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1

Delineation of a volcanic ash body using electrical resistivity profiling  

NASA Astrophysics Data System (ADS)

Four lines of electrical resistivity profiling (ERP) were performed to define the extent of a shallow Quaternary volcanic ash deposit being mined in the United States. Inversion results of ERP proved suitable for defining the thickness and lateral extent of the volcanic ash deposit at this testing site. These interpretations were confirmed by shallow borehole drilling. The model sensitivity information indicates that inverted models possess sufficient resolving power down to a depth of 7 m and are fairly consistent in terms of horizontal resolution along the four ERP lines. The bottom of most of the volcanic ash deposit in the study area is less than 7 m in depth. Based on synthesis of the ERP and drill information, the limits of the mineable ash bed resources were clearly defined. Moreover, by integrating the ERP results with a minimal number of optimally placed borings, the volume of the volcanic ash deposit was established at a lesser cost, and with greater accuracy than would be possible with a traditionally designed grid drilling programme.

Xia, Jianghai; Ludvigson, Greg; Miller, Richard D.; Mayer, Lindsay; Haj, Adel

2010-09-01

2

Mapping Refuse Profile in Singapore Old Dumping Ground through Electrical Resistivity, S-Wave Velocity and Geotechnical Monitoring.  

PubMed

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

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

2014-11-27

3

State Electricity Profiles  

EIA Publications

The annual report contains data tables describing the electricity industry in each state. Data include generating capability, electricity generation, fuel use and prices, retail sales, emissions, and net interstate transfers of electricity.

2014-01-01

4

State Renewable Electricity Profiles  

EIA Publications

Presents a summary of current and recent historical data for the renewable electric power industry. The data focuses on net summer capacity and net generation for each type of renewable generator, as well as fossil-fired and nuclear power plant types, for the period 2006 through 2010.

2012-01-01

5

Electrical resistivity investigations over limestone caverns  

E-print Network

- urement. Vertical profiles 25 ft. south of stone wall, Schoharie Caverns. Figure 21. Comparison of vertical profiles centered above and offset from passage to Alabaster Room, Knox Cave. 64 Figure 22. Apparent resistivity vs. electrode spacing. Con..., they afford interesting possibilities for verifying theoretical electrical potential-distri- bution predictions. The eastern New York field sites where this research was con- ducted (s. t Knox and Schoharie caves) feature an even surface topography...

Porter, Charles Osgood

2012-06-07

6

Molecular Expressions: Electricity & Magnetism: Resistance  

NSDL National Science Digital Library

Comprehensive tutorial on resistance, accompanied by three interactive simulations. One allows the user to glimpse resistance at a molecular level; the second explores Ohm's Law; and the third introduces the use of color coding in composition resistors. The author uses diagrams to illustrate arrangements of resistors in series and parallel circuits, with explanations of how to calculate equivalent resistances. This item is part of a larger collection on Electricity and Magnetism sponsored by Florida State University..

Davidson, Michael

7

Electrically Variable Resistive Memory Devices  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

8

Electrical Resistivity Tomography Using MODFLOW  

NASA Astrophysics Data System (ADS)

Numerical studies and laboratory experiments have been conducted to initiate and explore electrical resistivity tomography (ERT) to better understand subsurface heterogeneity and characterization of heterogeneous porous media. ERT is a geophysical method which calculates the electrical resistivity distribution in the subsurface environment from a large number of electrical potential measurements made from electrodes. The electrostatic model is solved by MODFLOW to investigate its application to ERT and parameterization of electrical resistivity. In this study, the ERT is formulated as a regularized least-squares (RLS) problem. The inversion of electrical resistivity is conducted through an adjoint-state method, where the Jacobian matrix is not necessary. At each optimization step we only need to solve the electrostatic model and the adjoint state model once to evaluate the gradients of RLS with respect to the unknown resistivity regardless of the dimensions of parameterization. The MODFLOW is also applied to the solution of the adjoint-state equation. We first numerically verified the inversion algorithm in a two-dimensional ERT problem. Then, we conducted ERT experiments in a three-dimensional sand box.

Tsai, F. T.; Pillala, M.

2008-12-01

9

State electricity profiles, March 1999  

SciTech Connect

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.

NONE

1999-03-01

10

Electrical resistance of muscle capillary endothelium.  

PubMed

A recently developed technique for in vivo determination of the electrical resistance of vascular endothelium in microvessels was applied to the vessels in a thin frog muscle, m. cutaneus pectoris. The technique consists of injection of current via a glass micropipette into a capillary and measurement of the resulting intra- and extravascular potential profiles with another micropipette placed at various distances from the current source. The theory of Peskoff and Eisenberg (1974) was used to handle the problems arising from distributed extravascular resistances and was experimentally shown to describe the external field satisfactorily. With this extension of one-dimensional cable theory the specific electrical resistance of arterial microvessels was 33 omega cm2 and of venous capillaries 23 omega cm2. The "length constants" were 135 and 112 micrometers, respectively. If results from arterial and venous vessels are taken together, the ionic permeabilities at 20 degrees C were PNa = 3.9 X 10(-5) cm X s-1, PK = 5.7 X 10(-5) cm X s-1, PCl = 5.9 X 10(-5) cm X s-1 and PHCO3 = 3.4 X 10(-5) cm X s-1. These figures agree with figures for capillary permeability obtained in tracer experiments on whole muscle. The study bridges a gap between single capillary and whole organ techniques with the conclusion that the two different approaches lead to similar results in muscle capillaries. PMID:6601500

Olesen, S P; Crone, C

1983-04-01

11

THE ELECTRICAL RESISTIVITY METER IN FISHERY INVESTIGATIONS  

E-print Network

THE ELECTRICAL RESISTIVITY METER IN FISHERY INVESTIGATIONS I Marine Biological Laboratory! WOODS RESISTIVITY METER IN FISHERY INVESTIGATIONS By Robert E. Lennon Fishery Research Biologist Appalachian Sport) BiblioKiMpliy : p. ]!. 1. Electric meters. 2. Water--Analysis. 3. Electric fishing. I. Title. ( Series

12

Electrical resistivity mechanism in magnetorheological elastomer  

Microsoft Academic Search

Magnetorheological elastomers (MREs) are smart materials made by aligning magnetic microparticles inside a liquid polymer. Once the polymer is cured, this anisotropic structure is kept, giving to the composite new properties such as a large change in electrical resistivity with applied pressure. In order to understand the conduction mechanism in such composites, the influence of pressure on the electrical resistivity

N. Kchit; G. Bossis

2009-01-01

13

Electrical resistivity tomography of vadose water movement  

Microsoft Academic Search

Cross borehole electrical resistivity tomography (ERT) was used to image the resistivity distribution before and during two infiltration experiments. In both cases water was introduced into the vadose zone, and the change in resistivity associated with the plume of wetted soil was imaged as a function of time. The primary purpose of this work was to study the capabilities and

William Daily; Abelardo Ramirez; Douglas LaBrecque; John Nitao

1992-01-01

14

Kuwait Energy Profile for Electrical Power Generation  

Microsoft Academic Search

The State of Kuwait, a major oil exporter, consumes a huge amount of its natural hydrocarbon resources to meet the rising demand for electricity. The forecasting of domestic energy demand and optimal allocation of energy resources are necessary requirements for a balanced energy policy. This article assesses the energy resources profile of Kuwait in order to reveal the potential base

Mohammad Ramadhan; Abdulhameed Hussain

2012-01-01

15

Vertical Soil Profiling Using a Galvanic Contact Resistivity Scanning Approach  

PubMed Central

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

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

2014-01-01

16

Vertical soil profiling using a galvanic contact resistivity scanning approach.  

PubMed

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

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

2014-01-01

17

Electrical resistivity survey in eastern Jeju Island  

NASA Astrophysics Data System (ADS)

Electrical resistivity survey was conducted to acquire basic geological layer information for regional hydrogeologic application by our own developed system in eastern Jeju island. The system mainly consists of a stand-alone TX(transmitter) module, of which the excitation current into the earth has been increased very much using a portable AC generator instead of batteries, a digital stacking RX(receiver), and a pair of programmable synchronization clock modules to achieve the initial synchronization between TX and RX. The waveform of the excitation current into the earth at transmitter side is double bipolar, and the power is 1000V-1A or 800V-5A with a portable AC generator. At the receiver part controlled through a notebook PC's serial port, the operator can observe the exact waveform and the averaged value with 24-bit A/D resolution and gain 1-10-100. The small portable synchronization clocks, operated by 12V/2A sealed battery, provides the precise basic measurement cycles and initial triggering. The control and measurement software which acquires the earth resistivity data was developed user-interactively. The system was field-tested in eastern part of Jeju Island with dipole spacing a=300m and 600m, to n=10, and stations=43, by the array of which the exploration depth has been increased to about 2,400 m. By the developed portable system we could conduct very easy and fast field work and acquire very satisfactory data. The inversion of measured data gave us the useful information about the sub-surface resistivity structure to about 2,400 m depth along a 13km survey profile. Further study will be focused on simultaneous multi receiver data acquisition system.

Jung, H.

2010-12-01

18

Resistive companion battery modeling for electric circuit simulations , R. Dougalb  

E-print Network

Resistive companion battery modeling for electric circuit simulations B. Wua , R. Dougalb , R for electric circuit simulations. With a RC numerical solver, simulations of complex electric systems can reserved. Keywords: Battery modeling; Battery simulation; Electric circuit simulation; Resistive companion

19

Electrical resistivity mechanism in magnetorheological elastomer  

E-print Network

Electrical resistivity mechanism in magnetorheological elastomer N Kchit, G Bossis L.P.M.C. UMR. Magnetorheological elastomers (MRE) are smart materials made by aligning magnetic microparticles inside a liquid

Paris-Sud XI, Université de

20

Cone-based Electrical Resistivity Tomography  

NASA Astrophysics Data System (ADS)

Determining the 3D 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, we have developed a minimally invasive technology that provides information about the 3D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer to measure the resultant potential field while advancing the cone into the subsurface. In addition to potential field measurements, we obtain the standard suite of cone-penetration measurements, including high resolution resistivity logs; these data can then be used to constrain the inversion of the potential field data. A major challenge of working with these data is that the cone penetrometer is highly conductive, and thus presents a large local perturbation around the measurement location. As the cone is very small (approximately 30mm in diameter) with respect to the total model space, explicitly modeling the cone is computationally demanding. We developed a method for solving the forward model that reduces computational time by an order of magnitude. This solution method, iteratively determined boundary conditions, makes it possible to correct for the cone effect before inversion of the data. Results from synthetic experiments suggest that the C-bert method of data acquisition can result in high quality electrical conductivity images of the subsurface. We tested the practicality of this technique by performing a field test of the C-bert system to image a salt water intrusion in a fresh water aquifer in Vancouver, British Columbia. A total of nine current electrodes were emplaced at the site and five C-bert profiles were obtained, resulting in approximately 6500 data points. We conclude, from this first field test, that this method is a promising new way to image the subsurface.

Pidlisecky, A.; Knight, R.; Haber, E.

2005-05-01

21

Release Resistant Electrical Interconnections For Mems Devices  

DOEpatents

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.

Peterson, Kenneth A. (Albuquerque, NM); Garrett, Stephen E. (Albuquerque, NM); Reber, Cathleen A. (Corrales, NM)

2005-02-22

22

On equivalent resistance of electrical circuits  

NASA Astrophysics Data System (ADS)

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.

Kagan, Mikhail

2015-01-01

23

Electrical resistance tomography for imaging concrete structures  

SciTech Connect

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.

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

1995-11-08

24

Estimating soil suction from electrical resistivity  

NASA Astrophysics Data System (ADS)

Soil suction and resistivity strongly depend on the degree of soil saturation and, therefore, both are used for estimating water content variations. The main difference between them is that soil suction is measured using tensiometers, which give point information, while resistivity is obtained by tomography surveys, which provide distributions of resistivity values in large volumes, although with less accuracy. In this paper, we have related soil suction to electrical resistivity with the aim of obtaining information about soil suction changes in large volumes, and not only for small areas around soil suction probes. We derived analytical relationships between soil matric suction and electrical resistivity by combining the empirical laws of van Genuchten and Archie. The obtained relationships were used to evaluate maps of soil suction values in different ashy layers originating in the explosive activity of the Mt Somma-Vesuvius volcano (southern Italy). Our findings provided a further example of the high potential of geophysical methods in contributing to more effective monitoring of soil stress conditions; this is of primary importance in areas where rainfall-induced landslides occur periodically.

Piegari, E.; Di Maio, R.

2013-09-01

25

Electrical Contact Resistance with Dissimilar Materials  

NASA Astrophysics Data System (ADS)

Electrical contact is important to wire-array Z pinches [1], high power microwave sources, and metal-insulator-vacuum junction, etc. It is also an important issue to ITER. Because of the surface roughness on a microscopic scale, true contact between two pieces of conductors occurs only at the asperities of the contacting surfaces, leading to contact resistance. In this paper, Holm's basic a-spot theory [2] for contact resistance is vastly extended to higher dimensions with dissimilar materials [3]. Scaling laws are constructed for both Cartesian and cylindrical channels. The theory was validated by simulations and experiments in several limiting cases [4]. [1] D. A. Chalenski et al., Phys. Plasmas 16, 082707 (2009); M. R. Gomez et al., Rev. Sci. Inst. 79, 093512 (2008). [2] R. Holm, Electric Contact (Springer-Verlag, 1967). [3] P. Zhang and Y. Y. Lau, J. Appl. Phys. (July 2010). [4] M. R. Gomez et al., Appl. Phys. Lett. 95, 072103 (2009).

Zhang, Peng; Lau, Y. Y.; Gomez, Matthew; French, David; Gilgenbach, R. M.; Tang, Wilkin

2010-11-01

26

Electrical resistance tomography of concrete structures  

SciTech Connect

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.

Daily, W.; Ramirez, A. [Lawrence Livermore National Lab., CA (United States); Binley, A.; Henry-Poulter, S. [Lancaster Univ. (United Kingdom). Dept. of Environmental Sciences

1993-10-01

27

Electrical resistance characteristics of starch foams  

Microsoft Academic Search

The insulative character of expanded polystyrene loose-fill packing material supports the immobile triboelectric charge on its surface, causing static cling. One beneficial property of starch-based loose-fill is its antistatic behavior, which prevents the buildup of electrostatic charges on the foam surface, resulting in no static cling. This investigation explores the electrical resistance characteristics of plasticized starch materials such as commercial

Paul D. Tatarka

1996-01-01

28

Rational Experimental Design for Electrical Resistivity Imaging  

NASA Astrophysics Data System (ADS)

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 information content of the source configurations. This approach requires minimal computational power, and, thus, it can be implemented in the field as information is acquired, allowing for modification of the current experimental design. We compare, through numerical modeling, results from arrays identified by this algorithm to those from traditional arrays for the case where we have a good starting model of the subsurface. We then test the performance of selected arrays in the case of uncertainty in the resistivity model and noise in the data. In all cases, our method provides comparable or superior results at low computational cost, providing a useful framework for rational experimental design.

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

2008-12-01

29

Cone-based electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

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 starting model for the inversion. Furthermore, the resistivity logs can be used as constraints in the inversion of the potential field data. Effective incorporation of resistivity logs into the inversion process, however, requires an understanding the spatial averaging that occurs during logging. I developed a forward modeling and inversion algorithm that allows us to understand and remove the averaging that is present in the logs. A successful field test of C-bert was conducted at the Kidd2 site in Richmond, British Columbia, leading me to conclude that C-bert is a promising new way to image the subsurface.

Pidlisecky, Adam

30

Electrical Resistance Tomography imaging of concrete  

SciTech Connect

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.

Karhunen, Kimmo [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Seppaenen, Aku, E-mail: Aku.Seppanen@uku.f [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Lehikoinen, Anssi [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California Berkeley, California (United States); Kaipio, Jari P. [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Department of Mathematics, University of Auckland, Auckland (New Zealand)

2010-01-15

31

Determination of electrical resistivity of dry coke beds  

SciTech Connect

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.

Eidem, P.A.; Tangstad, M.; Bakken, J.A. [NTNU, Trondheim (Norway)

2008-02-15

32

Probabilistic electrical resistivity tomography of a CO2 sequestration analog  

E-print Network

Probabilistic electrical resistivity tomography of a CO2 sequestration analog Tobias Lochbühler a sequestration, where electrical resistivity tomography (ERT) has shown great potential (al Hagrey, 2011; al 2014 Keywords: ERT CO2 sequestration Probabilistic inversion Model parameterization Electrical

Vrugt, Jasper A.

33

Monitoring of Tunneling Activities with Electrical Resistivity Imaging Methods  

Microsoft Academic Search

We demonstrate the effectiveness of electrical resistivity imaging methods for monitoring of tunneling activities with numerical modeling. The sharp resistivity contrast between an air-filled tunnel and surrounding materials presents an excellent opportunity for resistivity imaging methods to locate a tunnel. However, the subsurface inhomogeneity and varying moisture conditions produce strong resistivity anomalies that sometimes overwhelm the tunnel signature. Therefore, tunnel

X. Yang; B. Carr; M. B. Lagmanson

2006-01-01

34

Scaling laws for electrical contact resistance with dissimilar materials  

NASA Astrophysics Data System (ADS)

This paper attempts to quantify the effects of contaminants on electrical contact resistance. Based on an idealized model, simple and explicit scaling laws for the electrical contact resistance with dissimilar materials are constructed. The model assumes arbitrary resistivity ratios and aspect ratios in the current channels and their contact region, for both Cartesian and cylindrical geometries. The scaling laws have been favorably tested in several limits, and in sample calculations using a numerical simulation code. From the scaling laws and a survey of the huge parameter space, some general conclusions are drawn on the parametric dependence of the contact resistance on the geometry and on the electrical resistivity in different regions.

Zhang, Peng; Lau, Y. Y.

2010-08-01

35

Spatial considerations on electrical resistance tomography measurements  

NASA Astrophysics Data System (ADS)

This work reports experimental evidence of the effect of certain geometrical parameters on the accuracy of electrical resistance tomography (ERT) measurements in two-phase systems. Emphasis is given to millimetre-size electrodes that suffer from significant electric field distortion due to (a) extension of the measuring volume beyond the electrode plane (fringe effect) and (b) the non-uniform distribution of field strength at the electrode plane. Water constitutes the continuous (conductive) phase, whereas Teflon rods constitute the dispersed (non-conductive) phase. The examined parameters include the diameter of the cylindrical test vessel, the size of electrodes and the number and size (radius and length) of the submerged Teflon rods. The variable in these tests is the axial and radial position of the Teflon rods inside the test cell. It is found that for homogeneously (axially and radially) dispersed rods, the void fraction measured by a set of electrodes at a plane agrees pretty well with 2D theoretical predictions. However, in cases of non-homogeneously dispersed rods, void fraction measurements deviate considerably from theoretical values. This is a manifestation of severe electric field distortion associated with the employed small electrodes. Moreover, evidence is provided that in the examined system, the fringe effect is more significant than the topography of the field strength in distorting measurements. To allow a quantitative analysis of the present data, nonlinear regression combined with dimensional analysis is conducted to derive an expression that describes the void fraction measurements by a set of electrodes at a plane for different axial and radial positions of the submerged rods. A parametric analysis of this expression illustrates the significance of different parameters on ERT measurements.

Lioumbas, John S.; Chatzidafni, Ariadni; Karapantsios, Thodoris D.

2014-05-01

36

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...

37

Repeatable change in electrical resistance of Si surface by mechanical and electrical nanoprocessing  

PubMed Central

The properties of mechanically and electrically processed silicon surfaces were evaluated by atomic force microscopy (AFM). Silicon specimens were processed using an electrically conductive diamond tip with and without vibration. After the electrical processing, protuberances were generated and the electric current through the silicon surface decreased because of local anodic oxidation. Grooves were formed by mechanical processing without vibration, and the electric current increased. In contrast, mechanical processing with vibration caused the surface to protuberate and the electrical resistance increased similar to that observed for electrical processing. With sequential processing, the local oxide layer formed by electrical processing can be removed by mechanical processing using the same tip without vibration. Although the electrical resistance is decreased by the mechanical processing without vibration, additional electrical processing on the mechanically processed area further increases the electrical resistance of the surface. PMID:25489276

2014-01-01

38

Electricity and Renewable Energy – Israel Profile  

Microsoft Academic Search

\\u000a Israel’s electricity sector faces the dual challenge of rapid economic growth – relative to most Western countries – and generation\\u000a capacity that is barely sufficient to meet current needs. Israel has been at the forefront of renewable energy development\\u000a for over 50 years, but, with the sole exception of solar water heating, has been unable to use these technological developments

Amit Mor; Shimon Seroussi; Malcolm Ainspan

39

ELECTRICAL IMPEDANCE TOMOGRAPHY ON A RESISTIVE NETWORK WITH INTERNAL CURRENTS  

E-print Network

ELECTRICAL IMPEDANCE TOMOGRAPHY ON A RESISTIVE NETWORK WITH INTERNAL CURRENTS YONG JUNG KIM AND MIN from internal currents and the boundary conductivity. An electrically conducting body is discretized. The conductivity of a body decides the interior electrical cur- rent if a boundary injection current is given

Kim, Yong Jung

40

A profile-aware resist model with variable threshold  

NASA Astrophysics Data System (ADS)

The pursuit of ever smaller transistors has pushed technological innovations in the field of lithography. In order to continue following the path of Moore's law, several solutions have been proposed: EUV, e-beam and double patterning lithography. As EUV and e-beam lithography are still not ready for mass production for 20 nm and 14 nm nodes, double patterning lithography play an important role for these nodes. In this work, we focus on a Self-Aligned Double-Patterning process (SADP) which consists of depositing a spacer material on each side of a mandrel exposed during a first lithography step, dividing the pitch into two, after being transferred into the substrate, and then cutting the unwanted patterns through a second lithography exposure. In the specific case where spacers are deposited directly on the flanks of the resist, it is crucial to control its profile as it could induce final CD errors or even spacer collapse. One possibility to prevent these defects from occurring is to predict the profile of the resist at the OPc verification stage. For that, we need an empirical resist model that is able to predict such behaviour. This work is a study of a profile-aware resist model that is calibrated using both atomic force microscopy (AFM) and scanning electron microscopy (SEM) data, both taken using a focus and exposure matrix (FEM).

Moulis, Sylvain; Farys, Vincent; Belledent, Jérôme; Thérèse, Romain; Lan, Song; Zhao, Qian; Feng, Mu; Depre, Laurent; Dover, Russell

2012-11-01

41

Iron aluminide useful as electrical resistance heating elements  

DOEpatents

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.

Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Oak Ridge, TN); Fleischhauer, Grier S. (Midlothian, VA); Hajaligol, Mohammad R. (Richmond, VA); Lilly, Jr., A. Clifton (Chesterfield, VA)

1997-01-01

42

Iron aluminide useful as electrical resistance heating elements  

DOEpatents

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.

Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Oak Ridge, TN); Fleischhauer, Grier S. (Midlothian, VA); Hajaligol, Mohammad R. (Richmond, VA); Lilly, Jr., A. Clifton (Chesterfield, VA)

1999-01-01

43

Iron aluminide useful as electrical resistance heating elements  

DOEpatents

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.

Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Oak Ridge, TN); Fleischhauer, Grier S. (Midlothian, VA); Hajaligol, Mohammad R. (Richmond, VA); Lilly, Jr., A. Clifton (Chesterfield, VA)

2001-01-01

44

Iron aluminide useful as electrical resistance heating elements  

DOEpatents

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.

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

1997-04-15

45

Sinkhole detection using electrical resistivity tomography in Saudi Arabia  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

46

Saline tracer visualized with three-dimensional electrical resistivity tomography: Field-scale spatial moment analysis  

E-print Network

Saline tracer visualized with three-dimensional electrical resistivity tomography: Field; accepted 14 February 2005; published 24 May 2005. [1] Cross-well electrical resistivity tomography (ERT using electrical resistivity tomography (ERT) there is a direct physical link between changes

Singha, Kamini

47

Parallel electric resistivity in the TFTR tokamak  

SciTech Connect

The average parallel resistivity and the location of the q = 1 surface are found to be consistent with the predictions of neoclassical transport theory and inconsistent with classical resistivity (uncorrected for toroidal effects) for ohmic plasmas in the TFTR tokamak, both in near-equilibrium and during ramping of the plasma current. These observations are incompatible with theories predicting anomalous parallel resistivity in concert with anomalous perpendicular transport. 41 refs., 9 figs., 1 tab.

Zarnstorff, M.C.; McGuire, K.; Bell, M.G.; Grek, B.; Johnson, D.; McCune, D.; Park, H.; Ramsey, A.; Taylor, G.

1990-05-01

48

Propagation through electrically coupled cells. Effects of a resistive barrier.  

PubMed Central

Action potential propagation through cardiac tissue occurs in a spatially inhomogeneous three-dimensional electrical syncytium composed of discrete cells with regional variations in membrane properties and intercellular resistance. In comparison with axons, cardiac tissue presents some differences in the application of core conductor cable theory. We have used analytical and numerical techniques to contrast the propagation of action potentials along nerve axons and along cardiac strands, including an explicit inclusion of cellular anatomical factors (the surface-to-volume ratio), the strand radius, and the regional distribution of longitudinal resistance. A localized decrease in the number of gap junctions will produce a functional resistive barrier, which can lead to unidirectional block of propagation if the tissue on two sides of the barrier in either excitability or passive electrical load. However, in some circumstances, a resistive barrier separating regions of different electrical load can actually facilitate propagation into the region of larger electrical load. PMID:6733238

Joyner, R W; Veenstra, R; Rawling, D; Chorro, A

1984-01-01

49

Electrical resistivity and thermal expansion of liquid titanium and zirconium  

SciTech Connect

The electrical resistivity and thermal expansion have been measured to twofold expanded states for titanium and to 60% expanded states for zirconium using the isobaric expansion apparatus. Results are consistent with the literature where there is overlap.

Gathers, G.R.

1983-01-01

50

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

PubMed Central

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 ?·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 ?·cm is obviously different from that with the electrical resistivity lower than 687 ?·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 machining ZnO/Al2O3 ceramic. PMID:25364912

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

2014-01-01

51

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

PubMed

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 ?·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 ?·cm is obviously different from that with the electrical resistivity lower than 687 ?·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 machining ZnO/Al2O3 ceramic. PMID:25364912

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

2014-01-01

52

Oil production response to in situ electrical resistance heating  

E-print Network

OIL PRODUCTION RESPONSE TO I? SITU ELECTRICAL RESISTANCE HEATING A Thesis by FRED WILLIAM MCDOUGAL Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May... 1987 Major Subject: Petroleum Engineering OIL PRODUCTION RESPONSE TO IN SITV ELECTRICAL RESISTANCE HEATING A Thesis by FRED WILLIAM MCDOUGAL Approved to style and content by: R. A. Wattenbar (Chair of Commi ee) L. D. Piper (Member) D. D. Van...

McDougal, Fred William

1987-01-01

53

Electrical resistance tomography using steel cased boreholes as electrodes  

DOEpatents

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.

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

1999-06-22

54

Monitoring an underground steam injection process using electrical resistance tomography  

Microsoft Academic Search

We used electrical resistance tomography (ERT) to map the subsurface distribution of a steam flood as a function of time as part of a prototype environmental restoration process performed by the Dynamic Underground Stripping Project. We evaluated the capability of ERT to monitor changes in the soil resistivity during the steam injection process using a dipole-dipole measurement technique to measure

A. Ramirez; W. Daily; D. LaBrecque; E. Owen; D. Chestnut

1993-01-01

55

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

SciTech Connect

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.

BENECKE, M.W.

2007-05-29

56

Electrolyte injection with electrical resistance heating  

E-print Network

enough to produce a significant change in the pressure profile near the wellbore and, consequently, an increase in the oil produccion rate. THE ELECTROLYTE INJECTION MODEL One way to reduce the problem of water vaporization in the hot spots...

Jaimes Gomez, Olmedo

1992-01-01

57

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...

58

Slime thickness evaluation of bored piles by electrical resistivity probe  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

59

Influence of resistive internal kink on runaway current profile  

NASA Astrophysics Data System (ADS)

An extended magnetohydrodynamic model including the effect of runaway current is developed and implemented in the M3D code. Based on this model, a simulation has been carried out to investigate the linear stability and the nonlinear evolution of the n = 1 resistive kink mode in the presence of runaway current. It is found that sawteeth oscillation is suppressed in a runaway plasma. The nonlinear evolution of the n = 1 mode only leads to a single sawtooth crash before reaching a new steady state axi-symmetric equilibrium with flattened current profile in the plasma core and q(0)>1.

Cai, Huishan; Fu, Guoyong

2015-02-01

60

Comparing Time Domain Reflectometry and Electrical Resistivity Tomography Measurements for Estimating Soil Water Distribution  

E-print Network

511 Comparing Time Domain Reflectometry and Electrical Resistivity Tomography Measurements compared with electrical resistivity tomography (ERT) measurements along the same cross's interior for the measurements. However, determining the soil water content from the resulting electrical

Sailhac, Pascal

61

Adding Resistances and Capacitances in Introductory Electricity  

NASA Astrophysics Data System (ADS)

All introductory physics textbooks, with or without calculus, cover the addition of both resistances and capacitances in series and in parallel as discrete summations. However, none includes problems that involve continuous versions of resistors in parallel or capacitors in series. This paper introduces a method for solving the continuous problems that is logical, straightforward, and within the mathematical preparation of students at the introductory level.

Efthimiou, C. J.; Llewellyn, R. A.

2005-09-01

62

Letter to the Editor Molecular profiling of platinum resistant ovarian cancer: Use of the  

E-print Network

Letter to the Editor Molecular profiling of platinum resistant ovarian cancer: Use of the model. Molecular profiling of platinum resistant ovar- ian cancer. Int J Cancer 2005;118:1963­71. 2. Thigpen T to predict platin resistance in ovarian cancer. The authors studied a training set obtained from 24 tumours

63

The borehole-fluid effect in electrical resistivity imaging  

NASA Astrophysics Data System (ADS)

Fluid that fills boreholes in crosswell electrical-resistivity investigations provides the necessary electrical contact between the electrodes and the rock formation, but it is also the source of image artifacts in standard inversions that do not account for the effects of the boreholes. The image distortions can be severe for large resistivity contrasts between the rock formation and borehole fluid and for large borehole diameters. We have carried out 3-D finite-element modeling using an unstructured-grid approach to quantify the magnitude of borehole effects for different resistivity contrasts, borehole diameters, and electrode configurations. Relatively common resistivity contrasts of 100 : 1 and borehole diameters of 10 and 20 cm yielded, for a bipole length 5 m, underestimates of apparent resistivity by ~12% and ~32% when using AB-MN configurations and overestimates of apparent resistivity by ~24% and ~95% when using AM-BN configurations. Effects are generally more severe at shorter bipole spacings. We report here the results obtained by either including or ignoring the boreholes in inversions of 3D field data from a test site in Switzerland, where ~10,000 crosswell resistivity tomography measurements were made across 6 acquisition planes between 4 boreholes. Inversions of raw data that ignored the boreholes filled with low resistivity fluid paradoxically produced high resistivity artifacts around the boreholes. Including correction factors based on the modeling results for a 1-D model with and without the boreholes did not markedly improve the images. The only satisfactory approach was to use a 3-D inversion code that explicitly incorporated the boreholes in the actual inversion. This new approach yielded an electrical resistivity image that was devoid of artifacts around the boreholes and that correlated well with co-incident crosswell radar images.

Doetsch, Joseph; Coscia, Ilaria; Greenhalgh, Stewart; Linde, Niklas; Green, Alan G.; Günther, Thomas

2010-05-01

64

Jones et al. Canada's lithospheric resistivity Page 1 The electrical resistivity of Canada's lithosphere and correlation  

E-print Network

Jones et al. Canada's lithospheric resistivity Page 1 The electrical resistivity of Canada and Jessica E. Spratt1,7 1: Geological Survey of Canada, 615 Booth St., Ottawa, ON, K1A 0E9, Canada. 2: Department of Geological Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada. Email: ij

Jones, Alan G.

65

Electrical resistivity borehole measurements: application to an urban tunnel site  

NASA Astrophysics Data System (ADS)

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.

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

2002-06-01

66

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

NASA Astrophysics Data System (ADS)

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 ? 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.

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

2014-10-01

67

Electrical resistance tomography to monitor vadose water movement  

SciTech Connect

We report results of one test in which Electrical Resistance Tomography (ERT) was used to map the changes in electrical resistivity in the vadose zone as a function of time while water infiltration occurred. The ERT images were used to infer shape and movement of the infiltration plume in the unsaturated soil. We supplied a continuous water source at a point about 10 feet below the surface (at the end of a shallow screened hole) for only a short time -- 2.5 hours. This pulsed source introduced a slug'' of water whose infiltration was followed to about 60 foot depth during a 23 hour period. The ERT images show resistivity decreases as the water content of the vadose zone increased while water was added to the soil; the resistivity of the soil later increased after the supply of water was cut-off and the induced soil moisture began to subside.

Ramirez, A.; Daily, W. (Lawrence Livermore National Lab., CA (United States)); LaBrecque, D. (Arizona Univ., Tucson, AZ (United States))

1991-09-01

68

Friction, wear and electrical contact resistance of precious metal alloys  

NASA Astrophysics Data System (ADS)

The preferred selection of precious metal electrical contact materials depends on the contact geometry, contact stress, test ambient values of electrical contact resistance and whether friction and/or wear must be controlled. Wiper-type contact couples that operate in dry hydrocarbon-free atmospheres, particularly if low and steady friction coefficients and minimal wear are required, are typically that of a palladium alloy pin (ASTM B540) sliding on a gold alloy plate (ASTM B541). These materials have a contact resistance of approximately ten milliohms and a friction coefficient less than 0.5 for the most common operational environments. Segregation of sulfur up to a few atomic percent to wear tracks formed on the gold alloy is not detrimental. The accumulation of larger concentrations of sulfur can form surface films of cuprous sulfide which increases the contact resistance to a few tens of milliohms. Large electrical contact resistances (greater than one ohm) are measured only when rider wear becomes dominant and ridges of Pd-containing material are formed in wear tracks. Ion implantation of carbon into the Au alloy decreases the friction coefficient without increasing the electrical contact resistance.

Pope, L. E.; Peebles, D. E.; Barton, B. M.

69

Electrical resistivity of Au-ZnO nanocomposite films  

SciTech Connect

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.

Argibay, N.; Goeke, R. S.; Dugger, M. T.; Rodriguez, M. A.; Michael, J. R.; Prasad, S. V. [Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)

2013-04-14

70

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

PubMed Central

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

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

2013-01-01

71

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

72

Comparing the Risk Profiles of Renewable and Natural Gas Electricity Contracts  

E-print Network

Comparing the Risk Profiles of Renewable and Natural Gas Electricity Contracts: A Summary Public Utilities Commission DWR California Department of Water Resources EEI Edison Electric Institute EOB California Electricity Oversight Board FERC Federal Energy Regulatory Commission ISO California

Kammen, Daniel M.

73

The Electrical Resistance of Rutherford-Type Superconducting Cable Splices  

E-print Network

The electrical resistance of Large Hadron Collider main busbar cable lap splices produced by soft soldering has been measured with two independent methods as a function of intercable contact area and for splices made of cables with various defects. For defect-free lap splices, the resistance increases from 0.3 to 10 n? (at 4.3 K in self-field) when reducing the cable overlap length from 120 to 3 mm, as expected assuming that the resistance is inversely proportional to the intercable contact area. The resistance of bridge splices that connect side-by-side cables can be predicted from the lap splice resistances and the overlap areas involved.

Heck, C; Fleiter, J; Bottura, L

2015-01-01

74

Flow pathways in porous media: electrical resistance tomography and dye staining image verification  

Microsoft Academic Search

Electrical resistance tomography permits the determination of the spatial distribution of electrical resistivity by non-destructive means. The technique may be applied to the study of flow through porous media by following the changes in resistivity distribution within a soil or rock core as an electrolytic tracer is passed through the specimen. Image reconstruction of the electrical resistance tomography data may

Andrew Binley; Ben Shaw; Siobhan Henry-Poulter

1996-01-01

75

Pyroclastic and Volcaniclastic Deposits Near Bishop, California: Geologic Controls on Near-Surface Electrical Resistivity and Radar Data  

E-print Network

on Near- Surface Electrical Resistivity and Radar Data * McGinnis, R N (rmcginnis@swri.org) , Department Institute, 1050 Walnut Street, Suite 400, Boulder, CO 80302, United States Heggy, E (heggy@lpi-penetrating radar (GPR) profiling to identify and interpret radar signatures obtained from these three analogs

Stillman, David E.

76

Image-guided inversion of electrical resistivity data  

NASA Astrophysics Data System (ADS)

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 second case, which corresponds to a geothermal site at Pagosa Springs, in Colorado.

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

2014-04-01

77

Electrical process tomography with known internal structures and resistivities  

Microsoft Academic Search

In process tomography the aim is to obtain information typically from the interior of the process vessels based on the measurements made on the surface of the vessel. Electrical impedance tomography (EIT) is an imaging modality in which the internal resistivity distribution is reconstructed based on the known injected currents and measured voltages on the surface. Since the reconstructed image

L. M. Heikkinen; M. Vauhkonen; T. Savolainen; K. Leinonen; J. P. Kaipio

2001-01-01

78

ESTABLISHEMENT OF CRACK INDEXES BY ELECTRICAL APPARENT RESISTIVITY DATA  

E-print Network

ESTABLISHEMENT OF CRACK INDEXES BY ELECTRICAL APPARENT RESISTIVITY DATA A. Samouelian (1,2), I 6759, 45067 Orleans Cedex 2 France. Soil cracks, whose formation are associated to natural climate phenomena, play an im- portant role in water and gas transfer. Detecting cracks by non

Boyer, Edmond

79

Electrical Resistivity Changes in Saturated Rock under Stress.  

PubMed

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

Brace, W F; Orange, A S

1966-09-23

80

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...

81

Electrical resistivity survey in soil science: a review  

Microsoft Academic Search

Electrical resistivity of the soil can be considered as a proxy for the spatial and temporal variability of many other soil physical properties (i.e. structure, water content, or fluid composition). Because the method is non-destructive and very sensitive, it offers a very attractive tool for describing the subsurface properties without digging. It has been already applied in various contexts like:

A. Samouëlian; I. Cousin; A. Tabbagh; A. Bruand; G. Richard

2005-01-01

82

Industrial monitoring of hydrocyclone operation using electrical resistance tomography  

Microsoft Academic Search

The development and application of electrical resistance tomography for on-line auditing of an industrial hydrocyclone separation is reported. The work demonstrates the retrofitting of electrodes into a commercially available separator and their use in laboratory, pilot plant scale investigations of clay refining. A number of new and significant applications are described including: the development of methodologies to allow observation of

R. A Williams; X Jia; R. M West; M Wang; J. C Cullivan; J Bond; I Faulks; T Dyakowski; S. J Wang; N Climpson; J. A Kostuch; D Payton

1999-01-01

83

BOSUMTWI IMPACT CRATER: USE OF ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)  

E-print Network

BOSUMTWI IMPACT CRATER: USE OF ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) TO MAP THE GEOMETRY OF THE INNER WALL OF THE CRATER AND THE IMPACT RELATED STRUCTURES A dissertation by Akwasi Acheampong Aning of the 1.07 Myr old Bosumtwi impact crater. The 10.5 km complex crater excavated in 2.1­2.2 Gyr Precambrian

Paris-Sud XI, Université de

84

Electrical conductivity of the Fennoscandian Shield margin from recent magnetotelluric profiles  

NASA Astrophysics Data System (ADS)

During the last decade several magnetotelluric profiles extending from Proterozoic East European Craton into younger domains have been measured. Magnetotelluric TOR profile crosses the Sorgenfrei-Tornquist-Zone (STZ) in the southwestern part of the Fennoscandian Shield. The STZ marks the border between the intact shield in Sweden to the north and the reactivated Danish basin and the Ringkobing-Fyn High (RFH) to the south. The STZ manifests itself electrically very clearly in the lower crust and upper lithospheric mantle as a narrow zone of high conductivity. The thickness of the electric lithosphere decreases across the STZ from about 300 km in the Fennoscandian Shield to about 100 km in the Danish basin. Jämtland-Trondelag magnetotelluric profile crosses the Central Scandinavian Caledonides from Baltic to Norwegian Sea. The results of the data analysis reveal the following main features: (1) An electrically highly conducting layer beneath the Caledonides images alum shales, the autochthonous Cambrian carbon-bearing black shales on top of the Precambrian basement. (2) Beneath the eastern part of the profile in the Fennoscandian Shield, proper, the first upper mantle conductor is detected at the depth of more than 250-300 km. A region of enhanced conductivity is identified at the depth of c.100- 150 km under the Caledonides in the central part of the profile. Further to the west, however, the lithosphere seems to thicken to 150-200 km. A large-scale international electromagnetic experiment has been carried out in northwest Poland and northeast Germany across the Trans European Suture Zone (TESZ), which is the most prominent tectonic boundary in Europe and which constitutes a complex transition between the European Paleozoic Platform towards the southeast and the Precambrian Craton towards the northeast. The results show the presence of highly conductive Cenozoic-Mesozoic sedimentary cover reaching depths up to 3 km. The significant conductivity anomaly in the 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.

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

2009-04-01

85

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

SciTech Connect

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.

Wang, Langning, E-mail: wanglangning@126.com; Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)] [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2014-04-15

86

The Influence of Basic Physical Properties of Soil on its Electrical Resistivity Value under Loose and Dense Condition  

NASA Astrophysics Data System (ADS)

Electrical resistivity technique has become a famous alternative tool in subsurface characterization. In the past, several interpretations of electrical resistivity results were unable to be delivered in a strong justification due to lack of appreciation of soil mechanics. Traditionally, interpreters will come out with different conclusion which commonly from qualitative point of view thus creating some uncertainty regarding the result reliability. Most engineers desire to apply any techniques in their project which are able to provide some clear justification with strong, reliable and meaningful results. In order to reduce the problem, this study presents the influence of basic physical properties of soil due to the electrical resistivity value under loose and dense condition. Two different conditions of soil embankment model were tested under electrical resistivity test and basic geotechnical test. It was found that the electrical resistivity value (ERV, ?) was highly influenced by the variations of soil basic physical properties (BPP) with particular reference to moisture content (w), densities (?bulk/dry), void ratio (e), porosity (?) and particle grain fraction (d) of soil. Strong relationship between ERV and BPP can be clearly presents such as ? ? 1/w, ? ? 1/?bulk/dry, ? ? e and ? ? ?. This study therefore contributes a means of ERV data interpretation using BPP in order to reduce ambiguity of ERV result and interpretation discussed among related persons such as geophysicist, engineers and geologist who applied these electrical resistivity techniques in subsurface profile assessment.

Abidin, M. H. Z.; Ahmad, F.; Wijeyesekera, D. C.; Saad, R.

2014-04-01

87

SEM viewing of gypsiferous material and study of their influence on electrical resistivity  

NASA Astrophysics Data System (ADS)

The gypsum rich material is often linked to the cavity formation due to the high solubility of cal-cium carbonate in the presence of acidic media. This work is dedicated to a close-up look to the structure of materials rich of gypsum and material of less or traces of sulfate ions. Electrical resistivity measurements were conducted along extended lines on sections involving cavities and the resulting profiles were examined for any changes. Forms and features of gypsum and minerals containing sulfates were studied and compared to sam-ples tested using SEM (scanning electron microscope). The chemical analyses (EDAX) using electron beam was carried out and the elements present within these samples were established. Quantitative chemical testing for some parameters including sulfate ions was carried out. Structural forms variation and changes are studied in view of the chemical composition. The electrical resistivity was measured using Syscal R1 electerical resis-tivity equipment for several spots near surface. Statistical correlations between sulfate ions content and elec-trical resistivity, for near surface soils, is presented. This study is aiming at utilizing the geophysical testing methods of sulfate rich soils and predicting future cavity formation in areas of high risk to cavities due to chemical weathering.

Dafalla, M.; Fouzan, F. Al

2012-04-01

88

Small-scale electrical resistivity tomography of wet fractured rocks.  

PubMed

This paper describes a series of experiments that tested the ability of the electrical resistivity tomography (ERT) method to locate correctly wet and dry fractures in a meso-scale model. The goal was to develop a method of monitoring the flow of water through a fractured rock matrix. The model was a four by six array of limestone blocks equipped with 28 stainless steel electrodes. Dry fractures were created by placing pieces of vinyl between one or more blocks. Wet fractures were created by injecting tap water into a joint between blocks. In electrical terms, the dry fractures are resistive and the wet fractures are conductive. The quantities measured by the ERT system are current and voltage around the outside edge of the model. The raw ERT data were translated to resistivity values inside the model using a three-dimensional Occam's inversion routine. This routine was one of the key components of ERT being tested. The model presented several challenges. First, the resistivity of both the blocks and the joints was highly variable. Second, the resistive targets introduced extreme changes the software could not precisely quantify. Third, the abrupt changes inherent in a fracture system were contrary to the smoothly varying changes expected by the Occam's inversion routine. Fourth, the response of the conductive fractures was small compared to the background variability. In general, ERT was able to locate correctly resistive fractures. Problems occurred, however, when the resistive fracture was near the edges of the model or when multiple fractures were close together. In particular, ERT tended to position the fracture closer to the model center than its true location. Conductive fractures yielded much smaller responses than the resistive case. A difference-inversion method was able to correctly locate these targets. PMID:14763623

LaBrecque, Douglas J; Sharpe, Roger; Wood, Thomas; Heath, Gail

2004-01-01

89

Antimicrobial Resistance and Integron Profiles in Multidrug-Resistant Escherichia coli Isolates from Pigs.  

PubMed

Abstract From July 2006 to June 2008, a total of 3876 Escherichia coli strains were collected from 1014 porcine intestinal contents to investigate antimicrobial resistance and related gene patterns. Average resistance rates of porcine E. coli isolates were 93.2% for tetracycline, 65.3% for ampicillin, 60.4% for chloramphenicol, 57.7% for streptomycin, 35.8% for nalidixic acid, 23.6% for gentamicin, 10.8% for ciprofloxacin, 10.0% for norfloxacin, 4.5% for cephalothin, 1.0% for cefoxitin, and 0.4% for cefazolin. The number of isolates resistant to more than 3 different classes of antimicrobials was 2537. Among these, 92 isolates were resistant to 5 or more classes of antimicrobials, and 69 isolates among 92 multidrug-resistant (MDR) isolates were integrase positive. Among 69 integrase-positive MDR isolates, only class I integron was detected in 19 isolates (20.7%). The class-1-integron-positive isolates had different sizes and gene contents (i.e., 1.0?kb containing aadA1 and 1.5?kb containing aadA1-dfrA1 and aadA1-aadB), and showed 15 distinct types by pulsed-field gel electrophoresis (PFGE) analysis, with 80% cut-off band pattern similarity. PFGE typing of four groups of isolates with identical antimicrobial resistance gene profiles showed two heterogeneous groups, while one group had very similar PFGE patterns; the fourth group was not typeable due to DNA degradation. In conjugation experiments, class I integron-harboring isolates transferred resistance to ampicillin, norfloxacin, gentamicin, and chloramphenicol to the recipient strain. This study showed that antimicrobial resistance rates and corresponding genes in porcine E. coli isolates are different from those in human isolates described by previous studies, and that transfer of antimicrobial-resistant genes from animal to human occurred. These data can be used as a baseline to evaluate the effect of antimicrobial use after implementation of the animal antimicrobial ban for prophylactic and growth promotion except for therapeutic use in 2012 in Korea. PMID:25303163

Lee, Minyoung; Shin, Eunju; Lee, Yeonhee

2014-12-01

90

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

USGS Publications Warehouse

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.

Brown, C.E.

1987-01-01

91

Electrical resistivity imaging of conductive plume dilution in fractured rock  

NASA Astrophysics Data System (ADS)

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced artificially during a 62-day monitoring period. Both surface ERT and cross-borehole ERT were used to monitor dilution and displacement of the plume. A square grid of land-surface electrodes was used with the surface ERT. Three-dimensional images of surface ERT delineated areas of increased and decreased resistivities. Increasing resistivities are attributed to dilution/displacement of the KCl solution by tap-water invasion or the influx of seasonal recharge. Decreasing resistivities resulted from redistribution of residual KCl solution. Cross-borehole ERT was conducted between the injection well and each of seven surrounding monitoring wells. Polar plots of the injection-well resistivity data in the direction of each monitoring well delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases. Monitoring-well data indicate locations of clustered and isolated regions of resistivity changes.

Nimmer, Robin E.; Osiensky, James L.; Binley, Andrew M.; Sprenke, Kenneth F.; Williams, Barbara C.

2007-08-01

92

Students' Understanding of Direct Current Resistive Electrical Circuits  

E-print Network

Research has shown that both high school and university students' reasoning patterns regarding direct current resistive electric circuits often differ from the currently accepted explanations. At present, there are no standard diagnostic examinations in electric circuits. Two versions of a diagnostic instrument called Determining and Interpreting Resistive Electric circuits Concepts Tests (DIRECT) were developed, each consisting of 29 questions. The information provided by the exam provides classroom instructors a means with which to evaluate the progress and conceptual difficulties of their students and their instructional methods. It can be used to evaluate curricular packages and/or other supplemental materials for their effectiveness in overcoming students' conceptual difficulties. The analyses indicate that students, especially females, tend to hold multiple misconceptions, even after instruction. During interviews, the idea that the battery is a constant source of current was used most often in answering the questions. Students tended to focus on current in solving the problems and to confuse terms, often assigning the properties of current to voltage and/or resistance. Results indicated that students do not have a clear understanding of the underlying mechanisms of electric circuit phenomena. On the other hand, students were able to translate easily from a "realistic" representation of a circuit to the corresponding schematic diagram.

Paula V. Engelhardt; Robert J. Beichner

2004-06-07

93

Micromechanical approach for electrical resistivity and conductivity of sandstone  

NASA Astrophysics Data System (ADS)

The objective of this work is to employ the micromechanical approach for the modeling of the electrical resistivity and of the conductivity of sandstone. This type of rock is considered as a mixture of solid mineral and porous space filled fully or partially by conductive water. The Eshelby's solution of a spheroidal inclusion in a homogeneous matrix is employed. The differential effective medium model (DEM) with different concepts of the microstructure is developed for the calculation of the resistivity. The parametric study clarifies the impact of the microscopic parameters on the macroscopic electrical properties. The simulations are compared with the classical empirical and theoretical approaches as well as with the laboratory measurements. The results show a strong impact of the microstructure (the shape of the pore, the presence of non-conductive fluids in the pore space, the connectivity of conductive fluid) on the macroscopic resistivity and conductivity of sandstone. This approach gives a link between the microscopic physical parameters of the rock and the macroscopic electrical parameters such as the cementation exponent and the electrical formation factor.

Nguyen, S. T.

2014-12-01

94

Electrical Resistance Technique to Monitor SiC Composite Detection  

NASA Technical Reports Server (NTRS)

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.

Smith, Craig; Morscher, Gregory; Xia, Zhenhai

2008-01-01

95

Electrical resistivity response due to elastic-plastic deformations  

SciTech Connect

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.

Stout, R.B.

1987-01-01

96

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

USGS Publications Warehouse

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.

McDougal, Robert R.

2006-01-01

97

Electrical Resistivity Monitoring of Voids: Results of Dynamic Modeling Experiments  

NASA Astrophysics Data System (ADS)

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.

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

2006-05-01

98

Adipocytokine Profile and Insulin Resistance in Childhood Obesity  

PubMed Central

ABSTRACT Background: Adipose tissue is a veritable "endocrine organ" due to its adipocytokines secretion implied in insulin sensitivity modulation and cardiovascular complications. Objective: To identify the adipocytokines' plasmatic profile (adiponectin, leptin, resistin, IL-6, TNF?) in obese children and adolescents and to assess their relationship with "classic" clinical/paraclinical markers of metabolic syndrome and insulin resistance. Material and Methods: A case-control study comparing a study group of 38 obese children and adolescents (age 13.5±2.3 years) to a normal weight age matched control group of 24 children. We measured body mass index (BMI) and waist circumference (WC), systolic and diastolic blood pressure (BP). The classical metabolic parameters (fasting glycemia, total cholesterol and its fractions, serum triglycerides) were measured in both groups. Insulin sensitivity was evaluated using fasting insulinemia, HOMA-index and insulin-resistance summary score (IRS). Adiponectin, leptin, resistin, IL-6 and TNF? were measured using ELISA method. Outcomes: Serum levels of leptin, resistin and IL-6 were signficantly higher (42.42±22.58 ng/ml versus 14.4±14.49 ng/ml, p <0.001; 9.69±3.47 ng/ml versus 7.92±2.13ng/ml, p = 0.029 and 2.66 ±2.87 pg/ml versus 0.89 ± 1.16 pg/ml, p = 0.006 respectively), while adiponectin levels were significantly lower (9.05±4.61 µg/ml versus 15.93±9.24 ?g/ml, p <0.001) in the obese group compared to control group. TNF? was not statistical different between groups. In multivariate regression analysis adiponectin was negatively and significantly correlated with WC (r = - 0.463, p = 0.003); leptin was positively and significantly related to WC, diastolic BP, fasting insulinemia and resistin (r = 0.775, p <0.001); resistin was positively related to leptin and IL-6 (r = 0.499, p <0.001), IL-6 was positively and significantly related to diastolic blood pressure (r = 0.333, p = 0.008). Conclusions: Serum levels of adiponectin, leptin, resistin and IL-6 are significantly different in obese children compared to normal weight controls; leptin was the only adipokine correlated with insulin resistance in children. There are significant correlations between plasmatic levels of leptin, resistin and IL-6. Simple plasmatic determination of TNF? is not a marker of the degree of obesity or its metabolic complications in pediatric population. PMID:23400230

GHERLAN, Iuliana; VLADOIU, Suzana; ALEXIU, Florin; GIURCANEANU, Mihaela; OROS, Sabina; BREHAR, Andreea; PROCOPIUC, Camelia; DUMITRACHE, Constantin

2012-01-01

99

Electrostatic multipole for electrical resistivity measurements at the decimetric scale  

NASA Astrophysics Data System (ADS)

Non-invasive electrical resistivity studies at the decimetric scale can be achieved by using electrostatic multipoles. The reduction of the influence of electromagnetic induction at this scale facilitates the choice of frequency. We first present the hexapole instrument (six poles) comprising one transmitting current pair of poles and two different voltage pairs corresponding to two different depths of analysis: roughly 7 and 15 cm. Two different examples are then presented, illustrating the wide range of possible applications of this technique. Firstly, by measuring the electrical resistivity of the stone blocks of an historical building, it is possible to verify whether its builders took into account the stresses these blocks had to support, when choosing their position. Secondly, the characterisation and monitoring of cultivated soil compaction is illustrated on an experimental plot of land.

Souffaché, B.; Cosenza, P.; Flageul, S.; Pencolé, J.-P.; Seladji, S.; Tabbagh, A.

2010-05-01

100

Electrical resistivity imaging of conductive plume dilution in fractured rock  

Microsoft Academic Search

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured\\u000a basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection\\u000a well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced

Robin E. Nimmer; James L. Osiensky; Andrew M. Binley; Kenneth F. Sprenke; Barbara C. Williams

2007-01-01

101

Development of mixing models using electrical resistance tomography  

Microsoft Academic Search

The network-of-zones concept provides a simplified basis for constructing mixing models appropriate to tomography. For miscible single-phase mixing in three-dimensions, of the order of 104 volume elements (voxels) are needed to interpret mixing results from 16 element electrical resistance tomographic (ERT) sensing rings stacked axially. Experimental mixing and dispersion in passive scalar pulse tests can be acquired at video frame

R. Mann; R. A. Williams; T. Dyakowski; F. J. Dickin; R. B. Edwards

1997-01-01

102

Fatigue assessment of an electrical resistance welded oil pipeline  

Microsoft Academic Search

A blowout in a 14in. diameter, 1\\/4in. thick API 5L X46 oil pipeline was due to the sudden propagation of a fracture at the longitudinal Electrical Resistance Welding (ERW) weld. The cracks initiated from small hook crack-type defects on the external surface of the tube, in the highly deformed and hardened central area of the ERW weld. Fatigue tests were

M. D Chapetti; J. L Otegui; J Motylicki

2002-01-01

103

Data acquisition system based on CompactPCI bus and FPGA for electrical resistance tomography  

Microsoft Academic Search

As a kind of visual measurement technique based upon variations in conductivity, electrical resistance tomography has great potential in process application. A new data acquisition system for electrical resistance tomography is described. This data acquisition system is built based on the CompactPCI bus and the FPGA. The application of the CompactPCI bus can make the single plane electrical resistance tomography

Zhiqiang Zhang; Feng Dong; Cong Xu

2011-01-01

104

Potential of electrical resistivity tomography to infer aquifer transport characteristics from tracer studies  

E-print Network

Potential of electrical resistivity tomography to infer aquifer transport characteristics from-lapse electrical resistivity tomography (ERT), transport processes in the subsurface can be imaged and monitored of electrical resistivity tomography to infer aquifer transport characteristics from tracer studies: A synthetic

Sailhac, Pascal

105

Electrical resistivity tomography investigations on a paleoseismological trenching study  

NASA Astrophysics Data System (ADS)

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.

Berge, Meriç Aziz

2014-10-01

106

Detecting Damage in Ceramic Matrix Composites Using Electrical Resistance  

NASA Technical Reports Server (NTRS)

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.

Smith, Craig E.; Gyekenyesi, Andrew

2011-01-01

107

Uncertainty analysis for common Seebeck and electrical resistivity measurement systems.  

PubMed

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

Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp

2014-08-01

108

Uncertainty analysis for common Seebeck and electrical resistivity measurement systems  

NASA Astrophysics Data System (ADS)

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.

Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp

2014-08-01

109

Metallic nanowire networks: effects of thermal annealing on electrical resistance.  

PubMed

Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing. Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 ? sq(-1). Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays. PMID:25267592

Langley, D P; Lagrange, M; Giusti, G; Jiménez, C; Bréchet, Y; Nguyen, N D; Bellet, D

2014-11-21

110

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

NASA Astrophysics Data System (ADS)

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.

Haile, Tigistu; Atsbaha, Solomun

2014-09-01

111

Numerical calculation and simulation analysis of electrical field characteristics for the electrical resistance tomography system  

Microsoft Academic Search

Sensitivity field in electrical resistance tomography system is affected by the distribution of multiphase medium, and the data of sensitivity distribution which are obtained by theoretical calculation can be used as prior experimental knowledge for image reconstruction, so it is necessary to analyze the distribution of the sensitivity field to decrease error of soft field and improve the quality of

Yanjun Zhang; Deyun Chen; Lili Wang

2009-01-01

112

Electrical Resistivity Structure of the Arabia-Eurasia Collision Zone in Eastern Anatolia  

NASA Astrophysics Data System (ADS)

The tectonics of eastern Anatolia is dominated by the collision of the Arabian and Eurasian plates. Recent passive seismic exploration has provided new constraints on the seismic velocity structure of this region and suggest that asthenosphere may be present at shallow depth within the collision zone. Magnetotelluric data can provide independent constraints on processes in regions of active tectonics by remotely sensing the electrical resistivity of the crust and upper mantle. From May to November 2005 magnetotelluric (MT) data were collected in Eastern Anatolia in a joint Canadian-Turkish project by the University of Alberta and Istanbul Technical University. Long period MT data give penetration to upper mantle depths and were collected on profiles extending from the Arabian plate to the Black Sea with a spacing of 10-15 km. More detailed broadband MT data were collected on shorter profiles crossing the North and East Anatolian Fault Zones with a spacing of 1-2 km. Preliminary resistivity models will be presented for each of the profiles and indicate that: (1) A mid-crustal conductor is present beneath the Anatolian Block in the vicinity of Elazig and terminates directly beneath the surface trace of the East Anatolian Fault. This geometry is very similar to that observed on major strike-slip faults in Northern and Eastern Tibet. (2)East of the Karliova triple junction, the Anatolian crust has a high resistivity. A low resistivity zone is present at depths of 40-50 km and may represent a shallow asthenosphere. (3)Low resistivity is observed in the upper mantle beneath Karacadag, a center of recent basaltic eruptions on the Arabian Plate, and in the crust beneath the Nemrut Golu - Suphan Dagi volcanic belt. The tectonic significance of these new MT data will be discussed in the context of other geological and geophysical data.

Turkoglu, E.; Unsworth, M.; Caglar, I.; Tuncer, V.; Avsar, U.; Tank, B.; Turkoglu, E.; Demir, T.; Sener, A.

2005-12-01

113

Comparing the risk profiles of renewable and natural gas-fired electricity contracts  

Microsoft Academic Search

Electricity policymakers, industry participants, analysts, and even consumers have become acutely aware of the ever-present risks that face the delivery of electricity. Recent instability in the electricity industry illustrates the need for thoughtful resource planning to balance the cost, reliability, and risk of electricity supply. This article evaluates the relative risk profiles of renewable and natural gas generating plants. It

Ryan Wiser; Devra Bachrach; Mark Bolinger; William Golove

2004-01-01

114

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

NASA Astrophysics Data System (ADS)

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 with different position, a fault and a tunnel. Results are quite encouraging; shapes and position of bodies are preserved. Unfortunately inverted resistivities are lower than the theoretical ones, mainly due to the array effects. Two field examples are presented, the subsurface study beneath a National Monument (The Morelia City Cathedral) to detect possible Colonial tunnels, and a fracture pattern characterization in one of the University of the City Mexico campus (Casa Libertad, Eastern campus), where such geological feature affects its infrastructure.

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

2010-12-01

115

Monitoring soil volume wetness in heterogeneous soils by electrical resistivity. A field-based pedotransfer function  

NASA Astrophysics Data System (ADS)

Modern irrigation techniques require accurate, rapid, cost-effective, spatial measurement of soil moisture. Electrical Resistivity Tomography (ERT) meets most of these requirements, but needs to be calibrated for each use because it is very sensitive to differences in soil characteristics. In this study, a pedotransfer function approach is used to remove the need for site-specific calibration, allowing ERT to be used directly to measure soil moisture. The study site was a hillslope vineyard, where eight calcaric-cambisol soil profiles were identified. From 2012 to 2013, 23 000 soil volume wetness measurements were acquired by Time Domain Reflectometry, and over 100 000 electrical resistivity data were collected in 160 ERT acquisitions. To better understand the ERT signal, soil texture, gravel content, cation exchange capacity, CaCO3, pH, organic carbon and total nitrogen were analysed in 64 soil samples from the study site. The sensitivity of ERT to differences in soil characteristics makes it difficult to establish a unique model linking electrical resistivity and soil moisture in heterogeneous soils. This study presents two possible solutions to overcome this problem, which are differentiated by the availability of data on soil characteristics. When these data are not available, it is possible to fit a number of different models for each homogeneous soil layer, but a site-specific calibration is necessary at least once. Conversely, when soil characteristics are available, they can be integrated into the model to build a pedotransfer function. A unique, accurate model is obtained in this way for all samples. In soils with similar characteristics to those observed, the function can be used directly to measure soil moisture by ERT. Developing pedotransfer functions such the one presented here could greatly improve, simplify and develop the use of electrical resistivity to measure soil moisture.

Brillante, Luca; Bois, Benjamin; Mathieu, Olivier; Bichet, Vincent; Michot, Didier; Lévêque, Jean

2014-08-01

116

Connection equation and shaly-sand correction for electrical resistivity  

USGS Publications Warehouse

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.

Lee, Myung W.

2011-01-01

117

Hydrologic Process-oriented Optimization of Electrical Resistivity Tomography  

NASA Astrophysics Data System (ADS)

Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances in joint and coupled hydrogeophysical inversion have enhanced the quantitative use of ERT to construct and condition hydrologic models (i.e. identify hydrologic structure and estimate hydrologic parameters). However the selection of which electrical resistivity data to collect and use is often determined by a combination of data requirements for geophysical analysis, intuition on the part of the hydrogeophysicist and logistical constraints of the laboratory or field site. One of the advantages of coupled hydrogeophysical inversion is the direct link between the hydrologic model and the individual geophysical data used to condition the model. That is, there is no requirement to collect geophysical data suitable for independent geophysical inversion. The geophysical measurements collected can be optimized for estimation of hydrologic model parameters rather than to develop a geophysical model. Using a synthetic model of drip irrigation we evaluate the value of individual resistivity measurements to describe the soil hydraulic properties and then use this information to build a data set optimized for characterizing hydrologic processes. We then compare the information content in the optimized data set with the information content in a data set optimized using a Jacobian sensitivity analysis.

Hinnell, A.; Bechtold, M.; Ferre, T. A.; van der Kruk, J.

2010-12-01

118

Functional classification of cellular proteome profiles support the identification of drug resistance signatures in melanoma cells.  

PubMed

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

Paulitschke, Verena; Haudek-Prinz, Verena; Griss, Johannes; Berger, Walter; Mohr, Thomas; Pehamberger, Hubert; Kunstfeld, Rainer; Gerner, Christopher

2013-07-01

119

Prediction of antibiotic resistance by gene expression profiles.  

PubMed

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

Suzuki, Shingo; Horinouchi, Takaaki; Furusawa, Chikara

2014-01-01

120

Determining and Interpreting Resistive Electric Circuit Concepts Test (DIRECT)  

NSDL National Science Digital Library

This 29-question research-based multiple-choice test is designed to evaluate students' reasoning regarding direct current resistive electric circuits. The test may be administered to students in algebra- or calculus-based introductory physics courses in high school or university settings. The test is based on investigations of students' difficulties with direct current circuits and should be given in a 30-minute period. Statistical results have shown the survey to be reliable and valid. A summary of the construction and analysis of the survey is available in, Studentsâ understanding of direct current resistive electrical circuits, Am. J. Phys. 72 (1), 98-115 (2004). Details are provided in Paula Engelhardt's dissertation, Examining students' understanding of electrical circuits through multiple-choice testing and interviews. This assessment is free for use by instructors in their classroom. However, as it takes years of development effort to create and validate reliable assessment instruments, the file is password-protected. Furthermore, the author requests that 1. students are not given copies following examination; and 2. none of the questions are incorporated into web-based question delivery systems without adequate security to prevent printing or unauthorized access by students. To obtain the password, please send a request with your name, email, institution, and a link to a page at your institution that confirms you are an instructor.

Engelhardt, Paula V.; Beichner, Robert J.

2013-03-03

121

Lipid Profiles in Wheat Cultivars Resistant and Susceptible to Tan Spot and the Effect of Disease on the Profiles  

PubMed Central

Lipid profiles in wheat leaves and the effects of tan spot on the profiles were quantified by mass spectrometry. Inoculation with Pyrenophora tritici-repentis significantly reduced the amount of leaf lipids, including the major plastidic lipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), which together accounted for 89% of the mass spectral signal of detected lipids in wheat leaves. Levels of these lipids in susceptible cultivars dropped much more quickly during infection than those in resistant cultivars. Furthermore, cultivars resistant or susceptible to tan spot displayed different lipid profiles; leaves of resistant cultivars had more MGDG and DGDG than susceptible ones, even in non-inoculated plants. Lipid compositional data from leaves of 20 non-inoculated winter wheat cultivars were regressed against an index of disease susceptibility and fitted with a linear model. This analysis demonstrated a significant relationship between resistance and levels of plastidic galactolipids and indicated that cultivars with high resistance to tan spot uniformly had more MGDG and DGDG than cultivars with high susceptibility. These findings suggest that lipid composition of wheat leaves may be a determining factor in the resistance response of cultivars to tan spot. PMID:23035632

Kim, Dongwon; Jeannotte, Richard; Welti, Ruth; Bockus, William W.

2013-01-01

122

Variations in antibiotic resistance profile in Enterobacteriaceae isolated from wild Australian mammals.  

PubMed

We carried out a retrospective analysis of 946 strains of Enterobacteriaceae isolated from wild Australian mammals between 1993 and 1997. The prevalence of resistance to fixed concentrations of 32 antimicrobial agents was determined, and the respective roles that taxonomic family of the host, state of origin and bacterial species play in defining prevalence and range of resistance were investigated. Our results demonstrated a low but widespread prevalence of antimicrobial resistance in wild isolates. Only amikacin, ciprofloxacin, meropenem and gentamicin inhibited growth in all 946 samples. There was extensive variation in the combination of antibiotics to which isolates were resistant, and multiple antibiotic resistance was common. Geographical location and host group significantly influenced the antibiotic resistance profile of an isolate, whereas bacterial species influenced both the resistance profile of an isolate and the number of antibiotics it was resistant to. The role of these factors in determining observed antibiotic resistance profiles suggests that any study measuring resistance in wild isolates should include the broadest possible range of bacterial species, host species and sampling locations. As such, this study provides an important new baseline for future measurements of antibiotic resistance in the Australian environment. PMID:11214795

Sherley, M; Gordon, D M; Collignon, P J

2000-12-01

123

Using electrical resistance probes for moisture determination in switchgrass windrows  

SciTech Connect

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.

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

2011-08-01

124

Building Better Electrodes for Electrical Resistivity and Induced Polarization Data  

NASA Astrophysics Data System (ADS)

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 polarization data and vice- versa.

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

2007-12-01

125

Evaluation of the radiation resistance of electrical insulation materials  

NASA Astrophysics Data System (ADS)

The qualification of insulating materials for electrical cables is often accomplished according to the IEC 60544 standard of the International Electrotechnical Commission. The mechanical properties of the polymeric insulators are tested prior and after irradiation at relatively high dose rates. To assess the ageing of selected materials under realistic service conditions, usually at lower dose rate, an IEC Working Group has proposed extrapolation methods (IEC 61244-2), one of which is applied here for a cable sheathing material from Huber+Suhner. The method is found to be suitable to compare radiation resistance data of different materials irradiated under different conditions.

Perrin, Sh.; Schönbacher, H.; Tavlet, M.; Widler, R.

2002-12-01

126

Rainfall infiltration process in mountain headwater region using electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

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 variations indicate the movement of subsurface water. Thus, we could estimate spatial and temporal distribution of subsurface water using resistivity data, and understand rainfall infiltration process precisely. Acknowledgements This study was financially supported by THE FUKADA GRANTS-IN-AIDS, Japan.

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

2008-12-01

127

Reservoir characterization combining elastic velocities and electrical resistivity measurements  

NASA Astrophysics Data System (ADS)

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 was quadratic, and not linear as in the case of Fontainebleau sandstones. There are other factors that influence this relationship in the case of these carbonates, which include pore geometry, and amount of micritic cement. We observed that the expression is almost linear, but it deviates as we approach lower resistivities. This deviation can be explained by the presence of stiff pores such as moldic or intra-granular pores, which causes high velocity but low resistivity values when water-saturated. In the same way, the effect of micrite cement on velocity is stronger than its effect on resistivity, and that also is responsible for some of the scatter that we observe. We also modeled both velocity and resistivity using self-consistent approximation with the same pore or inclusion geometries in both carbonate and sandstone laboratory datasets. In the case of carbonates, we found that we had to include needle-like pores to explain the low resistivity but high velocities. Needle is one of the geometries that allow us to have connected stiff pores. However, we also found that a fraction of compliant pores also had to be included in order to explain the velocity measurements on the carbonate dataset. The self-consistent model also approximated well the velocity and resistivity laboratory measurements on the Fontainebleau sandstones, using similar aspect ratios for both the velocity and the resistivity. As far as semi-empirical and empirical models, we observed how the stiff-sand model fit well the Fontainebleau data at 40MPa, including S-wave velocities. The Raymer-Hunt-Gardner relation also did a good job at predicting P-wave velocity. Archie's equation with cementation exponent between 1.6 and 2.1 fits the resistivity measurements on the Fontainebleau sandstones. These two relationships can be combined to create a resistivity---P-wave velocity transform for this dataset. When we attempted to use CSEM data to limit the shallow and low-frequency acoustic impedance trend for seismic inversion, we found that appropriate elastic and resistivity models must be chosen in

Gomez, Carmen Teresa

2009-12-01

128

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

USGS Publications Warehouse

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 sufficient rock samples were not available.

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

2009-01-01

129

Improvement of electrical resistivity tomography for leachate injection monitoring  

SciTech Connect

Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a 'minimum length' constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills.

Clement, R., E-mail: remi.clement@hmg.inpg.f [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Descloitres, M. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Guenther, T., E-mail: Thomas.Guenther@liag-hannover.d [Leibniz Institute for Applied Geophysics, Stilleweg 2, D-30655 Hannover (Germany); Oxarango, L. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Morra, C., E-mail: christophemorra@yahoo.f [PROKHEM/Floralis, 6 allee de Bethleem, 38610 Gieres (France); Laurent, J.-P.; Gourc, J.-P. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France)

2010-03-15

130

Numerical calculation and simulation analysis of electrical field characteristics for the electrical resistance tomography system  

NASA Astrophysics Data System (ADS)

Sensitivity field in electrical resistance tomography system is affected by the distribution of multiphase medium, and the data of sensitivity distribution which are obtained by theoretical calculation can be used as prior experimental knowledge for image reconstruction, so it is necessary to analyze the distribution of the sensitivity field to decrease error of soft field and improve the quality of the image reconstruction. In this paper at the basis of analyzing the principle of electrical resistance tomography system, the mathematical model of sensitivity field is built by utilizing finite element method. Through study field with disperse phase, the factors affecting the distribution of the sensitivity field and rules are analyzed, the calculation of sensitivity distribution and visualized simulation are achieved The experiments show that the finite element model is right, the sensitivity field proposed is in accordance with the practice and the computation velocity is about 10seconds, which provides the basis for related image reconstruction algorithms.

Zhang, Yanjun; Chen, Deyun; Wang, Lili

2009-07-01

131

Embryonic Carcinoma Cells Show Specific Dielectric Resistance Profiles during Induced Differentiation  

PubMed Central

Induction of differentiation in cancer stem cells by drug treatment represents an important approach for cancer therapy. The understanding of the mechanisms that regulate such a forced exit from malignant pluripotency is fundamental to enhance our knowledge of tumour stability. Certain nucleoside analogues, such as 2?-deoxy-5-azacytidine and 1?-arabinofuranosylcytosine, can induce the differentiation of the embryonic cancer stem cell line NTERA 2 D1 (NT2). Such induced differentiation is associated with drug-dependent DNA-damage, cellular stress and the proteolytic depletion of stem cell factors. In order to further elucidate the mode of action of these nucleoside drugs, we monitored differentiation-specific changes of the dielectric properties of growing NT2 cultures using electric cell-substrate impedance sensing (ECIS). We measured resistance values of untreated and retinoic acid treated NT2 cells in real-time and compared their impedance profiles to those of cell populations triggered to differentiate with several established substances, including nucleoside drugs. Here we show that treatment with retinoic acid and differentiation-inducing drugs can trigger specific, concentration-dependent changes in dielectric resistance of NT2 cultures, which can be observed as early as 24 hours after treatment. Further, low concentrations of nucleoside drugs induce differentiation-dependent impedance values comparable to those obtained after retinoic acid treatment, whereas higher concentrations induce proliferation defects. Finally, we show that impedance profiles of substance-induced NT2 cells and those triggered to differentiate by depletion of the stem cell factor OCT4 are very similar, suggesting that reduction of OCT4 levels has a dominant function for differentiation induced by nucleoside drugs and retinoic acid. The data presented show that NT2 cells have specific dielectric properties, which allow the early identification of differentiating cultures and real-time label-free monitoring of differentiation processes. This work might provide a basis for further analyses of drug candidates for differentiation therapy of cancers. PMID:23533658

Öz, Simin; Maercker, Christian; Breiling, Achim

2013-01-01

132

Embryonic carcinoma cells show specific dielectric resistance profiles during induced differentiation.  

PubMed

Induction of differentiation in cancer stem cells by drug treatment represents an important approach for cancer therapy. The understanding of the mechanisms that regulate such a forced exit from malignant pluripotency is fundamental to enhance our knowledge of tumour stability. Certain nucleoside analogues, such as 2'-deoxy-5-azacytidine and 1?-arabinofuranosylcytosine, can induce the differentiation of the embryonic cancer stem cell line NTERA 2 D1 (NT2). Such induced differentiation is associated with drug-dependent DNA-damage, cellular stress and the proteolytic depletion of stem cell factors. In order to further elucidate the mode of action of these nucleoside drugs, we monitored differentiation-specific changes of the dielectric properties of growing NT2 cultures using electric cell-substrate impedance sensing (ECIS). We measured resistance values of untreated and retinoic acid treated NT2 cells in real-time and compared their impedance profiles to those of cell populations triggered to differentiate with several established substances, including nucleoside drugs. Here we show that treatment with retinoic acid and differentiation-inducing drugs can trigger specific, concentration-dependent changes in dielectric resistance of NT2 cultures, which can be observed as early as 24 hours after treatment. Further, low concentrations of nucleoside drugs induce differentiation-dependent impedance values comparable to those obtained after retinoic acid treatment, whereas higher concentrations induce proliferation defects. Finally, we show that impedance profiles of substance-induced NT2 cells and those triggered to differentiate by depletion of the stem cell factor OCT4 are very similar, suggesting that reduction of OCT4 levels has a dominant function for differentiation induced by nucleoside drugs and retinoic acid. The data presented show that NT2 cells have specific dielectric properties, which allow the early identification of differentiating cultures and real-time label-free monitoring of differentiation processes. This work might provide a basis for further analyses of drug candidates for differentiation therapy of cancers. PMID:23533658

Öz, Simin; Maercker, Christian; Breiling, Achim

2013-01-01

133

Gene expression profiling discriminates cerebral malaria-susceptible mice and cerebral malaria-resistant mice  

E-print Network

Gene expression profiling discriminates cerebral malaria-susceptible mice and cerebral malaria-resistant mice Short title: Gene expression profiles in mouse malaria Nicolas F. Delahaye1 , Nicolas Coltel2;2 Abstract The development of mouse cerebral malaria (CM) upon Plasmodium berghei ANKA infection is under

Paris-Sud XI, Université de

134

Students' understanding of direct current resistive electrical circuits Paula Vetter Engelhardta)  

E-print Network

Students' understanding of direct current resistive electrical circuits Paula Vetter Engelhardta regarding direct current resistive electric circuits often differ from the accepted explanations. At present, there are no standard diagnostic tests on electric circuits. Two versions of a diagnostic instrument were developed

Zollman, Dean

135

MONITORING LANDFILL COVER BY ELECTRICAL RESISTIVITY1 TOMOGRAPHY ON AN EXPERIMENTAL SITE2  

E-print Network

1 MONITORING LANDFILL COVER BY ELECTRICAL RESISTIVITY1 TOMOGRAPHY ON AN EXPERIMENTAL SITE2 3 4 infiltrate the stored waste. In order to locate such leaks, electrical resistivity tomography was18 used conditions for detecting defects in22 the cover. A statistical analysis carried out on the electrical

Paris-Sud XI, Université de

136

Geophys. J. Int. () , 1?? Cross-section electrical resistance tomography of La Soufri`ere of  

E-print Network

Geophys. J. Int. () , 1­?? Cross-section electrical resistance tomography of La Soufri. Key words: Electrical properties ­ tomography ­ image processing ­ Volcanic hazards and risks 1´eosciences Rennes, Univ Rennes 1, UMR 6118 CNRS, Rennes, France. SUMMARY The electrical resistivity distribution

Adler, Andy

137

Variability of Behaviour in Electricity Load Profile Clustering; Who Does Things at the  

E-print Network

Variability of Behaviour in Electricity Load Profile Clustering; Who Does Things at the Same Time://ima.ac.uk/dent 2 The James Hutton Institute, Aberdeen, UK Abstract. UK electricity market changes provide opportunities to alter households' electricity usage patterns for the benefit of the overall elec- tricity

Aickelin, Uwe

138

Tetrodotoxin-resistant electric activity in presynaptic terminals  

PubMed Central

1. The electric properties of the giant synapse in the stellate ganglion of the squid have been further investigated. 2. During tetrodotoxin (TTX) paralysis, a local response can be elicited from the terminal parts of the presynaptic axons after intracellular injection of tetraethyl ammonium ions (TEA). 3. The response is characterized by an action potential of variable size and duration, whose fall is often preceded by a prolonged plateau. The response, especially the duration of the plateau, is subject to `fatigue' during repetitive stimulation. 4. The TTX-resistant form of activity is localized in the region of the synaptic contacts, and shows a marked electrotonic decrement even within less than 1 mm from the synapse. It is found only on the afferent, not on the efferent, side of the synapse. 5. During the plateau of the response, the membrane resistance is greatly reduced below its resting value. 6. The response depends on presence of external calcium and increases in size and duration with the calcium concentration. Strontium and barium substitute effectively for calcium. Manganese and, to a lesser extent, magnesium, counteract calcium and reduce the response. The response also declines, and ultimately disappears, if sodium is withdrawn for long periods. 7. The relation of the local TTX-resistant response to the influx of calcium ions and to the release of the synaptic transmitter is discussed. PMID:4307710

Katz, B.; Miledi, R.

1969-01-01

139

Chronological change of electrical resistance in GeCu2Te3 amorphous film induced by surface oxidation  

NASA Astrophysics Data System (ADS)

Unusual chronological electrical resistance change behavior was investigated for amorphous GeCu2Te3 phase change material. More than a 1 order decrease of electrical resistance was observed in the air even at room temperature. The resistance of the amorphous film gradually increased with increasing temperature and then showed a drop upon crystallization. Such unusual behavior was attributed to the oxidation of the amorphous GeCu2Te3 film. From the compositional depth profile measurement, the GeCu2Te3 film without any capping layer was oxidized in air at room temperature and the formed oxide was mainly composed of germanium oxide. Consequently, a highly-conductive Cu-rich layer was formed in the vicinity of the surface of the film, which reduced the total resistance of the film. The present results could provide insight into the chronological change of electrical resistance in amorphous chalcogenide materials, indicating that not only relaxation of the amorphous, but also a large atomic diffusion contributes to the chronological resistance change.

Saito, Yuta; Shindo, Satoshi; Sutou, Yuji; Koike, Junichi

2014-11-01

140

Probabilistic electrical resistivity tomography of a CO2 sequestration analog  

NASA Astrophysics Data System (ADS)

Electrical resistivity tomography (ERT) is a well-established method for geophysical characterization and has shown potential for monitoring geologic CO2 sequestration, due to its sensitivity to electrical resistivity contrasts generated by liquid/gas saturation variability. In contrast to deterministic inversion approaches, probabilistic inversion provides the full posterior probability density function of the saturation field and accounts for the uncertainties inherent in the petrophysical parameters relating the resistivity to saturation. In this study, the data are from benchtop ERT experiments conducted during gas injection into a quasi-2D brine-saturated sand chamber with a packing that mimics a simple anticlinal geological reservoir. The saturation fields are estimated by Markov chain Monte Carlo inversion of the measured data and compared to independent saturation measurements from light transmission through the chamber. Different model parameterizations are evaluated in terms of the recovered saturation and petrophysical parameter values. The saturation field is parameterized (1) in Cartesian coordinates, (2) by means of its discrete cosine transform coefficients, and (3) by fixed saturation values in structural elements whose shape and location is assumed known or represented by an arbitrary Gaussian Bell structure. Results show that the estimated saturation fields are in overall agreement with saturations measured by light transmission, but differ strongly in terms of parameter estimates, parameter uncertainties and computational intensity. Discretization in the frequency domain (as in the discrete cosine transform parameterization) provides more accurate models at a lower computational cost compared to spatially discretized (Cartesian) models. A priori knowledge about the expected geologic structures allows for non-discretized model descriptions with markedly reduced degrees of freedom. Constraining the solutions to the known injected gas volume improved estimates of saturation and parameter values of the petrophysical relationship.

Lochbühler, Tobias; Breen, Stephen J.; Detwiler, Russell L.; Vrugt, Jasper A.; Linde, Niklas

2014-08-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

142

Numerical analysis for resist profile after thermal process in display manufacturing  

NASA Astrophysics Data System (ADS)

The screen size growth of mobile displays is accompanied with the drastically increased resolution. A display should have high pixel resolution to meet demanding readability and legibility expectations. The manufacturing process should be advanced to meet final device requirements. One of the important process steps is the post-development hardbake, where resist reflow is used to tune the final profile which influences subsequent process steps. Moreover, 3D resist profiles become one of critical design factors for mechanical and optical properties of display pixels. The resist reflow is the main time- and temperature-dependent effect of post-development bake process step. Since the resist is in transitional state (crystalline glassy/amorphous rubbery/viscous melt) the resist profile dynamics are very complex and predictive modeling is necessary. The model presented in this paper is based on a lattice-Boltzmann method, where the resist is considered as multicomponent (polymer-solvent) and multiphase (solid-liquid-vapor) mixture. Simulated resist profile dynamics with time are analyzed in dependency of material parameters (solvent diffusivity and evaporation rate, polymer solid fraction and adhesion with substrate). Temperature-dependent parameter descriptions are used for model calibration. Validation against experimental data shows good model consistency and predictability, demonstrating the benefit of simulation in process development and optimization.

Domnenko, Vitaliy; Stock, Hans-Jürgen; Shin, Sangmin; Ryu, Jonghyoek; Choi, Sung Won; Cho, Hyunwoo; Jeong, Eun-Soo; Choi, Jung-Hoe

2014-03-01

143

Gene Expression Profiling and Molecular Characterization of Antimony Resistance in Leishmania amazonensis  

PubMed Central

Background Drug resistance is a major problem in leishmaniasis chemotherapy. RNA expression profiling using DNA microarrays is a suitable approach to study simultaneous events leading to a drug-resistance phenotype. Genomic analysis has been performed primarily with Old World Leishmania species and here we investigate molecular alterations in antimony resistance in the New World species L. amazonensis. Methods/Principal Findings We selected populations of L. amazonensis promastigotes for resistance to antimony by step-wise drug pressure. Gene expression of highly resistant mutants was studied using DNA microarrays. RNA expression profiling of antimony-resistant L. amazonensis revealed the overexpression of genes involved in drug resistance including the ABC transporter MRPA and several genes related to thiol metabolism. The MRPA overexpression was validated by quantitative real-time RT-PCR and further analysis revealed that this increased expression was correlated to gene amplification as part of extrachromosomal linear amplicons in some mutants and as part of supernumerary chromosomes in other mutants. The expression of several other genes encoding hypothetical proteins but also nucleobase and glucose transporter encoding genes were found to be modulated. Conclusions/Significance Mechanisms classically found in Old World antimony resistant Leishmania were also highlighted in New World antimony-resistant L. amazonensis. These studies were useful to the identification of resistance molecular markers. PMID:21629719

do Monte-Neto, Rubens L.; Coelho, Adriano C.; Raymond, Frédéric; Légaré, Danielle; Corbeil, Jacques; Melo, Maria N.; Frézard, Frédéric; Ouellette, Marc

2011-01-01

144

Changes in electrical resistivity track changes in tectonic plate coupling  

NASA Astrophysics Data System (ADS)

coupling on the Hikurangi subduction margin along the east coast of New Zealand's North Island changes north to south from almost uncoupled to locked. Clay-rich sediments and aqueous fluids at the subduction interface have been invoked as key factors in the frictional processes that control interplate coupling. Here we use magnetotelluric data to show that the subduction interface in the weakly coupled region is electrically conductive but is resistive in the locked region. These results indicate the presence of a layer of fluid- and clay-rich sediments in the weakly coupled region and support the idea that the presence of fluid and hydrated clays at the interface is a major factor controlling plate coupling.

Heise, Wiebke; Caldwell, T. Grant; Bertrand, Edward A.; Hill, Graham J.; Bennie, Stewart L.; Ogawa, Yasuo

2013-10-01

145

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...

146

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...

147

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

NASA Astrophysics Data System (ADS)

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.

Rey, J.; Martínez, J.; Hidalgo, M. C.

2013-09-01

148

ELECTRICAL RESISTIVITY OF SOME LIQUID CADMIUM ANTIMONY ALLOYS AS A FUNCTION OF TEMPERATURE  

E-print Network

L-93 ELECTRICAL RESISTIVITY OF SOME LIQUID CADMIUM ANTIMONY ALLOYS AS A FUNCTION OF TEMPERATURE J The electrical resistivity of several Cd1-xSbx antimony rich alloys has been investiga- ted between the liquidus the measurements to high tempera- tures (up to 900 OC) for the antimony rich alloys for which few measurements

Paris-Sud XI, Université de

149

Monitoring the Excavation Damaged Zone in Opalinus clay by three dimensional reconstruction of the electrical resistivity  

E-print Network

to reconstruct three dimensional images of the resistivity in the vicinity of the electrodes. A finite element, F. & Hoteit, N., 2006. Electrical tomography monitoring of the excavation damaged zone of the electrical resistivity in the Mont Terri gallery G-04 Authors: Lesparre N., Adler A., Nicollin F., Gibert D

Adler, Andy

150

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

NASA Astrophysics Data System (ADS)

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 transported from the ridge area. This diversity indicates notably active slope processes during the Pleistocene. The results confirmed the usefulness of geophysical methods to identify the geological structure of rocks with highly variable lithology with faults and folding features.

Stan, Dominika; Stan-K?eczek, Iwona

2014-09-01

151

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

NASA Astrophysics Data System (ADS)

The Tabular Middle Atlas reservoir is one of the most important aquifers in northern Morocco. It is mainly a water table fractured reservoir consisting of Lias limestone and dolomite. The matrix permeability is very low and water flows essentially along open fractures and karsts. The Bittit Spring belongs to this karstic system and constitutes an important aquifer lying at the junction between the tabular reservoir and the Sais basin. Bittit spring, with an average annual discharge of about 1600 l/s, contributes largely to water supply of the big city of Meknes. Groundwater circulation is complex due to tectonics and to presence of karstic Quaternary travertine overlying Lias carbonate. In Bittit area, travertine is mostly covered by Quaternary basalt. Up to now water flow paths and the underground karst organization remain misknown, and turbidity affects the water quality after rain events. To highlight these issues, an integrated geophysical survey was performed in this area in the framework of a French-Moroccan scientific project. The geophysical imaging was carried out mainly by Electrical Resistivity Tomography (ERT). Resistivity data were acquired by an ABEM Terrameter SAS1000 and a multi-electrode Lund system imaging using a Wenner array configuration of 64 electrodes and 5m spacing, reaching a depth of about 50m. Topographic corrections and 2D inversion models were performed using Res2Dinv software package. Seven 2D resistivity high resolution images have been obtained allowing to detect, delineate important fractures and also to hydrogeological characterization of the underground karst. A borehole of 100m depth was drilled in order to correlate and calibrate geophysical data and proposed models. Two sub-vertical fracture families have been identified with NE-SW and NW-SE directions respectively. These results correlate well with fracture data analysis gathered from remote sensing Spot images at large scale, and from local field fracture scanline surveys. A 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.

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

2009-04-01

152

Interpretation of dipole-dipole electrical resistivity survey, Colado geothermal area, Pershing County, Nevada  

Microsoft Academic Search

An electrical resistivity survey in the Colado geothermal area, Pershing County, Nevada has defined areas of low resistivity on each of five lines surveyed. Some of these areas appear to be fault controlled. Thermal fluids encountered in several drill holes support the assumption that the hot fluids may be associated with areas of low resistivity. The evidence of faulting as

C. E. Mackelprang

1980-01-01

153

The electric resistance and electron viscosity of Z-pinch plasma  

SciTech Connect

The electron magnetohydrodynamic equations imply that electron gas viscosity can have a significant influence on a plasma's electric resistance. For a long inhomogeneous plasma column with axial symmetry, as in a z-pinch, the viscous part of the resistance can be several orders of magnitude larger than the usual frictional resistance.

Esaulov, A. A.; Sasorov, P. V. [Institute for Theoretical and Experimental Physics B. Cheremushkinskaya St. 25, Moscow 117259 (Russian Federation)

1997-05-05

154

Investigating electrical contact resistance losses in lithium-ion battery assemblies for hybrid and electric vehicles  

NASA Astrophysics Data System (ADS)

Lithium-ion (Li-ion) batteries are favored in hybrid-electric vehicles and electric vehicles for their outstanding power characteristics. In this paper the energy loss due to electrical contact resistance (ECR) at the interface of electrodes and current-collector bars in Li-ion battery assemblies is investigated for the first time. ECR is a direct result of contact surface imperfections, i.e., roughness and out-of-flatness, and acts as an ohmic resistance at the electrode-collector joints. A custom-designed testbed is developed to conduct a systematic experimental study. ECR is measured at separable bolted electrode connections of a sample Li-ion battery, and a straightforward analysis to evaluate the relevant energy loss is presented. Through the experiments, it is observed that ECR is an important issue in energy management of Li-ion batteries. Effects of surface imperfection, contact pressure, joint type, collector bar material, and interfacial materials on ECR are highlighted. The obtained data show that in the considered Li-ion battery, the energy loss due to ECR can be as high as 20% of the total energy flow in and out of the battery under normal operating conditions. However, ECR loss can be reduced to 6% when proper joint pressure and/or surface treatment are used. A poor connection at the electrode-collector interface can lead to a significant battery energy loss as heat generated at the interface. Consequently, a heat flow can be initiated from the electrodes towards the internal battery structure, which results in a considerable temperature increase and onset of thermal runaway. At sever conditions, heat generation due to ECR might cause serious safety issues, sparks, and even melting of the electrodes.

Taheri, Peyman; Hsieh, Scott; Bahrami, Majid

2011-08-01

155

Chapter 5 Electrical Capacitance, Electrical Resistance, and Positron Emission Tomography Techniques and Their Applications in Multi-Phase Flow Systems  

Microsoft Academic Search

This article describes the recent progress in research and development on electrical capacitance tomography (ECT), electrical resistance tomography (ERT), and positron emission tomography (PET). Specifically, the article highlights several aspects of the three technologies and illustrates their application and performance through selected demonstration cases studies. The principles and results from the methods provide quantitative and\\/or qualitative assessment of the significance

Fei Wang; Qussai Marashdeh; Liang-Shih Fan; Richard A Williams

2009-01-01

156

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

NASA Astrophysics Data System (ADS)

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 dynamic system. GPR Profile with Glacial Till Interface.

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

2013-12-01

157

Determination of surface electric charge profile in pyroelectric crystals  

NASA Astrophysics Data System (ADS)

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.

Ghaderi, R.; Davani, F. Abbasi

2014-12-01

158

Use of electrical resistivity to detect underground mine voids in Ohio  

USGS Publications Warehouse

Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could identify areas where coal was mined, leaving air- or water-filled voids. These voids can be local sources of potable water or acid mine drainage. They could also result in potentially dangerous collapse of roads or buildings that overlie the voids. The resistivity response of air- or water-filled voids compared to the surrounding bedrock may allow electrical resistivity surveys to delineate areas underlain by such voids. Surface deformation along State Route 32 in Jackson County led to a site investigation, which included electrical resistivity surveys. Several highly resistive areas were identified using axial dipole-dipole and Wenner resistivity surveys. Subsequent drilling and excavation led to the discovery of several air-filled abandoned underground mine tunnels. A site along State Route 32 in Vinton County, Ohio, was drilled as part of a mining permit application process. A mine void under the highway was instrumented with a pressure transducer to monitor water levels. During a period of high water level, electrical resistivity surveys were completed. The electrical response was dominated by a thin, low-resistivity layer of iron ore above where the coal was mined out. Nearby overhead powerlines also affected the results.

Sheets, Rodney A.

2002-01-01

159

Electrical depth profiling in thin SiON layers  

SciTech Connect

The internal structure of SiON films is extracted electrically, demonstrating an efficient, noncontact, nondestructive means for depth compositional analysis in gate oxides. The electrical data, obtained using x-ray photoelectron spectroscopy (XPS) based controlled surface charging (CSC), are compared with independent time of flight secondary ion mass spectroscopy and angle resolved XPS data. Inhomogeneous composition with significant nitrogen enrichment at the top of the oxide layer is observed. Capabilities of the CSC method in treating heterostructures of poor chemical contrast are discussed.

Rozenblat, A. [Materials Science and Engineering, Tel-Aviv University, Ramat-Aviv 69978 (Israel); Rosenwaks, Y. [School of Electrical Engineering, Tel-Aviv University, Ramat-Aviv 69978 (Israel); Segev, L. [Materials and Interfaces, The Weizmann Institute of Science, Rehovot 76100 (Israel); Cohen, H. [Chemical Research Support, The Weizmann Institute, Rehovot 76100 (Israel)

2009-02-02

160

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

USGS Publications Warehouse

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.

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

2006-01-01

161

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

PubMed

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

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

2006-01-01

162

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

PubMed Central

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

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

2011-01-01

163

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

SciTech Connect

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.

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

2009-12-11

164

Archeo Sciences n33-2009 2D Electrical Resistivity Tomography surveys optimisation of solutes  

E-print Network

Archeo Sciences n°33-2009 2D Electrical Resistivity Tomography surveys optimisation of solutes ERT models with Video analysis shows remarkable agreement. Introduction Subsurface electrical imaging on the cementation factor (Jackson & al, 1978) and main electrical anisotropic directions (Rey & Jongmans, 2007

Paris-Sud XI, Université de

165

Plume and lithologic profiling with surface resistivity and seismic tomography.  

PubMed

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

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

2005-01-01

166

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

DOEpatents

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.

Carter, J. David (Bolingbrook, IL); Mawdsley, Jennifer R. (Woodridge, IL); Niyogi, Suhas (Woodridge, IL); Wang, Xiaoping (Naperville, IL); Cruse, Terry (Lisle, IL); Santos, Lilia (Lombard, IL)

2010-04-20

167

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

NASA Technical Reports Server (NTRS)

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.

Lei, Jih-Fen

1987-01-01

168

Gene Expression Profiling Analysis of Castration-Resistant Prostate Cancer  

PubMed Central

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

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

2015-01-01

169

Electrical resistivity and piezoresistivity of Ni-CNT filled epoxy-based composites  

NASA Astrophysics Data System (ADS)

This paper investigates properties about electrical resistivity and piezoresistivity of multi-wall carbon nanotubes (MWCNTs)-filled epoxy-based composite and its further use for strain sensing. The MWCNTs dispersed epoxy resin, using MWCNTs in the amount of 1.5~3.0 vol.%, was first prepared by combined high-speed stirring and sonication methods. Then, the MWCNTs dispersed epoxy resin was cast into an aluminum mold to form specimens measuring 10×10×36 mm. After curing, DC electrical resistance measurements were performed along the longitudinal axis using the four-probe method, in which copper nets served as electrical contacts. The percolation threshold zone of resistivity was got as MWCNTs in the amount of 2.00-2.50 vol.%. Further compressive testing of these specimens was conducted with four-probe method for resistance measurements at the same time. Testing results show that the electrical resistivity of the composites changes with the strain's development, namely piezoresistivity. While for practical strain sensing use, signals of electric resistance and current in the acquisition circuits were both studied. Results show that the signal of current, compared with that of resistance, had better linear relationship with the compressive strain, better stability and longer effective section to reflect the whole deformation process of the specimens under pressure. Further works about the effects of low magnetic field on the electrical resistivity and piezoresistivity of Ni-CNTs filled epoxy-based composites were presented briefly at the end of the paper.

Jiang, Jinbao; Xiao, Huigang; Li, Hui

2013-04-01

170

Electric resistivity anomaly and martensitic phase transformation in Au-Cu-Zn alloys  

SciTech Connect

The martensitic phase transformation in the beta-1 phase of Au-Cd alloys exhibits very complicated behaviours (1). In the case of Au-47.5 at % Cd alloy, for example, the electric resistivity of the slowly cooled beta-1 phase tends downward during the martensitic phase transformation while the reverse change occurs in the quenched one. When the quenched alloy is heated, the electric resistivity increases linearly and then its temperature gradient begins to decrease at about 385K. Above 420K, the electric resistivity rises again linearly with increasing temperature. Such a resistivity anomaly is an irreversible phenomenonon the thermal cycles. We confirm by the X-ray analysis that it is not concerned with any structural change. In the case of the slowly cooled alloy, on the other hand, the resistivity anomaly does not occur. We conclude that the resistivity anomaly is originated from the annihilation of quenched-in vacancies introduced into the beta-1 phase.

Makita, T.; Nagasawa, A.

1984-11-01

171

Electrical resistivity imaging for characterizing dynamic hydrologic systems  

NASA Astrophysics Data System (ADS)

Electrical resistivity imaging (ERI) is widely used in hydrogeophysical studies for monitoring spatiotemporal variations in hydrologic properties and processes. Its applications to hydrologic settings found in sandy and other coarse-grained soils have been demonstrated. However, there has been limited use of the method for characterization of dynamic hydrologic systems such as those found in Vertisols (typical heavy-clay soils) and water layers in lakes. One reason for this is that principles that work well in sandy and loamy soils often produce erroneous results in clay soils. In addition, because of the dynamic nature of such systems, detailed empirical and computational studies are required to fully understand various properties, which vary spatially within a few meters or less, and temporally in less than few days. This dissertation investigates the effectiveness of ERI for characterizing dynamic hydrologic systems. Two specific questions are addressed: (1) Can spatiotemporal hydrologic variations in such systems be effectively characterized using ERI? (2) How accurately can the true resistivity distribution in the systems be determined? To address the first question, geoelectric studies of seasonal wetting and drying of a Texas Vertisol were carried out. Data processing involved inversion, temperature corrections and time-lapse analysis. In addition, a van Genuchten water retention function was incorporated into the study to estimate moisture flux. To answer the second question, theoretical and field geoelectric data from Lake Whitney, Texas, USA, were analyzed. Following an introduction to the research in chapter one, results of geoelectric studies of seasonal wetting and drying of the Texas Vertisol are presented in chapter two. Results reveal the seasonal hydrodynamics of the soil as they are controlled by micro-relief topography (gilgai) and cracks. In chapter three, time-lapse analysis and computations of the apparent moisture flux are discussed. This study shows that integrative hydrogeophysical and hydropedological method is a viable approach for visualizing moisture flux in soils. In chapter four, results of geoelectric studies in Lake Whitney are discussed with recommendations for advancing the ERI as a tool in limnological research for mapping freshwater zones within impacted lakes and water reservoirs. Chapter five presents brief summary and conclusion of the research.

Amidu, Sikiru Adetona

172

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

NASA Astrophysics Data System (ADS)

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 results were obtained along the Sand Coulee and Onoway transects where the contrast between the bedrock and valley-fill was large and the surficial sediment was homogeneous. The effects of decreasing reliability with depth, 3-D anomalies, principles of equivalence and suppression, and surface inhomogeneity on the image quality are discussed.

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

2004-05-01

173

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

USGS Publications Warehouse

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.

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

2011-01-01

174

Change in the electrical resistance of the metallic composite material-steel contact under friction and electric current  

NASA Astrophysics Data System (ADS)

The I- V characteristics of the sliding contact of metallic composites of grade 45 steel without a lubricant are presented. Steel-based composites are shown to increase the actual electric-contact area due to the appearance of electric discharges, which provide the main passage of an electric current with a density up to 300 A/cm2. Copper-based composites cannot initiate electric-discharge conduction because of the fracture of the contact zone material at a current density higher than 50 A/cm2. The electrical resistivity of the contact layer of metallic composites is calculated. It is found that, during friction with a high current density, the electrical resistivity of the contact layer approaches the electrical resistivity of graphite. It is experimentally shown that the actual electric-contact area can be increased by the introduction of a Pb-Sn melt into the friction zone and reaching a current density higher than 300 A/cm2 in the contact.

Fadin, V. V.; Aleutdinova, M. I.

2010-12-01

175

3rd World Congress on Industrial Process Tomography, Banff, Canada Non Iterative Inversion Method for Electrical Resistance,  

E-print Network

Method for Electrical Resistance, Capacitance and Inductance Tomography for Two Phase Materials the retrieval of the resistivity of a conductor (electrical resistance tomography and magnetic induction tomography) and one technique concerns the retrieval of the permittivity of a dielectric material (electrical

Lionheart, Bill

176

In Vitro Cross-Resistance Profile of Nucleoside Reverse Transcriptase Inhibitor (NRTI) BMS-986001 against Known NRTI Resistance Mutations  

PubMed Central

BMS-986001 is a novel HIV nucleoside reverse transcriptase inhibitor (NRTI). To date, little is known about its resistance profile. In order to examine the cross-resistance profile of BMS-986001 to NRTI mutations, a replicating virus system was used to examine specific amino acid mutations known to confer resistance to various NRTIs. In addition, reverse transcriptases from 19 clinical isolates with various NRTI mutations were examined in the Monogram PhenoSense HIV assay. In the site-directed mutagenesis studies, a virus containing a K65R substitution exhibited a 0.4-fold change in 50% effective concentration (EC50) versus the wild type, while the majority of viruses with the Q151M constellation (without M184V) exhibited changes in EC50 versus wild type of 0.23- to 0.48-fold. Susceptibility to BMS-986001 was also maintained in an L74V-containing virus (0.7-fold change), while an M184V-only-containing virus induced a 2- to 3-fold decrease in susceptibility. Increasing numbers of thymidine analog mutation pattern 1 (TAM-1) pathway mutations correlated with decreases in susceptibility to BMS-986001, while viruses with TAM-2 pathway mutations exhibited a 5- to 8-fold decrease in susceptibility, regardless of the number of TAMs. A 22-fold decrease in susceptibility to BMS-986001 was observed in a site-directed mutant containing the T69 insertion complex. Common non-NRTI (NNRTI) mutations had little impact on susceptibility to BMS-986001. The results from the site-directed mutants correlated well with the more complicated genotypes found in NRTI-resistant clinical isolates. Data from clinical studies are needed to determine the clinically relevant resistance cutoff values for BMS-986001. PMID:23979732

Li, Zhufang; Terry, Brian; Olds, William; Protack, Tricia; Deminie, Carol; Minassian, Beatrice; Nowicka-Sans, Beata; Sun, Yongnian; Dicker, Ira; Hwang, Carey; Lataillade, Max; Hanna, George J.

2013-01-01

177

Electrical resistivity of some Zintl phase and the precursors  

SciTech Connect

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).

Wolfe, L.

1990-09-21

178

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

PubMed

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

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

2015-01-01

179

Electrically stimulated resistance training in SCI individuals increases muscle fatigue resistance but not femoral artery size or blood flow  

Microsoft Academic Search

Study design:Longitudinal.Objectives:The purpose of this study was to evaluate the effect of lower extremity resistance training on quadriceps fatigability, femoral artery diameter, and femoral artery blood flow.Setting:Academic Institution.Methods:Five male chronic spinal cord injury (SCI) individuals (American Spinal Injury Association (ASIA): A complete; C5–T10; 36±5 years old) completed 18 weeks of home-based neuromuscular electrical stimulation (NMES) resistance training. Subjects trained the

M J Sabatier; L Stoner; E T Mahoney; C Black; C Elder; G A Dudley; K McCully

2006-01-01

180

Multiple drug resistance patterns and plasmid profiles of non-typhi salmonellae in Turkey.  

PubMed Central

A total of 259 clinical isolates of nonrepetitive non-typhi salmonellae (NTS) were examined for antibiotic resistance patterns and plasmid content. The antibiotics used were amoxicillin-clavulanic acid (AMC), ampicillin (AM), aztreonam (ATM), carbenicillin (CB), cefixime (CFM), cefotaxime (CTX), cefoxitin (FOX), ceftazidime (CAZ), ceftriaxone (CRO), chloramphenicol (C), ciprofloxacin (CIP), gentamicin (GM), imipenem (IPM), ofloxacin (OFX), tetracycline (TE), trimethoprim-sulfomethoxazole (SXT). Multi-drug resistant (MDR) strains comprised 19.3% of the total isolates (50/259) and almost all were S. typhimurium (49/50). Fifteen different patterns of resistance was observed, AM/CB/C/AMC/TE and AM/CB/C/AMC/SXT/GM/CTX/CRO/CAZ/CFM/ATM being the most frequent patterns. Twenty-eight out of 50 multiresistant isolates were found to contain at least one plasmid (mean five) and the size of the plasmids ranged between 1.7 and 158 kb. Plasmid profiles of multiresistant NTS strains were heterogenous as 21 different profiles were detected in a total of 28 plasmid-bearing isolates. No direct correlation was established between antibiotic resistance patterns and plasmid profiles. PMID:9825781

Yildirmak, T.; Yazgan, A.; Ozcengiz, G.

1998-01-01

181

Comparative Genomics of Klebsiella pneumoniae Strains with Different Antibiotic Resistance Profiles?†  

PubMed Central

There is a global emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae, a Gram-negative enteric bacterium that causes nosocomial and urinary tract infections. While the epidemiology of K. pneumoniae strains and occurrences of specific antibiotic resistance genes, such as plasmid-borne extended-spectrum ?-lactamases (ESBLs), have been extensively studied, only four complete genomes of K. pneumoniae are available. To better understand the multidrug resistance factors in K. pneumoniae, we determined by pyrosequencing the nearly complete genome DNA sequences of two strains with disparate antibiotic resistance profiles, broadly drug-susceptible strain JH1 and strain 1162281, which is resistant to multiple clinically used antibiotics, including extended-spectrum ?-lactams, fluoroquinolones, aminoglycosides, trimethoprim, and sulfamethoxazoles. Comparative genomic analysis of JH1, 1162281, and other published K. pneumoniae genomes revealed a core set of 3,631 conserved orthologous proteins, which were used for reconstruction of whole-genome phylogenetic trees. The close evolutionary relationship between JH1 and 1162281 relative to other K. pneumoniae strains suggests that a large component of the genetic and phenotypic diversity of clinical isolates is due to horizontal gene transfer. Using curated lists of over 400 antibiotic resistance genes, we identified all of the elements that differentiated the antibiotic profile of MDR strain 1162281 from that of susceptible strain JH1, such as the presence of additional efflux pumps, ESBLs, and multiple mechanisms of fluoroquinolone resistance. Our study adds new and significant DNA sequence data on K. pneumoniae strains and demonstrates the value of whole-genome sequencing in characterizing multidrug resistance in clinical isolates. PMID:21746949

Kumar, Vinod; Sun, Peng; Vamathevan, Jessica; Li, Yong; Ingraham, Karen; Palmer, Leslie; Huang, Jianzhong; Brown, James R.

2011-01-01

182

Comparative genomics of Klebsiella pneumoniae strains with different antibiotic resistance profiles.  

PubMed

There is a global emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae, a Gram-negative enteric bacterium that causes nosocomial and urinary tract infections. While the epidemiology of K. pneumoniae strains and occurrences of specific antibiotic resistance genes, such as plasmid-borne extended-spectrum ?-lactamases (ESBLs), have been extensively studied, only four complete genomes of K. pneumoniae are available. To better understand the multidrug resistance factors in K. pneumoniae, we determined by pyrosequencing the nearly complete genome DNA sequences of two strains with disparate antibiotic resistance profiles, broadly drug-susceptible strain JH1 and strain 1162281, which is resistant to multiple clinically used antibiotics, including extended-spectrum ?-lactams, fluoroquinolones, aminoglycosides, trimethoprim, and sulfamethoxazoles. Comparative genomic analysis of JH1, 1162281, and other published K. pneumoniae genomes revealed a core set of 3,631 conserved orthologous proteins, which were used for reconstruction of whole-genome phylogenetic trees. The close evolutionary relationship between JH1 and 1162281 relative to other K. pneumoniae strains suggests that a large component of the genetic and phenotypic diversity of clinical isolates is due to horizontal gene transfer. Using curated lists of over 400 antibiotic resistance genes, we identified all of the elements that differentiated the antibiotic profile of MDR strain 1162281 from that of susceptible strain JH1, such as the presence of additional efflux pumps, ESBLs, and multiple mechanisms of fluoroquinolone resistance. Our study adds new and significant DNA sequence data on K. pneumoniae strains and demonstrates the value of whole-genome sequencing in characterizing multidrug resistance in clinical isolates. PMID:21746949

Kumar, Vinod; Sun, Peng; Vamathevan, Jessica; Li, Yong; Ingraham, Karen; Palmer, Leslie; Huang, Jianzhong; Brown, James R

2011-09-01

183

Microbial uropathogens and their antibiotic resistance profile from hospitalized patients in Central Alabama.  

PubMed

Urinary tract infections remain a common problem in inpatient care. They are highly challenging to provide effective initial therapy without sensitivity data. The purpose of this study was to survey the uropathogens and their sensitivity profile at a hospital in Central Alabama and to guide experiential antibiotic selection. This was the first reported study on bacterial uropathogens and their antibiotic resistance profile at this Central Alabama hospital. The survey period was between July 2009 and June 2010, a total of 473 urine cultures were reviewed and susceptibility testing was determined using the Clinical and Laboratory Standards Institute (CLSI) microdilution method. The results indicated that Escherichia coli (45.5%) was the most common organism, followed by Klebsiella pneumoniae (18.2%), Pseudomonas aeruginosa (10.1%), Proteus mirabilis (7.8%), Enterobacter cloacae (4.2%), methicillin-resistant Staphylococcus aureus (3.0%), Klebsiella oxytoca and Citrobacter freundii (1.5%), Morganella morganii (1.3%), and the other species (7.0%). For the 215 E. coli isolates, imipenem and cephalosporins (except for cefazolin) had the highest sensitivity (99-100%, P < 0.05). In contrast, ampicillin had the highest resistance (57%, P < 0.05) as compared to other antibiotics (about 30%) including ampicillin/ sulbactam, ciprofloxacin, levofloxacin, tetracycline, and trimethoprim/sulfamethoxazole. The major finding of this study was that ciprofloxacin, levofloxacin and trimethoprim/sulfamethoxazole had comparable sensitivity patterns for Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter cloacae, the most common uropathogens at this Central Alabama hospital. Additionally, this study found that E. coli had a resistant rate of 31% to ciprofloxacin and levofloxacin compared to the resistance rate of 28.4% and 15.8% in earlier reports (Lee et al. 2010; Rattanaumpawan et al. 2010), likely indicating the continuing evolution of resistance due to antibiotic exposure. It is imperative to monitor the resistance of P. aeruginosa considering their high resistance to imipenem found in this study. PMID:23330509

Qian, Li; Camara, Tracy; Taylor, J Kyle; Jones, Kathy W

2012-01-01

184

Accounting for spatially variable resolution in electrical resistivity tomography through field-scale rock-physics relations  

E-print Network

Accounting for spatially variable resolution in electrical resistivity tomography through field of the voltages measured in an electrical resistivity tomography ERT survey produces maps of electrical-scale rock-physics relations Kamini Singha1 and Stephen Moysey2 ABSTRACT A number of issues impact electrical

Singha, Kamini

185

Resistance Training Improves Hemodynamic Function, Collagen Deposition and Inflammatory Profiles: Experimental Model of Heart Failure  

PubMed Central

The role of resistance training on collagen deposition, the inflammatory profile and muscle weakness in heart failure remains unclear. Therefore, this study evaluated the influence of a resistance training program on hemodynamic function, maximum strength gain, collagen deposition and inflammatory profile in chronic heart failure rats. Thirty-two male Wistar rats submitted to myocardial infarction by coronary artery ligation or sham surgery were assigned into four groups: sedentary sham (S-Sham, n?=?8); trained sham (T-Sham, n?=?8); sedentary chronic heart failure (S-CHF, n?=?8) and trained chronic heart failure (T-CHF, n?=?8). The maximum strength capacity was evaluated by the one maximum repetition test. Trained groups were submitted to an 8-week resistance training program (4 days/week, 4 sets of 10–12 repetitions/session, at 65% to 75% of one maximum repetition). After 8 weeks of the resistance training program, the T-CHF group showed lower left ventricular end diastolic pressure (P<0.001), higher left ventricular systolic pressure (P<0.05), higher systolic blood pressure (P<0.05), an improvement in the maximal positive derivative of ventricular pressure (P<0.05) and maximal negative derivative of ventricular pressure (P<0.05) when compared to the S-CHF group; no differences were observed when compared to Sham groups. In addition, resistance training was able to reduce myocardial hypertrophy (P<0.05), left ventricular total collagen volume fraction (P<0.01), IL-6 (P<0.05), and TNF-?/IL-10 ratio (P<0.05), as well as increasing IL-10 (P<0.05) in chronic heart failure rats when compared to the S-CHF group. Eight weeks of resistance training promotes an improvement of cardiac function, strength gain, collagen deposition and inflammatory profile in chronic heart failure rats. PMID:25340545

Alves, Jadson P.; Nunes, Ramiro B.; Stefani, Giuseppe P.; Dal Lago, Pedro

2014-01-01

186

Modeling the electrical resistivity of deformation processed metal-metal composites  

SciTech Connect

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.

Tian, Liang [Ames Laboratory; Anderson, Iver [Ames Laboratory; Riedemann, Trevor [Ames Laboratory; Russell, Alan [Ames Laboratory

2014-09-01

187

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

PubMed

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

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

188

An Ultra-Precise System for Electrical Resistivity Tomography Measurements  

SciTech Connect

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 the highest gain range of 125 to 1. The receiver also uses very high precision and high temperature stability components. The goal is to improve the accuracy to better than 0.1%. The system has more receiver channels, eight, to allow efficient data collection at lower base frequencies. We are also implementing a frequency-domain acquisition mode in addition to the time-domain acquisition mode used in the earlier systems. Initial field tests were started in the fall of 2008. We conducted tests on a number of types of cable commonly used for resistivity surveys. A series of different tests were designed to determine if the couplings were primarily resistive, capacitive, or inductive in nature and to ascertain that the response was due to the cable cross-talk and did not depend on the receiver electronics. The results show that the problem appears to be primarily capacitive in nature and does not appear to be due to problems in the receiver electronics. Thus a great deal of emphasis has been placed on finding appropriate cables as well as stable electrodes that have low contact impedance at the very low current flows observed at the receiver. One of the issues in survey design and data collection has been determining how long one must wait before using the same electrode as a transmitter and as a receiver. A series of tests was completed in the laboratory sand tank where four-electrode measurements were made using the same dipole transmitters and dipole receivers (the dipoles used adjacent electrodes). For each data series, a single set of normal measurements were collected with no reciprocals and electrodes were never reused as a receiver after being used as a transmitter. After waiting a specified length of time, the reciprocal measurements were collected using a schedule of measurements. The order of this second schedule was rearranged such that if this second set of measurements were performed without first using the normal schedule, no electrode would be used as a receiver after being used as a transmitter. For this study, we cannot conclude that increasing the

LaBrecque, Douglas J; Adkins, Paula L

2008-12-09

189

Fracture network characterisation of a landslide by electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

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 be distributed uniformly with about 10 m distance between them and predicting mass movements which may prevent the slump along the visible fracture. Similar unidirectional fracture systems could be investigated by the ERT method for any hydrogeological or engineering geological aim.

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

2014-06-01

190

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

PubMed

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

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

2007-04-01

191

An electric double-layer capacitor with high capacitance and low resistance  

Microsoft Academic Search

The development of the electric double-layer capacitor with ultra-high capacitance and extremely low DC resistance is described. The capacitance ranges from 1 to 500 F and the DC resistance is less than one fifth of that of the conventional capacitor with organic electrolytes. The capacitor consists of an activated carbon layer on aluminum foil collector electrodes, a separator, and an

Akihiko Yoshida; Kiyoaki Imoto; Hajime Yoneda; A. Nishimo

1992-01-01

192

The concentration of deep sea gas hydrates from downhole electrical resistivity logs and laboratory data  

Microsoft Academic Search

The concentration of gas hydrate at an Ocean Drilling Program Site on the continental slope off the coast of Vancouver Island has been estimated using a combination of downhole electrical resistivity logs, resistivity and porosity of recovered core, and core pore fluid salinity. From a depth of 100m to the base of gas hydrate stability (bottom-simulating reflector, or BSR) at

R. D. Hyndman; T. Yuan; K. Moran

1999-01-01

193

ELECTRICAL RESISTANCE OF A SODIUM SHORT ACROSS A TWO-CONDUCTOR CONSTANTAN LEAK DETECTION CABLE  

Microsoft Academic Search

An attempt was made to measure the electrical resistance of a 300, 500, ; and 800 F sodium short over a length of 3 in. from an approximate 10 ft length ; of the present two-conductor constantan, ceramic beaded leak detection cable. ; The resistances measured in a bridge-type circuit were very small, the highest ; being 0.32 ohms. For

W. Milich; E. C. King

1955-01-01

194

Electrical resistivity measurements of brine saturated porous media near reservoir conditions: Awibengkok preliminary results  

Microsoft Academic Search

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

B Bonner; A Duba; J Roberts

1999-01-01

195

Effect of pressure on the electrical resistivity of water-saturated crystalline rocks  

Microsoft Academic Search

Electrical r.esistivity of eight igneous rocks and two crystalline limestones was measured at pressures to 10 kb. The rocks were saturated with tap water or salt solution, and the pore pressure was maintained near zero. The dependence of resistivity on temperature, porosity, and pore fluid salinity suggested that conduction was primarily electrolytic through- out the .entire pressure range, even though

W. F. Brace; A. S. Orange; T. R. Madden

1965-01-01

196

Plasmonic Nanopore for Electrical Profiling of Optical Intensity Magnus P. Jonsson and Cees Dekker*  

E-print Network

Plasmonic Nanopore for Electrical Profiling of Optical Intensity Landscapes Magnus P. Jonsson-limited resolution. This is achieved with a novel device, a plasmonic nanopore, which combines a plasmonic bowtie nanoantenna with a 10 nm-in- diameter solid-state nanopore. Variations in the local optical intensity modulate

Dekker, Cees

197

In situ electrical resistivity and bulk porosity of the oceanic crust Costa Rica Rift  

NASA Astrophysics Data System (ADS)

In situ electrical resistivity was measured in DSDP Hole 504B to a depth of 1,013 m into oceanic basement. Apparent resistivities are about 10 ? m in about 600 m of pillow lavas, sharply increasing to nearly 1,000 ? m in the underlying dykes. Bulk porosities calculated from resistivities show a distinct layering, apparently corresponding to geophysical layers 2A, 2B and 2C.

Becker, Keir; von Herzen, R. P.; Francis, T. J. G.; Anderson, R. N.; Honnorez, J.; Adamson, A. C.; Alt, J. C.; Emmermann, R.; Kempton, P. D.; Kinoshita, H.; Laverne, C.; Mottl, M. J.; Newmark, R. L.

1982-12-01

198

In situ electrical resistivity and bulk porosity of the oceanic crust Costa Rica Rift  

Microsoft Academic Search

In situ electrical resistivity was measured in DSDP Hole 504B to a depth of 1,013 m into oceanic basement. Apparent resistivities are about 10 Omega m in about 600 m of pillow lavas, sharply increasing to nearly 1,000 Omega m in the underlying dykes. Bulk porosities calculated from resistivities show a distinct layering, apparently corresponding to geophysical layers 2A, 2B

Keir Becker; R. P. von Herzen; T. J. G. Francis; R. N. Anderson; J. Honnorez; A. C. Adamson; J. C. Alt; R. Emmermann; P. D. Kempton; H. Kinoshita; C. Laverne; M. J. Mottl; R. L. Newmark

1982-01-01

199

Focused subsurface flow in the Amargosa Desert characterized by direct-current resistivity profiling  

NASA Astrophysics Data System (ADS)

Environmental-tracer studies have shown that ground-water recharge in the thick alluvial fill of the Amargosa Desert is localized beneath ephemeral stream channels and anthropogenic sources of water, with little recharge beneath native vegetation on interfluvial areas under current climatic conditions. These borehole-based studies provided relatively robust but limited, one-dimensional (vertical) information that can be only tentatively regionalized using geomorphologic, pedologic, and vegetational mapping. The ability of direct-current (DC) resistivity profiling to complement and extend studies of the spatial distribution of subsurface flow was examined by making surface-based measurements ("soundings") along one transect normal to the depositional fabric in each of three geomorphologically distinct settings: a well-incised ephemeral channel system, a poorly incised (distributory) ephemeral channel system, and an interfluvial upland. Linear arrays of 32 to 80 electrodes were deployed with a uniform 2 to 5-m spacing between adjacent electrodes. A multiplexing 8-channel resistivity instrument made automated inverse-Schlumberger-array soundings along the deployed line, using up to 10 electrodes at a time. The line was shifted piecemeal until composite transects consisted of 168 to 232 electrode positions. This approach allowed rapid profiling of long transects at high resolution. Numerical inversions assumed horizontal constancy normal to the vertical slices being imaged, producing solution sets of optimized resistivity values for several thousand points within each modeled slice. Imaged slices were ˜30 to 80 m deep and ˜1 km wide. RMS errors between apparent resistivities in the model inversions and field-measured apparent resistivities were ˜10%. On the basis of borehole studies, inverted resistivity (? ) values denoted three categories of alluvium: (1) low-water-content coarse gravel and highly desiccated surface materials, with ? > ˜200 ? -m, (2) vertical plumes of moist alluvium in areas of active recharge, with ? < ˜20 ? -m, and (3) other low to low-medium water-content alluvium in areas without active recharge, with intermediate values of ? . The upland profile revealed a laterally extensive gravel layer (category 1 alluvium) at a depth of ˜25 m that intersects instrumented boreholes at the Amargosa Desert Research Site. This layer coincides with peak concentrations of radioactive gases and volatile organic compounds moving through the unsaturated zone from a nearby waste-disposal facility. DC-resistivity profiling appears useful for locating areas of active ground-water recharge as well as potential passageways for preferential gas transport in the Amargosa Desert and similar environments.

Stonestrom, D. A.; Abraham, J. D.; Lucius, J. E.; Prudic, D. E.

2003-12-01

200

Spatial and temporal monitoring of soil water content with an irrigated corn crop cover using surface electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

A nondestructive and spatially integrated multielectrode method for measuring soil electrical resistivity was tested in the Beauce region of France during a period of corn crop irrigation to monitor soil water flow over time and in two-dimensional (2-D) with simultaneous measurements of soil moisture and thermal profiles. The results suggested the potential of surface electrical resistivity tomography (ERT) for improving soil science and agronomy studies. The method was able to produce a 2-D delimitation of soil horizons as well as to monitor soil water movement. Soil drainage through water uptake by the roots, the progression of the infiltration front with preferential flow zones, and the drainage of the plowed horizon were well identified. At the studied stage of corn development (3 months) the soil zones where infiltration and drainage occurred were mainly located under the corn rows. The structural soil characteristics resulting from agricultural practices or the passage of agricultural equipment were also shown. Two-dimensional sections of soil moisture content were calculated using ERT. The estimates were made by using independently established "in situ" calibration relationships between the moisture and electrical resistivity of typical soil horizons. The thermal soil profile was also considered in the modeling. The results showed a reliable linear relationship between the calculated and measured water contents in the crop horizon. The precision of the calculation of the specific soil water content, quantified by the root mean square error (RMSE), was 3.63% with a bias corresponding to an overestimation of 1.45%. The analysis and monitoring of the spatial variability of the soil moisture content with ERT represent two components of a significant tool for better management of soil water reserves and rational irrigation practices.

Michot, Didier; Benderitter, Yves; Dorigny, Abel; Nicoullaud, Bernard; King, Dominique; Tabbagh, Alain

2003-05-01

201

Molecular characterization and antibiotic resistance profiling of Campylobacter isolated from cattle in Polish slaughterhouses.  

PubMed

A total of 812 samples from bovine hides and the corresponding carcasses collected at the slaughterhouse level in the eastern part of Poland were examined for the presence of Campylobacter jejuni and Campylobacter coli. Recovered isolates were confirmed using species-specific PCR, characterized by the presence of 11 putative virulence genes and antimicrobial susceptibility was determined using a microbroth dilution method. Furthermore, the genotypic relatedness of the isolates was determined by PFGE profiling and virulence pattern cluster analysis. The prevalence of Campylobacter was 25.6% and 2.7% in bovine hide and carcass samples, respectively. The presence of virulence markers varied between C. jejuni and C. coli species however, the majority of strains possessed the cadF, flhA, flaA genes, irrespective of the bacterial species and origin. The lower number of the strains was positive for the invasive associated markers -virB11 and wlaN. Antibiotic profiling showed that campylobacters were most frequently resistant to quinolones and fluoroquinolones (nalidixic acid and ciprofloxacin, 38.3% of each, respectively) followed by streptomycin (24.3%) and tetracycline (20.9%). Resistance to erythromycin and gentamicin was demonstrated in 4.3% and 2.6% of strains, respectively. Comparisons of the PFGE and virulence marker profiles of the isolates reflected the high genetic diversity of Campylobacter tested. Moreover, a poor correlation between the PFGE type, pathogenic gene marker and antimicrobial resistance patterns was observed. PMID:23498189

Wieczorek, Kinga; Denis, Edyta; Lynch, Orla; Osek, Jacek

2013-05-01

202

A novel method of modeling and simulation for electrical resistance tomography system  

Microsoft Academic Search

A new method of modeling and simulation for electrical resistance tomography (ERT) system applied to two phase flow measurement is presented in the paper. Based on the Matlab PDE (partial differential equations) tool box, the mathematical model is established, the forward problem is solved and the distributions of electric potential and current density in sensitive field are obtained. The results

Xiang Deng; Zengwei Yan; Zheng Wei

2009-01-01

203

Monitoring chemical diffusion in a porous media using electrical resistivity tomography  

Microsoft Academic Search

Electrical resistivity tomography (ERT) is a non-invasive imaging technique capable of evaluating the distribution of electrical properties within cross-sections of soil specimens. The technique provides an alternative for the monitoring of processes in soils that may not yield mechanical or density contrasts. In this paper, a series of experimental test results is presented, where the diffusion of chemical fronts, in

V. Damasceno; D. Fratta

2006-01-01

204

Electrical resistance measurements of highly inhibited SiC coated carbon-carbon laminates  

E-print Network

The effect of oxidation damage at 900'C of highly inhibited, SiC coated carbon-carbon laminates on shear modulus, mass loss, and electrical resistance are studied. The approach taken enabled the interpretation of the shear modulus and electrical...

Parker, Paul Albert

2012-06-07

205

Damage detection of CFRP laminates using electrical resistance measurement and neural network  

Microsoft Academic Search

As carbon fibers are electrical conductors, the measurement of the electrical resistance appears to be a valuable technique for the in situ detection of various types of damage in carbon fiber reinforced polymers (CFRP) laminates. In such cases, carbon fibers are both the reinforcement and the sensor to detect damage in CFRP laminates. The damage-detecting method of CFRP laminates by

Dae-Cheol Seo; Jung-Ju Lee

1999-01-01

206

Model 'zero-age' lunar thermal profiles resulting from electrical induction  

NASA Technical Reports Server (NTRS)

Thermal profiles for the moon are calculated under the assumption that a pre-main-sequence T-Tauri-like solar wind excites both transverse magnetic and transverse electric induction while the moon is accreting. A substantial initial temperature rise occurs, possibly of sufficient magnitude to cause subsequent early extensive melting throughout the moon in conjunction with nominal long-lived radioactives. In these models, accretion is an unimportant direct source of thermal energy but is important because even small temperature rises from accretion cause significant changes in bulk electrical conductivity. Induction depends upon the radius of the moon, which we take to be accumulating while it is being heated electrically. The 'zero-age' profiles calculated in this paper are proposed as initial conditions for long-term thermal evolution of the moon.

Herbert, F.; Sonett, C. P.; Wiskerchen, M. J.

1977-01-01

207

Velocity profiles in pores with undulating opening diameter and their importance for resistive-pulse experiments.  

PubMed

Pores with undulating opening diameters have emerged as an analytical tool enhancing the speed of resistive-pulse experiments, with a potential to simultaneously characterize size and mechanical properties of translocating objects. In this work, we present a detailed study of the characteristics of resistive-pulses of charged and uncharged polymer particles in pores with different aspect ratios and pore topography. Although no external pressure difference was applied, our experiments and modeling indicated the existence of local pressure drops, which modified axial and radial velocities of the solution. As a consequence of the complex velocity profiles, pores with undulating pore diameter and low-aspect ratio exhibited large dispersion of the translocation times. Distribution of the pulse amplitude, which is a measure of the object size, was not significantly affected by the pore topography. The importance of tuning pore geometry for the application in resistive-sensing and multipronged characterization of physical properties of translocating objects is discussed. PMID:25245282

Innes, Laura M; Chen, Chin-Hsuan; Schiel, Matthew; Pevarnik, Matthew; Haurais, Florian; Toimil-Molares, Maria Eugenia; Vlassiouk, Ivan; Theogarajan, Luke; Siwy, Zuzanna S

2014-10-21

208

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

209

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

SciTech Connect

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.

Faraby, H. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States); DiBattista, M. [Qualcomm Technologies Incorporated, San Diego, California 92121 (United States); Bandaru, P. R., E-mail: pbandaru@ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

2014-04-28

210

Thermal conductivity, electrical resistivity, and permeability of saturated soils at various porosities  

E-print Network

Circuit 26. Results of Initial Vert1cal Electr1cal Resistiv1ty Test Using Circu1t Shown in F1gure 25 . 27. Results of Vertical Electrical Resist1vity Tests Using 73 74 75 76 28. 29, 30, 31. Plate Electrodes and Direct Current . Results of Vert...1cal Electrical Resist1vity Tests Using Plate Electrodes and Alternat1ng Current Formation Res1stivity Factor versus Porosity from Erchul (8) Permeabil1ty versus Porosity for Kaolinite at 20 C from Lee (18) Permeability versus Porosity...

Enderby, James Keith

2012-06-07

211

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

PubMed Central

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

2011-01-01

212

Scientific evidence of three different insecticide-resistant profiles in Triatoma infestans (Hemiptera: Reduviidae) populations from Argentina and Bolivia.  

PubMed

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

Germano, M D; Santo-Orihuela, P; Roca-Acevedo, G; Toloza, A C; Vassena, C; Picollo, M I; Mougabure-Cueto, G

2012-11-01

213

Effects of contact resistance on electrical conductivity measurements of SiC-based materials  

NASA Astrophysics Data System (ADS)

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 ? cm2 at RT, decreasing continuously to ˜1-10 ? 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. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.

Youngblood, G. E.; Thomsen, E. C.; Henager, C. H.

2013-11-01

214

An experimental evaluation of joint electrical resistance on power lead thermal performance  

SciTech Connect

The amount of electrical resistance in braze joints is not known for certain. In addition annealing processes that occurs during a braze or solder operation can change the residual resistivity ratio (RRR) of the copper. The change in the electrical resistivity of samples of copper because of exposure to conditions that a high current lead would see during a brazing operation were experimentally investigated. A sample was taken from a manufacturing and brazing trial of the high current power leads for the Superconducting Super Collider (SSC), and from oxygen free high conductivity copper (OFHC) 101 rod similar to that used in the trial. The samples were heated under conditions that a current lead would undergo during the brazing process. Measurements were made of the electrical resistance of the copper specimens and across abraze joint in the manufacturing trial sample for temperatures ranging from liquid helium to room temperature.

Datskov, V.I.; Demko, J.A.; Augustynowicz, S.D.; Hutton, R.D.

1993-03-01

215

Electrical contact resistances of thermoelectric thin films measured by Kelvin probe microscopy  

NASA Astrophysics Data System (ADS)

This work presents an approach for measuring cross plane electrical contact resistances directly using Kelvin Probe Microscopy. With this technique we were able to measure the electrical contact resistances of a cross section of a thermoelectric thin film made of Bi2Te3 sandwiched between two gold electrodes. On the one hand, the bottom gold electrode, which is located on top of the silicon substrate, was used as a cathode in electro-deposition process to grow the sample. On the other hand, the gold electrode on top was made via physical evaporation. The electrical contact resistances measured at both interfaces were 0.11 ± 0.01? and 0.15 ± 0.01?, respectively. These differences are related to differences between the top and bottom gold/bismuth-telluride film, obtaining smaller contact resistance where the film was grown by electro-deposition.

Muñoz-Rojo, Miguel; Caballero-Calero, Olga; Martín-González, Marisol

2013-10-01

216

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

NASA Astrophysics Data System (ADS)

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.

Lesparre, Nolwenn; Grychtol, Bart?omiej; Gibert, Dominique; Komorowski, Jean-Christophe; Adler, Andy

2014-06-01

217

Identification of transcription factors potential related to brown planthopper resistance in rice via microarray expression profiling  

PubMed Central

Background Brown planthopper (BPH), Nilaparvata lugens Stål, is one of the most destructive insect pests of rice. The molecular responses of plants to sucking insects resemble responses to pathogen infection. However, the molecular mechanism of BPH-resistance in rice remains unclear. Transcription factors (TF) are up-stream regulators of various genes that bind to specific DNA sequences, thereby controlling the transcription from DNA to mRNA. They are key regulators for transcriptional expression in biological processes, and are probably involved in the BPH-induced pathways in resistant rice varieties. Results We conducted a microarray experiment to analyze TF genes related to BPH resistance in a Sri Lankan rice cultivar, Rathu Heenati (RHT). We compared the expression profiles of TF genes in RHT with those of the susceptible rice cultivar Taichun Native 1 (TN1). We detected 2038 TF genes showing differential expression signals between the two rice varieties. Of these, 442 TF genes were probably related to BPH-induced resistance in RHT and TN1, and 229 may be related to constitutive resistance only in RHT. These genes showed a fold change (FC) of more than 2.0 (P<0.05). Among the 442 TF genes related to BPH-induced resistance, most of them were readily induced in TN1 than in RHT by BPH feeding, for instance, 154 TF genes were up-regulated in TN1, but only 31 TF genes were up-regulated in RHT at 24 hours after BPH infestation; 2–4 times more TF genes were induced in TN1 than in RHT by BPH. At an FC threshold of >10, there were 37 induced TF genes and 26 constitutive resistance TF genes. Of these, 13 were probably involved in BPH-induced resistance, and 8 in constitutive resistance to BPH in RHT. Conclusions We explored the molecular mechanism of resistance to BPH in rice by comparing expressions of TF genes between RHT and TN1. We speculate that the level of gene repression, especially for early TF genes, plays an important role in the defense response. The fundamental point of the resistance strategy is that plants protect themselves by reducing their metabolic level to inhibit feeding by BPH and prevent damage from water and nutrient loss. We have selected 21 TF genes related to BPH resistance for further analyses to understand the molecular responses to BPH feeding in rice. PMID:23228240

2012-01-01

218

Monitoring strain and damage in multi-phase composite materials using electrical resistance methods  

NASA Astrophysics Data System (ADS)

The variation of the electrical properties of fiber reinforced polymers when subjected to load offer the ability of strain and damage monitoring. This is performed via electrical resistance and electrical potential measurements. On the other hand Carbon Nanotubes (CNTs) have proved to be an efficient additive to polymers and matrices of composites with respect to structural enhancement and improvement of the electrical properties. The induction of CNTs increases the conductivity of the matrix, transforming it to an antistatic or a conducting phase. The key issue of the structural and electrical properties optimization is the dispersion quality of the nano-scale in the polymer phase. Well dispersed CNTs provide an electrical network within the insulating matrix. If the fibers are conductive, the CNT network mediates the electrical anisotropy and reduces the critical flaw size that is detectable by the change in conductivity. Thus, the network performs as an inherent sensor in the composite structure, since every invisible crack or delamination is manifested as an increase in the electrical resistance. The scope of this work is to further exploit the information provided by the electrical properties with a view to identify strain variation and global damage via bulk resistance measurements. The aforementioned techniques were employed to monitor, strain and damage in fiber reinforced composite laminates both with and without conductive nanofillers.

Grammatikos, S. A.; Gkikas, G.; Paipetis, A.

2011-04-01

219

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

220

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

221

Simultaneous electrical resistivity and mass uptake measurements in bromine intercalated fibers  

NASA Technical Reports Server (NTRS)

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.

Jaworske, D. A.

1986-01-01

222

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

PubMed

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

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

2014-08-01

223

Transcriptional Profiles Uncover Aspergillus flavus-Induced Resistance in Maize Kernels  

PubMed Central

Aflatoxin contamination caused by the opportunistic pathogen A. flavus is a major concern in maize production prior to harvest and through storage. Previous studies have highlighted the constitutive production of proteins involved in maize kernel resistance against A. flavus’ infection. However, little is known about induced resistance nor about defense gene expression and regulation in kernels. In this study, maize oligonucleotide arrays and a pair of closely-related maize lines varying in aflatoxin accumulation were used to reveal the gene expression network in imbibed mature kernels in response to A. flavus’ challenge. Inoculated kernels were incubated 72 h via the laboratory-based Kernel Screening Assay (KSA), which highlights kernel responses to fungal challenge. Gene expression profiling detected 6955 genes in resistant and 6565 genes in susceptible controls; 214 genes induced in resistant and 2159 genes induced in susceptible inoculated kernels. Defense related and regulation related genes were identified in both treatments. Comparisons between the resistant and susceptible lines indicate differences in the gene expression network which may enhance our understanding of the maize-A. flavus interaction. PMID:22069739

Luo, Meng; Brown, Robert L.; Chen, Zhi-Yuan; Menkir, Abebe; Yu, Jiujiang; Bhatnagar, Deepak

2011-01-01

224

The Emerging Profile of Cross-Resistance among the Nonnucleoside HIV-1 Reverse Transcriptase Inhibitors  

PubMed Central

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are widely used to treat HIV-1-infected individuals; indeed most first-line antiretroviral therapies typically include one NNRTI in combination with two nucleoside analogs. In 2008, the next-generation NNRTI etravirine was approved for the treatment of HIV-infected antiretroviral therapy-experienced individuals, including those with prior NNRTI exposure. NNRTIs are also increasingly being included in strategies to prevent HIV-1 infection. For example: (1) nevirapine is used to prevent mother-to-child transmission; (2) the ASPIRE (MTN 020) study will test whether a vaginal ring containing dapivirine can prevent HIV-1 infection in women; (3) a microbicide gel formulation containing the urea-PETT derivative MIV-150 is in a phase I study to evaluate safety, pharmacokinetics, pharmacodynamics and acceptability; and (4) a long acting rilpivirine formulation is under-development for pre-exposure prophylaxis. Given their widespread use, particularly in resource-limited settings, as well as their low genetic barriers to resistance, there are concerns about overlapping resistance between the different NNRTIs. Consequently, a better understanding of the resistance and cross-resistance profiles among the NNRTI class is important for predicting response to treatment, and surveillance of transmitted drug-resistance. PMID:25089538

Sluis-Cremer, Nicolas

2014-01-01

225

Young Men’s Condom Use Resistance Tactics: A Latent Profile Analysis  

PubMed Central

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

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

2013-01-01

226

Antibiotic susceptibility profile of Haemophilus influenzae and transfer of co-trimoxazole resistance determinants.  

PubMed

Prior to the implementation of Haemophilus influenzae type b vaccination worldwide, H. influenzae has been one of the main causative agents of community acquired pneumonia and meningitis in children. Due to the lack of information on the characteristics of the H. influenzae isolates that have previously been collected in Malaysia, the H. influenzae were assessed of their microbial susceptibility to commonly used antibiotics. Emphasis was made on strains that were resistance to co-trimoxazole (SXT) and their mode of transfer of the antibiotic resistance determinants were examined. A collection of 34 H. influenzae isolates was serotyped and antimicrobial susceptibility tests were performed to 11 antibiotics. To the isolates that were found to be resistant to co-trimoxazole, minimum inhibition concentration (MIC) to SXT was performed using Etest while agar dilution method was used to measure the individual MICs of trimethoprim (TMP) and sulfamethoxazole (SUL). These isolates were also examined for presence of plasmid by PCR and isolation method. Conjugal transfers of SXT-resistant genes to SXT-susceptible hosts were performed to determine their rate of transfer. Result showed that 20.6% of the total number of isolates was serotype B while the remaining was non-typeable. Antimicrobial susceptibility profile of all the isolates revealed that 58.8% was resistant to at least one antibiotic. Majority of these isolates were equally resistant to ampicillin and tetracycline (29.4% each), followed by resistance to SXT (26.5%). From nine isolates that were found to be SXT-resistant, five contained plasmid/s. Conjugal transfer experiment showed that these five isolates with plasmid transferred SXT-resistance determinants at a higher frequency than those without. From these observations, it is postulated that plasmid is not involved in the transfer of SXT-resistance genes but presence of plasmid facilitates their transfer. The information obtained from this study provides some basic knowledge on the antimicrobial susceptibility pattern of the H. influenzae isolates and their mode of transfer of SXT-resistance genes. PMID:23018500

Mohd-Zain, Z; Kamsani, N H; Ismail, I S; Ahmad, N

2012-09-01

227

Digital photogrammetric analysis and electrical resistivity tomography for investigating the Picerno landslide (Basilicata region, southern Italy)  

NASA Astrophysics Data System (ADS)

Digital photogrammetric analysis and Electrical Resistivity Tomography (ERT) techniques were applied to evaluate the volume of material involved in a complex roto-translational slide occurred in the territory of Picerno (Basilicata region, southern Italy). Analytical and digital photogrammetric techniques facilitated a multi-temporal analysis of aerial photos for the years 1997, 2004 and 2006. In order to identify different geomorphologic features (scarps, terraces and trenches) of the landslide and their development, the analytical and digital photo interpretation was performed at the maximum scale of 1:5000. Geological and geomorphological surveys were carried out to verify photo-interpretation results. Digital Elevation Models (DEMs) for 1997, 2004 and 2006 were produced by applying the Grid Adaptive method. The differential DEMs (2006-1997; 2006-2004; 2004-1997) for the most dangerous part of the landslide allowed us to recognize the areas affected either by deposition or erosion and also estimate any altitudinal changes in each geomorphologic unit. To detect the sliding surface and estimate the thickness of the sliding material, several transversal and longitudinal ERT profiles were obtained. The electrical images of subsurface supported by stratigraphical data from boreholes were integrated with the information from the DEMs. The altitudinal changes and the sizes of the source and accumulation areas allowed us to estimate the volume of material involved in the mass movement. The fusion of data from different sensors allows us to gather indications on the surface and subsurface characteristics of the landslide providing useful information for landslide mitigation activities. Such an approach can help both to improve our knowledge and overcome the drawbacks of each methodology.

de Bari, Claudia; Lapenna, Vincenzo; Perrone, Angela; Puglisi, Claudio; Sdao, Francesco

2011-10-01

228

[Antibiotic resistance profiles of Acinetobacter species isolated from several clinical samples between 2007-2010].  

PubMed

This study was aimed to investigate the changes in antibiotic resistance profiles of Acinetobacter spp. in our hospital during a four-year period. The study included a total of 465 non-duplicate Acinetobacter spp. isolated from various samples sent from intensive care (n= 274, 58.9%), inpatient (n= 141, 30.3%) and outpatient (n= 49, 10.5%) units of our hospital between 2007 and 2010. Sample distribution was as follows: 184 tracheal aspirates (39.5%), 70 blood (15.3%), 92 (19.8%) wound, 40 urine (8.6%), 24 sputum (5.1%), 22 (4.7%) bronchial lavage and 22 (4.7%) other (catheter tip, cerebrospinal fluid, thorasynthesis material) samples. The isolates were identified as A.baumannii (n= 340, 73.1%), A.lwoffii (n= 64, 13.7%) and Acinetobacter spp. (n= 61, 13.1%). The susceptibility profiles were investigated by Kirby-Bauer disc diffusion method. Overall, the results indicated an increase in resistance against all tested drugs since 2007. A steady increase of resistance from 2007 to 2009, followed by a tendency to decrease in 2010 was also noted for all drugs, except for ceftazidime (CAZ), trimethoprim-sulfomethoxazole (SXT), netilmicin (NET), imipenem (IPM), meropenem (MER) and gentamicin (CN). NET, IPM, cefepime and MER resistance rates increased regularly from 2007 to 2010. CAZ resistance followed a fluctuating course, while CN resistance displayed a decreasing trend since 2009. According to the statistical analyses (X2 and Fisher?s exact test), there was a regular resistance increase between 2007-2009 except for amikacin (AK), SXT and PIP. Resistance rates were also increased for AK and PIP, but only between 2007 and 2009; as well as for piperacillin-tazobactam, ticarcilin-clavulanate, NET, MER and IPM between 2008 and 2009. A significant increase from 2008 to 2010 was observed for NET; and a significant resistance decrease in 2010 was noted for only sultamicillin, cefotaxime, CN and tobramycin (TOB) (p< 0.05). As of 2010, the results indicated high resistance rates against ciprofloxacin [resistance rate (RR): 79%], NET (RR: 60%) and all beta-lactam drugs, including carbapenems (mean RR: 80%). Moreover, there was a progressive increase in resistance to carbapenems and NET, two very important treatment alternatives. Tigecycline (RR: 5.5%), TOB (RR: 19%), CN (RR: 34%) and cefoperazone-sulbactam (RR: 38%) appeared to remain as relatively effective treatment choices. The resistance rates of inpatient and outpatient isolates which were usually lower than those of the intensive care unit isolates, also displayed a noteworthy increase over the past four years. Evidently, pan-resistant Acinetobacter spp. will become a serious health problem in the near future, unless efficient and appropriate precautions are taken. PMID:21935786

Ozdem, Birsen; Gürelik, Feryal C; Celikbilek, Nevreste; Bal?kç?, Hilal; Aç?kgöz, Ziya Cibali

2011-07-01

229

Non-homogeneous extracellular resistivity affects the current-source density profiles of up–down state oscillations  

PubMed Central

Rhythmic local field potential (LFP) oscillations observed during deep sleep are the result of synchronized electrical activities of large neuronal ensembles, which consist of alternating periods of activity and silence, termed ‘up’ and ‘down’ states, respectively. Current-source density (CSD) analysis indicates that the up states of these slow oscillations are associated with current sources in superficial cortical layers and sinks in deep layers, while the down states display the opposite pattern of source–sink distribution. We show here that a network model of up and down states displays this CSD profile only if a frequency-filtering extracellular medium is assumed. When frequency filtering was modelled as inhomogeneous conductivity, this simple model had considerably more power in slow frequencies, resulting in significant differences in LFP and CSD profiles compared with the constant-resistivity model. These results suggest that the frequency-filtering properties of extracellular media may have important consequences for the interpretation of the results of CSD analysis. PMID:21893529

Bazhenov, Maxim; Lonjers, Peter; Skorheim, Steven; Bedard, Claude; Dstexhe, Alain

2011-01-01

230

Non-homogeneous extracellular resistivity affects the current-source density profiles of up-down state oscillations.  

PubMed

Rhythmic local field potential (LFP) oscillations observed during deep sleep are the result of synchronized electrical activities of large neuronal ensembles, which consist of alternating periods of activity and silence, termed 'up' and 'down' states, respectively. Current-source density (CSD) analysis indicates that the up states of these slow oscillations are associated with current sources in superficial cortical layers and sinks in deep layers, while the down states display the opposite pattern of source-sink distribution. We show here that a network model of up and down states displays this CSD profile only if a frequency-filtering extracellular medium is assumed. When frequency filtering was modelled as inhomogeneous conductivity, this simple model had considerably more power in slow frequencies, resulting in significant differences in LFP and CSD profiles compared with the constant-resistivity model. These results suggest that the frequency-filtering properties of extracellular media may have important consequences for the interpretation of the results of CSD analysis. PMID:21893529

Bazhenov, Maxim; Lonjers, Peter; Skorheim, Steven; Bedard, Claude; Dstexhe, Alain

2011-10-13

231

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

NASA Astrophysics Data System (ADS)

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 apparent resistivity, from the surface to 0.5 m, 1 m and 1.7 m depth respectively. Soil sampling at 0.1-0.3 m and 0.5-0.7 m was carried out with hand auger on a regular grid sampling scheme (35-40 m per 20 m). Soil samples were analysed for moisture, particle size, and electrical conductivity in water. The spatial viticultural behaviour was appreciated in both vineyards through image analysis of aerial photographs and, in vineyard 2, by means of a grape sampling and analysis of the must at harvest. The vines chosen for the sampling were selected according to the results of the geoelectrical survey. Results and discussion Laboratory analysis showed that the most frequent texture class in both vineyards was clay loam, followed by clay. ER spatial variability however was different in the two vineyards. In vineyard 1, the occurrence of low ER values at 0-0.5 and 0-1 m depths correlated with the presence of clayey and saline soil horizons. In vineyard 2, only ER at 0-1 m depth correlated with clay and soil water content. In vineyard 1, the relationship between ER and clay content allowed the evaluation of the loss of accuracy caused by the reduction of the number of analysed soil samples. Passing from the initial 51 samples, to 25, 12, and 6, the accuracy in clay prediction passed from 100% to 79.4, 79.1, and 74%, respectively. The reduction of accuracy of ER prediction at less intense surveys, was limited, in spite of the relatively high soil variability. In fact, doubling the distance between the passages of the machinery between the vine rows, the accuracy of ER prediction was still of 74%, and even widening it at 24 m, from the initial 6 m, the accuracy remained 64%. The density of vegetation in vineyard 1 was positively correlated with ER, while it was inverse in vineyard 2. The opposite behaviour was due to the soil salinity of vineyard 1, which inversely correlated with ER and vegetation vigour. In vineyard 2, on the other hand, the lack of soil salinity enhanced the relationship between vine vigour and water content. In the same vineyard, the sugar content of

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

2009-04-01

232

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

NASA Astrophysics Data System (ADS)

The extreme rainfall events and the quick snowmelt occurrences play an important role in the triggering of the landslides. The occurrence of one of these factors can determine the variation of water content in the first layers of the subsoil and as a consequence a quick soil saturation inducing both an increase in pore-water pressures and the overloaded of the slopes progressively collapsing. The electrical resistivity, self-potential, electromagnetic induction and GPR methods can be considered as the most appropriate for assessing the presence of water in the underground. Such methods allow us to study the behavior of water content over much wider and deeper areas than those offered by traditional methods (thermo-gravimetric, tensiometric, TDR, etc) based on spot measures and concerning small volumes. In particular, the Electrical Resistivity Tomography (ERT), which has already proved to be a powerful tool both for the geometrical reconstruction of a landslide body (location of sliding surface, estimation of the thickness of the slide material) and the individuation of high water content areas, can be considered as an alternative tool to be employed for a qualitative and quantitative water content monitoring in the first layers of the subsoil. Indeed, time-lapse 2D ERT can be tested in order to gather information on the temporal and spatial patterns of water infiltration processes and water content variation. This work reports the preliminary results from a new prototype system planned to obtain time-lapse 2D ERTs, TDR and precipitation measurements in two landslide areas located in the Southern Apennine chain (Italy). The system was planned with the aim to estimate the variation of the resistivity parameter on a long period considering the water content variation, the rain water infiltration and the seasonal changes. The prototype system, linked to a pc used for storing data and managing the time interval acquisition, consists of: a resistivimeter connected to a 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.

Perrone, A.

2011-12-01

233

Impact of terminal dimethylation on the resistance profile of ?-N-heterocyclic thiosemicarbazones  

PubMed Central

Triapine is an ?-N-heterocyclic thiosemicarbazone with promising anticancer activity against hematologic malignancies but widely ineffective against solid tumor types in clinical trials. The anticancer activity of thiosemicarbazones can be dramatically increased by terminal dimethylation. KP1089 is a gallium compound containing two terminal dimethylated thiosemicarbazone ligands. To gain insights on the vulnerability of this highly active terminal dimethylated thiosemicarbazone to drug resistance mechanisms, a new cell model with acquired resistance against the lead compound KP1089 was established. Subsequent genomic analyses (arrayCGH and FISH) revealed amplification of the ABCC1 gene on double minute chromosomal DNA in KP1089-resistant cells as well as overexpression of ABCC1 and ABCG2 on the protein level. KP1089 was further confirmed as a substrate of ABCC1 and ABCG2 but not of ABCB1 using a panel of ABC transporter-overexpressing cell models as well as ABC transporter inhibitors. Moreover, glutathione depletion strongly enhanced KP1089 activity, although no glutathione conjugate formation by glutathione-S-transferase was observed. Thus, a co-transport of KP1089 together with glutathione is suggested. Finally, a panel of thiosemicarbazone derivatives was tested on the new KP1089-resistant cell line. Notably, KP1089-resistant cells were not cross-resistant against thiosemicarbazones lacking terminal dimethylation (e.g. Triapine) which are less active than KP1089. This suggests that terminal dimethylation of thiosemicarbazones – linked with distinctly enhanced anticancer activity – leads to altered resistance profiles compared to classical thiosemicarbazones making this compound class of interest for further (pre)clinical evaluation. PMID:22426010

Heffeter, Petra; Pirker, Christine; Kowol, Christian R.; Herrman, Gerrit; Dornetshuber, Rita; Miklos, Walter; Jungwirth, Ute; Koellensperger, Gunda; Keppler, Bernhard K.; Berger, Walter

2012-01-01

234

Module Three: Resistance; Basic Electricity and Electronics Individualized Learning System.  

ERIC Educational Resources Information Center

In this module the student will learn of the opposition offered to electron flow, what this opposition does, why it is needed, and how it is used. The module is divided into four lessons: characteristics of resistance, resistors, resistor values, and ohmmeters. Each lesson consists of an overview, a list of study resources, lesson narratives,…

Bureau of Naval Personnel, Washington, DC.

235

Grounding resistance for control of static electricity ignition hazards  

Microsoft Academic Search

The flow of hydrocarbon product in pipes generates static electricity at density levels that may be sufficient to cause sparks and ignition when product is delivered to a tank. This paper describes the formulation of a method that can be used to control such electrostatic ignition hazards during tank filling operations. The grounding current for a grounded metallic tank being

Etim S. Udoetok; Anh N. Nguyen

2011-01-01

236

Comparison of HIV-1 drug resistance profiles generated from novel software applications for routine patient care  

PubMed Central

Introduction Clinical laboratories performing routine HIV-1 genotyping antiviral drug resistance (DR) testing need reliable and up-to-date information systems to provide accurate and timely test results to optimize antiretroviral treatment in HIV-1-infected patients. Materials and Methods Three software applications were used to compare DR profiles generated from the analysis of HIV-1 protease (PR) and reverse transcriptase (RT) gene sequences obtained by Sanger sequencing assay in 100 selected clinical plasma samples from March 2013 through May 2014. Interpretative results obtained from the Trugene HIV-1 Genotyping assay (TG; Guidelines v17.0) were compared with a newly FDA-registered data processing module (DPM v1.0) and the research-use-only ViroScore-HIV (VS) software, both of which use the latest versions of Stanford HIVdb (SD v7.0) and geno2pheno (G2P v3.3) interpretive algorithms (IA). Differences among the DR interpretive algorithms were compared according to drug class (NRTI, NNRTI, PI) and each drug. HIV-1 tropism and integrase inhibitor resistance were not evaluated (not available in TG). Results Overall, only 17 of the 100 TG sequences obtained yielded equivalent DR profiles among all 3 software applications for every IA and for all drug classes. DPM and VS generated equivalent results with >99.9% agreement. Excluding AZT, DDI, D4T and rilpivirine (not available in G2P), ranges of agreement in DR profiles among the three IA (using the DPM) are shown in Table 1. Conclusions Substantial discrepancies (<75% agreement) exist among the three interpretive algorithms for ETR, while G2P differed from TG and SD for resistance to TDF and TPV/r. Use of more than one DR interpretive algorithm using well-validated software applications, such as DPM v1.0 and VS, would enable clinical laboratories to provide clinically useful and accurate DR results for patient care needs. PMID:25397496

Gonzalez, Dimitri; Digmann, Benjamin; Barralon, Matthieu; Boulme, Ronan; Sayada, Chalom; Yao, Joseph

2014-01-01

237

[Characterization of Alcaligenes species using analysis of esterase electrophoretic polymorphism and analysis of antibiotic resistance profiles].  

PubMed

The species of an Alcaligenes bacterial strain may be difficult to determine on the basis of conventional phenotype features. Esterase pattern analysis using acrylamide-agar gel electrophoresis and determination of the antimicrobial resistance profile (agar diffusion method) were performed for A. faecalis (34 strains). A. denitrificans subsp xylosoxydans (16 strains) and A. piechaudi (5 strains). The Cistat program (D2 Software) was used for statistical representation of results. The homogeneous, species-specific esterase patterns ensured correct assignment of each strain to one of the three species. Antimicrobial susceptibility was greatest for A. faecalis which was susceptible to both cephalosporins of all generations and aminoglycosides. A. xylosoxydans was the species with the greatest resistance to antimicrobials. A. piechaudii exhibited intermediate susceptibility. PMID:1495848

Bizet, C; Picard, B; Philippon, A; Goullet, P

1992-05-01

238

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

SciTech Connect

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.

Miccio, Luis A. [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), JB. Justo 4302, Mar del Plata, Buenos Aires (Argentina); Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Kummali, Mohammed M.; Alegria, Angel [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, 20080 San Sebastian (Spain); Montemartini, Pablo E.; Oyanguren, Patricia A. [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), JB. Justo 4302, Mar del Plata, Buenos Aires (Argentina); Schwartz, Gustavo A. [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Colmenero, Juan [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, 20080 San Sebastian (Spain); Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain)

2011-08-14

239

Electrical Resistivity of Silane Multiply Shock-Compressed to 106 GPa  

NASA Astrophysics Data System (ADS)

The liquid silane sample, prepared by liquifying pure silane gas at 88.5 K, is multiply shock-compressed to 106 GPa by means of a two-stage light-gas gun and a coolant target system. Electrical resistivity is measured for fluid silane during the period of multi-shock compression in the pressure range from 63.5 GPa to 106 GPa. It is shown that the electrical resistivity reduces to the order of 10?3–10?4 ohm·m after the second shock arrived, which is two orders higher than those of typical melt metals. Though the metallization transition could not be confirmed under the loading condition of our shock experiments, its resistivity drops sharply along with the pressure rise. The phenomenon might be caused by silane decomposed during the pressure loading, due to the fact that, above 100 GPa, we find that its resistivity is close to hydrogen under the same pressure.

Zhong, Xiao-Feng; Liu, Fu-Sheng; Cai, Ling-Cang; Xi, Feng; Zhang, Ming-Jian; Liu, Qi-Jun; Wang, Ya-Ping; Hao, Bin-Bin

2014-12-01

240

Electrical contact resistance of a thin oxide layer with a low mechanical load  

NASA Astrophysics Data System (ADS)

The electrical contact resistance of a vertical binary contact between stainless steel balls with a low mechanical load was investigated. Using a statistical approach, we measured the voltage at which the dielectric breakdown occurs within a thin surface oxide layer and the distribution of the contact resistance. Electrical load-bearing conduction through a thin insulating layer was found to occur through two possible sequential processes. In both cases, once a conduction path is formed, the melting of bridges as in conventional contact theory is involved. This suggests that conduction through an oxide layer with a low mechanical load depends mainly on breakdown-induced bridges. Furthermore, the distribution of such path's resistance shows the log-normal distribution with a long tail toward high resistance.

Kim, Sang-Kuk; Kwak, Han; Lee, Jongjin; Yu, Insuk

2013-12-01

241

Metagenomic Profiling of Microbial Composition and Antibiotic Resistance Determinants in Puget Sound  

PubMed Central

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 ?-Proteobacteria (in particular Rhodobacterales sp.), ?-Proteobacteria and Bacteroidetes while the marina and effluent had increased abundances of Actinobacteria, ?-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 initial public health monitoring as well as more targeted and functionally-based investigations. PMID:23144718

Port, Jesse A.; Wallace, James C.; Griffith, William C.; Faustman, Elaine M.

2012-01-01

242

Procedure for contact electrical resistance measurements as developed for use at Sandia National Laboratories  

SciTech Connect

Military Specifications call out general procedures and guidelines for conducting contact resistance measurements on chemical conversion coated panels. This paper deals with a test procedure developed at Sandia National Laboratories used to conduct contact electrical resistance on non-chromated conversion coated test panels. MIL-C-81706 {open_quotes}Chemical Conversion Materials For Coating Aluminum and Aluminum Alloys{close_quotes} was the reference specification used for guidance.

Finch, J.L.

1994-06-01

243

Electrical Resistivity Characterization of a Reclaimed Gold Mine to Delineate Acid Rock Drainage Pathways  

Microsoft Academic Search

An electrical resistivity survey was completed at the Landusky mine. The survey consisted of 15 lines on the surface of the\\u000a reclaimed Suprise pit, Queen Rose pit, and the region immediately south of Swift Gulch. Additionally, wells and seeps were\\u000a used by energizing electrodes in direct contact with ground water to increase the sensitivity of the resistivity method at\\u000a depth.

Dale F. Rucker; Danney R. Glaser; Tom Osborne; William C. Maehl

2009-01-01

244

Electrical resistivity of ultrafine-grained copper with nanoscale growth twins  

NASA Astrophysics Data System (ADS)

We have investigated electrical resistivities of high-purity ultrafine-grained Cu containing different concentrations of nanoscale growth twins, but having identical grain size. The samples were synthesized by pulsed electrodeposition, wherein the density of twins was varied systematically by adjusting the processing parameters. The electrical resistivity of the Cu specimen with a twin spacing of 15nm at room temperature (RT) is 1.75??cm (the conductivity is about 97% IACS), which is comparable to that of coarse-grained (CG) pure Cu specimen. A reduction in twin density for the same grain size (with twin lamellar spacings of 35 and 90nm, respectively) results in an increment in electrical resistivity from 1.75to2.12??cm. However, the temperature coefficient of resistivity at RT for these Cu specimens is insensitive to the twin spacing and shows a consistent value of ˜3.78×10-3/K, which is slightly smaller than that of CG Cu (3.98×10-3/K). The increased electrical resistivities of the Cu samples were ascribed dominantly to the intrinsic grain boundary (GB) scattering, while the GB defects and GB energy would decrease with increasing twin density. Transmission electron microscope observations revealed the GB configuration difference from the Cu samples with various twin densities. Plastic deformation would induce an apparent increase in the resistivity. The higher of the twin density, the higher increment of RT resistivity was detected in the Cu specimens subjected to 40% rolling strain. Both the deviated twin boundaries and strained GBs may give rise to an increase in the resistivity.

Chen, X. H.; Lu, L.; Lu, K.

2007-10-01

245

Saline tracer visualized with three-dimensional electrical resistivity tomography: Field-scale spatial moment analysis  

Microsoft Academic Search

Cross-well electrical resistivity tomography (ERT) was used to monitor the migration of a saline tracer in a two-well pumping-injection experiment conducted at the Massachusetts Military Reservation in Cape Cod, Massachusetts. After injecting 2200 mg\\/L of sodium chloride for 9 hours, ERT data sets were collected from four wells every 6 hours for 20 days. More than 180,000 resistance measurements were

Kamini Singha; Steven M. Gorelick

2005-01-01

246

Electrical resistivity of iron-silicon alloys under high pressure and temperature  

NASA Astrophysics Data System (ADS)

Very recent experiments and calculations of electrical resistivity of the Earth's core (Gomi et al. 2011; de Koker et al. 2012; Pozzo et al. 2013) suggest the thermal conductivity of the outer core to be a factor of 2-3 higher than previous estimates. This renews interest and calls for electrical conductivity measurements on iron and iron alloys in order to better understand core heat flow. Considering silicon as a strong candidate for a light alloying element in the Earth's core, electrical resistivity measurements on iron silicon alloys up to 17wt% silicon have been carried out at pressure up to 5 GPa and at temperatures beyond melting in a 1000 ton cubic anvil press. These findings show that in contrast to the electrical resistivity behavior of pure iron, iron-silicon alloys of ~ 17 wt% silicon undergo a drop in resistivity at the melting temperature. The application of these results on iron silicon alloys to the thermal conductivity of the outer core is based on the tendency for resistivity to saturate at very high temperatures. By using the Wiedemann-Franz law, we compare our results with the recent high thermal conductivity estimates of the Earth's core.

Kiarasi, S.; Secco, R.

2013-12-01

247

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

NASA Astrophysics Data System (ADS)

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 ?, ? and ? 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.

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

2013-12-01

248

Electrical resistivity of high energy density matter generated by high intensity heavy ion beams  

NASA Astrophysics Data System (ADS)

Development of new diagnostic techniques allowed, during the past few years, for a first series of measurements on the electrical resistivity of heavy ion beam generated high energy density (HED) matter. The experimental investigations have been carried out at the HHT laboratory of the Plasma Physics Department of the Gesellschaft für Schwerionenforschung in Darmstadt. In this report we review the results of these experiments and discuss future experimental and theoretical work planned to be carried out within the framework of the HEDgeHOB collaboration for precise determination of the electrical resistivity of HED matter.

Udrea, S.; Shilkin, N.; Varentsov, D.; Tahir, N. A.; Bock, R.; Constantin, C.; Dewald, E.; Fortov, V. E.; Hoffmann, D. H. H.; Jacoby, J.; Kulish, M.; Lomonosov, I.; Mintsev, V.; Ni, P.; Nikolaev, D.; Shutov, A.

2006-06-01

249

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

NASA Technical Reports Server (NTRS)

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.

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

1971-01-01

250

Electrical resistivity investigations at Memphis, and Bolivar, Tennessee  

USGS Publications Warehouse

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.

Spicer, H. Cecil

1948-01-01

251

Pb-17Li-bismuth interactions: an electrical resistivity study  

NASA Astrophysics Data System (ADS)

The reaction of bismuth with Pb-Li alloys has been studied using resistivity-composition and resistance — temperature measurements to monitor the lithium content of the alloy. The process follows a solution — precipitation mechanism. The solubility of bismuth was found to be 1.5 × 10 -1 mol% (1800 wppm) in Pb-17.04Li (i.e., a Pb-Li alloy containing 17.04 mol% Li) at 723 K and 1.4 × 10 -1 mol% (1800 wppm) in Pb-22.13Li at 673 K. The Li:Bi ratio in the solid product was found to be 3.07 for Pb-17.04Li, 3.21 for Pb-22.13Li and 3.28 for Pb-17.16Li, indicating Li 3Bi formation. These observations are interpreted using a phase diagram developed for the Pb-Bi-Li ternary system from the phase relationships in the constituent binary systems. It is dominated by the precipitation field for Li 3Bi which extends from the Bi-Li side almost as far as the Pb-Li side. The dominance of Li 3Bi is attributed to its extreme stability as evidenced by both its high melting point (1418 K) and free energy of formation ( ?fG°( Li3Bi, c, 723 K) = -212.8 kJ mol -1).

Hubberstey, Peter; Sample, Tony; Capaldi, Michael J.; Barker, Marten G.

1994-11-01

252

Assessment of Continuous Resistivity Profiling for the Characterization of Paved Roads  

NASA Astrophysics Data System (ADS)

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, France), a capacitively-coupled resistivity towed equatorial array that continuously record data collected with six receiver dipoles and one transmitter dipole. Typical acquisition sampling and velocity were 0,20-0,50 m and 1 to 2 km/h respectively. Although the system is not optimally designed for the applications described above it provides useful diagnostic information about the state of deterioration of pavement. Data have been imaged using 2D resistivity inversion. In general it shows a high resistivity for the shallow depth related to the asphalt layer and a decreasing resistivity with depth related to the concrete slab first and the granular foundation below. Lateral variations appear to be correlated with degradation of the concrete slab.

Chouteau, M.; Vallieres, S.; Miralles, M.

2004-05-01

253

Parallel electric fields in extragalactic jets - Double layers and anomalous resistivity in symbiotic relationships  

NASA Technical Reports Server (NTRS)

After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves.

Borovsky, J. E.

1986-01-01

254

Mechanical flexible and electric fatigue resistant behavior of relaxor ferroelectric terpolymer  

NASA Astrophysics Data System (ADS)

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.

Fang, Fei; Yang, Wei; Yang, Wen

2009-08-01

255

Temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys  

NASA Astrophysics Data System (ADS)

The temperature dependence of the electrical resistivity of amorphous Co 80-xEr xB 20 alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum Tmin. In addition, the resistivity shows quadratic temperature behavior in the interval Tmin< T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity ? shows a change in structural short range occurring in the composition range 8-9 at%.

Touraghe, O.; Khatami, M.; Menny, A.; Lassri, H.; Nouneh, K.

2008-06-01

256

Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag  

PubMed Central

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???·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

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

257

A study of the deposition of carbide coatings on graphite fibers. [to increase electrical resistance  

NASA Technical Reports Server (NTRS)

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.

Suplinskas, R. J.; Henze, T. W.

1979-01-01

258

Application of resistivity image profiling method and laser scanning to monitor landside  

NASA Astrophysics Data System (ADS)

Taiwan, located at the Western Pacific, bears the threats from both typhoons and earthquakes. The 921 earthquake resulted in the unstable ground so that typhoons or torrential rain could cause serious disasters. Currently, the hazard mitigation is the target of the authorities. However, using the traditional approaches not only wastes a lot of time but also is ineffectively. The deformation of slope terrain is detected by physical measured instrument traditionally. Collecting deformation data of tiltmeter and piezometer inner well drilling. A few of wells are limited by terrain and cost. The wells can not cover all landslide area. The results of analysis data are debated. The collapse slope once has more probabilistic collapse. Particularly designing engineering against natural calamities with debated conclusion and the rebuilt slope will be instable. This paper demonstrates the possibility of using resistivity image profiling method (RIP) and 3d laser scanning to monitor a landside at No.3 freeway of 85 km in Taiwan. The slope was rebuilt by grid-beam engineering, spraying concrete engineering and cut-slope engineering. The first, exploring underground substance by resistivity image profiling method . To obtain the destructive sliding position of slope, the range of slope with the same sliding position and groundwater data. Time-lapse RIP sections for different time period also indicate that the obvious resistivity change zones were limited under a strongest topography change surface.Fitting 3d laser scanner on suitable site for scanning research target. To analyze overlay scanning data by correcting the cloud-points with the different periods. The study utilizes the 3d scanning technology and geoelectric resistivity technology to obtain analysis information of slope probability and terrain deformation trend. The way of detecting deformation of rebuilt slope that combines RIP and 3D laser scanner is overall technology. The RIP detects the sensitive area of underground and the 3D laser scanner detects terrain surface of slope. Especial collecting the data by period observation. The data can provide the trend of rebuilt slope creeping and the policy decision of remaking engineering. Keyword¡Gresistivity image profiling ,3d laser scanning,landslide

Liu, H.; Yang, C.

2007-12-01

259

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)

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.

Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.

2011-01-01

260

Online Monitoring of the Electrical Power Transfer Stability and Voltage Profile Stability Margins in Electric Power Transmission Systems Using Phasor Measurement Units Data Sets  

Microsoft Academic Search

An innovative method to monitor the electric power transfer stability on power transmission paths and the voltage profile stability at the power systems nodes in real time modus is proposed. Based on the laws of electric circuit theory, the transfer operating mode of each relevant transmission line is formulated in an active power-voltage PV characteristic. The relevant transmission line parameters

Yves Nguegan; Albert Claudi; Carsten Strunge

2009-01-01

261

Metabolic Profiling for Detection of Staphylococcus aureus Infection and Antibiotic Resistance  

PubMed Central

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 proof of concept of the utility of analyzing metabolite patterns in blood for early differentiation between ineffective and effective antibiotic treatment in acute S. aureus infections. PMID:23451124

Näsström, Elin; Kouremenos, Konstantinos; Sundén-Cullberg, Jonas; Guo, YongZhi; Moritz, Thomas; Wolf-Watz, Hans; Johansson, Anders; Fallman, Maria

2013-01-01

262

Insulin resistance, adipokine profile and hepatic expression of SOCS-3 gene in chronic hepatitis C  

PubMed Central

AIM: To analyze adipokine concentrations, insulin resistance and hepatic expression of suppressor of cytokine signaling 3 (SOCS-3) in patients with chronic hepatitis C genotype 1 with normal body weight, glucose and lipid profile. METHODS: The study group consisted of 31 patients with chronic hepatitis C and 9 healthy subjects. Total levels of adiponectin, leptin, resistin, visfatin, omentin, osteopontin and insulin were measured using an ELISA kit. The hepatic expression of SOCS-3 was determined by the use of the reverse transcription polymerase chain reaction method. RESULTS: Homeostasis model assessment for insulin resistance (HOMA-IR) values were significantly higher in hepatitis C virus (HCV) infected patients without metabolic disorders compared to healthy controls (2.24 vs 0.59, P = 0.0003). Hepatic steatosis was observed in 32.2% of patients with HCV infection and was found in patients with increased HOMA-IR index (2.81 vs 1.99, P = 0.05) and reduced adiponectin level (5.96 vs 8.37, P = 0.04). Inflammatory activity (G ? 2) was related to increased osteopontin concentration (34.04 vs 23.35, P = 0.03). Advanced liver fibrosis (S ? 2) was associated with increased levels of omentin and osteopontin (436.94 vs 360.09, P = 0.03 and 32.84 vs 20.29, P = 0.03) and reduced resistin concentration (1.40 vs 1.74, P = 0.047). No correlations were reported between adipokine profile, HOMA-IR values and hepatic expression of the SOCS-3 gene. CONCLUSION: We speculated that no relationship between adipokines and HOMA-IR values may indicate that HCV can induce insulin resistance itself. Some adipokines appear to be biochemical markers of steatosis, inflammation and fibrosis in patients with chronic HCV infection. © 2014 Baishideng Publishing Group Inc. All rights reserved. PMID:25132761

Wójcik, Kamila; Jab?onowska, El?bieta; Omulecka, Aleksandra; Piekarska, Anna

2014-01-01

263

Evolution of low-profile and lightweight electrical connectors for soldier-worn applications  

NASA Astrophysics Data System (ADS)

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.

Gans, Eric; Lee, Kang; Jannson, Tomasz; Walter, Kevin

2011-06-01

264

Ion Permeability of Artificial Membranes Evaluated by Diffusion Potential and Electrical Resistance Measurements  

ERIC Educational Resources Information Center

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…

Shlyonsky, Vadim

2013-01-01

265

Corrosion properties of sputter-deposited steel thin film for electrical resistance sensor material  

Microsoft Academic Search

Steel thin films for an electrical resistance sensor were prepared by sputter deposition. It was revealed that the electrochemical properties of the thin films were influenced by the surface roughness. Using an Al2O3 substrate with high surface roughness, it was possible to obtain a steel thin film with corrosion characteristics similar to bulk steel. The corrosion rate of the thin

Sungwon Jung; SeonYeob Li; Young-Geun Kim

2006-01-01

266

High school students' understanding of resistance in simple series electric circuits  

Microsoft Academic Search

In view of the lack of work on the understanding of resistance concept, we studied the understanding that high school students (from the eighth to the twelfth grades) were able to develop with regard to the interrelationships between this concept, and the potential difference and current concepts (Ohm's law). In addition, we explored the immediate effects of exposure to electricity

Laurent Liégeois; Etienne Mullet

2002-01-01

267

Time-lapse electrical resistivity tomography applied to cave sustainability (Barbados) and groundwater exploration (Saint Lucia)  

E-print Network

In this work we apply the method of two-dimensional time-lapse electrical resistivity tomography (2D time-lapse ERT) for two different problems. In the first problem, we monitor the structural stability of the roof of the ...

Agramakova, Yulia

2011-01-01

268

Drying Kinetics of Tomato by Using Electric Resistance and Heat Pump Dryers  

Microsoft Academic Search

Drying kinetics of tomato was studied by using heat pump dryer (HPD) and electric resistance dryers with parallel and crossed airflow. The performance of both systems was evaluated and compared and the influence of temperature, air velocity, and tomato type on the drying kinetics was analyzed. The use of HPD showed to be adequate in the drying process of tomatoes,

R. Queiroz; A. L. Gabas; V. R. N. Telis

2004-01-01

269

SEASONAL VARIATION IN CAMBIAL ELECTRICAL RESISTANCE IN JUVENILE GREEN ASH FROM DIFFERENT PROVENANCES1  

Microsoft Academic Search

Electrical resistance (ER) in the cambial zone of juvenile green ash from various provenances was highly cor- related with growth rate and with certain climatic features of provenance origin. Initiation of cambial activity in the spring was related to ER but not dependent on provenance origin. Cessation of cambial activity in the fall, as indicated by ER, was significantly related

Frank S. Santamour

270

The electrical resistivity of Canada's lithosphere and correlation with other parameters: contributions from  

E-print Network

ARTICLE The electrical resistivity of Canada's lithosphere and correlation with other parameters into the lithosphere and underlying asthenosphere have been made at over 6000 sites across Canada in all provinces of Nunavut. Prior publications from individual studies have added significantly to the wealth of Canada

Jones, Alan G.

271

Remote-Controlled Electrical Resistivity Tomography and Concurrent Ground-Penetrating Radar Laboratory  

Microsoft Academic Search

A team of researchers at The University of Iowa, Ohio State University, and the University of Arizona have developed an over-the-internet experimental setup that enables researchers and educators at remote locations to make concurrent electrical resistivity tomography (ERT) and ground penetrating radar (GPR) measurements. The setup is comprised of a carefully constructed sandbox with known layers of sand with embedded

A. Kruger; J. J. Daniels; T. J. Yeh; J. Zhu; J. J. Niemeier; T. J. Mansheim; T. R. Hart; K. S. Shaelek; W. A. Illman; A. J. Craig

2008-01-01

272

The effect of alloy contents on electrical resistance accumulation of polycrystalline constantan under cycle loading  

Microsoft Academic Search

To get a good electrical resistance accumulation behavior under cycle loading, the alloy content in the polycrystalline constantan is one of the key issues. Based on the principle of the orthogonal experiment design, in the paper, 8 kinds of polycrystalline constantan foils containing different levels of alloy components were prepared using the same technology. Through a series of fatigue experiments

Wei-Xin Ren; Dan Xiao; Ge-Wei Chen

2011-01-01

273

Examination of solute transport in an undisturbed soil column using electrical resistance tomography  

Microsoft Academic Search

In an effort to determine the internal spatial characteristics of solute transport in naturally heterogeneous soils, recent applications of electrical resistance tomography to soil core tracing are reported. Using a high-speed, biomedical type data acquisition system, migration of an electrolytic tracer in an undisturbed soil column was monitored. Quantitative images produced from the collected data display an interesting sequence of

Andrew Binley; Siobhan Henry-Poulter; Ben Shaw

1996-01-01

274

Imaging and characterisation of subsurface solute transport using electrical resistivity tomography (ERT) and equivalent transport models  

Microsoft Academic Search

We assess the usefulness of electrical resistivity tomography (ERT) in imaging and characterising subsurface solute transport in heterogeneous unconfined aquifers. A field tracer experiment was conducted at the Krauthausen test site, Germany. The spatial and temporal evolution of the injected NaBr solute plume was monitored in a 2D ERT image plane located downstream of the injection well for 90 days.

Andreas Kemna; Bernd Kulessa; Harry Vereecken

2002-01-01

275

Effects of Entrapped Bubble Formation on Flow Through Porous Media During Electrical Resistance Heating  

Microsoft Academic Search

In-situ thermal remediation technologies such as electrical resistance heating (ERH) have been used effectively to treat volatile organic compounds (VOCs) in a variety of subsurface conditions. Field applications have shown significant reductions in total contaminant mass over relatively short time periods. The mechanism of these technologies is well understood; the subsurface temperature is increased to boil the groundwater and the

R. B. Thoms; R. L. Johnson

2006-01-01

276

Self-diagnosis of damage in fibrous composites using electrical resistance measurements  

Microsoft Academic Search

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in situ damage detection and sensing in carbon fiber reinforced plastic (CFRP) composite structures. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and

Ji Ho Kang; Spandana Paty; Ran Y. Kim; G. P. Tandon

2006-01-01

277

High Pressure Electrical Resistivity Study on Nonlinear Single Crystal Zinc Thiourea Chloride  

NASA Astrophysics Data System (ADS)

Zinc thiourea chloride (ZTC) crystals were crystallized by slow evaporation technique. The lattice parameters of the grown crystals were determined by angle dispersive X-ray powder diffraction technique (XRD) and the structure was confirmed. High pressure electrical resistivity study was carried out on this crystal and the results are reported here.

Ariponnammal, S.; Selva Vennila, R.; Radhika, S.; Ushasree, P. M.

278

High Pressure Electrical Resistivity Study on Nonlinear Single Crystal Zinc Thiourea Chloride  

Microsoft Academic Search

Zinc thiourea chloride (ZTC) crystals were crystallized by slow evaporation technique. The lattice parameters of the grown crystals were determined by angle dispersive X-ray powder diffraction technique (XRD) and the structure was confirmed. High pressure electrical resistivity study was carried out on this crystal and the results are reported here.

S. Ariponnammal; R. Selva Vennila; S. Radhika; P. M. Ushasree

2007-01-01

279

Electrical resistance determination of actual contact area of cold welded metal joints  

NASA Technical Reports Server (NTRS)

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.

Hordon, M. J.

1970-01-01

280

Defining electrical communication in skeletal muscle resistance arteries: a computational approach  

PubMed Central

Vascular cells communicate electrically to coordinate their activity and control tissue blood flow. To foster a quantitative understanding of this fundamental process, we developed a computational model that was structured to mimic a skeletal muscle resistance artery. Each endothelial cell and smooth muscle cell in our virtual artery was treated as the electrical equivalent of a capacitor coupled in parallel with a non-linear resistor representing ionic conductance; intercellular gap junctions were represented by ohmic resistors. Simulations revealed that the vessel wall is not a syncytium in which electrical stimuli spread equally to all constitutive cells. Indeed, electrical signals spread in a differential manner among and between endothelial cells and smooth muscle cells according to the initial stimulus. The predictions of our model agree with physiological data from the feed artery of the hamster retractor muscle. Cell orientation and coupling resistance were the principal factors that enable electrical signals to spread differentially along and between the two cell types. Our computational observations also illustrated how gap junctional coupling enables the vessel wall to filter and transform transient electrical events into sustained voltage responses. Functionally, differential electrical communication would permit discrete regions of smooth muscle activity to locally regulate blood flow and the endothelium to coordinate regional changes in tissue perfusion. PMID:16002449

Diep, Hai K; Vigmond, Edward J; Segal, Steven S; Welsh, Donald G

2005-01-01

281

2D Magnetotelluric interpretation of the crust electrical resistivity across the Pampean terrane Río de la Plata suture, in central Argentina  

NASA Astrophysics Data System (ADS)

Magnetotelluric data were obtained along a 450 km, almost west-east profile at approximately 31.5° S, which extends from La Rioja to Santa Fé provinces in central Argentina. The profile crosses two main crustal domains that were juxtaposed during the Early-Middle Cambrian Pampean Orogeny: the Pampean terrane to the west and the Río de la Plata craton to the east. The electrical resistivity structure of the crustal domains together with their boundary is presented. Through dimensionality analysis of the data, it was demonstrated that regional-scale electrical structures are mainly two-dimensional with a strike direction oriented parallel to the surface geological strike. The resistivity model shows a subvertical limit approximately along the eastern border of the Sierra Chica de Córdoba. To the east, the shallower structure is the Chaco-Paranense basin extending to a depth of 6 km with resistivities between 1 and 30 Ohm-m, whereas below the basin the ca 2.1-2.3 Ga Río de la Plata craton shows resistivities in a range of 300-10,000 Ohm-m. The Pampean terrane presents a 6 km layer with a resistivity higher than 10,000 Ohm-m whereas below this layer the resistivity values range from 50 to 200 Ohm-m. Based on both the geological information and the magnetotelluric results, the sharp lateral discontinuity observed in the resistivity model to the east of the Sierras de Córdoba is conjectured to represent the boundary between the Río de la Plata craton and the Pampean terrane which may correspond to the Early Cambrian suture.

Favetto, Alicia; Pomposiello, Cristina; López de Luchi, Mónica G.; Booker, John

2008-11-01

282

On electrical resistivity of AISI D2 steel during various stages of cryogenic treatment  

NASA Astrophysics Data System (ADS)

The effect of dislocation densities and residual stresses is well known in tool steels. Measurement of electrical resistivity in order to monitor dislocation densities or residual stresses has seldom been used in investigating the effect of cryogenic treatment on tool steels. Monitoring residual stresses during cryogenic treatment becomes important as it is directly related to changes due to cryogenic treatment of tool steels. For high carbon high chromium (HCHC- AISI D2) steels, not only wear resistance but dimensional stability is an important issue as the steels are extensively used in dies, precision measuring instruments. This work comprises of study of measurement of electrical resistivity of AISI D2 steel at various stages of cryogenic treatment. Use of these measurements in order to assess the dimensional stability of these steels is discussed in this paper.

Lomte, Sachin Vijay; Gogte, Chandrashekhar Laxman; Peshwe, Dilip

2012-06-01

283

Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers  

NASA Astrophysics Data System (ADS)

Single gap (gas gap = 2 mm) bakelite Resistive Plate Chamber (RPC) modules of various sizes from 10 cm × 10 cm to 1 m × 1 m have been fabricated, characterized and optimized for efficiency and time resolution. Thin layers of different grades of silicone compound are applied to the inner electrode surfaces to make them smooth and also to reduce the surface resistivity. In the silicone coated RPCs an efficiency ~ 96% and time resolution ~ 2 ns (FWHM) have been obtained for both the streamer and the avalanche modes of operation. Before fabrication of detectors the electrical properties such as bulk resistivity and surface resistivity of the electrode materials are measured carefully. Effectiveness of different silicone coating in modifying the surface resistivity was evaluated by an instrument developed for monitoring the I-V curve of a high resistive surface. The results indicate definite correlation of the detector efficiency for the atmospheric muons and the RPC noise rates with the surface resistivity and its variation with the applied bias voltage. It was also found that the surface resistivity varies for different grades of silicone material applied as coating, and the results are found to be consistent with the detector efficiency and noise rate measurements done with these RPCs.

Meghna, K. K.; Banerjee, A.; Biswas, S.; Bhattacharya, S.; Bose, S.; Chattopadhyay, S.; Das, G.; Marick, C.; Saha, S.; Viyogi, Y. P.

2012-10-01

284

Electrical resistance response of polyaniline films to water, ethanol, and nitric acid solution  

NASA Astrophysics Data System (ADS)

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.

Yin, Hong-Xing; Li, Meng-Meng; Yang, H.; Long, Yun-Ze; Sun, Xin

2010-08-01

285

Aerodynamic resistance reduction of electric and hybrid vehicles  

NASA Technical Reports Server (NTRS)

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.

1979-01-01

286

Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements  

SciTech Connect

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.

Whelchel, R. [Georgia Institute of Technology; Gerhardt, Dr. Rosario [Georgia Institute of Technology; Littrell, Ken [ORNL

2010-01-01

287

Antibiotic resistance profile and virulence genes of uropathogenic Escherichia coli isolates in relation to phylogeny.  

PubMed

Escherichia coli (E. coli) strains are the major cause of urinary tract infections (UTI) and belong to the large group of extra-intestinal pathogenic E. coli. The purposes of this study were to determine the antibiotic resistance profile, virulence genes and phylogenetic background of E. coli isolates from UTI cases. A total of 137 E. coli isolates were obtained from UTI samples. The antimicrobial susceptibility of confirmed isolates was determined by disk diffusion method against eight antibiotics. The isolates were examined to determine the presence and prevalence of selected virulence genes including iucD, sfa/focDE, papEF and hly. ECOR phylo-groups of isolates were determined by detection of yjaA and chuA genes and fragment TspE4.C2. The antibiogram results showed that 71% of the isolates were resistant to cefazolin, 60.42% to co-trimoxazole, 54.16% to nalidixic acid, 36.45% to gentamicin, 29.18% to ciprofloxacin, 14.58% to cefepime, 6.25% to nitrofurantoin and 0.00% to imipenem. Twenty-two antibiotic resistance patterns were observed among the isolates. Virulence genotyping of isolates revealed that 58.39% isolates had at least one of the four virulence genes. The iucD gene was the most prevalent gene (43.06%). The other genes including sfa/focDE, papEF and hly genes were detected in 35.76%, 18.97% and 2.18% isolates, respectively. Nine combination patterns of the virulence genes were detected in isolates. Phylotyping of 137 isolates revealed that the isolates fell into A (45.99%), B1 (13.14%), B2 (19.71%) and D (21.16%) groups. Phylotyping of multidrug resistant isolates indicated that these isolates are mostly in A (60.34%) and D (20.38%) groups. In conclusion, the isolates that possessed the iucD, sfa/focDE, papEF and hly virulence genes mostly belonged to A and B2 groups, whereas antibiotic resistant isolates were in groups A and D. Escherichia coli strains carrying virulence factors and antibiotic resistance are distributed in specific phylogenetic background. PMID:24862040

Adib, N; Ghanbarpour, R; Solatzadeh, H; Alizade, H

2014-03-01

288

Effects of borehole design on complex electrical resistivity measurements: laboratory validation and numerical experiments  

NASA Astrophysics Data System (ADS)

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 measurements with different electrode configurations are affected by borehole design. Finally, the plausibility of our results was verified by comparing the simulation results with borehole EIT measurements made at the test site Krauthausen.

Treichel, A.; Huisman, J. A.; Zhao, Y.; Zimmermann, E.; Esser, O.; Kemna, A.; Vereecken, H.

2012-12-01

289

A four-probe dc method for measuring the electrical resistivities of molten metals  

SciTech Connect

In the past decade there has been an increased use of process modeling in the casting industry. The driving force for such process modeling is improved productivity through lower energy costs, lower scrap losses, improved product quality, and product consistency. This has been recognized by the Department of Trade and Industry, U.K., who have initiated a number of programs to improve measurement methods for thermophysical properties. Here, a four-probe dc technique for measuring liquid-metal electrical resistivities has been developed, and liquid-resistivity measurements on gallium, tin, lead, copper, a lead tin alloy, a copper tin alloy, and a zinc alloy have been presented. The Lorenz relation has been used to calculate thermal conductivities from these resistivity measurements. The thermal conductivities calculated from these resistivity measurements are (where data are available) in good agreement with recommended liquid-metal thermal conductivities.

Monaghan, B.J. [National Physical Lab., London (United Kingdom)] [National Physical Lab., London (United Kingdom)

1999-03-01

290

Pressure-induced positive electrical resistivity coefficient in Ni-Nb-Zr-H glassy alloy  

NASA Astrophysics Data System (ADS)

Measurements under hydrostatic pressure of the electrical resistivity of (Ni0.36Nb0.24Zr0.40)100-xHx (x = 9.8, 11.5, and 14) glassy alloys have been made in the range of 0-8 GPa and 0.5-300 K. The resistivity of the (Ni0.36Nb0.24Zr0.40)86H14 alloy changed its sign from negative to positive under application of 2-8 GPa in the temperature range of 300-22 K, coming from electron-phonon interaction in the cluster structure under pressure, accompanied by deformation of the clusters. In temperature region below 22 K, the resistivity showed negative thermal coefficient resistance by Debye-Waller factor contribution, and superconductivity was observed at 1.5 K.

Fukuhara, M.; Gangli, C.; Matsubayashi, K.; Uwatoko, Y.

2012-06-01

291

Monitoring radio-frequency heating of contaminated soils using electrical resistance tomography  

SciTech Connect

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.

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

1993-09-01

292

Electrical resistivity of single crystals of LaFeAsO under applied pressure  

NASA Astrophysics Data System (ADS)

Measurements of electrical resistivity under applied pressure were performed on single-crystalline samples of LaFeAsO grown in a molten NaAs flux. We observe a smooth suppression of spin-density wave order under nearly hydrostatic applied pressures up to 2.6 GPa and in quasihydrostatic pressures up to 14.7 GPa. Similar to some of the other reports on single and polycrystalline samples of LaFeAsO, these crystals exhibit a resistivity that increases as temperature is lowered. By fitting an Arrhenius law to the the semiconducting-like temperature dependence of the electrical resistivity, we extract an energy gap that is suppressed with pressure and vanishes near 10 GPa. This is accompanied by the emergence of a metallic temperature dependence of the electrical resistivity. A similar behavior is also observed in diamond anvil cell experiments carried out to ˜37GPa. Complete transitions to a bulk superconducting phase are not observed in any of the experiments.

McElroy, C. A.; Hamlin, J. J.; White, B. D.; Weir, S. T.; Vohra, Y. K.; Maple, M. B.

2014-09-01

293

Electrical resistance tomography for imaging the spatial distribution of moisture in pavement sections  

SciTech Connect

Electrical Resistance Tomography (ERT) was used to image spatial moisture distribution and movement in pavement sections during an infiltration test. 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. Four arrays of ERT electrodes were installed in vertical drill holes 1.22 m (4 ft) placed at the comers of a square 61 cm (2 ft) on a side into a pavement section which is used for a truck scale ramp on U.S. Highway 99 just north of Sacramento, CA. Water was introduced slowly into the pavement through a shallow hole in the center of this pattern and ERT data were collected in various planes as the water infiltrated into the pavement and subgrade materials over a period of several hours. The ERT data were inverted, and the resulting images show (1) the basic structure of the pavement section and (2) the movement of water through the image planes as a function of time during infiltration. An interesting result is that the water does not appear to drain from the section toward the shoulder as had been expected based on the design.

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

1995-11-08

294

Using Electrical Resistivity Tomography for Constraining a Hydrogeological Model in a Data Sparse Region  

NASA Astrophysics Data System (ADS)

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 continuity of the hydrogeological units at a larger scale, and the results were digitized and integrated to construct a three dimensional hydrogeological model of the watershed.

Foster, S.; Allen, D. M.

2013-12-01

295

Effects of moxifloxacin exposure on the conjunctival flora and antibiotic resistance profile following repeated intravitreal injections  

PubMed Central

AIM To evaluate the effects of moxifloxacin exposure on the conjunctival flora and antibiotic resistance profile following repeated intravitreal injections. METHODS Seventy-two eyes of 36 patients [36 eyes in control group, 36 eyes in intravitreal injection (IVI) group] were enrolled in the study. All the eyes had at least one IVI and had diabetic macular edema (DME) or age-related macular degeneration (ARMD). Moxifloxacin was prescribed to all the patients four times a day for five days following injection. Conjunctival cultures were obtained from the lower fornix via standardized technique with every possible effort made to minimize contamination from the lids, lashes, or skin. Before the application of any ophthalmic medication, conjunctival cultures were obtained from both eyes using sterile cotton culture. An automated microbiology system was used to identify the growing bacteria and determine antibiotic sensitivity. RESULTS The bacterial cultures were isolated from 72 eyes of 36 patients, sixteen of whom patients (44.4%) were male and twenty (55.6%) were female. Average age was 68.4±9.0 (range 50-86). The average number of injections before taking cultures was 3.1+1.0. Forty-eight (66.7%) of 72 eyes had at least one significant organism. There was no bacterial growth in 8 (20.5%) of IVI eyes and in 16 (44.4%) of control eyes (P=0.03). Of the bacteria isolated from culture, 53.8% of coagulase negative staphylococci (CoNS) in IVI eyes and 47.2% CoNS in control eyes. This difference between IVI eyes and control eyes about bacteria isolated from culture was not statistically significant (P=0.2). Eleven of 25 bacteria (44.0%) isolated from IVI eyes and 11 (57.9%) of 19 bacteria isolated from control eyes were resistant to oxacillin. The difference in frequency of moxifloxacine resistance between two groups was not statistically significant (12.0% in IVI eyes and 21.1% in control eyes) (P=0.44). There were no cases of resistance to vancomycin, teicoplanin and linezolid. CONCLUSION There was no difference in species of bacteria isolated from cultures, or in the frequency of resistance to antibiotics between eyes that had recurrent IVI followed by moxifloxacin exposure compared with control eyes. However, the number of eyes that had bacterial growth was higher in IVI group than in the control group. PMID:25349806

Ata?, Mustafa; Ba?kan, Burhan; Özköse, Ay?e; Mutlu Sar?güzel, Fatma; Demircan, Süleyman; Pangal, Emine

2014-01-01

296

Genotypic resistance profiles of HIV-2-treated patients in West Africa  

PubMed Central

Objective To assess the virological response, genotypic resistance profiles, and antiretroviral plasma concentrations in HIV-2 antiretroviral-treated (antiretroviral therapy, ART) patients in Côte d‘Ivoire. Methods A cross-sectional survey was conducted among HIV-2 patients receiving ART. Plasma HIV-2 viral load was performed using the Agence Nationale de Recherche sur le SIDA et les hépatites virales (ANRS) assay. Protease and reverse transcriptase sequencing was performed using in-house methods and antiretroviral plasma concentrations were assessed using ultra performance liquid chromatography combined with tandem mass spectrometry. Results One hundred and forty-five HIV-2-treated patients were enrolled with a median CD4+ cell count of 360 cells/µl (interquartile range, IQR = 215–528). Median duration of ART was 4 years (IQR = 2–7) and 74% of patients displayed viral load less than 50 copies/ml. Median plasma HIV-2 RNA among patients with viral load more than 50 copies/ml was 3016 copies/ml (IQR = 436–5156). Most patients (84%) received a lopinavir/ritonavir-based regimen. HIV-2 resistance mutations to nucleoside reverse transcriptase inhibitors and protease inhibitors were detected in 21 of 25 (84%) and 20 of 29 (69%) samples, respectively. The most prevalent nucleoside reverse transcriptase inhibitor resistance mutations were M184I/V (90%), Q151M (24%), and S215F/Y (24%). The most prevalent protease inhibitor resistance mutations were V47A (60%) and I54M (30%). Median CD4+ cell counts were 434 cells/µl (292–573) and 204 cells/µl (122–281) in patients with viral load less than 50 copies/ml and those exhibiting virological failure (P < 0.0001), respectively. The proportions of patients with adequate antiretroviral plasma concentrations were 81 and 93% in patients displaying virological failure and in those with viral load less than 50 copies/ml, respectively (P = 0.046), suggesting good treatment adherence. Conclusion We observed adequate drug plasma concentrations and virological suppression in a high proportion of HIV-2-infected patients. However, in cases of virological failure, the limited HIV-2 therapeutic arsenal and cross-resistance dramatically reduced treatment options. PMID:24583671

Charpentier, Charlotte; Eholié, Serge; Anglaret, Xavier; Bertine, Mélanie; Rouzioux, Christine; Avettand-Fenoël, Véronique; Messou, Eugène; Minga, Albert; Damond, Florence; Plantier, Jean-Christophe; Dabis, François; Peytavin, Gilles; Brun-Vézinet, Françoise; Ekouevi, Didier K.

2014-01-01

297

Toxin profile, antibiotic resistance, and phenotypic and molecular characterization of Bacillus cereus in Sunsik.  

PubMed

Sunsik, a ready-to-eat food in Korea, is comprised of various agricultural and marine products, and has been an important concern in Bacillus cereus food poisoning. The aim of this study was to investigate the toxin profiles, genotypic and phenotypic patterns as well as antibiotic resistance of B. cereus strains isolated from Sunsik. A subtyping method known as automated repetitive sequence-based PCR system (DiversiLab™) was used to assess the intraspecific biodiversity of these isolates. Thirty-five B. cereus strains were isolated from 100 commercial Sunsik samples, all of which harbored at least 1 enterotoxin gene. The detection rates of nheABC, hblCDA, cytK, and entFM enterotoxin gene among all isolates were 97%, 86%, 77%, and 100%, respectively. Most strains also produced corresponding enterotoxins such as HBL (83%) and NHE (94%). One strain (2.9%) carried the emetic toxin genes, including ces and EM1, and was positive for the HEp-2 cell emetic toxin assay. Most strains were positive for various biochemical tests such as salicin hydrolysis (86%), starch fermentation (89%), hemolysis (89%), motility test (100%) and lecithinase hydrolysis (89%). All isolates were susceptible to most antibiotics although they were highly resistant to ?-lactam antibiotics. By using the automated rep-PCR system, all isolates were successfully differentiated, indicating the diversity of B. cereus strains present in Sunsik. PMID:22850397

Chon, Jung-Whan; Kim, Jong-Hyun; Lee, Sun-Jin; Hyeon, Ji-Yeon; Seo, Kun-Ho

2012-10-01

298

High throughput profiling of antibiotic resistance genes in urban park soils with reclaimed water irrigation.  

PubMed

Reclaimed water irrigation (RWI) in urban environments is becoming popular, due to rapid urbanization and water shortage. The continuous release of residual antibiotics and antibiotic resistance genes (ARGs) from reclaimed water could result in the dissemination of ARGs in the downstream environment. This study provides a comprehensive profile of ARGs in park soils exposed to RWI through a high-throughput quantitative PCR approach. 147 ARGs encoding for resistance to a broad-spectrum of antibiotics were detected among all park soil samples. Aminoglycoside and beta-lactam were the two most dominant types of ARGs, and antibiotic deactivation and efflux pump were the two most dominant mechanisms in these RWI samples. The total enrichment of ARGs varied from 99.3-fold to 8655.3-fold compared to respective controls. Six to 60 ARGs were statistically enriched among these RWI samples. Four transposase genes were detected in RWI samples. TnpA-04 was the most enriched transposase gene with an enrichment was up to 2501.3-fold in Urumqi RWI samples compared with control soil samples. Furthermore, significantly positive correlation was found between ARGs and transposase abundances, indicating that transposase might be involved in the propagation of ARGs. This study demonstrated that RWI resulted in the enrichment of ARGs in urban park soils. PMID:25057898

Wang, Feng-Hua; Qiao, Min; Su, Jian-Qiang; Chen, Zheng; Zhou, Xue; Zhu, Yong-Guan

2014-08-19

299

Contamination profiles of antibiotic resistance genes in the sediments at a catchment scale.  

PubMed

The aim of this study was to investigate the contamination profiles of tetracycline, sulfonamide, and macrolide resistance genes, as well as integrons in sediments of Dongjiang River basin of South China by real time quantitative polymerase chain reaction. sul2 was the most abundant resistance gene, with the average concentration of 6.97×10(8) copies/g and 1.00×10(8) copies/g in the dry and wet seasons, respectively, followed by ermF, sul3, sul1, intI1, tetA, ermB, tetX, tetM, tetQ, tetO, tetW, tetS, ermC, and tetB. The abundance of intI2 gene was the lowest in the sediment samples. Significant correlations existed between the ARGs and sediment properties as well as metals (Cu and Zn) and corresponding antibiotic classes, suggesting that the contamination of ARGs is related to chemical pollution of the sediments in the river basin. Principal component analysis showed distinct groupings of the sampling sites, reflecting that human activities are the key player in the dissemination of ARGs in the catchment environment. PMID:24907606

Su, Hao-Chang; Pan, Chang-Gui; Ying, Guang-Guo; Zhao, Jian-Liang; Zhou, Li-Jun; Liu, You-Sheng; Tao, Ran; Zhang, Rui-Quan; He, Liang-Ying

2014-08-15

300

Whole Blood Gene Expression Profiles in Insulin Resistant Latinos with the Metabolic Syndrome  

PubMed Central

Although insulin resistance in skeletal muscle is well-characterized, the role of circulating whole blood in the metabolic syndrome phenotype is not well understood. We set out to test the hypothesis that genes involved in inflammation, insulin signaling and mitochondrial function would be altered in expression in the whole blood of individuals with metabolic syndrome. We further wanted to examine whether similar relationships that we have found previously in skeletal muscle exist in peripheral whole blood cells. All subjects (n=184) were Latino descent from the Arizona Insulin Resistance registry. Subjects were classified based on the metabolic syndrome phenotype according to the National Cholesterol Education Program’s Adult Treatment Panel III. Of the 184 Latino subjects in the study, 74 were classified with the metabolic syndrome and 110 were without. Whole blood gene expression profiling was performed using the Agilent 4x44K Whole Human Genome Microarray. Whole blood microarray analysis identified 1,432 probes that were altered in expression ?1.2 fold and P<0.05 after Benjamini-Hochberg in the metabolic syndrome subjects. KEGG pathway analysis revealed significant enrichment for pathways including ribosome, oxidative phosphorylation and MAPK signaling (all Benjamini-Hochberg P<0.05). Whole blood mRNA expression changes observed in the microarray data were confirmed by quantitative RT-PCR. Transcription factor binding motif enrichment analysis revealed E2F1, ELK1, NF-kappaB, STAT1 and STAT3 significantly enriched after Bonferroni correction (all P<0.05). The results of the present study demonstrate that whole blood is a useful tissue for studying the metabolic syndrome and its underlying insulin resistance although the relationship between blood and skeletal muscle differs. PMID:24358323

Tangen, Samantha E.; Tsinajinnie, Darwin; Nuñez, Martha; Shaibi, Gabriel Q.; Mandarino, Lawrence J.; Coletta, Dawn K.

2013-01-01

301

Direct-push hydrostratigraphic profiling: coupling electrical logging and slug tests.  

PubMed

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. PMID:15726921

Sellwood, Stephen M; Healey, John M; Birk, Steffen; Butler, James J

2005-01-01

302

Direct-push hydrostratigraphic profiling: Coupling electrical logging and slug tests  

USGS Publications Warehouse

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.

Sellwood, S.M.; Healey, J.M.; Birk, S.; Butler, J.J., Jr.

2005-01-01

303

Untargeted Metabolomic Profiling of Amphenicol-Resistant Campylobacter jejuni by Ultra-High-Performance Liquid Chromatography-Mass Spectrometry.  

PubMed

Campylobacter jejuni, an important foodborne microorganism, poses severe and emergent threats to human health as antibiotic resistance becomes increasingly prevalent. The mechanisms of drug resistance are hard to decipher, and little is known at the metabolic level. Here we apply metabolomic profiling to discover metabolic changes associated with amphenicol (chloramphenicol and florfenicol) resistance mutations of Campylobacter jejuni. An optimized sample preparation method was combined with ultra-high-performance liquid chromatography-time-of-flight mass spectrometry (UHPLC-TOF/MS) and pattern recognition for the analysis of small-molecule biomarkers of drug resistance. UHPLC-triple quadrupole MS operated in multiple reaction monitoring mode was used for quantitative analysis of metabolic features from UHPLC-TOF/MS profiling. Up to 41 differential metabolites involved in glycerophospholipid metabolism, sphingolipid metabolism, and fatty acid metabolism were observed in a chloramphenicol-resistant mutant strain of Campylobacter jejuni. A panel of 40 features was identified in florfenicol-resistant mutants, demonstrating changes in glycerophospholipid metabolism, sphingolipid metabolism, and tryptophan metabolism. This study shows that the UHPLC-MS-based metabolomics platform is a promising and valuable tool to generate new insights into the drug-resistant mechanism of Campylobacter jejuni. PMID:25491530

Li, Hui; Xia, Xi; Li, Xiaowei; Naren, Gaowa; Fu, Qin; Wang, Yang; Wu, Congming; Ding, Shuangyang; Zhang, Suxia; Jiang, Haiyang; Li, Jiancheng; Shen, Jianzhong

2015-02-01

304

In Situ Electrical Resistivity and Hall Effect Measurement of ?-HgS under High Pressure  

NASA Astrophysics Data System (ADS)

With in situ electrical resistivity and Hall effect measurement, the transport properties and carrier behavior of ?-HgS under high pressure are investigated up to 32.9 GPa. The electrical resistivity changes discontinuously at 5.4, 14.6, and 25.0 GPa. These discontinuities correspond to the phase transitions of ?-HgS from zinc blende to cinnabar, then to rock salt structure. For the zinc blende structure, the decrease of carrier concentration and the increase of mobility indicate that the originally overlapped valence band and conduction band separate with pressure. For the rock salt phase, the increase of ionized impurity concentration leads to the decrease of mobility with pressure.

Hu, Ting-Jing; Cui, Xiao-Yan; Li, Xue-Fei; Wang, Jing-Shu; Yang, Jing-Hai; Gao, Chun-Xiao

2015-01-01

305

Influence of surfactants on the electrical resistivity and thermopower of Ni nanoparticles  

NASA Astrophysics Data System (ADS)

Compacted pellets of nanocrystalline nickel (NC-Ni) with an average particle size ranging from 18 to 33 nm were prepared using a variety of surfactants. They were characterized well and were studied with regard to the influence of the surfactants on the electrical resistivity and thermopower in the temperature range from 5 to 300 K. It was found that the type of surfactant used is more important than the average particle size in their electrical transport and detail transport behaviors. Moreover, the observed thermopower and resistivity features were different than those normally seen in well-known materials. This is interpreted to be indicative of the attractive features of these surfactants can bring to the design of nanostructured thermoelectric materials with enhanced thermoelectric figures of merit.

Kaurav, Netram; Okram, Gunadhor S.; Ganesan, V.

2014-12-01

306

Interpretation of a dipole-dipole electrical resistivity survey, Colado geothermal area, Pershing County, Nevada  

SciTech Connect

An electrical resistivity survey in the Colado geothermal area, Pershing County, Nevada has defined areas of low resistivity on each of five lines surveyed. Some of these areas appear to be fault controlled. Thermal fluids encountered in several drill holes support the assumption that the hot fluids may be associated with areas of low resistivity. The evidence of faulting as interpreted from modeling of the observed resistivity data is therefore particularly significant since these structures may be the conduits for the thermal fluids. Sub-allurial fault zones are interpreted to occur between stations 0 to 5 NW on Line D and on Line A between stations 4 NW and 4 SE. Fault zones are also interpreted on Line C near stations 1 NW, 1 SE, and 3 SE, and on Line E between stations 2 to 4 NW and near 1 SE. No faulting is evident under the alluvial cover on the southwest end of Line B. A deep conductive zone is noted within the mountain range on two resistivity lines. There is no definite indication that thermal fluids are associated with this resistivity feature.

Mackelprang, C.E.

1980-09-01

307

Interpretation of dipole-dipole electrical resistivity survey, Colado geothermal area, Pershing County, Nevada  

NASA Astrophysics Data System (ADS)

An electrical resistivity survey in the Colado geothermal area, Pershing County, Nevada has defined areas of low resistivity on each of five lines surveyed. Some of these areas appear to be fault controlled. Thermal fluids encountered in several drill holes support the assumption that the hot fluids may be associated with areas of low resistivity. The evidence of faulting as interpreted from modeling of the observed resistivity data is therefore particularly significant since these structures may be the conduits for the thermal fluids. Sub-alluvial fault zones are interpreted to occur between stations 0-5 NW on Line D and on Line A between stations 4 NW and 4 SE. Fault zones are also interpreted on Line C near stations 1 NW, 1 SE, and 3 SE, and on Line E between stations 2-4 NW and near 1 SE. No faulting is evident under the alluvial cover on the southwest end of Line B. A deep conductive zone is noted within the mountain range on two resistivity lines. There is no definite indication that thermal fluids are associated with this resistivity feature.

Mackelprang, C. E.

1980-09-01

308

Genome Sequences of Four Clinical Staphylococcus aureus Strains with Diverse Drug Resistance Profiles Isolated from Diabetic Foot Ulcers  

PubMed Central

Staphylococcus aureus is a major pathogen associated with diabetic foot ulcer infections. To gain insight into their pathogenicity and virulence potential, we report draft genome sequences of four strains of Staphylococcus aureus, isolated from diabetic foot ulcers, showing profiles with various degrees of resistance to common antibiotics. PMID:24652982

Murali, Thokur Sreepathy; Paul, Bobby; Parikh, Hersh; Singh, Rana Pratap; Kavitha, Shettigar; Bhat, Manoj K.

2014-01-01

309

Limitations and Perspectives of Electrical Resistivity and Refraction Seismic Tomography in Frozen Ground  

NASA Astrophysics Data System (ADS)

Determining the subsurface ice and unfrozen water content in cold regions are important tasks in all kind of cryospheric studies, but especially on perennial or seasonal frozen ground, where little insights can be gained from direct observations at the surface. In the absence of boreholes, geophysical methods are often the only possibility for visualising the subsurface characteristics, and their successful application in recent years included 2D/3D monitoring and even quantifying the ice and unfrozen water content evolution within the subsurface. Due to the strong sensitivity of electrical resistivity, permittivity and seismic velocity to the phase change from unfrozen water to ice, the application of electrical, electromagnetic and seismic techniques has been especially successful. Within these methods, Electrical Resistivity Tomography (ERT) is often favoured due to its comparatively easy and fast data processing, its robustness against ambient noise and its good performance even in cold and irregular environments. Numerous studies have now shown that ERT is principally suitable to map ground ice, differentiate between ice-poor and ice-rich occurrences, monitor freezing, thawing and infiltration processes, and determine the origin of the ice, i.e. a differentiation between buried glacier ice and segregation ice. However, in practice, a number of uncertainties often prohibit a reliable determination of the material composition from ERT surveys alone. Sources of uncertainty are based on the necessity to choose a set of inversion parameters for calculating the specific resistivity distribution from the measured apparent resistivity data set. In addition, high contact resistances at the surface, large topographic gradients, measurement geometry and the presence of fine material or saline pore water can influence the obtained specific resistivity values. Consequently, it is generally advisable to apply a combination of different geophysical methods at each field site. In this contribution we will analyse the reliability of ERT and refraction seismic results regarding the above uncertainties by using multiple inversions and forward modelling techniques for data sets from different permafrost occurrences in the European Alps and Antarctica. Addressing the inherent uncertainty of ERT an inversion ensemble approach is introduced using multiple inversions of the same data set and clustering techniques to obtain the dominant, and therefore most reliable, subsurface features. In addition, combined electrical resistivity and seismic surveys are presented for a detailed quantification of the material composition in frozen ground.

Hauck, C.; Rings, J.

2007-12-01

310

Resolving Large Preglacial Valleys Buried by Glacial Sediment Using Electric Resistivity Imaging (ERI)  

Microsoft Academic Search

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

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

2004-01-01

311

Electrical resistance tomography system based on CompactPCI for multiphase flow measurement  

Microsoft Academic Search

As a non-radiant and unperturbed 2D\\/3D boundary technique, Electrical resistance tomography (ERT) provides an effective way of monitoring and on-line measurements for multi- phase fluid. To better satisfy industrial requirements, a parallel ERT system based on CompactPCI is described in this paper. The performance of this system have been tested, and the results show that the system works properly with

Cong Xu; Feng Dong

2011-01-01

312

High temperature static strain measurement with an electrical resistance strain gage  

NASA Technical Reports Server (NTRS)

An electrical resistance strain gage that can supply accurate static strain measurement for NASP application is being developed both in thin film and fine wire forms. This gage is designed to compensate for temperature effects on substrate materials with a wide range of thermal expansion coefficients. Some experimental results of the wire gage tested on one of the NASP structure materials, i.e., titanium matrix composites, are presented.

Lei, Jih-Fen

1992-01-01

313

Application of electrical resistance tomography to interrogate mixing processes at plant scale  

Microsoft Academic Search

This paper presents an application of electrical resistance tomography to the investigation of mixing processes at plant scale. An 8-plane 16-electrode ring sensor installed within a stirred tank with a 1.5 m inner diameter is described. Three-dimensional and non-stationary behaviour of mixing processes are illustrated by the images obtained simultaneously from eight axial levels along the tank height. The results

R. Mann; F. J. Dickin; M. Wang; T. Dyakowski; R. A. Williams; R. B. Edwards; A. E. Forrest; P. J. Holden

1997-01-01

314

Preparation of Fe–Pt perpendicular double-layered media with high electric resistivity backlayer  

Microsoft Academic Search

High electric resistivity materials, oxide-added Fe–Si, were investigated as a soft-magnetic backlayer for Fe–Pt perpendicular double-layered media. It was found that there is a possibility of using (Fe–Si)–MgO as a backlayer. To promote a hetero-epitaxial growth of ordered Fe–Pt FCT(001), the backlayer needed a BCC(200) crystal orientation, in a situation where surface topology also played an important role.

Masaru Uchida; Toshio Suzuki; Kazuhiro Ouchi

2001-01-01

315

Model tank electrical resistivity characterization of LNAPL migration in a clayey-sand formation  

Microsoft Academic Search

A modeling tank time-lapse 2D electrical resistivity experiment was undertaken to model the leakage of petroleum products from underground pipelines into a clayey-sand aquifer. Numerical modeling was employed to simulate the electrode arrays that would resolve the post-leakage subsurface image most efficiently. Of the four arrays tested, the dipole–dipole array proved most effective and was adopted for the laboratory studies.

A. A. Adepelumi; A. A. Solanke; O. B. Sanusi; A. M. Shallangwa

2006-01-01

316

Microbial Susceptibility and Plasmid Profiles of Methicillin-Resistant Staphylococcus aureus and Methicillin-Susceptible S. aureus  

PubMed Central

Background: Today, significant increase in the prevalence and emergence of methicillin-resistant Staphylococcus aureus (MRSA) is a serious public health concern and is likely to have a dramatic negative impact on many current medical practices. Therefore, identification of MRSA strains is important for both clinical and epidemiological implications. Objectives: The present study was carried out to determine the frequency of methicillin resistant; antibiotic susceptibility and plasmid profiles of S. aureus recovered from different types of clinical samples of patients in Zabol, Iran. Material and Methods: Clinical samples from 500 outpatient and hospitalized patients were tested for S. aureus. The susceptibility of 106 S. aureus to 11 antibiotics was evaluated by the disk diffusion method and Etest oxacillin strips. The presence of mecA gene was investigated by polymerase chain reaction (PCR). The plasmid profile patterns of all isolates were determined by a modified alkaline lysis method. Results: A total of 67 (63.20%) strains were found to be MRSA isolates. Most of MRSA isolates showed high level of resistance to ampicillin, erythromycin, nalidixic acid, penicillin, and tetracycline. Twenty-six percent of MRSA isolates showed high level of resistance to oxacillin (minimum inhibitory concentration [MIC] ? 256 ?g/mL). mecA gene was detected among 62 MRSA isolates. Totally, 75 isolates of both strains harbored plasmid. Conclusions: Resistance to oxacillin and other antibiotics was high, and most of the isolates were found to be multi-drug resistance (MDR). Plasmid analysis of representative S. aureus isolates also demonstrates the presence of a wide range of plasmid sizes, with no consistent relationship between plasmid profiles and resistance phenotypes. Regular surveillance of hospital infections and monitoring of their antibiotic sensitivity patterns are required to reduce MRSA prevalence. High prevalence and multi-drug resistance of MRSA isolates in southeast of Iran could be considered as an urgent warning for public health. PMID:25368805

Shahkarami, Fatemeh; Rashki, Ahmad; Rashki Ghalehnoo, Zahra

2014-01-01

317

Microbiota and anthropic interference on antimicrobial resistance profile of bacteria isolated from Brazilian Maned-wolf (Chrysocyon brachyurus).  

PubMed

Both the study of Brazilian wild mammal fauna and the conditions that foster the preservation of endangered species, such as Brazilian Maned-wolf (Chrysocyon brachyurus), in wild life are of extreme importance. In order to study the resistance profile of microbiota bacterial colonizing Brazilian Maned-wolf, this work investigated samples from eight male captive and free roaming animals originating from different Brazilian geographical regions. Samples for microbiological purposes were collected with swabs and kept in appropriate transport medium. Using routine microbiological techniques, the isolated bacteria were tested toward antimicrobial drugs by the agar disk diffusion method. Results showed that all samples from wild animals were sensitive toward all drugs tested. Conversely, the resistance profile of bacteria isolated from captive animals varied among strains and animal body site location. Escherichia coli samples from prepuce, anus and ear showed multi-resistance toward at least four drugs, especially against erythromycin and tetracycline, followed by Proteus mirabilis and P. vulgaris strains isolated from anus and ear. Among Gram-positive bacteria, strains of coagulase-negative staphylococci showed multi-resistance mainly toward erythromycin and amoxicillin. The work discusses these findings and suggests that profile of multi-resistance bacteria from captive subjects may be attributed to direct contact with human or through lifestyle factors such as feeding, predation or contact of animals with urban animals such as birds, rodents, and insects from surrounding environments. PMID:24688529

Vieira-da-Motta, Olney; Eckhardt-de-Pontes, Luiz Antonio; Petrucci, Melissa Paes; dos Santos, Israel Pereira; da Cunha, Isabel Candia Nunes; Morato, Ronaldo Gonçalves

2013-12-01

318

Microbiota and anthropic interference on antimicrobial resistance profile of bacteria isolated from Brazilian maned-wolf (Chrysocyon brachyurus)  

PubMed Central

Both the study of Brazilian wild mammal fauna and the conditions that foster the preservation of endangered species, such as Brazilian Maned-wolf (Chrysocyon brachyurus), in wild life are of extreme importance. In order to study the resistance profile of microbiota bacterial colonizing Brazilian Maned-wolf, this work investigated samples from eight male captive and free roaming animals originating from different Brazilian geographical regions. Samples for microbiological purposes were collected with swabs and kept in appropriate transport medium. Using routine microbiological techniques, the isolated bacteria were tested toward antimicrobial drugs by the agar disk diffusion method. Results showed that all samples from wild animals were sensitive toward all drugs tested. Conversely, the resistance profile of bacteria isolated from captive animals varied among strains and animal body site location. Escherichia coli samples from prepuce, anus and ear showed multi-resistance toward at least four drugs, especially against erythromycin and tetracycline, followed by Proteus mirabilis and P. vulgaris strains isolated from anus and ear. Among Gram-positive bacteria, strains of coagulase-negative staphylococci showed multi-resistance mainly toward erythromycin and amoxicillin. The work discusses these findings and suggests that profile of multi-resistance bacteria from captive subjects may be attributed to direct contact with human or through lifestyle factors such as feeding, predation or contact of animals with urban animals such as birds, rodents, and insects from surrounding environments. PMID:24688529

Vieira-da-Motta, Olney; Eckhardt-de-Pontes, Luiz Antonio; Petrucci, Melissa Paes; dos Santos, Israel Pereira; da Cunha, Isabel Candia Nunes; Morato, Ronaldo Gonçalves

2013-01-01

319

Electrical resistivity measurements of brine saturated porous media near reservoir conditions: Awibengkok preliminary results  

SciTech Connect

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.

Bonner, B; Duba, A; Roberts, J

1999-06-28

320

Electrical Resistivity and Thermal Expansion Measurements of URu2Si2 under Pressure  

NASA Astrophysics Data System (ADS)

We carried out simultaneous measurements of electrical resistivity and thermal expansion of the heavy-fermion compound URu2Si2 under pressure using a single crystal. We observed a phase transition anomaly between hidden (HO) and antiferromagnetic (AFM) ordered states at TM in the temperature dependence of both measurements. For the electrical resistivity, the anomaly at TM was very small compared with the distinct hump anomaly at the phase transition temperature T0 between the paramagnetic state (PM) and HO, and exhibited only a slight increase and decrease for the I \\parallel a-axis and c-axis, respectively. We estimated each excitation gap of HO, ?HO, and AFM, ?AFM, from the temperature dependence of electrical resistivity; ?HO and ?AFM have different pressure dependences from each other. On the other hand, the temperature dependence of thermal expansion exhibited a small anomaly at T0 and a large anomaly at TM. The pressure dependence of the phase boundaries of T0 and TM indicates that there is no critical end point and the two phase boundaries meet at the critical point.

Motoyama, Gaku; Yokoyama, Nobuyuki; Sumiyama, Akihiko; Oda, Yasukage

2008-12-01

321

Electrical Resistivity Investigation of Gas Hydrate Distribution in Mississippi Canyon Block 118, Gulf of Mexico  

SciTech Connect

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.

Dunbar, John

2012-12-31

322

Microgravity conditions and electrical resistivity of liquid alloys with critical mixing  

SciTech Connect

The phenomena of two-liquid phase separations are significantly influenced by the gravity on the ground because of the difference in the densities of the constituent components, particularly, in the case of liquid alloys with critical mixing. In this paper, experimental techniques and results ar reported for the measurements of the electrical resistivity for typical liquid alloys with critical mixing, such as Bi-Ga, under microgravity by the use of a rocket S520-19 belonging to ISAS (Institute of Space and Astronautical Science, Japan). It was found that the temperature coefficient of the electrical resistivity, on cooling of the homogeneous liquid phase, increases with the approach to the critical temperature. This trend under microgravity by the rocket experiment is more pronounced compared to the trend of the reference experiment on the ground. In addition, the supercooling of homogeneous liquids under microgravity is larger than that on the ground. These differences are explained by the difference in the degree of the growth of concentration fluctuations, the concentration fluctuations are far greater under microgravity than on the ground. Therefore, it is found to be very important to study the process and the critical phenomena of two-liquid phase separations under microgravity. Measurement of electrical resistivity is an effective method to obtain information about the process, the critical phenomena, and the supercooling of two-liquid phase separations in liquid alloys with critical mixing.

Itami, T.; Masaki, T. [Hokkaido Univ., Sapporo (Japan). Dept. of Chemistry; Kuribayashi, K.; Sato, E.; Hinada, M.; Yamashita, M. [Inst. of Space and Astronautical Science, Sagamihara (Japan); Kawasaki, K. [Nissan Motor Company, Ltd., Tokyo (Japan)

1997-03-01

323

Influence of salinity and moisture content in electrical resistivity tomography readings in geomaterials used in construction  

NASA Astrophysics Data System (ADS)

Wetness and salts are among the main agents hindering the performance of any porous building material. There are a number of techniques based on electrical properties for the detection of these agents in buildings, such as portable moisture meters and electric resistivity tomography (ERT). These methods are used to locate wet areas based on the lower electrical resistivity wet materials have in relation to dry ones. However, as both moisture and salts contribute to low resistivity readings, the ERT readings may have a degree of uncertainty. This research aims to study the contribution of salinity and moisture content on the readings of ERT by testing laminated gypsum boards in the laboratory with solutions with different compositions (i.e. sodium chloride, magnesium sulphate and a mixture of both) and concentrations of salts. An industrial product, such as the laminated gypsum board, was chosen to minimize the effects that heterogeneities in composition and physical properties could have in the ERT readings and facilitate the interpretation of the wetness/salt content difference. Gypsum board was soaked with a fixed amount of the chosen solutions and several ERT transects were performed with a GeoTom device (Geolog2000) while drying. Results show the influence salinity of solutions have in drying process, and how the salt content remaining within the pores of geomaterials impact on ERT results. Research funded by Geomateriales (S2009/MAT-16) and CEI Moncloa (UPM, UCM, CSIC) through a PICATA contract and the equipment from RedLAbPAt Network

Gomez-Heras, Miguel; Fort, Rafael; Garcia Morales, Soledad

2014-05-01

324

Monitoring crack development in fiber concrete beam by using electrical resistivity imaging  

NASA Astrophysics Data System (ADS)

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 ?m 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.

Wiwattanachang, N.; Giao, P. H.

2011-10-01

325

Electron-phonon interactions and the intrinsic electrical resistivity of graphene.  

PubMed

We present a first-principles study of the temperature- and density-dependent intrinsic electrical resistivity of graphene. We use density-functional theory and density-functional perturbation theory together with very accurate Wannier interpolations to compute all electronic and vibrational properties and electron-phonon coupling matrix elements; the phonon-limited resistivity is then calculated within a Boltzmann-transport approach. An effective tight-binding model, validated against first-principles results, is also used to study the role of electron-electron interactions at the level of many-body perturbation theory. The results found are in excellent agreement with recent experimental data on graphene samples at high carrier densities and elucidate the role of the different phonon modes in limiting electron mobility. Moreover, we find that the resistivity arising from scattering with transverse acoustic phonons is 2.5 times higher than that from longitudinal acoustic phonons. Last, high-energy, optical, and zone-boundary phonons contribute as much as acoustic phonons to the intrinsic electrical resistivity even at room temperature and become dominant at higher temperatures. PMID:24524418

Park, Cheol-Hwan; Bonini, Nicola; Sohier, Thibault; Samsonidze, Georgy; Kozinsky, Boris; Calandra, Matteo; Mauri, Francesco; Marzari, Nicola

2014-03-12

326

Noncontact technique for measuring the electrical resistivity and magnetic susceptibility of electrostatically levitated materials  

NASA Astrophysics Data System (ADS)

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.

Rustan, G. E.; Spyrison, N. S.; Kreyssig, A.; Prozorov, R.; Goldman, A. I.

2012-10-01

327

Imaging Beneath Hanford's Tank Farms with Electrical Resistivity Geophysics - An innovative approach  

SciTech Connect

An electrical resistivity geophysical survey was conducted in and around the T tank farm at the Hanford Site. The geophysical survey was deployed in two methods to identify soils that are electrically conductive from waste introduced through planned and unplanned releases. The first method relied on the traditional use of surface electrodes arranged along linear transects. This method was highly successful outside the tank footprint and over the cribs and trenches on the periphery of the farm. The surface resistivity data showed low resistivity anomalies directly beneath these waste disposal areas. The second deployment strategy relied on using site infrastructure for transmitting current and conducting the voltage measurements. Wells, which penetrate below the metal pipes and tanks that caused the unsuccessful surface deployment inside the farm, were very successful at imaging low resistivity anomalies that were likely caused from the leaking tanks. In particular, tank T106 showed a large area of affected soil, which matches hydrological expectations and borehole data obtained from the area. Overall, the method proves valuable in imaging parts of the subsurface previously not possible with other approaches. (authors)

Rucker, D.F.; Levitt, M.T. [hydroGEOPHYSICS, Inc., Tucson, AZ (United States); Myers, D.A. [CH2M Hill Hanford Group, Richland, WA (United States)

2007-07-01

328

Geophysical evaluation of solute plume spatial moments using an adaptive POD algorithm for electrical resistivity imaging  

NASA Astrophysics Data System (ADS)

We investigate the potential for characterizing spatial moments of subsurface solute plumes from surface-based electrical resistivity images produced within a Proper Orthogonal Decomposition (POD) inversion framework. The existing POD algorithm is improved here to allow for adaptive conditioning of the POD training images on resistivity measurements. The efficacy of the suggested technique is evaluated with two hypothetical transport scenarios: synthetic #1 is based on the case where the target plume and POD training images follow the same (unimodal) plume morphology, whereas a second source location in synthetic #2 makes the target plume bimodal and inconsistent with the POD training images. The resistivity imaging results indicate that the adaptive algorithm efficiently and robustly updates the POD training images to obtain good quality resistivity images of the target plumes, both in the presence of data noise and when conceptual model inaccuracies exist in the training simulations. Spatial moments of the solute plumes recovered from the resistivity images are also favorable, with relative mass recovery errors in the range of 0.6-4.4%, center of mass errors in the range of 0.6-9.6%, and spatial variance errors in the range of 3.4-45% for cases where the voltage data had 0-10% noise. These results are consistent with or improved upon those reported in the literature. Comparison of the resistivity-based moment estimates to those obtained from direct concentration sampling suggests that for cases with good quality resistivity data (i.e., <3% noise), the imaging results provide more accurate moments until 6-10 multi-level sampling wells are installed. While the specific number of wells will depend on the actual field scenario, we suggest that this finding illustrates the general value of POD-based resistivity imaging techniques for non-invasively estimating the spatial moments of a solute plume.

Oware, E. K.; Moysey, S. M. J.

2014-09-01

329

Dielectric and thermoanalytical behavior and spectroscopic and kinetic evaluation of water in heat-resistant electrical insulating films  

Microsoft Academic Search

Nowadays, along with requirements for developing heat-resistant electrical insulating materials, various kinds of high polymers with polar structures are used, which are characterized by high heat-stability, good electrical properties, hydrophilic nature, etc. While their heat-stability is beneficial to their uses, their hydrophilic nature is sometimes detrimental, since the existence of water in electrical insulation is apt to deteriorate their electrical

Sachio Yasufuku

2003-01-01

330

Electrical Resistivity Monitoring for Leachate Distribution at Two Foot-and-Mouth- Disease (FMD) Burial Sites  

NASA Astrophysics Data System (ADS)

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 ?m 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)'.

Lee, S.; Kaown, D.; Lee, K.; Leem, K.; Ko, K.

2011-12-01

331

Development of Resistance in Wild-Type and Hypermutable Pseudomonas aeruginosa Strains Exposed to Clinical Pharmacokinetic Profiles of Meropenem and Ceftazidime Simulated In Vitro  

Microsoft Academic Search

In this study we investigated the interplay of antibiotic pharmacokinetic profiles and the development of mutation-mediated resistance in wild-type and hypermutable Pseudomonas aeruginosa strains. We used in vitro models simulating profiles of the commonly used therapeutic drugs meropenem and ceftazidime, two agents with high levels of antipseudomonal activity said to have different potentials for stimulating resistance development. During ceftazidime treatment

Beate Henrichfreise; Irith Wiegand; Ingeborg Luhmer-Becker; Bernd Wiedemann

2007-01-01

332

In Situ Measurement of Electrical Resistivity of Deep Sea Sediments: Results From Cascadia Basin, Eastern Flank of Juan de Fuca Ridge.  

NASA Astrophysics Data System (ADS)

The electrical properties of deep sea sediments are linked to other physical properties through a series of empirical relationships. They allow the calculation of thermal conductivity from porosity which is derived from electrical resistivity using Archie's Law. In order to complement in situ thermal conductivity measurements made with our violin-bow type heat probe, we designed and built a sensor which is attached to the tip of our probe and allows to measure a continuous profile of electrical resistivity - and therefore porosity and calculated thermal conductivity - as the heat probe penetrates the seafloor. The operating principle of our sensor is based on two identical 4-point electrode arrays arranged on the circumference of the sensor tip and separated by 10 cm. They are mounted in an electrically insulating, highly abrasion resistant plastic material. Both arrays are operated independently. A DC constant power source delivering 10 mA is reversed with a frequency of 1000 Hz to provide a 500 Hz alternating rectangular waveform current. The resulting signal at the electrodes is measured in a time-multipexed fashion with a final frequency of 250 Hz. Data are digitized and stored on a hard drive under control of a Tattletale data logger. Penetration is monitored by a pressure and acceleration sensor. The signal of the latter is used to convert the recorded electrical signals from time to depth. We will present results from multi-penetration measurements along profiles located at the Eastern flank of the Juan de Fuca Ridge and also from a site on Cascadia Margin, where on previous cruises Canadian colleagues cored gas hydrate bearing sediments. The measurements were made during cruise SO-149 (fall 2000) on the German research vessel SONNE. Our data show that we are able to measure high resolution resistivity profiles over a depth range of 3 - 4 m which allow to characterize the overall porosity of the sediments and to identify turbidite layers present everywhere in Cascadia Basin. The calculated porosities are compared with existing porosity data from the same area. The developed instrument worked very reliably and delivered data of very good quality. Of course the sensor and its electronics can also be used separately for spatially detailed geotechnical work in shallow water.

Villinger, H.; Heesemann, B.; Jansen, D.; Pfender, M.; Rosenberger, A.; Spindeldreher, C.

2001-12-01

333

Transcriptome profiling identified novel genes associated with aluminum toxicity, resistance and tolerance in Medicago truncatula.  

PubMed

Oligonucleotide microarrays corresponding to over 16,000 genes were used to analyze changes in transcript accumulation in root tips of the Al-sensitive Medicago truncatula cultivar Jemalong genotype A17 in response to Al treatment. Out of 2,782 genes with significant changes in transcript accumulation, 324 genes were up-regulated and 267 genes were down-regulated at least twofold by Al. Up-regulated genes were enriched in transcripts involved in cell-wall modification and abiotic and biotic stress responses while down-regulated genes were enriched in transcripts involved in primary metabolism, secondary metabolism, protein synthesis and processing, and the cell cycle. Known markers of Al-induced gene expression including genes associated with oxidative stress and cell wall stiffening were differentially regulated in this study. Transcript profiling identified novel genes associated with processes involved in Al toxicity including cell wall modification, cell cycle arrest and ethylene production. Novel genes potentially associated with Al resistance and tolerance in M. truncatula including organic acid transporters, cell wall loosening enzymes, Ca(2+) homeostasis maintaining genes, and Al-binding were also identified. In addition, expression analysis of nine genes in the mature regions of the root revealed that Al-induced gene expression in these regions may play a role in Al tolerance. Finally, interfering RNA-induced silencing of two Al-induced genes, pectin acetylesterase and annexin, in A17 hairy roots slightly increased the sensitivity of A17 to Al suggesting that these genes may play a role in Al resistance. PMID:18351384

Chandran, Divya; Sharopova, Natasha; Ivashuta, Sergey; Gantt, J Stephen; Vandenbosch, Kathryn A; Samac, Deborah A

2008-06-01

334

Mining Genes Involved in Insecticide Resistance of Liposcelis bostrychophila Badonnel by Transcriptome and Expression Profile Analysis  

PubMed Central

Background Recent studies indicate that infestations of psocids pose a new risk for global food security. Among the psocids species, Liposcelis bostrychophila Badonnel has gained recognition in importance because of its parthenogenic reproduction, rapid adaptation, and increased worldwide distribution. To date, the molecular data available for L. bostrychophila is largely limited to genes identified through homology. Also, no transcriptome data relevant to psocids infection is available. Methodology and Principal Findings In this study, we generated de novo assembly of L. bostrychophila transcriptome performed through the short read sequencing technology (Illumina). In a single run, we obtained more than 51 million sequencing reads that were assembled into 60,012 unigenes (mean size?=?711 bp) by Trinity. The transcriptome sequences from different developmental stages of L. bostrychophila including egg, nymph and adult were annotated with non-redundant (Nr) protein database, gene ontology (GO), cluster of orthologous groups of proteins (COG), and KEGG orthology (KO). The analysis revealed three major enzyme families involved in insecticide metabolism as differentially expressed in the L. bostrychophila transcriptome. A total of 49 P450-, 31 GST- and 21 CES-specific genes representing the three enzyme families were identified. Besides, 16 transcripts were identified to contain target site sequences of resistance genes. Furthermore, we profiled gene expression patterns upon insecticide (malathion and deltamethrin) exposure using the tag-based digital gene expression (DGE) method. Conclusion The L. bostrychophila transcriptome and DGE data provide gene expression data that would further our understanding of molecular mechanisms in psocids. In particular, the findings of this investigation will facilitate identification of genes involved in insecticide resistance and designing of new compounds for control of psocids. PMID:24278202

Dou, Wei; Shen, Guang-Mao; Niu, Jin-Zhi; Ding, Tian-Bo; Wei, Dan-Dan; Wang, Jin-Jun

2013-01-01

335

The pleiotropic profile of the indirubin derivative 6BIO overcomes TRAIL resistance in cancer.  

PubMed

TRAIL (TNF?-related apoptosis-inducing factor) has been promoted as a promising anti-cancer agent. Unfortunately many tumor cells develop resistance towards TRAIL due to numerous defects in apoptotic signaling. To handle this problem combination therapy with compounds affecting as many different anti-apoptotic targets as possible might be a feasible approach. The bromo-substituted indirubin derivative 6BIO meets this challenge: Treatment of breast cancer and bladder carcinoma cell lines with micromolar concentrations of 6BIO abrogates cellular growth and induces apoptosis. Combination of subtoxic amounts of 6BIO with ineffective doses of TRAIL completely abolishes proliferation and long-term survival of cancer cells. As shown in two-dimensional as well as three-dimensional cell culture models, 6BIO potently augments TRAIL-induced apoptosis in cancer cell lines. The potent chemosensitizing effect of 6BIO to TRAIL-mediated cell death is due to the pleiotropic inhibitory profile of 6BIO. As shown previously, 6BIO abrogates STAT3, PDK1 as well as GSK3 signaling and moreover, inhibits the expression of the anti-apoptotic Bcl-2 family members Bcl-xL and Mcl-1 on mRNA as well as on protein level, as demonstrated in this study. Moreover, the expression of cFLIP and cIAP1 is significantly downregulated in 6BIO treated cancer cell lines. In sum (subtoxic concentration of) the multi-kinase inhibitor 6BIO serves as a potent chemosensitizing agent fighting TRAIL resistant cancer cells. PMID:25069048

Braig, Simone; Bischoff, Fabian; Abhari, Behnaz A; Meijer, Laurent; Fulda, Simone; Skaltsounis, Leandros; Vollmar, Angelika M

2014-09-15

336

Electrical current profile of a confined isotropic liquid sample: Biological systems and liquid crystals applications  

NASA Astrophysics Data System (ADS)

The electrical current profile in a liquid sample containing ionic impurities, submitted to a time-dependent external voltage, is determined in the framework of the Poisson-Nernst-Planck (PNP) diffusional model. The boundary conditions at the limiting electrodes include the situations of blocking electrodes, generalized Chang-Jaffé (specific adsorption), and the adsorption-desorption of positive and negative ions at the interface, governed by a kinetic equation in the Langmuir's approximation. The current-voltage characteristics of the confined system are obtained in the presence of an arbitrary time-dependent applied potential of small amplitude (linear approximation). The calculations are potentially useful for modeling and interpreting experimental situations found in biological cells and liquid crystals samples.

Ribeiro de Almeida, R. R.; Michels, F. S.; Steffen, V.; Lenzi, E. K.; Zola, R. S.; Evangelista, L. R.

2013-11-01

337

Geometry and faults tectonic activity of the Okavango Rift Zone, Botswana: Evidence from magnetotelluric and electrical resistivity tomography imaging  

NASA Astrophysics Data System (ADS)

We used Magnetotelluric (MT) and Electrical Resistivity Tomography (ERT) to investigate the geometry and nature of faults activity of the Okavango Rift Zone (ORZ) in Botswana, an incipient rift at the southern tip of the Southwestern Branch of the East African Rift System. The ORZ forms a subtle topographic depression filled with Quaternary lacustrine and fluvio-deltaic sediments and is bounded by NE-trending normal faults that are more prominent in the southeastern portion of the rift basin. An MT model from a regional (˜140 km) NW-SE trending MT transect shows that much of the rift basin is underlain by a broad asymmetrical low resistivity anomaly that slopes gently (˜1°) from NW to SE reaching a depth of ˜300 m. This anomaly suggests that faults in the southeastern part of the rift form a NW-dipping border fault zone and that the lacustrine and fluvio-deltaic sediments contain brackish to saline water filling the broad half-graben structure. Furthermore, MT and ERT models from detailed (4-13 km long) MT transects and resistivity profiles show that one border fault (Thamalakane) and two within-basin faults (Lecha and Tsau) in the southeastern part of the ORZ are characterized by a localized high conductivity anomaly while another border fault (Kunyere) lacks such an anomaly. These localized anomalies are attributed to channelized fresh surface water and saline groundwater percolating through these faults forming "fault zone conductors" and suggest actively displacing faults. The lack of a "fault zone conductor" in the Kunyere fault is interpreted as indicating diminishing displacement on this fault, and that strain was transferred to the Thamalakane fault further to the east. The fluids provide lubricant for the ORZ faults, hence preventing infrequent large magnitude earthquakes, but favoring frequent micro-seismicity.

Bufford, Kelsey Mosley; Atekwana, Estella A.; Abdelsalam, Mohamed G.; Shemang, Elijah; Atekwana, Eliot A.; Mickus, Kevin; Moidaki, Moikwathai; Modisi, Motsoptse P.; Molwalefhe, Loago

2012-04-01

338

Electrical resistivity monitoring of the thermomechanical heater test in yucca mountain  

SciTech Connect

Of the several thermal, mechanical nd hydrological measurements being used to monitor the rock mass response, electrical resistance tomography (ERT) is being used to monitor the movement of liquid water with a special interest in the the movement of condensate out of the system. Four boreholes, containing a total of 30 ERT electrodes, were drilled to form the sides of a 30 foot square with the heater at the center and perpendicular to the plane of the electrodes. Images of resistivity change were calculated using data collected before and during the heating episode. The changes recovered show a region of decreasing resistivity approximately centered around the heater. the size this region grows with time and the resistivity decreases become stronger. The changes in resistivity are caused by both temperature and saturation changes. The Waxman Smits model has been sued to calculate rock saturation after accounting for temperature effects. The saturation estimates suggest that a region of drying develops around the heater and grows over time. The estimates also show regions increase in saturation over time, primarily below and to the sides of the heater. The accuracy of the saturation estimates depends on several factors that are only partly understood at the time of writing.

Ramirez, A., LLNL

1998-02-19

339

Virulence and resistance gene profiles of staphylococcus aureus strains isolated from ready-to-eat foods.  

PubMed

Staphylococcal food poisoning represents the most prevalent foodborne intoxication worldwide. Oral intake of staphylococcal enterotoxins from food can result in emesis and diarrhea and can be fatal in children and the elderly. Few data have been available on the characteristics and sources of Staphylococcus aureus strains isolated from ready-to-eat (RTE) foods. In this study, we used a DNA microarray to determine virulence and antimicrobial resistance gene profiles of S. aureus from RTE foods. A total of 267 S. aureus strains isolated from 244 RTE foods were investigated. The isolates originated from precooked foods (41% of isolates), meat and fish products (17%), cheese (13%), delicatessen salads (8%), sandwiches and canapés (8%), confectionery and bakery products (6%), and various other RTE foods (7%). Eleven samples (5%), of which 9 were raw milk cheeses, contained > 10(5) CFU/g, which is considered a health risk. Four S. aureus strains were associated with intoxications; three cases were linked to consumption of cheese and one case was linked to consumption of potato salad. DNA microarray results revealed that one-third of the tested strains had at least one major enterotoxin gene (sea through see). We also detected the toxic shock syndrome gene (18% of isolates) and various genes conferring antimicrobial resistance, including genes involved in resistance to beta-lactams (blaZ, 72% of isolates), methicillin (mecA, 1% of isolates), and vancomycin (vanB, 1% of isolates). S. aureus strains were most frequently assigned to clonal complex (CC) 30 (17% of isolates), CC8 (12%), CC15 (11%), and CC45 (10%), which are commonly detected in humans colonized or infected with S. aureus. Although a large proportion of the tested food items contained milk, we did not detect CC705, the most prevalent clonal complex among S. aureus isolates from bovine mastitis milk. Our results suggest that S. aureus isolates from RTE foods do not commonly originate from animals but more likely come from food handlers who contaminate foods. PMID:24988036

Baumgartner, Andreas; Niederhauser, Isabel; Johler, Sophia

2014-07-01

340

Three dimensional modeling and inversion of Borehole-surface Electrical Resistivity Data  

NASA Astrophysics Data System (ADS)

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 inversion procedure can be implemented by using open source software R3t (Lancaster University, UK). First, establish triangular prism meshes for the BSERT model by using the freeware gmsh (Geuzaine and Remacle, 2009). Second, transform the mesh data file into R3t required format and set the inversion areas in the mesh. Third, attach resistivity to the elements in the mesh according to the local geology analysis and resistivity logging results. Fourth, assign the field measured electric potential data to electrodes. Finally, set the inversion parameters and solve the inversion problem. Inversion results of synthetic modeling data can match well with the positions of anomalies and validate that the method works on the inversion of the borehole-surface electric resistivity data. Then filed example of Changqing oil field in China is carried out using the inversing method.

Zhang, Y.; Liu, D.; Liu, Y.; Qin, M.

2013-12-01

341

Correlation between Electrical Resistivity, Particle Dissolution, Precipitation of Dispersoids, and Recrystallization Behavior of AA7020 Aluminum Alloy  

NASA Astrophysics Data System (ADS)

This research concerns the effect of homogenization treatment on the electrical resistivity of AA7020 aluminum alloy variants with different Zr and Cr contents. Small changes in the Zr and Cr contents of the as-cast alloy increase the electrical resistivity significantly. After employing various homogenization treatments, the electrical resistivity decreases, which is due to the depletion of Zr, Cr, and Mn in the matrix, by forming small dispersoids. The optimum treatment proposed in order to obtain the smallest recrystallized grains is to hold the material at 550 °C for 24 hours, which results in the lowest electrical resistivity. The viability of the proposed treatment was tested through hot compression tests and static annealing. Indeed, the samples homogenized at 550 °C for 24 hours showed the smallest recrystallized grains compared to those homogenized at other temperatures.

Eivani, A. R.; Ahmed, H.; Zhou, J.; Duszczyk, J.

2009-10-01

342

Quantification and size-profiling of extracellular vesicles using tunable resistive pulse sensing.  

PubMed

Extracellular vesicles (EVs), including 'microvesicles' and 'exosomes', are highly abundant in bodily fluids. Recent years have witnessed a tremendous increase in interest in EVs. EVs have been shown to play important roles in various physiological and pathological processes, including coagulation, immune responses, and cancer. In addition, EVs have potential as therapeutic agents, for instance as drug delivery vehicles or as regenerative medicine. Because of their small size (50 to 1,000 nm) accurate quantification and size profiling of EVs is technically challenging. This protocol describes how tunable resistive pulse sensing (tRPS) technology, using the qNano system, can be used to determine the concentration and size of EVs. The method, which relies on the detection of EVs upon their transfer through a nano sized pore, is relatively fast, suffices the use of small sample volumes and does not require the purification and concentration of EVs. Next to the regular operation protocol an alternative approach is described using samples spiked with polystyrene beads of known size and concentration. This real-time calibration technique can be used to overcome technical hurdles encountered when measuring EVs directly in biological fluids. PMID:25350417

Maas, Sybren L N; De Vrij, Jeroen; Broekman, Marike L D

2014-01-01

343

Self-diagnosis of damage in fibrous composites using electrical resistance measurements  

NASA Astrophysics Data System (ADS)

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in situ damage detection and sensing in carbon fiber reinforced plastic (CFRP) composite structures. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and established quantitative relationships with the electrical resistance measurements. For processing of numerous measurement data, an autonomous data acquisition system was devised. We also established a specimen preparation procedure and a method for electrode setup. Coupon and panel CFRP laminate specimens with several known damage were tested and post-processed with the measurement data. Coupon specimens with various sizes of artificial delaminations obtained by inserting Teflon film were manufactured and the resistance was measured. The measurement results showed that increase of delamination size led to increase of resistance implying that it is possible to sense the existence and size of delamination. Encouraged by the results of coupon specimens, we implemented the measurement system on panel specimens. Three different quasi-isotropic panels were designed and manufactured: a panel with artificial delamination by inserting Teflon film at the midplane, a panel with artificial delamination by inserting Teflon film between the second and third plies from the surface, and an undamaged panel. The first two panels were designed to determine the feasibility of detecting delamination using the developed measurement system. The third panel had no damage at first, and then three different sizes of holes were drilled at a chosen location. Panels were prepared using the established procedures with six electrode connections on each side making a total of twenty-four electrode connections for a panel. All possible pairs of electrodes were scanned and the resistance was measured for each pair. The measurement results showed the possibility of the established measurement system for an in-situ damage detection method for CFRP composite structures.

Kang, Ji Ho; Paty, Spandana; Kim, Ran Y.; Tandon, G. P.

2006-03-01

344

Total plastic strain and electrical resistivity in high purity aluminum cyclically strained at 4.2 K  

E-print Network

TOTAL PLASTIC STRAIN AND ELECTRICAL RESISTIVITY IN HIGH PURITY ALUMINUM CYCLICALLY STRAINED AT 4. 2 K A Thesis by JAMES TERENCE GEHAN Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1988 Ulajor Subject: 1VIechanical Engineering TOTAL PLASTIC STRAIN AND ELECTRICAL RESISTIVITY IN HIGH PURITY ALUMINUM CYCLICALLY STRAINED AT 4. 2 K A Thesis by JAMES TERENCE GEHAN Approved...

Gehan, James Terence

1988-01-01

345

Novel laboratory methods for determining the fine scale electrical resistivity structure of core  

NASA Astrophysics Data System (ADS)

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 reduced to between 0.5 and 0.75 mm. Improvements to this resolution may be achieved by further reducing the electrode footprint to 0.1 mm × 0.1 mm using a novel high-impedance, non-contact potential probe. Initial results with this non-contact electric potential sensor indicate the possibility for generating images with grain-scale resolution.

Haslam, E. P.; Gunn, D. A.; Jackson, P. D.; Lovell, M. A.; Aydin, A.; Prance, R. J.; Watson, P.

2014-12-01

346

3-D Time-lapse Electrical Resistivity Monitoring of Injected CO2 in a Shallow Aquifer  

NASA Astrophysics Data System (ADS)

Contamination of potable groundwater by leaking CO2 is a potential risk of carbon sequestration. With the help of a field experiment, we investigate if surface electrical resistivity tomography (ERT) can detect dissolved CO2 in a shallow aquifer. For this purpose, we injected CO2 at a depth of 5 and 10 m and monitored its migration using 320 electrodes on a 126 m × 20 m surface grid. A fully automated acquisition system continuously collected data and uploaded it into an online database. The large amount of data allows for time-series analysis using geostatistical techniques for noise estimation and data interpolation to compensate for intermittent instrument failure. We estimate a time-dependent noise level for each ERT configuration, taking data variation and measurement frequency into account. A baseline inversion reveals the geology at the site consisting of aeolian sands near the surface and glacial sands below 5 m depth. Directly following the injection, we image the CO2 gas phase in the aquifer as an increase in resistivity and the higher water saturation in the unsaturated zone as a decrease in resistivity. At later times, the 2-D and 3-D time-lapse inversions clearly image the dissolved CO2 plume with decreased electrical resistivity values. We can image the geochemical changes induced by the dissolved CO2 until the end of the acquisition, 120 days after the injection start. During these 120 days, the CO2 migrates about 40 m in the expected groundwater flow direction (towards south-west). Water electrical conductivity (EC) sampling using 68 sensors in 31 wells allows for very good verification of the ERT results. Water EC and ERT results generally agree very well, with the water sampling showing some fine scale variations that cannot be resolved by the ERT. The ERT images have their strength in outlining the plume's shape in three dimensions and in being able to image the plume outside the well field. These results highlight the potential for imaging dissolved CO2 using non-intrusive surface electrical resistivity tomography.

Doetsch, J.; Vest Christiansen, A.; Auken, E.; Fiandaca, G.; Graham Cahill, A.

2013-12-01

347

Electrical resistivity change in amorphous Ta42Si13N45 films by stress relaxation  

NASA Astrophysics Data System (ADS)

In a first experiment, a reactively sputtered amorphous Ta42Si13N45 film about 260 nm thick deposited on a flat and smooth alumina substrate was thermally annealed in air for 30 min and let cooled again repeatedly at successively higher temperatures from 200 to 500 °C. This treatment successively and irreversibly increases the room temperature resistivity of the film monotonically from its initial value of 670 ?? cm to a maximum of 705 ?? cm (+5.2 %). Subsequent heat treatments at temperatures below 500 °C and up to 6 h have no further effect on the room temperature resistivity. The new value remains unchanged after 3.8 years of storage at room temperature. In a second experiment, the evolution of the initially compressive stress of a film similarly deposited by reactive sputtering on a 2-inch silicon wafer was measured by tracking the wafer curvature during similar thermal annealing cycles. A similar pattern of irreversible and reversible changes of stress was observed as for the film resistivity. Transmission electron micrographs and secondary ion mass profiles of the film taken before and after thermal annealing in air establish that both the structure and the composition of the film scarcely change during the annealing cycles. We reason that the film stress is implicated in the resistivity change. In particular, to interpret the observations, a model is proposed where the interface between the film and the substrate is mechanically unyielding.

Nicolet, M.-A.; Ryser, M.; Romano, V.

2014-12-01

348

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines  

DOEpatents

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.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2000-01-01

349

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines  

DOEpatents

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.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2001-01-01

350

Monitoring Shallow Vadose Zone Moisture Dynamics using Electrical Resistivity Tomography and Electromagnetic Induction  

NASA Astrophysics Data System (ADS)

High-resolution electrical resistivity tomography (ERT) and electromagnetic induction (EMI) surveys are currently being used to monitor changes in shallow moisture conditions at five different locations within a clayey vineyard site located in Vineland, Ontario, Canada. These geophysical measurements have been collected every 2-3 weeks since late summer 2010. Our current data set consists of a 12 month period encompassing a wide range of seasonal soil conditions including dry summer, wet fall and spring, and frozen winter periods. At each monitoring location, an ERT survey is collected using a half meter electrode spacing with 48 electrodes. EMI surveys using EM-38 and EM-31 devices are concurrently collected in both vertical and horizontal dipole modes. In addition, gravimetric water content data has been collected at each location. Preliminary analysis of these data show significant temporal variation in both ERT and EMI response due to seasonal moisture changes in the shallow subsurface overlying relatively stable moisture conditions. Gravimetric water content data supports these geophysical observations. Through the inversion of ERT data, differences in the seasonal evolution of resistivity at various depths down to 3 metres can be extracted. Future analysis will focus on how these depth-varying conductivities can be quantitatively extracted from EM-38 and EM-31 data. Additionally, ongoing studies are looking into the use of ERT-acquired resistivity data to calibrate the apparent electrical conductivity values obtained from EM-38 surveys.

Endres, A. L.; Toy, C. W.; Steelman, C. M.

2011-12-01

351

Time-lapse electrical resistivity investigations for imaging the grouting injection in shallow subsurface cavities.  

PubMed

The highway of Yongweol-ri, Muan-gun, south-western part of the South Korean Peninsula, is underlain by the abandoned of subsurface cavities, which were discovered in 2005. These cavities lie at shallow depths with the range of 5?15 meters below the ground surface. Numerous subsidence events have repeatedly occurred in the past few years, damaging infrastructure and highway. As a result of continuing subsidence issues, the Korean Institute of Geosciences and Mineral Resources (KIGAM) was requested by local administration to resolve the issue. The KIGAM used geophysical methods to delineate subsurface cavities and improve more refined understanding of the cavities network in the study area. Cement based grouting has been widely employed in the construction industry to reinforce subsurface ground. In this research work, time-lapse electrical resistivity surveys were accomplished to monitor the grouting injection in the subsurface cavities beneath the highway, which have provided a quasi-real-time monitoring for modifying the subsurface cavities related to ground reinforcement, which would be difficult with direct methods. The results obtained from time-lapse electrical resistivity technique have satisfactory imaged the grouting injection experiment in the subsurface cavities beneath the highway. Furthermore, the borehole camera confirmed the presence of grouting material in the subsurface cavities, and hence this procedure increases the mechanical resistance of subsurface cavities below the highway. PMID:24578621

Farooq, Muhammad; Park, Samgyu; Kim, Jung Ho; Song, Young Soo; Amjad Sabir, Mohammad; Umar, Muhammad; Tariq, Mohammad; Muhammad, Said

2014-01-01

352

Analytical model for the dynamic resistivity of electrically-exploded conductors  

SciTech Connect

A detailed model for the dynamic resistivity of an exploding conductor presents many difficulties. An electrically-exploded conductor undergoes significant hydrodynamic expansion as it is heated. Resistivity is a function of both the temperature and density of a conductor and realistic models for resistivity over the range of parameter space experienced by an exploding conductor are quite complex. See for example, the model of Lee and More (1984). Calculation of the hydrodynamic expansion of the conductor during and subsequent to the explosion is likewise dependent on detailed knowledge of the equation of state for the conductor in a range where few experimental data exist. A further complication is the strong magnetic field which couples the hydrodynamic expansion to the currents flowing in the expanding material. In spite of the difficulties, progress is being made on detailed modeling of fuses and exploding conductors (Lidemuth and co-workers, 1985). A simpler approach has proved to be quite useful for modeling the electrical behavior of exploding bridgewire and slapper detonators and for modeling the explosionss of large conductors exploded with large capacitor banks. In the work described here, a simple, empirical model was developed which can be expressed as a closed-form algebraic expression involving four parameters. This model has been used in a computer code which will calculate the burst times and burst currents for up to 15 conductors exploded in series in a capacitor-discharge circuit.

Lee, R.S.

1986-10-10

353

Time-Lapse Electrical Resistivity Investigations for Imaging the Grouting Injection in Shallow Subsurface Cavities  

PubMed Central

The highway of Yongweol-ri, Muan-gun, south-western part of the South Korean Peninsula, is underlain by the abandoned of subsurface cavities, which were discovered in 2005. These cavities lie at shallow depths with the range of 5?15 meters below the ground surface. Numerous subsidence events have repeatedly occurred in the past few years, damaging infrastructure and highway. As a result of continuing subsidence issues, the Korean Institute of Geosciences and Mineral Resources (KIGAM) was requested by local administration to resolve the issue. The KIGAM used geophysical methods to delineate subsurface cavities and improve more refined understanding of the cavities network in the study area. Cement based grouting has been widely employed in the construction industry to reinforce subsurface ground. In this research work, time-lapse electrical resistivity surveys were accomplished to monitor the grouting injection in the subsurface cavities beneath the highway, which have provided a quasi-real-time monitoring for modifying the subsurface cavities related to ground reinforcement, which would be difficult with direct methods. The results obtained from time-lapse electrical resistivity technique have satisfactory imaged the grouting injection experiment in the subsurface cavities beneath the highway. Furthermore, the borehole camera confirmed the presence of grouting material in the subsurface cavities, and hence this procedure increases the mechanical resistance of subsurface cavities below the highway. PMID:24578621

Farooq, Muhammad; Kim, Jung Ho; Song, Young Soo; Amjad Sabir, Mohammad; Umar, Muhammad; Tariq, Mohammad; Muhammad, Said

2014-01-01

354

State-of-health monitoring of lithium-ion batteries in electric vehicles by on-board internal resistance estimation  

Microsoft Academic Search

For reliable and safe operation of lithium-ion batteries in electric or hybrid vehicles, diagnosis of the cell degradation is necessary. This can be achieved by monitoring the increase of the internal resistance of the battery cells over the whole lifetime of the battery. In this paper, a method to identify the internal resistance in a hybrid vehicle is presented. Therefore,

Jürgen Remmlinger; Michael Buchholz; Markus Meiler; Peter Bernreuter; Klaus Dietmayer

2011-01-01

355

Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping  

NASA Astrophysics Data System (ADS)

The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm2, with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells.

Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A.; Rühle, Sven; Anderson, Assaf Y.; Zaban, Arie

2014-05-01

356

Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping.  

PubMed

The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm(2), with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells. PMID:24880411

Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A; Rühle, Sven; Anderson, Assaf Y; Zaban, Arie

2014-05-01

357

Expression Profile of Genes during Resistance Reversal in a Temephos Selected Strain of the Dengue Vector, Aedes aegypti  

PubMed Central

Background The mosquito Aedes aegypti is one of the most important disease vectors because it transmits two major arboviruses, dengue and yellow fever, which cause significant global morbidity and mortality. Chemical insecticides form the cornerstone of vector control. The organophosphate temephos a larvicide recommended by WHO for controlling Ae. aegypti, however, resistance to this compound has been reported in many countries, including Brazil. Methodology/Principal Findings The aim of this study was to identify genes implicated in metabolic resistance in an Ae. aegypti temephos resistant strain, named RecR, through microarray analysis. We utilized a custom ‘Ae. aegypti detox chip’ and validated microarray data through RT-PCR comparing susceptible and resistant individuals. In addition, we analyzed gene expression in 4th instar larvae from a reversed susceptible strain (RecRev), exposed and unexposed to temephos. The results obtained revealed a set of 13 and 6 genes significantly over expressed in resistant adult mosquitoes and larvae, respectively. One of these genes, the cytochrome P450 CYP6N12, was up-regulated in both stages. RT-PCR confirmed the microarray results and, additionally, showed no difference in gene expression between temephos exposed and unexposed RecRev mosquitoes. This suggested that the differences in the transcript profiles among the strains are heritable due to a selection process and are not caused by immediate insecticide exposure. Reversal of temephos resistance was demonstrated and, importantly, there was a positive correlation between a decrease in the resistance ratio and an accompanying decrease in the expression levels of previously over expressed genes. Some of the genes identified here have also been implicated in metabolic resistance in other mosquito species and insecticide resistant populations of Ae. aegypti. Conclusions/Significance The identification of gene expression signatures associated to insecticide resistance and their suppression could greatly aid the development of improved strategies of vector control. PMID:22870187

Strode, Clare; de Melo-Santos, Maria; Magalhães, Tereza; Araújo, Ana; Ayres, Contancia

2012-01-01

358

Integrated Very Low Frequency EM, electrical resistivity and Geological studies on the Lanta Khola landslide, North Sikkim, India  

NASA Astrophysics Data System (ADS)

Landslides are very common in high altitude Himalayan terrains. Major roads in the Himalayas are frequently blocked due to heavy landslides, and remain closed for long periods of time. Lanta Khola is one of the oldest landslides on the North Sikkim Highway (71.2 km north of the state capital of Sikkim, Gangtok) which is active since 1975. Rock types on either sides of the landslide are different (augen gneiss in the east and metapelitic schist in the west), and it is believed that the Main Central Thrust (MCT) passes through the slide zone. Permanent solutions to these landslides are required to keep the highway open. Delineation of subsurface structures below the landslide is very important in order to understand the triggers on slide activity. In such terrains, this can only be accomplished by geophysical survey. However, the steep slopes make it very difficult to find stretches of stable ground in these areas that are suitable for carrying out geophysical survey, especially electrical and electromagnetic. Very low frequency (VLF) electromagnetic survey is performed over Lanta Khola landside in North Sikkim Highway in order to depict the subsurface structure. Even though very limited numbers of VLF transmitters are available worldwide, it was possible to pick up the VLF signal from a number of VLF stations even in this high altitude mountainous terrain. VLF measurements along five profiles perpendicular to strike are recorded. High conducting zones are delineated from VLF observations. This conducting zone is also correlated with the low resistive zone delineated using gradient resistivity profiling. The anomalies confirm that there is a water saturated zone (‘soggy zone’) even in the subsurface of the slide, parallel to the geological gneiss-schist contact within the Lanta Khola slide. This indicates that the conductive feature correlates with a weak water-saturated debris layer that lies along, and is parallel to the geological contact. Resistive structures on either side of the landslide zone can thus be correlated with the stable ground. To minimize slide activity, it is therefore necessary to drain water from the soggy zone, since this zone appears to penetrate into the body of the slide

Sharma, S. P.; Anbarasu, K.; Gupta, S.; Sengupta, A.

2009-12-01

359

Investigation of karst by combined analysis of seismic and electrical resistivity anisotropy  

NASA Astrophysics Data System (ADS)

Seismic and electrical resistivity anisotropy of a fractured karstic limestone massif in sub-parallel underground galleries of the LSBB (Laboratoire Souterrain à Bas Bruit; Low Noise Underground Laboratory, Rustrel, France) have been studied in a massif composed of a rather homogeneous sub-horizontal thick sedimentary layer of limestone (100m) with vertically oriented fractures. If such fractures are oriented in a predominant direction, physical properties are dependent on the direction of measurements, producing seismic and electric anisotropy. Due to the dominantly vertical orientation of the fractures in the studied site, the resulting anisotropy is approximated by a horizontal transverse isotropic (- HTI) body. In addition, fractured limestone rock is prone to exhibit physical properties differing during seasonal changes which are connected with different sub-surface water contents. Two geophysical methods are sensible to the variations of water content. Acoustic waves have different propagation velocities in fractures filled with water than in those filled with air. Similarly, the rock resistivity is dependent on water content. Dry limestone has higher resistivities than limestone containing mineralised water within the fractures. Several data treatment methods and programs were applied to datasets of first arrival seismic travel-times (qP-wave and qS-wave) and resistivities. The applied seismic methods include: isotropic tomography, homogeneous Monte-Carlo anisotropic inversion for horizontal transverse isotropic body and anisotropic tomography for tilted transverse isotropic bodies. The applied resistivity method is azimuthal Monte-Carlo anisotropy resistivity fit. All methods lead to the conclusion that there is indeed an anisotropy present in the rock massif and all coincide on the calculated (inverted) values of searched parameters (such as maximum and minimum velocity, angle deviation of symmetry axis, variation of resistivities with respect to the angle). Strong seismic anisotropy of about 15-20% is present in the studied area. data from two different years show that this anisotropy varies over time. This variation is interpreted as being due to water content changes, being 10% larger for seismic properties in dry period than wet period of the year.

Beres, Jan; Zeyen, Hermann; Sénéchal, Guy; Rousset, Dominique; Gaffet, Stéphane

2013-04-01

360

Modelling the electrical resistivity response to CO2 plumes generated in a laboratory, cylindrical sandbox  

NASA Astrophysics Data System (ADS)

CO2 capture and storage into deep geological formations is one of the main solutions proposed to reduce the concentration of anthropic CO2 in the atmosphere. The monitoring of injection sites is a crucial issue to assess for the long term viability of CO2 storage. With the intention of detecting potential leakages, we are investigating the possibility of using electrical resistivity tomography (ERT) techniques to detect CO2 transfers in the shallow sub-surface. ERT measurements were performed during a CO2 injection in a cylindrical tank filled with Fontainebleau sand and saturated with water. Several measurements protocols were tested. The inversion of the resistances measured with the software R3T (Binley and Kemna (2005)) clearly showed that the CO2 injection induces significant changes in the resistivity distribution of the medium, and that ERT has a promising potential for the detection and survey of CO2 transfers through unconsolidated saturated media. We modeled this experiment using Matlab by building a 3D cellular automaton that describes the CO2 spreading, following the geometric and stochastic approach described by Selker et al. (2007). The CO2 circulation is described as independents, circular and continuous gas channels whose horizontal spread depends on a Gaussian probability law. From the channel distribution we define the corresponding gas concentration distribution and calculate the resistivity of the medium by applying Archie's law for unsaturated conditions. The forward modelling was performed with the software R3T to convert the resistivity distribution into resistances values, each corresponding to one of the electrode arrays used in the experimental measurements. Modelled and measured resistances show a good correlation, except for the electrode arrays located at the top or the bottom of the tank. We improved the precision of the model by considering the effects due to CO2 dissolution in the water which increases the conductivity of the saturated water in the vicinity of the plume. Finally, a special interest is given to the electrode configurations and measurement protocols. A numerical study was realized using R3T to assess the information that each electrode configuration can provide. We built a map of their sensitivity to resistivity changes. From these results, we studied the resolution of several electrode combinations by inverting the associated resistance in order to reduce the number of data really necessary to get a good imaging of the plume and thus accelerate the acquisition time.

Kremer, T.; Maineult, A. J.; Binley, A.; Vieira, C.; Zamora, M.

2012-12-01

361

Phase boundary estimation in electrical resistance tomography with weighted multi-layered neural networks and front point approach  

Microsoft Academic Search

This work presents a boundary estimation approach in electrical impedance imaging for binary mixture fields based on weighted multi-layered neural network and front point approach. The interfacial boundary is expressed with front points and the unknown front points are estimated with the weighted multi-layered neural network. Numerical experiments show that the proposed electrical resistance imaging approach has a good possibility

Jae Hyoung Kim; Byoung Chae Kang; Seong Hun Lee; Bong Yeol Choi; Min Chan Kim; Bong Seok Kim; Umer Zeeshan Ijaz; Kyung Youn Kim; Sin Kim

2006-01-01

362

Carbon fiber polymer-matrix structural composites for electrical-resistance-based sensing  

NASA Astrophysics Data System (ADS)

This dissertation has advanced the science and technology of electrical-resistance-based sensing of strain/stress and damage using continuous carbon fiber epoxy-matrix composites, which are widely used for aircraft structures. In particular, it has extended the technology of self-sensing of carbon fiber polymer-matrix composites from uniaxial longitudinal loading and flexural loading to uniaxial through-thickness loading and has extended the technology from structural composite self-sensing to the use of the composite (specifically a one-lamina composite) as an attached sensor. Through-thickness compression is encountered in the joining of composite components by fastening. Uniaxial through-thickness compression results in strain-induced reversible decreases in the through-thickness and longitudinal volume resistivities, due to increase in the fiber-fiber contact in the through-thickness direction, and minor-damage-induced irreversible changes in these resistivities. The Poisson effect plays a minor role. The effects in the longitudinal resistivity are small compared to those in the through-thickness direction, but longitudinal resistance measurement is more amenable to practical implementation in structures than through-thickness resistance measurement. The irreversible effects are associated with an increase in the through-thickness resistivity and a decrease in the longitudinal resistivity. The through-thickness gage factor is up to 5.1 and decreases with increasing compressive strain above 0.2%. The reversible fractional change in through-thickness resistivity per through-thickness strain is up to 4.0 and decreases with increasing compressive strain. The irreversible fractional change in through-thickness resistivity per unit through-thickness strain is around -1.1 and is independent of the strain. The sensing is feasible by measuring the resistance away from the stressed region, though the effectiveness is less than that at the stressed region. A one-lamina carbon fiber epoxy-matrix composite is an effective attached flexural sensor, with effectiveness comparable to a commercially manufactured self-sensing 24-lamina quasi-isotropic carbon fiber epoxy-matrix composite. In the one-lamina sensor, the arrangement of the fibers is such that adjacent fibers make contact with one another at points along their length, as shown by the substantial conductivity in the transverse direction. The surface resistance of the sensor attached to the tension surface of the beam increases upon flexure, due to decrease in the degree of current penetration within thickness of the sensor. The surface resistance of the sensor attached to the compression surface of the beam decreases upon flexure, due to increase in the degree of current penetration. The sensing effectiveness is superior for the tension surface than the compression surface. Minor/major/catastrophic damage and damage evolution during flexure are indicated by characteristic increases in the surface resistance of the one-lamina sensor; the characteristics are simpler and easier to interpret than those of previously reported 24-lamina quasi-isotropic carbon fiber composites without glass fiber.

Wang, Daojun

363

Xenopus laevis oocytes infected with multi-drug–resistant bacteria: implications for electrical recordings  

PubMed Central

The Xenopus laevis oocyte has been the workhorse for the investigation of ion transport proteins. These large cells have spawned a multitude of novel techniques that are unfathomable in mammalian cells, yet the fickleness of the oocyte has driven many researchers to use other membrane protein expression systems. Here, we show that some colonies of Xenopus laevis are infected with three multi-drug–resistant bacteria: Pseudomonas fluorescens, Pseudomonas putida, and Stenotrophomonas maltophilia. Oocytes extracted from infected frogs quickly (3–4 d) develop multiple black foci on the animal pole, similar to microinjection scars, which render the extracted eggs useless for electrical recordings. Although multi-drug resistant, the bacteria were susceptible to amikacin and ciprofloxacin in growth assays. Supplementing the oocyte storage media with these two antibiotics prevented the appearance of the black foci and afforded oocytes suitable for whole-cell recordings. Given that P. fluorescens associated with X. laevis has become rapidly drug resistant, it is imperative that researchers store the extracted oocytes in the antibiotic cocktail and not treat the animals harboring the multi-drug–resistant bacteria. PMID:21788613

O'Connell, Denice; Mruk, Karen; Rocheleau, Jessica M.

2011-01-01

364

Electron mean free path of tungsten and the electrical resistivity of epitaxial (110) tungsten films  

NASA Astrophysics Data System (ADS)

This work describes a study of the classical electrical resistivity size effect in tungsten. The important length scale for this size effect is the isotropic average electron mean free path (EMFP), which was determined to be 19.1 nm for W at 293 K by employing density functional theory. To explore the size effect experimentally, (110) oriented epitaxial W films with thicknesses ranging from 9.8 to 299.7 nm were prepared by sputter deposition onto (112¯0) Al2O3 substrates at 520 °C followed by postdeposition annealing in Ar-4%H2 at 850 °C. Film resistivities were measured at room temperature and at liquid He temperature. The Fuchs-Sondheimer (FS) surface scattering model with a low specularity parameter (p = 0.11) was shown to provide a good description of the film resistivity as a function of film thickness. Further, it is shown that an upper bound to the EMFP cannot be established by fitting resistivity data to the FS model, whereas a lower bound can be assessed.

Choi, Dooho; Kim, Chang Soo; Naveh, Doron; Chung, Suk; Warren, Andrew P.; Nuhfer, Noel T.; Toney, Michael F.; Coffey, Kevin R.; Barmak, Katayun

2012-07-01

365

Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature.  

PubMed

A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ~10 × 1 × 1 mm(3). It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (~±2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ~3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ~7 × 1.5 × 0.5 mm(3) with very good agreement with literature. PMID:24182159

Rouleau, O; Alleno, E

2013-10-01

366

Eradication of multidrug-resistant A. baumannii in burn wounds by antiseptic pulsed electric field  

PubMed Central

Emerging bacterial resistance to multiple drugs is an increasing problem in burn wound management. New non-pharmacologic interventions are needed for burn wound disinfection. Here we report on a novel physical method for disinfection: antiseptic pulsed electric field (PEF) applied externally to the infected burns. In a mice model, we show that PEF can reduce the load of multidrug resistant Acinetobacter baumannii present in a full thickness burn wound by more than four orders of magnitude, as detected by bioluminescence imaging. Furthermore, using a finite element numerical model, we demonstrate that PEF provides non-thermal, homogeneous, full thickness treatment for the burn wound, thus, overcoming the limitation of treatment depth for many topical antimicrobials. These modeling tools and our in vivo results will be extremely useful for further translation of the PEF technology to the clinical setting, as they provide the essential elements for planning of electrode design and treatment protocol. PMID:25089285

Golberg, Alexander; Broelsch, G. Felix; Vecchio, Daniela; Khan, Saiqa; Hamblin, Michael R.; Austen, William G.; Sheridan, Robert L.; Yarmush, Martin L.

2014-01-01

367

Electrical resistivity of some palladium-silver alloys containing hydrogen at 4.2 K  

NASA Technical Reports Server (NTRS)

The electrical resistivities of the alloys 90at.%Pd - 10at.%Ag, 80at.%Pd - 20at.%Ag, 70at.%Pd - 30at.%Ag, 60at.%Pd - 40at.%Ag, and 50at.%Pd - 50at.%Ag were measured as functions of absorbed hydrogen x at 4.2 K. These results show a minimum in the resistivity for all the alloys except 90Pd-10Ag; they show a maximum for all the alloys except for 50Pd-Ag. We associate the shapes of the plots with a modification of the Pd D-band because of the substitutional alloying of Ag and the interstitial absorption of hydrogen.

Smith, R. J.; Otterson, D. A.

1974-01-01

368

Damage Characterization in SiC/SiC Composites using Electrical Resistance  

NASA Technical Reports Server (NTRS)

SiC/SiC ceramic matrix composites (CMCs) under creep-rupture loading accumulate damage by means of local matrix cracks that typically form near a stress concentration, such as a 90o fiber tow or large matrix pore, and grow over time. Such damage is difficult to detect through conventional techniques. Electrical resistance changes can be correlated with matrix cracking to provide a means of damage detection. Sylramic-iBN fiber-reinforced SiC composites with both melt infiltrated (MI) and chemical vapor infiltrated (CVI) matrix types are compared here. Results for both systems exhibit an increase in resistance prior to fracture, which can be detected either in situ or post-damage.

Smith, Craig E.; Xia, Zhenhai

2011-01-01

369

Epikarstic storage and doline structural characterization with time-lapse geophysics (seismic refraction & electrical resistivity)  

NASA Astrophysics Data System (ADS)

Karst formations are one of the most challenging environments in terms of groundwater, engineering and environmental issues. Geophysical methods can provide useful subsurface information in karst regions concerning groundwater vulnerability assessment, exploitation or hazard estimation. First, dolines are studied as preferential pathways for the protection of karstic aquifer in south France. Geophysics helps to characterize lateral and underground morphologies of such objects and is able to detect doline hidden by the soil cover too. Electrical resistivity and seismic refraction tomographies provide information about dolines filling and could help to propose a genesis scenario. Time-lapse resistivity measurements show that the studied doline is more vulnerable to infiltration on its sides than at its centre. The epikarst could be defined as a perched aquifer above the massive carbonate rocks; it constitutes a highly fractured zone, which water stock capacities. So, the epikarst was investigated with 3D seismic refraction and results show an important velocity anisotropy linked to the fracturing and weathering of the dolostone. The 3D model presents also some large heterogeneities: a corridor with highly weathered dolostone and an unweathered pinnacle. The corridor is probably situated on vertical joints, which have conducted aggressive water. The associated weathering with residual weathered-rock keeping its initial volume could create a "ghost-rock" corridor. So, the epikarst in the dolostones of the Causse du Larzac (France) seems to be composed by "ghost-rock" developed around a specific direction of fractures. Time-lapse electrical resistivity and seismic refraction velocity were carried out on this epikarst to observe the influence of water saturation on the measurements. The results show important variations for both seismic and electrical methods and are localized in the first 6 m: in the weathered zone. So, time-lapse measurements could more easily identify the storage of the epikarst and its bottom than one-time measurements; and with some calibration, semi-quantitative estimation of water saturation could be realized.

Valois, R.; Galibert, P.; Guérin, R.; Mendes, M.; Plagnes, V.

2011-12-01

370

High resolution electrical resistivity tomography of golf course greens irrigated with reclaimed wastewater: Hydrological approach  

NASA Astrophysics Data System (ADS)

Actually, there are over 300 golf courses and more than three thousand licensed players in Spain. For this reason golf cannot be considered simply a hobby or a sport, but a very significant economic activity. Considered as one of the most rapidly expanding land-use and water demanding business in the Mediterranean, golf course development generates controversy. In the recent years there has been a considerable demand for golf courses to adopt environmentally sustainable strategies and particularly water authorities are forcing by law golf managers to irrigate with alternative water resources, mainly reclaimed wastewater. Watering practices must be based on soil properties that are characterized by samples removed from the different zones of the golf course and submitted to an accredited physical soil testing laboratory. Watering schedules are critical on greens with poor drainage or on greens with excessively high infiltration rates. The geophysical survey was conducted over the greens of the Girona Golf Club. Eighteen electrical resistivity tomographies were acquired using a mixed Wenner-Schlumberger configuration with electrodes placed 0.5 meter apart. Small stainless-steel nails were used as electrodes to avoid any damage in the fine turfgrass of greens The resistivity meter was set for systematically and automatically selects current electrodes and measurement electrodes to sample apparent resistivity values. Particle size analysis (PSA) has been performed on soil materials of any putting green. The PSA analysis has been composed of two distinct phases. The first has been the textural analysis of the soils for determining the content of sand, silt, and clay fraction via the use of a stack of sieves with decreasing sized openings from the top sieve to the bottom. Subsequently, the hydraulic conductivity of the substrates has been evaluated by means of Bredding and Hazen empirical relationships. The results of this research show that the electrical resistivity tomography is a non-invasive and cost-effective technique for high resolution characterizing the subsurface below golf course greens. The obtained models have provided detailed information on the lateral and vertical variability of each the subsurface and from an empirical correlation between the values of electrical resistivity and hydraulic permeability to assess the preferred areas of drainage that could pose in risk to the vulnerability of the underlying aquifers.

Tapias, Josefina C.; Lovera, Raúl; Himi, Mahjoub; Gallardo, Helena; Sendrós, Alexandre; Marguí, Eva; Queralt, Ignasi; Casas, Albert

2014-05-01

371

Skid resistance performance of asphalt wearing courses with electric arc furnace slag aggregates.  

PubMed

Metallurgical slags are by-products of the iron and steel industry and are subdivided into blast furnace slag and steel slag according to the different steel-producing processes. In Greece, slags are mostly produced from steelmaking using the electric arc furnace process, and subsequently are either disposed in a random way or utilized by the cement industry. Steel slag has been recently used, worldwide, as hard aggregates in wearing courses in order to improve the skidding resistance of asphalt pavements. At the Highway Laboratory, Department of Civil Engineering of Aristotle University of Thessaloniki research has been carried out in the field of steel slags, and especially in electric arc furnace (EAF) slag, to evaluate their possible use in highway engineering. In this paper, the recent results of anti-skidding performance of steel slag aggregates in highway pavements are presented. PMID:19423603

Kehagia, Fotini

2009-05-01

372

Electric field effects in low resistance CoFeB-MgO magnetic tunnel junctions with perpendicular anisotropy  

NASA Astrophysics Data System (ADS)

We have investigated the electric field effects in low resistance perpendicular magnetic tunnel junction (MTJ) devices and found that the electric field can effectively reduce the coercivity (Hc) of free layer (FL) by 30% for a bias voltage Vb = -0.2 V. In addition, the bias field (Hb) on free layer is almost linearly dependent on Vb yet independent on the device size. The demonstrated Vb dependences of Hc and Hb in low resistance MTJ devices present the potential to extend the scalability of the electric field assisted spin transfer torque magnetic random access memory and improve its access speed.

Meng, H.; Sbiaa, R.; Akhtar, M. A. K.; Liu, R. S.; Naik, V. B.; Wang, C. C.

2012-03-01

373

A magnetron sputtering system for the preparation of patterned thin films and in situ thin film electrical resistance measurements  

SciTech Connect

We describe a versatile three gun magnetron sputtering system with a custom made sample holder for in situ electrical resistance measurements, both during film growth and ambient changes on film electrical properties. The sample holder allows for the preparation of patterned thin film structures, using up to five different shadow masks without breaking vacuum. We show how the system is used to monitor the electrical resistance of thin metallic films during growth and to study the thermodynamics of hydrogen uptake in metallic thin films. Furthermore, we demonstrate the growth of thin film capacitors, where patterned films are created using shadow masks.

Arnalds, U. B.; Agustsson, J. S.; Ingason, A. S.; Eriksson, A. K.; Gylfason, K. B.; Gudmundsson, J. T.; Olafsson, S. [Matvice, Dunhaga 3, IS-107 Reykjavik (Iceland); Mentis Cura ehf., Grandagardi 7, IS-107 Reykjavik (Iceland); Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland); Microsystem Technology Laboratory, School of Electrical Engineering, KTH-Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland) and Department of Electrical and Computer Engineering, University of Iceland, Hjardarhaga 2-6, IS-107 Reykjavik (Iceland); Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland)

2007-10-15

374

Reduced electrical resistivity in TiO2:Nb/ZnO:Ga film by thermal annealing  

NASA Astrophysics Data System (ADS)

Layered films consisting of transparent conducting oxides, Ga-doped ZnO (GZO) and Nb-doped TiO2 (TNO), were fabricated on glass substrates and their electrical properties were investigated. As-deposited TNO/GZO films showed the mean resistivity of TNO and GZO films. Thermal annealing reduced the resistivity of these films; however, TNO/GZO films exhibited the lowest value among them. The carrier concentration and Hall mobility of TNO/GZO films increased with the reduction in electrical resistivity. The thickness dependence, annealing temperature dependence, and crystalline orientation of the TNO and GZO layers in TNO/GZO films indicated that the improvement of the electrical properties of the GZO underlayer contributed to the resistivity reduction behavior of TNO/GZO films induced by thermal annealing.

Yamada, Yasuji; Funaki, Shuhei; Ichiyanagi, Seiji; Kikuchi, Hiroki; Inoue, Sota

2014-01-01

375

Changes in electrical transport and density of states of phase change materials upon resistance drift  

NASA Astrophysics Data System (ADS)

Phase-change memory technology has become more mature in recent years. But some fundamental problems linked to the electrical transport properties in the amorphous phase of phase-change materials still need to be solved. The increase of resistance over time, called resistance drift, for example, poses a major challenge for the implementation of multilevel storage, which will eventually be necessary to remain competitive in terms of high storage densities. To link structural properties with electrical transport, a broader knowledge of (i) changes in the density of states (DoS) upon structural relaxation and (ii) the influence of defects on electrical transport is required. In this paper, we present temperature-dependent conductivity and photo-conductivity measurements on the archetype phase change material GeTe. It is shown that trap-limited band transport at high temperatures (above 165 K) and variable range hopping at low temperatures are the predominating transport mechanism. Based on measurements of the temperature dependence of the optical band gap, modulated photo-conductivity and photo-thermal deflection spectroscopy, a DoS model for GeTe was proposed. Using this DoS, the temperature dependence of conductivity and photo-conductivity has been simulated. Our work shows how changes in the DoS (band gap and defect distributions) will affect the electrical transport before and after temperature-accelerated drift. The decrease in conductivity upon annealing can be explained entirely by an increase of the band gap by about 12%. However, low-temperature photo-conductivity measurements revealed that a change in the defect density may also play a role.

Krebs, Daniel; Bachmann, Tobias; Jonnalagadda, Prasad; Dellmann, Laurent; Raoux, Simone

2014-04-01

376

Monitoring Carbon Dioxide Sequestration Using Electrical Resistance Tomography (ERT): A Minimally Invasive Method  

SciTech Connect

Successful geologic sequestration of carbon dioxide (CO{sub 2}), will require monitoring the CO{sub 2} injection to confirm the performance of the caprock/reservoir system, assess leaks and flow paths, and understand the geophysical and geochemical interactions between the CO{sub 2} and the geologic minerals and fluids. Electrical methods are especially well suited for monitoring processes involving fluids, as electrical properties are sensitive to the presence and nature of the formation fluids. High resolution tomographs of electrical properties are now used for site characterization and to monitor subsurface migration of fluids (i.e., leaking underground tanks, infiltration events, steam floods, contaminant movement, and to assess the integrity of engineered barriers). When electrical resistance tomography (ERT) imaging can be performed using existing well casings as long electrodes, the method is nearly transparent to reservoir operators, and reduces the need for additional drilling. Using numerical simulations and laboratory experiments, we have conducted sensitivity studies to determine the potential of ERT methods to detect and monitor the migration of CO{sub 2} in the subsurface. These studies have in turn been applied to the design and implementation of the first field casing surveys conducted in an oil field undergoing a CO{sub 2} flood.

Newmark, R L; Ramirez, A L; Daily, W D

2002-08-05

377

A One-Dimensional Model of the Electrical Resistance Sintering Process  

NASA Astrophysics Data System (ADS)

In this work, a theoretical model for the processing technique usually known as electrical resistance sintering (ERS) under pressure is proposed and validated. This technique consists of the consolidation of a metallic powder mass under compression by means of a high-intensity electrical current that passes through the aggregate. The electrical current heats the powder mass by the Joule effect. The model is numerically solved by the finite differential method, in which the added difficulty of the thermal-mechanical coupling of the process has been taken into account. To simplify the numerical resolution, a one-dimensional scheme has been considered for both the powder densification mechanical problem and the heat generation and transmission problem. Furthermore, the theoretical predictions obtained after solving the model are compared with the data recorded by the ERS equipment sensors during electrical consolidation experiments with iron and titanium powders. The reasonable agreement between the theoretical and experimental curves suggests that the model, despite its simplifications, reproduces the main characteristics of the process.

Montes, J. M.; Cuevas, F. G.; Cintas, J.; Urban, P.

2015-02-01

378

Genetic diversity and antimicrobial resistance profiles of Salmonella enterica serotype derby isolated from pigs, pork, and humans in France.  

PubMed

In France, Salmonella enterica serotypes Typhimurium and Derby are the most often isolated serotypes in pigs. Moreover, serotype Derby usually ranks between third and fourth in prevalence among human isolates in France. The aim of this study was to evaluate the genetic relationships between human and pig Salmonella Derby isolates based on their pulsed-field gel electrophoresis (PFGE) patterns after XbaI, BlnI, and SpeI restriction and on their antimicrobial resistance profiles. The 196 studied isolates were isolated in 2006 and 2007: 73 from fattening pigs, 27 from pork, and 96 from humans. Forty-four PFGE XbaI patterns were identified. A major pattern (SDX01) was identified for 96 isolates (49%). This pattern was common to pig, pork, and human isolates. Among the 146 isolates tested for their antimicrobial resistance, 84.2% (n=123) showed resistance to at least one antibiotic and 69.2% (n=101) were simultaneously resistant to at least streptomycin, sulfonamides, and tetracycline. Most of the isolates that are resistant to these three antibiotics also displayed the major SDX01 pattern. The use of two other restriction enzymes on a part of the panel (155 isolates) brought a significant increase in the discriminatory index, in particular for SDX01 strains. As Salmonella Derby is essentially isolated from pigs, and major resistance and PFGE patterns of isolates from pigs and pork were very similar to human isolates, human salmonellosis due to Salmonella Derby may be related to pigs. PMID:23944749

Kerouanton, Annaëlle; Rose, Valérie; Weill, François-Xavier; Granier, Sophie A; Denis, Martine

2013-11-01

379

Drug resistance profile and biofilm forming potential of Pseudomonas aeruginosa isolated from contact lenses in Karachi-Pakistan  

PubMed Central

Background The contaminated contact lens provides Pseudomonas aeruginosa an ideal site for attachment and biofilm production. Continuous contact of the eye to the biofilm-infested lens can lead to serious ocular diseases, such as keratitis (corneal ulcers). The biofilms also prevent effective penetration of the antibiotics, which increase the chances of antibiotic resistance. Methods For this study, 22 Pseudomonas aeruginosa isolates were obtained from 36 contact lenses and 14 contact lens protective fluid samples. These isolates were tested against eight commonly used antibiotics using Kirby-Bauer disk diffusion method. The biofilm forming potential of these isolates was also evaluated using various qualitative and quantitative techniques. Finally, a relationship between biofilm formation and antibiotic resistance was also examined. Results The isolates of Pseudomonas aeruginosa tested were found resistant to most of the antibiotics tested. Qualitative and quantitative biofilm analysis revealed that most of the isolates exhibited strong biofilm production. The biofilm production was significantly higher in isolates that were multi-drug resistant (p?resistant, biofilm forming Pseudomonas aeruginosa isolates are mainly involved in contact lens associated infections. This appears to be the first report from Pakistan, which analyzes both antibiotic resistance profile and biofilm forming potential of Pseudomonas aeruginosa isolates from contact lens of the patients with contact lens associated infections. PMID:24134792

2013-01-01

380

Pulsed-field gel electrophoresis typing, antibiotic resistance, and plasmid profiles of Escherichia coli strains isolated from foods.  

PubMed

Bacterial contamination in foods and antimicrobial resistance levels of common pathogenic strains causing food-borne disease are important in human health. Thus, typing technologies are important tools to determine primary sources of bacterial contamination. In this study, 40 Escherichia coli strains isolated from 85 food samples were evaluated in terms of genetic diversity, susceptibility to certain antibiotics, and plasmid profiles. Pulsed-field gel electrophoresis was used to identify the genetic relations of E. coli isolates. It was determined that the 40 E. coli strains revealed 32 different pulsotypes represented by 6 subtypes. Antibiotic susceptibility tests conducted by using a disc diffusion method against 15 antibiotics showed that although the isolates revealed 14 different types of resistance profiles, the strains showed the greatest resistance to ampicillin (77.5%), followed by ticarcillin-clavulanic acid (30%), tetracycline (22.5%), and cephalothin (14.5%). Plasmid isolations studies of the strains conducted by the method of alkaline lysis revealed that 18 (45%) of 40 E. coli strains contain 31 different plasmid bands ranging between 64.4 and 1 kb. The results showed that PFGE was a powerful method in tracking sources of food contamination and that the antibiotic resistance levels of food isolates were high and should be monitored. PMID:23145825

Uysal, Ahmet; Durak, Yusuf

2012-11-01

381

Comparison of virulence factors and antibiotic resistance profiles of Escherichia coli strains from humans and dogs with urinary tract infections.  

PubMed

The purpose of this study was to compare virulence factors and antibiotic resistance profiles of Escherichia coli strains isolated from dogs and humans with urinary tract infections. Factors studied included resistance to antibiotics and the transferability of R-plasmids to a recipient E. coli; production of colicins, hemolysins, beta-lactamase, and urease; hemagglutination of erythrocytes; and fermentation of dulcitol. The canine E. coli isolates had a wider range of antibiotic resistance and a higher R-plasmid transmissibility rate. A higher percentage of the canine isolates produced colicins (40% vs. 24%), hemolysins (44% vs. 16%), beta-lactamase (52% vs. 4%), and fermented dulcitol (84% vs. 80%) as compared with the human isolates. The human isolates had a greater ability to hemagglutinate erythrocytes as compared with the canine isolates (24% vs. 8%). None of the isolates produced urease. PMID:3333412

Nolan, L K; Wooley, R E; Brown, J; Blue, J L; Camp, M

1987-01-01

382

Permafrost Changes along the Alaska Highway Corridor, Southern Yukon, from Ground Temperature Measurements and DC Electrical Resistivity Tomography  

NASA Astrophysics Data System (ADS)

A natural gas pipeline running across permafrost terrain from Prudhoe Bay, Alaska, through Canada to US markets was first proposed more than 30 years ago. In the intervening period, mean annual air temperatures in the region have risen by 0.5-1.0°C and it is probable that the ground has also warmed. Renewed interest in the pipeline has meant that information on permafrost and geotechnical conditions within the Alaska Highway Corridor of the southern Yukon must be updated for engineering design and the assessment of environmental impacts. To accomplish this goal, results from 1977-1981 drilling and ground temperature monitoring programs within the proposed pipeline corridor were used in combination with air photo analysis to select sites potentially sensitive to climate change. The sites are distributed across the extensive and sporadic discontinuous permafrost zones over a distance of 475 km between Beaver Creek and Whitehorse. To date, 11 targeted boreholes with permafrost have been found and cased to permit renewed ground temperature monitoring. By the end of summer 2011, it is expected that another 7 will have been instrumented. Measurable temperature increases relative to the 1970s are expected, except where values were previously just below 0°C. In the latter case, if the sites are still in permafrost, latent heat effects may have substantially moderated the temperature increase. Electrical resistivity tomography surveys are also being conducted to characterize the local permafrost distribution and geotechnical conditions. These 2D resistivity profiles will be used with the ground temperatures to examine current conditions and response to climate change and vegetation disturbance.

Duguay, M. A.; Lewkowicz, A. G.; Smith, S.

2011-12-01

383

Mutations Conferring Resistance to Viral DNA Polymerase Inhibitors in Camelpox Virus Give Different Drug-Susceptibility Profiles in Vaccinia Virus  

PubMed Central

Cidofovir or (S)-HPMPC is one of the three antiviral drugs that might be used for the treatment of orthopoxvirus infections. (S)-HPMPC and its 2,6-diaminopurine counterpart, (S)-HPMPDAP, have been described to select, in vitro, for drug resistance mutations in the viral DNA polymerase (E9L) gene of vaccinia virus (VACV). Here, to extend our knowledge of drug resistance development among orthopoxviruses, we selected, in vitro, camelpox viruses (CMLV) resistant to (S)-HPMPDAP and identified a single amino acid change, T831I, and a double mutation, A314V+A684V, within E9L. The production of recombinant CMLV and VACV carrying these amino acid substitutions (T831I, A314V, or A314V+A684V) demonstrated clearly their involvement in conferring reduced sensitivity to viral DNA polymerase inhibitors, including (S)-HPMPDAP. Both CMLV and VACV harboring the A314V change showed comparable drug-susceptibility profiles to various antivirals and similar impairments in viral growth. In contrast, the single change T831I and the double change A314V+A684V in VACV were responsible for increased levels of drug resistance and for cross-resistance to viral DNA polymerase antivirals that were not observed with their CMLV counterparts. Each amino acid change accounted for an attenuated phenotype of VACV in vivo. Modeling of E9L suggested that the T?I change at position 831 might abolish hydrogen bonds between E9L and the DNA backbone and have a direct impact on the incorporation of the acyclic nucleoside phosphonates. Our findings demonstrate that drug-resistance development in two related orthopoxvirus species may impact drug-susceptibility profiles and viral fitness differently. PMID:22532673

Andrei, Graciela; Topalis, Dimitri; Kre?merová, Marcela; Crance, Jean-Marc; Garin, Daniel; Snoeck, Robert

2012-01-01

384

Discovery of genes implicated in whirling disease infection and resistance in rainbow trout using genome-wide expression profiling  

PubMed Central

Background Whirling disease, caused by the pathogen Myxobolus cerebralis, afflicts several salmonid species. Rainbow trout are particularly susceptible and may suffer high mortality rates. The disease is persistent and spreading in hatcheries and natural waters of several countries, including the U.S.A., and the economic losses attributed to whirling disease are substantial. In this study, genome-wide expression profiling using cDNA microarrays was conducted for resistant Hofer and susceptible Trout Lodge rainbow trout strains following pathogen exposure with the primary objective of identifying specific genes implicated in whirling disease resistance. Results Several genes were significantly up-regulated in skin following pathogen exposure for both the resistant and susceptible rainbow trout strains. For both strains, response to infection appears to be linked with the interferon system. Expression profiles for three genes identified with microarrays were confirmed with qRT-PCR. Ubiquitin-like protein 1 was up-regulated over 100 fold and interferon regulating factor 1 was up-regulated over 15 fold following pathogen exposure for both strains. Expression of metallothionein B, which has known roles in inflammation and immune response, was up-regulated over 5 fold in the resistant Hofer strain but was unchanged in the susceptible Trout Lodge strain following pathogen exposure. Conclusion The present study has provided an initial view into the genetic basis underlying immune response and resistance of rainbow trout to the whirling disease parasite. The identified genes have allowed us to gain insight into the molecular mechanisms implicated in salmonid immune response and resistance to whirling disease infection. PMID:18218127

Baerwald, Melinda R; Welsh, Amy B; Hedrick, Ronald P; May, Bernie

2008-01-01

385

Impact of nitrogen depth profiles on the electrical properties of crystalline high-K gate dielectrics  

NASA Astrophysics Data System (ADS)

The electrical characteristics of crystalline ZrO2 gate dielectrics with different nitrogen depth profiles were investigated, which were treated by the in-situ atomic layer doping of nitrogen and post-deposition nitridation processes, respectively, using remote NH3 plasma at a low treatment temperature of 250 °C. The crystalline ZrO2 gate dielectric of the tetragonal/cubic phase was formed by post-metallization annealing (PMA) at a low temperature of 450 °C, resulting in an increase of the dielectric constant. As compared with the in-situ atomic layer doping of nitrogen, the post-deposition nitrogen process leads to a lower capacitance equivalent thickness of 1.13 nm with a low leakage current density of 1.35 × 10-5 A/cm2. The enhanced capacitance density caused by the post-deposition nitrogen treatment may be ascribed to the high nitrogen concentration at the top surface of gate dielectric, giving rise to the suppression of oxygen diffusion from the ambient toward the interface and so a thinner interfacial layer. The result reveals that the nitrogen incorporation at the top surface of gate oxide is favorable to the scaling of crystalline high-K gate dielectrics.

Huang, Jhih-Jie; Tsai, Yi-Jen; Tsai, Meng-Chen; Huang, Li-Tien; Lee, Min-Hung; Chen, Miin-Jang

2015-01-01

386

Resistivity profiling to locate an infiltration area and the possible recovery of the dried Andara lake (Picos de Europa National Park, Spain)  

NASA Astrophysics Data System (ADS)

The Ándara Lake constituted the third mass of water by extension (approximately 19000 m2) within the calcareous Picos de Europa Massif in NW Spain, but only a small pond remains today (about 1250 m2). The lake developed in a former glacial valley and its sudden draining occurred in the second decade of the 20th century, during the development of underground Pb-Zn mining, between 1889 and 1929, in the vicinity. Old mining maps show that there were shallow galleries active below the bottom of the ancient lake. The present study was requested by the Picos de Europa National Park Administration (Spanish Ministry of Environment) with the purpose of: i) localizing the areas of water infiltration and ii) establishing the cause of the draining, specially its possible relation with the mining activity in the surroundings. With this aim a geological study of the substrate of the lake was made, followed by a series of electrical resistivity profiles. Three resistivity parallel profiles were recorded along the axis of the dried lake on the 29th July. Each profile included 56 electrodes with 5 m spacing for a total profile length of 275 m. Data was recorded in both dipole-dipole and Schlumberger array configuration. The western profile had been recorded earlier in the summer (30th June) and was also repeated towards the end of the season (3rd September) in order to evaluate the evolution of the infiltrations. The results showed two areas of infiltration to the NE and SW of the present-day pond. Both of them cut across the underlying carboniferous limestone. However. the southwestern anomaly does not reach the surface and may be related with water flowing in karstic conduits in the limestone. The northeastern one reached the surface and the anomaly decreased as the pond dried during the summer allowing us to interpret it as the main area of infiltration. This area coincides with the intersection of two seams exploited both on the surface and by underground mining. This corroborates the relationship between the water disappearance and the mining activities, which is an indispensable condition for the National Park management to consider taking any future actions aimed to a possible recovery of the original water mass.

Gallastegui, Jorge; Olona, Javier; Farias, Pedro; González-Cortina, Juan Manuel; Fernández-Viejo, Gabriela; López, Carlos; Cadenas, Patricia

2013-04-01

387

A cylindrical electrical resistivity tomography array for three-dimensional monitoring of hydrate formation and dissociation.  

PubMed

The LArge Reservoir Simulator (LARS) was developed to investigate various processes during gas hydrate formation and dissociation under simulated in situ conditions of relatively high pressure and low temperature (close to natural conditions). To monitor the spatial hydrate distribution during hydrate formation and the mobility of the free gas phase generated during hydrate dissociation, a cylindrical Electrical Resistivity Tomography (ERT) array was implemented into LARS. The ERT contains 375 electrodes, arranged in 25 circular rings featuring 15 electrodes each. The electrodes were attached to a neoprene jacket surrounding the sediment sample. Circular (2D) dipole-dipole measurements are performed which can be extended with additional 3D cross measurements to provide supplemental data. The data quality is satisfactory, with the mean standard deviation due to permanent background noise and data scattering found to be in the order of 2.12%. The measured data are processed using the inversion software tool Boundless Electrical Resistivity Tomography to solve the inverse problem. Here, we use data recorded in LARS to demonstrate the data quality, sensitivity, and spatial resolution that can be obtained with this ERT array. PMID:24182137

Priegnitz, Mike; Thaler, Jan; Spangenberg, Erik; Rücker, Carsten; Schicks, Judith M

2013-10-01

388

Monitoring freshwater salinization in analog transport models by time-lapse electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

Deep saline aquifers are target formations both for the geological storage of carbon dioxide as well as for geothermal applications. High pressure gradients, resulting from fluid or gas injection processes, provide a potential driving force for the displacement of native formation waters, implicating a potential salinization of shallow freshwater resources. Geoelectrical monitoring techniques are sensitive to compositional changes of groundwater resources, and hence capable to detect salinization processes at an early stage. In this context, numerical simulations and analog modeling can provide a valuable contribution by identifying probable salinization scenarios, and thereby guiding an optimum sensor network layout within the scope of an early warning system. In this study, coupled numerical flow and transport simulations of a laterally uniform salinization scenario were carried out and used to support a subsequent realization in a laboratory sandbox model. During the experiment, electrical resistivity tomography (ERT) was applied in a practical surface-borehole setup in order to determine the spatio-temporal variations of electrical properties influenced by saltwater intrusion. Inversion results of different electrode configurations were evaluated and compared to numerical simulations. With regard to surface-borehole measurements, good results were obtained using crossed bipoles, while regular bipole measurements were more susceptible to noise. Within the scope of a single-hole tomography, the underlying resistivity distribution was best reproduced using the Wenner configuration, which was substantiated by synthetic modeling.

Wagner, Florian M.; Möller, Marcus; Schmidt-Hattenberger, Cornelia; Kempka, Thomas; Maurer, Hansruedi

2013-02-01

389

Development of an Electrical Resistivity Imaging Program for Subsurface Characterization at Hanford  

SciTech Connect

Recent successes in subsurface plume imaging over waste storage and disposal facilities using electrical resistivity geophysics has prompted the expansion of the science into a full program for environmental characterization. Characterization using direct current electrical resistivity imaging (ERI) was first tested over liquid waste disposal trenches at the BC Cribs and Trenches (BCCT) site, south of the 200 East area of Hanford. The geophysical data were compared to borehole data with favorable conclusions. Since the initial deployment at BCCT, the method has been applied at several other facilities within the Hanford Nuclear Reservation and significant achievements have been made to solve the complex nature of the industrial environment, namely metallic infrastructure such as storage tanks, pipes, wells, and other objects that interfere with plume imaging. The solution was to directly include the infrastructure into the measurement strategy. Other achievements include placement of deep subsurface electrodes during decommissioning of small-diameter characterization boreholes, permanent electrodes on the surface to allow reoccupation for time-lapsed imaging, enhancements in computer hardware and software to solve larger problems with increased resolution, and the installation of a quality assurance program to ensure instrument and data integrity. (authors)

Rucker, D.F.; Levitt, M.T. [hydroGEOPHYSICS, Inc., Tucson, AZ (United States); Myers, D.A. [CH2M Hill Hanford Group, Richland, WA (United States); Henderson, C. [Columbia Energy and Environmental Services, Richland, WA (United States)

2008-07-01

390

Electrical resistivity and dielectric properties of helical microorganism cells coated with silver by electroless plating  

NASA Astrophysics Data System (ADS)

In this paper, microorganism cells (Spirulina platens) were used as forming templates for the fabrication of the helical functional particles by electroless silver plating process. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer. The crystal structures were characterized by employing the X-ray diffraction. The electrical resistivity and dielectric properties of samples containing different volume faction of sliver-coated Spirulina cells were measured and investigated by four-probe meter and vector network analyzer. The results showed that the Spirulina cells were successfully coated with a uniform silver coating and their initial helical shapes were perfectly kept. The electrical resistivity and dielectric properties of the samples had a strong dependence on the volume content of sliver-coated Spirulina cells and the samples could achieve a low percolation value owing to high aspect ratio and preferable helical shape of Spirulina cells. Furthermore, the conductive mechanism was analyzed with the classic percolation theory, and the values of ? and t were obtained.

Cai, Jun; Lan, Mingming; Zhang, Deyuan; Zhang, Wenqiang

2012-09-01