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1

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

2

Electrical Resistivity Imaging  

EPA Science Inventory

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

3

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

4

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

5

Electrical resistivity of thin bismuth films  

Microsoft Academic Search

The thickness dependence of electrical resistivity of thin bismuth films deposited on to glass substrates has been studied in the temperature range 77 to 350 K. The structural studies show that films are polycrystalline with grain size increasing with thickness. The electrical resistivity decreases with increasing temperature. This type of temperature dependence of electrical resistivity arises due to the competition

A. Kumar; O. P. Katyal

1990-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

7

From spatial-continuous electrical resistivity measurements to the soil hydraulic functioning at the field scale  

Microsoft Academic Search

The aim of this article is to present a strategy to interpret the hydraulic functioning of a small field area by using measurements of the soil electrical resistivity. The spatial soil electrical resistivity was recorded at a high resolution on a 2ha area by the MultiContinous Electrical Profiling (MuCEP) device at two dates. These apparent electrical resistivity measurements were firstly

Isabelle Cousin; Arlène Besson; Hocine Bourennane; Catherine Pasquier; Bernard Nicoullaud; Dominique King; Guy Richard

2009-01-01

8

Electrical resistivity investigations over limestone caverns  

E-print Network

submerged in salt solution. 26 Figure 4. Location of' thesis area. Figure 5. Topography neer Knox Cave. Figure o. Topography near Schoharie Caverns, Figure 7. Cross-sections of passages traversed at Schoharie Caverns. Figure B. Cross-sections of pass... . Vertical profiles over passage south of Dungeon, Knox Cave. 61 viii Figure 19. Apparent resistivity vs. effective depth of meas- urement ~ Vertical profiles over Dome, Knox Cave. page 62 Figure 20. Apparent resistivity vs. effective depth of meas...

Porter, Charles Osgood

2012-06-07

9

Electrical Trades. Ohio's Competency Analysis Profile.  

ERIC Educational Resources Information Center

Developed through a modified DACUM (Developing a Curriculum) process involving business, industry, labor, and community agency representatives in Ohio, this document is a comprehensive and verified employer competency profile for electrical trades. The list contains units (with and without subunits), competencies, and competency builders that…

Ohio State Univ., Columbus. Vocational Instructional Materials Lab.

10

Electrical Trades. Occupational Competency Analysis Profile.  

ERIC Educational Resources Information Center

This Occupational Competency Analysis Profile (OCAP), which is one of a series of OCAPs developed to identify the skills that Ohio employers deem necessary to entering a given occupation/occupational area, lists the occupational, academic, and employability skills required of individuals entering the electrical trades. The introduction explains…

Ohio State Univ., Columbus. Vocational Instructional Materials Lab.

11

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

12

The electrical resistivity of cytoplasm.  

PubMed Central

The apparent cytoplasmic resistivity of two different giant cells has been measured using an extension of a previously developed single microelectrode technique. Each cell is penetrated by a metal microelectrode whose complex impedance is measured as a function of frequency between 500 kHz and 5.7 MHz. By plotting the measured impedance data on the complex Z plane and extrapolating the data to infinite frequency, the substantial effects of electrode polarization can be overcome. For Aplysia giant neurons and muscle fibers of the giant barnacle, the extrapolated cytoplasmic specific resistivities are 40 and 74 omega-cm, respectively, at infinite frequency. The barnacle data are in excellent agreement with sarcoplasmic resistivity values derived from the measured cable properties of other marine organisms, and from high frequency conductivity cell measurements in intact barnacle muscle tissue. In the Aplysia neurons, the frequency-dependent part of the electrode impedance is larger when the electrode is in a cell than when it is in an electrolyte solution with the same specific resistivity as the aqueous cytoplasm; however, the phase angle of the frequency-dependent component of the electrode impedance is the same in both cases. This suggests that the high apparent values of cytoplasmic resistivity found using the single microelectrode technique at lower frequencies probably reflect an artifact caused by reduction of the effective surface area of the electrode by intracellular membranes, with a corresponding increase in its polarization impedance. PMID:963211

Foster, K R; Bidinger, J M; Carpenter, D O

1976-01-01

13

Electrical resistance of carbon-nanofiber concrete  

NASA Astrophysics Data System (ADS)

Concrete is the most widely used construction material, and carbon nanofibers have many advantages in both mechanical and electrical properties such as high strength, high Young's modulus and high conductivity. In this paper, the mechanical and electrical properties of concrete containing carbon nanofibers (CNF) are experimentally studied. The test results indicate that the compressive strength and per cent reduction in electrical resistance while loading concrete containing CNF are much greater than those of plain concrete. Finally, a reasonable concentration of CNF is obtained for use in concrete which not only enhances compressive strength, but also improves the electrical properties required for strain monitoring, damage evaluation and self-health monitoring of concrete.

Gao, Di; Sturm, Mariel; Mo, Y. L.

2009-09-01

14

Electrical resistivity of potassium at low temperatures  

Microsoft Academic Search

The low-temperature electrical resistivity of potassium is calculated and compared with the recent, highly accurate measurements in the range 2-20 °K. Excellent agreement with experiment is obtained. It is found that explicity including phonon drag accounts precisely for the exponential temperature dependence observed for the resistivity below 4 °K. We show how to determine the screened electron-ion interaction matrix elements,

Moshe Kaveh; Nathan Wiser

1974-01-01

15

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

16

Electrical Resistivity and Viscosity of Tektite Glass  

Microsoft Academic Search

The electrical resistivity of 25 tektites from seven different strewn fields has been measured as a function of temperature from 330-450øK by a time of discharge technique. From these data the activation energy for each specimen has been determined. It is shown that by using an equation similar to that found empirically by Littleton a viscosity curve be- tween 1370

A. I-IOYTE; F. SENFTLE; P. WIRTZ

1985-01-01

17

Electrical resistance tomography from measurements inside a steel cased borehole  

DOEpatents

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

Daily, William D. (Livermore, CA); Schenkel, Clifford (Walnut Creek, CA); Ramirez, Abelardo L. (Pleasanton, CA)

2000-01-01

18

Electrical resistivity and seismic refraction studies for groundwater in the Jodhpura area, Rajasthan  

Microsoft Academic Search

The results of geophysical investigations carried out for groundwater employing seismic refraction and electrical resistivity methods near Jodhpura (27o47'30?N:75o42'40?E) in the Jhunjhunu District, Rajasthan, are presented. Prominent resistivity low zones, revealed by the resistivity profiles, are indicative of deeper section of unconsolidated sediments overlying the bedrock and are usually favourable locations for groundwater. An equiresistivity and water-level contour map based

P. C. Paul; N. P. Dutta

1968-01-01

19

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

20

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 reserved. Keywords: Battery modeling; Battery simulation; Electric circuit simulation; Resistive companion 2000; accepted 27 August 2000 Abstract Resistive companion (RC) modeling is an easy-to-use approach

21

Electrical Resistivity Inversion Constrained by Resistivity Cone Penetrometry (RCPT): Application to Landfill Site Characterisation  

NASA Astrophysics Data System (ADS)

Areas of clay-rich tills in the UK are attractive sites for landfills. The relatively impermeable clays act as a barrier between landfill contents and surrounding permeable materials, but tills often contain sand and gravel deposits, which may be water-bearing and/or hydraulically connected to aquifers or surface water bodies. The sands and gravels may be missed by borehole and trial-pit led site investigations but cause flooding of landfill excavations or act as leachate flow routes. Electrical resistance tomography (ERT) is potentially an appropriate subsurface imaging tool for landfill site characterisation, due to its ability to distinguish permeable sand and gravel from clays.. However, engineers want more accurate identification of interface depth than standard ERT inversions supply. Here, the use of reference geoelectrical models based on Resistivity Cone Penetrometry (RCPT) data is investigated. The use of RCPT data can potentially guide the inversion algorithm towards improved solutions. A series of synthetic electrical resistivity and RCPT data from model profiles with various shaped sand bodies within a clay background were generated, and inverted with and without RCPT constraints. The ability of the guided inversion to reconstruct the original geoelectrical model was assessed quantitatively. Preliminary results indicate that using RCPT data as a constraint can significantly improve interfacial depth accuracy in the inverted data. The use of depth information to constrain 1-D layer models in resistivity sounding is already well established. Hence, an alternative approach to the incorporation of depth information is construction of a pseudo-2D resistivity profile from 1-D soundings extracted from ERT data, inverted using depth-constrained layer models. The accuracy and limitations of this approach will be compared with the reference model approach described above. Future work will include the acquisition and processing of field RCPT and ERT data.

Catt, L. M.; West, L. J.; Clark, R.; Murray, T.

2005-05-01

22

From spatial-continuous electrical resistivity measurements to the soil hydraulic functioning at the field scale  

NASA Astrophysics Data System (ADS)

The aim of this article is to present a strategy to interpret the hydraulic functioning of a small field area by using measurements of the soil electrical resistivity. The spatial soil electrical resistivity was recorded at a high resolution on a 2 ha area by the MultiContinous Electrical Profiling (MuCEP) device at two dates. These apparent electrical resistivity measurements were firstly interpreted in terms of local electrical resistivity by 1D inverse modelling to estimate the real resistivity of the soil. These interpreted electrical resistivity data were then transformed into soil water content values and soil water potential values by the use of independent punctual data of water content and the use of the water retention curve determined by laboratory data. Our analysis has permitted us to describe the spatial variability and temporal evolution of the hydraulic functioning at high resolution from electrical resistivity data. The interpretation of the water content and matric potential maps demonstrated that some soil hydraulic processes, such as lateral overland flow, can occur in the studied zone. They would never have been detected by local measurements of soil characteristics or by the use of the soil map.

Cousin, Isabelle; Besson, Arlène; Bourennane, Hocine; Pasquier, Catherine; Nicoullaud, Bernard; King, Dominique; Richard, Guy

2009-10-01

23

Evaluation of pozzolanic activity by the electric resistance measurement method  

SciTech Connect

Measurements of electric resistance and amount of consumption of portlandite were carried out in accelerated curing conditions by preparing pastes of Fine Ceraments, fly ash, silica fume, kaolin, acid clay, zeolite and quartz activated with portlandite. Electric resistances of reactive pozzolans showed sharp rises except that of kaolin, whereas that of inactive material, quartz, showed no sharp rise. Electric resistances are proportional to the consumptions of portlandite except for fly ashes. The electric resistance measurement method combined with portlandite consumption measurement is useful to the rapid evaluation of pozzolanic activity.

Tashiro, Chuichi; Ikeda, Ko (Yamaguchi Univ., Ube (Japan). Dept. of Advanced Materials Science and Engineering); Inoue, Yoshihiro (Fuji Denki Kagaku Co., Ltd., Kosai (Japan))

1994-01-01

24

Resistance to Cognitive Interference as a Function of MMPI Profile  

ERIC Educational Resources Information Center

This study tests the hypothesis that resistance to interference as measured by Stroop Color and Word Test is related to psychopathology. College student subjects were classified into three groups on the basis of their Minnesota Multiphasic Personality Inventory (MMPI) profile high points. Subjects' cognitive interference scores significantly…

Golden, Charles J.; Golden, Ellen E.

1975-01-01

25

Resistance Profiles of Novel Electrostatically Constrained HIV-1 Fusion Inhibitors*  

PubMed Central

Human immunodeficiency virus (HIV) gp41 plays a key role in viral fusion; the N- and C-terminal heptad repeats (N-HR and C-HR) of gp41 form a stable 6-helical conformation for fusion. Therefore, HR-derived peptides, such as enfuvirtide (T-20), inhibit HIV-1 fusion by acting as decoys, and have been used for the treatment of HIV-1 infection. However, the efficacy of T-20 is attenuated by resistance mutations in gp41, including V38A and N43D. To suppress the resistant variants, we previously developed electrostatically constrained peptides, SC34 and SC34EK, and showed that both exhibited potent anti-HIV-1 activity against wild-type and T-20-resistant variants. In this study, to clarify the resistance mechanism to this next generation of fusion inhibitors, we selected variants with resistance to SC34 and SC34EK in vitro. The resistant variants had multiple mutations in gp41. All of these mutations individually caused less than 6-fold resistance to SC34 and SC34EK, indicating that there is a significant genetic barrier for high-level resistance. Cross-resistance to SC34 and SC34EK was reduced by a simple difference in the polarity of two intramolecular electrostatic pairs. Furthermore, the selected mutations enhanced the physicochemical interactions with N-HR variants and restored activities of the parental peptide, C34, even to resistant variants. These results demonstrate that our approach of designing gp41-binding inhibitors using electrostatic constraints and information derived from resistance studies produces inhibitors with enhanced activity, high genetic barrier, and distinct resistance profile from T-20 and other inhibitors. Hence, this is a promising approach for the design of future generation peptide fusion inhibitors. PMID:20937812

Shimura, Kazuya; Nameki, Daisuke; Kajiwara, Keiko; Watanabe, Kentaro; Sakagami, Yasuko; Oishi, Shinya; Fujii, Nobutaka; Matsuoka, Masao; Sarafianos, Stefan G.; Kodama, Eiichi N.

2010-01-01

26

MicroRNA expression profile of bromocriptine-resistant prolactinomas.  

PubMed

MicroRNAs (miRNA) have been implicated in the resistance of tumors to chemotherapy. However, little is known about miRNA expression in bromocriptine-resistant prolactinomas. In this study, 23 prolactinoma samples were classified as bromocriptine-sensitive or -resistant according to the clinical definition of bromocriptine resistance, and their miRNA expression profiles were determined using Solexa sequencing. We found 41 miRNAs that were differentially expressed between the two groups, and 12 of these were validated by stem-loop qRT-PCR. Hsa-mir-93, hsa-mir-17, hsa-mir-22*, hsa-mir-126*, hsa-mir-142-3p, hsa-mir-144*, hsa-mir-486-5p, hsa-mir-451, and hsa-mir-92a were up-regulated and hsa-mir-30a, hsa-mir-382, and hsa-mir-136 were down-regulated in bromocriptine-resistant prolactinomas in comparison with bromocriptine-sensitive prolactinomas. Furthermore, silencing of mir-93 significantly increased the sensitivity of MMQ cells to dopamine agonist treatment. Mir-93 directly affected p21 expression in MMQ cells by targeting the 3'-UTR. Our study is the first to identify a miRNA expression profile associated with bromocriptine-resistant prolactinoma. PMID:25064468

Wu, Zhe Bao; Li, Wei Qiang; Lin, Shao Jian; Wang, Cheng De; Cai, Lin; Lu, Jiang Long; Chen, Yun Xiang; Su, Zhi Peng; Shang, Han Bing; Yang, Wen Lei; Zhao, Wei Guo

2014-09-01

27

Detection of sinkholes using 2D electrical resistivity imaging  

Microsoft Academic Search

Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging, or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. RESTOM surveys were conducted at two sinkhole sites near Pretoria, South Africa. The survey

Michael van Schoor

2002-01-01

28

Detection of sinkholes using 2D electrical resistivity imaging  

Microsoft Academic Search

Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging, or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. RESTOM surveys were conducted at two sinkhole sites near Pretoria, South Africa. The survey

Michael van Schoor

29

Electrical Stimulation for Drug-Resistant Epilepsy  

PubMed Central

Objective The objective of this analysis was to evaluate the effectiveness of deep brain stimulation (DBS) and vagus nerve stimulation (VNS) for the treatment of drug-resistant epilepsy in adults and children. Data Sources A literature search was performed using MEDLINE, EMBASE, the Cochrane Library, and the Centre for Reviews and Dissemination database, for studies published from January 2007 until December 2012. Review Methods Systematic reviews, meta-analyses, randomized controlled trials (RCTs), and observational studies (in the absence of RCTs) of adults or children were included. DBS studies were included if they specified that the anterior nucleus of thalamus was the area of the brain stimulated. Outcomes of interest were seizure frequency, health resource utilization, and safety. A cost analysis was also performed. Results The search identified 6 studies that assessed changes in seizure frequency after electrical stimulation: 1 RCT on DBS in adults, 4 RCTs on VNS in adults, and 1 RCT on VNS in children. The studies of DBS and VNS in adults found significantly improved rates of seizure frequency, but the study of VNS in children did not find a significant difference in seizure frequency between the high and low stimulation groups. Significant reductions in hospitalizations and emergency department visits were found for adults and children who received VNS. No studies addressed the use of health resources for patients undergoing DBS. Five studies reported on adverse events, which ranged from serious to transient for both procedures in adults and were mostly transient in the 1 study of VNS in children. Limitations We found no evidence on DBS in children or on health care use related to DBS. The measurement of seizure frequency is self-reported and is therefore subject to bias and issues of compliance. Conclusions Based on evidence of low to moderate quality, both DBS and VNS seemed to reduce seizure frequency in adults. In children, VNS did not appear to be as effective at reducing seizure frequency, but children had significantly fewer hospitalizations and ED visits after VNS implantation. Despite the considerable risks associated with these invasive procedures, long-term adverse events appear to be limited. Plain Language Summary Electrical stimulation of specific areas of the brain is a procedure used to control epileptic seizures when more conventional treatments are not working. Most adults and children with epilepsy are able to control their seizures with medication, but for some patients, drugs are not effective and surgery to remove the part of the brain where the seizures start is not an appropriate option. This study looked at the research available on the effectiveness, safety, and cost of two types of electrical stimulation devices currently licensed for treatment of epilepsy for adults and children in Canada: vagus nerve stimulation (VNS) and deep brain stimulation (DBS). Both approaches appear to be effective at reducing the frequency of seizures in adults. However, the evidence on DBS is limited to a single study with adults; we found no studies of DBS with children. Studies on VNS showed that both adults and children had fewer hospitalizations and emergency department visits after the procedure. Both procedures carry serious risks, but several longer-term studies have found that adverse events appear to be limited. The cost of VNS, including the process of assessing whether or not patients are good candidates for the procedure, is estimated to be about $40,000 per person (and higher for DBS because the device is more expensive and the operating time is longer). Of the 70,000 people in Ontario with epilepsy, about 1,400 (300 children and 1,110 adults) may be candidates for VNS to reduce their seizures. PMID:24228081

Chambers, A; Bowen, JM

2013-01-01

30

Electrical Resistance Decrease Due to Grain Coarsening Under Cyclic Deformation  

NASA Astrophysics Data System (ADS)

Electrical resistance of polymer-supported thin metal films subjected to cyclic tensile loading typically is expected to grow with the cycle number due to fatigue-induced damage. Here it is demonstrated that electrical resistance can also decrease with the cycle number. Using electron backscatter diffraction analysis, it is shown that significant strain-induced, room-temperature grain coarsening is responsible for the resistance decrease. Grain coarsening has a vital effect on the electrical stability of metal films in a low-cycle fatigue regime.

Glushko, O.; Cordill, M. J.

2014-04-01

31

The Physics Classroom: Electrical Resistance: Journey of a Typical Electron  

NSDL National Science Digital Library

This is an interactive tutorial for introductory physics on resistance and Ohm's Law. It explores the journey of an electron through the wires of an electric circuit, explaining how countless collisions between the charge carriers and atoms within the wires result in loss of electrical energy. In the second part of the tutorial, students learn about factors affecting resistance, resistivity values, and how to calculate resistance mathematically. This page is part of The Physics Classroom, a comprehensive set of interactive tutorials, labs, and simulations for students of introductory physics. The Physics Classroom is one of the ComPADRE digital library collections.

Henderson, Tom

2010-06-22

32

Electrical resistivity of low temperature sintered perovskites  

Microsoft Academic Search

Lanthanum–Manganese perovskites are suitable for application as a cathode contact layer in SOFC-stacks. This work describes the resistivity of Lanthanum–Manganese samples which were pre-sintered at different temperatures before annealing at 850 °C in air. Due to the different degrees of sintering, measured resistivity values of low temperature sintered perovskites are higher than resistivity values reported in the literature. For a low

Stefan Megel; Klaus Eichler; Nikolai Trofimenko; Soeren Hoehn

2006-01-01

33

Structureactivity profiles of eleutherobin analogs and their cross-resistance in Taxol-resistant cell lines  

Microsoft Academic Search

Purpose: Eleutherobin, a natural product, is an antimitotic agent that promotes the polymerization of stable microtubules. Although\\u000a its mechanism of action is similar to that of Taxol, its structure is distinct. A structure-activity profile of synthetic\\u000a eleutherobin derivatives that have modifications at C3, C8 and C15 was undertaken to define the structural requirements for\\u000a microtubule stabilization and cross-resistance in Taxol-resistant

Hayley M. McDaid; Samit K. Bhattacharya; Xiao-Tao Chen; Lifeng He; Heng-Jia Shen; Clare E. Gutteridge; Susan Band Horwitz; Samuel J. Danishefsky

1999-01-01

34

Resist profile control in immersion lithography using scatterometry measurements  

NASA Astrophysics Data System (ADS)

Control of critical dimension (CD) and resist profile is increasingly important in low-k1 lithography, and becomes more difficult in thin resist processing due to the chemical interaction occurring at the resist surfaces. Implementation of immersion lithography will make the control even more challenging since more sources of chemical interaction can play a role, e.g. leaching of photo active material from the resist into the water, or diffusion of the water into the resist. Moreover, the contact of the liquid in the scanner showerhead with the wafer surface is a dynamic and local interaction, which needs to be understood and quantified, since variations in soak time are a possible source of intra-field and across wafer CD-variations. In this paper we developed a methodology to understand and to quantify the impact of immersion scanner soak on resist profile control and CD-control. The methodology is on the one hand based on the simulation of the showerhead movements over the wafer during the immersion lithography process, where for a particular location on the wafer the soak time is calculated by accumulating the interaction time every time the showerhead is passing that particular location. On the other hand the methodology quantifies experimentally how much resist profile change and CD-variation is caused by a particular pre- and post-soak time, by testing the process in a virtual immersion set-up and measuring the CD-response with high-precision scatterometry. In this way, we were able to predict CD-variations related to immersion soak. Using the initial resist and topcoat processes, we recently experimentally verified on the ASML XT:1250Di immersion tool at IMEC that these soak related CD-variations exist. The effects are small, but in line with the soak time simulations and the CD-response obtained on the virtual immersion set-up. This demonstrates that the methodology described above could be very useful to select materials for lithography processes and to set specifications for allowed CD-variations in line with to the over-all allowed CD-budget.

Pollentier, I.; Ercken, M.; Foubert, P.; Cheng, S. Y.

2005-05-01

35

Electrical Resistivity as an Indicator of Saturation in Fractured Geothermal Reservoir Rocks: Experimental Data and Modeling  

SciTech Connect

The electrical resistivity of rock cores under conditions representative of geothermal reservoirs is strongly influenced by the state and phase (liquid/vapor) of the pore fluid. In fractured samples, phase change (vaporization/condensation) can result in resistivity changes that are more than an order of magnitude greater than those measured in intact samples. These results suggest that electrical resistivity monitoring of geothermal reservoirs may provide a useful tool for remotely detecting the movement of water and steam within fractures, the development and evolution of fracture systems and the formation of steam caps. We measured the electrical resistivity of cores of welded tuff containing fractures of various geometries to investigate the resistivity contrast caused by active boiling and to determine the effects of variable fracture dimensions and surface area on water extraction from the matrix. We then used the Nonisothermal Unsaturated Flow and Transport model (NUFT) (Nitao, 1998) to simulate the propagation of boiling fronts through the samples. The simulated saturation profiles combined with previously reported measurements of resistivity-saturation curves allow us to estimate the evolution of the sample resistivity as the boiling front propagates into the rock matrix. These simulations provide qualitative agreement with experimental measurements suggesting that our modeling approach may be used to estimate resistivity changes induced by boiling in more complex systems.

Detwiler, R L; Roberts, J J

2003-06-23

36

Modeling Fluid Flow and Electrical Resistivity in Fractured Geothermal Reservoir Rocks  

SciTech Connect

Phase change of pore fluid (boiling/condensing) in rock cores under conditions representative of geothermal reservoirs results in alterations of the electrical resistivity of the samples. In fractured samples, phase change can result in resistivity changes that are more than an order of magnitude greater than those measured in intact samples. These results suggest that electrical resistivity monitoring may provide a useful tool for monitoring the movement of water and steam within fractured geothermal reservoirs. We measured the electrical resistivity of cores of welded tuff containing fractures of various geometries to investigate the resistivity contrast caused by active boiling and to determine the effects of variable fracture dimensions and surface area on water extraction. We then used the Nonisothermal Unsaturated Flow and Transport model (NUFT) (Nitao, 1998) to simulate the propagation of boiling fronts through the samples. The simulated saturation profiles combined with previously reported measurements of resistivity-saturation curves allow us to estimate the evolution of the sample resistivity as the boiling front propagates into the rock matrix. These simulations provide qualitative agreement with experimental measurements suggesting that our modeling approach may be used to estimate resistivity changes induced by boiling in more complex systems.

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

2003-01-14

37

Electrical resistivity and phase transformation of hematite under shock compression  

Microsoft Academic Search

Electrical resistivity measurements of hematite (alpha-Fe2O3) were performed under shock compression in the range of 240-760kbar. The specimens used were coarsely polycrystalline natural material from Brazil. The electrical resistivity decreases gradually with increasing shock pressure to 440 kbar and decreases discontinuously to less than 1 Omega cm from several tens of ohm centimeters at pressures of 440-520 kbar. The phase

Ken-ichi Kondo; Tsutomu Mashimo; Akira Sawaoka

1980-01-01

38

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

39

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

40

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

41

Marine permafrost detection using galvanic electrical resistivity methods  

SciTech Connect

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

Corwin, R.F.

1983-05-01

42

The electrical resistivity during pre-precipitation processes  

Microsoft Academic Search

The behaviour of the electrical resistivity of a binary alloy during preprecipitation is discussed on the basis of a model in which the conduction electrons are described by free wave-functions and are scattered by deviations from the average lattice potential due to localized atomic clustering. The maximum in the resistivity which appears during ageing is shown to occur when the

P. L. Rossiter; P. Wells

1971-01-01

43

Resistivity of flame plasma in an electric field  

Microsoft Academic Search

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

Kazunari Ikuta

1989-01-01

44

The instantaneous apparent resistivity tensor: a visualization scheme for LOTEM electric field measurements  

NASA Astrophysics Data System (ADS)

Long-offset transient electromagnetic (LOTEM) data have traditionally been represented as early- and late-time apparent resistivities. Time-varying electric field data recorded in a LOTEM survey made with multiple sources can be represented by an `instantaneous apparent resistivity tensor'. Three independent, coordinate-invariant, time-varying apparent resistivities can be derived from this tensor. For dipolar sources, the invariants are also independent of source orientation. In a uniform-resistivity half-space, the invariant given by the square root of the tensor determinant remains almost constant with time, deviating from the half-space resistivity by a maximum of 6 per cent. For a layered half-space, a distance-time pseudo-section of the determinant apparent resistivity produces an image of the layering beneath the measurement profile. As time increases, the instantaneous apparent resistivity tensor approaches the direct current apparent resistivity tensor. An approximate time-to-depth conversion can be achieved by integrating the diffusion depth formula with time, using the determinant apparent resistivity at each instant to represent the resistivity of the conductive medium. Localized near-surface inhomogeneities produce shifts in the time-domain apparent resistivity sounding curves that preserve the gradient, analogous to static shifts seen in magnetotelluric soundings. Instantaneous apparent resistivity tensors calculated for 3-D resistivity models suggest that profiles of LOTEM measurements across a simple 3-D structure can be used to create an image that reproduces the main features of the subsurface resistivity. Where measurements are distributed over an area, maps of the tensor invariants can be made into a sequence of images, which provides a way of `time slicing' down through the target structure.

Caldwell, T. Grant; Bibby, Hugh M.

1998-12-01

45

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...

46

Electrical resistance of copper conductors during pulsed heating  

Microsoft Academic Search

An oscilloscopic method was used to measure the energy dependence of the electrical resistance of copper wires during pulsed heating. The results are compared with those found in direct measurements. An explanation is offered for the appearance of a current pause during the electrical explosion of metal conductors under various conditions. An analysis is made of the conversion of copper

M. M. Martynyuk; N. F. Ganzhela

1970-01-01

47

Nonlinear electrical modeling for the resistance spot welding process  

Microsoft Academic Search

This paper deals with the nonlinear modeling of the electrical subsystem associated with the resistance spot welding (RSW) process. This will be used in the design of model-based nonlinear control strategies to achieve welds of good quality. Switched-state, thyristor driven, linear and nonlinear transformer models have been developed that characterize the electrical dynamics. A detailed parameter estimation algorithm has also

Siva Dhandapani; Michael Bridges

1999-01-01

48

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

49

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

NASA Astrophysics Data System (ADS)

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

Yeboah-Forson, A.; Whitman, D.

2012-12-01

50

Lattice defect investigation of ECAP-Cu by means of X-ray line profile analysis, calorimetry and electrical resistometry  

Microsoft Academic Search

Cu rods have been deformed by equal channel angular pressing (ECAP) up to shear strains ??5 while applying various deformation paths A, BC and C. X-ray Bragg profile analyses (XPA), differential scanning calorimetry (DSC) as well as residual electrical resistivity (RER) measurements have been performed, in order to detect the densities of various deformation induced lattice defects and\\/or their arrangements.

E. Schafler; G. Steiner; E. Korznikova; M. Kerber; M. J. Zehetbauer

2005-01-01

51

Assist feature printability prediction by 3-D resist profile reconstruction  

NASA Astrophysics Data System (ADS)

Sub-resolution Assist Features (SRAFs) are powerful tools to enhance the focus margin of drawn patterns. SRAFs are placed and sized so they do not print on the wafer, but the larger the SRAF, the more effective it becomes at enhancing through-focus stability. The size and location of an SRAF that will image on a wafer is highly dependent upon neighboring patterns and models of SRAF printability are, at present, unreliable. Model-based SRAF placement has been used to enhance resolution at 20nm node processes and below with stringent requirements that inserted SRAFs will not be imaged on wafer. However, despite widespread SRAF use and hard data as to SRAF effectiveness, it has been very difficult to develop a process model that accurately predicts under what process conditions an SRAF will image on a wafer. More accurate models of SRAF printing should allow model based SRAF placement to be relaxed, resulting in more effective SRAF placement and broader focus margins. One of the first problems with the concept of SRAF printability is the definition of an SRAF printing on a wafer. This is not obvious because two different states of printing exist. The first print state is when a residue is left on a wafer from the SRAF. The first state can be considered printing from the point of view that photoresist is on the wafer and the photoresist may even lift off and cause defects. However, the first state can be considered non-printing because the over etch from the etch process will generally remove the photoresist residual and the material underneath. The second state is when a pattern is formed and etched into the substrate, a state at which the pattern has clearly printed on the wafer. Of course, intermediate states may also be defined. In order to be applicable, an SRAF printability model must be able to predict both printing states. In addition, the model must be able to extrapolate to configurations beyond those used to develop the model in the first place. These model properties may then be used to optimize the printability vs. efficacy of an SRAF either prior to or during an Optical Proximity Correction (OPC) run. The process models that are used during OPC have never been able to reliably predict which SRAFs will print. This appears to be due to the fact that OPC process models are generally created using data that does not include printed subresolution patterns. An enhancement to compact modeling capability to predict Assist Features (AF) printability is developed and discussed. A hypsometric map representing 3-D resist profile was built by applying a first principle approximation to estimate the "energy loss" from the resist top to bottom. Such a 3-D resist profile is an extrapolation of a well calibrated traditional OPC model without any additional information. Assist features are detected at either top of resist (dark field) or bottom of resist (bright field). Such detection can be done by just extracting top or bottom resist models from our 3-D resist model. There is no measurement of assist features needed when we build AF but it can be included if interested but focusing on resist calibration to account for both exposure dosage and focus change sensitivities. This approach significantly increases resist model's capability for predicting printed SRAF accuracy. And we don't need to calibrate an SRAF model in addition to the OPC model. Without increase in computation time, this compact model can draw assist feature contour with real placement and size at any vertical plane. The result is compared and validated with 3-D rigorous modeling as well as SEM images. Since this method does not change any form of compact modeling, it can be integrated into current MBAF solutions without any additional work.

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

2012-06-01

52

Effect of Electropolishing ProFile Nickel–Titanium Rotary Instruments on Cyclic Fatigue Resistance, Torsional Resistance, and Cutting Efficiency  

Microsoft Academic Search

This study investigated the effect of electropolishing ProFile nickel titanium rotary instruments on torque resistance, fatigue resistance, and cutting efficiency. Size 25\\/.04 ProFile files (Dentsply Maillefer, Switzerland) that were nonpolished for the control group (n = 15) and electropolished for the experimental group (n = 15) were used for each experiment. Cyclical fatigue was determined by counting rotations until breakage

Tung B. Bui; John C. Mitchell; J. Craig Baumgartner

2008-01-01

53

Electrolyte injection with electrical resistance heating  

E-print Network

that the electrolyte injection leads to an improvement in the heating pattern, by permitting the flow of electrical energy farther into the reservoir. The basis of the work is numerical simulation. For this purpose, an ERH simulator developed at Texas A&M University... to the ERH simulator before implementing the electrolyte equations is presented in Appendix B. The main equations upon which the electrolyte injection model is based are the equations describing the flow and conservation of electrolyte in the reservoir...

Jaimes Gomez, Olmedo

2012-06-07

54

High electrical resistivity carbon/graphite fibers  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

55

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

56

Structure and electrical properties of heat-resistant bimetallic conductors  

Microsoft Academic Search

From 1964 to the present, many works have been devoted to studying bimetallic wire with a heat-resistant jacket of nickel\\u000a or corrosion-resistant steel and a core of a metal with a high electrical conductivity such as copper or silver. This wire\\u000a retains its operating capacity up to 700C and is widely used as a high-temperature conductor in various fields of

V. I. Bokshitskii; A. M. Glezer; E. K. Zakharov; G. A. Sveshnikova

1997-01-01

57

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

58

Using electrical resistance tomography to map subsurface temperatures  

DOEpatents

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

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

1994-09-13

59

Using electrical resistance tomography to map subsurface temperatures  

DOEpatents

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

Ramirez, Abelardo L. (Pleasanton, CA); Chesnut, Dwayne A. (San Francisco, CA); Daily, William D. (Livermore, CA)

1994-01-01

60

Electrical resistance tomography experiments at the Oregon Graduate Institute  

NASA Astrophysics Data System (ADS)

Three controlled experiments were conducted at the Oregon Graduate Institute (OGI) with the purpose of evaluating electrical resistance tomography for imaging underground processes associated with in-situ site assessment and remediation. The OGI facilities are unique: a double-wall tank 10 m square and 5 m deep, filled with river bottom sediments and instrumented for geophysical and hydrological studies. At this facility, liquid contaminants could be released into the confined soil at a scale sufficiently large to represent real-world physical phenomena. In the first test, images of electrical resistivity were made before and during a controlled spill of gasoline into a sandy soil. The primary purpose was to determine if electrical resistivity images could detect the hydrocarbon in either the vadose or saturated zone. Definite changes in electrical resistivity were observed in both the vadose and saturated soils. The effects were an increase in resistivity of as much as 10% above pre-release values. A single resistive anomaly was imaged, directly below the release point, principally within the vadose zone but extending below the phreatic surface. The anomaly remained identifiable in tomograms taken two days after the release ended with clear indications of lateral spreading along the water table. The second test involved electrical resistance measurements before, during, and after air sparging in a saturated soil. The primary purpose was to determine if the electrical images could be used to detect and delineate the extent of the zone influenced by sparging. The images showed an increase of about 20% in resistivity over background values within the sparged zone and the extent of the imaged zone agreed with that inferred from other information. Electrical resistivity tomography measurements were made under a simulated oil storage tank in the third test. Comparison of images taken before and during separate releases of brine and water showed effects of changes induced by the water or brine. The simulated leak and its location were imaged as a conductive anomaly centered near the point of origin and were observed to spread with time during the release.

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

1995-04-01

61

Electrical resistivity investigations at the Olkaria geothermal field, Kenya  

SciTech Connect

The bipole-dipole, Schlumberger and in line dipole-dipole electrical resistivity configurations were used to delineate the Olkaria geothermal reservoir with the view to site boreholes for the production of electric power using the geopressurized hot water. The dipole-dipole resistivity data provided the least ambiguous and most usable data for assessing the resource. Deep drilling into two of the anomalies outlined by this survey has proved the existence of high-temperature reservoirs and a 15MW power station is under construction.

Bhogal, P.S.

1980-09-01

62

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

63

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

64

Resistance after firing protected electric match. [Patent application  

DOEpatents

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

Montoya, A.P.

1980-03-20

65

Detection of sinkholes using 2D electrical resistivity imaging  

NASA Astrophysics Data System (ADS)

Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging, or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. RESTOM surveys were conducted at two sinkhole sites near Pretoria, South Africa. The survey areas are located in the dolomites of the Lyttelton Formation, which forms part of the Malamani Subgroup and Chuniespoort Group of the Transvaal Supergroup. The survey results suggest that RESTOM is an ideal geophysical tool to aid in the detection and monitoring of sinkholes and other subsurface cavities.

van Schoor, Michael

2002-07-01

66

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

NASA Astrophysics Data System (ADS)

Resistivity imaging (RI) is a promising approach to obtaining continuous profile of soil subsurface. This method offers simple technique to identify moisture variation and heterogeneity of the investigated area. However, at present, only qualitative information of subsurface can be obtained using RI. A study on the quantification of geotechnical properties has become important for rigorous use of this method in the evaluation of geohazard potential and construction quality control of landfill liner system. Several studies have been performed to describe electrical resistivity of soil as a function of pore fluid conductivity and surface conductance. However, characterization tests on pore water and surface charge are not typically performed in a conventional geotechnical investigation. The overall objective of this study is to develop correlations between geotechnical parameters and electrical resistivity of soil, which would provide a mean to estimate geotechnical properties from RI. As a part of the study, multiple regression analyses were conducted to develop practically applicable models correlating resistivity with influential geotechnical parameters. The soil samples considered in this study were classified as highly plastic clay (CH) and low plasticity clay (CL) according to Unified Soil Classification System (USCS). Based on the physical tests, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) analysis, kaolinite was identified as the dominant mineral with some traces of magnesium, calcium, potassium, and iron. Electrical resistivity tests were conducted on compacted clays and undisturbed samples under varied geotechnical conditions. The experimental results indicated that the degree of saturation substantially influenced electrical resistivity. Electrical resistivity decreased as much as 11 times from initial value for the increase of degree of saturation from 23 to 100% in the laboratory tests on compacted clays. In case of undisturbed soil samples, resistivity decreased as much as sixteen fold (49.4 to 3.2 Ohm-m) for an increase of saturation from 31 to 100%. Furthermore, the resistivity results were different for the specimens at a specific degree of saturation because of varied surface activity and isomorphous substitution of clayey soils. In addition to physical properties, compressibility of clays was correlated with electrical conductivity. Based on the investigation, it was determined that the electrical conductivity vs. pressure curves followed similar trends as e vs. logp curves. Multiple linear regression (MLR) models were developed for compacted and undisturbed samples using statistical analysis software SAS (2009). During model development, degree of saturation and CEC were selected as independent variables. The proposed models were validated using experimental results on a different set of samples. Moreover, the applicability of the models in the determination of degrees of saturation was evaluated using field RI tests.

Kibria, Golam

67

Energy Saving Through High Frequency Electric Resistance Welding  

E-print Network

High-Frequency electric resistance heating systems have been widely used for many years for both welding and heat treating. In the past the major reason for using High-Frequency heating processes has been because of their very much higher speeds...

Udall, H. N.

1983-01-01

68

Electrical Resistance of the Low Dimensional Critical Branching Random Walk  

NASA Astrophysics Data System (ADS)

We show that the electrical resistance between the origin and generation n of the incipient infinite oriented branching random walk in dimensions d < 6 is O( n 1- ? ) for some universal constant ? > 0. This answers a question of Barlow et al. (Commun Math Phys 278:385-431, 2008).

Járai, Antal A.; Nachmias, Asaf

2014-10-01

69

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

70

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

71

TEACHER NOTES The Effect of Temperature on Electrical Resistance  

E-print Network

, a standard 1 resistor, and a piece of BSCCO 2223 superconducting tape. Using liquid nitrogen that it was indistinguishable from zero. This phenomenon was given the name superconductivity. Over the past century, scientists of the relationship between temperature and electrical resistance for a wire, a resistor, and a superconductor

Quigg, Chris

72

Rolling resistance of electric-vehicle tires from track tests  

SciTech Connect

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

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

1982-06-01

73

Comparison of two years of snowmelt infiltration using electrical resistivity and TDR  

NASA Astrophysics Data System (ADS)

Infiltration during snowmelt can be highly heterogeneous due to the formation of ice on the ground surface below the snow cover. In cases where snow is contaminated such as e.g. along highways and airports due to de-icing agents and other contaminants, it is important to be able to predict the zone of infiltration since this will determine the potential for retention and degradation in the unsaturated zone. The infiltration processes was monitored using time-lapse electrical resistivity measured in shallow electrodes in a glacial deposit near Oslo airport. TDR measurements were used to calibrate changes in water contents with changes in electrical resistivity values. In the first snowmelting event (April, 2006) there was hardly any ground frost, while in the second event (March, 2007) ground frost caused redistribution of meltwater and focussed infiltration. The observed infiltration pattern is supported by numerical simulation of infiltration in a 2D unsaturated profile.

French, H. K.; Binley, A.; Leijnse, A.

2007-12-01

74

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

PubMed

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. PMID:24784634

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

2014-04-01

75

Mantle electrical conductivity profile of Niger delta region  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

76

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

77

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

78

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

79

The stimulation of heavy oil reservoirs with electrical resistance heating  

E-print Network

, the process can be called electrical resistance heating (ERH). Energy is converted to heat by the resistance of the formation to current flow. ERH is also known as eElectrothermic Heating". At high frequencies (those between radio frequency and microwave... of Oil Sand and Other Earth-Type and Biological Materials, " Cdn. Elec. Eng. J. (1979) 4 19-28. Wall, E. , Damraur, R. , Lutz, W. , Bies, R. , and Cranny, M. "Retorting Oil Shale By Microwave Power, " Advances in Chemistry Series 183 (1979) 329...

Baylor, Blake Allen

2012-06-07

80

Aeromagnetic and electrical resistivity surveys of Ascension Island  

SciTech Connect

As part of an evaluation of the geothermal energy potential, the University of Utah Research Institute conducted a detailed aeromagnetic survey of Ascension Island, South Atlantic Ocean, in 1983. Interpretation of the data, supported by three-dimensional numerical modeling, indicated structural features and a low-magnetization area near the center of the island. Reconnaissance and detailed electrical resistivity surveys were completed in 1984 and these identified a zone of low apparent resistivity which corresponds to anomalous temperatures and alteration well above a high-temperature geothermal system.

Ross, H.P.; Nielson, D.L. [Univ. of Utah, Salt Lake City, UT (United States)

1995-12-31

81

Acquisition of electrical resistivity data. Application to soil moisture content  

NASA Astrophysics Data System (ADS)

Geophysical investigation such as detecting electrical resistivity or conductivity of soil has been applied in other to seek correlations between soil properties and soil state. There may be a lot of reasons for variation of the electrical soil apparent resistivity (bulk density, hydraulic conductivity, pore distribution, porosity), but in the same type of non polluted soil, the changes of electrical resistivity data are mainly due to the differential water retention. Detecting even small modification in soil moisture content (<5?m) it is possible if optimum acquisition and processing techniques are applied. Apparent resistivity acquisition is mainly due by using Wenner, Schlumberger or the hybrid Wenner-Schlumberger and Gradient-Dipol arrays. Investigating the same area with the different array may lead to slight different results (differences of the extent or intensity of the electrical resistivity anomalies). This is mainly a cause of the specific sensitivity functions for each of the above mentioned arrays. Comparing the sensitivity function for various array disadvantages and recommendation for using one or another in a specific site location can be outlined and it is a recommended step before starting the acquisition campaign. Other important parameter that must be considered when geoelectric measurements are designed is the distance between electrodes. Electrical prospecting in DC makes use of metal electrodes implanted into the soil. Consequently, current electrodes, as well as potential electrodes, can only approximately be described as point source electrodes. Geoelectrical measurements made on cultivated soil showed that in case of the improper choose of the distance between the electrodes (1m) small changes in the soil moisture content at shallow depths could not be delineated, resulting an higher estimation of the soil water content, as has been revealed by apparent resistivity measurements made with electrodes positioned at half distance. The results will be of high quality if the distance between electrodes is smaller, but placing too close the electrodes the point-source approximation of the injection electrodes may not accomplish. If the point-source approximation cannot be accomplished certain difficulties in the results interpretation will be encountered. In order to illustrate the difference between values computed under the assumption of a point-electrode, and values obtained under the more realistic assumption that a real electrode, of finite length, was utilized. There has been computed the potential generated in a certain point , by a current source of length , that injected a current of intensity into a homogeneous and isotropic half-space of resistivity . Analyzes made for the Schlumberger array indicates that the apparent resistivity computed in the case of a line-electrode is equal to the apparent resistivity corresponding to a point-electrode only if the distance between the current source and the point (where the electrical potential is measured) is much larger that the electrode burying-depth . The distance between the current source and the point has to be at least four times larger than the electrode burying-depth, in order to secure differences smaller than 5% between the actually computed resistivity values and values existing in the ideal case. In addition, by taking into account the circumstance that both the current electrodes, and the potential electrodes, are actually linear, the electrodes separation must be at least 5-7 times larger than their burying-depth. The latter observation is of utmost importance in carrying out resistivity tomographies for soils, when shallow depth investigation it is needed. The scientific researches were performed with financial support from the CNCSIS-UEFISCU 992/2009 and 998/2009 scientific projects.

Chitea, Florina

2010-05-01

82

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

83

Deep Electrical structure along the Meigu-Suijiang profile in the eastern margin of Tibetan plateau  

NASA Astrophysics Data System (ADS)

Magnetoteluric (MT) data were collected at 87 locations along a 135km long traverse from Meigu to Suijiang in the eastern margin of Tibetan plateau. This profile yields data in the period range 0.003-2000s across the active tectonic belt of Sichuan-Yunnan block. MT transfer functions were computed after robust processing of single site and remote reference sites. The dimensionality analysis and strike direction are carried out by phase tensor, conjugate transform impedance method and WAL invariants criteria. Only TM mode data is used in two-dimensional inversion. New approaches are adopted in inversion, one is Site-Center Mesh which is used to construct initial model, and another is the determination of regularization parameter by segmental calculation. The validity of inversion model is checked by using effective skin depth of complex structure and invariants of phase tensor. According to horizontal variation of electrical structure, this profile can be divided into two parts. One part in the west is Daliangshan block, the other part in the east is South China block, the electrical boundary between them is Mabian fault. In general, the electrical resistivity of crust in the east is larger than that of the crust in the west.

Cai, J.; Zhao, G.; Tang, J.; Chen, X.

2011-12-01

84

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

85

Electrical Resistivity of Ten Selected Binary Alloy Systems  

Microsoft Academic Search

This work compiles, reviews, and discusses the available data and information on the electrical resistivity of ten selected binary alloy systems and presents the recommended values resulting from critical evaluation, correlation, analysis, and synthesis of the available data and information. The ten binary alloy systems selected are the systems of aluminum–copper, aluminum–magnesium, copper–gold, copper–nickel, copper–palladium, copper–zinc, gold–palladium, gold–silver, iron–nickel, and

C. Y. Ho; M. W. Ackerman; K. Y. Wu; T. N. Havill; R. H. Bogaard; R. A. Matula; S. G. Oh; H. M. James

1983-01-01

86

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

87

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

88

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

89

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

90

Detecting Cracks in Ceramic Matrix Composites by 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 90o fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.

Smith, Craig; Gyekenyesi, Andrew

2011-01-01

91

Investigation on dissolution rate effect of newly prepared polystyrene copolymer on the profiles of DUV resists  

NASA Astrophysics Data System (ADS)

Dissolution rate of polymer has known as one of the most profound factors to determine profiles of DUV resists. A novel copolymer, poly[4-hydroxystyrene-co-4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene)] (PHSCBPS), was prepared and blended with poly(4-hydroxystyrene-co-4-(1-ethylethoxystyrene)) (EEPHS) to study the effect of dissolution rate on the KrF resist profile. The dissolution rates of the blends in aqueous alkaline solution were measured by dissolution rate monitor (DRM). Molecular weight and polydispersity were measured by GPC. Without altering other components of the resist, the profile was clearly affected by the dissolution rates of the polymer blends. In this paper we will describe resist profile change according to dissolution rate, molecular weight and polydispersity of polymer blend. For given blends, the best and optimum resist profile was found in the range of 200~300 Angstroms/min dissolution rate, 12,000 of molecular weight and 1.2~1.3 of polydispersity. In case of PAG, profile of KrF resist is also influenced by counter ion of PAG. Based on the results, high performance KrF resist composition was found by incorporating appropriate photo acid generator (PAG) and other additives. Optimized resist produced rectangular profile without losing process margin and resolution.

Kim, Hyun-Jin; Chung, Yoon-Sik; Choi, Yong-Jun; Kim, Yang-Sook; Kim, Deog-Bae

2001-08-01

92

Rolling resistance of electric vehicle tires from track tests  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

93

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

2014-10-24

94

Simultaneously improving electrical properties and stabilizing contact resistance of electrically conductive adhesives by using aminoaldehydes  

Microsoft Academic Search

In order to simultaneously improve the conductivity and stabilize the contact resistance of electrically conductive adhesives (ECAs) containing silver flakes, different types of aminoaldehydes as multifunctional additives, N, N-dimethyl-4-aminobenzaldehyde (DABA), benzaldehyde (BA) as a comparison and formamide (FA), were introduced into ECAs formulations. The results showed that when the optimal levels of FA, BA and DABA were individually added into

HONG GAO; LAN LIU; YUAN-FANG LUO; DE-MIN JIA; JIA-SHENG LU

2011-01-01

95

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

96

Electrical Resistivity Imaging for Studying Dynamics of Vadose Zone Processes  

NASA Astrophysics Data System (ADS)

Determining the spatial distribution of subsurface hydrologic properties is critical to developing efficient groundwater management strategies. Electrical resistivity imaging (ERI) provides continuous maps of the subsurface electrical conductivity, which can be related to water content, making it particularly useful to groundwater studies. We present an application of ERI to monitoring infiltration in the top 20 m of the subsurface at the Harkins Slough Recharge Pond, located in an agricultural region on the northern California coast. The purpose of the recharge pond is two-fold: to store diverted storm-flow run-off to meet groundwater delivery demands and to replenish underlying aquifers, which have been overdrawn for several decades, allowing saltwater intrusion. Operators of the pond have rights to divert 2.5e6 m3 of surface water to the pond each year, but decreasing infiltration rates during diversion reduces the operational efficiency, only allowing infiltration of ~1e6 m3 each year. It is hypothesized that deposition of fine-sediments from diverted water, run-off from adjacent fields, and/or microbial activity reduce the hydraulic conductivity over time by clogging pore spaces. As part of an effort to better understand the hydrologic processes controlling infiltration to improve operational efficiency of the recharge pond we conducted time-lapse ERI experiments to monitor infiltration processes beneath the pond during the winters of 2008-2009 and 2009-2010. Each year measurements were made using four 3-m long permanent probes installed in the base of the pond in a T-shape configuration, with 20 m between each probe. The probes allow for monitoring of the conductivity profile to a depth of 2 m; the top meter of each probe monitors bulk conductivity of the pond water. In addition, a number of surface electrodes were laid out in lines between the four probes. In 2008-2009, 20-m lines were used. In 2009-2010, three lines of lengths 10 m, 65 m, and 75 m were deployed. Acquisition geometries designed to target different regions of the subsurface were used to acquire measurements every 1.5 hours. In 2008-2009 ~2000 data sets were acquired; each data set included measurements from probes and surface lines. In 2009-2010 ~1000 data sets were acquired. Data were processed using an extended Kalman filter (EKF) approach. The EKF was chosen for processing time-series ERI data because it models evolution of the physical system and the observation process, incorporating previous information into data-inversion at each time-step. In this application, the first for surface-based ERI field data, we modify the classical Kalman filter cost functional to incorporate spatial smoothing and impose an update constraint to account for slow state evolution with respect to the sampling interval. Results identified more hydrologic complexity than was originally assumed and indicated that processes in the top 0.5 m of the subsurface control infiltration rates. The results of ERI monitoring demonstrate that integrating geophysics into hydrologic studies can provide increased information about spatial and temporal evolution of vadose zone processes.

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

2010-12-01

97

Resistivity Profiling for Mapping Gravel Layers That May Control Contaminant Migration at the Amargosa Desert Research Site, Nevada  

USGS Publications Warehouse

Gaseous contaminants, including CFC 113, chloroform, and tritiated compounds, move preferentially in unsaturated subsurface gravel layers away from disposal trenches at a closed low-level radioactive waste-disposal facility in the Amargosa Desert about 17 kilometers south of Beatty, Nevada. Two distinct gravel layers are involved in contaminant transport: a thin, shallow layer between about 0.5 and 2.2 meters below the surface and a layer of variable thickness between about 15 and 30 meters below land surface. From 2003 to 2005, the U.S. Geological Survey used multielectrode DC and AC resistivity surveys to map these gravel layers. Previous core sampling indicates the fine-grained sediments generally have higher water content than the gravel layers or the sediments near the surface. The relatively higher electrical resistivity of the dry gravel layers, compared to that of the surrounding finer sediments, makes the gravel readily mappable using electrical resistivity profiling. The upper gravel layer is not easily distinguished from the very dry, fine-grained deposits at the surface. Two-dimensional resistivity models, however, clearly identify the resistive lower gravel layer, which is continuous near the facility except to the southeast. Multielectrode resistivity surveys provide a practical noninvasive method to image hydrogeologic features in the arid environment of the Amargosa Desert.

Lucius, Jeffrey E.; Abraham, Jared D.; Burton, Bethany L.

2008-01-01

98

Cyclic electric field stress on bipolar resistive switching devices  

NASA Astrophysics Data System (ADS)

We have studied the effects of accumulating cyclic electrical pulses of increasing amplitude on the non-volatile resistance state of interfaces made by sputtering a metal (Au, Pt) on top of the surface of a cuprate superconductor YBa2Cu3O7-?. We have analyzed the influence of the number of applied pulses N on the relative amplitude of the remnant resistance change between the high (RH) and the low (RL) state [(?=(RH-RL)/RL] at different temperatures (T). We show that the critical voltage (Vc) needed to produce a resistive switching (RS, i.e., ? >0) decreases with increasing N or T. We also find a power law relation between the voltage of the pulses and the number of pulses N?0 required to produce a RS of ? =?0. This relation remains very similar to the Basquin equation used to describe the stress-fatigue lifetime curves in mechanical tests. This points out to the similarity between the physics of the RS, associated with the diffusion of oxygen vacancies induced by electrical pulses, and the propagation of defects in materials subjected to repeated mechanical stress.

Schulman, A.; Acha, C.

2013-12-01

99

Time-lapse electrical resistivity monitoring of salt-affected soil and groundwater  

NASA Astrophysics Data System (ADS)

In order to develop and test a methodology for incorporating time-lapse electrical resistivity imaging (ERI) into the monitoring of salt-affected soil and groundwater, a multifaceted study including time-lapse electrical resistivity imaging, push tool conductivity (PTC), and core analysis was conducted to monitor the movement of a saline contaminant plume over the span of 3 years. The survey was done on a field site containing salt-affected soils and groundwater to depths of over 7 m. The site contained a tile drain system at approximately 2 m below ground level. Temperature and saturation changes were accounted for in electrical conductivity (EC) measurements to isolate changes in electrical conductivity due to changes in salt distribution. ERI inversion parameters were selected so that the inverse models gave the best match to PTC depth profiles and the best correlation with core EC data. A strong correlation between the core data and the ERI results was observed. Time-lapse ERI difference images showed that the subsurface EC distribution was consistent with preferential solute removal above the tile drains in some locations. The ERI-delineated reduction in solute concentration is consistent with nonuniform flushing due to depression-focused recharge. The addition of time-lapse ERI to the study allowed delineation of details of solute redistribution that would not have been possible with point measurements alone.

Hayley, Kevin; Bentley, L. R.; Gharibi, M.

2009-07-01

100

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

PubMed Central

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

2013-01-01

101

Local Resistance Profiling of Ultra-Shallow Junction with Spike Lamp and Laser Annealing Using Scanning Spreading Resistance Microscopy  

NASA Astrophysics Data System (ADS)

Local resistance profiles of ultra-shallow arsenic implanted into silicon with an energy of 3.5 keV and a dose of 1.2×1015 ions/cm2 activated by conventional spike lamp and laser annealing were measured by SSRM in a nitrogen atmosphere with a depth resolution of less than 10 nm for investigating the combination of the conventional spike lamp and laser annealing. Spike lamp annealing at 1050 °C followed by laser annealing at a power density of 0.42 kW/mm2 was found to give the lowest sheet resistance. The resistance profiles obtained by SSRM also indicated the lowest resistance for the sample after spike lamp annealing at 1050 °C followed by laser annealing with a power density of 0.42 kW/mm2. Laser annealing alone with a power density of 0.42 kW/mm2 resulted in the higher sheet resistance, though the shallower resistance profile could be obtained. Spike lamp annealing followed by laser annealing procedures are effective in activating shallow arsenic profiles.

Abo, Satoshi; Tanaka, Yuji; Nishikawa, Kazuhisa; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio

2008-11-01

102

Lipid profiles in wheat cultivars resistant and susceptible to tan spot and the effect of disease on the profiles.  

PubMed

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 noninoculated plants. Lipid compositional data from leaves of 20 noninoculated 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

103

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

104

Marine seismic profiling and shallow marine sand resistivity investigations in Jervis Bay, NSW, Australia  

NASA Astrophysics Data System (ADS)

A marine continuous seismic profiling (CSP) study and a resistivity study of vibrocore samples of shallow marine sands were undertaken in Jervis Bay, NSW, Australia, to characterise the seabed. The CSP study also included Crookhaven Bight, adjacent to Jervis Bay facing north-east to the ocean. The overall aims were: (i) to estimate sediment thickness, and surficial sediment resistivity (upper 3m) at selected sites, to explore the features of the bedrock topography; and (ii) combined with upper layer (sea water) parameters that can be accurately measured, to provide a simplified geo-electrical model of the ground (sea water/seabed) to support interpretation of airborne electromagnetic survey data. The results of the CSP studies indicate very dense sands (tighter packing) and variably weathered sandstones, suggesting variable geological conditions below the seabed. The bedrock surface was also highly irregular in places suggesting an erosional pulse(s) under rapidly falling sea levels at various times in the past. Bedrock was found to form the sea floor in some locations and is deeply incised by palaeochannels extending to 62m below sea level in the Crookhaven Bight and Jervis Bay entrance areas. The laboratory resistivity values, obtained from four electrode measurements on seawater saturated subsamples, averaged 0.88?m (20°C). Inter- and intra-site changes in mineralogy (shell/sand), grain packing, grain size, grain shape, cohesion, and inferred porosity were thought to be responsible for minor variations in resistivity. Archie Equation plots showed some scatter, but the data indicate a cementation factor of ~1.6 and an average formation factor of 4.3 for the suites of sands. These values are consistent with values cited in the literature.

Vrbancich, Julian; Whiteley, Robert J.; Emerson, Don W.

2011-06-01

105

A fully automated precise electrical resistance measurement system  

NASA Astrophysics Data System (ADS)

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

Marhas, Manmeet Kaur; Balakrishnan, K.; Ganesan, V.; Srinivasan, R.

1996-08-01

106

Optical device with low electrical and thermal resistance Bragg reflectors  

DOEpatents

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

Lear, K.L.

1996-10-22

107

Oil production response to in situ electrical resistance heating  

E-print Network

Fleet (Member) . D. Von Gonten ( ad of Department) May 1987 ABSTRACT Oil Production Response to In Situ Electrical Resistance Heating (ERH). (May 1987) Fred William McDougal, B. S. , Texas A&M University Chair of Advisory Committee: Dr. R. A... to my father, Fred H. McDougal, whose encouragement and support culminated in the completion of my Master's work here at Texas ASM University. ACKNOWLEDGMENTS I would like to thank my wife, Carla, for her endless support and Dr. R. A. Wattenbarger...

McDougal, Fred William

2012-06-07

108

Application of electrical resistivity tomography techniques for mapping man-made sinkholes  

NASA Astrophysics Data System (ADS)

The suitability of the geophysical prospecting by electrical resistivity tomography to detect and map man-made subsurface cavities and related sinkholes has been studied in the Linares abandoned mining district (Spain). We have selected for this study four mined sectors constituted of different lithologies: granite and phyllites of Paleozoic age, and Triassic shales and sandstones. In three of these sectors, detail underground topographic surveys were carried out to chart the position and dimensions of the mining voids (galleries and chamber), in order to analyze the resolution of this methodology to characterize these cavities by using different electrode arrays. The results are variable, depending on the depth and diameter of the void, the selected electrode array, the spacing between electrodes, geological complexity and data density. These results also indicate that when the cavity is empty, an anomaly with a steep gradient and high resistivity values is registered, because the air that fills the mining void is dielectric, while when the cavities are filled with fine grain sediments, frequently saturated in water, the electrical resistance is lower. In relation with the three different multi-electrode arrays tested, the Wenner-Schlumberger array has resulted to offer the maximum resolution in all these cases, with lower and more stable values for the RMS than the other arrays. Therefore, this electrode array has been applied in the fourth studied sector, a former mine near the city centre of Linares, in an area of urban expansion in which there are problems of subsidence. Two sets of four electrical tomography profiles have been carried out, perpendicular to each other, and which have allowed reaching depths of research between 30-35 m. This net-array allowed the identification of two shallow anomalies of low resistivity values, interpreted as old mining galleries filled with fine material saturated in water. It also allows detecting two fractures, correlated in the profiles and which can be mapped to more than 25 m in depth. As showed by this case study, electrical resistivity tomography can be a suitable tool in sub-surface cavities detection and man-made sinkhole investigations.

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

2012-04-01

109

Studies on the Electrical Potential Profile across Rabbit Ileum  

PubMed Central

When isolated strips of mucosal rabbit ileum are bathed by physiological electrolyte solution the electrical potential difference (PD) across the brush border (?mc) averages 36 mv, cell interior negative. Rapid replacement of Na in the mucosal solution with less permeant cations, Tris or choline, results in an immediate hyperpolarization of ?mc. Conversely, replacement of choline in the mucosal solution with Na results in an abrupt depolarization of ?mc. These findings indicate that Na contributes to the conductance across the brush border. The presence of actively transported sugars or amino acids in the mucosal solution brings about a marked depolarization of ?mc and a smaller increase in the transmural PD (??ms). It appears that the Na influx that is coupled to the influxes of amino acids and sugars is electrogenic and responsible for the depolarization of ?mc. Under control conditions ??ms can be attributed to the depolarization of ?mc together with the presence of a low resistance transepithelial shunt, possibly the lateral intercellular spaces. However, quantitatively similar effects of amino acids on ?mc are also seen in tissues poisoned with metabolic inhibitors or ouabain. Under these conditions ??mc is much smaller than under control conditions. Thus, the depolarization of ?mc might not account for the entire ??ms, observed in nonpoisoned tissue. An additional electromotive force which is directly coupled to metabolic processes might contribute to the normal ??ms. PMID:5576764

Rose, Richard C.; Schultz, Stanley G.

1971-01-01

110

Monitoring water flows with time-lapse Electrical Resistivity Tomography on the Super-Sauze landslide  

NASA Astrophysics Data System (ADS)

This work presents results of a permanent hydro-geophysical monitoring of an active landslide developed in clay-shales. Hydrology has been proved to be a major factor controlling the Super-Sauze earthflow behavior, but it knowledge still limited mainly because of the importance of spatial heterogeneities. The geometry of the bedrock creates internal crests and gullies that can guide waterflows or create a lock and engender an excess of pore water pressure; the soil surface characteristics plays also a large role in the surface hydraulic conductivity, and therefore, on the infiltration pattern. To understand in detail these processes, it is therefore important to monitor spatially at large scale (with high resolution) those phenomena and to overcome the monitoring difficulties inherent to a fast-moving clayey earthflow. The objectives of the survey are to identify and characterize spatially and temporarily the water flow circulation within the landslide body over a period of one year. The studied profile measures 114 m long and is surveyed with 93 electrodes spaced from 0.5, 1 or 2 meter according the soil surface cracking. Four resistivity datasets of 4300 measurements are acquired each day using a gradient array since May 2011. The monitoring is performed with the GEOMON4D system, developed by the Geological Survey of Austria. To facilitate the interpretation, humidity, conductivity, temperature, and piezometer sensors are placed along the profile. Two dGPS antenna placed upstream and downstream the profile allow to correlate the results with soil displacement. Lefranc tests and granulometry results realized on several samples have shown the important heterogeneities of the near surface. The objective of this work is to present the data processing strategy for the analysis of long periods time-lapse ERT survey of natural rain events taking into account changes through time of the position of the electrodes, changes in the soil surface state and important changes in sub-surface soil temperature. Two high-resolution optical cameras are installed on stable crests on the side of the cross-sections and time-lapse stereoscopy is used to reconstruct the displacement field to locate the electrodes in space and time (in order to take into account changes in the dipole geometry). The apparent electrical resistivity values were inverted with a time-lapse approach using an initial model constructed from statistical analysis of resistivity data and a priori knowledge on the landslide structure from a previous geotechnical model. The near surface apparent resistivity can vary of ten percent without any input of water. This shows the importance of temperature effect on the measurement. The temperature correction is handled from a complete study of the soil temperature propagation solving the heat equation with several temperature probes placed at different depths in soil and in the water table. The results are interpreted in combination to hydrological data (rain, water table level). The acquisition of 8 ERT all over the studied area, in different directions permits to create by interpolation a 3D electrical resistivity model of the area. This model shows the importance of the bedrock topography because high water content areas are visible at the theoretical hydrological network computed from the 3D geotechnical model of Travelletti and Malet (2011). Transversal waterflow circulation not predicted are also visible and permit to interpret the results taking into account the 3D structure of the landslide. A 250 m long P-wave tomography acquired on the studied profile and inversed with a quasi-Newton algorithm that uses Fresnel wavepaths and the finite bandwidth of the source signal, specially developed for the study of very heterogeneous soils, shows a very good correlation with electrical resistivity and permits to propose a geotechnical model of the profile. Spatially heterogeneous water flow patterns are identified and the presence of a deep water supply is hypothesized downstream of the investigated profile. The presentation will fo

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

2012-04-01

111

An electrical resistivity crustal section from the Alps to the Baltic Sea (central segment of the EGT)  

NASA Astrophysics Data System (ADS)

Electrical resistivity models derived from magnetotelluric and magnetovariational measurements in the past 10 years have been compiled along the Central Segment of the European Geotraverse. Along the profile low-resistivity structures exist particularly in the middle and upper crust and probably mask deeper low-resistivity zones. These structures can be related to different tectonic units along the profile. The prominent features are the two-dimensional low-resistivity structures at the transition from the Moldanubian to the Saxothuringian and from the Saxothuringian to the Rhenohercynian unit of the Variscan belt, the depth correlation of the low-resistivity horizon in the Rhenish Massif with a seismic low-reflectivity band, the very high conductance of an upper to middle crustal layer in the North German Lowlands and its cessation at the river Elbe towards the Baltic Sea. The reduction in the resistivity of these zones is very likely due to graphite at mid-crustal depths. It is obvious that there exists a general increase of electrical conductance in the upper half of the crust from south to north of the Central Segment which may be due to increasing accumulation of graphite and successive tectonically controlled ordering processes. This phenomenon may, by relating it to the growing crustal age from south to north, be the indicator of a maturing continental crust.

Erceugt-Group

112

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

113

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

Code of Federal Regulations, 2010 CFR

...false Test for flame resistance of electric cables and...407 Test for flame resistance of electric cables and...removing 5 inches of jacket material and 21/2 ...order to reduce contact resistance. (7) Energize all...the burn time of any material that falls from...

2010-07-01

114

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

Microsoft Academic Search

We describe a stochastic inversion method for mapping subsurface regions where the electrical resistivity is changing. The technique combines prior information, electrical resistance data and forward models to produce subsurface resistivity models that are most consistent with all available data. Bayesian inference and a Metropolis simulation algorithm form the basis for this approach. Attractive features include its ability to: (1)

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

2004-01-01

115

Stochastic inversion of electrical resistivity changes using a Markov Chain Monte Carlo approach  

Microsoft Academic Search

We describe a stochastic inversion method for mapping subsurface regions where the electrical resistivity is changing. The technique combines prior information, electrical resistance data, and forward models to produce subsurface resistivity models that are most consistent with all available data. Bayesian inference and a Metropolis simulation algorithm form the basis for this approach. Attractive features include its ability (1) to

A. L. Ramirez; J. J. Nitao; W. G. Hanley; R. Aines; R. E. Glaser; S. K. Sengupta; K. M. Dyer; T. L. Hickling; W. D. Daily

2005-01-01

116

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

117

Genotype and antibiotic resistance profile of Escherichia coli strains involved in canine pyometra  

Microsoft Academic Search

Eighty-four Escherichia coli isolates from canine pyometra were examined to detect the antibiotic resistance profiles, phylogroup\\/subgroups and virulence\\u000a genes. Twenty-seven (32.14%) antibiotic-resistant isolates were recovered, which were classified into 19 different antibiotic\\u000a resistance patterns. The maximum resistance was against sulfadiazine and tetracycline. The antibiotic resistant isolates mostly\\u000a belonged to A (40.74%) and D (29.62%) phylogroups. Among other examined isolates, 19.04%

Reza Ghanbarpour; Baharak Akhtardanesh

118

Antimicrobial Resistance Profiles of Campylobacter jejuni Isolates from Wild Birds in Sweden†  

PubMed Central

In order to determine the occurrence and frequency of resistant strains of the bacterium Campylobacter jejuni and to establish baseline MICs in isolates from an environmental reservoir, the resistance profiles of 10 antimicrobial substances were determined for 137 C. jejuni isolates from wild birds in Sweden. Observed MICs were generally low, with only low to moderate incidence of resistance to the tested compounds. One isolate, however, was resistant to nalidixic acid and ciprofloxacin, indicating that quinolone-resistant genotypes of C. jejuni have the potential to spread to wild bird hosts. PMID:15870331

Waldenstrom, Jonas; Mevius, Dik; Veldman, Kees; Broman, Tina; Hasselquist, Dennis; Olsen, Bjorn

2005-01-01

119

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

120

Antibiotic resistance profile of staphylococci from clinical sources recovered from infants  

Microsoft Academic Search

Infants, children and the aged are among the groups most vulnerable to microbial infections more so when these microbial agents become resistant to antimicrobials. The antibiotic resistant profile of Staphylococcus aureus and selected coagulase negative staphylococci were determined by standard methods. Of the 178 staphylococcal isolates evaluated, 122 were S. aureus and the rest coagulase negative staphylococci. 68% of S.

Ako-Nai AK; Adeyemi FM; Aboderin OA; Kassim OO

121

Influences of acute resistance and aerobic exercises on plasma homocysteine level and lipid profiles  

Microsoft Academic Search

Purpose: The aim of the present study was to compare the effects of two different types (aerobic and resistance) of acute exercise on plasma homocysteine level and lipid profiles. Material and methods: 51 students were included. Resistance exercise group (n=20) performed moderate resistance and aerobic exercise group (n=18) performed sub-maximal aerobic exercise for one session. Control group (n=13) did not

Sevgi Sevi; Nihal Gelecek; Nursen Özdemir; Murat Örmen

2009-01-01

122

Fabrication of an Electrically-Resistive, Varistor-Polymer Composite  

PubMed Central

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

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

2012-01-01

123

Observation of infiltration experiments with time lapse electrical resistivity tomography  

NASA Astrophysics Data System (ADS)

Recent progress in the development of resistivity equipment enables the real time observation of infiltration processes through the vadose zone. In order to study the advantages and limitations of the method infiltration experiments are carried out for different soil types at various locations. All sites are subsequently excavated and investigated in detail. For an improved verification of the resistivity data the most recent experiment is conducted using a colour tracer. Two infiltration experiments are carried out in sandy soil. The location is Fuhrberg, close to Hannover, Germany. The area has been intensively studied for soil research purposes for more than 30 years. During both infiltration experiments water (110 l/80 l) is infiltrated for a period of 4.5 h and 8 h, respectively, and the infiltration process is observed by ERT. The resistivity measurements are conducted using a 3D-dipole-dipole configuration with electrode distances of 20 cm in the centre of the infiltration field. The whole resistivity array consists of 200 and 300 electrodes, respectively. The second experiment uses increased electrode spacing in the border area in order to enable the resolution of the deeper groundwater table (3.5 m during the second experiment compared to about 1.2 m for the first experiment). Immediately after completion of the resistivity measurements TDR and tensiometer measurements are carried out in 5-8 slices of the excavated infiltration area over a period of several days. The colour tracer used during the second experiment clearly outlines the infiltration plume with sharp outer limits. The ERT inversion depicts the shape of the plume successfully. Time lapse ERT interpretation reveals the development of the plume in time. The combination of ERT interpretation and TDR measurements enables the construction of the relationship between water content and resistivity as reconstructed by ERT using an Archie approach. By using this function water content changes can be analysed quantitatively. For the first experiment this calculation shows one day after the infiltration about 40% of the infiltrated water being lost to the groundwater. For the second experiment the quantitative interpretation takes into account the increased conductivity of the infiltrating tracer solution compared to the pore water of the vadose zone before infiltration. Another infiltration experiment is done on Loess. Due to the low infiltration rate only about 9l of water could be infiltrated within about 3 h (38mm/h). The time lapse ERT clearly reveals the water remaining close to surface and no sign of resistivity change due to the infiltration is observed to penetrate deeper than 30cm. At this depth the plough pan seems to inhibit the infiltration. The analysis shows the high sensitivity of the ERT method. Although the original water content is quite high and therefore the resistivity changes due to water content changes are small (the flat part of the Archie function) the time lapse ERT inversion depicts the changes of resistivity quite clearly. The experiments show the advantages of ERT measurements to observe the infiltration process in real time. However, the interpretation of such measurements still poses difficulties mainly due to the limited resolution and the ill posedness of the inversion problem of electrical resistivity tomography (ERT). These problems are investigated further in order to advance the applicability of the method to infiltration problems showing signs of preferential flow.

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

2010-05-01

124

Principles of spatial surface electric field filtering in magnetotellurics: Electromagnetic array profiling (EMAP)  

Microsoft Academic Search

Electromagnetic Array Profiling (EMAP) is an ad- aptation of magnetotellurics to overcome spatial alias- ing effects associated with the sampling of the surface electric field. Undersampling lateral electric field vari- ations can result in misleading geoelectric interpreta- tions of the subsurface, particularly under the common presence of static distortion. In the EMAP field pro- cedure, electric dipoles are positioned end-to-end

Carlos Torres-Verdin; Francis X. Bostick

125

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

SciTech Connect

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

Phelps, Amanda C. (Malibu, CA); Kirby, Kevin K. (Calabasas Hills, CA); Gregoire, Daniel J. (Thousand Oaks, CA)

2012-02-14

126

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

127

Material morphology and electrical resistivity differences in EPDM rubbers.  

SciTech Connect

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

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

2008-03-01

128

Electrical resistivity tomography at the DOE Hanford site  

SciTech Connect

Recent work at the DOE Hanford site has established the potential of applying Electrical Resistivity Tomography (ERT) for early leak detection under hazardous waste storage facilities. Several studies have been concluded to test the capabilities and limitations of ERT for two different applications. First, field experiments have been conducted to determine the utility of ERT to detect and map leaks from underground storage tanks during waste removal processes. Second, the use of ERT for long term vadose zone monitoring has been tested under different field conditions of depth, installation design, acquisition mode/equipment and infiltration chemistry. This work involves transferring the technology from Lawrence Livermore National Laboratory (LLNL) to the Resource Conservation and Recovery Act (RCRA) program at the DOE Hanford Site. This paper covers field training studies relevant to the second application for long term vadose zone monitoring.

Narbutovskih, S.M.; Halter, T.D.; Sweeney, M.D. [Westinghouse Hanford Co., Richland, WA (United States); Daily, W.; Ramirez, A.L. [Lawrence Livermore National Lab., CA (United States)

1996-01-01

129

Electrical resistivity tomography study of Taal volcano hydrothermal system, Philippines  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

130

Plume and lithologic profiling with surface resistivity and seismic tomography  

Microsoft Academic Search

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

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

2005-01-01

131

Marine seismic profiling and shallow marine sand resistivity investigations in Broken Bay, NSW, Australia  

NASA Astrophysics Data System (ADS)

A marine continuous seismic profiling (CSP) study and a resistivity study of vibrocore samples of shallow marine sands were undertaken in Broken Bay, NSW, Australia, to characterise the seabed. The overall aims were to provide an estimate of the sediment thickness using CSP and an estimate of sediment resistivity in the upper 4 m of the seabed at selected sites. This information can provide a simplified geo-electrical model to assess the accuracy of interpreted seabed and bedrock depths obtained independently from AEM data and to assist the calibration of AEM instrumentation for bathymetric surveys. The acoustic impedance contrast between deeper sediments and the anticipated basement sandstone was variable suggesting irregularly layered sediments. These sediments contained very dense (tightly packed) sands, owing to marine regression and transgression of sea level, and variably weathered underlying sandstones. Interpreted bedrock levels vary considerably across the survey area and represent drowned river valleys of the inner continental shelf. A broad deep channel representing a high-energy palaeo-fluvial drainage system in the Hawkesbury River outreaches was identified; it extended to approximately -80 m AHD. Another area revealed a dendritic fluvial pattern extending to approximately -70 m AHD. A moderately narrow palaeovalley extending to -90 m AHD either side of the Palm Beach tombolo was clearly identified. This same feature was also clearly identified from airborne electromagnetic data which, when interpreted, showed very good agreement with seismic depths. Sand samples from 17 sites were obtained from vibrocores with a penetration depth of 4.5m. The laboratory resistivity values, obtained from four-electrode measurements on 64 seawater saturated subsamples ranged from 1.3 to 0.6?m (20°C) 0.92?m average. Inter- and intra-site changes in composition (shell/sand), grain packing, grain size, grain shape, cohesion, and inferred porosity were thought to be responsible for minor variations in resistivity. Archie Equation plots showed some scatter, but the data indicate a cementation factor of ~1.6 and an average formation factor of 4.2 for the suites of sands. These values are consistent with values cited in the literature for similar lithologies.

Vrbancich, Julian; Whiteley, Robert J.; Caffi, Peter; Emerson, Don W.

2011-11-01

132

Electrical Resistance Tomography Field Trials to Image CO2 Sequestration  

NASA Astrophysics Data System (ADS)

If geologic formations are used to sequester or store carbon dioxide (CO2) for long periods of time, it will be necessary to verify the containment of injected CO2 by assessing leaks and flow paths, and by understanding the geophysical and geochemical interactions between the CO2 and the geologic minerals and fluids. Remote monitoring methods are preferred, to minimize cost and impact to the integrity of the disposal reservoir. Electrical methods are especially well suited for monitoring processes involving fluids, as electrical properties are most sensitive to the presence and nature of the fluids contained in the medium. High resolution tomographs of electrical properties have been used with success for site characterization, monitoring subsurface migration of fluids in instances of leaking underground tanks, water infiltration events, subsurface steam floods, contaminant movement, and assessing the integrity of subsurface barriers. These surveys are commonly conducted utilizing vertical arrays of point electrodes in a crosswell configuration. Alternative ways of monitoring the reservoir are desirable due to the high costs of drilling the required monitoring boreholes Recent field results obtained using steel well casings as long electrodes are also promising. We have conducted field trials to evaluate the effectiveness of long electrode ERT as a potential monitoring approach for CO2 sequestration. In these trials, CO2 is not being sequestered but rather is being used as a solvent for enhanced oil recovery. This setting offers the same conditions expected during sequestration so monitoring secondary oil recovery allows a test of the method under realistic physical conditions and operational constraints. Field experience has confirmed the challenges identified during model studies. The principal difficulty are the very small signals due to the fact that formation changes occur only over a small segment of the 5000 foot length of the electrodes. In addition, telluric noise can be comparable to the signal levels during periods of geomagnetic activity. Finally, instrumentation stability over long periods is necessary to follow trends in reservoir behavior for several years. Solutions to these and other problems will be presented along with results from the first two years of work at a producing field undergoing CO2 flood. If electrical resistance tomography (ERT) imaging can be performed using existing well casings as long electrodes, it will substantially reduce the cost to monitor CO2 sequestration. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Newmark, R.

2003-12-01

133

Load profile estimation in electric transmission networks using independent component analysis  

Microsoft Academic Search

It is important to estimate electric loads profiles in the deregulated environment where competing entities need to assess the load demands based on partial knowledge of the system. Independent component analysis (ICA) is a statistical technique used to separate linear mixtures of statistical independent source signals by maximization of negentropy. In this paper, we apply ICA to estimate load profiles

Huaiwei Liao; Dagmar Niebur

2003-01-01

134

THE ELECTRICAL RESISTIVITY OF MOLTEN AND SOLID THORIUM-MAGNESIUM EUTETIC  

Microsoft Academic Search

Electrical resistivity properties of polycrystalline 39 wt % thorium-- ; magnesium eutectic are reported for the solid from room temperature to its ; melting point at 589 deg C and as a liquid from its melting point to 900 deg C. ; The electrical resistivity of the eutectic at the melting point was 69.5 microhm-; centimeters; it decreased to a

D. M. Provow; R. W. Fisher

1962-01-01

135

Study of critical dependence of stable phases in Nitinol on heat treatment using electrical resistivity probe  

Microsoft Academic Search

Phase transformations in 40% cold-worked Nitinol as a function of heat treatment have been studied using electrical resistivity variation with temperature. The stabilisation of austenitic, rhombohedral and martensitic phases is shown to critically depend on the temperatures of heat treatment by the analysis of temperature dependence of electrical resistivity in heating and cooling parts of the cycle. Characteristic values of

J Uchil; K. P Mohanchandra; K. Ganesh Kumara; K. K Mahesh

1998-01-01

136

Electrical resistivity of minerals and rocks at high temperature and pressure  

Microsoft Academic Search

After a general discussion of semiconductor and dielectric physics, experimental data on the dependence of electrical resistivity of different minerals on their cation composition within a wide temperature interval (up to 1100°C) are described. The different types of dependence of resistivity on pressure are noted for minerals with a predominantly ionic type of electrical conductivity and for those whose conductivity

E. I. Parkhomenko

1982-01-01

137

Shape memory alloy servo actuator system with electric resistance feedback and application for active endoscope  

Microsoft Academic Search

A control system for a shape memory alloy (SMA) servo actuator, and its application to a unique medical tool, are considered. It is thought that the electric resistance value of an SMA can be utilized to monitor the transformation of the SMA directly. Therefore, an antagonistic transformation control scheme using electric resistance feedback is proposed and is verified by several

Koji Ikuta; M. Tsukamoto; Shigeo Hirose

1988-01-01

138

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

139

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 the plasmonic heating, which we measure electrically through changes in the ionic conductance of the nanopore

Dekker, Cees

140

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

NASA Astrophysics Data System (ADS)

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

Durand, J. M.; Wong, T.

2013-12-01

141

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

142

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

143

On the Intensity Profile of Electric Lamps and Light Bulbs  

ERIC Educational Resources Information Center

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

Bacalla, Xavier; Salumbides, Edcel John

2013-01-01

144

Using high-temperature electrical resistivity measurements to determine the quality of diamond films  

Microsoft Academic Search

The electrical resistivity of undoped diamond films has been measured between room temperature and 1200 °C. The films were grown by either microwave plasma CVD or combustion flame at various different companies. It was found that the room temperature resistivities were all around 1015–1016 ? cm, which has been shown to be the apparatus-limited value (higher resistivities cannot be measured).

J. W. Vandersande; L. D. Zoltan

1995-01-01

145

Application of two electrical methods for the rapid assessment of freezing resistance in Salix eriocephala  

Microsoft Academic Search

The importance of early selection of frost-resistant Salix clones makes it desirable to select a rapid and accurate screening method for assessing freezing resistance among several genotypes. Two electrical methods, stem electrical impedance to 1 and 10kHz alternating current, and electrolyte leakage of leaf tissue, were evaluated for detecting freezing resistance on three North America Salix eriocephala Michx., clones after

V. Tsarouhas; W. A. Kenney; L. Zsuffa

2000-01-01

146

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

147

Plume and lithologic profiling with surface resistivity and seismic tomography  

SciTech Connect

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.

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

2005-03-01

148

Electrical characterization and Auger depth profiling of nanogap electrodes fabricated by I2-assisted focused ion beam  

NASA Astrophysics Data System (ADS)

Iodine (I2)-assisted, 30keV Ga+ focused ion beam (FIB) has been employed to fabricate nanogap Au electrodes and has been compared to conventional FIB milling. Electrical characterization shows that I2 assistance improves insulation resistance from 300-400G?to20-50T?. Auger depth profiling reveals that the Ga concentration profile in FIB-milled samples has a peak value of 25at.% at 7nm and extends, with a decreasing Gaussian tail, down to 40nm, whereas in I2-processed samples Ga concentration is reduced below 5at.%. I2 assistance is found to increase minimum gap size from 8to16nm and to markedly roughen Au surface morphology.

Gazzadi, G. C.; Angeli, E.; Facci, P.; Frabboni, S.

2006-10-01

149

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

150

Antimicrobial resistance profiling and molecular subtyping of Campylobacter spp. from processed turkey  

PubMed Central

Background Campylobacter is a major cause of human disease worldwide and poultry are identified as a significant source of this pathogen. Most disease in humans is associated with the consumption of contaminated poultry or cross-contamination with other foods. The primary drugs of choice for treatment of human campylobacteriosis include erythromycin and ciprofloxacin. In this study, we investigated the prevalence of resistance to erythromycin and ciprofloxacin in Campylobacter isolates recovered from turkey carcasses at two processing plants in the Upper Midwest US. Further analysis of a subset of isolates was carried out to assess resistance and genotype profiles. Results Campylobacter isolates from plant A (n = 439; including 196 C. coli and 217 C. jejuni) and plant B (n = 362, including 281 C. coli and 62 C. jejuni) were tested for susceptibility to ciprofloxacin and erythromycin using agar dilution. C. coli were more frequently resistant than C. jejuni in both plants, including resistance to ciprofloxacin (28% of C. jejuni and 63% of C. coli, plant B; and 11% of C. coli, plant A). Erythromycin resistance was low among C. jejuni (0% plant A and 0.3% plant B) compared to C. coli (41%, plant A and 17%, plant B). One hundred resistant and susceptible isolates were selected for additional antimicrobial susceptibility testing, restriction fragment length polymorphism analysis of the flaA gene (fla typing), and pulsed-field gel electrophoresis (PFGE). Fla-PFGE types obtained (n = 37) were associated with a specific plant with the exception of one type that was isolated from both plants. C. coli isolates (n = 65) were grouped into 20 types, while C. jejuni isolates (n = 35) were grouped into 17 types. Most isolates with identical fla-PFGE patterns shared identical or very similar antimicrobial resistance profiles. PFGE alone and composite analysis using fla-PFGE with resistance profiles separated C. jejuni and C. coli into distinct groups. Conclusion Ciprofloxacin and erythromycin resistance in Campylobacter recovered from processed turkey occurred more frequently among C. coli than C. jejuni. Fla-PFGE types were associated with a particular species, antimicrobial resistance profiles, and a specific plant. Molecular subtyping in this study provided more information about the relationships among antimicrobial-resistant Campylobacter at the processing level. PMID:19772592

2009-01-01

151

Effect of Coulomb blockade, gold resistance, and thermal expansion on the electrical resistance of ultrathin gold films  

NASA Astrophysics Data System (ADS)

Controlling the electrical resistance of granular thin films is of great importance for many applications, yet a full understanding of electron transport in such films remains a major challenge. We have studied experimentally and by model calculations the temperature dependence of the electrical resistance of ultrathin gold films at temperatures between 2 K and 300 K. Using sputter deposition, the film morphology was varied from a discontinuous film of weakly coupled meandering islands to a continuous film of strongly coupled coalesced islands. In the weak-coupling regime, we compare the regular island array model, the cotunneling model, and the conduction percolation model with our experimental data. We show that the tunnel barriers and the Coulomb blockade energies are important at low temperatures and that the thermal expansion of the substrate and the island resistance affect the resistance at high temperatures. At low temperatures our experimental data show evidence for a transition from electron cotunneling to sequential tunneling but the data can also be interpreted in terms of conduction percolation. The resistivity and temperature coefficient of resistance of the meandering gold islands are found to resemble those of gold nanowires. We derive a simple expression for the temperature at which the resistance changes from non-metal-like behavior into metal-like behavior. In the case of strong island coupling, the total resistance is solely determined by the Ohmic island resistance.

Yajadda, M. M. A.; Müller, K.-H.; Ostrikov, K.

2011-12-01

152

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

153

Contact resistance of micromachined electrical switches incorporating a chevron-type bi-stable spring  

NASA Astrophysics Data System (ADS)

Micromachined electrical switches with bi-stable springs, which can stay at one of the two stable states without consuming energy, are proposed. Cascaded bent beams are incorporated as thermoelastic microactuators and are characterized through a coupled electro-thermo-mechanical analysis using ANSYS. For improved electrical switch performance, the contact resistances should be kept as low as possible. Therefore, the shape of the contact head needs to be optimized, though to date there have been few studies pertaining to the contact heads of electrical switches reported, except for a flat contact shape. In this paper, the effects of contact angle on the electrical resistance are investigated for contact angles of 30°, 45°, and 60°. It is subsequently observed that the contact resistance decreases with the contact angle due to a greater normal contact force; the minimum contact resistance is 0.22 ? at a contact angle of 60°. The contact resistance shows negligible change during repeated ON/OFF switching operations.

Nallamuthu, Punithavelan; Hwang, Il-Han; Jeong, Dae-Hun; Moon, Seung-Hwan; Seo, Seung-Wan; Lee, Jong-Hyun

2011-01-01

154

Temperature Dependence of Electrical Resistance of Individual Carbon Nanotubes and Carbon Nanotubes Network  

NASA Astrophysics Data System (ADS)

We present a model to understand the effect of temperature on the electrical resistance of individual semiconducting single wall carbon nanotubes (s-SWCNTs) of various diameters under various electric fields. The temperature dependence of the resistance of s-SWCNTs and metallic SWCNTs (m-SWCNTs) are compared. These results help us to understand the temperature dependence of the resistance of SWCNTs network. We experimentally examine the temperature dependence of the resistance of random networks of SWCNTs, prepared by dispersing CNTs in ethanol and drop-casting the solution on prefabricated metallic electrodes. Examining various samples with different electrode materials and spacings, we find that the dominant resistance in determination of the temperature dependence of resistance of the network is the resistance of individual tubes, rather than the tube-tube resistance or tube-metal contact resistance. It is also found that the tube-tube resistance depends on the electrode spacing and it is more important for larger electrode spacings. By applying high electric field to burn the all-metallic paths of the SWCNTs network, the temperature dependence of the resistance of s-SWCNTs is also examined. We also investigate the effect of acid treatment of CNTs on the temperature dependence of the resistance of SWCNTs and also multi-wall CNTs (MWCNTs) networks.

Dehghani, Sajjad; Moravvej-Farshi, Mohammad Kazem; Sheikhi, Mohammad Hossein

2012-08-01

155

Calculated electrical and thermal resistivities of Nb and Pd  

NASA Astrophysics Data System (ADS)

The electrical and thermal resistivities (? and W) of pure Nb and Pd are calculated from nearly first principles. Realistic Korringa-Kohn-Rostoker energy bands and wave functions, experimental phonon frequencies and Born-von Kármán eigenvectors, and rigid muffin-tin electron-phonon potentials are used to generate the velocities and scattering probabilities in the Bloch-Boltzmann equation, at a mesh of nearly 48 000 points on the Fermi surface. Solutions for ? and W are exhibited at three levels of accuracy: (1) the lowest-order variational approximation (LOVA) where the Fermi surface displaces rigidly; (2) the N-sheet approximation where different sheets of Fermi surface displace independently; (3) a fully inelastic calculation where the N-sheet approximation is used and the distribution function is allowed arbitrary variations with energy (normal to the Fermi surface) to reflect the inelasticity of electron-phonon scattering. Above T=100 K, corrections to LOVA are of order 1%, but below T=100 K, both the N-sheet approximation and inelasticity give large corrections to the LOVA results. These results are also compared with Bloch-Grüneisen formulas fitted at T~?D. In the range 100 K<~T<~300 K, calculations exceed experimental results by ~ 10%. Good agreement persists into the range 10 K<~T<~100 K, except that in Nb theory underestimates experiment significantly at the lower-temperature end, suggesting a possible error of rigid muffin-tin models for small Q--> scattering. In Pd the interpretation is complicated by Coulomb effects. Below T=10 K, finite mesh size prevents reliable calculations. Simple models such as Bloch-Grüneisen theory are inadequate to account for the data. Mott's (1936) "s-d" picture is shown to be qualitatively correct for Pd. Extension of this picture to Nb was suggested subsequently by various authors, but the present calculation does not support this.

Pinski, F. J.; Allen, P. B.; Butler, W. H.

1981-05-01

156

Investigation of real field application issues for resistive type SFCLs for distribution electric power networks  

NASA Astrophysics Data System (ADS)

Conventional electric power networks were designed and operated not considering fault current limiting devices. Therefore, the performance and characteristics of resistive superconducting fault current limiter (SFCL) should be reviewed considering the coordination with other electric circuit protecting devices. In this paper, real field application issues of resistive SFCL were investigated considering utilities’ demands and coordination with other protection devices. Pure resistive SFCL and hybrid resistive SFCL were compared in order to determine suitable solutions for electric power systems. SFCLs were modeled and analyzed using electro-magnetic transients program (EMTP) and their performances were compared to identify the adaptability to the conventional power networks. Consequently, Simulation results showed that hybrid resistive SFCL have more advantages than pure resistive SFCL considering the requirements and specification for the distribution networks.

Rhee, S. B.; Lee, B. W.

2010-11-01

157

From spatial-continuous electrical resistivity measurements to the soil hydric functioning at the field scale: a case study in a small field area  

NASA Astrophysics Data System (ADS)

The aim of this paper was to discuss the hydric functioning of a small field area by using measurements of the soil electrical resistivity. We made the hypothesis that the difference in electrical resistivity data recorded at different dates in the field were only due to differences in water content: indeed, the data were corrected for temperature by the Keller & Frischknecht equation (1966) and ancillary laboratory experiments showed that the influence of the electrical conductivity of the soil solution did not influence significantly the soil electrical resistivity. As The studied 2 ha field area comprised several soil units developed either in white calcareous or in cryoturbated calcareous. A pedological prospection by auger holes enabled to determine the real soil depth in each soil unit. The spatial soil electrical resistivity was recorded at a high resolution on a 2 ha area by the MuCEP device -MultiContinuous Electrical Profiling- (Panissod et al., 1997) at two dates. The MuCEP enabled the measurements of electrical resistivity at three pseudo-depth, due to interelectrode spacings equal to 0.5m, 1m and 2m. The interpretation of the electrical resistivity measurements was analysed in four steps: - firstly, the apparent electrical resistivity measurements were interpreted in terms of local electrical resistivity by 1D inverse modelling; - secondly, the interpreted electrical values were translated in soil volumetric water content by using an empirical law, that was independently demonstrated in the field by a temporal monitoring of both electrical resistivity and water content; - thirdly, the soil volumetric water content were transformed into soil water potential values by using the water retention curve of the studied soil (the latter was independently determined on undisturbed samples in the laboratory). The interpretation of both the water content and matric potential maps demonstrated that these two state variables are not constant in a given soil unit. Some soil hydric processes, like lateral overland flow, could occur in some soils of the studied zone. They would never have been detected by local measurements of soil characteristics or by the use of the soil map. As a consequence, this study demonstrated the interest of spatial electrical resistivity at high resolution to interpret the soil spatial hydric functioning, and will be achieved and improved in the Digisoil project.

Cousin, I.; Besson, A.; Pasquier, C.; Giot, G.; Courtemanche, P.; Le Lay, C.; Nicoullaud, B.; Bourennane, H.; Richard, G.

2009-04-01

158

Profiling of Circulating MicroRNAs after a Bout of Acute Resistance Exercise in Humans  

PubMed Central

Recent studies have revealed a new aspect of physiological regulation in which microRNAs (miRNAs) play fundamental roles in diverse biological and pathological processes. Furthermore, it was recently discovered that miRNAs are stably secreted into blood and that circulating miRNAs may play important roles in cell–cell communication. Here, we examined whether the circulating miRNA profile is affected by acute resistance exercise. Twelve males performed a resistance exercise session (bench press and leg press), consisting of five sets of 10 repetitions at 70% of maximum strength, with a 1 min rest between sets. Blood samples were taken before exercise, and at 0 and 60 min, 1 day, and 3 days after exercise. The circulating miRNA profile was determined by microarray analysis. Quantitative real-time PCR confirmed that the miR-149* level increased three days after resistance exercise. In contrast, the miR-146a and miR-221 levels decreased three days after resistance exercise. Our findings suggest that circulating miRNA levels change in response to acute resistance exercise, and miRNAs may play important roles in resistance-exercise-induced adaptation. PMID:23923026

Wada, Shogo; Ushida, Takashi; Suzuki, Katsuhiko; Akimoto, Takayuki

2013-01-01

159

Study concerning the electrical resistivity of some liquid metals in ultrasonic field  

NASA Astrophysics Data System (ADS)

The increasing of the electrical resistivity values for the overheated high-purity liquid aluminium in range 934 K to 1043 K and for aluminium-silicon eutectic alloy in range 850 K to 960 K, during high-energy ultrasonic field presence is reported. We used DC electrical resistivity measurements. The modification of electrical resistivity values in ultrasonic field due to electron-ion interaction processes and the limited current density in liquid metals is discussed. The effect of cavitation at the high temperature is debated.

Moraru, Luminita

1999-02-01

160

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

SciTech Connect

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

Park, J.-H. [Argonne National Lab., IL (United States); Cho, W.D. [Utah Univ., Salt Lake City, UT (United States). Dept. of Metallurgical Engineering

1996-11-01

161

Electrical resistivity behaviors of liquid Pb-Sn binary alloy in the presence of ultrasonic field.  

PubMed

Electrical resistivity behaviors of liquid Pb-Sn alloys have been investigated in the presence of ultrasonic field. The process demonstrated significantly that electrical resistivity could reveal the precise influence caused by ultrasound. Details revealed by applying the resistivity measuring approach to the liquid Pb-Sn alloy show that the short ordered structures in the liquid could be modified by ultrasonic irradiation, and the resistivity approach could have application value in the ultrasonic irradiation process on the specific liquid metals and alloys. PMID:25113776

Liu, Xuan; Zhang, Jianfeng; Li, Haoyu; Le, Qichi; Zhang, Zhiqiang; Hu, Wenyi; Bao, Lei

2015-01-01

162

Characterizing heterogeneous coastal groundwater pathways using multi-scale onshore-to-offshore electrical resistivity surveys  

NASA Astrophysics Data System (ADS)

Electrical resistivity (ER) imaging techniques are useful for investigating porewater salinity distributions and dynamics within coastal environments. However, complex coastal geology can obscure the hydrologic target of ER surveys. We investigated the geologic controls on groundwater pathways in Rarotonga, a high volcanic island with a carbonate fringe. We used three ER survey configurations to explore this hydrogeologic setting: 1) waterborne, continuous resistivity profiling in the lagoon, 2) submerged cable surveys across the terrestrial-marine interface, and 3) traditional surveys on land. We designed overlapping portions of these surveys to reveal differences in how the deployment methods image subsurface ER structure. Using both the field data and forward modeling, we quantified the resolvability of ER features imaged by overlapping configurations, where the sensitivity changed both as a function of electrode spacing and boundary conditions (i.e. influence of seawater). Waterborne ER results revealed large scale variations in the ER structure of the lagoon geology. These heterogeneities are products of Rarotonga's volcanic history and reef diagenesis that change both the electrical signature and hydrogeologic properties of the subsurface. Time-lapse, submersed ER surveys imaged groundwater salinity dynamics and resolved select ER features more effectively than the waterborne surveys. Terrestrial ER surveys traced the extent of the freshwater lens and the transition from the unsaturated-saturated conditions, i.e., the water table. The ER responses of the three field configurations were concordant but imaged different scales hydrogeologic variability. The unique spatial signatures of both methodology and the geologic setting must be incorporated into future coastal ER applications.

Befus, K. M.; Cardenas, M.; Tait, D. R.; Erler, D.

2013-12-01

163

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

PubMed Central

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

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

2014-01-01

164

Forced magnetic reconnection in a plasma sheet with localized resistivity profile excited by lower hybrid drift type instability  

NASA Technical Reports Server (NTRS)

A forced magnetic reconnection process with a temporal evolution of resistivity is studied for a plasma sheet with a nonuniform resistivity profile based on the nonlocal mode structure of the lower hybrid drift type instability. The growth rate of the mode found is almost independent of the resistivity at the neutral sheet, but depends on the resistivity of the region of maximum density gradient away from the neutral sheet. This is studied by using both a nonlinear numerical MHD simulation and a linear theory. The mode may be relevant to the prevalent theoretical concept of MHD reconnection and the localized anomalous resistivity profile based on the lower hybrid drift instability.

Hoshino, M.

1991-01-01

165

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

166

Association of Multiple-Antibiotic-Resistance Profiles with Point and Nonpoint Sources of Escherichia coli in Apalachicola Bay  

Microsoft Academic Search

A total of 765 Escherichia coli isolates from point and nonpoint sources were collected from the Apalachicola National Estuarine Research Reserve, and their multiple-antibiotic-resistance (MAR) profiles were deter- mined with 10 antibiotics. E. coli isolates from point sources showed significantly greater resistance (P < 0.05) to antibiotics and higher MAR indices than isolates from nonpoint sources. Specifically, 65 different resistance

SALINA PARVEEN; RENDI L. MURPHREE; LEE EDMISTON; CHARLES W. KASPAR; KENNETH M. PORTIER; MARK L. TAMPLIN

1997-01-01

167

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

168

The Quantum Hall Eect as an Electrical Resistance Standard  

Microsoft Academic Search

The quantum Hall eect (QHE) provides an invariant reference for resistance linked to natural constants. It is used worldwide to maintain and compare the unit of resistance. The reproducibility reached today is almost two orders of magnitude better than the uncertainty of the determination of the ohm in the International System of Units SI. This article is a summary of

B. Jeckelmann; B. Jeanneret

2004-01-01

169

Leucine supplementation combined with resistance exercise improves the plasma lipid profile of dexamethasone-treated rats  

PubMed Central

The impact of leucine supplementation and resistance exercise (RE) on plasma lipid profile was evaluated in adult rats treated with dexamethasone, an experimental model of dyslipidemia. Total cholesterol did not differ among groups. Furthermore, leucine supplementation did not promote improvement in the plasma total cholesterol and LDL-c of the animals. However, plasma TG and VLDL-c were significantly decreased and HDL-c increased after 7 days of leucine supplementation combined with RE. In conclusion, leucine supplementation combined with RE, but not isolated, improved the plasma lipid profile of dexamethasone-induced dyslipidemic rats. PMID:22236609

2012-01-01

170

Electrical Resistivity and Thermal Conductivity of Nine Selected AISI Stainless Steels.  

National Technical Information Service (NTIS)

This technical report reviews the available experimental data and information on the electrical resistivity and thermal conductivity of nine selected AISI stainless steels and presents the recommended values from near absolute zero (1 K) to above the melt...

C. Y. Ho T. K. Chu

1977-01-01

171

Optimized design of a low-resistance electrical conductor for the multimegahertz range  

E-print Network

We propose a design for a conductive wire composed of several mutually insulated coaxial conducting shells. With the help of numerical optimization, it is possible to obtain electrical resistances significantly lower than ...

Kurs, Andre B.

172

PERFORMANCE OF AN ELECTRICAL RESISTIVITY TECHNIQUE FOR DETECTING AND LOCATING GEOMEMBRANE FAILURES  

EPA Science Inventory

An electrical resistivity survey technique has been developed and tested for assessing the integrity of geomembrane liner systems installed in fluid impoundments. Development of the technique has included two-dimensional computer modeling and three-dimensional physical model test...

173

'Mjuk' elvaerme. Styrning av direktverkande elradiatorer. ('Soft' electric heating. Control of resistance heating radiators).  

National Technical Information Service (NTIS)

The possibility of reducing the heating effect demand, by using microprocessor based control systems for resistance heating, is studied. Most of the study treats experimental measurements. A comparison is made between this 'soft' electricity system and co...

T. Andersson

1992-01-01

174

On the stability of the electrical resistivity and the contact resistance of electrically conductive modified silicone elastomers  

Microsoft Academic Search

Cable accessories for medium- and high voltage applications contain field grading and field zoning parts or layers. These parts often consist of electrically conductive modified silicone elastomers. The electrical conductivity is achieved by using selected and long-term tested carbon blacks. Conductive layers and parts are used to provide safety against exposure, inner shielding and an electrical contact to metallic parts

Jens Lambrecht; Martin Grunwald; Roland Bärsch

2010-01-01

175

High-temperature electrical resistivity of rare-earth metals with variable valence  

SciTech Connect

The electrical resistivity of compounds of rare-earth metals at high temperatures is calculated on the basis of allowance for the background mechanism of scattering and the hybridization of local electron states with the states of conduction electrons. An analytic expression is obtained for resistivity in a strong hybridization approximation. It follows from the expression that electrical resistivity may have a negative temperature coefficient within a broad range of high temperatures. The use of a three-band (s, d, f) model makes it possible to explain experimental data on the resistivity of certain rare-earth metals, particularly the connection between the sign of the temperature coefficient of electrical resistivity and the curvature of the relation (T).

Povzner, A.A.; Abel'skii, S.S.

1986-11-01

176

Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding  

Microsoft Academic Search

In this study, the effects of welding time on the tensile-peel strength and tensile-shear strength of welding joints in electrical resistance spot welding of chromate micro-alloyed steel sheets having 1.2mm thicknesses were investigated. A timer and current controlled electrical resistance spot welding machine having 120kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the

S. Aslanlar; A. Ogur; U. Ozsarac; E. Ilhan

2008-01-01

177

Aggregated Impact of Plug-in Hybrid Electric Vehicles on Electricity Demand Profile  

Microsoft Academic Search

Greenhouse gas emissions, air pollution i nu rban areas, and dependence on fossil fuels are among the challenges threatening the sustainable development of the transportation sector. Plug-in hybrid electric vehicle (PHEV) technology is one of the most promising solutions to tackle the situation. While PHEVs partially rely on electricity from the power grid, they raise concerns about their negative impacts

Zahra Darabi; Mehdi Ferdowsi

2011-01-01

178

Correlation between Electrical Resistivity and Soil-Water Content based Artificial Intelligent Techniques  

NASA Astrophysics Data System (ADS)

By using a artificial intelligent approaches, the purpose of this study is to compare water content of soils obtained from electrical resistivity in order to better results from conventional techniques system. The input variables for this system are the electrical resistivity reading, the water content laboratory measurements. The output variable is water content of soils. In this study, 148 data sets are clustered into 120 training sets and 28 testing sets for constructing the fuzzy system and validating the ability of system prediction, respectively. Soil is a heterogeneous medium consisted of liquid, solid, and gaseous phases. The solid and liquid phases play an essential role in soil spontaneous electrical phenomena and in behavior of electrical fields, artificially created in soil. For our aim, study area is selected in Istanbul (Yesilkoy, Florya, Basinkoy) and Golcuk. In this area, it is measured the electrical resistivity by VES (Vertical Electrical Sounding) in many points of these locations by field resistivity equipment. For geotechnical purposes, on the soil samples from borings, it was applied soil mechanics laboratory procedures and is determined the soil water contents from these samples. Relationships between soil water content and electrical parameters were obtained by curvilinear models. The ranges of our samples are changed between 1-50 ohm.m (for resistivity) and 20-60 (%, for water content). A artificial intelligent system (artificial neural networks, Fuzzy logic applications: Mamdani and Sugeno approaches) based on some comparisons about correlation between electrical resistivity and soil-water content, for Istanbul and Golcuk Soils in Turkey was constructed for identifying water content with electrical resistivity of soils.

Ozcep, Ferhat; Yildirim, Eray; Tezel, Okan; Asci, Metin; Karabulut, Savas

2010-05-01

179

Oxidative resistance, carotenes, tocopherols and lipid profile of liver oil of the ray Rhinoptera steindechneri  

Microsoft Academic Search

The liver oil of the tecolote ray (Rhinoptera steindechneri) was characterized in terms of its lipid by-class composition and fatty acid profile, natural antioxidants content, oxidative resistance and physicochemical properties. The liver oil content was considered high and fluctuated between 57% and 67% of the liver weight (w\\/w). The carotenes and ?-tocopherols levels varied from 2.9 to 17.4mg\\/100g of oil

G. Navarro-Garc??a; L. Bringas-Alvarado; R. Pacheco-Aguilar; J. Ortega-Garc??a

2004-01-01

180

MEASUREMENTS OF SPECIFIC ELECTRICAL CONTACT RESISTANCE BETWEEN SIC AND LEAD-LITHIUM EUTECTIC ALLOY  

E-print Network

MEASUREMENTS OF SPECIFIC ELECTRICAL CONTACT RESISTANCE BETWEEN SIC AND LEAD-LITHIUM EUTECTIC ALLOY resistance of disks of high purity CVD SiC were measured with liquid lead-lithium eutectic (LLE) alloy melts to be addressed. I. INTRODUCTION In the Dual Coolant Lead Lithium (DCLL) blanket [1,2] concept, silicon carbide

Abdou, Mohamed

181

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

182

Study on Optimal Location of a Resistive SFCL Applied to an Electric Power Grid  

Microsoft Academic Search

This paper describes a study on the optimal location of a resistive superconducting fault current limiter (SFCL) applied to an electric power grid. The resistive SFCL, which is designed to provide the quick system protection in the event of a fault, can have different effects on the planning and operation of a power system depending on its location. To select

Byung Chul Sung; Dong Keun Park; Jung-Wook Park; Tae Kuk Ko

2009-01-01

183

Early fatigue damage in carbon-fibre composites observed by electrical resistance measurement  

Microsoft Academic Search

Early fatigue damage during the first tenth (or less) of the fatigue life was observed in carbon fibre composites by d.c. electrical resistance measurement. The damage was most severe in the first loading cycle and the incremental damage in each subsequent cycle diminished cycle by cycle. For the continuous carbon fibre carbon-matrix composite, the resistance increased irreversibly during early fatigue

S. Wang; X. Shui; X. Fu; D. D. L. Chung

1998-01-01

184

Optimized design of a low-resistance electrical conductor for the multimegahertz range  

Microsoft Academic Search

We propose a design for a conductive wire composed of several mutually insulated coaxial conducting shells. With the help of numerical optimization, it is possible to obtain electrical resistances significantly lower than those of a heavy-gauge copper wire or litz wire in the 2-20 MHz range. Moreover, much of the reduction in resistance can be achieved for just a few

André Kurs; Morris Kesler; Steven G. Johnson

2011-01-01

185

Experimental study of electrical conduction in RuO 2 -based thick resistive films  

Microsoft Academic Search

Electrical conduction and noise of thick resistive films prepared from RuO2 and lead borosilicate glass were studied. Two series of pastes were prepared differing by the specific surface area of RuO2 powder (77 m2\\/g and 24 m2\\/g). It was concluded that two regions on resistanceR versus volume fractionv of conducting component characteristics may be specified. For small values ofv resistance

K. Bobran

1989-01-01

186

Electrical resistivities and thermopowers of transparent Sn-doped indium oxide films  

Microsoft Academic Search

We have systematically measured the electrical resistivities and thermopowers of transparent tin-doped indium oxide films. We found that the resistivities obey the Bloch-Grüneisen law between 25 and 300 K, whereas below 25 K, the resistivities slightly increase logarithmically with the decreasing temperature due to the weak-localization and electron-electron interaction effects. The thermopowers are negative and decrease linearly with temperature from

Z. Q. Li; J. J. Lin

2004-01-01

187

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

188

Generated on 04/07/13 by the Office of Institutional Research and Planning. Doctoral Program Profile: Electrical Engineering  

E-print Network

Profile: Electrical Engineering This program is part of the Department of Electrical Engineering://www.eecs.ku.edu/prospective_students/graduate Notes: Faculty data include all faculty in the Department of Electrical Engineering and Computer Science. Department Faculty: Electrical Engineering and Computer Science Fall 2012 Total Faculty 34 Tenured and Tenure

189

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

190

Method and device with adjustable focusing for measuring the electric resistivity of geological formations  

SciTech Connect

The method of the invention comprises determining the variation of the electric potential on both sides of a central electrode in a borehole, detecting the two levels of the borehole where the potential gradient is zero, and measuring the electric resistivity of the geological formation between these two levels.

Desbrandes, R.

1983-10-25

191

Electrothermal analysis of electric resistance spot welding processes by a 3-D finite element method  

Microsoft Academic Search

Electric resistance spot welding which is an important process in auto-body assebly is simulated by a 3-D finite element code developed. The main interest in the simulation is the quality of welding and the durability of electrodes, which needs electrothermal analysis for temperature distribution in both electrodes and welded sheets. A finite element formulation is derived for both electric analysis

H. Huh; W. J. Kang

1997-01-01

192

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

193

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

194

Concentration dependence of electrical resistivity of binary liquid alloy HgZn: Ab-initio study  

NASA Astrophysics Data System (ADS)

The electrical resistivity of HgZn liquid alloy has been made calculated using Troullier and Martins ab-initio pseudopotential as a function of concentration. Hard sphere diameters of Hg and Zn are obtained through the inter-ionic pair potential have been used to calculate partial structure factors. Considering the liquid alloy to be a ternary mixture Ziman's formula for calculating the resistivity of binary liquid alloys, modified for complex formation, has been used. These results suggest that ab-initio approach for calculating electrical resistivity is quite successful in explaining the electronic transport properties of binary Liquid alloys.

Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

2013-06-01

195

ELECTRICAL RESISTIVITY TECHNIQUE TO ASSESS THE INTEGRITY OF GEOMEMBRANE LINERS  

EPA Science Inventory

Two-dimensional electrical modeling of a liner system was performed using computer techniques. The modeling effort examined the voltage distributions in cross sections of lined facilities with different leak locations. Results confirmed that leaks in the liner influenced voltage ...

196

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

NASA Astrophysics Data System (ADS)

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.

Mohiuddin, Mohammad; van Hoa, Suong

2011-06-01

197

DEPENDENCE OF THE ANOMALOUS RESISTIVITY ON THE INDUCED ELECTRIC FIELD IN SOLAR FLARES  

SciTech Connect

Anomalous resistivity is a critical parameter for triggering the fast magnetic reconnection and interpreting the eruption of solar flares in the nearly collisionless coronal plasma. However, the mechanism for the production of anomalous resistivity and its evolution are weakly understood. In this paper, the one-dimensional Vlasov equation was numerically solved with the typical solar coronal parameters and realistic mass ratio in the presence of strong inductive electric field, and the relationship between the anomalous resistivity and the reconnecting electric field was inferred for the area near the center of reconnecting current sheets. Our principal findings are summarized as follows. (1) The relationship between the anomalous resistivity and the reconnecting electric field E {sub 0} may be represented by {eta}{sub eff} = [10.82-10.99 exp (-0.36 E {sub 0})]{Omega} m. (2) If E{sub 0} is small enough, it may be described by {eta}{sub eff} = [4.02 E {sub 0} - 0.18]{Omega} m, which is basically consistent with the early experimental results on the plasma response to the applied electric field. (3) In comparison with theoretical formulas for the current-driven ion-acoustic and Buneman anomalous resistivities, if E{sub 0} is small, the anomalous resistivity may be due to the ion-acoustic instability; if E{sub 0} is large, the anomalous resistivity may be due to the Buneman instability. These results are also basically consistent with early experiments.

Wu Guiping [Department of Physics, Southeast University, Nanjing, Jiangsu 210096 (China); Huang Guangli; Ji Haisheng, E-mail: wuguiping@seu.edu.c, E-mail: glhuang@pmo.ac.c, E-mail: jihs@pmo.ac.c [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, Jiangsu 210008 (China)

2010-09-01

198

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

199

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

DOEpatents

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

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

1997-08-26

200

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

DOEpatents

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

Daily, William D. (Livermore, CA); Laine, Daren L. (San Anotonio, TX); Laine, Edwin F. (Penn Valley, CA)

2001-01-01

201

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

DOEpatents

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

Daily, William D. (Livermore, CA); Laine, Daren L. (San Antonio, TX); Laine, Edwin F. (Alamo, CA)

1997-01-01

202

Deformation dependent electrical resistance of MWCNT layer and MWCNT/PEO composite films  

NASA Astrophysics Data System (ADS)

It has been well documented that the electrical properties of a carbon nanotube (CNT) can be either metallic or semiconducting depending upon the tube's chirality. Theoretical aspects of the unique electrical properties of CNTs are reviewed. Based upon the fundamental understanding of this special feature, the deformation-dependent electrical resistance of multiwalled carbon nanotube (MWCNT) layer and MWCNT/polyethylene oxide (PEO) composite in the macroscopic scale are investigated considering both experimental and theoretical aspects. In the first set of experiments, a MWCNT layer was grown by plasma enhanced chemical vapor deposition (PECVD) process on a surface of copper substrate and a copper probe was applied to this surface inducing compressive deformation onto the MWCNT layer. It was found that the electrical resistance of the MWCNT layer under compression was reduced by 80 percent. The possible mechanisms for electrical resistance reduction were analyzed and suggested. Also, the MWCNT-enhanced surface showed a finite slope of electrical resistance as a function of contact force, thereby making possible the use of this arrangement as a small-scale force or pressure sensor. However, there is limitation on the direct use of MWCNT grown directly onto copper substrates for real applications due to the easy separation of the MWCNTs from the copper surface and the low yield of MWCNTs by the given metal deposition and PECVD system. The processing method developed for the second set of experiments uses intentional coagulation of dispersed MWCNT in polymer solution. This process is simple and effective to fabricate MWCNT-filled polymer films. MWCNT/PEO composite was selected after comparative resistivity measurement and microstructure analysis. The percolation threshold of MWCNT/PEO was determined experimentally to be between 0.14 to 0.28 vol% of MWCNT. Films having MWCNT content above the percolation threshold were conductive and exhibited repeatable values of electrical conductivity. Unique and repeatable relationships of resistance versus strain were obtained for multiple samples with different volume fractions of MWCNT. The overall pattern of electrical resistance change versus strain for the samples of each volume fraction of MWCNT consists of linear and non-linear regions. A model to describe the combination of linear and non-linear modes of electrical resistance change as a function of strain is suggested. The unique characteristics in electrical resistance change for different volume fractions implies that nanotube-based composites can be used as tunable strain sensors for application into embedded sensor systems in structures.

Park, Myounggu

203

PROGRESS REPORT. COMPLEX ELECTRICAL RESISTIVITY FOR MONITORING DNAPL CONTAMINATION  

EPA Science Inventory

There is an increasing need for external or non-invasive sensing techniques to locate DNAPLs in the subsurface and to track their spread and monitor their break-down or removal by natural or engineered means. We have proposed to bring the field measurement of complex resistivity ...

204

Fatigue Resistant Muscle by Cell Transplantation and Electrical Conditioning  

Microsoft Academic Search

Congestive heart failure refractory to medical therapy can be managed with cardiac trans- plantation or artificial heart. Due to the scarcity of donor organs and unsatisfactory long- term outcomes of mechanical devices, skeletal muscle has been used to augment circulatory function. Dynamic cardiomyoplasty, skeletal muscle ventricle, aortomyoplasty, and muscle powered assist devices all require the fatigue resistant muscle to support

Race L. Kao; Janet Davis; Elizabeth Lamb; William Browder

205

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

206

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

207

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

208

Specific features in the behavior of electrical resistivity of the pine biocarbon preform/copper composite  

NASA Astrophysics Data System (ADS)

The electrical resistivity ?( T) of the novel type of composites prepared by infiltrating melted copper in vacuum in empty sap channels of white pine high-porosity biocarbon preforms has been measured in the temperature range 5-300 K. Biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two carbonization temperatures, 1000 and 2400°C. The electrical resistivity of the composites has been found to vary relatively weakly with temperature and to pass through a characteristic minimum near 40-50 K, which can be ascribed to iron and manganese impurities penetrating into copper from the carbon preform when liquid copper is infiltrated into it. It has been shown that the electrical resistivity ?( T) of the composites is governed primarily by the specific microstructure of the preform, which is made up of parallel channels with an average diameter of about 50 ?m interrupted by systems of thin capillaries. The small cross section of the copper-filled capillaries accounts for these regions providing the major contribution to the electrical resistivity of the composites. An increase in the wood carbonization temperature brings about a noticeable increase in the effective capillary cross section and a decrease in the electrical resistivity ?( T) of the composite.

Burkov, A. T.; Orlova, T. S.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Jezowski, A.

2010-11-01

209

Molecular Expressions: Electricity & Magnetism - Resistance at the Molecular Level  

NSDL National Science Digital Library

This item is an interactive Java tutorial that simulates the movement of free electrons when voltage is applied across a conductor. As the user adjusts the current flow, the resulting changes are represented on both a macro and nanoscale. The design of the simulation helps the beginner understand how electron collision causes resistance within a system. This applet is part of a larger collection sponsored by Florida State University.

Davidson, Michael

2007-06-12

210

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.

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

2014-01-01

211

Electrical resistivity of thermally evaporated bismuth telluride thin films  

Microsoft Academic Search

Semiconducting chalcogenide thin films have been receiving considerable attention in the recent years because of their wide applications in the various fields of science and technology. The studies of the electronic properties of semiconductors have been largely stimulated by attractive micro-electronic device applications. Among the various V–VI compounds, Bismuth Telluride (Bi2Te3) is an established low-temperature thermo electric material and is

J. Dheepa; R. Sathyamoorthy; S. Velumani; A. Subbarayan; K. Natarajan; P. J. Sebastian

2004-01-01

212

The gene expression profiles of medulloblastoma cell lines resistant to preactivated cyclophosphamide  

PubMed Central

The total expression profiles of two medulloblastoma cell lines resistant to the preactivated form of cyclophosphamide (4-hydroperoxycyclophosphamide, 4-HC) were examined using the Affymetrix GeneChip U133A array. Our primary objective was to look for possible genes, other than the well-studied aldehyde dehydrogenases (ALDH) that may be involved in cyclophosphamide (CP) resistance in medulloblastomas. We present here the lists of the most highly upregulated [30 for D341 MED (4-HCR); 20 for D283 MED (4-HCR)] and downregulated [19 for D341 MED (4-HCR); 15 for D283 MED (4-HCR)] genes which may be involved in conferring CP-resistance to the two medullobalstoma cell lines. The lists of genes from the two sublines almost had no overlap, suggesting different mechanisms of CP-resistance. One of the most noteworthy upregulated gene is TAP1 [90-fold increase in D341 MED (4-HCR) relative to D341 MED]. TAP1, a protein belonging to the ABC transporter family is normally involved in major histocompatibility class I (MHC I) antigen processing. This suggests the possible role of multidrug resistance (MDR), albeit atypical (which means it does not involve the usual MDR1 and MRP glycoproteins), in medulloblastoma’s CP-resistance. Apart from TAP1, a number of other genes involved in MHC1 processing were upregulated in D341 MED (4HCR). D341 MED (4-HCR) also had a 20-fold increase in the expression of the aldo-keto reductase gene, AKR1B10, which may deactivate the reactive cyclophosphamide metabolite, aldophosphamide. For D283 MED (4-HCR), the most notable increase in expression is that of ALDH1B1, a member of the aldehyde dehydrogenase (ALDH) family of proteins. PMID:18473730

Lin, S.M.; Johnson, S. P.; Bullock, N.S.; Colvin, M.; Bigner, D.D.; Friedman, H.S.

2013-01-01

213

MicroRNA expression profiles associated with acquired gefitinib?resistance in human lung adenocarcinoma cells.  

PubMed

The aim of the present study was to establish, characterize and elucidate the potential mechanisms of acquired gefitinb resistance, using the A549 human lung cancer cell line. A gefitinib?resistant A549 sub?clone was established by exposure to escalating gefitinib concentrations over a period of 16?24 months. Half maximal inhibitory concentration (IC50) values were quantified using a real time cytotoxicity assay. The expression profiles of the parent and resistant sub?clone A549 cells were detected using the µParaflo® Microfluidics Biochip microRNA (miRNA) Microarray. The ArrayPro software was used to analyze the differential expression levels of the miRNA, and bioinformatics software was used to predict the potential target genes of the differentially expressed miRNAs. Quantitative polymerase chain reaction (qPCR) was used to confirm the results of the miRNA microarray. A miRNA mimic was transfected into the gefitinib?resistant cells, in order to predict target gene interaction effects, following gefitinib treatment. Protein expression level differences were confirmed by western?blot analysis. Real time cytotoxicity assays revealed a 3?fold increase in the IC50 values of the gefitinib?resistant sub?clones, as compared with the parent cells. There were marked morphological differences between the parent and resistant cells. In the microarray analysis, the gefitinib?resistant sub?clones had 25 upregulated and 18 downregulated miRNAs, as compared with the parent cells. The qPCR revealed that miR?7 was significantly downregulated, which was concordant with the results of the microarray. The results of the present study suggest that miR?7 may significantly improve the sensitivity of cancer cells to gefitinib. The data presented in the present study provides an experimental basis and theory that miRNAs may be involved in acquired gefitinib?resistance of lung adenocarcinoma, and miR?7 may have potential clinical effects in the reversal of drug resistance. PMID:25339453

Ge, Xiaojun; Zheng, Limei; Huang, Min; Wang, Yonglun; Bi, Feng

2015-01-01

214

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

215

Electrical properties measurements on individual carbon nanofibers by scanning spreading resistance microscopy  

NASA Astrophysics Data System (ADS)

Vertically aligned 850-nm-long carbon nanofibers (CNFs) are grown on a titanium nitride (TiN) layer by a radio-frequency plasma system at 560 °C. Electrical properties of individual CNFs are statistically determined by a current sensing atomic force microscopy mode. An interpretation based on electrical contact resistance model classically used to describe macroscopic observations, combined with a semiclassical approach commonly used for such nano-objects, is proposed here to explain dispersion in obtained values. Roughness of the TiN layer is responsible for this dispersion by varying contact surface between CNF and the TiN layer, while interface oxidation equally affects the transport by adding a barrier at the interface. Some CNFs exhibit very low resistances (few kilohms), implying that good contact is obtained between the nanofiber and the substrate, while others CNFs exhibit high resistance, attributed to local poor electrical contacts between CNFs and TiN layer.

Fourdrinier, L.; Le Poche, H.; Chevalier, N.; Mariolle, D.; Rouviere, E.

2008-12-01

216

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

SciTech Connect

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

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

2004-09-21

217

High thermal stability and low electrical resistivity carbon-containing Cu film on barrierless Si  

SciTech Connect

Interfacial structures and electrical resistivities of a carbon-doped Cu film at different annealing temperatures and times were investigated. The film was prepared by magnetron sputtering on barrierless silicon. After annealing, grain growth was distinctly hindered and a carbon-containing nanometer thick passive amorphous layer was formed at the film/substrate interface. The film had a resistivity of about 2.7 muOMEGA cm after annealing at 400 deg. C for 1 h and maintained a low resistivity of 3.8 muOMEGA cm even after 9 h annealing at 400 deg. C. The low electrical resistivity in combination with the high thermal stability makes carbon doping a promising technique for future Cu interconnects on barrierless Si.

Nie, L. F.; Li, X. N.; Wang, Q.; Dong, C. [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams-Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Chu, J. P. [Department of Polymer Engineering and Graduate Institute of Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Lin, C. H. [Department of Electronic Materials, Chin-Min Institute of Technology, Tou-Fen 35153, Taiwan (China)

2010-05-03

218

Electrical resistivity of HTSC-normal metal interface  

NASA Astrophysics Data System (ADS)

It is analytically shown that the specific resistivity ? of the contact layer in a hole-type HTSC abutting upon a metal Me with electronic conductivity is a non-monotonous function of the distance from the interface. The maximum value of ? corresponds to ?AF of HTSC in the antiferromagnetic dielectric state at the distance x where the difference between the density of Fermi guest electrons and native holes nfe(x)-nfh(x)=0. In the case of nfe(x)=const, the value of contact resistivity rc of the HTSC/Me interface can serve as an indicator of changes in nfh(x), especially the temperature-related ones. The temperature dependences rc(T) in HTSC/Pb and HTSC/In interfaces were measured for optimally and lightly doped biphasic bismuth ceramics BiSrPbCaCuO. The anomalies observed in the measured temperature dependences agree with the concept of local pairs existing in the pseudogap phase up to the temperature of depairing, the idea of fluctuation superconductivity, and the transition into the superconducting state.

Sokolenko, V. I.; Frolov, V. A.

2013-02-01

219

Electrical Resistivity Imaging and Quantification of Water Content Distribution during Infiltration and Redistribution in Soils  

Microsoft Academic Search

Controlled by precipitation, evapotranspiration, recharge, and soil-hydraulic properties, water content is difficult to measure extensively in heterogeneous, natural environments without disturbing the subsurface. Time-lapse electrical resistivity imaging (ERI) is a cost-effective, minimally invasive method for imaging changes in water content in the vadose zone. Quantifying the relation between resistivity and water content, however, is challenging due to 1) spatially variable

K. Singha; B. B. Mirus; J. R. Nimmo; K. Perkins

2006-01-01

220

Automated Monitoring of High-Resistance Connections in the Electrical Distribution System of Industrial Facilities  

Microsoft Academic Search

High-resistance(R) connections due to poor contacts in the electrical distribution system can cause failures due to overheating, reduce efficiency, and pose safety risks in the industrial facility. The methods currently available for detection of high-R connections such as infrared thermography, resistance or voltage unbalance tests are inconvenient since they are off-line or walk-around type tests that do not provide continuous

Jangho Yoon; Jangho Yun; Sang Bin Lee; Ernesto J. Wiedenbrug

2008-01-01

221

Electrical resistivity and absolute thermopower of liquid GaSb and InSb alloys  

Microsoft Academic Search

The electrical resistivity and absolute thermoelectric power of liquid GaSb and InSb alloys have been carefully measured as functions of temperature. A U-shaped quartz cell was used in the measurement and more accurate data than those reported by other authors were obtained. The resistivity of liquid InSb and that of GaSb are 106.49 µOmega cm and 93.16 µOmega cm at

Qiang Wang; Xiumei Chen; Kunquan Lu

2000-01-01

222

Low electrical resistivity carbon nanotube and polyethylene nanocomposites for aerospace and energy exploration applications  

NASA Astrophysics Data System (ADS)

An investigation was conducted towards the development and optimization of low electrical resistivity carbon nanotube (CNT) and thermoplastic composites as potential materials for future wire and cable applications in aerospace and energy exploration. Fundamental properties of the polymer, medium density polyethylene (MDPE), such as crystallinity were studied and improved for composite use. A parallel effort was undertaken on a broad selection of CNT, including single wall, double wall and multi wall carbon nanotubes, and included research of material aspects relevant to composite application and low resistivity such as purity, diameter and chirality. With an emphasis on scalability, manufacturing and purification methods were developed, and a solvent-based composite fabrication method was optimized. CNT MDPE composites were characterized via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Raman spectroscopy, and multiple routes of electron microscopy. Techniques including annealing and pressure treatments were used to further improve the composites' resulting electrical performance. Enhancement of conductivity was explored via exposure to a focused microwave beam. A novel doping method was developed using antimony pentafluoride (SbF5) to reduce the resistivity of the bulk CNT. Flexible composites, malleable under heat and pressure, were produced with exceptional electrical resistivities reaching as low as 2*10-6O·m (5*105S/m). A unique gas sensor application utilizing the unique electrical resistivities of the produced CNT-MDPE composites was developed. The materials proved suitable as a low weight and low energy sensing material for dimethyl methylphosphonate (DMMP), a nerve gas simulant.

Moloney, Padraig G.

223

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

224

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

225

Temperature dependence of the electron density of states and dc electrical resistivity of disordered binary alloys.  

NASA Technical Reports Server (NTRS)

A model calculation of the temperature dependence of the electronic density of states and the electrical conductivity of disordered binary alloys, based on the coherent-potential approximation is made by introducing thermal disorder in the single-band model (Velicky and others). Thermal disorder is found to broaden and smear the static-alloy density of states. The electrical resistivity in weak-scattering alloys always increases with temperature. However, in the strong-scattering case, the temperature coefficient of resistivity can be positive, zero, or negative, depending on the location of the Fermi energy.-

Chen, A.-B.; Weisz, G.; Sher, A.

1972-01-01

226

Use of Artificial Neural Networks to Invert 3D Electrical Resistivity Imaging Data  

NASA Astrophysics Data System (ADS)

The artificial neural network approach has presented to solve 3D resistivity inverse problems included in complex subsurface structure. The 3D synthetic data sets were generated to train the neural network using a finite element forward modeling code. Several artificial neural network algorithms have been tested on a basis of trial and error for training data set. The resilient back propagation paradigm was efficient in training stage. After 1340 epochs, the MSE error as a function of epochs for the combined training data reduced a threshold value (0.00034) and the network was converged. To test the trained network with real field data, the 3D electrical resistivity data was conducted on certain structure with known resistivity and was acquired with the Pole-Pole configuration. The interpreted results showed, the artificial neural network approach was capable to invert 3D electrical resistivity data as well as synthetic data. The main advantage of this approach for resistivity inversion is that, once the neural network has been trained it can invert any 3D electrical resistivity imaging data rapidly.

Neyamadpour, Ahmad; Wan Abdullah, W. A. T.; Taib, Samsudin

2009-07-01

227

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

228

Quantifying the Effect of Kerogen on Electrical Resistivity Measurements on Organic-rich Source Rocks  

E-print Network

This chapter presents a pore-scale numerical simulation approach for assessment of effective electrical resistivity of rock-fluid media. In this approach, a digital porous medium was created based on SEM (scanning electron microscopy) images of rock...-rich source rocks. The first section in this chapter provides the theoretical basis behind simulation of electrical conduction phenomena at the pore-scale level in porous media. Section 3.2 describes the modeling process and the development...

Kethireddy, Nikhil Reddy

2013-12-04

229

Time-lapse 2D electrical resistivity tomographies for investigating the Picerno landslide (Basilicata Region, southern Italy)  

NASA Astrophysics Data System (ADS)

The rainwater infiltration into the soil and the increase of pore water pressure in the vadose zone can be considered the main causes of shallow landslides triggering. The standard techniques used to measure the water content of the soil and the piezometric levels in areas of potential instability are the TDR method and the piezometric measurements, respectively. These techniques, while allowing to obtain direct information of the considered parameter, provide a punctual information about the specific hydrological characteristics of the investigated soil. Recently, the literature reports many examples of applications of indirect methods for the study and the estimate of water content in the first layers of the subsoil. In particular, the 2D electrical resistivity tomography has been applied for obtaining information about the temporal and spatial patterns of water infiltration processes. This paper reports the results obtained in the area affected by the Picerno landslide (Basilicata Region, Southern Italy), which represents one of the test sites of Morfeo project (Monitoraggio e Rischio da Frana mediante dati EO) funded by the Italian Space Agency (ASI). The studied slope has been frequently involved in reactivation phenomena the most recent of which occurred on March 2006. In the area, we have installed a prototype system for time-dependent analysis of electrical resistivity images and TDR measurements. The geophysical results are opportunely integrated with the piezometric data. The system is composed of a 48-channel cable connected to the georesistivimeter Syscal Pro Switch 48, the electrodes are placed at a distance of 1 m. Two holes used to measure the piezometric level and another four equipped with TDR probes are located along the acquisition profile. The electrical resistivity tomographies and the water content measurements are performed with time intervals selected by considering the rainfall intensity and frequency. The first preliminary result of this experiment are presented and discussed.

Luongo, Raffaele; de Bari, Claudia; Calamita, Giuseppe; Loperte, Antonio; Perrone, Angela; Satriani, Antonio; Votta, Mario; Lapenna, Vincenzo

2010-05-01

230

A Serum Protein Profile Predictive of the Resistance to Neoadjuvant Chemotherapy in Advanced Breast Cancers*  

PubMed Central

Prediction of the responses to neoadjuvant chemotherapy (NACT) can improve the treatment of patients with advanced breast cancer. Genes and proteins predictive of chemoresistance have been extensively studied in breast cancer tissues. However, noninvasive serum biomarkers capable of such prediction have been rarely exploited. Here, we performed profiling of N-glycosylated proteins in serum from fifteen advanced breast cancer patients (ten patients sensitive to and five patients resistant to NACT) to discover serum biomarkers of chemoresistance using a label-free liquid chromatography-tandem MS method. By performing a series of statistical analyses of the proteomic data, we selected thirteen biomarker candidates and tested their differential serum levels by Western blotting in 13 independent samples (eight patients sensitive to and five patients resistant to NACT). Among the candidates, we then selected the final set of six potential serum biomarkers (AHSG, APOB, C3, C9, CP, and ORM1) whose differential expression was confirmed in the independent samples. Finally, we demonstrated that a multivariate classification model using the six proteins could predict responses to NACT and further predict relapse-free survival of patients. In summary, global N-glycoproteome profile in serum revealed a protein pattern predictive of the responses to NACT, which can be further validated in large clinical studies. PMID:21799047

Hyung, Seok-Won; Lee, Min Young; Yu, Jong-Han; Shin, Byunghee; Jung, Hee-Jung; Park, Jong-Moon; Han, Wonshik; Lee, Kyung-Min; Moon, Hyeong-Gon; Zhang, Hui; Aebersold, Ruedi; Hwang, Daehee; Lee, Sang-Won; Yu, Myeong-Hee; Noh, Dong-Young

2011-01-01

231

Improvements on the electrical resistivity of chemical bath deposited CdS films by laser annealing  

NASA Astrophysics Data System (ADS)

The dark resistivity of cw Ar+ ion laser annealed chemical bath deposited CdS films has been measured. A two-decade decrement of the electrical resistivity, as compared to the unannealed samples, is reported. A threshold laser power density for reproducible annealing has been found to be ?50 W/cm2. Log ? vs 1/T plots were used to calculate the mobility ratio b = ?n/?p. This ratio shows a slight increment on laser annealed but it is not sufficient to explain the resistivity changes.

Martínez, G.; Martínez, J. L.; Zehe, A.

1982-06-01

232

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

SciTech Connect

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. 102 references.

Borovsky, J.E.

1986-07-01

233

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

234

Microfluidic genome-wide profiling of intrinsic electrical properties in Saccharomyces cerevisiae  

PubMed Central

Methods to analyze the intrinsic physical properties of cells – for example, size, density, rigidity, or electrical properties – are an active area of interest in the microfluidics community. Although the physical properties of cells are determined at a fundamental level by gene expression, the relationship between the two remains exceptionally complex and poorly characterized, limiting the adoption of intrinsic separation technologies. To improve our current understanding of how a cell's genotype maps to a measurable physical characteristic and quantitatively investigate the potential of using these characteristics as biomarkers, we have developed a novel screen that combines microfluidic cell sorting with high-throughput sequencing and the haploid yeast deletion library to identify genes whose functions modulate one such characteristic - intrinsic electrical properties. Using this screen, we are able to establish a high-content electrical profile of the haploid yeast gene deletion strains. We find that individual genetic deletions can appreciably alter the electrical properties of cells, affecting ~10% of the 4432 gene deletion strains screened. Additionally, we find that gene deletions affecting electrical properties in specific ways (i.e. increasing or decreasing effective conductivity at higher or lower electric field frequencies) are strongly associated with an enriched subset of fundamental biological processes that can be traced to specific pathways and complexes. The screening approach demonstrated here and the attendant results are immediately applicable to the intrinsic separations community. PMID:23661198

Vahey, Michael D.; Pesudo, Laia Quiros; Svensson, J. Peter; Samson, Leona D.; Voldman, Joel

2013-01-01

235

Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging  

PubMed Central

Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head. PMID:18799394

Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin

2008-01-01

236

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

PubMed

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

237

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

238

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

239

Pulse number control of electrical resistance for multi-level storage based on phase change  

NASA Astrophysics Data System (ADS)

Phase change nonvolatile memory devices composed of SeSbTe chalcogenide semiconductor thin film were fabricated. The resistivity of the SeSbTe system was investigated to apply to multi-level data storage. The chalcogenide semiconductor acts as a programmable resistor that has a large dynamic range. The resistance of the chalcogenide semiconductor can be set to intermediate resistances between the amorphous and crystalline states using electric pulses of a specified power, and it can be controlled by repetition of the electric pulses. The size of the memory cell used in this work is 200 nm thick with a contact area of 1 µm diameter. The resistance of the chalcogenide semiconductor gradually varies from 41 k? to 840 ? within octal steps. The resistance of the chalcogenide semiconductor decreases with increasing number of applied pulses. The step-down characteristic of the resistance can be explained as the crystalline region of the active phase change region increases with increasing number of applied pulses. The extent of crystallization was also estimated by the overall resistivity of the active region of the memory cell.

Nakayama, K.; Takata, M.; Kasai, T.; Kitagawa, A.; Akita, J.

2007-09-01

240

A theoretical study of electrical and thermal response in resistance spot welding  

SciTech Connect

The effect of contact resistance including constriction and contamination resistance has been a major hurdle for the thermoelectrical analysis of the resistance spot welding process. In this paper, a simple model was suggested and used for calculating the electrical and thermal response of the resistance spot welding process to investigate the influence of contacting forces on the formation of weld nuggets. The electrode surface of the contact interface was assumed to be axisymmetric and its microasperities to have a trapezoidal cross-section. These microasperities were considered as the one-dimensional contact resistance elements in the finite element formulation. The contamination film was assumed to be a nonconducting oxide layer, which is very brittle, so that it is broken to some number of pieces when a contacting pressure is being applied. The crushed films were assumed to be distributed at regular intervals and to conserve their size and number during the welding process. The simulation results revealed that the proposed model can be successfully used to predict the effect of the contact resistance on the electrical and thermal response of the resistance spot welding process.

Na, S.J.; Park, S.W. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Precision Engineering and Mechatronics

1996-08-01

241

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

242

Effects of IR Laser Shots on the Surface Hardness and Electrical Resistivity of High-Purity Iron  

NASA Astrophysics Data System (ADS)

Annealed specimens of 99.99% pure iron were irradiated with 500, 750, 1000, and 1250 Nd:YAG laser shots. The laser fluence and laser intensity at the laser irradiation spot on the target surface were 4.4 × 103 J/cm2 and 4.8 × 1011 W/cm2, respectively. Vickers hardness of irradiated specimens was measured at various points separated by 0.5 mm in four different mutually perpendicular directions around the laser irradiation spot. The surface hardness profile for each irradiated specimen shows an increasing trend in surface hardness till a distance of 3.5 mm from the reference point. The average surface hardness (ASH) is found to increase up to 21% and electrical resistivity increases up to 50% as the number of laser shots is increased to 1250. A linear relationship between electrical resistivity and ASH is observed. Moreover, the ASH follows the well-known Hall-Petch relation, indicating that the crystallite boundaries impede the motion of dislocations to a greater extent as the crystallite size gets smaller.

Butt, M. Z.; Ali, Dilawar; Bashir, Farooq; Ishtiaq, M.

2014-03-01

243

Analytical Procedure for Measuring Electrical Resistivity of Anisotropic Materials  

NASA Astrophysics Data System (ADS)

The Montgomery method is used to determine the resistivity tensor of anisotropic materials [1] such as high-TC and FeAs superconductors, 2-layer Mn oxides, organic conductors, and quasi-1D conductors. It uses the Wasscher transformation [2], which calculates an isotropic equivalent sample of the anisotropic sample. This is a timing-consuming task because it is a numerical method based upon graphical analyses obtained from calculations by Logan, Rice, and Wick [3]. In this work we report a simplification of the Montgomery method. Analytical equations are derived and applied to several isotropic and anisotropic samples (Cu, Al, Bi2Sr2CaCu2O8+?, Graphite, SrNbOx, ?-Mo4O11). Comparisons with results obtained by using the standard four-probe method demonstrate the quality and simplicity of the procedure, which can easily be extended to data acquisition systems. This material is based upon work supported by FAPESP (grant No. 07-04572-8), NSF (grants Nos. DMR-0504769 and 0552458), and CNPq (grant Nos. 301334/2007-2 and 201439/2007-7). [1] H. C. Montgomery, J. Appl. Phys. 42, 2971 (1971). [2] J. D. Wasscher, Philips Res. Repts. 16, 301 (1961). [3] B. F. Logan, S. O. Rice, and R. F. Wick, J. Appl. Phys. 42, 2975 (1971).

Dos Santos, C. A. M.; de Lima, B. S.; Shigue, C. Y.; de Campos, A.; da Luz, M. S.; Rice, A. T.; White, B. D.; Neumeier, J. J.

2009-03-01

244

Aerodynamic Resistance Reduction of Electric and Hybrid Vehicles. Progress Report, September 1978.  

National Technical Information Service (NTIS)

The objectives, approach, and FY'78 progress and results of the Aerodynamic Resistance Reduction work element of the Electric and Hybrid Vehicle System R and D Project are described. The generation of an EHV aerodynamic data base was initiated by conducti...

1979-01-01

245

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

246

Resonant impurity scattering and electron-phonon scattering in the electrical resistivity of Cr thin films  

E-print Network

Resonant impurity scattering and electron-phonon scattering in the electrical resistivity of Cr is presented and fit to a model which includes electron-phonon scattering and resonant impurity scattering. Resonant impurity scattering from localized defect states in the spin-density wave gap leads to very high

Hellman, Frances

247

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

248

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

249

ELECTRICAL RESISTIVITY RECOVERY IN COLD-WORKED AND ELECTRON-IRRADIATED NICKEL  

Microsoft Academic Search

Pure nickel wires were subjected to electron irradiation and cold work. ; Electrical resistivity recovery, starting at room temperature and extending to ; the recrystallization range, was studied. Recovery stages near 100 C (Stage ; III) and 270 C (Stage IV) were found to occur by a diffuslon process following ; cold work; dlslocatiors are believed to be the defect

A. Sosin; J. A. Brinkman

1959-01-01

250

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

251

Optical fibres and electrical resistance measurement for in-situ monitoring of composite fatigue  

Microsoft Academic Search

The use of fibre-reinforced thermoplastics, for example in the aeronautical industry, is increasing rapidly. Therefore, there is an increasing need for in-situ monitoring tools, which preferably have limited influence on the behaviour of the material and which are easy to use. For this study, two options are explored: optical fibres and electrical resistance measurement. The used material is a carbon

Ives De Baere; Wim Van Paepegem; Joris Degrieck

252

Modeling temporal variations of electrical resistivity associated with pore pressure change in a kilometer-scale  

E-print Network

of electric field variations possibly associated with tectonic activity. The galvanic coupling model proposed resistivity of underground structures. This is important for hydrogeological problems but also in active tectonics where fluids are known to play an important role in the seismic cycle [Nur and Booker, 1972; Muir

Paris-Sud XI, Université de

253

RRR OF COPPER COATING AND LOW TEMPERATURE ELECTRICAL RESISTIVITY OF MATERIAL FOR TTF COUPLERS  

E-print Network

RRR OF COPPER COATING AND LOW TEMPERATURE ELECTRICAL RESISTIVITY OF MATERIAL FOR TTF COUPLERS M performance copper coating for the different parts of the power coupler (e.g. inner conductor, outer conductor The inner and outer conductors are made of 316L stainless steel with copper plating, while the antenna

Paris-Sud XI, Université de

254

Monitoring Cracking of a Smectitic Vertisol using Three-dimensional Electrical Resistivity Tomography  

E-print Network

for cracking due in part to a lack of reliable information on the development and morphology of cracks. Electrical resistivity tomography (ERT) has shown promise as a new, non-destructive method of monitoring cracking in the field. We investigated the use...

Ackerson, Jason Paul

2013-11-20

255

VARIATION OF THE ELECTRIC RESISTANCE OF PLANT TISSUES FOR ALTERNATING CURRENTS OF DIFFERENT FREQUENCIES DURING DEATH  

Microsoft Academic Search

The study of the electric resistance of riving ceils, in relation to variation of frequency of alternating current, developed during the last 20 years by HtJber (1910), Gildemeister (1919), Phirippson (1920), Waterman (1922), Fricke (1923), McClendon (1924), Fricke and Morse (1925), Brinks (1928), and Remington (1929), has been used chiefly in determining physical characteristics of various tissues such as muscle,

BASILE J. LUYET

1932-01-01

256

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

257

Characterization and monitoring of subsurface processes using parallel computing and electrical resistivity imaging  

SciTech Connect

This newsletter discusses recent advancement in subsurface resistivity characterization and monitoring capabilities. The BC Cribs field desiccation treatability test resistivity monitoring data is use an example to demonstrate near-real time 3D subsurface imaging capabilities. Electrical resistivity tomography (ERT) is a method of imaging the electrical resistivity distribution of the subsurface. An ERT data collection system consists of an array of electrodes, deployed on the ground surface or within boreholes, that are connected to a control unit which can access each electrode independently (Figure 1). A single measurement is collected by injecting current across a pair of current injection electrodes (source and sink), and measuring the resulting potential generated across a pair of potential measurement electrodes (positive and negative). An ERT data set is generated by collecting many such measurements using strategically selected current and potential electrode pairs. This data set is then processed using an inversion algorithm, which reconstructs an estimate (or image) of the electrical conductivity (i.e. the inverse of resistivity) distribution that gave rise to the measured data.

Johnson, Timothy C.; Truex, Michael J.; Wellman, Dawn M.; Marble, Justin

2011-12-01

258

3D Electrical Resistivity Imaging to Predict Slope Failure in USM Campus, Penang, Malaysia  

NASA Astrophysics Data System (ADS)

3D electrical resistivity imaging was carried out to monitor slope failure in the USM campus. The natural disasters that occur suddenly such as landslides can cause loss of life, and money by damaging roads and cars. The prediction of a landslide before it occurs will reduce or stop these hazards. Geophysical techniques can be used to image slopes and monitor slope failure. The geophysical technique that was used in this study is electrical resistivity imaging. The results from the resistivity sections show that there are two different regions made up of granite, and sand zone. The results show that there are two factors which make the landslide possible. The first factor is the subsurface boulders and the other factor is saturated sand which may results subsidence of the surface.

Moussa, Hussein A.; Nawawi, Mohd M. N.; Abdullah, Khiruddin

2010-07-01

259

An automated, externally heated opposed anvil high pressure-high temperature system for electrical resistivity studies  

NASA Astrophysics Data System (ADS)

A simple, externally heated opposed (Bridgman) anvil system has been developed for electrical resistivity measurements up to 8 GPa pressure and 400 °C. The whole system is automated, in which the application and measurement of pressure and heating of the sample are undertaken using an IBM PC and associated electronic and mechanical hardware. The system developed has a pressure control of about ±1% and temperature control better than ±2%. The setup has been calibrated using the high pressure-high temperature transitions in the electrical resistivity of Bi and Yb. The usefulness of the system developed has been demonstrated, by studying the resistivity behavior of glassy chalcogenide semiconductors at high pressure and high temperature.

Mondal, T. K.; Murugavel, S.; Asokan, S.

1999-01-01

260

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

261

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

262

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

263

Subsurface electrical resistivity structure around the Noubi fault system, central Japan, by MT survey  

NASA Astrophysics Data System (ADS)

Subsurface electrical resistivity around active faults is an important property to investigate the position and the geometry of the faults, the scale of the fracture zones related to the fault activity, and the amount of water and/or clay minerals in fault zones. We performed MT (magnetotelluric) surveys with remote reference method across the Noubi active fault system, central Japan, in order to image the electrical resistivity structure in and around the faults, and to obtain fundamental information on the earthquake generation mechanism. The Noubi fault system, about 80 km long, activated at 1891 Noubi Earthquake, consisting of the Nukumi, the Neodani, and the Umehara faults, which slipped left laterally by 1 - 7 m at the 1891 earthquake. Seismological and geomorphologic studies revealed different features between these three faults; the amount of lateral slip of the Neodani fault was larger than those of the Nukumi and the Umehara fault at 1891 Noubi earthquake (Matsuda, 1974; Mikumo and Ando, 1976); the average recurrence intervals of activation of the Nukumi and the Neodani fault were shorter than that of the Umehara fault (The Headquarters for Earthquake Research Promotion, 2005). Survey areas are mainly covered by the Mino sedimentary complex formed in the Jurassic - Cretaceous period that consists of mudstone, sandstone, limestone, basalt, chart, and siliceous mudstone. But the Hida belt that consists of metamorphic and granitic rocks covers northeast area of the Nukumi fault. Three survey lines of about 20 km length were set crossing normal to the surface fault traces of the Nukumi, Neodani and Umehara faults. And 10 - 12 MT measurement sites were arranged with the same interval on the survey lines. We measured two components of electric field and three components of magnetic field by a 'MTU-5' system made by Phoenix Geophysics Ltd. at three different sampling frequencies to cover frequency bands of 0.0003 - 317 Hz of electric and magnetic field. Applying two-dimensional inversion technique assuming that the electrical resistivity is homogeneous along the fault, cross-sections of electrical resistivity structure were imaged in the areas of about 20km wide area and 20 km deep for the Nukumi, the Neodani and the Umehara faults. The two dimensional images showed that the low resistivity (< 50 ohm m) region of about several km^2 are recognized below the faults down to the lower crust. In the areas beside the low resistivity regions, the resistivity's are middle (several hundreds ohm m) and high (> 1000 ohm m) and are consistent to the distribution of middle resistivity rocks, such as mud stone, and high resistivity rocks, such as limestone, basalt and metamorphic rocks, respectively. The low resistivity regions below the faults suggest the existence of fluid flowing through the fault zones from the lower crust. But, the widths and values of resistivity in the low resistivity regions are significantly different among the three faults. For instance, the low resistivity region below the Umehara fault is wider than that below the Neodani fault. The different features among the low resistivity regions of the three faults may be related to differences of the long-term fault activities.

Omura, K.; Matsuda, T.; Yamada, R.

2009-12-01

264

The effect of plasticizing agent on strain-induced change of electric resistivity of carbon–polyisoprene nano-composites  

Microsoft Academic Search

The effect of a plasticizer on the change of the electrical resistance under deformation at stretch is studied in polyisoprene (PI) composites containing dispersed conducting nano-size carbon particles at concentrations in the vicinity of percolation threshold. A change of the electrical resistance by more than four orders of magnitude has been earlier observed at 40% stretch of the composite containing

M. Knite; V. Teteris; A. Kiploka

2003-01-01

265

Time-lapse Inversion of Electrical Resistivity Data  

NASA Astrophysics Data System (ADS)

Time-lapse geophysical measurements (also known as monitoring, repeat or multi-frame survey) now play a critical role for monitoring -non-destructively- changes induced by human, as reservoir compaction, or to study natural processes, as flow and transport in porous media. To invert such data sets into time-varying subsurface properties, several strategies are found in different engineering or scientific fields (e.g., in biomedical, process tomography, or geophysical applications). Indeed, for time-lapse surveys, the data sets and the models at each time frame have the particularity to be closely related to their "neighbors", if the process does not induce chaotic or very high variations. Therefore, the information contained in the different frames can be used for constraining the inversion in the others. A first strategy consists in imposing constraints to the model based on prior estimation, a priori spatiotemporal or temporal behavior (arbitrary or based on a law describing the monitored process), restriction of changes in certain areas, or data changes reproducibility. A second strategy aims to invert directly the model changes, where the objective function penalizes those models whose spatial, temporal, or spatiotemporal behavior differs from a prior assumption or from a computed a priori. Clearly, the incorporation of time-lapse a priori information, determined from data sets or assumed, in the inversion process has been proven to improve significantly the resolving capability, mainly by removing artifacts. However, there is a lack of comparison of these methods. In this paper, we focus on Tikhonov-like inversion approaches for electrical tomography imaging to evaluate the capability of the different existing strategies, and to propose new ones. To evaluate the bias inevitably introduced by time-lapse regularization, we quantified the relative contribution of the different approaches to the resolving power of the method. Furthermore, we incorporated different noise levels and types (random and/or systematic) to determine the strategies' ability to cope with real data. Introducing additional regularization terms yields also more regularization parameters to compute. Since this is a difficult and computationally costly task, we propose that it should be proportional to the velocity of the process. To achieve these objectives, we tested the different methods using synthetic models, and experimental data, taking noise and error propagation into account. Our study shows that the choice of the inversion strategy highly depends on the nature and magnitude of noise, whereas the choice of the regularization term strongly influences the resulting image according to the a priori assumption. This study was developed under the scope of the European project ALERT (GOCE-CT-2004-505329).

Nguyen, F.; Kemna, A.

2005-12-01

266

Some considerations on electrical resistivity imaging for characterization of waterbed sediments  

NASA Astrophysics Data System (ADS)

The paper focuses on defining the performance and limits of ERI in the detection and sedimentary characterization of near-bottom thin layers. The analysis of the resolution of floating and submerged cables, and the effect of the accuracy of a priori information (resistivity and thickness) in the data inversion, is based on theory, models and actual data. Theoretical models show that the actual reconstruction of the near water-bottom sediments, in terms of geometry and resistivity, can be obtained only with the submerged cable, however, the data, unlike that acquired with the floating cable, require a priori information on water resistivity and thickness for the data inversion. Theoretical forward models based on wrong a priori water thickness and resistivity information influence the inverted model in different ways, depending on the under- and over-estimation of water resistivity and thickness, and the resistivity contrast of the water-solid layer; however a water-solid resistivity contrast of less than 2 and within 10% of error in water resistivity has no effect. Overestimating water resistivity depicts a ground similar to the actual ground in terms of resistivity, more so than the underestimation of water resistivity. Moreover, the data inversion is less influenced by water parameter error in the case of low resistivity contrast in the water-solid layer, than it is for high resistivity contrast. Wenner and Schlumberger arrays give comparable results, while a dipole-dipole array seems to be more sensitive to the accuracy of apparent resistivity measurements and a priori information on water. The theoretical considerations were validated by actual data acquired with a submerged cable on the Tiber River. The study has shown that if highly accurate measurements are made of water thickness and resistivity, then electrical resistivity imaging from the submerged cable can be used in addition to, or even to substitute, seismic data for the reconstruction of the features and sedimentary characterization of near-bed sediments where seismic data fail to give a suitable resolution.

Orlando, Luciana

2013-08-01

267

Local Resistance Profiling of Ultra Shallow Junction Annealed with Combination of Spike Lamp and Laser Annealing Processes using Scanning Spreading Resistance Microscope  

NASA Astrophysics Data System (ADS)

Local resistance profiles of ultra shallow boron and arsenic implanted into silicon with energies of 2.0 and 4.0 keV and doses of 2.0×1015 and 1.0×1015 ions/cm2 activated by a combination of conventional spike lamp and laser annealing processes were measured by scanning spreading resistance microscope (SSRM) with a depth resolution of less than 10 nm. The lowest local resistance at the low resistance region in 2.0 keV boron implanted silicon with 1050 °C spike lamp annealing followed by 0.35 kW/mm2 laser annealing was half of that without laser annealing. The lowest local resistance at the low resistance region in the arsenic implanted silicon activated by 1050 °C spike lamp annealing followed by 0.39 kW/mm2 laser annealing was 74% lower than that followed by 0.36 kW/mm2 laser annealing. The lowest local resistances at the low resistance regions in the arsenic implanted silicon with 0.36 and 0.39 kW/mm2 laser annealing followed by 1050 °C spike lamp annealing were 41 and 33% lower than those with spike lamp annealing followed by laser annealing. Laser annealing followed by spike lamp annealing could suppress the diffusion of the impurities and was suitable for making the ultra shallow and low resistance regions.

Abo, Satoshi; Nishikawa, Kazuhisa; Ushigome, Naoya; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio

2011-01-01

268

Nearly Constant Electrical Resistance over Large Temperature Range in Cu3NMx (M = Cu, Ag, Au) Compounds  

NASA Astrophysics Data System (ADS)

Electrical resistance is a material property that usually varies enormously with temperature. Constant electrical resistivity over large temperature range has been rarely measured in a single solid. Here we report the growth of Cu3NMx (M = Cu, Ag, Au) compound films by magnetron sputtering, aiming at obtaining single solids of nearly constant electrical resistance in some temperature ranges. The increasing interstitial doping of cubic Cu3N lattice by extra metal atoms induces the semiconductor-to-metal transition in all the three systems. Nearly constant electrical resistance over 200 K, from room temperature downward, was measured in some semimetallic Cu3NMx samples, resulting from opposite temperature dependence of carrier density and carrier mobility, as revealed by Hall measurement. Cu3NAgx samples have the best performance with regard to the range of both temperature and doping level wherein a nearly constant electrical resistance can be realized. This work can inspire the search of other materials of such a quality.

Lu, Nianpeng; Ji, Ailing; Cao, Zexian

2013-10-01

269

Electric charging of dust particles: Impact on the variations of electric field and electric resistivity of air  

NASA Astrophysics Data System (ADS)

Abstract. Short Dipole Antenna is proposed in the frame of the Dust Package onboard the ROSCOSMOS- ESA ExoMars Lander. The SDA is developed to measure the electric field from few ?V m-1 to few tens kV m-1 in the frequency range form DC to few kHz. The SDA concept and the model of its electric coupling with the air were tested and justified in the Nevada desert, in the conditions of dust devils generation. We illustrate our presentation with few examples of earth's observations, present simple models that explain the measured electric field and its correlation with the electric charge of the dust/sand particles, their density and motion. Comparative analysis between Earth and Mars cases is discussed.

Seran, Elena; Zakharov, Alexander; Godefroy, Michel; Dolnikov, Gennady

270

Time to virologic failure for patients taking their first antiretroviral regimen and the subsequent resistance profiles  

PubMed Central

Introduction The resistance profiles of first-line antiretroviral therapy (ART) regimens after virologic failure have yet to be studied in a clinic setting in the modern treatment era. Time to virologic failure among three standard first-line regimens and the resistance profiles of these failures were compared. Materials and Methods All HIV-positive persons aged 16 and over starting a three-drug first-line ART regimen were retrospectively identified at a Toronto community clinic (1 January 2006–1 January 2013). The regimens included a backbone of two NRTIs and a third agent; a PI, an NNRTI, or an II. Patients must have been on treatment for at least 14 days and have at least one VL test within 6 months after starting treatment. The primary outcome was virologic failure defined as either: no suppression by 6 months, or after suppression, two consecutive, detectable VL200 copies/mL at least 14 days apart or one VL>200 copies/mL. Time to failure was compared using a proportional hazards model adjusting for demographic and clinical factors. Resistance profiles of NRTIs and third agents are described in patients with virologic failure who had both baseline and virologic failure genotypes. Results Six hundred sixty patients (93% male) were included with a mean age of 38.9 and a median follow-up period of 35.3 (32.2–39.3) months. Distribution of third agent use was: PI 37.3% (n=246), NNRTI 55.9% (n=369) and II 6.8% (n=45). Virologic failures occurred in 81/246 (33%) with PI, 87/369 (24%) with NNRTI and 11/45 (24%) with II. Compare to PIs, time to failure was longer with NNRTIs (p=0.0013) and similar for IIs (p=0.1562). No evidence that failure with NNRTIs was different from IIs (p=0.9139). Of the 660 patients, 567 (86%) had a baseline genotype. Of the 567 patients, 179 had virological failure. Of the 179, 145(81%) had a baseline genotype and only 37 (21%) had both a baseline and follow-up genotype. Upon failure, emerging ART resistance was rare. No new PI or II mutations were identified and one new NNRTI (Y181C) mutation was identified. Three patients taking PI-based regimens developed NRTI mutations (M184V, M184I, T215Y). Conclusions Time to virologic failure was significantly greater in the NNRTI group compared to the PI group. If failure did occur, ART resistance rarely developed with no PI mutations but a few NRTI mutations in those taking PI-based regimens, and NNRTI mutations in those taking NNRTI-based regimen. PMID:25397502

Crouzat, Frederic; Benoit, Anita; Kovacs, Colin; Smith, Graham; Taback, Nathan; Sandler, Ina; Brunetta, Jason; Chang, Benny; Merkley, Barry; Tilley, David; Fletcher, David; Kalaria, Dipen; Loutfy, Mona

2014-01-01

271

Monitoring six-phase ohmic heating of contaminated soils using electrical resistance tomography  

SciTech Connect

Electrical resistance tomography (ERT) was used to monitor six-phase ohmic heating used for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. The changes in electrical conductivity caused by six-phase ohmic-heating in a clay layer located in the vadose zone were monitored during a period of approximately 2 months, before, during and after heating. From an array of electrodes located in 4 boreholes, we collected electrical resistivity data between five pairs of adjacent holes pairs. This data was used to calculate tomographs which showed the electrical conductivity changes along five vertical planes. The difference tomographs show the combined effects of moisture redistribution and heating caused by six-phase heating and vapor extraction. The tomographs show that most of the clay layer increased in electrical conductivity during the first 3 weeks of the 4 week long heating phase. At this time, the electrical conductivities near the center of the heating array were twice as large as the pre-heat conductivities. Then the electrical conductivity started to decrease for portions of the clay layer closest to the vapor extraction well. We propose that the conductivity decreases are due to the removal of moisture by the heating and vacuum extraction. Parts of the clay layer near the extraction well reached electrical conductivities as low as 40% of the pre-heating values. We propose that these regions of lower than ambient electrical conductivities are indicators of regions where the vapor removal by vacuum extraction was most effective. At the end of the heating phase, our estimates suggest that the clay saturation may have dropped to as low as 10% based on the observed conductivity changes.

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

1994-09-01

272

Investigating preferential flow processes in soils using anisotropy in electrical resistivity  

NASA Astrophysics Data System (ADS)

Macropores occupy a small volume fraction of the pore space in the vadose zone. Water and solutes can quickly bypass the vadose zone through these macropores in a process known as macropore preferential flow. In the last few decades, many efforts were made to improve understanding the macropore preferential flow processes because of their importance in transporting agrochemicals and contaminants to the groundwater. Unfortunately, very few measurement methods provide insights into these preferential flow processes. In this context, the objective of this study is to evaluate whether anisotropy in electrical resistivity can be used to identify the existence of flow in macropores and perhaps even to characterize the exchange between macropores and bulk soil. In a first step, infiltration into a soil column with an artificial macropore was simulated using the HYDRUS software package that solves the pseudo three-dimensional axisymmetric Richards equation. The simulated temporal development of the resistivity anisotropy was obtained by solving the Poisson equation in MATLAB after converting the simulated water content distributions to electrical resistivity distributions. At the beginning of the simulation, a small anisotropy ratio was simulated because of the presence of the empty ('deactivated') macropore in the moist matrix. As soon as the infiltration process started, macropore flow occurred and both the horizontal and vertical resistivity decreased strongly. However, the vertical and horizontal resistivity reacted differently because of the presence of the conductive ('activated') macropore, which led to anisotropy in the resistivity. As soon as infiltration into the macropore stopped, water re-distributed from the macropore to the matrix domain and contrasts in electrical resistivity decreased within the column. To verify the simulation results in the laboratory, we measured the temporal dynamics of the anisotropy in resistivity during water infiltration into a soil column of 9 cm diameter and 40 cm length with an artificial macropore of 2 cm diameter in the center of the column. The first experimental results confirmed that the anisotropy in electrical resistivity can indeed be used to identify and perhaps even quantify macropore flow.

Al-Hazaimay, S.; Huisman, J. A.; Zimmermann, E.; Kemna, A.; Vereecken, H.

2012-12-01

273

Electric-Pulse Induced Resistive (EPIR) Switch Effect of Manganite Films for Non-volatile Memory Applications  

Microsoft Academic Search

A novel electrical pulse induced resistance (EPIR) change effect found in thin films of perovskite oxide materials, such as Pr_1-xCa_xMnO_3, has generated a new kind of nonvolatile memory, which exhibits large reproducible resistance changes in a wide temperature range, and providing the possibility to built an electrically operated, directly rewritable, fast switching, low power consumption, and multileveled high density resistive

Yibo Nian; Yanqi Wang; Papagianni Christina; Xin Chen; Wu Naijuan; Jiarui Liu; Alex Ignatiev

2004-01-01

274

Laboratory measurements of electrical resistivity versus water content on small soil cores  

NASA Astrophysics Data System (ADS)

The assessment of soil water content variations more and more leans on geophysical methods that are non invasive and that allow a high spatial sampling. Among the different methods, DC electrical imaging is moving forward. DC Electrical resistivity shows indeed strong seasonal variations that principally depend on soil water content variations. Nevertheless, the widely used Archie's empirical law [1], that links resistivity with voids saturation and water conductivity is not well suited to soil materials with high clay content. Furthermore, the shrinking and swelling properties of soil materials have to be considered. Hence, it is relevant to develop new laboratory experiments in order to establish a relation between electrical resistivity and water content taking into account the rheological and granulometrical specificities of soil materials. The experimental device developed in IRD laboratory allows to monitor simultaneously (i) the water content, (ii) the electrical resistivity and (iii) the volume of a small cylindrical soil core (100cm3) put in a temperature controlled incubator (30°C). It provides both the shrinkage curve of the soil core (voids volume versus water content) and the electrical resistivity versus water content curve The modelisation of the shrinkage curve gives for each moisture state the water respectively contained in macro and micro voids [2], and then allows to propose a generalized Archie's like law as following : 1/Rs = 1/Fma.Rma + 1/Fmi.Rmi and Fi = Ai/(Vi^Mi.Si^Ni) with Rs : the soil resistivity. Fma and Fmi : the so called "formation factor" for macro and micro voids, respectively. Rma and Rmi : the resistivity of the water contained in macro and micro voids, respectively. Vi : the volume of macro and micro voids, respectively. Si : the saturation of macro and micro voids, respectively. Ai, Mi and Ni : adjustment coefficients. The variations of Rmi are calculated, assuming that Rma is a constant. Indeed, the rise of ionic concentration in water may be neglected during the sewage of macro voids as it corresponds to a small quantity of water for the studied samples. Soil solid components are generally electrical insulators, the conduction of electrical current only lies on two phenomenon occurring in water : (i) volume conduction controlled by the electrolyte concentration in water and the geometrical characteristics of macro voids network ; (ii) surface conduction controlled by the double diffuse layer that depends on the solid-liquid interactions, the specific surface of clay minerals and the geometry of particles contacts. For the water contained in macro voids the preeminent phenomenon seems to be volume conduction while for the water contained in micro voids, it seems to be surface conduction. This hypothesis satisfyingly explains the shape of the electrical resistivity versus water content curves obtained for three different oxisols with clayey, clayey-sandy and sandy-clayey texture. [1] Archie G.E. 1942. The electrical resistivity log as an aid in determining some reservoirs characteristics. Trans. AIME, 146, 54-67. [2] Braudeau E. et al. 1999. New device and method for soil shrinkage curve measurement and characterization. S.S.S.A.J., 63(3), 525-535.

Robain, H.; Camerlynck, C.; Bellier, G.; Tabbagh, A.

2003-04-01

275

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

276

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; Eholie, Serge; Anglaret, Xavier; Bertine, Melanie; Rouzioux, Christine; Avettand-Fenoel, Veronique; Messou, Eugene; Minga, Albert; Damond, Florence; Plantier, Jean-Christophe; Dabis, Francois; Peytavin, Gilles; Brun-Vezinet, Francoise; Ekouevi, Didier K.

2014-01-01

277

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.

Atas, Mustafa; Baskan, Burhan; Ozkose, Ayse; Mutlu Sar?guzel, Fatma; Demircan, Suleyman; Pangal, Emine

2014-01-01

278

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

279

Multifractal analysis of vertical profiles of soil penetration resistance at the field scale  

NASA Astrophysics Data System (ADS)

Soil penetration resistance (PR) is widely used as an indirect indicator of soil strength. Soil PR is linked to basic soil properties and correlated to root growth and plant production, and as such it is extensively used as a practical tool for assessing soil compaction and to evaluate the effects of soil management. This study investigates how results from multifractal analysis can quantify key elements of depth-dependent soil PR profiles and how this information can be used at the field scale. We analysed multifractality of 50 PR vertical profiles, measured from 0 to 60 cm depth and randomly located on a 6.5 ha sugar cane field in northeastern Brazil. The scaling property of each profile was typified by singularity, and Rényi spectra estimated by the method of moments. The Hurst exponent was used to parameterize the autocorrelation of the vertical PR data sets. The singularity and Rènyi spectra showed that the vertical PR data sets exhibited a well-defined multifractal structure. Hurst exponent values were close to 1, ranging from 0.944 to 0.988, indicating strong persistence in PR variation with soil depth. Also, the Hurst exponent was negatively and significantly correlated to coefficient of variation (CV), skewness and maximum values of the depth-dependent PR. Multifractal analysis added valuable information to describe the spatial arrangement of depth-dependent penetrometer data sets, which was not taken into account by classical statistical indices. Multifractal parameters were mapped over the experimental field and compared with mean and maximum values of PR. Combination of spatial variability survey and multifractal analysis appear to be useful to manage soil compaction.

Siqueira, G. M.; Silva, E. F. F.; Montenegro, A. A. A.; Vidal Vázquez, E.; Paz-Ferreiro, J.

2013-07-01

280

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; Nunez, Martha; Shaibi, Gabriel Q.; Mandarino, Lawrence J.; Coletta, Dawn K.

2013-01-01

281

Electrical Resistivity Imaging for Investigating Slope Stability, Fort St. John, British Columbia  

NASA Astrophysics Data System (ADS)

The Peace River District of northeastern British Columbia is characterized by steep river valleys that have been incised up to 300 m deep in poorly consolidated Cretaceous and Quaternary sediments. Since the area is a major producer of oil and gas, numerous pipelines and roads transect these valleys. Slope stability has been a major problem at several locations and will continue to pose a problem for future development in the area. Understanding the mechanisms of slope stability will allow better assessment of the risks to infrastructure. The Geological Survey of Canada is conducting studies to determine the role that groundwater infiltration and flow have in controlling slope movements. Near-surface geophysical surveys provide a quick non-invasive method of investigating ground conditions. Since moisture content of the underlying strata plays an important role in slope stability, electrical methods are particularly suitable. For this study, two-dimensional electrical resistivity imaging was conducted along three pipeline route slopes in the Fort St. John area during July 2002. An automated electrical resistivity imaging system was used to acquire continuous Wenner array images up to 1300 m in length. The system used 48 electrodes spaced 5 m apart, to obtain a high-resolution image of the sub-surface with an exploration depth of approximately 40 m. Two-dimensional inversion software was used to obtain topography-corrected electrical resistivity models for each slope. Borehole information was incorporated in the interpretation of the results. Electrical resistivity imaging proved to be a fast and effective method for investigating the extremely steep slopes encountered in the Fort St. John area. The results indicate that the method is very useful in identifying seepage zones and extending hydrostratigraphy from borehole observations. These studies will assist modeling of groundwater flow by confirming areas of predicted groundwater discharge and by delineating areas where moisture content changes are taking place.

Calvert, H. T.; Dyke, L. D.; Sladen, W. E.; Raymond, E. L.

2004-05-01

282

Monitoring of olive oil mills' wastes using electrical resistivity tomography techniques  

NASA Astrophysics Data System (ADS)

Olive oil mills' wastes (OOMW) are one of the byproducts of the oil production that can lead to serious environmental pollution when they are deposited in ponds dug on the ground surface. Electrical Resistivity Tomography (ERT) method can provide a valuable tool in order to monitor through time the physical flow of the wastes into the subsurface. ERT could potentially locate the electrical signature due to lower resistivity values resulting from the leakage of OOMW to the subsurface. For this purpose, two vertical boreholes were installed (12m depth, 9 m apart) in the vicinity of an existing pond which is filled with OOMW during the oil production period. The test site is situated in Saint Andreas village about 15km south of the city of Rethymno (Crete, Greece). Surface ERT measurements were collected along multiple lines in order to reconstruct the subsurface resistivity models. Data acquisition was performed with standard and optimized electrode configuration protocols. The monitoring survey includes the ERT data collection for a period of time. The study was initiated before the OOMW were deposited in the pond, so resistivity fluctuations are expected due to the flow of OOMW in the porous subsurface media through time. Preliminary results show the good correlation of the ERT images with the drilled geological formations and the identification of low resistivity subsurface zone that could be attributed to the flow of the wastes within the porous layers.

Simyrdanis, Kleanthis; Papadopoulos, Nikos; Kirkou, Stella; Sarris, Apostolos; Tsourlos, Panagiotis

2014-08-01

283

Laser-induced change of electrical resistivity of metals and its applications  

NASA Astrophysics Data System (ADS)

Applying of laser alloying for modification of electrical resistivity of metals with significant importance in electrical and electronic engineering and utilization of this method for producing passive elements of electric circuit have been presented. The alloyed metals were obtained by means of laser beams with different wave length and various mode of working (cw or pulse), by different methods for the supplying of alloying elements. It was possible to form alloyed layers of metals forming different types of metallurgical systems: with full (Cu-Au, Cu-Ni) or partial solubility (Mo-Ni, W-Ni, Cu-Al, Ag-Sn), insoluble (Mo-Au and Cu-Cr) and immiscible (Ag-Ni and Ni-Au) metals, with metallic as well as non-metallic additions (oxide). It has been shown as well that it is possible to achieve resistive elements modified in whole cross section, in a single technological process. The results of systematic investigations into the resistivity of alloyed metals in the temperature range of 77-450 K have been presented. The alloyed layers, obtained, were characterised by a range of resistivity from 2.8 x 10-8 ?m (Cu-Cr) to 128 x 10-8 ?m (W-Ni). The microstructure and composition of alloyed layers were examined by means of SEM-microscopy and EDX analyser. In selected cases it was shown how results of investigations could be utilized for modification of surface layer of contact materials or to optimize the resistance of laser welded joints. In addition the results of investigations of new developed microtechnology -- producing micro-areas with extremely high resistivity -- have been presented.

Pawlak, Ryszard; Kostrubiec, Franciszek; Tomczyk, Mariusz; Walczak, Maria

2005-01-01

284

ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY  

SciTech Connect

Highly industrialized areas pose challenges for surface electrical resistivity characterization due to metallic infrastructure. The infrastructure is typically more conductive than the desired targets and will mask the deeper subsurface information. These challenges may be minimized if steel-cased wells are used as long electrodes in the area near the target. We demonstrate a method of using long electrodes to electrically monitor a simulated leak from an underground storage tank with both synthetic examples and a field demonstration. The synthetic examples place a simple target of varying electrical properties beneath a very low resistivity layer. The layer is meant to replicate the effects of infrastructure. Both surface and long electrodes are tested on the synthetic domain. The leak demonstration for the field experiment is simulated by injecting a high conductivity fluid in a perforated well within the S tank farm at Hanford, and the resistivity measurements are made before and after the leak test. All data are processed in four dimensions, where a regularization procedure is applied in both the time and space domains. The synthetic test case shows that the long electrode ERM could detect relative changes in resistivity that are commensurate with the differing target properties. The surface electrodes, on the other hand, had a more difficult time matching the original target's footprint. The field results shows a lowered resistivity feature develop south of the injection site after cessation of the injections. The time lapsed regularization parameter has a strong influence on the differences in inverted resistivity between the pre and post injection datasets, but the interpretation of the target is consistent across all values of the parameter. The long electrode ERM method may provide a tool for near real-time monitoring of leaking underground storage tanks.

MYERS DA; RUCKER DF; FINK JB; LOKE MH

2009-12-16

285

Magnetic Field Effect on the In-plane Electrical Resistivity of FeTe1-xSex Single Crystals  

NASA Astrophysics Data System (ADS)

The in-plane electrical resistivity (?ab) of FeTe1- xSex single crystals is measured as a function of temperature (T), magnetic field (H), and the angle (?) between H and electric current (I). The results reveal that ?ab strongly depends on both H and ?, indicating the participation of spin scattering in the electrical transport. The underlying physics will be discussed.

Xiong, Yimin; Karki, Amar; Sales, Brian; Jin, Rongying

2011-03-01

286

Changes in gene expression profile in two multidrug resistant cell lines derived from a same drug sensitive cell line.  

PubMed

Resistance to chemotherapy is one of the most relevant aspects of treatment failure in cancer. Cell lines are used as models to study resistance. We analyzed the transcriptional profile of two multidrug resistant (MDR) cell lines (Lucena 1 and FEPS) derived from the same drug-sensitive cell K562. Microarray data identified 130 differentially expressed genes (DEG) between K562 vs. Lucena 1, 1932 between K562 vs. FEPS, and 1211 between Lucena 1 versus FEPS. The NOTCH pathway was affected in FEPS with overexpression of NOTCH2 and HEY1. The highly overexpressed gene in MDR cell lines was ABCB1, and both presented the ABCB1 promoter unmethylated. PMID:24996974

Moreira, Miguel Angelo Martins; Bagni, Carolina; de Pinho, Marcos Barcelos; Mac-Cormick, Thaís Messias; dos Santos Mota, Mateus; Pinto-Silva, Flávio Eduardo; Daflon-Yunes, Nathalia; Rumjanek, Vivian Mary

2014-08-01

287

In Vitro Efficacies and Resistance Profiles of Rifampin-Based Combination Regimens for Biofilm-Embedded Methicillin-Resistant Staphylococcus aureus  

PubMed Central

To compare the in vitro antibacterial efficacies and resistance profiles of rifampin-based combinations against methicillin-resistant Staphylococcus aureus (MRSA) in a biofilm model, the antibacterial activities of vancomycin, teicoplanin, daptomycin, minocycline, linezolid, fusidic acid, fosfomycin, and tigecycline alone or in combination with rifampin against biofilm-embedded MRSA were measured. The rifampin-resistant mutation frequencies were evaluated. Of the rifampin-based combinations, rifampin enhances the antibacterial activities of and even synergizes with fusidic acid, tigecycline, and, to a lesser extent, linezolid, fosfomycin, and minocycline against biofilm-embedded MRSA. Such combinations with weaker rifampin resistance induction activities may provide a therapeutic advantage in MRSA biofilm-related infections. PMID:23959320

Tang, Hung-Jen; Chen, Chi-Chung; Cheng, Kuo-Chen; Wu, Kuan-Ying; Lin, Yi-Chung; Zhang, Chun-Cheng; Weng, Tzu-Chieh; Yu, Wen-Liang; Chiu, Yu-Hsin; Toh, Han-Siong; Chiang, Shyh-Ren; Su, Bo An

2013-01-01

288

Petrologically-based Electrical Profiles vs. Geophysical Observations through the Upper Mantle (Invited)  

NASA Astrophysics Data System (ADS)

Mineralogical transformations in the up-welling mantle play a critical role on the dynamics of mass and heat transfers at mid-ocean-ridgeS. The melting event producing ridge basalts occur at 60 km depth below the ridge axis, but because of small amounts of H2O and CO2 in the source region of MOR-basalts, incipient melting can initiate at much greater depth. Such incipient melts concentrate incompatible elements, and are particularly rich in volatile species. These juices evolve from carbonatites, carbonated basalts, to CO2-H2O-rich basalts as recently exposed by petrological surveys; the passage from carbonate to silicate melts is a complex pathway that is strongly non-linear. This picture has recently been complicated further by studies showing that oxygen increasingly partitions into garnet as pressure increases; this implies that incipient melting may be prevented at depth exceeding 200 km because not enough oxygen is available in the system to stabilize carbonate melts. The aim of this work is twofold: - We modelled the complex pathway of mantle melting in presence of C-O-H volatiles by adjusting the thermodynamic properties of mixing in the multi-component C-O-H-melt system. This allows us to calculate the change in melt composition vs. depth following any sortS of adiabat. - We modelled the continuous change in electrical properties from carbonatites, carbonated basalts, to CO2-H2O-rich basalts. We then successfully converted this petrological evolution along a ridge adiabat into electrical conductivity vs. depth signal. The discussion that follows is about comparison of this petrologically-based conductivity profile with the recent profiles obtained by inversion of the long-period electromagnetic signals from the East-Pacific-Rise. These geophysically-based profiles reveal the electrical conductivity structure down to 400 km depth and they show some intriguing highly conductive sections. We will discuss heterogeneity in electrical conductivity of the upper mantle underneath the ridge in terms of melting processes. Our prime conclusion is that the redox melting process, universally predicted by petrological models, might not be universal and that incipient melting can extend down to the transition zone.

Gaillard, F.; Massuyeau, M.; Sifre, D.; Tarits, P.

2013-12-01

289

Electric potential profile of a spherical soft particle with a charged core  

E-print Network

The electrostatic potential profile of a spherical soft particle is derived by solving the Poisson-Boltzmann equations on a spherical system both numerically and analytically. The soft particle is assumed to consist of an ion-permeable charged outer layer and a non-permeable charged core with constant charged density. The contribution of the core to the potential profile is calculated for different charges and dielectric constants. Our results show that the charged core heavily influences the local potential within the soft particle. In contrast, the potential distribution outside the particle in the salt solution is found to be weakly dependent on the core features. These findings are consistent with previous experiments showing the minor impact of the core of the MS2 virus on its overall electrical properties. Our studies also indicate that while a change in temperature from 290 K to 310 K only slightly varies the potential, the ionic strength in the range of 1-600 mM has a significant effect on the potential profile. Our studies would provide good understanding for experimental research in the field of biophysics and nanomedicine.

Anh D. Phan; Dustin A. Tracy; T. L. Hoai Nguyen; N. A. Viet; The-Long Phan; Thanh H. Nguyen

2013-12-05

290

Integral equation analysis of an arbitrary-profile and varying-resistivity cylindrical reflector illuminated by an E-polarized complex-source-point beam.  

PubMed

A two-dimensional reflector with resistive-type boundary conditions and varying resistivity is considered. The incident wave is a beam emitted by a complex-source-point feed simulating an aperture source. The problem is formulated as an electromagnetic time-harmonic boundary value problem and cast into the electric field integral equation form. This is a Fredholm second kind equation that can be solved numerically in several ways. We develop a Galerkin projection scheme with entire-domain expansion functions defined on an auxiliary circle and demonstrate its advantage over a conventional moment-method solution in terms of faster convergence. Hence, larger reflectors can be computed with a higher accuracy. The results presented relate to the elliptic, parabolic, and hyperbolic profile reflectors fed by in-focus feeds. They demonstrate that a partially or fully resistive parabolic reflector is able to form a sharp main beam of the far-field pattern in the forward half-space; however, partial transparency leads to a drop in the overall directivity of emission due to the leakage of the field to the shadow half-space. This can be avoided if only small parts of the reflector near the edges are made resistive, with resisitivity increasing to the edge. PMID:19568286

O?uzer, Taner; Altintas, Ayhan; Nosich, Alexander I

2009-07-01

291

Association of multiple-antibiotic-resistance profiles with point and nonpoint sources of Escherichia coli in Apalachicola Bay.  

PubMed Central

A total of 765 Escherichia coli isolates from point and nonpoint sources were collected from the Apalachicola National Estuarine Research Reserve, and their multiple-antibiotic-resistance (MAR) profiles were determined with 10 antibiotics. E. coli isolates from point sources showed significantly greater resistance (P < 0.05) to antibiotics and higher MAR indices than isolates from nonpoint sources. Specifically, 65 different resistance patterns were observed among point source isolates, compared to 32 among nonpoint source isolates. Examples of this contrast in MAR profiles included percentages of isolates with resistance to chlortetracycline-sulfathiazole of 33.7% and to chlortetracycline-penicillin G-sulfathiazole of 14.5% for point source isolates versus 15.4 and 1.7%, respectively, for nonpoint source isolates. MAR profile homology, based on coefficient similarity, showed that isolates from point sources were markedly more diverse than isolates from nonpoint sources. Seven clusters were observed among point source isolates, with a coefficient value of approximately 1.8. In contrast, only four clusters were observed among nonpoint source isolates. Covariance matrices of data displayed six very distinct foci representing nonpoint source E. coli isolates. Importantly, E. coli isolates obtained directly from human and animal feces also clustered among point and nonpoint sources, respectively. We conclude that E. coli MAR profiles were associated with point and nonpoint sources of pollution within Apalachicola Bay and that this method may be useful in facilitating management of other estuaries. PMID:9212410

Parveen, S; Murphree, R L; Edmiston, L; Kaspar, C W; Portier, K M; Tamplin, M L

1997-01-01

292

The underlayer effects on the electrical resistivity of Ag thin film  

Microsoft Academic Search

The effects of AZO (Aluminium-doped Zinc Oxide) undercoats on electrical resistivity of Ag thin films have been investigated. The characteristics of Ag films in 20 nm Ag \\/ 15 nm AZO \\/ glass stacks have been analyzed. In the layer stacks, the AZO films were deposited with various sputtering conditions, such as applied power (0.1–1.2 kW), gas pressure (0.3–5.0 Pa)

Yasutaka Tsuda; Hideo Omoto; Katsuto Tanaka; Hisashi Ohsaki

2006-01-01

293

Electrical resistivity variations associated with earthquakes on the san andreas fault.  

PubMed

A 24 percent precursory change in apparent electrical resistivity was observed before a magnitude 3.9 earthquake of strike-slip nature on the San Andreas fault in central California. The experimental configuration and numerical calculations suggest that the change is associated with a volume at depth rather than some near-surface phenomenon. The character and duration of the precursor period agree well with those of other earthquake studies and support a dilatant earthquake mechanism model. PMID:17833697

Mazzella, A; Morrison, H F

1974-09-01

294

Electrical Resistivity Variations Associated with Earthquakes on the San Andreas Fault  

Microsoft Academic Search

A 24 percent precursory change in apparent electrical resistivity was observed before a magnitude 3.9 earthquake of strike-slip nature on the San Andreas fault in central California. The experimental configuration and numerical calculations suggest that the change is associated with a volume at depth rather than some near-surface phenomenon. The character and duration of the precursor period agree well with

Aldo Mazzella; H. Frank Morrison

1974-01-01

295

FW2_5D: A MATLAB 2.5-D electrical resistivity modeling code  

Microsoft Academic Search

We present a 2.5-D forward modeling algorithm for electrical resistivity data. The algorithm incorporates a boundary condition and source singularity correction that greatly reduces the need to pad the model space. In addition, the algorithm includes an optimization method for estimating the appropriate Fourier coefficients to achieve an accurate 2.5-D approximation. The optimization scheme uses a gradient-based search to find

Adam Pidlisecky; Rosemary Knight

2008-01-01

296

Interface in mechanically fastened steel joint, studied by contact electrical resistance measurement  

NASA Astrophysics Data System (ADS)

A steel-to-steel joint obtained by mechanical fastening at a compressive stress of 7% (or less) of the yield strength was found to exhibit irreversible changes in the contact electrical resistance upon repeated fastening (loading) and unfastening (unloading). These changes occurred even after many cycles of fastening and unfastening, although the changes were more severe during the initial few cycles. They were primarily due to plastic deformation at asperities.

Luo, Xiangcheng; Chung, D. D. L.

2000-02-01

297

General theory of the electrical resistivity of the alkali metals at low temperatures  

Microsoft Academic Search

A complete analysis is presented for the temperature dependence of the electrical resistivity of the alkali metals at low temperatures. New results are found for the temperature dependence of the umklapp-scattering term. We find one expression appropriate to the low-temperature limit and a different expression appropriate to somewhat higher temperatures. These results are used to explain the reported T5 behavior

Moshe Kaveh; Nathan Wiser

1974-01-01

298

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

299

In situ electrical resistivity changes during bromine intercalation in carbon fibers  

Microsoft Academic Search

In situ reaction kinetics of bromine intercalation in carbon fibers have been followed by measuring changes in their electrical resistivity during an intercalation and de-intercalation cycle. The study suggests that for well-graphitized P-55 (HTT 3000 °C) and P-120 carbon fibers the reaction starts instantaneously and most of the charge transfer takes place within the first ten minutes with only 6%

R. B. Mathur; O. P. Bahl; A. Kannan; S. Flandrois; A. Marchand; V. Gupta

1996-01-01

300

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

301

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

302

High electrical resistance hot-pressed NdFeB magnet for low loss motors  

NASA Astrophysics Data System (ADS)

Fluoride-coated hot-pressed NdFeB magnets with electrical resistivity of 1.4m?cm, which is ten times larger than that of a noncoated sintered NdFeB magnet, were prepared using fluoride coating powders. The high resistive NdFeB magnets consist of coated powders and are sintered with a neodymium fluoride layer, which was grown using a fluoride solution. No degradation of coercivity was observed in the fluoride coated NdFeB powders. The increase in magnet temperature caused by an alternating magnetic field (Eddy currents) was eightfold with the use of a fluoride-treated magnet. Furthermore, the increase in temperature at the magnet's rotor was reduced by 50% when the high resistive hot-pressed magnet was substituted for the conventional commercial magnet.

Komuro, Matahiro; Satsu, Yuichi; Enomoto, Yuji; Koharagi, Haruo

2007-09-01

303

Electrical Resistivity Tomography Monitoring of Soil Remediation for a Garbage Dump  

NASA Astrophysics Data System (ADS)

Electrical resistivity tomography (ERT) survey was firstly used to investigate the distribution of contaminated soil in a garbage dump area, Wuhan city, China. The result shows that sulfated soil resistivity is about 4 to 7 ohm-m, which is relatively lower than normal soil resistivity of about 15 to 25 ohm-m. The distribution of contaminated soil was delineated using ERT images. Then, ERT survey was carried out in this area for monitoring of remediation of contaminated soil and groundwater. Werner measurements with 60 electrodes of 1 m spacing were taken during the 9-well oxygen injection and nutrition liquid injection period. The difference of apparent resistivity between before gas injection and after gas injection was used to delineate the channel of gas and the trace of gas migration in the porous garbage dump. The electrical resitivity changes between before and after nutrition liquid injection were used to analyze the liquid migration and distribution. The dynamic procedures of gas and water migration are outlined. The results suggest that ERT is a powerful technique for monitoring of soil remediation.

shi, X.; Luo, Z.; Zhang, Y.; Fu, Q.; Xu, Z.

2011-12-01

304

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

305

Temporal changes of the structure of a loamy soil tilled layers as described by 2D Electrical Resistivity Tomography  

NASA Astrophysics Data System (ADS)

The soil structure is complex, heterogeneous, space and time scale dependent, submitted to the climate, biological activity and human practices. For instance, in agricultural context, when soil management practices aim at developing desirable soil conditions for a seedbed and establishing specific surface configuration for planting, drainage or harvesting operations, they can also induce soil structural disturbances, as compaction resulting on in-field wheel traffic. These intense soil degradations have a drastic impact on soil functioning and plant growth but are not absolutely irreversible. Indeed, earthworm's activity, root growth and climate improve the soil structure by cracking, by developing voids, channels, by a progressive fragmentation and disaggregation of the initial dense matrix. Despite this natural structural resilience process of soils is well known, its empirical evidence at the macroscopic scale remains challenging. This requires a well detailed characterization of structural components in space and time. The objective of this study was to monitor the structural changes of a loamy tilled layer initially compacted locally by wheel traffic. In the field, two zones were analysed: (1) a bare soil in view of describing mainly the impact of the climate on the soil structure and (2) a cultivated soil in view of describing the cumulative effect of the climate and root growth on the soil structure. For both, the non destructive and exhaustive method of Electrical Resistivity Tomography (ERT) has been used to monitor the structural changes from April to August, i.e. during the complete growing season. In addition, the interpretation of ERT was comforted by several visual descriptions of soil structure, realized on soil pits dug at the same location than the ERT profiles and by bulk density measurements from soil samples. Due to their high impact on electrical resistivity, water content and soil temperature were also monitored during the experiment. The temperature effect was corrected with the Keller and Frischknecht equation (1966). Our results enhanced clearly the location of compacted clods in the trafficked zone with small values of electrical resistivity (close to 15 ohm.m). During the dessication period, the electrical values increased progressively according to the changes in water content. However, very high values of electrical resistivity were observed (up to 250 ohm.m) in the cultivated zone: according to experiments conducted in laboratory, these high resistivity values could not be only related to the decrease of the water content but also, to the formation of cracks in the compacted and non-compacted zones. Due to the cumulative effects of evapotranspiration and root water uptake, soil cracking was more pronounced in the cropping system than in bare soil. These results were consistent with visual descriptions of soil pits. We show then the adequacy of ERT to describe in space and time the structural resilience of the soil tilled layer and we discuss on the main influences of structural changes in space and time. This work was part of the FP7-DIGISOIL project on "Integrated system of data collection technologies for mapping soil properties".

Besson, Arlène; Seger, Maud; Richard, Guy; Nicoullaud, Bernard; Giot, Guillaume; Cousin, Isabelle

2010-05-01

306

A method to investigate the electron scattering characteristics of ultrathin metallic films by in situ electrical resistance measurements  

SciTech Connect

In this article, a method to measure the electrical resistivity/conductivity of metallic thin films during layer growth on specific underlayers is described. The in situ monitoring of an underlayer electrical resistance, its change upon the incoming of new material atoms/molecules, and the growth of a new layer are presented. The method is easy to implement and allows obtaining in situ experimental curves of electrical resistivity dependence upon film thickness with a subatomic resolution, providing insight in film growth microstructure characteristics, specular/diffuse electron scattering surfaces, and optimum film thicknesses.

Trindade, I. G.; Sousa, J. B. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal); Department of Physics, FCUP, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Fermento, R. [Instituto de Microelectronica de Madrid, Isaac Newton 8, 28760 Tres Cantos, Madrid (Spain); Leitao, D. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal)

2009-07-15

307

Distribution functions for anisotropic electrical resistivities due to hydrogen diffusivity in aligned peridotite and their application to the lithosphere-asthenosphere boundary  

NASA Astrophysics Data System (ADS)

The scaling properties of electrical anisotropy due to hydrogen diffusivity are investigated by representing the lattice-preferred-orientation (LPO) of a naturally-deformed peridotite xenolith using resistor network models. Whereas hydrogen diffusivities are approximately 40 (or 20) times faster along the a-axis of olivine single crystals than along their c-axes (or b-axes), a highly strained aggregate produces bulk electrical anisotropy factors of less than 4 (i.e. the more conductive direction can be expected to be less than 4 times more conductive than the less conductive direction) with 95% confidence. The bulk resistivities in both directions lie between those of the a-axes and the c-axes of olivine single crystals. Resistivity-depth profiles derived by assuming self-diffusion of hydrogen in a highly strained mantle indicate that for a realistic geotherm, electrical anisotropy arising due to hydrogen diffusivity within the thermal lithosphere is unlikely to be resolvable using magnetotelluric (MT) sounding, because the increase in resistivity with depth in the more resistive direction obscures the anisotropy. This is a consequence of the inherent lack of vertical resolution - i.e. inability to resolve vertical layering - of the MT method. Therefore, electrical anisotropy due to hydrogen self-diffusion in mantle minerals aligned within the lithosphere by palaeoflow is unresolvable using MT methods. However, a resolvable signature of such electrical anisotropy should be detectable, if present, in the adiabatic region below the thermal lithosphere or thermal boundary layer (TBL), where the geotherm is shallower. Since the mechanical lid or plate is generally assumed to be thinner than the TBL, this raises the question whether any anisotropic signature detected by MT can be attributed to LPO of olivine as a consequence of plate motion. If so, what does this tell us about heat transfer and strain dissipation in the enigmatic region between the mechanical lid and the TBL?

Simpson, Fiona

2013-04-01

308

A simple apparatus for measuring electrical resistance of materials at high temperatures  

SciTech Connect

Electrical resistance measurements in a wide temperature range are very important for understanding the physical properties of materials. It is often difficult to carry out the measurements at high temperatures since taking electrical leads reliably from specimens is a nontrivial problem. In this note we describe in detail a simple apparatus which can be used for studying any foil or pellet-shaped sample at temperatures up to 800{degree}C in vacuum or in an inert atmosphere. The apparatus uses spring loaded pins for electrical contact, obviating the need for silver paint or spot welding, thus avoiding any possible change in the properties of the sample. The springs used for loading are far removed from the high temperature zone; the load, therefore, remains unchanged during the experiment and the contacts remain uniformly reliable. {copyright} {ital 1996 American Institute of Physics.}

Rao, G.V.; Sastry, V.S.; Radhakrishnan, T.S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)] [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Seshagiri, V. [Department of Chemistry, Sri Krishnadevaraya University, Anantapur, Andhra Pradesh (India)] [Department of Chemistry, Sri Krishnadevaraya University, Anantapur, Andhra Pradesh (India)

1996-01-01

309

A simple apparatus for measuring electrical resistance of materials at high temperatures  

NASA Astrophysics Data System (ADS)

Electrical resistance measurements in a wide temperature range are very important for understanding the physical properties of materials. It is often difficult to carry out the measurements at high temperatures since taking electrical leads reliably from specimens is a nontrivial problem. In this note we describe in detail a simple apparatus which can be used for studying any foil or pellet-shaped sample at temperatures up to 800 °C in vacuum or in an inert atmosphere. The apparatus uses spring loaded pins for electrical contact, obviating the need for silver paint or spot welding, thus avoiding any possible change in the properties of the sample. The springs used for loading are far removed from the high temperature zone; the load, therefore, remains unchanged during the experiment and the contacts remain uniformly reliable.

Rao, G. V. Narasimha; Sastry, V. S.; Radhakrishnan, T. S.; Seshagiri, V.

1996-01-01

310

Drug Resistance Profiles of Mycobacterium tuberculosis Complex and Factors Associated with Drug Resistance in the Northwest and Southwest Regions of Cameroon  

PubMed Central

Background Anti-tuberculosis drug resistance continues to be a major obstacle to tuberculosis (TB) control programmes with HIV being a major risk factor in developing TB. We investigated anti-TB drug resistance profiles and the impact of socioeconomic as well as behavioural factors on the prevalence of TB and drug resistance in two regions of Cameroon with such data paucity. Methods This was a hospital-based study in which 1706 participants, comprising 1133 females and 573 males consecutively enrolled from selected TB and HIV treatment centres of the Northwest and Southwest regions. Demographic, clinical and self-reported risk behaviours and socioeconomic data were obtained with the consent of participants using questionnaires. Culture and drug resistance testing were performed according to standard procedures. Results The prevalence of resistance to at least one anti-TB drug was 27.7% and multi-drug resistance was 5.9%. Smoking, concurrent alcohol consumption and smoking, being on antiretroviral therapy for ? 12 months and previous household contact with TB patient were independently associated with tuberculosis prevalence, while only previous tuberculosis infection was associated with drug resistance in a univariate analysis. Conclusion The study showed a high prevalence of drug resistance TB in the study population with only previous TB infection associated with drug resistance in a univariate analysis. It also provides evidence in our context, of the role of alcohol and smoking in increasing the risk of developing TB, which is more likely in people living with HIV/AIDS. Therefore, it is important for public health authorities to integrate and intensify alcohol/smoking abstention interventions in TB and HIV control programs in Cameroon. PMID:24146991

Meriki, Henry D.; Tufon, Kukwah A.; Atanga, Pascal N.; Ane-Anyangwe, Irene N.; Anong, Damian N.; Cho-Ngwa, Fidelis; Nkuo-Akenji, Theresa

2013-01-01

311

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

312

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

313

Metabolite profiles of rice cultivars containing bacterial blight-resistant genes are distinctive from susceptible rice.  

PubMed

The metabolic changes of bacterial blight-resistant line C418/Xa23 generated by molecular marker-assisted selection (n= 12), transgenic variety C418-Xa21 generated by using the Agrobacterium-mediated system (n= 12), and progenitor cultivar C418 (n= 12) were monitored using gas chromatography/mass spectrometry. The validation, discrimination, and establishment of correlative relationships between metabolite signals were performed by cluster analysis, principal component analysis, and partial least squares-discriminant analysis. Significant and unintended changes were observed in 154 components in C418/Xa23 and 48 components in C418-Xa21 compared with C418 (P< 0.05, Fold change > 2.0). The most significant decreases detected (P< 0.001) in both C418/Xa23 and C418-Xa21 were in three amino acids: glycine, tyrosine, and alanine, and four identified metabolites: malic acid, ferulic acid, succinic acid, and glycerol. Linoleic acid was increased specifically in C418/Xa23 which was derived from traditional breeding. This line, possessing a distinctive metabolite profile as a positive control, shows more differences vs. the parental than the transgenic line. Only succinic acid that falls outside the boundaries of natural variability between the two non-transgenic varieties C418 and C418/Xa23 should be further investigated with respect to safety or nutritional impact. PMID:22687573

Wu, Jiao; Yu, Haichuan; Dai, Haofu; Mei, Wenli; Huang, Xin; Zhu, Shuifang; Peng, Ming

2012-08-01

314

Numerical modeling and interpretation of dipole-dipole resistivity and IP profiles Cove Fort-Sulphurdale KGRA, Utah  

Microsoft Academic Search

The Cove Fort-Sulphurdale Known Geothermal Resource Area (KGRA) is located near the junction of the Pavant Range and the Tushar Mountains in south-central Utah. The area has been the site of an intensive geothermal exploration effort since 1975. The electrical resistivity data obtained by Union Oil Company and a subsequent survey conducted for the Earth Science Laboratory and a detailed

1979-01-01

315

Electrical Resistivity Measurements in Sandstone During CH4 Hydrate Formation and CH4-CO2 Exchange  

NASA Astrophysics Data System (ADS)

The electrical properties of hydrate bearing sediments change with mineralogy, porosity, hydrate saturation, brine salinity, and mobility of the formation brine. Reliable calibration data is therefore essential for correct interpretation. Electrical resistivity measurements have been conducted on homogeneous Bentheim sand during CH4 hydrate formation. Various initial conditions (salinity and Sw) were used to determine the robustness of resistivity as a measure of hydrate saturation. Two setups with different electrode-arrangements were used; the first setup was a four electrode core holder without imaging capabilities, the second a two-electrode core holder used in combination with MRI to calibrate saturation data. The agreement between the two setups was good and there was little variation in phase angle. An initial resistivity decrease was observed at the initiation of hydrate growth for all experiments. This effect was more pronounced with lower initial salinities. Further increase in hydrate saturation resulted in reduced pore connectivity and increased tortuosity which resulted in increased resistivity (45-2487 k?). Only CH4 and water were used to form hydrate. The brine NaCl concentration of the remaining brine solution therefore increased during hydrate growth. Dynamic Rw and R0 values were incorporated into Archie's equations to account for changes in brine composition during hydrate formation. Resistivity was also measured during exchange between CH4-hydrate and CO2. There was an immediate resistivity and pressure response as CO2 was introduced to the system. This may be explained by higher water activity and CO2-hydrate growth at the trans-axial core face as CO2 is the preferred guest molecule at the experimental conditions. A spontaneous exchange therefore occurs, where the change in enthalpy accelerates the exchange. The resistivity showed a continuous decreasing trend after CO2 was introduced. This is explained by local in-equilibrium where dissociation and reformation occurs as simultaneous events, causing rearrangement of hydrate crystals and water. Trapped water re-organizing with a continuous conductive brine layer will result in a resistivity decrease. The performance of the CO2 injection was sensitive to heterogeneities in initial saturation distribution.

Birkedal, K.; Hauge, L.; Ersland, G.; Graue, A.

2012-12-01

316

Routine use of antibiotic laden bone cement for primary total knee arthroplasty: impact on infecting microbial patterns and resistance profiles.  

PubMed

Antibiotic-laden bone cement (ALBC) is used in primary arthroplasties throughout Europe. In North America, ALBC is only FDA approved for revision arthroplasty after periprosthetic joint infection (PJI). No article has evaluated whether infecting microbial profile and resistance has changed with the introduction of ALBC. We hypothesized that prophylactic use of ALBC in primary total knee arthroplasty (TKA) has not had a significant impact on infecting pathogens, and antibiotic resistance profiles. A retrospective cohort analysis was conducted of all PJI patients undergoing primary TKA and total hip arthroplasty (THA) between January 2000 and January 2009. No significant change in the patterns of infecting PJI pathogens, and no notable increase in percentage resistance was found among organisms grown from patients with PJI that had received prophylactic antibiotic-loaded cement in their primary joint arthroplasty. Early findings suggest that routine prophylactic use of ALBC has not led to changes in infecting pathogen profile, nor has led to the emergence of antimicrobial resistance at our institution. PMID:24418770

Hansen, Erik N; Adeli, Bahar; Kenyon, Robert; Parvizi, Javad

2014-06-01

317

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

318

Characteristics of microstructure and electrical resistivity of inkjet-printed nanoparticle silver films annealed under ambient air  

Microsoft Academic Search

The microstructure and electrical resistivity of inkjet-printed silver (Ag) films annealed under ambient air were characterized. Analyses of the impurity amounts in the films using secondary-ion mass spectrometry showed that the decomposition temperature of the capping molecules was just below 170°C. Both the characteristics of the microstructure and electrical resistivity when annealed at low temperatures (lower than the decomposition temperature)

J.-K. Jung; S.-H. Choi; I. Kim; H. C. Jung; J. Joung; Y.-C. Joo

2008-01-01

319

Effect of welding current on mechanical properties of galvanized chromided steel sheets in electrical resistance spot welding  

Microsoft Academic Search

In this study, the effect of welding current on the quality of weld joint and obviously on tensile-shear and tensile-peel strengths of galvanized chromate steel sheets having 1.2mm thickness in electrical resistance spot welding was investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity and pneumatic application mechanism with a single lever was used

S. Aslanlar; A. Ogur; U. Ozsarac; E. Ilhan; Z. Demir

2007-01-01

320

The effect of nucleus size on mechanical properties in electrical resistance spot welding of sheets used in automotive industry  

Microsoft Academic Search

In this study, the effects of welding current and time on the tensile-peel strength and tensile-shear strength of welding joint in electrical resistance spot welding of chromided micro-alloyed steel sheets having 0.8 mm thickness and galvanized chromided micro-alloyed steel sheets having 1.0 mm thickness were investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity

S. Aslanlar

2006-01-01

321

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

322

Lunar magnetic field measurements, electrical conductivity calculations and thermal profile inferences  

NASA Technical Reports Server (NTRS)

Steady magnetic field measurements of magnitude 30 to 100 gamma on the lunar surface impose problems of interpretation when coupled with the nondetectability of a lunar field at 0.4 lunar radius altitude and the limb induced perturbations of the solar wind at the Explorer orbit. The lunar time-varying magnetic field clearly indicates the presence of eddy currents in the lunar interior and permits calculation of an electrical conductivity profile. The problem is complicated by the day-night asymmetry of the moon's electromagnetic environment, the possible presence of the transverse magnetic mode, and the variable wave directions of the driving function. The electrical conductivity is calculated to be low near the surface, rising to a peak of .006/ohm meter at 250 km, dropping steeply inwards to a value of about .00005/ohm meter, and then rising toward the interior. A transition at 250 km depth from a high conductivity to a low conductivity material is inferred, suggesting an olivine-like core at approximately 800 C, although other models are possible.

Colburn, D. S.

1971-01-01

323

Tube thickness influence in the sheet/tube joint deformation obtained by electrical resistance spot welding  

SciTech Connect

Currently, the automotive industries have been trying to reduce the excessive weight of the vehicles structure, utilizing steel sheets of greater mechanical resistance and smaller thickness, as well as reducing the low carbon steel tubes thickness. The electrical resistance spot welding process has been used in the automotive industry in the sheet joints welding over square section tube, both steels are of low carbon with different chemical compositions, thickness and coatings. During this kind of joint welding it can happen a deformation in the inner part of the tube, with a reduction of the internal height which can compromise the weld quality. So, by means of a comparative analyses of the sheet/sheet joints (with a thickness of 0.95/2.0 mm and 0.95/3.0 mm) and sheet/tube joints (with a thickness of 0.95/2.0 mm and 0.95/3.0 mm) electrical resistance spot welded, it has been possible to observe that the thin wall sheet tube presents a greater deformation, but the biggest fracture axial traction load.

Damasco, A.; Ferreira, I. [Campinas State Univ., Sao Paulo (Brazil). Dept. of Materials; Duboc do Natal, Y. [Companhia Siderurgica Nacional, Volta Redonda, Rio de Janeiro (Brazil)

1996-12-01

324

Numerical modelling of direct current electrical resistivity for the characterisation of cracks in soils  

NASA Astrophysics Data System (ADS)

Fractures or cracks in rocks and soils are thin planar features of high resistivity, embedded in a more conductive bulk volume. In soils, several processes, particularly swelling and shrinkage of clays, result in cracks and can regenerate macroporosity. Their detection and the assessment of their evolution necessitate the use of non-invasive techniques. Although cracks have a major influence on the electrical resistivity of bulk material their complete geometrical characterisation achieved through the use of electrical resistivity measurements remains difficult due to the lack of appropriate inversion models. An inversion model based on the method of moments (MoM) has been developed, and is presented here. Direct simulations demonstrate the model's ability to reconstruct real experimental data. The influence of various object parameters on the model's accuracy was tested, showing that the model is sensitive to all the geometric characteristics of a crack. The inversion of both simulated and experimental data has demonstrated the model's ability to calculate the initial position, width and depth of several different cracks.

Tabbagh, Jeanne; Samouëlian, Anatja; Tabbagh, Alain; Cousin, Isabelle

2007-08-01

325

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

326

Environmental monitoring of leaks using time-lapsed long electrode electrical resistivity  

NASA Astrophysics Data System (ADS)

Highly industrialized areas pose challenges for surface electrical resistivity characterization due to metallic infrastructure. The infrastructure is typically more conductive than the desired targets and will mask the deeper subsurface information. The risk of this occurring may be minimized if steel-cased wells are used as long electrodes in the area near the target. We demonstrate a method of using long electrodes to electrically monitor a simulated leak from an underground storage tank with both synthetic examples and a field demonstration. Although the method of using long electrodes has been proposed by others, no time-lapse resistivity data have been collected, modeled, and analyzed within a nuclear waste tank farm environment. Therefore, the main objective of this work was to test whether the long electrode method using steel-cased wells can be employed to spatially and temporally track simulated leaks in a highly industrialized setting. A secondary objective was to apply a time-lapse regularization procedure in the inverse modeling code, similar to the 4D tomography approach by Kim et al. (2009), and to test the procedure's effect on the quality of the outcome regarding plume intensity and position. For the synthetic examples, a simple target of varying electrical properties was placed beneath different types of layers of low resistivity to simulate the effects of the infrastructure. Both surface and long electrodes were tested on the synthetic domain, and the test cases covered a variety of survey parameters including low and high electrode density, noise, array type, and the explicit location of the wells relative to the target. All data were processed in four dimensions, where the regularization procedure was applied in both the time and space domains. The synthetic test case showed that the long electrode resistivity method could detect relative changes in resistivity that was commensurate with the differing target properties. The surface electrodes, on the other hand, had a more difficult time matching the original target's footprint unless the electrodes were distributed at a greater density on the surface. The simulated tank leak in the field experiment was conducted by injecting a high conductivity fluid in a perforated well within the S tank farm at the Hanford Site, and the resistivity measurements were made before and after the leak test. The field results showed a lowered resistivity feature develops south of the injection site after cessation of the injections. The parameter used in the time-lapsed inversion had a strong influence on the differences in inverted resistivity between the pre- and post-injection datasets, but the interpretation of the target was consistent across all values of the parameter. The long electrode electrical resistivity monitoring (ERM) method may provide a tool for near real-time monitoring of leaking underground storage tanks given a sufficient density of wells.

Rucker, Dale F.; Fink, James B.; Loke, Meng H.

2011-08-01

327

Determination of the correlation between the electrical resistivity of non-cohesive soils and the degree of compaction  

NASA Astrophysics Data System (ADS)

Electrical resistivity measurements provide potentially powerful tool for estimation of physical parameters of soils and materials used in earthworks and constructions like embankments and dams. The study demonstrates the correlation between the resistivity of non-cohesive soils and the degree of compaction, which is an indicator of important and possibly risks bearing hydraulic piping or tunneling. In this paper we investigate the relationship between electrical resistivity of non-cohesive soils and granulated materials used in earth-works and constructions such as road embankments, and degree of compaction. Laboratory analyses of the last parameter are time consuming and estimated using parameters such as moisture content, bulk density and porosity, the same parameters (mostly obviously porosity and moisture content and including pore water mineralization) determine electrical resistivity. In consequence, electrical resistivity is a potentially well adapted alternative method for determination of the degree of compaction. To investigate the problem, electrical resistivity survey was conducted in a laboratory using soil samples representing fine, medium and coarse sands, submitted to successive steps of compaction. The measurements were carried out in the box, which may be compared with the construction such as an embankment. Obtained resistivity values were analyzed taking into consideration electrode spacing and the physical parameters of soil at each step of compaction.

Kowalczyk, Sebastian; Ma?lakowski, Maciej; Tucholka, Piotr

2014-11-01

328

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

329

RESISTANCE OF PLANT COVER TYPES TO TREE SEEDLING INVASION ON AN ELECTRIC TRANSMISSION RIGHT-OF-WAY  

Microsoft Academic Search

A study of resistance of common plant covers to tree invasion was made on an electric transmission right-of- way (ROW) in an oak-hickory forest in central Pennsylvania. Tree seedling counts were made on belt transects in 1984, 1985, and 1986 after ROW maintenance was applied in 1982. Cover types dominated by dense patches of grasses and herbs were highly resistant

W. C. Bramble; W. R. Byrnes; R. J. Hutnik

330

Negatively strain-dependent electrical resistance of magnetically arranged nickel composites: application to highly stretchable electrodes and stretchable lighting devices.  

PubMed

A novel property of the negatively strain-dependent electrical resistance change of nickel conductive composites is presented. The composite shows negatively strain-dependent resistance change when magnetically arranged, while most conductive materials show opposite behavior. This negative dependency is utilized to produce highly stretchable electrodes and to demonstrate a new conceptual resolution-sustainable stretchable lighting/display device. PMID:24615882

Kim, Sangwoo; Byun, Junghwan; Choi, Seongdae; Kim, Donghyun; Kim, Taehoon; Chung, Seungjun; Hong, Yongtaek

2014-05-21

331

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; Magalhaes, Tereza; Araujo, Ana; Ayres, Contancia

2012-01-01

332

Electrical Resistivity Imaging and Quantification of Water Content Distribution during Infiltration and Redistribution in Soils  

NASA Astrophysics Data System (ADS)

Controlled by precipitation, evapotranspiration, recharge, and soil-hydraulic properties, water content is difficult to measure extensively in heterogeneous, natural environments without disturbing the subsurface. Time-lapse electrical resistivity imaging (ERI) is a cost-effective, minimally invasive method for imaging changes in water content in the vadose zone. Quantifying the relation between resistivity and water content, however, is challenging due to 1) spatially variable resolution, 2) spatial variability in the properties that relate resistivity to water content, 3) possible variability of soil-water salinity, and 4) the need for introduction of auxiliary information to achieve a unique solution of the inverse problem. Although quantitative integration of ERI data into hydrogeologic studies is complicated by these problems, the ERI technique provides copious and spatially exhaustive soft data that would otherwise be unavailable in this heterogeneous environment, especially over the multi-meter scale. We developed a methodology for analyzing ERI measurements in terms of water content, and applied it to ERI data collected during infiltration/redistribution experiments conducted in two soil types in the Mojave National Preserve. One experiment was conducted in an active wash, the other in a highly developed Pleistocene soil. In both, changes in water content through time were estimated from ERI to a depth of approximately 1.5 m during and after ponded infiltration in a 1-m diameter ring. Approximately 40 snapshots over approximately one week along intersecting two-dimensional lines were collected through time for both experiments. To reduce ambiguities in our interpretation, we use numerical simulations of water and electrical flow to convert estimated resistivity to water content, calibrating for variations in resolution, spatially variable petrophysical properties, and fluid salinity on the relation between water content and estimated resistivity. Additionally, we evaluate the application of local non-stationary relations between the resistivity and water content to quantify spatially variable resolution and the impact of image reconstruction in the inverse problem. The resistivity results compare favorably with measurements of water content from time-domain reflectometry probes at selected points in the subsurface. The ERI inversions indicate that flow is not one-dimensional even in the comparatively homogeneous active wash, and that the more mature soil retains moisture for a longer time. Application and interpretation of conventional infiltrometer measurements based on the assumption of one-dimensional flow, could lead potentially to inaccurate or misleading results. This work moves toward using ERI as a quantitative tool to improve estimation of water content dynamics.

Singha, K.; Mirus, B. B.; Nimmo, J. R.; Perkins, K.

2006-12-01

333

Electrical Resistivity and Seismic Characterization of Submarine Groundwater Discharge in Long Bay, SC  

NASA Astrophysics Data System (ADS)

Submarine groundwater discharge (SGD) has been identified as a significant contributor of dissolved nutrients and contaminants to near-shore waters. Little is known, however, about geologic controls on the spatial distribution of SGD seeps. Discharge estimates are typically derived from geochemical tracers such as Rn-222. Such estimates of total fluxes over a given area do not consider the potential for spatial variability in discharge rates. Higher fluxes of chemically distinct SGD over smaller areas could have complex effects on localized water masses, ecosystems, and geological features. In an effort to assess the distribution of SGD, electrical resistivity and seismic surveys were conducted along the inner shelf of Long Bay, South Carolina during a series of cruises between October, 2005 and November 2006. In addition, basic bottom water quality parameters including dissolved oxygen, temperature, salinity, and pH were measured. Preliminary submarine groundwater flux estimates for northern Long Bay were also generated from measurements of Rn-222. The resistivity signal is highly variable along shore with several instances of elevated values suggesting presence of relatively fresher pore waters. In some cases, elevated resistivity measurements were spatially co-registered with seismically defined paleochannels extending across the shelf. Other areas of elevated resistivity values correlate with smaller discontinuities in seismic reflectors. A third category of resistivity anomalies does not correlate with seismically defined features. Overall, anomaly frequency and intensity decrease rapidly with increasing distance from shore. At distances > 1 km from shore, the resistivity signal is uniform in space and low in magnitude, implying less of a fresh water contribution. Water quality parameters are variable along shore and may reflect the influence of SGD. Rn-derived fluxes suggest SGD equivalent to as much as 50% of riverine discharge into Long Bay. Ongoing work is focused on sampling pore water in a variety of geologic settings for redox conditions, nutrients and Rn-222. This information will ultimately provide the basis for determination of SGD-related nutrient fluxes to nearshore waters.

Viso, R. F.; McCoy, C.; Quafisi, D.; Gayes, P. T.

2007-12-01

334

Improvement of corrosion resistance and electrical conductivity of 304 stainless steel using close field unbalanced magnetron sputtered carbon film  

Microsoft Academic Search

Carbon film has been deposited on 304 stainless steel (SS304) using close field unbalanced magnetron sputter ion plating (CFUBMSIP) to improve the corrosion resistance and electrical conductivity of SS304 acting as bipolar plates for proton exchange membrane fuel cells (PEMFCs). The corrosion resistance, interfacial contact resistance (ICR), surface morphology and contact angle with water of the bare and carbon-coated SS304

Weihong Jin; Kai Feng; Zhuguo Li; Xun Cai; Lei Yu; Danhua Zhou

2011-01-01

335

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

336

ENVIRONMENTAL MONITORING OF LEAKS USING TIME LAPSED LONG ELECTRODE ELECTRICAL RESISTIVITY  

SciTech Connect

Highly industrialized areas pose significant challenges for surface based electrical resistivity characterization and monitoring due to the high degree of metallic infrastructure. The infrastructure is typically several orders of magnitude more conductive than the desired targets, preventing the geophysicist from obtaining a clear picture of the subsurface. These challenges may be minimized if steel-cased wells are used as long electrodes. We demonstrate a method of using long electrodes in a complex nuclear waste facility to monitor a simulated leak from an underground storage tank. The leak was simulated by injecting high conductivity fluid in a perforated well and the resistivity measurements were made before and after the leak test. The data were processed in four dimensions, where a regularization procedure was applied in both the time and space domains. The results showed a lowered resistivity feature develop south of the injection site. The time lapsed regularization parameter had a strong influence on the differences in inverted resistivity between the pre and post datasets, potentially making calibration of the results to specific hydrogeologic parameters difficult.

RUCKER DF; FINK JB; LOKE MH; MYERS DA

2009-11-05

337

Observation of superconductivity and anomalous electrical resistivity in single-crystal Ir3Te8  

NASA Astrophysics Data System (ADS)

We observe an unusual combination of normal and superconducting state properties without any signature of strong spin fluctuations in single-crystal Ir3Te8. The electrical resistivity does not saturate by 700 K but exhibits a low-resistivity ratio, and it exhibits two extended linear regimes (approximately 20-330 and 370-700 K) with the same slope, separated by a small hysteretic interval marking a strong first-order phase transition from cubic to rhombohedral lattice symmetry at TS = 350 K. The electronic heat-capacity coefficient (11mJmol-1K-2) is consistent with a net diamagnetic, rather than a Pauli paramagnetic, normal state that yields to superconductivity below a critical temperature TC = 1.8 K. The size of the heat-capacity jump near TC indicates bulk superconductivity.

Li, L.; Qi, T. F.; Lin, L. S.; Wu, X. X.; Zhang, X. T.; Butrouna, K.; Cao, V. S.; Zhang, Y. H.; Hu, Jiangping; Yuan, S. J.; Schlottmann, P.; De Long, L. E.; Cao, G.

2013-05-01

338

Anisotropic electrical resistivity of the Kondo insulator CeRu4Sn6  

NASA Astrophysics Data System (ADS)

The intermetallic compound CeRu4Sn6 has tentatively been classified as anisotropic Kondo insulator. Here we present electrical resistivity measurements on CeRu4Sn6 single crystals, both along the main directions a and c of the tetragonal crystal structure, and v along the diagonal c' of the a-a plane. This direction was selected because c' = differs from c by only 0.2 %, suggesting that the coumpound might alternatively be regarded as quasi-cubic. Amazingly, strong anisotropy is observed not only between a and c but also between c and c'. We analyse the temperature dependent resistivities both with a simple semiconductor model and within a Kondo insulator picture.

Winkler, H.; Lorenzer, K.-A.; Prokofiev, A.; Paschen, S.

2012-12-01

339

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

340

Effect of Scattering by Fluidization of Electrically Conductive Beads on Electrical Field Intensity Profile in Microwave Dryers  

Microsoft Academic Search

A technology to apply a fluidized bed of electrically conductive beads is proposed to improve uniformity of the electric field intensity in microwave dryers, which are required for uniform heating of wet media. The principle of this effectiveness lies in a dynamic random scattering of microwave due to motion of the conductive beads in the bed. The electrically conductive beads

Yoshinori Itaya; Shigeru Uchiyama; Shigenobu Hatano; Shigekatsu Mori

2005-01-01

341

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

Microsoft Academic Search

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

U. B. Arnalds; J. S. Agustsson; A. S. Ingason; A. K. Eriksson; K. B. Gylfason; J. T. Gudmundsson; S. Olafsson

2007-01-01

342

Comparative analysis of virulence and resistance profiles of Salmonella Enteritidis isolates from poultry meat and foodborne outbreaks in northern Jordan.  

PubMed

This study was conducted to isolate Salmonella Enteritidis from poultry samples and compare their virulence and antibiotic resistance profiles to S. Enteritidis isolated from outbreaks in northern Jordan. Two hundred presumptive isolates were obtained from 302 raw poultry samples and were subjected to further analysis and confirmation. A phylogenic tree based on 16S rRNA sequencing was constructed and selected isolates representing each cluster were further studied for their virulence in normal adult Swiss white mice. The most virulent strains were isolated from poultry samples and had an LD 50 of 1.55 × 10 (5) CFU, while some of the outbreak isolates were avirulent in mice. Antibiotic resistance profiling revealed that the isolates were resistant to seven of eight antibiotics screened with each isolate resistant to multiple antibiotics (from two to six). Of the poultry isolates, 100%, 88.9%, 77.8%, 66.7%, and 50% showed resistance to nalidixic acid, ciprofloxacin, ampicillin, cephalothin, and cefoperazone, respectively. Two outbreak isolates were sensitive to all tested antibiotics, while 71.4% were resistant to cefoperazone and only 28.6% showed resistance to nalidixic acid. Salmonella outbreak isolates were genetically related to poultry isolates as inferred from the 16S rRNA sequencing, yet were phenotypically different. Although outbreak strains were similar to poultry isolates, when tested in the mouse model, some of the outbreak isolates were highly virulent while others were avirulent. This might be due to a variation in susceptibility of the mouse to different S. Enteritidis isolates. PMID:24780883

Jaradat, Ziad W; Abedel Hafiz, Leena; Ababneh, Mustafa M; Ababneh, Qotaibah O; Al Mousa, Waseem; Al-Nabulsi, Anas; Osaili, Tareq M; Holley, Richard

2014-07-01

343

Use of plasmid profiles in epidemiologic surveillance of disease outbreaks and in tracing the transmission of antibiotic resistance.  

PubMed Central

Plasmids are circular deoxyribonucleic acid molecules that exist in bacteria, usually independent of the chromosome. The study of plasmids is important to medical microbiology because plasmids can encode genes for antibiotic resistance or virulence factors. Plasmids can also serve as markers of various bacterial strains when a typing system referred to as plasmid profiling, or plasmid fingerprinting is used. In these methods partially purified plasma deoxyribonucleic acid species are separated according to molecular size by agarose gel electrophoresis. In a second procedure, plasmid deoxyribonucleic acid which has been cleaved by restriction endonucleases can be separated by agarose gel electrophoresis and the resulting pattern of fragments can be used to verify the identity of bacterial isolates. Because many species of bacteria contain plasmids, plasmid profile typing has been used to investigate outbreaks of many bacterial diseases and to trace inter- and intra-species spread of antibiotic resistance. Images PMID:2852997

Mayer, L W

1988-01-01

344

Critical roles of cappants on the electrical resistivity of Ni nanoparticles  

NASA Astrophysics Data System (ADS)

We demonstrate here a very noteworthy nature of the critical roles of type of cappants, in addition to the particle size, on the electrical resistivity of compacted pellets of nickel nanoparticles (Ni-NPs) in the temperature range from 5 to 300 K that deviate significantly from highly conducting nature of a good metal yet without much deviation of the slopes. For this, face-centered cubic structured Ni-NPs of average particle size ranging from 18 to 33 nm were prepared using different polyol methods in the presence of various additional capping agents.

Singh, J.; Kaurav, N.; Ganesan, V.; Okram, Gunadhor S.

2014-04-01

345

Nonlinear input resistance of a low-frequency electric oscillator in the ionospheric plasma  

NASA Astrophysics Data System (ADS)

Knowledge of the characteristics of low-frequency antennas in a magnetoactive ionospheric plasma is important in radiophysical experiments aimed at the study of the radiation and propagation of VLF electromagnetic waves using space-borne measuring equipment. Here, the effect of the ionospheric plasma on the input resistance of an electric antenna is investigated analytically assuming that the antenna potential is determined solely by the floating potential and induction emf generated during the motion of the antenna in the geomagnetic field. The potential range from -0.2 to -1.5, corresponding to floating potential values at 200-1500 km above the earth surface, is considered as an example.

Lishin, I. V.; Sorokina, R. K.

1990-05-01

346

Profile  

Microsoft Academic Search

This article is an operational profile of a grant funded phone-in Computer Assisted Legal Research (CALR) project. The project is funded by the Legal Services Corporation: (1) to provide WESTLAW research to attorneys working on behalf of LSC clients located in ten states throughout the Southeast, and (2) to participate with other grantees in the development of a private, automated

Sandra L. OConnor

1985-01-01

347

Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids  

DOEpatents

This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination. 1 fig.

Ramirez, A.L.; Cooper, J.F.; Daily, W.D.

1996-02-27

348

Antibiotic resistance profiles of Escherichia coli isolated from rural and urban environments  

Microsoft Academic Search

Sludge and waste water samples from a variety of locations (in the United States and from one location in Mexico) were evaluated to determine whether multiple antibiotic resistant resistance patterns correlated with location and type of waste. The occurrence of antibiotic resistant strains of Escherichia coli was dependent upon site among the eleven locations sampled (P < 0.001). The E.

S. D. Pillai; K. W. Widmer; K. G. Maciorowski; S. C. Ricke

1997-01-01

349

Comparison of Single and Multilocus Sequence Typing and Toxin Gene Profiling for Characterization of Methicillin-Resistant Staphylococcus aureus  

Microsoft Academic Search

We compared three novel methicillin-resistant Staphylococcus aureus (MRSA) genotyping methods with multilocus sequence typing (MLST) and spa typing to assess their utility for routine strain typing. The new methods were femA and nuc sequence typing and toxin gene profiling (TGP), using a multiplex-PCR-based reverse line blot assay to detect 13 pyrogenic superantigen and exfoliative toxin genes. Forty-two well-charac- terized MRSA

Yongwei Cai; Fanrong Kong; Qinning Wang; Zhongsheng Tong; Vitali Sintchenko; Xianyu Zeng; Gwendolyn L. Gilbert

2007-01-01

350

Antimicrobial resistance profile of Staphylococcus aureus isolated from raw meat: A research for methicillin resistant Staphylococcus aureus (MRSA)  

Microsoft Academic Search

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a risk factor for patients in general population and particularly in immunocompromised patients. As a matter of fact, it can produce serious infections that may then evolve in septicaemia. However, transmission of MRSA from food to people can represent a serious problem only for immunocompromised people. Vancomycin is the elective antimicrobial commonly used

G. Pesavento; B. Ducci; N. Comodo; A. Lo Nostro

2007-01-01

351

Flexural fatigue performance and electrical resistance response of carbon nanotube-based polymer composites at cryogenic temperatures  

NASA Astrophysics Data System (ADS)

We study the flexural failure and electrical resistance change of carbon nanotube (CNT)-based polymer composites under cyclic loading at cryogenic temperatures. Fatigue tests were performed on CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K) using the three-point bending method, and the measurements of the specimen electrical resistance were made during the tests. Also, the specimen fracture surfaces were examined by scanning electron microscopy (SEM) to verify the failure mechanisms of the nanocomposites. The dependence of the mechanical and electrical responses of the nanocomposites on the temperature and the nanotube content was then discussed.

Wei, Zhijuan; Takeda, Tomo; Narita, Fumio; Shindo, Yasuhide

2014-01-01

352

Applications of electrical resistivity imaging for characterizing groundwater-surface water interactions from local to regional scales  

NASA Astrophysics Data System (ADS)

Surface water (SW) and groundwater (GW) interact across multiple spatial and temporal scales and their interaction is important for ecological and biogeochemical functions. The mixing of GW and SW has been challenging to simultaneously map with sufficient detail and coverage. Fortunately, ambient differences in salinity of waters occupying geologic formations and sediment are an ideal target for electrical resistivity imaging (ERI). We present examples of the application of ERI for mapping GW discharge and for understanding GW-SW interactions at: (1) a large regulated river, (2) neighboring lakes with differing salinity, (3) fringing coral reefs and lagoons, (4) beaches, and (5) estuaries. In all these cases, the ER tomograms were critical for improving conceptual understanding of GW-SW interactions. At the Lower Colorado River in Austin, Texas (USA), time-lapse ERI was conducted across a 12-hour dam-release cycle when the river stage varied by 0.7 m. Using temporal variability in electrical resistivity (ER) signatures, we identified a shallow well-flushed hyporheic zone, a transition zone where SW and GW mix, and a stable deep zone hosting only GW. In alkaline lakes in the Nebraska Sand Hills (Nebraska, USA), ER surveys using boat-towed cables allowed for mapping the 3D electrical structure underneath the lake. The tomograms were used to distinguish flow-through lakes, which have decreasing subsurface ER from GW inflow to outflow area, from pure GW discharge lakes, which have uniformly stratified increasing-with-depth ER profiles. Moreover, GW plumes in both discharge and recharge zones were clearly outlined underneath the lake. More than 30 km of ER profiles collected via boat-towed surveys over a fringing coral reef in the Philippines identified areas of high ER within the reef that coincide with resistive zones in the seawater. Analysis of 222Rn of bottom waters and vertical conductivity-temperature-depth measurements show the persistence of fresh GW input into the ocean where low salinity and high 222Rn areas coincided with high ER areas. In Muri Lagoon in Rarotonga Island of the Cook Islands, boat-towed ER surveys similarly showed areas underneath the lagoon that have groundwater that is fresher than seawater. Likewise, there was 222Rn high concentrations throughout the lagoon. Closer to shore, ER surveys using fixed electrodes showed complex 3D mixing processes between seawater and terrestrial-sourced fresh groundwater in beach sediment. Lastly, both boat-towed and fixed surveys across the salt wedge of Werribee Estuary west of Melbourne, Australia, outlined the estuarine salt wedge and its relationship with and effect on fresh and nutrient-laden groundwater discharging to the estuary. The examples discussed illustrate that ERI is a powerful and convenient tool for mapping GW discharge and GW-SW interactions across different scales and diverse environments.

Cardenas, M. B.; Befus, K. M.; Zamora, P. B.; Ong, J.; Zlotnik, V. A.; Cook, P. L.; Tait, D. R.; Erler, D.; Santos, I. R.; Siringan, F. P.

2012-12-01

353

The histone deacetylase inhibitor trichostatin A alters microRNA expression profiles in apoptosis-resistant breast cancer cells  

PubMed Central

The development of drug resistance represents a major complication in the effective treatment of breast cancer. Epigenetic therapy, through the use of histone deacetylase inhibitors (HDACi) or demethylation agents, is an emerging area of therapeutic targeting in a number of ontological entities, particularly in the setting of aggressive therapy-resistant disease. Using the well-described HDAC inhibitor trichostatin A (TSA) we demonstrate the suppression of in vitro clonogenicity in the previously described apoptosis-resistant MCF-7TN-R breast carcinoma cell line. Additionally, recent work has demonstrated that these agents can alter the expression profile of microRNA signatures in malignant cells. Using an unbiased microRNA microarray analysis, changes in miRNA expression of MCF-7TN-R cells treated with TSA for 24 h were analyzed. We observed significant up-regulation of 22 miRNAs and down-regulation of 10 miRNAs in response to TSA treatment. Our results demonstrate that the HDACi, TSA, exerts anticancer activity in the apoptosis-resistant MCF-7TN-R breast carcinoma cell line. This activity is correlated with TSA alteration of microRNA expression profiles indicative of a less aggressive phenotype. PMID:21971930

RHODES, LYNDSAY V.; NITSCHKE, ASHLEY M.; SEGAR, H. CHRIS; MARTIN, ELIZABETH C.; DRIVER, JENNIFER L.; ELLIOTT, STEVEN; NAM, SEUNG YOON; LI, MENG; NEPHEW, KENNETH P.; BUROW, MATTHEW E.; COLLINS-BUROW, BRIDGETTE M.

2012-01-01

354

Evidence for an oxygen diffusion model for the electric pulse induced resistance change effect in transition-metal oxides.  

PubMed

Electric-pulse induced resistance hysteresis switching loops for Pr0.7Ca0.3MnO3 perovskite oxide films were found to exhibit an additional sharp "shuttle tail" peak around the negative pulse maximum for films deposited in an oxygen-deficient ambient. The resistance relaxation in time of this "shuttle tail" peak as well as resistance relaxation in the transition regions of the resistance hysteresis loop show evidence of oxygen diffusion under electric pulsing, and support a proposed oxygen diffusion model with oxygen vacancy pileup at the metal electrode interface region as the active process for the nonvolatile resistance switching effect in transition-metal oxides. PMID:17501295

Nian, Y B; Strozier, J; Wu, N J; Chen, X; Ignatiev, A

2007-04-01

355

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

356

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

357

Mutations conferring resistance to viral DNA polymerase inhibitors in camelpox virus give different drug-susceptibility profiles in vaccinia virus.  

PubMed

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

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

2012-07-01

358

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; Krecmerova, Marcela; Crance, Jean-Marc; Garin, Daniel; Snoeck, Robert

2012-01-01

359

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

360

Correlating scanning tunneling spectroscopy with the electrical resistivity of Al-based quasicrystals and approximants  

NASA Astrophysics Data System (ADS)

We present detailed low-temperature scanning tunneling spectroscopy (STS) investigations of the local electronic density of states (DOS) on the fivefold and twofold i-Al70Pd21Mn9; pseudo tenfold ?'-Al72Pd25Mn3; tenfold d-Al77Ni17Co6; twofold-(12110) d-Al72.9Ni10.4Co16.7; (100) Y-Al75.8Ni2.1Co22.1; and (111) Al surface in the range of +/- 1 eV around the Fermi energy. All these quasicrystals and approximants exhibit the theoretically predicted electronic pseudogap. We observe no evidence for a correlation between the depth of this pseudogap, as measured by STS, and the remarkably high electrical resistivity of the investigated quasicrystals and approximants. A parametrization of the spatial variability of STS spectra is introduced as a measure of the magnitude of the electron localization for a given system. The resulting ? parameter is found to be proportional to the square root of the electrical resistivity. This finding supports the validity of interpreting spatial variations of fine-structure features in the STS spectra of Al-based quasicrystals and approximants in terms of electron localization.

Mäder, Ruben; Widmer, Roland; Gröning, Pierangelo; Steurer, Walter; Gröning, Oliver

2013-02-01

361

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

362

Electron-phonon effects in copper. II. Electrical and thermal resistivities and Hall coefficient  

NASA Astrophysics Data System (ADS)

The electrical and thermal resistivities (? and W) and Hall coefficient (RH) of pure and impure Cu are calculated. Realistic Korringa-Kohn-Rostocker energy bands and wave functions, experimental phonon frequencies, and Born-von Kármán eigenvectors, and the rigid-muffin-tin model for electron-phonon scattering are used to generate the velocities and scattering probabilities in the Bloch-Boltzmann equation, on a mesh of nearly 24000 points on the Fermi surface. The effect of impurities is approximated by an isotropic impurity scattering rate. Solutions for ?, W, and RH are exhibited at three levels of accuracy: (1) the lowest-order variational approximation (LOVA) where the Fermi surface displaces rigidly; (2) a fully inelastic calculation where the distribution function is allowed arbitrary variations with energy (normal to Fermi surface) to reflect the inelasticity of electron-phonon scattering; (3) inelasticity plus somewhat increased angular freedom in the distribution function. For ? and W we find that above T=100 K the corrections to LOVA are negligible and that, except at the lowest temperatures T~20 K, our angular corrections are negligible. For RH the lowest-order approximation is temperature independent and the addition of both inelasticity and increased angular freedom are not negligible at any temperature. Agreement with experiment for all three quantities is good throughout the range T=10 to 300 K. The use of a phenomenological impurity relaxation time to study deviations from Matthiessen's rule in the electrical resistivity agrees qualitatively with experiment.

Beaulac, T. P.; Allen, P. B.; Pinski, F. J.

1982-08-01

363

Electrical Resistivity, Crustal Melting and Strain Localization beneath the Himalayan-Tibetan Belt  

NASA Astrophysics Data System (ADS)

The construction of mountain belts resulting from continental collisions involves crustal thickening, regional deformation and high-grade metamorphism. As observed in many ancient orogenic terrains, elevated temperatures locally induce melting and strain weakening, which may profoundly affect the rheology of the continental crust, its deformation regime and hence the development of these orogens. The Himalaya-Tibetan system is an active collisional belt allowing us to probe the three-dimensional thermo-mechanical distribution of an archetypal continent-continent orogen. Several magnetotelluric and seismic field campaigns (INDEPTH, Hi-CLIMB and HIMPROBE projects) have identified low resistivity layers with well-constrained tops at a depth of 10-15 km in southern Tibet (10 ?.m) and 20-25 km in northwestern Himalaya (3 ?.m), coincident with low velocity zones. Such electrical anomalies have been interpreted as evidence of high concentrations of interconnected fluids. Despite numerous field and numerical studies on the Himalayan range, identification and quantification of hydrous melting and potential strain weakening of the crust remains unaddressed by the appropriate experimental studies. Laboratory resistivity and viscosity measurements were performed in a gas-medium deformation apparatus (Paterson press), which was coupled to an impedance spectrometer. These measurements were conducted on natural muscovite-bearing metapelitic samples containing ca. 2 wt% water. Dehydration-melting of muscovite crystals leads to the production of hydrous melts. Electrical measurements show that with increasing temperature, the electrical resistivity decreases dramatically from 1830 ?.m at 550°C to 8 ?.m at 850°C. Image and chemical analyses of the partially molten samples after experiments indicate 23 vol.% hydrous melts, which are leucogranitic in composition. Our electrical measurements thus show that geophysical data clearly pinpoint ca. 25 vol.% partial melting at 750-800°C and 18-24 km depth beneath southern Tibet (10 ?.m) and crystal-free leucogranite magma bodies at 800°C and 12 km depth beneath northwestern Himalaya (3 ?.m). Presence of partial melting and fully molten bodies has serious impact on the rheological behavior of the middle crust. Our viscosity measurements show that ca. 25 vol.% partial melting reduces the viscosity, ?, to 1011.5 Pa.s, whereas pure melt bodies have been shown to present lower ?, i.e. 104 Pa.s. These viscosity values are several orders of magnitude lower than previous estimations used in thermo-mechanical models of crustal channel flow and ductile extrusion (? = 1018-1019 Pa.s). Our quantitative results represent a benchmark for conceptual models on the development and sustainment of mountain belts relying on an internally consistent set of petrological-geophysical-rheological constraints.

Hashim, L.; Gaillard, F.; Champallier, R.; Le Breton, N.; Arbaret, L.; Scaillet, B.

2012-12-01

364

Can we use Electrical Resistivity Tomography to measure root zone moisture dynamics in fields with multiple crops?  

NASA Astrophysics Data System (ADS)

Agriculture on shallow or steep soils in the humid tropics often leads to low resource use efficiency. Contour hedgerow intercropping systems have been proposed to reduce run-off and control soil erosion. However, competition for water and nutrients between crops and associated hedgerows may reduce the overall performance of contour hedgerow systems. Electrical resistivity tomography (ERT) is a valuable technique to assess the distribution and dynamics of soil moisture non-invasively. Root water uptake is a spatially variable and small-scale process, which requires at least decimeter resolution and a high sensitivity in order to be able to monitor changes in time and space. Careful experimental design is of uttermost importance in order to maximize the information content of the ERT survey and to gain insights in the possibilities and limitations of the survey. Virtual experiments in combination with absolute and spatial performance measures provide a way to optimize the information that can be retrieved from an ERT experiment. We used this approach to identify a suitable measurement methodology to monitor water fluxes in a contour hedgerow intercropping system in Ratchaburi province, Thailand. The virtual experiment showed that there are important differences between the tested measurement configurations. We saw that the optimal ERT array was capable of recognizing distinct water depletion zones under the different crops. However, sharp contrasts in the 1-D water depletion profile are smoothened. ERT measurements conducted in Thailand showed that the soils of our experimental plots were very heterogeneous both along the slope as with depth. This observation highlighted some constraints of the ERT method for soil moisture monitoring in the field, such as the difficulty to define a relationship between electrical conductivity and soil moisture in very heterogeneous soils. Nevertheless, the data indeed revealed contrasting water depletion patterns under monocropping and intercropping systems. ERT allowed us to access information about the vadose zone moisture dynamics that would be unavailable with classical soil moisture measurements.

Garre, S.; Coteur, I.; Wongleecharoen, C.; Diels, J.; Vanderborght, J.

2012-12-01

365

Characterization of electric vehicle velocity and power profiles using road test data  

SciTech Connect

The use of electric vehicle road test data to characterize various missions in terms of velocity time-histories and battery power profiles is discussed. The data utilized were taken on the Griffon Van at Detroit Edison using the VDAS on-board data system, which stores the data in several frequency-of-occurrence matrices. Time-based data are not available from VDAS. Construction of velocity-time cycles from the mechanical power-velocity matrices has proven to be difficult. A new VDAS, which stores the vehicle/battery data in time-based files, has been designed and built at the INEL. Bench testing of the unit is near completion and in-vehicle testing should begin in June 1989. The new VDAS utilizes the same sensors as in the original VDAS and will yield essentially the same data variables. The frequency-of-occurrence matrices can be constructed from the time-based data using a Vax 2000 workstation and commercially available software. Work is continuing on developing vehicle and battery test cycles from VDAS field data for the various missions. The availability of vehicle and battery data taken with an on-board data system permits the characterization of a variety of missions for different vehicle powertrains and batteries. Vehicle and battery designers will then have the information needed to assess the suitability of particular vehicle and battery designs for particular missions and applications. 6 refs., 8 figs., 4 tabs.

Burke, A.F.; Fink, R.K.; Richardson, R.A.; Dowgiallo, E.J. (EG and G Idaho, Inc., Idaho Falls, ID (USA); USDOE, Washington, DC (USA))

1989-01-01

366

Meso-scale measurement of the electrical spreading resistance in highly anisotropic media  

NASA Astrophysics Data System (ADS)

The spreading resistance of circular contacts with a radius in the range from 60 nm to 500 nm has been measured in highly oriented pyrolytic graphite which is known to exhibit an extremely large electrical conductance anisotropy due to the layered structure. The experimental data are compatible with a diffusive transport model characterized by an inverse scaling of the spreading resistance with contact radius with an effective resistivity of ?eff = 5.7 ± 0.3 × 10-5 ? m. Based on a scaling theory of the conduction in anisotropic media, we infer a ratio of the in-plane to out-of-plane conductance of 3.6 × 104 in agreement with literature. Accordingly, the radius of the effective area probed is on the order of 100 ?m, which is much larger than the radius of contact, whereas the penetration depth into the sample is around 1 nm to 5 nm corresponding to 3-15 graphite layers. Remarkably, no deviation from the scaling model is observed despite the fact that only a small number of graphite layers are involved in the conduction.

Koren, E.; Knoll, A. W.; Lörtscher, E.; Duerig, U.

2014-09-01

367

DC-Electrical Resistivity Imaging for embankment dike investigation: A 3D extended normalisation approach  

NASA Astrophysics Data System (ADS)

Levee, dike and earth embankment dam structures are difficult to assess because of their length and complexity. Managers often include geophysical investigations in the overall dike condition assessment and the DC-Electrical Resistivity Imaging (ERI) method is particularly applicable owing to its cost-effectiveness and its potential sensitivity to internal erosion. However, due to the truly 3D nature of embankment dikes, implementing inline longitudinal tomographies along with conventional 2D inversion is likely to yield image artefacts. 3D effects from external causes (geometry, water reservoir) can be predicted and therefore we present a new approach based on redefining the normalisation principle to derive apparent resistivities from the measured data. The aim is to provide a set of pre-processed apparent resistivities that are not contaminated by external 3D effects and that yield more reliable results when processed within a 2D conventional inversion scheme. The presented approach is successfully applied to synthetic and real data sets, proving superior to the conventional 2D approach, although data acquisition approach is the same thus keeping the same cost-effectiveness.

Fargier, Yannick; Lopes, Sérgio Palma; Fauchard, Cyrille; François, Daniel; Côte, Philippe

2014-04-01

368

Oxidation Resistant, Cr Retaining, Electrically Conductive Coatings on Metallic Alloys for SOFC Interconnects  

SciTech Connect

This report describes significant results from an on-going, collaborative effort to enable the use of inexpensive metallic alloys as interconnects in planar solid oxide fuel cells (SOFCs) through the use of advanced coating technologies. Arcomac Surface Engineering, LLC, under the leadership of Dr. Vladimir Gorokhovsky, is investigating filtered-arc and filtered-arc plasma-assisted hybrid coating deposition technologies to promote oxidation resistance, eliminate Cr volatility, and stabilize the electrical conductivity of both standard and specialty steel alloys of interest for SOFC metallic interconnect (IC) applications. Arcomac has successfully developed technologies and processes to deposit coatings with excellent adhesion, which have demonstrated a substantial increase in high temperature oxidation resistance, stabilization of low Area Specific Resistance values and significantly decrease Cr volatility. An extensive matrix of deposition processes, coating compositions and architectures was evaluated. Technical performance of coated and uncoated sample coupons during exposures to SOFC interconnect-relevant conditions is discussed, and promising future directions are considered. Cost analyses have been prepared based on assessment of plasma processing parameters, which demonstrate the feasibility of the proposed surface engineering process for SOFC metallic IC applications.

Vladimir Gorokhovsky

2008-03-31

369

Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system  

SciTech Connect

Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are semi-metals or low density of states metals. With the exception of MoSi{sub 2}, all single phase materials in this study were also found to have low temperature coefficient of resistivity(TCR) values. These values ranged from 2.10 x 10{sup {minus}10} to 4.74 x 10{sup {minus}10}{Omega}-m/{degree} C, and MoSi{sub 2} had a TCR of 13.77 x 10{sup {minus}10}{Omega}-m/{degree} C. The results from the single phase sample measurements were employed in a natural log rule-of-mixtures model to relate the individual phase resistivity values to those of multiphase composites. Three Mo-Si-B phase regions were analyzed: the binary Mo{sub 5}Si{sub 3}-MoSi{sub 2} system, the ternary phase field Mo{sub 5}Si{sub 3}B{sub x}MoB-MoSi{sub 2}, and the Mo{sub 3}Si-Mo{sub 5}SiB{sub 2}-Mo{sub 5} Si{sub 3}B{sub x} ternary region. The experimental data for samples in each of these regions agreed with the natural log model and illustrated that this model can predict the electrical resistivity as a function of temperature of multi-phase, sintered samples within an error of one standard deviation.

Beckman, Sarah E.

1999-12-10

370

Virulence and antimicrobial resistance profiles among Escherichia coli strains isolated from human and animal wastewater  

Microsoft Academic Search

To gain insight into whether Escherichia coli isolated from humans and resistant to some common antimicrobial agents are derived from animals, 85 E. coli strains were selected by ERIC-PCR from human and animal wastewater samples. Phylogroup, pathogenicity islands (PAIs), resistance to quinolones, fluoroquinolones and presence of extended-spectrum beta-lactamases (ESBLs) were analyzed. Among the total, 55% were resistant to nalidixic acid

Montserrat Sabaté; Guillem Prats; Eva Moreno; Elisenda Ballesté; Anicet R. Blanch; Antonia Andreu

2008-01-01

371

Characterization of a dismissed landfill via electrical resistivity tomography and mise-à-la-masse method  

NASA Astrophysics Data System (ADS)

Electrical resistivity methods are widely used for environmental applications, and they are particularly useful for the characterization and monitoring of sites where the presence of contamination requires a thorough understanding of the location and movement of water, that can act as a carrier of solutes. One such application is landfill studies, where the strong electrical contrasts between waste, leachate and surrounding formations make electrical methods a nearly ideal tool for investigation. In spite of the advantages, however, electrical investigation of landfills poses also challenges, both logistical and interpretational. This paper presents the results of a study conducted on a dismissed landfill, close to the city of Corigliano d'Otranto, in the Apulia region (Southern Italy). The landfill is located in an abandoned quarry, that was subsequently re-utilized about thirty years ago as a site for urban waste disposal. The waste was thought to be more than 20 m thick, and the landfill bottom was expected to be confined with an HDPE (high-density poli-ethylene) liner. During the digging operations performed to build a nearby new landfill, leachate was found, triggering an in-depth investigation including also non-invasive methods. The principal goal was to verify whether the leachate is indeed confined, and to what extent, by the HDPE liner. We performed both surface electrical resistivity tomography (ERT) and mise-à-la-masse (MALM) surveys, facing the severe challenges posed by the rugged terrain of the abandoned quarry complex. A conductive body, probably associated with leachate, was found as deep as 40 m below the current landfill surface i.e. at a depth much larger than the expected 20 m thickness of waste. Given the logistical difficulties that limit the geometry of acquisition, we utilized synthetic forward modeling in order to confirm/dismiss interpretational hypotheses emerging from the ERT and MALM results. This integration between measurements and modeling helped narrow the alternative interpretations and strengthened the confidence in results, confirming the effectiveness of non-invasive methods in landfill investigation and the importance of modeling in the interpretation of geophysical results.

De Carlo, Lorenzo; Perri, Maria Teresa; Caputo, Maria Clementina; Deiana, Rita; Vurro, Michele; Cassiani, Giorgio

2013-11-01

372

Towards improved 3D cross-borehole electrical resistivity imaging of discrete fracture networks  

NASA Astrophysics Data System (ADS)

There is a need to better characterize discrete fractures in contaminated bedrock aquifers to determine the migration of injected remediation amendments away from boreholes. A synthetic cross-borehole electrical resistivity study was conducted assuming a discrete fracture model of an existing contaminated site with known fracture locations. Four boreholes and two discrete fracture zones, assumed to be the dominant electrical and hydraulically conductive pathways, were explicitly modeled within an unstructured tetrahedral finite-element mesh. To simulate field conditions, 5% random Gaussian noise was added to all synthetic datasets. We first evaluated different regularization constraints starting with an uninformed smoothness-constrained inversion, to which a priori information was incrementally added. We found major improvements when (1) smoothness regularization constraints were relaxed (or disconnected) along boreholes and fractures, (2) a homogeneous conductivity was assumed along boreholes, and (3) borehole conductivity constraints, which could be determined from a fluid specific-conductance log, were applied. We also evaluated the effect of including borehole packers on the fracture-zone model recovery. We found the estimated fracture-zone conductivities with the inclusion of packers were comparable to similar trials excluding the use of packers regardless of electrical potential changes. The misplacement of fracture regularization disconnects easily can be misinterpreted as actual fracture locations. Conductivities within misplaced disconnects were near the starting model value and removing smoothing between boreholes and assumed fracture locations helped in identifying incorrectly located fracture regularization disconnects. Model sensitivity structure improved when regularization disconnects were (1) applied along the boreholes and fracture zones, and (2) fracture-zone regularization disconnects were placed where actual fractures existed. A field study being conducted at a contaminated fractured rock site, the Naval Air Warfare Center (NAWC) in West Trenton, New Jersey, is being used to validate our approach. Electrical resistance measurements, borehole geophysical logs and hydraulic tests are being acquired from seven, 10 cm (4 in.) boreholes to characterize fractures in the contaminated fractured rock and monitor time-lapse amendment injections to determine the amendment transport path at the field scale. Our findings, to be validated in a field study, demonstrate that structural constraints used after careful evaluation of a priori information are critical to improving imaging of fracture electrical conductivities, locations and orientations.

Robinson, J.; Slater, L. D.; Johnson, T. J.; Ntarlagiannis, D.; Lacombe, P.; Johnson, C. D.; Tiedeman, C. R.; Goode, D.; Day-Lewis, F. D.; Shapiro, A. M.; Lane, J. W.

2012-12-01

373

Electrical resistivity and Curie temperature studies on (YGdx)(Fe0.7Co0.3)2 intermetallics  

NASA Astrophysics Data System (ADS)

This paper looks at synthesis, electrical resistivity and Mössbauer effect studies on intermetallic compounds (YGdx)(Fe0.7Co0.3)2. Cubic Laves phase of MgCu2-type were observed across the series. The lattice parameters linearly increase with Gd concentration and the lattice parameters of the intermetallics series (YGdx)(Fe0.7Co0.3)2 are compared to data previously observed for the R(FeCox)2 series (R=Y, Dy, Gd) and (YGdx)M2 series (M=Fe, Co). Electrical resistivity for the (YGdx)(Fe0.7Co0.3)2 intermetallic series was measured in the temperature range 15-1100 K. Parameters characterizing the resistivity dependence on temperature were determined. Residual, phonon and magnetic resistivity were separated from the measured electrical resistivity using both the Matthiesen formula and the Bloch-Gruneisen formula. Curie temperatures of the studied series were determined using both electrical resistivity and Mössbauer effect measurements, with the Mössbauer effect measured in the temperature range around the magnetic ordering temperature. The Curie temperature increases with x. The obtained Curie temperatures for the (YGdx)(Fe0.7Co0.3)2 are similar to data known for the R(FeCox)2 series (R=Y, Dy, Gd) and (YGdx)M2 series (M=Fe, Co).

Guzdek, P.; Pszczo?a, J.; Chmist, J.; Stoch, P.; Zachariasz, P.; Onak, M.

2013-01-01

374

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

NASA Technical Reports Server (NTRS)

Ceramic matrix composites (CMC) are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems due to their low density high thermal conductivity. The employment of these materials in such applications is limited by the ability to accurately monitor and predict damage evolution. 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. CMC is a multifunctional material in which the damage is coupled with the material s electrical resistance, providing the possibility of real-time information about the damage state through monitoring of resistance. Here, resistance measurement of SiC/SiC composites under mechanical load at both room temperature monotonic and high temperature creep conditions, coupled with a modal acoustic emission technique, can relate the effects of temperature, strain, matrix cracks, fiber breaks, and oxidation to the change in electrical resistance. A multiscale model can in turn be developed for life prediction of in-service composites, based on electrical resistance methods. Results of tensile mechanical testing of SiC/SiC composites at room and high temperatures will be discussed. Data relating electrical resistivity to composite constituent content, fiber architecture, temperature, matrix crack formation, and oxidation will be explained, along with progress in modeling such properties.

Smith, Craig; Morscher, Gregory; Xia, Zhenhai

2009-01-01

375

Microgravity and Electrical Resistivity Techniques for Detection of Caves and Clandestine Tunnels  

NASA Astrophysics Data System (ADS)

The Center for Cave and Karst Studies, CCKS, has been using microgravity to locate caves from the ground's surface since 1985. The geophysical subsurface investigations began during a period when explosive and toxic vapors were rising from the karst aquifer under Bowling Green into homes, businesses, and schools. The USEPA provided the funding for this Superfund Emergency, and the CCKS was able to drill numerous wells into low-gravity anomalies to confirm and even map the route of caves in the underlying limestone bedrock. In every case, a low-gravity anomaly indicated a bedrock cave, a cave with a collapsed roof or locations where a bedrock cave had collapsed and filled with alluvium. At numerous locations, several wells were cored into microgravity anomalies and in every case, additional wells were drilled on both sides of the anomalies to confirm that the technique was in fact reliable. The wells cored on both sides of the anomalies did not intersect caves but instead intersected virtually solid limestone. Microgravity also easily detected storm sewers and even sanitary sewers, sometimes six meters (twenty feet) beneath the surface. Microgravity has also been used on many occasions to investigate sinkhole collapses. It identified potential collapse areas by detecting voids in the unconsolidated material above bedrock. The system will soon be tested over known tunnels and then during a blind test along a section of the U.S. border at Nogales, Arizona. The CCKS has experimented with other geophysical techniques, particularly ground penetrating radar, seismic and electrical resistivity. In the late 1990s the CCKS started using the Swift/Sting resistivity meter to perform karst geophysical subsurface investigations. The system provides good depth to bedrock data, but it is often difficult to interpret bedrock caves from the modeled data. The system typically used now by the CCKS to perform karst subsurface investigations is to use electrical resistivity traverses followed by microgravity over suspect areas identified on the modeled resistivity data. Some areas of high resistivity indicate caves, but others simply indicate pockets of dry limestone, and the signatures looks virtually identical. Therefore, the CCKS performs microgravity over all suspect areas along the resistivity traverses. A low-gravity anomaly that corresponds with a high-resistivity anomaly indicates a cave location. A high-resistivity anomaly that does not also have a low- gravity anomaly indicates a pocket of dry limestone. Numerous cored wells have been drilled both into the anomalies and on both sides to confirm the cave locations and to establish that the technique is accurate. The September 11, 2001 World Trade Center catastrophe was the catalyst for the formation of a program within the CCKS to use the techniques for locating bedrock caves and voids in unconsolidated materials for search and rescue and for locating clandestine tunnels. We are now into our third year of a grant from the Kentucky Science and Technology Center to develop a robot that will measure microgravity and other geophysical techniques. The robot has the potential for detecting clandestine tunnels under the U.S. border as well as military applications. The system will soon be tested over known tunnels and then during a blind test along a section of the U.S. border at Nogales, Arizona.

Crawford, N. C.; Croft, L. A.; Cesin, G. L.; Wilson, S.

2006-05-01

376

Antimicrobial resistance profiles of common mastitis pathogens on Canadian dairy farms.  

PubMed

Monitoring of antimicrobial resistance (AMR) in bacteria has clinical and public health significance. The present study determined prevalence of AMR in common mastitis pathogens Staphylococcus aureus, including methicillin-resistant Staph. aureus (MRSA; n=1,810), Escherichia coli (n=394), and Klebsiella species (n=139), including extended-spectrum ?-lactamase (ESBL)-producing E. coli and Klebsiella species, isolated from milk samples on 89 dairy farms in 6 Canadian provinces. Minimum inhibitory concentrations (MIC) were determined using the Sensititer bovine mastitis plate (Trek Diagnostic Systems Inc., Cleveland, OH) and a National Antimicrobial Resistance Monitoring System gram-negative panel containing antimicrobials commonly used for mastitis treatment and control. Denim blue chromogenic agar and real-time PCR were used to screen and confirm MRSA, respectively. Resistance proportion estimates ranged from 0% for cephalothin and oxacillin to 8.8% for penicillin in Staph. aureus isolates, and 15% of the resistant Staph. aureus isolates were multidrug resistant. One MRSA isolate was confirmed (prevalence: 0.05%). Resistance proportion estimates ranged from 0% for ceftriaxone and ciprofloxacin to 14.8% for tetracycline in E. coli, and 0% for amikacin, ceftiofur, ciprofloxacin, and nalidixic acid to 18.6% for tetracycline in Klebsiella species isolates. Further, 62.8 and 55% of the resistant E. coli and Klebsiella species isolates were multidrug resistant, respectively. Resistance to >5 and >2 antimicrobials was most common in E. coli and Klebsiella species isolates, respectively, and no ESBL producers were found. Prevalence of AMR in bovine mastitis pathogens was low. Most gram-negative udder pathogens were multidrug resistant; MRSA was rarely found, and ESBL E. coli and Klebsiella species isolates were absent in Canadian milk samples. PMID:22818446

Saini, V; McClure, J T; Léger, D; Keefe, G P; Scholl, D T; Morck, D W; Barkema, H W

2012-08-01

377

Dynamic Inversion for Hydrological Process Monitoring with Electrical Resistance Tomography Under Model Uncertainty  

SciTech Connect

We propose an approach for imaging the dynamics of complex hydrological processes. The evolution of electrically conductive fluids in porous media is imaged using time-lapse electrical resistance tomography. The related dynamic inversion problem is solved using Bayesian filtering techniques, that is, it is formulated as a sequential state estimation problem in which the target is an evolving posterior probability density of the system state. The dynamical inversion framework is based on the state space representation of the system, which involves the construction of a stochastic evolution model and an observation model. The observation model used in this paper consists of the complete electrode model for ERT, with Archie's law relating saturations to electrical conductivity. The evolution model is an approximate model for simulating flow through partially saturated porous media. Unavoidable modeling and approximation errors in both the observation and evolution models are considered by computing approximate statistics for these errors. These models are then included in the construction of the posterior probability density of the estimated system state. This approximation error method allows the use of approximate - and therefore computationally efficient - observation and evolution models in the Bayesian filtering. We consider a synthetic example and show that the incorporation of an explicit model for the model uncertainties in the state space representation can yield better estimates than a frame-by-frame imaging approach.

Lehikoinen, A.; Huttunen, J.M.J.; Finsterle, S.; Kowalsky, M.B.; Kaipio, J.P.

2009-08-01

378

Genomic analysis of drug resistant gastric cancer cell lines by combining mRNA and microRNA expression profiling.  

PubMed

Understanding the mechanism underlying multidrug resistance and identifying effective targets that can overcome it is of critical importance. In this study, mRNA and miRNA expression profiling of the drug resistant sublines, SGC7901/VCR and SGC7901/ADR, and their parental gastric cancer cell line SGC7901 were performed. A significant number of genes and a limited subset of miRNAs were commonly dysregulated, which were further validated using qRT-PCR. GO and KEGG pathway analyses of the commonly dysregulated genes indicated that the MAPK signalling pathway may be involved in multidrug resistance, which was further validated using immunoblotting and MTT assay. Finally a primary multidrug resistance network in gastric cancer, consisting of the commonly dysregulated genes and miRNAs, was established and functional miRNA-mRNA pairs were identified. The commonly dysregulated genes and miRNAs identified in this study may represent good therapeutic targets and further study of these targets may increase our understanding of the mechanisms underlying multidrug resistance. PMID:24759738

Chen, Zhangqian; Zhang, Lin; Xia, Limin; Jin, Yangsheng; Wu, Qing; Guo, Hao; Shang, Xin; Dou, Jianhua; Wu, Kaichun; Nie, Yongzhan; Fan, Daiming

2014-08-01

379

Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007  

SciTech Connect

In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear- (S) and compressional- (P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected two-dimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S- and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P- and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show clear first arrivals that we inverted, yielding a velocity model that shows lateral heterogeneity similar to the 2006 DC resistivity models. Finally, we collected P-wave data along a second transect in Area 2, located north of the first line and in an area of a very minor fault that was targeted by another 2006 DC resistivity survey. The P-wave refraction velocity model shows generally high velocities, with a zone of somewhat lower velocities in the central part of the transect. The position of the low velocity zone corresponds with the location of a minor fault, though it is unclear whether the two are related. Together, these results demonstrate the value of geophysical data for mapping the subsurface extent of faults. The 2007 DC resistivity data complement the 2006 data and provide important new detail of the overlapping fault splays. The seismic data demonstrate the ability of P-wave refraction methods to identify the damage zones at faults, and they show the difficulties associated with S-wave methods in areas with caliche. Combining all of the geophysical data from the Area 7 studies, we are able to develop a coherent interpretation of the relation between the site geology, the fault, and the observations.

Seth S. Haines; Bethany L. Burton; Donald S. Sweetkind; Theodore H. Asch

2009-03-30

380

Simulated Fuel Economy and Performance of Advanced Hybrid Electric and Plug-in Hybrid Electric Vehicles Using In-Use Travel Profiles  

SciTech Connect

As vehicle powertrain efficiency increases through electrification, consumer travel and driving behavior have significantly more influence on the potential fuel consumption of these vehicles. Therefore, it is critical to have a good understanding of in-use or 'real world' driving behavior if accurate fuel consumption estimates of electric drive vehicles are to be achieved. Regional travel surveys using Global Positioning System (GPS) equipment have been found to provide an excellent source of in-use driving profiles. In this study, a variety of vehicle powertrain options were developed and their performance was simulated over GPS-derived driving profiles for 783 vehicles operating in Texas. The results include statistical comparisons of the driving profiles versus national data sets, driving performance characteristics compared with standard drive cycles, and expected petroleum displacement benefits from the electrified vehicles given various vehicle charging scenarios.

Earleywine, M.; Gonder, J.; Markel, T.; Thornton, M.

2010-01-01

381

Electrical Resistance of Nb3Sn/Cu Splices Produced by Electromagnetic Pulse Technology and Soft Soldering  

E-print Network

The electrical interconnection of Nb3Sn/Cu strands is a key issue for the construction of Nb3Sn based damping ring wigglers and insertion devices for third generation light sources. We compare the electrical resistance of Nb3Sn/Cu splices manufactured by solid state welding using Electromagnetic Pulse Technology (EMPT) with that of splices produced by soft soldering with two different solders. The resistance of splices produced by soft soldering depends strongly on the resistivity of the solder alloy at the operating temperature. By solid state welding splice resistances below 10 nOhm can be achieved with 1 cm strand overlap length only, which is about 4 times lower than the resistance of Sn96Ag4 soldered splices with the same overlap length. The comparison of experimental results with Finite Element simulations shows that the electrical resistance of EMPT welded splices is determined by the resistance of the stabilizing copper between the superconducting filaments and confirms that welding of the strand matr...

Schoerling, D; Scheuerlein, C; Atieh, S; Schaefer, R

2011-01-01

382

Profile and prevalence of aspirin resistance in patients with cardiovascular disease  

Microsoft Academic Search

We determined the prevalence and clinical predictors of aspirin resistance by prospectively studying 325 patients with stable cardiovascular disease who were receiving aspirin (325 mg\\/day for ?7 days) but no other antiplatelet agents. We also compared the detection of aspirin resistance with optical platelet aggregation, a widely accepted method, with a newer, more rapid method, the platelet function analyzer (PFA)-100,

Patricia A Gum; Kandice Kottke-Marchant; Emilio D Poggio; Hitinder Gurm; Patricia A Welsh; Linda Brooks; Shelly K Sapp; Eric J Topol

2001-01-01

383

Transcription profile of soybean-root-knot nematode interaction reveals a key role of phythormones in the resistance reaction  

PubMed Central

Background Root-knot nematodes (RKN– Meloidogyne genus) present extensive challenges to soybean crop. The soybean line (PI 595099) is known to be resistant against specific strains and races of nematode species, thus its differential gene expression analysis can lead to a comprehensive gene expression profiling in the incompatible soybean-RKN interaction. Even though many disease resistance genes have been studied, little has been reported about phytohormone crosstalk on modulation of ROS signaling during soybean-RKN interaction. Results Using 454 technology to explore the common aspects of resistance reaction during both parasitism and resistance phases it was verified that hormone, carbohydrate metabolism and stress related genes were consistently expressed at high levels in infected roots as compared to mock control. Most noteworthy genes include those encoding glycosyltransferases, peroxidases, auxin-responsive proteins and gibberellin-regulated genes. Our data analysis suggests the key role of glycosyltransferases, auxins and components of gibberellin signal transduction, biosynthesis and deactivation pathways in the resistance reaction and their participation in jasmonate signaling and redox homeostasis in mediating aspects of plant growth and responses to biotic stress. Conclusions Based on this study we suggest a reasonable model regarding to the complex mechanisms of crosstalk between plant hormones, mainly gibberellins and auxins, which can be crucial to modulate the levels of ROS in the resistance reaction to nematode invasion. The model also includes recent findings concerning to the participation of DELLA-like proteins and ROS signaling controlling plant immune or stress responses. Furthermore, this study provides a dataset of potential candidate genes involved in both nematode parasitism and resistance, which can be tested further for their role in this biological process using functional genomics approaches. PMID:23663436

2013-01-01

384

Antimicrobial resistance, virulence genes and PFGE-profiling of Escherichia coli isolates from South Korean cattle farms.  

PubMed

To estimate the prevalence of Escherichia coli with potential pathogenicity in cattle farm in South Korea, a total of 290 E. coli isolates were isolated from cattle farms over a period of 2 years in South Korea. These were examined for phenotypic and genotypic characteristics including antimicrobial susceptibility, serotype, and gene profiles of virulence and antimicrobial resistance. The most dominant virulence gene was f17 (26.2%), followed by stx2 (15.9%), ehxA (11.0%), stx1 (8.3%), eae (5.2%), and sta (4.1%). Some shiga-toxin producing E. coli isolates possessed eae (15.9%). All isolates except for one showed resistance to one or more antimicrobials, with 152 isolates exhibiting multidrug-resistance. The most prevalent resistance phenotype detected was streptomycin (63.1%), followed by tetracycline (54.5%), neomycin (40.3%), cephalothin (32.8%), amoxicillin (30.0%), ampicillin (29.7%), and sulphamethoxazole/trimethoprim (16.6%). The associated resistance determinants detected were strA-strB (39.0%), tet(E) (80.0%), tet(A) (27.6%), aac(3)-IV (33.1%), aphA1 (21.4%), bla TEM (23.8%), and sul2 (22.1%). When investigated by O serotyping and PFGE molecular subtyping, the high degree of diversity was exhibited in E. coli isolates. These results suggest that E. coli isolates from South Korean cattle farms are significantly diverse in terms of virulence and antimicrobial resistance. In conclusion, the gastroinstestinal flora of cattle could be a significant reservoir of diverse virulence and antimicrobial resistance determinants, which is potentially hazardous to public health. PMID:25079954

Shin, Seung Won; Byun, Jae-Won; Jung, Myounghwan; Shin, Min-Kyoung; Yoo, Han Sang

2014-09-01

385