Science.gov

Sample records for aggregate generational current

  1. Continental aggregation, subduction initiation, and plume generation

    NASA Astrophysics Data System (ADS)

    Heron, P. J.; Lowman, J. P.

    2013-12-01

    Several processes unfold during the supercontinent cycle, more than one of which might result in an elevation in subcontinental mantle temperatures through the generation of mantle plumes. Paleogeographic plate reconstructions have indicated that sub-continental mantle upwellings appear below large continents that are extensively ringed by subduction zones. Moreover, several numerical simulations of supercontinent formation and dispersal attribute the genesis of sub-continental plumes to the generation of subduction zones on the edges of the supercontinent, rather than resulting from continental insulation. However, the role of the location of downwellings in producing a return-flow upwelling, and on increasing sub-continental mantle temperatures, is not fully understood. In this mantle convection study, we examine the evolution of mantle dynamics after supercontinent accretion over a subduction zone (analogous to the formation of Pangea) for a range of continental coverage. We present 2D and 3D Cartesian geometry mantle convection simulations, featuring geotherm- and pressure-dependent viscosity with thermally and mechanically distinct oceanic and continental plates. Through changing the size of the continent we are able to analyze the factors involved in the generation of mantle plumes in purely thermal convection. Furthermore, we change the upper and lower mantle viscosity to determine their relation to plume formation in vigorous mantle convection simulations. Elevated sub-continental temperatures are analyzed in relation to continental coverage to further understand the influence of continental tectonics on the thermal evolution of the mantle.

  2. Underwater slow current turbo generator

    SciTech Connect

    Wracsaricht, L.J.

    1981-12-15

    A self-contained electrical generating device for placement in a naturally flowing stream. The generating device converts the kinetic energy generated by fluid flow or gravity contained within the flowing stream whether river or ocean current into useful electric energy using blade configuration and placement to maximize the usable energy. The present invention also using auxiliary means to increase the rate of flow of the fluid by the blades of the generator thus increasing the energy capable of conversion. The rotor and the stator are located radially outwardly from the rotating hub of the generating system and are supported by spoke like legs thus greatly reducing any resistance to water flow, minimizing the disturbance to the flowing stream and maximizing the relative linear velocity between the rotor and the stator.

  3. Current responsive devices for synchronous generators

    DOEpatents

    Karlicek, Robert F.

    1983-01-01

    A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current.

  4. Current responsive devices for synchronous generators

    DOEpatents

    Karlicek, R.F.

    1983-09-27

    A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current. 11 figs.

  5. 40 CFR 279.32 - Used oil aggregation points owned by the generator.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Collection Centers and Aggregation Points § 279.32 Used oil aggregation points owned by the generator. (a... aggregation points must comply with the generator standards in subpart C of this part....

  6. 40 CFR 279.32 - Used oil aggregation points owned by the generator.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Collection Centers and Aggregation Points § 279.32 Used oil aggregation points owned by the generator. (a... aggregation points must comply with the generator standards in subpart C of this part....

  7. 40 CFR 279.32 - Used oil aggregation points owned by the generator.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Collection Centers and Aggregation Points § 279.32 Used oil aggregation points owned by the generator. (a... aggregation points must comply with the generator standards in subpart C of this part....

  8. 40 CFR 279.32 - Used oil aggregation points owned by the generator.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Collection Centers and Aggregation Points § 279.32 Used oil aggregation points owned by the generator. (a... aggregation points must comply with the generator standards in subpart C of this part....

  9. 40 CFR 279.32 - Used oil aggregation points owned by the generator.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Collection Centers and Aggregation Points § 279.32 Used oil aggregation points owned by the generator. (a... aggregation points must comply with the generator standards in subpart C of this part....

  10. What is the role of pyroclastic density currents in volcanic ash aggregation? Perspectives from a phreatoplinian eruption deposit, New Zealand

    NASA Astrophysics Data System (ADS)

    Van Eaton, A. R.; Wilson, C. J.

    2012-12-01

    This study documents the processes and products of volcanic ash aggregation within individual phases of the 25.4 ka Oruanui super-eruption from Taupo volcano, New Zealand. Textural and stratigraphic relationships of aggregates are examined in seven of the ten erupted units, which range from relatively dry styles of eruption and deposition (fall units 2, 5) to mixed (units 6, 7, 8) and dominantly wet (unit 3). Aggregate structures and grain size distributions shift abruptly over vertical scales of cm to dm within and between eruptive units, providing diagnostic features that identify deposits emplaced as vertical fallout or pyroclastic density currents (PDCs). The six categories of ash aggregates documented here are used to infer distinct volcanic and meteorological interactions in the eruption cloud related to dispersal characteristics and mode of emplacement. Our field observations support the notion that deposits bearing matrix-supported accretionary lapilli with complex internal layering and abundant rim fragments are associated with emplacement of PDCs. However, on the basis of grain size distributions and field relationships, it is inferred that these types of ash aggregates formed their ultrafine (<10 μm ash) outer layers in the overriding fine ash cloud elutriated from PDCs, not during transport within the basal portion of ground-hugging currents. The propagation of voluminous PDCs beneath an overriding buoyant plume - whether coignimbrite or vent-derived in origin - is proposed to generate the observed, concentrically layered accretionary lapilli by producing wedge-like updrafts of convectively unstable, ash-laden air. The apparent coarsening of mean grain size with distance from source, which is observed in the aggregate-bearing fall deposits, reflects a combination of multi-level plume transport and preferential scavenging of fine ash <250 μm. Proximal fallout and melting of ice in the clouds was likely to have contributed a key source of liquid water

  11. Stray currents -- Generation, interference effects and control

    SciTech Connect

    Nikolakakos, S.

    1998-12-31

    Stray currents, mostly known for their detrimental corrosion affects on the underground structures, can be effectively controlled by the implementation of specific measures at both the source of generation and at the affected structure(s). This paper discusses the most serious sources of stray current generation, the resulting problems and the numerous control methods that can be utilized to minimize corrosion and safety problems. Safety concerns associated with dc power systems are also discussed.

  12. Alternative generation of spin current in graphene

    NASA Astrophysics Data System (ADS)

    Yoo, Jung-Woo; Jin, Mi-Jin; Park, Jungmin; Modepalli, Vijayakumar; Jo, Jun-Hyeon

    2014-03-01

    The manipulation of spin current which can be achieved in various device configurations has been under intense research in recent years. The spin current is typically obtained by injecting electrons from the ferromagnetic electrodes. In this study, we employed alternative methods for the generation of spin current in graphene. The first method we studied is using spin Hall effect. In the spin Hall effect, the charge current generates spin current due to a relativistic spin-orbit coupling. Generally the spin-orbit coupling in graphene is extremely weak to produce substantial spin current. We employed physical doping of heavy atoms on top of the graphene layer for the spin Hall induced spin current in graphene. The second alternative method we investigated is seebeck spin tunneling. The ferromagnetic electrode together with thin tunnel barrier (1-3nm of Al2O3 layer) was employed to introduce thermally induced spin imbalance in graphene. The gate dependence of generated spin current reflects unique electronic structure of graphene. This work was supported in part by future challenge project of UNIST and Basic Science Research Program of NRF Korea.

  13. A compact submicrosecond, high current generator

    NASA Astrophysics Data System (ADS)

    Kovalchuk, B. M.; Kharlov, A. V.; Zorin, V. B.; Zherlitsyn, A. A.

    2009-08-01

    Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6 Ω damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (˜0.08 Ω). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70-100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70-100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24×1.2×0.18 m3 and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus.

  14. High current high accuracy IGBT pulse generator

    SciTech Connect

    Nesterov, V.V.; Donaldson, A.R.

    1995-05-01

    A solid state pulse generator capable of delivering high current triangular or trapezoidal pulses into an inductive load has been developed at SLAC. Energy stored in a capacitor bank of the pulse generator is switched to the load through a pair of insulated gate bipolar transistors (IGBT). The circuit can then recover the remaining energy and transfer it back to the capacitor bank without reversing the capacitor voltage. A third IGBT device is employed to control the initial charge to the capacitor bank, a command charging technique, and to compensate for pulse to pulse power losses. The rack mounted pulse generator contains a 525 {mu}F capacitor bank. It can deliver 500 A at 900V into inductive loads up to 3 mH. The current amplitude and discharge time are controlled to 0.02% accuracy by a precision controller through the SLAC central computer system. This pulse generator drives a series pair of extraction dipoles.

  15. Recombination-generation currents in degenerate semiconductors

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1978-01-01

    The classical Shockley-Read-Hall theory of free carrier recombination and generation via traps is extended to degenerate semiconductors. A concise and simple expression is found which avoids completely the concept of a Fermi level, a concept which is alien to nonequilibrium situations. Assumptions made in deriving the recombination generation current are carefully delineated and are found to be basically identical to those made in the original theory applicable to nondegenerate semiconductors.

  16. Generation and exploration of aggregation abstractions for scheduling and resource allocation

    NASA Technical Reports Server (NTRS)

    Lowry, Michael R.; Linden, Theodore A.

    1993-01-01

    This paper presents research on the abstraction of computational theories for scheduling and resource allocation. The paper describes both theory and methods for the automated generation of aggregation abstractions and approximations in which detailed resource allocation constraints are replaced by constraints between aggregate demand and capacity. The interaction of aggregation abstraction generation with the more thoroughly investigated abstractions of weakening operator preconditions is briefly discussed. The purpose of generating abstract theories for aggregated demand and resources includes: answering queries about aggregate properties, such as gross feasibility; reducing computational costs by using the solution of aggregate problems to guide the solution of detailed problems; facilitating reformulating theories to approximate problems for which there are efficient problem-solving methods; and reducing computational costs of scheduling by providing more opportunities for variable and value-ordering heuristics to be effective. Experiments are being developed to characterize the properties of aggregations that make them cost effective. Both abstract and concrete theories are represented in a variant of first-order predicate calculus, which is a parameterized multi-sorted logic that facilitates specification of large problems. A particular problem is conceptually represented as a set of ground sentences that is consistent with a quantified theory.

  17. Generation of Aggregates of Mouse Embryonic Stem Cells that Show Symmetry Breaking, Polarization and Emergent Collective Behaviour In Vitro

    PubMed Central

    Baillie-Johnson, Peter; van den Brink, Susanne Carina; Balayo, Tina; Turner, David Andrew; Martinez Arias, Alfonso

    2015-01-01

    We have developed a protocol improving current Embryoid Body (EB) culture which allows the study of self-organization, symmetry breaking, axial elongation and cell fate specification using aggregates of mouse embryonic stem cells (mESCs) in suspension culture. Small numbers of mESCs are aggregated in basal medium for 48 hr in non-tissue-culture-treated, U-bottomed 96-well plates, after which they are competent to respond to experimental signals. Following treatment, these aggregates begin to show signs of polarized gene expression and gradually alter their morphology from a spherical mass of cells to an elongated, well organized structure in the absence of external asymmetry cues. These structures are not only able to display markers of the three germ layers, but actively display gastrulation-like movements, evidenced by a directional dislodgement of individual cells from the aggregate, which crucially occurs at one region of the elongated structure. This protocol provides a detailed method for the reproducible formation of these aggregates, their stimulation with signals such as Wnt/β-Catenin activation and BMP inhibition and their analysis by single time-point or time-lapse fluorescent microscopy. In addition, we describe modifications to current whole-mount mouse embryo staining procedures for immunocytochemical analysis of specific markers within fixed aggregates. The changes in morphology, gene expression and length of the aggregates can be quantitatively measured, providing information on how signals can alter axial fates. It is envisaged that this system can be applied both to the study of early developmental events such as axial development and organization, and more broadly, the processes of self-organization and cellular decision-making. It may also provide a suitable niche for the generation of cell types present in the embryo that are unobtainable from conventional adherent culture such as spinal cord and motor neurones. PMID:26650833

  18. Current generation by phased injection of pellets

    SciTech Connect

    Fisch, N.J.

    1983-08-01

    By phasing the injection of frozen pellets into a tokamak plasma, it is possible to generate current. The current occurs when the electron flux to individual members of an array of pellets is asymmetric with respect to the magnetic field. The utility of this method for tokamak reactors, however, is unclear; the current, even though free in a pellet-fueled reactor, may not be large enough to be worth the trouble. Uncertainty as to the utility of this method is, in part, due to uncertainty as to proper modeling of the one-pellet problem.

  19. Antiresonance induced spin-polarized current generation

    NASA Astrophysics Data System (ADS)

    Yin, Sun; Min, Wen-Jing; Gao, Kun; Xie, Shi-Jie; Liu, De-Sheng

    2011-12-01

    According to the one-dimensional antiresonance effect (Wang X R, Wang Y and Sun Z Z 2003 Phys. Rev. B 65 193402), we propose a possible spin-polarized current generation device. Our proposed model consists of one chain and an impurity coupling to the chain. The energy level of the impurity can be occupied by an electron with a specific spin, and the electron with such a spin is blocked because of the antiresonance effect. Based on this phenomenon our model can generate the spin-polarized current flowing through the chain due to different polarization rates. On the other hand, the device can also be used to measure the generated spin accumulation. Our model is feasible with today's technology.

  20. Force generation by the growth of amyloid aggregates

    PubMed Central

    Herling, Therese W.; Garcia, Gonzalo A.; Michaels, Thomas C. T.; Grentz, Wolfgang; Dean, James; Shimanovich, Ulyana; Gang, Hongze; Müller, Thomas; Kav, Batuhan; Terentjev, Eugene M.; Dobson, Christopher M.; Knowles, Tuomas P. J.

    2015-01-01

    The generation of mechanical forces are central to a wide range of vital biological processes, including the function of the cytoskeleton. Although the forces emerging from the polymerization of native proteins have been studied in detail, the potential for force generation by aberrant protein polymerization has not yet been explored. Here, we show that the growth of amyloid fibrils, archetypical aberrant protein polymers, is capable of unleashing mechanical forces on the piconewton scale for individual filaments. We apply microfluidic techniques to measure the forces released by amyloid growth for two systems: insulin and lysozyme. The level of force measured for amyloid growth in both systems is comparable to that observed for actin and tubulin, systems that have evolved to generate force during their native functions and, unlike amyloid growth, rely on the input of external energy in the form of nucleotide hydrolysis for maximum force generation. Furthermore, we find that the power density released from growing amyloid fibrils is comparable to that of high-performance synthetic polymer actuators. These findings highlight the potential of amyloid structures as active materials and shed light on the criteria for regulation and reversibility that guide molecular evolution of functional polymers. PMID:26195762

  1. Generation and Exploitation of Aggregation Abstractions for Scheduling and Resource Allocation

    NASA Technical Reports Server (NTRS)

    Linden, Theodore A.; Lowry, Michael R.

    1992-01-01

    Our research is investigating abstraction of computational theories for scheduling and resource allocation. These theories are represented in a variant of first order predicate calculus, parameterized multisorted logic, that facilitates specification of large problems. A particular problem is conceptually stated as a set of ground sentences that are consistent with a quantified theory. We are mainly investigating the automated generation of aggregation abstractions and approximations in which detailed resource allocation constraints are replaced by constraints between aggregate demand and capacity. We are also investigating the interaction of aggregation abstractions with the more thoroughly investigated abstractions of weakening operator preconditions. The purpose of the theories for aggregated demand/capacity is threefold: first, to answer queries about aggregate properties, such as gross feasibility; second, to reduce computational costs by using the solution of aggregate problems to guide the solution of detailed problems; and third, to facilitate reformulating theories to approximate problems for which there are efficient problem solving methods. We also describe novel methods for exploiting aggregation abstractions.

  2. Sequence-Specific Protein Aggregation Generates Defined Protein Knockdowns in Plants1[OPEN

    PubMed Central

    Vuylsteke, Marnik; Aesaert, Stijn; Rombaut, Debbie; De Smet, Frederik; Xu, Jie; Van Lijsebettens, Mieke; Rousseau, Frederic

    2016-01-01

    Protein aggregation is determined by short (5–15 amino acids) aggregation-prone regions (APRs) of the polypeptide sequence that self-associate in a specific manner to form β-structured inclusions. Here, we demonstrate that the sequence specificity of APRs can be exploited to selectively knock down proteins with different localization and function in plants. Synthetic aggregation-prone peptides derived from the APRs of either the negative regulators of the brassinosteroid (BR) signaling, the glycogen synthase kinase 3/Arabidopsis SHAGGY-like kinases (GSK3/ASKs), or the starch-degrading enzyme α-glucan water dikinase were designed. Stable expression of the APRs in Arabidopsis (Arabidopsis thaliana) and maize (Zea mays) induced aggregation of the target proteins, giving rise to plants displaying constitutive BR responses and increased starch content, respectively. Overall, we show that the sequence specificity of APRs can be harnessed to generate aggregation-associated phenotypes in a targeted manner in different subcellular compartments. This study points toward the potential application of induced targeted aggregation as a useful tool to knock down protein functions in plants and, especially, to generate beneficial traits in crops. PMID:27208282

  3. Sequence-Specific Protein Aggregation Generates Defined Protein Knockdowns in Plants.

    PubMed

    Betti, Camilla; Vanhoutte, Isabelle; Coutuer, Silvie; De Rycke, Riet; Mishev, Kiril; Vuylsteke, Marnik; Aesaert, Stijn; Rombaut, Debbie; Gallardo, Rodrigo; De Smet, Frederik; Xu, Jie; Van Lijsebettens, Mieke; Van Breusegem, Frank; Inzé, Dirk; Rousseau, Frederic; Schymkowitz, Joost; Russinova, Eugenia

    2016-06-01

    Protein aggregation is determined by short (5-15 amino acids) aggregation-prone regions (APRs) of the polypeptide sequence that self-associate in a specific manner to form β-structured inclusions. Here, we demonstrate that the sequence specificity of APRs can be exploited to selectively knock down proteins with different localization and function in plants. Synthetic aggregation-prone peptides derived from the APRs of either the negative regulators of the brassinosteroid (BR) signaling, the glycogen synthase kinase 3/Arabidopsis SHAGGY-like kinases (GSK3/ASKs), or the starch-degrading enzyme α-glucan water dikinase were designed. Stable expression of the APRs in Arabidopsis (Arabidopsis thaliana) and maize (Zea mays) induced aggregation of the target proteins, giving rise to plants displaying constitutive BR responses and increased starch content, respectively. Overall, we show that the sequence specificity of APRs can be harnessed to generate aggregation-associated phenotypes in a targeted manner in different subcellular compartments. This study points toward the potential application of induced targeted aggregation as a useful tool to knock down protein functions in plants and, especially, to generate beneficial traits in crops. PMID:27208282

  4. Generation of urban road dust from anti-skid and asphalt concrete aggregates.

    PubMed

    Tervahattu, Heikki; Kupiainen, Kaarle J; Räisänen, Mika; Mäkelä, Timo; Hillamo, Risto

    2006-04-30

    Road dust forms an important component of airborne particulate matter in urban areas. In many winter cities the use of anti-skid aggregates and studded tires enhance the generation of mineral particles. The abrasion particles dominate the PM10 during springtime when the material deposited in snow is resuspended. This paper summarizes the results from three test series performed in a test facility to assess the factors that affect the generation of abrasion components of road dust. Concentrations, mass size distribution and composition of the particles were studied. Over 90% of the particles were aluminosilicates from either anti-skid or asphalt concrete aggregates. Mineral particles were observed mainly in the PM10 fraction, the fine fraction being 12% and submicron size being 6% of PM10 mass. The PM10 concentrations increased as a function of the amount of anti-skid aggregate dispersed. The use of anti-skid aggregate increased substantially the amount of PM10 originated from the asphalt concrete. It was concluded that anti-skid aggregate grains contribute to pavement wear. The particle size distribution of the anti-skid aggregates had great impact on PM10 emissions which were additionally enhanced by studded tires, modal composition, and texture of anti-skid aggregates. The results emphasize the interaction of tires, anti-skid aggregate, and asphalt concrete pavement in the production of dust emissions. They all must be taken into account when measures to reduce road dust are considered. The winter maintenance and springtime cleaning must be performed properly with methods which are efficient in reducing PM10 dust. PMID:16426748

  5. Laboratory Experiments of Rip Current Generation

    NASA Astrophysics Data System (ADS)

    Garnier, R.; Coco, G.; Lomonaco, P.; Dalrymple, R. A.; Alvarez, A.; Gonzalez, M.; Medina, R.

    2014-12-01

    The hypothesis of rip current generation from purely hydrodynamic processes is here investigated through laboratory experiments. The experiments have been performed at the Cantabria Coastal and Ocean Basin (CCOB) with a segmented wavemaker consisting of 64 waveboards. The basin measures 25m in the cross-shore and 32m in the alongshore direction and the water depth at the wavemaker is 1m. A concrete plane sloping (1:5) beach has been built in the opposite side of the wave machine, its toe is 15m from the waveboards. Reflective lateral walls covered the full length of the basin. The set of instruments consists of 33 wave gauges deployed along two longshore and two cross-shore transects, 7 acoustic Doppler velocimeters and 15 run-up wires. Furthermore a set of two cameras has been synchronized with the data acquisition system. Two types of experiments have been performed to specifically study the generation of rip currents under wave group forcing. First, similarly to the experiments of Fowler and Dalrymple (Proc. 22nd Int. Conf. Coast. Eng.,1990), two intersecting wave trains with opposite directions have been imposed. They give rise to the formation of a non-migrating rip current system with a wavelength that depends on wave frequency and direction. Second, single wave trains with alongshore periodic amplitude attenuation have been imposed. Although the attenuation has been set such that the incident wave field has the same envelope as in the first type of experiments, the rip current system differs due to diffraction and interference processes. The results for different wave conditions (maximum incident wave height from 0.2m to 0.4m, wave period from 1.4s to 2s) will be presented and the intensity of the rip currents will be compared to the alongshore variation in wave set-up. This research is part of the ANIMO project funded by the Spanish Government under contract BIA2012-36822.

  6. Configuration and Generation of Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Chu, Xiangning

    The substorm current wedge (SCW), a core element of substorm dynamics coupling the magnetotail to the ionosphere, is crucial in understanding substorms. It has been suggested that the field-aligned currents (FACs) in the SCW are caused by either pressure gradients or flow vortices, or both. Our understanding of FAC generations is based predominately on numerical simulations, because it has not been possible to organize spacecraft observations in a coordinate system determined by the SCW. This dissertation develops an empirical inversion model of the current wedge and inverts midlatitude magnetometer data to obtain the parameters of the current wedge for three solar cycles. This database enables statistical data analysis of spacecraft plasma and magnetic field observations relative to the SCW coordinate. In chapter 2, a new midlatitude positive bay (MPB) index is developed and calculated for three solar cycles of data. The MPB index is processed to determine the substorm onset time, which is shown to correspond to the auroral breakup onset with at most 1-2 minutes difference. Substorm occurrence rate is found to depend on solar wind speed while substorm duration is rather constant, suggesting that substorm process has an intrinsic pattern independent of external driving. In chapter 3, an SCW inversion technique is developed to determine the strength and locations of the FACs in an SCW. The inversion parameters for FAC strength and location, and ring current strength are validated by comparison with other measurements. In chapter 4, the connection between earthward flows and auroral poleward expansion is examined using improved mapping, obtained from a newly-developed dynamic magnetospheric model by superimposing a standard magnetospheric field model with substorm current wedge obtained from the inversion technique. It is shown that the ionospheric projection of flows observed at a fixed point in the equatorial plane map to the bright aurora as it expands poleward

  7. Advanced Eddy current NDE steam generator tubing.

    SciTech Connect

    Bakhtiari, S.

    1999-03-29

    As part of a multifaceted project on steam generator integrity funded by the U.S. Nuclear Regulatory Commission, Argonne National Laboratory is carrying out research on the reliability of nondestructive evaluation (NDE). A particular area of interest is the impact of advanced eddy current (EC) NDE technology. This paper presents an overview of work that supports this effort in the areas of numerical electromagnetic (EM) modeling, data analysis, signal processing, and visualization of EC inspection results. Finite-element modeling has been utilized to study conventional and emerging EC probe designs. This research is aimed at determining probe responses to flaw morphologies of current interest. Application of signal processing and automated data analysis algorithms has also been addressed. Efforts have focused on assessment of frequency and spatial domain filters and implementation of more effective data analysis and display methods. Data analysis studies have dealt with implementation of linear and nonlinear multivariate models to relate EC inspection parameters to steam generator tubing defect size and structural integrity. Various signal enhancement and visualization schemes are also being evaluated and will serve as integral parts of computer-aided data analysis algorithms. Results from this research will ultimately be substantiated through testing on laboratory-grown and in-service-degraded tubes.

  8. Red blood cell generation by three-dimensional aggregate cultivation of late erythroblasts.

    PubMed

    Lee, EunMi; Han, So Yeon; Choi, Hye Sook; Chun, Bokhwan; Hwang, Byunghee; Baek, Eun Jung

    2015-02-01

    Stem cell-derived erythroid cells hold great potential for the treatment of blood-loss anemia and for erythropoiesis research; however, cultures using conventional flat plates or bioreactors have failed to show promising results. By mimicking the in vivo bone marrow (BM) environment in which most erythroid cells are physically aggregated, we show that a three-dimensional (3D) aggregate culture system facilitates erythroid cell maturation and red blood cell (RBC) production more effectively than two-dimensional high-density cell cultivation. Late erythroblasts (polychromatic or orthochromatic erythroblasts) were differentiated from cord blood CD34(+) cells over 15 days and then allowed to form tight aggregates at a minimum density of 1×10(7) cells/mL for 2-3 days. To scale up the cell culture and to make the media supply efficient throughout the cell aggregates, several macroporous microcarriers and porous scaffolds were applied to the 3D culture system. In comparison to control culture conditions, erythroid cells in 3D aggregates were significantly more differentiated toward RBCs with significantly reduced nuclear dysplasia. When 3D culture was performed inside macroporous microcarriers, the cell culture scale was increased and cells exhibited enhanced differentiation and enucleation. Microcarriers with a pore diameter of approximately 400 μm produced more mature cells than those with a smaller pore diameter. In addition, this aggregate culture method minimized the culture space and media volume required. In conclusion, a 3D aggregate culture system can be used to generate transfusable human erythrocytes at the terminal maturation stage, mimicking the in vivo BM microenvironment. Porous structures can efficiently maximize the culture scale, enabling large-scale production of RBCs. These results enhance our understanding of the importance of physical contact among late erythroblasts for their final maturation into RBCs. PMID:25314917

  9. Particle-bubble aggregate stability on static bubble generated by single nozzle on flotation process

    NASA Astrophysics Data System (ADS)

    Warjito, Harinaldi, Setyantono, Manus; Siregar, Sahala D.

    2016-06-01

    There are three sub-processes on flotation. These processes are intervening liquid film into critical thickness, rupture of liquid film forming three phase contact line, and expansion three phase contact line forming aggregate stability. Aggregate stability factor contribute to determine flotation efficiency. Aggregate stability has some important factors such as reagent and particle geometry. This research focussed on to understand effect of particle geometry to aggregate stability. Experimental setup consists of 9 x 9 x26 cm flotation column made of glass, bubble generator, particle feeding system, and high speed video camera. Bubble generator made from single nozzle with 0.3 mm diameter attached to programmable syringe pump. Particle feeding system made of pipette. Particle used in this research is taken from open pit Grasberg in Timika, Papua. Particle has sub-angular geometry and its size varies from 38 to 300 µm. Bubble-particle interaction are recorded using high speed video camera. Recordings from high speed video camera analyzed using image processing software. Experiment result shows that aggregate particle-bubble and induction time depends on particle size. Small particle (38-106 µm) has long induction time and able to rupture liquid film and also forming three phase contact line. Big particle (150-300 µm) has short induction time, so it unable to attach with bubble easily. This phenomenon is caused by apparent gravity work on particle-bubble interaction. Apparent gravity worked during particle sliding on bubble surface experience increase and reached its maximum magnitude at bubble equator. After particle passed bubble equator, apparent gravity force experience decrease. In conclusion particle size from 38-300 µm can form stable aggregate if particle attached with bubble in certain condition.

  10. 12. GENERATING UNIT NO. 2, WITH (LR) CONTINUOUS CURRENT EXCITER, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. GENERATING UNIT NO. 2, WITH (L-R) CONTINUOUS CURRENT EXCITER, ALTERNATING CURRENT GENERATOR, AND TURBINE GOVERNOR. VIEW TO SOUTH. - Cooke Hydroelectric Plant, Powerhouse, Cook Dam Road at Au Sable River, Oscoda, Iosco County, MI

  11. Where the wild things are: Predicting hotspots of seabird aggregations in the California Current System

    USGS Publications Warehouse

    Nur, N.; Jahncke, J.; Herzog, M.P.; Howar, J.; Hyrenbach, K.D.; Zamon, J.E.; Ainley, D.G.; Wiens, J.A.; Morgan, K.; Balance, L.T.; Stralberg, D.

    2011-01-01

    Marine Protected Areas (MPAs) provide an important tool for conservation of marine ecosystems. To be most effective, these areas should be strategically located in a manner that supports ecosystem function. To inform marine spatial planning and support strategic establishment of MPAs within the California Current System, we identified areas predicted to support multispecies aggregations of seabirds ("hotspot????). We developed habitat-association models for 16 species using information from at-sea observations collected over an 11-year period (1997-2008), bathymetric data, and remotely sensed oceanographic data for an area from north of Vancouver Island, Canada, to the USA/Mexico border and seaward 600 km from the coast. This approach enabled us to predict distribution and abundance of seabirds even in areas of few or no surveys. We developed single-species predictive models using a machine-learning algorithm: bagged decision trees. Single-species predictions were then combined to identify potential hotspots of seabird aggregation, using three criteria: (1) overall abundance among species, (2) importance of specific areas ("core area????) to individual species, and (3) predicted persistence of hotspots across years. Model predictions were applied to the entire California Current for four seasons (represented by February, May, July, and October) in each of 11 years. Overall, bathymetric variables were often important predictive variables, whereas oceanographic variables derived from remotely sensed data were generally less important. Predicted hotspots often aligned with currently protected areas (e.g., National Marine Sanctuaries), but we also identified potential hotspots in Northern California/Southern Oregon (from Cape Mendocino to Heceta Bank), Southern California (adjacent to the Channel Islands), and adjacent to Vancouver Island, British Columbia, that are not currently included in protected areas. Prioritization and identification of multispecies hotspots

  12. Wasteless combined aggregate-coal-fired steam-generator/melting-converter.

    PubMed

    Pioro, L S; Pioro, I L

    2003-01-01

    A method of reprocessing coal sludge and ash into granulate for the building industry in a combined wasteless aggregate-steam-generator/melting-converter was developed and tested. The method involves melting sludge and ash from coal-fired steam-generators of power plants in a melting-converter installed under the steam-generator, with direct sludge drain from the steam generator combustion chamber. The direct drain of sludge into converter allows burnup of coal with high ash levels in the steam-generator without an additional source of ignition (natural gas, heating oil, etc.). Specific to the melting process is the use of a gas-air mixture with direct combustion inside a melt. This feature provides melt bubbling and helps to achieve maximum heat transfer from combustion products to the melt, to improve mixing, to increase rate of chemical reactions and to improve the conditions for burning the carbon residue from the sludge and ash. The "gross" thermal efficiency of the combined aggregate is about 93% and the converter capacity is about 18 t of melt in 100 min. The experimental data for different aspects of the proposed method are presented. The effective ash/charging materials feeding system is also discussed. The reprocessed coal ash and sludge in the form of granules can be used as fillers for concrete and as additives in the production of cement, bricks and other building materials. PMID:12781221

  13. Generation in Human Plasma of Misfolded, Aggregation-Prone Electronegative Low Density Lipoprotein

    PubMed Central

    Greco, Giulia; Balogh, Gabor; Brunelli, Roberto; Costa, Graziella; De Spirito, Marco; Lenzi, Laura; Mei, Giampiero; Ursini, Fulvio; Parasassi, Tiziana

    2009-01-01

    Abstract Human plasma contains small amounts of a low density lipoprotein in which apoprotein is misfolded. Originally identified and isolated by means of anion-exchange chromatography, this component was subsequently described as electronegative low density lipoprotein (LDL)(−), with increased concentrations associated with elevated cardiovascular disease risk. It has been recognized recently as the trigger of LDL amyloidogenesis, which produces aggregates similar to subendothelial droplets observed in vivo in early atherogenesis. Although LDL(−) has been produced in vitro through various manipulations, the mechanisms involved in its generation in vivo remain obscure. By using a more physiological model, we demonstrate spontaneous, sustained and noticeable production of LDL(−) during incubation of unprocessed human plasma at 37°C. In addition to a higher fraction of amyloidogenic LDL(−), LDL purified from incubated plasma contains an increased level of lysophospholipids and free fatty acids; analysis of LDL lipids packing shows their loosening. As a result, during plasma incubation, lipid destabilization and protein misfolding take place, and aggregation-prone particles are generated. All these phenomena can be prevented by inhibiting calcium-dependent secretory phospholipases A2. Our plasma incubation model, without removal of reaction products, effectively shows a lipid-protein interplay in LDL, where lipid destabilization after lipolysis threatens the apoprotein's structure, which misfolds and becomes aggregation-prone. PMID:19619478

  14. Optimization of Gear Ratio in the Tidal Current Generation System based on Generated Energy

    NASA Astrophysics Data System (ADS)

    Naoi, Kazuhisa; Shiono, Mitsuhiro; Suzuki, Katsuyuki

    It is possible to predict generating power of the tidal current generation, because of the tidal current's periodicity. Tidal current generation is more advantageous than other renewable energy sources, when the tidal current generation system is connected to the power system and operated. In this paper, we propose a method used to optimize the gear ratio and generator capacity, that is fundamental design items in the tidal current generation system which is composed of Darrieus type water turbine and squirrel-cage induction generator coupled with gear. The proposed method is applied to the tidal current generation system including the most large-sized turbine that we have developed and studied. This paper shows optimum gear ratio and generator capacity that make generated energy maximum, and verify effectiveness of the proposed method. The paper also proposes a method of selecting maximum generating current velocity in order to reduce the generator capacity, from the viewpoint of economics.

  15. Organized Aggregation of Porphyrins in Lipid Bilayers for Third Harmonic Generation Microscopy.

    PubMed

    Cui, Liyang; Tokarz, Danielle; Cisek, Richard; Ng, Kenneth K; Wang, Fan; Chen, Juan; Barzda, Virginijus; Zheng, Gang

    2015-11-16

    Nonlinear optical microscopy has become a powerful tool for high-resolution imaging of cellular and subcellular composition, morphology, and interactions because of its high spatial resolution, deep penetration, and low photo-damage to tissue. Developing specific harmonic probes is essential for exploiting nonlinear microscopic imaging for biomedical applications. We report an organized aggregate of porphyrins (OAP) that formed within lipidic nanoparticles showing fingerprint spectroscopic properties, structure-associated second harmonic generation, and superradiant third harmonic generation. The OAP facilitated harmonic microscopic imaging of living cells with significantly enhanced contrast. The structure-dependent switch between harmonic (OAP-intact) and fluorescence (OAP-disrupted) generation enabled real-time multi-modality imaging of the cellular fate of nanoparticles. Robustly produced under various conditions and easily incorporated into pre-formed lipid nanovesicles, OAP provides a biocompatible nanoplatform for harmonic imaging. PMID:26418395

  16. Cytotoxicity and reactive oxygen species generation from aggregated carbon and carbonaceous nanoparticulate materials.

    PubMed

    Garza, Kristine M; Soto, Karla F; Murr, Lawrence E

    2008-01-01

    We have investigated the cytotoxicity and reactive oxygen species (ROS) generation for indoor and outdoor soots: candle, wood, diesel, tire, and natural gas burner soots--along with surrogate black carbon, various multiwall carbon nanotube aggregate materials, TiO2 (anatase) and chrysotile asbestos as reference materials. All soots were observed utilizing TEM and FESEM to be composed of aggregated, primary spherules (20-80 nm diameter) forming complex, branched fractal structures. These spherules were composed of intercalated, turbostratic arrangements of curved graphene fragments with varying concentrations ofpolycyclic aromatic hydrocarbon (PAH) isomers. In vitro cultures with an immortalized human lung epithelial carcinoma cell line (A549) treated with these materials showed decreased cell viability and variations in ROS production, with no correlations to PAH content. The data demonstrate that soots are cytotoxic and that cytotoxicity is not related to PAH content but is related to ROS generation, suggesting that soot induces cellular oxidative stress and that cell viability assays can be indicators of ROS production. PMID:18488419

  17. Cytotoxicity and reactive oxygen species generation from aggregated carbon and carbonaceous nanoparticulate materials

    PubMed Central

    Garza, Kristine M; Soto, Karla F; Murr, Lawrence E

    2008-01-01

    We have investigated the cytotoxicity and reactive oxygen species (ROS) generation for indoor and outdoor soots: candle, wood, diesel, tire, and natural gas burner soots – along with surrogate black carbon, various multiwall carbon nanotube aggregate materials, TiO2 (anatase) and chrysotile asbestos as reference materials. All soots were observed utilizing TEM and FESEM to be composed of aggregated, primary spherules (20–80 nm diameter) forming complex, branched fractal structures. These spherules were composed of intercalated, turbostratic arrangements of curved graphene fragments with varying concentrations of polycyclic aromatic hydrocarbon (PAH) isomers. In vitro cultures with an immortalized human lung epithelial carcinoma cell line (A549) treated with these materials showed decreased cell viability and variations in ROS production, with no correlations to PAH content. The data demonstrate that soots are cytotoxic and that cytotoxicity is not related to PAH content but is related to ROS generation, suggesting that soot induces cellular oxidative stress and that cell viability assays can be indicators of ROS production. PMID:18488419

  18. An Intracellular Arrangement of Histoplasma capsulatum Yeast-Aggregates Generates Nuclear Damage to the Cultured Murine Alveolar Macrophages.

    PubMed

    Pitangui, Nayla de Souza; Sardi, Janaina de Cássia Orlandi; Voltan, Aline R; Dos Santos, Claudia T; da Silva, Julhiany de Fátima; da Silva, Rosangela A M; Souza, Felipe O; Soares, Christiane P; Rodríguez-Arellanes, Gabriela; Taylor, Maria Lucia; Mendes-Giannini, Maria J S; Fusco-Almeida, Ana M

    2015-01-01

    Histoplasma capsulatum is responsible for a human systemic mycosis that primarily affects lung tissue. Macrophages are the major effector cells in humans that respond to the fungus, and the development of respiratory disease depends on the ability of Histoplasma yeast cells to survive and replicate within alveolar macrophages. Therefore, the interaction between macrophages and H. capsulatum is a decisive step in the yeast dissemination into host tissues. Although the role played by components of cell-mediated immunity in the host's defense system and the mechanisms used by the pathogen to evade the host immune response are well understood, knowledge regarding the effects induced by H. capsulatum in host cells at the nuclear level is limited. According to the present findings, H. capsulatum yeast cells display a unique architectural arrangement during the intracellular infection of cultured murine alveolar macrophages, characterized as a formation of aggregates that seem to surround the host cell nucleus, resembling a "crown." This extranuclear organization of yeast-aggregates generates damage on the nucleus of the host cell, producing DNA fragmentation and inducing apoptosis, even though the yeast cells are not located inside the nucleus and do not trigger changes in nuclear proteins. The current study highlights a singular intracellular arrangement of H. capsulatum yeast near to the nucleus of infected murine alveolar macrophages that may contribute to the yeast's persistence under intracellular conditions, since this fungal pathogen may display different strategies to prevent elimination by the host's phagocytic mechanisms. PMID:26793172

  19. An Intracellular Arrangement of Histoplasma capsulatum Yeast-Aggregates Generates Nuclear Damage to the Cultured Murine Alveolar Macrophages

    PubMed Central

    Pitangui, Nayla de Souza; Sardi, Janaina de Cássia Orlandi; Voltan, Aline R.; dos Santos, Claudia T.; da Silva, Julhiany de Fátima; da Silva, Rosangela A. M.; Souza, Felipe O.; Soares, Christiane P.; Rodríguez-Arellanes, Gabriela; Taylor, Maria Lucia; Mendes-Giannini, Maria J. S.; Fusco-Almeida, Ana M.

    2016-01-01

    Histoplasma capsulatum is responsible for a human systemic mycosis that primarily affects lung tissue. Macrophages are the major effector cells in humans that respond to the fungus, and the development of respiratory disease depends on the ability of Histoplasma yeast cells to survive and replicate within alveolar macrophages. Therefore, the interaction between macrophages and H. capsulatum is a decisive step in the yeast dissemination into host tissues. Although the role played by components of cell-mediated immunity in the host's defense system and the mechanisms used by the pathogen to evade the host immune response are well understood, knowledge regarding the effects induced by H. capsulatum in host cells at the nuclear level is limited. According to the present findings, H. capsulatum yeast cells display a unique architectural arrangement during the intracellular infection of cultured murine alveolar macrophages, characterized as a formation of aggregates that seem to surround the host cell nucleus, resembling a “crown.” This extranuclear organization of yeast-aggregates generates damage on the nucleus of the host cell, producing DNA fragmentation and inducing apoptosis, even though the yeast cells are not located inside the nucleus and do not trigger changes in nuclear proteins. The current study highlights a singular intracellular arrangement of H. capsulatum yeast near to the nucleus of infected murine alveolar macrophages that may contribute to the yeast's persistence under intracellular conditions, since this fungal pathogen may display different strategies to prevent elimination by the host's phagocytic mechanisms. PMID:26793172

  20. The Dynamical Generation of Current Sheets in Astrophysical Plasma Turbulence

    NASA Astrophysics Data System (ADS)

    Howes, Gregory G.

    2016-08-01

    Turbulence profoundly affects particle transport and plasma heating in many astrophysical plasma environments, from galaxy clusters to the solar corona and solar wind to Earth's magnetosphere. Both fluid and kinetic simulations of plasma turbulence ubiquitously generate coherent structures, in the form of current sheets, at small scales, and the locations of these current sheets appear to be associated with enhanced rates of dissipation of the turbulent energy. Therefore, illuminating the origin and nature of these current sheets is critical to identifying the dominant physical mechanisms of dissipation, a primary aim at the forefront of plasma turbulence research. Here, we present evidence from nonlinear gyrokinetic simulations that strong nonlinear interactions between counterpropagating Alfvén waves, or strong Alfvén wave collisions, are a natural mechanism for the generation of current sheets in plasma turbulence. Furthermore, we conceptually explain this current sheet development in terms of the nonlinear dynamics of Alfvén wave collisions, showing that these current sheets arise through constructive interference among the initial Alfvén waves and nonlinearly generated modes. The properties of current sheets generated by strong Alfvén wave collisions are compared to published observations of current sheets in the Earth's magnetosheath and the solar wind, and the nature of these current sheets leads to the expectation that Landau damping of the constituent Alfvén waves plays a dominant role in the damping of turbulently generated current sheets.

  1. Generation of Pure Bulk Valley Current in Graphene

    NASA Astrophysics Data System (ADS)

    Jiang, Yongjin; Low, Tony; Chang, Kai; Katsnelson, Mikhail I.; Guinea, Francisco

    2013-01-01

    The generation of valley current is a fundamental goal in graphene valleytronics but no practical ways of its realization are known yet. We propose a workable scheme for the generation of bulk valley current in a graphene mechanical resonator through adiabatic cyclic deformations of the strains and a chemical potential in the suspended region. The accompanied strain gauge fields can break the spatial mirror symmetry of the problem within each of the two inequivalent valleys, leading to a finite valley current due to quantum pumping. An all-electrical measurement configuration is designed to detect the novel state with pure bulk valley currents.

  2. Detail of backup exciter showing direct current generator Mystic ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of backup exciter showing direct current generator - Mystic Lake Hydroelectric Facility, Powerhouse, Along West Rosebud Creek, 1 3/4 miles northeast of Mystic Lake Dam, Fishtail, Stillwater County, MT

  3. Islet-Like Cell Aggregates Generated from Human Adipose Tissue Derived Stem Cells Ameliorate Experimental Diabetes in Mice

    PubMed Central

    Chandra, Vikash; G, Swetha; Muthyala, Sudhakar; Jaiswal, Amit K.; Bellare, Jayesh R.; Nair, Prabha D.; Bhonde, Ramesh R.

    2011-01-01

    Background Type 1 Diabetes Mellitus is caused by auto immune destruction of insulin producing beta cells in the pancreas. Currently available treatments include transplantation of isolated islets from donor pancreas to the patient. However, this method is limited by inadequate means of immuno-suppression to prevent islet rejection and importantly, limited supply of islets for transplantation. Autologous adult stem cells are now considered for cell replacement therapy in diabetes as it has the potential to generate neo-islets which are genetically part of the treated individual. Adopting methods of islet encapsulation in immuno-isolatory devices would eliminate the need for immuno-suppressants. Methodology/Principal Findings In the present study we explore the potential of human adipose tissue derived adult stem cells (h-ASCs) to differentiate into functional islet like cell aggregates (ICAs). Our stage specific differentiation protocol permit the conversion of mesodermic h-ASCs to definitive endoderm (Hnf3β, TCF2 and Sox17) and to PDX1, Ngn3, NeuroD, Pax4 positive pancreatic endoderm which further matures in vitro to secrete insulin. These ICAs are shown to produce human C-peptide in a glucose dependent manner exhibiting in-vitro functionality. Transplantation of mature ICAs, packed in immuno-isolatory biocompatible capsules to STZ induced diabetic mice restored near normoglycemia within 3–4 weeks. The detection of human C-peptide, 1155±165 pM in blood serum of experimental mice demonstrate the efficacy of our differentiation approach. Conclusions h-ASC is an ideal population of personal stem cells for cell replacement therapy, given that they are abundant, easily available and autologous in origin. Our findings present evidence that h-ASCs could be induced to differentiate into physiologically competent functional islet like cell aggregates, which may provide as a source of alternative islets for cell replacement therapy in type 1 diabetes. PMID:21687731

  4. Characterizing generated charged inverse micelles with transient current measurements.

    PubMed

    Strubbe, Filip; Prasad, Manoj; Beunis, Filip

    2015-02-01

    We investigate the generation of charged inverse micelles in nonpolar surfactant solutions relevant for applications such as electronic ink displays and liquid toners. When a voltage is applied across a thin layer of a nonpolar surfactant solution between planar electrodes, the generation of charged inverse micelles leads to a generation current. From current measurements it appears that such charged inverse micelles generated in the presence of an electric field behave differently compared to those present in equilibrium in the absence of a field. To examine the origin of this difference, transient current measurements in which the applied voltage is suddenly increased are used to measure the mobility and the amount of generated charged inverse micelles. The mobility and the corresponding hydrodynamic size are found to be similar to those of charged inverse micelles present in equilibrium, which indicates that other properties determine their different behavior. The amplitude and shape of the transient currents measured as a function of the surfactant concentration confirm that the charged inverse micelles are generated by bulk disproportionation. A theoretical model based on bulk disproportionation with simulations and analytical approximations is developed to analyze the experimental transient currents. PMID:25580883

  5. A fluid mechanical model for current-generating-feeding jellyfish

    NASA Astrophysics Data System (ADS)

    Peng, Jifeng; Dabiri, John

    2008-11-01

    Many jellyfish species, e.g. moon jellyfish Aurelia aurita, use body motion to generate fluid currents which carry their prey to the vicinity of their capture appendages. In this study, a model was developed to understand the fluid mechanics for this current-generating-feeding mode of jellyfish. The flow generated by free-swimming Aurelia aurita was measured using digital particle image velocimetry. The dynamics of prey (e.g., brine shrimp Artemia) in the flow field were described by a modified Maxey-Riley equation which takes into consideration the inertia of prey and the escape forces, which prey exert in the presence of predator. A Lagrangian analysis was used to identify the region of the flow in which prey can be captured by the jellyfish and the clearance rate was quantified. The study provides a new methodology to study biological current-generating-feeding and the transport and mixing of particles in fluid flow in general.

  6. Dying Flow Bursts as Generators of the Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2016-07-01

    Many theories or conjectures exist on the driver of the substorm current wedge, e.g. rerouting of the tail current, current disruption, flow braking, vortex formation, and current sheet collapse. Magnitude, spatial scale, and temporal development of the related magnetic perturbations suggest that the generator is related to the interaction of the flow bursts with the dipolar magnetosphere after onset of reconnection in the near-Earth tail. The question remains whether it is the flow energy that feeds the wedge current or the internal energy of the arriving plasma. In this presentation I argue for the latter. The current generation is attributed to the force exerted by the dipolarized magnetic field of the flow bursts on the preceding layer of high-beta plasma after flow braking. The generator current is the grad-B current at the outer boundary of the compressed high-beta plasma layers. It needs the sequential arrival of several flow bursts to account for duration and magnitude of the ionospheric closure current.

  7. Spin current generated by thermally driven ultrafast demagnetization.

    PubMed

    Choi, Gyung-Min; Min, Byoung-Chul; Lee, Kyung-Jin; Cahill, David G

    2014-01-01

    Spin current is the key element for nanoscale spintronic devices. For ultrafast operation of such nano-devices, generation of spin current in picoseconds, a timescale that is difficult to achieve using electrical circuits, is highly desired. Here we show thermally driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The temperature difference between electrons and magnons is the driving force for spin current generation by ultrafast demagnetization. On longer timescales, a few picoseconds following laser excitation, we also observe a small contribution to spin current by a temperature gradient and the spin-dependent Seebeck effect. PMID:25007978

  8. Solar wind-generated current in the Lunar Dust Experiment

    NASA Astrophysics Data System (ADS)

    Xie, Lianghai; Zhang, Xiaoping; Zheng, Yongchun; Guo, Dawei

    2016-04-01

    Measurements from the Lunar Dust Experiment (LDEX) show that the current associated with lofted lunar dust lacks an altitude dependence, implying that the current may come from other sources. Here we present some evidences for solar wind (SW)-generated current. Direct SW influx on the nightside can cause a large current, and the backscattered energetic neutral atoms (ENAs) on the dayside can bring a good correlation between the current and SW density. It is found that the current favors a lower SW speed and a smaller SW incident angle, but the dependences are also affected by the solar zenith angle (SZA) and the scattering function of ENAs. Picked-up ions can enhance the current when the angle between the convection electric field and LDEX's normal is larger than 90°. But when the angle is smaller than 90°, the enhancement is negligible.

  9. Laser-induced breakdown detection of temperature-ramp generated aggregates of therapeutic monoclonal antibody.

    PubMed

    Menzen, Tim; Friess, Wolfgang; Niessner, Reinhard; Haisch, Christoph

    2015-08-01

    The detection and characterization of protein aggregation is essential during development and quality control of therapeutic proteins, as aggregates are typically inactive and may trigger anti-drug-antibody formation in patients. Especially large multi-domain molecules, such as the important class of therapeutic monoclonal antibodies (mAbs), can form various aggregates that differ in size and morphology. Although particle analysis advanced over the recent years, new techniques and orthogonal methods are highly valued. To our knowledge, the physical principle of laser-induced breakdown detection (LIBD) was not yet applied to sense aggregates in therapeutic protein formulations. We established a LIBD setup to monitor the temperature-induced aggregation of a mAb. The obtained temperature of aggregation was in good agreement with the results from previously published temperature-ramped turbidity and dynamic light scattering measurements. This study demonstrates the promising applicability of LIBD to investigate aggregates from therapeutic proteins. The technique is also adaptive to online detection and size determination, and offers interesting opportunities for morphologic characterization of protein particles and impurities, which will be part of future studies. PMID:26158409

  10. Harnessing Chaperones to Generate Small-Molecule Inhibitors of Amyloid β Aggregation

    NASA Astrophysics Data System (ADS)

    Gestwicki, Jason E.; Crabtree, Gerald R.; Graef, Isabella A.

    2004-10-01

    Protein aggregation is involved in the pathogenesis of neurodegenerative diseases and hence is considered an attractive target for therapeutic intervention. However, protein-protein interactions are exceedingly difficult to inhibit. Small molecules lack sufficient steric bulk to prevent interactions between large peptide surfaces. To yield potent inhibitors of β-amyloid (Aβ) aggregation, we synthesized small molecules that increase their steric bulk by binding to chaperones but also have a moiety available for interaction with Aβ. This strategy yields potent inhibitors of Aβ aggregation and could lead to therapeutics for Alzheimer's disease and other forms of neurodegeneration.

  11. Design and Performance Study of an Ocean Current Turbine Generator

    NASA Astrophysics Data System (ADS)

    Chiang, Hsiao-Wei D.; Lin, Chen-Yin; Hsu, Chih-Neng

    2013-09-01

    The relatively constant flow of the ocean currents carries large amounts of energy that can be captured and converted to a usable form. In this paper, design and performance simulation of a horizontal axial ocean current turbine (OCT) are studied. Also, study on varying the turbine duct housing design parameters and a series of simulation analyses were performed. Our model simulations with and without the turbine duct housing design were compared with existing literature results and very good agreements were obtained. The results also showed that unducted ocean current turbine power output is proportional to the cube of the current speed. Therefore, if we can increase the flow rate, the ocean current turbine generator performance is expected to be greatly enhanced. By adding the turbine duct housing, under the current velocity of 1 and 2 m/s, parametric studies including the duct housing type, duct entrance area, tilt angle, and duct length-to-diameter ratio are performed. After obtaining the optimized set of design values for our current design, a complete system analysis of the ocean current turbine generator was performed to provide future design guidelines.

  12. Hall current effects in the Lewis magnetohydrodynamic generator

    NASA Technical Reports Server (NTRS)

    Nichols, L. D.; Sovie, R. J.

    1972-01-01

    Data obtained in a magnetohydrodynamic generator are compared with theoretical values calculated by using the Dzung theory. The generator was operated with cesium-seeded argon as the working fluid. The gas temperature varied from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from 0.3 to 0.5, and the magnetic field strength from 0.2 to 1.6 T. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) limit generator performance.

  13. Hall current effects in the Lewis magnetohydrodynamic generator.

    NASA Technical Reports Server (NTRS)

    Nichols, L. D.; Sovie, R. J.

    1972-01-01

    Data obtained in the Lewis MHD generator are compared with theoretical values calculated using the Dzung (1966) theory. The generator is operated with cesium seeded argon as the working fluid. The gas temperature varies from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from .3 to .5, and the magnetic field strength from .2 to 1.6 tesla. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) are limiting generator performance.

  14. Generation of spin currents by surface plasmon resonance

    PubMed Central

    Uchida, K.; Adachi, H.; Kikuchi, D.; Ito, S.; Qiu, Z.; Maekawa, S.; Saitoh, E.

    2015-01-01

    Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light–electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY2Fe5O12 bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY2Fe5O12 interface. This spin-current generation cannot be explained by conventional heating effects, requiring us to introduce nonequilibrium magnons excited by surface-plasmon-induced evanescent electromagnetic fields in BiY2Fe5O12. This plasmonic spin pumping integrates surface plasmons with spin-current physics, opening the door to plasmonic spintronics. PMID:25569821

  15. Stationary auroral current oscillations resulting from the magnetospheric generator

    NASA Technical Reports Server (NTRS)

    Weimer, D. R.; Maynard, N. C.; Burke, W. J.; Sugiura, M.

    1988-01-01

    The origin of the steady state spatial current oscillations in the auroral field-aligned currents, which was detected in the measurements by the two Dynamics Explorer (DE) satellites DE 1 and DE 2, is explained in the framework of a simple steady state model of the magnetosphere-ionosphere current system. The model has only three parameters, including the magnetic-field-aligned conductivity, the ionospheric height-integrated Pedersen conductivity, and the conductivity of a generator or dynamo at the magnetospheric equator. Good agreement between this model and the measurements from the DE satellites was obtained.

  16. Comparing Current Students to a Pre-Millennial Generation: Are They Really Different?

    ERIC Educational Resources Information Center

    Yahr, Michael A.; Schimmel, Kurt

    2013-01-01

    The Millennial generation, also known as Generation Y, has garnered much attention in the print and broadcast media and at academic conferences because of the challenges that they pose to universities and corporations. Aggregate characteristics and preferences of the Millennial generation and of Generation X, their immediate predecessors, have…

  17. Direct current voltage generated in metallic layers by spin pumping

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    We report an investigation of the dc voltage generated in a normal-metal (NM) layer by spin pumping from an adjacent ferromagnetic (FM) layer under ferromagnetic resonance (FMR) excitation. The spin-current injected across the FM/NM interface by the spin pumping effect generates a charge current along the NM layer by means of the inverse spin Hall effect. Room temperature field scan measurements were made in a series of Ni81Fe19/Pt bilayers with several thicknesses of the FM and Pt layers. By varying the angle of the in-plane magnetization we are able to accurately separate the contributions arising from anisotropic magnetoresistance and from the spin-current pumped into the NM layer by the precessing magnetization of the FM layer. The data for the spin pumping dc voltage is in excellent agreement with a theory incorporating the full dependence on the thicknesses of the FM and NM layers.

  18. Depolarization of subalfvenic plasma jet generating field-aligned currents

    NASA Astrophysics Data System (ADS)

    Sobyanin, D. B.; Gavrilov, B. G.; Podgorny, I. M.

    2004-01-01

    The subalfvenic magnetized plasma jet propagating across the geomagnetic field generates the field-aligned currents in ionospheric plasma. The transverse polarization electric field Ep = - V × B in the jet is reduced due to a leakage of polarization charges through the field-aligned currents (plasma jet depolarization). These phenomena are investigated in the laboratory experiment. It was revealed that the depolarization is accompanied by appearing of the electric field Ea along the plasma velocity vector and creation of an additional pair of the field-aligned currents being generated at the leading and trailing edge of the moving plasma. The value of Ea is comparable with the transverse electric field Ep. The depolarization results in the plasma jet deflection. The possibility of a manifestation of these effects in the NORTH STAR Russian-American active rocket experiment is discussed.

  19. Training Course for Power Operating Personnel. Lesson No. 6: Alternating-Current Generator Excitation.

    ERIC Educational Resources Information Center

    Department of the Interior, Denver, CO. Engineering and Research Center.

    Subjects covered in this text are controlling the hydroelectric generator, generator excitation, basic principles of direct current generation, direction of current flow, basic alternating current generator, alternating and direct current voltage outputs, converting alternating current to direct current, review of the basic generator and…

  20. Generation of field-aligned current in the auroral zone

    NASA Technical Reports Server (NTRS)

    Okuda, Hideo

    1991-01-01

    Generation of a magnetic field-aligned current in the auroral zone connecting the magnetospheric and ionospheric plasmas has been studied by means of a three dimensional particle simulation model. The model is of a magnetostatic variety appropriate for a low beta plasma in which the high frequency transverse displacement current has been eliminated. The simulation model is highly elongated along the magnetic field lines in order to model a highly elongated flux tube in the auroral zone. An enhanced field-aligned current was generated by injection of a magnetospheric plasma across the auroral zone magnetic field at the center of the model. Such a plasma injection may correspond to a plasmoid injection at the geomagnetic tail associated with magnetic reconnection during a substorm or a transverse plasma flow along the low latitude magnetopause boundary layer. The results of the simulations show that the field-aligned current can be enhanced over the thermal current by a factor of 5 - 10 via such injection. Associated with the enhanced current are the electrostatic ion cyclotron waves and shear Alfven waves excited in the auroral zone.

  1. Transient Current Analysis of Induction Generators for Wind Power Generating System

    NASA Astrophysics Data System (ADS)

    Senjyu, Tomonobu; Sueyoshi, Norihide; Uezato, Katsumi; Fujita, Hideki

    In recent year, non-conventional energy generation is coming up for effective use of natural energy, such as wind energy. Induction generators consisting squirrel-cage rotors are widly used as wind generators because of their salient features like robust rotor design, simple in the construction, maintenance free operation, etc. However these induction generators will draw large transient inrush current, several times as large as the machine rated current, the instant when they are connected to utility grid or restored after the fault clearance. Under such situations, there will be a severe voltage fluctuations in the power system. In this paper, we present transient analysis of induction generators before and after a three-phase fault conditions. Theoretical discission is developed to determine the initial phase angle and the time at which maximum transient currents flow in the system.

  2. Low-voltage, wide-range, current-controlled DC current generator

    NASA Astrophysics Data System (ADS)

    Mathew, M.; Hart, B. L.; Hayatleh, K.; Lidgey, F. J.

    2011-08-01

    Operating from a 1 V rail supply, a proposed CMOS current-controlled DC current generator can function as a repeater, attenuator or amplifier over the input current range, 1 µA to 1 mA, with a current-transfer ratio accuracy better than 1% using IBM technology, characterised by a process with a 0.13 µm minimum feature size. In repeater mode, the incremental output resistance exceeds 30 MΩ for an output current of 500 µA at an output voltage of 0.20 V, and exceeds 1 MΩ for an output current of 1 mA at an output voltage of 0.22 V. For zero input current, the circuit dissipation is 117 µW.

  3. Short Circuit Current Contribution for Different Wind Turbine Generator Types

    SciTech Connect

    Muljadi, E.; Samaan, Nader A.; Gevorgian, Vahan; Li, Jun; Pasupulati, Subbaiah

    2010-09-28

    An important aspect of wind power plant (WPP) impact studies is to evaluate the short circuit (SC) current contribution of the plant into the transmission network under different fault conditions. This task can be challenging to protection engineers due to the topology differences between different types of wind turbine generators (WTGs) and the conventional generating units. This paper represents simulation results for short circuit current contribution for different types of WTGs obtained through transient analysis using generic WTG models. The obtained waveforms are analyzed to explain the behavior, such as peak values and rate of decay, of the WTG. The effect of fault types and location, and the effect of the control algorithms of power converters on SC current contribution are investigated. It is shown that the response of the WPP to faults will vary based on the type of the installed WTGs. While in Type 1 and Type 2 WTGs, short circuit current will be determined by the physical characteristics of the induction generator, the contribu-tion of Type 3 and Type 4 WTG will be mostly characterized by the power converters control algorithms which are usually considered proprietary information by the wind turbine manufacturers.

  4. Meson exchange current (MEC) models in neutrino interaction generators

    SciTech Connect

    Katori, Teppei

    2015-05-15

    Understanding of the so-called 2 particle-2 hole (2p-2h) effect is an urgent program in neutrino interaction physics for current and future oscillation experiments. Such processes are believed to be responsible for the event excesses observed by recent neutrino experiments. The 2p-2h effect is dominated by the meson exchange current (MEC), and is accompanied by a 2-nucleon emission from the primary vertex, instead of a single nucleon emission from the charged-current quasi-elastic (CCQE) interaction. Current and future high resolution experiments can potentially nail down this effect. For this reason, there are world wide efforts to model and implement this process in neutrino interaction simulations. In these proceedings, I would like to describe how this channel is modeled in neutrino interaction generators.

  5. Leakage Currents and Gas Generation in Advanced Wet Tantalum Capacitors

    NASA Technical Reports Server (NTRS)

    Teverovsky, Alexander

    2015-01-01

    Currently, military grade, established reliability wet tantalum capacitors are among the most reliable parts used for space applications. This has been achieved over the years by extensive testing and improvements in design and materials. However, a rapid insertion of new types of advanced, high volumetric efficiency capacitors in space systems without proper testing and analysis of degradation mechanisms might increase risks of failures. The specifics of leakage currents in wet electrolytic capacitors is that the conduction process is associated with electrolysis of electrolyte and gas generation resulting in building up of internal gas pressure in the parts. The risk associated with excessive leakage currents and increased pressure is greater for high value advanced wet tantalum capacitors, but it has not been properly evaluated yet. In this work, in Part I, leakages currents in various types of tantalum capacitors have been analyzed in a wide range of voltages, temperatures, and time under bias. Gas generation and the level of internal pressure have been calculated in Part II for different case sizes and different hermeticity leak rates to assess maximal allowable leakage currents. Effects related to electrolyte penetration to the glass seal area have been studied and the possibility of failures analyzed in Part III. Recommendations for screening and qualification to reduce risks of failures have been suggested.

  6. Submerged electricity generation plane with marine current-driven motors

    DOEpatents

    Dehlsen, James G.P.; Dehlsen, James B.; Fleming, Alexander

    2014-07-01

    An underwater apparatus for generating electric power from ocean currents and deep water tides. A submersible platform including two or more power pods, each having a rotor with fixed-pitch blades, with drivetrains housed in pressure vessels that are connected by a transverse structure providing buoyancy, which can be a wing depressor, hydrofoil, truss, or faired tube. The platform is connected to anchors on the seafloor by forward mooring lines and a vertical mooring line that restricts the depth of the device in the water column. The platform operates using passive, rather than active, depth control. The wing depressor, along with rotor drag loads, ensures the platform seeks the desired operational current velocity. The rotors are directly coupled to a hydraulic pump that drives at least one constant-speed hydraulic-motor generator set and enables hydraulic braking. A fluidic bearing decouples non-torque rotor loads to the main shaft driving the hydraulic pumps.

  7. Practical Application of Eddy Currents Generated by Wind

    NASA Astrophysics Data System (ADS)

    Dirba, I.; Kleperis, J.

    2011-06-01

    When a conductive material is subjected to time-varying magnetic fluxes, eddy (Foucault) currents are generated in it and magnetic field of opposite polarity as the applied one arises. Due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat (Joule heating). Conventional domestic water heaters utilize gas burners or electric resistance heating elements to heat the water in the tank and substantial part of the energy to use for it is wasted. In this paper the origin of electromagnetic induction heat generated by wind turbine in special heat exchange camera connected to water boiler is discussed and material evaluation performed using mathematical modelling (comparing the 2D finite element model with analytical and numerical calculation results).

  8. Electroluminescence from Spontaneously Generated Single-Vesicle Aggregates Using Solution-Processed Small Organic Molecules.

    PubMed

    Tsai, Yu-Tang; Tseng, Kuo-Pi; Chen, Yan-Fang; Wu, Chung-Chih; Fan, Gang-Lun; Wong, Ken-Tsung; Wantz, Guillaume; Hirsch, Lionel; Raffy, Guillaume; Del Guerzo, Andre; Bassani, Dario M

    2016-01-26

    Self-assembled aggregates offer great potential for tuning the morphology of organic semiconductors, thereby controlling their size and shape. This is particularly interesting for applications in electroluminescent (EL) devices, but there has been, to date, no reports of a functional EL device in which the size and color of the emissive domains could be controlled using self-assembly. We now report a series of molecules that spontaneously self-organize into small EL domains of sub-micrometer dimensions. By tailoring the emissive chromophores in solution, spherical aggregates that have an average size of 300 nm in diameter and emit any one color, including CIE D65 white, are spontaneously formed in solution. We show that the individual aggregates can be used in EL devices built either using small patterned electrodes or using a sandwich architecture to produce devices emitting in the blue, green, red, and white. Furthermore, sequential deposition of the three primary colors yields an RGB device in which single aggregates of each color are present in close proximity. PMID:26730851

  9. Eddy-current steam generator data analysis performance. Final report

    SciTech Connect

    Harris, D.H.

    1993-06-01

    This study assessed the accuracy of eddy current, bobbin coil data analysis of steam generator tubes conducted under the structure of the PWR Steam Generator Examination Guidelines, Individual and team performance measures were obtained from independent analyses of data from 1619 locations in a sample of 199 steam generator tubes. The 92 reportable indications contained in the tube sample, including 64 repairable indications, were attributable to: wear at anti-vibration bars, intergranular attack/stress-corrosion cracking (IGA/SCC) within tube sheet crevice regions, primary-water stress-corrosion cracking (PWSCC) at tube roll transitions, or thinning at cold-leg tube supports. Analyses were conducted by 20 analysts, four each from five vendors of eddy current steam generator examination services. In accordance with the guidelines, site orientation was provided with plant-specific guidelines; preanalysis practice was completed on plant-specific data; analysts were qualified by performance testing; and independent primary-secondary analyses were conducted with resolution of discrepancies (team analyses). Measures of analysis performance included percentages of indications correctly reported, percentages of false reports, and relative operating characteristic (ROC) curves. ROC curves presented comprehensive pictures of analysis accuracy generalizable beyond the specific conditions of this study. They also provided single-value measures of analysis accuracy. Conclusions and recommendations were provided relative to analysis accuracy, effect of primary-secondary analyses, analyses of tube sheet crevice regions, establishment of reporting criteria, improvement of examination guidelines, and needed research.

  10. System and method for generating current by selective electron heating

    DOEpatents

    Fisch, Nathaniel J.; Boozer, Allen H.

    1984-01-01

    A system for the generation of toroidal current in a plasma which is prepared in a toroidal magnetic field. The system utilizes the injection of high-frequency waves into the plasma by means of waveguides. The wave frequency and polarization are chosen such that when the waveguides are tilted in a predetermined fashion, the wave energy is absorbed preferentially by electrons traveling in one toroidal direction. The absorption of energy in this manner produces a toroidal electric current even when the injected waves themselves do not have substantial toroidal momentum. This current can be continuously maintained at modest cost in power and may be used to confine the plasma. The system can operate efficiently on fusion grade tokamak plasmas.

  11. Effect of active synthetic 2-substituted quinazolinones on anti-platelet aggregation and the inhibition of superoxide anion generation by neutrophils.

    PubMed

    Chang, Fang-Rong; Wu, Chin-Chung; Hwang, Tsong-Long; Patnam, Ramesh; Kuo, Reen-Yen; Wang, Wei-Ya; Lan, Yu-Hsuan; Wu, Yang-Chang

    2003-07-01

    Quinazolinones, 2-substituted and 3-substituted, mainly synthesized by microwave irradiation, were subjected to anti-platelet aggregation and inhibition of superoxide anion generation assays. Interestingly, 2-phenyl-4-quinazolinone (4) exhibited significant inhibitory activities toward platelet aggregation and neutrophil activation, and it might therefore serve as a prototype lead compound. PMID:12934640

  12. Gradual recruitment and selective clearing generate germ plasm aggregates in the zebrafish embryo.

    PubMed

    Eno, Celeste; Pelegri, Francisco

    2013-01-01

    Determination of primordial germ cells (PGCs) is one of the earliest decisions in animal embryogenesis. In many species, PGCs are determined through maternally-inherited germ plasm ribonucleoparticles (RNPs). In zebrafish, these are transmitted during oogenesis as dispersed RNPs, which after fertilization multimerize and become recruited as large aggregates at furrows for the first and second cell cycles. Here, we show that the number of recruited germ plasm RNPs is halved every cell cycle. We also show that germ plasm RNPs are recruited during the third cell cycle, but only transiently. Our data support a mechanism in which systematic local gathering of germ plasm RNPs during cytokinesis and threshold-dependent clearing contribute to forming germ plasm aggregates with the highest RNP number and germ cell-inducing potential. PMID:24721731

  13. Compact high current generator for x-ray radiography

    NASA Astrophysics Data System (ADS)

    Kharlov, A. V.; Kovalchuk, B. M.; Zorin, V. B.

    2006-12-01

    We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, X pinch, plasma focus, vacuum spark, etc. The X generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (20nF, 25nH, 0.2Ω, 100kV). It stores ˜0.8kJ at 80kV charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At 76kV charging voltage the generator provides ˜260kA with 120ns rise time and 5nH inductive load and ˜220kA with 145ns rise time and 10nH. Delay of output pulse relative to high voltage triggering pulse is ˜65ns with 5ns jitter. The dimensions of the generator are 1240×1240×225mm3 and the weight is ˜250kg, and only one high voltage power supply is required as additional equipment for the generator. The generator with a pumping system is placed on area about 0.5m2. Operation and handling are very simple, because no oil nor purified gases are required for the generator. The X generator has been successfully employed for experiments on the Ni X pinch load. X-ray pulse duration (full width at half maximum above 1keV) was about 5ns. Radiation yield Wr⩾500mJ was observed in the 1.2-1.5KeV range and Wr⩾20mJ in the 3-5keV energy range, which is comparable to results, obtained on the nanosecond accelerators. Clearly resolved images of 6μm wire indicate micron level size of hot spot. These results demonstrate possibility of this generator for application for x-ray backlighting.

  14. Chiral current generation in QED by longitudinal photons

    NASA Astrophysics Data System (ADS)

    Acosta Avalo, J. L.; Pérez Rojas, H.

    2016-08-01

    We report the generation of a pseudovector electric current having imbalanced chirality in an electron-positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. An electromagnetic chemical potential was introduced, but our results remain valid even when it vanishes. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler-Bell-Jackiw anomaly. From the expression for the chiral current in terms of the photon self-energy tensor in a medium, it is obtained that electrons and positrons scattered by longitudinal photons (inside the light cone) contribute to the chiral current, as well as the to pair creation due to longitudinal photons (out of light cone). In the static limit, an electric pseudovector current is obtained in the lowest Landau level.

  15. Current turbine for water pumping and electricity generation

    SciTech Connect

    Mohamed, A.I.E.

    1983-12-01

    This paper describes work on Phase I of ''Mini Hydropower Research and Development Project'' in the Department of Mechanical Engineering, University of Khartoum, in cooperation with the National Council for Research in Sudan. The main purpose of Phase I of the project has been to demonstrate and evaluate the use of water current energy for powering small-scale pumping units and for generating electricity. Power requirements for pumping water for irrigation on typical small land holdings in the Sudan will be of the order of 5-10 Kw. The same sizes of power should sufficiently meet power requirements of home factories for processing farm produce of these lands and of domestic uses. A vertical shaft impulse turbine of innovative design has been built in the Faculty of Engineering, University of Khartoum, to extract energy from water current of canals, rivers or streams. The useful shaft power from the turbine is used for pumping water or electricity generation. The turbine set is suspended from a floating pontoon (made from plastic drums) which is secured in the current by means of two horizontal supporting poles and steel cables. Field trials of a number of model turbine systems are currently being carried out and valuable findings are being obtained about the desirable features to be developed in these machines. However, concrete results are still to be finalized with a view to facilitating analytical design of pump-turbine and generatorturbine systems. Indications are that this work should lead to an efficient, cheap and simple-to-build current turbine. Detailed information on system design and performance are expected to be ready in time for the conference.

  16. Spin-polarized currents generated by magnetic Fe atomic chains.

    PubMed

    Lin, Zheng-Zhe; Chen, Xi

    2014-06-13

    Fe-based devices are widely used in spintronics because of high spin-polarization and magnetism. In this work, freestanding Fe atomic chains, the thinnest wires, were used to generate spin-polarized currents due to the spin-polarized energy bands. By ab initio calculations, the zigzag structure was found to be more stable than the wide-angle zigzag structure and had a higher ratio of spin-up and spin-down currents. By our theoretical prediction, Fe atomic chains have a sufficiently long thermal lifetime only at T ≦̸ 150 K, while C atomic chains are very stable even at T = 1000 K. This means that the spintronic devices based on Fe chains could work only at low temperatures. A system constructed by a short Fe chain sandwiched between two graphene electrodes could be used as a spin-polarized current generator, while a C chain could not be used in this way. The present work may be instructive and meaningful to further practical applications based on recent technical developments on the preparation of metal atomic chains (Proc. Natl. Acad. Sci. USA 107 9055 (2010)). PMID:24849670

  17. Voltage-Current Curves to Characterize Thermoelectric Generators

    NASA Astrophysics Data System (ADS)

    McCarty, Robin; Piper, Robert

    2015-06-01

    There are many ways to experimentally characterize thermoelectric generator (TEG) performance, but most methods provide an incomplete picture. The authors propose using voltage-current ( V- I) curves generated at two different thermal conditions to provide an estimation of maximum power, optimum efficiency, ZT of the device, and thermal resistance due to ceramics and thermal interface materials on the outside of the thermoelectric material (HSR). The two thermal conditions are both steady state, electrically open in one case and electrically shorted in the other, and the heat flow into the device is adjusted to keep the hot-side and cold-side temperatures of the exterior of the module the same in both thermal conditions. The V- I curves are generated from four data points by instantaneously changing the external electrical load such that the TEG does not have time to respond thermally. After these two V- I curves are generated, the performance at any electrical condition can be predicted for the given hot-side and cold-side device temperatures. The authors present experimental data for a bismuth telluride (Bi2Te3) device as verification of this characterization method.

  18. Generation of currents in the solar atmosphere by acoustic waves

    NASA Astrophysics Data System (ADS)

    Riutov, D. D.; Riutova, M. P.

    The novel mechanism presented for current and magnetic field generation by acoustic-wave fluxes in solar plasmas is especially potent in the region where acoustic-wave damping is due to such nonlinear effects as weak-shock formation. An evaluation is made of the significance of this effect for the solar atmosphere, under the proviso that this treatment is restricted to effects due to the usual acoustic waves. Wave absorption is governed by the classical collisional effects of thermal conductivity, viscosity, and ohmic losses.

  19. Simulation of Current Generation in a 3-D Plasma Model

    NASA Astrophysics Data System (ADS)

    Tsung, F. S.; Dawson, J. M.

    1996-11-01

    In the advanced tokamak regime, transport phenomena can account for a signficant fraction of the toroidal current, possibly over that driven directly by the ohmic heating electric fields. Bootstrap theory accounts for contributions of the collisional modification of banana orbits on the toroidal currents. In our previous simulations in 21/2-D, currents were spontaneously generated in both the cylindrical and the toroidal geometries, contrary to neoclassical predictions. In these calculations, it was believed that the driving mechanism is the preferential loss of particles whose initial velocity is opposite to that of the plasma current. We are extending these simulations to three dimensions. A parallel 3-D electromagnetic PIC code running on the IBM SP2, with a localized field-solver has been developed to investigate the effects of perturbations parallel to the field lines, and direct comparisons has been made between the 21/2-D and 3-D simulations and we have found good agreements between the 2 1/2-D calculations and the 3-D results. We will present our new results at the meeting. Research partially supported by NSF and DOE.

  20. Thermal generation of spin current in a multiferroic helimagnet

    NASA Astrophysics Data System (ADS)

    Takagi, R.; Tokunaga, Y.; Ideue, T.; Taguchi, Y.; Tokura, Y.; Seki, S.

    2016-03-01

    We report the experimental observation of longitudinal spin Seebeck effect in a multiferroic helimagnet Ba0.5Sr1.5Zn2Fe12O22. Temperature gradient applied normal to Ba0.5Sr1.5Zn2Fe12O22/Pt interface generates inverse spin Hall voltage of spin current origin in Pt, whose magnitude was found to be proportional to bulk magnetization of Ba0.5Sr1.5Zn2Fe12O22 even through the successive magnetic transitions among various helimagnetic and ferrimagnetic phases. This finding demonstrates that the helimagnetic spin wave can be an effective carrier of spin current. By controlling the population ratio of spin-helicity domains characterized by clockwise/counter-clockwise manner of spin rotation with use of poling electric field in the ferroelectric helimagnetic phase, we found that spin-helicity domain distribution does not affect the magnitude of spin current injected into Pt. The results suggest that the spin-wave spin current is rather robust against the spin-helicity domain wall, unlike the case with the conventional ferromagnetic domain wall.

  1. Effects of black carbon on aggregate stability, runoff generation, splash erosion and slopewash of a clay loam under simulated rainfall

    NASA Astrophysics Data System (ADS)

    Aston, Steve; Doerr, Stefan; Street-Perrott, Alayne

    2013-04-01

    Black (pyrogenic) carbon (BC) was produced from native hardwoods pyrolysed in a ring kiln at ~400° C and ground and sieved to < 2 mm. The BC was then added to a clay loam (sieved to 3.35 mm remaining. After 200 days of incubation, the remainder of each sample was air-dried and sieved to < 5 mm. Each sample was then placed in a square plot and subjected to 40 minutes of simulated rainfall. Runoff and subsurface drainage were measured at 2 minute intervals and runoff was collected at 5 minute intervals to enable subsequent determination of sediment concentrations, sediment yields and erosion rates of soil and BC. Splash cups were placed on each side of the plot to allow measurement of overall splash detachment for each simulation. A BC content of 5g kg-1 did not affect the mean aggregate stability of the clay loam, but a content of 25 g kg-1 led to a decrease in mean aggregate stability of >40%, with a further significant reduction observed when the BC content was 50 g kg-1. There were no statistically significant changes in aggregate stability between 50, 100 and 150 days of incubation for any of the application rates. Results showing the effects of BC on runoff generation, splash erosion and slopewash will also be presented.

  2. Utilization of lignite power generation residues for the production of lightweight aggregates.

    PubMed

    Anagnostopoulos, Iason M; Stivanakis, Victor E

    2009-04-15

    A novel process is proposed for the utilization of lignite combustion solid residues in the production of inflammable lightweight aggregates (LWA). The process consists of two stages, pelletization and sintering, and carbon contained in BA was used as the process fuel. The main residues bottom ash (BA) and fly ash (FA) from Megalopolis power plant were characterized, mixed in different proportions and treated through pelletization and sintering process. Sintering benefits from combustion of BA carbon content and the product is a hardened porous cake. The energy required for achievement of high temperatures, in the range of 1250 degrees C, was offered by carbon combustion and CO(2) evolution is responsible for porous structure formation. Selected physical properties of sintered material relevant to use as lightweight aggregates were determined, including bulk density, porosity and water absorption. Bulk density varies from 0.83 to 0.91 g/cm(3), porosity varies from 60% to 64% and water absorption varies from 66% to 80%. LWA formed is used for the production of lightweight aggregate concrete (LWAC). Thermal conductivity coefficient varies from 0.25 to 0.37 W/mK (lower than maximum limit 0.43 W/mK) and compressive strength varies from 19 to 23 MPa (higher than minimum limit 17 MPa). The results indicate that sintering of lignite combustion residues is an efficient method of utilization of carbon containing BA and production of LWA for structural and insulating purposes. Carbon content of BA is a key factor in LWA production. Finally, this research work comprises the first proposed application for utilization of BA in Greece. PMID:18804911

  3. Production efficiencies of U.S. electric generation plants: Effects of data aggregation and greenhouse gas and renewable energy policy

    NASA Astrophysics Data System (ADS)

    Lynes, Melissa Kate

    Over the last few decades there has been a shift in electricity production in the U.S. Renewable energy sources are becoming more widely used. In addition, electric generation plants that use coal inputs are more heavily regulated than a couple decades ago. This shift in electricity production was brought on by changes in federal policy -- a desire for electricity produced in the U.S. which led to policies being adopted that encourage the use of renewable energy. The change in production practices due to policies may have led to changes in the productivity of electric generation plants. Multiple studies have examined the most efficient electric generation plants using the data envelopment analysis (DEA) approach. This study builds on past research to answer three questions: 1) Does the level of aggregation of fuel input variables affect the plant efficiency scores and how does the efficiency of renewable energy input compare to nonrenewable energy inputs; 2) Are policies geared toward directly or indirectly reducing greenhouse gas emissions affecting the production efficiencies of greenhouse gas emitting electric generation plants; and 3) Do renewable energy policies and the use of intermittent energy sources (i.e. wind and solar) affect the productivity growth of electric generation plants. All three analysis, presented in three essays, use U.S. plant level data obtained from the Energy Information Administration to answer these questions. The first two essays use DEA to determine the pure technical, overall technical, and scale efficiencies of electric generation plants. The third essay uses DEA within the Malmquist index to assess the change in productivity over time. Results indicate that the level of aggregation does matter particularly for scale efficiency. This implies that valuable information is likely lost when fuel inputs are aggregated together. Policies directly focused on reducing greenhouse gas emissions may improve the production efficiencies of

  4. Modeling of eddy current NDE probe for steam generator tubes.

    SciTech Connect

    Chang, F. C.; Bakhtiari, S.; Kupperman, D.

    2003-01-29

    Calculations were performed with a three-dimensional (3-D) finite-element model to describe the response of an eddy current (EC) probe to defects in steam generator (SG) tubing of a nuclear reactor. Such calculations could be very helpful in understanding and interpreting the EC probe response to complex tube/defect geometries associated with longitudinal inner/outer notches, roll transitions, sludge, and through-wall holes in SG tubes. The governing field equations are derived in terms of coupled magnetic vector and electric scalar potentials in the conducting media and total or reduced scalar potentials in the non-conducting regions. To assess the validity of the model, we compared the signal responses for two numerical approaches, stored-energy-and-power-loss approach and magnetic-flux approach for various tube/defect geometries. Simulation results are also presented on the tube/defect geometries for the pancake coil response and the transmitter/receiver (T/R) probe response. The results indicate that the eddy-current NDE modeling is capable of predicting EC probe response to flaws in steam generator tubes.

  5. Modeling of a single-cycle current generator while forming a quasi-sinusoidal current

    NASA Astrophysics Data System (ADS)

    Grebennikov, V. V.; Yaroslavtsev, E. V.; Slobodenuk, A. B.; Evtushenko, T. G.

    2016-04-01

    The paper presents the results of investigation of the influence of the output voltage magnitude on the operating frequency of the switch in the single-cycle quasi-sinusoidal current generator circuit. Analytical expressions for calculating the time parameters for transients in the circuit under given assumptions have been obtained. The results presented in the paper can be used in the design of converters of this type.

  6. Compact submicrosecond, high current generator for wire explosion experiments

    NASA Astrophysics Data System (ADS)

    Aranchuk, L. E.; Chuvatin, A. S.; Larour, J.

    2004-01-01

    The PIAF generator was designed for low total energy and high energy density experiments with liners, X-pinch or fiber Z-pinch loads. These studies are of interest for such applications as surface and material science, microscopy of biological specimens, lithography of x-ray sensitive resists, and x-ray backlighting of pulsed-power plasmas. The generator is based on an RLC circuit that includes six NWL 180 nF-50 kV capacitors that store up to 1.3 kJ. The capacitors are connected in parallel to a single multispark switch designed to operate at atmospheric pressure. The switch allows reaching a time delay between the trigger pulse and the current pulse of less than 80 ns and has jitter of 6 ns. The total inductance without a load compartment was optimized to be as low as 16 nH, which leads to extremely low impedance of ˜0.12 Ω. A 40 kV initial voltage provides 250 kA maximum current in a 6 nH inductive load with a 180 ns current rise time. PIAF has dimensions of 660×660×490 mm and weight of less than 100 kg, thus manifesting itself as robust, simple to operate, and cost effective. A description of the PIAF generator and the initial experimental results on PIAF with an X-pinch type load are reported. The generator was demonstrated to operate successfully with an X-pinch type load. The experiments first started with investigation of the previously unexplored X-pinch conduction time range, 100 ns-1 μs. A single short radiation pulse was obtained that came from a small, point-like plasma. The following x-ray source characteristics were achieved: typical hot spot size of 50-100 μm, radiation pulse duration of 1.5-2 ns, and radiation yield of about 250-500 mJ in the softer spectral range (hν⩾700 eV) and 50-100 mJ in the harder one (hν⩾1 keV). These results provide the potential for further application of this source, such as use as a backlight diagnostic tool.

  7. Direct current power generation in self-excited liquid metal magnetohydrodynamic generators

    NASA Astrophysics Data System (ADS)

    Marty, Ph.

    1991-12-01

    Results of an analytical and experimental study of a self-excitated liquid-metal magnetohydrodynamic dc generator are reported. Expressions are proposed for the critical velocity and electrical efficiency; the calculated values of these parameters are compared with experimental results obtained for a mercury loop. The transition to the self-excitation regime is investigated numerically, and time dependences of the velocity and generated current are determined. It is shown that the magnitude of the remanent field has a strong effect on the transient period.

  8. DWPF CATALYTIC HYDROGEN GENERATION PROGRAM - REVIEW OF CURRENT STATUS

    SciTech Connect

    Koopman, D.

    2009-07-10

    Significant progress has been made in the past two years in improving the understanding of acid consumption and catalytic hydrogen generation during the Defense Waste Processing Facility (DWPF) processing of waste sludges in the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME). This report reviews issues listed in prior internal reviews, describes progress with respect to the recommendations made by the December 2006 external review panel, and presents a summary of the current understanding of catalytic hydrogen generation in the DWPF Chemical Process Cell (CPC). Noble metals, such as Pd, Rh, and Ru, are historically known catalysts for the conversion of formic acid into hydrogen and carbon dioxide. Rh, Ru, and Pd are present in the DWPF SRAT feed as by-products of thermal neutron fission of {sup 235}U in the original waste. Rhodium appears to become most active for hydrogen as the nitrite ion concentration becomes low (within a factor of ten of the Rh concentration). Prior to hydrogen generation, Rh is definitely active for nitrite destruction to N{sub 2}O and potentially active for nitrite to NO formation. These reactions are all consistent with the presence of a nitro-Rh complex catalyst, although definite proof for the existence of this complex during Savannah River Site (SRS) waste processing does not exist. Ruthenium does not appear to become active for hydrogen generation until nitrite destruction is nearly complete (perhaps less nitrite than Ru in the system). Catalytic activity of Ru during nitrite destruction is significantly lower than that of either Rh or Pd. Ru appears to start activating as Rh is deactivating from its maximum catalytic activity for hydrogen generation. The slow activation of the Ru, as inferred from the slow rate of increase in hydrogen generation that occurs after initiation, may imply that some species (perhaps Ru itself) has some bound nitrite on it. Ru, rather than Rh, is primarily responsible for the

  9. Improved eddy-current inspection for steam generator tubing

    SciTech Connect

    Dodd, C.V.; Pate, J.R.; Allen, J.D. Jr.; Allen , Knoxville, TN )

    1989-01-01

    Computer programs have been written to allow the analysis of different types of eddy-current probes and their performance under different steam generator test conditions. The probe types include the differential bobbin probe, the absolute bobbin probe, the pancake probe and the reflection probe. The generator test conditions include tube supports, copper deposits, magnetite deposits, denting, wastage, pitting, cracking and IGA. These studies are based mostly on computed values, with the limited number of test specimens available used to verify the computed results. The instrument readings were computed for a complete matrix of the different test conditions, and then the test conditions determined as a function of the readings by a least-squares technique. A comparison was made of the errors in fit and instrument drift for the different probe types. The computations of the change in instrument reading due to the defects have led to an inversion'' technique in which the defect properties can be computed from the instrument readings. This has been done both experimentally and analytically for each of these probe types. 3 refs., 13 figs., 1 tab.

  10. Steam generator degradation: Current mitigation strategies for controlling corrosion

    SciTech Connect

    Millett, P.

    1997-02-01

    Steam Generator degradation has caused substantial losses of power generation, resulted in large repair and maintenance costs, and contributed to significant personnel radiation exposures in Pressurized Water Reactors (PWRs) operating throughout the world. EPRI has just published the revised Steam Generator Reference Book, which reviews all of the major forms of SG degradation. This paper discusses the types of SG degradation that have been experienced with emphasis on the mitigation strategies that have been developed and implemented in the field. SG degradation is presented from a world wide perspective as all countries operating PWRs have been effected to one degree or another. The paper is written from a US. perspective where the utility industry is currently undergoing tremendous change as a result of deregulation of the electricity marketplace. Competitive pressures are causing utilities to strive to reduce Operations and Maintenance (O&M) and capital costs. SG corrosion is a major contributor to the O&M costs of PWR plants, and therefore US utilities are evaluating and implementing the most cost effective solutions to their corrosion problems. Mitigation strategies developed over the past few years reflect a trend towards plant specific solutions to SG corrosion problems. Since SG degradation is in most cases an economic problem and not a safety problem, utilities can focus their mitigation strategies on their unique financial situation. Accordingly, the focus of R&D has shifted from the development of more expensive, prescriptive solutions (e.g. reduced impurity limits) to corrosion problems to providing the utilities with a number of cost effective mitigation options (e.g. molar ratio control, boric acid treatment).

  11. Structural Characterization of IgG1 mAb Aggregates and Particles Generated under Various Stress Conditions

    PubMed Central

    Telikepalli, Srivalli N.; Kumru, Ozan S.; Kalonia, Cavan; Esfandiary, Reza; Joshi, Sangeeta B.; Middaugh, C. Russell; Volkin, David B.

    2014-01-01

    IgG1 mAb solutions were prepared with and without sodium chloride and subjected to different environmental stresses. Formation of aggregates and particles of varying size was monitored by a combination of size exclusion chromatography (SEC), Nanosight Tracking Analysis (NTA), Micro-flow Imaging (MFI), turbidity, and visual assessments. Stirring and heating induced the highest concentration of particles. In general, the presence of NaCl enhanced this effect. The morphology of the particles formed from mAb samples exposed to different stresses was analyzed from TEM and MFI images. Shaking samples without NaCl generated the most fibrillar particles, while stirring created largely spherical particles. The composition of the particles was evaluated for covalent cross-linking by SDS-PAGE, overall secondary structure by FTIR microscopy, and surface apolarity by extrinsic fluorescence spectroscopy. Freeze-thaw and shaking led to particles containing protein with native-like secondary structure. Heating and stirring produced IgG1 containing aggregates and particles with some non-native disulfide crosslinks, varying levels of intermolecular beta sheet content, and increased surface hydrophobicity. These results highlight the importance of evaluating protein particle morphology and composition, in addition to particle number and size distributions, to better understand the effect of solution conditions and environmental stresses on the formation of protein particles in mAb solutions. PMID:24452866

  12. A state tendency measurement for a hydro-turbine generating unit based on aggregated EEMD and SVR

    NASA Astrophysics Data System (ADS)

    Fu, Wenlong; Zhou, Jianzhong; Zhang, Yongchuan; Zhu, Wenlong; Xue, Xiaoming; Xu, Yanhe

    2015-12-01

    The reliable measurement of state tendency for a hydro-turbine generating unit (HGU) is significant in guaranteeing the security of the unit and promoting stability of the power system. For this purpose, an aggregated ensemble empirical mode decomposition (AEEMD) and optimized support vector regression (SVR)-based hybrid model is developed in this paper in order to enhance the measuring accuracy of state tendency for a HGU. First of all, the non-stationary time series of the state signal are decomposed into a collection of intrinsic mode functions (IMFs) by EEMD. Subsequently, to obtain the refactored intrinsic mode functions (RIMFs), the IMFs with different scales are aggregated with the proposed reconstruction strategy in consideration of the frequency and energy conditions. Later, the phase-space matrix in accordance with each RIMF is deduced by phase-space reconstruction and all the RIMFs are predicted through establishing homologous optimal SVR forecasting models with a grid search. Finally, the ultimate measuring values of state tendency can be determined through the accumulation of all the RIMF forecasting values. Furthermore, the effectiveness of the proposed method is validated in engineering experiments and comparative analyses.

  13. Current status of the UCSF second-generation PACS

    NASA Astrophysics Data System (ADS)

    Huang, H. K.; Arenson, Ronald L.; Wong, Albert W. K.; Bazzill, Todd M.; Lou, Shyhliang A.; Andriole, Katherine P.; Wang, Jun; Zhang, Jianguo; Wong, Stephen T. C.

    1996-05-01

    This paper describes the current status of the second generation PACS at UCSF commenced in October 1992. The UCSF PACS is designed in-house as a hospital-integrated PACS based on an open architecture concept using industrial standards including UNIX operating system, C programming language, X-Window user interface, TCP/IP communication protocol, DICOM 3.0 image standard and HL7 health data format. Other manufacturer's PACS components which conform with these standards can be easily integrated into the system. Relevant data from HIS and RIS is automatically incorporated into the PACS using HL7 data format and TCP/IP communication protocol. The UCSF system also takes advantage of state-of-the-art communication, storage, and software technologies in ATM, multiple storage media, automatic programming, multilevel processes for a better cost-performance system. The primary PACS network is the 155 Mbits/sec OC3 ATM with the Ethernet as the back-up. The UCSF PACS also connects Mt. Zion Hospital and San Francisco VA Medical Center in the San Francisco Bay area via an ATM wide area network with a T1 line as the back-up. Currently, five MR and five CT scanners from multiple sites, two computed radiography systems, two film digitizers, one US PACS module, the hospital HIS and the department RIS have been connected to the PACS network. The image data is managed by a mirrored database (Sybase). The PACS controller, with its 1.3 terabyte optical disk library, acquires 2.5 gigabytes digital data daily. Four 2K, five, 1,600-line multiple monitor display workstations are on line in neuroradiology, pediatric radiology and intensive care units for clinical use. In addition, the PACS supports over 100 Macintosh users in the department and selected hospital sites for both images and textual retrieval through a client/server mechanism. We are also developing a computation and visualization node in the PACS network for advancing radiology research.

  14. The Aggregate Description of Semi-Arid Vegetation with Precipitation-Generated Soil Moisture Heterogeneity

    NASA Technical Reports Server (NTRS)

    White, Cary B.; Houser, Paul R.; Arain, Altaf M.; Yang, Zong-Liang; Syed, Kamran; Shuttleworth, W. James

    1997-01-01

    Meteorological measurements in the Walnut Gulch catchment in Arizona were used to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area with a grid resolution of 480 m for a continuous 18-month period which included two seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the acceptability (for modelling purposes) of assuming uniformity in all meteorological variables other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain gauges. These meteorological data were used as forcing variables for an equivalent array of stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the evolution of soil moisture and surface energy fluxes in response to the prevalent, heterogeneous pattern of convective precipitation. The calculated area-average behaviour was compared with that given by a single aggregate BATS simulation forced with area-average meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating differences in the transpiration and the intercepted rainfall components of total evaporation during rain storms. However, the calculated area-average surface energy fluxes given by the two simulations in rain-free conditions with strong heterogeneity in soil moisture were always close to identical, a result which is independent of whether default or site-specific vegetation and soil parameters were used. Because the spatial variability in soil moisture throughout the catchment has the same order of magnitude as the amount of rain failing in a typical convective storm (commonly 10% of the vegetation's root zone saturation) in a semi-arid environment, non-linearitv in the relationship between transpiration and the soil moisture available to the vegetation has limited influence on area-average surface fluxes.

  15. Current interruption and particle beam generation by a plasma focus

    NASA Astrophysics Data System (ADS)

    Gerdin, G.; Venneri, F.

    1982-11-01

    Through collaboration with Dr. K. H. Schoenbach of Texas Tech University the plasma focus opening switch (PFOS) was revised to answer basic questions as to utility of the concept. To estimate the plasma temperature and classical resistivity a soft X-ray spectrometer and X-ray pinhole camera were developed. The temperature was estimated from a coronal model to range between 0.4 to 0.5 keV for either a nitrogen or neon impurity (1 to 2%) in deuterium at 3 torr. Strong pinches were observed in pure neon (0.6 torr) with an electron temperature in the same range. The corresponding classical resistance of the pinch is 9 m omega whereas 500 m omega is more consistent with output voltage pulse and current flow at interruption indicating anomalous resistivity is present. A one-dimensional two-fluid computer code has been developed to model anomalous resistivity in the pinch phase and preliminary results are consistent with the snowplow model. The final analysis of the plasma focus particle beam generation experiments was completed and a strong correlation was found for the beam-target model as the mechanism for neutron production in the Illinois plasma focus device.

  16. Generating Within-Plant Spatial Distributions of an Insect Herbivore Based on Aggregation Patterns and Per-Node Infestation Probabilities.

    PubMed

    Rincon, Diego F; Hoy, Casey W; Cañas, Luis A

    2015-04-01

    Most predator-prey models extrapolate functional responses from small-scale experiments assuming spatially uniform within-plant predator-prey interactions. However, some predators focus their search in certain plant regions, and herbivores tend to select leaves to balance their nutrient uptake and exposure to plant defenses. Individual-based models that account for heterogeneous within-plant predator-prey interactions can be used to scale-up functional responses, but they would require the generation of explicit prey spatial distributions within-plant architecture models. The silverleaf whitefly, Bemisia tabaci biotype B (Gennadius) (Hemiptera: Aleyrodidae), is a significant pest of tomato crops worldwide that exhibits highly aggregated populations at several spatial scales, including within the plant. As part of an analytical framework to understand predator-silverleaf whitefly interactions, the objective of this research was to develop an algorithm to generate explicit spatial counts of silverleaf whitefly nymphs within tomato plants. The algorithm requires the plant size and the number of silverleaf whitefly individuals to distribute as inputs, and includes models that describe infestation probabilities per leaf nodal position and the aggregation pattern of the silverleaf whitefly within tomato plants and leaves. The output is a simulated number of silverleaf whitefly individuals for each leaf and leaflet on one or more plants. Parameter estimation was performed using nymph counts per leaflet censused from 30 artificially infested tomato plants. Validation revealed a substantial agreement between algorithm outputs and independent data that included the distribution of counts of both eggs and nymphs. This algorithm can be used in simulation models that explore the effect of local heterogeneity on whitefly-predator dynamics. PMID:26313173

  17. TGF-β induces TIAF1 self-aggregation via type II receptor-independent signaling that leads to generation of amyloid β plaques in Alzheimer's disease

    PubMed Central

    Lee, M-H; Lin, S-R; Chang, J-Y; Schultz, L; Heath, J; Hsu, L-J; Kuo, Y-M; Hong, Q; Chiang, M-F; Gong, C-X; Sze, C-I; Chang, N-S

    2010-01-01

    The role of a small transforming growth factor beta (TGF-β)-induced TIAF1 (TGF-β1-induced antiapoptotic factor) in the pathogenesis of Alzheimer's disease (AD) was investigated. TIAF1 physically interacts with mothers against DPP homolog 4 (Smad4), and blocks SMAD-dependent promoter activation when overexpressed. Accordingly, knockdown of TIAF1 by small interfering RNA resulted in spontaneous accumulation of Smad proteins in the nucleus and activation of the promoter governed by the SMAD complex. TGF-β1 and environmental stress (e.g., alterations in pericellular environment) may induce TIAF1 self-aggregation in a type II TGF-β receptor-independent manner in cells, and Smad4 interrupts the aggregation. Aggregated TIAF1 induces apoptosis in a caspase-dependent manner. By filter retardation assay, TIAF1 aggregates were found in the hippocampi of nondemented humans and AD patients. Total TIAF1-positive samples containing amyloid β (Aβ) aggregates are 17 and 48%, respectively, in the nondemented and AD groups, suggesting that TIAF1 aggregation occurs preceding formation of Aβ. To test this hypothesis, in vitro analysis showed that TGF-β-regulated TIAF1 aggregation leads to dephosphorylation of amyloid precursor protein (APP) at Thr668, followed by degradation and generation of APP intracellular domain (AICD), Aβ and amyloid fibrils. Polymerized TIAF1 physically interacts with amyloid fibrils, which would favorably support plaque formation in vivo. PMID:21368882

  18. Apparatus for electrode current control in linear MHD generators

    DOEpatents

    Demirjian, Ara M.; Solbes, Albert

    1984-01-01

    Apparatus for controlling a plurality of opposing, electrode, direct-currents at pre-set locations across a channel that comprises a converter for converting each electrode current into first and second periodic control signals which are 180.degree. out of phase with respect to each other and which have equal magnitudes corresponding to the magnitude of the associated electrode current; and couplers for magnetically coupling individual ones of the first control signals and for magnetically coupling individual ones of the second signals such that the corresponding electrode currents are equalized or rendered proportional by balancing the same in the same or constant ratios in accordance with the locations of the electrode currents.

  19. Heat generation by optically and thermally interacting aggregates of gold nanoparticles under illumination

    NASA Astrophysics Data System (ADS)

    Zeng, Nan; Murphy, Anthony B.

    2009-09-01

    The generation of heat by clusters and arrays of gold nanoparticles under illumination is investigated theoretically. The nanoparticles are embedded in a homogeneous dielectric medium, and the finite thermal resistance at the interface between the nanoparticle and the medium is taken into account. An analytic solution is derived for the case of a single nanoparticle. The T-matrix method is used to calculate the energy absorption efficiency of groups of nanoparticles, taking into account their optical interactions. Heat transfer equations are developed that take into account thermal interactions between nanoparticles. The equations are solved numerically using the finite element software COMSOL. Periodic boundary conditions are applied to treat the thermal interactions between the nanoparticles for arrays of nanoparticles. Results are presented for illumination by a standard xenon flash lamp. The thermal resistance at the nanoparticle-medium interface is found to strongly influence the nanoparticle temperature, but to have negligible influence on the temperature of the dielectric medium after a few tens of nanoseconds of exposure to the flash lamp pulse. Optical interactions are found to be important if particle centres are separated by about twice the particle diameter or less. Thermal interactions between nanoparticles via the medium are found to be the dominant factor in determining the temperature increase in the dielectric medium. The maximum temperature increase is proportional to the volume fraction of the nanoparticles in the medium.

  20. Heat generation by optically and thermally interacting aggregates of gold nanoparticles under illumination.

    PubMed

    Zeng, Nan; Murphy, Anthony B

    2009-09-16

    The generation of heat by clusters and arrays of gold nanoparticles under illumination is investigated theoretically. The nanoparticles are embedded in a homogeneous dielectric medium, and the finite thermal resistance at the interface between the nanoparticle and the medium is taken into account. An analytic solution is derived for the case of a single nanoparticle. The T-matrix method is used to calculate the energy absorption efficiency of groups of nanoparticles, taking into account their optical interactions. Heat transfer equations are developed that take into account thermal interactions between nanoparticles. The equations are solved numerically using the finite element software COMSOL. Periodic boundary conditions are applied to treat the thermal interactions between the nanoparticles for arrays of nanoparticles. Results are presented for illumination by a standard xenon flash lamp. The thermal resistance at the nanoparticle-medium interface is found to strongly influence the nanoparticle temperature, but to have negligible influence on the temperature of the dielectric medium after a few tens of nanoseconds of exposure to the flash lamp pulse. Optical interactions are found to be important if particle centres are separated by about twice the particle diameter or less. Thermal interactions between nanoparticles via the medium are found to be the dominant factor in determining the temperature increase in the dielectric medium. The maximum temperature increase is proportional to the volume fraction of the nanoparticles in the medium. PMID:19706944

  1. Noninductive Current Generation in NSTX using Coaxial Helicity Injection

    SciTech Connect

    Raman, R.; Jarboe, T.R.; Mueller, D.; Schaffer, M.J.; Maqueda, R.; Nelson, B.A.; Sabbagh, S.; Bell, M.; Ewig, R.; Fredrickson, E.; Gates, D.; Hosea, J.; Jardin, S.; Ji, H.; Kaita, R.; Kaye, S.M.; Kugel, H.; Lao, L.; Maingi, R.; Menard, J.; Ono, M.; Orvis, D.; Paul, S.; Peng, M.; Skinner, C.H.; Wilgen, J.B.; Zweben, S.; and the NSTX Research Team

    2001-05-10

    Coaxial Helicity Injection (CHI) on the National Spherical Torus Experiment (NSTX) has produced 240 kA of toroidal current without the use of the central solenoid. Values of the current multiplication ratio (CHI produced toroidal current/injector current) up to 10 were obtained, in agreement with predictions. The discharges which lasted for up to 200 ms, limited only by the programmed waveform, are more than an order of magnitude longer in duration that any CHI discharges previously produced in a Spheromak or a Spherical Torus (ST).

  2. The receptor subunits generating NMDA receptor mediated currents in oligodendrocytes

    PubMed Central

    Burzomato, Valeria; Frugier, Guillaume; Pérez-Otaño, Isabel; Kittler, Josef T; Attwell, David

    2010-01-01

    NMDA receptors have been shown to contribute to glutamate-evoked currents in oligodendrocytes. Activation of these receptors damages myelin in ischaemia, in part because they are more weakly blocked by Mg2+ than are most neuronal NMDA receptors. This weak Mg2+ block was suggested to reflect an unusual subunit composition including the NR2C and NR3A subunits. Here we expressed NR1/NR2C and triplet NR1/NR2C/NR3A recombinant receptors in HEK cells and compared their currents with those of NMDA-evoked currents in rat cerebellar oligodendrocytes. NR1/NR2C/3A receptors were less blocked by 2 mm Mg2+ than were NR1/NR2C receptors (the remaining current was 30% and 18%, respectively, of that seen without added Mg2+) and showed less channel noise, suggesting a smaller single channel conductance. NMDA-evoked currents in oligodendrocytes showed a Mg2+ block (to 32%) similar to that observed for NR1/NR2C/NR3A and significantly different from that for NR1/NR2C receptors. Co-immunoprecipitation revealed interactions between NR1, NR2C and NR3A subunits in a purified myelin preparation from rat brain. These data are consistent with NMDA-evoked currents in oligodendrocytes reflecting the activation of receptors containing NR1, NR2C and NR3A subunits. PMID:20660562

  3. Displacement current and the generation of parallel electric fields.

    PubMed

    Song, Yan; Lysak, Robert L

    2006-04-14

    We show for the first time the dynamical relationship between the generation of magnetic field-aligned electric field (E||) and the temporal changes and spatial gradients of magnetic and velocity shears, and the plasma density in Earth's magnetosphere. We predict that the signatures of reconnection and auroral particle acceleration should have a correlation with low plasma density, and a localized voltage drop (V||) should often be associated with a localized magnetic stress concentration. Previous interpretations of the E|| generation are mostly based on the generalized Ohm's law, causing serious confusion in understanding the nature of reconnection and auroral acceleration. PMID:16712084

  4. Displacement Current and the Generation of Parallel Electric Fields

    SciTech Connect

    Song Yan; Lysak, Robert L.

    2006-04-14

    We show for the first time the dynamical relationship between the generation of magnetic field-aligned electric field (E{sub parallel}) and the temporal changes and spatial gradients of magnetic and velocity shears, and the plasma density in Earth's magnetosphere. We predict that the signatures of reconnection and auroral particle acceleration should have a correlation with low plasma density, and a localized voltage drop (V{sub parallel}) should often be associated with a localized magnetic stress concentration. Previous interpretations of the E{sub parallel} generation are mostly based on the generalized Ohm's law, causing serious confusion in understanding the nature of reconnection and auroral acceleration.

  5. Current and Next Generation Portable Screening Devices for Diabetic Retinopathy.

    PubMed

    Micheletti, J Morgan; Hendrick, Andrew M; Khan, Farah N; Ziemer, David C; Pasquel, Francisco J

    2016-03-01

    Diabetic retinopathy (DR) is the leading cause of legal blindness in the United States, and with the growing epidemic of diabetes, a global increase in the incidence of DR is inevitable, so it is of utmost importance to identify the most cost-effective tools for DR screening. Emerging technology may provide advancements to offset the burden of care, simplify the process, and provide financially responsible methods to safely and effectively optimize care for patients with diabetes mellitus (DM). We review here currently available technology, both in production and under development, for DR screening. Preliminary results of smartphone-based devices, "all-in-one" devices, and alternative technologies are encouraging, but are largely pending verification of utility when used by nonophthalmic personnel. Further research comparing these devices to current nonportable telemedicine strategies and clinical fundus examination is necessary to validate these techniques and to potentially overcome the poor compliance around the globe of current strategies for DR screening. PMID:26888973

  6. Thermal Generation of Spin Current in an Antiferromagnet.

    PubMed

    Seki, S; Ideue, T; Kubota, M; Kozuka, Y; Takagi, R; Nakamura, M; Kaneko, Y; Kawasaki, M; Tokura, Y

    2015-12-31

    The longitudinal spin Seebeck effect has been investigated for a uniaxial antiferromagnetic insulator Cr(2)O(3), characterized by a spin-flop transition under magnetic field along the c axis. We have found that a temperature gradient applied normal to the Cr(2)O(3)/Pt interface induces inverse spin Hall voltage of spin-current origin in Pt, whose magnitude turns out to be always proportional to magnetization in Cr(2)O(3). The possible contribution of the anomalous Nernst effect is confirmed to be negligibly small. The above results establish that an antiferromagnetic spin wave can be an effective carrier of spin current. PMID:26765011

  7. Electronic constant current and current pulse signal generator for nuclear instrumentation testing

    DOEpatents

    Brown, Roger A.

    1994-01-01

    Circuitry for testing the ability of an intermediate range nuclear instrut to detect and measure a constant current and a periodic current pulse. The invention simulates the resistance and capacitance of the signal connection of a nuclear instrument ion chamber detector and interconnecting cable. An LED flasher/oscillator illuminates an LED at a periodic rate established by a timing capacitor and circuitry internal to the flasher/oscillator. When the LED is on, a periodic current pulse is applied to the instrument. When the LED is off, a constant current is applied. An inductor opposes battery current flow when the LED is on.

  8. Electronic constant current and current pulse signal generator for nuclear instrumentation testing

    DOEpatents

    Brown, R.A.

    1994-04-19

    Circuitry is described for testing the ability of an intermediate range nuclear instrument to detect and measure a constant current and a periodic current pulse. The invention simulates the resistance and capacitance of the signal connection of a nuclear instrument ion chamber detector and interconnecting cable. An LED flasher/oscillator illuminates an LED at a periodic rate established by a timing capacitor and circuitry internal to the flasher/oscillator. When the LED is on, a periodic current pulse is applied to the instrument. When the LED is off, a constant current is applied. An inductor opposes battery current flow when the LED is on. 1 figures.

  9. Small Molecules Detected by Second-Harmonic Generation Modulate the Conformation of Monomeric α-Synuclein and Reduce Its Aggregation in Cells*

    PubMed Central

    Moree, Ben; Yin, Guowei; Lázaro, Diana F.; Munari, Francesca; Strohäker, Timo; Giller, Karin; Becker, Stefan; Outeiro, Tiago F.; Zweckstetter, Markus; Salafsky, Joshua

    2015-01-01

    Proteins are structurally dynamic molecules that perform specialized functions through unique conformational changes accessible in physiological environments. An ability to specifically and selectively control protein function via conformational modulation is an important goal for development of novel therapeutics and studies of protein mechanism in biological networks and disease. Here we applied a second-harmonic generation-based technique for studying protein conformation in solution and in real time to the intrinsically disordered, Parkinson disease related protein α-synuclein. From a fragment library, we identified small molecule modulators that bind to monomeric α-synuclein in vitro and significantly reduce α-synuclein aggregation in a neuronal cell culture model. Our results indicate that the conformation of α-synuclein is linked to the aggregation of protein in cells. They also provide support for a therapeutic strategy of targeting specific conformations of the protein to suppress or control its aggregation. PMID:26396193

  10. Exploiting current-generation graphics hardware for synthetic-scene generation

    NASA Astrophysics Data System (ADS)

    Tanner, Michael A.; Keen, Wayne A.

    2010-04-01

    Increasing seeker frame rate and pixel count, as well as the demand for higher levels of scene fidelity, have driven scene generation software for hardware-in-the-loop (HWIL) and software-in-the-loop (SWIL) testing to higher levels of parallelization. Because modern PC graphics cards provide multiple computational cores (240 shader cores for a current NVIDIA Corporation GeForce and Quadro cards), implementation of phenomenology codes on graphics processing units (GPUs) offers significant potential for simultaneous enhancement of simulation frame rate and fidelity. To take advantage of this potential requires algorithm implementation that is structured to minimize data transfers between the central processing unit (CPU) and the GPU. In this paper, preliminary methodologies developed at the Kinetic Hardware In-The-Loop Simulator (KHILS) will be presented. Included in this paper will be various language tradeoffs between conventional shader programming, Compute Unified Device Architecture (CUDA) and Open Computing Language (OpenCL), including performance trades and possible pathways for future tool development.

  11. Generation of sheet currents by high frequency fast MHD waves

    NASA Astrophysics Data System (ADS)

    Núñez, Manuel

    2016-07-01

    The evolution of fast magnetosonic waves of high frequency propagating into an axisymmetric equilibrium plasma is studied. By using the methods of weakly nonlinear geometrical optics, it is shown that the perturbation travels in the equatorial plane while satisfying a transport equation which enables us to predict the time and location of formation of shock waves. For plasmas of large magnetic Prandtl number, this would result into the creation of sheet currents which may give rise to magnetic reconnection and destruction of the original equilibrium.

  12. Ocean currents generate large footprints in marine palaeoclimate proxies.

    PubMed

    van Sebille, Erik; Scussolini, Paolo; Durgadoo, Jonathan V; Peeters, Frank J C; Biastoch, Arne; Weijer, Wilbert; Turney, Chris; Paris, Claire B; Zahn, Rainer

    2015-01-01

    Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5 °C for species living for a month and 3.0 °C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals. PMID:25735516

  13. Axial current generation from electric field: chiral electric separation effect.

    PubMed

    Huang, Xu-Guang; Liao, Jinfeng

    2013-06-01

    We study a relativistic plasma containing charged chiral fermions in an external electric field. We show that with the presence of both vector and axial charge densities, the electric field can induce an axial current along its direction and thus cause chirality separation. We call it the chiral electric separation effect (CESE). On a very general basis, we argue that the strength of CESE is proportional to μ(V)μ(A) with μ(V) and μ(A) the chemical potentials for vector charge and axial charge. We then explicitly calculate this CESE conductivity coefficient in thermal QED at leading-log order. The CESE can manifest a new gapless wave mode propagating along the electric field. Potential observable effects of CESE in heavy-ion collisions are also discussed. PMID:25167486

  14. Evaluation of the Genetic Basis of Familial Aggregation of Pacemaker Implantation by a Large Next Generation Sequencing Panel

    PubMed Central

    Steiner, Hillel A.; Uradu, Andrea; Lynnes, Ty C.; Groh, William J.; Miller, John M.; Lin, Hai; Gao, Hongyu; Wang, Zhiping; Liu, Yunlong; Chen, Peng-Sheng; Vatta, Matteo

    2015-01-01

    Background The etiology of conduction disturbances necessitating permanent pacemaker (PPM) implantation is often unknown, although familial aggregation of PPM (faPPM) suggests a possible genetic basis. We developed a pan-cardiovascular next generation sequencing (NGS) panel to genetically characterize a selected cohort of faPPM. Materials and Methods We designed and validated a custom NGS panel targeting the coding and splicing regions of 246 genes with involvement in cardiac pathogenicity. We enrolled 112 PPM patients and selected nine (8%) with faPPM to be analyzed by NGS. Results Our NGS panel covers 95% of the intended target with an average of 229x read depth at a minimum of 15-fold depth, reaching a SNP true positive rate of 98%. The faPPM patients presented with isolated cardiac conduction disease (ICCD) or sick sinus syndrome (SSS) without overt structural heart disease or identifiable secondary etiology. Three patients (33.3%) had heterozygous deleterious variants previously reported in autosomal dominant cardiac diseases including CCD: LDB3 (p.D117N) and TRPM4 (p.G844D) variants in patient 4; TRPM4 (p.G844D) and ABCC9 (p.V734I) variants in patient 6; and SCN5A (p.T220I) and APOB (p.R3527Q) variants in patient 7. Conclusion FaPPM occurred in 8% of our PPM clinic population. The employment of massive parallel sequencing for a large selected panel of cardiovascular genes identified a high percentage (33.3%) of the faPPM patients with deleterious variants previously reported in autosomal dominant cardiac diseases, suggesting that genetic variants may play a role in faPPM. PMID:26636822

  15. Shift in aggregation, ROS generation, antioxidative defense, lysozyme and acetylcholinesterase activities in the cells of an Indian freshwater sponge exposed to washing soda (sodium carbonate).

    PubMed

    Mukherjee, Soumalya; Ray, Mitali; Ray, Sajal

    2016-09-01

    Washing soda, chemically identified as anhydrous sodium carbonate, is a popular cleaning agent among the rural and urban populations of India which often contaminates the freshwater ponds and lakes, the natural habitat of sponge Eunapius carteri. Present investigation deals with estimation of cellular aggregation, generation of ROS and activities of antioxidant enzymes, lysozyme and acetylcholinesterase in the cells of E. carteri under the environmentally realistic concentrations of washing soda. Prolonged treatment of washing soda inhibited the degree of cellular aggregation. Experimental exposure of 8 and 16mg/l of sodium carbonate for 48h elevated the physiological level of reactive oxygen species (ROS) generation in the agranulocytes, semigranulocytes and granulocytes of E. carteri, whereas, treatment of 192h inhibited the ROS generation in three cellular morphotypes. Activities of superoxide dismutase, catalase and glutathione-S-transferase were recorded to be inhibited under prolonged exposure of washing soda. Washing soda mediated inhibition of ROS generation and depletion in the activities of antioxidant enzymes were indicative to an undesirable shift in cytotoxic status and antioxidative defense in E. carteri. Inhibition in the activity of lysozyme under the treatment of sodium carbonate was suggestive to a severe impairment of the innate immunological efficiency of E. carteri distributed in the washing soda contaminated habitat. Washing soda mediated inhibition in the activity of acetylcholinesterase indicated its neurotoxicity in E. carteri. Washing soda, a reported environmental contaminant, affected adversely the immunophysiological status of E. carteri with reference to cellular aggregation, oxidative stress, antioxidative defense, lysozyme and acetylcholinesterase activity. PMID:27178357

  16. Current Status of Development of Methods to Assess Effects of Cumulative or Aggregated Underwater Sounds on Marine Mammals.

    PubMed

    Fleishman, Erica; Streever, Bill; Angliss, Robyn; Clark, Christopher W; Ellison, William T; Frankel, Adam; Gedamke, Jason; Leu, Matthias; McKenna, Megan; Racca, Roberto; Simmons, Samantha; Suydam, Robert

    2016-01-01

    There are no standards for assessment of the cumulative effects of underwater sound. Quantitative assessments typically consider a single source, whereas qualitative assessments may include multiple sources but rarely identify response variables. As a step toward understanding the cumulative effects of underwater sound, we assessed the aggregated sounds of multiple sources received by migrating bowhead whales (Balaena mysticetus). The quantitative method models the sound field from multiple sources and simulates movement of a population through it. The qualitative method uses experts to assess the responses of individuals and populations to sound sources and identify the potential mechanisms. These methods increase the transparency of assessments. PMID:26610973

  17. Return Current Electron Beams and Their Generation of "Raman" Scattering

    NASA Astrophysics Data System (ADS)

    Simon, A.

    1998-11-01

    For some years, we(A. Simon and R. W. Short, Phys. Rev. Lett. 53), 1912 (1984). have proposed that the only reasonable explanation for many of the observations of "Raman" scattering is the presence of an electron beam in the plasma. (The beam creates a bump-on-tail instability.) Two major objections to this picture have been observation of Raman when no n_c/4 surface was present, with no likely source for the electron beam, and the necessity for the initially outward directed beam to bounce once to create the proper waves. Now new observations on LLE's OMEGA(R. Petrasso et al), this conference. and at LULI(C. Labaune et al)., Phys. Plasma 5, 234 (1998). have suggested a new origin for the electron beam. This new scenario answers the previous objections, maintains electron beams as the explanation of the older experiments, and may clear up puzzling observations that have remained unexplained. The new scenario is based on two assumptions: (1) High positive potentials develop in target plasmas during their creation. (2) A high-intensity laser beam initiates spark discharges from nearby surfaces to the target plasma. The resulting return current of electrons should be much more delta-like, is initially inwardly directed, and no longer requires the continued presence of a n_c/4 surface. Scattering of the interaction beam from the BOT waves yields the observed Raman signal. Experimental observations that support this picture will be cited. ``Pulsation'' of the scattering and broadband ``flashes'' are a natural part of this scenario. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  18. Generation of coronal electric currents due to convective motions on the photosphere

    NASA Technical Reports Server (NTRS)

    Sakurai, T.; Levine, R. H.

    1981-01-01

    Generation of electric currents in a magnetized plasma overlying a dense convective layer is studied, assuming that the magnetic field perturbation is small and satisfies the force-free equation. Currents are produced by rotational motions on the boundary in the case of a uniform equilibrium field. In a simple two-dimensional bipolar configuration, however, both irrotational and incompressible motions give rise to currents, and the current density has a peak at the magnetic neutral line. Scaling laws for the current density as well as for the stored magnetic energy are derived, and the possibility of heating the solar corona through the dissipation of coronal currents generated in this way is discussed.

  19. Magnetic field generated by shielding current in high Tc superconducting coils for NMR magnets

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Akachi, Ken

    2008-09-01

    Numerical electromagnetic field analyses of high Tc superconducting tape in coils were carried out to calculate the magnetic field generated by the shielding (magnetization) current in superconducting tape. The numerical model employs the power law electric field-current density characteristic and the thin strip approximation, in which the current component normal to the wide face of the tape is neglected. The shielding (magnetization) currents lead to non-uniform current distributions in the superconducting tape in the coils. The magnetic field generated by the shielding (magnetization) current can deteriorate the field quality and could be a concern in insert coils for NMR magnets using high Tc superconducting tape.

  20. Family Aggregation and Risk Factors in Phobic Disorders over Three-Generations in a Nation-Wide Study

    PubMed Central

    Steinhausen, Hans-Christoph; Jakobsen, Helle; Meyer, Andrea; Jørgensen, Povl Munk; Lieb, Roselind

    2016-01-01

    Objective This nation-wide register-based study investigated how often phobic disorders (PHO) and co-morbid disorders occur in affected families compared to control families. Furthermore, the study addressed the impact of sex, year of birth, and degree of urbanization in terms of risk factors. Method A total of N = 746 child and adolescent psychiatric participants born between 1969 and 1986 and registered in the Danish Psychiatric Central Research Register (DPCRR) with a diagnosis of a mental disorder before the age of 18, and developed PHO at some point during their life-time until a maximum age of 40 years were included. In addition, N = 2229 controls without any diagnosis of mental disorders before age 18 and that were matched for age, sex, and residential region were included. Diagnoses of mental disorders were also obtained from the first- degree relatives as a part of the Danish Three Generation Study (3GS). A family load component was obtained by using various mixed regression models. Results PHO occurred significantly more often in case than in control families, in particular, in mothers and siblings. Substance use disorders (SUD), Depressive disorders (DEP), anxiety disorders (ANX) and personality disorders (PERS) in the family were significantly associated with specific phobia in the case-probands. After controlling for various mental disorders comorbid to PHO it was found that some of the family transmission could be caused by various other mental disorders in family members rather than the PHO itself. Female sex and more recent year of birth were further risk factors while region of residence was not related to the manifestation of PHO. Case-relatives did not develop PHO earlier than control relatives. After adjusting for various additional explanatory variables, the family load explained only 0.0013% of the variance in the manifestation of PHO in the case-probands Discussion These findings, based on a very large and representative dataset, provide

  1. Effects of diode current on high power microwave generation in a vircator

    NASA Astrophysics Data System (ADS)

    Liu, Guozhi; Huang, Wenhua; Shao, Hao; Qiu, Shi; Wang, Hongjun; Liu, Jingyue; Wang, Feng; Yang, Zhanfeng; Qiao, Yongzhi

    2009-12-01

    An experiment of a virtual cathode oscillator (vircator) built on the low impedance intense electron beam accelerator Flash II is reported. A novel spectrum diagnosis method—a circulating dispersion line—is proposed. A thin oil layer coated graphite cathode is introduced in the experiment to decrease the delay time of the explosive emission process and obtain a homogeneous electron beam emission for improving the high-power microwave (HPM) generation efficiency. The effect of diode current on HPM generation in the vircator system is discussed. The HPM pulse width has a strong connection with the diode current waveform. For most shots, corresponding to the time that microwave emission starts, there is an inflection point in the diode current pulse. Compared with the case that no microwave is generated, the diode current increases more slowly following the inflection point. HPM generation terminates when the beam current reaches the self-pinching critical current of the diode.

  2. Formation of current filaments and magnetic field generation in a quantum current-carrying plasma

    SciTech Connect

    Niknam, A. R.; Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M.

    2013-09-15

    The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.

  3. Effects of Humic Acid and Sunlight on the Generation and Aggregation State of Aqu/C60 Nanoparticles

    EPA Science Inventory

    Aqueous suspensions of nanoscale C60 aggregates (aqu/C60) were produced by stirring in water with Suwanee River Humic Acid (humic acid) and water from Call’s Creek, a small stream near Athens, GA. Time course experiments were conducted to determine the effects of sunlight and sol...

  4. Aggregation Kinetics of Metal Chalcogenide Nanocrystals: Generation of Transparent CdSe(ZnS) Core(Shell) Gels

    SciTech Connect

    Korala, Lasantha; Brock, Stephanie

    2012-08-16

    Transparent CdSe (ZnS) core (shell) sol–gel materials have potential uses in optoelectronic applications such as light-emitting diodes (LEDs) due to their strong luminescence properties and the potential for charge transport through the prewired nanocrystal (NC) network of the gel. However, typical syntheses of metal chalcogenide gels yield materials with poor transparency. In this work, the mechanism and kinetics of aggregation of two sizes of CdSe (ZnS) core (shell) NCs, initiated by removal of surface thiolate ligands using tetranitromethane (TNM) as an oxidant, were studied by means of time-resolved dynamic light scattering (TRDLS); the characteristics of the resultant gels were probed by optical absorption, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). At low concentrations of NCs (ca. 4 × 10{sup –7} M), the smaller, green-emitting NCs aggregate faster than the larger, orange-emitting NCs, for a specific oxidant concentration. The kinetics of aggregation have a significant impact on the macroscopic properties (i.e., transparency) of the resultant gels, with the transparency of the gels decreasing with the increase of oxidant concentration due the formation of larger clusters at the gel point and a shift away from a reaction-limited cluster-aggregation (RLCA) mechanism. This is further confirmed by analyses of the gel structures by SAXS and TEM. Likewise, the larger orange-emitting particles also produce larger aggregates at the gel point, leading to lower transparency. The ability to control the transparency of chalcogenide gels will enable their properties to be tuned in order to address application-specific needs in optoelectronics.

  5. Effect of Time Dependent Bending of Current Sheets in Response to Generation of Plasma Jets and Reverse Currents

    NASA Astrophysics Data System (ADS)

    Frank, Anna

    Magnetic reconnection is a basis for many impulsive phenomena in space and laboratory plasmas accompanied by effective transformation of magnetic energy. Reconnection processes usually occur in relatively thin current sheets (CSs), which separate magnetic fields of different or opposite directions. We report on recent observations of time dependent bending of CSs, which results from plasma dynamics inside the sheet. The experiments are carried out with the CS-3D laboratory device (Institute of General Physics RAS, Moscow) [1]. The CS magnetic structure with an X line provides excitation of the Hall currents and plasma acceleration from the X line to both side edges [2]. In the presence of the guide field By the Hall currents give rise to bending of the sheet: the peripheral regions located away from the X line are deflected from CS middle plane (z=0) in the opposite directions ±z [3]. We have revealed generation of reverse currents jy near the CS edges, i.e. the currents flowing in the opposite direction to the main current in the sheet [4]. There are strong grounds to believe that reverse currents are generated by the outflow plasma jets [5], accelerated inside the sheet and penetrated into the regions with strong normal magnetic field component Bz [4]. An impressive effect of sudden change in the sign of the CS bend has been disclosed recently, when analyzing distributions of plasma density [6] and current away from the X line, in the presence of the guide field By. The CS configuration suddenly becomes opposite from that observed at the initial stage, and this effect correlates well with generation of reverse currents. Consequently this effect can be related to excitation of the reverse Hall currents owing to generation of reverse currents jy in the CS. Hence it may be concluded that CSs may exhibit time dependent vertical z-displacements, and the sheet geometry depends on excitation of the Hall currents, acceleration of plasma jets and generation of reverse

  6. The ups and downs of coral reef fishes: the genetic characteristics of a formerly severely overfished but currently recovering Nassau grouper fish spawning aggregation

    NASA Astrophysics Data System (ADS)

    Bernard, A. M.; Feldheim, K. A.; Nemeth, R.; Kadison, E.; Blondeau, J.; Semmens, B. X.; Shivji, M. S.

    2016-03-01

    The Nassau grouper ( Epinephelus striatus) has sustained large declines across its distribution, including extirpation of many of its fish spawning aggregations (FSAs). Within US Virgin Islands (USVI) waters, Nassau grouper FSAs were overfished until their disappearance in the 1970s and 1980s. In the early 2000s, however, Nassau grouper were found gathering at Grammanik Bank, USVI, a mesophotic coral reef adjacent to one of the extinct aggregation sites, and regulatory protective measures were implemented to protect this fledgling FSA. The population genetic dynamics of this rapid FSA deterioration followed by protection-facilitated, incipient recovery are unknown. We addressed two objectives: (1) we explored which factors (i.e., local vs. external recruitment) might be key in shaping the USVI FSA recovery; and (2) we examined the consequences of severe past overfishing on this FSA's current genetic status. We genotyped individuals (15 microsatellites) from the USVI FSA comprising three successive spawning years (2008-2010), as well as individuals from a much larger, presumably less impacted, Nassau grouper FSA in the Cayman Islands, to assess their comparative population dynamics. No population structure was detected between the USVI and Cayman FSAs ( F ST = -0.0004); however, a temporally waning, genetic bottleneck signal was detected in the USVI FSA. Parentage analysis failed to identify any parent-offspring matches between USVI FSA adults and nearby juveniles, and relatedness analysis showed low levels of genetic relatedness among USVI FSA individuals. Genetic diversity across USVI FSA temporal collections was relatively high, and no marked differences were found between the USVI and Cayman FSAs. These collective results suggest that external recruitment is an important driver of the USVI FSA recovery. Furthermore, despite an apparent genetic bottleneck, the genetic diversity of USVI Nassau grouper has not been severely compromised. Our findings also provide a

  7. Generation of Spin and Orbital Current in Carbon Nanotubes by Spin-rotation Coupling

    NASA Astrophysics Data System (ADS)

    Hamada, Masato; Murakami, Shuichi

    2015-03-01

    Spin-rotation coupling represents a coupling between the electron spins and mechanical rotations, and may be used for generation of spin currents by mechanical rotation. In our presentation we consider carbon nanotubes, and use one of the phonon modes called a twist mode. This mode gives rise to a rotation around the tube axis and eventually an effective Zeeman field parallel to the axis is generated by spin-rotation coupling. We calculate a generated spin current by solving the spin diffusion equation. In addition to the effective Zeeman field along the axis, the rotation also generates an effective orbital magnetic field in the radial direction. We calculate diamagnetic susceptibility for the radial magnetic field, and discuss the generated orbital current.

  8. Impact of slow K(+) currents on spike generation can be described by an adaptive threshold model.

    PubMed

    Kobayashi, Ryota; Kitano, Katsunori

    2016-06-01

    A neuron that is stimulated by rectangular current injections initially responds with a high firing rate, followed by a decrease in the firing rate. This phenomenon is called spike-frequency adaptation and is usually mediated by slow K(+) currents, such as the M-type K(+) current (I M ) or the Ca(2+)-activated K(+) current (I AHP ). It is not clear how the detailed biophysical mechanisms regulate spike generation in a cortical neuron. In this study, we investigated the impact of slow K(+) currents on spike generation mechanism by reducing a detailed conductance-based neuron model. We showed that the detailed model can be reduced to a multi-timescale adaptive threshold model, and derived the formulae that describe the relationship between slow K(+) current parameters and reduced model parameters. Our analysis of the reduced model suggests that slow K(+) currents have a differential effect on the noise tolerance in neural coding. PMID:27085337

  9. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    NASA Astrophysics Data System (ADS)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  10. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    SciTech Connect

    Bouda, N. R. Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  11. Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

    NASA Astrophysics Data System (ADS)

    Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

    In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

  12. Generation of pure spin currents via Auger recombination in quantum wells with Rashba splitting

    SciTech Connect

    Afanasiev, A. N. Greshnov, A. A. Greshnov, A. A.

    2015-10-15

    We propose a nonoptical mechanism for generating spin current via Auger recombination in semiconductor quantum wells (QWs) with spin–orbit splitting associated with structural QW asymmetry. It is shown that Auger recombination in narrow-bandgap semiconductors makes it possible to produce spin currents that exceed those that are obtained in the case of intraband as well as interband optical excitation. Analysis shows that the interference term in the expression for the Auger-recombination rate is responsible for the generation of spin currents.

  13. Mapping return currents in laser-generated Z-pinch plasmas using proton deflectometry

    SciTech Connect

    Manuel, M. J.-E.; Sinenian, N.; Seguin, F. H.; Li, C. K.; Frenje, J. A.; Rinderknecht, H. G.; Casey, D. T.; Zylstra, A. B.; Petrasso, R. D.; Beg, F. N.

    2012-05-14

    Dynamic return currents and electromagnetic field structure in laser-generated Z-pinch plasmas have been measured using proton deflectometry. Experiments were modeled to accurately interpret deflections observed in proton radiographs. Current flow is shown to begin on axis and migrate outwards with the expanding coronal plasma. Magnetic field strengths of {approx}1 T are generated by currents that increase from {approx}2 kA to {approx}7 kA over the course of the laser pulse. Proton deflectometry has been demonstrated to be a practical alternative to other magnetic field diagnostics for these types of plasmas.

  14. The Feasibility of a Current-Source Thermoelectric Power Generator and Its Corresponding Structure Design

    NASA Astrophysics Data System (ADS)

    Wu, Guangxi; Yu, Xiong

    2015-06-01

    Traditional thermoelectric power generators consist of thermoelectric elements connected electrically in series and thermally in parallel. Current flowing inside the thermoelectric power generator is conventionally considered to be driven by the Seebeck effect-induced electric field and the output voltage-induced reverse electric field. This paper proposes a more comprehensive model that implies that current is also driven by chemical potential and carrier density variation. Therefore, the thermoelectric power generator can be treated as a current-source power supplier when the current driven by carrier density variation dominates. This paper performs holistic finite element implementation of the new holistic model where a thermoelectric power generator unit behaves like a current-source while the working temperature conditions maintain stability. This result validates that the thermoelectric element shows the behaviors of a current-source power supply under certain conditions. This discovery brings a new perspective on the behaviors of thermoelectric elements, which potentially will lead to the development of novel thermoelectric power generator design.

  15. Stray neutral current problems and analysis associated with multiple ATS generator installations

    NASA Astrophysics Data System (ADS)

    Dunn, Samuel Douglas

    In generator installations where there is more than one 3-pole automatic-transfer-switch (ATS) on a 4-wire system, stray neutral currents and unwanted magnetic fields may arise. These stray currents and fields can cause a multitude of problems. Magnetic fields created by stray neutral currents can cause objectionable current on the conduit system. Objectionable current of this type can cause voltage rises on the grounding system. Geometries of stray neutral current paths can cause magnetic fields through areas of buildings that may cause problems with sensitive electronic equipment. Ground fault protection devices may detect incorrect ground fault condition. The presence of stray ground currents in multi-ATS installations is dependent on equipment selection and bonding connection points, whereas the magnitude of these currents depend on the system geometry, raceway size/types, and other factors. This paper looks at several stray neutral configurations tested in the Vanderbilt Power Laboratory.

  16. Noninductive plasma generation and current drive in the Globus-M spherical tokamak

    SciTech Connect

    D'yachenko, V. V.; Gusev, V. K.; Larionov, M. M.; Mel'nik, A. D.; Novokhatskii, A. N.; Petrov, Yu. V.; Rozhdestvenskii, V. V.; Sakharov, N. V.; Stepanov, A. Yu.; Khitrov, S. A.; Khromov, N. A.; Chernyshev, F. V.; Shevelev, A. E.; Shcherbinin, O. N.; Bender, S. E.; Kavin, A. A.; Lobanov, K. M.

    2013-03-15

    Experimental results on the generation and maintenance of the toroidal current in the Globus-M spherical tokamak by using waves in the lower hybrid frequency range without applying an inductive vortex electric field are presented. For this purpose, the original ridge guide antennas forming a field distribution similar to that produced by multiwaveguide grills were used. The high-frequency field (900 MHz) was used for both plasma generation and current drive. The magnitude of the generated current reached 21 kA, and its direction depended on the direction of the vertical magnetic field. Analysis of the experimental results indicates that the major fraction of the current is carried by the suprathermal electron beam.

  17. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  18. Effects of current on droplet generation and arc plasma in gas metal arc welding

    NASA Astrophysics Data System (ADS)

    Hu, J.; Tsai, H. L.

    2006-09-01

    In gas metal arc welding (GMAW), a technology using pulsed currents has been employed to achieve the one-droplet-per-pulse (ODPP) metal transfer mode with the advantages of low average currents, a stable and controllable droplet generation, and reduced spatter. In this paper, a comprehensive model was developed to study the effects of different current profiles on the droplet formation, plasma generation, metal transfer, and weld pool dynamics in GMAW. Five types of welding currents were studied, including two constant currents and three wave form currents. In each type, the transient temperature and velocity distributions of the arc plasma and the molten metal, and the shapes of the droplet and the weld pool were calculated. The results showed that a higher current generates smaller droplets, higher droplet frequency, and higher electromagnetic force that becomes the dominant factor detaching the droplet from the electrode tip. The model has demonstrated that a stable ODPP metal transfer mode can be achieved by choosing a current with proper wave form for given welding conditions.

  19. Heat generation by electronic current in a quantum dot spin-valve

    SciTech Connect

    Chi, Feng; Sun, Lian-Liang; Guo, Yu

    2014-10-28

    Electric-current-induced heat generation in an interacting single-level quantum dot connected to ferromagnetic leads with noncollinear magnetizations is theoretically investigated. We find that when the two leads' spin polarization rates are identical and much smaller than unit, the magnitude of the heat generation is almost monotonously enhanced as the angle between the leads' magnetic moments is varied from zero to π, while the magnitude of the electric current is continuously suppressed. Moreover, the properties of the heat generation depend on the lead's spin polarization rate in different ways when the angle is varied. If at least one of the leads' spin polarization rate approaches to unit, the spin-valve effect of the heat generation is identical to that of the electric current. Now the previously found negative differential of the heat generation disappears when the angle approaches to π. As compared to the current, the heat generation is more sensitive to the system's asymmetry when one of the electrodes is half-metallic in noncollinear configurations.

  20. Generation and coherent control of pure spin currents via terahertz pulses

    SciTech Connect

    Schüler, Michael Berakdar, Jamal

    2014-04-21

    We inspect the time and spin-dependent, inelastic tunneling in engineered semiconductor-based double quantum well driven by time-structured terahertz pulses. An essential ingredient is an embedded spin-active structure with vibrational modes that scatter the pulse driven carriers. Due to the different time scales of the charge and spin dynamics, the spin-dependent electron-vibron coupling may result in pure net spin current (with negligible charge current). Heating the vibrational site may affect the resulting spin current. Furthermore, by controlling the charge dynamics, the spin dynamics and the generated spin current can be manipulated and switched on and off coherently.

  1. Photophoretic force on aggregate grains

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin S.; Kimery, Jesse B.; Wurm, Gerhard; de Beule, Caroline; Kuepper, Markus; Hyde, Truell W.

    2016-01-01

    The photophoretic force may impact planetary formation by selectively moving solid particles based on their composition and structure. This generates collision velocities between grains of different sizes and sorts the dust in protoplanetary discs by composition. This numerical simulation studied the photophoretic force acting on fractal dust aggregates of μm-scale radii. Results show that aggregates tend to have greater photophoretic drift velocities than spheres of similar mass or radii, though with a greater spread in the velocity. While the drift velocities of compact aggregates continue to increase as the aggregates grow larger in size, fluffy aggregates have drift velocities which are relatively constant with size. Aggregates formed from an initially polydisperse size distribution of dust grains behave differently from aggregates formed from a monodisperse population, having smaller drift velocities with directions which deviate substantially from the direction of illumination. Results agree with microgravity experiments which show the difference of photophoretic forces with aggregation state.

  2. Design of a Torque Current Generator for Strapdown Gyroscopes. Ph.D. Thesis; [and performance prediction

    NASA Technical Reports Server (NTRS)

    Mcknight, R. D.; Blalock, T. V.; Kennedy, E. J.

    1974-01-01

    The design, analysis, and experimental evaluation of an optimum performance torque current generator for use with strapdown gyroscopes, is presented. Among the criteria used to evaluate the design were the following: (1) steady-state accuracy; (2) margins of stability against self-oscillation; (3) temperature variations; (4) aging; (5) static errors drift errors, and transient errors, (6) classical frequency and time domain characteristics; and (7) the equivalent noise at the input of the comparater operational amplifier. The DC feedback loop of the torque current generator was approximated as a second-order system. Stability calculations for gain margins are discussed. Circuit diagrams are shown and block diagrams showing the implementation of the torque current generator are discussed.

  3. Evaluation and field validation of Eddy-Current array probes for steam generator tube inspection

    SciTech Connect

    Dodd, C.V.; Pate, J.R.

    1996-07-01

    The objective of the Improved Eddy-Current ISI for Steam Generator Tubing program is to upgrade and validate eddy-current inspections, including probes, instrumentation, and data processing techniques for inservice inspection of new, used, and repaired steam generator tubes; to improve defect detection, classification, and characterization as affected by diameter and thickness variations, denting, probe wobble, tube sheet, tube supports, copper and sludge deposits, even when defect types and other variables occur in combination; to transfer this advanced technology to NRC`s mobile NDE laboratory and staff. This report describes the design of specialized high-speed 16-coil eddy-current array probes. Both pancake and reflection coils are considered. Test results from inspections using the probes in working steam generators are given. Computer programs developed for probe calculations are also supplied.

  4. Note: Human heartbeat measurement on the basis of current generated by electrostatic induction

    NASA Astrophysics Data System (ADS)

    Kurita, Koichi

    2011-02-01

    In this study, we developed an effective nonattached, noncontact technique for measurement of the human heartbeat. This method detects the human heartbeat by measuring the current generated by variations in the capacitance between a given electrode and the human body. An electrode is placed a few centimeters from the subject's chest, and the electrostatic induction current (on the order of picoamperes) flowing through the electrode is then detected. We propose an occurrence model for the electrostatic induction current generated by variations in the electrostatic capacitance generated because of the human heartbeat, with respect to a given measurement electrode. Furthermore, we compared waveforms of the human heartbeat simultaneously obtained by using conventional electrocardiography (ECG) and our proposed electrostatic induction method. The waveform obtained using the proposed method had the same cycle as that obtained using conventional ECG. This confirms that we can detect the human heartbeat under nonattached, noncontact conditions.

  5. Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation

    NASA Astrophysics Data System (ADS)

    Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo

    2013-06-01

    Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

  6. Research Resource: dkCOIN, the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) Consortium Interconnectivity Network: A Pilot Program to Aggregate Research Resources Generated by Multiple Research Consortia

    PubMed Central

    McKenna, Neil J.; Howard, Christopher L.; Aufiero, Michael; Easton-Marks, Jeremy; Steffen, David L.; Becnel, Lauren B.; Magnuson, Mark A.; McIndoe, Richard A.

    2012-01-01

    The National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) supports multiple basic science consortia that generate high-content datasets, reagent resources, and methodologies, in the fields of kidney, urology, hematology, digestive, and endocrine diseases, as well as metabolic diseases such as diabetes and obesity. These currently include the Beta Cell Biology Consortium, the Nuclear Receptor Signaling Atlas, the Diabetic Complications Consortium, and the Mouse Metabolic Phenotyping Centers. Recognizing the synergy that would accrue from aggregating information generated and curated by these initiatives in a contiguous informatics network, we created the NIDDK Consortium Interconnectivity Network (dkCOIN; www.dkcoin.org). The goal of this pilot project, organized by the NIDDK, was to establish a single point of access to a toolkit of interconnected resources (datasets, reagents, and protocols) generated from individual consortia that could be readily accessed by biologists of diverse backgrounds and research interests. During the pilot phase of this activity dkCOIN collected nearly 2000 consortium-curated resources, including datasets (functional genomics) and reagents (mouse strains, antibodies, and adenoviral constructs) and built nearly 3000 resource-to-resource connections, thereby demonstrating the feasibility of further extending this database in the future. Thus, dkCOIN promises to be a useful informatics solution for rapidly identifying useful resources generated by participating research consortia. PMID:22734043

  7. Weighted aggregation

    NASA Technical Reports Server (NTRS)

    Feiveson, A. H. (Principal Investigator)

    1979-01-01

    The use of a weighted aggregation technique to improve the precision of the overall LACIE estimate is considered. The manner in which a weighted aggregation technique is implemented given a set of weights is described. The problem of variance estimation is discussed and the question of how to obtain the weights in an operational environment is addressed.

  8. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    SciTech Connect

    Davydenko, V. I. Ivanov, A. A. Shul’zhenko, G. I.

    2015-11-15

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB{sub 6} washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  9. Eddy current signal deconvolution technique for the improvement of steam generator tubing burst pressure predictions.

    SciTech Connect

    Petri, M. C.; Wei, T. Y. C.; Kupperman, D. S.; Reifman, J.; Morman, J. A.

    2000-01-01

    Eddy current techniques are extremely sensitive to the presence of axial cracks in nuclear power plant steam generator tube walls, but they are equally sensitive to the presence of dents, fretting, support structures, corrosion products, and other artifacts. Eddy current signal interpretation is further complicated by cracking geometries more complex than a single axial crack. Although there has been limited success in classifying and sizing defects through artificial neural networks, the ability to predict tubing integrity has, so far, eluded modelers. In large part, this lack of success stems from an inability to distinguish crack signals from those arising from artifacts. We present here a new signal processing technique that deconvolves raw eddy current voltage signals into separate signal contributions from different sources, which allows signals associated with a dominant crack to be identified. The signal deconvolution technique, combined with artificial neural network modeling, significantly improves the prediction of tube burst pressure from bobbin-coil eddy current measurements of steam generator tubing.

  10. Oxygen suppresses light-driven anodic current generation by a mixed phototrophic culture.

    PubMed

    Darus, Libertus; Ledezma, Pablo; Keller, Jürg; Freguia, Stefano

    2014-12-01

    This paper describes the detrimental effect of photosynthetically evolved oxygen on anodic current generation in the presence of riboflavin upon illumination of a mixed phototrophic culture enriched from a freshwater pond at +0.6 V vs standard hydrogen electrode. In the presence of riboflavin, the phototrophic biomass in the anodic compartment produced an electrical current in response to light/dark cycles (12 h/12 h) over 12 months of operation, generating a maximum current density of 17.5 mA x m(-2) during the dark phase, whereas a much lower current of approximately 2 mA x m(-2) was generated during illumination. We found that the low current generation under light exposure was caused by high rates of reoxidation of reduced riboflavin by oxygen produced during photosynthesis. Quantification of biomass by fluorescence in situ hybridization images suggested that green algae were predominant in both the anode-based biofilm (55.1%) and the anolyte suspension (87.9%) with the remaining biovolume accounted for by bacteria. Genus-level sequencing analysis revealed that bacteria were dominated by cyanobacterium Leptolyngbia (∼35%), while the prevailing algae were Dictyosphaerium, Coelastrum, and Auxenochlorella. This study offers a key comprehension of mediator sensitivity to reoxidation by dissolved oxygen for improvement of microbial solar cell performance. PMID:25364824

  11. Generation of Islet-like Cell Aggregates from Human Adipose Tissue-derived Stem Cells by Lentiviral Overexpression of PDX-1

    PubMed Central

    Bahrebar, M.; Soleimani, M.; Karimi, M. H.; Vahdati, A.; Yaghobi, R.

    2015-01-01

    Background: Pancreatic duodenal homeobox1 (PDX-1) is a transcription factor that is important in regulating pancreas development and maintaining β-cell function. β-cell replacement is an effective approach for the treatment of type 1 diabetes. Human adipose-mesenchymal stem cells (hAMSCs) are the ideal population cells for differentiating into insulin-producing cells. Objective: To determine if islet-like cell aggregates production could be generated from hAMSCs by lentiviral overexpression of PDX-1. Methods: After isolation of hAMSCs, characteristics of these cells were identified by flow-cytometic analysis and multilineage differentiation studies. PDX-1 gene delivered into hAMSCs through lentiviral vector for differentiating hAMSCs into insulin-producing cells (IPCs) at the utilized protocol for 14 days. Characteristics of IPCs were evaluated by immunocytofluorescence, dithizone staining, and quantitative reverse transcription PCR. In response to high glucose medium, insulin release was detected by chemiluminescence enzyme immunoassay. Results: The islet-like cell aggregates appeared about 10 days after introduction of PDX-1 into hAMSCs. PDX-1 induced its own expression (auto-induction), a number of islet-related genes such as Ngn3, Nkx2-2, and insulin. The insulin-positive cells were detected in the PDX-1 transduced cells. In response to glucose challenge test, secretion of insulin hormone in the medium with high glucose concentration significantly increased in the PDX-1-transduced cells related to medium with low glucose concentration. Conclusion: Introduction of lentiviral PDX-1 significantly induces hAMSCs to differentiate into islet-like cell aggregates, which may provide a source of adipose stem cells-derived insulin-producing cells for cell replacement therapy in type 1 diabetes. PMID:26082830

  12. Scaling and multiscaling behavior of the perimeter of a diffusion-limited aggregation generated by the Hastings-Levitov method

    NASA Astrophysics Data System (ADS)

    Mohammadi, F.; Saberi, A. A.; Rouhani, S.

    2009-09-01

    In this paper, we analyze the scaling behavior of a diffusion-limited aggregation (DLA) simulated by the Hastings-Levitov method. We obtain the fractal dimension of the clusters by direct analysis of the geometrical patterns, in good agreement with one obtained from an analytical approach. We compute the two-point density correlation function and we show that, in the large-size limit, it agrees with the obtained fractal dimension. These support the statistical agreement between the patterns and DLA clusters. We also investigate the scaling properties of various length scales and their fluctuations, related to the boundary of the cluster. We find that all of the length scales do not have a simple scaling with the same correction to scaling exponent. The fractal dimension of the perimeter is obtained equal to that of the cluster. The growth exponent is computed from the evolution of the interface width equal to β = 0.557(2). We also show that the perimeter of the DLA cluster has an asymptotic multiscaling behavior.

  13. Scaling and multiscaling behavior of the perimeter of a diffusion-limited aggregation generated by the Hastings-Levitov method.

    PubMed

    Mohammadi, F; Saberi, A A; Rouhani, S

    2009-09-16

    In this paper, we analyze the scaling behavior of a diffusion-limited aggregation (DLA) simulated by the Hastings-Levitov method. We obtain the fractal dimension of the clusters by direct analysis of the geometrical patterns, in good agreement with one obtained from an analytical approach. We compute the two-point density correlation function and we show that, in the large-size limit, it agrees with the obtained fractal dimension. These support the statistical agreement between the patterns and DLA clusters. We also investigate the scaling properties of various length scales and their fluctuations, related to the boundary of the cluster. We find that all of the length scales do not have a simple scaling with the same correction to scaling exponent. The fractal dimension of the perimeter is obtained equal to that of the cluster. The growth exponent is computed from the evolution of the interface width equal to β = 0.557(2). We also show that the perimeter of the DLA cluster has an asymptotic multiscaling behavior. PMID:21832341

  14. Numerical simulations of current generation and dynamo excitation in a mechanically forced turbulent flow.

    PubMed

    Bayliss, R A; Forest, C B; Nornberg, M D; Spence, E J; Terry, P W

    2007-02-01

    The role of turbulence in current generation and self-excitation of magnetic fields has been studied in the geometry of a mechanically driven, spherical dynamo experiment, using a three-dimensional numerical computation. A simple impeller model drives a flow that can generate a growing magnetic field, depending on the magnetic Reynolds number Rm=micro0sigmaVa and the fluid Reynolds number Re=Vanu of the flow. For Re<420, the flow is laminar and the dynamo transition is governed by a threshold of Rmcrit=100, above which a growing magnetic eigenmode is observed that is primarily a dipole field transverse to the axis of symmetry of the flow. In saturation, the Lorentz force slows the flow such that the magnetic eigenmode becomes marginally stable. For Re>420 and Rm approximately 100 the flow becomes turbulent and the dynamo eigenmode is suppressed. The mechanism of suppression is a combination of a time varying large-scale field and the presence of fluctuation driven currents (such as those predicted by the mean-field theory), which effectively enhance the magnetic diffusivity. For higher Rm, a dynamo reappears; however, the structure of the magnetic field is often different from the laminar dynamo. It is dominated by a dipolar magnetic field aligned with the axis of symmetry of the mean-flow, which is apparently generated by fluctuation-driven currents. The magnitude and structure of the fluctuation-driven currents have been studied by applying a weak, axisymmetric seed magnetic field to laminar and turbulent flows. An Ohm's law analysis of the axisymmetric currents allows the fluctuation-driven currents to be identified. The magnetic fields generated by the fluctuations are significant: a dipole moment aligned with the symmetry axis of the mean-flow is generated similar to those observed in the experiment, and both toroidal and poloidal flux expulsion are observed. PMID:17358418

  15. Guarana (Paullinia cupana Mart.) prevents β-amyloid aggregation, generation of advanced glycation-end products (AGEs), and acrolein-induced cytotoxicity on human neuronal-like cells.

    PubMed

    Bittencourt, Leonardo da Silva; Zeidán-Chuliá, Fares; Yatsu, Francini Kiyono Jorge; Schnorr, Carlos Eduardo; Moresco, Karla Suzana; Kolling, Eduardo Antônio; Gelain, Daniel Pens; Bassani, Valquiria Linck; Moreira, José Cláudio Fonseca

    2014-11-01

    Advanced glycation end-products (AGEs) are considered potent molecules capable of promoting neuronal cell death and participating in the development of neurodegenerative disorders such as Alzheimer's disease (AD). Previous studies have shown that AGEs exacerbate β-amyloid (Aβ) aggregation and AGE-related cross-links are also detected in senile plaques. Acrolein (ACR) is an α, β-unsaturated aldehyde found in the environment and thermally processed foods, which can additionally be generated through endogenous metabolism. The role of ACR in AD is widely accepted in the literature. Guarana (Paullinia cupana Mart.) is popularly consumed by the population in Brazil, mainly for its stimulant activity. In the present study, we showed that guarana (10, 100, and 1000 µg/mL) is able to prevent protein glycation, β-amyloid aggregation, in vitro methylglyoxal, glyoxal, and ACR (20 μM)-induced toxicity on neuronal-like cells (SH-SY5Y). Since these are considered typical AD pathological hallmarks, we propose that guarana may deserve further research as a potential therapeutic agent in such a neurodegenerative disease. PMID:24840232

  16. Axial current generation by P-odd domains in QCD matter

    DOE PAGESBeta

    Iatrakis, Ioannis; Yin, Yi; Lin, Shu

    2015-06-23

    The dynamics of topological domains which break parity (P) and charge-parity (CP) symmetry of QCD are studied. We derive in a general setting that those local domains will generate an axial current and quantify the strength of the induced axial current. Thus, our findings are verified in a top-down holographic model. The relation between the real time dynamics of those local domains and the chiral magnetic field is also elucidated. We finally argue that such an induced axial current would be phenomenologically important in a heavy-ion collisions experiment.

  17. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  18. Transient interaction model of electromagnetic field generated by lightning current pulses and human body

    NASA Astrophysics Data System (ADS)

    Iváncsy, T.; Kiss, I.; Szücs, L.; Tamus, Z. Á.

    2015-10-01

    The lightning current generates time-varying magnetic field near the down- conductor and the down-conductors are mounted on the wall of the buildings where residential places might be situated. It is well known that the rapidly changing magnetic fields can generate dangerous eddy currents in the human body.The higher duration and gradient of the magnetic field can cause potentially life threatening cardiac stimulation. The coupling mechanism between the electromagnetic field and the human body is based on a well-known physical phenomena (e.g. Faradays law of induction). However, the calculation of the induced current is very complicated because the shape of the organs is complex and the determination of the material properties of living tissues is difficult, as well. Our previous study revealed that the cardiac stimulation is independent of the rising time of the lightning current and only the peak of the current counts. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near down-conductor and human body. Our previous models are based on the quasi stationer field calculations, the new improved model is a transient model. This is because the magnetic field around the down-conductor and in the human body can be determined more precisely, therefore the dangerous currents in the body can be estimated.

  19. Stress-induced leakage current and trap generation in HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Mannequin, C.; Gonon, P.; Vallée, C.; Latu-Romain, L.; Bsiesy, A.; Grampeix, H.; Salaün, A.; Jousseaume, V.

    2012-10-01

    Stress-induced leakage current (SILC) is studied in 10 nm HfO2 metal-insulator-metal capacitors. Three regimes are observed in the current-time characteristics, namely, (1) an absorption current, (2) a quasi linear increase of current with time (SILC), and (3) thermal breakdown. Magnitude of SILC is strongly correlated to the nature of the cathode (being large for TiN and weak for Pt and Au), showing that SILC is governed by electron injection. Recovery is observed when short-circuiting the samples, pointing out that SILC is a reversible phenomenon. Desorption current and SILC are not correlated, which indicates that different defects control the absorption current and SILC. SILC is ascribed to the generation of oxygen vacancies upon hot electron injection, while recovery is ascribed to the recombination of oxygen ions with vacancies. In the SILC regime, the current varies as Ktn (n = 1.15 at room temperature). Bias and temperature dependence of K and n are studied. The dependence of K on bias can be described either by a Fowler-Nordheim law or by an exponential law, while the exponent n is almost independent of bias. When temperature is increased, K increases according to an Arrhenius law and n decreases. SILC is modeled by considering the generation of oxygen vacancies by hot electron impact and subsequent electron trapping at vacancies (hopping conduction). An analytical expression for SILC growth is obtained from first order kinetics.

  20. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics

    NASA Astrophysics Data System (ADS)

    Lopatin, I. V.; Akhmadeev, Yu. H.; Koval, N. N.

    2015-10-01

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8-12 h. Using a cathode consisting of several parallel-connected tungsten filaments ˜0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa).

  1. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics.

    PubMed

    Lopatin, I V; Akhmadeev, Yu H; Koval, N N

    2015-10-01

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8-12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa). PMID:26520947

  2. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics

    SciTech Connect

    Lopatin, I. V. Akhmadeev, Yu. H.; Koval, N. N.

    2015-10-15

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8–12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa)

  3. Health effects of electromagnetic field generated by lightning current pulses near down conductors

    NASA Astrophysics Data System (ADS)

    Tamus, Z. Á.; Novák, B.; Szücs, L.; Kiss, I.

    2011-06-01

    The lightning current generates a time varying magnetic field near down conductors, when lightning strikes the connected Franklin-rod. The down conductors are mounted on the wall of buildings, where residential places can be situated. It is well known that the rapidly changing magnetic fields could generate dangerous eddy currents in the human body. If the duration and the gradient of the magnetic field were high enough, the peripheral nerves are excited. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near a down conductor with the human body. The interaction model has two parts: estimation of the magnetic fields surrounding the down conductor and evaluation of health effects of rapid changing magnetic fields on the human body.

  4. Three dimensional potential and current distributions in a Hall generator with assumed velocity profiles

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.; Palmer, R. W.

    1972-01-01

    Three-dimensional potential and current distributions in a Faraday segmented MHD generator operating in the Hall mode are computed. Constant conductivity and a Hall parameter of 1.0 is assumed. The electric fields and currents are assumed to be coperiodic with the electrode structure. The flow is assumed to be fully developed and a family of power-law velocity profiles, ranging from parabolic to turbulent, is used to show the effect of the fullness of the velocity profile. Calculation of the square of the current density shows that nonequilibrium heating is not likely to occur along the boundaries. This seems to discount the idea that the generator insulating walls are regions of high conductivity and are therefore responsible for boundary-layer shorting, unless the shorting is a surface phenomenon on the insulating material.

  5. Voltage-controllable generator of pure spin current: A three-terminal model

    SciTech Connect

    Ma, Zheng; Wu, Reng-Lai; Yu, Ya-Bin Wang, Miao

    2014-07-28

    Three-terminal devices have been frequently proposed to generate the pure spin current. However, the controllability and stability of pure spin current still needs to be improved. In this paper, a three-terminal device, composed of a ferromagnetic metallic lead and two nonmagnetic semiconductor leads coupled with a quantum dot, is employed to study the properties of electron spin transport. The results show that when the external voltage on one of nonmagnetic semiconductor leads is adjusted to a proper range, a pure spin current plateau or a fully spin-polarized current plateau appears in another nonmagnetic semiconductor lead. In a wide range of external voltage, the pure spin current or the spin-polarized current is kept unchanged. Since the change of temperature may considerably influence the spin-polarization of current and is inevitable actually, we studied the corresponding compensation to keep the pure spin current unchanged. Furthermore, the effect of device parameters on the pure spin current is also investigated.

  6. Spin generation via bulk spin current in three-dimensional topological insulators

    NASA Astrophysics Data System (ADS)

    Peng, Xingyue; Yang, Yiming; Singh, Rajiv R. P.; Savrasov, Sergey Y.; Yu, Dong

    2016-03-01

    To date, spin generation in three-dimensional topological insulators is primarily modelled as a single-surface phenomenon, attributed to the momentum-spin locking on each individual surface. In this article, we propose a mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a three-dimensional topological insulator, which transports spins between the top and bottom surfaces. Under sufficiently high surface disorder, the spin relaxation time can be extended via the Dyakonov-Perel mechanism. Consequently, both the spin generation efficiency and surface conductivity are largely enhanced. Numerical simulation confirms that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two-dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion.

  7. Spin generation via bulk spin current in three-dimensional topological insulators.

    PubMed

    Peng, Xingyue; Yang, Yiming; Singh, Rajiv R P; Savrasov, Sergey Y; Yu, Dong

    2016-01-01

    To date, spin generation in three-dimensional topological insulators is primarily modelled as a single-surface phenomenon, attributed to the momentum-spin locking on each individual surface. In this article, we propose a mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a three-dimensional topological insulator, which transports spins between the top and bottom surfaces. Under sufficiently high surface disorder, the spin relaxation time can be extended via the Dyakonov-Perel mechanism. Consequently, both the spin generation efficiency and surface conductivity are largely enhanced. Numerical simulation confirms that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two-dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion. PMID:26932574

  8. Spin generation via bulk spin current in three-dimensional topological insulators

    PubMed Central

    Peng, Xingyue; Yang, Yiming; Singh, Rajiv R.P.; Savrasov, Sergey Y.; Yu, Dong

    2016-01-01

    To date, spin generation in three-dimensional topological insulators is primarily modelled as a single-surface phenomenon, attributed to the momentum-spin locking on each individual surface. In this article, we propose a mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a three-dimensional topological insulator, which transports spins between the top and bottom surfaces. Under sufficiently high surface disorder, the spin relaxation time can be extended via the Dyakonov–Perel mechanism. Consequently, both the spin generation efficiency and surface conductivity are largely enhanced. Numerical simulation confirms that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two-dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion. PMID:26932574

  9. Generation of Crowbar Current using the Polarity Effect of the Triggered Vacuum Gaps

    NASA Astrophysics Data System (ADS)

    Sugawara, Akira; Tanaka, Tsuyoshi; Itagaki, Kouichi; Abe, Hayato; Zashibo, Toshihito; Samaulah, Hazairin; Kitamura, Hiroshi

    The triggered vacuum gap (TVG) is a closing switch for generating large current pulse and can work in the wide range of voltage for several kV to tens kV. Main electrodes are made of Ag-WC. One of main electrode has a hole for trigger electrode (Mo). The switching time is short, if the polarity of the holed-electrode is negative. It is called polarity effect. We devised a crowbar circuit using the polarity effect of the TVGs. The crowbar current of this circuit was investigated experimentally by varying applied voltage, inductance, capacitance, gap length of TVGs, and trigger current duration. A crowbar current, crest of which is 2.4 kA and 4.9/270µs for example, was observed. The probability of generating the crowbar current was more than about 90 %, in the following condition: the trigger current duration of 6.65 µs and the gap length of 2-6 mm.

  10. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  11. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  12. Generation of field-aligned currents and Alfven waves by 3D magnetic reconnection

    SciTech Connect

    Ma, Z.W.; Lee, L.C.; Otto, A.

    1995-07-01

    The authors have carried out a three-dimensional compressible MHD simulation to study the generation of field-aligned currents (FAC`s) and Alfven waves by magnetic reconnection for locally antiparallel magnetic fields across the current sheet. Reconnection is triggered by a localized resistivity. The results indicate that both FAC`s and Alfven waves are generated by the three-dimensional reconnection process. Two pairs of FAC`s are generated on each side of current sheet. The polarities of the resulting FAC pair in the leading bulge region are opposite to those of a FAC pair in the trailing quasi-steady region. It is further found that a large portion of the FAC`s ({approximately}40%) is located in the closed field line region. They examine the Walen relation between FAC and parallel vorticity and find that Alfven waves are generated and propagate away from the reconnection site. They discuss the relevance of the results to the observed Region 1 FAC`s at noon. 15 refs., 4 figs.

  13. Generation of murine cardiac pacemaker cell aggregates based on ES-cell-programming in combination with Myh6-promoter-selection.

    PubMed

    Rimmbach, Christian; Jung, Julia J; David, Robert

    2015-01-01

    Treatment of the "sick sinus syndrome" is based on artificial pacemakers. These bear hazards such as battery failure and infections. Moreover, they lack hormone responsiveness and the overall procedure is cost-intensive. "Biological pacemakers" generated from PSCs may become an alternative, yet the typical content of pacemaker cells in Embryoid Bodies (EBs) is extremely low. The described protocol combines "forward programming" of murine PSCs via the sinus node inducer TBX3 with Myh6-promoter based antibiotic selection. This yields cardiomyocyte aggregates consistent of >80% physiologically functional pacemaker cells. These "induced-sinoatrial-bodies" ("iSABs") are spontaneously contracting at yet unreached frequencies (400-500 bpm) corresponding to nodal cells isolated from mouse hearts and are able to pace murine myocardium ex vivo. Using the described protocol highly pure sinus nodal single cells can be generated which e.g. can be used for in vitro drug testing. Furthermore, the iSABs generated according to this protocol may become a crucial step towards heart tissue engineering. PMID:25742394

  14. Application of active quenching of second generation wire for current limiting

    SciTech Connect

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-10-19

    Superconducting fault current limiters (SFCL's) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCL's are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggers a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.

  15. Spin current generation and magnetic response in carbon nanotubes by the twisting phonon mode

    NASA Astrophysics Data System (ADS)

    Hamada, Masato; Yokoyama, Takehito; Murakami, Shuichi

    2015-08-01

    We theoretically investigate spin current and magnetic response induced by the twisting phonon mode in carbon nanotubes via the spin-rotation coupling. An effective magnetic field due to the twisting mode induces both spin and orbital magnetizations. The induced spin and orbital magnetizations have both radial and axial components. We show that ac pure spin current is generated by the twisting phonon mode. The magnitude of the spin current and orbital magnetization for a (10,10) armchair nanotube is estimated as an example. We find that the ac pure spin current is detectable in magnitude when the frequency of the twisting mode is of the order of GHz, and that the orbital magnetization is found to be larger than the spin magnetization.

  16. Application of active quenching of second generation wire for current limiting

    DOE PAGESBeta

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-10-19

    Superconducting fault current limiters (SFCL's) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCL's are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggersmore » a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.« less

  17. Influence of electropolishing current densities on sulfur generation at niobium surface

    NASA Astrophysics Data System (ADS)

    Tyagi, P. V.; Nishiwaki, M.; Noguchi, T.; Sawabe, M.; Saeki, T.; Hayano, H.; Kato, S.

    2013-11-01

    We report the effect of different current densities on sulfur generation at Nb surface in the electropolishing (EP) with aged electrolyte. In this regard, we conducted a series of electropolishing (EP) experiments in aged EP electrolyte with high (≈50 mA/cm2) and low (≈30 mA/cm2) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). Sample's surfaces were investigated by XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive X-ray spectroscopy). The surface analysis showed that the EP with a high current density produced a huge amount of sulfate/sulfite particles at Nb surface whereas the EP with a low current density was very helpful to mitigate sulfate/sulfite at Nb surface in both the experiments.

  18. The eddy-current technique for nondestructive evaluation of generator retaining rings: Feasibility study: Interim report

    SciTech Connect

    Elmo, P.M.; Nottingham, L.D.

    1988-05-01

    An evaluation of the feasibility of using eddy current nondestructive inspection techniques to detect intergranular stress corrosion in generator rotor retaining rings was conducted by the EPRI NDE Center. Experiments were conducted using a bend-bar containing representative stress corrosion damage, a calibration block containing electrical discharge machined (EDM) notches, and four retired retaining rings containing EDM notches and stress corrosion damage. An eddy current transducer transport was designed and fabricated to interface with an existing computer-controlled, two-axis positioner and digital eddy current data acquisition system. Test results of experiments performed with this equipment on the retaining ring test-bed provided experimental validation of the eddy current method's feasibility as a retaining ring inspection method. Details are given of the system and its performance under laboratory and simulated service-inspection conditions. 9 refs., 47 figs.

  19. Spike train generation and current-to-frequency conversion in silicon diodes

    NASA Technical Reports Server (NTRS)

    Coon, D. D.; Perera, A. G. U.

    1989-01-01

    A device physics model is developed to analyze spontaneous neuron-like spike train generation in current driven silicon p(+)-n-n(+) devices in cryogenic environments. The model is shown to explain the very high dynamic range (0 to the 7th) current-to-frequency conversion and experimental features of the spike train frequency as a function of input current. The devices are interesting components for implementation of parallel asynchronous processing adjacent to cryogenically cooled focal planes because of their extremely low current and power requirements, their electronic simplicity, and their pulse coding capability, and could be used to form the hardware basis for neural networks which employ biologically plausible means of information coding.

  20. Application of active quenching of second generation wire for current limiting

    NASA Astrophysics Data System (ADS)

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-12-01

    Superconducting fault current limiters (SFCLs) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCLs are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggers a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.

  1. Generation of two-dimensional dust vortex flows in a direct current discharge plasma

    SciTech Connect

    Uchida, Giichiro; Iizuka, Satoru; Kamimura, Tetsuo; Sato, Noriyoshi

    2009-05-15

    The two-dimensional dust vortex flows are observed in a direct current discharge plasma near the edge of a metal plate which is situated in the dust-particle levitation region. Applying negative dc potential to the metal plate, dust particles are strongly accelerated toward the metal plate edge, and two symmetric dust vortex flows are generated on both sides of the metal plate. Numerical calculation including the effect of the ion drag force well demonstrates the dust vortex formation as in the experiment. A mechanism of the dust vortex generation could be explained by effect of an asymmetry of ion drag force near the metal plate.

  2. Simulation of current generations in a three-dimensional particle model

    NASA Astrophysics Data System (ADS)

    Tsung, Frank Shih-Yu

    1999-07-01

    Noninductively generated current is important for the steady state operation of tokamak plasmas. In the CCT (Continuous Current Tokamak) experiment here at UCLA, a continuous current has been observed in ECRH-generated plasmas, and in plasmas generated by electron beams, in both co- and counter-streaming cases. In 2+1/2D simulation works done by Nunan et al, a continuous toroidal current was maintained by particle fueling alone. In Nunan's work, the ``preferential loss'' model was proposed to explain the noninductive generation of toroidal currents in magnetized plasmas. However, this model assumes the conservation of the canonical toroidal momentum and therefore may not exist in three dimensional simulations. The aim of this thesis is to demonstrate this effect in a 3-D plasma model. A scalable 3-D electromagnetic PIC (Particle-in-Cell) code was developed for this purpose. Because the electromagnetic signals travels a short distance during each time-step, this code need not communicate globally and therefore has a parallel overhead independent of the number of processors. On the SP2 at Cornell Theory Center, the program is over 96% efficient on 128 nodes. Optimization techniques for RISC- based processors are also discussed. Using the parallel 3-D code, we have carried out the TDC simulations using 32 grids in the previously ignorable (toroidal) direction and 160 times as many particles as before ( 1.6˙107 particles). These 3-D calculations agree qualitatively with the 2+1/2D results. In addition, particle scans were performed in both the 2+1/2D and 3-D to identify the source of particle transport in these simulations. In addition, test particle calculations were carried out to address issues related to the TDC problem. In one test charge calculation, we showed how the curvature drift breaks up the toroidal symmetry during start-up and generates current. Because of the 1/r dependence of the curvature drift, this effect becomes important when the radius is small

  3. High-Resolution SQUID imaging of Magnetic Fields Generated by Propagating Cardiac Action Currents

    NASA Astrophysics Data System (ADS)

    Holzer, Jenny R.; Sidorov, Veniamin; Fong, Luis; Peters, Nicholas; Baudenbacher, Petra; Baudenbacher, Franz

    2004-03-01

    The heart's magnetic field is exquisitely sensitive to anisotropy ratios in the cardiac bidomain model; Therefore, magnetic imaging of cardiac action currents is an ideally suited technique for testing the accuracy of cardiac models and elucidating the effects of anisotropy in the spread of stimulus and action currents. We mapped the magnetocardiogram (MCG) as a function of position over a 10mm x 10mm area of the left ventricle of a Langendorff perfused isolated rabbit heart using high-resolution scanning SQUID microscopy and epi-fluorescent imaging with a high speed CCD camera and the transmembrane voltage sensitive dye di-4-ANEPPS. The combination of these two methods allowed us to map the transmembrane potential, the magnetic field, and consequently the total current, over the same area. The MCGs were combined to produce a time series of 2D field maps that show a clear octupolar pattern during the cathodal current injection, a similar pattern with a reversal of currents immediately after terminating the stimulus, and the generation and propagation of an elliptical action current wave front. The observed patterns are in agreement with predictions using a bidomain model. Our high-resolution SQUID images have confirmed that unequal anisotropies in the intra- and extracellular spaces must be considered to explain the magnetic field associated with action current propagation However, a realistic cardiac bidomain model incorporating fiber rotation, cleavage planes, and tissue heterogeneities are required to reproduce the complete experimental observations.

  4. Generation of longitudinal current by a transverse electromagnetic field in classical and quantum plasmas

    SciTech Connect

    Latyshev, A. V. Yushkanov, A. A.

    2015-09-15

    A distribution function for collisionless plasma is derived from the Vlasov kinetic equation in the quadratic approximation with respect to the electromagnetic field. Formulas for calculation of the electric current at an arbitrary temperature (arbitrary degree of degeneration of the electron gas) are deduced. The case of small wavenumbers is considered. It is shown that nonlinearity leads to the generation of an electric current directed along the wave vector. This longitudinal current is orthogonal to the classical transverse current, well known in the linear theory. A distribution function for collisionless quantum plasma is derived from the kinetic equation with the Wigner integral in the quadratic approximation with respect to the vector potential. Formulas for calculation of the electric current at an arbitrary temperature are deduced. The case of small wavenumbers is considered. It is shown that, at small values of the wavenumber, the value of the longitudinal current for quantum plasma coincides with that for classical plasma. The dimensionless currents in quantum and classical plasmas are compared graphically.

  5. Generation and Measurement of Relativistic Electron Bunches Characterized by a Linearly Ramped Current Profile

    SciTech Connect

    England, R. J.; Rosenzweig, J. B.; Travish, G.

    2008-05-30

    We report the first successful attempt to generate ultrashort (1-10 ps) relativistic electron bunches characterized by a ramped longitudinal current profile that rises linearly from head to tail and then falls sharply to zero. Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free-electron lasers as a means of reducing asymmetry in microbunching due to slippage. The scheme used to generate the ramped bunches employs an anisochronous dogleg beam line with nonlinear correction elements to compress a beam having an initial positive time-energy chirp. The beam current profile is measured using a deflecting mode cavity, and a pseudoreconstruction of the beam's longitudinal phase space distribution is obtained by using this diagnostic with a residual horizontal dispersion after the dogleg.

  6. Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

    NASA Astrophysics Data System (ADS)

    Gao, Lan; Ji, Hantao; Fiksel, Gennady; Fox, William; Evans, Michelle; Alfonso, Noel

    2016-04-01

    Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ˜1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ˜3 × 1016 W/cm2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ˜40-50 T magnetic fields at the center of the coil ˜3-4 ns after laser irradiation. The experiments provide significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.

  7. Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

    DOE PAGESBeta

    Gao, Lan; Ji, Hantao; Fiksel, Gennady; Fox, William; Evans, Michelle; Alfonso, Noel

    2016-04-15

    Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ~ 1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ~ 3 x 1016 W/cm2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ~ 40-50 T magnetic fields at the center of the coil ~ 3-4 ns after laser irradiation. In conclusion, the experiments providemore » significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.« less

  8. Measurement of current-generated torques in transition metal dichalcogenide / ferromagnet bilayers

    NASA Astrophysics Data System (ADS)

    Stiehl, Gregory M.; MacNeill, David; Guimarães, Marcos H. D.; Gao, Hui; Park, Jiwoong; Ralph, Daniel C.

    We present measurements of current-generated torques in ferromagnet / transition metal dichalcogenide (TMD) bilayers for a wide range of semi-conducting TMDs, including MoS2, MoSe2, WS2 and WSe2. TMDs present a unique opportunity to study interfacial spin-orbit torques at the two dimensional limit due to a wide range in material properties and large spin-orbit coupling. Thin TMD films are either grown by chemical vapor deposition or exfoliated from readily available TMD crystals and are incorporated into ferromagnet / TMD bilayers by either evaporation or off-axis sputtering of the ferromagnet to avoid damage to the TMD surface. Measurements of the current-generated torque are made by spin transfer ferromagnetic resonance and the magneto-optical Kerr effect. Dependence on layer number, spin-orbit coupling strength, mobility and gate dependence will be explored.

  9. Control of the electrode metal transfer by means of the welding current pulse generator

    NASA Astrophysics Data System (ADS)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Knyaz'kov, S.; Tyasto, A.

    2016-04-01

    The paper presents a generator of welding current pulses to transfer an electrode metal into the molten pool. A homogeneous artificial line is used to produce near rectangular pulses. The homogeneous artificial line provides the minimum heat input with in the pulse to transfer the electrode metal, and it significantly decreases the impact of disturbances affecting this transfer. The pulse frequency does not exceed 300 Hz, and the duration is 0.6 ÷ 0.9 ms.

  10. Current practices and guidelines for clinical next-generation sequencing oncology testing

    PubMed Central

    Strom, Samuel P.

    2016-01-01

    Next-generation sequencing (NGS) has been rapidly integrated into molecular pathology, dramatically increasing the breadth genomic of information available to oncologists and their patients. This review will explore the ways in which this new technology is currently applied to bolster care for patients with solid tumors and hematological malignancies, focusing on practices and guidelines for assessing the technical validity and clinical utility of DNA variants identified during clinical NGS oncology testing. PMID:27144058

  11. Computational comparison of mediated current generation capacity of Chlamydomonas reinhardtii in photosynthetic and respiratory growth modes.

    PubMed

    Mao, Longfei; Verwoerd, Wynand S

    2014-11-01

    Chlamydomonas reinhardtii possesses many potential advantages to be exploited as a biocatalyst in microbial fuel cells (MFCs) for electricity generation. In the present study, we performed computational studies based on flux balance analysis (FBA) to probe the maximum potential of C. reinhardtii for current output and identify the metabolic mechanisms supporting a high current generation in three different cultivation conditions, i.e., heterotrophic, photoautotrophic and mixotrophic growth. The results showed that flux balance limitations allow the highest current output for C. reinhardtii in the mixotrophic growth mode (2.368 A/gDW), followed by heterotrophic growth (1.141 A/gDW) and photoautotrophic growth the lowest (0.7035 A/gDW). The significantly higher mediated electron transfer (MET) rate in the mixotrophic mode is in complete contrast to previous findings for a photosynthetic cyanobacterium, and was attributed to the fact that for C. reinhardtii the photophosphorylation improved the efficiency of converting the acetate into biomass and NADH production. Overall, the cytosolic NADH-dependent current production was mainly associated with five reactions in both mixotrophic and photoautotrophic nutritional modes, whereas four reactions participated in the heterotrophic mode. The mixotrophic and photoautotrophic metabolisms were alike and shared the same set of reactions for maximizing current production, whereas in the heterotrophic mode, the current production was additionally contributed by the metabolic activities in the two organelles: glyoxysome and chloroplast. In conclusion, C. reinhardtii has a potential to be exploited in MFCs of MET mode to produce a high current output. PMID:24875305

  12. Edge instability in a chiral stripe domain under an electric current and skyrmion generation

    NASA Astrophysics Data System (ADS)

    Lin, Shi-Zeng

    2016-07-01

    Motivated by the recent experimental observations on the skyrmion creation by cutting chiral stripe domains under a current drive [Jiang et al., Science 349, 283 (2015), 10.1126/science.aaa1442], we study the mechanism of skyrmion generation by simulating the dynamics of stripe domains. Our theory for skyrmion generation is based on the fact that there are two half skyrmions attached to the ends of a stripe domain. These half skyrmions move due to the coupling between the skyrmion topological charge and current. As a consequence, the stripe domain is bent or stretched depending on the direction of motion of the half skyrmions. For a large current, skyrmions are created by chopping the stripe domains via strong bending or stretching. Our theory provides an explanation to the experiments and is supported by the new experiments. Furthermore, we predict that skyrmions can also be generated using a Bloch stripe domain under a spin transfer torque which can be realized in B20 compounds.

  13. Theoretical analysis of shock induced depolarization and current generation in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Agrawal, Vinamra; Bhattacharya, Kaushik

    Ferroelectric generators are used to generate large magnitude current pulse by impacting a polarized ferroelectric material. The impact causes depolarization of the material and at high impact speeds, dielectric breakdown. Depending on the loading conditions and the electromechanical boundary conditions, the current or voltage profiles obtained vary. In this study, we explore the large deformation dynamic response of a ferroelectric material. Using the Maxwell's equations, conservation laws and the second law of thermodynamics, we derive the governing equations for the phase boundary propagation as well as the driving force acting on it. We allow for the phase boundary to contain surface charges which introduces the contribution of curvature of phase boundary in the governing equations and the driving force. This type of analysis accounts for the dielectric breakdown and resulting conduction in the material. Next, we implement the equations derived to solve a one dimensional impact problem on a ferroelectric material under different electrical boundary conditions. The constitutive law is chosen to be piecewise quadratic in polarization and quadratic in the strain. We solve for the current profile generated in short circuit case and for voltage profile in open circuited case. This work was made possible by the financial support of the US Air Force Office of Scientific Research through the Center of Excellence in High Rate Deformation Physics of Heterogeneous Materials (Grant: FA 9550-12-1-0091).

  14. Analysis of shock induced depolarization and current generation in ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Agrawal, Vinamra; Bhattacharya, Kaushik

    2015-06-01

    Ferroelectric generators are used to generate large magnitude current pulse by impacting a polarized ferroelectric material. The impact causes depolarization of the material and at high impact speeds, dielectric breakdown. The current or voltage profiles obtained vary depending on the loading conditions. In this study, we explore the large deformation dynamic response of a ferroelectric material. Using the Maxwell's equations, conservation laws and the second law of thermodynamics, we derive the governing equations for the phase boundary propagation as well as the driving force acting on it. We allow for the phase boundary to contain surface charges which introduces the contribution of curvature of phase boundary in the governing equations and the driving force. This type of analysis accounts for the dielectric breakdown and resulting conduction in the material. Next, we implement the equations derived to solve a one dimensional impact problem on a ferroelectric material under different electrical boundary conditions. The constitutive law is chosen to be piecewise quadratic in polarization and quadratic in the strain. We solve for the current profile generated in short circuit case and for voltage profile in open circuited case. This work was made possible by the financial support of the US Air Force Office of Scientific Research through the Center of Excellence in High Rate Deformation Physics of Heterogeneous Materials (Grant: FA 9550-12-1-0091).

  15. Edge instability in a chiral stripe domain under an electric current and skyrmion generation

    DOE PAGESBeta

    Lin, Shi -Zeng

    2016-07-01

    Motivated by the recent experimental observations on the skyrmion creation by cutting chiral stripe domains under a current drive [Jiang et al., Science 349, 283 (2015)], we study the mechanism of skyrmion generation by simulating the dynamics of stripe domains. Our theory for skyrmion generation is based on the fact that there are two half skyrmions attached to the ends of a stripe domain. These half skyrmions move due to the coupling between the skyrmion topological charge and current. As a consequence, the stripe domain is bent or stretched depending on the direction of motion of the half skyrmions. Formore » a large current, skyrmions are created by chopping the stripe domains via strong bending or stretching. Our theory provides an explanation to the experiments and is supported by the new experiments. Moreover, we predict that skyrmions can also be generated using a Bloch stripe domain under a spin transfer torque which can be realized in B20 compounds.« less

  16. Wire array experiments in a low impedance and low current generator

    NASA Astrophysics Data System (ADS)

    Cabrini, Nibaldo; Pavez, Cristian; Avaria, Gonzalo; San Martin, Patricio; Veloso, Felipe; Zúñiga, Barbara; Sepúlveda, Adolfo; Soto, Leopoldo

    2015-03-01

    In this work, a preliminary study about the behavior of a low impedance generator on different wire array configurations is reported. The experimental measurements were carried out on a small multi-purpose generator (1.2μF, 345J, 47.5nH, T/4 = 375 ns and Z = 0.2Ω in short circuit) which produces currents up to 122 kA with 500 ns quarter period, when a charging voltage of 24kV and a wire load are used. Two types of configurations were tested: parallel wires (two and four) and X-pinch configurations. The experiments were carried out on W, Al, and Cu wires with different diameters. The discharge was characterized by means of a set of diagnostics which included: Rogowski coil; filtered PCD detector; filtered PIN diode; gated VUV/soft X-ray pinhole camera, Shadow diagnostic and dark field Schlieren technique. From the set of experimental results, the following observations can be established: (i) The generator is highly sensitive to the changes of load impedance due to its low impedance design. (ii) Every shot shows a dip in the current derivative signal shortly after the discharge onset time (from 6 to 40 ns), which is inversely related to the load resistance. (iii) Both configurations show a similar dynamic to those observed in experiments of higher current and shorter quarter period. (iv) At the X-pinch experiments, two or more hard X-ray bursts are detected, around 200 ns from the current onset time. These X-ray bursts are correlated with the dips observed in the current derivative signal.

  17. Spin Generation Via Bulk Spin Current in Three Dimensional Topological Insulators

    NASA Astrophysics Data System (ADS)

    Peng, Xingyue

    To date, charge transport and spin generation in three-dimensional topological insulators (3D TIs) are primarily modeled as a single-surface phenomenon. We propose a new mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a 3D TI, which transports spins between the top and bottom surfaces and leads to spin accumulation on both. The surface spin density and charge current are then proportional to the spin relaxation time, which for a sufficiently high disorder level can be extended by nonmagnetic scattering analogous to the Dyakonov-Perel spin relaxation mechanism. This new spin generation mechanism suggests a distinct and practical strategy for the enhancement of surface spin polarization by increasing nonmagnetic impurity concentration. Numerical results obtained by coherent potential approximation (CPA) based on a 4-band lattice model confirm that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion.

  18. An Experimental Study on the Darrieus-Savonius Turbine for the Tidal Current Power Generation

    NASA Astrophysics Data System (ADS)

    Kyozuka, Yusaku

    The Darrieus turbine is popular for tidal current power generation in Japan. It is simple in structure with straight wings rotating around a vertical axis, so that it has no directionality against the motion of tidal flow which changes its direction twice a day. However, there is one defect in the Darrieus turbine; its small starting torque. Once it stops, a Darrieus turbine is hard to re-start until a fairly fast current is exerted on it. To improve the starting torque of the Darrieus turbine used for tidal power generation, a hybrid turbine, composed of a Darrieus turbine and a Savonius rotor is proposed. Hydrodynamic characteristics of a semi-circular section used for the Savonius bucket were measured in a wind tunnel. The torque of a two bucket Savonius rotor was measured in a circulating water channel, where four different configurations of the bucket were compared. A combined Darrieus and Savonius turbine was tested in the circulating water channel, where the effect of the attaching angle between Darrieus wing and Savonius rotor was studied. Finally, power generation experiments using a 48 pole electric generator were conducted in a towing tank and the power coefficients were compared with the results of experiments obtained in the circulating water channel.

  19. Transmit-receive eddy current probes for defect detection and sizing in steam generator tubes

    SciTech Connect

    Obrutsky, L.S.; Cecco, V.S.; Sullivan, S.P.

    1997-02-01

    Inspection of steam generator tubes in aging Nuclear Generating Stations is increasingly important. Defect detection and sizing, especially in defect prone areas such as the tubesheet, support plates and U-bend regions, are required to assess the fitness-for-service of the steam generators. Information about defect morphology is required to address operational integrity issues, i.e., risk of tube rupture, number of tubes at risk, consequential leakage. A major challenge continues to be the detection and sizing of circumferential cracks. Utilities around the world have experienced this type of tube failure. Conventional in-service inspection, performed with eddy current bobbin probes, is ineffectual in detecting circumferential cracks in tubing. It has been demonstrated in CANDU steam generators, with deformation, magnetite and copper deposits that multi-channel probes with transmit-receive eddy current coils are superior to those using surface impedance coils. Transmit-receive probes have strong directional properties, permitting probe optimization according to crack orientation. They are less sensitive to lift-off noise and magnetite deposits and possess good discrimination to internal defects. A single pass C3 array transmit-receive probe developed by AECL can detect and size circumferential stress corrosion cracks as shallow as 40% through-wall. Since its first trial in 1992, it has been used routinely for steam generator in-service inspection of four CANDU plants, preventing unscheduled shutdowns due to leaking steam generator tubes. More recently, a need has surfaced for simultaneous detection of both circumferential and axial cracks. The C5 probe was designed to address this concern. It combines transmit-receive array probe technology for equal sensitivity to axial and circumferential cracks with a bobbin probe for historical reference. This paper will discuss the operating principles of transmit-receive probes, along with inspection results.

  20. The fluorescent bioprobe with aggregation-induced emission features for monitoring to carbon dioxide generation rate in single living cell and early identification of cancer cells.

    PubMed

    Chen, Didi; Wang, Huan; Dong, Lichao; Liu, Pai; Zhang, Yahui; Shi, Jianbing; Feng, Xiao; Zhi, Junge; Tong, Bin; Dong, Yuping

    2016-10-01

    A novel fluorescent probe, tris (2-(dimethylamino) ethyl)-4,4',4″-(1H-pyrrole-1,2,5-triyl) tribenzoate (TPP-TMAE), with aggregation-enhanced emission (AEE) feature showed a simple, highly selective, specific, and instant response to trace amount carbon dioxide (CO2). Because of this special characteristic, TPP-TMAE is ideal to be a biomarker for in-situ monitoring of the CO2 generation rate during the metabolism of single living cell. The rates in single living HeLa cell, MCF-7 cell, and MEF cell were 6.40 × 10(-6)±6.0 × 10(-8) μg/h, 5.78 × 10(-6)±6.0 × 10(-8) μg/h, and 4.27 × 10(-7)±4.0 × 10(-9) μg/h, respectively. The distinct responses of TPP-TMAE to CO2 generated from cancer cells and normal cells suggested TPP-TMAE as a useful tool for deeper understanding metabolism process and distinguishing cancer cells from normal cells during the early diagnosis of cancers. PMID:27372422

  1. Training the next generation of vascular specialists: current status and future perspectives.

    PubMed

    Kwolek, Christopher J; Crawford, Robert S

    2009-02-01

    Several challenges exist with respect to training the current and next generation of vascular specialists. Current advances in technology have led to changes in the length and type of training required to master new endovascular techniques. At the same time, the number of open surgical cases being provided to trainees may not be sufficient to allow them to manage complex open procedures. This growth is occurring at a time when increased external pressures are being applied to shorten training programs. Finally, the next generation of vascular specialists will come from medical students who are accruing a large educational debt during their course of training. Vascular specialists outside the US have already begun to successfully deal with many of these issues, and insight can be gained from their successes and difficulties. In this article, we review the current status of training for vascular and endovascular specialists and discuss the need for changes in current US training paradigms. While this will touch on initiatives in other specialties, including cardiology, vascular medicine, and interventional and neuroradiology, we will focus primarily on changes that are occurring with respect to the training of surgical specialists who manage vascular disease. PMID:19317585

  2. The generation of rapid solar flare hard X-ray and microwave fluctuations in current sheets

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    1986-01-01

    The generation of rapid fluctuations, or spikes, in hard X-ray and microwave bursts via the disruption of electron heating and acceleration in current sheets is studied. It is found that 20 msec hard X-ray fluctuations can be thermally generated in a current sheet if the resistivity in the sheet is highly anomalous, the plasma density in the emitting region is relatively high, and the volume of the emitting region is greater than that of the current sheet. A specific mechanism for producing the fluctuations, involving heating in the presence of ion acoustic turbulence and a constant driving electric field, and interruption of the heating by a strong two-stream instability, is discussed. Variations upon this mechanism are also discussed. This mechanism also modulates electron acceleration, as required for the microwave spike emission. If the hard X-ray emission at energies less than approx. 1000 keV is nonthermal bremsstrahlung, the coherent modulation of electron acceleration in a large number of current sheets is required.

  3. Gyrotron-driven high current ECR ion source for boron-neutron capture therapy neutron generator

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Razin, S.; Sidorov, A.; Maslennikova, A.; Volovecky, A.; Kalvas, T.; Koivisto, H.; Tarvainen, O.

    2014-12-01

    Boron-neutron capture therapy (BNCT) is a perspective treatment method for radiation resistant tumors. Unfortunately its development is strongly held back by a several physical and medical problems. Neutron sources for BNCT currently are limited to nuclear reactors and accelerators. For wide spread of BNCT investigations more compact and cheap neutron source would be much more preferable. In present paper an approach for compact D-D neutron generator creation based on a high current ECR ion source is suggested. Results on dense proton beams production are presented. A possibility of ion beams formation with current density up to 600 mA/cm2 is demonstrated. Estimations based on obtained experimental results show that neutron target bombarded by such deuteron beams would theoretically yield a neutron flux density up to 6·1010 cm-2/s. Thus, neutron generator based on a high-current deuteron ECR source with a powerful plasma heating by gyrotron radiation could fulfill the BNCT requirements significantly lower price, smaller size and ease of operation in comparison with existing reactors and accelerators.

  4. Study of second generation, high-temperature superconducting coils: Determination of critical current

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Kim, Jae-Ho; Pamidi, Sastry; Chudy, Michal; Yuan, Weijia; Coombs, T. A.

    2012-04-01

    This paper presents the modeling of second generation (2 G) high-temperature superconducting (HTS) pancake coils using finite element method. The axial symmetric model can be used to calculate current and magnetic field distribution inside the coil. The anisotropic characteristics of 2 G tapes are included in the model by direct interpolation. The model is validated by comparing to experimental results. We use the model to study critical currents of 2 G coils and find that 100 μV/m is too high a criterion to determine long-term operating current of the coils, because the innermost turns of a coil will, due to the effect of local magnetic field, reach their critical current much earlier than outer turns. Our modeling shows that an average voltage criterion of 20 μV/m over the coil corresponds to the point at which the innermost turns' electric field exceeds 100 μV/m. So 20 μV/m is suggested to be the critical current criterion of the HTS coil. The influence of background field on the coil critical current is also studied in the paper.

  5. System and method for generating current by selective minority species heating

    DOEpatents

    Fisch, Nathaniel J.

    1983-01-01

    A system for the generation of toroidal current in a plasma which is prepared in a toroidal magnetic field. The system utilizes the injection of low-frequency waves into the plasma by means of phased antenna arrays or phased waveguide arrays. The plasma is prepared with a minority ion species of different charge state and different gyrofrequency from the majority ion species. The wave frequency and wave phasing are chosen such that the wave energy is absorbed preferentially by minority species ions traveling in one toroidal direction. The absorption of energy in this manner produces a toroidal electric current even when the injected waves themselves do not have substantial toroidal momentum. This current can be continuously maintained at modest cost in power and may be used to confine the plasma. The system can operate efficiently on fusion grade tokamak plasmas.

  6. Observation of self-generated flows in tokamak plasmas with lower-hybrid-driven current.

    PubMed

    Ince-Cushman, A; Rice, J E; Reinke, M; Greenwald, M; Wallace, G; Parker, R; Fiore, C; Hughes, J W; Bonoli, P; Shiraiwa, S; Hubbard, A; Wolfe, S; Hutchinson, I H; Marmar, E; Bitter, M; Wilson, J; Hill, K

    2009-01-23

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a approximately <0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (approximately 100 ms) but longer than the energy and momentum confinement times (approximately 20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch. PMID:19257362

  7. Low-impedance plasma systems for generation of high-current low-energy electron beams

    NASA Astrophysics Data System (ADS)

    Agafonov, A. V.

    2006-12-01

    The results of experimental investigation and numerical modeling of the generation of low-energy (tens of keV) high-current (up to tens of kA) electron beams in a low-impedance system consisting of a plasma-filled diode with a long plasma anode, an auxiliary hot cathode, and an explosive emission cathode. The low-current low-voltage beam from the auxiliary cathode in an external longitudinal magnetic field is used to produce a long plasma anode, which is simultaneously the channel of beam transportation by residual gas ionization. The high-current electron beam is formed from the explosive emission cathode placed in the preliminarily formed plasma. Numerical modeling is performed using the KARAT PIC code.

  8. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

    SciTech Connect

    Ince-Cushman, A.; Rice, J. E.; Reinke, M.; Greenwald, M.; Wallace, G.; Parker, R.; Fiore, C.; Hughes, J. W.; Bonoli, P.; Shiraiwa, S.; Hubbard, A.; Wolfe, S.; Hutchinson, I. H.; Marmar, E.; Bitter, M.; Wilson, J.; Hill, K.

    2009-01-23

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a{approx}<0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time ({approx}100 ms) but longer than the energy and momentum confinement times ({approx}20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch.

  9. Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating.

    PubMed

    Skalyga, V; Izotov, I; Golubev, S; Razin, S; Sidorov, A; Maslennikova, A; Volovecky, A; Kalvas, T; Koivisto, H; Tarvainen, O

    2015-12-01

    BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beams with current density up to 700-800 mA/cm(2). Generation of the neutron flux with density at the level of 7-8·10(10) s(-1) cm(-2) at the target surface could be obtained in case of TiD2 target bombardment with deuteron beam accelerated to 100 keV. Estimations show that it is enough for formation of epithermal neutron flux with density higher than 10(9) s(-1) cm(-2) suitable for BNCT. Important advantage of described approach is absence of Tritium in the scheme. First experiments performed in pulsed regime with 300 mA, 45 kV deuteron beam directed to D2O target demonstrated 10(9) s(-1) neutron flux. This value corresponds to theoretical estimations and proofs prospects of neutron generator development based on high current quasi-gasdynamic ECR ion source. PMID:26302662

  10. Turbidity current flow over an erodible obstacle and phases of sediment wave generation

    NASA Astrophysics Data System (ADS)

    Strauss, Moshe; Glinsky, Michael E.

    2012-06-01

    We study the flow of particle-laden turbidity currents down a slope and over an obstacle. A high-resolution 2-D computer simulation model is used, based on the Navier-Stokes equations. It includes poly-disperse particle grain sizes in the current and substrate. Particular attention is paid to the erosion and deposition of the substrate particles, including application of an active layer model. Multiple flows are modeled from a lock release that can show the development of sediment waves (SW). These are stream-wise waves that are triggered by the increasing slope on the downstream side of the obstacle. The initial obstacle is completely erased by the resuspension after a few flows leading to self consistent and self generated SW that are weakly dependant on the initial obstacle. The growth of these waves is directly related to the turbidity current being self sustaining, that is, the net erosion is more than the net deposition. Four system parameters are found to influence the SW growth: (1) slope, (2) current lock height, (3) grain lock concentration, and (4) particle diameters. Three phases are discovered for the system: (1) "no SW," (2) "SW buildup," and (3) "SW growth". The second phase consists of a soliton-like SW structure with a preserved shape. The phase diagram of the system is defined by isolating regions divided by critical slope angles as functions of current lock height, grain lock concentration, and particle diameters.

  11. C-axis critical current density of second-generation YBCO tapes.

    SciTech Connect

    Jia, Y.; Hua, J.; Crabtree, G. W.; Kwok, W. K.; Welp, U.; Malozemoff, A. P.; Rupich, M.; Fleshler, S.; Materials Science Division; American Superconductor Corp.

    2010-10-01

    We report on measurements of the temperature and field dependence of the c-axis critical current density (J{sub c}{sup c}) obtained on mesa structures that were patterned into the YBCO layer of second-generation HTS tapes. We find the J{sub c}{sup c}-values of {approx}4 kA cm{sup -2} at 77 K and self-field, corresponding to an unexpectedly high anisotropy in the critical current density J{sub c}{sup ab}/J{sub c}{sup c} of 500-600. C-axis current flow is expected to arise in applications such as the helically wound wires in HTS cables. A simple estimate is given of the fraction of tape width for such a c-axis flow; while in our samples this fraction is approximately 5% for a typical geometry, the fraction will grow linearly with increasing current density anisotropy and could affect the current-carrying ability of the tape.

  12. C-Axis critical current density of second-generation YBCO tapes

    SciTech Connect

    Jia, Y.; Hua, J.; Crabtree, G.W.; Kwok, W.K.; Welp, U.; Malozemoff, A.P.; Rupich, M.; Fleshler, S.

    2010-10-21

    We report on measurements of the temperature and field dependence of the c-axis critical current density (Jcc) obtained on mesa structures that were patterned into the YBCO layer of second-generation HTS tapes. We find the Jcc—values of ~ 4 kA cm-2 at 77 K and self-field, corresponding to an unexpectedly high anisotropy in the critical current density Jcab/Jcc of 500–600. C-axis current flow is expected to arise in applications such as the helically wound wires in HTS cables. A simple estimate is given of the fraction of tape width for such a c-axis flow; while in our samples this fraction is approximately 5% for a typical geometry, the fraction will grow linearly with increasing current density anisotropy and could affect the current-carrying ability of the tape.

  13. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Fisch, Nathaniel J.

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to establish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated in the plasma.

  14. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Bers, Abraham

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to estalish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated inthe plasma.

  15. Generation and Detection of Spin Currents in Semiconductor Nanostructures with Strong Spin-Orbit Interaction

    NASA Astrophysics Data System (ADS)

    Nichele, Fabrizio; Hennel, Szymon; Pietsch, Patrick; Wegscheider, Werner; Stano, Peter; Jacquod, Philippe; Ihn, Thomas; Ensslin, Klaus

    2015-05-01

    Storing, transmitting, and manipulating information using the electron spin resides at the heart of spintronics. Fundamental for future spintronics applications is the ability to control spin currents in solid state systems. Among the different platforms proposed so far, semiconductors with strong spin-orbit interaction are especially attractive as they promise fast and scalable spin control with all-electrical protocols. Here we demonstrate both the generation and measurement of pure spin currents in semiconductor nanostructures. Generation is purely electrical and mediated by the spin dynamics in materials with a strong spin-orbit field. Measurement is accomplished using a spin-to-charge conversion technique, based on the magnetic field symmetry of easily measurable electrical quantities. Calibrating the spin-to-charge conversion via the conductance of a quantum point contact, we quantitatively measure the mesoscopic spin Hall effect in a multiterminal GaAs dot. We report spin currents of 174 pA, corresponding to a spin Hall angle of 34%.

  16. GENERATION OF ELECTRIC CURRENTS IN THE CHROMOSPHERE VIA NEUTRAL-ION DRAG

    SciTech Connect

    Krasnoselskikh, V.; Vekstein, G.; Hudson, H. S.; Bale, S. D.; Abbett, W. P.

    2010-12-01

    We consider the generation of electric currents in the solar chromosphere where the ionization level is typically low. We show that ambient electrons become magnetized even for weak magnetic fields (30 G); that is, their gyrofrequency becomes larger than the collision frequency while ion motions continue to be dominated by ion-neutral collisions. Under such conditions, ions are dragged by neutrals, and the magnetic field acts as if it is frozen-in to the dynamics of the neutral gas. However, magnetized electrons drift under the action of the electric and magnetic fields induced in the reference frame of ions moving with the neutral gas. We find that this relative motion of electrons and ions results in the generation of quite intense electric currents. The dissipation of these currents leads to resistive electron heating and efficient gas ionization. Ionization by electron-neutral impact does not alter the dynamics of the heavy particles; thus, the gas turbulent motions continue even when the plasma becomes fully ionized, and resistive dissipation continues to heat electrons and ions. This heating process is so efficient that it can result in typical temperature increases with altitude as large as 0.1-0.3 eV km{sup -1}. We conclude that this process can play a major role in the heating of the chromosphere and corona.

  17. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Sidorov, A.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-01

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm2 are demonstrated. Neutron yield from D2O and TiD2 targets was measured in case of its bombardment by pulsed 300 mA D+ beam with 45 keV energy. Neutron yield density at target surface of 109 s-1 cm-2 was detected with a system of two 3He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD2 target bombarded by D+ beam demonstrated in present work accelerated to 100 keV could reach 6 × 1010 s-1 cm-2. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  18. Generation of magnetic skyrmion bubbles by inhomogeneous spin-Hall currents

    NASA Astrophysics Data System (ADS)

    Heinonen, Olle; Jiang, Wanjun; Somaily, Hamoud; Te Velthuis, Suzanne G. E.; Hoffmann, Axel

    Recent experiments have shown that magnetic skyrmion bubbles can be generated and injected at room temperature in thin films1. Here, we demonstrate, using micromagnetic modeling, that such skyrmions can be generated by an inhomogeneous spin Hall torque in the presence of Dzyaloshinskii- Moriya interactions (DMIs). In the experimental Ta-Co20Fe60B20 thin films, the DMI is rather small; nevertheless, the skyrmion bubbles are stable, or at least metastable on observational time scales. We identify two different mechanisms, one in a low-current regime and the other in a high current regime, that destabilize a domain wall injected from a narrow region into an expanding region with inhomogeneous spin-Hall torque. In the first, asymmetric torques on the domain wall lead to a cascade of bubble formation and subsequent fragmentation. In the second, an approximately steady-state texture is injected into the wide region. When the current is turned off, the inhomogeneous spin texture relaxes and regions can coalesce into bubbles that attain a definite chirality because of the DMI. This work was funded by the Department of Energy Office of Science, Materials Science and Engineering Division.

  19. Role of the current young generation within the space exploration sector

    NASA Astrophysics Data System (ADS)

    Calzada-Diaz, A.; Dayas-Codina, M.; MacArthur, J. L.; Bielicki, D. M.

    2014-08-01

    The space sector gathers together people from a variety of fields who work in the industry on different levels and with different expertise. What is often forgotten is the impact and role of the current young generation. Their engagement is of great importance as undeniably today's young 'space generation' will be defining the direction of future space exploration. Today's vision of future human and robotic space exploration has been set out in the Global Exploration Roadmap (GER). This focuses on sustainable, affordable and productive long-term goals. The strategy begins with the International Space Station (ISS) and then expands human presence into the solar system, including a human mission to Mars. This paper presents a general overview of the role of today's youth within the space exploration sector and the challenges to overcome. To complete this perspective, we present results from a survey made among students and young professionals about their levels of awareness of the GER. The respondents presented their opinion about current aspects of the GER and prioritised the GER's objectives. It is hoped that the paper will bring a new perspective into the GER and a contribution to the current GER strategy.

  20. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    SciTech Connect

    Skalyga, V.; Sidorov, A.; Izotov, I.; Golubev, S.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-07

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm{sup 2} are demonstrated. Neutron yield from D{sub 2}O and TiD{sub 2} targets was measured in case of its bombardment by pulsed 300 mA D{sup +} beam with 45 keV energy. Neutron yield density at target surface of 10{sup 9} s{sup −1} cm{sup −2} was detected with a system of two {sup 3}He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD{sub 2} target bombarded by D{sup +} beam demonstrated in present work accelerated to 100 keV could reach 6 × 10{sup 10} s{sup −1} cm{sup −2}. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  1. Attosecond-magnetic-field-pulse generation by electronic currents in bichromatic circularly polarized UV laser fields

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2015-12-01

    Attosecond-magnetic-field-pulse generation is simulated from numerical solutions of time-dependent Schrödinger equations for oriented H2 +. Two schemes with high frequency co- and counter-rotating bichromatic ω2=2 ω1 circularly polarized UV laser pulses are investigated. Results show that comparing to single color processes, stronger induced localized magnetic fields B at the molecular center O (r =0 ) are obtained with attosecond duration. This is attributed to frequent recollision and to interference effects of two pathways in photoionization. The induced magnetic fields are shown to be sensitive to (i) the helicity of the combined laser pulses due to different recollision laser-induced electron trajectories and currents, and (ii) also the carrier envelope phases of the combined attosecond laser pulses. The sensitivity of recollision to bichromatic pulses thus allows one to control the induced magnetic-field-pulse generation.

  2. Large-Scale Physical Modelling of Complex Tsunami-Generated Currents

    NASA Astrophysics Data System (ADS)

    Lynett, P. J.; Kalligeris, N.; Ayca, A.

    2014-12-01

    For tsunamis passing through sharp bathymetric variability, such as a shoal or a harbor entrance channel, z-axis vortical motions are created. These structures are often characterized by a horizontal length scale that is much greater than the local depth and are herein called shallow turbulent coherent structures (TCS). These shallow TCS can greatly increase the drag force on affected infrastructure and the ability of the flow to transport debris and floating objects. Shallow TCS typically manifest as large "whirlpools" during tsunamis, very commonly in ports and harbors. Such structures have been observed numerous times in the tsunamis over the past decade, and are postulated as the cause of large vessels parting their mooring lines due to yaw induced by the rotational eddy. Through the NSF NEES program, a laboratory study to examine a shallow TCS was performed during the summer of 2014. To generate this phenomenon, a 60 second period long wave was created and then interacted with a breakwater in the basin, forcing the generation of a large and stable TCS. The model scale is 1:30, equating to a 5.5 minute period and 0.5 m amplitude in the prototype scale. Surface tracers, dye studies, AVD's, wave gages, and bottom pressure sensors are used to characterize the flow. Complex patterns of surface convergence and divergence are easily seen in the data, indicating three-dimensional flow patterns. Dye studies show areas of relatively high and low spatial mixing. Model vessels are placed in the basin such that ship motion in the presence of these rapidly varying currents might be captured. The data obtained from this laboratory study should permit a better physical understanding of the nearshore currents that tsunamis are known to generate, as well as provide a benchmark for numerical modelers who wish to simulate currents.

  3. A current generation by Compton scattering in a relativistic plasma with velocity shear and temperature gradient

    NASA Technical Reports Server (NTRS)

    Hinata, S.

    1984-01-01

    Current generation by Thomson scattering in a non-relativistic plasma with the velocity shear and the temperature gradient (Hinata and Daneshvar, 1983) is extended to a relativistic plasma by replacing Thomson cross section by the Klein-Nishina formula. Because of the energy dependence of the cross-section, a numerical rather than analytic result is presented. The present calculation may be applied to a supernova implosion where the temperature may reach several MeV and a strong differential rotation is expected. It may also find applications in the early universe, and laser-pellet interaction.

  4. Generation and characterization of electron bunches with ramped current profile at the FLASH facility

    SciTech Connect

    Piot, P.; Behrens, C.; Gerth, C.; Lemery, F.; Mihalcea, D.; Vogt, M.; /DESY

    2011-09-01

    We report on the successful generation of electron bunches with current prof les that have a quasi-linear dependency on the longitudinal coordinate. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a linac operating at two frequencies (1.3 and 3.9 GHz) and a bunch compressor. Data taken for various accelerator settings demonstrate the versatility of the method. The produced bunches have parameters well matched to drive high-gradient accelerating field with enhanced transformer ratio in beam-driven accelerators based on sub-mm-sizes dielectric or plasma structures.

  5. Cesium telluride cathodes for the next generation of high-average current high-brightness photoinjectors

    SciTech Connect

    Filippetto, D. Qian, H.; Sannibale, F.

    2015-07-27

    We report on the performances of a Cs{sub 2}Te photocathode under extreme conditions of high peak time-dependent accelerating fields, continuous wave operations, and MHz pulse extraction with up to 0.3 mA average current. The measurements, performed in a normal conducting cavity, show extended lifetime and robustness, elucidate the main mechanisms for cathode degradation, and set the required system vacuum performance for compatibility with the operations of a high average power X-ray free electron laser user facility, opening the doors to the next generation of MHz-scale ultrafast scientific instruments.

  6. Modeling of new/commercial eddy current probe for steam generator inspection

    NASA Astrophysics Data System (ADS)

    Lei, Naiguang; Xin, Junjun; Udpa, Lalita; Udpa, Satish S.

    2012-05-01

    Computational models serve an important role in Non-Destructive Evaluation applications for enabling effective use of the technology. The solution of simulation models provide valuable insight into the underlying physics, help visualize the field/flaw interaction and help optimize sensor design and develop algorithms for interpreting the measured signals. This paper presents a simulation model for predicting defect signals in Steam Generator tube inspections using commercial eddy current probe used in industry. The model, based on finite element analysis, uses reduced vector potential formulation and novel strategies for modeling ferrite core probes. Experimental validations of model predictions for a number of defect geometries are presented.

  7. Polarization electric field in subalfvenic plasma jet under condition of field- aligned currents generation

    NASA Astrophysics Data System (ADS)

    Sobyanin, D.; Gavrilov, B.; Podgorny, I.

    The subalfvenic magnetized plasma jet propagating across the geomagnetic field generates field-aligned currents in the ionospheric plasma. As a result the transverse polarization electric field Ep =-VxB/c in the jet should be reduced (plasma jet depolarization). These phenomena are investigated in the laboratory experiment. It was revealed that the depolarization is accompanied by the appearing of the electric field E along the plasma velocity vector. The value of E is comparable with theaa transverse electric field. It results in the plasma jet deflection. The possibility of manifestation of these effects in the NORTH STAR Russian-American active rocket experiment is discussed.

  8. Experimental study on hydrodynamic characteristics of vertical-axis floating tidal current energy power generation device

    NASA Astrophysics Data System (ADS)

    Ma, Yong; Li, Teng-fei; Zhang, Liang; Sheng, Qi-hu; Zhang, Xue-wei; Jiang, Jin

    2016-01-01

    To study the characteristics of attenuation, hydrostatic towage and wave response of the vertical-axis floating tidal current energy power generation device (VAFTCEPGD), a prototype is designed and experiment is carried out in the towing tank. Free decay is conducted to obtain attenuation characteristics of the VAFTCEPGD, and characteristics of mooring forces and motion response, floating condition, especially the lateral displacement of the VAFTCEPGD are obtained from the towing in still water. Tension response of the #1 mooring line and vibration characteristics of the VAFTCEPGD in regular waves as well as in level 4 irregular wave sea state with the current velocity of 0.6 m/s. The results can be reference for theoretical study and engineering applications related to VAFTCEPGD.

  9. A self-consistent turbulence generated scenario for L-H transition. [Banana polarization currents

    SciTech Connect

    Zhang, Y.Z.; Mahajan, S.M.

    1992-10-01

    The turbulence-induced ion banana polarization current associated with steep ion temperature gradients is explored as a possible mechanism for generating poloidal momentum at the tokamak edge. In the light of a recently developed two-dimensional turbulence theory, one can obtain a simple closed expression relating this current (determined by turbulence levels) to the derivatives of the poloidal rotation speed. A self-consistent system, then, emerges, if we balance the turbulence-induced poloidal momentum with that dissipated by viscosity. Under suitable conditions this system may show a bifurcation controlled by a parameter dependent on temperature gradients. Both the bifurcation point, and the shear layer width are predicted for a prescribed flow in terms of a scale characterizing the nonlinearity of viscosity. The crucial relevance of the flow parity with the turbulence scenario is analyzed.

  10. Plasmonic enhancement of second harmonic generation from nonlinear RbTiOPO4 crystals by aggregates of silver nanostructures.

    PubMed

    Sánchez-García, Laura; Tserkezis, Christos; Ramírez, Mariola O; Molina, Pablo; Carvajal, Joan J; Aguiló, Magdalena; Díaz, Francesc; Aizpurua, Javier; Bausá, Luisa E

    2016-04-18

    We demonstrate a 60-fold enhancement of the second harmonic generation (SHG) response at the nanoscale in a hybrid metal-dielectric system. By using complex silver nanostructures photochemically deposited on the polar surface of a ferroelectric crystal, we tune the plasmonic resonances from the visible to the near-infrared (NIR) spectral region, matching either the SH or the fundamental frequency. In both cases the SHG signal at the metal-dielectric interface is enhanced, although with substantially different enhancement values: around 5 times when the plasmonic resonance is at the SH frequency or up to 60 times when it matches the fundamental NIR radiation. The results are consistent with the more spatially-extended near-field response of complex metallic nanostructures and can be well explained by taking into account the quadratic character of the SHG process. The work points out the potential of aggregates of silver nanostructures for enhancing optical nonlinearities at the nanoscale and provides an alternative approach for the development of nanometric nonlinear photonic devices in a scalable way. PMID:27137287

  11. An atmospheric turbulence model for spatiotemporal variability of geographically-diverse, aggregated wind-generated electricity to accelerate wide-scale wind energy deployment (Invited)

    NASA Astrophysics Data System (ADS)

    Lundquist, J. K.; Handschy, M.

    2013-12-01

    During the year 2012, the cumulative wind power capacity installed in the United States could provide roughly 4.4% of electricity demand. Although the wind resource can provide many times over the entire US electrical needs, and costs for onshore wind deployment are continually dropping, the variability of the wind represents one of the greatest remaining barriers to wide-scale wind deployment. This study focuses on the nature of this variability. We quantify the axiom 'geographic diversity reduces variability' (of wind generation) by relating resource variability characteristics to the well-understood physical phenomena of turbulence in the Earth's atmosphere. Many existing studies focus on datasets of a few years' duration in a particular geographic area; such results are difficult to generalize. Our approach builds on the fundamental nonlinear characteristics of turbulence in the atmosphere to characterize wind speed and power generation correlations between wind plants from local to continental scales. The resulting general principles enable estimation of the benefits of geographic aggregation absent detailed site-specific historical data, thereby enabling more efficient transmission grid models, expediting transmission plans, and providing a framework for evaluating the requirements and benefits of electric storage at higher wind penetrations. To validate these general principles, we compare them to observed inter-station correlations in a number of wind-speed data sets, including a 40-year Canadian dataset that spans the continent of North America, as well as shorter-duration datasets in smaller regions within the United States. This presentation will present general rules for the dependence of correlation between wind turbines on separation and time scale. We suggest these general rules could help shift renewable integration planning from simulation towards optimization.

  12. The Energy-Efficient Quarry: Towards improved understanding and optimisation of energy use and minimisation of CO2 generation in the aggregates industry.

    NASA Astrophysics Data System (ADS)

    Hill, Ian; White, Toby; Owen, Sarah

    2014-05-01

    Extraction and processing of rock materials to produce aggregates is carried out at some 20,000 quarries across the EU. All stages of the processing and transport of hard and dense materials inevitably consume high levels of energy and have consequent significant carbon footprints. The FP7 project "the Energy Efficient Quarry" (EE-Quarry) has been addressing this problem and has devised strategies, supported by modelling software, to assist the quarrying industry to assess and optimise its energy use, and to minimise its carbon footprint. Aggregate quarries across Europe vary enormously in the scale of the quarrying operations, the nature of the worked mineral, and the processing to produce a final market product. Nevertheless most quarries involve most or all of a series of essential stages; deposit assessment, drilling and blasting, loading and hauling, and crushing and screening. The process of determining the energy-efficiency of each stage is complex, but is broadly understood in principle and there are numerous sources of information and guidance available in the literature and on-line. More complex still is the interaction between each of these stages. For example, using a little more energy in blasting to increase fragmentation may save much greater energy in later crushing and screening, but also generate more fines material which is discarded as waste and the embedded energy in this material is lost. Thus the calculation of the embedded energy in the waste material becomes an input to the determination of the blasting strategy. Such feedback loops abound in the overall quarry optimisation. The project has involved research and demonstration operations at a number of quarries distributed across Europe carried out by all partners in the EE-Quarry project, working in collaboration with many of the major quarrying companies operating in the EU. The EE-Quarry project is developing a sophisticated modelling tool, the "EE-Quarry Model" available to the quarrying

  13. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  14. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  15. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  16. Experimental research of different plasma cathodes for generation of high-current electron beams

    SciTech Connect

    Shafir, G.; Kreif, M.; Gleizer, J. Z.; Gleizer, S.; Krasik, Ya. E.; Gunin, A. V.; Kutenkov, O. P.; Rostov, V. V.; Pegel, I. V.

    2015-11-21

    The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (∼2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods and carbon-epoxy capillaries operating with an average current density up to 1 kA/cm{sup 2} showed insignificant erosion along 10{sup 6} pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.

  17. Experimental research of different plasma cathodes for generation of high-current electron beams

    NASA Astrophysics Data System (ADS)

    Shafir, G.; Kreif, M.; Gleizer, J. Z.; Gleizer, S.; Krasik, Ya. E.; Gunin, A. V.; Kutenkov, O. P.; Pegel, I. V.; Rostov, V. V.

    2015-11-01

    The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (˜2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods and carbon-epoxy capillaries operating with an average current density up to 1 kA/cm2 showed insignificant erosion along 106 pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.

  18. Electric current generation by sulfur-reducing bacteria in microbial-anode fuel cell

    NASA Astrophysics Data System (ADS)

    Vasyliv, Oresta M.; Bilyy, Oleksandr I.; Ferensovych, Yaroslav P.; Hnatush, Svitlana O.

    2012-10-01

    Sulfur - reducing bacteria are a part of normal microflora of natural environment. Their main function is supporting of reductive stage of sulfur cycle by hydrogen sulfide production in the process of dissimilative sulfur-reduction. At the same time these bacteria completely oxidize organic compounds with CO2 and H2O formation. It was shown that they are able to generate electric current in the two chamber microbial-anode fuel cell (MAFC) by interaction between these two processes. Microbial-anode fuel cell on the basis of sulfur- and ferric iron-reducing Desulfuromonas acetoxidans bacteria has been constructed. It has been shown that the amount of electricity generation by investigated bacteria is influenced by the concentrations of carbon source (lactate) and ferric iron chloride. The maximal obtained electric current and potential difference between electrodes equaled respectively 0.28-0.29 mA and 0.19-0.2 V per 0.3 l of bacterial suspension with 0.4 g/l of initial biomass that was grown under the influence of 0.45 mM of FeCl3 and 3 g/l of sodium lactate as primal carbon source. It has also been shown that these bacteria are resistant to different concentrations of silver ions.

  19. Search for a fourth generation charge {minus}1/3 quark via flavor changing neutral currents

    SciTech Connect

    The D0 Collaboration

    1996-07-01

    There is some likelihood that a light (< m{sub t}) fourth generation charge -1/3 quark (b{prime}) would decay predominantly via loop induced flavor changing neutral currents. The charged current decay of b{prime} to charm would be highly Cabibbo suppressed due to the fact that it changes the generation number by two. The D0 experiment has searched for b{prime} pair production where one or both b{prime} quarks decays via b{prime} {r_arrow} b+{gamma}, giving signatures photon + three jets and two photons + two jets. WE don not see a significant excess of such events over background. In both modes, we set an upper limit on the cross section times branching ratio that is sufficient to rule out a standard sequential b{prime} decaying predominantly via FCNC in the mass range m{sub Z}/2 < m{sub b{prime}} < m{sub Z} + m{sub b}. For b{prime} masses larger than this, the dominant FCNC decay mode is expected to be b{prime} {r_arrow} b + Z. 14 refs., 13 figs., 5 tabs.

  20. Start-to-end beam dynamics simulation of double triangular current profile generation in Argonne Wakefield Accelerator

    SciTech Connect

    Ha, G.; Power, J.; Kim, S. H.; Gai, W.; Kim, K.-J.; Cho, M. H.; Namkung, W.

    2012-12-21

    Double triangular current profile (DT) gives a high transformer ratio which is the determining factor of the performance of collinear wakefield accelerator. This current profile can be generated using the emittance exchange (EEX) beam line. Argonne Wakefield Accelerator (AWA) facility plans to generate DT using the EEX beam line. We conducted start-to-end simulation for the AWA beam line using PARMELA code. Also, we discuss requirements of beam parameters for the generation of DT.

  1. Current status and future prospects of power generators using dielectric elastomers

    NASA Astrophysics Data System (ADS)

    Chiba, Seiki; Waki, Mikio; Kornbluh, Roy; Pelrine, Ron

    2011-12-01

    Electroactive polymer artificial muscle (EPAM), known collectively as dielectric elastomers in the literature, has been shown to offer unique capabilities as an actuator and is now being developed for a wide variety of generator applications. EPAM has several characteristics that make it potentially well suited for wave, water current, wind, human motion, and other environmental energy harvesting systems including a high energy density allowing for minimal EPAM material quantities, high energy conversion efficiency independent of frequency of operation and non-toxic and low-cost materials not susceptible to corrosion. Experiments have been performed on push-button and heel-mounted generator devices powered by human motion, ocean wave power harvesters mounted on buoys and water turbines. While the power output levels of such demonstration devices is small, the performance of these devices has supported the potential benefits of EPAM. For example, an electrical energy conversion efficiency of over 70% was achieved with small wave heights. The ability of EPAM to produce hydrogen fuel for energy storage was also demonstrated. Because the energy conversion principle of EPAM is capacitive in nature, the performance is largely independent of size and it should eventually be possible to scale up EPAM generators to the megawatt level to address a variety of electrical power needs.

  2. Ensemble forecasting for renewable energy applications - status and current challenges for their generation and verification

    NASA Astrophysics Data System (ADS)

    Pinson, Pierre

    2016-04-01

    The operational management of renewable energy generation in power systems and electricity markets requires forecasts in various forms, e.g., deterministic or probabilistic, continuous or categorical, depending upon the decision process at hand. Besides, such forecasts may also be necessary at various spatial and temporal scales, from high temporal resolutions (in the order of minutes) and very localized for an offshore wind farm, to coarser temporal resolutions (hours) and covering a whole country for day-ahead power scheduling problems. As of today, weather predictions are a common input to forecasting methodologies for renewable energy generation. Since for most decision processes, optimal decisions can only be made if accounting for forecast uncertainties, ensemble predictions and density forecasts are increasingly seen as the product of choice. After discussing some of the basic approaches to obtaining ensemble forecasts of renewable power generation, it will be argued that space-time trajectories of renewable power production may or may not be necessitate post-processing ensemble forecasts for relevant weather variables. Example approaches and test case applications will be covered, e.g., looking at the Horns Rev offshore wind farm in Denmark, or gridded forecasts for the whole continental Europe. Eventually, we will illustrate some of the limitations of current frameworks to forecast verification, which actually make it difficult to fully assess the quality of post-processing approaches to obtain renewable energy predictions.

  3. Liner velocity, current, and symmetry measurements on the 32 MEGAMP flux compression generator experiment ALT-1

    SciTech Connect

    Anderson, B. G.; Rodriguez, G.; Stokes, J. L.; Tabaka, L. J.; Clark, D. A.

    2001-01-01

    A flux compression generator pulse power system, designed, built, and fielded by a Russian team at the All Russian Scientific Research Institute of Experimental Physics (VNIIEF), was used to successfully drive an aluminum liner to velocities greater than 12 km/sec. The experiment objective was to demonstrate performance of a precision liner implosion at an Atlas current of 30 MA or greater. Diagnostics to measure liner performance were an essential part of the experiment. An experimental team from Los Alamos National Laboratory (LANL) provided a suite of diagnostics to measure liner performance. Three diagnostics were fielded: (1) A velocity interferometer (VISAR) to continuously measure the liner innersurface velocity throughout the entire range of travel, (2) Two Faraday rotation devices to measure liner current during the implosion, and, (3) Sixteen fiber optic impact pins to record liner impact time and provide axial and azimuthal symmetry information. All diagnostics performed very well. Major results are maximum current: 32.3 MA, velocity at impact: greater than 12 km/sec, symmetry: the impact pins indicated that the liner was smooth, solid, and axially symmetric upon arrival at the diagnostic package. The LANL team fabricated, installed, and recorded the three diagnostics presented here. All necessary equipment was brought to the site in Russia. The VNIIEF team fielded other diagnostics to measure machine performance. Results of machine diagnostics are reported in other presentations.

  4. Spin current generation from sputtered Y₃Fe₅O₁₂ films

    SciTech Connect

    Lustikova, J. Shiomi, Y.; Kikkawa, T.; Iguchi, R.; Qiu, Z.; Uchida, K.; Saitoh, E.

    2014-10-21

    Spin current injection from sputtered yttrium iron garnet (YIG) films into an adjacent platinum layer has been investigated by means of the spin pumping and the spin Seebeck effects. Films with a thickness of 83 and 96 nanometers were fabricated by on-axis magnetron rf sputtering at room temperature and subsequent post-annealing. From the frequency dependence of the ferromagnetic resonance linewidth, the damping constant has been estimated to be (7.0 ± 1.0) × 10⁻⁴. Magnitudes of the spin current generated by the spin pumping and the spin Seebeck effect are of the same order as values for YIG films prepared by liquid phase epitaxy. The efficient spin current injection can be ascribed to a good YIG|Pt interface, which is confirmed by the large spin-mixing conductance (2.0 ± 0.2) × 10¹⁸m⁻².

  5. Ceramic ware waste as coarse aggregate for structural concrete production.

    PubMed

    García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-Del Pozo, Julia M; Guerra-Romero, M Ignacio

    2015-01-01

    The manufacture of any kind of product inevitably entails the production of waste. The quantity of waste generated by the ceramic industry, a very important sector in Spain, is between 5% and 8% of the final output and it is therefore necessary to find an effective waste recovery method. The aim of the study reported in the present article was to seek a sustainable means of managing waste from the ceramic industry through the incorporation of this type of waste in the total replacement of conventional aggregate (gravel) used in structural concrete. Having verified that the recycled ceramic aggregates met all the technical requirements imposed by current Spanish legislation, established in the Code on Structural Concrete (EHE-08), then it is prepared a control concrete mix and the recycled concrete mix using 100% recycled ceramic aggregate instead of coarse natural aggregate. The concretes obtained were subjected to the appropriate tests in order to conduct a comparison of their mechanical properties. The results show that the concretes made using ceramic sanitary ware aggregate possessed the same mechanical properties as those made with conventional aggregate. It is therefore possible to conclude that the reuse of recycled ceramic aggregate to produce recycled concrete is a feasible alternative for the sustainable management of this waste. PMID:25188783

  6. Field-aligned currents and magnetospheric generator in experiments on a laser-produced plasma flowing around a magnetic dipole

    NASA Astrophysics Data System (ADS)

    Shaikhislamov, I. F.; Antonov, V. M.; Zakharov, Yu. P.; Boyarintsev, E. L.; Melekhov, A. V.; Posukh, V. G.; Ponomarenko, A. G.

    2014-07-01

    A laboratory experiment on modeling the magnetospheric generator of the field-aligned currents and the Earth's transpolar potential in the absence of IMF is illustrated. The measurements of the total field-aligned current in the generator shorted mode and the transpolar potential in the circuit disconnection mode made it possible to determine the generator internal resistance. A model that explains the saturation current and internal resistance by the feedback between the field-aligned current and plasma flank motions has been proposed. This feedback is described through the effective resistance, which is proportional to the flow rate and the ratio of the boundary layer to the dimension of the magnetosphere. For the experimental conditions, the calculated generator resistance was in good agreement with the measured value. The estimates for the Earth's magnetosphere indicate that the MHD generator internal resistance in the boundary layer is usually much lower than the reverse integral conductivity of the ionosphere.

  7. Aggregates of a hetero-oligophenylene derivative as reactors for the generation of palladium nanoparticles: a potential catalyst in the Sonogashira coupling reaction under aerial conditions.

    PubMed

    Walia, Preet Kamal; Pramanik, Subhamay; Bhalla, Vandana; Kumar, Manoj

    2015-12-18

    The utilization of Pd nanoparticles stabilized by aggregates of hetero-oligophenylene derivative 3 as an excellent catalyst in a copper/amine free Sonogashira coupling reaction under aerial conditions at room temperature has been demonstrated. PMID:26460180

  8. Construction aggregates

    USGS Publications Warehouse

    Bolen, W.P.; Tepordei, V.V.

    2001-01-01

    The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

  9. Aggregated Authentication (AMAC) Using Universal Hash Functions

    NASA Astrophysics Data System (ADS)

    Znaidi, Wassim; Minier, Marine; Lauradoux, Cédric

    Aggregation is a very important issue to reduce the energy consumption in Wireless Sensors Networks (WSNs). There is currently a lack of cryptographic primitives for authentication of aggregated data. The theoretical background for Aggregated Message Authentication Codes (AMACs) has been proposed by Chan and Castelluccia at ISIT 08.

  10. Neural network inversion of synthetic eddy current testing signals from flaws in steam generator tubes

    NASA Astrophysics Data System (ADS)

    Song, S. J.; Kim, C. H.; Shin, Y. K.; Lee, H. B.; Park, Y. W.; Yim, C. J.

    2001-04-01

    This paper reports our recent endeavor to develop automated, systematic inversion tools by the novel combination of neural networks and finite element modeling for eddy current flaw characterization in steam generator tubes. Specifically, this paper describes 1) development of the finite element models that can simulate synthetic ECT signals from axisymmetric flaws with arbitrary cross-sections, 2) construction of databases with abundant flaw signals, 3) implementation of effective feature extraction software and proposition of feature selection criteria, and finally 4) development of inversion tools by use of two neural networks for flaw classification and sizing. In addition, this paper also presents the performance of the proposed inversion tools for solving two sample problems: classification of flaws with non-symmetric cross-sections, and classification and sizing of flaws with tip variation.

  11. Evidence of underground electric current generation during the 2009 L'Aquila earthquake: Real or instrumental?

    NASA Astrophysics Data System (ADS)

    Masci, F.; Thomas, J. N.

    2016-06-01

    We investigate magnetic effects in correspondence of the Mw6.1 L'Aquila earthquake. Magnetic and seismic records are analyzed. Rapid and distinct changes and an offset can be seen in magnetic field components after the main shock. We show that these effects result from electromagnetic induction due to the movement of the sensors through the Earth's magnetic field and from a permanent displacement of the sensors from their original position caused by the passing seismic waves. A transient signal in total field data from an overhauser magnetometer apparently occurs in correspondence with the earthquake. Our analysis shows that the transient was not observed by other sensors that were operating in close proximity to the overhauser. Thus, the transient signal in the total magnetic field data, and the offset in the magnetic field components, cannot be associated with a hypothetical underground electric current generated by the earthquake, as suggested by Nenovski (2015).

  12. A Sodium Leak Current Regulates Pacemaker Activity of Adult Central Pattern Generator Neurons in Lymnaea Stagnalis

    PubMed Central

    Lu, Tom Z.; Feng, Zhong-Ping

    2011-01-01

    The resting membrane potential of the pacemaker neurons is one of the essential mechanisms underlying rhythm generation. In this study, we described the biophysical properties of an uncharacterized channel (U-type channel) and investigated the role of the channel in the rhythmic activity of a respiratory pacemaker neuron and the respiratory behaviour in adult freshwater snail Lymnaea stagnalis. Our results show that the channel conducts an inward leak current carried by Na+ (ILeak-Na). The ILeak-Na contributed to the resting membrane potential and was required for maintaining rhythmic action potential bursting activity of the identified pacemaker RPeD1 neurons. Partial knockdown of the U-type channel suppressed the aerial respiratory behaviour of the adult snail in vivo. These findings identified the Na+ leak conductance via the U-type channel, likely a NALCN-like channel, as one of the fundamental mechanisms regulating rhythm activity of pacemaker neurons and respiratory behaviour in adult animals. PMID:21526173

  13. Performance demonstration tests for eddy current inspection of steam generator tubing

    SciTech Connect

    Kurtz, R.J.; Heasler, P.G.; Anderson, C.M.

    1996-05-01

    This report describes the methodology and results for development of performance demonstration tests for eddy current (ET) inspection of steam generator tubes. Statistical test design principles were used to develop the performance demonstration tests. Thresholds on ET system inspection performance were selected to ensure that field inspection systems would have a high probability of detecting and and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented in detail. Statistical test design calculations for probability of detection and flaw sizing tests are described. A recommended performance demonstration test based on the design calculations is presented. A computer program for grading the probability of detection portion of the performance demonstration test is given.

  14. Thermal generation of spin current in epitaxial CoFe2O4 thin films

    DOE PAGESBeta

    Guo, Er -Jia; Herklotz, Andreas; Kehlberger, Andreas; Cramer, Joel; Jakob, Gerhard; Klaeui, Mathias

    2016-01-12

    The longitudinal spin Seebeck effect (LSSE) has been investigated in high-quality epitaxial CoFe2O4 (CFO) thin films. The thermally excited spin currents in the CFO films are electrically detected in adjacent Pt layers due to the inverse spin Hall effect (ISHE). The LSSE signal exhibits a linear increase with increasing temperature gradient, yielding a LSSE coefficient of –100 nV/K at room temperature. The temperature dependence of the LSSE is investigated from room temperature down to 30 K, showing a significant reduction at low temperatures, revealing that the total amount of thermally generated magnons decreases. Moreover, we demonstrate that the spin Seebeckmore » effect is an effective tool to study the magnetic anisotropy induced by epitaxial strain, especially in ultrathin films with low magnetic moments.« less

  15. Next-Generation Transcatheter Heart Valves: Current Trials in Europe and the USA

    PubMed Central

    Werner, Nikos; Nickenig, Georg

    2012-01-01

    Transcatheter aortic valve implantation (TAVI) has proven to be a viable alternative for patients with symptomatic severe aortic stenosis who are at high risk for surgical aortic valve replacement. At the same time, there is increasing evidence that moderate-to-severe periprosthetic aortic regurgitation after TAVI is associated with dramatically increased mortality and morbidity. The issue of proper positioning of the valve, including the ability to reposition and recapture the device, must be dealt with before the use of TAVI can be extended to younger, healthier patients. The next generation of transcatheter heart valves will most likely address repositionability to facilitate accurate placement with additional features that minimize paravalvular leakage. Upcoming devices promise to improve outcomes and usability of current TAVI systems. PMID:22891121

  16. Particle Diffusion in Chaotic Magnetic Fields Generated by Asymmetric Current Configurations

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Dasgupta, B.

    2008-12-01

    The observed cross-field diffusion of charged particles in cosmic rays is assumed to be due to the chaotic nature of the interplanetary/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and Jokipii [2]. Parker considered the passage of cosmic ray particles and energetic solar particles in a large scale magnetic field containing small scale irregularities. In the context of cosmic ray propagation, Jokipii considered a small fluctuating component, added on to a uniform magnetic field, to study the spatial transport of particles. In these studies the irregular component of the magnetic field is prescribed in an ad hoc fashion. In contrast, we consider asymmetric, nonlinear, steady-state magnetic fields, in three spatial dimensions, generated by currents flowing in circular loops and straight lines [3]. These magnetic fields are completely deterministic and, for certain range of parameters, chaotic. We will present analytical and numerical studies on the spatial characteristics of these fields. The motion of charged particles in the nonlinear and chaotic magnetic fields is determined using the Lorentz equation. A particle moving in a deterministic chaotic magnetic field superposed on a uniform background magnetic field is found to undergo spatial transport. This shows that chaotic magnetic fields generated by simple current configurations can produce cross-field diffusion. A detailed analysis of particle motion and diffusion along with application to space plasmas will be presented. [1] E.N. Parker, Planet. Space Sci. 13, 9 (1965). [2] J.R. Jokipii, Astrophys. J. 146, 480 (1966), and J.R. Jokipii, Astrophys. J. 149, 405 (1967). [3] A.K. Ram and B. Dasgupta, Eos Trans. AGU 87 (52), Fall Meet. Suppl. Abstract NG31B-1593 (2006); and Eos Trans. AGU 88 (52), Fall Meet. Suppl. Abstract NG21B-0522 (2007).

  17. Wolf (Canis lupus) generation time and proportion of current breeding females by age

    USGS Publications Warehouse

    Mech, L. David; Barber-Meyer, Shannon M.; Erb, John

    2016-01-01

    Information is sparse about aspects of female wolf (Canis lupus) breeding in the wild, including age of first reproduction, mean age of primiparity, generation time, and proportion of each age that breeds in any given year. We studied these subjects in 86 wolves (113 captures) in the Superior National Forest (SNF), Minnesota (MN), during 1972–2013 where wolves were legally protected for most of the period, and in 159 harvested wolves from throughout MN wolf range during 2012–2014. Breeding status of SNF wolves were assessed via nipple measurements, and wolves from throughout MN wolf range, by placental scars. In the SNF, proportions of currently breeding females (those breeding in the year sampled) ranged from 19% at age 2 to 80% at age 5, and from throughout wolf range, from 33% at age 2 to 100% at age 7. Excluding pups and yearlings, only 33% to 36% of SNF females and 58% of females from throughout MN wolf range bred in any given year. Generation time for SNF wolves was 4.3 years and for MN wolf range, 4.7 years. These findings will be useful in modeling wolf population dynamics and in wolf genetic and dog-domestication studies.

  18. Second-generation prophylactic HPV vaccines: current options and future strategies for vaccines development.

    PubMed

    Fruscalzo, Arrigo; Londero, Ambrogio P; Bertozzi, Serena; Lellè, Ralf J

    2016-02-01

    Two vaccines focused on the prevention of HPV-related diseases have been introduced in the last decade, the quadrivalent vaccine Gardasil and the bivalent vaccine Cervarix. They are targeted to prevent precancerous and cancerous lesions not only of the cervix, but also of the vulva, vagina, anal and head-neck region. Furthermore, the protection of the quadrivalent vaccine Gardasil includes also genital warts and recurrent respiratory Papillomatosis, two benign conditions with high socio-economic impact. Although their efficacy in reducing the burden of HPV-related pathologies has been already documented, second-generation HPV vaccines are being developed in order to overcome major limitations, above all the cost of production, distribution and acceptance, thus promoting an easier access to vaccination, especially in developing countries. Recently a new multivalent VLP vaccine active against nine HPV subtypes, called Gardasil 9 (Merck & Co., Inc., Whitehouse Station, NJ, USA), has been approved, showing promising preliminary results. In this article, we outline the strategies adopted for second-generation HPV vaccine engineering, the latest HPV vaccines available at this time, as well as those currently in development. PMID:26473283

  19. Wolf (Canis lupus) Generation Time and Proportion of Current Breeding Females by Age

    PubMed Central

    2016-01-01

    Information is sparse about aspects of female wolf (Canis lupus) breeding in the wild, including age of first reproduction, mean age of primiparity, generation time, and proportion of each age that breeds in any given year. We studied these subjects in 86 wolves (113 captures) in the Superior National Forest (SNF), Minnesota (MN), during 1972–2013 where wolves were legally protected for most of the period, and in 159 harvested wolves from throughout MN wolf range during 2012–2014. Breeding status of SNF wolves were assessed via nipple measurements, and wolves from throughout MN wolf range, by placental scars. In the SNF, proportions of currently breeding females (those breeding in the year sampled) ranged from 19% at age 2 to 80% at age 5, and from throughout wolf range, from 33% at age 2 to 100% at age 7. Excluding pups and yearlings, only 33% to 36% of SNF females and 58% of females from throughout MN wolf range bred in any given year. Generation time for SNF wolves was 4.3 years and for MN wolf range, 4.7 years. These findings will be useful in modeling wolf population dynamics and in wolf genetic and dog-domestication studies. PMID:27258193

  20. Wolf (Canis lupus) Generation Time and Proportion of Current Breeding Females by Age.

    PubMed

    Mech, L David; Barber-Meyer, Shannon M; Erb, John

    2016-01-01

    Information is sparse about aspects of female wolf (Canis lupus) breeding in the wild, including age of first reproduction, mean age of primiparity, generation time, and proportion of each age that breeds in any given year. We studied these subjects in 86 wolves (113 captures) in the Superior National Forest (SNF), Minnesota (MN), during 1972-2013 where wolves were legally protected for most of the period, and in 159 harvested wolves from throughout MN wolf range during 2012-2014. Breeding status of SNF wolves were assessed via nipple measurements, and wolves from throughout MN wolf range, by placental scars. In the SNF, proportions of currently breeding females (those breeding in the year sampled) ranged from 19% at age 2 to 80% at age 5, and from throughout wolf range, from 33% at age 2 to 100% at age 7. Excluding pups and yearlings, only 33% to 36% of SNF females and 58% of females from throughout MN wolf range bred in any given year. Generation time for SNF wolves was 4.3 years and for MN wolf range, 4.7 years. These findings will be useful in modeling wolf population dynamics and in wolf genetic and dog-domestication studies. PMID:27258193

  1. Spin-current-driven thermoelectric generation based on interfacial spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Yagmur, A.; Karube, S.; Uchida, K.; Kondou, K.; Iguchi, R.; Kikkawa, T.; Otani, Y.; Saitoh, E.

    2016-06-01

    The longitudinal spin Seebeck effect (SSE) in Bi2O3/Cu/yttrium-iron-garnet (YIG) devices has been investigated. When an out-of-plane temperature gradient is applied to the Bi2O3/Cu/YIG device, a spin current is generated across the Cu/YIG interface via the SSE and then converted into electric voltage due to the spin-orbit coupling at the Bi2O3/Cu interface. The sign of the SSE voltage in the Bi2O3/Cu/YIG devices is opposite to that induced by the conventional inverse spin Hall effect in Pt/YIG devices. The SSE voltage in the Bi2O3/Cu/YIG devices disappears in the absence of the Bi2O3 layer and its thermoelectric conversion efficiency is independent of the Cu thickness, indicating the important role of the Bi2O3/Cu interface. This result demonstrates that not only the bulk inverse spin Hall effect but also the spin-orbit coupling near the interface can be used for SSE-based thermoelectric generation.

  2. Analysis of pulsed eddy current data using regression models for steam generator tube support structure inspection

    NASA Astrophysics Data System (ADS)

    Buck, J. A.; Underhill, P. R.; Morelli, J.; Krause, T. W.

    2016-02-01

    Nuclear steam generators (SGs) are a critical component for ensuring safe and efficient operation of a reactor. Life management strategies are implemented in which SG tubes are regularly inspected by conventional eddy current testing (ECT) and ultrasonic testing (UT) technologies to size flaws, and safe operating life of SGs is predicted based on growth models. ECT, the more commonly used technique, due to the rapidity with which full SG tube wall inspection can be performed, is challenged when inspecting ferromagnetic support structure materials in the presence of magnetite sludge and multiple overlapping degradation modes. In this work, an emerging inspection method, pulsed eddy current (PEC), is being investigated to address some of these particular inspection conditions. Time-domain signals were collected by an 8 coil array PEC probe in which ferromagnetic drilled support hole diameter, depth of rectangular tube frets and 2D tube off-centering were varied. Data sets were analyzed with a modified principal components analysis (MPCA) to extract dominant signal features. Multiple linear regression models were applied to MPCA scores to size hole diameter as well as size rectangular outer diameter tube frets. Models were improved through exploratory factor analysis, which was applied to MPCA scores to refine selection for regression models inputs by removing nonessential information.

  3. Remote field eddy current technique applied to the inspection of nonmagnetic steam generator tubes

    NASA Astrophysics Data System (ADS)

    Shin, Young-Kil; Chung, Tae-Eon; Lord, William

    2001-04-01

    As steam generator (SG) tubes have aged, new and subtle degradations have appeared. Most of them start growing from outside the tubes. Since outer diameter defects might not be detected by conventional eddy current testing due to skin effect phenomena, this paper studies the feasibility of using the remote field eddy current (RFEC) technique, which has shown equal sensitivity to inner diameter (ID) and outer diameter (OD) defects in ferromagnetic pipe inspection. Finite element modeling studies show that the operating frequency needs to be increased up to a few hundred kHz in order for RFEC effects to occur in the nonmagnetic SG tube. The proper distance between exciter and sensor coils is also found to be 1.5 OD, which is half of the distance used in ferromagnetic pipe inspection. The resulting defect signals show equal sensitivity to ID and OD defects. These results demonstrate superior capability of the proposed RFEC probe compared to the differential ECT probe in detecting OD defects.

  4. Thyristor-based current-fed drive with direct power control for permanent magnet-assisted synchronous reluctance generator

    NASA Astrophysics Data System (ADS)

    Baek, J.; Kwak, S.-S.; Toliyat, H. A.

    2015-03-01

    This paper proposes a robust and simple direct power control (DPC) of a thyristor-based current-fed drive for generator applications. A current-fed drive and permanent magnet-assisted synchronous reluctance generator (PMa-SynRG) are investigated to deliver 3 kW power using a combustion engine. The current-fed drive utilises a thyristor-based three-phase rectifier to convert generator power to DC-link power and a single-phase current-fed inverter to supply a single-phase inductive load. In addition, a new control algorithm is developed based on DPC for the current-fed drive. The DC-link voltage-based DPC is proposed in order to directly control the output power. The goal of the DPC is to maintain the DC-link voltage at the required output power operating point. The DPC has advantages such as a simple algorithm for constant speed operation. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG.

  5. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    NASA Astrophysics Data System (ADS)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  6. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    NASA Astrophysics Data System (ADS)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  7. Numerical analysis of internal solitary wave generation around a Island in Kuroshio Current using MITgcm.

    NASA Astrophysics Data System (ADS)

    Kodaira, Tsubasa; Waseda, Takuji

    2013-04-01

    We have conducted ADCP and CTD measurements from 31/8/2010 to 2/9/2010 at the Miyake Island, located approximately 180 km south of Tokyo. The Kuroshio Current approached the island in this period, and the PALSAR image showed parabolic bright line upstream of the island. This bright line may be a surface signature of large amplitude internal solitary wave. Although our measurements did not explicitly show evidence of the internal solitary wave, critical condition might have been satisfied because of the Kuroshio Current and strong seasonal thermocline. To discover the generation mechanism of the large amplitude internal solitary wave at the Miyake Island, we have conducted non-hydrostatic numerical simulation with the MITgcm. A simple box domain, with open boundaries at all sides, is used. The island is simplified to circular cylinder or Gaussian Bell whose radius is 3km at ocean surface level. The size of the domain is 40kmx40kmx500m for circular cylinder cases and 80kmx80kmx500m for Gaussian bell cases. By looking at our CTD data, we have chosen for initial and boundary conditions a tanh function for vertical temperature profile. Salinity was kept constant for simplicity. Vertical density profile is also described by tanh function because we adopt linear type of equation of state. Vertical velocity profile is constant or linearly changed with depth; the vertical mean speed corresponds to the linear phase speed of the first baroclinic mode obtained by solving the eigen-value problem. With these configurations, we have conducted two series of simulations: shear flow through cylinder and uniform flow going through Gaussian Bell topography. Internal solitary waves were generated in front of the cylinder for the first series of simulations with shear flow. The generated internal waves almost purely consisted of 1st baroclinic component. Their intensities were linearly related with upstream vertical shear strength. As the internal solitary wave became larger, its width

  8. Immunogenicity of Therapeutic Protein Aggregates.

    PubMed

    Moussa, Ehab M; Panchal, Jainik P; Moorthy, Balakrishnan S; Blum, Janice S; Joubert, Marisa K; Narhi, Linda O; Topp, Elizabeth M

    2016-02-01

    Therapeutic proteins have a propensity for aggregation during manufacturing, shipping, and storage. The presence of aggregates in protein drug products can induce adverse immune responses in patients that may affect safety and efficacy, and so it is of concern to both manufacturers and regulatory agencies. In this vein, there is a lack of understanding of the physicochemical determinants of immunological responses and a lack of standardized analytical methods to survey the molecular properties of aggregates associated with immune activation. In this review, we provide an overview of the basic immune mechanisms in the context of interactions with protein aggregates. We then critically examine the literature with emphasis on the underlying immune mechanisms as they relate to aggregate properties. Finally, we highlight the gaps in our current understanding of this issue and offer recommendations for future research. PMID:26869409

  9. Redox chemistry of copper-amyloid-beta: the generation of hydroxyl radical in the presence of ascorbate is linked to redox-potentials and aggregation state.

    PubMed

    Guilloreau, Luc; Combalbert, Sarah; Sournia-Saquet, Alix; Mazarguil, Honoré; Faller, Peter

    2007-07-23

    Aggregation of the beta-amyloid peptide (Abeta) to amyloid plaques is a key event in Alzheimer's disease. According to the amyloid-cascade hypothesis, Abeta aggregates are toxic to neurons through the production of reactive oxygen species (ROS). Copper ions play an important role, because they are able to bind to Abeta and influence its aggregation properties. Moreover, Cu-Abeta is supposed to be directly involved in ROS production. To get a better understanding of these reactions, we measured the production of HO(.) and the redox potential of Cu-Abeta. The results were compared to other biological copper-peptide complexes in order to get an insight into the biological relevance. Cu-Abeta produced more HO(.) than the complex of copper with Asp-Ala-His-Lys (Cu-DAHK), but less than with Gly-His-Lys (Cu-GHK). Cyclic voltammetry revealed that the order for reduction potential is Cu-GHK>Cu-Abeta>Cu-DAHK, but for the oxidation potential the order is reversed. Thus, easier copper redox cycling correlated to higher HO(.) production. The copper complex of the form Abeta1-42 showed a HO(.) production five-times higher than that of the form Abeta1-40. Time-dependence and aggregation studies suggest that an aggregation intermediate is responsible for this increased HO(.) production. PMID:17577900

  10. The Next Generation Advanced Video Guidance Sensor: Flight Heritage and Current Development

    NASA Technical Reports Server (NTRS)

    Howard, Richard T.; Bryan, Thomas C.

    2009-01-01

    The Next Generation Advanced Video Guidance Sensor (NGAVGS) is the latest in a line of sensors that have flown four times in the last 10 years. The NGAVGS has been under development for the last two years as a long-range proximity operations and docking sensor for use in an Automated Rendezvous and Docking (AR&D) system. The first autonomous rendezvous and docking in the history of the U.S. Space Program was successfully accomplished by Orbital Express, using the Advanced Video Guidance Sensor (AVGS) as the primary docking sensor. That flight proved that the United States now has a mature and flight proven sensor technology for supporting Crew Exploration Vehicles (CEV) and Commercial Orbital Transport Systems (COTS) Automated Rendezvous and Docking (AR&D). NASA video sensors have worked well in the past: the AVGS used on the Demonstration of Autonomous Rendezvous Technology (DART) mission operated successfully in "spot mode" out to 2 km, and the first generation rendezvous and docking sensor, the Video Guidance Sensor (VGS), was developed and successfully flown on Space Shuttle flights in 1997 and 1998. This paper presents the flight heritage and results of the sensor technology, some hardware trades for the current sensor, and discusses the needs of future vehicles that may rendezvous and dock with the International Space Station (ISS) and other Constellation vehicles. It also discusses approaches for upgrading AVGS to address parts obsolescence, and concepts for minimizing the sensor footprint, weight, and power requirements. In addition, the testing of the various NGAVGS development units will be discussed along with the use of the NGAVGS as a proximity operations and docking sensor.

  11. Experimental and numerical study of a dual configuration for a flapping tidal current generator.

    PubMed

    Kim, Jihoon; Quang Le, Tuyen; Hwan Ko, Jin; Ebenezer Sitorus, Patar; Hartarto Tambunan, Indra; Kang, Taesam

    2015-08-01

    In this study, we conduct experimental and consecutive numerical analyses of a flapping tidal current generator with a mirror-type dual configuration with front-swing and rear-swing flappers. An experimental analysis of a small-scale prototype is conducted in a towing tank, and a numerical analysis is conducted by means of two-dimensional computational fluid dynamics simulations with an in-house code. An experimental study with a controller to determine the target arm angle shows that the resultant arm angle is dependent on the input arm angle, the frequency, and the applied load, while a high pitch is obtained simply with a high input arm angle. Through a parametric analysis conducted while varying these factors, a high applied load and a high input arm angle were found to be advantageous. Moreover, the optimal reduced frequency was found to be 0.125 in terms of the power extraction. In consecutive numerical investigations with the kinematics selected from the experiments, it was found that a rear-swing flapper contributes to the total amount of power more than a front-swing flapper with a distance of two times the chord length and with a 90° phase difference between the two. The high contribution stems from the high power generated by the rear-swing flapper, which mimics the tail fin movement of a dolphin along a flow, compared to a plunge system or a front-swing system, which mimics the tail fin movement of a dolphin against a flow. It is also due to the fact that the shed vorticities of the front-swing flapper slightly affect negatively or even positively the power performance of the rear-swing system at a given distance and phase angle. PMID:26225469

  12. Generations of Monic Polynomials such that the Coefficients of Each Polynomial of the Next Generation Coincide with the Zeros of a Polynomial of the Current Generation, and New Solvable Many-Body Problems

    NASA Astrophysics Data System (ADS)

    Bihun, Oksana; Calogero, Francesco

    2016-07-01

    The notion of generations of monic polynomials such that the coefficients of each polynomial of the next generation coincide with the zeros of a polynomial of the current generation is introduced, and its relevance to the identification of endless sequences of new solvable many-body problems "of goldfish type" is demonstrated.

  13. Generation of nonlinear currents and low-frequency radiation upon interaction of a laser pulse with a metal

    SciTech Connect

    Bezhanov, S G; Uryupin, S A

    2013-11-30

    Nonlinear currents slowly varying in time are found in the skin layer of a metal irradiated by short laser pulses. The low-frequency field generated by the nonlinear currents in metal and vacuum is studied. The spectral composition, energy and shape of the low-frequency radiation pulse are described. (nonlinear optical phenomena)

  14. Analysis and comparison for rotor eddy current losses of permanent magnet synchronous generator according to dc and ac load conditions

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Kim, Hyun-Kyu; Choi, Jang-Young; Ko, Kyoung-Jin

    2009-04-01

    This paper presents an analytical procedure for the calculation of the eddy current losses of permanent magnet synchronous generator (PMSG). The dc and ac loading effects on the eddy current is examined through the suggested analytical procedure that considers the radial and tangential flux density waveform through a phase current harmonic analysis. The corresponding test results are also presented to quantify and compare those loading effects on the eddy current. The results verified the suggested analytical procedures and show that the rotor eddy current losses for PMSG with the dc loads turned out to be more significant than those with the ac loads.

  15. Development of a twin-flapping-foils unit to generate hydroelectric power from a water current

    NASA Astrophysics Data System (ADS)

    Abiru, H.; Yoshitake, A.; Nishi, M.

    2014-03-01

    Most of the conventional hydraulic turbines have been used for those sites having the static head larger than around 1 m. To extensively utilize not only large hydro-power but small one, which is one of renewable energy resources, development of an energy conversion system being operable under an extremely low head stream is crucial. A twin-flapping-foils unit which works based on the lift acting on the flapping foils in a stream is proposed. The foils oscillate in the transverse direction of the flow due to the lift. The pitching motion of the foils is caused by their own transverse movement through the mechanism consisting of crankshafts and con-rods. In the unit, each foil is supported vertically with a shaft in a manner of a cantilever so that no other parts need to be submerged in a water current. An experimental model with symmetric foils of 100 mm chord and 300 mm span was designed to generate average power output of 10 W at a flow velocity of 1 m/s. Through the tests carried out in the circulating water channel, the performance of the unit was verified to satisfy the design specifications. Further, the demonstration tests by using an irrigation stream performed for over a half year clarified the performance equivalent to that in the in-door water channel and the durability to a certain extent, and showed the applicability to the practical use of lighting a LED street lamp during night even at this scale model.

  16. The effect of practice on random number generation task: a transcranial direct current stimulation study.

    PubMed

    Capone, Fioravante; Capone, Gianluca; Ranieri, Federico; Di Pino, Giovanni; Oricchio, Gianluca; Di Lazzaro, Vincenzo

    2014-10-01

    Random number generation (RNG) is a procedurally-simple task related to specific executive functions, such as updating and monitoring of information and inhibition of automatic responses. The effect of practice on executive functions has been widely investigated, however little is known on the impact of practice on RNG. Transcranial direct current stimulation (tDCS) allows to modulate, non-invasively, brain activity and to enhance the effects of training on executive functions. Hence, this study aims to investigate the effect of practice on RNG and to explore the possibility to influence it by tDCS applied over dorsolateral prefrontal cortex. Twenty-six healthy volunteers have been evaluated within single session and between different sessions of RNG using several measures of randomness, which are informative of separable cognitive components servicing random behavior. We found that repetition measures significantly change within single session, seriation measures significantly change both within and between sessions, while cycling measures are not affected by practice. tDCS does not produce any additional effect, however a sub-analysis limited to the first session revealed an increasing trend in seriation measure after anodal compared to cathodal stimulation. Our findings support the hypothesis that practice selectively and consistently influences specific cognitive components related to random behavior, while tDCS transiently affects RNG performance. PMID:24811195

  17. Hurricane-generated currents on the outer continental shelf. 2. Model sensitivity studies

    NASA Astrophysics Data System (ADS)

    Cooper, Cortis; Thompson, J. Dana

    1989-09-01

    A numerical model described and verified in part 1 of this two-part series (Cooper and Thompson, this issue) is applied to study the sensitivity of hurricane-generated currents on the outer shelf and slope. Numerical experiments are performed in a simple basin with a straight shelf. The sensitivity of the response to changes in storm parameters, direction of storm approach, and topography is quantified. Response is measured in terms of the mixed-layer velocity and depth at sites along the storm track. Results reveal the most important factors are (in decreasing order) wind speed, storm translation speed, direction of storm approach, asymmetry in the wind field, entrainment parameterization, and advection at slower storm translation speeds. Response is largely insensitive (less than 10%) to radius of maximum wind, shelf and slope configuration, bottom friction, atmospheric pressure gradients, and further reductions in the model grid size. For a storm approaching cross shelf, the response is primarily baroclinic (greater than 90%) and only weakly dependent (less than 10%) on the water depth at the site.

  18. Understanding the impact of prior depression on stress generation: examining the roles of current depressive symptoms and interpersonal behaviours.

    PubMed

    Shih, Josephine H; Eberhart, Nicole K

    2008-08-01

    Stress generation is a process in which individuals contribute to stressful life events. While research has supported an association between current depression and stress generation, it has been noted that individuals with prior depression tend to contribute to stressors even when they are no longer experiencing a depressive episode. The aim of the study is to elucidate the pathways through which prior major depression predicts interpersonal stress generation in women. Specifically, we examined current subsyndromal depressive symptoms and problematic interpersonal behaviours as potential mediators. Fifty-one college women were followed prospectively for 6 weeks. Participants were interviewed to assess current and past depression as well as stressful life events they experienced over the 6-week period. The findings suggest that prior major depression continues to have an impact even after the episode has ended, as the disorder continues to contribute to stress generation through residual depressive symptoms. PMID:17908367

  19. New Development of Power Distribution System Resulting from Dispersed Generations and Current Interruption

    NASA Astrophysics Data System (ADS)

    Yokomizu, Yasunobu

    Dispersed generation systems, such as micro gas-turbines and fuel cells, have been installed on some of commercial facilities. Smaller dispersed generators like solar photovoltaics have been also located on the several of individual homes. The trends in the introduction of the these generation systems seem to continue in the future and to cause the power system to have the enormous number of the dispersed generation systems. The present report discusses the near-future power distribution systems.

  20. Detection of Upper Airway Status and Respiratory Events by a Current Generation Positive Airway Pressure Device

    PubMed Central

    Li, Qing Yun; Berry, Richard B.; Goetting, Mark G.; Staley, Bethany; Soto-Calderon, Haideliza; Tsai, Sheila C.; Jasko, Jeffrey G.; Pack, Allan I.; Kuna, Samuel T.

    2015-01-01

    Study Objectives: To compare a positive airway pressure (PAP) device's detection of respiratory events and airway status during device-detected apneas with events scored on simultaneous polysomnography (PSG). Design: Prospective PSGs of patients with sleep apnea using a new-generation PAP device. Settings: Four clinical and academic sleep centers. Patients: Forty-five patients with obstructive sleep apnea (OSA) and complex sleep apnea (Comp SA) performed a PSG on PAP levels adjusted to induce respiratory events. Interventions: None. Measurements and Results: PAP device data identifying the type of respiratory event and whether the airway during a device-detected apnea was open or obstructed were compared to time-synced, manually scored respiratory events on simultaneous PSG recording. Intraclass correlation coefficients between device-detected and PSG scored events were 0.854 for apnea-hypopnea index (AHI), 0.783 for apnea index, 0.252 for hypopnea index, and 0.098 for respiratory event-related arousals index. At a device AHI (AHIFlow) of 10 events/h, area under the receiver operating characteristic curve was 0.98, with sensitivity 0.92 and specificity 0.84. AHIFlow tended to overestimate AHI on PSG at values less than 10 events/h. The device detected that the airway was obstructed in 87.4% of manually scored obstructive apneas. Of the device-detected apneas with clear airway, a minority (15.8%) were manually scored as obstructive apneas. Conclusions: A device-detected apnea-hypopnea index (AHIFlow) < 10 events/h on a positive airway pressure device is strong evidence of good treatment efficacy. Device-detected airway status agrees closely with the presumed airway status during polysomnography scored events, but should not be equated with a specific type of respiratory event. Citation: Li QY, Berry RB, Goetting MG, Staley B, Soto-Calderon H, Tsai SC, Jasko JG, Pack AI, Kuna ST. Detection of upper airway status and respiratory events by a current generation positive

  1. Strategies for the Use of Tidal Stream Currents for Power Generation

    NASA Astrophysics Data System (ADS)

    Orhan, Kadir; Mayerle, Roberto

    2015-04-01

    Indonesia is one of the priority countries in Southeast Asia for the development of ocean renewable energy facilities and The National Energy Council intends to increase the role of ocean energy significantly in the energy mix for 2010-2050. To this end, the joint German-Indonesian project "Ocean Renewable Energy ORE-12" aims at the identification of marine environments in the Indonesian Archipelago, which are suitable for the efficient generation of electric power by converter facilities. This study, within the ORE-12 project, is focused on the tidal stream currents on the straits between the Indian Ocean and Flores Sea to estimate the energy potentials and to develop strategies for producing renewable energy. FLOW module of Delft3D has been used to run hydrodynamic models for site assessment and design development. In site assessment phase, 2D models have been operated for a-month long periods and with a resolution of 500 m. Later on, in design development phase, detailed 3D models have been developed and operated for three-month long periods and with a resolution of 50 m. Bathymetric data for models have been obtained from the GEBCO_08 Grid and wind data from the Global Forecast System of NOAA's National Climatic Data Center. To set the boundary conditions of models, tidal forcing with 11 harmonic constituents was supplied from TPXO Indian Ocean Atlas (1/12° regional model) and data from HYCOM+NCODA Global 1/12° Analysis have been used to determine salinity and temperature on open boundaries. After the field survey is complete, water level time-series supplied from a tidal gauge located in the domain of interest (8° 20΄ 9.7" S, 122° 54΄ 51.9" E) have been used to verify the models and then energy potentials of the straits have been estimated. As a next step, correspondence between model outputs and measurements taken by the radar system of TerraSAR-X satellite (DLR) will be analysed. Also for the assessment of environmental impacts caused by tidal stream

  2. Plasmas generated in bubbles immersed in liquids: direct current streamers versus microwave plasma

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Sharma, Ashish; Raja, Laxminarayan L.

    2016-07-01

    Two approaches to generate non-equilibrium atmospheric-pressure plasma in bubbles immersed in liquids are compared using high-fidelity 2D fluid simulations. In the first approach, corona/streamer like plasma is generated using high-voltage negative and positive pulses applied between two electrodes (pin-to-plane geometry) immersed in liquid. In the second, the plasma is generated using a remote microwave source (frequency 2.45 GHz). We find that the microwave approach requires less energy, while generating a denser, more chemically reactive and more uniform plasma within the bubble volume, as compared to the plasma generated using high-voltage pulsing.

  3. High conversion Th-U{sup 233} fuel assembly for current generation of PWRs

    SciTech Connect

    Baldova, D.; Fridman, E.

    2012-07-01

    This paper presents a preliminary design of a high conversion Th-U{sup 233} fuel assembly applicable for current generation of Pressurized Water Reactor (PWRs). The considered fuel assembly has a typical 17 x 17 PWR lattice. However in order to increase the conversion of Th{sup 232} to U{sup 233}, the assembly was subdivided into the two regions called seed and blanket. The central seed region has a higher than blanket U{sup 233} content and acts as a neutron source for the peripheral blanket region. The latest acts as a U{sup 233} breeder. While the seed fuel pins have a standard dimensions the blanket fuel radius was increased in order to reduce the moderation and to facilitate the resonance neutron absorption in blanket Th{sup 232}. The U{sup 233} content in the seed and blanket regions was optimized to achieve maximal initial to discharged fissile inventory ratio (FIR) taking into account the target fuel cycle length of 12 months with 3-batch reloading scheme. In this study the neutronic calculations were performed on the fuel assembly level using Helios deterministic lattice transport code. The fuel cycle length and the core k{sub eff} were estimated by applying the Non Linear Reactivity Model. The applicability of the HELIOS code for the analysis of the Th-based high conversion designs was confirmed with the help of continuous-energy Monte-Carlo code SERPENT. The results of optimization studies show that for the heterogeneous seed and blanket (SB) fuel assembly the FIR of about 0.95 can be achieved. (authors)

  4. A pulsed-power generator merging inductive voltage and current adders and its switch trigger application example

    NASA Astrophysics Data System (ADS)

    Li, Lee; Yafeng, Ge; Heqin, Zhong; Bin, Yu; Longjun, Xie

    2013-07-01

    A pulsed-power generator using inductive adder technology is proposed for the case of a discharge gap. The merit of this generator is to merge the pulsed-voltage and pulsed-current adders via the dual secondary windings with special circuit. For the nonlinear impedance in any discharge gap, the standalone voltage-pulse and current-pulse can be outputted successively by this generator. The proposed generator is especially useful for the common resolution of implementing pulse discharge at less cost. As an application example, a compact trigger prototype was developed to compatibly use in the gas-insulated and vacuum switches. Experiments achieved good results that the triggered switches showed stable performance and long life. If the basic circuit of this proposed generator is regarded as a pulsed-generating unit, a certain number of such units connected in parallel can be expected to form a general device with generating greater breakdown-voltage and sustained-current pulses for discharge gaps.

  5. An Analysis of Superconducting Fault Current Limiter for Stabilization of Synchronous Generators in Multi-Machine System

    NASA Astrophysics Data System (ADS)

    Yagami, Masaki; Shibata, Shinsuke; Murata, Toshiaki; Tamura, Junji

    This paper presents the results of analyses of the effectiveness of a superconducting fault current limiter (SFCL) to stabilize the synchronous generators, suppress turbine shaft torque oscillations, and limit the fault current in a two-machine-infinite bus system. In this study, the system model with two SFCLs having shunt resistance installed at each generator terminal was used taking 3LG (three lines to ground) fault at 12 fault points into account. These analyses were performed using EMTP/ATP. It is concluded that the use of SFCL with shunt resistance value of 1.1 pu is most effective for all fault points for the stabilization of synchronous generators, the suppression of turbine shaft torque oscillations, and the limitation of fault current.

  6. Pioneering experiments on atomic-beam-assisted generation of drag currents in the Globus-M spherical tokamak

    NASA Astrophysics Data System (ADS)

    Shchegolev, P. B.; Bakharev, N. N.; Gusev, V. K.; Kurskiev, G. S.; Minaev, V. B.; Patrov, M. I.; Petrov, Yu. V.; Sakharov, N. V.

    2015-09-01

    Research data for drag currents in the Globus-M spherical tokamak are presented. The currents are generated by injecting atomic beams of hydrogen and deuterium. Experiments were carried out in the hydrogen and deuterium plasma of the tokamak. It has a divertor configuration with a lower X-point, a displacement along the larger radius from-1.0 to-2.5 cm, and a toroidal field of 0.4 T at a plasma current of 0.17-0.23 MA. The beam is injected into the tokamak in the equatorial plane tangentially to the magnetic axis of the plasma filament with an impact diameter of 32 cm. To provide a 28-keV 0.5-MW atomic beam with geometrical sizes of 4 × 20 cm (at a power level of 1/ e), an IPM-2 ion source is used. The generation of noninductive currents is detected from a rise in the loop current and a simultaneous dip of the loop voltage. The injection of the hydrogen and deuterium atomic beams into the deuterium plasma results in a noticeable and reproducible dip of the loop voltage (up to 0.5 V). Using the ASTRA transport code, a model is constructed that allows rapid calculation of noninductive currents. Calculations performed for a specific discharge confirm that the model adequately describes the effect of drag current generation.

  7. The properties of ULF/VLF signals generated by the SURA facility without ionospheric currents modulation

    NASA Astrophysics Data System (ADS)

    Kotik, D. S.; Raybov, A. V.; Ermakova, E. N.

    2012-12-01

    During the last three years the comprehensive study of ionospheric generation of the artificial signals in ULF/VLF band was carried out at SURA facility. This research was stimulated by successive HAARP experiments on detection the low frequency signals genreated due the action of the ponderomotive forces. Two experimental campaigns under different ionospheric, geomagnetic and facility operation mode conditions was undertaken every year from 2010 to 2012. Here we are summarizing the main features of the artificial ULF/VLF signals observed in vicinity the SURA site. The signals in the 2-20 Hz band were observed in the small area around the facility with the radius approximately 15 km. It was not signal detection at the 30 km distance. The maximum of the amplitude was detected in the nearest receiving point about 3 km away from the transmitting array. The amplitude increased about 3 times when the beam was inclined on16 degrees to the south so the footprint of the geomagnetic field line comes close to the point of observation. The ULF signals increased slightly when the SURA operating frequency overlaps the critical foF2 frequency. As a rule the daytime signals are smaller then nighttime one. No any correlation was observed with geomagnetic disturbances. The time delay of the ionospheric ULF signals measured by phase method was estimated as 300-400 ms. Polarization of the ULF signals has a pronounced elliptical character. Sometimes it was linear. The part of measurements in June 2012 was coincide with magnetic storm (June 16-18, Kp=6). It was observed broadening of the signal line at frequencies of 11 and 17 Hz up to 0.2 Hz at the recovery stage of the storm at June 18 (see the figure). This fact can be interpreted as the result of the signal interaction with the radiation belt protons appeared over there during the storm time. In 2012 campaigns it was firstly observed at SURA signals on frequencies of several kilohertz at nightime which could not be explained by

  8. Generation of Localized Noninductive Current by Electron Cyclotron Waves on the DIII-D Tokamak

    SciTech Connect

    Luce, T. C.; Lin-Liu, Y. R.; Harvey, R. W.; Giruzzi, G.; Politzer, P. A.; Rice, B. W.; Lohr, J. M.; Petty, C. C.; Prater, R.

    1999-11-29

    Localized currents due to electron cyclotron current drive have been measured for the first time in experiments on the DIII-D tokamak. The location of driven current in the plasma has been varied from near the center of the tokamak out to half of the minor radius. The measured current drive efficiency agrees with quasilinear Fokker-Planck calculations near the center and exceeds the predicted value with increasing minor radius. Reduction of the trapped electron fraction due to finite collisionality is a leading candidate to explain the discrepancy. (c) 1999 The American Physical Society.

  9. Diffusion Limited Aggregation: Algorithm optimization revisited

    NASA Astrophysics Data System (ADS)

    Braga, F. L.; Ribeiro, M. S.

    2011-08-01

    The Diffusion Limited Aggregation (DLA) model developed by Witten and Sander in 1978 is useful in modeling a large class of growth phenomena with local dependence. Besides its simplicity this aggregation model has a complex behavior that can be observed at the patterns generated. We propose on this work a brief review of some important proprieties of this model and present an algorithm to simulate a DLA aggregates that simpler and efficient compared to others found in the literature.

  10. Impact of uniform electrode current distribution on ETF. [Engineering Test Facility MHD generator

    NASA Technical Reports Server (NTRS)

    Bents, D. J.

    1982-01-01

    A basic reason for the complexity and sheer volume of electrode consolidation hardware in the MHD ETF Powertrain system is the channel electrode current distribution, which is non-uniform. If the channel design is altered to provide uniform electrode current distribution, the amount of hardware required decreases considerably, but at the possible expense of degraded channel performance. This paper explains the design impacts on the ETF electrode consolidation network associated with uniform channel electrode current distribution, and presents the alternate consolidation designs which occur. They are compared to the baseline (non-uniform current) design with respect to performance, and hardware requirements. A rational basis is presented for comparing the requirements for the different designs and the savings that result from uniform current distribution. Performance and cost impacts upon the combined cycle plant are discussed.

  11. Unconventional spin Hall effect and axial current generation in a Dirac semimetal

    NASA Astrophysics Data System (ADS)

    Okuma, Nobuyuki; Ogata, Masao

    2016-04-01

    We investigate electrical transport in a three-dimensional massless Dirac fermion model that describes a Dirac semimetal state realized in topological materials. We derive a set of interdependent diffusion equations with eight local degrees of freedom, including the electric charge density and the spin density, that respond to an external electric field. By solving the diffusion equations for a system with a boundary, we demonstrate that a spin Hall effect with spin accumulation occurs even though the conventional spin current operator is zero. The Noether current associated with chiral symmetry, known as the axial current, is also discussed. We demonstrate that the axial current flows near the boundary and that it is perpendicular to the electric current.

  12. Direct Electric Current Treatment under Physiologic Saline Conditions Kills Staphylococcus epidermidis Biofilms via Electrolytic Generation of Hypochlorous Acid

    PubMed Central

    Sandvik, Elizabeth L.; McLeod, Bruce R.; Parker, Albert E.; Stewart, Philip S.

    2013-01-01

    The purpose of this study was to investigate the mechanism by which a direct electrical current reduced the viability of Staphylococcus epidermidis biofilms in conjunction with ciprofloxacin at physiologic saline conditions meant to approximate those in an infected artificial joint. Biofilms grown in CDC biofilm reactors were exposed to current for 24 hours in 1/10th strength tryptic soy broth containing 9 g/L total NaCl. Dose-dependent log reductions up to 6.7 log10 CFU/cm2 were observed with the application of direct current at all four levels (0.7 to 1.8 mA/cm2) both in the presence and absence of ciprofloxacin. There were no significant differences in log reductions for wells with ciprofloxacin compared to those without at the same current levels. When current exposures were repeated without biofilm or organics in the medium, significant generation of free chlorine was measured. Free chlorine doses equivalent to the 24 hour endpoint concentration for each current level were shown to mimic killing achieved by current application. Current exposure (1.8 mA/cm2) in medium lacking chloride and amended with sulfate, nitrate, or phosphate as alternative electrolytes produced diminished kills of 3, 2, and 0 log reduction, respectively. Direct current also killed Pseudomonas aeruginosa biofilms when NaCl was present. Together these results indicate that electrolysis reactions generating hypochlorous acid from chloride are likely a main contributor to the efficacy of direct current application. A physiologically relevant NaCl concentration is thus a critical parameter in experimental design if direct current is to be investigated for in vivo medical applications. PMID:23390518

  13. Direct electric current treatment under physiologic saline conditions kills Staphylococcus epidermidis biofilms via electrolytic generation of hypochlorous acid.

    PubMed

    Sandvik, Elizabeth L; McLeod, Bruce R; Parker, Albert E; Stewart, Philip S

    2013-01-01

    The purpose of this study was to investigate the mechanism by which a direct electrical current reduced the viability of Staphylococcus epidermidis biofilms in conjunction with ciprofloxacin at physiologic saline conditions meant to approximate those in an infected artificial joint. Biofilms grown in CDC biofilm reactors were exposed to current for 24 hours in 1/10(th) strength tryptic soy broth containing 9 g/L total NaCl. Dose-dependent log reductions up to 6.7 log(10) CFU/cm(2) were observed with the application of direct current at all four levels (0.7 to 1.8 mA/cm(2)) both in the presence and absence of ciprofloxacin. There were no significant differences in log reductions for wells with ciprofloxacin compared to those without at the same current levels. When current exposures were repeated without biofilm or organics in the medium, significant generation of free chlorine was measured. Free chlorine doses equivalent to the 24 hour endpoint concentration for each current level were shown to mimic killing achieved by current application. Current exposure (1.8 mA/cm(2)) in medium lacking chloride and amended with sulfate, nitrate, or phosphate as alternative electrolytes produced diminished kills of 3, 2, and 0 log reduction, respectively. Direct current also killed Pseudomonas aeruginosa biofilms when NaCl was present. Together these results indicate that electrolysis reactions generating hypochlorous acid from chloride are likely a main contributor to the efficacy of direct current application. A physiologically relevant NaCl concentration is thus a critical parameter in experimental design if direct current is to be investigated for in vivo medical applications. PMID:23390518

  14. Phospholipase A2 action on planar lipid bilayers generates a small, transitory current that is voltage independent.

    PubMed Central

    Alix, S N; Woodbury, D J

    1997-01-01

    Addition of either bee venom or Trimeresurus flavoviridis phospholipase A2 (PLA2) to the solution bathing the front side of a voltage-clamped, planar lipid bilayer consistently produced a transitory current lasting approximately 100 s. This current is consistent with anions moving through the membrane to the rear side. The peak current is independent of holding potential. PLA2 activity on phospholipid membranes not only produced a current but also led to membrane rupture within 300 s. The current depends on Ca2+ and lipid type. Addition of PLA2 in the absence of Ca2+ or to membranes made of nonsubstrate lipids (e.g., glycerol monooleate or lysophosphatidylcholine) produced no current and did not break the bilayer. Peak current height, signal decay time, and time to membrane rupture all depended on PLA2 dose, whereas total charge produced was constant. This current does not flow through ion channels because there are no channels present and the current is not voltage dependent. The evidence is consistent with the hypothesis that the current is generated by the movement of ionized fatty acid produced by PLA2 action. These results demonstrate a simple method to measure enzyme activity in the presence of different substrates and varied environmental conditions. Images FIGURE 1 FIGURE 6 PMID:8994609

  15. Current and projected liquid low-level waste generation at ORNL

    SciTech Connect

    DePaoli, S.M.; West, G.D.

    1996-04-01

    Liquid low-level waste (LLLW) is generated by various programs and projects throughout Oak Ridge National Laboratory (ORNL). This waste is collected in bottles, by trucks, or in underground collection tanks; it is then neutralized with sodium hydroxide and reduced in volume at the ORNL LLLW evaporator. This report presents historical and projected data concerning the volume and the characterization of LLLW, both prior to and after evaporation. Storage space for projected waste generation is also discussed.

  16. Excitation of a Hall-current Generator by Field-Aligned-Current Closure, via an Ionospheric, Divergent Hall Current, During the Transient Phase of MagnetosphereIonosphere Coupling

    NASA Astrophysics Data System (ADS)

    Yoshikawa, A.

    2001-12-01

    To clarify the process by which an ionospheric current system is formed by field-aligned-current (FAC) closure in the ionosphere, an inclusive formulation of magnetosphereionosphere (MI) coupling is undertaken. The Hall-current generator that is excited during the transient phase of MI coupling, plays a crucial role in the formation of the ionospheric rotational current system. It extracts energy from the FAC system through the divergent Hall current, and pumps it into the rotational Hall current. The energy of the rotational current accumulates as an evanescent poloidal magnetic field, associated with the ionospheric surface-wave. This accumulated energy is also fed back to the FAC system through the change in energy flow of the Hall-current generator. It is found that there is a typical time-scale for the rotational current system to accumulate or extract the poloidal magnetic energy of ionospheric surface wave. This depends on the inductance of the rotational current system, and the effective conductivity of the ionospheric rotational conduction-current. This characteristic time scale becomes the cause of an ionospheric inductive effect, such as a time delay or phase-lag between the source electromagnetic field of the FAC and the corresponding poloidal magnetic field on the ground. This latter causes an inductive shielding effect on the amplitude of the geomagnetic disturbance. Numerical simulation has been able to explain the details of physical process that occurs when the incident FAC is developing and decaying, and how the energy and current are redistributed into the other elements during the transient MI-coupling process.

  17. Excitation of a Hall-current generator by field-aligned current closure, via an ionospheric, divergent Hall-current, during the transient phase of magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Akimasa

    2002-12-01

    To clarify the process by which an ionospheric current system is formed by field-aligned current (FAC) closure in the ionosphere, an inclusive formulation of magnetosphere-ionosphere (MI) coupling is undertaken. The "Hall-current generator", which is excited during the transient phase of MI coupling, plays a crucial role in the formation of the ionospheric rotational-current system. It extracts energy from the FAC system through the divergent Hall-current and pumps it into the rotational Hall-current. The energy of the rotational current accumulates as an evanescent poloidal magnetic field, associated with the ionospheric surface wave. This accumulated energy is also fed back to the FAC system through the change in energy flow of the Hall-current generator. It is found that there is a typical timescale for the rotational-current system to accumulate or extract the poloidal magnetic energy of ionospheric surface waves. This depends on the inductance of the rotational-current system and the effective conductivity of the ionospheric rotational current. This characteristic timescale becomes the cause of an ionospheric inductive effect, such as a time delay or phase lag between the source electromagnetic field of the FAC and the corresponding poloidal magnetic field on the ground. The latter causes an inductive shielding effect on the amplitude of the geomagnetic disturbance. Numerical simulation has been able to explain the details of the physical process that occurs when the incident FAC is developing and decaying, and how the energy and current are redistributed into the other elements during the transient MI-coupling process.

  18. Disposition of Radioisotope Thermoelectric Generators Currently Located at the Oak Ridge National Laboratory - 12232

    SciTech Connect

    Glenn, J.; Patterson, J.; DeRoos, K.; Patterson, J.E.; Mitchell, K.G.

    2012-07-01

    Under the American Recovery and Reinvestment Act (ARRA), the U.S. Department of Energy (DOE) awarded SEC Federal Services Corporation (SEC) a 34-building demolition and disposal (D and D) project at the Oak Ridge National Laboratory (ORNL) that included the disposition of six Strontium (Sr-90) powered Radioisotope Thermoelectric Generators (RTGs) stored outside of ORNL Building 3517. Disposition of the RTGs is very complex both in terms of complying with disposal facility waste acceptance criteria (WAC) and U.S. Department of Transportation (DOT) requirements for packaging and transportation in commerce. Two of the RTGs contain elemental mercury which requires them to be Land Disposal Restrictions (LDR) compliant prior to disposal. In addition, all of the RTGs exceed the Class C waste concentration limits under Nuclear Regulatory Commission (NRC) Waste Classification Guidelines. In order to meet the LDR requirements and Nevada National Security Site (NNSS) WAC, a site specific treatability variance for mercury was submitted to the U.S. Environmental Protection Agency (EPA) to allow macro-encapsulation to be an acceptable treatment standard for elemental mercury. By identifying and confirming the design configuration of the mercury containing RTGs, the SEC team proved that the current configuration met the macro-encapsulation standard of 40 Code of Federal Regulations (CFR) 268.45. The SEC Team also worked with NNSS to demonstrate that all radioisotope considerations are compliant with the NNSS low-level waste (LLW) disposal facility performance assessment and WAC. Lastly, the SEC team determined that the GE2000 Type B cask met the necessary size, weight, and thermal loading requirements for five of the six RTGs. The sixth RTG (BUP-500) required a one-time DOT shipment exemption request due to the RTG's large size. The DOT exemption justification for the BUP-500 relies on the inherent robust construction and material make-up of the BUP- 500 RTG. DOE-ORO, SEC, and

  19. Periodic magnetic structures generated by spin–polarized currents in nanostripes

    SciTech Connect

    Volkov, Oleksii M. Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri; Mertens, Franz G.

    2013-11-25

    The influence of a transverse spin–polarized current on long ferromagnetic nanostripes is studied numerically. The magnetization behavior is analyzed for all range of the applied currents, up to the saturation. It is shown that the saturation current is a nonmonotonic function of the stripe width. A number of stable periodic magnetization structures are observed below the saturation. Type of the periodical structure depends on the stripe width. Besides the one–dimensional domain structure, typical for narrow wires, and the two–dimensional vortex–antivortex lattice, typical for wide films, a number of intermediate structures are observed, e.g., cross–tie and diamond state.

  20. Familial myopathy with tubular aggregates associated with abnormal pupils.

    PubMed

    Shahrizaila, Nortina; Lowe, James; Wills, Adrian

    2004-09-28

    The authors describe familial tubular aggregate myopathy associated with abnormal pupils. Four family members from two generations had myopathy and pupillary abnormalities. The myopathologic findings consisted of tubular aggregates in many fibers but predominantly type I fibers. PMID:15452313

  1. CHARACTERIZATION OF CURRENTLY GENERATED TRANUSRANIC WASTE AT THE LOS ALAMOS NATIONAL LABORATORY'S PLUTONIUM PRODUCTION FACILITY

    SciTech Connect

    Dodge, Robert L.; Montoya, Andy M.

    2003-02-27

    By the time the Waste Isolation Pilot Plant (WIPP) completes its Disposal Phase in FY 2034, the Department of Energy (DOE) will have disposed of approximately 109,378 cubic meters (m3) of Transuranic (TRU) waste in WIPP (1). If DOE adheres to its 2005 Pollution Prevention Goal of generating less than 141m3/yr of TRU waste, approximately 5000 m3 (4%) of that TRU waste will be newly generated (2). Because of the overwhelming majority (96%) of TRU waste destined for disposal at WIPP is legacy waste, the characterization and certification requirements were developed to resolve those issues related to legacy waste. Like many other DOE facilities Los Alamos National Laboratory (LANL) has a large volume (9,010m3) of legacy Transuranic Waste in storage (3). Unlike most DOE facilities LANL will generate approximately 140m3 of newly generated TRU waste each year3. LANL's certification program was established to meet the WIPP requirements for legacy waste and does not take advantage of the fundamental differences in waste knowledge between newly generated and legacy TRU waste.

  2. Superlinear generation of exciton and related paramagnetism induced by forward current in a diamond p-i-n junction

    SciTech Connect

    Natori, Kenji

    2015-02-07

    The concentration of excitons generated in a high-quality diamond p-i-n junction is investigated considering the forward current characteristics of the junction. As the forward current in the junction increases, the exciton concentration increases superlinearly, contrary to the linear increases of the electron and hole concentration. This tendency suggests a superlinear increase in emission intensity due to exciton recombination. The increase rate is more radical than quadratic, in accordance with the observed increase of the integrated intensity of free exciton emission. To estimate the concentration of triplet excitons generated in the p-i-n junction, observation of the paramagnetism due to the exciton spin moment is proposed. The magnetic susceptibility superlinearly increases with the increase in the forward current, unlike any other magnetic property of the device.

  3. Participation of a persistent sodium current and calcium-activated nonspecific cationic current to burst generation in trigeminal principal sensory neurons.

    PubMed

    Tsuruyama, Kentaro; Hsiao, Chie-Fang; Chandler, Scott H

    2013-10-01

    The properties of neurons participating in masticatory rhythmogenesis are not clearly understood. Neurons within the dorsal trigeminal principal sensory nucleus (dPrV) are potential candidates as components of the masticatory central pattern generator (CPG). The present study examines in detail the ionic mechanisms controlling burst generation in dPrV neurons in rat (postnatal day 8-12) brain stem slices using whole cell and perforated patch-clamp methods. Nominal extracellular Ca(2+) concentration transformed tonic discharge in response to a maintained step pulse of current into rhythmical bursting in 38% of nonbursting neurons. This change in discharge mode was suppressed by riluzole, a persistent Na(+) current (INaP) antagonist. Veratridine, which suppresses the Na(+) channel inactivation mechanism, induced rhythmical bursting in nonbursting neurons in normal artificial cerebrospinal fluid, suggesting that INaP contributes to burst generation. Nominal extracellular Ca(2+) exposed a prominent afterdepolarizing potential (ADP) following a single spike induced by a 3-ms current pulse, which was suppressed, but not completely blocked, by riluzole. Application of BAPTA, a Ca(2+) chelator, intracellularly, or flufenamic acid, a Ca(2+)-activated nonspecific cationic channel (ICAN) antagonist, extracellularly to the bath, suppressed rhythmical bursting and the postspike ADP. Application of drugs to alter Ca(2+) release from endoplasmic reticulum also suppressed bursting. Finally, voltage-clamp methods demonstrated that nominal Ca(2+) facilitated INaP and induced ICAN. These data demonstrate for the first time that the previously observed induction in dPrV neurons of rhythmical bursting in nominal Ca(2+) is mediated by enhancement of INaP and onset of ICAN, which are dependent on intracellular Ca(2+). PMID:23883859

  4. Inverse problem analysis of pluripotent stem cell aggregation dynamics in stirred-suspension cultures.

    PubMed

    Rostami, Mahboubeh Rahmati; Wu, Jincheng; Tzanakakis, Emmanuel S

    2015-08-20

    The cultivation of stem cells as aggregates in scalable bioreactor cultures is an appealing modality for the large-scale manufacturing of stem cell products. Aggregation phenomena are central to such bioprocesses affecting the viability, proliferation and differentiation trajectory of stem cells but a quantitative framework is currently lacking. A population balance equation (PBE) model was used to describe the temporal evolution of the embryonic stem cell (ESC) cluster size distribution by considering collision-induced aggregation and cell proliferation in a stirred-suspension vessel. For ESC cultures at different agitation rates, the aggregation kernel representing the aggregation dynamics was successfully recovered as a solution of the inverse problem. The rate of change of the average aggregate size was greater at the intermediate rate tested suggesting a trade-off between increased collisions and agitation-induced shear. Results from forward simulation with obtained aggregation kernels were in agreement with transient aggregate size data from experiments. We conclude that the framework presented here can complement mechanistic studies offering insights into relevant stem cell clustering processes. More importantly from a process development standpoint, this strategy can be employed in the design and control of bioreactors for the generation of stem cell derivatives for drug screening, tissue engineering and regenerative medicine. PMID:26036699

  5. Small file aggregation in a parallel computing system

    DOEpatents

    Faibish, Sorin; Bent, John M.; Tzelnic, Percy; Grider, Gary; Zhang, Jingwang

    2014-09-02

    Techniques are provided for small file aggregation in a parallel computing system. An exemplary method for storing a plurality of files generated by a plurality of processes in a parallel computing system comprises aggregating the plurality of files into a single aggregated file; and generating metadata for the single aggregated file. The metadata comprises an offset and a length of each of the plurality of files in the single aggregated file. The metadata can be used to unpack one or more of the files from the single aggregated file.

  6. Autoimmune Responses to Soluble Aggregates of Amyloidogenic Proteins Involved in Neurodegenerative Diseases: Overlapping Aggregation Prone and Autoimmunogenic regions

    PubMed Central

    Kumar, Sandeep; Thangakani, A. Mary; Nagarajan, R.; Singh, Satish K.; Velmurugan, D.; Gromiha, M. Michael

    2016-01-01

    Why do patients suffering from neurodegenerative diseases generate autoantibodies that selectively bind soluble aggregates of amyloidogenic proteins? Presently, molecular basis of interactions between the soluble aggregates and human immune system is unknown. By analyzing sequences of experimentally validated T-cell autoimmune epitopes, aggregating peptides, amyloidogenic proteins and randomly generated peptides, here we report overlapping regions that likely drive aggregation as well as generate autoantibodies against the aggregates. Sequence features, that make short peptides susceptible to aggregation, increase their incidence in human T-cell autoimmune epitopes by 4–6 times. Many epitopes are predicted to be significantly aggregation prone (aggregation propensities ≥10%) and the ones containing experimentally validated aggregating regions are enriched in hydrophobicity by 10–20%. Aggregate morphologies also influence Human Leukocyte Antigen (HLA) - types recognized by the aggregating regions containing epitopes. Most (88%) epitopes that contain amyloid fibril forming regions bind HLA-DR, while majority (63%) of those containing amorphous β-aggregating regions bind HLA-DQ. More than two-thirds (70%) of human amyloidogenic proteins contain overlapping regions that are simultaneously aggregation prone and auto-immunogenic. Such regions help clear soluble aggregates by generating selective autoantibodies against them. This can be harnessed for early diagnosis of proteinopathies and for drug/vaccine design against them. PMID:26924748

  7. Spin force and the generation of sustained spin current in time-dependent Rashba and Dresselhaus systems

    SciTech Connect

    Ho, Cong Son Tan, Seng Ghee; Jalil, Mansoor B. A.

    2014-05-14

    The generation of spin current and spin polarization in a two-dimensional electron gas structure is studied in the presence of Dresselhaus and Rashba spin-orbit couplings (SOC), the strength of the latter being modulated in time by an ac gate voltage. By means of the non-Abelian gauge field approach, we established the relation between the Lorentz spin force and the spin current in the SOC system, and showed that the longitudinal component of the spin force induces a transverse spin current. For a constant (time-invariant) Rashba system, we recover the universal spin Hall conductivity of e/(8π) , derived previously via the Berry phase and semi-classical methods. In the case of a time-dependent SOC system, the spin current is sustained even under strong impurity scattering. We evaluated the ac spin current generated by a time-modulated Rashba SOC in the absence of any dc electric field. The magnitude of the spin current reaches a maximum when the modulation frequency matches the Larmor frequency of the electrons.

  8. 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.

  9. Microstructure dependence of the c-axis critical current density in second-generation YBCO tapes.

    SciTech Connect

    Jia, Y.; Welp, U.; Crabtree, G. W.; Kwok, W. K.; Malozemoff, A. P.; Rupich, M. W.; Fleshler, S.; Clem, J. R.

    2011-10-01

    C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.

  10. Microstructure dependence of the c-axis critical current density in second generation YBCO tapes

    SciTech Connect

    Jia, Y. Welp, U. Crabtree, G.W.; Kwok, W.K.; Malozemoff, A.P.; Rupich, M.W.; Fleshler, S.; Clem, J.R.

    2011-10-31

    C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.

  11. Historical and Current U.S. Strategies for Boosting Distributed Generation

    SciTech Connect

    Lowder, Travis; Schwabe, Paul; Zhou, Ella; Arent, Douglas J.

    2015-10-29

    This report seeks to introduce a variety of top-down and bottom-up practices that, in concert with the macro-environment of cost-reduction globally and early adoption in Europe, helped boost the distributed generation photovoltaic market in the United States. These experiences may serve as a reference in China's quest to promote distributed renewable energy.

  12. Evaluation of eddy-current procedures for measuring wear scars in preheat steam generators

    SciTech Connect

    Brown, S.D.

    1985-04-01

    Tests show that flat wear scar procedures will provide more accurate measurements of the depth of wear scars in steam generator tubes if they are supplemented by two new techniques. Used together, these methods can detect as little as 5% increase in scar depth.

  13. 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.

  14. 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.

  15. The generation of magnetic fields and electric currents in cometary plasma tails

    NASA Technical Reports Server (NTRS)

    Ip, W.-H.; Mendis, D. A.

    1976-01-01

    Due to the folding of the interplanetary magnetic field into the tail as a comet sweeps through the interplanetary medium, the magnetic field in the tail can be built up to the order of 100 gammas at a heliocentric distance of about 1 AU. This folding of magnetic flux tubes also results in a cross-tail electric current passing through a neutral sheet. When streams of enhanced plasma density merge with the main tail, cross-tail currents as large as 1 billion A may result. A condition could arise which causes a significant fraction of this current to be discharged through the inner coma, resulting in rapid ionization. The typical time scale for such outbursts of ionization is estimated to be of the order of 10,000 sec, which is in reasonable agreement with observation.

  16. Comparison of Galvanic Currents Generated Between Different Combinations of Orthodontic Brackets and Archwires Using Potentiostat: An In Vitro Study

    PubMed Central

    Nayak, Rabindra S; Shafiuddin, Bareera; Pasha, Azam; Vinay, K; Narayan, Anjali; Shetty, Smitha V

    2015-01-01

    Background: Technological advances in wire selection and bracket design have led to improved treatment efficiency and allowed longer time intervals between appliance adjustments. The wires remain in the mouth for a longer duration and are subjected to electrochemical reactions, mechanical forces of mastication and generalized wear. These cause different types of corrosion. This study was done to compare the galvanic currents generated between different combinations of brackets and archwires commonly used in orthodontic practices. Materials and Methods: The materials used for the study included different commercially available orthodontic archwires and brackets. The galvanic current generated by individual materials and different combinations of these materials was tested and compared. The orthodontic archwires used were 0.019″ × 0.025″ heat-activated nickel-titanium (3M Unitek), 0.019″ × 0.025″ beta-titanium (3M Unitek) and 0.019″ × 0.025″ stainless steel (3M Unitek). The orthodontic brackets used were 0.022″ MBT laser-cut (Victory Series, 3M Unitek) and metal-injection molded (Leone Company) maxillary central incisor brackets respectively. The ligature wire used for ligation was 0.009″ stainless steel ligature (HP Company). The galvanic current for individual archwires, brackets, and the different bracket-archwire-ligature combinations was measured by using a Potentiostat machine. The data were generated using the Linear Sweep Voltammetry and OriginPro 8.5 Graphing and Data Analysis Softwares. The study was conducted in two phases. Phase I comprised of five groups for open circuit potential (OCP) and galvanic current (I), whereas Phase II comprised of six groups for galvanic current alone. Results: Mean, standard deviation and range were computed for the OCP and galvanic current (I) values obtained. Results were subjected to statistical analysis through ANOVA. In Phase I, higher mean OCP was recorded in stainless steel archwire, followed by beta

  17. Generator localization by current source density (CSD): implications of volume conduction and field closure at intracranial and scalp resolutions.

    PubMed

    Tenke, Craig E; Kayser, Jürgen

    2012-12-01

    The topographic ambiguity and reference-dependency that has plagued EEG/ERP research throughout its history are largely attributable to volume conduction, which may be concisely described by a vector form of Ohm's Law. This biophysical relationship is common to popular algorithms that infer neuronal generators via inverse solutions. It may be further simplified as Poisson's source equation, which identifies underlying current generators from estimates of the second spatial derivative of the field potential (Laplacian transformation). Intracranial current source density (CSD) studies have dissected the "cortical dipole" into intracortical sources and sinks, corresponding to physiologically-meaningful patterns of neuronal activity at a sublaminar resolution, much of which is locally cancelled (i.e., closed field). By virtue of the macroscopic scale of the scalp-recorded EEG, a surface Laplacian reflects the radial projections of these underlying currents, representing a unique, unambiguous measure of neuronal activity at scalp. Although the surface Laplacian requires minimal assumptions compared to complex, model-sensitive inverses, the resulting waveform topographies faithfully summarize and simplify essential constraints that must be placed on putative generators of a scalp potential topography, even if they arise from deep or partially-closed fields. CSD methods thereby provide a global empirical and biophysical context for generator localization, spanning scales from intracortical to scalp recordings. PMID:22796039

  18. NON-NEUTRALIZED ELECTRIC CURRENT PATTERNS IN SOLAR ACTIVE REGIONS: ORIGIN OF THE SHEAR-GENERATING LORENTZ FORCE

    SciTech Connect

    Georgoulis, Manolis K.; Titov, Viacheslav S.; Mikic, Zoran

    2012-12-10

    Using solar vector magnetograms of the highest available spatial resolution and signal-to-noise ratio, we perform a detailed study of electric current patterns in two solar active regions (ARs): a flaring/eruptive and a flare-quiet one. We aim to determine whether ARs inject non-neutralized (net) electric currents in the solar atmosphere, responding to a debate initiated nearly two decades ago that remains inconclusive. We find that well-formed, intense magnetic polarity inversion lines (PILs) within ARs are the only photospheric magnetic structures that support significant net current. More intense PILs seem to imply stronger non-neutralized current patterns per polarity. This finding revises previous works that claim frequent injections of intense non-neutralized currents by most ARs appearing in the solar disk but also works that altogether rule out injection of non-neutralized currents. In agreement with previous studies, we also find that magnetically isolated ARs remain globally current-balanced. In addition, we confirm and quantify the preference of a given magnetic polarity to follow a given sense of electric currents, indicating a dominant sense of twist in ARs. This coherence effect is more pronounced in more compact ARs with stronger PILs and must be of sub-photospheric origin. Our results yield a natural explanation of the Lorentz force, invariably generating velocity and magnetic shear along strong PILs, thus setting a physical context for the observed pre-eruption evolution in solar ARs.

  19. 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

  20. Ash Aggregates in Proximal Settings

    NASA Astrophysics Data System (ADS)

    Porritt, L. A.; Russell, K.

    2012-12-01

    Ash aggregates are thought to have formed within and been deposited by the eruption column and plume and dilute density currents and their associated ash clouds. Moist, turbulent ash clouds are considered critical to ash aggregate formation by facilitating both collision and adhesion of particles. Consequently, they are most commonly found in distal deposits. Proximal deposits containing ash aggregates are less commonly observed but do occur. Here we describe two occurrences of vent proximal ash aggregate-rich deposits; the first within a kimberlite pipe where coated ash pellets and accretionary lapilli are found within the intra-vent sequence; and the second in a glaciovolcanic setting where cored pellets (armoured lapilli) occur within <1 km of the vent. The deposits within the A418 pipe, Diavik Diamond Mine, Canada, are the residual deposits within the conduit and vent of the volcano and are characterised by an abundance of ash aggregates. Coated ash pellets are dominant but are followed in abundance by ash pellets, accretionary lapilli and rare cored pellets. The coated ash pellets typically range from 1 - 5 mm in diameter and have core to rim ratios of approximately 10:1. The formation and preservation of these aggregates elucidates the style and nature of the explosive phase of kimberlite eruption at A418 (and other pipes?). First, these pyroclasts dictate the intensity of the kimberlite eruption; it must be energetic enough to cause intense fragmentation of the kimberlite to produce a substantial volume of very fine ash (<62 μm). Secondly, the ash aggregates indicate the involvement of moisture coupled with the presence of dilute expanded eruption clouds. The structure and distribution of these deposits throughout the kimberlite conduit demand that aggregation and deposition operate entirely within the confines of the vent; this indicates that aggregation is a rapid process. Ash aggregates within glaciovolcanic sequences are also rarely documented. The

  1. NASA's Current and Next Generation Coastal Remote Sensing Missions and Coral Reef Projects.

    NASA Technical Reports Server (NTRS)

    Guild, Liane S.

    2015-01-01

    The LLILAS Faculty Research Initiative presents a two-day symposium, Caribbean Coral Reefs at Risk. This international symposium examines the current state and future of coral reef conservation efforts throughout the Caribbean from the perspective of government agencies, nongovernment organizations, and academia.

  2. The Self-Consistent Generation of Current Sheets in Astrophysical Plasma Turbulence

    NASA Astrophysics Data System (ADS)

    Howes, Gregory

    2014-10-01

    In space and astrophysical plasma turbulence, it has long been recognized that dissipation occurs predominantly in intermittent current sheets, with vigorous activity in the past few years focused on obtaining observational evidence for such localized dissipation in the near-Earth solar wind. The nature of these magnetic discontinuities and their associated current sheets measured in the solar wind remains unclear--are these discontinuities due to filamentary magnetic structure in the solar wind, or do they arise dynamically from turbulent interactions? Recent analytical solution, numerical validation, and experimental verification of the nonlinear energy transfer in Alfven wave collisions, the nonlinear interactions between counterpropagating Alfven waves, has established this interaction as the fundamental building block of astrophysical plasma turbulence. Here I will present first-principles analytical calculations and supporting numerical simulations that Alfven wave collisions in the strong turbulence limit naturally produce current sheets, providing the first theoretical unification of models of plasma turbulence mediated by Alfven waves with ideas on localized dissipation in current sheets. Supported by NSF CAREER Award AGS-1054061, NSF Grant PHY-10033446, and NASA Grant NNX10AC91G.

  3. Analysis of Advanced Fuel Assemblies and Core Designs for the Current and Next Generations of LWRs

    SciTech Connect

    Ragusa, Jean; Vierow, Karen

    2011-09-01

    The objective of the project is to design and analyze advanced fuel assemblies for use in current and future light water reactors and to assess their ability to reduce the inventory of transuranic elements, while preserving operational safety. The reprocessing of spent nuclear fuel can delay or avoid the need for a second geological repository in the US. Current light water reactor fuel assembly designs under investigation could reduce the plutonium inventory of reprocessed fuel. Nevertheless, these designs are not effective in stabilizing or reducing the inventory of minor actinides. In the course of this project, we developed and analyzed advanced fuel assembly designs with improved thermal transmutation capability regarding transuranic elements and especially minor actinides. These designs will be intended for use in thermal spectrum (e.g., current and future fleet of light water reactors in the US). We investigated various fuel types, namely high burn-up advanced mixed oxides and inert matrix fuels, in various geometrical designs that are compliant with the core internals of current and future light water reactors. Neutronic/thermal hydraulic effects were included. Transmutation efficiency and safety parameters were used to rank and down-select the various designs.

  4. Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

    NASA Astrophysics Data System (ADS)

    Piot, P.; Behrens, C.; Gerth, C.; Dohlus, M.; Lemery, F.; Mihalcea, D.; Stoltz, P.; Vogt, M.

    2012-01-01

    We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ˜700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.

  5. Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

    DOE PAGESBeta

    Piot, P.; Behrens, C.; Gerth, C.; Dohlus, M.; Lemery, F.; Mihalcea, D.; Stoltz, P.; Vogt, M.

    2011-09-07

    We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radiofrequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced {approx} 700-MeV bunches have peak currents of the order of a kilo-Ampere. Data taken for various accelerator settings demonstrate the versatility of the method and in particular its ability to produce current profiles that have a quasi-linear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak acceleratingmore » electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.« less

  6. Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

    SciTech Connect

    Piot, P.; Behrens, C.; Gerth, C.; Dohlus, M.; Lemery, F.; Mihalcea, D.; Stoltz, P.; Vogt, M.

    2011-09-07

    We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radiofrequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced {approx} 700-MeV bunches have peak currents of the order of a kilo-Ampere. Data taken for various accelerator settings demonstrate the versatility of the method and in particular its ability to produce current profiles that have a quasi-linear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.

  7. Electromagnetic Fields Generated by Ocean Currents and the Potential for Using Geomagnetic Data in Ocean and Climate Studies.

    NASA Astrophysics Data System (ADS)

    Tyler, Robert H.

    1995-01-01

    The ocean currents flowing through the earth's main magnetic field are known to induce secondary magnetic fields. Hence, variations in the ocean circulation induce variations in the net magnetic field. This research is aimed at exploring the potential for using geomagnetic data to study variability in ocean circulation and climate. First, general relativity theory is used to formally establish the proper set of electromagnetic equations to be used for observers in a rotating (accelerating) frame of reference observing a medium (the ocean, in this case) with relative velocity. Extra terms due to rotation are derived and described and a generalized Schiff's charge density is shown to be potentially significant for the application to ocean circulation. We extend the theory of electromagnetic fields generated by ocean currents. Many analytical solutions are found for idealized ocean features including sheared flow, jets, and a Stommel gyre. Results indicate that the ocean-induced magnetic fields will typically have magnitudes of 10's-100's of nT within the ocean. Outside of the ocean, the magnitudes are smaller (typically 1-10 nT) but decay on scales set by the horizontal scale of the ocean feature. We investigate the time-scales associated with the adjustment of electromagnetic fields generated by low -frequency ocean currents. We find that the time scales can be quite long, prohibiting a quasistatic assumption in the treatment of the electromagnetic fields generated by the important tidal, inertial, and diurnal-frequency ocean currents. Three-dimensional explicit time-dependent and steady-state finite-difference numerical models are constructed to study the electromagnetic fields generated by more realistic ocean current and conductivity features. The ocean currents generate electromagnetic forces on the fluid at the surface of the earth's core. If these forces lead to significant core motion, the effect of the oceans on the generation and variability of the earth

  8. 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.

  9. Protein engineering for metabolic engineering: Current and next-generation tools

    SciTech Connect

    Marcheschi, RJ; Gronenberg, LS; Liao, JC

    2013-04-16

    Protein engineering in the context of metabolic engineering is increasingly important to the field of industrial biotechnology. As the demand for biologically produced food, fuels, chemicals, food additives, and pharmaceuticals continues to grow, the ability to design and modify proteins to accomplish new functions will be required to meet the high productivity demands for the metabolism of engineered organisms. We review advances in selecting, modeling, and engineering proteins to improve or alter their activity. Some of the methods have only recently been developed for general use and are just beginning to find greater application in the metabolic engineering community. We also discuss methods of generating random and targeted diversity in proteins to generate mutant libraries for analysis. Recent uses of these techniques to alter cofactor use; produce non-natural amino acids, alcohols, and carboxylic acids; and alter organism phenotypes are presented and discussed as examples of the successful engineering of proteins for metabolic engineering purposes.

  10. Effect of second-generation antipsychotics on cognition: current issues and future challenges

    PubMed Central

    Hill, S Kristian; Bishop, Jeffrey R; Palumbo, Donna; Sweeney, John A.

    2010-01-01

    Generalized cognitive impairments are stable deficits linked to schizophrenia and key factors associated with functional disability in the disorder. Preclinical data suggest that second-generation antipsychotics could potentially reduce cognitive impairments; however, recent large clinical trials indicate only modest cognitive benefits relative to first-generation antipsychotics. This might reflect a limited drug effect in humans, a differential drug effect due to brain alterations associated with schizophrenia, or limited sensitivity of the neuropsychological tests for evaluating cognitive outcomes. New adjunctive procognitive drugs may be needed to achieve robust cognitive and functional improvement. Drug discovery may benefit from greater utilization of translational neurocognitive biomarkers to bridge preclinical and clinical proof-of-concept studies, to optimize assay sensitivity, enhance cost efficiency, and speed progress in drug development. PMID:20021320

  11. Protein engineering for metabolic engineering: current and next-generation tools

    PubMed Central

    Marcheschi, Ryan J.; Gronenberg, Luisa S.; Liao, James C.

    2014-01-01

    Protein engineering in the context of metabolic engineering is increasingly important to the field of industrial biotechnology. As the demand for biologically-produced food, fuels, chemicals, food additives, and pharmaceuticals continues to grow, the ability to design and modify proteins to accomplish new functions will be required to meet the high productivity demands for the metabolism of engineered organisms. This article reviews advances of selecting, modeling, and engineering proteins to improve or alter their activity. Some of the methods have only recently been developed for general use and are just beginning to find greater application in the metabolic engineering community. We also discuss methods of generating random and targeted diversity in proteins to generate mutant libraries for analysis. Recent uses of these techniques to alter cofactor use, produce non-natural amino acids, alcohols, and carboxylic acids, and alter organism phenotypes are presented and discussed as examples of the successful engineering of proteins for metabolic engineering purposes. PMID:23589443

  12. Current Grid Generation Strategies and Future Requirements in Hypersonic Vehicle Design, Analysis and Testing

    NASA Technical Reports Server (NTRS)

    Papadopoulos, Periklis; Venkatapathy, Ethiraj; Prabhu, Dinesh; Loomis, Mark P.; Olynick, Dave; Arnold, James O. (Technical Monitor)

    1998-01-01

    Recent advances in computational power enable computational fluid dynamic modeling of increasingly complex configurations. A review of grid generation methodologies implemented in support of the computational work performed for the X-38 and X-33 are presented. In strategizing topological constructs and blocking structures factors considered are the geometric configuration, optimal grid size, numerical algorithms, accuracy requirements, physics of the problem at hand, computational expense, and the available computer hardware. Also addressed are grid refinement strategies, the effects of wall spacing, and convergence. The significance of grid is demonstrated through a comparison of computational and experimental results of the aeroheating environment experienced by the X-38 vehicle. Special topics on grid generation strategies are also addressed to model control surface deflections, and material mapping.

  13. Historical and Current U.S. Strategies for Boosting Distributed Generation (Chinese Translation)

    SciTech Connect

    Lowder, Travis; Schwabe, Paul; Zhou, Ella; Arent, Douglas J.

    2015-08-01

    This is the Chinese translation of NREL/TP-6A20-64843. This report seeks to introduce a variety of top-down and bottom-up practices that, in concert with the macro-environment of cost-reduction globally and early adoption in Europe, helped boost the distributed generation photovoltaic market in the United States. These experiences may serve as a reference in China's quest to promote distributed renewable energy.

  14. Rhenium-188: Availability from the W-188/Re-188 Generator and Status of Current Applications

    SciTech Connect

    Pillai, M R A; Dash, A; Knapp Jr, Russ F

    2012-01-01

    Rhenium-188 is one of the most readily available generator derived and useful radionuclides for therapy emitting - particles (2.12 MeV, 71.1% and 1.965 MeV, 25.6%) and imageable gammas (155 KeV, 15.1%). The 188W/188Re generator is an ideal source for the long term (4-6 months) continuous availability of no carrier added (nca) 188Re suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The challenges associated with the double neutron capture route of production of the parent 188W radionuclide have been a major impediment in the progress of application of 188Re. Tungsten-188 of adequate specific activity can be prepared only in 2-3 of the high flux reactors operating in the World. Several useful technologies have been developed for the preparation of clinical grade 188W/188Re generator. Since the specific activity of 188W used in the generator is relatively low (<5 Ci/g), the eluted 188ReO4- can have low radioactive concentration often insufficient for radiopharmaceutical preparation. However, several efficient post elution concentration techniques have been developed that yield clinically useful 188ReO4-. Rhenium-188 has been used for the preparation of therapeutic radiopharmaceuticals for the management of diseases such as bone metastasis, rheumatoid arthritis and primary cancers. Several early phase clinical studies using radiopharmaceuticals based on 188Re-labeled phosphonates, antibodies, peptides, lipiodol and particulates have been reported. This article reviews the availability, and use of188Re including a discussion of why broader use of 188Re has not progressed as ecpected as a popular radionuclide for therapy.

  15. Rhenium-188: availability from the (188)W/(188)Re generator and status of current applications.

    PubMed

    Pillai, M R A; Dash, Ashutosh; Knapp, F F

    2012-07-01

    Rhenium-188 is one of the most readily available generator derived and useful radionuclides for therapy emitting β(-) particles (2.12 MeV, 71.1% and 1.965 MeV, 25.6%) and imageable gammas (155 keV, 15.1%). The (188)W/(188)Re generator is an ideal source for the long term (4-6 months) continuous availability of no carrier added (nca) (188)Re suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The challenges associated with the double neutron capture route of production of the parent (188)W radionuclide have been a major impediment in the progress of application of (188)Re. Tungsten-188 of adequate specific activity can be prepared only in 2-3 of the high flux reactors operating in the World. Several useful technologies have been developed for the preparation of clinical grade (188)W/(188)Re generators. Since the specific activity of (188)W used in the generator is relatively low 185 GBq( < 5 Ci)/g], the eluted (188)ReO(4)(-) can have low radioactive concentration often insufficient for radiopharmaceutical preparation. However, several efficient post elution concentration techniques have been developed that yield clinically useful (188)ReO(4)(-) solutions. Rhenium-188 has been used for the preparation of therapeutic radiopharmaceuticals for the management of diseases such as bone metastasis, rheumatoid arthritis and primary cancers. Several early phase clinical studies using radiopharmaceuticals based on (188)Re-labeled phosphonates, antibodies, peptides, lipiodol and particulates have been reported. This article reviews the availability and use of (188)Re including a discussion of why broader use of (188)Re has not progressed as expected as a popular radionuclide for therapy. PMID:22642385

  16. Eddy Current Signature Classification of Steam Generator Tube Defects Using A Learning Vector Quantization Neural Network

    SciTech Connect

    Gabe V. Garcia

    2005-01-03

    A major cause of failure in nuclear steam generators is degradation of their tubes. Although seven primary defect categories exist, one of the principal causes of tube failure is intergranular attack/stress corrosion cracking (IGA/SCC). This type of defect usually begins on the secondary side surface of the tubes and propagates both inwards and laterally. In many cases this defect is found at or near the tube support plates.

  17. A dimension map for molecular aggregates.

    PubMed

    Jian, Cuiying; Tang, Tian; Bhattacharjee, Subir

    2015-05-01

    A pair of gyradius ratios, defined from the principal radii of gyration, are used to generate a dimension map that describes the geometry of molecular aggregates in water and in organic solvents. Molecular dynamics simulations were performed on the aggregation of representative biomolecules and polyaromatic compounds to demonstrate application of the dimension map. It was shown that molecular aggregate data on the dimension map were bounded by two boundary curves, and that the map could be separated into three regions representing three groups of structures: one-dimensional rod-like structures; two-dimensional planar structures or short-cylinder-like structures; and three-dimensional sphere-like structures. Examining the location of the aggregates on the dimension map and how the location changes with solvent type and solute material parameter provides a simple yet effective way to infer the aggregation manner and to study solubility and mechanism of aggregation. PMID:25768393

  18. Effect of electron mediators on current generation and fermentation in a microbial fuel cell.

    PubMed

    Sund, Christian J; McMasters, Sun; Crittenden, Scott R; Harrell, Lee E; Sumner, James J

    2007-09-01

    Effects of select electron mediators [9,10-anthraquinone-2,6-disulfonic acid disodium salt (AQDS), safranine O, resazurin, methylene blue, and humic acids] on metabolic end-products and current production from cellulose digestion by Clostridium cellulolyticum in microbial fuel cells (MFCs) were studied using capillary electrophoresis and traditional electrochemical techniques. Addition of the mediator resazurin greatly enhanced current production but did not appear to alter the examined fermentation end-products compared to MFCs with no mediator. Assays for lactate, acetate, and ethanol indicate that the presence of safranine O, methylene blue, and humic acids alters metabolite production in the MFC: safranine O decreased the examined metabolites, methylene blue increased lactate formation, and humic acids increased the examined metabolites. Mediator standard redox potentials (E (0)) reported in the literature do not coincide with redox potentials in MFCs due presumably to the electrolytic complexity of media that supports bacterial survival and growth. Current production in MFCs: (1) can be effected by the mediator redox potential while in the media, which may be significantly shifted from E (0), and (2) depended on the ability of the mediator to access the bacterial electron source, which may be cytoplasmic. In addition, some electron mediators had significant effects on metabolic end-products and therefore the metabolism of the organism itself. PMID:17562040

  19. Duty Cycling Influences Current Generation in Multi-Anode Environmental Microbial Fuel Cells

    SciTech Connect

    Gardel, EJ; Nielsen, ME; Grisdela, PT; Girguis, PR

    2012-05-01

    Improving microbial fuel cell (MFC) performance continues to be the subject of research, yet the role of operating conditions, specifically duty cycling, on MFC performance has been modestly addressed. We present a series of studies in which we use a 15-anode environmental MFC to explore how duty cycling (variations in the time an anode is connected) influences cumulative charge, current, and microbial composition. The data reveal particular switching intervals that result in the greatest time-normalized current. When disconnection times are sufficiently short, there is a striking decrease in current due to an increase in the overall electrode reaction resistance. This was observed over a number of whole cell potentials. Based on these results, we posit that replenishment of depleted electron donors within the biofilm and surrounding diffusion layer is necessary for maximum charge transfer, and that proton flux may be not limiting in the highly buffered aqueous phases that are common among environmental MFCs. Surprisingly, microbial diversity analyses found no discernible difference in gross community composition among duty cycling treatments, suggesting that duty cycling itself has little or no effect. Such duty cycling experiments are valuable in determining which factors govern performance of bioelectrochemical systems and might also be used to optimize field-deployed systems.

  20. Crystallographic orientation and electrode nature are key factors for electric current generation by Geobacter sulfurreducens.

    PubMed

    Maestro, Beatriz; Ortiz, Juan M; Schrott, Germán; Busalmen, Juan P; Climent, Víctor; Feliu, Juan M

    2014-08-01

    We have investigated the influence of electrode material and crystallographic structure on electron transfer and biofilm formation of Geobacter sulfurreducens. Single-crystal gold-Au(110), Au(111), Au(210)-and platinum-Pt(100), Pt(110), Pt(111), Pt(210)-electrodes were tested and compared to graphite rods. G. sulfurreducens electrochemically interacts with all these materials with different attachment kinetics and final current production, although redox species involved in the electron transfer to the anode are virtually the same in all cases. Initial bacterial colonization was fastest on graphite up to the monolayer level, whereas gold electrodes led to higher final current densities. Crystal geometry was shown to have an important influence, with Au(210) sustaining a current density of up to 1442±101μAcm(-2) at the steady state, over Au(111) with 961±94μAcm(-2) and Au(110) with 944±89μAcm(-2). On the other hand, the platinum electrodes displayed the lowest performances, including Pt(210). Our results indicate that both crystal geometry and electrode material are key parameters for the efficient interaction of bacteria with the substrate and should be considered for the design of novel materials and microbial devices to optimize energy production. PMID:24642203

  1. Self-assembling photosynthetic reaction centers on electrodes for current generation.

    PubMed

    Nakamura, C; Hasegawa, M; Yasuda, Y; Miyake, J

    2000-01-01

    Photosynthetic reaction centers (RCs) made from photosynthetic organisms can be used in solar batteries because their molecules cause light-induced charge separation. We present a simple immobilization system of the intact RCs from Rhodobacter sphaeroides on an electrode that uses nickel ligand binding by the hexameric histidine tag on H subunit (HHisRC). The binding constant of HHisRC to the nickel-nitrilotriacetic acid (Ni-NTA) chip measured with a surface plasmon resonance instrument was 1.6 x 10(8) M-1. HHisRCs were immobilized on an indium tin oxide electrode overlaid with an Ni-NTA gold substrate. The photoinduced displacement current of this electrode was measured to estimate the orientation of HHisRC on the electrode, and the detachability of HHisRC from the electrode was determined by using an imidazole solution wash. The direction of the flash-light-induced displacement current suggested that the H subunit side of the immobilized HHisRC faced the surface of the electrode. The photoinduced current disappeared after the electrode was washed in the imidazole solution. This simple immobilization and detachment of HHisRC to the electrode might be useful for making a reproducible photocurrent device. PMID:10849806

  2. Alternating current loss of second-generation high-temperature superconducting coils with magnetic and non-magnetic substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Kvitkovic, J.; Kim, Jae-Ho.; Kim, C. H.; Pamidi, S. V.; Coombs, T. A.

    2012-09-01

    It is widely believed that the second-generation high-temperature superconducting (2G HTS) tapes with magnetic substrates suffer higher transport loss compared to those with non-magnetic substrates. To test this, we prepared two identical coils with magnetic and non-magnetic substrates, respectively. The experimental result was rather surprising that they generated roughly the same amount of transport loss. We used finite element method to understand this result. It is found that, unlike in the single tape where the magnetic field-dependent critical current characteristic can be neglected and the effect of magnetic substrate dominates, the magnetic field-dependent critical current characteristic of 2G tape plays as an equally important role as magnetic substrate in terms of HTS coils.

  3. The selection of convertible engines with current gas generator technology for high speed rotorcraft

    NASA Technical Reports Server (NTRS)

    Eisenberg, Joseph D.

    1990-01-01

    NASA-Lewis has sponsored two studies to determine the most promising convertible engine concepts for high speed rotorcraft. These studies projected year 2000 convertible technology limited to present gas generator technology. Propulsion systems for utilization on aircraft needing thrust only during cruise and those aircraft needing both power and thrust at cruise were investigated. Mission calculations for the two contractors involved were based upon the fold tilt rotor concept. Analysis and comparison of the General Electric concepts (geared UDF, clutched fan, and VIGV fan), and the Allison Gas Turbine concepts (clutched fan, VIGV fan, variable pitch fan, single rotation tractor propfan, and counter rotation tractor propfan) are presented.

  4. The selection of convertible engines with current gas generator technology for high speed rotorcraft

    NASA Technical Reports Server (NTRS)

    Eisenberg, Joseph D.

    1990-01-01

    NASA-Lewis sponsored two studies to determine the most promising convertible engine concepts for high speed rotorcraft. These studies projected year 2000 convertible technology limited to present gas generator technology. Propulsion systems for utilization on aircraft needing thrust only during cruise and those aircraft needing both power and thrust at cruise were investigated. Mission calculations for the two contractors involved were based upon the fold tilt rotor concept. Analysis and comparison of the General Electric concepts (geared UDF, clutched fan, and Variable Inlet Guide Vane (VIGV) fan), and the Allison Gas Turbine concepts (clutched fan, VIGV fan, variable pitch fan, single rotation tractor propfan, and counter rotation tractor propfan) are presented.

  5. Investigation of eddy current examination on OD fatigue crack for steam generator tubes

    NASA Astrophysics Data System (ADS)

    Kong, Yuying; Ding, Boyuan; Li, Ming; Liu, Jinhong; Chen, Huaidong; Meyendorf, Norbert G.

    2015-03-01

    The opening width of fatigue crack was very small, and conventional Bobbin probe was very difficult to detect it in steam generator tubes. Different sizes of 8 fatigue cracks were inspected using bobbin probe rotating probe. The analysis results showed that, bobbin probe was not sensitive for fatigue crack even for small through wall crack mixed with denting signal. On the other hand, the rotating probe was easily to detect all cracks. Finally, the OD phase to depth curve for fatigue crack using rotating probe was established and the results agreed very well with the true crack size.

  6. A review of volcanic ash aggregation

    NASA Astrophysics Data System (ADS)

    Brown, R. J.; Bonadonna, C.; Durant, A. J.

    2012-01-01

    Most volcanic ash particles with diameters <63 μm settle from eruption clouds as particle aggregates that cumulatively have larger sizes, lower densities, and higher terminal fall velocities than individual constituent particles. Particle aggregation reduces the atmospheric residence time of fine ash, which results in a proportional increase in fine ash fallout within 10-100 s km from the volcano and a reduction in airborne fine ash mass concentrations 1000 s km from the volcano. Aggregate characteristics vary with distance from the volcano: proximal aggregates are typically larger (up to cm size) with concentric structures, while distal aggregates are typically smaller (sub-millimetre size). Particles comprising ash aggregates are bound through hydro-bonds (liquid and ice water) and electrostatic forces, and the rate of particle aggregation correlates with cloud liquid water availability. Eruption source parameters (including initial particle size distribution, erupted mass, eruption column height, cloud water content and temperature) and the eruption plume temperature lapse rate, coupled with the environmental parameters, determines the type and spatiotemporal distribution of aggregates. Field studies, lab experiments and modelling investigations have already provided important insights on the process of particle aggregation. However, new integrated observations that combine remote sensing studies of ash clouds with field measurement and sampling, and lab experiments are required to fill current gaps in knowledge surrounding the theory of ash aggregate formation.

  7. The Next Generation Advanced Video Guidance Sensor: Flight Heritage and Current Development

    NASA Astrophysics Data System (ADS)

    Howard, Richard T.; Bryan, Thomas C.

    2009-03-01

    The Next Generation Advanced Video Guidance Sensor (NGAVGS) is the latest in a line of sensors that have flown four times in the last 10 years. The NGAVGS has been under development for the last two years as a long-range proximity operations and docking sensor for use in an Automated Rendezvous and Docking (AR&D) system. The first autonomous rendezvous and docking in the history of the U.S. Space Program was successfully accomplished by Orbital Express, using the Advanced Video Guidance Sensor (AVGS) as the primary docking sensor. That flight proved that the United States now has a mature and flight proven sensor technology for supporting Crew Exploration Vehicles (CEV) and Commercial Orbital Transport Systems (COTS) Automated Rendezvous and Docking (AR&D). NASA video sensors have worked well in the past: the AVGS used on the Demonstration of Autonomous Rendezvous Technology (DART) mission operated successfully in "spot mode" out to 2 km, and the first generation rendezvous and docking sensor, the Video Guidance Sensor (VGS), was developed and successfully flown on Space Shuttle flights in 1997 and 1998.

  8. Excited-state dynamics of astaxanthin aggregates

    NASA Astrophysics Data System (ADS)

    Fuciman, Marcel; Durchan, Milan; Šlouf, Václav; Keşan, Gürkan; Polívka, Tomáš

    2013-05-01

    Astaxanthin forms three types of aggregates in hydrated dimethyl sulfoxide (DMSO). In DMSO/water ratio of 1:1, a red-shifted J-aggregate with maximum at 570 nm is generated, while a ratio of 1:9 produces blue-shifted H-aggregates with peaks at 386 nm (H1) and 460 nm (H2). Monomeric astaxanthin in DMSO has an S1 lifetime of 5.3 ps, but a long-lived (33 ps) S∗ signal was also identified. Aggregation changes the S1 lifetimes to 17 ps (H1), 30 ps (H2), and 14 ps (J). Triplet state of astaxanthin, most likely generated via singlet homofission, was observed in H1 and H2 aggregates.

  9. Development of a High-Brightness and High-Current Electron Gun for High-Flux γ-Ray Generation

    NASA Astrophysics Data System (ADS)

    Nishimori, N.; Nagai, R.; Matsuba, S.; Hajima, R.; Yamamoto, M.; Honda, Y.; Miyajima, T.; Uchiyama, T.; Kuriki, M.

    2015-10-01

    A high-flux mono-energetic γ-ray beam can be generated via Compton scattering of high-power laser by high-brightness electron beam. We have developed a high-brightness and high-current electron gun for generation of the high-flux γ-ray beam. Recently we demonstrated 500 keV electron beam generation, which meets the high-brightness requirement, from our DC photocathode gun at Japan Atomic Energy Agency. The gun was transported to High Energy Accelerator Research Organization (KEK) and connected to the following accelerator system. The gun operational status at KEK and our plan to develop a multialkali photocathode with a long lifetime are presented.

  10. Broadband sidebands generated by parametric instability in lower hybrid current drive experiments on EAST

    SciTech Connect

    Amicucci, L. Castaldo, C.; Cesario, R.; Giovannozzi, E.; Tuccillo, A. A.; Ding, B. J.; Li, M. H.

    2015-12-10

    Modern research on nuclear fusion energy, based on the tokamak concept, has strong need of tools for actively driving non-inductive current especially at the periphery of plasma column, where tools available so far have poor efficiency. This is essential for solving one of the most critical problems for thermonuclear reactor, consisting in how to achieve the figure of fusion gain in the context of sufficient stability. The lower hybrid current drive (LHCD) effect has the potential capability of driving current at large radii of reactor plasma with high efficiency [1]. Experiments recently carried out on EAST showed that a strong activity of LH sideband waves (from the RF probe spectra), accompanied by weak core penetration of the coupled LH power, is present when operating at relatively high plasma densities. Previous theoretical results, confirmed by experiments on FTU, showed that the LH sideband phenomenon is produced by parametric instability (PI), which are mitigated by higher plasma edge temperatures. This condition is thus useful for enabling the LH power propagation when operating with profiles having high plasma densities even at the edge. In the present work, we show new PI modeling of EAST plasmas data, obtained in condition of higher plasma edge temperature due to chamber lithisation. The obtained trend of the PI frequencies and growth rates is consistent with data of RF probe spectra, available in different regimes of lithisated and not lithisated vessel. Moreover, these spectra are interpreted as PI effect occurring at the periphery of plasma column, however in the low field side where the LH power is coupled.

  11. Broadband sidebands generated by parametric instability in lower hybrid current drive experiments on EAST

    NASA Astrophysics Data System (ADS)

    Amicucci, L.; Ding, B. J.; Castaldo, C.; Cesario, R.; Giovannozzi, E.; Li, M. H.; Tuccillo, A. A.

    2015-12-01

    Modern research on nuclear fusion energy, based on the tokamak concept, has strong need of tools for actively driving non-inductive current especially at the periphery of plasma column, where tools available so far have poor efficiency. This is essential for solving one of the most critical problems for thermonuclear reactor, consisting in how to achieve the figure of fusion gain in the context of sufficient stability. The lower hybrid current drive (LHCD) effect has the potential capability of driving current at large radii of reactor plasma with high efficiency [1]. Experiments recently carried out on EAST showed that a strong activity of LH sideband waves (from the RF probe spectra), accompanied by weak core penetration of the coupled LH power, is present when operating at relatively high plasma densities. Previous theoretical results, confirmed by experiments on FTU, showed that the LH sideband phenomenon is produced by parametric instability (PI), which are mitigated by higher plasma edge temperatures. This condition is thus useful for enabling the LH power propagation when operating with profiles having high plasma densities even at the edge. In the present work, we show new PI modeling of EAST plasmas data, obtained in condition of higher plasma edge temperature due to chamber lithisation. The obtained trend of the PI frequencies and growth rates is consistent with data of RF probe spectra, available in different regimes of lithisated and not lithisated vessel. Moreover, these spectra are interpreted as PI effect occurring at the periphery of plasma column, however in the low field side where the LH power is coupled.

  12. In vitro investigation of eddy current effect on pacemaker operation generated by low frequency magnetic field.

    PubMed

    Babouri, A; Hedjeidj, A

    2007-01-01

    This paper presents in vitro investigation of the eddy current induction effects to the cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based to the interaction by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. In this article we present experimental results, analytical calculations and numerical simulations using the finite element method. PMID:18003302

  13. Generation of noninductive current by electron-Bernstein waves on the COMPASS-D Tokamak.

    PubMed

    Shevchenko, V; Baranov, Y; O'Brien, M; Saveliev, A

    2002-12-23

    Electron-Bernstein waves (EBW) were excited in the plasma by mode converted extraordinary (X) waves launched from the high field side of the COMPASS-D tokamak at different toroidal angles. It has been found experimentally that X-mode injection perpendicular to the magnetic field provides maximum heating efficiency. Noninductive currents of up to 100 kA were found to be driven by the EBW mode with countercurrent drive. These results are consistent with ray tracing and quasilinear Fokker-Planck simulations. PMID:12484831

  14. Arc driver operation for either efficient energy transfer or high-current generator

    NASA Technical Reports Server (NTRS)

    Dannenberg, R. E.; Silva, A. F.

    1972-01-01

    An investigation is made to establish predictable electric arcs along triggered paths for research purposes, the intended application being the heating of the driver gas of a 1 MJ electrically driven shock tube. Trigger conductors consisting of wires, open tubes, and tubes pressurized with different gases were investigated either on the axis of the arc chamber or spiraled along the chamber walls. Design criteria are presented for successful arc initiation with reproducible voltage-current characteristics. Results are compared with other facilities and several application areas are discussed.

  15. Statistical characteristic in time-domain of direct current corona-generated audible noise from conductor in corona cage

    NASA Astrophysics Data System (ADS)

    Li, Xuebao; Cui, Xiang; Lu, Tiebing; Ma, Wenzuo; Bian, Xingming; Wang, Donglai; Hiziroglu, Huseyin

    2016-03-01

    The corona-generated audible noise (AN) has become one of decisive factors in the design of high voltage direct current (HVDC) transmission lines. The AN from transmission lines can be attributed to sound pressure pulses which are generated by the multiple corona sources formed on the conductor, i.e., transmission lines. In this paper, a detailed time-domain characteristics of the sound pressure pulses, which are generated by the DC corona discharges formed over the surfaces of a stranded conductors, are investigated systematically in a laboratory settings using a corona cage structure. The amplitude of sound pressure pulse and its time intervals are extracted by observing a direct correlation between corona current pulses and corona-generated sound pressure pulses. Based on the statistical characteristics, a stochastic model is presented for simulating the sound pressure pulses due to DC corona discharges occurring on conductors. The proposed stochastic model is validated by comparing the calculated and measured A-weighted sound pressure level (SPL). The proposed model is then used to analyze the influence of the pulse amplitudes and pulse rate on the SPL. Furthermore, a mathematical relationship is found between the SPL and conductor diameter, electric field, and radial distance.

  16. Platelet aggregation test

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003669.htm Platelet aggregation test To use the sharing features on this page, please enable JavaScript. The platelet aggregation blood test checks how well platelets , a ...

  17. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  18. Platelet aggregation test

    MedlinePlus

    The platelet aggregation blood test checks how well platelets , a part of blood, clump together and cause blood to clot. ... Decreased platelet aggregation may be due to: Autoimmune ... Fibrin degradation products Inherited platelet function defects ...

  19. Current experiences with internet telepathology and possible evolution in the next generation of Internet services.

    PubMed

    Della Mea, V; Beltrami, C A

    2000-01-01

    The last five years experience has definitely demonstrated the possible applications of the Internet for telepathology. They may be listed as follows: (a) teleconsultation via multimedia e-mail; (b) teleconsultation via web-based tools; (c) distant education by means of World Wide Web; (d) virtual microscope management through Web and Java interfaces; (e) real-time consultations through Internet-based videoconferencing. Such applications have led to the recognition of some important limits of the Internet, when dealing with telemedicine: (i) no guarantees on the quality of service (QoS); (ii) inadequate security and privacy; (iii) for some countries, low bandwidth and thus low responsiveness for real-time applications. Currently, there are several innovations in the world of the Internet. Different initiatives have been aimed at an amelioration of the Internet protocols, in order to have quality of service, multimedia support, security and other advanced services, together with greater bandwidth. The forthcoming Internet improvements, although induced by electronic commerce, video on demand, and other commercial needs, are of real interest also for telemedicine, because they solve the limits currently slowing down the use of Internet. When such new services will be available, telepathology applications may switch from research to daily practice in a fast way. PMID:11339559

  20. Current and future greenhouse gas emissions associated with electricity generation in China: implications for electric vehicles.

    PubMed

    Shen, Wei; Han, Weijian; Wallington, Timothy J

    2014-06-17

    China's oil imports and greenhouse gas (GHG) emissions have grown rapidly over the past decade. Addressing energy security and GHG emissions is a national priority. Replacing conventional vehicles with electric vehicles (EVs) offers a potential solution to both issues. While the reduction in petroleum use and hence the energy security benefits of switching to EVs are obvious, the GHG benefits are less obvious. We examine the current Chinese electric grid and its evolution and discuss the implications for EVs. China's electric grid will be dominated by coal for the next few decades. In 2015 in Beijing, Shanghai, and Guangzhou, EVs will need to use less than 14, 19, and 23 kWh/100 km, respectively, to match the 183 gCO2/km WTW emissions for energy saving vehicles. In 2020, in Beijing, Shanghai, and Guangzhou EVs will need to use less than 13, 18, and 20 kWh/100 km, respectively, to match the 137 gCO2/km WTW emissions for energy saving vehicles. EVs currently demonstrated in China use 24-32 kWh/100 km. Electrification will reduce petroleum imports; however, it will be very challenging for EVs to contribute to government targets for GHGs emissions reduction. PMID:24853334

  1. Baroclinic tidal generation in the Kauai Channel inferred from high-frequency radio Doppler current meters

    NASA Astrophysics Data System (ADS)

    Zaron, Edward D.; Chavanne, Cedric; Egbert, Gary D.; Flament, Pierre

    2009-10-01

    A data-assimilating three-dimensional primitive equations model is used in conjunction with high-frequency radio Doppler current data to infer tidal conversion during two 3-month periods in Kauai Channel, Hawaii. It is estimated that the M barotropic tide loses energy at rates of 1.1 and 1.2 GW during these periods, values 25% lower than predicted with the prior model. Of this total conversion rate, approximately 85% exits the model domain to enter the deep ocean as a coherent propagating internal tide. Although the inferred tidal currents differ in detail during the 3-month periods, the domain-averaged tidal energetics do not. The tidal solutions obtained by the data-assimilative model do not exactly satisfy the primitive equations dynamics since a residual forcing is permitted in the horizontal momentum and mass conservation equations. An analysis of these residuals indicates that they are consistent with the expected amplitude of tidal-mesoscale interactions; however, the residual forcing in the mass equation, which represents refraction by the mesoscale buoyancy field, is much too small. An attempt to reconcile the forcing residuals with known processes suggests, by elimination, that tidal-mesoscale interactions are of leading-order significance and should be included in future analysis of baroclinic tidal energy budgets.

  2. Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities

    SciTech Connect

    Meriles, Carlos A.; Doherty, Marcus W.

    2014-07-14

    Key to future spintronics and spin-based information processing technologies is the generation, manipulation, and detection of spin polarization in a solid state platform. Here, we theoretically explore an alternative route to spin injection via the use of dynamically polarized nitrogen-vacancy (NV) centers in diamond. We focus on the geometry where carriers and NV centers are confined to proximate, parallel layers and use a “trap-and-release” model to calculate the spin cross-relaxation probabilities between the charge carriers and neighboring NV centers. We identify near-unity regimes of carrier polarization depending on the NV spin state, applied magnetic field, and carrier g-factor. In particular, we find that unlike holes, electron spins are distinctively robust against spin-lattice relaxation by other, unpolarized paramagnetic centers. Further, the polarization process is only weakly dependent on the carrier hopping dynamics, which makes this approach potentially applicable over a broad range of temperatures.

  3. [Current topic of next generation of angiotensin II type 1 receptor blockers].

    PubMed

    Mogi, Masaki; Horiuchi, Masatsugu

    2012-09-01

    Angiotensin receptor blockers(ARBs) are used as the first-choice anti-hypertensives for prevention of multiple organ damage. Recently, the next-generation ARBs have been expected to have more preventive effect for cardiovascular diseases. For example, metabosartans which have a partial agonistic effect of peroxisome proliferator-activated receptor gamma induce an improvement of metabolism compared with ordinary ARBs. Moreover, LCZ696, ARB with a neprilysin inhibitor which increases natriuretic peptides has a significant reduction in blood pressure compared with ARB. Furthermore, ARBs with nitric oxide donor or endothelin receptor blocker have been reported to have a benefit beyond ordinary ARBs. Dual action in the next multi-functional ARBs may be a strong therapeutic contributor for patients with multiple organ dysfunction. PMID:23012813

  4. Current and emerging second-generation triptans in acute migraine therapy: a comparative review.

    PubMed

    Deleu, D; Hanssens, Y

    2000-07-01

    Sterile neurogenic inflammation within cephalic tissue, involving vasodilation and plasma protein extravasation, has been proposed as a pathophysiological mechanism in acute migraine. The action of 5-hydroxytryptamine (5-HT1B/1D) agonists--so-called triptans--on receptors located in meningeal arteries (5-HT1B) and trigeminovascular fiber endings (5-HT1D) has an inhibitory effect on this neurogenic inflammation. Recently, a series of second-generation 5-HT1B/1D agonists (almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, and zolmitriptan) have been developed and are reviewed in this article. Their in vitro pharmacological properties, pharmacokinetics, clinical efficacy, drug interactions, and adverse effects are evaluated and compared to the golden standard in the treatment of acute migraine, sumatriptan. PMID:10883409

  5. The next generation mass storage devices - Physical principles and current status

    NASA Astrophysics Data System (ADS)

    Wang, L.; Gai, S.

    2014-04-01

    The amount of digital data today has been increasing at a phenomenal rate due to the widespread digitalisation service in almost every industry. The need to store such ever-increasing data aggressively triggers the requirement to augment the storage capacity of the conventional storage technologies. Unfortunately, the physical limitations that conventional forms face have severely handicapped their potential to meet the storage need from both consumer and industry point of view. The focus has therefore been switched into the development of the innovative data storage technologies such as scanning probe memory, nanocrystal memory, carbon nanotube memory, DNA memory, and organic memory. In this paper, we review the physical principles of these emerging storage technologies and their superiorities as the next generation data storage device, as well as their respective technical challenges on further enhancing the storage capacity. We also compare these novel technologies with the mainstream data storage means according to the technology roadmap on areal density.

  6. Photo current generation in RGO - CdS nanorod thin film device

    NASA Astrophysics Data System (ADS)

    Chakraborty, Koushik; Chakrabarty, Sankalpita; Ibrahim, Sk.; Pal, Tanusri; Ghosh, Surajit

    2016-05-01

    Herein, we report the synthesis and characterization of reduced graphene oxide (RGO) - cadmium sulfide (CdS) nanocomposite materials. The reduction of GO, formation of CdS and decoration of CdS onto RGO sheets were done in a one- pot solvothermal process. We have observed that the PL intensity for CdS nanorods remarkably quenched after the attachment of RGO, which established the photo induced charge transformation from the CdS nanorod to RGO sheets through the RGO-CdS interface. The optoelectronic transport properties of our fabricated large area thin film device exhibits excellent photo induced charge generation under simulated solar light illumination. The photo sensitivity of the device increases linearly with the increase of illuminated light intensity. The RGO-CdS composite exhibits enhance photocatalytic dye degradation efficiency in compare to control CdS under simulated solar light illumination.

  7. Generation of Soluble Advanced Glycation End Products Receptor (sRAGE)-Binding Ligands during Extensive Heat Treatment of Whey Protein/Lactose Mixtures Is Dependent on Glycation and Aggregation.

    PubMed

    Liu, Fahui; Teodorowicz, Małgorzata; Wichers, Harry J; van Boekel, Martinus A J S; Hettinga, Kasper A

    2016-08-24

    Heating of protein- and sugar-containing materials is considered the primary factor affecting the formation of advanced glycation end products (AGEs). This study aimed to investigate the influence of heating conditions, digestion, and aggregation on the binding capacity of AGEs to the soluble AGE receptor (sRAGE). Samples consisting of mixtures of whey protein and lactose were heated at 130 °C. An in vitro infant digestion model was used to study the influence of heat treatment on the digestibility of whey proteins. The amount of sRAGE-binding ligands before and after digestion was measured by an ELISA-based sRAGE-binding assay. Water activity did not significantly affect the extent of digestibility of whey proteins dry heated at pH 5 (ranging from 3.3 ± 0.2 to 3.6 ± 0.1% for gastric digestion and from 53.5 ± 1.5 to 64.7 ± 1.1% for duodenal digestion), but there were differences in cleavage patterns of peptides among the samples heated at different pH values. Formation of sRAGE-binding ligands depended on the formation of aggregates and was limited in the samples heated at pH 5. Moreover, the sRAGE-binding activity of digested sample was changed by protease degradation and correlated with the digestibility of samples. In conclusion, generation of sRAGE-binding ligands during extensive heat treatment of whey protein/lactose mixtures is limited in acidic heating condition and dependent on glycation and aggregation. PMID:27460534

  8. Direct optical detection of current induced spin accumulation in metals by magnetization-induced second harmonic generation

    SciTech Connect

    Pattabi, A. Gu, Z.; Yang, Y.; Finley, J.; Lee, O. J.; Raziq, H. A.; Gorchon, J.; Salahuddin, S.; Bokor, J.

    2015-10-12

    Strong spin-orbit coupling in non-magnetic heavy metals has been shown to lead to large spin currents flowing transverse to a charge current in such a metal wire. This in turn leads to the buildup of a net spin accumulation at the lateral surfaces of the wire. Spin-orbit torque effects enable the use of the accumulated spins to exert useful magnetic torques on adjacent magnetic layers in spintronic devices. We report the direct detection of spin accumulation at the free surface of nonmagnetic metal films using magnetization-induced optical surface second harmonic generation. The technique is applied to probe the current induced surface spin accumulation in various heavy metals such as Pt, β-Ta, and Au with high sensitivity. The sensitivity of the technique enables us to measure the time dynamics on a sub-ns time scale of the spin accumulation arising from a short current pulse. The ability of optical surface second harmonic generation to probe interfaces suggests that this technique will also be useful for studying the dynamics of spin accumulation and transport across interfaces between non-magnetic and ferromagnetic materials, where spin-orbit torque effects are of considerable interest.

  9. Role of Multicellular Aggregates in Biofilm Formation

    PubMed Central

    Kragh, Kasper N.; Hutchison, Jaime B.; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled E. L.; Irie, Yasuhiko; Jensen, Peter Ø.; Diggle, Stephen P.; Allen, Rosalind J.

    2016-01-01

    ABSTRACT In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation. PMID:27006463

  10. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams

    NASA Astrophysics Data System (ADS)

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a ˜450 kV, ˜400 ns pulse. It was found that 300-400 MW, ˜250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.

  11. Heat generation by spin-polarized current in a quantum dot connected to spin battery and ferromagnetic lead

    NASA Astrophysics Data System (ADS)

    Bai, Xu-Fang; Sun, Lian-Liang; Chi, Feng

    2015-05-01

    We study theoretically the heat originated from electron-phonon coupling in a spintronic device composed of a semiconductor quantum dot attached to one spin battery and one ferromagnetic lead. It is found that the phenomenon of the negative differential of the heat current, which has previously been predicted in the charge-based device, disappears due to the Pauli exclusion principle resulted from the presence of the spin battery. Under some conditions, huge heat in the heat generation induced by resonant phonon emitting processes also disappears in this spin-based device. Furthermore, we find that the ferromagnetism of the lead can be used to effectively adjust the magnitude of the heat current in different dot level ranges. The proposed system is realizable by current technology and may be useful in designing high-efficiency spintronic components. Project supported by the National Natural Science Foundation of China (Grant No. 61274101).

  12. Current generation by helicons and lower hybrid waves in modern tokamaks and reactors ITER and DEMO. Scenarios, modeling and antennae

    SciTech Connect

    Vdovin, V. L.

    2013-02-15

    The innovative concept and 3D full-wave code modeling the off-axis current drive by radio-frequency (RF) waves in large-scale tokamaks, ITER and DEMO, for steady-state operation with high efficiency is proposed. The scheme uses the helicon radiation (fast magnetosonic waves at high (20-40) ion cyclotron frequency harmonics) at frequencies of 500-700 MHz propagating in the outer regions of the plasmas with a rotational transform. It is expected that the current generated by helicons, in conjunction with the bootstrap current, ensure the maintenance of a given value of the total current in the stability margin q(0) {>=} 2 and q(a) {>=} 4, and will help to have regimes with a negative magnetic shear and internal transport barrier to ensure stability at high normalized plasma pressure {beta}{sub N} > 3 (the so-called advanced scenarios) of interest for the commercial reactor. Modeling with full-wave three-dimensional codes PSTELION and STELEC showed flexible control of the current profile in the reactor plasmas of ITER and DEMO, using multiple frequencies, the positions of the antennae and toroidal wave slow down. Also presented are the results of simulations of current generation by helicons in the DIII-D, T-15MD, and JT-60AS tokamaks. Commercially available continuous-wave klystrons of the MW/tube range are promising for commercial stationary fusion reactors. The compact antennae of the waveguide type are proposed, and an example of a possible RF system for today's tokamaks is given. The advantages of the scheme (partially tested at lower frequencies in tokamaks) are a significant decline in the role of parametric instabilities in the plasma periphery, the use of electrically strong resonator-waveguide type antennae, and substantially greater antenna-plasma coupling.

  13. Defect-controlled vortex generation in current-carrying narrow superconducting strips

    NASA Astrophysics Data System (ADS)

    Vodolazov, D. Yu; Ilin, K.; Merker, M.; Siegel, M.

    2016-02-01

    We experimentally study the effect of a single circular hole on the critical current I c of narrow superconducting strip with width W much smaller than Pearl penetration depth Λ. We found non-monotonous dependence of I c on the location of a hole across the strip and a weak dependence of I c on the radius of a hole in the case of a hole with ξ \\ll R\\ll W (ξ is a superconducting coherence length) which is placed in the center of strip. The observed effects are caused by competition of two mechanisms of destruction of superconductivity—the entrance of vortex via the edge of the strip and the nucleation of the vortex-antivortex pair near the hole. The mechanisms are clearly distinguishable by a difference in dependence of I c on weak magnetic field.

  14. Generation of cAMP-Activated Chloride Currents by Expression of CFTR

    NASA Astrophysics Data System (ADS)

    Anderson, Matthew P.; Rich, Devra P.; Gregory, Richard J.; Smith, Alan E.; Welsh, Michael J.

    1991-02-01

    Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis. In order to evaluate its function, CFTR was expressed in HeLa, Chinese hamster ovary (CHO), and NIH 3T3 fibroblast cells, and anion permeability was assessed with a fluorescence microscopic assay and the whole-cell patch-clamp technique. Adenosine 3',5'-monophosphate (cAMP) increased anion permeability and chloride currents in cells expressing CFTR, but not in cells expressing a mutant CFTR (ΔF508) or in nontransfected cells. The simplest interpretation of these observations is that CFTR is itself a cAMP-activated chloride channel. The alternative interpretation, that CFTR directly or indirectly regulates chloride channels, requires that these cells have endogenous cryptic, chloride channels that are stimulated by cAMP only in the presence of CFTR.

  15. Numerical simulation of the generation of secondary electrons in the High Current Experiment

    SciTech Connect

    Stoltz, P.H.; Furman, M.A.; Vay, J.-L.; Molvik, A.W.; Cohen, R.H.

    2003-04-01

    Electron effects in the High Current Experiment (HCX) are studied via computer simulation. An approximate expression for the secondary electron yield for a potassium ion striking stainless steel is derived and compared with experimental results. This approximate expression has a peak of roughly 55 electrons at normal incidence at an ion energy of 60 MeV. Using an empirical angular dependence, the secondary electron yield is combined with a numerical simulation of the HCX ion beam dynamics to obtain an estimate for the number of secondary electrons expected per ion-wall collision in the HCX. This estimate is that approximately 150-200 electrons per ion collision may result in the HCX.

  16. Monitoring ocean heat content from the current generation of global ocean observing systems

    NASA Astrophysics Data System (ADS)

    von Schuckmann, K.; Sallée, J.-B.; Chambers, D.; Le Traon, P.-Y.; Cabanes, C.; Gaillard, F.; Speich, S.; Hamon, M.

    2013-06-01

    Variations in the world's ocean heat storage and its associated volume changes are a key factor to gauge global warming and to assess the Earth's energy budget. It is also directly link to sea level change, which has a direct impact on coastal populations. Understanding and monitoring heat and sea level change is therefore one of the major legacies of current global ocean observing systems. In this study, we present an inter-comparison of the three of these global ocean observing systems: the ocean temperature/salinity network Argo, the gravimeter GRACE and the satellite altimeters. Their consistency is investigated at global and regional scale during the period 2005-2010 of overlapping time window of re-qualified data. These three datasets allow closing the recent global ocean sea level budget within uncertainties. However, sampling inconsistencies need to be corrected for an accurate budget at global scale. The Argo network allows estimating global ocean heat content and global sea level and reveals a positive change of 0.5 ± 0.1W m-2 and 0.5 ± 0.1 mm yr-1 over the last 8 yr (2005-2012). Regional inter-comparison of the global observing systems highlights the importance of specific ocean basins for the global estimates. Specifically, the Indonesian Archipelago appears as a key region for the global ocean variability. Both the large regional variability and the uncertainties in the current observing systems, prevent us to shed light, from the global sea level perspective, on the climatically important deep ocean changes. This emphasises, once more, the importance of continuing sustained effort in measuring the deep ocean from ship platforms and by setting up a much needed automated deep-Argo network.

  17. Internal structure of a contourite drift generated by the Antarctic Circumpolar Current

    NASA Astrophysics Data System (ADS)

    Koenitz, Dorit; White, Nicky; McCave, I. Nick; Hobbs, Richard

    2008-06-01

    We describe the internal structure and stratigraphy of a well-imaged contourite drift from the Southern Ocean. This drift, which we have named the South Falkland Slope Drift, lies on the northern flank of the Falkland Trough due south of the Falkland Islands. Drifts which occur directly in the path of the Antarctic Circumpolar Current (ACC), downstream of the Drake Passage gateway, are of considerable paleoceanographic significance since their detailed stratigraphic record will help to constrain the history of the ACC. We have reprocessed a grid of seismic reflection profiles generously provided by WesternGeco Ltd. in order to enhance imaging of the South Falkland Slope Drift and of drift deposits within the trough. The resultant high-quality images enable us to map the internal architecture of these drifts in unprecedented detail. By combining seismic stratigraphic mapping with measured sedimentation rates from nearby boreholes, we have inferred ages of the principal mappable horizons. With minor adjustments to sedimentation rates through time, we can show that these ages correspond to significant Southern Ocean events. We propose that the South Falkland Slope Drift initiated at 24.5-20.5 Ma, in accordance with some, but not all, published estimates of ACC establishment. A highly reflective horizon with an estimated age of 14.5 Ma corresponds to growth of the East Antarctic Ice Sheet, which led to a period of significant global cooling. A similarly bright reflective horizon with an estimated age of 9 Ma is thought to be related to a reorganization of bottom current flow which just predated establishment of grounded ice sheets on the Antarctic Peninsular shelf. Finally, a prominent early Pliocene unconformity at 4.5 Ma may be linked with the onset of major Northern Hemisphere glaciation or with Antarctic ice sheet expansion. We conclude that this well-imaged drift is an important, and largely continuous, stratigraphic record of ACC activity and suggest that it

  18. Ion velocities in direct current arc plasma generated from compound cathodes

    SciTech Connect

    Zhirkov, I.; Rosen, J.; Eriksson, A. O.

    2013-12-07

    Arc plasma from Ti-C, Ti-Al, and Ti-Si cathodes was characterized with respect to charge-state-resolved ion energy. The evaluated peak velocities of different ion species in plasma generated from a compound cathode were found to be equal and independent on ion mass. Therefore, measured difference in kinetic energies can be inferred from the difference in ion mass, with no dependence on ion charge state. The latter is consistent with previous work. These findings can be explained by plasma quasineutrality, ion acceleration by pressure gradients, and electron-ion coupling. Increasing the C concentration in Ti-C cathodes resulted in increasing average and peak ion energies for all ion species. This effect can be explained by the “cohesive energy rule,” where material and phases of higher cohesive energy generally result in increasing energies (velocities). This is also consistent with the here obtained peak velocities around 1.37, 1.42, and 1.55 (10{sup 4} m/s) for ions from Ti{sub 0.84}Al{sub 0.16}, Ti{sub 0.90}Si{sub 0.10}, and Ti{sub 0.90}C{sub 0.10} cathodes, respectively.

  19. Flow structure and transport characteristics of feeding and exchange currents generated by upside-down Cassiopea jellyfish.

    PubMed

    Santhanakrishnan, Arvind; Dollinger, Makani; Hamlet, Christina L; Colin, Sean P; Miller, Laura A

    2012-07-15

    Quantifying the flows generated by the pulsations of jellyfish bells is crucial for understanding the mechanics and efficiency of their swimming and feeding. Recent experimental and theoretical work has focused on the dynamics of vortices in the wakes of swimming jellyfish with relatively simple oral arms and tentacles. The significance of bell pulsations for generating feeding currents through elaborate oral arms and the consequences for particle capture are not as well understood. To isolate the generation of feeding currents from swimming, the pulsing kinematics and fluid flow around the benthic jellyfish Cassiopea spp. were investigated using a combination of videography, digital particle image velocimetry and direct numerical simulation. During the rapid contraction phase of the bell, fluid is pulled into a starting vortex ring that translates through the oral arms with peak velocities that can be of the order of 10 cm s(-1). Strong shear flows are also generated across the top of the oral arms throughout the entire pulse cycle. A coherent train of vortex rings is not observed, unlike in the case of swimming oblate medusae such as Aurelia aurita. The phase-averaged flow generated by bell pulsations is similar to a vertical jet, with induced flow velocities averaged over the cycle of the order of 1-10 mm s(-1). This introduces a strong near-horizontal entrainment of the fluid along the substrate and towards the oral arms. Continual flow along the substrate towards the jellyfish is reproduced by numerical simulations that model the oral arms as a porous Brinkman layer of finite thickness. This two-dimensional numerical model does not, however, capture the far-field flow above the medusa, suggesting that either the three-dimensionality or the complex structure of the oral arms helps to direct flow towards the central axis and up and away from the animal. PMID:22723475

  20. Generation of complex motor patterns in american grasshopper via current-controlled thoracic electrical interfacing.

    PubMed

    Giampalmo, Susan L; Absher, Benjamin F; Bourne, W Tucker; Steves, Lida E; Vodenski, Vassil V; O'Donnell, Peter M; Erickson, Jonathan C

    2011-01-01

    Micro-air vehicles (MAVs) have attracted attention for their potential application to military applications, environmental sensing, and search and rescue missions. While progress is being made toward fabrication of a completely human-engineered MAV, another promising approach seeks to interface to, and take control of, an insect's nervous system. Cyborg insects take advantage of their innate exquisite loco-motor, navigation, and sensing abilities. Recently, several groups have demonstrated the feasibility of radio-controlled flight in the hawkmoth and beetle via electrical neural interfaces. Here, we report a method for eliciting the "jump" response in the American grasshopper (S. Americana). We found that stimulating the metathoracic T3 ganglion with constant-current square wave pulses with amplitude 186 ± 40 μA and frequency 190 ± 13 Hz reproducibly evoked (≥95% success rate) the desired motor activity in N=3 test subjects. To the best of our knowledge, this is the first report of an insect cyborg with a synchronous neuromuscular system. PMID:22254549

  1. Miscibility Evaluation Of The Next Generation Solvent With Polymers Currently Used At DWPF, MCU, And Saltstone

    SciTech Connect

    Fondeur, F. F.

    2013-04-17

    The Office of Waste Processing, within the Office of Technology Innovation and Development, funded the development of an enhanced Caustic-Side Solvent Extraction (CSSX) solvent for deployment at the Savannah River Site for removal of cesium from High Level Waste. This effort lead to the development of the Next Generation Solvent (NGS) with Tris (3,7-dimethyl octyl) guanidine (TiDG). The first deployment target for the NGS solvent is within the Modular CSSX Unit (MCU). Deployment of a new chemical within an existing facility requires verification that the new chemical components are compatible with the installed equipment. In the instance of a new organic solvent, the primary focus is on compatibility of the solvent with organic polymers used in the affected facility. This report provides the calculated data from exposing these polymers to the Next Generation Solvent. An assessment of the dimensional stability of polymers known to be used or present in the MCU, Defense Waste Processing Facility (DWPF), and Saltstone facilities that will be exposed to the NGS showed that TiDG could selectively affect the elastomers and some thermoplastics to varying extents, but the typical use of these polymers in a confined geometry will likely prevent the NGS from impacting component performance. The polymers identified as of primary concern include Grafoil® (flexible graphite), Tefzel®, Isolast®, ethylene-propylene-diene monomer (EPDM) rubber, nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), ultra high molecular weight polyethylene (UHMWPE), and fluorocarbon rubber (FKM). Certain polymers like NBR and EPDM were found to interact mildly with NGS but their calculated swelling and the confined geometry will impede interaction with NGS. In addition, it was found that Vellumoid (cellulose fibers-reinforced glycerin and protein) may leach protein and Polyvinyl Chloride (PVC) may leach plasticizer (such as Bis-Ethylhexyl-Phthalates) into the NGS solvent. Either case

  2. Archean Earth Atmosphere Fractal Haze Aggregates: Light Scattering Calculations and the Faint Young Sun Paradox

    NASA Astrophysics Data System (ADS)

    Boness, D. A.; Terrell-Martinez, B.

    2010-12-01

    As part of an ongoing undergraduate research project of light scattering calculations involving fractal carbonaceous soot aggregates relevant to current anthropogenic and natural sources in Earth's atmosphere, we have read with interest a recent paper [E.T. Wolf and O.B Toon,Science 328, 1266 (2010)] claiming that the Faint Young Sun paradox discussed four decades ago by Carl Sagan and others can be resolved without invoking heavy CO2 concentrations as a greenhouse gas warming the early Earth enough to sustain liquid water and hence allow the origin of life. Wolf and Toon report that a Titan-like Archean Earth haze, with a fractal haze aggregate nature due to nitrogen-methane photochemistry at high altitudes, should block enough UV light to protect the warming greenhouse gas NH3 while allowing enough visible light to reach the surface of the Earth. To test this hypothesis, we have employed a rigorous T-Matrix arbitrary-particle light scattering technique, to avoid the simplifications inherent in Mie-sphere scattering, on haze fractal aggregates at UV and visible wavelenths of incident light. We generate these model aggregates using diffusion-limited cluster aggregation (DLCA) algorithms, which much more closely fit actual haze fractal aggregates than do diffusion-limited aggregation (DLA) algorithms.

  3. Influence of a new generation of operations support systems on current spacecraft operations philosophy: The users feedback

    NASA Technical Reports Server (NTRS)

    Darroy, Jean Michel

    1993-01-01

    Current trends in the spacecraft mission operations area (spacecraft & mission complexity, project duration, required flexibility are requiring a breakthrough for what concerns philosophy, organization, and support tools. A major evolution is related to space operations 'informationalization', i.e adding to existing operations support & data processing systems a new generation of tools based on advanced information technologies (object-oriented programming, artificial intelligence, data bases, hypertext) that automate, at least partially, operations tasks that used be performed manually (mission & project planning/scheduling, operations procedures elaboration & execution, data analysis & failure diagnosis). All the major facets of this 'informationalization' are addressed at MATRA MARCONI SPACE, operational applications were fielded and generic products are becoming available. These various applications have generated a significant feedback from the users (at ESA, CNES, ARIANESPACE, MATRA MARCONI SPACE), which is now allowing us to precisely measure how the deployment of this new generation of tools, that we called OPSWARE, can 'reengineer' current spacecraft mission operations philosophy, how it can make space operations faster, better, and cheaper. This paper can be considered as an update of the keynote address 'Knowledge-Based Systems for Spacecraft Control' presented during the first 'Ground Data Systems for Spacecraft Control' conference in Darmstadt, June 1990, with a special emphasis on these last two years users feedback.

  4. Experimental volcanic ash aggregation: Internal structuring of accretionary lapilli and the role of liquid bonding

    NASA Astrophysics Data System (ADS)

    Mueller, Sebastian B.; Kueppers, Ulrich; Ayris, Paul M.; Jacob, Michael; Dingwell, Donald B.

    2016-01-01

    Explosive volcanic eruptions can release vast quantities of pyroclastic material into Earth's atmosphere, including volcanic ash, particles with diameters less than two millimeters. Ash particles can cluster together to form aggregates, in some cases reaching up to several centimeters in size. Aggregation alters ash transport and settling behavior compared to un-aggregated particles, influencing ash distribution and deposit stratigraphy. Accretionary lapilli, the most commonly preserved type of aggregates within the geologic record, can exhibit complex internal stratigraphy. The processes involved in the formation and preservation of these aggregates remain poorly constrained quantitatively. In this study, we simulate the variable gas-particle flow conditions which may be encountered within eruption plumes and pyroclastic density currents via laboratory experiments using the ProCell Lab System® of Glatt Ingenieurtechnik GmbH. In this apparatus, solid particles are set into motion in a fluidized bed over a range of well-controlled boundary conditions (particle concentration, air flow rate, gas temperature, humidity, liquid composition). Experiments were conducted with soda-lime glass beads and natural volcanic ash particles under a range of experimental conditions. Both glass beads and volcanic ash exhibited the capacity for aggregation, but stable aggregates could only be produced when materials were coated with high but volcanically-relevant concentrations of NaCl. The growth and structure of aggregates was dependent on the initial granulometry, while the rate of aggregate formation increased exponentially with increasing relative humidity (12-45% RH), before overwetting promoted mud droplet formation. Notably, by use of a broad granulometry, we generated spherical, internally structured aggregates similar to some accretionary pellets found in volcanic deposits. Adaptation of a powder-technology model offers an explanation for the origin of natural accretionary

  5. Ozone generation by negative direct current corona discharges in dry air fed coaxial wire-cylinder reactors

    SciTech Connect

    Yehia, Ashraf; Mizuno, Akira

    2013-05-14

    An analytical study was made in this paper for calculating the ozone generation by negative dc corona discharges. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature, and stressed by a negative dc voltage. The current-voltage characteristics of the negative dc corona discharges formed inside the reactor were measured in parallel with concentration of the generated ozone under different operating conditions. An empirical equation was derived from the experimental results for calculating the ozone concentration generated inside the reactor. The results, that have been recalculated by using the derived equation, have agreed with the experimental results over the whole range of the investigated parameters, except in the saturation range for the ozone concentration. Therefore, the derived equation represents a suitable criterion for expecting the ozone concentration generated by negative dc corona discharges in dry air fed coaxial wire-cylinder reactors under any operating conditions in range of the investigated parameters.

  6. From Chemical Gardens to Fuel Cells: Generation of Electrical Potential and Current Across Self-Assembling Iron Mineral Membranes.

    PubMed

    Barge, Laura M; Abedian, Yeghegis; Russell, Michael J; Doloboff, Ivria J; Cartwright, Julyan H E; Kidd, Richard D; Kanik, Isik

    2015-07-01

    We examine the electrochemical gradients that form across chemical garden membranes and investigate how self-assembling, out-of-equilibrium inorganic precipitates-mimicking in some ways those generated in far-from-equilibrium natural systems-can generate electrochemical energy. Measurements of electrical potential and current were made across membranes precipitated both by injection and solution interface methods in iron-sulfide and iron-hydroxide reaction systems. The battery-like nature of chemical gardens was demonstrated by linking multiple experiments in series which produced sufficient electrical energy to light an external light-emitting diode (LED). This work paves the way for determining relevant properties of geological precipitates that may have played a role in hydrothermal redox chemistry at the origin of life, and materials applications that utilize the electrochemical properties of self-organizing chemical systems. PMID:25968422

  7. Dynamics of the microstructure of current channels and the generation of high-energy electrons in nanosecond discharges in air

    SciTech Connect

    Karelin, V. I.; Trenkin, A. A. Fedoseev, I. G.

    2015-12-15

    The results of the three-dimensional numerical simulation of the dynamics of the microstructure of high-voltage nanosecond discharges in air at atmospheric pressure are presented. It is established that the fast (at a time of ≈10 ns) broadening and significant decrease in the gas concentration in the microchannels occur as a result of the ohmic heating of microchannels with the diameter of 1–30 μm. It was shown that the broadening of microchannels in a nanosecond diffusive discharge provides an increase in the ratio of the electric field strength to the gas concentration in microchannels to values sufficient for the generation highenergy electron beams and X-ray bremsstrahlung in them. Features of the dynamics of the system of microchannels and its effect on the efficiency of the generation of high-energy electrons in discharges developing in the microstructuring regime of the current channels are considered.

  8. A HIGH CURRENT, HIGH VOLTAGE SOLID-STATE PULSE GENERATOR FOR THE NIF PLASMA ELECTRODE POCKELS CELL

    SciTech Connect

    Arnold, P A; Barbosa, F; Cook, E G; Hickman, B C; Akana, G L; Brooksby, C A

    2007-07-27

    A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-switched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17 kV flattop pulses into a 6 {Omega} load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs.

  9. Finite element modeling of wall-loss sizing in a steam generator tube using a pulsed eddy current probe

    NASA Astrophysics Data System (ADS)

    Babbar, V. K.; Lepine, B.; Buck, J.; Underhill, P. R.; Morelli, J.; Krause, T. W.

    2015-03-01

    Inspection of steam generator (SG) tubes by conventional eddy current may, in general, involve analysis of indications from volumetric wall loss, cracks, fouling and support-plate degradation; however, it may be difficult to size or quantify effects from support-to-tube gap and tube tilt, especially in the presence of support plates. Pulsed eddy current (PEC) technology is being developed to investigate such complex tube and flaw geometries. The present work employs finite element modeling to investigate the effectiveness of PEC in identifying and sizing the outer diameter wall-loss in SG tubes. The signals analyzed using a modified principal components analysis (PCA) method reveal the potential success of a PEC-PCA combination to produce scores that can be used to size the wall-loss in the presence of support plates. The modeling results are in good agreement with experimental observations.

  10. Generation of geometrical phases and persistent spin currents in 1-dimensional rings by Lorentz-violating terms

    NASA Astrophysics Data System (ADS)

    Casana, R.; Ferreira, M. M.; Mouchrek-Santos, V. E.; Silva, Edilberto O.

    2015-06-01

    We have demonstrated that Lorentz-violating terms stemming from the fermion sector of the SME are able to generate geometrical phases on the wave function of electrons confined in 1-dimensional rings, as well as persistent spin currents, in the total absence of electromagnetic fields. We have explicitly evaluated the eigenenergies and eigenspinors of the electrons modified by the Lorentz-violating terms, using them to calculate the dynamic and the Aharonov-Anandan phases in the sequel. The total phase presents a pattern very similar to the Aharonov-Casher phase accumulated by electrons in rings under the action of the Rashba interaction. Finally, the persistent spin current were carried out and used to impose upper bounds on the Lorentz-violating parameters.

  11. Ion and electron dynamics generating the Hall current in the exhaust far downstream of the reconnection x-line

    NASA Astrophysics Data System (ADS)

    Fujimoto, Keizo; Takamoto, Makoto

    2016-01-01

    We have investigated the ion and electron dynamics generating the Hall current in the reconnection exhaust far downstream of the x-line where the exhaust width is much larger than the ion gyro-radius. A large-scale particle-in-cell simulation shows that most ions are accelerated through the Speiser-type motion in the current sheet formed at the center of the exhaust. The transition layers formed at the exhaust boundary are not identified as slow mode shocks. (The layers satisfy mostly the Rankine-Hugoniot conditions for a slow mode shock, but the energy conversion hardly occurs there.) We find that the ion drift velocity is modified around the layer due to a finite Larmor radius effect. As a result, the ions are accumulated in the downstream side of the layer, so that collimated ion jets are generated. The electrons experience two steps of acceleration in the exhaust. The first is a parallel acceleration due to the out-of-plane electric field Ey which has a parallel component in most area of the exhaust. The second is a perpendicular acceleration due to Ey at the center of the current sheet and the motion is converted to the parallel direction. Because of the second acceleration, the electron outflow velocity becomes almost uniform over the exhaust. The difference in the outflow profile between the ions and electrons results in the Hall current in large area of the exhaust. The present study demonstrates the importance of the kinetic treatments for collisionless magnetic reconnection even far downstream from the x-line.

  12. High resolution imaging of biomagnetic fields generated by action currents in cardiac tissue using a LTS-SQUID microscope

    NASA Astrophysics Data System (ADS)

    Baudenbacher, F.; Peters, N. T.; Baudenbacher, P.; Wikswo, J. P.

    2002-03-01

    We have developed a scanning superconducting quantum interference device (SQUID) microscope for imaging magnetic fields of room-temperature samples with sub-millimeter resolution. In our design, we use hand-wound niobium pickup coils coupled to commercially available low temperature SQUID sensors. The SQUID sensor and the pickup coil are located in the vacuum space of the cryostat and are separated by a 25 μm sapphire window from the room-temperature sample. The spacing between the tip of the pickup coil and the sample is typically <100 μm. We have used pickup coil diameters of 250 and 500 μm with various numbers of turns depending on the desired spatial resolution. For a 500 μm diameter pickup coil we achieved a field sensitivity of 330 fT Hz -1/2 for frequencies above 1 Hz. This allows us to record magnetocardiograms (MCGs) on the surface of an isolated Langendorff perfused rabbit heart. We recorded MCGs at 1600 locations on a 16×16 mm 2 grid on the surface of an isolated rabbit heart stimulated with a point electrode in the center of the grid. The MCGs were combined to produce a time series of two-dimensional magnetic field maps, which show a clear, octopolar pattern during the current injection, a similar pattern with a reversal in currents immediately after current injection, and the generation and propagation of an elliptical action-current wave front.

  13. Modeling the Microwave Single-scattering Properties of Aggregate Snowflakes

    NASA Astrophysics Data System (ADS)

    Nowell, H.; Honeyager, R. E.; Liu, G.

    2014-12-01

    A new snowflake aggregation model is developed to study single-scattering properties of aggregate snowflakes. Snowflakes are generated by random aggregation of 6-bullet rosette crystals and constrained by size-density relationships derived from previous field observations. Due to random generation, aggregates may have the same size or mass, yet differing morphology allowing for a study into how shape influences their scattering properties. Furthermore, three different aggregate shapes are created: randomly generated, oblate and prolate flakes. The single-scattering properties of the aggregates are investigated using the discrete dipole approximation (DDA) at 10 frequencies. Results are compared to those of Mie theory for solid and soft spheres (density 10% that of solid ice) and to T-matrix results for solid and soft spheroidal cases with aspect ratios of 0.8 (randomly generated) and 0.6 (oblate and prolate). Above size parameter 0.75, neither the solid nor the soft sphere and spheroidal approximations accurately represent the DDA results for the randomly generated or oblate aggregates. Asymmetry and the normalized scattering and backscattering cross-sections of the randomly generated and oblate aggregates fall between the soft and solid spherical and spheroidal approximations. This implies that evaluating snow scattering properties using realistic shapes, such as the aggregates created in this study instead of a simplified crystal shape, is of paramount importance. The dependence of the single-scattering properties on each aggregate's detailed structure seems of secondary importance. Oblate and prolate preliminary results indicate that backscattering for prolate and oblate flakes is lower than that of the randomly generated flakes. Detailed analyses are conducted to answer: (a) why aggregates of similar size yet dissimilar shape backscatter differently and (b) why prolate and oblate aggregates backscatter differently than randomly generated aggregates.

  14. Impact of Particle Aggregation on Nanoparticle Reactivity

    NASA Astrophysics Data System (ADS)

    Jassby, David

    2011-12-01

    nanoparticle that photoluminesces after exposure to UV; TiO2 and ZnO nanoparticles---photocatalytic nanoparticles that generate reactive oxygen species upon UV irradition; and, fullerene nanoparticles used in the filtration experiments, selected for their potential use, small size, and surface chemistry. Our primary methods used to characterize particle and aggregate characteristics include dynamic light scattering used to describe particle size, static light scattering used to characterize aggregate structure (fractal dimension), transmission electron microscopy used to verify primary particle sizes, and electrophoretic mobility measurements to evaluate suspension stability. The reactive property of ZnS that was measured as a function of aggregation was photoluminescence, which was measured using a spectrofluorometer. The reactive property of TiO2 and ZnO that was studied was their ability to generate hydroxyl radicals; these were measured by employing a fluorescent probe that becomes luminescent upon interaction with the hydroxyl radical. To detect the presence of fullerene nanoparticles and calculate removal efficiencies, we used total organic carbon measurements. Additionally, we used UV-vis spectroscopy to approximate the impact of particle shadowing in TiO2 and ZnO aggregates, and Fourier transformed infrared spectroscopy to determine how different electrolytes interact with fullerene surface groups. Our findings indicate that the impact of aggregation on nanoparticle reactivity is material specific. ZnS nanoparticles exhibit a 2-fold increase in band-edge photoluminescence alongside a significant decrease in defect-site photoluminescence. This is attributed to aggregate size-dependent surface tension. Additionally, we used photoluminescence measurements to develop a new method for calculating the critical coagulation concentration of a nanoparticle suspension. The ability of both TiO2 and ZnO to generate hydroxyl radicals was significantly hampered by aggregation. The

  15. Characteristics of drain-modulated generation current in n-type metal-oxide-semiconductor field-effect transistor

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Feng; Guo, Li-Xin; Zheng, Pu-Yang; Dong, Zhao; Zhang, Qian

    2015-07-01

    Drain-modulated generation current IDMG induced by interface traps in an n-type metal-oxide-semiconductor field-effect transistor (nMOSFET) is investigated. The formation of IDMG ascribes to the change of the Si surface potential φ s. This change makes the channel suffer transformation from the inversion state, depletion I state to depletion II state. The simulation result agrees with the experiment in the inversion and depletion I states. In the depletion II state, the theoretical curve goes into saturation, while the experimental curve drops quickly as VD increases. The reason for this unconformity is that the drain-to-gate voltage VDG lessens φ s around the drain corner and controls the falling edge of the IDMG curve. The experiments of gate-modulated generation and recombination currents are also applied to verify the reasonability of the mechanism. Based on this mechanism, a theoretical model of the IDMG falling edge is set up in which IDMG has an exponential attenuation relation with VDG. Finally, the critical fitting coefficient t of the experimental curves is extracted. It is found that t = 80 mV = 3kT/q. This result fully shows the accuracy of the above mechanism. Project supported by the National Natural Science Foundation of China (Grant No. 61306131) and the Research Project of Education Department of Shaanxi Province, China (Grant No. 2013JK1095).

  16. Barometric and magnetic observations of vertical acoustic resonance and resultant generation of field-aligned current associated with earthquakes

    NASA Astrophysics Data System (ADS)

    Iyemori, Toshihiko; Tanaka, Yoshikazu; Odagi, Yoko; Sano, Yasuharu; Takeda, Masahiko; Nose, Masahito; Utsugi, Mitsuru; Rosales, Domingo; Choque, Edwin; Ishitsuka, Jose; Yamanaka, Sadato; Nakanishi, Kunihito; Matsumura, Mitsuru; Shinagawa, Hiroyuki

    2013-08-01

    Three rare occasions are introduced, where the excitation of vertical acoustic resonance between the ground and the ionosphere, and the resultant generation of a field-aligned current, just after earthquakes are observationally confirmed. In the case of two inland earthquakes, barometric observations very close to the epicenters (i.e., only 30 km apart) were available, and they showed a sharp spectral peak which appeared within one hour after the origin time and lasted a few hours. The observed periods of the spectral peaks around 260 seconds are close to the period of the theoretically-expected fundamental mode of the resonance. On the other hand, magnetic observations on the ground showed a dominant period at 220-230 seconds which corresponds to the first overtone among theoretically-expected major resonance peaks. In the third case, i.e., during the 2010 Chile earthquake, a long-period magnetic oscillation in the east-west direction, which has two major resonance periods at 265 and 190-195 seconds, was observed on the night-side magnetic dip equator in Peru, where the distance is more than 2600 km from the epicenter, under a very quiet geomagnetic condition. The oscillation was interpreted as the effect of field-aligned current generated through a dynamo process in the ionosphere over the epicenter caused by the resonance.

  17. Space-charge effects in ultra-high current electron bunches generated by laser-plasma accelerators

    SciTech Connect

    Grinner, F. J.; Schroeder, C. B.; Maier, A. R.; Becker, S.; Mikhailova, J. M.

    2009-02-11

    Recent advances in laser-plasma accelerators, including the generation of GeV-scale electron bunches, enable applications such as driving a compact free-electron-laser (FEL). Significant reduction in size of the FEL is facilitated by the expected ultra-high peak beam currents (10-100 kA) generated in laser-plasma accelerators. At low electron energies such peak currents are expected to cause space-charge effects such as bunch expansion and induced energy variations along the bunch, potentially hindering the FEL process. In this paper we discuss a self-consistent approach to modeling space-charge effects for the regime of laser-plasma-accelerated ultra-compact electron bunches at low or moderate energies. Analytical treatments are considered as well as point-to-point particle simulations, including the beam transport from the laser-plasma accelerator through focusing devices and the undulator. In contradiction to non-self-consistent analyses (i.e., neglecting bunch evolution), which predict a linearly growing energy chirp, we have found the energy chirp reaches a maximum and decreases thereafter. The impact of the space-charge induced chirp on FEL performance is discussed and possible solutions are presented.

  18. Protein aggregates stimulate macropinocytosis facilitating their propagation.

    PubMed

    Yerbury, Justin J

    2016-03-01

    Temporal and spatial patterns of pathological changes such as loss of neurons and presence of pathological protein aggregates are characteristic of neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Frontotemporal Dementia, Alzheimer's disease and Parkinson's disease. These patterns are consistent with the propagation of protein misfolding and aggregation reminiscent of the prion diseases. There is a surge of evidence that suggests that large protein aggregates of a range of proteins are able to enter cells via macropinocytosis. Our recent work suggests that this process is activated by the binding of aggregates to the neuron cell surface. The current review considers the potential role of cell surface receptors in the triggering of macropinocytosis by protein aggregates and the possibility of utilizing macropinocytosis pathways as a therapeutic target. PMID:26963158

  19. Electron transfer capacity dependence of quinone-mediated Fe(III) reduction and current generation by Klebsiella pneumoniae L17.

    PubMed

    Li, Xiaomin; Liu, Liang; Liu, Tongxu; Yuan, Tian; Zhang, Wei; Li, Fangbai; Zhou, Shungui; Li, Yongtao

    2013-06-01

    Quinone groups in exogenous electron shuttles can accelerate extracellular electron transfer (EET) from bacteria to insoluble terminal electron acceptors, such as Fe(III) oxides and electrodes, which are important in biogeochemical redox processes and microbial electricity generation. However, the relationship between quinone-mediated EET performance and electron-shuttling properties of the quinones remains incompletely characterized. This study investigates the effects of a series of synthetic quinones (SQs) on goethite reduction and current generation by a fermenting bacterium Klebsiella pneumoniae L17. In addition, the voltammetric behavior and electron transfer capacities (ETCs) of SQ, including electron accepting (EAC) and donating (EDC) capacities, is also examined using electrochemical methods. The results showed that SQ can significantly increase both the Fe(III) reduction rates and current outputs of L17. Each tested SQ reversibly accepted and donated electrons as indicated by the cyclic voltammograms. The EAC and EDC results showed that Carmine and Alizarin had low relative capacities of electron transfer, whereas 9,10-anthraquinone-2,6-disulfonic acid (AQDS), 2-hydroxy-1,4-naphthoquinone (2-HNQ), and 5-hydroxy-1,4-naphthoquinone (5-HNQ) showed stronger relative ETC, and 9,10-anthraquinone-2-carboxylic acid (AQC) and 9,10-anthraquinone-2-sulfonic acid (AQS) had high relative ETC. Enhancement of microbial goethite reduction kinetics and current outputs by SQ had a good linear relationship with their ETC, indicating that the effectiveness of quinone-mediated EET may be strongly dependent on the ETC of the quinones. Therefore, the presence of quinone compounds and fermenting microorganisms may increase the diversity of microbial populations that contribute to element transformation in natural environments. Moreover, ETC determination of different SQ would help to evaluate their performance for microbial EET under anoxic conditions. PMID:23461838

  20. A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments

    NASA Astrophysics Data System (ADS)

    Wang, Guiji; Chen, Xuemiao; Cai, Jintao; Zhang, Xuping; Chong, Tao; Luo, Binqiang; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Liu, Cangli; Wu, Gang

    2016-06-01

    A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10-2 Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak

  1. A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments.

    PubMed

    Wang, Guiji; Chen, Xuemiao; Cai, Jintao; Zhang, Xuping; Chong, Tao; Luo, Binqiang; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Liu, Cangli; Wu, Gang

    2016-06-01

    A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10(-2) Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak

  2. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams.

    PubMed

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a approximately 450 kV, approximately 400 ns pulse. It was found that 300-400 MW, approximately 250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources. PMID:19256641

  3. Internal heating of lithium-ion batteries using alternating current based on the heat generation model in frequency domain

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbo; Ge, Hao; Li, Zhe; Ding, Zhanming

    2015-01-01

    This study develops a method to internally preheat lithium-ion batteries at low temperatures with sinusoidal alternating current (AC). A heat generation rate model in frequency domain is developed based on the equivalent electrical circuit. Using this model as the source term, a lumped energy conservation model is adopted to predict the temperature rise. These models are validated against the experimental results of preheating an 18650 cell at different thermal insulation conditions. The effects of current amplitude and frequency on the heating rate are illustrated with a series of simulated contours of heating time. These contours indicate that the heating rate increases with higher amplitude, lower frequency and better thermal insulation. The cell subjected to an alternating current with an amplitude of 7 A (2.25 C) and a frequency of 1 Hz, under a calibrated heat transfer coefficient of 15.9 W m-2 K-1, can be heated from -20 °C to 5 °C within 15 min and the temperature distribution remains essentially uniform. No capacity loss is found after repeated AC preheating tests, indicating this method incurs little damage to the battery health. These models are computationally-efficient and can be used in real time to control the preheating devices in electric vehicles.

  4. High Non-inductive Fraction H-mode Discharges Generated by High-harmonic Fast Wave Heating and Current Drive in the National Spherical Torus Experiment

    SciTech Connect

    Taylor, G.; Hosea, J.; Kessel, C. E.; LeBlanc, B; Mueller, D.; Phillips, C. K.; Valeo, E. J.; Wilson, J. R.; Ryan, Philip Michael; Bonoli, P.; Harvey, R. W.

    2012-01-01

    A deuterium H-mode discharge with a plasma current of 300 kA, an axial toroidal magnetic field of 0.55 T, and a calculated non-inductive plasma current fraction of 0.7 1 has been generated in the National Spherical Torus Experiment by 1.4MW of 30MHz high-harmonic fast wave (HHFW) heating and current drive. Seventy-five percent of the non-inductive current was generated inside an internal transport barrier that formed at a normalized minor radius 0.4. Three quarters of the non-inductive current was bootstrap current, and the remaining non-inductive current was generated directly by HHFW power inside a normalized minor radius 0.2. VC 2012 American Institute of Physics.

  5. Generations.

    PubMed

    Chambers, David W

    2005-01-01

    Groups naturally promote their strengths and prefer values and rules that give them an identity and an advantage. This shows up as generational tensions across cohorts who share common experiences, including common elders. Dramatic cultural events in America since 1925 can help create an understanding of the differing value structures of the Silents, the Boomers, Gen Xers, and the Millennials. Differences in how these generations see motivation and values, fundamental reality, relations with others, and work are presented, as are some applications of these differences to the dental profession. PMID:16623137

  6. Eddy-current inspection for steam generator tubing program. Annual progress report for period ending December 31, 1979

    SciTech Connect

    Dodd, C.V.; Deeds, W.E.; McClung, R.W.

    1980-07-01

    Eddy-current methods provide the best in-service inspection of steam generator tubing, but present techniques can produce ambiguity because of the many independent variables that affect the signals. The current development program has used mathematical models and developed or modified computer programs to design optimum probes, instrumentation, and techniques for multifrequency, multiproperty examinations. Interactive calculations and experimental measurements have been made with the use of modular eddy-current instrumentation and a minicomputer. These establish the coefficients for the complex equations that define the values of the desired properties (and the attainable accuracy) despite changes in other significant variables. The computer programs for calculating the accuracy with which various properties can be measured indicate that the tubing wall thickness and the defect size can be measured much more accurately than is currently required, even when other properties are varying. Our experimental measurements have confirmed these results, although more testing is needed for all the different combinations of cases and different types of defects. To facilitate the extensive laboratory scanning of the matrix of specimens that are necessary to develop algorithms for detection and analysis for all the possible combinations of positions of flaws, tube supports, and probe coils, we have designed, constructed, and begun operation of a computer-controlled automatic positioner. We have demonstrated the ability to overcome the large signals produced by the edge of the tube supports. An advanced microcomputer has been designed, constructed, and installed in the instrumentation to control the examination and provide real-time calculations of the desired properties for display recording during the scanning of the tube.

  7. Critical current density and ac harmonic voltage generation in YBaCuO thin films by the screening technique

    NASA Astrophysics Data System (ADS)

    Pérez-López, Israel O.; Gamboa, Fidel; Sosa, Víctor

    2010-12-01

    The temperature and field dependence of harmonics in voltage Vn=Vn‧-iVn″ using the screening technique have been measured for YBaCuO superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density Jc(T). In addition, we applied the criterion proposed by Acosta et al. to compute Jc(T). Also, we made used of the empirical law Jc∝(1-T/Tc)n as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.

  8. Laminar analysis of human neocortical interictal spike generation and propagation: current source density and multiunit analysis in vivo.

    PubMed

    Ulbert, Istvan; Heit, Gary; Madsen, Joseph; Karmos, George; Halgren, Eric

    2004-01-01

    Multicontact microelectrodes were chronically implanted in epilepsy patients undergoing subdural grid implantation for seizure localization. Current source density and multiple unit activity of interictal spikes (IISs) were sampled every approximately 150 microm in a line traversing all layers of a cortical column. Our data suggest that interictal epileptiform events in humans are initiated by large postsynaptic depolarizations, consistent with the hypothesis that human IISs correspond to animal paroxysmal depolarization shifts. Furthermore, the cortical layer where the initial depolarization occurs may differ according to whether the IIS is locally generated or propagated from a distant location, and among the propagated IISs, whether the IIS is in the direct path of propagation or on the periphery of that path. PMID:15281959

  9. Investigation of Frequency Mixing Techniques for Eddy Current Testing of Steam Generator Tubes in Nuclear Power Plants

    NASA Astrophysics Data System (ADS)

    Jung, H. J.; Kong, Y. B.; Song, S.-J.; Kim, C.-H.; Choi, Y. H.; Kang, S.-C.; Song, M. H.

    2007-03-01

    In eddy current testing (ECT) of steam generator tubes in nuclear power plants, it is very important to extract flaw signals from the signals compound by flaws and supporting structures. To perform such an important task, the multifrequency ECT methods are widely adopted since they have a well-known capability of extracting the flaw signal from the compound signals. Therefore, various frequency mixing algorithms have been proposed up to now. In the present work, two different frequency mixing algorithms, a time-domain optimization method and a discrete cosine transform (DCT) based optimization method, are investigated using experimental signals captured from a ASME standard tube. In this paper, we discuss the basic principles and the performances of these two frequency mixing techniques.

  10. Improving complex medical care while awaiting next-generation CFTR potentiators and correctors: The current pipeline of therapeutics.

    PubMed

    Goralski, Jennifer L; Davis, Stephanie D

    2015-10-01

    While a major target in cystic fibrosis (CF) research in recent years has been the development of corrector and potentiator drugs targeting the cystic fibrosis transmembrane conductance regulator (CFTR) protein, these therapies have not yet proven robust enough to replace or eliminate other therapies that have demonstrated improved health outcomes and quality of life in patients with CF. Further, ivacaftor is only indicated for approximately 5% of the US CF population, although the FDA has recently approved lumacaftor/ivacaftor, a combination therapy intended for those homozygous for Phe508del, which should reach a much larger number of patients. This review appraises therapeutics currently available or being studied while we await the next generation of CFTR potentiators and correctors. PMID:26335956

  11. Study of recovery characteristics of 2nd generation HTS tapes with different stabilizers for resistive type superconducting fault current limiters

    NASA Astrophysics Data System (ADS)

    Sheng, Jie; Zeng, Weina; Ma, Jun; Yao, Zhihao; Li, Zhuyong; Jin, Zhijian; Hong, Zhiyong

    2016-02-01

    The resistive type superconducting fault current limiter (SFCL) is one of the most important superconducting power applications nowadays. As known, this type of SFCL is settled directly in the power transmission line. When a short fault happens, the temperature of the superconductors in the SFCL will increase sharply due to the huge generated heat. This means the superconductors need time to recover the superconducting properties and be ready for the next short fault. So the recovery characteristics become one of the most crucial features of the resistive type SFCL. In this paper, several different kinds of measuring methods are presented to calculate the recovery time of the HTS tapes, and comparison of these methods is also carried out by a standard test. On basis of this, samples with different kinds of stabilizers are used to explore the influence of stabilizer on their recovery characteristics. In addition, the influence of the encapsulation technology is also discussed in this paper.

  12. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  13. Classification and Characterization of Therapeutic Antibody Aggregates

    PubMed Central

    Joubert, Marisa K.; Luo, Quanzhou; Nashed-Samuel, Yasser; Wypych, Jette; Narhi, Linda O.

    2011-01-01

    A host of diverse stress techniques was applied to a monoclonal antibody (IgG2) to yield protein particles with varying attributes and morphologies. Aggregated solutions were evaluated for percent aggregation, particle counts, size distribution, morphology, changes in secondary and tertiary structure, surface hydrophobicity, metal content, and reversibility. Chemical modifications were also identified in a separate report (Luo, Q., Joubert, M. K., Stevenson, R., Narhi, L. O., and Wypych, J. (2011) J. Biol. Chem. 286, 25134–25144). Aggregates were categorized into seven discrete classes, based on the traits described. Several additional molecules (from the IgG1 and IgG2 subtypes as well as intravenous IgG) were stressed and found to be defined with the same classification system. The mechanism of protein aggregation and the type of aggregate formed depends on the nature of the stress applied. Different IgG molecules appear to aggregate by a similar mechanism under the same applied stress. Aggregates created by harsh mechanical stress showed the largest number of subvisible particles, and the class generated by thermal stress displayed the largest number of visible particles. Most classes showed a disruption of the higher order structure, with the degree of disorder depending on the stress process. Particles in all classes (except thermal stress) were at least partially reversible upon dilution in pH 5 buffer. High copper content was detected in isolated metal-catalyzed aggregates, a stress previously shown to produce immunogenic aggregates. In conclusion, protein aggregates can be a very heterogeneous population, whose qualities are the result of the type of stress that was experienced. PMID:21454532

  14. Generation Of High Non-inductive Plasma Current Fraction H-mode Discharges By High-harmonic Last Wave Heating In The National Spherical Torus Experiment

    SciTech Connect

    Taylor, G; Kessel, C E; LeBlanc, B P; Mueller, D; Phillips, D K; Valeo, E J; Wilson, J R; Ryan, P M; Bonoli, P T; Wright, J C

    2012-02-13

    1.4 MW of 30 MHz high-harmonic fast wave (HHFW) heating, with current drive antenna phasing, has generated a Ip = 300kA, BT (0) = 0.55T deuterium H-mode plasma in the National Spherical Torus Experiment that has a non-inductive plasma current fraction, fNI = 0.7-1. Seventy-five percent of the non-inductive current was generated inside an internal transport barrier that formed at a normalized minor radius, r/a {approx} 0.4 . Three quarters of the non-inductive current was bootstrap current and the remaining non-inductive current was generated directly by HHFW power inside r/a {approx} 0.2.

  15. A pulsed eddy current probe for inspection of support plates from within Alloy-800 steam generator tubes

    SciTech Connect

    Krause, T. W.; Babbar, V. K.; Underhill, P. R.

    2014-02-18

    Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed eddy current (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.

  16. A pulsed eddy current probe for inspection of support plates from within Alloy-800 steam generator tubes

    NASA Astrophysics Data System (ADS)

    Krause, T. W.; Babbar, V. K.; Underhill, P. R.

    2014-02-01

    Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed eddy current (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.

  17. Protein Aggregates Are Recruited to Aggresome by Histone Deacetylase 6 via Unanchored Ubiquitin C Termini

    SciTech Connect

    Ouyang, Hui; Ali, Yousuf O.; Ravichandran, Mani; Dong, Aiping; Qiu, Wei; MacKenzie, Farrell; Dhe-Paganon, Sirano; Arrowsmith, Cheryl H.; Zhai, R. Grace

    2012-07-11

    The aggresome pathway is activated when proteasomal clearance of misfolded proteins is hindered. Misfolded polyubiquitinated protein aggregates are recruited and transported to the aggresome via the microtubule network by a protein complex consisting of histone deacetylase 6 (HDAC6) and the dynein motor complex. The current model suggests that HDAC6 recognizes protein aggregates by binding directly to polyubiquitinated proteins. Here, we show that there are substantial amounts of unanchored ubiquitin in protein aggregates with solvent-accessible C termini. The ubiquitin-binding domain (ZnF-UBP) of HDAC6 binds exclusively to the unanchored C-terminal diglycine motif of ubiquitin instead of conjugated polyubiquitin. The unanchored ubiquitin C termini in the aggregates are generated in situ by aggregate-associated deubiquitinase ataxin-3. These results provide structural and mechanistic bases for the role of HDAC6 in aggresome formation and further suggest a novel ubiquitin-mediated signaling pathway, where the exposure of ubiquitin C termini within protein aggregates enables HDAC6 recognition and transport to the aggresome.

  18. Coherence properties of the electric field generated by an incoherent source of currents distributed on the surface of a sphere.

    PubMed

    Zurita-Sánchez, Jorge R

    2016-01-01

    We derive analytical expressions of the cross-spectral density of the electric field arising from an incoherent source whose current density is located on the surface of a sphere. Our approach is based on the series expansion in terms of vector spherical harmonics of the electric field generated by the aforementioned current distribution. We analyze in detail the spectrum, the degree of coherence, and the degree of polarization of the electric field for all regions in space (from the near field to the far field). The relationship of the high-order harmonics to the coherence properties is discussed. The spectrum turns out to be isotropic and it is different from that of the source. We found that the degree of coherence and degree of polarization are strongly influenced by the size of the source. We show the appearance of special features: a zone with a high degree of coherence in the near field for a subwavelength source, the radial degree of coherence is nearly constant in an extended region where two radial points belong to the far field, and a particular radial distance for which the degree of polarization vanishes (3D unpolarized light). PMID:26831593

  19. Effects of surface charge and hydrophobicity on anodic biofilm formation, community composition, and current generation in bioelectrochemical systems.

    PubMed

    Guo, Kun; Freguia, Stefano; Dennis, Paul G; Chen, Xin; Donose, Bogdan C; Keller, Jurg; Gooding, J Justin; Rabaey, Korneel

    2013-07-01

    The focus of this study was to investigate the effects of surface charge and surface hydrophobicity on anodic biofilm formation, biofilm community composition, and current generation in bioelectrochemical systems (BESs). Glassy carbon surfaces were modified with -OH, -CH3, -SO3(-), or -N(+)(CH3)3 functional groups by electrochemical reduction of aryl diazonium salts and then used as anodes with poised potential of -0.2 V (vs Ag/AgCl). The average startup times and final current densities for the -N(+)(CH3)3, -OH, -SO3(-), and -CH3, electrodes were (23 d, 0.204 mA/cm(2)), (25.4 d, 0.149 mA/cm(2)), (25.9 d, 0.114 mA/cm(2)), and (37.2 d, 0.048 mA/cm(2)), respectively. Biofilms on different surfaces were analyzed by nonturnover cyclic voltammetry (CV), fluorescence in situ hybridization (FISH), and 16S rRNA gene amplicon pyrosequencing. The results demonstrated that 1) differences in the maximum current output between surface modifications was correlated with biomass quantity, and 2) all biofilms were dominated by Geobacter populations, but the composition of -CH3-associated biofilms differed from those formed on surfaces with different chemical modification. This study shows that anode surface charge and hydrophobicity influences biofilm development and can lead to significant differences in BESs performance. Positively charged and hydrophilic surfaces were more selective to electroactive microbes (e.g. Geobacter) and more conducive for electroactive biofilm formation. PMID:23745742

  20. Current response for a single redox moiety trapped in a closed generator-collector system: the role of capacitive coupling.

    PubMed

    Feldberg, Stephen W; Edwards, Martin A

    2015-04-01

    A theoretical model is proposed to describe the steady-state average limiting current associated with a single redox moiety (ox or red) trapped in a closed generator-collector system along with excess supporting electrolyte. By "closed" we mean that neither solvent nor solutes can enter or leave the system. The potential difference, EOE - ERE, between the oxidizing electrode (OE) and the reducing electrode (RE) is maintained constant with the values of EOE and ERE chosen so that the operative faradaic electrode processes are very fast, i.e., red = ox + nETe(-) (kox = ∞) at the OE and ox + nETe(-) = red (kred = ∞) at the RE. Because there is only a single redox moiety the faradaic process occurs at only one electrode at a time while current at the other electrode is purely capacitive (we refer to this as capacitive coupling). We propose that a two-step process is required to transfer nETqe coulombs (qe is the absolute value of the elemental electronic charge). The first step is associated with diffusion (approximated as a random walk) of a single red moiety to the OE where it is oxidized to ox with a concomitant transfer of qstep1 (= nETqe/(1 + AOECOE/ARECRE)) coulombs; the second step is associated with the diffusion (random walk) of the newly formed single ox moiety to the RE with the concomitant transfer of qstep2 (= nETqe/(1 + ARECRE/AOECOE)) coulombs (ARE,AOE andCRE,COEare the areas (cm(2)) and differential capacitances (farads cm(-2)) of the corresponding electrodes). The total charge transferred in the two steps is nETqe(= qstep1 + qstep2). Transport of the redox moiety from one electrode to the other is accomplished by a random walk. The probability density function (pdf) and cumulative density function (CDF) for the duration of a full redox cycle are presented as the analytical solution to a 1-dimensional bounded random-walk problem (confirmed by numerical simulation). These show that tfull, the average time for the full redox cycle (step 1 + step 2

  1. 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.

  2. Effects of tau domain-specific antibodies and intravenous immunoglobulin on tau aggregation and aggregate degradation.

    PubMed

    Esteves-Villanueva, Jose O; Trzeciakiewicz, Hanna; Loeffler, David A; Martić, Sanela

    2015-01-20

    Tau pathology, including neurofibrillary tangles, develops in Alzheimer's disease (AD). The aggregation and hyperphosphorylation of tau are potential therapeutic targets for AD. Administration of anti-tau antibodies reduces tau pathology in transgenic "tauopathy" mice; however, the optimal tau epitopes and conformations to target are unclear. Also unknown is whether intravenous immunoglobulin (IVIG) products, currently being evaluated in AD trials, exert effects on pathological tau. This study examined the effects of anti-tau antibodies targeting different tau epitopes and the IVIG Gammagard on tau aggregation and preformed tau aggregates. Tau aggregation was assessed by transmission electron microscopy and fluorescence spectroscopy, and the binding affinity of the anti-tau antibodies for tau was evaluated by enzyme-linked immunosorbent assays. Antibodies used were anti-tau 1-150 ("D-8"), anti-tau 259-266 ("Paired-262"), anti-tau 341-360 ("A-10"), and anti-tau 404-441 ("Tau-46"), which bind to tau's N-terminus, microtubule binding domain (MBD) repeat sequences R1 and R4, and the C-terminus, respectively. The antibodies Paired-262 and A-10, but not D-8 and Tau-46, reduced tau fibrillization and degraded preformed tau aggregates, whereas the IVIG reduced tau aggregation but did not alter preformed aggregates. The binding affinities of the antibodies for the epitope for which they were specific did not appear to be related to their effects on tau aggregation. These results confirm that antibody binding to tau's MBD repeat sequences may inhibit tau aggregation and indicate that such antibodies may also degrade preformed tau aggregates. In the presence of anti-tau antibodies, the resulting tau morphologies were antigen-dependent. The results also suggested the possibility of different pathways regulating antibody-mediated inhibition of tau aggregation and antibody-mediated degradation of preformed tau aggregates. PMID:25545358

  3. Online Intrusion Alert Aggregation Through Mobile

    NASA Astrophysics Data System (ADS)

    kumar, S. Magesh; Mohan, K.; Kadirvelu, G.; Muruganandam, S.

    2012-08-01

    Online Intrusion Alert Aggregation with Generative Data Stream Modeling is a generative modeling approach using probabilistic methods. Assuming that attack instances can be regarded as random processes ìproducingî alerts, we aim at modeling these processes using approximative maximum likelihood parameterestimation techniques. Thus, the beginning as well as the completion of attack instances can be detected. In the proposed scheme of Online Intrusion Alert Aggregation, we extend our idea of sending Intrusion alerts to the mobile. This makes the process easier and comfortable. Online Intrusion Alert Aggregation with Generative Data Stream Modeling does not degrade system performance as individual layers are independent and are trained with only a small number of features, thereby, resulting in an efficient system

  4. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  5. Active matter model of Myxococcus xanthus aggregation

    NASA Astrophysics Data System (ADS)

    Patch, Adam; Bahar, Fatmagul; Liu, Guannan; Thutupalli, Shashi; Welch, Roy; Yllanes, David; Shaevitz, Joshua; Marchetti, M. Cristina

    Myxococcus xanthus is a soil-dwelling bacterium that exhibits several fascinating collective behaviors including streaming, swarming, and generation of fruiting bodies. A striking feature of M. xanthus is that it periodically reverses its motility direction. The first stage of fruiting body formation is characterized by the aggregation of cells on a surface into round mesoscopic structures. Experiments have shown that this aggregation relies heavily on regulation of the reversal rate and local mechanical interactions, suggesting motility-induced phase separation may play an important role. We have adapted self-propelled particle models to include cell reversal and motility suppression resulting from sporulation observed in aggregates. Using 2D molecular dynamics simulations, we map the phase behavior in the space of Péclet number and local density and examine the kinetics of aggregation for comparison to experiments.

  6. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  7. Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

    SciTech Connect

    Silaev, A. A. Vvedenskii, N. V.

    2015-05-15

    When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a few-cycle laser pulse is developed for the first time. The dependences of the RCD on the carrier-envelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCD corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schrödinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization.

  8. Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

    NASA Astrophysics Data System (ADS)

    Silaev, A. A.; Vvedenskii, N. V.

    2015-05-01

    When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a few-cycle laser pulse is developed for the first time. The dependences of the RCD on the carrier-envelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCD corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schrödinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization.

  9. Low-level intermittent quadriceps activity during transcranial direct current stimulation facilitates knee extensor force-generating capacity.

    PubMed

    Washabaugh, Edward P; Santos, Luciana; Claflin, Edward S; Krishnan, Chandramouli

    2016-08-01

    Anodal transcranial direct current stimulation (tDCS) is known to increase the force-generating capacity of the skeletal muscles. However, when tDCS is concurrently combined with a motor task, interference may occur that hinders tDCS effects. Here, we tested the interaction and time course of tDCS effects on force production when paired with a low-level force-matching task. Twenty-two subjects were randomized into two groups: tDCS-Matching and tDCS-Resting. Each group received tDCS and a sham stimulation, separated by one week. Maximal knee extensor and flexor torques were measured before and up to twenty-five minutes following the stimulation. The tDCS-Matching group produced greater knee extension torques relative to sham when compared with the tDCS-Resting group. There was no significant effect for knee flexion. This suggests that interference does not occur for force production tasks when tDCS is combined with a motor task. Rather, the task appears to aid and isolate the effects to the muscle groups involved in the task. PMID:27138643

  10. Fractional diffusion analysis of the electromagnetic fields generated by a transient straight current source over a porous geological media

    NASA Astrophysics Data System (ADS)

    Ge, J.; Everett, M. E.; Weiss, C. J.

    2010-12-01

    An interpretation based on the Continuous Time Random Walk theory (CTRW) to the diffusion of electromagnetic fields generated by a transient straight current source over a porous geological media is presented here. The CTRW theory is demonstrated to be a powerful tool to concisely and more accurately model a transport process in a fractal medium with complex structures, comparing to the classical transport theory. In the controlled-source electromagnetic (EM) induction setting, the time dependent evolution of the EM field of some sources over a rough medium are governed by the fractional diffusion EM equation in a CTRW sense. The master equation can be solved for a uniform conducting half-space in the Laplace domain semi-analytically. We use 2D finite difference method to calculate the solution numerically for the assigned space and transform to time domain with Gaver-Stehfest algorithm. Here we adopt a spatially uniform roughness parameter β in the solution to characterize the complexity of the geoelectrical structure of the geological medium. To introduce the heterogeneity to our model, we set up the space as several 2 D blocks with different conductivities and βs. Then we compare our results with the synthetic data we got from the high resolution numerical simulations. We are able to show that by introducing the heterogeneity to the fractional diffusion perspective, our approach is competent for tracing the diffusion process with less model parameters.

  11. Current interruption and particle beam generation by a plasma focus. Interim report (annual), 30 Sep 81-30 Sep 82

    SciTech Connect

    Gerdin, G.; Venneri, F.

    1982-11-30

    Through collaboration with Dr. K. H. Schoenbach of Texas Tech University the plasma focus opening switch (PFOS) was revised to answer basic questions as to utility of the concept. To estimate the plasma temperature and classical resistivity a soft X-ray spectrometer and X-ray pinhole camera were developed. The temperature was estimated from a coronal model to range between 0.4 to 0.5 keV for either a nitrogen or neon impurity (1 to 2%) in deuterium at 3 torr. Strong pinches were observed in pure neon (0.6 torr) with an electron temperature in the same range. The corresponding classical resistance of the pinch is 9 m omega whereas 500 m omega is more consistent with output voltage pulse and current flow at interruption indicating anomalous resistivity is present. A one-dimensional two-fluid computer code has been developed to model anomalous resistivity in the pinch phase and preliminary results are consistent with the snowplow model. The final analysis of the plasma focus particle beam generation experiments was completed and a strong correlation was found for the beam-target model as the mechanism for neutron production in the Illinois plasma focus device.

  12. Ontology-based aggregation of biological pathway datasets.

    PubMed

    Jiang, Keyuan; Nash, Christopher

    2005-01-01

    The massive accumulation of biological data in the past decades has generated a significant amount of biological knowledge which is represented in one way as biological pathways. The existence of over 150 pathway databases reflects the diversity of the biological data and heterogeneity of data models, storage formats and access methods. To address an intriguing biological question, it is not uncommon for a biologist to query more one pathway database to acquire a more complete picture of current understanding of biology. To facility life scientists in searching biological pathway data, we designed a biological pathway aggregator which aggregates various pathway datasets via the BioPAX ontology, a community-developed ontology based upon the concept of Semantic Web for integrating and exchanging biological pathway data. Our aggregator is composed of modules that retrieve the data from various sources, transform the raw data to BioPAX format, persist the converted data in the persistent data store, and enable queries by other applications. PMID:17282076

  13. Variable Speed Wind Power Generation System Using Direct Torque Control Suited for Maximum Power Control within Voltage and Current Limitations of Converter

    NASA Astrophysics Data System (ADS)

    Inoue, Yukinori; Morimoto, Shigeo; Sanada, Masayuki

    This paper proposes a variable speed wind generation system using a direct torque controlled interior permanent magnet synchronous generator. The proposed system has no wind speed and generator position sensors, and thus, it is considered that the proposed system has cost and reliability advantages. The proposed direct torque control (DTC) system in wind power generation has several advantages over conventional current control. First, DTC is well suited for the maximum power point tracking (MPPT) control that is implemented by controlling the generator torque. Second, the method of flux-weakening to maintain the terminal voltage at the limiting value of the converter is simple. Finally, a novel method is proposed for torque limiting, which makes it easy to maintain the armature current at the limiting value. The proposed method accomplishes current limiting using the reactive torque, which is calculated as the inner product of the flux and current. This does not require generator parameters such as magnet flux and inductances. Experimental results demonstrate the effectiveness of the proposed system using a wind turbine emulator instead of the actual wind turbine.

  14. Concrete Waste Recycling Process for High Quality Aggregate

    SciTech Connect

    Ishikura, Takeshi; Fujii, Shin-ichi

    2008-01-15

    Large amount of concrete waste generates during nuclear power plant (NPP) dismantling. Non-contaminated concrete waste is assumed to be disposed in a landfill site, but that will not be the solution especially in the future, because of decreasing tendency of the site availability and natural resources. Concerning concrete recycling, demand for roadbeds and backfill tends to be less than the amount of dismantled concrete generated in a single rural site, and conventional recycled aggregate is limited of its use to non-structural concrete, because of its inferior quality to ordinary natural aggregate. Therefore, it is vital to develop high quality recycled aggregate for general uses of dismantled concrete. If recycled aggregate is available for high structural concrete, the dismantling concrete is recyclable as aggregate for industry including nuclear field. Authors developed techniques on high quality aggregate reclamation for large amount of concrete generated during NPP decommissioning. Concrete of NPP buildings has good features for recycling aggregate; large quantity of high quality aggregate from same origin, record keeping of the aggregate origin, and little impurities in dismantled concrete such as wood and plastics. The target of recycled aggregate in this development is to meet the quality criteria for NPP concrete as prescribed in JASS 5N 'Specification for Nuclear Power Facility Reinforced Concrete' and JASS 5 'Specification for Reinforced Concrete Work'. The target of recycled aggregate concrete is to be comparable performance with ordinary aggregate concrete. The high quality recycled aggregate production techniques are assumed to apply for recycling for large amount of non-contaminated concrete. These techniques can also be applied for slightly contaminated concrete dismantled from radiological control area (RCA), together with free release survey. In conclusion: a technology on dismantled concrete recycling for high quality aggregate was developed

  15. X-pinch source of subnanosecond soft X-ray pulses based on small-sized low-inductance current generator

    SciTech Connect

    Mesyats, G. A.; Shelkovenko, T. A.; Ivanenkov, G. V.; Agafonov, A. V.; Savinov, S. Yu.; Pikuz, S. A.; Tilikin, I. N.; Tkachenko, S. I.; Chaikovskii, S. A.; Ratakhin, N. A.; Fedushchak, V. F.; Oreshkin, V. I.; Fedyunin, A. V.; Russkikh, A. G.; Labetskaya, N. A.; Artemov, A. P.; Hammer, D. A.; Sinars, D. B.

    2010-09-15

    For the first time, the regime of a micrometer-size hot spot formation is impemented for an X-pinch in a plasma, which is fed from a current generator based on low-inductance capacitors and rapid current switches. The configurations of X-pinches, which can be used effectively as point sources of soft X-rays with this type of current generator, are determined. A prototype of a small-size radiation source for high-resolution point projection X-ray radiography has been constructed. The main parameters of X-pinch as a radiation source are analyzed and compared with X-pinch parameters in high-voltage setups with shaping lines. An analysis of the data on the operation of X-pinches in generators with different parameters has led to simple relations that can be used to select optimal initial X-pinch parameters.

  16. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  17. Lateral current generation in n-AlGaAs/GaAs heterojunction channels by Schottky-barrier gate illumination

    SciTech Connect

    Kawazu, Takuya; Noda, Takeshi; Sakuma, Yoshiki; Sakaki, Hiroyuki

    2015-01-12

    We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate.

  18. Modeling and visualization of carrier motion in organic films by optical second harmonic generation and Maxwell-displacement current

    NASA Astrophysics Data System (ADS)

    Iwamoto, Mitsumasa; Manaka, Takaaki; Taguchi, Dai

    2015-09-01

    The probing and modeling of carrier motions in materials as well as in electronic devices is a fundamental research subject in science and electronics. According to the Maxwell electromagnetic field theory, carriers are a source of electric field. Therefore, by probing the dielectric polarization caused by the electric field arising from moving carriers and dipoles, we can find a way to visualize the carrier motions in materials and in devices. The techniques used here are an electrical Maxwell-displacement current (MDC) measurement and a novel optical method based on the electric field induced optical second harmonic generation (EFISHG) measurement. The MDC measurement probes changes of induced charge on electrodes, while the EFISHG probes nonlinear polarization induced in organic active layers due to the coupling of electron clouds of molecules and electro-magnetic waves of an incident laser beam in the presence of a DC field caused by electrons and holes. Both measurements allow us to probe dynamical carrier motions in solids through the detection of dielectric polarization phenomena originated from dipolar motions and electron transport. In this topical review, on the basis of Maxwell’s electro-magnetism theory of 1873, which stems from Faraday’s idea, the concept for probing electron and hole transport in solids by using the EFISHG is discussed in comparison with the conventional time of flight (TOF) measurement. We then visualize carrier transit in organic devices, i.e. organic field effect transistors, organic light emitting diodes, organic solar cells, and others. We also show that visualizing an EFISHG microscopic image is a novel way for characterizing anisotropic carrier transport in organic thin films. We also discuss the concept of the detection of rotational dipolar motions in monolayers by means of the MDC measurement, which is capable of probing the change of dielectric spontaneous polarization formed by dipoles in organic monolayers. Finally we

  19. A comparison of thermal zone aggregation methods

    SciTech Connect

    Dobbs, Justin R.; Hencey, Brandon M.

    2012-12-10

    The impact of increasing energy prices on building operation budgets has fueled demand for more energy-efficient structures. Existing building energy simulation tools generate an immense amount of data yet comparatively little knowledge. This paper introduces a framework that allows aggregation-based model reduction to operate on geometric building information models. The resulting aggregation sequence provides designers with faster simulations and affords insight into complex multi-scale thermal interactions. A comparison of the trade-off between simulation speed and accuracy for three hierarchical cluster partitioning methods concludes the discussion.

  20. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... same floodplain, and are currently under review by the Department (or by a grant recipient subject to 24 CFR part 58), individual or aggregated approvals may be issued. A single compliance review and... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.24...

  1. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... same floodplain, and are currently under review by the Department (or by a grant recipient subject to 24 CFR part 58), individual or aggregated approvals may be issued. A single compliance review and... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.24...

  2. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... same floodplain, and are currently under review by the Department (or by a grant recipient subject to 24 CFR part 58), individual or aggregated approvals may be issued. A single compliance review and... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.24...

  3. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... same floodplain, and are currently under review by the Department (or by a grant recipient subject to 24 CFR part 58), individual or aggregated approvals may be issued. A single compliance review and... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.24...

  4. 24 CFR 55.24 - Aggregation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., require compliance with subpart C of this part, affect the same floodplain or wetland, and are currently under review by HUD (or by a responsible entity authorized by 24 CFR part 58), individual or aggregated... FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS Procedures for Making Determinations on...

  5. Aggregates, broccoli and cauliflower

    NASA Astrophysics Data System (ADS)

    Grey, Francois; Kjems, Jørgen K.

    1989-09-01

    Naturally grown structures with fractal characters like broccoli and cauliflower are discussed and compared with DLA-type aggregates. It is suggested that the branching density can be used to characterize the growth process and an experimental method to determine this parameter is proposed.

  6. Generation of super-size macroparticles in a direct current vacuum arc discharge from a Mo-Cu cathode

    NASA Astrophysics Data System (ADS)

    Zhirkov, Igor; Petruhins, Andrejs; Polcik, Peter; Kolozsvári, Szilard; Rosen, Johanna

    2016-02-01

    An inherent property of cathodic arc is the generation of macroparticles, of a typical size ranging from submicrometer up to a few tens of μm. In this work, we have studied macroparticle generation from a Mo0.78Cu0.22 cathode used in a dc vacuum arc discharge, and we present evidence for super-size macroparticles of up to 0.7 mm in diameter. All analyzed particles are found to be rich in Mo (≥98 at. %). The particle generation is studied by visual observation of the cathode surface during arcing, by analysis of composition and geometrical features of the used cathode surface, and by examination of the generated macroparticles with respect to shape and composition. A mechanism for super-size macroparticle generation is suggested based on observed segregated layers of Mo and Cu identified in the topmost part of the cathode surface, likely due to the discrepancy in melting and evaporation temperatures of Mo and Cu. The results are of importance for increasing the fundamental understanding of macroparticle generation, which in turn may lead to increased process control and potentially provide paths for tuning, or even mitigating, macroparticle generation.

  7. Protein aggregate turbidity: Simulation of turbidity profiles for mixed-aggregation reactions.

    PubMed

    Hall, Damien; Zhao, Ran; Dehlsen, Ian; Bloomfield, Nathaniel; Williams, Steven R; Arisaka, Fumio; Goto, Yuji; Carver, John A

    2016-04-01

    Due to their colloidal nature, all protein aggregates scatter light in the visible wavelength region when formed in aqueous solution. This phenomenon makes solution turbidity, a quantity proportional to the relative loss in forward intensity of scattered light, a convenient method for monitoring protein aggregation in biochemical assays. Although turbidity is often taken to be a linear descriptor of the progress of aggregation reactions, this assumption is usually made without performing the necessary checks to provide it with a firm underlying basis. In this article, we outline utilitarian methods for simulating the turbidity generated by homogeneous and mixed-protein aggregation reactions containing fibrous, amorphous, and crystalline structures. The approach is based on a combination of Rayleigh-Gans-Debye theory and approximate forms of the Mie scattering equations. PMID:26763936

  8. Enhancing Therapeutic Efficacy through Designed Aggregation of Nanoparticles

    PubMed Central

    Sadhukha, Tanmoy; Wiedmann, Timothy Scott; Panyama, Jayanth

    2015-01-01

    Particle size is a key determinant of biological performance of sub-micron size delivery systems. Previous studies investigating the effect of particle size have primarily focused on well-dispersed nanoparticles. However, inorganic nanoparticles are prone to aggregation in biological environments. In our studies, we examined the consequence of aggregation on superparamagnetic iron oxide (SPIO) nanoparticle-induced magnetic hyperthermia. Here we show that the extent and mechanism of hyperthermia-induced cell kill is highly dependent on the aggregation state of SPIO nanoparticles. Well-dispersed nanoparticles induced apoptosis, similar to that observed with conventional hyperthermia. Sub-micron size aggregates, on the other hand, induced temperature-dependent autophagy through generation of oxidative stress. Micron size aggregates caused rapid membrane damage, resulting in acute cell kill. Overall, this work highlights the potential for developing highly effective anticancer therapeutics through designed aggregation of nano delivery systems. PMID:24947232

  9. Volcanic ash aggregation in the lab - can we mimic natural processes?

    NASA Astrophysics Data System (ADS)

    Mueller, Sebastian B.; Kueppers, Ulrich; Jacob, Michael; Ayris, Paul; Cimarelli, Corrado; Dingwell, Donald B.; Guttzeit, Melanie; Hess, Kai-Uwe; Walter, Ulrich

    2015-04-01

    Explosive volcanic eruptions release large amounts of particles into the atmosphere. Volcanic ash, by definition pyroclasts smaller than 2 mm, can be distributed around the globe by prevailing winds. Ash poses hazards to aviation industry by melting in jet turbines, to human health by entering respiration systems and to society by damaging infrastructure. Under certain circumstances, ash particles can cluster together and build ash aggregates. Aggregates range in size from few mm to few cm and may exhibit complex internal stratigraphy. During growth, weight, density and aerodynamic properties change, leading to a significantly different settling behavior compared to individual ash particles. Although ash aggregation has been frequently observed in the geologic record, the physical and chemical mechanisms generating the aggregates remain poorly understood. During several field campaigns, we collected numerous ash aggregates and analyzed their textural, chemical and mechanical properties. Based on this knowledge, we have designed experiments using the ProCell Lab System® of Glatt Ingenieurtechnik GmbH, Germany. In this device, a continuous fluidized bed can be applied on solid particles and simulate gas-particle flow conditions as they would be expected in volcanic plumes or pyroclastic density currents. The geological record and direct observations have shown that both processes are capable of producing ash aggregates. As starting material we used Na-glass beads as an analogue and volcanic ash from Laacher See Volcano, Eifel Volcanic Field, Germany. We define parameters such as grainsize, specific surface area and concentration of the starting material, degree of turbulence, temperature and moisture in the process chamber and the composition of the liquid phase to influence form, size, stability and production rate of aggregates. We were able to experimentally produce round, unstructured ash pellets up to 5mm in diameter. A detailed textural description highlights

  10. Aggregation Trade Offs in Family Based Recommendations

    NASA Astrophysics Data System (ADS)

    Berkovsky, Shlomo; Freyne, Jill; Coombe, Mac

    Personalized information access tools are frequently based on collaborative filtering recommendation algorithms. Collaborative filtering recommender systems typically suffer from a data sparsity problem, where systems do not have sufficient user data to generate accurate and reliable predictions. Prior research suggested using group-based user data in the collaborative filtering recommendation process to generate group-based predictions and partially resolve the sparsity problem. Although group recommendations are less accurate than personalized recommendations, they are more accurate than general non-personalized recommendations, which are the natural fall back when personalized recommendations cannot be generated. In this work we present initial results of a study that exploits the browsing logs of real families of users gathered in an eHealth portal. The browsing logs allowed us to experimentally compare the accuracy of two group-based recommendation strategies: aggregated group models and aggregated predictions. Our results showed that aggregating individual models into group models resulted in more accurate predictions than aggregating individual predictions into group predictions.

  11. Organic carbon, water repellency and soil stability to slaking at aggregate and intra-aggregate scales

    NASA Astrophysics Data System (ADS)

    Jordán López, Antonio; García-Moreno, Jorge; Gordillo-Rivero, Ángel J.; Zavala, Lorena M.; Cerdà, Artemi; Alanís, Nancy; Jiménez-Compán, Elizabeth

    2015-04-01

    Water repellency (WR) is a property of some soils that inhibits or delays water infiltration between a few seconds and days or weeks. Inhibited or delayed infiltration contributes to ponding and increases runoff flow generation, often increasing soil erosion risk. In water-repellent soils, water infiltrates preferentially through cracks or macropores, causing irregular soil wetting patterns, the development of preferential flow paths and accelerated leaching of nutrients. Although low inputs of hydrophobic organic substances and high mineralization rates lead to low degrees of WR in cropped soils, it has been reported that conservative agricultural practices may induce soil WR. Although there are many studies at catchment, slope or plot scales very few studies have been carried out at particle or aggregate scale. Intra-aggregate heterogeneity of physical, biological and chemical properties conditions the transport of substances, microbial activity and biochemical processes, including changes in the amount, distribution and chemical properties of organic matter. Some authors have reported positive relationships between soil WR and aggregate stability, since it may delay the entry of water into aggregates, increase structural stability and contribute to reduce soil erosion risk. Organic C (OC) content, aggregate stability and WR are therefore strongly related parameters. In the case of agricultural soils, where both the type of management as crops can influence all these parameters, it is important to evaluate the interactions among them and their consequences. Studies focused on the intra-aggregate distribution of OC and WR are necessary to shed light on the soil processes at a detailed scale. It is extremely important to understand how the spatial distribution of OC in soil aggregates can protect against rapid water entry and help stabilize larger structural units or lead to preferential flow. The objectives of this research are to study [i] the OC content and the

  12. Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

    NASA Astrophysics Data System (ADS)

    Garanin, S. G.; Ivanovskiy, A. V.

    2015-12-01

    The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

  13. Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

    SciTech Connect

    Garanin, S. G.; Ivanovskiy, A. V.

    2015-12-15

    The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

  14. Ground-Based Experiment of Current Collection to Bare Tether in High-Speed and High-Density Plasma Generated by Hall Thrusters

    SciTech Connect

    Kohori, Tatsuya; Ikeda, Tomoyuki; Shimizu, Masaharu; Takagi, Hiroki; Yamada, Minetsugu; Tahara, Hirokazu

    2008-12-31

    Bare-tether systems are one of the greatest-efficiency electrodynamic tethered systems. The system with an uninsulated portion of the metallic tether itself to collect electrons from the space plasma is operated as a thruster or a power generator on a satellite. Ground-based experiments were carried out to understand phenomena of electron collection by a bare tether in space. Metallic tether samples were exposed to a simulating Low-Earth-Orbit plasma flow as varying tether sample diameter and length, and plasma velocity. A magnetic field was also applied. The normalized collection current increased with normalized tether sample potential. The tether sample diameter did not influence the normalized collection current characteristics although an increase in tether sample length decreased the normalized collection current in this experiment. The collection current characteristics were independent of plasma velocity under meso-thermal conditions. The existence of magnetic field raised the collection current because of the three-dimensional current collection effect at the edge of a tether sample under the magnetic field. Although the existence of magnetic field may raise the collection current, the effect will be small with a long tether. Accordingly, the dependence of tether diameter and length, plasma velocity and magnetic field on collection current characteristics of a bare tether in space might be small. The collection current may not exceed the OML current.

  15. Investigation of parameters of the three phase high-voltage alternating current plasma generator with power up to 100 kW working on steam

    NASA Astrophysics Data System (ADS)

    Rutberg, Ph G.; Lukyanov, S. A.; Kiselev, A. A.; Kuschev, S. A.; Nakonechny, Gh V.; Nikonov, A. V.; Popov, S. D.; Serba, E. O.; Spodobin, V. A.; Surov, A. V.

    2011-01-01

    The paper presents the results of experimental investigation of parameters of the three-phase high voltage alternating current plasma generator with power up to 100 kW operating on steam with gas protection of the electrodes. Researches were carried out over a range of arc current from 25 to 50 A and range of steam consumption of 3-5 g/s. Current-voltage and volt consumable characteristics, operation oscillograms and dependence of power versus the flow rate of steam and protective gas are presented.

  16. Sectoral shifts and aggregate unemployment

    SciTech Connect

    Loungani, P.

    1986-01-01

    Some recent research has taken the view that sectoral or industry-specific shocks significantly affect aggregate unemployment by increasing the amount of inter-industry labor reallocation required. The empirical evidence for this view rests on the finding that during the 1950s - and again during the 1970s - there was a positive correlation between aggregate unemployment and the dispersion of employment growth rates. This thesis demonstrates that this correlation arises largely because oil price shocks affect both unemployment and the dispersion of employment growth. Once the dispersion due to oil shocks is accounted for, the residual dispersion in employment has very low explanatory power for unemployment. Since the dispersion index does not measure pure sectoral shifts, an alternate measure of dispersion is developed that serves as a better proxy for the amount of inter-industry labor reallocation required each period. Estimates using this measure suggest that, during the 1950s, temporary increases in the relative price of oil were responsible for generating the observed correlation. On the other hand, sectoral shifts were important during the 1970s; in particular, the 1973 oil price increase has had significant reallocative effects on the economy. This contention is subjected to further tests by looking at the time-series behavior of employment in durable-goods industries and also by following the inter-industry movements of workers over time through the use of panel data.

  17. A theory of field-aligned current generation from the plasma sheet and the poleward expansion of aurora sub-storms

    SciTech Connect

    Yamauchi, Masatoshi.

    1990-01-01

    Generation of field-aligned currents in the plasma sheet in terms of magnetosphere-ionosphere coupling was studied. The plasma sheet and the ionosphere were treated as two-dimensional layers by height integration. In the magnetosphere between them, the Alfven-wave transition time through this region is assumed to be zero. The ionospheric momentum is allowed to be transferred to the plasma sheet. Both linear analyses and numerical simulation are performed to study the field-aligned current generation. In the linear analysis, evolution from initial perturbations is studied. Zero-order configurations are steady state without field-aligned currents. The field-aligned currents are treated as a perturbed quantity and linearly related with the other perturbed quantities. One result for the linear waves is that the magnetohydrodynamics (MHD) fast mode and Alfven mode are coupled through the ionospheric Hall current. The Hall current causes the dawn-dusk asymmetry: a westward-travelling wave is amplified on the region 1 current system, while an eastward-travelling wave is amplified elsewhere. The expansion phase of the magnetospheric substorm after the onset is numerically simulated on the near-earth plasma sheet.

  18. Role of Carbonyl Modifications on Aging-Associated Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Tanase, Maya; Urbanska, Aleksandra M.; Zolla, Valerio; Clement, Cristina C.; Huang, Liling; Morozova, Kateryna; Follo, Carlo; Goldberg, Michael; Roda, Barbara; Reschiglian, Pierluigi; Santambrogio, Laura

    2016-01-01

    Protein aggregation is a common biological phenomenon, observed in different physiological and pathological conditions. Decreased protein solubility and a tendency to aggregate is also observed during physiological aging but the causes are currently unknown. Herein we performed a biophysical separation of aging-related high molecular weight aggregates, isolated from the bone marrow and splenic cells of aging mice and followed by biochemical and mass spectrometric analysis. The analysis indicated that compared to younger mice an increase in protein post-translational carbonylation was observed. The causative role of these modifications in inducing protein misfolding and aggregation was determined by inducing carbonyl stress in young mice, which recapitulated the increased protein aggregation observed in old mice. Altogether our analysis indicates that oxidative stress-related post-translational modifications accumulate in the aging proteome and are responsible for increased protein aggregation and altered cell proteostasis.

  19. Role of Carbonyl Modifications on Aging-Associated Protein Aggregation

    PubMed Central

    Tanase, Maya; Urbanska, Aleksandra M.; Zolla, Valerio; Clement, Cristina C.; Huang, Liling; Morozova, Kateryna; Follo, Carlo; Goldberg, Michael; Roda, Barbara; Reschiglian, Pierluigi; Santambrogio, Laura

    2016-01-01

    Protein aggregation is a common biological phenomenon, observed in different physiological and pathological conditions. Decreased protein solubility and a tendency to aggregate is also observed during physiological aging but the causes are currently unknown. Herein we performed a biophysical separation of aging-related high molecular weight aggregates, isolated from the bone marrow and splenic cells of aging mice and followed by biochemical and mass spectrometric analysis. The analysis indicated that compared to younger mice an increase in protein post-translational carbonylation was observed. The causative role of these modifications in inducing protein misfolding and aggregation was determined by inducing carbonyl stress in young mice, which recapitulated the increased protein aggregation observed in old mice. Altogether our analysis indicates that oxidative stress-related post-translational modifications accumulate in the aging proteome and are responsible for increased protein aggregation and altered cell proteostasis. PMID:26776680

  20. Generation of low-frequency nonlinear currents in plasma by an ultrashort pulse of high-frequency radiation

    SciTech Connect

    Grishkov, V. E.; Uryupin, S. A.

    2015-07-15

    A kinetic theory of low-frequency currents induced in plasma by an ultrashort high-frequency radiation pulse is developed. General expressions for the currents flowing along the propagation direction of the pulse and along the gradient of the field energy density are analyzed both analytically and numerically for pulse durations longer or shorter than or comparable with the electron collision time in plasma. It is demonstrated that the nonlinear current flowing along the gradient of the field energy density can be described correctly only when the modification of the isotropic part of the electron distribution function is taken into account.

  1. Currents produced by explosive driven transverse shock wave ferromagnetic source of primary power in a coaxial single-turn seeding coil of a magnetocumulative generator

    NASA Astrophysics Data System (ADS)

    Shkuratov, Sergey I.; Talantsev, Evgueni F.; Dickens, James C.; Kristiansen, Magne

    2003-04-01

    Experimental and digital simulation studies of the generation of seed currents by an ultracompact (8.66-8.75 cm3 in volume) ferromagnetic explosive-driven generator of primary power (FMG) loaded on the coaxial single-turn seeding coil of a magnetocumulative generator (MCG) have been performed. The operation of the FMG is based on transverse shock wave demagnetization of Nd2Fe14B high-energy hard ferromagnets. The FMG is capable of producing in the coaxial seeding coil of MCG a seed current with peak amplitude I(t)max=3.0 kA and full width at half maximum of 60 μs. The methodology was developed for digital simulation of the seeding processes in the combined FMG/MCG system.

  2. A Study on the Observation of Direct Lightning Current through the Wind Turbine Generator System in the Coast of the Japan Sea

    NASA Astrophysics Data System (ADS)

    Shiraishi, Yasuhiro; Otsuka, Takahiro; Matsuura, Hideki

    As clean energy that solves energy resources, many wind turbine generator systems have developed up to now, in Japan. The generation capacity of wind power is above 1 million kW, and the construction also continues from now on. The wind turbine generator systems are built in the good place of the wind condition, and those many are built on the coast of the Japan Sea. However, the coast of the Japan Sea is known as a place with much winter lightning, and wind turbine generator systems also often suffer the damage by winter lightning. The authors observed the lightning current that strikes through the wind turbine generator systems directly, in order to establish on the lightning protection of them. The authors acquired dozens of data as a result of observation in Akita Japan for 17 months. Based on these data, some considerations were performed about the performance of winter lightning that struck through the wind turbine generator systems. As the result of consideration, we found some interesting knowledge following sentence. It made clear anew that the tower which is a place of high position from the ground and on the windward has much number of lightning flash and many total flash charges. The lightning stroke current divided the tower pipe and ground leads. About 70% of the observed lightning current flowed to the tower pipe, and about 30% is divided into two grounding leads connected to the leg of tower. All of steep current that is on a wave front flow a tower side, it dose not flow to a grounding leads side. The distributions of lightning parameters between our observation results and past one are in good conformity.

  3. Design of a high-current low-energy beam transport line for an intense D-T/D-D neutron generator

    NASA Astrophysics Data System (ADS)

    Lu, Xiaolong; Wang, Junrun; Zhang, Yu; Li, Jianyi; Xia, Li; Zhang, Jie; Ding, Yanyan; Jiang, Bing; Huang, Zhiwu; Ma, Zhanwen; Wei, Zheng; Qian, Xiangping; Xu, Dapeng; Lan, Changlin; Yao, Zeen

    2016-03-01

    An intense D-T/D-D neutron generator is currently being developed at the Lanzhou University. The Cockcroft-Walton accelerator, as a part of the neutron generator, will be used to accelerate and transport the high-current low-energy beam from the duoplasmatron ion source to the rotating target. The design of a high-current low-energy beam transport (LEBT) line and the dynamics simulations of the mixed beam were carried out using the TRACK code. The results illustrate that the designed beam line facilitates smooth transportation of a deuteron beam of 40 mA, and the number of undesired ions can be reduced effectively using two apertures.

  4. Bed bug aggregation pheromone finally identified.

    PubMed

    Gries, Regine; Britton, Robert; Holmes, Michael; Zhai, Huimin; Draper, Jason; Gries, Gerhard

    2015-01-19

    Bed bugs have become a global epidemic and current detection tools are poorly suited for routine surveillance. Despite intense research on bed bug aggregation behavior and the aggregation pheromone, which could be used as a chemical lure, the complete composition of this pheromone has thus far proven elusive. Here, we report that the bed bug aggregation pheromone comprises five volatile components (dimethyl disulfide, dimethyl trisulfide, (E)-2-hexenal, (E)-2-octenal, 2-hexanone), which attract bed bugs to safe shelters, and one less-volatile component (histamine), which causes their arrestment upon contact. In infested premises, a blend of all six components is highly effective at luring bed bugs into traps. The trapping of juvenile and adult bed bugs, with or without recent blood meals, provides strong evidence that this unique pheromone bait could become an effective and inexpensive tool for bed bug detection and potentially their control. PMID:25529634

  5. Lanosterol reverses protein aggregation in cataracts.

    PubMed

    Zhao, Ling; Chen, Xiang-Jun; Zhu, Jie; Xi, Yi-Bo; Yang, Xu; Hu, Li-Dan; Ouyang, Hong; Patel, Sherrina H; Jin, Xin; Lin, Danni; Wu, Frances; Flagg, Ken; Cai, Huimin; Li, Gen; Cao, Guiqun; Lin, Ying; Chen, Daniel; Wen, Cindy; Chung, Christopher; Wang, Yandong; Qiu, Austin; Yeh, Emily; Wang, Wenqiu; Hu, Xun; Grob, Seanna; Abagyan, Ruben; Su, Zhiguang; Tjondro, Harry Christianto; Zhao, Xi-Juan; Luo, Hongrong; Hou, Rui; Perry, J Jefferson P; Gao, Weiwei; Kozak, Igor; Granet, David; Li, Yingrui; Sun, Xiaodong; Wang, Jun; Zhang, Liangfang; Liu, Yizhi; Yan, Yong-Bin; Zhang, Kang

    2015-07-30

    The human lens is comprised largely of crystallin proteins assembled into a highly ordered, interactive macro-structure essential for lens transparency and refractive index. Any disruption of intra- or inter-protein interactions will alter this delicate structure, exposing hydrophobic surfaces, with consequent protein aggregation and cataract formation. Cataracts are the most common cause of blindness worldwide, affecting tens of millions of people, and currently the only treatment is surgical removal of cataractous lenses. The precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown. Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cyclization reaction of a cholesterol synthesis pathway. Here we identify two distinct homozygous LSS missense mutations (W581R and G588S) in two families with extensive congenital cataracts. Both of these mutations affect highly conserved amino acid residues and impair key catalytic functions of LSS. Engineered expression of wild-type, but not mutant, LSS prevents intracellular protein aggregation of various cataract-causing mutant crystallins. Treatment by lanosterol, but not cholesterol, significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. We further show that lanosterol treatment could reduce cataract severity and increase transparency in dissected rabbit cataractous lenses in vitro and cataract severity in vivo in dogs. Our study identifies lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment. PMID:26200341

  6. Proteins aggregation and human diseases

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2015-04-01

    Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

  7. New-generation empirical magnetic field models: Increasing resolution of equatorial and Birkeland currents and transition from modeling to nowcasting

    NASA Astrophysics Data System (ADS)

    Stephens, G. K.; Sitnov, M. I.; Redmon, R. J.

    2015-12-01

    Classical empirical geomagnetic field models were built using rigid electric current modules whose amplitude and size were determined by predefined functions of solar wind and global parameters, which limited their ability to reconstruct the global morphology of the magnetosphere and its dynamic evolution during geomagnetic storms. The TS07D model mitigated these limitations by replacing the equatorial current modules with basis-function expansions and by introducing a dynamical binning approach based on nearest neighbors. Here we further progress this avenue. Firstly, the number of basis functions is increased and new data from Van Allen Probes and THEMIS missions is added, allowing the model to resolve the spatial structure and evolution of the innermost eastward and banana currents. Then, an enhanced Birkeland current module that more accurately reconstructs the realistic morphology, including the Harang discontinuity and IMF By dependence, is discussed. Lastly, the performance of various nowcasting versions of the model with different sets of the binning parameters is examined for the first time using their direct validation by in-situ geomagnetic field observations, leading to an optimum nowcasting version of the model. Furthermore, the plasma pressure is reconstructed assuming force balance with the empirical magnetic field, and the role of pressure-driven currents is examined.

  8. Chiral Tunneling of Topological States: Towards the Efficient Generation of Spin Current Using Spin-Momentum Locking

    NASA Astrophysics Data System (ADS)

    Habib, K. M. Masum; Sajjad, Redwan N.; Ghosh, Avik W.

    2015-05-01

    We show that the interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D topological insulator (TI). Our calculations show that the chiral tunneling across a TI p n junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, gate-tunable spin-to-charge current ratio (˜20 ) at the reflected end. At the transmitted end, the ratio stays close to 1 and the electrons are completely spin polarized.

  9. Evaluation of local electric fields generated by transcranial direct current stimulation with an extracephalic reference electrode based on realistic 3D body modeling

    NASA Astrophysics Data System (ADS)

    Im, Chang-Hwan; Park, Ji-Hye; Shim, Miseon; Chang, Won Hyuk; Kim, Yun-Hee

    2012-04-01

    In this study, local electric field distributions generated by transcranial direct current stimulation (tDCS) with an extracephalic reference electrode were evaluated to address extracephalic tDCS safety issues. To this aim, we generated a numerical model of an adult male human upper body and applied the 3D finite element method to electric current conduction analysis. In our simulations, the active electrode was placed over the left primary motor cortex (M1) and the reference electrode was placed at six different locations: over the right temporal lobe, on the right supraorbital region, on the right deltoid, on the left deltoid, under the chin, and on the right buccinator muscle. The maximum current density and electric field intensity values in the brainstem generated by the extracephalic reference electrodes were comparable to, or even less than, those generated by the cephalic reference electrodes. These results suggest that extracephalic reference electrodes do not lead to unwanted modulation of the brainstem cardio-respiratory and autonomic centers, as indicated by recent experimental studies. The volume energy density was concentrated at the neck area by the use of deltoid reference electrodes, but was still smaller than that around the active electrode locations. In addition, the distributions of elicited cortical electric fields demonstrated that the use of extracephalic reference electrodes might allow for the robust prediction of cortical modulations with little dependence on the reference electrode locations.

  10. Collisional Aggregation Due to Turbulence

    NASA Astrophysics Data System (ADS)

    Pumir, Alain; Wilkinson, Michael

    2016-03-01

    Collisions between particles suspended in a fluid play an important role in many physical processes. As an example, collisions of microscopic water droplets in clouds are a necessary step in the production of macroscopic raindrops. Collisions of dust grains are also conjectured to be important for planet formation in the gas surrounding young stars and to play a role in the dynamics of sand storms. In these processes, collisions are favored by fast turbulent motions. Here we review recent advances in the understanding of collisional aggregation due to turbulence. We discuss the role of fractal clustering of particles and caustic singularities of their velocities. We also discuss limitations of the Smoluchowski equation for modeling such processes. These advances lead to a semiquantitative understanding on the influence of turbulence on collision rates and point to deficiencies in the current understanding of rainfall and planet formation.

  11. 17 CFR 5.8 - Aggregate retail forex assets.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... merchant may not include aggregate retail forex assets as current assets or otherwise record any property received from retail forex customers as an asset without recording a corresponding liability to the...

  12. Power transfer and current generation of fast ions with large-{ital k}{sub {theta}} waves in tokamak plasmas

    SciTech Connect

    Heikkinen, J.A.; Sipilae, S.K.

    1995-10-01

    The direction and magnitude of power and momentum exchange between fast ions and electrostatic waves in slab and toroidal systems are obtained from global Monte Carlo simulations that include the quasilinear wave-induced ion diffusion both in velocity space and through a radially localized (lower hybrid) wave structure with propagation in one preferential poloidal direction in tokamaks. The model considers a full linearized collision model, finite fast ion orbits, and losses in toroidal geometry, and can properly treat the boundary effects on the particle--wave interaction in the configuration space. For an isotropic steady ion source, reduction of wave Landau damping but no wave amplification by wave localization is found for a Gaussian wave intensity distribution in radius, irrespective of the steepness of the radial gradient of the fast ion source rate. Enhanced wave-driven fast ion current, with magnitude, direction, and profile determined by the boundary conditions, net power transfer, and fast ion radial transport, is found to follow from the asymmetry in the parallel wave number spectrum created by the finite poloidal magnetic field. In the presence of intense well-penetrated waves the current carried by fusion {alpha} particles can be controlled by the choice of the poloidal wave number spectrum and the total current can greatly exceed the neoclassical bootstrap current of the {alpha} particles in a reactor. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  13. Increased cytoplasm viscosity hampers aggregate polar segregation in Escherichia coli.

    PubMed

    Oliveira, Samuel M D; Neeli-Venkata, Ramakanth; Goncalves, Nadia S M; Santinha, João A; Martins, Leonardo; Tran, Huy; Mäkelä, Jarno; Gupta, Abhishekh; Barandas, Marilia; Häkkinen, Antti; Lloyd-Price, Jason; Fonseca, José M; Ribeiro, Andre S

    2016-02-01

    In Escherichia coli, under optimal conditions, protein aggregates associated with cellular aging are excluded from midcell by the nucleoid. We study the functionality of this process under sub-optimal temperatures from population and time lapse images of individual cells and aggregates and nucleoids within. We show that, as temperature decreases, aggregates become homogeneously distributed and uncorrelated with nucleoid size and location. We present evidence that this is due to increased cytoplasm viscosity, which weakens the anisotropy in aggregate displacements at the nucleoid borders that is responsible for their preference for polar localisation. Next, we show that in plasmolysed cells, which have increased cytoplasm viscosity, aggregates are also not preferentially located at the poles. Finally, we show that the inability of cells with increased viscosity to exclude aggregates from midcell results in enhanced aggregate concentration in between the nucleoids in cells close to dividing. This weakens the asymmetries in aggregate numbers between sister cells of subsequent generations required for rejuvenating cell lineages. We conclude that the process of exclusion of protein aggregates from midcell is not immune to stress conditions affecting the cytoplasm viscosity. The findings contribute to our understanding of E. coli's internal organisation and functioning, and its fragility to stressful conditions. PMID:26507787

  14. Determination of the dynamic elastic constants of recycled aggregate concrete

    NASA Astrophysics Data System (ADS)

    Tsoumani, A. A.; Barkoula, N.-M.; Matikas, T. E.

    2015-03-01

    Nowadays, construction and demolition waste constitutes a major portion of the total solid waste production in the world. Due to both environmental and economical reasons, an increasing interest concerning the use of recycled aggregate to replace aggregate from natural sources is generated. This paper presents an investigation on the properties of recycled aggregate concrete. Concrete mixes are prepared using recycled aggregates at a substitution level between 0 and 100% of the total coarse aggregate. The influence of this replacement on strengthened concrete's properties is being investigated. The properties estimated are: density and dynamic modulus of elasticity at the age of both 7 and 28 days. Also, flexural strength of 28 days specimens is estimated. The determination of the dynamic elastic modulus was made using the ultrasonic pulse velocity method. The results reveal that the existence of recycled aggregates affects the properties of concrete negatively; however, in low levels of substitution the influence of using recycled aggregates is almost negligible. Concluding, the controlled use of recycled aggregates in concrete production may help solve a vital environmental issue apart from being a solution to the problem of inadequate concrete aggregates.

  15. IgG Conformer's Binding to Amyloidogenic Aggregates

    PubMed Central

    Phay, Monichan; Welzel, Alfred T.; Williams, Angela D.; McWilliams-Koeppen, Helen P.; Blinder, Veronika; O'Malley, Tiernan T.; Solomon, Alan; Walsh, Dominic M.; O'Nuallain, Brian

    2015-01-01

    Amyloid-reactive IgGs isolated from pooled blood of normal individuals (pAbs) have demonstrated clinical utility for amyloid diseases by in vivo targeting and clearing amyloidogenic proteins and peptides. We now report the following three novel findings on pAb conformer's binding to amyloidogenic aggregates: 1) pAb aggregates have greater activity than monomers (HMW species > dimers > monomers), 2) pAbs interactions with amyloidogenic aggregates at least partially involves unconventional (non-CDR) interactions of F(ab) regions, and 3) pAb's activity can be easily modulated by trace aggregates generated during sample processing. Specifically, we show that HMW aggregates and dimeric pAbs present in commercial preparations of pAbs, intravenous immunoglobulin (IVIg), had up to ~200- and ~7-fold stronger binding to aggregates of Aβ and transthyretin (TTR) than the monomeric antibody. Notably, HMW aggregates were primarily responsible for the enhanced anti-amyloid activities of Aβ- and Cibacron blue-isolated IVIg IgGs. Human pAb conformer's binding to amyloidogenic aggregates was retained in normal human sera, and mimicked by murine pAbs isolated from normal pooled plasmas. An unconventional (non-CDR) component to pAb's activity was indicated from control human mAbs, generated against non-amyloid targets, binding to aggregated Aβ and TTR. Similar to pAbs, HMW and dimeric mAb conformers bound stronger than their monomeric forms to amyloidogenic aggregates. However, mAbs had lower maximum binding signals, indicating that pAbs were required to saturate a diverse collection of binding sites. Taken together, our findings strongly support further investigations on the physiological function and clinical utility of the inherent anti-amyloid activities of monomeric but not aggregated IgGs. PMID:26367058

  16. Dynamics of fire ant aggregations

    NASA Astrophysics Data System (ADS)

    Tennenbaum, Michael; Hu, David; Fernandez-Nieves, Alberto

    Fire ant aggregations are an inherently active system. Each ant harvests its own energy and can convert it into motion. The motion of individual ants contributes non-trivially to the bulk material properties of the aggregation. We have measured some of these properties using plate-plate rheology, where the response to an applied external force or deformation is measured. In this talk, we will present data pertaining to the aggregation behavior in the absence of any external force. We quantify the aggregation dynamics by monitoring the rotation of the top plate and by measuring the normal force. We then compare the results with visualizations of 2D aggregations.

  17. Optical properties of the atmospheric pressure helium plasma jet generated by alternative current (a.c.) power supply

    NASA Astrophysics Data System (ADS)

    Ilik, Erkan; Akan, Tamer

    2016-05-01

    In this work, an atmospheric pressure plasma jet (APPJ) was produced to generate cold flowing post-discharge plasma of pure helium gas. The main aim of this study was to generate cold flowing APPJ of pure helium gas and to determine how their optical emission spectrum change influences varying different flow rates. Lengths of early, middle, and late post-discharge plasma (jet) regions and their fluctuations were determined, respectively. Then, ignition condition dependence of the post-discharge plasma for flow rate was specified at a constant voltage. Spectroscopic studies of an atmospheric pressure plasma jet of helium were presented via analyzing OH, N2, N2+, oxygen, and helium intensities for various flow rates.

  18. Asphaltene Aggregation and Fouling Behavior

    NASA Astrophysics Data System (ADS)

    Derakhshesh, Marzie

    This thesis explored the properties of asphaltene nano-aggregates in crude oil and toluene based solutions and fouling at process furnace temperatures, and the links between these two phenomena. The link between stability of asphaltenes at ambient conditions and fouling at the conditions of a delayed coker furnace, at over 450 °C, was examined by blending crude oil with an aliphatic diluent in different ratios. The stability of the blends were measured using a S-value analyzer, then fouling rates were measured on electrically heated stainless steel 316 wires in an autoclave reactor. The less stable the blend, the greater the rate and extent of fouling. The most severe fouling occurred with the unstable asphaltenes. SEM imaging of the foulant illustrates very different textures, with the structure becoming more porous with lower stability. Under cross-polarized light, the coke shows the presence of mesophase in the foulant layer. These data suggest a correlation between the fouling rate at high temperature furnace conditions and the stability index of the crude oil. Three organic polysulfides were introduced to the crude oil to examine their effect on fouling. The polysulfides are able to reduce coking and carbon monoxide generation in steam crackers. The fouling results demonstrated that polysulfide with more sulfur content increased the amount of corrosion-fouling of the wire. Various additives, solvents, ultrasound, and heat were employed to attempt to completely disaggregate the asphaltene nano-aggregates in solution at room temperature. The primary analytical technique used to monitor the nano-aggregation state of the asphaltenes in solution was the UV-visible spectroscopy. The results indicate that stronger solvents, such as pyridine and quinoline, combined with ionic liquids yield a slight reduction in the apparent absorbance at longer wavelengths, indicative of a decrease in the nano-aggregate size although the magnitude of the decrease is not significant

  19. Protein Aggregation and Its Impact on Product Quality

    PubMed Central

    Roberts, Christopher J.

    2014-01-01

    Protein pharmaceutical products are typically active as folded monomers that are composed of one or more protein chains, such as the heavy and light chains in monoclonal antibodies that are a mainstay of current drug pipelines. There are numerous possible aggregated states for a given protein, some of which are potentially useful, while most of which are considered deleterious from the perspective of pharmaceutical product quality and performance. This review provides an overview of how and why different aggregated states of proteins occur, how this potentially impacts product quality and performance, fundamental approaches to control aggregate formation, and the practical approaches that are currently used in the pharmaceutical industry. PMID:25173826

  20. The Dynomak: An advanced spheromak reactor system with imposed-dynamo current drive and next-generation nuclear power technologies

    NASA Astrophysics Data System (ADS)

    Sutherland, D. A.; Jarboe, T. R.; Marklin, G.; Morgan, K. D.; Nelson, B. A.

    2013-10-01

    A high-beta spheromak reactor system has been designed with an overnight capital cost that is competitive with conventional power sources. This reactor system utilizes recently discovered imposed-dynamo current drive (IDCD) and a molten salt blanket system for first wall cooling, neutron moderation and tritium breeding. Currently available materials and ITER developed cryogenic pumping systems were implemented in this design on the basis of technological feasibility. A tritium breeding ratio of greater than 1.1 has been calculated using a Monte Carlo N-Particle (MCNP5) neutron transport simulation. High-temperature superconducting tapes (YBCO) were used for the equilibrium coil set, substantially reducing the recirculating power fraction when compared to previous spheromak reactor studies. Using zirconium hydride for neutron shielding, a limiting equilibrium coil lifetime of at least thirty full-power years has been achieved. The primary FLiBe loop was coupled to a supercritical carbon dioxide Brayton cycle due to attractive economics and high thermal efficiencies. With these advancements, an electrical output of 1000 MW from a thermal output of 2486 MW was achieved, yielding an overall plant efficiency of approximately 40%. A paper concerning the Dynomak reactor design is currently being reviewed for publication.

  1. System performance and cost sensitivity comparisons of stretched membrane heliostat reflectors with current generation glass/metal concepts

    SciTech Connect

    Murphy, L.M.; Anderson, J.V.; Short, W.; Wendelin, T.

    1985-12-01

    Heliostat costs have long been recognized as a major factor in the cost of solar central receiver plants. Research on stretched membrane heliostats has been emphasized because of their potential as a cost-effective alternative to current glass/metal designs. However, the cost and performance potential of stretched membrane heliostats from a system perspective has not been studied until this time. The optical performance of individual heliostats is predicted here using results established in previous structural studies. These performance predictions are used to compare both focused and unfocused stretched membrane heliostats with state-of-the-art glass/metal heliostats from a systems perspective. We investigated the sensitivity of the relative cost and performance of fields of heliostats to a large number of parameter variations, including system size, delivery temperature, heliostat module size, surface specularity, hemispherical reflectance, and macroscopic surface quality. The results indicate that focused stretched membrane systems should have comparable performance levels to those of current glass/metal heliostat systems. Further, because of their relatively lower cost, stretched membrane heliostats should provide an economically attractive alternative to current glass/metal heliostats over essentially the entire range of design parameters studied. Unfocused stretched membrane heliostats may also be attractive for a somewhat more limited range of applications, including the larger plant sizes and lower delivery temperatures.

  2. Analysis on operational power and eddy current losses for applying coreless double-sided permanent magnet synchronous motor/generator to high-power flywheel energy storage system

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Park, Ji-Hoon; You, Dae-Joon; Choi, Sang-Ho

    2009-04-01

    This paper deals with analytical approach of operational power defined as load power and rotor loss represented as eddy current loss for applying a permanent magnet (PM) synchronous motor/generator to the high-power flywheel energy storage system. The used model is composed of a double-sided Halbach magnetized PM rotor and coreless three-phase winding stator. For one such motor/generator structure, we provide the magnetic field and eddy current with space and time harmonics via magnetic vector potential in two-dimensional (2D) polar coordinate system. From these, the operational power is estimated by backelectromotive force according to the PM rotor speed, and the rotor loss is also calculated from Poynting theorem.

  3. VERIFICATION OF 3-PHASES COMPOSITE MODEL FOR DRYING SHRINKAGE OF CONCRETE WITH DEFFERENT AGGREGATE PROPERTIES

    NASA Astrophysics Data System (ADS)

    Tanaka, Kie; Shima, Hiroshi

    Properties of aggregate are not taken into account in current codes for drying shrinkage of concrete although the drying shrinkage is affected by the properties of aggregate. Aggregate restrains cement paste from shrinkage so that the drying shrinkage of concrete is controlled by drying shrinkage and Young's modulus of aggregate itself. The effect of the aggregate properties on drying shrinkage of concrete can be calculated by composite model in which concrete consists of cement paste and aggregate. Several different kind of coarse aggregate were used in order to verify a 3-phases composite model for drying shrinkage. Drying shrinkage and Young's modulus of cement paste, aggregate and concrete were measured. It was verified that drying shrinkage of concrete can be estimated accurately by the composite model associating with both drying shrinkage and Young's modulus of aggregate.

  4. Hot moments in spawning aggregations: implications for ecosystem-scale nutrient cycling

    NASA Astrophysics Data System (ADS)

    Archer, Stephanie K.; Allgeier, Jacob E.; Semmens, Brice X.; Heppell, Scott A.; Pattengill-Semmens, Christy V.; Rosemond, Amy D.; Bush, Phillippe G.; McCoy, Croy M.; Johnson, Bradley C.; Layman, Craig A.

    2015-03-01

    Biogeochemical hot moments occur when a temporary increase in availability of one or more limiting reactants results in elevated rates of biogeochemical reactions. Many marine fish form transient spawning aggregations, temporarily increasing their local abundance and thus nutrients supplied via excretion at the aggregation site. In this way, nutrients released by aggregating fish could create a biogeochemical hot moment. Using a combination of empirical and modeling approaches, we estimate nitrogen and phosphorus supplied by aggregating Nassau grouper ( Epinephelus striatus). Data suggest aggregating grouper supply up to an order-of-magnitude more nitrogen and phosphorus than daily consumer-derived nutrient supply on coral reefs without aggregating fish. Comparing current and historic aggregation-level excretion estimates shows that overfishing reduced nutrients supplied by aggregating fish by up to 87 %. Our study illustrates a previously unrecognized ecosystem viewpoint regarding fish spawning aggregations and provides an additional perspective on the repercussions of their overexploitation.

  5. Aggregation and vertical migration behavior of Euphausia superba

    NASA Astrophysics Data System (ADS)

    Zhou, Meng; Dorland, Ryan D.

    2004-08-01

    Aggregation and vertical migration behavior of Euphausia superba were studied in Marguerite Bay and its vicinity west of the Antarctic Peninsula using a vessel-mounted, Acoustic Doppler Current Profiler, and a Multiple Opening and Closing Nets and Environmental Sensing System, during the 2001 and 2002 fall US Southern Ocean GLOBEC project cruises. The kinematics of aggregation behavior of E. superba associated with diel migration is studied using observations of their abundance and swimming velocities: during the day, E. superba reduce their swimming at a depth of 250 m; and at night, they swim randomly at their cruising speed in the upper part of an aggregation near the surface, and coherently as schooling in the lower part of an aggregation. The causes for the aggregation behavior and vertical migration of krill are explored by examining the relationship with ice coverage and presence of predators. The motion of euphausiids is further analyzed in terms of kinetic energy and force balance, leading to new considerations of mathematical theories and models of aggregation behavior. The results show a diel variation of the energy demand for maintaining their locomotion. The horizontal scale of an aggregation is studied in conjunction with horizontal gradients of currents. Results indicate that the swimming capability of euphausiids determines the maintenance of an aggregation in the mesoscale circulation field.

  6. Making Graphene Resist Aggregation

    NASA Astrophysics Data System (ADS)

    Luo, Jiayan

    Graphene-based sheets have stimulated great interest in many scientific disciplines and shown promise for wide potential applications. Among various ways of creating single atomic layer carbon sheets, a promising route for bulk production is to first chemically exfoliate graphite powders to graphene oxide (GO) sheets, followed by reduction to form chemically modified graphene (CMG). Due to the strong van der Waals attraction between graphene sheets, CMG tends to aggregate. The restacking of sheets is largely uncontrollable and irreversible, thus it reduces their processability and compromises properties such as accessible surface area. Strategies based on colloidal chemistry have been applied to keep CMG dispersed in solvents by introducing electrostatic repulsion to overcome the van der Waals attraction or adding spacers to increase the inter-sheet spacing. In this dissertation, two very different ideas that can prevent CMG aggregation without extensively modifying the material or introducing foreign spacer materials are introduced. The van der Waals potential decreases with reduced overlapping area between sheets. For CMG, reducing the lateral dimension from micrometer to nanometer scale should greatly enhance their colloidal stability with additional advantages of increased charge density and decreased probability to interact. The enhanced colloidal stability of GO and CMG nanocolloids makes them especially promising for spectroscopy based bio-sensing applications. For potential applications in a compact bulk solid form, the sheets were converted into paper-ball like structure using capillary compression in evaporating aerosol droplets. The crumpled graphene balls are stabilized by locally folded pi-pi stacked ridges, and do not unfold or collapse during common processing steps. They can tightly pack without greatly reducing the surface area. This form of graphene leads to scalable performance in energy storage. For example, planer sheets tend to aggregate and

  7. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  8. Current status of third-generation implantable left ventricular assist devices in Japan, Duraheart and HeartWare.

    PubMed

    Sawa, Yoshiki

    2015-06-01

    Recently, left ventricular assist devices (LVADs) have become a viable therapeutic approach as a bridge to cardiac transplantation, as well as destination therapy or as part of the bridge to recovery. In Japan, paracorporeal pneumatic devices are the only choice for such therapy, as implantable LVADs are not yet generally available due to device lag, which represents a serious problem in this field. Clinical trials of four different continuous-flow pumps, both axial and centrifugal flow types, were completed at about the same time, and two of those devices, DuraHeart and EVAHEART, have already been approved for use in Japan. Thus, reports of advanced treatment for severe heart failure with these devices are expected. The DuraHeart (Terumo Heart, Ann Arbor, MI, USA) and another device named the HeartWare (HeartWare Inc, Miami Lakes, FL, USA) are so-called third-generation devices, as they have achieved miniaturization and improvements in performance from the use of magnetic levitation. Based on our experiences from both clinical research and experimental use, we herein discuss the DuraHeart and HeartWare devices, with a focus on the clinical outcomes and management strategies. Because of the long waiting period for heart transplantation in Japan, these two devices are considered to have important roles in the near future for the treatment of severe heart failure, and a comprehensive strategy for LVAD therapy including such third-generation implantable devices is expected. PMID:25139211

  9. Influence of Hall Current and Viscous Dissipation on Pressure Driven Flow of Pseudoplastic Fluid with Heat Generation: A Mathematical Study.

    PubMed

    Noreen, Saima; Qasim, Muhammad

    2015-01-01

    In this paper, we study the influence of heat sink (or source) on the peristaltic motion of pseudoplastic fluid in the presence of Hall current, where channel walls are non-conducting in nature. Flow analysis has been carried out under the approximations of a low Reynolds number and long wavelength. Coupled equations are solved using shooting method for numerical solution for the axial velocity function, temperature and pressure gradient distributions. We analyze the influence of various interesting parameters on flow quantities. The present study can be considered as a mathematical presentation of the dynamics of physiological organs with stones. PMID:26083027

  10. Influence of Hall Current and Viscous Dissipation on Pressure Driven Flow of Pseudoplastic Fluid with Heat Generation: A Mathematical Study

    PubMed Central

    Noreen, Saima; Qasim, Muhammad

    2015-01-01

    In this paper, we study the influence of heat sink (or source) on the peristaltic motion of pseudoplastic fluid in the presence of Hall current, where channel walls are non-conducting in nature. Flow analysis has been carried out under the approximations of a low Reynolds number and long wavelength. Coupled equations are solved using shooting method for numerical solution for the axial velocity function, temperature and pressure gradient distributions. We analyze the influence of various interesting parameters on flow quantities. The present study can be considered as a mathematical presentation of the dynamics of physiological organs with stones. PMID:26083027

  11. Dielectric approach to investigation of erythrocyte aggregation. II. Kinetics of erythrocyte aggregation-disaggregation in quiescent and flowing blood.

    PubMed

    Pribush, A; Meiselman, H J; Meyerstein, D; Meyerstein, N

    2000-01-01

    A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break-up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the beta-dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady-state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face-to-face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face-to-side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy. PMID:11204548

  12. Generating high-current monoenergetic proton beams by a circularly polarized laser pulse in the phase-stable acceleration regime.

    PubMed

    Yan, X Q; Lin, C; Sheng, Z M; Guo, Z Y; Liu, B C; Lu, Y R; Fang, J X; Chen, J E

    2008-04-01

    A new ion acceleration method, namely, phase-stable acceleration, using circularly-polarized laser pulses is proposed. When the initial target density n(0) and thickness D satisfy a(L) approximately (n(0)/n(c))D/lambda(L) and D>l(s) with a(L), lambda(L), l(s), and n(c) the normalized laser amplitude, the laser wavelength in vacuum, the plasma skin depth, and the critical density of the incident laser pulse, respectively, a quasiequilibrium for the electrons is established by the light pressure and the space charge electrostatic field at the interacting front of the laser pulse. The ions within the skin depth of the laser pulse are synchronously accelerated and bunched by the electrostatic field, and thereby a high-intensity monoenergetic proton beam can be generated. The proton dynamics is investigated analytically and the results are verified by one- and two-dimensional particle-in-cell simulations. PMID:18517963

  13. Next-generation sequencing (NGS) for assessment of microbial water quality: current progress, challenges, and future opportunities

    PubMed Central

    Tan, BoonFei; Ng, Charmaine; Nshimyimana, Jean Pierre; Loh, Lay Leng; Gin, Karina Y.-H.; Thompson, Janelle R.

    2015-01-01

    Water quality is an emergent property of a complex system comprised of interacting microbial populations and introduced microbial and chemical contaminants. Studies leveraging next-generation sequencing (NGS) technologies are providing new insights into the ecology of microbially mediated processes that influence fresh water quality such as algal blooms, contaminant biodegradation, and pathogen dissemination. In addition, sequencing methods targeting small subunit (SSU) rRNA hypervariable regions have allowed identification of signature microbial species that serve as bioindicators for sewage contamination in these environments. Beyond amplicon sequencing, metagenomic and metatranscriptomic analyses of microbial communities in fresh water environments reveal the genetic capabilities and interplay of waterborne microorganisms, shedding light on the mechanisms for production and biodegradation of toxins and other contaminants. This review discusses the challenges and benefits of applying NGS-based methods to water quality research and assessment. We will consider the suitability and biases inherent in the application of NGS as a screening tool for assessment of biological risks and discuss the potential and limitations for direct quantitative interpretation of NGS data. Secondly, we will examine case studies from recent literature where NGS based methods have been applied to topics in water quality assessment, including development of bioindicators for sewage pollution and microbial source tracking, characterizing the distribution of toxin and antibiotic resistance genes in water samples, and investigating mechanisms of biodegradation of harmful pollutants that threaten water quality. Finally, we provide a short review of emerging NGS platforms and their potential applications to the next generation of water quality assessment tools. PMID:26441948

  14. Next-generation sequencing (NGS) for assessment of microbial water quality: current progress, challenges, and future opportunities.

    PubMed

    Tan, BoonFei; Ng, Charmaine; Nshimyimana, Jean Pierre; Loh, Lay Leng; Gin, Karina Y-H; Thompson, Janelle R

    2015-01-01

    Water quality is an emergent property of a complex system comprised of interacting microbial populations and introduced microbial and chemical contaminants. Studies leveraging next-generation sequencing (NGS) technologies are providing new insights into the ecology of microbially mediated processes that influence fresh water quality such as algal blooms, contaminant biodegradation, and pathogen dissemination. In addition, sequencing methods targeting small subunit (SSU) rRNA hypervariable regions have allowed identification of signature microbial species that serve as bioindicators for sewage contamination in these environments. Beyond amplicon sequencing, metagenomic and metatranscriptomic analyses of microbial communities in fresh water environments reveal the genetic capabilities and interplay of waterborne microorganisms, shedding light on the mechanisms for production and biodegradation of toxins and other contaminants. This review discusses the challenges and benefits of applying NGS-based methods to water quality research and assessment. We will consider the suitability and biases inherent in the application of NGS as a screening tool for assessment of biological risks and discuss the potential and limitations for direct quantitative interpretation of NGS data. Secondly, we will examine case studies from recent literature where NGS based methods have been applied to topics in water quality assessment, including development of bioindicators for sewage pollution and microbial source tracking, characterizing the distribution of toxin and antibiotic resistance genes in water samples, and investigating mechanisms of biodegradation of harmful pollutants that threaten water quality. Finally, we provide a short review of emerging NGS platforms and their potential applications to the next generation of water quality assessment tools. PMID:26441948

  15. Taurine and platelet aggregation

    SciTech Connect

    Nauss-Karol, C.; VanderWende, C.; Gaut, Z.N.

    1986-03-01

    Taurine is a putative neurotransmitter or neuromodulator. The endogenous taurine concentration in human platelets, determined by amino acid analysis, is 15 ..mu..M/g. In spite of this high level, taurine is actively accumulated. Uptake is saturable, Na/sup +/ and temperature dependent, and suppressed by metabolic inhibitors, structural analogues, and several classes of centrally active substances. High, medium and low affinity transport processes have been characterized, and the platelet may represent a model system for taurine transport in the CNS. When platelets were incubated with /sup 14/C-taurine for 30 minutes, then resuspended in fresh medium and reincubated for one hour, essentially all of the taurine was retained within the cells. Taurine, at concentrations ranging from 10-1000 ..mu..M, had no effect on platelet aggregation induced by ADP or epinephrine. However, taurine may have a role in platelet aggregation since 35-39% of the taurine taken up by human platelets appears to be secreted during the release reaction induced by low concentrations of either epinephrine or ADP, respectively. This release phenomenon would imply that part of the taurine taken up is stored directly in the dense bodies of the platelet.

  16. Generation of a pulsed high-current low-energy beam in a plasma electron source with a self-heated cathode

    NASA Astrophysics Data System (ADS)

    Gavrilov, N. V.; Men'shakov, A. I.

    2016-05-01

    The transition of a low-current discharge with a self-heated hollow cathode to a high-current discharge is studied, and stability conditions for the latter in the pulsed-periodic mode with a current of 0.1-1.0 kA, pulse width of 0.1-1.0 ms, and a pulse repetition rate of 0.1-1.0 kHz are determined. The thermal conditions of the hollow cathode are analyzed, and the conclusion is drawn that the emission current high density is due to pulsed self-heating of the cathode's surface layer. Conditions for stable emission from a plasma cathode with a grid acting as a plasma boundary using such a discharge are found at low accelerating voltage (100-200 eV) and a gas pressure of 0.1-0.4 Pa. The density of the ion current from a plasma generated by a pulsed beam with a current of 100 A is found to reach 0.1 A/cm2. Probe diagnostics data for the emitting and beam plasmas in the electron source are presented, and a mechanism behind the instability of electron emission from the plasma is suggested on their basis.

  17. Analytical solution for the effect of the permittivity of coating layer on eddy current generated in an aluminum sample by EMAT

    NASA Astrophysics Data System (ADS)

    Sun, Feiran; Sun, Zhenguo; Chen, Qiang

    2016-02-01

    In order to improve the ultrasonic wave amplitude excited by electromagnetic acoustic transducers (EMATs), many researchers have proposed models. But they always ignored displacement current or the effect of the permittivity of the air or the metal sample during modeling, due to its low permittivity. However, more durable dielectric materials are replacing or coating with metals in many applications which have a much higher permittivity than air or metal sample so that the effect of permittivity cannot be ignored. Based on an analytical model, the effect of the permittivity of coating layer on the eddy current generated in an aluminum sample by EMAT has been studied. The analytical analysis indicates that the eddy current density excited by the spiral coil of EMAT slowly increases in the beginning and then decreases rapidly while the permittivity increases, and it has much relation to the thickness of the coating layer and the exciting frequency, which is verified by the simulation result.

  18. A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

    NASA Astrophysics Data System (ADS)

    Shen, Yang-Wu; Ke, De-Ping; Sun, Yuan-Zhang; Daniel, Kirschen; Wang, Yi-Shen; Hu, Yuan-Chao

    2015-07-01

    A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method. Project supported by the National Natural Science Foundation of China (Grant No. 51307124) and the Major Program of the National Natural Science Foundation of China (Grant No. 51190105).

  19. Signature of the Schwinger pair creation rate via radiation generated in graphene by a strong electric current

    SciTech Connect

    Lewkowicz, M.; Kao, H. C.; Rosenstein, B.

    2011-07-15

    Electron-hole pairs are copiously created by an applied electric field near the Dirac point in graphene or similar two-dimensional electronic systems. It was shown recently that for sufficiently large electric fields E and ballistic times the I-V characteristics become strongly nonlinear due to Schwinger's pair creation rate, proportional to E{sup 3/2}. Since there is no energy gap the radiation from the pairs' annihilation is enhanced. The spectrum of radiation is calculated and exhibits a maximum at {omega}={radical}(eEv{sub g}/({h_bar}/2{pi})). The angular and polarization dependence of the emitted photons with respect to the graphene sheet is quite distinctive. For very large currents the recombination rate becomes so large that it leads to the second Ohmic regime due to radiation friction.

  20. Holographic characterization of protein aggregates

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhong, Xiao; Ruffner, David; Stutt, Alexandra; Philips, Laura; Ward, Michael; Grier, David

    Holographic characterization directly measures the size distribution of subvisible protein aggregates in suspension and offers insights into their morphology. Based on holographic video microscopy, this analytical technique records and interprets holograms of individual aggregates in protein solutions as they flow down a microfluidic channel, without requiring labeling or other exceptional sample preparation. The hologram of an individual protein aggregate is analyzed in real time with the Lorenz-Mie theory of light scattering to measure that aggregate's size and optical properties. Detecting, counting and characterizing subvisible aggregates proceeds fast enough for time-resolved studies, and lends itself to tracking trends in protein aggregation arising from changing environmental factors. No other analytical technique provides such a wealth of particle-resolved characterization data in situ. Holographic characterization promises accelerated development of therapeutic protein formulations, improved process control during manufacturing, and streamlined quality assurance during storage and at the point of use. Mrsec and MRI program of the NSF, Spheryx Inc.