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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. 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...

  9. 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.

  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 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

  12. 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

  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. 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.

  14. 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.

  15. 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.

  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. 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.

  20. 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

  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. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  14. 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.

  15. 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.

  16. 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

  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. "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…

  3. 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.

  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. 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

  8. 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

  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. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  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. 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

  11. 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

  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. 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

  18. 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.

  19. 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

  20. 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

  1. 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.

  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. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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…

  15. 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.

  16. 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.

  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. 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.

  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. 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.

  4. 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

  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. 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.

  7. 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

  8. 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

  9. 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

  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. 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.

  12. 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

  13. 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.

  14. 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

  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. 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.

  18. 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.

  19. 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.

  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. 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.

  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. 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.

  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. 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

  6. 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

  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. 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.).

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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

  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. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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}.

  10. 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

  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. 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.

  16. 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.

  17. 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.

  18. 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%.

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  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. 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

  18. 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

  19. 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.

  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. 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

  2. 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

  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. 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

  7. 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

  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. 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.

  16. 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.

  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. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  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. 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…

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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

  11. Enhanced current quantization in high-frequency electron pumps in a perpendicular magnetic field

    SciTech Connect

    Wright, S. J.; Blumenthal, M. D.; Gumbs, Godfrey; Thorn, A. L.; Pepper, M.; Anderson, D.; Jones, G. A. C.; Nicoll, C. A.; Ritchie, D. A.; Janssen, T. J. B. M.; Holmes, S. N.

    2008-12-15

    We present experimental results of high-frequency quantized charge pumping through a quantum dot formed by the electric field arising from applied voltages in a GaAs/AlGaAs system in the presence of a perpendicular magnetic field B. Clear changes are observed in the quantized current plateaus as a function of applied magnetic field. We report on the robustness in the length of the quantized plateaus and improvements in the quantization as a result of the applied B field.

  12. Ginsenoside Rg3 Enhances Large Conductance Ca2+-Activated Potassium Channel Currents: A Role of Tyr360 Residue

    PubMed Central

    Choi, Sun-Hye; Shin, Tae-Joon; Lee, Byung-Hwan; Hwang, Sung Hee; Lee, Sang-Mok; Lee, Byung-Cheol; Park, Cheol-Seung; Ha, Tal Soo; Nah, Seung-Yeol

    2011-01-01

    Ginsenosides, active ingredients of Panax ginseng, are known to exhibit neuroprotective effects. Large-conductance Ca2+-activated K+ (BKCa) channels are key modulators of cellular excitability of neurons and vascular smooth muscle cells. In the present study, we examined the effects of ginsenosides on rat brain BKCa (rSlo) channel activity heterologously expressed in Xenopus oocytes to elucidate the molecular mechanisms how ginsenoside regulates the BKCa channel activity. Ginsenoside Rg3 (Rg3) enhanced outward BKCa channel currents. The Rg3-enhancement of outward BKCa channel currents was concentration-dependent, voltage-dependent, and reversible. The EC50 was 15.1 ± 3.1 μM. Rg3 actions were not desensitized by repeated treatment. Tetraetylammonium (TEA), a K+ channel blocker, inhibited BKCa channel currents. We examined whether extracellular TEA treatment could alter the Rg3 action and vice versa. TEA caused a rightward shift of the Rg3 concentration-response curve (i.e., much higher concentration of Rg3 is required for the activation of BKCa channel compared to the absence of TEA), while Rg3 caused a rightward shift of the TEA concentration-response curve in wild-type channels. Mutation of the extracellular TEA binding site Y360 to Y360I caused a rightward shift of the TEA concentration-response curve and almost abolished both the Rg3 action and Rg3-induced rightward shift of TEA concentration-response curve. These results indicate that Tyr360 residue of BKCa channel plays an important role in the Rg3-enhancement of BKCa channel currents. PMID:21191818

  13. Enhancement of the critical current of intrinsic Josephson junctions by carrier injection

    NASA Astrophysics Data System (ADS)

    Kizilaslan, O.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Müller, P.

    2015-08-01

    We present a study of the doping effect by carrier injection of high-Tc superconducting Bi-based whiskers. The current was injected in the c-axis direction, i.e., perpendicular to the superconducting planes. Superconducting properties were investigated systematically as a function of the doping level. The doping level of one and the same sample was changed by current injection in very small steps from an underdoped state up to a slightly overdoped state. We have observed that Tc versus log (jc) exhibits a dome-shaped characteristic, which can be fitted by a parabola. As Tc versus carrier concentration has a parabolic form, too, it can be concluded that the critical current density jc increases exponentially with the doping level. The electron-trapping mechanism is interpreted in the framework of Phillips’ microscopic theory. In addition, the Joule heating effect in the intrinsic Josephson junction (IJJ) was controlled by carrier injection, and the effect of the non-equilibrium quasiparticle on the I-V curves of the IJJs was also discussed.

  14. Enhanced Cyclability of Li/Polysulfide Batteries by a Polymer-Modified Carbon Paper Current Collector.

    PubMed

    Cui, Yi; Fu, Yongzhu

    2015-09-16

    Lithium-sulfur (Li-S) batteries are considered to be the next-generation rechargeable systems due to their high energy densities and low cost. However, significant capacity decay over cycling is a major impediment for their practical applications. Polysulfides Li2Sx (3current collector in Li/polysulfide cells. PVP is soluble in the electrolyte solvent, but shows strong affinity with lithium polysulfides. The retention of polysulfides in the CP-PVP current collector is improved by ∼50%, which is measured by a linear sweep voltammetry method. Without LiNO3 additive in the electrolyte, the CP-PVP current collector with 50 μg of PVP can significantly improve cycling stability with a capacity retention of >90% over 50 cycles at C/10 rate. With LiNO3 additive in the electrolyte, the cell shows a reversible capacity of >1000 mAh g(-1) and a capacity retention of >80% over 100 cycles at C/5 rate. PMID:26305234

  15. Multi-point, multi-scale observation of the near-Earth current sheet reconfiguration during storm-time multi-onset substorms

    NASA Astrophysics Data System (ADS)

    Nakamura, R.; Baumjohann, W.; Plaschke, F.; Narita, Y.; Schmid, D.; Panov, E. V.; Andriopoulou, M.; Voros, Z.; Magnes, W.; Fischer, D.; Steller, M.; Burch, J. L.; Torbert, R. B.; Russell, C. T.; Strangeway, R. J.; Leinweber, H. K.; Le, G.; Bromund, K. R.; Anderson, B. J.; Chutter, M.; Slavin, J. A.; Kepko, L.; Vaith, H.; Le Contel, O.; Argall, M. R.; Ergun, R. E.; Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Pollock, C. J.; Dorelli, J.; Gershman, D. J.; Fuselier, S. A.; Mauk, B.; Baker, D. N.; Giles, B. L.; Moore, T. E.; Singer, H. J.; Sergeev, V. A.; Escoubet, C. P.

    2015-12-01

    On June 23, 2015 between 03 and 06 UT, during the recovery phase of a storm, signatures of two major substorms with multiple-onsets are detected by a fleet of spacecraft in the near-Earth region providing an unique opportunity to study the evolution of the near-Earth current sheet reconfiguration from sub-ion scale to larger scale across the inner magnetosphere. The two onsets around 0315 and 0505 are observed by MMS near the boundary of the premidnight-plasma sheet as a thinning of the current sheet and as dipolarization at GOES 13 and 15 in the dusk to premidnight region, then followed by crossing of an active separatrix region. By using high-resolution magnetic field data onboard MMS, we investigate the detailed propagation properties of the disturbances and structures based on different multi-point analysis techniques (timing, gradient, and wave telescope analysis). By also comparing with current wedge model from ground-based data we identify the 3D evolution of the near-Earth current sheet.

  16. Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

    SciTech Connect

    Koizumi, H.; Uda, S.; Fujiwara, K.; Nozawa, J.; Tachibana, M.; Kojima, K.

    2014-10-06

    X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

  17. Enhanced critical current density in the pressure-induced magnetic state of the high-temperature superconductor FeSe.

    PubMed

    Jung, Soon-Gil; Kang, Ji-Hoon; Park, Eunsung; Lee, Sangyun; Lin, Jiunn-Yuan; Chareev, Dmitriy A; Vasiliev, Alexander N; Park, Tuson

    2015-01-01

    We investigate the relation of the critical current density (Jc) and the remarkably increased superconducting transition temperature (Tc) for the FeSe single crystals under pressures up to 2.43 GPa, where the Tc is increased by ~8 K/GPa. The critical current density corresponding to the free flux flow is monotonically enhanced by pressure which is due to the increase in Tc, whereas the depinning critical current density at which the vortex starts to move is more influenced by the pressure-induced magnetic state compared to the increase of Tc. Unlike other high-Tc superconductors, FeSe is not magnetic, but superconducting at ambient pressure. Above a critical pressure where magnetic state is induced and coexists with superconductivity, the depinning Jc abruptly increases even though the increase of the zero-resistivity Tc is negligible, directly indicating that the flux pinning property compared to the Tc enhancement is a more crucial factor for an achievement of a large Jc. In addition, the sharp increase in Jc in the coexisting superconducting phase of FeSe demonstrates that vortices can be effectively trapped by the competing antiferromagnetic order, even though its antagonistic nature against superconductivity is well documented. These results provide new guidance toward technological applications of high-temperature superconductors. PMID:26548444

  18. Enhanced critical current density in the pressure-induced magnetic state of the high-temperature superconductor FeSe

    PubMed Central

    Jung, Soon-Gil; Kang, Ji-Hoon; Park, Eunsung; Lee, Sangyun; Lin, Jiunn-Yuan; Chareev, Dmitriy A.; Vasiliev, Alexander N.; Park, Tuson

    2015-01-01

    We investigate the relation of the critical current density (Jc) and the remarkably increased superconducting transition temperature (Tc) for the FeSe single crystals under pressures up to 2.43 GPa, where the Tc is increased by ~8 K/GPa. The critical current density corresponding to the free flux flow is monotonically enhanced by pressure which is due to the increase in Tc, whereas the depinning critical current density at which the vortex starts to move is more influenced by the pressure-induced magnetic state compared to the increase of Tc. Unlike other high-Tc superconductors, FeSe is not magnetic, but superconducting at ambient pressure. Above a critical pressure where magnetic state is induced and coexists with superconductivity, the depinning Jc abruptly increases even though the increase of the zero-resistivity Tc is negligible, directly indicating that the flux pinning property compared to the Tc enhancement is a more crucial factor for an achievement of a large Jc. In addition, the sharp increase in Jc in the coexisting superconducting phase of FeSe demonstrates that vortices can be effectively trapped by the competing antiferromagnetic order, even though its antagonistic nature against superconductivity is well documented. These results provide new guidance toward technological applications of high-temperature superconductors. PMID:26548444

  19. Forskolin Suppresses Delayed-Rectifier K+ Currents and Enhances Spike Frequency-Dependent Adaptation of Sympathetic Neurons

    PubMed Central

    Castro, Elena; Cruzblanca, Humberto

    2015-01-01

    In signal transduction research natural or synthetic molecules are commonly used to target a great variety of signaling proteins. For instance, forskolin, a diterpene activator of adenylate cyclase, has been widely used in cellular preparations to increase the intracellular cAMP level. However, it has been shown that forskolin directly inhibits some cloned K+ channels, which in excitable cells set up the resting membrane potential, the shape of action potential and regulate repetitive firing. Despite the growing evidence indicating that K+ channels are blocked by forskolin, there are no studies yet assessing the impact of this mechanism of action on neuron excitability and firing patterns. In sympathetic neurons, we find that forskolin and its derivative 1,9-Dideoxyforskolin, reversibly suppress the delayed rectifier K+ current (IKV). Besides, forskolin reduced the spike afterhyperpolarization and enhanced the spike frequency-dependent adaptation. Given that IKV is mostly generated by Kv2.1 channels, HEK-293 cells were transfected with cDNA encoding for the Kv2.1 α subunit, to characterize the mechanism of forskolin action. Both drugs reversible suppressed the Kv2.1-mediated K+ currents. Forskolin inhibited Kv2.1 currents and IKV with an IC50 of ~32 μM and ~24 µM, respectively. Besides, the drug induced an apparent current inactivation and slowed-down current deactivation. We suggest that forskolin reduces the excitability of sympathetic neurons by enhancing the spike frequency-dependent adaptation, partially through a direct block of their native Kv2.1 channels. PMID:25962132

  20. Enhanced Magnetic Field Perturbations and Electric Currents Observed Downstream of the High Power Helicon

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    The high power helicon (HPH) is a compact plasma source that can generate downstream densities of 10^17-10^18 m-3 and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the source. 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. This magnetic field perturbation (δB) peaks at more than 15 gauss in strength downstream of the plasma source and propagates tens of centimeters downstream, cancelling the base magnetic field as it propagates. Taking the curl of this measured magnetic perturbation and assuming azimuthal symmetry suggests a peak current density of 20 kA m-2. Data will be presented that relates the cancellation of the base magnetic field to the propagation of the helicon wave and the region where the plasma current system closes.

  1. Optical diagnostics of sputtering in magnetically enhanced high-current discharges

    NASA Astrophysics Data System (ADS)

    Smith, David; Aceto, Steven; Trotter, Jason; Sommerer, Timothy; Lawler, James

    2014-10-01

    We have investigated a gallium-based liquid cathode for use in a high-voltage, high-power gas switch for grid-scale electric power conversion. The cathode requirements include conduction of high current density (1--10 A cm-2) , preferably at low voltage, along with minimal loss by evaporation and/or sputtering. The approach to satisfy these criteria has been to operate with a modified commercial magnetron system at high pressure where the choice of working comprises the light elements, such as hydrogen or helium. A separate anode is used to form a plane-parallel geometry. We have demonstrated pulsed operation with current densities exceeding 2 A cm-2 and voltages below 200 V, over a pressure range of 50--800 mTorr. The sputtering rate on gallium and other cathode materials has been estimated for various plasma conditions using a line ratio emission spectroscopy diagnostic based on analysis of the radiation trapping. The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000298.

  2. Hybridization of photoanode and bioanode to enhance the current production of bioelectrochemical systems.

    PubMed

    Feng, Huajun; Liang, Yuxiang; Guo, Kun; Li, Na; Shen, Dongsheng; Cong, Yanqing; Zhou, Yuyang; Wang, Yanfeng; Wang, Meizhen; Long, Yuyang

    2016-10-01

    Bacterial extracellular electron transfer is one of the main bottlenecks in determining the efficiency of bioelectrochemical systems. Here, we report a photobioanode that combines carbon material with a photocatalyst (α-Fe2O3), utilizing visible light to accelerate biofilm formation and extracellular electron transfer in bioelectrochemical systems. Cyclic voltammetric studies of this photobioanode revealed active electron transfer at the anode/biofilm interface. The charge-transfer resistance of the anode/biofilm was ca. 46.6 Ω, which is half that of the unmodified anode. In addition, the results of confocal laser scanning microscopy and bacterial community analysis indicate that the photobioanode and light can accelerate biofilm formation and enrich exoelectrogens. When equipped in photo-bioelectrochemical systems, the start-up time was shortened from about 2.5 days to 1.1 days. The maximum current density of photo-bioelectrochemical systems was almost twice that of a control bioelectrochemical system. In addition, the current density of the photo-bio-electrochemical cell (PBEC) showed almost no decrease after being subjected to 40 d of illumination. This photobioanode is therefore a cost-effective, energy-clean, environment-friendly anode with high electrocatalytic activity and long-term stability, which has broad prospects in various processes, including wastewater treatment, bioelectricity generation, bioelectricity synthesis, and hydrogen production. PMID:27395027

  3. Enhancement of spin Hall effect induced torques for current-driven magnetic domain wall motion: Inner interface effect

    NASA Astrophysics Data System (ADS)

    Bang, Do; Yu, Jiawei; Qiu, Xuepeng; Wang, Yi; Awano, Hiroyuki; Manchon, Aurelien; Yang, Hyunsoo

    2016-05-01

    We investigate the current-induced domain wall motion in perpendicular magnetized Tb/Co wires with structure inversion asymmetry and different layered structures. We find that the critical current density to drive domain wall motion strongly depends on the layered structure. The lowest critical current density ˜15 MA /c m2 and the highest slope of domain wall velocity curve are obtained for the wire having thin Co sublayers and more inner Tb/Co interfaces, while the largest critical current density ˜26 MA /c m2 required to drive domain walls is observed in the Tb-Co alloy magnetic wire. It is found that the Co/Tb interface contributes negligibly to Dzyaloshinskii-Moriya interaction, while the effective spin-orbit torque strongly depends on the number of Tb/Co inner interfaces (n ). An enhancement of the antidamping torques by extrinsic spin Hall effect due to Tb rare-earth impurity-induced skew scattering is suggested to explain the high efficiency of current-induced domain wall motion.

  4. Current enhancement of aluminum doped ZnO/n-Si isotype heterojunction solar cells by embedding silver nanoparticles.

    PubMed

    Yun, Juhyung; Kim, Joondong; Kojori, Hossein Shokri; Kim, Sung Jim; Tong, Chong; Anderson, Wayne A

    2013-08-01

    To improve Plasmonic energy harvesting, the Al doped ZnO (AZO) and Si heterojunction was studied for plasmonic photovoltaic applications. Silver nanoparticles (Ag NPs) were embedded in AZO, resulting in direct energy absoption from Ag NPs, positioned close to the junction. This structure has a benefit of avoiding highly doped lossy layers of conventional solar cell structures. Al doped ZnO (AZO) was deposited on n-Si substrate by dual beam sputtering method to fabricate AZO/Si heterojunction solar cells. AZO provides a transparent current spreading effect and rectifying junction with n type silicon (Si). Silver nanoparticles (Ag NPs) were embedded in AZO film (240-270 nm thick) with a sandwich-like structure. The position of Ag NPs in the AZO film was controlled to be located at 10, 20 and 40 nm distance from the Si absorber layer. Fabricated solar cells show improved performance in terms of the short circuit current (J(sc)) and the quantum efficiency (QE). Finite difference time domain (FDTD) simulations were carried out to investigate the QE enhancement and optimize photocurrent gain under an AM1.5G solar spectrum. In calculation, absorption enhancement is maximized when Ag NPs are located close to the Si layer in the range of 10-40 nm. Experimentally, 20 nm distance of Ag NPs from the Si showed the best performance with 0.36 V of open circuit voltage (V(oc)), 28.3 mA/cm2 of J(sc) and 5.91% of coversion efficiency. The QE showed 15% of enhancement around lambda = 435 nm and 5-10% of enhancement within lambda = 600-1000 nm. PMID:23882792

  5. Fluid modeling for plasma-enhanced direct current chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ismagilov, Rinat R.; Khamidullin, Ildar R.; Kleshch, Victor I.; Malykhin, Sergei A.; Alexeev, Andrey M.; Obraztsov, Alexander N.

    2016-01-01

    A self-consistent continuum (fluid) model for a direct current discharge used in a chemical vapor deposition system is developed. The model is built for a two-dimensional axisymmetric system and incorporates an electron energy balance for low-pressure Ar gas. The underlying physics of the fluid model is briefly discussed. The fluid and Poisson equations for plasma species are used as the model background. The plasma species considered in the model include electrons, Ar+ ions, and Ar atoms in ground and excited states. Nine reactions between these species are taken into account, including surface reactions. The densities of various plasma species as well as the relative contributions of generation and annihilation processes for electrons, ions, and atoms are calculated. The concentrations for electrons and Ar+ ions on the order of 1020 m-3 are obtained for the plasma in the computer simulations.

  6. Optimization of Direct Current-Enhanced Radiofrequency Ablation: An Ex Vivo Study

    SciTech Connect

    Tanaka, Toshihiro Isfort, Peter; Bruners, Philipp; Penzkofer, Tobias; Kichikawa, Kimihiko; Schmitz-Rode, Thomas; Mahnken, Andreas H.

    2010-10-15

    The purpose of this study was to investigate the optimal setting for radiofrequency (RF) ablation combined with direct electrical current (DC) ablation in ex vivo bovine liver. An electrical circuit combining a commercially available RF ablation system with DC was developed. The negative electrode of a rectifier that provides DC was connected to a 3-cm multitined expandable RF probe. A 100-mH inductor was used to prevent electrical leakage from the RF generator. DC was applied for 15 min and followed by RF ablation in freshly excised bovine livers. Electric current was measured by an ammeter. Coagulation volume, ablation duration, and mean amperage were assessed for various DC voltages (no DC, 2.2, 4.5, and 9.0 V) and different RF ablation protocols (stepwise increase from 40 to 80 W, 40 W fixed, and 80 W fixed). Results were compared using Kruskal-Wallis and Mann-Whitney U test. Applying DC with 4.5 or 9.0 V, in combination with 40 W fixed or a stepwise increase of RF energy, resulted in significantly increased zone of ablation size compared with 2.2 V or no DC (P = 0.009). At 4.5 V DC, the stepwise increase of RF energy resulted in the same necrosis size as a 40 W fixed protocol (26.6 {+-} 3.9 vs. 26.5 {+-} 4.0 ml), but ablation duration was significantly decreased (296 {+-} 85 s vs. 423 {+-} 104 s; P = 0.028). Mean amperage was significantly lower at 4.5 V compared with 9.0 V (P = 0.028). Combining a stepwise increase of RF energy with a DC voltage of 4.5 V is most appropriate to increase coagulation volume and to minimize procedure time.

  7. Resolution enhancement using pulse width modulation in digital micromirror device-based point-array scanning pattern exposure

    NASA Astrophysics Data System (ADS)

    Kuo, Hung-Fei; Huang, Yi-Jun

    2016-04-01

    Digital-mask lithography systems, with a digital micromirror device (DMD) as their central piece, have been widely used for defining patterns on printed circuit board (PCB). This study designed optical module parameters for point-array projection lithography based on field tracing technique to improve the quality of the aerial image on the exposure plane. In the realized optical module for the point-array projection lithography, a DMD was used as the dynamic digital-mask, and a 405-nm-wavelength laser was used to illuminate the DMD. The laser was then focused through the micro-lens array in the optical module to form a point array and was projected onto a dynamic scanning stage. By calculating the beam-overlapping rate, stage velocity, spot diameter, and DMD frame rate and programming them into the stage- and DMD-synchronized controller, the point array formed line patterns on the photoresist. Furthermore, using pulse width modulation (PWM) technique to operate the activation periods of the DMD mirrors effectively controlled the exposure and achieved a feature linewidth of less than 10 μm.

  8. Point Reward System: A Method of Assessment That Accommodates a Diversity of Student Abilities and Interests and Enhances Learning

    ERIC Educational Resources Information Center

    Derado, Josip; Garner, Mary L.; Tran, Thu-Hang

    2016-01-01

    Students' abilities and interests vary dramatically in the college mathematics classroom. How do we teach all of these students effectively? In this paper, we present the Point Reward System (PRS), a new method of assessment that addresses this problem. We designed the PRS with three main goals in mind: to increase the retention rates; to keep all…

  9. Screen-Capturing System with Two-Layer Display for PowerPoint Presentation to Enhance Classroom Education

    ERIC Educational Resources Information Center

    Lai, Yen-Shou; Tsai, Hung-Hsu; Yu, Pao-Ta

    2011-01-01

    This paper proposes a new presentation system integrating a Microsoft PowerPoint presentation in a two-layer method, called the TL system, to promote learning in a physical classroom. With the TL system, teachers can readily control hints or annotations as a way of making them visible or invisible to students so as to reduce information load. In…

  10. Radiation-enhanced gate-induced-drain-leakage current in the 130 nm partially-depleted SOI pMOSFET

    NASA Astrophysics Data System (ADS)

    Peng, Chao; Hu, Zhiyuan; Ning, Bingxu; Dai, Lihua; Bi, Dawei; Zhang, Zhengxuan

    2015-04-01

    The total ionizing dose (TID) effect of the pMOSFET from 130 nm partially-depleted silicon-on-insulator (PDSOI) is investigated. The data obtained from 60Co γ-ray irradiation experiments indicate that input/output (I/O) device is more susceptible to TID effect than the core device. An anomalous off-state leakage increase is observed for I/O pMOSFET when drain is biased at a high voltage after irradiation. It is proved that this radiation-induced leakage relates to the enhanced gate-induce-drain-leakage (GIDL). Both the radiation-induced interface traps at the gate-oxide/body interface and the oxide trapped charges in the buried oxide (BOX) are responsible for the growth of the leakage current. These conclusions are also verified by the TCAD simulations. The isothermal annealing can recover the leakage current to the pre-irradiation level.

  11. Utilizing the Iterative Closest Point (ICP) algorithm for enhanced registration of high resolution surface models - more than a simple black-box application

    NASA Astrophysics Data System (ADS)

    Stöcker, Claudia; Eltner, Anette

    2016-04-01

    Advances in computer vision and digital photogrammetry (i.e. structure from motion) allow for fast and flexible high resolution data supply. Within geoscience applications and especially in the field of small surface topography, high resolution digital terrain models and dense 3D point clouds are valuable data sources to capture actual states as well as for multi-temporal studies. However, there are still some limitations regarding robust registration and accuracy demands (e.g. systematic positional errors) which impede the comparison and/or combination of multi-sensor data products. Therefore, post-processing of 3D point clouds can heavily enhance data quality. In this matter the Iterative Closest Point (ICP) algorithm represents an alignment tool which iteratively minimizes distances of corresponding points within two datasets. Even though tool is widely used; it is often applied as a black-box application within 3D data post-processing for surface reconstruction. Aiming for precise and accurate combination of multi-sensor data sets, this study looks closely at different variants of the ICP algorithm including sub-steps of point selection, point matching, weighting, rejection, error metric and minimization. Therefore, an agricultural utilized field was investigated simultaneously by terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) sensors two times (once covered with sparse vegetation and once bare soil). Due to different perspectives both data sets show diverse consistency in terms of shadowed areas and thus gaps so that data merging would provide consistent surface reconstruction. Although photogrammetric processing already included sub-cm accurate ground control surveys, UAV point cloud exhibits an offset towards TLS point cloud. In order to achieve the transformation matrix for fine registration of UAV point clouds, different ICP variants were tested. Statistical analyses of the results show that final success of registration and therefore

  12. Enhanced critical currents of commercial 2G superconducting coated conductors through proton irradiation

    NASA Astrophysics Data System (ADS)

    Welp, Ulrich; Leroux, M.; Kihlstrom, K. J.; Kwok, W.-K.; Koshelev, A. E.; Miller, D. J.; Rupich, M. W.; Fleshler, S.; Malozemoff, A. P.; Kayani, A.

    2015-03-01

    We report on magnetization and transport measurements of the critical current density, Jc, of commercial 2G YBCO coated conductors before and after proton irradiation. The samples were irradiated along the c-axis with 4 MeV protons. Proton irradiation produces a mixed pinning landscape composed of pre-existing rare earth particles and a uniform distribution of irradiation induced nm-sized defects. This pinning landscape strongly reduces the suppression of Jc in magnetic fields resulting in a doubling of Jc in a field of ~ 4T. The irradiation dose-dependence of Jc is characterized by a temperature and field dependent sweat spot that at 5 K and 6 T occurs around 20x1016 p/cm2. Large-scale time dependent Ginzburg-Landau simulations yield a good description of our results. 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 (KK, ML, AEK) and by the D.O.E, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 (UW, WKK).

  13. Light-enhanced liquid-phase exfoliation and current photoswitching in graphene-azobenzene composites.

    PubMed

    Döbbelin, Markus; Ciesielski, Artur; Haar, Sébastien; Osella, Silvio; Bruna, Matteo; Minoia, Andrea; Grisanti, Luca; Mosciatti, Thomas; Richard, Fanny; Prasetyanto, Eko Adi; De Cola, Luisa; Palermo, Vincenzo; Mazzaro, Raffaello; Morandi, Vittorio; Lazzaroni, Roberto; Ferrari, Andrea C; Beljonne, David; Samorì, Paolo

    2016-01-01

    Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans-cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene-azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors. PMID:27052205

  14. Enhancement of Localized ICRF Heating and Current Drive in TFTR D-T Plasmas

    SciTech Connect

    = G Schilling, First Author

    1997-04-15

    Theoretical advantages have led to an increased importance of the modification and sustainment of pressure and magnetic shear profiles in plasmas. We have demonstrated electron heating and current drive in TFTR (Tokamak Fusion Test Reactor) plasmas with the existing 43/63.6 MHz ICRF (ion cyclotron range of frequencies) system, both via the fast wave and via mode conversion of the fast wave to an ion-Bernstein wave. In order to achieve both on- and off-axis mode conversion in a pure D-T (deuterium-tritium) plasma, we have changed the operating frequency of two of our transmitters and antennas to 30 MHz and improved the launched directional wave spectrum. As a second step, two new four-strap fast-wave antennas have been installed, and a new four-strap direct-launch IBW antenna has been added as well. This reconfiguration and the resulting operating characteristics of the TFTR ICRF system in a variety of discharges will be presented.

  15. Enhancing Breastfeeding Rates Among African American Women: A Systematic Review of Current Psychosocial Interventions

    PubMed Central

    Johnson, Angela; Kirk, Rosalind; Rosenblum, Katherine Lisa

    2015-01-01

    Abstract The goals of this article are to provide a review of key interventions and strategies that impact initiation and duration of breastfeeding with particular focus on low-income African American mothers' maternal psychological vulnerabilities during the early postpartum period using a social ecological perspective as a guiding framework. Although modest gains have been achieved in breastfeeding initiation rates in the United States, a projected gap remains between infant feeding practices and national Healthy People breastfeeding goals set for 2020, particularly among African Americans. These disparities raise concerns that socially disadvantaged mothers and babies may be at increased risk for poor postnatal outcomes because of poorer mental health and increased vulnerability to chronic health conditions. Breastfeeding can be a protective factor, strengthening the relationship between mother and baby and increasing infant health and resilience. Evidence suggests that no single intervention can sufficiently address the multiple breastfeeding barriers faced by mothers. Effective intervention strategies require a multilevel approach. A social ecological perspective highlights that individual knowledge, behavior, and attitudes are shaped by interactions between the individual woman, her friends and family, and her wider historical, social, political, economic, institutional, and community contexts, and therefore effective breastfeeding interventions must reflect all these aspects. Current breastfeeding interventions are disjointed and inadequately meet all African American women's social and psychological breastfeeding needs. Poor outcomes indicate a need for an integrative approach to address the complexity of interrelated breastfeeding barriers mothers' experience across layers of the social ecological system. PMID:25423601

  16. Enhancing our understanding of current therapies for Hepatitis C virus (HCV)

    PubMed Central

    Gogela, Neliswa A.; Lin, Ming V.; Wisocky, Jessica L.; Chung, Raymond T.

    2015-01-01

    Great progress has been made in understanding the HCV genome and its molecular virology. This understanding has culminated in the development of direct acting antiviral (DAA) agents targeting HCV viral proteins. Telaprevir (TVR) and boceprevir (BOC) were the first DAAs introduced for treatment of genotype1 HCV in 2011; when used in combination with pegylated interferon (pegIFN) and ribavirin (RBV), these protease inhibitors improved efficacy in patients with chronic HCV infection compared to the traditional dual therapy. However, this combination was associated with adverse events that often led to early termination of therapy. In late 2013, the FDA approved a second wave of DAAs, sofosbuvir (SOF) and simeprevir (SMV). The use of SOF with SMV opened the door for IFN-free combination regimens. This combination was highly efficacious and well tolerated in patients with HCV genotype 1. Sofosbuvir and ledipasvir (LDV) fixed dose oral combination (FDC) therapy were recently approved, elevating SVR rates to over 95%. We are anticipating the approval of additional IFN-free regimens with comparable efficacy and tolerability but with the addition of pangenotypic coverage, fewer drug-drug interactions and a high barrier to resistance. This review will summarize current management for chronic HCV infection. PMID:25761432

  17. An exploratory study of recycled sputtering and CsF2- current enhancement for AMS

    NASA Astrophysics Data System (ADS)

    Zhao, X.-L.; Charles, C. R. J.; Cornett, R. J.; Kieser, W. E.; MacDonald, C.; Kazi, Z.; St-Jean, N.

    2016-01-01

    The analysis of 135Cs/Cs ratios at levels below 10-12 by accelerator mass spectrometry (AMS) would preferably use commonly available negative ion injection systems. The sputter ion sources in these injectors should ideally produce currents of Cs- or Cs-containing molecular anions approaching μA levels from targets containing mg quantities of Cs. However, since Cs is the most electro-positive stable element in nature with a low electron affinity, the generation of large negative atomic, or molecular beams containing Cs, has been very challenging. In addition, the reduction of the interferences from the 135Ba isobar and the primary 133Cs+ beam used for sputtering are also necessary. The measurement of a wide range of the isotope ratios also requires the ion source memory of previous samples be minimized. This paper describes some progresses towards a potential solution of all these problems by recycled sputtering using fluorinating targets of PbF2 with mg CsF mixed in. The problems encountered indicate that considerable further studies and some redesign of the present ion sources will be desirable.

  18. Enhancing the fidelity of neurotransmission by activity-dependent facilitation of presynaptic potassium currents.

    PubMed

    Yang, Yi-Mei; Wang, Wei; Fedchyshyn, Michael J; Zhou, Zhuan; Ding, Jiuping; Wang, Lu-Yang

    2014-01-01

    Neurons convey information in bursts of spikes across chemical synapses where the fidelity of information transfer critically depends on synaptic input-output relationship. With a limited number of synaptic vesicles (SVs) in the readily releasable pool (RRP), how nerve terminals sustain transmitter release during intense activity remains poorly understood. Here we report that presynaptic K(+) currents evoked by spikes facilitate in a Ca(2+)-independent but frequency- and voltage-dependent manner. Experimental evidence and computer simulations demonstrate that this facilitation originates from dynamic transition of intermediate gating states of voltage-gated K(+) channels (Kvs), and specifically attenuates spike amplitude and inter-spike potential during high-frequency firing. Single or paired recordings from a mammalian central synapse further reveal that facilitation of Kvs constrains presynaptic Ca(2+) influx, thereby efficiently allocating SVs in the RRP to drive postsynaptic spiking at high rates. We conclude that presynaptic Kv facilitation imparts neurons with a powerful control of transmitter release to dynamically support high-fidelity neurotransmission. PMID:25078759

  19. Enhancing our understanding of current therapies for hepatitis C virus (HCV).

    PubMed

    Gogela, Neliswa A; Lin, Ming V; Wisocky, Jessica L; Chung, Raymond T

    2015-03-01

    Great progress has been made in understanding the HCV genome and its molecular virology. This understanding has culminated in the development of direct-acting antiviral (DAA) agents targeting HCV viral proteins. Telaprevir (TVR) and boceprevir (BOC) were the first DAAs introduced for treatment of genotype 1 HCV in 2011; when used in combination with pegylated interferon (pegIFN) and ribavirin (RBV), these protease inhibitors improved efficacy in patients with chronic HCV infection compared to the traditional dual therapy. However, this combination was associated with adverse events that often led to early termination of therapy. In late 2013, the FDA approved a second wave of DAAs, sofosbuvir (SOF) and simeprevir (SMV). The use of SOF with SMV opened the door for IFN-free combination regimens. This combination was highly efficacious and well tolerated in patients with HCV genotype 1. Sofosbuvir and ledipasvir (LDV) fixed-dose oral combination (FDC) therapy, and paritaprevir/ritonavir, ombitasvir and dasabuvir ± RBV were recently approved, elevating sustained virologic response (SVR) rates to over 95 %. We are anticipating the approval of additional IFN-free regimens with comparable efficacy and tolerability but with the addition of pangenotypic coverage, fewer drug-drug interactions, and a high barrier to resistance. This review will summarize current management for chronic HCV infection. PMID:25761432

  20. Light-enhanced liquid-phase exfoliation and current photoswitching in graphene-azobenzene composites

    NASA Astrophysics Data System (ADS)

    Döbbelin, Markus; Ciesielski, Artur; Haar, Sébastien; Osella, Silvio; Bruna, Matteo; Minoia, Andrea; Grisanti, Luca; Mosciatti, Thomas; Richard, Fanny; Prasetyanto, Eko Adi; de Cola, Luisa; Palermo, Vincenzo; Mazzaro, Raffaello; Morandi, Vittorio; Lazzaroni, Roberto; Ferrari, Andrea C.; Beljonne, David; Samorì, Paolo

    2016-04-01

    Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans-cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene-azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors.

  1. Light-enhanced liquid-phase exfoliation and current photoswitching in graphene–azobenzene composites

    PubMed Central

    Döbbelin, Markus; Ciesielski, Artur; Haar, Sébastien; Osella, Silvio; Bruna, Matteo; Minoia, Andrea; Grisanti, Luca; Mosciatti, Thomas; Richard, Fanny; Prasetyanto, Eko Adi; De Cola, Luisa; Palermo, Vincenzo; Mazzaro, Raffaello; Morandi, Vittorio; Lazzaroni, Roberto; Ferrari, Andrea C.; Beljonne, David; Samorì, Paolo

    2016-01-01

    Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans–cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene–azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors. PMID:27052205

  2. Enhanced critical currents by high-pressure impregnation of 1-2-3 systems with normal conductors

    NASA Astrophysics Data System (ADS)

    Ortabasi, Ugur; Watson, J. H.; Black, James A.

    1990-10-01

    In this paper we present the preliminary analytical and experimental results of a novel low temperature metal impregnation method to increase the critical currents in thick film and bulk HTSC materials. The method described results in a structurally more controllable and effective microcomposite than the ones obtained with metal- and metal-oxide precursors. The physical procedure involves the infiltration of the interstices of the porous, fully treated superconductor with low-melting point, low T superconductor under high pressure. Deep penetration of the metal into the granular superconducting matrix creates large surface areas of strong Proximity Effect. Improved intergrain coupling increases the DC Josephson current and therefore J, the critical current. Prior to the experimental work a theoretical study was conducted. Indium was chosen as the impregnation material. Computations showed.that the infiltrated system should have at least a four orders higher critical current (4.47 x 104 A/cm2) as compared to the same array with vacuum barriers of 20A thickness between the grains (0.31 A/cm2). On the experimental side, high T, porous, 1-2-3 samples impregnated with gallium exhibited very low contact resistance (2. 1 x 10-6 cm2) at 85°K, a value about two orders of magnitude better than the 1-2-3 systems containing intergranular silver. Further experiments with indium impregnated samples are planned. This new low temperature method allows the manufacture of highly flexible wires and films when used with suitable substrates.

  3. Enhanced low current, voltage, and power dissipation measurements via Arduino Uno microcontroller with modified commercially available sensors

    NASA Astrophysics Data System (ADS)

    Tanner, Meghan; Eckel, Ryan; Senevirathne, Indrajith

    The versatility, simplicity, and robustness of Arduino microcontroller architecture have won a huge following with increasingly serious engineering and physical science applications. Arduino microcontroller environment coupled with commercially available sensors have been used to systematically measure, record, and analyze low currents, low voltages and corresponding dissipated power for assessing secondary physical properties in a diverse array of engineering systems. Setup was assembled via breadboard, wire, and simple soldering with an Arduino Uno with ATmega328P microcontroller connected to a PC. The microcontroller was programmed with Arduino Software while the bootloader was used to upload the code. Commercial Hall effect current sensor modules ACS712 and INA169 current shunt monitor was used to measure corresponding low to ultra-low currents and voltages. Stable measurement data was obtained via sensors and compared with corresponding oscilloscope measurements to assess reliability and uncertainty. Sensor breakout boards were modified to enhance the sensitivity of the measurements and to expand the applicability. Discussion of these measurements will focus on capabilities, capacities and limitations of the systems with examples of possible applications. Lock Haven Nanotechnology Program.

  4. Bihemispheric Transcranial Direct Current Stimulation Enhances Effector-Independent Representations of Motor Synergy and Sequence Learning

    PubMed Central

    Husain, Masud; Wiestler, Tobias; Diedrichsen, Jörn

    2014-01-01

    Complex manual tasks—everything from buttoning up a shirt to playing the piano—fundamentally involve two components: (1) generating specific patterns of muscle activity (here, termed “synergies”); and (2) stringing these into purposeful sequences. Although transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) has been found to increase the learning of motor sequences, it is unknown whether it can similarly facilitate motor synergy learning. Here, we determined the effects of tDCS on the learning of motor synergies using a novel hand configuration task that required the production of difficult muscular activation patterns. Bihemispheric tDCS was applied to M1 of healthy, right-handed human participants during 4 d of repetitive left-hand configuration training in a double-blind design. tDCS augmented synergy learning, leading subsequently to faster and more synchronized execution. This effect persisted for at least 4 weeks after training. Qualitatively similar tDCS-associated improvements occurred during training of finger sequences in a separate subject cohort. We additionally determined whether tDCS only improved the acquisition of motor memories for specific synergies/sequences or whether it also facilitated more general parts of the motor representations, which could be transferred to novel movements. Critically, we observed that tDCS effects generalized to untrained hand configurations and untrained finger sequences (i.e., were nonspecific), as well as to the untrained hand (i.e., were effector-independent). Hence, bihemispheric tDCS may be a promising adjunct to neurorehabilitative training regimes, in which broad transfer to everyday tasks is highly desirable. PMID:24431461

  5. [Non-invasive brain stimulation in neurology : Transcranial direct current stimulation to enhance cognitive functioning].

    PubMed

    Antonenko, D; Flöel, A

    2016-08-01

    Transcranial direct current stimulation (tDCS) has been successfully used in neuroscientific research to modulate cognitive functions. Recent studies suggested that improvement of behavioral performance is associated with tDCS-induced modulation of neuronal activity and connectivity. Thus, tDCS may also represent a promising tool for reconstitution of cognitive functions in the context of memory decline related to Alzheimer's disease or aphasia following stroke; however, evidence from randomized sham-controlled clinical trials is still scarce. Initial results of tDCS-induced behavioral improvement in patients with Alzheimer's dementia and its precursors indicated that an intense memory training combined with tDCS may be effective. Early interventions in the stage of mild cognitive impairment could be crucial but further evidence is needed to substantiate this. In patients with aphasia following stroke tDCS was applied to the left and right hemispheres, with varying results depending on the severity of the symptoms and polarity of the stimulation. Patients with mild aphasia can benefit from tDCS of the language dominant hemisphere while in patients with severe aphasia tDCS of right hemispheric homologous brain language areas may be particularly relevant. Moreover, recent studies suggested that an intervention in the subacute phase of aphasia could be most promising. In summary, tDCS could provide the exciting possibility to reconstitute cognitive functions in patients with neurological disorders. Future studies have to elucidate whether tDCS can be used in the clinical routine to prevent further cognitive decline in neurodegenerative diseases and whether beneficial effects from experimental studies translate into long-term improvement in activities of daily life. PMID:27167887

  6. Does transcranial direct current stimulation enhance cognitive and motor functions in the ageing brain? A systematic review and meta- analysis.

    PubMed

    Summers, Jeffery J; Kang, Nyeonju; Cauraugh, James H

    2016-01-01

    The use of transcranial direct current stimulation (tDCS) to enhance cognitive and motor functions has enjoyed a massive increase in popularity. Modifying neuroplasticity via non-invasive cortical stimulation has enormous potential to slow or even reverse declines in functions associated with ageing. The current meta-analysis evaluated the effects of tDCS on cognitive and motor performance in healthy older adults. Of the 81 studies identified, 25 qualified for inclusion. A random effects model meta-analysis revealed a significant overall standardized mean difference equal to 0.53 (SE=0.09; medium heterogeneity: I(2)=57.08%; and high fail-safe: N=448). Five analyses on moderator variables indicated significant tDCS beneficial effects: (a) on both cognitive and motor task performances, (b) across a wide-range of cognitive tasks, (c) on specific brain areas, (d) stimulation offline (before) or online (during) the cognitive and motor tasks. Although the meta-analysis revealed robust support for enhancing both cognitive and motor performance, we outline a number of caveats on the use of tDCS. PMID:26607412

  7. Improving Surface Geostrophic Current from a GOCE-Derived Mean Dynamic Topography Using Edge-Enhancing Diffusion Filtering

    NASA Astrophysics Data System (ADS)

    Sánchez-Reales, J. M.; Andersen, O. B.; Vigo, M. I.

    2016-03-01

    With increased geoid resolution provided by the gravity and steady-state ocean circulation explorer (GOCE) mission, the ocean's mean dynamic topography (MDT) can be now estimated with an accuracy not available prior to using geodetic methods. However, an altimetric-derived MDT still needs filtering in order to remove short wavelength noise unless integrated methods are used in which the three quantities are determined simultaneously using appropriate covariance functions. We studied nonlinear anisotropic diffusive filtering applied to the oceańs MDT and a new approach based on edge-enhancing diffusion (EED) filtering is presented. EED filters enable controlling the direction and magnitude of the filtering, with subsequent enhancement of computations of the associated surface geostrophic currents (SGCs). Applying this method to a smooth MDT and to a noisy MDT, both for a region in the Northwestern Pacific Ocean, we found that EED filtering provides similar estimation of the current velocities in both cases, whereas a non-linear isotropic filter (the Perona and Malik filter) returns results influenced by local residual noise when a difficult case is tested. We found that EED filtering preserves all the advantages that the Perona and Malik filter have over the standard linear isotropic Gaussian filters. Moreover, EED is shown to be more stable and less influenced by outliers. This suggests that the EED filtering strategy would be preferred given its capabilities in controlling/preserving the SGCs.

  8. Application of a combined superconducting fault current limiter and STATCOM to enhancement of power system transient stability

    NASA Astrophysics Data System (ADS)

    Mahdad, Belkacem; Srairi, K.

    2013-12-01

    Stable and reliable operation of the power system network is dependent on the dynamic equilibrium between energy production and power demand under large disturbance such as short circuit or important line tripping. This paper investigates the use of combined model based superconducting fault current limiter (SFCL) and shunt FACTS Controller (STATCOM) for assessing the transient stability of a power system considering the automatic voltage regulator. The combined model located at a specified branch based on voltage stability index using continuation power flow. The main role of the proposed combined model is to achieve simultaneously a flexible control of reactive power using STATCOM Controller and to reduce fault current using superconducting technology based SFCL. The proposed combined model has been successfully adapted within the transient stability program and applied to enhance the transient power system stability of the WSCC9-Bus system. Critical clearing time (CCT) has been used as an index to evaluate and validate the contribution of the proposed coordinated Controller. Simulation results confirm the effectiveness and perspective of this combined Controller to enhance the dynamic power system performances.

  9. Au nanoparticles embedded at the interface of Al/4H-SiC Schottky contacts for current density enhancement

    NASA Astrophysics Data System (ADS)

    Gorji, Mohammad Saleh; Cheong, Kuan Yew

    2015-01-01

    Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of contact/semiconductor, offer a viable solution in modification of Schottky barrier height (SBH) in Schottky contacts. The successful performance of devices with such nanostructured contacts requires a feasible selection of NPs/contact material based on theoretical calculations and a cost effective and reproducible route for NPs deposition. Acidification of commercially available colloidal Au NPs solution by HF has been selected here as a simple bench-top technique for deposition of Au NPs on n- and p-type 4H-SiC substrates. Theoretical calculations based on the model of inhomogeneity in SBH (ISBH) were used to make a more appropriate selection of NPs type (Au) and size (5 and 10 nm, diameter) with respect to contact metal (Al). Al/Au NPs/SiC Schottky barrier diodes were then fabricated, and their electrical characteristics exhibited current density enhancement due to the SBH lowering. The source of SBH lowering was determined to be the local electric field enhancement due to NPs effect, which was further investigated using the models of ISBH and tunneling enhancement at triple interface.

  10. InN/InGaN complementary heterojunction-enhanced tunneling field-effect transistor with enhanced subthreshold swing and tunneling current

    NASA Astrophysics Data System (ADS)

    Peng, Yue; Han, Genquan; Wang, Hongjuan; Zhang, Chunfu; Liu, Yan; Wang, Yibo; Zhao, Shenglei; Zhang, Jincheng; Hao, Yue

    2016-05-01

    InN/In0.75Ga0.25N complementary heterojunction-enhanced tunneling field-effect transistors (HE-TFETs) were characterized using the numerical simulation. InN/In0.75Ga0.25N HE-TFET has an InN/In0.75Ga0.25N heterojunction located in the channel region with a distance of LT-H from the source/channel tunneling junction. We demonstrate that, for both n- and p-channel devices, HE-TFETs have a delay of onset voltage VONSET, a steeper subthreshold swing (SS), and an enhanced on-state current ION in comparison with the homo-TFETs. InN/In0.75Ga0.25N n- and p-channel HE-TFETs with a gate length LG of 25 nm and a LT-H of 5 nm achieve a 7 and 9 times ION improvement in comparison with the homo devices, respectively, at a supply voltage of 0.3 V. The performance enhancement in HE-TFETs is attributed to the modulating effect of heterojunction on band-to-band tunneling (BTBT). Because InN/In0.75Ga0.25N heterointerface shows the similar band offsets at conduction and valence bands, the InN/In0.75Ga0.25N heterojunction exhibits the improved effect on BTBT for both n- and p-channel devices. This makes InN/In0.75Ga0.25N heterojunction a promising structure for high performance complementary TFETs.

  11. Insights from the Fungus Fusarium oxysporum Point to High Affinity Glucose Transporters as Targets for Enhancing Ethanol Production from Lignocellulose

    PubMed Central

    Ali, Shahin S.; Nugent, Brian; Mullins, Ewen; Doohan, Fiona M.

    2013-01-01

    Ethanol is the most-widely used biofuel in the world today. Lignocellulosic plant biomass derived from agricultural residue can be converted to ethanol via microbial bioprocessing. Fungi such as Fusarium oxysporum can simultaneously saccharify straw to sugars and ferment sugars to ethanol. But there are many bottlenecks that need to be overcome to increase the efficacy of microbial production of ethanol from straw, not least enhancement of the rate of fermentation of both hexose and pentose sugars. This research tested the hypothesis that the rate of sugar uptake by F. oxysporum would enhance the ethanol yields from lignocellulosic straw and that high affinity glucose transporters can enhance ethanol yields from this substrate. We characterized a novel hexose transporter (Hxt) from this fungus. The F. oxysporum Hxt represents a novel transporter with homology to yeast glucose signaling/transporter proteins Rgt2 and Snf3, but it lacks their C-terminal domain which is necessary for glucose signalling. Its expression level decreased with increasing glucose concentration in the medium and in a glucose uptake study the Km(glucose) was 0.9 mM, which indicated that the protein is a high affinity glucose transporter. Post-translational gene silencing or over expression of the Hxt in F. oxysporum directly affected the glucose and xylose transport capacity and ethanol yielded by F. oxysporum from straw, glucose and xylose. Thus we conclude that this Hxt has the capacity to transport both C5 and C6 sugars and to enhance ethanol yields from lignocellulosic material. This study has confirmed that high affinity glucose transporters are ideal candidates for improving ethanol yields from lignocellulose because their activity and level of expression is high in low glucose concentrations, which is very common during the process of consolidated processing. PMID:23382943

  12. SPARSE: Seed Point Auto-Generation for Random Walks Segmentation Enhancement in medical inhomogeneous targets delineation of morphological MR and CT images.

    PubMed

    Chen, Haibin; Zhen, Xin; Gu, Xuejun; Yan, Hao; Cervino, Laura; Xiao, Yang; Zhou, Linghong

    2015-01-01

    In medical image processing, robust segmentation of inhomogeneous targets is a challenging problem. Because of the complexity and diversity in medical images, the commonly used semiautomatic segmentation algorithms usually fail in the segmentation of inhomogeneous objects. In this study, we propose a novel algorithm imbedded with a seed point autogeneration for random walks segmentation enhancement, namely SPARSE, for better segmentation of inhomogeneous objects. With a few user-labeled points, SPARSE is able to generate extended seed points by estimating the probability of each voxel with respect to the labels. The random walks algorithm is then applied upon the extended seed points to achieve improved segmentation result. SPARSE is implemented under the compute unified device architecture (CUDA) programming environment on graphic processing unit (GPU) hardware platform. Quantitative evaluations are performed using clinical homogeneous and inhomogeneous cases. It is found that the SPARSE can greatly decrease the sensitiveness to initial seed points in terms of location and quantity, as well as the freedom of selecting parameters in edge weighting function. The evaluation results of SPARSE also demonstrate substantial improvements in accuracy and robustness to inhomogeneous target segmentation over the original random walks algorithm. PMID:26103201

  13. ICan: An Optimized Ion-Current-Based Quantification Procedure with Enhanced Quantitative Accuracy and Sensitivity in Biomarker Discovery

    PubMed Central

    2015-01-01

    The rapidly expanding availability of high-resolution mass spectrometry has substantially enhanced the ion-current-based relative quantification techniques. Despite the increasing interest in ion-current-based methods, quantitative sensitivity, accuracy, and false discovery rate remain the major concerns; consequently, comprehensive evaluation and development in these regards are urgently needed. Here we describe an integrated, new procedure for data normalization and protein ratio estimation, termed ICan, for improved ion-current-based analysis of data generated by high-resolution mass spectrometry (MS). ICan achieved significantly better accuracy and precision, and lower false-positive rate for discovering altered proteins, over current popular pipelines. A spiked-in experiment was used to evaluate the performance of ICan to detect small changes. In this study E. coli extracts were spiked with moderate-abundance proteins from human plasma (MAP, enriched by IgY14-SuperMix procedure) at two different levels to set a small change of 1.5-fold. Forty-five (92%, with an average ratio of 1.71 ± 0.13) of 49 identified MAP protein (i.e., the true positives) and none of the reference proteins (1.0-fold) were determined as significantly altered proteins, with cutoff thresholds of ≥1.3-fold change and p ≤ 0.05. This is the first study to evaluate and prove competitive performance of the ion-current-based approach for assigning significance to proteins with small changes. By comparison, other methods showed remarkably inferior performance. ICan can be broadly applicable to reliable and sensitive proteomic survey of multiple biological samples with the use of high-resolution MS. Moreover, many key features evaluated and optimized here such as normalization, protein ratio determination, and statistical analyses are also valuable for data analysis by isotope-labeling methods. PMID:25285707

  14. Enhancing Cross-functional Collaboration and Effective Problem Solving Through an Innovation Challenge for Point-of-Care Providers.

    PubMed

    Bakallbashi, Eni; Vyas, Anjali; Vaswani, Nikita; Rosales, David; Russell, David; Dowding, Dawn; Bernstein, Michael; Abdelaal, Hany; Hawkey, Regina

    2015-01-01

    An internal employee challenge competition is a way to promote staff engagement and generate innovative business solutions. This Spotlight on Leadership focuses on the approach that a large not-for-profit healthcare organization, the Visiting Nurse Service of New York, took in designing and executing an innovation challenge. The challenge leveraged internal staff expertise and promoted wide participation. This model is 1 that can be replicated by organizations as leaders work to engage employees at the point of service in organization-wide problem solving. PMID:26204375

  15. Voltage control for a wind power plant based on the available reactive current of a DFIG and its impacts on the point of interconnection

    DOE PAGESBeta

    Usman, Yasir; Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

    2016-01-01

    Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gainmore » of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Furthermore, simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.« less

  16. Voltage control for a wind power plant based on the available reactive current of a DFIG and its impacts on the point of interconnection

    SciTech Connect

    Usman, Yasir; Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

    2016-01-01

    Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gain of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Furthermore, simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.

  17. Synergistic enhancement effect of room temperature ionic liquids for cloud point extraction combined with UV-vis spectrophotometric determination nickel in environmental samples

    NASA Astrophysics Data System (ADS)

    Zeng, Chujie; Xu, Xili; Zhou, Neng; Lin, Yao

    A new method based on enhancement effect of room temperature ionic liquids for cloud point extraction trace amounts of nickel combined with UV-vis spectrophotometric determination was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagent and chelating reagent, respectively. The addition of room temperature ionic liquids leads to 3.0 times improvement in the determination of nickel. The nonionic surfactant Triton X-100 was used as the extractant. When the temperature of the system was higher than the cloud point of Triton X-100, Ni-DTC complex was extracted into Triton X-100 and separation of the analyte from the matrix was achieved. Some parameters that influenced cloud point extraction and subsequent determination were evaluated in detail, such as the concentrations of RTILs, DDTC and Triton X-100; pH of sample solution, as well as interferences. Under optimized conditions, an enrichment factor of 72 could be obtained, and the detection limit (LOD) for Ni was 0.5 ng mL-1. Relative standard deviations for five replicate determinations of the standard solution containing 50 ng mL-1 Ni was 3.9%. The proposed method was successfully applied to the determination of nickel in certified reference materials with satisfactory results.

  18. Enhancement in field emission current density of Ni nanoparticles embedded in thin silica matrix by swift heavy ion irradiation

    SciTech Connect

    Sarker, Debalaya; Patra, Rajkumar; Srivastava, P.; Ghosh, S.; Kumar, H.; Kabiraj, D.; Avasthi, D. K.; Vayalil, Sarathlal K.; Roth, S. V.

    2014-05-07

    The field emission (FE) properties of nickel nanoparticles embedded in thin silica matrix irradiated with 100 MeV Au{sup +7} ions at various fluences are studied here. A large increase in FE current density is observed in the irradiated films as compared to their as deposited counterpart. The dependence of FE properties on irradiation fluence is correlated with surface roughness, density of states of valence band and size distribution of nanoparticles as examined with atomic force microscope, X-ray photoelectron spectroscopy, and grazing incidence small angle x-ray scattering. A current density as high as 0.48 mA/cm{sup 2} at an applied field 15 V/μm has been found for the first time for planar field emitters in the film irradiated with fluence of 5.0 × 10{sup 13} ions/cm{sup 2}. This significant enhancement in the current density is attributed to an optimized size distribution along with highest surface roughness of the same. This new member of field emission family meets most of the requirements of cold cathodes for vacuum micro/nanoelectronic devices.

  19. Usefulness of two-point Dixon fat-water separation technique in gadoxetic acid-enhanced liver magnetic resonance imaging

    PubMed Central

    Ding, Ying; Rao, Sheng-Xiang; Chen, Cai-Zhong; Li, Ren-Chen; Zeng, Meng-Su

    2015-01-01

    AIM: To compare differences between volumetric interpolated breath-hold examination (VIBE) using two-point Dixon fat-water separation (Dixon-VIBE) and chemically selective fat saturation (FS-VIBE) with magnetic resonance imaging examination. METHODS: Forty-nine patients were included, who were scanned with two VIBE sequences (Dixon-VIBE and FS-VIBE) in hepatobiliary phase after gadoxetic acid administration. Subjective evaluations including sharpness of tumor, sharpness of vessels, strength and homogeneity of fat suppression, and artifacts that were scored using a 4-point scale. The liver-to-lesion contrast was also calculated and compared. RESULTS: Dixon-VIBE with water reconstruction had significantly higher subjective scores than FS-VIBE in strength and homogeneity of fat suppression (< 0.0001) but lower scores in sharpness of tumor (P < 0.0001), sharpness of vessels (P = 0.0001), and artifacts (P = 0.034). The liver-to-lesion contrast on Dixon-VIBE images was significantly lower than that on FS-VIBE (16.6% ± 9.4% vs 23.9% ± 12.1%, P = 0.0001). CONCLUSION: Dixon-VIBE provides stronger and more homogenous fat suppression than FS-VIBE, while has lower clarity of focal liver lesions in hepatobiliary phase after gadoxetic acid administration. PMID:25945017

  20. Influence of discharge production conditions, gas pressure, current intensity and voltage type, on SF6 dissociation under point-plane corona discharges

    NASA Astrophysics Data System (ADS)

    Belarbi, A.; Pradayrol, C.; Casanovas, J.; Casanovas, A. M.

    1995-02-01

    The study of the formation of Sulfur Hexafluoride (SF6) dissociation products under point to plane corona discharges was carried out at P(sub SF(6)) = 300 kPa using different discharges production conditions (50 Hz ac voltage, dc negative polarity voltage, mean discharge current intensity bar-I varying between 2 and 45 micro-A for dc negative polarity voltage), for two plane electrode materials (aluminum and stainless steel), and moisture levels (200 and 2000 ppm(sub v) H2O). The stable gaseous by-products formed (SO2F2, SOF4, SOF2, and S2F10) were assayed by gas-phase chromatography. The results indicate an important effect of the metal constituting the plane electrode and of the moisture conditions whatever the SF6 pressure (100-300 kPa), discharges intensity (bar-I) and voltage type studied. An effect of the increase of SF6 pressure up to 300 kPa was mainly observed for S2F10 and corresponds to a greater formation of this compound with P(sub SF(6)). The influence of the mean discharge current intensity on SF6 by-product formation carried out for a transported charge of 1 C showed that for I less than or equal to 10 micro-A, the effect varies according to the compound considered and depends on the water content of the SF6 and/or on the plane electrode material, whereas for bar-I greater than 10 micro-A, the levels of the four compound studied hardly vary with the current. Comparison of results obtained under ac and dc voltage for a cumulated charge of between 0.5 and 11 C showed that (SO2F2+SOF4) and SOF2 were formed in larger quantities with ac than with dc, unlike S2F10 for which the opposite effect was observed.

  1. Point mutations in the tumor suppressor Smad4/DPC4 enhance its phosphorylation by GSK3 and reversibly inactivate TGF-β signaling

    PubMed Central

    Demagny, Hadrien; De Robertis, Edward M

    2016-01-01

    The tumor suppressor Smad4/DPC4 is an essential transcription factor in the TGF-β pathway and is frequently mutated or deleted in prostate, colorectal, and pancreatic carcinomas. We recently discovered that Smad4 activity and stability are regulated by the FGF/EGF and Wnt signaling pathways through a series of MAPK and GSK3 phosphorylation sites located in its linker region. In the present study, we report that loss-of-function associated with 2 point mutations commonly found in colorectal and pancreatic cancers results from enhanced Smad4 phosphorylation by GSK3, generating a phosphodegron that leads to subsequent β-TrCP–mediated polyubiquitination and proteasomal degradation. Using chemical GSK3 inhibitors, we show that Smad4 point mutant proteins can be stabilized and TGF-β signaling restored in cancer cells harboring such mutations. PMID:27308538

  2. Analysis of enhanced current-generating mechanism of Geobacter sulfurreducens strain via model-driven metabolism simulation.

    PubMed

    Meng, Jing; Xu, Zixiang; Guo, Jing; Yue, Yunxia; Sun, Xiao

    2013-01-01

    Microbial fuel cells (MFCs) are a class of ideal technologies that function via anaerobic respiration of electricigens, which bring current generation and environmental restoration together. An in-depth understanding of microbial metabolism is of great importance in engineering microbes to further improve their respiration. We employed flux balance analysis and selected Fe(iii) as a substitute for the electrode to simulate current-generating metabolism of Geobacter sulfurreducens PCA with a fixed acetate uptake rate. Simulation results indicated the fluxes of reactions directing acetate towards dissimilation to generate electrons increased under the suboptimal growth condition, resulting in an increase in the respiration rate and a decrease in the growth rate. The results revealed the competitive relationship between oxidative respiration and cell growth during the metabolism of microbe current generation. The results helped us quantitatively understand why microbes growing slowly have the potential to make good use of fuel in MFCs. At the same time, slow growth does not necessarily result in speedy respiration. Alternative respirations may exist under the same growth state due to redundant pathways in the metabolic network. The big difference between the maximum and minimum respiration mainly results from the total formate secretion. With iterative flux variability analysis, a relatively ideal model of variant of G. sulfurreducens PCA was reconstructed by deleting several enzymes in the wild model, which could reach simultaneous suboptimal growth and maximum respiration. Under this ideal condition, flux towards extracellular electron transfer rather than for biosynthesis is beneficial for the conversion of organic matter to electricity without large accumulations of biomass and electricigens may maximize utilization of limited fuel. Our simulations will provide an insight into the enhanced current-generating mechanism and identify theoretical range of respiration

  3. Simulation for System Change: Holland Bloorview's Experience Using Simulation to Enhance the Use of Technology at the Point-Of-Care.

    PubMed

    Hubley, Darlene; Peacocke, Sean; Maxwell, Joanne; Parker, Kathryn

    2015-01-01

    Simulation has the potential to invigorate teaching practices, facilitate professional development and impact client care. However, there is little literature on using simulation at the level of organizational change in healthcare. In this paper, the authors explore Holland Bloorview Kids Rehabilitation Hospital's experience using simulation to enhance the use of technology at the point-of-care. The simulation event demonstrated documentation using technology in two typical practice environments and allowed learners to discuss the challenges and opportunities. Participant feedback was positive overall, and this article reveals important lessons to support the future use of simulation as an educational tool for organizational change. PMID:26168391

  4. Measurement of the Total Active 8B Solar Neutrino Flux at the Sudbury Neutrino Observatory with Enhanced Neutral Current Sensitivity

    NASA Astrophysics Data System (ADS)

    Ahmed, S. N.; Anthony, A. E.; Beier, E. W.; Bellerive, A.; Biller, S. D.; Boger, J.; Boulay, M. G.; Bowler, M. G.; Bowles, T. J.; Brice, S. J.; Bullard, T. V.; Chan, Y. D.; Chen, M.; Chen, X.; Cleveland, B. T.; Cox, G. A.; Dai, X.; Dalnoki-Veress, F.; Doe, P. J.; Dosanjh, R. S.; Doucas, G.; Dragowsky, M. R.; Duba, C. A.; Duncan, F. A.; Dunford, M.; Dunmore, J. A.; Earle, E. D.; Elliott, S. R.; Evans, H. C.; Ewan, G. T.; Farine, J.; Fergani, H.; Fleurot, F.; Formaggio, J. A.; Fowler, M. M.; Frame, K.; Fulsom, B. G.; Gagnon, N.; Graham, K.; Grant, D. R.; Hahn, R. L.; Hall, J. C.; Hallin, A. L.; Hallman, E. D.; Hamer, A. S.; Handler, W. B.; Hargrove, C. K.; Harvey, P. J.; Hazama, R.; Heeger, K. M.; Heintzelman, W. J.; Heise, J.; Helmer, R. L.; Hemingway, R. J.; Hime, A.; Howe, M. A.; Jagam, P.; Jelley, N. A.; Klein, J. R.; Kos, M. S.; Krumins, A. V.; Kutter, T.; Kyba, C. C.; Labranche, H.; Lange, R.; Law, J.; Lawson, I. T.; Lesko, K. T.; Leslie, J. R.; Levine, I.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H. B.; Maneira, J.; Marino, A. D.; McCauley, N.; McDonald, A. B.; McGee, S.; McGregor, G.; Mifflin, C.; Miknaitis, K. K.; Miller, G. G.; Moffat, B. A.; Nally, C. W.; Nickel, B. G.; Noble, A. J.; Norman, E. B.; Oblath, N. S.; Okada, C. E.; Ollerhead, R. W.; Orrell, J. L.; Oser, S. M.; Ouellet, C.; Peeters, S. J.; Poon, A. W.; Robertson, B. C.; Robertson, R. G.; Rollin, E.; Rosendahl, S. S.; Rusu, V. L.; Schwendener, M. H.; Simard, O.; Simpson, J. J.; Sims, C. J.; Sinclair, D.; Skensved, P.; Smith, M. W.; Starinsky, N.; Stokstad, R. G.; Stonehill, L. C.; Tafirout, R.; Takeuchi, Y.; Tešić, G.; Thomson, M.; Thorman, M.; van Berg, R.; van de Water, R. G.; Virtue, C. J.; Wall, B. L.; Waller, D.; Waltham, C. E.; Tseung, H. Wan; Wark, D. L.; West, N.; Wilhelmy, J. B.; Wilkerson, J. F.; Wilson, J. R.; Wouters, J. M.; Yeh, M.; Zuber, K.

    2004-05-01

    The Sudbury Neutrino Observatory has precisely determined the total active (νx) 8B solar neutrino flux without assumptions about the energy dependence of the νe survival probability. The measurements were made with dissolved NaCl in heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21±0.27(stat)±0.38(syst)×106 cm-2 s-1, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Δm2=7.1+1.2-0.6×10-5 eV2 and θ=32.5+2.4-2.3 degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations.

  5. Enhancing language performance with non-invasive brain stimulation--a transcranial direct current stimulation study in healthy humans.

    PubMed

    Sparing, Roland; Dafotakis, Manuel; Meister, Ingo G; Thirugnanasambandam, Nivethida; Fink, Gereon R

    2008-01-15

    In humans, transcranial direct current stimulation (tDCS) can be used to induce, depending on polarity, increases or decreases of cortical excitability by polarization of the underlying brain tissue. Cognitive enhancement as a result of tDCS has been reported. The purpose of this study was to test whether weak tDCS (current density, 57 microA/cm(2)) can be used to modify language processing. Fifteen healthy subjects performed a visual picture naming task before, during and after tDCS applied over the posterior perisylvian region (PPR), i.e. an area which includes Wernicke's area [BA 22]. Four different sessions were carried out: (1) anodal and (2) cathodal stimulation of left PPR and, for control, (3) anodal stimulation of the homologous region of the right hemisphere and (4) sham stimulation. We found that subjects responded significantly faster following anodal tDCS to the left PPR (p<0.01). No decreases in performance were detected. Our finding of a transient improvement in a language task following the application of tDCS together with previous studies which investigated the modulation of picture naming latency by transcranial magnetic stimulation (TMS) and repetitive TMS (rTMS) suggest that tDCS applied to the left PPR (including Wernicke's area [BA 22]) can be used to enhance language processing in healthy subjects. Whether this safe, low cost, and easy to use brain stimulation technique can be used to ameliorate deficits of picture naming in aphasic patients needs further investigations. PMID:17804023

  6. Enhancing Protein Capture Using a Combination of Nanoyeast Single-Chain Fragment Affinity Reagents and Alternating Current Electrohydrodynamic Forces.

    PubMed

    Vaidyanathan, Ramanathan; Rauf, Sakandar; Grewal, Yadveer S; Spadafora, Lauren J; Shiddiky, Muhammad J A; Cangelosi, Gerard A; Trau, Matt

    2015-12-01

    New high-performance detection technologies and more robust protein capture agents can be combined to both rapidly and specifically capture and detect protein biomarkers associated with disease in complex biological samples. Here we demonstrate the use of recently developed recombinant affinity reagents, namely nanoyeast-scFv, in combination with alternating current electrohydrodynamic (ac-EHD)-induced shear forces, to enhance capture performance during protein biomarker analysis. The use of ac-EHD significantly improves fluid transport across the capture domain, resulting in enhanced sensor-target interaction and simultaneous displacement of nonspecific molecules from the electrode surface. We demonstrate this simple proof-of-concept approach for the capture and detection of Entamoeba histolytica antigens from disinfected stool, within a span of 5 min using an ac-EHD microfluidic device. Under an ac-EHD field, antigens were captured on a nanoyeast-scFv immobilized device and subsequently detected using a quantum dot conjugated antibody. This immunosensor specifically detected antigen in disinfected stool with low background noise at concentrations down to 58.8 fM with an interassay reproducibility (%RSD of n = 3) < 17.2%, and in buffer down to 5.88 fM with an interassay reproducibility (% RSD, n = 3) of 8.4%. Furthermore, antigen detection using this immunosensor was 10 times more sensitive than previously obtained with the same nanoyeast-scFv reagents in a microfluidic device employing surface-enhanced Raman scattering (SERS) detection in buffer and at least 200 times more sensitive than methods using screen printed gold electrodes in disinfected stool. We predict this rapid and sensitive approach using these stable affinity reagents may offer a new methodology to detect protein disease biomarkers from biological matrices. PMID:26551436

  7. High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J.; Bell, R. E.; LeBlanc, B. P.; Phillips, C. K.; Taylor, G.; Valeo, E.; Wilson, J. R.; Jaeger, E. F.; Ryan, P. M.; Wilgen, J.; Yuh, H.; Levinton, F.; Sabbagh, S.; Tritz, K.; Parker, J.; Bonoli, P. T.; Harvey, R.

    2008-05-15

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency ({eta}) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap {phi}=-90 deg., k{sub {phi}}=-8 m{sup -1}) by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (n{sub onset}{proportional_to}Bxk{sub parallel}{sup 2}/{omega}) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k{sub parallel} can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  8. High Harmonic Fast Wave Heating Efficiency Enhancement and Current Drive at Longer Wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J.; Bell, R. E.; LeBlanc, B; Phillips, Cynthia; Taylor, G.; Valeo, Dr Ernest; Wilson, J. R.; Jaeger, Erwin Frederick; Ryan, Philip Michael; Wilgen, John B; Yuh, H.; Levinton, F.; Sabbagh, S. A.; Tritz, K.; Parker, J.; Bonoli, P.; Harvey, R. W.

    2008-01-01

    High harmonic fast wave heating and current drive CD are being developed on the National Spherical Torus Experiment M. Ono et al., Nucl. Fusion 41, 1435 2001 for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency from 44% to 65% has been obtained for CD phasing of the antenna strap-to-strap = 90 , k= 8 m 1 by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation nonsetBk 2 / away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency RF waves propagating close to the wall at lower B and k can enhance power losses from both the parametric decay instability PDI and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  9. Bilateral Transcranial Direct Current Stimulation Language Treatment Enhances Functional Connectivity in the Left Hemisphere: Preliminary Data from Aphasia.

    PubMed

    Marangolo, Paola; Fiori, Valentina; Sabatini, Umberto; De Pasquale, Giada; Razzano, Carmela; Caltagirone, Carlo; Gili, Tommaso

    2016-05-01

    Several studies have already shown that transcranial direct current stimulation (tDCS) is a useful tool for enhancing recovery in aphasia. However, no reports to date have investigated functional connectivity changes on cortical activity because of tDCS language treatment. Here, nine aphasic persons with articulatory disorders underwent an intensive language therapy in two different conditions: bilateral anodic stimulation over the left Broca's area and cathodic contralesional stimulation over the right homologue of Broca's area and a sham condition. The language treatment lasted 3 weeks (Monday to Friday, 15 sessions). In all patients, language measures were collected before (T0) and at the end of treatment (T15). Before and after each treatment condition (real vs. sham), each participant underwent a resting-state fMRI study. Results showed that, after real stimulation, patients exhibited the greatest recovery not only in terms of better accuracy in articulating the treated stimuli but also for untreated items on different tasks of the language test. Moreover, although after the sham condition connectivity changes were confined to the right brain hemisphere, real stimulation yielded to stronger functional connectivity increase in the left hemisphere. In conclusion, our data provide converging evidence from behavioral and functional imaging data that bilateral tDCS determines functional connectivity changes within the lesioned hemisphere, enhancing the language recovery process in stroke patients. PMID:26807842

  10. Multi-point observations of energetic particle injection deep into the inner magnetosphere: Implications for the ring current and radiation belts

    NASA Astrophysics Data System (ADS)

    Reeves, G. D.; Larsen, B.; Friedel, R. H. W.; Henderson, M. G.; Skoug, R. M.; Funsten, H. O.; Claudepierre, S. G.; Fennell, J.; Tu, W.; Cunningham, G.; Spence, H. E.

    2014-12-01

    For thirty years, the "injection boundary" model of substorm injections has provided a framework for studies of the impulsive transport of energetic electrons and ions into the inner magnetosphere. New, multi-satellite observations of substorm injections show signatures that require revision and rethinking of the classical picture. Recent observations by the LANL-GEO and GOES energetic particle instruments provide unprecedented coverage at geosynchronous orbit while the Van Allen Probes satellites provide simultaneous multi-point measurements inside geosynchronous orbit. With these satellites we can observe injections at three different radial distances and up to ten different local times - simultaneously. These observations reveal a complex and varied set of dynamics that have important implications for the development of the radiation belts and ring current. In this study we look specifically at the radial penetration of energetic particle injections in storms and substorms. Radial alignments of satellites confirm and extend the CRRES/LANL-GEO observations of relatively slow inward propagation of the injection region inside geosynchronous orbit [1]. At the same time, synoptic Van Allen Probes observations show frequent storm-time "injection" of energetic (~50-500 keV) electrons to very low L-shells (L < 3) that have not previously been reported. The radial distribution of electrons and ions injected during storms and substorms have profound implications for the generation of waves, for the availability of a radiation belt "seed population", and for the radial distribution of ring current ions. In this paper we will use multi-point satellite observations to understand the processes that inject energetic particles into the inner magnetosphere, the Earthward propagation of these injections, the conditions that control variation in Earthward extent of energetic particle injections, and how particles can be injected deep inside the plasmasphere and even through the

  11. Stereo ENA Imaging of the Ring Current and Multi-point Measurements of Suprathermal Particles and Magnetic Fields by TRIO-CINEMA

    NASA Astrophysics Data System (ADS)

    Lin, R. P.; Sample, J. G.; Immel, T. J.; Lee, D.; Horbury, T. S.; Jin, H.; SEON, J.; Wang, L.; Roelof, E. C.; Lee, E.; Parks, G. K.; Vo, H.

    2012-12-01

    The TRIO (Triplet Ionospheric Observatory) - CINEMA (Cubesat for Ions, Neutrals, Electrons, & Magnetic fields) mission consists of three identical 3-u cubesats to provide high sensitivity, high cadence, stereo measurements of Energetic Neutral Atoms (ENAs) from the Earth's ring current with ~1 keV FWHM energy resolution from ~4 to ~200 keV, as well as multi-point in situ measurements of magnetic fields and suprathermal electrons (~2 -200 keV) and ions (~ 4 -200 keV) in the auroral and ring current precipitation regions in low Earth orbit (LEO). A new Suprathermal Electron, Ion, Neutral (STEIN) instrument, using a 32-pixel silicon semiconductor detector with an electrostatic deflection system to separate ENAs from ions and from electrons below 30 keV, will sweep over most of the sky every 15 s as the spacecraft spins at 4 rpm. In addition, inboard and outboard (on an extendable 1m boom) miniature magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. An S-band transmitter will be used to provide ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station.The first CINEMA (funded by NSF) is scheduled for launch on August 14, 2012 into a 65 deg. inclination LEO. Two more identical CINEMAs are being developed by Kyung Hee University (KHU) in Korea under the World Class University (WCU) program, for launch in November 2012 into a Sun-synchronous LEO to form TRIO-CINEMA. A fourth CINEMA is being developed for a 2013 launch into LEO. This LEO constellation of nanosatellites will provide unique measurements highly complementary to NASA's RBSP and THEMIS missions. Furthermore, CINEMA's development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft may be important for future constellation space missions. Initial results from the first CINEMA will be presented if available.

  12. In-plane current-driven spin-orbit torque switching in perpendicularly magnetized films with enhanced thermal tolerance

    NASA Astrophysics Data System (ADS)

    Wu, Di; Yu, Guoqiang; Shao, Qiming; Li, Xiang; Wu, Hao; Wong, Kin L.; Zhang, Zongzhi; Han, Xiufeng; Khalili Amiri, Pedram; Wang, Kang L.

    2016-05-01

    We study spin-orbit-torque (SOT)-driven magnetization switching in perpendicularly magnetized Ta/Mo/Co40Fe40B20 (CoFeB)/MgO films. The thermal tolerance of the perpendicular magnetic anisotropy (PMA) is enhanced, and the films sustain the PMA at annealing temperatures of up to 430 °C, due to the ultra-thin Mo layer inserted between the Ta and CoFeB layers. More importantly, the Mo insertion layer also allows for the transmission of the spin current generated in the Ta layer due to spin Hall effect, which generates a damping-like SOT and is able to switch the perpendicular magnetization. When the Ta layer is replaced by a Pt layer, i.e., in a Pt/Mo/CoFeB/MgO multilayer, the direction of the SOT-induced damping-like effective field becomes opposite because of the opposite sign of spin Hall angle in Pt, which indicates that the SOT-driven switching is dominated by the spin current generated in the Ta or Pt layer rather than the Mo layer. Quantitative characterization through harmonic measurements reveals that the large SOT effective field is preserved for high annealing temperatures. This work provides a route to applying SOT in devices requiring high temperature processing steps during the back-end-of-line processes.

  13. Reduced Hyperpolarization-Activated Current Contributes to Enhanced Intrinsic Excitability in Cultured Hippocampal Neurons from PrP−/− Mice

    PubMed Central

    Fan, Jing; Stemkowski, Patrick L.; Gandini, Maria A.; Black, Stefanie A.; Zhang, Zizhen; Souza, Ivana A.; Chen, Lina; Zamponi, Gerald W.

    2016-01-01

    Genetic ablation of cellular prion protein (PrPC) has been linked to increased neuronal excitability and synaptic activity in the hippocampus. We have previously shown that synaptic activity in hippocampi of PrP-null mice is increased due to enhanced N-methyl-D-aspartate receptor (NMDAR) function. Here, we focused on the effect of PRNP gene knock-out (KO) on intrinsic neuronal excitability, and in particular, the underlying ionic mechanism in hippocampal neurons cultured from P0 mouse pups. We found that the absence of PrPC profoundly affected the firing properties of cultured hippocampal neurons in the presence of synaptic blockers. The membrane impedance was greater in PrP-null neurons, and this difference was abolished by the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker ZD7288 (100 μM). HCN channel activity appeared to be functionally regulated by PrPC. The amplitude of voltage sag, a characteristic of activating HCN channel current (Ih), was decreased in null mice. Moreover, Ih peak current was reduced, along with a hyperpolarizing shift in activation gating and slower kinetics. However, neither HCN1 nor HCN2 formed a biochemical complex with PrPC. These results suggest that the absence of PrP downregulates the activity of HCN channels through activation of a cell signaling pathway rather than through direct interactions. This in turn contributes to an increase in membrane impedance to potentiate neuronal excitability. PMID:27047338

  14. Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

    SciTech Connect

    Xiong, Ying; Wang, Bing; Yi, Yong; Xia, Liansheng; Zhang, Huang

    2013-09-15

    The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels (∼0.40 Pa L), slower cathode plasma expansion velocity (∼2.30 cm/μs), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacent pulses is significantly improved in double-pulsed emission mode with ∼500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes.

  15. Knockout of Slo2.2 enhances itch, abolishes KNa current, and increases action potential firing frequency in DRG neurons

    PubMed Central

    Martinez-Espinosa, Pedro L; Wu, Jianping; Yang, Chengtao; Gonzalez-Perez, Vivian; Zhou, Huifang; Liang, Hongwu; Xia, Xiao-Ming; Lingle, Christopher J

    2015-01-01

    Two mammalian genes, Kcnt1 and Kcnt2, encode pore-forming subunits of Na+-dependent K+ (KNa) channels. Progress in understanding KNa channels has been hampered by the absence of specific tools and methods for rigorous KNa identification in native cells. Here, we report the genetic disruption of both Kcnt1 and Kcnt2, confirm the loss of Slo2.2 and Slo2.1 protein, respectively, in KO animals, and define tissues enriched in Slo2 expression. Noting the prevalence of Slo2.2 in dorsal root ganglion, we find that KO of Slo2.2, but not Slo2.1, results in enhanced itch and pain responses. In dissociated small diameter DRG neurons, KO of Slo2.2, but not Slo2.1, abolishes KNa current. Utilizing isolectin B4+ neurons, the absence of KNa current results in an increase in action potential (AP) firing and a decrease in AP threshold. Activation of KNa acts as a brake to initiation of the first depolarization-elicited AP with no discernible effect on afterhyperpolarizations. DOI: http://dx.doi.org/10.7554/eLife.10013.001 PMID:26559620

  16. A Stratigraphic, Granulometric, and Textural Comparison of recent pyroclastic density current deposits exposed at West Island and Burr Point, Augustine Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Rath, C. A.; Browne, B. L.

    2011-12-01

    Augustine Volcano (Alaska) is the most active volcano in the eastern Aleutian Islands, with 6 violent eruptions over the past 200 years and at least 12 catastrophic debris-avalanche deposits over the past ~2,000 years. The frequency and destructive nature of these eruptions combined with the proximity of Augustine Volcano to commercial ports and populated areas represents a significant hazard to the Cook Inlet region of Alaska. The focus of this study examines the relationship between debris-avalanche events and the subsequent emplacement of pyroclastic density currents by comparing the stratigraphic, granulometric, and petrographic characteristics of pyroclastic deposits emplaced following the 1883 A.D. Burr Point debris-avalanche and those emplaced following the ~370 14C yr B.P. West Island debris-avalanche. Data from this study combines grain size and componentry analysis of pyroclastic deposits with density, textural, and compositional analysis of juvenile clasts contained in the pyroclastic deposits. The 1883 A.D. Burr Point pyroclastic unit immediately overlies the 1883 debris avalanche deposit and underlies the 1912 Katmai ash. It ranges in thickness from 4 to 48 cm and consists of fine to medium sand-sized particles and coarser fragments of andesite. In places, this unit is normally graded and exhibits cross-bedding. Many of these samples are fines-enriched, with sorting coefficients ranging from -0.1 to 1.9 and median grain size ranging from 0.1 to 2.4 mm. The ~370 14C yr B.P. West Island pyroclastic unit is sandwiched between the underlying West Island debris-avalanche deposit and the overlying 1912 Katmai Ash deposit, and at times a fine-grained gray ash originating from the 1883 eruption. West Island pyroclastic deposit is sand to coarse-sand-sized and either normally graded or massive with sorting coefficients ranging from 0.9 to 2.8 and median grain sizes ranging from 0.4 to 2.6 mm. Some samples display a bimodal distribution of grain sizes, while

  17. 'The waiting game': are current chlamydia and gonorrhoea near-patient/point-of-care tests acceptable to service users and will they impact on treatment?

    PubMed

    Atkinson, Lindsay M; Vijeratnam, Dayan; Mani, Reena; Patel, Raj

    2016-07-01

    The objective of this study was to assess the length of time service users were prepared to wait for chlamydia and gonorrhoea (CT/GC) near-patient/point-of-care test (NP-POCT) results and to determine the possible effect on management. Individuals attending two UK clinics from November 2013 to February 2014 were surveyed asking the maximum length of time they would wait for CT/GC NP-POCT results after consultation. Linked CT/GC prevalence and treatment rates were analysed. A total of 1817 participants were surveyed, and 1356 provided CT/GC NAAT samples, in which it was found that 115 (8.5%) could wait over 90 minutes in clinic for their result. 115 received treatment at consultation, of which 50 were CT/GC negative and 12 were treated for urethritis or cervicitis; 38 attended as CT/GC contacts. Six of this population would have waited over 90 minutes were NP-POCTs available. A total of 129 tested CT/GC positive, of whom 65 were treated at their consultation, 61 at a later date, and three were untreated. Twelve of these 129 patients would also have waited over 90 minutes for a NP-POCT result. We conclude that 90-minute NP-POCTs are not acceptable to most clinic attendees and would not have impacted on treatment rates or inappropriate prescribing, and 20-minute NP-POCTs show a marginal benefit in treating CT/GC. While NP-POCTs for CT/GC are promising, they must meet client expectations and enhance disease management in order to be accepted by patients and clinicians. PMID:26092579

  18. Tmc1 Point Mutation Affects Ca2+ Sensitivity and Block by Dihydrostreptomycin of the Mechanoelectrical Transducer Current of Mouse Outer Hair Cells

    PubMed Central

    Corns, Laura F.; Johnson, Stuart L.; Kros, Corné J.

    2016-01-01

    The transduction of sound into electrical signals depends on mechanically sensitive ion channels in the stereociliary bundle. The molecular composition of this mechanoelectrical transducer (MET) channel is not yet known. Transmembrane channel-like protein isoforms 1 (TMC1) and 2 (TMC2) have been proposed to form part of the MET channel, although their exact roles are still unclear. Using Beethoven (Tmc1Bth/Bth) mice, which have an M412K point mutation in TMC1 that adds a positive charge, we found that Ca2+ permeability and conductance of the MET channel of outer hair cells (OHCs) were reduced. Tmc1Bth/Bth OHCs were also less sensitive to block by the permeant MET channel blocker dihydrostreptomycin, whether applied extracellularly or intracellularly. These findings suggest that the amino acid that is mutated in Bth is situated at or near the negatively charged binding site for dihydrostreptomycin within the permeation pore of the channel. We also found that the Ca2+ dependence of the operating range of the MET channel was altered by the M412K mutation. Depolarization did not increase the resting open probability of the MET current of Tmc1Bth/Bth OHCs, whereas raising the intracellular concentration of the Ca2+ chelator BAPTA caused smaller increases in resting open probability in Bth mutant OHCs than in wild-type control cells. We propose that these observations can be explained by the reduced Ca2+ permeability of the mutated MET channel indirectly causing the Ca2+ sensor for adaptation, at or near the intracellular face of the MET channel, to become more sensitive to Ca2+ influx as a compensatory mechanism. SIGNIFICANCE STATEMENT In the auditory system, the hair cells convert sound-induced mechanical movement of the hair bundles atop these cells into electrical signals through the opening of mechanically gated ion channels at the tips of the bundles. Although the nature of these mechanoelectrical transducer (MET) channels is still unclear, recent studies implicate

  19. Electro-enhanced Permeable Reactive Barrier : Optimal Design of PRB System With External Current for Effective TCE Removal From Groundwater

    NASA Astrophysics Data System (ADS)

    Moon, J.; Moon, H.; Roh, Y.; Kim, H.; Song, Y.

    2002-12-01

    The objective of this study was to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC). A series of column experiments were conducted to evaluate the location of Fe0 permeable reactive barrier (PRB) and the effects of electrode arrangement in the column on the TCE removal efficiency and iron corrosion processes. In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved with simultaneous application of both ZVI and DC compared to that used ZVI only to evaluate the synergistic effect (SE). The most effective arrangement of electrode and ZVI for TCE removal from simulated groundwater was a column set with ZVI and cathode installed at the down gradient (outlet side). Based on the electrochemical study in the E2PRB system, application of direct current provided external electrons to the system so that the system did not depend entirely on the oxidation of the medium for the reductive dechlorination of TCE. The enhanced dechlorination rate of TCE in ZVI-DC systems is considered to attributed to more generation and fast formation kinetic of electron by following reactions: (1) direct supply of electrons from external DC source (2) the electrolysis of water generating additional electrons at the vicinity of the anode (3) the electro-reduction of the compound by released electrons on the ZVI surfaces by oxidation (4) released electron through oxidation of dissolved ferrous iron, and (5) oxidation of atomic hydrogen at the cathode. The competition between five different electron sources generated from five sources evidently influenced on the TCE removal efficiency, valid lifetime of E2PRB system, and reduction of energy expenditure in both of electrochemical and electrokinetic aspects. The results from a series of experiments with twelve columns showed a

  20. Multiple Modes of α7 nAChR Noncompetitive Antagonism of Control Agonist-Evoked and Allosterically Enhanced Currents

    PubMed Central

    Peng, Can; Kimbrell, Matthew R.; Tian, Chengju; Pack, Thomas F.; Crooks, Peter A.; Fifer, E. Kim

    2013-01-01

    Positive allosteric modulators (PAMs) of α7 nicotinic acetylcholine receptors can enhance ion channel currents and downstream effects of α7 stimulation. We investigated the approach of using noncompetitive antagonists to regulate α7 receptor function, potentially distinguishing effects requiring ion channel currents from signaling induced by nonconducting states. Three small readily reversible antagonists, (1S,2R,4R)-N,2,3,3-tetramethylbicyclo[2.2.1]heptan-2-amine (mecamylamine), N-(2.6-dimethylphenylcarbamoylmethyl)triethylammonium bromide (QX-314), and 2-(dimethylamino)ethyl 4-(butylamino)benzoate (tetracaine), as well as three large slowly reversible antagonists, bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (BTMPS), 2,2,6,6-tetramethylpiperidin-4-yl heptanoate (TMPH), and 1,2,4,5-tetra-{5-[1-(3-benzyl)pyridinium]pent-1-yl}benzene tetrabromide (tkP3BzPB), were investigated for their effectiveness and voltage dependence in the inhibition of responses evoked by acetylcholine alone or augmented by the α7-selective PAM N-(5-chloro-2,4-dimethoxyphenyl)-N′-(5-methyl-3-isoxazolyl)-urea (PNU-120596). Analyses of the small antagonists on PNU-120596–potentiated single-channel bursts indicated that each agent had a distinct mechanism of inhibition and only that of QX-314 was consistent with simple open channel block. In addition to decreasing channel open times and burst durations, mecamylamine and tetracaine induced unique subconductance states. To determine whether channel-blocking activity alone would be sufficient to prevent cell death, the antagonists were tested for their ability to protect α7-expressing cells from cytotoxic effects of the α7 agonist choline in combination with PNU-120596. Only tetracaine and tkP3BzPB, the two agents that had effects least consistent with simple ion channel block, were fully cytoprotective at concentrations that gave submaximal inhibition of macroscopic currents in oocytes. Further analyses indicated that toxicity

  1. Involvement of PKC and PKA in the enhancement of L-type calcium current by GABAB receptor activation in neonatal hippocampus

    PubMed Central

    Bray, Jennifer G.; Mynlieff, Michelle

    2011-01-01

    In the early neonatal period activation of GABAB receptors attenuates calcium current through N-type calcium channels while enhancing current through L-type calcium channels in rat hippocampal neurons. The attenuation of N-type calcium current has been previously demonstrated to occur through direct interactions of the βγ subunits of Gi/o G-proteins, but the signal transduction pathway for the enhancement of L-type calcium channels in mammalian neurons remains unknown. In the present study, calcium currents were elicited in acute cultures from postnatal day 6–8 rat hippocampi in the presence of various modulators of protein kinase A (PKA) and protein kinase C (PKC) pathways. Overnight treatment with an inhibitor of Gi/o (pertussis toxin, 200 ng/ml) abolished the attenuation of calcium current by the GABAB agonist, baclofen (10 μM) with no effect on the enhancement of calcium current. These data indicate that while the attenuation of N-type calcium current is mediated by the Gi/o subtype of G-protein, the enhancement of L-type calcium current requires activation of a different G-protein. The enhancement of the sustained component of calcium current by baclofen was blocked by PKC inhibitors, GF-109203X (500 nM), chelerythrine chloride (5 μM), and PKC fragment 19–36 (2 μM) and mimicked by the PKC activator phorbol-12-myristate-13-acetate (1 μM). The enhancement of the sustained component of calcium current was blocked by PKA inhibitors H-89 (1 μM) and PKA fragment 6–22 (500 nM) but not Rp-cAMPS (30 μM) and it was not mimicked by the PKA activator, 8-Br-cAMP (500 μM – 1 mM). The data suggest that activation of PKC alone is sufficient to enhance L-type calcium current but that PKA may also be involved in the GABAB receptor mediated effect. PMID:21277353

  2. Viscosity of nitrogen near the critical point

    NASA Technical Reports Server (NTRS)

    Basu, R. S.; Sengers, J. V.

    1978-01-01

    The formulation of a quantitative description of the critical enhancement in the shear viscosity of fluids near the gas-liquid critical point is considered. The critical point is a point of marginal thermodynamic stability. In the vicinity of the critical point, large-scale density fluctuations are present in the fluid. The critical enhancement of the transport properties is related to the correlation length. The correlation length is related to the compressibility, thus providing consistency between the equations for the transport properties and the equation of state in the critical region. The critical region parameters for nitrogen are presented in a table. It is found that the critical viscosity enhancement observed by Zozulya and Blagoi (1974) for nitrogen is consistent with current theoretical predictions

  3. Enhanced current flow through a plasma cloud by induction of plasma turbulence. [electrodynamic tethers for generating power for spacecraft in low earth orbit

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.; Gioulekas, A.

    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 lower hybrid 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 (lower hybrid instability) mode of operation depending on the current density.

  4. Enhanced anisotropic effective g factors of an Al0.25Ga0.75N/GaN heterostructure based quantum point contact.

    PubMed

    Lu, Fangchao; Tang, Ning; Huang, Shaoyun; Larsson, Marcus; Maximov, Ivan; Graczyk, Mariusz; Duan, Junxi; Liu, Sidong; Ge, Weikun; Xu, Fujun; Shen, Bo

    2013-10-01

    Gate-defined quantum point contacts (QPCs) were fabricated with Al0.25Ga0.75N/GaN heterostructures grown by metal-organic chemical vapor deposition (MOCVD). In the transport study of the Zeeman effect, greatly enhanced effective g factors (g*) were obtained. The in-plane g* is found to be 5.5 ± 0.6, 4.8 ± 0.4, and 4.2 ± 0.4 for the first to the third subband, respectively. Similarly, the out-of-plane g* is 8.3 ± 0.6, 6.7 ± 0.7, and 5.1 ± 0.7. Increasing g* with the population of odd-numbered spin-splitted subbands are obtained at 14 T. This portion of increase is assumed to arise from the exchange interaction in one-dimensional systems. A careful analysis shows that not only the exchange interaction but the spin-orbit interaction (SOI) in the strongly confined QPC contributes to the enhancement and anisotropy of g* in different subbands. An approach to distinguish the respective contributions from the SOI and exchange interaction is therefore proposed. PMID:24041238

  5. Van Allen Probes based investigation of storm time enhancements in the duskward electric field to lower L shells and its effect on ring current formation and plasmasphere erosion.

    NASA Astrophysics Data System (ADS)

    Thaller, S. A.; Wygant, J. R.; Dai, L.; Breneman, A. W.; Kersten, K.; Kletzing, C.; Kurth, W. S.; De Pascuale, S.; Bonnell, J. W.; Hospodarsky, G. B.; Gkioulidou, M.; Fennell, J. F.

    2014-12-01

    The large scale convection electric field plays a central role in the dynamics of the inner magnetosphere; among which processes are ring current particle injection and plasmasphere erosion. Both of these are important for radiation belt dynamics. The ring current affects magnetic field geometry which in turn affects particle drift paths and plasmasphere erosion shrinks the region characterized by plasmaspheric hiss which would otherwise be present to scatter population of radiation belt seed electrons. Using the Van Allen Probes we investigate enhancements in the duskward electric field to lower L shells (L < 4 RE) and its role in ring current particle energization and erosion of the plasmasphere during two major storms; June 1, 2013 and February 19, 2014. During these storms, the electric field enhanced to low L shells with magnitudes ~1-2 mV/m in the co-rotating frame. The corresponding storm time ring current enhancements and plasmasphere erosions are examined in the context of these electric fields. The intensification in the duskward electric field is of long enough duration to transport particles from locations characteristic of the earthward edge of the plasma sheet (L shells ~ 8-10 RE) to the observed location of the ring current while energizing them though conservation of the first adiabatic invariant to energies typical of the ring current. It is also observed that the range in L shell over which the most intense nightside, duskward, electric field is observed is also that over which the higher pressure region of the ring current is located.

  6. Anodal transcranial direct current stimulation enhances the effects of motor imagery training in a finger tapping task.

    PubMed

    Saimpont, Arnaud; Mercier, Catherine; Malouin, Francine; Guillot, Aymeric; Collet, Christian; Doyon, Julien; Jackson, Philip L

    2016-01-01

    Motor imagery (MI) training and anodal transcranial direct current stimulation (tDCS) applied over the primary motor cortex can independently improve hand motor function. The main objective of this double-blind, sham-controlled study was to examine whether anodal tDCS over the primary motor cortex could enhance the effects of MI training on the learning of a finger tapping sequence. Thirty-six right-handed young human adults were assigned to one of three groups: (i) who performed MI training combined with anodal tDCS applied over the primary motor cortex; (ii) who performed MI training combined with sham tDCS; and (iii) who received tDCS while reading a book. The MI training consisted of mentally rehearsing an eight-item complex finger sequence for 13 min. Before (Pre-test), immediately after (Post-test 1), and at 90 min after (Post-test 2) MI training, the participants physically repeated the sequence as fast and as accurately as possible. An anova showed that the number of sequences correctly performed significantly increased between Pre-test and Post-test 1 and remained stable at Post-test 2 in the three groups (P < 0.001). Furthermore, the percentage increase in performance between Pre-test and Post-test 1 and Post-test 2 was significantly greater in the group that performed MI training combined with anodal tDCS compared with the other two groups (P < 0.05). As a potential physiological explanation, the synaptic strength within the primary motor cortex could have been reinforced by the association of MI training and tDCS compared with MI training alone and tDCS alone. PMID:26540137

  7. Transcranial Direct Current Stimulation to Enhance Dual-Task Gait Training in Parkinson’s Disease: A Pilot RCT

    PubMed Central

    Schabrun, Siobhan M.; Lamont, Robyn M.; Brauer, Sandra G.

    2016-01-01

    Objective To investigate the feasibility and safety of a combined anodal transcranial direct current stimulation (tDCS) and dual task gait training intervention in people with Parkinson’s Disease (PD) and to provide data to support a sample size calculation for a fully powered trial should trends of effectiveness be present. Design A pilot, randomized, double-blind, sham-controlled parallel group trial with 12 week follow-up. Setting A university physiotherapy department. Interventions Sixteen participants diagnosed with PD received nine dual task gait training sessions over 3 weeks. Participants were randomized to receive either active or sham tDCS applied for the first 20 minutes of each session. Main Measures The primary outcome was gait speed while undertaking concurrent cognitive tasks (word lists, counting, conversation). Secondary measures included step length, cadence, Timed Up and Go, bradykinesia and motor speed. Results Gait speed, step length and cadence improved in both groups, under all dual task conditions. This effect was maintained at follow-up. There was no difference between the active and sham tDCS groups. Time taken to perform the TUGwords also improved, with no difference between groups. The active tDCS group did however increase their correct cognitive response rate during the TUGwords and TUGcount. Bradykinesia improved after training in both groups. Conclusion Three weeks of dual task gait training resulted in improved gait under dual task conditions, and bradykinesia, immediately following training and at 12 weeks follow-up. The only parameter enhanced by tDCS was the number of correct responses while performing the dual task TUG. tDCS applied to M1 may not be an effective adjunct to dual task gait training in PD. Trial Registration Australia-New Zealand Clinical Trials Registry ACTRN12613001093774 PMID:27359338

  8. Enhancement of the Stabilization Efficiency of a Neoclassical Magnetic Island by Modulated Electron Cyclotron Current Drive in the ASDEX Upgrade Tokamak

    SciTech Connect

    Maraschek, M.; Yu, Q.; Zohm, H.; Guenter, S.; Leuterer, F.; Manini, A.; Gantenbein, G.

    2007-01-12

    The efficiency of generating a helical current in magnetic islands for the purpose of suppression of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) is studied experimentally in the ASDEX Upgrade tokamak. It is found that the efficiency of generating helical current by continuous current drive in a rotating island drops drastically as the width 2d of the co-ECCD driven current becomes larger than the island width W. However, by modulating the co-ECCD in phase with the rotating islands O point, the efficiency can be recovered. The results are in good agreement with theoretical calculations taking into account the equilibration of the externally driven current on the island flux surfaces. The result is especially important for large next-step fusion devices, such as ITER, where 2d>W is expected to be unavoidable during NTM suppression, suggesting that modulation capability should be foreseen.

  9. Enhancement of magnetic properties in magnesium diboride and characterization of Josephson and quasiparticle currents in magesium diboride contact junctions

    NASA Astrophysics Data System (ADS)

    Shen, Yi

    Methods to produce MgB2 thin films and tunneling devices have been developed. Thin films have been optimized for high field applications by exploring a range of doping and growth conditions. Josephson junction devices have been produced using a novel technique to optimize the quality of the barrier and near-interface superconducting materials. The effects of impurities incorporation in MgB2 thin films in the physical properties were studied. First, rubidium and cesium were ex-situ introduced into thin films by annealing in quartz ampoules containing elemental alkali metals. No significant change in transition temperature (Tc) was observed by resistivity measurement, in contrast to an earlier report of enhanced Tcs (>50 K) from susceptibility measurements. A significant drop in Jc and an increase in Deltarho (rho 300-rho40) arise from a decrease in inter-granular connectivity during annealing. Second, oxygen was incorporated using in-situ post-growth anneals in an oxygen environment. Analysis of the electrical data indicates that oxygen is distributed both within and between the grains. High values of Jc (˜4x105 A/cm2 at 8 T and 4.2 K), extrapolated Hc2(0) > 45 T and |dHc2/dT| Tc| ≈ 1.4 T/K are observed. A novel deposition approach allows films of magnesium plus boron to be deposited on unheated c-plane sapphire substrates by co-evaporation, and then subsequently annealed in a reducing atmosphere at temperatures below 600°C. The use of a combination of a magnesium rich stoichiometry (Mg/B > 1/2) in the as-deposited film, and a two-step annealing process, was found to be critical in obtaining unusual high values of Hc2(0) > 43 T and |dH c2/dT|Tc| ≈ 2.5 T/K. Josephson junctions fabricated by pressing two oxidized MgB2 thin films together. This facilitates the production of Josephson Junctions with two MgB2 electrodes without exposure to the high second electrode deposition temperature. These junctions, with electrode Tcs of ˜32 K, have critical currents up to

  10. Development of Point of Care Testing Device for Neurovascular Coupling From Simultaneous Recording of EEG and NIRS During Anodal Transcranial Direct Current Stimulation

    PubMed Central

    Jindal, Utkarsh; Sood, Mehak; Dutta, Anirban; Chowdhury, Shubhajit Roy

    2015-01-01

    This paper presents a point of care testing device for neurovascular coupling (NVC) from simultaneous recording of electroencephalogram (EEG) and near infrared spectroscopy (NIRS) during anodal transcranial direct current stimulation (tDCS). Here, anodal tDCS modulated cortical neural activity leading to hemodynamic response can be used to identify the impaired cerebral microvessels functionality. The impairments in the cerebral microvessels functionality may lead to impairments in the cerebrovascular reactivity (CVR), where severely reduced CVR predicts the chances of transient ischemic attack and ipsilateral stroke. The neural and hemodynamic responses to anodal tDCS were studied through joint imaging with EEG and NIRS, where NIRS provided optical measurement of changes in tissue oxy-(\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$HbO2)$ \\end{document} and deoxy-(\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$Hb$ \\end{document}) hemoglobin concentration and EEG captured alterations in the underlying neuronal current generators. Then, a cross-correlation method for the assessment of NVC underlying the site of anodal tDCS is presented. The feasibility studies on healthy subjects and stroke survivors showed detectable changes in the EEG and the NIRS responses to a 0.526 A/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\mathrm{m}^{2}$ \\end{document} of anodal tDCS. The NIRS system

  11. 77 FR 12321 - Intent To Request Renewal From OMB of One Current Public Collection of Information: Enhanced...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-29

    ...) when required to be onboard. The operator's last point of departure must be from a Fixed Base Operator..., and property carried in the cargo hold. For each passenger and crewmember onboard an aircraft...

  12. Effect of hot implantation on ON-current enhancement utilizing isoelectronic trap in Si-based tunnel field-effect transistors

    NASA Astrophysics Data System (ADS)

    Mori, Takahiro; Mizubayashi, Wataru; Morita, Yukinori; Migita, Shinji; Fukuda, Koichi; Miyata, Noriyuki; Yasuda, Tetsuji; Masahara, Meishoku; Ota, Hiroyuki

    2015-03-01

    A tunneling-current enhancement technology for Si-based tunnel field-effect transistors (TFETs) utilizing an Al-N isoelectronic trap (IET) has been proposed recently. In this study, we investigate hot implantation as a doping technique for Al-N isoelectronic impurity. Hot implantation reduces the damage induced by Al and N implantation processes, resulting in performance improvement of IET-assisted TFETs, e.g., a 12-fold enhancement in the driving current at an operation voltage of 0.5 V and an approximately one-third reduction in the subthreshold slope. By hot implantation, we can achieve a higher driving current in Si-based TFETs using the IET technology.

  13. Detection of cardiac biomarkers exploiting surface enhanced Raman scattering (SERS) using a nanofluidic channel based biosensor towards coronary point-of-care diagnostics

    NASA Astrophysics Data System (ADS)

    Benford, Melodie E.; Wang, Miao; Kameoka, Jun; Coté, Gerard L.

    2009-02-01

    According to the World Health Organization, cardiovascular disease is the most common cause of death in the world. In the US, over 115 million people visit the emergency department (ED), 5 million of which may have acute coronary syndrome (ACS). Cardiac biomarkers can provide early identification and diagnosis of ACS, and can provide information on the prognosis of the patient by assessing the risk of death. In addition, the biomarkers can serve as criteria for admission, indicate possibility of re-infarction, or eliminate ACS as a diagnosis altogether. We propose a SERSbased multi-marker approach towards a point-of-care diagnostic system for ACS. Using a nanofluidic device consisting of a microchannel leading into a nanochannel, we formed SERS active sites by mechanically aggregating gold particles (60 nm) at the entrance to the nanochannel (40nm×1μm). The induced capillary flow produces a high density of aggregated nanoparticles at this precise region, creating areas with enhanced electromagnetic fields within the aggregates, shifting the plasmon resonance to the near infrared region, in resonance with incident laser wavelength. With this robust sensing platform, we were able to obtain qualitative information of brain natriuretic peptide (biomarker of ventricular dysfunction or pulmonary stress), troponin I (biomarker of myocardial necrosis), and C-reactive protein (biomarker of inflammation potentially caused by atherosclerosis).

  14. Impact of an indigenous microbial enhanced oil recovery field trial on microbial community structure in a high pour-point oil reservoir.

    PubMed

    Zhang, Fan; She, Yue-Hui; Li, Hua-Min; Zhang, Xiao-Tao; Shu, Fu-Chang; Wang, Zheng-Liang; Yu, Long-Jiang; Hou, Du-Jie

    2012-08-01

    Based on preliminary investigation of microbial populations in a high pour-point oil reservoir, an indigenous microbial enhanced oil recovery (MEOR) field trial was carried out. The purpose of the study is to reveal the impact of the indigenous MEOR process on microbial community structure in the oil reservoir using 16Sr DNA clone library technique. The detailed monitoring results showed significant response of microbial communities during the field trial and large discrepancies of stimulated microorganisms in the laboratory and in the natural oil reservoir. More specifically, after nutrients injection, the original dominant populations of Petrobacter and Alishewanella in the production wells almost disappeared. The expected desirable population of Pseudomonas aeruginosa, determined by enrichment experiments in laboratory, was stimulated successfully in two wells of the five monitored wells. Unexpectedly, another potential population of Pseudomonas pseudoalcaligenes which were not detected in the enrichment culture in laboratory was stimulated in the other three monitored production wells. In this study, monitoring of microbial community displayed a comprehensive alteration of microbial populations during the field trial to remedy the deficiency of culture-dependent monitoring methods. The results would help to develop and apply more MEOR processes. PMID:22159733

  15. Targeting key metabolic points for an enhanced phytoremediation of wastewaters pre-treated by the photo-Fenton process using Solanum nigrum L.

    PubMed

    Teixeira, Jorge; Ferraz, Pedro; Gouveia, Carlota; Azevedo, Frederico; Neves, Simão; Fidalgo, Fernanda; Silva, Adrián M T

    2015-10-01

    Several physiological, biochemical and molecular biology responses were analysed in Solanum nigrum L. plants exposed for 28 days to an effluent that resulted from the photo-Fenton treatment of a highly concentrated pesticide and systemic fungicide aqueous solution, containing metalaxyl as active compound (150mgL(-1)), in order to pinpoint metabolic steps for a future increase of these plants' capacity to deal with the chemical process by-products. Although plants suffered oxidative stress, as indicated by increased membrane damage and a negative effect on plant biomass, they absorbed the excess iron and acted on the resulting by-products present in the effluent after the photo-Fenton process. Nitrogen assimilation and metallothionein gene expression were down regulated, while glutathione biosynthesis increased. These results suggest an enhanced nitrogen assimilation and/or metallothionein accumulation as relevant key points for further plant improvement in order to increase the efficiency of this innovative strategy that considers integration of the photo-Fenton process (as chemical primary treatment) with S. nigrum L. plants (as biological remediation post-treatment) for heavily polluted wastewaters. PMID:26057079

  16. Time-dependent current decline in cyclic GMP-gated bovine channels caused by point mutations in the pore region expressed in Xenopus oocytes.

    PubMed Central

    Bucossi, G; Eismann, E; Sesti, F; Nizzari, M; Seri, M; Kaupp, U B; Torre, V

    1996-01-01

    1. Amino acids with a charged or a polar residue in the putative pore region, between lysine 346 and glutamate 372 of the alpha-subunit of the cGMP-gated channel from bovine rods were mutated to a different amino acid. The mRNA encoding for the wild-type, i.e. the alpha-subunit, or mutant channels was injected in Xenopus laevis oocytes. 2. When glutamate 363 was mutated to asparagine, serine or alanine, the current activated by a steady cGMP concentration declined in mutant channels. No current decline was observed when glutamate 363 was mutated to aspartate, glutamine or glycine, when theronine 359, 360 and 364 were mutated to alanine or when other charged residues in the pore region were neutralized. 3. The amount of current decline and its time course were significantly voltage dependent. In mutant E363A the current decline developed within about 1.5 s at -100 mV, but in about 6 s at +100 mV. In the same mutant, the current declined to about 55% of its initial level at +100 mV and to about 10% at -100 mV. 4. The current decline in mutants E363A, E363S and E363N was only moderately dependent on the cGMP concentration (from 10 to 1000 microM) and was not caused by a reduced affinity of the mutant channels for cGMP. Analysis of current fluctuations at a single-channel level indicated that current decline was primarily caused by a decrease of the open probability. 5. The wild-type channel was not permeable to dimethylammonium. When glutamate 363 was replaced by a smaller residue such as serine, mutant channels became permeable to dimethylammonium. 6. The current decline observed in mutant channels is reminiscent of desensitization of ligand-gated channels and of inactivation of voltage-gated channels. These results suggest also that gating and permeation through the cGMP-gated channel from bovine rods are intrinsically coupled and that glutamate 363 is part of the molecular structure controlling both the gating and the narrowest region of the pore. PMID:8782105

  17. Current evidence for the diagnostic value of gadoxetic acid-enhanced magnetic resonance imaging for liver metastasis.

    PubMed

    Tsurusaki, Masakatsu; Sofue, Keitaro; Murakami, Takamichi

    2016-08-01

    A variety of imaging techniques, including ultrasonography (US), multidetector computed tomography (MDCT), magnetic resonance imaging (MRI) and positron emission tomography combined with CT scan (PET/CT), are available for diagnosis and treatment planning in liver metastasis. Contrast-enhanced MDCT is a relatively non-invasive, widely available and standardized method for hepatic work-up. Gadoxetic acid (gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid; EOB Primovist®]) is a recently developed liver-specific hepatobiliary MR contrast agent that offers both dynamic imaging as well as liver-specific static hepatocyte imaging, referred to as the hepatobiliary phase. Following contrast injection, this technique reveals dynamic vascular phases (arterial, portal venous and delayed phases), in addition to the hepatobiliary phase upon uptake by functional hepatocytes. The overall sensitivity of gadoxetic acid-enhanced MRI was significantly higher than that of contrast-enhanced CT. Specifically, the higher sensitivity of gadoxetic acid-enhanced MRI was observed in lesions smaller than 1 cm in diameter. Gadoxetic acid-enhanced MRI is considered an extremely useful tool for the diagnosis of liver metastases. Future studies will focus on diagnostic algorithms involving combinations of modalities such as MRI, MDCT and/or (18) F-fluorodeoxyglucose PET/CT, which may impact the treatment plan for these patients. PMID:26750497

  18. Enhanced hexadecane degradation and low biomass production by Aspergillus niger exposed to an electric current in a model system.

    PubMed

    Velasco-Alvarez, Nancy; González, Ignacio; Damian-Matsumura, Pablo; Gutiérrez-Rojas, Mariano

    2011-01-01

    The effects of an electric current on growth and hexadecane (HXD) degradation by Aspergillus niger growth were determined. A 450-mL electrochemical cell with titanium ruthenium-oxide coated electrodes and packed with 15 g of perlite (inert biomass support) was inoculated with A. niger (2.0×10(7) spores (g of dry inert support)(-1)) and incubated for 12 days (30 °C; constant ventilation). 4.5 days after starting culture a current of 0.42 mA cm(-2) was applied for 24h. The current reduced (52±11%) growth of the culture as compared to that of a culture not exposed to current. However, HXD degradation was 96±1.4% after 8 days whereas it was 81±1.2% after 12 days in control cultures. Carbon balances of cultures not exposed to current suggested an assimilative metabolism, but a non-assimilative metabolism when the current was applied. This change can be related to an increase in total ATP content. The study contributes to the knowledge on the effects of current on the mycelial growth phase of A. niger, and suggests the possibility of manipulating the metabolism of this organism with electric current. PMID:20739180

  19. A low-power magnetic-field-assisted plasma jet generated by dielectric-barrier discharge enhanced direct-current glow discharge at atmospheric pressure

    SciTech Connect

    Jiang, Weiman; Tang, Jie Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2014-01-06

    A magnetic field is introduced to the dielectric-barrier discharge enhanced direct-current glow discharge for efficient plasma generation, with the discharge power of 2.7 W and total energy consumption reduced to 34% of the original. By spatially examining the emission spectra and plasma temperature, it is found that their peaks shift from edges to the center and the negative and anode glows merge into the positive column and disappear, accompanied by improvement of uniformity and chemical activity of the enlarged plasma. This lies in the enhancement of ionization in the curved and lengthened electron path and the dispersion of discharge domains.

  20. Is There Any Point in Wearing Dead Men's Spectacles? How the Theoretical Insights of Adler and Colleagues Relate to Current Practice with Children Experiencing EBD

    ERIC Educational Resources Information Center

    Blamires, Mike

    2006-01-01

    This article explores the legacy of Adlerian approaches to behaviour. Mike Blamires offers an opportunity to consider the impact of Adler's premise that education is fundamentally about encouragement and the promotion of democratic principles. In so doing he challenges us to interrogate the term "behaviour management", and its current use by…

  1. Current Trends in Self-Emulsifying Drug Delivery Systems (SEDDSs) to Enhance the Bioavailability of Poorly Water-Soluble Drugs.

    PubMed

    Karwal, Rohit; Garg, Tarun; Rath, Goutam; Markandeywar, Tanmay S

    2016-01-01

    The main object of the self-emulsifying drug-delivery system (SEDDS) is oral bioavailability (BA) enhancement of a poorly water-soluble drug. Low aqueous solubility and low oral BA are major concerns for formulation scientists. As many drugs are lipophilic in nature, their lower solubility and dissolution are major drawbacks for their successful formulation into oral dosage forms. More than 60% of drugs have a lipophilic nature and exhibit poor aqueous solubility. Various strategies are reported in the literature to improve the solubility and enhance BA of lipophilic drugs, including the formation of a cyclodextrin complex, solid dispersions, and micronization. SEDDSs are ideally isotropic mixtures of drug, oil, surfactant, and/or cosurfactant. SEDDSs have gained increasing attention for enhancing oral BA and reducing drug dose. SEDDSs also provide an effective and excellent solution to the various issues related to the formulation of hydrophobic drugs that have limited solubility in gastrointestinal fluid. Our major focus of this review is to highlight the importance of SEDDSs in oral BA enhancement of poorly water-soluble drugs. PMID:27279337

  2. ENHANCED IN SITU BIOREMEDIATION DEMONSTRATED IN FRACTURED BEDROCK IN: GROUND WATER CURRENTS NEWSLETTER, ISSUE 38, P. 2-3, 2000

    EPA Science Inventory

    The USEPA's SITE Program conducted a demonstration of the Enhanced In Situ Bioremediation Process at the ITT Industries Night Vision Facility in Roanoke, VA. The biostimulation process, developed by the USEOE and licensed to Earth Tech, Inc., involves injecting a mixture of air, ...

  3. Enhanced wall-plug efficiency in AlGaN-based deep-ultraviolet light-emitting diodes with uniform current spreading p-electrode structures

    NASA Astrophysics Data System (ADS)

    Hao, Guo-Dong; Taniguchi, Manabu; Tamari, Naoki; Inoue, Shin-ichiro

    2016-06-01

    The current crowding is an especially severe issue in AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) because of the low conductivity of the n-AlGaN cladding layer that has a high Al fraction. We theoretically investigated the improvement in internal quantum efficiency and total resistances in DUV-LEDs with an emission wavelength of 265 nm by a well-designed p-electrode geometry to produce uniform current spreading. As a result, the wall-plug efficiency was enhanced by a factor of 60% at an injection current of 350 mA in the designed uniform-current-spreading p-electrode LED when compared with an LED with a conventional cross-bar p-electrode pattern.

  4. A possible mechanism of the enhancement and maintenance of the shear magnetic field component in the current sheet of the Earth’s magnetotail

    SciTech Connect

    Grigorenko, E. E. Malova, H. V.; Malykhin, A. Yu.; Zelenyi, L. M.

    2015-01-15

    The influence of the shear magnetic field component, which is directed along the electric current in the current sheet (CS) of the Earth’s magnetotail and enhanced near the neutral plane of the CS, on the nonadiabatic dynamics of ions interacting with the CS is studied. The results of simulation of the nonadiabatic ion motion in the prescribed magnetic configuration similar to that observed in the magnetotail CS by the CLUSTER spacecraft demonstrated that, in the presence of some initial shear magnetic field, the north-south asymmetry in the ion reflection/refraction in the CS is observed. This asymmetry leads to the formation of an additional current system formed by the oppositely directed electric currents flowing in the northern and southern parts of the plasma sheet in the planes tangential to the CS plane and in the direction perpendicular to the direction of the electric current in the CS. The formation of this current system perhaps is responsible for the enhancement and further maintenance of the shear magnetic field near the neutral plane of the CS. The CS structure and ion dynamics observed in 17 intervals of the CS crossings by the CLUSTER spacecraft is analyzed. In these intervals, the shear magnetic field was increased near the neutral plane of the CS, so that the bell-shaped spatial distribution of this field across the CS plane was observed. The results of the present analysis confirm the suggested scenario of the enhancement of the shear magnetic field near the neutral plane of the CS due to the peculiarities of the nonadiabatic ion dynamics.

  5. Current and Future Challenges in Point-of-Care Technologies: A Paradigm-Shift in Affordable Global Healthcare With Personalized and Preventive Medicine

    PubMed Central

    Heetderks, William J.; Pavel, Misha; Acharya, Soumyadipta; Akay, Metin; Mairal, Anurag; Wheeler, Bruce; Dacso, Clifford C.; Sunder, T.; Lovell, Nigel; Gerber, Martin; Shah, Milind; Senthilvel, S. G.; Wang, May D.; Bhargava, Balram

    2015-01-01

    This paper summarizes the panel discussion at the IEEE Engineering in Medicine and Biology Point-of-Care Healthcare Technology Conference (POCHT 2013) held in Bangalore India from Jan 16–18, 2013. Modern medicine has witnessed interdisciplinary technology innovations in healthcare with a continuous growth in life expectancy across the globe. However, there is also a growing global concern on the affordability of rapidly rising healthcare costs. To provide quality healthcare at reasonable costs, there has to be a convergence of preventive, personalized, and precision medicine with the help of technology innovations across the entire spectrum of point-of-care (POC) to critical care at hospitals. The first IEEE EMBS Special Topic POCHT conference held in Bangalore, India provided an international forum with clinicians, healthcare providers, industry experts, innovators, researchers, and students to define clinical needs and technology solutions toward commercialization and translation to clinical applications across different environments and infrastructures. This paper presents a summary of discussions that took place during the keynote presentations, panel discussions, and breakout sessions on needs, challenges, and technology innovations in POC technologies toward improving global healthcare. Also presented is an overview of challenges and trends in developing and developed economies with respect to priority clinical needs, technology innovations in medical devices, translational engineering, information and communication technologies, infrastructure support, and patient and clinician acceptance of POC healthcare technologies. PMID:27170902

  6. Current and Future Challenges in Point-of-Care Technologies: A Paradigm-Shift in Affordable Global Healthcare With Personalized and Preventive Medicine.

    PubMed

    Dhawan, Atam P; Heetderks, William J; Pavel, Misha; Acharya, Soumyadipta; Akay, Metin; Mairal, Anurag; Wheeler, Bruce; Dacso, Clifford C; Sunder, T; Lovell, Nigel; Gerber, Martin; Shah, Milind; Senthilvel, S G; Wang, May D; Bhargava, Balram

    2015-01-01

    This paper summarizes the panel discussion at the IEEE Engineering in Medicine and Biology Point-of-Care Healthcare Technology Conference (POCHT 2013) held in Bangalore India from Jan 16-18, 2013. Modern medicine has witnessed interdisciplinary technology innovations in healthcare with a continuous growth in life expectancy across the globe. However, there is also a growing global concern on the affordability of rapidly rising healthcare costs. To provide quality healthcare at reasonable costs, there has to be a convergence of preventive, personalized, and precision medicine with the help of technology innovations across the entire spectrum of point-of-care (POC) to critical care at hospitals. The first IEEE EMBS Special Topic POCHT conference held in Bangalore, India provided an international forum with clinicians, healthcare providers, industry experts, innovators, researchers, and students to define clinical needs and technology solutions toward commercialization and translation to clinical applications across different environments and infrastructures. This paper presents a summary of discussions that took place during the keynote presentations, panel discussions, and breakout sessions on needs, challenges, and technology innovations in POC technologies toward improving global healthcare. Also presented is an overview of challenges and trends in developing and developed economies with respect to priority clinical needs, technology innovations in medical devices, translational engineering, information and communication technologies, infrastructure support, and patient and clinician acceptance of POC healthcare technologies. PMID:27170902

  7. Enhancement of spin wave excitation by spin currents due to thermal gradient and spin pumping in yttrium iron garnet/Pt

    NASA Astrophysics Data System (ADS)

    da Silva, G. L.; Vilela-Leão, L. H.; Rezende, S. M.; Azevedo, A.

    2013-01-01

    We investigate the interplay between spin currents produced by thermal gradients and spin pumping in hybrid yttrium iron garnet/Pt structures (YIG/Pt). By combining a spin pumping experiment with the application of a temperature gradient, we observe the excitation of local spin wave modes at the YIG/Pt interface. Strong enhancement of these modes was observed when the temperature gradient was applied along one direction and attenuation was observed by reversing the temperature gradient. The results provide support for a recent theoretical proposal, in which some spin wave modes are preferentially excited by spin currents traversing a YIG/Pt interface.

  8. Prelinguistic Vocalizations Distinguish Pointing Acts

    ERIC Educational Resources Information Center

    Grunloh, Thomas; Liszkowski, Ulf

    2015-01-01

    The current study investigated whether point-accompanying characteristics, like vocalizations and hand shape, differentiate infants' underlying motives of prelinguistic pointing. We elicited imperative (requestive) and declarative (expressive and informative) pointing acts in experimentally controlled situations, and analyzed accompanying…

  9. Thalamocortical neurons display suppressed burst-firing due to an enhanced Ih current in a genetic model of absence epilepsy.

    PubMed

    Cain, Stuart M; Tyson, John R; Jones, Karen L; Snutch, Terrance P

    2015-06-01

    Burst-firing in distinct subsets of thalamic relay (TR) neurons is thought to be a key requirement for the propagation of absence seizures. However, in the well-regarded Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model as yet there has been no link described between burst-firing in TR neurons and spike-and-wave discharges (SWDs). GAERS ventrobasal (VB) neurons are a specific subset of TR neurons that do not normally display burst-firing during absence seizures in the GAERS model, and here, we assessed the underlying relationship of VB burst-firing with Ih and T-type calcium currents between GAERS and non-epileptic control (NEC) animals. In response to 200-ms hyperpolarizing current injections, adult epileptic but not pre-epileptic GAERS VB neurons displayed suppressed burst-firing compared to NEC. In response to longer duration 1,000-ms hyperpolarizing current injections, both pre-epileptic and epileptic GAERS VB neurons required significantly more hyperpolarizing current injection to burst-fire than those of NEC animals. The current density of the Hyperpolarization and Cyclic Nucleotide-activated (HCN) current (Ih) was found to be increased in GAERS VB neurons, and the blockade of Ih relieved the suppressed burst-firing in both pre-epileptic P15-P20 and adult animals. In support, levels of HCN-1 and HCN-3 isoform channel proteins were increased in GAERS VB thalamic tissue. T-type calcium channel whole-cell currents were found to be decreased in P7-P9 GAERS VB neurons, and also noted was a decrease in CaV3.1 mRNA and protein levels in adults. Z944, a potent T-type calcium channel blocker with anti-epileptic properties, completely abolished hyperpolarization-induced VB burst-firing in both NEC and GAERS VB neurons. PMID:24953239

  10. Functionality of bismuth sulfide quantum dots/wires-glass nanocomposite as an optical current sensor with enhanced Verdet constant

    NASA Astrophysics Data System (ADS)

    Panmand, Rajendra P.; Kumar, Ganapathy; Mahajan, Satish M.; Kulkarni, Milind V.; Amalnerkar, D. P.; Kale, Bharat B.; Gosavi, Suresh. W.

    2011-02-01

    We report optical studies with magneto-optic properties of Bi2S3 quantum dot/wires-glass nanocomposite. The size of the Q-dot was observed to be in the range 3-15 nm along with 11 nm Q-wires. Optical study clearly demonstrated the size quantization effect with drastic band gap variation with size. Faraday rotation tests on the glass nanocomposites show variation in Verdet constant with Q-dot size. Bi2S3 Q-dot/wires glass nanocomposite demonstrated 190 times enhanced Verdet constant compared to the host glass. Prima facie observations exemplify the significant enhancement in Verdet constant of Q-dot glass nanocomposites and will have potential application in magneto-optical devices.

  11. Search for the Enhancement of the Thermal Expansion Coefficient of Superfluid ^4He near T_λ by a Heat Current

    NASA Astrophysics Data System (ADS)

    Liu, Yuanming; Israelsson, Ulf E.; Larson, Melora

    2001-03-01

    The superfluid transition in ^4He in the presence of a heat current (Q) provides an ideal system for the study of phase transitions under non-equilibrium, dynamical conditions. Many physical properties become nonlinear and Q-dependent near the transition temperature, T_ λ. For instance, the heat capacity enhancement by a heat current was predicted theoretically(R. Haussmann and V. Dohm, Phys. Rev. Lett. 72), 3060 (1994); T.C.P. Chui phet al., Phys. Rev. Lett. 77, 1793 (1996)., and observed experimentally(A.W. Harter phet al)., Phys. Rev. Lett. 84, 2195 (2000).. Because the thermal expansion coefficient is a linear function of the specific heat near T_ λ, both exhibit similar critical behaviors under equilibrium conditions. An enhancement of the thermal expansion coefficient is also expected if a similar relationship exists under non-equilibrium conditions. We report our experimental search of the enhancement of the thermal expansion of superfluid ^4He by a heat current (0 <= Q <= 100 μW/cm^2). We conducted the measurements in a thermal conductivity cell at sample pressures of SVP and 21.2 bar. The measurements were also performed in a reduced gravity environment of 0.01g provided by the low-gravity simulator we have developed at JPL.

  12. Enhanced Brain Responses to Pain-Related Words in Chronic Back Pain Patients and Their Modulation by Current Pain.

    PubMed

    Ritter, Alexander; Franz, Marcel; Puta, Christian; Dietrich, Caroline; Miltner, Wolfgang H R; Weiss, Thomas

    2016-01-01

    Previous functional magnetic resonance imaging (fMRI) studies in healthy controls (HC) and pain-free migraine patients found activations to pain-related words in brain regions known to be activated while subjects experience pain. The aim of the present study was to identify neural activations induced by pain-related words in a sample of chronic back pain (CBP) patients experiencing current chronic pain compared to HC. In particular, we were interested in how current pain influences brain activations induced by pain-related adjectives. Subjects viewed pain-related, negative, positive, and neutral words; subjects were asked to generate mental images related to these words during fMRI scanning. Brain activation was compared between CBP patients and HC in response to the different word categories and examined in relation to current pain in CBP patients. Pain-related words vs. neutral words activated a network of brain regions including cingulate cortex and insula in subjects and patients. There was stronger activation in medial and dorsolateral prefrontal cortex (DLPFC) and anterior midcingulate cortex in CPB patients than in HC. The magnitude of activation for pain-related vs. negative words showed a negative linear relationship to CBP patients' current pain. Our findings confirm earlier observations showing that pain-related words activate brain networks similar to noxious stimulation. Importantly, CBP patients show even stronger activation of these structures while merely processing pain-related words. Current pain directly influences on this activation. PMID:27517967

  13. Low-frequency electrical stimulation enhances the effectiveness of phenobarbital on GABAergic currents in hippocampal slices of kindled rats.

    PubMed

    Asgari, Azam; Semnanian, Saeed; Atapour, Nafiseh; Shojaei, Amir; Moradi-Chameh, Homeira; Ghafouri, Samireh; Sheibani, Vahid; Mirnajafi-Zadeh, Javad

    2016-08-25

    Low frequency stimulation (LFS) has been proposed as a new approach in the treatment of epilepsy. The anticonvulsant mechanism of LFS may be through its effect on GABAA receptors, which are the main target of phenobarbital anticonvulsant action. We supposed that co-application of LFS and phenobarbital may increase the efficacy of phenobarbital. Therefore, the interaction of LFS and phenobarbital on GABAergic inhibitory post-synaptic currents (IPSCs) in kindled and control rats was investigated. Animals were kindled by electrical stimulation of basolateral amygdala in a semi rapid manner (12 stimulations/day). The effect of phenobarbital, LFS and phenobarbital+LFS was investigated on GABAA-mediated evoked and miniature IPSCs in the hippocampal brain slices in control and fully kindled animals. Phenobarbital and LFS had positive interaction on GABAergic currents. In vitro co-application of an ineffective pattern of LFS (100 pulses at afterdischarge threshold intensity) and a sub-threshold dose of phenobarbital (100μM) which had no significant effect on GABAergic currents alone, increased the amplitude and area under curve of GABAergic currents in CA1 pyramidal neurons of hippocampal slices significantly. Interestingly, the sub-threshold dose of phenobarbital potentiated the GABAergic currents when applied on the hippocampal slices of kindled animals which received LFS in vivo. Post-synaptic mechanisms may be involved in observed interactions. Obtained results implied a positive interaction between LFS and phenobarbital through GABAA currents. It may be suggested that a combined therapy of phenobarbital and LFS may be a useful manner for reinforcing the anticonvulsant action of phenobarbital. PMID:27235746

  14. Is Substorm Onset Seeded by Cross-Tail Current Enhancement Resulting from Parallel Energization of Oxygen Ion Polar Cap Outflow?

    NASA Astrophysics Data System (ADS)

    Sofko, G. J.; Hussey, G. C.; McWilliams, K. A.

    2015-12-01

    The parallel energization of polar cap outflow (PCO) has been shown to be highly effective along newly-created lobe lines where the geometry is such that the Coulomb force due to the dawn-to-dusk electric field is roughly parallel to the curvature drift of the ions. This "Coulomb-curvature" interaction can produce a parallel energization rate that raises the parallel energy of the ions to about 5-6 keV before they reach the Neutral Sheet (NSh) at about 11 earth radii downtail. Then, in the outer NSh, they produce a strong westward curvature current. When they enter the inner neutral sheet (INSh) where they become "unmagnetized", they are accelerated westward by the dawn-dusk electric field. This causes their perpendicular energy and their pitch angle to increase such that the ions essentially become trapped in the inner NSh while continuing to accelerate westward. This additional westward current in the inner NSh accompanies the westward curvature current produced in the two outer NSh layers. This total ion current is supplemented by the westward curvature current caused by the eastward curvature drift of the electrons. The combined total ion and electron current is sufficient to severely decrease the magnetic field near the earthward end of the NSh. The magnetic pressure decrease is compensated by the particle pressure increase due to inflow of oxygen ions from the northern and southern polar caps. The conditions near the earthward edge of the NSh and in the adjoining plasmasheet regions neighbouring the NSh become ideal for reconnection and the dipolarization that follows.

  15. "Physiology in the News": Using Press Releases to Enhance Lay Communication and Introduce Current Physiology Research to Undergraduates

    ERIC Educational Resources Information Center

    Kelly, Kevin L.; Poteracki, James M.; Steury, Michael D.; Wehrwein, Erica A.

    2015-01-01

    Michigan State University's senior-level undergraduate physiology capstone laboratory uses a simple exercise termed "Physiology in the News," to help students explore the current research within the field of physiology while also learning to communicate science in lay terms. "Physiology in the News" is an activity that charges…

  16. Solutions Network Formulation Report. Improving NOAA's Tides and Currents Through Enhanced Data Inputs from NASA's Ocean Surface Topography Mission

    NASA Technical Reports Server (NTRS)

    Guest, DeNeice C.

    2006-01-01

    The Nation uses water-level data for a variety of practical purposes, including hydrography, nautical charting, maritime navigation, coastal engineering, and tsunami and storm surge warnings (NOAA, 2002; Digby et al., 1999). Long-term applications include marine boundary determinations, tidal predictions, sea-level trend monitoring, oceanographic research, and climate research. Accurate and timely information concerning sea-level height, tide, and ocean current is needed to understand their impact on coastal management, disaster management, and public health. Satellite altimeter data products are currently used by hundreds of researchers and operational users to monitor ocean circulation and to improve scientists understanding of the role of the oceans in climate and weather. The NOAA (National Oceanic and Atmospheric Administration) National Ocean Service has been monitoring sea-level variations for many years (NOAA, 2006). NOAA s Tides & Currents DST (decision support tool, managed by the Center for Operational Oceanographic Products and Services, is the portal to a vast collection of oceanographic and meteorological data (historical and real-time), predictions, and nowcasts and forecasts. This report assesses the capacity of NASA s satellite altimeter data to meet societal decision support needs through incorporation into NOAA s Tides & Currents.

  17. FMRFamide-like peptides (FLPs) enhance voltage-gated calcium currents to elicit muscle contraction in the human parasite Schistosoma mansoni.

    PubMed

    Novozhilova, Ekaterina; Kimber, Michael J; Qian, Hai; McVeigh, Paul; Robertson, Alan P; Zamanian, Mostafa; Maule, Aaron G; Day, Tim A

    2010-01-01

    Schistosomes are amongst the most important and neglected pathogens in the world, and schistosomiasis control relies almost exclusively on a single drug. The neuromuscular system of schistosomes is fertile ground for therapeutic intervention, yet the details of physiological events involved in neuromuscular function remain largely unknown. Short amidated neuropeptides, FMRFamide-like peptides (FLPs), are distributed abundantly throughout the nervous system of every flatworm examined and they produce potent myoexcitation. Our goal here was to determine the mechanism by which FLPs elicit contractions of schistosome muscle fibers. Contraction studies showed that the FLP Tyr-Ile-Arg-Phe-amide (YIRFamide) contracts the muscle fibers through a mechanism that requires Ca(2+) influx through sarcolemmal voltage operated Ca(2+) channels (VOCCs), as the contractions are inhibited by classical VOCC blockers nicardipine, verapamil and methoxyverapamil. Whole-cell patch-clamp experiments revealed that inward currents through VOCCs are significantly and reversibly enhanced by the application of 1 microM YIRFamide; the sustained inward currents were increased to 190% of controls and the peak currents were increased to 180%. In order to examine the biochemical link between the FLP receptor and the VOCCs, PKC inhibitors calphostin C, RO 31-8220 and chelerythrine were tested and all produced concentration dependent block of the contractions elicited by 1 microM YIRFamide. Taken together, the data show that FLPs elicit contractions by enhancing Ca(2+) influx through VOCC currents using a PKC-dependent pathway. PMID:20706630

  18. Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study

    SciTech Connect

    Sogabe, Tomah Shoji, Yasushi; Tamayo, Efrain; Okada, Yoshitaka; Mulder, Peter; Schermer, John

    2014-09-15

    We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (∼0.91 mA/cm{sup 2}) in the ELO-InAs QD cell within the wavelength range of 700 nm–900 nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (∼0.16 mA/cm{sup 2}) from the wavelength range of 900 nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700 nm–900 nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.

  19. Unraveling simultaneously enhanced open-circuit voltage and short-circuit current density in P3HT:ICBA:2,3-pyridinediol blended film based photovoltaics

    NASA Astrophysics Data System (ADS)

    Hsiung Chang, Sheng; Chiang, Chien-Hung; Tseng, Zong-Liang; Chiu, Kuo-Yuan; Tai, Chao-Yi; Wu, Chun-Guey

    2015-03-01

    A comprehensive study was carried out to understand the simultaneous enhancement of the open-circuit voltage and short-circuit current density in P3HT:ICBA:2,3-pyridinediol blended film based photovoltaics. Femtosecond time-resolved photoluminescence, steady-state absorption spectrum, atomic force microscopy and 2D grazing-incidence wide-angle x-ray scattering were used to explore the transport characteristics of excitons. The comparatively faster exciton dissociation in the P3HT:ICBA:2,3-pyridinediol blended film is attributed to the higher mobility of the excitons in P3HT. The space-charge limited-current measurements show the carrier mobility to be more balanced in the P3HT:ICBA:2,3-pyridinediol blended film than in the P3HT:PCBM:2,3-pyridinediol blended film, which is beneficial to the photo-induced current extraction. The enhanced short-circuit current density originates from the higher exciton dissociation yield in combination with the more balanced electron-hole mobility. The results should aid the design of an organic film for high-efficiency photovoltaics.

  20. Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study

    NASA Astrophysics Data System (ADS)

    Sogabe, Tomah; Shoji, Yasushi; Mulder, Peter; Schermer, John; Tamayo, Efrain; Okada, Yoshitaka

    2014-09-01

    We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (˜0.91 mA/cm2) in the ELO-InAs QD cell within the wavelength range of 700 nm-900 nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (˜0.16 mA/cm2) from the wavelength range of 900 nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700 nm-900 nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.

  1. Current status and future directions in computer-enhanced video- and robotic-assisted coronary bypass surgery.

    PubMed

    Boyd, W Douglas; Kodera, Kojiro; Stahl, Kenneth D; Rayman, Reiza

    2002-01-01

    Since 1997, both the Cleveland Clinic and London Health Sciences Centre groups have embraced robotic assistance and more recently demonstrated the efficacy of this technology in totally closed-chest, beating heart myocardial revascularization. This endeavor involved an orderly progression and the learning of new surgical skill sets. We review the evolution of robot-enhanced coronary surgery and forecast the future of endoscopic and computer-enhanced, robotic-enabling technology for coronary revascularization. This report describes a computer-assisted totally closed-chest coronary bypass operation, and preliminary results are discussed. The internal thoracic artery (ITA) was harvested through three 5-mm access ports and prepared and controlled endoscopically. A prototype sternal elevator was used to increase intrathoracic working space. A 10-mm endoscopic stabilizer was placed through the second intercostal space, and the left anterior descending coronary artery was controlled with silastic snares. Telerobotic anastomoses were completed end-to-side using custom-made, double-armed 8-0 polytetrafluroethylene sutures. To date, 84 patients have undergone successful myocardial revascularization with robotic assistance with a 0% surgical mortality rate. ITA harvest, anastomotic, and operating times for the entire group have been longer than for conventional surgery at 61.3 +/- 17.9 minutes, 28.5 +/- 28.2 minutes, and 368 +/- 129 minutes, respectively. Bleeding, ventilatory times, arrhythmias, hospital lengths of stay, and return to normal activity have been reduced. Recently, we have developed a new robotic revascularization strategy called Atraumatic Coronary Artery Bypass that is a promising mid-term step on the pathway to totally endoscopic, beating-heart coronary artery bypass. We conclude that computer-enhanced robotic techniques are safe, and further clinical studies are required to define the full potential of this evolving technology. PMID:11977023

  2. Strongly enhanced current densities in superconducting coated conductors of YBa2Cu3O7-x + BaZrO3.

    PubMed

    MacManus-Driscoll, J L; Foltyn, S R; Jia, Q X; Wang, H; Serquis, A; Civale, L; Maiorov, B; Hawley, M E; Maley, M P; Peterson, D E

    2004-07-01

    There are numerous potential applications for superconducting tapes based on YBa(2)Cu(3)O(7-x) (YBCO) films coated onto metallic substrates. A long-established goal of more than 15 years has been to understand the magnetic-flux pinning mechanisms that allow films to maintain high current densities out to high magnetic fields. In fact, films carry one to two orders of magnitude higher current densities than any other form of the material. For this reason, the idea of further improving pinning has received little attention. Now that commercialization of YBCO-tape conductors is much closer, an important goal for both better performance and lower fabrication costs is to achieve enhanced pinning in a practical way. In this work, we demonstrate a simple and industrially scaleable route that yields a 1.5-5-fold improvement in the in-magnetic-field current densities of conductors that are already of high quality. PMID:15170180

  3. Roll-to-roll, shrink-induced superhydrophobic surfaces for antibacterial applications, enhanced point-of-care detection, and blood anticoagulation

    NASA Astrophysics Data System (ADS)

    Nokes, Jolie McLane

    Superhydrophobic (SH) surfaces are desirable because of their unique anti-wetting behavior. Fluid prefers to bead up (contact angle >150°) and roll off (contact angle hysteresis <10°) a SH surface because micro- and nanostructure features trap air pockets. Fluid only adheres to the peaks of the structures, causing minimal adhesion to the surface. Here, shrink-induced SH plastics are fabricated for a plethora of applications, including antibacterial applications, enhanced point-of-care (POC) detection, and reduced blood coagulation. Additionally, these purely structural SH surfaces are achieved in a roll-to-roll (R2R) platform for scalable manufacturing. Because their self-cleaning and water resistant properties, structurally modified SH surfaces prohibit bacterial growth and obviate bacterial chemical resistance. Antibacterial properties are demonstrated in a variety of SH plastics by preventing gram-negative Escherichia coli (E. coli) bacterial growth >150x compared to flat when fluid is rinsed and >20x without rinsing. Therefore, a robust and stable means to prevent bacteria growth is possible. Next, protein in urine is detected using a simple colorimetric output by evaporating droplets on a SH surface. Contrary to evaporation on a flat surface, evaporation on a SH surface allows fluid to dramatically concentrate because the weak adhesion constantly decreases the footprint area. On a SH surface, molecules in solution are confined to a footprint area 8.5x smaller than the original. By concentrating molecules, greater than 160x improvements in detection sensitivity are achieved compared to controls. Utility is demonstrated by detecting protein in urine in the pre-eclampsia range (150-300microgmL -1) for pregnant women. Further, SH surfaces repel bodily fluids including blood, urine, and saliva. Importantly, the surfaces minimize blood adhesion, leading to reduced blood coagulation without the need for anticoagulants. SH surfaces have >4200x and >28x reduction of

  4. Barbiturates require the N terminus and first transmembrane domain of the delta subunit for enhancement of alpha1beta3delta GABAA receptor currents.

    PubMed

    Feng, Hua-Jun; Macdonald, Robert L

    2010-07-30

    GABA(A) receptors are composed predominantly of alphabetagamma receptors, which mediate primarily synaptic inhibition, and alphabetadelta receptors, which mediate primarily extrasynaptic inhibition. At saturating GABA concentrations, the barbiturate pentobarbital substantially increased the amplitude and desensitization of the alpha1beta3delta receptor but not the alpha1beta3gamma2L receptor currents. To explore the structural domains of the delta subunit that are involved in pentobarbital potentiation and increased desensitization of alpha1beta3delta currents, chimeric cDNAs were constructed by progressive replacement of gamma2L subunit sequence with a delta subunit sequence or a delta subunit sequence with a gamma2L subunit sequence, and HEK293T cells were co-transfected with alpha1 and beta3 subunits or alpha1 and beta3 subunits and a gamma2L, delta, or chimeric subunit. Currents evoked by a saturating concentration of GABA or by co-application of GABA and pentobarbital were recorded using the patch clamp technique. By comparing the extent of enhancement and changes in kinetic properties produced by pentobarbital among chimeric and wild type receptors, we concluded that although potentiation of alpha1beta3delta currents by pentobarbital required the delta subunit sequence from the N terminus to proline 241 in the first transmembrane domain (M1), increasing desensitization of alpha1beta3delta currents required a delta subunit sequence from the N terminus to isoleucine 235 in M1. These findings suggest that the delta subunit N terminus and N-terminal portion of the M1 domain are, at least in part, involved in transduction of the allosteric effect of pentobarbital to enhance alpha1beta3delta currents and that this effect involves a distinct but overlapping structural domain from that involved in altering desensitization. PMID:20525684

  5. Current smoking-specific gene expression signature in normal bronchial epithelium is enhanced in squamous cell lung cancer.

    PubMed

    Boelens, Mirjam C; van den Berg, Anke; Fehrmann, Rudolf S N; Geerlings, Marie; de Jong, Wouter K; te Meerman, Gerard J; Sietsma, Hannie; Timens, Wim; Postma, Dirkje S; Groen, Harry J M

    2009-06-01

    Cigarette smoking is the main risk factor for the development of squamous cell lung carcinoma (SCC). However, the smoking-related molecular changes in SCC have not been studied. Gene expression studies in both histologically normal bronchial epithelium and SCC epithelial samples identified genes differentially expressed between current and ex-smokers. Subsequently, expression levels of the smoking-related genes in normal bronchial epithelium were compared with those in SCC cells, since we hypothesized that the smoking-induced changes would be also deregulated in SCC. Gene expression profiles were generated using Agilent whole human genome microarrays on laser-microdissected normal bronchial epithelium and SCC samples. Expression levels of 246 genes, mainly related to oxidative stress response, were significantly different between normal bronchial epithelium of current and ex-smokers. Such a differential gene expression profile did not exist in SCC cells of smokers and ex-smokers. Interestingly, when comparing SCC and normal bronchial epithelium from ex-smokers, the vast majority of these 246 genes were also deregulated in SCC. When comparing SCC with normal epithelium from smokers, 22% of the up-regulated genes showed a similar high expression in SCC whereas 79% of the down-regulated genes were even further reduced in SCC as compared to current smokers. The down-regulated genes included several tumour suppressor genes, such as C9orf9, INHBB, LRIG1, SCGB3A1, SERPINI2, STEAP3 and ZMYND10. Thus, our study shows that the majority of genes up-regulated in normal bronchial epithelium of current smokers show similar high expression levels in SCC, while down-regulated genes are even further repressed in SCC. Our data indicate that smoking-related changes in normal bronchial epithelial cells persist in malignant transformed squamous cells. PMID:19334046

  6. Combined current-modulation annealing induced enhancement of giant magnetoimpedance effect of Co-rich amorphous microwires

    NASA Astrophysics Data System (ADS)

    Liu, Jingshun; Qin, Faxiang; Chen, Dongming; Shen, Hongxian; Wang, Huan; Xing, Dawei; Phan, Manh-Huong; Sun, Jianfei

    2014-05-01

    We report on a combined current-modulation annealing (CCMA) method, which integrates the optimized pulsed current (PC) and DC annealing techniques, for improving the giant magnetoimpedance (GMI) effect and its field sensitivity of Co-rich amorphous microwires. Relative to an as-prepared Co68.2Fe4.3B15Si12.5 wire, CCMA is shown to remarkably improve the GMI response of the wire. At 10 MHz, the maximum GMI ratio and its field sensitivity of the as-prepared wire were, respectively, increased by 3.5 and 2.28 times when subjected to CCMA. CCMA increased atomic order orientation and circumferential permeability of the wire by the co-action of high-density pulsed magnetic field energy and thermal activation energy at a PC annealing stage, as well as the formation of uniform circular magnetic domains by a stable DC magnetic field at a DC annealing stage. The magnetic moment can overcome eddy-current damping or nail-sticked action in rotational magnetization, giving rise to a double-peak feature and wider working field range (up to ±2 Oe) at relatively higher frequency (f ≥ 1 MHz).

  7. Combined current-modulation annealing induced enhancement of giant magnetoimpedance effect of Co-rich amorphous microwires

    SciTech Connect

    Liu, Jingshun E-mail: faxiang.qin@gmail.com; Qin, Faxiang E-mail: faxiang.qin@gmail.com; Chen, Dongming; Shen, Hongxian; Wang, Huan; Xing, Dawei; Sun, Jianfei; Phan, Manh-Huong

    2014-05-07

    We report on a combined current-modulation annealing (CCMA) method, which integrates the optimized pulsed current (PC) and DC annealing techniques, for improving the giant magnetoimpedance (GMI) effect and its field sensitivity of Co-rich amorphous microwires. Relative to an as-prepared Co{sub 68.2}Fe{sub 4.3}B{sub 15}Si{sub 12.5} wire, CCMA is shown to remarkably improve the GMI response of the wire. At 10 MHz, the maximum GMI ratio and its field sensitivity of the as-prepared wire were, respectively, increased by 3.5 and 2.28 times when subjected to CCMA. CCMA increased atomic order orientation and circumferential permeability of the wire by the co-action of high-density pulsed magnetic field energy and thermal activation energy at a PC annealing stage, as well as the formation of uniform circular magnetic domains by a stable DC magnetic field at a DC annealing stage. The magnetic moment can overcome eddy-current damping or nail-sticked action in rotational magnetization, giving rise to a double-peak feature and wider working field range (up to ±2 Oe) at relatively higher frequency (f ≥ 1 MHz)

  8. Current Challenges in Home Nutrition Services for Frail Older Adults in Japan—A Qualitative Research Study from the Point of View of Care Managers

    PubMed Central

    Hirakawa, Yoshihisa; Kimata, Takaya; Uemura, Kazumasa

    2013-01-01

    Preventive care for frail older adults includes providing tailor-made diet information suited to their health conditions. The present study aims to explore the current situation and challenges of home nutrition advice for Japanese frail older adults using qualitative data from a ten-person group discussion among care managers. As the results of our analysis, nine themes were identified: (1) Homebound older adults develop poor eating habits; meals turn into a lonely and unpleasant experience; (2) With age, people’s eating and drinking patterns tend to deteriorate; (3) Many older adults and their family know little about food management according to condition and medication; (4) Many older adults do not understand the importance of maintaining a proper diet; (5) Many homebound older adults do not worry about oral hygiene and swallowing ability; (6) Some older adults are at high risk for food safety problems; (7) Only a limited range of boil-in-the-bag meal options are available for older adults; (8) Many older adults feel unduly confident in their own nutrition management skills; and (9) For many family caregivers, nutrition management is a burden. We conclude that the provision of tailor-made information by skilled dietitians and high-quality home-delivered meal service are essential for the successful nutrition management of the older adults.

  9. Enhancement of critical current density in YBa{sub 2}Cu{sub 3}O{sub 7} films using a semiconductor ion implanter

    SciTech Connect

    Matsui, H. Ootsuka, T.; Ogiso, H.; Yamasaki, H.; Sohma, M.; Yamaguchi, I.; Kumagai, T.; Manabe, T.

    2015-01-28

    An up-to-11-fold enhancement was observed in the in-magnetic-field critical current density (J{sub c}) in epitaxial YBa{sub 2}Cu{sub 3}O{sub 7} films on CeO{sub 2}-buffered SrTiO{sub 3} substrates by irradiation with 200- to 750-keV Si and 200-keV B ions. This enhancement indicates that ion beams in the range of 100 to 1000 keV, which are widely used for modifying the conductive properties of semiconducting materials, can significantly improve the vortex-pinning properties in second-generation superconducting wires. Also observed was a scaling relation between J{sub c} and the density of the vacancies (i.e., of Frenkel pairs) produced by the nuclear collisions between incident ions and target atoms, suggesting that this density is a key parameter in determining the magnitude of the J{sub c} enhancement. Also observed was an additional J{sub c} enhancement by a modification of the depth distribution of the vacancies, thus demonstrating the flexibility in controlling artificial pinning center (APC) properties in physical APC introduction.

  10. Enhancing the photo-currents of CdTe thin-film solar cells in both short and long wavelength regions

    NASA Astrophysics Data System (ADS)

    Paudel, Naba R.; Yan, Yanfa

    2014-11-01

    The recent increases in the record efficiency of CdTe thin-film solar cell technology largely benefited from enhancements in short circuit current densities (JSC) in the short-wavelength regions by reducing the thicknesses of CdS window layers. Here, we report that the JSC can be enhanced in both short and long wavelength regions by using CdSe as the window layer. Comparing to CdS, CdSe has a higher solubility in CdTe, resulting in stronger interdiffusion at the CdSe/CdTe interface and the formation of CdTe1-xSex alloys with high x values. Due to bowing effects, the CdTe1-xSex alloys exhibit narrower band gaps than CdTe, enhancing the JSC in the CdTe-based solar cells for long-wavelengths. We further report that the use of combined CdS/CdSe window layers can realize high open circuit voltages and maintain the JSC enhancements. Our results suggest a viable approach to improve the performance of CdTe thin-film solar cells.

  11. Intrinsic plasticity induced by group II metabotropic glutamate receptors via enhancement of high-threshold KV currents in sound localizing neurons.

    PubMed

    Hamlet, W R; Lu, Y

    2016-06-01

    Intrinsic plasticity has emerged as an important mechanism regulating neuronal excitability and output under physiological and pathological conditions. Here, we report a novel form of intrinsic plasticity. Using perforated patch clamp recordings, we examined the modulatory effects of group II metabotropic glutamate receptors (mGluR II) on voltage-gated potassium (KV) currents and the firing properties of neurons in the chicken nucleus laminaris (NL), the first central auditory station where interaural time cues are analyzed for sound localization. We found that activation of mGluR II by synthetic agonists resulted in a selective increase of the high-threshold KV currents. More importantly, synaptically released glutamate (with reuptake blocked) also enhanced the high-threshold KV currents. The enhancement was frequency-coding region dependent, being more pronounced in low-frequency neurons compared to middle- and high-frequency neurons. The intracellular mechanism involved the Gβγ signaling pathway associated with phospholipase C and protein kinase C. The modulation strengthened membrane outward rectification, sharpened action potentials, and improved the ability of NL neurons to follow high-frequency inputs. These data suggest that mGluR II provides a feedforward modulatory mechanism that may regulate temporal processing under the condition of heightened synaptic inputs. PMID:26964678

  12. Strongly enhanced current densities in Sr0.6K0.4Fe2As2 + Sn superconducting tapes

    PubMed Central

    Lin, He; Yao, Chao; Zhang, Xianping; Zhang, Haitao; Wang, Dongliang; Zhang, Qianjun; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

    2014-01-01

    Improving transport current has been the primary topic for practical application of superconducting wires and tapes. However, the porous nature of powder-in-tube (PIT) processed iron-based tapes is one of the important reasons for low critical current density (Jc) values. In this work, the superconducting core density of ex-situ Sr0.6K0.4Fe2As2 + Sn tapes, prepared from optimized precursors, was significantly improved by employing a simple hot pressing as an alternative route for final sintering. The resulting samples exhibited optimal critical temperature (Tc), sharp resistive transition, small resistivity and high Vickers hardness (Hv) value. Consequently, the transport Jc reached excellent values of 5.1 × 104 A/cm2 in 10 T and 4.3 × 104 A/cm2 in 14 T at 4.2 K, respectively. Our tapes also exhibited high upper critical field Hc2 and almost field-independent Jc. These results clearly demonstrate that PIT pnictide wire conductors are very promising for high-field magnet applications. PMID:24663054

  13. Development of a resonant repeater tag for the enhancement of sensitivity and specificity in a wireless eddy current sensing scheme

    NASA Astrophysics Data System (ADS)

    Woo, Byungki; Andringa, Matthew; Wood, Sharon; Neikirk, Dean P.

    2006-03-01

    Eddy current sensing has been successfully used in various applications from testing heat exchange tubes for nuclear power plants to assessing dielectric thickness on printed circuit boards. However, in civil infrastructures cosmetic or cementitious surface material often keeps the probe or reader coil from accessing conductive medium inside the structure, resulting in reduced coupling as the distance increases between the DUT (device under test) and probe. Thus, the direct application of existing eddy current sensing technique is not very useful to detect flaws in civil infrastructures. To address this weak coupling problem, a simple scheme is proposed in which a resonant passive repeater tag is placed between the reader coil and the conducting test target. In this paper, the feasibility of detecting defects like cracks or fractures in conductive medium using a passive resonant tag and remote inductive pick-up as a method of interrogation is shown. Experimental data taken from simple setups to demonstrate the advantage of the proposed scheme are presented.

  14. True alignment of preclinical and clinical research to enhance success in CNS drug development: a review of the current evidence.

    PubMed

    Goetghebeur, Pascal Jd; Swartz, Jina E

    2016-07-01

    Central nervous system pharmacological research and development has reached a critical turning point. Patients suffering from disorders afflicting the central nervous system are numerous and command significant attention from the pharmaceutical industry. However, given the numerous failures of promising drugs, many companies are no longer investing in or, indeed, are divesting from this therapeutic area. Central nervous system drug development must change in order to develop effective therapies to treat these patients. Preclinical research is a cornerstone of drug development; however, it is frequently criticised for its lack of predictive validity. Animal models and assays can be shown to be more predictive than reported and, on many occasions, the lack of thorough preclinical testing is potentially to blame for some of the clinical failures. Important factors such as translational aspects, nature of animal models, variances in acute versus chronic dosing, development of add-on therapies and understanding of the full dose-response relationship are too often neglected. Reducing the attrition rate in central nervous system drug development could be achieved by addressing these important questions before novel compounds enter the clinical phase. This review illustrates the relevance of employing these criteria to translational central nervous system research, better to ensure success in developing new drugs in this therapeutic area. PMID:27147593

  15. Simultaneous Measurements of Fast Optical and Proton Current Kinetics in the Bacteriorhodopsin Photocycle using an Enhanced Spectrophotometer

    PubMed Central

    Kakareka, John W.; Smith, Paul D.; Pohida, Thomas J.; Hendler, Richard W.

    2008-01-01

    A one-of-a-kind high speed optical multichannel spectrometer was designed and built at NIH and described in this journal in 1997 [Cole et al. Vol 35, pages 161–174]. The most unique aspect of this instrument was the ability to follow an entire time course from a single activation using a single sample. The instrument has been used to study rapid kinetic processes in the photon-driven bacteriorhodopsin photocycle and electron transport from cytochrome c to cytochrome aa3 and from cytochrome aa3 to oxygen. The present paper describes a second generation instrument with a number of important enhancements which significantly improve its capabilities for multichannel kinetic studies. An example application is presented in which the kinetics of photon-induced proton flow across the biological membrane is measured simultaneously with the individual steps of the photocycle determined optically. Matching the time constants for the two processes indicates which molecular transformations are associated with major proton movements. PMID:18160131

  16. Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current

    SciTech Connect

    Yano, Keisuke Kurisu, Yosuke; Nozaki, Dai; Kimura, Daiju; Imai, Youta; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-15

    Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS.

  17. Robot-assisted and computer-enhanced therapies for children with cerebral palsy: current state and clinical implementation.

    PubMed

    Meyer-Heim, Andreas; van Hedel, Hubertus J A

    2013-06-01

    The field of pediatric neurorehabilitation has rapidly evolved with the introduction of technological advancements over recent years. Rehabilitation robotics and computer-assisted systems can complement conventional physiotherapeutics or occupational therapies. These systems appear promising, especially in children, where exciting and challenging virtual reality scenarios could increase motivation to train intensely in a playful therapeutic environment. Despite promising experience and a large acceptance by the patients and parents, so far, only a few therapy systems have been evaluated in children, and well-designed randomized controlled studies in this field are still lacking. This narrative review aims to provide an overview about the to-date robot-assisted and computer-based therapies and the current level of evidence and to share the authors experience about the clinical implication of these new technologies available for children with cerebral palsy. PMID:23948688

  18. Enhancement of critical current of SiC and malic acid codoped MgB2/Fe wires

    NASA Astrophysics Data System (ADS)

    Li, W. X.; Chen, R. H.; Xu, X.; Hu, Y. M.; Zhu, M. Y.; Li, Y.; Dou, S. X.

    2015-09-01

    The influences of microstructure, connectivity, and disorder on the critical current density, Jc, are discussed to clarify the different mechanisms of Jc(H) in different magnetic field ranges for in situ and combined in situ/ex situ MgB2/Fe wires with nano SiC and malic acid codoping. Sintering temperature plays a very important role in the electromagnetic properties at different temperatures and under various magnetic fields. Connectivity, upper critical field, Hc2, and irreversibility field, Hirr, are studied to demonstrate the mechanism of Jc dependence on magnetic field. The combined in situ/ex situ process is proved to be a promising technique for fabrication of practical MgB2 wires.

  19. Enhancement of low temperature Critical current density of MgB2 thin films by Au coating

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Mi; Lee, Hyun-Sook; Kim, Heon-Jung; Lee, Sung-Ik; Kim, Hyeong-Jin; Kang, W. N.

    2004-03-01

    We measured the superconducting critical current densities (J_c) from the magnetization hysteresis (M-H) loop while depositing the gold on top of the MgB2 thin film. The purpose of this experiment is whether the vortex avalanche phenomena which suppress the Jc for low temperature ( T < 15 K ) and low field (H ≤ 1000 Oe) can be cured by gold deposition. This avalanche called flux noise has been headache for the application of the MgB2 thin films. As increasing the thickness of Au film, fortunately, the flux noise in the M-H loop is suppressed and finally disappears when thickness of the gold becomes 2.55 ¥im. From this experiment, the obstacles of the application of MgB2 thin film are completely overcome

  20. Enhancement at low temperatures of the critical current density for Au-coated MgB2 thin films

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Mi; Lee, Hyun-Sook; Kim, Heon-Jung; Lee, Sung-Ik; Kim, Hyeong-Jin; Kang, W. N.

    2004-01-01

    We measured the superconducting critical current densities (Jc) from the magnetization hysteresis (M-H) loop for Au-coated MgB2 thin films. The purpose of this experiment was to determine whether the vortex avalanche phenomenon which suppresses the Jc for low temperature (T<15 K) and low field (H⩽1000 Oe) could be cured by gold deposition. This avalanche, called flux noise, has been a headache in applications of MgB2 thin films. Fortunately, the flux noise in the M-H loop is suppressed with increasing Au-film thickness and finally disappears when the thickness of the gold becomes 2.55 μm. We found a way to remove one obstacle for applications of MgB2 thin films as an superconducting device.

  1. Vertical current-flow enhancement via fabrication of GaN nanorod p-n junction diode on graphene

    NASA Astrophysics Data System (ADS)

    Ryu, Sung Ryong; Ram, S. D. Gopal; Lee, Seung Joo; Cho, Hak-dong; Lee, Sejoon; Kang, Tae Won; Kwon, Sangwoo; Yang, Woochul; Shin, Sunhye; Woo, Yongdeuk

    2015-08-01

    Mg doped GaN nanorods were grown on undoped n-type GaN nanorods uniaxial on monolayer graphene by hydride vapor phase epitaxy (HVPE) method. The monolayer graphene used as the bottom electrode and a substrate as well provides good electrical contact, acts as a current spreading layer, well suitable for the growth of hexagonal GaN nanorod. In addition it has a work function suitable to that of n-GaN. The formed p-n nanorods show a Schottky behavior with a turn on voltage of 3 V. Using graphene as the substrate, the resistance of the nanorod is reduced by 700 times when compared with the case without using graphene as the current spreading layer. The low resistance of graphene acts in parallel with the resistance of the GaN buffer layer, and reduces the resistance drastically. The formed p-n junction in a single GaN nanorod is visualized by Kelvin Force Probe Microscopy (KPFM) to have distinctively contrast p and n regions. The measured contact potential difference of p-and n-region has a difference of 103 mV which well confirms the formed regions are electronically different. Low temperature photoluminescence (PL) spectra give evidence of dopant related acceptor bound emission at 3.2 eV different from 3.4 eV of undoped GaN. The crystalline structure, compositional purity is confirmed by X-ray diffraction (XRD), Transmission and Scanning electron microcopies (SEM), (TEM), Energy dispersive analysis by X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS) as well.

  2. Enhancement of current commensurate with mutual noise-noise correlation in a symmetric periodic substrate: The benefits of noise and nonlinearity

    NASA Astrophysics Data System (ADS)

    Ghosh, Pradipta; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray

    2012-06-01

    Starting from a Langevin description of a particle submerged in a heat bath that offers a state dependent dissipation, we examine the noise-induced transport of a Brownian particle in the presence of two external, mutually correlated noises and envisage that in a symmetric periodic potential, the steady state current increases with an increase in the extent of correlation. The study of inhomogeneous diffusion in the presence of colored noise makes the present development formally interesting since this brings in a direct implication that exercising control on the degree of correlation can enhance the current in a properly designed experiment. As an offshoot of this development, we also envisage an effective temperature that depends on the correlation time and the extent of correlation.

  3. Nanocoating of particles for optimal doping and universal enhancement of current-carrying ability in ''organic''MgB{sub 2-x}C{sub x} superconductors

    SciTech Connect

    Shcherbakova, O. V.; Pan, A. V.; Dou, S. X.; Nigam, R.; Wexler, D.

    2010-05-15

    The universal approach of liquid mixing has been found to produce 'organic' MgB{sub 2-x}C{sub x} superconductors with structural and supercurrent-carrying properties unattainable by other techniques. We show by transmission electron microscopy combined with energy dispersive spectroscopy that these unique properties are enabled through coating of boron particles with a nanolayer of carbon. The subsequent reaction between carbon-encapsulated boron and magnesium results in enhanced carbon content x in the crystal lattice, as determined by x-ray diffraction pattern analysis. Among various carbon-containing compounds investigated, polycarbosilane has been found to be the optimal dopant for MgB{sub 2} superconductor, producing the largest critical current density due to the formation of wide range of nanodefects with pinning properties within the MgB{sub 2} crystal lattice, as well as due to minimal formation of current-blocking layers around the grains.

  4. AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with reduced leakage current and enhanced breakdown voltage using aluminum ion implantation

    NASA Astrophysics Data System (ADS)

    Sun, Shichuang; Fu, Kai; Yu, Guohao; Zhang, Zhili; Song, Liang; Deng, Xuguang; Qi, Zhiqiang; Li, Shuiming; Sun, Qian; Cai, Yong; Dai, Jiangnan; Chen, Changqing; Zhang, Baoshun

    2016-01-01

    This letter has studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors on silicon substrate with GaN buffer treated by aluminum ion implantation for insulating followed by a channel regrown by metal-organic chemical vapor deposition. For samples with Al ion implantation of multiple energies of 140 keV (dose: 1.4 × 1014 cm-2) and 90 keV (dose: 1 × 1014 cm-2), the OFF-state leakage current is decreased by more than 3 orders and the breakdown voltage is enhanced by nearly 6 times compared to the samples without Al ion implantation. Besides, little degradation of electrical properties of the 2D electron gas channel is observed where the maximum drain current IDSmax at a gate voltage of 3 V was 701 mA/mm and the maximum transconductance gmmax was 83 mS/mm.

  5. Nanocoating of particles for optimal doping and universal enhancement of current-carrying ability in ``organic'' MgB2-xCx superconductors

    NASA Astrophysics Data System (ADS)

    Shcherbakova, O. V.; Pan, A. V.; Dou, S. X.; Nigam, R.; Wexler, D.

    2010-05-01

    The universal approach of liquid mixing has been found to produce "organic" MgB2-xCx superconductors with structural and supercurrent-carrying properties unattainable by other techniques. We show by transmission electron microscopy combined with energy dispersive spectroscopy that these unique properties are enabled through coating of boron particles with a nanolayer of carbon. The subsequent reaction between carbon-encapsulated boron and magnesium results in enhanced carbon content x in the crystal lattice, as determined by x-ray diffraction pattern analysis. Among various carbon-containing compounds investigated, polycarbosilane has been found to be the optimal dopant for MgB2 superconductor, producing the largest critical current density due to the formation of wide range of nanodefects with pinning properties within the MgB2 crystal lattice, as well as due to minimal formation of current-blocking layers around the grains.

  6. Model Breaking Points Conceptualized

    ERIC Educational Resources Information Center

    Vig, Rozy; Murray, Eileen; Star, Jon R.

    2014-01-01

    Current curriculum initiatives (e.g., National Governors Association Center for Best Practices and Council of Chief State School Officers 2010) advocate that models be used in the mathematics classroom. However, despite their apparent promise, there comes a point when models break, a point in the mathematical problem space where the model cannot,…

  7. Radial direct bandgap p-i-n GaNP microwire solar cells with enhanced short circuit current

    NASA Astrophysics Data System (ADS)

    Sukrittanon, Supanee; Liu, Ren; Breeden, Michael C.; Pan, Janet L.; Jungjohann, K. L.; Tu, Charles W.; Dayeh, Shadi A.

    2016-08-01

    We report the demonstration of dilute nitride heterostructure core/shell microwire solar cells utilizing the combination of top-down reactive-ion etching to create the cores (GaP) and molecular beam epitaxy to create the shells (GaNP). Systematic studies of cell performance over a series of microwire lengths, array periods, and microwire sidewall morphologies examined by transmission electron microscopy were conducted to shed light on performance-limiting factors and to optimize the cell efficiency. We show by microscopy and correlated external quantum efficiency characterization that the open circuit voltage is degraded primarily due to the presence of defects at the GaP/GaNP interface and in the GaNP shells, and is not limited by surface recombination. Compared to thin film solar cells in the same growth run, the microwire solar cells exhibit greater short circuit current but poorer open circuit voltage due to greater light absorption and number of defects in the microwire structure, respectively. The comprehensive understanding presented in this work suggests that performance benefits of dilute nitride microwire solar cells can be achieved by further tuning of the epitaxial quality of the underlying materials.

  8. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    PubMed Central

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-01-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters. PMID:26842997

  9. Determination of trace elements in high purity alumina powder by helium enhanced direct current glow discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Jung, Sehoon; Kim, Sunhye; Hinrichs, Joachim

    2016-08-01

    Trace impurities in high purity alumina powder were determined by fast flow direct current glow discharge mass spectrometry (GD-MS). The non-conductive samples were prepared with high purity graphite powder and used as a sample binder and as a secondary cathode. To improve the sensitivity of the GD-MS analysis, helium was introduced as an additional glow discharge gas to argon plasma. The quantification results of the GD-MS measurement were calculated by external calibration with matrix matched certified reference materials. The GD-MS results for the determination of Na, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn and Ga in the alumina samples agreed well with the certified values of a reference material and the results of chemical analysis using wet sample digestion with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The GD-MS analysis is a rapid analysis technique to determine trace elements in non-conductive alumina to below mg·kg- 1 levels.

  10. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current.

    PubMed

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-01-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters. PMID:26842997

  11. Quantitative Myocardial Perfusion with Dynamic Contrast-Enhanced Imaging in MRI and CT: Theoretical Models and Current Implementation

    PubMed Central

    Handayani, A.; Dijkstra, H.; Prakken, N. H. J.; Slart, R. H. J. A.; Oudkerk, M.; Van Ooijen, P. M. A.; Vliegenthart, R.; Sijens, P. E.

    2016-01-01

    Technological advances in magnetic resonance imaging (MRI) and computed tomography (CT), including higher spatial and temporal resolution, have made the prospect of performing absolute myocardial perfusion quantification possible, previously only achievable with positron emission tomography (PET). This could facilitate integration of myocardial perfusion biomarkers into the current workup for coronary artery disease (CAD), as MRI and CT systems are more widely available than PET scanners. Cardiac PET scanning remains expensive and is restricted by the requirement of a nearby cyclotron. Clinical evidence is needed to demonstrate that MRI and CT have similar accuracy for myocardial perfusion quantification as PET. However, lack of standardization of acquisition protocols and tracer kinetic model selection complicates comparison between different studies and modalities. The aim of this overview is to provide insight into the different tracer kinetic models for quantitative myocardial perfusion analysis and to address typical implementation issues in MRI and CT. We compare different models based on their theoretical derivations and present the respective consequences for MRI and CT acquisition parameters, highlighting the interplay between tracer kinetic modeling and acquisition settings. PMID:27088083

  12. Quantitative Myocardial Perfusion with Dynamic Contrast-Enhanced Imaging in MRI and CT: Theoretical Models and Current Implementation.

    PubMed

    Pelgrim, G J; Handayani, A; Dijkstra, H; Prakken, N H J; Slart, R H J A; Oudkerk, M; Van Ooijen, P M A; Vliegenthart, R; Sijens, P E

    2016-01-01

    Technological advances in magnetic resonance imaging (MRI) and computed tomography (CT), including higher spatial and temporal resolution, have made the prospect of performing absolute myocardial perfusion quantification possible, previously only achievable with positron emission tomography (PET). This could facilitate integration of myocardial perfusion biomarkers into the current workup for coronary artery disease (CAD), as MRI and CT systems are more widely available than PET scanners. Cardiac PET scanning remains expensive and is restricted by the requirement of a nearby cyclotron. Clinical evidence is needed to demonstrate that MRI and CT have similar accuracy for myocardial perfusion quantification as PET. However, lack of standardization of acquisition protocols and tracer kinetic model selection complicates comparison between different studies and modalities. The aim of this overview is to provide insight into the different tracer kinetic models for quantitative myocardial perfusion analysis and to address typical implementation issues in MRI and CT. We compare different models based on their theoretical derivations and present the respective consequences for MRI and CT acquisition parameters, highlighting the interplay between tracer kinetic modeling and acquisition settings. PMID:27088083

  13. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    NASA Astrophysics Data System (ADS)

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-02-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters.

  14. Nano-scale investigations of electric-dipole-layer enhanced field and thermionic emission from high current density cathodes

    NASA Astrophysics Data System (ADS)

    Vlahos, Vasilios

    Cesium iodide coated graphitic fibers and scandate cathodes are two important electron emission technologies. The coated fibers are utilized as field emitters for high power microwave sources. The scandate cathodes are promising thermionic cathode materials for pulsed power vacuum electron devices. This work attempts to understand the fundamental physical and chemical relationships between the atomic structure of the emitting cathode surfaces and the superior emission characteristics of these cathodes. Ab initio computational modeling in conjunction with experimental investigations was performed on coated fiber cathodes to understand the origin of their very low turn on electric field, which can be reduced by as much as ten-fold compared to uncoated fibers. Copious amounts of cesium and oxygen were found co-localized on the fiber, but no iodine was detected on the surface. Additional ab initio studies confirmed that cesium oxide dimers could lower the work function significantly. Surface cesium oxide dipoles are therefore proposed as the source of the observed reduction in the turn on electric field. It is also proposed that emission may be further enhanced by secondary electrons from cesium oxide during operation. Thermal conditioning of the coated cathode may be a mechanism by which surface cesium iodide is converted into cesium oxide, promoting the depletion of iodine by formation of volatile gas. Ab initio modeling was also utilized to investigate the stability and work functions of scandate structures. The work demonstrated that monolayer barium-scandium-oxygen surface structures on tungsten can dramatically lower the work function of the underlying tungsten substrate from 4.6 eV down to 1.16 eV, by the formation of multiple surface dipoles. On the basis of this work, we conclude that high temperature kinetics force conventional dispenser cathodes (barium-oxygen monolayers on tungsten) to operate in a non-equilibrium compositional steady state with higher than

  15. MO-C-17A-11: A Segmentation and Point Matching Enhanced Deformable Image Registration Method for Dose Accumulation Between HDR CT Images

    SciTech Connect

    Zhen, X; Chen, H; Zhou, L; Yan, H; Jiang, S; Jia, X; Gu, X; Mell, L; Yashar, C; Cervino, L

    2014-06-15

    Purpose: To propose and validate a novel and accurate deformable image registration (DIR) scheme to facilitate dose accumulation among treatment fractions of high-dose-rate (HDR) gynecological brachytherapy. Method: We have developed a method to adapt DIR algorithms to gynecologic anatomies with HDR applicators by incorporating a segmentation step and a point-matching step into an existing DIR framework. In the segmentation step, random walks algorithm is used to accurately segment and remove the applicator region (AR) in the HDR CT image. A semi-automatic seed point generation approach is developed to obtain the incremented foreground and background point sets to feed the random walks algorithm. In the subsequent point-matching step, a feature-based thin-plate spline-robust point matching (TPS-RPM) algorithm is employed for AR surface point matching. With the resulting mapping, a DVF characteristic of the deformation between the two AR surfaces is generated by B-spline approximation, which serves as the initial DVF for the following Demons DIR between the two AR-free HDR CT images. Finally, the calculated DVF via Demons combined with the initial one serve as the final DVF to map doses between HDR fractions. Results: The segmentation and registration accuracy are quantitatively assessed by nine clinical HDR cases from three gynecological cancer patients. The quantitative results as well as the visual inspection of the DIR indicate that our proposed method can suppress the interference of the applicator with the DIR algorithm, and accurately register HDR CT images as well as deform and add interfractional HDR doses. Conclusions: We have developed a novel and robust DIR scheme that can perform registration between HDR gynecological CT images and yield accurate registration results. This new DIR scheme has potential for accurate interfractional HDR dose accumulation. This work is supported in part by the National Natural ScienceFoundation of China (no 30970866 and no

  16. Kv7.5 Potassium Channel Subunits Are the Primary Targets for PKA-Dependent Enhancement of Vascular Smooth Muscle Kv7 Currents.

    PubMed

    Mani, Bharath K; Robakowski, Christina; Brueggemann, Lyubov I; Cribbs, Leanne L; Tripathi, Abhishek; Majetschak, Matthias; Byron, Kenneth L

    2016-03-01

    Kv7 (KCNQ) channels, formed as homo- or heterotetramers of Kv7.4 and Kv7.5 α-subunits, are important regulators of vascular smooth muscle cell (VSMC) membrane voltage. Recent studies demonstrate that direct pharmacological modulation of VSMC Kv7 channel activity can influence blood vessel contractility and diameter. However, the physiologic regulation of Kv7 channel activity is still poorly understood. Here, we study the effect of cAMP/protein kinase A (PKA) activation on whole cell K(+) currents through endogenous Kv7.5 channels in A7r5 rat aortic smooth muscle cells or through Kv7.4/Kv7.5 heteromeric channels natively expressed in rat mesenteric artery smooth muscle cells. The contributions of specific α-subunits are further dissected using exogenously expressed human Kv7.4 and Kv7.5 homo- or heterotetrameric channels in A7r5 cells. Stimulation of Gαs-coupled β-adrenergic receptors with isoproterenol induced PKA-dependent activation of endogenous Kv7.5 currents in A7r5 cells. The receptor-mediated enhancement of Kv7.5 currents was mimicked by pharmacological agents that increase [cAMP] (forskolin, rolipram, 3-isobutyl-1-methylxanthine, and papaverine) or mimic cAMP (8-bromo-cAMP); the 2- to 4-fold PKA-dependent enhancement of currents was also observed with exogenously expressed Kv7.5 channels. In contrast, exogenously-expressed heterotetrameric Kv7.4/7.5 channels in A7r5 cells or native mesenteric artery smooth muscle Kv7.4/7.5 channels were only modestly enhanced, and homo-tetrameric Kv7.4 channels were insensitive to this regulatory pathway. Correspondingly, proximity ligation assays indicated that isoproterenol induced PKA-dependent phosphorylation of exogenously expressed Kv7.5 channel subunits, but not of Kv7.4 subunits. These results suggest that signal transduction-mediated responsiveness of vascular smooth muscle Kv7 channel subunits to cAMP/PKA activation follows the order of Kv7.5 > Kv7.4/Kv7.5 > Kv7.4. PMID:26700561

  17. Why Data Citation Currently Misses the Point

    NASA Astrophysics Data System (ADS)

    Parsons, M. A.; Fox, P. A.

    2014-12-01

    The concept of data citation is as old as the concept of citation itself. Yet with the birth of digital data, researchers largely stopped formally citing specific data sets. Over the last couple of decades, the data management community has worked to codify data citation practices and associated technologies such as persistent identifiers and automated indices. Nonetheless, digital data sets are rarely cited formally. There are myriad reasons for this, but we believe one problem is that data managers expect too much from data citation and assume false parallels to literature citation. We believe there needs to be a close examination of the purpose as well as practice of data citation, and a careful separation of concerns. We will present some initial ideas and then engage the audience in an open conversation on the topic.

  18. Theory of microwave-assisted supercurrent in quantum point contacts.

    PubMed

    Bergeret, F S; Virtanen, P; Heikkilä, T T; Cuevas, J C

    2010-09-10

    We present a microscopic theory of the effect of a microwave field on the supercurrent through a quantum point contact of arbitrary transmission. Our theory predicts that (i) for low temperatures and weak fields, the supercurrent is suppressed at certain values of the superconducting phase, (ii) at strong fields, the current-phase relation is strongly modified and the current can even reverse its sign, and (iii) at finite temperatures, the microwave field can enhance the critical current of the junction. Apart from their fundamental interest, our findings are also important for the description of experiments that aim at the manipulation of the quantum state of atomic point contacts. PMID:20867598

  19. Web-Based Learning Enhancements: Video Lectures through Voice-Over PowerPoint in a Majors-Level Biology Course

    ERIC Educational Resources Information Center

    Lents, Nathan H.; Cifuentes, Oscar E.

    2009-01-01

    This study is an experimental introduction of web-based lecture delivery into a majors-level introductory biology course. Web-based delivery, achieved through the use of prerecorded Voice-Over PowerPoint video lectures, was introduced on a limited basis to an experimental section while a control group, with the same instructor, received standard…

  20. Backscattering enhancement for Marshall-Palmer distributed rains for a W-band nadir-pointing radar with a finite beam width

    NASA Technical Reports Server (NTRS)

    Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood; Oguchi, Tomohiro

    2005-01-01

    In this paper, we expand the previous theory to be applied to a generic drop size distribution with spheroidal raindrops including spherical raindrops. Results will be used to discuss the multiple scattering effects on the backscatter measurements acquired by a W-band nadir-pointing radar.

  1. Enhancement of the Chaperone Activity of Alkyl Hydroperoxide Reductase C from Pseudomonas aeruginosa PAO1 Resulting from a Point-Specific Mutation Confers Heat Tolerance in Escherichia coli.

    PubMed

    Lee, Jae Taek; Lee, Seung Sik; Mondal, Suvendu; Tripathi, Bhumi Nath; Kim, Siu; Lee, Keun Woo; Hong, Sung Hyun; Bai, Hyoung-Woo; Cho, Jae-Young; Chung, Byung Yeoup

    2016-08-31

    Alkyl hydroperoxide reductase subunit C from Pseudomonas aeruginosa PAO1 (PaAhpC) is a member of the 2-Cys peroxiredoxin family. Here, we examined the peroxidase and molecular chaperone functions of PaAhpC using a site-directed mutagenesis approach by substitution of Ser and Thr residues with Cys at positions 78 and 105 located between two catalytic cysteines. Substitution of Ser with Cys at position 78 enhanced the chaperone activity of the mutant (S78C-PaAhpC) by approximately 9-fold compared with that of the wild-type protein (WT-PaAhpC). This increased activity may have been associated with the proportionate increase in the high-molecular-weight (HMW) fraction and enhanced hydrophobicity of S78C-PaAhpC. Homology modeling revealed that mutation of Ser(78) to Cys(78) resulted in a more compact decameric structure than that observed in WT-PaAhpC and decreased the atomic distance between the two neighboring sulfur atoms of Cys(78) in the dimer-dimer interface of S78C-PaAhpC, which could be responsible for the enhanced hydrophobic interaction at the dimer-dimer interface. Furthermore, complementation assays showed that S78C-PaAhpC exhibited greatly improved the heat tolerance, resulting in enhanced survival under thermal stress. Thus, addition of Cys at position 78 in PaAhpC modulated the functional shifting of this protein from a peroxidase to a chaperone. PMID:27457208

  2. Enhancement of the Chaperone Activity of Alkyl Hydroperoxide Reductase C from Pseudomonas aeruginosa PAO1 Resulting from a Point-Specific Mutation Confers Heat Tolerance in Escherichia coli

    PubMed Central

    Lee, Jae Taek; Lee, Seung Sik; Mondal, Suvendu; Tripathi, Bhumi Nath; Kim, Siu; Lee, Keun Woo; Hong, Sung Hyun; Bai, Hyoung-Woo; Cho, Jae-Young; Chung, Byung Yeoup

    2016-01-01

    Alkyl hydroperoxide reductase subunit C from Pseudomonas aeruginosa PAO1 (PaAhpC) is a member of the 2-Cys peroxiredoxin family. Here, we examined the peroxidase and molecular chaperone functions of PaAhpC using a site-directed mutagenesis approach by substitution of Ser and Thr residues with Cys at positions 78 and 105 located between two catalytic cysteines. Substitution of Ser with Cys at position 78 enhanced the chaperone activity of the mutant (S78C-PaAhpC) by approximately 9-fold compared with that of the wild-type protein (WT-PaAhpC). This increased activity may have been associated with the proportionate increase in the high-molecular-weight (HMW) fraction and enhanced hydrophobicity of S78C-PaAhpC. Homology modeling revealed that mutation of Ser78 to Cys78 resulted in a more compact decameric structure than that observed in WT-PaAhpC and decreased the atomic distance between the two neighboring sulfur atoms of Cys78 in the dimer-dimer interface of S78C-PaAhpC, which could be responsible for the enhanced hydrophobic interaction at the dimer-dimer interface. Furthermore, complementation assays showed that S78C-PaAhpC exhibited greatly improved the heat tolerance, resulting in enhanced survival under thermal stress. Thus, addition of Cys at position 78 in PaAhpC modulated the functional shifting of this protein from a peroxidase to a chaperone. PMID:27457208

  3. N-type calcium current, Cav2.2, is enhanced in small-diameter sensory neurons isolated from Nf1+/- mice.

    PubMed

    Duan, J-H; Hodgdon, K E; Hingtgen, C M; Nicol, G D

    2014-06-13

    Major aspects of neuronal function are regulated by Ca(2+) including neurotransmitter release, excitability, developmental plasticity, and gene expression. We reported previously that sensory neurons isolated from a mouse model with a heterozygous mutation of the Nf1 gene (Nf1+/-) exhibited both greater excitability and evoked release of neuropeptides compared to wildtype mice. Furthermore, augmented voltage-dependent sodium currents but not potassium currents contribute to the enhanced excitability. To determine the mechanisms giving rise to the enhanced release of substance P and calcitonin gene-related peptide in the Nf1+/- sensory neurons, the potential differences in the total voltage-dependent calcium current (ICa) as well as the contributions of individual Ca(2+) channel subtypes were assessed. Whole-cell patch-clamp recordings from small-diameter capsaicin-sensitive sensory neurons demonstrated that the average peak ICa densities were not different between the two genotypes. However, by using selective blockers of channel subtypes, the current density of N-type (Cav2.2) ICa was significantly larger in Nf1+/- neurons compared to wildtype neurons. In contrast, there were no significant differences in L-, P/Q- and R-type currents between the two genotypes. Quantitative real-time polymerase chain reaction measurements made from the isolated but intact dorsal root ganglia indicated that N-type (Cav2.2) and P/Q-type (Cav2.1) Ca(2+) channels exhibited the highest mRNA expression levels although there were no significant differences in the levels of mRNA expression between the genotypes. These results suggest that the augmented N-type (Cav2.2) ICa observed in the Nf1+/- sensory neurons does not result from genomic differences but may reflect post-translational or some other non-genomic modifications. Thus, our results demonstrate that sensory neurons from Nf1+/- mice, exhibit increased N-type ICa and likely account for the increased release of substance P and

  4. N-type calcium current, Cav2.2, is enhanced in small diameter sensory neurons isolated from Nf1+/− mice

    PubMed Central

    Duan, J-H.; Hodgdon, K. E.; Hingtgen, C. M.; Nicol, G. D.

    2014-01-01

    Major aspects of neuronal function are regulated by Ca2+ including neurotransmitter release, excitability, developmental plasticity, and gene expression. We reported previously that sensory neurons isolated from a mouse model with a heterozygous mutation of the Nf1 gene (Nf1+/−) exhibited both greater excitability and evoked release of neuropeptides compared to wildtype mice. Furthermore, augmented voltage-dependent sodium currents but not potassium currents contribute to the enhanced excitability. To determine the mechanisms giving rise to the enhanced release of substance P and calcitonin gene-related peptide in the Nf1+/− sensory neurons, the potential differences in the total voltage-dependent calcium current (ICa) as well as the contributions of individual Ca2+ channel subtypes were assessed. Whole-cell patch-clamp recordings from small diameter capsaicin-sensitive sensory neurons demonstrated that the average peak ICa densities were not different between the two genotypes. However, by using selective blockers of channel subtypes, the current density of N-type (Cav2.2) ICa was significantly larger in Nf1+/− neurons compared to wildtype neurons. In contrast, there were no significant differences in L-, P/Q- and R-type currents between the two genotypes. Quantitative real-time PCR measurements made from the isolated but intact dorsal root ganglia indicated that N-type (Cav2.2) and P/Q-type (Cav2.1) Ca2+ channels exhibited the highest mRNA expression levels although there were no significant differences in the levels of mRNA expression between the genotypes. These results suggest that the augmented N-type (Cav2.2) ICa observed in the Nf1+/− sensory neurons does not result from genomic differences but may reflect post-translational or some other non-genomic modifications. Thus, our results demonstrate that sensory neurons from Nf1+/− mice, exhibit increased N-type ICa and likely account for the increased release of substance P and calcitonin gene

  5. Enhanced light output power in InGaN/GaN light-emitting diodes with a high reflective current blocking layer

    NASA Astrophysics Data System (ADS)

    Xiaojie, Zhang; Ruixia, Yang; Jinghui, Wang

    2012-07-01

    The light output power of an InGaN/GaN light-emitting diode is improved by using a SiO2/TiO2 distributed Bragg reflector (DBR) and an Al mirror as a hybrid reflective current blocking layer (CBL). Such a hybrid reflective CBL not only plays the role of the CBL by enhancing current spreading but also plays the role of a reflector by preventing photons near the p-electrode pad from being absorbed by a metal electrode. At a wavelength of 455 nm, a 1.5-pair of SiO2/TiO2 DBR and an Al mirror (i.e. 1.5-pair DBR+Al) deposited on a p-GaN layer showed a normal-incidence reflectivity as high as 97.8%. With 20 mA current injection, it was found that the output power was 25.26, 24.45, 23.58 and 22.45 mW for the LED with a 1.5-pair DBR+Al CBL, a 3-pair DBR CBL, SiO2 CBL and without a CBL, respectively.

  6. Tipping Point

    MedlinePlus Videos and Cool Tools

    ... Tipping Point by CPSC Blogger September 22 appliance child Childproofing CPSC danger death electrical fall furniture head ... TV falls with about the same force as child falling from the third story of a building. ...

  7. Repeated cocaine administration decreases calcineurin (PP2B) but enhances DARPP-32 modulation of sodium currents in rat nucleus accumbens neurons.

    PubMed

    Hu, Xiu-Ti; Ford, Kerstin; White, Francis J

    2005-05-01

    Our previous studies have demonstrated that repeated cocaine (COC) administration reduces voltage-sensitive sodium and calcium currents (I(Na) or VSSCs and I(Ca) or VSCCs, respectively) in medium spiny nucleus accumbens (NAc) neurons of rats. The present findings further indicate that chronic COC-induced I(Na) reduction in NAc neurons is regulated by decreased dephosphorylation and enhanced phosphorylation of Na(+) channels. Whole-cell voltage-clamp recordings revealed that dephosphorylation of Na(+) channels by calcineurin (CaN) enhanced I(Na), while inhibition of protein phosphatase 1 (PP1) by phosphorylated dopamine- and cAMP-regulated phosphoprotein (M(r)=32 kDa) (DARPP-32) at the site of threonine 34 (p-Thr.34-DARPP-32) suppressed I(Na), in freshly dissociated NAc neurons of saline-pretreated rats. However, the effects of CaN on enhancing I(Na) were significantly attenuated, and the action of p-Thr.34-DARPP-32 to decrease I(Na) was mimicked, although not potentiated, by repeated COC pretreatment. Dephosphorylation of Na(+) channels by PP1 also enhanced I(Na), but this effect of PP1 on I(Na) was not apparently affected by repeated COC administration. Western blot analysis indicates that the protein levels of CaN and DARPP-32 were significantly decreased and increased, respectively, while the PP1 levels were unchanged, in the COC-withdrawn NAc as compared to saline-pretreated controls. Combined with previous findings, our results indicate that both CaN and PP1 modulate the increase in I(Na) via enhancing dephosphorylation, while p-Thr.34-DARPP-32 reduces I(Na) by inhibiting PP1-induced dephosphorylation, thereby stabilizing the phosphorylation state, of Na(+) channels in NAc neurons. They also suggest that chronic COC-induced I(Na) reduction may be attributed to a reduction in Ca(2+) signaling, which disrupts the physiological balance of phosphorylation and dephosphorylation of Na(+) channels. PMID:15726118

  8. Early maladaptive schema-related impairment and co-occurring current major depressive episode-related enhancement of mental state decoding ability in borderline personality disorder.

    PubMed

    Unoka, Zsolt Szabolcs; Fogd, Dóra; Seres, Imola; Kéri, Szabolcs; Csukly, Gábor

    2015-04-01

    Disturbed interpersonal relationships specific to borderline personality disorder (BPD) suggest biased processing of social information. The goal of this study was to examine alterations in mental state decoding (MSD) and their associations with early maladaptive schemas (EMS) that may lead to the misinterpretation of incoming information. In addition, the authors' aim was to evaluate the effects of a co-occurring current major depressive episode (MDE) on the MSD performance of BPD patients. Seventy-eight BPD patients (34 with MDE) and 76 matched healthy controls (HC) were assessed for Reading the Mind in the Eyes Test (RMET) and the level of EMS. The authors found that impairment in the total RMET performance, as well as specific impairment regarding the recognition of positive and neutral items, was associated with EMS, and enhanced vigilance to negative mental states was characteristic to BPD with MDE. Results suggest that MSD ability is altered in two independent ways in BPD. PMID:24932871

  9. Specific Intensity Direct Current (DC) Electric Field Improves Neural Stem Cell Migration and Enhances Differentiation towards βIII-Tubulin+ Neurons

    PubMed Central

    Zhao, Huiping; Steiger, Amanda; Nohner, Mitch; Ye, Hui

    2015-01-01

    Control of stem cell migration and differentiation is vital for efficient stem cell therapy. Literature reporting electric field–guided migration and differentiation is emerging. However, it is unknown if a field that causes cell migration is also capable of guiding cell differentiation—and the mechanisms for these processes remain unclear. Here, we report that a 115 V/m direct current (DC) electric field can induce directional migration of neural precursor cells (NPCs). Whole cell patching revealed that the cell membrane depolarized in the electric field, and buffering of extracellular calcium via EGTA prevented cell migration under these conditions. Immunocytochemical staining indicated that the same electric intensity could also be used to enhance differentiation and increase the percentage of cell differentiation into neurons, but not astrocytes and oligodendrocytes. The results indicate that DC electric field of this specific intensity is capable of promoting cell directional migration and orchestrating functional differentiation, suggestively mediated by calcium influx during DC field exposure. PMID:26068466

  10. Point and Shoot Astronomy

    NASA Astrophysics Data System (ADS)

    Hoot, John E.

    2011-05-01

    A new generation of point and shoot digital cameras, when combined with open source firmware enhancements can operate as astrographs. This paper explores the research and astro-photographic opportunities and capabilities offered by this pairing of mass production optics and open source functional extensions that retail for as little as $200.

  11. Enhancement of contraction and L-type Ca(2+) current by murrayafoline-A via protein kinase C in rat ventricular myocytes.

    PubMed

    Chidipi, Bojjibabu; Son, Min-Jeong; Kim, Joon-Chul; Lee, Jeong Hyun; Toan, Tran Quoc; Cuong, Nguyen Manh; Lee, Byung Ho; Woo, Sun-Hee

    2016-08-01

    We previously reported that murrayafoline-A (1-methoxy-3-methyl-9H-carbazole, Mu-A) increases the contractility of ventricular myocytes, in part, via enhancing Ca(2+) influx through L-type Ca(2+) channels, and that it increases the Ca(2+) transients by activation of protein kinase C (PKC). In the present study, we further examined the cellular mechanisms for the enhancement of contractility and L-type Ca(2+) current (ICa,L) by Mu-A. Cell shortening and ICa,L were measured in rat ventricular myocytes using a video edge detection method and perforated patch-clamp technique, respectively. We found that the positive inotropic effect of Mu-A was not affected by pre-exposure to the β-adrenoceptor antagonist propranolol, the protein kinase A (PKA) inhibitors KT5720 or H-89, or the phospholipase C inhibitor U73122. Interestingly, the Mu-A-mediated increases in cell shortening and in the rate of contraction were completely suppressed by pre-treatment with the PKC inhibitor GF109203X. The stimulatory effect of Mu-A on ICa,L was not altered by inhibition of PKA (KT5720), G-protein coupled receptors (suramin), or α1-adrenoceptor (prazosin). However, pre-exposure to the PKC inhibitor, GF109203X or chelerythrine, abolished the Mu-A-induced increase in ICa,L. Pre-exposure to the Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93 slightly reduced the stimulatory effects on contraction and ICa,L by Mu-A. Phosphorylation of PKC was enhanced by Mu-A in ventricular myocytes. These data suggest that Mu-A increases contraction and ICa,L via PKC in rat ventricular myocytes, and that the PKC-mediated responses in the presence of Mu-A may be partly mediated by CaMKII. PMID:27158118

  12. Giant enhancement in critical current density, up to a hundredfold, in superconducting NaFe0.97Co0.03 As single crystals under hydrostatic pressure.

    PubMed

    Shabbir, Babar; Wang, Xiaolin; Ghorbani, S R; Wang, A F; Dou, Shixue; Chen, X H

    2015-01-01

    Tremendous efforts towards improvement in the critical current density "Jc" of iron based superconductors (FeSCs), especially at relatively low temperatures and magnetic fields, have been made so far through different methods, resulting in real progress. Jc at high temperatures in high fields still needs to be further improved, however, in order to meet the requirements of practical applications. Here, we demonstrate a simple approach to achieve this. Hydrostatic pressure can significantly enhance Jc in NaFe0.97Co0.03As single crystals by at least tenfold at low field and more than a hundredfold at high fields. Significant enhancement in the in-field performance of NaFe0.97Co0.03As single crystal in terms of pinning force density (Fp) is found at high pressures. At high fields, the Fp is over 20 and 80 times higher than under ambient pressure at12 K and 14 K, respectively, at P = 1 GPa. We believe that the Co-doped NaFeAs compounds are very exciting and deserve to be more intensively investigated. Finally, it is worthwhile to say that by using hydrostatic pressure, we can achieve more milestones in terms of high Jc values in tapes, wires or films of other Fe-based superconductors. PMID:26030085

  13. Enhancement of current-perpendicular-to-plane giant magnetoresistance in Heusler-alloy based pseudo spin valves by using a CuZn spacer layer

    SciTech Connect

    Furubayashi, T. Takahashi, Y. K.; Sasaki, T. T.; Hono, K.

    2015-10-28

    Enhancement of magnetoresistance output was attained in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices by using a bcc CuZn alloy for the spacer. Pseudo spin valves that consisted of the Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5}) Heusler alloy for ferromagnetic layers and CuZn alloy with the composition of Cu{sub 52.4}Zn{sub 47.6} for a spacer showed the large change of the resistance-area products, ΔRA, up to 8 mΩ·μm{sup 2} for a low annealing temperature of 350 °C. The ΔRA value is one of the highest reported so far for the CPP-GMR devices for the low annealing temperature, which is essential for processing read heads for hard disk drives. We consider that the enhancement of ΔRA is produced from the spin-dependent resistance at the Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5})/CuZn interfaces.

  14. Giant enhancement in critical current density, up to a hundredfold, in superconducting NaFe0.97Co0.03 As single crystals under hydrostatic pressure

    PubMed Central

    Shabbir, Babar; Wang, Xiaolin; Ghorbani, S. R.; Wang, A. F.; Dou, Shixue; Chen, X. H.

    2015-01-01

    Tremendous efforts towards improvement in the critical current density “Jc” of iron based superconductors (FeSCs), especially at relatively low temperatures and magnetic fields, have been made so far through different methods, resulting in real progress. Jc at high temperatures in high fields still needs to be further improved, however, in order to meet the requirements of practical applications. Here, we demonstrate a simple approach to achieve this. Hydrostatic pressure can significantly enhance Jc in NaFe0.97Co0.03As single crystals by at least tenfold at low field and more than a hundredfold at high fields. Significant enhancement in the in-field performance of NaFe0.97Co0.03As single crystal in terms of pinning force density (Fp) is found at high pressures. At high fields, the Fp is over 20 and 80 times higher than under ambient pressure at12 K and 14 K, respectively, at P = 1 GPa. We believe that the Co-doped NaFeAs compounds are very exciting and deserve to be more intensively investigated. Finally, it is worthwhile to say that by using hydrostatic pressure, we can achieve more milestones in terms of high Jc values in tapes, wires or films of other Fe-based superconductors. PMID:26030085

  15. Reproducible Volume Restoration and Efficient Long-term Volume Retention after Point-of-care Standardized Cell-enhanced Fat Grafting in Breast Surgery

    PubMed Central

    Dos Anjos, Severiano; Matas-Palau, Aina; Mercader, Josep; Katz, Adam J.

    2015-01-01

    Background: Lipoaspirated fat grafts are used to reconstruct volume defects in breast surgery. Although intraoperative treatment decisions are influenced by volume changes observed immediately after grafting, clinical effect and patient satisfaction are dependent on volume retention over time. The study objectives were to determine how immediate breast volume changes correlate to implanted graft volumes, to understand long-term adipose graft volume changes, and to study the “dose” effect of adding autologous stromal vascular fraction (SVF) cells to fat grafts on long-term volume retention. Methods: A total of 74 patients underwent 77 cell-enhanced fat grafting procedures to restore breast volume deficits associated with cosmetic and reconstructive indications. Although all procedures used standardized fat grafts, 21 of the fat grafts were enriched with a low dose of SVF cells and 56 were enriched with a high SVF cell dose. Three-dimensional imaging was used to quantify volume retention over time Results: For each milliliter of injected fat graft, immediate changes in breast volume were shown to be lower than the actual volume implanted for all methods and clinical indications treated. Long-term breast volume changes stabilize by 90–120 days after grafting. Final volume retention in the long-term was higher with high cell-enhanced fat grafts. Conclusions: Intraoperative immediate breast volume changes do not correspond with implanted fat graft volumes. In the early postoperative period (7–21 days), breast volume increases more than the implanted volume and then rapidly decreases in the subsequent 30–60 days. High-dose cell-enhanced fat grafts decrease early postsurgical breast edema and significantly improve long-term volume retention. PMID:26579353

  16. X-ray bright points and He I lambda 10830 dark points

    NASA Technical Reports Server (NTRS)

    Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F.

    1989-01-01

    Using near-simultaneous full disk Solar X-ray images and He I 10830 lambda, spectroheliograms from three recent rocket flights, dark points identified on the He I maps were compared with X-ray bright points identified on the X-ray images. It was found that for the largest and most obvious features there is a strong correlation: most He I dark points correspond to X-ray bright points. However, about 2/3 of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced He I absorption which, however, would not a priori have been selected as a dark point. Therefore, the He I dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. He I dark points do, however, identify the locations of the stronger X-ray bright points.

  17. X-ray bright points and He I lambda 10830 dark points

    NASA Technical Reports Server (NTRS)

    Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F.

    1989-01-01

    Using near-simultaneous full disk Solar X-ray images and He I 10830 lambda, spectroheliograms from three recent rocket flights, dark points identified on the He I maps were compared with x-ray bright points identified on the X-ray images. It was found that for the largest and most obvious features there is a strong correlation: most He I dark points correspond to X-ray bright points. However, about 2/3 of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced He I absorption which, however, would not a priori have been selected as a dark point. Therefore, the He I dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. He I dark points do, however, identify the locations of the stronger X-ray bright points.

  18. Enhanced excitability and suppression of A-type K+ currents in joint sensory neurons in a murine model of antigen-induced arthritis

    PubMed Central

    Qu, Lintao; Caterina, Michael J.

    2016-01-01

    Pain is a dominant symptom of rheumatoid arthritis (RA) and its adequate treatment represents a major unmet need. However, the cellular mechanisms that drive arthritis pain are largely unexplored. Here, we examined the changes in the activity of joint sensory neurons and the associated ionic mechanisms using an animal model of antigen-induced arthritis (AIA). Methylated-bovine serum albumin (mBSA), but not vehicle challenge, in the ankle of previously immunized mice produced time-dependent symptoms of arthritis, including joint inflammation, primary mechanical hyperalgesia in the ipsilateral ankle, and secondary mechanical and heat hyperalgesia in the ipsilateral hindpaw. In vivo electrophysiological recordings revealed that Dil-labeled joint sensory neurons in AIA mice exhibited a greater incidence of spontaneous activity, mechanically evoked after-discharges, and/or increased responses to mechanical stimulation of their receptive fields, compared to control animals. Whole-cell recordings in vitro showed that AIA enhanced the excitability of joint sensory neurons. These signs of neuronal hyperexcitability were associated with a significant reduction in the density of A-type K+ currents. Thus, our data suggest that neuronal hyperexcitability, brought about in part by reduced A-type K+ currents, may contribute to pain-related behaviors that accompany antigen-induced arthritis and/or other antigen-mediated diseases. PMID:27363579

  19. Enhanced excitability and suppression of A-type K(+) currents in joint sensory neurons in a murine model of antigen-induced arthritis.

    PubMed

    Qu, Lintao; Caterina, Michael J

    2016-01-01

    Pain is a dominant symptom of rheumatoid arthritis (RA) and its adequate treatment represents a major unmet need. However, the cellular mechanisms that drive arthritis pain are largely unexplored. Here, we examined the changes in the activity of joint sensory neurons and the associated ionic mechanisms using an animal model of antigen-induced arthritis (AIA). Methylated-bovine serum albumin (mBSA), but not vehicle challenge, in the ankle of previously immunized mice produced time-dependent symptoms of arthritis, including joint inflammation, primary mechanical hyperalgesia in the ipsilateral ankle, and secondary mechanical and heat hyperalgesia in the ipsilateral hindpaw. In vivo electrophysiological recordings revealed that Dil-labeled joint sensory neurons in AIA mice exhibited a greater incidence of spontaneous activity, mechanically evoked after-discharges, and/or increased responses to mechanical stimulation of their receptive fields, compared to control animals. Whole-cell recordings in vitro showed that AIA enhanced the excitability of joint sensory neurons. These signs of neuronal hyperexcitability were associated with a significant reduction in the density of A-type K(+) currents. Thus, our data suggest that neuronal hyperexcitability, brought about in part by reduced A-type K(+) currents, may contribute to pain-related behaviors that accompany antigen-induced arthritis and/or other antigen-mediated diseases. PMID:27363579

  20. Enhancement of Photo-Current Conversion Efficiency in a CdS/CdSe Quantum-Dot-Sensitized Solar Cell Incorporated with Single-Walled Carbon Nanotubes.

    PubMed

    Park, Hyunjune; Lee, Jongtaek; Park, Taehee; Lee, Sanghun; Yi, Whikun

    2015-02-01

    Cadmium sulfide (CdS) and cadmium selenide (CdSe) are sequentially assembled onto a nanocrystalline TiO2 film to create a quantum-dot (QD)-sensitized solar cell application by a successive ionic layer adsorption and reaction (SILAR) method. The results show that CdS and CdSe QDs have a complementary effect in the performance of light harvest of solar cell. Single-walled carbon nanotubes (SWNTs) are incorporated with a CdS/CdSe QDs solar cell by mixing them with TiC2 film to enhance electron transfer. SWNTs are also sprayed onto CdSe QDs (SWNTs onto CdSe) to apply p+ type properties of SWNTs. Absorbance is increased in a wide wavelength range. In particular, cells having the sprayed SWNTs onto the QDs show a clear increase in absorbance at a low wavelength region. The fill factor of CdS/CdSe QDs solar cell with SWNTs is higher than that without SWNTs, indicating the decrease in loss of electron from TiO2 to QDs. Short-circuit current in a QD-sensitized solar cell having SWNTs on CdSe shows maximum value. Photo-current conversion efficiency of cells is increased in both cell types containing SWNTs at 10~17% compared with pristine cells. We expect that solar cells using SWNTs will affect future energy technology and devices. PMID:26353701

  1. Arctic climate tipping points.

    PubMed

    Lenton, Timothy M

    2012-02-01

    There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points. PMID:22270703

  2. The power of PowerPoint.

    PubMed

    Niamtu, J

    2001-08-01

    Carousel slide presentations have been used for academic and clinical presentations since the late 1950s. However, advances in computer technology have caused a paradigm shift, and digital presentations are quickly becoming standard for clinical presentations. The advantages of digital presentations include cost savings; portability; easy updating capability; Internet access; multimedia functions, such as animation, pictures, video, and sound; and customization to augment audience interest and attention. Microsoft PowerPoint has emerged as the most popular digital presentation software and is currently used by many practitioners with and without significant computer expertise. The user-friendly platform of PowerPoint enables even the novice presenter to incorporate digital presentations into his or her profession. PowerPoint offers many advanced options that, with a minimal investment of time, can be used to create more interactive and professional presentations for lectures, patient education, and marketing. Examples of advanced PowerPoint applications are presented in a stepwise manner to unveil the full power of PowerPoint. By incorporating these techniques, medical practitioners can easily personalize, customize, and enhance their PowerPoint presentations. Complications, pitfalls, and caveats are discussed to detour and prevent misadventures in digital presentations. Relevant Web sites are listed to further update, customize, and communicate PowerPoint techniques. PMID:11496193

  3. Etomidate blocks LTP and impairs learning but does not enhance tonic inhibition in mice carrying the N265M point mutation in the beta3 subunit of the GABA(A) receptor.

    PubMed

    Zarnowska, E D; Rodgers, F C; Oh, I; Rau, V; Lor, C; Laha, K T; Jurd, R; Rudolph, U; Eger, E I; Pearce, R A

    2015-06-01

    Enhancement of tonic inhibition mediated by extrasynaptic α5-subunit containing GABAA receptors (GABAARs) has been proposed as the mechanism by which a variety of anesthetics, including the general anesthetic etomidate, impair learning and memory. Since α5 subunits preferentially partner with β3 subunits, we tested the hypothesis that etomidate acts through β3-subunit containing GABAARs to enhance tonic inhibition, block LTP, and impair memory. We measured the effects of etomidate in wild type mice and in mice carrying a point mutation in the GABAAR β3-subunit (β3-N265M) that renders these receptors insensitive to etomidate. Etomidate enhanced tonic inhibition in CA1 pyramidal cells of the hippocampus in wild type but not in mutant mice, demonstrating that tonic inhibition is mediated by β3-subunit containing GABAARs. However, despite its inability to enhance tonic inhibition, etomidate did block LTP in brain slices from mutant mice as well as in those from wild type mice. Etomidate also impaired fear conditioning to context, with no differences between genotypes. In studies of recombinant receptors expressed in HEK293 cells, α5β1γ2L GABAARs were insensitive to amnestic concentrations of etomidate (1 μM and below), whereas α5β2γ2L and α5β3γ2L GABAARs were enhanced. We conclude that etomidate enhances tonic inhibition in pyramidal cells through its action on α5β3-containing GABAA receptors, but blocks LTP and impairs learning by other means - most likely by modulating α5β2-containing GABAA receptors. The critical anesthetic targets underlying amnesia might include other forms of inhibition imposed on pyramidal neurons (e.g. slow phasic inhibition), or inhibitory processes on non-pyramidal cells (e.g. interneurons). PMID:25680234

  4. Multispectral Image Feature Points

    PubMed Central

    Aguilera, Cristhian; Barrera, Fernando; Lumbreras, Felipe; Sappa, Angel D.; Toledo, Ricardo

    2012-01-01

    This paper presents a novel feature point descriptor for the multispectral image case Far-Infrared and Visible Spectrum images. It allows matching interest points on images of the same scene but acquired in different spectral bands. Initially, points of interest are detected on both images through a SIFT-like based scale space representation. Then, these points are characterized using an Edge Oriented Histogram (EOH) descriptor. Finally, points of interest from multispectral images are matched by finding nearest couples using the information from the descriptor. The provided experimental results and comparisons with similar methods show both the validity of the proposed approach as well as the improvements it offers with respect to the current state-of-the-art.

  5. Modulation of Training by Single-Session Transcranial Direct Current Stimulation to the Intact Motor Cortex Enhances Motor Skill Acquisition of the Paretic Hand

    PubMed Central

    Zimerman, Máximo; Heise, Kirstin F.; Hoppe, Julia; Cohen, Leonardo G.; Gerloff, Christian; Hummel, Friedhelm C.

    2016-01-01

    Background and Purpose Mechanisms of skill learning are paramount components for stroke recovery. Recent noninvasive brain stimulation studies demonstrated that decreasing activity in the contralesional motor cortex might be beneficial, providing transient functional improvements after stroke. The more crucial question, however, is whether this intervention can also enhance the acquisition of complex motor tasks, yielding longer-lasting functional improvements. In the present study, we tested the capacity of cathodal transcranial direct current stimulation (tDCS) applied over the contralesional motor cortex during training to enhance the acquisition and retention of complex sequential finger movements of the paretic hand. Method Twelve well-recovered chronic patients with subcortical stroke attended 2 training sessions during which either cathodal tDCS or a sham intervention were applied to the contralesional motor cortex in a double-blind, crossover design. Two different motor sequences, matched for their degree of complexity, were tested in a counterbalanced order during as well as 90 minutes and 24 hours after the intervention. Potential underlying mechanisms were evaluated with transcranial magnetic stimulation. Results tDCS facilitated the acquisition of a new motor skill compared with sham stimulation (P=0.04) yielding better task retention results. A significant correlation was observed between the tDCS-induced improvement during training and the tDCS-induced changes of intracortical inhibition (R2=0.63). Conclusions These results indicate that tDCS is a promising tool to improve not only motor behavior, but also procedural learning. They further underline the potential of noninvasive brain stimulation as an adjuvant treatment for long-term recovery, at least in patients with mild functional impairment after stroke. PMID:22618381

  6. Disruption of RB/E2F-1 interaction by single point mutations in E2F-1 enhances S-phase entry and apoptosis.

    PubMed Central

    Shan, B; Durfee, T; Lee, W H

    1996-01-01

    The retinoblastoma protein (RB) has been proposed to function as a negative regulator of cell proliferation by complexing with cellular proteins such as the transcription factor E2F. To study the biological consequences of the RB/E2F-1 interaction, point mutants of E2F-1 which fail to bind to RB were isolated by using the yeast two-hybrid system. Sequence analysis revealed that within the minimal 18-amino acid peptide of E2F-1 required for RB binding, five residues, Tyr (position 411), Glu (419), and Asp-Leu-Phe (423-425), are critical. These amino acids are conserved among the known E2F family members. While mutation of any of these five amino acids abolished binding to RB, all mutants retained their full transactivation potential. Expression of mutated E2F-1, when compared with that of wild-type, significantly accelerated entry into S phase and subsequent apoptosis. These results provide direct genetic evidence for the biological significance of the RB/E2F interaction and strongly suggest that the interplay between RB and E2F is critical for proper cell cycle progression. Images Fig. 3 Fig. 4 PMID:8570615

  7. An X-point ergodic divertor

    SciTech Connect

    Chu, M.S.; Jensen, T.H.; La Haye, R.J.; Taylor, T.S.; Evans, T.E.

    1991-10-01

    A new ergodic divertor is proposed. It utilizes a system of external (n = 3) coils arranged to generate overlapping magnetic islands in the edge region of a diverted tokamak and connect the randomized field lines to the external (cold) divertor plate. The novel feature in the configuration is the placement of the external coils close to the X-point. A realistic design of the external coil set is studied by using the field line tracing method for a low aspect ratio (A {approx equal} 3) tokamak. Two types of effects are observed. First, by placing the coils close to the X-point, where the poloidal magnetic field is weak and the rational surfaces are closely packed only a moderate amount of current in the external coils is needed to ergodize the edge region. This ergodized edge enhances the edge transport in the X-point region and leads to the potential of edge profile control and the avoidance of edge localized modes (ELMs). Furthermore, the trajectories of the field lines close to the X-point are modified by the external coil set, causing the hit points on the external divertor plates to be randomized and spread out in the major radius direction. A time-dependent modulation of the currents in the external (n = 3) coils can potentially spread the heat flux more uniformly on the divertor plate avoiding high concentration of the heat flux. 10 refs., 9 figs.

  8. Immunogenetic influences on acquisition of HIV-1 infection: consensus findings from two African cohorts point to an enhancer element in IL19 (1q32.2).

    PubMed

    Li, X; Zhang, K; Pajewski, N M; Brill, I; Prentice, H A; Shrestha, S; Kilembe, W; Karita, E; Allen, S; Hunter, E; Kaslow, R A; Tang, J

    2015-01-01

    Numerous reports have suggested that immunogenetic factors may influence human immunodeficiency virus (HIV)-1 acquisition, yet replicated findings that translate between study cohorts remain elusive. Our work aimed to test several hypotheses about genetic variants within the IL10-IL24 gene cluster that encodes interleukin (IL)-10, IL-19, IL-20 and IL-24. In aggregated data from 515 Rwandans and 762 Zambians with up to 12 years of follow-up, 190 single-nucleotide polymorphisms passed quality control procedures. When HIV-1-exposed seronegative subjects (n=486) were compared with newly seroconverted individuals (n=313) and seroprevalent subjects (n=478) who were already infected at enrollment, rs12407485 (G>A) in IL19 showed a robust association signal in adjusted logistic regression models (odds ratio=0.64, P=1.7 × 10(-4) and q=0.033). Sensitivity analyses demonstrated that (i) results from both cohorts and subgroups within each cohort were highly consistent; (ii) verification of HIV-1 infection status after enrollment was critical; and (iii) supporting evidence was readily obtained from Cox proportional hazards models. Data from public databases indicate that rs12407485 is part of an enhancer element for three transcription factors. Overall, these findings suggest that molecular features at the IL19 locus may modestly alter the establishment of HIV-1 infection. PMID:25633979

  9. Point Mutations in FimH Adhesin of Crohn's Disease-Associated Adherent-Invasive Escherichia coli Enhance Intestinal Inflammatory Response

    PubMed Central

    Dreux, Nicolas; Denizot, Jérémy; Martinez-Medina, Margarita; Mellmann, Alexander; Billig, Maria; Kisiela, Dagmara; Chattopadhyay, Sujay; Sokurenko, Evgeni; Neut, Christel; Gower-Rousseau, Corinne; Colombel, Jean-Frédéric; Bonnet, Richard; Darfeuille-Michaud, Arlette; Barnich, Nicolas

    2013-01-01

    Adherent-invasive Escherichia coli (AIEC) are abnormally predominant on Crohn's disease (CD) ileal mucosa. AIEC reference strain LF82 adheres to ileal enterocytes via the common type 1 pili adhesin FimH and recognizes CEACAM6 receptors abnormally expressed on CD ileal epithelial cells. The fimH genes of 45 AIEC and 47 non-AIEC strains were sequenced. The phylogenetic tree based on fimH DNA sequences indicated that AIEC strains predominantly express FimH with amino acid mutations of a recent evolutionary origin - a typical signature of pathoadaptive changes of bacterial pathogens. Point mutations in FimH, some of a unique AIEC-associated nature, confer AIEC bacteria a significantly higher ability to adhere to CEACAM-expressing T84 intestinal epithelial cells. Moreover, in the LF82 strain, the replacement of fimHLF82 (expressing FimH with an AIEC-associated mutation) with fimHK12 (expressing FimH of commensal E. coli K12) decreased the ability of bacteria to persist and to induce severe colitis and gut inflammation in infected CEABAC10 transgenic mice expressing human CEACAM receptors. Our results highlight a mechanism of AIEC virulence evolution that involves selection of amino acid mutations in the common bacterial traits, such as FimH protein, and leads to the development of chronic inflammatory bowel disease (IBD) in a genetically susceptible host. The analysis of fimH SNPs may be a useful method to predict the potential virulence of E. coli isolated from IBD patients for diagnostic or epidemiological studies and to identify new strategies for therapeutic intervention to block the interaction between AIEC and gut mucosa in the early stages of IBD. PMID:23358328

  10. Enhancing the quality of radiographic images acquired with point-like gamma-ray sources through correction of the beam divergence and attenuation

    SciTech Connect

    Silvani, M. I.; Almeida, G. L.; Lopes, R. T.

    2014-11-11

    Radiographic images acquired with point-like gamma-ray sources exhibit a desirable low penumbra effects specially when positioned far away from the set object-detector. Such an arrangement frequently is not affordable due to the limited flux provided by a distant source. A closer source, however, has two main drawbacks, namely the degradation of the spatial resolution - as actual sources are only approximately punctual - and the non-homogeneity of the beam hitting the detector, which creates a false attenuation map of the object being inspected. This non-homogeneity is caused by the beam divergence itself and by the different thicknesses traversed the beam even if the object were an homogeneous flat plate. In this work, radiographic images of objects with different geometries, such as flat plates and pipes have undergone a correction of beam divergence and attenuation addressing the experimental verification of the capability and soundness of an algorithm formerly developed to generate and process synthetic images. The impact of other parameters, including source-detector gap, attenuation coefficient, ratio defective-to-main hull thickness and counting statistics have been assessed for specifically tailored test-objects aiming at the evaluation of the ability of the proposed method to deal with different boundary conditions. All experiments have been carried out with an X-ray sensitive Imaging Plate and reactor-produced {sup 198}Au and {sup 165}Dy sources. The results have been compared with other technique showing a better capability to correct the attenuation map of inspected objects unveiling their inner structure otherwise concealed by the poor contrast caused by the beam divergence and attenuation, in particular for those regions far apart from the vertical of the source.

  11. Significantly enhanced critical current density in nano-MgB2 grains rapidly formed at low temperature with homogeneous carbon doping

    NASA Astrophysics Data System (ADS)

    Liu, Yongchang; Lan, Feng; Ma, Zongqing; Chen, Ning; Li, Huijun; Barua, Shaon; Patel, Dipak; Shahriar, M.; Hossain, Al; Acar, S.; Kim, Jung Ho; Xue Dou, Shi

    2015-05-01

    High performance MgB2 bulks using carbon-coated amorphous boron as a boron precursor were fabricated by Cu-activated sintering at low temperature (600 °C, below the Mg melting point). Dense nano-MgB2 grains with a high level of homogeneous carbon doping were formed in these MgB2 samples. This type of microstructure can provide a stronger flux pinning force, together with depressed volatility and oxidation of Mg owing to the low-temperature Cu-activated sintering, leading to a significant improvement of critical current density (Jc) in the as-prepared samples. In particular, the value of Jc for the carbon-coated (Mg1.1B2)Cu0.05 sample prepared here is even above 1 × 105 A cm-2 at 20 K, 2 T. The results herein suggest that the combination of low-temperature Cu-activated sintering and employment of carbon-coated amorphous boron as a precursor could be a promising technique for the industrial production of practical MgB2 bulks or wires with excellent Jc, as the carbon-coated amorphous boron powder can be produced commercially at low cost, while the addition of Cu is very convenient and inexpensive.

  12. Turning Point.

    ERIC Educational Resources Information Center

    Zemsky, Robert, Ed.

    1997-01-01

    This document summarizes roundtable discussions held in November 1996 to address the current condition of higher education, the process of change, and possible joint projects under the new Knight Collaborative group. The group defined the four fundamental steps believed necessary to create a framework for institutional change: (1) establishing a…

  13. The Fabry disease-associated lipid Lyso-Gb3 enhances voltage-gated calcium currents in sensory neurons and causes pain.

    PubMed

    Choi, L; Vernon, J; Kopach, O; Minett, M S; Mills, K; Clayton, P T; Meert, T; Wood, J N

    2015-05-01

    Fabry disease is an X-linked lysosomal storage disorder characterised by accumulation of glycosphingolipids, and accompanied by clinical manifestations, such as cardiac disorders, renal failure, pain and peripheral neuropathy. Globotriaosylsphingosine (lyso-Gb3), a deacylated form of globotriaosylceramide (Gb3), has emerged as a marker of Fabry disease. We investigated the link between Gb3, lyso-Gb3 and pain. Plantar administration of lyso-Gb3 or Gb3 caused mechanical allodynia in healthy mice. In vitro application of 100nM lyso-Gb3 caused uptake of extracellular calcium in 10% of sensory neurons expressing nociceptor markers, rising to 40% of neurons at 1μM, a concentration that may occur in Fabry disease patients. Peak current densities of voltage-dependent Ca(2+) channels were substantially enhanced by application of 1μM lyso-Gb3. These studies suggest a direct role for lyso-Gb3 in the sensitisation of peripheral nociceptive neurons that may provide an opportunity for therapeutic intervention in the treatment of Fabry disease-associated pain. PMID:25697597

  14. Structure, mechanical, and frictional properties of hydrogenated fullerene-like amorphous carbon film prepared by direct current plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Yongfu; Gao, Kaixiong; Zhang, Junyan

    2016-07-01

    In this study, fullerene like carbon (FL-C) is introduced in hydrogenated amorphous carbon (a-C:H) film by employing a direct current plasma enhanced chemical vapor deposition. The film has a low friction and wear, such as 0.011 and 2.3 × 10-9mm3/N m in the N2, and 0.014 and 8.4 × 10-8mm3/N m in the humid air, and high hardness and elasticity (25.8 GPa and 83.1%), to make further engineering applications in practice. It has several nanometers ordered domains consisting of less frequently cross-linked graphitic sheet stacks. We provide new evidences for understanding the reported Raman fit model involving four vibrational frequencies from five, six, and seven C-atom rings of FL-C structures, and discuss the structure evolution before or after friction according to the change in the 1200 cm-1 Raman band intensity caused by five- and seven-carbon rings. Friction inevitably facilitates the transformation of carbon into FL-C nanostructures, namely, the ultra low friction comes from both such structures within the carbon film and the sliding induced at friction interface.

  15. Enhancement of the critical current density by increasing the collective pinning energy in heavy ion irradiated Co-doped BaFe2As2 single crystals

    NASA Astrophysics Data System (ADS)

    Haberkorn, N.; Kim, Jeehoon; Gofryk, K.; Ronning, F.; Sefat, A. S.; Fang, L.; Welp, U.; Kwok, W. K.; Civale, L.

    2015-05-01

    We investigate the effect of heavy ion irradiation (1.4 GeV Pb) on the vortex matter in Ba(Fe0.92Co0.08)2As2 single crystals by superconducting quantum interference device (SQUID) magnetometry. The defects created by the irradiation are discontinuous amorphous tracks, resulting in an effective track density smaller than 25% of the nominal doses. We observe large increases in the critical current density (Jc), ranging from a factor of ∼3 at low magnetic fields to a factor of ∼10 at fields close to 1 T after irradiation with a nominal fluence of BΦ = 3.5 T. From the normalized flux creep rates (S) and the Maley analysis, we determine that the Jc increase can be mainly attributed to a large increment in the pinning energy, from <50 K to ≈500 K, while the glassy exponent μ changes from ∼1.5 to <1. Although the enhancement of Jc is substantial in the entire temperature range and S is strongly suppressed, the artificial pinning landscape induced by the irradiation does not modify significantly the crossover to fast creep in the field-temperature vortex phase diagram.

  16. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  17. Chemokine CCL2 enhances NMDA receptor-mediated excitatory postsynaptic current in rat hippocampal slices-a potential mechanism for HIV-1-associated neuropathy?

    PubMed

    Zhou, Yan; Tang, Hongmei; Xiong, Huangui

    2016-06-01

    Human immunodeficiency virus type 1 (HIV-1)-infected mononuclear phagocytes (brain macrophages and microglial cells) release proinflammatory cytokines and chemokines. Elevated levels of chemokine CC motif ligand 2 (CCL2, known previously as monocyte chemoattractant protein-1) have been detected in serum and cerebrospinal fluid (CSF) of HIV-1-infected individuals and the raised CCL2 in the CSF correlates with HIV-1-associated neurocognitive disorders. To understand how elevated CCL2 induces HIV-1-associated neuropathy, we studied effects of CCL2 on excitatory postsynaptic current (EPSCs) in the CA1 region of rat hippocampal brain slices using whole-cell patch recording techniques. The AMPA receptor (AMPAR)-mediated EPSC (EPSCAMPAR) and N-Methyl-D-aspartate (NMDA) receptor (NMDAR)-mediated EPSCs (EPSCNMDAR) were isolated pharmacologically. Bath application of CCL2 produced a significant enhancement of the amplitudes of EPSCs, EPSCAMPAR and EPSCNMDAR. Further studies revealed that CCL2 potentiated NMDAR subtype NR2A-mediated EPSC (EPSCNR2AR) and NR2B-mediated EPSC (EPSCNR2BR). To determine the site of action, we recorded spontaneous mini EPSCs (mEPSC) before and during bath application of CCL2. Our results showed that CCL2 decreased inter event interval (IEI) and increased the frequency of mEPSCs without change on the amplitude, suggesting a presynaptic site of CCL2 action. CCL2 was also found to injure primary rat hippocampal neuronal cultures and neuronal dendrites in the CA1 region of hippocampal slices. The CCL2-associated neuronal and dendritic injuries were blocked by a specific NMDAR antagonist or by a CCR2 receptor antagonist, indicating that CCL2-associated neural injury was mediated via NMDARs and/or CCR2 receptors. Taken together, these results suggest a potential role CCL2 may play in HIV-1-associated neuropathology. PMID:26968849

  18. Intracellular accumulation of mercury enhances P450 CYP1A1 expression and Cl- currents in cultured shark rectal gland cells.

    PubMed

    Ke, Qingen; Yang, Yinke; Ratner, Martha; Zeind, John; Jiang, Canwen; Forrest, John N; Xiao, Yong-Fu

    2002-04-21

    The effects of acute and subchronic exposure to mercury on the Cl- current (ICl) were investigated in cultured shark rectal gland (SRG) cells. The effects of intracellular accumulation of mercury on cytochrome P450 (P450) were also assessed. Bath perfusion of a cocktail solution containing forskolin, 1-isobutyl-3-methylxanthine, and 8-bromoadenosine monophosphate enhanced ICl. Addition of 10 microM HgCl2 significantly inhibited the cAMP-activated ICl (p < 0.05, n = 11). Intracellular dialysis with ATP gamma S did not prevent the inhibitory effect of mercury on ICl. In contrast, incubation of SRG cells with 10 microM HgCl2 for 48 hrs markedly increased ICl (p < 0.01, n = 12). Dephosphorylation of the channel by intracellular dialysis with phosphatase I and II abolished the mercury-incubated increase in ICl. The P450-mediated metabolite of arachidonic acid, 11,12-epoxyeicosatrienoic acid (11,12-EET), significantly increased ICl. However, application of 11,12-dihydroxyeicosatrienoic acid (11,12-DHT) did not alter ICl. Mercury incubation for 48 hrs did not alter the protein expression of Cl- channels, but caused an induction of CYP1A1 in cultured SRG cells. In addition, co-incubation of SRG cells with mercury and the P450 inhibitor clotrimazole prevented the mercury-incubated increase in ICl. Our results demonstrate that acute and subchronic application of mercury has opposing effects on ICl in cultured SRG cells. The acute effect of mercury on ICl may result from mercury blockade of Cl- channels. The subchronic effect of mercury on ICl may be due to an induction of P450 CYP1A1 and its mediated metabolites, but not due to an over-expression of Cl- channels. PMID:12173417

  19. An enhancement of the threshold current in InGaAsP heterolasers in the process of aging at an elevated temperature

    NASA Astrophysics Data System (ADS)

    Andreeva, R. I.; Kochetkov, A. A.

    1991-02-01

    Data are presented on changes in the threshold current of InGaAsP lasers due to aging at 65 C for up to 30,000 hrs. Results showed a linear increase in the threshold current with aging, indicating that measurements of threshold current can be used as a method for selecting heterolasers with the longest lifetime and for rejecting low-quality lasers.

  20. Single point mutations in the helicase domain of the NS3 protein enhance dengue virus replicative capacity in human monocyte-derived dendritic cells and circumvent the type I interferon response.

    PubMed

    Silveira, G F; Strottmann, D M; de Borba, L; Mansur, D S; Zanchin, N I T; Bordignon, J; dos Santos, C N Duarte

    2016-01-01

    Dengue is the most prevalent arboviral disease worldwide. The outcome of the infection is determined by the interplay of viral and host factors. In the present study, we evaluated the cellular response of human monocyte-derived DCs (mdDCs) infected with recombinant dengue virus type 1 (DV1) strains carrying a single point mutation in the NS3hel protein (L435S or L480S). Both mutated viruses infect and replicate more efficiently and produce more viral progeny in infected mdDCs compared with the parental, non-mutated virus (vBACDV1). Additionally, global gene expression analysis using cDNA microarrays revealed that the mutated DVs induce the up-regulation of the interferon (IFN) signalling and pattern recognition receptor (PRR) canonical pathways in mdDCs. Pronounced production of type I IFN were detected specifically in mdDCs infected with DV1-NS3hel-mutated virus compared with mdDCs infected with the parental virus. In addition, we showed that the type I IFN produced by mdDCs is able to reduce DV1 infection rates, suggesting that cytokine function is effective but not sufficient to mediate viral clearance of DV1-NS3hel-mutated strains. Our results demonstrate that single point mutations in subdomain 2 have important implications for adenosine triphosphatase (ATPase) activity of DV1-NS3hel. Although a direct functional connection between the increased ATPase activity and viral replication still requires further studies, these mutations speed up viral RNA replication and are sufficient to enhance viral replicative capacity in human primary cell infection and circumvent type I IFN activity. This information may have particular relevance for attenuated vaccine protocols designed for DV. PMID:26340409

  1. Syntheses of the current model applications for managing water and needs for experimental data and model improvements to enhance these applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This volume of the Advances in Agricultural Systems Modeling series presents 14 different case studies of model applications to help make the best use of limited water in agriculture. These examples show that models have tremendous potential and value in enhancing site-specific water management for ...

  2. GLAS Spacecraft Pointing Study

    NASA Technical Reports Server (NTRS)

    Born, George H.; Gold, Kenn; Ondrey, Michael; Kubitschek, Dan; Axelrad, Penina; Komjathy, Attila

    1998-01-01

    Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 m of the location of the previous repeat ground track. The satellite will be flown in a repeat orbit of 182 days. Operationally, the required pointing information will be determined on the ground using the nominal ground track, to which pointing is desired, and the current propagated orbit of the satellite as inputs to the roll computation algorithm developed by CCAR. The roll profile will be used to generate a set of fit coefficients which can be uploaded on a daily basis and used by the on-board attitude control system. In addition, an algorithm has been developed for computation of the associated command quaternions which will be necessary when pointing at targets of opportunity. It may be desirable in the future to perform the roll calculation in an autonomous real-time mode on-board the spacecraft. GPS can provide near real-time tracking of the satellite, and the nominal ground track can be stored in the on-board computer. It will be necessary to choose the spacing of this nominal ground track to meet storage requirements in the on-board environment. Several methods for generating the roll profile from a sparse reference ground track are presented.

  3. Strong enhancement of s-wave superconductivity near a quantum critical point of (Ca1-xSrx)3Ir4Sn13 and (Ca1-xSrx)3Rh4Sn13

    NASA Astrophysics Data System (ADS)

    Morenzoni, Elvezio; Biswas, Pabitra; Guguchia, Zurab; Khasanov, Rustem; Chinotti, Manuel; Krieger, Jonas; Li, L.; Wang, Kefeng; Petrovic, Cedomir; Pomjakushina, Ekaterina

    We report microscopic studies by muon spin rotation as a function of pressure of the (Ca1-xSrx)3Ir4Sn13 and (Ca1-xSrx)3Rh4Sn13 cubic compounds, which display superconductivity and a structural phase transition associated with the formation of a charge density wave (CDW). In Ca3Ir4Sn13 we find 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. Similar behavior is found in the other family. In spite of the conventional phonon-mediated BCS character of these weakly correlated 3-4-13 systems, the dependence of the effective superfluid density on the critical temperature put these compounds in the ``Uemura'' plot close to unconventional superconductors. These systems exemplify that conventional BCS superconductors can also display characteristics of unconventional superconductors. Supported by the Swiss National Science Foundation and by the U.S. DOE under Contract No. DE-SC00112704.

  4. Enhancement of critical current density and vortex activation energy in proton-irradiated Co-doped BaFe2As2

    NASA Astrophysics Data System (ADS)

    Taen, Toshihiro; Nakajima, Yasuyuki; Tamegai, Tsuyoshi; Kitamura, Hisashi

    2012-09-01

    The effect of proton irradiation in Ba(Fe0.93Co0.07)2As2 single crystals is reported. We analyze temperature dependence of the current density and normalized flux relaxation rate in the framework of the collective-creep model. The glassy exponent and barrier height for flux creep are directly determined by Maley's method. Our model functions for barrier height and critical current density in the absence of flux creep are explained by the superposition of δTc and δl pinnings. We also approach true critical current density by means of the generalized inversion scheme, and the obtained result is in reasonable agreement with our model function. The proton-irradiation effect on temperature dependence of the current density and normalized relaxation rate can be summarized as doubling of the barrier height at the beginning of flux creep.

  5. Davies Critical Point and Tunneling

    NASA Astrophysics Data System (ADS)

    La, Hoseong

    2012-04-01

    From the point of view of tunneling, the physical meaning of the Davies critical point of a second-order phase transition in the black hole thermodynamics is clarified. At the critical point, the nonthermal contribution vanishes so that the black hole radiation is entirely thermal. It separates two phases: one with radiation enhanced by the nonthermal contribution, the other suppressed by the nonthermal contribution. We show this in both charged and rotating black holes. The phase transition is also analyzed in the cases in which emissions of charges and angular momenta are incorporated.

  6. Dielectric and enhanced pyroelectric properties of (Pb0.325Sr0.675)TiO3 ceramics under direct current bias field

    NASA Astrophysics Data System (ADS)

    Lei, Xiuyun; Dong, Xianlin; Mao, Chaoliang; Chen, Ying; Cao, Fei; Wang, Genshui

    2012-12-01

    (Pb0.325Sr0.675)TiO3 (PST) ceramics were prepared by a traditional solid-state reaction technique. The dielectric and enhanced pyroelectric properties of PST ceramics were investigated under a DC bias field. The dielectric permittivity and dielectric loss of PST ceramics at Curie temperature were 2.97 × 10-4 and 0.006 without DC bias field, respectively. With a DC electric field of 0-500 V/mm, the maximum pyroelectric coefficient and the largest figure of merit (Fd) of PST ceramics were obtained, about 60 × 10-8 C cm-2 K-1 and 26 × 10-5 Pa-1/2, respectively. PST ceramics with such superior electric field enhanced pyroelectric properties have the potential for uncooled focal plane array detectors application.

  7. Teaching English as a Global Language in Smart Classrooms with PowerPoint Presentation

    ERIC Educational Resources Information Center

    Oommen, Abraham

    2012-01-01

    The current study, as part of an ongoing investigation to examine teacher perceptions about the teaching of English as a global language at the tertiary level education, aims at examining learner perceptions about PowerPoint presentations used in English classroom instruction for enhancement and integration of four language skills and effective…

  8. Enhancement of signal-to-noise ratio and phase locking for small inputs by a low-threshold outward current in auditory neurons.

    PubMed

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

    2002-12-15

    Neurons possess multiple voltage-dependent conductances specific for their function. To investigate how low-threshold outward currents improve the detection of small signals in a noisy background, we recorded from gerbil medial superior olivary (MSO) neurons in vitro. MSO neurons responded phasically, with a single spike to a step current injection. When bathed in dendrotoxin (DTX), most cells switched to tonic firing, suggesting that low-threshold potassium currents (I(KLT)) participated in shaping these phasic responses. Neurons 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"). DTX reduced the signal-to-noise ratio (SNR), defined as the ratio of probability to fire in response to the EPSG and the probability to fire spontaneously in response to noise. The reduction was mainly attributable to the increase of spontaneous firing in DTX. The spike-triggered reverse correlation indicated that, for spike generation, the neuron with I(KLT) required faster inward current transients. This narrow temporal integration window contributed to superior phase locking of firing to periodic stimuli before application of DTX. A computer model including Hodgkin-Huxley type conductances for spike generation and for I(KLT) (Rathouz and Trussell, 1998) showed similar response statistics. The dynamic low-threshold outward current increased SNR and the temporal precision of integration of weak subthreshold signals in auditory neurons by suppressing false positives. PMID:12486197

  9. Search for the enhancement of the thermal expansion coefficient of superfluid 4HE Near T_Lambada by a heat current

    NASA Technical Reports Server (NTRS)

    Liu, Y.; Israelsson, U.; Larson, M.

    2001-01-01

    Presentation on the transition in 4He in the presence of a heat current (Q) provides an ideal system for the study of phase transitions under non-equlibrium, dynamical conditions. Many physical properties become nonlinear and Q-dependant near the transition temperature, T_Lambada.

  10. High-field critical current enhancement by irradiation induced correlated and random defects in (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2}

    SciTech Connect

    Kihlstrom, K. J.; Crabtree, G. W.; Fang, L.; Jia, Y.; Shen, B.; Koshelev, A. E.; Welp, U.; Kwok, W.-K.; Kayani, A.; Zhu, S. F.; Wen, H.-H.

    2013-11-11

    Mixed pinning landscapes in superconductors are emerging as an effective strategy to achieve high critical currents in high, applied magnetic fields. Here, we use heavy-ion and proton irradiation to create correlated and point defects to explore the vortex pinning behavior of each and combined constituent defects in the iron-based superconductor Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} and find that the pinning mechanisms are non-additive. The major effect of p-irradiation in mixed pinning landscapes is the generation of field-independent critical currents in very high fields. At 7 T ‖ c and 5 K, the critical current density exceeds 5 MA/cm{sup 2}.

  11. Fast and highly sensitive fiber-enhanced Raman spectroscopic monitoring of molecular H2 and CH4 for point-of-care diagnosis of malabsorption disorders in exhaled human breath.

    PubMed

    Hanf, Stefan; Bögözi, Timea; Keiner, Robert; Frosch, Torsten; Popp, Jürgen

    2015-01-20

    Breath gas analysis is a novel powerful technique for noninvasive, early-stage diagnosis of metabolic disorders or diseases. Molecular hydrogen and methane are biomarkers for colonic fermentation, because of malabsorption of oligosaccharides (e.g., lactose or fructose) and for small intestinal bacterial overgrowth. Recently, the presence of these gases in exhaled breath was also correlated with obesity. Here, we report on the highly selective and sensitive detection of molecular hydrogen and methane within a complex gas mixture (consisting of H2, CH4, N2, O2, and CO2) by means of fiber-enhanced Raman spectroscopy (FERS). An elaborate FERS setup with a microstructured hollow core photonic crystal fiber (HCPCF) provided a highly improved analytical sensitivity. The simultaneous monitoring of H2 with all other gases was achieved by a combination of rotational (H2) and vibrational (other gases) Raman spectroscopy within the limited spectral transmission range of the HCPCF. The HCPCF was combined with an adjustable image-plane aperture pinhole, in order to separate the H2 rotational Raman bands from the silica background signal and improve the sensitivity down to a limit of detection (LOD) of 4.7 ppm (for only 26 fmol H2). The ability to monitor the levels of H2 and CH4 in a positive hydrogen breath test (HBT) was demonstrated. The FERS sensor possesses a high dynamic range (∼5 orders of magnitude) with a fast response time of few seconds and provides great potential for miniaturization. We foresee that this technique will pave the way for fast, noninvasive, and painless point-of-care diagnosis of metabolic diseases in exhaled human breath. PMID:25545503

  12. Enhancer Analysis

    NASA Astrophysics Data System (ADS)

    Uchikawa, Masanori; Takemoto, Tatsuya

    During embryonic development, genes are expressed under a strict spatial and temporal order in cells and tissues. This regulation is governed by regulatory regions in the genome, usually identified as enhancers (Kondoh, 2008). The identification and mapping of a set of enhancers allow clarification of essential regulatory elements involved in the enhancer action and their interacting protein factors. Enhancer analysis also determines upstream signaling cascades that regulate interacting protein factors. If the regulatory regions do not function properly, spatio-temporal order of the gene expression will be disrupted, and this may cause abnormal development and dis eases (Kleinjan & van Heyningen, 2005; Sabherwal et al., 2007). Thus, identifica tion of the regulatory regions provides an important entry point to clarify regulatory mechanisms underlying embryonic development.

  13. Ultrafast demagnetization enhancement in CoFeB/MgO/CoFeB magnetic tunneling junction driven by spin tunneling current

    PubMed Central

    He, Wei; Zhu, Tao; Zhang, Xiang-Qun; Yang, Hai-Tao; Cheng, Zhao-Hua

    2013-01-01

    The laser-induced ultrafast demagnetization of CoFeB/MgO/CoFeB magnetic tunneling junction is exploited by time-resolved magneto-optical Kerr effect (TRMOKE) for both the parallel state (P state) and the antiparallel state (AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electrons tunneling current. It opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions. PMID:24097037

  14. Ultrafast demagnetization enhancement in CoFeB/MgO/CoFeB magnetic tunneling junction driven by spin tunneling current.

    PubMed

    He, Wei; Zhu, Tao; Zhang, Xiang-Qun; Yang, Hai-Tao; Cheng, Zhao-Hua

    2013-01-01

    The laser-induced ultrafast demagnetization of CoFeB/MgO/CoFeB magnetic tunneling junction is exploited by time-resolved magneto-optical Kerr effect (TRMOKE) for both the parallel state (P state) and the antiparallel state (AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electrons tunneling current. It opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions. PMID:24097037

  15. Ultrafast demagnetization enhancement in CoFeB/MgO/CoFeB magnetic tunneling junction driven by spin tunneling current

    NASA Astrophysics Data System (ADS)

    He, Wei; Zhu, Tao; Zhang, Xiang-Qun; Yang, Hai-Tao; Cheng, Zhao-Hua

    2013-10-01

    The laser-induced ultrafast demagnetization of CoFeB/MgO/CoFeB magnetic tunneling junction is exploited by time-resolved magneto-optical Kerr effect (TRMOKE) for both the parallel state (P state) and the antiparallel state (AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electrons tunneling current. It opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions.

  16. Mutual enhancement of the current density and the coulombic efficiency for a bioanode by entrapping bi-enzymes with Os-complex modified electrodeposition paints.

    PubMed

    Shao, Minling; Zafar, Muhammad Nadeem; Sygmund, Christoph; Guschin, Dmitrii A; Ludwig, Roland; Peterbauer, Clemens K; Schuhmann, Wolfgang; Gorton, Lo

    2013-02-15

    A bioanode with high current density and coulombic efficiency was developed by co-immobilization of pyranose dehydrogenase from Agaricus meleagris (AmPDH) with the dehydrogenase domain of cellobiose dehydrogenase from Corynascus thermophiles (recDHCtCDH) expressed recombinantly in Escherichia coli. The two enzymes were entrapped in Os-complex modified electrodeposition polymers (Os-EDPs) with specifically adapted redox potential by means of chemical co-deposition. AmPDH oxidizes glucose at both the C2 and C3 positions whereas recDHCtCDH oxidizes glucose only at the C1 position. Electrochemical measurements reveal that maximally 6 electrons can be harvested from one glucose molecule at the two-enzyme anode via a cascade reaction, as AmPDH oxidizes the products formed from of the recDHCtCDH catalyzed substrate oxidation and vice versa. Furthermore, a significant increase in current density can be obtained by combining AmPDH and recDHCtCDH in a single modified electrode. We propose the use of this bioanode in biofuel cells with increased current density and coulombic efficiency. PMID:22959203

  17. The study of tropospheric ozone column enhancements over North America using a regional model and the current versions of the Aura satelite data

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Cunnold, D.; Choi, Y.; Wang, Y.

    2008-05-01

    A new set of tropospheric ozone columns (TCOs) is being computed from the difference between the Aura Ozone Monitoring Instrument (OMI) total ozone retrieved using Differential Optical Absorption Spectroscopy (DOAS) algorithm (level 2 collection 3) and the Aura Microwave Limb Sounding (MLS) measurements of stratospheric ozone (version 2.2). Previous comparisons of earlier version of OMI/MLS against ozonesonde measurements showed considerable variability in the differences (Yang et al., 2007). Similar comparisons have been made using the newer version of OMI/MLS TCOs and ozonesonde measurements from the Intercontinental Chemical Transport Experiment (Intex) Ozonesonde Network Study (IONS) campaign in spring and summer, 2006. These ozonesonde measurements possess the advantage that they are closer in times and locations to the MLS measurements. A spring time ozone enhancement event over North America in spring, 2005 has been revisited using the updated versions of OMI/MLS TCOs, a 3-D Regional chEmical trAnsport Model (REAM), and the Tropospheric Emission Spectrometer (TES) measurements. The high ozone concentration in mid- and lower- troposphere over the west coast of California was concluded to have been under the influence of cross-Pacific transport in spring, 2005 while the high ozone concentration in the upper troposphere over the west coast of California and the high TCOs over the Baja peninsula (Mexico) were associated with a stratospheric intrusion through a deep Rossby wave breaking event. The correlation between REAM TCOs and the surface ozone from Environmental Protection Agency ground network measurements suggest that the TCO enhancement over the west coast was associated with an increase of surface ozone. Correlations with geopotential height, wind fields, and tropopause height suggest that TCO enhancement was best characterized during the studied spring period by geopotential height decreases on the 500 mb surface. Comparisons are being made against TCO

  18. Pyroelectric response mechanism of barium strontium titanate ceramics in dielectric bolometer mode: The underlying essence of the enhancing effect of direct current bias field

    SciTech Connect

    Mao, Chaoliang; Cao, Sheng; Yan, Shiguang; Yao, Chunhua; Cao, Fei; Wang, Genshui; Dong, Xianlin; Hu, Xu; Yang, Chunli

    2013-06-17

    Pyroelectric response mechanism of Ba{sub 0.70}Sr{sub 0.30}TiO{sub 3} ceramics under dielectric bolometer (DB) mode was investigated by dielectric and pyroelectric properties measurement. The variations of total, intrinsic, and induced pyroelectric coefficients (p{sub tot}, p{sub int}, p{sub ind}) with temperatures and bias fields were analyzed. p{sub int} plays the dominant role to p{sub tot} through most of the temperature range and p{sub ind} will be slightly higher than p{sub int} above T{sub 0}. The essence of the enhancing effect of DC bias field on pyroelectric coefficient can be attributed to the high value of p{sub int}. This mechanism is useful for the pyroelectric materials (DB mode) applications.

  19. A study of enhancing critical current densities (J(sub c)) and critical temperature (T(sub c)) of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Vlasse, Marcus

    1992-01-01

    The development of pure phase 123 and Bi-based 2223 superconductors has been optimized. The pre-heat processing appears to be a very important parameter in achieving optimal physical properties. The synthesis of pure phases in the Bi-based system involves effects due to oxygen partial pressure, time, and temperature. Orientation/melt-sintering effects include the extreme c-axis orientation of Yttrium 123 and Bismuth 2223, 2212, and 2201 phases. This orientation is conductive to increasing critical currents. A procedure was established to substitute Sr for Ba in Y-123 single crystals.

  20. High-Performance Reaction Wheel Optimization for Fine-Pointing Space Platforms: Minimizing Induced Vibration Effects on Jitter Performance plus Lessons Learned from Hubble Space Telescope for Current and Future Spacecraft Applications

    NASA Technical Reports Server (NTRS)

    Hasha, Martin D.

    2016-01-01

    The Hubble Space Telescope (HST) applies large-diameter optics (2.5-m primary mirror) for diffraction-limited resolution spanning an extended wavelength range (approx. 100-2500 nm). Its Pointing Control System (PCS) Reaction Wheel Assemblies (RWAs), in the Support Systems Module (SSM), acquired an unprecedented set of high-sensitivity Induced Vibration (IV) data for 5 flight-certified RWAs: dwelling at set rotation rates. Focused on 4 key ratios, force and moment harmonic values (in 3 local principal directions) are extracted in the RWA operating range (0-3000 RPM). The IV test data, obtained under ambient lab conditions, are investigated in detail, evaluated, compiled, and curve-fitted; variational trends, core causes, and unforeseen anomalies are addressed. In aggregate, these values constitute a statistically-valid basis to quantify ground test-to-test variations and facilitate extrapolations to on-orbit conditions. Accumulated knowledge of bearing-rotor vibrational sources, corresponding harmonic contributions, and salient elements of IV key variability factors are discussed. An evolved methodology is presented for absolute assessments and relative comparisons of macro-level IV signal magnitude due to micro-level construction-assembly geometric details/imperfections stemming from both electrical drive and primary bearing design parameters. Based upon studies of same-size/similar-design momentum wheels' IV changes, upper estimates due to transitions from ground tests to orbital conditions are derived. Recommended HST RWA choices are discussed relative to system optimization/tradeoffs of Line-Of-Sight (LOS) vector-pointing focal-plane error driven by higher IV transmissibilities through low-damped structural dynamics that stimulate optical elements. Unique analytical disturbance results for orbital HST accelerations are described applicable to microgravity efforts. Conclusions, lessons learned, historical context/insights, and perspectives on future applications

  1. Does Powerpoint enhance learning?

    PubMed

    Penciner, Rick

    2013-03-01

    The ubiquitous nature of PowerPoint begs the question, does PowerPoint enhance learning? This narrative explores the evidence for the effectiveness of PowerPoint and multimedia presentations in learning and information processing. Practical recommendations are provided for presentations. PMID:23458142

  2. Current sensor

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-01-16

    A current sensor is described that uses a plurality of magnetic field sensors positioned around a current carrying conductor. The sensor can be hinged to allow clamping to a conductor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging.

  3. Enhancement of critical current density in a Ca0.85La0.15Fe(As0.92Sb0.08)2 superconductor with T c = 47 K through 3 MeV proton irradiation

    NASA Astrophysics Data System (ADS)

    Park, Akiyoshi; Mine, Akinori; Yamada, Tatsuhiro; Ohtake, Fumiaki; Akiyama, Hiroki; Sun, Yue; Pyon, Sunseng; Tamegai, Tsuyoshi; Kitahama, Yutaka; Mizukami, Tasuku; Kudo, Kazutaka; Nohara, Minoru; Kitamura, Hisashi

    2016-05-01

    We examine the critical current density (J c) of Ca{}1-xLa x Fe(As{}1-ySb y )2, a 112-type iron-based superconductor (IBS) with {T}{{c}} = 47 K, via magneto-optical imaging and magnetization measurements. We assert that the large self-field J c of 2.2× {10}6 A cm- 2 at 2 K is a strong indication that it is a bulk superconductor with spatially homogeneous superconductivity. A 2.8-fold enhancement in J c to 6.2× {10}6 A cm- 2 was achieved through artificially engineering pinning centers by irradiating 3 MeV protons with a total dosage of 1.0× {10}16 {{cm}}-2. The results not only demonstrate the potential of 112-type IBSs for application but also enrich the current understanding of the role of artificial defects in IBSs.

  4. Enhancement in current density and energy conversion efficiency of 3-dimensional MFC anodes using pre-enriched consortium and continuous supply of electron donors

    SciTech Connect

    Borole, Abhijeet P; Hamilton, Choo Yieng; Vishnivetskaya, Tatiana A

    2011-01-01

    Using a pre-enriched microbial consortium as the inoculum and continuous supply of carbon source, improvement in performance of a three-dimensional, flow-through MFC anode utilizing ferricyanide cathode was investigated. The power density increased from 170 W/m3 (1800 mW/m2) to 580 W/m3 (6130 mW/m2), when the carbon loading increased from 2.5 g/l-day to 50 g/l-day. The coulombic efficiency (CE) decreased from 90% to 23% with increasing carbon loading. The CEs are among the highest reported for glucose and lactate as the substrate with the maximum current density reaching 15.1 A/m2. This suggests establishment of a very high performance exoelectrogenic microbial consortium at the anode. A maximum energy conversion efficiency of 54% was observed at a loading of 2.5 g/l-day. Biological characterization of the consortium showed presence of Burkholderiales and Rhodocyclales as the dominant members. Imaging of the biofilms revealed thinner biofilms compared to the inoculum MFC, but a 1.9-fold higher power density.

  5. The Photosystem II D1-K238E mutation enhances electrical current production using cyanobacterial thylakoid membranes in a bio-photoelectrochemical cell.

    PubMed

    Larom, Shirley; Kallmann, Dan; Saper, Gadiel; Pinhassi, Roy; Rothschild, Avner; Dotan, Hen; Ankonina, Guy; Schuster, Gadi; Adir, Noam

    2015-10-01

    The conversion of solar energy (SEC) to storable chemical energy by photosynthesis has been performed by photosynthetic organisms, including oxygenic cyanobacteria for over 3 billion years. We have previously shown that crude thylakoid membranes from the cyanobacterium Synechocytis sp. PCC 6803 can reduce the electron transfer (ET) protein cytochrome c even in the presence of the PSII inhibitor DCMU. Mutation of lysine 238 of the Photosystem II D1 protein to glutamic acid increased the cytochrome reduction rates, indicating the possible position of this unknown ET pathway. In this contribution, we show that D1-K238E is rather unique, as other mutations to K238, or to other residues in the same vicinity, are not as successful in cytochrome c reduction. This observation indicates the sensitivity of ET reactions to minor changes. As the next step in obtaining useful SEC from biological material, we describe the use of crude Synechocystis membranes in a bio-photovoltaic cell containing an N-acetyl cysteine-modified gold electrode. We show the production of significant current for prolonged time durations, in the presence of DCMU. Surprisingly, the presence of cytochrome c was not found to be necessary for ET to the bio-voltaic cell. PMID:25588957

  6. Bedrock geologic map of the Spring Valley, West Plains, and parts of the Piedmont and Poplar Bluff 30'x60' quadrangles, Missouri, including the upper Current River and Eleven Point River drainage basins

    USGS Publications Warehouse

    Weary, David J.; Harrison, Richard W.; Orndorff, Randall C.; Weems, Robert E.; Schindler, J. Stephen; Repetski, John E.; Pierce, Herbert A.

    2015-01-01

    Potentially economic mineral resources are present in the subsurface in the map area. Exploration drill-hole data indicate that anomalously high concentrations of base-metal sulfides locally occur within the Cambrian Bonneterre Formation. The geologic setting of these anomalous concentrations is similar to that found in the Viburnum Trend, part of the largest lead-mining district in the world. The southernmost part of the Viburnum Trend extends into the northern part of the map area and is exploited by the Sweetwater Mine. Undeveloped and potentially economic occurrences of base metals are known also beneath Blair Creek, a tributary to the Current River in the north-central part of the map area.

  7. Enhancing the output current of a CdTe solar cell via a CN-free hydrocarbon luminescent down-shifting fluorophore with intramolecular energy transfer and restricted internal rotation characteristics.

    PubMed

    Li, Yilin; Olsen, Joseph; Dong, Wen-Ji

    2015-04-01

    A CN-free hydrocarbon fluorophore (Perylene-TPE) was synthesized as a new luminescent down-shifting (LDS) material. Its photophysical properties in both the solution state and the solid state were studied. The unity fluorescence quantum yield of Perylene-TPE observed in its solid state is considered to be from the characteristics of intramolecular energy transfer (IET) and restricted internal rotation (RIR). This is supported by the results from theoretical calculations and spectroscopic measurements. For the photovoltaic application of Perylene-TPE, a theoretical modeling study suggests that using the LDS film of Perylene-TPE may increase the output short circuit current density (Jsc) of a CdTe solar cell by 2.95%, enhance the spectral response of a CdTe solar cell at 400 nm by 41%, and shift the incident solar photon distribution from short-wavelength (<500 nm) to long-wavelength (>500 nm). Experimentally, placing a LDS film of Perylene-TPE on a CdTe solar cell can enhance its output Jsc by as high as 3.30 ± 0.31%, which is comparable to the current commercially available LDS material – Y083 (3.28% ± 0.37%). PMID:25679960

  8. Do physicians make their articles readable for their blind or low-vision patients? An analysis of current image processing practices in biomedical journals from the point of view of accessibility.

    PubMed

    Splendiani, Bruno; Ribera, Mireia; Garcia, Roberto; Termens, Miquel

    2014-08-01

    Visual content in biomedical academic papers is a growing source of critical information, but it is not always fully readable for people with visual impairments. We aimed to assess current image processing practices, accessibility policies, and submission policies in a sample of 12 highly cited biomedical journals. We manually checked the application of text-based alternative image descriptions for every image in 12 articles (one for each journal). We determined whether the journals claimed to follow an accessibility policy and we reviewed their submission policy and their guidelines related to the visual content. We identified important features concerning the processing of images and the characteristics of the visual and the retrieval options of visual content offered by the publishers. The evaluation shows that the actual practices of textual image description in highly cited biomedical journals do not follow general guidelines on accessibility. The images within the articles analyzed lack alternative descriptions or have uninformative descriptions, even in the case of journals claiming to follow an accessibility policy. Consequently, the visual information of scientific articles is not accessible to people with severe visual disabilities. Instructions on image submission are heterogeneous and a declaration of accessibility guidelines was only found in two thirds of the sample of journals, with one third not explicitly following any accessibility policy, although they are required to by law. PMID:24504831

  9. Floating Point Control Library

    Energy Science and Technology Software Center (ESTSC)

    2007-08-02

    Floating Point Control is a Library that allows for the manipulation of floating point unit exception masking funtions control exceptions in both the Streaming "Single Instruction, Multiple Data" Extension 2 (SSE2) unit and the floating point unit simultaneously. FPC also provides macros to set floating point rounding and precision control.

  10. Myofascial trigger point pain.

    PubMed

    Jaeger, Bernadette

    2013-01-01

    Myofascial trigger point pain is an extremely prevalent cause of persistent pain disorders in all parts of the body, not just the head, neck, and face. Features include deep aching pain in any structure, referred from focally tender points in taut bands of skeletal muscle (the trigger points). Diagnosis depends on accurate palpation with 2-4 kg/cm2 of pressure for 10 to 20 seconds over the suspected trigger point to allow the referred pain pattern to develop. In the head and neck region, cervical muscle trigger points (key trigger points) often incite and perpetuate trigger points (satellite trigger points) and referred pain from masticatory muscles. Management requires identification and control of as many perpetuating factors as possible (posture, body mechanics, psychological stress or depression, poor sleep or nutrition). Trigger point therapies such as spray and stretch or trigger point injections are best used as adjunctive therapy. PMID:24864393

  11. Enhancement of critical currents in (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Bi-2223) superconducting tapes.

    SciTech Connect

    Balachandran, U.

    1998-11-11

    The performance of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Bi-2223) superconducting tapes in magnetic fields at 77 K is critical for winding this material into high-field magnets. We have recently enhanced the transport current (I{sub c}) of multifilament Ag-clad Bi-2223 tapes in a self-field at 77 K by increasing the packing density of the precursor powder improving the mechanical deformation, optimizing the conductor design, and adjusting the cooling rate. I{sub c} values of >40 A were obtained repeatedly. However, a transport current of 42 A in a self-field declined to 4 A in a 0.2 T magnetic field applied parallel to the c-axis at 77 K. A new composite tape was then fabricated in which a YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (Y-123) film was deposited on the top of the Ag-sheathed Bi-2223 tape to shield the applied magnetic field and protect the central Bi-2223 filaments. Magnetization measurements showed that the critical current densities of the Y-123-coated, Ag-sheathed Bi-2223 tapes were higher than those of an uncoated tape. These preliminary results may provide the basis for further improving the processing of long-length Bi-2223 tapes for high-field applications.

  12. Automated detection and location of indications in eddy current signals

    DOEpatents

    Brudnoy, David M.; Oppenlander, Jane E.; Levy, Arthur J.

    2000-01-01

    A computer implemented information extraction process that locates and identifies eddy current signal features in digital point-ordered signals, signals representing data from inspection of test materials, by enhancing the signal features relative to signal noise, detecting features of the signals, verifying the location of the signal features that can be known in advance, and outputting information about the identity and location of all detected signal features.

  13. Automated Detection and Location of Indications in Eddy Current Signals

    SciTech Connect

    Brudnoy, David M.; Oppenlander, Jane E.; Levy, Arthur J.

    1998-06-30

    A computer implemented information extraction process that locates and identifies eddy current signal features in digital point-ordered signals, said signals representing data from inspection of test materials, by enhancing the signal features relative to signal noise, detecting features of the signals, verifying the location of the signal features that can be known in advance, and outputting information about the identity and location of all detected signal features.

  14. Temperature calculations of heat loads in rotating target wheels exposed to high beam currents.

    SciTech Connect

    Greene, J. P.; Gabor, R.; Neubauer, J.

    2000-11-29

    In heavy-ion physics, high beam currents can eventually melt or destroy the target. Tightly focused beams on stationary targets of modest melting point will exhibit short lifetimes. Defocused or wobbled beams are employed to enhance target survival. Rotating targets using large diameter wheels can help overcome target melting and allow for higher beam currents to be used in experiments. The purpose of the calculations in this work is to try and predict the safe maximum beam currents which produce heat loads below the melting point of the target material.

  15. Anatase TiO₂ films with dominant {001} facets fabricated by direct-current reactive magnetron sputtering at room temperature: oxygen defects and enhanced visible-light photocatalytic behaviors.

    PubMed

    Zheng, Jian-Yun; Bao, Shan-Hu; Guo, Yu; Jin, Ping

    2014-04-23

    A TiO2 film with dominant anatase {001} facets is directly prepared by direct-current reactive magnetron sputtering at room temperature without using morphology-controlling agents. The formation mechanism of anatase TiO2 films with dominant {001} facets is explained by the competition between thermodynamics and ion impinging in the deposition process. The crystalline TiO2 film shows a superior photocatalytic efficiency for the degradation of Rhodamine B under UV-visible (λ > 250 nm) lights. Furthermore, a comparable photodegradation of Rhodamine B is also found on the TiO2 film surface by using visible (λ > 420 nm) lights. During film growth, the surface bombarded by high energy of ions yields plenty of oxygen defects, which can enhance the photocatalytic activity of the films irradiated under visible light. PMID:24720367

  16. Current Capabilities and Planned Enhancements of SUSTAIN

    EPA Science Inventory

    Efforts have been under way by the U.S. Environmental Protection Agency (EPA) since 2003 to develop a decision-support system for placement of BMPs at strategic locations in urban watersheds. This system is call the System for Urban Stormwater Treatment and Analysis INtergration...

  17. Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation

    PubMed Central

    2011-01-01

    Active myofascial trigger points are one of the major peripheral pain generators for regional and generalized musculoskeletal pain conditions. Myofascial trigger points are also the targets for acupuncture and/or dry needling therapies. Recent evidence in the understanding of the pathophysiology of myofascial trigger points supports The Integrated Hypothesis for the trigger point formation; however unanswered questions remain. Current evidence shows that spontaneous electrical activity at myofascial trigger point originates from the extrafusal motor endplate. The spontaneous electrical activity represents focal muscle fiber contraction and/or muscle cramp potentials depending on trigger point sensitivity. Local pain and tenderness at myofascial trigger points are largely due to nociceptor sensitization with a lesser contribution from non-nociceptor sensitization. Nociceptor and non-nociceptor sensitization at myofascial trigger points may be part of the process of muscle ischemia associated with sustained focal muscle contraction and/or muscle cramps. Referred pain is dependent on the sensitivity of myofascial trigger points. Active myofascial trigger points may play an important role in the transition from localized pain to generalized pain conditions via the enhanced central sensitization, decreased descending inhibition and dysfunctional motor control strategy. PMID:21439050

  18. Point-to-Point Multicast Communications Protocol

    NASA Technical Reports Server (NTRS)

    Byrd, Gregory T.; Nakano, Russell; Delagi, Bruce A.

    1987-01-01

    This paper describes a protocol to support point-to-point interprocessor communications with multicast. Dynamic, cut-through routing with local flow control is used to provide a high-throughput, low-latency communications path between processors. In addition multicast transmissions are available, in which copies of a packet are sent to multiple destinations using common resources as much as possible. Special packet terminators and selective buffering are introduced to avoid a deadlock during multicasts. A simulated implementation of the protocol is also described.

  19. Keeping Science Current.

    ERIC Educational Resources Information Center

    Timmerman, Barbara

    2002-01-01

    Points out old-dated information provided in textbooks and recommends using current events to close the knowledge gap between the real world and textbooks. Uses year-long journal writings in which students choose a science article and analyze it. Provides an example of the activity sheet. (YDS)

  20. Magnetic Null Points in Kinetic Simulations of Space Plasmas

    NASA Astrophysics Data System (ADS)

    Olshevsky, Vyacheslav; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni

    2016-03-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind, and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3-9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their cross sections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data.

  1. Development of POINTS as a planetology instrument

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.

    1994-01-01

    During the reporting period, we carried out investigations required to enhance our design of POINTS as a tool for the search for and characterization of extra-solar planetary systems. The results of that work were included in a paper on POINTS as well as one on Newcomb, which will soon appear in the proceedings of SPIE Conference 2200. (Newcomb is a spinoff of POINTS. It is a small astrometric interferometer now being developed jointly by SAO and the U.S. Navy. It could help establish some of the technology needed for POINTS.) These papers are appended.

  2. Point by Point: Adding up Motivation

    ERIC Educational Resources Information Center

    Marchionda, Denise

    2010-01-01

    Students often view their course grades as a mysterious equation of teacher-given grades, teacher-given grace, and some other ethereal components based on luck. However, giving students the power to earn points based on numerous daily/weekly assignments and attendance makes the grading process objective and personal, freeing the instructor to…

  3. Splitting the Cartesian point

    SciTech Connect

    Blodwell, J.F.

    1987-10-01

    It is argued that the point structure of space and time must be constructed from the primitive extensional character of space and time. A procedure for doing this is laid down and applied to one-dimensional and two-dimensional systems of abstract extensions. Topological and metrical properties of the constructed point systems, which differ nontrivially from the usual R and R/sup 2/ models, are examined. Briefly, constructed points are associated with directions and the Cartesian point is split. In one-dimension each point splits into a point pair compatible with the linear ordering. An application to one-dimensional particle motion is given, with the result that natural topological assumptions force the number of left point, right point transitions to remain locally finite in a continuous motion. In general, Cartesian points are seen to correspond to certain filters on a suitable Boolean algebra. Constructed points correspond to ultrafilters. Thus, point construction gives a natural refinement of the Cartesian systems.

  4. The magnetohydrodynamics of current sheets

    NASA Technical Reports Server (NTRS)

    Priest, E. R.

    1985-01-01

    Examples of current sheets are summarized and their formation is described. A universal phenomenon in cosmic plasmas is the creation of sheets off intense current near X-type neutral points (where the magnetic field vanishes). These sheets are important as sites where the magnetic-field energy is converted efficiently into heat and bulk kinetic energy and where particles can be accelerated to high energies. Examples include disruptions in laboratory tokamaks, substorms in the earth's magnetosphere, and flares on the sun. The basic behavior of a one-dimensional sheet is presented, together with an account of the linear tearing-mode instability that can cause the field lines in such a sheet to reconnect. Such reconnection may develop in different ways: it may arise from a spontaneous instability or it may be driven, either from outside by motions or locally by a resistivity enhancement. Various processes are described that may occur during the nonlinear development of tearing, along with the many numerical and laboratory experiments that are aiding our understanding of this intriguing cosmical process.

  5. Current research on fatigue cracks

    SciTech Connect

    Tanaka, T.; Jono, M.; Komai, K.

    1987-01-01

    This first volume of CJMR (Current Japanese Materials Research), contains thirteen chapters concerning the above three themes of fatigue cracks. Each chapter is not a single paper as appearing in many academic journals and transactions, but a systematic review of the current achievement by each author with the emphasis on important points. The common feature is that the elaborated experimental techniques and theoretical approaches, some of which are quite unique, are introduced by respective authors to make clear the difficulty arising in the observation of small cracks and analysis of data. Theoretical models are proposed from the viewpoint of fracture mechanics to link the two thresholds of fatigue limit and crack growth, and intensive discussions are made for further development of the theory. Threshold stress intensity factors and the growth rate of medium and long sized cracks are also discussed, together with their opening behavior. The influencing factors are plastic zone size, the stress ratio and residual stress distribution occurring in welded joints. Mode II crack growth is of great significance since the initial fatigue cracks propagate mainly in shear mode. The problems of fatigue crack growth in corrosive environment is highly important since its retardation and enhancement take place in structural steels affected by the variety of factors. Life prediction in such environments poses another important problem. These are systematically discussed in this book.

  6. Optical vs. electronic enhancement of remote sensing imagery

    NASA Technical Reports Server (NTRS)

    Colwell, R. N.; Katibah, E. F.

    1976-01-01

    Basic aspects of remote sensing are considered and a description is provided of the methods which are employed in connection with the optical or electronic enhancement of remote sensing imagery. The advantages and limitations of various image enhancement methods and techniques are evaluated. It is pointed out that optical enhancement methods and techniques are currently superior to electronic ones with respect to spatial resolution and equipment cost considerations. Advantages of electronic procedures, on the other hand, are related to a greater flexibility regarding the presentation of the information as an aid for the interpretation by the image analyst.

  7. Current-wave spectra coupling project. Volume III. Cumulative distribution of forces on structures subjected to the combined action of currents and random waves for potential OTEC sites: (A) Keahole Point, Hawaii, 100 year hurricane; (B) Punta Tuna, Puerto Rico, 100 year hurricane; (C) New Orleans, Louisiana, 100 year hurricane; (D) West Coast of Florida, 100 year hurricane. [CUFOR code

    SciTech Connect

    Venezian, G.; Bretschneider, C.L.

    1980-08-01

    This volume details a new methodology to analyze statistically the forces experienced by a structure at sea. Conventionally a wave climate is defined using a spectral function. The wave climate is described using a joint distribution of wave heights and periods (wave lengths), characterizing actual sea conditions through some measured or estimated parameters like the significant wave height, maximum spectral density, etc. Random wave heights and periods satisfying the joint distribution are then generated. Wave kinetics are obtained using linear or non-linear theory. In the case of currents a linear wave-current interaction theory of Venezian (1979) is used. The peak force experienced by the structure for each individual wave is identified. Finally, the probability of exceedance of any given peak force on the structure may be obtained. A three-parameter Longuet-Higgins type joint distribution of wave heights and periods is discussed in detail. This joint distribution was used to model sea conditions at four potential OTEC locations. A uniform cylindrical pipe of 3 m diameter, extending to a depth of 550 m was used as a sample structure. Wave-current interactions were included and forces computed using Morison's equation. The drag and virtual mass coefficients were interpolated from published data. A Fortran program CUFOR was written to execute the above procedure. Tabulated and graphic results of peak forces experienced by the structure, for each location, are presented. A listing of CUFOR is included. Considerable flexibility of structural definition has been incorporated. The program can easily be modified in the case of an alternative joint distribution or for inclusion of effects like non-linearity of waves, transverse forces and diffraction.

  8. High performance of PbSe/PbS core/shell quantum dot heterojunction solar cells: short circuit current enhancement without the loss of open circuit voltage by shell thickness control

    NASA Astrophysics Data System (ADS)

    Choi, Hyekyoung; Song, Jung Hoon; Jang, Jihoon; Mai, Xuan Dung; Kim, Sungwoo; Jeong, Sohee

    2015-10-01

    We fabricated heterojunction solar cells with PbSe/PbS core shell quantum dots and studied the precisely controlled PbS shell thickness dependency in terms of optical properties, electronic structure, and solar cell performances. When the PbS shell thickness increases, the short circuit current density (JSC) increases from 6.4 to 11.8 mA cm-2 and the fill factor (FF) enhances from 30 to 49% while the open circuit voltage (VOC) remains unchanged at 0.46 V even with the decreased effective band gap. We found that the Fermi level and the valence band maximum level remain unchanged in both the PbSe core and PbSe/PbS core/shell with a less than 1 nm thick PbS shell as probed via ultraviolet photoelectron spectroscopy (UPS). The PbS shell reduces their surface trap density as confirmed by relative quantum yield measurements. Consequently, PbS shell formation on the PbSe core mitigates the trade-off relationship between the open circuit voltage and the short circuit current density. Finally, under the optimized conditions, the PbSe core with a 0.9 nm thick shell yielded a power conversion efficiency of 6.5% under AM 1.5.We fabricated heterojunction solar cells with PbSe/PbS core shell quantum dots and studied the precisely controlled PbS shell thickness dependency in terms of optical properties, electronic structure, and solar cell performances. When the PbS shell thickness increases, the short circuit current density (JSC) increases from 6.4 to 11.8 mA cm-2 and the fill factor (FF) enhances from 30 to 49% while the open circuit voltage (VOC) remains unchanged at 0.46 V even with the decreased effective band gap. We found that the Fermi level and the valence band maximum level remain unchanged in both the PbSe core and PbSe/PbS core/shell with a less than 1 nm thick PbS shell as probed via ultraviolet photoelectron spectroscopy (UPS). The PbS shell reduces their surface trap density as confirmed by relative quantum yield measurements. Consequently, PbS shell formation on

  9. Nickel Curie Point Engine

    ERIC Educational Resources Information Center

    Chiaverina, Chris; Lisensky, George

    2014-01-01

    Ferromagnetic materials such as nickel, iron, or cobalt lose the electron alignment that makes them attracted to a magnet when sufficient thermal energy is added. The temperature at which this change occurs is called the "Curie temperature," or "Curie point." Nickel has a Curie point of 627 K, so a candle flame is a sufficient…

  10. Torsade de pointes.

    PubMed

    Munro, P T; Graham, C A

    2002-09-01

    A case is described of torsade de pointes in a 41 year old woman with pre-existing QTc prolongation, potentially exacerbated by treatment with sotalol. Previous cardiac investigations had been normal and after a second episode of ventricular fibrillation the patient was referred for electrophysiological studies. The authors review the physiology, causes, and treatment of QTc prolongation and torsade de pointes. PMID:12205024

  11. Sensing with Superconducting Point Contacts

    PubMed Central

    Nurbawono, Argo; Zhang, Chun

    2012-01-01

    Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors. PMID:22778630

  12. Gravity Currents

    NASA Astrophysics Data System (ADS)

    Simpson, John E.

    1997-03-01

    This book comprehensively describes all aspects of gravity flow, a physical process in the environment that is covered by many disciplines including meteorology, oceanography, the earth sciences and industrial processes. The first edition was very well received, and the author has brought the new edition completely up to date, with much new material. Simpson describes gravity currents with a variety of laboratory experiments, many from his own work. Gravity Currents is a valuable supplementary textbook for undergraduates and a reference work for research workers. The general reader will also find much of interest, since the author clearly describes the physics of flows involved without advanced mathematics, and with numerous photographs and illustrations.

  13. Gravity Currents

    NASA Astrophysics Data System (ADS)

    Simpson, John E.

    1999-11-01

    This book comprehensively describes all aspects of gravity flow, a physical process in the environment that is covered by many disciplines including meteorology, oceanography, the earth sciences and industrial processes. The first edition was very well received, and the author has brought the new edition completely up to date, with much new material. Simpson describes gravity currents with a variety of laboratory experiments, many from his own work. Gravity Currents is a valuable supplementary textbook for undergraduates and a reference work for research workers. The general reader will also find much of interest, since the author clearly describes the physics of flows involved without advanced mathematics, and with numerous photographs and illustrations.

  14. The Galileo scan platform pointing control system - A modern control theoretic viewpoint

    NASA Astrophysics Data System (ADS)

    Sevaston, G. E.; Macala, G. A.; Man, G. K.

    The current Galileo scan platform pointing control system (SPPCS) is described, and ways in which modern control concepts could serve to enhance it are considered. Of particular interest are: the multi-variable design model and overall control system architecture, command input filtering, feedback compensator and command input design, stability robustness constraint for both continuous time control systems and for sampled data control systems, and digital implementation of the control system. The proposed approach leads to the design of a system that is similar to current Galileo SPPCS configuration, but promises to be more systematic.

  15. Feedback cooling of currents

    NASA Astrophysics Data System (ADS)

    Washburn, Sean

    1989-02-01

    Just as feedback can be used to correct errors in the output voltages of amplifiers, it can also be used to remove noise from the current through a resistor. Such a feedback amplifier behaves as a refrigerator cooling the electrons in a resistor connnected to it. This principle has been recognized since the 1940s but has been largely ignored because the cooling power available from such refrigerators is miniscule. It is pointed out here that the method might be practical for cooling the currents in the microscopic circuits that are typical of modern electrical engineering and recent studies in transport physics.

  16. Current Titles

    SciTech Connect

    Various

    2006-06-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

  17. Point tenderness - abdomen

    MedlinePlus

    ... medlineplus.gov/ency/article/003273.htm Point tenderness - abdomen To use the sharing features on this page, ... over a certain part of the belly area (abdomen). Considerations The abdomen is an area of the ...

  18. Triple Point Topological Metals

    NASA Astrophysics Data System (ADS)

    Zhu, Ziming; Winkler, Georg W.; Wu, QuanSheng; Li, Ju; Soluyanov, Alexey A.

    2016-07-01

    Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here, we report on a new type of topological quasiparticles—triple point fermions—realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies, and topological Lifshitz transitions.

  19. Nickel Curie point engine

    NASA Astrophysics Data System (ADS)

    Chiaverina, Chris; Lisensky, George

    2014-04-01

    Ferromagnetic materials such as nickel, iron, or cobalt lose the electron alignment that makes them attracted to a magnet when sufficient thermal energy is added. The temperature at which this change occurs is called the "Curie temperature," or "Curie point." Nickel has a Curie point of 627 K, so a candle flame is a sufficient heat source. A simple but elegant device illustrates this phenomenon beautifully.

  20. Bloch points are sticky

    NASA Astrophysics Data System (ADS)

    Tchernyshyov, Oleg; Kim, Se Kwon

    2014-03-01

    Bloch points are zero-dimensional topological defects in three-dimensional ferromagnets. A representative magnetic configuration is a hedgehog with magnetization pointing away from a center. The singular nature of a Bloch point's core leads to interesting and observable consequences. A simple argument based on dimensional analysis shows that a magnetic lattice creates a periodic potential that can pin a Bloch point even if the lattice has no defects. The pinning force is of the order of the micromagnetic exchange constant, a few piconewtons in a typical ferromagnet. A domain wall in a cylindrical ferromagnetic wire with the diameter of a few tens of nanometers may contain a Bloch point. Such a domain wall will have a sizable depinning field, tens of oersteds. A Bloch point moving through an atomic lattice should emit electromagnetic waves at the frequency of a few hundred gigahertz. Research supported in part by the U.S. National Science Foundation under Grants No. DMR-0520491 and No. DMR-1104753.