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. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. F-Layer Polar Cap Arcs.

    DTIC Science & Technology

    1987-09-01

    the electric fields. The particles may also be accelerated; they typically have a * higher range of energies than that of their solar ,.-.., wind ...spread F masking in the ionogram indicates the presence of structured irregularities in the arcs. Irregularities also cause dmplitude scintillation. and

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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

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

    DTIC Science & Technology

    1991-02-01

    IoUit y ( diii 15111 ward flow oil tilie dawnit ed (ge 0 (itth arc Iihjijk like !oCaio)1 of’ S1101 I-f~ ersi IC lt J 00 (C hk:iir driven by (fowrrwir...design is based on what we know of their morphology by combining the optical emissions associated with S-A arcs from optical imagery. The essence of...8217:en h% BrcAW ct al. 119741 and /ca lcilojirdfierc cI (it. 1 1977. I IL! t imirit dei- idijxi.] hull the &OLtl Ck)[ rC~ph) lllt ! Ili Ilt I I . _1lt

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  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. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  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. Polarization of positronium in amorphous polar polymers: A case study

    SciTech Connect

    Consolati, G. Quasso, F.

    2013-11-28

    The features of positronium in an amorphous copolymer (polyvinyl acetate-crotonic acid) in a range of temperatures including the glass transition were investigated by means of positron annihilation lifetime spectroscopy. In particular, para-positronium lifetime was found to be longer than in a vacuum and to decrease with the temperature. This was attributed to the electron density at the positron (contact density), which is lower than in vacuo due to the presence of polar groups in the copolymer. A three quantum yield experiment confirmed the lifetime results.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. High-Resolution Studies of the Solar Polar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Varsik, J. R.; Wilson, P. R.; Li, Y.

    1999-02-01

    We present high-resolution studies of the solar polar magnetic fields near sunspot maximum in 1989 and towards sunspot minimum in 1995. We show that, in 1989, the polar latitudes were covered by several unipolar regions of both polarities. In 1995, however, after the polar field reversal was complete, each pole exhibited only one dominant polarity region. Each unipolar region contains magnetic knots of both polarities but the number count of the knots of the dominant polarity exceeds that of the opposite polarity by a ratio of order 4:1, and it is rare to find opposite polarity pairs, i.e., magnetic bipoles. These knots have lifetimes greater than 7hours but less than 24hours. We interpret the longitudinal displacement of the knots over a 7-hour period as a measure of the local rotation rate. This rotation rate is found to be generally consistent with Snodgrass' (1983) magnetic rotation law. In an attempt to obtain some insight into the operation of the solar dynamo, sketches of postulated subsurface field configurations corresponding to the observed surface fields at these two epochs of the solar cycle are presented.

  14. 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.

  15. 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.

  16. 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.

  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

    2017-02-01

    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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  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. 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.

  8. 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.

  9. 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.

  10. 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)

  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. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. [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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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).

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  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. 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.

  7. 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.

  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. [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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  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. 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.

  20. 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.

  1. 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}.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Polar bear aerial survey in the eastern Chukchi Sea: A pilot study

    USGS Publications Warehouse

    Evans, Thomas J.; Fischbach, Anthony S.; Schliebe, Scott; Manly, Bryan; Kalxdorff, Susanne; 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. Application of polarization modulation spectroscopy to the study of magnetic materials (abstract) (invited)

    NASA Astrophysics Data System (ADS)

    Sanchez-Hanke, C.; Lott, D.; Stohr, J.; Kao, C.-C.

    2002-03-01

    Over the last decade, x-ray magnetic circular dichroism (XMCD) and x-ray resonant magnetic scattering (XRMS) have become important experimental techniques in the study of magnetic materials. In order to reduce systematic errors in these measurements, typical XMCD and XRMS experiments are carried out using magnetization switching, although there are many situations where polarization switching is clearly desirable. Recently, fast polarization modulation techniques have been developed using either polarization conversion optical elements, such as phase plate, or special insertion devices. At the National Synchrotron Light Source (NSLS), an elliptically polarized wiggler (EPW), jointly developed by NSLS, Advanced Photon Source, and BINP of Novosibirsk, for this purpose. The EPW consists of a permanent magnet vertical wiggler and an electromagnet horizontal wiggler. The polarization of the device can be switched up to 100 Hz by switching the electromagnet. To take advantage of the fast switching capability, a phase sensitive detection system was also implemented. The sensitivity of using fast polarization modulation is demonstrated by measuring the element specific hysteresis loop and MCD spectrum of Cu induced moment at the interface of a Co/Cu multilayer. By comparing with results obtained using conventional measurements from similar samples, it clearly shows the advantages of using polarization modulation for small MCD effects. The sensitivity of this technique and the possibility of performing magnetic field dependent measurements of using polarization modulation have been applied to a number of magnetic systems. First, the spatial distribution of Cr induced moment in an ideal exchange-biased Fe/Cr multilayer was measured using soft-x-ray XRMS. Specular reflectivity was measured as a function of both angle and energy near Cr and Fe L3 edges. The Cr induced moment was clearly observed. Moreover, the spatial distribution of the induced Cr moment was determined by

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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).

  3. 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)

  4. 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

  5. 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

  6. 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.

  7. 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%.

  8. 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).…

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Defect studies on as-synthesized and purified carbon nanostructures produced by arc-discharge in solution process.

    PubMed

    Bera, Debasis; Perrault, Jean-Philippe; Heinrich, Helge; Seal, Sudipta

    2006-04-01

    Carbon nanostructures are synthesized using a novel arc-discharge in solution process. A multitude of defects on nanotubes and nanostructures is found. Evidence of these defects in as-synthesized carbon nanostructures is explored using high-resolution transmission electron microscopy (HRTEM). Tri-, tetra-, penta-, hexa-, heptagonal, toroidal, oval, and spherical nanoshells are found in HRTEM investigation along with carbon nanotubes, carbon nanohorns, carbon rods, nanoporous carbon, dislodged graphene sheets, and amorphous carbon. Purifications are carried out through two oxidation methods to eliminate the amorphous carbon. Several different defects caused by oxidations are also found in purified samples.

  8. 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.

  9. 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.

  10. 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.

  11. The Feasibility Study of a Hybrid Coplanar Arc Technique Versus Hybrid Intensity-modulated Radiotherapy in Treatment of Early-stage Left-sided Breast Cancer with Simultaneous-integrated Boost

    PubMed Central

    Chen, Yuan-Gui; Li, An-Chuan; Li, Wen-Yao; Huang, Miao-Yun; Li, Xiao-Bo; Chen, Ming-Qiu; Zhang, Mutian; Xu, Ben-Hua

    2017-01-01

    This study demonstrated the feasibility and advantages of a hybrid, volumetric arc therapy technique that used two 90° coplanar arcs and two three-dimensional conformal tangential beams in the simultaneous-integrated boost radiotherapy of left-sided breast cancer after breast-conserving surgery. A total of nine patients with stage I, left-sided breast cancer who underwent breast-conserving surgery were selected for this retrospective study. For each patient, a hybrid arc plan was generated and then compared with two hybrid intensity-modulated radiotherapy plans. All plans were optimized using the same objectives and dose constraints. The prescription dose was 50.4 Gy to the planning target volume with simultaneous boost to 60 Gy to the expanded gross target volume in 28 fractions. The differences among these hybrid plans were analyzed by the Kolmogorov–Smirnov test or the Wilcoxon rank sum test. The hybrid arc plans achieved the clinical requirements of target dose coverage and normal tissue (NT) dose constraints. It was found that the hybrid arc plans showed advantages in the conformity index of the expanded gross target volume, the V5 of the heart, the D2 of the left ventricle, and the D2 and V50.4 of NTs. The average beam-on time and monitor units of the hybrid arc plans were significantly lower (P < 0.001).

  12. Dosimetric study of volumetric arc modulation with RapidArc and intensity-modulated radiotherapy in patients with cervical cancer and comparison with 3-dimensional conformal technique for definitive radiotherapy in patients with cervical cancer

    SciTech Connect

    Guy, Jean-Baptiste; Falk, Alexander T.; Auberdiac, Pierre; Cartier, Lysian; Vallard, Alexis; Ollier, Edouard; Trone, Jane-Chloé; Khodri, Moustapha; Chargari, Cyrus; Magné, Nicolas

    2016-04-01

    Introduction: For patients with cervical cancer, intensity-modulated radiation therapy (IMRT) improves target coverage and allows dose escalation while reducing the radiation dose to organs at risk (OARs). In this study, we compared dosimetric parameters among 3-dimensional conformal radiotherapy (3D-CRT), “step-and-shoot” IMRT, and volumetric intensity-modulated arc radiotherapy (VMAT) in a series of patients with cervical cancer receiving definitive radiotherapy. Computed tomography (CT) scans of 10 patients with histologically proven cervical cancer treated with definitive radiation therapy (RT) from December 2008 to March 2010 at our department were selected for this study. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated following the guidelines of the Gyn IMRT consortium that included cervix, uterus, parametrial tissues, and the pelvic nodes including presacral. The median age was 57 years (range: 30 to 85 years). All 10 patients had squamous cell carcinoma with Federation of Gynecology and Obstetrics (FIGO) stage IB-IIIB. All patients were treated by VMAT. OAR doses were significantly reduced for plans with intensity-modulated technique compared with 3D-CRT except for the dose to the vagina. Between the 2 intensity-modulated techniques, significant difference was observed for the mean dose to the small intestine, to the benefit of VMAT (p < 0.001). There was no improvement in terms of OARs sparing for VMAT although there was a tendency for a slightly decreased average dose to the rectum: − 0.65 Gy but not significant (p = 0.07). The intensity modulation techniques have many advantages in terms of quality indexes, and particularly OAR sparing, compared with 3D-CRT. Following the ongoing technologic developments in modern radiotherapy, it is essential to evaluate the intensity-modulated techniques on prospective studies of a larger scale.

  13. A shear-wave polarization study in the Wellington region New Zealand

    SciTech Connect

    Gledhill, K.R. )

    1990-08-01

    A month of digital data from two three component seismograph stations near Wellington, New Zealand, was analyzed as part of a feasibility study for a major project to investigate shear-wave splitting. Although the total number of earthquakes studies was small (14), some suggestive results were obtained. Almost all events recorded within the shear wave window showed a phase reversal of the horizontal components after one or two shear wave cycles, suggesting that there are actually two shear-wave arrivals. The measured polarization of the first shear wave arrivals was N (31 {plus minus} 11) E. This polarization alignment cannot be explained by focal mechanisms, and it is unlikely to be due to topography because of the station-to-station correlation. The present evidence suggests the most likely cause is crustal anistropy due to the geological structure at shallow depth, rather than stress aligned micro-cracks.

  14. 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.

  15. 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.

  16. Filtered cathodic arc source

    DOEpatents

    Falabella, S.; Sanders, D.M.

    1994-01-18

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge is described. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45[degree] to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles. 3 figures.

  17. Filtered cathodic arc source

    DOEpatents

    Falabella, Steven; Sanders, David M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45.degree. to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

  18. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Study of Squeezed Excitons in Polar Semiconductors

    NASA Astrophysics Data System (ADS)

    Yin, Miao; Cheng, Ze; Wu, Zi-Xia; Ping, Yun-Xia

    2009-03-01

    Some properties of excitons in polar semiconductors are studied theoretically by means of squeezed state variational approach. This method makes it possible to consider bilinear terms of the phonon operators as well as linear terms arising from the Lee-Low-Pines (LLP)-like transformation. The exciton ground state energy and binding energy are calculated numerically. It is shown that the squeezing effect is significant in the case of strong exciton-phonon coupling region.

  19. 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.

  20. THE REDSHIFT DISTRIBUTION OF GIANT ARCS IN THE SLOAN GIANT ARCS SURVEY

    SciTech Connect

    Bayliss, Matthew B.; Gladders, Michael D.; Koester, Benjamin P.; Oguri, Masamune; Hennawi, Joseph F.; Sharon, Keren; Dahle, Haakon

    2011-01-20

    We measure the redshift distribution of a sample of 28 giant arcs discovered as a part of the Sloan Giant Arcs Survey. Gemini/GMOS-North spectroscopy provides precise redshifts for 24 arcs, and 'redshift desert' constrains for the remaining 4 arcs. This is a direct measurement of the redshift distribution of a uniformly selected sample of bright giant arcs, which is an observable that can be used to inform efforts to predict giant arc statistics. Our primary giant arc sample has a median redshift z = 1.821 and nearly two-thirds of the arcs, 64%, are sources at z {approx}> 1.4, indicating that the population of background sources that are strongly lensed into bright giant arcs resides primarily at high redshift. We also analyze the distribution of redshifts for 19 secondary strongly lensed background sources that are not visually apparent in Sloan Digital Sky Survey imaging, but were identified in deeper follow-up imaging of the lensing cluster fields. Our redshift sample for the secondary sources is not spectroscopically complete, but combining it with our primary giant arc sample suggests that a large fraction of all background galaxies that are strongly lensed by foreground clusters reside at z {approx}> 1.4. Kolmogorov-Smirnov tests indicate that our well-selected, spectroscopically complete primary giant arc redshift sample can be reproduced with a model distribution that is constructed from a combination of results from studies of strong-lensing clusters in numerical simulations and observational constraints on the galaxy luminosity function.

  1. First clinical pilot study with intravascular polarization sensitive optical coherence tomography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Villiger, Martin; Karanasos, Antonios; Ren, Jian; Lippok, Norman; Shishkov, Milen; Daemen, Joost; Van Mieghem, Nicolas; Diletti, Roberto; Valgimigli, Marco; van Geuns, Robert-Jan; de Jaegere, Peter; Zijlstra, Felix; van Soest, Gijs; Nadkarni, Seemantini; Regar, Evelyn; Bouma, Brett E.

    2016-02-01

    Polarization sensitive (PS) OCT measures the polarization states of the light backscattered by tissue and provides measures of tissue birefringence and depolarization in addition to the structural OCT signal. Ex vivo studies have demonstrated that birefringence is increased in tissue rich in collagen and with elevated smooth muscle cell content. Preliminary data further suggests that depolarization can identify regions of macrophage infiltration, lipid, and irregularly arranged collagen fibers. These are important aspects of the mechanical integrity and vulnerability of atherosclerotic plaques. To evaluate the potential of PS-OCT in the clinical setting, we combined our custom PS-OCT system with commercially available OCT catheters (Fastview, Terumo Corporation) and performed a pilot study in 30 patients, scheduled to undergo percutaneous coronary intervention (PCI) on the grounds of stable or unstable angina. A total of 82 pullbacks in 39 vessels were performed, either in the native coronary arteries or post procedure. Comparing consecutive pullbacks of the same coronary artery, we found excellent agreement between the polarization features in the repeat pullbacks, validating the repeatability and robustness of PS-OCT in the clinical in vivo setting. In addition we observed that the birefringence and depolarization features vary significantly across lesions with identical structural OCT appearance, suggesting morphological subtypes. This first human pilot study proved the feasibility and robustness of intravascular PS-OCT. PS-OCT achieves improved tissue characterization and may help in identifying high-risk plaques, with the potential to ultimately improve risk stratification and help guiding PCI.

  2. FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

    2002-01-01

    The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identity the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral SnapshoT (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data was used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and a long-system particle-in-cell simulation to model the magnetically connected region between the two satellites.

  3. Molecular dynamics study of DNA binding by INT-DBD under a polarized force field.

    PubMed

    Yao, Xue X; Ji, Chang G; Xie, Dai Q; Zhang, John Z H

    2013-05-15

    The DNA binding domain of transposon Tn916 integrase (INT-DBD) binds to DNA target site by positioning the face of a three-stranded antiparallel β-sheet within the major groove. As the negatively charged DNA directly interacts with the positively charged residues (such as Arg and Lys) of INT-DBD, the electrostatic interaction is expected to play an important role in the dynamical stability of the protein-DNA binding complex. In the current work, the combined use of quantum-based polarized protein-specific charge (PPC) for protein and polarized nucleic acid-specific charge (PNC) for DNA were employed in molecular dynamics simulation to study the interaction dynamics between INT-DBD and DNA. Our study shows that the protein-DNA structure is stabilized by polarization and the calculated protein-DNA binding free energy is in good agreement with the experimental data. Furthermore, our study revealed a positive correlation between the measured binding energy difference in alanine mutation and the occupancy of the corresponding residue's hydrogen bond. This correlation relation directly relates the contribution of a specific residue to protein-DNA binding energy to the strength of the hydrogen bond formed between the specific residue and DNA.

  4. Comparative Study of Subduction Zone Thermal Structure: Implications for Slab Dehydration and Fluid Supply for Mantle Wedge Serpentinization and Arc Volcanism

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; He, J.; Hyndman, R. D.

    2007-12-01

    Aqueous fluid from the dehydrating slab is critical to the processes of forearc mantle wedge serpentinization and arc volcanism. Its availability depends mainly on the thermal structure of the subducting slab, which is strongly controlled by the age of the slab and mantle wedge flow. In this study, we develop 2-D steady state numerical thermal models for a number of subduction zones to investigate how the thermal structure affects the fluid supply. Subduction zones investigated in this comparative study include Cascadia, Chile, Colombia-Ecuador, Costa Rica, Hikurangi, Kermadec, Mariana, Mexico, Nankai, NE Japan, and Sumatra. Geophysical and geological observations indicate that the shallow part of the forearc mantle wedge is decoupled from the subducting slab and does not participate in the wedge flow. The maximum depth of the slab-mantle wedge decoupling is one of the most important parameters controlling the subduction zone thermal structure. In our models, the depth of downdip transition from decoupling to coupling is constrained by surface heat flow and the location of the arc, beneath which the mantle wedge temperature is required to be greater than 1200°C. We find that the optimal transition depth for most subduction zones is in the range of 70 to 90 km; too shallow a transition will over-predict the forearc heat flow, and too deep a transition will under-predict the mantle temperature beneath the arc. The model results show that, for all subduction zones, the stagnant part of the forearc mantle wedge is sufficiently cold to allow serpentine to be stable, but the actual degree of its serpentinization should differ between different subduction zones depending on the availability of fluids. For subduction zones with a young and warm slab such as Cascadia and Nankai, dehydration of the subducting crust peaks at depths shallower than the decoupling-coupling transition depth and therefore provides ample fluid to serpentinize the overlying stagnant mantle wedge

  5. Comparative Study of Subduction Zone Thermal Structure: Implications for Slab Dehydration and Fluid Supply for Mantle Wedge Serpentinization and Arc Volcanism

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; He, J.; Hyndman, R. D.

    2004-12-01

    Aqueous fluid from the dehydrating slab is critical to the processes of forearc mantle wedge serpentinization and arc volcanism. Its availability depends mainly on the thermal structure of the subducting slab, which is strongly controlled by the age of the slab and mantle wedge flow. In this study, we develop 2-D steady state numerical thermal models for a number of subduction zones to investigate how the thermal structure affects the fluid supply. Subduction zones investigated in this comparative study include Cascadia, Chile, Colombia-Ecuador, Costa Rica, Hikurangi, Kermadec, Mariana, Mexico, Nankai, NE Japan, and Sumatra. Geophysical and geological observations indicate that the shallow part of the forearc mantle wedge is decoupled from the subducting slab and does not participate in the wedge flow. The maximum depth of the slab-mantle wedge decoupling is one of the most important parameters controlling the subduction zone thermal structure. In our models, the depth of downdip transition from decoupling to coupling is constrained by surface heat flow and the location of the arc, beneath which the mantle wedge temperature is required to be greater than 1200°C. We find that the optimal transition depth for most subduction zones is in the range of 70 to 90 km; too shallow a transition will over-predict the forearc heat flow, and too deep a transition will under-predict the mantle temperature beneath the arc. The model results show that, for all subduction zones, the stagnant part of the forearc mantle wedge is sufficiently cold to allow serpentine to be stable, but the actual degree of its serpentinization should differ between different subduction zones depending on the availability of fluids. For subduction zones with a young and warm slab such as Cascadia and Nankai, dehydration of the subducting crust peaks at depths shallower than the decoupling-coupling transition depth and therefore provides ample fluid to serpentinize the overlying stagnant mantle wedge

  6. Spin polarization transfer mechanisms of SABRE: A magnetic field dependent study.

    PubMed

    Pravdivtsev, Andrey N; Ivanov, Konstantin L; Yurkovskaya, Alexandra V; Petrov, Pavel A; Limbach, Hans-Heinrich; Kaptein, Robert; Vieth, Hans-Martin

    2015-12-01

    We have investigated the magnetic field dependence of Signal Amplification By Reversible Exchange (SABRE) arising from binding of para-hydrogen (p-H2) and a substrate to a suitable transition metal complex. The magnetic field dependence of the amplification of the (1)H Nuclear Magnetic Resonance (NMR) signals of the released substrates and dihydrogen, and the transient transition metal dihydride species shows characteristic patterns, which is explained using the theory presented here. The generation of SABRE is most efficient at low magnetic fields due to coherent spin mixing at nuclear spin Level Anti-Crossings (LACs) in the SABRE complexes. We studied two Ir-complexes and have shown that the presence of a (31)P atom in the SABRE complex doubles the number of LACs and, consequently, the number of peaks in the SABRE field dependence. Interestingly, the polarization of SABRE substrates is always accompanied by the para-to-ortho conversion in dihydride species that results in enhancement of the NMR signal of free (H2) and catalyst-bound H2 (Ir-HH). The field dependences of hyperpolarized H2 and Ir-HH by means of SABRE are studied here, for the first time, in detail. The field dependences depend on the chemical shifts and coupling constants of Ir-HH, in which the polarization transfer takes place. A negative coupling constant of -7Hz between the two chemically equivalent but magnetically inequivalent hydride nuclei is determined, which indicates that Ir-HH is a dihydride with an HH distance larger than 2Å. Finally, the field dependence of SABRE at high fields as found earlier has been investigated and attributed to polarization transfer to the substrate by cross-relaxation. The present study provides further evidence for the key role of LACs in the formation of SABRE-derived polarization. Understanding the spin dynamics behind the SABRE method opens the way to optimizing its performance and overcoming the main limitation of NMR, its notoriously low sensitivity.

  7. First Experimental Study of Photon Polarization in Radiative B_{s}^{0} Decays.

    PubMed

    Aaij, R; Adeva, B; Adinolfi, M; Ajaltouni, Z; Akar, S; Albrecht, J; Alessio, F; Alexander, M; Ali, S; Alkhazov, G; Alvarez Cartelle, P; Alves, A A; Amato, S; Amerio, S; Amhis, Y; An, L; Anderlini, L; Andreassi, G; Andreotti, M; Andrews, J E; Appleby, R B; Archilli, F; d'Argent, P; Arnau Romeu, J; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Baalouch, M; Babuschkin, I; Bachmann, S; Back, J J; Badalov, A; Baesso, C; Baker, S; Baldini, W; Barlow, R J; Barschel, C; Barsuk, S; Barter, W; Baszczyk, M; Batozskaya, V; Batsukh, B; Battista, V; Bay, A; Beaucourt, L; Beddow, J; Bedeschi, F; Bediaga, I; Bel, L J; Bellee, V; Belloli, N; Belous, K; Belyaev, I; Ben-Haim, E; Bencivenni, G; Benson, S; Benton, J; Berezhnoy, A; Bernet, R; Bertolin, A; Betti, F; Bettler, M-O; van Beuzekom, M; Bezshyiko, I; Bifani, S; Billoir, P; Bird, T; Birnkraut, A; Bitadze, A; Bizzeti, A; Blake, T; Blanc, F; Blouw, J; Blusk, S; Bocci, V; Boettcher, T; Bondar, A; Bondar, N; Bonivento, W; Borgheresi, A; Borghi, S; Borisyak, M; Borsato, M; Bossu, F; Boubdir, M; Bowcock, T J V; Bowen, E; Bozzi, C; Braun, S; Britsch, M; Britton, T; Brodzicka, J; Buchanan, E; Burr, C; Bursche, A; Buytaert, J; Cadeddu, S; Calabrese, R; Calvi, M; Calvo Gomez, M; Camboni, A; Campana, P; Campora Perez, D; Campora Perez, D H; Capriotti, L; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carniti, P; Carson, L; Carvalho Akiba, K; Casse, G; Cassina, L; Castillo Garcia, L; Cattaneo, M; Cauet, Ch; Cavallero, G; Cenci, R; Charles, M; Charpentier, Ph; Chatzikonstantinidis, G; Chefdeville, M; Chen, S; Cheung, S-F; Chobanova, V; Chrzaszcz, M; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Coco, V; Cogan, J; Cogneras, E; Cogoni, V; Cojocariu, L; Collazuol, G; Collins, P; Comerma-Montells, A; Contu, A; Cook, A; Coombs, G; Coquereau, S; Corti, G; Corvo, M; Costa Sobral, C M; Couturier, B; Cowan, G A; Craik, D C; Crocombe, A; Cruz Torres, M; Cunliffe, S; Currie, R; D'Ambrosio, C; Da Cunha Marinho, F; Dall'Occo, E; Dalseno, J; David, P N Y; Davis, A; De Aguiar Francisco, O; De Bruyn, K; De Capua, S; De Cian, M; De Miranda, J M; De Paula, L; De Serio, M; De Simone, P; Dean, C-T; Decamp, D; Deckenhoff, M; Del Buono, L; Demmer, M; Derkach, D; Deschamps, O; Dettori, F; Dey, B; Di Canto, A; Dijkstra, H; Dordei, F; Dorigo, M; Dosil Suárez, A; Dovbnya, A; Dreimanis, K; Dufour, L; Dujany, G; Dungs, K; Durante, P; Dzhelyadin, R; Dziurda, A; Dzyuba, A; Déléage, N; Easo, S; Ebert, M; Egede, U; Egorychev, V; Eidelman, S; Eisenhardt, S; Eitschberger, U; Ekelhof, R; Eklund, L; Elsasser, Ch; Ely, S; Esen, S; Evans, H M; Evans, T; Falabella, A; Farley, N; Farry, S; Fay, R; Fazzini, D; Ferguson, D; Fernandez Albor, V; Fernandez Prieto, A; Ferrari, F; Ferreira Rodrigues, F; Ferro-Luzzi, M; Filippov, S; Fini, R A; Fiore, M; Fiorini, M; Firlej, M; Fitzpatrick, C; Fiutowski, T; Fleuret, F; Fohl, K; Fontana, M; Fontanelli, F; Forshaw, D C; Forty, R; Franco Lima, V; Frank, M; Frei, C; Fu, J; Furfaro, E; Färber, C; Gallas Torreira, A; Galli, D; Gallorini, S; Gambetta, S; Gandelman, M; Gandini, P; Gao, Y; Garcia Martin, L M; García Pardiñas, J; Garra Tico, J; Garrido, L; Garsed, P J; Gascon, D; Gaspar, C; Gavardi, L; Gazzoni, G; Gerick, D; Gersabeck, E; Gersabeck, M; Gershon, T; Ghez, Ph; Gianì, S; Gibson, V; Girard, O G; Giubega, L; Gizdov, K; Gligorov, V V; Golubkov, D; Golutvin, A; Gomes, A; Gorelov, I V; Gotti, C; Grabalosa Gándara, M; Graciani Diaz, R; Granado Cardoso, L A; Graugés, E; Graverini, E; Graziani, G; Grecu, A; Griffith, P; Grillo, L; Gruberg Cazon, B R; Grünberg, O; Gushchin, E; Guz, Yu; Gys, T; Göbel, C; Hadavizadeh, T; Hadjivasiliou, C; Haefeli, G; Haen, C; Haines, S C; Hall, S; Hamilton, B; Han, X; Hansmann-Menzemer, S; Harnew, N; Harnew, S T; Harrison, J; Hatch, M; He, J; Head, T; Heister, A; Hennessy, K; Henrard, P; Henry, L; Hernando Morata, J A; van Herwijnen, E; Heß, M; Hicheur, A; Hill, D; Hombach, C; Hopchev, H; Hulsbergen, W; Humair, T; Hushchyn, M; Hussain, N; Hutchcroft, D; Idzik, M; Ilten, P; Jacobsson, R; Jaeger, A; Jalocha, J; Jans, E; Jawahery, A; Jiang, F; John, M; Johnson, D; Jones, C R; Joram, C; Jost, B; Jurik, N; Kandybei, S; Kanso, W; Karacson, M; Kariuki, J M; Karodia, S; Kecke, M; Kelsey, M; Kenyon, I R; Kenzie, M; Ketel, T; Khairullin, E; Khanji, B; Khurewathanakul, C; Kirn, T; Klaver, S; Klimaszewski, K; Koliiev, S; Kolpin, M; Komarov, I; Koopman, R F; Koppenburg, P; Kosmyntseva, A; Kozachuk, A; Kozeiha, M; Kravchuk, L; Kreplin, K; Kreps, M; Krokovny, P; Kruse, F; Krzemien, W; Kucewicz, W; Kucharczyk, M; Kudryavtsev, V; Kuonen, A K; Kurek, K; Kvaratskheliya, T; Lacarrere, D; Lafferty, G; Lai, A; Lambert, D; Lanfranchi, G; Langenbruch, C; Latham, T; Lazzeroni, C; Le Gac, R; van Leerdam, J; Lees, J-P; Leflat, A; Lefrançois, J; Lefèvre, R; Lemaitre, F; Lemos Cid, E; Leroy, O; Lesiak, T; Leverington, B; Li, Y; Likhomanenko, T; Lindner, R; Linn, C; Lionetto, F; Liu, B; Liu, X; Loh, D; Longstaff, I; Lopes, J H; Lucchesi, D; Lucio Martinez, M; Luo, H; Lupato, A; Luppi, E; Lupton, O; Lusiani, A; Lyu, X; Machefert, F; Maciuc, F; Maev, O; Maguire, K; Malde, S; Malinin, A; Maltsev, T; Manca, G; Mancinelli, G; Manning, P; Maratas, J; Marchand, J F; Marconi, U; Marin Benito, C; Marino, P; Marks, J; Martellotti, G; Martin, M; Martinelli, M; Martinez Santos, D; Martinez Vidal, F; Martins Tostes, D; Massacrier, L M; Massafferri, A; Matev, R; Mathad, A; Mathe, Z; Matteuzzi, C; Mauri, A; Maurin, B; Mazurov, A; McCann, M; McCarthy, J; McNab, A; McNulty, R; Meadows, B; Meier, F; Meissner, M; Melnychuk, D; Merk, M; Merli, A; Michielin, E; Milanes, D A; Minard, M-N; Mitzel, D S; Mogini, A; Molina Rodriguez, J; Monroy, I A; Monteil, S; Morandin, M; Morawski, P; Mordà, A; Morello, M J; Moron, J; Morris, A B; Mountain, R; Muheim, F; Mulder, M; Mussini, M; Müller, D; Müller, J; Müller, K; Müller, V; Naik, P; Nakada, T; Nandakumar, R; Nandi, A; Nasteva, I; Needham, M; Neri, N; Neubert, S; Neufeld, N; Neuner, M; Nguyen, A D; Nguyen-Mau, C; Nieswand, S; Niet, R; Nikitin, N; Nikodem, T; Novoselov, A; O'Hanlon, D P; Oblakowska-Mucha, A; Obraztsov, V; Ogilvy, S; Oldeman, R; Onderwater, C J G; Otalora Goicochea, J M; Otto, A; Owen, P; Oyanguren, A; Pais, P R; Palano, A; Palombo, F; Palutan, M; Panman, J; Papanestis, A; Pappagallo, M; Pappalardo, L L; Parker, W; Parkes, C; Passaleva, G; Pastore, A; Patel, G D; Patel, M; Patrignani, C; Pearce, A; Pellegrino, A; Penso, G; Pepe Altarelli, M; Perazzini, S; Perret, P; Pescatore, L; Petridis, K; Petrolini, A; Petrov, A; Petruzzo, M; Picatoste Olloqui, E; Pietrzyk, B; Pikies, M; Pinci, D; Pistone, A; Piucci, A; Playfer, S; Plo Casasus, M; Poikela, T; Polci, F; Poluektov, A; Polyakov, I; Polycarpo, E; Pomery, G J; Popov, A; Popov, D; Popovici, B; Poslavskii, S; Potterat, C; Price, E; Price, J D; Prisciandaro, J; Pritchard, A; Prouve, C; Pugatch, V; Puig Navarro, A; Punzi, G; Qian, W; Quagliani, R; Rachwal, B; Rademacker, J H; Rama, M; Ramos Pernas, M; Rangel, M S; Raniuk, I; Raven, G; Redi, F; Reichert, S; Dos Reis, A C; Remon Alepuz, C; Renaudin, V; Ricciardi, S; Richards, S; Rihl, M; Rinnert, K; Rives Molina, V; Robbe, P; Rodrigues, A B; Rodrigues, E; Rodriguez Lopez, J A; Rodriguez Perez, P; Rogozhnikov, A; Roiser, S; Rollings, A; Romanovskiy, V; Romero Vidal, A; Ronayne, J W; Rotondo, M; Rudolph, M S; Ruf, T; Ruiz Valls, P; Saborido Silva, J J; Sadykhov, E; Sagidova, N; Saitta, B; Salustino Guimaraes, V; Sanchez Mayordomo, C; Sanmartin Sedes, B; Santacesaria, R; Santamarina Rios, C; Santimaria, M; Santovetti, E; Sarti, A; Satriano, C; Satta, A; Saunders, D M; Savrina, D; Schael, S; Schellenberg, M; Schiller, M; Schindler, H; Schlupp, M; Schmelling, M; Schmelzer, T; Schmidt, B; Schneider, O; Schopper, A; Schubert, K; Schubiger, M; Schune, M-H; Schwemmer, R; Sciascia, B; Sciubba, A; Semennikov, A; Sergi, A; Serra, N; Serrano, J; Sestini, L; Seyfert, P; Shapkin, M; Shapoval, I; Shcheglov, Y; Shears, T; Shekhtman, L; Shevchenko, V; Shires, A; Siddi, B G; Silva Coutinho, R; Silva de Oliveira, L; Simi, G; Simone, S; Sirendi, M; Skidmore, N; Skwarnicki, T; Smith, E; Smith, I T; Smith, J; Smith, M; Snoek, H; Sokoloff, M D; Soler, F J P; Souza De Paula, B; Spaan, B; Spradlin, P; Sridharan, S; Stagni, F; Stahl, M; Stahl, S; Stefko, P; Stefkova, S; Steinkamp, O; Stemmle, S; Stenyakin, O; Stevenson, S; Stoica, S; Stone, S; Storaci, B; Stracka, S; Straticiuc, M; Straumann, U; Sun, L; Sutcliffe, W; Swientek, K; Syropoulos, V; Szczekowski, M; Szumlak, T; T'Jampens, S; Tayduganov, A; Tekampe, T; Tellarini, G; Teubert, F; Thomas, E; van Tilburg, J; Tilley, M J; Tisserand, V; Tobin, M; Tolk, S; Tomassetti, L; Tonelli, D; Topp-Joergensen, S; Toriello, F; Tournefier, E; Tourneur, S; Trabelsi, K; Traill, M; Tran, M T; Tresch, M; Trisovic, A; Tsaregorodtsev, A; Tsopelas, P; Tully, A; Tuning, N; Ukleja, A; Ustyuzhanin, A; Uwer, U; Vacca, C; Vagnoni, V; Valassi, A; Valat, S; Valenti, G; Vallier, A; Vazquez Gomez, R; Vazquez Regueiro, P; Vecchi, S; van Veghel, M; Velthuis, J J; Veltri, M; Veneziano, G; Venkateswaran, A; Vernet, M; Vesterinen, M; Viaud, B; Vieira, D; Vieites Diaz, M; Vilasis-Cardona, X; Volkov, V; Vollhardt, A; Voneki, B; Vorobyev, A; Vorobyev, V; Voß, C; de Vries, J A; Vázquez Sierra, C; Waldi, R; Wallace, C; Wallace, R; Walsh, J; Wang, J; Ward, D R; Wark, H M; Watson, N K; Websdale, D; Weiden, A; Whitehead, M; Wicht, J; Wilkinson, G; Wilkinson, M; Williams, M; Williams, M P; Williams, M; Williams, T; Wilson, F F; Wimberley, J; Wishahi, J; Wislicki, W; Witek, M; Wormser, G; Wotton, S A; Wraight, K; Wright, S; Wyllie, K; Xie, Y; Xing, Z; Xu, Z; Yang, Z; Yin, H; Yu, J; Yuan, X; Yushchenko, O; Zarebski, K A; Zavertyaev, M; Zhang, L; Zhang, Y; Zhang, Y; Zhelezov, A; Zheng, Y; Zhokhov, A; Zhu, X; Zhukov, V; Zucchelli, S

    2017-01-13

    The polarization of photons produced in radiative B_{s}^{0} decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3  fb^{-1} at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B_{s}^{0}→ϕγ decay rate is conducted to determine the parameter A^{Δ}, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A^{Δ}=-0.98_{-0.52}^{+0.46}_{-0.20}^{+0.23} is measured. This result is consistent with the standard model prediction within 2 standard deviations.

  8. Vitamin E Circular Dichroism Studies: Insights into Conformational Changes Induced by the Solvent's Polarity.

    PubMed

    Marquardt, Drew; Van Oosten, Brad J; Ghelfi, Mikel; Atkinson, Jeffrey; Harroun, Thad A

    2016-12-14

    We used circular dichroism (CD) to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index-a measure of the solvent's ionizing ability, and a direct measurement of solvent-solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first step in examining the hydrogen bonding abilities of vitamin E in a lipid bilayer.

  9. Structure-Function Study of Tertiary Amines as Switchable Polarity Solvents

    SciTech Connect

    Aaron D. Wilson; Frederick F. Stewart

    2014-02-01

    A series of tertiary amines have been screened for their function as switchable polarity solvents (SPS). The relative ratios of tertiary amine and carbonate species as well as maximum possible concentration were determined through quantitative 1H and 13C NMR spectroscopy. The viscosities of the polar SPS solutions were measured and ranged from near water in dilute systems through to gel formation at high concentrations. The van't Hoff indices for SPS solutions were measured through freezing point depression studies as a proxy for osmotic pressures. A new form of SPS with an amine : carbonate ratio significantly greater than unity has been identified. Tertiary amines that function as SPS at ambient pressures appear to be limited to molecules with fewer than 12 carbons. The N,N-dimethyl-n-alkylamine structure has been identified as important to the function of an SPS.

  10. Polar Diels-Alder reactions using electrophilic nitrobenzothiophenes. A combined experimental and DFT study

    NASA Astrophysics Data System (ADS)

    Della Rosa, Claudia D.; Mancini, Pedro M. E.; Kneeteman, Maria N.; Lopez Baena, Anna F.; Suligoy, Melisa A.; Domingo, Luis R.

    2015-01-01

    The reactions between 2- and 3-nitrobenzothiophenes with three dienes of different nucleophilicity, 1-methoxy-3-trimethylsilyloxy-1,3-butadiene, 1-trimethylsilyloxy-1,3-butadiene and isoprene developed in anhydrous benzene and alternative under microwave irradiation with molecular solvents or in free solvent conditions, respectively, for produce dibenzothiophenes permit to conclude that both nitroheterocycles act as electrophile with the cited dienes. In the cases of the dienes 1-methoxy-3-trimethylsilyloxy-1,3-butadiene and 1-trimethylsilyloxy-1,3-butadiene which posses major nucleophilicity the observed product is the normal cycloaddition one. However when the diene is isoprene the product with both electrophiles follow the hetero Diels-Alder way. These reactions are considered polar cycloaddition reactions and the yields are reasonables. Moreover the polar Diels-Alder reactions of nitrobenzothiophenes with electron rich dienes 1-trimethylsilyloxy-1,3-butadiene have been theoretically studied using DFT methods.

  11. First Experimental Study of Photon Polarization in Radiative Bs0 Decays

    NASA Astrophysics Data System (ADS)

    Aaij, R.; Adeva, B.; Adinolfi, M.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Archilli, F.; d'Argent, P.; Arnau Romeu, J.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Babuschkin, I.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baker, S.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Baszczyk, M.; Batozskaya, V.; Batsukh, B.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Bel, L. J.; Bellee, V.; Belloli, N.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bertolin, A.; Betti, F.; Bettler, M.-O.; van Beuzekom, M.; Bezshyiko, I.; Bifani, S.; Billoir, P.; Bird, T.; Birnkraut, A.; Bitadze, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Boettcher, T.; Bondar, A.; Bondar, N.; Bonivento, W.; Borgheresi, A.; Borghi, S.; Borisyak, M.; Borsato, M.; Bossu, F.; Boubdir, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britsch, M.; Britton, T.; Brodzicka, J.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D.; Campora Perez, D. H.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cavallero, G.; Cenci, R.; Charles, M.; Charpentier, Ph.; Chatzikonstantinidis, G.; Chefdeville, M.; Chen, S.; Cheung, S.-F.; Chobanova, V.; Chrzaszcz, M.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coco, V.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collazuol, G.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombs, G.; Coquereau, S.; Corti, G.; Corvo, M.; Costa Sobral, C. M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Da Cunha Marinho, F.; Dall'Occo, E.; Dalseno, J.; David, P. N. Y.; Davis, A.; De Aguiar Francisco, O.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Serio, M.; De Simone, P.; Dean, C.-T.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Demmer, M.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Dijkstra, H.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Dungs, K.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Déléage, N.; Easo, S.; Ebert, M.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; Elsasser, Ch.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Farley, N.; Farry, S.; Fay, R.; Fazzini, D.; Ferguson, D.; Fernandez Albor, V.; Fernandez Prieto, A.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fini, R. A.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fleuret, F.; Fohl, K.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Franco Lima, V.; Frank, M.; Frei, C.; Fu, J.; Furfaro, E.; Färber, C.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; Garcia Martin, L. M.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Garsed, P. J.; Gascon, D.; Gaspar, C.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianı, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gizdov, K.; Gligorov, V. V.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gorelov, I. V.; Gotti, C.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Griffith, P.; Grillo, L.; Gruberg Cazon, B. R.; Grünberg, O.; Gushchin, E.; Guz, Yu.; Gys, T.; Göbel, C.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hall, S.; Hamilton, B.; Han, X.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; Hatch, M.; He, J.; Head, T.; Heister, A.; Hennessy, K.; Henrard, P.; Henry, L.; Hernando Morata, J. A.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hombach, C.; Hopchev, H.; Hulsbergen, W.; Humair, T.; Hushchyn, M.; Hussain, N.; Hutchcroft, D.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jalocha, J.; Jans, E.; Jawahery, A.; Jiang, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Kanso, W.; Karacson, M.; Kariuki, J. M.; Karodia, S.; Kecke, M.; Kelsey, M.; Kenyon, I. R.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Kirn, T.; Klaver, S.; Klimaszewski, K.; Koliiev, S.; Kolpin, M.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Kosmyntseva, A.; Kozachuk, A.; Kozeiha, M.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Leflat, A.; Lefrançois, J.; Lefèvre, R.; Lemaitre, F.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Likhomanenko, T.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, X.; Loh, D.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Lyu, X.; Machefert, F.; Maciuc, F.; Maev, O.; Maguire, K.; Malde, S.; Malinin, A.; Maltsev, T.; Manca, G.; Mancinelli, G.; Manning, P.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massacrier, L. M.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurin, B.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; Meadows, B.; Meier, F.; Meissner, M.; Melnychuk, D.; Merk, M.; Merli, A.; Michielin, E.; Milanes, D. A.; Minard, M.-N.; Mitzel, D. S.; Mogini, A.; Molina Rodriguez, J.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morawski, P.; Mordà, A.; Morello, M. J.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Mulder, M.; Mussini, M.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, A. D.; Nguyen-Mau, C.; Nieswand, S.; Niet, R.; Nikitin, N.; Nikodem, T.; Novoselov, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Oldeman, R.; Onderwater, C. J. G.; Otalora Goicochea, J. M.; Otto, A.; Owen, P.; Oyanguren, A.; Pais, P. R.; Palano, A.; Palombo, F.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Parker, W.; Parkes, C.; Passaleva, G.; Pastore, A.; Patel, G. D.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petrov, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pikies, M.; Pinci, D.; Pistone, A.; Piucci, A.; Playfer, S.; Plo Casasus, M.; Poikela, T.; Polci, F.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Pomery, G. J.; Popov, A.; Popov, D.; Popovici, B.; Poslavskii, S.; Potterat, C.; Price, E.; Price, J. D.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Quagliani, R.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Raven, G.; Redi, F.; Reichert, S.; dos Reis, A. C.; Remon Alepuz, C.; Renaudin, V.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Rogozhnikov, A.; Roiser, S.; Rollings, A.; Romanovskiy, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Rudolph, M. S.; Ruf, T.; Ruiz Valls, P.; Saborido Silva, J. J.; Sadykhov, E.; Sagidova, N.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schael, S.; Schellenberg, M.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schubert, K.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Sergi, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Shires, A.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Simone, S.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Snoek, H.; Sokoloff, M. D.; Soler, F. J. P.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefko, P.; Stefkova, S.; Steinkamp, O.; Stemmle, S.; Stenyakin, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Sun, L.; Sutcliffe, W.; Swientek, K.; Syropoulos, V.; Szczekowski, M.; Szumlak, T.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Tellarini, G.; Teubert, F.; Thomas, E.; van Tilburg, J.; Tilley, M. J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Toriello, F.; Tournefier, E.; Tourneur, S.; Trabelsi, K.; Traill, M.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tully, A.; Tuning, N.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagnoni, V.; Valassi, A.; Valat, S.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vecchi, S.; van Veghel, M.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Venkateswaran, A.; Vernet, M.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Vilasis-Cardona, X.; Volkov, V.; Vollhardt, A.; Voneki, B.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Vázquez Sierra, C.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wang, J.; Ward, D. R.; Wark, H. M.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wicht, J.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wraight, K.; Wright, S.; Wyllie, K.; Xie, Y.; Xing, Z.; Xu, Z.; Yang, Z.; Yin, H.; Yu, J.; Yuan, X.; Yushchenko, O.; Zarebski, K. A.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhang, Y.; Zhelezov, A.; Zheng, Y.; Zhokhov, A.; Zhu, X.; Zhukov, V.; Zucchelli, S.; LHCb Collaboration

    2017-01-01

    The polarization of photons produced in radiative Bs0 decays is studied for the first time. The data are recorded by the LHCb experiment in p p collisions corresponding to an integrated luminosity of 3 fb-1 at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the Bs0→ϕ γ decay rate is conducted to determine the parameter AΔ, which is related to the ratio of right- over left-handed photon polarization amplitudes in b →s γ transitions. A value of AΔ=-0.98-0.52-0.20+0.46+0.23

  12. Posterior rat eye during acute intraocular pressure elevation studied using polarization sensitive optical coherence tomography

    PubMed Central

    Fialová, Stanislava; Augustin, Marco; Fischak, Corinna; Schmetterer, Leopold; Handschuh, Stephan; Glösmann, Martin; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

    2016-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) operating at 840 nm with axial resolution of 3.8 µm in tissue was used for investigating the posterior rat eye during an acute intraocular pressure (IOP) increase experiment. IOP was elevated in the eyes of anesthetized Sprague Dawley rats by cannulation of the anterior chamber. Three dimensional PS-OCT data sets were acquired at IOP levels between 14 mmHg and 105 mmHg. Maps of scleral birefringence, retinal nerve fiber layer (RNFL) retardation and relative RNFL/retina reflectivity were generated in the peripapillary area and quantitatively analyzed. All investigated parameters showed a substantial correlation with IOP. In the low IOP range of 14-45 mmHg only scleral birefringence showed statistically significant correlation. The polarization changes observed in the PS-OCT imaging study presented in this work suggest that birefringence of the sclera may be a promising IOP-related parameter to investigate. PMID:28101419

  13. Vitamin E Circular Dichroism Studies: Insights into Conformational Changes Induced by the Solvent’s Polarity

    PubMed Central

    Marquardt, Drew; Van Oosten, Brad J.; Ghelfi, Mikel; Atkinson, Jeffrey; Harroun, Thad A.

    2016-01-01

    We used circular dichroism (CD) to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index—a measure of the solvent’s ionizing ability, and a direct measurement of solvent–solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first step in examining the hydrogen bonding abilities of vitamin E in a lipid bilayer. PMID:27983631

  14. An overview of NLC-91: A rocket/radar study of the polar summer mesosphere

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    In late July and early August of 1991, a major suborbital scientific campaign (NLC-91) involving scientists from eight countries was conducted as ESRANGE, Kiruna, Sweden and at Heiss Island, Russia. The purpose of the program was to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. Thirty one rocket flights were coordinated with two coherent radar facilities, EISCAT and CUPRI, and with other ground-based observatories and facilities. This permitted direct comparison between the in situ measurements and those obtained by remote sensing of the mesosphere via continuous ground-based monitoring. The primary objectives of the campaign were to study noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs), including their possible relationship to local aerosols and/or small scale turbulence. This overview describes the scientific program, discusses the geophysical conditions during launch activities, and reviews some of the preliminary results. More detailed results can be found in the papers which follow.

  15. Small-molecule axon-polarization studies enabled by a shear-free microfluidic gradient generator

    PubMed Central

    Xu, Hui; Ferreira, Meghaan M.

    2014-01-01

    A deep understanding of the mechanisms behind neurite polarization and axon path-finding is important for interpreting how the human body guides neurite growth during development and response to injury. Further, it is of great clinical importance to identify diffusible chemical cues that promote neurite regeneration for nervous tissue repair. Despite the fast development of various types of concentration gradient generators, it has been challenging to fabricate neuron friendly (i.e. shear-free and biocompatible for neuron growth and maturation) devices to create stable gradients, particularly for fast diffusing small molecules, which typically require high flow and shear rates. Here we present a finite element analysis for a polydimethylsiloxane/polyethylene glycol diacrylate (PDMS/PEG-DA) based gradient generator, describe the microfabrication process, and validate its use for neuronal axon polarization studies. This device provides a totally shear-free, biocompatible microenvironment with a linear and stable concentration gradient of small molecules such as forskolin. The gradient profile in this device can be customized by changing the composition or width of the PEG-DA barriers during direct UV photo-patterning within a permanently bonded PDMS device. Primary rat cortical neurons (embryonic E18) exposed to soluble forskolin gradients for 72 hr exhibited statistically significant polarization and guidance of their axons. This device provides a useful platform for both chemotaxis and directional guidance studies, particularly for shear sensitive and non-adhesive cell cultures, while allowing fast new device design prototyping at a low cost. PMID:24781157

  16. Modeling study of the impacts of inertial gravity wave forcing in middle atmosphere polar region

    NASA Astrophysics Data System (ADS)

    Tan, B.; Liu, H.; Chu, X.

    2012-12-01

    The 'cold pole' problem refers to the cold bias of polar stratosphere temperature in the Southern Hemisphere in most general circulation models (GCMs) and chemistry climate models (CCMs) during the winter and spring. Accompanying the 'cold pole' is the excessively strong jet in the stratosphere and late vortex breaking. It is a long-standing problem in most models, implying the lack of wave forcing in the southern stratosphere. In current study we investigate the feasibility of using parameterized inertial gravity wave forcing to reduce the cold bias. The NCAR Whole Atmosphere Community Climate Model (WACCM 4.0) is used for this study. A new scheme that parameterizes inertial gravity waves is included in the WACCM. Although the inertial gravity waves are likely to break in the stratosphere and impact the middle atmosphere circulation, they are not well resolved by the model nor properly parameterized. Using the new gravity wave scheme, the simulated wintertime temperature is ~20 K warmer in the southern polar region while the simulated wintertime zonal wind jet is about 10 to 30 m/s slower than the originals. Also, the polar vortex in the Southern Hemisphere breaks earlier and the wind reversal level during spring is lower. All these changes make the WACCM simulations closer to ERA-40, suggesting that additional gravity waves are able to reduce the 'cold pole' bias.

  17. Small-molecule axon-polarization studies enabled by a shear-free microfluidic gradient generator.

    PubMed

    Xu, Hui; Ferreira, Meghaan M; Heilshorn, Sarah C

    2014-06-21

    A deep understanding of the mechanisms behind neurite polarization and axon path-finding is important for interpreting how the human body guides neurite growth during development and response to injury. Further, it is of great clinical importance to identify diffusible chemical cues that promote neurite regeneration for nervous tissue repair. Despite the fast development of various types of concentration gradient generators, it has been challenging to fabricate neuron-friendly (i.e. shear-free and biocompatible for neuron growth and maturation) devices to create stable gradients, particularly for fast diffusing small molecules, which typically require high flow and shear rates. Here we present a finite element analysis for a polydimethylsiloxane/polyethylene glycol diacrylate (PDMS/PEG-DA) based gradient generator, describe the microfabrication process, and validate its use for neuronal axon polarization studies. This device provides a totally shear-free, biocompatible microenvironment with a linear and stable concentration gradient of small molecules such as forskolin. The gradient profile in this device can be customized by changing the composition or width of the PEG-DA barriers during direct UV photo-patterning within a permanently bonded PDMS device. Primary rat cortical neurons (embryonic E18) exposed to soluble forskolin gradients for 72 h exhibited statistically significant polarization and guidance of their axons. This device provides a useful platform for both chemotaxis and directional guidance studies, particularly for shear sensitive and non-adhesive cell cultures, while allowing fast new device design prototyping at a low cost.

  18. Simulation studies of protein folding/unfolding equilibrium under polar and nonpolar confinement.

    PubMed

    Tian, Jianhui; Garcia, Angel E

    2011-09-28

    We study the equilibrium folding/unfolding thermodynamics of a small globular miniprotein, the Trp cage, that is confined to the interior of a 2 nm radius fullerene ball. The interactions of the fullerene surface are changed from nonpolar to polar to mimic the interior of the GroEL/ES chaperonin that assists proteins to fold in vivo. We find that nonpolar confinement stabilizes the folded state of the protein due to the effects of volume reduction that destabilize the unfolded state and also due to interactions with the fullerene surface. For the Trp cage, polar confinement has a net destabilizing effect that results from the stabilizing confinement and the competitive exclusion effect that keeps the protein away from the surface hydration shell and stronger interactions between charged side chains in the protein and the polar surface that compete against the formation of an ion pair that stabilizes the protein folded state. We show that confinement effects due to volume reduction can be overcome by sequence-specific interactions of the protein side chains with the encapsulating surface. This study shows that there is a complex balance among many competing effects that determine the mechanism of GroEL chaperonin in enhancing the folding rate of polypeptide inside its cavity.

  19. The DROPPS Program: A Rocket/Lidar/Radar Study of the Polar Summer Mesosphere

    NASA Technical Reports Server (NTRS)

    Goldberg, Richard A.; Holzworth, R. H.; Schmidlin, F. J.; Voss, H. D.; Tuzzolino, A. J.; Croskey, C. L.; Mitchell, J. D.; vonZhan, U.; Singer, W.

    1999-01-01

    During July of 1999, two sequences of rockets were launched from the Norwegian rocket range in Andoya, Norway. The purpose of these studies was to investigate the properties of the polar summer mesosphere, particularly relating to polar mesospheric summer echoes (PMSE) and their possible relationship to noctilucent clouds (NLC). Each of two sequences was anchored with a DROPPS Black Brant payload, consisting of 20 instruments to measure the electrodynamic and optical structure of the mesosphere and lower thermosphere. These were provided by participants from five American and two European scientific laboratories. The DROPPS (Distribution and Role of Particles in the Polar Summer) payloads were each accompanied by a sequence of meteorological rockets, and by several European payloads designed to study electrodynamics structure of the same region. ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) Lidars, and MF (Medium Frequency) and MST (Mesosphere, Stratosphere, and Troposphere) Radars were used to continuously monitor the mesosphere for NLCs and PMSEs respectively. EISCAT VHF (European Incoherent Scatter Radar Very High Frequency) radar provided similar information about PMSEs downstream from the launch site. Sequence 1 was launched on the night of 5-6 July into a strong PMSE display coupled with a weak NLC at the low end of the PMSE. Sequence 2 was launched on the early morning of 14 July into a strong NLC with no PMSE evident. Here we describe the details of the program along with preliminary results.

  20. Study on the time difference of solar polar field reversal between the north and south hemisphere

    NASA Astrophysics Data System (ADS)

    Shukuya, D.; Kusano, K.

    2013-12-01

    Dynamo is a mechanism whereby the kinetic energy of plasma is converted to the magnetic energy. This mechanism works to generate and maintain the solar and stellar magnetic field. Since the sun is only a star whose magnetic field can be directly observed, the understanding of solar dynamo can provide clues to clarify dynamo mechanisms. On the other hand, because solar activities, which are caused by solar dynamo, can influence the Earth's climate, solar variability is an important issue also to understand long-term evolution of the Earth's climate. It is widely known that the polarity of the solar magnetic fields on the north and south poles periodically reverses at every sunspot maxima. It is also known that the reversal at one pole is followed by that on the other pole. The time difference of magnetic field reversal between the poles was first noted by Babcock (1959) from the very first observation of polar field. Recently, it was confirmed by detailed observations with the HINODE satellite (Shiota et al. 2012). Svalgaard and Kamide (2013) indicated that there is a relationship between the time difference of the polarity reversal and the hemispheric asymmetry of the sunspot activity. However, the mechanisms for the hemispheric asymmetry are still open to be revealed. In this paper, we study the asymmetric feature of the solar dynamo based on the flux transport dynamo model (Chatterjee et al. 2004) to explain the time difference of magnetic polarity reversal between the north and south poles. In order to calculate long-term variations of solar activities, we use the mean field kinematic dynamo model, which is derived from magnetohydrodynamics (MHD) equation through the mean field and other approximations. We carried out the mean field dynamo simulations using the updated SURYA code which was developed originally by Choudhuri and his collaborators (2004). We decomposed the symmetric and asymmetric components of magnetic field, which correspond respectively to the

  1. 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.

  2. Evolution of the Late Cretaceous-Paleogene Cordilleran arc magmatism in NW Mexico: a review from updated geochronological studies.

    NASA Astrophysics Data System (ADS)

    Valencia-Moreno, M.; Iriondo, A.; Perez-Segura, E.; Noguez-Alcantara, B.

    2007-05-01

    During most of the Mesozoic and Cenozoic, the locus of subduction related arc magmatism in northwestern Mexico was relatively mobile, probably due to changes in the mechanical conditions of the Farallon-North America plate convergence. The older Mesozoic events recognized in this region occurred in the Late Triassic and Jurassic, but the associated rocks are poorly preserved. However, a belt of Late Cretaceous through Paleogene magmatic rocks is well exposed along Baja California, Sonora and Sinaloa. Since the late 70's, it was noted that during the Early Cretaceous the igneous activity along this belt remained relatively static in the westernmost part, but migrated eastward in the Late Cretaceous, penetrating more than 1000 km into the continent. The arc magmatism reached western Sonora at about 90 Ma, and then it started to move faster inland, presumably due to flattening of the subducted oceanic slab. Recent U-Pb zircon data revealed unexpected old ages (89-95 Ma) near the eastern edge of Sonora, which are difficult to explain on the basis of the classic tectonic interpretations. A model based on two synchronic sites for magma emplacement may explain the age overlapping observed along the belt; however, a profound re-evaluation a proper geodynamic scenario to support this model is required. Even if restoration of the large Neogene crustal extension is made, particularly for central and northern Sonora, the relatively flat-subduction regime commonly accepted for the Laramide event appears unable to explain the anomalously broad expression of the magmatic belt in northwestern Mexico. An alternative model based on two synchronic sites of magma emplacement, as suggested by the new age data, may better explain the large volume of igneous rocks produced during this time in Sonora and most of Chihuahua. This mechanism may differ southwards in Sinaloa, where the magmatic belt becomes considerably narrower. Moreover, the possible existence of two spatially distinct sites

  3. Characteristic of a triple-cathode vacuum arc plasma source.

    PubMed

    Xiang, W; Li, M; Chen, L

    2012-02-01

    In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.

  4. Study the polarization and depolarization properties of atmospheric aerosol multiple scattering based on the successive order of scattering

    NASA Astrophysics Data System (ADS)

    Hou, Weizhen; Sun, Bin; Li, Zhengqiang; Sun, Xiaobing; Hong, Jin; Qie, Lili; Wang, Han

    2015-10-01

    With the polynomial fitting of source function in each order of scattering calculation and the effective process of aerosol forward scattering peak, a polarized radiative transfer (RT) model based on the improved successive order of scattering (SOS) method has been developed to solve the vector radiative transfer equation. By our RT model, not only the total Stokes parameters [I, Q, U] measured by the satellite (aircraft) and ground-based sensors with linear polarization could be approximately simulated, but also the results of parameters for each scattering order event could conveniently calculated, which are very helpful to study the polarization properties for the atmospheric aerosol multiple scattering. In this study, the synchronous measured aerosol results including aerosol optical depth, complex refractive index and particle size distribution from AERONET under different air conditions, are considered as the input parameters for the successive scattering simulations. With our polarized RT model and the Mie code combined, the Stokes parameters as well as the degree of polarization for each scattering order are simulated and presented; meanwhile, the polarization (depolarization) properties of multiply scattering are preliminary analyzed and compared with different air quality (clear and pollution). Those results could provide a significant support for the further research of polarized aerosol remote sensing and inversion. Polarization properties of aerosol, successive order of scattering, vector radiative transfer equation, polynomial fitting of source function , multiply scattering

  5. Infrared studies of sulfuric acid and its impact on polar and global ozone

    NASA Astrophysics Data System (ADS)

    Iraci, Laura Tracy

    Sulfuric acid aerosols are present throughout the lower stratosphere and play an important role in both polar and global ozone depletion. In the polar regions, stratospheric sulfate aerosols (SSAs) act as nuclei for the growth of polar stratospheric clouds (PSCs). Heterogeneous reactions can occur on these PSCs, leading to chlorine activation and catalytic ozone destruction. This thesis addresses the issue of polar ozone depletion through laboratory studies which examine the nucleation of PSCs on sulfuric acid. In addition, chemistry which occurs directly on sulfate aerosols may impact ozone at midlatitudes, and studies describing one such reaction are presented as well. To study the growth of type I PSCs on sulfuric acid, thin H2SO4 films were exposed to water and nitric acid vapors at stratospheric temperatures. Fourier transform infrared spectroscopy was used to probe the phase of the sulfuric acid and to identify the HNO3/H2O films which condensed. Supercooled liquid sulfuric acid films showed uptake of HNO3 to form ternary solutions, followed by crystallization of nitric acid trihydrate (NAT). When crystalline sulfuric acid tetrahydrate (SAT) films were exposed to nitric acid and water, condensation of a supercooled HNO3/H2O layer was often observed. As predicted by theory, some of the SAT crystal then dissolved, creating a ternary H2SO4/HNO3/H2O solution. From this solution, NAT nearly always crystallized, halting the phase change of sulfuric acid. If a supercooled nitric acid layer did not condense on frozen sulfuric acid, crystalline NAT was not deposited from the gas phase when SNAT/leq41. At significantly higher supersaturations, NAT could be forced to condense on sulfuric acid, regardless of its phase. Calculations of the contact parameter from experimental data indicate that m<0.79 for NAT on SAT, predicting a significant barrier to nucleation of NAT from the gas phase. While PSCs can form only in the cold polar regions of the stratosphere, sulfuric

  6. Hepatocyte Polarity

    PubMed Central

    Treyer, Aleksandr; Müsch, Anne

    2013-01-01

    Hepatocytes, like other epithelia, are situated at the interface between the organism’s exterior and the underlying internal milieu and organize the vectorial exchange of macromolecules between these two spaces. To mediate this function, epithelial cells, including hepatocytes, are polarized with distinct luminal domains that are separated by tight junctions from lateral domains engaged in cell-cell adhesion and from basal domains that interact with the underlying extracellular matrix. Despite these universal principles, hepatocytes distinguish themselves from other nonstriated epithelia by their multipolar organization. Each hepatocyte participates in multiple, narrow lumina, the bile canaliculi, and has multiple basal surfaces that face the endothelial lining. Hepatocytes also differ in the mechanism of luminal protein trafficking from other epithelia studied. They lack polarized protein secretion to the luminal domain and target single-spanning and glycosylphosphatidylinositol-anchored bile canalicular membrane proteins via transcytosis from the basolateral domain. We compare this unique hepatic polarity phenotype with that of the more common columnar epithelial organization and review our current knowledge of the signaling mechanisms and the organization of polarized protein trafficking that govern the establishment and maintenance of hepatic polarity. The serine/threonine kinase LKB1, which is activated by the bile acid taurocholate and, in turn, activates adenosine monophosphate kinase-related kinases including AMPK1/2 and Par1 paralogues has emerged as a key determinant of hepatic polarity. We propose that the absence of a hepatocyte basal lamina and differences in cell-cell adhesion signaling that determine the positioning of tight junctions are two crucial determinants for the distinct hepatic and columnar polarity phenotypes. PMID:23720287

  7. A Science Mission for QSAT Project: Study of FACs in the Polar and Equatorial Regions

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akiko; Ueno, Tamiki; Yumoto, Kiyohumi

    2009-04-01

    Kyushu University, Kyushu Institute of Technology and Fukuoka Institute of Technology are now designing, developing and building a micro-satellite called “QSAT”. The primary objective of QSAT is understanding the mechanism of spacecraft charging, which can be achieved with the onboard magnetometer, high-frequency probe (HP) and Langmuir probe (LP). The magnetometer measures the magnetic field variations caused by field-aligned currents (FACs) in the polar and equatorial regions. Polar FACs are well understood, while equatorial FACs are not. The science goals are as follows: (1) to better understand FACs in the polar region, (2) to compare the FACs observed in orbit with ground-based MAGDAS observations, (3) to investigate spatial distribution of FACs in the equatorial region. FACs play a crucial role in the coupling between solar wind, magnetosphere and ionosphere in terms of energy transfer. Also if we understand the relationship between the space and ground-based FACs data, then we can conduct long-term study on the solar wind-magnetosphere-ionosphere coupling in the future by mainly using data from ground-based magnetometer arrays.

  8. Surface anchoring structure of a liquid crystal monolayer studied via dual polarization interferometry

    NASA Astrophysics Data System (ADS)

    Tan, Osbert; Cross, Graham H.

    2009-02-01

    The self-organization of liquid crystal molecules of 4- n -pentyl- 4' -cyanobiphenyl (5CB) forming an oriented monolayer by condensation from the vapor phase onto a silicon oxynitride surface has been observed using the evanescent wave dual slab waveguide dual polarization mode interferometry (DPI) technique. Two distinct stages to the layer formation are observed: After the formation of a layer of molecules lying prone on the surface, further condensation begins to densify the layer and produces a gradual mutual alignment of the molecules until the fully condensed, fully aligned monolayer is reached. At this limit the full coverage 5CB monolayer on this surface and at a temperature of 25°C , is found to be anchored with an average molecular axis polar angle of 56±1° and with a measured thickness of 16.6±0.5Å . These results are in reasonable agreement with the molecular dimensions provided by molecular models. The apparent precision and accuracy of these results resolves some wide disparity between earlier studies of such systems. Previous difficulties in determining optogeometrical properties of such ultrathin birefringent films using ellipsometry or in the need for complex modeling of the film layer structure using x-ray reflectivity are overcome in this instance. We provide a technique for analyzing the dual polarization data from DPI such that the bulk refractive index values, when known, can be used to determine the orientation and thickness of a layer that is on the nanometer or subnanometer scale.

  9. Polarized-neutron-scattering studies on the chiral magnetism in multiferroic MnWO4

    NASA Astrophysics Data System (ADS)

    Finger, T.; Senff, D.; Schmalzl, K.; Schmidt, W.; Regnault, L. P.; Becker, P.; Bohatý, L.; Braden, M.

    2010-02-01

    Neutron diffraction with spherical polarization analysis is a powerful tool for studying the multiferroic materials where the ferroelectric polarization arises from a complex magnetic structure. Analyzing the off-diagonal terms in the polarization matrix one may directly detect the chiral contributions even in a multidomain arrangement. In MnWO4 one can control the chiral magnetism by varying an electric field at constant temperature. The analysis of multiferroic hysteresis cycles at four equivalent magnetic Bragg peaks fully agrees with a nearly monodomain chiral arrangement controlled by the electric field. A pronounced asymmetry of the hysteresis cycles and memory effects point to strong pinning of the chiral magnetism in MnWO4. We find a second-order harmonic modulation which exhibits both magnetic and structural character and which may be related with the domain pinning. The observed interference between the nuclear and the magnetic modulation is another manifestation of the coupling between the crystal structure and the magnetism in the multiferroic oxides.

  10. Study case - Induced Polarization response from a BTEX contaminated site in Brazil

    NASA Astrophysics Data System (ADS)

    Ustra, A.; Elis, V.; Minozzo, M.

    2011-12-01

    A hydrocarbon contaminated site in Brazil was investigated using DC-resistivity and Induced Polarization (IP) methods. The study area is a chemical industry facility that manufactures paint for automobiles. The industrial process involves the use of many hydrocarbon derivative products, including BTEX (benzene, toluene, ethyl benzene and xylene) and organic chlorides. The area was contaminated by some (not documented) accidental spills of BTEX throughout many years. Monitoring wells revealed concentrations from a few ppm to hundreds ppm of BTEX around the area, as well as other compounds. Two soil samples were collected from an area where some spills where known to have happened. Soil analyses of these samples found the presence of microbes, and therefore biodegradation is believed to be occurring at the site. The objective of this study is to relate the IP response distribution to the presence of contamination and/or microbial activity. The geophysical survey consisted in a rectangular mesh composed of 15 parallel lines with 60 meters of extension, using dipole-dipole array. Lines were spaced by 3 meters. Metallic electrodes were used for current injection, and non-polarizing electrodes (Cu/CuSO4) for potential measurement. Current was injected in cycles of 2 seconds. IP measurements were recorded after 160 milliseconds delay of current shut off, and integration time windows were 120, 220, 420, and 820 milliseconds. All data were concatenated into a single data set and submitted to 3D inversion routine. A conductive zone (resistivity less than 100 ohm.m and chargeability less than 2mV/V) was observed where microbes were found. This feature was interpreted as possibly due to natural biodegradation process, that increases total dissolved salts as a result of mineral weathering by organic acids produced in the degradation process. Normalized chargeability (chargeability divided by resistivity) showed an enhanced polarization zone where microbes were detected. This

  11. Molecular signatures identify a candidate target of balancing selection in an arcD-like gene of Staphylococcus epidermidis.

    PubMed

    Zhang, Liangfen; Thomas, Jonathan C; Didelot, Xavier; Robinson, D Ashley

    2012-08-01

    A comparative population genetics study revealed high levels of nucleotide polymorphism and intermediate-frequency alleles in an arcC gene of Staphylococcus epidermidis, but not in a homologous gene of the more aggressive human pathogen, Staphylococcus aureus. Further investigation showed that the arcC genes used in the multilocus sequence typing schemes of these two species were paralogs. Phylogenetic analyses of arcC-containing loci, including the arginine catabolic mobile element, from both species, suggested that these loci had an eventful history involving gene duplications, rearrangements, deletions, and horizontal transfers. The peak signatures in the polymorphic S. epidermidis locus were traced to an arcD-like gene adjacent to arcC; these signatures consisted of unusually elevated Tajima's D and π/K ratios, which were robust to assumptions about recombination and species divergence time and among the most elevated in the S. epidermidis genome. Amino acid polymorphisms, including one that differed in polarity and hydropathy, were located in the peak signatures and defined two allelic lineages. Recombination events were detected between these allelic lineages and potential donors and recipients of S. epidermidis were identified in each case. By comparison, the orthologous gene of S. aureus showed no unusual signatures. The ArcD-like protein belonged to the unknown ion transporter 3 family and appeared to be unrelated to ArcD from the arginine deiminase pathway. These studies report the first comparative population genetics results for staphylococci and the first statistical evidence for a candidate target of balancing selection in S. epidermidis.

  12. From Back-Arc Drifting to Arc Accretion: the Late Jurassic-Early Cretaceous Evolution of the Guerrero Terrane in Central Mexico (Sierra de Guanajuato)

    NASA Astrophysics Data System (ADS)

    Martini, M.; Solari, L.; Centeno-García, E.; Mori, L.; Camprubi, A.

    2011-12-01

    Three paleogeographic scenarios have been proposed for the Mesozoic volcano-sedimentary successions that compose the Guerrero terrane, western Mexico. In the "type 1" scenario the Guerrero terrane is an exotic Pacific arc accreted to nuclear Mexico by the consumption of a pre-Cretaceous oceanic basin, named Arperos Basin. The "type 2" scenario considers the Guerrero terrane as a fringing multi-arc system, accreted by the closure of relatively small pre-Cretaceous oceanic basins at multiple subduction zones with varying polarities. Alternatively, in the "type 3" scenario the Guerrero terrane is interpreted as a North American west-facing para-autochthonous arc, which drifted into the paleo-Pacific domain by the opening of the Cretaceous back-arc oceanic Arperos Basin, and subsequently accreted back to the Mexican mainland. In order to test these reconstructions and understand the dynamics of the arc accretion, we present here a combined study that includes sandstone provenance, U-Pb geochronology, and structural data from the Arperos Basin in the Sierra de Guanajuato, central Mexico. Our data document that the Arperos Basin developed in a back-arc setting, and evolved from continental to oceanic conditions from the Late Jurassic to the Early Cretaceous. Sandstone provenance analysis shows an asymmetric distribution of the infill sources for the Arperos Basin: continent-recycled sedimentary rocks were deposited along its north-eastern side, whereas magmatic arc-recycled clastic rocks developed at its south-western side. Such an asymmetric distribution closely fits with sedimentological models proposed for present-day continent-influenced back-arc basins. Based on these evidences, we favor a "type 3" scenario for the Guerrero terrane, which is then considered to represent a detached slice of the Mexican leading-edge that drifted in the paleo-Pacific domain during Late Jurassic-lower Early Cretaceous back-arc extension, and subsequently accreted back to the Mexican

  13. Stretched arc discharge in produced water.

    PubMed

    Cho, Y I; Wright, K C; Kim, H S; Cho, D J; Rabinovich, A; Fridman, A

    2015-01-01

    The objective of the present study was to investigate the feasibility of stretching an arc discharge in produced water to increase the volume of produced water treated by plasma. Produced water is the wastewater generated by hydraulic fracturing of shale during the production phase in shale-oil or shale-gas exploration. The electric conductivity of produced water is in the range of 50-200 mS/cm, which provides both a challenge and opportunity for the application of plasmas. Stretching of an arc discharge in produced water was accomplished using a ground electrode and two high-voltage electrodes: one positioned close to the ground electrode and the other positioned farther away from the ground. The benefit of stretching the arc is that the contact between the arc and water is significantly increased, resulting in more efficient plasma treatment in both performance and energy cost.

  14. Arc tracks on nanostructured surfaces after microbreakdowns

    NASA Astrophysics Data System (ADS)

    Sinelnikov, D.; Bulgadaryan, D.; Hwangbo, D.; Kajita, S.; Kolodko, D.; Kurnaev, V.; Ohno, N.

    2016-09-01

    Studying of initial steps of unipolar arc ignition process is important for reduction of probability of arcing between the plasma and the wall in thermonuclear devices. Tungsten nano-fuzz surface formed by helium plasma irradiation at high fluences and temperatures is a perfect material for arc ignition. Snowflake-like craters were detected on the fuzzy surfaces after short micro-breakdowns. Such sort of craters have not been observed before on any other metallic surfaces. These specific traces are formed due to unique properties of the fuzz structure. The nano-fuzz could be easily melted and vaporized by micro-breakdown current, due to its porosity and bad thermal conductivity, and formation of low conducting metallic vapour under the cathode spot causes discharge movement to the nearest place. Thus, even low current arc can easily move and leave traces, which could be easily observed by a secondary electron microscope.

  15. Polarization sensitivity in Collembola: an experimental study of polarotaxis in the water-surface-inhabiting springtail Podura aquatica.

    PubMed

    Egri, Ádám; Farkas, Alexandra; Kriska, György; Horváth, Gábor

    2016-08-15

    The ventral eye of the water-surface-inhabiting springtail Podura aquatica has six ommatidia with horizontal and vertical microvilli and perceives light from the ventral, frontal and frontodorsal regions, whereas the dorsal eye possesses two upward-looking ommatidia with vertical microvilli. The ventral eye may detect water by its polarization sensitivity, even if the insect is resting with its head slightly tipped down on a raised surface. The polarization sensitivity and polarotaxis in springtails (Collembola) have not been investigated. Therefore, we performed behavioural choice experiments to study them in P. aquatica We found that the strength of phototaxis in P. aquatica depends on the polarization characteristics of stimulating light. Horizontally and vertically polarized light were the most and least attractive, respectively, while unpolarized stimulus elicited moderate attraction. We show that horizontally polarized light attracts more springtails than unpolarized, even if the polarized stimulus was 10 times dimmer. Thus, besides phototaxis, P. aquatica also performs polarotaxis with the ability to measure or at least estimate the degree of polarization. Our results indicate that the threshold d* of polarization sensitivity in P. aquatica is between 10.1 and 25.5%.

  16. Interaction of alpha-lactalbumin with dimyristoyl phosphatidylcholine vesicles. II. A fluorescence polarization study.

    PubMed

    Herreman, W; van Tornout, P; van Cauwelaert, F H; Hanssens, I

    1981-01-22

    The interaction of alpha-lactalbumin with dimyristoyl phosphatidylcholine vesicles was studied as a function of temperature, pH and the molar ratio of phospholipid to protein. The method consisted of measuring the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene used as a probe embedded in the vesicles. After incubation of the protein with the phospholipid for 2 h at 23 degrees C, the polarization of the light emitted by this probe shifted to higher values; the shift was greater at acidic pH than at neutral pH. After incubation at 37 degrees C, no shift in polarization was found at pH 7, 6 and 5 while a strong increase occurred at pH 4. Lowering the temperature, after incubation at 37 degrees C, had little effect on the polarization at neutral pH. At pH 5, however, and in the transition range of the phospholipid, the polarization increased greatly. A kinetic study of the interaction carried out around the transition temperature of dimyristoyl phosphatidylcholine as a function of pH shows that the speed of complex formation between alpha-lactalbumin and the lipid increases from neutral to acidic pH. From the present results and in agreement with our earlier calorimetric and fluorescence data (Hanssens, I., Houthuys, C., Herreman, W. and van Cauwelaert, F.H. (1980) Biochim. Biophys, Acta 602, 539--557), it is concluded that at neutral pH the interaction mechanism is probably different from that at acidic pH. At neutral pH and at all temperatures, alpha-lactalbumin is mainly absorbed electrostatically to the outer surface of the vesicle with little or no influence on the transition temperature of the phospholipid. At this pH, only around the transition temperature is penetration possible. At pH 4, however, the protein is able to penetrate the vesicle at all temperatures and to interact hydrophobically with the phospholipid fatty acid chains. As a result of this interaction, the transition temperature is increased by about 4 degrees C. This different

  17. Analysis and study of the distribution of polar and non-polar pesticides in wastewater effluents from modern and conventional treatments.

    PubMed

    Barco-Bonilla, Nieves; Romero-González, Roberto; Plaza-Bolaños, Patricia; Garrido Frenich, Antonia; Martínez Vidal, José Luis

    2010-12-10

    The analysis of a wide range of pesticides in wastewaters (WWs) undergoing different treatments (both modern and conventional) has been studied. The need for optimizing specific extraction methods for each WW effluent based on their physico-chemical characteristics has been considered. A distribution study was performed to establish if the filtration step before extraction is a correct procedure since pesticides can be more prone to be in the aqueous or the solid phase, depending on their hydrophobicity. This evaluation demonstrated that pesticides are distributed between the aqueous phase and the suspended particulate matter (SPM; e.g. pyrethroids are only found in the SPM). The proposed methodologies involved the determination of 39 polar and 139 non-polar pesticides using solid-phase extraction (SPE) and pressurized-liquid extraction (PLE) for the extraction of the aqueous phase and the SPM, respectively. Ultra high pressure liquid chromatography and gas chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS, GC-MS/MS) were used in the determination stage. WW samples from four different technologies were evaluated: membrane bioreactor, extended aeration, maturation pond and anaerobic pond. Validation data for the four effluents studied were generated, obtaining adequate precision values (estimated as % relative standard deviation, RSD) in almost all cases (<25%). The methods showed limits of detection at 0.01-0.20μgL(-1) and limits of quantification from 0.02 to 0.50μgL(-1). The proposed methods were applied to the analysis of real samples collected from an experimental WW treatment plant, detecting non-polar and polar pesticides at concentrations in the range 0.02-1.94μgL(-1) and 0.02-0.33μgL(-1), respectively.

  18. Consolidating NASA's Arc Jets

    NASA Technical Reports Server (NTRS)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  19. Multi-proxies study on the paleoceanography and terrigenous input in the polar Nodic Sea since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Liu, Yanguang

    2016-04-01

    The polar Nodic Sea (NS) lies between the Arctic and Antlantic Oceans and the poleward-directed Atlantic heat and water transfer system plays a key role in affecting the ocean changes and sediments input. A suite of well-proven proxy methods for sediment core ARC5-BB03 (72°26.606'N, 7°35.890'E, water depth 2598 m) are used to address issues that are critical to the understanding of paleoceanographic conditions and sediments supplies over the Last Glacial Maximum (LGM) in this region. The methods include grain size analysis, AMS14C dating, color reflectance, high-resolution XRF scanning, oxygen isotope of planktic foraminifera and organic geochemistry measuring. The principal component analysis of the XRF data is applied for identification of sedimentary sources. Variations of grain size and elements' content indicate that the sedimentary sources of the polar NS have undergone dramatic changes over the past 26 ka BP. Changes of terrigenous input in the polar NS show close relationship with the variations of the North Atlantic Current (NAC), the melting of sea ice and ice sheet, the establishment of the Thermohaline Circulation (TC) and the forming of the North Atlantic Deep Water. The coarse grain size sediments before 21.5 ka BP implies different source from those in the later period because the terrigenous input is dominant in this period and occupied by an orderly layer of expandable minerals (OLEM). Strengthened sea ice extension is deemed to the main reason for the high terrigenous input in the polar NS before 21.5 ka BP. Between 21.5~16.5 cal. ka BP, biogenic materials increase accompanied with the decrease of terrigenous contribution indicates the impact of northward intrusion of NAC and the strenghthen of water ventilaiton in polar NS. The decrease of biogenic substance and the increase of terrigenous input during 16.5~10 cal. ka BP is consistent with the fluctuation in the melting of ice sheet and intensity of NAC during the last deglaciation. Compare

  20. Slab Roll-Back and Trench Retreat As Controlling Factor for Island-Arc Related Basin Evolution: A Case Study from Southern Central America

    NASA Astrophysics Data System (ADS)

    Brandes, C.; Winsemann, J.

    2014-12-01

    Slab roll-back and trench retreat are important factors for basin subsidence, magma generation and volcanism in arc-trench systems. From the sedimentary and tectonic record of the Central American island-arc it is evident that repeated slab roll-back and trench retreats occurred since the Late Cretaceous. These trench retreats were most probably related to the subduction of oceanic plateaus and seamounts. Evidence for trench retreats is given by pulses of uplift in the outer-arc area, followed by subsidence in both the fore-arc and back-arc basins. The first slab roll-back probably occurred during the Early Paleocene indicated by the collapse of carbonate platforms, and the re-deposition of large carbonate blocks into deep-water turbidites. At this time the island-arc was transformed from an incipient non-extensional stage into an extensional stage. A new pulse of uplift or decreased subsidence, respectively during the Late Eocene is attributed to subduction of rough crust, a subsequent slab detachment and the establishment of a new subduction zone further westward. Strong uplift especially affected the outer arc of the North Costa Rican arc segment. In the Sandino Fore-arc basin very coarse-grained deep-water channel-levee complexes were deposited. These deposits contain large well-rounded andesitic boulders and are rich in reworked shallow-water carbonates pointing to uplift of the inner fore-arc. Evidence for the subsequent trench retreat is given by an increased subsidence during the early Oligocene in the Sandino Fore-arc Basin and the collapse of the Barra Honda platform in North Costa Rica. Another trench retreat might have occurred in Miocene times. A phase of higher subsidence from 18 to 13 Ma is documented in the geohistory curve of the North Limon Back-arc Basin. After a short pulse of uplift the subsidence increased to approx. 300 m/myr.

  1. Typical Motion and Extinction Characteristics of the Secondary Arcs Associated with Half-Wavelength Transmission Lines

    NASA Astrophysics Data System (ADS)

    Cong, Haoxi; Li, Qingmin; Xing, Jinyuan; Li, Jinsong

    2014-09-01

    Secondary arc discharge is a complicated physical phenomenon and one of the key fundamental issues associated with ultra high voltage (UHV) half-wavelength transmission lines (HWTL). With the establishment of a physical simulation platform for the HWTLs, experiments were carried out regarding the motion and extinction characteristics of secondary arcs. The cathode arc root and the anode arc root were found to show an obvious polarity effect while the arc column was moving in a spiral, due to their different motion mechanisms. The extinction behavior was also recorded and experiments were designed with different compensation conditions. Results show that the arcing time can be greatly reduced if there exists an electrical compensation network. The research provides fundamentals for understanding the physics involved, especially the motion and extinction mechanisms of the secondary arcs.

  2. Control of arc length during gas metal arc welding

    SciTech Connect

    Madigan, R.B.; Quinn, T.P.

    1994-12-31

    An arc-length control system has been developed for gas metal arc welding (GMAW) under spray transfer welding conditions. The ability to monitor and control arc length during arc welding allows consistent weld characteristics to be maintained and therefore improves weld quality. Arc length control has only been implemented for gas tungsten arc welding (GTAW), where an automatic voltage control (AVC) unit adjusts torch-to-work distance. The system developed here compliments the voltage- and current-sensing techniques commonly used for control of GMAW. The system consists of an arc light intensity sensor (photodiode), a Hall-effect current sensor, a personal computer and software implementing a data interpretation and control algorithms. Arc length was measured using both arc light and arc current signals. Welding current was adjusted to maintain constant arc length. A proportional-integral-derivative (PID) controller was used. Gains were automatically selected based on the desired welding conditions. In performance evaluation welds, arc length varied from 2.5 to 6.5 mm while welding up a sloped workpiece (ramp in CTWD) without the control. Arc length was maintained within 1 mm of the desired (5 mm ) with the control.

  3. The geochemistry and petrogenesis of the Paleoproterozoic Green Mountain arc: A composite(?), bimodal, oceanic, fringing arc

    USGS Publications Warehouse

    Jones, D.S.; Barnes, C.G.; Premo, W.R.; Snoke, A.W.

    2011-01-01

    The inferred subduction affinity of the ~1780-Ma Green Mountain arc, a dominantly bimodal igneous terrane (together with immature marine and volcaniclastic sedimentary rocks) accreted to the southern margin of the Wyoming province, is integral to arc-accretion models of the Paleoproterozoic growth of southern Laurentia. Conversely, the dominantly bimodal nature of many putative arc-related igneous suites throughout southern Laurentia, including the Green Mountain arc, has also been used to support models of growth by extension of pre-existing crust. We report new geochemical and isotopic data from ~1780-Ma gabbroic and granodioritic to tonalitic rocks of the Big Creek Gneiss, interpreted as consanguineous with previously studied metavolcanic rocks of the Green Mountain Formation.The ~1780-Ma Big Creek Gneiss mafic rocks show clear geochemical signatures of a subduction origin and provide no supporting evidence for extensional tectonism. The ~1780-Ma Big Creek Gneiss felsic rocks are attributed to partial melting of mafic and/or mixed lower-crustal material. The bimodal nature of the suite results from the combination of arc basalts and felsic crustal melts. The lack of andesite is consistent with the observed tholeiitic differentiation trend of the mafic magmas. The lower e{open}Nd(1780Ma) values for the felsic rocks vs. the mafic rocks suggest that the unexposed lower crust of the arc may be older than the arc and that Trans-Hudson- or Penokean-aged rocks possibly form the substratum of the arc. Our results reinforce previous interpretations that arc-related magmatism played a key role in the Paleoproterozoic crustal growth of southern Laurentia, but also support the possibility of unexposed older crust as basement to the arcs. ?? 2011 Elsevier B.V.

  4. Progressive-arc- vs. strike-slip-related rotations in curved orogenic belts: a case study from the Northern Apennines (Italy).

    NASA Astrophysics Data System (ADS)

    Turtù, Antonio; Satolli, Sara; Maniscalco, Rosanna; Calamita, Fernando; Speranza, Fabio

    2013-04-01

    A detailed paleomagnetic study has been performed in the southern sector of the Olevano-Antrodoco-Sibillini (OAS) thrust front (i. e. the southern limb of the Northern Apennines, Italy). The oroclinal/progressive-arc vs. non rotational nature of the OAS thrust is still a matter of debate, as it has been interpreted in the literature as dextral strike-slip fault, dextral transpressive fault, or as a frontal to oblique ramp complex. We document the paleomagnetism of 52 sites from Jurassic to Eocene pelagic limestones and Messinian siliciclastic turbidites from both the OAS hanging wall and footwall. In the hanging wall, sampling was designed to follow two transects perpendicular to two thrust segments oriented roughly NE-SW and NNW-SSE. Paleomagnetic data have been integrated with biostratigraphical and structural data, in order to understand both the rotational nature of the OAS arc and the kinematics of the thrust front. All samples were paleomagnetically investigated by a 2G DC-SQUID cryogenic magnetometer at the INGV of Rome. Thermal cleaning was used throughout. A characteristic component of magnetization was successfully isolated in 39 (over 52) sites. The tilt-corrected directions were compared to the coeval directions expected for the Adriatic-African foreland, in order to calculate rotations due to Apennine orogenesis. On the basis of cluster analysis and tectonic constrains, we document a peculiar pattern of tectonic rotations along the OAS thrust with four rotational domains: 1. a strongly rotated clockwise (CW) domain (54.78° ±5.46° ) in the hanging wall, close to the NE-SW-trending segment of the thrust; 2. a less CW-rotated domain in the hanging wall (15.1° ±5.8° ) that includes both the NNW-SSE oriented thrust segment and sites far from the thrust; 3. a uniform counterclockwise (CCW) rotation (-30.79° ±4.73° ) in the footwall; 4. an approximately null rotation (-5.2° ±3.8° ) in the external footwall. The strong CW domain in the hanging wall

  5. Characteristics of trough region auroral patches and detached arcs observed by Isis 2

    NASA Technical Reports Server (NTRS)

    Moshupi, M. C.; Anger, C. D.; Murphree, J. S.; Wallis, D. D.; Whitteker, J. H.; Brace, L. H.

    1979-01-01

    All of the data presented in this paper were obtained from the Isis 2 satellite, which was launched into a 1400-km near-circular polar orbit in April 1971. Instruments used in this study include the topside sounder for providing vertical profiles of the electron density, the Langmuir probe for measuring electron temperature and concentration, and the auroral scanning photometer for detecting optical emissions at 5577 A and 3914 A. Two distinct types of auroras (east-west-aligned oval-shaped 'patches', and isolated east-west 'detached arcs') are observed in the trough region (almost exclusively in the Northern Hemisphere) equatorward of the diffuse auroral boundary. Attention is given to comparison of patches and detached arcs, relation to magnetic indices, and relation to detached plasma and ELF hiss.

  6. Time evolution of a rifted continental arc: Integrated ID-TIMS and LA-ICPMS study of magmatic zircons from the Eastern Srednogorie, Bulgaria

    NASA Astrophysics Data System (ADS)

    Georgiev, S.; von Quadt, A.; Heinrich, C. A.; Peytcheva, I.; Marchev, P.

    2012-12-01

    Ca) parental melts, produced from partial remelting of amphibole clinopyroxenites upon interaction with subduction-modified mantle wedge melts, according to earlier petrological studies. This peak of dominantly extrusive activity in the Yambol-Burgas region extended into the Strandzha region further south, in the form of numerous tholeiitic, calc-alkaline and high-K intrusions emplaced in the same time period between 81 and 78 Ma. Granitic rocks from exposed basement of Eastern Srednogorie zone are dated as Permian/Carboniferous (~ 275-300 Ma). Zircons with similar ages occur in Upper Cretaceous rocks from the East Balkan and Strandzha regions, indicating local incorporation as xenocrysts. In contrast, magmatic rocks from the intermediate Yambol-Burgas region contain mostly Ordovician (~ 460 Ma) or older inherited zircons, suggesting a either a different basement history or, more likely, a different level of magma storage and crustal assimilation. Integrating these geochronological results with a synthesis of the regional geology, we propose a two-stage geodynamic evolution for the Eastern Srednogorie segment of the Tethyan arc. The earlier stage of normal arc magmatism was driven by a southward slab retreat, which formed the ~ 92 Ma calc-alkaline to high-K shallow intrusions and volcanics in the north (East Balkan), 87-86 Ma old tholeiitic and calc-alkaline intrusions in the south (Strandzha), and the voluminous 81-78 Ma old gabbroic to granitic intrusions with predominantly calc-alkaline to high-K composition throughout the Strandzha region. This stage continued westward into the Central Srednogorie zone, where the southward younging of calc-alkaline magmatism correlates well with an increased input of primitive mantle melts, indicating asthenospheric incursion into a widening mantle wedge as a result of slab roll-back. The second stage proceeded in the Eastern Srednogorie zone only, where more extreme extension associated with the opening of the Black Sea back-arc

  7. Pulsed Long Arc Welding

    NASA Astrophysics Data System (ADS)

    Krampit, N. Yu

    2016-04-01

    The paper presents a method and an appliance for pulsed arc welding. The method supports dosage of energy required for melting each bead of electrode metal starting from the detachment of a bead. The appliance including a sensor to register bead detachment shows this moment due to the voltage burst in the arc space. Transferred beads of electrode metal are of similar size because of the dosage of energy used for melting each bead, as the consequence, the process is more stable and starting conditions to transfer electrode metal are similar, as the result, a produced weld is improved.

  8. Study of polarization properties of fiber-optics probes with use of a binary phase plate.

    PubMed

    Alferov, S V; Khonina, S N; Karpeev, S V

    2014-04-01

    We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

  9. EDITORIAL Metal vapour in atmospheric-pressure arcs Metal vapour in atmospheric-pressure arcs

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2010-11-01

    low-voltage circuit breakers, metal vapour is formed by evaporation of the electrodes (runners) and the splitter plates, and can have a major influence on the dynamics of arc motion. While the influence of metal vapour on arcs is now understood in general terms, there are many unresolved questions. Areas in which improvements and new insights are required include: diagnostic techniques for measurements of arc properties in the presence of metal vapour, and understanding of the possible deviations from local thermodynamic equilibrium and their influence on such measurements; measurements of the influence of metal vapour in circuit breakers, in which the arc occurs within a solid enclosure, and in gas-metal arc welding, in which the formation of metal droplets and arc instabilities can disrupt standard techniques; determination of the concentration of metal vapour species in different types of arcs; understanding of the relative importance of the different effects of metal vapour (such as increased radiation and electrical conductivity, and the rapid influx of relatively cold gas) on the arc for different configurations; the influence of metal vapour on the electrode boundary and sheath regions; the treatment of radiative and mass transport in computational models; understanding and treatment of the vaporization, condensation and nucleation of metal species, and methods of incorporation of these processes in computational models. In this cluster issue, many of these and related issues are addressed. The twelve contributions cover gas-metal arc welding, gas-tungsten arc welding and low-voltage circuit breakers, and include both experimental and computational studies, in some cases with striking results. A review of the influence of metal vapour in welding arcs is followed by three accounts of spectroscopic measurements of gas-metal arc welding, which are difficult to perform and until recently have rarely been attempted. The application of spectroscopic techniques to

  10. High Temperature Corrosion studies on Pulsed Current Gas Tungsten Arc Welded Alloy C-276 in Molten Salt Environment

    NASA Astrophysics Data System (ADS)

    Manikandan, M.; Arivarasu, M.; Arivazhagan, N.; Puneeth, T.; Sivakumar, N.; Murugan, B. Arul; Sathishkumar, M.; Sivalingam, S.

    2016-09-01

    Alloy C-276 is widely used in the power plant environment due to high strength and corrosion in highly aggressive environment. The investigation on high- temperature corrosion resistance of the alloy C-276 PCGTA weldment is necessary for prolonged service lifetime of the components used in corrosive environments. Investigation has been carried out on Pulsed Current Gas Tungsten Arc Welding by autogenous and different filler wires (ERNiCrMo-3 and ERNiCrMo-4) under molten state of K2SO4-60% NaCl environment at 675oC under cyclic condition. Thermogravimetric technique was used to establish the kinetics of corrosion. Weight gained in the molten salt reveals a steady-state parabolic rate law while the kinetics with salt deposits displays multi-stage growth rates. PCGTA ERNiCrMo-3 shows the higher parabolic constant compared to others. The scale formed on the weldment samples upon hot corrosion was characterized by using X-ray diffraction, SEM and EDAX analysis to understand the degradation mechanisms. From the results of the experiment the major phases are identified as Cr2O3, Fe2O3, and NiCr2O4. The result showed that weld fabricated by ERNiCrMo-3 found to be more prone to degradation than base metal and ERNiCrMo-4 filler wire due to higher segregation of alloying element of Mo and W in the weldment

  11. Electrode polarization studies in hot corrosion systems. Progress report, 1 June 1979-31 April 1980

    SciTech Connect

    Devereux, O.F.

    1980-02-01

    Work on the following discrete tasks is reported: Electrode Polarization Studies in Molten Sodium Carbonate: A comprehensive set of tests has been performed on iron, nickel, and types 304 and 316 stainless steel in gas mixtures of controlled CO, CO/sub 2/, H/sub 2/, and H/sub 2/S pressures at a total pressure of one atmosphere and in a temperature range of 900 to 1000/sup 0/C. The polarization curves thus derived have been reduced to a set of empirical kinetic constants via computer modelling. Gas/Metal Reactions in Mixed Oxidants: Oxidation of iron in gas mixtures of controlled P/sub CO/, P/sub CO//sub 2/, P/sub H//sub 2/ and P/sub H//sub 2//sub S/ at a total pressure of one atmosphere and a temperature of 900/sup 0/C has been studied. In the P/sub S//sub 2/ and P/sub O//sub 2/ ranges employed sulfide scales were formed; P/sub O//sub 2/ influenced the short term sulfidation kinetics. Specimen geometry was seen as a significant factor influencing long term kinetics. Liquid Line Corrosion: A reproducible corrosive attack is seen at the metal/molten carbonate/gas phase junction. This attack can be quantitatively evaluated and explained in terms of a diffusion model. Evaluation of Reaction Kinetics from Polarization Data (addendum): previous modelling procedures have been expanded to include one or more anodic reactions displaying passive behavior.

  12. Efficient cross-polarization using a composite 0 degrees pulse for NMR studies on static solids.

    PubMed

    Fukuchi, Masashi; Ramamoorthy, Ayyalusamy; Takegoshi, K

    2009-02-01

    In most solid-state NMR experiments, cross-polarization is an essential step to detect low-gamma nuclei such as (13)C and (15)N. In this study, we present a new cross-polarization scheme using spin-locks composed of composite 0 degrees pulses in the RF channels of high-gamma and low-gamma nuclei to establish the Hartmann-Hahn match. The composite 0 degrees pulses with no net nutation-angle{(2pi)(X)-(2pi)(-X)-(2pi)(Y)-(2pi)(-Y) -}(n) applied simultaneously to both high-gamma (I) and low-gamma (S) nuclei create an effective heteronuclear dipolar Hamiltonian H(d)((0))=d/2(2I(Z)S(Z)+I(X)S(X)+I(Y)S(Y)), which is capable of transferring the Z-component of the I spin magnetization to the Z-component of the S spin magnetization. It also retains a homonuclear dipolar coupling Hamiltonian that enables the flip-flop transfer among abundant spins. While our experimental results indicate that the new pulse sequence, called composite zero cross-polarization (COMPOZER-CP) performs well on adamantane, it is expected to be more valuable to study semi-solids like liquid crystalline materials and model lipid membranes. Theoretical analysis of COMPOZER-CP is presented along with experimental results. Our experimental results demonstrate that COMPOZER-CP overcomes the RF field inhomogeneity and Hartmann-Hahn mismatch for static solids. Experimental results comparing the performance of COMPOZER-CP with that of the traditional constant-amplitude CP and rampCP sequences are also presented in this paper.

  13. Spin polarized tunneling study on spin hall metals and topological insulators (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Liu, Luqiao

    2016-10-01

    Spin orbit interactions give rise to interesting physics phenomena in solid state materials such as the spin Hall effect (SHE) and topological insulator surface states. Those effects have been extensively studied using various electrical detection methods. However, to date most experiments focus only on characterizing electrons near the Fermi surface, while spin-orbit interaction is expected to be energy dependent. Here we developed a tunneling spectroscopy technique to measure spin Hall materials and topological insulators under finite bias voltages. By electrically injecting spin polarized electrons into spin Hall metals or topological insulators using tunnel junctions and measuring the induced transverse voltage, we are able to study SHE in typical 5d transition metals and the spin momentum locking in topological insulators. For spin Hall effect metals, the magnitude of the spin Hall angle has been a highly controversial topic in previous studies. Results obtained from various techniques can differ by more than an order of magnitude. Our results from this transport measurement turned out to be consistent with the values obtained from spin Hall torque measurements, which can help to address the long debating issue. Besides the magnitude, the voltage dependent spectra from our experiment also provide useful information in distinguishing between different potential mechanisms. Finally, because of the impedance matching capability of tunnel junctions, the spin polarized tunneling technique can also be used as a powerful tool to measure resistive materials such as the topological insulators. Orders of magnitude improvement in the effective spin Hall angle was demonstrated through our measurement

  14. ARc Welding (Industrial Processing Series).

    DTIC Science & Technology

    ARC WELDING , *BIBLIOGRAPHIES), (*ARC WELDS, BIBLIOGRAPHIES), ALUMINUM ALLOYS, TITANIUM ALLOYS, CHROMIUM ALLOYS, METAL PLATES, SPOT WELDING , STEEL...INERT GAS WELDING , MARAGING STEELS, MICROSTRUCTURE, HEAT RESISTANT ALLOYS, HEAT RESISTANT METALS, WELDABILITY, MECHANICAL PROPERTIES, MOLYBDENUM ALLOYS, NICKEL ALLOYS, RESISTANCE WELDING

  15. Thermal Arc Spray Overview

    NASA Astrophysics Data System (ADS)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  16. Gas tungsten arc welder

    DOEpatents

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  17. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  18. The Polar Regions and Martian Climate: Studies with a Global Climate Model

    NASA Technical Reports Server (NTRS)

    Wilson, R. J.; Richardson, M. I.; Smith, M. D.

    2003-01-01

    Much of the interest in the polar regions centers on the fact that they likely contain the best record of Martian climate change on time scales from years to eons. This expectation is based upon the observed occurrence of weathering product deposits and volatile reservoirs that are coupled to the climate. Interpretation and understanding of these records requires understanding of the mechanisms that involve the exchange of dust, water, and carbon dioxide between the surface and atmosphere, and the atmospheric redistribution of these species. We will summarize our use of the GFDL Mars general circulation model (MGCM), to exploration aspects of the interaction between the global climate and the polar regions. For example, our studies have shown that while the northern polar cap is the dominant seasonal source for water, it can act as a net annual source or sink for water, depending upon the cap temperatures and the bulk humidity of the atmosphere. This behavior regulates the annual and global average humidity of the atmosphere, as the cap acts as a sink if the atmosphere is too wet and a source if it is too dry. We will then focus our presentation on the ability of the MGCM to simulate the observed diurnal variations of surface temperature. We are particularly interested in assessing the influence of dust aerosol and water ice clouds on simulated surface temperature and the comparison with observations. Surface thermal inertia and albedo are critical boundary inputs for MGCM simulations. Thermal inertia is also of intrinsic interest as it may be related to properties of the surface such as particle size and surface character.

  19. Design, testing, and clinical studies of a handheld polarized light camera.

    PubMed

    Ramella-Roman, Jessica C; Lee, Ken; Prahl, Scott A; Jacques, Steven L

    2004-01-01

    Polarized light imaging has been used to detect the borders of skin cancer and facilitate assessment of cancer boundaries. A design for an inexpensive handheld polarized camera is presented and clinical images acquired with this prototype are shown. The camera is built with two universal serial bus (USB) color video cameras, a polarizing beamsplitter cube, and a 4x objective lens. Illumination is provided by three white LEDs and a sheet polarizer. Horizontal and vertical linearly polarized reflected images are processed at 7 frames/s and a resulting polarized image is displayed on screen. We compare the performances of cheap USB camera and a 16-bit electronically cooled camera. Dark noise and image repeatability are compared. In both cases, the 16-bit camera outperforms the USB cameras. Despite these limitations, the results obtained with this USB prototype are very satisfactory. Examples of polarized images of lesions taken prior to surgery are presented.

  20. Theoretical and experimental studies of polarization fluctuations over atmospheric turbulent channels for wireless optical communication systems.

    PubMed

    Zhang, Jiankun; Ding, Shengli; Zhai, Huili; Dang, Anhong

    2014-12-29

    In wireless optical communications (WOC), polarization multiplexing systems and coherent polarization systems have excellent performance and wide applications, while its state of polarization affected by atmospheric turbulence is not clearly understood. This paper focuses on the polarization fluctuations caused by atmospheric turbulence in a WOC link. Firstly, the relationship between the polarization fluctuations and the index of refraction structure parameter is introduced and the distribution of received polarization angle is obtained through theoretical derivations. Then, turbulent conditions are adjusted and measured elaborately in a wide range of scintillation indexes (SI). As a result, the root-mean-square (RMS) variation and probability distribution function (PDF) of polarization angle conforms closely to that of theoretical model.

  1. Mechanics of back arc deformation in Costa Rica: Evidence from an aftershock study of the April 22, 1991, Valle de la Estrella, Costa Rica, earthquake (Mw =7.7)

    NASA Astrophysics Data System (ADS)

    Protti, Marino; Schwartz, Susan Y.

    1994-10-01

    The April 22, 1991, Mw=7.7 Valle de la Estrella, Costa Rica, earthquake represents back arc thrusting of the Caribbean plate beneath the Panama block along the North Panama Thrust Belt. Large back arc thrusting events are quite rare, occurring in only two other locations along the Sunda Arc and Japan Sea. To better understand the mechanics of back arc thrusting, we constrain the faulting geometry associated with the 1991 Costa Rica earthquake using aftershock locations and focal mechanisms obtained from a three-component portable digital network deployed in and around the aftershock area following the mainshock. The spatial distribution of aftershocks reveals a complicated faulting geometry in the rupture area. Focal mechanisms determined from inversion of P wave and tangentially and radially polarized S wave (SH and SV, respectively) amplitudes recorded by this temporary network confirm fault complexity and indicate active thrust, normal and strike-slip faults in the back arc of Costa Rica. Most of the thrust events are confined to the southern portion of the aftershock zone in the vicinity of the mainshock. Their distribution suggests the existence of a near-horizontal basal fault plane at a depth of about 15 km, with many imbricate faults having steeper dips extending from the basal plane toward the surface. Events with strike-slip mechanisms locate northwest of the thrust events and define a SW-NE trending, left-lateral strike-slip fault zone that represents the NW termination of the mainshock rupture and possibly the maximum NW extension of the Panama block. The superposition of the aftershock locations on a geologic map of the region shows that aftershocks are restricted to occur in the older, more competent rock units (volcanic and volcaniclastic rocks interbedded with carbonates) of the back arc sedimentary basin. Shallow events (depth<5 km) occur only where these oldest units are exposed at the surface. This suggests that (1) exposure of the lower units

  2. Polarized cells, polar actions.

    PubMed

    Maddock, J R; Alley, M R; Shapiro, L

    1993-11-01

    The recognition of polar bacterial organization is just emerging. The examples of polar localization given here are from a variety of bacterial species and concern a disparate array of cellular functions. A number of well-characterized instances of polar localization of bacterial proteins, including the chemoreceptor complex in both C. crescentus and E. coli, the maltose-binding protein in E. coli, the B. japonicum surface attachment proteins, and the actin tail of L. monocytogenes within a mammalian cell, involve proteins or protein complexes that facilitate bacterial interaction with the environment, either the extracellular milieux or that within a plant or mammalian host. The significance of this observation remains unclear. Polarity in bacteria poses many problems, including the necessity for a mechanism for asymmetrically distributing proteins as well as a mechanism by which polar localization is maintained. Large structures, such as a flagellum, are anchored at the pole by means of the basal body that traverses the peptidoglycan wall. But for proteins and small complexes, whether in the periplasm or the membrane, one must invoke a mechanism that prevents the diffusion of these proteins away from the cell pole. Perhaps the periplasmic proteins are retained at the pole by the presence of the periseptal annulus (35). The constraining features for membrane components are not known. For large aggregates, such as the clusters of MCP, CheA, and CheW complexes, perhaps the size of the aggregate alone prevents displacement. In most cases of cellular asymmetry, bacteria are able to discriminate between the new pole and the old pole and to utilize this information for localization specificity. The maturation of new pole to old pole appears to be a common theme as well. Given numerous examples reported thus far, we propose that bacterial polarity displays specific rules and is a more general phenomenon than has been previously recognized.

  3. A Study on the Application of Submerged Arc Welding for Thin Plate of A-Grade 3.2 Thickness Steel in Ship Structure

    NASA Astrophysics Data System (ADS)

    Lee, Jeong-Soo; Yun, Jin-Oh; Lim, Dong-Yong; Jang, Yong-Won; Kim, Bong-Joon; Oh, Chong-In

    2010-06-01

    This paper is focused on application submerged arc welding process, which offers many advantages compared to conventional CO2 welding process, for thin plate in ship structure. For this purpose, optimized welding conditions are determined according to combination of wire & flux, relationship between welding parameters, bead shapes and mechanical tests such as tensile, bend and hardness. Also finite element(FE) based numerical simulation of thermal history and welding residual stress in welded joint of A-grade 3.2 thickness steel has been checked to qualitative tendency in this paper. In conclusion our company applied to this method in work piece and it was no problem. From the result of this study, it makes substantial saving of time and manufacturing cost and raises the welding quality of product.

  4. SU-E-T-421: Feasibility Study of Volumetric Modulated Arc Therapy with Constant Dose Rate for Endometrial Cancer

    SciTech Connect

    Yang, R; Wang, J

    2014-06-01

    Purpose: 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. Methods: 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. Results: Compared with IMRT, the VMAT-CDR plans delivered a slightly greater V20 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. Conclusion: 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. This work is supported by the grant project, National Natural; Science Foundation of China (No. 81071237)

  5. Why does the perpendicular electric field increase at the edge of auroral arcs?

    NASA Technical Reports Server (NTRS)

    Bruening, K.; Wilhelm, K.; Goertz, C. K.

    1985-01-01

    Radar, rocket and satellite measurements often indicate that there is a strong increase and subsequent decrease in the perpendicular electric field when traversing one edge of an auroral arc. The analysis of rocket measurements, presented here, shows that above an auroral arc there is a small gradient in the electric field due to polarization effects in the ionosphere, but that the strong increase at the edge of the arc can only be explained if the field-aligned currents associated with the arc are taken into account.

  6. A comparative study of two rear-arc plutons and implications for the Fuegian Andes tectonic evolution: Mount Kranck Pluton and Jeu-Jepén Monzonite, Argentina

    NASA Astrophysics Data System (ADS)

    González-Guillot, M.; Prezzi, C.; Acevedo, R. D.; Escayola, M.

    2012-10-01

    A petrologic, geochemical and geophysical study of two Late Cretaceous plutons of the Fuegian Andes is carried out: the Jeu-Jepén Monzonite (JJM) and the Mt. Kranck Pluton (MKP). The plutons show a wide lithological spectrum from ultramafic lithologies (clinopyroxenites and hornblendites), gabbros, diorites to late stage K-feldspar syenite veins. They represent the top of magmatic chambers exposed at or close to the roof level. Mode and chemistry indicate a monzonitic-mildly alkaline trend with high K2O content, equivalent to shoshonitic series. Trace element composition is typical of arc magmas. These features plus their high LILE content (Ba 320-1600 ppm, Sr 475-1560 ppm), high LILE/HFSE ratio (Rb/Zr 0.6-1.6) and age confirm they belong to a rear-arc, monzonitic to mildly alkaline suite (the Fuegian Potassic Magmatism). Therefore, they represent the farthest-from-the-trench plutons in the suite. The petrographical and chemical characteristics of the plutons suggest the lithological spectrum is the result of magmatic differentiation. The process involved crystal accumulation and magma mingling at the early stages, favored either by injections of fresh magma from deeper reservoirs and/or the action of convective currents within the chamber. Country rock assimilation also took part simultaneously with crystallization. The JJM and MKP lie along the trace of a Cenozoic left-lateral strike-slip fault (Magallanes-Fagnano fault system), on opposite blocks. However, lithological, chemical and geophysical subtle differences between these two plutons suggest they evolved in individual magmatic chambers and therefore the distance between them cannot be used as an estimation of total offset along the fault, as was indicated in previous studies.

  7. Insights on the Quaternary Tectonic Evolution of the SE Indonesia Arc-Continent Collision from the Study of Uplifted Coral Terraces on Sumba Island.

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Rigaud, S.; Chiang, H. W.; Djamil, Y. S.; Herdiyanti, T.; Johnny, J.; Ildefonso, S.; Meilano, I.; Bijaksana, S.; Abidin, H. Z.; Tapponnier, P.; Wang, X.

    2015-12-01

    Sumba Island is uniquely positioned within the Sunda-Banda forearc, at the transition between oceanic subduction and arc-continent collision. There, the convergence between the Sunda and Australian plates is accommodated along at least three major structures: the megathrust, the Savu backthrust located south of Sumba and the Flores backthrust located north of the volcanic arc. The incipient collision in the vicinity of Sumba is responsible for coastal vertical movements. Quaternary reefal deposits form spectacular uplifted flights of terraces, which directly overlie Mid Miocene - Early Pliocene deep carbonate and volcaniclastic rocks at elevations exceeding 500m. Although aerial fossil reefs extensively rim the northern and eastern coasts of Sumba, studies have been limited to Cape Laundi where an uplift rate of 0.2-0.5 m/kyr is estimated for the last 400 kyr, partly on the basis of alpha-spectrometric U/Th dating. At the island scale, the relief morphology and the hydrographic network point to a N-S asymmetry, indicating a general tilt toward the north. A subducting seafloor asperity and south-dipping normal faults have been postulated to generate this asymmetry. However as the pattern and kinematics of the deformation remain partially determined, structures and processes capable of driving such deformation and accommodating the nascent collision may be undisclosed. New topographic data coupled with field observations and coral mass-spectrometric U/Th dating allow investigating the morphology, stratigraphy and age of the fossil reef terraces at the island scale. Tectonic structures disrupting the topography are identified and their activities are relatively dated with respect to fossil reef terraces. The deformation pattern of Sumba is characterized, especially in Cape Laundi where the uplift rate is re-evaluated. Through a multi-disciplinary study, we intend to reconstruct the tectonic evolution of Sumba island and, at a larger scale, of the collision in SE

  8. A new radiative forcing data set comprising the major volcanic eruptions from the Central American Volcanic Arc for paleo climate studies

    NASA Astrophysics Data System (ADS)

    Metzner, D.; Krüger, K.; Timmreck, C.; Kutterolf, S.; Freundt, A.

    2009-04-01

    Of all the natural causes of climate change, major volcanic eruptions are most important as they have a significant impact on Earth's global climate system, especially on the stratosphere and troposphere, the atmospheric circulation and chemical composition. The direct injection of gases, aerosols and volcanic ash into the stratosphere has a strong and long lasting radiative influence, which leads to a global cooling of surface temperatures for several years, probably decades. In this study we will investigate the climate feedbacks of large Plinian eruptions from volcanoes at the Central American Arc within the last 200ka with the help of state of the art climate models. To evaluate the radiative forcing of the climate system, we need reliable estimates of the paleo volcanic stratospheric aerosol loading. Here we use a newly derived volcanic data set for Central America based on a) new eruptive mass estimations that are based on compositional land-sea correlations of widespread tephra layers and b) incoporation of measured degassed volatile fractions (S, Cl, F, Br, I) derived from those tephras by the "petrological method" into the mass calculations (Kutterolf et al. 2008a,b). This facilitates the consideration of large eruptions of the past for climate modelling. Using information about strength and height of the volcanic sulphur injection we create a new data set of aerosol optical depth comprising the major volcanic eruptions of Central American Volcanic Arc over the last 200ka. The poster will introduce the underlying steps to derive an aerosol optical depth set from the petrologic derived sulfate aerosol loading in more detail and discuss possible uncertainties. As soon as possible climate sensitivity studies will follow, in which different SO2 scenarios will be applied, for low, medium and large size SO2 eruptions. To assess the climate impact of past CAVA eruptions on a paleo time scale an earth system climate model of intermediate complexity will be

  9. Determining the source region of auroral emissions in the prenoon oval using coordinated Polar BEAR UV-imaging and DMSP particle measurements

    NASA Technical Reports Server (NTRS)

    Newell, Patrick T.; Meng, CHING-I.; Huffman, Robert E.

    1992-01-01

    The Polar Beacon Experiment and Auroral Research (Polar BEAR) satellite included the capability for imaging the dayside auroral oval in full sunlight at several wavelengths. Particle observations from the DMSP F7 satellite during dayside auroral oval crossings are compared with approximately simultaneous Polar BEAR 1356-A images to determine the magnetospheric source region of the dayside auroral oval. The source region is determined from the DMSP particle data, according to recent work concerning the classification and identification of precipitation source regions. The close DMSP/Polar BEAR coincidences all occur when the former satellite is located between 0945 and 1000 MLT. Instances of auroral arcs mapping to each of several different regions, including the boundary plasma sheet, the low-latitude boundary layer, and the plasma mantle were found. It was determined that about half the time the most prominent auroral arcs are located at the interfaces between distinct plasma regions, at least at the local time studied here.

  10. Geochemical differences between along-arc and across-arc volcanics in west-central Nicaragua

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Freundt, Armin; Wörner, Gerhard; Kutterolf, Steffen

    2012-04-01

    The La Paz Centro - Malpaisillo Lineament (LPML) in west-central Nicaragua is a north-south striking, 20 km long chain of maars and cinder cones, which intersects the northwest-southeast striking main volcanic front. A tectonic control of LPML volcanism is likely but only evident for the Malpaisillo fissure at the northern end of the LPML. Previous work demonstrated geochemical variations implying changes in mantle-source composition (i.e., added slab components) along the Central American Volcanic Arc at spatial scales of some 10's of kilometers. Our study of the LPML shows that minor but systematic changes also occur across the arc within 20 km distance. Variations in trace element ratios such as Zr/Nb, Ba/Th, Ba/La, Th/Zr, U/La and La/Yb along the LPML, i.e. across the volcanic front indicate little change in the degree of partial melting but an increase particularly in the hemipelagic sediment component in the mantle source from the fore arc towards the arc front, followed by a decrease behind the arc. Interestingly, the slab component is most prominent just in front of the arc. About 60 km southeast of the LPML, the Nejapa-Miraflores volcanic and tectonic lineament, which marks a 20 km north-south offset in the arc, differs substantially from the LPML. There is a wide scatter in incompatible trace element ratios indicating a heterogeneous mantle source at small spatial scales (c. 1 km). This mantle heterogeneity may represent vertical rather than across-arc variations and is probably related to the arc offset, because in the absence of such offset at the LPML mantle source conditions vary much less but more systematically.

  11. Crustal rifting and magmatic underplating in the Izu-Ogasawara (Bonin) intra-oceanic arc detected by active source seismic studies

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Kodaira, S.; Yamashita, M.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.; Kaneda, Y.

    2009-12-01

    Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic experiments using a multichannel reflection system and ocean bottom seismographs (OBSs) in the Izu-Ogasawara (Bonin)-Mariana (IBM) arc region since 2002 to understand growth process of continental crust. The source was an airgun array with a total capacity of 12,000 cubic inches and the OBSs as the receiver were deployed with an interval of 5 km for all seismic refraction experiments. As the results, we obtained crustal structures across the whole IBM arc with an interval of 50 km and detected the structural characteristics showing the crustal growth process. The IBM arc is one of typical oceanic island arc, which crustal growth started from subduction of an oceanic crust beneath the other oceanic crust. The arc crust has developed through repeatedly magmatic accretion from subduction slab and backarc opening. The volcanism has activated in Eocene, Oligocene, Miocene and Quaternary (e.g., Taylor, 1992), however, these detailed locations of past volcanic arc has been remained as one of unknown issues. In addition, a role of crustal rifting for the crustal growth has also been still unknown issue yet. Our seismic structures show three rows of past volcanic arc crusts except current arc. A rear arc and a forearc side have one and two, respectively. The first one, which was already reported by Kodaira et al. (2008), distributes in northern side from 27 N of the rear arc region. The second one, which develops in the forearc region next to the recent volcanic front, distributes in whole of the Izu-Ogasawara arc having crustal variation along arc direction. Ones of them sometimes have thicker crust than that beneath current volcanic front and no clear topographic high. Last one in the forearc connects to the Ogasawara Ridge. However, thickest crust is not always located beneath these volcanic arcs. The initial rifting region like the northern end of the Mariana Trough and the Sumisu

  12. Laterally patterned spin-valve superlattice: Magnetometry and polarized neutron scattering study

    SciTech Connect

    Brüssing, F.; Devishvili, A.; Zabel, H.; Toperverg, B. P.; Badini Confalonieri, G. A.; Theis-Bröhl, K.

    2015-04-07

    The magnetization reversal of magnetic multilayers with spin-valve like characteristics, patterned into an array of parallel stripes, was structurally and magnetically analyzed, in detail, via x-ray scattering, magnetometry, and polarized neutron reflectivity. Each stripe contains a multiple repetition of the layer sequence [Fe/Cr/Co/Cr]. X-ray and neutron scattering maps of the patterned multilayer show rich details resulting from the superposition of Bragg peaks representing the lateral in-plane periodicity and the out-of-plane multilayer period. Detailed analysis of specular and off-specular polarized neutron intensity was used to ascertain the antiparallel alignment of the Co and Fe magnetization within the kink region of their combined hysteresis loop between the coercive fields of Fe and Co layers. This includes also an examination of domain formation and inter- as well as intra-stripe correlation effects upon magnetization reversal. Our combined study shows that the shape induced anisotropy via patterning is capable of overriding the four-fold crystal anisotropy but is unable to eliminate the ripple domain state of the Co layers, already present in the continuous multilayer.

  13. Study of Microheterogeneity in Acetonitrile-Water Binary Mixtures by using Polarity-Resolved Solvation Dynamics.

    PubMed

    Koley, Somnath; Ghosh, Subhadip

    2015-11-16

    The solvation dynamics of three coumarin dyes with widely varying polarities were studied in acetonitrile-water (ACN-H2O) mixtures across the entire composition range. At low ACN concentrations [ACN mole fractions (X(ACN))≤0.1], the solvation dynamics are fast (<40 ps), indicating a nearly homogeneous environment. This fast region is followed by a sudden retardation of the average solvation time (230-1120 ps) at higher ACN concentrations (X(ACN)≈0.2), thus indicating the onset of nonideality within the mixture that continues until X(ACN)≈0.8. This nonideality regime (X(ACN)≈0.2-0.8) comprises of multiple dye-dependent anomalous regions. At very high ACN concentrations (X(ACN)≈0.8-1), the ACN-H2O mixtures regain homogeneity, with faster solvation times. The source of the inherent nonideality of the ACN-H2O mixtures is a subject of debate. However, a careful examination of the widths of time-resolved emission spectra shows that the origin of the slow dynamics may be due to the diffusion of polar solvent molecules into the first solvation shell of the excited coumarin dipole.

  14. An experimental study of growth and phase change of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hallett, John; Teets, Edward

    1992-01-01

    This report describes the progress made on understanding phase changes related to solutions which may comprise Polar Stratospheric Clouds. In particular, it is concerned with techniques for investigating specific classes of metastability and phase change which may be important not only in Polar Stratospheric Clouds but in all atmospheric aerosols in general. While the lower level atmospheric aerosol consists of mixtures of (NH4)(SO4)2, NH4HSO4, NaCl among others, there is evidence that aerosol at PSC levels is composed of acid aerosol, either injected from volcanic events (such as Pinatubo) or having diffused upward from the lower atmosphere. In particular, sulfuric acid and nitric acid are known to occur at PSC levels, and are suspected of catalyzing ozone destruction reactions by adsorption on surfaces of crystallized particles. The present study has centered on two approaches: (1) the extent of supercooling (with respect to ice) and supersaturation (with respect to hydrate) and the nature of crystal growth in acid solutions of specific molality; and (2) the nature of growth from the vapor of HNO3 - H2O crystals both on a substrate and on a pre-existing aerosol.

  15. An overview of NLC-91: A rocket/radar study of the polar summer mesophere

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    In late July and early August of 1991, a major suborbital scientific campaign (NLC-91) involving scientists from eight countries was conducted at ESRANGE, Kiruna, Sweden and at Heiss Island, Russia. The purpose of the program was to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. Thirty one rocket flights were coordinated with two coherent radar facilities, European Incoherent Scatter (EISCAT) and Cornell Univesity Portable Radar Interferometer (CUPRI), and with other ground-based observatories and facilities. This permitted direct comparison between the in situ measurements and those obtained by remote sensing of the mesosphere via continuous ground-based monitoring. The primary objectives of the campaign were to study noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs), including their possible relationship to local aerosols and/or small scale turbulence. This overview describes the scientific program, discusses the geophysical conditions during launch activities, and reviews some of the preliminary results. More detailed results can be found in the papers which follow.

  16. Fourier transform infrared studies of the interaction of HCl with model polar stratospheric cloud films

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Heterogeneous reactions involving hydrochloric acid adsorbed on the surfaces of polar stratospheric clouds (PSCs) are postulated to contribute to polar ozone loss. Using FTIR spectroscopy to probe the condensed phase, we have examined the interaction of HCl with ice and nitric acid trihydrate (NAT) films representative of types II and I PSCs, respectively. For HCl pressures in the range of 10 exp -7 to 10 exp -5 Torr, our FTIR studies show that a small amount of crystalline HCl-6H2O formed on or in ice at 155 K. However, for higher HCl pressures, we observed that the entire film of ice rapidly converted into an amorphous 4:1 H2O:HCl mixture. From HCl-uptake experiments with P(HCl) = 8 x 10 exp -7 Torr, we estimate roughly that the diffusion coefficient of HCl in ice is around 2 x 10 exp -12 sq cm/s at 158 K. For higher temperatures more closely approximating those found in the stratosphere, we were unable to detect bulk HCl uptake by ice. Indirect evidence suggests that HCl adsorption onto the surface of model PSC films inhibited the evaporation of both ice and NAT by 3-5 K.

  17. An overview of NLC-91: A rocket/radar study of the polar summer mesophere

    NASA Astrophysics Data System (ADS)

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

    1993-10-01

    In late July and early August of 1991, a major suborbital scientific campaign (NLC-91) involving scientists from eight countries was conducted at ESRANGE, Kiruna, Sweden and at Heiss Island, Russia. The purpose of the program was to investigate the chemical, dynamical, and electrodynamical properties of the polar summer mesosphere. Thirty one rocket flights were coordinated with two coherent radar facilities, European Incoherent Scatter (EISCAT) and Cornell Univesity Portable Radar Interferometer (CUPRI), and with other ground-based observatories and facilities. This permitted direct comparison between the in situ measurements and those obtained by remote sensing of the mesosphere via continuous ground-based monitoring. The primary objectives of the campaign were to study noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs), including their possible relationship to local aerosols and/or small scale turbulence. This overview describes the scientific program, discusses the geophysical conditions during launch activities, and reviews some of the preliminary results. More detailed results can be found in the papers which follow.

  18. [Study on the polarized reflectance characteristics of single greenhouse tomato nutrient deficiency leaves].

    PubMed

    Zhu, Wen-Jing; Mao, Han-Ping; Liu, Hong-Yu; Zhang, Xiao-Dong; Ni, Ji-Heng

    2014-01-01

    In order to improve accuracy of quantitative analysis model for the greenhouse tomato nitrogen, phosphorus and potassium nutrient stress, and explore the advantages of polarization non-destructive detection in single-leaf plants scale, polarized reflectance characteristics of greenhouse nutrient deficiency tomato leaves in different growing seasons and different deficiency extents were both examined via means of polarized reflectance spectroscopy system, which was self-developed by the research group. The main factors with effects on the polarized reflectance characteristics of tomato leaves were discussed, such as incident zenith angle, azimuth angle, detection zenith angle, light source polarizer degree, and detector polarizer degree. Experiments were carried out to verify the optimum level of above five parameters by means of range analysis of orthogonal experiments, through that way we can know the best angle combination of five parameters. Based on the above analysis, the angle combination and sorting of detecting tomato nutrients deficiency leaves via means of polarization spectroscopy system were obtained as follows: incident zenith angle 60 degrees, light source polarizer degree 0 degrees, detection zenith angle 45 degrees, detector polarizer degree 45 degrees and azimuth angle 180 degrees. At the same time, both the spectra of nitrogen, phosphorus and potassium deficiency leaves in different growth stages and different deficiency extent leaves were compared with each other. Results show that there is a positive correlation between the greenhouse nutrient deficiency tomato leaves growth cycle and tomato leaves polarized reflectance spectra. Nutrient excess or nutrient deficiency can both lead to polarized reflectance decline and polarized reflectance decline extent of greenhouse tomato leaves is more obvious during the fruiting and harvest period. This paper has a certain theoretical and practical significance in the research on nutrition rapid detection on

  19. Computational Modeling of Arc-Slag Interaction in DC Furnaces

    NASA Astrophysics Data System (ADS)

    Reynolds, Quinn G.

    2017-02-01

    The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc's interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc-slag interaction effects.

  20. Computational Modeling of Arc-Slag Interaction in DC Furnaces

    NASA Astrophysics Data System (ADS)

    Reynolds, Quinn G.

    2016-11-01

    The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc's interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc-slag interaction effects.

  1. Comparison of aerial survey procedures for estimating polar bear density: Results of pilot studies in northern Alaska

    USGS Publications Warehouse

    McDonald, Lyman L.; Garner, Gerald W.; Garner, Gerald W.; Amstrup, Steven C.; Laake, Jeffrey L.; Manly, Bryan F.J.; McDonald, Lyman L.; Robertson, Donna G.

    1999-01-01

    The U.S. Marine Mammal Protection Act (MMPA) and International Agreement on the Conservation of Polar Bears mandate that boundaries and sizes of polar bear (Ursus maritimus) populations be known so they can be managed at optimum sustainable levels. However, data to estimate polar bear numbers for the Chukchi/Bering Sea and Beaufort Sea populations in Alaska are limited. We evaluated aerial line transect methodology for assessing the size of these Alaskan polar bear populations during pilot studies in spring 1987 and summer 1994. In April and May 1987 we flew 12.239 km of transect lines in the northern Bering, Chukchi, and western Beaufort seas. In June 1994 we flew 6.244 km of transect lines in a primary survey unit using a helicopter, and 5,701 km of transect lines in a secondary survey unit using a fixed-wing aircraft in the Beaufort Sea. We examined visibility bias in aerial transect surveys, double counts by independent observers, single-season mark-resight methods, the suitability of using polar bear sign to stratify the study area, and adaptive sampling methods. Fifteen polar bear groups were observed during the 1987 study. Probability of detecting bears decreased with increasing perpendicular distance from the transect line, and probability of detecting polar bear groups likely increased with increasing group size. We estimated population density in high density areas to be 446 km2/bear. In 1994, 15 polar bear groups were observed by independent front and rear seat observers on transect lines in the primary survey unit. Density estimates ranged from 284 km2/bear to 197 km2/bear depending on the model selected. Low polar bear numbers scattered over large areas of polar ice in 1987 indicated that spring is a poor time to conduct aerial surveys. Based on the 1994 survey we determined that ship-based helicopter or land-based fixed-wing aerial surveys conducted at the ice-edge in late summer-early fall may produce robust density estimates for polar bear

  2. Alignment and Polarization Sensitivity Study for the Cassini-Composite InfraRed Spectrometer (CIRS) Far InfraRed (FIR) Interferometer

    NASA Technical Reports Server (NTRS)

    Crooke, Julie A.; Hagopian, John G.

    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 gm wide copper wires, with 2 gm spacing (4 micron pitch) photolithographically deposited on the substrate. This paper details the polarization sensitivity studies performed on the output polarizer/analyzer, and the alignment sensitivity studies performed on the input polarizer and beamsplitter components in the FIR interferometer.

  3. Multi-institutional comparison of volumetric modulated arc therapy vs. intensity-modulated radiation therapy for head-and-neck cancer: a planning study

    PubMed Central

    2013-01-01

    Background Compared to static beam Intensity-Modulated Radiation Therapy (IMRT), the main advantage of Volumetric Modulated Arc Therapy (VMAT) is a shortened delivery time, which leads to improved patient comfort and possibly smaller intra-fraction movements. This study aims at a treatment planner-independent comparison of radiotherapy treatment planning of IMRT and VMAT for head-and-neck cancer performed by several institutes and based on the same CT- and contouring data. Methods Five institutes generated IMRT and VMAT plans for five oropharyngeal cancer patients using either Pinnacle3 or Oncentra Masterplan to be delivered on Elekta linear accelerators. Results Comparison of VMAT and IMRT plans within the same patient and institute showed significantly better sparing for almost all OARs with VMAT. The average mean dose to the parotid glands and oral cavity was reduced from 27.2 Gy and 39.4 Gy for IMRT to 25.0 Gy and 36.7 Gy for VMAT, respectively. The dose conformity at 95% of the prescribed dose for PTVboost and PTVtotal was 1.45 and 1.62 for IMRT and 1.37 and 1.50 for VMAT, respectively. The average effective delivery time was reduced from 13:15 min for IMRT to 5:54 min for VMAT. Conclusions Independently of institution-specific optimization strategies, the quality of the VMAT plans including double arcs was superior to step-and-shoot IMRT plans including 5–9 beam ports, while the effective treatment delivery time was shortened by ~50% with VMAT. PMID:23369221

  4. Hall-effect arc protector

    DOEpatents

    Rankin, Richard A.; Kotter, Dale K.

    1997-01-01

    The Hall-Effect Arc Protector is used to protect sensitive electronics from high energy arcs. The apparatus detects arcs by monitoring an electrical conductor, of the instrument, for changes in the electromagnetic field surrounding the conductor which would be indicative of a possible arcing condition. When the magnitude of the monitored electromagnetic field exceeds a predetermined threshold, the potential for an instrument damaging are exists and the control system logic activates a high speed circuit breaker. The activation of the breaker shunts the energy imparted to the input signal through a dummy load to the ground. After the arc condition is terminated, the normal signal path is restored.

  5. Hall-effect arc protector

    DOEpatents

    Rankin, R.A.; Kotter, D.K.

    1997-05-13

    The Hall-Effect Arc Protector is used to protect sensitive electronics from high energy arcs. The apparatus detects arcs by monitoring an electrical conductor, of the instrument, for changes in the electromagnetic field surrounding the conductor which would be indicative of a possible arcing condition. When the magnitude of the monitored electromagnetic field exceeds a predetermined threshold, the potential for an instrument damaging are exists and the control system logic activates a high speed circuit breaker. The activation of the breaker shunts the energy imparted to the input signal through a dummy load to the ground. After the arc condition is terminated, the normal signal path is restored. 2 figs.

  6. Seismic anisotropy along the Cyprean arc and northeast Mediterranean Sea inferred from shear wave splitting analysis

    NASA Astrophysics Data System (ADS)

    Yolsal-Çevikbilen, Seda

    2014-08-01

    The Cyprean arc is considered to be a convergent boundary in the Eastern Mediterranean where the African plate is being subducted beneath the Anatolian plate. Mapping the lateral variations of seismic anisotropy parameters can provide essential hints to mantle dynamics and flow patterns in relation to the geometry and style of deformation developed under different pressure, temperature conditions around the subducting African lithosphere. In this study, seismic anisotropy parameters, fast polarization directions (ϕ) and delay times (δt) beneath the Cyprean arc and NE Mediterranean Sea are inferred from the shear wave splitting analysis performed on core-mantle refracted teleseismic shear waves (SKS phases). Earthquake data used in the present work are extracted from the continuous recordings of 8 broad-band seismic stations located in the study region for a time period during 1999 and 2012. The overall results exhibits clear evidences of mantle anisotropy with relatively uniform NE-SW aligned fast polarization directions. No abrupt changes in fast polarization directions (ϕ) are observed. However, near the Dead Sea Transform Fault, ϕ values tend to rotate from NE-SW to N-S and NW-SE in accordance with Pn anisotropy observations. Delay times (δt) vary between 0.61 s ± 0.10 s and 1.90 s ± 0.13 s. The range of delay times are generally consistent with those observed in the mantle rather than implying a crustal anisotropy. A predominant pattern of NNE-SSW fast polarization directions that is coherent with earlier SKS splitting measurements observed beneath north, central and East Anatolia suggests a SW directed asthenospheric flow caused by slab rollback process along the Hellenic and Cyprean arcs. Furthermore, apparent splitting parameters did not exhibit any significant directional dependence which may imply possibility of the presence of anisotropic models with two-layer anisotropy or dipping axis of symmetry beneath the northeast Mediterranean Sea and

  7. Physics with Polarized Nuclei.

    ERIC Educational Resources Information Center

    Thompson, William J.; Clegg, Thomas B.

    1979-01-01

    Discusses recent advances in polarization techniques, specifically those dealing with polarization of atomic nuclei, and how polarized beams and targets are produced. These techniques have greatly increased the scope of possible studies, and provided the tools for testing fundamental symmetries and the spin dependence of nuclear forces. (GA)

  8. FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

    2003-01-01

    The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identi@ the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral Snapshot (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data were used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and/or a long-system particle in cell simulation to model the magnetically connected region between the two satellites. Results from the study indicate that there are three main drivers of auroral acceleration: (1) field-aligned currents that lead to quasistatic parallel potential drops (parallel electric fields), (2) earthward flow of high-energy plasma beams from the magnetotail into the auroral zone that lead to quasistatic parallel potential drops, and (3) large-amplitude Alfven waves that propagate into the auroral region from the magnetotail. The events examined thus far confm the previously established invariant latitudinal dependence of the drivers and show a strong dependence on magnetic activity. Alfven waves tend to occur primarily at the poleward edge of the auroral region during more magnetically active times and are correlated with intense electron precipitation. At lower latitudes away

  9. Influence of quasi-spherical polarization on results of bioelectromagnetic studies.

    PubMed

    Dlugosz, Tomasz

    2015-01-01

    One of the most interesting questions in bioelectromagnetic and compatibility studies is differences between results of experiments performed in different labs in "identical" conditions, especially in bioelectromagnetics studies. A reason of these differences may be due to differences in investigated objects, particularly in in vivo experiments. However, the author, as engineer, would like to focus the readers' attention on the technical aspects of exposure systems namely: presence and role of mutual interaction between the object under test and the exposure system, interaction between exposure objects, the role of polarization and the similarity of real-life exposure to those applied in experiments, etc. All these factors may change the results of experiments and lead to false conclusions.

  10. Differential preservation in the geologic record of intraoceanic arc sedimentary and tectonic processes

    USGS Publications Warehouse

    Draut, Amy; Clift, Peter D.

    2013-01-01

    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are commonly used to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence for some arc processes and loss of evidence for others. In this synthesis we examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forward-facing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In a ‘backward-facing’ collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in a state of tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern intraoceanic arcs implies that valuable records of arc processes are commonly destroyed even before the arc collides with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest and tectonic accretion prevailed. Collision geometry

  11. Plasma arc melting of zirconium

    SciTech Connect

    Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

    1997-12-31

    Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming.

  12. Application of the Quanta image sensor concept to linear polarization imaging-a theoretical study.

    PubMed

    Anzagira, Leo; Fossum, Eric R

    2016-06-01

    Research efforts in linear polarization imaging have largely targeted the development of novel polarizing filters with improved performance and the monolithic integration of image sensors and polarization filter arrays. However, as pixel sizes in CMOS image sensors continue to decrease, the same limitations that have an impact on color and monochrome CMOS image sensors will undoubtedly affect polarization imagers. Issues of low signal capacity and dynamic range in small pixels will severely limit the useful polarization information that can be obtained. In this paper, we propose to leverage the benefits of the relatively new Quanta image sensor (QIS) concept to mitigate the anticipated limitations of linear polarization imaging as pixel sizes decrease. We address, by theoretical calculation and simulation, implementation issues such as alignment of polarization filters over extremely small pixels used in the QIS concept and polarization image formation from single-bit output of such pixels. We also present design innovations aimed at exploiting the benefits of this new imaging concept for simultaneous color and linear polarization imaging.

  13. Polarization at SLAC

    SciTech Connect

    Woods, M.

    1995-01-01

    A highly polarized electron beam is a key feature. for the Current physics program at SLAC. An electron beam polarization of 80% can now be routinely achieved for typically 5000 hours of machine operation per year. Two main Physics programs utilize the polarized beam. Fixed target experiments in End Station A study the collision of polarized electrons with polarized nuclear targets to elucidate the spin structure of the nucleon and to provide an important test of QCD. Using the SLAC Linear Collider, collisions of polarized electrons with unpolarized positrons allow precise measurements of parity violation in the Z-fermion couplings and provide a very precise measurement of tile weak mixing angle. This paper discusses polarized beam operation at SLAC, and gives an overview of the polarized physics program.

  14. HOLLOW CARBON ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-10-11

    A device is described for producing an energetic, direct current, hollow, carbon-arc discharge in an evacuated container and within a strong magnetic field. Such discharges are particularly useful not only in dissociation and ionization of high energy molecular ion beams, but also in acting as a shield or barrier against the instreaming of lowenergy neutral particles into a plasma formed within the hollow discharge when it is used as a dissociating mechanism for forming the plasma. There is maintained a predetermined ratio of gas particles to carbon particles released from the arc electrodes during operation of the discharge. The carbon particles absorb some of the gas particles and are pumped along and by the discharge out of the device, with the result that smaller diffusion pumps are required than would otherwise be necessary to dispose of the excess gas.

  15. Polarization measurement through combination polarizers

    NASA Astrophysics Data System (ADS)

    Bai, Yunfeng; Li, Linjun; He, Zhelong; Liu, Yanwei; Ma, Cheng; Shi, Guang; Liu, Lu

    2014-02-01

    Polarization measurement approaches only using polarizer and grating is present. The combination polarizers consists of two polarizers: one is γ degree with the X axis; the other is along the Y axis. Binary grating is covered by the combination polarizers, and based on Fraunhofer diffraction, the diffraction intensity formula is deduced. The polarization state of incident light can be gotten by fitting the diffraction pattern with the deduced formula. Compared with the traditional polarization measurement method, this measurement only uses polarizer and grating, therefore, it can be applied to measure a wide wavelength range without replacing device in theory.

  16. Study of the Nortern polar ionosphere by all-sky imager, riometer and magnetometer data

    NASA Astrophysics Data System (ADS)

    Guineva, Veneta; Trondsen, Espen; Marple, Steve; Dahle, Kolbjorn; Stauning, Peter

    The variety of the auroral forms and their behaviour, as a result of the complexity of the processes in the upper atmosphere at high latitudes and the connection between them as well as the large number of influencing factors give a lot of possibilities for new investigations. The opportunity for simultaneous multi-instrument observations by different instruments, as well by sets of instruments of the same kind, nowadays is a precondition for an extensive research of the polar ionosphere phenomena. For this study, simultaneous observations' data of the OI 5577 ´˚ and 6300 ´˚ emissions, the electron precipitation flux and the terrestrial magnetic A A field have been used from the following instruments: the All-Sky Imager (ASI), ALOMAR Imaging Riometer for Ionospheric Studies (AIRIS) and the magnetometer, positioned at Andøya Rocket Range (ARR), Andenes (69.3° N, 16.03° E); ASI, 64-beam Imaging Riometer and the magnetometer at the Auroral Observatory, Longyearbyen, Svalbard (78.20° N, 15.83° E); IRIS at Kilpisj¨rvi, Finland (69.05° N, 20.79° E). The fields of view of the instruments cover a large a area of the auroral oval and the polar cap. The distribution and the behaviour of the optical emissions and the absorption features have been analysed. A good correlation between the spatial and temporal evolutions of the optical emissions, the precipitating electron fluxes and the terrestrial magnetic field has been observed. The response of the ionosphere to the solar and geomagnetic activity changes has been studied. Data access has been provided under the Project "ALOMAR eARI" (RITA-CT-2003-506208), Andenes, Norway. This Project received research funding from the European Community's 6th Framework Program.

  17. Spectral invariance hypothesis study of polarized reflectance with Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI)

    NASA Astrophysics Data System (ADS)

    Bradley, Christine L.; Kupinski, Meredith; Diner, David J.; Xu, Feng; Chipman, Russell A.

    2015-09-01

    Many models used to represent the boundary condition for the separation of atmospheric scattering from the surface reflectance in polarized remote sensing measurements assume that the polarized surface reflectance is spectrally neutral. The Spectral Invariance Hypothesis asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is equal for all wavelengths. In order to test this hypothesis, JPL's Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) is used to measure polarization information of different outdoor surface types. GroundMSPI measures the linear polarization Stokes parameters (I, Q, U), at three wavelengths, 470 nm, 660 nm, and 865 nm. The camera is mounted on a two-axis gimbal to accurately select the view azimuth and elevation directions. On clear sky days we acquired day-long scans of scenes that contain various surface types such as grass, dirt, cement, brick, and asphalt and placed a Spectralon panel in the camera field of view to provide a reflectance reference. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The polarized bidirectional reflectance factor (pBRF) is measured for the three wavelengths and the best fit slope of the spectral correlation is reported. This work reports the range of best fit slopes measured for five region types.

  18. Arc Inception Mechanism on a Solar Array Immersed in a Low-Density Plasma

    NASA Technical Reports Server (NTRS)

    Vayner, B.; Galofaro, J.; Ferguson, D.

    2001-01-01

    In this report, results are presented of an experimental and theoretical study of arc phenomena and snapover for two samples of solar arrays immersed in argon plasma. The effects of arcing and snapover are investigated. I-V curves are measured, and arc and snapover inception voltages and arc rates are determined within the wide range of plasma parameters. A considerable increase in arc rate due to absorption of molecules from atmospheric air has been confirmed. It is shown that increasing gas pressure causes increasing ion current collection and, consequently, arc rate even though the effect of conditioning also takes place. Arc sites have been determined by employing a video-camera. It is confirmed that keeping sample under high vacuum for a long time results in shifting arc threshold voltage well below -300 V. The results obtained seem to be important for the understanding of arc inception mechanism.

  19. Site selection and traverse planning to support a lunar polar rover mission: A case study at Haworth Crater

    NASA Astrophysics Data System (ADS)

    Heldmann, Jennifer L.; Colaprete, Anthony; Elphic, Richard C.; Bussey, Ben; McGovern, Andrew; Beyer, Ross; Lees, David; Deans, Matt

    2016-10-01

    Studies of lunar polar volatile deposits are of interest for scientific purposes to understand the nature and evolution of the volatiles, and also for exploration reasons as a possible in situ resource to enable long term human exploration and settlement of the Moon. Both theoretical and observational studies have suggested that significant quantities of volatiles exist in the polar regions, although the lateral and horizontal distribution remains unknown at the km scale and finer resolution. A lunar polar rover mission is required to further characterize the distribution, quantity, and character of lunar polar volatile deposits at these higher spatial resolutions. Here we present a case study for NASA's Resource Prospector (RP) mission concept for a lunar polar rover and utilize this mission architecture and associated constraints to evaluate whether a suitable landing site exists to support an RP flight mission. We evaluate the landing site criteria to characterize the Haworth Crater region in terms of expected hydrogen abundance, surface topography, and prevalence of shadowed regions, as well as solar illumination and direct to Earth communications as a function of time to develop a notional rover traverse plan that addresses both science and engineering requirements. We also present lessons-learned regarding lunar traverse path planning focusing on the critical nature of landing site selection, the influence of illumination patterns on traverse planning, the effects of performing shadowed rover operations, the influence of communications coverage on traverse plan development, and strategic planning to maximize rover lifetime and science at end of mission. Here we present a detailed traverse path scenario for a lunar polar volatiles rover mission and find that the particular site north of Haworth Crater studied here is suitable for further characterization of polar volatile deposits.

  20. Arc jet diagnostics tests

    NASA Technical Reports Server (NTRS)

    Willey, Ronald J.

    1989-01-01

    Two objectives were addressed during a 10 week 1988 NASA/ASEE summer faculty fellowship at the Johnson Space Center Atmospheric Reentry Materials Structures Evaluation Facility (ARMSEF). These objectives were the evaluation of mass spectrometry for the measurement of atomic and molecular species in an arc jet environment, and the determination of atomic recombination coefficients for reaction cured glass (RCG) coated high temperature surface insulation (HRSI) materials subjected to simulated reentry conditions. Evaluation of mass spectrometry for the measurement of atomic and molecular species provided some of the first measurements of point compositions in arc jet tunnel environments. A major objective of this project centered around the sampling residence time. A three staged vacuum sampling system pulled the molecules and atoms from the arc jet to a quadrupole ionization mass spectrometer in 400 milliseconds. Conditions investigated included a composition survey across the nozzle exit at 3 cm z-distance from the nozzle exit for 3 different currents. Also, a point composition survey was taken around a shock created by the presence of a blunt body.

  1. Investigation of polarization-sensitive optical coherence tomography towards the study of microstructure of articular cartilage

    NASA Astrophysics Data System (ADS)

    Kasaragod, Deepa; Lu, Zenghai; Le Maitre, Christine; Wilkinson, J. Mark; Matcher, Stephen

    2013-03-01

    This paper highlights the extended Jones matrix calculus based multi-angle study carried out to understand the depth dependent structural orientation of the collagen fibers in articular cartilage using polarization-sensitive optical coherence tomography (PS-OCT). A 3D lamellar model for the collagen fiber orientation, with a quadratic profile for the arching of the collagen fibers in transitional zone which points towards an ordered arrangement of fibers in that zone is the basis of the organization architecture of collagen fibers in articular cartilage. Experimental data for both ex-vivo bovine fetlock and human patellar cartilage samples are compared with theoretical predictions, with a good quantitative agreement for bovine and a reasonable qualitative agreement for human articular cartilage samples being obtained

  2. Laboratory studies of the nitric acid trihydrate - Implications for the south polar stratosphere

    NASA Technical Reports Server (NTRS)

    Hanson, David; Mauersberger, Konrad

    1988-01-01

    Vapor pressures of HNO3 and H2O have been measured over the trihydrate crystal, formed by vapor deposit on a glass surface. In the temperature range 190 to 205 K the two phase-equilibrium trihydrate/vapor was studied by adding and removing H2O. Coexistence equilibria vapor pressures of trihydrate/solid solutions of HNO3 in ice and of mono-/trihydrate were also measured. Results show that for typical mixing ratios of H2O and HNO3 found in the lower stratosphere (3 ppm H2O, 5 ppb HNO3) the trihydrate would start to form at temperatures about 7 K higher than the ice point. The pressure of atmospheric HNO3 would rapidly decrease as the atmosphere cools without large changes in partial pressures of H2O. These laboratory results provide information on the formation of polar stratospheric clouds containing H2O and HNO3.

  3. Study of gas-fluidization dynamics with laser-polarized 129Xe.

    PubMed

    Wang, Ruopeng; Rosen, Matthew Scott; Candela, Donald; Mair, Ross William; Walsworth, Ronald Lee

    2005-02-01

    We report initial NMR studies of gas dynamics in a particle bed fluidized by laser-polarized xenon (129Xe) gas. We have made preliminary measurements of two important characteristics: gas exchange between the bubble and emulsion phases and the gas velocity distribution in the bed. We used T2* contrast to differentiate the bubble and emulsion phases by choosing solid particles with large magnetic susceptibility. Experimental tests demonstrated that this method was successful in eliminating 129Xe magnetization in the emulsion phase, which enabled us to observe the time dependence of the bubble magnetization. By employing the pulsed field gradient method, we also measured the gas velocity distribution within the bed. These results clearly show the onset of bubbling and can be used to deduce information about gas and particle motion in the fluidized bed.

  4. Microwave dielectric relaxation studies of hydrogen bonded polar binary mixtures of isobutanol and aniline

    NASA Astrophysics Data System (ADS)

    Vishwam, T.; Murthy, V. R. K.

    2013-03-01

    The molecular interaction between the polar systems of isobutanol and aniline for various mole fractions at different temperatures were studied by determining the frequency dependent complex dielectric permittivity by using the open-ended coaxial probe technique method in the microwave frequency range from 20 MHz to 20 GHz. The geometries are optimized at HF and B3LYP with 6-31G and 6-31G+ basis sets. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the theoretical results. Conformational analysis of the formation of hydrogen bond between the isobutanol and aniline is supported by the FT-IR and molecular polarizability calculations. The average relaxation times are calculated from their respective Cole-Cole plots. The activation entropy, activation enthalpy and Kirkwood correlation 'g' factor, excess permittivities (ɛE), Bruggeman parameters (fB) have also been determined for isobutanol and aniline and the results were correlated.

  5. Mitigation of polar pesticides across a vegetative filter strip. A mesocosm study.

    PubMed

    Franco, Jorge; Matamoros, Víctor

    2016-12-01

    Vegetated filter strips (VFSs) are planted at the edge of agricultural fields to reduce pesticide run-off and its consequent potential toxicological effects on ecosystem biota; however, little attention has been paid to date to the attenuation of highly polar and ionisable pesticides such as phenoxyacid herbicides. This study assesses the effect of soil moisture, run-off flow and vegetation on the attenuation of MCPA, mecoprop, dicamba, dichlorprop, fenitrothion, atrazine and simazine by VFSs. Reactors measuring 5 m long by 0.1 m wide were each filled with 60 kg of soil from a real field VFS. VFSs planted with Phragmites australis and unvegetated control reactors were assessed. After a simulated rainfall event of 50 mm, two hydraulic loading rates (HLRs) were assessed (1 and 2 cm h(-1)). These results were compared to those from the same systems under water-saturated conditions. The results show that VFSs reduced the peak inlet concentration and pesticide mass by more than 90 % and that the presence of vegetation increased that attenuation (82-90 % without vegetation and 90-93 % with vegetation, on average). The laboratory-scale study showed that such attenuation was due to sorption into the soil. The toxicity units of pesticides fell by more than 90 % in all cases, except under the water-saturated conditions, in which the decrease was lower (16 vs 54 %, for unvegetated and vegetated reactors). Therefore, the presence of vegetation was shown to be effective for reducing mass discharge of ionisable and highly polar pesticides into surface-water bodies.

  6. Water in Aleutian Arc Volcanoes

    NASA Astrophysics Data System (ADS)

    Plank, T.; Zimmer, M. M.; Hauri, E. H.

    2011-12-01

    In the past decade, baseline data have been obtained on pre-eruptive water contents for several volcanic arcs worldwide. One surprising observation is that parental magmas contain ~ 4 wt% H2O on average at each arc worldwide [1]. Within each arc, the variation from volcano to volcano is from 2 to 6 w% H2O, with few exceptions. The similar averages at different arcs are unexpected given the order of magnitude variations in the concentration of other slab tracers. H2O is clearly different from other tracers, however, being both a major driver of melting in the mantle and a major control of buoyancy and viscosity in the crust. Some process, such as mantle melting or crustal storage, apparently modulates the water content of mafic magmas at arcs. Mantle melting may deliver a fairly uniform product to the Moho, if the wet melt process includes a negative feedback. On the other hand, magmas with variable water content may be generated in the mantle, but a crustal filter may lead to magma degassing up to a common mid-to-upper crustal storage region. Testing between these two end-member scenarios is critical to our understanding of subduction dehydration, global water budgets, magmatic plumbing systems, melt generation and eruptive potential. The Alaska-Aleutian arc is a prime location to explore this fundamental problem in the subduction water cycle, because active volcanoes vary more than elsewhere in the world in parental H2O contents (based on least-degassed, mafic melt inclusions hosted primarily in olivine). For example, Shishaldin volcano taps magma with among the lowest H2O contents globally (~ 2 wt%) and records low pressure crystal fractionation [2], consistent with a shallow magma system (< 1 km bsl). At the other extreme, Augustine volcano is fed by a mafic parent that contains among the highest H2O globally (~ 7 wt%), and has evolved by deep crystal fractionation [2], consistent with a deep magma system (~ 14 km bsl). Do these magmas stall at different depths

  7. Cathodoluminescence study of Mg activation in non-polar and semi-polar faces of undoped/Mg-doped GaN core-shell nanorods.

    PubMed

    Hortelano, V; Martínez, O; Cuscó, R; Artús, L; Jiménez, J

    2016-03-04

    Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanorods grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanorods is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatment. For lower Mg/Ga flow ratios, the annealed nanorods clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanorod shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping.

  8. Fluid simulation of carbon arc plasma

    NASA Astrophysics Data System (ADS)

    Hara, Kentaro; Raitses, Yevgeny; Kaganovich, Igor

    2016-09-01

    An arc discharge using graphite electrodes is known to produce carbon nanomaterials, e.g. nanotubes and fullerenes. In order to understand where and how such nanomaterials are synthesized, the plasma properties inside the arc discharge must be characterized. The mechanism of the carbon arc plasma is as follows. Carbon particles evaporate from the graphite anode, which is mainly heated by the electrons. Carbon atoms and ions condensate and form a deposit on the cathode, from which the electrons are thermionically emitted. A one-dimensional fluid model is developed to study the characteristics of the carbon arc plasma in atmospheric pressures. Sheath models for the anode and cathode are coupled to the fluid simulation to obtain the material temperature and sheath potential. In the model, thermal nonequilibrium is assumed and atomic carbon, dimer, and trimer are considered. A typical operating condition of a carbon arc plasma is discharge voltage of 20 V, discharge current of 60 A, the electron radius of 6 to 12 mm, and background pressure of 500 Torr. Transition from low to high ablation mode is obtained from the simulations with a smaller electrode radius and with a larger discharge current, which agrees with experimental observations. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  9. Cathodic ARC surface cleaning prior to brazing

    SciTech Connect

    Dave, V. R.; Hollis, K. J.; Castro, R. G.; Smith, F. M.; Javernick, D. A.

    2002-01-01

    Surface cleanliness is one the critical process variables in vacuum furnace brazing operations. For a large number of metallic components, cleaning is usually accomplished either by water-based alkali cleaning, but may also involve acid etching or solvent cleaning / rinsing. Nickel plating may also be necessary to ensure proper wetting. All of these cleaning or plating technologies have associated waste disposal issues, and this article explores an alternative cleaning process that generates minimal waste. Cathodic arc, or reserve polarity, is well known for welding of materials with tenacious oxide layers such as aluminum alloys. In this work the reverse polarity effect is used to clean austenitic stainless steel substrates prior to brazing with Ag-28%Cu. This cleaning process is compared to acid pickling and is shown to produce similar wetting behavior as measured by dynamic contact angle experiments. Additionally, dynamic contact angle measurements with water drops are conducted to show that cathodic arc cleaning can remove organic contaminants as well. The process does have its limitations however, and alloys with high titanium and aluminum content such as nickel-based superalloys may still require plating to ensure adequate wetting.

  10. Study on the measurement system of the target polarization characteristics and test

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; Zhu, Yong; Zhang, Su; Duan, Jin; Yang, Di; Zhan, Juntong; Wang, Xiaoman; Jiang, Hui-Lin

    2015-10-01

    The polarization imaging detection technology increased the polarization information on the basis of the intensity imaging, which is extensive application in the military and civil and other fields, the research on the polarization characteristics of target is particularly important. The research of the polarization reflection model was introduced in this paper, which describes the scattering vector light energy distribution in reflecting hemisphere polarization characteristics, the target polarization characteristics test system solutions was put forward, by the irradiation light source, measuring turntable and camera, etc, which illuminate light source shall direct light source, with laser light sources and xenon lamp light source, light source can be replaced according to the test need; Hemispherical structure is used in measuring circumarotate placed near its base material sample, equipped with azimuth and pitching rotation mechanism, the manual in order to adjust the azimuth Angle and high Angle observation; Measuring camera pump works, through the different in the way of motor control polaroid polarization test, to ensure the accuracy of measurement and imaging resolution. The test platform has set up by existing laboratory equipment, the laser is 532 nm, line polaroid camera, at the same time also set the sending and receiving optical system. According to the different materials such as wood, metal, plastic, azimuth Angle and zenith Angle in different observation conditions, measurement of target in the polarization scattering properties of different exposure conditions, implementation of hemisphere space pBRDF measurement.

  11. Study of the effect of scattering from turbid water on the polarization of a laser beam

    NASA Technical Reports Server (NTRS)

    Henderson, R. G.; Hovanlou, A. H.

    1978-01-01

    A Monte Carlo simulation method was used to determine the effect of scattering from turbid water on the polarization of a backscattered beam of laser light. The relationship between the polarization and the type and amount of suspended particulates in the water was investigated.

  12. Polarization study of a supercontinuum light source for different wavelengths through a photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Valle-Atilano, F. J.; Estudillo-Ayala, J. M.; Filoteo-Razo, J. D.; Hernández-Garcia, J. C.; Lauterio-Cruz, J. P.; Jáuregui-Vázquez, D.; Ibarra-Escamilla, B.; Rojas-Laguna, R.; Pottiez, O.; Kuzin, E. A.

    2016-03-01

    In this work we show the changes of polarization at different wavelengths in the end of a photonic crystal fiber (PCF) by means bandpass filters in a supercontinuum light source. A linear and circular polarization was introduced in a piece of PCF, showing the changes of the polarization for each wavelength of each one of the filters from 450 to 700nm. We used a microchip laser as pumping source with wavelength of 532nm and short pulses of 650ps with repetition rate of 5kHz. We obtained a continuous spectrum in the visible spectral region, showing a comparison of the polarization state at the fiber input with respect to polarization state in the fiber output for different wavelengths by rotating the axes of the PCF.

  13. Polarization sensitivity analysis of an earth remote sensing instrument - The MODIS-N phase B study

    NASA Technical Reports Server (NTRS)

    Waluschka, E.; Silverglate, P.; Ftaclas, C.; Turner, A.

    1992-01-01

    Polarization analysis software that employs Jones matrix formalism to calculate the polarization sensitivity of an instrument design was developed at Hughes Danbury Optical Systems. The code is capable of analyzing the full ray bundle at its angles of incidence for each optical surface. Input is based on the system ray trace and the thin film coating design at each surface. The MODIS-N (Moderate Resolution Imaging Spectrometer) system is used to demonstrate that it is possible to meet stringent requirements on polarization insensitivity associated with planned remote sensing instruments. Analysis indicates that a polarization sensitivity less than or equal to 2 percent was achieved in all desired spectral bands at all pointing angles, per specification. Polarization sensitivities were as high as 10 percent in similar remote sensing instruments.

  14. The use of syntaxin chimeras to study polarized protein trafficking in epithelial cells.

    PubMed

    ter Beest, Martin B A

    2008-01-01

    The plasma membrane of epithelial cells has two physically separated membrane domains. This membrane polarization is essential for the function of epithelial cells. It has been well established that different plasma membrane syntaxin forms are expressed in epithelial cells. In addition, these syntaxin forms can have a polarized localization, suggesting that they may play a direct role in the specificity of polarized membrane delivery. To determine the mechanism of the polarized syntaxin localization, we have made several chimeras of syntaxin 3 and 4. This allowed us to identify the protein sequences involved in this polarized localization. Using this technique, we showed that targeting information of syntaxin 3 and 4 is located in the first 30 amino acids.

  15. Polarized Fluorescence Microscopy to Study Cytoskeleton Assembly and Organization in live cells

    PubMed Central

    McQuilken, Molly; Mehta, Shalin B.; Verma, Amitabh; Harris, Grant; Oldenbourg, Rudolf; Gladfelter, Amy S.

    2015-01-01

    The measurement of not only the location but also the organization of molecules in live cells is crucial to understanding diverse biological processes. Polarized light microscopy provides a nondestructive means to evaluate order within subcellular domains. When combined with fluorescence microscopy and GFP-tagged proteins, the approach can reveal organization within specific populations of molecules. This unit describes a protocol for measuring the architectural dynamics of cytoskeletal components using polarized fluorescence microscopy and OpenPolScope open-access software (www.openpolscope.org). The protocol describes installation of linear polarizers or a liquid crystal (LC) universal compensator, calibration of the system, polarized fluorescence imaging, and analysis. The use of OpenPolScope software and hardware allows for reliable, user-friendly image acquisition to measure and analyze polarized fluorescence. PMID:26061244

  16. Effects of Pulse Shape and Polarity on Sensitivity to Cochlear Implant Stimulation: A Chronic Study in Guinea Pigs.

    PubMed

    Macherey, Olivier; Cazals, Yves

    2016-01-01

    Most cochlear implants (CIs) stimulate the auditory nerve with trains of symmetric biphasic pulses consisting of two phases of opposite polarity. Animal and human studies have shown that both polarities can elicit neural responses. In human CI listeners, studies have shown that at suprathreshold levels, the anodic phase is more effective than the cathodic phase. In contrast, animal studies usually show the opposite trend. Although the reason for this discrepancy remains unclear, computational modelling results have proposed that the degeneration of the peripheral processes of the neurons could lead to a higher efficiency of anodic stimulation. We tested this hypothesis in ten guinea pigs who were deafened with an injection of sysomycin and implanted with a single ball electrode inserted in the first turn of the cochlea. Animals were tested at regular intervals between 1 week after deafening and up to 1 year for some of them. Our hypothesis was that if the effect of polarity is determined by the presence or absence of peripheral processes, the difference in polarity efficiency should change over time because of a progressive neural degeneration. Stimuli consisted of charge-balanced symmetric and asymmetric pulses allowing us to observe the response to each polarity individually. For all stimuli, the inferior colliculus evoked potential was measured. Results show that the cathodic phase was more effective than the anodic phase and that this remained so even several months after deafening. This suggests that neural degeneration cannot entirely account for the higher efficiency of anodic stimulation observed in human CI listeners.

  17. Conversion of polar and non-polar algae oil lipids to fatty acid methyl esters with solid acid catalysts--A model compound study.

    PubMed

    Asikainen, Martta; Munter, Tony; Linnekoski, Juha

    2015-09-01

    Bio-based fuels are becoming more and more important due to the depleting fossil resources. The production of biodiesel from algae oil is challenging compared to terrestrial vegetable oils, as algae oil consists of polar fatty acids, such as phospholipids and glycolipids, as well as non-polar triglycerides and free fatty acids common in vegetable oils. It is shown that a single sulphonated solid acid catalyst can perform the esterification and transesterification reactions of both polar and non-polar lipids. In mild reaction conditions (60-70 °C) Nafion NR50 catalyst produces methyl palmitate (FAME) from the palmitic acid derivatives of di-, and tri-glyceride, free fatty acid, and phospholipid with over 80% yields, with the glycolipid derivative giving nearly 40% yields of FAME. These results demonstrate how the polar and non-polar lipid derivatives of algal oil can be utilised as feedstocks for biodiesel production with a single catalyst in one reaction step.

  18. A comparative study of the optical pulsations in the intermediate polars

    NASA Astrophysics Data System (ADS)

    Welsh, William F.; Martell, Phillip J.

    1996-10-01

    An attempt is made to assemble all known published measurements of the optical spectrum of the pulsations in the intermediate polar stars, and to convert these measurements to an absolute flux scale for the purpose of examining similarities and correlations among this class of cataclysmic variables. By using only absolute amplitudes (not relative or fractional amplitudes), we may investigate the intrinsic nature of the pulsations. For all systems studied, a power law is able to provide a good fit to the pulse spectrum. With the exception of DQ Her itself, all the pulses are intrinsically blue, generally declining monotonically with wavelength. We find no universal features common to all systems, not do we find any strong correlations. For some systems a blackbody can adequately fit the data, and from these fits we derive estimates for the temperatures and areas of the pulse-emitting region. For the two cases where data are available, the sideband pulse spectra are flatter in their energy distribution than the spin pulse spectra, lending credibility to the belief that they are the result of reprocessing. Although not a sideband pulse, the pulse in DQ Her itself does come from reprocessing, and from our blackbody fit we estimate that between 6 and 23 per cent of the disc area is involved in the reprocessing. We speculate that in many of the intermediate polars, optically thin emission should be able to provide a good fit to the pulse spectrum; indeed, for those spectra whose slope is bluer than the Rayleigh-Jeans slope, this is the only simple and plausible emission mechanism.

  19. Water versus acetonitrile coordination to uranyl. Density functional study of cooperative polarization effects in solution.

    PubMed

    Bühl, Michael; Sieffert, Nicolas; Chaumont, Alain; Wipff, Georges

    2011-01-03

    Optimizations at the BLYP and B3LYP levels are reported for mixed uranyl-water/acetonitrile complexes [UO(2)(H(2)O)(5-n)(MeCN)(n)](2+) (n = 0-5), in both the gas phase and a polarizable continuum modeling acetonitrile. Car-Parrinello molecular dynamics (CPMD) simulations have been performed for these complexes in the gas phase, and for selected species (n = 0, 1, 3, 5) in a periodic box of liquid acetonitrile. According to structural and energetic data, uranyl has a higher affinity for acetonitrile than for water in the gas phase, in keeping with the higher dipole moment and polarizability of acetonitrile. In acetonitrile solution, however, water is the better ligand because of specific solvation effects. Analysis of the dipole moment of the coordinated water molecule in [UO(2)(H(2)O)(MeCN)(4)](2+) reveals that the interaction with the second-shell solvent molecules (through fairly strong and persistent O-H···N hydrogen bonds) causes a significant increase of this dipole moment (by more than 1 D). This cooperative polarization of water reinforces the uranyl-water bond as well as the water solvation via strengthened (UO(2))OH(2)···NCMe hydrogen bonds. Such cooperativity is essentially absent in the acetonitrile ligands that make much weaker (UO(2))NCMe···NCMe hydrogen bonds. Beyond the uranyl case, this study points to the importance of cooperative polarization effects to enhance the M(n+) ion affinity for water in condensed phases involving M(n+)-OH(2)···A fragments, where A is a H-bond proton acceptor and M(n+) is a hard cation.

  20. Molecular hydraulic properties of montmorillonite: a polarized fourier transform infrared spectroscopic study.

    PubMed

    Amarasinghe, Priyanthi M; Katti, Kalpana S; Katti, Dinesh R

    2008-12-01

    Understanding the rates at which fluid flows into clay interlayers at the molecular level is fundamental to designing an effective clay barrier system. In this work, molecular interactions at the Na-montmorillonite (MMT)-water interface, emphasizing the flow properties of the clay interlayer, have been studied at the molecular and nanoscale level using polarized Fourier transform infrared (FT-IR) spectroscopic and X-ray diffraction (XRD) techniques. Clay-water slurries were smeared on inert gold-coated metal substrates for FT-IR experiments and slurries were smeared on quartz plates for XRD experiments. By analyzing the O-H stretching and H-O-H bending vibrations in clay slurries, it was concluded that the molecular behavior of interlayer water is significantly different from the molecular behavior of bulk water. With increasing clay-water interaction time, it was also seen that the Si-O stretching bands of clay are being significantly altered by the water molecules in the interlayer. Using these spectroscopic techniques we have estimated the time required for water to flow into the clay interlayer. Further, by analyzing the particle size of the clay using atomic force microscopy (AFM) imaging, we were able to estimate the flow velocity of the water in the clay interlayer. This velocity is found to be 3.23 x 10(-9) cm/s. This flow velocity was found to be of the same order of magnitude as the hydraulic conductivity of smectite-type clay reported elsewhere. Also described in this work is the correct positioning of the Si-O out-of-plane vibration band of MMT at the two-layer saturation level in the interlayer. This band was only observed in p-polarized spectra at 1211 cm(-1). Thus, we attribute this band to the Si-O out-of-plane vibration band.

  1. Aggregate dust model to study the polarization properties of comet C/1996 B2 Hyakutake

    NASA Astrophysics Data System (ADS)

    Das, Himadri Sekhar; Suklabaidya, Abinash; Majumder, Saonli Datta; Sen, Asoke Kumar

    2010-04-01

    The observed linear polarization data of comet Hyakutake are studied at wavelengths λ = 0.365 μm, λ = 0.485 μm and 0.684μm through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate aggregates of 128 spherical monomers. We first found that the size parameter of the monomer, x ~ 1.56-1.70, turned out to be the most suitable which provides the best fits to the observed dust scattering properties at three wavelengths: λ = 0.365 μm, 0.485 μm and 0.684 μm. Thus, the effective radius of the aggregate (r) lies in the range 0.45 μm <= r <= 0.49 μm at λ = 0.365 μm 0.60 μm <= r <= 0.66 μm at λ = 0.485 μm and 0.88 μm <= r <= 0.94 μm at λ = 0.684 μm. Now using superposition t-matrix code and the power-law size distribution, n(r) ~ r-3, the best-fitting values of complex refractive indices are calculated for the observed polarization data at the above three wavelengths. The best-fitting complex refractive indices (n, k) are found to be (1.745, 0.095) at λ = 0.365 μm, (1.743, 0.100) at λ = 0.485 μm and (1.695, 0.100) at λ = 0.684 μm. The refractive indices derived from the present analysis correspond to a mixture of both silicates and organics, which are in good agreement with the in situ measurement of comets by different spacecraft.

  2. Controlling Arc Length in Plasma Welding

    NASA Technical Reports Server (NTRS)

    Iceland, W. F.

    1986-01-01

    Circuit maintains arc length on irregularly shaped workpieces. Length of plasma arc continuously adjusted by control circuit to maintain commanded value. After pilot arc is established, contactor closed and transfers arc to workpiece. Control circuit then half-wave rectifies ac arc voltage to produce dc control signal proportional to arc length. Circuit added to plasma arc welding machines with few wiring changes. Welds made with circuit cleaner and require less rework than welds made without it. Beads smooth and free of inclusions.

  3. Nonlinear identification of the total baroreflex arc.

    PubMed

    Moslehpour, Mohsen; Kawada, Toru; Sunagawa, Kenji; Sugimachi, Masaru; Mukkamala, Ramakrishna

    2015-12-15

    The total baroreflex arc [the open-loop system relating carotid sinus pressure (CSP) to arterial pressure (AP)] is known to exhibit nonlinear behaviors. However, few studies have quantitatively characterized its nonlinear dynamics. The aim of this study was to develop a nonlinear model of the sympathetically mediated total arc without assuming any model form. Normal rats were studied under anesthesia. The vagal and aortic depressor nerves were sectioned, the carotid sinus regions were isolated and attached to a servo-controlled piston pump, and the AP and sympathetic nerve activity (SNA) were measured. CSP was perturbed using a Gaussian white noise signal. A second-order Volterra model was developed by applying nonparametric identification to the measurements. The second-order kernel was mainly diagonal, but the diagonal differed in shape from the first-order kernel. Hence, a reduced second-order model was similarly developed comprising a linear dynamic system in parallel with a squaring system in cascade with a slower linear dynamic system. This "Uryson" model predicted AP changes 12% better (P < 0.01) than a linear model in response to new Gaussian white noise CSP. The model also predicted nonlinear behaviors, including thresholding and mean responses to CSP changes about the mean. Models of the neural arc (the system relating CSP to SNA) and peripheral arc (the system relating SNA to AP) were likewise developed and tested. However, these models of subsystems of the total arc showed approximately linear behaviors. In conclusion, the validated nonlinear model of the total arc revealed that the system takes on an Uryson structure.

  4. Nonlinear identification of the total baroreflex arc

    PubMed Central

    Moslehpour, Mohsen; Kawada, Toru; Sunagawa, Kenji; Sugimachi, Masaru

    2015-01-01

    The total baroreflex arc [the open-loop system relating carotid sinus pressure (CSP) to arterial pressure (AP)] is known to exhibit nonlinear behaviors. However, few studies have quantitatively characterized its nonlinear dynamics. The aim of this study was to develop a nonlinear model of the sympathetically mediated total arc without assuming any model form. Normal rats were studied under anesthesia. The vagal and aortic depressor nerves were sectioned, the carotid sinus regions were isolated and attached to a servo-controlled piston pump, and the AP and sympathetic nerve activity (SNA) were measured. CSP was perturbed using a Gaussian white noise signal. A second-order Volterra model was developed by applying nonparametric identification to the measurements. The second-order kernel was mainly diagonal, but the diagonal differed in shape from the first-order kernel. Hence, a reduced second-order model was similarly developed comprising a linear dynamic system in parallel with a squaring system in cascade with a slower linear dynamic system. This “Uryson” model predicted AP changes 12% better (P < 0.01) than a linear model in response to new Gaussian white noise CSP. The model also predicted nonlinear behaviors, including thresholding and mean responses to CSP changes about the mean. Models of the neural arc (the system relating CSP to SNA) and peripheral arc (the system relating SNA to AP) were likewise developed and tested. However, these models of subsystems of the total arc showed approximately linear behaviors. In conclusion, the validated nonlinear model of the total arc revealed that the system takes on an Uryson structure. PMID:26354845

  5. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matthew J.; Le Friant, Anne; Ishizuka, Osamu; Stroncik, Nicole; Adachi, Tatsuya; Aljahdali, Mohammed; Boudon, Georges; Breitkreuz, Christoph; Fraass, Andrew; Fujinawa, Akihiko; Hatfield, Robert; Jutzeler, Martin; Kataoka, Kyoko; Lafuerza, Sara; Maeno, Fukashi; Martinez-Colon, Michael; McCanta, Molly; Morgan, Sally; Palmer, Martin R.; Saito, Takeshi; Slagle, Angela; Stinton, Adam J.; Subramanyam, K. S. V.; Tamura, Yoshihiko; Talling, Peter J.; Villemant, Benoit; Wall-Palmer, Deborah; Wang, Fei

    2012-08-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present-day volcanism is confined to the region with the highest heat flow.

  6. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, M.; Hornbach, M. J.; Le Friant, A.; Ishizuka, O.; Stroncik, N.

    2012-12-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  7. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matt; Le Friant, Anne; Ishizuka, Osamu

    2014-05-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  8. Oceanic, island arc, and back-arc remnants into eastern Kamchatka accretionary complexes

    SciTech Connect

    Fedorchuk, A.V.; Vishnevskaya, V.S.; Izvekov, I.N. )

    1990-06-01

    The Kamchatsky Mts. accretionary complex in the Eastern Kamchatka orogenic belt was studied for identification of the oceanic and suprasubduction components into accretionary wedges. That complex is divided into two tectonic units. The Lower unit is formed sedimentary and tectonic melanges containing arc-related components (Late Senonian volcaniclastics and boninitic gabbro) and oceanic fragments (Fe-Ti-tholeiites, ocean island basalts, and pelagic sediments of Valanginian to Turonian age). The Upper unit consists of ductile deformed oceanic cumulates from troctolites to Fe-Ti-gabbro, 151 to 172 Ma, which are intruded MORB-like diabases with suprasubduction characteristics, 122 to 141 Ma, and are overlain by basalts similar to latter. The Lower and Upper units are separated by a SW-dipping thrust, which is related by an ophiolitoclastic olistostrome of Late Campanian to Early Maestrichtian age. Both units are covered by Paleocene authoclastic deposits. They are all thrusted over the early Neogene island arc complex, 16 to 20 Ma. The Lower unit of the Kamchatsky Mys accretionary complex was originated in a shear zone between a Late Cretaceous island arc and an Early Cretaceous oceanic plate. The Upper unit represents a Jurassic oceanic remnant that formed a basement of Early Cretaceous back-arc or fore-arc basin. Both units were superposed in the latest Cretaceous. The Kamchatsky Mys accretionary complex was emplaced into the Eastern Kamchatka orogenic belt during late Neogene by collision of the early Neogene island arc.

  9. The loss of material from the cathode of metal arcs

    NASA Technical Reports Server (NTRS)

    Seeliger, R.; Wulfhekel, H.

    1985-01-01

    A study was made of the effect of arc length, cathode thickness, current strength, gas pressure and the chemical nature of the cathode material and filling gases upon the material loss from Cu, Fe, and Ag cathodes in arcs. The results show that the analysis of the phenomenon is complex and the energy balance is difficult to formulate.

  10. Models for Jupiter's decametric arcs

    NASA Technical Reports Server (NTRS)

    Warwick, J. W.

    1981-01-01

    Arc-shaped structures that dominate Jupiter's decametric emission are discussed in terms of a magnetic fine structure. The sequence of arcs manifest the occurence of widespread fine structures similar to the white ovals on Jupiter's visible surface. An arc concave toward increasing time occurs at the east limb passage, and an arc convex occurs at the west limb passage, which is consistent with the early source producing vertex early arcs, and the late source producing vertex late arcs. Due to the geometry of the Io plasma torus (IPT) which is arranged so that Io skims the northern surface of the IPT, for any connection between Io and Jupiter's surface that involves Alfven waves, the propagation time, the refraction and the directional defocusing of these waves must be strongly influenced by the amount of Alfven wave path length between the instantaneous position of Io and the surface of the IPT.

  11. POLAR NETWORK INDEX AS A MAGNETIC PROXY FOR THE SOLAR CYCLE STUDIES

    SciTech Connect

    Priyal, Muthu; Banerjee, Dipankar; Ravindra, B.; Singh, Jagdev; Karak, Bidya Binay; Muñoz-Jaramillo, Andrés; Choudhuri, Arnab Rai E-mail: dipu@iiap.res.in

    2014-09-20

    The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot cycle. We have direct systematic measurements of the Sun's polar magnetic field only from about the mid-1970s. There are, however, indirect proxies which give us information about this field at earlier times. The Ca-K spectroheliograms taken at the Kodaikanal Solar Observatory during 1904-2007 have now been digitized with 4k × 4k CCD and have higher resolution (∼0.86 arcsec) than the other available historical data sets. From these Ca-K spectroheliograms, we have developed a completely new proxy (polar network index, hereafter PNI) for the Sun's polar magnetic field. We calculate PNI from the digitized images using an automated algorithm and calibrate our measured PNI against the polar field as measured by the Wilcox Solar Observatory for the period 1976-1990. This calibration allows us to estimate the polar fields for the earlier period up to 1904. The dynamo calculations performed with this proxy as input data reproduce reasonably well the Sun's magnetic behavior for the past century.

  12. Polar Network Index as a Magnetic Proxy for the Solar Cycle Studies

    NASA Astrophysics Data System (ADS)

    Priyal, Muthu; Banerjee, Dipankar; Karak, Bidya Binay; Muñoz-Jaramillo, Andrés; Ravindra, B.; Choudhuri, Arnab Rai; Singh, Jagdev

    2014-09-01

    The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot cycle. We have direct systematic measurements of the Sun's polar magnetic field only from about the mid-1970s. There are, however, indirect proxies which give us information about this field at earlier times. The Ca-K spectroheliograms taken at the Kodaikanal Solar Observatory during 1904-2007 have now been digitized with 4k × 4k CCD and have higher resolution (~0.86 arcsec) than the other available historical data sets. From these Ca-K spectroheliograms, we have developed a completely new proxy (polar network index, hereafter PNI) for the Sun's polar magnetic field. We calculate PNI from the digitized images using an automated algorithm and calibrate our measured PNI against the polar field as measured by the Wilcox Solar Observatory for the period 1976-1990. This calibration allows us to estimate the polar fields for the earlier period up to 1904. The dynamo calculations performed with this proxy as input data reproduce reasonably well the Sun's magnetic behavior for the past century.

  13. Corrosion Behavior of Pulsed Gas Tungsten Arc Weldments in Power Plant Carbon Steel

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    Welding plays an essential role in fabrication of components such as boiler drum, pipe work, heat exchangers, etc., used in power plants. Gas tungsten arc welding (GTAW) is mainly used for welding of boiler components. Pulsed GTAW is another process widely used where high quality and precision welds are required. In all arc-welding processes, the intense heat produced by the arc and the associated local heating and cooling lead to varied corrosion behavior and several metallurgical phase changes. Since the occurrence of corrosion is due to electrochemical potential gradient developed in the adjacent site of a weld metal, it is proposed to study the effects of welding on the corrosion behavior of these steels. This paper describes the experimental work carried out to evaluate and compare corrosion and its inhibition in SA 516 Gr.70 carbon steel by pulsed GTAW process in HCl 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 made at room temperature (R.T.) and at 100 °C. Electrochemical polarization techniques such as Tafel line extrapolation (Tafel), linear polarization resistance (LPR), and ac impedance method 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, surface characterization, and morphology using SEM and XRD studies have been made on samples exposed at 100 °C in order to highlight the nature and extent of film formation.

  14. Fabrication of a Lateral Polarity GaN MESFET: An Exploratory Study

    DTIC Science & Technology

    2007-06-27

    the sheet resistance between Ga- polar and mixed-polar GaN films. Highly resistive Ga-polar GaN is advantageous in optoelectronic and electronic device...re si st an ce [ M Ω /s q. ] 108642 2nd nitridation time [min] (b) Figure 5. Sheet resistance of GaN grown on AlN region for the first set of LT...AlN layers deposited for 4, 6, and 8 min. 2nd nitridation time after ex-situ process was kept at 950°C for 1 min. (b) Sheet resistance of GaN grown on

  15. Polarization studies of Zeeman affected spectral lines using the MSFC magnetograph

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, K. S.; West, E. A.

    1990-01-01

    The Marshall Space Flight Center (MSFC) vector magnetograph records polarization images of absorption lines that are sensitive to magnetic fields. A method is presented for analyzing the Stokes spectral-line profiles of a photospheric Fe I absorption line (5250.2 A) which is influenced by the Zeeman effect. Using nonlinear least-square optimization, the observed Stokes profiles are compared with those generated from the theoretical solution of the polarized radiative transfer equations. The optimization process accounts for the spectral convolution of the source and the MSFC vector magnetograph. The resulting physical properties of the active region producing the polarized light are discussed.

  16. Nuclear polarization study: new frontiers for tests of QED in heavy highly charged ions.

    PubMed

    Volotka, Andrey V; Plunien, Günter

    2014-07-11

    A systematic investigation of the nuclear polarization effects in one- and few-electron heavy ions is presented. The nuclear polarization corrections in the zeroth and first orders in 1/Z are evaluated to the binding energies, the hyperfine splitting, and the bound-electron g factor. It is shown that the nuclear polarization contributions can be substantially canceled simultaneously with the rigid nuclear corrections. This allows for new prospects for probing the QED effects in a strong electromagnetic field and the determination of fundamental constants.

  17. Joan of Arc.

    PubMed

    Foote-Smith, E; Bayne, L

    1991-01-01

    For centuries, romantics have praised and historians and scientists debated the mystery of Joan of Arc's exceptional achievements. How could an uneducated farmer's daughter, raised in harsh isolation in a remote village in medieval France, have found the strength and resolution to alter the course of history? Hypotheses have ranged from miraculous intervention to creative psychopathy. We suggest, based on her own words and the contemporary descriptions of observers, that the source of her visions and convictions was in part ecstatic epileptic auras and that she joins the host of creative religious thinkers suspected or known to have epilepsy, from St. Paul and Mohammed to Dostoevsky, who have changed western civilization.

  18. APPARATUS FOR ARC WELDING

    DOEpatents

    Lingafelter, J.W.

    1960-04-01

    An apparatus is described in which a welding arc created between an annular electrode and a workpiece moves under the influence of an electromagnetic field about the electrode in a closed or annular path. This mode of welding is specially suited to the enclosing of nuclear-fuel slugs in a protective casing. For example, a uranium slug is placed in an aluminum can, and an aluminum closure is welded to the open end of the can along a closed or annular path conforming to the periphery of the end closure.

  19. Early osseointegration of implants with cortex-like TiO2 coatings formed by micro-arc oxidation: A histomorphometric study in rabbits.

    PubMed

    Zhou, Hong-Zhi; Li, Ya-da; Liu, Lin; Chen, Xiao-Dong; Wang, Wei-Qiang; Ma, Guo-Wu; Su, Yu-Cheng; Qi, Min; Shi, Bin

    2017-02-01

    In our previous studies, a novel cortex-like TiO2 coating was prepared on Ti surface through micro-arc oxidation (MAO) by using sodium tetraborate as electrolyte, and the effects of the coating on cell attachment were testified. This study aimed to investigate the effects of this cortex-like MAO coating on osseointegration. A sand-blasting and acid-etching (SLA) coating that has been widely used in clinical practice served as control. Topographical and chemical characterizations were conducted by scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, contact angle meter, and step profiler. Results showed that the cortex-like coating had microslots and nanopores and it was superhydrophilic, whereas the SLA surface was hydrophobic. The roughness of MAO was similar to that of SLA. The MAO and SLA implants were implanted into the femoral condyles of New Zealand rabbits to evaluate their in-vivo performance through micro-CT, histological analysis, and fluorescent labeling at the bone-implant interface four weeks after surgery. The micro-CT showed that the bone volume ratio and mean trabecular thickness were similar between MAO and SLA groups four weeks after implantation. Histological analysis and fluorescent labeling showed no significant differences in the bone-implant contact between the MAO and SLA surfaces. It was suggested that with micro/nanostructure and superhydrophilicity, the cortex-like MAO coating causes excellent osseointegration, holding a promise of an application to implant modification.

  20. On the distribution and bonding environment of Zn and Fe in glasses containing electric arc furnace dust: a mu-XAFS and mu-XRF study.

    PubMed

    Pinakidou, F; Katsikini, M; Paloura, E C; Kavouras, P; Kehagias, Th; Komninou, Ph; Karakostas, Th; Erko, A

    2007-04-02

    We apply synchrotron radiation assisted X-ray fluorescence (SR-XRF), SR-XRF mapping as well as micro- and conventional X-ray absorption fine structure (mu-XAFS and XAFS) spectroscopies in order to study the bonding environment of Fe and Zn in vitrified samples that contain electric arc furnace dust from metal processing industries. The samples are studied in the as-cast state as well as after annealing at 900 degrees C. The SR-XRF results demonstrate that annealing does not induce any significant changes in the distribution of either Fe or Zn, in both the as-cast and annealed glasses. The mu-XAFS spectra recorded at the Fe-K and Zn-K edges reveal that the structural role of both Fe and Zn remains unaffected by the annealing procedure. More specifically, Fe forms both FeO(6) and FeO(4) polyhedra, i.e. acts as an intermediate oxide while Zn occupies tetrahedral sites.

  1. Hybrid QM/MM study of FMO complex with polarized protein-specific charge

    PubMed Central

    Jia, Xiangyu; Mei, Ye; Zhang, John Z.H.; Mo, Yan

    2015-01-01

    The Fenna-Matthews-Olson (FMO) light-harvesting complex is now one of the primary model systems for the study of excitation energy transfer (EET). However, the mechanism of the EET in this system is still controversial. In this work, molecular dynamics simulations and the electrostatic-embedding quantum-mechanics/molecular-mechanics single-point calculations have been employed to predict the energy transfer pathways utilizing the polarized protein-specific charge (PPC), which provides a more realistic description of Coulomb interaction potential in the protein than conventional mean-field charge scheme. The recently discovered eighth pigment has also been included in this study. Comparing with the conventional mean-field charges, more stable structures of FMO complex were found under PPC scheme during molecular dynamic simulation. Based on the electronic structure calculations, an exciton model was constructed to consider the couplings during excitation. The results show that pigments 3 and 4 dominate the lowest exciton levels whereas the highest exciton level are mainly constituted of pigments 1 and 6. This observation agrees well with the assumption based on the spatial distribution of the pigments. Moreover, the obtained spectral density in this study gives a reliable description of the diverse local environment embedding each pigment. PMID:26611739

  2. An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization

    PubMed Central

    Erbel, Christian; Rupp, Gregor; Helmes, Christian M.; Tyka, Mirjam; Linden, Fabian; Doesch, Andreas O.; Katus, Hugo A.; Gleissner, Christian A.

    2013-01-01

    Monocyte-derived macrophages represent an important cell type of the innate immune system. Mouse models studying macrophage biology suffer from the phenotypic and functional differences between murine and human monocyte-derived macrophages. Therefore, we here describe an in vitro model to generate and study primary human macrophages. Briefly, after density gradient centrifugation of peripheral blood drawn from a forearm vein, monocytes are isolated from peripheral blood mononuclear cells using negative magnetic bead isolation. These monocytes are then cultured for six days under specific conditions to induce different types of macrophage differentiation or polarization. The model is easy to use and circumvents the problems caused by species-specific differences between mouse and man. Furthermore, it is closer to the in vivo conditions than the use of immortalized cell lines. In conclusion, the model described here is suitable to study macrophage biology, identify disease mechanisms and novel therapeutic targets. Even though not fully replacing experiments with animals or human tissues obtained post mortem, the model described here allows identification and validation of disease mechanisms and therapeutic targets that may be highly relevant to various human diseases. PMID:23792882

  3. The guanidine and benzoic acid (1:1) complex. The polarized vibrational studies and theoretical investigations

    NASA Astrophysics Data System (ADS)

    Drozd, M.; Dudzic, D.

    2015-03-01

    The structure of guanidinium benzoate was discovered by Silva et al. On the basis of these X-ray crystallographic studies the detailed DFT investigation are performed. According to this result the infrared spectrum for one theoretical molecule was calculated. On the basis of potential energy distribution (PED) analysis the clear-cut assignments of observed bands were performed. For the calculated molecule with energy minimum the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were obtained. The energy difference between HOMO and LUMO was analyzed. According to theoretical calculations the direction of dipole moments (TDM) for bands observed in infrared spectra are analyzed. Verification of theoretical TDM behaviors is performed on the basis of experimental polarized specular reflection infrared spectra. The detailed assignments of observed bands is presented. Both theoretical and experimental spectra are compared. Crucial role of three different hydrogen bonds is studied in detail. Additionally, on the basis of differential scanning calorimetric