Science.gov

Sample records for study polar arcs

  1. Semicircular Rashba arc spin polarizer

    SciTech Connect

    Bin Siu, Zhuo; Jalil, Mansoor B. A.; Ghee Tan, Seng

    2014-05-07

    In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.

  2. Variable polarity arc welding

    NASA Technical Reports Server (NTRS)

    Bayless, E. O., Jr.

    1991-01-01

    Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

  3. Convection and electrodynamic signatures in the vicinity of a Sun-aligned arc: Results from the Polar Acceleration Regions and Convection Study (Polar ARCS)

    NASA Technical Reports Server (NTRS)

    Weiss, L. A.; Weber, E. J.; Reiff, P. H.; Sharber, J. R.; Winningham, J. D.; Primdahl, F.; Mikkelsen, I. S.; Seifring, C.; Wescott, Eugene M.

    1994-01-01

    An experimental campaign designed to study high-latitude auroral arcs was conducted in Sondre Stromfjord, Greenland, on February 26, 1987. The Polar Acceleration Regions and Convection Study (Polar ARCS) consisted of a coordinated set of ground-based, airborne, and sounding rocket measurements of a weak, sun-aligned arc system within the duskside polar cap. A rocket-borne barium release experiment, two DMSP satellite overflights, all-sky photography, and incoherent scatter radar measurements provided information on the large-scale plasma convection over the polar cap region while a second rocket instrumented with a DC magnetometer, Langmuir and electric field probes, and an electron spectrometer provided measurements of small-scale electrodynamics. The large-scale data indicate that small, sun-aligned precipitation events formed within a region of antisunward convection between the duskside auroral oval and a large sun-aligned arc further poleward. This convection signature, used to assess the relationship of the sun-aligned arc to the large-scale magnetospheric configuration, is found to be consistent with either a model in which the arc formed on open field lines on the dusk side of a bifurcated polar cap or on closed field lines threading an expanded low-latitude boundary layer, but not a model in which the polar cap arc field lines map to an expanded plasma sheet. The antisunward convection signature may also be explained by a model in which the polar cap arc formed on long field lines recently reconnected through a highly skewed plasma sheet. The small-scale measurements indicate the rocket passed through three narrow (less than 20 km) regions of low-energy (less than 100 eV) electron precipitation in which the electric and magnetic field perturbations were well correlated. These precipitation events are shown to be associated with regions of downward Poynting flux and small-scale upward and downward field-aligned currents of 1-2 micro-A/sq m. The paired field

  4. Alternating-Polarity Arc Welding

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1987-01-01

    Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

  5. Parry Arc: A Polarization Lidar, Ray-Tracing, and Aircraft Case Study

    NASA Astrophysics Data System (ADS)

    Sassen, Kenneth; Takano, Yoshihide

    2000-12-01

    Using simple ray-tracing simulations, the cause of the rare Parry arc has been linked historically to horizontally oriented columns that display the peculiar ability to fall with a pair of prism faces closely parallel to the ground. Although we understand the aerodynamic forces that orient the long-column axis in the horizontal plane, which gives rise to the relatively common tangent arcs of the 22 halo, the mechanism leading to the Parry crystal orientation has never been resolved adequately. On 16 November 1998, at the University of Utah Facility for Atmospheric Remote Sensing, we studied a cirrus cloud producing a classic upper Parry arc using polarization lidar and an aircraft with a new high-resolution ice crystal imaging probe. Scanning lidar data, which reveal extremely high linear depolarization ratios a few degrees off the zenith direction, are simulated with ray-tracing theory to determine the ice crystal properties that reproduce this previously unknown behavior. It is found that a limited range of thick-plate crystal axis (length-to-diameter) ratios from 0.75 to 0.93 generates a maximum 2.0 5.0 for vertically polarized 0.532- m light when the lidar is tilted 1 2 off the zenith. Halo simulations based on these crystal properties also generate a Parry arc. However, although such particles are abundant in the in situ data in the height interval indicated by the lidar, one still has to invoke an aerodynamic stabilization force to produce properly oriented particles. Although we speculate on a possible mechanism, further research is needed into this new explanation for the Parry arc.

  6. Parry arc: a polarization lidar, ray-tracing, and aircraft case study.

    PubMed

    Sassen, K; Takano, Y

    2000-12-20

    Using simple ray-tracing simulations, the cause of the rare Parry arc has been linked historically to horizontally oriented columns that display the peculiar ability to fall with a pair of prism faces closely parallel to the ground. Although we understand the aerodynamic forces that orient the long-column axis in the horizontal plane, which gives rise to the relatively common tangent arcs of the 22 degrees halo, the mechanism leading to the Parry crystal orientation has never been resolved adequately. On 16 November 1998, at the University of Utah Facility for Atmospheric Remote Sensing, we studied a cirrus cloud producing a classic upper Parry arc using polarization lidar and an aircraft with a new high-resolution ice crystal imaging probe. Scanning lidar data, which reveal extremely high linear depolarization ratios delta a few degrees off the zenith direction, are simulated with ray-tracing theory to determine the ice crystal properties that reproduce this previously unknown behavior. It is found that a limited range of thick-plate crystal axis (length-to-diameter) ratios from approximately 0.75 to 0.93 generates a maximum delta approximately 2.0-5.0 for vertically polarized 0.532-microm light when the lidar is tilted 1 degrees -2 degrees off the zenith. Halo simulations based on these crystal properties also generate a Parry arc. However, although such particles are abundant in the in situ data in the height interval indicated by the lidar, one still has to invoke an aerodynamic stabilization force to produce properly oriented particles. Although we speculate on a possible mechanism, further research is needed into this new explanation for the Parry arc.

  7. A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Mcclure, John C.; Hou, Haihui Ron

    1994-01-01

    A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.

  8. The statistical difference between bending arcs and regular polar arcs

    NASA Astrophysics Data System (ADS)

    Kullen, A.; Fear, R. C.; Milan, S. E.; Carter, J. A.; Karlsson, T.

    2015-12-01

    In this work, the Polar UVI data set by Kullen et al. (2002) of 74 polar arcs is reinvestigated, focusing on bending arcs. Bending arcs are typically faint and form (depending on interplanetary magnetic field (IMF) By direction) on the dawnside or duskside oval with the tip of the arc splitting off the dayside oval. The tip subsequently moves into the polar cap in the antisunward direction, while the arc's nightside end remains attached to the oval, eventually becoming hook-shaped. Our investigation shows that bending arcs appear on the opposite oval side from and farther sunward than most regular polar arcs. They form during By-dominated IMF conditions: typically, the IMF clock angle increases from 60 to 90° about 20 min before the arc forms. Antisunward plasma flows from the oval into the polar cap just poleward of bending arcs are seen in Super Dual Auroral Radar Network data, indicating dayside reconnection. For regular polar arcs, recently reported characteristics are confirmed in contrast to bending arcs. This includes plasma flows along the nightside oval that originate close to the initial arc location and a significant delay in the correlation between IMF By and initial arc location. In our data set, the highest correlations are found with IMF By appearing at least 1-2 h before arc formation. In summary, bending arcs are distinctly different from regular arcs and cannot be explained by existing polar arc models. Instead, these results are consistent with the formation mechanism described in Carter et al. (2015), suggesting that bending arcs are caused by dayside reconnection.

  9. Variable-Polarity Plasma Arc Welding Of Alloy 2219

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.; Nunes, Arthur C., Jr.

    1989-01-01

    Report presents results of study of variable-polarity plasma arc (VPPA) welding of aluminum alloy 2219. Consists of two parts: Examination of effects of microsegregation and transient weld stress on macrosegregation in weld pool and, electrical characterization of straight- and reverse-polarity portions of arc cycle.

  10. F-layer polar-cap arcs. Master's thesis

    SciTech Connect

    Fite, D.D.

    1987-09-01

    Two types of ionospheric anomalies were discovered recently in the polar cap: patches and arcs. Polar-cap arcs are the focus of this study, which seeks correlation between arcs and total election content (TEC) enhancements and amplitude scintillation effects. Simultaneous optical and radio-frequency measurements were taken at Thule AFB and Qanaaq, Greenland, using the All-Sky Imaging Photometer (ASIP) and a specially equipped Global Positioning System (GPS) receiver. Arcs were discovered to produce significant, rapidly varying TEC increases, and small but measurable amplitude scintillation.

  11. Automated Variable-Polarity Plasma-Arc Welding

    NASA Technical Reports Server (NTRS)

    Numes, A. C., Jr.; Bayless, E. O., Jr.; Jones, S. C., III; Munafo, P.; Munafo, A.; Biddle, A.; Wilson, W.

    1984-01-01

    Variable-polarity plasma-arc methods produces better welds at lower cost than gas-shielded tungsten-arc welding in assemblies. Weld porosity very low and costs of joint preparation, depeaking, inspection, and weld repair minimized.

  12. The Relation of Polar Arcs to Magnetotail Twisting and IMF Direction

    NASA Astrophysics Data System (ADS)

    Kullen, A.; Janhunen, P.

    2002-12-01

    A large statistical study of polar arcs utilizing the Polar UV imager reveals a strong solar wind control of large-scale polar arcs. They occur preferably for a high solar wind energy flux during northward IMF. Different types of polar arcs are triggered by different IMF clock angle changes. Oval-aligned arcs appear often during constant IMF, moving transpolar arcs usually develop after an IMF By sign change. The relation of these two polar arc types to changes in the magnetotail topology are investigated with help of the GUMICS-4 MHD code by Janhunen. The simulations show that for northward IMF with a nonzero IMF By component the magnetotail becomes long and highly twisted at its tailward end. The closed field line region reaches in this case high into the near-Earth tail lobes and poleward of the average polar cap boundary. The poleward displaced part of the polar cap boundary is a probable location for polar arcs to occur. In the case of an IMF By sign change the tail twist rotates such that in an intermediate state near-Earth and far-tail regions are oppositely twisted. This causes a bifurcation of the closed field line region in the tail and a bridge of closed field lines in the polar cap. The over the entire polar cap moving closed bridge indicates a moving transpolar arc.

  13. Physics Of Variable-Polarity Plasma Arc Welding

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.; Nunes, Arthur C., Jr.

    1990-01-01

    Report describes experimental study of some of the physical and chemical effects that occur during variable-polarity plasma arc (VPPA) keyhole welding of 2219 aluminum alloy. Comprised three major programs: (1) determination of effects of chemical additions (i.e., impurities) on structure and shape of bead and keyhole; (2) determination of flow in regions surrounding keyhole; (3) development of analog used easily to study flow in keyhole region.

  14. High altitude chemical release systems for project BIME (Brazilian Ionospheric Modification Experiments) project IMS (Ionospheric Modification Studies) project PIIE (Polar Ionospheric Irregularities Experiment) project polar arcs

    NASA Astrophysics Data System (ADS)

    Stokes, Charles S.; Murphy, William J.

    1987-07-01

    Project BIME, a Spread F observation program involved the launching of two Nike-Black Brant rockets each containing a payload of Ammonium Nitrate Fuel Oil (ANFO). The rockets were launched from Barriera Do Inferno Launch Site in Natal, Brazil in August of 1982. Project IMS, an F-layer modification experiment involved three launch vehicles, a Nike-Tomahawk and two Sonda III rockets. The Nike-Tomahawk carried a sulfur hexafluoride (SF6) payload. One of the Sonda III rockets carried a payload that consisted of an SF6 canister and a samarium/strontium thermite canister. The remaining Sonda III carried a trifluorobromo methane (CF3Br) canister and a samarium thermite canister. The rockets were launched from Wallops Island Launch Facility, Virginia in November of 1984. Project PIIE and Polar Arcs, a program to investigate polar ionospheric irregularities, involved a Nike-Black Brant rocket carrying one samarium thermite canister and six barium canisters. An attempted launch failed when launch criteria could not be met. The rocket was launched successfully from Sondrestrom Air Base, Greenland in March 1987.

  15. Robotic Variable Polarity Plasma Arc (VPPA) Welding

    NASA Technical Reports Server (NTRS)

    Jaffery, Waris S.

    1993-01-01

    The need for automated plasma welding was identified in the early stages of the Space Station Freedom Program (SSFP) because it requires approximately 1.3 miles of welding for assembly. As a result of the Variable Polarity Plasma Arc Welding (VPPAW) process's ability to make virtually defect-free welds in aluminum, it was chosen to fulfill the welding needs. Space Station Freedom will be constructed of 2219 aluminum utilizing the computer controlled VPPAW process. The 'Node Radial Docking Port', with it's saddle shaped weld path, has a constantly changing surface angle over 360 deg of the 282 inch weld. The automated robotic VPPAW process requires eight-axes of motion (six-axes of robot and two-axes of positioner movement). The robot control system is programmed to maintain Torch Center Point (TCP) orientation perpendicular to the part while the part positioner is tilted and rotated to maintain the vertical up orientation as required by the VPPAW process. The combined speed of the robot and the positioner are integrated to maintain a constant speed between the part and the torch. A laser-based vision sensor system has also been integrated to track the seam and map the surface of the profile during welding.

  16. Robotic Variable Polarity Plasma Arc (VPPA) welding

    NASA Astrophysics Data System (ADS)

    Jaffery, Waris S.

    1993-02-01

    The need for automated plasma welding was identified in the early stages of the Space Station Freedom Program (SSFP) because it requires approximately 1.3 miles of welding for assembly. As a result of the Variable Polarity Plasma Arc Welding (VPPAW) process's ability to make virtually defect-free welds in aluminum, it was chosen to fulfill the welding needs. Space Station Freedom will be constructed of 2219 aluminum utilizing the computer controlled VPPAW process. The 'Node Radial Docking Port', with it's saddle shaped weld path, has a constantly changing surface angle over 360 deg of the 282 inch weld. The automated robotic VPPAW process requires eight-axes of motion (six-axes of robot and two-axes of positioner movement). The robot control system is programmed to maintain Torch Center Point (TCP) orientation perpendicular to the part while the part positioner is tilted and rotated to maintain the vertical up orientation as required by the VPPAW process. The combined speed of the robot and the positioner are integrated to maintain a constant speed between the part and the torch. A laser-based vision sensor system has also been integrated to track the seam and map the surface of the profile during welding.

  17. Arc electrode interaction study

    NASA Technical Reports Server (NTRS)

    Zhou, X.; Berns, D.; Heberlein, J.

    1994-01-01

    The project consisted of two parts: (1) the cathode interaction studies which were a continuation of previous work and had the objective of increasing our understanding of the microscopic phenomena controlling cathode erosion in arc jet thrusters, and (2) the studies of the anode attachment in arc jet thrusters. The cathode interaction studies consisted of (1) a continuation of some modeling work in which the previously derived model for the cathode heating was applied to some specific gases and electrode materials, and (2) experimental work in which various diagnostics was applied to the cathode. The specific diagnostics used were observation of the cathode tip during arcing using a Laser Strobe Video system in conjunction with a tele-microscope, a monochromator with an optical multichannel analyzer for the determination of the cathode temperature distribution, and various ex situ materials analysis methods. The emphasis of our effort was shifted to the cathode materials analysis because a parallel project was in place during the second half of 1993 with a visiting scientist pursuing arc electrode materials studies. As a consequence, the diagnostic investigations of the arc in front of the cathode had to be postponed to the first half of 1994, and we are presently preparing these measurements. The results of last year's study showed some unexpected effects influencing the cathode erosion behavior, such as increased erosion away from the cathode tip, and our understanding of these effects should improve our ability to control cathode erosion. The arc jet anode attachment studies concentrated on diagnostics of the instabilities in subsonic anode attachment arc jet thrusters, and were supplemental measurements to work which was performed by one of the authors who spent the summer as an intern at NASA Lewis Research Center. A summary of the results obtained during the internship are included because they formed an integral part of the study. Two tasks for 1994, the

  18. The variable polarity plasma arc welding process: Its application to the Space Shuttle external tank

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Bayless, O. E., Jr.; Jones, C. S., III; Munafo, A. P.; Wilson, W. A.

    1983-01-01

    The technical history of the variable polarity plasma arc (VPPA) welding process being introduced as a partial replacement for the gas shielded tungsten arc process in assembly welding of the space shuttle external tank is described. Interim results of the weld strength qualification studies, and plans for further work on the implementation of the VPPA process are included.

  19. Mathematical Model Of Variable-Polarity Plasma Arc Welding

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1996-01-01

    Mathematical model of variable-polarity plasma arc (VPPA) welding process developed for use in predicting characteristics of welds and thus serves as guide for selection of process parameters. Parameters include welding electric currents in, and durations of, straight and reverse polarities; rates of flow of plasma and shielding gases; and sizes and relative positions of welding electrode, welding orifice, and workpiece.

  20. Polar cap precursor of nightside auroral oval intensifications using polar cap arcs

    NASA Astrophysics Data System (ADS)

    Zou, Ying; Nishimura, Yukitoshi; Lyons, Larry R.; Donovan, Eric F.; Shiokawa, Kazuo; Ruohoniemi, J. Michael; McWilliams, Kathryn A.; Nishitani, Nozomu

    2015-12-01

    Recent radar and optical observations suggested that localized fast flows in the polar cap precede disturbances within the nightside auroral oval. However, how commonly this connection occurs has been difficult to examine due to limited coverage of radar flow measurements and diffuse and dim nature of airglow patches. Polar cap arcs are also associated with fast flows in the polar cap and appear much brighter than patches, allowing evaluation of the interaction between polar cap structures and nightside aurora more definitively. We have surveyed data during six winter seasons and selected quasi-steady polar cap arcs lasting >1 h. Thirty-four arcs are found, and for the majority (~85%) of them, as they extend equatorward from high latitude, their contact with the nightside auroral poleward boundary is associated with new and substantial intensifications within the oval. These intensifications are localized (< ~1 h magnetic local time (MLT)) and statistically occur within 10 min and ±1 h MLT from the contact. They appear as poleward boundary intensifications in a thick auroral oval or an intensification of the only resolvable arc within a thin oval, and the latter can also exhibit substantial poleward expansion. When radar echoes are available, they corroborate the association of polar cap arcs with localized enhanced antisunward flows. That the observed oval intensifications are major disturbances that only occur after the impingement of polar cap arcs and near the contact longitude suggest that they are triggered by localized fast flows coming from deep in the polar cap.

  1. Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc

    NASA Astrophysics Data System (ADS)

    van der Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag A.; Paxton, Larry J.; Clausen, Lasse B. N.

    2016-06-01

    In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data and lasted at least 3 h between 1700 and 2000 UT. The arc was more intense than the main oval during this time. From all-sky imagers on Svalbard we were able to study the evolution of the arc, which drifted slowly westward toward the dusk cell. The intensity of the arc as observed from ground was 10-17 kR in 557.7 nm and 2-3.5 kR in 630.0 nm, i.e., significant emissions in both green and red emission lines. We have used high-resolution raw data from global navigation satellite systems (GNSS) receivers and backscatter from Super Dual Auroral Radar Network (SuperDARN) radars to study irregularities and scintillation in relation to the polar cap arc. Even though the literature has suggested that polar cap arcs are potential sources for irregularities, our results indicate only very weak irregularities. This may be due to the background density in the northward IMF polar cap being too low for significant irregularities to be created.

  2. Heat flow in variable polarity plasma arc welds

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.

    1992-01-01

    The space shuttle external tank and the space station Freedom are fabricated by the variable polarity plasma arc (VPPA) welding. Heat sink effects (taper) are observed when there are irregularities in the work-piece configuration especially if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, and in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of the previous, present, and consecutive research studies is to investigate the effect of irregularities in the work-piece configuration and fixture differences on the weld bead geometry with the ultimate objective to compensate automatically for the heat sink effects and achieve a perfect weld.

  3. Heat sink effects in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.

    1991-01-01

    The Space Shuttle External Tank is fabricated by the variable polarity plasma arc (VPPA) welding process. In VPPA welding, a noble gas, usually argon, is directed through an arc to emerge from the torch as a hot plasma jet. This jet is surrounded by a shielding gas, usually helium, to protect the weld from contamination with air. The high velocity, hot plasma jet completely penetrates the workpiece (resembling a line heat source) when operated in the 'keyhole' mode. The metal melts on touching the side of the jet, as the torch travels in the perpendicular direction to the direction of the jet, and melted metal moves around the plasma jet in the keyhole forming a puddle which solidifies behind the jet. Heat sink effects are observed when there are irregularities in the workpiece configuration, especially, if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, i.e., in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of this research is to study the effect of irregularities in workpiece configuration and fixture differences (heat sink effects) on the weld bead geometry with the ultimate objective to compensate for the heat sink effects and achieve a perfect weld. Experiments were performed on different workpiece geometries and compared to approximate models.

  4. Unique variable polarity plasma arc welding for space shuttle

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1985-01-01

    Since the introduction of the Plasma Arc Torch in 1955 and subsequent to the work at Boeing in the 1960's, significant improvements crucial to success have been made in the Variable Polarity Plasma Arc (VPPA) Process at the Marshall Space Flight Center. Several very important advantages to this process are given, and the genesis of PA welding, the genesis of VPPA welding, special equiment requirements, weld property development, results with other aluminum alloys, and the eventual successful VPPA transition to production operations are discussed.

  5. Solar illumination control of ionospheric outflow above polar cap arcs

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; De Keyser, J.; Dandouras, I.; Fear, R. C.; Fontaine, D.; Haaland, S.

    2015-03-01

    We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between ˜94° and ˜107°, with the O+ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O+ upflow occurs locally above the polar ionosphere. The same is found for H+, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

  6. Eddy intrustion of hot plasma into the polar cap and formation of polar-cap arcs

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Gorney, D. J.

    1983-01-01

    Under the simple postulate that multiple large scale detachable magnetospheric convection eddies can exist in the vicinity of the convection reversal boundary and in the polar cap, by Kelvin-Helmholtz instability or otherwise, it is shown that a number of seemingly disconnected plasma and electric field observations in the polar cap can be organized into a theory of magnetosheath and plasmasheet plasma intrusion into the polar cap. Current theory of inverted V structures then predicts existence of similar, but weaker, structures at the eddy convection reversal boundaries in the polar cap. A possible consequence is that the polar cap auroras are natural offshoots from discrete oval arcs and evidently are formed by similar processes. The two arc systems can occassionally produce an optical image in the form of the theta aurora.

  7. Intensification and fading of auroral arcs in the dusk-midnight sector of the polar cap

    SciTech Connect

    Wu, Q.; Rosenberg, T.J. ); Berkey, F.T. ); Eather, R.H. )

    1991-05-01

    Observations of the aurora from South Pole station (magnetic latitude = {minus}74.2{degree}) have been used to study the intensification and fading of polar arcs observed near the dusk meridian. Most of the cases examined have the following features in common: (1) a preexisting auroral form intensifies for about 10 min; (2) this activation is followed by a pronounced decrease of luminosity; (3) the auroral fade terminates after 30-60 min with the onset of intense aurora which sweeps rapidly overhead. The availability of all-sky camera, auroral electrojet (AE) index and interplanetary magnetic field (IMF) data for some of the cases enables the following additional characterizations of these events. The preexisting form is a Sun- or oval-aligned arc (or part of a multiple arc system) which disappears following the activation; equatorward drift of the arc (or system) accompanies the luminosity change. There is some evidence to suggest that the arc is poleward of the auroral oval. The brief intensification and/or the onset of fading occurs during the growth phase or near the start of the expansive phase of a substorm; termination of the fade is near the maximum in AE and is probably indicative of the beginning of the recovery phase of the substorm. For all three cases for which IMF data were available the onset of fading occurred 20-30 min after B{sub z} turned southward. Sun-aligned arcs are a common feature of the polar cap during northward B{sub z} but disappear during the increasingly disturbed conditions that accompany southward B{sub z}. The present results suggest that brief intensifications of southern hemisphere polar cap arcs near dusk may be linked in part to the sunward orientation of the IMF which favors enhanced electron fluxes in the southern lobe of the magnetotail.

  8. The variable polarity plasma arc welding process: Characteristics and performance

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Zhu, G. J.

    1991-01-01

    Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. The power distribution was analyzed for an argon plasma gas flow constituting the fluid in the VPPA Welding Process. The major heat loss at the torch nozzle is convective heat transfer; in the space between the outlet of the nozzle and the workpiece; radiative heat transfer; and in the keyhole in the workpiece, convective heat transfer. The power absorbed at the workpiece produces the molten puddle that solidifies into the weld bead. Crown and root widths, and crown and root heights of the weld bead are predicted. The basis is provided for an algorithm for automatic control of VPPA welding machine parameters to obtain desired weld bead dimensions.

  9. Electrically polarized micro-arc oxidized TiO2 coatings with enhanced surface hydrophilicity.

    PubMed

    Ma, Chufan; Nagai, Akiko; Yamazaki, Yuko; Toyama, Takeshi; Tsutsumi, Yusuke; Hanawa, Takao; Wang, Wei; Yamashita, Kimihiro

    2012-02-01

    The use of micro-arc oxidation titania (MAO TiO2) coatings to modify titanium surfaces improves the biocompatibility of implant surfaces. To obtain hydrophilic MAO TiO2 coating surfaces electric polarization, which induces surface electric fields in the materials and produces surface charges, was performed in this study. Electric polarization of the MAO TiO2 coatings was confirmed by measuring the thermally stimulated depolarization current. After electric polarization treatment the MAO TiO2 coatings did not exhibit any obvious changes in surface roughness, morphology, or phase components. X-ray photoelectron spectroscopy results indicated that electric polarization resulted in oxidation of the cathodic-faced surfaces and reduction of the anodic-faced surfaces. This result suggests that the existence of a concentration gradient of oxide ions/oxygen vacancies produced the stored space charge in the coatings. Reduction of the deionized water contact angle on the polarized MAO TiO2 surfaces was maintained for longer periods compared with the non-polarized surface. Our study demonstrated that metastable electric fields across the MAO TiO2 coating produced by electric polarization made it durably wettable by reducing the interfacial surface tension between the material and water.

  10. Martian polar geological studies

    NASA Technical Reports Server (NTRS)

    Cutts, J. A. J.

    1977-01-01

    Multiple arcs of rugged mountains and adjacent plains on the surface of Mars were examined. These features, located in the southern polar region were photographed by Mariner 9. Comparisons are made with characteristics of a lunar basin and mare; Mare imbrium in particular. The martian feature is interpreted to have originated in the same way as its lunar analog- by volcanic flooding of a large impact basin. Key data and methodology leading to this conclusion are cited.

  11. Formation and eruption of Sun-aligned arcs at the polar cap-auroral oval boundary

    SciTech Connect

    Berg, G.A.; Kelley, M.C.; Mendillo, M.

    1994-09-01

    This paper reports on results from a study of the poleward edge of the auroral oval in the morning sector using a comprehensive blend of in situ and ground-based measurements. Three rockets, equipped to measure electric and magnetic fields, energetic particles, and plasma density flew into an auroral display whose dynamical features were recorded with a digital image intensified all-sky camera as well as with an incoherent scatter radar. In addition, a number of DMSP satellite measurements bracketed that launch time. Evidence is presented here that in a condition of declining magnetic activity Sun-aligned arcs are injected into the polar cap at velocities {approximately}7 km/s from locations of periodic brightening along the morningside of the auroral oval. The multipoint in situ measurements allow some separation of temporal and spatial effects and strongly suggest a poleward contraction of the convection pattern of about 0.25{degrees} INVL in 70 s. The most equatorward of the two brightest arcs studied erupted into a region which already was characterized by strong sunward convection. The most poleward, however, pushed into a region that had been convecting in an antisunward direction at velocities exceeding 1 km/s less than 2 min earlier, and it is likely that sunward convection subsequently pertained poleward of that arc as well. The authors believe that these events mark the reconfiguration of the magnetosphere into a system characterized by a smaller polar cap. 34 refs., 14 figs.

  12. Spin Polarization and Texture of the Fermi Arcs in the Weyl Fermion Semimetal TaAs.

    PubMed

    Xu, Su-Yang; Belopolski, Ilya; Sanchez, Daniel S; Neupane, Madhab; Chang, Guoqing; Yaji, Koichiro; Yuan, Zhujun; Zhang, Chenglong; Kuroda, Kenta; Bian, Guang; Guo, Cheng; Lu, Hong; Chang, Tay-Rong; Alidoust, Nasser; Zheng, Hao; Lee, Chi-Cheng; Huang, Shin-Ming; Hsu, Chuang-Han; Jeng, Horng-Tay; Bansil, Arun; Neupert, Titus; Komori, Fumio; Kondo, Takeshi; Shin, Shik; Lin, Hsin; Jia, Shuang; Hasan, M Zahid

    2016-03-04

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as quasiparticle excitations. The Weyl fermions at zero energy correspond to points of bulk-band degeneracy, called Weyl nodes, which are separated in momentum space and are connected only through the crystal's boundary by an exotic Fermi arc surface state. We experimentally measure the spin polarization of the Fermi arcs in the first experimentally discovered Weyl semimetal TaAs. Our spin data, for the first time, reveal that the Fermi arcs' spin-polarization magnitude is as large as 80% and lies completely in the plane of the surface. Moreover, we demonstrate that the chirality of the Weyl nodes in TaAs cannot be inferred by the spin texture of the Fermi arcs. The observed nondegenerate property of the Fermi arcs is important for establishing its exact topological nature, which reveals that spins on the arc form a novel type of 2D matter. Additionally, the nearly full spin polarization we observed (∼80%) may be useful in spintronic applications.

  13. A comparative study on the arc and melting efficiencies of arc welding processes

    SciTech Connect

    DuPont, J.N.; Marder, A.R.

    1996-12-31

    A study was conducted on the arc and melting efficiency of the plasma arc, gas tungsten arc, gas metal arc, and submerged arc welding processes. Arc efficiency was determined as a function of current for each process using A36 steel base metal. Melting efficiency was evaluated with variations in arc power and travel speed during deposition of austenitic stainless steel filler wire onto A36 steel substrates. The arc efficiency did not vary significantly within a given process over the range of currents investigated. The consumable electrode processes exhibited the highest arc efficiency (0.84), followed by the gas tungsten arc (0.67) and plasma arc (0.47) processes. A semi-empirical relation was developed for the melting efficiency as a function of net arc power and travel speed which described the experimental data reasonably well. An interaction was observed between the arc and melting efficiency. A low arc efficiency factor limits the power delivered to the substrate which, in turn, limits the maximum travel speed for a given set of conditions. High melting efficiency is favored by high arc powers and travel speeds. As a result, a low arc efficiency can limit the maximum obtainable melting efficiency.

  14. UAH mathematical model of the variable polarity plasma ARC welding system calculation

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1994-01-01

    Significant advantages of Variable Polarity Plasma Arc (VPPA) welding process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. A mathematical model is presented to analyze the VPPA welding process. Results of the mathematical model were compared with the experimental observation accomplished by the GDI team.

  15. The Variable Polarity Plasma Arc Welding Process: Its Application to the Space Shuttle External Tank

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Bayless, E. O., Jr.; Wilson, W. A.

    1984-01-01

    This report describes progress in the implementation of the Variable Polarity Plasma Arc Welding (VPPAW) process at the External Tank (ET) assembly facility. Design allowable data has been developed for thicknesses up to 1.00 in. More than 24,000 in. of welding on liquid oxygen and liquid hydrogen cylinders has been made without an internal defect.

  16. Arc-Polarized, Nonlinear Alfven Waves and Rotational Discontinuities: Directions of Propogation?

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Ho, C. M.; Sakurai, R.; Arballo, J. K.; Riley, P.; Balogh, A.

    1996-01-01

    Large amplitude, noncompressive Alfven waves and rotational discontinuities are shown to be arc-polarized. The slowly rotating Alfven wave portion plus the fast rotating discontinuity comprise 360(deg) in phase rotation. The magnetic field vector perturbation lies in a plane. There are two (or more) possible interpretations to the observations.

  17. Electrodynamic, thermal, and energetic character of intense sun-aligned arcs in the polar cap

    SciTech Connect

    Valladares, C.E.; Carlson, H.C.

    1991-02-01

    The electrodynamic, thermal and energetic character of stable Sun-aligned arcs in the polar cap can be meaningfully diagnosed by an incoherent scatter radar, provided a suitable observing scheme is selected. The authors report here such measurements of two intense Sun-aligned arcs. The two arcs were diagnosed on two different nights (February 26 and March 1, 1987) using the Sondre Stomfjord radar as a stand-alone diagnostic. Repeatable patterns are found in mesoscale area maps of altitude profiles for observed electron and ion gas number densities, temperatures, and line-of-sight velocities, and projected mesoscale area maps of derived electric fields, Pedersen and Hall conductivities, horizontal and field-aligned currents, Joule heating rate, and Poynting flux. They confirm, for the first time with continuous mesoscale area maps, that the arcs have the anticipated simple arc electrodynamics. That is, the visual and enhanced ionization signatures of the arc are produced by incoming energetic electrons carrying the outgoing current from the electric field convergence in the arc.

  18. The effect of impurity gasses on variable polarity plasma arc welded 2219 aluminum

    NASA Technical Reports Server (NTRS)

    Mcclure, John C.; Torres, Martin R.; Gurevitch, Alan C.; Newman, Robert A.

    1989-01-01

    Variable polarity plasma arc (VPPA) welding has been used with considerable success by NASA for the welds on the Space Shuttle External Tank as well as by others concerned with high quality welded structures. The effects of gaseous contaminants on the appearance of VPPA welds on 2219 aluminum are examined so that a welder can recognize that such contamination is present and take corrective measures. There are many possible sources of such contamination including, contaminated gas bottles, leaks in the gas plumbing, inadequate shield gas flow, condensed moisture in the gas lines or torch body, or excessive contaminants on the workpiece. The gasses chosen for study in the program were nitrogen, oxygen, methane, and hydrogen. Welds were made in a carefully controlled environment and comparisons were made between welds with various levels of these contaminants and welds made with research purity (99.9999 percent) gasses. Photographs of the weld front and backside as well as polished and etched cross sections are presented.

  19. Rocket measurements within a polar cap arc - Plasma, particle, and electric circuit parameters

    NASA Technical Reports Server (NTRS)

    Weber, E. J.; Ballenthin, J. O.; Basu, S.; Carlson, H. C.; Hardy, D. A.; Maynard, N. C.; Kelley, M. C.; Fleischman, J. R.; Pfaff, R. F.

    1989-01-01

    Results are presented from the Polar Ionospheric Irregularities Experiment (PIIE), conducted from Sondrestrom, Greenland, on March 15, 1985, designed for an investigation of processes which lead to the generation of small-scale (less than 1 km) ionospheric irregularities within polar-cap F-layer auroras. An instrumented rocket was launched into a polar cap F layer aurora to measure energetic electron flux, plasma, and electric circuit parameters of a sun-aligned arc, coordinated with simultaneous measurements from the Sondrestrom incoherent scatter radar and the AFGL Airborne Ionospheric Observatory. Results indicated the existence of two different generation mechanisms on the dawnside and duskside of the arc. On the duskside, parameters are suggestive of an interchange process, while on the dawnside, fluctuation parameters are consistent with a velocity shear instability.

  20. Rocket measurements within a polar cap arc - Plasma, particle, and electric circuit parameters

    NASA Technical Reports Server (NTRS)

    Weber, E. J.; Ballenthin, J. O.; Basu, S.; Carlson, H. C.; Hardy, D. A.; Maynard, N. C.; Kelley, M. C.; Fleischman, J. R.; Pfaff, R. F.

    1989-01-01

    Results are presented from the Polar Ionospheric Irregularities Experiment (PIIE), conducted from Sondrestrom, Greenland, on March 15, 1985, designed for an investigation of processes which lead to the generation of small-scale (less than 1 km) ionospheric irregularities within polar-cap F-layer auroras. An instrumented rocket was launched into a polar cap F layer aurora to measure energetic electron flux, plasma, and electric circuit parameters of a sun-aligned arc, coordinated with simultaneous measurements from the Sondrestrom incoherent scatter radar and the AFGL Airborne Ionospheric Observatory. Results indicated the existence of two different generation mechanisms on the dawnside and duskside of the arc. On the duskside, parameters are suggestive of an interchange process, while on the dawnside, fluctuation parameters are consistent with a velocity shear instability.

  1. Examination of the physical processes associated with the keyhole region of variable polarity plasma arc welds in aluminum alloy 2219

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1987-01-01

    The morphology and properties of the Variable Polarity Plasma Arc (VPPA) weld composite zone are intimately related to the physical processes associated with the keyhole. This study examined the effects of oxide, halide, and sulfate additions to the weld plate on the keyhole and the weld pool. Changes in both the arc plasma character and the bead morphology were correlated to the chemical environment of the weld. Pool behavior was observed by adding flow markers to actual VPPA welds. A low temperature analog to the welding process was developed. The results of the study indicate that oxygen, even at low partial pressures, can disrupt the stable keyhole and weld pool. The results also indicate that the Marangoni surface tension driven flows dominate the weld pool over the range of welding currents studied.

  2. Polarization of the far-infrared emission from the thermal filaments of the Galactic center arc

    NASA Technical Reports Server (NTRS)

    Morris, M.; Davidson, J. A.; Werner, M.; Dotson, J.; Figer, D. F.; Hildebrand, R.; Novak, G.; Platt, S.

    1992-01-01

    The polarization of the 100 micron continuum emission has been measured at 14 positions in the dense, warm molecular cloud associated with the arched filaments, or the 'bridge', of the radio arc near the Galactic center. At all positions the percent polarization is found to be quite large, ranging up to 6.5 percent. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains. The directions of the polarization vectors then indicate that the magnetic field is (1) parallel to the long dimension of the thermal radio filaments, and (2) very uniform on scales of 1-10 pc. Of several explanations for the inferred field geometry, the simplest is that it results from the unusually large dynamical shear in the emitting cloud.

  3. Polarization of the far-infrared emission from the thermal filaments of the Galactic center arc

    NASA Technical Reports Server (NTRS)

    Morris, M.; Davidson, J. A.; Werner, M.; Dotson, J.; Figer, D. F.; Hildebrand, R.; Novak, G.; Platt, S.

    1992-01-01

    The polarization of the 100 micron continuum emission has been measured at 14 positions in the dense, warm molecular cloud associated with the arched filaments, or the 'bridge', of the radio arc near the Galactic center. At all positions the percent polarization is found to be quite large, ranging up to 6.5 percent. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains. The directions of the polarization vectors then indicate that the magnetic field is (1) parallel to the long dimension of the thermal radio filaments, and (2) very uniform on scales of 1-10 pc. Of several explanations for the inferred field geometry, the simplest is that it results from the unusually large dynamical shear in the emitting cloud.

  4. Hybrid Arc Cell Studies: Status Report

    SciTech Connect

    Berg J. S.

    2012-09-28

    I report on the status, at the end of FY12, of the studies of an arc cell for a hybrid synchrotron accelerating from 375 GeV/c to 750 GeV/c in momentum. Garren produced a complete lattice that gives a good outline of the structure of a hybrid synchrotron lattice. It is, however, lacking in some details: it does not maintain a constant time of flight, it lacks chromaticity correction, its cell structure is not ideal for removing aberrations from chromaticity correction, and it probably needs more space between magnets. I have begun studying cell structures for the arc cells to optimize the lattice performance and cost. I present some preliminary results for two magnets per half cell. I then discuss difficulties encountered, some preliminary attempts at resolving them, and the future plans for this work.

  5. The Electrodynamic, Thermal, and Energetic Character of Intense Sun- Aligned Arcs in the Polar Cap

    DTIC Science & Technology

    1991-02-01

    Vici’jewski et 0/.. 19891. with " detailed analysis of its optical. ion production-loss rates, and u 200 ionizing flux properties. Observed in the UV by...kIEMNr INsmrumE 1IICAi 0 MIlL N ORCANIZATION I (if aipplicable) r~ lk. AD01MV; (Cafy, 5ldtV.,J#dli /If’COUdt) 10 Stu JICI. U FUNUING NUNiIRS ’l-IJiAM...sented by R’ifl and Run h 119851. Their analysis implies a 1380 VALLADARES AND CARLSON: POLAR ARC ELECTRODYNAMICS/ENERGETICS four-cell convection

  6. Extreme F-region gradients generated by patch-arc interactions in the polar cap

    NASA Astrophysics Data System (ADS)

    Semeter, J. L.; Dahlgren, H.; Zettergren, M. D.; Swoboda, J.; Perry, G. W.; St-Maurice, J. P.; Hosokawa, K.; Shiokawa, K.; Nicolls, M. J.

    2014-12-01

    We report observations of electrodyamic interactions between drifting F-region plasma structure and discrete polar cap arcs. Three-dimensional time-dependent images of ionospheric state variables (Ne, Te, Ti, Vi) are produced using multi-beam measurements by the Resolute Bay Incoherent Scatter Radar (RISR). The resulting parameter maps are registered with all-sky images of 630-nm and 557-nm emissions acquired by the collocated OMTI imager. The combined analysis allows us to disambiguate spatial and temporal effects, revealing the formation of a deep density depletion between the arc and the plasma patch, formed by the combined action of electrodynamic evacuation and enhanced chemical recombination in the auroral downward current region. This mechanism results in a steep density gradient (gradient scale length <5-km) extending for at least 800-km in a direction tangential to the arc. This region should be highly unstable to gradient drift instability, and a likely source of enhanced HF scatter. Interpretations are supported through three-dimensional transport modeling.

  7. Polar UVI Observations of Auroral Oval Intensifications during a Transpolar Arc Event on December 7, 1996

    NASA Technical Reports Server (NTRS)

    Cumnock, J. A.; Spann, J. F.; Germany, G. A.; Blomberg, L. G.; Coley, W. R.; Brittnacher, M. J.; Parks, G. K.; Clauer, C. R.

    1999-01-01

    The evolution of the northern hemisphere aurora is examined during a time when the Interplanetary Magnetic Field (IMF) makes three brief southward excursions after an extended period of northward IMF. POLAR UltraViolet Imager (UVI) provides images of the aurora while DMSP provides in situ measurements of precipitating particles, ionospheric plasma flows and ion density. Substorm-like events are correlated with northward turnings of the IMF, while the intensity of the ionospheric response is correlated with the duration of the southward IMF period prior to the northward turning. Observations indicate that when the transpolar arc reaches the highest latitudes it is located on a spatially narrow region of closed field lines which extends along the noon-midnight meridian. UV observations indicate a connection between the transpolar arc and the nightside auroral enhancements. Precipitating particles associated with both features are attributed to a plasma sheet boundary layer source in the magnetotail implying a magnetospheric connection between the transpolar arc and the nightside auroral oval intensification.

  8. Variable polarity plasma arc welding on the Space Shuttle external tank

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Bayless, E. O., Jr.; Jones, C. S., III; Munafo, P. M.; Biddle, A. P.; Wilson, W. A.

    1984-01-01

    Variable polarity plasma arc (VPPA) techniques used at NASA's Marshall Space Flight Center for the fabrication of the Space Shuttle External Tank are presentedd. The high plasma arc jet velocities of 300-2000 m/s are produced by heating the plasma gas as it passes through a constraining orifice, with the plasma arc torch becoming a miniature jet engine. As compared to the GTA jet, the VPPA has the following advantages: (1) less sensitive to contamination, (2) a more symmetrical fusion zone, and (3) greater joint penetration. The VPPA welding system is computerized, operating with a microprocessor, to set welding variables in accordance with set points inputs, including the manipulator and wire feeder, as well as torch control and power supply. Some other VPPA welding technique advantages are: reduction in weld repair costs by elimination of porosity; reduction of joint preparation costs through elimination of the need to scrape or file faying surfaces; reduction in depeaking costs; eventual reduction of the 100 percent-X-ray inspection requirements. The paper includes a series of schematic and block diagrams.

  9. GUI for studying the parameters influence of the electric arc model for a three-phase electric arc furnace

    NASA Astrophysics Data System (ADS)

    Ghiormez, L.; Prostean, O.; Panoiu, M.; Panoiu, C.

    2017-01-01

    This paper presents an analysis regarding the modeling of the behavior for a three-phase electric arc furnace installation. Therefore, a block diagram is implemented in Simulink that represents the modeling of the entire electric arc furnace installation. This block diagram contains also the modeling of the electric arc which is the element that makes the electric arc furnace behaving as a nonlinear load. The values for the model parameters of the electric arc furnace installation are like the ones from the real installation taken into consideration. Other model parameters are the electric arc model ones. In order to study the influence of the parameters of the electric arc models, it is developed a Matlab program that contains the graphical user interfaces. These interfaces make connection with the models of the electric arc implemented in Simulink. The interfaces allow the user to modify parameters for each of the electric arc model. Current and voltage of the electric arc are the variables taken into account to study the influence of the parameters on the electric arc models. Waveforms for voltage and current of the electric arc are illustrated when a parameter of the model is modified in order to analyze the importance of this parameter on the electric arc model. Also, for each of the models is presented the voltage-current characteristic of the electric arc because this characteristic gives information about the behavior of the electric arc furnace installation.

  10. Two Types of Transpolar Arc Development, Event Studies with Data Set of ASTRID-2, DMSP, FAST, and SuperDARN

    NASA Technical Reports Server (NTRS)

    Narita, Yasuhito; Maezawa, Kiyoshi; Toshinori, Mukai; Kullen, A.; Ivchenko, N.; Marklund, G.; Frederick, R.; Carlson, C. W.; Spann, J. F.; Parks, G. K.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Aurorae which appear in the polar cap are called transpolar arcs, polar cap arcs, sun-aligned arcs, or occasionally Theta-aurora because of its spatial distribution resembling Greek character 'Theta.' Morphology, IMF (Interplanetary Magnetic Field) relationship, and ionospheric convection patterns were studied in quest of mechanisms of transpolar arcs. Four events were analyzed: 1999/Jan/22/19:00 - 23/01:30 (1 event: a) 1999/Jan/24/06:00 - 10:00 (1 event: b) 1999/Feb/1 1/20:00 - 12/02:00 (2 events: c, d), with data set of ExB drift velocity data obtained by electric field measurements of ASTRID-2 and FAST, DMSP ion driftmeter data, and line-of-sight velocity data of SuperDARN. POLAR-UVI image data were used for spatial and temporal variations of transpolar arcs and ACE data set were used for investigation of IMF relationship. IMF-Bz was strongly positive (Bz from +8nT to +20 nT) during periods of all four transpolar arcs. In events (a),(b),(c), transpolar arcs appeared immediately after the direction of IMF turned northward, though IMF was fluctuating in event (b). A sudden increase of IMF-By, from +3nT to +18nT, was observed in event (d). Two different types of transpolar arc development were observed in POLAR-UVI: one which begins as a split from dawn or dusk sector of auroral oval and shifts poleward in event (a),(c),(d), and another which is initially a patch of auroral oval disturbed by substorm but develops as a transpolar arc, forming a growing finger-like shape from midnight sector (event b). Sunward flow, associated with positive IMF-Bz, were observed within newly-created polar caps in event (a),(c),(d). Not clear ionospheric convection pattern was seen across the polar cap arc in event (b) die to limitation of data set. In event (c), O+ with energy more than 1 keV were observed by FAST within a transpolar arc, suggesting that their origin be from plasma sheet. Transpolar arcs are thought to be projection of plasma sheet bifurcation into lobe regime. There

  11. Two Types of Transpolar Arc Development, Event Studies with Data Set of ASTRID-2, DMSP, FAST, and SuperDARN

    NASA Technical Reports Server (NTRS)

    Narita, Yasuhito; Maezawa, Kiyoshi; Toshinori, Mukai; Kullen, A.; Ivchenko, N.; Marklund, G.; Frederick, R.; Carlson, C. W.; Spann, J. F.; Parks, G. K.; hide

    2002-01-01

    Aurorae which appear in the polar cap are called transpolar arcs, polar cap arcs, sun-aligned arcs, or occasionally Theta-aurora because of its spatial distribution resembling Greek character 'Theta.' Morphology, IMF (Interplanetary Magnetic Field) relationship, and ionospheric convection patterns were studied in quest of mechanisms of transpolar arcs. Four events were analyzed: 1999/Jan/22/19:00 - 23/01:30 (1 event: a) 1999/Jan/24/06:00 - 10:00 (1 event: b) 1999/Feb/1 1/20:00 - 12/02:00 (2 events: c, d), with data set of ExB drift velocity data obtained by electric field measurements of ASTRID-2 and FAST, DMSP ion driftmeter data, and line-of-sight velocity data of SuperDARN. POLAR-UVI image data were used for spatial and temporal variations of transpolar arcs and ACE data set were used for investigation of IMF relationship. IMF-Bz was strongly positive (Bz from +8nT to +20 nT) during periods of all four transpolar arcs. In events (a),(b),(c), transpolar arcs appeared immediately after the direction of IMF turned northward, though IMF was fluctuating in event (b). A sudden increase of IMF-By, from +3nT to +18nT, was observed in event (d). Two different types of transpolar arc development were observed in POLAR-UVI: one which begins as a split from dawn or dusk sector of auroral oval and shifts poleward in event (a),(c),(d), and another which is initially a patch of auroral oval disturbed by substorm but develops as a transpolar arc, forming a growing finger-like shape from midnight sector (event b). Sunward flow, associated with positive IMF-Bz, were observed within newly-created polar caps in event (a),(c),(d). Not clear ionospheric convection pattern was seen across the polar cap arc in event (b) die to limitation of data set. In event (c), O+ with energy more than 1 keV were observed by FAST within a transpolar arc, suggesting that their origin be from plasma sheet. Transpolar arcs are thought to be projection of plasma sheet bifurcation into lobe regime. There

  12. A study of auroral activity in the nightside polar cap

    SciTech Connect

    Wu, Q.

    1989-01-01

    Using various ground observations at South Pole, Antarctica (invariant magnetic latitude -74{degree}) and its conjugate point, Frobisher Bay, Canada, the author has studied the following aspects of nightside polar cap auroral activity: the appearance and disappearance of polar cap auroras (diffuse and discrete) associated with substorms and interplanetary magnetic field (IMF) variations; auroral optical emission line intensities; and the seasonal variation of auroral conjugacy. The observations show that the polar cap auroras usually fade away before the expansive phase of a substorm and bright auroral arcs reach high latitude (-74{degree}) near the recovery phase. Just before the auroras fade away the discrete polar cap auroral arcs, which are usually on the poleward boundary of the diffuse aurora, intensify for 1 to 2 minutes. The observations also indicate the IMF may have stronger control over polar cap auroral activity than do substorms. A search for energy spectral variation of precipitating electrons using the intensities of 630.0 nm (0) and 427 nm (N{sub 2}{sup +}) auroral emission lines reveals no dramatic changes in the energy spectrum; instead, the data show possible atmospheric scattering and geometric effects on the photometric measurements while the bright auroral arc is moving into the polar cap. The conjugate observations show that the stormtime auroral electrojet current, which is associated with the bright auroral arc, in most cases reaches higher (lower) latitudes in the winter (summer) hemisphere. An asymmetric plasma sheet (with respect to the neutral sheet) is proposed, which expands deeper into the winter lobe, under a tilted geomagnetic dipole. Accordingly, the winter polar cap would have smaller area and the auroral electrojet would be at higher latitude.

  13. Observation of spin-polarized bands and domain-dependent Fermi arcs in polar Weyl semimetal MoT e2

    NASA Astrophysics Data System (ADS)

    Sakano, M.; Bahramy, M. S.; Tsuji, H.; Araya, I.; Ikeura, K.; Sakai, H.; Ishiwata, S.; Yaji, K.; Kuroda, K.; Harasawa, A.; Shin, S.; Ishizaka, K.

    2017-03-01

    We investigate the surface electronic structures of polar 1 T'-MoT e2 , the Weyl semimetal candidate realized through the nonpolar-polar structural phase transition, by utilizing the laser angle-resolved photoemission spectroscopy combined with first-principles calculations. Two kinds of domains with different surface band dispersions are observed from a single-crystalline sample. The spin-resolved measurements further reveal that the spin polarizations of the surface and the bulk-derived states show the different domain dependences, indicating the opposite bulk polarity. For both domains, some segmentlike band features resembling the Fermi arcs are clearly observed. The patterns of the arcs present the marked contrast between the two domains, respectively agreeing well with the slab calculation of (0 0 1) and (0 0 -1) surfaces. The present result strongly suggests that the Fermi arc connects the identical pair of Weyl nodes on one side of the polar crystal surface, whereas it connects between the different pairs of Weyl nodes on the other side.

  14. On the influence of localized electric fields and field-aligned currents associated with polar arcs on the global potential distribution

    SciTech Connect

    Marklund, G.T.; Blomberg, L.G. )

    1991-08-01

    The influence of localized field-aligned current, associated with intense transpolar arcs mostly occurring during periods of northward interplaentary magnetic field (IMF), on the global electrodynamics has been investigated using a numerical simulation model. Idealized field-aligned current distributions representing both the region 1/2 system of the auroral oval and the transpolar arc as well as a corresponding ionospheric conductivity distribution are fed into the model to calculate the potential distributions. The transpolar arc has been represented by a few alternative field-aligned current distributions which are different in the way the downward return currents are distributed in the ionosphere. If the conductivity of the main auroral oval is comparable to that of the polar arc the dusk cell will have two local potential minima and thus a region of weak antisunward convection in between. Depending on the direction of the polar arc current sheets the dawn-dusk electric field will either be reversed (or weakened) or intensified at the location of the transpolar arc. The presence of a reversal depend, however, not only on the relative magnitude between the polar arc current sand those of the region 1/2 system but also on the characteristics of the acceleration region and of the conductivity distribution associated with the polar arc. Comparisons are made between the model results and Viking electric field data for a number of polar arc crossings to reveal the most common electrodynamical signatures of these auroral phenomena.

  15. A Circumzenithal Arc to Study Optics Concepts with Geometrical Optics

    ERIC Educational Resources Information Center

    Isik, Hakan

    2017-01-01

    This paper describes the formation of a circumzenithal arc for the purpose of teaching light and optics. A circumzenithal arc, an optic formation rarely witnessed by people, is formed in this study using a water-filled cylindrical glass illuminated by sunlight. Sunlight refracted at the top and side surfaces of the glass of water is dispersed into…

  16. [Study on the arc spectral information for welding quality diagnosis].

    PubMed

    Li, Zhi-Yong; Gu, Xiao-Yan; Li, Huan; Yang, Li-Jun

    2009-03-01

    Through collecting the spectral signals of TIG and MIG welding arc with spectrometer, the arc light radiations were analyzed based on the basic theory of plasma physics. The radiation of welding arc distributes over a broad range of frequency, from infrared to ultraviolet. The arc spectrum is composed of line spectra and continuous spectra. Due to the variation of metal density in the welding arc, there is great difference between the welding arc spectra of TIG and MIG in both their intensity and distribution. The MIG welding arc provides more line spectra of metal and the intensity of radiation is greater than TIG. The arc spectrum of TIG welding is stable during the welding process, disturbance factors that cause the spectral variations can be reflected by the spectral line related to the corresponding element entering the welding arc. The arc spectrum of MIG welding will fluctuate severely due to droplet transfer, which produces "noise" in the line spectrum aggregation zone. So for MIG welding, the spectral zone lacking spectral line is suitable for welding quality diagnosis. According to the characteristic of TIG and MIG, special spectral zones were selected for welding quality diagnosis. For TIG welding, the selected zone is in ultraviolet zone (230-300 nm). For MIG welding, the selected zone is in visible zone (570-590 nm). With the basic theory provided for welding quality diagnosis, the integral intensity of spectral signal in the selected zone of welding process with disturbing factor was studied to prove the theory. The results show that the welding quality and disturbance factors can be diagnosed with good signal to noise ratio in the selected spectral zone compared with signal in other spectral zone. The spectral signal can be used for real-time diagnosis of the welding quality.

  17. The Galactic Center Radio Arc: A Multi-Frequency Spectro-Polarimetric Study

    NASA Astrophysics Data System (ADS)

    Toomey, James Edward; Lang, Cornelia C.; Ludovici, Dominic

    2014-06-01

    Despite the Radio Arc non-thermal filaments (NTFs) being discovered 30 years ago, their origin remain poorly understood. The Radio Arc NTFs have an unusually flat spectrum in the centimeter to millimeter spectrum with a predicted, though poorly constrained, turn-over between 30- 200 GHz. With the recently upgraded wide-band capabilities of the VLA, we conducted a multi-frequency spectro-polarimetric study of the Radio Arc region. With observations at a set of low radio frequencies (continuous coverage over 2-6 GHz & 10-12 GHz), we imaged both the total and polarized intensity distributions at high angular resolution (≤ 1”). Presented here are the preliminary results from four observations spanning May 2013 to February 2014 using the DnC, CnB, B & BnA array configurations. This study has produced the deepest continuum intensity images of the Radio Arc region to date, with a sensitivity an order of magnitude greater than previous surveys, and resulted in the detection of new structure and compact emission sources. These observations will serve as a pilot polarization study for larger, more complete polarimetric surveys of the Galactic center region.

  18. The galactic center radio arc: A multi-frequency polarimetric study

    NASA Astrophysics Data System (ADS)

    Toomey, James, IV

    Despite the Radio Arc non-thermal filaments (NTFs) being discovered 30 years ago, their origin remain poorly understood. The Radio Arc NTFs have an unusually flat spectrum in the centimeter to millimeter spectrum with a predicted, though poorly constrained, turn-over between 30-200 GHz. With the recently upgraded wide-band capabilities of the VLA, we conducted a multi-frequency polarimetric study of the Radio Arc region. With observations at a set of low radio frequencies (continuous coverage over 2-6 GHz & 10-12 GHz), we imaged both the total and polarized intensity distributions at high angular resolution (< 1''). Presented here are the preliminary results from four observations spanning May 2013 to February 2014 using the DnC, CnB, B & BnA array configurations. This study has produced the deepest continuum intensity images of the Radio Arc region to date, with a sensitivity an order of magnitude greater than previous surveys, and resulted in the detection of new structure and compact emission sources. These observations will serve as a pilot polarization study for larger, more complete polarimetric surveys of the Galactic center region.

  19. The Arc Cloud Complex. A Case Study.

    DTIC Science & Technology

    1984-08-01

    evaporationally-driven downdrafts. At the surface, The citations on the following pages follow the style of The Jounal gf the Atmospheric Sciences. 2...categories shown in Fig. 4. The wind direction behind the gust front is indicated by the arrows. A Type 2 pattern has a clear-cut, arc-shaped leading edge...500, 700, and 850 mb) from the NWS were reanalyzed by hand in order to seek indications -of the mesoscale features aloft which may have been

  20. A Detailed Geochemical Study of Island Arc Crust: The Talkeetna Arc Section, South-central Alaska

    NASA Astrophysics Data System (ADS)

    Greene, A. R.; Debari, S. M.; Kelemen, P. B.; Clift, P. D.; Blusztajn, J.

    2002-12-01

    The Talkeetna arc section in south-central Alaska is recognized as the exposed upper mantle and crust of an accreted, Late Triassic to Middle Jurassic island arc. Detailed geochemical studies of layered gabbronorite from the middle and lower crust of this arc and a diverse suite of volcanic and plutonic rocks from the middle and upper crust provide crucial data for understanding arc magma evolution. We also present new data on parental magma compositions for the arc. The deepest level of the arc section consists of residual mantle and ultramafic cumulates adjacent to garnet gabbro and basal gabbronorite interlayered with pyroxenite. The middle crust is primarily layered gabbronorite, ranging from anorthosite to pyroxenite in composition, and is the most widespread plutonic lithology. The upper mid crust is a heterogenous assemblage of dioritic to tonalitic rocks mixed with gabbro and intruded by abundant mafic dikes and chilled pillows. The upper crust of the arc is comprised of volcanic rocks of the Talkeetna Formation ranging from basalt to rhyolite. Most of these volcanic rocks have evolved compositions (<5% MgO, Mg# <60) and overlap the composition of intermediate to felsic plutonic rocks (<3.5% MgO, Mg# <45). However, several chilled mafic rocks and one basalt have primitive characteristics (>8% MgO, Mg# >60). Ion microprobe analyses of clinopyroxene in mid-crustal layered gabbronorites have parallel REE patterns with positive-sloping LREE segments (La/Sm(N)=0.05-0.17; mean 0.11) and flat HREE segments (5-25xchondrite; mean 10xchondrite). Liquids in REE equilibrium with the clinopyroxene in these gabbronorite cumulates were calculated in order to constrain parental magmas. These calculated liquids(La/Sm(N)=0.77-1.83; mean 1.26) all fall within the range of dike and volcanic rock(La/Sm(N)=0.78-2.12; mean 1.23) compositions. However, three lavas out of the 44 we have analyzed show strong HREE depletion, which is not observed in any of the liquid compositions

  1. Polarized-interferometer feasibility study

    NASA Technical Reports Server (NTRS)

    Raab, F. H.

    1983-01-01

    The feasibility of using a polarized-interferometer system as a rendezvous and docking sensor for two cooperating spacecraft was studied. The polarized interferometer is a radio frequency system for long range, real time determination of relative position and attitude. Range is determined by round trip signal timing. Direction is determined by radio interferometry. Relative roll is determined from signal polarization. Each spacecraft is equipped with a transponder and an antenna array. The antenna arrays consist of four crossed dipoles that can transmit or receive either circularly or linearly polarized signals. The active spacecraft is equipped with a sophisticated transponder and makes all measurements. The transponder on the passive spacecraft is a relatively simple repeater. An initialization algorithm is developed to estimate position and attitude without any a priori information. A tracking algorithm based upon minimum variance linear estimators is also developed. Techniques to simplify the transponder on the passive spacecraft are investigated and a suitable configuration is determined. A multiple carrier CW signal format is selected. The dependence of range accuracy and ambiguity resolution error probability are derived and used to design a candidate system. The validity of the design and the feasibility of the polarized interferometer concept are verified by simulation.

  2. A circumzenithal arc to study optics concepts with geometrical optics

    NASA Astrophysics Data System (ADS)

    Isik, Hakan

    2017-05-01

    This paper describes the formation of a circumzenithal arc for the purpose of teaching light and optics. A circumzenithal arc, an optic formation rarely witnessed by people, is formed in this study using a water-filled cylindrical glass illuminated by sunlight. Sunlight refracted at the top and side surfaces of the glass of water is dispersed into its constituent colours. First, multi-colour arcs are observed on paper at the bottom of the glass. Then, a single arc for each colour is observed on the floor when the rays are allowed to propagate to the furthest points from the glass. The change in observations is explained by formulating an equation for the geometry of the situation. The formula relates each point on the first refracting surface for an incoming light ray to a point further from the second refracting surface. Then, a parallel graph is drawn to visualize the superposition of colours to the formation of a single arc. The geometrical optics studies in this paper exemplify the concept of Snell’s law, total internal reflection and dispersion. The duration of the observation on a circumzenithal arc is limited by the altitude of the Sun in the sky. This study depends on the use of astronomy software to track solar altitude. Pedagogical aspects of the study are discussed for inquiry-based teaching and learning of light and optics concepts.

  3. Polarization technology for tissue study

    NASA Astrophysics Data System (ADS)

    Simonenko, Georgy V.; Denisova, Tatyana P.; Lakodina, Nina A.; Tuchin, Valery V.; Papaev, Alexander V.

    2002-06-01

    The study of optical clearing dynamics of various connective tissues was carried out by means of polarization microscopy. Rate difference of optical clearing of such types of tissues as cartilage, meniscus, nasal septum tissues, sclera and tunica testis was found. The areas of unidirectional orientation of collagen fibers in cartilage and tunica testis were determined.

  4. Formation of the Sun-aligned arc region and the void (polar slot) under the null-separator structure

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Obara, T.; Watanabe, M.; Fujita, S.; Ebihara, Y.; Kataoka, R.

    2017-04-01

    From the global magnetosphere-ionosphere coupling simulation, we examined the formation of the Sun-aligned arc region and the void (polar slot) under the northward interplanetary magnetic field (IMF) with negative By condition. In the magnetospheric null-separator structure, the separatrices generated from two null points and two separators divide the entire space into four types of magnetic region, i.e., the IMF, the northern open magnetic field, the southern open magnetic field, and the closed magnetic field. In the ionosphere, the Sun-aligned arc region and the void are reproduced in the distributions of simulated plasma pressure and field-aligned current. The outermost closed magnetic field lines on the boundary (separatrix) between the northern open magnetic field and the closed magnetic field are projected to the northern ionosphere at the boundary between the Sun-aligned arc region and the void, both on the morning and evening sides. The magnetic field lines at the plasma sheet inner edge are projected to the equatorward boundary of the oval. Therefore, the Sun-aligned arc region is on the closed magnetic field lines of the plasma sheet. In the plasma sheet, an inflated structure (bulge) is generated at the junction of the tilted plasma sheet in the far-to-middle tail and nontilted plasma sheet in the ring current region. In the Northern Hemisphere, the bulge is on the evening side wrapped by the outermost closed magnetic field lines that are connected to the northern evening ionosphere. This inflated structure (bulge) is associated with shear flows that cause the Sun-aligned arc.

  5. Submarine Arc Volcanism in the Southern Mariana Arc: Results of Recent ROV studies

    NASA Astrophysics Data System (ADS)

    Nichols, A. R.; Tamura, Y.; Stern, R. J.; Embley, R. W.; Hein, J. R.; Jordan, E.; Ribeiro, J. M.; Sica, N.; Kohut, E. J.; Whattam, S. A.; Hirahara, Y.; Senda, R.; Nunokawa, A.

    2009-12-01

    The submarine Diamante cross-arc volcanoes (~16°N) and the Sarigan-Zealandia Bank Multi-Volcano Complex (SZBMVC; ~16°45’N), north and south, respectively, of Anatahan Island in the southern Mariana Arc, were studied during several dives in June 2009 using the ROV Hyper-Dolphin, cruise NT09-08 (R/V Natsushima); neither has been studied in detail before. The data collected provide a new perspective on how the subduction factory operates to complement previous studies on other cross-arc volcanic chains in the Izu-Bonin-Mariana Arc. The Diamante complex consists of three major edifices, two cones (West and Central Diamante) and a more complex caldera-like edifice at the volcanic front (East Diamante). West and Central Diamante are basaltic volcanoes but East Diamante has a more complex history. Our studies indicate initial construction of a basaltic volcano. Magmatic evolution led to a violent caldera-forming and quieter dome-building events. Post-caldera quiescence allowed a carbonate platform to grow, now preserved on the eastern caldera wall. Felsic magma or hot rock provides a heat source for an active hydrothermal field associated with felsic domes in the caldera, which NOAA investigators discovered in 2004. A new type of hydrothermal deposit was discovered in the hydrothermal field, consisting of large sulfide-sulfate mounds topped by bulbous constructions of low-temperature Fe and Mn oxides. Vents on the mounds were observed to emit shimmering water. The SZBMVC consists of six closely spaced edifices whose loci are aligned along two parallel trends, one along the volcanic front (Zealandia Bank, Sarigan and South Sarigan), and one about 15 km west towards the rear-arc (Northwest Zealandia, West Zealandia and West Sarigan). Zealandia Bank dives revealed that, as with East Diamante, initial activity was basaltic and became more evolved with time. The western half of Zealandia Bank is dominated by felsic lavas centered on a small (~2 km diameter) caldera and

  6. A statistical study of evening sector arcs and electrojets

    NASA Astrophysics Data System (ADS)

    Kauristie, K.; Syrjäsuo, M. T.; Amm, O.; Viljanen, A.; Pulkkinen, T. I.; Opgenoorth, H. J.

    2001-01-01

    We present results of a statistical study of evening sector auroral arcs associated with electrojets. The study (including ˜ 1000 all-sky camera (ASC) frames) is based on data of the MIRACLE instrument network. An automatic search engine is used to define the arc periods from ASC data and the recordings of the IMAGE magnetometer network are used to estimate the strength and location of the equivalent electrojet currents. The maximum current densities and intensities of the equivalent electrojets vary in the ranges 200-600 A/km and 200-400 kA, respectively. In 85 % of cases with single arcs the current system is of a convection reversal type (an eastward electrojet equatorward of a westward electrojet). Usually the arc is within 1° distance from the latitude of maximum eastward current density which is ≤4° south from the transition region between the westward and eastward electrojets. Most of such events were observed in the dusk sector, not in the premidnight-sector, which is generally considered as the typical Harang discontinuity (HD) region of convection reversal type currents. Furthermore, the poleward boundary of the westward current is very often poleward of the northernmost IMAGE station (CGM lat. ˜76), which may mean that the westward currents are not real horizontal currents but equivalent currents due to field aligned R1 currents. This implies that a stable arc often resides a few degrees equatorward to the evening shell potential minimum. We discuss the implications of these findings from the viewpoint of previous HD-studies.

  7. Characteristics and performance of the variable polarity plasma arc welding process used in the Space Shuttle external tank

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Lee, C. C.; Liu, J. W.

    1990-01-01

    Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. Flow profiles and power distribution of argon plasma gas as a working fluid to produce plasma arc jet in the VPPA welding process was analyzed. Major loss of heat transfer for flow through the nozzle is convective heat transfer; for the plasma jet flow between the outlet of the nozzle and workpiece is radiative heat transfer; and for the flow through the keyhole of the workpiece is convective heat transfer. The majority of the power absorbed by the keyhole of the workpiece is used for melting the solid metal workpiece into a molten metallic puddle. The crown and root widths and the crown and root heights can be predicted. An algorithm for promoting automatic control of flow parameters and the dimensions of the final product of the welding specification to be used for the VPPA Welding System operated at MSFC are provided.

  8. Experimental studies of auroral arc generators

    SciTech Connect

    Suszcynsky, D.M.; Borovsky, J.E.; Thomsen, M.F.

    1997-08-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). An all-sky video camera system was deployed in Eagle, Alaska at the foot of the magnetic field line that threads geosynchronous satellite 1989-046 as part of a campaign to study correlations of ground-based auroral activity with satellite-based plasma and energetic particle measurements. The overall intent of the project was to study magnetosphere-ionosphere coupling as it relates to the aurora, and, in particular, to look for signatures that may help to identify various auroral generator mechanism(s). During this study, our efforts were primarily directed towards identifying the generator mechanism(s) for pulsating aurora. Our data, though not conclusive, are found to support theories that propose a cyclotron resonance mechanism for the generation of auroral pulsations.

  9. High Temperature Corrosion and Characterization Studies in Flux Cored Arc Welded 2.25Cr-1Mo Power Plant Steel

    NASA Astrophysics Data System (ADS)

    Kumaresh Babu, S. P.; Natarajan, S.

    2010-07-01

    Higher productivity is registered with Flux cored arc welding (FCAW) process in many applications. Further, it combines the characteristics of shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. This article describes the experimental work carried out to evaluate and compare corrosion and its inhibition in SA 387 Gr.22 (2.25Cr-1Mo) steel weldments prepared by FCAW process with four different heat inputs exposed to hydrochloric acid medium at 0.1, 0.5, and 1.0 M concentrations. The parent metal, weld metal, and heat-affected zone are chosen as regions of exposure for the study carried out at 100 °C. Electrochemical polarization techniques such as Tafel line extrapolation (Tafel) and linear polarization resistance (LPR) have been used to measure the corrosion current. The role of hexamine and mixed inhibitor (thiourea + hexamine in 0.5 M HCl), each at 100 ppm concentration is studied in these experiments. Microstructural observation, hardness survey, surface characterization, and morphology using scanning electron microscope (SEM) and x-ray diffraction (XRD) have been made on samples to highlight the nature and extent of film formation. The film is found to contain Fe2Si, FeSi2, FeMn3, Fe7Mo3, Fe3O4, FeO, FeCr, AlO7Fe3SiO3, and KFe4Mn77Si19.

  10. Experimental Study of Arcing on High-voltage Solar Arrays

    NASA Technical Reports Server (NTRS)

    Vayner, Boris; Galofaro, Joel; Ferguson, Dale

    2005-01-01

    The main obstacle to the implementation of a high-voltage solar array in space is arcing on the conductor-dielectric junctions exposed to the surrounding plasma. One obvious solution to this problem would be the installation of fully encapsulated solar arrays which were not having exposed conductors at all. However, there are many technological difficulties that must be overcome before the employment of fully encapsulated arrays will turn into reality. An alternative solution to raise arc threshold by modifications of conventionally designed solar arrays looks more appealing, at least in the nearest future. A comprehensive study of arc inception mechanism [1-4] suggests that such modifications can be done in the following directions: i) to insulate conductor-dielectric junction from a plasma environment (wrapthrough interconnects); ii) to change a coverglass geometry (overhang); iii) to increase a coverglass thickness; iiii) to outgas areas of conductor-dielectric junctions. The operation of high-voltage array in LEO produces also the parasitic current power drain on the electrical system. Moreover, the current collected from space plasma by solar arrays determines the spacecraft floating potential that is very important for the design of spacecraft and its scientific apparatus. In order to verify the validity of suggested modifications and to measure current collection five different solar array samples have been tested in large vacuum chamber. Each sample (36 silicon based cells) consists of three strings containing 12 cells connected in series. Thus, arc rate and current collection can be measured on every string independently, or on a whole sample when strings are connected in parallel. The heater installed in the chamber provides the possibility to test samples under temperature as high as 80 C that simulates the LEO operational temperature. The experimental setup is described below.

  11. Mechanistic studies of the genetically encoded fluorescent protein voltage probe ArcLight.

    PubMed

    Han, Zhou; Jin, Lei; Chen, Fuyi; Loturco, Joseph J; Cohen, Lawrence B; Bondar, Alexey; Lazar, Josef; Pieribone, Vincent A

    2014-01-01

    ArcLight, a genetically encoded fluorescent protein voltage probe with a large ΔF/ΔV, is a fusion between the voltage sensing domain of the Ciona instestinalis voltage sensitive phosphatase and super ecliptic pHluorin carrying a single mutation (A227D in the fluorescent protein). Without this mutation the probe produces only a very small change in fluorescence in response to voltage deflections (∼ 1%). The large signal afforded by this mutation allows optical detection of action potentials and sub-threshold electrical events in single-trials in vitro and in vivo. However, it is unclear how this single mutation produces a probe with such a large modulation of its fluorescence output with changes in membrane potential. In this study, we identified which residues in super ecliptic pHluorin (vs eGFP) are critical for the ArcLight response, as a similarly constructed probe based on eGFP also exhibits large response amplitude if it carries these critical residues. We found that D147 is responsible for determining the pH sensitivity of the fluorescent protein used in these probes but by itself does not result in a voltage probe with a large signal. We also provide evidence that the voltage dependent signal of ArcLight is not simply sensing environmental pH changes. A two-photon polarization microscopy study showed that ArcLight's response to changes in membrane potential includes a reorientation of the super ecliptic pHluorin. We also explored different changes including modification of linker length, deletion of non-essential amino acids in the super ecliptic pHluorin, adding a farnesylation site, using tandem fluorescent proteins and other pH sensitive fluorescent proteins.

  12. A second generation EMET railgun for secondary arc studies

    SciTech Connect

    Witherspoon, F.D.; Burton, R.L.; Goldstein, S.A. )

    1991-01-01

    Since 1985 GT-Devices has been operating a pair of railguns with lengths of 0.9 m and 3.6 m respectively. Although velocities up to 5.65 km/s have been obtained with clean plasma armature structures devoid of secondary arcs, performance on most shots is degraded to one degree or another by the formation of parasitic secondary arcs. These experimental results, however, have not been very reproducible, making controlled studies of these secondary arcs difficult. A new second generation railgun is now being constructed to improve straightness, stiffness, sealing, and diagnostic access. The basic design consists of a steel tube with a thin lengthwise slit forming two halves in cross section with bolt preloading. The internal structure consists of split tubular G-10 compression blocks with Glidcop AL-15 rails and polycarbonate insulators formed from 90 degree tube sections. Machining tolerance mismatch is adjusted with compliant layers as required. An adjustable diameter, helical diamond lap is used to produce a finished round bore of nominally 1 cm diameter in the assembled launcher and for bore refurbishment between shots. This paper discusses the design details of the new railgun, injector, and diagnostics and presents some initial experimental results.

  13. Study on Seismic Zoning of Sino-Mongolia Arc Areas

    NASA Astrophysics Data System (ADS)

    Xu, G.

    2015-12-01

    According to the agreement of Cooperation on seismic zoning between Institute of Geophysics, China Earthquake Administration and Research Center of Astronomy and Geophysics, Mongolian Academy of Science, the data of geotectonics, active faults, seismicity and geophysical field were collected and analyzed, then field investigation proceeded for Bolnay Faults, Ar Hutul Faults and Gobi Altay Faults, and a uniform earthquake catalogue of Mongolia and North China were established for the seismic hazard study in Sino-Mongolia arc areas. Furthermore the active faults and epicenters were mapped and 2 seismic belts and their 54 potential seismic sources are determined. Based on the data and results above mentioned the seismicity parameters for the two seismic belts and their potential sources were studied. Finally, the seismic zoning with different probability in Sino-Mongolia arc areas was carried out using China probabilistic hazard analysis method. By analyzing the data and results, we draw the following main conclusions. Firstly, the origin of tectonic stress field in the study areas is the collision and pressure of the India Plate to Eurasian Plate, passing from the Qinghai-Tibet Plateau. This is the reason why the seismicity is higher in the west than in the east, and all of earthquakes with magnitude 8 or greater occurred in the west. Secondly, the determination of the 2 arc seismic belts, Altay seismic belt and Bolnay-Baikal seismic belt, are reasonable in terms of their geotectonic location, geodynamic origin and seismicity characteristics. Finally, there are some differences between our results and the Mongolia Intensity Zoning map published in 1985 in terms of shape of seismic zoning map, especially in the areas near Ulaanbaatar. We argue that our relsults are reasonable if we take into account the data use of recent study of active faults and their parameters, so it can be used as a reference for seismic design.

  14. A Study of the Thermal Profiles During Autogenous Arc Welding

    DTIC Science & Technology

    1989-03-01

    NAVAL POSTGRADUATE SCHOOL Monterey, California STA DTIC RAD ELECTE JUN 2 9 1989 • D THESIS A STUDY OF THE THERMAL PROFILES DURING AUTOGENOUS ARC...WELDING by Robert L. Ue March 1989 Thesis Advisor Yogendra Joshi Approved for public release; distribution is unlimited. j 7 .. 43 Unclassified security...L. LIe 13a T)pe of Report 13b Time Covered 14 Date of Report (year. month, day) 15 Page Count Master’s Thesis From To March 1989 163 16 Supplementary

  15. A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy.

    PubMed

    Cozzi, Luca; Dinshaw, Ketayun Ardeshir; Shrivastava, Shyam Kishore; Mahantshetty, Umesh; Engineer, Reena; Deshpande, Deepak Dattatray; Jamema, S V; Vanetti, Eugenio; Clivio, Alessandro; Nicolini, Giorgia; Fogliata, Antonella

    2008-11-01

    A treatment planning study was performed to evaluate the performance of the novel volumetric modulated single arc radiotherapy on cervix uteri cancer patients. Conventional fixed field IMRT was used as benchmark. CT datasets of eight patients were included in the study. Plans were optimised with the aim to assess organs at risk and healthy tissue sparing while enforcing highly conformal target coverage. Planning objectives for PTV were: maximum significant dose lower than 52.5 Gy and minimum significant dose higher than 47.5 Gy. For organs at risk, the median and maximum doses were constrained to be lower than 30 (rectum), 35 (bladder) and 25 Gy (small bowel) and 47.5 Gy; additional objectives were set on various volume thresholds. Plans were evaluated on parameters derived from dose volume histograms and on NTCP estimates. Peripheral doses at 5, 10 and 15 cm from the PTV surface were recorded to assess the low-level dose bath. The MU and delivery time were scored to measure expected treatment efficiency. Both RapidArc and IMRT resulted in equivalent target coverage but RapidArc had an improved homogeneity (D(5%)-D(95%) = 3.5 +/- 0.6 Gy for RapidArc and 4.3 +/- 0.8 Gy for IMRT) and conformity index (CI(90%) = 1.30 +/- 0.06 for RapidArc and 1.41 +/- 0.15 for IMRT). On rectum the mean dose was reduced by about 6 Gy (10 Gy for the rectum fraction not included in the PTV). Similar trends were observed for the various dose levels with reductions ranging from approximately 3 to 14.4 Gy. For the bladder, RapidArc allowed a reduction of mean dose ranging from approximately 4 to 6Gy and a reduction from approximately 3 to 9 Gy w.r.t. IMRT. Similar trends but with smaller absolute differences were observed for the small bowel and left and right femur. NTCP calculations on bladder and rectum confirmed the DVH data with a potential relative reduction ranging from 30 to 70% from IMRT to RapidArc. The healthy tissue was significantly less irradiated in the medium to high dose

  16. Directed Evolution of Key Residues in Fluorescent Protein Inverses the Polarity of Voltage Sensitivity in the Genetically Encoded Indicator ArcLight

    PubMed Central

    2017-01-01

    Genetically encoded calcium indicators (GECIs) produce unprecedentedly large signals that have enabled routine optical recording of single neuron activity in vivo in rodent brain. Genetically encoded voltage indicators (GEVIs) offer a more direct measure of neuronal electrical status, however the signal-to-noise characteristics and signal polarity of the probes developed to date have precluded routine use in vivo. We applied directed evolution to target modulable areas of the fluorescent protein in GEVI ArcLight to create the first GFP-based GEVI (Marina) that exhibits a ΔF/ΔV with a positive slope relationship. We found that only three rounds of site-directed mutagenesis produced a family of “brightening” GEVIs with voltage sensitivities comparable to that seen in the parent probe ArcLight. This shift in signal polarity is an essential first step to producing voltage indicators with signal-to-noise characteristics comparable to GECIs to support widespread use in vivo. PMID:28045247

  17. Directed Evolution of Key Residues in Fluorescent Protein Inverses the Polarity of Voltage Sensitivity in the Genetically Encoded Indicator ArcLight.

    PubMed

    Platisa, Jelena; Vasan, Ganesh; Yang, Amy; Pieribone, Vincent A

    2017-02-02

    Genetically encoded calcium indicators (GECIs) produce unprecedentedly large signals that have enabled routine optical recording of single neuron activity in vivo in rodent brain. Genetically encoded voltage indicators (GEVIs) offer a more direct measure of neuronal electrical status, however the signal-to-noise characteristics and signal polarity of the probes developed to date have precluded routine use in vivo. We applied directed evolution to target modulable areas of the fluorescent protein in GEVI ArcLight to create the first GFP-based GEVI (Marina) that exhibits a ΔF/ΔV with a positive slope relationship. We found that only three rounds of site-directed mutagenesis produced a family of "brightening" GEVIs with voltage sensitivities comparable to that seen in the parent probe ArcLight. This shift in signal polarity is an essential first step to producing voltage indicators with signal-to-noise characteristics comparable to GECIs to support widespread use in vivo.

  18. EXPERIMENTAL STUDY OF A TRANSPIRATION-COOLED, CONSTRICTED ARC.

    DTIC Science & Technology

    PLASMA GENERATORS, COOLING), (*ELECTRIC ARCS, PLASMA GENERATORS), EVAPOTRANSPIRATION, HEAT FLUX, POROUS MATERIALS, MATHEMATICAL MODELS, PRESSURE, DISTRIBUTION, ARGON, CERAMIC MATERIALS, PERFORMANCE(ENGINEERING), PLASMA JETS

  19. A comparative study of arc behaviour in an auto-expansion circuit breaker with different arc durations

    NASA Astrophysics Data System (ADS)

    Pei, Y.; Zhong, J.; Zhang, J.; Yan, J. D.

    2014-08-01

    A computational study of the thermal interruption performance of a 145 kV, 60 Hz auto-expansion circuit breaker has been carried out. The pressure peak in the expansion volume has a delay of 2.8-3.4 ms with reference to the current peak when the arc duration varies. A reasonable indicator of the interruption environment is the average mass flux in the main nozzle. The short arc duration case (12.25 ms) is the most difficult case with the lowest critical rate of rise of recovery voltage (RRRV) of 10 kV µs-1, just above the initial system applied RRRV of 9 kV µs-1. This is a result of an insufficient gas flow cross sectional area between the live contact and the main nozzle to develop rapid gas flow for arc cooling. The auxiliary nozzle plays two roles. It provides blockage in the high current phase to reduce gas exhaustion from the main nozzle into the hollow contact; after current zero the hollow contact shares a considerable portion of the system recovery voltage, especially for the short arc duration case (36%). Therefore the proper design and use of an auxiliary nozzle is key to enhancing the thermal interruption capability of high voltage auto-expansion circuit breakers.

  20. Immunotoxicology of arc welding fume: worker and experimental animal studies.

    PubMed

    Zeidler-Erdely, Patti C; Erdely, Aaron; Antonini, James M

    2012-01-01

    Arc welding processes generate complex aerosols composed of potentially hazardous metal fumes and gases. Millions of workers worldwide are exposed to welding aerosols daily. A health effect of welding that is of concern to the occupational health community is the development of immune system dysfunction. Increased severity, frequency, and duration of upper and lower respiratory tract infections have been reported among welders. Specifically, multiple studies have observed an excess mortality from pneumonia in welders and workers exposed to metal fumes. Although several welder cohort and experimental animal studies investigating the adverse effects of welding fume exposure on immune function have been performed, the potential mechanisms responsible for these effects are limited. The objective of this report was to review both human and animal studies that have examined the effect of welding fume pulmonary exposure on local and systemic immune responses.

  1. Immunotoxicology of arc welding fume: Worker and experimental animal studies

    PubMed Central

    Zeidler-Erdely, Patti C.; Erdely, Aaron; Antonini, James M.

    2015-01-01

    Arc welding processes generate complex aerosols composed of potentially hazardous metal fumes and gases. Millions of workers worldwide are exposed to welding aerosols daily. A health effect of welding that is of concern to the occupational health community is the development of immune system dysfunction. Increased severity, frequency, and duration of upper and lower respiratory tract infections have been reported among welders. Specifically, multiple studies have observed an excess mortality from pneumonia in welders and workers exposed to metal fumes. Although several welder cohort and experimental animal studies investigating the adverse effects of welding fume exposure on immune function have been performed, the potential mechanisms responsible for these effects are limited. The objective of this report was to review both human and animal studies that have examined the effect of welding fume pulmonary exposure on local and systemic immune responses. PMID:22734811

  2. Optical studies of polar stratospheric clouds

    NASA Astrophysics Data System (ADS)

    Enell, Carl-Fredrik; Gustavsson, Bjorn; Steen, Ake; Brandstrom, Urban; Rydesater, Peter; Johansson, P.; Wagner, T.; Friess, U.; Pfeilsticker, K.; Platt, Ulrich

    1999-12-01

    Polar Stratospheric Clouds (PSC) appear in the polar zones of the Earth in the winter. These clouds are known to cause enhanced chemical ozone destruction. Methods for optical remote-sensing of PSC in use or under development at the Swedish Institute of Space Physics are discussed with respect to their advantages and limitations. Especially multistatic imaging may become a valuable additional tool for PSC studies.

  3. Arc Jet Testing of Thermal Protection Materials: 3 Case Studies

    NASA Technical Reports Server (NTRS)

    Johnson, Sylvia; Conley, Joe

    2015-01-01

    Arc jet testing is used to simulate entry to test thermal protection materials. This paper discusses the usefulness of arc jet testing for 3 cases. Case 1 is MSL and PICA, Case 2 is Advanced TUFROC, and Case 3 is conformable ablators.

  4. Study of an ablation-dominated arc in a model circuit breaker

    NASA Astrophysics Data System (ADS)

    Eichhoff, D.; Kurz, A.; Kozakov, R.; Gött, G.; Uhrlandt, D.; Schnettler, A.

    2012-08-01

    A switching arc in a model circuit breaker is studied by means of CFD simulations and optical emission spectroscopy. The arc is initiated between tungsten-copper electrodes in a carbon dioxide atmosphere and is led through PTFE (polytetrafluorethylene) nozzles. Radiation emitted by the arc plasma is absorbed by the surface of the nozzles leading to ablation of the wall material. The CFD simulations are based on a model of the arcing zone including a consistent treatment of the radiation transport and wall ablation. Carbon ion line radiation is analysed in the experiment using an optical path in the heating channel between the nozzles. Temperature profiles obtained from spectroscopy and simulations are compared. The pressure value in the arc is estimated based on the line width-intensity dependence. The obtained values correspond to the measured pressure outside the arc. Coincidence in temperature for the peak current and discrepancy on the falling edge are found and discussed.

  5. Study of the arc-electrode interaction in a SF6 self-blast circuit breaker

    NASA Astrophysics Data System (ADS)

    Chévrier, P.; Fiévet, C.; Ciobanu, S. S.; Fleurier, C.; Scarpa, P.

    1999-07-01

    To study the interaction between the electrode and the electrical arc in a SF6 self-blast circuit breaker, a coupling between experimental and theoretical approaches is proposed. The experimental approach allows physical variables such as the temperature just below the contact surface and the total metallic vapour mass in the electrical arc to be measured. The theoretical study is based on a hydrodynamic model for electrical arc modelling, which takes into account Joule heating, radiation and real-gas effects. The arc/electrode interaction model is built on an energy balance at the boundary between the gas flow (the arc) and the electrode (cathode or anode). The validation is obtained through comparisons between measured and calculated results.

  6. New Studies of Polar Spicules

    NASA Astrophysics Data System (ADS)

    Zirin, H.; Cameron, R.

    1998-05-01

    We have studied several hundred images of solar spicules obtained on June 18 and 19 and July 15 of 1997. The observations were made at BBSO with the 65cm telescope feeding a Zeiss 1/4 Angstroms filter and a 1536x1024 Kodak CCD. Overexposed observations were made above the limb as well as normal exposures on the limb. The filter was tuned to Hα -0.65A and a 30sec interval was used. We were limited to a single wavelength because new software was being installed in a new control computer. The images obtained were processed by high-pass digital filtering of the original FITS images and reregistered by an FFT technique. The image scale is 0.17 arcsec per pixel. The disk was observed on June 18, 1997 to detect the sources of macrospicules and the limb was observed by overexposure on June 19 to determine the height trajectory of the faintest Hα We found that: Many more spicules go up than come down. There are numerous double and multiple spicules. The macrospicules come from normal network elements and start with an "Eiffel tower" shape. There is evidence of magnetic changes underlying these features. Both long macrospicules and complex eruptions are important at the pole. There is some evidence for rotation in spicules.

  7. Nuclear Structure Studies with Polarized Radioactive Beams

    SciTech Connect

    Asahi, K.; Uchida, M.; Inoue, T.; Hatakeyama, M.; Kagami, S.; Hasama, Y.; Suzuki, K.; Ueno, H.; Nagatomo, T.; Yoshimi, A.; Kameda, D.; Ishihara, M.; Shimada, K.; Nagae, D.; Murata, J.; Narita, K.; Kawamura, H.

    2009-08-04

    Nuclear moment studies on nuclei far from the beta-stability line, performed by taking advantage of the projectile fragmentation reaction, are reviewed. A method to produce spin polarization/alignment in the projectile fragments was developed and utilized for the beta-NMR/NQR measurements. Several new findings in nuclear structure physics were obtained from the nuclear moment experiments done with these techniques.

  8. Total dural irradiation: RapidArc versus static-field IMRT: A case study

    SciTech Connect

    Kelly, Paul J.

    2012-07-01

    The purpose of this study was to compare conventional fixed-gantry angle intensity-modulated radiation therapy (IMRT) with RapidArc for total dural irradiation. We also hypothesize that target volume-individualized collimator angles may produce substantial normal tissue sparing when planning with RapidArc. Five-, 7-, and 9-field fixed-gantry angle sliding-window IMRT plans were generated for comparison with RapidArc plans. Optimization and normal tissue constraints were constant for all plans. All plans were normalized so that 95% of the planning target volume (PTV) received at least 100% of the dose. RapidArc was delivered using 350 Degree-Sign clockwise and counterclockwise arcs. Conventional collimator angles of 45 Degree-Sign and 315 Degree-Sign were compared with 90 Degree-Sign on both arcs. Dose prescription was 59.4 Gy in 33 fractions. PTV metrics used for comparison were coverage, V{sub 107}%, D1%, conformality index (CI{sub 95}%), and heterogeneity index (D{sub 5}%-D{sub 95}%). Brain dose, the main challenge of this case, was compared using D{sub 1}%, Dmean, and V{sub 5} Gy. Dose to optic chiasm, optic nerves, globes, and lenses was also compared. The use of unconventional collimator angles (90 Degree-Sign on both arcs) substantially reduced dose to normal brain. All plans achieved acceptable target coverage. Homogeneity was similar for RapidArc and 9-field IMRT plans. However, heterogeneity increased with decreasing number of IMRT fields, resulting in unacceptable hotspots within the brain. Conformality was marginally better with RapidArc relative to IMRT. Low dose to brain, as indicated by V5Gy, was comparable in all plans. Doses to organs at risk (OARs) showed no clinically meaningful differences. The number of monitor units was lower and delivery time was reduced with RapidArc. The case-individualized RapidArc plan compared favorably with the 9-field conventional IMRT plan. In view of lower monitor unit requirements and shorter delivery time, RapidArc

  9. Validation study of Polar V800 accelerometer

    PubMed Central

    Hernández-Vicente, Adrián; De Cocker, Katrien; Garatachea, Nuria

    2016-01-01

    Background The correct quantification of physical activity (PA) and energy expenditure (EE) in daily life is an important target for researchers and professionals. The objective of this paper is to study the validity of the Polar V800 for the quantification of PA and the estimation of EE against the ActiGraph (ActiTrainer) in healthy young adults. Methods Eighteen Caucasian active people (50% women) aged between 19–23 years wore an ActiTrainer on the right hip and a Polar V800 on the preferred wrist during 7 days. Paired samples t-tests were used to analyze differences in outcomes between devices, and Pearson’s correlation coefficients to examine the correlation between outcomes. The agreement was studied using the Bland-Altman method. Also, the association between the difference and the magnitude of the measurement (heteroscedasticity) was examined. Sensitivity, specificity and area under the receiver operating characteristic curve (ROC-AUC value) were calculated to evaluate the ability of the devices to accurately define a person who fulfills the recommendation of 10,000 daily steps. Results The devices significantly differed from each other on all outcomes (P<0.05), except for Polar V800’s alerts vs. ActiTrainer’s 1 hour sedentary bouts (P=0.595) and Polar V800’s walking time vs. ActiTrainer’s lifestyle time (P=0.484). Heteroscedasticity analyses were significant for all outcomes, except for Kcal and sitting time. The ROC-AUC value was fair (0.781±0.048) and the sensitivity and specificity was 98% and 58%, respectively. Conclusions The Polar V800 accelerometer has a comparable validity to the accelerometer in free-living conditions, regarding “1 hour sedentary bouts” and “V800’s walking time vs. ActiTrainer’s lifestyle time” in young adults. PMID:27570772

  10. Validation study of Polar V800 accelerometer.

    PubMed

    Hernández-Vicente, Adrián; Santos-Lozano, Alejandro; De Cocker, Katrien; Garatachea, Nuria

    2016-08-01

    The correct quantification of physical activity (PA) and energy expenditure (EE) in daily life is an important target for researchers and professionals. The objective of this paper is to study the validity of the Polar V800 for the quantification of PA and the estimation of EE against the ActiGraph (ActiTrainer) in healthy young adults. Eighteen Caucasian active people (50% women) aged between 19-23 years wore an ActiTrainer on the right hip and a Polar V800 on the preferred wrist during 7 days. Paired samples t-tests were used to analyze differences in outcomes between devices, and Pearson's correlation coefficients to examine the correlation between outcomes. The agreement was studied using the Bland-Altman method. Also, the association between the difference and the magnitude of the measurement (heteroscedasticity) was examined. Sensitivity, specificity and area under the receiver operating characteristic curve (ROC-AUC value) were calculated to evaluate the ability of the devices to accurately define a person who fulfills the recommendation of 10,000 daily steps. The devices significantly differed from each other on all outcomes (P<0.05), except for Polar V800's alerts vs. ActiTrainer's 1 hour sedentary bouts (P=0.595) and Polar V800's walking time vs. ActiTrainer's lifestyle time (P=0.484). Heteroscedasticity analyses were significant for all outcomes, except for Kcal and sitting time. The ROC-AUC value was fair (0.781±0.048) and the sensitivity and specificity was 98% and 58%, respectively. The Polar V800 accelerometer has a comparable validity to the accelerometer in free-living conditions, regarding "1 hour sedentary bouts" and "V800's walking time vs. ActiTrainer's lifestyle time" in young adults.

  11. Study of the Polarization Deterioration During Physics Stores in RHIC Polarized Proton Runs

    NASA Astrophysics Data System (ADS)

    Duan, Z.; Qin, Q.; Bai, M.; Roser, T.

    2016-02-01

    As the only high energy polarized proton collider in the world, the Relativistic Heavy Ion Collider (RHIC) has achieved a great success in colliding polarized proton beams up to 255GeV per beam energy with over 50% average store polarizations for spin physics studies. With the help of Siberian snakes as well as outstanding beam control during the acceleration, polarization loss during acceleration up to 100 GeV is negligible. However, about 10% polarization loss was observed between acceleration from 100 GeV to 255 GeV. In addition, a mild polarization deterioration during long store for physics data taking was also observed. In this paper, studies in understanding the store depolarizing mechanism is reported, including the analysis of polarization deterioration data based on the past couple of RHIC polarized proton runs.

  12. Preliminary Study of the Feasibility of Inverse Problem Algorithms Used for Arc Magnetic Measurement Method

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Li, Xingwen; Song, Haoyong; Rong, Mingzhe

    2010-04-01

    Non-contact magnetic measurement method is an effective way to study the air arc behavior experimentally One of the crucial techniques is to solve an inverse problem for the electromagnetic field. This study is devoted to investigating different algorithms for this kind of inverse problem preliminarily, including the preconditioned conjugate gradient method, penalty function method and genetic algorithm. The feasibility of each algorithm is analyzed. It is shown that the preconditioned conjugate gradient method is valid only for few arc segments, the estimation accuracy of the penalty function method is dependent on the initial conditions, and the convergence of genetic algorithm should be studied further for more segments in an arc current.

  13. Dynamic electron arc radiotherapy (DEAR): a feasibility study.

    PubMed

    Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen

    2014-01-20

    Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm(2) and 3×10 cm(2) for a 15×15 cm(2) applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min(-1)). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors.

  14. Dynamic electron arc radiotherapy (DEAR): a feasibility study

    NASA Astrophysics Data System (ADS)

    Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen

    2014-01-01

    Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm2 and 3×10 cm2 for a 15×15 cm2 applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min-1). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors.

  15. A receiver function study of crustal properties in the Lesser Antilles Arc

    NASA Astrophysics Data System (ADS)

    Arnaiz-Rodríguez, M. S.; Niu, F.; Schmitz, M.

    2014-12-01

    In the present study, we report the crustal thickness and mechanical properties along the Lesser Antilles Arc by employing receiver function technique. To do so, we collected teleseismic data, available in the IRIS online database, recorded by several broadband stations that have been deployed in the arc. The selected events have epicentral distances from 30° to 90°, and magnitudes of 5.7 or larger. Unfortunately, we were only able to apply the method to 9 of the 25 stations deployed in the arc, due to nosy data (possibly because of the effects of strong winds, waves and tides), recording problems, and short recording periods. We used the recordings from P-to-S conversion in order to estimate the crustal thickness by depth staking the computed receiver functions. We also analyzed crustal reverberations found in some stations to estimate the crustal thickness and the average crustal Vp/Vs ratio, as well as the Poisson's ratio, by applying H-k matrix-search methodology. We found large variations in the crustal thickness along the arc: the thinnest crust (~22 km) was found in Barbuda Island at the northern-exterior section of the arc, while the thickest crust (~36.8 km) was found in Anguilla Island at the northern-central section of the arc. In general, the northern sections of the arc have a thicker crust with a mean value of ~29 km, while the southern sections have a thinner crust with a mean value ~23 km, and this might be related to the general asymmetry of the arc (the northern part is much more active and complex than the southern part). Poisson's ratio estimated along the arc vary from 0.266 (Vp/Vs=1.777) to 0.3 (Vp/Vs=1.87) which are relatively consistent with mafic island arc origin, although the carbonatic cover of the island might influence the lower values in the range, while higher values could be associated to the old Cretaceous basement of some of the northern islands. We hope to be able collect more information from relatively new stations of the

  16. Study on a negative hydrogen ion source with hot cathode arc discharge

    NASA Astrophysics Data System (ADS)

    Lin, S. H.; Fang, X.; Zhang, H. J.; Qian, C.; Ma, B. H.; Wang, H.; Li, X. X.; Zhang, X. Z.; Sun, L. T.; Zhang, Z. M.; Yuan, P.; Zhao, H. W.

    2014-02-01

    A negative hydrogen (H-) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H- beam with ɛ N, RMS = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I_{e^ - } /I_{H^ - } were experimentally studied. The discussion on the result, and opinions to improve the source were given.

  17. Study of the anodic arc discharge for carbon nanotube production

    NASA Astrophysics Data System (ADS)

    Waldorff, Erik; Keidar, Michael; Wass, Anthony; Friedmann, Peretz

    2003-10-01

    Carbon nanotubes (CNTs) are unique nanostructures with remarkable electronic and mechanical properties. CNTs are currently considered to be a promising candidate as a next generation material having various applications. To-date, a variety of CNT fabrication methods have been developed, among them is an arc discharge method. Arc discharge is a relatively simple method having high rate of CNT production. In this method single-wall and multi-wall nanotubes are produced from an ionized carbon plasma with joule heating from the discharge used to generate the plasma. The University of Michigan carbon nanotube production facility in the Aerospace Engineering Department utilizes the anodic arc discharge. In this type of discharge, the Carbon plasma is supplied mainly by the anode ablation. In addition a buffer gas (Helium) with a pressure range of 100-1000 torr is introduced into the discharge chamber. The experimental anode ablation rate is about 2-4 m3/s and generally increases with the background gas pressure in the considered pressure range.A model of the anodic arc discharge is developed. The main component of this model is the anode ablation kinetics that takes into account the non-free nature of ablation due to the presence of a high-density discharge plasma. Different characteristic sub-regions near the surface, namely, space-charge sheath, Knudsen layer, presheath and a hydrodynamic layer are considered. The ablation rate is determined by the flow velocity at the edge of the Knudsen layer. Coupling solution of the non-equilibrium, Knudsen layer, with hydrodynamic layer and discharge column provides self-consistent solution for the ablation rate and plasma parameter distribution.

  18. Electron beam, laser beam and plasma arc welding studies

    NASA Technical Reports Server (NTRS)

    Banas, C. M.

    1974-01-01

    This program was undertaken as an initial step in establishing an evaluation framework which would permit a priori selection of advanced welding processes for specific applications. To this end, a direct comparison of laser beam, electron beam and arc welding of Ti-6Al-4V alloy was undertaken. Ti-6Al-4V was selected for use in view of its established welding characteristics and its importance in aerospace applications.

  19. BEAM-BASED SEXTUPOLE POLARITY VERIFICATION IN THE RHIC

    SciTech Connect

    LUO,Y.; SATOGATA, T.; CAMERON, P.; DELLAPENNA, A.; TRBOJEVIC, D.

    2007-06-25

    This article presents a beam-based method to check RHIC arc sextupole polarities using local horizontal orbit three-bumps at injection energy. We use 11 bumps in each arc, each covering two SFs (focusing sextupoles) and one SD (defocusing sextupole). If there are no wrong sextupole polarities, the tune shifts from bump to bump and the tune shift patterns from arc to arc should be similar. Wrong sextupole polarities can be easily identified from mismatched signs or amplitudes of tune shifts from bump to bump and/or from arc to arc. Tune shifts in both planes during this study were tracked with a high-resolution base-band tunemeter (BBQ) system. This method was successfully used to the sextupole polarity check in RHIC Blue and Yellow rings in the RHIC 2006 and 2007 runs.

  20. Effect of beam profile measurement on arc therapy plan quality assurance: a case study.

    PubMed

    Kim, Leonard H; Malajovich, Irina; Reyhan, Meral L; Xue, Jinyu; Park, Joo Han

    2017-05-01

    We present an example when profile measurement and modeling of an Elekta Agility multileaf collimator (MLC) had a large effect specifically on arc therapy plan quality assurance (QA) results using ArcCheck. ArcCheck absolute dose measurements of these plans were systematically lower than planned by 3-10%. Failing QA results were seen even with unmodulated static and conformal arcs. Furthermore, the effect was found to be dependent on collimator angle, with worse results associated with near-zero collimator angles. In contrast, step-and-shoot QA results were not affected. Changing the beam model to match steeper profile measurements obtained using a different measurement device resolved the problem. This case study demonstrates that conventional gamma index analysis can be sensitive to small profile modeling changes. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  1. A study on the influence of reflected arc light on vision sensors for welding automation

    SciTech Connect

    Lee, C.W.; Na, S.J.

    1996-12-01

    Vision sensors using optical triangulation have been widely sued for automatic welding systems in various ways. Their reliability is, however, seriously influenced by the arc light reflected from the base metal surface. In this study, the reliability of vision sensors was analyzed for the variation of the arc noise by considering the reflectance of the base metal surface. The property of the surface reflection of the base metal was modeled using the bidirectional reflectance-distribution function (BRDF), and then the intensity variation of the reflected arc was formulated for various configurations of the torch, base metal and sensor. The experimental data of the arc light reflection were obtained for two materials, mild steel and stainless steel, each having different surface reflection characteristics. It was found that the results calculated from the proposed model were in good agreement with the experimental data.

  2. Comparative study on interactions between laser and arc plasma during laser-GTA welding and laser-GMA welding

    NASA Astrophysics Data System (ADS)

    Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa

    2016-10-01

    This paper describes an investigation on differences in interactions between laser and arc plasma during laser-gas tungsten arc (LT) welding and laser-gas metal arc (LM) welding. The characteristics of LT heat source and LM heat source, such as plasma behavior, heat penetration ability and spectral information were comparably studied. Based on the plasma discharge theory, the interactions during plasma discharge were modeled and analyzed. Results show that in both LT and LM welding, coupling discharge between the laser keyhole plasma and arc happens, which strongly enhance the arc. But, the enhancing effect in LT welding is much more sensitive than that in LM welding when parameters are adjusted.

  3. The Lesser Antilles volcanic chain: a study in arc magmatism

    NASA Astrophysics Data System (ADS)

    Macdonald, R.; Hawkesworth, C. J.; Heath, E.

    2000-03-01

    The Lesser Antilles volcanic arc is related to subduction of the American plate under the Caribbean plate. The rate of subduction is low, 2-4 cm a -1, and this has been reflected, at least over the past 0.1 Ma, in relatively low magma production rates (3-5 km 3 Ma -1 km -1 of arc). The arc is segmented; a northern segment trends 330° and the Benioff zone dips at 50-60°, whilst the southern segment trends 020° and the dip varies from 45° to 50° in the north to vertical in the south. Pleistocene-Recent volcanism (<2 Ma) occurs in narrow zones less than 10 km wide and seems to define three segments, the break between the central and southern segments being in the same location as the kink in the Benioff zone. Magma production over the past 0.1 Ma has been higher in islands of the central segment (8-40 km 3) than in the northern and southern segments (0-5 km 3); the variations may be related to the degree of obliquity of subduction along the arc. Cenozoic volcanic rocks of the arc are divided into low-K and medium-K series, each of which contains basaltic (MgO>6%) members ranging from hypersthene- to nepheline-normative. It is likely that all the Lesser Antilles eruptives had picritic (or, more rarely, ankaramitic), possibly silica-undersaturated, primary magmas. The medium-K rocks show wide variations in trace-element and isotopic characteristics. A generalised sequence of phenocryst assemblages, applicable to both groups, is: olivine+spinel±clinopyroxene→olivine+spinel+clinopyroxene+plagioclase→plagioclase+clinopyroxene+titanomagnetite+orthopyroxene±amphibole±quartz. Phenocryst crystallisation temperatures were: basalts 1180-1130°C; basaltic andesites 1060-1050°C; and andesites-dacites 960-740°C. Magmas inferred to be primary to the eruptive suites equilibrated within the spinel peridotite facies in the mantle wedge at pressures between 1.5 and 3 GPa. fO 2 conditions of magma crystallisation were rather oxidising (NNO +0.5 to NNO +3). Estimates of

  4. Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

    NASA Astrophysics Data System (ADS)

    Chau, S. W.; Hsu, K. L.; Lin, D. L.; Tzeng, C. C.

    2007-04-01

    The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter

  5. Balloon Borne Arc-Second Pointer Feasibility Study

    NASA Technical Reports Server (NTRS)

    Ward, Philip R.; DeWeese, Keith D.

    2003-01-01

    For many years scientists have been utilizing stratospheric balloons as low-cost platforms on which to conduct space science experiments. A major hurdle in extending the range of experiments for which these vehicles are useful has been the imposition of the gondola dynamics on the accuracy with which an instrument can be kept pointed at a celestial target. A significant number of scientists have sought the ability to point their instruments with jitter in the arc-second range. This paper presents the design and analysis of a stratospheric balloon borne pointing system that is able to meet this requirement. The foundation for a high fidelity controller simulation is presented. The flexibility of the flight train is represented through generalized modal analysis. A multiple controller scheme is introduced for coarse and fine pointing. Coarse azimuth pointing is accomplished by an established pointing system, with extensive flight history, residing above the gondola structure. A pitch-yaw gimbal mount is used for fine pointing, providing orthogonal axes when nominally on target. Fine pointing actuation is from direct drive dc motors, eliminating backlash problems. An analysis of friction nonlinearities and a demonstration of the necessity in eliminating static fiction are provided. A unique bearing hub design is introduced that eliminates static fiction from the system dynamics. A control scheme involving linear accelerometers for enhanced disturbance rejection is also presented. Results from a linear analysis of the total system and the high fidelity simulation are given. This paper establishes that the proposed control strategy can be made robustly stable with significant design margins. Also demonstrated is the efficacy of the proposed system in rejecting disturbances larger than those considered realistic. Finally, we see that sub arc-second pointing stability can be achieved for a large instrument pointing at an inertial target.

  6. Treatment planning and dosimetric comparison study on two different volumetric modulated arc therapy delivery techniques

    PubMed Central

    Kumar, S.A. Syam; Holla, Raghavendra; Sukumar, Prabakar; Padmanaban, Sriram; Vivekanandan, Nagarajan

    2012-01-01

    Aim To compare and evaluate the performance of two different volumetric modulated arc therapy delivery techniques. Background Volumetric modulated arc therapy is a novel technique that has recently been made available for clinical use. Planning and dosimetric comparison study was done for Elekta VMAT and Varian RapidArc for different treatment sites. Materials and methods Ten patients were selected for the planning comparison study. This includes 2 head and neck, 2 oesophagus, 1 bladder, 3 cervix and 2 rectum cases. Total dose of 50 Gy was given for all the plans. All plans were done for RapidArc using Eclipse and for Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both RapidArc and Elekta VMAT. Plans were evaluated based on the ability to meet the dose volume histogram, dose homogeneity index, radiation conformity index, estimated radiation delivery time, integral dose and monitor units needed to deliver the prescribed dose. Results RapidArc plans achieved the best conformity (CI95% = 1.08 ± 0.07) while Elekta VMAT plans were slightly inferior (CI95% = 1.10 ± 0.05). The in-homogeneity in the PTV was highest with Elekta VMAT with HI equal to 0.12 ± 0.02 Gy when compared to RapidArc with 0.08 ± 0.03. Significant changes were observed between the RapidArc and Elekta VMAT plans in terms of the healthy tissue mean dose and integral dose. Elekta VMAT plans show a reduction in the healthy tissue mean dose (6.92 ± 2.90) Gy when compared to RapidArc (7.83 ± 3.31) Gy. The integral dose is found to be inferior with Elekta VMAT (11.50 ± 6.49) × 104 Gy cm3 when compared to RapidArc (13.11 ± 7.52) × 104 Gy cm3. Both Varian RapidArc and Elekta VMAT respected the planning objective for all organs at risk. Gamma analysis result for the pre-treatment quality assurance shows good agreement between the planned and delivered fluence for 3 mm DTA, 3% DD for all the evaluated points inside the

  7. Multi-Instrument Studies of an Arc in Saturn's G Ring

    NASA Astrophysics Data System (ADS)

    Hedman, M. M.; Burns, J. A.; Tiscareno, M. S.; Nicholson, P. D.; Porco, C. C.; Jones, G. H.; Roussos, E.; Krupp, N.; Paranicas, C.

    2006-12-01

    The G ring is a narrow, faint ring located between the orbits of Janus and Mimas. The first evidence for material in this region came from a series of charged particle absorptions detected by Pioneer 11 in 1979, and the ring itself was first imaged by the Voyager spacecraft. Now a combination of in-situ and optical remote sensing instruments onboard the Cassini spacecraft are providing new insights into the dynamics and origin of this obscure ring. During a pass over the G ring on day 248 of 2005, the MIMI instrument detected a deep, narrow charged particle absorption signature in the vicinity of the G ring. Similarly deep and narrow charged particle absorptions were not seen during Cassini's other passages near this region. The magnitude of the charged particle absorption on day 248 suggested either the presence of a solid body or a much higher particle density in the G ring than one might expect from other observations.Images obtained by the cameras onboard Cassini reveal that the likely explanation for this anomaly is a bright arc located on the inner edge of the G ring (around 167,500 km) and extending over 30 degrees in longitude. By tracking this arc over the first two years of the Cassini Mission, we have established that Cassini passed close to the arc on day 248 of 2005, and that Cassini was not near the arc during other passages near the G ring. The orbital period of the arc is 0.80813 day, corresponding to a semi-major axis of 167,496 km. This places the arc within 6 km of the Mimas 7:6 Co-rotation Eccentricity Resonance and within 12 km of the Mimas 7:6 Inner Lindblad Resonance. The arc is therefore likely confined in longitude by Mimas in the same way that the arcs in Neptune's ring are held in place by Galatea. Cassini now has the opportunity to study the dynamics of this sort of system in detail over a period of years. The arc may also be the source of the material for the rest of the G ring. A combination of photometric and spectroscopic data from

  8. Natural polarization studies at Balcova geothermal field

    SciTech Connect

    Ercan, A.; Drahor, M.; Atasoy, E.

    1986-06-01

    Contrasting resistivity, temperature, pressure, porosity and fluid migrations are the main causes of ion accumulations along the discontinuities which create coupling-induced natural current flow which is observed as the Natural Polarization Potential (NPP) on the surface. Natural Polarization Electric Field (NPE) variations were recorded along 13 profiles about 2.5 km each in a north-south direction. Interpretation of the coincident anomalies of the NPP and the NPE field resulted in determination of the polarization angle, polarization focal depth and the azimuths of the polarized interfaces. Considerable agreement between faults delineated by previous geological and geophysical investigations and polarization discontinuities was observed. The polarization plane was observed to be horizontal in high temperature areas but steepened gradually in relatively colder regions in the northern costal area. From the polarization depth distribution two depression zones were observed, separated by an uplifted section elongated in a north-south direction. The basin at the eastern side had an estimated polarization depth of 1.1 km and was limited by the Agamemnon-2 and -1 faults, while the western basin had an estimated depth of 1.3 km and extended in the east-west direction not previously reported. The eastern basin extends on the north side around the town of Inciralti, the western basin appeared to be elongated towards the town of Cesme.

  9. A study on crustal shear wave splitting in the western part of the Banda arc-continent collision

    SciTech Connect

    Syuhada; Hananto, Nugroho D.; Puspito, Nanang T.; Yudistira, Tedi; Anggono, Titi

    2016-03-11

    We analyzed shear wave splitting parameters from local shallow (< 30 km) earthquakes recorded at six seismic stations in the western part of the Banda arc-continent collision. We determined fast polarization and delay time for 195 event-stations pairs calculated from good signal-to-noise ratio waveforms. We observed that there is evidence for shear wave splitting at all stations with dominant fast polarization directions oriented about NE-SW, which are parallel to the collision direction of the Australian plate. However, minor fast polarization directions are oriented around NW-SE being perpendicular to the strike of Timor through. Furthermore, the changes in fast azimuths with the earthquake-station back azimuth suggest that the crustal anisotropy in the study area is not uniform. Splitting delay times are within the range of 0.05 s to 0.8 s, with a mean value of 0.29±0.18 s. Major seismic stations exhibit a weak tendency increasing of delay times with increasing hypocentral distance suggesting the main anisotropy contribution of the shallow crust. In addition, these variations in fast azimuths and delay times indicate that the crustal anisotropy in this region might not only be caused by extensive dilatancy anisotropy (EDA), but also by heterogeneity shallow structure such as the presence of foliations in the rock fabric and the fracture zones associated with active faults.

  10. Exchange bias studied with polarized neutron reflectivity

    SciTech Connect

    te Velthuis, S. G. E.

    2000-01-05

    The role of Polarized Neutron Reflectivity (PNR) for studying natural and synthetic exchange biased systems is illustrated. For a partially oxidized thin film of Co, cycling of the magnetic field causes a considerable reduction of the bias, which the onset of diffuse neutron scattering shows to be due to the loosening of the ferromagnetic domains. On the other hand, PNR measurements of a model exchange bias junction consisting of an n-layered Fe/Cr antiferromagnetic (AF) superlattice coupled with an m-layered Fe/Cr ferromagnetic (F) superlattice confirm the predicted collinear magnetization in the two superlattices. The two magnetized states of the F (along or opposite to the bias field) differ only in the relative orientation of the F and adjacent AF layer. The possibility of reading clearly the magnetic state at the interface pinpoints the commanding role that PNR is having in solving this intriguing problem.

  11. Black phosphorus edges: a polarized Raman study

    NASA Astrophysics Data System (ADS)

    Ribeiro, H.; Villegas, C.; Bahamon, D.; Castro Neto, A.; de Souza, E.; Rocha, A.; Pimenta, M.; de Matos, C.

    Black phosphorus (BP) has been recently exfoliated down to few-layer thicknesses revealing numerous interesting features such as a tunable direct bandgap. Ever since, demonstrations of BP electronic devices have bloomed, as well as studies of the electric, optical, mechanical and thermal properties of its bulk and few-layer forms. However, the edges of BP crystals have, so far, been poorly characterized, even though the terminations of layered crystals are known to possess a range of interesting properties. In this work, the edges of exfoliated BP flakes are characterized by polarized confocal Raman spectroscopy. We will present experimental Raman spectra at zigzag and armchair edges, as well as density functional theory calculations that explain the peculiarities of the experimental data. Fapesp, INCT/Nanocarbono, Fapemig, CNPq, MackPesquisa, Grid-Unesp, CENAPAD-SP, and NRF.

  12. Emission polarization study on quartz and calcite.

    NASA Technical Reports Server (NTRS)

    Vincent, R. K.

    1972-01-01

    Calculation of the spectral emission polarization of quartz and calcite polished plates for observation angles of 20 and 70 deg by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected medium-width filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

  13. Experimental study of metal nanoparticle synthesis by an arc evaporation/condensation process

    NASA Astrophysics Data System (ADS)

    Förster, Henning; Wolfrum, Christian; Peukert, Wolfgang

    2012-07-01

    The generation of copper nanoparticles in an arc furnace by the evaporation/condensation method is systematically investigated. The evaporation/condensation process is advantageous because it allows direct synthesis using pure metals as starting materials avoiding reactions of expensive and potentially poisonous precursors. In the presented system, a transferred direct current arc provides the energy for evaporation of the metal target. In order to prevent an oxidation of the particles in the process, the synthesis is conducted in an atmosphere of inert gases (purity grade 5.0). The arc stability and its effect on particle synthesis are investigated. The experiments reveal excellent long-term arc stability for at least 8 h continuous operation delivering aerosols with high reproducibility (±10 % of average particle size). The influences of the arc current and length, the flow rates of the applied gases and the injection of hydrogen in the plasma zone on the particle size distributions and the agglomerate structure are studied. The produced copper nanoparticles are characterized by scanning mobility particle sizing and scanning electron microscopy. The average particle size could be well controlled in a size range 4-50 nm by selecting appropriate operating parameters.

  14. Numerical study of arc plasmas and weld pools for GTAW with applied axial magnetic fields

    NASA Astrophysics Data System (ADS)

    Yin, Xianqing; Gou, Jianjun; Zhang, Jianxun; Sun, Jiangtao

    2012-07-01

    A 3D numerical model containing the welding arc and the weld pool for gas tungsten arc welding (GTAW) with applied axial magnetic fields is established. The model is validated by comparing the calculated arc temperature with the measured ones. The influence of the magnetic field on the welding process is studied by changing the magnetic inductions, from 0 T to 0.06 T. For welding arcs, a radial spread is discovered, and a reverse flow appears over the anode. The distribution of temperature, heat flux, current density and pressure on the anode surface becomes double-peaked, while the voltage distributes in a double-valley type. For weld pools, the fluid flow cycle brings about a wide and shallow pool. In the circumferential direction, the fluid in the centre areas rotates in an opposite direction to that in the outer regions; in the axial direction, the fluid flows upwards at the centre while downwards in the edge area of the weld pool. All the driving forces including the surface tension, the shear stress from the arc plasma, the electromagnetic force and the buoyancy force that influence the fluid flow are analysed to explain these phenomena. The mechanism of how the applied axial magnetic field regulates the GTAW process is thus clarified.

  15. Influence of Smile Arc and Buccal Corridors on Facial Attractiveness: A Cross-sectional Study

    PubMed Central

    Gaikwad, Shashank; Vaz, Anna C; Singh, Baldeep; Taneja, Lavina; Vinod, KS; Verma, Prateek

    2016-01-01

    Introduction Two aspects of the smile: the Smile Arc (SA) and Buccal Corridors (BC) have been the interest of the orthodontist in recent years. Aim The present study was undertaken to evaluate the influence of the smile arc and buccal corridors on facial attractiveness as evaluated by orthodontists, general dentists and laymen. Materials and Methods Two subjects (one male & one female) were selected from the regional population fulfilling the criteria of an ideal smile arc and ideal buccal corridors. Frontal smile view photographs of these subjects were taken and modified by using adobe photoshop 7.0 to create combination of three smile arc variance and three buccal corridors variations respectively which were shown to 25 orthodontists, 25 general dentists & 25 laymen, to rate the facial attractiveness of each image on a rating scale. Results All the three groups (laypersons, dentists and orthodontists) showed significant difference in ratings, indicating that they had different perceptions on the facial attractiveness. Conclusion Orthodontists were more precise in discerning the smile arc and buccal corridors compared to dentists and laypersons. PMID:27790573

  16. Polarized IR studies of silica glasses exposed to polarized excimer radiation

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.; Tingley, James E.

    2006-12-15

    Silica glass exhibits a permanent anisotropic response, polarization-induced birefringence (PIB), when exposed to short-wavelength polarized light. This behavior has been correlated with the OH content of the glass. In this paper we describe polarized infrared studies of silica glasses of different OH content exposed with polarized 157 nm laser light. Changes in the fundamental OH band as a consequence of exposure are shown. We find differential bleaching of a particular OH band where OH species that are oriented parallel to the incident exposing polarization undergo greater bleaching than those oriented perpendicular. The preferential bleaching as a function of exposure time correlates strongly with the evolution of PIB, leading to a bleaching model of OH that is causally linked to PIB.

  17. Feasibility study of a periodic arc compressor in the presence of coherent synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Di Mitri, S.

    2016-01-01

    The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. Beam optics control has been proposed to mitigate that CSR effect. In this article, we enlarge on the existing literature by reviewing the validity of the linear optics approach in a periodic, achromatic arc compressor. We then study the dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge. The analytical findings are compared with particle tracking results. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor for driving, for example, a free electron laser or a linear collider.

  18. Study on a negative hydrogen ion source with hot cathode arc discharge

    SciTech Connect

    Lin, S. H. Fang, X.; Zhang, H. J.; Qian, C.; Ma, B. H.; Wang, H.; Li, X. X.; Zhang, X. Z.; Sun, L. T.; Zhang, Z. M.; Yuan, P.; Zhao, H. W.

    2014-02-15

    A negative hydrogen (H{sup −}) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H{sup −} beam with ε {sub N,} {sub RMS} = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I{sub e{sup −}}/I{sub H{sup −}} were experimentally studied. The discussion on the result, and opinions to improve the source were given.

  19. Numerical Study on Plasma Jet and Particle Behavior in Multi-arc Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Schein, J.; Zimmermann, S.

    2017-06-01

    Plasma jet and particle behavior in conventional single-arc plasma spraying has been subject to intensive numerical research. However, multi-arc plasma spraying is a different case which has yet to be investigated more closely. Numerical models developed to investigate the characteristics of multi-arc plasma spraying (plasma generator, plasma jet, and plasma-particle interaction models) were introduced in previous publications by the authors. The plasma generator and plasma jet models were already validated by comparing calculated plasma temperatures with results of emission spectroscopic computed tomography. In this study, the above-mentioned models were subjected to further validation effort. Calculated particle in-flight characteristics were compared with those determined by means of particle diagnostics and high-speed videography. The results show very good agreement. The main aim of the current publication is to derive conclusions regarding the general characteristics of plasma jet and particle in-flight behavior in multi-arc plasma spraying. For this purpose, a numerical parameter study is conducted in which the validated models are used to allow variations in the process parameters. Results regarding plasma jet/particle in-flight temperatures and velocities are presented. Furthermore, the general characteristics of plasma jet and particle behavior in multi-arc plasma spraying are discussed and explained. This contributes to better understanding of the multi-arc plasma spraying process, in particular regarding the injection behavior of particles into hot regions of the plasma jet. Finally, an example test case showing a possible practical application area of the models is introduced.

  20. Multicolor Polarization Study of ARA OB1

    NASA Astrophysics Data System (ADS)

    Waldhausen, Silvia; Martínez, Ruben E.; Feinstein, Carlos

    1999-06-01

    We present the results of a multicolor polarimetric study of stars in the association Ara OB1. Several objects belonging to the clusters NGC 6204, 6193, and 6167 and the local field were observed as part of a global study of the region. The polarimetry shows that the orientation of the polarimetric vectors of each star is very similar within each cluster. The average values are 35.5d+/-15.1d and 52.2d+/-16 deg for NGC 6204 and 6193, respectively. An average value of 106.5d+/-9.9d is found for NGC 6167, but the angle distribution is asymmetric, and a second component can be fitted to the angle histogram (P.A.~120.8d+/-11.6d), showing a behavior not observed in NGC 6204 and 6193. So, we suggest that some of the observed stars perhaps belong to another stars grouping, located behind NGC 6167 and between a dust layer with a different orientation of the grains. The large difference in the polarization angle between NGC 6167 and the other two clusters could also be explained because NGC 6167 is supposed to be at the center of a gas-expanding structure and it is possible that this cluster was the origin of the star formation process in the Ara OB1 association, triggered by stellar winds or supernova explosions.

  1. Welding arc plasma physics

    NASA Technical Reports Server (NTRS)

    Cain, Bruce L.

    1990-01-01

    The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

  2. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, P.R.

    1983-08-08

    A portable, hand-held electric arc saw apparatus comprising a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc between the blade and a workpiece of opposite polarity. Electrically conducting means are provided on said frame for transmitting current to said blade. A pair of freely movable endless belts in the form of crawler treads are employed to facilitate movement of the apparatus relative to the workpiece.

  3. Ionization and electric field properties of auroral arcs during magnetic quiescence

    SciTech Connect

    Robinson, R.M.; Mende, S.B. )

    1990-12-01

    Studies of the morphology of auroral precipitation during times of magnetic quiescence indicate that the polar cap shrinks and becomes distorted into a teardrop or pear-shaped region. On November 16, 1987, incoherent scatter radar and all-sky imaging photometer measurements were made of auroral arcs over Sondre Stromfjord, Greenland. The arcs were generally oriented in a geographic east-west direction which is approximately Sun aligned at a local time just after dusk. Kp was 1, and the interlplanetary magnetic field was northward during the time of observation, so tha the arcs occurred under magnetically quiet conditions. The Sondrestrom radar measurements were used to determine the electron density and plasma drifts associated with the arcs; the all-sky imaging photometer data were used to relate the radar measurements to the arc morphology. Assuming the arcs were produced by precipitating electrons, the height profiles of electron density indicate average energies less than about 2 keV and energy fluxes of 1 erg/(cm{sup 2}s). F region electron densities were high in the polar cap north of the arcs and low within the region of the arcs. The poleward boundary of the arc system was a convection reversal boundary across which plasma exited the polar cap region moving antisunward and then turned sunward (westward). The observed arc-associated convection is consistent with that expected under these geomagnetic conditions. Comparison of these results with the electrodynamic properties of other arcs observed in the afternoon and early evening suggests that there is a system of arcs that delineates the afternoon convection cell. The observed gradient in F region electron density across the arc can be explained in terms of the recombination of ionization drifting in response to the arc-associated convection pattern.

  4. OpenARC: Extensible OpenACC Compiler Framework for Directive-Based Accelerator Programming Study

    SciTech Connect

    Lee, Seyong; Vetter, Jeffrey S

    2014-01-01

    Directive-based, accelerator programming models such as OpenACC have arisen as an alternative solution to program emerging Scalable Heterogeneous Computing (SHC) platforms. However, the increased complexity in the SHC systems incurs several challenges in terms of portability and productivity. This paper presents an open-sourced OpenACC compiler, called OpenARC, which serves as an extensible research framework to address those issues in the directive-based accelerator programming. This paper explains important design strategies and key compiler transformation techniques needed to implement the reference OpenACC compiler. Moreover, this paper demonstrates the efficacy of OpenARC as a research framework for directive-based programming study, by proposing and implementing OpenACC extensions in the OpenARC framework to 1) support hybrid programming of the unified memory and separate memory and 2) exploit architecture-specific features in an abstract manner. Porting thirteen standard OpenACC programs and three extended OpenACC programs to CUDA GPUs shows that OpenARC performs similarly to a commercial OpenACC compiler, while it serves as a high-level research framework.

  5. Ionospheric flow shear associated with the preexisting auroral arc: A statistical study from the FAST spacecraft data

    NASA Astrophysics Data System (ADS)

    Jiang, Feifei; Kivelson, Margaret G.; Strangeway, Robert J.; Khurana, Krishan K.; Walker, Raymond

    2015-06-01

    An auroral substorm is a disturbance in the magnetosphere that releases energy stored in the magnetotail into the high-latitude ionosphere. By definition, an auroral substorm commences when a discrete auroral arc brightens and subsequently expands poleward and azimuthally. The arc that brightens is usually the most equatorward of several auroral arcs that remain quiescent for ~5 to ~60 min before the breakup commences. This arc is often referred to as the "preexisting auroral arc (PAA)" or the "growth-phase arc." In this study, we use FAST measurements to establish the statistics of flow patterns near PAAs in the ionosphere. We find that flow shear is present in the vicinity of a preexisting arc. When a PAA appears in the evening sector, enhanced westward flow develops equatorward of the arc, whereas when a PAA appears in the morning sector, enhanced eastward flow develops poleward of the arc. We benchmark locations of the PAAs relative to large-scale field-aligned currents (FACs) and convective flows in the ionosphere, finding that the arc forms in the upward current region within ~1° of the Region 1/Region 2 boundary in all local time sectors from 20 MLT to 03 MLT. We also find that near midnight in the Harang region, most of the PAAs lie within 0.5° poleward of the low-latitude Region 1/Region 2 currents boundary and sit between the westward and eastward flow peak but equatorward of the flow reversal point. Finally, we examine arc-associated electrodynamics and find that the FAC of the PAA is mainly closed by the north-south Pedersen current in the ionosphere.

  6. Arc-Plasma Wire Spraying: An Optical Study of Process Phenomenology

    NASA Astrophysics Data System (ADS)

    Gulyaev, I. P.; Dolmatov, A. V.; Kharlamov, M. Yu.; Gulyaev, P. Yu.; Jordan, V. I.; Krivtsun, I. V.; Korzhyk, V. M.; Demyanov, O. I.

    2015-12-01

    In the present paper, we report on the results of an experimental study of heat- and mass-transfer processes in a Plazer 30-PL-W plasma-jet facility used for arc-plasma wire spraying. Using an original optical diagnostic system, we have studied melting behavior of the metal wire, break up and atomization of liquid metal. For the first time, experimental data on the in-flight velocity and temperature of spray particles in arc-plasma wire spraying were obtained. In spite of moderate particle velocities (about 50 m/s), the obtained steel coatings proved to have a low porosity of 1.5%. While studying the spraying process of tungsten wire, we observed the occurrence of anomalous high-velocity (over 4000 m/s) outbursts ejected from the surface of liquid metal droplets. The nature of such outbursts calls for further study.

  7. Note: A high Mach number arc-driven shock tube for turbulence studies

    NASA Astrophysics Data System (ADS)

    Titus, J. B.; Alexander, A. B.; Johnson, J. A.

    2013-04-01

    A high Mach arc-driven shock tube has been built at the Center for Plasma Science and Technology of Florida A&M University to study shock waves. A larger apparatus with higher voltage was built to study more stable shock waves and subsequent plasmas. Initial measurements of the apparatus conclude that the desired Mach numbers can be reached using only two-thirds the maximum possible energy that the circuit can provide.

  8. Note: A high Mach number arc-driven shock tube for turbulence studies.

    PubMed

    Titus, J B; Alexander, A B; Johnson, J A

    2013-04-01

    A high Mach arc-driven shock tube has been built at the Center for Plasma Science and Technology of Florida A&M University to study shock waves. A larger apparatus with higher voltage was built to study more stable shock waves and subsequent plasmas. Initial measurements of the apparatus conclude that the desired Mach numbers can be reached using only two-thirds the maximum possible energy that the circuit can provide.

  9. Polarization Tracking Study of Earth Station in Satellite Communications

    NASA Astrophysics Data System (ADS)

    Ma, Lihua; Hu, Chao; Pei, Jun

    2016-01-01

    Satellite communications, in telecommunications, the use of satellite can provide communications links between various points on the earth. Typical satellite communication is composed of a communication satellite, a signal transmitter and a signal receiver. As the signal transmitter or the signal receiver, an earth station plays a vital role in the satellite communications. Accurately adjustment of antenna azimuth, elevation and polarization angles on the earth station is the key to satellite communications. In the present paper, a study of polarization tracking of earth station is presented, and a detailed adjustment procession of the polarization angle is given. Combing with observation series of MEASAT-2 satellite in geostationary orbit, the polarization tracking accuracy is verified. The method can be embeded into computer program of antenna polarization adjustment in earth station.

  10. Quantitative methods to study epithelial morphogenesis and polarity.

    PubMed

    Aigouy, B; Collinet, C; Merkel, M; Sagner, A

    2017-01-01

    Morphogenesis of an epithelial tissue emerges from the behavior of its constituent cells, including changes in shape, rearrangements, and divisions. In many instances the directionality of these cellular events is controlled by the polarized distribution of specific molecular components. In recent years, our understanding of morphogenesis and polarity highly benefited from advances in genetics, microscopy, and image analysis. They now make it possible to measure cellular dynamics and polarity with unprecedented precision for entire tissues throughout their development. Here we review recent approaches to visualize and measure cell polarity and tissue morphogenesis. The chapter is organized like an experiment. We first discuss the choice of cell and polarity reporters and describe the use of mosaics to reveal hidden cell polarities or local morphogenetic events. Then, we outline application-specific advantages and disadvantages of different microscopy techniques and image projection algorithms. Next, we present methods to extract cell outlines to measure cell polarity and detect cellular events underlying morphogenesis. Finally, we bridge scales by presenting approaches to quantify the specific contribution of each cellular event to global tissue deformation. Taken together, we provide an in-depth description of available tools and theoretical concepts to quantitatively study cell polarity and tissue morphogenesis over multiple scales.

  11. Contribution to the study of the electric arc: Erosion of metallic electrodes. Thesis

    NASA Technical Reports Server (NTRS)

    Castro, A.

    1986-01-01

    A procedure is described for determining the extent of arc electrode erosion (excluding erosion due to transfer of material) from measurements of emitted spectral beam intensity. The relation between emission intensity and plasma temperature is ascertained. Experimental study of several combinations of monometallic electrodes shows that the method is suitable for determining cathode erosion, although the anode metal affects the extent of erosion. Combinations of electrodes which lead to low erosion of silver are reported.

  12. Polarization-correlation study of biotissue multifractal structure

    NASA Astrophysics Data System (ADS)

    Olar, O. I.; Ushenko, A. G.

    2003-09-01

    This paper presents the results of polarization-correlation study of multifractal collagen structure of physiologically normal and pathologically changed tissues of women"s reproductive sphere and skin. The technique of polarization selection of coherent images of biotissues with further determination of their autocorrelation functions and spectral densities is suggested. The correlation-optical criteria of early diagnostics of appearance of pathological changes in the cases of myometry (forming the germ of fibromyoma) and skin (psoriasis) are determined. This study is directed to investigate the possibilities of recognition of pathological changes of biotissue morphological structure by determining the polarization-dependent autocorrelation functions (ACF) and corresponding spectral densities of tissue coherent images.

  13. Surface Plasma Arc by Radio-Frequency Control Study (SPARCS)

    SciTech Connect

    Ruzic, David N.

    2013-04-29

    This paper is to summarize the work carried out between April 2012 and April 2013 for development of an experimental device to simulate interactions of o -normal detrimental events in a tokamak and ICRF antenna. The work was mainly focused on development of a pulsed plasma source using theta pinch and coaxial plasma gun. This device, once completed, will have a possible application as a test stand for high voltage breakdown of an ICRF antenna in extreme events in a tokamak such as edge-localized modes or disruption. Currently, DEVeX does not produce plasma with high temperature enough to requirement for an ELM simulator. However, theta pinch is a good way to produce high temperature ions. The unique characteristic of plasma heating by a theta pinch is advantageous for an ELM simulator due to its effective ion heating. The objective of the proposed work, therefore, is to build a test facility using the existing theta pinch facility in addition to a coaxial plasma gun. It is expected to produce a similar pulsed-plasma heat load to the extreme events in tokamaks and to be applied for studying interactions of hot plasma and ICRF antennas.

  14. Numerical study of low-current steady arcs

    NASA Technical Reports Server (NTRS)

    Kim, S. C.; Nagamatsu, H. T.

    1992-01-01

    The development of a high-efficiency CW YLF laser doped with Er,Tm,Ho: and featuring a strongly focusing resonator that collects a high density of pump power on the active crystal is described. The emission is investigated at 2.06 microns and a tuning range both at liquid-nitrogen (77 K) and at dry-ice (210 K) temperature. The noise characteristics and the long-term power stability of the laser is studied with an eye to employing this source for high-resolution spectroscopy in the 2-micron wavelength region. The detection of several absorption lines of NH3 at low pressure is described. The output power of the laser as a function of the power impinging on the crystal for different transmission of the output mirror is illustrated. The best result obtained is 1.46 W output for 3.2 W of argon pump. The minimum threshold achieved is 3.5 mW with a 1-percent transmission mirror. It is concluded that it is possible to develop a highly efficient Ho:YLF laser featuring low noise and sufficient tunability for high-resolution spectroscopy in the 2-micron region.

  15. Studies of interactive plasma processes in the polar cusp

    NASA Technical Reports Server (NTRS)

    Waite, J. Hunter, Jr.

    1992-01-01

    Progress during the reporting period is presented. Several distinctly different areas of research are presently being pursued: (1) studies of the thermal structure of polar outflows; (2) Prognoz data analysis; and (3) Ulysses Jupiter encounter.

  16. A Study on the Tribological Behavior of Vanadium-Doped Arc Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Tillmann, Wolfgang; Hagen, Leif; Kokalj, David; Paulus, Michael; Tolan, Metin

    2017-02-01

    The formation of thin reactive films in sliding contacts under elevated temperature provides enhanced tribological properties since the formation of Magnéli phases leads to the ability of self-lubricating behavior. This phenomenon was studied for vanadium-doped coating systems which were produced using CVD and PVD technology. Vanadium-containing arc sprayed coatings were not widely examined so far. The aim of this study was to characterize Fe-V coatings deposited by the Twin Wire Arc Spraying process with respect to their oxidation behavior at elevated temperatures and to correlate the formation of oxides to the tribological properties. Dry sliding experiments were performed in the temperature range between 25 and 750 °C. The Fe-V coating possesses a reduced coefficient of friction and wear coefficient ( k) at 650 and 750 °C, which were significant lower when compared to conventional Fe-based coatings. The evolution of oxide phases was identified in situ by x-ray diffraction for the investigated temperature range. Further oxidation of (pre-oxidized) arc sprayed Fe-V coatings, as verified by differential thermal analysis and thermo-gravimetric analysis, starts at about 500 °C.

  17. A Study on the Tribological Behavior of Vanadium-Doped Arc Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Tillmann, Wolfgang; Hagen, Leif; Kokalj, David; Paulus, Michael; Tolan, Metin

    2017-01-01

    The formation of thin reactive films in sliding contacts under elevated temperature provides enhanced tribological properties since the formation of Magnéli phases leads to the ability of self-lubricating behavior. This phenomenon was studied for vanadium-doped coating systems which were produced using CVD and PVD technology. Vanadium-containing arc sprayed coatings were not widely examined so far. The aim of this study was to characterize Fe-V coatings deposited by the Twin Wire Arc Spraying process with respect to their oxidation behavior at elevated temperatures and to correlate the formation of oxides to the tribological properties. Dry sliding experiments were performed in the temperature range between 25 and 750 °C. The Fe-V coating possesses a reduced coefficient of friction and wear coefficient (k) at 650 and 750 °C, which were significant lower when compared to conventional Fe-based coatings. The evolution of oxide phases was identified in situ by x-ray diffraction for the investigated temperature range. Further oxidation of (pre-oxidized) arc sprayed Fe-V coatings, as verified by differential thermal analysis and thermo-gravimetric analysis, starts at about 500 °C.

  18. Schizosaccharomyces pombe Arc3 is a conserved subunit of the Arp2/3 complex required for polarity, actin organization, and endocytosis

    PubMed Central

    Cabrera, Rodrigo; Suo, Jinfeng; Young, Evelin; Chang, Eric C.

    2011-01-01

    We characterized the Schizosaccharomyces pombe arc3 gene, whose product shares sequence homology with that of the budding yeast ARC18 and human ARPC3/p21 subunits of the Arp2/3 complex. Our data showed that Arc3p co-localizes with F-actin patches at the cell ends, but not with F-actin cables or the equatorial actin ring, and binds other subunits of the Arp2/3 complex. Gene deletion analysis showed that arc3 is essential for viability. When arc3 expression was repressed, F-actin patches became dispersed throughout the cell with greatly reduced mobility. Furthermore in arc3-repressed cells, endocytosis was also inhibited. Human ARPC3 rescued the viability of the S. pombe arc3 null mutant; in addition, ARPC3 also localizes to F-actin patches in human cells. These data suggest that Arc3p is an evolutionarily conserved subunit of the Arp2/3 complex required for proper F-actin organization and efficient endocytosis. PMID:21449051

  19. Bivergent thrust wedges surrounding oceanic island arcs: Insight from observations and sandbox models of the northeastern caribbean plate

    USGS Publications Warehouse

    ten Brink, U.S.; Marshak, S.; Granja, Bruna J. L.

    2009-01-01

    At several localities around the world, thrust belts have developed on both sides of oceanic island arcs (e.g., Java-Timor, Panama, Vanuatu, and the northeastern Caribbean). In these localities, the overall vergence of the backarc thrust belt is opposite to that of the forearc thrust belt. For example, in the northeastern Caribbean, a north-verging accretionary prism lies to the north of the Eastern Greater Antilles arc (Hispaniola and Puerto Rico), whereas a south-verging thrust belt called the Muertos thrust belt lies to the south. Researchers have attributed such bivergent geometry to several processes, including: reversal of subduction polarity; subduction-driven mantle flow; stress transmission across the arc; gravitational spreading of the arc; and magmatic inflation within the arc. New observations of deformational features in the Muertos thrust belt and of fault geometries produced in sandbox kinematic models, along with examination of published studies of island arcs, lead to the conclusion that the bivergence of thrusting in island arcs can develop without reversal of subduction polarity, without subarc mantle flow, and without magmatic inflation. We suggest that the Eastern Greater Antilles arc and comparable arcs are simply crustalscale bivergent (or "doubly vergent") thrust wedges formed during unidirectional subduction. Sandbox kinematic modeling suggests, in addition, that a broad retrowedge containing an imbricate fan of thrusts develops only where the arc behaves relatively rigidly. In such cases, the arc acts as a backstop that transmits compressive stress into the backarc region. Further, modeling shows that when arcs behave as rigid blocks, the strike-slip component of oblique convergence is accommodated entirely within the prowedge and the arc-the retrowedge hosts only dip-slip faulting ("frontal thrusting"). The existence of large retrowedges and the distribution of faulting in an island arc may, therefore, be evidence that the arc is

  20. Astronomical polarization studies at radio and infrared wavelengths. Part 2: Far infrared polarization of dust clouds

    NASA Technical Reports Server (NTRS)

    Dennison, B. K.

    1976-01-01

    Far infrared polarization of dust clouds is examined. The recently observed 10 micron polarization of the Orion Nebula and the Galactic Center suggests that far infrared polarization may be found in these objects. Estimates are made of the degree of far infrared polarization that may exist in the Orion Nebula. An attempt to observe far infrared polarization from the Orion Nebula was carried out.

  1. Spectroscopic Study of the Polar BS Tri

    NASA Astrophysics Data System (ADS)

    Borisov, N. V.; Gabdeev, M. M.; Shimansky, V. V.; Katysheva, N. A.; Shugarov, S. Yu.

    2015-11-01

    We have analyzed the spectra of the cataclysmic variable BS Tri taken in September 2011 and August 2012 with the 6-m BTA SAO RAS telescope. The object's spectra exhibit a flat continuum with superimposed strong hydrogen Balmer, neutral and ionized helium emission lines. Our analysis of the line profiles has shown that they consist of several components that are formed in the accretion structure and on the irradiated red dwarf surface. The measured radial velocities of one of the components of the line forming in a spot on the red dwarf surface have allowed the parameters of the system to be estimated: M 1 = 0.75 ± 0.02 M ⊙, M 2 = 0.16 ± 0.01 M ⊙, q = 0.21 ± 0.02, and R L2 = 0.18 ± 0.02 R ⊙. The Doppler maps constructed from the emission lines show no disk accretion, defining the system as a polar.

  2. Time-resolved polarization study of anisotropy in bacteriorhodopsin

    SciTech Connect

    Wan, Chaozhi; Qian, Jun; Johnson, C.K. )

    1990-11-01

    Time-resolved polarization spectroscopy is sensitive to the orientational dynamics of chromophores, and as a result it can be applied to study internal motion in restrictive environments. This paper describes the application of polarization spectroscopy to the photoactive protein bacteriorhodopsin on time scales from picoseconds to hundreds of microseconds. Anisotropy persists in both the ground-state bacteriorhodopsin population and in the photocycle intermediates due to a population bottleneck in the bacteriorhodopsin photocycle. The time dependence of the polarization signal expected for a sequence of intermediates is described and is shown to be sensitive both to population kinetics and to internal motion. The observed time dependence of the polarization signal reveals internal motion in the purple membrane fragments on the time scale of the K {yields} L transition ({approximately} 1 {mu}s). The results are consistent with the known kinetics of the bacteriorhodopsin photocycle. Evidence is also presented and discussed for a decay component on a time scale of < 50 ps.

  3. Fluorescence polarization studies of rat intestinal microvillus membranes.

    PubMed Central

    Schachter, D; Shinitzky, M

    1977-01-01

    Rat intestinal microvillus membranes and lipid extracts prepared from them have been studied by fluorescence polarization with three lipid-soluble fluorophores: diphenylhexatriene, retinol, and anthroyl-stearate. The degree of fluorescence polarization of diphenylhexatriene, which provides an index of the "microviscosity" of the lipid regions of the membrane, is exceptionally high in microvillus membranes, the highest yet reported in normal biological membranes. Both the membrane proteins and lipids were found to contribute to the high values. With each of the three probes the polarization values are higher in ileal microvillus membranes as compared to membranes from proximal intestinal segments. Temperature-dependence studies of the fluorescence polarization of diphenylhexatriene and anthroylstearate demonstrate a phase transition in microvillus membranes and in liposomes prepared from their lipid extracts at approximately 26+/-2 degrees C. Ambient pH influences markedly the diphenylhexatriene fluorescence polarization in microvillus membranes but has little effect on that of human erythrocyte ghost membranes. The "microviscosity" of jejunal microvillus membranes is maximal at pH 6.5-7.0 and decreases as much as 50% at pH 3.0, an effect which depends largely upon the membrane proteins. Addition of calcium ions to suspensions of microvillus membranes increases the fluorescence polarization of retinol and anthroyl-stearate, but not that of diphenyl-hexatriene. This confirms the localization of the last compound to the hydrophobic interior of the membrane, relatively distant from the hydrophilic head groups of the polar lipids. Microvillus membrane proteins solubilized with Triton X-100 give relatively high fluorescence polarization and intensity values with retinol, suggesting the presence of binding proteins which could play a role in the normal absorptive mechanism for the vitamin. PMID:14174

  4. Experimental Study on the Electrochemical Anti-Corrosion Properties of Steel Structures Applying the Arc Thermal Metal Spraying Method

    PubMed Central

    Choe, Hong-Bok; Lee, Han-Seung; Shin, Jun-Ho

    2014-01-01

    The arc thermal metal spraying method (ATMSM) provides proven long-term protective coating systems using zinc, aluminum and their alloys for steel work in a marine environment. This paper focuses on studying experimentally the anti-corrosion criteria of ATMSM on steel specimens. The effects of the types of spraying metal and the presence or absence of sealing treatment from the thermal spraying of film on the anti-corrosion performance of TMSM were quantitatively evaluated by electrochemical techniques. The results showed that ATMSM represented a sufficient corrosion resistance with the driving force based on the potential difference of more than approximately 0.60 V between the thermal spraying layer and the base substrate steel. Furthermore, it was found that the sealing treatment of specimens had suppressed the dissolution of metals, increased the corrosion potential, decreased the corrosion current density and increased the polarization resistance. Metal alloy Al–Mg (95%:5%) by mass with epoxy sealing coating led to the most successful anti-corrosion performance in these electrochemical experiments. PMID:28788271

  5. Study on the influence factors of camouflage target polarization detection

    NASA Astrophysics Data System (ADS)

    Huang, Yanhua; Chen, Lei; Li, Xia; Wu, Wenyuan

    2016-10-01

    The degree of linear polarization (DOLP) expressions at any polarizer direction (PD) was deduced based on the Stokes vector and Mueller matrix. The outdoors experiments were carried out to demonstrate the expressions. This paper mainly explored the DOLP-image-Contrast (DOLPC) between the target image and the background image, and the PD and RGB waveband that be considered two important influence factors were studied for camouflage target polarization detection. It was found that the DOLPC of target and background was obviously higher than intensity image. When setting the reference direction that polarizer was perpendicular to the incident face, the DOLP image of interval angle 60 degree between PD and reference direction had relatively high DOLPC, the interval angle 45 degree was the second, and the interval angle 35 degree was the third. The outdoors polarization detection experiment of controlling waveband showed that the DOLPC results was significantly different to use 650nm, 550nm and 450nm waveband, and the polarization detection performance by using 650nm band was an optimization method.

  6. Parametric Studies Of Weld Quality Of Tungsten Inert Gas Arc Welding Of Stainless Steel

    SciTech Connect

    Kumar Pal, Pradip; Nandi, Goutam; Ghosh, Nabendu

    2011-01-17

    Effect of current and gas flow rate on quality of weld in tungsten inter gas arc welding of austenitic stainless steel has been studied in the present work through experiments and analyses. Butt welded joints have been made by using several levels of current and gas flow rate. The quality of the weld has been evaluated in terms of ultimate and breaking strengths of the welded specimens. The observed data have been interpreted, discussed and analyzed by using Grey--Taguchi methodology. Optimum parametric setting has been predicted and validated as well.

  7. Anatomical study of the medial gastrocnemius muscle flap: a quantitative assessment of the arc of rotation.

    PubMed

    Veber, Michaël; Vaz, Gualter; Braye, Fabienne; Carret, Jean-Paul; Saint-Cyr, Michel; Rohrich, Rod J; Mojallal, Ali

    2011-07-01

    The authors compared the arc of rotation of medial gastrocnemius flaps according to three methods: standard harvesting, dissection of the "pes anserinus" muscle, and dissection of the medial condyle. This study was performed using 20 fresh cadavers in two anatomy laboratories in Lyon, France; and Dallas, Texas. The area covered by each flap was calculated. The arc of rotation was calculated using distance from a fixed point, the anterior tibial tuberosity, to the distal flap (segment 1), to the lateral knee (segment 2), to the upper knee (segment 3), and to the medial thigh (segment 4). All measurements were done with leg stretched, applying a tensile strength of 1 daN on the muscle. The average surface of the flaps (32.5 ± 8.55 cm) did not vary with the technique used; neither did the length of segment 1 (19.6 ± 3.53 cm). Segment 2 (9.6 ± 3.1 cm) and segment 3 (13.6 ± 2.76 cm) were increased by 7.3 ± 11.1 percent and 21.3 ± 13.9 percent, respectively, when using pes anserinus dissection; and by 30.2 ± 23 percent and 49.3 ± 34 percent when combining with medial condyle dissection. Segment 4 (22.9 ± 2.21 cm) increased by 15.3 ± 12.8 percent with pes anserinus dissection alone and 36.2 ± 13 percent when combining with medial condyle dissection. This study allowed precise measurement of the flaps and arcs of rotation according to the type of harvest. A marked length gain was achieved by pes anserinus dissection alone or the combination with medial condyle dissection. The authors' results support the importance of assessing the benefit/risk balance between different techniques according to the type and extent of soft-tissue loss requiring reconstruction.

  8. Customizing ArcGIS for spatial decision support: case study on locating potential small water resevoirs in Benin

    NASA Astrophysics Data System (ADS)

    Laudien, R.; Thamm, H.-P.; Giertz, S.; Diekkrüger, B.; Bareth, G.

    2006-10-01

    This paper presents a software development approach to customize the GIS software ArcGIS (by ESRI) for spatial decision support. For the case study, example data of the Queme catchment in Benin (Africa) is used to program such a system which will be used to plan the establishment of potential small water reservoirs. Therefore, a new user menu in ArcGIS is introduced which allows (i) the integration of available GIS data from geo-databases, (ii) the easy application of spatial analyses by using implemented expert knowledge, and (iii) the automatic production of maps and reports for potential locations. To fulfil these requirements, the developer software Visual Basic for Applications (VBA) in combination with the ArcObjects library is used as the programming environment. ArcGIS comes with a VBA interface and with the above-mentioned library. Therefore, the software engineer is able to create a comprehensive and user friendly system for spatial decision support which includes numerous analyses tools of ArcGIS. Additionally, various user views can be realized basing on the same platform. First preliminary results show the potential capability of the above-described approach and justify the usage of the ArcGIS software to create spatial decision support systems.

  9. Simulations to study the static polarization limit for RHIC lattice

    NASA Astrophysics Data System (ADS)

    Duan, Zhe; Qin, Qing

    2016-01-01

    A study of spin dynamics based on simulations with the Polymorphic Tracking Code (PTC) is reported, exploring the dependence of the static polarization limit on various beam parameters and lattice settings for a practical RHIC lattice. It is shown that the behavior of the static polarization limit is dominantly affected by the vertical motion, while the effect of beam-beam interaction is small. In addition, the “nonresonant beam polarization” observed and studied in the lattice-independent model is also observed in this lattice-dependent model. Therefore, this simulation study gives insights of polarization evolution at fixed beam energies, that are not available in simple spin tracking. Supported by the U.S. Department of Energy (DE-AC02-98CH10886), Hundred-Talent Program (Chinese Academy of Sciences), and National Natural Science Foundation of China (11105164)

  10. Sci—Thur AM: YIS - 04: Gold Nanoparticle Enhanced Arc Radiotherapy: A Monte Carlo Feasibility Study

    SciTech Connect

    Koger, B; Kirkby, C

    2014-08-15

    Introduction: The use of gold nanoparticles (GNPs) in radiotherapy has shown promise for therapeutic enhancement. In this study, we explore the feasibility of enhancing radiotherapy with GNPs in an arc-therapy context. We use Monte Carlo simulations to quantify the macroscopic dose-enhancement ratio (DER) and tumour to normal tissue ratio (TNTR) as functions of photon energy over various tumour and body geometries. Methods: GNP-enhanced arc radiotherapy (GEART) was simulated using the PENELOPE Monte Carlo code and penEasy main program. We simulated 360° arc-therapy with monoenergetic photon energies 50 – 1000 keV and several clinical spectra used to treat a spherical tumour containing uniformly distributed GNPs in a cylindrical tissue phantom. Various geometries were used to simulate different tumour sizes and depths. Voxel dose was used to calculate DERs and TNTRs. Inhomogeneity effects were examined through skull dose in brain tumour treatment simulations. Results: Below 100 keV, DERs greater than 2.0 were observed. Compared to 6 MV, tumour dose at low energies was more conformai, with lower normal tissue dose and higher TNTRs. Both the DER and TNTR increased with increasing cylinder radius and decreasing tumour radius. The inclusion of bone showed excellent tumour conformality at low energies, though with an increase in skull dose (40% of tumour dose with 100 keV compared to 25% with 6 MV). Conclusions: Even in the presence of inhomogeneities, our results show promise for the treatment of deep-seated tumours with low-energy GEART, with greater tumour dose conformality and lower normal tissue dose than 6 MV.

  11. Cathodic arcs

    SciTech Connect

    Anders, Andre

    2003-10-29

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

  12. A comparative study of standard intensity-modulated radiotherapy and RapidArc planning techniques for ipsilateral and bilateral head and neck irradiation.

    PubMed

    Pursley, Jennifer; Damato, Antonio L; Czerminska, Maria A; Margalit, Danielle N; Sher, David J; Tishler, Roy B

    2017-01-01

    The purpose of this study was to investigate class solutions using RapidArc volumetric-modulated arc therapy (VMAT) planning for ipsilateral and bilateral head and neck (H&N) irradiation, and to compare dosimetric results with intensity-modulated radiotherapy (IMRT) plans. A total of 14 patients who received ipsilateral and 10 patients who received bilateral head and neck irradiation were retrospectively replanned with several volumetric-modulated arc therapy techniques. For ipsilateral neck irradiation, the volumetric-modulated arc therapy techniques included two 360° arcs, two 360° arcs with avoidance sectors around the contralateral parotid, two 260° or 270° arcs, and two 210° arcs. For bilateral neck irradiation, the volumetric-modulated arc therapy techniques included two 360° arcs, two 360° arcs with avoidance sectors around the shoulders, and 3 arcs. All patients had a sliding-window-delivery intensity-modulated radiotherapy plan that was used as the benchmark for dosimetric comparison. For ipsilateral neck irradiation, a volumetric-modulated arc therapy technique using two 360° arcs with avoidance sectors around the contralateral parotid was dosimetrically comparable to intensity-modulated radiotherapy, with improved conformity (conformity index = 1.22 vs 1.36, p < 0.04) and lower contralateral parotid mean dose (5.6 vs 6.8Gy, p < 0.03). For bilateral neck irradiation, 3-arc volumetric-modulated arc therapy techniques were dosimetrically comparable to intensity-modulated radiotherapy while also avoiding irradiation through the shoulders. All volumetric-modulated arc therapy techniques required fewer monitor units than sliding-window intensity-modulated radiotherapy to deliver treatment, with an average reduction of 35% for ipsilateral plans and 67% for bilateral plans. Thus, for ipsilateral head and neck irradiation a volumetric-modulated arc therapy technique using two 360° arcs with avoidance sectors around the contralateral parotid is

  13. Study of Arc-Related RF Faults in the CEBAF Cryomodules

    SciTech Connect

    Douglas Curry; Ganapati Myneni; Ganapati Rao Myneni; John Musson; Thomas Powers; Timothy Whitlatch; Isidoro Campisi; Haipeng Wang

    2004-07-01

    A series of measurements has been conducted on two superconducting radio-frequency (RF) cavity pairs, installed in cryomodules and routinely operated in the Continuous Electron Beam Accelerator Facility, in order to study the RF-vacuum interaction during an RF fault. These arc-related fault rates increase with increasing machine energy, contribute to system downtime, and directly affect the accelerator's availability. For this study, the fundamental power coupler waveguides have been instrumented with vacuum gauges, additional arc detectors, additional infrared sensors, and temperature sensors in order to measure the system response during both steady-state operations and RF fault conditions. Residual gas analyzers have been installed on the waveguide vacuum manifolds to monitor the gas species present during cooldown, RF processing, and operation. Measurements of the signals are presented, a comparison with analysis is shown and results are discussed. The goal of this study is to characterize the RF-vacuum interaction during normal operations. With a better understanding of the installed system response, methods for reducing the fault rate may be devised, ultimately leading to improvements in availability.

  14. Arc characteristics of submerged arc welding with stainless steel wire

    NASA Astrophysics Data System (ADS)

    Li, Ke; Wu, Zhi-sheng; Liu, Cui-rong; Chen, Feng-hua

    2014-08-01

    The arc characteristics of submerged arc welding (SAW) with stainless steel wire were studied by using Analysator Hannover (AH). The tests were carried out under the same preset arc voltage combined with different welding currents. By comparing the probability density distribution (PDD) curves of arc voltage and welding current, the changes were analyzed, the metal transfer mode in SAW was deduced, and the characteristics of a stable arc were summarized. The analysis results show that, with an increase of welding parameters, the short-circuiting peak in the PDD curves of arc voltage decreases gradually until it disappears, and the dominant metal transfer mode changes from flux-wall guided transfer to projected transfer and then to streaming transfer. Moreover, when the PDD curves of arc voltage are both unimodal and generally symmetrical, the greater the peak probability and the smaller the peak span, the more stable the arc becomes.

  15. ArcS, the cognate sensor kinase in an atypical Arc system of Shewanella oneidensis MR-1.

    PubMed

    Lassak, Jürgen; Henche, Anna-Lena; Binnenkade, Lucas; Thormann, Kai M

    2010-05-01

    The availability of oxygen is a major environmental factor for many microbes, in particular for bacteria such as Shewanella species, which thrive in redox-stratified environments. One of the best-studied systems involved in mediating the response to changes in environmental oxygen levels is the Arc two-component system of Escherichia coli, consisting of the sensor kinase ArcB and the cognate response regulator ArcA. An ArcA ortholog was previously identified in Shewanella, and as in Escherichia coli, Shewanella ArcA is involved in regulating the response to shifts in oxygen levels. Here, we identified the hybrid sensor kinase SO_0577, now designated ArcS, as the previously elusive cognate sensor kinase of the Arc system in Shewanella oneidensis MR-1. Phenotypic mutant characterization, transcriptomic analysis, protein-protein interaction, and phosphotransfer studies revealed that the Shewanella Arc system consists of the sensor kinase ArcS, the single phosphotransfer domain protein HptA, and the response regulator ArcA. Phylogenetic analyses suggest that HptA might be a relict of ArcB. Conversely, ArcS is substantially different with respect to overall sequence homologies and domain organizations. Thus, we speculate that ArcS might have adopted the role of ArcB after a loss of the original sensor kinase, perhaps as a consequence of regulatory adaptation to a redox-stratified environment.

  16. Studies of polarized beam acceleration and Siberian Snakes

    SciTech Connect

    Lee, S.Y.

    1992-12-31

    We studied depolarization mechanisms of polarized proton acceleration in high energy accelerators with snakes and found that the perturbed spin tune due to the imperfection resonance plays an important role in beam depolarization at snake resonances. We also found that even order snake resonances exist in the overlapping intrinsic and imperfection resonances. Due to the perturbed spin tune of imperfection resonances, each snake resonance splits into two. Thus the available betatron tune space becomes smaller. Some constraints on polarized beam colliders were also examined.

  17. A Study of Polarized Proton Acceleration in J-PARC

    SciTech Connect

    Luccio, A. U.; Bai, M.; Roser, T.; Molodojentsev, A.; Ohmori, C.; Sato, H.; Hatanaka, K.

    2007-06-13

    We have studied the feasibility of polarized proton acceleration in rhe J-PARC accelerator facility, consisting of a 400 MeV linac, a 3 GeV rapid cycling synchrotron (RCS) and a 50 GeV synchrotron (MR). We show how the polarization of the beam can be preserved using an rf dipole in the RCS and two superconductve partial helical Siberian snakes in the MR. The lattice of the MR will be modified with the addition of quadrupoles to compensate for the focusing properties of the snakes.

  18. A STUDY OF POLARIZED PROTON ACCELERATION IN J-PARC.

    SciTech Connect

    LUCCIO, A.U.; BAI, M.; ROSER, T.

    2006-10-02

    We have studied the feasibility of polarized proton acceleration in rhe J-PARC accelerator facility, consisting of a 400 MeV linac, a 3 GeV rapid cycling synchrotron (RCS) and a 50 GeV synchrotron (MR). We show how the polarization of the beam can be preserved using an rf dipole in the RCS and two superconductive partial helical Siberian snakes in the MR. The lattice of the MR will be modified with the addition of quadrupoles to compensate for the focusing properties of the snakes.

  19. Impaired behavior of female tg-ArcSwe APP mice in the IntelliCage: A longitudinal study.

    PubMed

    Codita, Alina; Gumucio, Astrid; Lannfelt, Lars; Gellerfors, Pär; Winblad, Bengt; Mohammed, Abdul H; Nilsson, Lars N G

    2010-12-20

    Transgenic animals expressing mutant human amyloid precursor protein (APP) are used as models for Alzheimer disease (AD). Ideally, behavioral tests improve the predictive validity of studies on animals by mirroring the functional impact of AD-like neuropathology. Learning and memory studies in APP transgenic models have been difficult to replicate. Standardization of procedures, automatization or improved protocol design can improve reproducibility. Here the IntelliCage, an automated system, was used for behavioral testing of APP female transgenic mice with both the Arctic and Swedish mutations, the tg-ArcSwe model. Protocols covering exploration, operant learning, place learning and extinction of place preference as well as passive avoidance tests were used for longitudinal characterization of behavior. Differences in exploratory activity were significant at four months of age, when plaque-free tg-ArcSwe mice visited less frequently the IntelliCage corners and initially performed fewer visits with licks compared to non-tg animals, inside the new environment. Fourteen months old tg-ArcSwe mice required a longer time to re-habituate to the IntelliCages than non-tg mice. At both ages tg-ArcSwe mice perseverated in place preference extinction test. Fourteen months old tg-ArcSwe mice were impaired in hippocampus-dependent spatial passive avoidance learning. This deficit was found to inversely correlate to calbindin-D28k immunoreactivity in the polymorphic layer of the dentate gyrus. Reduced water intake and body weight were observed in 4 months old tg-ArcSwe animals. The body weight difference increased with age. Thus behavioral and metabolic changes in the tg-ArcSwe APP model were detected using the IntelliCage, a system which provides the opportunity for standardized automated longitudinal behavioral phenotyping.

  20. Experimental study of the heat transfer process of air around atmospheric arc plasma

    NASA Astrophysics Data System (ADS)

    Salimi Meidanshahi, F.; Madanipour, Kh.; Shokri, Babak

    2011-05-01

    The experimental investigation of thermodynamic properties such heat and mass transfer of plasmas has many applications in different industries. Laboratory atmospheric arc plasma is studied in this work. The refractive index of the air around the plasma is changed because of convection phenomena. When the convection creates the air flowing around the plasma, the density and consequently, the refractive index of air are distributed symmetrically. Moiré deflectometry is a technique of wave front analysis which in both Talbot effect and moiré technique is applied for measuring phase objects. Deflection of light beam passing through the inhomogeneous medium is utilized to obtain the refractive index distribution. In experimental set-up, an expanded collimated He-Ne laser propagate through the arc plasma and the around air. The temperature distribution is obtained by use of thermo-optic coefficient of air. To calculate the thermo- optic coefficient and the refractive index of air for a given wavelength of light and given atmospheric conditions (air temperature, pressure, and humidity), the Edlén equation is used. The convective heat transfer coefficient is obtained by calculating the temperature gradient on the plasma border. This method is not expensive, complicated and sensitive to environmental vibrations.

  1. Study the Effect of SiO2 Based Flux on Dilution in Submerged Arc Welding

    NASA Astrophysics Data System (ADS)

    kumar, Aditya; Maheshwari, Sachin

    2017-08-01

    This paper highlights the method for prediction of dilution in submerged arc welding (SAW). The most important factors of weld bead geometry are governed by the weld dilution which controls the chemical and mechanical properties. Submerged arc welding process is used generally due to its very easy control of process variables, good penetration, high weld quality, and smooth finish. Machining parameters, with suitable weld quality can be achieved with the different composition of the flux in the weld. In the present study Si02-Al2O3-CaO flux system was used. In SiO2 based flux NiO, MnO, MgO were mixed in various proportions. The paper investigates the relationship between the process parameters like voltage, % of flux constituents and dilution with the help of Taguchi’s method. The experiments were designed according to Taguchi L9 orthogonal array, while varying the voltage at two different levels in addition to alloying elements. Then the optimal results conditions were verified by confirmatory experiments.

  2. Numerical Study for Gta Weld Shape Variation by Coupling Welding Arc and Weld Pool

    NASA Astrophysics Data System (ADS)

    Dong, Wenchao; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.

  3. Studies of interactive plasma processes in the polar cusp

    NASA Technical Reports Server (NTRS)

    Waite, J. Hunter, Jr.

    1992-01-01

    The final report for NAGW-1657 (SwRI Project 15-2783) is presented. Several distinctly different areas of research are discussed: (1) studies of the thermal structure of polar outflows; (2) Prognoz-8 data analysis; and (3) the Ulysses Jupiter encounter.

  4. SHORT CIRCUIT COORDINATION STUDY & ARC FLASH EVALUATION FOR LIQUID PROCESSING & CAPSULE STORAGE 310 FACILITY

    SciTech Connect

    TOWNE, C.M.

    2003-12-26

    The objective of this study is to provide a design basis document for the electrical distribution system for the 310 Facility in the 300 Area. The study must assure that electrical equipment is rated to withstand the available fault current under abnormal (short circuit) conditions. Under-rated equipment would result in property damage, prolonged facility outages, and possible personal injury. Also to be considered, is the coordination of protective devices. This assures that the protection device nearest a fault will open and isolate the problem area from the remainder of facility systems. The study must specify what settings are required on adjustable protective devices to achieve optimum coordination. Lastly, the study must calculate Arc Blast energies at all parts of the system so that proper Personal Protective Equipment (PPE) can be specified for energized work.

  5. Study of issues in difficult-to-weld thick materials by hybrid laser arc welding

    NASA Astrophysics Data System (ADS)

    Mazar Atabaki, Mehdi

    There is a high interest for the high strength-to-weight ratio with good ductility for the welds of advanced alloys. The concern about the welding of thick materials (Advanced high strength steels (AHSS) and 5xxx and 6xxx series of aluminum alloys) has stimulated the development of manufacturing processes to overcome the associated issues. The need to weld the dissimilar materials (AHSS and aluminum alloys) is also required for some specific applications in different industries. Hence, the requirement in the development of a state-of-the-art welding procedure can be helpful to fulfill the constraints. Among the welding methods hybrid laser/arc welding (HLAW) has shown to be an effective method to join thick and difficult-to-weld materials. This process benefits from both advantages of the gas metal arc welding (GMAW) and laser welding processes. The interaction of the arc and laser can help to have enough penetration of weld in thick plates. However, as the welding of dissimilar aluminum alloys and steels is very difficult because of the formation of brittle intermetallics the present work proposed a procedure to effectively join the alloys. The reports showed that the explosively welded aluminum alloys to steels have the highest toughness, and that could be used as an "insert" (TRICLAD) for welding the thick plates of AHSS to aluminum alloys. Therefore, the HLAW of the TRICLAD-Flange side (Aluminum alloy (AA 5456)) to the Web side (Aluminum alloys (AA 6061 and AA 5456)) and the TRICLAD-Flange side (ASTM A516) to the Web side (AHSS) was studied in the present work. However, there are many issues related to HLAW of the dissimilar steels as well as dissimilar aluminum alloys that have to be resolved in order to obtain sound welds. To address the challenges, the most recent welding methods for joining aluminum alloys to steels were studied and the microstructural development, mechanical properties, and on-line monitoring of the welding processes were discussed as well

  6. Combining seismology and petrology to study the variation in crustal discontinuity strength along the Lesser Antilles Arc

    NASA Astrophysics Data System (ADS)

    Schlaphorst, D.; Melekhova, E.; Kendall, J. M.; Blundy, J. D.; Baptie, B.; Latchman, J. L.

    2016-12-01

    Globally, volcanic arcs exhibit significant differences in crustal velocity structure. This variability occurs between arcs, but also within single arcs. The Mohorovičić discontinuity (Moho), separating the crust from the mantle, is thought to be the dominating discontinuity, but subduction processes can influence both its depth and seismic velocity contrast. In this study, we map the crustal structure variation in the Lesser Antilles Arc, a volcanic island arc formed by the subduction of the North and South American plates beneath the Caribbean plate. We use seismic data from 26 three-component broadband stations on all major islands along the arc. A purely seismological initial approach based on H-κ stacking of receiver functions revealed that results are prone to misinterpretations and do not necessarily map the Moho, which may be weakened by a change in water content or temperature. Hence, we combine seismic and petrological data to model depth-velocity profiles derived from a suite of different inversion techniques. The melting experiments provide compositional insight considering the effects of water and temperature on seismic properties that can be used as input values and provide the input structure containing two major crustal layers. The modelled profiles are in agreement with seismology and petrology constraints. Our results show significant variation in the thicknesses of the two crustal layers on short length scales, changing from island to island. The Moho depth varies between 20km and 45km, whilst the depth of the inter-crustal discontinuity varies between 10k and 20km. For some islands the inter-crustal discontinuity is seismically stronger than the Moho. Our work highlights the significance of combining results from seismology and petrology to gain results that can explain both the seismological and petrological observations. A key interpretation is that the thermal and water conditions are laterally variable along the arc on short length scales

  7. Astronomical polarization studies at radio and infrared wavelengths. Part 1: Gravitational deflection of polarized radiation

    NASA Technical Reports Server (NTRS)

    Dennison, B. K.

    1976-01-01

    The gravitational field is probed in a search for polarization dependence in the light bending. This involves searching for a splitting of a source image into orthogonal polarizations as the radiation passes through the solar gravitational field. This search was carried out using the techniques of very long and intermediate baseline interferometry, and by seeking a relative phase delay in orthogonal polarizations of microwaves passing through the solar gravitational field. In this last technique a change in the total polarization of the Helios 1 carrier wave was sought as the spacecraft passed behind the sun. No polarization splitting was detected.

  8. Observational study of the candidate polar-ring galaxies NGC 304 and NGC 7625

    NASA Astrophysics Data System (ADS)

    Karataeva, G. M.; Kuznetsov, A. N.

    2008-09-01

    We present the results of our photometric ( BV R) and spectroscopic CCD observations of NGC 304 and NGC 7625, candidate polar-ring galaxies, performed with the 6-m Special Astrophysical Observatory telescope. For NGC 304, such a study has been carried out for the first time. We have obtained basic integrated characteristics of the galaxies and determined their morphological types (S0 for NGC 304 and Sa for NGC 7625). The absolute magnitudes of the galaxies, M B = -20m.81 for NGC 304 and M B = -19m.34 for NGC7625, are indicative of their fairly high luminosities. The disk and bulge parameters have been determined forNGC 304 (µ0 = 20m.60, h = 3.86 kpc, µ e = 21m.59, r e = 1.26 kpc in the B band); these correspond to the parameters of S0-type objects. The rotation velocity for NGC 304 (200 km s-1) reaches its maximum at a galactocentric distance of 3.1 kpc, which yields a mass estimate for the galaxy of 2.8 × 1010 mathcal{M}_ odot . The observed photometric features at the center of NGC 304 indicate that it may have an inner ring structure, although we have failed to confirm the existence of two kinematic systems based on our spectroscopic observations. In NGC 7625, the disk makes a dominant contribution to the total brightness. The derived integrated color indices ( B-V = 0m.81 and V-R = 0m.61) agree with previous determinations of other authors. We have estimated the учештсешщт in the inner galactic regions. In the outer regions, we have detected structures with bluer colors ( B-V = 0m.60), which may be indicative of a polar ring with a minor stellar component.

  9. A Lagrangian study of the Antarctic polar vortex

    NASA Astrophysics Data System (ADS)

    Paparella, F.; Babiano, A.; Basdevant, C.; Provenzale, A.; Tanga, P.

    1997-03-01

    We study the dynamics of passively advected tracers in the Antarctic polar vortex, using the wind fields provided by the European Centre for Medium-Range Weather Forecasts' (ECMWF) analysis from August to October 1993. Advection on both isopycnal (0.0938 kg/m3) and isentropic surfaces (470°K) is considered. A new definition of the vortex edge, identified as the maximum of kinetic energy, is compared with the definition based on the maximum gradient of Ertel potential vorticity. Using the kinetic energy criterion, we study the permeability of the polar vortex in the framework of the launch strategy of the Stratospheric EoIe (Strateole) polar ozone experiment. We compare the dynamics of balloons launched from the latitudes corresponding to three different possible launching sites for the Strateole experiment, and we provide a quantitative estimate of the probability that a passive tracer may cross the vortex edge, confirming the strong impermeability of the polar vortex to inward and outward particle motions.

  10. Study on forest landscape diversity based on ArcGIS and GS +

    NASA Astrophysics Data System (ADS)

    Zhang, Yujuan; Qu, Jianguang; Liu, Dandan; Yang, Jinling; Li, Dan

    2015-12-01

    This paper analyses the forest landscape diversity of the study area with the help of ArcGIS10 and GS+ software. The forest landscape diversity and spatial interpolation and spatial differentiation are also carried out. The result shows that the maximum value of SHDI in 1997is 2.0463 and the minimum value is 0.2544 , which are 1.9722 and 0.2418 in the year of 2009. The advantage religion of SHDI mainly distributes in the middle of the study region , showing a band region from southwest to northeast . The forest landscape diversity and the space location have a moderate spatial correlation and a obvious structural under a forest level.

  11. Plasma arc versus halogen light curing of orthodontic brackets: a 12-month clinical study of bond failures.

    PubMed

    Sfondrini, Maria Francesca; Cacciafesta, Vittorio; Scribante, Andrea; Klersy, Catherine

    2004-03-01

    The purpose of this randomized clinical trial was to evaluate the clinical performance of brackets cured with 2 different light-curing units (conventional halogen light and plasma arc light); 83 patients treated with fixed appliances were included in the study. With the "split-mouth" design, each patient's mouth was divided into 4 quadrants. In 42 randomly selected patients, the maxillary left and mandibular right quadrants were cured with the halogen light, and the remaining quadrants were cured with the plasma arc light. In the other 41 patients, the quadrants were inverted. A total of 1434 stainless steel brackets were examined: 717 were cured with a conventional halogen light for 20 seconds; the remaining 717 were cured with the plasma arc light for 5 seconds. The number, cause, and date of bracket failures were recorded for each light-curing unit over 12 months. Statistical analysis was performed with the Fisher exact test, the Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences were found between the total bond failure rates of the brackets cured with the halogen light and those cured with the plasma arc light. Neither were significant differences found when the clinical performances of the maxillary versus mandibular arches or the anterior versus posterior segments were compared. These findings demonstrate that plasma arc lights are an advantageous alternative to conventional light curing, because they significantly reduce the curing time of orthodontic brackets without affecting the bond failure rate.

  12. Study on polarization features of carbonaceous particles in atmosphere pollutants

    NASA Astrophysics Data System (ADS)

    Li, Da; Zeng, Nan; Wang, Yunfei; Chen, Dongsheng; Chen, Yuerong; Ma, Hui

    2016-09-01

    The carbonaceous particles are the main source of the light absorption in atmospheric aerosol. Different from the case in tissue-like turbid media, the light absorption in atmospheric environments can be described as an inherent attribute on scatterers rather than an interstitial propagation effect. In this paper, we simulated the optical absorption due to carbonaceous scatterers and analyzed the influence of various parameters on their polarization properties, such as the imaginary part refractive index, the size and shape. Also we compare these results with our previous research work on absorption effect in ambient medium. For the single scattering, the polarization scattering angular distribution implies the potential of distinguishing different carbonaceous particles with different structural and absorption parameters. In the other hand, for the week scattering case of suspension system, using the backward Mueller matrix polar decomposition method, we can find out that the additional absorption effect on carbonaceous particles can enhance their depolarization and moreover produce more diattenuation and linear retardance for those anisotropic particles. The subsequent experiments of standard samples show a good agreement with simulation results. The paper further studies the phase function of single scattering and the distribution of scattering numbers, which can explain these unique polarization scattering phenomena. We hope these fundamental results can help to investigate how to identify the carbonaceous particles and characterize their optical features from the atmospheric hybrid suspension system.

  13. Simulation studies of nucleation of ferroelectric polarization reversal.

    SciTech Connect

    Brennecka, Geoffrey L.; Winchester, Benjamin Michael

    2014-08-01

    Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but also ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.

  14. Clinical implications of predominant polarity and the polarity index in bipolar disorder: a naturalistic study.

    PubMed

    Popovic, D; Torrent, C; Goikolea, J M; Cruz, N; Sánchez-Moreno, J; González-Pinto, A; Vieta, E

    2014-05-01

    Predominant polarity (PP) is an important variable in maintenance treatment of bipolar disorder (BD). This study aimed at determining the role of polarity index (PI), a metric indicating antimanic versus antidepressive prophylactic potential of drugs, in clinical decision-making. Two hundred and fifty-seven of 604 (43%) of patients with BD-I or II fulfilled criteria for manic (MPP) or depressive PP (DPP). The PI, representing the ratio of number needed to treat (NNT) for depression prevention to NNT for mania prevention, was calculated for patients' current treatment. MPP and DPP groups were compared regarding sociodemographic, clinical and therapeutic characteristics. One hundred and forty-three patients (55.6%) fulfilled criteria for DPP and 114 (44.4%) for MPP. Total PI, Antipsychotics' PI, and mood stabilizers PI were higher, indicating a stronger antimanic action, in MPP. MPP presented higher prevalence of BD-I, male gender, younger age, age at onset and at first hospitalization, more hospitalizations, primary substance misuse, and psychotic symptoms. DP correlated with BD-II, depressive onset, primary life events, melancholia, and suicide attempts. The results confirm the usefulness of the PI. In this large sample, clinical differences among these groups justify differential treatment approach. The PI appears to be a useful operationalization of what clinicians do for maintenance therapy in BD. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. Feasibility study on dosimetry verification of volumetric-modulated arc therapy-based total marrow irradiation.

    PubMed

    Liang, Yun; Kim, Gwe-Ya; Pawlicki, Todd; Mundt, Arno J; Mell, Loren K

    2013-03-04

    The purpose of this study was to develop dosimetry verification procedures for volumetric-modulated arc therapy (VMAT)-based total marrow irradiation (TMI). The VMAT based TMI plans were generated for three patients: one child and two adults. The planning target volume (PTV) was defined as bony skeleton, from head to mid-femur, with a 3 mm margin. The plan strategy similar to published studies was adopted. The PTV was divided into head and neck, chest, and pelvic regions, with separate plans each of which is composed of 2-3 arcs/fields. Multiple isocenters were evenly distributed along the patient's axial direction. The focus of this study is to establish a dosimetry quality assurance procedure involving both two-dimensional (2D) and three-dimensional (3D) volumetric verifications, which is desirable for a large PTV treated with multiple isocenters. The 2D dose verification was performed with film for gamma evaluation and absolute point dose was measured with ion chamber, with attention to the junction between neighboring plans regarding hot/cold spots. The 3D volumetric dose verification used commercial dose reconstruction software to reconstruct dose from electronic portal imaging devices (EPID) images. The gamma evaluation criteria in both 2D and 3D verification were 5% absolute point dose difference and 3 mm of distance to agreement. With film dosimetry, the overall average gamma passing rate was 98.2% and absolute dose difference was 3.9% in junction areas among the test patients; with volumetric portal dosimetry, the corresponding numbers were 90.7% and 2.4%. A dosimetry verification procedure involving both 2D and 3D was developed for VMAT-based TMI. The initial results are encouraging and warrant further investigation in clinical trials.

  16. Real-time prostate trajectory estimation with a single imager in arc radiotherapy: a simulation study

    NASA Astrophysics Data System (ADS)

    Poulsen, Per Rugaard; Cho, Byungchul; Keall, Paul J.

    2009-07-01

    Real-time prostate tracking during intensity-modulated arc radiotherapy requires a reliable prostate position signal during treatment. Many modern linear accelerators have a single gantry-mounted x-ray imager that could be used for intrafraction imaging of implanted prostate markers. The aim of this study was to develop a method to use such a single x-ray imager to estimate the three-dimensional (3D) prostate position in real time during arc treatment delivery and quantify the accuracy of this method in simulations based on 548 prostate trajectories for 17 patients measured with electromagnetic transponders. Imaging at 0.5, 1, 2 and 5 Hz during 360° arc treatments of 1, 2 and 3 min duration was simulated by projecting the prostate position onto the rotating imager. When an image was acquired, a Gaussian probability density function (PDF) for the prostate position was first estimated by maximum likelihood optimization from the set of images acquired so far and then used to estimate the 3D prostate position from the projected position in the image. Since this method needed a PDF right from the onset of the treatment, an initial PDF was obtained with a series of pre-treatment images acquired in 10 s, 20 s or 30 s during a gantry rotation of 60°, 120° or 180°. The accuracy of the estimations was quantified by calculating the root-mean-square (RMS) estimation error for each simulated treatment. The 3D RMS estimation error had a mean value of 0.22 mm and exceeded 1 mm in 0.8% of the cases for 1 min treatments with 5 Hz imaging and 20 s pre-treatment imaging. The position estimation accuracy degraded slightly with reduced imaging frequency or reduced pre-treatment imaging duration. Prolonged treatment duration of 2 and 3 min increased the mean 3D RMS errors to 0.27 mm and 0.30 mm, respectively. The single-imager trajectory estimation method would allow image-guided real-time prostate tracking based on standard equipment for modern linear accelerators.

  17. Mass-spectroscopic study of the influence of nozzle material on high-pressure SF6 arcs

    NASA Astrophysics Data System (ADS)

    Meier, R.; Kneubühl, F. K.; Schötzau, H. J.

    1989-03-01

    The interrupting capability of a gas-blast high-voltage circuit breaker (CB) is mainly determined by the self-induced pressure rise caused by the thermal arc energy, the composition of the arc plasma and the chemical reactions occuring during and after current interruption. We have studied the nozzle materials boron nitride (BN), quartz (SiO2), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), polyethylene (PE) and epoxy resin (ER) with respect to their influence on these processes with the aid of a model circuit breaker (MCB). Direct measurements of the arc-induced pressure rise reveal that the portion of the arc energy available for the pressure rise varies greatly (˜20% 65%) with the properties of the nozzle material. Nozzle erosion is significantly higher for materials with high values (e.g. polymers). Therefore, the lifetime of polymer nozzles is considerably shorter than that of ceramic nozzles. We have investigated the influence of the nozzle material on the decomposition products formed in the arc discharge of our MCB by studying the composition and time dependence of these products. The MCB was directly attached to the time-of-flight mass spectrometer (TOFMS) with the aid of a molecular-beam sampling system, which allowed real-time measurements of the arced gas during and after current interruption, thus providing information on the ablation mechanism and on the reaction kinetics of vaporised nozzle material with dissociated SF6. The most abundant long-lived reaction products are SF4, SOF2, C2H2, CO, and CS2. Their formation rates have been determined as functions of the nozzle material. With respect to quantities and properties of decomposition products, ceramics are superior to polymers since they form only small concentrations of corrosive and toxic products.

  18. A polarized photobleaching study of DNA reorientation in agarose gels

    SciTech Connect

    Scalettar, B.A.; Klein, M.P. ); Selvin, P.R.; Hearst, J.E. Univ. of California, Berkeley ); Axelrod, D. )

    1990-05-22

    Polarized fluorescence recovery after photobleaching (pFRAP) has been used to study the internal dynamics of relatively long DNA molecules embedded in gels that range in concentration from 1% to 5% agarose. The data indicate that, even in very congested gels, rapid internal relaxation of DNA is largely unhindered; however, interactions with gel matrices apparently do perturb the larger amplitude, more slowly (microseconds to milliseconds) relaxing internal motions of large DNAs. The relationship between this work and recent studies which indicate that internal motions of DNA play an important role in the separation achieved with pulsed-field gel electrophoresis techniques is discussed. The polarized photobleaching technique is also analyzed in some detail. In particular, it is shown that reversible photobleaching phenomena are probably related to depletion of the ground state by intersystem crossing to the triplet state.

  19. Geochemistry of Cretaceous Magmatism in Eastern Cuba: Recycling of North American Continental Sediments and Implications for the Subduction Polarity in the Greater Antilles Paleo-arc

    NASA Astrophysics Data System (ADS)

    Marchesi, C.; Garrido, C. J.; Bosch, D.; Proenza, J. A.; Gervilla, F.

    2007-12-01

    We present whole rock major and trace element data and Nd-Sr-Pb radiogenic isotope ratios of Cretaceous igneous suites from eastern Cuba. These rocks are related to the Greater Antilles paleo-island arc magmatism and have three different igneous styles. Group 1 consists of tholeiitic basalts and rare basaltic andesites that have N-MORB-like compositions similar to those found in back-arc basin basalts (TiO2 = 1.2-2.9 wt%; La/Yb(N) = 0.7-0.9, Th/Nb = 0.06-0.08, and initial 208Pb/204Pb = 37.65-37.74). Group 2 comprises basaltic and rare basaltic andesitic subvolcanic dykes with major-, trace-element and isotopic compositions similar to island arc tholeiites (TiO2 = 0.7-1.4 wt%; La/Yb(N) = 0.6-0.9, Th/Nb = 0.06-0.68, and initial 208Pb/204Pb = 37.74-38.25). Group 3 is composed of low-Ti (TiO2 = 0.3-0.9 wt%) calcalkaline igneous rocks that have an unambiguous subduction- related character (La/Yb(N) = 1.1-5.0, Th/Nb = 0.35-1.55, and initial 208Pb/204Pb = 37.94-38.39). The parental magmas of the three groups formed by variable melting degrees (< 5-25%) of spinel lherzolite, with the more depleted mantle sources for Groups 2 and 3 than Group 1. The trace element and radiogenic isotope compositions of primitive Group 3 samples are strongly bimodal. One subgroup of samples is characterized by low Ta/Yb (0.02-0.03) and Th/La (0.10-0.13), slightly subchondritic Nb/Ta (13.3-17.3), and relatively high initial 206Pb/204Pb (18.57-18.62) and åNd (7.6-9.4). The remaining primitive Group 3 samples have higher Ta/Yb (0.06-0.11) and Th/La (0.24-0.32), highly subchondritic Nb/Ta (7.6-9.1), coupled with lower initial 206Pb/204Pb (18.24-18.29) and åNd (3.4-5.5). These signatures were induced by two distinct slab components that mainly reflect the contributions of Cretaceous Atlantic marine and North American continental sediments, respectively. Nb/Ta in the first subgroup was induced by melting of rutile-bearing subducted crust, whereas in the second it was inherited from recycled

  20. Geochemistry of Cretaceous Magmatism in Eastern Cuba: Recycling of North American Continental Sediments and Implications for the Subduction Polarity in the Greater Antilles Paleo-arc

    NASA Astrophysics Data System (ADS)

    Marchesi, C.; Garrido, C. J.; Bosch, D.; Proenza, J. A.; Gervilla, F.

    2004-12-01

    We present whole rock major and trace element data and Nd-Sr-Pb radiogenic isotope ratios of Cretaceous igneous suites from eastern Cuba. These rocks are related to the Greater Antilles paleo-island arc magmatism and have three different igneous styles. Group 1 consists of tholeiitic basalts and rare basaltic andesites that have N-MORB-like compositions similar to those found in back-arc basin basalts (TiO2 = 1.2-2.9 wt%; La/Yb(N) = 0.7-0.9, Th/Nb = 0.06-0.08, and initial 208Pb/204Pb = 37.65-37.74). Group 2 comprises basaltic and rare basaltic andesitic subvolcanic dykes with major-, trace-element and isotopic compositions similar to island arc tholeiites (TiO2 = 0.7-1.4 wt%; La/Yb(N) = 0.6-0.9, Th/Nb = 0.06-0.68, and initial 208Pb/204Pb = 37.74-38.25). Group 3 is composed of low-Ti (TiO2 = 0.3-0.9 wt%) calcalkaline igneous rocks that have an unambiguous subduction- related character (La/Yb(N) = 1.1-5.0, Th/Nb = 0.35-1.55, and initial 208Pb/204Pb = 37.94-38.39). The parental magmas of the three groups formed by variable melting degrees (< 5-25%) of spinel lherzolite, with the more depleted mantle sources for Groups 2 and 3 than Group 1. The trace element and radiogenic isotope compositions of primitive Group 3 samples are strongly bimodal. One subgroup of samples is characterized by low Ta/Yb (0.02-0.03) and Th/La (0.10-0.13), slightly subchondritic Nb/Ta (13.3-17.3), and relatively high initial 206Pb/204Pb (18.57-18.62) and åNd (7.6-9.4). The remaining primitive Group 3 samples have higher Ta/Yb (0.06-0.11) and Th/La (0.24-0.32), highly subchondritic Nb/Ta (7.6-9.1), coupled with lower initial 206Pb/204Pb (18.24-18.29) and åNd (3.4-5.5). These signatures were induced by two distinct slab components that mainly reflect the contributions of Cretaceous Atlantic marine and North American continental sediments, respectively. Nb/Ta in the first subgroup was induced by melting of rutile-bearing subducted crust, whereas in the second it was inherited from recycled

  1. Theoretical model and experimental investigation of current density boundary condition for welding arc study

    NASA Astrophysics Data System (ADS)

    Boutaghane, A.; Bouhadef, K.; Valensi, F.; Pellerin, S.; Benkedda, Y.

    2011-04-01

    This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 A m-2 for a 1.2 mm diameter welding electrode.

  2. Study of Different Variants of Mo Enzyme crARC and the Interaction with Its Partners crCytb5-R and crCytb5-1.

    PubMed

    Chamizo-Ampudia, Alejandro; Galvan, Aurora; Fernandez, Emilio; Llamas, Angel

    2017-03-21

    The mARC (mitochondrial Amidoxime Reducing Component) proteins are recently discovered molybdenum (Mo) Cofactor containing enzymes. They are involved in the reduction of several N-hydroxylated compounds (NHC) and nitrite. Some NHC are prodrugs containing an amidoxime structure or mutagens such as 6-hydroxylaminopurine (HAP). We have studied this protein in the green alga Chlamydomonas reinhardtii (crARC). Interestingly, all the ARC proteins need the reducing power supplied by other proteins. It is known that crARC requires a cytochrome b₅ (crCytb5-1) and a cytochrome b₅ reductase (crCytb5-R) that form an electron transport chain from NADH to the substrates. Here, we have investigated NHC reduction by crARC, the interaction with its partners and the function of important conserved amino acids. Interactions among crARC, crCytb5-1 and crCytb5-R have been studied by size-exclusion chromatography. A protein complex between crARC, crCytb5-1 and crCytb5-R was identified. Twelve conserved crARC amino acids have been substituted by alanine by in vitro mutagenesis. We have determined that the amino acids D182, F210 and R276 are essential for NHC reduction activity, R276 is important and F210 is critical for the Mo Cofactor chelation. Finally, the crARC C-termini were shown to be involved in protein aggregation or oligomerization.

  3. Study of Different Variants of Mo Enzyme crARC and the Interaction with Its Partners crCytb5-R and crCytb5-1

    PubMed Central

    Chamizo-Ampudia, Alejandro; Galvan, Aurora; Fernandez, Emilio; Llamas, Angel

    2017-01-01

    The mARC (mitochondrial Amidoxime Reducing Component) proteins are recently discovered molybdenum (Mo) Cofactor containing enzymes. They are involved in the reduction of several N-hydroxylated compounds (NHC) and nitrite. Some NHC are prodrugs containing an amidoxime structure or mutagens such as 6-hydroxylaminopurine (HAP). We have studied this protein in the green alga Chlamydomonas reinhardtii (crARC). Interestingly, all the ARC proteins need the reducing power supplied by other proteins. It is known that crARC requires a cytochrome b5 (crCytb5-1) and a cytochrome b5 reductase (crCytb5-R) that form an electron transport chain from NADH to the substrates. Here, we have investigated NHC reduction by crARC, the interaction with its partners and the function of important conserved amino acids. Interactions among crARC, crCytb5-1 and crCytb5-R have been studied by size-exclusion chromatography. A protein complex between crARC, crCytb5-1 and crCytb5-R was identified. Twelve conserved crARC amino acids have been substituted by alanine by in vitro mutagenesis. We have determined that the amino acids D182, F210 and R276 are essential for NHC reduction activity, R276 is important and F210 is critical for the Mo Cofactor chelation. Finally, the crARC C-termini were shown to be involved in protein aggregation or oligomerization. PMID:28335548

  4. NLC-91: An experimental study of the polar summer mesosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Kopp, E.; Witt, G.

    1994-01-01

    In the summer of 1991, a major scientific campaign (NLC-91) involving 31 rocket flights was conducted from ESRANGE, Kiruna, Sweden and from Heiss Island, Russia to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. The rocket flights were also coordinated with two coherent radar facilities, EISCAT (European Incoherent Scatter Scientific Association) and CUPRI (Cornell University Portable Radar Instrument), as well as other ground facilities, to provide continual monitoring of the mesosphere by remote sensing techniques. The primary objectives of the campaign were to study noctilucent clouds (NLC's) and polar mesospheric summer echoes (PMSE's), including their possible relationship to local aerosols and/or small scale turbulence. The program involved scientific participation from eight countries, and promises to produce many results during the next few years. This overview considers the scientific campaign and briefly discusses preliminary results. These results are provided in more detail in papers following this overview.

  5. NLC-91: An experimental study of the polar summer mesosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Kopp, E.; Witt, G.

    1994-01-01

    In the summer of 1991, a major scientific campaign (NLC-91) involving 31 rocket flights was conducted from ESRANGE, Kiruna, Sweden and from Heiss Island, Russia to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. The rocket flights were also coordinated with two coherent radar facilities, EISCAT (European Incoherent Scatter Scientific Association) and CUPRI (Cornell University Portable Radar Instrument), as well as other ground facilities, to provide continual monitoring of the mesosphere by remote sensing techniques. The primary objectives of the campaign were to study noctilucent clouds (NLC's) and polar mesospheric summer echoes (PMSE's), including their possible relationship to local aerosols and/or small scale turbulence. The program involved scientific participation from eight countries, and promises to produce many results during the next few years. This overview considers the scientific campaign and briefly discusses preliminary results. These results are provided in more detail in papers following this overview.

  6. Convergent evolution of the arginine deiminase pathway: the ArcD and ArcE arginine/ornithine exchangers.

    PubMed

    Noens, Elke E E; Lolkema, Juke S

    2017-02-01

    The arginine deiminase (ADI) pathway converts L-arginine into L-ornithine and yields 1 mol of ATP per mol of L-arginine consumed. The L-arginine/L-ornithine exchanger in the pathway takes up L-arginine and excretes L-ornithine from the cytoplasm. Analysis of the genomes of 1281 bacterial species revealed the presence of 124 arc gene clusters encoding the pathway. About half of the clusters contained the gene encoding the well-studied L-arginine/L-ornithine exchanger ArcD, while the other half contained a gene, termed here arcE, encoding a membrane protein that is not a homolog of ArcD. The arcE gene product of Streptococcus pneumoniae was shown to take up L-arginine and L-ornithine with affinities of 0.6 and 1 μmol/L, respectively, and to catalyze metabolic energy-independent, electroneutral exchange. ArcE of S. pneumoniae could replace ArcD in the ADI pathway of Lactococcus lactis and provided the cells with a growth advantage. In contrast to ArcD, ArcE catalyzed translocation of the pathway intermediate L-citrulline with high efficiency. A short version of the ADI pathway is proposed for L-citrulline catabolism and the presence of the evolutionary unrelated arcD and arcE genes in different organisms is discussed in the context of the evolution of the ADI pathway.

  7. Elements of arc welding

    SciTech Connect

    Not Available

    1993-07-01

    This paper looks at the following arc welding techniques: (1) shielded metal-arc welding; (2) submerged-arc welding; (3) gas metal-arc welding; (4) flux-cored arc welding; (5) electrogas welding; (6) gas tungsten-arc welding; and (7) plasma-arc welding.

  8. Identification of new susceptibility loci for osteoarthritis (arcOGEN): a genome-wide association study.

    PubMed

    Zeggini, Eleftheria; Panoutsopoulou, Kalliope; Southam, Lorraine; Rayner, Nigel W; Day-Williams, Aaron G; Lopes, Margarida C; Boraska, Vesna; Esko, Tonu; Evangelou, Evangelos; Hoffman, Albert; Houwing-Duistermaat, Jeanine J; Ingvarsson, Thorvaldur; Jonsdottir, Ingileif; Jonnson, Helgi; Kerkhof, Hanneke J; Kloppenburg, Margreet; Bos, Steffan D; Mangino, Massimo; Metrustry, Sarah; Slagboom, P Eline; Thorleifsson, Gudmar; Raine, Emma V A; Ratnayake, Madhushika; Ricketts, Michelle; Beazley, Claude; Blackburn, Hannah; Bumpstead, Suzannah; Elliott, Katherine S; Hunt, Sarah E; Potter, Simon C; Shin, So-Youn; Yadav, Vijay K; Zhai, Guangju; Sherburn, Kate; Dixon, Kate; Arden, Elizabeth; Aslam, Nadim; Battley, Phillippa-kate; Carluke, Ian; Doherty, Sally; Gordon, Andrew; Joseph, John; Keen, Richard; Koller, Nicola C; Mitchell, Sheryl; O'Neill, Fiona; Paling, Ellen; Reed, Mike R; Rivadeneira, Fernando; Swift, Diane; Walker, Kirsten; Watkins, Bridget; Wheeler, Maggie; Birrell, Fraser; Ioannidis, John P A; Meulenbelt, Ingrid; Metspalu, Andres; Rai, Ashok; Salter, Donald; Stefansson, Kari; Stykarsdottir, Unnur; Uitterlinden, André G; van Meurs, Joyce B J; Chapman, Kay; Deloukas, Panos; Ollier, William E R; Wallis, Gillian A; Arden, Nigel; Carr, Andrew; Doherty, Michael; McCaskie, Andrew; Willkinson, J Mark; Ralston, Stuart H; Valdes, Ana M; Spector, Tim D; Loughlin, John

    2012-09-01

    Osteoarthritis is the most common form of arthritis worldwide and is a major cause of pain and disability in elderly people. The health economic burden of osteoarthritis is increasing commensurate with obesity prevalence and longevity. Osteoarthritis has a strong genetic component but the success of previous genetic studies has been restricted due to insufficient sample sizes and phenotype heterogeneity. We undertook a large genome-wide association study (GWAS) in 7410 unrelated and retrospectively and prospectively selected patients with severe osteoarthritis in the arcOGEN study, 80% of whom had undergone total joint replacement, and 11,009 unrelated controls from the UK. We replicated the most promising signals in an independent set of up to 7473 cases and 42,938 controls, from studies in Iceland, Estonia, the Netherlands, and the UK. All patients and controls were of European descent. We identified five genome-wide significant loci (binomial test p≤5·0×10(-8)) for association with osteoarthritis and three loci just below this threshold. The strongest association was on chromosome 3 with rs6976 (odds ratio 1·12 [95% CI 1·08-1·16]; p=7·24×10(-11)), which is in perfect linkage disequilibrium with rs11177. This SNP encodes a missense polymorphism within the nucleostemin-encoding gene GNL3. Levels of nucleostemin were raised in chondrocytes from patients with osteoarthritis in functional studies. Other significant loci were on chromosome 9 close to ASTN2, chromosome 6 between FILIP1 and SENP6, chromosome 12 close to KLHDC5 and PTHLH, and in another region of chromosome 12 close to CHST11. One of the signals close to genome-wide significance was within the FTO gene, which is involved in regulation of bodyweight-a strong risk factor for osteoarthritis. All risk variants were common in frequency and exerted small effects. Our findings provide insight into the genetics of arthritis and identify new pathways that might be amenable to future therapeutic

  9. Identification of new susceptibility loci for osteoarthritis (arcOGEN): a genome-wide association study

    PubMed Central

    2012-01-01

    Summary Background Osteoarthritis is the most common form of arthritis worldwide and is a major cause of pain and disability in elderly people. The health economic burden of osteoarthritis is increasing commensurate with obesity prevalence and longevity. Osteoarthritis has a strong genetic component but the success of previous genetic studies has been restricted due to insufficient sample sizes and phenotype heterogeneity. Methods We undertook a large genome-wide association study (GWAS) in 7410 unrelated and retrospectively and prospectively selected patients with severe osteoarthritis in the arcOGEN study, 80% of whom had undergone total joint replacement, and 11 009 unrelated controls from the UK. We replicated the most promising signals in an independent set of up to 7473 cases and 42 938 controls, from studies in Iceland, Estonia, the Netherlands, and the UK. All patients and controls were of European descent. Findings We identified five genome-wide significant loci (binomial test p≤5·0×10−8) for association with osteoarthritis and three loci just below this threshold. The strongest association was on chromosome 3 with rs6976 (odds ratio 1·12 [95% CI 1·08–1·16]; p=7·24×10−11), which is in perfect linkage disequilibrium with rs11177. This SNP encodes a missense polymorphism within the nucleostemin-encoding gene GNL3. Levels of nucleostemin were raised in chondrocytes from patients with osteoarthritis in functional studies. Other significant loci were on chromosome 9 close to ASTN2, chromosome 6 between FILIP1 and SENP6, chromosome 12 close to KLHDC5 and PTHLH, and in another region of chromosome 12 close to CHST11. One of the signals close to genome-wide significance was within the FTO gene, which is involved in regulation of bodyweight—a strong risk factor for osteoarthritis. All risk variants were common in frequency and exerted small effects. Interpretation Our findings provide insight into the genetics of arthritis and identify new

  10. Hybrid em wave - polar semiconductor interaction: A polaronic study

    SciTech Connect

    Paliwal, Ayushi Dubey, Swati; Ghosh, S.

    2015-07-31

    Present paper considers incidence of a most realistic hybrid pump wave on a weakly polar semiconductor having a very small coupling constant. Possibility of optical parametric interaction has been explored in the presence of an external transverse magnetic field. The effect of doping concentrations and transverse magnetostatic field on threshold characteristics of optical parametric interaction in polar semiconductor plasma has been studied, using hydrodynamic model of semiconductors, in the far infrared regime. Numerical estimations have been carried out by using data of weakly polar III-V GaAs semiconductor and influence of control parameters on electron-LO phonon interaction has been analyzed. A particular range of physical parameters is found to be suitable for minimum threshold. The choice of nonlinear medium and favorable range of operating parameters are crucial aspects in design and fabrication of parametric amplifiers and oscillators. The hybrid mode of the pump is found to be favorable for the onset of the said process and realization of a low cost amplifier.

  11. Computer simulation studies on significance of lipid polar head orientation.

    PubMed

    Kubica, Krystian

    2002-06-01

    Models of lipid bilayer were extended and dipole structure of polar head in lipid molecules was included. As a result a wavy structure, resembling experimentally observed 'ripple phase', was obtained. The discussion on significance of interactions between dipoles that constitute polar part of the model membrane is presented. Assumptions of the model are closer to the real conditions and reflect the real phenomena much better. Dependence of the model system behaviour on dielectric permeability, ionic strength, and temperature was studied. An influence of reduced number of freedom degrees in the dipole system on the membrane properties was also considered. It was proved that if dielectric permeability of membrane polar part is significantly smaller than water dielectric permeability then the membrane model does not have to take into account changeability of dipole tilt towards membrane surface. This assumption becomes more significant for dielectric permeability epsilon approaching epsilon = 80. Packing degree of hydrocarbon chains in hydrophobic part of the membrane is also responsible for the angle value between dipoles and the membrane surface. The model results are compared to experimental results obtained by means of fluorescence probe fluorescein-PE.

  12. [Stereoscopic neuroanatomy: comparative study between anaglyphic and light polarization techniques].

    PubMed

    Meneses, Murilo Sousa; Cruz, André Vieira; Castro, Izara Almeida; Pedrozo, Ari A

    2002-09-01

    The need of didactic material is increasing in medical science nowadays. The lack of anatomical specimens, and the toxicity of conservators, have originated an intense search for alternative ways of demonstrating the human anatomy. As a solution for this difficulty, three-dimensional (3-D) images may be used, facilitating the learning process. This study aims at comparing and describing two techniques of reproduction of bi-dimensional images into three dimensions, which is called stereoscopy. The methods evaluated are filter of colors (anaglyphic) and polarized light. Techniques were analyzed for clearness and 3-D effect. Fourteen images were evaluated by 5 people, with scores ranging from 0 to 4. Total mean scores of polarized light was superior compared to the anaglyphic technique. Both methods use the codification of the image, which means separation and exclusivity with each eye seeing its corresponding image. After several photographic essays and gradual adaptation to a better technique, based on optical physics, photography and neuroanatomical knowledge, we concluded that both techniques are suitable means for production of 3-D images. The best technique, however, considering the final quality of image was polarized light, which did not alter the natural color of the specimen, conserving clearness of images with lower cost.

  13. Using GPS Radio Occultation to study polar boundary layer properties

    NASA Astrophysics Data System (ADS)

    Ganeshan, M.; Wu, D. L.

    2015-12-01

    The sensitivity of GPS RO refractivity to moisture and temperature variations in polar regions is explored using radiosonde observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. A retrieval algorithm for the boundary layer inversion height and surface-based inversion (SBI) frequency is developed for dry atmospheric conditions (total precipitable water < 3.6 mm) that typically exist during polar winter, as well as in high-latitude, elevated regions such as eastern Antarctica and central Greenland. The algorithm is applied to the high-resolution refractivity profiles obtained over the polar Arctic region using the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) dataset for the period 2006-2013. The method is found useful for capturing the spatiotemporal variability in Arctic inversion properties. For the Arctic Ocean, the spatial patterns show a minimum inversion height (maximum SBI frequency) over the ice-covered Pacific sector similar to that observed in past studies. Monthly evolution of the inversion characteristics suggests a surface temperature control in the multi-year sea ice region, with the peak in SBI frequency occurring during the transition period from winter to spring. For central Greenland, the seasonal peak in SBI frequency occurs during winter. The diurnal variability in SBI frequency is forced mainly by solar heating, consistent with past observations. Despite some limitations, the RO refractivity profile is found quite useful for monitoring the Arctic boundary layer, and is able to capture the interannual variability of inversion characteristics.

  14. A study of multifrequency polarization pulse profiles of millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Dai, S.; Hobbs, G.; Manchester, R. N.; Kerr, M.; Shannon, R. M.; van Straten, W.; Mata, A.; Bailes, M.; Bhat, N. D. R.; Burke-Spolaor, S.; Coles, W. A.; Johnston, S.; Keith, M. J.; Levin, Y.; Osłowski, S.; Reardon, D.; Ravi, V.; Sarkissian, J. M.; Tiburzi, C.; Toomey, L.; Wang, H. G.; Wang, J.-B.; Wen, L.; Xu, R. X.; Yan, W. M.; Zhu, X.-J.

    2015-05-01

    We present high signal-to-noise ratio, multifrequency polarization pulse profiles for 24 millisecond pulsars that are being observed as part of the Parkes Pulsar Timing Array project. The pulsars are observed in three bands, centred close to 730, 1400 and 3100 MHz, using a dual-band 10 cm/50 cm receiver and the central beam of the 20-cm multibeam receiver. Observations spanning approximately six years have been carefully calibrated and summed to produce high S/N profiles. This allows us to study the individual profile components and in particular how they evolve with frequency. We also identify previously undetected profile features. For many pulsars we show that pulsed emission extends across almost the entire pulse profile. The pulse component widths and component separations follow a complex evolution with frequency; in some cases these parameters increase and in other cases they decrease with increasing frequency. The evolution with frequency of the polarization properties of the profile is also non-trivial. We provide evidence that the pre- and post-cursors generally have higher fractional linear polarization than the main pulse. We have obtained the spectral index and rotation measure for each pulsar by fitting across all three observing bands. For the majority of pulsars, the spectra follow a single power-law and the position angles follow a λ2 relation, as expected. However, clear deviations are seen for some pulsars. We also present phase-resolved measurements of the spectral index, fractional linear polarization and rotation measure. All these properties are shown to vary systematically over the pulse profile.

  15. Multiparametric study of polar ionosphere on both hemispheres

    NASA Astrophysics Data System (ADS)

    D'Angelo, Giulia; Alfonsi, Lucilla; Spogli, Luca; Cesaroni, Claudio; Sgrigna, Vittorio

    2016-04-01

    The polar ionosphere is a complex system in which several actors concur to establish the observed medium. Indeed the coupling between the interplanetary magnetic field and the earth magnetic field determines a high degree of complexity of the polar ionosphere, which is directly exposed to the variations of the solar wind. This configuration results in a strong sensitivity of the polar ionosphere to the perturbation phenomena caused by solar events which may result in a wide variety of spatial and temporal dimensions of the plasma electron density irregularities. Polar ionospheric irregularities may seriously jeopardize performance and reliability level of the navigation and positioning technological systems, such as GPS or the nascent Galileo. Therefore, knowledge of the physical state of the upper atmosphere ionized layers becomes essential to predict and mitigate events that may affect the use of modern technology, causing economic damage and, in severe cases, even jeopardizing the safety of human beings. In this context, a careful and thorough investigation that covers a wide range of geospatial different disturbances, observed in circumterrestrial space and on the ground, can provide the necessary basis for a real advance of the current knowledge. In this frame, the aim of this work is to contribute to the study of the effects of perturbation induced by the Sun on the polar ionosphere of both the hemispheres, through the analysis and interpretation of the measures available before, during and after the occurrence of an event of disturbance. We propose a multiparametric approach, that combines the information derived from measurements acquired by ground-based and space-based stations, to have a broad spectrum of information necessary to characterize the ionospheric disturbances on different time scales (from milliseconds to days) and spatial scales (from millimetres to hundreds meters/kilometres). The period chosen for this study is the entire month of March

  16. Cirrus and Polar Stratospheric Cloud Studies using CLAES Data

    NASA Technical Reports Server (NTRS)

    Mergenthaler, John L.; Douglass, A. (Technical Monitor)

    2001-01-01

    We've concluded a 3 year (Period of Performance- January 21, 1998 to February 28, 2001) study of cirrus and polar stratospheric clouds using CLAES (Cryogenic Limb Array Etalon Spectrometer) data. We have described the progress of this study in monthly reports, UARS (Upper Atmosphere Research Satellite) science team meetings, American Geophysical Society Meetings, refereed publications and collaborative publications. Work undertaken includes the establishment of CLAES cloud detection criteria, the refinement of CLAES temperature retrieval techniques, compare the findings of CLAES with those of other instruments, and present findings to the larger community. This report describes the progress made in these areas.

  17. Polarization Studies in Fast-Ion Beam Spectroscopy

    SciTech Connect

    Trabert, E

    2001-12-20

    In a historical review, the observations and the insight gained from polarization studies of fast ions interacting with solid targets are presented. These began with J. Macek's recognition of zero-field quantum beats in beam-foil spectroscopy as indicating alignment, and D.G. Ellis' density operator analysis that suggested the observability of orientation when using tilted foils. Lastly H. Winter's studies of the ion-beam surface interaction at grazing incidence yielded the means to produce a high degree of nuclear orientation in ion beams.

  18. Spin polarized photoemission studies of interfacial and thin film magnetism

    SciTech Connect

    Johnson, P.D.; Brookes, N.B.; Chang, Y.; Garrison, K.

    1993-01-01

    Spin polarized photoemission is used to study the electronic structure of noble metals deposited on ferromagnetic substrates. Studies of Ag deposited on an Fe(001) substrate reveal a series of minority spin interface or quantum well states with binding energies dependent on the thickness of the silver. Similar behavior is observed for Cu films deposited on a fct Co(001) substrate. Tight-binding modeling reproduces many of the observations and shows that hybridization of the sp-bands with the noble metal d-bands cannot be ignored.

  19. Spin polarized photoemission studies of interfacial and thin film magnetism

    SciTech Connect

    Johnson, P.D.; Brookes, N.B.; Chang, Y.; Garrison, K.

    1993-06-01

    Spin polarized photoemission is used to study the electronic structure of noble metals deposited on ferromagnetic substrates. Studies of Ag deposited on an Fe(001) substrate reveal a series of minority spin interface or quantum well states with binding energies dependent on the thickness of the silver. Similar behavior is observed for Cu films deposited on a fct Co(001) substrate. Tight-binding modeling reproduces many of the observations and shows that hybridization of the sp-bands with the noble metal d-bands cannot be ignored.

  20. A comparative study of silver nanoparticles synthesized by arc discharge and femtosecond laser ablation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhang, Hongqiang; Zou, Guisheng; Liu, Lei; Li, Yong; Tong, Hao; Sun, Zhenguo; Zhou, Y. Norman

    2016-10-01

    Silver nanoparticles have been synthesized by arc discharge and femtosecond laser ablation in polyvinylpyrrolidone (PVP) aqueous solution. Both methods are the simple, cost-effective and environment-friendly way to obtain the purity silver nanoparticles. In this study, the structure, composition, morphology, size and distribution, stability, production rate and sintering properties of silver nanoparticles synthesized by both methods were compared. The spherical or pseudo-spherical silver nanoparticles were synthesized by both methods, and the diameters were below 50 nm. The arc discharge-synthesized particle distribution varied with the breakdown voltage, and laser-synthesized particle size mainly depended on the laser energy. PVP solution could cap and stabilize the silver nanoparticles by Ag-O bond, while arc discharge and laser ablation resulted in some level of PVP degradation during processing. Sliver nanoparticle colloids synthesized by both methods had the high negative values of zeta potential and exhibited the good stability. The maximum production rates of the silver nanoparticles synthesized by arc discharge and femtosecond laser ablation were 6.0 and 3.0 mg/min, respectively. In addition, the sintering properties of silver nanoparticles synthesized by both methods were also discussed.

  1. Experimental study of the mechanical stabilization of electric arc furnace dust using fluid cement mortars.

    PubMed

    Ledesma, E F; Jiménez, J R; Ayuso, J; Fernández, J M; Brito, J de

    2017-03-15

    This article shows the results of an experimental study carried out in order to determine the maximum amount of electric arc furnace dust (EAFD) that can be incorporated into fluid cement-based mortars to produce mechanically stable monolithic blocks. The leaching performance of all mixes was studied in order to classify them according to the EU Council Decision 2003/33/EC. Two mortars were used as reference and three levels of EAFD incorporation were tested in each of the reference mortars. As the incorporation ratio of EAFD/cement increases, the mechanical strength decreases. This is due to the greater EAFD/cement and water/cement ratios, besides the presence of a double-hydrated hydroxide of Ca and Zn (CaZn2(OH)6·2H2O) instead of the portlandite phase (Ca(OH)2) in the mixes made with EAFD, as well as non-hydrated tricalcium silicate. A mass ratio of 2:1 (EAFD: cement-based mortar) can be added maintaining a stable mechanical strength. The mechanical stabilization process also reduced the leaching of metals, although it was not able to reduce the Pb concentration below the limit for hazardous waste. The high amount of EAFD mechanically stabilized in this experimental study can be useful to reduce the storage volume required in hazardous waste landfills.

  2. The global relevance of the Scotia Arc: An introduction

    NASA Astrophysics Data System (ADS)

    Maldonado, Andrés; Dalziel, Ian W. D.; Leat, Philip T.

    2015-02-01

    The Scotia Arc, situated between South America and Antarctica, is one of the Earth's most important ocean gateways and former land bridges. Understanding its structure and development is critical for the knowledge of tectonic, paleoenvironmental and biological processes in the southern oceans and Antarctica. It extends from the Drake Passage in the west, where the Shackleton Fracture Zone forms a prominent, but discontinuous, bathymetric ridge between the southern South American continent and the northern tip of the Antarctic Peninsula to the active intra-oceanic volcanic arc forming the South Sandwich Island in the east. The tectonic arc comprises the NSR to the north and to the south the South Scotia Ridge, both transcurrent plate margins that respectively include the South Georgia and South Orkney microcontinents. The Scotia and Sandwich tectonic plates form the major basin within these margins. As the basins opened, formation of first shallow sea ways and then deep ocean connections controlled the initiation and development of the Antarctic Circumpolar Current, which is widely thought to have been important in providing the climatic conditions for formation of the polar ice-sheets. The evolution of the Scotia Arc is therefore of global palaeoclimatic significance. The Scotia Arc has been the focus of increasing international research interest. Many recent studies have stressed the links and interactions between the solid Earth, oceanographic, paleoenvironmental and biological processes in the area. This special issue presents new works that summarize significant recent research results and synthesize the current state of knowledge for the Scotia Arc.

  3. Comparative studies of efficiency droop in polar and non-polar InGaN quantum wells

    SciTech Connect

    Davies, M. J.; Dawson, P.; Hammersley, S.; Zhu, T.; Kappers, M. J.; Humphreys, C. J.; Oliver, R. A.

    2016-06-20

    We report on a comparative study of efficiency droop in polar and non-polar InGaN quantum well structures at T = 10 K. To ensure that the experiments were carried out with identical carrier densities for any particular excitation power density, we used laser pulses of duration ∼100 fs at a repetition rate of 400 kHz. For both types of structures, efficiency droop was observed to occur for carrier densities of above 7 × 10{sup 11 }cm{sup −2 }pulse{sup −1} per quantum well; also both structures exhibited similar spectral broadening in the droop regime. These results show that efficiency droop is intrinsic in InGaN quantum wells, whether polar or non-polar, and is a function, specifically, of carrier density.

  4. Study on effect of plasma surface treatments for diamond deposition by DC arc plasmatron.

    PubMed

    Kang, In-Je; Joa, Sang-Beom; Lee, Heon-Ju

    2013-11-01

    To improve the thermal conductivity and wear resistance of ceramic materials in the field of renewable energy technologies, diamond coating by plasma processing has been carried out in recent years. This study's goal is to improve diamond deposition on Al2O3 ceramic substrates by plasma surface treatments. Before diamond deposition was carried out in a vacuum, plasma surface treatments using Ar gas were conducted to improve conditions for deposition. We also conducted plasma processing for diamond deposition on Al2O3 ceramic substrates using a DC arc Plasmatron. The Al2O3 ceramic substrates with diamond film (5 x 15 mm2), were investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then, the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) was studied. We identified nanocrystalline diamond films on the Al2O3 ceramic substrates. The results showed us that the deposition rate of diamond films was 2.3 microm/h after plasma surface treatments. Comparing the above result with untreated ceramic substrates, the deposition rate improved with the surface roughness of the deposited diamond films.

  5. A petrological and geochemical study on time-series samples from Klyuchevskoy volcano, Kamchatka arc

    NASA Astrophysics Data System (ADS)

    Bergal-Kuvikas, Olga; Nakagawa, Mitsuhiro; Kuritani, Takeshi; Muravyev, Yaroslav; Malik, Nataliya; Klimenko, Elena; Amma-Miyasaka, Mizuho; Matsumoto, Akiko; Shimada, Shunjiro

    2017-05-01

    To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0-55.5 wt.% SiO2), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by 13% melting of a source mantle with 0.7 wt.% H2O at 1245-1260 °C and 1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937-1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from AD 1960 to present.

  6. Fractional crystallization of primitive, hydrous arc magmas: an experimental study at 0.7 GPa

    NASA Astrophysics Data System (ADS)

    Nandedkar, Rohit H.; Ulmer, Peter; Müntener, Othmar

    2014-06-01

    Differentiation of mantle-derived, hydrous, basaltic magmas is a fundamental process to produce evolved intermediate to SiO2-rich magmas that form the bulk of the middle to shallow continental and island arc crust. This study reports the results of fractional crystallization experiments conducted in a piston cylinder apparatus at 0.7 GPa for hydrous, calc-alkaline to arc tholeiitic magmas. Fractional crystallization was approached by synthesis of starting materials representing the liquid composition of the previous, higher temperature experiment. Temperatures ranged from near-liquidus at 1,170 °C to near-solidus conditions at 700 °C. H2O contents varied from 3.0 to more than 10 wt%. The liquid line of descent covers the entire compositional range from olivine-tholeiite (1,170 °C) to high-silica rhyolite (700 °C) and evolves from metaluminous to peraluminous compositions. The following crystallization sequence has been established: olivine → clinopyroxene → plagioclase, spinel → orthopyroxene, amphibole, titanomagnetite → apatite → quartz, biotite. Anorthite-rich plagioclase and spinel are responsible for a marked increase in SiO2-content (from 51 to 53 wt%) at 1,040 °C. At lower temperatures, fractionation of amphibole, plagioclase and Fe-Ti oxide over a temperature interval of 280 °C drives the SiO2 content continuously from 53 to 78 wt%. Largest crystallization steps were recorded around 1,040 °C and at 700 °C. About 40 % of ultramafic plutonic rocks have to crystallize to generate basaltic-andesitic liquids, and an additional 40 % of amphibole-gabbroic cumulate to produce granitic melts. Andesitic liquids with a liquidus temperature of 1,010 °C only crystallize 50 % over an 280 °C wide range to 730 °C implying that such liquids form mobile crystal mushes (<50 % crystals) in long-lived magmatic systems in the middle crust, allowing for extensive fractionation, assimilation and hybridization with periodic replenishment of more mafic magmas

  7. Methods of studying polarization of variable star radiation

    NASA Technical Reports Server (NTRS)

    Shakhovskoy, N. M.

    1973-01-01

    Polarized light from variable stars can be used to determine radiation intensity and wavelength. Various types of polarization analyzers are discussed (single-beam and double-beam) as well as their modes of use (continuous and discrete). Modulation of polarizers and determination of measurement accuracy are also covered.

  8. Theoretical study of the seasonal and solar cycle variations of stable aurora red arcs

    SciTech Connect

    Kozyra, J.U.; Valladares, C.E.; Carlson, H.C.; Buonsanto, M.J.; Slater, D.W.

    1990-08-01

    SAR arc statistic provide information on the seasonal and solar cycle variations in the subauroral region electron temperature peak and associated magnetospheric energy source. There are two sources of long-term (solar cycle and seasonal) variability in the magnitude of the subauroral region electron temperature peak and associated SAR are emission intensity: (1) the neutral atmosphere and ionosphere and (2) the magnetospheric energy source. The results of this study indicate that the observed seasonal variation in SAR are intensities can be explained reasonably well by seasonal variations in the neutral atmosphere and ionosphere. True solstice effect are unlikely to result from difference in a near-equatorial magnetospheric heat source since the same heat source supplies both the summer and the winter hemispheres at opposite ends of a common flux tube. Observed solar cycle variations in SAR are intensity for a fixed ring current strength (as represented by the D sub st index) are not consistent with variations predicted solely on the basis of a solar cycle changes in the neutral atmosphere and ionosphere. A reduction of the magnetospheric heat flux by a factor of between 5 and 20 from solar maximum to solar minimum conditions is necessary to bring model electron temperatures and 6300 emission intensity into agreement with observational results for moderately disturbed conditions D sub st approx - 80 gamma. The required reduction in the magnetospheric energy source with decreasing solar cycle is attributed to compositional changes in the magnetospheric plasma.

  9. A pilot study of volumetric-modulated arc therapy for malignant pleural mesothelioma.

    PubMed

    Runxiao, Li; Yankun, Cao; Lan, Wang

    2016-03-08

    Malignant pleural mesothelioma (MPM) is an extremely difficult disease to treat. This pilot study investigates the feasibility of using volumetric-modulated arc therapy (VMAT) for malignant pleural mesothelioma (MPM), and compares VMAT to static field intensity-modulated radiotherapy (IMRT) for five patients. To identify the best treatment technique for MPM, in five patients, we made a representative comparative analysis of two kinds of techniques for radiation therapy planning: IMRT and VMAT. The plans were created for an Elekta Synergy linear accelerator with 6 MV photons using Oncentra version 4.3 treatment planning system. Dose prescription was 50 Gy to the average of the planning target volume (PTV). PTV coverage and homogeneity, dose of organs at risk, numbers of segments, MUs, and delivery time were evaluated for all techniques. VMAT allowed better homogeneous and conformity indices compared with IMRT (HI = 0.17 vs. 0.12, CI = 0.64 vs. 0.77, respectively, p < 0.05). VMAT plan had a significantly shorter delivery time (326 s) compared with in IMRT plans (510 s), (p < 0.05). In the dose verification, an average of 93.16% of the detector points passed the 3%/3 mmγ criterion for VMAT plans, while in IMRT plans the dose verification was 95.12%.(p > 0.05).

  10. Dissolution Dynamic Nuclear Polarization capability study with fluid path.

    PubMed

    Malinowski, Ronja M; Lipsø, Kasper W; Lerche, Mathilde H; Ardenkjær-Larsen, Jan H

    2016-11-01

    Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Dissolution Dynamic Nuclear Polarization capability study with fluid path

    NASA Astrophysics Data System (ADS)

    Malinowski, Ronja M.; Lipsø, Kasper W.; Lerche, Mathilde H.; Ardenkjær-Larsen, Jan H.

    2016-11-01

    Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies.

  12. A study for polarized illumination effects in photo resist

    NASA Astrophysics Data System (ADS)

    Lei, Junjiang; Bai, Min; Shiely, Jim; Zhang, Lin

    2005-06-01

    Using a polarized illumination source is a promising RET technique for improvement of wafer printability for features of 65 nm and below. Polarization effects could be considered in several different stages of lithography modeling and simulation. For example, light propagation in thin films, wave superstition and interference in the thin film stack, and mask-induced polarization all deserve special attention and delicate treatment because TE and TM waves have different behaviors through these stages. In this paper we consider effects of polarized illumination in photo resist, using the Kirchhoff approximation for masks. We discuss some theoretical aspects of our vector modeling methods and show an example of simulation for polarized illumination effects.

  13. Study of polarization control model for piezoelectric actuator.

    PubMed

    Ru, Changhai; Sun, Lining

    2006-12-22

    A major deficiency of piezoelectric actuator is that their control accuracy is seriously limited by hysteresis. In this paper, the reason why hysteresis can be reduced by controlling polarization is explained according to the analysis of microscopic polarization mechanism and domain wall theory of piezoelectric actuator. The reason of occurring hysteresis in voltage control mode is also given. Then a control model based polarization is derived. In order to evaluate its effectiveness, the control method based on polarization is realized by controlling the charge of piezoelectric actuator. The experimental results show that the polarization control method is significantly more linear and less hysteresis than the voltage control method.

  14. Performance study of the gamma-ray bursts polarimeter POLAR

    NASA Astrophysics Data System (ADS)

    Sun, J. C.; Wu, B. B.; Bao, T. W.; Batsch, T.; Bernasconi, T.; Britvitch, I.; Cadoux, F.; Cernuda, I.; Chai, J. Y.; Dong, Y. W.; Gauvin, N.; Hajdas, W.; He, J. J.; Kole, M.; Kong, M. N.; Kong, S. W.; Lechanoine-Leluc, C.; Li, Lu; Liu, J. T.; Liu, X.; Marcinkowski, R.; Orsi, S.; Pohl, M.; Produit, N.; Rapin, D.; Rutczynska, A.; Rybka, D.; Shi, H. L.; Song, L. M.; Szabelski, J.; Wang, R. J.; Wen, X.; Xiao, H. L.; Xiong, S. L.; Xu, H. H.; Xu, M.; Zhang, L.; Zhang, L. Y.; Zhang, S. N.; Zhang, X. F.; Zhang, Y. J.; Zwolinska, A.

    2016-07-01

    The Gamma-ray Burst Polarimeter-POLAR is a highly sensitive detector which is dedicated to the measurement of GRB's polarization with a large effective detection area and a large field of view (FOV). The optimized performance of POLAR will contribute to the capture and measurement of the transient sources like GRBs and Solar Flares. The detection energy range of POLAR is 50 keV 500 keV, and mainly dominated by the Compton scattering effect. POLAR consists of 25 detector modular units (DMUs), and each DMU is composed of low Z material Plastic Scintillators (PS), multi-anode photomultipliers (MAPMT) and multi-channel ASIC Front-end Electronics (FEE). POLAR experiment is an international collaboration project involving China, Switzerland and Poland, and is expected to be launched in September in 2016 onboard the Chinese space laboratory "Tiangong-2 (TG-2)". With the efforts from the collaborations, POLAR has experienced the Demonstration Model (DM) phase, Engineering and Qualification Model (EQM) phase, Qualification Model (QM) phase, and now a full Flight Model (FM) of POLAR has been constructed. The FM of POLAR has passed the environmental acceptance tests (thermal cycling, vibration, shock and thermal vacuum tests) and experienced the calibration tests with both radioactive sources and 100% polarized Gamma-Ray beam at ESRF after its construction. The design of POLAR, Monte-Carlo simulation analysis, as well as the performance test results will all be introduced in this paper.

  15. Study of the Polarization Strategy for Electron Cyclotron Heating Systems on HL-2M

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Huang, M.; Xia, D. H.; Song, S. D.; Wang, J. Q.; Huang, B.; Wang, H.

    2016-06-01

    As important components integrated in transmission lines of electron cyclotron heating systems, polarizers are mainly used to obtain the desired polarization for highly efficient coupling between electron cyclotron waves and plasma. The polarization strategy for 105-GHz electron cyclotron heating systems of HL-2M tokamak is studied in this paper. Considering the polarizers need high efficiency, stability, and low loss to realize any polarization states, two sinusoidal-grooved polarizers, which include a linear polarizer and an elliptical polarizer, are designed with the coordinate transformation method. The parameters, the period p and the depth d, of two sinusoidal-grooved polarizers are optimized by a phase difference analysis method to achieve an almost arbitrary polarization. Finally, the optimized polarizers are manufactured and their polarization characteristics are tested with a low-power test platform. The experimental results agree well with the numerical calculations, indicating that the designed polarizers can meet the polarization requirements of the electron cyclotron heating systems of HL-2M tokamak.

  16. Dynamic nuclear polarization studies on deuterated nitroxyl spin probes.

    PubMed

    David Jebaraj, D; Utsumi, Hideo; Milton Franklin Benial, A

    2017-10-01

    Detailed dynamic nuclear polarization and electron spin resonance studies were carried out for 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl,3-methoxycarbonyl-2,2,5,5-tetramethy pyrolidine-1-oxyl nitroxyl radicals and their corresponding deuterated nitroxyl radicals, used in Overhauser-enhanced magnetic resonance imaging for the first time. The dynamic nuclear polarization parameters such as dynamic nuclear polarization (DNP) factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for deuterated nitroxyl radicals. DNP enhancement increases with agent concentration up to 3 mm and decreases above 3 mm. The proton spin-lattice relaxation time and the longitudinal relaxivity parameters were estimated. The leakage factor increases with increasing agent concentration up to 3 mm and reaches plateau in the region 3-5 mm. The coupling parameter shows the interaction between the electron and nuclear spins to be mainly dipolar in origin. DNP spectrum exhibits that the full width at half maximum values are higher for undeuterated nitroxyl radicals compared with deuterated nitroxyl radicals, which leads to the increase in DNP enhancement. The ESR parameters such as, the line width, line shape, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were calculated. The narrow line width was observed for deuterated nitroxyl radicals compared with undeuterated nitroxyl radicals, which leads to the higher saturation parameter value and DNP enhancement. The novelty of the work permits clear understanding of the DNP parameters determining the higher DNP enhancement compared with the undeuterated nitroxyl radicals. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  17. Tropospheric ozone surface depletion (spring) and pollution (summer) in 2008 from the ARCTAS Intensive Ozonesonde Network Study (ARC-IONS) soundings

    NASA Astrophysics Data System (ADS)

    Thompson, A. M.; Luzik, A. M.; Doughty, D. C.; Gallagher, S. D.; Miller, S. K.; Oltmans, S. J.; Tarasick, D. W.; Witte, J. C.; Bryan, A. M.; Walker, T.; Osterman, G. B.; Worden, J.

    2008-12-01

    During NASA's ARCTAS (Arctic Research of the Composition of the Troposphere with Aircraft and Satellites; http://espo.nasa.gov/arctas) spring and summer 2008 campaigns, an ozonesonde network, ARC- IONS (ARCTAS Intensive Ozonesonde Network Study), launched ozonesonde-radiosonde packages each day (1-20 April, 26 June-12 July) during the A-Train satellite constellation overpass, ~1300 local. Seventeen ARC-IONS stations were located across the northern tier of North America, over both Alaska and Canada, with one site in Greenland and two in the western US; map at (http://croc.gsfc.nasa.gov/arcions). In addition to satellite validation, the soundings provided a coherent, well-distributed set of ozone profiles for: (1) comparison with and interpretation of airborne measurements; (2) complementarity to ARCTAS and IPY (International Polar Year) ground bases at Greenland, Barrow, Eureka, Yellowknife; (3) model evaluation; (4) investigations of processes affecting day-to-day ozone variability. Two aspects of tropospheric ozone variability are described here. First, ozone depletion likely associated with rapid halogen reactions, is prominent in spring at Barrow (71N, 157W) and Resolute (75N, 95W). Second, during summer, relationships among long-range transport of Asian pollution (industrial and fires), California and Canadian fires and daily ozone budgets are established with trajectories, satellite smoke/fire data and laminar identification, the latter method developed in Thompson et al. (2007) and Yorks et al. (2008). Canadian maritime stations display eastern seaboard pollution and stratospheric influences as in IONS-04 (INTEX Ozonesonde Network Study).

  18. Large optical conductivity of Dirac semimetal Fermi arc surface states

    NASA Astrophysics Data System (ADS)

    Shi, Li-kun; Song, Justin C. W.

    2017-08-01

    Fermi arc surface states, a hallmark of topological Dirac semimetals, can host carriers that exhibit unusual dynamics distinct from that of their parent bulk. Here we find that Fermi arc carriers in intrinsic Dirac semimetals possess a strong and anisotropic light-matter interaction. This is characterized by a large Fermi arc optical conductivity when light is polarized transverse to the Fermi arc; when light is polarized along the Fermi arc, Fermi arc optical conductivity is significantly muted. The large surface spectral weight is locked to the wide separation between Dirac nodes and persists as a large Drude weight of Fermi arc carriers when the system is doped. As a result, large and anisotropic Fermi arc conductivity provides a novel means of optically interrogating the topological surfaces states of Dirac semimetals.

  19. Studies of Interactions Between Nano-Objects and Polarized Light

    NASA Astrophysics Data System (ADS)

    Xie, Dan

    Optical studies of nano-objects that have dimensions 10--1000 nm have become a flourishing field of research. This special dimension category, connecting the smaller (molecular) world and the larger (cellular) world, have enabled these nano-objects to be widely utilized as novel optical tools in many fields. In addition to the extensive applications of nano objects, increasing efforts are also being put to better understand their interactions with light at a fundamental level. The work presented in this dissertation is part of such efforts, in which I selected three types of nano-objects and studied their optical properties both in theory and experiment. Second-harmonic and sum-frequency generations are among the most well-known nonlinear optical processes. Dielectric nanocrystals that are SHG- and SFG-active are favored tools in bioimaging. For a nanocrystal, its SHG/SFG intensity depends on the geometry of the light-particle system, i.e., the relationship between the nanocrystal orientation and the laser polarization. Using BaTiO 3 nanocrystals as an example, I carried out an in-depth, theoretical investigation of such dependence. Particularly, I studied the possibility of selectively maximizing the contrast between light signals from two or more nanocrystals by manipulating laser polarization. I will present a discussion on how the capacity of this selective illumination depends on the relative orientation between the two nanocrystals and the polarization of the excitation field. The optical responses of non-spherical plasmonic particles, being dynamic and complex, are only partially understood. Gold nanorods (AuNRs) are one of the most popular members in this nanoparticle family. They can produce two-photon luminescence (TPL) and amplify molecular events occurring at their surface. Both phenomena are known to be associated with surface plasmon resonances (SPR) of AuNRs, but details of the mechanisms are yet to be understood and quantified. I constructed a two

  20. Alignment and Polarization Sensitivity Study on the Cassini: CIRS FIR Interferometer

    NASA Technical Reports Server (NTRS)

    Crooke, Julie; Hagopian, John

    1998-01-01

    The Composite InfraRed Spectrometer (CIRS) instrument flying on the Cassini spacecraft to Saturn is a cryogenic spectrometer with far-infrared (FIR) and mid-infrared (MIR) channels. The CIRS FIR channel is a polarizing interferometer that contains three polarizing grid components. These components are an input polarizer, a polarizing beamsplitter, and an output polarizer/analyzer. They consist of a 1.5 micron thick mylar substrate with 2 microns wide copper wires, with 2 microns spacing (4 microns pitch) photolithographically deposited on the substrate. This paper details the alignment sensitivity studies performed on the polarizing beamsplitter, and the polarization sensitivity studies performed on all three polarizing components in the FIR interferometer.

  1. Spectroscopic studies of plasma in a carbon arc discharge for synthesis of nanomaterials

    NASA Astrophysics Data System (ADS)

    Vekselman, Vladislav; Feurer, Matthew; Yeh, Yao-Wen; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-09-01

    An atmospheric pressure arc discharge with graphite electrodes is commonly used for synthesis of carbon nanomaterials such as buckyballs, nanotubes and graphene. In operation, the graphite anode ablates providing a feedstock material for synthesis these carbon nanostructures. Existing models predict that nucleation and growth of these nanomaterials in an arc discharge are governed by spatial distributions of density and temperature of plasma species. Control of these distributions can potentially enable optimization of nanosynthesis processes, to achieve the best combination of synthesis selectivity at the synthesis yield. In this work, we report first detail measurements of spatial distribution of arc plasma parameters obtained with a set of in-situ diagnostics, including optical emission spectroscopy and fast framing imaging. These parameters were measured in low- and high- anode ablation modes. Results of these measurements demonstrate a strong correlation between arc plasma and synthesis processes. This work was supported by U.S. Department of Energy, Office of Science, Basic Sciences, Materials Sciences and Engineering Division.

  2. Arc-furnace model for the study of flicker compensation in electrical networks

    SciTech Connect

    Montanari, G.C.; Loggini, M.; Cavallini, A.; Pitti, L. . Istituto di Elettrotecnica Industriale); Zaninelli, D. . Dipt. di Elettrotecnica)

    1994-10-01

    This paper presents an arc-furnace model consisting of non-linear, time varying resistance where two different time-variation laws of arc length are considered. One consists of a periodic, sinusoidal law, the other of a band-limited white-noise law. The arc-furnace model is implemented by EMTP, referring to actual electric-plant configurations. Simulations are reported where the values of flicker sensation and short-term flicker severity, P[sub ST], are determined according to UIE specifications. It results that the model based on sinusoidal time-variation law can be useful for worst-case approximations, while the model using white-noise law is able to fit flicker measurements made in electric plants supplying arc furnaces. The models are used to investigate the effect on flicker compensation of the insertion of series inductors at the supply side of the furnace transformer. It is shown that considerable reduction of P[sub ST] is obtained at the point of common coupling by series inductor installation at constant furnace active power.

  3. Sources and timing of pyroxenite formation in the sub-arc mantle: Case study of the Cabo Ortegal Complex, Spain

    NASA Astrophysics Data System (ADS)

    Tilhac, Romain; Grégoire, Michel; O'Reilly, Suzanne Y.; Griffin, William L.; Henry, Hadrien; Ceuleneer, Georges

    2017-09-01

    on the sources of the metasomatic agents involved (and potentially the parental melts) and notably indicate the contributions from enriched mantle components (EM I and/or II). This suggests the involvement of an old crustal component, which is consistent with the derivation of the pyroxenites and granulites from an ensialic island arc, potentially built on the northern margin of either Gondwana or a pre-Gondwanan continental block. This case study thus documents the role of melt-rock reactions as major pyroxenite-forming processes in the sub-arc mantle, providing further constraints on their sources and timing in the Cabo Ortegal Complex.

  4. Spin-exchange polarization study at the TRIUMF OPPIS

    SciTech Connect

    Zelenski, A.N.; Levy, C.D.P.; van Oers, W.T.H.; Schmor, P.W.; Welz, J.; Wight, G.W.

    1995-07-15

    The TRIUMF optically pumped polarized ion source (OPPIS) now produces 56 {mu}A H{sup {minus}} ion current and 85% polarization for routine operation and 120 {mu}A and 78% polarization in high current mode. This is a result of the latest ECR primary proton source improvements and optimization of optical pumping efficiency. It has been shown that in a pulsed mode suitable for high energy accelerator applications, it is possible to produce 1--2 mA of polarized H{sup {minus}} current in a charge-exchange OPPIS based on the INR-scheme(1). A possible INR-scheme upgrade to the 10 mA range is discussed. The experimental results on spin-exchange polarization presented in this paper hold promise of polarized H{sup {minus}} current increasing to the 10 mA range.

  5. Unpolarized nucleon structure studies utilizing polarized electromagnetic probes.

    SciTech Connect

    Arrington, J.; Physics

    2009-08-15

    By the mid-1980s, measurements of the nucleon form factors had reached a stage where only slow, incremental progress was possible using unpolarized electron scattering. The development of high quality polarized beams, polarized targets, and recoil polarimeters led to a renaissance in the experimental program. I provide an overview of the changes in the field in the last ten years, which were driven by the dramatically improved data made possible by a new family of tools to measure polarization observables.

  6. Morphological study of graphite-encapsulated iron composite nanoparticles fabricated by a one-step arc discharge method

    NASA Astrophysics Data System (ADS)

    Hu, Rui; Furukawa, Taiki; Wang, Xiangke; Nagatsu, Masaaki

    2017-09-01

    Arc discharge is one of the most efficient approaches to fabricate graphite-encapsulated magnetic nanoparticles. However, given the ultra-fast synthetic procedure, the understanding of tailoring shell morphology and quality over magnetic core has been a long standing challenge. To better comprehend the mechanism of the encapsulating shell growth in plasma, a series of synthetic parameters were investigated systematically in this study. Specifically, (1) the surface morphology of the outmost shell evolved with high integrity by adding CH4 concentration from 0% to 50% to He background gas; (2) a smooth surface with higher graphitization degree was achieved by changing collecting zone closer to the arc center; (3) carbon nano loops on the outmost shell expanded volumetrically to be continuous amorphous cover as the working gas pressure decreases from 100 to 25 Torr. The surface properties (i.e., zeta potential and acid-base character) were also evaluated and explained through XPS technique.

  7. STUDY OF MECHANICAL ENGINEERING FEATURES OF POLAR WATER SUPPLY

    DTIC Science & Technology

    WATER SUPPLIES, ALGAE, CHEMICAL ANALYSIS, GROWTH(PHYSIOLOGY), MECHANICAL ENGINEERING , PERMAFROST, PHYSICAL PROPERTIES, POLAR REGIONS, PURIFICATION, SANITARY ENGINEERING, WATER, WATER FILTERS, WATER SOFTENERS

  8. Mineralogical and Fluid Inclusion Studies on Seafloor Hydrothermal Vents at TA25 Caldera, Tonga Arc

    NASA Astrophysics Data System (ADS)

    Choi, S. K.; Pak, S. J.; Choi, S. H.; Lee, K. Y.; Kim, H. S.; Lee, I. K.

    2015-12-01

    The extensive hydrothermal vent field was discovered at TA25("V18s-HR" in the SO-167 cruise) caldera in the Tonga arc, southwest Pacific. The TA25 caldera is a submarine volcano of dacitic composition and hosts the NE- and NW-trending hydrothermal vent on the western caldera wall. These active hydrothermal crusters are mostly small (chimney: <0.5m in tall; sulfide mound: <3m in diameter) and immature, and emit the transparent fluids of which temperature range from 150℃ to 242℃ (average = 203℃). The hydrothermal sulfide ores, recovered by ROV and/or TV-grab, are mainly composed of sphalerite, pyrite, marcasite, galena, chalcopyrite, covellite, tennantite, enargite and sulfates such as barite, gypsum/anhydrite. It is observed that three distinct mineralogical zonation from exterior to interior of the chimneys: (1) barite-gypsum/anhydrite-pyrite-sphalerite; (2) sphalerite-pyrite-galena±chalcopyrite; (3) sphaleirte-pyrite-chalcopyrite-enargite-tennantite±galena±covellite. FeS content in sphalerite increases from chimney exterior to interior. Chalcopyrite is more abundant in the mound than in the chimney, implying fluid temperatures in mound are greater than in the chimney. The enargite assemblage (pyrite-chalcopyrite-enargite-tennantite) is indicative of high-sulfidation epithermal deposits. Fluid inclusions on barite crystals from mound samples show mono-type inclusion (two-phase liquid-rich inclusions) which is less than 20㎛ in diameter. Homogenization temperatures and salinities from fluid inclusion study range from 148℃ to 341℃ (average = 213℃) and 0.4 to 3.6 equiv. wt.% NaCl, respectively. The main mineralization temperature in mound might be greater than 200℃ since barite on fluid inclusion is early stage mineral.

  9. SU-E-T-78: A Study of Dose Falloff Gradient in RapidArc Planning of Lung SBRT

    SciTech Connect

    Desai, D; Srinivasan, S; Elasmar, H; Johnson, E

    2015-06-15

    Purpose: Rapid dose falloff beyond PTV is an important criterion for normal tissue sparing in SBRT. RTOG protocols use D2cm and R50% for plan quality evaluation. This study is aimed at analyzing the dose falloff gradient beyond the PTV extending into normal tissue structures and to ascertain the impact of PTV geometry and location on the dose falloff gradient in RapidArc planning of lung SBRT Methods: In this retrospective study, we analyzed 39 clinical RapidArc lung SBRT treatment plans that met RTOG-0915 criteria. Planning was done on Eclipse 8.9 for delivery on either Novalis NTx or TrueBeam STx equipped with HD MLCs. PTV volumes ranged between 5.3 and 113 cc (2.2 to 6 cm sphere equivalent diameter respectively) and their geographic locations were distributed in both lungs. 6X, 6X-FFF, 10X, and 10X-FFF energies were used for planning. All of these SBRT plans were planned using either 2 or 3 full or hemi arcs, with moderate couch kicks. Dose falloff gradients were obtained by generating 7 concentric 5 mm rings beyond PTV surface. Mean dose in each ring is used to evaluate percentage dose falloff gradient as a function of distance from the PTV surface. Results: The mean percentage dose falloff beyond PTV surface in all plans followed an exponential decay and the data was modeled with double exponential decay fit. Photon energy selection in the plan had a minimal impact on the mean percentage dose fall off beyond PTV surface. Conclusion: Dose falloff beyond PTV surface as a function of distance can be ascertained by the use of the double exponential decay fit coefficients in RapidArc planning of lung SBRT. This will help also in plan quality evaluation in addition to D2cm and R50% defined by RTOG.

  10. Planning Study of Flattening Filter Free Beams for Volumetric Modulated Arc Therapy in Squamous Cell Carcinoma of the Scalp

    PubMed Central

    Lai, Youqun; Shi, Liwan; Lin, Qin; Fu, Lirong; Ha, Huiming

    2014-01-01

    Purpose Flattening filter free (FFF) beams show the potential for a higher dose rate and lower peripheral dose. We investigated the planning study of FFF beams with their role for volumetric modulated arc therapy (VMAT) in squamous cell carcinoma of the scalp. Methods and Materials One patient with squamous cell carcinoma which had involvement of entire scalp was subjected to VMAT using TrueBeam linear accelerator. As it was a rare skin malignancy, CT data of 7 patients with brain tumors were also included in this study, and their entire scalps were outlined as target volumes. Three VMAT plans were employed with RapidArc form: two half-field full-arcs VMAT using 6 MV standard beams (HFF-VMAT-FF), eight half-field quarter-arcs VMAT using 6 MV standard beams (HFQ-VMAT-FF), and HFQ-VMAT using FFF beams (HFQ-VMAT-FFF). Prescribed dose was 25×2 Gy (50 Gy). Plan quality and efficiency were assessed for all plans. Results There were no statistically significant differences among the three VMAT plans in target volume coverage, conformity, and homogeneity. For HFQ-VMAT-FF plans, there was a significant decrease by 12.6% in the mean dose to the brain compared with HFF-VMAT-FF. By the use of FFF beams, the mean dose to brain in HFQ-VMAT-FFF plans was further decreased by 7.4% compared with HFQ-VMAT-FF. Beam delivery times were similar for each technique. Conclusions The HFQ-VMAT-FF plans showed the superiority in dose distributions compared with HFF-VMAT-FF. HFQ-VMAT-FFF plans might provide further normal tissue sparing, particularly in the brain, showing their potential for radiation therapy in squamous cell carcinoma of the scalp. PMID:25506701

  11. Simultaneous couch and gantry dynamic arc rotation (CG-Darc) in the treatment of breast cancer with accelerated partial breast irradiation (APBI): a feasibility study.

    PubMed

    Popescu, Carmen C; Beckham, Wayne A; Patenaude, Veronica V; Olivotto, Ivo A; Vlachaki, Maria T

    2013-01-07

    The purpose of this study was to compare the dosimetry of CG-Darc with three-dimensional conformal radiation therapy (3D CRT) and volumetric-modulated arc therapy (RapidArc) in the treatment of breast cancer with APBI. CG-Darc plans were generated using two tangential couch arcs combined with a simultaneous noncoplanar gantry arc. The dynamic couch arc was modeled by consecutive IMRT fields at 10° intervals. RapidArc plans used a single partial arc with an avoidance sector, preventing direct beam exit into the thorax. CG-Darc and RapidArc plans were compared with 3D CRT in 20 patients previously treated with 3D CRT (group A), and in 15 additional patients who failed the dosimetric constraints of the Canadian trial and of NSABP B-39/RTOG 0413 for APBI (group B). CG-Darc resulted in superior target coverage compared to 3D CRT and RapidArc (V95%: 98.2% vs. 97.1% and 95.7%). For outer breast lesions, CG-Darc and RapidArc significantly reduced the ipsilateral breast V50% by 8% in group A and 15% in group B (p < 0.05) as compared with 3D CRT. For inner and centrally located lesions, CG-Darc resulted in significant ipsilateral lung V10% reduction when compared to 3D CRT and RapidArc (10.7% vs. 12.6% and 20.7% for group A, and 15.1% vs. 25.2% and 27.3% for group B). Similar advantage was observed in the dosimetry of contralateral breast where the percent maximum dose for CG-Darc, 3D CRT, and RapidArc were 3.9%, 6.3%, and 5.8% for group A and 4.3%, 9.2%, and 6.3% for group B, respectively (p < 0.05). CG-Darc achieved superior target coverage while decreasing normal tissue dose even in patients failing APBI dose constraints. Consequently, this technique has the potential of expanding the use of APBI to patients currently ineligible for such treatment. Modification of the RapidArc algorithm will be necessary to link couch and gantry rotation with variable dose rate and, therefore, enable the use of CG-Darc in clinical practice.

  12. Overhauser Dynamic Nuclear Polarization Studies on Local Water Dynamics.

    PubMed

    Kaminker, Ilia; Barnes, Ryan; Han, Songi

    2015-01-01

    Overhauser dynamic nuclear polarization (ODNP) is an emerging technique for quantifying translational water dynamics in the vicinity (<1 nm) of stable radicals that can be chemically attached to macromolecules of interest. This has led to many in-depth and enlightening studies of hydration water of biomolecules, revolving around the role of solvent dynamics in the structure and function of proteins, nucleic acids, and lipid bilayer membranes. Still to date, a complete and fully automated ODNP instrument is not commercialized. The purpose of this chapter is to share the technical know-how of the hardware, theory, measurement, and data analysis method needed to successfully utilize and disseminate the ODNP technique. © 2015 Elsevier Inc. All rights reserved.

  13. Polarized Raman study of random copolymers of propylene with olefins

    NASA Astrophysics Data System (ADS)

    Gen, D. E.; Chernyshov, K. B.; Prokhorov, K. A.; Nikolaeva, G. Yu.; Sagitova, E. A.; Pashinin, P. P.; Kovalchuk, A. A.; Klyamkina, A. N.; Nedorezova, P. M.; Optov, V. A.; Shklyaruk, B. F.

    2010-06-01

    The polarized Raman spectroscopy is employed in the study of structural modifications in the films of isotactic polypropylene (PP) whose chain contains ethylene, 1-butene, 1-hexene, 1-octene, and 4-metyl-pentene-1, which represents an isomer of 1-hexene. It is demonstrated that the phase and conformational compositions of copolymer molecules depend on the comonomer content and the side-chain length of the second monomer. The content of the PP molecules in the helical conformation in the crystalline and amorphous phases of the copolymers monotonically decreases with increasing content of the second monomer. The decrease in the content of helical macromolecules in the crystalline phase is faster than the decrease in the amorphous phase. At a certain content of comonomers, the total content of the helical fragments decreases with increasing length of the side chain of the second monomer. The structures and Raman spectra of the copolymers of propylene with 1-hexene and 4-methyl-1-pentene are similar.

  14. Feasibility studies for the follow-on EUMETSAT polar system

    NASA Astrophysics Data System (ADS)

    Banfi, S.; Schlüssel, P.; Diebel, D.; Clarke, P.; Betto, M.; Lin, Chung-Chi; Kangas, V.; Kraft, S.; Bensi, P.; Zerfowski, I.; Saccoccio, M.; Maciaszek, T.

    2010-10-01

    replace the current satellite system in the 2020 timeframe and contribute to the Joint Polar System to be set up with NOAA. Through consultation with users and application experts, requirements have been defined for a range of candidate missions mainly in support of operational meteorology and climate monitoring. A number of on-board instruments, satellite platforms and ground support infrastructure are under study in coordination with ESA, NOAA, DLR and CNES. The satellites will fly in a sun synchronous, low earth orbit at 817 km altitude and 09:30 descending equatorial crossing time, providing observations with global coverage every 12 to 24 hours depending on instrument. The instruments exploit a range of techniques including multi spectral imaging, atmospheric sounding in the optical and microwave spectral domains, radio occultation sounding, scatterometry and microwave imaging. The raw instrument data will be broadcast directly by the satellites, as well as being stored on board for their transmission, in sets spanning up to a full orbit, to polar ground stations. These data will be collected at EUMETSAT facilities and processed to obtain calibrated and geo-located measurements, and records of well defined geophysical variables. The data will be distributed to the users in near real time and archived together with the data of other EUMETSAT satellite systems, making available long term records also suitable for climate monitoring. Feasibility studies for the space and ground systems will be done until early 2012 with the main objective to select the baseline configuration for preliminary definition, development and operation programmes to be proposed and coordinated within the involved organisations.

  15. SU-E-T-187: Feasibility Study of Stereotactic Liver Radiation Therapy Using Multiple Divided Partial Arcs in Volumetric Modulated Arc Therapy

    SciTech Connect

    Lin, Y; Ozawa, S; Tsegmed, U; Nakashima, T; Shintaro, T; Ochi, Y; Kawahara, D; Kimura, T; Nagata, Y

    2014-06-01

    Purpose: To verify volumetric modulated arc therapy (VMAT) using flattening filter free (FFF) mode with jaw tracking (JT) feature for single breath hold as long as 15 s per arc in liver stereotactic body radiation therapy (SBRT) against intensity modulated radiation therapy (IMRT) FFF-JT. Methods: Ten hepatocellular carcinoma (HCC) cases were planned with 10 MV FFF using Pinnacle3 treatment planning system which delivered by TrueBeam to administer 48 Gy/ 4 fractions. Eight non-coplanar beams were assigned to IMRT using step-and-shoot technique. For VMAT, two or three non-coplanar partial arcs (up to 180 degrees) were further divided into subarcs with gantry rotation less than 80 degrees to limit delivery time within 15 s. Dose distributions were verified using OCTAVIUS II system and pass rates were evaluated using gamma analysis with criteria of 3%/3 mm at threshold of 5% to the maximum dose. The actual irradiation time was measured. Results: The VMAT-FFF-JT of partial-arcs with sub-divided arcs was able to produce a highly conformal plan as well as IMRT-FFF-JT. Isodose lines and DVH showed slight improvement in dosimetry when JT was employed for both IMRT and VMAT. Consequently, VMAT-FFF-JT was superior in reducing the dose to liver minus gross tumor volume. VMAT-FFF-JT has shorter total treatment time compared with 3D conformal radiation therapy (3D-CRT) FFF because the gantry was rotated simultaneously with the beam delivery in VMAT. Moreover, due to the small and regular shape of HCC, VMAT-FFF-JT offered less multileaf collimator motion, thus the interplay effect is expected to be reduced. The patient specific QA of IMRT and VMAT acquired the pass rates higher than 90%. Conclusion: VMAT-FFF-JT could be a promising technique for liver SBRT as the sub-divided arcs method was able to accommodate a single breath hold irradiation time of less than 15 s without deterioration of the dose distribution compared with IMRT-FFF-JT.

  16. Study of deep inelastic scattering of polarized electrons off polarized deuterons

    SciTech Connect

    Kuriki, M.

    1996-03-01

    This thesis describes a 29GeV electron - nucleon scattering experiment carried out at Stanford Linear Accelerator Center (SLAC). Highly polarized electrons are scattered off a polarized ND{sub 3} target. Scattered electrons are detected by two spectrometers located in End Station A (ESA) at angles of 4.5{degrees} and 7{degrees} with respect to the beam axis. We have measured the spin structure function g{sub 1} of deuteron over the range of 0.029 < x < 0.8 and 1. 0 < Q{sup 2} < 12.0(GeV/c){sup 2}. This integral indicates a discrepancy of more than three standard deviations from the prediction of the Ellis-Jaffe sum rule, 0.068{+-}0.005 at Q{sup 2} = 3.0(GeV/c){sup 2} while our result of g{sub 1}{sup d} in good agreement with SMC results. Combined with g{sub 1} of the proton, the measurement of {integral}{sub 0}{sup 1}(g{sub 1}{sup d}-g{sub 1}{sup n}) is 0.169{+-}0.008. We also obtained the strong coupling constant at Q{sup 2} = 3.0(GeV/c){sup 2} to be 0.417{sub -0.110}{sup +0.086}, using the power correction for the sum rule up to third order of {alpha}{sub s}. This result is in agreement with the strong coupling constant {alpha}{sub s}(Q{sup 2}) = 3.0(GeV/c{sup 2}) obtained from various experiments. Using our deuteron results and the axial vector couplings of hyperon decays, the total quark polarization along the nucleon spin is found to be 0.286{+-}.055, implying that quarks carry only 30% of the nucleon spin. The strange sea quark polarization is also determined to be -0.101 {+-} .023. These measurements are in agreement with other experiments and provide the world`s most precise measurement of these quark polarizations. 80 refs., 151 figs., 23 tabs.

  17. Theoretical estimation and experimental studies on gas dissociation in TEA CO2 laser for long term arc free operation

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Biswas, A. K.; Bhargav, Pankaj; Reghu, T.; Sahu, Shashikiran; Pakhare, J. S.; Bhagat, M. S.; Kukreja, L. M.

    2013-11-01

    Gas dissociation in a high energy, high repetition rate Transversely Excited Atmospheric (TEA) CO2 laser in both sealed-off and gas replenishment modes were studied for nitrogen lean gas mixture. A comprehensive theoretical model based on the Boltzmann transport equation and the discharge excitation circuit equations was adopted to calculate the amount of CO2 dissociated during a single discharge pulse. Theoretically it is shown that inclusion of superelastic collisions in the Boltzmann transport equation is necessary for precise estimation of dissociation per pulse, particularly at high discharge energy loadings and for nitrogen rich gas mixtures. Gas lifetime for repetitively pulsed operations was found experimentally by measuring the amount of CO formed when frequent arcing sets in under sealed off operation. Using this model, the optimum replenishment rate of CO2 either by gas purging and/or by catalytic regeneration needed for arc free long term operation of the laser was estimated. The measured saturation values of CO concentration in the laser chamber agreed well with the calculated values for various operating conditions. Arc free, long term repetitively pulsed operation of the laser was achieved in the gas replenishment mode with gas purging and/or catalytic regeneration.

  18. The Central Sierra Nevada Volcanic Field: A Geochemical Study of a Transitional Arc

    NASA Astrophysics Data System (ADS)

    Jean, M. M.; Putirka, K.; Busby, C.; Hagan, J.

    2006-12-01

    The Central Sierra Nevada (CSN) offers evidence about the effects of an arc/post-arc transition, which occurred in the middle to late Miocene. With passage of the Mendocino Triple Junction (MTJ), there should be a reflection of this new tectonic regime in the geochemistry of the resulting volcanic rocks. We conducted a search for systematic changes in magma chemistry, with regard to time and/or geography that may yield clues regarding tectonic origin, post 6 M.a. Major oxide and trace element analysis of 42 volcanic rock samples from the Sierra Nevada have been collected to assess the characteristics of ancestral Cascade volcanism. Major oxide element variation of 35 samples displayed high total alkalis (Na2O + K2O), medium to high K calc-alkaline compositions, and lavas that range from 50-75 wt% SiO2; all key signatures for Cascade volcanism. The remaining 7 samples displayed tholeiitic affinities. We looked for distinct chemical signatures to examine whether CSN volcanism was indicative of arcs. Spider-diagrams assisted in illustrating that the CSN suite is enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). Arcs contain Ba/Nb between 52 and 151 (Lange et. al., 1996), low Zr/Ba ratios, Y + Nb from 10 to 100 ppm, and high Sr/P2O5 ratios. The CSN volcanic field has geochemical characteristics that agree with each of these criteria that define subduction-related lavas. Two models were tested to explain the evolution of the CSN suite: fractional crystallization (FC) and combined assimilation-fractional crystallization (AFC). FC better explains both major oxide and trace element variations, compared to AFC. Our initial magma crystallized along the following liquid line of descent: ol+cpx, ol+cpx+plag, ol+cpx+plag+opx+hbl, ol+cpx+plag+opx+hbl+mag+ap.

  19. Study of the spray to globular transition in gas metal arc welding: a spectroscopic investigation

    NASA Astrophysics Data System (ADS)

    Valensi, F.; Pellerin, S.; Castillon, Q.; Boutaghane, A.; Dzierzega, K.; Zielinska, S.; Pellerin, N.; Briand, F.

    2013-06-01

    The gas metal arc welding (GMAW) process is strongly influenced by the composition of the shielding gas. In particular, addition of CO2 increases the threshold current for the transition from unstable globular to more stable spray transfer mode. We report on the diagnostics—using optical emission spectroscopy—of a GMAW plasma in pure argon and in mixtures of argon, CO2 and N2 while operated in spray and globular transfer modes. The spatially resolved plasma parameters are obtained by applying the Abel transformation to laterally integrated emission data. The Stark widths of some iron lines are used to determine both electron density and temperature, and line intensities yield relative contents of neutral and ionized iron to argon. Our experimental results indicate a temperature drop on the arc axis in the case of spray arc transfer. This drop reduces with addition of N2 and disappears in globular transfer mode when CO2 is added. Despite the temperature increase, the electron density decreases with CO2 concentration. The highest concentration of iron is observed in the plasma column upper part (close to the anode) and for GMAW with CO2. Our results are compared with recently published works where the effect of non-homogeneous metal vapour concentration has been taken into account.

  20. The Tertiary Arc Chain in the Western Pacific

    NASA Astrophysics Data System (ADS)

    Honza, E.

    1991-02-01

    The arcs bordering the Pacific Plate on the Western and Southwestern Pacific rim are reconstructed since their initiation in the Eocene and Oligocene. They occur in a zone forming an arc chain from the Western Pacific tropics to the eastern margin of Australia. They are the Bonin, Mariana, Yap, Palau, Halmahera, North New Guinea-West Melanesia, Solomon, Vanuatu, and Tonga-Kermadec Arcs, designated here the Tertiary Arc Chain. They are associated with the formation and consumption of backarc basins. Reversals of arc polarity and episodic subduction has occurred in some of them. The Tertiary Arc Chain is characterized by four major stages in its evolution which can be seen characteristically in some of the arcs. The first stage is the occurrence of the arc chain from the middle Eocene to earliest Oligocene. The second stage is the formation of the backarc basins from the early to late Oligocene. The third stage is the occurrence of double arcs on the inner side of the arc chain in the early to middle Miocene and the fourth stage is the reversal of arc polarities due to collisions since the late Miocene. The backarc basins associated with the arcs of the Tertiary Arc Chain have fixed limits of duration in their evolution. The backarc basins initially form 15 million years after the initiation of the volcanic arc. Several to 10 million years after the initial opening, backarc spreading terminates. Approximately 20 million years after the cessation of the backarc spreading, a second phase of opening occurs in the backarc region. In the case of arc collision, reversal of the arc polarity occurs if there is oceanic crust on the backarc side, and opening of a backarc basin occurs within several million years. These occurrences and durations have a variation of ca. 3-5 million years.

  1. Rock Magnetic Study in the Methanogenesis Zone, Site U1437, IODP Exp 350, Izu Rear Arc

    NASA Astrophysics Data System (ADS)

    Kars, M. A. C.; Musgrave, R. J.; Kodama, K.; Jonas, A. S.

    2015-12-01

    In 2014, IODP Expedition 350 drilled a 1806.5 m deep hole at Site U1437 in the Izu Bonin rear arc. The Site presents an unusual deep methanogenesis zone because of a release of sulfate below the sulfate reduction zone (27-83 mbsf) which may buffer methanogenesis by anaerobic methanogens. Methane abundance gradually increases with depth, with significant abundance at ~750-1459 mbsf with a maximum value at 920 mbsf. The rock magnetic study carried out in Hole U1437D from ~775 to ~1000 mbsf shows a drastic change of the magnetic properties at ~850 mbsf coincidently with a stronger release of methane from < 60 ppm at 841 mbsf to ~300 ppm at 854 mbsf. That also corresponds to a depth interval where no core was recovered (~846-854 mbsf). For the sake of clarity, we call hereafter zone A the depth interval above this non-recovered interval (775-846 mbsf) and zone B the interval below (854-1000 mbsf). Both belong to the same lithostratigraphic unit composed of tuffaceous mudstones intercalated with volcanoclastics. In the zone A, NRM, magnetic susceptibility, ARM, SIRM, HIRM display high values. In the zone B, these parameters show much lower values of one order of magnitude less, except for the interval 936-950 mbsf that corresponds to a local maximum (but still lower values than the zone A). Besides, the rock magnetic parameters for grain size and coercivity, such as ARM/χ, S-ratio and Bcr do not show any variations throughout the entire studied interval, although S-ratio displays slightly lower values from ~850 to ~930 mbsf. Grains are low coercivity pseudo-single domain sized. According to the present data, two preliminary hypotheses can be proposed to explain the observations. 1) The non-recovered interval between the zones A and B can be caused by the presence of a sedimentary hiatus and/or a fault, which may be consistent with the observed change in sedimentation rate. 2) No hiatus in the sedimentation. The changes in the magnetic properties can be explained by a

  2. The influence of contacts erosion on the SF6 arc

    NASA Astrophysics Data System (ADS)

    Liau, V. K.; Lee, B. Y.; Song, K. D.; Park, K. Y.

    2006-05-01

    In circuit breakers, high temperature arcing may lead to material erosion at the contacts. In this paper, numerical investigations have been performed in order to study the arc behaviours under the influence of copper vapours contamination in a simple Laval nozzle. The arc is assumed to be in local thermodynamic equilibrium. The erosion rate is estimated by considering the energy balance processes at the contact surface. Computations have been performed by a commercial computational fluids dynamics package (PHOENICS). The effects of contact polarity have also been investigated. It has been found that the presence of copper vapours cools down the arc temperature at the region close to the contacts. However, at current zero, the copper vapours concentration is very low. Post arc simulation has been performed in order to determine the critical rate of rise of recovery voltage (RRRV). Good agreement has been achieved with the experimental measurement of RRRV. It has been predicted that the contact erosion has a negligible effect on the interruption capability of the breaker.

  3. Experimental studies and modeling on concentration polarization in forward osmosis.

    PubMed

    Qin, Jian-Jun; Chen, Sijie; Oo, Maung Htun; Kekre, Kiran A; Cornelissen, Emile R; Ruiken, Chris J

    2010-01-01

    Concentration polarization (CP) is an important issue in forward osmosis (FO) processes and it is believed that the coupled effect of dilutive internal CP (DICP) and concentrative external CP (CECP) limits FO flux. The objective of this study was to distinguish individual contribution of different types of DICP and CECP via modeling and to validate it by pilot studies. The influence of DICP/CECP on FO flux has been investigated in this study. The CP model presented in this work was derived from a previous study and evaluated by bench-scale FO experiments. Experiments were conducted with drinking water as the feed and NaCl/MgSO(4) as draw solutions at different concentrations and velocities. Modeling results indicated that DICP contributed to a flux reduction by 99.9% for 0.5 M NaCl as a draw solution although the flow pattern of both feed and draw solutions was turbulent. DICP could be improved via selection of the draw solution. The modeling results were well fit with the experimental data. It was concluded that the model could be used for selection of the draw solution and prediction of water flux under similar situation. A draw solution with greater diffusion coefficient or a thinner substrate of an asymmetric FO membrane resulted in a higher flux.

  4. Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes

    SciTech Connect

    Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

    2008-02-15

    A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones

  5. Geochemical and temporal relationships between plutonic and volcanic rocks from the Aleutian arc: a pilot study

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Rioux, M. E.; Kelemen, P. B.; Goldstein, S. L.

    2013-12-01

    Aleutian arc volcanics are predominantly basaltic while known plutonic rocks are systematically more felsic and have compositions that overlap estimates for the bulk composition of the continental crust. The Aleutian arc is unique among active intra-oceanic arcs in its widespread exposure of Paleogene and Neogene mid-crustal plutonic rocks, as well as the lavas and sediments that these plutons intruded. Thus, understanding the genesis of Aleutian plutonic rocks is a key to understanding continental genesis and evolution via arc magmatism. We have measured major, trace element contents and Sr-Nd-Hf-Pb isotope compositions of 26 mafic to intermediate plutonic rocks, ranging in age from ~32-9 Ma, across the Aleutian arc and compared them with spatially associated Quaternary volcanic rocks. The samples cover a large range of Mg# (73 to 35). Most samples do not show substantial Eu anomalies, and they represent primary magmas rather than differentiated cumulates. Compared to associated volcanics, the plutonic rocks show similar to slightly higher SiO2 and K2O contents at a given Mg#. For many trace elements, the plutonic and volcanic rocks are similar (e.g., elemental concentrations and La/Sm, Th/Nd, Lu/Hf, Dy/Yb ratios). However, the plutonic rocks show on average higher Nd and Hf isotope ratios and lower Pb isotope ratios than volcanic rocks from the same island. The difference in isotope compositions between the plutonic rocks and their volcanic neighbors indicates differences in the mantle sources. This could reflect temporal variation of mantle composition under the Aleutians. Based on U-Pb zircon geochronology of representative samples, the data may indicate decreasing Nd (-Hf) isotope ratios of the sub-Aleutians mantle through time in some regions. However, more data is necessary from plutonic rocks to determine if this will hold up. Alternatively, the compositional differences (e.g. higher Si and K) between the plutonics and the volcanics could reflect different

  6. ALVIN-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc

    NASA Astrophysics Data System (ADS)

    Taylor, B.; Brown, G.; Fryer, P.; Gill, J. B.; Hochstaedter, A. G.; Hotta, H.; Langmuir, C. H.; Leinen, M.; Nishimura, A.; Urabe, T.

    1990-10-01

    Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50-700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven ALVIN heat flow measurements at 30°48.5'N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine

  7. Lower crustal assimilation in oceanic arcs: insights from an osmium isotopic study of the Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Bezard, R. C.; Schaefer, B. F.; Turner, S.; Davidson, J.; Selby, D. S.

    2013-12-01

    We investigated the whole rock 187Os/188Os of the most mafic lavas along the Lesser Antilles arc (MgO=17-5 wt.%) and of the subducting slab to test: (1) the mobility of Os in the subduction zone and the potential of magmatic 187Os/188Os to reflect the slab composition, (2) the sensitivity of lava 187Os/188Os to crustal assimilation. 187Os/188Os varies from 0.127-0.202 in the lavas. A correlation between 187Os/188Os and indexes of differentiation such as Os and MgO shows that assimilation, rather than source variation, is responsible for the range of 187Os/188Os observed. Magmatic compositions from all islands plot along a single trend indicating the presence of a common assimilant in the basement of every island. 87Sr/86Sr, La/Sm and Sr/Th are also modified by assimilation since they all correlate with 187Os/188Os. The assimilant displays a MORB-like 87Sr/86Sr with high Sr (> 700 ppm), low L/M-HREE (La/Sm < 1.6) and 187Os/188Os > 0.2. Such a composition could correspond to a plagioclase rich cumulate. Given that assimilation affects lavas that were last stored at more than 5 kbar [1], assimilation must occur in the middle-lower crust. In the whole arc, only a Grenada high MgO picrite escaped assimilation (MgO = 17%) and could represent the source characteristics. It displays a very radiogenic 87Sr/86Sr (0.705) but 187Os/188Os overlapping the mantle range (0.127). 187Os/188Os and 87Sr/86Sr of the sediments and basalt from the subducting slab vary from 0.18-3.52 and 0.708-0.714. We therefore suggest that, unlike for Sr, no Os from the slab was involved in the primitive magma source. The later may be either retained in the mantle or in the subducting slab. Finally, unlike the other lavas of the arc, Grenada picrites are silica undersaturated which suggests that, before assimilation, primitive magmas from across the arc could be of similar nature. [1] Heath, E., Macdonald, R., Belkin, H., Hawkesworth, C., Sigurdsson, H., 1998. Magmagenesis at Soufriere Volcano, St

  8. Feasibility of single-isocenter, multi-arc non-coplanar volumetric modulated arc therapy for multiple brain tumors using a linear accelerator with a 160-leaf multileaf collimator: a phantom study.

    PubMed

    Iwai, Yoshio; Ozawa, Shuichi; Ageishi, Tatsuya; Pellegrini, Roberto; Yoda, Kiyoshi

    2014-09-01

    The feasibility of single isocenter, multi-arc non-coplanar volumetric modulated arc therapy (VMAT) for multiple brain tumors was studied using an Elekta Synergy linear accelerator with an Agility multileaf collimator and a Monaco treatment planning system. Two VMAT radiosurgery plans consisting of a full arc and three half arcs were created with a prescribed dose of 20 Gy in a single fraction. After dose delivery to a phantom, ionization chambers and radiochromic films were used for dose measurement. The first VMAT radiosurgery plan had nine targets inside the phantom, and the doses were measured by the chambers at two different points and by the films on three sagittal and three coronal planes. The differences between the calculated dose and the dose measured by a Farmer ionization chamber and a pinpoint ionization chamber were <1.00% and <2.30%, respectively, and the average pass rates of gamma indices among the six planes under each of 3%/3 mm and 2%/2 mm criteria were 98.6% and 92.6%, respectively. The second VMAT radiosurgery plan was based on a clinical 14 brain metastases. Differences between calculated and film-measured doses were evaluated on two sagittal planes. The average pass rates of the gamma indices on the planes under each of 3%/3 mm and 2%/2 mm criteria were 97.8% and 88.8%, respectively. It was confirmed that single-isocenter, non-coplanar multi-arc VMAT radiosurgery for multiple brain metastases was feasible using Elekta Synergy with Agility and Monaco treatment planning systems. It was further shown that film dosimetry was accurately performed for a dose of up to nearly 25 Gy. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  9. Feasibility of single-isocenter, multi-arc non-coplanar volumetric modulated arc therapy for multiple brain tumors using a linear accelerator with a 160-leaf multileaf collimator: a phantom study

    PubMed Central

    Iwai, Yoshio; Ozawa, Shuichi; Ageishi, Tatsuya; Pellegrini, Roberto; Yoda, Kiyoshi

    2014-01-01

    The feasibility of single isocenter, multi-arc non-coplanar volumetric modulated arc therapy (VMAT) for multiple brain tumors was studied using an Elekta Synergy linear accelerator with an Agility multileaf collimator and a Monaco treatment planning system. Two VMAT radiosurgery plans consisting of a full arc and three half arcs were created with a prescribed dose of 20 Gy in a single fraction. After dose delivery to a phantom, ionization chambers and radiochromic films were used for dose measurement. The first VMAT radiosurgery plan had nine targets inside the phantom, and the doses were measured by the chambers at two different points and by the films on three sagittal and three coronal planes. The differences between the calculated dose and the dose measured by a Farmer ionization chamber and a pinpoint ionization chamber were <1.00% and <2.30%, respectively, and the average pass rates of gamma indices among the six planes under each of 3%/3 mm and 2%/2 mm criteria were 98.6% and 92.6%, respectively. The second VMAT radiosurgery plan was based on a clinical 14 brain metastases. Differences between calculated and film-measured doses were evaluated on two sagittal planes. The average pass rates of the gamma indices on the planes under each of 3%/3 mm and 2%/2 mm criteria were 97.8% and 88.8%, respectively. It was confirmed that single-isocenter, non-coplanar multi-arc VMAT radiosurgery for multiple brain metastases was feasible using Elekta Synergy with Agility and Monaco treatment planning systems. It was further shown that film dosimetry was accurately performed for a dose of up to nearly 25 Gy. PMID:24944266

  10. A planning study investigating dual-gated volumetric arc stereotactic treatment of primary renal cell carcinoma.

    PubMed

    Devereux, Thomas; Pham, Daniel; Kron, Tomas; Foroudi, Farshad; Supple, Jeremy; Siva, Shankar

    2015-01-01

    This is a planning study investigating the dosimetric advantages of gated volumetric-modulated arc therapy (VMAT) to the end-exhale and end-inhale breathing phases for patients undergoing stereotactic treatment of primary renal cell carcinoma. VMAT plans were developed from the end-inhale (VMATinh) and the end-exhale (VMATexh) phases of the breathing cycle as well as a VMAT plan and 3-dimensional conformal radiation therapy plan based on an internal target volume (ITV) (VMATitv). An additional VMAT plan was created by giving the respective gated VMAT plan a 50% weighting and summing the inhale and exhale plans together to create a summed gated plan. Dose to organs at risk (OARs) as well as comparison of intermediate and low-dose conformity was evaluated. There was no difference in the volume of healthy tissue receiving the prescribed dose for the planned target volume (PTV) (CI100%) for all the VMAT plans; however, the mean volume of healthy tissue receiving 50% of the prescribed dose for the PTV (CI50%) values were 4.7 (± 0.2), 4.6 (± 0.2), and 4.7 (± 0.6) for the VMATitv, VMATinh, and VMATexh plans, respectively. The VMAT plans based on the exhale and inhale breathing phases showed a 4.8% and 2.4% reduction in dose to 30cm(3) of the small bowel, respectively, compared with that of the ITV-based VMAT plan. The summed gated VMAT plans showed a 6.2% reduction in dose to 30cm(3) of the small bowel compared with that of the VMAT plans based on the ITV. Additionally, when compared with the inhale and the exhale VMAT plans, a 4% and 1.5%, respectively, reduction was observed. Gating VMAT was able to reduce the amount of prescribed, intermediate, and integral dose to healthy tissue when compared with VMAT plans based on an ITV. When summing the inhale and exhale plans together, dose to healthy tissue and OARs was optimized. However, gating VMAT plans would take longer to treat and is a factor that needs to be considered. Crown Copyright © 2015. Published by Elsevier

  11. A planning study investigating dual-gated volumetric arc stereotactic treatment of primary renal cell carcinoma

    SciTech Connect

    Devereux, Thomas; Pham, Daniel; Kron, Tomas; Foroudi, Farshad; Supple, Jeremy; Siva, Shankar

    2015-04-01

    This is a planning study investigating the dosimetric advantages of gated volumetric-modulated arc therapy (VMAT) to the end-exhale and end-inhale breathing phases for patients undergoing stereotactic treatment of primary renal cell carcinoma. VMAT plans were developed from the end-inhale (VMATinh) and the end-exhale (VMATexh) phases of the breathing cycle as well as a VMAT plan and 3-dimensional conformal radiation therapy plan based on an internal target volume (ITV) (VMATitv). An additional VMAT plan was created by giving the respective gated VMAT plan a 50% weighting and summing the inhale and exhale plans together to create a summed gated plan. Dose to organs at risk (OARs) as well as comparison of intermediate and low-dose conformity was evaluated. There was no difference in the volume of healthy tissue receiving the prescribed dose for the planned target volume (PTV) (CI100%) for all the VMAT plans; however, the mean volume of healthy tissue receiving 50% of the prescribed dose for the PTV (CI50%) values were 4.7 (± 0.2), 4.6 (± 0.2), and 4.7 (± 0.6) for the VMATitv, VMATinh, and VMATexh plans, respectively. The VMAT plans based on the exhale and inhale breathing phases showed a 4.8% and 2.4% reduction in dose to 30 cm{sup 3} of the small bowel, respectively, compared with that of the ITV-based VMAT plan. The summed gated VMAT plans showed a 6.2% reduction in dose to 30 cm{sup 3} of the small bowel compared with that of the VMAT plans based on the ITV. Additionally, when compared with the inhale and the exhale VMAT plans, a 4% and 1.5%, respectively, reduction was observed. Gating VMAT was able to reduce the amount of prescribed, intermediate, and integral dose to healthy tissue when compared with VMAT plans based on an ITV. When summing the inhale and exhale plans together, dose to healthy tissue and OARs was optimized. However, gating VMAT plans would take longer to treat and is a factor that needs to be considered.

  12. The first Shinkai dive study of the southwestern Mariana arc system

    NASA Astrophysics Data System (ADS)

    Ohara, Y.; Martinez, F.; Brounce, M. N.; Pujana, I.; Ishii, T.; Stern, R. J.; Ribeiro, J.; Michibayashi, K.; Kelley, K. A.; Reagan, M. K.; Watanabe, H.; Okumura, T.; Oya, S.; Mizuno, T.

    2014-12-01

    The 3000 km long Izu-Bonin-Mariana (IBM) arc system is an outstanding example of an intraoceanic convergent plate margin. The IBM forearc is a typical nonaccretionary convergent plate margin; the inner trench slope exposes lithologies found in many ophiolites. To more clearly delineate the geology of the forearc, we have been investigating a ~500 km long region of the Mariana forearc south of ~13°N using the DSV Shinkai 6500 and deep-tow camera since 2006. Discoveries includes the presence of MORB-like basalts that formed during subduction initiation (~51 Ma) [Reagan et al., 2010, G3], a region of forearc rifting unusually close to the trench axis, the Southeast Mariana Forearc Rift [Ribeiro et al., 2013, G3], and a serpentinite-hosted ecosystem near the Challenger Deep, the Shinkai Seep Field [Ohara et al., 2012, PNAS]. However, there have been no studies on the southern Mariana area west of the Challenger Deep except one [Hawkins and Batiza, 1977, EPSL], hindering our understanding of the IBM system. To advance our biogeoscientific understanding of this region, a Shinkai 6500 diving cruise (YK14-13) was conducted in July 2014 on two major sites: the inner trench slope west of the Challenger Deep (Site A), and the southwesternmost tip of the Mariana Trough (Site B). Dives at Site A recovered very fresh mantle peridotite associated with troctolite and limestone. The limestone preserves the remnants of corals, clearly indicating that the limestone is an accreted material originating from the incoming (colliding) Caroline Ridge. The freshness of the peridotites also indicates that the collision is an ongoing event, resulting in a protruding peridotite ridge along the inner trench slope west of the Challenger Deep. Dives at Site B recovered basalt and gabbro, which is either new backarc basin crust or rifted West Mariana Ridge crust. This cruise allowed for continued sampling of the inner trench slope of the Mariana Trench, from south of Guam to the Yap Trench

  13. Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Visani, A.; Patil, C.; Patel, B. K.; Sharma, P. K.; John, P. I.; Nema, S. K.

    2014-08-01

    Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

  14. Spectroscopic studies of model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Koehler, Birgit G.; Middlebrook, Ann M.

    1993-01-01

    Fourier transform infrared (FTIR) spectroscopy has been used to study nitric-acid/ice films representative of type I polar stratospheric clouds (PSCs). These studies reveal that in addition to amorphous nitric acid/ice mixtures, there are three stable stoichiometric hydrates of nitric acid: nitric-acid monohydrate (NAM), dihydrate (NAD), and trihydrate (NAT). We also observe two distinct crystalline forms of the trihydrate, which we denote alpha- and beta-NAT. These two forms appear to differ in their concentration of crystalline defects, but not in their chemical composition. In addition to probing the composition of type I PSCs, we have also used FTIR spectroscopy to study the interaction of HCl with model PSC films. In this work we find that for HCl pressures in the range 10 exp -5 to 10 exp -7 Torr, HCl is taken up by ice at 155 K to form a thin layer of HCl.6H2O. At 193 K, the uptake of HCl by ice was consistent with less than or equal to monolayer coverage. Uptake of HCl by alpha and beta-NAT at 175 K was also consistent with less than or equal to monolayer coverage.

  15. A study of the first and second polar bodies in mouse oogenesis

    SciTech Connect

    Evsikov, A.V.; Evsikov, S.V.

    1995-05-01

    The possibility of using a polar body for biopsy of human oocytes and early embryos has recently been shown. Genetic analysis of polar bodies can also provide additional information about the mechanisms underlying oocyte maturation. The first polar body is extremely unstable: in mouse oocytes, it disintegrates within several hours. Thus, the possibilities for its analysis are limited. We obtained karyoplasts of mouse eggs that contained the metaphase II spindle. By using them as a model for the first polar body, we studied the causes of its rapid disintegration. The rates of disintegration of the karyoplasts treated with various inhibitors of the cytoskeleton indicate that disintegration of the first polar body may be due to interaction between the actin cytoskeleton, chromatin, and the plasma membrane. The second polar body is found in mouse embryos until the blastocyst stage. Fusion of the second polar body with the enucleated zygote allowed analysis of its chromosomes. 22 refs., 5 figs., 1 tab.

  16. Monte-Carlo-based studies of a polarized positron source for International Linear Collider (ILC)

    NASA Astrophysics Data System (ADS)

    Dollan, Ralph; Laihem, Karim; Schälicke, Andreas

    2006-04-01

    The full exploitation of the physics potential of an International Linear Collider (ILC) requires the development of a polarized positron beam. New concepts of polarized positron sources are based on the development of circularly polarized photon sources. The polarized photons create electron-positron pairs in a thin target and transfer their polarization state to the outgoing leptons. To achieve a high level of positron polarization the understanding of the production mechanisms in the target is crucial. Therefore, a general framework for the simulation of polarized processes with GEANT4 is under development. In this contribution the current status of the project and its application to a study of the positron production process for the ILC is presented.

  17. Thermal efficiency of arc welding processes

    SciTech Connect

    DuPont, J.N.; Marder, A.R.

    1995-12-01

    A study was conducted on the arc and melting efficiency of the plasma arc, gas tungsten arc, gas metal arc, and submerged arc welding processes. The results of this work are extended to develop a quantitative method for estimating weld metal dilution in a companion paper. Arc efficiency was determined as a function of current for each process using A36 steel base metal. Melting efficiency was evaluated with variations in arc power and travel speed during deposition of austenitic stainless steel filler metal onto A36 steel substrates. The arc efficiency did not vary significantly within a given process over the range of currents investigated. A semi-empirical relation was developed for the melting efficiency as a function of net arc power and travel speed, which described the experimental data well. An interaction was observed between the arc and melting efficiency. A low arc efficiency factor limits the power delivered to the substrate which, in turn, limits the maximum travel speed for a given set of conditions. High melting efficiency is favored by high arc powers and travel speeds. As a result, a low arc efficiency can limit the maximum obtainable melting efficiency.

  18. Rifting process of the Izu-Ogasawara-Mariana arc-backarc system inferred from active source seismic studies

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Kodaira, S.; Miura, S.; Sato, T.; Yamashita, M.; No, T.; Takizawa, K.; Kaiho, Y.; Kaneda, Y.

    2008-12-01

    The Izu-Ogasawara-Mariana (IBM) arc-backarc system has continued the crustal growth through crustal thickening by magmatic activities and crustal thinning by backarc opening. Tatsumi et al (2008) proposed petrological crustal growth model started from basaltic magmas rising from the slab, and showed the consistency with the seismic velocity model. Although crustal growth by the crustal thickening are modeled, crustal structural change by the backarc opening are not still unknown yet. The Shikoku Basin and Parece Vela Basin were formed by the backarc opening during approximately 15-30 Ma. Since 6 Ma, the Mariana Trough has opened and the stage already moved to spreading process from rifting process. In the northern Izu-Ogasawara arc, the Sumisu rift is in the initial rifting stage. Therefore, understanding of the crustal change by the backarc opening from rifting to spreading is indispensable to know the crustal growth of whole Izu-Ogasawara-Mariana island arc. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic studies using a multichannel reflection survey system and ocean bottom seismographs (OBSs) around the IBM arc since 2003 (Takahashi et al., 2007; Kodaira et al., 2007; Takahashi et al., 2008; Kodaira et al., 2008). We already obtained eight P-wave velocity models across the IBM arc and these structures record the crustal structural change during the backarc opening process from the rifting stage to the spreading stage. As the results, we identified characteristics of the crustal structural change accompanied with backarc opening as follows. (1) Beneath the initial rifting stage without normal faults, for example, in the northern tip of the Mariana Trough, crustal thickening are identified. (2) Beneath the initial rifting stage with normal faults, for example, in the Sumisu Rift, the crustal thickness is almost similar to that beneath the volcanic front. Although an existence of the crust-mantle transition layer with

  19. Energy balance in MIG arcs

    NASA Astrophysics Data System (ADS)

    Schnick, M.; Hertel, M.; Fuessel, U.; Uhrlandt, D.

    2013-06-01

    Recent studies of metal inert gas (MIG) processes by spectroscopy and fluid simulations have shown that metal evaporation causes a specific spatial structure of the arc, and among others a minimum of plasma temperature at the arc centre. Changes in the arc structure and in the heat transfer to the material are closely connected with the arc energy balance; its detailed analysis has not been carried out so far under the specific impact of metal vapour. In this paper, magnetohydrodynamic (MHD) simulations of an MIG arc in argon including iron evaporation at the wire tip are considered. The main terms in the energy balance are discussed focusing on a comparison of the arc regions with and without metal vapour. In addition, a simple approach of the energy balance at a cross section of the MIG arc is proposed where all details of the heat transport are neglected. The MHD model and the simplified approach are in good agreement and clearly demonstrate that the specific structure in an MIG arc is mainly caused by the different temperature dependence of the plasma radiation and the electrical conductivity in argon or in argon mixtures with iron vapour.

  20. Satellite Observation Systems for Polar Climate Change Studies

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2012-01-01

    The key observational tools for detecting large scale changes of various parameters in the polar regions have been satellite sensors. The sensors include passive and active satellite systems in the visible, infrared and microwave frequencies. The monitoring started with Tiros and Nimbus research satellites series in the 1970s but during the period, not much data was stored digitally because of limitations and cost of the needed storage systems. Continuous global data came about starting with the launch of ocean color, passive microwave, and thermal infrared sensors on board Nimbus-7 and Synthetic Aperture Radar, Radar Altimeter and Scatterometer on board SeaSat satellite both launched in 1978. The Nimbus-7 lasted longer than expected and provided about 9 years of useful data while SeaSat quit working after 3 months but provided very useful data that became the baseline for follow-up systems with similar capabilities. Over the years, many new sensors were launched, some from Japan Aeronautics and Space Agency (JAXA), some from the European Space Agency (ESA) and more recently, from RuSSia, China, Korea, Canada and India. For polar studies, among the most useful sensors has been the passive microwave sensor which provides day/night and almost all weather observation of the surface. The sensor provide sea surface temperature, precipitation, wind, water vapor and sea ice concentration data that have been very useful in monitoring the climate of the region. More than 30 years of such data are now available, starting with the Scanning Multichannel Microwave Radiometer (SMMR) on board the Nimbus-7, the Special Scanning Microwave/Imager (SSM/I) on board a Defense Meteorological Satellite Program (DMSP) and the Advanced Microwave Scanning Radiometer on board the EOS/ Aqua satellite. The techniques that have been developed to derive geophysical parameters from data provided by these and other sensors and associated instrumental and algorithm errors and validation techniques

  1. Lower crustal assimilation in oceanic arcs: Insights from an osmium isotopic study of the Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Bezard, Rachel; Schaefer, Bruce F.; Turner, Simon; Davidson, Jon P.; Selby, David

    2015-02-01

    We present whole rock 187Os/188Os data for the most mafic lavas along the Lesser Antilles arc (MgO = 5-17 wt.%) and for the subducting basalt and sediments. 187Os/188Os ratios vary from 0.127 to 0.202 in the arc lavas. Inverse correlations between 187Os/188Os and Os concentrations and between 187Os/188Os and indices of differentiation such as MgO suggests that assimilation, rather than source variation, is responsible for the range of Os isotopic variation observed. 87Sr/86Sr, La/Sm and Sr/Th are also modified by assimilation since they all correlate with 187Os/188Os. The assimilant is inferred to have a MORB-like 87Sr/86Sr with high Sr (>700 ppm), low light on middle and heavy rare earth elements (L/M-HREE; La/Sm ∼2.5) and 187Os/188Os > 0.2. Such compositional features are likely to correspond to a plagioclase-rich early-arc cumulate. Given that assimilation affects lavas that were last stored at more than 5 kbar, assimilation must occur in the middle-lower crust. Only a high MgO picrite from Grenada escaped obvious assimilation (MgO = 17% wt.%) and could reflect mantle source composition. It has a very radiogenic 87Sr/86Sr (0.705) but a 187Os/188Os ratio that overlaps the mantle range (0.127). 187Os/188Os and 87Sr/88Sr ratios of the sediments and an altered basalt from the subducting slab vary from 0.18 to 3.52 and 0.708 to 0.714. We therefore suggest that, unlike Sr, no Os from the slab was transferred to the parental magmas. Os may be either retained in the mantle wedge or even returned to the deep mantle in the subducting slab.

  2. Multidisciplinary exploratory study of a geothermal resource in the active volcanic arc of Basse-Terre (Guadeloupe, Lesser Antilles)

    NASA Astrophysics Data System (ADS)

    Navelot, Vivien; Favier, Alexiane; Géraud, Yves; Diraison, Marc; Corsini, Michel; Verati, Chrystèle; Lardeaux, Jean-Marc; Mercier de Lépinay, Jeanne; Munschy, Marc

    2017-04-01

    The GEOTREF project (high enthalpy geothermal energy in fractured reservoirs), supported by the French government program, "Investissements d'avenir" develops a sustainable geothermal resource in the Vieux Habitants area, 8-km south of the currently exploited Bouillante geothermal field. The Basse Terre Island is a recent volcanic arc (< 3 Myr) belonging to the Lesser Antilles subduction zone. It is composed of arc typical calc-alkaline volcanic rocks. Outcrops of the studied area consist either of andesitic lava flows, volcanic sedimentary facies or dikes. Field studies allow to propose a structural framework and highlight three major directions N000˚ E, N050˚ E and N090˚ E, which are consistent with the regional tectonic trends of the arc. Petrographical and petrophysical studies displayed that the major part of outcropping facies in the Vieux-Habitants area are not altered. Andesitic lava flows have poor reservoir properties with porosity and permeability lower than 5 % and 10-15m2 respectively. These results are in contrast with measurements performed in volcano-sedimentary rocks, which have heterogeneous petrophysical properties ranging from 15 to 50 % for porosity and from 10-15to 10-9m2 for permeability. Such surface data would probably change and decrease when depth increases. As there is a lack of underground data under the Vieux-Habitants area (wireline, drill core), exhumated rocks outcropping in the northern part of Basse-Terre Island (Basal Complex) have been studied. Such rocks have been identified in the Basal Complex (2.5 - 3 Myr) located in the northern part of the Basse-Terre Island. Previous works have demonstrated a 1000 m/Myr erosional rate, which corresponds at least to a 2 - 3 km exhumation. The petrography study of the Basal Complex reveals sub-greenschist type mineralogical transformations (chlorite, white mica, quartz...) changing the andesitic protolith in a meta-andesite. This metamorphism forms cleavage plans thanks to a pressure

  3. A diagnostic study of baroclinic disturbances in polar air streams

    NASA Technical Reports Server (NTRS)

    Sinclair, Mark R.; Elsberry, Russell L.

    1986-01-01

    Quasi-Lagrangian budgets of mass, vorticity and heat are calculated following disturbances that form within polar air streams. Observed cases are extracted from the European Centre for Medium-range Weather Forecasts analyses during the First GARP Global Experiment. Model-generated cases are extracted from the simulations of extratropical cyclogenesis by Sandgathe. These polar lows grow primarily through basic baroclinic instability processes and exhibit many features of larger maritime extratropical cyclones. Polar lows that originate on the poleward (or Cyclonic - Type C) side of the jet and have considerable midtropospheric positive vorticity advection at formation time are contrasted with lows that form on the equatorward (or Anticyclonic - Type A) side of a nearly straight upper-level jet. The midtropospheric positive vorticity advection must be present to enhance the vertical circulation when the large surface fluxes that are associated with strong outbreaks act to damp the thermal wave amplification. Although latent heat release is an important factor in both types, it is an essential energy source for the Type A low developments on the equatorward side. Although the vorticity balance is initially different for the two types of polar lows, the vorticity budgets during later stages are similar. The heat budget and the thickness tendency equation demonstrated that the self-development process that is present in larger maritime cyclones is also important for polar low intensification. The absence of favorable coupling to a jet stream is the missing factor in a model-generated Type A polar low that failed to develop. Consequently, the mid- and upper-tropospheric wind fields determine which polar lows will intensify to significant amplitudes.

  4. Functional genomics in the study of yeast cell polarity: moving in the right direction

    PubMed Central

    Styles, Erin; Youn, Ji-Young; Mattiazzi Usaj, Mojca; Andrews, Brenda

    2013-01-01

    The budding yeast Saccharomyces cerevisiae has been used extensively for the study of cell polarity, owing to both its experimental tractability and the high conservation of cell polarity and other basic biological processes among eukaryotes. The budding yeast has also served as a pioneer model organism for virtually all genome-scale approaches, including functional genomics, which aims to define gene function and biological pathways systematically through the analysis of high-throughput experimental data. Here, we outline the contributions of functional genomics and high-throughput methodologies to the study of cell polarity in the budding yeast. We integrate data from published genetic screens that use a variety of functional genomics approaches to query different aspects of polarity. Our integrated dataset is enriched for polarity processes, as well as some processes that are not intrinsically linked to cell polarity, and may provide new areas for future study. PMID:24062589

  5. Functional genomics in the study of yeast cell polarity: moving in the right direction.

    PubMed

    Styles, Erin; Youn, Ji-Young; Mattiazzi Usaj, Mojca; Andrews, Brenda

    2013-01-01

    The budding yeast Saccharomyces cerevisiae has been used extensively for the study of cell polarity, owing to both its experimental tractability and the high conservation of cell polarity and other basic biological processes among eukaryotes. The budding yeast has also served as a pioneer model organism for virtually all genome-scale approaches, including functional genomics, which aims to define gene function and biological pathways systematically through the analysis of high-throughput experimental data. Here, we outline the contributions of functional genomics and high-throughput methodologies to the study of cell polarity in the budding yeast. We integrate data from published genetic screens that use a variety of functional genomics approaches to query different aspects of polarity. Our integrated dataset is enriched for polarity processes, as well as some processes that are not intrinsically linked to cell polarity, and may provide new areas for future study.

  6. XPS and XRD study of FeCl3-graphite intercalation compounds prepared by arc discharge in aqueous solution.

    PubMed

    Yan, Zhang; Zhuxia, Zhang; Tianbao, Li; Xuguang, Liu; Bingshe, Xu

    2008-10-01

    A novel one-step synthesis method of FeCl3-graphite intercalation compounds (FeCl3-GICs) by an arc discharge in aqueous solution was reported for the first time. It presented a simply and controllable way to synthesize FeCl3-GICs. The structure of the stage 7 GICs was examined and characterized by X-ray diffraction. X-ray photoelectron spectroscopic study of stage 7 of FeCl3-GICs was also carried out. The change in the binding energy suggests the nature of charge transfer and lowering of Fermi level as has been reported previously for other acceptor intercalation compounds.

  7. A case-study of the evolution of polar-cap currents and auroral electrojets during polar geomagnetic disturbances with IMS magnetometer data

    NASA Technical Reports Server (NTRS)

    Iijima, T.; Kim, J. S.; Sugiura, M.

    1984-01-01

    The development of the polar cap current and the relationship of that development to the evolution of auroral electrojets during individual polar geomagnetic disturbances is studied using 1 min average data from US-Canada IMS network stations and standard magnetograms from sites on the polar cap and in the auroral zone. It is found that even when the auroral electrojet activity is weak, polar cap currents producing fields of magnitude approximately 100-200 nT almost always exist. A normal convection current system exists quasi-persistently in the polar cap during extended quiet or weakly disturbed periods of auroral electrojet activity. After one such period, some drastic changes occur in the polar cap currents, which are followed by phases of growth, expansion, and recovery. Polar cap currents cannot all be completely ascribed to a single source mechanism.

  8. Are arc lower crustal metasediments derived from above or below? A detrital zircon study in the lower crust of the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Klein, B. Z.; Jagoutz, O. E.; VanTongeren, J. A.

    2016-12-01

    Multiple hypotheses exist to explain the presence of metasedimentary rocks within arc lower crust. Relamination and subduction underplating require that sediments are derived from the subducted slab, while processes such as wall-rock return flow and retro-arc underthrusting imply that the sediments originated in the crust of the upper plate. Evaluating these proposed mechanisms has wide-reaching implications, including better constraining the mass-balance of active arcs, characterizing a theorized trigger mechanism for magmatic flare-up events, and more broadly for describing the tectonic construction of continental arcs. The southernmost Sierra Nevada, California, exposes a continuous continental arc cross-section that spans pressures from 3 to <10 kbar. Metasedimentary rocks are exposed at all crustal levels within this section and are intruded by 100 Ma igneous rocks. These metasediments offer a unique opportunity to evaluate the source, and emplacement of lower crustal metasediments into an active arc. The proposed mechanisms for the transport of sediments to the lower crust predict distinct sedimentary protoliths with unique detrital zircon (DZ) age spectra. Specifically, slab-derived sediments are likely to resemble the underplated Polona-Oroccopia-Rand schists to the south, with dominantly Mesozoic DZ peaks and few to no older grains. Upper plate derived sediments are predicted to have significant Paleozoic and Proterozoic DZ populations, in addition to arc-derived, Mesozoic meta-volcanic material. We have conducted a detailed DZ study of metasedimentary rocks in the Sierran lower and middle crust to assess these hypotheses. Initial results show that at least some of this material has an unambiguous slab-derived signature implying that relamination and/or subduction underplating were active processes during the construction of the Sierran arc system. We explore the implications of these processes for the magmatic and tectonic history of the Sierra Nevada, as

  9. Aligning Plasma-Arc Welding Oscillations

    NASA Technical Reports Server (NTRS)

    Norris, Jeff; Fairley, Mike

    1989-01-01

    Tool aids in alignment of oscillator probe on variable-polarity plasma-arc welding torch. Probe magnetically pulls arc from side to side as it moves along joint. Tensile strength of joint depends on alignment of weld bead and on alignment of probe. Operator installs new tool on front of torch body, levels it with built-in bubble glass, inserts probe in slot on tool, and locks probe in place. Procedure faster and easier and resulting alignment more accurate and repeatable.

  10. Ground-Sensing Circuit For Arc Welders

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1989-01-01

    Ground-sensing circuit for arc-welding power supply prevents arc burns at loose ground connections on workpiece. Used with ac supply or dc supply of either polarity. Includes oscillator/detector pairs normally shorted out by ground connections to workpiece. When one or more of these four connections broken, one or more oscillator signals applied across power diodes and detected. Detected oscillator signal trips shutoff relay.

  11. Exploring Links Between Global Climate and Explosive Arc Volcanism in Tephra-Rich Quaternary Sediments: A Pilot Study from IODP Expedition 350 Site 1437B, Izu Bonin Rear-Arc Region

    NASA Astrophysics Data System (ADS)

    Corry-Saavedra, K.; Straub, S. M.; Bolge, L.; Schindlbeck, J. C.; Kutterolf, S.; Woodhead, J. D.

    2015-12-01

    Fallout tephra in marine sediment provide an excellent archive of explosive arc volcanism that can be directly related to the other parameters of climate change, such as ice volume data, IRD (ice-rafted debris) input, etc. Current studies are based on 'discrete' tephra beds, which are produced by major eruptions and visible with the naked eye. Yet the more common, but less explosive arc eruptions that are more continuous through time produce 'disperse' tephra, which is concealed by the non-volcanic host sediment and invisible to the eye. The proportion of disperse tephra in marine sediments is known to be significant and may be critical in elucidating potential synchronicity between arc volcanism and glacial cycles. We conducted a pilot study in young sediments of IODP Hole 1437B drilled at 31°47.3911'N and 139°01.5788'E at the rear-arc of the Izu Bonin volcanic arc. By means of δ18O (Vautravers, in revision), eleven climatic cycles are recorded in uppermost 120 meter of carbonate mud that is interspersed by cm-thick tephra fallout layers. We selected six tephra layers, ranging from 0.2 to 1.16 million years in age, and sampled those vertically, starting from carbonate mud below the basal contact throughout the typical gradational top into the carbonate mud above. From each tephra bed, volcanic particles (>125 micrometer) were handpicked. All other samples were powdered and leached in buffered acetic acid and hydroxylamine hydrochloride to remove the carbonate and authigenous fraction, respectively. Major and trace element abundances (except for SiO2) from all samples were determined by ICP-MS and ICP-OES methods. Strong binary mixing trends are revealed between the pure tephra end member, and detrital sediment component. The tephra is derived from the Izu Bonin volcanic front and rear-arc, while the sediment component is presumably transported by ocean surface currents from the East China Sea. Our data show that mixing proportions change systematically with

  12. Threshold photoneutron angular distribution and polarization studies of nuclei

    SciTech Connect

    Holt, R.J.

    1980-01-01

    The photoneutron method was applied to the study of: (1) deuteron photodisintegration; (2) giant magnetic dipole resonances in heavy nuclei; (3) mechanism of radiative capture in light nuclei; and (4) isospin splitting of the giant dipole resonance in /sup 60/Ni. These studies were performed with the pulsed bremsstrahlung beam and high-resolution spectrometer available at the Argonne high-current electron linac. A threshold photoneutron polarization method was developed in order to search for the giant M1 resonance in heavy nuclei. A surprisingly small amount of M1 strength was found in /sup 208/Pb. Furthermore, the M1 strength for the 5.08-MeV excitation in /sup 17/O, the best example of a single-particle M1 resonance in nuclei, was found to be strongly quenched. In addition, the /sup 17/O(..gamma..,n/sub 0/)/sup 16/O reaction was found to provide an ideal example of the Lane-Lynn theory of radiative capture. The interplay among the three components of the theory, internal, channel and potential capture, were evident from the data. An electron beam transport system was developed which allows the bremsstrahlung to impinge on the photoneutron target on an axis perpendicular to the usual reaction plane. This system provides an accurate method for the measurement of relative angular distributions in (..gamma..,n) reactions. This system was applied to a high-accuracy measurement of the relative angular distribution for the D(..gamma..,n)H reaction. The question of isospin-splitting of the giant dipole resonance in /sup 60/Ni was studied by using the unique pico-pulse from the accelerator and the newly installed 25-m, neutron flight paths. The results provide clear evidence for the effect of isospin splitting.

  13. Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1980-February 28, 1981

    SciTech Connect

    Jacob, K.H.; Davies, J.N.; House, L.

    1981-01-01

    Refined hypocenter locations beneath the Shumagin Islands seismic network of the eastern Aleutian arc, Alaska, provide for the first time conclusive evidence for a double-sheeted dipping seismic (Benioff) zone in this arc. This refined seismicity structure was obtained in the arc section centered on the Shumagin seismic gap. A thorough review of three seismic gaps in the eastern Aleutian arc shows a high potential for great earthquakes within the next one to two decades in the Shumagin and Yakataga seismic gaps, and a less certain potential for a large or great earthquake in the possible Unalaska gap. A tilt reversal was geodetically observed to have occurred in 1978/79 in the forearc region of the Shumagin gap and could indicate the onset of a precursory strain relief episode prior to a great quake. A comparative study of the Pavlof volcano seismicity with that of other recently active volcanoes (i.e., Mt. St. Helens) indicates that island-arc (explosive-type) volcanoes respond to small ambient, periodic stress changes (i.e., tides). Stress drop measurements from earthquakes on the main thrust zone indicate high stress drops within the seismic gap regions of the Aleutian arc and low stress drops outside the gap region.

  14. Single-Wall Carbon Nanotube Production by the Arc Process: A Parametric Study

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Gorelik, Olga; Proft, William J.

    2000-01-01

    Single wall carbon nanotubes are produced using the arc discharge process. Graphite anodes are filled with a mixture of nickel and yttrium metallic powders, then vaporized by creating a high current arc. By varying the current, gap distance, and ambient pressure it is shown that the best yield of single wall carbon nanotubes is obtained within a narrow range of conditions. The relative yield and purity of the product are indicated semi-quantitatively from scanning electric microscopy (SEM) and thermogravimetric analysis (TGA). Two types of anodes have been investigated. The first is hollow and filled with a powder mixture of graphite, nickel and yttrium. The second is filled with a paste made of a mixture of metal nitrates, graphite powder and carbon adhesive, then reduced in an argon atmosphere at high temperature. Product purity and yield will be compared for the two types of anodes. The graphite in the anodes may have hydrogen attached in the pores. To remove this impurity anodes have been baked up to 1400 - 1500 C. The effect of baking the anodes on impurities in the product will be given.

  15. Traceability study of optical fiber degree of polarization (DOP) measurement

    NASA Astrophysics Data System (ADS)

    Xu, Nan; Li, Jianwei; Li, Jian; Zhang, Zhixin

    2013-09-01

    Degree of polarization (DOP) is an important physical quantity for describing the optical polarization effect and is widely applied in optical fiber communication, optical fiber gyro and the related technologies. Currently, the optical polarization degree tester for the purpose of communication uses mainly two kinds of measurement methods: Stokes vector method and extremum method. At present, there isn't a standard to measure the accuracy and consistency of DOP parameter measurement by the devices listed above, affecting seriously the application of DOP parameter measurement in the fields of optical fiber gyro and optical fiber communication. So, it is urgent to table the accurate guarantees to trace the source of quantitative values of the DOP measuring devices and testers. In this paper, the polarization beam combination method is raised to research and manufacture the standard optical fiber light source device with the variable DOP, and an indicated error measurement has been conducted for a DOP meter. A kind of standard optical fiber light source device that uses a single light source to realize the variable DOP is put forward. It is used to provide the accurate and variable optical fiber polarization degree light with a scope of 0~100%. It is used to calibrate the DOP meters and widely applied in the field of national defense and optical communication fields. By using the standard optical power meter, DOP value by which the optical power meter calculates the optical signal can be measured, which will be used ultimately for calibration of the DOP meter. A measurement uncertainty of 0.5% is obtained using the polarization beam combination method.

  16. Study of the mesosphere using wide-field twilight polarization measurements: Early results beyond the polar circle

    NASA Astrophysics Data System (ADS)

    Ugolnikov, O. S.; Kozelov, B. V.

    2016-07-01

    This paper discusses the results of early measurements of temperature and dust in the mesosphere on the basis of wide-field twilight sky polarimetry, which began in 2015 in Apatity (North of Russia, 67.6° N, 33.4° E) using the original entire-sky camera. These measurements have been performed for the first time beyond the Polar Circle in the winter and early spring period. The general polarization properties of the twilight sky and the procedure for identifying single scattering are described. The key results of the study include the Boltzmann temperature values at altitudes higher than 70 km and the conclusion on a weak effect of dust on scattering properties of the mesosphere during this period.

  17. Fluorescence polarization studies of autoionization in CS2

    NASA Astrophysics Data System (ADS)

    Poliakoff, E. D.; Dehmer, J. L.; Parr, A. C.; Leroi, G. E.

    1987-03-01

    The fluorescence polarization spectrum of CS2(+) produced by photoionization of CS2 (using synchrotron radiation from the NBS SURF-II electron-storage ring) at excitation wavelengths 875-967 A is investigated experimentally, with a focus on autoionization features. The results of polarization measurements for the A2Pi-X2Pi transition are presented in graphs and compared with spectra simulated using the procedure of Poliakoff et al. (1982); qualitative agreement is obtained, but quantitative discrepancies are noted, especially on the low-wavelength side of the resonance. The spectral assignments of Ogawa and Chang (1970) for the autoionizing Rydberg states are confirmed.

  18. Smile arcs of Caucasian and Korean youth.

    PubMed

    Dong, Jin-Keun; Rashid, Robert G; Rosenstiel, Stephen F

    2009-01-01

    This study was designed to measure and compare the smile arcs (tooth and lip arcs) of young Caucasian and Korean subjects. Two hundred subjects (100 male and 100 female) were selected from Caucasian and Korean students. Class photographs taken with a digital camera showing the subjects with a posed smile were used for this study. Curves were rendered as semitransparent overlays, which were manipulated over the images using Adobe Photoshop to determine the best fit for tooth and lip arcs. There were statistically significant differences due to ethnicity and gender. Mean lip arcs had greater curvature than mean tooth arcs.

  19. POLARIZED RADIO SOURCES: A STUDY OF LUMINOSITY, REDSHIFT, AND INFRARED COLORS

    SciTech Connect

    Banfield, Julie K.; George, Samuel J.; Taylor, A. Russ; Stil, Jeroen M.; Kothes, Roland; Scott, Douglas

    2011-05-20

    The Dominion Radio Astrophysical Observatory Deep Field polarization study has been matched with the Spitzer Wide-Area Infrared Extragalactic Survey of the European Large Area Infrared Space Observatory Survey North 1 field. We have used Very Large Array observations with a total intensity rms of 87 {mu}Jy beam{sup -1} to match SWIRE counterparts to the radio sources. Infrared color analysis of our radio sample shows that the majority of polarized sources are elliptical galaxies with an embedded active galactic nucleus. Using available redshift catalogs, we found 429 radio sources of which 69 are polarized with redshifts in the range of 0.04 < z < 3.2. We find no correlation between redshift and percentage polarization for our sample. However, for polarized radio sources, we find a weak correlation between increasing percentage polarization and decreasing luminosity.

  20. Aerocapture Design Study for a Titan Polar Orbiter

    NASA Astrophysics Data System (ADS)

    Nixon, C. A.; Kirchman, F.; Esper, J.; Folta, D.; Mashiku, A.

    2016-03-01

    In 2014 a team at NASA Goddard Space Flight Center (GSFC) studied the feasibility of using active aerocapture to reduce the chemical ΔV requirements for inserting a small scientific satellite into Titan polar orbit. The scientific goals of the mission would be multi-spectral imaging and active radar mapping of Titan's surface and subsurface. The study objectives were to: (i) identify and select from launch window opportunities and refine the trajectory to Titan; (ii) study the aerocapture flight path and refine the entry corridor; (iii) design a carrier spacecraft and systems architecture; (iv) develop a scientific and engineering plan for the orbital portion of the mission. Study results include: (i) a launch in October 2021 on an Atlas V vehicle, using gravity assists from Earth and Venus to arrive at Titan in January 2031; (ii) initial aerocapture via an 8-km wide entry corridor to reach an initial 350-6000 km orbit, followed by aerobraking to reach a 350-1500 km orbit, and a periapse raise maneuver to reach a final 1500 km circular orbit; (iii) a three-part spacecraft system consisting of a cruise stage, radiator module, and orbiter inside a heat shield; (iv) a 22-month mission including station keeping to prevent orbital decay due to Saturn perturbations, with 240 Gb of compressed data returned. High-level issues identified include: (i) downlink capability - realistic downlink rates preclude the desired multi- spectral, global coverage of Titan's surface; (ii) power - demise of the NASA ASRG (Advanced Stirling Radioisotope Generator) program, and limited availability at present of MMRTGs (Multi-Mission Radioisotope Generators) needed for competed outer planet missions; (iii) thermal - external radiators must be carried to remove 4 kW of waste heat from MMRTGs inside the aeroshell, requiring heat pipes that pass through the aeroshell lid, compromising shielding ability; (iv) optical navigation to reach the entry corridor; (v) the NASA requirement of continuous

  1. Aerocapture Design Study for a Titan Polar Orbiter

    NASA Technical Reports Server (NTRS)

    Nixon, Conor A.; Kirchman, Frank; Esper, Jaime; Folta, David; Mashiku, Alinda

    2016-01-01

    In 2014 a team at NASA Goddard Space Flight Center (GSFC) studied the feasibility of using active aerocapture to reduce the chemical Delta V requirements for inserting a small scientific satellite into Titan polar orbit. The scientific goals of the mission would be multi-spectral imaging and active radar mapping of Titan's surface and subsurface. The study objectives were to: (i) identify and select from launch window opportunities and refine the trajectory to Titan; (ii) study the aerocapture flight path and refine the entry corridor; (iii) design a carrier spacecraft and systems architecture; (iv) develop a scientific and engineering plan for the orbital portion of the mission. Study results include: (i) a launch in October 2021 on an Atlas V vehicle, using gravity assists from Earth and Venus to arrive at Titan in January 2031; (ii) initial aerocapture via an 8-km wide entry corridor to reach an initial 350X6000 km orbit, followed by aerobraking to reach a 350X1500 km orbit, and a periapse raise maneuver to reach a final 1500 km circular orbit; (iii) a three-part spacecraft system consisting of a cruise stage, radiator module, and orbiter inside a heat shield; (iv) a 22-month mission including station keeping to prevent orbital decay due to Saturn perturbations, with 240 Gb of compressed data returned. High-level issues identified include: (i) downlink capability - realistic downlink rates preclude the desired multi-spectral, global coverage of Titan's surface; (ii) power - demise of the NASA ASRG (Advanced Stirling Radioisotope Generator) program, and limited availability at present of MMRTGs (Multi-Mission Radioisotope Generators) needed for competed outer planet missions; (iii) thermal - external radiators must be carried to remove 4 kW of waste heat from MMRTGs inside the aeroshell, requiring heat pipes that pass through the aeroshell lid, compromising shielding ability; (iv) optical navigation to reach the entry corridor; (v) the NASA requirement of

  2. Thomas Paine's "Common Sense": A Study in Polarity.

    ERIC Educational Resources Information Center

    Blair, Carole

    Thomas Paine's "Common Sense," published in 1776, was a significant rhetorical event, having a polarizing effect on a situation marked by confusion and conflicting loyalties, in which prevailing views favored reconciliation of the American colonies with England. Paine's rhetoric intensified the conflict, forcing a cognitive restructuring…

  3. A STUDY OF RADIO POLARIZATION IN PROTOSTELLAR JETS

    SciTech Connect

    Cécere, Mariana; Velázquez, Pablo F.; De Colle, Fabio; Esquivel, Alejandro; Araudo, Anabella T.; Carrasco-González, Carlos; Rodríguez, Luis F.

    2016-01-10

    Synchrotron radiation is commonly observed in connection with shocks of different velocities, ranging from relativistic shocks associated with active galactic nuclei, gamma-ray bursts, or microquasars, to weakly or non-relativistic flows such as those observed in supernova remnants. Recent observations of synchrotron emission in protostellar jets are important not only because they extend the range over which the acceleration process works, but also because they allow us to determine the jet and/or interstellar magnetic field structure, thus giving insights into the jet ejection and collimation mechanisms. In this paper, we compute for the first time polarized (synchrotron) and non-polarized (thermal X-ray) synthetic emission maps from axisymmetrical simulations of magnetized protostellar jets. We consider models with different jet velocities and variability, as well as a toroidal or helical magnetic field. Our simulations show that variable, low-density jets with velocities of ∼1000 km s{sup −1} and ∼10 times lighter than the environment can produce internal knots with significant synchrotron emission and thermal X-rays in the shocked region of the leading bow shock moving in a dense medium. While models with a purely toroidal magnetic field show a very large degree of polarization, models with a helical magnetic field show lower values and a decrease of the degree of polarization, in agreement with observations of protostellar jets.

  4. Thomas Paine's "Common Sense": A Study in Polarity.

    ERIC Educational Resources Information Center

    Blair, Carole

    Thomas Paine's "Common Sense," published in 1776, was a significant rhetorical event, having a polarizing effect on a situation marked by confusion and conflicting loyalties, in which prevailing views favored reconciliation of the American colonies with England. Paine's rhetoric intensified the conflict, forcing a cognitive restructuring…

  5. Atomic and electronic structure of polar oxide interfaces: Electron microscopy and density functional theory study

    NASA Astrophysics Data System (ADS)

    Lazarov, Vlado

    Polar oxide interfaces are formed when two polar oxide surfaces join. The apparent presence of an electric dipole moment in the repeat unit parallel to the surface/interface closely relate the polar oxide interfaces instability to that of the of polar oxide surfaces. In this thesis, we combined Electron Microscopy and Density Functional Theory to study how the interface polarity affects the atomic and electronic structure of polar oxide interfaces, by using Fe3O4(111)/MgO(111) as a model system. The formation of Fe nanoinclusions found at the interface and within the polar Fe3 O4(111) film is proposed to be new stabilization mechanism for the magnetite film. High-resolution electron microscopy imaging of the interface together with first principle calculations suggest an atomically abrupt substrate-film interface determined with Fe monolayer in octahedral position (FeB). This interface stacking (O/Mg/O/3FeB/O) provides lowest total interface (system) energy and the most effectively screening of the MgO(111) substrate surface polarity. The results of our study suggest that surface polarity could be used as an additional growth parameter in creating novel material structures, such as metals in oxide matrices.

  6. [Study on ecological suitability of Gardenia jasminoides based on ArcGIS and Maxent model].

    PubMed

    Miao, Qi; Yuan, Yuan-Jian; Luo, Guang-Ming; Wei, Chun-Hua; Rao, Ya-Qi; Gong, Yu-Hong; Zhang, Lan; Shao, Jian; Dong, Yan-Kai

    2016-09-01

    The application of ArcGIS and Maxent modelto analyze the ecological suitability of Gardenia jasminoides.Taking 85 batches of Gardenia as the basis of analysis, the selection of ecological factors for the growth of Gardenia. The results showed that the average precipitation in April, the average precipitation in November and the average precipitation in August were the most important factors affecting the growth of Gardenia. The relative concentration of Gardenia suitable growth region,north to the south of Shaanxi province, south of Henan, central Anhui, south to the north of Hainan province, west to central Sichuan province, east of Zhejiang coastal area, northeast of Taiwan. Copyright© by the Chinese Pharmaceutical Association.

  7. [Effect of welding arcs on the eyes of patients with contact lenses (literature study)].

    PubMed

    Stahler, D; Teubel, H; Karsten, H

    1989-01-01

    Two accidents had been reported from abroad, within which contact lense users grew blind after staying quite near at electrical arcs. It is supposed that the contact lenses had been "welded" with the cornea by influence of the electromagnetic radiation. Removal of lenses shall have caused the cornea "ablation" and thus the subjects permanent blindness. Nilsson et al. (1, 2, 5) performed intensive animal tests which proved, that contact lenses get hot in special spectral ranges thus underlying a certain drying up. The "welding" between contact lenses and the cornea could not be confirmed by test animals, but partial glueing of contact lenses and cornea and surface lesions of the epithelium as well in some cases. Hüer and Conrads (3, 4) experimenting on enucleated pigs' eyes, reported on similar results.

  8. Thermodynamic study on the formation of acetylene during coal pyrolysis in the arc plasma jet

    SciTech Connect

    Bao, W.; Li, F.; Cai, G.; Lu, Y.; Chang, L.

    2009-07-01

    Based on the principle of minimizing the Gibbs free energy, the composition of C-H-O-N-S equilibrium system about acetylene formation during the pyrolysis in arc plasma jet for four kinds of different rank-ordered coals such as Datong, Xianfeng, Yangcheng, and Luan was analyzed and calculated. The results indicated that hydrogen, as the reactive atmosphere, was beneficial to the acetylene formation. The coal ranks and the hydrogen, oxygen, nitrogen, and sulfur in coal all could obviously affect the acetylene yield. The mole fraction of acetylene is the maximum when the ratio value of atom H/C was 2. The content of oxygen was related to the acetylene yield, but it does not compete with CO formation. These agreed with the experimental results, and they could help to select the coal type for the production of acetylene through plasma pyrolysis process.

  9. CIDEP study of two photochemical processes of triplet-state benzophenone and N,N-diethylaniline system in polar and non-polar media

    NASA Astrophysics Data System (ADS)

    Miyagawa, K.; Murai, H.; I'Haya, Y. J.

    1985-07-01

    The photochemical reactions between nπ * triplet benzophenone and N,N-diethylaniline have been studied by the CIDEP method in both polar and non-polar media. The total emission pattern of the spectrum detected after pulsed excitation reveals a predominant contribution of the triplet mechanism in both media. The observed CIDEP clearly indicates the existence of two different processes depending on the polarity of the solvents.

  10. A radial velocity study of the intermediate polar EX Hydrae

    NASA Astrophysics Data System (ADS)

    Echevarría, J.; Ramírez-Torres, A.; Michel, R.; Hernández Santisteban, J. V.

    2016-09-01

    A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high-dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated with the orbital modulation. Since our eclipse timings have been obtained almost 91 000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system shows double-peaked H α, H β and He I λ5876 Å emission lines, with almost no other lines present. As H α is the only line with enough S/N ratio in our observations, we have concentrated our efforts in its study, in order to obtain a reliable radial velocity semi-amplitude. From the profile of this line, we find two important components; one with a steep rise and velocities not larger than ˜1000 km s-1 and another broader component extending up to ˜2000 km s-1, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to K1 = 58 ± 5 km s-1 from H α, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving K1. This value is compatible with the values found in high resolution both in the ultraviolet and X-ray. Using the published inclination angle of i =78° ± 1° and semi-amplitude K2 = 432 ± 5 km s-1, we find: M1 = 0.78 ± 0.03 M⊙, M2 = 0.10 ± 0.02 M⊙ and a = 0.67 ± 0.01 R⊙. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions

  11. Weld arc simulator

    DOEpatents

    Burr, Melvin J.

    1990-01-30

    An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  12. Weld arc simulator

    SciTech Connect

    Burr, M.J.

    1989-03-01

    An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  13. Weld arc simulator

    SciTech Connect

    Burr, M.J.

    1990-01-30

    This patent describes an arc voltage simulator for an arc welder which permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  14. Modelization of nanospace interaction involving a ferromagnetic atom: a spin polarization effect study by thermogravimetric analysis.

    PubMed

    Santhanam, K S V; Chen, Xu; Gupta, S

    2014-04-01

    Ab initio studies of ferromagnetic atom interacting with carbon nanotubes have been reported in the literature that predict when the interaction is strong, a higher hybridization with confinement effect will result in spin polarization in the ferromagnetic atom. The spin polarization effect on the thermal oxidation to form its oxide is modeled here for the ferromagnetic atom and its alloy, as the above studies predict the 4s electrons are polarized in the atom. The four models developed here provide a pathway for distinguishing the type of interaction that exists in the real system. The extent of spin polarization in the ferromagnetic atom has been examined by varying the amount of carbon nanotubes in the composites in the thermogravimetric experiments. In this study we report the experimental results on the CoNi alloy which appears to show selective spin polarization. The products of the thermal oxidation has been analyzed by Fourier Transform Infrared Spectroscopy.

  15. Lunar polarization studies at 3.1 mm wavelength

    NASA Technical Reports Server (NTRS)

    White, T. L.; Cogdell, J. R.

    1973-01-01

    Observations of the distribution of linearly polarized lunar thermal emission were made at a wavelength of 3.1 mm with The University of Texas 4.88 m parabolic reflector (0.042 deg HPBW). A shadow corrected, rough surface, thermal emission model for a homogeneous moon was least-squares-fitted to the polarization data. Results indicate an effective lunar dielectric constant of 1.34 plus or minus 0.04 with surface roughness characterized by a standard deviation of 17 (plus or minus 5) deg for surface slopes with a normal probability density, independent of lunar phase. A comparison of these results with published values at other wavelengths suggests that the effective lunar dielectric constant, as obtained by lunar emission measurements, decreases with decreasing wavelength of observation. This wavelength dependence may be interpreted in terms of an inhomogeneous surface and/or a surface that possesses intermediate scale surface roughness.

  16. Studies of Martian polar regions. [using CO2 flow

    NASA Technical Reports Server (NTRS)

    Smith, C. I.; Clark, B. R.; Eschman, D. F.

    1974-01-01

    The flow law determined experimentally for solid CO2 establishes that an hypothesis of glacial flow of CO2 at the Martian poles is not physically unrealistic. Compression experiments carried out under 1 atmosphere pressure and constant strain rate conditions demonstrate that the strength of CO2 near its sublimation point is considerably less than the strength of water ice near its melting point. A plausible glacial model for the Martian polar caps was constructed. The CO2 deposited near the pole would have flowed outward laterally to relieve high internal shear stresses. The topography of the polar caps, and the uniform layering and general extent of the layered deposits were explained using this model.

  17. Gamma-Ray Polarization Studies with CGRO/COMPTEL

    NASA Astrophysics Data System (ADS)

    McConnell, Mark

    We propose a two year program to re-analyze COMPTEL data in search for evidence of polarization in both transient sources and in brighter steady sources. We propose to pursue this work because of the heightened interest in high energy polarimetry, the recognition that some high energy sources may be highly polarized (thus improving our chances of a making useful measurements), and the ready availability of modern computing resources that provide the ability to carry out more comprehensive simulations in support of the analysis. The only significant work done to date with regards to COMPTEL polarimetry was published almost 20 years ago and used a simplified mass model of COMPTEL for simulating the instrument response. Estimates of the minimum detectable polarization (MDP) near 1 MeV included 30% for a two-week observation of the Crab, as low as 10% for bright GRBs, and as low as 10% for bright solar flares. The data analysis performed at the time led to inconclusive results and suggested some unknown systematic error. We contend that a self-consistent analysis will be feasible with high fidelity simulations, simulations that were not easily generated 20 years ago. Our analysis will utilize the latest GEANT4 simulation tools in conjunction with a high-fidelity mass model of the COMPTEL instrument, and incorporate updated analysis tools originally developed by the COMPTEL collaboration. Given the nine years of COMPTEL data, we expect that this work will likely add to our understanding of the polarization properties of transient sources (GRBs and solar flares), as well as brighter steady sources, such as the Crab and Cyg X-1.

  18. Ab Initio Study of Ultracold Polar Molecules in Optical Lattices

    DTIC Science & Technology

    2010-01-01

    polar molecules by using optical lattices and microwave fields’’, US-Japan Joint Seminar on Coherent Quantum Systems, Breckenridge, USA, August (2006...corresponds to the dissociation energy of both 40K and 87Rb in the energetically lowest hyperfine state . The levels are grouped by the projection quantum ...vibrational state . The J = 1 to J = 2 transition occurs at a larger photon frequency. For the near-resonance frequencies the polarizabilities in Fig

  19. Airborne antenna polarization study for the microwave landing system

    NASA Technical Reports Server (NTRS)

    Gilreath, M. C.

    1976-01-01

    The feasibility of the microwave landing system (MLS) airborne antenna pattern coverage requirements are investigated for a large commercial aircraft using a single omnidirectional antenna. Omnidirectional antennas having vertical and horizontal polarizations were evaluated at several different station locations on a one-eleventh scale model Boeing 737 aircraft. The results obtained during this experimental program are presented which include principal plane antenna patterns and complete volumetric coverage plots.

  20. Study of electronic structure and spin polarization of dysprosium

    SciTech Connect

    Mund, H. S.

    2015-06-24

    In this paper, I have presented the spin-dependent momentum density of ferromagnetic dysprosium using spin polarized relativistic Korringa-Kohn-Rostoker method. A fully relativistic approach has been used to determine the magnetic Compton profile. The density of state in term of majority-spin and minority-spin of Dy also calculated using SPR-KKR. The magnetic Compton profile discussed in term of 4f and diffused electrons.

  1. Study on the Polarity Riddle of the Dense Plasma Focus

    NASA Astrophysics Data System (ADS)

    Jiang, Sheng; Link, Anthony; Higginson, Drew; Schmidt, Andrea

    2016-10-01

    The dense plasma focus (DPF) Z-pinch devices are capable of producing intense pulses of X-rays and neutrons, thus can serve as portable sources for active interrogation. DPF devices are normally operated with the inner electrode as anode. It has been found that interchanging the polarity of the electrodes can cause orders of magnitude decrease in the neutron yield1. The reason for this severe decay remains unclear. Here we use the particle-in-cell (PIC) code LSP2,3 to model a portable DPF with both polarities. The filling gas is deuterium. The simulations are run in the fluid mode for the rundown phase and are switched to kinetic to capture the anomalous resistivity and beam acceleration process during the pinch. The difference in the shape of the sheath, the voltage and current traces, and the electric and magnetic fields in the pinch region due to different polarities all have great effects on the deuteron ion spectrum, which further determines the neutron yield. A detailed comparison will be presented. Prepared by LLNL under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (15-ERD-034) at LLNL.

  2. Polarization studies of strained GaAs photocathodes at the SLAC Gun Test Laboratory

    SciTech Connect

    Saez, P.; Alley, R.; Clendenin, J.; Frisch, J.; Kirby, R.; Mair, R.; Maruyama, T.; Miller, R.; Mulhollan, G.; Prescott, C.

    1995-08-01

    The SLAC Gun Test Laboratory apparatus, the first two meters of which is a replica of the SLAC injector, is used to study the production of intense, highly-polarized electron beams required for the Stanford Linear Collider and future linear colliders. The facility has been upgraded with a Mott polarimeter in order to characterize the electron polarization from photocathodes operating in a DC gun. In particular, SLAC utilizes p-type, biaxially strained GaAs photocathodes which have produced longitudinal electron polarizations greater than 80% while yielding pulses of 5 A/sq cm at an operating voltage of 120 kV. Among the experiments performed include studying the influences of the active layer thickness, temperature, quantum efficiency and cessation on the polarization. The results might help to develop strained photocathodes with higher polarization.

  3. Fatigue Crack Growth Rate Test Results for Al-Li 2195 Parent Metal, Variable Polarity Plasma Arc Welds and Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Hafley, Robert A.; Wagner, John A.; Domack, Marcia S.

    2000-01-01

    The fatigue crack growth rate of aluminum-lithium (Al-Li) alloy 2195 plate and weldments was determined at 200-F, ambient temperature and -320-F. The effects of stress ratio (R), welding process, orientation and thickness were studied. Results are compared with plate data from the Space Shuttle Super Lightweight Tank (SLWT) allowables program. Data from the current series of tests, both plate and weldment, falls within the range of data generated during the SLWT allowables program.

  4. Arc spot grouping: An entanglement of arc spot cells

    SciTech Connect

    Kajita, Shin; Hwangbo, Dogyun; Ohno, Noriyasu; Tsventoukh, Mikhail M.; Barengolts, Sergey A.

    2014-12-21

    In recent experiments, clear transitions in velocity and trail width of an arc spot initiated on nanostructured tungsten were observed on the boundary of the thick and thin nanostructured layer regions. The velocity of arc spot was significantly decreased on the thick nanostructured region. It was suggested that the grouping decreased the velocity of arc spot. In this study, we try to explain the phenomena using a simple random walk model that has properties of directionality and self-avoidance. And grouping feature was added by installing an attractive force between spot cells with dealing with multi-spots. It was revealed that an entanglement of arc spot cells decreased the spot velocity, and spot cells tend to stamp at the same location many times.

  5. Trench-parallel crustal anisotropy along the trench in the fore-arc region of Japan

    NASA Astrophysics Data System (ADS)

    Iidaka, Takashi; Muto, Jun; Obara, Kazushige; Igarashi, Toshihiro; Shibazaki, Bunichiro

    2014-03-01

    In northeastern Japan, the Pacific plate is descending beneath the North American plate. It is generally understood that trench-normal principal stress is dominant in the crust along the Japanese island arc, because the stress field is controlled by the force of the subducting slab. Observations of shear wave splitting using crustal earthquakes reveal a marked lateral variation in fast-polarization direction with distance from the trench. Trench-normal and trench-parallel fast-polarization directions are observed on the back-arc and fore-arc sides, respectively. In this study, two-dimensional finite element modeling with subducting slab was conducted to investigate the interseismic stress field during earthquake cycles, taking into account linear viscoelasticity. In the model, trench-normal compression is found to dominate in the island arc region. However, an extensional field appears in the shallow upper crust of the fore-arc region during earthquake cycles. The trench-parallel crustal anisotropy can be explained by this extensional field.

  6. Electron microscopy and small angle neutron scattering study of precipitation in low alloy steel submerged-arc welds

    SciTech Connect

    Williams, T.J.; Phythian, W.J.

    1996-12-31

    In previous studies, submerged-arc welds with a range of compositions were irradiated in test reactors over a range of dose and dose-rates. The effect of irradiation was measured by Charpy V-notch and hardness tests, and an irradiation response model was developed. In this paper the authors report the results of a combined electron microscopy and small angle neutron scattering (SANS) study on material from some of the Charpy specimens. The results have been interpreted in terms of the Russell and Brown modulus hardening model. In general they have confirmed the predictions of the irradiation response model, and shown that the copper precipitation contribution to the observed macroscopic to the observed macroscopic hardening is strongly dependent on nickel, dose and dose-rate.

  7. Detection of degree-scale B-mode polarization and studying cosmic polarization rotation with the BICEP1 and BICEP2 telescopes

    NASA Astrophysics Data System (ADS)

    Kaufman, Jonathan Philip

    The BICEP1 and BICEP2 telescopes studied the temperature and polarization of the Cosmic Microwave Background (CMB) from 2006 -- 2008 and 2010 -- 2012, respectively, producing the deepest maps of polarization created to date. From BICEP2 three-year data, we detect B-mode polarization at the degree-scale above the expectation from lensed-ΛCDM to greater than 5sigma significance, consistent with that expected from gravitational waves created during Inflation. Instrumental systematic effects have been characterized and ruled out, and galactic foreground contamination is disfavored by the data. Additionally, correlations between temperature and B-mode polarization and between E-mode and B-mode polarization show evidence of polarization rotation of --1° to 5sigma significance; however, adding systematic uncertainty reduces this significance to ˜ 2sigma. These measurements, combined with other CMB and astrophysical measurements, point to possible parity violating physics like cosmic birefringence, but more precise calibration techniques are required to break the degeneracy between cosmic polarization rotation and systematic effects. Improved calibration is possible with current generation technology and may be achieved within the next few years. In this work, I present experimental and analysis techniques employed for BICEP1 and BICEP2 to measure B-mode polarization and temperature and polarization correlations, as well as the scientific motivation, results, and a path forward for future measurements.

  8. In vitro studies on silver implanted pure iron by metal vapor vacuum arc technique.

    PubMed

    Huang, Tao; Cheng, Yan; Zheng, Yufeng

    2016-06-01

    Pure iron has been verified as a promising biodegradable metal for absorbable cardiovascular stent usage. However, the degradation rate of pure iron is too slow. To accelerate the degradation of the surface of pure iron, silver ions were implanted into pure iron by metal vapor vacuum arc (MEVVA) source at an extracted voltage of 40keV. The implanted influence was up to 2×10(17)ions/cm(2). The composition and depth profiles, corrosion behavior and biocompatibility of Ag ion implanted pure iron were investigated. The implantation depths of Ag was around 60nm. The element Ag existed as Ag2O in the outermost layer, then gradually transited to metal atoms in zero valent state with depth increase. The implantation of Ag ions accelerated the corrosion rate of pure iron matrix, and exhibited much more uniform corrosion behavior. For cytotoxicity assessment, the implantation of Ag ions slightly decreased the viability of all kinds of cell lines used in these tests. The hemolysis rate of Ag ion implanted pure iron was lower than 2%, which was acceptable, whereas the platelet adhesion tests indicated the implantation of Ag ions might increase the risk of thrombosis.

  9. Feasibility study of volumetric modulated arc therapy with constant dose rate for endometrial cancer

    SciTech Connect

    Yang, Ruijie; Wang, Junjie; Xu, Feng; Li, Hua; Zhang, Xile

    2013-10-01

    To investigate the feasibility, efficiency, and delivery accuracy of volumetric modulated arc therapy with constant dose rate (VMAT-CDR) for whole-pelvic radiotherapy (WPRT) of endometrial cancer. The nine-field intensity-modulated radiotherapy (IMRT), VMAT with variable dose-rate (VMAT-VDR), and VMAT-CDR plans were created for 9 patients with endometrial cancer undergoing WPRT. The dose distribution of planning target volume (PTV), organs at risk (OARs), and normal tissue (NT) were compared. The monitor units (MUs) and treatment delivery time were also evaluated. For each VMAT-CDR plan, a dry run was performed to assess the dosimetric accuracy with MatriXX from IBA. Compared with IMRT, the VMAT-CDR plans delivered a slightly greater V{sub 20} of the bowel, bladder, pelvis bone, and NT, but significantly decreased the dose to the high-dose region of the rectum and pelvis bone. The MUs decreased from 1105 with IMRT to 628 with VMAT-CDR. The delivery time also decreased from 9.5 to 3.2 minutes. The average gamma pass rate was 95.6% at the 3%/3 mm criteria with MatriXX pretreatment verification for 9 patients. VMAT-CDR can achieve comparable plan quality with significant shorter delivery time and smaller number of MUs compared with IMRT for patients with endometrial cancer undergoing WPRT. It can be accurately delivered and be an alternative to IMRT on the linear accelerator without VDR capability.

  10. Study on visual image information detection of external angle weld based on arc welding robot

    NASA Astrophysics Data System (ADS)

    Liu, Xiaorui; Liu, Nansheng; Sheng, Wei; Hu, Xian; Ai, Xiaopu; Wei, Yiqing

    2009-11-01

    Nowadays, the chief development trend in modern welding technology is welding automation and welding intelligence. External angle weld has a certain proportion in mechanical manufacture industries. In the real-time welding process, due to hot deformation and the fixture of workpieces used frequently, torch will detach welding orbit causes deviation, which will affect welding quality. Therefore, elimination weld deviation is the key to the weld automatic tracking system. In this paper, the authors use the self-developed structured light vision sensor system which has significant advantage compared with arc sensors to capture real-time weld images. In the project of VC++6.0 real-time weld image processing, after binaryzation with threshold value seventy, 3*1 median filter, thinning, obtain weld main stripe. Then, using the extraction algorithm this paper proposed to obtain weld feature points, and compute position of weld. Experiment result verified that the extraction algorithm can locate feature points rapidly and compute the weld deviation accurately.

  11. Microstructural Study of 17-4PH Stainless Steel after Plasma-Transferred Arc Welding

    PubMed Central

    Deng, Dewei; Chen, Rui; Sun, Qi; Li, Xiaona

    2015-01-01

    The improvement of the surface qualities and surface hardening of precipitation hardened martensitic stainless steel 17-4PH was achieved by the plasma-transferred arc welding (PTAW) process deposited with Co-based alloy. The microstructure of the heat affected zone (HAZ) and base metal were characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that there are obvious microstructural differences between the base metal and HAZ. For example, base material is transformed from lath martensite to austenite due to the heateffect of the welding process. On the other hand, the precipitate in the matrix (bar-like shape Cr7C3 phase with a width of about one hundred nanometres and a length of hundreds of nanometres) grows to a rectangular appearance with a width of about two hundred nanometres and a length of about one micron. Stacking fault could also be observed in the Cr7C3 after PTAW. The above means that welding can obviously improve the surface qualities. PMID:28787947

  12. Determination of the partial pressure of thallium in high-pressure lamp arcs: A comparative study

    SciTech Connect

    Karabourniotis, D.; Couris, S.; Damelincourt, J.J.; Aubes, M.

    1986-08-01

    The partial pressure of thallium in high-pressure Hg-TlI discharges with different mercury, thallium, and electron pressures has been measured by using the optically thin line Tl 655 nm and the self-reversed line Tl 535 nm. The partial pressure of the arc axis has been measured from the line Tl 655nm. The effective partial pressure has been measured from the self-reversed line Tl 535 nm on the basis of the multiparameter method, and it has been calculated from the known axis pressure of thallium and the calculation of its radial variation by taking into account the chemical reactions. The experimental results confirm the dispersion character of the blue wing of the line Tl 535 nm. The systematic difference obtained between the measured and calculated effective pressure, particularly at the moment of minimum electron density, may be interpreted by deviations from the local thermodynamic equilibrium (LTE) caused by overpopulation of the upper level of the line Tl 535 nm.

  13. A microstructural study of phosphorus segregation and intergranular fracture in neutron irradiated submerged-arc welds

    SciTech Connect

    Bischler, P.J.E.; Wild, R.K.

    1996-12-31

    Accelerated irradiation experiments have been carried out on submerged-arc welds to obtain validation of trend curves built up from surveillance results. This was done by withdrawing surveillance specimens and re-irradiating them in higher flux positions. One batch, from weld HS, showed a significantly higher increase in the Charpy {Delta}T{sub 40J} value than that for weld LS at a similar dose. Work done to explain this difference is described in this paper. Selected Charpy specimens were examined using a shielded scanning electron microscope to determine the fracture modes present. Regions of mixed cleavage, micro-void coalescence (MVC) and intergranular failure (IGF) were found on HS weld specimens fractured in the transition region. The IFG was confined to certain regions within each weld bead. Significantly less IGF was found on LS weld specimens. Sub-fracture surface matchstick specimens were removed from embrittled regions and fractured within a scanning Auger microscope. IGF occurred in these specimens, and phosphorus was found to be the main grain boundary segregant. The levels of phosphorus increased with increasing neutron dose. No other embrittling element was consistently found at any significant level, but carbon was also found on grain boundary surfaces in some cases. The grain boundary coverage of phosphorus was determined for each weld at several neutron dose levels.

  14. Microstructural Study of 17-4PH Stainless Steel after Plasma-Transferred Arc Welding.

    PubMed

    Deng, Dewei; Chen, Rui; Sun, Qi; Li, Xiaona

    2015-01-29

    The improvement of the surface qualities and surface hardening of precipitation hardened martensitic stainless steel 17-4PH was achieved by the plasma-transferred arc welding (PTAW) process deposited with Co-based alloy. The microstructure of the heat affected zone (HAZ) and base metal were characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that there are obvious microstructural differences between the base metal and HAZ. For example, base material is transformed from lath martensite to austenite due to the heateffect of the welding process. On the other hand, the precipitate in the matrix (bar-like shape Cr₇C₃ phase with a width of about one hundred nanometres and a length of hundreds of nanometres) grows to a rectangular appearance with a width of about two hundred nanometres and a length of about one micron. Stacking fault could also be observed in the Cr₇C₃ after PTAW. The above means that welding can obviously improve the surface qualities.

  15. Study for the electric arc of alternative current at the single phase welding machine using the Matlab/Simulink environment

    NASA Astrophysics Data System (ADS)

    Baciu, I.; Ghiormez, L.; Vasar, C.

    2017-01-01

    In this paper is presented a mathematical model of the electric arc for an alternative current welding machine of low power. The electric arc model is based on dividing the voltage-current characteristic of the electric arc in many functioning zones. For the model of the entire welding machine are used real parameters as the ones of the proper welding machine. The voltage and current harmonics spectrum that is obtained during the welding process is presented. Also, the waveforms for the current and voltage of the electric arc plotted against time and the voltage-current characteristic of the electric arc are illustrated. The electric arc is considered as being supplied by alternative voltage from the electrical power network using a single phase transformer which has the output voltage of 80 volts. The model of the welding machine is developed in Simulink and the variations of some parameters of the electric arc are obtained by modifying of them in a Matlab function. Also, in this paper is presented the total harmonic distortion for the voltage and current of the electric arc obtained during simulation of the welding machine.

  16. Experimental research on electric propulsion. Note 5: Experimental study of a magnetic field stabilized arc-jet

    NASA Technical Reports Server (NTRS)

    Robotti, A. C.; Oggero, M.

    1984-01-01

    The possibility of using an electric arc under the influence of a magnetic field in ambient air to transform the heat energy of the working fluid arc into the kinetic energy of the jet was investigated. A convergent-divergent type nozzle was used. Variation of specific thrust and chamber pressure are discussed. Nitrogen was the propellant used.

  17. Polarization and charge limit studies of strained GaAs photocathodes

    SciTech Connect

    Saez, P.J.

    1997-03-01

    This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of {approximately} 2.5 A/cm{sup 2} at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don`t have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes.

  18. Dynamic nuclear-polarization studies of paramagnetic species in solution

    SciTech Connect

    Glad, W.E.

    1982-07-01

    Dynamic Nuclear Polarization (DNP) was used to measure the electron spin lattice relaxation times, T/sub 1/, of transition metal ions in aqueous solution. Saturation which is induced in the electron spin system is transferred to the solvent proton spins by dipole-dipole interactions. The change in the polarization of the proton spins is much larger than it is in the electron spins. The change in proton polarization is easily measured by proton Nuclear Magnetic Resonance (NMR). In one experimental arrangement the sample solution was continuously flowed through a microwave cavity to the NMR coil. The NMR was observed with a continuous wave NMR spectrometer. In a second arrangement the whole sample tube was moved from within the microwave cavity to the NMR coil in less than 40 ms by a blast of compressed air. The NMR was then observed with a pulse-Fourier-transform spectrometer. With the second arrangement a mean-square microwave magnetic field at the sample of more than 10 G/sup 2/ is obtainable with 14 W of microwave power. Measurements of DNP at 9 GHz were made on aqueous solutions of VO/sup 2 +/, Mn/sup 2 +/, Cr(CN)/sub 6//sup 3 -/, Cu/sup 2 +/ and Cu(ethylenediamine)/sub 2/(H/sub 2/0)/sub 2//sup 2 +/ ions from 3 to 60/sup 0/C. It was also possible to observe DNP on resolved proton resonances from mixed water-acetonitrile solutions of VO/sup 2 +/ and Cr(CN)/sub 6//sup 3 -/ ions.

  19. A Polarization and Spectral Study of the Mouse

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.; Gaensler, B.; Law, C.

    Recent detection of a young pulsar powering the Mouse G359.23-0.82 (Camilo et al. 2002) as well as the discovery of diffuse X-ray emission from the nebula (Gaensler et al. 2004) have motivated us to investigate the structural details of this remarkable source in radio wavelengths. We present multi-configuration VLA observations of the Mouse with its pulsar powered bow shock between 2 and 90cm wavelengths and compare the morphological details of its polarized and total intensity emission. We also show the spectral characteristics across this elongated radio and X-ray source

  20. Polarization Studies of Resonant Forbidden Reflections in Liquid Crystals

    SciTech Connect

    Fernandes, P.; Barois, P.; Nguyen, H. T.; Wang, S. T.; Liu, Z. Q.; McCoy, B. K.; Huang, C. C.; Pindak, R.; Caliebe, W.

    2007-11-30

    We report the results of resonant x-ray diffraction experiments performed on thick films of a biaxial liquid crystal made of achiral bent-core molecules. Polarization properties of forbidden reflections are observed as a function of the sample rotation angle {phi} about the scattering vector Q for the first time on a fluid material. The experimental data are successfully analyzed within a tensor structure factor model by taking the nonperfect alignment of the liquid crystal into account. The local structure of the B{sub 2} mesophase is hence determined to be SmC{sub S}P{sub A}.

  1. Modified elliptically polarized light Z-scan method for studying third-order nonlinear susceptibility components.

    PubMed

    Yan, Xiao-Qing; Liu, Zhi-Bo; Zhang, Xiao-Liang; Zang, Wei-Ping; Tian, Jian-Guo

    2010-05-10

    The normal elliptically polarized light Z-scan method is modified by adding a quarter-wave plate and an analyzer before the detector. The normalized transmittance formulas of modified elliptically polarized light Z-scan are obtained for media with negligible nonlinear absorption. Compared with normal linearly and elliptically polarized light Z-scan methods, an increase of sensitivity by a factor of larger than 4 is achieved for the real part of third-order susceptibility component's measurements using this modified elliptically polarized light Z-scan method. The analytical results are verified by studying the real part of independent susceptibility components of CS(2) liquid. Moreover, the potential application for cross-polarized wave generation is discussed. (c) 2010 Optical Society of America.

  2. The surface magnetization study of Cr2O3 by spin polarized low energy electron microscopy

    NASA Astrophysics Data System (ADS)

    Cao, Shi; Wu, Ning; Zhang, Xin; N'diaye, Alpha; Chen, Gong; Schmid, Andreas; Echtenkamp, Will; Lauter, Valeria; Binek, Christian; Dowben, Peter

    2014-03-01

    The boundary magnetization at the surface of a Cr2O3 single crystal has been demonstrated by using spin-polarized low-energy electron microscopy (SPLEEM), indicating net surface spin polarization. This work shows that the placement of Cr2O3 single crystal in the single domain state, will result in net Cr2O3 spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the spin-polarized low-energy electron microscopy (SPLEEM) contrast for the two polarizations states is different. In addition, the boundary magnetization protected by the symmetry exists despite of the surface roughness/softness which was studied by the non-spin neutron reflectometry and low energy electron diffraction. Unoccupied surface oxygen sites and chromium sites are possible mechanism contributing to the surface ``softness,'' which will be discussed.

  3. Gas arc constriction for plasma arc welding

    NASA Technical Reports Server (NTRS)

    McGee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

    1994-01-01

    A welding torch for plasma arc welding apparatus has an inert gas applied circumferentially about the arc column externally of the constricting nozzle so as to apply a constricting force on the arc after it has exited the nozzle orifice and downstream of the auxiliary shielding gas. The constricting inert gas is supplied to a plenum chamber about the body of the torch and exits through a series of circumferentially disposed orifices in an annular wall forming a closure at the forward end of the constricting gas plenum chamber. The constricting force of the circumferential gas flow about the arc concentrates and focuses the arc column into a more narrow and dense column of energy after exiting the nozzle orifice so that the arc better retains its energy density prior to contacting the workpiece.

  4. Cluster observations of the plasma sheet at very high latitudes: The in situ signature of a transpolar arc

    NASA Astrophysics Data System (ADS)

    Fear, R. C.; Milan, S. E.; Maggiolo, R.

    2013-12-01

    Transpolar arcs are auroral features which extend into the polar cap, which is the dim region poleward of the main auroral oval. Several case and statistical studies have shown that they are formed by the closure of lobe magnetic flux by magnetotail reconnection, and that the transpolar arc forms at the footprints of the newly-closed field lines which are embedded within the open flux of the polar cap. Therefore, when transpolar arcs occur, the magnetotail should contain closed magnetic field lines even at high latitudes (but in a localised sector), embedded within the open lobe flux. We present in situ observations of this phenomenon, taken by the Cluster spacecraft on 15th September 2005. Cluster was located at high latitudes in the southern hemisphere lobe (far from the typical location of the plasma sheet), and a transpolar arc was observed by the FUV cameras on the IMAGE satellite. An initial analysis reveals that Cluster periodically observed plasma similar to a typical plasma sheet distribution, but at much higher latitudes - indicative of closed flux embedded within the high latitude lobe. Each time that this plasma distribution was observed, the footprint of the spacecraft mapped to the transpolar arc (significantly poleward of the main auroral oval). These observations are consistent with closed flux being trapped in the magnetotail and embedded within the lobe, and provide further evidence for transpolar arcs being formed by magnetotail reconnection.

  5. Study of Radiographic Linear Indications and Subsequent Microstructural Features in Gas Tungsten Arc Welds of Inconel 718

    NASA Technical Reports Server (NTRS)

    Walley, J. L.; Nunes, A. C.; Clounch, J. L.; Russell, C. K.

    2007-01-01

    This study presents examples and considerations for differentiating linear radiographic indications produced by gas tungsten arc welds in a 0.05-in-thick sheet of Inconel 718. A series of welds with different structural features, including the enigma indications and other defect indications such as lack of fusion and penetration, were produced, radiographed, and examined metallographically. The enigma indications were produced by a large columnar grain running along the center of the weld nugget occurring when the weld speed was reduced sufficiently below nominal. Examples of respective indications, including the effect of changing the x-ray source location, are presented as an aid to differentiation. Enigma, nominal, and hot-weld specimens were tensile tested to demonstrate the harmlessness of the enigma indication. Statistical analysis showed that there is no difference between the strengths of these three weld conditions.

  6. Volumetric Modulation Arc Radiotherapy Compared With Static Gantry Intensity-Modulated Radiotherapy for Malignant Pleural Mesothelioma Tumor: A Feasibility Study

    SciTech Connect

    Scorsetti, Marta; Bignardi, Mario; Clivio, Alessandro

    2010-07-01

    Purpose: A planning study was performed to evaluate RapidArc (RA), a volumetric modulated arc technique, on malignant pleural mesothelioma. The benchmark was conventional fixed-field intensity-modulated radiotherapy (IMRT). Methods and materials: The computed tomography data sets of 6 patients were included. The plans for IMRT with nine fixed beams were compared against double-modulated arcs with a single isocenter. All plans were optimized for 15-MV photon beams. The dose prescription was 54 Gy to the planning target volume. The planning objectives for the planning target volume were a minimal dose of >95% and maximal dose of <107%. For the organs at risk, the parameters were as follows: contralateral lung, percentage of volume receiving 5 Gy (V{sub 5Gy}) <60%, V{sub 20Gy} < 10%, mean <10.0 Gy; liver, V{sub 30Gy} <33%, mean <31 Gy; heart, V{sub 45Gy} <30%, V{sub 50Gy} <20%, dose received by 1% of the volume (D{sub 1%}) <60 Gy; contralateral kidney, V{sub 15Gy} <20%; spine, D{sub 1%} <45 Gy; esophagus, V{sub 55Gy} <30%; and spleen, V{sub 40Gy} <50%. The monitor units (MUs) and delivery time were scored to measure the treatment efficiency. The pretreatment portal dosimetry scored delivery to the calculation agreement with the Gamma Agreement Index. Results: RA and IMRT provided equivalent coverage and homogeneity. Both techniques fulfilled objectives on organs at risk with a tendency of RA to improve sparing. The conformity index was 1.9 {+-} 0.1 for RA and IMRT. The number of MU/2Gy was 734 {+-} 82 for RA and 2,195 {+-} 317 for IMRT. The planning vs. delivery agreement revealed a Gamma Agreement Index for IMRT of 96.0% {+-} 2.6% and for RA of 95.7% {+-} 1.5%. The treatment time was 3.7 {+-} 0.3min for RA and 13.4 {+-} 0.1min for IMRT. Conclusion: RA demonstrated compared with conventional IMRT, similar target coverage and better dose sparing to the organs at risks. The number of MUs and the time required to deliver a 2-Gy fraction were much lower for RA, allowing

  7. A Comparative Study of the Dispersion of Multi-Wall Carbon Nanotubes Made by Arc-Discharge and Chemical Vapour Deposition.

    PubMed

    Frømyr, Tomas-Roll; Bourgeaux-Goget, Marie; Hansen, Finn Knut

    2015-05-01

    A method has been developed to characterize the dispersion of multi-wall carbon nanotubes in water using a disc centrifuge for the detection of individual carbon nanotubes, residual aggregates, and contaminants. Carbon nanotubes produced by arc-discharge have been measured and compared with carbon nanotubes produced by chemical vapour deposition. Studies performed on both pristine (see text) arc-discharge nanotubes is rather strong and that high ultra-sound intensity is required to achieve complete dispersion of carbon nanotube bundles. The logarithm of the mode of the particle size distribution of the arc-discharge carbon nanotubes was found to be a linear function of the logarithm of the total ultrasonic energy input in the dispersion process.

  8. Study of nitrogen containing compounds in the polar troposphere.

    PubMed

    Ianniello, Antonietta; Sparapani, Roberto; Allegrini, Ivo; Vazzana, Caterina; Mazziotti, Carla; De Teran, Gomez; Montagnoli, Mauro; Fino, Alessandra; Felici, Andrea

    2003-01-01

    Atmospheric nitrogen compounds play a critical role in tropospheric photochemistry and are crucial to understand the chemical and physical evolution of atmospheric pollutants in polar areas. Measurements of these species in remote areas are rare, although their relevance is well established. Sampling campaigns of gaseous and particulate atmospheric trace species were performed in Arctic and in Antarctica during three consecutive years (1997-1999), using a proper combination of annular denuders and filter pack. After sampling, the ionic species were extracted with aqueous solutions and analysed by means of ion chromatography. Quality assurance on the sampling and analytical steps allowed accurate and precise measurements of all relevant compounds, which are thought to be important to nitrogen chemistry, at very low concentration levels. In addition, the measurements also included a multistage low-pressure impactor for the collection of particulate matter in different size regions (0.035-15.9 mm). Results obtained from these campaigns demonstrate that the minor components may be measured at levels as low as a few nanograms per cubic meter. The reported concentrations are to be considered among the first observations of nitrogen containing compounds in polar sites.

  9. Numerical study of turbulence-influence mechanism on arc characteristics in an air direct current circuit breaker

    SciTech Connect

    Wu, Mingliang; Yang, Fei Rong, Mingzhe; Wu, Yi; Qi, Yang; Cui, Yufei; Liu, Zirui; Guo, Anxiang

    2016-04-15

    This paper focuses on the numerical investigation of arc characteristics in an air direct current circuit breaker (air DCCB). Using magneto-hydrodynamics (MHD) theory, 3D laminar model and turbulence model are constructed and calculated. The standard k-epsilon model is utilized to consider the turbulence effect in the arc chamber of the DCCB. Several important phenomena are found: the arc column in the turbulence-model case is more extensive, moves much more slowly than the counterpart in the laminar-model case, and shows stagnation at the entrance of the chamber, unlike in the laminar-model case. Moreover, the arc voltage in the turbulence-model case is much lower than in the laminar-model case. However, the results in the turbulence-model case show a much better agreement with the results of the breaking experiments under DC condition than in the laminar-model case, which is contradictory to the previous conclusions from the arc researches of both the low-voltage circuit breaker and the sulfur hexafluoride (SF6) nozzle. First, in the previous air-arc research of the low-voltage circuit breaker, it is assumed that the air plasma inside the chamber is in the state of laminar, and the laminar-model application gives quite satisfactory results compared with the experiments, while in this paper, the laminar-model application works badly. Second, the turbulence-model application in the arc research of the SF6-nozzle performs much better and gives higher arc voltage than the laminar-model application does, whereas in this paper, the turbulence-model application predicts lower arc voltage than the laminar-model application does. Based on the analysis of simulation results in detail, the mechanism of the above phenomena is revealed. The transport coefficients are strongly changed by turbulence, which will enhance the arc diffusion and make the arc volume much larger. Consequently, the arc appearance and the distribution of Lorentz force in the turbulence-model case

  10. Numerical study of turbulence-influence mechanism on arc characteristics in an air direct current circuit breaker

    NASA Astrophysics Data System (ADS)

    Wu, Mingliang; Yang, Fei; Rong, Mingzhe; Wu, Yi; Qi, Yang; Cui, Yufei; Liu, Zirui; Guo, Anxiang

    2016-04-01

    This paper focuses on the numerical investigation of arc characteristics in an air direct current circuit breaker (air DCCB). Using magneto-hydrodynamics (MHD) theory, 3D laminar model and turbulence model are constructed and calculated. The standard k-epsilon model is utilized to consider the turbulence effect in the arc chamber of the DCCB. Several important phenomena are found: the arc column in the turbulence-model case is more extensive, moves much more slowly than the counterpart in the laminar-model case, and shows stagnation at the entrance of the chamber, unlike in the laminar-model case. Moreover, the arc voltage in the turbulence-model case is much lower than in the laminar-model case. However, the results in the turbulence-model case show a much better agreement with the results of the breaking experiments under DC condition than in the laminar-model case, which is contradictory to the previous conclusions from the arc researches of both the low-voltage circuit breaker and the sulfur hexafluoride (SF6) nozzle. First, in the previous air-arc research of the low-voltage circuit breaker, it is assumed that the air plasma inside the chamber is in the state of laminar, and the laminar-model application gives quite satisfactory results compared with the experiments, while in this paper, the laminar-model application works badly. Second, the turbulence-model application in the arc research of the SF6-nozzle performs much better and gives higher arc voltage than the laminar-model application does, whereas in this paper, the turbulence-model application predicts lower arc voltage than the laminar-model application does. Based on the analysis of simulation results in detail, the mechanism of the above phenomena is revealed. The transport coefficients are strongly changed by turbulence, which will enhance the arc diffusion and make the arc volume much larger. Consequently, the arc appearance and the distribution of Lorentz force in the turbulence-model case

  11. F-Layer Polar Cap Arcs.

    DTIC Science & Technology

    1987-09-01

    IONOSPHERE .... ......... 9 B. PRODUCTION AND LOSS IN THE D, E, AND Ft REGIONS 9 C. THE F2 LAYER ........ ................. I1 D. THE HIGH LATITUDE...1000" kilometers. Ionospheric behavior is governed by processes which result in the production /destruction and transport of ionization; different...radiation--a production mechanism--is deposited according to the absorption characteristics of the atmospheric constituents; (b) recombination--a

  12. Target tracking using DMLC for volumetric modulated arc therapy: A simulation study

    SciTech Connect

    Sun Baozhou; Rangaraj, Dharanipathy; Papiez, Lech; Oddiraju, Swetha; Yang Deshan; Li, H. Harold

    2010-12-15

    Purpose: Target tracking using dynamic multileaf collimator (DMLC) is a promising approach for intrafraction motion management in radiation therapy. The purpose of this work is to develop a DMLC tracking algorithm capable of delivering volumetric-modulated arc therapy (VMAT) to the targets that experience two-dimensional (2D) rigid motion in the beam's eye view. Methods: The problem of VMAT delivery to moving targets is formulated as a control problem with constraints. The relationships between gantry speed, gantry acceleration, MLC leaf-velocity, dose rate, and target motion are derived. An iterative search algorithm is developed to find numerical solutions for efficient delivery of a specific VMAT plan to the moving target using 2D DMLC tracking. The delivery of five VMAT lung plans is simulated. The planned and delivered fluence maps in the target-reference frame are calculated and compared. Results: The simulation demonstrates that the 2D tracking algorithm is capable of delivering the VMAT plan to a moving target fast and accurately without violating the machine constraints and the integrity of the treatment plan. The average delivery time is only 29 s longer than that of no-tracking delivery, 101 versus 72 s, respectively. The fluence maps are normalized to 200 MU and the average root-mean-square error between the desired and the delivered fluence is 2.1 MU, compared to 14.8 MU for no-tracking and 3.6 MU for one-dimensional tracking. Conclusions: A locally optimal MLC tracking algorithm for VMAT delivery is proposed, aiming at shortest delivery time while maintaining treatment plan invariant. The inconsequential increase of treatment time due to DMLC tracking is clinically desirable, which makes VMAT with DMLC tracking attractive in treating moving tumors.

  13. Bright X-ray arcs and the emergence of solar magnetic flux

    NASA Technical Reports Server (NTRS)

    Chapman, G. A.; Broussard, R. M.

    1977-01-01

    The Skylab S-056 and S-082A experiments and ground-based magnetograms have been used to study the role of bright X-ray arcs and the emergence of solar magnetic flux in the McMath region 12476. The S-056 X-ray images show a system of one or sometimes two bright arcs within a diffuse emitting region. The arcs seem to directly connect regions of opposite magnetic polarity in the photosphere. Magnetograms suggest the possible emergence of a magnetic flux. The width of the main arc is approximately 6 arcsec when most clearly defined, and the length is approximately 30-50 arcsec. Although the arc system is observed to vary in brightness over a period exceeding 24 hours, it remains fixed in orientation. The temperature of the main arc is approximately 3 x 10 to the 6th K. It is suggested that merging magnetic fields may provide the primary energy source, perhaps accompanied by resistive heating from a force-free current.

  14. A Study of the Spin Structure on the Neutron in Deep Inelastic Scattering of Polarized Electrons on Polarized Neutrons

    SciTech Connect

    Spengos, M

    2004-01-06

    The internal spin structure of the neutron, was studied in deep inelastic scattering of longitudinally polarized electrons from a polarized {sup 3}He target in the End Station A of the Stanford Linear Accelerator Center (SLAC). The spin asymmetry of the neutron was measured at energies between 19 and 26 GeV in the range 0.03 {le} x {le} 0.06 at an average Q{sup 2} of 2 (GeV/c){sup 2}. The results are in agreement with a new measurement of the asymmetry by SMC within their six times larger uncertainties. The spin dependent structure function g{sub 1}(x) for the neutron was determined from the asymmetry measurement and, its integral over x is found to be {integral}g{sub 1}{sup n}(x)dx = -0.038 {+-} 0.009. This result is 2.7 standard deviations from the Ellis-Jaffe Sum Rule and combined with the EMC results from the proton in very good agreement with the Bjorken Sum Rule. In the Quark Parton Model (QPM), in conjunction with the weak coupling constants F and D, from baryon decay, the result implies that the quarks contribute approximately 32% of the nucleon helicity. Finally, different ways of evolving the data, based on various theoretical models, is attempted and future aspects for spin physics, with emphasis at spin physics at SLAC, are discussed.

  15. The Polarized Target for Spin Filtering Studies at COSY and AD

    SciTech Connect

    Nass, A.; Steffens, E.; Barion, L.; Capiluppi, M.; Lenisa, P.; Stancari, M.; Kleines, H.; Rathmann, F.; Sarkadi, J.

    2007-06-13

    The setup of the polarized target for the spin filtering studies at COSY and AD will be shown together with the planned measurements. The target fulfills all the requirements coming from the experiment.

  16. Volumetric modulated Arc therapy and conventional intensity-modulated radiotherapy for simultaneous maximal intraprostatic boost: a planning comparison study.

    PubMed

    Shaffer, R; Morris, W J; Moiseenko, V; Welsh, M; Crumley, C; Nakano, S; Schmuland, M; Pickles, T; Otto, K

    2009-06-01

    Volumetric modulated arc therapy (VMAT) is a novel extension of intensity-modulated radiotherapy (IMRT) where an optimised three-dimensional dose distribution may be delivered in a single gantry rotation. This optimisation algorithm is the predecessor to Varian's RapidArc. The aim of this study was to compare the ability of conventional static nine-field IMRT (cIMRT) and VMAT to boost as much of the clinical target volume (CTV) as possible to 88.8Gy without exceeding organ at risk (OAR) dose-volume constraints. Optimal cIMRT and VMAT radiotherapy plans were produced for 10 patients with localised prostate cancer using common planning objectives: (1) Treat >or=98% of the planning target volume (PTV) to >or=95% of the prescription dose (74Gy in 37 fractions); (2) keep OAR doses within predefined limits; (3) treat as much of prostate CTV (minus urethra) as possible to >or=120% of prescription dose (=88.8Gy); (4) keep within maximum dose limits in and out of target volumes; (5) conformality index (volume of 95% isodose/volume of PTV)or=120% of the prescription dose (P=0.002). All dose constraints were kept within predefined limits. VMAT and cIMRT required an average of 949 and 1819 monitor units and 3.7 and 9.6min, respectively, to deliver a single radiation fraction. VMAT is able to boost more of the CTV to >or=120% than cIMRT without contravening OAR dose constraints, and uses 48% fewer monitor units. Treatment times were 61% less than with cIMRT.

  17. The impact of transferred vascularized toe joint length on motion arc of reconstructed finger proximal interphalangeal joints: a cadaveric study.

    PubMed

    Hsu, Chung-Chen; Loh, Charles Yuen Yung; Kao, Dennis; Moran, Steven L; Lin, Yu-Te

    2017-10-01

    Vascularized toe joint transfer for finger proximal interphalangeal joint reconstruction can result in sub-optimal arc of motion and extension lag due to inappropriate intercalated bony segment length. We investigated the impact of intercalated segment length on passive arc of motion and extension lag of the reconstructed proximal interphalangeal joint. Cadaveric intercalated joint grafts were harvested from lesser toes and transferred to cadaveric fingers. The pre-determined finger proximal interphalangeal joint defect size was 2 cm. Three different intercalated segment lengths were inserted and resulting proximal interphalangeal joint arc of motion and extension lag were measured. The average arc of motion of finger proximal interphalangeal joints was 81° and 54° for toe proximal interphalangeal joints. Long intercalated segments had an average arc of motion of 30° with 32° extension lag. Equal-length intercalated segments had an average 49° arc of motion with 15° extension lag. Short intercalated segments had an average arc of motion of 71° with 8° extension lag. Shorter intercalated segments provide the greatest reduction in extension lag.

  18. Initial development of the Banda Volcanic Arc

    SciTech Connect

    Hartono, H.M.S. )

    1990-06-01

    The initial development of the Banda Volcanic Arc can be determined by obtaining absolute ages of granites or volcanics, stratigraphy of the Eocene Metan Volcanics of Timor as the oldest formation containing Banda Volcanic Arc extrusives, and tectonic analysis. Banda Arc volcanism is the result of subduction of oceanic crust under the volcanic arc. The time of initial subduction is related to initial seafloor spreading between Australia and Antarctica, which is identical to geomagnetic polarity time 34 (82 mybp). Therefore, 82 mybp can be used as one of the criteria to determine the birth of the Banda Volcanic Arc. With present available time data for determining the birth of the Banda Volcanic Arc, the minimum age coincides with the age of the Metan Volcanics (Eocene, 39-56 mybp) and the maximum age coincides with initial seafloor spreading between Australia and Antarctica (82 mybp). This time span is too long. With the assumption that it needs some time to develop from transcurrent faulting to subduction and volcanism, it is proposed that the initial development of Banda Arc volcanism was during early Tertiary.

  19. SU-E-T-185: Feasibility Study of Dose Rate Modulated Arc Therapy (DrMAT) for Lung SBRT

    SciTech Connect

    KO, Y; Cho, B; Yi, B; Kwak, J; Song, S; Je, H; Ahn, S; Noh, Y

    2014-06-01

    Purpose: To show the feasibility of clinical application of DrMAT for SBRT in lung cancer patients. DrMAT is a form of dynamic conformal arc therapy where MLC segments and dose rates are controlled through simple field weight optimization. Methods: To show feasibility a new treatment plan was created based on the CT of SBRT lung cancer patients. Static plans with 33 fields are made, which have 11deg in between each field and are acquired rotating gantry angle from 180deg to 188deg in CCW direction, total 352deg is rotated. MLC maintained static aperture for each field. To optimize 33 individual fields, field weight was adjusted accordingly using weight optimization algorithm. Keeping weights and MU of static plan, static MLC aperture was converted to multiple arc segments. Arc plan could be created with the fields in the intervals of 11deg. Static MLC should be converted to arc segment MLC. Dynamic conformal arc therapy plan consists of 33 arc fields, is converted to one dose rate modulated arc therapy (DrMAT) plan. DrMAT plan consists of 166 control points which becomes a single arc plan that changes the shape of MLC for every 2.2deg. The resulting DrMAT plan is not an inverse plan it is a simple form of dynamic conformal arc plan using field weight obtained from static plan. This is compared and evaluated with the VMAT plan. Results: DrMAT and VMAT plans have been compared based on the RTOG1021. Both DrMAT and VMAT plans satisfy 100% irradiation to 95% of PTV and critical organs did not exceed dose limit suggested in RTOG1021. DrMAT plan is almost similar with VMAT plan in Result. Conclusion: Field weight optimization method did not show better Resultcompared to VMAT optimization. However, considering simplicity, DrMAT satisfies the condition in RTOG1021. Therefore clinical application of DrMAT is feasible.

  20. Polarization Gradient Study of Interstellar Medium Turbulence Using the Canadian Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Herron, C. A.; Geisbuesch, J.; Landecker, T. L.; Kothes, R.; Gaensler, B. M.; Lewis, G. F.; McClure-Griffiths, N. M.; Petroff, E.

    2017-02-01

    We have investigated the magneto-ionic turbulence in the interstellar medium through spatial gradients of the complex radio polarization vector in the Canadian Galactic Plane Survey (CGPS). The CGPS data cover 1300 square degrees, over the range 53^\\circ ≤slant {\\ell }≤slant 192^\\circ , -3^\\circ ≤slant b≤slant 5^\\circ , with an extension to b=17\\buildrel{\\circ}\\over{.} 5 in the range 101^\\circ ≤slant {\\ell }≤slant 116^\\circ , and arcminute resolution at 1420 MHz. Previous studies found a correlation between the skewness and kurtosis of the polarization gradient and the Mach number of the turbulence, or assumed this correlation to deduce the Mach number of an observed turbulent region. We present polarization gradient images of the entire CGPS data set, and analyze the dependence of these images on angular resolution. The polarization gradients are filamentary, and the length of these filaments is largest toward the Galactic anti-center, with the smallest toward the inner Galaxy. This may imply that small-scale turbulence is stronger in the inner Galaxy, or that we observe more distant features at low Galactic longitudes. For every resolution studied, the skewness of the polarization gradient is influenced by the edges of bright polarization gradient regions, which are not related to the turbulence revealed by the polarization gradients. We also find that the skewness of the polarization gradient is sensitive to the size of the box used to calculate the skewness, but insensitive to Galactic longitude, implying that the skewness only probes the number and magnitude of the inhomogeneities within the box. We conclude that the skewness and kurtosis of the polarization gradient are not ideal statistics for probing natural magneto-ionic turbulence.

  1. Low pressure arc electrode

    NASA Technical Reports Server (NTRS)

    Lenn, P. D.; Richter, R.

    1970-01-01

    Reducing the pressure in the vicinity of the arc attachment point by allowing the gas to flow through a supersonic nozzle minimizes local heating rates, prevents ablation, and increases the efficiency of coaxial gas-flow arcs.

  2. Mathematical modeling of melting rates for submerged arc welding

    SciTech Connect

    Chandel, R.S.

    1987-05-01

    The effects of welding current, arc voltage, wire diameter, electrode extension (EE), electrode polarity, power source type and flux classification on melting rates (MR) have been evaluated for the submerged arc welding process. The results show that for a given heat input, greater melting rates are obtained when higher current, longer electrode extension, smaller diameter electrodes and electrode negative polarity are used. Arc voltage, power source type and flux classification do not have any significant influence on melting rates. Mathematical models to correlate process variables and melting rates have been computed from the data.

  3. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    SciTech Connect

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

  4. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    PubMed Central

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  5. Study of the feasibility of distributed cathodic arc as a plasma source for development of the technology for plasma separation of SNF and radioactive wastes

    NASA Astrophysics Data System (ADS)

    Amirov, R. Kh.; Vorona, N. A.; Gavrikov, A. V.; Liziakin, G. D.; Polistchook, V. P.; Samoylov, I. S.; Smirnov, V. P.; Usmanov, R. A.; Yartsev, I. M.

    2015-12-01

    One of the key problems in the development of plasma separation technology is designing a plasma source which uses condensed spent nuclear fuel (SNF) or nuclear wastes as a raw material. This paper covers the experimental study of the evaporation and ionization of model materials (gadolinium, niobium oxide, and titanium oxide). For these purposes, a vacuum arc with a heated cathode on the studied material was initiated and its parameters in different regimes were studied. During the experiment, the cathode temperature, arc current, arc voltage, and plasma radiation spectra were measured, and also probe measurements were carried out. It was found that the increase in the cathode heating power leads to the decrease in the arc voltage (to 3 V). This fact makes it possible to reduce the electron energy and achieve singly ionized plasma with a high degree of ionization to fulfill one of the requirements for plasma separation of SNF. This finding is supported by the analysis of the plasma radiation spectrum and the results of the probe diagnostics.

  6. Study of the feasibility of distributed cathodic arc as a plasma source for development of the technology for plasma separation of SNF and radioactive wastes

    SciTech Connect

    Amirov, R. Kh.; Vorona, N. A.; Gavrikov, A. V.; Liziakin, G. D.; Polistchook, V. P.; Samoylov, I. S.; Smirnov, V. P.; Usmanov, R. A. Yartsev, I. M.

    2015-12-15

    One of the key problems in the development of plasma separation technology is designing a plasma source which uses condensed spent nuclear fuel (SNF) or nuclear wastes as a raw material. This paper covers the experimental study of the evaporation and ionization of model materials (gadolinium, niobium oxide, and titanium oxide). For these purposes, a vacuum arc with a heated cathode on the studied material was initiated and its parameters in different regimes were studied. During the experiment, the cathode temperature, arc current, arc voltage, and plasma radiation spectra were measured, and also probe measurements were carried out. It was found that the increase in the cathode heating power leads to the decrease in the arc voltage (to 3 V). This fact makes it possible to reduce the electron energy and achieve singly ionized plasma with a high degree of ionization to fulfill one of the requirements for plasma separation of SNF. This finding is supported by the analysis of the plasma radiation spectrum and the results of the probe diagnostics.

  7. Rotating arc spark plug

    DOEpatents

    Whealton, John H.; Tsai, Chin-Chi

    2003-05-27

    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  8. On the electrodynamical state of the auroral ionosphere during northward interplanetary magnetic field: A transpolar arc case study

    SciTech Connect

    Marklund, G.T.; Blomberg, L.G. ); Murphree, J.S.; Elphinstone, R.D. ); Zanetti, L.J.; Erlandson, R.E. ); Sandahl, I. ); de la Beaujardiere, O. ); Opgenoorth, H. ); Rich, F.J. )

    1991-06-01

    The ionospheric electrodynamical state has been reconstructed for a transpolar arc event during northward interplanetary magnetic field conditions. An extensive set of observations by Viking and other satellites and by ground-based radars has been used to provide realistic model input data or to verify the modeling results. The resulting convection pattern is found to be consistent with the Viking electric field and intimately linked to the prevalent auroral distribution. It is characterized by a large evening cell, well extended across noon and split up by two separated potential minima, and a minor crescent-shaped morning cell. The convection signatures are found to vary a lot along the transpolar arc depending on the relative role of the arc-associated convection and the ambient convection. The transpolar arc is generally embedded in antisunward convective flow except near the connection points with the auroral oval, where sunward flow exists in localized regions.

  9. A polarized photoluminescence study of strained layer GaAs photocathodes

    SciTech Connect

    Mair, R.A.

    1996-07-01

    Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to {approximately}0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, {approx}78 K and {approx}12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16{+-}.21 eV, b = -2.00{+-}.05 eV and d = -4.87{+-}.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data.

  10. Propagation of polarized light in the biological tissue: a numerical study by polarized geometric Monte Carlo method.

    PubMed

    Zhang, Yong; Chen, Bin; Li, Dong

    2016-04-01

    To investigate the influence of polarization on the polarized light propagation in biological tissue, a polarized geometric Monte Carlo method is developed. The Stokes-Mueller formalism is expounded to describe the shifting of light polarization during propagation events, including scattering and interface interaction. The scattering amplitudes and optical parameters of different tissue structures are obtained using Mie theory. Through simulations of polarized light (pulsed dye laser at wavelength of 585 nm) propagation in an infinite slab tissue model and a discrete vessel tissue model, energy depositions in tissue structures are calculated and compared with those obtained through general geometric Monte Carlo simulation under the same parameters but without consideration of polarization effect. It is found that the absorption depth of the polarized light is about one half of that determined by conventional simulations. In the discrete vessel model, low penetrability manifests in three aspects: diffuse reflection became the main contributor to the energy escape, the proportion of epidermal energy deposition increased significantly, and energy deposition in the blood became weaker and more uneven. This may indicate that the actual thermal damage of epidermis during the real-world treatment is higher and the deep buried blood vessels are insufficiently damaged by consideration of polarization effect, compared with the conventional prediction.

  11. A design study of a CMB polarization satellite S AMPAN and bolometric camera developments

    NASA Astrophysics Data System (ADS)

    Désert, F.-X.

    2007-03-01

    There is a strong theoretical case for measuring the primordial gravitational wave background that is expected in inflation-based Big Bang scenario. A promising route is via the polarization B-modes of the CMB anisotropies. We discuss a recent design study called S AMPAN for a moderate angular resolution (20 arcmin. at 217 GHz) but highly sensitive (5 μK arcmin.) polarization mapper satellite. In parallel, we describe recent efforts in France to build bolometric cameras.

  12. Femtosecond Raman induced polarization spectroscopy studies of coherent rotational dynamics in molecular fluids

    SciTech Connect

    Morgen, Michael Mark

    1997-05-01

    We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we are able to extract information concerning the effects of molecular interactions on the rotational motion. The technique is quite sensitive because of the zero background detection method, and is also versatile due to its nonresonant nature.

  13. mARC Treatment of Hypopharynx Carcinoma with Flat and Flattening-Filter-Free Beam Energies – A Planning Study

    PubMed Central

    Bell, Katharina; Fleckenstein, Jochen; Nuesken, Frank; Licht, Norbert; Rübe, Christian; Dzierma, Yvonne

    2016-01-01

    Background The recently implemented mARC-rotation-technique is capable to deliver high dose rate bursts. For the case of hypopharynx cancer plans we evaluate whether the mARC can achieve an advantage in treatment time in comparison to IMRT. These plans consider two arcs with flat and flattening filter free (FFF) beam energies. Materials and Methods For 8 hypopharynx-cancer patients step-and-shoot-IMRT and mARC plans were created retrospectively using flat and FFF beam energy. The comparison of the plan scenarios considered measures of quality for PTV coverage and sparing of organs at risk. All plans were irradiated on an anthromorphic phantom equipped with thermoluminescent dosimeters to measure scattered dose and treatment times. Results A visual comparison of the dose distribution did not show a marked preference for either technique or energy. The statistical evaluation yielded significant differences in favor of the mARC technique and the FFF energy. Scattered dose could be decreased markedly by the use of the mARC technique. Treatment times could be reduced up to 3 minutes with the use of mARC in comparison to IMRT. The high dose rate energy results in another time advantage of about 1 minute. Conclusions All four plan scenarios yielded equally good quality plans. A combination of the mARC technique with FFF 7 MV high dose rate resulted in a decrease of treatment times from about 9 minutes to 5–6 minutes in comparison to 6 MV IMRT. PMID:27741272

  14. A telluric method for natural field induced polarization studies

    NASA Astrophysics Data System (ADS)

    Zorin, Nikita; Epishkin, Dmitrii; Yakovlev, Andrey

    2016-12-01

    Natural field induced polarization (NFIP) is a branch of low-frequency electromagnetics designed for detection of buried polarizable objects from magnetotelluric (MT) data. The conventional approach to the method deals with normalized MT apparent resistivity. We show that it is more favorable to extract the IP effect from solely electric (telluric) transfer functions instead. For lateral localization of polarizable bodies it is convenient to work with the telluric tensor determinant, which does not depend on the rotation of the receiving electric dipoles. Applicability of the new method was verified in the course of a large-scale field research. The field work was conducted in a well-explored area in East Kazakhstan known for the presence of various IP sources such as graphite, magnetite, and sulfide mineralization. A new multichannel processing approach allowed the determination of the telluric tensor components with very good accuracy. This holds out a hope that in some cases NFIP data may be used not only for detection of polarizable objects, but also for a rough estimation of their spectral IP characteristics.

  15. Aircraft laser infrared absorption spectrometer (ALIAS) for polar ozone studies

    NASA Technical Reports Server (NTRS)

    Webster, C. R.; May, R. D.

    1991-01-01

    The ALIAS instrument is a very high resolution (0.0003/cm) scanning, tunable diode laser spectrometer designed to make direct, simultaneous measurements of NO2, HNO3, HCl, CH4, and either O3 or N2O (including vertical profiles of CH4 and N2O) in the polar stratosphere at sub-part-per-billion level sensitivities over integration times from 3 to 30 s. Unique features include a sample inlet/throttle system designed to achieve near-isokinetic sampling, in PSC events, an in-flight wavelength reference cell rack, mechanical fringe-spoilers, a four-laser/four-detector dewar with 24-hr hold-time operating at a fixed temperature without electrical regulation, and in-flight fast correlation routines for spectral drift compensation prior to spectral addition. Instrument design and test flight results are discussed in the light of ALIAS's role in the Winter 1991 Arctic aircraft stratospheric ozone campaigns out of Fairbanks, Alaska, and Bangor, Maine.

  16. Spin polarized photoemission studies of magnetic quantum well states

    SciTech Connect

    Johnson, P.D.

    1994-12-01

    There is currently considerable technological interest in the properties of transition metal multilayers. In these multilayers, which include Fe/Cr(001) and Cu/Co(001), it is possible to achieve either ferromagnetic or antiferromagnetic coupling of the adjacent ferromagnetic layers depending on the thickness of the intervening layer. The related giant magnetoresistance properties and the large enhancement of the Kerr rotation in these systems make them particularly interesting. In this paper, quantum well states with discrete binding energies dependent on the thickness of the film are observed in copper films deposited on a Co(001) substrate. They are found to be spin polarized, preferentially with minority spin. These states pass up to and through the Fermi level with a frequency identical to the long period of oscillation in the associated magnetic multilayers. In the pre-asymptotic limit the dispersion of these states away from the center of the zone is described by enhanced effective masses. This has implications for theories of the oscillatory exchange coupling that invoke the bulk Fermi surface.

  17. Circumpolar study of perfluoroalkyl contaminants in polar bears (Ursus maritimus).

    PubMed

    Smithwick, Marla; Mabury, Scott A; Solomon, Keith R; Sonne, Christian; Martin, Jonathan W; Born, Erik W; Dietz, Rune; Derocher, Andrew E; Letcher, Robert J; Evans, Thomas J; Gabrielsen, Geir W; Nagy, John; Stirling, Ian; Taylor, Mitch K; Muir, Derek C G

    2005-08-01

    Perfluoroalkyl substances were determined in liver tissues and blood of polar bears (Ursus maritimus) from five locations in the North American Arctic and two locations in the European Arctic. Concentrations of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate, heptadecafluorooctane sulfonamide, and perfluoroalkyl carboxylates with C(8)-C(15) perfluorinated carbon chains were determined using liquid chromatography tandem mass spectrometry. PFOS concentrations were significantly correlated with age at four of seven sampling locations, while gender was not correlated to concentration for any compound measured. Populations in South Hudson Bay (2000-2730 ng/g wet wt), East Greenland (911-2140 ng/g wet wt), and Svalbard (756-1290 ng/g wet wt) had significantly (P < 0.05) higher PFOS concentrations than western populations such as the Chukchi Sea (435-729 ng/g wet wt). Concentrations of perfluorocarboxylic acids (PFCAs) with adjacent chain lengths (i.e., C9:C10 and C10:C11) were significantly correlated (P < 0.05), suggesting PFCAs have a common source within a location, but there were differences in proportions of PFCAs between eastern and western location sources. Concentrations of PFOS in liver tissue at five locations were correlated with concentrations of four polychlorinated biphenyl congeners (180, 153, 138, and 99) in adipose tissue of bears in the same populations, suggesting similar transport pathways and source regions of PFOS or precursors.

  18. A study of Type I polar stratospheric cloud formation

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Turco, R. P.; Drdla, K.; Jacobson, M. Z.; Toon, O. B.

    1994-01-01

    Mechanisms for the formation of Type I (nitric acid-based) polar stratospheric clouds (PSCs) are discussed. If the pre-existing sulfate aerosols are liquid prior to PSC formation, then nitric acid particles (Type Ib) form by HNO3 dissolution in aqueous H2SO4 solution droplets. This process does not require a nucleation step for the formation of HNO3 aerosols, so most pre-existing aerosols grow to become relatively small HNO3-containing particles. At significantly lower temperatures, the resulting supercooled solutions (Type Ib) may freeze to form HNO3 ice particles (Type Ia). If the pre-existing sulfate aerosols are initially solid before PSC formation, then HNO3 vapor can be deposited directly on the frozen sulfate particles. However, because an energy barrier to the condensation exists a nucleation mechanism is involved. Here, we suggest a unique nucleation mechanism that involves formation of HNO3/H20 solutions on the sulfate ice particles. These nucleation processes may be highly selective, resulting in the formation of relatively small number of large particles.

  19. DC arc weld starter

    DOEpatents

    Campiotti, Richard H.; Hopwood, James E.

    1990-01-01

    A system for starting an arc for welding uses three DC power supplies, a high voltage supply for initiating the arc, an intermediate voltage supply for sustaining the arc, and a low voltage welding supply directly connected across the gap after the high voltage supply is disconnected.

  20. The characteristics of primary and secondary arcs on a solar array in low earth orbit

    NASA Astrophysics Data System (ADS)

    Zhu, Liying; Fu, Linchun; Qiao, Ming; Cui, Bo; Chen, Qi; Lin, Junyi

    2017-05-01

    In this paper, the characteristics of the primary arc and secondary arc on a solar array in low earth orbit (LEO) are investigated. The vacuum plasma environment in LEO has been used to study the primary arc and secondary arc of a high-voltage solar array. Silicon solar cells with rigid substrate specimens are used for the experiment. The series-parallel spacing of the silicon solar cells is 1 mm. The string currents of the solar cells are 0.7 A, 1.5 A and 2 A. The primary arc and secondary arc are photographed by high-speed cameras. The differences between the primary arc and secondary arc are observed. The secondary arc can be observed before the primary arc is extinguished. The primary arc is a single arc when the string current is 0.7 A. Multiple arc columns are accompanied by higher arc current. Two arc columns of the primary arc can be observed at 1.5 A string current and 2 A string current. The multiple primary arc columns are related to higher bias voltage. The threshold for sustained arcing is near 145 V/0.7 A, 105 V/1.5 A and 100 V/2 A at 1 mm string gap. Moreover, the transition time of secondary arc formation is analyzed, and found to be about 10-13 μs. The string currents, string voltages and primary arc have no effect on the transition time of the secondary arc formation.

  1. The dependence of induced polarization on fluid salinity and pH, studied with an extended model of membrane polarization

    NASA Astrophysics Data System (ADS)

    Hördt, Andreas; Bairlein, Katharina; Bielefeld, Anja; Bücker, Matthias; Kuhn, Eva; Nordsiek, Sven; Stebner, Hermann

    2016-12-01

    The estimation of hydraulic parameters from spectral induced polarization (SIP) measurements is difficult partly because the electrical impedance of sediments depends on several parameters that are not related to the texture. Important parameters that influence the spectral response are fluid salinity and pH. In order to understand the behaviour of SIP spectra from a mechanistic point of view, we carry out simulations with a membrane polarization model. The geometry consists of a sequence of wide and narrow pores with finite radii. The charge distribution at the mineral surface is described by a triple layer model, characterized by the zeta potential and the partition coefficient. We extended an existing model by incorporating known dependencies of the zeta potential and the partition coefficient on fluid salinity and pH. Our simulation results predict a decrease of the maximum phase shift of the complex electrical conductivity with increasing salinity, consistent with experimental observations. For very small pore radii, the phase shift may also show the opposite behaviour and increase with salinity. The imaginary conductivity at 1 Hz increases with increasing salinity, followed by a peak and a decrease at high salinities. The fact that our model predicts a decrease of the imaginary conductivity at high salinities is particularly important, because strong experimental evidence was recently found for such a decrease, which was theoretically unexplained so far. Both the maximum phase shift and the imaginary conductivity at 1 Hz decrease when pH decreases. The reason is that at low pH, the zeta potential and the partition coefficient both decrease, corresponding to a smaller charge density at the mineral surface, resulting in a weaker impact of the electrical double layer. The few existing experimental studies on pH dependence are qualitatively consistent with our simulation results.

  2. Dilution in single pass arc welds

    SciTech Connect

    DuPont, J.N.; Marder, A.R.

    1996-06-01

    A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

  3. Transpolar arc observation after solar wind entry into the high-latitude magnetosphere

    NASA Astrophysics Data System (ADS)

    Mailyan, B.; Shi, Q. Q.; Kullen, A.; Maggiolo, R.; Zhang, Y.; Fear, R. C.; Zong, Q.-G.; Fu, S. Y.; Gou, X. C.; Cao, X.; Yao, Z. H.; Sun, W. J.; Wei, Y.; Pu, Z. Y.

    2015-05-01

    Recently, Cluster observations have revealed the presence of new regions of solar wind plasma entry at the high-latitude magnetospheric lobes tailward of the cusp region, mostly during periods of northward interplanetary magnetic field. In this study, observations from the Global Ultraviolet Imager (GUVI) experiment on board the TIMED spacecraft and Wideband Imaging Camera imager on board the IMAGE satellite are used to investigate a possible link between solar wind entry and the formation of transpolar arcs in the polar cap. We focus on a case when transpolar arc formation was observed twice right after the two solar wind entry events were detected by the Cluster spacecraft. In addition, GUVI and IMAGE observations show a simultaneous occurrence of auroral activity at low and high latitudes after the second entry event, possibly indicating a two-part structure of the continuous band of the transpolar arc.

  4. Three-dimensional modeling of the plasma arc in arc welding

    NASA Astrophysics Data System (ADS)

    Xu, G.; Hu, J.; Tsai, H. L.

    2008-11-01

    Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.

  5. Three-dimensional modeling of the plasma arc in arc welding

    SciTech Connect

    Xu, G.; Tsai, H. L.; Hu, J.

    2008-11-15

    Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.

  6. Along-strike variation of strain partition modes: a case study in a regime of oblique plate convergence (External Betics, northern branch of the Gibraltar Arc)

    NASA Astrophysics Data System (ADS)

    Balanyá, Juan Carlos; Crespo-Blanc, Ana; Díaz-Azpiroz, Manuel; Expósito, Inmaculada; Torcal, Federico; Vicente, Pérez; Booth-Rea, Guillermo

    2010-05-01

    consists of a highly partitioned, E-W directed, dextral transpressive shear zone, built up by a set of an echelon NE-SW trending relieves, in turn affected by an array of NW-SE oriented normal conjugate faults. Numerical kinematic models suggest that their extrusion was nearly vertical and controlled by the pure shear component, as the simple shear component was mostly localized at the shear zone walls. Coeval extension is predicted by the model. This situation is still active, as earthquake focal solution data from this region indicate that dextral strike-slip earthquakes (NW-SE trending) are dominant, although they coexist with a complex network of thrust and normal fault earthquakes. c) In the central Betics, NE-SW to ENE-WSW trending, shortening in the external wedge was accommodated by folding and thrusting. The variation of the trend line pattern between the central zone and the "recess" zone has been reproduced through analogue experiments of a rigid, concave indenter (the Alboran Domain) pushing-from-behind a sand pack floored by silicone (the Triassic evaporites). The main shortening occurred earlier than in the Western Gibraltar Arc. In this zone, extensional faulting accommodating arc-parallel stretching is nearly absent and large-scale strike-slip faults striking parallel to the main structural trend line developed. The analysis of the variation of along strike strain partition modes in the northern branch of the Gibraltar Arc shows that several structural domains can be characterized within its external wedge, which indicates strong horizontal and vertical decoupling at upper crustal levels. Although situated in a regime of oblique plate convergence as a whole, strain partition modes indicate that only the E-W directed segment of the "recess" zone of the Gibraltar Arc external wedge and part of the Central Betics have structural associations that reveal a transpressive character. Acknowledgements: This study was supported by projects CGL2009-11384, RNM 3713

  7. Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Clausen, L. B. N.; Miloch, W. J.; Lofstad, V.; Jin, Y.; Moen, J. I.

    2017-03-01

    The Swarm satellites offer an unprecedented opportunity for improving our knowledge about polar cap patches, which are regarded as the main space weather issue in the polar caps. We present a new robust algorithm that automatically detects polar cap patches using in situ plasma density data from Swarm. For both hemispheres, we compute the spatial and seasonal distributions of the patches identified separately by Swarm A and Swarm B between December 2013 and August 2016. We show a clear seasonal dependency of patch occurrence. In the Northern Hemisphere (NH), patches are essentially a winter phenomenon, as their occurrence rate is enhanced during local winter and very low during local summer. Although not as pronounced as in the NH, the same pattern is seen for the Southern Hemisphere (SH). Furthermore, the rate of polar cap patch detection is generally higher in the SH than in the NH, especially on the dayside at about 77° magnetic latitude. Additionally, we show that in the NH the number of patches is higher in the postnoon and prenoon sectors for interplanetary magnetic field (IMF) By<0 and IMF By>0, respectively, and that this trend is mirrored in the SH, consistent with the ionospheric flow convection. Overall, our results confirm previous studies in the NH, shed more light regarding the SH, and provide further insight into polar cap patch climatology. Along with this algorithm, we provide a large data set of patches automatically detected with in situ measurements, which opens new horizons in studies of polar cap phenomena.

  8. Are Unmanned Aerial Systems in the Future for Polar Ozone Studies?

    NASA Astrophysics Data System (ADS)

    Elkins, J. W.; Hurst, D. F.; Moore, F. L.; Dutton, G. S.; Oltmans, S. J.; Vasel, B. A.; Montzka, S. A.; Fahey, D. W.

    2005-12-01

    Ozone loss studies in the polar stratosphere have benefited from the combination of ozone and other trace gas measurements (nitrous oxide, chlorofluorocarbons, etc.) to account for transport of ozone from other regions of the atmosphere. Trace gases versus ozone correlations and transport calculations have permitted the calculation of ozone loss on airborne missions during the polar stratospheric winter. NOAA/CMDL has successfully operated a combined ozone analyzer and gas chromatograph during the first phase of the NOAA UAS demonstration using the NASA Unmanned Aerial System (UAS) Altair (a civilian version of the military Predator B UAS). UAS, like Altair and Global Hawk, are ideal for polar studies because of their long range (7200+ km), long duration (30+ hours), and high altitude (>14 km) flying capabilities. They offer advantages over manned aircraft, most importantly safety of pilots where few airports exist and flights must be of long duration to reach the polar vortex. There are major obstacles in using UAS over Polar Regions including satellite coverage, and UAS access to civilian air space. A government/industry group, ACCESS-5 (means ACCESS to the national airspace in 5 years), is planning a mission to Hawaii to test procedures for flying in the national airspace which could be as early as May 2006. NOAA and other agencies are investigating the possibility of flying a UAS during the International Polar Year (2007-2008). Observational data will be presented from the NOAA UAS demo.

  9. Fundamental study and development of a hydrogen pellet accelerator using a fuseless two-stage plasma-arc-driven electromagnetic railgun

    SciTech Connect

    Honig, J.

    1986-01-01

    A detailed experimental study has, for the first time, successfully demonstrated the acceleration of frozen hydrogen pellets by means of a fuseless two-stage electromagnetic railgun system. This system consists of a pneumatic hydrogen pellet injector, which freezes and pneumatically pre-accelerates (with high-pressure helium as the propellant gas) cylindrical 1.6-mm-dia. by 1.75-mm-long hydrogen pellets, and a 60-cm-long 1.6-mm-dia. circular-bore electromagnetic railgun. The pellet is introduced into the railgun by means of a coupling piece, and a plasma-arc armature is created from the propellant gas by means of a very unique, fuseless, arc-initiation scheme. (A slightly different, yet equally effective fuseless arc-initiation scheme was employed in a prototype room temperature two stage railgun system.) Railgun-accelerated hydrogen pellet velocities of 1.6 km/s were achieved from pneumatically-accelerated injection velocities of 800 m/s. Streak-camera and current-probe data showed that the plasm-arc armature moves at a velocity proportional to the railgun current, I, and not to the often-quoted I/sup 2/. Insight to this I-dependence has been gained through the use of streak photography and current probes for varying bore geometries and gas pressures.

  10. Effect of high-latitude ionospheric convection on Sun-aligned polar caps

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Zhu, L.; Crain, D. J.; Schunk, R. W.

    1994-01-01

    A coupled magnetospheric-ionospheric (M-I) magnetohydrodynamic (MHD) model has been used to simulate the formation of Sun-aligned polar cap arcs for a variety of interplanetary magnetic field (IMF) dependent polar cap convection fields. The formation process involves launching an Alfven shear wave from the magnetosphere to the ionosphere where the ionospheric conductance can react self-consistently to changes in the upward currents. We assume that the initial Alfven shear wave is the result of solar wind-magnetosphere interactions. The simulations show how the E region density is affected by the changes in the electron precipitation that are associated with the upward currents. These changes in conductance lead to both a modified Alfven wave reflection at the ionosphere and the generation of secondary Alfven waves in the ionosphere. The ensuing bouncing of the Alfven waves between the ionosphere and magnetosphere is followed until an asymptotic solution is obtained. At the magnetosphere the Alfven waves reflect at a fixed boundary. The coupled M-I Sun-aligned polar cap arc model of Zhu et al.(1993a) is used to carry out the simulations. This study focuses on the dependence of the polar cap arc formation on the background (global) convection pattern. Since the polar cap arcs occur for northward and strong B(sub y) IMF conditions, a variety of background convection patterns can exist when the arcs are present. The study shows that polar cap arcs can be formed for all these convection patterns; however, the arc features are dramatically different for the different patterns. For weak sunward convection a relatively confined single pair of current sheets is associated with the imposed Alfven shear wave structure. However, when the electric field exceeds a threshold, the arc structure intensifies, and the conductance increases as does the local Joule heating rate. These increases are faster than a linear dependence on the background electric field strength. Furthermore

  11. Anode energy transfer in a transient arc

    NASA Astrophysics Data System (ADS)

    Valensi, F.; Ratovoson, P.; Razafinimanana, M.; Gleizes, A.

    2017-04-01

    This work deals with experimental investigation of a transient arc. Arc configuration and electrode erosion were studied in order to quantify the energy transfer to the electrodes as a function of maximal current, time constant and electrodes material. Experiments with two consecutive arcs allow demonstrating non stationary behaviour of the arc electrode interaction. This is due to the fact that while the duration of the experiments is far larger than plasma phenomena time constants, it is comparable to those of electrode heating and melting processes.

  12. Theoretical and experimental study of a high-current vacuum arc in a uniform axial magnetic field

    NASA Astrophysics Data System (ADS)

    Morimiya, Osami

    1992-01-01

    Measurements of the electron temperature, floating potential, plasma density, and average plasma pressure in a magnetically confined high-current vacuum arc are described. A 40-mm-diam, 30-mm-long arc was initiated between OFCu copper electrodes in a uniform axial magnetic field by triggering the gap. The crest values of the arc current ranged from 3 to 20 kA. The electron temperature by Langmuir probe measurement was Te= 2.5-3.0 eV with a uniform space distribution and was independent of the arc current. The space distribution of the ion density was parabolic in the radial direction and with a zero derivative in the axial direction. The average plasma pressure by paramagnetic measurement increased with the square of the arc current. The experiment showed that the arc column could be considered as an infinitely long column in which the plasma parameters have zero axial derivatives. Theoretical analysis has been carried out under the following assumptions. An infinitely long cylindrical and fully ionized steady-state plasma in which all quantities varied in the r direction only was considered. The anisotropy factor σ∥/σ⊥ for electrical conductivities was taken into account in the theoretical analysis, where σ∥ and σ⊥ were electrical conductivities parallel to the magnetic field and perpendicular to it, respectively. The plasma parameters determined from the experiments and theoretical analysis agreed closely with each other when the factor σ∥/σ⊥ was equal to ˜2, which is the theoretical upper limit in a high magnetic field. Constant temperature characteristics independent of the arc current have been found to be clearly seen by using line radiation as the dominant power loss in the power balance equation.

  13. Polar bear aerial survey in the eastern Chukchi Sea: A pilot study

    USGS Publications Warehouse

    Evans, Thomas J.; Fischbach, Anthony S.; Schliebe, Scott L.; Manly, Bryan; Kalxdorff, Susanne B.; York, Geoff S.

    2003-01-01

    Alaska has two polar bear populations: the Southern Beaufort Sea population, shared with Canada, and the Chukchi/Bering Seas population, shared with Russia. Currently a reliable population estimate for the Chukchi/Bering Seas population does not exist. Land-based aerial and mark-recapture population surveys may not be possible in the Chukchi Sea because variable ice conditions, the limited range of helicopters, extremely large polar bear home ranges, and severe weather conditions may limit access to remote areas. Thus line-transect aerial surveys from icebreakers may be the best available tool to monitor this polar bear stock. In August 2000, a line-transect survey was conducted in the eastern Chukchi Sea and western Beaufort Sea from helicopters based on a U.S. Coast Guard icebreaker under the "Ship of Opportunity" program. The objectives of this pilot study were to estimate polar bear density in the eastern Chukchi and western Beaufort Seas and to assess the logistical feasibility of using ship-based aerial surveys to develop polar bear population estimates. Twenty-nine polar bears in 25 groups were sighted on 94 transects (8257 km). The density of bears was estimated as 1 bear per 147 km² (CV = 38%). Additional aerial surveys in late fall, using dedicated icebreakers, would be required to achieve the number of sightings, survey effort, coverage, and precision needed for more effective monitoring of population trends in the Chukchi Sea.

  14. Is the polar bear (Ursus maritimus) a hibernator? Continued studies on opioids and hibernation

    USGS Publications Warehouse

    Bruce, David S.; Darling, Nancy K.; Seeland, Katheleen J.; Oeltgen, Peter R.; Nilekani, Sita P.; Amstrup, Steven C.

    1990-01-01

    Polar bear behavior and biochemistry suggest they may have the ability to hibernate year-round, even though this species is not considered to be a true hibernator. This observation, plus the discovery of a hibernation-induced trigger (HIT) in the blood of black bears, prompted the examination of polar bear blood collected thoughout the year for evidence ofr HIT, and to determine if it displayed opioid activity, as black bear blood does. A bioassay was conducted by injected summer 13-lined ground squirrels with serum collected from polar bears at different seasons. One group of squirrels was previously implanted with osmotic pumps containing naloxone. The rest had pumps containing saline. Squirrels with saline pumps all hibernated significantly more than those with naloxone, except the group receiving blood from a November polar bear, observed to be highly active and hyperphagic. An in vitro study, using guinea pig ileum, showed that 400 nM morphine inhibited induced contractions and 100 nM naloxone reversed the inhibition. Ten mg of winter polar bear serum albumin fraction (to which HIT binds in ground squirrels and woodchucks) had a similar inhibiting effect, but naloxone, even at 4,000 nM, didn't reverse it. It is concluded that polar bear contains HIT, that it has an opioid effct, but may not itself be an opioid.

  15. A study of the polarization of light scattered by vegetation. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Woessner, P. N.

    1985-01-01

    This study was undertaken in order to better understand the factors that govern the polarization of light scattered from vegetation and soils. The intensity and polarization of light scattered by clover and grass in vivo and soil were measured at a number of different angles of incidence and reflectance. Both individual leaves and natural patches of leaves were measured. The light transmitted through the leaves was found to be negatively polarized. The light scattered from the upper leaf surface was found to be positively polarized in a manner which could be accounted for qualitatively but not quantitatively by the Fresnel reflection coefficients modified by a shadowing function of the form cos sup2 (g/2), where g is the phase angle. Findings indicate that the polarization of light scattered by vegetation is a more complex process than previously thought, and that besides the surface-scattered component of light, the volume-scattered and multiply-scattered components also contribute significantly to the polarization.

  16. Polarization modulation study of transmissive liquid crystal spatial light modulator using digital holographic polariscope

    NASA Astrophysics Data System (ADS)

    Dev, Kapil; Asundi, Anand

    2013-04-01

    The study of phase modulation from the transmissive twisted nematic liquid crystal spatial light modulator (TN-LCSLM) with different incident states of polarization on its active area using Digital Holography method is presented. A pair of polarizer and quarter waveplate is used to illuminate the TN-LCSLM with elliptically polarized optical wavefront and transmitted optical wavefront is analyzed with a rotating analyzer. A single digital hologram is recorded from a complex optical wavefront passing through active display area of the TN-LCSLM at particular setting of different optical elements and quantitative phase is evaluated. We demonstrated that elliptically polarized light with certain ellipticity produces maximum phase modulation through the TN-LCSLM and the results are in good agreement with the eigenvectors suggested by Mueller matrix polarimetric characterization. This experimental setup can also be used as Grey-field Polariscope (GFP) in order to characterize important physical parameters such as the orientation of LC director molecules at input face and phase retardation with respect to addressed gray scale value on the TN-LCSLM active area. The TN-LCSLM is illuminated with circularly polarized light and change in this incident polarization after passing through the TN-LCSLM is recorded by four phase shifted digital holograms at four different analyzer orientations to measure these physical parameters.

  17. Comparative studies on polar ionosphere and magnetotail dynamics based on simultaneous multi-point observations

    NASA Astrophysics Data System (ADS)

    Fukuda, Yoko; Hirahara, Masafumi; Sakanoi, Takeshi; Ebihara, Yusuke; Asamura, Kazushi; Yamazaki, Atsushi; Seki, Kanako; Miyashita, Yukinaga

    For observations of the nightside polar ionosphere, the Reimei satellite is capable of simultane-ous observations for auroral 2D distribution by Multi-spectral Aurora Imaging Camera (MAC) and auroral particles by Electron/Ion Energy Spectrum Analyzer (ESA/ISA). Reimei has been observing the auroral fine structures at altitudes of about 640km by the unprecedented high spatial and temporal resolutions and promoting the understanding of the their fine structures. On the other hand, the field-aligned electric field and Alfven waves have been investigated in the auroral acceleration region by using data of FAST, Polar, Akebono and the other satel-lites. The phenomena in this region are thought to be due to the fluctuation of plasma and electromagnetic field in the magnetotail. In addition to the auroral observations of the polar ionosphere, the data comparison between in the magnetotail and in the polar ionosphere will give us more comprehensive understandings of the auroral phenomena. For observations of the magnetotail, we use data by THEMIS satellites consisting of 5 probes. The simultaneous multipoint observations by these satellites are useful for the distinction between temporal vari-ation and spatial distribution. THEMIS-GBOs(Ground-based observatories) which are located on the Northern America also enable us to observe global aurora. In this presentation, in the dataset for 1.5-years interval possibly providing the simultaneous observations by Reimei and THEMIS, we focus on the data obtained on Feb. 9, 2008. When Reimei passed over Canada(70ILAT) from poleward to equatorward, the Inverted-V precipitating electrons signa-tures lasted about 13 seconds corresponding to 0.7 ILAT width, and the characteristic electron energy was 1-5keV according to the ESA measurement. Near the poleward edge observed for three seconds, a south-eastward flow and a folded arc were observed and then stable and faint aurora was observed according to the MAC. These two types of auroras

  18. Study of Nanodispersed Iron Oxides Produced in Steel Drilling by Contracted Electric-Arc Air Plasma Torch

    NASA Astrophysics Data System (ADS)

    Stefanov, P.; Galanov, D.; Vissokov, G.; Paneva, D.; Kunev, B.; Mitov, I.

    2008-06-01

    The optimal conditions on the plasma-forming gas flowrate, discharge current and voltage, distance between the plasma-torch nozzle and the metal plate surface for the process of penetration in and vaporization of steel plates by the contracted electric-arc air plasma torch accompanied by water quenching, were determined. The X-ray structural and phase studies as well as Mössbauer and electron microscope studies on the samples treated were performed. It was demonstrated that the vaporized elemental iron was oxidized by the oxygen present in the air plasma jet to form iron oxides (wüstite, magnetite, hematite), which, depending on their mass ratios, determined the color of the iron oxide pigments, namely, beginning from light yellow, through deep yellow, light brown, deep brown, violet, red-violet, to black. A high degree of dispersity of the iron oxides is thus produced, with an averaged diameter of the particles below 500 nm, and their defective crystal structure form the basis of their potential application as components of iron-containing catalysts and pigments.

  19. Whole-brain hippocampal sparing radiation therapy: Volume-modulated arc therapy vs intensity-modulated radiation therapy case study

    SciTech Connect

    Lee, Katrina Lenards, Nishele; Holson, Janice

    2016-04-01

    The hippocampus is responsible for memory and cognitive function. An ongoing phase II clinical trial suggests that sparing dose to the hippocampus during whole-brain radiation therapy can help preserve a patient's neurocognitive function. Progressive research and advancements in treatment techniques have made treatment planning more sophisticated but beneficial for patients undergoing treatment. The aim of this study is to evaluate and compare hippocampal sparing whole-brain (HS-WB) radiation therapy treatment planning techniques using volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). We randomly selected 3 patients to compare different treatment techniques that could be used for reducing dose to the hippocampal region. We created 2 treatment plans, a VMAT and an IMRT, from each patient's data set and planned on the Eclipse 11.0 treatment planning system (TPS). A total of 6 plans (3 IMRT and 3 VMAT) were created and evaluated for this case study. The physician contoured the hippocampus as per the Radiation Therapy Oncology Group (RTOG) 0933 protocol atlas. The organs at risk (OR) were contoured and evaluated for the plan comparison, which included the spinal cord, optic chiasm, the right and left eyes, lenses, and optic nerves. Both treatment plans produced adequate coverage on the planning target volume (PTV) while significantly reducing dose to the hippocampal region. The VMAT treatment plans produced a more homogenous dose distribution throughout the PTV while decreasing the maximum point dose to the target. However, both treatment techniques demonstrated hippocampal sparing when irradiating the whole brain.

  20. The Neogene-Quaternary geodynamic evolution of the central Calabrian Arc: A case study from the western Catanzaro Trough basin

    NASA Astrophysics Data System (ADS)

    Brutto, F.; Muto, F.; Loreto, M. F.; Paola, N. De; Tripodi, V.; Critelli, S.; Facchin, L.

    2016-12-01

    The Catanzaro Trough is a Neogene-Quaternary basin developed in the central Calabrian Arc, between the Serre and the Sila Massifs, and filled by up to 2000 m of continental to marine deposits. It extends from the Sant'Eufemia Basin (SE Tyrrhenian Sea), offshore, to the Catanzaro Basin, onshore. Here, onshore structural data have been integrated with structural features interpreted using marine geophysical data to infer the main tectonic processes that have controlled the geodynamic evolution of the western portion of the Catanzaro Trough, since Upper Miocene to present. The data show a complex tectonostratigraphic architecture of the basin, which is mainly controlled by the activity of NW-SE and NE-SW trending fault systems. In particular, during late Miocene, the NW-SE oriented faults system was characterized by left lateral kinematics. The same structural regime produces secondary fault systems represented by E-W and NE-SW oriented faults. The ca. E-W lineaments show extensional kinematics, which may have played an important role during the opening of the WNW-ESE paleo-strait; whereas the NE-SW oriented system represents the conjugate faults of the NW-SE oriented structural system, showing a right lateral component of motion. During the Piacenzian-Lower Pleistocene, structural field and geophysical data show a switch from left-lateral to right-lateral kinematics of the NW-SE oriented faults, due to a change of the stress field. This new structural regime influenced the kinematics of the NE-SW faults system, which registered left lateral movement. Since Middle Pleistocene, the study area experienced an extensional phase, WNW-ESE oriented, controlled mainly by NE-SW and, subordinately, N-S oriented normal faults. This type of faulting splits obliquely the western Catanzaro Trough, producing up-faulted and down-faulted blocks, arranged as graben-type system (i.e Lamezia Basin). The multidisciplinary approach adopted, allowed us to constrain the structural setting of

  1. SU-E-T-562: Motion Tracking Optimization for Conformal Arc Radiotherapy Plans: A QUASAR Phantom Based Study

    SciTech Connect

    Xu, Z; Wang, I; Yao, R; Podgorsak, M

    2015-06-15

    Purpose: This study is to use plan parameters optimization (Dose rate, collimator angle, couch angle, initial starting phase) to improve the performance of conformal arc radiotherapy plans with motion tracking by increasing the plan performance score (PPS). Methods: Two types of 3D conformal arc plans were created based on QUASAR respiratory motion phantom with spherical and cylindrical targets. Sinusoidal model was applied to the MLC leaves to generate motion tracking plans. A MATLAB program was developed to calculate PPS of each plan (ranges from 0–1) and optimize plan parameters. We first selected the dose rate for motion tracking plans and then used simulated annealing algorithm to search for the combination of the other parameters that resulted in the plan of the maximal PPS. The optimized motion tracking plan was delivered by Varian Truebeam Linac. In-room cameras and stopwatch were used for starting phase selection and synchronization between phantom motion and plan delivery. Gaf-EBT2 dosimetry films were used to measure the dose delivered to the target in QUASAR phantom. Dose profiles and Truebeam trajectory log files were used for plan delivery performance evaluation. Results: For spherical target, the maximal PPS (PPSsph) of the optimized plan was 0.79: (Dose rate: 500MU/min, Collimator: 90°, Couch: +10°, starting phase: 0.83π). For cylindrical target, the maximal PPScyl was 0.75 (Dose rate: 300MU/min, Collimator: 87°, starting phase: 0.97π) with couch at 0°. Differences of dose profiles between motion tracking plans (with the maximal and the minimal PPS) and 3D conformal plans were as follows: PPSsph=0.79: %ΔFWHM: 8.9%, %Dmax: 3.1%; PPSsph=0.52: %ΔFWHM: 10.4%, %Dmax: 6.1%. PPScyl=0.75: %ΔFWHM: 4.7%, %Dmax: 3.6%; PPScyl=0.42: %ΔFWHM: 12.5%, %Dmax: 9.6%. Conclusion: By achieving high plan performance score through parameters optimization, we can improve target dose conformity of motion tracking plan by decreasing total MLC leaf travel distance

  2. ARC-1989-A89-7042

    NASA Image and Video Library

    1989-08-11

    P-34578 BW One of two new ring arcs, or partial rings, discovered by Voyager 2, is faintly visible just outside the orbit of the Neptunian moon 1989N4.The 155-second exposure taken by the spacecraft's narrow-angle camera shows the glare of an overexposed Neptune to the right of the moon and ring arc. The two bright streaks below the moon and ring arc are stars. The ring arc is approximately 50,000 kilometers (30,000 miles) long. The second ring arc, not apparent here, is about 10,000 kilometers (6,000 miles) long and is assoiciated with moon 1989N3. The ring arc, along with 1989N4, orbits about 62,000 kilometers (38,000 miles) from the planet's cloud tops. Astronomers long suspected the existence of such an irregular ring system around Neptune. Data from repeated ground-based observations hinted at the existence of irregular strands of partial rings orbiting Neptune. Voyager's photographs of the ring arcs are the first photographic evidence that such a ring system exists. Voyager scientists said the ring arcs may be comprised of debris associated with the nearby moons, or may be the remnants of moons that have been torn apart or ground down through collisions. Close-up studies of the ring arcs by Voyager 2 will help determine their composition.

  3. Thermo-optical and polarized light studies of MWCNT doped PDLCs

    NASA Astrophysics Data System (ADS)

    Mahajan, Jyoti; Gupta, Sureshchandra J.; Saxena, S.; Swati, K.

    2016-05-01

    Optical properties of liquid crystals (LCs) are very essential in an understanding of the technological applications of the LCs. Polymer Dispersed Liquid Crystals (PDLCs) are prepared by dispersing the liquid crystal droplets in polymer matrix. Experiments to study thermo-optical properties and polarized light studies are considered in the present work. PDLCs used in the present work are composed of poly (methyl methacrylate) and cholestric liquid crystal namely cholesteryl propionate. These are further doped with Multi-walled carbon Nanotubes (MWCNTs). Thermo-optical study reveals that there is decrease in the nematic-isotropic phase transition temperature (Clearing point temperature i.e. CPT) with increase in the concentration of MWCNTs. The effect of polarized light is studied by means of change in polarization which is characteristic of the material properties. The optical constants graphs obtained from ellipsometry provides the possibility of the use of composite material for optical switching systems.

  4. Dilution control in single-wire stainless steel submerged arc cladding

    SciTech Connect

    Kotecki, D.J.

    1996-02-01

    An experimental study of the effects of bead-to-bead stepover, wire size, wire feed speed, voltage, flux chromium content, and polarity on dilution and ferrite in single-wire submerged arc cladding of ER309L on mild steel plate is described. Low dilution was found to be promoted by reduced stepover, reduced wire feed speed, and DC electrode negative polarity. Use of a high-chromium flux can broaden the tolerance for dilution, providing an austenitic deposit free of martensite, and containing at least 4 FN for assurance of freedom from hot cracking over a broader range of dilutions.

  5. Study of Traverse Speed Effects on Residual Stress State and Cavitation Erosion Behavior of Arc-Sprayed Aluminum Bronze Coatings

    NASA Astrophysics Data System (ADS)

    Hauer, Michél; Henkel, Knuth Michael; Krebs, Sebastian; Kroemmer, Werner

    2017-01-01

    Within a research project regarding cavitation erosion-resistant coatings, arc spraying was used with different traverse speeds to influence heat transfer and the resulting residual stress state. The major reason for this study is the lack of knowledge concerning the influence of residual stress distribution on mechanical properties and coating adhesion, especially with respect to heterogeneous aluminum bronze alloys. The materials used for spray experiments were the highly cavitation erosion-resistant propeller alloys CuAl9Ni5Fe4Mn (Ni-Al-Bronze) and CuMn13Al8Fe3Ni2 (Mn-Al-Bronze). Analyses of cavitation erosion behavior were carried out to evaluate the suitability for use in marine environments. Further microstructural, chemical and mechanical analyses were realized to examine adhesive and cohesive coating properties. Residual stress distribution was measured by modified hole drilling method using electronic speckle pattern interferometry (ESPI). It was found that the highest traverse speed led to higher tensile residual stresses near the surface and less cavitation erosion resistance of the coatings. Moreover, high oxygen affinity of main alloying element aluminum was identified to severely influence the microstructures by the formation of large oxides and hence the coating properties. Overall, Mn-Al-Bronze coatings showed lower residual stresses, a more homogeneous pore and oxide distribution and less material loss by cavitation than Ni-Al-Bronze coatings.

  6. Determinants of occupational exposure to metals by gas metal arc welding and risk management measures: a biomonitoring study.

    PubMed

    Persoons, Renaud; Arnoux, Damien; Monssu, Théodora; Culié, Olivier; Roche, Gaëlle; Duffaud, Béatrice; Chalaye, Denis; Maitre, Anne

    2014-12-01

    Welding fumes contain various toxic metals including chromium (Cr), nickel (Ni) and manganese (Mn). An assessment of the risk to health of local and systemic exposure to welding fumes requires the assessment of both external and internal doses. The aims of this study were to test the relevance in small and medium sized enterprises of a biomonitoring strategy based on urine spot-samples, to characterize the factors influencing the internal doses of metals in gas metal arc welders and to recommend effective risk management measures. 137 welders were recruited and urinary levels of metals were measured by ICP-MS on post-shift samples collected at the end of the working week. Cr, Ni and Mn mean concentrations (respectively 0.43, 1.69 and 0.27 μg/g creatinine) were well below occupational health guidance values, but still higher than background levels observed in the general population, confirming the absorption of metals generated in welding fumes. Both welding parameters (nature of base metal, welding technique) and working conditions (confinement, welding and grinding durations, mechanical ventilation and welding experience) were predictive of occupational exposure. Our results confirm the interest of biomonitoring for assessing health risks and recommending risk management measures for welders.

  7. Rethinking Recycling in Arcs

    NASA Astrophysics Data System (ADS)

    Kelemen, P.; Behn, M. D.; Jagoutz, O.

    2012-12-01

    Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800

  8. Generation of supercontinuum light in micro-structured fiber and polarization study at different wavelengths

    NASA Astrophysics Data System (ADS)

    Valle-Atilano, F. J.; Estudillo-Ayala, J. M.; Filoteo-Razo, J. D.; Hernández-García, J. C.; Jáuregui-Vázquez, D.; Sierra-Hernández, J. M.; Rojas-Laguna, R.; Mata-Chavez, R. I.; Samano-Aguilar, L. F.

    2016-09-01

    In this work, we study the changes of polarization at different wavelengths in a supercontinuum source generated through a microchip laser in the IR spectrum. We use a microchip laser pulsed as pumped source, 1064 nm of wavelength, and a photonic crystal fiber by generated a supercontinuum spectrum. We twist the fiber to the purpose to induce birefringence and study the changes of the state of polarization, and through bandpass filters we observe a single wavelength of the broad spectrum obtained. Besides, ellipticity study for different filters and its relation with the supercontinuum results is discussed.

  9. Arc initiation in cathodic arc plasma sources

    SciTech Connect

    Anders, Andre

    2002-01-01

    A "triggerless" arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-1 kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation. A conductive surface layer, such as graphite or the material being deposited, is formed on the surface of the insulator which separates the cathode from the anode. The mechanism of plasma production (and arc initiation) is based on explosive destruction of the layer-cathode interface caused by joule heating. The current flow between the thin insulator coating and cathode occurs at only a few contact points so the current density is high.

  10. Effects of low-intensity polarized visible laser radiation on skin burns: a light microscopy study.

    PubMed

    Ribeiro, Martha Simões; Da Silva, Daniela De Fátima Teixeira; De Araújo, Carlos Eugênio Nabuco; De Oliveira, Sérgio Ferreira; Pelegrini, Cleusa Maria Raspantini; Zorn, Telma Maria Tenório; Zezell, Denise Maria

    2004-02-01

    This study was carried out to investigate the influence of low-intensity polarized visible laser radiation on the acceleration of skin wound healing. Low-level laser therapy (LLLT) at adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still unclear information about light characteristics, such as coherence and polarization. Some studies indicate that linearly polarized light can survive through long propagation distance in biological tissue. Three burns about 6 mm in diameter were created on the back of rats with liquid N(2). Lesion "L(//)" was irradiated by He-Ne laser (lambda = 632.8 nm), D= 1.0 J/cm(2), with linear polarization parallel to the spinal column of the rat. Lesion "L(inverted v)" was irradiated using the same laser and dose, but the light polarization was aligned perpendicularly to the relative orientation. Lesion "C" was not irradiated in order to be considered as control. The animals were sacrificed at day 3-17 after lesion creation. Samples were collected and prepared for histological analysis. Histological analysis showed that the healing of irradiated wounds was faster than that of non-irradiated wounds. Moreover, it was observed that skin wound repair is dependent on polarization orientation with respect to a referential axis as the animal's spinal column. Consequently, "L(//)" was completely healed after 17 days, whereas "L (perpendicular) " showed a moderate degree of healing after the same period. These results indicate that the relative direction of the laser polarization plays an important role in the wound healing process when highly coherent He-Ne laser is used.

  11. Study of Mechanical Properties and Characterization of Pipe Steel welded by Hybrid (Friction Stir Weld + Root Arc Weld) Approach

    SciTech Connect

    Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; Wasson, Andrew J; Fairchild, Doug P; Wang, Yanli; Feng, Zhili

    2015-01-01

    Friction stir welding (FSW) has recently attracted attention as an alternative construction process for gas/oil transportation applications due to advantages compared to fusion welding techniques. A significant advantage is the ability of FSW to weld the entire or nearly the entire wall thickness in a single pass, while fusion welding requires multiple passes. However, when FSW is applied to a pipe or tube geometry, an internal back support anvil is required to resist the plunging forces exerted during FSW. Unfortunately, it may not be convenient or economical to use internal backing support due to limited access for some applications. To overcome this issue, ExxonMobil recently developed a new concept, combining root arc welding and FSW. That is, a root arc weld is made prior to FSW that supports the normal loads associated with FSW. In the present work, mechanical properties of a FSW + root arc welded pipe steel are reported including microstructure and microhardness.

  12. Experimental study and modeling of the deuterium releasing quantity in a pulsed vacuum arc discharge with a metal deuteride cathode

    NASA Astrophysics Data System (ADS)

    Liu, Fei-Xiang; Long, Ji-Dong; Zheng, Le; Dong, Pan; Li, Chen; Chen, Wei

    2017-04-01

    The pulsed vacuum arc discharge using a metal deuteride cathode is widely applied as a deuterium ion source, where the upper limit of the deuterium ion yield is largely determined by the deuterium releasing quantity (DRQ) from the cathode. This work aims to measure the DRQ at various discharge conditions, and meanwhile develop a simple thermoelectric model to evaluate the deuterium liberation from different sources, such as the crater vicinity during the arc power-on phase and the hot crater in the afterglow. The calculated DRQ are in accordance with the experimental results obtained by measuring the D2 pressure evolution in the early afterglow using a quadrupole mass spectrometer. Furthermore, the model reveals that at low arc current (<10 A), the DRQ orginates dominantly from the crater vicinity, leading to a low conversion efficiency of the released deuterium to ions and a high D:Ti elemental ratio in the released cathode vapor.

  13. Study of nanostructured (Ti-Zr-Nb)N coatings’ physical- mechanical properties obtained by vacuum arc evaporation

    NASA Astrophysics Data System (ADS)

    Plotnikov, S. V.; Pogrebnjak, A. D.; Yerokhina, L. N.; Yeskermessov, D. K.; erdybaeva, N. K. Y.

    2016-02-01

    The coatings were formed by vacuum arc deposition. Unit cast target (cathodes) was used on the basis of 30 atm. % Ti, 35 at. % Zr and 35 atm. % Nb as the vaporized materials. Molecular nitrogen was used as the working gas. The thickness of the coatings in the experiments was 4.0 microns. The surface morphology fractograph fracture, track friction were investigated in a scanning electron microscope JSM-6390 LV. The use of multicoatings based on carbides is very promising to ensure the high performance properties of the complex, nitrides and silicides of transition metals. Findings - nanostructured coating of (Ti-Zr-Nb) N was obtained by vacuum arc evaporation cathode-cast in a nitrogen gas reaction medium. Multicomponent films have a pronounced columnar structure. Elemental composition was obtained by the vacuum arc deposition of coatings (Ti-Zr-Nb) N, depending on the physical parameters of the deposition process, in particular the pressure of the reaction gas nitrogen.

  14. Flat panel detector-based cone beam computed tomography with a circle-plus-two-arcs data acquisition orbit: preliminary phantom study.

    PubMed

    Ning, Ruola; Tang, Xiangyang; Conover, David; Yu, Rongfeng

    2003-07-01

    Cone beam computed tomography (CBCT) has been investigated in the past two decades due to its potential advantages over a fan beam CT. These advantages include (a) great improvement in data acquisition efficiency, spatial resolution, and spatial resolution uniformity, (b) substantially better utilization of x-ray photons generated by the x-ray tube compared to a fan beam CT, and (c) significant advancement in clinical three-dimensional (3D) CT applications. However, most studies of CBCT in the past are focused on cone beam data acquisition theories and reconstruction algorithms. The recent development of x-ray flat panel detectors (FPD) has made CBCT imaging feasible and practical. This paper reports a newly built flat panel detector-based CBCT prototype scanner and presents the results of the preliminary evaluation of the prototype through a phantom study. The prototype consisted of an x-ray tube, a flat panel detector, a GE 8800 CT gantry, a patient table and a computer system. The prototype was constructed by modifying a GE 8800 CT gantry such that both a single-circle cone beam acquisition orbit and a circle-plus-two-arcs orbit can be achieved. With a circle-plus-two-arcs orbit, a complete set of cone beam projection data can be obtained, consisting of a set of circle projections and a set of arc projections. Using the prototype scanner, the set of circle projections were acquired by rotating the x-ray tube and the FPD together on the gantry, and the set of arc projections were obtained by tilting the gantry while the x-ray tube and detector were at the 12 and 6 o'clock positions, respectively. A filtered backprojection exact cone beam reconstruction algorithm based on a circle-plus-two-arcs orbit was used for cone beam reconstruction from both the circle and arc projections. The system was first characterized in terms of the linearity and dynamic range of the detector. Then the uniformity, spatial resolution and low contrast resolution were assessed using

  15. Electrochemical transfer of oxygen during direct current arc welding

    SciTech Connect

    Kim, J.H.; Frost, R.H.; Olson, D.L.

    1994-12-31

    Weld metal oxygen content is important for control of weld metal microstructure and notch toughness. Low oxygen contents promote low toughness bainitic structures. Moderate oxygen levels favor a tough acicular ferrite structure, and high oxygen levels promote lower toughness grain boundary and Widmanstaetten side plate structures. The objective of this research was to examine electrochemical oxygen transfer as a function of welding process variables, polarity, and the relative importance of conduction across plasma-metal and slag-metal interfaces for: submerged arc welding (SAW), shielded metal arc welding (SMAW), and gas tungsten arc welding (GTAW) processes. SAW and SMAW were made in DCEN and DCEP polarities on structural steel and copper substrates. GTAW were made on steel substrates in DCEN polarity. The experimental results show that both thermochemical and electrochemical reactions are important for oxygen transfer, and that there are differences in the electrochemical reactions at slag-metal and plasma-metal interfaces. Both electrochemical and thermochemical reactions are significant for direct current arc welding processes. The arc plasma acts as an electrolyte for arc welding processes and electrochemical reactions occur at the plasma-metal interface have chemical effects opposite to those at the slag metal interface. This is caused by the fact that only positive ions exist in the arc plasma in large concentrations.

  16. Experimental study of gliding arc plasma channel motion: buoyancy and gas flow phenomena under normal and hypergravity conditions

    NASA Astrophysics Data System (ADS)

    Potočňáková, Lucia; Šperka, Jiří; Zikán, Petr; van Loon, Jack J. W. A.; Beckers, Job; Kudrle, Vít

    2017-04-01

    The details of plasma channel motion are investigated by frame-by-frame image analysis of high speed recording of a gliding arc. The gliding arc is operated in several noble gases at various flow rates, voltages and artificial gravity levels. Several peculiarities in evolution of individual glides are observed, described and discussed, such as accelerating motion of plasma channel or shortcutting events of various kinds. Statistics of averaged parameters are significantly different for buoyancy and gas drag dominated regimes, which is put into relation with differing flow patterns for hypergravity and high gas flow.

  17. The Study of Complex (Ti, Zr, Cs) Nanopowder Influencing the Effective Ionization Potential of Arc Discharge When Mma Welding

    NASA Astrophysics Data System (ADS)

    Sapozhkov, S. B.; Burakova, E. M.

    2016-08-01

    Strength is one of the most important characteristics of a weld joint. Mechanical properties of a weld metal can be improved in a variety of ways. One of the possibilities is to add a nanopowder to the weld metal. Authors of the paper suggest changing the production process of MMA welding electrodes via adding nanopowder Ti, Zr, Cs to electrode components through liquid glass. Theoretical research into the nanopowder influence on the effective ionization potential (Ueff) of welding arc discharge is also necessitated. These measures support arcing stability, improve strength of a weld joint, as the consequence, ensure quality enhancing of a weld joint and the structure on the whole.

  18. Long arc stabilities with various arc gas flow rates

    NASA Astrophysics Data System (ADS)

    Maruyama, K.; Takeda, K.; Sugimoto, M.; Noguchi, Y.

    2014-11-01

    A new arc torch for use in magnetically driven arc device was developed with a commercially available TIG welding arc torch. The torch has a water-cooling system to the torch nozzle and has a nozzle nut to supply a swirling-free plasma gas flow. Its endurance against arc thermal load is examined. Features of its generated arc are investigated.

  19. Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses

    PubMed Central

    Mitchell, D M; Montabone, L; Thomson, S; Read, P L

    2015-01-01

    Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth. PMID:26300564

  20. Is the polar bear (Ursus maritimus) a hibernator? Continued studies on opioids and hibernation.

    PubMed

    Bruce, D S; Darling, N K; Seeland, K J; Oeltgen, P R; Nilekani, S P; Amstrup, S C

    1990-03-01

    Polar bear behavior and biochemistry suggest they may have the ability to hibernate year-round, even though this species is not considered to be a true hibernator. This observation, plus the discovery of a hibernation-induction trigger (HIT) in the blood of black bears, prompted the examination of polar bear blood collected throughout the year for evidence of HIT, and to determine if it displayed opioid activity, as black bear blood does. A bioassay was conducted by injecting summer 13-lined ground squirrels with serum collected from polar bears at different seasons. One group of squirrels was previously implanted with osmotic pumps containing naloxone. The rest had pumps containing saline. Squirrels with saline pumps all hibernated significantly more than those with naloxone, except the group receiving blood from a November polar bear, observed to be highly active and hyperphagic. An in vitro study, using guinea pig ileum, showed that 400 nM morphine inhibited induced contractions and 100 nM naloxone reversed the inhibition. Ten mg of winter polar bear serum albumin fraction (to which HIT binds in ground squirrels and woodchucks) had a similar inhibiting effect, but naloxone, even at 4,000 nM, didn't reverse it. It is concluded that polar bear blood contains HIT, that it has an inhibiting effect, but naloxone, even at 4,000 nM, didn't reverse it. It is concluded that polar bear blood contains HIT, that it has an opioid effect, but may not itself be an opioid.

  1. Polar Glaciology

    NASA Technical Reports Server (NTRS)

    Robin, G. D.

    1984-01-01

    Two fields of research on polar ice sheets are likely to be of dominant interest during the 1990s. These are: the role of polar ice sheets in the hydrological cycle ocean-atmosphere-ice sheets-oceans, especially in relation to climate change; and the study and interpretation of material in deep ice cores to provide improved knowledge of past climates and of the varying levels of atmospheric constituents such as CO2, NOx, SO2, aerosols, etc., over the past 200,000 years. Both topics require a better knowledge of ice dynamics. Many of the studies that should be undertaken in polar regions by Earth Observing System require similar instruments and techniques to those used elsewhere over oceans and inland surfaces. However to study polar regions two special requirements need to be met: Earth Observing System satellite(s) need to be in a sufficiently high inclination orbit to cover most of the polar regions. Instruments must also be adapted, often by relatively limited changes, to give satisfactory data over polar ice. The observational requirements for polar ice sheets in the 1990s are summarized.

  2. Studies of Polar Mesospheric Clouds from Observations by the Student Nitric Oxide Explorer

    NASA Technical Reports Server (NTRS)

    Bailey, Scott M.

    2005-01-01

    The Geospace Sciences SR&T award NAG5-12648 "Studies of polar mesospheric clouds from observations by the Student Nitric Oxide Explorer" has been completed. The project was very successful in completing the proposed objectives and brought forth unexpected results in the study of Polar Mesospheric Clouds (PMCs). This work has provided key results to the community, provided valuable experience to two students, and inspired new research and collaborations with other research groups. Here we briefly summarize the progress and the scientific results.

  3. Application of remote polarization studies of the Earth in the national economy

    NASA Astrophysics Data System (ADS)

    Nevodovskyi, P. V.; Vidmachenko, A. P.; Morozhenko, O. V.; Zbrutskyi, O. V.; Ivahiv, O. V.

    2017-05-01

    Polarization remote investigation is a powerful method to study the physical properties of the planets and their atmospheres. It allows you to study objects both in situ, so in vitro. For application of this method we have developed, produced and continue to develop polarimeters. We have developed an optical scheme of spectropolarimeter, its electronic parts and related software. Using a special algorithm, it allows to calculate the degree of polarization and phase depending of solar radiation, diffusely reflected by discrete areas of Earth's surface.

  4. Inflammation and macrophage polarization in cutaneous melanoma: Histopathological and immunohistochemical study.

    PubMed

    Scali, Elisabetta; Mignogna, Chiara; Di Vito, Anna; Presta, Ivan; Camastra, Caterina; Donato, Giuseppe; Bottoni, Ugo

    2016-12-01

    Tumor-associated macrophages (TAMs) are considered to affect tumor growth and progression. Macrophages can be classified into two states of polarized activation, namely classically activated M1 macrophages and alternatively activated M2 macrophages. The dynamic balance between TAMs and tumor cells has an important impact on tumor homeostasis and progression. The aim of this study was to characterize the phenotype of TAMs present in different subtypes of superficial spreading cutaneous melanoma and their relationship with the lymphocytic infiltrate in order to identify new histopathological tools for melanoma prognosis and suitable targets for melanoma therapy. We selected four groups of patients with malignant melanoma in order to analyze the profile of polarized macrophage activation using immunohistochemical methods. Histopathological analysis showed that the macrophage polarization state appears to be more related to the lymphocytic infiltrate than to the thickness of the lesions. Further studies are necessary to increase understanding of the immunopathological dynamic of melanoma that may be modulated by future targeted immunotherapies.

  5. 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.

  6. A Study on Cavitation Erosion and Corrosion Behavior of Al-, Zn-, Cu-, and Fe-Based Coatings Prepared by Arc Spraying

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hong; Lee, Myeong-Hoon

    2010-12-01

    Investigation to find a suitable coating material for a rudder application has been carried out in this study. Ten different coatings were prepared by arc spraying with Al-, Zn-, Cu-, and Fe-based wire feedstock. Both the cavitation erosion and marine corrosion behavior of the arc-sprayed coatings were evaluated, and compared with the conventional anti-corrosion paint. In terms of marine corrosion resistance, aluminum coating was the best among the tested coating systems while stainless steel coating showed the highest resistance against cavitation erosion. In addition, the effects of both the Si composition in Al-based coatings and the Ni composition in Cu- and Fe- based coatings were discussed in this study.

  7. Radar polarization studies of volcanic and impact cratered terrains on the Earth, Venus, and the Moon

    NASA Astrophysics Data System (ADS)

    Campbell, Bruce Allan

    The results of four research projects which utilized imaging radar polarization data for remote sensing of volcanic and impact cratered terrains on the Earth, Venus, and the Moon are presented. The first project is an analysis of airborne multi-polarization radar data. A technique is developed for decomposing the polarized radar echo into components attributed to quasi-specular, small-perturbation, and 'dihedral' mechanisms. The second and third projects analyze the geomorphology and radar polarization properties of deposits on two volcanoes, Sif and Gula Montes, in western Eistla Regio, Venus. These analyses utilize radar images collected at Arecibo Observatory in 1988 (spatial resolution 1 km). Changes in the radar brightness of lava flows with downslope distance from possible vents are inconsistent with trends observed for single terrestrial lava flow. This observation, coupled with evidence of multiple eruptive vents, suggests that most of the large flows in western Eistla Regio are formed by coalescence of numerous smaller flows. The third project also compares the radar polarization properties of volcanic deposits on Sif and Gula Montes to data for terrestrial lava flows and a smooth desert area. The fourth project presents a study of lunar crater rays using high-resolution (30 m) radar images collected at Haystack Observatory, and focuses on the bright ray in Mare Serenitatis and ray segments attributed to Tycho and Copernicus craters.

  8. Multiple arcs and Pc5 pulsations in the postnoon sector: an inter- hemispheric conjugate observation

    NASA Astrophysics Data System (ADS)

    Yang, H.; Moen, J.; Sato, N.; Hu, H.; Liu, R.; Kikuchi, M.; Zhou, X.; Sakurai, T.; Makita, K.

    Massive statistics with satellite observations shown that there exists an auroral occurrence peak around 1500MLT, which has thus been named as '15MLT hot spot'. Chinese Zhongshan Station (69.37°S, 76.38°E, invariant latitude -74.49° in Antarctica locates on the passage of this 'hot spot' region and its magnetically conjugate point falls around Svalbard in the northern hemisphere. All sky TV observations there have confirmed this auroral peak and found that m ltiple arcu aurora is one of well appearing auroral forms in this region, of which the occurring mechanism is still in many debates. An inter-hemispheric study of a multiple arc aurora event happened on 27 May, 1997, is presented in this paper, where ground observations of Zhongshan are compared with simultaneous ground observations of the IMAGE magnetometer network and ones onboard satellites close its conjugate location. Pc5 pulsations in IMAGE magnetometers and the Geotail satellite magnetometer observations appeared simu ltaneously with multiple arc aurora in Zhongshan's all sky TV observation in the postnoon sector. `Bright spots' auroral activity in the POLAR UV images covering the northern hemisphere can be mapped to the conjugate counterpart of the southern multiple arc activity. Brightenings on multiple auroral arcs were found to swap westward/noonward in the Zhongshan all sky image sequence. This observation seems to offer a new fact favor the kinetic Alfven wave hypothesis for the multiple arc formation, in which MHD surface waves caused by intensive K-H instability are attributed to generate kinetic Alfven waves which can propagate across field lines, activate arcs on different field lines and form multiple arc aurora.

  9. Resolving arc processes through detrital zircon U-Pb geochronology and geochemistry: a case study from the southern California Mesozoic convergent margin

    NASA Astrophysics Data System (ADS)

    Johnston, S. M.; Kylander-Clark, A. R.

    2015-12-01

    Detrital zircon geochronology has been widely exploited to establish temporal characteristics in sedimentary source terranes. Detrital zircon geochemistry, however, has been largely overlooked given results from continentally derived igneous zircon that show subtle intersample variation in trace-element concentrations, and which make correlation between detrital zircon and their host terrane difficult. Nevertheless, recent studies suggest systematically variable geochemistry in McCoy Mountain detrital zircons derived from the southern California Mesozoic arc, and our preliminary data from the Peninsular Ranges batholith indicates strong correlations between whole-rock and zircon geochemistry. Here, we present coupled U-Pb geochronology and geochemistry measured by laser ablation split stream ICPMS on detrital zircons from Nacimiento block forearc sediments in Central California to characterize temporal and geochemical trends in the adjacent Mesozoic arc terrane. 1098 grains of Mesozoic age analyzed from 22 samples in the Nacimiento block define three periods of high magmatic flux in the Permian (270-250 Ma), Jurassic (170-140 Ma), and late Cretaceous (115-90 Ma). Zircon from the Permian arc is the least abundant of the three magmatic pulses, although they consistently display elevated Yb/Gd and U/Yb. Jurassic zircons display consistently low U/Yb, variably elevated Yb/Gd, abruptly higher Th/U and LREE from 155-145, and abruptly lower REE concentrations from 145-140 Ma. Zircon from the Cretaceous arc displays gradually increasing U/Yb, Th/U and LREE, with abruptly decreasing Yb/Gd at 95 Ma. The geochemical trends observed in the Nacimiento block detrital zircons of Cretaceous age are strikingly similar to temporal changes in geochemistry known from Cretaceous arc rocks of the Mojave and Peninsular Ranges, and strongly suggest a southern California provenance for Nacimiento block sediments. Furthermore, the similarity of geochemical trends between Cretaceous detrital

  10. Shape evolution of arc volcanoes, a case study of Concepción and Maderas (Nicaragua)

    NASA Astrophysics Data System (ADS)

    van Wyk de Vries, B.; Grosse, P.; Mathieu, L.; Cecchi, E.

    2009-12-01

    Volcanoes change shape as they grow due to the interplay of several processes such as eruption style, intrusion, vent migration, erosion, and through the effects of tectonic and gravitational deformation. Their shapes can thus hold clues as to their volcano-tectonic state and their structural evolution. We have recently carried out a study on volcano shape evolution by the morphometric analyses of 115 volcanoes from Central America and the southern Central Andes using Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM) (Grosse et al., 2009, Geology). The study allowed us to obtain a classification of volcanic edifices (cones, sub-cones, and massifs) and to recognize several evolutionary trends, which seem to be mainly related to magma flux, edifice strength and structural / tectonic conditions. In order to test some of the hypotheses on specific cases, we here explore the morphometric evolution of the two volcanoes that make up the island of Ometepe (Nicaragua), Concepción and Maderas. From basic geological mapping we have a detailed knowledge of the stratigraphy, lithology and architecture of these two volcanoes. Both volcanoes have experienced or are experiencing gravitational spreading, but they differ in that Concepción is a rapidly growing active cone, whereas Maderas is a squat and dormant sub-cone. In addition to the SRTM DEM, we use a higher resolution 30-meter DEM from the Instituto Nicaragüense de Estudios Territoriales (INETER) and combine the morphometric analysis with our field data. We find clear differences in the morphology of the two volcanoes and more subtle variations within discrete sectors of each volcano that are associated with local lava/tephra ratios, the prevailing winds, eruption and erosion rates, and gravitational spreading. The effects of gravitational spreading on the morphometry of the volcanoes are further investigated by comparing with 3-D analogue experiments. This specific case study shows how detailed

  11. The Use of an Arc Image Furnace for Solid Propellant Ignition Studies. An Undergraduate Student Report

    DTIC Science & Technology

    1980-05-01

    Wotan Company High pressure Xenon lamps. Technical data, June 1964 4 Gardon , R . A transducer for the measurement of heat flow rate. Reprinted from...Journal of Heat Transfer, Series C of Transactions of the ASME, November 1960 5 Gardon , R . An instrument for the direct measurement of intense thermal...E-st. a1 ;dS"i U C [ry~I 1 z -cr he s f nA-c Imag-IM~ r Fu acesfory Solid Propellant !gxionl Studies an Undergraduatp 3tudent Report J B’DAWES May 1

  12. Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

    NASA Astrophysics Data System (ADS)

    Cong, Haoxi; Li, Qingmin; Xing, Jinyuan; Li, Jinsong; Chen, Qiang

    2015-06-01

    The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low-voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines. supported by National Natural Science Foundation of China (Nos. 51277061 and 51420105011)

  13. Polarization Analysis Equipment in SANS-J-II: Study of Polymer Electrolyte Membrane for Fuel Cell

    NASA Astrophysics Data System (ADS)

    Noda, Yohei; Yamaguchi, Daisuke; Putra, Ananda; Koizumi, Satoshi; Sakaguchi, Yoshifumi; Oku, Takayuki; Suzuki, Jun-ichi

    In small angle neutron scattering spectrometer, SANS-J-II at Japan Research Reactor No. 3 (JRR-3), a polarization analysis setup has been equipped, which is composed of transmission-type supermirror polarizer, radial-bender-type supermirror analyzer, π flipper, and solenoids for generating guide magnetic field. This setup was applied to the structural study of polymer electrolyte membrane, Nafion under water-swollen state. The sample is known to exhibit several characteristic peaks at wide angle region, which is related to water transporting channels. By use of polarization analysis technique, the coherent and incoherent contributions were successfully separated. Consequently, we obtained reliable information about decaying power law of ionic cluster peak and the shape of the broad peak, relating to ordering with short distance (5.6 Å).

  14. A retrospective study of end-stage renal disease in captive polar bears (Ursus maritimus).

    PubMed

    LaDouceur, Elise E B; Davis, Barbara; Tseng, Flo

    2014-03-01

    This retrospective study summarizes 11 cases of end-stage renal disease (ESRD) in captive polar bears (Ursus maritimus) from eight zoologic institutions across the United States and Canada. Ten bears were female, one was male, and the mean age at the time of death was 24 yr old. The most common clinical signs were lethargy, inappetence, and polyuria-polydipsia. Biochemical findings included azotemia, anemia, hyperphosphatemia, and isosthenuria. Histologic examination commonly showed glomerulonephropathies and interstitial fibrosis. Based on submissions to a private diagnostic institution over a 16-yr period, ESRD was the most commonly diagnosed cause of death or euthanasia in captive polar bears in the United States, with an estimated prevalence of over 20%. Further research is needed to discern the etiology of this apparently common disease of captive polar bears.

  15. Results of a study on polarization mix selection for the NSCAT scatterometer

    NASA Technical Reports Server (NTRS)

    Long, David G.; Dunbar, R. Scott; Shaffer, Scott; Freilich, Michael H.; Hsiao, S. Vincent

    1989-01-01

    The NASA scatterometer (NSCAT) is an instrument designed to measure the radar backscatter of the ocean's surface for estimating the near-surface wind velocity. A given resolution element is observed from several different azimuth angles. From these measurements the near-surface vector wind over the ocean may be inferred using a geophysical model function relating the normalized radar backscatter coefficient (sigma0) to the near-surface wind. The results of a study to select a polarization mix for NSCAT using an end-to-end simulation of the NSCAT scatterometer and ground processing of the sigma0 measurements into unambiguous wind fields using a median-filter-based ambiguity-removal algorithm are presented. The system simulation was used to compare the wind measurement accuracy and ambiguity removal skill over a set of realistic mesoscale wind fields for various polarization mixes. Considerations in the analysis and simulation are discussed, and a recommended polarization mix is given.

  16. Cross-relaxation in nuclear polarization. A flash-CIDNP study

    NASA Astrophysics Data System (ADS)

    Yurkovskaya, A. V.; Tsentalovich, Yu. P.; Sagdeev, R. Z.

    1990-08-01

    CIDNP with microsecond time resolution was used to study the kinetics of nuclear polarization formation during the photolysis of acetone in isopropanol over a wide temperature range. The coincidence of signs of multiplet effects of CIDNP (A/E) for cage and escape reaction products as well as the presence of net polarization (E) changing its sign with decreasing temperature have been revealed. The account of scalar electron-nuclear cross-relaxation has been shown to be necessary for the interpretation of the results obtained.

  17. Study of the influence of filler wire carbon and residual element content on the mechanical properties of mechanized gas-metal-arc-welds: Final report

    SciTech Connect

    Not Available

    1988-06-01

    The individual and interactive roles of carbon, oxygen, and nitrogen and residual or tramp elements such as titanium, chromium, copper, sulfur, phosphorus, aluminum, arsenic, tin, and antimony on weld metal mechanical properties in pipeline steels are poorly documented. Further, most of the research has been done with the submerged-arc process. Systematic studies of the microstructures and toughnesses of GMAW welds are limited. A better understanding of the effects of carbon and the residual elements on weld metal toughnesses is needed so that appropriate filler wires can be produced. Accordingly, the objective of this research program was to attempt to determine the reason for the variable toughness of mechanized gas-metal-arc (GMA) girth welds and to identify means of improving toughness levels, particularly CTOD test values. This report is available from the American Gas Association Order Processing Department, 1515 Wilson Boulevard, Arlington, VA 2209-2470 (703/841-8558). 5 refs., 36 figs., 9 tabs.

  18. Lidar studies of atmospheric dynamics near polar mesopause

    NASA Astrophysics Data System (ADS)

    She, C. Y.; Vance, Joe D.; Williams, B. P.; Krueger, David A.; Moosmüller, Hans; Gibson-Wilde, Dorothy; Fritts, Dave

    Global change, space weather, and their possible adverse impacts on human activities are not only of scientific interest, but also of great public concern. Since the Arctic middle and upper atmosphere exhibits significant sensitivity to internal and external perturbations, systematic studies at high latitudes have become a scientific priority.Several international research programs are being conducted at the Arctic Light Detection and Ranging Observatory for Middle Atmosphere Research (ALOMAR), which was established at Andøya, Norway (69°N, 16°E) in 1994 to perform regular Arctic light detection and ranging (lidar) observations in tandem with other radio and optical instrumentation, as well as with in situ rocket and balloon measurements [von Zahn, 1997].

  19. Exposure to soluble barium compounds: an interventional study in arc welders.

    PubMed

    Zschiesche, W; Schaller, K H; Weltle, D

    1992-01-01

    Soluble barium (Ba) compounds are well-known toxicants. Intoxications are mainly known in an acute form from casual or suicidal oral ingestion. No scientifically based data are available on possible health effects of inhalative exposure to soluble Ba salts at the workplace. Therefore, we investigated 18 welders in an interventional study over 1 week. They performed welding of Ba-containing stick electrodes and self-shielded flux cored wires under conditions similar to real working conditions. The welding fumes contained 31%-37% Ba, more than 90% of which was soluble in acids. Without appropriate preventive measures, a high rate of measurements exceeded the TLV values for total welding fumes of 5 mg/m3 and for soluble Ba of 0.5 mg/m3. The median fume concentrations were 13.2 mg/m3 in stick electrode welding and 12.3 mg/m3 in flux cored wire welding. The median Ba concentrations were 4.4 and 2.0 mg/m3 respectively. An integrated exhaust system built into the gun proved to be efficient in flux cored wire welding. The internal exposure to Ba reached median urine levels up to 101.7 micrograms/l (normal: below 20 micrograms/l) and median plasma concentrations of up to 24.7 micrograms/l (normal: below 8 micrograms/l). No health impact on the welders could be proven, but hypokalemia may have occurred as a result of the Ba exposure.

  20. Volumetric intensity-modulated arc therapy vs conventional intensity-modulated radiation therapy in nasopharyngeal carcinoma: a dosimetric study

    PubMed Central

    White, Peter; Chan, Kit Chi; Cheng, Ka Wai; Chan, Ka Yiu; Chau, Ming Chun

    2013-01-01

    Dosimetric comparisons between RapidArc (RA) and conventional Intensity-Modulated Radiation Therapy (IMRT) techniques for nasopharyngeal carcinoma (NPC) were performed to address differences in dose coverage of the target, sparing of organs-at-risk (OARs), delivery of monitor units (MUs) and time, to assess whether the RA technique was more beneficial for treatment of NPC. Eight NPC patients (Stages I–IV), who had completed RA treatment, were selected for this study. Computed tomography data sets were re-planned using 7-fields fixed beam IMRT. Quantitative measurements of dose-endpoint values on the dose-volume histograms were carried out for evaluation of: (i) dose homogeneity (D5% – D95%); (ii) degree of conformity (CI95%); (iii) tumor control probability (TCP); (iv) doses to OARs; (v) normal tissue complication probability (NTCP); (vi) treatment time; and (vii) MUs. RA plans achieved better dose conformity and TCP in planning target volumes (PTVs). Target dose homogeneity was not as high as for IMRT plans. Doses to tempero-mandibular joints, clavicles, parotid glands and posterior neck, and their NTCPs were significantly lower in RA plans (P < 0.05). Mean doses to the brainstem and spinal cord were slightly lower in IMRT plans. RA plans allowed for a mean reduction in MUs by 78% (P = 0.006), and a four-fold reduction in treatment delivery times, relative to IMRT plans. RA plans showed superior, or comparable, target coverage and dose conformity in PTVs, but at the expense of inferior dose homogeneity. RA plans also achieved significant improvements in dose reduction to OARs and healthy tissue sparing. A significant reduction in treatment delivery time for RA treatment technique was also noted. PMID:23188186

  1. Study of The Maximum Uptake Capacity on Various Sizes of Electric Arc Furnace Slag in Phosphorus Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Afnizan, W. M. W.; Hamdan, R.; Othman, N.

    2016-07-01

    The high content of uncontrolled phosphorus concentration in wastewater has emerged as a major problem recently. The excessive amount of phosphorus that is originated from domestic waste, unproper treated waste from septic tanks, as well as agricultural activities have led to the eutrophication problem. Therefore, a laboratory experiment was initiated to evaluate the potential of the Electric Arc Furnace Slag (EAFS), a by-product waste from steel making industry in removing phosphorus concentrations in aqueous solutions. In this work several particle sizes ranging from (9.5-12.4 mm, 12.5-15.9 mm, 16.0-19.9 mm, 20.0-24.9 mm, 25-37.4 mm) with a known weight (20±0.28 g, 40±0.27 g, 60±0.30 g, 80±0.29 g and 100±0.38 g) were used to study the effect of different particle sizes towards phosphorus removal. Each particle size of EAFS was shaken in synthetic phosphorus solutions (10 mg/l, 20 mg/l, 30 mg/l, 40 mg/l and 50 mg/l) at a contact time of 2 hours. Final concentrations of phosphorus were sampled and the measurement was made using WESTCO Discrete Analyzer equipment. Results showed that the highest of the maximum uptake capacity of each EAFS particle size distribution achieved at 0.287, 0.313, 0.266, 0.241 and 0.25 mg/g as particle size range was varied from 9.5-12.4 mm to 25-37.4 mm. In conclusion, the maximum uptake capacity of each EAFS mostly was determined to occur at adsorbent weight of 20 to 40 g in most conditions.

  2. Vacuum Gas Tungsten Arc Welding

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  3. Protons in polar media: An ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    von Rosenvinge, Tycho

    1998-10-01

    The hydrates of hydrogen chloride are ionic crystals that contain hydronium (H3O+). The hydronium in the monohydrate has been reported to be statistically disordered between two possible sites related by inversion symmetry. Ab initio molecular dynamics calculations are presented for the monohydrate, as well as the di-, and tri-hydrates, of hydrogen chloride using the density functional based Car-Parrinello technique. The simulations were carried out with the goal of investigating proton disorder in these crystals. The possible role of nuclear quantum effects has been explored via path integral molecular dynamic simulations. The present results suggest that the proposed disordered sites in the monohydrate are dynamically unstable and therefore unlikely to be responsible for the reported disorder. No useful information was obtained for the dihydrate because the large unit cell leads to difficulties in carrying out the simulations. Nuclear quantum effects are shown to be important for characterizing the proton distributions in the trihydrate. The structure and dynamical behavior of liquid HF with dissolved KF have been investigated using the Car- Parrinello ab initio molecular dynamics scheme. Specifically, a system with stoichiometry KFċ2HF was studied at temperatures of 400K and 1000K. This system, which was started from a phase separated mixture, rapidly formed into solvated potassium ions and HnFn+1/sp- polyfluoride anions with n = 1, 2, 3, and 4. The resulting polyfluoride anions were classified, and their structures and dynamical behavior were compared with the known structures and spectra of crystalline compounds KF/cdot xHF and with theoretical predictions of isolated gas phase species. The present study reveals dramatic frequency shifts in the H atom vibrational modes with variation in the HF coordination number of the polyfluoride anion. In particular the FH wagging motion red shifts while the FH stretch blue shifts as n increases. The present calculations

  4. Research on the activating flux gas tungsten arc welding and plasma arc welding for stainless steel

    NASA Astrophysics Data System (ADS)

    Huang, Her-Yueh

    2010-10-01

    A systematic study of the effects of activating flux in the weld morphology, arc profile, and angular distortion and microstructure of two different arc welding processes, namely, Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW), was carried out. The results showed that the activating fluxes affected the penetration capability of arc welding on stainless steel. An increase in energy density resulting from the arc constriction and anode spot reduction enhanced the penetration capability. The Depth/Width (D/W) ratio of the weld played a major role in causing angular distortion of the weldment. Also, changes in the cooling rate, due to different heat source characteristics, influenced the microstructure from the fusion line to the centre of the weld.

  5. CyberArc: a non-coplanar-arc optimization algorithm for CyberKnife

    NASA Astrophysics Data System (ADS)

    Kearney, Vasant; Cheung, Joey P.; McGuinness, Christopher; Solberg, Timothy D.

    2017-07-01

    The goal of this study is to demonstrate the feasibility of a novel non-coplanar-arc optimization algorithm (CyberArc). This method aims to reduce the delivery time of conventional CyberKnife treatments by allowing for continuous beam delivery. CyberArc uses a 4 step optimization strategy, in which nodes, beams, and collimator sizes are determined, source trajectories are calculated, intermediate radiation models are generated, and final monitor units are calculated, for the continuous radiation source model. The dosimetric results as well as the time reduction factors for CyberArc are presented for 7 prostate and 2 brain cases. The dosimetric quality of the CyberArc plans are evaluated using conformity index, heterogeneity index, local confined normalized-mutual-information, and various clinically relevant dosimetric parameters. The results indicate that the CyberArc algorithm dramatically reduces the treatment time of CyberKnife plans while simultaneously preserving the dosimetric quality of the original plans.

  6. An on-chip study on the influence of geometrical confinement and chemical gradient on cell polarity.

    PubMed

    Zheng, Wenfu; Xie, Yunyan; Sun, Kang; Wang, Dong; Zhang, Yi; Wang, Chen; Chen, Yong; Jiang, Xingyu

    2014-09-01

    Cell polarity plays key roles in tissue development, regeneration, and pathological processes. However, how the cells establish and maintain polarity is still obscure so far. In this study, by employing microfluidic techniques, we explored the influence of geometrical confinement and chemical stimulation on the cell polarity and their interplay. We found that teardrop shape-induced anterior/posterior polarization of cells displayed homogeneous distribution of epidermal growth factor receptor, and the polarity could be maintained in a uniform epidermal growth factor (EGF) solution, but be broken by a reverse gradient of EGF, implying different mechanism of geometrical and chemical cue-induced cell polarity. Further studies indicated that a teardrop pattern could cause polarized distribution of microtubule-organization center and nucleus-Golgi complex, and this polarity was weakened when the cells were released from the confinement. Our study provides the evidence regarding the difference between geometrical and chemical cue-induced cell polarity and would be useful for understanding relationship between polarity and directional migration of cells.

  7. Polarization matching design of InGaN-based semi-polar quantum wells—A case study of (112{sup ¯}2) orientation

    SciTech Connect

    Kozlowski, Grzegorz Schulz, Stefan; Corbett, Brian

    2014-02-03

    We present a theoretical study of the polarization engineering in semi-polar III-nitrides heterostructures. As a case study, we investigate the influence of GaN, AlGaN, and AlInN barrier material on the performance of semi-polar (112{sup ¯}2) InGaN-based quantum wells (QWs) for blue (450 nm) and yellow (560 nm) emission. We show that the magnitude of the total built-in electric field across the QW can be controlled by the barrier material. Our results indicate that AlInN is a promising candidate to achieve (i) reduced wavelength shifts with increasing currents and (ii) strongly increased electron-hole wave function overlap, important for reduced optical recombination times.

  8. Tunneling Spectroscopy Study of Spin-Polarized Quasiparticle Injection Effects in Cuparate/Manganite Heterostructures

    NASA Technical Reports Server (NTRS)

    Wei, J. Y. T.; Yeh, N. C.; Vasquez, R. P.

    1998-01-01

    Scanning tunneling spectroscopy was performed at 4.2K on epitaxial thin-film heterostructures comprising YBa2Cu3O7 and La0.7Ca0.3MnO3, to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high-Tc cuprate superconductor.

  9. Celebrate with SATELLITES: An International Polar Year Partnership to Study Earth's Materials

    ERIC Educational Resources Information Center

    Hedley, Mikell Lynne; Czajkowski, Kevin; Struble, Janet; Benko, Terri; Shellito, Brad; Sheridan, Scott; Stasiuk, Mandy Munroe

    2009-01-01

    The SATELLITES program uses geospatial technologies to study surface temperatures of Earth's materials, such as sand, soil, grass, and water. Data are collected using Global Learning and Observations to Benefit the Environment (GLOBE) protocols, which are then used in research projects that are a part of the International Polar Year (IPY).…

  10. Tunneling Spectroscopy Study of Spin-Polarized Quasiparticle Injection Effects in Cuparate/Manganite Heterostructures

    NASA Technical Reports Server (NTRS)

    Wei, J. Y. T.; Yeh, N. C.; Vasquez, R. P.

    1998-01-01

    Scanning tunneling spectroscopy was performed at 4.2K on epitaxial thin-film heterostructures comprising YBa2Cu3O7 and La0.7Ca0.3MnO3, to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high-Tc cuprate superconductor.

  11. Celebrate with SATELLITES: An International Polar Year Partnership to Study Earth's Materials

    ERIC Educational Resources Information Center

    Hedley, Mikell Lynne; Czajkowski, Kevin; Struble, Janet; Benko, Terri; Shellito, Brad; Sheridan, Scott; Stasiuk, Mandy Munroe

    2009-01-01

    The SATELLITES program uses geospatial technologies to study surface temperatures of Earth's materials, such as sand, soil, grass, and water. Data are collected using Global Learning and Observations to Benefit the Environment (GLOBE) protocols, which are then used in research projects that are a part of the International Polar Year (IPY).…

  12. Are the Arcs of Neptune Really Stable?

    NASA Astrophysics Data System (ADS)

    Hanninen, J.; Porco, C.

    1994-12-01

    The Voyager mission discovered a system of rings and ring arcs around Neptune. It was later found that the arcs appear to be azimuthally and radially confined by resonant interactions with the nearby satellite, Galatea, yielding a maximum spread in ring particle semimajor axes of 0.6 km and a spread in forced eccentricities large enough to explain the arc's 15 km radial widths (Porco, 1991, Science 253, 995). We have modified an N-body simulation method (e.g. Hanninen and Salo, 1992, Icarus 97, 228) to include Neptune's second and fourth gravitational harmonics in order to be able to study the effects of collisions and self-gravity on the stability of the ring arcs. We have tested the simulation method and verified the shepherding mechanism in the collisionless and non-self-gravitational case. Preliminary simulation results with collisions over (1)/(2) a libration period indicate that collisions among putative 10-m sized source bodies within the arcs are indeed capable of arc disruption. However, whether or not collisions occur over this time scale depends, among other factors, on the number density of such bodies. We will explore the effects on arc stability of varying simulation parameters, such as the sizes and number density of the source bodies and the coefficient of restitution. Also, we will examine the effect of Galatea's previously neglected nearby vertical resonance on arc particle orbits.

  13. Polar Cap and Polar Cap Boundary Phenomena

    DTIC Science & Technology

    2009-06-25

    On the relationship between thin Birkeland current arcs and reversed flow channels in the winter cusp/cleft ionosphere Moen J., Y. Rinne, H...C. Carlson, K. Oksavik, R. Fujii, H. Opgenoorth Abstract: In this paper we study reversed flow events (RFEs) that seem regulated by Birkeland...current arcs in the winter cusp ionosphere above Svalbard. An RFE is a longitudinally elongated, 100–200 km wide channel, in which the flow direction is

  14. An explanation for Neptune's ring arcs

    NASA Astrophysics Data System (ADS)

    Porco, Carolyn C.

    1991-08-01

    The Voyager mission revealed a complex system of rings and ring arcs around Neptune and uncovered six new satellites, four of which occupy orbits well inside the ring region. Analysis of Voyager data shows that a radial distortion with an amplitude of approximately 30 kilometers is traveling through the ring arcs, a perturbation attributable to the nearby satellite Galatea. Moreover, the arcs appear to be azimuthally confined by a resonant interaction with the same satellite, yielding a maximum spread in ring particle semimajor axes of 0.6 kilometer and a spread in forced eccentricities large enough to explain the arc's 15-kilometer radial widths. Additional ring arcs discovered in the course of this study give further support to this model.

  15. An explanation for Neptune's ring arcs

    NASA Technical Reports Server (NTRS)

    Porco, Carolyn C.

    1991-01-01

    The Voyager mission revealed a complex system of rings and ring arcs around Neptune and uncovered six new satellites, four of which occupy orbits well inside the ring region. Analysis of Voyager data shows that a radial distortion with an amplitude of approximately 30 kilometers is traveling through the ring arcs, a perturbation attributable to the nearby satellite Galatea. Moreover, the arcs appear to be azimuthally confined by a resonant interaction with the same satellite, yielding a maximum spread in ring particle semimajor axes of 0.6 kilometer and a spread in forced eccentricities large enough to explain the arc's 15-kilometer radial widths. Additional ring arcs discovered in the course of this study give further support to this model.

  16. An Explanation for Neptune's Ring Arcs.

    PubMed

    Porco, C C

    1991-08-30

    The Voyager mission revealed a complex system of rings and ring arcs around Neptune and uncovered six new satellites, four of which occupy orbits well inside the ring region. Analysis of Voyager data shows that a radial distortion with an amplitude of approximately 30 kilometers is traveling through the ring arcs, a perturbation attributable to the nearby satellite Galatea. Moreover, the arcs appear to be azimuthally confined by a resonant interaction with the same satellite, yielding a maximum spread in ring particle semimajor axes of 0.6 kilometer and a spread in forced eccentricities large enough to explain the arcs' 15-kilometer radial widths. Additional ring arcs discovered in the course of this study give further support to this model.

  17. Numerical simulation of ac plasma arc thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequnecy range of 10-10(exp 2) Hz which includes most industry ac arc frequencies.

  18. Numerical Simulation of AC Plasma Arc Thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-102 Hz which includes most industry ac arc frequencies.

  19. Neoproterozoic oceanic arc remnants in the Moroccan Anti-Atlas: reconstructing deep to shallow arc crustal sequence and tracking Pan-African subduction-accretion processes

    NASA Astrophysics Data System (ADS)

    Triantafyllou, Antoine; Berger, Julien; Baele, Jean-Marc; Bruguier, Olivier; Diot, Hervé; Ennih, Nasser; Plissart, Gaëlle; Monnier, Christophe; Spagna, Paul; Watlet, Arnaud; Vandycke, Sara

    2015-04-01

    established that they were recrystallized under garnet-granulites P-T conditions (up to ~1000°C at 12 kbar). Preliminary geochemical data of hornblende-gabbros and garnet-bearing granulites portray similar trace geochemical signatures ((La/Sm)N: 0.8-1.6 ; (Nb/La) < 0.46) as studied paleo-arc complexes. These P-T results and new geochemical data argue that Asmlil mafic complex could represent a deep arc root comparable to the deep section of exposed oceanic arcs (i.e. Kohistan, Talkeetna, Amalaoulaou). We propose that Iriri and Asmlil units depict the deep-to-shallow sequence of a single Cryogenian oceanic arc (760-740 Ma), as discrete exposures along the southern edge of Anti-Atlas ophiolitic assemblages. Nevertheless, this primary arc has been likely broke up and intruded by subsequent hydrous arc-related magmas under medium- to high-grade P-T conditions (700 to 650 Ma). We interpret this period as an oceanic pre-collision stage when subduction geometry is intensively perturbed (c.g. composite subductions, polarity inversion), doping production of typical hydrous arc magma that intrudes original arc. This complex arc melange has been lastly accreted and sealed on the West African Craton margin.

  20. Enhancing NASA's Contribution to Arctic Terrestrial Hydrology and the Study of Polar Change

    NASA Astrophysics Data System (ADS)

    Walsh, J. E.; Elfring, C.; Vorosmarty, C. J.; McGuire, A. D.

    2001-12-01

    In a recent report by the National Academies, an interdisciplinary committee assessed NASA's polar geophysical datasets in the context of the science questions driving the Earth Science Enterprise (ESE) and other avenues of polar research. The report examines data sets in terms of the major ESE themes: ongoing changes in polar climate and the biosphere, forcings of the polar climate system, responses and feedbacks to the forcing, consequences of change in the polar regions, and prediction of such changes. It includes a matrix of science needs and available data sets and, from that, identifies high-priority measurement needs, many of which are directly relevant to Arctic hydrology. The greatest needs are improved measurements of polar precipitation, surface albedo, freshwater discharge from terrestrial regions, surface temperatures and turbulent fluxes, permafrost extent and dynamics, ocean salinity, ice sheet mass flux, land surface (especially vegetative) characteristics, and sea ice thickness. For Arctic hydrological studies, key needs include surface radiation parameters (albedo, roughness), especially with regard to the timing of ice-out in rivers and lakes, the associated pulse of freshwater discharge, biogeochemical fluxes, and aquatic biology. There is a particular need for pan-Arctic datasets of vegetative characteristics such as leaf area index, structural composition, canopy density, albedo, disturbance characteristics, wetland extent, and nitrogen deposition. Pan-Arctic information of this type will require novel efforts in the synthesis of different products, often from different sensors. Such information, as well as high-resolution surface elevation and topography, is needed for Arctic land system models that include hydrology and ecosystem dynamics. Key changes to be anticipated or predicted by these models include changes in water supplies from snow and snow-fed rivers, effects of physical environmental change on terrestrial productivity and

  1. Evaluation of the clinical usefulness of modulated arc treatment

    NASA Astrophysics Data System (ADS)

    Lee, Young Kyu; Jang, Hong Seok; Kim, Yeon Sil; Choi, Byung Ock; Kang, Young-Nam; Nam, Sang Hee; Park, Hyeong Wook; Kim, Shin Wook; Shin, Hun Joo; Lee, Jae Choon; Kim, Ji Na; Park, Sung Kwang; Kim, Jin Young

    2015-07-01

    The purpose of this study is to evaluate the clinical usefulness of modulated arc (mARC) treatment techniques. The mARC treatment plans for non-small-cell lung cancer (NSCLC) patients were made in order to verify the clinical usefulness of mARC. A pre-study was conducted to find the best plan condition for mARC treatment, and the usefulness of the mARC treatment plan was evaluated by comparing it with other Arc treatment plans such as tomotherapy and RapidArc plans. In the case of mARC, the optimal condition for the mARC plan was determined by comparing the dosimetric performance of the mARC plans developed by using various parameters, which included the photon energy (6 MV, 10 MV), the optimization point angle (6°- 10°intervals), and the total number of segments (36 - 59 segments). The best dosimetric performance of mARC was observed at a 10 MV photon energy, a point angle 6 degrees, and 59 segments. The treatment plans for the three different techniques were compared by using the following parameters: the conformity index (CI), homogeneity index (HI), the target coverage, the dose to the OARs, the number of monitor units (MU), the beam on time, and the normal tissue complication probability (NTCP). As a result, the three different treatment techniques showed similar target coverages. The mARC plan had the lowest V20 (volume of lung receiving > 20 Gy) and MU per fraction compared with both the RapidArc and the tomotherapy plans. The mARC plan reduced the beam on time as well. Therefore, the results of this study provide satisfactory evidence that the mARC technique can be considered as a useful clinical technique for radiation treatment.

  2. Total Marrow Irradiation With RapidArc Volumetric Arc Therapy

    SciTech Connect

    Aydogan, Bulent; Yeginer, Mete; Kavak, Gulbin O.; Fan, John; Radosevich, James A.; Gwe-Ya, Kim

    2011-10-01

    Purpose: To develop a volumetric arc therapy (VMAT)-total marrow irradiation (TMI) technique for patients with hematologic malignancies. Methods and Materials: VMAT planning was performed for 6 patients using RapidArc technology. The planning target volume consisted of all the bones in the body from the head to the mid-femur, excluding the extremities, except for the humerus, plus a 3.0-mm margin. The organs at risk included the lungs, heart, liver, kidneys, bowels, brain, eyes, and oral cavity. The VMAT-TMI technique consisted of three plans: the head and neck, the chest, and the pelvis, each with three 330{sup o} arcs. The plans were prescribed to ensure, at a minimum, 95% planning target volume dose coverage with the prescription dose (percentage of volume receiving dose of {>=}12 Gy was 95%). The treatments were delivered and verified using MapCheck and ion chamber measurements. Results: The VMAT-TMI technique reported in the present study provided comparable dose distributions with respect to the fixed gantry linear accelerator intensity-modulated TMI. RapidArc planning was less subjective and easier, and, most importantly, the delivery was more efficient. RapidArc reduced the treatment delivery time to approximately 18 min from 45 min with the fixed gantry linear accelerator intensity-modulated TMI. When the prescription dose coverage was reduced to 85% from 95% and the mandible and maxillary structures were not included in the planning target volume as reported in a tomotherapy study, a considerable organ at risk dose reduction of 4.2-51% was observed. The average median dose for the lungs and lenses was reduced to 5.6 Gy from 7.2 Gy and 2.4 Gy from 4.5 Gy, respectively. Conclusion: The RapidArc VMAT technique improved the treatment planning, dose conformality, and, most importantly, treatment delivery efficiency. The results from our study suggest that the RapidArc VMAT technology can be expected to facilitate the clinical transition of TMI.

  3. Lower Stratospheric Temperature Differences In Meteorological Analyses and Their Impact On Polar Processing Studies

    NASA Astrophysics Data System (ADS)

    Manney, G.; Sabutis, J.; Pawson, S.; Santee, M.; Naujokat, B.; Swinbank, R.; Gelman, M.; Ebisuzaki, W.

    Models - chemical transport models (CTMs), trajectory and Eulerian transport mod- els, microphysical models - used in polar processing studies typically rely on winds and/or temperatures from one of several meteorological analyses to drive the transport and control processes such as polar stratospheric cloud (PSC) formation and chemical reaction rates. Using different analyzed data sets to obtain temperatures and temper- ature histories can have significant consequences. A quantitative comparison of six meteorological analyses (UK Met Office, National Centers for Environmental Pre- diction/Climate Prediction Center (NCEP), NCEP/National Center for Atmospheric Research Reanalysis (REAN), Freie Universität Berlin, European Centre for Medium- Range Weather Forecasts (ECMWF), NASA Data Assimilation Office (DAO)) is pre- sented for the cold 1999-2000 and 1995-1996 Arctic winters, showing substantial dif- ferences in diagnostics related to polar processing between the different analyses. Bi- ases between analyses vary from year to year. Temperature history case studies show substantial differences using Met Office, NCEP, REAN, ECMWF, and DAO analyses. Different meteorological conditions in the comparably cold winters of 1995-1996 and 1999-2000 had a large impact on both expectations for PSC formation and on the ef- fects of discrepancies between different meteorological analyses. Met Office, NCEP, REAN, ECMWF, and DAO analyses are commonly used in modeling polar processes; the choice of analysis can strongly influence the results of such studies.

  4. Cognitive impairments and predominant polarity in bipolar disorder: a cross-sectional study.

    PubMed

    Belizario, Gabriel Okawa; Gigante, Alexandre Duarte; de Almeida Rocca, Cristiana Castanho; Lafer, Beny

    2017-12-01

    Bipolar disorder (BD) patients exhibit cognitive impairments during euthymic states. Studies suggest that manic episodes may be correlated to cognitive impairments. The present study investigated the relationship between predominant polarity and the cognitive deficits frequently detected in bipolar patients. We hypothesize that mania predominant polarity (MPP) patients should exhibit greater cognitive impairments in comparison to depressive (DPP) and indefinite predominant polarity (IPP) patients and healthy control (HC) individuals. The study evaluated 55 euthymic BD patients, type I and II, and 31 HCs. Patients were divided into 3 groups: MPP (n = 17), DPP (n = 22), and IPP (n = 16), and compared regarding demographic and clinical variables, and performance on a 7-test neuropsychological battery. MPP patients demonstrated greater cognitive impairments in alternating attention, verbal fluency, and delayed memory in comparison to DPP, IPP, and HC. Compared to HC, IPP patients exhibit cognitive deficits in verbal fluency and alternating attention and DPP patients solely in verbal fluency. Furthermore, DPP patients did not exhibit, in none of the seven neuropsychological tests, significant poorer performances than MPP or IPP patients, although having significant more episodes than MPP patients. MPP patients exhibit increased cognitive impairments in comparison to DPP, IPP, and HC subjects. Manic episodes may play an important role in the development of cognitive deficits and thus, in potential neuroprogression. Predominant polarity may be an important specifier for predicting future cognitive impairments.

  5. Studying the Inter-Hemispheric Coupling During Polar Summer Mesosphere Warming in 2002

    NASA Technical Reports Server (NTRS)

    Goldberg, Richard A.; Feofilov, Artem; Pesnell, William; Kutepov, Alexander A.

    2010-01-01

    It has been found that the northern summer polar mesopause region in 2002 was warmer than normal and of shorter duration than for other years analyzed. Theoretical studies have implied that the abnormal characteristics of this polar summer were generated by unusual dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these processes for polar summer periods of 2002-2009. For background, SABER is a broadband limb scanning radiometer that measures a large number of minor atmospheric constituents as well as pressure and temperature in the 13-110 km altitude range over most of the globe.We will use SABER temperature data to illustrate the correlated heating seen between the southern and northern hemispheres during June and July 2002. We will then describe the approach to study the wave characteristics of the atmospheric temperature profiles and demonstrate the features that were unique for 2002 compared to the other years.

  6. Studying the Inter-Hemispheric Coupling During Polar Summer Mesosphere Warming in 2002

    NASA Technical Reports Server (NTRS)

    Goldberg, Richard A.; Feofilov, Artem; Pesnell, William; Kutepov, Alexander A.

    2010-01-01

    It has been found that the northern summer polar mesopause region in 2002 was warmer than normal and of shorter duration than for other years analyzed. Theoretical studies have implied that the abnormal characteristics of this polar summer were generated by unusual dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these processes for polar summer periods of 2002-2009. For background, SABER is a broadband limb scanning radiometer that measures a large number of minor atmospheric constituents as well as pressure and temperature in the 13-110 km altitude range over most of the globe.We will use SABER temperature data to illustrate the correlated heating seen between the southern and northern hemispheres during June and July 2002. We will then describe the approach to study the wave characteristics of the atmospheric temperature profiles and demonstrate the features that were unique for 2002 compared to the other years.

  7. Arc and resistance welding and tumours of the endocrine glands: a Swedish case-control study with focus on extremely low frequency magnetic fields

    PubMed Central

    Hakansson, N; Stenlund, C; Gustavsson, P; Johansen, C; Floderus, B

    2005-01-01

    Background: Mechanisms for potential effects of extremely low frequency (ELF) magnetic fields on carcinogenesis have not been identified. A potential pathway could be an interaction with the endocrine system. Aims: To analyse occupational exposure to ELF magnetic fields from welding, and tumours of the endocrine glands. Methods: This case-control study was based on a cohort with an increased prevalence of high exposed individuals. A total of 174 incident cases of tumours of the endocrine glands, 1985–94, were identified and data were obtained from 140 (80%) of these cases; 1692 controls frequency matched on sex and age were selected, and information on 1306 (77%) individuals was obtained. A short questionnaire was sent to a work administrator at the workplaces of the cases and controls. The exposure assessment was based on questions about job tasks, exposure to different types of welding, and exposure to solvents. Results: There was an overall increased risk for all tumours of the endocrine glands for individuals who had been welding sometime during the follow up. The increased risk was attributable to arc welding; for resistance welding there was no clear evidence of an association. We found an increased risk for the adrenal glands in relation to arc welding, and for the parathyroid glands in relation to both arc welding and resistance welding. An imprecise increase in risk was also noted for tumours of the pituitary gland for arc welding. No confounding effect was found for solvent exposure, and there was no sign of biological interaction. Conclusion: The increased risks of endocrine gland tumours related to welding might be explained by exposure to high levels of ELF magnetic fields. PMID:15837851

  8. Domain Analysis of ArcS, the Hybrid Sensor Kinase of the Shewanella oneidensis MR-1 Arc Two-Component System, Reveals Functional Differentiation of Its Two Receiver Domains

    PubMed Central

    Bubendorfer, Sebastian

    2013-01-01

    In all species of the genus Shewanella, the redox-sensing Arc two-component system consists of the response regulator ArcA, the sensor kinase ArcS, and the separate phosphotransfer protein HptA. Compared to its counterpart ArcB in Escherichia coli, ArcS has a significantly different domain structure. Resequencing and reannotation revealed that in the N-terminal part, ArcS possesses a periplasmic CaChe-sensing domain bracketed by two transmembrane domains and, moreover, that ArcS has two cytoplasmic PAS-sensing domains and two receiver domains, compared to a single one of each in ArcB. Here, we used a combination of in vitro phosphotransfer studies on purified proteins and phenotypic in vivo mutant analysis to determine the roles of the different domains in ArcS function. The analysis revealed that phosphotransfer occurs from and toward the response regulator ArcA and involves mainly the C-terminal RecII domain. However, RecI also can receive a phosphate from HptA. In addition, the PAS-II domain, located upstream of the histidine kinase domain, is crucial for function. The results support a model in which phosphorylation of RecI stimulates histidine kinase activity of ArcS in order to maintain an appropriate level of phosphorylated ArcA according to environmental conditions. In addition, the study reveals some fundamental mechanistic differences between ArcS/HptA and ArcB with respect to signal perception and phosphotransfer despite functional conservation of the Arc system in Shewanella and E. coli. PMID:23161031

  9. Sensitivity of collapsed arc QA method for delivery errors in Volumetric Modulated Arc Therapy (VMAT)

    NASA Astrophysics Data System (ADS)

    Young, Tony; Xing, Aitang; Vial, Philp; Thwaites, David; Holloway, Lois; Arumugam, Sankar

    2015-01-01

    In this paper the sensitivity of an Electronic Portal Imaging Device (EPID) to detecting introduced Volumetric Arc Therapy (VMAT) treatment errors was studied using the Collapsed Arc method. Two clinical Head and Neck (H&N) and Prostate treatment plans had gantry dependent dose and MLC errors introduced to the plans. These plans were then delivered to an Elekta Synergy Linear Accelerator EPID and compared to the original treatment planning system Collapsed Arc dose matrix. With the Collapsed Arc technique the EPID was able to detect MLC errors down to 2mm and dose errors of down to 3% depending on the treatment plan complexity and gamma tolerance used.

  10. In the Arc

    NASA Image and Video Library

    2010-04-15

    NASA Cassini spacecraft image holds an unseen treasure orbiting within the bright arc of Saturn G ring: the tiny moonlet Aegaeon. Too small to be seen here, it is thought to be the source of the debris forming the bright arc in the lower right.

  11. TIGER Arc Modification Application

    SciTech Connect

    Armstrong, Hillary

    1995-03-06

    The application enables the geometric correction of TIGER arcs to a more accurate spatial data set. This is done in a structured automated environment according to Census Bureau guidelines and New Mexico state GIS standards. Arcs may be deleted, added, combined, split, and moved relative to a coverage or image displayed in the background.

  12. WSTF electrical arc projects

    NASA Astrophysics Data System (ADS)

    Linley, Larry

    1994-09-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  13. WSTF electrical arc projects

    NASA Technical Reports Server (NTRS)

    Linley, Larry

    1994-01-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  14. In vivo Study on the Corrosion Behavior of Magnesium Alloy Surface Treated with Micro-arc Oxidation and Hydrothermal Deposition.

    PubMed

    Bai, Chuan-Yi; Li, Jian-Wu; Ta, Wan-Bao; Li, Bo; Han, Yong

    2017-08-01

    To study the corrosion behavior of magnesium alloy surface treated with micro-arc oxidation and hydrothermal deposition in living animals. A magnesium oxide (MgO) layer was prepared on Mg alloy using micro-arc oxidation technology, and then a composite coating composed of magnesium hydroxide, hydroxyapatite, and MgO was coated on the MgO layer using the hydrothermal deposition method for 2 h and 24 h. Male 3-month-old white New Zealand rabbits (n = 48) weighting 2200-2300 g, were divided into four groups randomly. The prepared Mg alloy samples with composite coatings were implanted into the femoral medullary cavity of rabbits. For the Mg group, bare Mg samples without any treatment were implanted; for the MgO group, bare Mg samples undergoing MAO treatment were implanted; for the HT2h group, samples of the MgO group undergoing hydrothermal treatment (HT) for 2 h were implanted; and for the HT24h group, samples of group MgO undergoing HT for 24 h were implanted. Then the in vivo corrosion behaviors of implants were evaluated by X-ray observation, micro-CT analysis and serum Mg(2+) examination. The X-ray showed that samples implanted in animals were decreased as time went by. The micro-CT showed that on the fourth week, the residual volume percentages (RVP) of samples of the Mg, MgO, HT2h, and HT24h groups were 72.81% ± 2.10%, 71.68% ± 1.49%, 81.14% ± 1.54%, and 82.04% ± 0.89%, respectively; on the eighth week, the RVP of four groups were 29.45% ± 1.06%, 41.82% ± 1.13%, 53.92% ± 0.37%, and 62.53% ± 2.06%, respectively; while on the 12th week, RVP were 8.45% ± 0.49%, 9.97% ± 0.75%, 37.09% ± 0.89%, 46.71% ± 1.87%. The RVP of the HT2h group and the HT24h group were higher than for the Mg group and the MgO group for all three time points (P < 0.05); the RVP for HT24h was higher than for HT2h at 8 and 12 weeks, and the differences were significant, indicating that the degradation of Mg alloy

  15. A dosimetric comparative study: Volumetric modulated arc therapy vs intensity-modulated radiation therapy in the treatment of nasal cavity carcinomas

    SciTech Connect

    Nguyen, Kham; Cummings, David; Lanza, Vincent C.; Morris, Kathleen; Wang, Congjun; Sutton, Jordan; Garcia, John

    2013-10-01

    The purpose of this study was to evaluate the differences between volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) in the treatment of nasal cavity carcinomas. The treatment of 10 patients, who had completed IMRT treatment for resected tumors of the nasal cavity, was replanned with the Philips Pinnacle{sup 3} Version 9 treatment-planning system. The IMRT plans used a 9-beam technique whereas the VMAT (known as SmartArc) plans used a 3-arc technique. Both types of plans were optimized using Philips Pinnacle{sup 3} Direct Machine Parameter Optimization algorithm. IMRT and VMAT plans' quality was compared by evaluating the maximum, minimum, and mean doses to the target volumes and organs at risk, monitor units (MUs), and the treatment delivery time. Our results indicate that VMAT is capable of greatly reducing treatment delivery time and MUs compared with IMRT. The reduction of treatment delivery time and MUs can decrease the effects of intrafractional uncertainties that can occur because of patient movement during treatment delivery. VMAT's plans further reduce doses to critical structures that are in close proximity to the target volume.

  16. Parametric studies on tensile strength in joining AA6061- T6 and AA7075-T6 by gas metal arc welding process

    NASA Astrophysics Data System (ADS)

    Ishak, M.; Noordin, N. F. M.; Shah, L. H.

    2015-12-01

    Proper selection of the welding parameters can result in better joining. In this study, the effects of various welding parameters on tensile strength in joining dissimilar aluminum alloys AA6061-T6 and AA7075-T6 were investigated. 2 mm thick samples of both base metals were welded by semi-automatic gas metal arc welding (GMAW) using filler wire ER5356. The welding current, arc voltage and welding speed were chosen as variables parameters. The strength of each specimen after the welding operations were tested and the effects of these parameters on tensile strength were identified by using Taguchi method. The range of parameter for welding current were chosen from 100 to 115 A, arc voltage from 17 to 20 V and welding speed from 2 to 5 mm/s. L16 orthogonal array was used to obtained 16 runs of experiments. It was found that the highest tensile strength (194.34 MPa) was obtained with the combination of a welding current of 115 A, welding voltage of 18 V and welding speed of 4 mm/s. Through analysis of variance (ANOVA), the welding voltage was the most effected parameter on tensile strength with percentage of contribution at 41.30%.

  17. Plasma Arc Welding: How it Works

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur

    2004-01-01

    The physical principles of PAW from basic arcs to keyholing to variable polarity are outlined. A very brief account of the physics of PAW with an eye to the needs of a welder is presented. Understanding is usually (but not always) superior to handbooks and is required (unless dumb luck intervenes) for innovation. And, in any case, all welders by nature desire to know. A bit of history of the rise and fall of the Variable Polarity (VP) PA process in fabrication of the Space Shuttle External Tank is included.

  18. Polarizing matter and antimatter: A new method. The study of a repetitive Stern-Gerlach on stored polarized protons and the spin-splitter experiment: Progress report

    SciTech Connect

    Onel, Y.

    1992-02-01

    Several years ago a self-polarization effect for stored (anti)- protons and ions was investigated theoretically. The effect is based on the well-known Stern-Gerlach effect in gradient fields. The aim of the ongoing measurements at the Indiana University Cyclotron Facility (IUCF) is to verify experimentally the various assumptions on which this effect is based. The final goal is to demonstrate this new polarization effect. The proposed effect could be a powerful tool to produce polarized stored hadron beams both in the low-energy range and at SSC and LHC energies. In this progress report we will describe our progress in three parts: (A) Experimental work at IUCF Cooler Ring; (B) Our extensive computer simulations of the spin stability for the IUCF Cooler Ring; and (C) Theoretical studies.

  19. Lazy arc consistency

    SciTech Connect

    Schiex, T.; Gaspin, C.; Regin, J.C.; Verfaillie, G.

    1996-12-31

    Arc consistency filtering is widely used in the framework of binary constraint satisfaction problems: with a low complexity, inconsistency may be detected and domains are filtered. In this paper, we show that when detecting inconsistency is the objective, a systematic domain filtering is useless and a lazy approach is more adequate. Whereas usual arc consistency algorithms produce the maximum arc consistent sub-domain, when it exists, we propose a method, called LAC{tau}, which only looks for any arc consistent sub-domain. The algorithm is then extended to provide the additional service of locating one variable with a minimum domain cardinality in the maximum arc consistent sub-domain, without necessarily computing all domain sizes. Finally, we compare traditional AC enforcing and lazy AC enforcing using several benchmark problems, both randomly generated CSP and real life problems.

  20. Polarized Neutron Studies on Antiferromagnetic Single Crystals: Technical Report No. 4

    DOE R&D Accomplishments Database

    Nathans, R.; Riste, T.; Shirane, G.; Shull, C.G.

    1958-11-26

    The theory of neutron scattering by magnetic crystals as given by Halpern and Johnson predicts changes in the polarization state of the neutron beam upon scattering which depend upon the relative orientation of the neutron polarization vector and the crystal magnetic axis. This was investigated experimentally with a polarized beam spectrometer using single crystals of Cr{sub 2}O{sub 3} and alpha - Fe{sub 2}O{sub 3} in which reside unique antiferromagnetic axes. Studies were made on several different reflections in both crystals for a number of different temperatures both below and above the Neel point. Results support the theoretical predictions and indicate directions for the moments in these crystals consistent with previous work. A more detailed study of the polarization changes in the (111) reflection in alpha - Fe{sub 2}O{sub 3} at room temperature on application of a magnetic field was carried out, The results indicate that the principal source of the parasitic ferromagnetism in hematite is essentially independent of the orientation of the antiferromagnetic domains within the crystal.

  1. A satellite based study of tropospheric bromine explosion events and their linkages to polar cyclone development

    NASA Astrophysics Data System (ADS)

    Blechschmidt, Anne-Marlene; Richter, Andreas; Burrows, John P.; Kaleschke, Lars; Strong, Kimberly; Theys, Nicolas; Weber, Mark; Zhao, Xiaoyi; Zien, Achim; Hodges, Kevin I.

    2016-04-01

    Intense, cyclone-like shaped plumes of tropospheric bromine monoxide (BrO) are regularly observed by the UV-vis satellite instruments GOME-2/MetOp-A and SCIAMACHY/Envisat over Arctic and Antarctic sea ice in polar spring. The plumes are associated with an autocatalytic chemical chain reaction involving tropospheric ozone depletion and initiated by the release of bromine from cold brine-covered ice or snow to the atmosphere. This influences atmospheric chemistry as it affects the oxidising capacity of the troposphere through OH production and may also influence the local weather/temperature of the polar atmosphere, as ozone is a major greenhouse gas. Here, we make combined use of satellite retrievals and numerical model simulations to study individual BrO plume cases in the polar atmosphere. In agreement with previous studies, our analysis shows that the plumes are often transported by high latitude cyclones, sometimes over several days despite the short atmospheric lifetime of BrO. Moreover, general characteristics of bromine explosion events linked to transport by polar weather systems, such as frequency, spatial distribution and favourable weather conditions are derived based on a new detection method. Our results show that BrO cyclone transport events are by far more common in the Antarctic than in the Arctic.

  2. Clinical study of imaging skin cancer margins using polarized light imaging

    NASA Astrophysics Data System (ADS)

    Samatham, Ravikant; Lee, Ken; Jacques, Steven L.

    2012-02-01

    Skin cancer is most commons type of cancer in United States that occur on sun-exposed cosmetically sensitive areas like face, neck, and forearms. Surgical excision of skin cancer is challenging as more than one-third the actual margins extend beyond the clinically determined margins. Polarized light camera (polCAM) provides images of the superficial layers of the tissue with enhanced contrast which was used to image skin cancer margins. In a NIH-funded pilot study polCAM was used to image skin cancer in patients undergoing Mohs micrographic surgery for skin cancer. Polarized light imaging utilizes the polarization properties of light to create an image of a lesion comprised only of light scattering from the superficial layers of the skin which yields a characteristic "fabric pattern" of the putative lesion and the surrounding normal tissue. In several case studies conducted with a system developed for the clinic, we have found that skin cancer disrupts this fabric pattern, allowing the doctor a new means of identifying the margins of the lesion. Data is acquired before the patient underwent surgery. The clinically determined skin cancer margins were compared with margins determined by examination of the polCAM images. The true margins were provided by the dermatophathologist on examination of the frozen sections. Our initial data suggests that the contrast due to polarization changes associated with cancerous lesions can elucidate margins that were not recognized by the surgeon under normal conditions but were later confirmed by the pathologist.

  3. An Arc in Saturn's G Ring

    NASA Astrophysics Data System (ADS)

    Burns, Joseph A.; Hedman, M.; Tiscareno, M.; Porco, C.; Jones, G.; Roussos, E.; Krupp, N.

    2006-09-01

    The G ring is a narrow, faint ring located between the orbits of Janus and Mimas. Approximately 4000 km wide, it has a strongly asymmetric brightness profile with a sharp inner edge between 167,000 km and 168,000 km from Saturn's center and a more diffuse outer part. In Cassini images, a portion of the ring contains a bright arc that abuts the G-ring's inner edge and extends over 30 degrees in longitude. By tracking this arc over the first two years of the Cassini Mission, we find its orbital period is 0.80813 day, corresponding to a semi-major axis of 167,496 km. Since this location places the arc within 6 km of the Mimas 7:6 Co-rotation Eccentricity Resonance and within 12 km of the Mimas 7:6 Inner Lindblad Resonance, the arc is likely confined in longitude by Mimas just as Neptune's ring arcs are held in place by Galatea. The arc's longitude relative to Mimas is consistent with this model. Cassini now has the opportunity to study the dynamics of this sort of system in detail over a period of years. The arc, which may be the debris of a fragmented moon, may also supply the particles found in the rest of the G ring; micron-sized grains drift outwards by non-gravitational processes in this region. The G-ring is responsible for a broad, relatively modest decrease in the fluxes of magnetospheric charged particles. When Cassini passed over the G ring in the vicinity of the arc, on September 5, 2005, the MIMI instrument detected a particularly sharp and deep charged particle absorption signature. Such a pronounced charged particle absorption was not seen in the other G-ring passages that occurred longitudinally far from the arc. The nature of this absorption provides constraints on the population of large particles in this arc.

  4. The Ophiolite - Oceanic Fore-Arc Connection

    NASA Astrophysics Data System (ADS)

    Reagan, M. K.; Pearce, J. A.; Stern, R. J.; Ishizuka, O.; Petronotis, K. E.

    2014-12-01

    Miyashiro (1973, EPSL) put forward the hypothesis that many ophiolites are generated in subduction zone settings. More recently, ophiolitic sequences including MORB-like basalts underlying boninites or other subduction-related rock types have been linked to near-trench spreading during subduction infancy (e.g., Stern and Bloomer, 1992, GSA Bull.; Shervais, 2001, G-cubed; Stern et al., 2012, Lithos.). These contentions were given strong support by the results of Shinkai 6500 diving in the Izu-Bonin-Mariana (IBM) fore-arc (e.g., Reagan et al., 2010, G-cubed; Ishizuka et al., 2011, EPSL; Reagan et al., 2013, EPSL). Based on widely spaced dives and grab sampling at disbursed dive stops, these studies concluded that the most abundant and most submerged volcanic rocks in the IBM fore-arc are MORB-like basalts (fore-arc basalts or FAB), and that these basalts appear to be part of a crustal sequence of gabbro, dolerite, FAB, boninite, and normal arc lavas overlying depleted peridotite. This ophiolitic sequence was further postulated to make up most or all of the IBM fore-arc from Guam to Japan, with similar magmatic ages (52 Ma FAB to 45 Ma arc) north to south, reflecting a western-Pacific wide subduction initiation event. At the time of this writing, IODP Expedition 352 is about to set sail, with a principal goal of drilling the entire volcanic sequence in the Bonin fore-arc. This drilling will define the compositional gradients through the volcanic sequence associated with subduction initiation and arc infancy, and test the hypothesized oceanic fore-arc - ophiolite genetic relationship. A primary goal of this expedition is to illustrate how mantle compositions and melting processes evolved during decompression melting of asthenosphere during subduction initiation to later flux melting of depleted mantle. These insights will provide important empirical constraints for geodynamic models of subduction initiation and early arc development.

  5. Red Arcs on Tethys

    NASA Image and Video Library

    2015-07-29

    Unusual arc-shaped, reddish streaks cut across the surface of Saturn's ice-rich moon Tethys in this enhanced-color mosaic. The red streaks are narrow, curved lines on the moon's surface, only a few miles (or kilometers) wide but several hundred miles (or kilometers) long. The red streaks are among the most unusual color features on Saturn's moons to be revealed by Cassini's cameras. A few of the red arcs can be faintly seen in Cassini imaging observations made earlier in the mission, but the color images for this observation, which were obtained in April 2015, were the first to show large northern areas of Tethys under the illumination and viewing conditions necessary to see the features clearly. As the Saturn system moved into its northern hemisphere summer over the past few years, northern latitudes have become increasingly well illuminated. As a result, the red arc features have become clearly visible for the first time. The origin of the features and their reddish color is currently a mystery to Cassini scientists. Possibilities being studied include ideas that the reddish material is exposed ice with chemical impurities, or the result of outgassing from inside Tethys. The streaks could also be associated with features like fractures that are below the resolution of the available images. Except for a few small craters on Dione, reddish tinted features are rare on other moons of Saturn. However, many reddish features are observed on the geologically young surface of Jupiter's moon Europa. Images taken using clear, green, infrared and ultraviolet spectral filters were combined to create the view, which highlights subtle color differences across Tethys' surface at wavelengths not visible to human eyes. The moon's surface is fairly uniform in natural color. The yellowish tones on the left side of the view are a result of alteration of the moon's surface by high-energy particles from Saturn's magnetosphere. This particle radiation slams into the moon's trailing

  6. SU-E-T-29: A Dosimetric Study of Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost for Rectal Cancer

    SciTech Connect

    Sun, T; Lin, X; Yin, Y; Liu, T

    2015-06-15

    Purpose: To compare the dosimetric differences among fixed field intensity-modulated radiotherapy (IMRT) and double-arc volumetricmodulated arc therapy (VMAT) plans with simultaneous integrated boost in rectal cancer. Methods: Ten patients with rectal cancer previously treated with IMRT were included in this analysis. For each patient, two treatment techniques were designed for each patient: the fixed 7 fields IMRT and double-arc VMAT with RapidArc technique. The treatment plan was designed to deliver in one process with simultaneous integrated boost (SIB). The prescribed doses to the planning target volume of the subclinical disease (PTV1) and the gross disease (PTV2) were 45 Gy and 55 Gy in 25 fractions, respectively. The dose distribution in the target, the dose to the organs at risk, total MU and the delivery time in two techniques were compared to explore the dosimetric differences. Results: For the target dose and homogeneity in PTV1 and PTV2, no statistically differences were observed in the two plans. VMAT plans showed a better conformity in PTV1. VMAT plans reduced the mean dose to bladder, small bowel, femur heads and iliac wings. For iliac wings, VMAT plans resulted in a statistically significant reduction in irradiated volume of 15 Gy, 20 Gy, 30 Gy but increased the 10 Gy irradiated volume. VMAT plans reduced the small bowel irradiated volume of 20 Gy and 30 Gy. Compared with IMRT plans, VMAT plans showed a significant reduction of monitor units by nearly 30% and reduced treatment time by an average of 70% Conclusion: Compared to IMRT plans, VMAT plans showed the similar target dose and reduced the dose of the organs at risk, especially for small bowel and iliac wings. For rectal cancer, VMAT with simultaneous integrated boost can be carried out with high quality and efficiency.

  7. Arc Distribution During the Vacuum Arc Remelting of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Woodside, C. Rigel; King, Paul E.; Nordlund, Chris

    2013-02-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot-Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  8. Arc distribution during the vacuum arc remelting of Ti-6Al-4V

    SciTech Connect

    Woodside, Charles Rigel; King, Paul E.; Nordlund, Chris

    2013-01-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot–Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  9. Coexistence of probe conformations in lipid phases-a polarized fluorescence microspectroscopy study.

    PubMed

    Urbančič, Iztok; Ljubetič, Ajasja; Arsov, Zoran; Strancar, Janez

    2013-08-20

    Several well-established fluorescence methods depend on environment-sensitive probes that report about molecular properties of their local environment. For reliable interpretation of experiments, careful characterization of probes' behavior is required. In this study, bleaching-corrected polarized fluorescence microspectroscopy with nanometer spectral peak position resolution was applied to characterize conformations of two alkyl chain-labeled 7-nitro-2-1,3-benzoxadiazol-4-yl phospholipids in three model membranes, representing the three main lipid phases. The combination of polarized and spectral detection revealed two main probe conformations with their preferential fluorophore dipole orientations roughly parallel and perpendicular to membrane normal. Their peak positions were separated by 2-6 nm because of different local polarities and depended on lipid environment. The relative populations of conformations, estimated by a numerical model, indicated a specific sensitivity of the two probes to molecular packing with cholesterol. The coexistence of probe conformations could be further exploited to investigate membrane organization below microscopy spatial resolution, such as lipid rafts. With the addition of polarized excitation or detection to any environment-sensitive fluorescence imaging technique, the conformational analysis can be directly applied to explore local membrane complexity.

  10. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals.

    PubMed

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-18

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone-center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm(-1) on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis.

  11. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals

    NASA Astrophysics Data System (ADS)

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V.; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V.; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-01

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone–center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm‑1 on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis.

  12. Coexistence of Probe Conformations in Lipid Phases—A Polarized Fluorescence Microspectroscopy Study

    PubMed Central

    Urbančič, Iztok; Ljubetič, Ajasja; Arsov, Zoran; Štrancar, Janez

    2013-01-01

    Several well-established fluorescence methods depend on environment-sensitive probes that report about molecular properties of their local environment. For reliable interpretation of experiments, careful characterization of probes’ behavior is required. In this study, bleaching-corrected polarized fluorescence microspectroscopy with nanometer spectral peak position resolution was applied to characterize conformations of two alkyl chain-labeled 7-nitro-2-1,3-benzoxadiazol-4-yl phospholipids in three model membranes, representing the three main lipid phases. The combination of polarized and spectral detection revealed two main probe conformations with their preferential fluorophore dipole orientations roughly parallel and perpendicular to membrane normal. Their peak positions were separated by 2–6 nm because of different local polarities and depended on lipid environment. The relative populations of conformations, estimated by a numerical model, indicated a specific sensitivity of the two probes to molecular packing with cholesterol. The coexistence of probe conformations could be further exploited to investigate membrane organization below microscopy spatial resolution, such as lipid rafts. With the addition of polarized excitation or detection to any environment-sensitive fluorescence imaging technique, the conformational analysis can be directly applied to explore local membrane complexity. PMID:23972844

  13. Ab initio thermodynamic study on two-dimensional atomic nucleation on ZnO polar surfaces

    NASA Astrophysics Data System (ADS)

    Zhu, Rui; Zhao, Qing; Xu, Jun; Liu, Banggui; Leprince-Wang, Yamin; Yu, Dapeng

    2017-08-01

    Structures of the two-dimensional atomic nuclei on ZnO (0001)-Zn and (000 1 bar)-O polar surfaces were studied by first principles density functional theory. The polarity-dependent nucleation dynamics was investigated by simulating two-dimensional (2D) nuclei consisting of 1-8 ZnO monomers on both polar surfaces. According to total energy calculations, average binding energy per ZnO monomer of the surface nuclei was analyzed to investigate if the nucleation and growth will proceed reasonably in physics. We found nucleation on (0001)-Zn surface was easier than that on (000 1 bar)-O surface. By using atomistic thermodynamics analysis, we calculated the Gibbs free energy of formation of these nuclei and made a comparison between the two polar surfaces. On (0001)-Zn surface, the critical Gibbs free energy of formation is much lower than that on (000 1 bar)-O surface under the same supersaturation, which leads to a much larger ZnO growth rate and rougher morphology, in accordance with experimental results. In addition, energetic analysis of nucleation at real thermodynamic conditions was achieved by introducing the temperature- and pressure-dependent chemical potentials of ZnO precursors.

  14. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals

    PubMed Central

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V.; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V.; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-01

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone–center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm−1 on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis. PMID:26776727

  15. Statistical study of the relationship between enhanced polar cap flows and PBIs

    NASA Astrophysics Data System (ADS)

    Zou, Y.; Nishimura, T.; Lyons, L. R.; Donovan, E.; Ruohoniemi, J. M.; Nishitani, N.; Sofko, G. J.

    2012-12-01

    Poleward boundary intensifications (PBIs) are auroral disturbances along the poleward boundary of the auroral oval and occur during all levels of geomagnetic activity. Using radar and all-sky imager observations, previous case studies have given evidence that longitudinally localized flow bursts in the polar cap that are directed toward the open-closed field line boundary precede PBIs. The present study analyzes a larger number of events and examines if this polar cap flow-PBI relationship is commonly observed. We use coordinated observations of THEMIS all sky imagers and Super Dual Auroral Radar Network (SuperDARN) at Rankin Inlet and mainly focus on isolated PBIs with weak preceding auroral activity and a step-like change of intensity in time. From January to March 2012, we find 19 PBIs satisfying our criteria and 17 of them were preceded by longitudinally narrow, equatorward directed flow bursts within the nightside polar cap having line-of-sight velocity >~150 m/s above the background,. Such flow enhancements were not detected for the other two events, although the flow data indicate weak enhancements >100 m/s. The flow bursts statistically occurred simultaneously with or 1-2 min before the PBI initiations, and the duration of flow bursts was comparable with that of the PBIs. We also find cases when multiple PBIs are preceded by multiple enhanced flows in the polar cap. The remarkably high occurrence of the association between enhanced polar cap flows and PBIs indicates that enhanced meso-scale flows within the open field line that traverse the open-closed field line boundary may be responsible for the formation of PBIs.

  16. Polarized Light in Astronomy.

    ERIC Educational Resources Information Center

    King, D. J.

    1983-01-01

    The application of very sensitive electronic detecting devices during the last decade has revolutionized and revitalized the study of polarization in celestial objects. The nature of polarization, how polaroids work, interstellar polarization, dichroic filters, polarization by scattering, and modern polarimetry are among the topics discussed. (JN)

  17. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    DOE PAGES

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; ...

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

  18. A first-principles study on Al-doped ZnO growth polarity on sapphire (0001) surface

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Gao, Qian; Hu, Zhen-Peng; Zhang, Li-Xin

    2016-06-01

    Based on the first-principles method, the polarity inversion mechanism of Al-doped ZnO grown on sapphire (0001) substrate was investigated. This study revealed that the Al dopant tends to float on the surface of the buffer layer and leads to form ZnO nucleation islands of Zn-polarity without changing in-plane orientation. Finally, these islands evolve to wall-like nanostructure with Zn-termination. The results can explain the reason of the polarity inversion phenomenon in the experiment and supply more information for controlling the ZnO growth polarity.

  19. SU-E-T-766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

    SciTech Connect

    Zhang, R; Xiaomei, F; Bai, W; Zhang, X; Gao, Y

    2015-06-15

    Purpose: To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques. Methods: Treatment plans were graded four (Low, Moderate, Moderate-High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate-High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose. Results: Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate-High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk. Conclusion: The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted. This work was supported by The Medical Science Foundation of The health department of Hebei Province (No

  20. Optical and magnetic studies on the phosphorescent state of phthalazine in polar and non-polar hosts

    NASA Astrophysics Data System (ADS)

    Yamauchi, Seigo; Ueno, Tetsuo; Hirota, Noboru

    The optical and magnetic properties of the lowest triplet state (T1) of phthalazine were investigated in benzoic acid (BAC), p-dichlorobenzene (DCB) and p-dibromobenzene (DBB) by means of phosphorescence spectroscopy, ODMR and E.P.R. at liquid helium temperatures. Well resolved phosphorescence spectra were observed in DCB and DBB and a vibrational analysis of the spectra was made. The transition energies of the T2(nπ*) and the S1(nπ*) states were estimated from the excitation spectra. The energy gaps between T1 and T2 were estimated to be 2150, 694 and 788 cm-1 in BAC, DCB and DBB, respectively. The sublevel schemes and the zero field splittings (ZFS) were determined. The observed changes of the ZFS on going from the polar to the non-polar hosts are discussed in terms of the vibronic and spin-orbit interactions with the nearby T2(nπ*) state. The most radiative sublevel was found to be T2 in DCB, but Ty in BAC. This difference is attributed to the shifts of the energy levels and the reduction of the molecular symmetry in the polar host. In the non-radiative decay Ty was found to be the most active. Tremendous increases in the non-radiative decay rate constants were observed on going from BAC to DCB. Possible explanations for these observations are presented. The external heavy atom effect on the phosphorescence was observed in the case of DBB. The mechanisms enhancing the radiative decay rates, including those for the vibronic bands are discussed.

  1. Study of myocardial cell inhomogeneity of the human heart: Simulation and validation using polarized light imaging.

    PubMed

    Desrosiers, Paul Audain; Michalowicz, Gabrielle; Jouk, Pierre-Simon; Usson, Yves; Zhu, Yuemin

    2016-05-01

    The arrangement or architecture of myocardial cells plays a fundamental role in the heart's function and its change was shown to be directly linked to heart diseases. Inhomogeneity level is an important index of myocardial cell arrangements in the human heart. The authors propose to investigate the inhomogeneity level of myocardial cells using polarized light imaging simulations and experiments. The idea is based on the fact that the myosin filaments in myocardial cells have the same properties as those of a uniaxial birefringent crystal. The method then consists in modeling the myosin filaments of myocardial cells as uniaxial birefringent crystal, simulating the behavior of the latter by means of the Mueller matrix, and measuring the final intensity of polarized light and consequently the inhomogeneity level of myocardial cells in each voxel through the use of crossed polarizers. The method was evaluated on both simulated and real tissues and under various myocardial cell configurations including parallel cells, crossed cells, and cells with random orientations. When myocardial cells run perfectly parallel to each other, all the polarized light was blocked by those parallel myocardial cells, and a high homogeneity level was observed. However, if myocardial cells were not parallel to each other, some leakage of the polarized light was observed, thus causing the decrease of the polarized light amplitude and homogeneity level. The greater the crossing angle between myocardial cells, the smaller the amplitude of the polarized light and the greater the inhomogeneity level. For two populations of myocardial cell crossing at an angle, the resulting azimuth angle of the voxel was the bisector of this angle. Moreover, the value of the inhomogeneity level began to decrease from a nonzero value when the voxel was not totally homogeneous, containing for example cell crossing. The proposed method enables the physical information of myocardial tissues to be estimated and the

  2. Numerical study of the polarization effect of GPR systems on the detection of buried objects

    NASA Astrophysics Data System (ADS)

    Sagnard, Florence

    2017-04-01

    This work is in line with the studies carried out in our department over the last few years on object detection in civil engineering structures and soils. In parallel to building of the second version of the Sense-City test site where several pipeline networks will be buried [1], we are developing numerical models using the FIT and the FDTD approaches to study more precisely the contribution of the polarization diversity in the detection of conductive and dielectric buried objects using the GPR technique. The simulations developed are based on a ultra-wide band SFCW GPR system that have been designed and evaluated in our laboratory. A parametric study is proposed to evaluate the influence of the antenna configurations and the antenna geometry when considering the polarization diversity in the detection and characterization of canonical objects. [1] http://www.sense-city.univ-paris-est.fr/index.php

  3. Analysis of arc emission spectra of stainless steel electric arc furnace slag affected by fluctuating arc voltage.

    PubMed

    Aula, Matti; Mäkinen, Ari; Fabritius, Timo

    2014-01-01

    Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful.

  4. Generating scientific models of knowledge using arcs.

    PubMed

    Kim, Jinshil; Pressler, Susan J; Jones, Josette; Graves, Judith R

    2008-01-01

    Systematic approaches are needed to review literature on nutrition in heart failure for its scientific merit, relevance, and usefulness and identify directions for future research. To evaluate the feasibility of arcs (J.R.G., Indianapolis, Indiana), a computer program for managing data from literature and modeling knowledge, the objectives were to conduct an integrative review of 10 studies of nutrition in heart failure and generate scientific models of knowledge using arcs. A unit of knowledge in arcs is 2 variables linked by a statistical relationship. The computer program arcs categorized variables and relationships found in the 10 explanatory observational studies. It also provided a scientific model for further empirical testing. The computer program arcs aggregated the following: 104 dependent and 93 independent operational variables and 60 associational, 16 predictive, 15 structural, 1 descriptive, and 85 difference relationships. A direct model produced by arcs postulated a structural relationship between cachexia and 18-month mortality, independent of age or New York Heart Association classification, which can be tested as a path theoretical model. The computer program arcs appeared to be feasible for conducting an integrative review of nutrition in heart failure. A larger, representative set of literature will enable generation of knowledge and identification of gaps and inconsistencies in findings.

  5. Green-synthesis, characterization, photostability and polarity studies of novel Schiff base dyes using spectroscopic methods.

    PubMed

    Marwani, Hadi M; Asiri, Abdullah M; Khan, Salman A

    2012-01-01

    Preparation, characterization, photostability and polarity studies of novel Schiff base dyes using spectroscopic methods were achieved. The Schiff base dyes were prepared by the reaction of salicylaldehyde/2-Hydroxy-1-naphthaldehyde with aminophenazone under microwave irradiation. The spectroscopic (FT-IR, 1H NMR, 13C-NMR, Mass) studies and elemental analyses were in good agreement with chemical structure of synthesized compounds. In addition, UV-Vis and fluorescence spectroscopic experiments showed that these dyes are good absorbent and fluorescent. Based on the photostability study of these dyes, minimal to no loss in fluorescence intensities of 4-[(2-Hydroxy-benzylidene)-amino] 1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (D1) (6.14%) and 4-[(2-Hydroxy-naphthalen-1-ylmethylene)-amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (D2) (2.95%) was observed with an increase in the exposure time using time-based fluorescence steady-state experiments. These studies also inferred that these Schiffbase dyes have a high photostability against photobleaching. In addition, Dye 2 is found to be more sensitive than Dye 1 to the polarity of the microenvironment provided by different solvents based on the results of fluorescence polarity studies.

  6. Welding arc initiator

    DOEpatents

    Correy, Thomas B.

    1989-01-01

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome.

  7. Welding arc initiator

    DOEpatents

    Correy, T.B.

    1989-05-09

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome. 3 figs.

  8. Arc spraying in China

    NASA Astrophysics Data System (ADS)

    Liu, Xianjun

    2001-03-01

    Although are spraying is not a new technique, recent development of arc spraying device systems, spray wires, research on the coating mechanism, and the dynamic behavior of spraying make it a most active thermal spray process. In China, the arc spraying technique is the most efficient way for long life corrosion protection of steel structures. In addition, the arc spraying process is widely used for renovation and surface modification of machine components, mold making for plastic products, high-temperature corrosion resistance for waterwalls of boilers, antisliding coatings, self-lubricating coatings, etc.

  9. Tokamak ARC damage

    SciTech Connect

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage.

  10. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, Paul R [Richland, WA

    1986-01-01

    A portable, hand held electric arc saw has a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc to erode a workpiece. Electric current is supplied to the blade by biased brushes and a slip ring which are mounted in the frame. A pair of freely movable endless belts in the form of crawler treads stretched between two pulleys are used to facilitate movement of the electric arc saw. The pulleys are formed of dielectric material to electrically insulate the crawler treads from the frame.

  11. The role of ring current nose events in producing stable auroral red arc intensifications during the main phase - Observations during the September 19-24, 1984, equinox transition study

    NASA Technical Reports Server (NTRS)

    Kozyra, J. U.; Chandler, M. O.; Hamilton, D. C.; Peterson, W. K.; Klumpar, D. M.; Slater, D. W.; Buonsanto, M. J.; Carlson, H. C.

    1993-01-01

    A set of observations describing ionospheric conditions, magnetospheric populations, and 6300-A emission intensities on stable auroral red (SAR) arc field lines during the solar minimum 19-24 Sept. 1984 magnetic storm period prompted a study of solar cycle and magnetic storm phase variations in SAR arc emissions and their magnetospheric energy source. It was found that medium-energy H(+) was significantly enhanced during the main phase compared to the late recovery phase of the 19-20 Sept. 1984 storm. Enhanced heating of the thermal electron plasma caused by this population resulted in more than an order of magnitude greater SAR arc emissions in the main phase compared to the recovery phase. O(+) was found to be the dominant energy source for SAR arcs in the late recovery phases of storms in the 19-24 Sept. period.

  12. The role of ring current nose events in producing stable auroral red arc intensifications during the main phase - Observations during the September 19-24, 1984, equinox transition study

    NASA Technical Reports Server (NTRS)

    Kozyra, J. U.; Chandler, M. O.; Hamilton, D. C.; Peterson, W. K.; Klumpar, D. M.; Slater, D. W.; Buonsanto, M. J.; Carlson, H. C.

    1993-01-01

    A set of observations describing ionospheric conditions, magnetospheric populations, and 6300-A emission intensities on stable auroral red (SAR) arc field lines during the solar minimum 19-24 Sept. 1984 magnetic storm period prompted a study of solar cycle and magnetic storm phase variations in SAR arc emissions and their magnetospheric energy source. It was found that medium-energy H(+) was significantly enhanced during the main phase compared to the late recovery phase of the 19-20 Sept. 1984 storm. Enhanced heating of the thermal electron plasma caused by this population resulted in more than an order of magnitude greater SAR arc emissions in the main phase compared to the recovery phase. O(+) was found to be the dominant energy source for SAR arcs in the late recovery phases of storms in the 19-24 Sept. period.

  13. Metal halide arc discharge lamp having short arc length

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  14. Etching on polar (111) surfaces of CdTe crystals studied with Auger electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Y.-C.; Stahle, C. M.; Feigelson, R. S.; Morimoto, J.

    1987-12-01

    Several reducing and oxidizing etches were applied to the polar (111) Cd and (111) Te surfaces in CdTe crystals, and Auger electron spectroscopy was used to study the effect of these etches on the surface composition. Auger sputter profiles revealed the effect of the etch below the surface of the samples. Dithionite etch left both surfaces Cd-rich. The surface composition of sulfur increased with increasing etch time and temperature, with a corresponding decrease of Te. Hydrazine etch left the surface composition Cd-to-Te ratio about one-to-one. However, the large oxygen peak was found to increase as the etch time and temperature increased. Hydrogen heat treatment left the surface stoichiometric, free of contamination, and crystalline. The surface offers a good reference for the study of crystallographic polarity and is ideal for device applications.

  15. Arc Voltage Between Deion Grid Affected by Division of Arc in Magnetic Driven Arc

    NASA Astrophysics Data System (ADS)

    Inuzuka, Yutaro; Yamato, Takashi; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Magnetic driven arc has been applied to DC breaker and fault current limiters. However, it has not been researched, especially stagnation and re-strike of the arc. In this paper, the arc voltage between deion grid affected by division of arc in magnetic driven arc and arc behavior are measured by using the oscilloscope and HSVC (High Speed Video Camera). As a result, arc voltage increased because of division of the arc. The arc mean moving speed increases with increasing the external magnetic field. However, when the arc was not stalemate, the arc moving speed does not change so much. The arc re-strike time increases and stalemate time decreases with increasing the external magnetic field. Therefore, the anode spot moving speed increases 8 times because arc re-strike occurs easily with the external magnetic field. Thus, the erosion of electrodes decreases and the arc movement becomes the smooth. When the arc is divided, the arc voltage increased because of the electrode fall voltage. Therefore, the arc voltage increases with increasing the number of deion grid.

  16. Formation of the G-ring arc

    NASA Astrophysics Data System (ADS)

    Araujo, N. C. S.; Vieira Neto, E.; Foryta, D. W.

    2016-09-01

    Since 2004, the images obtained by the Cassini spacecraft's on-board cameras have revealed the existence of several small satellites in the Saturn system. Some of these small satellites are embedded in arcs of particles. While these satellites and their arcs are known to be in corotation resonances with Mimas, their origin remains unknown. This work investigates one possible process for capturing bodies into a corotation resonance, which involves increasing the eccentricity of a perturbing body. Therefore, through numerical simulations and analytical studies, we show a scenario in which the excitation of Mimas's eccentricity could capture particles in a corotation resonance. This is a possible explanation for the origin of the arcs.

  17. Modeling Multi-Arc Spraying Systems

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.

    2016-06-01

    The use of plasma as energy source in thermal spraying enables among others the processing of feed stock materials with very high melting temperatures as coating materials. New generation multi-arc plasma spraying systems are widely spread and promise several advantages in comparison to the conventional single-arc systems. Numerical modeling of multi-arc plasma spraying offers the possibility to increase the understanding about this process. This study focuses on the numerical modeling of three-cathode spraying systems, introducing the recent activities in this field and discussing the numerical aspects which influence the prediction power of the models.

  18. Electric arc discharge damage to ion thruster grids

    NASA Technical Reports Server (NTRS)

    Beebe, D. D.; Nakanishi, S.; Finke, R. C.

    1974-01-01

    Arcs representative of those occurring between the grids of a mercury ion thruster were simulated. Parameters affecting an arc and the resulting damage were studied. The parameters investigated were arc energy, arc duration, and grid geometry. Arc attenuation techniques were also investigated. Potentially serious damage occurred at all energy levels representative of actual thruster operating conditions. Of the grids tested, the lowest open-area configuration sustained the least damage for given conditions. At a fixed energy level a long duration discharge caused greater damage than a short discharge. Attenuation of arc current using various impedances proved to be effective in reducing arc damage. Faults were also deliberately caused using chips of sputtered materials formed during the operation of an actual thruster. These faults were cleared with no serious grid damage resulting using the principles and methods developed in this study.

  19. The polarization properties of a tilted polarizer.

    PubMed

    Korger, Jan; Kolb, Tobias; Banzer, Peter; Aiello, Andrea; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd

    2013-11-04

    Polarizers are key components in optical science and technology. Thus, understanding the action of a polarizer beyond oversimplifying approximations is crucial. In this work, we study the interaction of a polarizing interface with an obliquely incident wave experimentally. To this end, a set of Mueller matrices is acquired employing a novel procedure robust against experimental imperfections. We connect our observation to a geometric model, useful to predict the effect of polarizers on complex light fields.

  20. The 2-8 GHz solar dynamic spectra and polarization measurement feasibility study

    NASA Technical Reports Ser