle. PMID:20809047

  6. A Longitudinal, Integrated, Clinical, Histological and mRNA Profiling Study of Resistance Exercise in Myositis

    PubMed Central

    Nader, Gustavo A; Dastmalchi, Maryam; Alexanderson, Helene; Grundtman, Cecilia; Gernapudi, Ramkishore; Esbjörnsson, Mona; Wang, Zuyi; Rönnelid, Johan; Hoffman, Eric P; Nagaraju, Kanneboyina; Lundberg, Ingrid E

    2010-01-01

    Polymyositis and dermatomyositis are orphan, chronic skeletal muscle disorders characterized by weakness, infiltrations by mononuclear inflammatory cells, and fibrosis. Until recently, patients were advised to refrain from physical activity because of fears of exacerbation of muscle inflammation. However, recent studies have shown that moderate exercise training in combination with immunosuppressive drugs can improve muscle performance. Despite the positive effects of exercise training, the molecular mechanisms underlying the exercise-associated clinical improvements remain poorly understood. The present study was designed to define, at the molecular level, the effects of resistance exercise training on muscle performance and disease progression in myositis patients. We evaluated changes in muscle strength, histology and genome-wide mRNA profiles to determine the beneficial effects of exercise and determine the possible molecular changes associated with improved muscle performance. A total of 8 myositis patients underwent a 7-wk resistance exercise training program that resulted in improved muscle strength and increased maximal oxygen uptake (VO2max). Training also resulted in marked reductions in gene expression, reflecting reductions in proinflammatory and profibrotic gene networks, changes that were also accompanied by a reduction in tissue fibrosis. Consistent with the exercise-associated increase in VO2max, a subset of transcripts was associated with a shift toward oxidative metabolism. The changes in gene expression reported in the present study are in agreement with the performance improvements induced by exercise and suggest that resistance exercise training can induce a reduction in inflammation and fibrosis in skeletal muscle. PMID:20809047

  7. Antibiotic resistance profiles and virulence markers of Pseudomonas aeruginosa strains isolated from composts.

    PubMed

    Kaszab, Edit; Szoboszlay, Sándor; Dobolyi, Csaba; Háhn, Judit; Pék, Nikoletta; Kriszt, Balázs

    2011-01-01

    The aim of our work was to determine the presence of Pseudomonas aeruginosa in compost raw materials, immature and mature compost, and compost-treated soil. Twenty-five strains of P. aeruginosa were isolated from a raw material (plant straw), immature and mature compost and compost-treated soil samples. The strains were identified using the PCR method for the detection of species specific variable regions of 16S rDNA. Strains were examined for the presence of five different virulence-related gene sequences (exoA, exoU, exoT, exoS and exoY) and their antibiotic resistance profiles were determined. Based on our results, species P. aeruginosa can reach significant numbers (up to 10(6) MPN/g sample) during composting and 92.0% of the isolated strains carrying at least two gene sequences encoding toxic proteins. Various types of drug resistance were detected among compost originating strains, mainly against third generation Cephalosporins and Carbapenems. Six isolates were able to resist two different classes of antibiotics (third generation Cephalosporins and Carbapenems, wide spectrum Penicillins or Aminoglycosides, respectively). Based on our results, composts can be a source of P. aeruginosa and might be a concern to individuals susceptible to this opportunistic pathogen. PMID:20817443

  8. Tyrosine Is Associated with Insulin Resistance in Longitudinal Metabolomic Profiling of Obese Children

    PubMed Central

    Hellmuth, Christian; Kirchberg, Franca Fabiana; Lass, Nina; Harder, Ulrike; Peissner, Wolfgang; Koletzko, Berthold; Reinehr, Thomas

    2016-01-01

    In obese children, hyperinsulinaemia induces adverse metabolic consequences related to the risk of cardiovascular and other disorders. Branched-chain amino acids (BCAA) and acylcarnitines (Carn), involved in amino acid (AA) degradation, were linked to obesity-associated insulin resistance, but these associations yet have not been studied longitudinally in obese children. We studied 80 obese children before and after a one-year lifestyle intervention programme inducing substantial weight loss >0.5 BMI standard deviation scores in 40 children and no weight loss in another 40 children. At baseline and after the 1-year intervention, we assessed insulin resistance (HOMA index), fasting glucose, HbA1c, 2 h glucose in an oral glucose tolerance test, AA, and Carn. BMI adjusted metabolite levels were associated with clinical markers at baseline and after intervention, and changes with the intervention period were evaluated. Only tyrosine was significantly associated with HOMA (p < 0.05) at baseline and end and with change during the intervention (p < 0.05). In contrast, ratios depicting BCAA metabolism were negatively associated with HOMA at baseline (p < 0.05), but not in the longitudinal profiling. Stratified analysis revealed that the children with substantial weight loss drove this association. We conclude that tyrosine alterations in association with insulin resistance precede alteration in BCAA metabolism. This trial is registered with ClinicalTrials.gov Identifier NCT00435734. PMID:26881241

  9. Imaging Rainfall Infiltration Processes with the Time-Lapse Electrical Resistivity Imaging Method

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhang, Gui-Bin; Chen, Chien-chih; Chang, Ping-Yu; Wang, Tzu-Pin; Yen, Horng-Yuan; Dong, Jia-Jyun; Ni, Chuen-Fa; Chen, Su-Chin; Chen, Chao-Wei; Jia, Zheng-yuan

    2016-02-01

    Electrical Resistivity Imaging (ERI) was carried out continuously for 10 days to map the subsurface resistivity distribution along a potentially hazardous hillslope at the Jieshou Junior High School in Taoyuan, Taiwan. The reliability of the inverted resistivity structures down to about 25 m depth was examined with synthetic modeling using the same electrode arrangements installed on land surface as in field surveys, together with a DOI (depth-of-investigation) index calculated from the ERI data. The subsurface resistivity distribution is consistent with results from well logging. These ERI recordings were taken daily and provided highly resolved imagery of the resistivity distribution underground and illustrated the dynamical fluid-flow behavior due to heavy rainfall infiltration. Using Archie's law, the resistivity distribution was transformed into a map of relative water saturation (RWS), which is strongly correlated with the rainfall infiltration process. We then found that the averaged RWS is significantly correlated with daily precipitation. Our observations indicate that time-lapse ERI is effective in monitoring subterraneous rainfall infiltration; moreover, the preferential flow paths can be delineated according to the changes in averaged RWS derived from the ERI data.

  10. Electrical resistance tomography of unsaturated flow and transport in Yucca Mountain

    SciTech Connect

    Buettner, H M; Bussod, G; Daily, W; Ramirez, A

    1998-12-28

    Electrical Resistance Tomography (ERT), a new geophysical imaging technique, was used to study the movement of a tracer through the test block at the Unsaturated Zone Transport Test (UZTT) at Busted Butte, Nevada. Data were collected four times starting in July and ending in early September, 1998. ERT baseline images show a resistivity structure which is consistent with the known lithology in the rear part of the test block. There appears to be a low resistivity region in the front half of the block, particularly near the bottom. Difference images from August 19 and September 9 show clear and consistent resistivity decreases in the region near injection holes 18, 20, and 21 which can be associated with the injection of conductive water. The images show very little effect in the region around the other injection holes, 23, and 24 through 27 where far less water was injected. Difference images from August 19 and September 9 show resistivity decreases which could be interpreted as water moving down into the block. This is the same region which has an anomalously low resistivity in the baseline image. These results should be considered preliminary, and are subject to further interpretation.

  11. Imaging Rainfall Infiltration Processes with the Time-Lapse Electrical Resistivity Imaging Method

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhang, Gui-Bin; Chen, Chien-chih; Chang, Ping-Yu; Wang, Tzu-Pin; Yen, Horng-Yuan; Dong, Jia-Jyun; Ni, Chuen-Fa; Chen, Su-Chin; Chen, Chao-Wei; Jia, Zheng-yuan

    2016-06-01

    Electrical Resistivity Imaging (ERI) was carried out continuously for 10 days to map the subsurface resistivity distribution along a potentially hazardous hillslope at the Jieshou Junior High School in Taoyuan, Taiwan. The reliability of the inverted resistivity structures down to about 25 m depth was examined with synthetic modeling using the same electrode arrangements installed on land surface as in field surveys, together with a DOI (depth-of-investigation) index calculated from the ERI data. The subsurface resistivity distribution is consistent with results from well logging. These ERI recordings were taken daily and provided highly resolved imagery of the resistivity distribution underground and illustrated the dynamical fluid-flow behavior due to heavy rainfall infiltration. Using Archie's law, the resistivity distribution was transformed into a map of relative water saturation (RWS), which is strongly correlated with the rainfall infiltration process. We then found that the averaged RWS is significantly correlated with daily precipitation. Our observations indicate that time-lapse ERI is effective in monitoring subterraneous rainfall infiltration; moreover, the preferential flow paths can be delineated according to the changes in averaged RWS derived from the ERI data.

  12. Joining characteristics of beta-titanium wires with electrical resistance welding.

    PubMed

    Iijima, Masahiro; Brantley, William A; Yuasa, Toshihiro; Kawashima, Isao; Mizoguchi, Itaru

    2008-05-01

    The goal of this research was to investigate the effects of different conditions for electrical resistance welding of beta-titanium orthodontic wires. Three electrode types were used with a range of power settings on an electrical resistance welding machine to join beta-titanium wires (Resolve, GAC International). Forces that caused bond failures for joined specimens were obtained with tensile loading, and the values were compared using one-way ANOVA and the Tukey test (alpha = 0.05). Metallurgical phases in the joint region were determined by micro-X-ray diffraction. Mean tensile forces for bond failure ranged from 5 to 20 kgf for the eight specimen groups and were dependent on electrode type and power setting. All X-ray diffraction peaks in the joint region were indexed to beta-titanium. Superior bond strength was achieved with the use of wide electrodes. The absence of phases other than beta-titanium in the joint area suggests that the electrical resistance welding may not adversely affect clinically important mechanical properties. Scanning microscope observations indicated that the localized permanent deformation and the formation of an undesirable equiaxed grain structure occurred with the use of narrow electrodes. PMID:17937410

  13. Electrical Resistivity Investigation of Gas Hydrate Distribution in Mississippi Canyon Block 118, Gulf of Mexico

    SciTech Connect

    Dunbar, John

    2012-12-31

    Electrical methods offer a geophysical approach for determining the sub-bottom distribution of hydrate in deep marine environments. Methane hydrate is essentially non-conductive. Hence, sediments containing hydrate are more resistive than sediments without hydrates. To date, the controlled source electromagnetic (CSEM) method has been used in marine hydrates studies. This project evaluated an alternative electrical method, direct current resistivity (DCR), for detecting marine hydrates. DCR involves the injection of direct current between two source electrodes and the simultaneous measurement of the electric potential (voltage) between multiple receiver electrodes. The DCR method provides subsurface information comparable to that produced by the CSEM method, but with less sophisticated instrumentation. Because the receivers are simple electrodes, large numbers can be deployed to achieve higher spatial resolution. In this project a prototype seafloor DCR system was developed and used to conduct a reconnaissance survey at a site of known hydrate occurrence in Mississippi Canyon Block 118. The resulting images of sub-bottom resistivities indicate that high-concentration hydrates at the site occur only in the upper 50 m, where deep-seated faults intersect the seafloor. Overall, there was evidence for much less hydrate at the site than previously thought based on available seismic and CSEM data alone.

  14. Electric resistance welded pipe for use in chemical plants and petroleum refineries

    SciTech Connect

    Isfeld, B.

    1984-02-01

    Cost effective material has been and will continue to be of increasing importance in the design and construction of chemical plants and petroleum refineries. A large percentage of the cost incurred in such projects may be attributed to the pipe required to transport numerous liquids and gases at a variety of temperatures and pressures. Pipe was first manufactured with a longitudinal seam some 150 years ago. Since then, the processes employed have progressed to the point where high frequency electric resistance welding has proved the most effective in the manufacture of pipe suitable for oil and gas transmission. To more readily understand the suitability and reliability of electric resistance welded pipe, a discussion relating to the processes involved in its manufacture was presented. Attention was focussed on the weld seam and inspections performed to confirm its integrity. Mechanical properties of the weld seam were compared to those of the pipe body. Using high frequency electric resistance welding and modern inspection techniques, it is possible to produce pipe with a longitudinal weld seam that is virtuously indistinguishable from the parent metal chemically, mechanically, and visually. Furthermore, ASME/ANSI B31.3 Chemical Plant and Petroleum Refinery Piping approves the use of ERW pipe for a variety of applications at temperatures up to and including 593 degrees Celsius.

  15. Correlation between index properties and electrical resistivity of hydrocarbon contaminated periodic marine clays

    NASA Astrophysics Data System (ADS)

    Tiwari, P.; Shah, M. V.

    2015-09-01

    Hydrocarbon contamination is a measure issue of concern as it adversely affects the soil inherent properties viz. index properties and strength properties.The main objective of this research work is to determine Electrical resistivity to study and correlate with soil index properties and engineering propertiescontaminated with hydrocarbon at the rate of 3%, 6% and 9% for the period of 15, 30 45 and 60 days and compare it with the results obtained for non-contaminated marine clay. Electrical resistivity of virgin marine clay (bentonite which is expansive in nature) and hydrocarbon contaminated clay for each percent of contamination is obtained in the laboratory for each period and its co-relation with index properties and engineering properties is proposed. CEC, EDAX tests were performed to evaluate the effect of ions of montmorillonite clays and their penetrability into hydrocarbon- clay matrix. The correlations at the end of each period for each percentage of contamination thus enabled to integrate index properties of non-contaminated and hydrocarbon contaminated marine clays with Electrical resistivity.

  16. Evaluation of ground penetrating radar and resistivity profilings for characterizing lithology and moisture content changes: a case study of the high-conductivity United Kingdom Triassic sandstones

    NASA Astrophysics Data System (ADS)

    Hossain, Delwar

    2013-12-01

    High-resolution geophysical techniques can be employed as a means of characterizing the lithological changes within materials frequently known to be variable. Ground penetrating radar (GPR) profiling using 50, 100, 200, and 400 MHz antennae and electrical resistivity imaging have been used to investigate high-conductivity United Kingdom Triassic sandstone lithology and moisture content changes. The investigation site is located outside the School of Geography, Earth and Environmental Sciences at the University of Birmingham on a gentle grassy slope. Three GPR and electrical imaging lines were completed over this site. The results of the observations reveal a higher degree of both vertical and lateral heterogeneity of the highly conductive sandstones. The results obtained using these two high-resolution geophysical tools agree reasonably well with each other. These techniques appear to be useful for high resolution and continuous mapping of the subsurface sediments.

  17. L- and Corner-arryas for 3D electric resistivity tomography: An alternative for geophysical surveys in urban zones

    NASA Astrophysics Data System (ADS)

    Chavez Segura, R. E.; Tejero-Andrade, A.; Delgado-Solorzano, C.; Cifuentes-Nava, G.; Hernández-Quintero, E.

    2011-12-01

    3D Electric Resitivity Tomography methods carried out on heavily urbanized areas become a difficult task, since buildings, houses or other type of obstacles do not allow parallel ERT arrays to be deployed. Therefore, insufficient information from the subsoil could be obtained. The present paper presents two new techniques, which allow acquiring information beneath a construction by simply surrounding the building or buildings to be studied by a series of ERT profiles. Apparent resistivities are obtained from L-shaped profiles, where alternations between current and potential electrodes along this array are carried out in an automatic way. Four L-arrays and four Corner-arrays are needed to cover the subsurface beneath the studied area. A field test was carried out on a small University of Mexico main Campus garden, where trees and other anthropogenic structures were the so called 'obstacles'. Geophysical work was performed employing parallel arrays (traditional methodology) and compared with this new method presented. Results show that the new method has a poor resolution towards the central portion of the area, mainly from anomalies produced by shallow structures as compared with the traditional grid method. However, the L- and Corner- arrays are more sensitive to anomalies produced by deeper objects, which cannot be observed in the traditional method. The final goal is to apply this method to study habitational complexes built on top of the ancient lake of Mexico City, where buildings are in constant risk due to fracturing and subsidence.

  18. A method to investigate the electron scattering characteristics of ultrathin metallic films by in situ electrical resistance measurements

    SciTech Connect

    Trindade, I. G.; Sousa, J. B.; Fermento, R.; Leitao, D.

    2009-07-15

    In this article, a method to measure the electrical resistivity/conductivity of metallic thin films during layer growth on specific underlayers is described. The in situ monitoring of an underlayer electrical resistance, its change upon the incoming of new material atoms/molecules, and the growth of a new layer are presented. The method is easy to implement and allows obtaining in situ experimental curves of electrical resistivity dependence upon film thickness with a subatomic resolution, providing insight in film growth microstructure characteristics, specular/diffuse electron scattering surfaces, and optimum film thicknesses.

  19. Electrical resistivity measurements of brine saturated porous media near reservoir conditions: Awibengkok preliminary results

    SciTech Connect

    Bonner, B; Duba, A; Roberts, J

    1999-06-28

    Laboratory measurements of the electrical resistivity of rocks and synthetic rocks with confining pressures up to 100 bars and temperatures between 20 and 211 C were performed to further investigate how the pore-size distribution and capillarity affects boiling in porous media. Similar to previous measurements on samples from The Geysers, CA, we observed a gradual increase in resistivity when pore pressure was decreased below the phase-boundary pressure of free water, an indication that boiling is controlled not only by temperature and pressure, but also by pore size distribution. Other important phenomena observed were strong resistance fluctuations during boiling that may be chaotic, and salt deposition that caused sample cracking. If confirmed in further experiments, these results may lead to a new geophysical diagnostic for locating boiling in high permeability areas of geothermal reservoirs and for methods of permeability alteration.

  20. An in vitro comparison of torsional stress and cyclic fatigue resistance of ProFile GT and ProFile GT Series X rotary nickel-titanium files.

    PubMed

    Kramkowski, Thomas R; Bahcall, James

    2009-03-01

    The purpose of this in vitro study was to compare the torsional stress and cyclic fatigue characteristics of ProFile GT (Dentsply Tulsa Dental, Tulsa, OK) and ProFile GT Series X (Dentsply Tulsa Dental). Files of 0.04 and 0.06 taper, 25 mm in length, and ISO sizes of 20 and 30 tips were compared (n = 25 per test group). Torque stress resistance was evaluated by measuring the torque in gram-centimeters (g-cm) and angle of deflection (degrees of rotation) required for instrument separation with use of a torsiometer instrument. Cyclic fatigue was determined by recording the time until breakage of a file rotating in a simulated canal with an applied 45 degrees or 60 degrees curve. The files were operated in a cyclic fatigue instrument that simulated clinical rotary file usage with a constant cyclical axial motion. There was no statistical difference (p > 0.05) when comparing the torque (g-cm) required to induce a torsional failure of ProFile GT and ProFile GT Series X files of identical file sizes. The angle of deflection (degrees of rotation) of ProFile GT was significantly greater (p < or = 0.001) before separation than ProFile GT Series X for all file sizes tested except 20/.04 (p > 0.05). There was no statistical difference (p > 0.05) in cyclic fatigue failure for ProFile GT and ProFile GT Series X in a canal with a curvature of 45 degrees . In the 60 degrees canal curvature, ProFile GT was found to be significantly more resistant (p = 0.005) to fracture because of cyclic fatigue than ProFile GT Series X for file size 30/.06 and significant (p < or = 0.001) for files sizes 20/.06 and 30/.04. There was no difference (p > 0.05) in cyclic fatigue resistance in the 60 degrees canal for ProFile GT and ProFile GT Series X for file size 20/.04. PMID:19249605

  1. Electrical Resistivity Tomography Monitoring of Soil Remediation for a Garbage Dump

    NASA Astrophysics Data System (ADS)

    shi, X.; Luo, Z.; Zhang, Y.; Fu, Q.; Xu, Z.

    2011-12-01

    Electrical resistivity tomography (ERT) survey was firstly used to investigate the distribution of contaminated soil in a garbage dump area, Wuhan city, China. The result shows that sulfated soil resistivity is about 4 to 7 ohm-m, which is relatively lower than normal soil resistivity of about 15 to 25 ohm-m. The distribution of contaminated soil was delineated using ERT images. Then, ERT survey was carried out in this area for monitoring of remediation of contaminated soil and groundwater. Werner measurements with 60 electrodes of 1 m spacing were taken during the 9-well oxygen injection and nutrition liquid injection period. The difference of apparent resistivity between before gas injection and after gas injection was used to delineate the channel of gas and the trace of gas migration in the porous garbage dump. The electrical resitivity changes between before and after nutrition liquid injection were used to analyze the liquid migration and distribution. The dynamic procedures of gas and water migration are outlined. The results suggest that ERT is a powerful technique for monitoring of soil remediation.

  2. Monitoring crack development in fiber concrete beam by using electrical resistivity imaging

    NASA Astrophysics Data System (ADS)

    Wiwattanachang, N.; Giao, P. H.

    2011-10-01

    Accurate detection of damaged concrete zones plays an important role in selecting the proper remedial technique. This study presents results from an application of the electrical imaging method to monitor the development of cracks in fiber concrete beams. The study showed that resistivity measurements on the concrete specimens were able to detect the increase of concrete resistivity with the curing time that reached about 65 Ωm after 28 days of curing. A similar development trend of concrete compressive strength was also found. Two types of cracks were investigated, i.e., artificial cracks made of plastic sheets inserted in concrete and cracks developed during a four-step loading test. A mini-electric imaging survey with Wenner array was conducted on the tension face of the beams. To deal with the effect of the beam size new procedures to correct resistivity measurements before inversion were proposed and successfully applied in this study. The results indicated that both crack direction and depth could be accurately determined in the inverted resistivity sections.

  3. Effects of boiling on electrical resistivity of microporous rocks from the Geysers

    SciTech Connect

    Roberts, J.; Duba, A.; Bonner, B.; Kasameyer, P.

    1997-12-31

    In a laboratory study of cores from borehole SB-15-D in The Geysers geothermal area, we measured the electrical resistivity of metashale with and without pore-pressure control, with confining pressures up to 100 bars and temperatures between 20 and 150{degrees}C, to determine how the pore-size distribution and capillarity affected boiling. We observed a gradual increase in resistivity when the downstream pore pressure or confining pressure decreased below the phase boundary of free water. For the conditions of this experiment, boiling, as indicated by an increase in resistivity, is initiated at pore pressures of approximately 0.5 to 1 bar (0.05 to 0.1 MPa) below the free-water boiling curve, and it continues to increase gradually as pressure is lowered to atmospheric. A simple model of the effects of capillarity suggests that at 145{degrees}C, less than 15% of the pore water can boil in these rocks. If subsequent experiments bear out these preliminary observations, then boiling within a geothermal reservoir is controlled not just by pressure and temperature but also by pore-size distribution. Thus, it may be possible to determine reservoir characteristics by monitoring changes in electrical resistivity as reservoir conditions change.

  4. Noncontact technique for measuring the electrical resistivity and magnetic susceptibility of electrostatically levitated materials.

    PubMed

    Rustan, G E; Spyrison, N S; Kreyssig, A; Prozorov, R; Goldman, A I

    2012-10-01

    We describe the development of a new method for measuring the electrical resistivity and magnetic susceptibility of high temperature liquids and solids. The technique combines a tunnel diode oscillator with an electrostatic levitation furnace to perform noncontact measurements on spherical samples 2-3 mm in diameter. The tank circuit of the oscillator is inductively coupled to the sample, and measurements of the oscillator frequency as a function of sample temperature can be translated into changes in the sample's electrical resistivity and magnetic susceptibility. Particular emphasis is given on the need to improve the positional stability of the levitated samples, as well as the need to stabilize the temperature of the measurement coil. To demonstrate the validity of the technique, measurements have been performed on solid spheres of pure zirconium and low-carbon steel. In the case of zirconium, while absolute values of the resistivity were not determined, the temperature dependence of the resistivity was measured over the range of 640-1770 K and found to be in good agreement with literature data. In the case of low-carbon steel, the ferromagnetic-paramagnetic transition was clearly observable and, when combined with thermal data, appears to occur simultaneously with the solid-solid structural transition. PMID:23126782

  5. Corrosion resistance and electrical properties of carbon/chromium-titanium-nitride multilayer coatings on stainless steel

    NASA Astrophysics Data System (ADS)

    Feng, Kai; Li, Zhuguo; Lu, Fenggui; Huang, Jian; Cai, Xun; Wu, Yixiong

    2014-03-01

    High electrical conductivity and corrosion resistance are central to advances in wider application of metallic bipolar plates in polymer electrolyte membrane fuel cell (PEMFC). In this study, C/Cr-Ti-N multilayer coatings are deposited by physical vapor deposition and the effect of Cr:Ti ratio on the corrosion resistance and interfacial contact resistance (ICR) are systematically investigated. Scanning electron microscopy (SEM) result shows that the carbon layer is compact and uniform. Excellent corrosion resistance of 0.127 μA cm-2 current density at operating voltage in PEMFC cathode environment and low ICR of 2.03 mΩ-cm2 at compaction force of 150 N cm-2 are achieved when Cr:Ti ratio is 2:4 and 3:3, respectively. The significant enhancement in surface conductivity is probably because that the current comes from carbon paper is homogenized by two electrically conductive layers and flows to the passive film with much more contact area. After polarization, ICR increase to 3.07 mΩ-cm2 and 3.02 mΩ-cm2 in the simulated PEMFC cathode and anode environment, respectively. However, the Raman spectroscopy results disclose that the bonding type of top carbon film before and after polarization shows little difference. The results indicate that C/Cr-Ti-N multilayer coating with Cr:Ti ratio of 2:4 achieves the optimal composition.

  6. The data preprocessing in apparent resistivity pesudo-section construction of two-dimensional electrical resistivity tomography survey

    NASA Astrophysics Data System (ADS)

    Zhou, Q.

    2015-12-01

    Although three-dimensional (3-D) electrical resistivity tomography (ERT) survey has become a popular practice in the site characterization and process monitoring, the two-dimensional (2-D) ERT survey is still often used in the field. This is because that the 2-D ERT survey is relatively easy to do and the focus of site characterization is on the information of 2-D cross section, not necessarily of the 3-D subsurface structure. Examples of such practice include tunnel line and crossing fault survey. In these cases, depending on the property of surface soil to be surveyed, the 2-D ERT survey with pole-pole array may occasionally make us obtain quality good data, however it often gives us a suit of data set both with real and erroneous ones that incorporated the effects of electrode contact and not far enough far electrodes. Without preprocessing, the apparent resistivity pseudo-section constructed from this kind of data set may quite deviate from the real one and the information obtained from it may be misleading and even completely incorrect. In this study, we developed a method of far electrode dynamic correction that is appropriate for raw data preprocessing from 2-D pole-pole array ERT survey. Based on this method, we not only can find and delete the abnormal data points easily, but also can position the coordinates of far electrodes actually working in the field, thus delete the far electrode effects and make best use of the looked strange data points. The method also makes us to be able to judge the effects of electrode contact and avoid using such data points in the following apparent resistivity pseudo-section construction. With this preprocessing to the data set, the constructed apparent resistivity pseudo-section is demonstrated to be more approximate to the real one. This makes the following reversion calculation more robust. We'll introduce this far electrode dynamic correction method and show application examples in the meeting.

  7. Interplay between interaction and chiral anomaly: Anisotropy in the electrical resistivity of interacting Weyl metals

    NASA Astrophysics Data System (ADS)

    Jho, Yong-Soo; Kim, Ki-Seok

    2013-05-01

    We predict that long-range interactions give rise to anisotropy in the electrical resistivity of Weyl metals at low temperatures, where the electrical resistivity becomes much reduced when electric fields are applied to the direction of the momentum vector to connect two paired Weyl points. Performing the renormalization group analysis, we find that the distance between two Weyl points becomes enhanced logarithmically at low temperatures although the coupling constant of such interactions vanishes inverse-logarithmically. Considering the Adler-Bell-Jackiw anomaly, scattering between these two Weyl points becomes suppressed to increase electrical conductivity in the “longitudinal” direction, counter intuitive in the respect that interactions are expected to reduce metallicity. We also propose that the anomalous contribution in the Hall effect shows the logarithmic enhancement as a function of temperature, originating from the fact that the anomalous Hall coefficient turns out to be proportional to the distance between two paired Weyl points. Correlations with topological constraints allow unexpected and exotic transport properties.

  8. Electrical conduction in low-resistivity (quasiamorphous) Ag1-xCux alloys

    NASA Astrophysics Data System (ADS)

    Vancea, J.; Pukowietz, S.; Reiss, G.; Hoffmann, H.

    1987-06-01

    UHV-evaporated Ag1-xCux alloy films show a strong dependence of the crystallite sizes on the composition: In the middle of the concentration range, the mean grain size is smaller than 2 nm. The resistivity, however, is much lower than expected for such extremely-fine-grained materials (ρ<9 μΩ cm). The electrical transport parameters for these films were obtained from the thickness dependence of the conductivity without any a priori assumptions. It will be shown that the electrical transport in these alloys can be well understood as a limit of the reflection model for the electrical conductivity in polycrystalline metals [G. Reiss, J. Vancea, and H. Hoffmann, Phys. Rev. Lett. 56, 2100 (1986)].

  9. A simple apparatus for measuring electrical resistance of materials at high temperatures

    SciTech Connect

    Rao, G.V.; Sastry, V.S.; Radhakrishnan, T.S.; Seshagiri, V.

    1996-01-01

    Electrical resistance measurements in a wide temperature range are very important for understanding the physical properties of materials. It is often difficult to carry out the measurements at high temperatures since taking electrical leads reliably from specimens is a nontrivial problem. In this note we describe in detail a simple apparatus which can be used for studying any foil or pellet-shaped sample at temperatures up to 800{degree}C in vacuum or in an inert atmosphere. The apparatus uses spring loaded pins for electrical contact, obviating the need for silver paint or spot welding, thus avoiding any possible change in the properties of the sample. The springs used for loading are far removed from the high temperature zone; the load, therefore, remains unchanged during the experiment and the contacts remain uniformly reliable. {copyright} {ital 1996 American Institute of Physics.}

  10. Electrical carotid sinus stimulation: chances and challenges in the management of treatment resistant arterial hypertension.

    PubMed

    Chobanyan-Jürgens, Kristine; Jordan, Jens

    2015-09-01

    Treatment resistant arterial hypertension is associated with excess cardiovascular morbidity and mortality. Electrical carotid sinus stimulators engaging baroreflex afferent activity have been developed for such patients. Indeed, baroreflex mechanisms contribute to long-term blood pressure control by governing efferent sympathetic and parasympathetic activity. The first-generation carotid sinus stimulator applying bilateral bipolar stimulation reduced blood pressure in a controlled clinical trial but nevertheless failed to meet the primary efficacy endpoint. The second-generation device utilizes smaller unilateral unipolar electrodes, thus decreasing invasiveness of the implantation while saving battery. An uncontrolled clinical study suggested improvement in blood pressure with the second-generation device. We hope that these findings as well as preliminary observations suggesting cardiovascular and renal organ protection with electrical carotid sinus stimulation will be confirmed in properly controlled clinical trials. Meanwhile, we should find ways to better identify patients who are most likely to benefit from electrical carotid sinus stimulation. PMID:26208917

  11. Hillslope characterization in terms of geophysical units based on the joint interpretation of electrical resistivity and seismic velocity data

    NASA Astrophysics Data System (ADS)

    Feskova, Tatiana; Dietrich, Peter

    2015-04-01

    Hydrological conditions in a catchment depend on many factors such as climatic, geological, geomorphological, biological and human, which interact with each other and influence water balance in a catchment. This interaction leads to the subordination in the landscape structure, namely the weak elements subordinate to the powerful elements. Thereby, geological and geomorphological factors play an essential role in catchment development and organization. A hillslope consequently can be allocated to one class of the representative units because the important flow processes run at the hillslope. Moreover, a hillslope can be subdivided into stratigraphic subsurface units and significant hillslope areas based on the lithological change of contrasting interfaces. The knowledge of subsurface structures is necessary to understand and predicate complex hydrological processes in a catchment. Geophysical techniques provide a good opportunity to explore the subsurface. A complete geophysical investigation of subsurface in a catchment with difficult environmental conditions never will be achieved because of large time effort in the field, equipment logistic, and ambiguity in the data interpretation. The case study demonstrates how a catchment can be investigated using geophysical methods in an effective manner in terms of characterization of representative units with respect to a functional role in the catchment. This case study aims to develop combined resistivity and seismic velocity hillslope subsurface models for the distinction of representative functional units. In order to identify the contrasting interfaces of the hillslope, to localize significant hillslope areas, and to address the ambiguity in the geophysical data interpretation, the case study combined resistivity surveys (vertical electrical soundings and electrical resistivity tomography) with refraction seismic method, and conducted these measurements at one single profile along the hillslope transect and

  12. Changes in multifractal parameters from profiles of soil penetration resistance obtained with increasing soil dryness

    NASA Astrophysics Data System (ADS)

    Germán Wilson, Marcelo; Lado Liñares, Marcos; González, Antonio Paz

    2015-04-01

    Soil penetration resistance (PR) is linked to basic soil physical properties and correlated to root growth and plant production, so that it has been extensively used as a practical tool for assessing soil compaction and to evaluate the effects of soil management on soil physical quality. We analyzed multifractality of PR vertical profiles, measured from 0 to 80 cm depth at 1 cm intervals. Soil PR was recorded at 10 successive dates with decreasing soil water content in Entre Ríos Province, Argentina, and 10 replicate PR profiles were obtained in each date. The scaling property of each depth-dependent PR profile was typified by the singularity spectrum, αs versus f(α)s and the generalized dimension spectrum, estimated by the method of moments. Both, singularity and Rènyi spectra showed the vertical PR data sets exhibited a well-defined multifractal structure. The multifractality (scaling heterogeneity) in our data series decreased as the mean soil water content decreased. Overall, singularity spectra were asymmetrical and shifted to the right, which is compatible with a greater heterogeneity of the low values in the PR data sets studied. The entropy dimension, D1, increased with decreasing soil water content, and mean values ranged from 0.956 to 0.981; this means that the wetter the soil the more homogeneously is distributed the measure over a large range of scales. Multifractal analysis yielded information about changes with scale of the higher moments, which gives a deep insight into the inner structure of soil PR depth-dependent profiles.

  13. Electrical Resistivity Monitoring for Leachate Distribution at Two Foot-and-Mouth- Disease (FMD) Burial Sites

    NASA Astrophysics Data System (ADS)

    Lee, S.; Kaown, D.; Lee, K.; Leem, K.; Ko, K.

    2011-12-01

    The main objective of this study was to provide the basic information on leachate distribution with time changes through the electrical resistivity monitoring for a certain period of time in the Foot-and-Mouth-Disease (FMD) burial facilities which is needed to prevent further soil and groundwater contamination and to build an effective plan for stabilization of the burial site. In this study, dipole-dipoles surveys were carried out around two FMD burial sites in Iceon-si, Gyeonggi-do. The FMD burial facility installed at Daewall-myeon is consists of one block but, at Yul-myeon, it is divided into 2 blocks named A and B blocks. Dipole-Dipole surveys with 8 lines at Yul-myeon and 3 lines at Daewall-myeon were carried out. The observed leachate distribution along survey lines was not clearly evident as time passes at Daewall-myeon site, but, at Yul-myeon site, the leachate distribution around the survey lines showed a decrease of resistivity around the burial facility. At and around A and B blocks of Yul-myeon site, interpretations of the survey data show low resistivity zones below 10 Ωm from a depth 3 m to 10 m and such low resistivity zones of the A block are thicker than the B block by about 5~10 m. From the geochemical data and resistivity survey at two FMD burial sites, it is inferred that the groundwater within a 50-meter radius around burial facilities of the Yul-myeon site are contaminated by leachate. The general resistivity distribution around the burial site is seemed affected by the leachate with high electrical conductivity. The detail distribution patterns can be explained by local distributions of soil and weathered rocks and associated leachate flow. This subject is supported by Brain Korea 21 and Korea Ministry of Environment as 'The GAIA Project (173-092-009)'.

  14. Monitoring active layer thaw and freeze-back in four different periglacial landforms in Svalbard using Electrical Resistivity Tomography (ERT)

    NASA Astrophysics Data System (ADS)

    Juliussen, H.; Oswald, A.; Watanabe, T.; Christiansen, H. H.; Matsuoka, N.

    2012-04-01

    Thawing and freezing of the active layer has an important impact on the underlying permafrost through latent heat effects and changes in effective thermal conductivity and mechanisms of heat transport. Information on the active layer freeze/thaw dynamics is therefore important to understand the permafrost response to climate variability. In addition, active layer deepening may be an early sign of permafrost degradation, making monitoring programs such as the CALM network important. Active layer depths are traditionally measured by mechanical probing in fine-grained sediments or by vertical arrays of ground temperature sensors. The first technique prevents measurements to be made in stony sediments, while the latter technique gives only a point value of the active layer depth. In this study we have tested Electrical Resistivity Tomography (ERT) as a tool to measure and monitor active layer depth and freeze/thaw dynamics. The electrical resistivity of the ground is largely dependent on the unfrozen water content, making resistivity monitoring a potentially valuable tool to delineate freeze and thaw extent, and patterns in soil moisture. The results presented here are part of the IPY 2007-2009 research project 'Permafrost Observatory Project: A Contribution to the Thermal State of Permafrost in Norway and Svalbard' (TSP NORWAY) and the IPA periglacial working group project on 'High-Resolution Periglacial Climate Indicators'. Electrode arrays were installed permanently in four different periglacial landforms in the Adventdalen valley area in central Svalbard; a solifluction slope in May 2007, a loess terrace (the UNISCALM site) in September 2007, and a mudboil site and ice-wedge site in June 2009 (Watanabe et al., submitted). The arrays were 16m long, giving maximum profile depths of 2m, and electrodes were installed with 0.2m spacing. Measurements were made with irregular but approximately two- to four-week time intervals, depending on weather conditions and

  15. Antimicrobial resistance, toxinotype, and genotypic profiling of Clostridium difficile isolates of swine origin.

    PubMed

    Fry, Pamela R; Thakur, Siddhartha; Abley, Melanie; Gebreyes, Wondwossen A

    2012-07-01

    The occurrence of Clostridium difficile infections in patients that do not fulfill the classical risk factors prompted us to investigate new risk factors of disease. The goal of this study was to characterize strains and associated antimicrobial resistance determinants of C. difficile isolated from swine raised in Ohio and North Carolina. Genotypic approaches used include PCR detection, toxinotyping, DNA sequencing, and pulsed-field gel electrophoresis (PFGE) DNA fingerprinting. Thirty-one percent (37/119) of isolates carried both tetM and tetW genes. The ermB gene was found in 91% of isolates that were resistant to erythromycin (68/75). Eighty-five percent (521/609) of isolates were toxin gene tcdB and tcdA positive. A total of 81% (494/609) of isolates were positive for cdtB and carry a tcdC gene (a toxin gene negative regulator) with a 39-bp deletion. Overall, 88% (196/223) of pigs carry a single C. difficile strain, while 12% (27/223) of pigs carried multiple strains. To the best of our knowledge, this is the first report of individual pigs found to carry more than one strain type of C. difficile. A significant difference in toxinotype profiles in the two geographic locations was noted, with a significantly (P < 0.001) higher prevalence of toxinotype V found in North Carolina (84%; 189/224) than in Ohio (55%; 99/181). Overall, the study findings indicate that significant proportions of C. difficile in swine are toxigenic and often are associated with antimicrobial resistance genes, although they are not resistant to drugs that are used to treat C. difficile infections. PMID:22518873

  16. Investigation of degree of saturation in landfill liners using electrical resistivity imaging.

    PubMed

    Kibria, Golam; Hossain, Md Sahadat

    2015-05-01

    During construction of compacted clay liners and evapotranspiration (ET) covers, quality control involves laboratory and field tests in individual lifts. However, the available methods may be inadequate to determine non-uniform compaction conditions, poor bonding of lifts, and/or variable soil composition. Moreover, the applicability of the available methods is restricted, in many instances, when spatial variability of the subsurface is expected. Resistivity Imaging (RI) is a geophysical method employed to investigate a large area in a rapid and non-destructive way. High resistivity of clay liner soil is an indication of a low degree of saturation, high air-filled voids, and poor lift bonding. To utilize RI as a quality control tool in a landfill liner, it is important to determine the saturation condition of the compacted soils because compaction and permeability of liner soil are functions of degrees of saturation. The objective of the present study is to evaluate the degree of saturation of a municipal solid waste (MSW) landfill liner, using RI. Electrical resistivity tests were performed in the laboratory, at varied moisture contents and dry unit weights, on four types of soil samples, i.e., highly plastic clay (CH), low plastic clay (CL), Ca-bentonite, and kaolinite. According to the experimental results, electrical resistivity of the specimens decreased as much as 15.3 times of initial value with increase in the degrees of saturation from 23% to 100%. In addition, cation exchange capacity (CEC) substantially affected resistivity. A multiple linear regression (MLR) model was developed to correlate electrical resistivity with degree of saturation and CEC using experimental results. Additionally, RI tests were conducted on compacted clay liners to determine the degrees of saturation, and predicted degrees of saturation were compared with the in-situ density tests. The study results indicated that the developed model can be utilized for liner soils having CEC

  17. Three dimensional modeling and inversion of Borehole-surface Electrical Resistivity Data

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, D.; Liu, Y.; Qin, M.

    2013-12-01

    After a long time of exploration, many oil fields have stepped into the high water-cut period. It is sorely needed to determining the oil-water distribution and water flooding front. Borehole-surface electrical resistivity tomography (BSERT) system is a low-cost measurement with wide measuring scope and small influence on the reservoir. So it is gaining more and more application in detecting water flooding areas and evaluating residual oil distribution in oil fields. In BSERT system, current is connected with the steel casing of the observation well. The current flows along the long casing and transmits to the surface through inhomogeneous layers. Then received electric potential difference data on the surface can be used to inverse the deep subsurface resistivity distribution. This study presents the 3D modeling and inversion method of electrical resistivity data. In an extensive literature, the steel casing is treated as a transmission line current source with infinite small radius and constant current density. However, in practical multi-layered formations with different resistivity, the current density along the casing is not constant. In this study, the steel casing is modeled by a 2.5e-7 ohm-m physical volume that the casing occupies in the finite element mesh. Radius of the casing can be set to a little bigger than the true radius, and this helps reduce the element number and computation time. The current supply point is set on the center of the top surface of the physical volume. The homogeneous formation modeling result shows the same precision as the transmission line current source model. The multi-layered formation modeling result shows that the current density along the casing is high in the low-resistivity layer, and low in the high-resistivity layer. These results are more reasonable. Moreover, the deviated and horizontal well can be simulated as simple as the vertical well using this modeling method. Based on this forward modeling method, the

  18. The Behaviour of Laboratory Soil Electrical Resistivity Value under Basic Soil Properties Influences

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Aziman, M.; Azhar, A. T. S.; Chitral, W. D.; Fauziah, A.; Rosli, S.

    2015-01-01

    Electrical resistivity method (ERM) was a popular indirect geophysical tools adopted in engineering, environmental and archaeological studies. In the past, results of the electrical resistivity value (ERV) were always subjected to a long discussion and debate among the related parties such as an engineers, geophysicists and geologists due to its lack of clarification and evidences in quantitative point of view. Most of the results produced in the past was always been justified using qualitative ways which difficult to be accept by certain parties. In order to reduce the knowledge gap between those parties, this study has performed a laboratory experiment of soil box resistivity test which supported by an additional basic geotechnical test as referred to particle size distribution test (d), moisture content test (w), density test (ρbulk) and Atterberg limit test (LL, PL and PI). The test was performed to establish a series of electrical resistivity value with different quantity of water content for Clayey SILT and Silty SAND soil. It was found that the ERV of Silty SAND (600 - 7300 Ωm) was higher than Clayey SILT (13 - 7700 Ωm) due to the different quantity of basic soil properties value obtained from the basic geotechnical test. This study was successfully demonstrated that the fluctuation of ERV has greatly influenced by the variations of the soil physical properties (d, w, ρbulk, LL, PL and PI). Hence, the confidence level of ERV interpretation will be increasingly meaningful since it able to be proved by others parameter generated by laboratory direct test.

  19. Continuous resistivity profiling data from Northport Harbor and Manhasset Bay, Long Island, New York

    USGS Publications Warehouse

    Cross, V.A.; Bratton, J.F.; Crusius, J.; Kroeger, K.D.; Worley, C.R.

    2012-01-01

    An investigation of coastal groundwater systems was performed along the North Shore of Long Island, New York, during May 2008 to constrain nutrient delivery to Northport Harbor and Manhasset Bay by delineating locations of likely groundwater discharge. The embayments are bounded by steep moraines and are underlain by thick, fine-grained sediments deposited in proglacial lakes during the last ice age. Beach sand and gravel overlie the glacial deposits along the coast. The continuous resistivity profiling (CRP) surveys that were conducted indicate the existence of low-salinity groundwater in shore-parallel bands, typically 25 to 50 meters wide, along the shorelines of both bays. Piezometer sampling and seepage meter deployments in intertidal and subtidal areas of the two bays confirmed the presence and discharge of brackish and low-salinity groundwater. The large tidal ranges (up to 3 meters) and the steep onshore topography and hydraulic gradients are important variables controlling coastal groundwater discharge in these areas.

  20. A Novel Blasted and Grooved Low Profile Pedicle Screw Able to Resist High Compression Bending Loads

    PubMed Central

    Kim, Young-Sung; Choi, Hong-June; Kim, Kyung-Hyun; Park, Jeong-Yoon; Jeong, Hyun-Yong; Chin, Dong-Kyu; Kim, Keun-Su; Yoon, Young-Sul; Lee, Yoon-Chul; Cho, Yong-Eun

    2012-01-01

    Objective Polyaxial pedicle screws are a safe, useful adjunct to transpedicular fixation. However, the large screw head size can cause soft tissue irritation, high rod positioning, and facet joint injury. However, the mechanical resistance provided by small and low profile pedicle screws is very limited. We therefore developed a novel, low profile pedicle screw using grooving and blasting treatment that is able to resist a high compression bending load. Methods We evaluated the compression bending force to displacement and yield loads for seven different screw head types that differed with regard to their groove intervals and whether or not they had been blasted. Results The rank order of screw types that had the greatest compression bending force to displacement was as follows: (1) universal polyaxial, (2) low polyaxial with 0.1mm grooves and blasting, (3) low polyaxial with blasting, (4) low polyaxial with 0.15mm grooves and blasting, (5) low polyaxial with 0.05mm grooves and blasting, (6) low polyaxial with 0.05mm grooves, (7) and low polyaxial. Low polyaxial screws with 0.1mm grooves and blasting had the maximum yield load and highest compression bending force to displacement of all seven polyaxial screw head systems evaluated. Conclusion Blasting and grooving treatment of pedicle screw heads resulted in screw heads with a high yield load and compression bending force relative to displacement because of increased friction. Low polyaxial pedicle screws with 0.1 mm grooves treated by blasting have mechanical characteristics similar to those of universal polyaxial pedicle screws. PMID:25983790

  1. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail III, William Banning; Momii, Steven Thomas

    2003-06-10

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  2. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail, III, William Banning; Momii, Steven Thomas

    2000-01-01

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  3. Electrical voltages and resistances measured to inspect metallic cased wells and pipelines

    DOEpatents

    Vail, III, William Banning; Momii, Steven Thomas

    2001-01-01

    A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

  4. Simulation of Fine Resist Profile Formation by Electron Beam Drawing and Development with Solubility Rate Based on Energy Deposition Distribution

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Komori, Takuya; Zhang, Yulong; Yin, You; Hosaka, Sumio

    2013-12-01

    We proposed a model for calculating the resist profile in electron beam drawing. The model predicts the solubility rate on the basis of the energy deposition distribution (EDD) for the development of latent patterns in the resist. By unifying the exposure dose D (via experiments) and EDDs (via calculations), we roughly determined solubility rates for three-dimensional EDDs, and established the proposed model. The development simulation was achieved by the sequential calculation method for solubility rates based on EDD which was calculated by Monte Carlo simulation. By determining a suitable EDD region to achieve good patterning, we obtained a sharp nanodot pattern of the resist. This simulation results are in good agreement with the experimental results obtained using a combination of 2.3 wt % tetramethylammonium hydroxide (TMAH) and 4 wt % NaCl as the developer. The model was demonstrated to be useful for predicting resist profiles with different experimental solubility rates of developers.

  5. Monitoring the geothermal fluid using time lapse electrical resistivity tomography: The Pisciarelli fumarolic field test site (Campi Flegrei, South Italy)

    NASA Astrophysics Data System (ADS)

    Fedele, Alessandro; Giulia Di Giuseppe, Maria; Troiano, Antonio; Somma, Reanto; Caputo, Teresa; Patella, Domenico; Troise, Claudia; De Natale, Giuseppe

    2015-04-01

    Pisciarelli area is a fumarolic field subject to very short time morphological changes. A number of critical problems affect this area, i.e. increase of temperature of the fumaroles above the average background temperature, local seismicity and occurrence of fumaroles mixed with jets of boiling water. The presence of a very shallow aquifer seem to have the control on the behavior and composition of the fumaroles. This fumarolic field is still largely unknown regarding geophysical surveys mainly because of its limited space, surrounded on the eastern side by intense urbanization inside the large Agnano crater (Troiano et al. 2014). Currently is mainly affected by geochemical, thermal and seismic monitoring which may not fully explain the behaviour of fluids surface. Many monitoring or time lapse (TL) applications are discussed in literature (e.g., White, 1994; Daily et al., 1995; Barker and Moore, 1998; Ramirez and Daily, 2001; Carter, 2002; Slater et al., 2002; Singha and Gorelick, 2005; Cassiani et al., 2006; Swarzenski et al., 2006; de Franco et al., 2009). However all these experiments are devoted to the use of the ERT for tracer tests or in contaminant hydrology and are characterized by a short monitoring period due to the complexity and problems of long-time instrument maintenance. We propose and present a first approach of a geophysical monitoring by time lapse electrical resistivity in a fumarolic field. The profiles were acquired in January 2013, in January, March, May, July, September and November 2014 respectively. They cross the Pisciarelli area following approximately the NS direction and were characterized by a 2.5 m electrode spacing and maximum penetration depth of about 20 m. and will supply fundamental evidences on the possible seasonal resistivity fluctuations or if the resistivity changes are indicative of an increase in volcanic gases present in the hydrothermal system.

  6. Lunar magnetic field measurements, electrical conductivity calculations and thermal profile inferences

    NASA Technical Reports Server (NTRS)

    Colburn, D. S.

    1971-01-01

    Steady magnetic field measurements of magnitude 30 to 100 gamma on the lunar surface impose problems of interpretation when coupled with the nondetectability of a lunar field at 0.4 lunar radius altitude and the limb induced perturbations of the solar wind at the Explorer orbit. The lunar time-varying magnetic field clearly indicates the presence of eddy currents in the lunar interior and permits calculation of an electrical conductivity profile. The problem is complicated by the day-night asymmetry of the moon's electromagnetic environment, the possible presence of the transverse magnetic mode, and the variable wave directions of the driving function. The electrical conductivity is calculated to be low near the surface, rising to a peak of .006/ohm meter at 250 km, dropping steeply inwards to a value of about .00005/ohm meter, and then rising toward the interior. A transition at 250 km depth from a high conductivity to a low conductivity material is inferred, suggesting an olivine-like core at approximately 800 C, although other models are possible.

  7. Influence of processing history on the mechanical properties and electrical resistivity of polycarbonate - multi-walled carbon nanotubes nanocomposites

    NASA Astrophysics Data System (ADS)

    Choong, Gabriel Y. H.; De Focatiis, Davide S. A.

    2015-05-01

    In this work we investigate the effects of compounding temperature and secondary melt processing on the mechanical response and electrical behaviour of polycarbonate filled with 3 wt% carbon nanotubes. The nanocomposites were melt compounded in an industrial setting at a range of temperatures, and subsequently injection moulded or compression moulded. The surface hardness, uniaxial tensile properties and electrical resistivity were measured. Secondary melt processing is found to be the dominant process in determining the final mechanical properties and resistivity of these materials.

  8. Profiling gene mutations, translocations, and multidrug resistance in pediatric acute lymphoblastic leukemia: a step forward to personalizing medicine.

    PubMed

    Rose-James, Alphy; Shiji, R; Kusumakumary, P; Nair, Manjusha; George, Suraj K; Sreelekha, T T

    2016-09-01

    Precise risk stratification and tailored therapy in acute lymphoblastic leukemia (ALL) can lead to enhanced survival rates among children. Translocations and mutations along with multidrug resistance markers are important factors that determine therapeutic efficacy. Gene mutation profiling of patients at the time of diagnosis can offer accurate clinical decision-making. Multiplex PCR was used to screen for various translocations, mutations, and P-glycoprotein (P-gp) status in pediatric ALL samples. The roles of P-gp were analyzed at the transcriptional and translational levels by using real-time PCR and immunoblotting, respectively. ALL specific cell line Jurkat was used to validate the functional role of P-gp in imparting drug resistance by siRNA knockdown studies. Co-occurrence of translocations and mutations contributes to cellular drug resistance. Presence of any translocation in addition to FLT3/ITD hints for overactive P-gp. Co-occurrence of E2A/PBX and TEL/AML has also been positively correlated with P-gp status. Multiplex PCR provides a rapid and cost effective technique for profiling translocations, mutations, and multidrug resistance status that determines what therapy patients could be administered. Mutation profiling in patients for analyzing genetic lesions along with drug resistance profiling will help improve risk stratification and personalized medicine, thereby increasing the treatment success rates among pediatric patients with leukemia. PMID:27449773

  9. Novel laboratory methods for determining the fine scale electrical resistivity structure of core

    NASA Astrophysics Data System (ADS)

    Haslam, E. P.; Gunn, D. A.; Jackson, P. D.; Lovell, M. A.; Aydin, A.; Prance, R. J.; Watson, P.

    2014-12-01

    High-resolution electrical resistivity measurements are made on saturated rocks using novel laboratory instrumentation and multiple electrical voltage measurements involving in principle a four-point electrode measurement but with a single, moving electrode. Flat, rectangular core samples are scanned by varying the electrode position over a range of hundreds of millimetres with an accuracy of a tenth of a millimetre. Two approaches are tested involving a contact electrode and a non-contact electrode arrangement. The first galvanic method uses balanced cycle switching of a floating direct current (DC) source to minimise charge polarisation effects masking the resistivity distribution related to fine scale structure. These contacting electrode measurements are made with high common mode noise rejection via differential amplification with respect to a reference point within the current flow path. A computer based multifunction data acquisition system logs the current through the sample and voltages along equipotentials from which the resistivity measurements are derived. Multiple measurements are combined to create images of the surface resistivity structure, with variable spatial resolution controlled by the electrode spacing. Fine scale sedimentary features and open fractures in saturated rocks are interpreted from the measurements with reference to established relationships between electrical resistivity and porosity. Our results successfully characterise grainfall lamination and sandflow cross-stratification in a brine saturated, dune bedded core sample representative of a southern North Sea reservoir sandstone, studied using the system in constant current, variable voltage mode. In contrast, in a low porosity marble, identification of open fracture porosity against a background very low matrix porosity is achieved using the constant voltage, variable current mode. This new system is limited by the diameter of the electrode that for practical reasons can only be

  10. Application of electrical resistivity tomography for investigating the internal structure of a translational landslide and characterizing its groundwater circulation (Kualiangzi landslide, Southwest China)

    NASA Astrophysics Data System (ADS)

    Ling, Chengpeng; Xu, Qiang; Zhang, Qiang; Ran, Jiaxin; Lv, Hongbin

    2016-08-01

    Electrical resistivity tomography (ERT) is a widely used tool in near surface geophysical surveys for the investigation of various geological and engineering problems, including landslides. In this study, the internal structure of the southern region of the Kualiangzi landslide, which is located in Sichuan province, China, was investigated using four ERT profiles, drill cores, and inclinometer data. The characteristics of the groundwater circulation were evaluated from variations in electrical resistivity and groundwater level. The results showed that the sliding surface corresponds to a deep zone with low resistivity and that the sliding material consists of clay, gravelly soil, and weathered sandstone and mudstone. The thickness of the sliding material is 50 m in the main tension trough and decreases to several meters in the direction of sliding. The dip angle of the sliding surface that has low resistivity is generally consistent with that of the bedrock. The groundwater level in the tension trough and in the middle transitional part from hill-country to flat terrain was highest in the landslide. The groundwater level close to the toe front of the landslide was the lowest. The groundwater is recharged by the precipitation and generally drains to the toe front by seasonal springs along the sliding surface. The rapid increment of the groundwater level in the tension trough kept pace with that of the displacement rate after intense rainfall. The improved understanding of internal structure and groundwater recirculation is beneficial for the analysis of the mechanisms of translational landslides and their hazard prevention.

  11. Using Metabolomic Profiles as Biomarkers for Insulin Resistance in Childhood Obesity: A Systematic Review.

    PubMed

    Zhao, Xue; Gang, Xiaokun; Liu, Yujia; Sun, Chenglin; Han, Qing; Wang, Guixia

    2016-01-01

    A growing body of evidence has shown the intimate relationship between metabolomic profiles and insulin resistance (IR) in obese adults, while little is known about childhood obesity. In this review, we searched available papers addressing metabolomic profiles and IR in obese children from inception to February 2016 on MEDLINE, Web of Science, the Cochrane Library, ClinicalTrials.gov, and EMASE. HOMA-IR was applied as surrogate markers of IR and related metabolic disorders at both baseline and follow-up. To minimize selection bias, two investigators independently completed this work. After critical selection, 10 studies (including 2,673 participants) were eligible and evaluated by using QUADOMICS for quality assessment. Six of the 10 studies were classified as "high quality." Then we generated all the metabolites identified in each study and found amino acid metabolism and lipid metabolism were the main affected metabolic pathways in obese children. Among identified metabolites, branched-chain amino acids (BCAAs), aromatic amino acids (AAAs), and acylcarnitines were reported to be associated with IR as biomarkers most frequently. Additionally, BCAAs and tyrosine seemed to be relevant to future metabolic risk in the long-term follow-up cohorts, emphasizing the importance of early diagnosis and prevention strategy. Because of limited scale and design heterogeneity of existing studies, future studies might focus on validating above findings in more large-scale and longitudinal studies with elaborate design. PMID:27517054

  12. Using Metabolomic Profiles as Biomarkers for Insulin Resistance in Childhood Obesity: A Systematic Review

    PubMed Central

    Sun, Chenglin

    2016-01-01

    A growing body of evidence has shown the intimate relationship between metabolomic profiles and insulin resistance (IR) in obese adults, while little is known about childhood obesity. In this review, we searched available papers addressing metabolomic profiles and IR in obese children from inception to February 2016 on MEDLINE, Web of Science, the Cochrane Library, ClinicalTrials.gov, and EMASE. HOMA-IR was applied as surrogate markers of IR and related metabolic disorders at both baseline and follow-up. To minimize selection bias, two investigators independently completed this work. After critical selection, 10 studies (including 2,673 participants) were eligible and evaluated by using QUADOMICS for quality assessment. Six of the 10 studies were classified as “high quality.” Then we generated all the metabolites identified in each study and found amino acid metabolism and lipid metabolism were the main affected metabolic pathways in obese children. Among identified metabolites, branched-chain amino acids (BCAAs), aromatic amino acids (AAAs), and acylcarnitines were reported to be associated with IR as biomarkers most frequently. Additionally, BCAAs and tyrosine seemed to be relevant to future metabolic risk in the long-term follow-up cohorts, emphasizing the importance of early diagnosis and prevention strategy. Because of limited scale and design heterogeneity of existing studies, future studies might focus on validating above findings in more large-scale and longitudinal studies with elaborate design. PMID:27517054

  13. Characterization of photoresist and simulation of a developed resist profile for the fabrication of gray-scale diffractive optic elements

    NASA Astrophysics Data System (ADS)

    Park, Jong Rak; Sierchio, Justin; Zaverton, Melissa; Kim, Youngsik; Milster, Tom D.

    2012-02-01

    We have characterized a photoresist used for the fabrication of gray-scale diffractive optic elements in terms of Dill's and Mack's model parameters. The resist model parameters were employed for the simulations of developed resist profiles for sawtooth patterns executed by solving the Eikonal equati