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Sample records for current enhanced point

  1. Eddy Current Testing and Four-Point Probe Measurement of - and Macromaterials Enhanced Polymeric Composites

    NASA Astrophysics Data System (ADS)

    Ko, Ray T.; Gibson, Thao; Fielding, Jennifer

    2010-02-01

    Nano- and macromaterials are being engineered into polymeric composites to enhance the electrical conductivity for lightning strike protection purposes. Electrical conductivity can be measured using a four-point probe method. Eddy current methods can provide a more localized measure of conductivity on the surface of a component. In this study, engineered composites containing both macro- and nanomaterials have been fabricated. Eddy current measurements were made on these specimens to quantify the sensitivity of this method to the relevant variables. Eddy current results in the sub-MHz frequency range agreed well with the electrical conductivity data from four-point probe measurements.

  2. Current enhancement update

    SciTech Connect

    Chambers, F.W.; Clark, J.C.; Struve, K.W.; Yu, S.S.

    1984-06-14

    Net current enhancement to levels in excess of the beam current has been observed in gases at pressures excess of 50 torr. We delineate the regimes where enhancement is observed. The experimental results fall into two very distinct classes; current enhancement at injection where the beam is only slightly displaced and current enhancement clearly associated with the high amplitude hose instability. A careful theoretical and experimental study of the diagnostics revealed no fundamental flaws although there are several complex and unlikely scenarios which could introduce fictitious current enhancement. Theoretical efforts indicate several mechanisms for generating enhancement but none of the theories can account for the detailed observations. 4 references, 4 figures.

  3. MOST CURRENT WATER QUALITY STANDARDS - POINT EVENTS

    EPA Science Inventory

    State Water Quality Standards' Designated Uses for river segments, lakes, and estuaries. Most current Water Quality Standards coded onto route.rch (Transport and Coastline Reach) feature of the National Hydrography Dataset (NHD) to create NHD - Point Events. Point events are...

  4. Cusp-points and current sheet dynamics

    NASA Astrophysics Data System (ADS)

    Vainshtein, S. I.

    1990-04-01

    Cusp points are produced in magnetic streamers of the solar corona. They may also be produced in the tail region of the earth's magnetosphere. This paper makes an analysis of such points in an equilibrium plasma. It is found that the very presence of a cusp point is inevitably associated with current sheets; these are the site of magnetic-field line reconnection. Special attention is paid to two examples. One examines a current sheet in a very much rarefield plasma (a problem formulated by Syrovatskii, 1966). The other one investigates the rosette structure of two merging magnetic islands. Analysis of the plasma behavior in the vicinity of the cusp points shows that, in the latter case, equilibrium cannot be realized. Therefore reconnection must proceed violently, at the high rates observed in numerical simulations.

  5. Current Pulses Momentarily Enhance Thermoelectric Cooling

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui

    2004-01-01

    The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum

  6. Current assessment practices for noncancer end points.

    PubMed Central

    Shoaf, C R

    1991-01-01

    The need for assessing noncancer risks for agents to which humans are routinely exposed indoors arises from the large amount of time spent indoors (i.e., employed persons spend about 60% of their time at home indoors, 30% at work indoors, and 5% in transit). Sources of air pollutants include heating and cooling systems, combustion appliances, personal use products, furnishings, tobacco products, pesticides, bioeffluents from humans and animals, and other microbial contamination such as toxins from molds. The purpose of this paper is to describe current dose-response assessment methods applicable to assessing risk following exposure to indoor air pollutants. The role of structure-activity relationships in hazard identification is also described. Risk assessments from exposure to indoor air pollutants require exposure assessments and dose-response assessments. Dose-response assessment methodologies include the inhalation reference concentration (RfC), structure-activity relationships, dose-response models, and the decision analytic approach. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. The current RfC method provides guidelines for making the necessary dosimetric adjustments for gases and aerosols. Human equivalent concentrations for no-observed-adverse-effect levels in animals are determined by using mathematical relationships that adjust for regional deposition, solubility, ventilation rate, and blood:air partition coefficients. The RfC methodology exists as an interim methodology. Future scientific advancements are expected to further refine the approach. PMID:1821364

  7. Enhancing critical current density of cuprate superconductors

    DOEpatents

    Chaudhari, Praveen

    2015-06-16

    The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

  8. Enhancing superconducting critical current by randomness

    NASA Astrophysics Data System (ADS)

    Wang, Y. L.; Thoutam, L. R.; Xiao, Z. L.; Shen, B.; Pearson, J. E.; Divan, R.; Ocola, L. E.; Crabtree, G. W.; Kwok, W. K.

    2016-01-01

    The key ingredient of high critical currents in a type-II superconductor is defect sites that pin vortices. Contrary to earlier understanding on nanopatterned artificial pinning, here we show unequivocally the advantages of a random pinscape over an ordered array in a wide magnetic field range. We reveal that the better performance of a random pinscape is due to the variation of its local density of pinning sites (LDOPS), which mitigates the motion of vortices. This is confirmed by achieving even higher enhancement of the critical current through a conformally mapped random pinscape, where the distribution of the LDOPS is further enlarged. The demonstrated key role of LDOPS in enhancing superconducting critical currents gets at the heart of random versus commensurate pinning. Our findings highlight the importance of random pinscapes in enhancing the superconducting critical currents of applied superconductors.

  9. MOST CURRENT SECTION 305(B) LISTED WATERS - POINT EVENTS

    EPA Science Inventory

    River segments, lakes, and estuaries designated under Section 305(b) of the Clean Water Act. Most Current 305(b) Waterbodies coded onto route.rch (Transport and Coastline Reach) feature of NHD to create Point Events. Point events are attached to a reach in NHD to represent assess...

  10. Enhanced precision pointing jitter suppression system

    NASA Astrophysics Data System (ADS)

    Gilmore, Jerold P.; Luniewicz, Michael F.; Sargent, Darryl

    2002-06-01

    Space based defense systems, such as a Space Based Laser (SBL), and space based surveillance systems share a common objective: extremely high resolution Line of Sight (LOS) target imaging. In order to achieve the mission objectives, their beam control subsystem must provide precise LOS pointing and tracking capabilities with suppression of LOS jitter. Draper Laboratory has developed concepts and instrumentation that address these needs based upon a stabilized inertial platform mechanization that holds a collimated light source, called the Inertial Pseudo Star Reference Unit (IPSRU). This paper describes the original IPSRU design and a design concept for a new High Performance version of the IPSRU system (HP-IPSRU) that meet the jitter stabilization needs of the SBL. The IPSRU provides an inertially stabilized optical probe beam that provides a precise pointing and tracking reference with nanoradian jitter performance. The IPSRU serves as a master reference for stabilizing imaging and weapon system pointing and tracking. This paper describes the IPSRU system, its measured error allocation and integrated performance. It presents the error budget required to achieving the 5 nrad rms jitter stabilization performance projected to be necessary for an operational Space Based Laser system. A conceptual design for the HP-IPSRU is presented.

  11. Non Pharmacological Cognitive Enhancers - Current Perspectives.

    PubMed

    Sachdeva, Ankur; Kumar, Kuldip; Anand, Kuljeet Singh

    2015-07-01

    Cognition refers to the mental processes involved in thinking, knowing, remembering, judging, and problem solving. Cognitive dysfunctions are an integral part of neuropsychiatric disorders as well as in healthy ageing. Cognitive Enhancers are molecules that help improve aspects of cognition like memory, intelligence, motivation, attention and concentration. Recently, Non Pharmacological Cognitive Enhancers have gained popularity as effective and safe alternative to various established drugs. Many of these Non Pharmacological Cognitive Enhancers seem to be more efficacious compared to currently available Pharmacological Cognitive Enhancers. This review describes and summarizes evidence on various Non Pharmacological Cognitive Enhancers such as physical exercise, sleep, meditation and yoga, spirituality, nutrients, computer training, brain stimulation, and music. We also discuss their role in ageing and different neuro-psychiatric disorders, and current status of Cochrane database recommendations. We searched the Pubmed database for the articles and reviews having the terms 'non pharmacological and cognitive' in the title, published from 2000 till 2014. A total of 11 results displayed, out of which 10 were relevant to the review. These were selected and reviewed. Appropriate cross-references within the articles along with Cochrane reviews were also considered and studied. PMID:26393186

  12. Non Pharmacological Cognitive EnhancersCurrent Perspectives

    PubMed Central

    Kumar, Kuldip; Anand, Kuljeet Singh

    2015-01-01

    Cognition refers to the mental processes involved in thinking, knowing, remembering, judging, and problem solving. Cognitive dysfunctions are an integral part of neuropsychiatric disorders as well as in healthy ageing. Cognitive Enhancers are molecules that help improve aspects of cognition like memory, intelligence, motivation, attention and concentration. Recently, Non Pharmacological Cognitive Enhancers have gained popularity as effective and safe alternative to various established drugs. Many of these Non Pharmacological Cognitive Enhancers seem to be more efficacious compared to currently available Pharmacological Cognitive Enhancers. This review describes and summarizes evidence on various Non Pharmacological Cognitive Enhancers such as physical exercise, sleep, meditation and yoga, spirituality, nutrients, computer training, brain stimulation, and music. We also discuss their role in ageing and different neuro-psychiatric disorders, and current status of Cochrane database recommendations. We searched the Pubmed database for the articles and reviews having the terms ‘non pharmacological and cognitive’ in the title, published from 2000 till 2014. A total of 11 results displayed, out of which 10 were relevant to the review. These were selected and reviewed. Appropriate cross-references within the articles along with Cochrane reviews were also considered and studied. PMID:26393186

  13. Structure of the magnetopause current layer at the subsolar point

    SciTech Connect

    Okuda, H.

    1991-12-01

    A one-dimensional electromagnetic particle simulation model developed for the magnetopause current layer between the shocked solar wind and the dipole magnetic field at the subsolar point has been extended to include the interplanetary magnetic field (IMF) in the solar wind. Interaction of the solar wind with the vacuum dipole field as well as the dipole field filled with a low density magnetospheric plasma are studied. It is found that the width and the structure of the magnetopause current layer differ markedly depending on the direction of the IMF. When the IMF is pointing southward, the current layer between the solar wind and the dipole field is narrow and the magnetic field has a single ramp structure caused by the reflection of the solar wind at that point. The current layer becomes several times wider and the magnetic field developes a multiple ramp structure when the IMF is northward. This broadening of the current layer is caused by the multiple reflection of the solar wind by the magnetic field. For the northward IMF, the magnetic field does not change its sign across the current layer so that the E {times} B drift of the solar wind electrons remains the same direction while for the southward IMF, it reverses the sign. This results in a single reflection of the solar wind for the southward IMF and multiple reflections for the northward IMF. When a low density mangetospheric plasma is present in the dipole magnetic field, a small fraction of the solar wind ions are found to penetrate into the dipole magnetic field beyond the reflection point of the solar wind electrons. The width of the ion current layer is of the order of the solar wind ion gyroradius, however, the current associated with the ions remains much smaller than the electron current so long as the density of the magnetospheric plasma is much smaller than the density of the solar wind. Comparisons of our simulation results with the magnetopause crossing near the subsolar point are provided.

  14. The critical current of point symmetric Josephson tunnel junctions

    NASA Astrophysics Data System (ADS)

    Monaco, Roberto

    2016-06-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations. The shape of the junction determines the specific form of the magnetic-field dependence of its Josephson current. Here we address the magnetic diffraction patterns of specially shaped planar Josephson tunnel junctions in the presence of an in-plane magnetic field of arbitrary orientations. We focus on a wide ensemble of junctions whose shape is invariant under point reflection. We analyze the implications of this type of isometry and derive the threshold curves of junctions whose shape is the union or the relative complement of two point symmetric plane figures.

  15. Enhancement of pumped current in quantum dots

    NASA Astrophysics Data System (ADS)

    Ramos, Juan Pablo; Foa, Luis; Apel, Victor Marcelo; Orellana, Pedro

    A direct current usually requires the application of a non-zero potential difference between source and drain, but on nanoscale systems (NSS) it is possible to obtain a non-zero current while the potential difference is zero. The effect is known as quantum charge pumping (QCP) and it is due to the interference provided by the existence of a time-dependent potential (TDP). QCP can be generated by a TDP in non-adiabatic limit. An example of this is a system composed by a ring with a dot embedded on it, under the application of an oscillating TDP. By the action of a magnetic field across the system, a pumped current is generated, since time reversal symmetry is broken. Decoherence is crucial, both from a scientific and technological point of view. In NSS it is expected that decoherence, among others things, decreases the QCP amplitude. In this context, we study what is the effect of a bath on the pumped current in our system. We find that for certain values of magnetic flux, the bath-system produce amplification of the pumped current.

  16. Edge Effects in Four Point Direct Current Potential Drop Measurement

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Bowler, John R.; Zhang, Chongxue; Bowler, Nicola

    2009-03-01

    The four point direct current potential drop (DCPD) technique is used to measure electrical conductivity and crack depth. It is also used, together with Hall voltage measurements, to evaluate carrier concentration and mobility in semiconductors. Here the theory of DCPD is studied for planar structures in which edge effects may have to be taken into account and correction made to ensure accuracy. The current injected at a point on the surface of an infinite plate of finite thickness gives rise to a field that can be expressed as a summation derived using image theory. Because the images are periodic in the direction perpendicular to the plate surface, the field can also be conveniently expressed in the form of a Fourier series. The two basic formulas; image summation and Fourier series, can be modified for the case where the probe points are near the edge of a plate by further applying image theory and summing image/Fourier terms in two dimensions. Both of these approaches agree with measurement results very well.

  17. Topographically Enhanced Subinertial Currents at Endeavour Ridge

    NASA Astrophysics Data System (ADS)

    Thomson, R. E.; Rabinovich, A. B.; Mihaly, S. F.; Veirs, S.; Stahr, F. R.; McDuff, R. E.; Subbotina, M. M.

    2001-12-01

    We use velocity records collected from moored current meters to examine the effects of seafloor topography and hydrothermal venting on near-bottom (\\~ 2000 m depth) currents flowing over the Endeavour Segment of Juan de Fuca Ridge. Focus is on the 50-m vertical resolution records collected from July-October 2000 near the main Endeavour vent field and on the 2-km lateral resolution records collected from July-October 2001 at three sites within the 100 m deep axial valley. Semidiurnal currents are found to be marginally more energetic than diurnal currents, and flow above the ridge crest is often dominated by wind-generated inertial events (periods \\~ 16 hrs at 48N) and low-frequency (O(10 day) period) clockwise rotary motions. Observations, supported by numerical modeling, reveal marked topographic amplification of subinertial motions within 100 m of the ridge crest. Motions within the diurnal, inertial, and wind-forced frequency bands undergo especially pronounced above-ridge amplification but attenuate equally rapidly within the confines of the narrow (\\~ 1 km) axial valley. Semidiurnal currents are much less affected by the ridge topography and have approximately uniform amplitudes with depth within the first 250 m of the bottom. Within a few tens of meters of the valley floor, the flow is dominated by \\~ 5 cm/s along-axis semidiurnal oscillations and a surprisingly strong (2 to 4 cm/s), persistently northward up-valley flow. The up-valley flow appears to be independent of, and generally counter to, the prevailing flow in the overlying water column. Initial findings suggest that the enhanced near-bottom flow is maintained by an along-valley pressure gradient created by turbulent entrainment of cold (\\~ 2 C) ambient water by the superheated (\\~ 350 C) hydrothermal plumes and low-temperature diffuse flow. If so, the mean-flow dynamics may be analogous to the summer sea-breeze in coastal fjords, with hydrothermal convection playing the role of summertime

  18. Mapping the current-current correlation function near a quantum critical point

    NASA Astrophysics Data System (ADS)

    Prodan, Emil; Bellissard, Jean

    2016-05-01

    The current-current correlation function is a useful concept in the theory of electron transport in homogeneous solids. The finite-temperature conductivity tensor as well as Anderson's localization length can be computed entirely from this correlation function. Based on the critical behavior of these two physical quantities near the plateau-insulator or plateau-plateau transitions in the integer quantum Hall effect, we derive an asymptotic formula for the current-current correlation function, which enables us to make several theoretical predictions about its generic behavior. For the disordered Hofstadter model, we employ numerical simulations to map the current-current correlation function, obtain its asymptotic form near a critical point and confirm the theoretical predictions.

  19. Electric Current Filamentation at a Non-potential Magnetic Null-point Due to Pressure Perturbation

    NASA Astrophysics Data System (ADS)

    Jelínek, P.; Karlický, M.; Murawski, K.

    2015-10-01

    An increase of electric current densities due to filamentation is an important process in any flare. We show that the pressure perturbation, followed by an entropy wave, triggers such a filamentation in the non-potential magnetic null-point. In the two-dimensional (2D), non-potential magnetic null-point, we generate the entropy wave by a negative or positive pressure pulse that is launched initially. Then, we study its evolution under the influence of the gravity field. We solve the full set of 2D time dependent, ideal magnetohydrodynamic equations numerically, making use of the FLASH code. The negative pulse leads to an entropy wave with a plasma density greater than in the ambient atmosphere and thus this wave falls down in the solar atmosphere, attracted by the gravity force. In the case of the positive pressure pulse, the plasma becomes evacuated and the entropy wave propagates upward. However, in both cases, owing to the Rayleigh-Taylor instability, the electric current in a non-potential magnetic null-point is rapidly filamented and at some locations the electric current density is strongly enhanced in comparison to its initial value. Using numerical simulations, we find that entropy waves initiated either by positive or negative pulses result in an increase of electric current densities close to the magnetic null-point and thus the energy accumulated here can be released as nanoflares or even flares.

  20. Underwater 3d Modeling: Image Enhancement and Point Cloud Filtering

    NASA Astrophysics Data System (ADS)

    Sarakinou, I.; Papadimitriou, K.; Georgoula, O.; Patias, P.

    2016-06-01

    This paper examines the results of image enhancement and point cloud filtering on the visual and geometric quality of 3D models for the representation of underwater features. Specifically it evaluates the combination of effects from the manual editing of images' radiometry (captured at shallow depths) and the selection of parameters for point cloud definition and mesh building (processed in 3D modeling software). Such datasets, are usually collected by divers, handled by scientists and used for geovisualization purposes. In the presented study, have been created 3D models from three sets of images (seafloor, part of a wreck and a small boat's wreck) captured at three different depths (3.5m, 10m and 14m respectively). Four models have been created from the first dataset (seafloor) in order to evaluate the results from the application of image enhancement techniques and point cloud filtering. The main process for this preliminary study included a) the definition of parameters for the point cloud filtering and the creation of a reference model, b) the radiometric editing of images, followed by the creation of three improved models and c) the assessment of results by comparing the visual and the geometric quality of improved models versus the reference one. Finally, the selected technique is tested on two other data sets in order to examine its appropriateness for different depths (at 10m and 14m) and different objects (part of a wreck and a small boat's wreck) in the context of an ongoing research in the Laboratory of Photogrammetry and Remote Sensing.

  1. Beauty is Attractive: Moduli Trapping at Enhanced Symmetry Points

    SciTech Connect

    Kofman, L

    2004-02-27

    We study quantum effects on moduli dynamics arising from the production of particles which are light at points of enhanced symmetry in moduli space. The resulting forces trap the moduli at these points. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in the presence of gravity, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of (spontaneously broken) symmetries.

  2. Adaptive image contrast enhancement algorithm for point-based rendering

    NASA Astrophysics Data System (ADS)

    Xu, Shaoping; Liu, Xiaoping P.

    2015-03-01

    Surgical simulation is a major application in computer graphics and virtual reality, and most of the existing work indicates that interactive real-time cutting simulation of soft tissue is a fundamental but challenging research problem in virtual surgery simulation systems. More specifically, it is difficult to achieve a fast enough graphic update rate (at least 30 Hz) on commodity PC hardware by utilizing traditional triangle-based rendering algorithms. In recent years, point-based rendering (PBR) has been shown to offer the potential to outperform the traditional triangle-based rendering in speed when it is applied to highly complex soft tissue cutting models. Nevertheless, the PBR algorithms are still limited in visual quality due to inherent contrast distortion. We propose an adaptive image contrast enhancement algorithm as a postprocessing module for PBR, providing high visual rendering quality as well as acceptable rendering efficiency. Our approach is based on a perceptible image quality technique with automatic parameter selection, resulting in a visual quality comparable to existing conventional PBR algorithms. Experimental results show that our adaptive image contrast enhancement algorithm produces encouraging results both visually and numerically compared to representative algorithms, and experiments conducted on the latest hardware demonstrate that the proposed PBR framework with the postprocessing module is superior to the conventional PBR algorithm and that the proposed contrast enhancement algorithm can be utilized in (or compatible with) various variants of the conventional PBR algorithm.

  3. MOST CURRENT SECTION 303(D) LISTED WATERS - POINT EVENTS

    EPA Science Inventory

    River segments, lakes, and estuaries designated under Section 303(d) of the Clean Water Act. Each State will establish Total Maximum Daily Loads (TMDLs) for these waters. Most Current 303(d) Waterbodies coded onto route.rch (Transport and Coastline Reach) feature of NHD to create...

  4. Current state of clinical end-points assessment in transplant: Key points.

    PubMed

    Hernández, Domingo; Muriel, Alfonso; Abraira, Víctor

    2016-04-01

    Solid organ transplantation is the treatment of choice for patients with end-stage organ disease. However, organ transplantation can stress the cardiovascular system and decrease immune surveillance, leading to early mortality and graft loss due to multiple underlying comorbidities. Clinical end-points in transplant include death and graft failure. Thus, generating accurate predictive models through regression models is crucial to test for definitive clinical post-transplantation end-points. Survival predictive models should assemble efficient surrogate markers or prognostic factors to generate a minimal set of variables derived from a proper modeling strategy through regression models. However, a few critical points should be considered when reporting survival analyses and regression models to achieve proper discrimination and calibration of the predictive models. Additionally, population-based risk scores may underestimate risk prediction in transplant. The application of predictive models in these patients should therefore incorporate both classical and non-classical risk factors, as well as community-based health indicators and transplant-specific factors to quantify the outcomes in terms of survival properly. This review focuses on assessment of clinical end-points in transplant through regression models by combining predictive and surrogate variables, and considering key points in these analyses to accurately predict definitive end-points, which could aid clinicians in decision making. PMID:26948088

  5. Current noise in three-terminal hybrid quantum point contacts.

    PubMed

    Wu, B H; Wang, C R; Chen, X S; Xu, G J

    2014-01-15

    We investigate the current noise of three-terminal hybrid structures at arbitrary bias voltages. Our results indicate that the noise can be a useful tool to extract dynamical information in multi-terminal hybrid structures. The zero-frequency noise is sensitive to the coupling with a normal lead. As a result, the characteristic multiple-step structure of the noise Fano factor due to multiple Andreev reflection will be suppressed as we increase this coupling. In addition, the internal dynamics due to processes of Andreev reflection and multiple Andreev reflection raises rich features in the noise spectrum corresponding to the energy differences of various dynamical processes. PMID:24305057

  6. Enhancement of Thermally Injected Spin Current through an Antiferromagnetic Insulator.

    PubMed

    Lin, Weiwei; Chen, Kai; Zhang, Shufeng; Chien, C L

    2016-05-01

    We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM/AF/YIG, with a pronounced maximum near the Néel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM/YIG interface for NM=3d, 4d, and 5d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results. PMID:27203336

  7. Enhancement of Thermally Injected Spin Current through an Antiferromagnetic Insulator

    NASA Astrophysics Data System (ADS)

    Lin, Weiwei; Chen, Kai; Zhang, Shufeng; Chien, C. L.

    2016-05-01

    We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM /AF /YIG , with a pronounced maximum near the Néel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM /YIG interface for NM =3 d , 4 d , and 5 d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results.

  8. Current data from the Kahe Point, Oahu OTEC benchmark site, June 1980-June 1981

    SciTech Connect

    Noda, E.K.

    1981-09-01

    The Kahe Point current measurement program and its results are described. Included in the appendices are data from the current measurement program, deployments 1, 2, and 3; XBT temperature profiles; and tide charts. (MHR)

  9. Material point method enhanced by modified gradient of shape function

    NASA Astrophysics Data System (ADS)

    Zhang, Duan Z.; Ma, Xia; Giguere, Paul T.

    2011-07-01

    A numerical scheme of computing quantities involving gradients of shape functions is introduced for the material point method (MPM), so that the quantities are continuous as material points move across cell boundaries. The noise and instability caused by cell crossing of the material points are then eliminated. In this scheme, the formulas used to compute these quantities can be expressed in the same forms as in the original material point method, but with the gradient of the shape function modified. For one-dimensional cases, the gradient of the shape function used in the generalized interpolation material point (GIMP) method is a special case of the modified gradient if the characteristic function of a material point is introduced. The characteristic function of a material point is not otherwise needed in this scheme, therefore difficulties in tracking its evolution are avoided. Although the support of the modified gradient of a shape function is enlarged from the cell containing the material point to also include the immediate neighbor cells, all the non-local effects of a material point can be accounted for by two consecutive local operations. Therefore this scheme can be used in calculations with unstructured grids. This scheme is proved to satisfy mass and momentum conservations exactly. The error in energy conservation is shown to be second order on both spatial and temporal discretizations. Although the error in energy conservation is the same order as that in the original material point method, numerical examples show that this scheme has significantly better energy conservation properties than those of the original material point method.

  10. Multiple-element eddy current probes for enhanced inspection

    SciTech Connect

    Clark, W.G. Jr. )

    1993-07-01

    Eddy current inspection methods are widely used for the nondestructive evaluation (NDE) of tubular products. Specifically, the sensors and instrumentation are designed to detect and characterize changes in a material's electrical and magnetic properties produced by the presence of discontinuities. A recent major enhancement in eddy current inspection technology has been the development of computer interfacing for data collection, analysis, and display. This breakthrough has led to multiple-frequency testing, eddy current imaging, and automated data interpretation systems that significantly enhance both capabilities and reliability of the eddy current inspection. In addition to the clear advantages in data processing, computer interfacing also permits the design and creation of unique sensors that further enhance eddy current inspection capabilities. Perhaps the most promising area of computer interactive probe design is multiple element sensors. Westinghouse engineers and scientists have pioneered this area of probe development. This paper describes four unique probes that illustrate the advantages of computer interactive multiple element sensors for additional eddy current inspection options.

  11. Enhancement of the Bootstrap Current in a Tokamak Pedestal

    SciTech Connect

    Kagan, Grigory; Catto, Peter J.

    2010-07-23

    The strong radial electric field in a subsonic tokamak pedestal modifies the neoclassical ion parallel flow velocity, as well as the radial ion heat flux. Existing experimental evidence of the resulting alteration in the poloidal flow of a trace impurity is discussed. We then demonstrate that the modified parallel ion flow can noticeably enhance the pedestal bootstrap current when the background ions are in the banana regime. Only the coefficient of the ion temperature gradient drive term is affected. The revised expression for the pedestal bootstrap current is presented. The prescription for inserting the modification into any existing banana regime bootstrap current expression is given.

  12. Enhancing the Impact of Quality Points in Interteaching

    ERIC Educational Resources Information Center

    Rosales, Rocío; Soldner, James L.; Crimando, William

    2014-01-01

    Interteaching is a classroom instruction approach based on behavioral principles that offers increased flexibility to instructors. There are several components of interteaching that may contribute to its demonstrated efficacy. In a prior analysis of one of these components, the quality points contingency, no significant difference was reported in…

  13. Improved micromorph tandem cell performance through enhanced top cell currents

    SciTech Connect

    Platz, R.; Vaucher, N.P.; Fischer, D.; Meier, J.; Shah, A.

    1997-12-31

    Two approaches to increasing the current in the amorphous silicon top cell of an amorphous silicon/microcrystalline silicon (a-Si:H/{micro}c-Si:H) tandem cell are presented. The goal is to raise the stabilized efficiency of such cells. The deposition of the amorphous top cell at higher than standard substrate temperature is shown to reduce the optical gap of the i-layer and to increase the current which is generated with a given i-layer thickness. Furthermore, a selectively reflecting ZnO interface layer between the component cells is presented as a viable tool for enhancing the current generation in the top cell by selective reflection of light. The authors present a micromorph tandem cell containing the amorphous top cell deposited at high substrate temperature, and additionally the ZnO mirror layer. A top cell thickness of 150 nm is shown to be sufficient to provide a current density of 13mA/cm{sup 2} in the top cell. Finally, the influence of such thin top cells on the stabilized efficiency of the tandem cell is investigated by experiment and by means of semi-empirical modeling. Model and experiment confirm that such reduced-gap top cells, together with current enhancement due to the mirror layer, have a high potential for improving the stabilized efficiency of micromorph tandem cells.

  14. Enhanced test facility for OTEC at Keahole Point

    SciTech Connect

    Hillis, D.L.; Stevens, H.C.; Panchal, C.B.

    1983-01-01

    Additional test facilities are being planned for Keahole Point, Hawaii, that would greatly increase the amounts of warm and cold water available for OTEC research and development. Present activities include the design of seawater systems and a pumping station, using the existing OTEC-1 cold-water pipe and pumps. Future options include the installation of available heat exchangers and ammonia-system equipment, the addition of a turbine generator, and facilities for open- and closed-cycle testing of components and systems.

  15. Marked point processes for enhancing seismic fault patterns

    NASA Astrophysics Data System (ADS)

    Barna, Keresztes; Szirányi, Tamás; Borda, Monica; Lavialle, Olivier

    2015-07-01

    In this paper we present a new method for fault extraction in seismic blocks, using marked point processes. Our goal is to increase the detection accuracy of the state of the art fault attributes by computing them on a system of objects based on an a priori knowledge about the faults. An original curved support has been developed to describe the faults in vertical sections of the seismic blocks. The results are compared with the previous models used for linear network extraction, such as the Candy model. Synthetic blocks were used to compare the results obtained thanks to the point processes with the classical attributes. To segment the whole blocks, a multi-2D approach was used. Several modifications of the algorithm were necessary in order to make the results easier to interpret for geologists. One interest of the high-level approach offered by the marked point processes is the possibility of using the objects as a common support for various fault detection operators. A whole detection framework can be proposed which acts like a decision fusion process.

  16. Spin current source based on a quantum point contact with local spin-orbit interaction

    SciTech Connect

    Nowak, M. P.; Szafran, B.

    2013-11-11

    Proposal for construction of a source of spin-polarized current based on quantum point contact (QPC) with local spin-orbit interaction is presented. We show that spin-orbit interaction present within the narrowing acts like a spin filter. The spin polarization of the current is discussed as a function of the Fermi energy and the width of the QPC.

  17. Development of Fault Point Locating System for Underground Transmission Lines using Optical Fiber Current Sensors

    NASA Astrophysics Data System (ADS)

    Kurosawa, Kiyoshi; Kondo, Reishi; Nasukawa, Shinsuke; Yamaguchi, Tatsushi; Amano, Kazuo

    Fault point locating systems based on surge current detection have recently been used for fast recovery of underground transmission line from the fault. Electromagnetic induction type sensors have mainly been used for detection of the surge current. However they are susceptible to electromagnetic noise which causes unstable system operation. To solve this problem, Tokyo Electric Power Co., Toko Electric Corporation and Fujikura Ltd., by a joint research, have developed a new system that applies optical fiber current sensors.

  18. Inflammatory Signals Enhance Piezo2-Mediated Mechanosensitive Currents

    PubMed Central

    Dubin, Adrienne E.; Schmidt, Manuela; Mathur, Jayanti; Petrus, Matthew J.; Xiao, Bailong; Coste, Bertrand; Patapoutian, Ardem

    2012-01-01

    Summary Heightened nociceptor function caused by inflammatory mediators such as bradykinin contributes to increased pain perception (hyperalgesia) to noxious mechanical and thermal stimuli. While sensitization of the heat transducer TRPV1 largely subserves thermal hyperalgesia, cellular mechanisms underlying mechanical hyperalgesia have been elusive. The role of the mechanically-activated (MA) channel piezo2 (known as FAM38B) present in mammalian sensory neurons is unknown. We test the hypothesis that piezo2 activity is enhanced by bradykinin, an algogenic peptide that induces mechanical hyperalgesia within minutes. Piezo2 current amplitude is increased and inactivation slowed by bradykinin 2 receptor (BDKRB2) activation in heterologous expression systems. Protein Kinase A (PKA) and Protein Kinase C (PKC) agonists enhance piezo2 activity. BDKRB2-mediated effects are abolished by PKA and PKC inhibitors. Finally, piezo2-dependent MA currents in a class of native sensory neurons are enhanced 8-fold by bradykinin via PKA and PKC. Thus, piezo2 sensitization may contribute to PKA- and PKC-mediated mechanical hyperalgesia. PMID:22921401

  19. Enhancing Working Memory Training with Transcranial Direct Current Stimulation.

    PubMed

    Au, Jacky; Katz, Benjamin; Buschkuehl, Martin; Bunarjo, Kimberly; Senger, Thea; Zabel, Chelsea; Jaeggi, Susanne M; Jonides, John

    2016-09-01

    Working memory (WM) is a fundamental cognitive ability that supports complex thought but is limited in capacity. Thus, WM training interventions have become very popular as a means of potentially improving WM-related skills. Another promising intervention that has gained increasing traction in recent years is transcranial direct current stimulation (tDCS), a noninvasive form of brain stimulation that can modulate cortical excitability and temporarily increase brain plasticity. As such, it has the potential to boost learning and enhance performance on cognitive tasks. This study assessed the efficacy of tDCS to supplement WM training. Sixty-two participants were randomized to receive either right prefrontal, left prefrontal, or sham stimulation with concurrent visuospatial WM training over the course of seven training sessions. Results showed that tDCS enhanced training performance, which was strikingly preserved several months after training completion. Furthermore, we observed stronger effects when tDCS was spaced over a weekend break relative to consecutive daily training, and we also demonstrated selective transfer in the right prefrontal group to nontrained tasks of visual and spatial WM. These findings shed light on how tDCS may be leveraged as a tool to enhance performance on WM-intensive learning tasks. PMID:27167403

  20. Current enhancement of CdTe-based solar cells

    SciTech Connect

    Paudel, Naba R.; Poplawsky, Jonathan D.; More, Karren Leslie; Yan, Yanfa

    2015-07-30

    We report on the realization of CdTe solar cell photocurrent enhancement using an n-type CdSe heterojunction partner sputtered on commercial SnO2/SnO2:F coated soda-lime glass substrates. With high-temperature close-space sublimation CdTe deposition followed by CdCl2 activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSexTe1-x alloy formation. The bowing effect causes a reduced optical bandgap of the alloyed absorber layer and, therefore, leads to current enhancement in the long-wavelength region and a decrease in open-circuit voltage (VOC). To overcome the VOC loss and maintain a high short-circuit current (JSC), the CdTe cell configuration has been modified using combined CdS:O/CdSe window layers. The new device structure has demonstrated enhanced collection from both short-and long-wavelength regions as well as a VOC improvement. With an optimized synthesis process, a small-area cell using CdS:O/CdSe window layer showed an efficiency of 15.2% with a VOC of 831 mV, a JSC of 26.3 mA/cm2, and a fill factor of 69.5%, measured under an AM1.5 illumination without antireflection coating. Furthermore, the results provide new directions for further improvement of CdTe-based solar cells.

  1. Current enhancement of CdTe-based solar cells

    DOE PAGESBeta

    Paudel, Naba R.; Poplawsky, Jonathan D.; More, Karren Leslie; Yan, Yanfa

    2015-07-30

    We report on the realization of CdTe solar cell photocurrent enhancement using an n-type CdSe heterojunction partner sputtered on commercial SnO2/SnO2:F coated soda-lime glass substrates. With high-temperature close-space sublimation CdTe deposition followed by CdCl2 activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSexTe1-x alloy formation. The bowing effect causes a reduced optical bandgap of the alloyed absorber layer and, therefore, leads to current enhancement in the long-wavelength region and a decrease in open-circuit voltage (VOC). To overcome the VOC loss and maintain a high short-circuit current (JSC), the CdTe cell configuration has been modifiedmore » using combined CdS:O/CdSe window layers. The new device structure has demonstrated enhanced collection from both short-and long-wavelength regions as well as a VOC improvement. With an optimized synthesis process, a small-area cell using CdS:O/CdSe window layer showed an efficiency of 15.2% with a VOC of 831 mV, a JSC of 26.3 mA/cm2, and a fill factor of 69.5%, measured under an AM1.5 illumination without antireflection coating. Furthermore, the results provide new directions for further improvement of CdTe-based solar cells.« less

  2. Application of point enhancement technique for ship target recognition by HRR

    NASA Astrophysics Data System (ADS)

    Cotuk, Nilufen; Ture, Sedat; Cetin, Mujdat

    2003-09-01

    We present an evaluation of the impact of a recently developed point-enhanced high range-resolution (HRR) radar profile reconstruction method on automatic target recognition (ATR) performance. We use several pattern recognition techniques to compare the performance of point-enhanced HRR profiles with conventional Fourier transform-based profiles. We use measured radar data of civilian ships and produce range profiles from such data. We use two types of classifiers to quantify recognition performance. The first type of classifier is based on the nearest neighbor technique. We demonstrate the performance of this classifier using a variety of extracted features, and a number of different distance metrics. The second classifier we use for target recognition involves position specific matrices, which have previously been used in gene sequencing. We compare the classification performance of point-enhanced HRR profiles with conventional profiles, and observe that point enhancement results in higher recognition rates in general.

  3. Subthreshold outward currents enhance temporal integration in auditory neurons.

    PubMed

    Svirskis, Gytis; Dodla, Ramana; Rinzel, John

    2003-11-01

    Many auditory neurons possess low-threshold potassium currents ( I(KLT)) that enhance their responsiveness to rapid and coincident inputs. We present recordings from gerbil medial superior olivary (MSO) neurons in vitro and modeling results that illustrate how I(KLT) improves the detection of brief signals, of weak signals in noise, and of the coincidence of signals (as needed for sound localization). We quantify the enhancing effect of I(KLT) on temporal processing with several measures: signal-to-noise ratio (SNR), reverse correlation or spike-triggered averaging of input currents, and interaural time difference (ITD) tuning curves. To characterize how I(KLT), which activates below spike threshold, influences a neuron's voltage rise toward threshold, i.e., how it filters the inputs, we focus first on the response to weak and noisy signals. Cells and models were stimulated with a computer-generated steady barrage of random inputs, mimicking weak synaptic conductance transients (the "noise"), together with a larger but still subthreshold postsynaptic conductance, EPSG (the "signal"). Reduction of I(KLT) decreased the SNR, mainly due to an increase in spontaneous firing (more "false positive"). The spike-triggered reverse correlation indicated that I(KLT) shortened the integration time for spike generation. I(KLT) also heightened the model's timing selectivity for coincidence detection of simulated binaural inputs. Further, ITD tuning is shifted in favor of a slope code rather than a place code by precise and rapid inhibition onto MSO cells (Brand et al. 2002). In several ways, low-threshold outward currents are seen to shape integration of weak and strong signals in auditory neurons. PMID:14669013

  4. The point spread function of the human head and its implications for transcranial current stimulation.

    PubMed

    Dmochowski, Jacek P; Bikson, Marom; Parra, Lucas C

    2012-10-21

    Rational development of transcranial current stimulation (tCS) requires solving the 'forward problem': the computation of the electric field distribution in the head resulting from the application of scalp currents. Derivation of forward models has represented a major effort in brain stimulation research, with model complexity ranging from spherical shells to individualized head models based on magnetic resonance imagery. Despite such effort, an easily accessible benchmark head model is greatly needed when individualized modeling is either undesired (to observe general population trends as opposed to individual differences) or unfeasible. Here, we derive a closed-form linear system which relates the applied current to the induced electric potential. It is shown that in the spherical harmonic (Fourier) domain, a simple scalar multiplication relates the current density on the scalp to the electric potential in the brain. Equivalently, the current density in the head follows as the spherical convolution between the scalp current distribution and the point spread function of the head, which we derive. Thus, if one knows the spherical harmonic representation of the scalp current (i.e. the electrode locations and current intensity to be employed), one can easily compute the resulting electric field at any point inside the head. Conversely, one may also readily determine the scalp current distribution required to generate an arbitrary electric field in the brain (the 'backward problem' in tCS). We demonstrate the simplicity and utility of the model with a series of characteristic curves which sweep across a variety of stimulation parameters: electrode size, depth of stimulation, head size and anode-cathode separation. Finally, theoretically optimal montages for targeting an infinitesimal point in the brain are shown. PMID:23001485

  5. Enhanced plasma current collection from weakly conducting solar array blankets

    NASA Technical Reports Server (NTRS)

    Hillard, G. Barry

    1993-01-01

    Among the solar cell technologies to be tested in space as part of the Solar Array Module Plasma Interactions Experiment (SAMPIE) will be the Advanced Photovoltaic Solar Array (APSA). Several prototype twelve cell coupons were built for NASA using different blanket materials and mounting techniques. The first conforms to the baseline design for APSA which calls for the cells to be mounted on a carbon loaded Kapton blanket to control charging in GEO. When deployed, this design has a flexible blanket supported around the edges. A second coupon was built with the cells mounted on Kapton-H, which was in turn cemented to a solid aluminum substrate. A final coupon was identical to the latter but used germanium coated Kapton to control atomic oxygen attack in LEO. Ground testing of these coupons in a plasma chamber showed considerable differences in plasma current collection. The Kapton-H coupon demonstrated current collection consistent with exposed interconnects and some degree of cell snapover. The other two coupons experienced anomalously large collection currents. This behavior is believed to be a consequence of enhanced plasma sheaths supported by the weakly conducting carbon and germanium used in these coupons. The results reported here are the first experimental evidence that the use of such materials can result in power losses to high voltage space power systems.

  6. Enhanced plasma current collection from weakly conducting solar array blankets

    NASA Astrophysics Data System (ADS)

    Hillard, G. Barry

    1993-05-01

    Among the solar cell technologies to be tested in space as part of the Solar Array Module Plasma Interactions Experiment (SAMPIE) will be the Advanced Photovoltaic Solar Array (APSA). Several prototype twelve cell coupons were built for NASA using different blanket materials and mounting techniques. The first conforms to the baseline design for APSA which calls for the cells to be mounted on a carbon loaded Kapton blanket to control charging in GEO. When deployed, this design has a flexible blanket supported around the edges. A second coupon was built with the cells mounted on Kapton-H, which was in turn cemented to a solid aluminum substrate. A final coupon was identical to the latter but used germanium coated Kapton to control atomic oxygen attack in LEO. Ground testing of these coupons in a plasma chamber showed considerable differences in plasma current collection. The Kapton-H coupon demonstrated current collection consistent with exposed interconnects and some degree of cell snapover. The other two coupons experienced anomalously large collection currents. This behavior is believed to be a consequence of enhanced plasma sheaths supported by the weakly conducting carbon and germanium used in these coupons. The results reported here are the first experimental evidence that the use of such materials can result in power losses to high voltage space power systems.

  7. Can we derive the current density from three point LEO measurements of the magnetic field perturbations?

    NASA Astrophysics Data System (ADS)

    Gjerloev, J. W.; Potter, M.; Muhleisen, M.; Friel, M. M.; Martin, P.; Le, G.; Stolle, C.; Luhr, H.

    2014-12-01

    In this paper, we perform critical test of the well-known curlometer technique. The curlometer technique allows a derivation of the current density using measurements of the magnetic field at spatially separated points. At LEO altitudes this generally three dimensionally problem is simplified to a two dimensions by the fact that the current is almost solely flowing along the magnetic field lines. Strictly speaking the current density is derived from integration around a closed loop but in the curlometer technique this integration is simplified to a summation over just three points. In this paper we present a critical analysis of when and to what extend this approximation is valid. We show some simple theoretical considerations, results from a series of simulations, and finally apply the knowledge to ESA SWARM measurements.

  8. Evaluation of the Transient Eddy Current Potential Drop of a Four Point Probe

    NASA Astrophysics Data System (ADS)

    Bowler, J. R.

    2009-03-01

    The transient electrical potential drop of a four point probe has been calculated for the case where a current pulse is injected into a conductive plate via two surface contact electrodes and the voltage measured between two other contact electrodes. The four contact points can be co-linear but this is not always case. For example, they can form a rectangle. Usually such probes carry direct current or alternating current and are used to measure electrical conductivity, crack dimensions or variations of conductivity and magnetic permeability with depth. However, the advantage of a current pulse excitation is that information on the variations of material properties with depth can be acquired rapidly and conveniently. What is needed is a means to infer material properties such as the conductivity variations with depth from the transient field measurements. Here, as an initial step in developing this analysis, we report on the evaluation of transient potential drop signals for four point probes on a homogeneous conductive plates.

  9. Non-equilibrium current cumulants and moments with a point-like defect

    NASA Astrophysics Data System (ADS)

    Mintchev, Mihail; Santoni, Luca; Sorba, Paul

    2016-07-01

    We derive the exact n-point current expectation values in the Landauer–Büttiker non-equilibrium steady state of a multi terminal system with star graph geometry and a point-like defect localised in the vertex. The current cumulants are extracted from the connected correlation functions and the cumulant generating function is established. We determine the moments, show that the associated moment problem has a unique solution and reconstruct explicitly the corresponding probability distribution. The basic building blocks of this distribution are the probabilities of particle emission and absorption from the heat reservoirs, driving the system away from equilibrium. We derive and analyse in detail these probabilities, showing that they fully describe the quantum transport problem in the system.

  10. Space Technology 5 Multi-Point Measurements of Auroral Field-Aligned Currents

    NASA Astrophysics Data System (ADS)

    Slavin, J. A.; Le, G.; Wang, Y.; Imber, S. M.; Strangeway, R. J.

    2009-04-01

    During its three month long technology validation mission, Space Technology 5 (ST-5) returned high quality multi-point measurements of the near-Earth magnetic field. Its three micro-satellites were launched into a 300 x 4500 km, dawn - dusk, sun synchronous orbit (inclination 105.6 deg) orbit with a period of 138 min by a Pegasus launch vehicle on March 22, 2006. The spacecraft were maintained in a "pearls on a string" constellation with controlled spacings ranging from just over 5000 km down to under 50 km. Each spacecraft carried a miniature tri-axial fluxgate magnetometer and the data allow the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured on time scales of 10 sec to 10 min. The constellation measurements are used to: 1) Determine FAC current density using the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation; 2) Measure FAC current density temporal variability over intervals up to 10 min; and 3) Determine the effect of geomagnetic activity on FAC current sheet motion and temporal variability.

  11. Limiting current enhancements for a relativistic electron beam propagating through coaxial cylinders

    SciTech Connect

    Baedke, W. C.

    2009-09-15

    An investigation of the space-charge-limited (SCL) currents for un-neutralized relativistic electron beams drifting through an infinitely long dielectrically lined coaxial cylindrical structure with a biased inner conductor is presented. To begin, an approximate limiting current expression is developed for an un-neutralized finite-width relativistic electron beam drifting through a biased coaxial cylindrical structure, which contains no dielectric liner. The SCL currents are then numerically calculated and compared to the approximation and it is shown that there is good agreement between the two. Building on this, the SCL currents are then numerically calculated when a dielectric liner, which encloses the finite-width electron beam, is present. It is shown that when a dielectric liner is present, there is a point at which increases in the SCL currents saturate and increasing the relative dielectric constant provides no additional increase in the expected SCL currents. In addition, it is demonstrated that the dielectric liner, in conjunction with the biased inner conductor, provides significant SCL current enhancements when compared to a system with no dielectric liner and no biased inner conductor. Finally, the possibility of dielectric breakdown is addressed as well as the amount of accumulated charge at the vacuum-dielectric interface.

  12. Surface enhanced Raman spectroscopy as a point-of-care diagnostic for infection in wound effluent

    NASA Astrophysics Data System (ADS)

    Ghebremedhin, Meron; Yesupriya, Shubha; Crane, Nicole J.

    2016-03-01

    In military medicine, one of the challenges in dealing with large combat-related injuries is the prevalence of bacterial infection, including multidrug resistant organisms. This can prolong the wound healing process and lead to wound dehiscence. Current methods of identifying bacterial infection rely on culturing microbes from patient material and performing biochemical tests, which together can take 2-3 days to complete. Surface Enhanced Raman Spectroscopy (SERS) is a powerful vibrational spectroscopy technique that allows for highly sensitive structural detection of analytes adsorbed onto specially prepared metal surfaces. In the past, we have been able to discriminate between bacterial isolates grown on solid culture media using standard Raman spectroscopic methods. Here, SERS is utilized to assess the presence of bacteria in wound effluent samples taken directly from patients. To our knowledge, this is the first attempt for the application of SERS directly to wound effluent. The utilization of SERS as a point-of-care diagnostic tool would enable physicians to determine course of treatment and drug administration in a matter of hours.

  13. Enhancing undergraduate community placements: a critical review of current literature.

    PubMed

    Dickson, Caroline A W; Morris, Gillian; Gable, Clare

    2015-04-01

    In the face of the UK-wide policy shift to increased home care, inspiring and enabling the next generation of community nurses is more urgent than ever. The quality of the pre-registration practice learning experience is highly influential on career choices at the point of qualification. Given that 50% of learning by pre-registration students takes place in practice, mentors have a crucial role to play in preparing the next generation of nurses to work in the community. This article discusses the findings of a systematic and critical literature review of pre-registration placements that was funded by the Queen's Nursing Institute Scotland. The review found that students' experiences of learning in community settings are variable, and perceptions of students and mentors are misaligned in terms of what a quality placement should look like. Although there is no clear definition of what constitutes a community placement and there is some underuse of learning environments in areas such as general practice nursing, there are also a number of examples of new and imaginative placements. While these innovations provide 'whole experience' placements, they are currently lacking robust evaluation, despite their potential usefulness on a larger scale. Mentors have the opportunity to provide students with a range of learning opportunities that increase preparedness for working in the community, allowing final year students in particular greater influence over their learning experience. Students undertaking community practice learning, where they have a managed level of autonomy, are more likely to feel confident to take on community nursing roles. PMID:25839877

  14. Specific characteristics of negative corona currents generated in short point-plane gap

    SciTech Connect

    Li, Zhen; Zhang, Bo; He, Jinliang

    2013-09-15

    The Trichel pulse is a typical kind of negative corona current observed in electronegative gases with a highly regular form. The characteristics of the Trichel pulse, such as the repetition frequency, the amplitude of each pulse, and the mean current, are dependent on different discharge conditions. Quite many scholars have studied the mean current and the current-voltage characteristic of Trichel pulses, yet the specific characteristics of the pulses have barely been investigated. In this paper, a series of experiments were carried out in a short point-to-plane discharge gap to investigate the detailed characteristics of Trichel pulses. After numerical fitting of the experiment results was performed, a new set of empirical formulas were derived to predict the specific characteristics of the negative corona current under different conditions. Different from existing literature, this paper uses as variables the average electric field intensity and the corona inception field intensity which is independent of the gap spacing in the empirical formulas. In the experiments, an inverse correlation between amplitude and repetition frequency of the pulses was observed. Based on the investigation of the remaining space charge in the discharge gap, this correlation is theoretically proved to be caused by the influence of space charges.

  15. Space Technology 5 Multi-Point Field-Aligned Current Measurements (Invited)

    NASA Astrophysics Data System (ADS)

    Slavin, J. A.; Le, G.; Gjerloev, J. W.

    2013-12-01

    NASA's Space Technology 5 (ST 5) microsatellite constellation technology mission was launched by a Pegasus launch vehicle on March 22, 2006. The three small (48 cm tall, 50 cm diameter, 25 kg mass, spin stabilized at 20 rpm) satellites were placid in a 300 x 4500 km, dawn to dusk, sun synchronous orbit (inclination = 105.6 deg) orbit with a period of 138 min. They were maintained in this 'pearls on a sting' formation with inter-satellite spacings ranging from over 5000 km to under 50 km. Each satellite carried a miniature tri-axial fluxgate magnetometer (MAG) provided by the University of California at Los Angeles. Field aligned currents (FACs) form in response to the stress exerted on the magnetosphere by the solar wind and act as the primary mechanism for dissipating solar wind energy into the ionosphere and upper atmosphere during the solar wind magnetosphere ionosphere coupling process. ST 5 returned the first direct, simultaneous, multipoint measurements of FAC motion, thickness, and temporal variability. Current density was measured using both 1) the 'standard method' based upon s/c velocity, but corrected for FAC current sheet motion, with the assumption of a time-stationary current density profile, and 2) for the first time at low altitudes, the 'gradiometer method' which uses simultaneous magnetic field measurements at two points with known separation. Here we review the ST 5 scientific results concerning FACs and discuss their implications for future investigations of field aligned currents systems using distributed systems of spaceborne magnetometers.

  16. Current-induced and interaction-driven Dirac point drag of massless quasirelativistic fermions

    NASA Astrophysics Data System (ADS)

    Sodemann, Inti

    2016-06-01

    We study the quasiparticle properties of two-dimensional massless Dirac fermions when the many-body states possess a finite momentum density in the clean limit. The lack of Galilean invariance endows the many-body states at finite momentum density with qualitative differences from those of the system at rest. At finite carrier densities we demonstrate the appearance of a current-induced distortion of the pseudospin texture in momentum space that can be viewed as a drag of the Dirac point and the origin of which lies entirely in electron-electron interactions. We discuss the potential observation of this effect in graphene.

  17. An Automatic K-Point Grid Generation Scheme for Enhanced Efficiency and Accuracy in DFT Calculations

    NASA Astrophysics Data System (ADS)

    Mohr, Jennifer A.-F.; Shepherd, James J.; Alavi, Ali

    2013-03-01

    We seek to create an automatic k-point grid generation scheme for density functional theory (DFT) calculations that improves the efficiency and accuracy of the calculations and is suitable for use in high-throughput computations. Current automated k-point generation schemes often result in calculations with insufficient k-points, which reduces the reliability of the results, or too many k-points, which can significantly increase computational cost. By controlling a wider range of k-point grid densities for the Brillouin zone based upon factors of conductivity and symmetry, a scalable k-point grid generation scheme can lower calculation runtimes and improve the accuracy of energy convergence. Johns Hopkins University

  18. Surface enhanced Raman spectroscopy based nanoparticle assays for rapid, point-of-care diagnostics

    NASA Astrophysics Data System (ADS)

    Driscoll, Ashley J.

    Nucleotide and immunoassays are important tools for disease diagnostics. Many of the current laboratory-based analytical diagnostic techniques require multiple assay steps and long incubation times before results are acquired. In the development of bioassays designed for detecting the emergence and spread of diseases in point-of-care (POC) and remote settings, more rapid and portable analytical methods are necessary. Nanoparticles provide simple and reproducible synthetic methods for the preparation of substrates that can be applied in colloidal assays, providing gains in kinetics due to miniaturization and plasmonic substrates for surface enhanced spectroscopies. Specifically, surface enhanced Raman spectroscopy (SERS) is finding broad application as a signal transduction method in immunological and nucleotide assays due to the production of narrow spectral peaks from the scattering molecules and the potential for simultaneous multiple analyte detection. The application of SERS to a no-wash, magnetic capture assay for the detection of West Nile Virus Envelope and Rift Valley Fever Virus N antigens is described. The platform utilizes colloid based capture of the target antigen in solution, magnetic collection of the immunocomplexes and acquisition of SERS spectra by a handheld Raman spectrometer. The reagents for a core-shell nanoparticle, SERS based assay designed for the capture of target microRNA implicated in acute myocardial infarction are also characterized. Several new, small molecule Raman scatterers are introduced and used to analyze the enhancing properties of the synthesized gold coated-magnetic nanoparticles. Nucleotide and immunoassay platforms have shown improvements in speed and analyte capture through the miniaturization of the capture surface and particle-based capture systems can provide a route to further surface miniaturization. A reaction-diffusion model of the colloidal assay platform is presented to understand the interplay of system

  19. Effective variable switching point predictive current control for ac low-voltage drives

    NASA Astrophysics Data System (ADS)

    Stolze, Peter; Karamanakos, Petros; Kennel, Ralph; Manias, Stefanos; Endisch, Christian

    2015-07-01

    This paper presents an effective model predictive current control scheme for induction machines driven by a three-level neutral point clamped inverter, called variable switching point predictive current control. Despite the fact that direct, enumeration-based model predictive control (MPC) strategies are very popular in the field of power electronics due to their numerous advantages such as design simplicity and straightforward implementation procedure, they carry two major drawbacks. These are the increased computational effort and the high ripples on the controlled variables, resulting in a limited applicability of such methods. The high ripples occur because in direct MPC algorithms the actuating variable can only be changed at the beginning of a sampling interval. A possible remedy for this would be to change the applied control input within the sampling interval, and thus to apply it for a shorter time than one sample. However, since such a solution would lead to an additional overhead which is crucial especially for multilevel inverters, a heuristic preselection of the optimal control action is adopted to keep the computational complexity at bay. Experimental results are provided to verify the potential advantages of the proposed strategy.

  20. Microwave Induced Enhancement of the Subgap Josephson dc Current

    NASA Astrophysics Data System (ADS)

    Lundin, N. I.; Shekhter, R. I.; Jonson, M.; Gorelik, L. Y.; Shumeiko, V. S.

    1998-03-01

    We introduce a mechanism for lifting the suppression of the subgap dc-Josephson current in a ballistic, normal, one-dimensional quantum channel between two superconducting electrodes with moderate amount of backscattering. The current appears when a non-equilibrium population of the Andreev levels carrying the current, is developed due to photon-induced Landua-Zener transitions.

  1. Field localization and enhancement near the Dirac point of a finite defectless photonic crystal

    NASA Astrophysics Data System (ADS)

    D'Aguanno, Giuseppe; Mattiucci, Nadia; Conti, Claudio; Bloemer, Mark J.

    2013-02-01

    We use a rigorous electromagnetic approach to show the existence of strongly localized modes in the stop band of a linear, two-dimensional, finite photonic crystal near its Dirac point. At normal incidence, the crystal exhibits a Dirac point with 100% transmission. At angles slightly off the normal, where the crystal is 100% reflective, instead of exponentially decaying fields as in a photonic stop band, the field becomes strongly localized and enhanced inside the crystal. We explain that this anomalous localization is due to guided mode resonances that are the foundation of the Dirac point itself and also shape its adjacent band gap. Besides shedding new light on the physical origin of Dirac points in finite photonic crystals, our results could have applications in many nonlinear light-matter interaction phenomena in which it is crucial to achieve a high degree of light localization.

  2. Defect enhanced funneling of diffusion current in silicon

    NASA Astrophysics Data System (ADS)

    Azimi, S.; Dang, Z. Y.; Song, J.; Breese, M. B. H.; Vittone, E.; Forneris, J.

    2013-01-01

    We report a current transport mechanism observed during electrochemical anodization of ion irradiated p-type silicon, in which a hole diffusion current is highly funneled along the gradient of modified doping profile towards the maximum ion induced defect density, dominating the total current flowing and hence the anodization behaviour. This study is characterized within the context of electrochemical anodization but relevant to other fields where any residual defect density may result in similar effects, which may adversely affect performance, such as in wafer gettering or satellite-based microelectronics. Increased photoluminescence intensity from localized buried regions of porous silicon is also shown.

  3. "PowerPoint" Is Not Just for Business Presentations and College Lectures: Using "PowerPoint" to Enhance Instruction for Students with Disabilities

    ERIC Educational Resources Information Center

    Coleman, Mari Beth

    2009-01-01

    Microsoft PowerPoint software is widely used in business and higher education and is growing in use with school-aged students. A small body of research has demonstrated that it can be effective in enhancing skill instruction for individuals with disabilities. PowerPoint is not a difficult program to learn, but it provides endless possibilities for…

  4. 75 FR 3249 - Wyeth Pharmaceuticals, a Subsidiary of Wyeth, Currently Known as Pfizer, Rouses Point, NY; Wyeth...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-20

    ... Employment and Training Administration Wyeth Pharmaceuticals, a Subsidiary of Wyeth, Currently Known as Pfizer, Rouses Point, NY; Wyeth Pharmaceuticals, a Subsidiary of Wyeth, Currently Known as Pfizer, Chazy, NY; Wyeth Pharmaceuticals, a Subsidiary of Wyeth, Currently Known as Pfizer, Plattsburgh, NY;...

  5. Point-of-care testing for respiratory viruses in adults: The current landscape and future potential.

    PubMed

    Brendish, Nathan J; Schiff, Hannah F; Clark, Tristan W

    2015-11-01

    Respiratory viruses are responsible for a large proportion of acute respiratory illness in adults as well as children, and are associated with a huge socio-economic burden worldwide. Development of accurate point-of-care tests (POCT) for respiratory viruses has been listed as a priority by the World Health Organisation and replacing the current paradigm of empirical antimicrobial use with directed use is a listed goal of the movement for reduction in antimicrobial resistance. POCTs for respiratory viruses have previously been limited by the poor sensitivity of antigen detection based tests and by a limited range of detectable viruses. Highly accurate molecular platforms are now able to test for a comprehensive range of viruses, can be operated by non-laboratory staff and can generate a result in approximately 1 h, making them potentially deployable as POCTs. The potential clinical benefits of POC testing for respiratory viruses in adults include a reduction in unnecessary antibiotic use, improved antiviral prescribing for influenza and rationalisation of isolation facilities. We review here the burden of disease, the currently available molecular platforms with potential for POCT use and the existing evidence for clinical and economic benefits of testing for respiratory viruses in adults. PMID:26215335

  6. Point-of-care testing in the diagnosis of gastrointestinal cancers: Current technology and future directions

    PubMed Central

    Huddy, Jeremy R; Ni, Melody Z; Markar, Sheraz R; Hanna, George B

    2015-01-01

    Point-of-care (POC) tests enable rapid results and are well established in medical practice. Recent advances in analytical techniques have led to a new generation of POC devices that will alter gastrointestinal diagnostic pathways. This review aims to identify current and new technologies for the POC diagnosis of gastrointestinal cancer. A structured search of the Embase and Medline databases was performed. Papers reporting diagnostic tests for gastrointestinal cancer available as a POC device or containing a description of feasibility for POC application were included. Studies recovered were heterogeneous and therefore results are presented as a narrative review. Six diagnostic methods were identified (fecal occult blood, fecal proteins, volatile organic compounds, pyruvate kinase isoenzyme type M2, tumour markers and DNA analysis). Fecal occult blood testing has a reported sensitivity of 66%-85% and specificity greater than 95%. The others are at a range of development and clinical application. POC devices have a proven role in the diagnosis of gastrointestinal cancer. Barriers to their implementation exist and the transition from experimental to clinical medicine is currently slow. New technologies demonstrate potential to provide accurate POC tests and an ability to diagnose gastrointestinal cancer at an early stage with improved clinical outcome and survival. PMID:25892860

  7. Current status of A1 adenosine receptor allosteric enhancers.

    PubMed

    Romagnoli, Romeo; Baraldi, Pier Giovanni; Moorman, Allan R; Borea, Pier Andrea; Varani, Katia

    2015-01-01

    Adenosine is an ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A1, A2A, A2B and A3 adenosine receptors (ARs). Allosteric enhancers to A1ARs may represent novel therapeutic agents because they increase the activity of these receptors by mediating a shift to their active form in the A1AR-G protein ternary complex. In this manner, they are able to amplify the action of endogenous adenosine, which is produced in high concentrations under conditions of metabolic stress. A1AR allosteric enhancers could be used as a justifiable alternative to the exogenous agonists that are characterized by receptor desensitization and downregulation. In this review, an analysis of some of the most interesting allosteric modulators of A1ARs has been reported. PMID:26144263

  8. Electrohydrodynamics of soft polyelectrolyte multilayers: point of zero-streaming current.

    PubMed

    Duval, Jérôme F L; Küttner, David; Werner, Carsten; Zimmermann, Ralf

    2011-09-01

    We report a comprehensive formalism for the electrokinetics (streaming current, I(str)) at soft multilayered polyelectrolyte films. These assemblies generally consist of a succession of permeable diffuse layers that differ in charge density, thickness, and hydrodynamic softness. The model, which extends one that we recently reported for the electrokinetics of monolayered soft thin films (Langmuir 2010, 26, 18169-18181), is valid without any restriction in the number and thickness of layers, or in the degree of dissociation and density of ionizable groups they carry. It further covers the limiting cases of hard and free draining films and correctly compares to semianalytical expressions derived for I(str) under conditions where the Debye-Hückel approximation applies. The flexibility of the theory is illustrated by simulations of I(str) for a two-layer assembly of cationic and anionic polymers over a large range of pH values and electrolyte concentrations. On this basis, it is shown that the point of zero streaming current (PZSC) of soft multilayered interphases, defined by the pH value where I(str) = 0, generally depends on the concentration of the (indifferent) electrolyte. The magnitude and direction of the shift in PZSC with varying salinity are intrinsically governed by the dissymmetry in protolytic characteristics and density of dissociable groups within each layer constituting the film, together with the respective film thickness and hydrodynamic softness. The fundamental effects covered by the theory are illustrated by streaming current measurements performed on two practically relevant systems, a polyelectrolyte bilayer prepared from poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA) and a polymer-cushioned (PEI) bilayer lipid membrane. PMID:21761889

  9. Enhanced Eddy-Current Detection Of Weld Flaws

    NASA Technical Reports Server (NTRS)

    Van Wyk, Lisa M.; Willenberg, James D.

    1992-01-01

    Mixing of impedances measured at different frequencies reduces noise and helps reveal flaws. In new method, one excites eddy-current probe simultaneously at two different frequencies; usually, one of which integral multiple of other. Resistive and reactive components of impedance of eddy-current probe measured at two frequencies, mixed in computer, and displayed in real time on video terminal of computer. Mixing of measurements obtained at two different frequencies often "cleans up" displayed signal in situations in which band-pass filtering alone cannot: mixing removes most noise, and displayed signal resolves flaws well.

  10. Detection of thin current sheets and associated reconnection in the Earth's turbulent magnetosheath using cluster multi-point measurements

    NASA Astrophysics Data System (ADS)

    Chasapis, Alexandros; Retino, Alessandro; Sahraoui, Fouad; Greco, Antonella; Vaivads, Andris; Sundkvist, David; Canu, Patrick

    2013-04-01

    Magnetic reconnection occurs in turbulent plasma within a large number of volume-filling thin current sheets and is one major candidate for energy dissipation of turbulent plasma. Such dissipation results in particle heating and non-thermal particle acceleration. In situ observations are needed to study the detailed properties of thin current sheets and associated reconnection, in order to determine its importance as a dissipation mechanism at small scales. In particular, multi-point measurements are crucial to unambiguously identify spatial scales (e.g current sheet thickness) and estimate key quantities such as E*J. Here we present a study of the properties of thin current sheets detected in the Earths magnetosheath downstream of the quasi-parallel shock by using Cluster spacecraft data. The current sheets were detected by the rotation of the magnetic field as computed by four-point measurements. We study the distribution of current sheets as a function of the magnetic shear angle θ, their duration and the waiting time between consecutive current sheets. We found that high shear (θ > 90 degrees) current sheets show different properties with respect to low shear current sheets (θ < 90 degrees). These high-shear current sheets account for about ˜ 20% of the total and have an average thickness comparable to the ion inertial length. We also compare our four-point detection method with other single-point methods (e.g. Partial Variance of Increments - PVI) and we discuss the results of such comparison.

  11. Current developments using emerging transdermal technologies in physical enhancement methods.

    PubMed

    Nanda, A; Nanda, S; Ghilzai, N M Khan

    2006-07-01

    Transdermal drug delivery using patches offers many advantages, but is limited primarily by the stratum corneum barrier. Amongst the various methods to overcome this barrier, physical methods are gaining in popularity and commercial devices development. Macroflux, MTS and Silex are based on microporation, involving use of microneedles that pierce thereby bypassing the stratum corneum. Intraject , Powderject and Helios are based on needleless jet injectors wherein very fine, solid particulate drug, is fired directly into the skin, using high-pressure gas. Med- Tats incorporate use of modified drug-containing tattoos, which bind to the skin, wherein the drug is absorbed. CHADD is based on use of heat, which increases skin - permeation of drugs. High-power, pulsed lasers transmit positive mechanical forces to the skin and create intercellular channels into the skin transiently. Sonophoresis involves use of ultrasound, which transiently disrupts the stratum corneum barrier. This technique offers a non-invasive transdermal extraction of interstitial fluids of sampling body fluids. Modified Liposomes include Ethosomes (containing alcohol) and Transferosomes (containing surfactants), which have enhanced skin permeability. Pulsed magnetic fields may create transient pores in cell membranes, including skin, resulting in increased permeation. Iontophoresis is based on application of electric potential for enhancing the movement of substances to and from the body. Dupel, Ionzyme, Liposite, ETrans, Phoresor and Drionic are based on iontophoresis. GlucoWatch offers non-invasive blood glucose monitoring, based on reverse iontophoresis. This review outlines recent commercial developments in physical transdermal drug delivery technology and the specific devices and applications being targeted by the pharmaceutical industry. PMID:16848725

  12. Multi-point Magnetic Field Observations of Field-Aligned Currents from Swarm Constellation Mission

    NASA Astrophysics Data System (ADS)

    Le, Guan; Chi, Peter; Lühr, Hermann; Gjerloev, Jesper; Stolle, Claudia; Park, Jaeheung; Rauberg, Jan

    2015-04-01

    In this paper, we report the results of case studies of multi-point magnetic field measurements of field-aligned currents (FACs) from Swarm constellation mission to understand their temporal characteristics and hemispheric asymmetry. For science operations (since April, 2014), the three spacecraft were placed in slightly different polar orbits: Swarm B spacecraft in a higher altitude orbit (507km x 512km) and Swarm A and C side-by-side in lower altitude orbits (459km x 462km). In the beginning of the science operational phase, the longitudinal separations of the orbital planes were small, and Swarm A/C pair and Swarm B were nearly out of phase in the orbit. This unique orbit configuration provides opportunities to study some new features of FACs. Specifically, the Swarm satellites make multiple crossings of a FAC region within a few hours. Such data enable us to study temporal variations in several time scales, from 1 minute up to about 3 hours. Furthermore, the three satellites make nearly simultaneous observations of FACs in northern and southern hemispheres, which provide us an opportunity to study the hemispheric asymmetry.

  13. The Goddard Integral Field Spectrograph at Apache Point Observatory: Current Status and Progress Towards Photon Counting

    NASA Astrophysics Data System (ADS)

    McElwain, Michael W.; Grady, Carol A.; Bally, John; Brinkmann, Jonathan V.; Bubeck, James; Gong, Qian; Hilton, George M.; Ketzeback, William F.; Lindler, Don; Llop Sayson, Jorge; Malatesta, Michael A.; Norton, Timothy; Rauscher, Bernard J.; Rothe, Johannes; Straka, Lorrie; Wilkins, Ashlee N.; Wisniewski, John P.; Woodgate, Bruce E.; York, Donald G.

    2015-01-01

    We present the current status and progress towards photon counting with the Goddard Integral Field Spectrograph (GIFS), a new instrument at the Apache Point Observatory's ARC 3.5m telescope. GIFS is a visible light imager and integral field spectrograph operating from 400-1000 nm over a 2.8' x 2.8' and 14' x 14' field of view, respectively. As an IFS, GIFS obtains over 1000 spectra simultaneously and its data reduction pipeline reconstructs them into an image cube that has 32 x 32 spatial elements and more than 200 spectral channels. The IFS mode can be applied to a wide variety of science programs including exoplanet transit spectroscopy, protostellar jets, the galactic interstellar medium probed by background quasars, Lyman-alpha emission line objects, and spectral imaging of galactic winds. An electron-multiplying CCD (EMCCD) detector enables photon counting in the high spectral resolution mode to be demonstrated at the ARC 3.5m in early 2015. The EMCCD work builds upon successful operational and characterization tests that have been conducted in the IFS laboratory at NASA Goddard. GIFS sets out to demonstrate an IFS photon-counting capability on-sky in preparation for future exoplanet direct imaging missions such as the AFTA-Coronagraph, Exo-C, and ATLAST mission concepts. This work is supported by the NASA APRA program under RTOP 10-APRA10-0103.

  14. Current-induced enhancement of DNA bubble creation

    NASA Astrophysics Data System (ADS)

    Gu, Lei; Fu, Hua-Hua

    2016-05-01

    Current-induced heating of short double-stranded DNA chains is studied within a two-probe transport setup by using the Langevin approach. The electrons are modeled by a tight-binding Hamiltonian. The DNA atomic motion is described by the Peyrard–Bishop–Dauxois atomic potential, coupled with electrons through the Holstein interaction. The solvent environment is accounted for as a classical heat bath. Voltage biases of 0.1∼ 0.5 {{V}} can effectively break the base pairs and lead to the melting transition, which can be detected from the resulting significant reduction of the conductance. When the bias increases, the opening of base pairs near the leads with higher chemical potential is suppressed and bubble (localized separation of the double strand) formation becomes asymmetric. Our results suggest that the voltage bias can excite the base pairs, hence increases the chemical activity of DNA.

  15. The EuroSITES network: Integrating and enhancing fixed-point open ocean observatories around Europe

    NASA Astrophysics Data System (ADS)

    Lampitt, Richard S.; Larkin, Kate E.; EuroSITES Consortium

    2010-05-01

    EuroSITES is a 3 year (2008-2011) EU collaborative project (3.5MEuro) with the objective to integrate and enhance the nine existing open ocean fixed point observatories around Europe (www.eurosites.info). These observatories are primarily composed of full depth moorings and make multidisciplinary in situ observations within the water column as the European contribution to the global array OceanSITES (www.oceansites.org). In the first 18 months, all 9 observatories have been active and integration has been significant through the maintenance and enhancement of observatory hardware. Highlights include the enhancement of observatories with sensors to measure O2, pCO2, chlorophyll, and nitrate in near real-time from the upper 1000 m. In addition, some seafloor missions are also actively supported. These include seafloor platforms currently deployed in the Mediterranean, one for tsunami detection and one to monitor fluid flow related to seismic activity and slope stability. Upcoming seafloor science missions in 2010 include monitoring benthic biological communities and associated biogeochemistry as indicators of climate change in both the Northeast Atlantic and Mediterranean. EuroSITES also promotes the development of innovative sensors and samplers in order to progress capability to measure climate-relevant properties of the ocean. These include further developing current technologies for autonomous long-term monitoring of oxygen consumption in the mesopelagic, pH and mesozooplankton abundance. Many of these science missions are directly related to complementary activities in other European projects such as EPOCA, HYPOX and ESONET. In 2010 a direct collaboration including in situ field work will take place between ESONET and EuroSITES. The demonstration mission MODOO (funded by ESONET) will be implemented in 2010 at the EuroSITES PAP observatory. Field work will include deployment of a seafloor lander system with various sensors which will send data to shore in real

  16. Imaging of biophoton emission from electrostimulated skin acupuncture point jg4: effect of light enhancers.

    PubMed

    Slawinski, Janusz; Gorski, Zbigniew

    2008-05-01

    Using an ultrasensitive CCD camera, an extremely low light intensity from the acupuncture-sensitive point JG4 at the left hand was recorded. As the intensity of the light was very weak and the time of electrostimulation exceeded the recommended period, the quality of biophoton images was poor. Chemiluminescent and fluorescent hydrophilic, hydrophobic and amphyphilic molecular probes were used to: (i) ensure penetration of probes into skin, (ii) enhance the intensity of BP emission, (iii) shorten time and (iv) obtain information about mechanisms of biophotons generation in EAP-sensitive points and channels. The results obtained partially fulfilled expectations and indicate on the necessity to elaborate special techniques of probes deposition on the skin. PMID:18697617

  17. Upper transition point for percolation on the enhanced binary tree: A sharpened lower bound

    NASA Astrophysics Data System (ADS)

    Baek, Seung Ki

    2012-05-01

    Hyperbolic structures are obtained by tiling a hyperbolic surface with negative Gaussian curvature. These structures generally exhibit two percolation transitions: a system-wide connection can be established at a certain occupation probability p=pc1, and there emerges a unique giant cluster at pc2>pc1. There have been debates about locating the upper transition point of a prototypical hyperbolic structure called the enhanced binary tree (EBT), which is constructed by adding loops to a binary tree. This work presents its lower bound as pc2≳0.55 by using phenomenological renormalization-group methods and discusses some solvable models related to the EBT.

  18. Enhancing the mirror illusion with transcranial direct current stimulation.

    PubMed

    Jax, Steven A; Rosa-Leyra, Diana L; Coslett, H Branch

    2015-05-01

    Visual feedback has a strong impact on upper-extremity movement production. One compelling example of this phenomena is the mirror illusion (MI), which has been used as a treatment for post-stroke movement deficits (mirror therapy). Previous research indicates that the MI increases primary motor cortex excitability, and this change in excitability is strongly correlated with the mirror's effects on behavioral performance of neurologically-intact controls. Based on evidence that primary motor cortex excitability can also be increased using transcranial direct current stimulation (tDCS), we tested whether bilateral tDCS to the primary motor cortices (anode right-cathode left and anode left-cathode right) would modify the MI. We measured the MI using a previously-developed task in which participants make reaching movements with the unseen arm behind a mirror while viewing the reflection of the other arm. When an offset in the positions of the two limbs relative to the mirror is introduced, reaching errors of the unseen arm are biased by the reflected arm's position. We found that active tDCS in the anode right-cathode left montage increased the magnitude of the MI relative to sham tDCS and anode left-cathode right tDCS. We take these data as a promising indication that tDCS could improve the effect of mirror therapy in patients with hemiparesis. PMID:25796410

  19. Enhanced current noise correlations in a Coulomb-Majorana device

    NASA Astrophysics Data System (ADS)

    Lü, Hai-Feng; Lu, Hai-Zhou; Shen, Shun-Qing

    2016-06-01

    Majorana bound states (MBSs) nested in a topological nanowire are predicted to manifest nonlocal correlations in the presence of a finite energy splitting between the MBSs. However, the signal of the nonlocal correlations has not yet been detected in experiments. A possible reason is that the energy splitting is too weak and seriously affected by many system parameters. Here we investigate the charging energy induced nonlocal correlations in a hybrid device of MBSs and quantum dots. The nanowire that hosts the MBSs is assumed in proximity to a mesoscopic superconducting island with a finite charging energy. Each end of the nanowire is coupled to one lead via a quantum dot with resonant levels. With a floating superconducting island, the devices show a negative differential conductance and giant super-Poissonian shot noise, due to the interplay between the nonlocality of the MBSs and dynamical Coulomb blockade effect. When the island is strongly coupled to a bulk superconductor, the current cross correlations at small lead chemical potentials are negative by tuning the dot energy levels. In contrast, the cross correlation is always positive in a non-Majorana setup. This difference may provide a signature for the existence of the MBSs.

  20. Pipette-surface interaction: current enhancement and intrinsic force.

    PubMed

    Clarke, Richard W; Zhukov, Alexander; Richards, Owen; Johnson, Nicholas; Ostanin, Victor; Klenerman, David

    2013-01-01

    There is an intrinsic repulsion between glass and cell surfaces that allows noninvasive scanning ion conductance microscopy (SICM) of cells and which must be overcome in order to form the gigaseals used for patch clamping investigations of ion channels. However, the interactions of surfaces in physiological solutions of electrolytes, including the presence of this repulsion, for example, do not obviously agree with the standard Derjaguin-Landau-Verwey-Overbeek (DLVO) colloid theory accurate at much lower salt concentrations. In this paper we investigate the interactions of glass nanopipettes in this high-salt regime with a variety of surfaces and propose a way to resolve DLVO theory with the results. We demonstrate the utility of this understanding to SICM by topographically mapping a live cell's cytoskeleton. We also report an interesting effect whereby the ion current though a nanopipette can increase under certain conditions upon approaching an insulating surface, rather than decreasing as would be expected. We propose that this is due to electroosmotic flow separation, a high-salt electrokinetic effect. Overall these experiments yield key insights into the fundamental interactions that take place between surfaces in strong solutions of electrolytes. PMID:23210472

  1. Polypeptide Point Modifications with Fatty Acid and Amphiphilic Block Copolymers for Enhanced Brain Delivery

    PubMed Central

    Batrakova, Elena V.; Vinogradov, Serguei V.; Robinson, Sandra M.; Niehoff, Michael L.; Banks, William A.; Kabanov, Alexander V.

    2009-01-01

    There is a tremendous need to enhance delivery of therapeutic polypeptides to the brain to treat disorders of the central nervous system (CNS). The brain delivery of many polypeptides is severely restricted by the blood—brain barrier (BBB). The present study demonstrates that point modifications of a BBB-impermeable polypeptide, horseradish peroxidase (HRP), with lipophilic (stearoyl) or amphiphilic (Pluronic block copolymer) moieties considerably enhance the transport of this polypeptide across the BBB and accumulation of the polypeptide in the brain in vitro and in vivo. The enzymatic activity of the HRP was preserved after the transport. The modifications of the HRP with amphiphilic block copolymer moieties through degradable disulfide links resulted in the most effective transport of the HRP across in vitro brain microvessel endothelial cell monolayers and efficient delivery of HRP to the brain. Stearoyl modification of HRP improved its penetration by about 60% but also increased the clearance from blood. Pluronic modification using increased penetration of the BBB and had no significant effect on clearance so that uptake by brain was almost doubled. These results show that point modification can improve delivery of even highly impermeable polypeptides to the brain. PMID:16029020

  2. Using sorbent waste materials to enhance treatment of micro-point source effluents by constructed wetlands

    NASA Astrophysics Data System (ADS)

    Green, Verity; Surridge, Ben; Quinton, John; Matthews, Mike

    2014-05-01

    Sorbent materials are widely used in environmental settings as a means of enhancing pollution remediation. A key area of environmental concern is that of water pollution, including the need to treat micro-point sources of wastewater pollution, such as from caravan sites or visitor centres. Constructed wetlands (CWs) represent one means for effective treatment of wastewater from small wastewater producers, in part because they are believed to be economically viable and environmentally sustainable. Constructed wetlands have the potential to remove a range of pollutants found in wastewater, including nitrogen (N), phosphorus (P), biochemical oxygen demand (BOD) and carbon (C), whilst also reducing the total suspended solids (TSS) concentration in effluents. However, there remain particular challenges for P and N removal from wastewater in CWs, as well as the sometimes limited BOD removal within these treatment systems, particularly for micro-point sources of wastewater. It has been hypothesised that the amendment of CWs with sorbent materials can enhance their potential to treat wastewater, particularly through enhancing the removal of N and P. This paper focuses on data from batch and mesocosm studies that were conducted to identify and assess sorbent materials suitable for use within CWs. The aim in using sorbent material was to enhance the combined removal of phosphate (PO4-P) and ammonium (NH4-N). The key selection criteria for the sorbent materials were that they possess effective PO4-P, NH4-N or combined pollutant removal, come from low cost and sustainable sources, have potential for reuse, for example as a fertiliser or soil conditioner, and show limited potential for re-release of adsorbed nutrients. The sorbent materials selected for testing were alum sludge from water treatment works, ochre derived from minewater treatment, biochar derived from various feedstocks, plasterboard and zeolite. The performance of the individual sorbents was assessed through

  3. Point splitting renormalization of Schwinger induced current in de Sitter spacetime

    NASA Astrophysics Data System (ADS)

    Hayashinaka, Takahiro; Yokoyama, Jun'ichi

    2016-07-01

    The covariant and gauge invariant calculation of the current expectation value in the homogeneous electric field in 1+3 dimensional de Sitter spacetime is shown. The result accords with previous work obtained by using adiabatic subtraction scheme. We therefore conclude the counterintuitive behaviors of the current in the infrared (IR) regime such as IR hyperconductivity and negative current are not artifacts of the renormalization scheme, but are real IR effects of the spacetime.

  4. Phase-shifting point diffraction interferometer focus-aid enhanced mask

    DOEpatents

    Naulleau, Patrick

    2000-01-01

    A phase-shifting point diffraction interferometer system (PS/PDI) employing a PS/PDI mask that includes a PDI focus aid is provided. The PDI focus aid mask includes a large or secondary reference pinhole that is slightly displaced from the true or primary reference pinhole. The secondary pinhole provides a larger capture tolerance for interferometrically performing fine focus. With the focus-aid enhanced mask, conventional methods such as the knife-edge test can be used to perform an initial (or rough) focus and the secondary (large) pinhole is used to perform interferometric fine focus. Once the system is well focused, high accuracy interferometry can be performed using the primary (small) pinhole.

  5. Prospects for point-of-care pathogen diagnostics using surface-enhanced Raman scattering (SERS).

    PubMed

    Granger, Jennifer H; Schlotter, Nicholas E; Crawford, Alexis C; Porter, Marc D

    2016-07-11

    Surface-enhanced Raman scattering (SERS) has enabled the detection of pathogens and disease markers at extremely low levels. This review examines the potential impact of SERS in addressing unmet needs in pathogen diagnostics both in a traditional clinical setting and in the point of care (POC) arena. It begins by describing the strengths and weaknesses of today's diagnostics technologies in order to set a contextual stage for an overview which highlights a few of the many recent developments using SERS in biodefense, human and animal health, and monitoring food and water safety. These sections are followed by discussions of the challenges for the translation of these developments to POC settings, including the performance attributes and metrics for quantification of analytical and clinical figures of merit (e.g., limit of detection and clinical accuracy), and the pathways for large-scale test validation and the build-out of instrumentation and tests kits for POC deployment. PMID:27048939

  6. Enhancing generalisation in biofeedback intervention using the challenge point framework: A case study

    PubMed Central

    HITCHCOCK, ELAINE R.; BYUN, TARA McALLISTER

    2014-01-01

    Biofeedback intervention can help children achieve correct production of a treatment-resistant error sound, but generalisation is often limited. This case study suggests that generalisation can be enhanced when biofeedback intervention is structured in accordance with a “challenge point” framework for speech-motor learning. The participant was an 11-year-old with residual /r/ misarticulation who had previously attained correct /r/ production through a structured course of ultrasound biofeedback treatment but did not generalise these gains beyond the word level. Treatment difficulty was adjusted in an adaptive manner following predetermined criteria for advancing, maintaining, or moving back a level in a multidimensional hierarchy of functional task complexity. The participant achieved and maintained virtually 100% accuracy in producing /r/ at both word and sentence levels. These preliminary results support the efficacy of a semi-structured implementation of the challenge point framework as a means of achieving generalisation and maintenance of treatment gains. PMID:25216375

  7. Current Structure and Nonideal Behavior at Magnetic Null Points in the Turbulent Magnetosheath

    NASA Technical Reports Server (NTRS)

    Wendel, D. E.; Adrian, M. L.

    2013-01-01

    The Poincaré index indicates that the Cluster spacecraft tetrahedron entraps a number of 3-D magnetic nulls during an encounter with the turbulent magnetosheath. Previous researchers have found evidence for reconnection at one of the many filamentary current layers observed by Cluster in this region. We find that many of the entrained nulls are also associated with strong currents. We dissect the current structure of a pair of spiral nulls that may be topologically connected. At both nulls, we find a strong current along the spine, accompanied by a somewhat more modest current perpendicular to the spine that tilts the fan toward the axis of the spine. The current along the fan is comparable to the that along the spine. At least one of the nulls manifests a rotational flow pattern in the fan plane that is consistent with torsional spine reconnection as predicted by theory. These results emphasize the importance of examining the magnetic topology in interpreting the nature of currents and reconnection in 3-D turbulence.

  8. Enhancement of binding kinetics on affinity substrates by laser point heating induced transport.

    PubMed

    Wang, Bu; Cheng, Xuanhong

    2016-03-01

    Enhancing the time response and detection limit of affinity-binding based biosensors is an area of active research. For diffusion limited reactions, introducing active mass transport is an effective strategy to reduce the equilibration time and improve surface binding. Here, a laser is focused on the ceiling of a microchamber to generate point heating, which introduces natural advection and thermophoresis to promote mass transport to the reactive floor. We first used the COMSOL simulation to study how the kinetics of ligand binding is influenced by the optothermal effect. Afterwards, binding of biotinylated nanoparticles to NeutrAvidin-treated substrates is quantitatively measured with and without laser heating. It is discovered that laser induced point heating reduces the reaction half-life locally, and the reduction improves with the natural advection velocity. In addition, non-uniform ligand binding on the substrate is induced by the laser with predictable binding patterns. This optothermal strategy holds promise to improve the time-response and sensitivity of biosensors and microarrays. PMID:26898559

  9. Methadone, QTc prolongation and torsades de pointes: Current concepts, management and a hidden twist in the tale?

    PubMed Central

    Mujtaba, Sobia; Romero, Jorge; Taub, Cynthia C.

    2013-01-01

    Methadone is a drug that has found widespread utility in the management of opioid addiction and pain. Along with its popularity, methadone has also earned an infamous reputation for causing prolongation of the QT interval and an increased risk of torsades de pointes. In this article we will give a brief overview of the long QT syndromes, followed by an in-depth look at the current pathophysiologic mechanisms of methadone induced QT prolongation, a review of the existing literature and the current concepts regarding the prevention and management of methadone induced torsades de pointes. In addition, we explore the idea and implications of a genetic link between methadone induced prolongation of the QT interval and torsades de pointes. PMID:24653586

  10. Cathodic current enhancement via manganese and oxygen related reactions in marine biofilms

    NASA Astrophysics Data System (ADS)

    Strom, Matthew James

    Corrosion is a threat that has economic, and environmental impacts worldwide. Many types of corrosive attack are the subject of ongoing research. One of these areas of research is microbiologically influenced corrosion, which is the enhancement and/or initiation of corrosion events caused by microorganisms. It is well known that colonies of microorganisms can enhance cathodic currents through biofilm formation. The aim of the present work was to elucidate the role of manganese in enhancing cathodic currents in the presence of biofilms. Repeated polarizations conducted in Delaware Bay waters, on biofilm coated Cr identified potentially sustainable reduction reactions. The reduction of MnO2 and the enhancement of the oxygen reduction reaction (ORR) were proven to be factors that influence cathodic current enhancement. The removal of ambient oxygen during polarizations resulted in a shutdown of cathodic current enhancement. These field data led to an exploration of the synergistic relationship between MnO2 and the ORR. Laboratory studies of the catalysis of peroxide disproportionation by MnO2 were monitored using a hanging mercury drop electrode. Experiments were run at an ambient sweater pH of 8 and pH 9, which simulated the near-surface conditions typical of cathodes immersed in seawater. Rapid reoxidation at the more basic pH was shown to allow manganese to behave as a persistent catalyst under the typical electrochemical surface conditions of a cathode. As a result a mechanism for ORR enhancement by manganese was proposed as a unique mechanism for cathodic current enhancement in biofilms. A separate field study of Delaware biofilms on stainless steel coupled to a sacrificial Al anode was carried out to identify the ORR enhancement mechanism and sustainable redox reactions at the cathode. Chemical treatments of glutaraldehyde and formaldoxime were applied to cathodes with biofilms to distinguish between enzymatic and MnO2 related ORR enhancement. The results ruled

  11. Surrogate end-point biomarker analysis in a retinol chemoprevention trial in current and former smokers with bronchial dysplasia.

    PubMed

    Lam, Stephen; Xu, Xiaochun; Parker-Klein, Helga; Le Riche, Jean C; Macaulay, Calum; Guillaud, Martial; Coldman, Andy; Gazdar, Adi; Lotan, Reuben

    2003-12-01

    Epidemiological studies suggested that vitamin A may be protective against lung cancer, however, recent chemoprevention trials with beta-carotene, a precursor of vitamin A, demonstrated enhancement of lung carcinogenesis among smokers. Whether vitamin A is beneficial or harmful in chemoprevention of lung cancer in smokers has not been resolved. This study was designed to determine the effect of retinol alone in current and former smokers using bronchial dysplasia, nuclear morphometry and retinoic acid receptor-beta (RAR-beta) mRNA expression as surrogate end-point biomarkers (SEBs). Eighty-one current or former smokers with a smoking history of >/=30 pack-years were randomized to receive either placebo or retinol (50,000 IU per day) for six months. Fluorescence bronchoscopy was performed prior to treatment to localize areas suggestive of dysplasia. At least 4 bronchial biopsies were taken per subject including at least two biopsies from apparently normal areas. The same areas were precisely re-biopsied after 6 months. Any new areas suggestive of dysplasia were also biopsied. Changes in the SEBs were assessed before and after treatment. At baseline, the frequency of biopsies negative for RAR-beta expression was: normal (23%), hyperplasia (28%), metaplasia (41%), mild dysplasia (41%), and moderate/severe dysplasia (44%). There was no significant difference in the regression rate between the retinol and placebo groups using histopathology and nuclear morphometry as SEBs. The likelihood of regression was found to be lower in those who continued to smoke during the study (OR=1.86 for those smoking >10 cigarettes per day, p=0.084 to OR=0.95, p=0.26 for those smoking 20+ per day compared to ex-smokers). Retinol was not effective in the up-regulation of RAR-beta in lesions with bronchial dysplasia. We postulate that the lack of effect of retinol on RAR-beta expression among individuals who continued to smoke while taking retinol may be due to suppressive effect of tobacco

  12. Current measurements off Keahole Point, Hawaii: application to OTEC-1 ocean test platform

    SciTech Connect

    Harms, V.W.

    1981-06-01

    Detailed current measurements from the OTEC-1 vessel permits a preliminary analysis to be made of current induced hydrodynamic loads on the cold water pipe and hydrodynamic mixing along the trajectory of the mixed sea-water plume. The measured equilibrium depth of the plume agrees well with that predicted by the plume model and occurs near the base of the ocean mixed layer. Ocean turbulence is found to provide some mixing. Several possible causes for excessive hydrodynamic loading on the cold water pipe are enumerated. (LEW)

  13. Phonon-induced enhancements of the energy gap and critical current in superconducting aluminum

    SciTech Connect

    Seligson, D.

    1983-05-01

    8 to 10 GHz phonons were generated by piezoelectric transduction of a microwave and by means of a quartz delay line, were allowed to enter the aluminum only after the microwaves had long since disappeared. The maximum enhancements detected were (deltaT/T/sub c/) = -0.07, for i/sub c/ and (deltaT/T/sub c/) = -0.03 for ..delta... The power- and temperature-dependence (0.82 less than or equal to T/T/sub c/ less than or equal to 0.994) of the enhancements were compared with the prediction of a theory given by Eliashberg. The gap-enhancement was in good agreement with the theory only for low input lower. The critical current measurements are predicted to be in rough agreement with the ..delta.. measurements but this was not observed. The magnitude of the critical current enhancements was typically more than twice the observed gap enhancements. The measured critical current enhancement was relatively independent of temperature whereas the gap enhancement decreased rapidly as the temperature was lowered.

  14. Hydrostatic pressure: a very effective approach to significantly enhance critical current density in granular iron pnictide superconductors.

    PubMed

    Shabbir, Babar; Wang, Xiaolin; Ghorbani, S R; Shekhar, Chandra; Dou, Shixue; Srivastava, O N

    2015-01-01

    Pressure is well known to significantly raise the superconducting transition temperature, Tc, in both iron pnictides and cuprate based superconductors. Little work has been done, however, on how pressure can affect the flux pinning and critical current density in the Fe-based superconductors. Here, we propose to use hydrostatic pressure to significantly enhance flux pinning and Tc in polycrystalline pnictide bulks. We have chosen Sr4V2O6Fe2As2 polycrystalline samples as a case study. We demonstrate that the hydrostatic pressure up to 1.2 GPa can not only significantly increase Tc from 15 K (underdoped) to 22 K, but also significantly enhance the irreversibility field, Hirr, by a factor of 4 at 7 K, as well as the critical current density, Jc, by up to 30 times at both low and high fields. It was found that pressure can induce more point defects, which are mainly responsible for the Jc enhancement. Our findings provide an effective method to significantly enhance Tc, Jc, Hirr, and the upper critical field, Hc2, for other families of Fe-based superconductors in the forms of wires/tapes, films, and single crystal and polycrystalline bulks. PMID:25645351

  15. Hydrostatic pressure: A very effective approach to significantly enhance critical current density in granular iron pnictide superconductors

    PubMed Central

    Shabbir, Babar; Wang, Xiaolin; Ghorbani, S. R.; Shekhar, Chandra; Dou, Shixue; Srivastava, O. N.

    2015-01-01

    Pressure is well known to significantly raise the superconducting transition temperature, Tc, in both iron pnictides and cuprate based superconductors. Little work has been done, however, on how pressure can affect the flux pinning and critical current density in the Fe-based superconductors. Here, we propose to use hydrostatic pressure to significantly enhance flux pinning and Tc in polycrystalline pnictide bulks. We have chosen Sr4V2O6Fe2As2 polycrystalline samples as a case study. We demonstrate that the hydrostatic pressure up to 1.2 GPa can not only significantly increase Tc from 15 K (underdoped) to 22 K, but also significantly enhance the irreversibility field, Hirr, by a factor of 4 at 7 K, as well as the critical current density, Jc, by up to 30 times at both low and high fields. It was found that pressure can induce more point defects, which are mainly responsible for the Jc enhancement. Our findings provide an effective method to significantly enhance Tc, Jc, Hirr, and the upper critical field, Hc2, for other families of Fe-based superconductors in the forms of wires/tapes, films, and single crystal and polycrystalline bulks. PMID:25645351

  16. Space-charge-limited currents for cathodes with electric field enhanced geometry

    NASA Astrophysics Data System (ADS)

    Lai, Dingguo; Qiu, Mengtong; Xu, Qifu; Huang, Zhongliang

    2016-08-01

    This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that the space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(βE)2J0, where J0 is the classical (1D) Child-Langmuir current density, βE is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.

  17. Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound.

    PubMed

    Yin, Xiulian; You, Qinghong; Ma, Haile; Dai, Chunhua; Zhang, Henan; Li, Kexin; Li, Yunliang

    2015-03-01

    Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound was studied. Effect of static probe ultrasonic enhanced transesterification (SPUE) and counter-current probe ultrasonic enhanced transesterification (CCPUE) on the biodiesel conversion were compared. The results indicated that CCPUE was a better method for enhancing transesterification. The working conditions of CCPUE were studied by single-factor experiment design and the results showed that the optimal conditions were: initial temperature 25 °C, methanol to triglyceride molar ratio 10:1, flow rate 200 mL/min, catalyst content 1.8%, ultrasound working on-time 4 s, off-time 2 s, total working time 50 min. Under these conditions, the average biodiesel conversion of three experiments was 96.1%. PMID:25199445

  18. Evidence-based point-of-care diagnostics: current status and emerging technologies.

    PubMed

    Chan, Cangel Pui Yee; Mak, Wing Cheung; Cheung, Kwan Yee; Sin, King Keung; Yu, Cheuk Man; Rainer, Timothy H; Renneberg, Reinhard

    2013-01-01

    Point-of-care (POC) diagnostics brings tests nearer to the site of patient care. The turnaround time is short, and minimal manual interference enables quick clinical management decisions. Growth in POC diagnostics is being continuously fueled by the global burden of cardiovascular and infectious diseases. Early diagnosis and rapid initiation of treatment are crucial in the management of such patients. This review provides the rationale for the use of POC tests in acute coronary syndrome, heart failure, human immunodeficiency virus, and tuberculosis. We also consider emerging technologies that are based on advanced nanomaterials and microfluidics, improved assay sensitivity, miniaturization in device design, reduced costs, and high-throughput multiplex detection, all of which may shape the future development of POC diagnostics. PMID:23527548

  19. Evidence-Based Point-of-Care Diagnostics: Current Status and Emerging Technologies

    NASA Astrophysics Data System (ADS)

    Chan, Cangel Pui Yee; Mak, Wing Cheung; Cheung, Kwan Yee; Sin, King Keung; Yu, Cheuk Man; Rainer, Timothy H.; Renneberg, Reinhard

    2013-06-01

    Point-of-care (POC) diagnostics brings tests nearer to the site of patient care. The turnaround time is short, and minimal manual interference enables quick clinical management decisions. Growth in POC diagnostics is being continuously fueled by the global burden of cardiovascular and infectious diseases. Early diagnosis and rapid initiation of treatment are crucial in the management of such patients. This review provides the rationale for the use of POC tests in acute coronary syndrome, heart failure, human immunodeficiency virus, and tuberculosis. We also consider emerging technologies that are based on advanced nanomaterials and microfluidics, improved assay sensitivity, miniaturization in device design, reduced costs, and high-throughput multiplex detection, all of which may shape the future development of POC diagnostics.

  20. Enhanced D-T supershot performance at high current using extensive lithium conditioning in TFTR

    SciTech Connect

    Mansfield, D.K.; Strachan, J.D.; Bell, M.G.; Scott, S.D.; Budny, R.; Bell, R.E.; Bitter, M.; Darrow, D.S.; Fredrickson, E.; Grek, B.

    1995-05-01

    A substantial improvement in supershot fusion plasma performance has been realized by combining the enhanced confinement due to tritium fueling with the enhanced confinement due to extensive Li conditioning of the TFTR limiter. This combination has resulted in not only significantly higher global energy confinement times than had previously been obtained in high current supershots, but also the highest ratio of central fusion output power to input power observed to date.

  1. Computationally Derived Points of Fragility of a Human Cascade Are Consistent with Current Therapeutic Strategies

    PubMed Central

    Luan, Deyan; Zai, Michael; Varner, Jeffrey D

    2007-01-01

    The role that mechanistic mathematical modeling and systems biology will play in molecular medicine and clinical development remains uncertain. In this study, mathematical modeling and sensitivity analysis were used to explore the working hypothesis that mechanistic models of human cascades, despite model uncertainty, can be computationally screened for points of fragility, and that these sensitive mechanisms could serve as therapeutic targets. We tested our working hypothesis by screening a model of the well-studied coagulation cascade, developed and validated from literature. The predicted sensitive mechanisms were then compared with the treatment literature. The model, composed of 92 proteins and 148 protein–protein interactions, was validated using 21 published datasets generated from two different quiescent in vitro coagulation models. Simulated platelet activation and thrombin generation profiles in the presence and absence of natural anticoagulants were consistent with measured values, with a mean correlation of 0.87 across all trials. Overall state sensitivity coefficients, which measure the robustness or fragility of a given mechanism, were calculated using a Monte Carlo strategy. In the absence of anticoagulants, fluid and surface phase factor X/activated factor X (fX/FXa) activity and thrombin-mediated platelet activation were found to be fragile, while fIX/FIXa and fVIII/FVIIIa activation and activity were robust. Both anti-fX/FXa and direct thrombin inhibitors are important classes of anticoagulants; for example, anti-fX/FXa inhibitors have FDA approval for the prevention of venous thromboembolism following surgical intervention and as an initial treatment for deep venous thrombosis and pulmonary embolism. Both in vitro and in vivo experimental evidence is reviewed supporting the prediction that fIX/FIXa activity is robust. When taken together, these results support our working hypothesis that computationally derived points of fragility of human

  2. Enhancement of critical current density and mechanism of vortex pinning in H+-irradiated FeSe single crystal

    NASA Astrophysics Data System (ADS)

    Sun, Yue; Pyon, Sunseng; Tamegai, Tsuyoshi; Kobayashi, Ryo; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada; Kitamura, Hisashi

    2015-11-01

    We report a comprehensive study of the effect of H+ irradiation on the critical current density Jc and vortex pinning in an FeSe single crystal. The value of Jc for FeSe is enhanced by more than a factor of 2 after 3-MeV H+ irradiation, which is explained by the introduction of point pinning centers. Vortex creep rates are found to be strongly suppressed after irradiation. Detailed analyses of the pinning energy based on collective-creep-theory and an extended Maley’s method show that the H+ irradiation enhances the value of Jc before the flux creep and also reduces the size of the flux bundle, which suppresses the field dependence of Jc owing to vortex motion.

  3. ENHANCING CRISIS STANDARDS OF CARE USING INNOVATIVE POINT-OF-CARE TESTING

    PubMed Central

    Kost, Gerald J.; Sakaguchi, Ann; Curtis, Corbin; Tran, Nam K.; Katip, Pratheep; Louie, Richard F.

    2011-01-01

    Objective To identify strategies with tactics that enable point-of-care (POC) testing (medical testing at or near the site of care) to improve outcomes effectively in emergencies, disasters, and public health crises, especially where community infrastructure is compromised. Design Logic model-critical path-feedback identified needs for improving practices. Reverse stress analysis showed POC should be integrated, responders properly trained, and devices staged in small-world networks (SWNs). We summarize first responder POC resources, strategize test clusters, address assay environmental vulnerabilities, and design tactics useful for SWNs, alternate care facilities, shelters, point-of-distribution centers, and community hospitals. Participants and Environment Emergency-disaster needs assessment survey respondents and Center experience. Outcomes Important tactics are: a) develop training/education courses and “just-in-time” on-line web resources to assure the competency of POC coordinators and high quality testing performance; b) protect equipment from environmental extremes by sealing reagents, controlling temperature and humidity to which they are exposed, and establishing near-patient testing in defined environments that operate within current FDA licensing claims (illustrated with HIV-1/2 tests); c) position testing in defined sites within SWNs and other environments; d) harden POC devices and reagents to withstand wider ranges of environmental extremes in field applications; e) promote new POC technologies for pathogen detection and other assays, per needs assessment results; and f) select tests according to mission objectives and value propositions. Conclusions Careful implementation of POC testing will facilitate evidence-based triage, diagnosis, treatment, and monitoring of victims and patients, while advancing standards of care in emergencies and disasters, as well as public health crises. PMID:22338316

  4. Projecting the Current & Future Impact of Storm Surges on Coastal Flood Extent at Pigeon Point, South-West Tobago, through Hydrodynamic Modelling Analyses

    NASA Astrophysics Data System (ADS)

    Seenath, Avidesh; Wilson, Matthew; Miller, Keith

    2014-05-01

    Under climate change, sea levels will continue to rise and the intensity of tropical storms and hurricanes will amplify. Consequently, the incidence rate of high magnitude storm surges may increase which will enhance the probability of coastal flood events in low lying coastal communities. The purpose of this study is to determine the current and potential future areas that may be at risk of flooding from storm surges, of different magnitudes, for the low lying Pigeon Point area of south-west Tobago. The objective of this research is to develop an understanding of the extent of flooding that these events can ensue on low lying coastal areas that are widespread through the Caribbean under current and future sea level conditions. A two-dimensional hydrodynamic flood model was created for Pigeon Point using the model code LISFLOOD-FP by incorporating topographic data of the terrain and sea bed referenced to mean sea level together with tides. This was used to assess the impact of different storm surge levels on the study area. Storm surge scenarios were computed using information acquired from the Saffir-Simpson hurricane scale which provides an estimate of storm surge height based on the category of hurricane, existing projections of global sea level rise and recorded values of high tide for Pigeon Point. Results indicate that the quantity of area likely to flood, in each surge scenario, increases significantly under future projected global sea level conditions compared to current conditions. The potential implications of this on the local population, island's economy and beach geomorphology are examined. Results obtained were incorporated into a Geographic Information System (GIS) to produce current and future flood maps indicating potential inundation extent based on storm surge height to guide coastal flood management programmes in south-west Tobago. We conclude that greater focus should be placed on implementing flood mitigation measures to protect our coasts and

  5. The enhancement of edge turbulence in tokamaks by a limiter current

    SciTech Connect

    Nedospasov, A.V. )

    1993-09-01

    The results indicating that enhanced electrostatic potential fluctuations had been observed in the scrape-off layer, due to biasing, were published recently. The qualitative explanation of these experimental results as an effect of current owing to the flute instability with the dissipation into the sheath layer near the surfaces is presented in this paper. The possibility of controlling the edge turbulence by a limiter current is shown.

  6. Enhancement of resistive switching under confined current path distribution enabled by insertion of atomically thin defective monolayer graphene

    NASA Astrophysics Data System (ADS)

    Lee, Keundong; Hwang, Inrok; Lee, Sangik; Oh, Sungtaek; Lee, Dukhyun; Kim, Cheol Kyeom; Nam, Yoonseung; Hong, Sahwan; Yoon, Chansoo; Morgan, Robert B.; Kim, Hakseong; Seo, Sunae; Seo, David H.; Lee, Sangwook; Park, Bae Ho

    2015-07-01

    Resistive random access memory (ReRAM) devices have been extensively investigated resulting in significant enhancement of switching properties. However fluctuations in switching parameters are still critical weak points which cause serious failures during ‘reading’ and ‘writing’ operations of ReRAM devices. It is believed that such fluctuations may be originated by random creation and rupture of conducting filaments inside ReRAM oxides. Here, we introduce defective monolayer graphene between an oxide film and an electrode to induce confined current path distribution inside the oxide film, and thus control the creation and rupture of conducting filaments. The ReRAM device with an atomically thin interlayer of defective monolayer graphene reveals much reduced fluctuations in switching parameters compared to a conventional one. Our results demonstrate that defective monolayer graphene paves the way to reliable ReRAM devices operating under confined current path distribution.

  7. Enhancement of resistive switching under confined current path distribution enabled by insertion of atomically thin defective monolayer graphene

    PubMed Central

    Lee, Keundong; Hwang, Inrok; Lee, Sangik; Oh, Sungtaek; Lee, Dukhyun; Kim, Cheol Kyeom; Nam, Yoonseung; Hong, Sahwan; Yoon, Chansoo; Morgan, Robert B.; Kim, Hakseong; Seo, Sunae; Seo, David H.; Lee, Sangwook; Park, Bae Ho

    2015-01-01

    Resistive random access memory (ReRAM) devices have been extensively investigated resulting in significant enhancement of switching properties. However fluctuations in switching parameters are still critical weak points which cause serious failures during ‘reading’ and ‘writing’ operations of ReRAM devices. It is believed that such fluctuations may be originated by random creation and rupture of conducting filaments inside ReRAM oxides. Here, we introduce defective monolayer graphene between an oxide film and an electrode to induce confined current path distribution inside the oxide film, and thus control the creation and rupture of conducting filaments. The ReRAM device with an atomically thin interlayer of defective monolayer graphene reveals much reduced fluctuations in switching parameters compared to a conventional one. Our results demonstrate that defective monolayer graphene paves the way to reliable ReRAM devices operating under confined current path distribution. PMID:26161992

  8. Enhancement of resistive switching under confined current path distribution enabled by insertion of atomically thin defective monolayer graphene.

    PubMed

    Lee, Keundong; Hwang, Inrok; Lee, Sangik; Oh, Sungtaek; Lee, Dukhyun; Kim, Cheol Kyeom; Nam, Yoonseung; Hong, Sahwan; Yoon, Chansoo; Morgan, Robert B; Kim, Hakseong; Seo, Sunae; Seo, David H; Lee, Sangwook; Park, Bae Ho

    2015-01-01

    Resistive random access memory (ReRAM) devices have been extensively investigated resulting in significant enhancement of switching properties. However fluctuations in switching parameters are still critical weak points which cause serious failures during 'reading' and 'writing' operations of ReRAM devices. It is believed that such fluctuations may be originated by random creation and rupture of conducting filaments inside ReRAM oxides. Here, we introduce defective monolayer graphene between an oxide film and an electrode to induce confined current path distribution inside the oxide film, and thus control the creation and rupture of conducting filaments. The ReRAM device with an atomically thin interlayer of defective monolayer graphene reveals much reduced fluctuations in switching parameters compared to a conventional one. Our results demonstrate that defective monolayer graphene paves the way to reliable ReRAM devices operating under confined current path distribution. PMID:26161992

  9. Enhancing multiple-point geostatistical modeling: 2. Iterative simulation and multiple distance function

    NASA Astrophysics Data System (ADS)

    Tahmasebi, Pejman; Sahimi, Muhammad

    2016-03-01

    This series addresses a fundamental issue in multiple-point statistical (MPS) simulation for generation of realizations of large-scale porous media. Past methods suffer from the fact that they generate discontinuities and patchiness in the realizations that, in turn, affect their flow and transport properties. Part I of this series addressed certain aspects of this fundamental issue, and proposed two ways of improving of one such MPS method, namely, the cross correlation-based simulation (CCSIM) method that was proposed by the authors. In the present paper, a new algorithm is proposed to further improve the quality of the realizations. The method utilizes the realizations generated by the algorithm introduced in Part I, iteratively removes any possible remaining discontinuities in them, and addresses the problem with honoring hard (quantitative) data, using an error map. The map represents the differences between the patterns in the training image (TI) and the current iteration of a realization. The resulting iterative CCSIM—the iCCSIM algorithm—utilizes a random path and the error map to identify the locations in the current realization in the iteration process that need further "repairing;" that is, those locations at which discontinuities may still exist. The computational time of the new iterative algorithm is considerably lower than one in which every cell of the simulation grid is visited in order to repair the discontinuities. Furthermore, several efficient distance functions are introduced by which one extracts effectively key information from the TIs. To increase the quality of the realizations and extracting the maximum amount of information from the TIs, the distance functions can be used simultaneously. The performance of the iCCSIM algorithm is studied using very complex 2-D and 3-D examples, including those that are process-based. Comparison is made between the quality and accuracy of the results with those generated by the original CCSIM

  10. Dynamic topology and flux rope evolution during non-linear tearing of 3D null point current sheets

    SciTech Connect

    Wyper, P. F. Pontin, D. I.

    2014-10-15

    In this work, the dynamic magnetic field within a tearing-unstable three-dimensional current sheet about a magnetic null point is described in detail. We focus on the evolution of the magnetic null points and flux ropes that are formed during the tearing process. Generally, we find that both magnetic structures are created prolifically within the layer and are non-trivially related. We examine how nulls are created and annihilated during bifurcation processes, and describe how they evolve within the current layer. The type of null bifurcation first observed is associated with the formation of pairs of flux ropes within the current layer. We also find that new nulls form within these flux ropes, both following internal reconnection and as adjacent flux ropes interact. The flux ropes exhibit a complex evolution, driven by a combination of ideal kinking and their interaction with the outflow jets from the main layer. The finite size of the unstable layer also allows us to consider the wider effects of flux rope generation. We find that the unstable current layer acts as a source of torsional magnetohydrodynamic waves and dynamic braiding of magnetic fields. The implications of these results to several areas of heliophysics are discussed.

  11. Infection control in implantation of cardiac implantable electronic devices: current evidence, controversial points, and unresolved issues.

    PubMed

    Korantzopoulos, Panagiotis; Sideris, Skevos; Dilaveris, Polychronis; Gatzoulis, Konstantinos; Goudevenos, John A

    2016-04-01

    A significant increase in the implantation of cardiac implantable electronic devices (CIEDs) is evident over the past years, while there is evidence for a disproportionate increase in CIED-related infections. The cumulative probability of device infection seems to be higher in implantable cardioverter defibrillator and in cardiac resynchronization therapy patients compared with permanent pacemaker patients. Given that more than a half of CIED infections are possibly related to the operative procedure, there is a need for effective periprocedural infection control. However, many of the current recommendations are empirical and not evidence-based, while questions, unresolved issues, and conflicting evidence arise. The perioperative systemic use of antibiotics confers significant benefit in prevention of CIED infections. However, there are no conclusive data regarding the specific value of each agent in different clinical settings, the value of post-operative antibiotic treatment as well as the optimal duration of therapy. The merit of local pocket irrigation with antibiotic and/or antiseptic agents remains unproved. Of note, recent evidence indicates that the application of antibacterial envelopes into the device pocket markedly decreases the infection risk. In addition, limited reports on strict integrated infection control protocols show a dramatic reduction in infection rates in this setting and therefore deserve further attention. Finally, the relative impact of particular factors on the infection risk, including the type of the CIED, patients' individual characteristics and comorbidities, should be further examined since it may facilitate the development of tailored prophylactic interventions for each patient. PMID:26516219

  12. Using Current Events to Enhance Learning: A Social Work Curricular Case Example

    ERIC Educational Resources Information Center

    Grise-Owens, Erlene; Cambron, Shannon; Valade, Rita

    2010-01-01

    Effective social work education that promotes social justice requires expanded curricular models and creative pedagogical approaches. This article presents a curricular case study demonstrating the use of current events to enhance both implicit and explicit curricula. How the cultural crisis of Hurricane Katrina was used to engender transformative…

  13. Building an Enhanced Vocabulary of the Robot Environment with a Ceiling Pointing Camera.

    PubMed

    Rituerto, Alejandro; Andreasson, Henrik; Murillo, Ana C; Lilienthal, Achim; Guerrero, José Jesús

    2016-01-01

    Mobile robots are of great help for automatic monitoring tasks in different environments. One of the first tasks that needs to be addressed when creating these kinds of robotic systems is modeling the robot environment. This work proposes a pipeline to build an enhanced visual model of a robot environment indoors. Vision based recognition approaches frequently use quantized feature spaces, commonly known as Bag of Words (BoW) or vocabulary representations. A drawback using standard BoW approaches is that semantic information is not considered as a criteria to create the visual words. To solve this challenging task, this paper studies how to leverage the standard vocabulary construction process to obtain a more meaningful visual vocabulary of the robot work environment using image sequences. We take advantage of spatio-temporal constraints and prior knowledge about the position of the camera. The key contribution of our work is the definition of a new pipeline to create a model of the environment. This pipeline incorporates (1) tracking information to the process of vocabulary construction and (2) geometric cues to the appearance descriptors. Motivated by long term robotic applications, such as the aforementioned monitoring tasks, we focus on a configuration where the robot camera points to the ceiling, which captures more stable regions of the environment. The experimental validation shows how our vocabulary models the environment in more detail than standard vocabulary approaches, without loss of recognition performance. We show different robotic tasks that could benefit of the use of our visual vocabulary approach, such as place recognition or object discovery. For this validation, we use our publicly available data-set. PMID:27070607

  14. Building an Enhanced Vocabulary of the Robot Environment with a Ceiling Pointing Camera

    PubMed Central

    Rituerto, Alejandro; Andreasson, Henrik; Murillo, Ana C.; Lilienthal, Achim; Guerrero, José Jesús

    2016-01-01

    Mobile robots are of great help for automatic monitoring tasks in different environments. One of the first tasks that needs to be addressed when creating these kinds of robotic systems is modeling the robot environment. This work proposes a pipeline to build an enhanced visual model of a robot environment indoors. Vision based recognition approaches frequently use quantized feature spaces, commonly known as Bag of Words (BoW) or vocabulary representations. A drawback using standard BoW approaches is that semantic information is not considered as a criteria to create the visual words. To solve this challenging task, this paper studies how to leverage the standard vocabulary construction process to obtain a more meaningful visual vocabulary of the robot work environment using image sequences. We take advantage of spatio-temporal constraints and prior knowledge about the position of the camera. The key contribution of our work is the definition of a new pipeline to create a model of the environment. This pipeline incorporates (1) tracking information to the process of vocabulary construction and (2) geometric cues to the appearance descriptors. Motivated by long term robotic applications, such as the aforementioned monitoring tasks, we focus on a configuration where the robot camera points to the ceiling, which captures more stable regions of the environment. The experimental validation shows how our vocabulary models the environment in more detail than standard vocabulary approaches, without loss of recognition performance. We show different robotic tasks that could benefit of the use of our visual vocabulary approach, such as place recognition or object discovery. For this validation, we use our publicly available data-set. PMID:27070607

  15. A hybrid superconducting fault current limiter for enhancing transient stability in Korean power systems

    NASA Astrophysics Data System (ADS)

    Seo, Sangsoo; Kim, Seog-Joo; Moon, Young-Hwan; Lee, Byongjun

    2013-11-01

    Additional power generation sites have been limited in Korea, despite the fact load demands are gradually increasing. In order to meet these increasing demands, Korea’s power system company has begun constructing new generators at existing sites. Thus, multi-unit plants can create problems in terms of transient stability when a large disturbance occurs. This paper proposes a hybrid superconducting fault current limiter (SFCL) application to enhance the transient stability of multi-unit power plants. SFCLs reduce fault currents, and limitation currents decrease the imbalance of the mechanical and electrical torque of the generators, resulting in an improvement in transient stability.

  16. Utilizing resonant magnetic perturbations to enhance neoclassical tearing mode stabilization by rf current

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Zhang, Xiaodong; Yu, Qingquan; Wu, Bin; Zhu, Sizheng; Wang, Jinfang; Zhang, Yang; Wang, Xiaojing

    2015-09-01

    A new method to stabilize the rotating neoclassical tearing mode (NTM) by using both the rf current drive and the static resonant magnetic perturbation (RMP) is investigated. When a non-uniform mode rotation is induced by the RMP, the stabilization of NTM by the rf current is found to be enhanced if the RMP phase has a half period difference from that of the rf wave deposition along the helical angle. The required rf current for mode stabilization is reduced by about one third if an appropriate RMP amplitude is applied.

  17. Sodium along with low-threshold potassium currents enhance coincidence detection of subthreshold noisy signals in MSO neurons.

    PubMed

    Svirskis, Gytis; Kotak, Vibhakar; Sanes, Dan H; Rinzel, John

    2004-06-01

    Voltage-dependent membrane conductances support specific neurophysiological properties. To investigate the mechanisms of coincidence detection, we activated gerbil medial superior olivary (MSO) neurons with dynamic current-clamp stimuli in vitro. Spike-triggered reverse-correlation analysis for injected current was used to evaluate the integration of subthreshold noisy signals. Consistent with previous reports, the partial blockade of low-threshold potassium channels (I(KLT)) reduced coincidence detection by slowing the rise of current needed on average to evoke a spike. However, two factors point toward the involvement of a second mechanism. First, the reverse correlation currents revealed that spike generation was associated with a preceding hyperpolarization. Second, rebound action potentials are 45% larger compared to depolarization-evoked spikes in the presence of an I(KLT) antagonist. These observations suggest that the sodium current (I(Na)) was substantially inactivated at rest. To test this idea, I(Na) was enhanced by increasing extracellular sodium concentration. This manipulation reduced coincidence detection, as reflected by slower spike-triggering current, and diminished the hyperpolarization phase in the reverse-correlation currents. As expected, a small outward bias current decreased the pre-spike hyperpolarization phase, and TTX blockade of I(Na) nearly eliminated the hyperpolarization phase in the reverse correlation current. A computer model including Hodgkin-Huxley type conductances for spike generation and for I(KLT) showed reduction in coincidence detection when I(KLT) was reduced or when I(Na) was increased. We hypothesize that desirable synaptic signals first remove some inactivation of I(Na) and reduce activation of I(KLT) to create a brief temporal window for coincidence detection of subthreshold noisy signals. PMID:14749317

  18. Application of a modified flux-coupling type superconducting fault current limiter to transient performance enhancement of micro-grid

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Zheng, Feng; Deng, Changhong; Li, Shichun; Li, Miao; Liu, Hui; Zhu, Lin; Guo, Fang

    2015-11-01

    Concerning the application and development of a micro-grid system which is designed to accommodate high penetration of intermittent renewable resources, one of the main issues is related to an increase in the fault-current level. It is crucial to ensure the micro-grid's operational stability and service reliability when a fault occurs in the main network. In this paper, our research group suggests a modified flux-coupling type superconducting fault current limiter (SFCL) to enhance the transient performance of a typical micro-grid system. The SFCL is installed at the point of common coupling (PCC) between the main network and the micro-grid, and it is expected to actively improve the micro-grid's fault ride-through capability. And for some specific faults, the micro-grid should disconnect from the main network, and the SFCL's contribution is to make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. Related theory derivation, technical discussion and simulation analysis are performed. From the demonstrated results, applying the SFCL can effectively limit the fault current, maintain the power balance, and enhance the voltage and frequency stability of the micro-grid.

  19. ON current enhancement of nanowire Schottky barrier tunnel field effect transistors

    NASA Astrophysics Data System (ADS)

    Takei, Kohei; Hashimoto, Shuichiro; Sun, Jing; Zhang, Xu; Asada, Shuhei; Xu, Taiyu; Matsukawa, Takashi; Masahara, Meishoku; Watanabe, Takanobu

    2016-04-01

    Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler-Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

  20. Current-enhanced SASE using an optical laser and its applicationto the LCLS

    SciTech Connect

    Zholents, Alexander A.; Fawley, William M.; Emma, Paul; Huang,Zhirong; Reiche, Sven; Stupakov, Gennady

    2004-08-25

    We propose a significant enhancement of the electron peak current entering a SASE undulator by inducing an energy modulation in an upstream wiggler magnet via resonant interaction with an optical laser, followed by microbunching of the energy-modulated electrons at the accelerator exit. This current enhancement allows a reduction of the FEL gain length. The x-ray output consists of a series of uniformly spaced spikes, each spike being temporally coherent. The duration of this series is controlled by the laser pulse and in principle can be narrowed down to just a single, 200-attosecond spike. Given potentially absolute temporal synchronization of the x-ray spikes to the energy-modulating laser pulse, this scheme naturally makes pump-probe experiments available to SASE FEL's. We also study various detrimental effects related to the high electron peak current.

  1. Enhanced CAD model for gate leakage current in heterostructure field effect transistors

    SciTech Connect

    Lee, K.Y. |; Lund, B.; Ytterdal, T.; Robertson, J.; Shur, M.S.; Robertson, P.; Martinez, E.J.

    1996-06-01

    A simple and accurate circuit model for Heterostructure Field Effect Transistors (HFET`s) is proposed to simulate both the gate and the drain current characteristics accounting for hot-electron effects on gate current and the effect of the gate current on the channel current. An analytical equation that describes the effective electron temperature is developed in a simple form. This equation is suitable for implementation in circuit simulators. The model describes both the drain and gate currents at high gate bias voltages. It has been implemented in the circuit simulator AIM-Spice, and good agreement between simulated and measured results is achieved for enhancement-mode HFET`s fabricated in different laboratories. The proposed equivalent circuit and model equations are applicable to other compound semiconductor FET`s, i.e., GaAs MESFET`s.

  2. Pressure-independent point in current-voltage characteristics of coplanar electrode microplasma devices operated in neon

    NASA Astrophysics Data System (ADS)

    Meng, Lingguo; Xing, Jianping; Liang, Zhihu; Liu, Chunliang; Lin, Zhaojun

    2010-05-01

    We introduce the idea of a pressure-independent point (PIP) in a group of current-voltage curves for the coplanar electrode microplasma device (CEMPD) at neon pressures ranging from 15 to 95 kPa. We studied four samples of CEMPDs with different sizes of the microcavity and observed the PIP phenomenon for each sample. The PIP voltage depends on the area of the microcavity and is independent of the height of the microcavity. The PIP discharge current, IPIP, is proportional to the volume (Vol) of the microcavity and can be expressed by the formula IPIP=IPIP0+D×Vol. For our samples, IPIP0 (the discharge current when Vol is zero) is about zero and D (discharge current density) is about 3.95 mA mm-3. The error in D is 0.411 mA mm-3 (less than 11% of D). When the CEMPD operates at VPIP, the discharge current is quite stable under different neon pressures.

  3. Pressure-independent point in current-voltage characteristics of coplanar electrode microplasma devices operated in neon

    SciTech Connect

    Meng Lingguo; Lin Zhaojun; Xing Jianping; Liang Zhihu; Liu Chunliang

    2010-05-10

    We introduce the idea of a pressure-independent point (PIP) in a group of current-voltage curves for the coplanar electrode microplasma device (CEMPD) at neon pressures ranging from 15 to 95 kPa. We studied four samples of CEMPDs with different sizes of the microcavity and observed the PIP phenomenon for each sample. The PIP voltage depends on the area of the microcavity and is independent of the height of the microcavity. The PIP discharge current, I{sub PIP}, is proportional to the volume (Vol) of the microcavity and can be expressed by the formula I{sub PIP}=I{sub PIP0}+DxVol. For our samples, I{sub PIP0} (the discharge current when Vol is zero) is about zero and D (discharge current density) is about 3.95 mA mm{sup -3}. The error in D is 0.411 mA mm{sup -3} (less than 11% of D). When the CEMPD operates at V{sub PIP}, the discharge current is quite stable under different neon pressures.

  4. Enhanced QSAR models for drug-triggered inhibition of the main cardiac ion currents.

    PubMed

    Wiśniowska, Barbara; Mendyk, Aleksander; Szlęk, Jakub; Kołaczkowski, Michał; Polak, Sebastian

    2015-09-01

    The currently changing cardiac safety testing paradigm suggests, among other things, a shift towards using in silico models of cellular electrophysiology and assessment of a concomitant block of multiple ion channels. In this study, a set of four enhanced QSAR models have been developed: for the rapid delayed rectifying potassium current (IKr), slow delayed rectifying potassium current (IKs), peak sodium current (INa) and late calcium current (ICaL), predicting ion currents changes for the specific in vitro experiment from the 2D structure of the compounds. The models are a combination of both in vitro study parameters and physico-chemical descriptors, which is a novel approach in drug-ion channels interactions modeling. Their predictive power assessed in the enhanced, more demanding than standard procedure, 10-fold cross validation was reasonably high. Rough comparison with published pure in silico hERG interaction models shows that the quality of the model predictions does not differ from other models available in the public domain, however, it takes its advantage in accounting for inter-experimental settings variability. Developed models are implemented in the Cardiac Safety Simulator, a commercially available platform enabling the in vitro-in vivo extrapolation of the drugs proarrhythmic effect and ECG simulation. A more comprehensive assessment of the effects of the compounds on ion channels allows for making more informed decisions regarding the risk - and thus avoidance - of exclusion of potentially safe and effective drugs. PMID:25559930

  5. Determination of work functions near melting points of refractory metals by using a direct-current arc

    NASA Technical Reports Server (NTRS)

    Gordon, W. A.; Chapman, G. B., II

    1972-01-01

    Effective work functions of refractory metals at temperatures near their melting points were determined by using a direct-current arc. A metal wire connected as the cathode was melted by striking an arc discharge in an argon atmosphere. A melted sphere was formed with a definite emitting area which was calculated from the sphere diameter measured after terminating the arc. Effective work functions were calculated from the Richardson-Dushman equation by using this emission area. The procedure is experimentally advantageous because surface cleanliness of the specimen is not critical, high vacuum is not required, and the anode-cathode spacing is not critical.

  6. Enhancing informatics competency under uncertainty at the point of decision: a knowing about knowing vision.

    PubMed

    Kaltoft, Mette Kjer; Nielsen, Jesper Bo; Salkeld, Glenn; Dowie, Jack

    2014-01-01

    Most informatics activity is aimed at reducing unnecessary errors, mistakes and misjudgements at the point of decision, insofar as these arise from inappropriate accessing and processing of data and information. Healthcare professionals use the results of scientific research, when available, and 'big data', when rigorously analysed, as inputs into the probability judgements that need to be made in decision making under uncertainty. But these judgements are needed irrespective of the state of 'the evidence' and personalised evidence on person/patient-important criteria is very often poor or lacking. This final stage in 'translation to the bedside' has received relatively little attention in the medical, nursing, or health informatics literature, until the recent appearance of 'cognitive informatics'. Positive experience and feed-back from several thousand students who have experienced exercises in assigning probabilities informs our future vision in which better decisions result from healthcare professionals--indeed all of us--having accepted that probability assignment is a skill, with the internal coherence and external correspondence of the probabilities assigned as twin evaluative criteria. As a route to improved correspondence--in the absence of the systematic recording and monitoring of real world judgments that would be the normal pathway to quality improvement--a 'Prober' is a set of statements to which the respondent supplies their personal probabilities that a statement is true. They receive the proper Brier score and its decomposition as analytical feedback, along with graphic representations of their discrimination and calibration, the two key components of good correspondence. Provided with estimates of their sensitivity (mean probability true for true statements) and specificity (1 minus mean probability true for false statements) they can visualise themselves as a 'test' when making diagnostic and prognostic judgements , thereby being given the

  7. Current Hypotheses on How Microsatellite Instability Leads to Enhanced Survival of Lynch Syndrome Patients

    PubMed Central

    Drescher, Kristen M.; Sharma, Poonam; Lynch, Henry T.

    2010-01-01

    High levels of microsatellite instability (MSI-high) are a cardinal feature of colorectal tumors from patients with Lynch Syndrome. Other key characteristics of Lynch Syndrome are that these patients experience fewer metastases and have enhanced survival when compared to patients diagnosed with microsatellite stable (MSS) colorectal cancer. Many of the characteristics associated with Lynch Syndrome including enhanced survival are also observed in patients with sporadic MSI-high colorectal cancer. In this review we will present the current state of knowledge regarding the mechanisms that are utilized by the host to control colorectal cancer in Lynch Syndrome and why these same mechanisms fail in MSS colorectal cancers. PMID:20631828

  8. Determination of work functions near melting points of refractory metals by using a direct-current arc.

    NASA Technical Reports Server (NTRS)

    Gordon, W. A.; Chapman, G. B., II

    1973-01-01

    A direct-current arc in argon at atmospheric pressure was used to determine effective work functions of refractory metals, including tantalum, tungsten, molybdenum, and niobium. The procedure is experimentally advantageous, because surface cleanliness of the specimen is not critical, high vacuum is not required, and the anode-cathode spacing is not critical. The experimental procedure involves striking an arc to a metal wire cathode to form a melted ball having an emitting area defined by its diameter. The literature melting point of the metal is taken as the emitting temperature. By using these parameters and the known arc current, effective work functions were calculated from the Richardson-Dushman equation. The calculated work functions agree with recommended handbook values to within about 0.1 V and have typical repeatabilities of 0.02 V.

  9. Enhancement of light extraction efficiency of vertical LED with patterned graphene as current spreading layer

    NASA Astrophysics Data System (ADS)

    Singh, Sumitra; Sai Nandini, Annam Deepthi; Pal, Suchandan; Dhanavantri, Chenna

    2016-01-01

    In this paper we report an optimised pattern of surface textured graphene current spreading layer (CSL) for the enhancement of light extraction efficiency (LEE) in InGaN/GaN vertical light emitting diodes (V-LEDs). It is found that by texturing graphene surface LEE improves drastically. This improvement is attributed to better current spreading of graphene and increased random and multiple scattering of light through textured surfaces. Simulation results illustrate that V-LEDs with surface textured (hexagonal pattern) ITO as CSL shows threefold improvement in light extraction efficiency compared to V-LEDs with no surface texturing on ITO CSL. Further, LEE of V-LEDs having patterned graphene CSL is compared with that for indium tin oxide (ITO) CSL. V-LEDs with optimised hexagonal patterning on graphene CSL shows 13.42% enhancement of LEE compared to that of LED with hexagonal patterning on ITO surface.

  10. Enhanced current injection from a quantum well to a quantum dash in magnetic field

    NASA Astrophysics Data System (ADS)

    Paravicini-Bagliani, Gian L.; Liverini, Valeria; Valmorra, Federico; Scalari, Giacomo; Gramm, Fabian; Faist, Jérôme

    2014-08-01

    Resonant tunneling injection is a key ingredient in achieving population inversion in a putative quantum dot cascade laser. In a quantum dot based structure, such resonant current requires a matching of the wavefunction shape in k-space between the injector and the quantum dot. We show experimentally that the injection into an excited state of a dash structure can be enhanced tenfold by an in-plane magnetic field that shifts the injector distribution in k-space. These experiments, performed on resonant tunneling diode structures, show unambiguously resonant tunneling into an ensemble of InAs dashes grown between two AlInAs barrier layers. They also show that interface roughness scattering can enhance the tunneling current.

  11. Single-point mutation-mediated local amphipathic adjustment dramatically enhances antibacterial activity of a fungal defensin.

    PubMed

    Wu, Jiajia; Gao, Bin; Zhu, Shunyi

    2016-07-01

    The emergence and rapid spread of multiresistant bacteria has lead to an urgent need for novel antimicrobials. Based on single-point substitutions, we generated a series of mutants of micasin, a dermatophytic defensin, with enhanced activities against multiple clinical isolates of Staphylococcus species, including 4 antibiotic-resistant strains. We first mapped the functional surface of micasin by alanine-scanning mutational analysis of its highly exposed residues, through which we found that substitution of site 8 (acidic Glu) dramatically enhanced bacterial killing of this peptide. Structural analysis indicates that this single point mutation could result in a functional local amphipathic architecture. Four different types of side chains (hydrophobic, cationic polar, neutral polar, and acidic polar) were introduced at site 8 to clarify the role of this local architecture in micasin function. The results show that all mutants displayed increased antibacterial activity with the exception of the acidic replacement. These mutants with enhanced activity exhibited low hemolysis and cytotoxicity and showed high serum stability, indicating their therapeutic potential. Our work represents the first example of structural fine-tuning to largely improve the antibacterial potency of a dermatophytic defensin.-Wu, J., Gao, B., Zhu, S. Single-point mutation-mediated local amphipathic adjustment dramatically enhances antibacterial activity of a fungal defensin. PMID:27084888

  12. Influence of electrolyte and voltage on the direct current enhanced transport of iron nanoparticles in clay.

    PubMed

    Gomes, Helena I; Dias-Ferreira, Celia; Ribeiro, Alexandra B; Pamukcu, Sibel

    2014-03-01

    Zero valent iron nanoparticles (nZVI) transport for soil and groundwater remediation is slowed down or halted by aggregation or fast depletion in the soil pores. Direct electric current can enhance the transport of nZVI in low permeability soils. However operational factors, including pH, oxidation-reduction potential (ORP), voltage and ionic strength of the electrolyte can play an important role in the treatment effectiveness. Experiments were conducted to enhance polymer coated nZVI mobility in a model low permeability soil medium (kaolin clay) using low direct current. Different electrolytes of varying ionic strengths and initial pH and high nZVI concentrations were applied. Results showed that the nZVI transport is enhanced by direct current, even considering concentrations typical of field application that favor nanoparticle aggregation. However, the factors considered (pH, ORP, voltage and electrolyte) failed to explain the iron concentration variation. The electrolyte and its ionic strength proved to be significant for pH and ORP measured during the experiments, and therefore will affect aggregation and fast oxidation of the particles. PMID:24252496

  13. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator.

    PubMed

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J J; Hwang, Y S

    2012-02-01

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction. PMID:22380295

  14. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator

    SciTech Connect

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J. J.; Hwang, Y. S.

    2012-02-15

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.

  15. The Plasma Physics Processes that Drive Ring Current Enhancements during Geomagnetic Storms and Substorms

    NASA Astrophysics Data System (ADS)

    Cash, Michele Diane

    Geomagnetic storms result when energetic particles of solar and ionospheric origin fill Earth's inner magnetosphere and create a strong westward current, known as the ring current. This dissertation presents results from investigating the plasma dynamics that contribute to the development of Earth's ring current from ionospheric outflow of H+ and O+ ions, and the role of ring current enhancements in the generation of geomagnetic storms and substorms. Modeling was carried via a combined multifluid and particle approach, which enables us to resolve the small-scale dynamics that are key to particle energization within the context of the global magnetosphere. The results presented in this dissertation substantially contribute to our understanding of the development and composition of the ring current during geomagnetic storms and substorms, and offer insight into the ionospheric sources regions for ring current ions, as well as the processes through which these particles are energized, injected, and trapped within the inner magnetosphere. This thesis presents results that show how small-scale particle dynamics within the current sheet, boundary layers, and reconnection regions drive the acceleration of ring current particles within the larger global context of the magnetosphere. Small-scale structures within the magnetotail are shown to be more important in determining when particles are accelerated than the time after particles are initialized in the ionosphere. It is also found that after a period of southward IMF, in which particle energization is observed, a northerly turning of the IMF is necessary in order to trap energetic particles in orbit around the Earth and form a symmetric ring current. Asymmetries in the acceleration mechanisms between ionospheric H+ and O + ions were observed with oxygen ions convecting duskward according to the cross-tail current and gaining more energy than protons, which moved earthward on reconnecting field lines and were accelerated

  16. Non-stationary corona around multi-point system in atmospheric electric field: I. Onset electric field and discharge current

    NASA Astrophysics Data System (ADS)

    Bazelyan, E. M.; Raizer, Yu. P.; Aleksandrov, N. L.

    2014-03-01

    The properties of a non-stationary glow corona maintained near the tips of a multi-point ground system in a time-varying thundercloud electric field have been studied numerically and analytically. Computer and analytical models were developed to simulate the corona discharge initiated from a system of identical vertical conductive electrodes distributed uniformly over a grounded plane surface. The simulation was based on a solution of the electrostatic equation for electric field and continuity equations for light and aerosol ions. The development of individual corona space charge layers from different points and the formation of a united plane layer were considered. The effect of system dimensions and that of the distance between electrodes on the external electric field corresponding to corona onset near the rod tips was investigated. The evolution in time of the corona current was calculated for systems with various numbers of coronating rods in time-varying atmospheric electric field. In the limit of infinite number of coronating rods, reasonable agreement was obtained between numerical calculations and analytical theory considering the effect of surrounding rods on the corona discharge from a given rod in a simplified integral way. Conditions were determined under which the corona properties of a multi-point system are similar to the properties of a plane surface emitting ions into the atmosphere. In this case, the corona current density is governed by the time derivative of the thundercloud electric field and is independent of the ion mobility and of the coronating system dimensions. The total corona space charge injected into the atmosphere per unit area by a given instant is controlled by the thundercloud electric field at this instant and depends on the geometrical parameters of the system only indirectly, through the corona onset atmospheric electric field. This simple model could be used to simulate a corona discharge during thunderstorms at the earth

  17. Enhancement-mode InAlN/GaN MISHEMT with low gate leakage current

    NASA Astrophysics Data System (ADS)

    Guodong, Gu; Yong, Cai; Zhihong, Feng; Bo, Liu; Chunhong, Zeng; Guohao, Yu; Zhihua, Dong; Baoshun, Zhang

    2012-06-01

    We report an enhancement-mode InAlN/GaN MISHEMT with a low gate leakage current by a thermal oxidation technique under gate. The off-state source-drain current density is as low as ~10-7 A/mm at VGS = 0 V and VDS = 5 V. The threshold voltage is measured to be +0.8 V by linear extrapolation from the transfer characteristics. The E-mode device exhibits a peak transconductance of 179 mS/mm at a gate bias of 3.4 V. A low reverse gate leakage current density of 4.9 × 10-7 A/mm is measured at VGS = -15 V.

  18. Enhanced current flow through a plasma cloud by induction of plasma turbulence

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.

    1987-01-01

    Electrodynamic tethers have been proposed as a means of generating power in low earth orbit. One of the limitations on the power generated is the relatively low electron current that can be collected. It is proposed that the electron current can be significantly enhanced by means of current-induced plasma turbulence in a plasma cloud around the collecting anode. This is examined for the specific case of ion acoustic turbulence. An important conclusion is that the use of plasma clouds in the ionosphere will entail a high-impedance (no instability) and a low-impedance (ion acoustic instability) mode of operation. The low-impedance mode of operation will have two submodes, one steady state and one pulsed.

  19. Access of energetic particles to storm time ring current through enhanced radial diffusion

    SciTech Connect

    Lyons, L.R.; Schulz, M. )

    1989-05-01

    Magnetic storms are distinguishable from other periods of geomagnetic activity by the injection of trapped electrons and ions to the 2{approx lt} L {approx lt} 4 region. It has been proposed previously that this injection results from an inward displacement of the preexisting trapped-particle population by enhanced storm time electric fields. However, high-energy ({approx gt} 40 keV) ring-current particles have drift periods that are typically shorter than the time of the main-phase development, and so the direct radial transport of these particles is restricted. The authors propose here that the transport of {approx gt} 40 keV particles into the storm time ring current can result from enhanced stochastic radial transport driven by fluctuating electric fields during a storm's main phase. They estimate the effects of such electric fields by applying radial-diffusion theory, assuming a preexisting trapped-particle population as the initial conditions, and they demonstrate the feasibility of explaining observed flux increases of {approx gt} 40-keV particles at L{approx lt} 4 by enhanced radial diffusion. It is necessary that new particles be injected near the outer boundary of the trapping region so as to maintain the fluxes there as an outer boundary condition, and they estimate that the {approx gt} 40-keV portion of the storm time ring current at L {approximately} 3 consists of about 50% preexisting and about 50% new particles. They thus find that formation of the storm time ring current may be explainable via a combination of direct radial transport at energies {approx lt} 40 keV and diffusive radial transport at higher energies.

  20. Effects of Multi-Point Current-Injection Feedback on Interchange Turbulence in a Dipole-Confined Plasma

    NASA Astrophysics Data System (ADS)

    Abler, Melissa C.; Battey, Alexander; Mauel, Michael; Roberts, T. Maximillian

    2015-11-01

    Plasma confined by a strong dipole field exhibits low-frequency interchange turbulence, which previous experiments have shown responds locally to active feedback, primarily in the direction of the electron magnetic drift. New experiments on the Collisionless Terella Experiment (CTX) use a system of two electrodes with 90° azimuthal separation to study the effects of multi-point current-injection feedback on interchange turbulence. Initial open-loop experiments to excite low-frequency waves at a variety of relative phases and amplitudes indicate a significantly stronger spatial coherence when two electrodes are used rather than one. These driven low-frequency waves also generate harmonics which can persist throughout the plasma. In a closed-loop active feedback configuration, this system may be used to regulate the turbulent dynamics in new ways. Supported by NSF-DOE Partnership for Plasma Science Grants DOE-DE-FG02-00ER54585 and NSF-PHY-1201896.

  1. Three-dimensional interaction force and tunneling current spectroscopy of point defects on rutile TiO2(110)

    NASA Astrophysics Data System (ADS)

    Baykara, Mehmet Z.; Mönig, Harry; Schwendemann, Todd C.; Ünverdi, Ã.-zhan; Altman, Eric I.; Schwarz, Udo D.

    2016-02-01

    The extent to which point defects affect the local chemical reactivity and electronic properties of an oxide surface was evaluated with picometer resolution in all three spatial dimensions using simultaneous atomic force/scanning tunneling microscopy measurements performed on the (110) face of rutile TiO2. Oxygen atoms were imaged as protrusions in both data channels, corresponding to a rarely observed imaging mode for this prototypical metal oxide surface. Three-dimensional spectroscopy of interaction forces and tunneling currents was performed on individual surface and subsurface defects as a function of tip-sample distance. An interstitial defect assigned to a subsurface hydrogen atom is found to have a distinct effect on the local density of electronic states on the surface, but no detectable influence on the tip-sample interaction force. Meanwhile, spectroscopic data acquired on an oxygen vacancy highlight the role of the probe tip in chemical reactivity measurements.

  2. Influence of random point defects introduced by proton irradiation on the flux creep rates and magnetic field dependence of the critical current density J c of co-evaporated GdBa2Cu3O7-δ coated conductors

    NASA Astrophysics Data System (ADS)

    Haberkorn, N.; Kim, Jeehoon; Suárez, S.; Lee, Jae-Hun; Moon, S. H.

    2015-12-01

    We report the influence of random point defects introduced by 3 MeV proton irradiation (doses of 0.5 × 1016, 1 × 1016, 2 × 1016 and 6 × 1016 cm-2) on the vortex dynamics of co-evaporated 1.3 μm thick, GdBa2Cu3O7-δ coated conductors. Our results indicate that the inclusion of additional random point defects reduces the low field and enhances the in-field critical current densities J c. The main in-field J c enhancement takes place below 40 K, which is in agreement with the expectations for pinning by random point defects. In addition, our data show a slight though clear increase in flux creep rates as a function of irradiation fluence. Maley analysis indicates that this increment can be associated with a reduction in the exponent μ characterizing the glassy behavior.

  3. Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

    NASA Astrophysics Data System (ADS)

    Bobrov, N. L.

    2015-08-01

    Nonlinear electrical effects in superconducting S-c-S contacts, including the spectroscopy of electron-phonon interactions (EPI) in these systems, and the recovery of the EPI function from experimental data are discussed. The effect of a magnetic field on the current-voltage characteristics (I-V curves) and their derivatives for ErNi2B2C point contacts (PC) with d ≥ ξ (where d is the diameter of the PC and ξ is the coherence length) is studied. It is found that in zero magnetic fields and in near-critical fields, when the size of the superconducting gap can be neglected, the position of the peaks in dV/dI coincides with the peaks in the Yanson EPI spectra. In low fields the peaks are shifted toward lower energies and in intermediate fields, the peaks split. For PC with diameters greater than or on the order of the coherence length, the relative size of the negative phonon contribution to the excess current is considerably greater than in ballistic contacts. This leads to substantial suppression of the high-frequency peaks in the spectra for the superconducting state. In order to recover the EPI function from these spectra it is necessary to correct their intensities at high energies. For "dirty" NbSe2 and Nb point-contacts with d ≥ ξ, which have no phonon features in the second derivative of the I-V curve in the normal state, the EPI can be reconstructed from the superconducting state.

  4. Enhancing Science Instruction through Student-Created PowerPoint Presentations

    ERIC Educational Resources Information Center

    Gerido, Leona; Curran, Mary Carla

    2014-01-01

    Technology use in science classes can enhance lessons and reinforce scientific content. The creation of multimedia projects is a great way to engage students in lessons about estuarine ecosystems. In this activity, students can learn about estuarine organisms and use their creativity to write a story, create artwork, and develop a multimedia…

  5. Contrast-Enhanced Magnetic Resonance Imaging in Pediatric Patients: Review and Recommendations for Current Practice

    PubMed Central

    Bhargava, Ravi; Hahn, Gabriele; Hirsch, Wolfgang; Kim, Myung-Joon; Mentzel, Hans-Joachim; Olsen, Øystein E.; Stokland, Eira; Triulzi, Fabio; Vazquez, Elida

    2013-01-01

    Magnetic resonance imaging (MRI), frequently with contrast enhancement, is the preferred imaging modality for many indications in children. Practice varies widely between centers, reflecting the rapid pace of change and the need for further research. Guide-line changes, for example on contrast-medium choice, require continued practice reappraisal. This article reviews recent developments in pediatric contrast-enhanced MRI and offers recommendations on current best practice. Nine leading pediatric radiologists from internationally recognized radiology centers convened at a consensus meeting in Bordeaux, France, to discuss applications of contrast-enhanced MRI across a range of indications in children. Review of the literature indicated that few published data provide guidance on best practice in pediatric MRI. Discussion among the experts concluded that MRI is preferred over ionizing-radiation modalities for many indications, with advantages in safety and efficacy. Awareness of age-specific adaptations in MRI technique can optimize image quality. Gadolinium-based contrast media are recommended for enhancing imaging quality. The choice of most appropriate contrast medium should be based on criteria of safety, tolerability, and efficacy, characterized in age-specific clinical trials and personal experience. PMID:25114547

  6. Enhancement of critical current through oxygen irradiation in optimized 2G superconducting coated conductors

    NASA Astrophysics Data System (ADS)

    Kihlstrom, Karen; Leroux, M.; Welp, U.; Kwok, W.-K.; Koshelev, A. E.; Crabtree, G. W.; Rupich, M. W.; Fleshler, S.; Malozemoff, A. P.; Kayani, A.; CES Collaboration

    2015-03-01

    We demonstrate the strong enhancement of the critical current density, Jc, of commercial coated conductors (CC) in high magnetic fields using 3 MeV oxygen irradiation. The rapid suppression of Jc of coated conductors in magnetic fields remains a barrier for application of CCs in motors, generators, transformers, solenoids, and MRI systems. Using TRIM simulations, we determined that 3-MeV O-ions produce an essentially uniform defect distribution in bare CC at a rate that is ~ 2500 faster than that achieved with proton irradiation. Irradiating with 3 MeV O-ions to a dose of 1x1013 O-ions/cm2 generates a near doubling of the critical current at low temperatures: at 5K, 5T, we enhanced the critical current from 6.4 MA/cm2 to 12.2 MA/cm2. This dose can be achieved in a couple of seconds, thus this irradiation technique could be incorporated into a viable reel-to-reel production process. This work supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. D.O.E., Office of Science, Office of Basic Energy Sciences (K.K, M.L.,A.K) and by the D.O.E, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 (U.W., W.K.).

  7. Muscarinic enhancement of persistent sodium current synchronizes striatal medium spiny neurons.

    PubMed

    Carrillo-Reid, Luis; Tecuapetla, Fatuel; Vautrelle, Nicolas; Hernández, Adán; Vergara, Ramiro; Galarraga, Elvira; Bargas, José

    2009-08-01

    Network dynamics denoted by synchronous firing of neuronal pools rely on synaptic interactions and intrinsic properties. In striatal medium spiny neurons, N-methyl-d-aspartate (NMDA) receptor activation endows neurons with nonlinear capabilities by inducing a negative-slope conductance region (NSCR) in the current-voltage relationship. Nonlinearities underlie associative learning, procedural memory, and the sequential organization of behavior in basal ganglia nuclei. The cholinergic system modulates the function of medium spiny projection neurons through the activation of muscarinic receptors, increasing the NMDA-induced NSCR. This enhancement is reflected as a change in the NMDA-induced network dynamics, making it more synchronous. Nevertheless, little is known about the contribution of intrinsic properties that promote this activity. To investigate the mechanisms underlying the cholinergic modulation of bistable behavior in the striatum, we used whole cell and calcium-imaging techniques. A persistent sodium current modulated by muscarinic receptor activation participated in the enhancement of the NSCR and the increased network synchrony. These experiments provide evidence that persistent sodium current generates bistable behavior in striatal neurons and contributes to the regulation of synchronous network activity. The neuromodulation of bistable properties could represent a cellular and network mechanism for cholinergic actions in the striatum. PMID:19474176

  8. Enhanced resistive switching phenomena using low-positive-voltage format and self-compliance IrOx/GdOx/W cross-point memories

    PubMed Central

    2014-01-01

    Enhanced resistive switching phenomena of IrOx/GdOx/W cross-point memory devices have been observed as compared to the via-hole devices. The as-deposited Gd2O3 films with a thickness of approximately 15 nm show polycrystalline that is observed using high-resolution transmission electron microscope. Via-hole memory device shows bipolar resistive switching phenomena with a large formation voltage of -6.4 V and high operation current of >1 mA, while the cross-point memory device shows also bipolar resistive switching with low-voltage format of +2 V and self-compliance operation current of <300 μA. Switching mechanism is based on the formation and rupture of conducting filament at the IrOx/GdOx interface, owing to oxygen ion migration. The oxygen-rich GdOx layer formation at the IrOx/GdOx interface will also help control the resistive switching characteristics. This cross-point memory device has also Repeatable 100 DC switching cycles, narrow distribution of LRS/HRS, excellent pulse endurance of >10,000 in every cycle, and good data retention of >104 s. This memory device has great potential for future nanoscale high-density non-volatile memory applications. PMID:24400888

  9. Current consensus and guidelines of contrast enhanced ultrasound for the characterization of focal liver lesions

    PubMed Central

    Jang, Jae Young; Kim, Moon Young; Jeong, Soung Won; Kim, Tae Yeob; Kim, Seung Up; Lee, Sae Hwan; Suk, Ki Tae; Park, Soo Young; Woo, Hyun Young; Kim, Sang Gyune; Heo, Jeong; Baik, Soon Koo; Kim, Hong Soo

    2013-01-01

    The application of ultrasound contrast agents (UCAs) is considered essential when evaluating focal liver lesions (FLLs) using ultrasonography (US). Microbubble UCAs are easy to use and robust; their use poses no risk of nephrotoxicity and requires no ionizing radiation. The unique features of contrast enhanced US (CEUS) are not only noninvasiveness but also real-time assessing of liver perfusion throughout the vascular phases. The later feature has led to dramatic improvement in the diagnostic accuracy of US for detection and characterization of FLLs as well as the guidance to therapeutic procedures and evaluation of response to treatment. This article describes the current consensus and guidelines for the use of UCAs for the FLLs that are commonly encountered in US. After a brief description of the bases of different CEUS techniques, contrast-enhancement patterns of different types of benign and malignant FLLs and other clinical applications are described and discussed on the basis of our experience and the literature data. PMID:23593604

  10. Enhancement of Overlimiting Current through an Ion-Selective Membrane via Surface Conductivity Patterning

    NASA Astrophysics Data System (ADS)

    Davidson, Scott; Wessling, Matthias; Mani, Ali

    2015-11-01

    Electroconvection's ability to enhance transport through ion-selective surfaces provides promising opportunities for improving many diffusion-limited electrochemical and microfluidic systems. We have investigated two sources of electroconvection at ion-selective surfaces, electrokinetic instability and surface-patterning with impermeable stripes and their interactions using direct numerical simulation of the governing equations. We show that despite the reduced surface area available for transport, patterned surfaces can lead to an up to 80% increase in current density relative to homogeneous surfaces. At applied voltages below the nominal threshold of instability, patterning enhances transport by inducing flow, while at higher voltages they do so by regularizing the chaotic electroconvective flows. Additionally, we show the formation of novel electroconvective patterns with multiple coexisting length scales due to electrokinetic instability at the homogeneous surface.

  11. Enhanced current-rectification in bilayer graphene with an electrically tuned sloped bandgap

    NASA Astrophysics Data System (ADS)

    Aparecido-Ferreira, Alex; Miyazaki, Hisao; Li, Song-Lin; Komatsu, Katsuyoshi; Nakaharai, Shu; Tsukagoshi, Kazuhito

    2012-11-01

    We propose a novel sloped dielectric geometry in graphene as a band engineering method for widening the depletion region and increasing the electrical rectification effect in graphene pn junctions. Enhanced current-rectification was achieved in a bilayer graphene with a sloped dielectric top gate and a normal back gate. A bias was applied to the top gate to induce a spatially modulated and sloped band configuration, while a back-gate bias was applied to open a bandgap. The sloped band can be tuned to separate n- and p-type regions in the bilayer graphene, depending on a suitable choice of gate voltage. The effective depletion region between the n- and p-type regions can be spatially enlarged due to the proposed top-gate structure. As a result, a strong non-linear electric current was observed during drain bias sweeping, demonstrating the expected rectification behavior with an on/off ratio higher than all previously reported values for graphene pn junctions. The observed rectification was modified to a linear current-voltage relationship by adjusting the biases of both gates to form an nn- or pp-type junction configuration. These results demonstrate that an external voltage can control the current flow in atomic film diodes.We propose a novel sloped dielectric geometry in graphene as a band engineering method for widening the depletion region and increasing the electrical rectification effect in graphene pn junctions. Enhanced current-rectification was achieved in a bilayer graphene with a sloped dielectric top gate and a normal back gate. A bias was applied to the top gate to induce a spatially modulated and sloped band configuration, while a back-gate bias was applied to open a bandgap. The sloped band can be tuned to separate n- and p-type regions in the bilayer graphene, depending on a suitable choice of gate voltage. The effective depletion region between the n- and p-type regions can be spatially enlarged due to the proposed top-gate structure. As a result, a

  12. Enhancing efficiency and quality of statistical estimation of immunogenicity assay cut points through standardization and automation.

    PubMed

    Su, Cheng; Zhou, Lei; Hu, Zheng; Weng, Winnie; Subramani, Jayanthi; Tadkod, Vineet; Hamilton, Kortney; Bautista, Ami; Wu, Yu; Chirmule, Narendra; Zhong, Zhandong Don

    2015-10-01

    Biotherapeutics can elicit immune responses, which can alter the exposure, safety, and efficacy of the therapeutics. A well-designed and robust bioanalytical method is critical for the detection and characterization of relevant anti-drug antibody (ADA) and the success of an immunogenicity study. As a fundamental criterion in immunogenicity testing, assay cut points need to be statistically established with a risk-based approach to reduce subjectivity. This manuscript describes the development of a validated, web-based, multi-tier customized assay statistical tool (CAST) for assessing cut points of ADA assays. The tool provides an intuitive web interface that allows users to import experimental data generated from a standardized experimental design, select the assay factors, run the standardized analysis algorithms, and generate tables, figures, and listings (TFL). It allows bioanalytical scientists to perform complex statistical analysis at a click of the button to produce reliable assay parameters in support of immunogenicity studies. PMID:26130368

  13. Heavy ion irradiation of Bi-2223 silver-clad tapes for superconducting current density enhancement

    SciTech Connect

    Malozcnoff, A.P.; Carter, W.L.; Riley, G.N. Jr.; Wheeler, R. IV; Kirk, M.A.; Civale, L.; Marwick, A.D.

    1993-07-01

    Silver-clad composite tapes of Bi(Pb)SrCaCuO-2223 were irradiated with 1 GeV Au{sup 23+} ions perpendicular to the tape plane, creating columnar tracks with 10 nm diameter. Detailed transmission electron microscopy shows continuous columns, but with variations in the track thickness of +/{minus}2 nm. Magnetic hystersis measurements show substantial enhancement of superconducting current density at most temperatures and fields. Granular and nongranular models for the origin of the magnetic signals are discussed. The results indicate the potential for further performance improvement in high temperature superconducting wire technology, as well as limits in the high-field performance at 77 K.

  14. Enhancement of MS2D Bartington point measurement of soil magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Fabijańczyk, Piotr; Zawadzki, Jarosław

    2015-04-01

    Field magnetometry is fast method used to assess the potential soil pollution. The most popular device used to measure the soil magnetic susceptibility on the soil surface is a MS2D Bartington. Single reading using MS2D device of soil magnetic susceptibility is low time-consuming but often characterized by considerable errors related to the instrument or environmental and lithogenic factors. Typically, in order to calculate the reliable average value of soil magnetic susceptibility, a series of MS2D readings is performed in the sample point. As it was analyzed previously, such methodology makes it possible to significantly reduce the nugget effect of the variograms of soil magnetic susceptibility that is related to the micro-scale variance and measurement errors. The goal of this study was to optimize the process of taking a series of MS2D readings, whose average value constitutes a single measurement, in order to take into account micro-scale variations of soil magnetic susceptibility in proper determination of this parameter. This was done using statistical and geostatistical analyses. The analyses were performed using field MS2D measurements that were carried out in the study area located in the direct vicinity of the Katowice agglomeration. At 150 sample points 10 MS2D readings of soil magnetic susceptibility were taken. Using this data set, series of experimental variograms were calculated and modeled. Firstly, using single random MS2D reading for each sample point, and next using the data set increased by adding one more MS2D reading, until their number reached 10. The parameters of variogram: nugget effect, sill and range of correlation were used to determine the most suitable number of MS2D readings at sample point. The distributions of soil magnetic susceptibility at sample point were also analyzed in order to determine adequate number of readings enabling to calculate reliable average soil magnetic susceptibility. The research leading to these results has

  15. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  16. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition.

    PubMed

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm(2). The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs. PMID:26666912

  17. Production of aromatics through current-enhanced catalytic conversion of bio-oil tar.

    PubMed

    Bi, Peiyan; Yuan, Yanni; Fan, Minghui; Jiang, Peiwen; Zhai, Qi; Li, Quanxin

    2013-05-01

    Biomass conversion into benzene, toluene and xylenes (BTX) can provide basic feedstocks for the petrochemical industry, which also serve as the most important aromatic platform molecules for development of high-end chemicals. Present work explored a new route for transformation of bio-oil tar into BTX through current-enhanced catalytic conversion (CECC), involving the synergistic effect between the zeolite catalyst and current to promote the deoxygenation and cracking reactions. The proposed transformation shows an excellent BTX aromatics selectivity of 92.9 C-mol% with 25.1 wt.% yield at 400 °C over usual HZSM-5 catalyst. The study of the model compounds revealed that the groups such as methoxy, hydroxyl and methyl in aromatics can be effectively removed in the CECC process. Present transformation potentially provides an important approach for production of the key petrochemicals of BTX and the overall use of bio-oil tar derived from bio-oil or biomass. PMID:23567684

  18. A segmentation and point-matching enhanced efficient deformable image registration method for dose accumulation between HDR CT images

    NASA Astrophysics Data System (ADS)

    Zhen, Xin; Chen, Haibin; Yan, Hao; Zhou, Linghong; Mell, Loren K.; Yashar, Catheryn M.; Jiang, Steve; Jia, Xun; Gu, Xuejun; Cervino, Laura

    2015-04-01

    Deformable image registration (DIR) of fractional high-dose-rate (HDR) CT images is challenging due to the presence of applicators in the brachytherapy image. Point-to-point correspondence fails because of the undesired deformation vector fields (DVF) propagated from the applicator region (AR) to the surrounding tissues, which can potentially introduce significant DIR errors in dose mapping. This paper proposes a novel segmentation and point-matching enhanced efficient DIR (named SPEED) scheme to facilitate dose accumulation among HDR treatment fractions. In SPEED, a semi-automatic seed point generation approach is developed to obtain the incremented fore/background point sets to feed the random walks algorithm, which is used to segment and remove the AR, leaving empty AR cavities in the HDR CT images. A feature-based ‘thin-plate-spline robust point matching’ algorithm is then employed for AR cavity surface points matching. With the resulting mapping, a DVF defining on each voxel is estimated by B-spline approximation, which serves as the initial DVF for the subsequent Demons-based DIR between the AR-free HDR CT images. The calculated DVF via Demons combined with the initial one serve as the final DVF to map doses between HDR fractions. The segmentation and registration accuracy are quantitatively assessed by nine clinical HDR cases from three gynecological cancer patients. The quantitative analysis and visual inspection of the DIR results indicate that SPEED can suppress the impact of applicator on DIR, and accurately register HDR CT images as well as deform and add interfractional HDR doses.

  19. A segmentation and point-matching enhanced efficient deformable image registration method for dose accumulation between HDR CT images.

    PubMed

    Zhen, Xin; Chen, Haibin; Yan, Hao; Zhou, Linghong; Mell, Loren K; Yashar, Catheryn M; Jiang, Steve; Jia, Xun; Gu, Xuejun; Cervino, Laura

    2015-04-01

    Deformable image registration (DIR) of fractional high-dose-rate (HDR) CT images is challenging due to the presence of applicators in the brachytherapy image. Point-to-point correspondence fails because of the undesired deformation vector fields (DVF) propagated from the applicator region (AR) to the surrounding tissues, which can potentially introduce significant DIR errors in dose mapping. This paper proposes a novel segmentation and point-matching enhanced efficient DIR (named SPEED) scheme to facilitate dose accumulation among HDR treatment fractions. In SPEED, a semi-automatic seed point generation approach is developed to obtain the incremented fore/background point sets to feed the random walks algorithm, which is used to segment and remove the AR, leaving empty AR cavities in the HDR CT images. A feature-based 'thin-plate-spline robust point matching' algorithm is then employed for AR cavity surface points matching. With the resulting mapping, a DVF defining on each voxel is estimated by B-spline approximation, which serves as the initial DVF for the subsequent Demons-based DIR between the AR-free HDR CT images. The calculated DVF via Demons combined with the initial one serve as the final DVF to map doses between HDR fractions. The segmentation and registration accuracy are quantitatively assessed by nine clinical HDR cases from three gynecological cancer patients. The quantitative analysis and visual inspection of the DIR results indicate that SPEED can suppress the impact of applicator on DIR, and accurately register HDR CT images as well as deform and add interfractional HDR doses. PMID:25790059

  20. Flame oxidation of stainless steel felt enhances anodic biofilm formation and current output in bioelectrochemical systems.

    PubMed

    Guo, Kun; Donose, Bogdan C; Soeriyadi, Alexander H; Prévoteau, Antonin; Patil, Sunil A; Freguia, Stefano; Gooding, J Justin; Rabaey, Korneel

    2014-06-17

    Stainless steel (SS) can be an attractive material to create large electrodes for microbial bioelectrochemical systems (BESs), due to its low cost and high conductivity. However, poor biocompatibility limits its successful application today. Here we report a simple and effective method to make SS electrodes biocompatible by means of flame oxidation. Physicochemical characterization of electrode surface indicated that iron oxide nanoparticles (IONPs) were generated in situ on an SS felt surface by flame oxidation. IONPs-coating dramatically enhanced the biocompatibility of SS felt and consequently resulted in a robust electroactive biofilm formation at its surface in BESs. The maximum current densities reached at IONPs-coated SS felt electrodes were 16.5 times and 4.8 times higher than the untreated SS felts and carbon felts, respectively. Furthermore, the maximum current density achieved with the IONPs-coated SS felt (1.92 mA/cm(2), 27.42 mA/cm(3)) is one of the highest current densities reported thus far. These results demonstrate for the first time that flame oxidized SS felts could be a good alternative to carbon-based electrodes for achieving high current densities in BESs. Most importantly, high conductivity, excellent mechanical strength, strong chemical stability, large specific surface area, and comparatively low cost of flame oxidized SS felts offer exciting opportunities for scaling-up of the anodes for BESs. PMID:24911921

  1. Transcranial direct current stimulation enhances recovery of stereopsis in adults with amblyopia.

    PubMed

    Spiegel, Daniel P; Li, Jinrong; Hess, Robert F; Byblow, Winston D; Deng, Daming; Yu, Minbin; Thompson, Benjamin

    2013-10-01

    Amblyopia is a neurodevelopmental disorder of vision caused by abnormal visual experience during early childhood that is often considered to be untreatable in adulthood. Recently, it has been shown that a novel dichoptic videogame-based treatment for amblyopia can improve visual function in adult patients, at least in part, by reducing inhibition of inputs from the amblyopic eye to the visual cortex. Non-invasive anodal transcranial direct current stimulation has been shown to reduce the activity of inhibitory cortical interneurons when applied to the primary motor or visual cortex. In this double-blind, sham-controlled cross-over study we tested the hypothesis that anodal transcranial direct current stimulation of the visual cortex would enhance the therapeutic effects of dichoptic videogame-based treatment. A homogeneous group of 16 young adults (mean age 22.1 ± 1.1 years) with amblyopia were studied to compare the effect of dichoptic treatment alone and dichoptic treatment combined with visual cortex direct current stimulation on measures of binocular (stereopsis) and monocular (visual acuity) visual function. The combined treatment led to greater improvements in stereoacuity than dichoptic treatment alone, indicating that direct current stimulation of the visual cortex boosts the efficacy of dichoptic videogame-based treatment. This intervention warrants further evaluation as a novel therapeutic approach for adults with amblyopia. PMID:23857313

  2. Method for producing silicon thin-film transistors with enhanced forward current drive

    DOEpatents

    Weiner, K.H.

    1998-06-30

    A method is disclosed for fabricating amorphous silicon thin film transistors (TFTs) with a polycrystalline silicon surface channel region for enhanced forward current drive. The method is particularly adapted for producing top-gate silicon TFTs which have the advantages of both amorphous and polycrystalline silicon TFTs, but without problem of leakage current of polycrystalline silicon TFTs. This is accomplished by selectively crystallizing a selected region of the amorphous silicon, using a pulsed excimer laser, to create a thin polycrystalline silicon layer at the silicon/gate-insulator surface. The thus created polysilicon layer has an increased mobility compared to the amorphous silicon during forward device operation so that increased drive currents are achieved. In reverse operation the polysilicon layer is relatively thin compared to the amorphous silicon, so that the transistor exhibits the low leakage currents inherent to amorphous silicon. A device made by this method can be used, for example, as a pixel switch in an active-matrix liquid crystal display to improve display refresh rates. 1 fig.

  3. Method for producing silicon thin-film transistors with enhanced forward current drive

    DOEpatents

    Weiner, Kurt H.

    1998-01-01

    A method for fabricating amorphous silicon thin film transistors (TFTs) with a polycrystalline silicon surface channel region for enhanced forward current drive. The method is particularly adapted for producing top-gate silicon TFTs which have the advantages of both amorphous and polycrystalline silicon TFTs, but without problem of leakage current of polycrystalline silicon TFTs. This is accomplished by selectively crystallizing a selected region of the amorphous silicon, using a pulsed excimer laser, to create a thin polycrystalline silicon layer at the silicon/gate-insulator surface. The thus created polysilicon layer has an increased mobility compared to the amorphous silicon during forward device operation so that increased drive currents are achieved. In reverse operation the polysilicon layer is relatively thin compared to the amorphous silicon, so that the transistor exhibits the low leakage currents inherent to amorphous silicon. A device made by this method can be used, for example, as a pixel switch in an active-matrix liquid crystal display to improve display refresh rates.

  4. Enhancement of emission currents in plasma electron sources based on a low-pressure arc discharge

    NASA Astrophysics Data System (ADS)

    Koval, T. V.; Devyatkov, V. N.; Hung, Nguyen Bao

    2015-11-01

    The paper reports on a theoretical and experimental study of the discharge plasma generation with an enhanced electron emission current in a plasma electron source based on a low-pressure arc discharge with a grid-stabilized plasma emission boundary. The source operates at a pressure in the working chamber of p = 0.02-0.05 Pa (Ar), accelerating voltage of up to Ua = 10 kV, and longitudinal magnetic field for electron beam transport of up to Bz = 0.1 T. The experiments show that in the mode of electron emission from the plasma, the voltage Ud between the cathode and grid electrode changes its sign. The numerical simulation demonstrates that the plasma potential and voltage Ud depend on the electric field penetrating from the acceleration gap into the discharge region through the grid meshes, and on the discharge current, gas pressure, geometric transparency of the grid, and gas kind. It is shown that the main mechanisms responsible for the increase in the discharge current and electron emission current from the plasma are associated with secondary ion-electron emission from the emission electrode and with positive feedback between the region of cathode plasma generation and the channel of electron beam transport.

  5. Paper-basd surface enhanced Raman spectroscopy of pnenobarbital sodium for point-of-care therapeutic drug monitoring

    NASA Astrophysics Data System (ADS)

    Yokoyama, Moe; Yamada, Kenji; Nishimura, Takahiro; Kido, Michiko; Jeong, Hieyong; Ohno, Yuko

    2015-03-01

    Therapeutic drug monitoring (TDM) contributes to safe and effective pharmacotherapy in clinical fields. A simple, rapid, low-cost, and minimally-invasive drug measurement method attracts much interest for point-of-care TDM. Tear fluids can be collected minimally-invasively compared to blood sampling and there is a correlation between a drug concentration in tears and that in bloods. Surface enhanced Raman spectroscopy (SERS) with paper-based substrate is useful for point-of-care TDM owing to inexpensiveness and high-sensitivity. Paper is also a safe tear collection tool. Then we are studying on a paper-based SERS of tear specimen for point-of-care TDM. In this paper, to improve sensitivity in measuring drug concentration in tear fluids, we fabricated a SERS substrate by coating gold nano-rods on a paper substrate and evaluated whether the fabricated substrate can enhance Raman scattering. Sodium phenobarbital (PB), an anti-convulsant agent, was used as a target. In experiment, the fabricated substrate indicated the lower detection limit of PB in a solution than a plain paper substrate. This result showed the potential of the paper based SERS substrate to measure drug concentration in tears simply and inexpensively.

  6. Enhancing pulsed eddy current for inspection of P-3 Orion lap-joint structures

    NASA Astrophysics Data System (ADS)

    Butt, D. M.; Underhill, P. R.; Krause, T. W.

    2016-02-01

    During flight, aircraft are subjected to cyclic loading. In the Lockheed P-3 Orion airframe, this cyclic loading can lead to development of fatigue cracks at steel fastener locations in the top and second layers of aluminum wing skin lap-joints. An inspection method that is capable of detecting these cracks, without fastener removal, is desirable as this can minimize aircraft downtime, while subsequently reducing the risk of collateral damage. The ability to detect second layer cracks has been demonstrated using a Pulsed Eddy Current (PEC) probe design that utilizes the ferrous fastener as a flux conduit. This allows for deeper penetration of flux into the lap-joint second layer and consequently, sensitivity to the presence of cracks. Differential pick-up coil pairs are used to sense the eddy current response due to the presence of a crack. The differential signal obtained from pick-up coils on opposing sides of the fastener is analyzed using a Modified Principal Components Analysis (MPCA). This is followed by a cluster analysis of the resulting MPCA scores to separate fastener locations with cracks from those without. Probe design features, data acquisition system parameters and signal post-processing can each have a strong impact on crack detection. Physical probe configurations and signal analysis processes, used to enhance the PEC system for detection of cracks in P-3 Orion lap-joint structures, are investigated and an enhanced probe design is identified.

  7. Chirally enhanced corrections to flavor-changing neutral current processes in the generic MSSM

    SciTech Connect

    Crivellin, Andreas; Nierste, Ulrich

    2010-05-01

    Chirally enhanced supersymmetric QCD corrections to flavor-changing neutral current processes are investigated in the framework of the minimal supersymmetric standard model with generic sources of flavor violation. These corrections arise from flavor-changing self-energy diagrams and can be absorbed into a finite renormalization of the squark-quark-gluino vertex. In this way enhanced two-loop and even three-loop diagrams can be efficiently included into a leading-order calculation. Our corrections substantially change the values of the parameters {delta}{sub 23}{sup dLL}, {delta}{sub 23}{sup dLR}, {delta}{sub 23}{sup dRL}, and {delta}{sub 23}{sup dRR} extracted from Br[B{yields}X{sub s{gamma}}] if tan{beta} is large. We find stronger (weaker) constraints compared to the leading-order result for negative (positive) values of {mu}. The constraints on {delta}{sub 13}{sup dLR,RL} and {delta}{sub 23}{sup dLR,RL} from B{sub d}-B{sub d} and B{sub s}-B{sub s} mixing change drastically if the third-generation squark masses differ from those of the first two generations. K-K mixing is more strongly affected by the chirally enhanced loop diagrams and even subpercent deviations from degenerate down and strange squark masses lead to profoundly stronger constraints on {delta}{sub 12}{sup dLR,RL}.

  8. Contrast-enhanced ultrasonography: advance and current status in abdominal imaging

    PubMed Central

    2015-01-01

    In the field of contrast-enhanced ultrasonography (US), contrast agents are classified as either first- or second-generation agents depending on the gas within the microbubbles. In the case of first-generation contrast agents, a high-mechanical-index technique is used and only intermittent scanning is possible due to the early destruction of the microbubbles during the scanning. The use of second-generation contrast agents in a low-mechanical-index technique enables continuous scanning. Besides the detection and characterization of focal liver lesions, contrastenhanced US is helpful in the monitoring of radiofrequency ablation therapy and in the targeting step of an US-guided biopsy. Recently, there has been a demand for new criteria to evaluate the treatment response obtained using anti-angiogenic agents because morphologic criteria alone may not reflect the treatment response of the tumor and contrast-enhanced US can provide quantitative markers of tissue perfusion. In spite of the concerns related to its cost-effectiveness, contrast-enhanced US has the potential to be more widely used as a complimentary tool or to substitute the current imaging modalities in some occasions. PMID:25342120

  9. A study of point discharge current observations in the thunderstorm environment at a tropical station during the year 1987 and 1988

    NASA Technical Reports Server (NTRS)

    Manohar, G. K.; Kandalgaonkar, S. S.; Sholapurkar, S. M.

    1991-01-01

    The results of the measurements of point discharge current observations at Pune, India, during years 1987 and 1988 are presented by categorizing and studying their number of spells, polar current average durations, and current magnitudes in day-time and night-time conditions. While the results showed that the thunderstorm activity occupies far more day-time than the night-time the level of current magnitudes remains nearly the same in the two categories.

  10. Enhanced orbital gyrocompassing by the optical flow sensed by an Earth-pointing camera

    NASA Technical Reports Server (NTRS)

    Topaz, Leora; Grunwald, Arthur J.

    1992-01-01

    A new method for improving the orbital gyrocompassing process involving the attitude angle estimation of an earth-pointing satellite in low-Earth orbit uses an electro-optical sensor for direct measurement of the satellite azimuth angle. Simulations have shown that this additional measurement drastically reduces the estimator convergence time, especially when the sun sensor is rendered ineffective, e.g., by high solar elevations. The azimuth-sensing method is based on estimation of the image shift between successive picture frames of an on-board, Earth-pointing, charge-coupled device (CCD) full-matrix camera. The shift-estimation algorithm is based on minimizing a cost function which expresses mean-squared differences in brightness patterns of selected areas of the two frames. An extensive evaluation program with a computer-controlled 2-axis light table and actual satellite images has demonstrated high robustness for a wide range of variation of parameters including image texture content; camera focal length; sampling rate; and number of pixels processed. It was shown to be possible to estimate the azimuth angle within 0.1-0.2 degrees, for a suitably chosen parameter set.

  11. Powerful model for the point source sky: Far-ultraviolet and enhanced midinfrared performance

    NASA Technical Reports Server (NTRS)

    Cohen, Martin

    1994-01-01

    I report further developments of the Wainscoat et al. (1992) model originally created for the point source infrared sky. The already detailed and realistic representation of the Galaxy (disk, spiral arms and local spur, molecular ring, bulge, spheroid) has been improved, guided by CO surveys of local molecular clouds, and by the inclusion of a component to represent Gould's Belt. The newest version of the model is very well validated by Infrared Astronomy Satellite (IRAS) source counts. A major new aspect is the extension of the same model down to the far ultraviolet. I compare predicted and observed far-utraviolet source counts from the Apollo 16 'S201' experiment (1400 A) and the TD1 satellite (for the 1565 A band).

  12. Monitoring hillslope moisture dynamics with surface ERT for enhancing spatial significance of hydrometric point measurements

    NASA Astrophysics Data System (ADS)

    Hübner, R.; Heller, K.; Günther, T.; Kleber, A.

    2015-01-01

    Besides floodplains, hillslopes are basic units that mainly control water movement and flow pathways within catchments of subdued mountain ranges. The structure of their shallow subsurface affects water balance, e.g. infiltration, retention, and runoff. Nevertheless, there is still a gap in the knowledge of the hydrological dynamics on hillslopes, notably due to the lack of generalization and transferability. This study presents a robust multi-method framework of electrical resistivity tomography (ERT) in addition to hydrometric point measurements, transferring hydrometric data into higher spatial scales to obtain additional patterns of distribution and dynamics of soil moisture on a hillslope. A geoelectrical monitoring in a small catchment in the eastern Ore Mountains was carried out at weekly intervals from May to December 2008 to image seasonal moisture dynamics on the hillslope scale. To link water content and electrical resistivity, the parameters of Archie's law were determined using different core samples. To optimize inversion parameters and methods, the derived spatial and temporal water content distribution was compared to tensiometer data. The results from ERT measurements show a strong correlation with the hydrometric data. The response is congruent to the soil tension data. Water content calculated from the ERT profile shows similar variations as that of water content from soil moisture sensors. Consequently, soil moisture dynamics on the hillslope scale may be determined not only by expensive invasive punctual hydrometric measurements, but also by minimally invasive time-lapse ERT, provided that pedo-/petrophysical relationships are known. Since ERT integrates larger spatial scales, a combination with hydrometric point measurements improves the understanding of the ongoing hydrological processes and better suits identification of heterogeneities.

  13. Selective plasmon enhancement of fluorescence towards point of care disease diagnostics

    NASA Astrophysics Data System (ADS)

    Sengupta, Bishwambhar; Zhu, Jingyi; Podila, Ramakrishna; Rao, Apparao

    Surface plasmon coupled emission (SPCE) is a novel analytical technique in which the isotropic emission of a fluorophore is combined with the surface plasmon resonance of a metal thin film to yield highly directional emission from the so-called plasmaphore and thus greatly increased sensitivity. The optimal SPCE enhancement is achieved by introducing a spacer layer to mitigate fluorescence-quenching arising from metal-fluorophore interactions. Here we report a >10-fold amplification of rhodamine B (RhB) fluorophore when carbon nanomaterials are used as the spacer layer. By combining experimental and density functional theory studies, we found that the rehybridization between CNMs and RhB results in emission redshift. We present SPCE-based biosensors for smart-phone based sensing of different analytes including biomarkers for diseases such as tuberculosis.

  14. Effects of Transcranial Direct Current Stimulation on the Recognition of Bodily Emotions from Point-Light Displays

    PubMed Central

    Vonck, Sharona; Swinnen, Stephan Patrick; Wenderoth, Nicole; Alaerts, Kaat

    2015-01-01

    Perceiving human motion, recognizing actions, and interpreting emotional body language are tasks we perform daily and which are supported by a network of brain areas including the human posterior superior temporal sulcus (pSTS). Here, we applied transcranial direct current stimulation (tDCS) with anodal (excitatory) or cathodal (inhibitory) electrodes mounted over right pSTS (target) and orbito-frontal cortex (reference) while healthy participants performed a bodily emotion recognition task using biological motion point-light displays (PLDs). Performance (accuracy and reaction times) was also assessed on a control task which was matched to the emotion recognition task in terms of cognitive and motor demands. Each subject participated in two experimental sessions, receiving either anodal or cathodal stimulation, which were separated by one week to avoid residual effects of previous stimulations. Overall, tDCS brain stimulation did not affect the recognition of emotional states from PLDs. However, when emotions with a negative or positive–neutral emotional valence were analyzed separately, effects of stimulation were shown for recognizing emotions with a negative emotional valence (sadness and anger), indicating increased recognition performance when receiving anodal (excitatory) stimulation compared to cathodal (inhibitory) stimulation over pSTS. No stimulation effects were shown for the recognition of emotions with positive–neutral emotional valences. These findings extend previous studies showing structure–function relationships between STS and biological motion processing from PLDs and provide indications that stimulation effects may be modulated by the emotional valence of the stimuli. PMID:26283952

  15. Origin and enhancement of spin polarized current in diluted magnetic oxides by oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Chou, Hsiung; Yang, Kung-Shang; Tsao, Yao-Chung; Dwivedi, G. D.; Lin, Cheng-Pang; Sun, Shih-Jye; Lin, L. K.; Lee, S. F.

    2016-04-01

    Spin polarized current (SPC) is a crucial characteristic of diluted magnetic oxides due to the potential application of oxides in spintronic devices. However, most research has been focused on ferromagnetic properties rather than polarization of electric current, because direct measurements are difficult and the origin of SPC has yet to be fully understood. The method to increase the SPC percentage is beyond practical consideration at present. To address this problem, we focus on the role of oxygen vacancies (VO) on SPC, which are controlled by growing the Co-doped ZnO thin-films at room temperature in a reducing atmosphere [Ar + (1%-30%)H2]. We found that the conductivity increases with an increase of VO via two independent channels: the variable range hopping (VRH) within localized states and the itinerant transport in the conduction band. The point contact Andreev reflection measurements at 4.2 K, where the electric conduction is governed only by the VRH mechanism, prove that the current flowing in the VRH hopping channel is SPC. The percentage of SPC increases with the introduction of VO and increase in its concentration. The transport measurement shows that by manipulating VO, one can control the percentage of VRH hopping conduction such that it can even dominate room temperature conduction. The highest achieved SPC ratio at room temperature was 80%.

  16. Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

    NASA Technical Reports Server (NTRS)

    Evans, R. W.

    1997-01-01

    These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

  17. Hypotonic stimuli enhance proton-gated currents of acid-sensing ion channel-1b

    SciTech Connect

    Ugawa, Shinya Ishida, Yusuke; Ueda, Takashi; Yu, Yong; Shimada, Shoichi

    2008-03-14

    Acid-sensing ion channels (ASICs) are strong candidates for mammalian mechanoreceptors. We investigated whether mouse acid-sensing ion channel-1b (ASIC1b) is sensitive to mechanical stimuli using oocyte electrophysiology, because ASIC1b is located in the mechanosensory stereocilia of cochlear hair cells. Hypotonic stimuli that induced membrane stretch of oocytes evoked no significant current in ASIC1b-expressing oocytes at pH 7.5. However, acid (pH 4.0 or 5.0)-evoked currents in the oocytes were substantially enhanced by the hypotonicity, showing mechanosensitivity of ASIC1b and possible mechanogating of the channel in the presence of other components. Interestingly, the ASIC1b channel was permeable to K{sup +} (a principal charge carrier for cochlear sensory transduction) and the affinity of the channel for amiloride (IC{sub 50} (inhibition constant) = approximately 48.3 {mu}M) was quite similar to that described for the mouse hair cell mechanotransducer current. Taken together, these data raise the possibility that ASIC1b participates in cochlear mechanoelectrical transduction.

  18. Enhancement of current carrying capacity of the strained ZnSe nanowire

    NASA Astrophysics Data System (ADS)

    Wang, Y. G.; Zeng, Y. P.; Qu, B. H.; Zhang, Q. L.

    2011-05-01

    The effect of strain on the current carrying capacity of ZnSe nanowire has been studied by in situ transmission electron microscopy (TEM). Under TEM inspection the strain can be created at the selected position in a single ZnSe nanowire by the compressive stress applied along its axial direction using a movable probe electrode. The induced strain is controllable in the magnitude of curvature of the ZnSe nanowire bent by careful manipulation of the movable probe electrode. In situ current-induced Joule heating has confirmed that the strained segment in a single ZnSe nanowire exhibited better ability than the unstrained segments against Joule heating. Consequently, the current carrying capacity of the ZnSe nanowire can be effectively enhanced by intentionally created strain. The experimental results have also proved that a significant increase of the electrical conductance and the thermal resistance can be achieved simultaneously in a single nanowire by the intentionally designed and created strain.

  19. Photo-Current Enhancement in Carbon Quantum Dots Functionalized Titania Nanotube Arrays.

    PubMed

    Rani, Sanju; Borse, Pramod H; Pareek, Alka; Rajalakshmi, N; Dhathathreyan, K S

    2016-06-01

    Highly aligned, vertically oriented, TiO2 nanotube arrays fabricated by electrochemical anodization were functionalised by carbon quantum dots (CQD) synthesized by an electrochemical reduction technique. Here, we report the photo-electrochemical properties of such TiO2 nanotubes array-CQD composite material and it has been found that the properties are significantly enhanced compared to that in pristine (bare) nanotubes. The TiO2 nanotubes were characterized by X-ray diffraction and scanning electron microscopy, whereas the CQD samples were characterized by transmission electron microscopy, optical absorption spectroscopy. CQDs synthesized under two different conditions showed a distinct size difference and corresponding absorption spectra revealed concominant shift in the absorption edges. Furthermore, the photo-electrochemical measurements were carried out with the help of photo-current, incident photon to current conversion efficiency (IPCE), Mott-Schottky plots and the impedance analysis. The photo-current data revealed 30% improvement in TiO2-CQD samples compared to bare TiO2 nanotubes samples. A higher photo-conversion efficiency was observed along with the shifting of the peak value towards visible wavelengths. The Mott-Schottky plots revealed shift in the flat-band potential in the CQD-TiO2 samples and corresponding lowering of the charge transfer resistance was observed through the impedance spectroscopy. PMID:27427662

  20. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  1. THEMIS two-point measurements of the cross-tail current density: A thick bifurcated current sheet in the near-Earth plasma sheet

    NASA Astrophysics Data System (ADS)

    Saito, Miho

    2015-08-01

    The basic properties of the near-Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail-like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets.

  2. Qualified life enhanced by environmental monitoring at Nine Mile Point Units 1 and 2

    SciTech Connect

    Jirousek, J.; Gleason, J.

    1991-06-01

    The Qualified Life of equipment in a Nuclear Plant Environmental Qualification program is typically originally based upon engineering estimates of ambient environmental conditions. These estimates are of necessity very conservative. Substantial increases of the qualified lives of equipment may be justified by establishment of the actual ambient environmental conditions. A life extension program is not essential for licensing or safe operation of the plant. However, the potential exists for substantial cost savings due to reduced equipment costs and maintenance requirements for component replacements and parts changeouts, as well as reduced schedules for plant outages. Temperature monitors were installed at specific environmental zones in both NMP-1 and NMP-2 to provide actual field measured data of these parameters. This has allowed re-calculation/extension of the qualified lives of the EQ equipment located in those zones. Additionally, radiation monitors have been installed in the Nine Mile Point Unit 2 drywell to assess the validity of the Total Integrated Dose assessments and similarly to adjust the qualification requirements with respect to radiation.

  3. Enhanced resolution edge and surface estimation from ladar point clouds containing multiple return data

    NASA Astrophysics Data System (ADS)

    Neilsen, Kevin D.; Budge, Scott E.

    2013-11-01

    Signal processing enables the detection of more returns in a digital ladar waveform by computing the surface response. Prior work has shown that obtaining the surface response can improve the range resolution by a factor of 2. However, this advantage presents a problem when forming a range image-each ladar shot crossing an edge contains multiple values. To exploit this information, the location of each return inside the spatial beam footprint is estimated by dividing the footprint into sections that correspond to each return and assigning the coordinates of the return to the centroid of the region. Increased resolution results on the edges of targets where multiple returns occur. Experiments focus on angled and slotted surfaces for both simulated and real data. Results show that the angle of incidence on a 75-deg surface is computed only using a single waveform with an error of 1.4 deg and that the width of a 19-cm-wide by 16-cm-deep slot is estimated with an error of 3.4 cm using real data. Point clouds show that the edges of the slotted surface are sharpened. These results can be used to improve features extracted from objects for applications such as automatic target recognition.

  4. Surface plasmon enhanced-field fluorescence biosensor for point-of-care testing using fluorescent nanoparticles

    NASA Astrophysics Data System (ADS)

    Horii, Kazuyoshi; Kimura, Toshihito; Ohtsuka, Hisashi; Kasagi, Noriyuki; Oohara, Tomoya; Matsuno, Tadahiro; Hakamata, Masashi; Komatsu, Akihiro; Sendai, Tomonari

    2012-03-01

    An optical biosensor system using surface-plasmon field-enhanced fluorescence has been developed, which allows high sensitivity and fast measurement available. Intensity of fluorophores in SPFS is highly dependent upon the distance from metal surface. The resonant evanescent electric field excites fluorophores within the penetration area. On the other hand, fluorescence quenching in close proximity to a metal surface interfere with the excitation. We have developed a new technology for fluorescent nanoparticles that could receive the energy from metal surface effectively. This enables technology of detecting strong and stable SPFS signals, as well as homogeneous assay method that allows us to eliminate binding/free separation process for unreacted fluorescent particles. A rate assay method has also been employed, which resolves affect from diffusion-limited access, in order to realize a fast surface immunoreaction in a microchannel. Taking advantage of these two developments, as eliminating an enzyme response process such as CLEIA, our system reaches much faster reaction time of 2 minutes to detect thyroid stimulating hormone (TSH) of canine serum sample at 0.1ng/mL. We believe our system with these new technologies is a powerful tool for in-vitro diagnosis which meets various clinical requirements.

  5. Low melting point pyridinium ionic liquid pretreatment for enhancing enzymatic saccharification of cellulosic biomass.

    PubMed

    Uju; Nakamoto, Aya; Shoda, Yasuhiro; Goto, Masahiro; Tokuhara, Wataru; Noritake, Yoshiyuki; Katahira, Satoshi; Ishida, Nobuhiro; Ogino, Chiaki; Kamiya, Noriho

    2013-05-01

    The potential of 1-hexylpyridinium chloride ([Hpy][Cl]), to pretreat cellulosic feedstocks was investigated using microcrystalline cellulose (Avicel) and Bagasse at 80 °C or 100 °C. Short [Hpy][Cl] pretreatments, <30 min, at lower temperature accelerate subsequent enzymatic saccharification of Avicel. Over 95% conversion of pretreated Avicel to glucose was attained after 24h enzymatic saccharification under optimal conditions, whereas regenerated Bagasse showed 1-3-fold higher conversion than untreated biomass. FT-IR analysis of both Avicel and Bagasse samples pretreated with [Hpy][Cl] or 1-ethyl-3-methyimidazolium acetate ([Emim][OAc]) revealed that these ionic liquids behaved differently during pretreatment. [Hpy][Cl] pretreatment for an extended duration (180 min) released mono- and disaccharides without using cellulase enzymes, suggesting [Hpy][Cl] has capability for direct saccharification of cellulosic feedstocks. On the basis of the results obtained, [Hpy][Cl] pretreatment enhanced initial reaction rates in enzymatic saccharification by either crystalline polymorphic alteration of cellulose or partial degradation of the crystalline cellulosic fraction in biomass. PMID:22850175

  6. Enhancement by T-type Ca2+ currents of odor sensitivity in olfactory receptor cells.

    PubMed

    Kawai, F; Miyachi, E

    2001-05-15

    Mechanisms underlying action potential initiation in olfactory receptor cells (ORCs) during odor stimulation were investigated using conventional and dynamic patch-clamp recording techniques. Under current-clamp conditions, action potentials generated by a least effective odor-induced depolarization were almost completely blocked by 0.1 mm Ni(2+), a T-type Ca(2+) channel blocker, but not by 0.1 mm Cd(2+), a high voltage-activated Ca(2+) channel blocker. Under voltage-clamp conditions, depolarizing voltage steps induced a fast transient inward current, which consisted of Na(+) (I(Na)) and T-type Ca(2+) (I(Ca,T)) currents. The amplitude of I(Ca,T) was approximately one-fourth of that of I(Na) (0.23 +/- 0.03, mean +/- SEM). Because both I(Na) and I(Ca,T) are known to show rapid inactivation, we examined how much I(Na) and I(Ca,T) are activated during the gradually depolarizing initial phase of receptor potentials. The ratio of I(Ca,T)/I(Na) during a ramp depolarization at the slope of 0.5 mV/msec was 0.56 +/- 0.03. Using the dynamic patch-clamp recording technique, we also recorded I(Ca,T) and I(Na) during the generation of odor-induced action potentials. This ratio of I(Ca,T)/I(Na) was 0.54 +/- 0.04. These ratios were more than twice as large as that (0.23) obtained from the experiment using voltage steps, suggesting that I(Ca,T) carries significant amount of current to generate the action potentials. We conclude that I(Ca,T) contributes to enhance odor sensitivity by lowering the threshold of spike generation in ORCs. PMID:11319242

  7. Enhanced current and power density of micro-scale microbial fuel cells with ultramicroelectrode anodes

    NASA Astrophysics Data System (ADS)

    Ren, Hao; Rangaswami, Sriram; Lee, Hyung-Sool; Chae, Junseok

    2016-09-01

    We present a micro-scale microbial fuel cell (MFC) with an ultramicroelectrode (UME) anode, with the aim of creating a miniaturized high-current/power-density converter using carbon-neutral and renewable energy sources. Micro-scale MFCs have been studied for more than a decade, yet their current and power densities are still an order of magnitude lower than those of their macro-scale counterparts. In order to enhance the current/power densities, we engineer a concentric ring-shaped UME, with a width of 20 μm, to facilitate the diffusion of ions in the vicinity of the micro-organisms that form biofilm on the UME. The biofilm extends approximately 15 μm from the edge of the UME, suggesting the effective biofilm area increases. Measured current/power densities per the effective area and the original anode area are 7.08  ±  0.01 A m‑2 & 3.09  ±  0.04 W m‑2 and 17.7  ±  0.03 A m‑2 & 7.72  ±  0.09 W m‑2, respectively. This is substantially higher than any prior work in micro-scale MFCs, and very close, or even higher, to that of macro-scale MFCs. A Coulombic efficiency, a measure of how efficiently an MFC harvests electrons from donor substrate, of 70%, and an energy conversion efficiency of 17% are marked, highlighting the micro-scale MFC as an attractive alternative within the existing energy conversion portfolio.

  8. Enhancing multiple-point geostatistical modeling: 1. Graph theory and pattern adjustment

    NASA Astrophysics Data System (ADS)

    Tahmasebi, Pejman; Sahimi, Muhammad

    2016-03-01

    In recent years, higher-order geostatistical methods have been used for modeling of a wide variety of large-scale porous media, such as groundwater aquifers and oil reservoirs. Their popularity stems from their ability to account for qualitative data and the great flexibility that they offer for conditioning the models to hard (quantitative) data, which endow them with the capability for generating realistic realizations of porous formations with very complex channels, as well as features that are mainly a barrier to fluid flow. One group of such models consists of pattern-based methods that use a set of data points for generating stochastic realizations by which the large-scale structure and highly-connected features are reproduced accurately. The cross correlation-based simulation (CCSIM) algorithm, proposed previously by the authors, is a member of this group that has been shown to be capable of simulating multimillion cell models in a matter of a few CPU seconds. The method is, however, sensitive to pattern's specifications, such as boundaries and the number of replicates. In this paper the original CCSIM algorithm is reconsidered and two significant improvements are proposed for accurately reproducing large-scale patterns of heterogeneities in porous media. First, an effective boundary-correction method based on the graph theory is presented by which one identifies the optimal cutting path/surface for removing the patchiness and discontinuities in the realization of a porous medium. Next, a new pattern adjustment method is proposed that automatically transfers the features in a pattern to one that seamlessly matches the surrounding patterns. The original CCSIM algorithm is then combined with the two methods and is tested using various complex two- and three-dimensional examples. It should, however, be emphasized that the methods that we propose in this paper are applicable to other pattern-based geostatistical simulation methods.

  9. A single-point mutation enhances dual functionality of a scorpion toxin.

    PubMed

    Wang, Xueli; Gao, Bin; Zhu, Shunyi

    2016-01-01

    Scorpion venom represents a tremendous, hitherto partially explored peptide library that has been proven to be useful not only for understanding ion channels but also for drug design. MeuTXKα3 is a functionally unknown scorpion toxin-like peptide. Here we describe new transcripts of this gene arising from alternative polyadenylation and its biological function as well as a mutant with a single-point substitution at site 30. Native-like MeuTXKα3 and its mutant were produced in Escherichia coli and their toxic function against Drosophila Shaker K(+) channel and its mammalian counterparts (rKv1.1-rKv1.3) were assayed by two-electrode voltage clamp technique. The results show that MeuTXKα3 is a weak toxin with a wide-spectrum of activity on both Drosophila and mammalian K(+) channels. The substitution of a proline at site 30 by an asparagine, an evolutionarily conserved functional residue in the scorpion α-KTx family, led to an increased activity on rKv1.2 and rKv1.3 but a decreased activity on the Shaker channel without changing the potency on rKv1.1, suggesting a key role of this site in species selectivity of scorpion toxins. MeuTXKα3 was also active on a variety of bacteria with lethal concentrations ranging from 4.66 to 52.01μM and the mutant even had stronger activity on some of these bacterial species. To the best of our knowledge, this is the first report on a bi-functional short-chain peptide in the lesser Asian scorpion venom. Further extensive mutations of MeuTXKα3 at site 30 could help improve its K(+) channel-blocking and antibacterial functions. PMID:26358403

  10. Current approaches to enhance CNS delivery of drugs across the brain barriers

    PubMed Central

    Lu, Cui-Tao; Zhao, Ying-Zheng; Wong, Ho Lun; Cai, Jun; Peng, Lei; Tian, Xin-Qiao

    2014-01-01

    Although many agents have therapeutic potentials for central nervous system (CNS) diseases, few of these agents have been clinically used because of the brain barriers. As the protective barrier of the CNS, the blood–brain barrier and the blood–cerebrospinal fluid barrier maintain the brain microenvironment, neuronal activity, and proper functioning of the CNS. Different strategies for efficient CNS delivery have been studied. This article reviews the current approaches to open or facilitate penetration across these barriers for enhanced drug delivery to the CNS. These approaches are summarized into three broad categories: noninvasive, invasive, and miscellaneous techniques. The progresses made using these approaches are reviewed, and the associated mechanisms and problems are discussed. PMID:24872687

  11. Contrast-enhanced ultrasound after endovascular aortic repair—current status and future perspectives

    PubMed Central

    Partovi, Sasan; Kaspar, Mathias; Aschwanden, Markus; Lopresti, Charles; Madan, Shivanshu; Uthoff, Heiko; Imfeld, Stephan

    2015-01-01

    An increasing number of patients with abdominal aortic aneurysms (AAAs) are undergoing endovascular aortic repair (EVAR) instead of open surgery. These patients require lifelong surveillance, and the follow-up imaging modality of choice has been traditionally computed tomography angiography (CTA). Repetitive CTA imaging is associated with cumulative radiation exposure and requires the administration of multiple doses of nephrotoxic contrast agents. Contrast-enhanced ultrasound (CEUS) has emerged as an alternative strategy in the follow-up of patients with EVAR and demonstrates high sensitivity and specificity for detection of endoleaks. In fact, a series of studies have shown that CEUS is at least performing equal to computed tomography for the detection and classification of endoleaks. This article summarizes current evidence of CEUS after EVAR and demonstrates its usefulness via various patient cases. PMID:26673398

  12. Delayed enhancement of multitasking performance: Effects of anodal transcranial direct current stimulation on the prefrontal cortex

    PubMed Central

    Hsu, Wan-Yu; Zanto, Theodore P.; Anguera, Joaquin A.; Lin, Yung-Yang; Gazzaley, Adam

    2015-01-01

    Background The dorsolateral prefrontal cortex (DLPFC) has been proposed to play an important role in neural processes that underlie multitasking performance. However, this claim is underexplored in terms of direct causal evidence. Objective The current study aimed to delineate the causal involvement of the DLPFC during multitasking by modulating neural activity with transcranial direct current stimulation (tDCS) prior to engagement in a demanding multitasking paradigm. Methods The study is a single-blind, crossover, sham-controlled experiment. Anodal tDCS or sham tDCS was applied over left DLPFC in forty-one healthy young adults (aged 18–35 years) immediately before they engaged in a 3-D video game designed to assess multitasking performance. Participants were separated into three subgroups: real-sham (i.e., real tDCS in the first session, followed by sham tDCS in the second session one hour later), sham-real (sham tDCS first session, real tDCS second session), and sham-sham (sham tDCS in both sessions). Results The real-sham group showed enhanced multitasking performance and decreased multitasking cost during the second session, compared to first session, suggesting delayed cognitive benefits of tDCS. Interestingly, performance benefits were observed only for multitasking and not on a single-task version of the game. No significant changes were found between the first and second sessions for either the sham-real or the sham-sham groups. Conclusions These results suggest a causal role of left prefrontal cortex in facilitating the simultaneous performance of more than one task, or multitasking. Moreover, these findings reveal that anodal tDCS may have delayed benefits that reflect an enhanced rate of learning. PMID:26073148

  13. Chronic Enhancement of Serotonin Facilitates Excitatory Transcranial Direct Current Stimulation-Induced Neuroplasticity.

    PubMed

    Kuo, Hsiao-I; Paulus, Walter; Batsikadze, Giorgi; Jamil, Asif; Kuo, Min-Fang; Nitsche, Michael A

    2016-04-01

    Serotonin affects memory formation via modulating long-term potentiation (LTP) and depression (LTD). Accordingly, acute selective serotonin reuptake inhibitor (SSRI) administration enhanced LTP-like plasticity induced by transcranial direct current stimulation (tDCS) in humans. However, it usually takes some time for SSRI to reduce clinical symptoms such as anxiety, negative mood, and related symptoms of depression and anxiety disorders. This might be related to an at least partially different effect of chronic serotonergic enhancement on plasticity, as compared with single-dose medication. Here we explored the impact of chronic application of the SSRI citalopram (CIT) on plasticity induced by tDCS in healthy humans in a partially double-blinded, placebo (PLC)-controlled, randomized crossover study. Furthermore, we explored the dependency of plasticity induction from the glutamatergic system via N-methyl-D-aspartate receptor antagonism. Twelve healthy subjects received PLC medication, combined with anodal or cathodal tDCS of the primary motor cortex. Afterwards, the same subjects took CIT (20 mg/day) consecutively for 35 days. During this period, four additional interventions were performed (CIT and PLC medication with anodal/cathodal tDCS, CIT and dextromethorphan (150 mg) with anodal/cathodal tDCS). Plasticity was monitored by motor-evoked potential amplitudes elicited by transcranial magnetic stimulation. Chronic application of CIT increased and prolonged the LTP-like plasticity induced by anodal tDCS for over 24 h, and converted cathodal tDCS-induced LTD-like plasticity into facilitation. These effects were abolished by dextromethorphan. Chronic serotonergic enhancement results in a strengthening of LTP-like glutamatergic plasticity, which might partially explain the therapeutic impact of SSRIs in depression and other neuropsychiatric diseases. PMID:26329381

  14. Cross-Field Current Instabilities in Thin Ionization Layers and the Enhanced Aurora

    SciTech Connect

    Jay R. Johnson and Hideo Okuda

    2008-05-20

    Nearly half of the time, auroral displays exhibit thin, bright layers known as \\enhanced aurora." There is a substantial body of evidence that connects these displays with thin, dense, heavy ion layers in the E-region. Based on the spectral characteristics of the enhanced layers, it is believed that they result when wave-particle interaction heats ambient electrons to energies at or just above the 17 eV ionization energy of N2. While there are several possible instabilities that could produce suprathermal electrons in thin layers, there has been no clear theoretical investigation which examines in detail how wave instabilities in the thin ionization layers could develop and produce the suprathermal electrons. We examine instabilities which would occur in thin, dense, heavy ion layers using extensive analytical analysis combined with particle simulations. We analyze a cross field current instability that is found to be strongly unstable in the heavy ion layers. Electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the N2 ionization energy.

  15. Spin caloritronics with superconductors: Enhanced thermoelectric effects, generalized Onsager response-matrix, and thermal spin currents

    NASA Astrophysics Data System (ADS)

    Linder, Jacob; Bathen, Marianne Etzelmüller

    2016-06-01

    It has recently been proposed and experimentally demonstrated that it is possible to generate large thermoelectric effects in ferromagnet/superconductor structures due to a spin-dependent particle-hole asymmetry. Here, we show theoretically that quasiparticle tunneling between two spin-split superconductors enhances the thermoelectric response manyfold compared to when only one such superconductor is used, generating Seebeck coefficients (S >1 mV/K) and figures of merit (Z T ≃40 ) far exceeding the best bulk thermoelectric materials, and it also becomes more resilient toward inelastic-scattering processes. We present a generalized Onsager response-matrix that takes into account spin-dependent voltage and temperature gradients. Moreover, we show that thermally induced spin currents created in such junctions, even in the absence of a polarized tunneling barrier, also become largest in the case in which spin-dependent particle-hole asymmetry exists on both sides of the barrier. We determine how these thermal spin-currents can be tuned both in magnitude and sign by several parameters, including the external field, the temperature, and the superconducting phase difference.

  16. Enhanced current transport at grain boundaries in high-T(c) superconductors.

    PubMed

    Klie, R F; Buban, J P; Varela, M; Franceschetti, A; Jooss, C; Zhu, Y; Browning, N D; Pantelides, S T; Pennycook, S J

    2005-05-26

    Large-scale applications of high-transition-temperature (high-T(c)) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals. The superconducting critical current density (J(c)) across a grain boundary drops exponentially if the misorientation angle exceeds 2 degrees -7 degrees. Grain texturing reduces the average misorientation angle, but problems persist. Adding impurities (such as Ca in YBa2Cu3O7-delta; YBCO) leads to increased J(c) (refs 9, 10), which is generally attributed to excess holes introduced by Ca2+ substituting for Y3+ (ref. 11). However, a comprehensive physical model for the role of grain boundaries and Ca doping has remained elusive. Here we report calculations, imaging and spectroscopy at the atomic scale that demonstrate that in poly-crystalline YBCO, highly strained grain-boundary regions contain excess O vacancies, which reduce the local hole concentration. The Ca impurities indeed substitute for Y, but in grain-boundary regions under compression and tension they also replace Ba and Cu, relieving strain and suppressing O-vacancy formation. Our results demonstrate that the ionic radii are more important than their electronic valences for enhancing J(c). PMID:15917804

  17. Enhancement of current injection in organic light emitting diodes with sputter treated molybdenum oxides as hole injection layers

    NASA Astrophysics Data System (ADS)

    Wang, Po-Sheng; Wu, I.-Wen; Tseng, Wei-Hsuan; Chen, Mei-Hsin; Wu, Chih-I.

    2011-04-01

    The enhancement of current density and luminance in organic light emitting diodes is achieved by treating molybdenum oxide (MoO3) hole-injection-layers with slight argon ion sputtering. The sputter treated MoO3 layers provide improvement in current injection efficiency, resulting in better current density which is about ten times higher than that of the reference devices. Photoemission spectroscopy shows that molybdenum in MoO3 is reduced to lower oxidation states after sputter treatment due to the removal of oxygen. As a result, gap states are formed to enhance metallic characteristics of the sputter treated MoO3 surface and facilitate better hole injection efficiency.

  18. Dental Student Academic Integrity in U.S. Dental Schools: Current Status and Recommendations for Enhancement.

    PubMed

    Graham, Bruce S; Knight, G William; Graham, Linda

    2016-01-01

    Cheating incidents in 2006-07 led U.S. dental schools to heighten their efforts to enhance the environment of academic integrity in their institutions. The aims of this study were to document the measures being used by U.S. dental schools to discourage student cheating, determine the current incidence of reported cheating, and make recommendations for enhancing a culture of integrity in dental education. In late 2014-early 2015, an online survey was distributed to academic deans of all 61 accredited U.S. dental schools that had four classes of dental students enrolled; 50 (82%) responded. Among measures used, 98% of respondents reported having policy statements regarding student academic integrity, 92% had an Honor Code, 96% provided student orientation to integrity policies, and most used proctoring of final exams (91%) and tests (93%). Regarding disciplinary processes, 27% reported their faculty members only rarely reported suspected cheating (though required in 76% of the schools), and 40% disseminated anonymous results of disciplinary hearings. A smaller number of schools (n=36) responded to the question about student cheating than to other questions; those results suggested that reported cheating had increased almost threefold since 1998. The authors recommend that schools add cheating case scenarios to professional ethics curricula; disseminate outcomes of cheating enforcement actions; have students sign a statement attesting to compliance with academic integrity policies at every testing activity; add curricular content on correct writing techniques to avoid plagiarism; require faculty to distribute retired test items; acquire examination-authoring software programs to enable faculty to generate new multiple-choice items and different versions of the same multiple-choice tests; avoid take-home exams when assessing independent student knowledge; and utilize student assessment methods directly relevant to clinical practice. PMID:26729679

  19. Methods for enhancing the efficiency of dental/oral health clinical trials: current status, future possibilities.

    PubMed

    Barnett, M L; Pihlstrom, B L

    2004-10-01

    In recent years, there has been an increasing demand for clinical trials to study oral, dental, and craniofacial diseases and conditions. This has resulted from such factors as the increasing pace of discoveries requiring translational research to develop them for clinical use, FDA requirements for product approval, a need for additional data to support evidence-based dental practice, and the expansion of the NIDCR's clinical research programs. The complexity, size, and duration of clinical trials often make them quite costly to conduct, and may impede the development of novel diagnostic, preventive, and therapeutic methods that could have a significant impact on clinical practice and inform public health policy. Recent advances in such areas as genomics and proteomics, coupled with the development of new technologies, have expanded our knowledge of the etiology and pathogenesis of disease and, from this, have provided new insights into the design and conduct of clinical trials. The workshop, "Methods for Enhancing the Efficiency of Dental/Oral Health Clinical Trials: Current Status, Future Possibilities", held on May 6-7, 2004, considered a variety of ways in which these insights are being, or have the potential to be, applied to clinical trials so as to enhance their efficiency and, hence, their cost-effectiveness, without diminishing the quality of information produced. The focus of this workshop was to assess the state of the science and identify research needs for the use of biomarkers, surrogate endpoints, and new technologies in oral disease clinical trials. Examples of ways in which clinical trials of other diseases have benefited from the use of new methods and technologies and FDA considerations were also discussed. PMID:15381712

  20. Enhancement of object detection with transcranial direct current stimulation is associated with increased attention

    PubMed Central

    2012-01-01

    Background We previously found that Transcranial Direct Current Stimulation (tDCS) improves learning and performance in a task where subjects learn to detect potential threats indicated by small target objects hidden in a complex virtual environment. In the present study, we examined the hypothesis that these effects on learning and performance are related to changes in attention. The effects of tDCS were tested for three forms of attention (alerting, orienting, and executive attention) using the Attention Network Task (ANT), which were compared with performance on the object-learning task. Results Participants received either 0.1 mA (N = 10) or 2.0 mA (N = 9) tDCS during training and were tested for performance in object-identification before training (baseline-test) and again immediately after training (immediate test). Participants next performed the Attention Networks Task (ANT), and were later tested for object-identification performance a final time (delayed test). Alerting, but not orienting or executive attention, was significantly higher for participants receiving 2.0 mA compared with 0.1 mA tDCS (p < 0.02). Furthermore, alerting scores were significantly correlated with the proportion of hits (p < 0.01) for participants receiving 2.0 mA. Conclusions These results indicate that tDCS enhancement of performance in this task may be related in part to the enhancement of alerting attention, which may benefit the initial identification, learning and/or subsequent recognition of target objects indicating potential threats. PMID:22963503

  1. Enhancing user acceptance of mandated mobile health information systems: the ePOC (electronic point-of-care project) experience.

    PubMed

    Burgess, Lois; Sargent, Jason

    2007-01-01

    From a clinical perspective, the use of mobile technologies, such as Personal Digital Assistants (PDAs) within hospital environments is not new. A paradigm shift however is underway towards the acceptance and utility of these systems within mobile-based healthcare environments. Introducing new technologies and associated work practices has intrinsic risks which must be addressed. This paper contends that intervening to address user concerns as they arise throughout the system development lifecycle will lead to greater levels of user acceptance, while ultimately enhancing the deliverability of a system that provides a best fit with end user needs. It is envisaged this research will lead to the development of a formalised user acceptance framework based on an agile approach to user acceptance measurement. The results of an ongoing study of user perceptions towards a mandated electronic point-of-care information system in the Northern Illawarra Ambulatory Care Team (TACT) are presented. PMID:17911883

  2. Enhancing the focal-resolution of aeroacoustic time-reversal using a point sponge-layer damping technique.

    PubMed

    Mimani, A; Doolan, C J; Medwell, P R

    2014-09-01

    This letter presents the Point-Time-Reversal-Sponge-Layer (PTRSL) technique to enhance the focal-resolution of aeroacoustic Time-Reversal (TR). A PTRSL is implemented on a square domain centered at the predicted source location and is based on damping the radial components of the incoming and outgoing fluxes propagating toward and away from the source, respectively. A PTRSL is shown to overcome the conventional half-wavelength diffraction-limit; its implementation significantly reduces the focal spot size to one-fifth of a wavelength for a monopole source. Furthermore, PTRSL reduces the focal spots of a dipole source to three-tenths of a wavelength, as compared to three-fifths without its implementation. PMID:25190421

  3. Enhancement of the critical current density in single-crystal Bi2Sr2CaCu2O8 superconductors by chemically induced disorder.

    PubMed Central

    Wang, Y L; Wu, X L; Chen, C C; Lieber, C M

    1990-01-01

    The effect of metal substitution on the critical current densities of single-crystal PbxBi2-xSr2CaCu2O8 (x = 0 or x = 0.7) superconductors has been investigated. Substitution of lead was found to increase the average critical current density from 1 x 10(5) A/cm2 to 2 x 10(6) A/cm2 at 5 K in an applied magnetic field of 10 kilooersteds (1 oersted = 80 A/m). The order of magnitude increase in the critical current density was observed for temperatures up to the flux vortex lattice melting point; the flux lattice melting point was also found to increase to 30 K (from 22 K) in the lead-substituted materials. Diffraction and microscopy investigations of the structural parameters indicate that the fundamental atomic lattices are virtually the same for both materials. Scanning tunneling microscopy images demonstrate, however, that lead substitution causes significant disorder (or defects) in the one-dimensional superstructure found in Bi2Sr2CaCu2O8. Since crystal defects can increase the critical current density by pinning the motion of flux vortices, it is likely that this lead-induced disorder enhances vortex pinning. The lead-induced disorder is specific to the nonsuperconducting Bi-O layers, and thus our results suggest that chemical substitutions may be utilized to control selectively flux pinning and the critical current density in these materials. Images PMID:11607103

  4. Enhancement of the Liquefaction Rate in Small-Scale Helium Liquefiers Working Near and Above the Critical Point

    NASA Astrophysics Data System (ADS)

    Rillo, C.; Gabal, M.; Lozano, M. P.; Sesé, J.; Spagna, S.; Diederichs, J.; Sager, R.; Chialvo, C.; Terry, J.; Rayner, G.; Warburton, R.; Reineman, R.

    2015-05-01

    Low-temperature research laboratories with typical liquid-helium consumption of the order of tens of liters per day have greatly benefited from the recent development of small-scale liquefiers. In general, these liquefiers are based on Gifford-McMahon or pulse-tube closed-cycle refrigerators with a nominal cooling power ranging from 1 to 1.5 W at 4.2 K. The liquefaction rate for these cryocooler-based liquefiers depends on the pressure at which the helium is liquefied, although the final user conditions of the produced liquid helium are always atmospheric pressure and boiling temperature (e.g., 4.2 K at 100 kPa). Here, we show a systematic study on this effect, in which an enhancement in excess of 70% in liquefaction rate is found experimentally for pressures near and above the critical point of helium (220 kPa). We propose that the underlying mechanism for the liquefaction enhancement is based on the increase in cryocooler cooling power with temperature and the decrease of the helium enthalpy with pressure.

  5. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique

    PubMed Central

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-01-01

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112

  6. Transcranial direct current stimulation for memory enhancement: from clinical research to animal models

    PubMed Central

    Bennabi, Djamila; Pedron, Solène; Haffen, Emmanuel; Monnin, Julie; Peterschmitt, Yvan; Van Waes, Vincent

    2014-01-01

    There is a growing demand for new brain-enhancing technologies to improve mental performance, both for patients with cognitive disorders and for healthy individuals. Transcranial direct current stimulation (tDCS) is a non-invasive, painless, and easy to use neuromodulatory technique that can improve performance on a variety of cognitive tasks in humans despite its exact mode of action remains unclear. We have conducted a mini-review of the literature to first briefly summarize the growing amount of data from clinical trials assessing the efficacy of tDCS, focusing exclusively on learning and memory performances in healthy human subjects and in patients with depression, schizophrenia, and other neurological disorders. We then discuss these findings in the context of the strikingly few studies resulting from animal research. Finally, we highlight future directions and limitations in this field and emphasize the need to develop translational studies to better understand how tDCS improves memory, a necessary condition before it can be used as a therapeutic tool. PMID:25237299

  7. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique.

    PubMed

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-01-01

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112

  8. Introductory Remarks: Points of Concern with Current Interpretations of the Effects of Early Malnutrition on Mental Development

    ERIC Educational Resources Information Center

    Barnes, R. H.

    1972-01-01

    Emphasizes that from a practical point of view, it is important that studies with malnourished children emphasize the interactions between nutrition and environment rather than attempt complex, costly experiments which hopefully will assess the contribution of each of the components alone. (Author/JM)

  9. Arachidonic acid mediates muscarinic inhibition and enhancement of N-type Ca2+ current in sympathetic neurons

    PubMed Central

    Liu, Liwang; Rittenhouse, Ann R.

    2003-01-01

    N-type Ca2+ channels participate in acute activity-dependent processes such as regulation of Ca2+-activated K+ channels and in more prolonged events such as gene transcription and long-term depression. A slow postsynaptic M1 muscarinic receptor-mediated modulation of N-type current in superior cervical ganglion neurons may be important in regulating these processes. This slow pathway inhibits N-type current by using a diffusible second messenger that has remained unidentified for more than a decade. Using whole-cell patch–clamp techniques, which isolate the slow pathway, we found that the muscarinic agonist oxotremorine methiodide not only inhibits currents at positive potentials but enhances N-type current at negative potentials. Enhancement was also observed in cell-attached patches. These findings provide evidence for N-type Ca2+-current enhancement by a classical neurotransmitter. Moreover, enhancement and inhibition of current by oxotremorine methiodide mimics modulation observed with direct application of a low concentration of arachidonic acid (AA). Although no transmitter has been reported to use AA as a second messenger to modulate any Ca2+ current in either neuronal or nonneuronal cells, we nevertheless tested whether a fatty acid signaling cascade was involved. Blocking phospholipase C, phospholipase A2, or AA but not AA metabolism minimized muscarinic modulation of N-type current, supporting the participation of these molecules in the slow pathway. A role for the G protein Gq was also confirmed by blocking muscarinic modulation of Ca2+ currents with anti-Gqα antibody. Our finding that AA participates in the slow pathway strongly suggests that it may be the previously unknown diffusible second messenger. PMID:12496347

  10. Strongly enhanced spin current in topological insulator/ferromagnetic metal heterostructures by spin pumping

    SciTech Connect

    Wu, C. N.; Hung, H. Y.; Lin, H. Y.; Lin, P. H.; Kwo, J. E-mail: raynien@phys.nthu.edu.tw; Lin, Y. H.; Fanchiang, Y. T.; Hong, M. E-mail: raynien@phys.nthu.edu.tw; Lin, J. G.; Lee, S. F.

    2015-05-07

    Spin pumping effect in Bi{sub 2}Se{sub 3}/Fe{sub 3}Si and Fe/Bi{sub 2}Te{sub 3} heterostructures was studied. High quality films of Bi{sub 2}Se{sub 3}(001) on ferromagnetic Fe{sub 3}Si(111) layer and Fe(111) films on Bi{sub 2}Te{sub 3}(001) layer were grown epitaxially by molecular beam epitaxy. Using a microwave cavity source, large voltages due to the Inverse Spin Hall Effect (V{sub ISHE}) were detected in Bi{sub 2}Se{sub 3}(001)/Fe{sub 3}Si(111) bi-layer at room temperature. V{sub ISHE} of up to 63.4 ± 4.0 μV at 100 mW microwave power (P{sub MW}) was observed. In addition, Fe(111)/Bi{sub 2}Te{sub 3}(001) bi-layer also showed a large V{sub ISHE} of 3.0 ± 0.1 μV at P{sub MW} of 25 mW. V{sub ISHE} of both structures showed microwave linear power dependence in accordance with the theoretical model of spin pumping. The spin Hall angle was calculated to be 0.0053 ± 0.002 in Bi{sub 2}Se{sub 3} and was estimated to be 0.0068 ± 0.003 in Bi{sub 2}Te{sub 3}. The charge current density (J{sub c}) of Bi{sub 2}Se{sub 3}/Fe{sub 3}Si and Fe/Bi{sub 2}Te{sub 3} structures are comparable and are about 2–5 times higher than the Fe{sub 3}Si/normal metal and Fe{sub 3}Si/GaAs results. The significant enhancement of spin current in topological insulator/ferromagnetic metal (TI/FM) and FM/TI bilayers is attributed to strong spin-orbit coupling inherent of TIs and demonstrates the high potential of exploiting TI-based structures for spintronic applications.

  11. Current state of Czech astronomy popularization and its potential for enhancing science career interest

    NASA Astrophysics Data System (ADS)

    Kříček, Radek

    2015-08-01

    The Czech Republic has a dense net of observatories, astronomical clubs and other activities for both adults and children. Can we use it to improve skills of our pupils and their motivation to choose their career in science? Does the situation in the Czech Republic differ from abroad? What can we improve in the future? These questions were not answered satisfactorily so far. We decided to contribute to solve this issue.We present our survey of current state based mainly on electronic sources and personal dealings. Besides of 56 observatories working with public and many interest clubs, there are other possibilities to meet astronomy. For example, Astronomical Olympiad attracts thousands of pupils across the country each year to solve both theoretical and practical tasks in astronomy. In other projects, children can visit Dark-Sky Parks, design experiments for a stratospheric balloon, observe with CCD or radio devices or build their own rockets.We outline our ongoing project to examine the link between popularization activities and pupils’ or high school students’ attitude toward science and science career. We plan to create a typology of both popularization activities and life stories of people dealing with astronomy. From the methodological point of view, the mixed method design, combining both the qualitative and quantitative approach, will be used to solve the research problems. The basic research plan will be a case study. So far the project is based on interviews with various subjects. We choose people with different life stories, all connected with astronomy or astronomy popularization in some period. We focus on important moments in their career, similarities between subjects, and various types of possible motivation to participate in astronomy-related activities or to study science at university.Future results can be used to help interested organizations such as universities, observatories or astronomical societies. They will be able to work more

  12. Nonlinear current-voltage characteristics and enhanced negative differential conductance in graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Chen, Xiaoshuang; Hu, Yibin; Yu, Anqi; Lu, Wei

    2014-10-01

    Recent observations of the negative differential conductance (NDC) phenomenon in graphene field-effect transistors (FET) open up new opportunities for their application in graphene-based fast switches, frequency multipliers and, most importantly, in high frequency oscillators up to the terahertz regime. Unlike conventional two-terminal NDC devices that rely on resonant tunneling and inter-valley transferring, in the present work, it has been shown that the universal NDC phenomenon of graphene-based FETs originates from their intrinsic nonlinear carrier transport under a strong electric field. The operation of graphene-NDC devices depends strongly on the interface between graphene and dielectric materials, the scattering-limited carrier mobility, and on the saturation velocity. To reveal such NDC behavior, the output characteristics of GFET are investigated rigorously, with both an analytical model and self-consistent transport equation, and with a multi-electrical parameter simulation. It is demonstrated that the contact-induced doping effect plays an important role in the operational efficiency of graphene-based NDC devices, rather than the ambipolar behavior associated with the competition between electron and hole conductances. In the absence of a NDC regime or beyond one, ambipolar transport starts at Vds > 2Vgs at the drain end, and as the dielectric layer begins to thin down, the kink-like saturation output characteristic is enhanced by the quantum capacitance contribution. These observations reveal the intrinsic mechanism of the NDC effect and open up new opportunities for the performance improvement of GFETs in future high-frequency applications, beyond the current paradigm based on two-terminal diodes.Recent observations of the negative differential conductance (NDC) phenomenon in graphene field-effect transistors (FET) open up new opportunities for their application in graphene-based fast switches, frequency multipliers and, most importantly, in high

  13. Enhancement of persistent current in mesoscopic rings and cylinders: shortest and next possible shortest higher-order hopping

    NASA Astrophysics Data System (ADS)

    Maiti, Santanu K.; Chowdhury, J.; Karmakar, S. N.

    2006-06-01

    We present a detailed study of persistent current and low-field magnetic susceptibility in single isolated normal metal mesoscopic rings and cylinders in the tight-binding model with higher-order hopping integral in the Hamiltonian. Our exact calculations show that order of magnitude enhancement of persistent current takes place even in the presence of disorder if we include the higher-order hopping integral in the Hamiltonian. In strictly one-channel mesoscopic rings the sign of the low-field currents can be predicted exactly even in the presence of impurity. We observe that perfect rings with both odd and even numbers of electrons support only diamagnetic currents. On the other hand in the disordered rings, irrespective of realization of the disordered configurations of the ring, we always get diamagnetic currents with odd numbers of electrons and paramagnetic currents with even numbers of electrons. In mesoscopic cylinders the sign of the low-field currents cannot be predicted exactly since it strongly depends on the total number of electrons, Ne, and also on the disordered configurations of the system. From the variation of persistent current amplitude with system size for constant electron density, we conclude that the enhancement of persistent current due to additional higher-order hopping integrals is visible only in the mesoscopic regime.

  14. Low noise signal-to-noise ratio enhancing readout circuit for current-mediated active pixel sensors

    SciTech Connect

    Ottaviani, Tony; Karim, Karim S.; Nathan, Arokia; Rowlands, John A.

    2006-05-15

    Diagnostic digital fluoroscopic applications continuously expose patients to low doses of x-ray radiation, posing a challenge to both the digital imaging pixel and readout electronics when amplifying small signal x-ray inputs. Traditional switch-based amorphous silicon imaging solutions, for instance, have produced poor signal-to-noise ratios (SNRs) at low exposure levels owing to noise sources from the pixel readout circuitry. Current-mediated amorphous silicon pixels are an improvement over conventional pixel amplifiers with an enhanced SNR across the same low-exposure range, but whose output also becomes nonlinear with increasing dosage. A low-noise SNR enhancing readout circuit has been developed that enhances the charge gain of the current-mediated active pixel sensor (C-APS). The solution takes advantage of the current-mediated approach, primarily integrating the signal input at the desired frequency necessary for large-area imaging, while adding minimal noise to the signal readout. Experimental data indicates that the readout circuit can detect pixel outputs over a large bandwidth suitable for real-time digital diagnostic x-ray fluoroscopy. Results from hardware testing indicate that the minimum achievable C-APS output current that can be discerned at the digital fluoroscopic output from the enhanced SNR readout circuit is 0.341 nA. The results serve to highlight the applicability of amorphous silicon current-mediated pixel amplifiers for large-area flat panel x-ray imagers.

  15. Direct imaging of enhanced current collection on grain boundaries of Cu(In,Ga)Se{sub 2} solar cells

    SciTech Connect

    Kim, JunHo; Kim, SeongYeon; Jiang, Chun-Sheng; Ramanathan, Kannan; Al-Jassim, Mowafak M.

    2014-02-10

    We report on direct imaging of current collection by performing conductive atomic force microscopy (C-AFM) measurement on a complete Cu(In,Ga)Se{sub 2} solar cell. The localized current was imaged by milling away the top conductive layer of the device by repeated C-AFM scans. The result exhibits enhanced photocurrent collection on grain boundaries (GBs) of CIGS films, consistent with the argument for electric-field-assisted carrier collection on the GBs.

  16. Current and future developments in civil aircraft non-destructive evaluation from an operator's point of view

    NASA Technical Reports Server (NTRS)

    Register, Jeff

    1992-01-01

    In June, 1988, the first International Conference on aging aircraft was held to address nondestructive tests (NDT) of aging aircraft and other issues. From this meeting, a research program was initiated and funded by the FAA. As a result of this program, a lot of work has been done to study current NDT practices in the aviation industry and secondly, to research and develop new NDT methods to improve the reliability and efficiency of in-service inspection of aircraft structures and powerplants. The following is an overview of the current and future developments in civil aircraft NDT, as viewed by an air carrier and the concerns for NDT in the future.

  17. Strong enhancement of s -wave superconductivity near a quantum critical point of Ca3Ir4Sn13

    DOE PAGESBeta

    Biswas, P. K.; Guguchia, Z.; Khasanov, R.; Chinotti, M.; Li, L.; Wang, Kefeng; Petrovic, C.; Morenzoni, E.

    2015-11-11

    We repormore » t microscopic studies by muon spin rotation/relaxation as a function of pressure of the Ca3Ir4Sn13 and Sr3Ir4Sn13 system displaying superconductivity and a structural phase transition associated with the formation of a charge density wave (CDW). Our findings show a strong enhancement of the superfluid density and a dramatic increase of the pairing strength above a pressure of ≈ 1.6 GPa giving direct evidence of the presence of a quantum critical point separating a superconducting phase coexisting with CDW from a pure superconducting phase. The superconducting order parameter in both phases has the same s-wave symmetry. In spite of the conventional phonon-mediated BCS character of the weakly correlated (Ca1-xSrx)3Ir4Sn13 system the dependence of the effective superfluid density on the critical temperature puts this compound in the “Uemura” plot close to unconventional superconductors. This system exemplifies that conventional BCS superconductors in the presence of competing orders or multi-band structure can also display characteristics of unconventional superconductors.« less

  18. The Current Status of e-Learning and Strategies to Enhance Educational Competitiveness in Korean Higher Education

    ERIC Educational Resources Information Center

    Leem, Junghoon; Lim, Byungro

    2007-01-01

    The purpose of this study was to examine the current status of e-Learning in Korean higher education and find ways to encourage the further use and development of e-Learning systems that aim to enhance Korea's academic competitiveness. A total of 201 universities in Korea (27 national and public, 163 private, and 11 national universities of…

  19. Band to Band Tunneling (BBT) Induced Leakage Current Enhancement in Irradiated Fully Depleted SOI Devices

    NASA Technical Reports Server (NTRS)

    Adell, Phillipe C.; Barnaby, H. J.; Schrimpf, R. D.; Vermeire, B.

    2007-01-01

    We propose a model, validated with simulations, describing how band-to-band tunneling (BBT) affects the leakage current degradation in some irradiated fully-depleted SOI devices. The dependence of drain current on gate voltage, including the apparent transition to a high current regime is explained.

  20. The role of interfacial defects in enhancing the critical current density of YBa2Cu3O7-delta coatings

    SciTech Connect

    Foltyn, Stephen R; Wang, Haiyan; Civale, Leonardo; Maiorov, Boris A; Jia, Quanxi

    2009-01-01

    The critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} (YBCO) films can approach 10 MA/cm{sup 2} at 77 K in self field , but only for very thin films. We have shown previously that strong thickness dependence results if J{sub c} is enhanced near the film-substrate interface. In the present work we investigate interfacial enhancement using laser-deposited YBCO films on NdGaO{sub 3} substrates, and find that we can adjust deposition conditions to switch the enhancement on and off. Interestingly, we find that the 'on' state is accompanied by interfacial misfit dislocations, establishing an unambiguous correlation between enhanced J{sub c} and dislocations at the film-substrate interface.

  1. Current data from the Keahole Point, Hawaii, OTEC benchmark sites, June 1980-April 1981. Part I. June 1980-December 1980; Part II. December 1980-April 1981

    SciTech Connect

    Frye, D; Leavitt, K; Noda, E K

    1981-10-01

    Physical oceanographic measurements made off Keahole Point, Hawaii between June and December 1980 and then between December 1980 and April 1981 are presented. These data include current, temperature, and pressure measurements from an array of current meter moorings deployed in the vicinity of the OTEC-1 site, salinity and temperature profiles collected at 17 stations of the OTEC-1 platform, velocity profiles collected at 4 stations during a cruise in August 1980, and temperature profiles from 21 casts of expendable bathythermographs in the area between the OTEC-1 platform and the south coast of Maui. (LEW)

  2. Swellable polymer films containing Au nanoparticles for point-of-care therapeutic drug monitoring using surface-enhanced Raman spectroscopy.

    PubMed

    Lee, Wendy W Y; McCoy, Colin P; Donnelly, Ryan F; Bell, Steven E J

    2016-03-17

    Large (10 × 10 cm) sheets of surface-enhanced Raman spectroscopy (SERS) active polymer have been prepared by stabilising metal nanoparticle aggregates within dry hydroxyethylcellulose (HEC) films. In these films the aggregates are protected by the polymer matrix during storage but in use they are released when aqueous analyte droplets cause the films to swell to their gel form. The fact that these "Poly-SERS" films can be prepared in bulk but then cut to size and stored in air before use means that they provide a cost effective and convenient method for routine SERS analysis. Here we have tested both Ag and Au Poly-SERS films for use in point-of-care monitoring of therapeutic drugs, using phenytoin as the test compound. Phenytoin in water could readily be detected using Ag Poly-SERS films but dissolving the compound in phosphate buffered saline (PBS) to mimic body fluid samples caused loss of the drug signal due to competition for metal surface sites from Cl(-) ions in the buffer solution. However, with Au Poly-SERS films there was no detectable interference from Cl(-) and these materials allowed phenytoin to be detected at 1.8 mg L(-1), even in PBS. The target range of detection of phenytoin in therapeutic drug monitoring is 10-20 mg L(-1). With the Au Poly-SERS films, the absolute signal generated by a given concentration of phenytoin was lower for the films than for the parent colloid but the SERS signals were still high enough to be used for therapeutic monitoring, so the cost in sensitivity for moving from simple aqueous colloids to films is not so large that it outweighs the advantages which the films bring for practical applications, in particular their ease of use and long shelf life. PMID:26920779

  3. Cathodal transcranial direct current stimulation over posterior parietal cortex enhances distinct aspects of visual working memory.

    PubMed

    Heinen, Klaartje; Sagliano, Laura; Candini, Michela; Husain, Masud; Cappelletti, Marinella; Zokaei, Nahid

    2016-07-01

    In this study, we investigated the effects of tDCS over the posterior parietal cortex (PPC) during a visual working memory (WM) task, which probes different sources of response error underlying the precision of WM recall. In two separate experiments, we demonstrated that tDCS enhanced WM precision when applied bilaterally over the PPC, independent of electrode configuration. In a third experiment, we demonstrated with unilateral electrode configuration over the right PPC, that only cathodal tDCS enhanced WM precision and only when baseline performance was low. Looking at the effects on underlying sources of error, we found that cathodal stimulation enhanced the probability of correct target response across all participants by reducing feature-misbinding. Only for low-baseline performers, cathodal stimulation also reduced variability of recall. We conclude that cathodal- but not anodal tDCS can improve WM precision by preventing feature-misbinding and hereby enhancing attentional selection. For low-baseline performers, cathodal tDCS also protects the memory trace. Furthermore, stimulation over bilateral PPC is more potent than unilateral cathodal tDCS in enhancing general WM precision. PMID:27143222

  4. Enhanced saturation current sensitivities to charge trapping and illumination in MOS tunnel diode by inserting metal in gate dielectric

    NASA Astrophysics Data System (ADS)

    Chen, Jun-Yao; Kao, Wei-Chih; Hwu, Jenn-Gwo

    2016-06-01

    The enlarged two-state phenomenon in the current-voltage (I-V) characteristic of metal-oxide-semiconductor (MOS) tunnel diode (TD) after negative/positive constant voltage stress (negative/positive CVS) was investigated. It was found that the reverse saturation tunnel current of MOS TD is proportional to the Schottky barrier height of holes, which is determined by the intensity of fringing field (FF) at device edge. With the aid of high permittivity dielectric and screening effect by embedded metal in the MOS structure, the FF was enhanced, which was confirmed by TCAD simulations. Because of the FF enhancement, after proper electrical treatments of voltage stressing, the intensified quantity of electron trapping/de-trapping was found at device edge, which augmented the modulation of Schottky barrier height of holes. As a result, much variation of reverse saturation tunnel current was exhibited, and hence, the enlarged two-state behavior was achieved. The endurance characteristics were also demonstrated to show that the trapped electrons are more stable in the MOS structure with embedded aluminum. Moreover, benefited from FF enhancement, the enlarged photosensitivity of the I-V characteristics of the sample with high permittivity dielectric and embedded aluminum was obtained. The mechanisms of the enlarged split of current behaviors after suitable CVS and illumination treatments are also discussed for these observations.

  5. Enhancement of Na+ Uptake Currents, Time-Dependent Inward-Rectifying K+ Channel Currents, and K+ Channel Transcripts by K+ Starvation in Wheat Root Cells1

    PubMed Central

    Buschmann, Peter H.; Vaidyanathan, Rama; Gassmann, Walter; Schroeder, Julian I.

    2000-01-01

    Excessive low-affinity Na+ uptake is toxic to the growth of glycophytic plants. Recently, several reports have suggested that the interaction between K+ and Na+ uptake might represent a key factor in determining the Na+ tolerance of plants. We investigated the effects of K+ starvation on Na+ and K+ uptake mechanisms in the plasma membrane of wheat (Triticum aestivum L.) root cortex cells using the patch-clamp technique. Unexpectedly, K+ starvation of wheat seedlings was found to enhance the magnitude and frequency of occurrence of time-dependent inward-rectifying K+ channel currents (IK+in). We examined whether the transcription of a wheat root K+in channel gene is induced by K+ starvation. A cDNA coding for a wheat root K+ channel homolog, TaAKT1 (accession no. AF207745), was isolated. TaAKT1 mRNA levels were up-regulated in roots in response to withdrawal of K+ from the growth medium. Furthermore, K+ starvation caused an enhancement of instantaneous Na+ currents (INa+). Electrophysiological analyses suggested that IK+in and INa+ are not mediated by the same transport protein based on: (a) different activation curves, (b) different time dependencies, (c) different sensitivities to external Ca2+, and (d) different cation selectivities. These data implicate a role for INa+ in Na+ uptake and stress during K+ starvation, and indicate that K+in channels may contribute to K+-starvation-induced K+ uptake in wheat roots. PMID:10759535

  6. Biomedical infertility care in sub-Saharan Africa: a social science review of current practices, experiences and view points

    PubMed Central

    Gerrits, T.; Shaw, M.

    2010-01-01

    Some sort of infertility treatments, including the use of advanced reproductive technologies (ARTs), is nowadays provided at several places in sub-Saharan Africa. Yet, to date only a few studies have actually looked into the way these treatments are offered, used and experienced. In this review article the authors present and discuss empirical study findings that give insight into the way biomedical infertility care is provided, considered, experienced and/or used in sub-Saharan African countries. They concentrate on four themes that were often referred to in the reviewed studies and underline the importance of taking into account the local sociocultural context and notions when developing and implementing infertility care, namely: counselling, male involvement, acceptability of ARTs and the use of donor material (semen and embryos). In the conclusion the authors emphasize the importance of preventing infertility as part of integrated reproductive health programs and the need to improve the quality of (low tech) infertility care in the public health sector by means of standardized guidelines, training of health staff and improved counselling. In addition, from a reproductive rights perspective, they support initiatives to introduce low cost ARTs to treat tubal factor related infertility. They also point to potential unintended side effects of the introduction of ARTs and the use of donor material in the sub-Saharan African context, affecting gender inequity and inequity between citizens from different social classes, and argue that such effects should be acknowledged and avoided by all possible means. Finally, they present an agenda for future social science research on this topic in sub-Saharan Africa. PMID:25013712

  7. A current overview of cannabinoids and glucocorticoids in facilitating extinction of aversive memories: potential extinction enhancers.

    PubMed

    de Bitencourt, Rafael Mariano; Pamplona, Fabrício Alano; Takahashi, Reinaldo Naoto

    2013-01-01

    Emotional learning is extremely important for the survival of an individual. However, once acquired, emotional associations are not always expressed. The regulation of emotional responses under different environmental conditions is essential for mental health. Indeed, pathologic feelings of fear and anxiety are defining features of many serious psychiatric illness, including post-traumatic stress disorder (PTSD) and specific phobias. The simplest form of regulation of emotional responses is extinction, in which the conditioned response to a stimulus decreases when reinforcement (stimulus) is omitted. In addition to modulating basal anxiety states, recent studies suggest an important role for the endocannabinoid (eCB) and glucocorticoid systems in the modulation of emotional states and extinction of aversive memories in animals. The purpose of this review is to briefly outline the animal models of fear extinction and to describe how these have been used to examine the potential of extinction enhancing agents which specifically alter the eCB and glucocorticoid systems. Pharmacological manipulations of these systems by agents such as cannabinoid or glucocorticoid agonists can enhance the extinction process and avoid the retention of memories which have the potential to trigger trauma. A better understanding of these findings through animal models highlights the possibilities of using combined extinction enhancing agents in exposure-based psychotherapies for anxiety disorders related to inappropriate retention of aversive memories. This article is part of a special issue entitled 'Cognitive Enhancers'. PMID:22687521

  8. Photoinduced current transient spectroscopy technique applied to the study of point defects in polycrystalline CdS thin films

    SciTech Connect

    El Akkad, Fikry; Ashour, Habib

    2009-05-01

    CdS thin films of variable thickness (between 160 and 1200 nm) were prepared using rf magnetron sputtering. X-ray diffraction measurements showed that the films have hexagonal structure and that the crystallites are preferentially oriented with the <002> axis perpendicular to the substrate surface. The results of electrical conductivity measurements as a function of film thickness and of temperature provide evidence that the conductivity is controlled by a thermally activated mobility in the presence of an intergrain barrier. The room temperature barrier height phi decreases with the increase in film thickness. Values of phi between 0 and 0.25 eV were determined. Photoinduced current transient spectroscopy performed on five samples having different thicknesses showed the presence of 11 traps with activation energies in the range 0.08-1.06 eV; deeper traps being observed on thinner films. By comparison with literature results, seven traps are attributed to native defects and foreign impurities (mainly Cu, Au, and Ag). Four other traps, not previously observed, are attributed to residual defects. The observation that deeper traps are detected in samples with larger barrier heights has been discussed and interpreted in terms of the energy band profile near the grain boundary.

  9. Study on pulsed-discharge devices with high current rising rate for point spot short-wavelength source in dense plasma observations

    NASA Astrophysics Data System (ADS)

    Tachinami, Fumitaka; Anzai, Nobuyuki; Sasaki, Toru; Kikuchi, Takashi; Harada, Nob.

    2014-01-01

    A pulsed-power generator with high current rise based on a pulse-forming-network was studied toward generating intense point-spot X-ray source. To obtain the high rate of current rise, we have designed the compact discharge device with low circuit inductance. The results indicate that the inductance of the compact discharge device was dominated by a gap switch inductance. To reduce the gap switch inductance and operation voltage, the feasible gap switch inductance in the vacuum chamber has been estimated by the circuit simulation. The gap switch inductance can be reduced by the lower pressure operation. It means that the designed discharge device achieves the rate of current rise of 1012 A/s.

  10. Enhancement of Accuracy in the Estimated Power-Angle Curve Considering Current Immediately after Fault Clearance

    NASA Astrophysics Data System (ADS)

    Iimura, Hayato; Sato, Masahiro

    A fault that occurs near a power station may cause a loss of synchronism of generators in the power station against the remaining generators and result in a widespread blackout. When swing of generators in the power station with respect to the remaining generators is similar to that of a generator in one machine and an infinite bus system, a power-angle curve (P-δ curve) is often used for studying the stability of the system and deciding the number of generators to be shed for stabilization. In operation, power system stabilizers predict loss of synchronism, determine the number of generators to be shed, and then shed them in a very short time period. Such stabilizers use data measured during a period of about 200 ms after fault occurence. The voltage and current measured on the bus and line connected to a power station are used to compute the P-δ curve. When a line is removed to clear a fault, the current in the damper circuit of a generator decays significantly in a very short period. This causes significant changes in the line current. However, when the P-δ curve is estimated using these data, and is applied to a stability study, the number of generators to be shed sometimes exceeds the optimum number. This is caused by the practice of measuring the current immediately after a fault is cleaed. Therefore, the authors propose a current detection method in which the portion of current that decays immediately after a fault is cleared. Such current has three distinct terms. Two are exponential functions in which one has extremely short time constant, while the other has a longer time constant. By using these estimated functions, the fast decaying component is removed from the measured current, which can then be used to estimate the P-δ curve more precisely. The method was verified via simulations using an infinite bus system model and the EAST10 model of IEEJ.

  11. Programming Current Reduction via Enhanced Asymmetry-Induced Thermoelectric Effects in Vertical Nanopillar Phase-Change Memory Cells

    NASA Astrophysics Data System (ADS)

    Bahl, Jyotsna; Rajendran, Bipin; Muralidharan, Bhaskaran

    2015-12-01

    Thermoelectric effects are envisioned to reduce programming currents in nanopillar phase change memory cells. However, due to the inherent symmetry in such a structure, the contribution due to thermoelectric effects on programming currents is minimal. In this work, we propose a hybrid phase change memory structure which incorporates a two-fold asymmetry specifically aimed to favorably enhance thermoelectric effects. The first asymmetry is introduced via an interface layer of low thermal conductivity and high negative Seebeck coefficient, such as, polycrystalline SiGe, between the bottom electrode contact and the active region comprising the phase change material. This results in an enhanced Peltier heating of the active material. The second one is introduced structurally via a taper that results in an angle dependent Thomson heating within the active region. Various device geometries are analyzed using 2D-axis-symmetric simulations to predict the effect on programming currents as well as for different thicknesses of the interface layer. A programming current reduction of up to $60\\%$ is predicted for specific cell geometries. Remarkably, we find that due to an interplay of Thomson cooling in the electrode and the asymmetric heating profile inside the active region, the predicted programming current reduction is resilient to fabrication variability.

  12. Enhanced critical currents in (Gd,Y)Ba2Cu3Ox superconducting tapes with high levels of Zr addition

    NASA Astrophysics Data System (ADS)

    Selvamanickam, V.; Chen, Y.; Shi, T.; Liu, Y.; Khatri, N. D.; Liu, J.; Yao, Y.; Xiong, X.; Lei, C.; Soloveichik, S.; Galstyan, E.; Majkic, G.

    2013-03-01

    The critical current and structural properties of (Gd,Y)BaCuO tapes made by metal organic chemical vapor deposition (MOCVD) with Zr addition levels up to 30 at.% have been investigated. The reduction in critical current beyond the previously optimized Zr addition level of 7.5 at.% was found to be due to structural deterioration of the (Gd,Y)Ba2Cu3Ox film. By a modified MOCVD process, enhanced critical current densities have been achieved with high levels of Zr addition, including 3.83 MA cm-2 in 15 at.% Zr-added 1.1 μm thick film at 77 K in zero magnetic field. Critical currents as high as 1072 A/12 mm have been reached in (Gd,Y)BaCuO tapes with 15 at.% Zr addition at 30 K in a field of 3 T applied perpendicular to the tape, corresponding to a pinning force value of 268 GN m-3. The enhanced critical currents achievable with a high density of nanoscale defects by employing high levels of second-phase additions enable the performance targets needed for the use of HTS tapes in coil applications involving high magnetic fields at temperatures below 50 K to be met.

  13. Enhanced critical currents in (Gd,Y)Ba2Cu3Ox superconducting tapes with high levels of Zr addition

    SciTech Connect

    Selvamanickam, V; Chen, Y; Shi, T; Liu, Y; Khatri, ND; Liu, J; Yao, Y; Xiong, X; Lei, C; Soloveichik, S; Galstyan, E; Majkic, G

    2013-01-21

    The critical current and structural properties of (Gd,Y)BaCuO tapes made by metal organic chemical vapor deposition (MOCVD) with Zr addition levels up to 30 at.% have been investigated. The reduction in critical current beyond the previously optimized Zr addition level of 7.5 at.% was found to be due to structural deterioration of the (Gd,Y)Ba2Cu3Ox film. By a modified MOCVD process,enhanced critical current densities have been achieved with high levels of Zr addition,including 3.83 MA cm(-2) in 15 at.% Zr- added 1.1 mu m thick film at 77 K in zero magnetic field. Critical currents as high as 1072 A/ 12 mm have been reached in (Gd,Y) BaCuO tapes with 15 at.% Zr addition at 30 K in a field of 3 T applied perpendicular to the tape,corresponding to a pinning force value of 268 GN m(-3). The enhanced critical currents achievable with a high density of nanoscale defects by employing high levels of second- phase additions enable the performance targets needed for the use of HTS tapes in coil applications involving high magnetic fields at temperatures below 50 K to be met.

  14. Relationships between ERTS radiances and gradients across ocean fronts. [image enhancement of Loop Current in Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Maul, G. A.; Gordon, H. R.

    1974-01-01

    A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation.

  15. A new approach to design an efficient micropost array for enhanced direct-current insulator-based dielectrophoretic trapping.

    PubMed

    Mohammadi, Mahdi; Zare, Mohammad Javad; Madadi, Hojjat; Sellarès, Jordi; Casals-Terré, Jasmina

    2016-07-01

    Direct-current insulator-based dielectrophoresis (DC-iDEP) is a well-known technique that benefits from the electric field gradients generated by an array of insulating posts to separate or trap biological particles. The aim of this study is to provide a first geometrical relationship of the post array that independent of the particles and/or medium, maximizes the trapping. A novel figure of merit is proposed to maximize the particle trapping in the post array while minimizing the required voltage, with a similar footprint and channel thickness. Different post array models with the variation of transversal distance (10 to 60 μm), longitudinal distance (10 to 80 μm), and post radius (10 to 150 μm) were analyzed using COMSOL Multiphysics finite element software. The obtained results indicated that a post radius of 40 μm larger than the transversal distance between posts could enhance the trapping condition between 56 % (for a transversal distance of 10 μm) and 341 % (for a transversal distance of 60 μm). For the validation of the numerical results, several microchannels with embedded post arrays were manufactured in polydimethylsiloxane (PDMS) and the particle trapping patterns of 6-μm-diameter polystyrene particles were measured experimentally. The experiments confirm the same trends as pointed out by the numerical analysis. The results show that this new figure of merit and geometrical relationship can be used to reduce the required electric field to achieve effective particle trapping and, therefore, avoid the negative effects of Joule heating in cells or viable particles. The main advantage of these results is that they depend only on the geometry of the micropost array and are valid for trapping different particles suspended in different media. Graphical abstract Analysis to maximize the particle trapping in the post array while minimizing the required voltage. I. Microfluidic channel design and experimental setup II. Numerical and experimental

  16. Optimization of Drive-Bunch Current Profile for Enhanced Transformer Ratio in Beam-Driven Acceleration Techniques

    SciTech Connect

    Lemery, F.; Mihalcea, D.; Prokop, C.R.; Piot, P.; /Northern Illinois U. /Fermilab

    2012-07-08

    In recent years, wakefield acceleration has gained attention due to its high acceleration gradients and cost effectiveness. In beam-driven wakefield acceleration, a critical parameter to optimize is the transformer ratio. It has been shown that current shaping of electron beams allows for enhanced (> 2) transformer ratios. In this paper we present the optimization of the pulse shape of the drive bunch for dielectric-wakefield acceleration.

  17. Enhancement of critical current through compound defect with proton irradiation and heavy ion irradiation in YBCO coated conductors and FeSexTe1-x crystals

    NASA Astrophysics Data System (ADS)

    Kihlstrom, Karen; Leroux, Maxime; Holleis, Sigrid; Harris, Danielle; Welp, Ulrich; Claus, Helmut; Kayani, Asghar; Gu, Genda; Rupch, Marty; Sathyamurthy, Srivatsan; Fleshler, Steven; Laviano, Francesco; Gozzelino, Laura; Gerbaldo, Roberto; Ghigo, Gianluca; Kwok, Wai-Kwong

    We investigate the enhancement of vortex pinning by both point and columnar defects and compare the results in 2G YBCO coated conductors (CC), with Tc 90K, and in FeSexTe1-x single crystals with Tc 14K. Both samples were irradiated with 250 MeV Au ions to a dose-matching field of 1T. The samples were then irradiated with 4 MeV protons to a dose of 4x1016 p/cm2 and 8x1016 p/cm2 in the CC and single crystal, respectively. The major effect of compound particle irradiation in both samples resulted in a synergetic enhancement of the critical current across a wide field range, beyond the enhancement from either individual irradiation type. This work supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. D.O.E., Office of Science, Office of Basic Energy Sciences. The work in Italy was supported by the INFN-TERASPARC project.

  18. Upgrading and enhancing the generator protection system by making use of current digital systems

    SciTech Connect

    Chau, N.H.; Gardell, J.D.; Patel, S.C.

    1996-06-01

    Upgrading of power plant systems and equipment is becoming a major theme for many utilities. Due to operational cost pressures, competitiveness, life extension, and the desire for better productivity, condition assessment programs are being implemented. One aspect of this is the enhancement/upgrade of existing generator protection schemes with digital systems. Traditionally this protection has been provided by a complement of discrete component relays. These relays have included both electromechanical and static types. Considering a digital enhancement/upgrade offers the owner of installed generation equipment several unique advantages. These include more complete machine protection, diagnostics capabilities for greater productivity and maintenance optimization, life extension with minimal implementation, and the operational advantages of sequence of events, present values and communications capabilities.

  19. Disorder-assisted transmission due to charge puddles in monolayer graphene: Transmission enhancement and local currents

    NASA Astrophysics Data System (ADS)

    Lima, Leandro R. F.; Lewenkopf, Caio H.

    2016-01-01

    We investigate the contribution of charge puddles to the nonvanishing conductivity minimum in disordered graphene flakes at the charge neutrality point. For that purpose, we study systems with a geometry that suppresses the transmission due to evanescent modes allowing us to single out the effect of charge fluctuations in the transport properties. We use the recursive Green's function technique to obtain local and total transmissions through systems that mimic vanishing density of states at the charge neutrality point in the presence of a local disordered local potential to model the charge puddles. Our microscopic model includes electron-electron interactions via a spin resolved Hubbard mean field term. We establish the relationship between the charge puddle disorder potential and the electronic transmission at the charge neutrality point. We find that electronic interactions do not play a significant role in this setting. We discuss the implications of our findings to high mobility graphene samples deposited on different substrates and provide a qualitative interpretation of recent experimental results.

  20. The evaluation of contrast-enhancing brain lesions: pitfalls in current practice.

    PubMed Central

    Piszczor, M.; Thornton, G.; Bia, F. J.

    1985-01-01

    The definitive diagnosis of space-occupying brain lesions can be established more readily since the advent of computerized tomographic (CT) scanning. Some brain lesions are more clearly defined when contrast-enhancing agents are utilized; however, so-called ring-enhancing lesions are not pathognomonic for specific neurological entities. Review of the literature suggests that at least four disorders must be considered in the differential diagnosis of contrast-enhancing lesions. These include mature brain abscesses of any etiology, cerebrovascular accidents, and primary or metastatic brain tumors. Since the medical and surgical management of these conditions is quite different, it is critical to establish a diagnosis before therapy is instituted. In many instances the combination of history, physical examination, laboratory, and radiologic examination will enable physicians to correctly diagnose the etiology of such brain lesions. However, we present two cases for which the above clinical and non-invasive parameters led to incorrect working diagnoses. Brain biopsy was required before appropriate management was eventually instituted. Potentially, such delays in diagnosis and institution of therapy can result in unnecessary morbidity and mortality. Each case illustrates the need to substantiate a presumptive diagnosis based on these clinical and radiographic criteria, regardless of how "typical" lesions may appear on CT scans. Images FIG. 1 FIG. 2 FIG. 3 PMID:4013370

  1. Enhanced diamagnetic perturbations and electric currents observed downstream of the high power helicon

    NASA Astrophysics Data System (ADS)

    Roberson, B. Race; Winglee, Robert; Prager, James

    2011-05-01

    The high power helicon (HPH) is capable of producing a high density plasma (1017-1018 m-3) and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the thruster. In order to understand the coupling mechanism between the helicon antenna and the plasma outside the immediate source region, measurements were made in the plasma plume downstream from the thruster of the propagating wave magnetic field and the perturbation of the axial bulk field using a type `R' helicon antenna. This magnetic field perturbation (ΔB) peaks at more than 15 G in strength downstream of the plasma source, and is 3-5 times larger than those previously reported from HPH. Taking the curl of this measured magnetic perturbation and assuming azimuthal symmetry suggests that this magnetic field is generated by a (predominantly) azimuthal current ring with a current density on the order of tens of kA m-2. At this current density the diamagnetic field is intense enough to cancel out the B0 axial magnetic field near the source region. The presence of the diamagnetic current is important as it demonstrates modification of the vacuum fields well beyond the source region and signifies the presence of a high density, collimated plasma stream. This diamagnetic current also modifies the propagation of the helicon wave, which facilitates a better understanding of coupling between the helicon wave and the resultant plasma acceleration.

  2. Enhanced diamagnetic perturbations and electric currents observed downstream of the high power helicon

    SciTech Connect

    Roberson, B. Race; Winglee, Robert; Prager, James

    2011-05-15

    The high power helicon (HPH) is capable of producing a high density plasma (10{sup 17}-10{sup 18} m{sup -3}) and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the thruster. In order to understand the coupling mechanism between the helicon antenna and the plasma outside the immediate source region, measurements were made in the plasma plume downstream from the thruster of the propagating wave magnetic field and the perturbation of the axial bulk field using a type 'R' helicon antenna. This magnetic field perturbation ({Delta}B) peaks at more than 15 G in strength downstream of the plasma source, and is 3-5 times larger than those previously reported from HPH. Taking the curl of this measured magnetic perturbation and assuming azimuthal symmetry suggests that this magnetic field is generated by a (predominantly) azimuthal current ring with a current density on the order of tens of kA m{sup -2}. At this current density the diamagnetic field is intense enough to cancel out the B{sub 0} axial magnetic field near the source region. The presence of the diamagnetic current is important as it demonstrates modification of the vacuum fields well beyond the source region and signifies the presence of a high density, collimated plasma stream. This diamagnetic current also modifies the propagation of the helicon wave, which facilitates a better understanding of coupling between the helicon wave and the resultant plasma acceleration.

  3. Current-driven domain wall motion enhanced by the microwave field

    SciTech Connect

    Wang, Xi-guang; Guo, Guang-hua Nie, Yao-zhuang; Wang, Dao-wei; Li, Zhi-xiong; Tang, Wei; Zeng, Zhong-ming

    2014-07-14

    The magnetic domain wall (DW) motion driven by a spin-polarized current opens a new concept for memory and logic devices. However, the critical current density required to overcome the intrinsic and/or extrinsic pinning of DW remains too large for practical applications. Here, we show, by using micromagnetic simulations and analytical approaches, that the application of a microwave field offers an effective solution to this problem. When a transverse microwave field is applied, the adiabatic spin-transfer torque (STT) alone can sustain a steady-state DW motion without the sign of Walker breakdown, meaning that the intrinsic pinning disappears. The extrinsic pinning can also be effectively reduced. Moreover, the DW velocity is increased greatly for the microwave-assisted DW motion. This provides a new way to manipulate the DW motion at low current densities.

  4. Method and apparatus for generating motor current spectra to enhance motor system fault detection

    DOEpatents

    Linehan, Daniel J.; Bunch, Stanley L.; Lyster, Carl T.

    1995-01-01

    A method and circuitry for sampling periodic amplitude modulations in a nonstationary periodic carrier wave to determine frequencies in the amplitude modulations. The method and circuit are described in terms of an improved motor current signature analysis. The method insures that the sampled data set contains an exact whole number of carrier wave cycles by defining the rate at which samples of motor current data are collected. The circuitry insures that a sampled data set containing stationary carrier waves is recreated from the analog motor current signal containing nonstationary carrier waves by conditioning the actual sampling rate to adjust with the frequency variations in the carrier wave. After the sampled data is transformed to the frequency domain via the Discrete Fourier Transform, the frequency distribution in the discrete spectra of those components due to the carrier wave and its harmonics will be minimized so that signals of interest are more easily analyzed.

  5. Origins of enhanced field-aligned current at the edge of an auroral arc

    NASA Astrophysics Data System (ADS)

    Greenspan, M. E.

    1989-09-01

    Consideration is given to observations showing that the upward field-aligned currents associated with auroral arcs are larger at their edges than within the arcs, focusing on the observations made with the Porcupine F4 rocket (Bruning and Geortz, 1985). It is found that an increase in the altitude of the top of the parallel electric field region does not sufficiently explain the increase in the upward field-aligned current at the edge of the arc crossed by the Porcupine F4. Other explanations are discussed, including the adiabatic acceleration of magnetospheric electrons through a field-aligned electrostatic potential. It is suggested that an increase in the density and/or a decrease in the perpendicular temperature of the magnetospheric electron population at the edge of the arc may explain the observed increase in upward field-aligned current.

  6. Method and apparatus for generating motor current spectra to enhance motor system fault detection

    DOEpatents

    Linehan, D.J.; Bunch, S.L.; Lyster, C.T.

    1995-10-24

    A method and circuitry are disclosed for sampling periodic amplitude modulations in a nonstationary periodic carrier wave to determine frequencies in the amplitude modulations. The method and circuit are described in terms of an improved motor current signature analysis. The method insures that the sampled data set contains an exact whole number of carrier wave cycles by defining the rate at which samples of motor current data are collected. The circuitry insures that a sampled data set containing stationary carrier waves is recreated from the analog motor current signal containing nonstationary carrier waves by conditioning the actual sampling rate to adjust with the frequency variations in the carrier wave. After the sampled data is transformed to the frequency domain via the Discrete Fourier Transform, the frequency distribution in the discrete spectra of those components due to the carrier wave and its harmonics will be minimized so that signals of interest are more easily analyzed. 29 figs.

  7. Proton Enhancement and Decreased O6+/H at the Heliospheric Current Sheet: Implications for the Origin of Slow Solar Wind

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.-M.; Galvin, A. B.; Popecki, M. A.; Simunac, K. D. C.; Kistler, L.; Farrugia, C.; Lee, M. A.; Klecker, B.; Bochsler, P.; Luhmann, J. L.; Jian, L. K.; Moebius, E.; Wimmer-Schweingruber, R.; Wurz, P.

    2010-03-01

    We investigated the proton enhancement and O6+/H depletion in the vicinity of the heliospheric current sheet (HCS) using data from STEREO/PLASTIC and STEREO/IMPACT. Three HCS crossing events were studied. For the first two events, the proton enhancement and O6+/H depletion are found to lie at one edge of the HCS. The proton density has a steep slope both at the HCS and at the other boundary of the enhancement. In the third event the proton enhancement and O6+/H depletion surround the HCS and last for 8 hours while the density profile is very different from the other two events. Velocity shear is observed at the HCS for the first two events but not for the third. The enhancement of hydrogen and depletion of oxygen at the streamer belt in the solar corona have been reported using UVCS observation. A potential connection with our observations is based on the similar features observed at 1 AU. How the plasma flows out of the streamer belt, and why there are different features in HCS encounters remain open questions for future study.

  8. Limits of PowerPoint's Power: Enhancing Students' Self-Efficacy and Attitudes but Not Their Behavior

    ERIC Educational Resources Information Center

    Susskind, Joshua E.

    2008-01-01

    The effects of accompanying lectures with computer-mediated PowerPoint presentations or PowerPoint generated overheads on students' self-efficacy, attitudes, course performance, and class-related behaviors were examined. Two Introduction to Developmental Psychology sections were initially taught with lectures accompanied by either overheads or…

  9. Application of contrast-enhanced ultrasound after liver transplantation: Current status and perspectives

    PubMed Central

    Ren, Jie; Wu, Tao; Zheng, Bo-Wen; Tan, Ying-Yi; Zheng, Rong-Qin; Chen, Gui-Hua

    2016-01-01

    Liver transplantation is an effective treatment for patients with end-stage liver disease. Accurate imaging evaluation of the transplanted patient is critical for ensuring that the limited donor liver is functioning appropriately. Ultrasound contrast agents (UCAs), in combination with contrast-specific imaging techniques, are increasingly accepted in clinical use for the assessment of the hepatic vasculature, bile ducts and liver parenchyma in pre-, intra- and post-transplant patients. We describe UCAs, their technical requirements, the recommended clinical indications, image interpretation and the limitations for contrast-enhanced ultrasound applications in liver transplantation. PMID:26819526

  10. Synergetic sustainability enhancement via current biofuel infrastructure: waste-to-energy concept for biodiesel production.

    PubMed

    Kwon, Eilhann; Yi, Haakrho; Jeon, Young Jae

    2013-03-19

    The concept of waste-to-energy (WtE) with regards to the utilization of byproducts from the bioethanol industry (e.g., distiller's dried grain with solubles: DDGS) was employed to enhance the renewability of biodiesel, which would be an initiative stage of a biorefinery due to the conjunction between bioethanol and biodiesel. For example, DDGS is a strong candidate for use as a biodiesel feedstock due to the tremendous amount that is regularly generated. On the basis of an estimation of possible lipid recovery from DDGS, ∼30% of the biodiesel feedstock demand in 2010 could be supported by the total DDGS generation in the same year. Considering the future expansion of the bioethanol industry up to 2020, the possible lipid recovery from DDGS would provide more than 6 times the biodiesel feedstock demand in 2010. In order to enhance the renewability of biodiesel, the transformation of lipid extracted from DDGS into fatty acid ethyl ester (FAEE) via a noncatalytic transesterification reaction under ambient pressure was investigated in this work. The newly introduced method reported here enables the combination of the esterification of free fatty acids (FFAs) and the transesterification of triglycerides into a single step. This was achieved in the presence of a porous material (i.e., charcoal), and the optimal conditions for transformation into biodiesel via this noncatalytic method were assessed at the fundamental level. PMID:23410120