Single element of the matrix source of negative hydrogen ions: Measurements of the extracted currents combined with diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yordanov, D., E-mail: yordanov@phys.uni-sofia.bg; Lishev, St.; Shivarova, A.

2016-02-15

Combining measurements of the extracted currents with probe and laser-photodetachment diagnostics, the study is an extension of recent tests of factors and gas-discharge conditions stimulating the extraction of volume produced negative ions. The experiment is in a single element of a rf source with the design of a matrix of small-radius inductively driven discharges. The results are for the electron and negative-ion densities, for the plasma potential and for the electronegativity in the vicinity of the plasma electrode as well as for the currents of the extracted negative ions and electrons. The plasma-electrode bias and the rf power have beenmore » varied. Necessity of a high bias to the plasma electrode and stable linear increase of the extracted currents with the rf power are the main conclusions.« less

Analysis of recoverable current from one component of magnetic flux density in MREIT and MRCDI.

PubMed

Park, Chunjae; Lee, Byung Il; Kwon, Oh In

2007-06-07

Magnetic resonance current density imaging (MRCDI) provides a current density image by measuring the induced magnetic flux density within the subject with a magnetic resonance imaging (MRI) scanner. Magnetic resonance electrical impedance tomography (MREIT) has been focused on extracting some useful information of the current density and conductivity distribution in the subject Omega using measured B(z), one component of the magnetic flux density B. In this paper, we analyze the map Tau from current density vector field J to one component of magnetic flux density B(z) without any assumption on the conductivity. The map Tau provides an orthogonal decomposition J = J(P) + J(N) of the current J where J(N) belongs to the null space of the map Tau. We explicitly describe the projected current density J(P) from measured B(z). Based on the decomposition, we prove that B(z) data due to one injection current guarantee a unique determination of the isotropic conductivity under assumptions that the current is two-dimensional and the conductivity value on the surface is known. For a two-dimensional dominating current case, the projected current density J(P) provides a good approximation of the true current J without accumulating noise effects. Numerical simulations show that J(P) from measured B(z) is quite similar to the target J. Biological tissue phantom experiments compare J(P) with the reconstructed J via the reconstructed isotropic conductivity using the harmonic B(z) algorithm.

Optimization of plasma parameters with magnetic filter field and pressure to maximize H{sup −} ion density in a negative hydrogen ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Won-Hwi; Dang, Jeong-Jeung; Kim, June Young

2016-02-15

Transverse magnetic filter field as well as operating pressure is considered to be an important control knob to enhance negative hydrogen ion production via plasma parameter optimization in volume-produced negative hydrogen ion sources. Stronger filter field to reduce electron temperature sufficiently in the extraction region is favorable, but generally known to be limited by electron density drop near the extraction region. In this study, unexpected electron density increase instead of density drop is observed in front of the extraction region when the applied transverse filter field increases monotonically toward the extraction aperture. Measurements of plasma parameters with a movable Langmuirmore » probe indicate that the increased electron density may be caused by low energy electron accumulation in the filter region decreasing perpendicular diffusion coefficients across the increasing filter field. Negative hydrogen ion populations are estimated from the measured profiles of electron temperatures and densities and confirmed to be consistent with laser photo-detachment measurements of the H{sup −} populations for various filter field strengths and pressures. Enhanced H{sup −} population near the extraction region due to the increased low energy electrons in the filter region may be utilized to increase negative hydrogen beam currents by moving the extraction position accordingly. This new finding can be used to design efficient H{sup −} sources with an optimal filtering system by maximizing high energy electron filtering while keeping low energy electrons available in the extraction region.« less

Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments.

PubMed

Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

2012-08-01

We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 10(17) m(-3), i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fertig, Fabian, E-mail: fabian.fertig@ise.fraunhofer.de; Greulich, Johannes; Rein, Stefan

We present a spatially resolved method to determine the short-circuit current density of crystalline silicon solar cells by means of lock-in thermography. The method utilizes the property of crystalline silicon solar cells that the short-circuit current does not differ significantly from the illuminated current under moderate reverse bias. Since lock-in thermography images locally dissipated power density, this information is exploited to extract values of spatially resolved current density under short-circuit conditions. In order to obtain an accurate result, one or two illuminated lock-in thermography images and one dark lock-in thermography image need to be recorded. The method can be simplifiedmore » in a way that only one image is required to generate a meaningful short-circuit current density map. The proposed method is theoretically motivated, and experimentally validated for monochromatic illumination in comparison to the reference method of light-beam induced current.« less

Extraction of the gluon density of the proton at x

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Schlereth, J.; Stanek, R.; Talaga, R. L.; Thron, J.; Arzarello, F.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; D'Auria, S.; Frasconi, F.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Geitz, G.; Grothe, M.; Hartmann, H.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mass, A.; Mengel, S.; Mollen, J.; Paul, E.; Rembser, Ch.; Schattevoy, R.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jelén, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kȩdzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Böttcher, S.; Coldewey, C.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Göttlicher, P.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heβling, H.; Hultschig, H.; Iga, Y.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Kröger, W.; Krüger, J.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mańczak, O.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Voβ, T.; Westphal, D.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, A.; Rethfeldt, C.; Schlenstedt, S.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Qian, S.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Schroeder, J.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, I.; Jamieson, V. A.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Fürtjes, A.; Hagge, L.; Lohrmann, E.; Mainusch, J.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Terron, J.; Zetsche, F.; Bacon, T. C.; Beuselinck, R.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Zhang, Y.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; del Peso, J.; Puga, J.; de Trocóniz, J. F.; Ikraiam, F.; Mayer, J. K.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Y. A.; Kobrin, V. D.; Kuzmin, V. A.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Bentvelsen, S.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Jong, P.; de Kamps, M.; Kooijman, P.; Kruse, A.; O'Dell, V.; Tenner, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Blair, G. A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Daniels, D.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Luffman, P. E.; Lindemann, L.; McFall, J.; Nath, C.; Quadt, A.; Uijterwaal, H.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Iori, M.; Marini, G.; Mattioli, M.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Dubbs, T.; Heusch, C.; Van Hook, M.; Hubbard, B.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Biltzinger, J.; Seifert, R. J.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nagira, T.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuł; a, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Zarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Revel, D.; Shapira, A.; Ali, I.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Tsurugai, T.; Bhadra, S.; Frisken, W. R.; Furutani, K. M.; Zeus Collaboration

1995-02-01

The gluon momentum density xg( x, Q2) of the proton was extracted at Q2 = 20 GeV 2 for small values of x between 4 × 10 -4 and 10 -2 from the scaling violations of the proton structure function F2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F2 at low x constrained by measurementsfrom NMC at larger x; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x.

EXPLORING PROOF OF CONCEPT IN OCEAN CURRENT ENERGY EXTRACTION

EPA Science Inventory

The small-scale OCEE is expected to yield a power density similar to that of an average wind turbine of comparable size. The project will result in specifications for materials, turbine geometries and turbine location/orientation that will extract the most energy from ocean curre...

High current density ion beam obtained by a transition to a highly focused state in extremely low-energy region.

PubMed

Hirano, Y; Kiyama, S; Fujiwara, Y; Koguchi, H; Sakakita, H

2015-11-01

A high current density (≈3 mA/cm(2)) hydrogen ion beam source operating in an extremely low-energy region (E(ib) ≈ 150-200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when E(ib) is being reduced. The radial profiles of the ion beam current density and the low temperature ion current density can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge.

High efficiency ion beam accelerator system

NASA Technical Reports Server (NTRS)

Aston, G.

1981-01-01

An ion accelerator system that successfully combines geometrical and electrostatic focusing principles is presented. This accelerator system uses thin, concave, multiple-hole, closely spaced graphite screen and focusing grids which are coupled to single slot accelerator and decelerator grids to provide high ion extraction efficiency and good focusing. Tests with the system showed a substantial improvement in ion beam current density and collimation as compared with a Pierce electrode configuration. Durability of the thin graphite screen and focusing grids has been proven, and tests are being performed to determine the minimum screen and focusing grid spacing and thickness required to extract the maximum reliable beam current density. Compared with present neutral beam injector accelerator systems, this one has more efficient ion extraction, easier grid alignment, easier fabrication, a less cumbersome design, and the capacity to be constructed in a modular fashion. Conceptual neutral beam injector designs using this modular approach have electrostatic beam deflection plates downstream of each module.

Electron current extraction from a permanent magnet waveguide plasma cathode.

PubMed

Weatherford, B R; Foster, J E; Kamhawi, H

2011-09-01

An electron cyclotron resonance plasma produced in a cylindrical waveguide with external permanent magnets was investigated as a possible plasma cathode electron source. The configuration is desirable in that it eliminates the need for a physical antenna inserted into the plasma, the erosion of which limits operating lifetime. Plasma bulk density was found to be overdense in the source. Extraction currents over 4 A were achieved with the device. Measurements of extracted electron currents were similar to calculated currents, which were estimated using Langmuir probe measurements at the plasma cathode orifice and along the length of the external plume. The influence of facility effects and trace ionization in the anode-cathode gap are also discussed. © 2011 American Institute of Physics

First results from negative ion beam extraction in ROBIN in surface mode

NASA Astrophysics Data System (ADS)

Pandya, Kaushal; Gahlaut, Agrajit; Yadav, Ratnakar K.; Bhuyan, Manas; Bandyopadhyay, Mainak; Das, B. K.; Bharathi, P.; Vupugalla, Mahesh; Parmar, K. G.; Tyagi, Himanshu; Patel, Kartik; Bhagora, Jignesh; Mistri, Hiren; Prajapati, Bhavesh; Pandey, Ravi; Chakraborty, Arun. K.

2017-08-01

ROBIN, the first step in the Indian R&D program on negative ion beams has reached an important milestone, with the production of negative ions in the surface conversion mode through Cesium (Cs) vapor injection into the source. In the present set-up, negative hydrogen ion beam extraction is effected through an extraction area of ˜73.38 cm2 (146 apertures of 8mm diameter). The three grid electrostatic accelerator system of ROBIN is fed by high voltage DC power supplies (Extraction Power Supply System: 11kV, 35A and Acceleration Power Supply System: 35kV, 15A). Though, a considerable reduction of co-extracted electron current is usually observed during surface mode operation, in order to increase the negative ion current, various other parameters such as plasma grid temperature, plasma grid bias, extraction to acceleration voltage ratio, impurity control and Cs recycling need to be optimized. In the present experiments, to control and to understand the impurity behavior, a Cryopump (14,000 l/s for Hydrogen) is installed along with a Residual Gas Analyzer (RGA). To characterize the source plasma, two sets of Langmuir probes are inserted through the diagnostic flange ports available at the extraction plane. To characterize the beam properties, thermal differential calorimeter, Doppler Shift Spectroscopy and electrical current measurements are implemented in ROBIN. In the present set up, all the negative ion beam extraction experiments have been performed by varying different experimental parameters e.g. RF power (30-70 kW), source operational pressure (0.3 - 0.6Pa), plasma grid bias voltage, extraction & acceleration voltage combination etc. The experiments in surface mode operation is resulted a reduction of co-extracted electron current having electron to ion ratio (e/i) ˜2 whereas the extracted negative ion current density was increased. However, further increase in negative ion current density is expected to be improved after a systematic optimization of the operational parameters and Cs conditioning of the source. It was also found out that a better performance of ROBIN is achieved in the pressure range: 0.5-0.6 Pa. In this paper, the preliminary results on parametric study of ROBIN operation and beam optimization in surface mode are discussed.

Kinetic modeling of ultrasound-assisted extraction of phenolic compounds from grape marc: influence of acoustic energy density and temperature.

PubMed

Tao, Yang; Zhang, Zhihang; Sun, Da-Wen

2014-07-01

The effects of acoustic energy density (6.8-47.4 W/L) and temperature (20-50 °C) on the extraction yields of total phenolics and tartaric esters during ultrasound-assisted extraction from grape marc were investigated in this study. The ultrasound treatment was performed in a 25-kHz ultrasound bath system and the 50% aqueous ethanol was used as the solvent. The initial extraction rate and final extraction yield increased with the increase of acoustic energy density and temperature. The two site kinetic model was used to simulate the kinetics of extraction process and the diffusion model based on the Fick's second law was employed to determine the effective diffusion coefficient of phenolics in grape marc. Both models gave satisfactory quality of data fit. The diffusion process was divided into one fast stage and one slow stage and the diffusion coefficients in both stages were calculated. Within the current experimental range, the diffusion coefficients of total phenolics and tartaric esters for both diffusion stages increased with acoustic energy density. Meanwhile, the rise of temperature also resulted in the increase of diffusion coefficients of phenolics except the diffusion coefficient of total phenolics in the fast stage, the value of which being the highest at 40 °C. Moreover, an empirical equation was suggested to correlate the effective diffusion coefficient of phenolics in grape marc with acoustic energy density and temperature. In addition, the performance comparison of ultrasound-assisted extraction and convention methods demonstrates that ultrasound is an effective and promising technology to extract bioactive substances from grape marc. Copyright © 2014 Elsevier B.V. All rights reserved.

Ion source and beam guiding studies for an API neutron generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sy, A.; Ji, Q.; Persaud, A.

2013-04-19

Recently developed neutron imaging methods require high neutron yields for fast imaging times and small beam widths for good imaging resolution. For ion sources with low current density to be viable for these types of imaging methods, large extraction apertures and beam focusing must be used. We present recent work on the optimization of a Penning-type ion source for neutron generator applications. Two multi-cusp magnet configurations have been tested and are shown to increase the extracted ion current density over operation without multi-cusp magnetic fields. The use of multi-cusp magnetic confinement and gold electrode surfaces have resulted in increased ionmore » current density, up to 2.2 mA/cm{sup 2}. Passive beam focusing using tapered dielectric capillaries has been explored due to its potential for beam compression without the cost and complexity issues associated with active focusing elements. Initial results from first experiments indicate the possibility of beam compression. Further work is required to evaluate the viability of such focusing methods for associated particle imaging (API) systems.« less

A Critical Evaluation of the Influence of the Dark Exchange Current on the Performance of Dye-Sensitized Solar Cells

PubMed Central

García-Rodríguez, Rodrigo; Villanueva-Cab, Julio; Anta, Juan A.; Oskam, Gerko

2016-01-01

The influence of the thickness of the nanostructured, mesoporous TiO2 film on several parameters determining the performance of a dye-sensitized solar cell is investigated both experimentally and theoretically. We pay special attention to the effect of the exchange current density in the dark, and we compare the values obtained by steady state measurements with values extracted from small perturbation techniques. We also evaluate the influence of exchange current density, the solar cell ideality factor, and the effective absorption coefficient of the cell on the optimal film thickness. The results show that the exchange current density in the dark is proportional to the TiO2 film thickness, however, the effective absorption coefficient is the parameter that ultimately defines the ideal thickness. We illustrate the importance of the exchange current density in the dark on the determination of the current–voltage characteristics and we show how an important improvement of the cell performance can be achieved by decreasing values of the total series resistance and the exchange current density in the dark. PMID:28787833

Analysis of factors that affect the potential of star fruit (Averhoa Bilimbi) and cactus (Gymnocalycium Hossei) extracts as alternative battery

NASA Astrophysics Data System (ADS)

Rahmawati, Sitti; Agnesstacia

2014-03-01

This research analyzes the factors that affect the work of the battery from the star fruit extract and the cactus extract. The value voltage and current generated are measure the work of the battery. Voltage measurement based on the electrode distance function, and electrode surface area. Voltage as a surface area electrode function and electrode distance function determined the current density and the voltage generated. From the experimental results obtained that the battery voltage is large enough, it is about 1.8 V for the extract of star fruit, and 1.7 V for the extract of cactus, which means that the juice extract from star fruit and the juice extract of cactus can become an alternative as battery replacement. The measurements with different electrode surface area on the star fruit and cactus extract which has the depth of the electrode 0.5 cm to 4 cm causes a decrease in the electric current generated from 12.5 mA to 1.0 mA, but obtained the same voltage.

Modeling of negative ion extraction from a magnetized plasma source: Derivation of scaling laws and description of the origins of aberrations in the ion beam

NASA Astrophysics Data System (ADS)

Fubiani, G.; Garrigues, L.; Boeuf, J. P.

2018-02-01

We model the extraction of negative ions from a high brightness high power magnetized negative ion source. The model is a Particle-In-Cell (PIC) algorithm with Monte-Carlo Collisions. The negative ions are generated only on the plasma grid surface (which separates the plasma from the electrostatic accelerator downstream). The scope of this work is to derive scaling laws for the negative ion beam properties versus the extraction voltage (potential of the first grid of the accelerator) and plasma density and investigate the origins of aberrations on the ion beam. We show that a given value of the negative ion beam perveance correlates rather well with the beam profile on the extraction grid independent of the simulated plasma density. Furthermore, the extracted beam current may be scaled to any value of the plasma density. The scaling factor must be derived numerically but the overall gain of computational cost compared to performing a PIC simulation at the real plasma density is significant. Aberrations appear for a meniscus curvature radius of the order of the radius of the grid aperture. These aberrations cannot be cancelled out by switching to a chamfered grid aperture (as in the case of positive ions).

Ion extraction from a plasma. Ph.D. Thesis. Progress Report, 1 Dec. 1979 - 1 Dec. 1980

NASA Technical Reports Server (NTRS)

Aston, G.

1980-01-01

An experimental investigation of the physical processes governing ion extraction from a plasma is presented. The screen hole plasma sheath of a multiaperture ion accelerator system is defined by equipotential plots for a variety of accelerator system geometries and operating conditions. A sheath thickness of at least fifteen Debye lengths is shown to be typical. The electron density variation within the sheath satisfies a Maxwell Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary to Maxwellian electron density ratio. Plasma ion flow up to and through the sheath is predominately one dimensional and the ions enter the sheath with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.

Impact of crystal orientation on the modulation bandwidth of InGaN/GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Monavarian, M.; Rashidi, A.; Aragon, A. A.; Oh, S. H.; Rishinaramangalam, A. K.; DenBaars, S. P.; Feezell, D.

2018-01-01

High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (10 1 ¯ 0 ), semipolar (20 2 ¯ 1 ¯) , and polar (" separators="|0001 ) orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and semipolar LEDs, especially at relatively low current densities. At 500 A/cm2, the nonpolar LED has a 3 dB bandwidth of ˜1 GHz, while the semipolar and polar LEDs exhibit bandwidths of 260 MHz and 75 MHz, respectively. A lower carrier density for a given current density is extracted from the RF measurements for the nonpolar and semipolar LEDs, consistent with the higher wavefunction overlaps in these orientations. At large current densities, the bandwidth of the polar LED approaches that of the nonpolar and semipolar LEDs due to coulomb screening of the polarization field. The results support using nonpolar and semipolar orientations to achieve high-speed LEDs at low current densities.

A zero-liquid-discharge scheme for vanadium extraction process by electrodialysis-based technology.

PubMed

Wang, Meng; Xing, Hong-Bo; Jia, Yu-Xiang; Ren, Qing-Chun

2015-12-30

The sharp increase of demand for vanadium makes the treatment of the wastewater generated from its extraction process become an urgent problem. In this study, a hybrid process coupling the electrodialysis with the cooling crystallization is put forward for upgrading the conventional vanadium extraction process to zero discharge. Accordingly, the objective of this work lies in evaluating the feasibility of the proposed scheme on the basis of a systematic study on the influences of membrane types and operating parameters on the electrodialysis performance. The results indicate that the relative importance of osmosis and electro-osmosis to overall water transport is closely related to the applied current density. The increase in the applied current density and the decrease in the mole ratio of water and salt flux will contribute to the concentration degree. Moreover, it is worth noting that a relatively large concentration ratio can result in the remarkable decrease of current efficiency and increase of energy consumption. In general, the reclamation scheme can easily achieve the recovered water with relatively low salt content and the highly concentrated Na2SO4 solution (e.g., 300 g/L) for producing high-purity sodium sulphate crystals. Copyright © 2015. Published by Elsevier B.V.

Beam Profile Studies for a One Eighth Betatron Wavelength Final Focusing Cell Following Phase Mixed Transport

DTIC Science & Technology

1988-10-26

concentrated into this off- axis peak is then considered. Estimates of the source brightness ( extraction ion diode source current density divided by the square...radioactive contamination of the accelerator. One possible scheme for avoiding this problem is to use extraction geometry ion diodes to focus the ion beams...annular region. These results will be coupled to two simple models of extraction ion diodes to determihe the ion source brightness requirements. These

Polymer bulk heterojunction solar cells with PEDOT:PSS bilayer structure as hole extraction layer.

PubMed

Kim, Wanjung; Kim, Namhun; Kim, Jung Kyu; Park, Insun; Choi, Yeong Suk; Wang, Dong Hwan; Chae, Heeyeop; Park, Jong Hyeok

2013-06-01

A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC₆₀BM and PCDTBT:PC₇₀BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion energy spread and current measurements of the rf-driven multicusp ion source

NASA Astrophysics Data System (ADS)

Lee, Y.; Gough, R. A.; Kunkel, W. B.; Leung, K. N.; Perkins, L. T.; Pickard, D. S.; Sun, L.; Vujic, J.; Williams, M. D.; Wutte, D.

1997-03-01

Axial energy spread and useful beam current of positive ion beams have been carried out using a radio frequency (rf)-driven multicusp ion source. Operating the source with a 13.56 MHz induction discharge, the axial energy spread is found to be approximately 3.2 eV. The extractable beam current of the rf-driven source is found to be comparable to that of filament-discharge sources. With a 0.6 mm diameter extraction aperture, a positive hydrogen ion beam current density of 80 mA/cm2 can be obtained at a rf input power of 2.5 kW. The expected source lifetime is much longer than that of filament discharges.

Dye-Sensitized Solar Cells Employing Extracts from Four Cassia Flowers as Natural Sensitizers: Studies on Dye Ingredient Effect on Photovoltaic Performance

NASA Astrophysics Data System (ADS)

Maurya, Ishwar Chandra; Singh, Shalini; Neetu; Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

2018-01-01

Natural dyes extracted from four different flowers, namely, Cassia surattensis, Cassia tora, Cassia alata and Cassia occidentalis were used as sensitizers for TiO2-based dye-sensitized solar cells (DSSC). The dye extracts from flowers were obtained by a simple extraction technique and used without any further purification. Optical characteristics of dye extracts were studied. Fourier-transform infrared (FTIR) spectra were used to identify the constituents of extracted dyes. The photovoltaic performance of DSSC employing dye-capped TiO2 photoanodes was measured. The sensitization performance related to anchoring groups present and interaction between dyes with TiO2 surface is demonstrated. An attempt has been made to rationalize the observations by light absorption of the dye extracts and their adsorption on TiO2. The short-circuit current density ( I SC) values ranged from 0.06 mA/cm2 to 0.20 mA/cm2; open circuit voltage ( V OC) from 0.292 V to 0.833 V; fill factor (FF) from 0.7 to 0.9; efficiencies ( η) from 0.013% to 0.15% and incident photon-to-current conversion efficiency from 13% to 20%, were obtained for DSSC using these natural dye extracts. Cassia occidentalis showed the highest current density of 0.20 mA/cm2 and power conversion efficiency of 0.15%, which was due to better interaction between the carbonyl and hydroxyl group of the anthocyanin molecule of C. occidentalis and surface of TiO2 film. The red and blue shift of absorption wavelength of C. surattensis and the blue shift of absorption wavelength of the C. tora, C. alata and C. occidentalis extract in ethanol solution compared to that on TiO2 film has been used for the interpretation of obtained results.

Measurements of beam current density and proton fraction of a permanent-magnet microwave ion source.

PubMed

Waldmann, Ole; Ludewigt, Bernhard

2011-11-01

A permanent-magnet microwave ion source has been built for use in a high-yield, compact neutron generator. The source has been designed to produce up to 100 mA of deuterium and tritium ions. The electron-cyclotron resonance condition is met at a microwave frequency of 2.45 GHz and a magnetic field strength of 87.5 mT. The source operates at a low hydrogen gas pressure of about 0.15 Pa. Hydrogen beams with a current density of 40 mA/cm(2) have been extracted at a microwave power of 450 W. The dependence of the extracted proton beam fraction on wall materials and operating parameters was measured and found to vary from 45% for steel to 95% for boron nitride as a wall liner material. © 2011 American Institute of Physics

Space charge effects on the current-voltage characteristics of gated field emitter arrays

NASA Astrophysics Data System (ADS)

Jensen, K. L.; Kodis, M. A.; Murphy, R. A.; Zaidman, E. G.

1997-07-01

Microfabricated field emitter arrays (FEAs) can provide the very high electron current densities required for rf amplifier applications, typically on the order of 100 A/cm2. Determining the dependence of emission current on gate voltage is important for the prediction of emitter performance for device applications. Field emitters use high applied fields to extract current, and therefore, unlike thermionic emitters, the current densities can exceed 103A/cm2 when averaged over an array. At such high current densities, space charge effects (i.e., the influence of charge between cathode and collector on emission) affect the emission process or initiate conditions which can lead to failure mechanisms for field emitters. A simple model of a field emitter will be used to calculate the one-dimensional space charge effects on the emission characteristics by examining two components: charge between the gate and anode, which leads to Child's law, and charge within the FEA unit cell, which gives rise to a field suppression effect which can exist for a single field emitter. The predictions of the analytical model are compared with recent experimental measurements designed to assess space charge effects and predict the onset of gate current. It is shown that negative convexity on a Fowler-Nordheim plot of Ianode(Vgate) data can be explained in terms of field depression at the emitter tip in addition to reflection of electrons by a virtual cathode created when the anode field is insufficient to extract all of the current; in particular, the effects present within the unit cell constitute a newly described effect.

Ion extraction from a plasma

NASA Technical Reports Server (NTRS)

Aston, G.; Wilbur, P. J.

1981-01-01

The physical processes governing ion extraction from a plasma have been examined experimentally. The screen hole plasma sheath (the transition region wherein significant ion acceleration and complete electron retardation occurs) has been defined by equipotential plots for a variety of ion accelerator system geometries and operating conditions. It was found that the screen hole plasma sheath extends over a large distance, and influences ion and electron trajectories at least 15 Debye lengths within the discharge chamber. The electron density variation within the screen hole plasma sheath satisfied a Maxwell-Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary-to-Maxwellian electron density ratio. Plasma ion flow up to and through the sheath was predominantly one-dimensional, and the ions entered the sheath region with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio were found to give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.

Apparent isotropic electrical property for electrical brain stimulation (EBS) using magnetic resonance diffusion weighted imaging (MR-DWI)

NASA Astrophysics Data System (ADS)

Lee, Mun Bae; Kwon, Oh-In

2018-04-01

Electrical brain stimulation (EBS) is an invasive electrotherapy and technique used in brain neurological disorders through direct or indirect stimulation using a small electric current. EBS has relied on computational modeling to achieve optimal stimulation effects and investigate the internal activations. Magnetic resonance diffusion weighted imaging (DWI) is commonly useful for diagnosis and investigation of tissue functions in various organs. The apparent diffusion coefficient (ADC) measures the intensity of water diffusion within biological tissues using DWI. By measuring trace ADC and magnetic flux density induced by the EBS, we propose a method to extract electrical properties including the effective extracellular ion-concentration (EEIC) and the apparent isotropic conductivity without any auxiliary additional current injection. First, the internal current density due to EBS is recovered using the measured one component of magnetic flux density. We update the EEIC by introducing a repetitive scheme called the diffusion weighting J-substitution algorithm using the recovered current density and the trace ADC. To verify the proposed method, we study an anesthetized canine brain to visualize electrical properties including electrical current density, effective extracellular ion-concentration, and effective isotropic conductivity by applying electrical stimulation of the brain.

Operation of large RF sources for H-: Lessons learned at ELISE

NASA Astrophysics Data System (ADS)

Fantz, U.; Wünderlich, D.; Heinemann, B.; Kraus, W.; Riedl, R.

2017-08-01

The goal of the ELISE test facility is to demonstrate that large RF-driven negative ion sources (1 × 1 m2 source area with 360 kW installed RF power) can achieve the parameters required for the ITER beam sources in terms of current densities and beam homogeneity at a filling pressure of 0.3 Pa for pulse lengths of up to one hour. With the experience in operation of the test facility, the beam source inspection and maintenance as well as with the results of the achieved source performance so far, conclusions are drawn for commissioning and operation of the ITER beam sources. Addressed are critical technical RF issues, extrapolations to the required RF power, Cs consumption and Cs ovens, the need of adjusting the magnetic filter field strength as well as the temporal dynamic and spatial asymmetry of the co-extracted electron current. It is proposed to relax the low pressure limit to 0.4 Pa and to replace the fixed electron-to-ion ratio by a power density limit for the extraction grid. This would be highly beneficial for controlling the co-extracted electrons.

Characterization and Performance of a High-Current-Density Ion Implanter with Magnetized Hollow-Cathode Plasma Source

NASA Astrophysics Data System (ADS)

Falkenstein, Zoran; Rej, Donald; Gavrilov, Nikolai

1998-10-01

In a collaboration between the Institute of Electrophysics (IEP) and the Los Alamos National Laboratory (LANL), the IEP has developed an industrial scalable, high-power, large-area ion source for the surface modification of materials. The plasma source of the ion beam source can be described as a pulsed glow discharge with a cold, hollow-cathode in a weak magnetic field. Extraction and focusing of positive ions by an acceleration and ion-optical plate system renders the generation of a homogeneous, large-area ion beam with an averaged total ion current of up to 50 mA at acceleration voltages of up to 50 kV. The principle set-up of the ion beam source as well as some electrical characteristics (gas discharge current and the extracted ion beam current) are presented for a lab-scale prototype. Measurements of the radial ion current density profiles within the ion beam for various discharge parameters, as well as results on surface modification by ion implantation of nitrogen into aluminum and chromium are presented. Finally, a comparison of the applied ion dose with the retained ion doses is given.

In-depth porosity control of mesoporous silicon layers by an anodization current adjustment

NASA Astrophysics Data System (ADS)

Lascaud, J.; Defforge, T.; Certon, D.; Valente, D.; Gautier, G.

2017-12-01

The formation of thick mesoporous silicon layers in P+-type substrates leads to an increase in the porosity from the surface to the interface with silicon. The adjustment of the current density during the electrochemical etching of porous silicon is an intuitive way to control the layer in-depth porosity. The duration and the current density during the anodization were varied to empirically model porosity variations with layer thickness and build a database. Current density profiles were extracted from the model in order to etch layer with in-depth control porosity. As a proof of principle, an 80 μm-thick porous silicon multilayer was synthetized with decreasing porosities from 55% to 35%. The results show that the assessment of the in-depth porosity could be significantly enhanced by taking into account the pure chemical etching of the layer in the hydrofluoric acid-based electrolyte.

Counter-current acid leaching process for copper azole treated wood waste.

PubMed

Janin, Amélie; Riche, Pauline; Blais, Jean-François; Mercier, Guy; Cooper, Paul; Morris, Paul

2012-09-01

This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H2SO4 at 75degrees C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving > or = 94% copper extraction from the wood during the 10 cycles; 80-90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

Optimization of flavanones extraction by modulating differential solvent densities and centrifuge temperatures.

PubMed

Chebrolu, Kranthi K; Jayaprakasha, G K; Jifon, J; Patil, Bhimanagouda S

2011-07-15

Understanding the factors influencing flavonone extraction is critical for the knowledge in sample preparation. The present study was focused on the extraction parameters such as solvent, heat, centrifugal speed, centrifuge temperature, sample to solvent ratio, extraction cycles, sonication time, microwave time and their interactions on sample preparation. Flavanones were analyzed in a high performance liquid chromatography (HPLC) and later identified by liquid chromatography and mass spectrometry (LC-MS). The five flavanones were eluted by a binary mobile phase with 0.03% phosphoric acid and acetonitrile in 20 min and detected at 280 nm, and later identified by mass spectral analysis. Dimethylsulfoxide (DMSO) and dimethyl formamide (DMF) had optimum extraction levels of narirutin, naringin, neohesperidin, didymin and poncirin compared to methanol (MeOH), ethanol (EtOH) and acetonitrile (ACN). Centrifuge temperature had a significant effect on flavanone distribution in the extracts. The DMSO and DMF extracts had homogeneous distribution of flavanones compared to MeOH, EtOH and ACN after centrifugation. Furthermore, ACN showed clear phase separation due to differential densities in the extracts after centrifugation. The number of extraction cycles significantly increased the flavanone levels during extraction. Modulating the sample to solvent ratio increased naringin quantity in the extracts. Current research provides critical information on the role of centrifuge temperature, extraction solvent and their interactions on flavanone distribution in extracts. Published by Elsevier B.V.

Predicting population survival under future climate change: density dependence, drought and extraction in an insular bighorn sheep.

PubMed

Colchero, Fernando; Medellin, Rodrigo A; Clark, James S; Lee, Raymond; Katul, Gabriel G

2009-05-01

1. Our understanding of the interplay between density dependence, climatic perturbations, and conservation practices on the dynamics of small populations is still limited. This can result in uninformed strategies that put endangered populations at risk. Moreover, the data available for a large number of populations in such circumstances are sparse and mined with missing data. Under the current climate change scenarios, it is essential to develop appropriate inferential methods that can make use of such data sets. 2. We studied a population of desert bighorn sheep introduced to Tiburon Island, Mexico in 1975 and subjected to irregular extractions for the last 10 years. The unique attributes of this population are absence of predation and disease, thereby permitting us to explore the combined effect of density dependence, environmental variability and extraction in a 'controlled setting.' Using a combination of nonlinear discrete models with long-term field data, we constructed three basic Bayesian state space models with increasing density dependence (DD), and the same three models with the addition of summer drought effects. 3. We subsequently used Monte Carlo simulations to evaluate the combined effect of drought, DD, and increasing extractions on the probability of population survival under two climate change scenarios (based on the Intergovernmental Panel on Climate Change predictions): (i) increase in drought variability; and (ii) increase in mean drought severity. 4. The population grew from 16 individuals introduced in 1975 to close to 700 by 1993. Our results show that the population's growth was dominated by DD, with drought having a secondary but still relevant effect on its dynamics. 5. Our predictions suggest that under climate change scenario (i), extraction dominates the fate of the population, while for scenario (ii), an increase in mean drought affects the population's probability of survival in an equivalent magnitude as extractions. Thus, for the long-term survival of the population, our results stress that a more variable environment is less threatening than one in which the mean conditions become harsher. Current climate change scenarios and their underlying uncertainty make studies such as this one crucial for understanding the dynamics of ungulate populations and their conservation.

Ion extraction capabilities of closely spaced grids

NASA Technical Reports Server (NTRS)

Rovang, D. C.; Wilbur, P. J.

1982-01-01

The ion extraction capabilities of accelerator systems with small screen hole diameters (less than 2.0 mm) are investigated at net-accelerating voltages of 100, 300, and 500 V. Results show that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 1.0 mm, but impingement-limited performance was found to be dependent on the grid separation distance, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained using small hole diameters and closely spaced grids indicate a new mode of grid operation where high current density operation can be achieved with a specified net acceleration voltage by operating the grids at a high rather than low net-to-total acceleration voltage. Beam current densities as high as 25 mA/sq cm were obtained using grids with 1.0 mm diameter holes operating at a net accelerating voltage of 500 V.

High current density ion beam obtained by a transition to a highly focused state in extremely low-energy region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirano, Y., E-mail: y.hirano@aist.go.jp, E-mail: hirano.yoichi@phys.cst.nihon-u.ac.jp; College of Science and Technologies, Nihon University, Chiyodaku, Tokyo 101-0897; Kiyama, S.

2015-11-15

A high current density (≈3 mA/cm{sup 2}) hydrogen ion beam source operating in an extremely low-energy region (E{sub ib} ≈ 150–200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when E{sub ib} is being reduced. The radial profiles of the ion beam current density and the low temperature ion current densitymore » can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge.« less

Recent charge-breeding developments with EBIS/T devices (invited).

PubMed

Schwarz, S; Lapierre, A

2016-02-01

Short breeding times, narrow charge state distributions, low background, high efficiency, and the flexible time structure of the ejected low-emittance ion pulses are among the most attractive features of electron beam ion source or trap (EBIS/T) based charge breeders. Significant progress has been made to further improve these properties: Several groups are working to increase current densities towards 10(3) or even 10(4) A/cm(2). These current densities will become necessary to deliver high charge states of heavy nuclei in a short time and/or provide sufficient space-charge capacity to handle high-current ion beams in next-generation rare-isotope beam (RIB) facilities. Efficient capture of continuous beams, attractive because of its potential of handling highest-current ion beams, has become possible with the development of high-density electron beams of >1 A. Requests for the time structure of the charge bred ion pulse range from ultra-short pulses to quasi-continuous beams. Progress is being made on both ends of this spectrum, by either dividing the extracted charge in many pulse-lets, adjusting the extraction potential for a near-uniform long pulse, or adding dedicated devices to spread the ion bunches delivered from the EBIS/T in time. Advances in EBIS/T charge state breeding are summarized, including recent results with NSCL's ReA EBIS/T charge breeder.

Recent charge-breeding developments with EBIS/T devices (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwarz, S., E-mail: schwarz@nscl.msu.edu; Lapierre, A.

Short breeding times, narrow charge state distributions, low background, high efficiency, and the flexible time structure of the ejected low-emittance ion pulses are among the most attractive features of electron beam ion source or trap (EBIS/T) based charge breeders. Significant progress has been made to further improve these properties: Several groups are working to increase current densities towards 10{sup 3} or even 10{sup 4} A/cm{sup 2}. These current densities will become necessary to deliver high charge states of heavy nuclei in a short time and/or provide sufficient space-charge capacity to handle high-current ion beams in next-generation rare-isotope beam (RIB) facilities.more » Efficient capture of continuous beams, attractive because of its potential of handling highest-current ion beams, has become possible with the development of high-density electron beams of >1 A. Requests for the time structure of the charge bred ion pulse range from ultra-short pulses to quasi-continuous beams. Progress is being made on both ends of this spectrum, by either dividing the extracted charge in many pulse-lets, adjusting the extraction potential for a near-uniform long pulse, or adding dedicated devices to spread the ion bunches delivered from the EBIS/T in time. Advances in EBIS/T charge state breeding are summarized, including recent results with NSCL’s ReA EBIS/T charge breeder.« less

Studies on the Extraction Region of the Type VI RF Driven H- Ion Source

NASA Astrophysics Data System (ADS)

McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.

2002-11-01

IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the vicinity of the peak of the external magnetic filter field) and changes to source parameters as a function of power, and argon addition are reported. The behaviour of the electron density is different when the plasma is argon seeded showing a strong increase with RF power. The plasma potential is decreased by 2 V when argon is added to the plasma. The effect of the presence of unwanted silver sputtered from the Faraday screen by Ar+ ions on both the source performance and the plasma parameters is also presented. The silver dramatically downgraded source performance in terms of current density and produced an early saturation of current with applied RF power. Recently, collaboration was begun with the Technical University of Augsburg to perform spectroscopic measurements on the Type VI ion source. The final results of this analysis are not yet ready but some interesting initial observations on the gas temperature, disassociation degree and impurity ions will be presented.

CdS-metal contact at higher current densities.

NASA Technical Reports Server (NTRS)

Stirn, R. J.; Boeer, K. W.; Dussel, G. A.

1973-01-01

An investigation is conducted concerning the mechanisms by which a steady flow of current proceeds through the contact when an external voltage is applied. The main characteristics of current mechanisms are examined, giving attention to photoemission from the cathode, thermionic emission, minority-carrier extraction, and the tunneling of electrons. A high-field domain analysis is conducted together with experimental studies. Particular attention is given to the range in which tunneling predominates.

Aberration of a negative ion beam caused by space charge effect.

PubMed

Miyamoto, K; Wada, S; Hatayama, A

2010-02-01

Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.

Low-Cost HTS Based Magnet System with an Inductively Coupled Pulsed Energy Extraction Protection System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agustsson, Ronald

In this project, RadiaBeam Technologies was tasked with developing a novel solution for a cost effective quench protection based on fast expansion of the normal zone. By inductively coupling a strong electromagnetic pulse via a resonant LC circuit, we attempted to demonstrate accelerated normal zone propagation. The AC field induces currents in the superconducting layer with the current density exceeding that of the critical current density, J c. This creates a large normal zone, uniformly distributing the dissipation through the magnet body. The method does not rely on thermal heating of the conductor, thus enabling nearly instantaneous protection. Through themore » course of the Phase II project, RadiaBeam Technologies continued extensive numerical modeling of the inductive quench system, re-designed and built several iterations of the POC system for testing and observed evidence of a transient partial quench being induced. However the final device was not fabricated. This was a consequence of the fundamentally complex nature of the energy extraction process and the challenges associated even with demonstrating the proof of concept in a bench top device.« less

Low pressure and high power rf sources for negative hydrogen ions for fusion applications (ITER neutral beam injection).

PubMed

Fantz, U; Franzen, P; Kraus, W; Falter, H D; Berger, M; Christ-Koch, S; Fröschle, M; Gutser, R; Heinemann, B; Martens, C; McNeely, P; Riedl, R; Speth, E; Wünderlich, D

2008-02-01

The international fusion experiment ITER requires for the plasma heating and current drive a neutral beam injection system based on negative hydrogen ion sources at 0.3 Pa. The ion source must deliver a current of 40 A D(-) for up to 1 h with an accelerated current density of 200 Am/(2) and a ratio of coextracted electrons to ions below 1. The extraction area is 0.2 m(2) from an aperture array with an envelope of 1.5 x 0.6 m(2). A high power rf-driven negative ion source has been successfully developed at the Max-Planck Institute for Plasma Physics (IPP) at three test facilities in parallel. Current densities of 330 and 230 Am/(2) have been achieved for hydrogen and deuterium, respectively, at a pressure of 0.3 Pa and an electron/ion ratio below 1 for a small extraction area (0.007 m(2)) and short pulses (<4 s). In the long pulse experiment, equipped with an extraction area of 0.02 m(2), the pulse length has been extended to 3600 s. A large rf source, with the width and half the height of the ITER source but without extraction system, is intended to demonstrate the size scaling and plasma homogeneity of rf ion sources. The source operates routinely now. First results on plasma homogeneity obtained from optical emission spectroscopy and Langmuir probes are very promising. Based on the success of the IPP development program, the high power rf-driven negative ion source has been chosen recently for the ITER beam systems in the ITER design review process.

High current proton beams production at Simple Mirror Ion Source 37.

PubMed

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

2014-02-01

This paper presents the latest results of high current proton beam production at Simple Mirror Ion Source (SMIS) 37 facility at the Institute of Applied Physics (IAP RAS). In this experimental setup, the plasma is created and the electrons are heated by 37.5 GHz gyrotron radiation with power up to 100 kW in a simple mirror trap fulfilling the ECR condition. Latest experiments at SMIS 37 were performed using a single-aperture two-electrode extraction system. Proton beams with currents up to 450 mA at high voltages below 45 kV were obtained. The maximum beam current density was measured to be 600 mA/cm(2). A possibility of further improvement through the development of an advanced extraction system is discussed.

Photoluminescence and cathodoluminescence properties of green emitting SrGa2{S}4 : Eu2+ thin film

NASA Astrophysics Data System (ADS)

Chartier, Céline; Benalloul, Paul; Barthou, Charles; Frigerio, Jean-Marc; Mueller, Gerd O.; Mueller-Mach, Regina; Trottier, Troy

2002-02-01

Photoluminescence and cathodoluminescence properties of SrGa2S4 : Eu2+ thin films prepared by reactive RF magnetron sputtering are investigated. Luminescence performances of the phosphor in the thin film form are compared to those of powder samples: the brightness efficiency of thin films is found to be about 30% of the efficiency of powder at low current density. A ratio higher than 40% is expected at higher current density. Thin film screens for FEDs will become a positive alternative to powder screens provided that film quality and light extraction could be improved by optimization of thickness and deposition parameters.

Impurities, temperature, and density in a miniature electrostatic plasma and current source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Den Hartog, D.J.; Craig, D.J.; Fiksel, G.

1996-10-01

We have spectroscopically investigated the Sterling Scientific miniature electrostatic plasma source-a plasma gun. This gun is a clean source of high density (10{sup 19} - 10{sup 20} m{sup -3}), low temperature (5 - 15 eV) plasma. A key result of our investigation is that molybdenum from the gun electrodes is largely trapped in the internal gun discharge; only a small amount escapes in the plasma flowing out of the gun. In addition, the gun plasma parameters actually improve (even lower impurity contamination and higher ion temperature) when up to 1 kA of electron current is extracted from the gun viamore » the application of an external bias. This improvement occurs because the internal gun anode no longer acts as the current return for the internal gun discharge. The gun plasma is a virtual plasma electrode capable of sourcing an electron emission current density of 1 kA/cm{sup 2}. The high emission current, small size (3 - 4 cm diameter), and low impurity generation make this gun attractive for a variety of fusion and plasma technology applications.« less

Development of a helicon ion source: Simulations and preliminary experiments.

PubMed

Afsharmanesh, M; Habibi, M

2018-03-01

In the present context, the extraction system of a helicon ion source has been simulated and constructed. Results of the ion source commissioning at up to 20 kV are presented as well as simulations of an ion beam extraction system. Argon current of more than 200 μA at up to 20 kV is extracted and is characterized with a Faraday cup and beam profile monitoring grid. By changing different ion source parameters such as RF power, extraction voltage, and working pressure, an ion beam with current distribution exhibiting a central core has been detected. Jump transition of ion beam current emerges at the RF power near to 700 W, which reveals that the helicon mode excitation has reached this power. Furthermore, measuring the emission line intensity of Ar ii at 434.8 nm is the other way we have used for demonstrating the mode transition from inductively coupled plasma to helicon. Due to asymmetrical longitudinal power absorption of a half-helix helicon antenna, it is used for the ion source development. The modeling of the plasma part of the ion source has been carried out using a code, HELIC. Simulations are carried out by taking into account a Gaussian radial plasma density profile and for plasma densities in range of 10 18 -10 19 m -3 . Power absorption spectrum and the excited helicon mode number are obtained. Longitudinal RF power absorption for two different antenna positions is compared. Our results indicate that positioning the antenna near to the plasma electrode is desirable for the ion beam extraction. The simulation of the extraction system was performed with the ion optical code IBSimu, making it the first helicon ion source extraction designed with the code. Ion beam emittance and Twiss parameters of the ellipse emittance are calculated at different iterations and mesh sizes, and the best values of the mesh size and iteration number have been obtained for the calculations. The simulated ion beam extraction system has been evaluated using optimized parameters such as the gap distance between electrodes, electrodes aperture, and extraction voltage. The gap distance, ground electrode aperture, and extraction voltage have been changed between 3 and 9 mm, 2-6.5 mm, and 10-35 kV in the simulations, respectively.

Development of a helicon ion source: Simulations and preliminary experiments

NASA Astrophysics Data System (ADS)

Afsharmanesh, M.; Habibi, M.

2018-03-01

In the present context, the extraction system of a helicon ion source has been simulated and constructed. Results of the ion source commissioning at up to 20 kV are presented as well as simulations of an ion beam extraction system. Argon current of more than 200 μA at up to 20 kV is extracted and is characterized with a Faraday cup and beam profile monitoring grid. By changing different ion source parameters such as RF power, extraction voltage, and working pressure, an ion beam with current distribution exhibiting a central core has been detected. Jump transition of ion beam current emerges at the RF power near to 700 W, which reveals that the helicon mode excitation has reached this power. Furthermore, measuring the emission line intensity of Ar ii at 434.8 nm is the other way we have used for demonstrating the mode transition from inductively coupled plasma to helicon. Due to asymmetrical longitudinal power absorption of a half-helix helicon antenna, it is used for the ion source development. The modeling of the plasma part of the ion source has been carried out using a code, HELIC. Simulations are carried out by taking into account a Gaussian radial plasma density profile and for plasma densities in range of 1018-1019 m-3. Power absorption spectrum and the excited helicon mode number are obtained. Longitudinal RF power absorption for two different antenna positions is compared. Our results indicate that positioning the antenna near to the plasma electrode is desirable for the ion beam extraction. The simulation of the extraction system was performed with the ion optical code IBSimu, making it the first helicon ion source extraction designed with the code. Ion beam emittance and Twiss parameters of the ellipse emittance are calculated at different iterations and mesh sizes, and the best values of the mesh size and iteration number have been obtained for the calculations. The simulated ion beam extraction system has been evaluated using optimized parameters such as the gap distance between electrodes, electrodes aperture, and extraction voltage. The gap distance, ground electrode aperture, and extraction voltage have been changed between 3 and 9 mm, 2-6.5 mm, and 10-35 kV in the simulations, respectively.

EM calibration based on Post OPC layout analysis

NASA Astrophysics Data System (ADS)

Sreedhar, Aswin; Kundu, Sandip

2010-03-01

Design for Manufacturability (DFM) involves changes to the design and CAD tools to help increase pattern printability and improve process control. Design for Reliability (DFR) performs the same to improve reliability of devices from failures such as Electromigration (EM), gate-oxide break down, hot carrier injection (HCI), Negative Bias Temperature Insatiability (NBTI) and mechanical stress effects. Electromigration (EM) occurs due to migration or displacement of atoms as a result of the movement of electrons through a conducting medium. The rate of migration determines the Mean Time to Failure (MTTF) which is modeled as a function of temperature and current density. The model itself is calibrated through failure analysis (FA) of parts that are deemed to have failed due to EM against design parameters such as linewidth. Reliability Verification (RV) of a design involves verifying that every conducting line in a design meets certain MTTF threshold. In order to perform RV, current density for each wire must be computed. Current itself is a function of the parasitics that are determined through RC extraction. The standard practice is to perform the RC extraction and current density calculation on drawn, pre-OPC layouts. If a wire fails to meet threshold for MTTF, it may be resized. Subsequently, mask preparation steps such as OPC and PSM introduce extra features such as SRAFs, jogs,hammerheads and serifs that change their resistance, capacitance and current density values. Hence, calibrating EM model based on pre-OPC layouts will lead to different results compared to post-OPC layouts. In this work, we compare EM model calibration and reliability check based on drawn layout versus predicted layout, where the drawn layout is pre-OPC layout and predicted layout is based on litho simulation of post-OPC layout. Results show significant divergence between these two approaches, making a case for methodology based on predicted layout.

High current ion source

DOEpatents

Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

1990-01-01

An ion source utilizing a cathode and anode for producing an electric arc therebetween. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma leaves the generation region and expands through another regon. The density profile of the plasma may be flattened using a magnetic field formed within a vacuum chamber. Ions are extracted from the plasma to produce a high current broad on beam.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

NASA Astrophysics Data System (ADS)

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma.

PubMed

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

Development of multi-ampered D{sup {minus}} source for fusion applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacquot, C.; Belchenko, Y.; Bucalossi, J.

1996-07-01

Large current and high current density deuterium negative ion sources are investigated on the MANTIS test bed with the objective of producing several amperes of D{sup {minus}} beams, at an accelerated current density in the range 10{endash}20 mA/cm{sup 2}, for possible application in future neutral beam injectors, e.g. ITER. As a first step, the DRAGON source, which was built by Culham Laboratory was tested on the MANTIS test bed in order to test this large source using only {open_quote}{open_quote}pure volume{close_quote}{close_quote} production of negative ions. The accelerated negative ion current is found to be a strong function of the source operatingmore » pressure and the arc power, and a significant isotopic effect is observed. The maximum accelerated currents are 1.3 A of H{sup {minus}} (3.3 mA/cm{sup 2}) and 0.5 A (1.3 mA/cm{sup 2}) at 110 kW of arc power. Cesium injection from a non conventional dispenser together with an improved extraction system, have significantly improved the D-current. A maximum of 14 mA/cm{sup 2} of D{sup {minus}1} are accelerated at 30 kV, which corresponds potentially, to more than 5 A for a full aperture extraction with an arc power of 140 kW (2250 A of arc current). {copyright} {ital 1996 American Institute of Physics.}« less

Weld defect identification in friction stir welding using power spectral density

NASA Astrophysics Data System (ADS)

Das, Bipul; Pal, Sukhomay; Bag, Swarup

2018-04-01

Power spectral density estimates are powerful in extraction of useful information retained in signal. In the current research work classical periodogram and Welch periodogram algorithms are used for the estimation of power spectral density for vertical force signal and transverse force signal acquired during friction stir welding process. The estimated spectral densities reveal notable insight in identification of defects in friction stir welded samples. It was observed that higher spectral density against each process signals is a key indication in identifying the presence of possible internal defects in the welded samples. The developed methodology can offer preliminary information regarding presence of internal defects in friction stir welded samples can be best accepted as first level of safeguard in monitoring the friction stir welding process.

Development of a plasma generator for a long pulse ion source for neutral beam injectors.

PubMed

Watanabe, K; Dairaku, M; Tobari, H; Kashiwagi, M; Inoue, T; Hanada, M; Jeong, S H; Chang, D H; Kim, T S; Kim, B R; Seo, C S; Jin, J T; Lee, K W; In, S R; Oh, B H; Kim, J; Bae, Y S

2011-06-01

A plasma generator for a long pulse H(+)/D(+) ion source has been developed. The plasma generator was designed to produce 65 A H(+)/D(+) beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and ±7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm(2). © 2011 American Institute of Physics

Valley current characterization of high current density resonant tunnelling diodes for terahertz-wave applications

NASA Astrophysics Data System (ADS)

Jacobs, K. J. P.; Stevens, B. J.; Baba, R.; Wada, O.; Mukai, T.; Hogg, R. A.

2017-10-01

We report valley current characterisation of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTDs) grown by metal-organic vapour phase epitaxy (MOVPE) for THz emission, with a view to investigate the origin of the valley current and optimize device performance. By applying a dual-pass fabrication technique, we are able to measure the RTD I-V characteristic for different perimeter/area ratios, which uniquely allows us to investigate the contribution of leakage current to the valley current and its effect on the PVCR from a single device. Temperature dependent (20 - 300 K) characteristics for a device are critically analysed and the effect of temperature on the maximum extractable power (PMAX) and the negative differential conductance (NDC) of the device is investigated. By performing theoretical modelling, we are able to explore the effect of typical variations in structural composition during the growth process on the tunnelling properties of the device, and hence the device performance.

A Multicusp Ion Source for Radioactive Ion Beams

NASA Astrophysics Data System (ADS)

Wutte, D.; Freedman, S.; Gough, R.; Lee, Y.; Leitner, M.; Leung, K. N.; Lyneis, C.; Picard, D. S.; Sun, L.; Williams, M. D.; Xie, Z. Q.

1997-05-01

In order to produce a radioactive ion beam of (14)O+, a 10-cm-diameter, 13.56 MHz radio frequency (rf) driven multicusp ion source is now being developed at Lawrence Berkeley National Laboratory. In this paper we describe the specific ion source design and the basic ion source characteristics using Ar, Xe and a 90types of measurements have been performed: extractable ion current, ion species distributions, gas efficiency, axial energy spread and ion beam emittance measurements. The source can generate ion current densities of approximately 60 mA/cm2 . In addition the design of the ion beam extraction/transport system for the actual experimental setup for the radioactive beam line will be presented.

Rapid extraction of auditory feature contingencies.

PubMed

Bendixen, Alexandra; Prinz, Wolfgang; Horváth, János; Trujillo-Barreto, Nelson J; Schröger, Erich

2008-07-01

Contingent relations between sensory events render the environment predictable and thus facilitate adaptive behavior. The human capacity to detect such relations has been comprehensively demonstrated in paradigms in which contingency rules were task-relevant or in which they applied to motor behavior. The extent to which contingencies can also be extracted from events that are unrelated to the current goals of the organism has remained largely unclear. The present study addressed the emergence of contingency-related effects for behaviorally irrelevant auditory stimuli and the cortical areas involved in the processing of such contingency rules. Contingent relations between different features of temporally separate events were embedded in a new dynamic protocol. Participants were presented with the auditory stimulus sequences while their attention was captured by a video. The mismatch negativity (MMN) component of the event-related brain potential (ERP) was employed as an electrophysiological correlate of contingency detection. MMN generators were localized by means of scalp current density (SCD) and primary current density (PCD) analyses with variable resolution electromagnetic tomography (VARETA). Results show that task-irrelevant contingencies can be extracted from about fifteen to twenty successive events conforming to the contingent relation. Topographic and tomographic analyses reveal the involvement of the auditory cortex in the processing of contingency violations. The present data provide evidence for the rapid encoding of complex extrapolative relations in sensory areas. This capacity is of fundamental importance for the organism in its attempt to model the sensory environment outside the focus of attention.

Progress of the ELISE test facility: towards one hour pulses in hydrogen

NASA Astrophysics Data System (ADS)

Wünderlich, D.; Fantz, U.; Heinemann, B.; Kraus, W.; Riedl, R.; Wimmer, C.; the NNBI Team

2016-10-01

In order to fulfil the ITER requirements, the negative hydrogen ion source used for NBI has to deliver a high source performance, i.e. a high extracted negative ion current and simultaneously a low co-extracted electron current over a pulse length up to 1 h. Negative ions will be generated by the surface process in a low-temperature low-pressure hydrogen or deuterium plasma. Therefore, a certain amount of caesium has to be deposited on the plasma grid in order to obtain a low surface work function and consequently a high negative ion production yield. This caesium is re-distributed by the influence of the plasma, resulting in temporal instabilities of the extracted negative ion current and the co-extracted electrons over long pulses. This paper describes experiments performed in hydrogen operation at the half-ITER-size NNBI test facility ELISE in order to develop a caesium conditioning technique for more stable long pulses at an ITER relevant filling pressure of 0.3 Pa. A significant improvement of the long pulse stability is achieved. Together with different plasma diagnostics it is demonstrated that this improvement is correlated to the interplay of very small variations of parameters like the electrostatic potential and the particle densities close to the extraction system.

Polypyrrole nanostructures and their field emission investigations

NASA Astrophysics Data System (ADS)

Harpale, Kashmira; More, Mahendra A.; Koinkar, Pankaj M.; Patil, Sandip S.; Sonawane, Kishor M.

2015-03-01

Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10-8mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm2 has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.

Comparison between the magnetic and transport critical current densities in high critical current density melt-textured yttrium barium copper-oxide

NASA Technical Reports Server (NTRS)

Gao, L.; Meng, R. L.; Xue, Y. Y.; Hor, P. H.; Chu, C. W.

1991-01-01

Using a recently developed pulsed critical current density (Jc) measuring system, the Jc of the high-Jc melt-textured YBa2Cu3O(7-delta) (Y123) bulk samples has been determined. I-V curves with a voltage resolution of 0.5 microV were obtained, and transport Jc's along the a-b plane as high as 7.2 x 10 to the 4th A/sq cm were extracted. These results are comparable to the values obtained magnetically. On the other hand, transport Jc along the c axis were found to be two orders of magnitude smaller, even though the magnetic Jc along the c axis is only about five times smaller than Jc along the a-b plane. It is suggested that for the high-temperature superconducting materials which are highly anisotropic, caution should be taken when using the nontransport magnetic methods to determine Jc.

Experimental validation of the dual positive and negative ion beam acceleration in the plasma propulsion with electronegative gases thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafalskyi, Dmytro, E-mail: dmytro.rafalskyi@lpp.polytechnique.fr; Popelier, Lara; Aanesland, Ane

The PEGASES (Plasma Propulsion with Electronegative Gases) thruster is a gridded ion thruster, where both positive and negative ions are accelerated to generate thrust. In this way, additional downstream neutralization by electrons is redundant. To achieve this, the thruster accelerates alternately positive and negative ions from an ion-ion plasma where the electron density is three orders of magnitude lower than the ion densities. This paper presents a first experimental study of the alternate acceleration in PEGASES, where SF{sub 6} is used as the working gas. Various electrostatic probes are used to investigate the source plasma potential and the energy, composition,more » and current of the extracted beams. We show here that the plasma potential control in such system is key parameter defining success of ion extraction and is sensitive to both parasitic electron current paths in the source region and deposition of sulphur containing dielectric films on the grids. In addition, large oscillations in the ion-ion plasma potential are found in the negative ion extraction phase. The oscillation occurs when the primary plasma approaches the grounded parts of the main core via sub-millimetres technological inputs. By controlling and suppressing the various undesired effects, we achieve perfect ion-ion plasma potential control with stable oscillation-free operation in the range of the available acceleration voltages (±350 V). The measured positive and negative ion currents in the beam are about 10 mA for each component at RF power of 100 W and non-optimized extraction system. Two different energy analyzers with and without magnetic electron suppression system are used to measure and compare the negative and positive ion and electron fluxes formed by the thruster. It is found that at alternate ion-ion extraction the positive and negative ion energy peaks are similar in areas and symmetrical in position with +/− ion energy corresponding to the amplitude of the applied acceleration voltage.« less

X-ray detection with zinc-blende (cubic) GaN Schottky diodes

NASA Astrophysics Data System (ADS)

Gohil, T.; Whale, J.; Lioliou, G.; Novikov, S. V.; Foxon, C. T.; Kent, A. J.; Barnett, A. M.

2016-07-01

The room temperature X-ray responses as functions of time of two n type cubic GaN Schottky diodes (200 μm and 400 μm diameters) are reported. The current densities as functions of time for both diodes showed fast turn-on transients and increases in current density when illuminated with X-ray photons of energy up to 35 keV. The diodes were also electrically characterized: capacitance, implied depletion width and dark current measurements as functions of applied bias at room temperature are presented. At -5 V reverse bias, the capacitances of the diodes were measured to be (84.05 ± 0.01) pF and (121.67 ± 0.02) pF, respectively. At -5 V reverse bias, the dark current densities of the diodes were measured to be (347.2 ± 0.4) mA cm-2 and (189.0 ± 0.2) mA cm-2, respectively. The Schottky barrier heights of the devices (0.52 ± 0.07) eV and (0.63 ± 0.09) eV, respectively, were extracted from the forward dark current characteristics.

New dye-sensitized solar cells obtained from extracted bracts of Bougainvillea glabra and spectabilis betalain pigments by different purification processes.

PubMed

Hernandez-Martinez, Angel Ramon; Estevez, Miriam; Vargas, Susana; Quintanilla, Fracisco; Rodriguez, Rogelio

2011-01-01

The performance of a new dye-sensitized solar cell (DSSC) based in a natural dye extracted from the Bougainvillea spectabilis' bracts, is reported. The performance of this solar cell was compared with cells prepared using extract of the Bougainvillea glabra and mixture of both extracts; in both cases the pigments were betalains, obtained from Reddish-purple extract. These dyes were purified to different extents and used for the construction of solar cells that were electrically characterized. The materials were characterized using FTIR and UV-Vis. Solar cells were assembled using TiO(2) thin film on indium tin oxide (ITO)-coated glass; a mesoporous film was sensitized with the Bougainvillea extracts. The obtained solar energy conversion efficiency was of 0.48% with a current density J(SC) of 2.29 mA/cm(2) using an irradiation of 100 mW/cm(2) at 25 °C.

A large-area RF source for negative hydrogen ions

NASA Astrophysics Data System (ADS)

Frank, P.; Feist, J. H.; Kraus, W.; Speth, E.; Heinemann, B.; Probst, F.; Trainham, R.; Jacquot, C.

1998-08-01

In a collaboration with CEA Cadarache, IPP is presently developing an rf source, in which the production of negative ions (H-/D-) is being investigated. It utilizes PINI-size rf sources with an external antenna and for the first step a small size extraction system with 48 cm2 net extraction area. First results from BATMAN (Ba¯varian T_est Ma¯chine for N_egative Ions) show (without Cs) a linear dependence of the negative ion yield with rf power, without any sign of saturation. At elevated pressure (1.6 Pa) a current density of 4.5 mA/cm2 H- (without Cs) has been found so far. At medium pressure (0.6 Pa) the current density is lower by approx. a factor of 5, but preliminary results with Cesium injection show a relative increase by almost the same factor in this pressure range. Langmuir probe measurements indicate an electron temperature Te>2 eV close to the plasma grid with a moderate magnetic filter (700 Gcm). Attempts to improve the performance by using different magnetic configurations and different wall materials are under way.

Increasing the Extracted Beam Current Density in Ion Thrusters

NASA Astrophysics Data System (ADS)

Arthur, Neil Anderson

Ion thrusters have seen application on space science missions and numerous satellite missions. Ion engines offer higher electrical efficiency and specific impulse capability coupled with longer demonstrated lifetime as compared to other space propulsion technologies. However, ion engines are considered to have low thrust. This work aims to address the low thrust conception; whereby improving ion thruster performance and thrust density will lead to expanded mission capabilities for ion thruster technology. This goal poses a challenge because the mechanism for accelerating ions, the ion optics, is space charge limited according to the Child-Langmuir law-there is a finite number of ions that can be extracted through the grids for a given voltage. Currently, ion thrusters operate at only 40% of this limit, suggesting there is another limit artificially constraining beam current. Experimental evidence suggests the beam current can become source limited-the ion density within the plasma is not large enough to sustain high beam currents. Increasing the discharge current will increase ion density, but ring cusp ion engines become anode area limited at high discharge currents. The ring cusp magnetic field increases ionization efficiency but limits the anode area available for electron collection. Above a threshold current, the plasma becomes unstable. Increasing the engine size is one approach to increasing the operational discharge current, ion density, and thus the beam current, but this presents engineering challenges. The ion optics are a pair of closely spaced grids. As the engine diameter increases, it becomes difficult to maintain a constant grid gap. Span-to-gap considerations for high perveance optics limit ion engines to 50 cm in diameter. NASA designed the annular ion engine to address the anode area limit and scale-up problems by changing the discharge chamber geometry. The annular engine provides a central mounting structure for the optics, allowing the beam area to increase while maintaining a fixed span-to-gap. The central stalk also provides additional surface area for electron collection. Circumventing the anode area limitation, the annular ion engine can operate closer to the Child-Langmuir limit as compared to a conventional cylindrical ion thruster. Preliminary discharge characterization of a 65 cm annular ion engine shows >90% uniformity and validates the scalability of the technology. Operating beyond the Child-Langmuir limit would allow for even larger performance gains. This classic law does not consider the ion injection velocity into the grid sheath. The Child-Langmuir limit shifts towards higher current as the ion velocity increases. Ion drift velocity can be created by enhancing the axially-directed electric field. One method for creating this field is to modify the plasma potential distribution. This can be accomplished by biasing individual magnetic cusps, through isolated, conformal electrodes placed on each magnet ring. Experiments on a 15 cm ion thruster have shown that plasma potential in the bulk can be modified by as much as 5 V and establish ion drift towards the grid plane. Increases in ion current density at the grid by up to 20% are demonstrated. Performance implications are also considered, and increases in simulated beam current of 15% and decreases in discharge losses of 5% are observed. Electron density measurements within the magnetic cusps revealed, surprisingly, as cusp current draw increases, the leak width does not change. This suggests that instead of increasing the electron collection area, cusp bias enhances electron mobility along field lines.

Reduction in Recombination Current Density in Boron Doped Silicon Using Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Young, Matthew Garett

The solar industry has grown immensely in recent years and has reached a point where solar energy has now become inexpensive enough that it is starting to emerge as a mainstream electrical generation source. However, recent economic analysis has suggested that for solar to become a truly wide spread source of electricity, the costs still need to plummet by a factor of 8x. This demands new and innovative concepts to help lower such cost. In pursuit of this goal, this dissertation examines the use of atomic hydrogen to lessen the recombination current density in the boron doped region of n-type silicon solar cells. This required the development of a boron diffusion process that maintained the bulk lifetime of n-type silicon such that the recombination current density could be extracted by photoconductance spectroscopy. It is demonstrated that by hydrogenating boron diffusions, the majority carrier concentration can be controlled. By using symmetrically diffused test structures with quinhydrone-methanol surface passivation the recombination current density of a hydrogenated boron profile is shown to be less than that of a standard boron profile, by as much as 30%. This is then applied to a modified industrial silicon solar cell process to demonstrate an efficiency enhancement of 0.4%.

Radial tunnel diodes based on InP/InGaAs core-shell nanowires

NASA Astrophysics Data System (ADS)

Tizno, Ofogh; Ganjipour, Bahram; Heurlin, Magnus; Thelander, Claes; Borgström, Magnus T.; Samuelson, Lars

2017-03-01

We report on the fabrication and characterization of radial tunnel diodes based on InP(n+)/InGaAs(p+) core-shell nanowires, where the effect of Zn-dopant precursor flow on the electrical properties of the devices is evaluated. Selective and local etching of the InGaAs shell is employed to access the nanowire core in the contact process. Devices with an n+-p doping profile show normal diode rectification, whereas n+-p+ junctions exhibit typical tunnel diode characteristics with peak-to-valley current ratios up to 14 at room temperature and 100 at 4.2 K. A maximum peak current density of 28 A/cm2 and a reverse current density of 7.3 kA/cm2 at VSD = -0.5 V are extracted at room temperature after normalization with the effective junction area.

Engineered cost-effective growth of Co-based nanoflakes as a sustainable water oxidation electrocatalyst

NASA Astrophysics Data System (ADS)

Pourreza, M.; Naseri, N.

2017-11-01

Developing low-cost, scalable and reproducible synthesis methods for water oxidation reaction (WOR) catalysts is highly desirable and also challenging in energy, environmental and industrial applications. In this context, electrochemical deposition is known as an easy and cost-effective technique in nanomaterial growth. Herein, cobalt-based nanoflakes were grown on a flexible and commercially available steel mesh substrate by electrodeposition approach with a crystalline structure as a mixture of oxide, hydroxide and oxyhydroxide phases. For the first time, the correlation between electrodeposition parameters, time and current density, and morphological characteristics of the grown nanoflakes (density and aspect ratio based on SEM results) has been derived. According to a comprehensive study of the flakes’ electrocatalytic performance in WOR, the optimized sample fabricated with a moderate electrodeposition current density (7 mA cm-2) and duration time (2000 s) revealed the highest density (7.6  ×  108 cm-2) and aspect ratio (7.1) as well as the lowest values for overpotential (OP  =  324 mV) and charge transfer resistance (14 Ω). This designed array of Co-based nanoflakes also showed the lowest value of overpotential for bare cobalt-based WOR electrocatalysts reported yet. High and low values for deposition current density and/or deposition time had a negative effect on the sample surface, leaving some areas without any flakes or with incomplete and inefficient formation of nanoflakes with low densities and aspect ratios. A similar effect was observed for annealed samples in the range of 200-400 °C. Based on recorded overpotentials and extracted surface morphological parameters, a linear and logarithmic behavior in overpotential-flake density dependency was proposed for current density and time controlled systems, respectively.

Fabrication and Characterization of Hybrid Organic-Inorganic Electron Extraction Layers for Polymer Solar Cells toward Improved Processing Robustness and Air Stability.

PubMed

Fredj, Donia; Pourcin, Florent; Alkarsifi, Riva; Kilinc, Volkan; Liu, Xianjie; Ben Dkhil, Sadok; Boudjada, Nassira Chniba; Fahlman, Mats; Videlot-Ackermann, Christine; Margeat, Olivier; Ackermann, Jörg; Boujelbene, Mohamed

2018-05-23

Organic-inorganic hybrid materials composed of bismuth and diaminopyridine are studied as novel materials for electron extraction layers in polymer solar cells using regular device structures. The hybrid materials are solution processed on top of two different low band gap polymers (PTB7 or PTB7-Th) as donor materials mixed with fullerene PC 70 BM as the acceptor. The intercalation of the hybrid layer between the photoactive layer and the aluminum cathode leads to solar cells with a power conversion efficiency of 7.8% because of significant improvements in all photovoltaic parameters, that is, short-circuit current density, fill factor, and open-circuit voltage, similar to the reference devices using ZnO as the interfacial layer. However when using thick layers of such hybrid materials for electron extraction, only small losses in photocurrent density are observed in contrast to the reference material ZnO of pronounced losses because of optical spacer effects. Importantly, these hybrid electron extraction layers also strongly improve the device stability in air compared with solar cells processed with ZnO interlayers. Both results underline the high potential of this new class of hybrid materials as electron extraction materials toward robust processing of air stable organic solar cells.

The Influence of Marcellus Shale Extraction Emissions on Regionally Monitored Dry Reactive Nitrogen Deposition.

PubMed

Coughlin, Justin G; Rose, Lucy A; Bain, Daniel J; Elliott, Emily M

2017-03-21

Emissions of nitrogen oxides (NO x ) in the United States (U.S.) from large stationary sources, such as electric generating units, have decreased since 1995, driving decreases in nitrogen deposition. However, increasing NO x emissions from emerging industries, such as unconventional natural gas (UNG) extraction, could offset stationary source emission reductions in shale gas producing regions of the U.S. The Marcellus Shale in the northeastern U.S. has seen dramatic increases in the number of wells and associated natural gas production during the past 10 years. In this study, we examine the potential impacts of shale gas development on regional NO x emission inventories and dry deposition fluxes to Clean Air Status and Trends (CASTNET) sites in Pennsylvania and New York. Our results demonstrate that the current distribution of CASTNET sites is ineffective for monitoring the influence of Marcellus well NO x emissions on regional nitrogen deposition. Despite the fact that existing CASTNET sites are not influenced by UNG extraction activity, NO x emissions densities from shale gas extraction are substantial and are estimated to reach up to 21 kg NO x ha -1 year -1 in some regions. If these emissions deposit locally, UNG extraction activity could contribute to critical nitrogen load exceedances in areas of high well density.

Observations of high-plasma density region in the inner coma of 67P/Churyumov-Gerasimenko during early activity

NASA Astrophysics Data System (ADS)

Yang, Lei; Paulsson, J. J. P.; Wedlund, C. Simon; Odelstad, E.; Edberg, N. J. T.; Koenders, C.; Eriksson, A. I.; Miloch, W. J.

2016-11-01

In 2014 September, as Rosetta transitioned to close bound orbits at 30 km from comet 67P/Churyumov-Gerasimenko, the Rosetta Plasma Consortium Langmuir probe (RPC-LAP) data showed large systematic fluctuations in both the spacecraft potential and the collected currents. We analyse the potential bias sweeps from RPC-LAP, from which we extract three sets of parameters: (1) knee potential, that we relate to the spacecraft potential, (2) the ion attraction current, which is composed of the photoelectron emission current from the probe as well as contributions from local ions, secondary emission, and low-energy electrons, and (3) an electron current whose variation is, in turn, an estimate of the electron density variation. We study the evolution of these parameters between 4 and 3.2 au in heliocentric and cometocentric frames. We find on September 9 a transition into a high-density plasma region characterized by increased knee potential fluctuations and plasma currents to the probe. In conjunction with previous studies, the early cometary plasma can be seen as composed of two regions: an outer region characterized by solar wind plasma, and small quantities of pick-up ions, and an inner region with enhanced plasma densities. This conclusion is in agreement with other RPC instruments such as RPC-MAG, RPC-IES and RPC-ICA, and numerical simulations.

Helicon plasma generator-assisted surface conversion ion source for the production of H- ion beams at the Los Alamos Neutron Science Centera)

NASA Astrophysics Data System (ADS)

Tarvainen, O.; Rouleau, G.; Keller, R.; Geros, E.; Stelzer, J.; Ferris, J.

2008-02-01

The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H- ion beams in a filament-driven discharge. In this kind of an ion source the extracted H- beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H- converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H- ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H- ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H- production (main discharge) in order to further improve the brightness of extracted H- ion beams.

Helicon plasma generator-assisted surface conversion ion source for the production of H(-) ion beams at the Los Alamos Neutron Science Center.

PubMed

Tarvainen, O; Rouleau, G; Keller, R; Geros, E; Stelzer, J; Ferris, J

2008-02-01

The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H(-) ion beams in a filament-driven discharge. In this kind of an ion source the extracted H(-) beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H(-) converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H(-) ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H(-) ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H(-) production (main discharge) in order to further improve the brightness of extracted H(-) ion beams.

Leakage current conduction mechanisms and electrical properties of atomic-layer-deposited HfO2/Ga2O3 MOS capacitors

NASA Astrophysics Data System (ADS)

Zhang, Hongpeng; Jia, Renxu; Lei, Yuan; Tang, Xiaoyan; Zhang, Yimen; Zhang, Yuming

2018-02-01

In this paper, current conduction mechanisms in HfO2/β-Ga2O3 metal-oxide-semiconductor (MOS) capacitors under positive and negative biases are investigated using the current-voltage (I-V) measurements conducted at temperatures from 298 K to 378 K. The Schottky emission is dominant under positively biased electric fields of 0.37-2.19 MV cm-1, and the extracted Schottky barrier height ranged from 0.88 eV to 0.91 eV at various temperatures. The Poole-Frenkel emission dominates under negatively biased fields of 1.92-4.83 MV cm-1, and the trap energy levels are from 0.71 eV to 0.77 eV at various temperatures. The conduction band offset (ΔE c) of HfO2/β-Ga2O3 is extracted to be 1.31  ±  0.05 eV via x-ray photoelectron spectroscopy, while a large negative sheet charge density of 1.04  ×  1013 cm-2 is induced at the oxide layer and/or HfO2/β-Ga2O3 interface. A low C-V hysteresis of 0.76 V, low interface state density (D it) close to 1  ×  1012 eV-1 cm-2, and low leakage current density of 2.38  ×  10-5 A cm-2 at a gate voltage of 7 V has been obtained, suggesting the great electrical properties of HfO2/β-Ga2O3 MOSCAP. According to the above analysis, ALD-HfO2 is an attractive candidate for high voltage β-Ga2O3 power devices.

Morinda citrifolia L. Leaf Extract Protects against Cerebral Ischemia and Osteoporosis in an In Vivo Experimental Model of Menopause

PubMed Central

Thipkaew, Cholathip; Thukham-mee, Wipawee; Wannanon, Panakaporn

2018-01-01

We aimed to determine the protective effects against cerebral ischemia and osteoporosis of Morinda citrifolia extract in experimental menopause. The neuroprotective effect was assessed by giving M. citrifolia leaf extract at doses of 2, 10, and 50 mg/kg BW to the bilateral ovariectomized (OVX) rats for 7 days. Then, they were occluded in the right middle cerebral artery (MCAO) for 90 minutes. The neurological score, brain infarction volume, oxidative stress status, and ERK1/2 and eNOS activities were assessed 24 hours later. M. citrifolia improved neurological score, brain infarction, and brain oxidative stress status in the cortex of OVX rats plus the MCAO. No changes in ERK 1/2 signal pathway and NOS expression were observed in this area. Our data suggested that the neuroprotective effect of the extract might occur partly via the improvement of oxidative stress status in the cortex. The antiosteoporotic effect in OVX rats was also assessed after an 84-day intervention of M. citrifolia. The serum levels of calcium, osteocalcin, and alkaline phosphatase and osteoblast density in the tibia were increased, but the density of osteoclast was decreased in OVX rats which received the extract. Therefore, the current data suggested that the extract possessed antiosteoporotic effect by increasing bone formation but decreasing bone resorption. PMID:29765488

Morinda citrifolia L. Leaf Extract Protects against Cerebral Ischemia and Osteoporosis in an In Vivo Experimental Model of Menopause.

PubMed

Wattanathorn, Jintanaporn; Thipkaew, Cholathip; Thukham-Mee, Wipawee; Muchimapura, Supaporn; Wannanon, Panakaporn; Tong-Un, Terdthai

2018-01-01

We aimed to determine the protective effects against cerebral ischemia and osteoporosis of Morinda citrifolia extract in experimental menopause. The neuroprotective effect was assessed by giving M. citrifolia leaf extract at doses of 2, 10, and 50 mg/kg BW to the bilateral ovariectomized (OVX) rats for 7 days. Then, they were occluded in the right middle cerebral artery (MCAO) for 90 minutes. The neurological score, brain infarction volume, oxidative stress status, and ERK1/2 and eNOS activities were assessed 24 hours later. M. citrifolia improved neurological score, brain infarction, and brain oxidative stress status in the cortex of OVX rats plus the MCAO. No changes in ERK 1/2 signal pathway and NOS expression were observed in this area. Our data suggested that the neuroprotective effect of the extract might occur partly via the improvement of oxidative stress status in the cortex. The antiosteoporotic effect in OVX rats was also assessed after an 84-day intervention of M. citrifolia . The serum levels of calcium, osteocalcin, and alkaline phosphatase and osteoblast density in the tibia were increased, but the density of osteoclast was decreased in OVX rats which received the extract. Therefore, the current data suggested that the extract possessed antiosteoporotic effect by increasing bone formation but decreasing bone resorption.

High performance of mixed halide perovskite solar cells: Role of halogen atom and plasmonic nanoparticles on the ideal current density of cell

NASA Astrophysics Data System (ADS)

Mohebpour, Mohammad Ali; Saffari, Mohaddeseh; Soleimani, Hamid Rahimpour; Tagani, Meysam Bagheri

2018-03-01

To be able to increase the efficiency of perovskite solar cells which is one of the most substantial challenges ahead in photovoltaic industry, the structural and optical properties of perovskite CH3NH3PbI3-xBrx for values x = 1-3 have been studied employing density functional theory (DFT). Using the optical constants extracted from DFT calculations, the amount of light reflectance and ideal current density of a simulated single-junction perovskite solar cell have been investigated. The results of DFT calculations indicate that adding halogen bromide to CH3NH3PbI3 compound causes the relocation of energy bands in band structure which its consequence is increasing the bandgap. In addition, the effect of increasing Br in this structure can be seen as a reduction in lattice constant, refractive index, extinction and absorption coefficient. As well, results of the simulation suggest a significant current density enhancement as much as 22% can be achieved by an optimized array of Platinum nanoparticles that is remarkable. This plan is able to be a prelude for accomplishment of solar cells with higher energy conversion efficiency.

Interface state density distribution in Au/n-ZnO nanorods Schottky diodes

NASA Astrophysics Data System (ADS)

Faraz, S. M.; Willander, M.; Wahab, Q.

2012-04-01

Interface states density (NSS) distribution is extracted in Au/ ZnO Schottky diodes. Nanorods of ZnO are grown on silver (Ag) using aqueous chemical growth (ACG) technique. Well aligned hexagonal-shaped vertical nanorods of a mean diameter of 300 - 450 nm and 1.3 -1.9 μm high are revealed in SEM. Gold (Au) Schottky contacts of thickness 60 nm and 1.5mm diameter were evaporated. For electrical characterization of Schottky diodes current-voltage (I-V) and capacitance-Voltage (C-V) measurements are performed. The diodes exhibited a typical non-linear rectifying behavior with a barrier height of 0.62eV and ideality factor of 4.3. Possible reasons for low barrier height and high ideality factor have been addressed. Series resistance (RS) has been calculated from forward I-V characteristics using Chueng's function. The density of interfacial states (NSS) below the conduction band (EC-ESS) is extracted using I-V and C-V measured values. A decrease in interface states density (NSS) is observed from 3.74 × 1011 - 7.98 × 1010 eV-1 cm-2 from 0.30eV - 0.61eV below the conduction band edge.

Improvement on the Repair Effect of Electrochemical Chloride Extraction Using a Modified Electrode Configuration

PubMed Central

Feng, Wei; Xu, Jinxia; Jiang, Linhua; Song, Yingbin; Cao, Yalong; Tan, Qiping

2018-01-01

To improve the repair effect of electrochemical chloride extraction, a modified electrode configuration is applied in this investigation. In this configuration, two auxiliary electrodes placed in the anodic and cathodic electrolytes were used as the anode and cathode, respectively. Besides this, the steel in the mortar was grounded to protect it from corrosion. By a comparative experiment, the potential evolution, various ions concentrations (Cl−, OH−, Na+, and K+) in different mortar depths, the corrosion potential, and the current density of the steel were measured. The results indicate that compared to electrochemical chloride extraction with the traditional electrode configuration, this electrochemical chloride extraction method with a modified electrode configuration has a similar chloride removal ratio. Besides this, potential of steel is just about 800 mV for a saturated calomel electrode (SCE) during the treatment, which did not reach the hydrogen evolution potential. The phenomenon of the accumulation of OH−, Na+, and K+ did not occur when the modified electrode configuration is applied. Additionally, higher corrosion potentials and lower corrosion current rates were measured after performing electrochemical chloride extraction with the modified electrode configuration. Additionally, it is a short period of time for the steel to go from activation to passivation. On this basis, the modified electrode configuration may overcome the drawbacks of electrochemical chloride extraction. PMID:29389855

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab

2012-02-15

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

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

PubMed

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

2012-02-01

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

Ultrahigh-current-density metal-ion implantation and diamondlike-hydrocarbon films for tribological applications

NASA Astrophysics Data System (ADS)

Wilbur, P. J.

1993-09-01

The metal-ion-implantation system used to implant metals into substrates are described. The metal vapor required for operation is supplied by drawing sufficient electron current from the plasma discharge to an anode-potential crucible so a solid, pure metal placed in the crucible will be heated to the point of vaporization. The ion-producing, plasma discharge is initiated within a graphite-ion-source body, which operates at high temperature, by using an argon flow that is turned off once the metal vapor is present. Extraction of ion beams several cm in diameter at current densities ranging to several hundred micro-A/sq cm on a target 50 cm downstream of the ion source were demonstrated using Mg, Ag, Cr, Cu, Si, Ti, V, B, and Zr. These metals were implanted into over 100 substrates (discs, pins, flats, wires). A model describing thermal stresses induced in materials (e.g. ceramic plates) during high-current-density implantation is presented. Tribological and microstructural characteristics of iron and 304-stainless-steel samples implanted with Ti or B are examined. Diamondlike-hydrocarbon coatings were applied to steel surfaces and found to exhibit good tribological performance.

Characterization of perovskite solar cells: Towards a reliable measurement protocol

NASA Astrophysics Data System (ADS)

Zimmermann, Eugen; Wong, Ka Kan; Müller, Michael; Hu, Hao; Ehrenreich, Philipp; Kohlstädt, Markus; Würfel, Uli; Mastroianni, Simone; Mathiazhagan, Gayathri; Hinsch, Andreas; Gujar, Tanaji P.; Thelakkat, Mukundan; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Lead halide perovskite solar cells have shown a tremendous rise in power conversion efficiency with reported record efficiencies of over 20% making this material very promising as a low cost alternative to conventional inorganic solar cells. However, due to a differently severe "hysteretic" behaviour during current density-voltage measurements, which strongly depends on scan rate, device and measurement history, preparation method, device architecture, etc., commonly used solar cell measurements do not give reliable or even reproducible results. For the aspect of commercialization and the possibility to compare results of different devices among different laboratories, it is necessary to establish a measurement protocol which gives reproducible results. Therefore, we compare device characteristics derived from standard current density-voltage measurements with stabilized values obtained from an adaptive tracking of the maximum power point and the open circuit voltage as well as characteristics extracted from time resolved current density-voltage measurements. Our results provide insight into the challenges of a correct determination of device performance and propose a measurement protocol for a reliable characterisation which is easy to implement and has been tested on varying perovskite solar cells fabricated in different laboratories.

Determination of fluid extraction and osmotic conductance sigma K in the lung with hypertonic NaCl infusion. I. Theory.

PubMed

Hunter, M; Lee, J

1992-11-01

A dispersion and extraction model of the lung is developed to assess how the infusion of hypertonic saline into the pulmonary artery changes the gravimetric density of pulmonary venous blood. The dispersion analysis is built on the indicator dilution curve measured for the pulmonary circulation. The extraction model consists of microvascular and interstitial compartments separated by a permeable pulmonary endothelium. Because the density of fluid extracted by the hypertonic disturbance is lower than the blood density, the extraction leads to a decrease in blood density. Two cases of fluid extraction are analyzed, a hypertonic infusion to elevate the osmotic pressure in the pulmonary arterial blood in the form of a step function and an infusion performed over a period of 1 sec. Both cases show that the dispersion significantly attenuates the changes in osmotic pressure and density as they are transported by the blood along the pulmonary vasculature. Because the model has taken into account the effect of dispersion and pulmonary blood flow, the equations developed here provide the basis to calculate from the density change in pulmonary venous blood the characteristics of osmotic extraction intrinsic to the lung.

Quantitative magneto-optical analysis of the role of finite temperatures on the critical state in YBCO thin films

NASA Astrophysics Data System (ADS)

Albrecht, Joachim; Brück, Sebastian; Stahl, Claudia; Ruoß, Stephen

2016-11-01

We use quantitative magneto-optical microscopy to investigate the influence of finite temperatures on the critical state of thin YBCO films. In particular, temperature and time dependence of supercurrents in inhomogeneous and anisotropic films are analyzed to extract the role of temperature on the supercurrents themselves and the influence of thermally activated relaxation. We find that inhomogeneities and anisotropies of the current density distribution correspond to a different temperature dependence of local supercurrents. In addition, the thermally activated decay of supercurrents can be used to extract local vortex pinning energies. With these results the modification of vortex pinning introduced by substrate structures is studied. In summary the local investigation of supercurrent densities allows the full description of the vortex pinning landscape with respect to pinning forces and energies in superconducting films with complex properties under the influence of finite temperatures.

Versatile plasma ion source with an internal evaporator

NASA Astrophysics Data System (ADS)

Turek, M.; Prucnal, S.; Drozdziel, A.; Pyszniak, K.

2011-04-01

A novel construction of an ion source with an evaporator placed inside a plasma chamber is presented. The crucible is heated to high temperatures directly by arc discharge, which makes the ion source suitable for substances with high melting points. The compact ion source enables production of intense ion beams for wide spectrum of solid elements with typical separated beam currents of ˜100-150 μA for Al +, Mn +, As + (which corresponds to emission current densities of 15-25 mA/cm 2) for the extraction voltage of 25 kV. The ion source works for approximately 50-70 h at 100% duty cycle, which enables high ion dose implantation. The typical power consumption of the ion source is 350-400 W. The paper presents detailed experimental data (e.g. dependences of ion currents and anode voltages on discharge and filament currents and magnetic flux densities) for Cr, Fe, Al, As, Mn and In. The discussion is supported by results of Monte Carlo method based numerical simulation of ionisation in the ion source.

Photocarrier extraction in GaAsSb/GaAsN type-II QW superlattice solar cells

NASA Astrophysics Data System (ADS)

Aeberhard, U.; Gonzalo, A.; Ulloa, J. M.

2018-05-01

Photocarrier transport and extraction in GaAsSb/GaAsN type-II quantum well superlattices are investigated by means of inelastic quantum transport calculations based on the non-equilibrium Green's function formalism. Evaluation of the local density of states and the spectral current flow enables the identification of different regimes for carrier localization, transport, and extraction as a function of configurational parameters. These include the number of periods, the thicknesses of the individual layers in one period, the built-in electric field, and the temperature of operation. The results for the carrier extraction efficiency are related to experimental data for different symmetric GaAsSb/GaAsN type-II quantum well superlattice solar cell devices and provide a qualitative explanation for the experimentally observed dependence of photovoltaic device performance on the period thickness.

New Dye-Sensitized Solar Cells Obtained from Extracted Bracts of Bougainvillea Glabra and Spectabilis Betalain Pigments by Different Purification Processes

PubMed Central

Hernandez-Martinez, Angel Ramon; Estevez, Miriam; Vargas, Susana; Quintanilla, Fracisco; Rodriguez, Rogelio

2011-01-01

The performance of a new dye-sensitized solar cell (DSSC) based in a natural dye extracted from the Bougainvillea spectabilis’ bracts, is reported. The performance of this solar cell was compared with cells prepared using extract of the Bougainvillea glabra and mixture of both extracts; in both cases the pigments were betalains, obtained from Reddish-purple extract. These dyes were purified to different extents and used for the construction of solar cells that were electrically characterized. The materials were characterized using FTIR and UV-Vis. Solar cells were assembled using TiO2 thin film on indium tin oxide (ITO)-coated glass; a mesoporous film was sensitized with the Bougainvillea extracts. The obtained solar energy conversion efficiency was of 0.48% with a current density JSC of 2.29 mA/cm2 using an irradiation of 100 mW/cm2 at 25 °C. PMID:22016609

Green synthesis of nitrogen-doped graphitic carbon sheets with use of Prunus persica for supercapacitor applications

NASA Astrophysics Data System (ADS)

Atchudan, Raji; Edison, Thomas Nesakumar Jebakumar Immanuel; Perumal, Suguna; Lee, Yong Rok

2017-01-01

Nitrogen-doped graphitic carbon sheets (N-GCSs) were prepared from the extract of unripe Prunus persica fruit by a direct hydrothermal method. The synthesized N-GCSs were examined by high resolution transmission electron microscopy (HRTEM), nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy. HRTEM showed that the synthesized carbon sheets were graphitic with lattice fringes and an inter-layer distance of 0.36 nm. Doping with the nitrogen moiety present over the synthesized GCSs was confirmed by XPS, FT-IR spectroscopy, and energy dispersive X-ray spectroscopy elemental mapping. The fruit extract associated with hydrothermal-carbonization method is economical and eco-friendly with a single step process. The resulting carbon sheets could be modified and are promising candidates for nano-electronic applications, including supercapacitors. The synthesized N-GCSs-2 provided a high specific capacitance of 176 F g-1 at a current density of 0.1 A g-1. This electrode material has excellent cyclic stability, even after 2000 cycles of charge-discharge at a current density of 0.5 A g-1.

Hot LO-phonon limited electron transport in ZnO/MgZnO channels

NASA Astrophysics Data System (ADS)

Šermukšnis, E.; Liberis, J.; Matulionis, A.; Avrutin, V.; Toporkov, M.; Özgür, Ü.; Morkoç, H.

2018-05-01

High-field electron transport in two-dimensional channels at ZnO/MgZnO heterointerfaces has been investigated experimentally. Pulsed current-voltage (I-V) and microwave noise measurements used voltage pulse widths down to 30 ns and electric fields up to 100 kV/cm. The samples investigated featured electron densities in the range of 4.2-6.5 × 1012 cm-2, and room temperature mobilities of 142-185 cm2/V s. The pulsed nature of the applied field ensured negligible, if any, change in the electron density, thereby allowing velocity extraction from current with confidence. The highest extracted electron drift velocity of ˜0.5 × 107 cm/s is somewhat smaller than that estimated for bulk ZnO; this difference is explained in the framework of longitudinal optical phonon accumulation (hot-phonon effect). The microwave noise data allowed us to rule out the effect of excess acoustic phonon temperature caused by Joule heating. Real-space transfer of hot electrons into the wider bandgap MgZnO layer was observed to be a limiting factor in samples with a high Mg content (48%), due to phase segregation and the associated local lowering of the potential barrier.

Determination of Charge-Carrier Mobility in Disordered Thin-Film Solar Cells as a Function of Current Density

NASA Astrophysics Data System (ADS)

Mäckel, Helmut; MacKenzie, Roderick C. I.

2018-03-01

Charge-carrier mobility is a fundamental material parameter, which plays an important role in determining solar-cell efficiency. The higher the mobility, the less time a charge carrier will spend in a device and the less likely it is that it will be lost to recombination. Despite the importance of this physical property, it is notoriously difficult to measure accurately in disordered thin-film solar cells under operating conditions. We, therefore, investigate a method previously proposed in the literature for the determination of mobility as a function of current density. The method is based on a simple analytical model that relates the mobility to carrier density and transport resistance. By revising the theoretical background of the method, we clearly demonstrate what type of mobility can be extracted (constant mobility or effective mobility of electrons and holes). We generalize the method to any combination of measurements that is able to determine the mean electron and hole carrier density, and the transport resistance at a given current density. We explore the robustness of the method by simulating typical organic solar-cell structures with a variety of physical properties, including unbalanced mobilities, unbalanced carrier densities, and for high or low carrier trapping rates. The simulations reveal that near VOC and JSC , the method fails due to the limitation of determining the transport resistance. However, away from these regions (and, importantly, around the maximum power point), the method can accurately determine charge-carrier mobility. In the presence of strong carrier trapping, the method overestimates the effective mobility due to an underestimation of the carrier density.

Electrical properties of radio-frequency sputtered HfO2 thin films for advanced CMOS technology

NASA Astrophysics Data System (ADS)

Sarkar, Pranab Kumar; Roy, Asim

2015-08-01

The Hafnium oxide (HfO2) high-k thin films have been deposited by radio frequency (rf) sputtering technique on p-type Si (100) substrate. The thickness, composition and phases of films in relation to annealing temperatures have been investigated by using cross sectional FE-SEM (Field Emission Scanning Electron Microscope) and grazing incidence x-ray diffraction (GI-XRD), respectively. GI-XRD analysis revealed that at annealing temperatures of 350°C, films phases change to crystalline from amorphous. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the annealed HfO2 film have been studied employing Al/HfO2/p-Si metal-oxide-semiconductor (MOS) structures. The electrical properties such as dielectric constant, interface trap density and leakage current density have been also extracted from C-V and I-V Measurements. The value of dielectric constant, interface trap density and leakage current density of annealed HfO2 film is obtained as 23,7.57×1011eV-1 cm-2 and 2.7×10-5 Acm-2, respectively. In this work we also reported the influence of post deposition annealing onto the trapping properties of hafnium oxide and optimized conditions under which no charge trapping is observed into the dielectric stack.

Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage.

PubMed

Venkatesan, Swaminathan; Ngo, Evan C; Chen, Qiliang; Dubey, Ashish; Mohammad, Lal; Adhikari, Nirmal; Mitul, Abu Farzan; Qiao, Qiquan

2014-06-21

Single and double junction solar cells with high open circuit voltage were fabricated using poly{thiophene-2,5-diyl-alt-[5,6-bis(dodecyloxy)benzo[c][1,2,5]thiadiazole]-4,7-diyl} (PBT-T1) blended with fullerene derivatives in different weight ratios. The role of fullerene loading on structural and morphological changes was investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD). The XRD and AFM measurements showed that a higher fullerene mixing ratio led to breaking of inter-chain packing and hence resulted in smaller disordered polymer domains. When the PBT-T1:PC60BM weight ratio was 1 : 1, the polymer retained its structural order; however, large aggregated domains formed, leading to poor device performance due to low fill factor and short circuit current density. When the ratio was increased to 1 : 2 and then 1 : 3, smaller amorphous domains were observed, which improved photovoltaic performance. The 1 : 2 blending ratio was optimal due to adequate charge transport pathways giving rise to moderate short circuit current density and fill factor. Adding 1,8-diiodooctane (DIO) additive into the 1 : 2 blend films further improved both the short circuit current density and fill factor, leading to an increased efficiency to 4.5% with PC60BM and 5.65% with PC70BM. These single junction solar cells exhibited a high open circuit voltage at ∼ 0.9 V. Photo-charge extraction by linearly increasing voltage (Photo-CELIV) measurements showed the highest charge carrier mobility in the 1 : 2 film among the three ratios, which was further enhanced by introducing the DIO. The Photo-CELIV measurements with varying delay times showed significantly higher extracted charge carrier density for cells processed with DIO. Tandem devices using P3HT:IC60BA as bottom cell and PBT-T1:PC60BM as top cell exhibited a high open circuit voltage of 1.62 V with 5.2% power conversion efficiency.

Preliminary results concerning the simulation of beam profiles from extracted ion current distributions for mini-STRIKE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agostinetti, P., E-mail: piero.agostinetti@igi.cnr.it; Serianni, G.; Veltri, P.

The Radio Frequency (RF) negative hydrogen ion source prototype has been chosen for the ITER neutral beam injectors due to its optimal performances and easier maintenance demonstrated at Max-Planck-Institut für Plasmaphysik, Garching in hydrogen and deuterium. One of the key information to better understand the operating behavior of the RF ion sources is the extracted negative ion current density distribution. This distribution—influenced by several factors like source geometry, particle drifts inside the source, cesium distribution, and layout of cesium ovens—is not straightforward to be evaluated. The main outcome of the present contribution is the development of a minimization method tomore » estimate the extracted current distribution using the footprint of the beam recorded with mini-STRIKE (Short-Time Retractable Instrumented Kalorimeter). To accomplish this, a series of four computational models have been set up, where the output of a model is the input of the following one. These models compute the optics of the ion beam, evaluate the distribution of the heat deposited on the mini-STRIKE diagnostic calorimeter, and finally give an estimate of the temperature distribution on the back of mini-STRIKE. Several iterations with different extracted current profiles are necessary to give an estimate of the profile most compatible with the experimental data. A first test of the application of the method to the BAvarian Test Machine for Negative ions beam is given.« less

Hepatoprotective Effect and Chemical Assessment of a Selected Egyptian Chickpea Cultivar

PubMed Central

Mekky, Reham H.; Fayed, Mostafa R.; El-Gindi, Mohamed R.; Abdel-Monem, Azza R.; Contreras, María del Mar; Segura-Carretero, Antonio; Abdel-Sattar, Essam

2016-01-01

Chickpea (Cicer arietinum) is a legume of the family Fabaceae, subfamily Faboideae. In Egypt, chickpea seeds are usually consumed at raw green and tender stage, or in the form of mature dry seeds. In our previous study, ‘Giza 1’ seeds exhibited stronger antioxidant activity and higher total phenol content than those from other Egyptian cultivars. In order to assess the biological potential of ‘Giza 1’ seeds in vivo, the extraction procedure was reproduced here. The extract was standardized using liquid chromatography coupled to diode array detector and tandem mass spectrometry (MS/MS) to evaluate their hepatoprotective effect on carbon tetrachloride (CCl4)-induced hepatotoxicity in rats and acute toxicity. Administration of the extract to rats in doses up to 2 g/Kg) did not cause any mortalities or observable signs of toxicity. Further, the plant extract showed a strong hepatoprotective activity based on assessing serum alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase and levels of albumen, globulin, total protein, total cholesterol, high density lipoprotein, triglycerides, and low density lipoprotein. The antioxidative activity was evaluated by assessing hepatic catalase and superoxide dismutase activity as well as reduced glutathione, and malondialdehyde levels. Additionally, anti-inflammatory activity was observed as the extract significantly lowered the hepatic tumor necrosis factor α content. Histopathological examination of liver tissues indicated that the extract-treated animals showed almost normal hepatic architecture with fewer pathological changes. In conclusion, the current results suggest that the chickpea extract possesses an excellent safety profile with very low acute toxicity. Also, it exhibits a significant hepatoprotective effect against CCl4-induced liver injury in rats. This can be attributed, at least partly, to the antioxidant and anti-inflammatory activity of the isoflavones and phenolic acids content of the extract. PMID:27733831

Hepatoprotective Effect and Chemical Assessment of a Selected Egyptian Chickpea Cultivar.

PubMed

Mekky, Reham H; Fayed, Mostafa R; El-Gindi, Mohamed R; Abdel-Monem, Azza R; Contreras, María Del Mar; Segura-Carretero, Antonio; Abdel-Sattar, Essam

2016-01-01

Chickpea ( Cicer arietinum ) is a legume of the family Fabaceae, subfamily Faboideae. In Egypt, chickpea seeds are usually consumed at raw green and tender stage, or in the form of mature dry seeds. In our previous study, 'Giza 1' seeds exhibited stronger antioxidant activity and higher total phenol content than those from other Egyptian cultivars. In order to assess the biological potential of 'Giza 1' seeds in vivo , the extraction procedure was reproduced here. The extract was standardized using liquid chromatography coupled to diode array detector and tandem mass spectrometry (MS/MS) to evaluate their hepatoprotective effect on carbon tetrachloride (CCl 4 )-induced hepatotoxicity in rats and acute toxicity. Administration of the extract to rats in doses up to 2 g/Kg) did not cause any mortalities or observable signs of toxicity. Further, the plant extract showed a strong hepatoprotective activity based on assessing serum alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase and levels of albumen, globulin, total protein, total cholesterol, high density lipoprotein, triglycerides, and low density lipoprotein. The antioxidative activity was evaluated by assessing hepatic catalase and superoxide dismutase activity as well as reduced glutathione, and malondialdehyde levels. Additionally, anti-inflammatory activity was observed as the extract significantly lowered the hepatic tumor necrosis factor α content. Histopathological examination of liver tissues indicated that the extract-treated animals showed almost normal hepatic architecture with fewer pathological changes. In conclusion, the current results suggest that the chickpea extract possesses an excellent safety profile with very low acute toxicity. Also, it exhibits a significant hepatoprotective effect against CCl 4 -induced liver injury in rats. This can be attributed, at least partly, to the antioxidant and anti-inflammatory activity of the isoflavones and phenolic acids content of the extract.

Automated extraction of natural drainage density patterns for the conterminous United States through high performance computing

USGS Publications Warehouse

Stanislawski, Larry V.; Falgout, Jeff T.; Buttenfield, Barbara P.

2015-01-01

Hydrographic networks form an important data foundation for cartographic base mapping and for hydrologic analysis. Drainage density patterns for these networks can be derived to characterize local landscape, bedrock and climate conditions, and further inform hydrologic and geomorphological analysis by indicating areas where too few headwater channels have been extracted. But natural drainage density patterns are not consistently available in existing hydrographic data for the United States because compilation and capture criteria historically varied, along with climate, during the period of data collection over the various terrain types throughout the country. This paper demonstrates an automated workflow that is being tested in a high-performance computing environment by the U.S. Geological Survey (USGS) to map natural drainage density patterns at the 1:24,000-scale (24K) for the conterminous United States. Hydrographic network drainage patterns may be extracted from elevation data to guide corrections for existing hydrographic network data. The paper describes three stages in this workflow including data pre-processing, natural channel extraction, and generation of drainage density patterns from extracted channels. The workflow is concurrently implemented by executing procedures on multiple subbasin watersheds within the U.S. National Hydrography Dataset (NHD). Pre-processing defines parameters that are needed for the extraction process. Extraction proceeds in standard fashion: filling sinks, developing flow direction and weighted flow accumulation rasters. Drainage channels with assigned Strahler stream order are extracted within a subbasin and simplified. Drainage density patterns are then estimated with 100-meter resolution and subsequently smoothed with a low-pass filter. The extraction process is found to be of better quality in higher slope terrains. Concurrent processing through the high performance computing environment is shown to facilitate and refine the choice of drainage density extraction parameters and more readily improve extraction procedures than conventional processing.

100 s extraction of negative ion beams by using actively temperature-controlled plasma grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, A., E-mail: kojima.atsushi@jaea.go.jp; Hanada, M.; Yoshida, M.

2014-02-15

Long pulse beam extraction with a current density of 120 A/m{sup 2} for 100 s has been achieved with a newly developed plasma grid (PG) for the JT-60SA negative ion source which is designed to produce high power and long pulse beams with a negative ion current of 130 A/m{sup 2} (22 A) and a pulse length of 100 s. The PG temperature is regulated by fluorinated fluids in order to keep the high PG temperature for the cesium-seeded negative ion production. The time constant for temperature controllability of the PG was measured to be below 10 s, which wasmore » mainly determined by the heat transfer coefficient of the fluorinated fluid. The measured decay time of the negative ion current extracted from the actively temperature-controlled PG was 430 s which was sufficient for the JT-60SA requirement, and much longer than that by inertial-cooling PG of 60 s. Obtained results of the long pulse capability are utilized to design the full size PG for the JT-60SA negative ion source.« less

Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y., E-mail: thuzhangyu@foxmail.com; Huang, S. L., E-mail: huangsling@tsinghua.edu.cn; Wang, S.

The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency formore » all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert–Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.« less

Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

PubMed

Zhang, Y; Huang, S L; Wang, S; Zhao, W

2016-05-01

The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

Estimation of Wheat Plant Density at Early Stages Using High Resolution Imagery

PubMed Central

Liu, Shouyang; Baret, Fred; Andrieu, Bruno; Burger, Philippe; Hemmerlé, Matthieu

2017-01-01

Crop density is a key agronomical trait used to manage wheat crops and estimate yield. Visual counting of plants in the field is currently the most common method used. However, it is tedious and time consuming. The main objective of this work is to develop a machine vision based method to automate the density survey of wheat at early stages. RGB images taken with a high resolution RGB camera are classified to identify the green pixels corresponding to the plants. Crop rows are extracted and the connected components (objects) are identified. A neural network is then trained to estimate the number of plants in the objects using the object features. The method was evaluated over three experiments showing contrasted conditions with sowing densities ranging from 100 to 600 seeds⋅m-2. Results demonstrate that the density is accurately estimated with an average relative error of 12%. The pipeline developed here provides an efficient and accurate estimate of wheat plant density at early stages. PMID:28559901

Enhancement of SPES source performances.

PubMed

Fagotti, E; Palmieri, A; Ren, X

2008-02-01

Installation of SPES source at LNL was finished in July 2006 and the first beam was extracted in September 2006. Commissioning results confirmed very good performance of the extracted current density. Conversely, source reliability was very poor due to glow-discharge phenomena, which were caused by the ion source axial magnetic field protruding in the high-voltage column. This problem was fixed by changing the stainless steel plasma electrode support with a ferromagnetic one. This new configuration required us to recalculate ion source solenoids positions and fields in order to recover the correct resonance pattern. Details on magnetic simulations and experimental results of high voltage column shielding are presented.

A comprehensive study of charge trapping in organic field-effect devices with promising semiconductors and different contact metals by displacement current measurements

NASA Astrophysics Data System (ADS)

Bisoyi, Sibani; Rödel, Reinhold; Zschieschang, Ute; Kang, Myeong Jin; Takimiya, Kazuo; Klauk, Hagen; Tiwari, Shree Prakash

2016-02-01

A systematic and comprehensive study on the charge-carrier injection and trapping behavior was performed using displacement current measurements in long-channel capacitors based on four promising small-molecule organic semiconductors (pentacene, DNTT, C10-DNTT and DPh-DNTT). In thin-film transistors, these semiconductors showed charge-carrier mobilities ranging from 1.0 to 7.8 cm2 V-1 s-1. The number of charges injected into and extracted from the semiconductor and the density of charges trapped in the device during each measurement were calculated from the displacement current characteristics and it was found that the density of trapped charges is very similar in all devices and of the order 1012 cm-2, despite the fact that the four semiconductors show significantly different charge-carrier mobilities. The choice of the contact metal (Au, Ag, Cu, Pd) was also found to have no significant effect on the trapping behavior.

Charge Transport in Spiro-OMeTAD Investigated through Space-Charge-Limited Current Measurements

NASA Astrophysics Data System (ADS)

Röhr, Jason A.; Shi, Xingyuan; Haque, Saif A.; Kirchartz, Thomas; Nelson, Jenny

2018-04-01

Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density-voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2 ,2',7 ,7' -tetrakis(N ,N -di-4-methoxyphenylamine)-9 ,9' -spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density-voltage curves from space-charge-limited current measurements.

GaN MOSFET with Boron Trichloride-Based Dry Recess Process

NASA Astrophysics Data System (ADS)

Jiang, Y.; Wang, Q. P.; Tamai, K.; Miyashita, T.; Motoyama, S.; Wang, D. J.; Ao, J. P.; Ohno, Y.

2013-06-01

The dry recessed-gate GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) on AlGaN/GaN heterostructure using boron trichloride (BCl3) as etching gas were fabricated and characterized. Etching with different etching power was conducted. Devices with silicon tetrachloride (SiCl4) etching gas were also prepared for comparison. Field-effect mobility and interface state density were extracted from current-voltage (I-V) characteristics. GaN MOSFETs on AlGaN/GaN heterostructure with BCl3 based dry recess achieved a high maximum electron mobility of 141.5 cm2V-1s-1 and a low interface state density.

Status report on the development of a tubular electron beam ion source

NASA Astrophysics Data System (ADS)

Donets, E. D.; Donets, E. E.; Becker, R.; Liljeby, L.; Rensfelt, K.-G.; Beebe, E. N.; Pikin, A. I.

2004-05-01

The theoretical estimations and numerical simulations of tubular electron beams in both beam and reflex mode of source operation as well as the off-axis ion extraction from a tubular electron beam ion source (TEBIS) are presented. Numerical simulations have been done with the use of the IGUN and OPERA-3D codes. Numerical simulations with IGUN code show that the effective electron current can reach more than 100 A with a beam current density of about 300-400 A/cm2 and the electron energy in the region of several KeV with a corresponding increase of the ion output. Off-axis ion extraction from the TEBIS, being the nonaxially symmetric problem, was simulated with OPERA-3D (SCALA) code. The conceptual design and main parameters of new tubular sources which are under consideration at JINR, MSL, and BNL are based on these simulations.

Theory of plasma contractors for electrodynamic tethered satellite systems

NASA Technical Reports Server (NTRS)

Parks, D. E.; Katz, I.

1986-01-01

Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source for example requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

Feature extraction using convolutional neural network for classifying breast density in mammographic images

NASA Astrophysics Data System (ADS)

Thomaz, Ricardo L.; Carneiro, Pedro C.; Patrocinio, Ana C.

2017-03-01

Breast cancer is the leading cause of death for women in most countries. The high levels of mortality relate mostly to late diagnosis and to the direct proportionally relationship between breast density and breast cancer development. Therefore, the correct assessment of breast density is important to provide better screening for higher risk patients. However, in modern digital mammography the discrimination among breast densities is highly complex due to increased contrast and visual information for all densities. Thus, a computational system for classifying breast density might be a useful tool for aiding medical staff. Several machine-learning algorithms are already capable of classifying small number of classes with good accuracy. However, machinelearning algorithms main constraint relates to the set of features extracted and used for classification. Although well-known feature extraction techniques might provide a good set of features, it is a complex task to select an initial set during design of a classifier. Thus, we propose feature extraction using a Convolutional Neural Network (CNN) for classifying breast density by a usual machine-learning classifier. We used 307 mammographic images downsampled to 260x200 pixels to train a CNN and extract features from a deep layer. After training, the activation of 8 neurons from a deep fully connected layer are extracted and used as features. Then, these features are feedforward to a single hidden layer neural network that is cross-validated using 10-folds to classify among four classes of breast density. The global accuracy of this method is 98.4%, presenting only 1.6% of misclassification. However, the small set of samples and memory constraints required the reuse of data in both CNN and MLP-NN, therefore overfitting might have influenced the results even though we cross-validated the network. Thus, although we presented a promising method for extracting features and classifying breast density, a greater database is still required for evaluating the results.

De-blending deep Herschel surveys: A multi-wavelength approach

NASA Astrophysics Data System (ADS)

Pearson, W. J.; Wang, L.; van der Tak, F. F. S.; Hurley, P. D.; Burgarella, D.; Oliver, S. J.

2017-07-01

Aims: Cosmological surveys in the far-infrared are known to suffer from confusion. The Bayesian de-blending tool, XID+, currently provides one of the best ways to de-confuse deep Herschel SPIRE images, using a flat flux density prior. This work is to demonstrate that existing multi-wavelength data sets can be exploited to improve XID+ by providing an informed prior, resulting in more accurate and precise extracted flux densities. Methods: Photometric data for galaxies in the COSMOS field were used to constrain spectral energy distributions (SEDs) using the fitting tool CIGALE. These SEDs were used to create Gaussian prior estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the extracted SPIRE flux densities were run through CIGALE again to allow us to compare the performance of the two priors. Inferred ALMA flux densities (FinferALMA), at 870 μm and 1250 μm, from the best fitting SEDs from the second CIGALE run were compared with measured ALMA flux densities (FmeasALMA) as an independent performance validation. Similar validations were conducted with the SED modelling and fitting tool MAGPHYS and modified black-body functions to test for model dependency. Results: We demonstrate a clear improvement in agreement between the flux densities extracted with XID+ and existing data at other wavelengths when using the new informed Gaussian prior over the original uninformed prior. The residuals between FmeasALMA and FinferALMA were calculated. For the Gaussian priors these residuals, expressed as a multiple of the ALMA error (σ), have a smaller standard deviation, 7.95σ for the Gaussian prior compared to 12.21σ for the flat prior; reduced mean, 1.83σ compared to 3.44σ; and have reduced skew to positive values, 7.97 compared to 11.50. These results were determined to not be significantly model dependent. This results in statistically more reliable SPIRE flux densities and hence statistically more reliable infrared luminosity estimates. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Phyllanthus Niruri Standardized Extract Alleviates the Progression of Non-Alcoholic Fatty Liver Disease and Decreases Atherosclerotic Risk in Sprague-Dawley Rats.

PubMed

Al Zarzour, Raghdaa Hamdan; Ahmad, Mariam; Asmawi, Mohd Zaini; Kaur, Gurjeet; Saeed, Mohammed Ali Ahmed; Al-Mansoub, Majed Ahmed; Saghir, Sultan Ayesh Mohammed; Usman, Nasiba Salisu; Al-Dulaimi, Dhamraa W; Yam, Mun Fei

2017-07-18

Non-alcoholic fatty liver disease (NAFLD) is one of the major global health issues, strongly correlated with insulin resistance, obesity and oxidative stress. The current study aimed to evaluate anti-NAFLD effects of three different extracts of Phyllanthus niruri ( P. niruri ) . NAFLD was induced in male Sprague-Dawley rats using a special high-fat diet (HFD). A 50% methanolic extract (50% ME) exhibited the highest inhibitory effect against NAFLD progression. It significantly reduced hepatomegaly (16%) and visceral fat weight (22%), decreased NAFLD score, prevented fibrosis, and reduced serum total cholesterol (TC) (48%), low-density lipoprotein (LDL) (65%), free fatty acids (FFAs) (25%), alanine aminotransferase (ALT) (45%), alkaline phosphatase (ALP) (38%), insulin concentration (67%), homeostatic model assessment of insulin resistance (HOMA-IR) (73%), serum atherogenic ratios TC/high-density lipoprotein (HDL) (29%), LDL/HDL (66%) and (TC-HDL)/HDL (64%), hepatic content of cholesterol (43%), triglyceride (29%) and malondialdehyde (MDA) (40%) compared to a non-treated HFD group. In vitro, 50% ME of P. niruri inhibited α-glucosidase, pancreatic lipase enzymes and cholesterol micellization. It also had higher total phenolic and total flavonoid contents compared to other extracts. Ellagic acid and phyllanthin were identified as major compounds. These results suggest that P. niruri could be further developed as a novel natural hepatoprotective agent against NAFLD and atherosclerosis.

Phyllanthus Niruri Standardized Extract Alleviates the Progression of Non-Alcoholic Fatty Liver Disease and Decreases Atherosclerotic Risk in Sprague–Dawley Rats

PubMed Central

Al Zarzour, Raghdaa Hamdan; Ahmad, Mariam; Asmawi, Mohd. Zaini; Kaur, Gurjeet; Al-Mansoub, Majed Ahmed; Saghir, Sultan Ayesh Mohammed; Usman, Nasiba Salisu; Al-Dulaimi, Dhamraa W.; Yam, Mun Fei

2017-01-01

Non-alcoholic fatty liver disease (NAFLD) is one of the major global health issues, strongly correlated with insulin resistance, obesity and oxidative stress. The current study aimed to evaluate anti-NAFLD effects of three different extracts of Phyllanthus niruri (P. niruri). NAFLD was induced in male Sprague–Dawley rats using a special high-fat diet (HFD). A 50% methanolic extract (50% ME) exhibited the highest inhibitory effect against NAFLD progression. It significantly reduced hepatomegaly (16%) and visceral fat weight (22%), decreased NAFLD score, prevented fibrosis, and reduced serum total cholesterol (TC) (48%), low-density lipoprotein (LDL) (65%), free fatty acids (FFAs) (25%), alanine aminotransferase (ALT) (45%), alkaline phosphatase (ALP) (38%), insulin concentration (67%), homeostatic model assessment of insulin resistance (HOMA-IR) (73%), serum atherogenic ratios TC/high-density lipoprotein (HDL) (29%), LDL/HDL (66%) and (TC–HDL)/HDL (64%), hepatic content of cholesterol (43%), triglyceride (29%) and malondialdehyde (MDA) (40%) compared to a non-treated HFD group. In vitro, 50% ME of P. niruri inhibited α-glucosidase, pancreatic lipase enzymes and cholesterol micellization. It also had higher total phenolic and total flavonoid contents compared to other extracts. Ellagic acid and phyllanthin were identified as major compounds. These results suggest that P. niruri could be further developed as a novel natural hepatoprotective agent against NAFLD and atherosclerosis. PMID:28718838

Effect of ethanol, dry extract and reducing sugars on density and viscosity of Brazilian red wines.

PubMed

Neto, Flávia S P P; de Castilhos, Maurício B M; Telis, Vânia R N; Telis-Romero, Javier

2015-05-01

Density and viscosity are properties that exert great influence on the body of wines. The present work aimed to evaluate the influence of the alcoholic content, dry extract, and reducing sugar content on density and viscosity of commercial dry red wines at different temperatures. The rheological assays were carried out on a controlled stress rheometer, using concentric cylinder geometry at seven temperatures (2, 8, 14, 16, 18, 20 and 26 °C). Wine viscosity decreased with increasing temperature and density was directly related to the wine alcohol content, whereas viscosity was closely linked to the dry extract. Reducing sugars did not influence viscosity or density. Wines produced from Italian grapes were presented as full-bodied with higher values for density and viscosity, which was linked to the higher alcohol content and dry extract, respectively. The results highlighted the major effects of certain physicochemical properties on the physical properties of wines, which in turn is important for guiding sensory assessments. © 2014 Society of Chemical Industry.

A new method for extracting near-surface mass-density anomalies from land-based gravity data, based on a special case of Poisson's PDE at the Earth's surface: A case study of salt diapirs in the south of Iran

NASA Astrophysics Data System (ADS)

AllahTavakoli, Y.; Safari, A.; Ardalan, A.; Bahroudi, A.

2015-12-01

The current research provides a method for tracking near-surface mass-density anomalies via using only land-based gravity data, which is based on a special version of Poisson's Partial Differential Equation (PDE) of the gravitational field at Earth's surface. The research demonstrates how the Poisson's PDE can provide us with a capability to extract the near-surface mass-density anomalies from land-based gravity data. Herein, this version of the Poisson's PDE is mathematically introduced to the Earth's surface and then it is used to develop the new method for approximating the mass-density via derivatives of the Earth's gravitational field (i.e. via the gradient tensor). Herein, the author believes that the PDE can give us new knowledge about the behavior of the Earth's gravitational field at the Earth's surface which can be so useful for developing new methods of Earth's mass-density determination. In a case study, the proposed method is applied to a set of gravity stations located in the south of Iran. The results were numerically validated via certain knowledge about the geological structures in the area of the case study. Also, the method was compared with two standard methods of mass-density determination. All the numerical experiments show that the proposed approach is well-suited for tracking near-surface mass-density anomalies via using only the gravity data. Finally, the approach is also applied to some petroleum exploration studies of salt diapirs in the south of Iran.

Electron cyclotron resonance plasma production by using pulse mode microwaves and dependences of ion beam current and plasma parameters on the pulse condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiriyama, Ryutaro; Takenaka, Tomoya; Kurisu, Yousuke

2012-02-15

We measure the ion beam current and the plasma parameters by using the pulse mode microwave operation in the first stage of a tandem type ECRIS. The time averaged extracted ion beam current in the pulse mode operation is larger than that of the cw mode operation with the same averaged microwave power. The electron density n{sub e} in the pulse mode is higher and the electron temperature T{sub e} is lower than those of the cw mode operation. These plasma parameters are considered to cause in the increase of the ion beam current and are suitable to produce molecularmore » or cluster ions.« less

Extracting black-hole rotational energy: The generalized Penrose process

NASA Astrophysics Data System (ADS)

Lasota, J.-P.; Gourgoulhon, E.; Abramowicz, M.; Tchekhovskoy, A.; Narayan, R.

2014-01-01

In the case involving particles, the necessary and sufficient condition for the Penrose process to extract energy from a rotating black hole is absorption of particles with negative energies and angular momenta. No torque at the black-hole horizon occurs. In this article we consider the case of arbitrary fields or matter described by an unspecified, general energy-momentum tensor Tμν and show that the necessary and sufficient condition for extraction of a black hole's rotational energy is analogous to that in the mechanical Penrose process: absorption of negative energy and negative angular momentum. We also show that a necessary condition for the Penrose process to occur is for the Noether current (the conserved energy-momentum density vector) to be spacelike or past directed (timelike or null) on some part of the horizon. In the particle case, our general criterion for the occurrence of a Penrose process reproduces the standard result. In the case of relativistic jet-producing "magnetically arrested disks," we show that the negative energy and angular-momentum absorption condition is obeyed when the Blandford-Znajek mechanism is at work, and hence the high energy extraction efficiency up to ˜300% found in recent numerical simulations of such accretion flows results from tapping the black hole's rotational energy through the Penrose process. We show how black-hole rotational energy extraction works in this case by describing the Penrose process in terms of the Noether current.

Development of the 2-MV Injector for HIF

NASA Astrophysics Data System (ADS)

Bieniosek, F. M.; Kwan, J. W.; Henestroza, E.; Kim, C.

2001-05-01

The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated.

Superfluid phase stiffness in electron doped superconducting Gd-123

NASA Astrophysics Data System (ADS)

Das, P.; Ghosh, Ajay Kumar

2018-05-01

Current-voltage characteristics of Ce substituted Gd-123 superconductor exhibits nonlinearity below a certain temperature below the critical temperature. An exponent is extracted using the nonlinearity of current-voltage relation. Superfluid phase stiffness has been studied as a function of temperature following the Ambegaokar-Halperin-Nelson-Siggia (AHNS) theory. Phase stiffness of the superfluid below the superconducting transition is found to be sensitive to the change in the carrier concentration in superconducting system. There may be a crucial electron density which affects superfluid stiffness strongly. Electron doping is found to be effective even if the coupling of the superconducting planes is changed.

Behavior of moving plasma in solenoidal magnetic field in a laser ion source

NASA Astrophysics Data System (ADS)

Ikeda, S.; Takahashi, K.; Okamura, M.; Horioka, K.

2016-02-01

In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

Behavior of moving plasma in solenoidal magnetic field in a laser ion source.

PubMed

Ikeda, S; Takahashi, K; Okamura, M; Horioka, K

2016-02-01

In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

Solution-processed parallel tandem polymer solar cells using silver nanowires as intermediate electrode.

PubMed

Guo, Fei; Kubis, Peter; Li, Ning; Przybilla, Thomas; Matt, Gebhard; Stubhan, Tobias; Ameri, Tayebeh; Butz, Benjamin; Spiecker, Erdmann; Forberich, Karen; Brabec, Christoph J

2014-12-23

Tandem architecture is the most relevant concept to overcome the efficiency limit of single-junction photovoltaic solar cells. Series-connected tandem polymer solar cells (PSCs) have advanced rapidly during the past decade. In contrast, the development of parallel-connected tandem cells is lagging far behind due to the big challenge in establishing an efficient interlayer with high transparency and high in-plane conductivity. Here, we report all-solution fabrication of parallel tandem PSCs using silver nanowires as intermediate charge collecting electrode. Through a rational interface design, a robust interlayer is established, enabling the efficient extraction and transport of electrons from subcells. The resulting parallel tandem cells exhibit high fill factors of ∼60% and enhanced current densities which are identical to the sum of the current densities of the subcells. These results suggest that solution-processed parallel tandem configuration provides an alternative avenue toward high performance photovoltaic devices.

Electric Field Screening with Backflow at Pulsar Polar Cap

NASA Astrophysics Data System (ADS)

Kisaka, Shota; Asano, Katsuaki; Terasawa, Toshio

2016-09-01

Recent γ-ray observations suggest that particle acceleration occurs at the outer region of the pulsar magnetosphere. The magnetic field lines in the outer acceleration region (OAR) are connected to the neutron star surface (NSS). If copious electron-positron pairs are produced near the NSS, such pairs flow into the OAR and screen the electric field there. To activate the OAR, the electromagnetic cascade due to the electric field near the NSS should be suppressed. However, since a return current is expected along the field lines through the OAR, the outflow extracted from the NSS alone cannot screen the electric field just above the NSS. In this paper, we analytically and numerically study the electric field screening at the NSS, taking into account the effects of the backflowing particles from the OAR. In certain limited cases, the electric field is screened without significant pair cascade if only ultra-relativistic particles (γ \\gg 1) flow back to the NSS. On the other hand, if electron-positron pairs with a significant number density and mildly relativistic temperature, expected to distribute in a wide region of the magnetosphere, flow back to the NSS, these particles adjust the current and charge densities so that the electric field can be screened without pair cascade. We obtain the condition needed for the number density of particles to screen the electric field at the NSS. We also find that in the ion-extracted case from the NSS, bunches of particles are ejected to the outer region quasi-periodically, which is a possible mechanism of observed radio emission.

Research progress on ionic plasmas generated in an intense hydrogen negative ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeiri, Y., E-mail: takeiri@nifs.ac.jp; Tsumori, K.; Nagaoka, K.

2015-04-08

Characteristics of ionic plasmas, observed in a high-density hydrogen negative ion source, are investigated with a multi-diagnostics system. The ionic plasma, which consists of hydrogen positive- and negative-ions with a significantly low-density of electrons, is generated in the ion extraction region, from which the negative ions are extracted through the plasma grid. The negative ion density, i.e., the ionic plasma density, as high as the order of 1×10{sup 17}m{sup −3}, is measured with cavity ring-down spectroscopy, while the electron density is lower than 1×10{sup 16}m{sup −3}, which is confirmed with millimeter-wave interferometer. Reduction of the negative ion density is observedmore » at the negative ion extraction, and at that time the electron flow into the ionic plasma region is observed to conserve the charge neutrality. Distribution of the plasma potential is measured in the extraction region in the direction normal to the plasma grid surface with a Langmuir probe, and the results suggest that the sheath is formed at the plasma boundary to the plasma grid to which the bias voltage is applied. The beam extraction should drive the negative ion transport in the ionic plasma across the sheath formed on the extraction surface. Larger reduction of the negative ions at the beam extraction is observed in a region above the extraction aperture on the plasma grid, which is confirmed with 2D image measurement of the Hα emission and cavity ring-down spectroscopy. The electron distribution is also measured near the plasma grid surface. These various properties observed in the ionic plasma are discussed.« less

Quasi-Ballistic Carbon Nanotube Array Transistors with Current Density Exceeding Si and GaAs

DTIC Science & Technology

2016-09-02

performance of surfactant- encapsulated and conjugated polymer –wrapped CNTs in aligned arrays prepared by dielectrophoresis (20) and shear-casting (21); how... conjugated polymer poly[(9,9-dioctylfluorenyl- 2,7-diyl)-alt-co-(6,60-(2,20-bipyridine))] (PFO-BPy) in toluene to se- lectively wrap the semiconducting...Malenfant, J. Humes, J. Kroeger, A hybrid enrichment process combining conjugated polymer extraction and silica gel adsorption for high purity

Extraction and Propagation of an Intense Rotating Electron Beam,

DTIC Science & Technology

1982-10-01

radiochromic foils positioned at z = 25 cm. The equal transmission density contours are ranked in linear order of increasing exposure (increasing current...flux encircled by the cathode e = %rc2Bc. Linearizing the equation of motion around the equilibrium, we can find the wavelength of small radial...the beam rotation. The mask which precedes the scint- illator is a linear array of dots while the projection is made up of two disjoint linear arrays

Electron beam extraction on plasma cathode electron sources system

NASA Astrophysics Data System (ADS)

Purwadi, Agus; Taufik, M., Lely Susita R.; Suprapto, Saefurrochman, H., Anjar A.; Wibowo, Kurnia; Aziz, Ihwanul; Siswanto, Bambang

2017-03-01

ELECTRON BEAM EXTRACTION ON PLASMA CATHODE ELECTRON SOURCES SYSTEM. The electron beam extraction through window of Plasma Generator Chamber (PGC) for Pulsed Electron Irradiator (PEI) device and simulation of plasma potential has been studied. Plasma electron beam is extracted to acceleration region for enlarging their power by the external accelerating high voltage (Vext) and then it is passed foil window of the PEI for being irradiated to any target (atmospheric pressure). Electron beam extraction from plasma surface must be able to overcome potential barrier at the extraction window region which is shown by estimate simulation (Opera program) based on data of plasma surface potential of 150 V with Ueks values are varied by 150 kV, 175 kV and 200 kV respectively. PGC is made of 304 stainless steel with cylindrical shape in 30 cm of diameter, 90 cm length, electrons extraction window as many as 975 holes on the area of (15 × 65) cm2 with extraction hole cell in 0.3 mm of radius each other, an cylindrical shape IEP chamber is made of 304 stainless steel in 70 cm diameter and 30 cm length. The research result shown that the acquisition of electron beam extraction current depends on plasma parameters (electron density ne, temperature Te), accelerating high voltage Vext, the value of discharge parameter G, anode area Sa, electron extraction window area Se and extraction efficiency value α.

Confirmation of the modified Bean model from simulations of superconducting vortices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richardson, R.A.; Pla, O.; Nori, F.

From a very simple description of vortices and pinning centers, we obtain nonlinear density profiles of vortices in type-II dirty superconductors that result from changing an external magnetic field. The results confirm a modified Bean model description of these systems, following the Kim empirical form that relates the current inside the material to the local magnetic field. We also obtain realistic magnetization hysteresis loops and examine the discrete evolution of the density profiles in our systems. This evolution is not continuous, but takes place by the occurrence of avalanches of vortices promoted by the addition or extraction of vortices frommore » the edges of the system.« less

Evaluation of the stability and antimicrobial activity of an ethanolic extract of Libidibia ferrea

PubMed Central

de Oliveira Marreiro, Raquel; Bandeira, Maria Fulgência Costa Lima; de Souza, Tatiane Pereira; de Almeida, Mailza Costa; Bendaham, Katiana; Venâncio, Gisely Naura; Rodrigues, Isis Costa; Coelho, Cristiane Nagai; Milério, Patrícia Sâmea Lêdo Lima; de Oliveira, Glauber Palma; de Oliveira Conde, Nikeila Chacon

2014-01-01

Biofilm is a dense, whitish, noncalcified aggregate of bacteria, with desquamated epithelial cells and food debris creating conditions for an imbalance of resident oral microflora and favoring the destruction of hard and soft tissues by development of caries and gingivitis. The aim of this study was to obtain and characterize an extract of Libidibia ferrea, ex Caesalpinia ferrea L. and to evaluate its feasibility for formulation as a mouthwash, according to current legislation. For this purpose, pH, sedimentation, density, and stability were evaluated, along with microbiological testing of the extract. The microbiological test was used to verify the presence of Staphylococcus aureus, Pseudomonas aeruginosa, fungi, yeasts, coliforms, and minimum inhibitory concentrations of Streptococcus mutans and Streptococcus oralis strains. Characterization, microbiological evaluation, and minimum inhibitory concentration results were tabulated and described using descriptive statistics. The L. ferrea extract showed stable characteristics, product quality, and antibacterial activity against the microorganisms tested irrespective of experimental time intervals. According to these results, it can be concluded that formulation of a mouthwash containing L. ferrea extract to control biofilm is feasible, but further studies are needed. PMID:24501546

Power Transmission From The ITER Model Negative Ion Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boilson, D.; Esch, H. P. L. de; Grand, C.

2007-08-10

In Cadarache development on negative ion sources is being carried out on the KAMABOKO III ion source on the MANTIS test bed. This is a model of the ion source designed for the neutral beam injectors of ITER. This ion source has been developed in collaboration with JAERI, Japan, who also designed and supplied the ion source. Its target performance is to accelerate a D- beam, with a current density of 200 A/m2 and <1 electron extracted per accelerated D- ion, at a source filling pressure of 0.3 Pa. For ITER a continuous ion beam must be assured for pulsemore » lengths of 1000 s, but beams of up to 3,600 s are also envisaged. The ion source is attached to a 3 grid 30 keV accelerator (also supplied by JAERI) and the accelerated negative ion current is determined from the energy deposited on a calorimeter. During long pulse operation ({<=}1000 s) it was found that the current density of both D- and H- beams, measured at the calorimeter was lower than expected and that a large discrepancy existed between the accelerated currents measured electrically and those transmitted to the calorimeter. The possibility that this discrepancy arose because the accelerated current included electrons (which would not be able to reach the calorimeter) was investigated and subsequently eliminated. Further studies have shown that the fraction of the electrical current reaching the calorimeter varies with the pulse length, which led to the suggestion that one or more of the accelerator grids were distorting due to the incident power during operation, leading to a progressive deterioration in the beam quality.. New extraction and acceleration grids have been designed and installed, which should have a better tolerance to thermal loads than those previously used. This paper describes the measurements of the power transmission and distribution using these grids.« less

Fault detection and diagnosis of induction motors using motor current signature analysis and a hybrid FMM-CART model.

PubMed

Seera, Manjeevan; Lim, Chee Peng; Ishak, Dahaman; Singh, Harapajan

2012-01-01

In this paper, a novel approach to detect and classify comprehensive fault conditions of induction motors using a hybrid fuzzy min-max (FMM) neural network and classification and regression tree (CART) is proposed. The hybrid model, known as FMM-CART, exploits the advantages of both FMM and CART for undertaking data classification and rule extraction problems. A series of real experiments is conducted, whereby the motor current signature analysis method is applied to form a database comprising stator current signatures under different motor conditions. The signal harmonics from the power spectral density are extracted as discriminative input features for fault detection and classification with FMM-CART. A comprehensive list of induction motor fault conditions, viz., broken rotor bars, unbalanced voltages, stator winding faults, and eccentricity problems, has been successfully classified using FMM-CART with good accuracy rates. The results are comparable, if not better, than those reported in the literature. Useful explanatory rules in the form of a decision tree are also elicited from FMM-CART to analyze and understand different fault conditions of induction motors.

Update on developments at SNIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacks, J., E-mail: jamie.zacks@ccfe.ac.uk; Turner, I.; Day, I.

The Small Negative Ion Facility (SNIF) at CCFE has been undergoing continuous development and enhancement to both improve operational reliability and increase diagnostic capability. SNIF uses a CW 13.56MHz, 5kW RF driven volume source with a 30kV triode accelerator. Improvement and characterisation work includes: Installation of a new “L” type RF matching unit, used to calculate the load on the RF generator. Use of the electron suppressing biased insert as a Langmuir probe under different beam extraction conditions. Measurement of the hydrogen Fulcher molecular spectrum, used to calculate gas temperature in the source. Beam optimisation through parameter scans, using coppermore » target plate and visible cameras, with results compared with AXCEL-INP to provide beam current estimate. Modelling of the beam power density profile on the target plate using ANSYS to estimate beam power and provide another estimate of beam current. This work is described, and has allowed an estimation of the extracted beam current of approximately 6mA (4mA/cm2) at 3.5kW RF power and a source pressure of 0.6Pa.« less

Plant extracts in the control of Phytophthora cryptogea.

PubMed

Orlikowski, L B

2001-01-01

Grapefruit extract at dose 40 micrograms/cm3 inhibited Phytophtora cryptogea linear growth about 50% and almost completely suppressed zoosporangia formation. Drenching of gerbera plants with the extract at dose 165 micrograms/cm3 reduced population density of the pathogen about 70% and this high efficacy was noted at least one month after application. Treatment of gerberas with grapefruit extract resulted in protection of about 50% of plants against the pathogen. Biological activity of purple coneflower extract was lower than extract from grapefruit. Significant decrease of population density of the pathogen during the first 5 days and increase of gerbera healthy stand was observed, however, in peat treated with that extract.

Process monitoring using automatic physical measurement based on electrical and physical variability analysis

NASA Astrophysics Data System (ADS)

Shauly, Eitan N.; Levi, Shimon; Schwarzband, Ishai; Adan, Ofer; Latinsky, Sergey

2015-04-01

A fully automated silicon-based methodology for systematic analysis of electrical features is shown. The system was developed for process monitoring and electrical variability reduction. A mapping step was created by dedicated structures such as static-random-access-memory (SRAM) array or standard cell library, or by using a simple design rule checking run-set. The resulting database was then used as an input for choosing locations for critical dimension scanning electron microscope images and for specific layout parameter extraction then was input to SPICE compact modeling simulation. Based on the experimental data, we identified two items that must be checked and monitored using the method described here: transistor's sensitivity to the distance between the poly end cap and edge of active area (AA) due to AA rounding, and SRAM leakage due to a too close N-well to P-well. Based on this example, for process monitoring and variability analyses, we extensively used this method to analyze transistor gates having different shapes. In addition, analysis for a large area of high density standard cell library was done. Another set of monitoring focused on a high density SRAM array is also presented. These examples provided information on the poly and AA layers, using transistor parameters such as leakage current and drive current. We successfully define "robust" and "less-robust" transistor configurations included in the library and identified unsymmetrical transistors in the SRAM bit-cells. These data were compared to data extracted from the same devices at the end of the line. Another set of analyses was done to samples after Cu M1 etch. Process monitoring information on M1 enclosed contact was extracted based on contact resistance as a feedback. Guidelines for the optimal M1 space for different layout configurations were also extracted. All these data showed the successful in-field implementation of our methodology as a useful process monitoring method.

Effect of the solenoid in various conditions of the laser ion source at Brookhaven National Laboratory

NASA Astrophysics Data System (ADS)

Ikeda, S.; Kumaki, M.; Kanesue, T.; Okamura, M.

2016-02-01

In the laser ion source (LIS) at the Brookhaven National Laboratory (BNL), a solenoid is used to guide the laser ablation plasma and modulate the extracted beam current. Many types of ion species are guided. In some cases, the plasma plume is injected into the solenoid away from the solenoidal axis. To investigate the effects of the solenoid on the beam extracted from the plasma that has different properties, the beam current was measured in the setup of the LIS at the BNL. The beam current of Li, Al, Si, Fe, and Au increased when the magnetic field was applied. For most of the species the peak current and the total charge within a single beam pulse increased around 10 times with a magnetic field less than 100 G. In addition, for some species the rate of increase of the peak currents became smaller when the magnetic flux densities were larger than certain values depending on the species. In this case, the current waveforms were distorted. At the same magnetic field value, the field was more effective on lighter species than on heavier ones. When plasma was injected offset from the axis of the solenoid, peak current and total charge became half of those without offset. The experimental data are useful for the operation of the LIS at the BNL.

Effect of the solenoid in various conditions of the laser ion source at Brookhaven National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeda, S., E-mail: ikeda.s.ae@m.titech.ac.jp; Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0108; Kumaki, M.

In the laser ion source (LIS) at the Brookhaven National Laboratory (BNL), a solenoid is used to guide the laser ablation plasma and modulate the extracted beam current. Many types of ion species are guided. In some cases, the plasma plume is injected into the solenoid away from the solenoidal axis. To investigate the effects of the solenoid on the beam extracted from the plasma that has different properties, the beam current was measured in the setup of the LIS at the BNL. The beam current of Li, Al, Si, Fe, and Au increased when the magnetic field was applied.more » For most of the species the peak current and the total charge within a single beam pulse increased around 10 times with a magnetic field less than 100 G. In addition, for some species the rate of increase of the peak currents became smaller when the magnetic flux densities were larger than certain values depending on the species. In this case, the current waveforms were distorted. At the same magnetic field value, the field was more effective on lighter species than on heavier ones. When plasma was injected offset from the axis of the solenoid, peak current and total charge became half of those without offset. The experimental data are useful for the operation of the LIS at the BNL.« less

Effect of the solenoid in various conditions of the laser ion source at Brookhaven National Laboratory.

PubMed

Ikeda, S; Kumaki, M; Kanesue, T; Okamura, M

2016-02-01

In the laser ion source (LIS) at the Brookhaven National Laboratory (BNL), a solenoid is used to guide the laser ablation plasma and modulate the extracted beam current. Many types of ion species are guided. In some cases, the plasma plume is injected into the solenoid away from the solenoidal axis. To investigate the effects of the solenoid on the beam extracted from the plasma that has different properties, the beam current was measured in the setup of the LIS at the BNL. The beam current of Li, Al, Si, Fe, and Au increased when the magnetic field was applied. For most of the species the peak current and the total charge within a single beam pulse increased around 10 times with a magnetic field less than 100 G. In addition, for some species the rate of increase of the peak currents became smaller when the magnetic flux densities were larger than certain values depending on the species. In this case, the current waveforms were distorted. At the same magnetic field value, the field was more effective on lighter species than on heavier ones. When plasma was injected offset from the axis of the solenoid, peak current and total charge became half of those without offset. The experimental data are useful for the operation of the LIS at the BNL.

Laser ion source activities at Brookhaven National Laboratory

DOE PAGES

Kanesue, Takeshi; Okamura, Masahiro

2015-07-31

In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 10more » 10 of C 6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.« less

The granule cell density of the dentate gyrus following administration of Urtica dioica extract to young diabetic rats.

PubMed

Fazeli, S A; Gharravi, A M; Ghafari, S; Jahanshahi, M; Golalipour, M J

2008-08-01

Urtica dioica L. Stinging nettle has long been known worldwide as a medicinal plant. To study the benefits of the nettle in diabetic encephalopathy, the granule cell density of the dentate gyrus of diabetic rats was studied following administration of Urtica dioica extract. A total of 24 male albino Wistar rats were allocated equally to normal, diabetic, preventive and treatment groups. Hyperglycaemia was induced by streptozotocin (80 mg/kg) in the animals of the diabetic and treatment groups. One week after injection of the streptozotocin the animals in the treatment group received a hydroalcoholic extract of Urtica dioica (100 mg/kg/day) for 4 weeks intraperitoneally. The rats of the preventive group received hydroalcoholic extract of U. dioica (100 mg/kg/day) IP for the first 5 days and an injection of streptozotocin (80 mg/kg) on the 6th day. After 5 weeks of study all the rats were sacrificed and coronal sections were taken from the dorsal hippocampal formation of the right cerebral hemispheres and stained with cresyl violet. The area densities of the granule cells were measured and compared in the four groups. The density was lower in the diabetic rats compared with the controls (p > 0.05). The preventive group showed lower cell density than the controls (p > 0.05). The densities in the treated rats were higher than in the diabetic rats (p > 0.05). Furthermore, the control and treated rats showed similar densities (p > 0.05). It seems that U. dioica extract can help compensate for granule cell loss in the diabetic rat dentate gyrus, which can ameliorate cognitive impairment in diabetes. However, preventive use of the extract showed no significant benefit.

On electrical and interfacial properties of iron and platinum Schottky barrier diodes on (111) n-type Si0.65Ge0.35

NASA Astrophysics Data System (ADS)

Hamri, D.; Teffahi, A.; Djeghlouf, A.; Chalabi, D.; Saidane, A.

2018-04-01

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) characteristics of Molecular Beam Epitaxy (MBE)-deposited Fe/n-Si0.65Ge0.35 (FM1) and Pt/n-Si0.65Ge0.35(PM2) (111) orientated Schottky barrier diodes (SBDs) have been investigated at room-temperature. Barrier height (ΦB0), ideality factor (n) and series resistance (RS) were extracted. Dominant current conduction mechanisms were determined. They revealed that Poole-Frenkel-type conduction mechanism dominated reverse current. Differences in shunt resistance confirmed the difference found in leakage current. Under forward bias, quasi-ohmic conduction is found at low voltage regions and space charge-limited conduction (SCLC) at higher voltage regions for both SBDs. Density of interface states (NSS) indicated a difference in interface reactivity. Distribution profiles of series resistance (RS) with bias gives a peak in depletion region at low-frequencies that disappears with increasing frequencies. These results show that interface states density and series resistance of Schottky diodes are important parameters that strongly influence electrical properties of FM1 and PM2 structures.

Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye.

PubMed

Suyitno, Suyitno; Saputra, Trisma Jaya; Supriyanto, Agus; Arifin, Zainal

2015-09-05

The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450 °C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8 g/100 mL. The absorbance spectra of the dyes were obtained by ultra-violet-visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5-4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it. Copyright © 2015 Elsevier B.V. All rights reserved.

Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye

NASA Astrophysics Data System (ADS)

Suyitno, Suyitno; Saputra, Trisma Jaya; Supriyanto, Agus; Arifin, Zainal

2015-09-01

The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450 °C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8 g/100 mL. The absorbance spectra of the dyes were obtained by ultra-violet-visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5-4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it.

Influence of grape density and harvest date on changes in phenolic composition, phenol extractability indices, and instrumental texture properties during ripening.

PubMed

Rolle, Luca; Segade, Susana Río; Torchio, Fabrizio; Giacosa, Simone; Cagnasso, Enzo; Marengo, Fabio; Gerbi, Vincenzo

2011-08-24

Changes in the phenolic composition, phenol extractability indices, and mechanical properties occur in grape berries during the ripening process, but the heterogeneity of the grapes harvested at different ripening stages affects the reliability of the results obtained. In this work, these changes were studied in Nebbiolo grapes harvested during five consecutive weeks and then separated according to three density classes. The changes observed in chemical and mechanical parameters through the ripening process are more related to berry density than harvest date. Therefore, the winemaker has to select the flotation density according to the objective quality properties of the wine to be elaborated. On the other hand, the stiffer grapes were associated with a higher accumulation of proanthocyanidins. The harder grapes provided the higher concentration and extractability of flavanols reactive to vanillin, whereas the thicker ones facilitated the extraction of proanthocyanidins.

Seasonal and Interannual Variation of Currents and Water Properties off the Mid-East Coast of Korea

NASA Astrophysics Data System (ADS)

Park, J. H.; Chang, K. I.; Nam, S.

2016-02-01

Since 1999, physical parameters such as current, temperature, and salinity off the mid-east coast of Korea have been continuously observed from the long-term buoy station called `East-Sea Real-time Ocean monitoring Buoy (ESROB)'. Applying harmonic analysis to 6-year-long (2007-2012) depth-averaged current data from the ESROB, a mean seasonal cycle of alongshore currents, characterized by poleward current in average and equatorward current in summer, is extracted which accounts for 5.8% of the variance of 40 hours low-pass filtered currents. In spite of the small variance explained, a robust seasonality of summertime equatorward reversal typifies the low-passed alongshore currents along with low-density water. To reveal the dynamics underlying the seasonal variation, each term of linearized, depth-averaged momentum equations is estimated using the data from ESROB, adjacent tide gauge stations, and serial hydrographic stations. The result indicates that the reversal of alongshore pressure gradient is a major driver of the equatorward reversals in summer. The reanalysis wind product (MERRA) and satellite altimeter-derived sea surface height (AVISO) data show correlated features between positive (negative) wind stress curl and sea surface depression (uplift). Quantitative estimates reveal that the wind-stress curl accounts for 42% of alongshore sea level variation. Summertime low-density water originating from the northern coastal region is a footprint of the buoyancy-driven equatorward current. An interannual variation (anomalies from the mean seasonal cycle) of alongshore currents and its possible driving mechanisms will be discussed.

Efficient Suppression of Defects and Charge Trapping in High Density In-Sn-Zn-O Thin Film Transistor Prepared using Microwave-Assisted Sputter.

PubMed

Goh, Youngin; Ahn, Jaehan; Lee, Jeong Rak; Park, Wan Woo; Ko Park, Sang-Hee; Jeon, Sanghun

2017-10-25

Amorphous oxide semiconductor-based thin film transistors (TFTs) have been considered as excellent switching elements for driving active-matrix organic light-emitting diodes (AMOLED) owing to their high mobility and process compatibility. However, oxide semiconductors have inherent defects, causing fast transient charge trapping and device instability. For the next-generation displays such as flexible, wearable, or transparent displays, an active semiconductor layer with ultrahigh mobility and high reliability at low deposition temperature is required. Therefore, we introduced high density plasma microwave-assisted (MWA) sputtering method as a promising deposition tool for the formation of high density and high-performance oxide semiconductor films. In this paper, we present the effect of the MWA sputtering method on the defects and fast charge trapping in In-Sn-Zn-O (ITZO) TFTs using various AC device characterization methodologies including fast I-V, pulsed I-V, transient current, low frequency noise, and discharge current analysis. Using these methods, we were able to analyze the charge trapping mechanism and intrinsic electrical characteristics, and extract the subgap density of the states of oxide TFTs quantitatively. In comparison to conventional sputtered ITZO, high density plasma MWA-sputtered ITZO exhibits outstanding electrical performance, negligible charge trapping characteristics and low subgap density of states. High-density plasma MWA sputtering method has high deposition rate even at low working pressure and control the ion bombardment energy, resulting in forming low defect generation in ITZO and presenting high performance ITZO TFT. We expect the proposed high density plasma sputtering method to be applicable to a wide range of oxide semiconductor device applications.

Simulated Beam Extraction Performance Characterization of a 50-cm Ion Thruster Discharge

NASA Technical Reports Server (NTRS)

Foster, John E.; Hubble, Aimee; Nowak-Gucker, Sarah; Davis, Chris; Peterson, Peter; Viges, Eric; Chen, Dave

2013-01-01

A 50 cm ion thruster is being developed to operate at >65 percent total efficiency at 11 kW, 2700 s Isp and over 25 kW, 4500 s Isp at a total efficiency of >75 percent. The engine is being developed to address the need for a multimode system that can provide a range of thrust-to- power to service national and commercial near-earth onboard propulsion needs such as station-keeping and orbit transfer. Operating characteristics of the 50 cm ion thruster were measured under simulated beam extraction. The discharge current distribution at the various magnet rings was measured over a range of operating conditions. The relationship between the anode current distribution and the resulting plasma uniformity and ion flux measured at the thruster exit plane is discussed. The thermal envelope will also be investigated through the monitoring of magnet temperatures over the range of discharge powers investigated. Discharge losses as a function of propellant utilization was also characterized at multiple simulated beam currents. Bulk plasma conditions such as electron temperature and electron density near engine centerline was measured over a range of operating conditions using an internal Langmuir probe. Sensitivity of discharge performance to chamber length is also discussed. This data acquired from this discharge study will be used in the refinement of a throttle table in anticipation for eventual beam extraction testing.

The design of an electron gun switchable between immersed and Brillouin flowa)

NASA Astrophysics Data System (ADS)

Becker, R.; Kester, O.

2012-02-01

An electron gun, which can be switched from immersed flow to Brillouin flow during operation, may have advantages for charge breeders as well as for electron beam ion sources and traps (EBISTs). For EBISTs this allows to change the current density according to the repetition frequency and charge state, for charge breeders and EBISTs a lower current density in immersed flow provides higher acceptance for injected ions, while the higher current density in Brillouin flow results in shorter breeding times and a lower emittance for the extracted beam. Therefore, we have designed such a gun for an EBIS with 5 T central magnetic field and without the use of iron and moving the gun. The gun was placed in the axial fringing field of the 5 T solenoid in such a position that a gate valve can be placed between the gun and the cryostat to allow for simple maintenance. The field at the cathode surface turned out to be only 0.05 T, which is not enough to focus 50 A/cm2 at a few kV. However, if a small normal conducting solenoid is placed over the vacuum tube in position of the gun, a field of 0.1 T may be obtained. With this the use of LaB6 as cathode material results in a magnetic compression of 44 and therewith in a focused current density in the trap region of more than 2000 A/cm2. By reversing the current in the gun solenoid the cathode field can easily compensated to zero. By proper design of the electrodes and the compression region, the gun will be able to deliver a beam in Brillouin flow. While this is interesting by itself - remember the "super-compression" reported on CRYEBIS-I - any magnetic field between zero and the value for immersed flow will result in an electron beam with a wide range of adjustable high current densities. The design tools used have been INTMAG(C) for the calculation of magnetic fields, EGN2(C) for the simulation of the gun and ANALYSE(C) for detailed analysis of the results (for more information see www.egun-igun.com).

The design of an electron gun switchable between immersed and Brillouin flow.

PubMed

Becker, R; Kester, O

2012-02-01

An electron gun, which can be switched from immersed flow to Brillouin flow during operation, may have advantages for charge breeders as well as for electron beam ion sources and traps (EBISTs). For EBISTs this allows to change the current density according to the repetition frequency and charge state, for charge breeders and EBISTs a lower current density in immersed flow provides higher acceptance for injected ions, while the higher current density in Brillouin flow results in shorter breeding times and a lower emittance for the extracted beam. Therefore, we have designed such a gun for an EBIS with 5 T central magnetic field and without the use of iron and moving the gun. The gun was placed in the axial fringing field of the 5 T solenoid in such a position that a gate valve can be placed between the gun and the cryostat to allow for simple maintenance. The field at the cathode surface turned out to be only 0.05 T, which is not enough to focus 50 A∕cm(2) at a few kV. However, if a small normal conducting solenoid is placed over the vacuum tube in position of the gun, a field of 0.1 T may be obtained. With this the use of LaB(6) as cathode material results in a magnetic compression of 44 and therewith in a focused current density in the trap region of more than 2000 A∕cm(2). By reversing the current in the gun solenoid the cathode field can easily compensated to zero. By proper design of the electrodes and the compression region, the gun will be able to deliver a beam in Brillouin flow. While this is interesting by itself--remember the "super-compression" reported on CRYEBIS-I--any magnetic field between zero and the value for immersed flow will result in an electron beam with a wide range of adjustable high current densities. The design tools used have been INTMAG(C) for the calculation of magnetic fields, EGN2(C) for the simulation of the gun and ANALYSE(C) for detailed analysis of the results (for more information see www.egun-igun.com).

Electrically injected GaAsBi/GaAs single quantum well laser diodes

NASA Astrophysics Data System (ADS)

Liu, Juanjuan; Pan, Wenwu; Wu, Xiaoyan; Cao, Chunfang; Li, Yaoyao; Chen, Xiren; Zhang, Yanchao; Wang, Lijuan; Yan, Jinyi; Zhang, Dongliang; Song, Yuxin; Shao, Jun; Wang, Shumin

2017-11-01

We present electrically injected GaAs/GaAsBi single quantum well laser diodes (LDs) emitting at a record long wavelength of 1141 nm at room temperature grown by molecular beam epitaxy. The LDs have excellent device performances with internal quantum efficiency of 86%, internal loss of 10 cm-1 and transparency current density of 196 A/cm2. The LDs can operate under continuous-wave mode up to 273 K. The characteristic temperature are extracted to be 125 K in the temperature range of 77˜150 K, and reduced to 90 K in the range of 150˜273 K. The temperature coefficient of 0.3 nm/K is extracted in the temperature range of 77˜273 K.

Ricci-Gauss-Bonnet holographic dark energy

NASA Astrophysics Data System (ADS)

Saridakis, Emmanuel N.

2018-03-01

We present a model of holographic dark energy in which the infrared cutoff is determined by both the Ricci and the Gauss-Bonnet invariants. Such a construction has the significant advantage that the infrared cutoff, and consequently the holographic dark energy density, does not depend on the future or the past evolution of the universe, but only on its current features, and moreover it is determined by invariants, whose role is fundamental in gravitational theories. We extract analytical solutions for the behavior of the dark energy density and equation-of-state parameters as functions of the redshift. These reveal the usual thermal history of the universe, with the sequence of radiation, matter and dark energy epochs, resulting in the future to a complete dark energy domination. The corresponding dark energy equation-of-state parameter can lie in the quintessence or phantom regime, or experience the phantom-divide crossing during the cosmological evolution, and its asymptotic value can be quintessencelike, phantomlike, or be exactly equal to the cosmological-constant value. Finally, we extract the constraints on the model parameters that arise from big bang nucleosynthesis.

Particle model of full-size ITER-relevant negative ion source.

PubMed

Taccogna, F; Minelli, P; Ippolito, N

2016-02-01

This work represents the first attempt to model the full-size ITER-relevant negative ion source including the expansion, extraction, and part of the acceleration regions keeping the mesh size fine enough to resolve every single aperture. The model consists of a 2.5D particle-in-cell Monte Carlo collision representation of the plane perpendicular to the filter field lines. Magnetic filter and electron deflection field have been included and a negative ion current density of j(H(-)) = 660 A/m(2) from the plasma grid (PG) is used as parameter for the neutral conversion. The driver is not yet included and a fixed ambipolar flux is emitted from the driver exit plane. Results show the strong asymmetry along the PG driven by the electron Hall (E × B and diamagnetic) drift perpendicular to the filter field. Such asymmetry creates an important dis-homogeneity in the electron current extracted from the different apertures. A steady state is not yet reached after 15 μs.

InGaN/GaN light-emitting diode having direct hole injection plugs and its high-current operation.

PubMed

Kim, Sungjoon; Cho, Seongjae; Jeong, Jaedeok; Kim, Sungjun; Hwang, Sungmin; Kim, Garam; Yoon, Sukho; Park, Byung-Gook

2017-03-20

The light-emitting diode (LED) with an improved hole injection and straightforward process integration is proposed. p-type GaN direct hole injection plugs (DHIPs) are formed on locally etched multiple-quantum wells (MQWs) by epitaxial lateral overgrowth (ELO) method. We confirm that the optical output power is increased up to 23.2% at an operating current density of 100 A/cm². Furthermore, in order to identify the origin of improvement in optical performance, the transient light decay time and light intensity distribution characteristics were analyzed on the DHIP LED devices. Through the calculation of the electroluminescence (EL) decay time, internal quantum efficiency (IQE) is extracted along with the recombination parameters, which reveals that the DHIPs have a significant effect on enhancement of radiative recombination and reduction of efficiency droop. Furthermore, the mapping PL reveals that the DHIP LED also has a potential to improve the light extraction efficiency by hexagonal pyramid shaped DHIPs.

An enhanced mangiferaindica for dye sensitized solar cell application

NASA Astrophysics Data System (ADS)

Uno, U. E.; Emetere, M. E.; Fadipe, L. A.; Oluranti, Jonathan

2016-02-01

Titanium dioxide (T1O2) is preferred to Zinc oxide as mesoporous oxide layer because it raised the efficiency of DSSCs from 1% to 7%. The chemistry of the process however seem rigorous to allow the light induced electron injection from the adsorbed dye into the nanocrystallites i.e. which renders the TiO2 conductive. The DSSC fabricated consist of 2.25 cm2 active area of titanium dioxide coated on FTO glass (fluorine tin oxide) immersed in ethanol solution of natural dye extracted as an anode (electrode) and counter electrode. These two electrodes were coupled together and the space between them was filled with the Iodolyte AN-50 as solid electrolyte or redox mediator. The photo electrochemical parameters of the dye extracted (Mango fruit Peel) from the results obtained are short circuit current (Isc)= 1.22×10-2, current density (Jsc)=4.07×10-2, open circuit voltage (voc) =0.53V, fill factor (FF) of 0.16 and the overall conversion efficiency (Eff) =0.345%.

Savanna elephant numbers are only a quarter of their expected values

PubMed Central

Robson, Ashley S.; Trimble, Morgan J.; Purdon, Andrew; Young-Overton, Kim D.; Pimm, Stuart L.; van Aarde, Rudi J.

2017-01-01

Savannas once constituted the range of many species that human encroachment has now reduced to a fraction of their former distribution. Many survive only in protected areas. Poaching reduces the savanna elephant, even where protected, likely to the detriment of savanna ecosystems. While resources go into estimating elephant populations, an ecological benchmark by which to assess counts is lacking. Knowing how many elephants there are and how many poachers kill is important, but on their own, such data lack context. We collated savanna elephant count data from 73 protected areas across the continent estimated to hold ~50% of Africa’s elephants and extracted densities from 18 broadly stable population time series. We modeled these densities using primary productivity, water availability, and an index of poaching as predictors. We then used the model to predict stable densities given current conditions and poaching for all 73 populations. Next, to generate ecological benchmarks, we predicted such densities for a scenario of zero poaching. Where historical data are available, they corroborate or exceed benchmarks. According to recent counts, collectively, the 73 savanna elephant populations are at 75% of the size predicted based on current conditions and poaching levels. However, populations are at <25% of ecological benchmarks given a scenario of zero poaching (~967,000)—a total deficit of ~730,000 elephants. Populations in 30% of the 73 protected areas were <5% of their benchmarks, and the median current density as a percentage of ecological benchmark across protected areas was just 13%. The ecological context provided by these benchmark values, in conjunction with ongoing census projects, allow efficient targeting of conservation efforts. PMID:28414784

Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

NASA Astrophysics Data System (ADS)

Zhu, X. P.; Zhang, Z. C.; Pushkarev, A. I.; Lei, M. K.

2016-01-01

High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200-300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.

Investigation of factors influencing chloride extraction efficiency during electrochemical chloride extraction from reinforcing concrete

NASA Astrophysics Data System (ADS)

Sharp, Stephen R.

2005-11-01

Electrochemical chloride extraction (ECE) is an accelerated bridge restoration method similar to cathodic protection, but operates at higher current densities and utilizes a temporary installation. Both techniques prolong the life of a bridge by reducing the corrosion rate of the reinforcing bar when properly applied. ECE achieves this by moving chlorides away from the reinforcement and out of the concrete while simultaneously increasing the alkalinity of the electrolyte near the reinforcing steel. Despite the proven success, significant use of ECE has not resulted in part due to an incomplete understanding in the following areas: (1) An estimation of the additional service life that can be expected following treatment when the treated member is again subjected to chlorides; (2) The cause of the decrease in current flow and, therefore, chloride removal rate during treatment; (3) Influence of water-to-cement (w/c) ratio and cover depth on the time required for treatment. This dissertation covers the research that is connected to the last two areas listed above. To begin examining these issues, plain carbon steel reinforcing bars (rebar) were embedded in portland cement concrete slabs of varying water-to-cement (w/c) ratios and cover depths, and then exposed to chlorides. A fraction of these slabs had sodium chloride added as an admixture, with all of the slabs subjected to cyclical ponding with a saturated solution of sodium chloride. ECE was then used to remove the chlorides from these slabs while making electrical measurements in the different layers between the rebar (cathode) and the titanium mat (anode) to follow the progress of the ECE process. During this study, it was revealed that the resistance of the outer concrete surface layer increases during ECE, inevitably restricting current flow, while the resistance of the underlying concrete decreases or remains constant. During ECE treatment, a white residue formed on the surface of the concrete. Analyses of the residue revealed that it contains calcium carbonate, calcium chloride, and other yet unidentified minor components when calcium hydroxide was used as the electrolyte. The surface film can be completely removed mechanically or to some extent inhibited chemically, with both of these processes resulting in an increase in the efficiency of the electrochemical chloride extraction process. In addition, an obvious relationship between the cover depth, water-to-cement ratio, and chloride extraction efficiency does not exist, however, cover depth does influence the current density. The final phase of this study will be presented in a VTRC/FHWA final report. This report will include the results that are presented in this dissertation, in addition to the results from the ongoing research. It will also include an estimation of the additional service life that can be expected following treatment.

Nano-particle based scattering layers for optical efficiency enhancement of organic light-emitting diodes and organic solar cells

NASA Astrophysics Data System (ADS)

Chang, Hong-Wei; Lee, Jonghee; Hofmann, Simone; Hyun Kim, Yong; Müller-Meskamp, Lars; Lüssem, Björn; Wu, Chung-Chih; Leo, Karl; Gather, Malte C.

2013-05-01

The performance of both organic light-emitting diodes (OLEDs) and organic solar cells (OSC) depends on efficient coupling between optical far field modes and the emitting/absorbing region of the device. Current approaches towards OLEDs with efficient light-extraction often are limited to single-color emission or require expensive, non-standard substrates or top-down structuring, which reduces compatibility with large-area light sources. Here, we report on integrating solution-processed nano-particle based light-scattering films close to the active region of organic semiconductor devices. In OLEDs, these films efficiently extract light that would otherwise remain trapped in the device. Without additional external outcoupling structures, translucent white OLEDs containing these scattering films achieve luminous efficacies of 46 lm W-1 and external quantum efficiencies of 33% (both at 1000 cd m-2). These are by far the highest numbers ever reported for translucent white OLEDs and the best values in the open literature for any white device on a conventional substrate. By applying additional light-extraction structures, 62 lm W-1 and 46% EQE are reached. Besides universally enhancing light-extraction in various OLED configurations, including flexible, translucent, single-color, and white OLEDs, the nano-particle scattering film boosts the short-circuit current density in translucent organic solar cells by up to 70%.

[The influence of nettle and burdock extracts in combination with different diets on dyslipidemia in diabetes mellitus model].

PubMed

Vengerovsky, A I; Yakimova, T V; Nasanova, O N

2015-01-01

The influence of low-fat diet, nettle (Urtica dioica) leafs and burdock (Arctium lappa) roots extracts on lipid metabolism and glycosylation reactions has been investigated in experimental diabetes mellitus. These extracts were applied in diets with both high and low fat content. The experiments were performed on 90 noninbred male albino rats (200–220 g) that were divided into 9 experimental groups. Diabetes mellitus was modeled with twice-repeated intraperitoneal streptozotocin (30 mg/kg) injections. The animals received food with increased fat content (proteins – 8%, fats – 30%, carbohydrates – 62% of total daily caloric content) during 4 weeks before streptozotocine injections and 8 weeks after its discontinuation. Simultaneously the rats were daily administered nettle leafs (100 mg/kg), burdock roots (25 mg/kg) extracts or metformin (100 mg/kg) into the stomach during 10 days. During the period of agents introduction half the animals continued to receive food with high fat content, the other half received low fat diet (proteins – 20%, fats – 8%, carbohydrates – 72% of the total daily caloric content). The forth (control) group received low fat food only without extracts or metformin administration. The levels of blood glucose, glycosylated hemoglobin, malonic dialdehyde, lipid and lipoprotein fractions content were measured. It has been shown that after streptozotocine injections and 30% fat diet consumption the blood glucose level increased by 5.3 fold compared to that of the intact animals, the content of atherogenic lipid fractions increased by 2–8.3 fold and the protein glycosylation reactions were intensified by 1.9–2.5 fold. In animals fed with 8% fat diet the blood glucose and malonic dialdehyde content decreased by 1.8–2.3 fold. In this experiment the levels of triglycerides, total cholesterol, cholesterol of nonhigh-density lipoproteins, low-density and very low-density lipoproteins, as well as the cholesterol and protein content of high-density lipoproteins normalized. The low fat food did not cause glycosylation reactions regression. With the administration of nettle, burdock extracts or metformin to animals that continued to receive high fat food the blood glucose, triglycerides, total cholesterol, cholesterol of nonhigh-density lipoproteins, low-density and very low-density lipoproteins levels decreased by l.6–7.l fold as compared to the parameters in streptozotocine diabetes mellitus. Cholesterol and protein content of high-density lipoproteins increased by l.4–3.7 fold. The herbal extracts also prevented malonic dialdehyde formation, high-density lipoproteins and hemoglobin glycosylation. The nettle and burdock extracts more effectively decreased hyperglycemia, hypertriglyceridemia and lipoperoxidation in animals fed with low fat food. Metformin in the experiment with low fat intake decreased the glucose, low-density and very low-density lipoproteins content to a maximal degree and prevented high-density lipoproteins glycosylation.

Direct current H- source for the medicine accelerator (invited)

NASA Astrophysics Data System (ADS)

Belchenko, Yu.; Savkin, V.

2004-05-01

A compact cw hydrogen negative ion source having reliable operation and a simplified maintenance is developed at Budker Institute of Nuclear Physics for a tandem accelerator of boron capture neutron therapy installation. The source uses a Penning discharge with a hydrogen and cesium feed through the hollows in the cathodes. Discharge voltage is about 60-80 V, current 9 A, hydrogen pressure 4-5 Pa, magnetic field 0.05-0.1 T, and cesium seed <1 mg/h. Negative ions are mainly produced on the cesiated anode surface due to conversion of hydrogen atoms. An optimal anode temperature is 250-350 °C. Negative ion beam current is directly proportional to the discharge current and to the emission hole area. A triode system for the beam extraction and acceleration system is used. The flux of accompanying extracted electrons was decreased by filtering in the transverse magnetic field. This electron flux was intercepted to the special electrode, biased at 4 kV potential with respect to the anode. Source stable cw operation for several hour runs was multiply tested. A H- ion beam with current up to 8 mA, beam energy 23 keV was produced regularly. Negative ion current of heavy impurities had a value of about 3% of the total beam current. Beam normalized emittance is about 0.3 π mm mrad and emission current density -0.1 A/cm2. A built-in cathode heater provides the operation quick start.

Highly temperature insensitive, low threshold-current density (λ = 8.7–8.8 μm) quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirch, J. D.; Chang, C.-C.; Boyle, C.

2015-04-13

By stepwise tapering, both the barrier heights and quantum-well depths in the active regions of 8.7–8.8 μm-emitting quantum-cascade-laser (QCL) structures, virtually complete carrier-leakage suppression is achieved. Such step-taper active-region-type QCLs possess, for 3 mm-long devices with high-reflectivity-coated back facets, threshold-current characteristic temperature coefficients, T{sub 0}, as high as 283 K and slope-efficiency characteristic temperature coefficients, T{sub 1}, as high as 561 K, over the 20–60 °C heatsink-temperature range. These high T{sub 0} and T{sub 1} values reflect at least a factor of four reduction in carrier-leakage current compared to conventional 8–9 μm-emitting QCLs. Room temperature, pulsed, threshold-current densities are 1.58 kA/cm{sup 2}; values comparable to those formore » 35-period conventional QCLs of similar injector-region doping level. Superlinear behavior of the light-current curves is shown to be the result of the onset of resonant extraction from the lower laser level at a drive level of ∼1.3× threshold. Maximum room-temperature slope efficiencies are 1.23 W/A; that is, slope efficiency per period values of 35 mW/A, which are 37%–40% higher than for same-geometry conventional 8–9 μm-emitting QCLs. Since the waveguide-loss coefficients are very similar, we estimate that the internal differential efficiency is at least 30% higher than in conventional QCLs. Such high internal differential efficiency values reflect the combined effect of nearly complete carrier-leakage suppression and high differential efficiency of the laser transition (∼90%), due to resonant extraction from the lower laser level.« less

Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy,and Related Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grisham, L. R.; Kwan, J. W.

2008-08-01

Some years ago it was suggested that halogen negative ions could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, andmore » with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons - can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion - ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.« less

Modeling space-charge-limited current transport in spatially disordered organic semiconductors

NASA Astrophysics Data System (ADS)

Zubair, M.; Ang, Y. S.; Ang, L. K.

Charge transport properties in organic semiconductors are determined by two kinds of microscopic disorder, namely energetic disorder and the spatial disorder. It is demonstrated that the thickness dependence of space-charge limited current (SCLC) can be related to spatial disorder within the framework of fractional-dimensional space. We present a modified Mott-Gurney (MG) law in different regimes to model the varying thickness dependence in such spatially disordered materials. We analyze multiple experimental results from literature where thickness dependence of SCLC shows that the classical MG law might lead to less accurate extraction of mobility parameter, whereas the modified MG law would be a better choice in such devices. Experimental SCLC measurement in a PPV-based structure was previously modeled using a carrier-density dependent model which contradicts with a recent experiment that confirms a carrier-density independent mobility originating from the disordered morphology of the polymer. Here, this is reconciled by the modified MG law which intrinsically takes into account the effect of spatial disorder without the need of using a carrier-density dependent model. This work is supported by Singapore Temasek Laboratories (TL) Seed Grant (IGDS S16 02 05 1).

Time-dependent i-DFT exchange-correlation potentials with memory: applications to the out-of-equilibrium Anderson model

NASA Astrophysics Data System (ADS)

Kurth, Stefan; Stefanucci, Gianluca

2018-06-01

We have recently put forward a steady-state density functional theory (i-DFT) to calculate the transport coefficients of quantum junctions. Within i-DFT it is possible to obtain the steady density on and the steady current through an interacting junction using a fictitious noninteracting junction subject to an effective gate and bias potential. In this work we extend i-DFT to the time domain for the single-impurity Anderson model. By a reverse engineering procedure we extract the exchange-correlation (xc) potential and xc bias at temperatures above the Kondo temperature T K. The derivation is based on a generalization of a recent paper by Dittmann et al. [N. Dittmann et al., Phys. Rev. Lett. 120, 157701 (2018)]. Interestingly the time-dependent (TD) i-DFT potentials depend on the system's history only through the first time-derivative of the density. We perform numerical simulations of the early transient current and investigate the role of the history dependence. We also empirically extend the history-dependent TD i-DFT potentials to temperatures below T K. For this purpose we use a recently proposed parametrization of the i-DFT potentials which yields highly accurate results in the steady state.

A method for the retrieval of atomic oxygen density and temperature profiles from ground-based measurements of the O(+)(2D-2P) 7320 A twilight airglow

NASA Technical Reports Server (NTRS)

Fennelly, J. A.; Torr, D. G.; Richards, P. G.; Torr, M. R.; Sharp, W. E.

1991-01-01

This paper describes a technique for extracting thermospheric profiles of the atomic-oxygen density and temperature, using ground-based measurements of the O(+)(2D-2P) doublet at 7320 and 7330 A in the twilight airglow. In this method, a local photochemical model is used to calculate the 7320-A intensity; the method also utilizes an iterative inversion procedure based on the Levenberg-Marquardt method described by Press et al. (1986). The results demonstrate that, if the measurements are only limited by errors due to Poisson noise, the altitude profiles of neutral temperature and atomic oxygen concentration can be determined accurately using currently available spectrometers.

A Shuttle Upper Atmosphere Mass Spectrometer /SUMS/ experiment

NASA Technical Reports Server (NTRS)

Blanchard, R. C.; Duckett, R. J.; Hinson, E. W.

1982-01-01

A magnetic mass spectrometer is currently being adapted to the Space Shuttle Orbiter to provide repeated high altitude atmosphere data to support in situ rarefied flow aerodynamics research, i.e., in the high velocity, low density flight regime. The experiment, called Shuttle Upper Atmosphere Mass Spectrometer (SUMS), is the first attempt to design mass spectrometer equipment for flight vehicle aerodynamic data extraction. The SUMS experiment will provide total freestream atmospheric quantitites, principally total mass density, above altitudes at which conventional pressure measurements are valid. Experiment concepts, the expected flight profile, tradeoffs in the design of the total system and flight data reduction plans are discussed. Development plans are based upon a SUMS first flight after the Orbiter initial development flights.

Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices.

PubMed

Nukala, Pavan; Lin, Chia-Chun; Composto, Russell; Agarwal, Ritesh

2016-01-25

Crystal-amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier-lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13-0.6 MA cm(-2)) compared with the melt-quench strategy (∼50 MA cm(-2)). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation.

Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices

PubMed Central

Nukala, Pavan; Lin, Chia-Chun; Composto, Russell; Agarwal, Ritesh

2016-01-01

Crystal–amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier–lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13–0.6 MA cm−2) compared with the melt-quench strategy (∼50 MA cm−2). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation. PMID:26805748

High Performance Li4Ti5O12/Si Composite Anodes for Li-Ion Batteries

PubMed Central

Chen, Chunhui; Agrawal, Richa; Wang, Chunlei

2015-01-01

Improving the energy capacity of spinel Li4Ti5O12 (LTO) is very important to utilize it as a high-performance Li-ion battery (LIB) electrode. In this work, LTO/Si composites with different weight ratios were prepared and tested as anodes. The anodic and cathodic peaks from both LTO and silicon were apparent in the composites, indicating that each component was active upon Li+ insertion and extraction. The composites with higher Si contents (LTO:Si = 35:35) exhibited superior specific capacity (1004 mAh·g−1) at lower current densities (0.22 A·g−1) but the capacity deteriorated at higher current densities. On the other hand, the electrodes with moderate Si contents (LTO:Si = 50:20) were able to deliver stable capacity (100 mAh·g−1) with good cycling performance, even at a very high current density of 7 A·g−1. The improvement in specific capacity and rate performance was a direct result of the synergy between LTO and Si; the former can alleviate the stresses from volumetric changes in Si upon cycling, while Si can add to the capacity of the composite. Therefore, it has been demonstrated that the addition of Si and concentration optimization is an easy yet an effective way to produce high performance LTO-based electrodes for lithium-ion batteries. PMID:28347076

Advances in the characterization of InAs/GaSb superlattice infrared photodetectors

NASA Astrophysics Data System (ADS)

Wörl, A.; Daumer, V.; Hugger, T.; Kohn, N.; Luppold, W.; Müller, R.; Niemasz, J.; Rehm, R.; Rutz, F.; Schmidt, J.; Schmitz, J.; Stadelmann, T.; Wauro, M.

2016-10-01

This paper reports on advances in the electro-optical characterization of InAs/GaSb short-period superlattice infrared photodetectors with cut-off wavelengths in the mid-wavelength and long-wavelength infrared ranges. To facilitate in-line monitoring of the electro-optical device performance at different processing stages we have integrated a semi-automated cryogenic wafer prober in our process line. The prober is configured for measuring current-voltage characteristics of individual photodiodes at 77 K. We employ it to compile a spatial map of the dark current density of a superlattice sample with a cut-off wavelength around 5 μm patterned into a regular array of 1760 quadratic mesa diodes with a pitch of 370 μm and side lengths varying from 60 to 350 μm. The different perimeter-to-area ratios make it possible to separate bulk current from sidewall current contributions. We find a sidewall contribution to the dark current of 1.2×10-11 A/cm and a corrected bulk dark current density of 1.1×10-7 A/cm2, both at 200 mV reverse bias voltage. An automated data analysis framework can extract bulk and sidewall current contributions for various subsets of the test device grid. With a suitable periodic arrangement of test diode sizes, the spatial distribution of the individual contributions can thus be investigated. We found a relatively homogeneous distribution of both bulk dark current density and sidewall current contribution across the sample. With the help of an improved capacitance-voltage measurement setup developed to complement this technique a residual carrier concentration of 1.3×1015 cm-3 is obtained. The work is motivated by research into high performance superlattice array sensors with demanding processing requirements. A novel long-wavelength infrared imager based on a heterojunction concept is presented as an example for this work. It achieves a noise equivalent temperature difference below 30 mK for realistic operating conditions.

Explanation of low efficiency droop in semipolar (202¯1¯) InGaN/GaN LEDs through evaluation of carrier recombination coefficients.

PubMed

Monavarian, Morteza; Rashidi, Arman; Aragon, Andrew; Oh, Sang H; Nami, Mohsen; DenBaars, Steve P; Feezell, Daniel

2017-08-07

We report the carrier dynamics and recombination coefficients in single-quantum-well semipolar (202¯1¯) InGaN/GaN light-emitting diodes emitting at 440 nm with 93% peak internal quantum efficiency. The differential carrier lifetime is analyzed for various injection current densities from 5 A/cm 2 to 10 kA/cm 2 , and the corresponding carrier densities are obtained. The coupling of internal quantum efficiency and differential carrier lifetime vs injected carrier density (n) enables the separation of the radiative and nonradiative recombination lifetimes and the extraction of the Shockley-Read-Hall (SRH) nonradiative (A), radiative (B), and Auger (C) recombination coefficients and their n-dependency considering the saturation of the SRH recombination rate and phase-space filling. The results indicate a three to four-fold higher A and a nearly two-fold higher B0 for this semipolar orientation compared to that of c-plane reported using a similar approach [A. David and M. J. Grundmann, Appl. Phys. Lett. 96, 103504 (2010)]. In addition, the carrier density in semipolar (202¯1¯) is found to be lower than the carrier density in c-plane for a given current density, which is important for suppressing efficiency droop. The semipolar LED also shows a two-fold lower C0 compared to c-plane, which is consistent with the lower relative efficiency droop for the semipolar LED (57% vs. 69%). The lower carrier density, higher B 0 coefficient, and lower C 0 (Auger) coefficient are directly responsible for the high efficiency and low efficiency droop reported in semipolar (202¯1¯) LEDs.

Explanation of low efficiency droop in semipolar (202¯1¯) InGaN/GaN LEDs through evaluation of carrier recombination coefficients

NASA Astrophysics Data System (ADS)

Monavarian, Morteza; Rashidi, Arman; Aragon, Andrew; Oh, Sang H.; Nami, Mohsen; DenBaars, Steve P.; Feezell, Daniel

2017-08-01

We report the carrier dynamics and recombination coefficients in single-quantum-well semipolar $(20\\bar 2\\bar 1)$ InGaN/GaN light-emitting diodes emitting at 440 nm with 93% peak internal quantum efficiency. The differential carrier lifetime is analyzed for various injection current densities from 5 $A/cm^2$ to 10 $kA/cm^2$, and the corresponding carrier densities are obtained. The coupling of internal quantum efficiency and differential carrier lifetime vs injected carrier density ($n$) enables the separation of the radiative and nonradiative recombination lifetimes and the extraction of the Shockley-Read-Hall (SRH) nonradiative ($A$), radiative ($B$), and Auger ($C$) recombination coefficients and their $n$-dependency considering the saturation of the SRH recombination rate and phase-space filling. The results indicate a three to four-fold higher $A$ and a nearly two-fold higher $B_0$ for this semipolar orientation compared to that of $c$-plane reported using a similar approach [A. David and M. J. Grundmann, Appl. Phys. Lett. 96, 103504 (2010)]. In addition, the carrier density in semipolar $(20\\bar 2\\bar 1)$ is found to be lower than the carrier density in $c$-plane for a given current density, which is important for suppressing efficiency droop. The semipolar LED also shows a two-fold lower $C_0$ compared to $c$-plane, which is consistent with the lower relative efficiency droop for the semipolar LED (57% vs. 69%). The lower carrier density, higher $B_0$ coefficient, and lower $C_0$ (Auger) coefficient are directly responsible for the high efficiency and low efficiency droop reported in semipolar $(20\\bar 2\\bar 1)$ LEDs.

Three-Dimensional Grain Shape-Fabric from Unconsolidated Pyroclastic Density Current Deposits: Implications for Extracting Flow Direction and Insights on Rheology

NASA Astrophysics Data System (ADS)

Hawkins, T. T.; Brand, B. D.; Sarrochi, D.; Pollock, N.

2016-12-01

One of the greatest challenges volcanologists face is the ability to extrapolate information about eruption dynamics and emplacement conditions from deposits. Pyroclastic density current (PDC) deposits are particularly challenging given the wide range of initial current conditions, (e.g., granular, fluidized, concentrated, dilute), and rapid flow transformations due to interaction with evolving topography. Analysis of particle shape-fabric can be used to determine flow direction, and may help to understand the rheological characteristics of the flows. However, extracting shape-fabric information from outcrop (2D) apparent fabric is limited, especially when outcrop exposure is incomplete or lacks context. To better understand and quantify the complex flow dynamics reflected in PDC deposits, we study the complete shape-fabric data in 3D using oriented samples. In the field, the prospective sample is carved from the unconsolidated deposit in blocks, the dimensions of which depend on the average clast size in the sample. The sample is saturated in situ with a water-based sodium silicate solution, then wrapped in plaster-soaked gauze to form a protective cast. The orientation of the sample is recorded on the block faces. The samples dry for five days and are then extracted in intact blocks. In the lab, the sample is vacuum impregnated with sodium silicate and cured in an oven. The fully lithified sample is first cut along the plan view to identify orientations of the long axes of the grains (flow direction), and then cut in the two plains perpendicular to grain elongation. 3D fabric analysis is performed using high resolution images of the cut-faces using computer assisted image analysis software devoted to shape-fabric analysis. Here we present the results of samples taken from the 18 May 1980 PDC deposit facies, including massive, diffuse-stratified and cross-stratified lapilli tuff. We show a relationship between the strength of iso-orientation of the elongated particles and different facies architectures, which is used to interpret rheological conditions of the flow. We chose the 18 May PDC deposits because their well-exposed and well-studied outcrops provide context, which allow us to test the method and extract information useful for interpreting ancient deposits that lack context.

A high intensity 200 mA proton source for the FRANZ-Project (Frankfurt-Neutron-Source at the Stern-Gerlach-Center)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schweizer, W., E-mail: schweizer@physik.uni-frankfurt.de; Ratzinger, U.; Klump, B.

At the University of Frankfurt a high current proton source has been developed and tested for the FRANZ-Project [U. Ratzinger, L. P. Chau, O. Meusel, A. Schempp, K. Volk, M. Heil, F. Käppeler, and R. Stieglitz, “Intense pulsed neutron source FRANZ in the 1–500 keV range,” ICANS-XVIII Proceedings, Dongguan, April 2007, p. 210]. The ion source is a filament driven arc discharge ion source. The new design consists of a plasma generator, equipped with a filter magnet to produce nearly pure proton beams (92 %), and a compact triode extraction system. The beam current density has been enhanced up tomore » 521 mA/cm{sup 2}. Using an emission opening radius of 4 mm, a proton beam current of 240 mA at 50 keV beam energy in continuous wave mode (cw) has been extracted. This paper will present the current status of the proton source including experimental results of detailed investigations of the beam composition in dependence of different plasma parameters. Both, cw and pulsed mode were studied. Furthermore, the performance of the ion source was studied with deuterium as working gas.« less

Relationship between exposure to vector bites and antibody responses to mosquito salivary gland extracts.

PubMed

Fontaine, Albin; Pascual, Aurélie; Orlandi-Pradines, Eve; Diouf, Ibrahima; Remoué, Franck; Pagès, Frédéric; Fusaï, Thierry; Rogier, Christophe; Almeras, Lionel

2011-01-01

Mosquito-borne diseases are major health problems worldwide. Serological responses to mosquito saliva proteins may be useful in estimating individual exposure to bites from mosquitoes transmitting these diseases. However, the relationships between the levels of these IgG responses and mosquito density as well as IgG response specificity at the genus and/or species level need to be clarified prior to develop new immunological markers to assess human/vector contact. To this end, a kinetic study of antibody levels against several mosquito salivary gland extracts from southeastern French individuals living in three areas with distinct ecological environments and, by implication, distinct Aedes caspius mosquito densities were compared using ELISA. A positive association was observed between the average levels of IgG responses against Ae. caspius salivary gland extracts and spatial Ae. caspius densities. Additionally, the average level of IgG responses increased significantly during the peak exposure to Ae. caspius at each site and returned to baseline four months later, suggesting short-lived IgG responses. The species-specificity of IgG antibody responses was determined by testing antibody responses to salivary gland extracts from Cx. pipiens, a mosquito that is present at these three sites at different density levels, and from two other Aedes species not present in the study area (Ae. aegypti and Ae. albopictus). The IgG responses observed against these mosquito salivary gland extracts contrasted with those observed against Ae. caspius salivary gland extracts, supporting the existence of species-specific serological responses. By considering different populations and densities of mosquitoes linked to environmental factors, this study shows, for the first time, that specific IgG antibody responses against Ae. caspius salivary gland extracts may be related to the seasonal and geographical variations in Ae. caspius density. Characterisation of such immunological-markers may allow the evaluation of the effectiveness of vector-control strategies or estimation of the risk of vector-borne disease transmission.

Relationship between Exposure to Vector Bites and Antibody Responses to Mosquito Salivary Gland Extracts

PubMed Central

Orlandi-Pradines, Eve; Diouf, Ibrahima; Remoué, Franck; Pagès, Frédéric; Fusaï, Thierry; Rogier, Christophe; Almeras, Lionel

2011-01-01

Mosquito-borne diseases are major health problems worldwide. Serological responses to mosquito saliva proteins may be useful in estimating individual exposure to bites from mosquitoes transmitting these diseases. However, the relationships between the levels of these IgG responses and mosquito density as well as IgG response specificity at the genus and/or species level need to be clarified prior to develop new immunological markers to assess human/vector contact. To this end, a kinetic study of antibody levels against several mosquito salivary gland extracts from southeastern French individuals living in three areas with distinct ecological environments and, by implication, distinct Aedes caspius mosquito densities were compared using ELISA. A positive association was observed between the average levels of IgG responses against Ae. caspius salivary gland extracts and spatial Ae. caspius densities. Additionally, the average level of IgG responses increased significantly during the peak exposure to Ae. caspius at each site and returned to baseline four months later, suggesting short-lived IgG responses. The species-specificity of IgG antibody responses was determined by testing antibody responses to salivary gland extracts from Cx. pipiens, a mosquito that is present at these three sites at different density levels, and from two other Aedes species not present in the study area (Ae. aegypti and Ae. albopictus). The IgG responses observed against these mosquito salivary gland extracts contrasted with those observed against Ae. caspius salivary gland extracts, supporting the existence of species-specific serological responses. By considering different populations and densities of mosquitoes linked to environmental factors, this study shows, for the first time, that specific IgG antibody responses against Ae. caspius salivary gland extracts may be related to the seasonal and geographical variations in Ae. caspius density. Characterisation of such immunological-markers may allow the evaluation of the effectiveness of vector-control strategies or estimation of the risk of vector-borne disease transmission. PMID:22195000

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

PubMed Central

Carmona, Jesús; Climent, Miguel-Ángel; Antón, Carlos; de Vera, Guillem; Garcés, Pedro

2015-01-01

This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Characterizing the Performance of the Princeton Advanced Test Stand Ion Source

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Kaganovich, I.; Davidson, R. C.

2012-10-01

The Princeton Advanced Test Stand (PATS) is a compact experimental facility for studying the physics of intense beam-plasma interactions relevant to the Neutralized Drift Compression Experiment - II (NDCX-II). The PATS facility consists of a multicusp RF ion source mounted on a 2 m-long vacuum chamber with numerous ports for diagnostic access. Ar+ beams are extracted from the source plasma with three-electrode (accel-decel) extraction optics. The RF power and extraction voltage (30 - 100 kV) are pulsed to produce 100 μsec duration beams at 0.5 Hz with excellent shot-to-shot repeatability. Diagnostics include Faraday cups, a double-slit emittance scanner, and scintillator imaging. This work reports measurements of beam parameters for a range of beam energies (30 - 50 keV) and currents to characterize the behavior of the ion source and extraction optics. Emittance scanner data is used to calculate the beam trace-space distribution and corresponding transverse emittance. If the plasma density is changing during a beam pulse, time-resolved emittance scanner data has been taken to study the corresponding evolution of the beam trace-space distribution.

Uncertainty analysis of wavelet-based feature extraction for isotope identification on NaI gamma-ray spectra

DOE PAGES

Stinnett, Jacob; Sullivan, Clair J.; Xiong, Hao

2017-03-02

Low-resolution isotope identifiers are widely deployed for nuclear security purposes, but these detectors currently demonstrate problems in making correct identifications in many typical usage scenarios. While there are many hardware alternatives and improvements that can be made, performance on existing low resolution isotope identifiers should be able to be improved by developing new identification algorithms. We have developed a wavelet-based peak extraction algorithm and an implementation of a Bayesian classifier for automated peak-based identification. The peak extraction algorithm has been extended to compute uncertainties in the peak area calculations. To build empirical joint probability distributions of the peak areas andmore » uncertainties, a large set of spectra were simulated in MCNP6 and processed with the wavelet-based feature extraction algorithm. Kernel density estimation was then used to create a new component of the likelihood function in the Bayesian classifier. Furthermore, identification performance is demonstrated on a variety of real low-resolution spectra, including Category I quantities of special nuclear material.« less

Neuroprotection by methanol extract of Uncaria rhynchophylla against global cerebral ischemia in rats.

PubMed

Suk, Kyoungho; Kim, Sun Yeou; Leem, Kanghyun; Kim, Young Ock; Park, Sun Young; Hur, Jinyoung; Baek, Jihwoon; Lee, Kang Jin; Zheng, Hu Zhan; Kim, Hocheol

2002-04-21

In traditional Oriental medicine, Uncaria rhynchophylla has been used to lower blood pressure and to relieve various neurological symptoms. However, scientific evidence related to its effectiveness or precise modes of action has not been available. Thus, in the current study, we evaluated neuroprotective effects of U. rhynchophylla after transient global ischemia using 4-vessel occlusion model in rats. Methanol extract of U. rhynchophylla administered intraperitoneally (100-1000 mg/kg at 0 and 90 min after reperfusion) significantly protected hippocampal CA1 neurons against 10 min transient forebrain ischemia. Measurement of neuronal cell density in CA1 region at 7 days after ischemia by Nissl staining revealed more than 70% protection in U. rhynchophylla-treated rats compared to saline-treated animals. In U. rhynchophylla-treated animals, induction of cyclooxygenase-2 in hippocampus at 24 hr after ischemia was significantly inhibited at both mRNA and protein levels. Furthermore, U. rhynchophylla extract inhibited TNF-alpha and nitric oxide production in BV-2 mouse microglial cells in vitro. These anti-inflammatory actions of U. rhynchophylla extract may contribute to its neuroprotective effects.

Trap densities and transport properties of pentacene metal-oxide-semiconductor transistors: II—Numerical modeling of dc characteristics

NASA Astrophysics Data System (ADS)

Basile, A. F.; Kyndiah, A.; Biscarini, F.; Fraboni, B.

2014-06-01

A numerical procedure to calculate the drain-current (ID) vs. gate-voltage (VG) characteristics from numerical solutions of the Poisson equation for organic Thin-Film Transistors (TFTs) is presented. Polaron transport is modeled as two-dimensional charge transport in a semiconductor having free-carrier density of states proportional to the density of molecules and traps with energy equal to the polaron-hopping barrier. The simulated ID-VG curves are proportional to the product of the density of free carriers, calculated as a function of VG, and the intrinsic mobility, assumed to be a constant independent of temperature. The presence of traps in the oxide was also taken into account in the model, which was applied to a TFT made with six monolayers of pentacene grown on an oxide substrate. The polaron-hopping barrier determines the temperature dependence of the simulated ID-VG curves, trapping in the oxide is responsible for current reduction at high bias and the slope of the characteristics near threshold is related to the metal-semiconductor work-function difference. The values of the model parameters yielding the best match between calculations and experiments are consistent with previous experimental results and theoretical predictions. Therefore, this model enables to extract both physical and technological properties of thin-film devices from the temperature-dependent dc characteristics.

Spontaneous-Desorption Ionizer for a TOF-MS

NASA Technical Reports Server (NTRS)

Schultz, J. Albert

2006-01-01

A time-of-flight mass spectrometer (TOF-MS) like the one mentioned in the immediately preceding article has been retrofitted with an ionizer based on a surface spontaneous-desorption process. This ionizer includes an electron multiplier in the form of a microchannel plate (MCP). Relative to an ionizer based on a hot-filament electron source, this ionizer offers advantages of less power consumption and greater mechanical ruggedness. The current density and stability characteristics of the electron emission of this ionizer are similar to those of a filament-based ionizer. In tests of various versions of this ionizer in the TOF-MS, electron currents up to 100 nA were registered. Currents of microamperes or more - great enough to satisfy requirements in most TOFMS applications - could be obtained by use of MCPs different from those used in the tests, albeit at the cost of greater bulk. One drawback of this ionizer is that the gain of the MCP decreases as a function of the charge extracted thus far; the total charge that can be extracted over the operational lifetime is about 1 coulomb. An MCP in the ion-detector portion of the TOF-MS is subject to the same limitation.

Carrier statistics and quantum capacitance effects on mobility extraction in two-dimensional crystal semiconductor field-effect transistors

NASA Astrophysics Data System (ADS)

Ma, Nan; Jena, Debdeep

2015-03-01

In this work, the consequence of the high band-edge density of states on the carrier statistics and quantum capacitance in transition metal dichalcogenide two-dimensional semiconductor devices is explored. The study questions the validity of commonly used expressions for extracting carrier densities and field-effect mobilities from the transfer characteristics of transistors with such channel materials. By comparison to experimental data, a new method for the accurate extraction of carrier densities and mobilities is outlined. The work thus highlights a fundamental difference between these materials and traditional semiconductors that must be considered in future experimental measurements.

Study on electrical current variations in electromembrane extraction process: Relation between extraction recovery and magnitude of electrical current.

PubMed

Rahmani, Turaj; Rahimi, Atyeh; Nojavan, Saeed

2016-01-15

This contribution presents an experimental approach to improve analytical performance of electromembrane extraction (EME) procedure, which is based on the scrutiny of current pattern under different extraction conditions such as using different organic solvents as supported liquid membrane, electrical potentials, pH values of donor and acceptor phases, variable extraction times, temperatures, stirring rates, different hollow fiber lengths and the addition of salts or organic solvents to the sample matrix. In this study, four basic drugs with different polarities were extracted under different conditions with the corresponding electrical current patterns compared against extraction recoveries. The extraction process was demonstrated in terms of EME-HPLC analyses of selected basic drugs. Comparing the obtained extraction recoveries with the electrical current patterns, most cases exhibited minimum recovery and repeatability at the highest investigated magnitude of electrical current. . It was further found that identical current patterns are associated with repeated extraction efficiencies. In other words, the pattern should be repeated for a successful extraction. The results showed completely different electrical currents under different extraction conditions, so that all variable parameters have contributions into the electrical current pattern. Finally, the current patterns of extractions from wastewater, plasma and urine samples were demonstrated. The results indicated an increase in the electrical current when extracting from complex matrices; this was seen to decrease the extraction efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes.

PubMed

Borzenets, I V; Amet, F; Ke, C T; Draelos, A W; Wei, M T; Seredinski, A; Watanabe, K; Taniguchi, T; Bomze, Y; Yamamoto, M; Tarucha, S; Finkelstein, G

2016-12-02

We investigate the critical current I_{C} of ballistic Josephson junctions made of encapsulated graphene-boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, I_{C} is found to scale as ∝exp(-k_{B}T/δE). The extracted energies δE are independent of the carrier density and proportional to the level spacing of the ballistic cavity. As T→0 the critical current of a long (or short) junction saturates at a level determined by the product of δE (or Δ) and the number of the junction's transversal modes.

Insight into the CH3NH3PbI3/C interface in hole-conductor-free mesoscopic perovskite solar cells

NASA Astrophysics Data System (ADS)

Li, Jiangwei; Niu, Guangda; Li, Wenzhe; Cao, Kun; Wang, Mingkui; Wang, Liduo

2016-07-01

Perovskite solar cells (PSCs) with hole-conductor-free mesoscopic architecture have shown superb stability and great potential in practical application. The printable carbon counter electrodes take full responsibility of extracting holes from the active CH3NH3PbI3 absorbers. However, an in depth study of the CH3NH3PbI3/C interface properties, such as the structural formation process and the effect of interfacial conditions on hole extraction, is still lacking. Herein, we present, for the first time, an insight into the spatial confinement induced CH3NH3PbI3/C interface formation by in situ photoluminescence observations during the crystallization process of CH3NH3PbI3. The derived reaction kinetics allows a quantitative description of the perovskite formation process. In addition, we found that the interfacial contact between carbon and perovskite was dominant for hole extraction efficiency and associated with the photovoltaic parameter of short circuit current density (JSC). Consequently, we conducted a solvent vapor assisted process of PbI2 diffusion to carefully control the CH3NH3PbI3/C interface with less unreacted PbI2 barrier. The improvement of interface conditions thereby contributes to a high hole extraction proved by the charge extraction resistance and PL lifetime change, resulting in the increased JSC valve.Perovskite solar cells (PSCs) with hole-conductor-free mesoscopic architecture have shown superb stability and great potential in practical application. The printable carbon counter electrodes take full responsibility of extracting holes from the active CH3NH3PbI3 absorbers. However, an in depth study of the CH3NH3PbI3/C interface properties, such as the structural formation process and the effect of interfacial conditions on hole extraction, is still lacking. Herein, we present, for the first time, an insight into the spatial confinement induced CH3NH3PbI3/C interface formation by in situ photoluminescence observations during the crystallization process of CH3NH3PbI3. The derived reaction kinetics allows a quantitative description of the perovskite formation process. In addition, we found that the interfacial contact between carbon and perovskite was dominant for hole extraction efficiency and associated with the photovoltaic parameter of short circuit current density (JSC). Consequently, we conducted a solvent vapor assisted process of PbI2 diffusion to carefully control the CH3NH3PbI3/C interface with less unreacted PbI2 barrier. The improvement of interface conditions thereby contributes to a high hole extraction proved by the charge extraction resistance and PL lifetime change, resulting in the increased JSC valve. Electronic supplementary information (ESI) available: Fig. S1-S11, Tables S1, S2 and details of the Avrami model for reaction kinetics. See DOI: 10.1039/c6nr03359h

Sensing Responses Based on Transfer Characteristics of InAs Nanowire Field-Effect Transistors

PubMed Central

Savelyev, Igor; Blumin, Marina; Wang, Shiliang; Ruda, Harry E.

2017-01-01

Nanowire-based field-effect transistors (FETs) have demonstrated considerable promise for a new generation of chemical and biological sensors. Indium arsenide (InAs), by virtue of its high electron mobility and intrinsic surface accumulation layer of electrons, holds properties beneficial for creating high performance sensors that can be used in applications such as point-of-care testing for patients diagnosed with chronic diseases. Here, we propose devices based on a parallel configuration of InAs nanowires and investigate sensor responses from measurements of conductance over time and FET characteristics. The devices were tested in controlled concentrations of vapour containing acetic acid, 2-butanone and methanol. After adsorption of analyte molecules, trends in the transient current and transfer curves are correlated with the nature of the surface interaction. Specifically, we observed proportionality between acetic acid concentration and relative conductance change, off current and surface charge density extracted from subthreshold behaviour. We suggest the origin of the sensing response to acetic acid as a two-part, reversible acid-base and redox reaction between acetic acid, InAs and its native oxide that forms slow, donor-like states at the nanowire surface. We further describe a simple model that is able to distinguish the occurrence of physical versus chemical adsorption by comparing the values of the extracted surface charge density. These studies demonstrate that InAs nanowires can produce a multitude of sensor responses for the purpose of developing next generation, multi-dimensional sensor applications. PMID:28714903

Cortisol extraction through human skin by reverse iontophoresis.

PubMed

Ventura, Stephanie A; Heikenfeld, Jason; Brooks, Tiffany; Esfandiari, Leyla; Boyce, Steven; Park, Yoonjee; Kasting, Gerald B

2017-04-01

Continuous monitoring of cortisol at the surface of the skin would advance the diagnosis and treatment of cortisol-related diseases, or of elevated cortisol levels related to stress in otherwise healthy populations. Reliable and accurate detection of cortisol at the skin surface remains a limiting factor in real-time monitoring of cortisol. To address this limitation, cortisol extraction through excised human skin by reverse iontophoresis was studied in vitro in side-by-side diffusion cells using a radiolabeled probe. The skin was subjected to four direct current regimens (0, 28, 56, 113μAcm -2 ) with the anode in the donor chamber and the cumulative cortisol concentrations recorded in the receiver chamber. The 56 and 113μAcm -2 regimens significantly increased transport of 3 H-cortisol through the skin, and current density correlated directly with transcutaneous transport of 3 H-cortisol. The threshold of detection of electroosmotic versus passive diffusion of cortisol through the skin was between 28 and 56μAcm -2 . The results of this study are significant in examining how lipophilic analytes found in the bloodstream respond to reverse iontophoresis across the skin. In addition, a device integration technique is presented which illustrates how continuous cortisol extraction and sensing could potentially be achieved in a conventional wearable format. Copyright © 2016 Elsevier B.V. All rights reserved.

A Permanent-Magnet Microwave Ion Source For A Compact High-Yield Neutron Generator

NASA Astrophysics Data System (ADS)

Waldmann, O.; Ludewigt, B.

2011-06-01

We present recent work on the development of a microwave ion source that will be used in a high-yield compact neutron generator for active interrogation applications. The sealed tube generator will be capable of producing high neutron yields, 5×1011 n/s for D-T and ˜1×1010 n/s for D-D reactions, while remaining transportable. We constructed a microwave ion source (2.45 GHz) with permanent magnets to provide the magnetic field strength of 87.5 mT necessary for satisfying the electron cyclotron resonance (ECR) condition. Microwave ion sources can produce high extracted beam currents at the low gas pressures required for sealed tube operation and at lower power levels than previously used RF-driven ion sources. A 100 mA deuterium/tritium beam will be extracted through a large slit (60×6 mm2) to spread the beam power over a larger target area. This paper describes the design of the permanent-magnet microwave ion source and discusses the impact of the magnetic field design on the source performance. The required equivalent proton beam current density of 40 mA/cm2 was extracted at a moderate microwave power of 400 W with an optimized magnetic field.

Non-Intrusive Magneto-Optic Detecting System for Investigations of Air Switching Arcs

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Zhang, Guogang; Dong, Jinlong; Liu, Wanying; Geng, Yingsan

2014-07-01

In current investigations of electric arc plasmas, experiments based on modern testing technology play an important role. To enrich the testing methods and contribute to the understanding and grasping of the inherent mechanism of air switching arcs, in this paper, a non-intrusive detecting system is described that combines the magneto-optic imaging (MOI) technique with the solution to inverse electromagnetic problems. The detecting system works in a sequence of main steps as follows: MOI of the variation of the arc flux density over a plane, magnetic field information extracted from the magneto-optic (MO) images, arc current density distribution and spatial pattern reconstruction by inverting the resulting field data. Correspondingly, in the system, an MOI set-up is designed based on the Faraday effect and the polarization properties of light, and an intelligent inversion algorithm is proposed that involves simulated annealing (SA). Experiments were carried out for high current (2 kA RMS) discharge cases in a typical low-voltage switchgear. The results show that the MO detection system possesses the advantages of visualization, high resolution and response, and electrical insulation, which provides a novel diagnostics tool for further studies of the arc.

Possible overexposure of pregnant women to emissions from a walk through metal detector.

PubMed

Wu, Dagang; Qiang, Rui; Chen, Ji; Seidman, Seth; Witters, Donald; Kainz, Wolfgang

2007-10-07

This paper presents a systematic procedure to evaluate the induced current densities and electric fields due to walk-through metal detector (WTMD) exposure. This procedure is then used to assess the exposure of nine pregnant women models exposed to one WTMD model. First, we measured the magnetic field generated by the WTMD, then we extracted the equivalent current source to represent the WTMD emissions and finally we calculated the induced current densities and electric fields using the impedance method. The WTMD emissions and the induced fields in the pregnant women and fetus models are then compared to the ICNIRP Guidelines and the IEEE C95.6 exposure safety standard. The results prove the consistency between maximum permissible exposure (MPE) levels and basic restrictions for the ICNIRP Guidelines and IEEE C95.6. We also found that this particular WTMD complies with the ICNIRP basic restrictions for month 1-5 models, but leads to both fetus and pregnant women overexposure for month 6-9 models. The IEEE C95.6 restrictions (MPEs and basic restrictions) are not exceeded. The fetus overexposure of this particular WTMD calls for carefully conducted safety evaluations of security systems before they are deployed.

Possible overexposure of pregnant women to emissions from a walk through metal detector

NASA Astrophysics Data System (ADS)

Wu, Dagang; Qiang, Rui; Chen, Ji; Seidman, Seth; Witters, Donald; Kainz, Wolfgang

2007-09-01

This paper presents a systematic procedure to evaluate the induced current densities and electric fields due to walk-through metal detector (WTMD) exposure. This procedure is then used to assess the exposure of nine pregnant women models exposed to one WTMD model. First, we measured the magnetic field generated by the WTMD, then we extracted the equivalent current source to represent the WTMD emissions and finally we calculated the induced current densities and electric fields using the impedance method. The WTMD emissions and the induced fields in the pregnant women and fetus models are then compared to the ICNIRP Guidelines and the IEEE C95.6 exposure safety standard. The results prove the consistency between maximum permissible exposure (MPE) levels and basic restrictions for the ICNIRP Guidelines and IEEE C95.6. We also found that this particular WTMD complies with the ICNIRP basic restrictions for month 1-5 models, but leads to both fetus and pregnant women overexposure for month 6-9 models. The IEEE C95.6 restrictions (MPEs and basic restrictions) are not exceeded. The fetus overexposure of this particular WTMD calls for carefully conducted safety evaluations of security systems before they are deployed.

The Effect of Storage and Extraction Methods on Amplification of Plasmodium falciparum DNA from Dried Blood Spots.

PubMed

Schwartz, Alanna; Baidjoe, Amrish; Rosenthal, Philip J; Dorsey, Grant; Bousema, Teun; Greenhouse, Bryan

2015-05-01

Extraction and amplification of DNA from dried blood spots (DBS) collected in field studies is commonly used for detection of Plasmodium falciparum. However, there have been few systematic efforts to determine the effects of storage and extraction methods on the sensitivity of DNA amplification. We investigated the effects of storage conditions, length of storage, and DNA extraction methods on amplification via three PCR-based assays using field samples and laboratory controls. Samples stored as DBS for 2 or more years at ambient temperature showed a significant loss of sensitivity that increased with time; after 10 years only 10% samples with parasite densities > 1,000 parasites/μL were detectable by nested polymerase chain reaction (PCR). Conversely, DBS and extracted DNA stored at -20°C showed no loss of sensitivity with time. Samples with low parasite densities amplified more successfully with saponin/Chelex compared with spin-column-based extraction, though the latter method performed better on samples with higher parasite densities stored for 2 years at ambient temperature. DNA extracted via both methods was stable after 20 freeze-thaw cycles. Our results suggest that DBS should be stored at -20°C or extracted immediately, especially if anticipating 2 or more years of storage. © The American Society of Tropical Medicine and Hygiene.

The Effect of Storage and Extraction Methods on Amplification of Plasmodium falciparum DNA from Dried Blood Spots

PubMed Central

Schwartz, Alanna; Baidjoe, Amrish; Rosenthal, Philip J.; Dorsey, Grant; Bousema, Teun; Greenhouse, Bryan

2015-01-01

Extraction and amplification of DNA from dried blood spots (DBS) collected in field studies is commonly used for detection of Plasmodium falciparum. However, there have been few systematic efforts to determine the effects of storage and extraction methods on the sensitivity of DNA amplification. We investigated the effects of storage conditions, length of storage, and DNA extraction methods on amplification via three PCR-based assays using field samples and laboratory controls. Samples stored as DBS for 2 or more years at ambient temperature showed a significant loss of sensitivity that increased with time; after 10 years only 10% samples with parasite densities > 1,000 parasites/μL were detectable by nested polymerase chain reaction (PCR). Conversely, DBS and extracted DNA stored at −20°C showed no loss of sensitivity with time. Samples with low parasite densities amplified more successfully with saponin/Chelex compared with spin-column-based extraction, though the latter method performed better on samples with higher parasite densities stored for 2 years at ambient temperature. DNA extracted via both methods was stable after 20 freeze-thaw cycles. Our results suggest that DBS should be stored at −20°C or extracted immediately, especially if anticipating 2 or more years of storage. PMID:25758652

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stinnett, Jacob; Sullivan, Clair J.; Xiong, Hao

Low-resolution isotope identifiers are widely deployed for nuclear security purposes, but these detectors currently demonstrate problems in making correct identifications in many typical usage scenarios. While there are many hardware alternatives and improvements that can be made, performance on existing low resolution isotope identifiers should be able to be improved by developing new identification algorithms. We have developed a wavelet-based peak extraction algorithm and an implementation of a Bayesian classifier for automated peak-based identification. The peak extraction algorithm has been extended to compute uncertainties in the peak area calculations. To build empirical joint probability distributions of the peak areas andmore » uncertainties, a large set of spectra were simulated in MCNP6 and processed with the wavelet-based feature extraction algorithm. Kernel density estimation was then used to create a new component of the likelihood function in the Bayesian classifier. Furthermore, identification performance is demonstrated on a variety of real low-resolution spectra, including Category I quantities of special nuclear material.« less

Two-color field enhancement at an STM junction for spatiotemporally resolved photoemission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Xiang; Jin, Wencan; Yang, Hao

Here, we report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The current from a nanoscopic tungsten tip across a ~1 nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements in driving the current is investigated using density functional theory and full three-dimensional finite-difference time-domain computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-colormore » photoexcited current with increasing tip–surface separation, as well as its optical-delay dependence. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.« less

Two-color field enhancement at an STM junction for spatiotemporally resolved photoemission

DOE PAGES

Meng, Xiang; Jin, Wencan; Yang, Hao; ...

2017-06-30

Here, we report measurements and numerical simulations of ultrafast laser-excited carrier flow across a scanning tunneling microscope (STM) junction. The current from a nanoscopic tungsten tip across a ~1 nm vacuum gap to a silver surface is driven by a two-color excitation scheme that uses an optical delay-modulation technique to extract the two-color signal from background contributions. The role of optical field enhancements in driving the current is investigated using density functional theory and full three-dimensional finite-difference time-domain computations. We find that simulated field-enhanced two-photon photoemission (2PPE) currents are in excellent agreement with the observed exponential decay of the two-colormore » photoexcited current with increasing tip–surface separation, as well as its optical-delay dependence. The results suggest an approach to 2PPE with simultaneous subpicosecond temporal and nanometer spatial resolution.« less

Antiosteoporotic Effect of Combined Extract of Morus alba and Polygonum odoratum

PubMed Central

Sungkamanee, Sudarat; Thukham-mee, Wipawee

2014-01-01

Due to the limitation of osteoporosis therapy, the alternative therapies from natural sources have been considered. In this study, we aimed to determine the antiosteoporotic effect of the combined extract of Morus alba and Polygonum odoratum leaves. Ovariectomized rats, weighing 200–220 g, were orally given the combined extract at doses of 5, 150, and 300 mg·kg−1 BW for 3 months. At the end of study, blood was collected to determine serum osteocalcin, calcium, and alkaline phosphatase level. In addition, tibia bone was isolated to determine bone oxidative stress markers, cortical bone thickness, and density of osteoblast. The combined extract decreased oxidative stress and osteoclast density but increased osteoblast density and cortical thickness. The elevation of serum calcium, alkaline phosphatase, and osteocalcin was also observed. These results suggested the antiosteoporotic effect of the combined extract via the increased growth formation together with the suppression of bone resorption. However, further studies concerning chronic toxicity and the underlying mechanism are required. PMID:25478061

Antidiabetic activity of aqueous extract and non polysaccharide fraction of Cynodon dactylon Pers.

PubMed

Jarald, E E; Joshi, S B; Jain, D C

2008-09-01

Petroleum ether (60 degrees-80 degrees C), chloroform, acetone, ethanol, aqueous and crude hot water extracts of the whole plant of C. dactylon and the two fractions of aqueous extract were tested for antihyperglycaemic activity in glucose overloaded hyperglycemic rats and in alloxan induced diabetic model at two-dose levels, 200 and 400 mg/kg (po) respectively. The aqueous extract of C. dactylon and the non polysaccharide fraction of aqueous extract were found to exhibit significant antihyperglycaemic activity and only the non polysaccharide fraction was found to produce hypoglycemia in fasted normal rats. Treatment of diabetic rats with aqueous extract and non polysaccharide fraction of the plant decreased the elevated biochemical parameters, glucose, urea, creatinine, serum cholesterol, serum triglyceride, high density lipoprotein, low density lipoprotein, haemoglobin and glycosylated haemoglobin significantly. Comparatively, the non polysaccharide fraction of aqueous extract was found to be more effective than the aqueous extract.

Surface leakage current in 12.5  μm long-wavelength HgCdTe infrared photodiode arrays.

PubMed

Qiu, Weicheng; Hu, Weida; Lin, Chun; Chen, Xiaoshuang; Lu, Wei

2016-02-15

Long-wavelength (especially >12  μm) focal plane array (FPA) infrared detection is the cutting edge technique for third-generation infrared remote sensing. However, dark currents, which are very sensitive to the growth of small Cd composition HgCdTe, strongly limits the performance of long wavelength HgCdTe photodiode arrays in FPAs. In this Letter, 12.5 μm long-wavelength Hg_1-xCd_xTe (x≈0.219) infrared photodiode arrays are reported. The variable-area and variable-temperature electrical characteristics of the long-wavelength infrared photodiodes are measured. The characteristics of the extracted zero-bias resistance-area product (l/R₀A) varying with the perimeter-to-area (P/A) ratio clearly show that surface leakage current mechanisms severely limit the overall device performance. A sophisticated model has been developed for investigating the leakage current mechanism in the photodiodes. Modeling of temperature-dependent I-V characteristic indicates that the trap-assisted tunneling effect dominates the dark current at 50 K resulting in nonuniformities in the arrays. The extracted trap density, approximately 10¹³-10¹⁴  cm^-3, with an ionized energy of 30 meV is determined by simulation. The work described in this Letter provides the basic mechanisms for a better understanding of the leakage current mechanism for long-wavelength (>12  μm) HgCdTe infrared photodiode arrays.

Estimation of option-implied risk-neutral into real-world density by using calibration function

NASA Astrophysics Data System (ADS)

Bahaludin, Hafizah; Abdullah, Mimi Hafizah

2017-04-01

Option prices contain crucial information that can be used as a reflection of future development of an underlying assets' price. The main objective of this study is to extract the risk-neutral density (RND) and the risk-world density (RWD) of option prices. A volatility function technique is applied by using a fourth order polynomial interpolation to obtain the RNDs. Then, a calibration function is used to convert the RNDs into RWDs. There are two types of calibration function which are parametric and non-parametric calibrations. The density is extracted from the Dow Jones Industrial Average (DJIA) index options with a one month constant maturity from January 2009 until December 2015. The performance of RNDs and RWDs extracted are evaluated by using a density forecasting test. This study found out that the RWDs obtain can provide an accurate information regarding the price of the underlying asset in future compared to that of the RNDs. In addition, empirical evidence suggests that RWDs from a non-parametric calibration has a better accuracy than other densities.

Effects of stream turbine array configuration on tidal current energy extraction near an island

NASA Astrophysics Data System (ADS)

Chen, Yaling; Lin, Binliang; Lin, Jie; Wang, Shujie

2015-04-01

Enhanced tidal currents around islands appear to present the potential for power extraction. In this research, a three-dimensional numerical model is applied to investigate the naturally occurring tidal dynamics and the extractable energy from turbines close to Zhaitang Island, located off the east coast of China. In the model, the effect of tidal turbine is represented by a horizontal thrust and added to the momentum equations. To determine a better configuration of turbine array, a detailed work has been undertaken to investigate the combined influences of the topographic features and array arrangement on the performance of power generation. First, three single row arrays are examined with lateral spacing being 2, 3 and 4 times rotor diameters. Then, corresponding to each lateral spacing, three multi-row arrays in a staggered manner with longitudinal spacing being 5, 10 and 15 times rotor diameters are developed. It has been found that single row arrays with higher local blockage outperform arrays with lower blockage. While for multi-row arrays, the performance of inside turbine is significantly experienced the wake influence of upstream turbines, which can be weakened with an increment of turbine spacing. And a remarkable improvement of turbine performance is observed as the longitudinal spacing increases to 10 times rotor diameters. However, the change pattern of power extraction is mainly dependent on that of naturally kinetic energy when the turbine density is further decreasing in the given region.

Comparative Efficiency of the Fenwick Can and Schuiling Centrifuge in Extracting Nematode Cysts from Different Soil Types

PubMed Central

Bellvert, Joaquim; Crombie, Kieran; Horgan, Finbarr G.

2008-01-01

The Fenwick can and Schuiling centrifuge are widely used to extract nematode cysts from soil samples. The comparative efficiencies of these two methods during cyst extraction have not been determined for different soil types under different cyst densities. Such information is vital for statutory laboratories that must choose a method for routine, high-throughput soil monitoring. In this study, samples of different soil types seeded with varying densities of potato cyst nematode (Globodera rostochiensis) cysts were processed using both methods. In one experiment, with 200 ml samples, recovery was similar between methods. In a second experiment with 500 ml samples, cyst recovery was higher using the Schuiling centrifuge. For each method and soil type, cyst extraction efficiency was similar across all densities tested. Extraction was efficient from pure sand (Fenwick 72%, Schuiling 84%) and naturally sandy soils (Fenwick 62%, Schuiling 73%), but was significantly less efficient from clay-soil (Fenwick 42%, Schuiling 44%) and peat-soil with high organic matter content (Fenwick 35%, Schuiling 33%). Residual moisture (<10% w/w) in samples prior to analyses reduced extraction efficiency, particularly for sand and sandy soils. For each soil type and method, there were significant linear relationships between the number of cysts extracted and the numbers of cysts in the samples. We discuss the advantages and disadvantages of each extraction method for cyst extraction in statutory soil laboratories. PMID:19259516

Improving GLOBALlAND30 Artificial Type Extraction Accuracy in Low-Density Residents

NASA Astrophysics Data System (ADS)

Hou, Lili; Zhu, Ling; Peng, Shu; Xie, Zhenlei; Chen, Xu

2016-06-01

GlobalLand 30 is the first 30m resolution land cover product in the world. It covers the area within 80°N and 80°S. There are ten classes including artificial cover, water bodies, woodland, lawn, bare land, cultivated land, wetland, sea area, shrub and snow,. The TM imagery from Landsat is the main data source of GlobalLand 30. In the artificial surface type, one of the omission error happened on low-density residents' part. In TM images, hash distribution is one of the typical characteristics of the low-density residents, and another one is there are a lot of cultivated lands surrounded the low-density residents. Thus made the low-density residents part being blurred with cultivated land. In order to solve this problem, nighttime light remote sensing image is used as a referenced data, and on the basis of NDBI, we add TM6 to calculate the amount of surface thermal radiation index TR-NDBI (Thermal Radiation Normalized Difference Building Index) to achieve the purpose of extracting low-density residents. The result shows that using TR-NDBI and the nighttime light remote sensing image are a feasible and effective method for extracting low-density residents' areas.

Extraction of space-charge-dominated ion beams from an ECR ion source: Theory and simulation

NASA Astrophysics Data System (ADS)

Alton, G. D.; Bilheux, H.

2004-05-01

Extraction of high quality space-charge-dominated ion beams from plasma ion sources constitutes an optimization problem centered about finding an optimal concave plasma emission boundary that minimizes half-angular divergence for a given charge state, independent of the presence or lack thereof of a magnetic field in the extraction region. The curvature of the emission boundary acts to converge/diverge the low velocity beam during extraction. Beams of highest quality are extracted whenever the half-angular divergence, ω, is minimized. Under minimum half-angular divergence conditions, the plasma emission boundary has an optimum curvature and the perveance, P, current density, j+ext, and extraction gap, d, have optimum values for a given charge state, q. Optimum values for each of the independent variables (P, j+ext and d) are found to be in close agreement with those derived from elementary analytical theory for extraction with a simple two-electrode extraction system, independent of the presence of a magnetic field. The magnetic field only increases the emittances of beams through additional aberrational effects caused by increased angular divergences through coupling of the longitudinal to the transverse velocity components of particles as they pass though the mirror region of the electron cyclotron resonance (ECR) ion source. This article reviews the underlying theory of elementary extraction optics and presents results derived from simulation studies of extraction of space-charge dominated heavy-ion beams of varying mass, charge state, and intensity from an ECR ion source with emphasis on magnetic field induced effects.

Charge relaxation and dynamics in organic semiconductors

NASA Astrophysics Data System (ADS)

Kwok, H. L.

2006-08-01

Charge relaxation in dispersive materials is often described in terms of the stretched exponential function (Kohlrausch law). The process can be explained using a "hopping" model which in principle, also applies to charge transport such as current conduction. This work analyzed reported transient photoconductivity data on functionalized pentacene single crystals using a geometric hopping model developed by B. Sturman et al and extracted values (or range of values) on the materials parameters relevant to charge relaxation as well as charge transport. Using the correlated disorder model (CDM), we estimated values of the carrier mobility for the pentacene samples. From these results, we observed the following: i) the transport site density appeared to be of the same order of magnitude as the carrier density; ii) it was possible to extract lower bound values on the materials parameters linked to the transport process; and iii) by matching the simulated charge decay to the transient photoconductivity data, we were able to refine estimates on the materials parameters. The data also allowed us to simulate the stretched exponential decay. Our observations suggested that the stretching index and the carrier mobility were related. Physically, such interdependence would allow one to demarcate between localized molecular interactions and distant coulomb interactions.

Dental panoramic image analysis for enhancement biomarker of mandibular condyle for osteoporosis early detection

NASA Astrophysics Data System (ADS)

Suprijanto; Azhari; Juliastuti, E.; Septyvergy, A.; Setyagar, N. P. P.

2016-03-01

Osteoporosis is a degenerative disease characterized by low Bone Mineral Density (BMD). Currently, a BMD level is determined by Dual Energy X-ray Absorptiometry (DXA) at the lumbar vertebrae and femur. Previous studies reported that dental panoramic radiography image has potential information for early osteoporosis detection. This work reported alternative scheme, that consists of the determination of the Region of Interest (ROI) the condyle mandibular in the image as biomarker and feature extraction from ROI and classification of bone conditions. The minimum value of intensity in the cavity area is used to compensate an offset on the ROI. For feature extraction, the fraction of intensity values in the ROI that represent high bone density and the ROI total area is perfomed. The classification will be evaluated from the ability of each feature and its combinations for the BMD detection in 2 classes (normal and abnormal), with the artificial neural network method. The evaluation system used 105 panoramic image data from menopause women which consist of 36 training data and 69 test data that were divided into 2 classes. The 2 classes of classification obtained 88.0% accuracy rate and 88.0% sensitivity rate.

Cumulative Industrial Activity Alters Lotic Fish Assemblages in Two Boreal Forest Watersheds of Alberta, Canada

NASA Astrophysics Data System (ADS)

Scrimgeour, Garry J.; Hvenegaard, Paul J.; Tchir, John

2008-12-01

We evaluated the cumulative effects of land use disturbance resulting from forest harvesting, and exploration and extraction of oil and gas resources on the occurrence and structure of stream fish assemblages in the Kakwa and Simonette watersheds in Alberta, Canada. Logistic regression models showed that the occurrence of numerically dominant species in both watersheds was related to two metrics defining industrial activity (i.e., percent disturbance and road density), in addition to stream wetted width, elevation, reach slope, and percent fines. Occurrences of bull trout, slimy sculpin, and white sucker were negatively related to percent disturbance and that of Arctic grayling, and mountain whitefish were positively related to percent disturbance and road density. Assessments of individual sites showed that 76% of the 74 and 46 test sites in the Kakwa and Simonette watersheds were possibly impaired or impaired. Impaired sites in the Kakwa Watershed supported lower densities of bull trout, mountain whitefish, and rainbow trout, but higher densities of Arctic grayling compared to appropriate reference sites. Impaired sites in the Simonette Watershed supported lower densities of bull trout, but higher densities of lake chub compared to reference sites. Our data suggest that current levels of land use disturbance alters the occurrence and structure of stream fish assemblages.

Effect of acoustic frequency and power density on the aqueous ultrasonic-assisted extraction of grape pomace (Vitis vinifera L.) - a response surface approach.

PubMed

González-Centeno, María Reyes; Knoerzer, Kai; Sabarez, Henry; Simal, Susana; Rosselló, Carmen; Femenia, Antoni

2014-11-01

Aqueous ultrasound-assisted extraction (UAE) of grape pomace was investigated by Response Surface Methodology (RSM) to evaluate the effect of acoustic frequency (40, 80, 120kHz), ultrasonic power density (50, 100, 150W/L) and extraction time (5, 15, 25min) on total phenolics, total flavonols and antioxidant capacity. All the process variables showed a significant effect on the aqueous UAE of grape pomace (p<0.05). The Box-Behnken Design (BBD) generated satisfactory mathematical models which accurately explain the behavior of the system; allowing to predict both the extraction yield of phenolic and flavonol compounds, and also the antioxidant capacity of the grape pomace extracts. The optimal UAE conditions for all response factors were a frequency of 40kHz, a power density of 150W/L and 25min of extraction time. Under these conditions, the aqueous UAE would achieve a maximum of 32.31mg GA/100g fw for total phenolics and 2.04mg quercetin/100g fw for total flavonols. Regarding the antioxidant capacity, the maximum predicted values were 53.47 and 43.66mg Trolox/100g fw for CUPRAC and FRAP assays, respectively. When comparing with organic UAE, in the present research, from 12% to 38% of total phenolic bibliographic values were obtained, but using only water as the extraction solvent, and applying lower temperatures and shorter extraction times. To the best of the authors' knowledge, no studies specifically addressing the optimization of both acoustic frequency and power density during aqueous-UAE of plant materials have been previously published. Copyright © 2014 Elsevier B.V. All rights reserved.

Spatiotemporal neural dynamics of moral judgment: A high-density ERP study

PubMed Central

Yoder, Keith J.

2014-01-01

Morality is a pervasive aspect of human nature across all cultures, and neuroscience investigations are necessary for identifying what computational mechanisms underpin moral cognition. The current study used high-density ERPs to examine how moral evaluations are mediated by automatic and controlled processes as well as how quickly information and causal-intentional representations can be extracted when viewing morally laden behavior. The study also explored the extent to which individual dispositions in affective and cognitive empathy as well as justice sensitivity influence the encoding of moral valence when healthy participants make moral judgments about prosocial (interpersonal assistance) and antisocial (interpersonal harm) actions. Moral judgment differences were reflected in differential amplitudes for components associated with cognitive appraisal (LPP) as well as early components associated with emotional salience (N1 and N2). Moreover, source estimation was performed to indicate potential neural generators. A posterior-to-anterior shift was observed, with current density peaks first in right inferior parietal cortex (at the temporoparietal junction), then later in medial prefrontal cortex. Cognitive empathy scores predicted behavioral ratings of blame as well as differential amplitudes in LPP and component activity at posterior sites. Overall, this study offers important insights into the temporal unfolding of moral evaluations, including when in time individual differences in empathy influence neural encoding of moral valence. PMID:24905282

High density FTA plates serve as efficient long-term sample storage for HLA genotyping.

PubMed

Lange, V; Arndt, K; Schwarzelt, C; Boehme, I; Giani, A S; Schmidt, A H; Ehninger, G; Wassmuth, R

2014-02-01

Storage of dried blood spots (DBS) on high-density FTA(®) plates could constitute an appealing alternative to frozen storage. However, it remains controversial whether DBS are suitable for high-resolution sequencing of human leukocyte antigen (HLA) alleles. Therefore, we extracted DNA from DBS that had been stored for up to 4 years, using six different methods. We identified those extraction methods that recovered sufficient high-quality DNA for reliable high-resolution HLA sequencing. Further, we confirmed that frozen whole blood samples that had been stored for several years can be transferred to filter paper without compromising HLA genotyping upon extraction. Concluding, DNA derived from high-density FTA(®) plates is suitable for high-resolution HLA sequencing, provided that appropriate extraction protocols are employed. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Accurate description of charge transport in organic field effect transistors using an experimentally extracted density of states

NASA Astrophysics Data System (ADS)

Roelofs, W. S. C.; Mathijssen, S. G. J.; Janssen, R. A. J.; de Leeuw, D. M.; Kemerink, M.

2012-02-01

The width and shape of the density of states (DOS) are key parameters to describe the charge transport of organic semiconductors. Here we extract the DOS using scanning Kelvin probe microscopy on a self-assembled monolayer field effect transistor (SAMFET). The semiconductor is only a single monolayer which has allowed extraction of the DOS over a wide energy range, pushing the methodology to its fundamental limit. The measured DOS consists of an exponential distribution of deep states with additional localized states on top. The charge transport has been calculated in a generic variable range-hopping model that allows any DOS as input. We show that with the experimentally extracted DOS an excellent agreement between measured and calculated transfer curves is obtained. This shows that detailed knowledge of the density of states is a prerequisite to consistently describe the transfer characteristics of organic field effect transistors.

Nitridation-driven conductive Li4Ti5O12 for lithium ion batteries.

PubMed

Park, Kyu-Sung; Benayad, Anass; Kang, Dae-Joon; Doo, Seok-Gwang

2008-11-12

To modify oxide structure and introduce a thin conductive film on Li4Ti5O12, thermal nitridation was adopted for the first time. NH3 decomposes surface Li4Ti5O12 to conductive TiN at high temperature, and surprisingly, it also modifies the surface structure in a way to accommodate the single phase Li insertion and extraction. The electrochemically induced Li4+deltaTi5O12 with a TiN coating layer shows great electrochemical properties at high current densities.

Study on Locally Confined Deposition of Si Nanocrystals in High-Aspect-Ratio Si Nano-Pillar Array for Nano-Electronic and Nano-Photonic Applications

DTIC Science & Technology

2010-02-23

reflection, thus increasing the quantum efficiency by one order of magnitude and improving the light extraction from the nano-roughened device surface by...respectively. At a biased current of 400 A, the highest external quantum efficiency is over 0.2% to obtain the maximum EL power of >1 W. In...processing techniques for improving the internal and external quantum efficiencies of Si MOSLEDs via detuning the size and density of high-aspect-ratio Si

A neutral lithium beam source

NASA Astrophysics Data System (ADS)

Zhang, XiaoDong; Wang, ZhengMin; Hu, LiQun

1994-04-01

A low energy neutral lithium beam source with energy about 6 keV and a neutral beam equivalent current of 20 μA/cm2 has been developed in ASIPP in order to measure the density gradient and the fluctuations in the edge plasma of the HT-6M tokamak. In the source, lithium ions are extracted from a solid emitter (β-eucryptite), focused in a two-tube immersion lens, and neutralized in a charge-exchange cell with sodium. This source operates in pulsed mode. The pulse length is adjustable from 10 to 100 ms.

Direct estimations of linear and nonlinear functionals of a quantum state.

PubMed

Ekert, Artur K; Alves, Carolina Moura; Oi, Daniel K L; Horodecki, Michał; Horodecki, Paweł; Kwek, L C

2002-05-27

We present a simple quantum network, based on the controlled-SWAP gate, that can extract certain properties of quantum states without recourse to quantum tomography. It can be used as a basic building block for direct quantum estimations of both linear and nonlinear functionals of any density operator. The network has many potential applications ranging from purity tests and eigenvalue estimations to direct characterization of some properties of quantum channels. Experimental realizations of the proposed network are within the reach of quantum technology that is currently being developed.

Joint measurement of lensing-galaxy correlations using SPT and DES SV data

DOE PAGES

Baxter, E. J.

2016-07-04

We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimeter-wave data from the 2500 square degree South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. The two lensing-galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy lensing measurements. We show that an attractive feature of these fits is that they are fairly insensitive to the clustering bias of the galaxies used as matter tracers. The measurement presented in this work confirms that DES and SPT data are consistent with each other and with the currently favoredmore » $$\\Lambda$$CDM cosmological model. In conclusion, it also demonstrates that joint lensing-galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.« less

An enhanced mangiferaindica for dye sensitized solar cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uno, U. E., E-mail: moses.emetere@covenantuniversity.edu.ng; Emetere, M. E., E-mail: uno-essang@yahoo.co.uk; Fadipe, L. A.

Titanium dioxide (T1O2) is preferred to Zinc oxide as mesoporous oxide layer because it raised the efficiency of DSSCs from 1% to 7%. The chemistry of the process however seem rigorous to allow the light induced electron injection from the adsorbed dye into the nanocrystallites i.e. which renders the TiO{sub 2} conductive. The DSSC fabricated consist of 2.25 cm{sup 2} active area of titanium dioxide coated on FTO glass (fluorine tin oxide) immersed in ethanol solution of natural dye extracted as an anode (electrode) and counter electrode. These two electrodes were coupled together and the space between them was filledmore » with the Iodolyte AN-50 as solid electrolyte or redox mediator. The photo electrochemical parameters of the dye extracted (Mango fruit Peel) from the results obtained are short circuit current (Isc)= 1.22×10{sup −2}, current density (Jsc)=4.07×10{sup −2}, open circuit voltage (voc) =0.53V, fill factor (FF) of 0.16 and the overall conversion efficiency (Eff) =0.345%.« less

Joint measurement of lensing-galaxy correlations using SPT and DES SV data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baxter, E. J.

We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimeter-wave data from the 2500 square degree South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. The two lensing-galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy lensing measurements. We show that an attractive feature of these fits is that they are fairly insensitive to the clustering bias of the galaxies used as matter tracers. The measurement presented in this work confirms that DES and SPT data are consistent with each other and with the currently favoredmore » $$\\Lambda$$CDM cosmological model. In conclusion, it also demonstrates that joint lensing-galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.« less

Joint measurement of lensing–galaxy correlations using SPT and DES SV data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baxter, E.; Clampitt, J.; Giannantonio, T.

We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimetre-wave data from the 2500 sq. deg. South Pole Telescope Sunyaev–Zel'dovich (SPT-SZ) survey. The two lensing–galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy-lensing measurements. We show that an attractive feature of these fits is that they are fairlymore » insensitive to the clustering bias of the galaxies used as matter tracers. The measurement presented in this work confirms that DES and SPT data are consistent with each other and with the currently favoured Λ cold dark matter cosmological model. It also demonstrates that joint lensing–galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.« less

Analysis of high field effects on the steady-state current-voltage response of semi-insulating 4H-SiC for photoconductive switch applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiskumara, R.; Joshi, R. P., E-mail: ravi.joshi@ttu.edu; Mauch, D.

A model-based analysis of the steady-state, current-voltage response of semi-insulating 4H-SiC is carried out to probe the internal mechanisms, focusing on electric field driven effects. Relevant physical processes, such as multiple defects, repulsive potential barriers to electron trapping, band-to-trap impact ionization, and field-dependent detrapping, are comprehensively included. Results of our model match the available experimental data fairly well over orders of magnitude variation in the current density. A number of important parameters are also extracted in the process through comparisons with available data. Finally, based on our analysis, the possible presence of holes in the samples can be discounted upmore » to applied fields as high as ∼275 kV/cm.« less

High Performance Microbial Fuel Cells and Supercapacitors Using Micro-Electro-Mechanical System (MEMS) Technology

NASA Astrophysics Data System (ADS)

Ren, Hao

A Microbial fuel cell (MFC) is a bio-inspired carbon-neutral, renewable electrochemical converter to extract electricity from catabolic reaction of micro-organisms. It is a promising technology capable of directly converting the abundant biomass on the planet into electricity and potentially alleviate the emerging global warming and energy crisis. The current and power density of MFCs are low compared with conventional energy conversion techniques. Since its debut in 2002, many studies have been performed by adopting a variety of new configurations and structures to improve the power density. The reported maximum areal and volumetric power densities range from 19 mW/m2 to 1.57 W/m2 and from 6.3 W/m3 to 392 W/m 3, respectively, which are still low compared with conventional energy conversion techniques. In this dissertation, the impact of scaling effect on the performance of MFCs are investigated, and it is found that by scaling down the characteristic length of MFCs, the surface area to volume ratio increases and the current and power density improves. As a result, a miniaturized MFC fabricated by Micro-Electro-Mechanical System (MEMS) technology with gold anode is presented in this dissertation, which demonstrate a high power density of 3300 W/m3. The performance of the MEMS MFC is further improved by adopting anodes with higher surface area to volume ratio, such as carbon nanotube (CNT) and graphene based anodes, and the maximum power density is further improved to a record high power density of 11220 W/m3. A novel supercapacitor by regulating the respiration of the bacteria is also presented, and a high power density of 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked, which are one to two orders of magnitude higher than any previously reported microbial electrochemical techniques.

Plasma research in electric propulsion at Colorado State University

NASA Technical Reports Server (NTRS)

Wilbur, P. J.; Kaufman, H. R.

1976-01-01

The effect of electron bombardment ion thruster magnetic field configurations on the uniformity of the plasma density and the ion beam current density are discussed. The optimum configuration is a right circular cylinder which has significant fields at its outer radii and one end but is nearly field free within the cylinder and at the extraction grid end. The production and loss of the doubly charged ions which effect sputtering damage within thrusters are modeled and the model is verified for the mercury propellant case. Electron bombardment of singly charged ions is found to be the dominant double ion production mechanism. The low density plasma (approx. one million elec/cubic centimeter which exists in the region outside of the beam of thrust producing ions which are drawn from the discharge chamber is discussed. This plasma is modeled by assuming the ions contained in it are generated by a charge exchange process in the ion beam itself. The theoretical predictions of this model are shown to agree with experimental measurements.

Improvements of the versatile multiaperture negative ion source NIO1

NASA Astrophysics Data System (ADS)

Cavenago, M.; Serianni, G.; De Muri, M.; Veltri, P.; Antoni, V.; Baltador, C.; Barbisan, M.; Brombin, M.; Galatá, A.; Ippolito, N.; Kulevoy, T.; Pasqualotto, R.; Petrenko, S.; Pimazzoni, A.; Recchia, M.; Sartori, E.; Taccogna, F.; Variale, V.; Zaniol, B.; Barbato, P.; Baseggio, L.; Cervaro, V.; Fasolo, D.; Franchin, L.; Ghiraldelli, R.; Laterza, B.; Maniero, M.; Martini, D.; Migliorato, L.; Minarello, A.; Molon, F.; Moro, G.; Patton, T.; Ravarotto, D.; Rizzieri, R.; Rizzolo, A.; Sattin, M.; Stivanello, F.; Zucchetti, S.

2017-08-01

The ion source NIO1 (Negative Ion Optimization 1) was developed and installed as a reduced-size model of multi-aperture sources used in neutral beam injectors. NIO1 beam optics is optimized for a 135 mA H- current (subdivided in 9 beamlets) at a Vs = 60 kV extraction voltage, with an electron-to-ion current ratio Rj up to 2. Depending on gas pressure used, NIO1 was up to now operated with Vs < 25 kV for beam extraction and Vs = 60 kV for insulation tests. The distinction between capacitively coupled plasma (E-mode, consistent with a low electron density plasma ne) and inductively coupled plasma (H-mode, requiring larger ne) was clearly related to several experimental signatures, and was confirmed for several gases, when applied radiofrequency power exceeds a given threshold Pt (with hysteresis). For hydrogen Pt was reduced below 1 kW, with a clean rf window and molybdenum liners on other walls; for oxygen Pt ≤ 400 W. Beams of H- and O- were separately extracted; since no caesium is yet introduced into the source, the expected ion currents are lower than 5 mA; this requires a lower acceleration voltage Vs (to keep the same perveance). NIO1 caesium oven was separately tested and Cs dispensers are in development. Increasing the current in the magnetic filter circuit, modifying its shape, and increasing the bias voltage were helpful to reduce Rj (still very large up to now, about 150 for oxygen, and 40 for hydrogen), in qualitative agreement with theoretical and numerical models. A second bias voltage was tested for hydrogen. Beam footprints and a spectral emission sample are shown.

Application of texture analysis method for mammogram density classification

NASA Astrophysics Data System (ADS)

Nithya, R.; Santhi, B.

2017-07-01

Mammographic density is considered a major risk factor for developing breast cancer. This paper proposes an automated approach to classify breast tissue types in digital mammogram. The main objective of the proposed Computer-Aided Diagnosis (CAD) system is to investigate various feature extraction methods and classifiers to improve the diagnostic accuracy in mammogram density classification. Texture analysis methods are used to extract the features from the mammogram. Texture features are extracted by using histogram, Gray Level Co-Occurrence Matrix (GLCM), Gray Level Run Length Matrix (GLRLM), Gray Level Difference Matrix (GLDM), Local Binary Pattern (LBP), Entropy, Discrete Wavelet Transform (DWT), Wavelet Packet Transform (WPT), Gabor transform and trace transform. These extracted features are selected using Analysis of Variance (ANOVA). The features selected by ANOVA are fed into the classifiers to characterize the mammogram into two-class (fatty/dense) and three-class (fatty/glandular/dense) breast density classification. This work has been carried out by using the mini-Mammographic Image Analysis Society (MIAS) database. Five classifiers are employed namely, Artificial Neural Network (ANN), Linear Discriminant Analysis (LDA), Naive Bayes (NB), K-Nearest Neighbor (KNN), and Support Vector Machine (SVM). Experimental results show that ANN provides better performance than LDA, NB, KNN and SVM classifiers. The proposed methodology has achieved 97.5% accuracy for three-class and 99.37% for two-class density classification.

Supercritical fluid extraction as a means of reducing the carbon contamination inherent in samples of silica aerogel destined for the capture of CHON cosmic dust particles in space

NASA Astrophysics Data System (ADS)

Huang, H.-P.; Wright, I. P.; Gilmour, I.; Pillinger, C. T.

1994-11-01

Silica aerogel represents an ideal material for use as a cosmic dust capture medium. Its low density enables impacting particles to decelerate and stop within a small quality of the material, but without any severe heating. Hence the particles, which remain unmelted, can subsequently be removed and studied. Since a large proportion of the prospective cosmic dust is likely to be enriched in elements such as carbon and hydrogen (typically 5 wt% C, 20 wt% H2O), it is imperative that the aerogel used in the capture cell contains minimal quantities of these elements. Unfortunately the lowest density aerogels contain carbon at levels of 5 wt%; water is present in even greater amounts. Thus, techniques need to be identified to remove these contaminants. Herein, an attempt is made to use supercritical fluid extraction to remove carbon (and water). The investigation was tried to identify the most suitable parameters (i.e. CO2 density, solvating power using single or multiple extractions, use of modifier, etc.) necessary for removal of contaminants. A set of conditions was derived which was able to remove 90% of carbon contaminants from an aerogel of 0.12 g/cu cm density. This involved the use of multiple extractions with gradient temperatures (i.e. variable CO2 density), but without the use of a methanol modifier. Unfortunately, the same technique was less efficacious at removing carbon from aerogels with densities less than 0.12 g/cu cm. At present the extraction procedure has only been tried on a laboratory scale, but clearly this could be scaled-up in the future.

An experimental evaluation of the anti-atherogenic potential of the plant, Piper betle, and its active constitutent, eugenol, in rats fed an atherogenic diet.

PubMed

Venkadeswaran, Karuppasamy; Thomas, Philip A; Geraldine, Pitchairaj

2016-05-01

Hypercholesterolemia is a major risk factor for systemic atherosclerosis and subsequent cardiovascular disease. Lipoperoxidation-mediated oxidative damage is believed to contribute strongly to the progression of atherogenesis. In the current investigation, putative anti-atherogenic and antioxidative properties of an ethanolic extract of Piper betle and of its active constituent, eugenol, were sought in an experimental animal model of chronic hypercholesterolemia. Atherogenic diet-fed rats that received either Piper betle extract orally (500mg/kg b.wt) or eugenol orally (5mg/kg b.wt) for 15days (commencing 30days after the atherogenic diet had been started) exhibited the following variations in different parameters, when compared to atherogenic diet-fed rats that received only saline: (1) significantly lower mean levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol and very low density lipoprotein cholesterol in both serum and hepatic tissue samples; (2) lower mean serum levels of aspartate amino-transferase, alanine amino-transferase, alkaline phosphatase, lactate dehydrogenase and lipid-metabolizing enzymes (lipoprotein lipase, 3-hydroxy-3-methyl-glutaryl-CoA reductase; (3) significantly lower mean levels of enzymatic antioxidants (catalase, superoxide dismutase, glutathione peroxidase, glutathione-S-transferase) and non-enzymatic antioxidants (reduced glutathione, vitamin C and vitamin E) and significantly higher mean levels of malondialdehyde in haemolysate and hepatic tissue samples. Histopathological findings suggested a protective effect of the Piper betle extract and a more pronounced protective effect of eugenol on the hepatic and aortic tissues of atherogenic diet-fed (presumed atherosclerotic) rats. These results strongly suggest that the Piper betle extract and its active constituent, eugenol, exhibit anti-atherogenic effects which may be due to their anti-oxidative properties. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Effect of direct current sputtering power on the behavior of amorphous indium-gallium-zinc-oxide thin-film transistors under negative bias illumination stress: A combination of experimental analyses and device simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Jun Tae; Kim, Dong Myong; Choi, Sung-Jin

The effect of direct current sputtering power of indium-gallium-zinc-oxide (IGZO) on the performance and stability of the corresponding thin-film transistor devices was studied. The field effect mobility increases as the IGZO sputter power increases, at the expense of device reliability under negative bias illumination stress (NBIS). Device simulation based on the extracted sub-gap density of states indicates that the field effect mobility is improved as a result of the number of acceptor-like states decreasing. The degradation by NBIS is suggested to be induced by the formation of peroxides in IGZO rather than charge trapping.

Development of a compact, rf-driven, pulsed ion source for neutron generation

NASA Astrophysics Data System (ADS)

Perkins, L. T.; Celata, C.; Lee, Y.; Leung, K. N.; Picard, D. S.; Vilaithong, R.; Williams, M. D.; Wutte, D.

1997-02-01

Lawrence Berkeley National Laboratory is currently developing a compact, sealed-accelerator-tube neutron generator capable of producing a neutron flux in the range of 109 to 1010 D-T neutrons per second. The ion source, a miniaturized variation of earlier radio-frequency (rf)-driven multicusp ion sources, is designed to fit within a ˜5 cm diameter borehole. Typical operating parameters include repetition rates up to 100 pps, with pulse widths between 10 and 80 μs (limited only by the available rf power supply) and source pressures as low as ˜5 mTorr. In this configuration, peak extractable hydrogen current densities exceeding 1180 mA/cm2 with H1+ yields over 94% having been achieved.

Tomographic diagnostic of the hydrogen beam from a negative ion source

NASA Astrophysics Data System (ADS)

Agostini, M.; Brombin, M.; Serianni, G.; Pasqualotto, R.

2011-10-01

In this paper the tomographic diagnostic developed to characterize the 2D density distribution of a particle beam from a negative ion source is described. In particular, the reliability of this diagnostic has been tested by considering the geometry of the source for the production of ions of deuterium extracted from an rf plasma (SPIDER). SPIDER is a low energy prototype negative ion source for the international thermonuclear experimental reactor (ITER) neutral beam injector, aimed at demonstrating the capability to create and extract a current of D- (H-) ions up to 50 A (60 A) accelerated at 100 kV. The ions are extracted over a wide surface (1.52×0.56m2) with a uniform plasma density which is prescribed to remain within 10% of the mean value. The main target of the tomographic diagnostic is the measurement of the beam uniformity with sufficient spatial resolution and of its evolution throughout the pulse duration. To reach this target, a tomographic algorithm based on the simultaneous algebraic reconstruction technique is developed and the geometry of the lines of sight is optimized so as to cover the whole area of the beam. Phantoms that reproduce different experimental beam configurations are simulated and reconstructed, and the role of the noise in the signals is studied. The simulated phantoms are correctly reconstructed and their two-dimensional spatial nonuniformity is correctly estimated, up to a noise level of 10% with respect to the signal.

Effects of the Particulate Matter₂.₅ (PM₂.₅) on Lipoprotein Metabolism, Uptake and Degradation, and Embryo Toxicity.

PubMed

Kim, Jae-Yong; Lee, Eun-Young; Choi, Inho; Kim, Jihoe; Cho, Kyung-Hyun

2015-12-01

Particulate matter2.5 (PM2.5) is notorious for its strong toxic effects on the cardiovascular, skin, nervous, and reproduction systems. However, the molecular mechanism by which PM2.5 aggravates disease progression is poorly understood, especially in a water-soluble state. In the current study, we investigated the putative physiological effects of aqueous PM2.5 solution on lipoprotein metabolism. Collected PM2.5 from Seoul, Korea was dissolved in water, and the water extract (final 3 and 30 ppm) was treated to human serum lipoproteins, macrophages, and dermal cells. PM2.5 extract resulted in degradation and aggregation of high-density lipoprotein (HDL) as well as low-density lipoprotein (LDL); apoA-I in HDL aggregated and apo-B in LDL disappeared. PM2.5 treatment (final 30 ppm) also induced cellular uptake of oxidized LDL (oxLDL) into macrophages, especially in the presence of fructose (final 50 mM). Uptake of oxLDL along with production of reactive oxygen species was accelerated by PM2.5 solution in a dose-dependent manner. Further, PM2.5 solution caused cellular senescence in human dermal fibroblast cells. Microinjection of PM2.5 solution into zebrafish embryos induced severe mortality accompanied by impairment of skeletal development. In conclusion, water extract of PM2.5 induced oxidative stress as a precursor to cardiovascular toxicity, skin cell senescence, and embryonic toxicity via aggregation and proteolytic degradation of serum lipoproteins.

Effects of the Particulate Matter2.5 (PM2.5) on Lipoprotein Metabolism, Uptake and Degradation, and Embryo Toxicity

PubMed Central

Kim, Jae-Yong; Lee, Eun-Young; Choi, Inho; Kim, Jihoe; Cho, Kyung-Hyun

2015-01-01

Particulate matter2.5 (PM2.5) is notorious for its strong toxic effects on the cardiovascular, skin, nervous, and reproduction systems. However, the molecular mechanism by which PM2.5 aggravates disease progression is poorly understood, especially in a water-soluble state. In the current study, we investigated the putative physiological effects of aqueous PM2.5 solution on lipoprotein metabolism. Collected PM2.5 from Seoul, Korea was dissolved in water, and the water extract (final 3 and 30 ppm) was treated to human serum lipoproteins, macrophages, and dermal cells. PM2.5 extract resulted in degradation and aggregation of high-density lipoprotein (HDL) as well as low-density lipoprotein (LDL); apoA-I in HDL aggregated and apo-B in LDL disappeared. PM2.5 treatment (final 30 ppm) also induced cellular uptake of oxidized LDL (oxLDL) into macrophages, especially in the presence of fructose (final 50 mM). Uptake of oxLDL along with production of reactive oxygen species was accelerated by PM2.5 solution in a dose-dependent manner. Further, PM2.5 solution caused cellular senescence in human dermal fibroblast cells. Microinjection of PM2.5 solution into zebrafish embryos induced severe mortality accompanied by impairment of skeletal development. In conclusion, water extract of PM2.5 induced oxidative stress as a precursor to cardiovascular toxicity, skin cell senescence, and embryonic toxicity via aggregation and proteolytic degradation of serum lipoproteins. PMID:26615830

Antidiabetic Effect of Hydroalcholic Urtica dioica Leaf Extract in Male Rats with Fructose-Induced Insulin Resistance

PubMed Central

Ahangarpour, Akram; Mohammadian, Maryam; Dianat, Mahin

2012-01-01

Background: Urtica dioica has been used as antihypertensive, antihyperlipidemic and antidiabetic herbal medicine. The purpose of this study was to study the effect of hydroalcoholic extract of Urtica dioica on fructose-induced insulin resistance rats. Methods: Forty male Wistar rats were randomly divided into five groups including control, fructose, extract 50, extract 100 and extract 200. The control rat received vehicle, the fructose and extract groups received fructose 10% for eight weeks. The extract groups received single daily injection of vehicle, 50, 100 or 200 mg/kg/day for the two weeks. Blood glucose, insulin, last fasting insulin resistance index (FIRI), serum triglyceride (TG), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), high-density lipoprotein (HDL), alanin trasaminase (AST) and alkaline phosphatase (ALP), leptin and LDL/HDL ratio were determined. Results: Compared to control group, daily administration of fructose was associated with significant increase in FIRI, blood glucose and insulin, significant decrease in lepin, and no significant change in TG, HDL, LDL, LDL/HDL ratio, VLDL, ALT, and ALP. The extract significantly decreased serum glucose, insulin, LDL and leptin, and LDL/HDL ratio and FIRI. It also significantly increased serum TG, VLDL, and AST, but did not change serum ALP. Conclusion: We suggest that Urtica dioica extract, by decreasing serum glucose, and FIRI, may be useful to improve type 2 diabetes mellitus. Also, by positive effect on lipid profile and by decreasing effect on leptin, it may improve metabolic syndrome. PMID:23115450

Development of a multi-space constrained density functional theory approach and its application to graphene-based vertical transistors

NASA Astrophysics Data System (ADS)

Kim, Han Seul; Kim, Yong-Hoon

We have been developing a multi-space-constrained density functional theory approach for the first-principles calculations of nano-scale junctions subjected to non-equilibrium conditions and charge transport through them. In this presentation, we apply the method to vertically-stacked graphene/hexagonal boron nitride (hBN)/graphene Van der Waals heterostructures in the context of tunneling transistor applications. Bias-dependent changes in energy level alignment, wavefunction hybridization, and current are extracted. In particular, we compare quantum transport properties of single-layer (graphene) and infinite (graphite) electrode limits on the same ground, which is not possible within the traditional non-equilibrium Green function formalism. The effects of point defects within hBN on the current-voltage characteristics will be also discussed. Global Frontier Program (2013M3A6B1078881), Nano-Material Technology Development Programs (2016M3A7B4024133, 2016M3A7B4909944, and 2012M3A7B4049888), and Pioneer Program (2016M3C1A3906149) of the National Research Foundation.

A 5 x 40 cm rectangular-beam multipole ion source

NASA Technical Reports Server (NTRS)

Robinson, R. S.; Kaufman, H. R.; Haynes, C. M.

1981-01-01

A rectangular ion source particularly suited for the continuous sputter processing of materials over a wide area is discussed. A multipole magnetic field configuration was used to design an ion source with a 5 x 40 cm beam area, while a three-grid ion optics system was used to maximize ion current density at the design ion energy of 500 eV. An average extracted current density of about 4 mA/sq cm could be obtained from 500 eV Ar ions. The difference between the experimental performance and the design value of 6 mA/sq cm is attributed to grid misalignment due to thermal expansion. The discharge losses at typical operating conditions ranged from about 600 to 1000 eV/ion, in reasonable agreement with the design value of 800 eV/ion. The use of multiple rectangular-beam ion sources to process wider areas than would be possible with a single source was also studied, and the most uniform coverage was found to be obtainable with a 0 to 2 cm overlap.

Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

NASA Technical Reports Server (NTRS)

Toda, Risaku; Bronikowski, Michael; Luong, Edward; Manohara, Harish

2008-01-01

A continuing effort to develop carbon-nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime a concept that was discussed in more detail in Arrays of Bundles of Carbon Nanotubes as Field Emitters (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located, such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

Using Two-Proton Transfer to Study H and He Burning Reactions of Type-1 X-Ray Bursts

NASA Astrophysics Data System (ADS)

Soltesz, Douglas; Massey, Thomas N.; Voinov, Alexander; Meisel, Zach

2017-09-01

The reaction rate of the 59Cu(p,γ)60Zn has been identified to have a significant impact on the light curve of X-ray bursts, controlling the reaction flow out of the Ni-Cu cycle impacting the late-time light curve. Using two proton transfer, 58Ni(3He,n)60Zn can be used to study the 59Cu(p,γ)60Zn reaction. We are currently using the neutron evaporation spectrum from 58Ni(3He,n)60Zn in order to extract the level density of 60Zn and constrain 59Cu(p,γ)60Zn. To augment the (3He,n) technique for lower level-density compound nuclides, a silicon detector array is currently being developed for use in determining charged-particle decay branching ratios from discrete states. The present status of data analysis and detector development will be discussed, as well as future plans. This work was supported in part by the U.S. DOE through Grant No. DE-FG02-88ER40387.

Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, X. P.; Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024; Zhang, Z. C.

High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, takingmore » into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200–300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.« less

Solvent selection in ultrasonic-assisted emulsification microextraction: Comparison between high- and low-density solvents by means of novel type of extraction vessel.

PubMed

Nojavan, Saeed; Gorji, Tayebeh; Davarani, Saied Saeed Hosseiny; Morteza-Najarian, Amin

2014-08-01

There are numerous published reports about dispersive liquid phase microextraction of the wide range of substances, however, till now no broadly accepted systematic and purpose oriented selection of extraction solvent has been proposed. Most works deal with the optimization of available solvents without adequate pre-consideration of properness. In this study, it is tried to compare the performances of low- and high-density solvents at the same conditions by means of novel type of extraction vessel with head and bottom conical shape. Extraction efficiencies of seven basic pharmaceutical compounds using eighteen common organic solvents were studied in this work. It was much easier to work with high-density solvents and they mostly showed better performances. This work shows that although exact predicting the performance of the solvents is multifaceted case but the pre-consideration of initial selection of solvents with attention to the physiochemical properties of the desired analytes is feasible and promising. Finally, the practicality of the method for extraction from urine and plasma samples was investigated. Copyright © 2014 Elsevier B.V. All rights reserved.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

PubMed Central

Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Peng, Junbiao

2018-01-01

A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously. PMID:29534492

Extracting a mix parameter from 2D radiography of variable density flow

NASA Astrophysics Data System (ADS)

Kurien, Susan; Doss, Forrest; Livescu, Daniel

2017-11-01

A methodology is presented for extracting quantities related to the statistical description of the mixing state from the 2D radiographic image of a flow. X-ray attenuation through a target flow is given by the Beer-Lambert law which exponentially damps the incident beam intensity by a factor proportional to the density, opacity and thickness of the target. By making reasonable assumptions for the mean density, opacity and effective thickness of the target flow, we estimate the contribution of density fluctuations to the attenuation. The fluctuations thus inferred may be used to form the correlation of density and specific-volume, averaged across the thickness of the flow in the direction of the beam. This correlation function, denoted by b in RANS modeling, quantifies turbulent mixing in variable density flows. The scheme is tested using DNS data computed for variable-density buoyancy-driven mixing. We quantify the deficits in the extracted value of b due to target thickness, Atwood number, and modeled noise in the incident beam. This analysis corroborates the proposed scheme to infer the mix parameter from thin targets at moderate to low Atwood numbers. The scheme is then applied to an image of counter-shear flow obtained from experiments at the National Ignition Facility. US Department of Energy.

Scanned-probe field-emission studies of vertically aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Merkulov, Vladimir I.; Lowndes, Douglas H.; Baylor, Larry R.

2001-02-01

Field emission properties of dense and sparse "forests" of randomly placed, vertically aligned carbon nanofibers (VACNFs) were studied using a scanned probe with a small tip diameter of ˜1 μm. The probe was scanned in directions perpendicular and parallel to the sample plane, which allowed for measuring not only the emission turn-on field at fixed locations but also the emission site density over large surface areas. The results show that dense forests of VACNFs are not good field emitters as they require high extracting (turn-on) fields. This is attributed to the screening of the local electric field by the neighboring VACNFs. In contrast, sparse forests of VACNFs exhibit moderate-to-low turn-on fields as well as high emission site and current densities, and long emission lifetime, which makes them very promising for various field emission applications.

Assessment of Power Potential of Tidal Currents and Impacts of Power Extraction on Flow Conditions in Indonesia

NASA Astrophysics Data System (ADS)

Orhan, Kadir; Mayerle, Roberto

2017-04-01

Climate change is an urgent and potentially irreversible threat to human societies and the planet and thus requires an effective and appropriate response, with a view to accelerating the reduction of global greenhouse gas emissions. At this point, a worldwide shift to renewable energy is crucial. In this study, a methodology comprising of the estimates of power yield, evaluation of the effects of power extraction on flow conditions, and near-field investigations to deliver wake characteristics, recovery and interactions is described and applied to several straits in Indonesia. Site selection is done with high-resolution, three-dimensional flow models providing sufficient spatiotemporal coverage. Much attention has been given to the meteorological forcing, and conditions at the open sea boundaries to adequately capture the density gradients and flow fields. Model verifications using tidal records show excellent agreement. Sites with adequate depth for the energy conversion using horizontal axis tidal turbines, average kinetic power density greater than 0.5 kW/m2, and surface area larger than 0.5km2 are defined as energy hotspots. Spatial variation of the average extractable electric power is determined, and annual tidal energy resource is estimated for the straits in question. The results showed that the potential for tidal power generation in Indonesia is likely to exceed previous predictions reaching around 4,800MW. Models with higher resolutions have been developed to assess the impacts of devices on flow conditions and to resolve near-field turbine wakes in greater detail. The energy is assumed to be removed uniformly by sub-grid scale arrays of turbines. An additional drag force resulting in dissipation of the pre-existing kinetic power from 10% to 60% within a flow cross-section is introduced to capture the impacts. k-ɛ model, which is a second order turbulence closure model is selected to involve the effects of the turbulent kinetic energy and turbulent kinetic energy dissipation. Preliminary results show the effectiveness of the method to capture the effects of power extraction, and wake characteristics and recovery reasonably well with low computational cost. It was found that although there is no significant change regarding water levels, an impact has been observed on current velocities as a result of velocity profile adjusting to the increased momentum transfer. It was also seen that, depending on the level of energy dissipation, currently recommended tidal farm configurations can be conservative regarding the spacing of the tidal turbines.

Investigation of helicon ion source extraction systems.

PubMed

Mordyk, S; Miroshnichenko, V; Shulha, D; Storizhko, V

2008-02-01

Various versions of an extraction system for a helicon ion source have been investigated in high plasma density (>10(12) cm(-3)) modes. The measurements of the plasma density were carried out with a microwave interferometer. Experiments were performed with hydrogen and helium gases. The preliminary results indicate that specially designed extractors are very promising for improving ion beam paraxial brightness.

Generalized spin filtering and an improved derivative-sign binary image method for the extraction of fringe skeletons

NASA Astrophysics Data System (ADS)

Yu, Qifeng; Liu, Xiaolin; Sun, Xiangyi

1998-07-01

Generalized spin filters, including several directional filters such as the directional median filter and the directional binary filter, are proposed for removal of the noise of fringe patterns and the extraction of fringe skeletons with the help of fringe-orientation maps (FOM s). The generalized spin filters can filter off noise on fringe patterns and binary fringe patterns efficiently, without distortion of fringe features. A quadrantal angle filter is developed to filter off the FOM. With these new filters, the derivative-sign binary image (DSBI) method for extraction of fringe skeletons is improved considerably. The improved DSBI method can extract high-density skeletons as well as common density skeletons.

Extraction of Volatile Flavor Compounds From Tobacco Leaf Through a Low-Density Polyethylene Membrane.

PubMed

Yokoi, Michinori; Shimoda, Mitsuya

2017-03-01

A low-density polyethylene (LDPE) membrane pouch method was developed to extract volatile flavor compounds from tobacco leaf. Tobacco leaf suspended in water was enclosed in a pouch prepared from a LDPE membrane of specific gravity 0.92 g/cm3 and 0.03 mm thickness and then extracted with diethyl ether. In comparison with direct solvent extraction, LDPE membrane excluded larger and higher boiling point compounds which could contaminate a gas chromatograph inlet and damage a column. Whilst being more convenient than a reduced-pressure steam distillation, it could extract volatile flavor compounds of wide range of molecular weight and polarity. Repeatabilities in the extracted amounts were ranged from 0.38% of 2.3-bipyridyl to 26% of β-ionone, and average value of 39 compounds was 5.9%. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Simulations of super-ellipse hohlraum targets as a path to high neutron yields

NASA Astrophysics Data System (ADS)

Milovich, Jose; Amendt, Peter; Storm, Erik; Robey, Harry; Haan, Steve; Landen, Otto; Meezan, Nathan; Lindl, John

2017-10-01

Recently neutron yields in excess of 1016 have been achieved at the National Ignition Facility (NIF) using a low-density gas fill hohlraum and a subscale high-density-carbon capsule. The laser power used was near the current maximum level allowed on the inner cones of the NIF laser. While more energy can be extracted from the laser to provide additional improvement on the neutron yield, a more efficient design is desired. A new effort has begun to investigate alternatives to the current cylinder-shaped hohlraum for driving larger capsules (1.1 mm outer radius). If these new hohlraums can preserve the implosion symmetry, the additional absorbed energy is expected to provide a path to high neutron yield and potential ignition. Super-ellipse hohlraums, a generalization of an earlier rugby hohlraum design, have the advantage of a larger waist diameter and reduced parasitic energy losses from the corners of cylindrical hohlraums while still being able to produce the required capsule drive at the current energy and power limits available at the NIF. We will present plausible designs of these hohlraums based on the Lamé mathematical construction, and discuss their prospects to reach high neutron gains. Prepared by LLNL under Contract DE-AC52-07NA27344.

Preliminary study of near surface detections at geothermal field using optic and SAR imageries

NASA Astrophysics Data System (ADS)

Kurniawahidayati, Beta; Agoes Nugroho, Indra; Syahputra Mulyana, Reza; Saepuloh, Asep

2017-12-01

Current remote sensing technologies shows that surface manifestation of geothermal system could be detected with optical and SAR remote sensing, but to assess target beneath near the surface layer with the surficial method needs a further study. This study conducts a preliminary result using Optic and SAR remote sensing imagery to detect near surface geothermal manifestation at and around Mt. Papandayan, West Java, Indonesia. The data used in this study were Landsat-8 OLI/TIRS for delineating geothermal manifestation prospect area and an Advanced Land Observing Satellite(ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) level 1.1 for extracting lineaments and their density. An assumption was raised that the lineaments correlated with near surface structures due to long L-band wavelength about 23.6 cm. Near surface manifestation prospect area are delineated using visual comparison between Landsat 8 RGB True Colour Composite band 4,3,2 (TCC), False Colour Composite band 5,6,7 (FCC), and lineament density map of ALOS PALSAR. Visual properties of ground object were distinguished from interaction of the electromagnetic radiation and object whether it reflect, scatter, absorb, or and emit electromagnetic radiation based on characteristic of their molecular composition and their macroscopic scale and geometry. TCC and FCC composite bands produced 6 and 7 surface manifestation zones according to its visual classification, respectively. Classified images were then compared to a Normalized Different Vegetation Index (NDVI) to obtain the influence of vegetation at the ground surface to the image. Geothermal area were classified based on vegetation index from NDVI. TCC image is more sensitive to the vegetation than FCC image. The later composite produced a better result for identifying visually geothermal manifestation showed by detail-detected zones. According to lineament density analysis high density area located on the peak of Papandayan overlaid with zone 1 and 2 of FCC. Comparing to the extracted lineament density, we interpreted that the near surface manifestation is located at zone 1 and 2 of FCC image.

High-Latitude Neutral Mass Density Maxima

NASA Astrophysics Data System (ADS)

Huang, C. Y.; Huang, Y.; Su, Y.-J.; Huang, T.; Sutton, E. K.

2017-10-01

Recent studies have reported that thermospheric effects due to solar wind driving can be observed poleward of auroral latitudes. In these papers, the measured neutral mass density perturbations appear as narrow, localized maxima in the cusp and polar cap. They conclude that Joule heating below the spacecraft is the cause of the mass density increases, which are sometimes associated with local field-aligned current structures, but not always. In this paper we investigate neutral mass densities measured by accelerometers on the CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) spacecraft from launch until years 2010 (CHAMP) and 2012 (GRACE), approximately 10 years of observations from each satellite. We extract local maxima in neutral mass densities over the background using a smoothing window with size of one quarter of the orbit. The maxima have been analyzed for each year and also for the duration of each set of satellite observations. We show where they occur, under what solar wind conditions, and their relation to magnetic activity. The region with the highest frequency of occurrence coincides approximately with the cusp and mantle, with little direct evidence of an auroral zone source. Our conclusions agree with the "hot polar cap" observations that have been reported and studied in the past.

Method for producing metal oxide aerogels having densities less than 0.02 g/cc

DOEpatents

Tillotson, Thomas M.; Poco, John F.; Hrubesh, Lawrence W.; Thomas, Ian M.

1994-01-01

A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm.sup.3 to those with a density of more than 0.8 g/cm.sup.3, by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm.sup.3. High temperature, direct supercritical extraction of the liquid phase of the gel produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, homogeneous silica aerogels with a density of less than 0.02 to higher than 0.8 g/cm.sup.3, with high thermal insulation capacity, improved mechanical strength and good optical transparency, are described.

Anode current density distribution in a cusped field thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Huan, E-mail: wuhuan58@qq.com; Liu, Hui, E-mail: hlying@gmail.com; Meng, Yingchao

2015-12-15

The cusped field thruster is a new electric propulsion device that is expected to have a non-uniform radial current density at the anode. To further study the anode current density distribution, a multi-annulus anode is designed to directly measure the anode current density for the first time. The anode current density decreases sharply at larger radii; the magnitude of collected current density at the center is far higher compared with the outer annuli. The anode current density non-uniformity does not demonstrate a significant change with varying working conditions.

Electron cyclotron resonance ion source plasma characterization by X-ray spectroscopy and X-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mascali, David, E-mail: davidmascali@lns.infn.it; Castro, Giuseppe; Celona, Luigi

2016-02-15

An experimental campaign aiming to investigate electron cyclotron resonance (ECR) plasma X-ray emission has been recently carried out at the ECRISs—Electron Cyclotron Resonance Ion Sources laboratory of Atomki based on a collaboration between the Debrecen and Catania ECR teams. In a first series, the X-ray spectroscopy was performed through silicon drift detectors and high purity germanium detectors, characterizing the volumetric plasma emission. The on-purpose developed collimation system was suitable for direct plasma density evaluation, performed “on-line” during beam extraction and charge state distribution characterization. A campaign for correlating the plasma density and temperature with the output charge states and themore » beam intensity for different pumping wave frequencies, different magnetic field profiles, and single-gas/gas-mixing configurations was carried out. The results reveal a surprisingly very good agreement between warm-electron density fluctuations, output beam currents, and the calculated electromagnetic modal density of the plasma chamber. A charge-coupled device camera coupled to a small pin-hole allowing X-ray imaging was installed and numerous X-ray photos were taken in order to study the peculiarities of the ECRIS plasma structure.« less

Conceptual Design of a 100kW Energy Integrated Type Bi-Directional Tidal Current Turbine

NASA Astrophysics Data System (ADS)

Kim, Ki Pyoung; Ahmed, M. Rafiuddin; Lee, Young Ho

2010-06-01

The development of a tidal current turbine that can extract maximum energy from the tidal current will be extremely beneficial for supplying continuous electric power. The present paper presents a conceptual design of a 100kW energy integrated type tidal current turbine for tidal power generation. The instantaneous power density of a flowing fluid incident on an underwater turbine is proportional to the cubic power of current velocity which is approximately 2.5m/s. A cross-flow turbine, provided with a nozzle and a diffuser, is designed and analyzed. The potential advantages of ducted and diffuser-augmented turbines were taken into consideration in order to achieve higher output at a relatively low speed. This study looks at a cross-flow turbine system which is placed in an augmentation channel to generate electricity bi-directionally. The compatibility of this turbine system is verified using a commercial CFD code, ANSYSCFX. This paper presents the results of the numerical analysis in terms of pressure, streaklines, velocity vectors and performance curves for energy integrated type bi-directional tidal current turbine (BDT) with augmentation.

Operating Mechanisms of Mesoscopic Perovskite Solar Cells through Impedance Spectroscopy and J-V Modeling.

PubMed

Zarazúa, Isaac; Sidhik, Siraj; Lopéz-Luke, Tzarara; Esparza, Diego; De la Rosa, Elder; Reyes-Gomez, Juan; Mora-Seró, Iván; Garcia-Belmonte, Germà

2017-12-21

The performance of perovskite solar cell (PSC) is highly sensitive to deposition conditions, the substrate, humidity, and the efficiency of solvent extraction. However, the physical mechanism involved in the observed changes of efficiency with different deposition conditions has not been elucidated yet. In this work, PSCs were fabricated by the antisolvent deposition (AD) and recently proposed air-extraction antisolvent (AAD) process. Impedance analysis and J-V curve fitting were used to analyze the photogeneration, charge transportation, recombination, and leakage properties of PSCs. It can be elucidated that the improvement in morphology of perovskite film promoted by AAD method leads to increase in light absorption, reduction in recombination sites, and interstitial defects, thus enhancing the short-circuit current density, open-circuit voltage, and fill factor. This study will open up doors for further improvement of device and help in understanding its physical mechanism and its relation to the deposition methods.

Field Testing of Rapid Electrokinetic Nanoparticle Treatment for Corrosion Control of Steel in Concrete

NASA Technical Reports Server (NTRS)

Cardenas, Henry E.; Alexander, Joshua B.; Kupwade-Patil,Kunal; Calle, Luz Marina

2009-01-01

This work field tested the use of electrokinetics for delivery of concrete sealing nanoparticles concurrent with the extraction of chlorides. Several cylinders of concrete were batched and placed in immersion at the Kennedy Space Center Beach Corrosion Test Site. The specimens were batched with steel reinforcement and a 4.5 wt.% (weight percent) content of sodium chloride. Upon arrival at Kennedy Space Center, the specimens were placed in the saltwater immersion pool at the Beach Corrosion Test Site. Following 30 days of saltwater exposure, the specimens were subjected to rapid chloride extraction concurrent with electrokinetic nanoparticle treatment. The treatments were operated at up to eight times the typical current density in order to complete the treatment in 7 days. The findings indicated that the short-term corrosion resistance of the concrete specimens was significantly enhanced as was the strength of the concrete.

Based on Cu as framework constructed nanoporous CuO/Cu composites by a dealloy method for sodium-ion battery anode

NASA Astrophysics Data System (ADS)

Zheng, Tian; Li, Guangda; Li, Deming; Meng, Xiangeng

2018-05-01

Nanoporous CuO/Cu composites with a continuous channel structure were fabricated through a corroding Cu-Al alloy process. The width of the continuous channels was about 20 50 nm. Nanoporous structure could effectively sustain the volume expansion during the Na+ insertion/extraction process and shorten the Na+ diffusion length as well, which thus helps improve the Na+ storage performance. Moreover, the nanoporous structure can improve the contact area between the electrolyte and the electrode, leading to an increment in the number of Na+ insertion/extraction sites. When used as the anode for sodium-ion batteries, the CuO/Cu exhibited an initial capacity of 580 mAh g-1, and the capacity is maintained at 200 mAh g-1 after 200 cycles at a current density of 500 mA g-1.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santhanagopalan, Shriram; White, Ralph E.

Rotating ring disc electrode (RRDE) experiments are a classic tool for investigating kinetics of electrochemical reactions. Several standardized methods exist for extracting transport parameters and reaction rate constants using RRDE measurements. Here in this work, we compare some approximate solutions to the convective diffusion used popularly in the literature to a rigorous numerical solution of the Nernst-Planck equations coupled to the three dimensional flow problem. In light of these computational advancements, we explore design aspects of the RRDE that will help improve sensitivity of our parameter estimation procedure to experimental data. We use the oxygen reduction in acidic media involvingmore » three charge transfer reactions and a chemical reaction as an example, and identify ways to isolate reaction currents for the individual processes in order to accurately estimate the exchange current densities.« less

Prospects for Determining the Mass Distributions of Galaxy Clusters on Large Scales Using Weak Gravitational Lensing

NASA Astrophysics Data System (ADS)

Fong, M.; Bowyer, R.; Whitehead, A.; Lee, B.; King, L.; Applegate, D.; McCarthy, I.

2018-05-01

For more than two decades, the Navarro, Frenk, and White (NFW) model has stood the test of time; it has been used to describe the distribution of mass in galaxy clusters out to their outskirts. Stacked weak lensing measurements of clusters are now revealing the distribution of mass out to and beyond their virial radii, where the NFW model is no longer applicable. In this study we assess how well the parameterised Diemer & Kravstov (DK) density profile describes the characteristic mass distribution of galaxy clusters extracted from cosmological simulations. This is determined from stacked synthetic lensing measurements of the 50 most massive clusters extracted from the Cosmo-OWLS simulations, using the Dark Matter Only run and also the run that most closely matches observations. The characteristics of the data reflect the Weighing the Giants survey and data from the future Large Synoptic Survey Telescope (LSST). In comparison with the NFW model, the DK model favored by the stacked data, in particular for the future LSST data, where the number density of background galaxies is higher. The DK profile depends on the accretion history of clusters which is specified in the current study. Eventually however subsamples of galaxy clusters with qualities indicative of disparate accretion histories could be studied.

Neuroprotective and cognitive-enhancing effects of the combined extract of Cyperus rotundus and Zingiber officinale.

PubMed

Sutalangka, Chatchada; Wattanathorn, Jintanaporn

2017-03-03

Currently, food supplements to improve age-related dementia are required. Therefore, we aimed to determine the effect of the combined extract of Cyperus rotundus and Zingiber officinale (CP1) on the improvement of age-related dementia in rats with AF64A-induced memory deficits. Male Wistar rats weighing 180-200 g were orally given CP1 at doses of 100, 200 and 300 mg.kg -1 BW for a period of 14 days after bilateral intracerebroventricular administration of AF64A. Spatial memory was assessed in all rats every 7 days throughout the 14 day-experimental period. At the end of the study, neuronal density, acetylcholinesterase (AChE) activity, oxidative stress status and the activation of MAPK cascades in the hippocampus were determined. Enhanced memory, increased neuronal density, decreased AChE activity and decreased oxidative stress status together with activated pERK1/2 were observed in the hippocampus of CP1-treated rats. These results suggested that CP1 might improve memory via enhanced cholinergic function and decreased neurodegeneration and oxidative stress. CP1 is a potential novel food supplement for dementia. However, further investigations on the subchronic toxicity of CP1 and drug interactions are required.

Nutrition quality of extraction mannan residue from palm kernel cake on brolier chicken

NASA Astrophysics Data System (ADS)

Tafsin, M.; Hanafi, N. D.; Kejora, E.; Yusraini, E.

2018-02-01

This study aims to find out the nutrient residue of palm kernel cake from mannan extraction on broiler chicken by evaluating physical quality (specific gravity, bulk density and compacted bulk density), chemical quality (proximate analysis and Van Soest Test) and biological test (metabolizable energy). Treatment composed of T0 : palm kernel cake extracted aquadest (control), T1 : palm kernel cake extracted acetic acid (CH3COOH) 1%, T2 : palm kernel cake extracted aquadest + mannanase enzyme 100 u/l and T3 : palm kernel cake extracted acetic acid (CH3COOH) 1% + enzyme mannanase 100 u/l. The results showed that mannan extraction had significant effect (P<0.05) in improving the quality of physical and numerically increase the value of crude protein and decrease the value of NDF (Neutral Detergent Fiber). Treatments had highly significant influence (P<0.01) on the metabolizable energy value of palm kernel cake residue in broiler chickens. It can be concluded that extraction with aquadest + enzyme mannanase 100 u/l yields the best nutrient quality of palm kernel cake residue for broiler chicken.

Voxel-wise prostate cell density prediction using multiparametric magnetic resonance imaging and machine learning.

PubMed

Sun, Yu; Reynolds, Hayley M; Wraith, Darren; Williams, Scott; Finnegan, Mary E; Mitchell, Catherine; Murphy, Declan; Haworth, Annette

2018-04-26

There are currently no methods to estimate cell density in the prostate. This study aimed to develop predictive models to estimate prostate cell density from multiparametric magnetic resonance imaging (mpMRI) data at a voxel level using machine learning techniques. In vivo mpMRI data were collected from 30 patients before radical prostatectomy. Sequences included T2-weighted imaging, diffusion-weighted imaging and dynamic contrast-enhanced imaging. Ground truth cell density maps were computed from histology and co-registered with mpMRI. Feature extraction and selection were performed on mpMRI data. Final models were fitted using three regression algorithms including multivariate adaptive regression spline (MARS), polynomial regression (PR) and generalised additive model (GAM). Model parameters were optimised using leave-one-out cross-validation on the training data and model performance was evaluated on test data using root mean square error (RMSE) measurements. Predictive models to estimate voxel-wise prostate cell density were successfully trained and tested using the three algorithms. The best model (GAM) achieved a RMSE of 1.06 (± 0.06) × 10 3 cells/mm 2 and a relative deviation of 13.3 ± 0.8%. Prostate cell density can be quantitatively estimated non-invasively from mpMRI data using high-quality co-registered data at a voxel level. These cell density predictions could be used for tissue classification, treatment response evaluation and personalised radiotherapy.

Ultracompact/ultralow power electron cyclotron resonance ion source for multipurpose applications.

PubMed

Sortais, P; Lamy, T; Médard, J; Angot, J; Latrasse, L; Thuillier, T

2010-02-01

In order to drastically reduce the power consumption of a microwave ion source, we have studied some specific discharge cavity geometries in order to reduce the operating point below 1 W of microwave power (at 2.45 GHz). We show that it is possible to drive an electron cyclotron resonance ion source with a transmitter technology similar to those used for cellular phones. By the reduction in the size and of the required microwave power, we have developed a new type of ultralow cost ion sources. This microwave discharge system (called COMIC, for COmpact MIcrowave and Coaxial) can be used as a source of light, plasma or ions. We will show geometries of conductive cavities where it is possible, in a 20 mm diameter chamber, to reduce the ignition of the plasma below 100 mW and define typical operating points around 5 W. Inside a simple vacuum chamber it is easy to place the source and its extraction system anywhere and fully under vacuum. In that case, current densities from 0.1 to 10 mA/cm(2) (Ar, extraction 4 mm, 1 mAe, 20 kV) have been observed. Preliminary measurements and calculations show the possibility, with a two electrodes system, to extract beams within a low emittance. The first application for these ion sources is the ion injection for charge breeding, surface analyzing system and surface treatment. For this purpose, a very small extraction hole is used (typically 3/10 mm for a 3 microA extracted current with 2 W of HF power). Mass spectrum and emittance measurements will be presented. In these conditions, values down to 1 pi mm mrad at 15 kV (1sigma) are observed, thus very close to the ones currently observed for a surface ionization source. A major interest of this approach is the possibility to connect together several COMIC devices. We will introduce some new on-going developments such as sources for high voltage implantation platforms, fully quartz radioactive ion source at ISOLDE or large plasma generators for plasma immersion, broad or ribbon beams generation.

Effects of pine needle extract on pacemaker currents in interstitial cells of Cajal from the murine small intestine.

PubMed

Cheong, Hyeonsook; Paudyal, Dilli Parasad; Jun, Jae Yeoul; Yeum, Cheol Ho; Yoon, Pyung Jin; Park, Chan Guk; Kim, Man Yoo; So, Insuk; Kim, Ki Whan; Choi, Seok

2005-10-31

Extracts of pine needles (Pinus densiflora Sieb. et Zucc.) have diverse physiological and pharmacological actions. In this study we show that pine needle extract alters pacemaker currents in interstitial cells of Cajal (ICC) by modulating ATP-sensitive K+ channels and that this effect is mediated by prostaglandins. In whole cell patches at 30 degrees , ICC generated spontaneous pacemaker potentials in the current clamp mode (I = 0), and inward currents (pacemaker currents) in the voltage clamp mode at a holding potential of -70 mV. Pine needle extract hyperpolarized the membrane potential, and in voltage clamp mode decreased both the frequency and amplitude of the pacemaker currents, and increased the resting currents in the outward direction. It also inhibited the pacemaker currents in a dose-dependent manner. Because the effects of pine needle extract on pacemaker currents were the same as those of pinacidil (an ATP-sensitive K+ channel opener) we tested the effect of glibenclamide (an ATP-sensitive K+ channels blocker) on ICC exposed to pine needle extract. The effects of pine needle extract on pacemaker currents were blocked by glibenclamide. To see whether production of prostaglandins (PGs) is involved in the inhibitory effect of pine needle extract on pacemaker currents, we tested the effects of naproxen, a non-selective cyclooxygenase (COX-1 and COX-2) inhibitor, and AH6809, a prostaglandin EP1 and EP2 receptor antagonist. Naproxen and AH6809 blocked the inhibitory effects of pine needle extract on ICC. These results indicate that pine needle extract inhibits the pacemaker currents of ICC by activating ATP-sensitive K+ channels via the production of PGs.

Long pulse acceleration of MeV class high power density negative H{sup −} ion beam for ITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umeda, N., E-mail: umeda.naotaka@jaea.go.jp; Kojima, A.; Kashiwagi, M.

2015-04-08

R and D of high power density negative ion beam acceleration has been carried out at MeV test facility in JAEA to realize ITER neutral beam accelerator. The main target is H{sup −} ion beam acceleration up to 1 MeV with 200 A/m{sup 2} for 60 s whose pulse length is the present facility limit. For long pulse acceleration at high power density, new extraction grid (EXG) has been developed with high cooling capability, which electron suppression magnet is placed under cooling channel similar to ITER. In addition, aperture size of electron suppression grid (ESG) is enlarged from 14 mmmore » to 16 mm to reduce direct interception on the ESG and emission of secondary electron which leads to high heat load on the upstream acceleration grid. By enlarging ESG aperture, beam current increased 10 % at high current beam and total acceleration grid heat load reduced from 13 % to 10 % of input power at long pulse beam. In addition, heat load by back stream positive ion into the EXG is measured for the first time and is estimated as 0.3 % of beam power, while heat load by back stream ion into the source chamber is estimated as 3.5 ~ 4.0 % of beam power. Beam acceleration up to 60 s which is the facility limit, has achieved at 683 keV, 100 A/m{sup 2} of negative ion beam, whose energy density increases two orders of magnitude since 2011.« less

Analyzing the antibacterial effects of food ingredients: model experiments with allicin and garlic extracts on biofilm formation and viability of Staphylococcus epidermidis

PubMed Central

Wu, Xueqing; Santos, Regiane R; Fink-Gremmels, Johanna

2015-01-01

To demonstrate different effects of garlic extracts and their main antibiotic substance allicin, as a template for investigations on the antibacterial activity of food ingredients. Staphylococcus epidermidis ATCC 12228 and the isogenic biofilm-forming strain ATCC 35984 were used to compare the activity of allicin against planktonic bacteria and bacterial biofilms. The minimal inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) for pure allicin were identical and reached at a concentration of 12.5 μg/mL. MBICs for standardized garlic extracts were significantly lower, with 1.56 and 0.78 μg/mL allicin for garlic water and ethanol extract, respectively. Biofilm density was impaired significantly at a concentration of 0.78 μg/mL allicin. Viability staining followed by confocal laser scanning microscopy showed, however, a 100% bactericidal effect on biofilm-embedded bacteria at a concentration of 3.13 μg/mL allicin. qRT-PCR analysis provided no convincing evidence for specific effects of allicin on biofilm-associated genes. Extracts of fresh garlic are more potent inhibitors of Staphylococcus epidermidis biofilms than pure allicin, but allicin exerts a unique bactericidal effect on biofilm-embedded bacteria. The current experimental protocol has proven to be a valid approach to characterize the antimicrobial activity of traditional food ingredients. PMID:25838894

Insight into the CH3NH3PbI3/C interface in hole-conductor-free mesoscopic perovskite solar cells.

PubMed

Li, Jiangwei; Niu, Guangda; Li, Wenzhe; Cao, Kun; Wang, Mingkui; Wang, Liduo

2016-08-07

Perovskite solar cells (PSCs) with hole-conductor-free mesoscopic architecture have shown superb stability and great potential in practical application. The printable carbon counter electrodes take full responsibility of extracting holes from the active CH3NH3PbI3 absorbers. However, an in depth study of the CH3NH3PbI3/C interface properties, such as the structural formation process and the effect of interfacial conditions on hole extraction, is still lacking. Herein, we present, for the first time, an insight into the spatial confinement induced CH3NH3PbI3/C interface formation by in situ photoluminescence observations during the crystallization process of CH3NH3PbI3. The derived reaction kinetics allows a quantitative description of the perovskite formation process. In addition, we found that the interfacial contact between carbon and perovskite was dominant for hole extraction efficiency and associated with the photovoltaic parameter of short circuit current density (JSC). Consequently, we conducted a solvent vapor assisted process of PbI2 diffusion to carefully control the CH3NH3PbI3/C interface with less unreacted PbI2 barrier. The improvement of interface conditions thereby contributes to a high hole extraction proved by the charge extraction resistance and PL lifetime change, resulting in the increased JSC valve.

A simple method for the extraction and identification of light density microplastics from soil.

PubMed

Zhang, Shaoliang; Yang, Xiaomei; Gertsen, Hennie; Peters, Piet; Salánki, Tamás; Geissen, Violette

2018-03-01

This article introduces a simple and cost-saving method developed to extract, distinguish and quantify light density microplastics of polyethylene (PE) and polypropylene (PP) in soil. A floatation method using distilled water was used to extract the light density microplastics from soil samples. Microplastics and impurities were identified using a heating method (3-5s at 130°C). The number and size of particles were determined using a camera (Leica DFC 425) connected to a microscope (Leica wild M3C, Type S, simple light, 6.4×). Quantification of the microplastics was conducted using a developed model. Results showed that the floatation method was effective in extracting microplastics from soils, with recovery rates of approximately 90%. After being exposed to heat, the microplastics in the soil samples melted and were transformed into circular transparent particles while other impurities, such as organic matter and silicates were not changed by the heat. Regression analysis of microplastics weight and particle volume (a calculation based on image J software analysis) after heating showed the best fit (y=1.14x+0.46, R 2 =99%, p<0.001). Recovery rates based on the empirical model method were >80%. Results from field samples collected from North-western China prove that our method of repetitive floatation and heating can be used to extract, distinguish and quantify light density polyethylene microplastics in soils. Microplastics mass can be evaluated using the empirical model. Copyright © 2017 Elsevier B.V. All rights reserved.

The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects

NASA Astrophysics Data System (ADS)

Kinney, Chris; Linares, Xioranny; Lee, Kyu-Oh; Morris, J. W.

2013-04-01

The work reported here explores the influence of crystal orientation on the growth of the interfacial intermetallic layer during electromigration in Cu||Sn||Cu solder joints. The samples were thin, planar Sn-Ag-Cu (SAC) solder layers between Cu bars subject to a uniaxial current. Electron backscatter diffraction (EBSD) was used to characterize the microstructure before and after testing. The most useful representation of the EBSD data identifies the Sn grain orientation by the angle between the Sn c-axis and the current direction. The tested samples included single-crystal joints with c-axis nearly parallel to the current ("green" samples) and with c-axis perpendicular to the current ("red" samples). At current density of 104 A/cm2 (steady-state temperature of ~150°C), an intermetallic layer grew at an observable rate in the "green" samples, but not in the "red" ones. A current density of 1.15 × 104 A/cm2 (temperature ~160°C) led to measurable intermetallic growth in both samples. The growth fronts were nearly planar and the growth rates constant (after an initial incubation period); the growth rates in the "green" samples were about 10× those in the "red" samples. The Cu concentrations were constant within the joints, showing that the intermetallic growth is dominated by the electromigration flux. The measured growth rates and literature values for the diffusion of Cu in Sn were used to extract values for the effective charge, z *, that governs the electromigration of Cu. The calculated value of z * is significantly larger for current perpendicular to the c-axis than along it.

Electron stripping processes of H⁻ ion beam in the 80 kV high voltage extraction column and low energy beam transport line at LANSCE.

PubMed

Draganic, I N

2016-02-01

Basic vacuum calculations were performed for various operating conditions of the Los Alamos National Neutron Science H(-) Cockcroft-Walton (CW) injector and the Ion Source Test Stand (ISTS). The vacuum pressure was estimated for both the CW and ISTS at five different points: (1) inside the H(-) ion source, (2) in front of the Pierce electrode, (3) at the extraction electrode, (4) at the column electrode, and (5) at the ground electrode. A static vacuum analysis of residual gases and the working hydrogen gas was completed for the normal ion source working regime. Gas density and partial pressure were estimated for the injected hydrogen gas. The attenuation of H(-) beam current and generation of electron current in the high voltage acceleration columns and low energy beam transport lines were calculated. The interaction of H(-) ions on molecular hydrogen (H2) is discussed as a dominant collision process in describing electron stripping rates. These results are used to estimate the observed increase in the ratio of electrons to H(-) ion beam in the ISTS beam transport line.

Method for producing metal oxide aerogels having densities less than 0. 02 g/cc

DOEpatents

Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

1994-01-04

A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm[sup 3] to those with a density of more than 0.8 g/cm[sup 3], by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm[sup 3]. High temperature, direct supercritical extraction of the liquid phase of the gel produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, homogeneous silica aerogels with a density of less than 0.02 to higher than 0.8 g/cm[sup 3], with high thermal insulation capacity, improved mechanical strength and good optical transparency, are described. 7 figures.

The influence of alendronate on the healing of extraction sockets of ovariectomized rats assessed by in vivo micro-computed tomography.

PubMed

Jee, Jeong-Hyun; Lee, Wan; Lee, Byung Do

2010-08-01

Many dental patients take bisphosphonates to reduce the risk of hip and vertebral fractures. In vivo micro-computed tomography (micro-CT) was used to examine the longitudinal inhibitory effect of alendronate on the healing of extraction sockets in ovariectomized rats. Twenty 5-week-old Sprague-Dawley rats were assigned randomly to 1 of 3 groups: sham-operated (n = 5), and 2 ovariectomized (OVX) groups: saline treated (0.1 mL/100 g/d, n = 7) and alendronate treated (1 mg/kg/d, n = 8). Before micro-CT scanning, the left maxillary first molars of the rats were extracted. In vivo micro-CT (spatial resolution 50 x 50 mum) of the jaw was performed at baseline and at 2-week intervals for 6 weeks. Alveolar-bone radiographic densities and dimensions were analyzed with repeated measures analysis of variance. The bony healing patterns of the extraction sockets were also evaluated in each group. The radiographic socket densities of the sham-treated and OVX-alendronate groups significantly increased during the first 4 weeks after extraction (P < .05). At 2 weeks, the radiographic densities of the sockets in the OVX-saline group increased, but the increase was significantly lower than for the other groups at 4 weeks (P < .05). Newly formed bone was identified in the extraction sockets in all groups 2 to 6 weeks after extraction. There was a significant loss of alveolar ridge height at the second week postextraction compared with baseline, and at the fourth week compared with the second week (P < .05) except in the alendronate group. Alendronate appears to promote the healing of extraction sockets in estrogen-deficient rats and helps resist the loss of alveolar bone adjacent to extraction sockets. Copyright 2010 Mosby, Inc. All rights reserved.

Investigation of the boundary layer during the transition from volume to surface dominated H- production at the BATMAN test facility

NASA Astrophysics Data System (ADS)

Wimmer, C.; Schiesko, L.; Fantz, U.

2016-02-01

BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 1/8 scale H- source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H- production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H- density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H- density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (jH-, je) exists with the Cs emission.

Investigation of the boundary layer during the transition from volume to surface dominated H⁻ production at the BATMAN test facility.

PubMed

Wimmer, C; Schiesko, L; Fantz, U

2016-02-01

BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 18 scale H(-) source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H(-) production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H(-) density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H(-) density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (j(H(-)), j(e)) exists with the Cs emission.

Fishery-independent data reveal negative effect of human population density on Caribbean predatory fish communities.

PubMed

Stallings, Christopher D

2009-01-01

Understanding the current status of predatory fish communities, and the effects fishing has on them, is vitally important information for management. However, data are often insufficient at region-wide scales to assess the effects of extraction in coral reef ecosystems of developing nations. Here, I overcome this difficulty by using a publicly accessible, fisheries-independent database to provide a broad scale, comprehensive analysis of human impacts on predatory reef fish communities across the greater Caribbean region. Specifically, this study analyzed presence and diversity of predatory reef fishes over a gradient of human population density. Across the region, as human population density increases, presence of large-bodied fishes declines, and fish communities become dominated by a few smaller-bodied species. Complete disappearance of several large-bodied fishes indicates ecological and local extinctions have occurred in some densely populated areas. These findings fill a fundamentally important gap in our knowledge of the ecosystem effects of artisanal fisheries in developing nations, and provide support for multiple approaches to data collection where they are commonly unavailable.

DNA Nucleotides Detection via capacitance properties of Graphene

NASA Astrophysics Data System (ADS)

Khadempar, Nahid; Berahman, Masoud; Yazdanpanah, Arash

2016-05-01

In the present paper a new method is suggested to detect the DNA nucleotides on a first-principles calculation of the electronic features of DNA bases which chemisorbed to a graphene sheet placed between two gold electrodes in a contact-channel-contact system. The capacitance properties of graphene in the channel are surveyed using non-equilibrium Green's function coupled with the Density Functional Theory. Thus, the capacitance properties of graphene are theoretically investigated in a biological environment, and, using a novel method, the effect of the chemisorbed DNA nucleotides on electrical charges on the surface of graphene is deciphered. Several parameters in this method are also extracted including Electrostatic energy, Induced density, induced electrostatic potential, Electron difference potential and Electron difference density. The qualitative and quantitative differences among these parameters can be used to identify DNA nucleotides. Some of the advantages of this approach include its ease and high accuracy. What distinguishes the current research is that it is the first experiment to investigate the capacitance properties of gaphene changes in the biological environment and the effect of chemisorbed DNA nucleotides on the surface of graphene on the charge.

Measurements of density dependent intensity ratios of extreme ultraviolet line emission from Fe X, XI, and XII

NASA Astrophysics Data System (ADS)

Shimizu, Erina; Ali, Safdar; Tsuda, Takashi; Sakaue, Hiroyuki A.; Kato, Daiji; Murakami, Izumi; Hara, Hirohisa; Watanabe, Tetsuya; Nakamura, Nobuyuki

2017-05-01

We report high-resolution density dependent intensity ratio measurements for middle charge states of iron in the extreme ultraviolet (EUV) spectral wavelength range of 160-200 Å. The measurements were performed at the Tokyo EBIT laboratory by employing a flat-field grazing incidence spectrometer installed on a low energy compact electron beam ion trap. The intensity ratios for several line pairs stemming from Fe X, Fe XI and Fe XII were extracted from spectra collected at the electron beam energies of 340 and 400 eV by varying the beam current between 7.5 and 12 mA at each energy. In addition, the effective electron densities were obtained experimentally by imaging the electron beam profile and ion cloud size with a pinhole camera and visible spectrometer, respectively. In this paper, the experimental results are compared with previous data from the literature and with the present calculations performed using a collisional-radiative model. Our experimental results show a rather good agreement with the calculations and previous reported results.

Enhancement of Device Performances in GaN-Based Light-Emitting Diodes Using Nano-Sized Surface Pit.

PubMed

Yeon, Seunghwan; Son, Taejoon; Shin, Dong Su; Jung, Kyung-Young; Park, Jinsub

2015-07-01

We report the improvement in optical and electrical properties of GaN-based green light-emitting diodes (LEDs) with nano-sized etch pits formed by the surface chemical etching. In order to control the density and sizes of etch pits formed on top surface of green LEDs, H3PO4 solution is used as a etchant with different etching time. When the etching time was increased from 0 min to 20 min, both the etch pit size and density were gradually increased. The improvement of extraction efficiency of LEDs using surface etching method can be attributed to the enlarged escape angle of generated photon by roughened p-GaN surface. The finite-difference time-domain (FDTD) simulation results well agreed with experimentally observed results. Moreover, the LED with etched p-GaN surface for 5 min shows the lowest leakage current value and the further increase of etching time resulting in increase of densities of the large-sized etch pit makes the degradation of electrical properties of LEDs.

Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities

PubMed Central

Stallings, Christopher D.

2009-01-01

Background Understanding the current status of predatory fish communities, and the effects fishing has on them, is vitally important information for management. However, data are often insufficient at region-wide scales to assess the effects of extraction in coral reef ecosystems of developing nations. Methodology/Principal Findings Here, I overcome this difficulty by using a publicly accessible, fisheries-independent database to provide a broad scale, comprehensive analysis of human impacts on predatory reef fish communities across the greater Caribbean region. Specifically, this study analyzed presence and diversity of predatory reef fishes over a gradient of human population density. Across the region, as human population density increases, presence of large-bodied fishes declines, and fish communities become dominated by a few smaller-bodied species. Conclusions/Significance Complete disappearance of several large-bodied fishes indicates ecological and local extinctions have occurred in some densely populated areas. These findings fill a fundamentally important gap in our knowledge of the ecosystem effects of artisanal fisheries in developing nations, and provide support for multiple approaches to data collection where they are commonly unavailable. PMID:19421312

Crataegus extract blocks potassium currents in guinea pig ventricular cardiac myocytes.

PubMed

Müller, A; Linke, W; Klaus, W

1999-05-01

Crataegus extract is used in cardiology for the treatment of mild to moderate heart failure (NYHA II) in Germany. However, little is known about the electrophysiological actions of Crataegus extract in the heart. Recently, it was shown that Crataegus extract prolongs the refractory period in isolated perfused hearts and increases action potential duration in guinea pig papillary muscle. It was the aim of this study to find out the mechanism of the increase in action potential duration caused by Crataegus extract. Using the patch-clamp technique, we measured the effects of Crataegus extract (10 mg/l; flavonoid content: 2.25%, total procyanidin content: 11.3 +/- 0.4%) on the inward rectifier and the delayed rectifier potassium current in isolated guinea pig ventricular myocytes. To get some insight into the mechanism underlying the positive inotropic effect of Crataegus extract, we also looked for effects on the L-type calcium current. Crataegus extract slightly blocked both the delayed and the inward rectifier potassium current. The inhibition amounted to 25% and about 15%, respectively. This amount of inhibition of these repolarising currents is sufficient to explain the prolongation of action potential duration caused by Crataegus extract. To our surprise we could not detect any influence of Crataegus extract on the L-type calcium current. In summary, our results show that Crataegus extract blocks repolarising potassium currents in ventricular myocytes. This effect is similar to the action of class III antiarrhythmic drugs and might be the basis of the antiarrhythmic effects described for Crataegus extract. Our measurements of the L-type calcium current indicate that Crataegus extract's positive inotropic effect is not caused by phosphodiesterase inhibition or a beta-sympathomimetic effect.

High extraction efficiency ultraviolet light-emitting diode

DOEpatents

Wierer, Jonathan; Montano, Ines; Allerman, Andrew A.

2015-11-24

Ultraviolet light-emitting diodes with tailored AlGaN quantum wells can achieve high extraction efficiency. For efficient bottom light extraction, parallel polarized light is preferred, because it propagates predominately perpendicular to the QW plane and into the typical and more efficient light escape cones. This is favored over perpendicular polarized light that propagates along the QW plane which requires multiple, lossy bounces before extraction. The thickness and carrier density of AlGaN QW layers have a strong influence on the valence subband structure, and the resulting optical polarization and light extraction of ultraviolet light-emitting diodes. At Al>0.3, thinner QW layers (<2.5 nm are preferred) result in light preferentially polarized parallel to the QW plane. Also, active regions consisting of six or more QWs, to reduce carrier density, and with thin barriers, to efficiently inject carriers in all the QWs, are preferred.

SUPERCRITICAL FLUID EXTRACTION OF POLYCYCLIC AROMATIC HYDROCARBON MIXTURES FROM CONTAMINATED SOILS

EPA Science Inventory

Highly contaminated (with PAHs) topsoils were extracted with supercritical CO₂ to determine the feasibility and mechanism of supercritical fluid extraction (SFE). Effect of SCF density, temperature, cosolvent type and amount, and of slurrying the soil with water were ...

The evolution equation for the flame surface density in turbulent premixed combustion

NASA Technical Reports Server (NTRS)

Trouve, Arnaud

1993-01-01

The mean reaction rate in flamelet models for turbulent premixed combustion depends on two basic quantities: a mean chemical rate, called the flamelet speed, and the flame surface density. Our previous work had been primarily focused on the problem of the structure and topology of turbulent premixed flames, and it was then determined that the flamelet speed, when space-averaged, is only weakly sensitive to the turbulent flow field. Consequently, the flame surface density is the key quantity that conveys most of the effects of the turbulence on the rate of energy release. In flamelet models, this quantity is obtained via a modeled transport equation called the Sigma-equation. Past theoretical work has produced a rigorous approach that leads to an exact but unclosed formulation for the turbulent Sigma-equation. In the exact Sigma-equation, it appears that the dynamical properties of the flame surface density are determined by a single parameter, namely the turbulent flame stretch. Unfortunately, the turbulent flame stretch as well as the flame surface density is not available from experiments, and, in the absence of experimental data, little is known on the validity of the closure assumptions used in current flamelet models. Direct Numerical Simulation (DNS) is the alternative approach to get basic information on these fundamental quantities. In the present work, three-dimensional DNS of premixed flames in isotropic turbulent flow is used to estimate the different terms appearing in the Sigma-equation. A new methodology is proposed to provide the source and sink terms for the flame surface density, resolved both temporally and spatially throughout the turbulent flame brush. Using this methodology, our objective is to extract the turbulent flame stretch from the DNS data base and then perform extensive comparisons with flamelet models. Thanks to the detailed information produced by the DNS-based analysis, it is expected that this type of comparison will not only underscore the shortcomings of current models, but also suggest ways to improve them.

Influence of femtosecond lenticule extraction and small incision lenticule extraction on corneal nerve density and ocular surface: a 1-year prospective, confocal, microscopic study.

PubMed

Ishii, Rie; Shimizu, Kimiya; Igarashi, Akihito; Kobashi, Hidenaga; Kamiya, Kazutaka

2015-01-01

To compare the influence of femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SMILE) on corneal nerve density and the ocular surface for equivalent degrees of correction of myopia. Sixty eyes of 30 patients (8 males and 22 females, mean age: 31.0 ± 6.0 years) were included in the study. The patients underwent FLEx in 1 eye and SMILE in the other eye by random assignment. Subbasal nerve density was measured using confocal microscopy preoperatively and at 1 week, 1 and 3 months, and 1 year postoperatively. Ocular surface parameters such as Schirmer's test results, tear film break-up time, and corneal sensation were performed preoperatively and at 1 and 3 months postoperatively. In the FLEx group, subbasal nerve density was 18,390 ± 6,090 µm/mm(2) preoperatively and 5,770 ± 3,490 µm/mm(2) at 1 year postoperatively (P < .001, Dunnett's test). In the SMILE group, subbasal nerve density was 16,810 ± 6,220 µm/mm(2) preoperatively and 11,870 ± 8,200 µm/mm(2) at 1 year postoperatively (P = .21). The decrease in corneal nerve density was significantly less after SMILE than after FLEx at all postoperative visits (Mann-Whitney U test, P < .05). FLEx resulted in a significant decrease in Schirmer's test results, tear film break-up time, and corneal sensation at all postoperative visits, whereas SMILE induced no significant changes in these parameters (P > .05). There was less damage to the sub-basal nerve plexus of the cornea and less effect on the ocular surface parameters after SMILE than after FLEx. Copyright 2015, SLACK Incorporated.

Space charge limited current measurements on conjugated polymer films using conductive atomic force microscopy.

PubMed

Reid, Obadiah G; Munechika, Keiko; Ginger, David S

2008-06-01

We describe local (~150 nm resolution), quantitative measurements of charge carrier mobility in conjugated polymer films that are commonly used in thin-film transistors and nanostructured solar cells. We measure space charge limited currents (SCLC) through these films using conductive atomic force microscopy (c-AFM) and in macroscopic diodes. The current densities we measure with c-AFM are substantially higher than those observed in planar devices at the same bias. This leads to an overestimation of carrier mobility by up to 3 orders of magnitude when using the standard Mott-Gurney law to fit the c-AFM data. We reconcile this apparent discrepancy between c-AFM and planar device measurements by accounting for the proper tip-sample geometry using finite element simulations of tip-sample currents. We show that a semiempirical scaling factor based on the ratio of the tip contact area diameter to the sample thickness can be used to correct c-AFM current-voltage curves and thus extract mobilities that are in good agreement with values measured in the conventional planar device geometry.

Light illumination intensity dependence of photovoltaic parameter in polymer solar cells with ammonium heptamolybdate as hole extraction layer.

PubMed

Liu, Zhiyong; Niu, Shengli; Wang, Ning

2018-01-01

A low-temperature, solution-processed molybdenum oxide (MoO X ) layer and a facile method for polymer solar cells (PSCs) is developed. The PSCs based on a MoO X layer as the hole extraction layer (HEL) is a significant advance for achieving higher photovoltaic performance, especially under weaker light illumination intensity. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements show that the (NH 4 ) 6 Mo 7 O 24 molecule decomposes and forms the molybdenum oxide (MoO X ) molecule when undergoing thermal annealing treatment. In this study, PSCs with the MoO X layer as the HEL exhibited better photovoltaic performance, especially under weak light illumination intensity (from 100 to 10mWcm -2 ) compared to poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based PSCs. Analysis of the current density-voltage (J-V) characteristics at various light intensities provides information on the different recombination mechanisms in the PSCs with a MoO X and PEDOT:PSS layer as the HEL. That the slopes of the open-circuit voltage (V OC ) versus light illumination intensity plots are close to 1 unity (kT/q) reveals that bimolecular recombination is the dominant and weaker monomolecular recombination mechanism in open-circuit conditions. That the slopes of the short-circuit current density (J SC ) versus light illumination intensity plots are close to 1 reveals that the effective charge carrier transport and collection mechanism of the MoO X /indium tin oxide (ITO) anode is the weaker bimolecular recombination in short-circuit conditions. Our results indicate that MoO X is an alternative candidate for high-performance PSCs, especially under weak light illumination intensity. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of two Chinese medical herbs, Huangbai and Qianniuzi, on influence of short circuit current across the rat intestinal epithelia.

PubMed

Tsai, Jong-Chang; Tsai, Shuli; Chang, Weng-Cheng

2004-07-01

Huangbai (Phellodendron spec.) and Qianniuzi (Pharbitis spec.) are two traditional Chinese medical herbs used for anti-diarrheal and laxative agents, respectively. Ethanol and water extracts of these two herbs were prepared and effects of the extracts on ion transport of the rat intestinal epithelia were studied. For measuring changes of the short circuit current across the epithelia, the rat intestinal epithelia were mounted in the Ussing chamber and attached with voltage/current clamp. The intestinal epithelia were firstly activated by serosal administration of 5 microM forskolin. As current raised and being stable, extracts of these herbs were added, respectively, and changes in the short circuit current were recorded. Ethanol extract of Huangbai attenuated the current increment; on the contrary, ethanol extract of Qianniuzi augmented the current increment additionally. Water extracts of the two herbs showed minor effects on the current in comparison to ethanol extracts. The results provide evidences to reveal the pharmacological mechanism of the two Chinese medical herbs on the intestinal tissue.

Assessment of Energy Production Potential from Ocean Currents along the United States Coastline

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haas, Kevin

Increasing energy consumption and depleting reserves of fossil fuels have resulted in growing interest in alternative renewable energy from the ocean. Ocean currents are an alternative source of clean energy due to their inherent reliability, persistence and sustainability. General ocean circulations exist in the form of large rotating ocean gyres, and feature extremely rapid current flow in the western boundaries due to the Coriolis Effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean that flows along the east coastline of the United States, and therefore is of particular interest as a potentialmore » energy resource for the United States. This project created a national database of ocean current energy resources to help advance awareness and market penetration in ocean current energy resource assessment. The database, consisting of joint velocity magnitude and direction probability histograms, was created from data created by seven years of numerical model simulations. The accuracy of the database was evaluated by ORNL?s independent validation effort documented in a separate report. Estimates of the total theoretical power resource contained in the ocean currents were calculated utilizing two separate approaches. Firstly, the theoretical energy balance in the Gulf Stream system was examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for subtropical gyres with the quasi-geostrophic balance between pressure gradient, Coriolis force, wind stress and friction driving the circulation. Parameters including water depth, natural dissipation rate and wind stress are calibrated in the model so that the model can reproduce reasonable flow properties including volume flux and energy flux. To represent flow dissipation due to turbines additional turbine drag coefficient is formulated and included in the model. Secondly, to determine the reasonableness of the total power estimates from the Stommel model and to help determine the size and capacity of arrays necessary to extract the maximum theoretical power, further estimates of the available power based on the distribution of the kinetic power density in the undisturbed flow was completed. This used estimates of the device spacing and scaling to sum up the total power that the devices would produce. The analysis has shown that considering extraction over a region comprised of the Florida Current portion of the Gulf Stream system, the average power dissipated ranges between 4-6 GW with a mean around 5.1 GW. This corresponds to an average of approximately 45 TWh/yr. However, if the extraction area comprises the entire portion of the Gulf Stream within 200 miles of the US coastline from Florida to North Carolina, the average power dissipated becomes 18.6 GW or 163 TWh/yr. A web based GIS interface, http://www.oceancurrentpower.gatech.edu/, was developed for dissemination of the data. The website includes GIS layers of monthly and yearly mean ocean current velocity and power density for ocean currents along the entire coastline of the United States, as well as joint and marginal probability histograms for current velocities at a horizontal resolution of 4-7 km with 10-25 bins over depth. Various tools are provided for viewing, identifying, filtering and downloading the data.« less

Schottky barrier parameters and low frequency noise characteristics of graphene-germanium Schottky barrier diode

NASA Astrophysics Data System (ADS)

Khurelbaatar, Zagarzusem; Kil, Yeon-Ho; Shim, Kyu-Hwan; Cho, Hyunjin; Kim, Myung-Jong; Lee, Sung-Nam; Jeong, Jae-chan; Hong, Hyobong; Choi, Chel-Jong

2016-03-01

We investigated the electrical properties of chemical vapor deposition-grown monolayer graphene/n-type germanium (Ge) Schottky barrier diodes (SBD) using current-voltage (I-V) characteristics and low frequency noise measurements. The Schottky barrier parameters of graphene/n-type Ge SBDs, such as Schottky barrier height (VB), ideality factor (n), and series resistance (Rs), were extracted using the forward I-V and Cheung's methods. The VB and n extracted from the forward ln(I)-V plot were found to be 0.63 eV and 1.78, respectively. In contrast, from Cheung method, the VB and n were calculated to be 0.53 eV and 1.76, respectively. Such a discrepancy between the values of VB calculated from the forward I-V and Cheung's methods indicated a deviation from the ideal thermionic emission of graphene/n-type Ge SBD associated with the voltage drop across graphene. The low frequency noise measurements performed at the frequencies in the range of 10 Hz-1 kHz showed that the graphene/n-type Ge SBD had 1/f γ frequency dependence, with γ ranging from 1.09 to 1.12, regardless of applied forward biases. Similar to forward-biased SBDs operating in the thermionic emission mode, the current noise power spectral density of graphene/n-type Ge SBD was linearly proportional to the forward current.

3D local feature BKD to extract road information from mobile laser scanning point clouds

NASA Astrophysics Data System (ADS)

Yang, Bisheng; Liu, Yuan; Dong, Zhen; Liang, Fuxun; Li, Bijun; Peng, Xiangyang

2017-08-01

Extracting road information from point clouds obtained through mobile laser scanning (MLS) is essential for autonomous vehicle navigation, and has hence garnered a growing amount of research interest in recent years. However, the performance of such systems is seriously affected due to varying point density and noise. This paper proposes a novel three-dimensional (3D) local feature called the binary kernel descriptor (BKD) to extract road information from MLS point clouds. The BKD consists of Gaussian kernel density estimation and binarization components to encode the shape and intensity information of the 3D point clouds that are fed to a random forest classifier to extract curbs and markings on the road. These are then used to derive road information, such as the number of lanes, the lane width, and intersections. In experiments, the precision and recall of the proposed feature for the detection of curbs and road markings on an urban dataset and a highway dataset were as high as 90%, thus showing that the BKD is accurate and robust against varying point density and noise.

Application of the Mattis-Bardeen theory in strongly disordered superconductors

NASA Astrophysics Data System (ADS)

Seibold, G.; Benfatto, L.; Castellani, C.

2017-10-01

The low-energy optical conductivity of conventional superconductors is usually well described by Mattis-Bardeen (MB) theory, which predicts the onset of absorption above an energy corresponding to twice the superconducing (SC) gap parameter Δ . Recent experiments on strongly disordered superconductors have challenged the application of the MB formulas due to the occurrence of additional spectral weight at low energies below 2 Δ . Here we identify three crucial items that have to be included in the analysis of optical-conductivity data for these systems: (a) the correct identification of the optical threshold in the Mattis-Bardeen theory and its relation with the gap value extracted from the measured density of states, (b) the gauge-invariant evaluation of the current-current response function needed to account for the optical absorption by SC collective modes, and (c) the inclusion into the MB formula of the energy dependence of the density of states present already above Tc. By computing the optical conductivity in the disordered attractive Hubbard model, we analyze the relevance of all these items, and we provide a compelling scheme for the analysis and interpretation of the optical data in real materials.

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2017-12-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage (J-V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density (J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance (R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode (C μ ) and electron lifetime (t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2018-03-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage ( J- V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density ( J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance ( R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode ( C μ ) and electron lifetime ( t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

Test bed ion engine development

NASA Technical Reports Server (NTRS)

Aston, G.; Deininger, W. D.

1984-01-01

A test bed ion (TBI) engine was developed to serve as a tool in exploring the limits of electrostatic ion thruster performance. A description of three key ion engine components, the decoupled extraction and amplified current (DE-AC) accelerator system, field enhanced refractory metal (FERM) hollow cathode and divergent line cusp (DLC) discharge chamber, whose designs and operating philosophies differ markedly from conventional thruster technology is given. Significant program achievements were: (1) high current density DE-AC accelerator system operation at low electric field stress with indicated feasibility of a 60 mA/sq cm argon ion beam; (2) reliable FERM cathode start up times of 1 to 2 secs. and demonstrated 35 ampere emission levels; (3) DLC discharge chamber plasma potentials negative of anode potential; and (4) identification of an efficient high plasma density engine operating mode. Using the performance projections of this program and reasonable estimates of other parameter values, a 1.0 Newton thrust ion engine is identified as a realizable technology goal. Calculations show that such an engine, comparable in beam area to a J series 30 cm thruster, could, operating on Xe or Hg, have thruster efficiencies as high as 0.76 and 0.78 respectively, with a 100 eV/ion discharge loss.

Interfacial characteristics and leakage current transfer mechanisms in organometal trihalide perovskite gate-controlled devices via doping of PCBM

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Zhang, Yuming; Liu, Yintao; Pang, Tiqiang; Hu, Ziyang; Zhu, Yuejin; Luan, Suzhen; Jia, Renxu

2017-11-01

Two types of perovskite (with and without doping of PCBM) based metal-oxide-semiconductor (MOS) gate-controlled devices were fabricated and characterized. The study of the interfacial characteristics and charge transfer mechanisms by doping of PCBM were analyzed by material and electrical measurements. Doping of PCBM does not affect the size and crystallinity of perovskite films, but has an impact on carrier extraction in perovskite MOS devices. The electrical hysteresis observed in capacitance-voltage and current-voltage measurements can be alleviated by doping of PCBM. Experimental results demonstrate that extremely low trap densities are found for the perovskite device without doping, while the doped sample leads to higher density of interface state. Three mechanisms including Ohm’s law, trap-filled-limit (TFL) emission, and child’s law were used to analyze possible charge transfer mechanisms. Ohm’s law mechanism is well suitable for charge transfer of both the perovskite MOS devices under light condition at large voltage, while TFL emission well addresses the behavior of charge transfer under dark at small voltage. This change of charge transfer mechanism is attributed to the impact of the ion drift within perovskites.

Simulation and optimization of a 10 A electron gun with electrostatic compression for the electron beam ion source.

PubMed

Pikin, A; Beebe, E N; Raparia, D

2013-03-01

Increasing the current density of the electron beam in the ion trap of the Electron Beam Ion Source (EBIS) in BNL's Relativistic Heavy Ion Collider facility would confer several essential benefits. They include increasing the ions' charge states, and therefore, the ions' energy out of the Booster for NASA applications, reducing the influx of residual ions in the ion trap, lowering the average power load on the electron collector, and possibly also reducing the emittance of the extracted ion beam. Here, we discuss our findings from a computer simulation of an electron gun with electrostatic compression for electron current up to 10 A that can deliver a high-current-density electron beam for EBIS. The magnetic field in the cathode-anode gap is formed with a magnetic shield surrounding the gun electrodes and the residual magnetic field on the cathode is (5 ÷ 6) Gs. It was demonstrated that for optimized gun geometry within the electron beam current range of (0.5 ÷ 10) A the amplitude of radial beam oscillations can be maintained close to 4% of the beam radius by adjusting the injection magnetic field generated by a separate magnetic coil. Simulating the performance of the gun by varying geometrical parameters indicated that the original gun model is close to optimum and the requirements to the precision of positioning the gun elements can be easily met with conventional technology.

Comparative analyses of plasma probe diagnostics techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Godyak, V. A.; Alexandrovich, B. M.

The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much asmore » an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.« less

Simulation and optimization of a 10 A electron gun with electrostatic compression for the electron beam ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pikin, A.; Beebe, E. N.; Raparia, D.

Increasing the current density of the electron beam in the ion trap of the Electron Beam Ion Source (EBIS) in BNL's Relativistic Heavy Ion Collider facility would confer several essential benefits. They include increasing the ions' charge states, and therefore, the ions' energy out of the Booster for NASA applications, reducing the influx of residual ions in the ion trap, lowering the average power load on the electron collector, and possibly also reducing the emittance of the extracted ion beam. Here, we discuss our findings from a computer simulation of an electron gun with electrostatic compression for electron current upmore » to 10 A that can deliver a high-current-density electron beam for EBIS. The magnetic field in the cathode-anode gap is formed with a magnetic shield surrounding the gun electrodes and the residual magnetic field on the cathode is (5 Division-Sign 6) Gs. It was demonstrated that for optimized gun geometry within the electron beam current range of (0.5 Division-Sign 10) A the amplitude of radial beam oscillations can be maintained close to 4% of the beam radius by adjusting the injection magnetic field generated by a separate magnetic coil. Simulating the performance of the gun by varying geometrical parameters indicated that the original gun model is close to optimum and the requirements to the precision of positioning the gun elements can be easily met with conventional technology.« less

Comparative analyses of plasma probe diagnostics techniques

NASA Astrophysics Data System (ADS)

Godyak, V. A.; Alexandrovich, B. M.

2015-12-01

The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much as an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.

Extracting functional components of neural dynamics with Independent Component Analysis and inverse Current Source Density.

PubMed

Lęski, Szymon; Kublik, Ewa; Swiejkowski, Daniel A; Wróbel, Andrzej; Wójcik, Daniel K

2010-12-01

Local field potentials have good temporal resolution but are blurred due to the slow spatial decay of the electric field. For simultaneous recordings on regular grids one can reconstruct efficiently the current sources (CSD) using the inverse Current Source Density method (iCSD). It is possible to decompose the resultant spatiotemporal information about the current dynamics into functional components using Independent Component Analysis (ICA). We show on test data modeling recordings of evoked potentials on a grid of 4 × 5 × 7 points that meaningful results are obtained with spatial ICA decomposition of reconstructed CSD. The components obtained through decomposition of CSD are better defined and allow easier physiological interpretation than the results of similar analysis of corresponding evoked potentials in the thalamus. We show that spatiotemporal ICA decompositions can perform better for certain types of sources but it does not seem to be the case for the experimental data studied. Having found the appropriate approach to decomposing neural dynamics into functional components we use the technique to study the somatosensory evoked potentials recorded on a grid spanning a large part of the forebrain. We discuss two example components associated with the first waves of activation of the somatosensory thalamus. We show that the proposed method brings up new, more detailed information on the time and spatial location of specific activity conveyed through various parts of the somatosensory thalamus in the rat.

Effect of Cuscuta reflexa Roxb on androgen-induced alopecia.

PubMed

Pandit, Shweta; Chauhan, Nagendra Singh; Dixit, V K

2008-09-01

Alopecia is a psychologically distressing condition. Androgenetic alopecia, which affects millions of men and women, is an androgen-driven disorder. Here, Cuscuta reflexa Roxb is evaluated for hair growth activity in androgen-induced alopecia. Petroleum ether extract of C. reflexa was studied for its hair growth-promoting activity. Alopecia was induced in albino mice by testosterone administration for 20 days. Its inhibition by simultaneous administration of extract was evaluated using follicular density, anagen/telogen ratio, and microscopic observation of skin sections. To investigate the mechanism of observed activity, in vitro experiments were performed to study the effect of extract and its major component on activity of 5alpha-reductase enzyme. Petroleum ether extract of C. reflexa exhibited promising hair growth-promoting activity as reflected from follicular density, anagen/telogen ratio, and skin sections. Inhibition of 5alpha-reductase activity by extract and isolate suggest that the extract reversed androgen-induced alopecia by inhibiting conversion of testosterone to dihydrotestosterone. The petroleum ether extract of C. reflexa and its isolate is useful in treatment of androgen-induced alopecia by inhibiting the enzyme 5alpha-reductase.

Removal of common organic solvents from aqueous waste streams via supercritical C02 extraction: a potential green approach to sustainable waste management in the pharmaceutical industry.

PubMed

Leazer, Johnnie L; Gant, Sean; Houck, Anthony; Leonard, William; Welch, Christopher J

2009-03-15

Supercritical CO2 extraction of aqueous streams is a convenient and effective method to remove commonly used solvents of varying polarities from aqueous waste streams. The resulting aqueous layers can potentially be sewered; whereas the organic layer can be recovered for potential reuse. Supercritical fluid extraction (SFE) is a technology that is increasingly being used in commercial processes (1). Supercritical fluids are well suited for extraction of a variety of media, including solids, natural products, and liquid products. Many supercritical fluids have low critical temperatures, allowing for extractions to be done at modestly low temperatures, thus avoiding any potential thermal decomposition of the solutes under study (2). Furthermore, the CO2 solvent strength is easily tuned by adjusting the density of the supercritical fluid (The density is proportional to the pressure of the extraction process). Since many supercritical fluids are gases at ambient temperature, the extract can be concentrated by simply venting the reaction mixture to a cyclone collection vessel, using appropriate safety protocols.

Analysis of correlation between initial alveolar bone density and apical root resorption after 12 months of orthodontic treatment without extraction

PubMed Central

Scheibel, Paula Cabrini; Ramos, Adilson Luiz; Iwaki, Lilian Cristina Vessoni; Micheletti, Kelly Regina

2014-01-01

OBJECTIVE: The aim of the present study was to investigate the correlation between initial alveolar bone density of upper central incisors (ABD-UI) and external apical root resorption (EARR) after 12 months of orthodontic movement in cases without extraction. METHODS: A total of 47 orthodontic patients 11 years old or older were submitted to periapical radiography of upper incisors prior to treatment (T1) and after 12 months of treatment (T2). ABD-UI and EARR were measured by means of densitometry. RESULTS: No statistically significant correlation was found between initial ABD-UI and EARR at T2 (r = 0.149; p = 0.157). CONCLUSION: Based on the present findings, alveolar density assessed through periapical radiography is not predictive of root resorption after 12 months of orthodontic treatment in cases without extraction. PMID:25715722

Globally optimal superconducting magnets part I: minimum stored energy (MSE) current density map.

PubMed

Tieng, Quang M; Vegh, Viktor; Brereton, Ian M

2009-01-01

An optimal current density map is crucial in magnet design to provide the initial values within search spaces in an optimization process for determining the final coil arrangement of the magnet. A strategy for obtaining globally optimal current density maps for the purpose of designing magnets with coaxial cylindrical coils in which the stored energy is minimized within a constrained domain is outlined. The current density maps obtained utilising the proposed method suggests that peak current densities occur around the perimeter of the magnet domain, where the adjacent peaks have alternating current directions for the most compact designs. As the dimensions of the domain are increased, the current density maps yield traditional magnet designs of positive current alone. These unique current density maps are obtained by minimizing the stored magnetic energy cost function and therefore suggest magnet coil designs of minimal system energy. Current density maps are provided for a number of different domain arrangements to illustrate the flexibility of the method and the quality of the achievable designs.

Feasibility of Surfactant-Free Supported Emulsion Liquid Membrane Extraction

NASA Technical Reports Server (NTRS)

Hu, Shih-Yao B.; Li, Jin; Wiencek, John M.

2001-01-01

Supported emulsion liquid membrane (SELM) is an effective means to conduct liquid-liquid extraction. SELM extraction is particularly attractive for separation tasks in the microgravity environment where density difference between the solvent and the internal phase of the emulsion is inconsequential and a stable dispersion can be maintained without surfactant. In this research, dispersed two-phase flow in SELM extraction is modeled using the Lagrangian method. The results show that SELM extraction process in the microgravity environment can be simulated on earth by matching the density of the solvent and the stripping phase. Feasibility of surfactant-free SELM (SFSELM) extraction is assessed by studying the coalescence behavior of the internal phase in the absence of the surfactant. Although the contacting area between the solvent and the internal phase in SFSELM extraction is significantly less than the area provided by regular emulsion due to drop coalescence, it is comparable to the area provided by a typical hollow-fiber membrane. Thus, the stripping process is highly unlikely to become the rate-limiting step in SFSELM extraction. SFSELM remains an effective way to achieve simultaneous extraction and stripping and is able to eliminate the equilibrium limitation in the typical solvent extraction processes. The SFSELM design is similar to the supported liquid membrane design in some aspects.

Two-dimensional relativistic space charge limited current flow in the drift space

NASA Astrophysics Data System (ADS)

Liu, Y. L.; Chen, S. H.; Koh, W. S.; Ang, L. K.

2014-04-01

Relativistic two-dimensional (2D) electrostatic (ES) formulations have been derived for studying the steady-state space charge limited (SCL) current flow of a finite width W in a drift space with a gap distance D. The theoretical analyses show that the 2D SCL current density in terms of the 1D SCL current density monotonically increases with D/W, and the theory recovers the 1D classical Child-Langmuir law in the drift space under the approximation of uniform charge density in the transverse direction. A 2D static model has also been constructed to study the dynamical behaviors of the current flow with current density exceeding the SCL current density, and the static theory for evaluating the transmitted current fraction and minimum potential position have been verified by using 2D ES particle-in-cell simulation. The results show the 2D SCL current density is mainly determined by the geometrical effects, but the dynamical behaviors of the current flow are mainly determined by the relativistic effect at the current density exceeding the SCL current density.

Component extraction on CT volumes of assembled products using geometric template matching

NASA Astrophysics Data System (ADS)

Muramatsu, Katsutoshi; Ohtake, Yutaka; Suzuki, Hiromasa; Nagai, Yukie

2017-03-01

As a method of non-destructive internal inspection, X-ray computed tomography (CT) is used not only in medical applications but also for product inspection. Some assembled products can be divided into separate components based on density, which is known to be approximately proportional to CT values. However, components whose densities are similar cannot be distinguished using the CT value driven approach. In this study, we proposed a new component extraction algorithm from the CT volume, using a set of voxels with an assigned CT value with the surface mesh as the template rather than the density. The method has two main stages: rough matching and fine matching. At the rough matching stage, the position of candidate targets is identified roughly from the CT volume, using the template of the target component. At the fine matching stage, these candidates are precisely matched with the templates, allowing the correct position of the components to be detected from the CT volume. The results of two computational experiments showed that the proposed algorithm is able to extract components with similar density within the assembled products on CT volumes.

A Robust Gradient Based Method for Building Extraction from LiDAR and Photogrammetric Imagery.

PubMed

Siddiqui, Fasahat Ullah; Teng, Shyh Wei; Awrangjeb, Mohammad; Lu, Guojun

2016-07-19

Existing automatic building extraction methods are not effective in extracting buildings which are small in size and have transparent roofs. The application of large area threshold prohibits detection of small buildings and the use of ground points in generating the building mask prevents detection of transparent buildings. In addition, the existing methods use numerous parameters to extract buildings in complex environments, e.g., hilly area and high vegetation. However, the empirical tuning of large number of parameters reduces the robustness of building extraction methods. This paper proposes a novel Gradient-based Building Extraction (GBE) method to address these limitations. The proposed method transforms the Light Detection And Ranging (LiDAR) height information into intensity image without interpolation of point heights and then analyses the gradient information in the image. Generally, building roof planes have a constant height change along the slope of a roof plane whereas trees have a random height change. With such an analysis, buildings of a greater range of sizes with a transparent or opaque roof can be extracted. In addition, a local colour matching approach is introduced as a post-processing stage to eliminate trees. This stage of our proposed method does not require any manual setting and all parameters are set automatically from the data. The other post processing stages including variance, point density and shadow elimination are also applied to verify the extracted buildings, where comparatively fewer empirically set parameters are used. The performance of the proposed GBE method is evaluated on two benchmark data sets by using the object and pixel based metrics (completeness, correctness and quality). Our experimental results show the effectiveness of the proposed method in eliminating trees, extracting buildings of all sizes, and extracting buildings with and without transparent roof. When compared with current state-of-the-art building extraction methods, the proposed method outperforms the existing methods in various evaluation metrics.

A Robust Gradient Based Method for Building Extraction from LiDAR and Photogrammetric Imagery

PubMed Central

Siddiqui, Fasahat Ullah; Teng, Shyh Wei; Awrangjeb, Mohammad; Lu, Guojun

2016-01-01

Existing automatic building extraction methods are not effective in extracting buildings which are small in size and have transparent roofs. The application of large area threshold prohibits detection of small buildings and the use of ground points in generating the building mask prevents detection of transparent buildings. In addition, the existing methods use numerous parameters to extract buildings in complex environments, e.g., hilly area and high vegetation. However, the empirical tuning of large number of parameters reduces the robustness of building extraction methods. This paper proposes a novel Gradient-based Building Extraction (GBE) method to address these limitations. The proposed method transforms the Light Detection And Ranging (LiDAR) height information into intensity image without interpolation of point heights and then analyses the gradient information in the image. Generally, building roof planes have a constant height change along the slope of a roof plane whereas trees have a random height change. With such an analysis, buildings of a greater range of sizes with a transparent or opaque roof can be extracted. In addition, a local colour matching approach is introduced as a post-processing stage to eliminate trees. This stage of our proposed method does not require any manual setting and all parameters are set automatically from the data. The other post processing stages including variance, point density and shadow elimination are also applied to verify the extracted buildings, where comparatively fewer empirically set parameters are used. The performance of the proposed GBE method is evaluated on two benchmark data sets by using the object and pixel based metrics (completeness, correctness and quality). Our experimental results show the effectiveness of the proposed method in eliminating trees, extracting buildings of all sizes, and extracting buildings with and without transparent roof. When compared with current state-of-the-art building extraction methods, the proposed method outperforms the existing methods in various evaluation metrics. PMID:27447631

Current density tensors

NASA Astrophysics Data System (ADS)

Lazzeretti, Paolo

2018-04-01

It is shown that nonsymmetric second-rank current density tensors, related to the current densities induced by magnetic fields and nuclear magnetic dipole moments, are fundamental properties of a molecule. Together with magnetizability, nuclear magnetic shielding, and nuclear spin-spin coupling, they completely characterize its response to magnetic perturbations. Gauge invariance, resolution into isotropic, deviatoric, and antisymmetric parts, and contributions of current density tensors to magnetic properties are discussed. The components of the second-rank tensor properties are rationalized via relationships explicitly connecting them to the direction of the induced current density vectors and to the components of the current density tensors. The contribution of the deviatoric part to the average value of magnetizability, nuclear shielding, and nuclear spin-spin coupling, uniquely determined by the antisymmetric part of current density tensors, vanishes identically. The physical meaning of isotropic and anisotropic invariants of current density tensors has been investigated, and the connection between anisotropy magnitude and electron delocalization has been discussed.

21 CFR 177.1610 - Polyethylene, chlorinated.

Code of Federal Regulations, 2014 CFR

2014-04-01

... chlorination of polyethylene conforming to the density, maximum n-hexane extractable fraction, and maximum..._federal_regulations/ibr_locations.html.), and has a 7.0 percent maximum extractable fraction in n-hexane...

Transcriptional effect of an Aframomum angustifolium seed extract on human cutaneous cells using low-density DNA chips.

PubMed

Bonnet-Duquennoy, Mathilde; Dumas, Marc; Debacker, Adeline; Lazou, Kristell; Talbourdet, Sylvie; Franchi, Jocelyne; Heusèle, Catherine; André, Patrice; Schnebert, Sylvianne; Bonté, Frédéric; Kurfürst, Robin

2007-06-01

Studying photoexposed and photoprotected skin biopsies from young and aged women, it has been found that a specific zone, composed of the basal layers of the epidermis, the dermal epidermal junction, and the superficial dermis, is major target of aging and reactive oxygen species. We showed that this zone is characterized by significant variations at a transcriptional and/or protein levels. Using low-density DNA chip technology, we evaluated the effect of a natural mixture of Aframomum angustifolium seed extract containing labdane diterpenoids on these aging markers. Expression profiles of normal human fibroblasts (NHF) were studied using a customized cDNA macroarray system containing genes covering dermal structure, inflammatory responses, and oxidative stress defense mechanisms. For normal human keratinocyte (NHK) investigations, we chose OLISA technique, a sensitive and quantitative method developed by BioMérieux specifically designed to investigate cell death, proliferation, epidermal structure, differentiation, and oxidative stress defense response. We observed that this extract strongly modified gene expression profiles of treated NHK, but weakly for NHF. This extract regulated antioxidant defenses, dermal-epidermal junction components, and epidermal renewal-related genes. Using low-density DNA chip technology, we identified new potential actions of A. angustifolium seed extract on skin aging.

Comparison between the Hypolipidemic Activity of Parsley and Carob in Hypercholesterolemic Male Rats

PubMed Central

Al-Seeni, Madeha N.; Al-Ghamdi, Habibah B.

2017-01-01

Hypercholesterolemia is commonly associated with obesity that leads to heart diseases and diabetes. The hepatocardioprotective activity of parsley and carob methanol extract was tested in hypercholesterolemic male rats. Twenty-four male albino rats were divided into four groups (n = 6). Group 1 was the negative control group fed with fat rich diet, group 2 (G2) was hypercholesterolemic rats fed with fat rich diet with 2% cholesterol, and group 3 and group 4 (G3 and G4) were hypercholesterolemic rats supplemented with 2% cholesterol and cotreated with 20% w/w parsley seed methanol extract and 20% w/w carob legume methanol extract, respectively. The experiment was conducted for eight weeks. The positive hypercholesterolemic rats showed significant increase in serum levels of total cholesterol, triglycerides, low density lipoprotein (LDL), very low density lipoprotein (VLDL), lactate dehydrogenase (LDH), creatine kinase-mb, liver function enzymes, and decrease in the high density lipoproteins (HDL). Moreover, heart and liver tissues were ameliorated and nearly restored their normal appearance. It could be concluded that both parsley and carob extracts supplementations have a protective effect against hyperlipidemia and improved the histological alteration in heart and liver tissues. The methanol extract of parsley appeared to be more efficient than that of carob in lowering hypercholesterolemia. PMID:29094044

Real-Time Counting People in Crowded Areas by Using Local Empirical Templates and Density Ratios

NASA Astrophysics Data System (ADS)

Hung, Dao-Huu; Hsu, Gee-Sern; Chung, Sheng-Luen; Saito, Hideo

In this paper, a fast and automated method of counting pedestrians in crowded areas is proposed along with three contributions. We firstly propose Local Empirical Templates (LET), which are able to outline the foregrounds, typically made by single pedestrians in a scene. LET are extracted by clustering foregrounds of single pedestrians with similar features in silhouettes. This process is done automatically for unknown scenes. Secondly, comparing the size of group foreground made by a group of pedestrians to that of appropriate LET captured in the same image patch with the group foreground produces the density ratio. Because of the local scale normalization between sizes, the density ratio appears to have a bound closely related to the number of pedestrians who induce the group foreground. Finally, to extract the bounds of density ratios for groups of different number of pedestrians, we propose a 3D human models based simulation in which camera viewpoints and pedestrians' proximity are easily manipulated. We collect hundreds of typical occluded-people patterns with distinct degrees of human proximity and under a variety of camera viewpoints. Distributions of density ratios with respect to the number of pedestrians are built based on the computed density ratios of these patterns for extracting density ratio bounds. The simulation is performed in the offline learning phase to extract the bounds from the distributions, which are used to count pedestrians in online settings. We reveal that the bounds seem to be invariant to camera viewpoints and humans' proximity. The performance of our proposed method is evaluated with our collected videos and PETS 2009's datasets. For our collected videos with the resolution of 320x240, our method runs in real-time with good accuracy and frame rate of around 30 fps, and consumes a small amount of computing resources. For PETS 2009's datasets, our proposed method achieves competitive results with other methods tested on the same datasets [1], [2].

Numerical investigation of split flows by gravity currents into two-layered stratified water bodies

NASA Astrophysics Data System (ADS)

Cortés, A.; Wells, M. G.; Fringer, O. B.; Arthur, R. S.; Rueda, F. J.

2015-07-01

The behavior of a two-dimensional (2-D) gravity current impinging upon a density step in a two-layered stratified basin is analyzed using a high-resolution Reynolds-Averaged Navier-Stokes model. The gravity current splits at the density step, and the portion of the buoyancy flux becoming an interflow is largely controlled by the vertical distribution of velocity and density within the gravity current and the magnitude of the density step between the two ambient layers. This is in agreement with recent laboratory observations. The strongest changes in the ambient density profiles occur as a result of the impingement of supercritical currents with strong density contrasts, for which a large portion of the gravity current detaches from the bottom and becomes an interflow. We characterize the current partition process in the simulated experiments using the densimetric Froude number of the current (Fr) across the density step (upstream and downstream). When underflows are formed, more supercritical currents are observed downstream of the density step compared to upstream (Fru < Frd), and thus, stronger mixing of the current with the ambient water downstream. However, when split flows and interflows are formed, smaller Fr values are identified after the current crosses the density step (Fru > Frd), which indicates lower mixing between the current and ambient water after the impingement due to the significant stripping of interfacial material at the density step.

Supplementation with Watermelon Extract Reduces Total Cholesterol and LDL Cholesterol in Adults with Dyslipidemia under the Influence of the MTHFR C677T Polymorphism.

PubMed

Massa, Nayara M L; Silva, Alexandre S; de Oliveira, Caio V C; Costa, Maria J C; Persuhn, Darlene C; Barbosa, Carlos V S; Gonçalves, Maria da C R

2016-08-01

Dyslipidemia and genetic polymorphisms are associated with increased risk for developing cardiovascular diseases, and watermelon appears to have the potential to improve hyperlipidemia due to the presence of nutrients such as arginine and citrulline. To test the hypolipidemic effect of watermelon extract (Citrullus lanatus) and the influence of the methylenetetrahydrofolate reductase genotype (MTHFR C677T) on supplementation response. This is an experimental clinical phase II randomized and double-blind study. Forty-three subjects with dyslipidemia were randomly divided into 2 groups: experimental (n = 22) and control (n = 21) groups. The subjects were supplemented daily for 42 days with 6 g of watermelon extract or a mixture of carbohydrates (sucrose/glucose/fructose). The use of watermelon extract reduced plasma total cholesterol (p < 0.05) and low-density lipoprotein (p < 0.01) without modifying triglycerides, high-density lipoprotein, and very low-density lipoprotein values. Only carriers of the T allele (MTHFR C677T) showed decreasing concentrations of low-density lipoprotein (p < 0.01). No changes in anthropometric parameters analyzed were observed. This is the first study to demonstrate the beneficial effect of the consumption of watermelon extract in reducing plasma levels of lipids in humans. The MTHFR C677T polymorphism did not affect the plasma lipid concentration but made individuals more responsive to treatment with watermelon. The consumption of this functional food represents an alternative therapy in the combined treatment of patients with dyslipidemia, promoting health and minimizing the development of risk factors for cardiovascular diseases.

A hybrid electron cyclotron resonance metal ion source with integrated sputter magnetron for the production of an intense Al{sup +} ion beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weichsel, T., E-mail: tim.weichsel@fep.fraunhofer.de; Hartung, U.; Kopte, T.

2015-09-15

A metal ion source prototype has been developed: a combination of magnetron sputter technology with 2.45 GHz electron cyclotron resonance (ECR) ion source technology—a so called magnetron ECR ion source (MECRIS). An integrated ring-shaped sputter magnetron with an Al target is acting as a powerful metal atom supply in order to produce an intense current of singly charged metal ions. Preliminary experiments show that an Al{sup +} ion current with a density of 167 μA/cm{sup 2} is extracted from the source at an acceleration voltage of 27 kV. Spatially resolved double Langmuir probe measurements and optical emission spectroscopy were usedmore » to study the plasma states of the ion source: sputter magnetron, ECR, and MECRIS plasma. Electron density and temperature as well as Al atom density were determined as a function of microwave and sputter magnetron power. The effect of ECR heating is strongly pronounced in the center of the source. There the electron density is increased by one order of magnitude from 6 × 10{sup 9} cm{sup −3} to 6 × 10{sup 10} cm{sup −3} and the electron temperature is enhanced from about 5 eV to 12 eV, when the ECR plasma is ignited to the magnetron plasma. Operating the magnetron at constant power, it was observed that its discharge current is raised from 1.8 A to 4.8 A, when the ECR discharge was superimposed with a microwave power of 2 kW. At the same time, the discharge voltage decreased from about 560 V to 210 V, clearly indicating a higher plasma density of the MECRIS mode. The optical emission spectrum of the MECRIS plasma is dominated by lines of excited Al atoms and shows a significant contribution of lines arising from singly ionized Al. Plasma emission photography with a CCD camera was used to prove probe measurements and to identify separated plasma emission zones originating from the ECR and magnetron discharge.« less

The Density Functional Theory of Flies: Predicting distributions of interacting active organisms

NASA Astrophysics Data System (ADS)

Kinkhabwala, Yunus; Valderrama, Juan; Cohen, Itai; Arias, Tomas

On October 2nd, 2016, 52 people were crushed in a stampede when a crowd panicked at a religious gathering in Ethiopia. The ability to predict the state of a crowd and whether it is susceptible to such transitions could help prevent such catastrophes. While current techniques such as agent based models can predict transitions in emergent behaviors of crowds, the assumptions used to describe the agents are often ad hoc and the simulations are computationally expensive making their application to real-time crowd prediction challenging. Here, we pursue an orthogonal approach and ask whether a reduced set of variables, such as the local densities, are sufficient to describe the state of a crowd. Inspired by the theoretical framework of Density Functional Theory, we have developed a system that uses only measurements of local densities to extract two independent crowd behavior functions: (1) preferences for locations and (2) interactions between individuals. With these two functions, we have accurately predicted how a model system of walking Drosophila melanogaster distributes itself in an arbitrary 2D environment. In addition, this density-based approach measures properties of the crowd from only observations of the crowd itself without any knowledge of the detailed interactions and thus it can make predictions about the resulting distributions of these flies in arbitrary environments, in real-time. This research was supported in part by ARO W911NF-16-1-0433.

Correlation between border traps and exposed surface properties in gate recessed normally-off Al2O3/GaN MOSFET

NASA Astrophysics Data System (ADS)

Yin, Ruiyuan; Li, Yue; Sun, Yu; Wen, Cheng P.; Hao, Yilong; Wang, Maojun

2018-06-01

We report the effect of the gate recess process and the surface of as-etched GaN on the gate oxide quality and first reveal the correlation between border traps and exposed surface properties in normally-off Al2O3/GaN MOSFET. The inductively coupled plasma (ICP) dry etching gate recess with large damage presents a rough and active surface that is prone to form detrimental GaxO validated by atomic force microscopy and X-ray photoelectron spectroscopy. Lower drain current noise spectral density of the 1/f form and less dispersive ac transconductance are observed in GaN MOSFETs fabricated with oxygen assisted wet etching compared with devices based on ICP dry etching. One decade lower density of border traps is extracted in devices with wet etching according to the carrier number fluctuation model, which is consistent with the result from the ac transconductance method. Both methods show that the density of border traps is skewed towards the interface, indicating that GaxO is of higher trap density than the bulk gate oxide. GaxO located close to the interface is the major location of border traps. The damage-free oxidation assisted wet etching gate recess technique presents a relatively smooth and stable surface, resulting in lower border trap density, which would lead to better MOS channel quality and improved device reliability.

Estimating parameters from rotating ring disc electrode measurements

DOE PAGES

Santhanagopalan, Shriram; White, Ralph E.

2017-10-21

Rotating ring disc electrode (RRDE) experiments are a classic tool for investigating kinetics of electrochemical reactions. Several standardized methods exist for extracting transport parameters and reaction rate constants using RRDE measurements. Here in this work, we compare some approximate solutions to the convective diffusion used popularly in the literature to a rigorous numerical solution of the Nernst-Planck equations coupled to the three dimensional flow problem. In light of these computational advancements, we explore design aspects of the RRDE that will help improve sensitivity of our parameter estimation procedure to experimental data. We use the oxygen reduction in acidic media involvingmore » three charge transfer reactions and a chemical reaction as an example, and identify ways to isolate reaction currents for the individual processes in order to accurately estimate the exchange current densities.« less

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

PubMed Central

2015-01-01

Abstract The basic properties of the near‐Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail‐like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets. PMID:27722039

Hypolipidemic and antioxidant activity of the aqueous extract from the uneaten pulp of the fruit from Cordia dichotoma in healthy and hyperlipidemic Wistar albino rats.

PubMed

El-Newary, Samah A; Sulieman, A M; El-Attar, S R; Sitohy, M Z

2016-07-01

Hyperlipidemia is a major risk factor for coronary heart disease. Hyperlipidemia increases the incidence of myocardial ischemia and cardiac events. This study evaluated the potential hypolipidemic and antioxidant action of the aqueous extract from the uneaten pulp of the fruit from Cordia dichotoma ("CDNP extract"). In vivo studies were performed for 10 weeks on dietary hyperlipidemic and healthy Wistar albino rat models that received two dose levels of the CDNP extract (0.50 and 1.00 g/kg body weight). Serum lipid profiles were determined for the experimental animals. Dietary hyperlipidemic rats were characterized by an elevated lipid profile compared to the healthy control, i.e., increased levels of serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), and triglycerides (TG), although the level of high-density lipoprotein (HDL-C) was reduced. Levels of antioxidant enzymes, i.e., glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT), were significantly higher in the dietary hyperlipidemic rats than in the normal healthy ones, while the level of malondialdehyde (MDA) was significantly lower. Force-feeding hyperlipidemic Wistar albino rats with the CDNP extract at two doses decreased TC, LDL-C, VLDL-C, and TG to normal levels. The risk ratio, which was as high as 870 % for the hyperlipidemic rats was decreased by the treatment to levels close to that calculated for the healthy control rats. Levels of high-density lipoprotein cholesterol (HDL-C) were very low in the hyperlipidemic Wistar albino rats but increased significantly when CDNP extract was adminstered, attaining similar HDL-C levels to those of healthy control rats. Treatment with the CDNP extract also improved the levels of antioxidant enzymes (GR, GST, GPx, SOD, and CAT) in hyperlipidemic Wistar albino rats. Thus, the CDNP extract improves the lipid metabolism of healthy and hyperlipidemic Wistar albino rats and can be employed in the management of dietary hyperlipidemia.

Demonstrating Test-Retest Reliability of Electrophysiological Measures for Healthy Adults in a Multisite Study of Biomarkers of Antidepressant Treatment Response

PubMed Central

Tenke, Craig E.; Kayser, Jürgen; Pechtel, Pia; Webb, Christian A.; Dillon, Daniel G.; Goer, Franziska; Murray, Laura; Deldin, Patricia; Kurian, Benji T.; McGrath, Patrick J.; Parsey, Ramin; Trivedi, Madhukar; Fava, Maurizio; Weissman, Myrna M.; McInnis, Melvin; Abraham, Karen; Alvarenga, Jorge; Alschuler, Daniel M.; Cooper, Crystal; Pizzagalli, Diego A.; Bruder, Gerard E.

2016-01-01

Growing evidence suggests that loudness dependency of auditory evoked potentials (LDAEP) and resting EEG alpha and theta may be biological markers for predicting response to antidepressants. In spite of this promise, little is known about the joint reliability of these markers, and thus their clinical applicability. New, standardized procedures were developed to improve the compatibility of data acquired with different EEG platforms, and used to examine test-retest reliability for the three electrophysiological measures selected for a multisite project—Establishing Moderators and Biosignatures of Antidepressant Response for Clinical Care (EMBARC). Thirty nine healthy controls across four clinical research sites were tested in two sessions separated by about one week. Resting EEG (eyes-open and eyes-closed conditions) was recorded and LDAEP measured using binaural tones (1000 Hz, 40 ms) at five intensities (60–100 dB SPL). Principal components analysis (PCA) of current source density (CSD) waveforms reduced volume conduction and provided reference-free measures of resting EEG alpha and N1 dipole activity to tones from auditory cortex. Low Resolution Electromagnetic Tomography (LORETA) extracted resting theta current density measures corresponding to rostral anterior cingulate (rACC), which has been implicated in treatment response. There were no significant differences in posterior alpha, N1 dipole or rACC theta across sessions. Test-retest reliability was .84 for alpha, .87 for N1 dipole, and .70 for theta rACC current density. The demonstration of good-to-excellent reliability for these measures provides a template for future EEG/ERP studies from multiple testing sites, and an important step for evaluating them as biomarkers for predicting treatment response. PMID:28000259

Advanced control of neutral beam injected power in DIII-D

DOE PAGES

Pawley, Carl J.; Crowley, Brendan J.; Pace, David C.; ...

2017-03-23

In the DIII-D tokamak, one of the most powerful techniques to control the density, temperature and plasma rotation is by eight independently modulated neutral beam sources with a total power of 20 MW. The rapid modulation requires a high degree of reproducibility and precise control of the ion source plasma and beam acceleration voltage. Recent changes have been made to the controls to provide a new capability to smoothly vary the beam current and beam voltage during a discharge, while maintaining the modulation capability. The ion source plasma inside the arc chamber is controlled through feedback from the Langmuir probesmore » measuring plasma density near the extraction end. To provide the new capability, the plasma control system (PCS) has been enabled to change the Langmuir probe set point and the beam voltage set point in real time. When the PCS varies the Langmuir set point, the plasma density is directly controlled in the arc chamber, thus changing the beam current (perveance) and power going into the tokamak. Alternately, the PCS can sweep the beam voltage set point by 20 kV or more and adjust the Langmuir probe setting to match, keeping the perveance constant and beam divergence at a minimum. This changes the beam power and average neutral particle energy, which changes deposition in the tokamak plasma. The ion separating magnetic field must accurately match the beam voltage to protect the beam line. To do this, the magnet current control accurately tracks the beam voltage set point. In conclusion, these new capabilities allow continuous in-shot variation of neutral beam ion energy to complement« less

Demonstrating test-retest reliability of electrophysiological measures for healthy adults in a multisite study of biomarkers of antidepressant treatment response.

PubMed

Tenke, Craig E; Kayser, Jürgen; Pechtel, Pia; Webb, Christian A; Dillon, Daniel G; Goer, Franziska; Murray, Laura; Deldin, Patricia; Kurian, Benji T; McGrath, Patrick J; Parsey, Ramin; Trivedi, Madhukar; Fava, Maurizio; Weissman, Myrna M; McInnis, Melvin; Abraham, Karen; E Alvarenga, Jorge; Alschuler, Daniel M; Cooper, Crystal; Pizzagalli, Diego A; Bruder, Gerard E

2017-01-01

Growing evidence suggests that loudness dependency of auditory evoked potentials (LDAEP) and resting EEG alpha and theta may be biological markers for predicting response to antidepressants. In spite of this promise, little is known about the joint reliability of these markers, and thus their clinical applicability. New standardized procedures were developed to improve the compatibility of data acquired with different EEG platforms, and used to examine test-retest reliability for the three electrophysiological measures selected for a multisite project-Establishing Moderators and Biosignatures of Antidepressant Response for Clinical Care (EMBARC). Thirty-nine healthy controls across four clinical research sites were tested in two sessions separated by about 1 week. Resting EEG (eyes-open and eyes-closed conditions) was recorded and LDAEP measured using binaural tones (1000 Hz, 40 ms) at five intensities (60-100 dB SPL). Principal components analysis of current source density waveforms reduced volume conduction and provided reference-free measures of resting EEG alpha and N1 dipole activity to tones from auditory cortex. Low-resolution electromagnetic tomography (LORETA) extracted resting theta current density measures corresponding to rostral anterior cingulate (rACC), which has been implicated in treatment response. There were no significant differences in posterior alpha, N1 dipole, or rACC theta across sessions. Test-retest reliability was .84 for alpha, .87 for N1 dipole, and .70 for theta rACC current density. The demonstration of good-to-excellent reliability for these measures provides a template for future EEG/ERP studies from multiple testing sites, and an important step for evaluating them as biomarkers for predicting treatment response. © 2016 Society for Psychophysiological Research.

Assessment of Power Potential of Tidal Currents and Impacts of Power Extraction on Flow Speeds in Indonesia

NASA Astrophysics Data System (ADS)

Orhan, K.; Mayerle, R.

2016-12-01

A methodology comprising of the estimates of power yield, evaluation of the effects of power extraction on flow conditions, and near-field investigations to deliver wake characteritics, recovery and interactions is described and applied to several straits in Indonesia. Site selection is done with high-resolution, three-dimensional flow models providing sufficient spatiotemporal coverage. Much attention has been given to the meteorological forcing, and conditions at the open sea boundaries to adequately capture the density gradients and flow fields. Model verification using tidal records shows excellent agreement. Sites with adequate depth for the energy conversion using horizontal axis tidal turbines, average kinetic power density greater than 0.5 kW/m2, and surface area larger than 0.5km2 are defined as energy hotspots. Spatial variation of the average extractable electric power is determined, and annual tidal energy resource is estimated for the straits in question. The results showed that the potential for tidal power generation in Indonesia is likely to exceed previous predictions reaching around 4,800MW. To assess the impact of the devices, flexible mesh models with higher resolutions have been developed. Effects on flow conditions, and near-field turbine wakes are resolved in greater detail with triangular horizontal grids. The energy is assumed to be removed uniformly by sub-grid scale arrays of turbines, and calculations are made based on velocities at the hub heights of the devices. An additional drag force resulting in dissipation of the pre-existing kinetic power from %10 to %60 within a flow cross-section is introduced to capture the impacts. It was found that the effect of power extraction on water levels and flow speeds in adjacent areas is not significant. Results show the effectivess of the method to capture wake characteritics and recovery reasonably well with low computational cost.

[Effect of Yunnan Baiyao capsules on the socket healing of impacted mandibular third molar extraction].

PubMed

Zhang, Kai; Wang, Xing; Zhang, Wei; Zhao, Ji-zhi; Dong, Hui

2012-04-01

To investigate the effect of the traditional Chinese medicine Yunan Baiyao on the socket healing of impacted mandibular third molar extraction. A total of 200 patients requiring extractions of impacted mandibular wisdom teeth were randomized into the treatment group and the control group in a double-blinded manner, and Yunan Baiyao capsules or placebo capsules (2 g/d) were orally administered for 28 days after the operation. Dental quantitative CT scan was performed, and the volume and density of new bone at the extraction site were measured two month after operation. A total of 188 patients completed the study. No adverse events related to the medication occurred. The volume of new bone was (477.39 ± 166.47) mm(3) in the treatment group and (442.65 ± 143.58) mm(3) in the control group, which was not significantly different between the two groups. The density of new bone was (296.90 ± 37.94) mg/cm(3) in the treatment group and (298.54 ± 40.21) mg/cm(3) in the control group, which was not significantly different between the two groups. The number of the teeth root, the impacted conditions, whether or not retainning the alveolar septum, suturing soft tissues of the extraction site and blood clot formation within 1 week after operation were significantly correlated with the volume of new bone. Yunnan Baiyao capsules has no effect on the volume and density of new bone at the extraction site two months after operation following extractions of impacted mandibular third molars.

IMMUNO-MODULATORY PROPERTIES OF PREBIOTICS EXTRACTED FROM vernonia amygdalina.

PubMed

Im, Ezeonu; Ae, Asuquo; Bn, Ukwah; Po, Ukoha

2016-01-01

Vernonia amygdalina , commonly called bitter-leaf, is widely consumed in many parts of Africa, and Nigeria, in particular. The leaf extract has been reported to have antimicrobial, anti-plasmodial, anti-helminthic, as well as prebiotic properties, but its immuno-modulatory effects have not been well-studied, neither have the prebiotics been identified. This study evaluated the immuno-modulatory properties of the aqueous leaf extract and identified the prebiotic components. The immuno-modulatory potential was evaluated by monitoring the effects of oral administration of the extract on immunological, haematological and lipid profiles of Rattus norvegicus , while the prebiotic components were identified by thin layer chromatography (TLC), following liquid-liquid fractionation of the extract. Consumption of the extract caused significant increases in CD4+-, white blood cell-, total lymphocyte- and high density lipid (HDL) counts; decreases in low density lipid (LDL) and triglycerides and no significant effect on haemoglobin (Hb) and packed cell volume (PCV) in the blood of test animals. The water-soluble fraction of the extract contained most of the phyto-constituents of the extract and Thin Layer Chromatographic analysis of the fraction revealed the presence of fructo-oligosaccharide and galacto-oligosaccharide prebiotics. The results from this study have shown that the aqueous leaf extract of V. amygdalina has positive immune-modulatory and haematologic effects and contains some important prebiotic compounds.

Novel nitrogen doped carbon dots for corrosion inhibition of carbon steel in 1 M HCl solution

NASA Astrophysics Data System (ADS)

Cui, Mingjun; Ren, Siming; Zhao, Haichao; Wang, Liping; Xue, Qunji

2018-06-01

Nitrogen doped carbon dots (NCDs) were synthesized and used for inhibiting the corrosion of Q235 carbon steel in hydrochloric acid (HCl) solution. Inhibition effectiveness in short- and long-term immersion was examined using electrochemical measurements, weight loss and surface analysis. Results revealed the inhibition efficiency was improved significantly after adding NCDs and strongly dependent on the concentration of NCDs. SVET results showed that the sample immersed in HCl solution with NCDs showed lower anodic current density mapping than that in blank HCl solution. According to the data extracted from the Langmuir adsorption, the absorption of NCDs involved both chemisorption and physisorption.

Analysis of Chameleonic Change of Red Cabbage Depending on Broad pH Range for Dye-Sensitized Solar Cells.

PubMed

Park, Kyung Hee; Kim, Tae Young; Ko, Hyun Seok; Han, Eun Mi; Lee, Suk-Ho; Kim, Jung-Hun; Lee, Jae Wook

2015-08-01

Dye-sensitized solar cells (DSSCs) were assembled using natural dyes extracted from red cabbage as a sensitizer. In this work, we investigated the adsorption characteristics and the electrochemical behavior for harvesting sunlight and electron transfer in red cabbage DSSCs under different solvents and pH. For the red cabbage dye-sensitized electrode adsorbed at pH 3.5, the solar cell yields a short-circuit current density (Jsc) of 1.60 mA/cm2, a photovoltage (Vcc) of 0.46 V, and a fill factor of 0.55, corresponding to an energy conversion efficiency (η) of 0.41%.

Investigation of terbium scandate as an alternative gate dielectric in fully depleted transistors

NASA Astrophysics Data System (ADS)

Roeckerath, M.; Lopes, J. M. J.; Özben, E. Durǧun; Urban, C.; Schubert, J.; Mantl, S.; Jia, Y.; Schlom, D. G.

2010-01-01

Terbium scandate thin films were deposited by e-gun evaporation on (100) silicon substrates. Rutherford backscattering spectrometry and x-ray diffraction studies revealed homogeneous chemical compositions of the films. A dielectric constant of 26 and CV-curves with small hystereses were measured as well as low leakage current densities of <1 nA/cm2. Fully depleted n-type field-effect transistors on thin silicon-on-insulator substrates with terbium scandate gate dielectrics were fabricated with a gate-last process. The devices show inverse subthreshold slopes of 80 mV/dec and a carrier mobility for electrons of 225 cm2/V•s was extracted.

Oxygen and iron production by electrolytic smelting of lunar soil

NASA Technical Reports Server (NTRS)

Colson, R. O.; Haskin, L. A.

1991-01-01

Oxygen, present in abundance in nearly all lunar materials, can theoretically be extracted by molten silicate electrolysis from any known lunar rock. Derivation of oxygen by this method has been amply demonstrated experimentally in silicate melts of a variety of compositions. This work can be divided into three categories: (1) measurement of solubilities of metals (atomic) in silicate melts; (2) electrolysis experiments under various conditions of temperature, container material, electrode configuration, current density, melt composition, and sample mass (100 to 2000 mg) measuring energy required and character of resulting products; and (3) theoretical assessment of compositional requirements for steady state operations of an electrolysis cell.

Resonant inelastic soft x-ray scattering of CdS: a two-dimensional electronic structure map approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinhardt, L.; Fuchs, O.; Fleszar, A.

2008-09-24

Resonant inelastic x-ray scattering (RIXS) with soft x-rays is uniquely suited to study the elec-tronic structure of a variety of materials, but is currently limited by low (fluorescence yield) count rates. This limitation is overcome with a new high-transmission spectrometer that allows to measure soft x-ray RIXS"maps." The S L2,3 RIXS map of CdS is discussed and compared with density functional calculations. The map allows the extraction of decay channel-specific"absorp-tion spectra," giving detailed insight into the wave functions of occupied and unoccupied elec-tronic states.

Origin of low-frequency noise in pentacene field-effect transistors

NASA Astrophysics Data System (ADS)

Xu, Yong; Minari, Takeo; Tsukagoshi, Kazuhito; Chroboczek, Jan; Balestra, Francis; Ghibaudo, Gerard

2011-07-01

Measurements of power spectral density (PSD) of low-frequency noise (LFN) in pentacene field-effect transistors reveal the preponderance of a 1/ f-type PSD behavior with the amplitude varying as the squared transistor gain and increasing as the inverse of the gate surface area. Such features impose an interpretation of LFN by carrier number fluctuations model involving capture/release of charges on traps uniformly distributed over the gate surface. The surface slow trap density extracted by the noise analysis is close to the surface states density deduced independently from static I(V) data, which confirms the validity of the proposed LFN interpretation. Further, we found that the trap densities in bottom-contact (BC) devices were higher than in their top-contact (TC) counterparts, in agreement with observations of a poorer crystal structure of BC devices, in the contact regions in particular. At the highest bias the noise originating from the contact resistance is also shown to be a dominant component in the PSD, and it is well explained by the noise originating from a gate-voltage dependent contact resistance. A gate area scaling was also performed, and the good scaling and the dispersion at the highest bias confirm the validity of the applied carrier number fluctuations model and the predominant contact noise at high current intensities.

Review of particle-in-cell modeling for the extraction region of large negative hydrogen ion sources for fusion

NASA Astrophysics Data System (ADS)

Wünderlich, D.; Mochalskyy, S.; Montellano, I. M.; Revel, A.

2018-05-01

Particle-in-cell (PIC) codes are used since the early 1960s for calculating self-consistently the motion of charged particles in plasmas, taking into account external electric and magnetic fields as well as the fields created by the particles itself. Due to the used very small time steps (in the order of the inverse plasma frequency) and mesh size, the computational requirements can be very high and they drastically increase with increasing plasma density and size of the calculation domain. Thus, usually small computational domains and/or reduced dimensionality are used. In the last years, the available central processing unit (CPU) power strongly increased. Together with a massive parallelization of the codes, it is now possible to describe in 3D the extraction of charged particles from a plasma, using calculation domains with an edge length of several centimeters, consisting of one extraction aperture, the plasma in direct vicinity of the aperture, and a part of the extraction system. Large negative hydrogen or deuterium ion sources are essential parts of the neutral beam injection (NBI) system in future fusion devices like the international fusion experiment ITER and the demonstration reactor (DEMO). For ITER NBI RF driven sources with a source area of 0.9 × 1.9 m2 and 1280 extraction apertures will be used. The extraction of negative ions is accompanied by the co-extraction of electrons which are deflected onto an electron dump. Typically, the maximum negative extracted ion current is limited by the amount and the temporal instability of the co-extracted electrons, especially for operation in deuterium. Different PIC codes are available for the extraction region of large driven negative ion sources for fusion. Additionally, some effort is ongoing in developing codes that describe in a simplified manner (coarser mesh or reduced dimensionality) the plasma of the whole ion source. The presentation first gives a brief overview of the current status of the ion source development for ITER NBI and of the PIC method. Different PIC codes for the extraction region are introduced as well as the coupling to codes describing the whole source (PIC codes or fluid codes). Presented and discussed are different physical and numerical aspects of applying PIC codes to negative hydrogen ion sources for fusion as well as selected code results. The main focus of future calculations will be the meniscus formation and identifying measures for reducing the co-extracted electrons, in particular for deuterium operation. The recent results of the 3D PIC code ONIX (calculation domain: one extraction aperture and its vicinity) for the ITER prototype source (1/8 size of the ITER NBI source) are presented.

High power density yeast catalyzed microbial fuel cells

NASA Astrophysics Data System (ADS)

Ganguli, Rahul

Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density increase was shown to quickly saturate with cell mass attached on the electrode. Based on recent modelling data that suggested that the electrode currents might be limited by the poor electrical conductivity of the anode, the power density versus electrical conductivity of a yeast-immobilized anode was investigated. Introduction of high aspect ratio carbon fiber filaments to the immobilization matrix increased the electrical conductivity of the anode. Although a higher electrical conductivity clearly led to an increase in power densities, it was shown that the principal limitation to power density increase was coming from proton transfer limitations in the immobilized anode. Partial overcoming of the gradients lead a power density of ca. 250 microW cm-2, which is the highest reported for yeast powered MFCs. A yeast-catalyzed microbial fuel cell was investigated as a power source for low power sensors using raw tree sap. It was shown that yeast can efficiently utilize the sucrose present in the raw tree sap to produce electricity when excess salt is added to the medium. Therefore the salinity of a potential energy source is an important consideration when MFCs are being considered for energy harvesting from natural sources.

Magneto-acousto-electrical tomography: a potential method for imaging current density and electrical impedance.

PubMed

Haider, S; Hrbek, A; Xu, Y

2008-06-01

Primarily this report outlines our investigation on utilizing magneto-acousto-electrical-tomography (MAET) to image the lead field current density in volume conductors. A lead field current density distribution is obtained when a current/voltage source is applied to a sample via a pair of electrodes. This is the first time a high-spatial-resolution image of current density is presented using MAET. We also compare an experimental image of current density in a sample with its corresponding numerical simulation. To image the lead field current density, rather than applying a current/voltage source directly to the sample, we place the sample in a static magnetic field and focus an ultrasonic pulse on the sample to simulate a point-like current dipole source at the focal point. Then by using electrodes we measure the voltage/current signal which, based on the reciprocity theorem, is proportional to a component of the lead field current density. In the theory section, we derive the equation relating the measured voltage to the lead field current density and the displacement velocity caused by ultrasound. The experimental data include the MAET signal and an image of the lead field current density for a thin sample. In addition, we discuss the potential improvements for MAET especially to overcome the limitation created by the observation that no signal was detected from the interior of a region having a uniform conductivity. As an auxiliary we offer a mathematical formula whereby the lead field current density may be utilized to reconstruct the distribution of the electrical impedance in a piecewise smooth object.

High current density cathode for electrorefining in molten electrolyte

DOEpatents

Li, Shelly X.

2010-06-29

A high current density cathode for electrorefining in a molten electrolyte for the continuous production and collection of loose dendritic or powdery deposits. The high current density cathode eliminates the requirement for mechanical scraping and electrochemical stripping of the deposits from the cathode in an anode/cathode module. The high current density cathode comprises a perforated electrical insulated material coating such that the current density is up to 3 A/cm.sup.2.

Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

NASA Technical Reports Server (NTRS)

Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

1976-01-01

Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

NASA Astrophysics Data System (ADS)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Howell, E. C.; Knowlton, S. F.; Maurer, D. A.; Traverso, P. J.

2018-01-01

Collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of q = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. This improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE PAGES

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; ...

2018-01-31

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Heat supply from municipal solid waste incineration plants in Japan: Current situation and future challenges.

PubMed

Tabata, Tomohiro; Tsai, Peii

2016-02-01

The use of waste-to-energy technology as part of a municipal solid waste management strategy could reduce the use of fossil fuels and contribute to prevention of global warming. In this study, we examined current heat and electricity production by incineration plants in Japan for external use. Herein, we discuss specific challenges to the promotion of heat utilisation and future municipal solid waste management strategies. We conducted a questionnaire survey to determine the actual conditions of heat production by incineration plants. From the survey results, information of about 498 incineration plants was extracted. When we investigated the relationship between heat production for external use and population density where incineration plants were located, we found that regions with a population density <1000 persons (km(2))(-1) produce <500 MJ t(-1) of heat. We also found that external use of such energy for factories, markets, and related use, was noted in cities with a population density of 2000 to 4000 persons (km(2))(-1). Several incineration plants have poor performance for heat production because there are few facilities near them to provide demand for the energy. This is the result of redundant capacity, and is reflected in the heat production performance. Given these results, we discussed future challenges to creating energy demand around incineration plants where there is presently none. We also examined the challenges involved in increasing heat supply beyond the present situation. © The Author(s) 2015.

Scalable preparation of porous micron-SnO2/C composites as high performance anode material for lithium ion battery

NASA Astrophysics Data System (ADS)

Wang, Ming-Shan; Lei, Ming; Wang, Zhi-Qiang; Zhao, Xing; Xu, Jun; Yang, Wei; Huang, Yun; Li, Xing

2016-03-01

Nano tin dioxide-carbon (SnO2/C) composites prepared by various carbon materials, such as carbon nanotubes, porous carbon, and graphene, have attracted extensive attention in wide fields. However, undesirable concerns of nanoparticles, including in higher surface area, low tap density, and self-agglomeration, greatly restricted their large-scale practical applications. In this study, novel porous micron-SnO2/C (p-SnO2/C) composites are scalable prepared by a simple hydrothermal approach using glucose as a carbon source and Pluronic F127 as a pore forming agent/soft template. The SnO2 nanoparticles were homogeneously dispersed in micron carbon spheres by assembly with F127/glucose. The continuous three-dimensional porous carbon networks have effectively provided strain relaxation for SnO2 volume expansion/shrinkage during lithium insertion/extraction. In addition, the carbon matrix could largely minimize the direct exposure of SnO2 to the electrolyte, thus ensure formation of stable solid electrolyte interface films. Moreover, the porous structure could also create efficient channels for the fast transport of lithium ions. As a consequence, the p-SnO2/C composites exhibit stable cycle performance, such as a high capacity retention of over 96% for 100 cycles at a current density of 200 mA g-1 and a long cycle life up to 800 times at a higher current density of 1000 mA g-1.

In vivo mapping of current density distribution in brain tissues during deep brain stimulation (DBS)

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-01-01

New methods for in vivo mapping of brain responses during deep brain stimulation (DBS) are indispensable to secure clinical applications. Assessment of current density distribution, induced by internally injected currents, may provide an alternative method for understanding the therapeutic effects of electrical stimulation. The current flow and pathway are affected by internal conductivity, and can be imaged using magnetic resonance-based conductivity imaging methods. Magnetic resonance electrical impedance tomography (MREIT) is an imaging method that can enable highly resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In the current study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The current density maps of three canine brains were calculated from the measured magnetic flux density data. The absolute current density values of brain tissues, including gray matter, white matter, and cerebrospinal fluid were compared to assess the active regions during DBS. The resulting current density in different tissue types may provide useful information about current pathways and volume activation for adjusting surgical planning and understanding the therapeutic effects of DBS.

Current-voltage characteristics influenced by the nanochannel diameter and surface charge density in a fluidic field-effect-transistor.

PubMed

Singh, Kunwar Pal; Guo, Chunlei

2017-06-21

The nanochannel diameter and surface charge density have a significant impact on current-voltage characteristics in a nanofluidic transistor. We have simulated the effect of the channel diameter and surface charge density on current-voltage characteristics of a fluidic nanochannel with positive surface charge on its walls and a gate electrode on its surface. Anion depletion/enrichment leads to a decrease/increase in ion current with gate potential. The ion current tends to increase linearly with gate potential for narrow channels at high surface charge densities and narrow channels are more effective to control the ion current at high surface charge densities. The current-voltage characteristics are highly nonlinear for wide channels at low surface charge densities and they show different regions of current change with gate potential. The ion current decreases with gate potential after attaining a peak value for wide channels at low values of surface charge densities. At low surface charge densities, the ion current can be controlled by a narrow range of gate potentials for wide channels. The current change with source drain voltage shows ohmic, limiting and overlimiting regions.

Accessing the Soil Metagenome for Studies of Microbial Diversity▿ †

PubMed Central

Delmont, Tom O.; Robe, Patrick; Cecillon, Sébastien; Clark, Ian M.; Constancias, Florentin; Simonet, Pascal; Hirsch, Penny R.; Vogel, Timothy M.

2011-01-01

Soil microbial communities contain the highest level of prokaryotic diversity of any environment, and metagenomic approaches involving the extraction of DNA from soil can improve our access to these communities. Most analyses of soil biodiversity and function assume that the DNA extracted represents the microbial community in the soil, but subsequent interpretations are limited by the DNA recovered from the soil. Unfortunately, extraction methods do not provide a uniform and unbiased subsample of metagenomic DNA, and as a consequence, accurate species distributions cannot be determined. Moreover, any bias will propagate errors in estimations of overall microbial diversity and may exclude some microbial classes from study and exploitation. To improve metagenomic approaches, investigate DNA extraction biases, and provide tools for assessing the relative abundances of different groups, we explored the biodiversity of the accessible community DNA by fractioning the metagenomic DNA as a function of (i) vertical soil sampling, (ii) density gradients (cell separation), (iii) cell lysis stringency, and (iv) DNA fragment size distribution. Each fraction had a unique genetic diversity, with different predominant and rare species (based on ribosomal intergenic spacer analysis [RISA] fingerprinting and phylochips). All fractions contributed to the number of bacterial groups uncovered in the metagenome, thus increasing the DNA pool for further applications. Indeed, we were able to access a more genetically diverse proportion of the metagenome (a gain of more than 80% compared to the best single extraction method), limit the predominance of a few genomes, and increase the species richness per sequencing effort. This work stresses the difference between extracted DNA pools and the currently inaccessible complete soil metagenome. PMID:21183646

Surface currents associated with external kink modes in tokamak plasmas during a major disruption

NASA Astrophysics Data System (ADS)

Ng, C. S.; Bhattacharjee, A.

2017-10-01

The surface current on the plasma-vacuum interface during a disruption event involving kink instability can play an important role in driving current into the vacuum vessel. However, there have been disagreements over the nature or even the sign of the surface current in recent theoretical calculations based on idealized step-function background plasma profiles. We revisit such calculations by replacing step-function profiles with more realistic profiles characterized by a strong but finite gradient along the radial direction. It is shown that the resulting surface current is no longer a delta-function current density, but a finite and smooth current density profile with an internal structure, concentrated within the region with a strong plasma pressure gradient. Moreover, this current density profile has peaks of both signs, unlike the delta-function case with a sign opposite to, or the same as the plasma current. We show analytically and numerically that such current density can be separated into two parts, with one of them, called the convective current density, describing the transport of the background plasma density by the displacement, and the other part that remains, called the residual current density. It is argued that consideration of both types of current density is important and can resolve past controversies.

In situ droplet surface tension and viscosity measurements in gas metal arc welding

NASA Astrophysics Data System (ADS)

Bachmann, B.; Siewert, E.; Schein, J.

2012-05-01

In this paper, we present an adaptation of a drop oscillation technique that enables in situ measurements of thermophysical properties of an industrial pulsed gas metal arc welding (GMAW) process. Surface tension, viscosity, density and temperature were derived expanding the portfolio of existing methods and previously published measurements of surface tension in pulsed GMAW. Natural oscillations of pure liquid iron droplets are recorded during the material transfer with a high-speed camera. Frame rates up to 30 000 fps were utilized to visualize iron droplet oscillations which were in the low kHz range. Image processing algorithms were employed for edge contour extraction of the droplets and to derive parameters such as oscillation frequencies and damping rates along different dimensions of the droplet. Accurate surface tension measurements were achieved incorporating the effect of temperature on density. These are compared with a second method that has been developed to accurately determine the mass of droplets produced during the GMAW process which enables precise surface tension measurements with accuracies up to 1% and permits the study of thermophysical properties also for metals whose density highly depends on temperature. Thermophysical properties of pure liquid iron droplets formed by a wire with 1.2 mm diameter were investigated in a pulsed GMAW process with a base current of 100 A and a pulse current of 600 A. Surface tension and viscosity of a sample droplet were 1.83 ± 0.02 N m-1 and 2.9 ± 0.3 mPa s, respectively. The corresponding droplet temperature and density are 2040 ± 50 K and 6830 ± 50 kg m-3, respectively.

Development of a compact ECR ion source for various ion production.

PubMed

Muramatsu, M; Hojo, S; Iwata, Y; Katagiri, K; Sakamoto, Y; Takahashi, N; Sasaki, N; Fukushima, K; Takahashi, K; Suzuki, T; Sasano, T; Uchida, T; Yoshida, Y; Hagino, S; Nishiokada, T; Kato, Y; Kitagawa, A

2016-02-01

There is a desire that a carbon-ion radiotherapy facility will produce various ion species for fundamental research. Although the present Kei2-type ion sources are dedicated for the carbon-ion production, a future ion source is expected that could provide: (1) carbon-ion production for medical use, (2) various ions with a charge-to-mass ratio of 1/3 for the existing Linac injector, and (3) low cost for modification. A prototype compact electron cyclotron resonance (ECR) ion source, named Kei3, based on the Kei series has been developed to correspond to the Kei2 type and to produce these various ions at the National Institute of Radiological Sciences (NIRS). The Kei3 has an outer diameter of 280 mm and a length of 1120 mm. The magnetic field is formed by the same permanent magnet as Kei2. The movable extraction electrode has been installed in order to optimize the beam extraction with various current densities. The gas-injection side of the vacuum chamber has enough space for an oven system. We measured dependence of microwave frequency, extraction voltage, and puller position. Charge state distributions of helium, carbon, nitrogen, oxygen, and neon were also measured.

Development of a compact ECR ion source for various ion production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muramatsu, M., E-mail: m-mura@nirs.go.jp; Hojo, S.; Iwata, Y.

2016-02-15

There is a desire that a carbon-ion radiotherapy facility will produce various ion species for fundamental research. Although the present Kei2-type ion sources are dedicated for the carbon-ion production, a future ion source is expected that could provide: (1) carbon-ion production for medical use, (2) various ions with a charge-to-mass ratio of 1/3 for the existing Linac injector, and (3) low cost for modification. A prototype compact electron cyclotron resonance (ECR) ion source, named Kei3, based on the Kei series has been developed to correspond to the Kei2 type and to produce these various ions at the National Institute ofmore » Radiological Sciences (NIRS). The Kei3 has an outer diameter of 280 mm and a length of 1120 mm. The magnetic field is formed by the same permanent magnet as Kei2. The movable extraction electrode has been installed in order to optimize the beam extraction with various current densities. The gas-injection side of the vacuum chamber has enough space for an oven system. We measured dependence of microwave frequency, extraction voltage, and puller position. Charge state distributions of helium, carbon, nitrogen, oxygen, and neon were also measured.« less

A nanoscale study of charge extraction in organic solar cells: the impact of interfacial molecular configurations.

PubMed

Tang, Fu-Ching; Wu, Fu-Chiao; Yen, Chia-Te; Chang, Jay; Chou, Wei-Yang; Gilbert Chang, Shih-Hui; Cheng, Horng-Long

2015-01-07

In the optimization of organic solar cells (OSCs), a key problem lies in the maximization of charge carriers from the active layer to the electrodes. Hence, this study focused on the interfacial molecular configurations in efficient OSC charge extraction by theoretical investigations and experiments, including small molecule-based bilayer-heterojunction (sm-BLHJ) and polymer-based bulk-heterojunction (p-BHJ) OSCs. We first examined a well-defined sm-BLHJ model system of OSC composed of p-type pentacene, an n-type perylene derivative, and a nanogroove-structured poly(3,4-ethylenedioxythiophene) (NS-PEDOT) hole extraction layer. The OSC with NS-PEDOT shows a 230% increment in the short circuit current density compared with that of the conventional planar PEDOT layer. Our theoretical calculations indicated that small variations in the microscopic intermolecular interaction among these interfacial configurations could induce significant differences in charge extraction efficiency. Experimentally, different interfacial configurations were generated between the photo-active layer and the nanostructured charge extraction layer with periodic nanogroove structures. In addition to pentacene, poly(3-hexylthiophene), the most commonly used electron-donor material system in p-BHJ OSCs was also explored in terms of its possible use as a photo-active layer. Local conductive atomic force microscopy was used to measure the nanoscale charge extraction efficiency at different locations within the nanogroove, thus highlighting the importance of interfacial molecular configurations in efficient charge extraction. This study enriches understanding regarding the optimization of the photovoltaic properties of several types of OSCs by conducting appropriate interfacial engineering based on organic/polymer molecular orientations. The ultimate power conversion efficiency beyond at least 15% is highly expected when the best state-of-the-art p-BHJ OSCs are combined with present arguments.

Electron beam induced current in the high injection regime.

PubMed

Haney, Paul M; Yoon, Heayoung P; Koirala, Prakash; Collins, Robert W; Zhitenev, Nikolai B

2015-07-24

Electron beam induced current (EBIC) is a powerful technique which measures the charge collection efficiency of photovoltaics with sub-micron spatial resolution. The exciting electron beam results in a high generation rate density of electron-hole pairs, which may drive the system into nonlinear regimes. An analytic model is presented which describes the EBIC response when the total electron-hole pair generation rate exceeds the rate at which carriers are extracted by the photovoltaic cell, and charge accumulation and screening occur. The model provides a simple estimate of the onset of the high injection regime in terms of the material resistivity and thickness, and provides a straightforward way to predict the EBIC lineshape in the high injection regime. The model is verified by comparing its predictions to numerical simulations in one- and two-dimensions. Features of the experimental data, such as the magnitude and position of maximum collection efficiency versus electron beam current, are consistent with the three-dimensional model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsubara, Y.; Tahara, H.; Nogawa, S.

A new type of electron source for ion sources, which serves as a cathode has been developed. In this cathode, a high-density microwave plasma is produced under the electron-cyclotron-resonance (ECR) condition, and a high electron current of several amperes can be extracted from it. The structure of this microwave plasma (MP) cathode is very simple and compact. A rod antenna connected to a coaxial line for introducing the microwave power (2.45 GHz) and a rare-earth metal permanent magnet for producing the ECR condition are major components. Since there is no filament in this MP cathode, it has a longer lifetimemore » than the equivalent thermionic filament electron emitter. It offers a great advantage to the operation with reactive as well as inert gases. This MP cathode has been adapted in Kaufman-type ion source and have successfully obtained an argon ion-beam current of 110 mA and an oxygen ion-beam current of 43 mA in 25 mm diameter.« less

A combined spectroscopic and TDDFT study of natural dyes extracted from fruit peels of Citrus reticulata and Musa acuminata for dye-sensitized solar cells.

PubMed

Prima, Eka Cahya; Hidayat, Novianto Nur; Yuliarto, Brian; Suyatman; Dipojono, Hermawan Kresno

2017-01-15

This study reports the novel spectroscopic investigations and enhanced the electron transfers of Citrus reticulata and Musa acuminata fruit peels as the photosensitizers for the dye-sensitized solar cells. The calculated TD-DFT-UB3LYP/6-31+G(d,p)-IEFPCM(UAKS), experiment spectra of ultra-violet-visible spectroscopy, and Fourier transform infrared spectroscopy studies indicate the main flavonoid (hesperidin and gallocatechin) structures of the dye extracts. The optimized flavonoid structures are calculated using Density functional theory (DFT) at 6-31+G(d,p) level. The rutinosyl group of the hesperidin pigment (Citrus reticulata) will be further investigated compared to the gallocatechin (Musa acuminata) pigment. The acidity of the dye extract is treated by adding 2% acetic acid. The energy levels of the HOMO-LUMO dyes are measured by a combined Tauc plot and cyclic voltammetry contrasted with the DFT data. The electrochemical impedance spectroscopy will be performed to model the dye electron transfer. As for the rutinosyl group presence and the acidic treatment, the acidified Citrus reticulata cell under continuous light exposure of 100mW·cm -2 yields a short-circuit current density (J sc ) of 3.23mA/cm 2 , a photovoltage (V oc ) of 0.48V, and a fill factor of 0.45 corresponding to an energy conversion efficiency (η) of 0.71% because the shifting down HOMO-LUMO edges and the broadening dye's absorbance evaluated by a combined spectroscopic and TD-DFT method. The result also leads to the longest diffusion length of 32.2μm, the fastest electron transit of 0.22ms, and the longest electron lifetime of 4.29ms. Copyright © 2016 Elsevier B.V. All rights reserved.

A combined spectroscopic and TDDFT study of natural dyes extracted from fruit peels of Citrus reticulata and Musa acuminata for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Prima, Eka Cahya; Hidayat, Novianto Nur; Yuliarto, Brian; Suyatman; Dipojono, Hermawan Kresno

2017-01-01

This study reports the novel spectroscopic investigations and enhanced the electron transfers of Citrus reticulata and Musa acuminata fruit peels as the photosensitizers for the dye-sensitized solar cells. The calculated TD-DFT-UB3LYP/6-31 + G(d,p)-IEFPCM(UAKS), experiment spectra of ultra-violet-visible spectroscopy, and Fourier transform infrared spectroscopy studies indicate the main flavonoid (hesperidin and gallocatechin) structures of the dye extracts. The optimized flavonoid structures are calculated using Density functional theory (DFT) at 6-31 + G(d,p) level. The rutinosyl group of the hesperidin pigment (Citrus reticulata) will be further investigated compared to the gallocatechin (Musa acuminata) pigment. The acidity of the dye extract is treated by adding 2% acetic acid. The energy levels of the HOMO-LUMO dyes are measured by a combined Tauc plot and cyclic voltammetry contrasted with the DFT data. The electrochemical impedance spectroscopy will be performed to model the dye electron transfer. As for the rutinosyl group presence and the acidic treatment, the acidified Citrus reticulata cell under continuous light exposure of 100 mW·cm- 2 yields a short-circuit current density (Jsc) of 3.23 mA/cm2, a photovoltage (Voc) of 0.48 V, and a fill factor of 0.45 corresponding to an energy conversion efficiency (η) of 0.71% because the shifting down HOMO-LUMO edges and the broadening dye's absorbance evaluated by a combined spectroscopic and TD-DFT method. The result also leads to the longest diffusion length of 32.2 μm, the fastest electron transit of 0.22 ms, and the longest electron lifetime of 4.29 ms.

Callindra haematocephata and Peltophorum pterocarpum flowers as natural sensitizers for TiO2 thin film based dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Maurya, Ishwar Chandra; Neetu; Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

2016-10-01

We have studied the performance of dye-sensitized solar cells employing natural dye extracted from the flowers Callindra haematocephata and Peltophorum pterocarpum as sensitizers for TiO2 photoanode. The extracts have shown appreciable absorption in the visible region. FTIR studies indicated the presence of anthocyanins and β-carotene in the flowers of C. haematocephata and P. pterocarpum respectively. The extracts were anchored on TiO2 film deposited on transparent conductive glass (FTO) which were used as photoanode. The dye coated TiO2 film electrode, Pt counter electrode and electrolyte (I-3) assembled into a cell module was illuminated by a light source with intensity 100 mW/cm2 to measure the photoelectric conversion efficiency of the DSSCs. From the J-V characteristic curves of cells, the parameters related to the solar cell performance were determined. The conversion efficiency of the DSSC employing natural dye extract from the flower C. haematocephata and P. pterocarpumwere was found as 0.06% and 0.04%, with open-circuit voltage (VOC) of 370 mV & 400 mV, short-circuit current density (JSC) of 0.25 mA/cm2 & 0.15 mA/cm2, fill factor (FF) of 0.70 & 0.71 and Pmax of 65 & 45 μW cm-2 respectively. The extract of the flower C. haematocephata exhibited better photosensitization action compared to the flower of P. pterocarpum.

Antidiabetic activity of flower buds of Michelia champaca Linn

PubMed Central

Jarald, E. Edwin; Joshi, S.B.; Jain, D.C.

2008-01-01

Objective: To identify the antihyperglycemic activity of various extracts, petroleum ether (60-80°), chloroform, acetone, ethanol, aqueous and crude aqueous, of the flower buds of Michelia champaca, and to identify the antidiabetic activity of active antihyperglycemic extract. Materials and Methods: Plant extracts were tested for antihyperglycemic activity in glucose overloaded hyperglycemic rats. The effective antihyperglycemic extract was tested for its hypoglycemic activity at two-dose levels, 200 and 400 mg/kg respectively. To confirm its utility in the higher model, the effective extract of M. champaca was subjected to antidiabetic study in alloxan induced diabetic model at two dose levels, 200 and 400 mg/kg respectively. The biochemical parameters, glucose, urea, creatinine, serum cholesterol, serum triglyceride, high density lipoprotein, low density lipoprotein, hemoglobin and glycosylated hemoglobin were also assessed in the experimental animals. Results: The ethanolic extract of M. champaca exhibited significant antihyperglycemic activity but did not produce hypoglycemia in fasted normal rats. Apart from this extract, the crude aqueous and petroleum ether extracts were found active only at the end of the first hour. Treatment of diabetic rats with ethanolic extract of this plant restored the elevated biochemical parameters significantly (P<0.05) (P<0.01) and the activity was found dose dependent. Conclusion: This study supports the traditional claim and the ethanolic extract of this plant could be added in traditional preparations for the ailment of various diabetes-associated complications. PMID:21279181

Extraction of bioactives from Orthosiphon stamineus using microwave and ultrasound-assisted techniques: Process optimization and scale up.

PubMed

Chan, Chung-Hung; See, Tiam-You; Yusoff, Rozita; Ngoh, Gek-Cheng; Kow, Kien-Woh

2017-04-15

This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) of bioactive compounds from Orthosiphon stamineus using energy-based parameters such as absorbed power density and absorbed energy density (APD-AED) and response surface methodology (RSM). The intensive optimum conditions of MAE obtained at 80% EtOH, 50mL/g, APD of 0.35W/mL, AED of 250J/mL can be used to determine the optimum conditions of the scale-dependent parameters i.e. microwave power and treatment time at various extraction scales (100-300mL solvent loading). The yields of the up scaled conditions were consistent with less than 8% discrepancy and they were about 91-98% of the Soxhlet extraction yield. By adapting APD-AED method in the case of UAE, the intensive optimum conditions of the extraction, i.e. 70% EtOH, 30mL/g, APD of 0.22W/mL, AED of 450J/mL are able to achieve similar scale up results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dispersive liquid-liquid microextraction based on the solidification of floating organic droplet for the determination of polychlorinated biphenyls in aqueous samples.

PubMed

Dai, Liping; Cheng, Jing; Matsadiq, Guzalnur; Liu, Lu; Li, Jun-Kai

2010-08-03

In the proposed method, an extraction solvent with a lower toxicity and density than the solvents typically used in dispersive liquid-liquid microextraction was used to extract seven polychlorinated biphenyls (PCBs) from aqueous samples. Due to the density and melting point of the extraction solvent, the extract which forms a layer on top of aqueous sample can be collected by solidifying it at low temperatures, which form a layer on top of the aqueous sample. Furthermore, the solidified phase can be easily removed from the aqueous phase. Based on preliminary studies, 1-undecanol was selected as the extraction solvent, and a series of parameters that affect the extraction efficiency were systematically investigated. Under the optimized conditions, enrichment factors for PCBs ranged between 494 and 606. Based on a signal-to-noise ratio of 3, the limit of detection for the method ranged between 3.3 and 5.4 ng L(-1). Good linearity, reproducibility and recovery were also obtained. 2010 Elsevier B.V. All rights reserved.

Extraction of basil leaves (ocimum canum) oleoresin with ethyl acetate solvent by using soxhletation method

NASA Astrophysics Data System (ADS)

Tambun, R.; Purba, R. R. H.; Ginting, H. K.

2017-09-01

The goal of this research is to produce oleoresin from basil leaves (Ocimum canum) by using soxhletation method and ethyl acetate as solvent. Basil commonly used in culinary as fresh vegetables. Basil contains essential oils and oleoresin that are used as flavouring agent in food, in cosmetic and ingredient in traditional medicine. The extraction method commonly used to obtain oleoresin is maceration. The problem of this method is many solvents necessary and need time to extract the raw material. To resolve the problem and to produce more oleoresin, we use soxhletation method with a combination of extraction time and ratio from the material with a solvent. The analysis consists of yield, density, refractive index, and essential oil content. The best treatment of basil leaves oleoresin extraction is at ratio of material and solvent 1:6 (w / v) for 6 hours extraction time. In this condition, the yield of basil oleoresin is 20.152%, 0.9688 g/cm3 of density, 1.502 of refractive index, 15.77% of essential oil content, and the colour of oleoresin product is dark-green.

Exact free oscillation spectra, splitting functions and the resolvability of Earth's density structure

NASA Astrophysics Data System (ADS)

Akbarashrafi, F.; Al-Attar, D.; Deuss, A.; Trampert, J.; Valentine, A. P.

2018-04-01

Seismic free oscillations, or normal modes, provide a convenient tool to calculate low-frequency seismograms in heterogeneous Earth models. A procedure called `full mode coupling' allows the seismic response of the Earth to be computed. However, in order to be theoretically exact, such calculations must involve an infinite set of modes. In practice, only a finite subset of modes can be used, introducing an error into the seismograms. By systematically increasing the number of modes beyond the highest frequency of interest in the seismograms, we investigate the convergence of full-coupling calculations. As a rule-of-thumb, it is necessary to couple modes 1-2 mHz above the highest frequency of interest, although results depend upon the details of the Earth model. This is significantly higher than has previously been assumed. Observations of free oscillations also provide important constraints on the heterogeneous structure of the Earth. Historically, this inference problem has been addressed by the measurement and interpretation of splitting functions. These can be seen as secondary data extracted from low frequency seismograms. The measurement step necessitates the calculation of synthetic seismograms, but current implementations rely on approximations referred to as self- or group-coupling and do not use fully accurate seismograms. We therefore also investigate whether a systematic error might be present in currently published splitting functions. We find no evidence for any systematic bias, but published uncertainties must be doubled to properly account for the errors due to theoretical omissions and regularization in the measurement process. Correspondingly, uncertainties in results derived from splitting functions must also be increased. As is well known, density has only a weak signal in low-frequency seismograms. Our results suggest this signal is of similar scale to the true uncertainties associated with currently published splitting functions. Thus, it seems that great care must be taken in any attempt to robustly infer details of Earth's density structure using current splitting functions.

Prevention by lactic acid bacteria of the oxidation of human LDL.

PubMed

Terahara, M; Kurama, S; Takemoto, N

2001-08-01

Ether extracts of lactic acid bacteria were analyzed for prevention of the oxidation of erythrocyte membrane and human low-density lipoprotein in vivo. Streptococcus thermophilus 1131 and Lactobacillus delbrueckii subsp. bulgaricus 2038, yogurt starters, were chosen as test-strains, and ether extracts of these cultures were used as samples. Both strain 1131 and strain 2038 produced radical scavengers and inhibited oxidation of erythrocyte membranes and low-density lipoproteins. The antioxidative activity of strain 2038 was higher than that of strain 1131.

The Space-Time Scales of Variability in Oceanic Thermal Structure Off the Central California Coast.

DTIC Science & Technology

1983-12-01

SST and sea- surface salinity (SSS) boundaries extracted from the shipboard (2m) thermalsalinograph (T/S) records (Figs. 23, 24, and 25). For these... extracted for comparison. At 175m the density gradient is sufficient to support vigorous internal wave activity in this region. As a result, the predominant... VB2 (VB squared) profiles were calculated from density profiles taken from each phase at a common location (Fig. 149). The location is approximately

Gate tunneling current and quantum capacitance in metal-oxide-semiconductor devices with graphene gate electrodes

NASA Astrophysics Data System (ADS)

An, Yanbin; Shekhawat, Aniruddh; Behnam, Ashkan; Pop, Eric; Ural, Ant

2016-11-01

Metal-oxide-semiconductor (MOS) devices with graphene as the metal gate electrode, silicon dioxide with thicknesses ranging from 5 to 20 nm as the dielectric, and p-type silicon as the semiconductor are fabricated and characterized. It is found that Fowler-Nordheim (F-N) tunneling dominates the gate tunneling current in these devices for oxide thicknesses of 10 nm and larger, whereas for devices with 5 nm oxide, direct tunneling starts to play a role in determining the total gate current. Furthermore, the temperature dependences of the F-N tunneling current for the 10 nm devices are characterized in the temperature range 77-300 K. The F-N coefficients and the effective tunneling barrier height are extracted as a function of temperature. It is found that the effective barrier height decreases with increasing temperature, which is in agreement with the results previously reported for conventional MOS devices with polysilicon or metal gate electrodes. In addition, high frequency capacitance-voltage measurements of these MOS devices are performed, which depict a local capacitance minimum under accumulation for thin oxides. By analyzing the data using numerical calculations based on the modified density of states of graphene in the presence of charged impurities, it is shown that this local minimum is due to the contribution of the quantum capacitance of graphene. Finally, the workfunction of the graphene gate electrode is extracted by determining the flat-band voltage as a function of oxide thickness. These results show that graphene is a promising candidate as the gate electrode in metal-oxide-semiconductor devices.

Silver Nanoparticles Mediated by Costus afer Leaf Extract: Synthesis, Antibacterial, Antioxidant and Electrochemical Properties.

PubMed

Elemike, Elias E; Fayemi, Omolola E; Ekennia, Anthony C; Onwudiwe, Damian C; Ebenso, Eno E

2017-04-29

Synthesis of metallic and semiconductor nanoparticles through physical and chemical routes has been extensively reported. However, green synthesized metal nanoparticles are currently in the limelight due to the simplicity, cost-effectiveness and eco-friendliness of their synthesis. This study explored the use of aqueous leaf extract of Costus afer in the synthesis of silver nanoparticles (CA-AgNPs). The optical and structural properties of the resulting silver nanoparticles were studied using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red spectrophotometer (FTIR). TEM images of the silver nanoparticles confirmed the existence of monodispersed spherical nanoparticles with a mean size of 20 nm. The FTIR spectra affirmed the presence of phytochemicals from the Costus afer leaf extract on the surface of the silver nanoparticles. The electrochemical characterization of a CA-AgNPs/multiwalled carbon nanotubes (MWCNT)-modified electrode was carried out to confirm the charge transfer properties of the nanocomposites. The comparative study showed that the CA-AgNPs/MWCNT-modified electrode demonstrated faster charge transport behaviour. The anodic current density of the electrodes in Fe(CN)₆] 4- /[Fe(CN)₆] 3- redox probe follows the order: GCE/CA-Ag/MWCNT (550 mA/cm²) > GCE/MWCNT (270 mA/cm²) > GCE (80 mA/cm²) > GCE/CA-Ag (7.93 mA/cm²). The silver nanoparticles were evaluated for their antibacterial properties against Gram negative ( Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa ) and Gram positive ( Bacillus subtilis and Staphylococcus aureus ) pathogens. The nanoparticles exhibited better inhibition of the bacterial strains compared to the precursors (leaf extract of Costus afer and silver nitrate). Furthermore, the ability of the nanoparticles to scavenge DPPH radicals at different concentrations was studied using the DPPH radical scavenging assay and compared to that of the leaf extract and ascorbic acid. The nanoparticles were better DPPH scavengers compared to the leaf extract and their antioxidant properties compared favorably the antioxidant results of ascorbic acid. The green approach to nanoparticles synthesis carried out in this research work is simple, non-polluting, inexpensive and non-hazardous.

The Extract of Roots of Sophora flavescens Enhances the Recovery of Motor Function by Axonal Growth in Mice with a Spinal Cord Injury.

PubMed

Tanabe, Norio; Kuboyama, Tomoharu; Kazuma, Kohei; Konno, Katsuhiro; Tohda, Chihiro

2015-01-01

Although axonal extension to reconstruct spinal tracts should be effective for restoring function after spinal cord injury (SCI), chondroitin sulfate proteoglycan (CSPG) levels increase at spinal cord lesion sites, and inhibit axonal regrowth. In this study, we found that the water extract of roots of Sophora flavescens extended the axons of mouse cortical neurons, even on a CSPG-coated surface. Consecutive oral administrations of S. flavescens extract to SCI mice for 31 days increased the density of 5-HT-positive axons at the lesion site and improved the motor function. Further, the active constituents in the S. flavescens extract were identified. The water and alkaloid fractions of the S. flavescens extract each exhibited axonal extension activity in vitro. LC/MS analysis revealed that these fractions mainly contain matrine and/or oxymatrine, which are well-known major compounds in S. flavescens. Matrine and oxymatrine promoted axonal extension on the CSPG-coated surface. This study is the first to demonstrate that S. flavescens extract, matrine, and oxymatrine enhance axonal growth in vitro, even on a CSPG-coated surface, and that S. flavescens extract improves motor function and increases axonal density in SCI mice.

Maximum density echogram analysis : a novel approach to study the characteristics of oblique echoes observed by MARSIS/Mars Express

NASA Astrophysics Data System (ADS)

P, M.; Narukull, V. R.; Rao, S. V. B.

2017-12-01

The ionograms of the Mars Advance Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard Mars Express spacecraft show vertical and oblique echoes from the Martian ionosphere. The vertical echoes are from the normal ionosphere while the oblique echoes are believed to be from ionization bulges that occur in regions of strong vertical magnetic fields. These oblique echoes appear as downward facing hyperbolas when plotted as radargram (at 1.9 MHz), which is a color coded plot of apparent altitude as a function of time at a single frequency. In order to extract further information from these ionization bulges, we considered the peak density of the oblique echoes and plotted them in a format similar to a radargram and called it as a 'maximum density radargram' (MDR). Thus, an MDR shows the peak densities in entire ionization bulge. This analysis revealed several new aspects of the ionization bulges. We found that there is an asymmetry in the ionization bulge so that the density on one side of the hyperbola is different than the other side. In some cases, the density on the same side of the hyperbola, between the edge and apex, changes. Occasionally, the radargrams show only one side of the hyperbola, while the MDRs show a full hyperbola. When the density structures are repeatedly observed over the same location with a few days interval, the MDR analysis shows that the density inside the bulge varies from one pass to another. Finally, the ionization bulges in the MDR displays are clearly observed on several nights. Several of these nighttime bulges were not apparent in radargram analysis. These observations are discussed in the light of current understanding on the ionization bulges.

Cyst-based measurements for assessing lymphangioleiomyomatosis in computed tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lo, P., E-mail: pechinlo@mednet.edu.ucla; Brown, M. S.; Kim, H.

Purpose: To investigate the efficacy of a new family of measurements made on individual pulmonary cysts extracted from computed tomography (CT) for assessing the severity of lymphangioleiomyomatosis (LAM). Methods: CT images were analyzed using thresholding to identify a cystic region of interest from chest CT of LAM patients. Individual cysts were then extracted from the cystic region by the watershed algorithm, which separates individual cysts based on subtle edges within the cystic regions. A family of measurements were then computed, which quantify the amount, distribution, and boundary appearance of the cysts. Sequential floating feature selection was used to select amore » small subset of features for quantification of the severity of LAM. Adjusted R{sup 2} from multiple linear regression and R{sup 2} from linear regression against measurements from spirometry were used to compare the performance of our proposed measurements with currently used density based CT measurements in the literature, namely, the relative area measure and the D measure. Results: Volumetric CT data, performed at total lung capacity and residual volume, from a total of 49 subjects enrolled in the MILES trial were used in our study. Our proposed measures had adjusted R{sup 2} ranging from 0.42 to 0.59 when regressing against the spirometry measures, with p < 0.05. For previously used density based CT measurements in the literature, the best R{sup 2} was 0.46 (for only one instance), with the majority being lower than 0.3 or p > 0.05. Conclusions: The proposed family of CT-based cyst measurements have better correlation with spirometric measures than previously used density based CT measurements. They show potential as a sensitive tool for quantitatively assessing the severity of LAM.« less

Electronic structure, magnetism, and exchange integrals in transition-metal oxides: Role of the spin polarization of the functional in DFT+U calculations

NASA Astrophysics Data System (ADS)

Keshavarz, Samara; Schött, Johan; Millis, Andrew J.; Kvashnin, Yaroslav O.

2018-05-01

Density functional theory augmented with Hubbard-U corrections (DFT+U ) is currently one of the most widely used methods for first-principles electronic structure modeling of insulating transition-metal oxides (TMOs). Since U is relatively large compared to bandwidths, the magnetic excitations in TMOs are expected to be well described by a Heisenberg model. However, in practice the calculated exchange parameters Ji j depend on the magnetic configuration from which they are extracted and on the functional used to compute them. In this work we investigate how the spin polarization dependence of the underlying exchange-correlation functional influences the calculated magnetic exchange constants of TMOs. We perform a systematic study of the predictions of calculations based on the local density approximation plus U (LDA+U ) and the local spin density approximation plus U (LSDA+U ) for the electronic structures, total energies, and magnetic exchange interactions Ji j extracted from ferromagnetic (FM) and antiferromagnetic (AFM) configurations of several transition-metal oxide materials. We report that for realistic choices of Hubbard U and Hund's J parameters, LSDA+U and LDA+U calculations result in different values of the magnetic exchange constants and band gap. The dependence of the band gap on the magnetic configuration is stronger in LDA+U than in LSDA+U and we argue that this is the main reason why the configuration dependence of Ji j is found to be systematically more pronounced in LDA+U than in LSDA+U calculations. We report a very good correspondence between the computed total energies and the parametrized Heisenberg model for LDA+U calculations, but not for LSDA+U , suggesting that LDA+U is a more appropriate method for estimating exchange interactions.

Red spinach (Amaranthus tricolor L.) ethanolic extract as prevention against atherosclerosis based on the level of Low-Density Lipoprotein and histopathological feature of aorta in male Sprague-Dawley rats

NASA Astrophysics Data System (ADS)

Pradana, Dimas Adhi; Pondawinata, Marizki; Widyarini, Sitarina

2017-03-01

This study aimed to determine the potential activity of standardized ethanolic extract of red spinach as prevention against atherosclerosis based on the level of Low-Density Lipoprotein (LDL) and histopathological feature of aorta in male Sprague-Dawley rats induced by high-fat, high-cholesterol diet. A total of 42 animals was divided into 6 groups: normal control group, negative control group, positive control group (0.9 mg/kgBW of simvastatin), first intervention group (200 mg/kgBW of red spinach extract), second intervention group (400 mg/kgBW of red spinach extract), and third intervention group (800 mg/kgBW of red spinach extract). From the first day up to the 66th day, all the groups, except the normal control group and negative control group, were administered simvastatin (positive control) and extract of amaranth (intervention). Then, from the eighth day until Day 66, induction of high-fat and high-cholesterol diet was given in two hours after the simvastatin and red spinach extract administration. The determination of LDL parameters was conducted on Day 0, Day 35, and Day 67. On the 67th day, the animals were dissected to examine the aortic histopathological parameters. The results showed that the ethanolic extract of red spinach with a dose of 200 mg/kgBW, 400 mg/kgBW, and 800 mg/kgBW statistically demonstrated a significant difference (p<0.05). The histopathological feature of the aorta in the treatment indicated the absence of fat in the blood vessel walls or even of foam cells supporting thereby the result of LDL level. This means there was a significant effect of ethanolic extract of red spinach on the prevention against atherosclerosis based on the level of Low-Density Lipoprotein and the histopathological feature of aorta in male Sprague-Dawley rats.

Strong light extraction enhancement using TiO2 nanoparticles-based microcone arrays embossed on III-Nitride light emitting diodes

NASA Astrophysics Data System (ADS)

Désières, Yohan; Chen, Ding Yuan; Visser, Dennis; Schippers, Casper; Anand, Srinivasan

2018-06-01

Colloidal TiO2 nanoparticles were used for embossing of composite microcone arrays on III-Nitride vertical-thin-film blue light emitting diodes (LEDs) as well as on silicon, glass, gallium arsenide, and gallium nitride surfaces. Ray tracing simulations were performed to optimize the design of microcones for light extraction and to explain the experimental results. An optical power enhancement of ˜2.08 was measured on III-Nitride blue LEDs embossed with a hexagonal array of TiO2 microcones of ˜1.35 μm in height and ˜2.6 μm in base width, without epoxy encapsulation. A voltage increase in ˜70 mV at an operating current density of ˜35 A/cm2 was measured for the embossed LEDs. The TiO2 microcone arrays were embossed on functioning LEDs, using low pressures (˜100 g/cm2) and temperatures ≤100 °C.

Parameters of Transportation of Tailings of Metals Lixiviating

NASA Astrophysics Data System (ADS)

Golik, Vladimir; Dmitrak, Yury

2017-11-01

The article shows that the change in the situation in the metals market with a steady increase in production volumes is intensified against the tendency of the transition of mining production from underground mining to underground mining for a certain group of ores. The possibility of a non-waste metals extraction from not only standard, but also from substandard raw materials, is currently provided only by technology with the lixiviating of metals from developing ores. The regular dependences of the magnitude of hydraulic resistances on the hydro-mixture velocity and its density are determined. The correct values of the experimental data convergence with the calculated values of these parameters are obtained. It is shown that the optimization of the transportation parameters of lixiviating tailings allows reducing the level of chemically dangerous pollution of the environment by leachate products. The direction of obtaining the ecological and technological effect from the use of simultaneously environmental and resource-saving technology for the extraction of the disclosed metals is indicated.

Extreme Threshold Failures Within a Heterogeneous Elastic Thin Sheet and the Spatial-Temporal Development of Induced Seismicity Within the Groningen Gas Field

NASA Astrophysics Data System (ADS)

Bourne, S. J.; Oates, S. J.

2017-12-01

Measurements of the strains and earthquakes induced by fluid extraction from a subsurface reservoir reveal a transient, exponential-like increase in seismicity relative to the volume of fluids extracted. If the frictional strength of these reactivating faults is heterogeneously and randomly distributed, then progressive failures of the weakest fault patches account in a general manner for this initial exponential-like trend. Allowing for the observable elastic and geometric heterogeneity of the reservoir, the spatiotemporal evolution of induced seismicity over 5 years is predictable without significant bias using a statistical physics model of poroelastic reservoir deformations inducing extreme threshold frictional failures of previously inactive faults. This model is used to forecast the temporal and spatial probability density of earthquakes within the Groningen natural gas reservoir, conditional on future gas production plans. Probabilistic seismic hazard and risk assessments based on these forecasts inform the current gas production policy and building strengthening plans.

[The effect of osteogenic inducer on healing of tooth extraction sockets].

PubMed

Chen, Junliang; Shan, Chuncheng; He, Yun; Xia, Delin

2012-06-01

To study the effect of osteogenic inducer (dexamethasone, beta-sodium glycerophosphate and Vitamin C) carried by gelatin sponge on healing and remodeling of tooth extraction sockets. Fifty rabbits were selected. After extracting the first premolars of bilateral maxillary, the right side tooth extraction sockets were filled with gelatin sponge containing osteogenic inducer as experimental side, tooth extraction sockets on left side were filled with gelatin sponge as control. Every ten rabbits were executed at the end of 1, 2, 4, 8, 12 weeks after tooth extraction. Bone density was measured through digital X-ray images. The specimens were examined by histology. The absorption height of alveolar bone at 12 weeks was measured. X-ray measurement showed that the bone density of experimental side was higher than that of control side at 2, 4, 8, 12 weeks, the difference had statistical significance (P<0.01). The histology examination showed that new bone formation in tooth extraction sockets of experimental side was earlier than that in control side. The absorptional height of alveolar bone had significant difference between experimental side and control side (P<0.01), of which experimental side was less. Filling the osteogenic inducer in tooth extraction sockets can promote the healing and new bone formation and prevent from alveolar bone absorption.

Effect of Piper betle on plasma antioxidant status and lipid profile against D-galactosamine-induced hepatitis in rats.

PubMed

Pushpavalli, Ganesan; Veeramani, Chinnadurai; Pugalendi, Kodukkur Viswanathan

2009-01-01

Betle leaf chewing is an old traditional practice in India and other countries of East Asia. We have investigated the antioxidant and antihyperlipidaemic potential of an alcoholic leaf-extract of Piper betle against D-galactosamine (D-GalN; 400 mg/kg body weight, i.p. single dose) intoxication in male albino Wistar rats. Rats were treated with leaf-extract (200 mg/kg body weight) by intragastric intubations daily for 20 days. The animals were divided randomly into five groups of six animals each as control, control plus extract, D-GalN control, D-GalN-rats on treatment with extract or silymarin, a standard drug. We observed an increase in the plasma levels of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides, and a decrease in vitamin C, vitamin E and reduced glutathione concentrations. Very low density lipoprotein cholesterol and low density lipoprotein cholesterol increased significantly while high density lipoprotein cholesterol decreased. Further, increase in the levels of total cholesterol, phospholipids, triglycerides, free fatty acids in the plasma and tissues of liver and kidney were observed in D-GalN-treated rats. Administration of P. betle leaf-extract prevented the increase or decrease of these parameters and brought towards normality. These results suggest that P. betle could afford a significant antioxidant and antihyperlipidaemic effect against D-GalN-intoxication.

Hibiscus sabdariffa calyx palliates insulin resistance, hyperglycemia, dyslipidemia and oxidative rout in fructose-induced metabolic syndrome rats.

PubMed

Ajiboye, Taofeek O; Raji, Hikmat O; Adeleye, Abdulwasiu O; Adigun, Nurudeen S; Giwa, Oluwayemisi B; Ojewuyi, Oluwayemisi B; Oladiji, Adenike T

2016-03-30

The effect of Hibiscus sabdariffa calyx extract was evaluated in high-fructose-induced metabolic syndrome rats. Insulin resistance, hyperglycemia, dyslipidemia and oxidative rout were induced in rats using high-fructose diet. High-fructose diet-fed rats were administered 100 and 200 mg kg(-1) body weight of H. sabdariffa extract for 3 weeks, starting from week 7 of high-fructose diet treatment. High-fructose diet significantly (P < 0.05) increased the serum levels of blood glucose, insulin, total cholesterol (TC), triacylglycerol (TAG), low-density lipoprotein cholesterol (LDLc) and very-low-density lipoprotein cholesterol (VLDLc), with a concomitant reduction in high-density lipoprotein cholesterol (HDLc). These alterations were significantly ameliorated by the extract. High-fructose diet-mediated decreases in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSH-red) and glucose 6-phosphate dehydrogenase (Glc 6-PD) were significantly (P < 0.05) attenuated. Altered levels of reduced glutathione (GSH) and glutathione disulfide (GSSG) were significantly (P < 0.05) restored to normal. High-fructose diet-mediated increases in the concentrations of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and percentage fragmented DNA were significantly (P < 0.05) lowered by the Hibiscus extract. Overall, aqueous extract of H. sabdariffa palliates insulin resistance, hyperglycemia, dyslipidemia and oxidative rout in high-fructose-induced metabolic syndrome rats. © 2015 Society of Chemical Industry.

Variation of magnetoimpedance of electrodeposited NiFe/Cu with deposition current density

NASA Astrophysics Data System (ADS)

Mishra, A. C.; Jha, A. K.

2017-12-01

An investigation about influence of deposition current density on electrodeposited magnetic film is reported in this paper. Ferromagnetic NiFe thin films were electrodeposited on copper wires of 100 μm diameter for various electrdepostion current densities ranging from 10 to 60 mA/cm2 maintaining equal thickness in all films. The composition of deposited film varied with deposition current density and in particular, a composition of Ni79Fe21 was achieved for a current density of 20 mA/cm2. The surface microstructure of the film deposited at the current density of 20 mA/cm2 was found to have excellent smoothness. The coercivity of the film was lowest and highest value of magnetoimpedance was measured for this film. The influence of current density on film composition and hence magnetic properties was attributed to the change of deposition mechanism.

Biochemical Evaluation of the Hypoglycemic Effects of Extract and Fraction of Cassia fistula Linn. in Alloxan-induced Diabetic Rats

PubMed Central

Jarald, E. E.; Joshi, S. B.; Jain, D. C.; Edwin, S.

2013-01-01

Various extracts of flowers of Cassia fistula Linn (Leguminosae) such as petroleum ether (60-80°), chloroform, acetone, ethanol, aqueous, and crude aqueous extracts and two fractions of ethanol extract were tested for antihyperglycemic activity in glucose-overloaded hyperglycemic rats. The effective antihyperglycemic extracts and fraction were tested for their hypoglycemic activity at two dose levels, 200 and 400 mg/kg, respectively. To confirm their utility in higher models, the effective extracts and fraction of C. fistula were subjected to antidiabetic study in an alloxan-induced diabetic model at two dose levels, 200 and 400 mg/kg, respectively. Biochemical parameters like glucose, urea, creatinine, serum cholesterol, serum triglyceride, high-density lipoprotein, low-density lipoprotein, hemoglobin, and glycosylated hemoglobin were also assessed in experimental animals. The petroleum ether and ethanol extracts of C. fistula and the water-soluble fraction of ethanol extract were found to exhibit significant antihyperglycemic activity. The extracts, at the given doses, did not produce hypoglycemia in fasted normal rats, and the fraction exhibited weak hypoglycemic effect after 2 h of the treatment. Treatment of diabetic rats with ethanol extract and water-soluble fraction of this plant restored the elevated biochemical parameters significantly (P<0.05) to the normal level. No activity was found in the petroleum ether extract of the plant. Comparatively, the water-soluble fraction of ethanol extract was found to be more effective than the ethanol extract, and the activity was comparable with that of the standard, glibenclamide (5 mg/kg). PMID:24302797

Efficient microplastics extraction from sand. A cost effective methodology based on sodium iodide recycling.

PubMed

Kedzierski, Mikaël; Le Tilly, Véronique; César, Guy; Sire, Olivier; Bruzaud, Stéphane

2017-02-15

Evaluating the microplastics pollution on the shores requires overcoming the technological and economical challenge of efficient plastic extraction from sand. The recovery of dense microplastics requires the use of NaI solutions, a costly process. The aim of this study is to decrease this cost by recycling the NaI solutions and to determine the impact of NaI storage. For studying the NaI recyclability, the solution density and the salt mass have been monitored during ten life cycles. Density, pH and salt mass have been measured for 40days to assess the storage effect. The results show that NaI solutions are recyclable without any density alterations with a total loss of 35.9% after the 10cycles of use. During storage, chemical reactions may appear but are reversible. Consequently, the use of recycling methods allows for a significant cost reduction. How far the plastic extraction by dense solutions is representative is discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Low-density solvent based ultrasound-assisted emulsification microextraction and on-column derivatization combined with gas chromatography-mass spectrometry for the determination of carbamate pesticides in environmental water samples.

PubMed

Guo, Liang; Lee, Hian Kee

2012-04-27

A fast and efficient method for the determination of trace level of carbamate pesticides using a lower-density-than-water solvent for ultrasound-assisted emulsification microextraction coupled to on-column derivatization and analysis by GC-MS has been developed and studied. In this approach, a soft plastic Pasteur pipette was employed as a convenient extraction device. Fifty microliters of extraction solvent, of lower density than water, was injected into the sample solution held in the pipette. The latter was immediately immersed in an ultrasound water bath to form an emulsion. After 2 min extraction, the emulsion was fractionated into two layers by centrifugation. The upper layer (organic extract) could be collected conveniently by squeezing the bulb of the pipette, now held upside down, to move it into the narrow stem of the device, facilitating its retrieval for analysis. The extract was then combined with trimethylphenylammonium hydroxide and directly injected into a gas chromatography-mass spectrometry (GC-MS) system for on-column derivatization and analysis. The on-column derivatization provided an added convenience (since a separate step was not necessary). Parameters affecting the derivatization and extraction were investigated. Under the most favorable conditions, the method demonstrated high extraction efficiency with low limits of detection of between 0.01 and 0.1 μg/L, good linearity in the range of 0.05-50 μg/L, to 0.5-100 μg/L, and good repeatability (RSD below 9.2%, n=5). The proposed method was evaluated by determining carbamate pesticides in river water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Electron stripping processes of H{sup −} ion beam in the 80 kV high voltage extraction column and low energy beam transport line at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Draganic, I. N., E-mail: draganic@lanl.gov

Basic vacuum calculations were performed for various operating conditions of the Los Alamos National Neutron Science H{sup −} Cockcroft-Walton (CW) injector and the Ion Source Test Stand (ISTS). The vacuum pressure was estimated for both the CW and ISTS at five different points: (1) inside the H{sup −} ion source, (2) in front of the Pierce electrode, (3) at the extraction electrode, (4) at the column electrode, and (5) at the ground electrode. A static vacuum analysis of residual gases and the working hydrogen gas was completed for the normal ion source working regime. Gas density and partial pressure weremore » estimated for the injected hydrogen gas. The attenuation of H{sup −} beam current and generation of electron current in the high voltage acceleration columns and low energy beam transport lines were calculated. The interaction of H{sup −} ions on molecular hydrogen (H{sub 2}) is discussed as a dominant collision process in describing electron stripping rates. These results are used to estimate the observed increase in the ratio of electrons to H{sup −} ion beam in the ISTS beam transport line.« less

Fabrication, Optimization and Characterization of Natural Dye Sensitized Solar Cell

PubMed Central

Ghann, William; Kang, Hyeonggon; Sheikh, Tajbik; Yadav, Sunil; Chavez-Gil, Tulio; Nesbitt, Fred; Uddin, Jamal

2017-01-01

The dyes extracted from pomegranate and berry fruits were successfully used in the fabrication of natural dye sensitized solar cells (NDSSC). The morphology, porosity, surface roughness, thickness, absorption and emission characteristics of the pomegranate dye sensitized photo-anode were studied using various analytical techniques including FESEM, EDS, TEM, AFM, FTIR, Raman, Fluorescence and Absorption Spectroscopy. Pomegranate dye extract has been shown to contain anthocyanin which is an excellent light harvesting pigment needed for the generation of charge carriers for the production of electricity. The solar cell’s photovoltic performance in terms of efficiency, voltage, and current was tested with a standard illumination of air-mass 1.5 global (AM 1.5 G) having an irradiance of 100 mW/cm2. After optimization of the photo-anode and counter electrode, a photoelectric conversion efficiency (η) of 2%, an open-circuit voltage (Voc) of 0.39 mV, and a short-circuit current density (Isc) of 12.2 mA/cm2 were obtained. Impedance determination showed a relatively low charge-transfer resistance (17.44 Ω) and a long lifetime, signifying a reduction in recombination losses. The relatively enhanced efficiency is attributable in part to the use of a highly concentrated pomegranate dye, graphite counter electrode and TiCl4 treatment of the photo-anode. PMID:28128369

Fabrication, Optimization and Characterization of Natural Dye Sensitized Solar Cell

NASA Astrophysics Data System (ADS)

Ghann, William; Kang, Hyeonggon; Sheikh, Tajbik; Yadav, Sunil; Chavez-Gil, Tulio; Nesbitt, Fred; Uddin, Jamal

2017-01-01

The dyes extracted from pomegranate and berry fruits were successfully used in the fabrication of natural dye sensitized solar cells (NDSSC). The morphology, porosity, surface roughness, thickness, absorption and emission characteristics of the pomegranate dye sensitized photo-anode were studied using various analytical techniques including FESEM, EDS, TEM, AFM, FTIR, Raman, Fluorescence and Absorption Spectroscopy. Pomegranate dye extract has been shown to contain anthocyanin which is an excellent light harvesting pigment needed for the generation of charge carriers for the production of electricity. The solar cell’s photovoltic performance in terms of efficiency, voltage, and current was tested with a standard illumination of air-mass 1.5 global (AM 1.5 G) having an irradiance of 100 mW/cm2. After optimization of the photo-anode and counter electrode, a photoelectric conversion efficiency (η) of 2%, an open-circuit voltage (Voc) of 0.39 mV, and a short-circuit current density (Isc) of 12.2 mA/cm2 were obtained. Impedance determination showed a relatively low charge-transfer resistance (17.44 Ω) and a long lifetime, signifying a reduction in recombination losses. The relatively enhanced efficiency is attributable in part to the use of a highly concentrated pomegranate dye, graphite counter electrode and TiCl4 treatment of the photo-anode.

Towards a realistic 3D simulation of the extraction region in ITER NBI relevant ion source

NASA Astrophysics Data System (ADS)

Mochalskyy, S.; Wünderlich, D.; Fantz, U.; Franzen, P.; Minea, T.

2015-03-01

The development of negative ion (NI) sources for ITER is strongly accompanied by modelling activities. The ONIX code addresses the physics of formation and extraction of negative hydrogen ions at caesiated sources as well as the amount of co-extracted electrons. In order to be closer to the experimental conditions the code has been improved. It includes now the bias potential applied to first grid (plasma grid) of the extraction system, and the presence of Cs+ ions in the plasma. The simulation results show that such aspects play an important role for the formation of an ion-ion plasma in the boundary region by reducing the depth of the negative potential well in vicinity to the plasma grid that limits the extraction of the NIs produced at the Cs covered plasma grid surface. The influence of the initial temperature of the surface produced NI and its emission rate on the NI density in the bulk plasma that in turn affects the beam formation region was analysed. The formation of the plasma meniscus, the boundary between the plasma and the beam, was investigated for the extraction potentials of 5 and 10 kV. At the smaller extraction potential the meniscus moves closer to the plasma grid but as in the case of 10 kV the deepest meniscus bend point is still outside of the aperture. Finally, a plasma containing the same amount of NI and electrons (nH- =ne =1017 m-3) , representing good source conditioning, was simulated. It is shown that at such conditions the extracted NI current can reach values of ˜32 mA cm-2 using ITER-relevant extraction potential of 10 kV and ˜19 mA cm-2 at 5 kV. These results are in good agreement with experimental measurements performed at the small scale ITER prototype source at the test facility BATMAN.

Ketosteroid Standardized Cissus quadrangularis L. Extract and its Anabolic Activity: Time to Look Beyond Ketosteroid?

PubMed

Jadhav, Atul N; Rafiq, Mohammed; Devanathan, Rajendran; Azeemuddin, Mohammed; Anturlikar, Suryakanth D; Ahmed, Akhil; Sundaram, Ramchandran; Babu, U V; Paramesh, Rangesh

2016-05-01

Cissus quadrangularis (CQ) L. reported to contain 3-ketosteroids and have bone health benefits. This study aimed at establishing the relationship between the ketosteroid content and anabolic as well as bone health-promoting activities of various Cissus extracts in well-established orchidectomized (ORX) rat model. Supercritical carbon dioxide, ethyl acetate, and aqueous extracts (AE) of CQ L. were prepared and standardized for ketosteroid content by two methods used in commerce. Moreover, ketosteroid standardized extracts of this plant were evaluated for anabolic activity in rats in well-established ORX rat model. The increase in the absolute weight was appreciable in the CQ-AE treated group. Similarly, with respect to bone parameters, a similar trend was seen. The mean bone density, strength, and calcium content were found to be highest in the group treated with CQ-AE compared to groups treated with other extracts. This study reveals for the first time that 3-ketosteroids are not linked to the beneficial activities on bone and highlights the need for extensive characterization of biological active principles from CQ L. In light of the above estimation studies, we believe that current standardization of Cissus extraction "3-ketosteroids" is incorrect. We also did not find any report suggesting the presence of androgenic steroids in this plant and hence the characterization based on "3-ketosteroids" is scientifically incorrect. This study highlights the insufficient understanding of biological active principles from CQ L. and underlines the need for extensive bioactivity guided studies. Cissus quadrangularis (CQ) L. reported to contain 3.ketosteroids and have bone health benefitsWe did not find correlation between ketosteroid content obtained by conventional methods and its biological effectStudies indicate that claims of ketosteroid content need not necessarily correlate to biological effects and hence warrants extensive phytochemical characterization of biological active principles from CQ L. Abbreviations used: CQ: Cissus quadrangularis, ORX: Orchidectomized, AE: Aqueous extract, EE: Ethyl acetate extract, SFE: Supercritical fluid extract.

Near-surface Density Currents Observed in the Southeast Pacific Stratocumulus-topped Marine Boundary Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilbanks, Matt C.; Yuter, S. E.; de Szoeke, S.

2015-09-01

Density currents (i.e. cold pools or outflows) beneath marine stratocumulus clouds are characterized using a 30-d data set of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An objective method identifies 71 density current fronts using an air density criterion and isolates each density current’s core (peak density) and tail (dissipating) zone. Compared to front and core zones, most density current tails exhibited weaker density gradients and wind anomalies elongated about the axis of the mean wind. The mean cloud-level advection relative to the surface layer windmore » (1.9 m s-1) nearly matches the mean density current propagation speed (1.8 m s-1). The similarity in speeds allows drizzle cells to deposit tails in their wakes. Based on high-resolution scanning Doppler lidar data, prefrontal updrafts had a mean intensity of 0.91 m s-1, reached an average altitude of 800 m, and were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. Nearly 90% of density currents were identified when C-band radar estimated 30-km diameter areal average rain rates exceeded 1 mm d-1. Rather than peaking when rain rates are highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurs with shallow subcloud dry and stable layers. The dry layers may contribute to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occur in regions of open cells but also occur in regions of closed cells.« less

Development of dye-sensitized solar cells based on naturally extracted dye from the maqui berry (Aristotelia chilensis)

NASA Astrophysics Data System (ADS)

Leyrer, Julio; Hunter, Renato; Rubilar, Monica; Pavez, Boris; Morales, Eduardo; Torres, Simonet

2016-10-01

The mini modules of dye-sensitized solar cells (DSSCs) were investigated for their conversion efficiency using anthocyanin-enriched extracts from maqui berry, which to date has never been tested in a DSSC. Anthocyanins are a group of red, purple, violet and blue water-soluble polyphenolic pigments widely found in berry fruits. Maqui berries are a particularly rich source. The aqueous extract concentrations of maqui fruit were tested at 750 and 1500 mg of anthocyanin/L. The immersion time to produce sensitized TiO2 film was 8 h. According to the experimental results, the conversion efficiency of the DSSC prepared with 750 mg of anthocyanin/L was 0.14%, with an open-circuit voltage (VOC) of 0.43 V, a short-circuit current density (JSC) of 0.38 mA/cm2, and a fill factor (FF) of 0.450. The conversion efficiency attained with 1500 mg of anthocyanin/L was 0.19%, with (VOC) of 0.45 V, (JSC) of 0.44 mA/cm2 and FF of 0.55. Therefore, a higher concentration brought about a higher photosensitized performance. The maqui extracts were successfully dye sensitized over a layer of TiO2 nanoparticles, providing useful information for further studies related to the use of natural pigments as sensitizers for solar cells.

21 CFR 177.1610 - Polyethylene, chlorinated.

Code of Federal Regulations, 2010 CFR

2010-04-01

... produced by the direct chlorination of polyethylene conforming to the density, maximum n-hexane extractable... extractable fraction in n-hexane at 50 °C, as determined by the method described in § 177.1520(d)(3)(ii). (b...

21 CFR 177.1610 - Polyethylene, chlorinated.

Code of Federal Regulations, 2011 CFR

2011-04-01

... produced by the direct chlorination of polyethylene conforming to the density, maximum n-hexane extractable... extractable fraction in n-hexane at 50 °C, as determined by the method described in § 177.1520(d)(3)(ii). (b...

21 CFR 177.1610 - Polyethylene, chlorinated.

Code of Federal Regulations, 2012 CFR

2012-04-01

... produced by the direct chlorination of polyethylene conforming to the density, maximum n-hexane extractable... extractable fraction in n-hexane at 50 °C, as determined by the method described in § 177.1520(d)(3)(ii). (b...

21 CFR 177.1610 - Polyethylene, chlorinated.

Code of Federal Regulations, 2013 CFR

2013-04-01

... produced by the direct chlorination of polyethylene conforming to the density, maximum n-hexane extractable... extractable fraction in n-hexane at 50 °C, as determined by the method described in § 177.1520(d)(3)(ii). (b...

Antioxidant effects of aqueous extracts from dried calyx of Hibiscus sabdariffa Linn. (Roselle) in vitro using rat low-density lipoprotein (LDL).

PubMed

Hirunpanich, Vilasinee; Utaipat, Anocha; Morales, Noppawan Phumala; Bunyapraphatsara, Nuntavan; Sato, Hitoshi; Herunsalee, Angkana; Suthisisang, Chuthamanee

2005-03-01

The present study quantitatively investigated the antioxidant effects of the aqueous extracts from dried calyx of Hibiscus sabdariffa LINN. (roselle) in vitro using rat low-density lipoprotein (LDL). Formations of the conjugated dienes and thiobarbituric acid reactive substances (TBARs) were monitored as markers of the early and later stages of the oxidation of LDL, respectively. Thus, we demonstrated that the dried calyx extracts of roselle exhibits strong antioxidant activity in Cu(2+)-mediated oxidation of LDL (p<0.05) in vitro. The inhibitory effect of the extracts on LDL oxidation was dose-dependent at concentrations ranging from 0.1 to 5 mg/ml. Moreover, 5 mg/ml of roselle inhibited TBARs-formation with greater potency than 100 microM of vitamin E. In conclusion, this study provides a quantitative insight into the potent antioxidant effect of roselle in vitro.

Studies for determining thermal ion extraction potential for aluminium plasma generated by electron beam evaporator

NASA Astrophysics Data System (ADS)

Dileep Kumar, V.; Barnwal, Tripti A.; Mukherjee, Jaya; Gantayet, L. M.

2010-02-01

For effective evaporation of refractory metal, electron beam is found to be most suitable vapour generator source. Using electron beam, high throughput laser based purification processes are carried out. But due to highly concentrated electron beam, the vapour gets ionised and these ions lead to dilution of the pure product of laser based separation process. To estimate the concentration of these ions and extraction potential requirement to remove these ions from vapour stream, experiments have been conducted using aluminium as evaporant. The aluminium ingots were placed in water cooled copper crucible. Inserts were used to hold the evaporant, in order to attain higher number density in the vapour processing zone and also for confining the liquid metal. Parametric studies with beam power, number density and extraction potential were conducted. In this paper we discuss the trend of the generation of thermal ions and electrostatic field requirement for extraction.

A parameter-free method to extract the superconductor’s J c(B,θ) field-dependence from in-field current-voltage characteristics of high temperature superconductor tapes

NASA Astrophysics Data System (ADS)

Zermeño, Víctor M. R.; Habelok, Krzysztof; Stępień, Mariusz; Grilli, Francesco

2017-03-01

The estimation of the critical current (I c) and AC losses of high-temperature superconductor devices through modeling and simulation requires the knowledge of the critical current density (J c) of the superconducting material. This J c is in general not constant and depends both on the magnitude (B loc) and the direction (θ, relative to the tape) of the local magnetic flux density. In principle, J c(B loc,θ) can be obtained from the experimentally measured critical current I c(B a,θ), where B a is the magnitude of the applied magnetic field. However, for applications where the superconducting materials experience a local field that is close to the self-field of an isolated conductor, obtaining J c(B loc,θ) from I c(B a,θ) is not a trivial task. It is necessary to solve an inverse problem to correct for the contribution derived from the self-field. The methods presented in the literature comprise a series of approaches dealing with different degrees of mathematical regularization to fit the parameters of preconceived nonlinear formulas by means of brute force or optimization methods. In this contribution, we present a parameter-free method that provides excellent reproduction of experimental data and requires no human interaction or preconception of the J c dependence with respect to the magnetic field. In particular, it allows going from the experimental data to a ready-to-run J c(B loc,θ) model in a few minutes.

Elucidation of mechanisms of actions of thymoquinone-enriched methanolic and volatile oil extracts from Nigella sativa against cardiovascular risk parameters in experimental hyperlipidemia.

PubMed

Ahmad, Shafeeque; Beg, Zafarul H

2013-06-13

Nigella sativa belonging to the Ranunculaceae family has been reported to use for thousands of years as protective and curative traditional medicine against a number of diseases. GC-MS analysis of methanolic extract (ME) and volatile oil (VO) extracted from Nigella sativa seed oil was performed by two different mass spectrometry libraries, WIlEY8 and NIST05s. The cholesterol lowering and antioxidant actions of VO and ME fractions were investigated in atherogenic suspension fed rats. In this study, four groups of male Wistar rats were used: normolipidemic control (NLP-C), hyperlipidemic control (HLP-C), methanolic extract (HLP-ME) and volatile oil treated (HLP-VO) groups for 30 days of duration. P value < 0.05 was assumed as significant data in groups. Administration of atherogenic suspension to male Wistar rats for 30 days resulted in a marked increase of plasma triglycerides and total cholesterol, and significant change in plasma lipoprotein levels along with a decrease in antioxidant arylesterase activity in hyperlipidemic control (HLP-C) group. The oral feeding of 100 mg ME or 20 mg VO per rat/day effectively reduced the plasma triglycerides to near normal level, while high density lipoprotein cholesterol and its subfraction along with arylesterase activity levels were significantly increased. The test fractions elicited a significant decrease in hepatic HMG-CoA reductase activity. The fractions significantly blocked the ex vivo basal and in vitro maximal formation of conjugated diene and malondialdehyde, and lengthened the lag times of low density lipoprotein, small dense low density lipoprotein and large buoyant low density lipoprotein. ME possessing ω-6 linoleic acid along with palmitic acid active compounds was more effective than VO extract containing thymol and isothymol phenolic antioxidant compounds, thymoquinone phenolic compound common to the both extracts, via reduction in hepatic HMG-CoA reductase activity as well as antioxidant mechanisms. The both extracts especially, ME significantly improve cardiovascular risk parameters in treated rats, and can be used in reactive oxygen species disorders such as cardiovascular diseases.

Carrier-density-dependent recombination dynamics of excitons and electron-hole plasma in m -plane InGaN/GaN quantum wells

NASA Astrophysics Data System (ADS)

Liu, W.; Butté, R.; Dussaigne, A.; Grandjean, N.; Deveaud, B.; Jacopin, G.

2016-11-01

We study the carrier-density-dependent recombination dynamics in m -plane InGaN/GaN multiple quantum wells in the presence of n -type background doping by time-resolved photoluminescence. Based on Fermi's golden rule and Saha's equation, we decompose the radiative recombination channel into an excitonic and an electron-hole pair contribution, and extract the injected carrier-density-dependent bimolecular recombination coefficients. Contrary to the standard electron-hole picture, our results confirm the strong influence of excitons even at room temperature. Indeed, at 300 K, excitons represent up to 63 ± 6% of the photoexcited carriers. In addition, following the Shockley-Read-Hall model, we extract the electron and hole capture rates by deep levels and demonstrate that the increase in the effective lifetime with injected carrier density is due to asymmetric capture rates in presence of an n -type background doping. Thanks to the proper determination of the density-dependent recombination coefficients up to high injection densities, our method provides a way to evaluate the importance of Auger recombination.

Determination of Energy Independent Neutron Densities using Dirac Phenomenology based on the RIA

NASA Astrophysics Data System (ADS)

Clark, B. C.; Kerr, L. J.; Hama, S.; Mercer, R. L.

2002-04-01

A new method for extracting neutron densities from intermediate energy elastic proton-nucleus scattering observables using a global Dirac phenomenological (DP) approach based on the Relativistic Impulse Approximation (RIA) is presented. (B. C. Clark, et al.) BAPS Vol 46, No. 7 pg.139, 2001. We have considered data sets for ^40Ca, ^48Ca and ^208Pb and energies from 500 MeV to 1040 MeV. The global fits are successful in reproducing the data and in predicting data sets not included in the analysis. Using this global DP approach we have obtained energy independent neutron densities. The vector point proton density distribution, ρ^p_v, is determined from the empirical charge density after unfolding the proton form factor. The other densities, ρ^n_v, ρ^p_s, ρ^n_s, are parameterized using the cosh form given in our paper on global DP optical potentials.(E. D. Cooper, et al.) Phys Rev. 47C, pg. 297, 1993 Neutron skin thicknesses extracted using the global analysis are compared to predictions from theoretical models.

Neuronavigation Based on Track Density Image Extracted from Deterministic High-Definition Fiber Tractography.

PubMed

Wei, Peng-Hu; Cong, Fei; Chen, Ge; Li, Ming-Chu; Yu, Xin-Guang; Bao, Yu-Hai

2017-02-01

Diffusion tensor imaging-based navigation is unable to resolve crossing fibers or to determine with accuracy the fanning, origin, and termination of fibers. It is important to improve the accuracy of localizing white matter fibers for improved surgical approaches. We propose a solution to this problem using navigation based on track density imaging extracted from high-definition fiber tractography (HDFT). A 28-year-old asymptomatic female patient with a left-lateral ventricle meningioma was enrolled in the present study. Language and visual tests, magnetic resonance imaging findings, both preoperative and postoperative HDFT, and the intraoperative navigation and surgery process are presented. Track density images were extracted from tracts derived using full q-space (514 directions) diffusion spectrum imaging (DSI) and integrated into a neuronavigation system. Navigation accuracy was verified via intraoperative records and postoperative DSI tractography, as well as a functional examination. DSI successfully represented the shape and range of the Meyer loop and arcuate fasciculus. Extracted track density images from the DSI were successfully integrated into the navigation system. The relationship between the operation channel and surrounding tracts was consistent with the postoperative findings, and the patient was functionally intact after the surgery. DSI-based TDI navigation allows for the visualization of anatomic features such as fanning and angling and helps to identify the range of a given tract. Moreover, our results show that our HDFT navigation method is a promising technique that preserves neural function. Copyright © 2016 Elsevier Inc. All rights reserved.

Inhibition of LDL oxidation and oxidized LDL-induced foam cell formation in RAW 264.7 cells show anti-atherogenic properties of a foliar methanol extract of Scoparia dulcis.

PubMed

Nambiar, Sinjitha S; Shetty, Nandini Prasad; Bhatt, Praveena; Neelwarne, Bhagyalakshmi

2014-04-01

Oxidation of low density lipoproteins and their further uptake by macrophages is known to result in the formation of foam cells, which are critical in the initiation of atherosclerosis through activation of inflammatory signalling cascades. Thus, powerful dietary antioxidants are receiving attention for the reversal of such pathological states. Extracts of Scoparia dulcis have been used as tea and health drinks with various health promoting effects. In the present study, we examined the reactive oxygen scavenging potential as well as anti-inflammatory and anti-atherogenic efficacies, using leaf extracts obtained after successive extraction with various solvents. A methanol extract showed potent antioxidant activity with an IC50 value of 570 μg/ml, caused hydrogen peroxide scavenging (28.9 µg/ml) and anti-inflammatory effects by improving human erythrocyte membrane stabilisation (about 86%). The methanol extract also efficiently inhibited lipid peroxidation and oxidation of low density lipoproteins, thus preventing foam cell formation in cultured RAW 264.7 cells. Furthermore, phytochemical screening of the extracts showed high accumulation of flavonoids. The foliar methanol extract of Scoparia dulcis has a strong anti-atherogenic potential and this property could be attributed maybe due to presence of flavonoids since HPLC analysis showed high concentrations of myricetin and rutin in the methanol extract.

Inhibition of LDL oxidation and oxidized LDL-induced foam cell formation in RAW 264.7 cells show anti-atherogenic properties of a foliar methanol extract of Scoparia dulcis

PubMed Central

Nambiar, Sinjitha S.; Shetty, Nandini Prasad; Bhatt, Praveena; Neelwarne, Bhagyalakshmi

2014-01-01

Background: Oxidation of low density lipoproteins and their further uptake by macrophages is known to result in the formation of foam cells, which are critical in the initiation of atherosclerosis through activation of inflammatory signalling cascades. Thus, powerful dietary antioxidants are receiving attention for the reversal of such pathological states. Materials and Methods: Extracts of Scoparia dulcis have been used as tea and health drinks with various health promoting effects. In the present study, we examined the reactive oxygen scavenging potential as well as anti-inflammatory and anti-atherogenic efficacies, using leaf extracts obtained after successive extraction with various solvents. Results: A methanol extract showed potent antioxidant activity with an IC50 value of 570 μg/ml, caused hydrogen peroxide scavenging (28.9 µg/ml) and anti-inflammatory effects by improving human erythrocyte membrane stabilisation (about 86%). The methanol extract also efficiently inhibited lipid peroxidation and oxidation of low density lipoproteins, thus preventing foam cell formation in cultured RAW 264.7 cells. Furthermore, phytochemical screening of the extracts showed high accumulation of flavonoids. Conclusions: The foliar methanol extract of Scoparia dulcis has a strong anti-atherogenic potential and this property could be attributed maybe due to presence of flavonoids since HPLC analysis showed high concentrations of myricetin and rutin in the methanol extract. PMID:24991098

The influence of pulsed electric fields and microwave pretreatments on some selected physicochemical properties of oil extracted from black cumin seed.

PubMed

Bakhshabadi, Hamid; Mirzaei, HabibOllah; Ghodsvali, Alireza; Jafari, Seid Mahdi; Ziaiifar, Aman Mohammad

2018-01-01

Application of novel technologies such as microwave and pulsed electric fields (PEF) might increase the speed and efficiency of oil extraction. In the present research, PEF (3.25 kV/cm electric field intensity and 30 pulse number) and microwave (540 W for 180 s) pretreatments were used to study the process of oil extraction from black cumin ( Nigella sativa ) seeds. After applying the selected pretreatments, the oil of seeds was extracted with the use of a screw press and the extraction efficiency, refractive index, oil density, color index, oxidative stability, and chemical components of oil and protein of meal were evaluated. The achieved results expressed that PEF and microwave pretreatments increased the oil extraction efficiency and its oxidative stability. Different pretreatments didn't have any significant influence on the refractive index of black cumin seed oil ( p >.05). When microwave and PEF were used, the oil density showed an enhancement as the following: 1.51% and 0.96%, respectively in comparison with the samples with no pretreatments. Evaluation of the extracted oils, using GC/MS analysis indicated that thymoquinone was the dominant phenolic component in the black cumin oil. Finally, the SEM analysis revealed that microwave and PEF can be useful in the extraction of oil from black cumin seeds since these treatments damaged cell walls and facilitated the oil extraction process.

Hot water extracted wood fiber for production of wood plastic composites (WPCs)

Treesearch

Manuel Raul Pelaez-Samaniego; Vikram Yadama; Eini Lowell; Thomas E. Amidon; Timothy L. Chaffee

2013-01-01

Undebarked ponderosa pine chips were treated by hot water extraction to modify the chemical composition. In the treated pine (TP) , the mass was reduced by approximately 20%, and the extract was composed mainly of degradation products of hemicelluloses. Wood flour produced from TP and unextracted chips (untreated pine, UP) was blended with high-density polyethylene (...

Extraction of minority carrier diffusion length of MWIR Type-II superlattice nBp detector

NASA Astrophysics Data System (ADS)

Taghipour, Zahra; Kazemi, Alireza; Myers, Stephen; Wijewarnasuriya, Priyalal; Mathews, Sen; Steenbergen, Elizabeth H.; Morath, Christian; Cowan, Vincent M.; Ariyawansa, Gamini; Scheihing, John; Krishna, Sanjay

2017-08-01

We present a model for the spectral external quantum efficiency (EQE) to extract the minority carrier diffusion length (Ln) of a unipolar nBp InAs/GaSb Type-II superlattice (T2SL) mid-wave infrared (MWIR) detector. The detector consists of a 4 μm thick p-doped 10ML InAs/10ML GaSb SL absorber with a 50% cut-off wavelength of 5 μm at 80 K and zero bias. The n-type doped InAs/AlSb SL barrier in the structure was included to reduce the GR dark current. By fitting the experimentally measured EQE data to the theoretically calculated QE based on the solution of the drift-diffusion equation, the p-type absorber was found the have Ln = 10 +/- 0.5 μm at 80K, and Ln = 12 +/- 0.5 μm at 120K and 150K. We performed the absorption coefficient measurement at different temperatures of interest. Also, we estimated the reduced background concentration and the built-in potential by utilizing a capacitance-voltage measurement technique. We used time-resolved-photoluminescence (TRPL) to determine the lifetime at 80K. With the result of the model and the lifetime measurement, we calculated the diffusion coefficient and the mobility in the T2SL detector at various temperatures. Also, we studied the behavior of different dark current mechanisms by fitting the experimentally measured and simulated dark current density under different operating temperatures and biases.

Ab-initio Pulsar Magnetosphere: Particle Acceleration in Oblique Rotators and High-energy Emission Modeling

NASA Astrophysics Data System (ADS)

Philippov, Alexander A.; Spitkovsky, Anatoly

2018-03-01

We perform global particle-in-cell simulations of pulsar magnetospheres, including pair production, ion extraction from the surface, frame-dragging corrections, and high-energy photon emission and propagation. In the case of oblique rotators, the effects of general relativity increase the fraction of the open field lines that support active pair discharge. We find that the plasma density and particle energy flux in the pulsar wind are highly non-uniform with latitude. A significant fraction of the outgoing particle energy flux is carried by energetic ions, which are extracted from the stellar surface. Their energies may extend up to a large fraction of the open field line voltage, making them interesting candidates for ultra-high-energy cosmic rays. We show that pulsar gamma-ray radiation is dominated by synchrotron emission, produced by particles that are energized by relativistic magnetic reconnection close to the Y-point and in the equatorial current sheet. In most cases, the calculated light curves contain two strong peaks, which is in general agreement with Fermi observations. The radiative efficiency decreases with increasing pulsar inclination and increasing efficiency of pair production in the current sheet, which explains the observed scatter in L γ versus \\dot{E}. We find that the high-frequency cutoff in the spectra is regulated by the pair-loading of the current sheet. Our findings lay the foundation for quantitative interpretation of Fermi observations of gamma-ray pulsars.

Application of low-frequency eddy current testing to the inspection of a double-walled tank in a reprocessing plant

NASA Astrophysics Data System (ADS)

Tajima, Naoki; Yusa, Noritaka; Hashizume, Hidetoshi

2018-04-01

This paper discusses the applicability of simple low-frequency eddy current testing to the detection of deeply embedded flaws. The study specifically considered a double tank in a reprocessing plant for extracting plutonium-uranium from spent nuclear fuels. The tank was modelled by two type 304 austenitic stainless steel plates situated with an air gap of 80 mm, and the change in the thickness of one of the plates was detected through the other plate and the air gap. Axisymmetric two-dimensional finite element simulations were conducted and found that a simple circular coil with a large diameter enabled to detect the thickness based on the magnetic flux density at the centre of the coil although the plates were as thick as 30 mm. The results of the numerical simulations were validated by experiments.

Mismatch Negativity with Visual-only and Audiovisual Speech

PubMed Central

Ponton, Curtis W.; Bernstein, Lynne E.; Auer, Edward T.

2009-01-01

The functional organization of cortical speech processing is thought to be hierarchical, increasing in complexity and proceeding from primary sensory areas centrifugally. The current study used the mismatch negativity (MMN) obtained with electrophysiology (EEG) to investigate the early latency period of visual speech processing under both visual-only (VO) and audiovisual (AV) conditions. Current density reconstruction (CDR) methods were used to model the cortical MMN generator locations. MMNs were obtained with VO and AV speech stimuli at early latencies (approximately 82-87 ms peak in time waveforms relative to the acoustic onset) and in regions of the right lateral temporal and parietal cortices. Latencies were consistent with bottom-up processing of the visible stimuli. We suggest that a visual pathway extracts phonetic cues from visible speech, and that previously reported effects of AV speech in classical early auditory areas, given later reported latencies, could be attributable to modulatory feedback from visual phonetic processing. PMID:19404730

Magnetic pinning in a superconducting film by a ferromagnetic layer with stripe domains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mancusi, D.; Di Giorgio, C.; Bobba, F.

2014-10-31

A magnetic study of superconductor/ferromagnet bilayers was performed by hysteresis loops and temperature-dependent magnetization measurements. The superconductor/ferromagnet bilayers consist of a Nb film deposited on a Py film with weak perpendicular magnetic anisotropy. By comparing the temperature-dependent magnetization data obtained on samples with different ferromagnetic layer thickness, a decrease of the magnetic pinning with increasing thickness of the ferromagnetic layer has been found. This is confirmed by the reduction of the Nb film critical current density at low fields extracted by using the magnetic irreversibility of the hysteresis loops. As the ferromagnetic layer exhibits a magnetic structure with stripe domains,more » whose width increases for increasing thickness as observed by magnetic force microscopy (MFM) measurements, we relate the reduction of the superconducting critical current in samples with thicker ferromagnetic layers to a weaker interaction between the vortices guided by the underlying magnetic template.« less

Performance Evaluation of III-V Hetero/Homojunction Esaki Tunnel Diodes on Si and Lattice Matched Substrates

NASA Astrophysics Data System (ADS)

Thomas, Paul M.

Understanding of quantum tunneling phenomenon in semiconductor systems is increasingly important as CMOS replacement technologies are investigated. This work studies a variety of heterojunction materials and types to increase tunnel currents to CMOS competitive levels and to understand how integration onto Si substrates affects performance. Esaki tunnel diodes were grown by Molecular Beam Epitaxy (MBE) on Si substrates via a graded buffer and control Esaki tunnel diodes grown on lattice matched substrates for this work. Peak current density for each diode is extracted and benchmarked to build an empirical data set for predicting diode performance. Additionally, statistics are used as tool to show peak to valley ratio for the III-V on Si sample and the control perform similarly below a threshold area. This work has applications beyond logic, as multijunction solar cell, heterojunction bipolar transistor, and light emitting diode designs all benefit from better tunnel contact design.

Neuroprotective Effects of Pomegranate Peel Extract after Chronic Infusion with Amyloid-β Peptide in Mice

PubMed Central

Morzelle, Maressa Caldeira; Salgado, Jocelem Mastrodi; Telles, Milena; Mourelle, Danilo; Bachiega, Patricia; Buck, Hudson Sousa

2016-01-01

Alzheimer’s disease is a chronic and degenerative condition that had no treatment until recently. The current therapeutic strategies reduce progression of the disease but are expensive and commonly cause side effects that are uncomfortable for treated patients. Functional foods to prevent and/or treat many conditions, including neurodegenerative diseases, represent a promising field of study currently gaining attention. To this end, here we demonstrate the effects of pomegranate (Punica granatum) peel extract (PPE) regarding spatial memory, biomarkers of neuroplasticity, oxidative stress and inflammation in a mouse model of neurodegeneration. Male C57Bl/6 mice were chronically infused for 35 days with amyloid-β peptide 1–42 (Aβ) or vehicle (control) using mini-osmotic pumps. Another group, also infused with Aβ, was treated with PPE (p.o.– βA+PPE, 800 mg/kg/day). Spatial memory was evaluated in the Barnes maze. Animals treated with PPE and in the control group exhibited a reduction in failure to find the escape box, a finding that was not observed in the Aβ group. The consumption of PPE reduced amyloid plaque density, increased the expression of neurotrophin BDNF and reduced the activity of acetylcholinesterase enzyme. A reduction in lipid peroxidation and in the concentration of the pro-inflammatory cytokine TNF-α was also observed in the PPE group. No hepatic lesions were observed in animals treated with PPE. In conclusion, administration of pomegranate peel extract has neuroprotective effects involving multiple mechanisms to prevent establishment and progression of the neurodegenerative process induced by infusion with amyloid-β peptide in mice. PMID:27829013

Supercapacitors based on pillared graphene nanostructures.

PubMed

Lin, Jian; Zhong, Jiebin; Bao, Duoduo; Reiber-Kyle, Jennifer; Wang, Wei; Vullev, Valentine; Ozkan, Mihrimah; Ozkan, Cengiz S

2012-03-01

We describe the fabrication of highly conductive and large-area three dimensional pillared graphene nanostructure (PGN) films from assembly of vertically aligned CNT pillars on flexible copper foils for applications in electric double layer capacitors (EDLC). The PGN films synthesized via a one-step chemical vapor deposition process on flexible copper foils exhibit high conductivity with sheet resistance as low as 1.6 ohms per square and possessing high mechanical flexibility. Raman spectroscopy indicates the presence of multi walled carbon nanotubes (MWCNT) and their morphology can be controlled by the growth conditions. It was discovered that nitric acid treatment can significantly increase the specific capacitance of the devices. EDLC devices based on PGN electrodes (surface area of 565 m2/g) demonstrate enhanced performance with specific capacitance value as high as 330 F/g extracted from the current density-voltage (CV) measurements and energy density value of 45.8 Wh/kg. The hybrid graphene-CNT nanostructures are attractive for applications including supercapacitors, fuel cells and batteries.

Compression of pulsed electron beams for material tests

NASA Astrophysics Data System (ADS)

Metel, Alexander S.

2018-03-01

In order to strengthen the surface of machine parts and investigate behavior of their materials exposed to highly dense energy fluxes an electron gun has been developed, which produces the pulsed beams of electrons with the energy up to 300 keV and the current up to 250 A at the pulse width of 100-200 µs. Electrons are extracted into the accelerating gap from the hollow cathode glow discharge plasma through a flat or a spherical grid. The flat grid produces 16-cm-diameter beams with the density of transported per one pulse energy not exceeding 15 J·cm-2, which is not enough even for the surface hardening. The spherical grid enables compression of the beams and regulation of the energy density from 15 J·cm-2 up to 15 kJ·cm-2, thus allowing hardening, pulsed melting of the machine part surface with the further high-speed recrystallization as well as an explosive ablation of the surface layer.

Driving ionospheric outflows and magnetospheric O + energy density with Alfvén waves

DOE PAGES

Chaston, C. C.; Bonnell, J. W.; Reeves, Geoffrey D.; ...

2016-05-11

We show how dispersive Alfvén waves observed in the inner magnetosphere during geomagnetic storms can extract O + ions from the topside ionosphere and accelerate these ions to energies exceeding 50 keV in the equatorial plane. This occurs through wave trapping, a variant of “shock” surfing, and stochastic ion acceleration. These processes in combination with the mirror force drive field-aligned beams of outflowing ionospheric ions into the equatorial plane that evolve to provide energetic O + distributions trapped near the equator. These waves also accelerate preexisting/injected ion populations on the same field lines. We show that the action of dispersivemore » Alfvén waves over several minutes may drive order of magnitude increases in O + ion pressure to make substantial contributions to magnetospheric ion energy density. These wave accelerated ions will enhance the ring current and play a role in the storm time evolution of the magnetosphere.« less

Semiconducting molecular crystals: Bulk in-gap states modified by structural and chemical defects

NASA Astrophysics Data System (ADS)

Haas, S.; Krellner, C.; Goldmann, C.; Pernstich, K. P.; Gundlach, D. J.; Batlogg, B.

2007-03-01

Charge transport in organic molecular crystals is strongly influenced by the density of localized in-gap states (traps). Thus, a profound knowledge of the defect states' origin is essential. Temperature-dependent space-charge limited current (TD-SCLC) spectroscopy was used as a powerful tool to quantitatively study the density of states (DOS) in high-quality rubrene and pentacene single crystals. In particular, changes of the DOS due to intentionally induced chemical and structural defects were monitored. For instance, the controlled exposure of pentacene and rubrene to x-ray radiation results in a broad over-all increase of the DOS. Namely, the ionizing radiation induces a variety of both chemical and structural defects. On the other hand, exposure of rubrene to UV-excited oxygen is reflected in a sharp peak in the DOS, whereas in a similar experiment with pentacene oxygen acts as a dopant, and possible defects are metastable on the time-scale of the measurement, thus leaving the extracted DOS virtually unchanged.

Many-Body Spectral Functions from Steady State Density Functional Theory.

PubMed

Jacob, David; Kurth, Stefan

2018-03-14

We propose a scheme to extract the many-body spectral function of an interacting many-electron system from an equilibrium density functional theory (DFT) calculation. To this end we devise an ideal scanning tunneling microscope (STM) setup and employ the recently proposed steady-state DFT formalism (i-DFT) which allows one to calculate the steady current through a nanoscopic region coupled to two biased electrodes. In our setup, one of the electrodes serves as a probe ("STM tip"), which is weakly coupled to the system we want to measure. In the ideal STM limit of vanishing coupling to the tip, the system is restored to quasi-equilibrium and the normalized differential conductance yields the exact equilibrium many-body spectral function. Calculating this quantity from i-DFT, we derive an exact relation expressing the interacting spectral function in terms of the Kohn-Sham one. As illustrative examples, we apply our scheme to calculate the spectral functions of two nontrivial model systems, namely the single Anderson impurity model and the Constant Interaction Model.

Comparation of Hypolipidemic and Antioxidant Effects of Aqueous and Ethanol Extracts of Crataegus pinnatifida Fruit in High-Fat Emulsion-Induced Hyperlipidemia Rats

PubMed Central

Shao, Feng; Gu, Lifei; Chen, Huijuan; Liu, Ronghua; Huang, Huilian; Ren, Gang

2016-01-01

Background: Hawthorn (Crataegus pinnatifida) is a Chinese medicinal plant traditionally used in the treatment of hyperlipidemia. Recently, studies indicated free radical scavenging was one of the major pathways to alleviate hyperlipidemia. Moreover, hawthorn fruit is a rich source of phenols, which quench free radical and attenuate hyperlipidemia. However, the phenols vary with processing methods, especially solvent type. Objective: Our aim was to compare hypolipidemic and antioxidant effects of aqueous and ethanol extracts of hawthorn fruit in hyperlipidemia rats. Materials and Methods: After a 4-week treatment of high-fat emulsion, lipid profile levels and antioxidant levels of two extracts were determined using commercial analysis. Total phenols content in the extract of hawthorn fruit was determined colorimetrically by the Folin–Ciocalteu method. Results: Both ethanol and aqueous extracts of hawthorn fruit possessed hypolipidemic and antioxidant activities. Simultaneously, stronger activities were observed in ethanol extract. Besides, total phenols content in ethanol extract from the same quality of hawthorn fruit was 3.9 times more than that in aqueous extract. Conclusion: The obvious difference of hypolipidemic and antioxidant effects between ethanol extract and aqueous extract of hawthorn fruit was probably due to the presence of total phenols content, under the influence of extraction solvent. SUMMARY Ethanol extract of hawthorn fruit exhibited more favorable hypolipidemic and antioxidant effects than aqueous extract. The higher effects could be due to the higher content of total phenols that varies with extraction solvent. Abbreviations used: TC: Total cholesterol, TG: Triglyceride, LDL-C: Low-density lipoprotein cholesterol, HDL-C: High-density lipoprotein cholesterol, GSH-Px: Glutathione peroxidase, SOD: Superoxide dismutase, MDA: Malondialdehyde, CAT: Catalase, NO: Nitric oxide, NOS: Nitric oxide synthase, SR-BI: Scavenger receptor Class B Type I PMID:27019563

Comparation of Hypolipidemic and Antioxidant Effects of Aqueous and Ethanol Extracts of Crataegus pinnatifida Fruit in High-Fat Emulsion-Induced Hyperlipidemia Rats.

PubMed

Shao, Feng; Gu, Lifei; Chen, Huijuan; Liu, Ronghua; Huang, Huilian; Ren, Gang

2016-01-01

Hawthorn (Crataegus pinnatifida) is a Chinese medicinal plant traditionally used in the treatment of hyperlipidemia. Recently, studies indicated free radical scavenging was one of the major pathways to alleviate hyperlipidemia. Moreover, hawthorn fruit is a rich source of phenols, which quench free radical and attenuate hyperlipidemia. However, the phenols vary with processing methods, especially solvent type. Our aim was to compare hypolipidemic and antioxidant effects of aqueous and ethanol extracts of hawthorn fruit in hyperlipidemia rats. After a 4-week treatment of high-fat emulsion, lipid profile levels and antioxidant levels of two extracts were determined using commercial analysis. Total phenols content in the extract of hawthorn fruit was determined colorimetrically by the Folin-Ciocalteu method. Both ethanol and aqueous extracts of hawthorn fruit possessed hypolipidemic and antioxidant activities. Simultaneously, stronger activities were observed in ethanol extract. Besides, total phenols content in ethanol extract from the same quality of hawthorn fruit was 3.9 times more than that in aqueous extract. The obvious difference of hypolipidemic and antioxidant effects between ethanol extract and aqueous extract of hawthorn fruit was probably due to the presence of total phenols content, under the influence of extraction solvent. Ethanol extract of hawthorn fruit exhibited more favorable hypolipidemic and antioxidant effects than aqueous extract. The higher effects could be due to the higher content of total phenols that varies with extraction solvent. Abbreviations used: TC: Total cholesterol, TG: Triglyceride, LDL-C: Low-density lipoprotein cholesterol, HDL-C: High-density lipoprotein cholesterol, GSH-Px: Glutathione peroxidase, SOD: Superoxide dismutase, MDA: Malondialdehyde, CAT: Catalase, NO: Nitric oxide, NOS: Nitric oxide synthase, SR-BI: Scavenger receptor Class B Type I.

Particle Image Velocimetry Study of Density Current Fronts

ERIC Educational Resources Information Center

Martin, Juan Ezequiel

2009-01-01

Gravity currents are flows that occur when a horizontal density difference causes fluid to move under the action of gravity; density currents are a particular case, for which the scalar causing the density difference is conserved. Flows with a strong effect of the horizontal density difference, even if only partially driven by it--such as the…

TRACTOGRAPHY DENSITY AND NETWORK MEASURES IN ALZHEIMER'S DISEASE.

PubMed

Prasad, Gautam; Nir, Talia M; Toga, Arthur W; Thompson, Paul M

2013-04-01

Brain connectivity declines in Alzheimer's disease (AD), both functionally and structurally. Connectivity maps and networks derived from diffusion-based tractography offer new ways to track disease progression and to understand how AD affects the brain. Here we set out to identify (1) which fiber network measures show greatest differences between AD patients and controls, and (2) how these effects depend on the density of fibers extracted by the tractography algorithm. We computed brain networks from diffusion-weighted images (DWI) of the brain, in 110 subjects (28 normal elderly, 56 with early and 11 with late mild cognitive impairment, and 15 with AD). We derived connectivity matrices and network topology measures, for each subject, from whole-brain tractography and cortical parcellations. We used an ODF lookup table to speed up fiber extraction, and to exploit the full information in the orientation distribution function (ODF). This made it feasible to compute high density connectivity maps. We used accelerated tractography to compute a large number of fibers to understand what effect fiber density has on network measures and in distinguishing different disease groups in our data. We focused on global efficiency, transitivity, path length, mean degree, density, modularity, small world, and assortativity measures computed from weighted and binary undirected connectivity matrices. Of all these measures, the mean nodal degree best distinguished diagnostic groups. High-density fiber matrices were most helpful for picking up the more subtle clinical differences, e.g. between mild cognitively impaired (MCI) and normals, or for distinguishing subtypes of MCI (early versus late). Care is needed in clinical analyses of brain connectivity, as the density of extracted fibers may affect how well a network measure can pick up differences between patients and controls.

Determination of element affinities by density fractionation of bulk coal samples

USGS Publications Warehouse

Querol, X.; Klika, Z.; Weiss, Z.; Finkelman, R.B.; Alastuey, A.; Juan, R.; Lopez-Soler, A.; Plana, F.; Kolker, A.; Chenery, S.R.N.

2001-01-01

A review has been made of the various methods of determining major and trace element affinities for different phases, both mineral and organic in coals, citing their various strengths and weaknesses. These include mathematical deconvolution of chemical analyses, direct microanalysis, sequential extraction procedures and density fractionation. A new methodology combining density fractionation with mathematical deconvolution of chemical analyses of whole coals and their density fractions has been evaluated. These coals formed part of the IEA-Coal Research project on the Modes of Occurrence of Trace Elements in Coal. Results were compared to a previously reported sequential extraction methodology and showed good agreement for most elements. For particular elements (Be, Mo, Cu, Se and REEs) in specific coals where disagreement was found, it was concluded that the occurrence of rare trace element bearing phases may account for the discrepancy, and modifications to the general procedure must be made to account for these.

Neutron density distributions of {sup 204,206,208}Pb deduced via proton elastic scattering at E{sub p}=295 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zenihiro, J.; Sakaguchi, H.; Murakami, T.

Cross sections and analyzing powers for polarized proton elastic scattering from {sup 58}Ni, and {sup 204,206,208}Pb were measured at intermediate energy E{sub p}=295 MeV. An effective relativistic Love-Franey interaction is tuned to reproduce {sup 58}Ni scattering data within the framework of the relativistic impulse approximation. The neutron densities of the lead isotopes are deduced using model-independent sum-of-Gaussians distributions. Their error envelopes are estimated by a new {chi}{sup 2} criterion including uncertainties associated with the reaction model. The systematic behaviors of extracted error envelopes of the neutron density distributions in {sup 204,206,208}Pb are presented. The extracted neutron and proton density distributionmore » of {sup 208}Pb gives a neutron skin thickness of {Delta}r{sub np}=0.211{sub -0.063}{sup +0.054} fm.« less

Microstructure and Corrosion Behavior of Laser Synthesized Cobalt Based Powder on Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Adesina, O. S.; Popoola, A. P. I.; Pityana, S. L.; Oloruntoba, D. T.

2018-05-01

The corrosion behavior of titanium alloys when used for various dynamic offshore components has been a major concern of titanium drilling risers in deepwater energy extraction. A way of achieving specified requirement is the development of coatings suitable to protect the base material against corrosion. In this work, laser cladding technique which is known as a leading edge due to its distinctive properties and outcomes was used in synthesizing Co-based powder on titanium alloy. The processing parameters used were laser power of 900W; scan speed of 0.6 to 1.2 m/min; powderfeedrate1.0g/min;beamspotsize3mm;gasflowrate1.2L/min.The effects of cobalt addition and laser parameters on corrosion behavior of laser clad Ti6AL4V coating in 0.5M sulfuric medium were investigated using linear potentiodynamic polarization. The changes in microstructure and corrosion behavior were analyzed using scanning electron microscopy (SEM) while the X –ray diffraction (XRD) indicates the intermetallics in the coatings. Results showed that the coatings displayed good metallurgical bonding with dendritic formations between the coatings and the substrate. The anodic current density increased with lower scan speed. However, the corrosion current densities of laser-clad samples were lower than Ti6Al4V alloy.

Carbon coated nano-LiTi2(PO4)3 electrodes for non-aqueous hybrid supercapacitors.

PubMed

Aravindan, V; Chuiling, W; Reddy, M V; Rao, G V Subba; Chowdari, B V R; Madhavi, S

2012-04-28

The Pechini type polymerizable complex decomposition method is employed to prepare LiTi(2)(PO(4))(3) at 1000 °C in air. High energy ball milling followed by carbon coating by the glucose-method yielded C-coated nano-LiTi(2)(PO(4))(3) (LTP) with a crystallite size of 80(±5) nm. The phase is characterized by X-ray diffraction, Rietveld refinement, thermogravimetry, SEM, HR-TEM and Raman spectra. Lithium cycling properties of LTP show that 1.75 moles of Li (~121 mA h g(-1) at 15 mA g(-1) current) per formula unit can be reversibly cycled between 2 and 3.4 V vs. Li with 83% capacity retention after 70 cycles. Cyclic voltammograms (CV) reveal the two-phase reaction mechanism during Li insertion/extraction. A hybrid electrochemical supercapacitor (HEC) with LTP as negative electrode and activated carbon (AC) as positive electrode in non-aqueous electrolyte is studied by CV at various scan rates and by galvanostatic cycling at various current rates up to 1000 cycles in the range 0-3 V. Results show that the HEC delivers a maximum energy density of 14 W h kg(-1) and a power density of 180 W kg(-1). This journal is © the Owner Societies 2012

The role of Hurst exponent on cold field electron emission from conducting materials: from electric field distribution to Fowler-Nordheim plots

PubMed Central

de Assis, T. A.

2015-01-01

This work considers the effects of the Hurst exponent (H) on the local electric field distribution and the slope of the Fowler-Nordheim (FN) plot when considering the cold field electron emission properties of rough Large-Area Conducting Field Emitter Surfaces (LACFESs). A LACFES is represented by a self-affine Weierstrass-Mandelbrot function in a given spatial direction. For 0.1 ≤ H < 0.5, the local electric field distribution exhibits two clear exponential regimes. Moreover, a scaling between the macroscopic current density () and the characteristic kernel current density (), , with an H-dependent exponent , has been found. This feature, which is less pronounced (but not absent) in the range where more smooth surfaces have been found (), is a consequence of the dependency between the area efficiency of emission of a LACFES and the macroscopic electric field, which is often neglected in the interpretation of cold field electron emission experiments. Considering the recent developments in orthodox field emission theory, we show that the exponent must be considered when calculating the slope characterization parameter (SCP) and thus provides a relevant method of more precisely extracting the characteristic field enhancement factor from the slope of the FN plot. PMID:26035290

Correcting magnetic probe perturbations on current density measurements of current carrying plasmas.

PubMed

Knoblauch, P; Raspa, V; Di Lorenzo, F; Lazarte, A; Clausse, A; Moreno, C

2010-09-01

A method to infer the current density distribution in the current sheath of a plasma focus discharge from a magnetic probe is formulated and then applied to experimental data obtained in a 1.1 kJ device. Distortions on the magnetic probe signal caused by current redistribution and by a time-dependent total discharge current are considered simultaneously, leading to an integral equation for the current density. Two distinct, easy to implement, numerical procedures are given to solve such equation. Experimental results show the coexistence of at least two maxima in the current density structure of a nitrogen sheath.

Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

2015-01-01

ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the same time.

Silicon-Based Lithium-Ion Capacitor for High Energy and High Power Application

NASA Technical Reports Server (NTRS)

Wu, James J.; Demattia, Brianne; Loyselle, Patricia; Reid, Concha; Kohout, Lisa

2017-01-01

Si-based Li-ion capacitor has been developed and demonstrated. The results show it is feasible to improve both power density and energy density in this configuration. The applied current density impacts the power and energy density: low current favors energy density while high current favors power density. Active carbon has a better rate capability than Si. Next StepsFuture Directions. Si electrode needs to be further studied and improved. Further optimization of SiAC ratio and evaluation of its impact on energy density and power density.

Dioscoreophyllum cumminsii (Stapf) Diels leaves halt high-fructose induced metabolic syndrome: Hyperglycemia, insulin resistance, inflammation and oxidative stress.

PubMed

Ajiboye, T O; Aliyu, H; Tanimu, M A; Muhammad, R M; Ibitoye, O B

2016-11-04

Dioscoreophyllum cumminsii is widely used in the management and treatment of diabetes and obesity in Nigeria. This study evaluates the effect of aqueous leaf extract of D. cumminsii on high-fructose diet-induced metabolic syndrome. Seventy male rats were randomized into seven groups. All rats were fed with high-fructose diet for 9 weeks except groups A and C rats, which received control diet. In addition to the diet treatment, groups A and B rats received distilled water for 3 weeks starting from the seventh week of the experimental period. Rats in groups C-F orally received 400, 100, 200 and 400mg/kg body weight of aqueous leaf extract of D. cumminsii respectively, while group G received 300mg/kg bodyweight of metformin for 3 weeks starting from the seventh week. There was significant (p<0.05) reduction in high-fructose diet-mediated increase in body weight, body mass index, abdominal circumference, blood glucose, insulin, leptin and insulin resistance by aqueous leaf extract of D. cumminsii. Conversely, high-fructose diet-mediated decrease in adiponectin was reversed by the extract. Increased levels of cholesterol, triglycerides, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, atherogenic index, cardiac index and coronary artery index were significantly lowered by the extract, while high-fructose diet mediated decrease in high-density lipoprotein cholesterol was increased by the extract. Tumour necrosis factor-α, interleukin-6 and interleukin-8 levels increased significantly in high-fructose diet-fed rats, which were significantly reversed by the extract. High-fructose mediated-decrease in superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase and glutathione reduced were significantly reversed by aqueous leaf extract of D. cumminsii. Conversely, elevated levels of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and fragmented DNA were significantly lowered by the extract. Data generated in this study further laid credence to the hypoglycemic activity of aqueous leaf extract of D. cumminsii as evident from the reversal of hyperglycemia, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome rats. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Fourier transform magnetic resonance current density imaging (FT-MRCDI) from one component of magnetic flux density.

PubMed

Ider, Yusuf Ziya; Birgul, Ozlem; Oran, Omer Faruk; Arikan, Orhan; Hamamura, Mark J; Muftuler, L Tugan

2010-06-07

Fourier transform (FT)-based algorithms for magnetic resonance current density imaging (MRCDI) from one component of magnetic flux density have been developed for 2D and 3D problems. For 2D problems, where current is confined to the xy-plane and z-component of the magnetic flux density is measured also on the xy-plane inside the object, an iterative FT-MRCDI algorithm is developed by which both the current distribution inside the object and the z-component of the magnetic flux density on the xy-plane outside the object are reconstructed. The method is applied to simulated as well as actual data from phantoms. The effect of measurement error on the spatial resolution of the current density reconstruction is also investigated. For 3D objects an iterative FT-based algorithm is developed whereby the projected current is reconstructed on any slice using as data the Laplacian of the z-component of magnetic flux density measured for that slice. In an injected current MRCDI scenario, the current is not divergence free on the boundary of the object. The method developed in this study also handles this situation.

In-vivo measurement of relationship between applied current amplitude and current density magnitude from 10 mA to 110 mA.

PubMed

DeMonte, Tim P; Wang, Dinghui; Ma, Weijing; Gao, Jia-Hong; Joy, Michael L G

2009-01-01

Current density imaging (CDI) is a magnetic resonance imaging (MRI) technique used to quantitatively measure current density vectors throughout the volume of an object/subject placed in the MRI system. Electrical current pulses are applied externally to the object/subject and are synchronized with the MRI sequence. In this work, CDI is used to measure average current density magnitude in the torso region of an in-vivo piglet for applied current pulse amplitudes ranging from 10 mA to 110 mA. The relationship between applied current amplitude and current density magnitude is linear in simple electronic elements such as wires and resistors; however, this relationship may not be linear in living tissue. An understanding of this relationship is useful for research in defibrillation, human electro-muscular incapacitation (e.g. TASER(R)) and other bioelectric stimulation devices. This work will show that the current amplitude to current density magnitude relationship is slightly nonlinear in living tissue in the range of 10 mA to 110 mA.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Dingguo, E-mail: laidingguo@nint.ac.cn; Qiu, Mengtong; Xu, Qifu

This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that themore » space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.« less

Current density imaging sequence for monitoring current distribution during delivery of electric pulses in irreversible electroporation.

PubMed

Serša, Igor; Kranjc, Matej; Miklavčič, Damijan

2015-01-01

Electroporation is gaining its importance in everyday clinical practice of cancer treatment. For its success it is extremely important that coverage of the target tissue, i.e. treated tumor, with electric field is within the specified range. Therefore, an efficient tool for the electric field monitoring in the tumor during delivery of electroporation pulses is needed. The electric field can be reconstructed by the magnetic resonance electric impedance tomography method from current density distribution data. In this study, the use of current density imaging with MRI for monitoring current density distribution during delivery of irreversible electroporation pulses was demonstrated. Using a modified single-shot RARE sequence, where four 3000 V and 100 μs long pulses were included at the start, current distribution between a pair of electrodes inserted in a liver tissue sample was imaged. Two repetitions of the sequence with phases of refocusing radiofrequency pulses 90° apart were needed to acquire one current density image. For each sample in total 45 current density images were acquired to follow a standard protocol for irreversible electroporation where 90 electric pulses are delivered at 1 Hz. Acquired current density images showed that the current density in the middle of the sample increased from first to last electric pulses by 60%, i.e. from 8 kA/m2 to 13 kA/m2 and that direction of the current path did not change with repeated electric pulses significantly. The presented single-shot RARE-based current density imaging sequence was used successfully to image current distribution during delivery of short high-voltage electric pulses. The method has a potential to enable monitoring of tumor coverage by electric field during irreversible electroporation tissue ablation.

Modeling of Optical Waveguide Poling and Thermally Stimulated Discharge (TSD) Charge and Current Densities for Guest/Host Electro Optic Polymers

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Ashley, Paul R.; Abushagur, Mustafa

2004-01-01

A charge density and current density model of a waveguide system has been developed to explore the effects of electric field electrode poling. An optical waveguide may be modeled during poling by considering the dielectric charge distribution, polarization charge distribution, and conduction charge generated by the poling field. These charge distributions are the source of poling current densities. The model shows that boundary charge current density and polarization current density are the major source of currents measured during poling and thermally stimulated discharge These charge distributions provide insight into the poling mechanisms and are directly related to E(sub A), and, alpha(sub r). Initial comparisons with experimental data show excellent correlation to the model results.

The role of the invasive bivalve Ensis directus as food source for fish and birds in the Dutch coastal zone

NASA Astrophysics Data System (ADS)

Tulp, Ingrid; Craeymeersch, Johan; Leopold, Mardik; van Damme, Cindy; Fey, Frouke; Verdaat, Hans

2010-12-01

The razor clam Ensis directus was introduced to Europe presumably as larvae in ballast water around 1978. Starting in the German Bight it spread northward and southward along the continental coastline. Currently it is the most common shellfish species in the Dutch coastal zone, where it mainly occurs in the Voordelta and off the Wadden Sea islands. The mean density of E. directus in the Dutch coastal zone increased from around 2-5 individuals m -2 in the late '90's to around 12-19 individuals m -2 from 2002 onwards. Diet studies show that E. directus makes up a significant proportion in the current diet of plaice, sole, dab, flounder and dragonet and in the diet of eider and common scoter. In recent years E. directus contributed 20-100% of the total wet weight in fish stomachs. The proportion E. directus in the diet increases with fish length. Based on stomach contents of oiled and beached birds and of faeces samples the recent frequency of occurrence is 85-90% in eider and 26% in common scoter. Also waders, gulls and corvids prey on E. directus but the contribution to the diet is still unquantified. Because of its great burying depth the species is not easily accessible. Fish either profit from massive die-offs that regularly occur, or they extract (probably only the smaller) individuals from the sediment. Sea ducks can extract E. directus from the sediment, while shorebirds and gulls feed on dying E. directus washing up on the shore. E. directus is possibly an important food item for fish and seabirds when they occur in high densities and in the right size classes. Since the availability depends greatly on massive die-offs, shell size, burying depth and water depth, it is probably not a very reliable food source. Judging from the role E. directus currently plays for the higher trophic levels, its introduction must have caused a major change in the food relations in its distribution area.

Electrical characteristics of silicon percolating nanonet-based field effect transistors in the presence of dispersion

NASA Astrophysics Data System (ADS)

Cazimajou, T.; Legallais, M.; Mouis, M.; Ternon, C.; Salem, B.; Ghibaudo, G.

2018-05-01

We studied the current-voltage characteristics of percolating networks of silicon nanowires (nanonets), operated in back-gated transistor mode, for future use as gas or biosensors. These devices featured P-type field-effect characteristics. It was found that a Lambert W function-based compact model could be used for parameter extraction of electrical parameters such as apparent low field mobility, threshold voltage and subthreshold slope ideality factor. Their variation with channel length and nanowire density was related to the change of conduction regime from direct source/drain connection by parallel nanowires to percolating channels. Experimental results could be related in part to an influence of the threshold voltage dispersion of individual nanowires.

Optimization of the Supercritical Carbon Dioxide Separation of Bergapten from Bergamot Essential Oil.

PubMed

Sicari, Vincenzo

2018-01-01

The possibility of following traditional cold-press extraction with the post process continuous separation of bergapten from bergamot essential oil was investigated. A fractionation tower was used in an experiment in which cold-pressed bergamot oil was extracted in a continuous countercurrent process by supercritical carbon dioxide under different conditions. Bergapten is fairly soluble in CO2 in its supercritical phase, in particular at a density of 277.90 kg⋅m-3, corresponding to a pressure of 8 MPa and temperature of 40°C. Under these conditions, an extract with 0.198% bergapten was obtained, a figure slightly below the percentage of bergapten contained in cold-pressed oil (0.21%). However, at densities below 200 kg⋅m-3, the amount of bergapten in the extracted oil was negligible. Of all tested conditions for separation, the best was found to be at a pressure of 8 MPa and temperature of 70°C, conditions under which bergapten was not detected. The results of the experiment showed that bergapten, and the non-volatile fraction in general, was extracted only in small quantities and was not extracted at all with at a CO2 pressure of 8 MPa.

Evaluation of hair growth promoting activity of Phyllanthus niruri

PubMed Central

Patel, Satish; Sharma, Vikas; S. Chauhan, Nagendra; Thakur, Mayank; Dixit, Vinod Kumar

2015-01-01

Objective: This study was designed to investigate the potential Phyllanthus niruri (P. niruri ) extracts in promotion of hair growth. Materials and Methods: Here, we studied the hair growth promoting activity of petroleum ether extract of P. niruri following its topical administration. Alopecia was induced in albino rats by subcutaneous administration of testosterone for 21 days. Evaluation of hair loss inhibition was done by concurrent administration of extract and monitoring parameters like follicular density, anagen/telogen (A/T) ratio and histological observation of animal skin sections. Finasteride solution was applied topically as standard. In vitro experiments were also performed to study the effect of extract on the activity of 5α-reductase enzyme Results: Groups treated with petroleum ether extract of plant showed hair re-growth as reflected by follicular density, A/T ratio and skin sections. Histopathology and morphologic observations of hair re-growth at shaved sites showed active follicular proliferation. In vitro experiments results showed inhibitory activity of petroleum ether extract on type-2 5α-reductase enzyme and an increase in the amount of testosterone with increasing concentrations. Conclusion: It could be concluded that petroleum ether extracts of P. niruri might be useful in the treatment of testosterone-induced alopecia in the experimental animal by inhibiting 5α-reductase enzyme. PMID:26693408

The Extract of Roots of Sophora flavescens Enhances the Recovery of Motor Function by Axonal Growth in Mice with a Spinal Cord Injury

PubMed Central

Tanabe, Norio; Kuboyama, Tomoharu; Kazuma, Kohei; Konno, Katsuhiro; Tohda, Chihiro

2016-01-01

Although axonal extension to reconstruct spinal tracts should be effective for restoring function after spinal cord injury (SCI), chondroitin sulfate proteoglycan (CSPG) levels increase at spinal cord lesion sites, and inhibit axonal regrowth. In this study, we found that the water extract of roots of Sophora flavescens extended the axons of mouse cortical neurons, even on a CSPG-coated surface. Consecutive oral administrations of S. flavescens extract to SCI mice for 31 days increased the density of 5-HT-positive axons at the lesion site and improved the motor function. Further, the active constituents in the S. flavescens extract were identified. The water and alkaloid fractions of the S. flavescens extract each exhibited axonal extension activity in vitro. LC/MS analysis revealed that these fractions mainly contain matrine and/or oxymatrine, which are well-known major compounds in S. flavescens. Matrine and oxymatrine promoted axonal extension on the CSPG-coated surface. This study is the first to demonstrate that S. flavescens extract, matrine, and oxymatrine enhance axonal growth in vitro, even on a CSPG-coated surface, and that S. flavescens extract improves motor function and increases axonal density in SCI mice. PMID:26834638

Automatic drawing for traffic marking with MMS LIDAR intensity

NASA Astrophysics Data System (ADS)

Takahashi, G.; Takeda, H.; Shimano, Y.

2014-05-01

Upgrading the database of CYBER JAPAN has been strategically promoted because the "Basic Act on Promotion of Utilization of Geographical Information", was enacted in May 2007. In particular, there is a high demand for road information that comprises a framework in this database. Therefore, road inventory mapping work has to be accurate and eliminate variation caused by individual human operators. Further, the large number of traffic markings that are periodically maintained and possibly changed require an efficient method for updating spatial data. Currently, we apply manual photogrammetry drawing for mapping traffic markings. However, this method is not sufficiently efficient in terms of the required productivity, and data variation can arise from individual operators. In contrast, Mobile Mapping Systems (MMS) and high-density Laser Imaging Detection and Ranging (LIDAR) scanners are rapidly gaining popularity. The aim in this study is to build an efficient method for automatically drawing traffic markings using MMS LIDAR data. The key idea in this method is extracting lines using a Hough transform strategically focused on changes in local reflection intensity along scan lines. However, also note that this method processes every traffic marking. In this paper, we discuss a highly accurate and non-human-operator-dependent method that applies the following steps: (1) Binarizing LIDAR points by intensity and extracting higher intensity points; (2) Generating a Triangulated Irregular Network (TIN) from higher intensity points; (3) Deleting arcs by length and generating outline polygons on the TIN; (4) Generating buffers from the outline polygons; (5) Extracting points from the buffers using the original LIDAR points; (6) Extracting local-intensity-changing points along scan lines using the extracted points; (7) Extracting lines from intensity-changing points through a Hough transform; and (8) Connecting lines to generate automated traffic marking mapping data.

Antihyperglycemic activity of Albizzia lebbeck bark extract in streptozotocin-nicotinamide induced type II diabetes mellitus rats.

PubMed

Patel, Priyank A; Parikh, Mihir P; Johari, Sarika; Gandhi, Tejal R

2015-01-01

Albizzia lebbeck (L.) Benth. (Family - Leguminosae) extract is a proven mast cell stabilizing agent. Mast cells are involved in the inflammatory processes leading to the diabetes mellitus. To evaluate the effect of A. lebbeck against experimentally induced type 2 diabetes mellitus in rats. Female Sprague-Dawley rats were randomly allocated to six groups (n = 6). Diabetes was induced by single intraperitoneal injection of streptozotocin (50 mg/kg) given after 15 min of nicotinamide administration (110 mg/kg). Treatment with methanolic extract of A. lebbeck bark (MEAL) and metformin drug as standard was given for 21 days. Serum glucose (GLU) levels were measured on the 0 day and on 1(st), 7(th), 14(th) and 21(st) day after diabetes induction. After completion of study period, various biochemical parameters in serum such as - GLU, lipid profile, urea and creatinine were estimated. One-way analysis of variance followed with post-hoc Dunnett's test was used to analyse the data. Statistical significance for the values was set at P< 0.05. MEAL significantly decreased the level of serum GLU, creatinine, urea, cholesterol, triglycerides, low-density lipoprotein-cholesterol, very low-density lipoprotein-cholesterol and increased high-density lipoprotein levels. A. lebbeck bark extract showed antihyperglycaemic activity along with antihyperlipidemic effect.

Rauvolfia Grandiflora (Apocynaceae) Extract Interferes With Staphylococcal Density, Enterotoxin Production And Antimicrobial Activity

PubMed Central

de Almeida Carlos, Lanamar; da Silva Amaral, Kenas Aguiar; Curcino Vieira, Ivo José; Mathias, Leda; Braz-Filho, Raimundo; Silva Samarão, Solange; Vieira-da-Motta, Olney

2010-01-01

Staphylococci bacteria are involved in many human and animal infections and development of alternative antimicrobial drugs against pathogenic bacteria is of great interest to the pharmaceutical industry. This study investigated the in vitro effect of Rauvolfia grandiflora methanol extract (root bark fraction) (RGE) on the density of ATCC strains of Staphylococcus aureus and Staphylococcus epidermidis, and a clinical enterotoxin-producer, S. aureus bovine strain. The alkaloid, isoreserpiline, obtained from dichloromethane extract of R. grandiflora was ineffective against the strains tested. After incubation of staphylococci strains in the presence of 1.2 μg.mL-1 RGE, a significant inhibition of cell growth was observed using both spectrophotometry and ELISA assays. Twelve drugs were evaluated for their antimicrobial effects on culture RGE-treated cells using the disk diffusion method. Penicillin resistant strains became sensitive to the drug after RGE treatment. Furthermore, enterotoxin production by RGE-treated S. aureus was evaluated using a standardized ELISA method. Although staphylococcal LSA 88 bovine strain cells remained viable after exposure to the extract, enterotoxin production was precluded in 20% after RGE treatment. Significant interference in staphylococci cell density, drug sensitivity and enterotoxin secretion was observed after treatment. The study highlights the necessity to find new methods of disease prevention and new antibiotic therapies against staphylococcal infections. PMID:24031536

Rauvolfia grandiflora (apocynaceae) extract interferes with staphylococcal density, enterotoxin production and antimicrobial activity.

PubMed

de Almeida Carlos, Lanamar; da Silva Amaral, Kenas Aguiar; Curcino Vieira, Ivo José; Mathias, Leda; Braz-Filho, Raimundo; Silva Samarão, Solange; Vieira-da-Motta, Olney

2010-07-01

Staphylococci bacteria are involved in many human and animal infections and development of alternative antimicrobial drugs against pathogenic bacteria is of great interest to the pharmaceutical industry. This study investigated the in vitro effect of Rauvolfia grandiflora methanol extract (root bark fraction) (RGE) on the density of ATCC strains of Staphylococcus aureus and Staphylococcus epidermidis, and a clinical enterotoxin-producer, S. aureus bovine strain. The alkaloid, isoreserpiline, obtained from dichloromethane extract of R. grandiflora was ineffective against the strains tested. After incubation of staphylococci strains in the presence of 1.2 μg.mL(-1) RGE, a significant inhibition of cell growth was observed using both spectrophotometry and ELISA assays. Twelve drugs were evaluated for their antimicrobial effects on culture RGE-treated cells using the disk diffusion method. Penicillin resistant strains became sensitive to the drug after RGE treatment. Furthermore, enterotoxin production by RGE-treated S. aureus was evaluated using a standardized ELISA method. Although staphylococcal LSA 88 bovine strain cells remained viable after exposure to the extract, enterotoxin production was precluded in 20% after RGE treatment. Significant interference in staphylococci cell density, drug sensitivity and enterotoxin secretion was observed after treatment. The study highlights the necessity to find new methods of disease prevention and new antibiotic therapies against staphylococcal infections.

Safety parameter considerations of anodal transcranial Direct Current Stimulation in rats.

PubMed

Jackson, Mark P; Truong, Dennis; Brownlow, Milene L; Wagner, Jessica A; McKinley, R Andy; Bikson, Marom; Jankord, Ryan

2017-08-01

A commonly referenced transcranial Direct Current Stimulation (tDCS) safety threshold derives from tDCS lesion studies in the rat and relies on electrode current density (and related electrode charge density) to support clinical guidelines. Concerns about the role of polarity (e.g. anodal tDCS), sub-lesion threshold injury (e.g. neuroinflammatory processes), and role of electrode montage across rodent and human studies support further investigation into animal models of tDCS safety. Thirty-two anesthetized rats received anodal tDCS between 0 and 5mA for 60min through one of three epicranial electrode montages. Tissue damage was evaluated using hemotoxylin and eosin (H&E) staining, Iba-1 immunohistochemistry, and computational brain current density modeling. Brain lesion occurred after anodal tDCS at and above 0.5mA using a 25.0mm 2 electrode (electrode current density: 20.0A/m 2 ). Lesion initially occurred using smaller 10.6mm 2 or 5.3mm 2 electrodes at 0.25mA (23.5A/m 2 ) and 0.5mA (94.2A/m 2 ), respectively. Histological damage was correlated with computational brain current density predictions. Changes in microglial phenotype occurred in higher stimulation groups. Lesions were observed using anodal tDCS at an electrode current density of 20.0A/m 2 , which is below the previously reported safety threshold of 142.9A/m 2 using cathodal tDCS. The lesion area is not simply predicted by electrode current density (and so not by charge density as duration was fixed); rather computational modeling suggests average brain current density as a better predictor for anodal tDCS. Nonetheless, under the assumption that rodent epicranial stimulation is a hypersensitive model, an electrode current density of 20.0A/m 2 represents a conservative threshold for clinical tDCS, which typically uses an electrode current density of 2A/m 2 when electrodes are placed on the skin (resulting in a lower brain current density). Copyright © 2017 Elsevier Inc. All rights reserved.

Breaking the current density threshold in spin-orbit-torque magnetic random access memory

NASA Astrophysics Data System (ADS)

Zhang, Yin; Yuan, H. Y.; Wang, X. S.; Wang, X. R.

2018-04-01

Spin-orbit-torque magnetic random access memory (SOT-MRAM) is a promising technology for the next generation of data storage devices. The main bottleneck of this technology is the high reversal current density threshold. This outstanding problem is now solved by a new strategy in which the magnitude of the driven current density is fixed while the current direction varies with time. The theoretical limit of minimal reversal current density is only a fraction (the Gilbert damping coefficient) of the threshold current density of the conventional strategy. The Euler-Lagrange equation for the fastest magnetization reversal path and the optimal current pulse is derived for an arbitrary magnetic cell and arbitrary spin-orbit torque. The theoretical limit of minimal reversal current density and current density for a GHz switching rate of the new reversal strategy for CoFeB/Ta SOT-MRAMs are, respectively, of the order of 105 A/cm 2 and 106 A/cm 2 far below 107 A/cm 2 and 108 A/cm 2 in the conventional strategy. Furthermore, no external magnetic field is needed for a deterministic reversal in the new strategy.

Antihypercholesterolemic and Antioxidative Potential of an Extract of the Plant, Piper betle, and Its Active Constituent, Eugenol, in Triton WR-1339-Induced Hypercholesterolemia in Experimental Rats.

PubMed

Venkadeswaran, Karuppasamy; Muralidharan, Arumugam Ramachandran; Annadurai, Thangaraj; Ruban, Vasanthakumar Vasantha; Sundararajan, Mahalingam; Anandhi, Ramalingam; Thomas, Philip A; Geraldine, Pitchairaj

2014-01-01

Hypercholesterolemia is a dominant risk factor for atherosclerosis and cardiovascular diseases. In the present study, the putative antihypercholesterolemic and antioxidative properties of an ethanolic extract of Piper betle and of its active constituent, eugenol, were evaluated in experimental hypercholesterolemia induced by a single intraperitoneal injection of Triton WR-1339 (300 mg/kg b.wt) in Wistar rats. Saline-treated hypercholesterolemic rats revealed significantly higher mean blood/serum levels of glucose, total cholesterol, triglycerides, low density and very low density lipoprotein cholesterol, and of serum hepatic marker enzymes; in addition, significantly lower mean serum levels of high density lipoprotein cholesterol and significantly lower mean activities of enzymatic antioxidants and nonenzymatic antioxidants were noted in hepatic tissue samples from saline-treated hypercholesterolemic rats, compared to controls. However, in hypercholesterolemic rats receiving the Piper betle extract (500 mg/kg b.wt) or eugenol (5 mg/kg b.wt) for seven days orally, all these parameters were significantly better than those in saline-treated hypercholesterolemic rats. The hypercholesterolemia-ameliorating effect was better defined in eugenol-treated than in Piper betle extract-treated rats, being as effective as that of the standard lipid-lowering drug, lovastatin (10 mg/kg b.wt). These results suggest that eugenol, an active constituent of the Piper betle extract, possesses antihypercholesterolemic and other activities in experimental hypercholesterolemic Wistar rats.

Antihypercholesterolemic and Antioxidative Potential of an Extract of the Plant, Piper betle, and Its Active Constituent, Eugenol, in Triton WR-1339-Induced Hypercholesterolemia in Experimental Rats

PubMed Central

Venkadeswaran, Karuppasamy; Muralidharan, Arumugam Ramachandran; Annadurai, Thangaraj; Ruban, Vasanthakumar Vasantha; Sundararajan, Mahalingam; Anandhi, Ramalingam; Thomas, Philip A.; Geraldine, Pitchairaj

2014-01-01

Hypercholesterolemia is a dominant risk factor for atherosclerosis and cardiovascular diseases. In the present study, the putative antihypercholesterolemic and antioxidative properties of an ethanolic extract of Piper betle and of its active constituent, eugenol, were evaluated in experimental hypercholesterolemia induced by a single intraperitoneal injection of Triton WR-1339 (300 mg/kg b.wt) in Wistar rats. Saline-treated hypercholesterolemic rats revealed significantly higher mean blood/serum levels of glucose, total cholesterol, triglycerides, low density and very low density lipoprotein cholesterol, and of serum hepatic marker enzymes; in addition, significantly lower mean serum levels of high density lipoprotein cholesterol and significantly lower mean activities of enzymatic antioxidants and nonenzymatic antioxidants were noted in hepatic tissue samples from saline-treated hypercholesterolemic rats, compared to controls. However, in hypercholesterolemic rats receiving the Piper betle extract (500 mg/kg b.wt) or eugenol (5 mg/kg b.wt) for seven days orally, all these parameters were significantly better than those in saline-treated hypercholesterolemic rats. The hypercholesterolemia-ameliorating effect was better defined in eugenol-treated than in Piper betle extract-treated rats, being as effective as that of the standard lipid-lowering drug, lovastatin (10 mg/kg b.wt). These results suggest that eugenol, an active constituent of the Piper betle extract, possesses antihypercholesterolemic and other activities in experimental hypercholesterolemic Wistar rats. PMID:24523820

Regulation of low-density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase expression by Zingiber officinale in the liver of high-fat diet-fed rats.

PubMed

Nammi, Srinivas; Kim, Moon S; Gavande, Navnath S; Li, George Q; Roufogalis, Basil D

2010-05-01

Zingiber officinale has been used to control lipid disorders and reported to possess remarkable cholesterol-lowering activity in experimental hyperlipidaemia. In the present study, the effect of a characterized and standardized extract of Zingiber officinale on the hepatic lipid levels as well as on the hepatic mRNA and protein expression of low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase was investigated in a high-fat diet-fed rat model. Rats were treated with an ethanol extract of Zingiber officinale (400 mg/kg) extract along with a high-fat diet for 6 weeks. The extract of Zingiber officinale significantly decreased hepatic triglyceride and tended to decrease hepatic cholesterol levels when administered over 6 weeks to the rats fed a high-fat diet. We found that in parallel, the extract up-regulated both LDL receptor mRNA and protein level and down-regulated HMG-CoA reductase protein expression in the liver of these rats. The metabolic control of body lipid homeostasis is in part due to enhanced cholesterol biosynthesis and reduced expression of LDL receptor sites following long-term consumption of high-fat diets. The present results show restoration of transcriptional and post-transcriptional changes in low-density lipoprotein and HMG CoA reductase by Zingiber officinale administration with a high-fat diet and provide a rational explanation for the effect of ginger in the treatment of hyperlipidaemia.

Optimal geometry toward uniform current density electrodes

NASA Astrophysics Data System (ADS)

Song, Yizhuang; Lee, Eunjung; Woo, Eung Je; Seo, Jin Keun

2011-07-01

Electrodes are commonly used to inject current into the human body in various biomedical applications such as functional electrical stimulation, defibrillation, electrosurgery, RF ablation, impedance imaging, and so on. When a highly conducting electrode makes direct contact with biological tissues, the induced current density has strong singularity along the periphery of the electrode, which may cause painful sensation or burn. Especially in impedance imaging methods such as the magnetic resonance electrical impedance tomography, we should avoid such singularity since more uniform current density underneath a current-injection electrode is desirable. In this paper, we study an optimal geometry of a recessed electrode to produce a well-distributed current density on the contact area under the electrode. We investigate the geometry of the electrode surface to minimize the edge singularity and produce nearly uniform current density on the contact area. We propose a mathematical framework for the uniform current density electrode and its optimal geometry. The theoretical results are supported by numerical simulations.

Comprehensive capacitance-voltage analysis including quantum effects for high-k interfaces on germanium and other alternative channel materials

NASA Astrophysics Data System (ADS)

Anwar, Sarkar R. M.

High mobility alternative channel materials to silicon are critical to the continued scaling of metal oxide semiconductor (MOS) devices. However, before they can be incorporated into advanced devices, some major issues need to be solved. The high mobility materials suffer from lower allowable thermal budgets compared to Si (before desorption and defect formation becomes an issue) and the absence of a good quality native oxide has further increased the interest in the use of high-k dielectrics. However, the high interface state density and high electric fields at these semiconductor/high-k interfaces can significantly impact the capacitance-voltage (C-V) profile, and current C-V modeling software cannot account for these effects. This in turn affects the parameters extracted from the C-V data of the high mobility semiconductor/high-k interface, which are crucial to fully understand the interface properties and expedite process development. To address this issue, we developed a model which takes into account quantum corrections which can be applied to a number of these alternative channel materials including SixGe1-x, Ge, InGaAs, and GaAs. The C-V simulation using this QM correction model is orders of magnitude faster compared to a full band Schrodinger-Poisson solver. The simulated C-V is directly benchmarked to a self consistent Schrodinger-Poisson solution for each bulk semiconductor material, and from the benchmarking process the QM correction parameters are extracted. The full program, C-V Alternative Channel Extraction (CV ACE), incorporates a quantum mechanical correction model, along with the interface state density model, and can extract device parameters such as equivalent oxide thickness (EOT), doping density and flat band voltage (Vfb) as well as the interface state density profile using multiple measurements performed at different frequencies and temperatures, simultaneously. The program was used to analyze experimentally measured C-V profiles and the extracted device parameters show excellent agreement with the known device structure and previously published results. CV ACE has been applied in the development of a process flow for germanium interface passivation in Ge based MOS devices using a GeOx interlayer. A post atomic layer deposition (ALD) plasma oxidation (PPO) process was developed using radio frequency (RF) plasma in a plasma enhanced chemical vapor deposition (PECVD) chamber and demonstrated significant surface passivation. Various gases were investigated and 1% O2/Ar was found to reduce the growth rate and provide excellent control over the degradation of EOT. A 100 W plasma with 1% O2/Ar was found to provide the best combination of EOT and low Dit and is concluded to be the optimum process for PPO of germanium surfaces. CV ACE and PPO were also utilized to investigate other process development challenges. A study of the impact of low temperature anneals on Ge-based MOS devices was found to result in a degradation of the electrical thickness and a change in fixed charge, indicating that the process window is very narrow and at much lower temperatures than for Si.

Validation of Ionosonde Electron Density Reconstruction Algorithms with IONOLAB-RAY in Central Europe

NASA Astrophysics Data System (ADS)

Gok, Gokhan; Mosna, Zbysek; Arikan, Feza; Arikan, Orhan; Erdem, Esra

2016-07-01

Ionospheric observation is essentially accomplished by specialized radar systems called ionosondes. The time delay between the transmitted and received signals versus frequency is measured by the ionosondes and the received signals are processed to generate ionogram plots, which show the time delay or reflection height of signals with respect to transmitted frequency. The critical frequencies of ionospheric layers and virtual heights, that provide useful information about ionospheric structurecan be extracted from ionograms . Ionograms also indicate the amount of variability or disturbances in the ionosphere. With special inversion algorithms and tomographical methods, electron density profiles can also be estimated from the ionograms. Although structural pictures of ionosphere in the vertical direction can be observed from ionosonde measurements, some errors may arise due to inaccuracies that arise from signal propagation, modeling, data processing and tomographic reconstruction algorithms. Recently IONOLAB group (www.ionolab.org) developed a new algorithm for effective and accurate extraction of ionospheric parameters and reconstruction of electron density profile from ionograms. The electron density reconstruction algorithm applies advanced optimization techniques to calculate parameters of any existing analytical function which defines electron density with respect to height using ionogram measurement data. The process of reconstructing electron density with respect to height is known as the ionogram scaling or true height analysis. IONOLAB-RAY algorithm is a tool to investigate the propagation path and parameters of HF wave in the ionosphere. The algorithm models the wave propagation using ray representation under geometrical optics approximation. In the algorithm , the structural ionospheric characteristics arerepresented as realistically as possible including anisotropicity, inhomogenity and time dependence in 3-D voxel structure. The algorithm is also used for various purposes including calculation of actual height and generation of ionograms. In this study, the performance of electron density reconstruction algorithm of IONOLAB group and standard electron density profile algorithms of ionosondes are compared with IONOLAB-RAY wave propagation simulation in near vertical incidence. The electron density reconstruction and parameter extraction algorithms of ionosondes are validated with the IONOLAB-RAY results both for quiet anddisturbed ionospheric states in Central Europe using ionosonde stations such as Pruhonice and Juliusruh . It is observed that IONOLAB ionosonde parameter extraction and electron density reconstruction algorithm performs significantly better compared to standard algorithms especially for disturbed ionospheric conditions. IONOLAB-RAY provides an efficient and reliable tool to investigate and validate ionosonde electron density reconstruction algorithms, especially in determination of reflection height (true height) of signals and critical parameters of ionosphere. This study is supported by TUBITAK 114E541, 115E915 and Joint TUBITAK 114E092 and AS CR 14/001 projects.

Method for solvent extraction with near-equal density solutions

DOEpatents

Birdwell, Joseph F.; Randolph, John D.; Singh, S. Paul

2001-01-01

Disclosed is a modified centrifugal contactor for separating solutions of near equal density. The modified contactor has a pressure differential establishing means that allows the application of a pressure differential across fluid in the rotor of the contactor. The pressure differential is such that it causes the boundary between solutions of near-equal density to shift, thereby facilitating separation of the phases. Also disclosed is a method of separating solutions of near-equal density.

Large Scale Data Analysis and Knowledge Extraction in Communication Data

DTIC Science & Technology

2017-03-31

this purpose, we developed a novel method the " Correlation Density Ran!C’ which finds probability density distribution of related frequent event on all...which is called " Correlation Density Rank", is developed to derive the community tree from the network. As in the real world, where a network is...Community Structure in Dynamic Social Networks using the Correlation Density Rank," 2014 ASE BigData/SocialCom/Cybersecurity Conference, Stanford

Method of synthesizing a low density material

DOEpatents

Lorensen, L.E.; Monaco, S.B.

1987-02-27

A novel method of synthesizing a polymeric material of low density of the order of 50mg/cc or less. Such a low density material has applications in many areas including laser target fabrication. The method comprises preparing a polymer blend of two incompatible polymers as a major and a minor phase by mixing them and extruding the mixture, and then selectively extracting the major component, to yield a fine, low density structure.

Optimization of ultrasound-assisted extraction of phenolic compounds from grapefruit (Citrus paradisi Macf.) leaves via D-optimal design and artificial neural network design with categorical and quantitative variables.

PubMed

Ciğeroğlu, Zeynep; Aras, Ömür; Pinto, Carlos A; Bayramoglu, Mahmut; Kırbaşlar, Ş İsmail; Lorenzo, José M; Barba, Francisco J; Saraiva, Jorge A; Şahin, Selin

2018-03-06

The extraction of phenolic compounds from grapefruit leaves assisted by ultrasound-assisted extraction (UAE) was optimized using response surface methodology (RSM) by means of D-optimal experimental design and artificial neural network (ANN). For this purpose, five numerical factors were selected: ethanol concentration (0-50%), extraction time (15-60 min), extraction temperature (25-50 °C), solid:liquid ratio (50-100 g L -1 ) and calorimetric energy density of ultrasound (0.25-0.50 kW L -1 ), whereas ultrasound probe horn diameter (13 or 19 mm) was chosen as categorical factor. The optimized experimental conditions yielded by RSM were: 10.80% for ethanol concentration; 58.52 min for extraction time; 30.37 °C for extraction temperature; 52.33 g L -1 for solid:liquid ratio; 0.457 kW L -1 for ultrasonic power density, with thick probe type. Under these conditions total phenolics content was found to be 19.04 mg gallic acid equivalents g -1 dried leaf. The same dataset was used to train multilayer feed-forward networks using different approaches via MATLAB, with ANN exhibiting superior performance to RSM (differences included categorical factor in one model and higher regression coefficients), while close values were obtained for the extraction variables under study, except for ethanol concentration and extraction time. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Olive Leaf Extract Elevates Hepatic PPAR α mRNA Expression and Improves Serum Lipid Profiles in Ovariectomized Rats.

PubMed

Yoon, Leena; Liu, Ya-Nan; Park, Hyunjin; Kim, Hyun-Sook

2015-07-01

We hypothesized that olive leaf extract might alleviate dyslipidemia resulting from estrogen deficiency. Serum lipid profile and mRNA expression of the related genes in the liver and adipose tissue were analyzed after providing olive leaf extract (200 or 400 mg/kg body weight; n=7 for each group) to ovariectomized rats for 10 weeks. After 10 weeks' administration, the rats in the olive leaf extract-administered groups showed significantly lower levels of serum triglyceride and very-low-density lipoprotein (VLDL)-cholesterol compared with the rats in the control group, whereas the administration of olive leaf extract did not significantly change the elevated low-density lipoprotein cholesterol levels. In addition, administration of high dose of olive leaf extract significantly decreased the liver triglyceride and increased serum estradiol levels. mRNA expressions of peroxisome proliferator-activated receptor alpha (PPAR α) and acyl-CoA oxidase (ACO) were not affected by ovariectomy, however, administration of olive leaf extract significantly increased both PPAR α and ACO mRNA expression. Expression of adiponectin mRNA in adipose tissue was significantly decreased in the ovariectomized control group. Rats administered low-dose olive leaf extract showed significantly elevated adiponectin mRNA expression compared with rats in the ovariectomized control group. Even though dose-dependent effects were not observed in most of the measurements, these results suggest that genes involved in lipid metabolism may be regulated by olive leaf extract administration in ovariectomized rats.

A photometric method for the estimation of the oil yield of oil shale

USGS Publications Warehouse

Cuttitta, Frank

1951-01-01

A method is presented for the distillation and photometric estimation of the oil yield of oil-bearing shales. The oil shale is distilled in a closed test tube and the oil extracted with toluene. The optical density of the toluene extract is used in the estimation of oil content and is converted to percentage of oil by reference to a standard curve. This curve is obtained by relating the oil yields determined by the Fischer assay method to the optical density of the toluene extract of the oil evolved by the new procedure. The new method gives results similar to those obtained by the Fischer assay method in a much shorter time. The applicability of the new method to oil-bearing shale and phosphatic shale has been tested.

The power of a single trajectory

NASA Astrophysics Data System (ADS)

Schnellbächer, Nikolas D.; Schwarz, Ulrich S.

2018-03-01

Random walks are often evaluated in terms of their mean squared displacements, either for a large number of trajectories or for one very long trajectory. An alternative evaluation is based on the power spectral density, but here it is less clear which information can be extracted from a single trajectory. For continuous-time Brownian motion, Krapf et al now have mathematically proven that the one property that can be reliably extracted from a single trajectory is the frequency dependence of the ensemble-averaged power spectral density (Krapf et al 2018 New J. Phys. 20 023029). Their mathematical analysis also identifies the appropriate frequency window for this procedure and shows that the diffusion coefficient can be extracted by averaging over a small number of trajectories. The authors have verified their analytical results both by computer simulations and experiments.

Computerized breast parenchymal analysis on DCE-MRI

NASA Astrophysics Data System (ADS)

Li, Hui; Giger, Maryellen L.; Yuan, Yading; Jansen, Sanaz A.; Lan, Li; Bhooshan, Neha; Newstead, Gillian M.

2009-02-01

Breast density has been shown to be associated with the risk of developing breast cancer, and MRI has been recommended for high-risk women screening, however, it is still unknown how the breast parenchymal enhancement on DCE-MRI is associated with breast density and breast cancer risk. Ninety-two DCE-MRI exams of asymptomatic women with normal MR findings were included in this study. The 3D breast volume was automatically segmented using a volume-growing based algorithm. The extracted breast volume was classified into fibroglandular and fatty regions based on the discriminant analysis method. The parenchymal kinetic curves within the breast fibroglandular region were extracted and categorized by use of fuzzy c-means clustering, and various parenchymal kinetic characteristics were extracted from the most enhancing voxels. Correlation analysis between the computer-extracted percent dense measures and radiologist-noted BIRADS density ratings yielded a correlation coefficient of 0.76 (p<0.0001). From kinetic analyses, 70% (64/92) of most enhancing curves showed persistent curve type and reached peak parenchymal intensity at the last postcontrast time point; with 89% (82/92) of most enhancing curves reaching peak intensity at either 4th or 5th post-contrast time points. Women with dense breast (BIRADS 3 and 4) were found to have more parenchymal enhancement at their peak time point (Ep) with an average Ep of 116.5% while those women with fatty breasts (BIRADS 1 and 2) demonstrated an average Ep of 62.0%. In conclusion, breast parenchymal enhancement may be associated with breast density and may be potential useful as an additional characteristic for assessing breast cancer risk.

Nephroprotective and Anti-Inflammatory Effects of Pistacia atlantica Leaf Hydroethanolic Extract Against Gentamicin-Induced Nephrotoxicity in Rats.

PubMed

Heidarian, Esfandiar; Jafari-Dehkordi, Effat; Valipour, Parisa; Ghatreh-Samani, Keihan; Ashrafi-Eshkaftaki, Leila

2017-09-03

Gentamicin in overdose can lead to tubular injury and kidney dysfunction. Some antioxidants can protect kidneys against nephrotoxicity. This study was undertaken to evaluate the protective effects of Pistacia atlantica (P. atlantica) leaf hydroethanolic extract against gentamicin-induced nephrotoxicity in rats. Forty rats were divided into five groups: the first group received a daily intraperitoneal (i.p.) injection of normal saline. The second group received gentamicin (120 mg/kg, i.p.). The third, fourth, and fifth groups were orally treated with 200, 400, and 800 mg/kg of P. atlantica leaf hydroethanolic extract, respectively, and they also received gentamicin (120 mg/kg, i.p.). After seven days, serum malondialdehyde (MDA), creatinine (Cr), urea, uric acid, lipids profile, protein carbonyl (PC), and tumor necrosis factor-α (TNF-α) were determined. Also, a piece of kidney was used to determine catalase (CAT) and superoxide dismutase (SOD) activities, vitamin C, the gene expression of TNF-α, and for subsequent histopathological studies. Treatment with P. atlantica leaf hydroethanolic extract resulted in a significant increase (p < 0.05) in CAT, SOD, vitamin C, and high-density lipoprotein cholesterol, and significantly decreased (p < 0.05) the levels of Cr, urea, uric acid, MDA, PC, triglyceride, total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, TNF-α protein, and the gene expression of TNF-α compared with the untreated group. Histopathological studies show that in lymphocyte infiltration, remarkable reduction was observed in P. atlantica leaf hydroethanolic extract-treated groups, compared with the untreated group. The present study suggests that P. atlantica leaf hydroethanolic extract has protective effects against gentamicin-induced nephrotoxicity.

In vitro antioxidant and antihyperlipidemic activities of Bauhinia variegata Linn

PubMed Central

Rajani, G.P.; Ashok, Purnima

2009-01-01

Objectives: To evaluate the ethanolic and aqueous extracts of Bauhinia variegata Linn. for in vitro antioxidant and antihyperlipidemic activity. Materials and Methods: Ethanolic and aqueous extracts of the stem bark and root of B. variegata Linn. were prepared and assessed for in vitro antioxidant activity by various methods namely total reducing power, scavenging of various free radicals such as 1,2-diphenyl-2-picrylhydrazyl (DPPH), super oxide, nitric oxide, and hydrogen peroxide. The percentage scavenging of various free radicals were compared with standard antioxidants such as ascorbic acid and butylated hydroxyl anisole (BHA). The extracts were also evaluated for antihyperlipidemic activity in Triton WR-1339 (iso-octyl polyoxyethylene phenol)-induced hyperlipidemic albino rats by estimating serum triglyceride, very low density lipids (VLDL), cholesterol, low-density lipids (LDL), and high-density lipid (HDL) levels. Result: Significant antioxidant activity was observed in all the methods, (P < 0.01) for reducing power and (P < 0.001) for scavenging DPPH, super oxide, nitric oxide, and hydrogen peroxide radicals. The extracts showed significant reduction (P < 0.01) in cholesterol at 6 and 24 h and (P < 0.05) at 48 h. There was significant reduction (P < 0.01) in triglyceride level at 6, 24, and 48 h. The VLDL level was also significantly (P < 0.05) reduced from 24 h and maximum reduction (P < 0.01) was seen at 48 h. There was significant increase (P < 0.01) in HDL at 6, 24, and 48 h. Conclusion: From the results, it is evident that alcoholic and aqueous extracts of B. variegata Linn. can effectively decrease plasma cholesterol, triglyceride, LDL, and VLDL and increase plasma HDL levels. In addition, the alcoholic and aqueous extracts have shown significant antioxidant activity. By the virtue of its antioxidant activity, B. variegata Linn. may show antihyperlipidemic activity. PMID:20177495

Magnesium supplementation through seaweed calcium extract rather than synthetic magnesium oxide improves femur bone mineral density and strength in ovariectomized rats.

PubMed

Bae, Yun Jung; Bu, So Young; Kim, Jae Young; Yeon, Jee-Young; Sohn, Eun-Wha; Jang, Ki-Hyo; Lee, Jae-Cheol; Kim, Mi-Hyun

2011-12-01

Commercially available seaweed calcium extract can supply high amounts of calcium as well as significant amounts of magnesium and other microminerals. The purpose of this study was to investigate the degree to which the high levels of magnesium in seaweed calcium extract affects the calcium balance and the bone status in ovariectomized rats in comparison to rats supplemented with calcium carbonate and magnesium oxide. A total of 40 Sprague-Dawley female rats (7 weeks) were divided into four groups and bred for 12 weeks: sham-operated group (Sham), ovariectomized group (OVX), ovariectomized with inorganic calcium and magnesium supplementation group (OVX-Mg), and ovariectomized with seaweed calcium and magnesium supplementation group (OVX-SCa). All experimental diets contained 0.5% calcium. The magnesium content in the experimental diet was 0.05% of the diet in the Sham and OVX groups and 0.1% of the diet in the OVX-Mg and OVX-SCa groups. In the calcium balance study, the OVX-Mg and OVX-SCa groups were not significantly different in calcium absorption compared to the OVX group. However, the femoral bone mineral density and strength of the OVX-SCa group were higher than those of the OVX-Mg and OVX groups. Seaweed calcium with magnesium supplementation or magnesium supplementation alone did not affect the serum ALP and CTx levels in ovariectomized rats. In summary, consumption of seaweed calcium extract or inorganic calcium carbonate with magnesium oxide demonstrated the same degree of intestinal calcium absorption, but only the consumption of seaweed calcium extract resulted in increased femoral bone mineral density and strength in ovariectomized rats. Our results suggest that seaweed calcium extract is an effective calcium and magnesium source for improving bone health compared to synthetic calcium and magnesium supplementation.

MgB2 wire diameter reduction by hot isostatic pressing—a route for enhanced critical current density

NASA Astrophysics Data System (ADS)

Morawski, A.; Cetner, T.; Gajda, D.; Zaleski, A. J.; Häßler, W.; Nenkov, K.; Rindfleisch, M. A.; Tomsic, M.; Przysłupski, P.

2018-07-01

The effect of wire diameter reduction on the critical current density of pristine MgB2 wire was studied. Wires were treated by a hot isostatic pressing method at 570 °C and at pressures of up to 1.1 GPa. It was found that the wire diameter reduction induces an increase of up to 70% in the mass density of the superconducting cores. This feature leads to increases in critical current, critical current density, and pinning force density. The magnitude and field dependence of the critical current density are related to both grain connectivity and structural defects, which act as effective pinning centers. High field transport properties were obtained without doping of the MgB2 phase. A critical current density jc of 3500 A mm‑2 was reached at 4 K, 6 T for the best sample, which was a five-fold increase compared to MgB2 samples synthesized at ambient pressure.

Comparison of volatility function technique for risk-neutral densities estimation

NASA Astrophysics Data System (ADS)

Bahaludin, Hafizah; Abdullah, Mimi Hafizah

2017-08-01

Volatility function technique by using interpolation approach plays an important role in extracting the risk-neutral density (RND) of options. The aim of this study is to compare the performances of two interpolation approaches namely smoothing spline and fourth order polynomial in extracting the RND. The implied volatility of options with respect to strike prices/delta are interpolated to obtain a well behaved density. The statistical analysis and forecast accuracy are tested using moments of distribution. The difference between the first moment of distribution and the price of underlying asset at maturity is used as an input to analyze forecast accuracy. RNDs are extracted from the Dow Jones Industrial Average (DJIA) index options with a one month constant maturity for the period from January 2011 until December 2015. The empirical results suggest that the estimation of RND using a fourth order polynomial is more appropriate to be used compared to a smoothing spline in which the fourth order polynomial gives the lowest mean square error (MSE). The results can be used to help market participants capture market expectations of the future developments of the underlying asset.

Inhibition of low-density lipoprotein oxidation and up-regulation of low-density lipoprotein receptor in HepG2 cells by tropical plant extracts.

PubMed

Salleh, Mohd Nizar; Runnie, Irine; Roach, Paul D; Mohamed, Suhaila; Abeywardena, Mahinda Y

2002-06-19

Twelve edible plant extracts rich in polyphenols were screened for their potential to inhibit oxidation of low-density lipoprotein (LDL) in vitro and to modulate LDL receptor (LDLr) activity in cultured HepG2 cells. The antioxidant activity (inhibition of LDL oxidation) was determined by measuring the formation of conjugated dienes (lag time) and thiobarbituric acid reagent substances (TBARS). Betel leaf (94%), cashew shoot (63%), Japanese mint (52%), semambu leaf (50%), palm frond (41%), sweet potato shoot, chilli fruit, papaya shoot, roselle calyx, and maman showed significantly increased lag time (>55 min, P < 0.05) and inhibition of TBARS formation (P < 0.05) compared to control. LDLr was significantly up-regulated (P < 0.05) by Japanese mint (67%), semambu (51%), cashew (50%), and noni (49%). Except for noni and betel leaf, most plant extracts studied demonstrated a positive association between antioxidant activity and the ability to up-regulate LDL receptor. Findings suggest that reported protective actions of plant polyphenols on lipoprotein metabolism might be exerted at different biochemical mechanisms.

Loop-mediated isothermal amplification with the Procedure for Ultra Rapid Extraction kit for the diagnosis of pneumocystis pneumonia.

PubMed

Kawano, Shuichi; Maeda, Takuya; Suzuki, Takefumi; Abe, Tatsuhiro; Mikita, Kei; Hamakawa, Yusuke; Ono, Takeshi; Sonehara, Wataru; Miyahira, Yasushi; Kawana, Akihiko

2015-03-01

Loop-mediated isothermal amplification (LAMP) is an innovative molecular technique requiring only a heating device and isothermal conditions to amplify a specific target gene. The results of current microscopic diagnostic tools for pneumocystis pneumonia are not sufficiently consistent for detecting infection with a low-density of Pneumocystis jirovecii. Although polymerase chain reaction (PCR) is highly sensitive, it is not suitable for resource-limited facilities. LAMP is a potential diagnostic replacement for PCR in such settings but a critical disadvantage of DNA extraction was still remained. Therefore, we employed the Procedure for Ultra Rapid Extraction (PURE) kit, which uses a porous material, to isolate the DNA from clinical samples in a simple way in combination with previously reported LAMP procedure for diagnosing PCP. The detection limit of the PURE-LAMP method applied to artificial bronchoalveolar lavage fluid samples was 100 copies/tube, even with the use of massive blood-contaminated solutions. In addition, we concluded the diagnostic procedure within 1 h without the need for additional equipment. PURE-LAMP coupled with suitable primers for specific pathogens has good potential for diagnosing various infectious diseases. Copyright © 2014 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Correlation of ion and beam current densities in Kaufman thrusters.

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1973-01-01

In the absence of direct impingement erosion, electrostatic thruster accelerator grid lifetime is defined by the charge exchange erosion that occurs at peak values of the ion beam current density. In order to maximize the thrust from an engine with a specified grid lifetime, the ion beam current density profile should therefore be as flat as possible. Knauer (1970) has suggested this can be achieved by establishing a radial plasma uniformity within the thruster discharge chamber; his tests with the radial field thruster provide an example of uniform plasma properties within the chamber and a flat ion beam profile occurring together. It is shown that, in particular, the ion density profile within the chamber determines the beam current density profile, and that a uniform ion density profile at the screen grid end of the discharge chamber should lead to a flat beam current density profile.

Experimental study on magnetically insulated transmission line electrode surface evolution process under MA/cm current density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, PengFei; Qiu, Aici; State Key Laboratory of Intense Pulse Radiation of Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

The design of high-current density magnetically insulated transmission line (MITL) is a difficult problem of current large-scale Z-pinch device. In particular, a thorough understanding of the MITL electrode surface evolution process under high current density is lacking. On the “QiangGuang-I” accelerator, the load area possesses a low inductance short-circuit structure with a diameter of 2.85 mm at the cathode, and three reflux columns with a diameter of 3 mm and uniformly distributed circumference at the anode. The length of the high density MITL area is 20 mm. A laser interferometer is used to assess and analyze the state of the MITL cathode andmore » anode gap, and their evolution process under high current density. Experimental results indicate that evident current loss is not observed in the current density area at pulse leading edge, and peak when the surface current density reaches MA/cm. Analysis on electrode surface working conditions indicates that when the current leading edge is at 71.5% of the peak, the total evaporation of MITL cathode structure can be realized by energy deposition caused by ohmic heating. The electrode state changes, and diffusion conditions are reflected in the laser interferometer image. The MITL cathode area mainly exists in metal vapor form. The metal vapor density in the cathode central region is higher than the upper limit of laser penetration density (∼4 × 10{sup 21}/cm{sup 3}), with an expansion velocity of ∼0.96 km/s. The metal vapor density in the electrode outer area may lead to evident distortion of fringes, and its expansion velocity is faster than that in the center area (1.53 km/s).« less

Study of sulfur bonding on gallium arsenide (100) surfaces using supercritical fluid extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabauy, P.; Darici, Y.; Furton, K.G.

1995-12-01

In the last decades Gallium Arsenide (GaAs) has been considered the semiconductor that will replace silicon because of its direct band gap and high electron mobility. Problems with GaAs Fermi level pinning has halted its widespread use in the electronics industry. The formation of oxides on GaAs results in a high density of surface states that effectively pin the surface Fermi level at the midgap. Studies on sulfur passivation have eliminated oxidation and virtually unpinned the Fermi level on the GaAs surface. This has given rise to interest in sulfur-GaAs bonds. In this presentation, we will discuss the types ofmore » sulfur bonds extracted from a sulfur passivated GaAs (100) using Supercritical Fluid (CO2) Extraction (SFE). SFE can be a valuable tool in the study of chemical speciations on semiconductor surfaces. The variables evaluated to effectively study the sulfur species from the GaAs surface include passivation techniques, supercritical fluid temperatures, densities, and extraction times.« less

Antidiabetic and hypolipidaemic effects of a methanol/methylene-chloride extract of Laportea ovalifolia (Urticaceae), measured in rats with alloxan-induced diabetes.

PubMed

Momo, C E N; Oben, J E; Tazoo, D; Dongo, E

2006-01-01

A decoction of the leaves of Laportea ovalifolia is widely used in Cameroon for the treatment of several illnesses, including diabetes mellitus. The antidiabetic and hypolipidaemic effects of a methanol/methylene-chloride extract of the aerial parts of L. ovalifolia have now been investigated, in normal rats and rats with diabetes induced by the intraperitoneal injection of alloxan (at 150 mg/kg bodyweight). In the diabetic rats, 2 weeks of daily, intragastric treatment with the L. ovalifolia extract not only produced a significant reduction in the fasting serum glucose concentrations but also lowered the serum concentrations of total cholesterol, triglycerides, and low-density-lipoprotein cholesterol, lowered the ratio of total cholesterol to high-density-lipoprotein (HDL) cholesterol, and increased the serum concentration of HDL cholesterol. At least in rats with alloxan-induced diabetes, the methanol/methylene-chloride extract of L. ovalifolia therefore appears to possess antidiabetic and hypolipidaemic properties.

Short Haul Civil Tiltrotor Contingency Power System Preliminary Design

NASA Technical Reports Server (NTRS)

Eames, David J. H.

2006-01-01

Single Langmuir probe measurements are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring cusp ion thruster over a range of thruster operating conditions encompassing the high-power half of the NASA throttling table. The Langmuir probe data were analyzed with two separate methods. All data were analyzed initially assuming an electron population consisting of Maxwellian electrons only. The on-axis data were then analyzed assuming both Maxwellian and primary electrons. Discharge plasma data taken with beam extraction exhibit a broadening of the higher electron temperature plume boundary compared to similar discharge conditions without beam extraction. The opposite effect is evident with the electron/ion number density as the data without began, extraction appears to be more collimated than the corresponding data with beam extraction. Primary electron energy and number densities are presented for one operating condition giving an order of magnitude of their value and the error associated with this calculation.

Hyperpolarized xenon NMR and MRI signal amplification by gas extraction

PubMed Central

Zhou, Xin; Graziani, Dominic; Pines, Alexander

2009-01-01

A method is reported for enhancing the sensitivity of NMR of dissolved xenon by detecting the signal after extraction to the gas phase. We demonstrate hyperpolarized xenon signal amplification by gas extraction (Hyper-SAGE) in both NMR spectra and magnetic resonance images with time-of-flight information. Hyper-SAGE takes advantage of a change in physical phase to increase the density of polarized gas in the detection coil. At equilibrium, the concentration of gas-phase xenon is ≈10 times higher than that of the dissolved-phase gas. After extraction the xenon density can be further increased by several orders of magnitude by compression and/or liquefaction. Additionally, being a remote detection technique, the Hyper-SAGE effect is further enhanced in situations where the sample of interest would occupy only a small proportion of the traditional NMR receiver. Coupled with targeted xenon biosensors, Hyper-SAGE offers another path to highly sensitive molecular imaging of specific cell markers by detection of exhaled xenon gas. PMID:19805177

Discharge Chamber Plasma Structure of a 30-cm NSTAR-Type Ion Engine

NASA Technical Reports Server (NTRS)

Herman, Daniel A.; Gallimore, Alec D.

2006-01-01

Single Langmuir probe measurements are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring cusp ion thruster over a range of thruster operating conditions encompassing the high-power half of the NASA throttling table. The Langmuir probe data were analyzed with two separate methods. All data were analyzed initially assuming an electron population consisting of Maxwellian electrons only. The on-axis data were then analyzed assuming both Maxwellian and primary electrons. Discharge plasma data taken with beam extraction exhibit a broadening of the higher electron temperature plume boundary compared to similar discharge conditions without beam extraction. The opposite effect is evident with the electron/ion number density as the data without began, extraction appears to be more collimated than the corresponding data with beam extraction. Primary electron energy and number densities are presented for one operating condition giving an order of magnitude of their value and the error associated with this calculation.

Optimizing density patterns to achieve desired light extraction for displays

NASA Astrophysics Data System (ADS)

Davenport, T. L. R.; Cassarly, W. J.

2007-01-01

In displays such as backlights and signage, it is often desirable to produce a particular spatial luminance distribution of light. This work demonstrates an iterative optimization technique for determining the density of light extractors required to produce desired luminance distributions.

Influence of the current density on the electrochemical treatment of concentrated 1-butyl-3-methylimidazolium chloride solutions on diamond electrodes.

PubMed

Marcionilio, Suzana M L de Oliveira; Alves, Gisele M; E Silva, Rachel B Góes; Marques, Pablo J Lima; Maia, Poliana D; Neto, Brenno A D; Linares, José J

2016-10-01

This paper focuses on the influence of the current density treatment of a concentrated 1-butyl-3-methylimidazolium chloride (BMImCl) solution on an electrochemical reactor with a boron-doped diamond (BDD) anode. The decrease in the total organic carbon (TOC) and the BMImCl concentration demonstrate the capability of BDD in oxidizing ionic liquids (ILs) and further mineralizing (to CO2 and NO3 (-)) more rapidly at higher current densities in spite of the reduced current efficiency of the process. Moreover, the presence of Cl(-) led to the formation of oxychlorinated anions (mostly ClO3 (-) and ClO4 (-)) and, in combination with the ammonia generated in the cathode from the nitrate reduction, chloramines, more intensely at higher current density. Finally, the analysis of the intermediates formed revealed no apparent influence of the current density on the BMImCl degradation mechanism. The current density presents therefore a complex influence on the IL treatment process that is discussed throughout this paper.

Characterization of silicon-on-insulator wafers

NASA Astrophysics Data System (ADS)

Park, Ki Hoon

The silicon-on-insulator (SOI) is attracting more interest as it is being used for an advanced complementary-metal-oxide-semiconductor (CMOS) and a base substrate for novel devices to overcome present obstacles in bulk Si scaling. Furthermore, SOI fabrication technology has improved greatly in recent years and industries produce high quality wafers with high yield. This dissertation investigated SOI material properties with simple, yet accurate methods. The electrical properties of as-grown wafers such as electron and hole mobilities, buried oxide (BOX) charges, interface trap densities, and carrier lifetimes were mainly studied. For this, various electrical measurement techniques were utilized such as pseudo-metal-oxide-semiconductor field-effect-transistor (PseudoMOSFET) static current-voltage (I-V) and transient drain current (I-t), Hall effect, and MOS capacitance-voltage/capacitance-time (C-V/C-t). The electrical characterization, however, mainly depends on the pseudo-MOSFET method, which takes advantage of the intrinsic SOI structure. From the static current-voltage and pulsed measurement, carrier mobilities, lifetimes and interface trap densities were extracted. During the course of this study, a pseudo-MOSFET drain current hysteresis regarding different gate voltage sweeping directions was discovered and the cause was revealed through systematic experiments and simulations. In addition to characterization of normal SOI, strain relaxation of strained silicon-on-insulator (sSOI) was also measured. As sSOI takes advantage of wafer bonding in its fabrication process, the tenacity of bonding between the sSOI and the BOX layer was investigated by means of thermal treatment and high dose energetic gamma-ray irradiation. It was found that the strain did not relax with processes more severe than standard CMOS processes, such as anneals at temperature as high as 1350 degree Celsius.

Noise performance limits of advanced x-ray imagers employing poly-Si-based active pixel architectures

NASA Astrophysics Data System (ADS)

Koniczek, Martin; El-Mohri, Youcef; Antonuk, Larry E.; Liang, Albert; Zhao, Qihua; Jiang, Hao

2011-03-01

A decade after the clinical introduction of active matrix, flat-panel imagers (AMFPIs), the performance of this technology continues to be limited by the relatively large additive electronic noise of these systems - resulting in significant loss of detective quantum efficiency (DQE) under conditions of low exposure or high spatial frequencies. An increasingly promising approach for overcoming such limitations involves the incorporation of in-pixel amplification circuits, referred to as active pixel architectures (AP) - based on low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFTs). In this study, a methodology for theoretically examining the limiting noise and DQE performance of circuits employing 1-stage in-pixel amplification is presented. This methodology involves sophisticated SPICE circuit simulations along with cascaded systems modeling. In these simulations, a device model based on the RPI poly-Si TFT model is used with additional controlled current sources corresponding to thermal and flicker (1/f) noise. From measurements of transfer and output characteristics (as well as current noise densities) performed upon individual, representative, poly-Si TFTs test devices, model parameters suitable for these simulations are extracted. The input stimuli and operating-point-dependent scaling of the current sources are derived from the measured current noise densities (for flicker noise), or from fundamental equations (for thermal noise). Noise parameters obtained from the simulations, along with other parametric information, is input to a cascaded systems model of an AP imager design to provide estimates of DQE performance. In this paper, this method of combining circuit simulations and cascaded systems analysis to predict the lower limits on additive noise (and upper limits on DQE) for large area AP imagers with signal levels representative of those generated at fluoroscopic exposures is described, and initial results are reported.

Factors controlling charge recombination under dark and light conditions in dye sensitised solar cells.

PubMed

Barnes, Piers R F; Anderson, Assaf Y; Juozapavicius, Mindaugas; Liu, Lingxuan; Li, Xiaoe; Palomares, Emilio; Forneli, Amparo; O'Regan, Brian C

2011-02-28

A simple and powerful approach for assessing the recombination losses in dye sensitised solar cells (DSSCs) across the current voltage curve (j-V) as a function of TiO(2) electron concentration (n) is demonstrated. The total flux of electrons recombining with iodine species in the electrolyte and oxidised dye molecules can be thought of as a recombination current density, defined as j(rec) = j(inj)-j where j(inj) is the current of electrons injected from optically excited dye states and j is the current density collected at cell voltage (V). The electron concentration at any given operating conditions is determined by charge extraction. This allows comparison of factors influencing electron recombination rates at matched n. We show that j(rec) is typically 2-3 times higher under 1 sun equivalent illumination (j(inj) > 0) relative to dark (j(inj) = 0) conditions. This difference was increased by increasing light intensity, electrolyte iodine concentration and electrolyte solvent viscosity. The difference was reduced by increasing the electrolyte iodide concentration and increasing the temperature. These results allowed us to verify a numerical model of complete operational cells (Barnes et al., Phys. Chem. Chem. Phys., DOI: 10.1039/c0cp01554g) and to relate the differences in j(rec) to physical processes in the devices. The difference between j(rec) in the light and dark can be explained by two factors: (1) an increase in the concentration of electron acceptor species (I(3)(-) and/or I(2)) when current is flowing under illumination relative to dark conditions where the current is flowing in the opposite direction, and (2) a non-trivial contribution from electron recombination to oxidised dye molecules under light conditions. More generally, the technique helps to assign the observed relationship between the components, processing and performance of DSSCs to more fundamental physical processes.

Exact thermal density functional theory for a model system: Correlation components and accuracy of the zero-temperature exchange-correlation approximation

DOE PAGES

Smith, J. C.; Pribram-Jones, A.; Burke, K.

2016-06-14

Thermal density functional theory calculations often use the Mermin-Kohn-Sham scheme, but employ ground-state approximations to the exchange-correlation (XC) free energy. In the simplest solvable nontrivial model, an asymmetric Hubbard dimer, we calculate the exact many-body energies and the exact Mermin-Kohn-Sham functionals for this system and extract the exact XC free energy. For moderate temperatures and weak correlation, we find this approximation to be excellent. Here we extract various exact free-energy correlation components and the exact adiabatic connection formula.

Exact thermal density functional theory for a model system: Correlation components and accuracy of the zero-temperature exchange-correlation approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, J. C.; Pribram-Jones, A.; Burke, K.

Thermal density functional theory calculations often use the Mermin-Kohn-Sham scheme, but employ ground-state approximations to the exchange-correlation (XC) free energy. In the simplest solvable nontrivial model, an asymmetric Hubbard dimer, we calculate the exact many-body energies and the exact Mermin-Kohn-Sham functionals for this system and extract the exact XC free energy. For moderate temperatures and weak correlation, we find this approximation to be excellent. Here we extract various exact free-energy correlation components and the exact adiabatic connection formula.

Echinacea purpurea (L.) Moench modulates human T-cell cytokine response☆

PubMed Central

Fonseca, Fabiana N.; Papanicolaou, Genovefa; Lin, Hong; Lau, Clara B.S.; Kennelly, Edward J.; Cassileth, Barrie R.; Cunningham-Rundles, Susanna

2014-01-01

The study objective was to evaluate the composition of a neutral and weakly acidic water-soluble extract from Echinacea purpurea (L.) Moench (EchNWA) previously shown to modify murine influenza infection, and to assess immunomodulatory effects on human T-cells. EchNWA extract from fresh aerial parts was extracted with water, ethanolic precipitation, and size-exclusion chromatography. The chemical profile of EchNWA was characterized by chromatography (size-exclusion, HPLC, GC–MS), and small molecule finger-print analysis performed by HPLC–PDA. Jurkat T-cells at high and low cell density were pretreated or not with doses of EchNWA, followed by activation with phorbol 12-myristate 13-acetate plus ionomycin (PMA+I). Interleukin-2 (IL-2) and interferon gamma (IFNg) cytokine secretions were measured by multi-cytokine luminex technology. Results showed that EchNWA contains 80% polysaccharides, predominantly a 10 kDa entity; phenolic compounds, cynarin, cichoric and caftaric acids, but no detectable alkylamides. Cytokine production required stimulation and was lower after PMA+I activation in high-density compared to low-density conditions. EchNWA mediated a strong dose-dependent enhancement of high-density T-cell production of IL-2 and IFNg response to PMA+I. EchNWA alone did not stimulate T-cells. EchNWA enhanced mean fluorescence intensity of IL-2 in Jurkat T-cells activated by PMA+1 or ionomycin alone. Conversely EchNWA mediated modest but significant suppression of IFNg response and reduced the percentage of CD25+ T-cells under low-density conditions. Conclusions are that EchNWA polysaccharides, but not phenolic compounds have dose-related adjuvant effects on human T-cell cytokine responses characterized by enhancing and suppressive effects that are regulated by T-cell density. PMID:24434371

Pulsed eddy current differential probe to detect the defects in a stainless steel pipe

NASA Astrophysics Data System (ADS)

Angani, C. S.; Park, D. G.; Kim, C. G.; Leela, P.; Kishore, M.; Cheong, Y. M.

2011-04-01

Pulsed eddy current (PEC) is an electromagnetic nondestructive technique widely used to detect and quantify the flaws in conducting materials. In the present study a differential Hall-sensor probe which is used in the PEC system has been fabricated for the detection of defects in stainless steel pipelines. The differential probe has an exciting coil with two Hall-sensors. A stainless steel test sample with electrical discharge machining (EDM) notches under different depths of 1-5 mm was made and the sample was laminated by plastic insulation having uniform thickness to simulate the pipelines in nuclear power plants (NPPs). The driving coil in the probe is excited by a rectangular current pulse and the resultant response, which is the difference of the two Hall-sensors, has been detected as the PEC probe signal. The discriminating time domain features of the detected pulse such as peak value and time to zero are used to interpret the experimental results with the defects in the test sample. A feature extraction technique such as spectral power density has been devised to infer the PEC response.

Increasing the intensity of an induction accelerator and reduction of the beam breakup instability

NASA Astrophysics Data System (ADS)

Coleman, J. E.; Moir, D. C.; Ekdahl, C. A.; Johnson, J. B.; McCuistian, B. T.; Sullivan, G. W.; Crawford, M. T.

2014-03-01

A 7 cm cathode has been deployed for use on a 3.8 MV, 80 ns (FWHM) Blumlein, to increase the extracted electron current from the nominal 1.7 to 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the space-charge limitations on the beam quality, its coupling with the beam breakup (BBU) instability, and provide an independent validation of the BBU theory in a higher current regime, I >2 kA. Time resolved centroid measurements indicate a reduction in BBU >10× with simply a 50% increase in the average B-field used to transport the beam through the accelerator. A qualitative comparison of experimental and calculated results are presented, which include time resolved current density distributions, radial BBU amplitude relative to the calculated beam envelope, and frequency analyzed BBU amplitude with different accelerator lattice tunes.

Estimation of π-π Electronic Couplings from Current Measurements.

PubMed

Trasobares, J; Rech, J; Jonckheere, T; Martin, T; Aleveque, O; Levillain, E; Diez-Cabanes, V; Olivier, Y; Cornil, J; Nys, J P; Sivakumarasamy, R; Smaali, K; Leclere, P; Fujiwara, A; Théron, D; Vuillaume, D; Clément, N

2017-05-10

The π-π interactions between organic molecules are among the most important parameters for optimizing the transport and optical properties of organic transistors, light-emitting diodes, and (bio-) molecular devices. Despite substantial theoretical progress, direct experimental measurement of the π-π electronic coupling energy parameter t has remained an old challenge due to molecular structural variability and the large number of parameters that affect the charge transport. Here, we propose a study of π-π interactions from electrochemical and current measurements on a large array of ferrocene-thiolated gold nanocrystals. We confirm the theoretical prediction that t can be assessed from a statistical analysis of current histograms. The extracted value of t ≈35 meV is in the expected range based on our density functional theory analysis. Furthermore, the t distribution is not necessarily Gaussian and could be used as an ultrasensitive technique to assess intermolecular distance fluctuation at the subangström level. The present work establishes a direct bridge between quantum chemistry, electrochemistry, organic electronics, and mesoscopic physics, all of which were used to discuss results and perspectives in a quantitative manner.

Individual differences in transcranial electrical stimulation current density

PubMed Central

Russell, Michael J; Goodman, Theodore; Pierson, Ronald; Shepherd, Shane; Wang, Qiang; Groshong, Bennett; Wiley, David F

2013-01-01

Transcranial electrical stimulation (TCES) is effective in treating many conditions, but it has not been possible to accurately forecast current density within the complex anatomy of a given subject's head. We sought to predict and verify TCES current densities and determine the variability of these current distributions in patient-specific models based on magnetic resonance imaging (MRI) data. Two experiments were performed. The first experiment estimated conductivity from MRIs and compared the current density results against actual measurements from the scalp surface of 3 subjects. In the second experiment, virtual electrodes were placed on the scalps of 18 subjects to model simulated current densities with 2 mA of virtually applied stimulation. This procedure was repeated for 4 electrode locations. Current densities were then calculated for 75 brain regions. Comparison of modeled and measured external current in experiment 1 yielded a correlation of r = .93. In experiment 2, modeled individual differences were greatest near the electrodes (ten-fold differences were common), but simulated current was found in all regions of the brain. Sites that were distant from the electrodes (e.g. hypothalamus) typically showed two-fold individual differences. MRI-based modeling can effectively predict current densities in individual brains. Significant variation occurs between subjects with the same applied electrode configuration. Individualized MRI-based modeling should be considered in place of the 10-20 system when accurate TCES is needed. PMID:24285948