WorldWideScience

Sample records for plasma sheath phenomena

  1. Comprehensive Study of Plasma-Wall Sheath Transport Phenomena

    Science.gov (United States)

    2016-10-26

    temperature is always well below that expected for significant thermionic emission from LaB6, and the heat flux from the plasma is also low given the order...measurements from HET materials is their low electrical conductivity. In a typical electron emission study, a primary electron beam is focused onto to...Transition Controlled by Secondary Electron Emission at Low Gas Pressure,” 67th Annual Gaseous Electronics Conference, Raleigh, NC, November 2-7, 2014

  2. Communication through Plasma Sheaths

    CERN Document Server

    Korotkevich, A O; Zakharov, V E

    2007-01-01

    We wish to transmit messages to and from a hypersonic vehicle around which a plasma sheath has formed. For long distance transmission, the signal carrying these messages must be necessarily low frequency, typically 2 GHz, to which the plasma sheath is opaque. The idea is to use the plasma properties to make the plasma sheath appear transparent.

  3. Dusty Sheaths in Magnetized Plasmas

    Institute of Scientific and Technical Information of China (English)

    Yu. I. Chutov; O. Yu. Kravchenko; S. Masuzaki; A. Sagara; R. D. Smirnov; Yu. Tomita

    2004-01-01

    Parameters of self-consistent magnetized dusty sheaths are investigated using computer simulations of a temporal evolution of one-dimensional slab plasma with dust particles. The evolution is caused by a collection of electrons and ions by both a wall (electrode) and dust particles, which are initially immersed into plasma and distributed in front of the electrode. Obtained results show the existence of oscillations of a self-consistent potential in magnetized dusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and create additional sheaths close to a boundary of dust particles. The magnetic field does not influence on the dust particle charge.

  4. Revisiting the plasma sheath - dust in plasma sheath

    CERN Document Server

    Das, G C; Bora, M P

    2015-01-01

    In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of lunar plasma sheath, though the results obtained in this work could be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisso...

  5. Sheath Structures of Strongly Electronegative Plasmas

    Institute of Scientific and Technical Information of China (English)

    段萍; 王正汹; 王文春; 刘金远; 刘悦; 王晓钢

    2005-01-01

    The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.

  6. Electron Sheaths: The Outsized Influence of Positive Boundaries on Plasmas

    CERN Document Server

    Yee, Benjamin T; Baalrud, Scott D; Barnat, Edward V; Hopkins, Matthew M

    2015-01-01

    Electron sheaths form near the surface of objects biased more positive than the plasma potential, such as in the electron saturation region of a Langmuir probe trace. They are commonly thought to be local phenomena that collect the random thermal electron current, but do not otherwise perturb a plasma. Here, using experiments, particle-in-cell simulations and theory, it is shown that under low temperature plasma conditions ($T_e \\gg T_i$) electron sheaths are far from local. Instead, a long presheath region extends into the plasma where electrons are accelerated via a pressure gradient to a flow speed exceeding the electron thermal speed at the sheath edge. This fast flow is found to excite instabilities, causing strong fluctuations near the sheath edge.

  7. Theory of sheath in a collisional multi-component plasma

    Indian Academy of Sciences (India)

    M K Mahanta; K S Goswami

    2001-04-01

    The aim of this brief report is to study the behaviour of sheath structure in a multicomponent plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.

  8. Sheath Characteristic in ECR Plasma Nitriding

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The sheath plasma characteristics changing with the negative bias applied to the substrate during electron cyclotron resonance plasma nitriding are studied. The sheath characteristics obtained by a Langmuir single probe and an ion energy analyzer show that when the negative bias applied to the substrate is increasing, the most probable energy of ions in the sheath and the full width of half maximum of ions energy distribution increase, the thickness of the sheath also increases, whereas the saturation current of ion decreases. It has been found from the optical emission spectrum that there are strong lines of N2 and N2+. Based on our experiment results the mechanism of plasma nitriding is discussed.

  9. Laser Diagnostic Method for Plasma Sheath Potential Mapping

    Science.gov (United States)

    Walsh, Sean P.

    fluorescence intensity and collection efficiency, and optimize the signal processing equipment. Doing so has allowed for a spatial resolution of 60 microns and a maximum depth of measurement of 2 mm depending on conditions. Sheaths surrounding common Hall thruster ceramics at various plasma conditions were measured in an attempt to determine the effect of SEE and a numerical analysis of the plasma-wall interactions was conducted to further understand the phenomena and compare against obtained data.

  10. Studies of anode sheath phenomena in a Hall-effect thruster discharge

    Science.gov (United States)

    Dorf, Leonid

    2005-10-01

    Crossed electric and magnetic fields devices (plasma thrusters, magnetrons, coaxial plasma guns, plasma opening switches, etc.) are routinely used for plasma production and in other applications. Despite these numerous applications, the fundamental anode sheath phenomena in many of these devices have received surprisingly little experimental scrutiny. We chose a Hall-effect thruster (HT) discharge for our study of the anode sheath. It has been typically assumed in most fluid models of an HT that its steady-state operation requires the presence of a negative anode fall (electron-repelling anode sheath). Such anode fall behavior, opposite to that in typical glow discharges or hollow-anode plasma sources, is the result of a relatively high degree of ionization in HTs, achieved by applying a radial magnetic field transverse to the direction of the discharge current. Our data from non-perturbing probe measurements showed for the first time that the anode fall in HTs can be either negative or positive (electron-attracting anode sheath), depending on conditions at the anode surface. The path for current closure to the anode turns out to be quite subtle in HTs. This path determines the mechanism of the anode fall formation. In varying the magnetic field topology in the channel from a more uniform to a cusp-like one, we uncover intriguing results. For cusp configurations, in which the radial magnetic field changes polarity somewhere along the channel, the anode fall is positive, whereas it is negative for a more uniform field. This polarity difference could be attributed to the decreased electron mobility across the magnetic field in the cusp-like configuration. Our theoretical modeling of the anode sheath correlates well with the experimental results in describing how the magnitude of the sheath varies with the discharge voltage and mass flow rate.

  11. Sheath Structure of an Electronegative Plasma

    Institute of Scientific and Technical Information of China (English)

    王正汹; 刘金远; 邹秀; 刘悦; 王晓钢

    2003-01-01

    We investigate the sheath structure of an electronegative plasma at steady state with the assumptions of cold positive ions and hot negative ions. The modified Bohm criterion is obtained with the Sagdeev potential by introducing a modified ion sound velocity. At the same time the electric potential, net space charge and particles densities in the sheath are analysed in several cases of different temperature ratios of electrons to negative ions and different density ratios of negative ions to positive ions.

  12. How to Patch Active Plasma and Collisionless Sheath: Pragmatical Guide

    Science.gov (United States)

    Shneider, Mikhail N.; Kaganovich, Igor D.

    2002-11-01

    Most plasmas have very thin sheath compared with plasma dimension. This necessitates separate calculation of plasma and sheath. Bohm criterion provides boundary condition for calculation of plasma profiles. To calculate sheath properties a value of electric field at the plasma-sheath interface has to be specified in addition to Bohm criterion. The value of the boundary electric field and robust procedure to approximately patch plasma and collisionless sheath with a very good accuracy is reported. Additional information on the subject will be posted in http://www.pppl.gov/pub/report/2002/ http://arxiv.org/abs/physics/ Work supported by the Princeton Plasma Physics Laboratory through a University Research Support Program.

  13. Modeling of polarization phenomena due to RF sheaths and electron beams in magnetized plasma; Modelisation de phenomenes de polarisation par des gaines rf et des faisceaux electroniques dans un plasma magnetise

    Energy Technology Data Exchange (ETDEWEB)

    Faudot, E

    2005-07-01

    This work investigates the problematic of hot spots induced by accelerated particle fluxes in tokamaks. It is shown that the polarization due to sheaths in the edge plasma in which an electron beam at a high level of energy is injected, can reach several hundreds volts and thus extend the deposition area. The notion of obstructed sheath is introduced and explains the acceleration of energy deposition by the decreasing of the sheath potential. Then, a 2-dimensional fluid modeling of flux tubes in front of ICRF antennae allows us to calculate the rectified potentials taking into account RF polarization currents transverse to magnetic field lines. The 2-dimensional fluid code designed validates the analytical results which show that the DC rectified potential is 50% greater with polarization currents than without. Finally, the simultaneous application of an electron beam and a RF potential reveals that the potentials due to each phenomenon are additives when RF potential is much greater than beam polarization. The density depletion of polarized flux tubes in 2-dimensional PIC (particles in cells) simulations is characterized but not yet explained. (author)

  14. Sheath Criterion for a Collisional Electronegative Plasma Sheath in an Applied Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    邹秀; 刘惠平; 邱明辉; 孙骁航

    2011-01-01

    The sheath criterion for a collisional electronegative plasma sheath in an applied magnetic field is investigated.It is assumed that the system consists of hot electrons,hot negative ions and cold positive ions.The effect of an applied magnetic field on the sheath criterion is discussed.The results reveal that the magnetic field has effects on both the upper and lower limits,which cause the range of the ion Mach number to increase.In addition,the numerical calculations of the electronegative plasma sheath are carried out to demonstrate the effects of sheath criterion on the characteristics of the sheath.%The sheath criterion for a collisioned electronegative plasma sheath in an applied magnetic Geld is investigated. It is assumed that the system consists of hot electrons, hot negative ions and cold positive ions. The effect of an applied magnetic Reid on the sheath criterion is discussed. The results reveal that the magnetic field has effects on both the upper and lower limits, which cause the range of the ion Mach number to increase. In addition, the numerical calculations of the electronegative plasma sheath are carried out to demonstrate the effects of sheath criterion on the characteristics of the sheath.

  15. Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique

    OpenAIRE

    Ensinger, Wolfgang

    1996-01-01

    Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique / B. Rauschenbach ... - In: Nuclear instruments and methods in physics research. B. 113. 1996. S. 266-269

  16. Characteristics of single and dual radio-frequency (RF) plasma sheaths

    Institute of Scientific and Technical Information of China (English)

    DAI Zhong-ling; WANG You-nian

    2006-01-01

    The characteristics of radio-frequency(RF)plasma sheaths have been topics of much scientific study for decades,and have also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS),as well as in the study of physical phenomena in dusty plasmas.The sheaths behave special properties under various situations where they can be treated as collisionless or collisional,single- or dual-RF,one- or two-dimensional (1D or 2D) sheaths,etc.This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations and Poission's equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined with the Monte-Carlo (MC)method.The structures of RF sheaths behave differently in various situations and plasma parameters such as the ion density,electron temperature,as well as the external parameters such as the applied frequency,power,gas pressure,magnetic field,are crucial for determining the characteristics of plasma sheaths.

  17. Electronegative Plasma Sheath Structure in a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiu; LIU Jin-Yuan; WANG Zheng-Xiong; GONG Ye; LIU Yue; WANG Xiao-Gang

    2004-01-01

    @@ The structure of an electronegative plasma sheath in an oblique magnetic field is investigated with a fluid model. We assume the system consists of hot electrons and negative ions as well as cold positive ions. Densities of particles and distributions of the spacious potential in various states of magnetic field are studied. The result shows that the existence of magnetic field and negative ions has great effects on the plasma sheath structures. In addition, the effects of negative ion density and temperature on the structure of the electronegative plasma sheath are discussed.

  18. Dust Charging in the Sheath of an Electronegative Plasma

    Institute of Scientific and Technical Information of China (English)

    王正汹; 王文春; 刘悦; 刘金远; 王晓钢

    2004-01-01

    We theoretically investigate the dust charging in the sheath of an electronegative plasma, by using a single dust grain model based on a previous sheath structure [Chin. Phys. Lett 20 (2003) 1537] in which cold positive ions and hot negative ions have been assumed. It is found that dust grains are first charged negatively at the sheath edge and then begin to be charged positively in the sheath. Moreover, both the temperature ratio of electrons to negative ions and the density ratio of negative ions to positive ions have effects on the neutral point of the dust charge.

  19. Experimental studies of anode sheath phenomena in a hall thruster.

    Energy Technology Data Exchange (ETDEWEB)

    Dorf, L. A. (Leonid A.); Fisch, N. J.; Raitses, Yevgeny F.

    2004-01-01

    Both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in a Hall thruster were identified experimentally by performing accurate, non-disturbing near-anode measurements with biased and emissive probes. An interesting new phenomenon revealed by the probe measurements is that the anode fall changes from positive to negative upon removal of the dielectric coating, which appears on the anode surface during the course of Hall thruster operation. Probe measurements in a Hall thruster with three different magnetic field configurations show that an anode fall at the clean anode is a function of the radial magnetic field profile inside the channel. A positive anode fall formation mechanism suggested in this work is that: (1) when the anode front surface is coated with dielectric, a discharge current closes to the anode at the surfaces that remain conductive, (2) a total thermal electron current toward the conductive area is significantly smaller than the discharge current, therefore an additional electron flux needs to be attracted toward the conductive surfaces by the electronattracting sheath that appears at these surfaces.

  20. Characteristics of Dust Plasma Sheath in an Oblique Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiu

    2006-01-01

    @@ The characteristics of dust plasma sheath in an oblique magnetic field are investigated with a fluid model. Hot electrons, cold ions, neutral particles, and dust grains are taken into account in this system.

  1. Wave rectification in plasma sheaths surrounding electric field antennas

    Science.gov (United States)

    Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Ergun, R. E.; Mozer, F. S.

    1994-01-01

    Combined measurements of Langmuir or broadband whistler wave intensity and lower-frequency electric field waveforms, all at 10-microsecond time resolution, were made on several recent sounding rockets in the auroral ionosphere. It is found that Langmuir and whistler waves are partically rectified in the plasma sheaths surrounding the payload and the spheres used as antennas. This sheath rectification occurs whenever the high frequency (HF) potential across the sheath becomes of the same order as the electron temperature or higher, for wave frequencies near or above the ion plasma frequency. This rectification can introduce false low-frequency waves into measurements of electric field spectra when strong high-frequency waves are present. Second harmonic signals are also generated, although at much lower levels. The effect occurs in many different plasma conditions, primarily producing false waves at frequencies that are low enough for the antenna coupling to the plasma to be resistive.

  2. Approximation analytical solutions for a unified plasma sheath model by double decomposition method

    Institute of Scientific and Technical Information of China (English)

    FangJin-Qing

    1998-01-01

    A unified plasma sheath model and its potential equation are proposed.Any higher-order approximation analytical solutions for the unified plasma sheath potential equation are derived by double decomposition method.

  3. Sheath overlap during very large scale plasma source ion implantation

    Science.gov (United States)

    Cluggish, B. P.; Munson, C. P.

    1998-12-01

    Measurements of plasma source ion implantation have been performed on a large target of complex geometry. The target consists of 1000 aluminum, automotive piston surrogates mounted on four racks; total surface area is over 16 m2. The four racks are positioned parallel to each other, 0.25 m apart, in an 8 m3 vacuum chamber. The racks of pistons are immersed in a capacitive radio frequency plasma, with an argon gas pressure of 20-65 mPa. Langmuir probe measurements indicate that the plasma density profile is highly nonuniform, due to particle losses to the racks of pistons. The plasma ions are implanted into the pistons by pulse biasing the workpiece to negative voltages as low as -18 kV for up to 20 μs. During the voltage pulse, the high-voltage sheaths from adjacent racks of pistons converge towards each other. At plasma densities less than 109 cm-3 the sheaths are observed to overlap. Measurements of the sheath overlap time are compared with standard analytic theory and with simulations run with a two-dimensional particle-in-cell code.

  4. Nonextensivity effect on radio-wave transmission in plasma sheath

    Science.gov (United States)

    Mousavi, A.; Esfandiari-Kalejahi, A.; Akbari-Moghanjoughi, M.

    2016-04-01

    In this paper, new theoretical findings on the application of magnetic field in effective transmission of electromagnetic (EM) waves through a plasma sheath around a hypersonic vehicle are reported. The results are obtained by assuming the plasma sheath to consist of nonextensive electrons and thermal ions. The expressions for the electric field and effective collision frequency are derived analytically in the framework of nonextensive statistics. Examination of the reflection, transmission, and absorption coefficients regarding the strength of the ambient magnetic field shows the significance of q-nonextensive parameter effect on these entities. For small values of the magnetic field, the transmission coefficient increases to unity only in the range of - 1 hypersonic flights.

  5. Plasma Processes : Sheath and plasma parameters in a magnetized plasma system

    Indian Academy of Sciences (India)

    Bornali Singha; A Sharma; J Chutia

    2000-11-01

    The variation of electron temperature and plasma density in a magnetized 2 plasma is studied experimentally in presence of a grid placed at the middle of the system. Plasma leaks through the negatively biased grid from the source region into the diffused region. It is observed that the electron temperature increases with the magnetic field in the diffused region whereas it decreases in the source region of the system for a constant grid biasing voltage. Also, investigation is done to see the change of electron temperature with grid biasing voltage for a constant magnetic field. This is accompanied by the study of the variation of sheath structure across the grid for different magnetic field and grid biasing voltage as well. It reveals that with increasing magnetic field and negative grid biasing voltage, the sheath thickness expands.

  6. Temporal behavior of microwave sheath-voltage combination plasma

    CERN Document Server

    Kar, Satyananda; Raja, Laxminarayan L

    2015-01-01

    Microwave sheath-Voltage combination Plasma (MVP) is a high density plasma source and can be used as a suitable plasma processing device (e.g., ionized physical vapor deposition). In the present report, the temporal behavior of an argon MVP sustained along a direct-current biased Ti rod is investigated. Two plasma modes are observed, one is an "oxidized state" (OS) at the early time of the microwave plasma and the other is "ionized sputter state" (ISS) at the later times. Transition of the plasma from OS to ISS, results a prominent change in the visible color of the plasma, resulting from a significant increase in the plasma density, as measured by a Langmuir probe. In the OS, plasma is dominated by Ar ions and the density is order 10^11 cm^-3. In the ISS, metal ions from the Ti rod contribute significantly to the ion composition and higher density plasma (10^12 cm^-3) is produced. Nearly uniform high density plasma along the length of the Ti rod is produced at very low input microwave powers (around 30 W). O...

  7. The Bohm criterion for a dusty plasma sheath

    Indian Academy of Sciences (India)

    B P Pandey; Anjan Dutta

    2005-07-01

    The formation of the sheath in a dusty plasma is investigated. The Bohm criterion is derived for two different cases: (a) when electrons are in thermodynamic equilibrium and dust grains provide the immobile, stationary background and (b) when both electrons and ions are in thermodynamic equilibrium and dust grains are moving. In the first case, Bohm criterion gets modified due to the fluctuation of the charge on the grain surface. In the second case, the collisional and Coulombic drag play important role in determining the Bohm criterion.

  8. The modeling and simulation of plasma sheath effect on GNSS system

    Science.gov (United States)

    Song, Zhongguo; Liu, Jiangfan; Du, Yongxing; Xi, Xiaoli

    2015-11-01

    Plasma sheath can potentially degrade global navigation satellite system (GNSS) through signal attenuation as well as phase noise when a hypersonic vehicle reenters the Earth's atmosphere. Modeling and simulation method of GNSS system disturbed by plasma sheath is introduced in this paper by means of electromagnetic wave propagation theory combined with the satellite signal simulation technique. The transmission function of the plasma sheath with stratified model is derived utilizing scattering matrix method. The effects of the plasma sheath on GPS signal reception and positioning performance are examined. Experimental results are presented and discussed, partly supporting the validity of the analytical method proposed.

  9. Colloidal Plasmas : Electrostatic sheath at the boundary of a collisional dusty plasma

    Indian Academy of Sciences (India)

    S K Baishya; G C Das; Joyanti Chutia

    2000-11-01

    Considering the Boltzmann response of the ions and electrons in plasma dynamics and inertial dynamics of the dust charged grains in a highly collisional dusty plasma, the nature of the electrostatic potential near a boundary is investigated. Based on the fluid approximation, the formation as well as the characteristic behaviours of the sheath is studied. It is expected that the presence of dust charged grains will lead to a very different behaviour of the sheath as compared to that of electron-ion plasma. Moreover, the collisions of the dust charged grains with the neutrals are expected to exhibit novel features.

  10. Collisional Sheath in the Electronegative Radio-Frequency Plasma

    Institute of Scientific and Technical Information of China (English)

    GAN Baoxia; DENG Wenjuan; CHEN Yinhua

    2007-01-01

    A model of collisional RF sheath with negative ions is discussed in this paper.The influences of collision and negative ions on the parameters of the sheath are studied through numerical simulation.It is found that when the collision coefficient increases and the RF power is fixed,the electrode potential and sheath electric field potential increase,the electrode current and thickness of the sheath decrease.When the negative ion content changes,the same phenomenon occurs.

  11. Nonmodal phenomena in differentially rotating dusty plasmas

    Science.gov (United States)

    Poedts, Stefaan; Rogava, Andria D.

    2000-10-01

    In this paper the foundation is layed for the nonmodal investigation of velocity shear induced phenomena in a differentially rotating flow of a dusty plasma. The simplest case of nonmagnetized flow is considered. It is shown that, together with the innate properties of the dusty plasma, the presence of differential rotation, Coriolis forces, and self-gravity casts a considerable richness on the nonmodal dynamics of linear perturbations in the flow. In particular: (i) dust-acoustic waves acquire the ability to extract energy from the mean flow and (ii) shear-induced, nonperiodic modes of collective plasma behavior-shear-dust-acoustic vortices-are generated. The presence of self-gravity and the nonzero Coriolis parameter (``epicyclic shaking'') makes these collective modes transiently unstable. .

  12. A Method for Measurement of Dynamic Sheath Behavior in Plasma Immersion Ion Implantation and Deposition Process

    Institute of Scientific and Technical Information of China (English)

    WU Hongchen; MA Guojia; PENG Liping; FENG Jianji; ZHANG Huafang; MA Tengcai

    2008-01-01

    A method to measure temporal and spatial evolution of sheath in plasma immersion ion implantation (PⅢ) process is presented.A long Langrnuir probe (φ 5 mm×φ 78 mm) with low bias is used to detect the sheath propagation and backup with time.The aubstrate made of Al cylinder (φ20 mm×φ150 mm) is immersed in nitrogen and argon plasma induced by magnetron self-sustained discharge.The maximum sheath sizes,at different plasma densities under different discharge currents,are measured and compared.

  13. Surface Potential of Dust Grains at the Sheath Edge of Electronegative Dusty Plasmas

    Institute of Scientific and Technical Information of China (English)

    段萍; 王正汹; 王文春; 刘金远; 刘悦; 王晓钢

    2004-01-01

    In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids.The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.

  14. Simulation methods of ion sheath dynamics in plasma source ion implantation

    Institute of Scientific and Technical Information of China (English)

    WANG Jiuli; ZHANG Guling; WANG Younian; LIU Yuanfu; LIU Chizi; YANG Size

    2004-01-01

    Progress of the theoretical studies on the ion sheath dynamics in plasma source ion implantation (PSII) is reviewed in this paper. Several models for simulating the ion sheath dynamics in PSII are provided. The main problem of nonuniform ion implantation on the target in PSII is discussed by analyzing some calculated results. In addition, based on the relative researches in our laboratory, some calculated results of the ion sheath dynamics in PSII for inner surface modification of a cylindrical bore are presented. Finally, new ideas and tendency for future researches on ion sheath dynamics in PSII are proposed.

  15. Effect of the shear viscosity on plasma sheath in an oblique magnetic field

    Science.gov (United States)

    Wang, Ting-Ting; Li, Jing-Ju; Ma, J. X.

    2016-12-01

    In a magnetized plasma sheath, strong velocity shear exists owing to the three-dimensional nature of ion velocity. Thus, the ion viscosity should have an important effect on the sheath structure, which has not been studied. This article presents the study of the effect of ion shear viscosity on the sheath in an oblique magnetic field within the framework of classical cross-field transport. It is shown that the inclusion of the shear viscosity in the ion momentum equation results in a significant reduction in the sheath thickness. It is also shown that the "generalized Bohm criterion" is not affected by the shear viscosity within the present model. However, additional boundary conditions such as the velocity shear arise in the viscous case. The appropriate boundary conditions are formulated, accounting for E × B and diamagnetic drifts at the sheath edge, which affects the criterion and sheath profiles.

  16. Dynamics of the plasma current sheath in plasma focus discharges in different gases

    Energy Technology Data Exchange (ETDEWEB)

    Vinogradov, V. P.; Krauz, V. I., E-mail: krauz-vi@nrcki.ru [National Research Center Kurchatov Institute (Russian Federation); Mokeev, A. N. [Project Center ITER (Russian Federation); Myalton, V. V.; Kharrasov, A. M. [National Research Center Kurchatov Institute (Russian Federation)

    2016-12-15

    The shape of the plasma current sheath (PCS) in the final stage of its radial compression, the dynamics of pinching, and the subsequent pinch decay in plasma focus (PF) discharges in different gases are studied using an improved multichannel system of electron-optical plasma photography and a newly elaborated synchronization system. The PCS structure in discharges in heavy gases (Ne, Ar) is found to differ significantly from that in discharges in hydrogen and deuterium. The influence of a heavy gas (Xe) additive to hydrogen and deuterium on the structure and compression dynamics of the PCS is investigated.

  17. Effects of Reentry Plasma Sheath on GPS Patch Antenna Polarization Property

    Directory of Open Access Journals (Sweden)

    L. Zhao

    2013-01-01

    Full Text Available A plasma sheath enveloping a reentry vehicle would affect performances of on-board antenna greatly, especially the navigation antennas. This paper studies the effects of reentry plasma sheath on a GPS right-hand circularly polarized (RHCP patch antenna polarization property during a typical reentry process. Utilizing the algorithm of finite integration technique, the polarization characteristic of a GPS antenna coated by a plasma sheath is obtained. Results show that the GPS RHCP patch antenna radiation pattern distortions as well as polarization deteriorations exist during the entire reentry process, and the worst polarization mismatch loss between a GPS antenna and RHCP GPS signal is nearly 3 dB. This paper also indicates that measures should be taken to alleviate the plasma sheath for maintaining the GPS communication during the reentry process.

  18. Double Layers: Potential Formation and Related Nonlinear Phenomena in Plasmas: Proceedings of the 5th Symposium

    Science.gov (United States)

    Iizuka, S.

    1998-02-01

    Parallel Velocity Shear Instability (Invited) * Low-Frequency Instabilities under a Cross-Field Electric Field in a K+-C60- Plasma * 3.3 Vortex Formation * Vortex Dynamics in Low Frequency Electrostatic Turbulence * Development of Spiral-Vortex Structures of the Plasma During Rotation in a Neutral Gas * Vortex Formation of Particles in Magnetized Dusty Plasmas (Invited) * CHAPTER 4: SOLITONS, SHOCKS, WAVES AND INSTABILITIES, AND RELATED NONLINEAR PHENOMENA * 4.1 Solitons and Shocks * Refraction and Reflection of Ion Acoustic Solitons by Space Charge Sheath * 2D and 3D Solitons in Plasma: Structure, Stability, Dynamics * Solitary Waves in an Ion-Beam Multi-Component Plasma System * Shock Formation in a Q-Machine Plasma with Negative Ions * 4.2 Waves and Instabilities * Single-Ended Q-Machine as a Source of Oscillations (Invited) * Numerical and Experimental Investigations of Period Doubling of the Potential Relaxation Instability in an Electron-Rich Q-Machine Plasma * Large Amplitude Electrostatic Ion Waves in an e- - e+ - p Plasma * Measurements of Alfvén Waves around the CRIT Releases-Implications for Current Limitation in Alfvén Wings * 4.3 Nonlinear Phenomena * Self-Organization Phenomena in a Q-Machine Plasma * Nonlinearity Related to Self-Organization in a Thermionic Vacuum Arc Discharge * Spontaneous Formation of Ordered Spatio-Temporal Structures in Laboratory and Nature * Nonlinear Evolution and Stabilization of Linearly Unstable Waves in an Electron-Beam Plasma * Disruption of an Electron Hole Due to its Interaction with Ion Acoustic Waves in a Plasma * Expanding Plasma Clouds with Dust Particles (Invited) * LIST OF PARTICIPANTS * AUTHOR INDEX

  19. A different way of looking at the Plasma-Sheath Boundary Region

    Science.gov (United States)

    Franklin, Raoul

    2003-10-01

    The plasma-sheath boundary region has been the subject of study for eighty years, but there are aspects that are still not well understood. At low pressures it is clear that the structure is - plasma-transition layer-thin electron sheath -(thick)ion sheath, and at high pressures it is plasma-collisional sheath, without the need to introduce further structure. As the plasma becomes collisional, there is a question as to how long it is appropriate to speak in terms of the Bohm criterion. Furthermore if the sheath is many ion mean free paths long, the ions may be brought back into collisional equilibrium with the electric field, even though their speed exceeds the ion sound speed of the plasma from which they derive. We examine computationally this intermediate pressure region in terms of how to describe the ion motion, showing how the two limits go over from the one to the other. Most practical gas discharge plasmas are in such a transitional pressure region.

  20. Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

    DEFF Research Database (Denmark)

    Stamate, Eugen; Yamaguchi, Masahito

    2015-01-01

    Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the...

  1. The Effect of Polarization on the Stability of Current Sheaths in Space Plasma

    Science.gov (United States)

    Lyahov, Vladimir; Neshchadim, Vladimir

    2013-04-01

    The procedure of study of the stability of current sheath taking into account the effect of plasma polarization is proposed. The kinetic equation with self-consistent electromagnetic field for perturbation of distribution function is solved. On the basis of this solution the tensor of dielectric permeability of nonelectroneutral sharply-irregular current sheath plasma is calculated and the dispersion equation to study the possible instability modes of this sheath is obtained. Instability of the current sheath of magnetospheric tail with respect to the tearing-perturbations as well as influence of the effect of plasma polarization on the development of tearing instability is investigated. As a result of application of the offered procedure the existence of low-frequency tearing-like modes which essentially differ from the formerly known tiring-perturbations is revealed even for the case of an electroneutral current sheath. The increment of growth of those modes is positive within very wide interval of wave lengths and attains much bigger quantities than it was supposed earlier for the tearing-instability. Due to this polarization effect, the area of existence of those low-frequency tearing-like modes is displaced from the area of strong stationary electric field more close to the magnitoneutral (and electroneutral) plane at the center of symmetry of the current sheath. The problem of structural stability of the nonelectroneutral current sheath is explored. The equilibrium model represents a system of four connected non-linear first-order differential equations and hence it should manifest the property of structural instability - sensitivity to infinitesimal changes of the parameters and initial conditions. The solution for such current sheath is realized only in some areas of 7-dimensional space of model parameters. The phase volume of those areas is small in comparison with the entire phase volume in the interval on which the parameters are defined. The above is

  2. Thermographic determination of the sheath heat transmission coefficient in a high density plasma

    NARCIS (Netherlands)

    van den Berg, M. A.; Bystrov, K.; Pasquet, R.; Zielinski, J. J.; De Temmerman, G.

    2013-01-01

    Experiments were performed in the Pilot-PSI linear plasma device, to determine the sheath heat transmission coefficients in a high recycling regime under various conditions of density (1–20 × 1020 m−3) and plasma composition (H2, Ar, N2) relevant for the

  3. Thermographic determination of the sheath heat transmission coefficient in a high density plasma

    NARCIS (Netherlands)

    van den Berg, M. A.; Bystrov, K.; Pasquet, R.; Zielinski, J. J.; De Temmerman, G.

    2013-01-01

    Experiments were performed in the Pilot-PSI linear plasma device, to determine the sheath heat transmission coefficients in a high recycling regime under various conditions of density (1–20 × 1020 m−3) and plasma composition (H2, Ar, N2) relevant for the

  4. Role of magnetospheric plasma physics for understanding cosmic phenomena

    Science.gov (United States)

    Das, Indra M. L.

    Cosmic phenomena occur in the remote regions of space where in situ observations are not possible. For a proper understanding of these phenomena, laboratory experiments are essential, but in situ observations of magnetospheric plasma provide an even better background to test various hypothesis of cosmic interest. This is because the ionospheric-magnetospheric plasma and the solar wind are the only cosmic plasmas accessible to extensive in situ observations and experiments.

  5. Plasma sheath properties in a magnetic field parallel to the wall

    Science.gov (United States)

    Moritz, J.; Faudot, E.; Devaux, S.; Heuraux, S.

    2016-06-01

    Particle in cell simulations were carried out with a plasma bounded by two absorbing walls and a magnetic field applied parallel to them. Both the sheath extent and the potential drop in it were derived from simulations for different plasma parameters, such as the electron and ion temperature Ti, particle density, and ion mass. Both of them exhibit a power law dependent on the Larmor to plasma ion pulsation ratio Ωi. For increasing values of the magnetic field, the potential drop within the sheath decreases from a few Ti/e down to zero, where e stands for the electron charge. The space charge extent increases with Ωi and saturates to 2.15 ion Larmor radius. A simple model of sheath formation in such a magnetic field configuration is presented. Assuming strongly magnetized electrons, and neglecting collisions and ionizations, a new typical length is evidenced, which depends on the ratio Ωi. The charge separation sheath width is theoretically found to increase from a combination of the electron gyroradius and the ion Debye length for low Ωi ratios up to several ion gyroradii for strongly magnetized ions. Both the calculated sheath extent and plasma potential show a fair agreement with the numerical simulations.

  6. A matching approach to communicate through the plasma sheath surrounding a hypersonic vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xiaotian; Jiang, Binhao, E-mail: jiangbh@hit.edu.cn [Harbin Institute of Technology, 92 West Dazhi Street, Nan Gang District, Harbin (China)

    2015-06-21

    In order to overcome the communication blackout problem suffered by hypersonic vehicles, a matching approach has been proposed for the first time in this paper. It utilizes a double-positive (DPS) material layer surrounding a hypersonic vehicle antenna to match with the plasma sheath enclosing the vehicle. Analytical analysis and numerical results indicate a resonance between the matched layer and the plasma sheath will be formed to mitigate the blackout problem in some conditions. The calculated results present a perfect radiated performance of the antenna, when the match is exactly built between these two layers. The effects of the parameters of the plasma sheath have been researched by numerical methods. Based on these results, the proposed approach is easier to realize and more flexible to the varying radiated conditions in hypersonic flight comparing with other methods.

  7. Fluid Simulation of the Ion Temperature Effects on a Collisional Magnetized Sheath of a Dusty Plasma

    Directory of Open Access Journals (Sweden)

    I Driouch

    2013-01-01

    Full Text Available The properties of magnetized dusty plasma sheath with finite ion temperature are studied using a fluid model. Hot electrons, fluid ions, neutral particles and cold fluid dust grains are taken into account in this system. Considering the cross section for collisions between the dust and neutrals has a power law dependence on the dust flow velocity, the fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures. A significant change is observed in the quantities characterizing the sheath with respect to the cold ion assumption. In addition, the result reveals that the effect of ion temperature is more obvious on the dust dynamics in collisional sheath with constant cross section.

  8. PIC Simulation of RF Plasma Sheath Formation and Initial Validation of Optical Diagnostics using HPC Resources

    Science.gov (United States)

    Icenhour, Casey; Exum, Ashe; Martin, Elijah; Green, David; Smithe, David; Shannon, Steven

    2014-10-01

    The coupling of experiment and simulation to elucidate near field physics above ICRF antennae presents challenges on both the experimental and computational side. In order to analyze this region, a new optical diagnostic utilizing active and passive spectroscopy is used to determine the structure of the electric fields within the sheath region. Parallel and perpendicular magnetic fields with respect to the sheath electric field have been presented. This work focuses on the validation of these measurements utilizing the Particle-in-Cell (PIC) simulation method in conjunction with High Performance Computing (HPC) resources on the Titan supercomputer at Oak Ridge National Laboratory (ORNL). Plasma parameters of interest include electron density, electron temperature, plasma potentials, and RF plasma sheath voltages and thicknesses. The plasma is modeled utilizing the VSim plasma simulation tool, developed by the Tech-X Corporation. The implementation used here is a two-dimensional electromagnetic model of the experimental setup. The overall goal of this study is to develop models for complex RF plasma systems and to help outline the physics of RF sheath formation and subsequent power loss on ICRF antennas in systems such as ITER. This work is carried out with the support of Oak Ridge National Laboratory and the Tech-X Corporation.

  9. Low-frequency sheath instability in a non-Maxwellian plasma with energetic ions.

    Science.gov (United States)

    Starodubtsev, Mikhail; Kamal-Al-Hassan, Md; Ito, Hiroaki; Yugami, Noboru; Nishida, Yasushi

    2004-01-30

    Spontaneous low-frequency oscillations have been observed in the circuit of a positively biased electrode when the ambient nonuniform plasma is irradiated by a microwave pulse of short duration, which is approximately equal to the ion-plasma period. The instability with its characteristic frequency below the ion-plasma frequency is driven by an accelerated ion component interacting with the sheath of the electrode. A qualitative model of the instability is suggested.

  10. Effect of sheath gas in atmospheric-pressure plasma jet for potato sprouting suppression

    Science.gov (United States)

    Nishiyama, S.; Monma, M.; Sasaki, K.

    2016-09-01

    Recently, low-temperature atmospheric-pressure plasma jets (APPJs) attract much interest for medical and agricultural applications. We try to apply APPJs for the suppression of potato sprouting in the long-term storage. In this study, we investigated the effect of sheath gas in APPJ on the suppression efficiency of the potato sprouting. Our APPJ was composed of an insulated thin wire electrode, a glass tube, a grounded electrode which was wound on the glass tube, and a sheath gas nozzle which was attached at the end of the glass tube. The wire electrode was connected to a rectangular-waveform power supply at a frequency of 3 kHz and a voltage of +/- 7 kV. Helium was fed through the glass tube, while we tested dry nitrogen, humid nitrogen, and oxygen as the sheath gas. Eyes of potatoes were irradiated by APPJ for 60 seconds. The sprouting probability was evaluated at two weeks after the plasma irradiation. The sprouting probability was 28% when we employed no sheath gases, whereas an improved probability of 10% was obtained when we applied dry nitrogen as the sheath gas. Optical emission spectroscopy was carried out to diagnose the plasma jet. It was suggested that reactive species originated from nitrogen worked for the efficient suppression of the potato sprouting.

  11. Measurements of the asymmetric, dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre; Wu, Hongchen; Anders, Andre

    2008-06-13

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1" (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVP) were 2 kV, 5 kV, 10 kV, and 2 mu s, 4 mu s, 10 mu s, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  12. Levitation and Oscillation of Dust Grains in Plasma Sheath with Wake Potential

    Institute of Scientific and Technical Information of China (English)

    练海俊; 谢柏松; 周宏余

    2002-01-01

    We investigate the equilibrium and levitation of dust grains in a plasma sheath with various forces, in particular the wake potential force. The vertical oscillation frequency of dust chains is also obtained by including the wake potential term. It is found that the wake potential has a significant role for the levitation and oscillation of dust grains.

  13. Dusty plasma liquid: structure and transfer phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Fortov, Vladimir E; Vaulina, Olga S; Petrov, Oleg F [Institute for High Energy Densities, Russian Academy of Sciences, Izhorskaya 13/19, Moscow (Russian Federation)

    2005-12-15

    Results are given of the experimental investigation of three-particle correlation for liquid plasma-dust structures formed in the electrode layer of a capacitive rf discharge. The obtained three-particle correlation functions for experimental and numerical data are analysed and compared with the superposition approximation. The forming of clusters of macroparticles in plasma-dust systems being analysed is revealed. The experiments in heat transfer were performed in plasma of a capacitive radio-frequency (rf) discharge in argon (P {approx} 20 Pa) with particles 4 {mu}m in mean diameter. The results are given of an experimental investigation of processes of heat transfer for fluid dust structures in rf-discharge. The analysis of steady-state, and unsteady-state heat transfer are used to obtain the thermal conductivity and diffusivity constants.

  14. Transmission Properties of Radar Wave through Reentry Plasma Sheath

    Institute of Scientific and Technical Information of China (English)

    GAO Zheng-ping; MA Zhao-guo; LIU Jing; LI Zhong-ping; ZHANG Da-hai

    2007-01-01

    In this paper, by taking into account the coupling of the ionization of ablation gas and atmosphere, an electrons density distribution model is built. Using this model, the transmission properties of different polarization radar wave through sheath are evaluated on the basis of the transmission matrix theory. Then, we discuss the effects of the electrons density, the added magnetic field, and the radar wave frequency on the transmission properties. As a result of this investigation,greater transmission power could be gained in order to efficiently shorten communication blackout,by reducing the electrons density or choosing proper added magnetic field and the frequency of the radar wave according to the different polarization form of the radar wave.

  15. Quantum Phenomena in High Energy Density Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, Margaret [Univ. of Colorado, Boulder, CO (United States); Kapteyn, Henry [Univ. of Colorado, Boulder, CO (United States)

    2017-05-10

    The possibility of implementing efficient (phase matched) HHG upconversion of deep- UV lasers in multiply-ionized plasmas, with potentially unprecedented conversion efficiency is a fascinating prospect. HHG results from the extreme nonlinear response of matter to intense laser light:high harmonics are radiated as a result of a quantum coherent electron recollision process that occurs during laser field ionization of an atom. Under current support from this grant in work published in Science in 2015, we discovered a new regime of bright HHG in highly-ionized plasmas driven by intense UV lasers, that generates bright harmonics to photon energies >280eV

  16. Confinement and structure of electrostatically coupled dust clouds in a direct current plasma-sheath

    Science.gov (United States)

    Nunomura, S.; Ohno, N.; Takamura, S.

    1998-10-01

    Mechanisms for the confinement and the internal structure of an electrostatically coupled dust cloud formed in a dc glow discharge have been investigated from a comparative viewpoint between experimental observations and a simple model. Two kinds of dust clouds with different internal structures are clearly observed, depending on the dispersion of the size distribution of dust particles. The dust cloud can be trapped only in the plasma-sheath boundary area, corresponding to the potential minimum region determined by gravitational and electrostatic forces in the cathode sheath. No dust particles were found deep inside of the sheath, which is consistent with the analysis because the dust particles may be charged positively due to an extreme reduction of the electron density. The internal structure of the electrostatically coupled dust cloud was found to be arranged so that the total potential energy, including the repulsive Coulomb interaction among negative dust particles, may become minimal.

  17. Laser Interaction and Related Plasma Phenomena

    Directory of Open Access Journals (Sweden)

    Frederick Osman

    2005-01-01

    Full Text Available Computations are to be performed using the laser driven inertial fusion energy option based on volume ignition with the natural adiabatic self-similarity compression and expansion hydrodynamics [1]. The numerical work includes the establishing of a multi-branch reaction code to be used for simultaneous fusion reactions of D-D, D-T D-He3 and mutual nuclear reaction products. This will permit the studies of neutron lean reactions as well as tritium-rich cases. The D-T reactions will stress the recent new results on one step laser fusion [2] as an alternative to the two-step fast ignitor scheme whose difficulties with new physics phenomena at petawatt laser interaction are more and more evident [3].

  18. Sheath structure in plasma with two species of positive ions and secondary electrons

    Science.gov (United States)

    Xiao-Yun, Zhao; Nong, Xiang; Jing, Ou; De-Hui, Li; Bin-Bin, Lin

    2016-02-01

    The properties of a collisionless plasma sheath are investigated by using a fluid model in which two species of positive ions and secondary electrons are taken into account. It is shown that the positive ion speeds at the sheath edge increase with secondary electron emission (SEE) coefficient, and the sheath structure is affected by the interplay between the two species of positive ions and secondary electrons. The critical SEE coefficients and the sheath widths depend strongly on the positive ion charge number, mass and concentration in the cases with and without SEE. In addition, ion kinetic energy flux to the wall and the impact of positive ion species on secondary electron density at the sheath edge are also discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475220 and 11405208), the Program of Fusion Reactor Physics and Digital Tokamak with the CAS “One-Three-Five” Strategic Planning, the National ITER Program of China (Grant No. 2015GB101003), and the Higher Education Natural Science Research Project of Anhui Province, China (Grant No. 2015KJ009).

  19. Helium metastable dynamics in sheath or bulk dominated rf micro-plasma jets

    CERN Document Server

    Niermann, B; Wollny, A; Böke, M; Brinkmann, R P; Mussenbrock, T; Winter, J

    2011-01-01

    Space resolved concentrations of helium He metastable atoms in an atmospheric pressure radio-frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. The spatial profile of metastable atoms in the volume between the electrodes was deduced for various electrode gap distances. Density profiles reveal the sheath structure and reflect the plasma excitation distribution, as well as the dominance of the alpha-mode discharge. Gap width variations show the transition from a normal glow plasma to a pure sheath discharge. In order to analyze and verify the experimentally observed profiles of the metastable atoms a 2-dimensional simulation model was set up. Applying an appropriate He/N2/O2 chemistry model the correlation between the metastable profiles and the underlying excitation mechanisms was obtained.

  20. The effect of intermediate frequency on sheath dynamics in collisionless current driven triple frequency capacitive plasmas

    Science.gov (United States)

    Sharma, S.; Mishra, S. K.; Kaw, P. K.; Turner, M. M.

    2017-01-01

    The Capacitively Coupled Plasma discharge featuring operation in current driven triple frequency configuration has analytically been investigated, and the outcome is verified by utilising the 1D3V particle-in-cell (PIC) simulation code. In this analysis, the role of middle frequency component of the applied signal has precisely been explored. The discharge parameters are seen to be sensitive to the ratio of the chosen middle frequency to lower and higher frequencies for fixed amplitudes of the three frequency components. On the basis of analysis and PIC simulation results, the middle frequency component is demonstrated to act as additional control over sheath potential, electron sheath heating, and ion energy distribution function (iedf) of the plasma discharge. For the electron sheath heating, effect of the middle frequency is seen to be pronounced as it approaches to the lower frequency component. On the other hand, for the iedf, the control is more sensitive as the middle frequency approaches towards the higher frequency. The PIC estimate for the electron sheath heating is found to be in reasonably good agreement with the analytical prediction based on the Kaganovich formulation.

  1. Collaborative Research: Understanding Ion Losses to Plasma Boundaries Sheaths and Presheaths

    Energy Technology Data Exchange (ETDEWEB)

    Hershkowitz, Noah [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-01

    Sheaths are common to all bounded steady-state plasmas. This includes laboratory, industrial, fusion, and in some cases even space plasmas. They form in general to balance particle loss and maintain quasi-neutrality in plasmas. Electrons are lighter than the ions by 2000 times or more (depending on the gas), and in most plasmas ion temperatures are rarely higher than the electron temperature and generally much lower. Thus in most cases, negative potential sheaths occur to confine electrons and allow ions to be freely lost. We have investigated how a plasma locally response to a positive bias on a small electrode, and have established area criteria which plasma reacts differently to the positive bias – first a pure electron sheath, and a global non-ambipolar regime where all electrons are lost to the electrode, and a double layer structure identified as a virtual cathode forms to limiting electron loss and maintain quasi-neutrality, and finally a anode spot regime where a secondary discharge occurs in front of the electrode, turning it into the major loss area of the entire plasma. Electrode area and plasma parameters criteria for these regimes were established, and the effect of the virtual cathode on the electrode’s I-V characteristics was investigated. We have also developed a global non-ambipolar electron source to replace hollow cathodes in a number of plasma applications. This eliminates the lifetime limitation and maintenance cost of hollow cathodes as they easily wear out easily and cannot be replaced in space applications.

  2. Self-consistent multicomponent plasma sheath theory for the extraction of H- ions (invited)

    Science.gov (United States)

    Becker, Reinard

    2004-05-01

    A self-consistent one-dimensional plasma sheath theory is presented to provide the basis for a correct numerical simulation of the extraction of volume produced H- ions. The plasma may consist not only of electrons and H- ions, but may also contain other positive ions such as protons, molecular ions and those of heavier elements, like cesium or tantalum. For the transition from the classical plasma sheath with a falling potential to the extraction region for H- ions with an increasing potential there exists the problem of a saddle point with adverse optical properties. This is eliminated by requiring sufficient space charge of H- ions near the extraction electrode. The formation of a virtual cathode in the extraction region by reflected positive ions is also taken into account. The integration of the Poisson equation in the extraction region establishes a criterion to avoid the creation of a nonphysical periodical sequence of potential maximums and minima. This criterion is an antithesis to the Bohm sheath criterion and has a corresponding interpretation: a virtual cathode in the extraction region can only be avoided, if the space charge of positive ions rapidly decreases. The acceptable range of parameters is thus reduced considerably. The resulting axial potential function is then used to derive the shape of the plasma wall electrode in the vicinity of the ion beam edge in order to obtain an aberration free beam boundary, this information being equivalent to the Pierce angle in the case of solid electron or ion emitters.

  3. Multipoint observations of plasma phenomena made in space by Cluster

    Science.gov (United States)

    Goldstein, M. L.; Escoubet, P.; Hwang, K.-Joo; Wendel, D. E.; Viñas, A.-F.; Fung, S. F.; Perri, S.; Servidio, S.; Pickett, J. S.; Parks, G. K.; Sahraoui, F.; Gurgiolo, C.; Matthaeus, W.; Weygand, J. M.

    2015-06-01

    Plasmas are ubiquitous in nature, surround our local geospace environment, and permeate the universe. Plasma phenomena in space give rise to energetic particles, the aurora, solar flares and coronal mass ejections, as well as many energetic phenomena in interstellar space. Although plasmas can be studied in laboratory settings, it is often difficult, if not impossible, to replicate the conditions (density, temperature, magnetic and electric fields, etc.) of space. Single-point space missions too numerous to list have described many properties of near-Earth and heliospheric plasmas as measured both in situ and remotely (see http://www.nasa.gov/missions/#.U1mcVmeweRY for a list of NASA-related missions). However, a full description of our plasma environment requires three-dimensional spatial measurements. Cluster is the first, and until data begin flowing from the Magnetospheric Multiscale Mission (MMS), the only mission designed to describe the three-dimensional spatial structure of plasma phenomena in geospace. In this paper, we concentrate on some of the many plasma phenomena that have been studied using data from Cluster. To date, there have been more than 2000 refereed papers published using Cluster data but in this paper we will, of necessity, refer to only a small fraction of the published work. We have focused on a few basic plasma phenomena, but, for example, have not dealt with most of the vast body of work describing dynamical phenomena in Earth's magnetosphere, including the dynamics of current sheets in Earth's magnetotail and the morphology of the dayside high latitude cusp. Several review articles and special publications are available that describe aspects of that research in detail and interested readers are referred to them (see for example, Escoubet et al. 2005 Multiscale Coupling of Sun-Earth Processes, p. 459, Keith et al. 2005 Sur. Geophys. 26, 307-339, Paschmann et al. 2005 Outer Magnetospheric Boundaries: Cluster Results, Space Sciences Series

  4. Potential application of X-ray communication through a plasma sheath encountered during spacecraft reentry into earth's atmosphere

    Science.gov (United States)

    Li, Huan; Tang, Xiaobin; Hang, Shuang; Liu, Yunpeng; Chen, Da

    2017-03-01

    Rapid progress in exploiting X-ray science has fueled its potential application in communication networks as a carrier wave for transmitting information through a plasma sheath during spacecraft reentry into earth's atmosphere. In this study, we addressed the physical transmission process of X-rays in the reentry plasma sheath and near-earth space theoretically. The interactions between the X-rays and reentry plasma sheath were investigated through the theoretical Wentzel-Kramers-Brillouin method, and the Monte Carlo simulation was employed to explore the transmission properties of X-rays in the near-earth space. The simulation results indicated that X-ray transmission was not influenced by the reentry plasma sheath compared with regular RF signals, and adopting various X-ray energies according to different spacecraft reentry altitudes is imperative when using X-ray uplink communication especially in the near-earth space. Additionally, the performance of the X-ray communication system was evaluated by applying the additive white Gaussian noise, Rayleigh fading channel, and plasma sheath channel. The Doppler shift, as a result of spacecraft velocity changes, was also calculated through the Matlab Simulink simulation, and various plasma sheath environments have no significant influence on X-ray communication owing to its exceedingly high carrier frequency.

  5. Oscillations of Magnetized Dust Grains in Plasma Sheath with Negative Ions

    Institute of Scientific and Technical Information of China (English)

    GAN Bao-Xia; CHEN Yin-Hua

    2007-01-01

    The oscillations of a single magnetized dust grain in electronegative plasma sheath are investigated taking into account the existence of an external magnetic field. The influence of the content of negative ions and the magnetic field intensity on the properties of the dust vibration is analysed. The result shows that the existence of the negative ions in plasma reduces the dust oscillation frequency and drops the equilibrium position of dust, whereas the magnetic field raises the equilibrium position and also reduces the dust oscillation frequency on the condition considered.

  6. Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Yongpeng; Shi, Zongqian; Jia, Shenli; Wang, Lijun [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Bai, Zhibin [State Grid Yulin Electric Power Supply Company, Shaanxi 719000 (China)

    2016-05-15

    The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process was rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.

  7. Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

    Science.gov (United States)

    Mo, Yongpeng; Shi, Zongqian; Bai, Zhibin; Jia, Shenli; Wang, Lijun

    2016-05-01

    The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process was rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.

  8. Study of negative ion transport phenomena in a plasma source

    Energy Technology Data Exchange (ETDEWEB)

    Riz, D.; Pamela, J. [Departement de Recherches sur la Fusion Controlee C. E., Cadarache, 13108 St-Paul-lez-Durance Cedex (France)

    1996-07-01

    NIETZSCHE (Negative Ions Extraction and Transport ZSimulation Code for HydrogEn species) is a negative ion (NI) transport code developed at Cadarache. This code calculates NI trajectories using a 3D Monte-Carlo technique, taking into account the main destruction processes, as well as elastic collisions (H{sup {minus}}/H{sup +}) and charge exchanges (H{sup {minus}}/H{sup 0}). It determines the extraction probability of a NI created at a given position. According to the simulations, we have seen that in the case of volume production, only NI produced close to the plasma grid (PG) can be extracted. Concerning the surface production, we have studied how NI produced on the PG and accelerated by the plasma sheath backward into the source could be extracted. We demonstrate that elastic collisions and charge exchanges play an important role, which in some conditions dominates the magnetic filter effect, which acts as a magnetic mirror. NI transport in various conditions will be discussed: volume/surface production, high/low plasmas density, tent filter/transverse filter. {copyright} {ital 1996 American Institute of Physics.}

  9. Study of negative ion transport phenomena in a plasma source

    Science.gov (United States)

    Riz, D.; Paméla, J.

    1996-07-01

    NIETZSCHE (Negative Ions Extraction and Transport ZSimulation Code for HydrogEn species) is a negative ion (NI) transport code developed at Cadarache. This code calculates NI trajectories using a 3D Monte-Carlo technique, taking into account the main destruction processes, as well as elastic collisions (H-/H+) and charge exchanges (H-/H0). It determines the extraction probability of a NI created at a given position. According to the simulations, we have seen that in the case of volume production, only NI produced close to the plasma grid (PG) can be extracted. Concerning the surface production, we have studied how NI produced on the PG and accelerated by the plasma sheath backward into the source could be extracted. We demonstrate that elastic collisions and charge exchanges play an important role, which in some conditions dominates the magnetic filter effect, which acts as a magnetic mirror. NI transport in various conditions will be discussed: volume/surface production, high/low plasmas density, tent filter/transverse filter.

  10. Online platform for simulations of ion energy distribution functions behind a plasma boundary sheath

    Science.gov (United States)

    Wollny, Alexander; Shihab, Mohammed; Brinkmann, Ralf Peter

    2012-10-01

    Plasma processes, particularly plasma etching and plasma deposition are crucial for a large variety of industrial manufacturing purposes. For these processes the knowledge of the ion energy distribution function plays a key role. Measurements of the ion energy and ion angular distribution functions (IEDF, IADF) are at least challenging and often impossible in industrial processes. An alternative to measurements of the IEDF are simulations. With this contribution we present a self-consistent model available online for everyone. The simulation of ion energy and ion angular distribution functions involves the well known plasma boundary sheath model by Brinkmann [1-4], which is controlled via a web interface (http://sheath.tet.rub.de). After a successful simulation run all results are evaluable within the browser and ready for download for further analysis.[4pt] [1] R.P. Brinkmann, J. Phys. D: Appl. Phys. 44, 042002 (2011)[0pt] [2] R.P. Brinkmann, J. Phys. D: Appl. Phys. 42, 194009 (2009)[0pt] [3] R.P. Brinkmann, J. App. Phys. 102, 093303 (2007)[0pt] [4] M. Kratzer et al., J. Appl. Phys. 90, 2169 (2001)

  11. Modelling of density limit phenomena in toroidal helical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, K. [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, S.-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Giannone, L. [Max Planck Institut fuer Plasmaphysik, EURATOM-IPP Association, Garching (Germany)

    2000-03-01

    The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the W7-AS stellarator. (author)

  12. Modelling of density limit phenomena in toroidal helical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, Sanae-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Giannone, Louis [EURATOM-IPP Association, Max Planck Institut fuer Plasmaphysik, Garching (Germany)

    2001-11-01

    The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the Wendelstein 7-AS (W7-AS) stellarator. (author)

  13. Some Nonlinear Phenomena in a Preformed Underdense Plasma

    Institute of Scientific and Technical Information of China (English)

    曹莉华; 刘智勇; 常文蔚; 岳宗五

    2001-01-01

    The propagation of a laser pulse with a peak intensity 1019 W/cm2 through the preformed underdense plasmawith the density 0.014nc are studied by using two-dimensional particle-in-cell simulations. The longitudinal electron heating is identified and verified, and its major property agrees with the theoretical prediction. The electron distributions in phase space, patterns of the electric fields, profiles of the ion or electron density and other plasma nonlinear phenomena are presented and discussed.

  14. Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, N. A.; Benilov, M. S. [Departamento de Fisica, CCCEE, Universidade da Madeira Largo do Municipio, 9000 Funchal (Portugal)

    2012-07-15

    A transformation of the ion momentum equation simplifies a mathematical description of the transition layer between a quasi-neutral plasma and a collisionless sheath and clearly reveals the physics involved. Balance of forces acting on the ion fluid is delicate in the vicinity of the sonic point and weak effects come into play. For this reason, the passage of the ion fluid through the sonic point, which occurs in the transition layer, is governed not only by inertia and electrostatic force but also by space charge and ion-atom collisions and/or ionization. Occurrence of different scenarios of asymptotic matching in the plasma-sheath transition is analyzed by means of simple mathematical examples, asymptotic estimates, and numerical calculations. In the case of a collisionless sheath, the ion speed distribution plotted on the logarithmic scale reveals a plateau in the intermediate region between the sheath and the presheath. The value corresponding to this plateau has the meaning of speed with which ions leave the presheath and enter the sheath; the Bohm speed. The plateau is pronounced reasonably well provided that the ratio of the Debye length to the ion mean free path is of the order of 10{sup -3} or smaller. There is no such plateau if the sheath is collisional and hence no sense in talking of a speed with which ions enter the sheath.

  15. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    CERN Document Server

    Auluck, S K H

    2014-01-01

    Experimental data compiled over five decades of dense plasma focus research is consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and wind pressure resisting its motion. The resulting sheath velocity, or the numerically proportional drive parameter, is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  16. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    Science.gov (United States)

    Auluck, S. K. H.

    2014-09-01

    Experimental data compiled over five decades of dense plasma focus research are consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and "wind pressure" resisting its motion. The resulting sheath velocity, or the numerically proportional "drive parameter," is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum, and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  17. Effect of Discharge Voltage on an Ion Sheath Formed at a Grid in a Multi-Dipole Discharge Plasma

    Institute of Scientific and Technical Information of China (English)

    M.K.Mishra; A.Phukan

    2008-01-01

    @@ It is experimentally demonstrated that a relatively strong ion-rich sheath formed at a fixed negative bias of the grid can be changed to arather weak ion sheath(sheath potential weakly retards dectrons)only by increasing the discharge voltage in the system.At sufficiently high negative grid bias,an increase of discharge voltage enhances the ion collection current at the grid.An explanation is put forward in support of this experimental observation.A slight density enhancement with a fall in plasma electron temperature is also observed with the increasing negative grid bias.

  18. Plasma-Sheath Instability in Hall Thrusters Due to Periodic Modulation of the Energy of Secondary Electrons in Cyclotron Motion

    Energy Technology Data Exchange (ETDEWEB)

    Sydorenko, D.; Smolyakov, A.; Kaganovich, I.; Raitses, Y.

    2008-04-23

    Particle-in-cell simulation of Hall thruster plasmas reveals a plasma-sheath instability manifesting itself as a rearrangement of the plasma sheath near the thruster channel walls accompanied by a sudden change of many discharge parameters. The instability develops when the sheath current as a function of the sheath voltage is in the negative conductivity regime. The major part of the sheath current is produced by beams of secondary electrons counter-streaming between the walls. The negative conductivity is the result of nonlinear dependence of beam-induced secondary electron emission on the plasma potential. The intensity of such emission is defined by the beam energy. The energy of the beam in crossed axial electric and radial magnetic fields is a quasi-periodical function of the phase of cyclotron rotation, which depends on the radial profile of the potential and the thruster channel width. There is a discrete set of stability intervals determined by the final phase of the cyclotron rotation of secondary electrons. As a result, a small variation of the thruster channel width may result in abrupt changes of plasma parameters if the plasma state jumps from one stability interval to another.

  19. Description of plasma focus current sheath as the Turner relaxed state of a Hall magnetofluid

    Science.gov (United States)

    Auluck, S. K. H.

    2009-12-01

    The central mystery of plasma focus research is the two orders-of-magnitude-higher-than-thermal fusion reaction rate and the fact that both the space-resolved neutron spectra and space-resolved reaction proton spectra show features which can be ascribed only to a rotational motion of the center-of-mass of the reacting deuteron population. It has been suggested earlier [S. K. H. Auluck, IEEE Trans. Plasma Sci. 25, 37 (1997)] that this and other experimental observations can be consistently explained in terms of a hypothesis involving rotation of the current carrying plasma annulus behind the imploding gas-dynamic shock. Such rotation (more generally, mass flow) is an in-built feature of relaxed state of a two-fluid plasma [R. N. Sudan, Phys. Rev. Lett. 42, 1277 (1979)]. Relaxation in the "Hall magnetofluid" approximation, in which the generalized Ohm's law includes the Hall effect term and the magnetic convection term but omits the contributions to the electric field from resistive dissipation, electron pressure gradient, thermoelectric effect, electron inertia, etc., has been extensively studied by many authors. In the present paper, Turner's [IEEE Trans. Plasma Sci. PS-14, 849 (1986)] degenerate solution for the relaxed state of the Hall magnetohydrodynamic plasma has been adapted to the case of an infinitely long annular current carrying plasma, a tractable idealization of the current sheath of a plasma focus. The resulting model is consistent with experimental values of ion kinetic energy and observation of predominantly radially directed neutron emission in good shots.

  20. Dusty plasma sheath-like structure in the region of lunar terminator

    Energy Technology Data Exchange (ETDEWEB)

    Popel, S. I.; Zelenyi, L. M. [Space Research Institute of the Russian Academy of Sciences, Moscow 117997, Russia and Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region 141700 (Russian Federation); Atamaniuk, B. [Space Research Center of the Polish Academy of Sciences, Warsaw 00-716 (Poland)

    2015-12-15

    The main properties of the dusty plasma layer near the surface over the illuminated and dark parts of the Moon are described. They are used to realize dusty plasma behaviour and to determine electric fields over the terminator region. Possibility of the existence of a dusty plasma sheath-like structure in the region of lunar terminator is shown. The electric fields excited in the terminator region are demonstrated to be on the order of 300 V/m. These electric fields can result in rise of dust particles of the size of 2–3 μm up to an altitude of about 30 cm over the lunar surface that explains the effect of “horizon glow” observed at the terminator by Surveyor lunar lander.

  1. Charge and Levitation of Grains in Plasma Sheath with Dust Thermic Emission

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    By taking into account thermic emission current from hot dust surface, the problem involved in dust charging and levitation of dust grains in plasma sheath has been researched. The results are compared to that without including thermal emission current while the system parameters are same. It is found that the thermal emission current has played a significant role on modifying the dust charging and balance levitations. Both of the charging numbers of dust and the dust radius in balance are dramatically reduced. The stability of dust levitation is also analyzed and discussed.

  2. First experimental studies of ion flow in 3 ion species plasmas at the presheath-sheath transition

    Science.gov (United States)

    Severn, Greg

    2016-09-01

    The Bohm sheath criterion is studied with laser-induced fluorescence (LIF) in three ion species plasmas using two tunable diode lasers. KrI or HeI is added to a low pressure unmagnetized dc hot filament discharge in a mixture of argon and xenon gas confined by surface multi-dipole magnetic fields. The argon and xenon ion velocity distribution functions are measured at the sheath-presheath boundary near a negatively biased boundary plate. The potential structures of the plasma sheath and presheath are measured by an emissive probe. Results are compared with previous experiments with Ar-Xe plasmas, where the two ion species were observed to reach the sheath edge at nearly the same speed. This speed was the ion sound speed of the system, which is consistent with the generalized Bohm criterion. In such two ion species plasmas instability enhanced collisional friction (IEF) was demonstrated to exist which accounted for the observed results. When three ion species are present, it is demonstrated under most circumstances the ions do not fall out of the plasma at their individual Bohm velocities. It is also shown that under most circumstances the ions do not fall out of the plasma at the system sound speed. Results are consistent with the presence of instabilities. Author gratefully acknowledges collaborators Dr. Noah Hershkowtiz, Dr. Chi-Shung Yip, Dept. of Engineering Physics, Univ. Wisconsin-Madison, and Dr. Scott Baalrud, Dept. Physics, Univ. Iowa. Thanks to US DOE, grant DE-SC00014226.

  3. Particle in cell calculation of plasma force on a small grain in a non-uniform collisional sheath

    CERN Document Server

    Hutchinson, I H

    2013-01-01

    The plasma force on grains of specified charge and height in a collisional plasma sheath are calculated using the multidimensional particle in cell code COPTIC. The background ion velocity distribution functions for the unperturbed sheath vary substantially with collisionality. The grain force is found to agree quite well with a combination of background electric field force plus ion drag force. However, the drag force must take account of the non-Maxwellian (and spatially varying) ion distribution function, and the collisional drag enhancement. It is shown how to translate the dimensionless results into practical equilibrium including other forces such as gravity.

  4. Pulsed ion sheath dynamics in a cylindrical bore for inner surface grid-enhanced plasma source ion implantation

    CERN Document Server

    Wang Jiu Li; Fan Song Hua; Yang Wu Bao; Yang Size

    2002-01-01

    Based on authors' recently proposed grid-enhanced plasma source ion implantation (GEPSII) technique for inner surface modification of materials with cylindrical geometry, the authors present the corresponding theoretical studies of the temporal evolution of the plasma ion sheath between the grid electrode and the target in a cylindrical bore. Typical results such as the ion sheath evolution, time-dependent ion density and time-integrated ion energy distribution at the target are calculated by solving Poisson's equation coupled with fluid equations for collisionless ions and Boltzmann assumption for electrons using finite difference methods. The calculated results can further verify the feasibility and superiority of this new technique

  5. Two-dimensional simulation and modeling for dynamic sheath expansion during plasma immersion ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Qin, S.; Zhou, Y.; Chan, C. [Northeastern Univ., Boston, MA (United States)

    1996-12-31

    Plasma immersion ion implantation (PIII) has been utilized as a low cost, low energy doping method for large area targets with applications to semiconductor manufacturing. They include doping, shallow junction formation, hydrogenation for poly-Si thin film transistors, and SIMOX (Separated by IMplant of OXygen) structure formation. The characteristics of the dynamic sheath expansion during PIII process is very important for the optimum PIII configuration design and process control in order to obtain more accurate doping results such as the implant dose and impurity profile. For example, the sheath thickness is critical to chamber design and monoenergetic ion implant for a more accurate control of as-implanted impurity profile of shallow junction and SIMOX structures. A PDP2 simulation code has been used to simulate PIII process which will aid in understanding the physics of PIII processes and obtain the optimum process parameters. This model was verified by comparing with the PDP2 computer simulations and the experimental results of the PIII doping processes.

  6. Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

    Directory of Open Access Journals (Sweden)

    K.-I. Nishikawa

    2013-09-01

    Full Text Available We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012, the structure of the kinetic Kelvin–Helmholtz instability (KKHI of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5 is larger than for a relativistic jet case (γj = 15.

  7. Dusty plasma sheath-like structure in the lunar terminator region

    Science.gov (United States)

    Popel, Sergey; Zelenyi, Lev; Atamaniuk, Barbara

    2016-07-01

    The main properties of the dusty plasma layer near the surface over the illuminated and dark parts of the Moon are described. They are used to realize dusty plasma behaviour and to determine electric fields over the terminator region. Possibility of the existence of a dusty plasma sheath-like structure [1] in the region of lunar terminator is shown. The electric fields excited in the terminator region are demonstrated to be on the order of 300 V/m. These electric fields can result in rise of dust particles of the size of a few micrometers up to an altitude of about 30 cm over the lunar surface that explains the effect of ``horizon glow" observed at the terminator by Surveyor lunar lander. This work was supported in part by the Presidium of the Russian Academy of Sciences (under Fundamental Research Program No. 7, ``Experimental and Theoretical Study of the Solar System Objects and Stellar Planet Systems. Transient Explosion Processes in Astrophysics" and the Russian Foundation for Basic Research (Project No. 15-02-05627-a). [1] S. I. Popel, L. M. Zelenyi, and B. Atamaniuk, Phys. Plasmas 22, 123701 (2015); doi: 10.1063/1.4937368.

  8. Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

    Science.gov (United States)

    Willis, Emily M.; Pour, Maria Z. A.

    2017-01-01

    High voltage solar array interactions with the space environment can have a significant impact on array performance and spacecraft charging. Over the past 10 years, data from the International Space Station has allowed for detailed observations of these interactions over long periods of time. Some of the surprising observations have been floating potential transients, which were not expected and are not reproduced by existing models. In order to understand the underlying processes producing these transients, the temporal evolution of the plasma sheath surrounding the solar cells in low Earth orbit is being investigated. This study includes lumped element modeling and particle-in-cell simulation methods. This presentation will focus on recent results from the on-going investigations.

  9. 2nd Workshop on Laser Interaction and Related Plasma Phenomena

    CERN Document Server

    Hora, Heinrich

    1972-01-01

    Paul Harteck Rensselaer Polytechnic Institute Troy, New York When the Maser and the Laser Were discovered, people were speculating if this was the beginning of a new page, or even a new chapter, in the Book of Physics. The Second Workshop on "Laser Interaction and Related Plasma Phenomena" held in Hartford made it clear that the perspective had changed, that people now question if the consequences of these discoveries constitute a new chapter, or possibly a new era in Physics. While the papers presented were all stimulating and of out­ standing quality, of special interest were the experiments which demonstrated that triggering of thermonuclear fusion by Laser techniques is indeed in the realm of the possible. Along these lines, I enjoy recalling an anecdote concerning the late F. G. Houtermans. I think that all who knew him will agree that he was an unusual genius and at the same time a very amusing colleague.

  10. Nonlinear friction modelling and compensation control of hysteresis phenomena for a pair of tendon-sheath actuated surgical robots

    Science.gov (United States)

    Do, T. N.; Tjahjowidodo, T.; Lau, M. W. S.; Phee, S. J.

    2015-08-01

    Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a special method that allows surgical operations via natural orifices like mouth, anus, and vagina, without leaving visible scars. The use of flexible tendon-sheath mechanism (TSM) is common in these systems because of its light weight in structure, flexibility, and easy transmission of power. However, nonlinear friction and backlash hysteresis pose many challenges to control of such systems; in addition, they do not provide haptic feedback to assist the surgeon in the operation of the systems. In this paper, we propose a new dynamic friction model and backlash hysteresis nonlinearity for a pair of TSM to deal with these problems. The proposed friction model, unlike current approaches in the literature, is smooth and able to capture the force at near zero velocity when the system is stationary or operates at small motion. This model can be used to estimate the friction force for haptic feedback purpose. To improve the system tracking performances, a backlash hysteresis model will be introduced, which can be used in a feedforward controller scheme. The controller involves a simple computation of the inverse hysteresis model. The proposed models are configuration independent and able to capture the nonlinearities for arbitrary tendon-sheath shapes. A representative experimental setup is used to validate the proposed models and to demonstrate the improvement in position tracking accuracy and the possibility of providing desired force information at the distal end of a pair of TSM slave manipulator for haptic feedback to the surgeons.

  11. Stability analysis of the Gravito-Electrostatic Sheath-based solar plasma equilibrium

    Science.gov (United States)

    Karmakar, P. K.; Goutam, H. P.; Lal, M.; Dwivedi, C. B.

    2016-08-01

    We present approximate solutions of non-local linear perturbational analysis for discussing the stability properties of the Gravito-Electrostatic Sheath (GES)-based solar plasma equilibrium, which is indeed non-uniform on both the bounded and unbounded scales. The relevant physical variables undergoing perturbations are the self-solar gravity, electrostatic potential and plasma flow along with plasma population density. We methodologically derive linear dispersion relation for the GES fluctuations, and solve it numerically to identify and characterize the existent possible natural normal modes. Three distinct natural normal modes are identified and named as the GES-oscillator mode, GES-wave mode and usual (classical) p-mode. In the solar wind plasma, only the p-mode survives. These modes are found to be linearly unstable in wide-range of the Jeans-normalized wavenumber, k. The local plane-wave approximation marginally limits the validity or reliability of the obtained results in certain radial- and k-domains only. The phase and group velocities, time periods of these fluctuation modes are investigated. It is interesting to note that, the oscillation time periods of these modes are 3-10 min, which match exactly with those of the observed helio-seismic waves and solar surface oscillations. The proposed GES model provides a novel physical view of the waves and oscillations of the Sun from a new perspective of plasma-wall interaction physics. Due to simplified nature of the considered GES equilibrium, it is a neonatal stage to highlight its applicability in the real Sun. The proposed GES model and subsequent fluctuation analysis need further improvements to make it more realistic.

  12. Whistler-mode phenomena in electron MHD plasmas

    Science.gov (United States)

    Stenzel, R. L.

    2003-12-01

    While the linear properties of plane whistler waves are well known, many new phenomena of bounded wavepackets and nonlinear effects are worth to describe. The present talk will review laboratory observations of whistler filaments, whistler vortices, whistler wings, whistler-sound modes in high-beta plasmas, nonlinear whistlers forming magnetic null points, and magnetic reconnection in EMHD plasmas. The time-varying magnetic field of a spatially bounded whistler wave packet consists of 3-D vortices. Each vortex can be decomposed into linked toroidal and poloidal field components. The self-helicity is positive for propagation along the field, negative for opposite propagation. Helicity injection from a suitable source produces unidirectional propagation. Magnetic helicity changes sign, i.e., is not conserved, when the propagation direction along B changes, for example due to reflection or propagation through a magnetic null point. In ideal EMHD the electric and magnetic forces on the electrons are equal, -n e E +J x B=0, i.e., the electron fluid is not compressed. Force-free vortices do not interact during collisions. Vortices are excited with pulsed magnetic antennas or pulsed electrodes. Both transient currents and fields can form vortices that propagate in the whistler mode. Moving dc magnets or dc current systems can also induce whistler modes in a magnetized plasma. These form a Cherenkov-like radiation pattern, a ``whistler wing.'' Nonlinear phenomena arise from wave-induced modifications of the electron temperature, density and magnetic field. In collisional plasmas electrons are heated by strong whistlers. Modifications of the classical conductivity leads to current filamentation. On a slower time scale density modifications arise from ambipolar fields associated with electron heating. In a filamentation instability a strong whistler wave is ducted along a narrow field-aligned density depression. The ion density is also modified by the ac electric field of

  13. Impact of plasma sheath on rocket-based E-region ion measurements

    Science.gov (United States)

    Imtiaz, Nadia; Burchill, Johnathan; Marchand, Richard

    2015-01-01

    We model the particle velocity distribution functions around the entrance window of the Suprathermal Ion Imager (SII). The SII sensor was mounted on a 1 m boom carried by the scientific payload of NASA rocket 36.234 as part of Joule II mission to investigate Joule heating in the E-region ionosphere. The rocket flew above Northern Alaska on 19 January 2007. The payload was spin-stabilized with a period of 1.6 s, giving an apparent rotation of the ion flow velocity in the frame of reference of the payload. The SII sensor is an electrostatic analyzer that measures two dimensional slices of the distribution of the kinetic energies and arrival-angles of low energy ions. The study is concerned with the interpretation of data obtained from the SII sensor. For this purpose, we numerically investigate ram velocity effects on ions velocity distributions in the vicinity of the SII sensor aperture at an altitudes of approximately 150 km. The electrostatic sheath profiles surrounding the SII sensor, boom and payload are calculated numerically with the PIC code PTetra. It is observed that the direction of the ion flow velocity modifies the plasma sheath potential profile. This in turn impacts the velocity distributions of NO+ and ions at the aperture of the particle sensor. The velocity distribution functions at the sensor aperture are calculated by using test-particle modeling. These particle distribution functions are then used to inject particles in the sensor, and calculate the fluxes on the sensor microchannel plate (MCP), from which comparisons with the measurements can be made.

  14. Characterization of the ionization degree evolution of the PF-400J plasma sheath by means of time resolved optical spectroscopy

    Science.gov (United States)

    Avaria, G.; Cuadrado, O.; Moreno, J.; Pavez, C.; Soto, L.

    2016-05-01

    Spectral measurements in the visible range of the plasma sheath ionization degree evolution on the plasma focus device PF-400J are presented. The measurements were done with temporal and spatial resolution in a plasma focus device of low stored energy: PF-400J (176-539 J, 880 nF, 20-35 kV, quarter period ∼ 300ns) [1]. An ICCD was attached to a 0.5 m focal length visible spectrometer, which enabled the acquisition of time resolved spectrum with 20 ns integration time throughout the whole current pulse evolution. The spatial resolution was attained using a set of lenses which allowed the focusing of a small volume of the plasma sheath in different positions of the inter-electrode space. Discharges were carried out in mixtures of Hydrogen with gases in different proportions: 5% Neon, 5% Krypton and 2% Nitrogen. Discharges using Neon as an impurity showed no ionization of the gas, just a very low intensity emission of Ne I at times much larger than the maximum current. Nitrogen, on the other hand, showed a high ionization reaching N V (N 4+) at the end of the axial phase, with a distinctive evolution of the ionization degree as the plasma sheath moved towards the end of the electrodes. A mixed result was found when using Krypton, since the ionization degree only reached levels around Kr II/III, even though it has an ionization potential lower than Neon.

  15. Expanding sheath in a bounded plasma in the context of the post-arc phase of a vacuum arc

    Energy Technology Data Exchange (ETDEWEB)

    Sarrailh, P [LAboratoire PLAsma et Conversion de l' Energie (LAPLACE), UMR5213, Universite Paul Sabatier, bat. 3R2, 118 route de Narbonne, 31062 Toulouse cedex 4 (France); Garrigues, L [LAboratoire PLAsma et Conversion de l' Energie (LAPLACE), UMR5213, Universite Paul Sabatier, bat. 3R2, 118 route de Narbonne, 31062 Toulouse cedex 4 (France); Hagelaar, G J M [LAboratoire PLAsma et Conversion de l' Energie (LAPLACE), UMR5213, Universite Paul Sabatier, bat. 3R2, 118 route de Narbonne, 31062 Toulouse cedex 4 (France); Sandolache, G [Schneider Electric Centre de Recherche, 38 TEC, 38050 Grenoble Cedex 09 (France); Rowe, S [Schneider Electric Centre de Recherche, 38 TEC, 38050 Grenoble Cedex 09 (France); Jusselin, B [Schneider Electric Centre de Recherche, 38 TEC, 38050 Grenoble Cedex 09 (France); Boeuf, J P [LAboratoire PLAsma et Conversion de l' Energie (LAPLACE), UMR5213, Universite Paul Sabatier, bat. 3R2, 118 route de Narbonne, 31062 Toulouse cedex 4 (France)

    2008-01-07

    A numerical model of sheath expansion and plasma decay in a bounded plasma subjected to a linearly increasing voltage has been developed. Numerical results obtained with a hybrid-MB model (Maxwell-Boltzmann electrons, particle ions and Poisson's equations) are compared with analytical theory and results from particle-in-cell (PIC) simulations. The hybrid-MB model is similar to models used for plasma immersion ion implantation except that plasma decay due to particle losses to the electrodes is taken into account. The comparisons with more accurate and much more time consuming PIC models show that the hybrid-MB model provides a very satisfactory description of the sheath expansion and plasma decay even for conditions where the grid spacing is much larger than the Debye length. The model is used for high plasma density conditions, corresponding to the post-arc phase of a vacuum arc circuit breaker where a vacuum gap is subject to a transient recovery voltage (TRV) after it has ceased to sustain a vacuum arc. The results show that the plasma sheath expansion is subsonic under these conditions, and that the plasma starts to decay exponentially after two rarefaction waves from the cathode and anode merge in the centre of the gap. A parametric study also shows the strong influence of the TRV rise rate and initial plasma density on the plasma decay time and on the ion current collected by each electrode. The effect of collisions between charged particles and metal atoms resulting for the electrode evaporation is also discussed.

  16. The Study Of Low-Frequency Instabilities Of Current Sheaths Of Space Plasma Within The Quasi-Linear Theory

    Science.gov (United States)

    Lyahov, Vladimir; Neshchadim, Vladimir

    2015-04-01

    Investigation of the stability nonelectroneutral current sheets in the linear approximation [1-4] gives information only on the initial stage of development of perturbations when their amplitudes are small. Within the framework of the quasi-linear theory one can give an answer to the question of how long the initial perturbations can grow and how change the equilibrium state of the plasma current sheet under the reverse effect of these perturbations. We derive a system of nonlinear kinetic equation with self-consistent electromagnetic field in order to study the evolution of the distribution function of the background plasma current sheet in the approximation of low-frequency eigenmodes of instabilities. Evolution equation was obtained for the perturbation of the electromagnetic field and the instability growth rate in the current sheet. Algorithms were tested for solutions of the equations obtained. 1. Lyahov V.V., Neshchadim V.M. Kinetic theory of the current sheath. I. On polarization of an equilibrium current sheath// Advances in Space Research. -2012. -Vol. 50. -P. 318-326. 2. Lyahov V.V., Neshchadim V.M. Kinetic theory of the current sheath. II. Effect of polarization on the stability of a current sheath.// Advances in Space Research.-2013. -Vol. 51. -P. 730-741. 3. Lyahov V.V., Neshchadim V.M. The Effect of Polarization on the Stability of Current Sheaths in Space Plasma // EGU General Assembly 2013, held 7-12 April, 2013 in Vienna, Austria, id. EGU2013-1379, 04/2013, Bibliographic Code: 2013EGUGA..15.1379L 4. Lyahov V.V., Neshchadim V.M. About the eguilibrium and stability of nonelectroneutral current sheats // Advances in Space Research.-2014. -Vol. 54. -P. 901-907.

  17. Theoretical study of nonlinear waves and shock-like phenomena in hot plasmas

    Science.gov (United States)

    Fried, B. D.; Banos, A., Jr.; Kennel, C. F.

    1973-01-01

    Summaries are presented of research in basic plasma physics. Nonlinear waves and shock-like phenomena were studied which are pertinent to space physics applications, and include specific problems of magnetospheric and solar wind plasma physics.

  18. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    Science.gov (United States)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  19. Numerical studies of wall–plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Lei [Beijing Research Institute of Precise Mechatronic Controls, Beijing 100076 (China); School of Astronautics, Beihang University, Beijing 100191 (China); Zeng, Guangshang; Huang, Yuping [Beijing Research Institute of Precise Mechatronic Controls, Beijing 100076 (China); Tang, Haibin [School of Astronautics, Beihang University, Beijing 100191 (China); Liu, Xiangyang [School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081 (China)

    2016-07-15

    Wall–plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall–plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall–plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  20. Probing the sheath electric field with a crystal lattice by using thermophoresis in dusty plasma

    CERN Document Server

    Land, Victor; Matthews, Lorin; Hyde, Truell

    2010-01-01

    A two-dimensional dust crystal levitated in the sheath of a modified Gaseous Electronics Conference (GEC) reference cell is manipulated by heating or cooling the lower electrode. The dust charge is obtained by measuring global characteristics of the levitated crystal obtained from top-view pictures. From the force balance, the electric field in the sheath is reconstructed. From the Bohm criterion, we conclude that the dust crystal is levitated mainly above and just below the classical Bohm point.

  1. Stochastic heating of a single Brownian particle by charge fluctuations in a radio-frequency produced plasma sheath.

    Science.gov (United States)

    Schmidt, Christian; Piel, Alexander

    2015-10-01

    The Brownian motion of a single particle in the plasma sheath is studied to separate the effect of stochastic heating by charge fluctuations from heating by collective effects. By measuring the particle velocities in the ballistic regime and by carefully determining the particle mass from the Epstein drag it is shown that for a pressure of 10 Pa, which is typical of many experiments, the proper kinetic temperature of the Brownian particle remains close to the gas temperature and rises only slightly with particle size. This weak effect is confirmed by a detailed model for charging and charge fluctuations in the sheath. A substantial temperature rise is found for decreasing pressure, which approximately shows the expected scaling with p(-2). The system under study is an example for non-equilibrium Brownian motion under the influence of white noise without corresponding dissipation.

  2. Re-entry communication through a plasma sheath using standing wave detection and adaptive data rate control

    Science.gov (United States)

    Xie, Kai; Yang, Min; Bai, Bowen; Li, Xiaoping; Zhou, Hui; Guo, Lixin

    2016-01-01

    Radio blackout during the re-entry has puzzled the aerospace industry for decades and has not yet been completely resolved. To achieve a continuous data link in the spacecraft's re-entry period, a simple and practicable communication method is proposed on the basis that (1) the electromagnetic-wave backscatter of the plasma sheath affects the voltage standing wave ratio (VSWR) of the antenna, and the backscatter is negatively correlated to transmission components, and (2) the transmission attenuation caused by the plasma sheath reduces the channel capacity. We detect the voltage standing wave ratio changes of the antenna and then adjust the information rate to accommodate the varying channel capacity, thus guaranteeing continuous transmission (for fewer critical data). The experiment was carried out in a plasma generator with an 18-cm-thick and 30-cm-diameter hollow propagation path, and the adaptive communication was implemented using spread spectrum frequency, shift key modulation with a variable spreading factor. The experimental results indicate that, when the over-threshold of VSWR was detected, the bit rate reduced to 250 bps from 4 Mbps automatically and the tolerated plasma density increased by an order of magnitude, which validates the proposed scheme. The proposed method has little additional cost, and the adaptive control does not require a feedback channel. The method is therefore applicable to data transmission in a single direction, such as that of a one-way telemetry system.

  3. Acoustic black hole evaporation as plasma diffusion phenomena

    CERN Document Server

    de Andrade, Garcia

    2008-01-01

    Acoustic analogues of Kerr black hole in plasmas are considered, by taking for granted the existence of acoustic ion waves in plasmas. An effective black holes (BH) in curved Riemannian spacetime in a random walk plasmas is endowed with a naked singularity, when plasmas are in the lowest diffusion mode. The plasma particle diffusion is encoded in the effective metric. The diffusive solution has a horizon when the plasma flow reaches the sound velocity in the medium and a shock wave is obtained inside the slab. The sonic black hole curved Riemannian metric is also found in terms of particle number density in plasmas. The sonic BH singularity is found at the center of the plasma diffusive slab from the study of the Ricci curvature scalar for constant diffusion coefficient. It is suggested and shown that the Hawking temperature is proportional to the plasma Kelvin temperature through diffusion coefficient dependence to this temperature. Therefore Unruh sonic or dumb BH is shown to have a relation between Hawking...

  4. A different way of looking at the Plasma-Sheath boundary when both the ion mean free path and the Debye length are finite

    Science.gov (United States)

    Franklin, Raoul

    2003-10-01

    The plasma-sheath boundary region has been the subject of study for eighty years, but there are aspects that are still not well understood. At low pressures it is clear that the structure is - plasma-transition layer-thin electron sheath-(thick)ion sheath, and at high pressures it is plasma-collisional sheath, without the need to introduce further structure. As the plasma becomes collisional, there is the question as to how long it is appropriate to talk in terms of the Bohm criterion. Furthermore if the total sheath region is many ion mean free paths long, then the ions may be brought back into collisional equilibrium with the electric field, even though their speed exceeds the ion sound speed of the plasma from which they derive. We examine computationally this intermediate pressure region in terms of of how to describe the ion motion, showing how the two limits go over from the one to the other. Most practical plasmas in gas discharges are in such a transitional pressure region.

  5. Surface rippling by oblique ion incidence during plasma etching of silicon: Experimental demonstration using sheath control plates

    Science.gov (United States)

    Nakazaki, Nobuya; Matsumoto, Haruka; Eriguchi, Koji; Ono, Kouichi

    2015-09-01

    In the microfabrication of 3D transistors (e.g. Fin-FET), the sidewall roughness, such as LER and LWR caused by off-normal or oblique ion incidence during plasma etching, is a critical issue to be resolved, which in turn requires a better understanding of the effects of ion incidence angle θi on surface roughening. This paper presents surface roughening and rippling by oblique ion incidence during inductively coupled plasma etching of Si in Cl2, using the experimental setup as in our previous study. The oblique ion incidence was achieved by sheath control plates, which were placed on and electrically connected to the wafer stage. The plates had slits to vary the sheath structure thereon and to extract ions from plasma to samples on the bottom and/or side of the slits. The results indicated that at θi ~ 40° or oblique incidence; ripple structures were formed on surfaces perpendicularly to the direction of ion incidence, on the other hand, at θi ~ 80° or grazing incidence, small ripples or slit like grooves were formed on surfaces parallel to the direction of ion incidence, as predicted in our previous numerical investigations.

  6. Transport phenomena in a plasma of confining gluons

    Directory of Open Access Journals (Sweden)

    Ryblewski Radoslaw

    2016-01-01

    Full Text Available The plasma of confining gluons resulting from the Gribov quantization is considered. In the fluid dynamical framework the non-equilibrium properties of the system are studied. In the linear response approximation the formulas for the bulk, ζ, and shear, η, viscosities of the plasma are calculated analytically. Surprisingly, the approximate scaling of the ζ/η ratio reveals the strong-coupling properties of the system under consideration.

  7. The expansion of a plasma into a vacuum - Basic phenomena and processes and applications to space plasma physics

    Science.gov (United States)

    Wright, K. H., Jr.; Stone, N. H.; Samir, U.

    1983-01-01

    In this review attention is called to basic phenomena and physical processes involved in the expansion of a plasma into a vacuum, or the expansion of a plasma into a more tenuous plasma, in particular the fact that upon the expansion, ions are accelerated and reach energies well above their thermal energy. Also, in the process of the expansion a rarefaction wave propagates into the ambient plasma, an ion front moves into the expansion volume, and discontinuities in plasma parameters occur. The physical processes which cause the above phenomena are discussed, and their possible application is suggested for the case of the distribution of ions and electrons (hence plasma potential and electric fields) in the wake region behind artificial and natural obstacles moving supersonically in a rarefied space plasma. To illustrate this, some in situ results are reexamined. Directions for future work in this area via the utilization of the Space Shuttle and laboratory work are also mentioned.

  8. Breakdown of a space charge limited regime of a sheath in a weakly collisional plasma bounded by walls with secondary electron emission.

    Science.gov (United States)

    Sydorenko, D; Kaganovich, I; Raitses, Y; Smolyakov, A

    2009-10-02

    A new regime of plasma-wall interaction is identified in particle-in-cell simulations of a hot plasma bounded by walls with secondary electron emission. Such a plasma has a strongly non-Maxwellian electron velocity distribution function and consists of bulk plasma electrons and beams of secondary electrons. In the new regime, the plasma sheath is not in a steady space charge limited state even though the secondary electron emission produced by the plasma bulk electrons is so intense that the corresponding partial emission coefficient exceeds unity. Instead, the plasma-sheath system performs relaxation oscillations by switching quasiperiodically between the space charge limited and non-space-charge limited states.

  9. Frequency upshift via flash ionization phenomena using semiconductor plasma

    Directory of Open Access Journals (Sweden)

    Nishida A.

    2013-11-01

    Full Text Available We have demonstrated frequency upshift in the terahertz region by flash ionization. The magnitude of upshift frequency is tuned by the laser intensity. A proof of principle experiment has been performed with a plasma creation time scale much shorter than the period of the electromagnetic wave and a plasma length longer than its wavelength. Frequency upshifted from 0.35 to 3.5 THz by irradiating a ZnSe crystal with a ultra-short laser pulse has been observed.

  10. Numerical solutions of sheath structures around a moderate negative biased electron-emitting cylindrical probe in low-density isotropic plasma

    Science.gov (United States)

    Din, Alif

    2017-09-01

    The potential structures around a moderate negative biased electron-emitting cylindrical probe in low-density isotropic plasma are calculated in the collisionless sheath region. The formalisms, equations, and solutions for the entire electron emitting range (i.e., subcritical, critical, and supercritical) from the cylindrical emitter and collector surface are discussed. The plasma-electron and emitted-electron are assumed to have half Maxwellian velocity distributions at their respective sheath entering boundaries with cold plasma ions. Poisson's equation is solved numerically in the sheath region for the subcritical, critical, and supercritical emissions. The I-V characteristics for these three cases are presented in tabular form. The results show that we need very high emitted-electron current to solve Poisson's equation for the critical and spercritical emissions. Thus, the floating potential is far away in these scenarios. Also, the number density of emitted-and plasma-electron are comparable at the sheath edge so we cannot neglect the density of former in comparison with latter at the sheath edge.

  11. Characteristics of sheath-driven tangential flow produced by a low-current DC surface glow discharge plasma actuator

    Science.gov (United States)

    Shin, Jichul; Shajid Rahman, Mohammad

    2014-08-01

    An experimental investigation of low-speed flow actuation at near-atmospheric pressure is presented. The flow actuation is achieved via low-current ( \\lesssim 1.0 mA) continuous or pulsed DC surface glow discharge plasma. The plasma actuator, consisting of two sharp-edged nickel electrodes, produces a tangential flow in a direction from anode to cathode, and is visualized using high-speed schlieren photography. The induced flow velocity estimated via the schlieren images reaches up to 5 m/s in test cases. The actuation capability increases with pressure and electrode gap distances, and the induced flow velocity increases logarithmically with the discharge power. Pulsed DC exhibits slightly improved actuation capability with better directionality. An analytic estimation of induced flow velocity obtained based on ion momentum in the cathode sheath and gas dynamics in one-dimensional flow yields values similar to those measured.

  12. Theoretical and experimental studies of space-related plasma wave propagation and resonance phenomena

    Science.gov (United States)

    Crawford, F. W.

    1975-01-01

    A ten year summary was given of university research on the nature and characteristics of space related plasma resonance phenomena, whistler propagation in laboratory plasmas, and theoretical and experimental studies of plasma wave propagation. Data are also given on long delayed echoes, low frequency instabilities, ionospheric heating, and backscatter, and pulse propagation. A list is included of all conference papers, publications, and reports resulting from the study.

  13. Observation of ion-ion counter streaming instability in presheath-sheath region of a mesh grid immersed in low temperature plasma

    Science.gov (United States)

    Prasad Kella, Vara; Ghosh, J.; Chattopadhyay, P. K.; Sharma, D.; Saxena, Y. C.

    2017-03-01

    Instabilities in the sheath-presheath region formed in plasma-boundary layers are known to modify the particle flow velocities and their distribution functions, hence influencing the particle transport in this region significantly. In this paper, experimental observations of the ion-ion counter streaming instability excited in the sheath-presheath region of Argon (Ar), Helium (He), and Ar + He plasmas have been reported. These instabilities are excited in the vicinity of a stainless steel mesh grid placed inside the plasma. Floating potential (FP) fluctuations from the grid and from a movable Langmuir probe placed in the sheath-presheath region are measured. The frequency spectra of FP fluctuations in an argon plasma show a dominant broad peak in the range of 10-20 kHz centering around 15 kHz, which is identified as due to the ion-ion counter streaming instability. This frequency peak exists only in the sheath-presheath region and ceases to exist when the mesh grid is covered with a thin metal foil from one side, which restricts the counter streaming of the ions. The measured wave number, k, of the wave matches quite well with the calculated one from the dispersion relation of ion-ion counter streaming instability. The experiments are repeated to study the instability in He and Ar + He (two ion species) plasmas in similar experimental conditions. The neutral pressure threshold for sustenance of this instability has also been observed.

  14. Plasma phenomena observed in the MAP-WINE campaign

    Science.gov (United States)

    Friedrich, M.

    The wealth of plasma data gathered in the MAP-WINE campaign allows insight into the generation and morphology of electron densities on a large scale, and the nature of the ions on a small scale. The associated measurements of winds and charged particles help to understand the morphology of the mid-latitude ionisation which turns out to correlate poorly with geomagnetic activity, but at least slightly with the prevailing winds. A somewhat clearer connection seems to exist between stratospheric warmings and radio wave absorption minima. On the local scale the interpretation of the rocket measurements of positive ions was helped by simultaneous observations of temperatures and atomic oxygen. The relevance of the description ``winter anomaly'' for high latitude electron density profiles will be examined.

  15. Pattern phenomena in an rf discharge dusty plasma system

    Institute of Scientific and Technical Information of China (English)

    HUANG Feng; YE Maofu; WANG Long

    2006-01-01

    Various dust patterns are observed in an rf discharge dusty plasma system.According to the dust growth process from small to large in size, the formation of different dust patterns can be divided into two stages: the small-particle stage (or dust cloud stage),and the large-particle stage (or dust crystal stage). The evolution relations between different dust patterns with gas pressure changing are investigated. Dust voids, dust acoustic waves and strong turbulence modes are presented at the small-particle stage. The self-organized dust lattices and dust clusters are investigated at the large-particle stage.The static structure of a dust lattice is characterized by means of the pair correlation function. Dust clusters formed by particles with different numbers and the regular evolution of the clusters with gas pressure are also investigated. The packing sequences of dust clusters are verified through two-dimensional confined molecular dynamics simulations.

  16. Model analysis of edge relaxation phenomena in Tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Matsukawa, Shogo [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka (Japan); Itoh, Sanae I.; Yagi, Masatoshi [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    2000-09-01

    From the view point of the oscillatory characteristics, the heat transport in the plasma edge region is investigated based on a transition transport model with hysteresis nature. A hysteresis type flux-force relation is incorporated into the model by introducing a transition model of the heat diffusivity. For a given influx from the upstream side, the one dimensional heat transport equitation is solved numerically. The time evolution of the heat flux oscillation due to the hysteresis nature and the parameter dependences of its amplitude and frequency are examined. The non-monotonous relation between the frequency of the flux oscillation and the influx is obtained. The critical behavior of the transition between transport mechanisms, i.e., the hysteresis type and the discontinuous one, is expressed as power law relations of them. The self-organized criticality like behavior, i.e., power spectrum obeying power law, is found in a limiting case of the model. (author)

  17. Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts

    Science.gov (United States)

    Zhai, Guofu; Bo, Kai; Chen, Mo; Zhou, Xue; Qiao, Xinlei

    2016-05-01

    Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit. We characterized the arc plasma jet flow appearance at different currents by using high-speed photography, and two polished contacts were used to search for the relationship between roughness and plasma jet flow. Then, to make the nature of arc plasma jet flow phenomena clear, a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated. The simulated DC arc plasma was presented with the temperature distribution and the current density distribution. Furthermore, the calculated arc flow velocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress. The combined action of volume force and contact surface was the main reason of the arc jet flow. supported by National Natural Science Foundation of China (Nos. 51307030, 51277038)

  18. Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts

    Institute of Scientific and Technical Information of China (English)

    ZHAI Guofu; BO Kai; CHEN Mo; ZHOU Xue; QIAO Xinlei

    2016-01-01

    Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit.We characterized the arc plasma jet flow appearance at different currents by using high-speed photography,and two polished contacts were used to search for the relationship between roughness and plasma jet flow.Then,to make the nature of arc plasma jet flow phenomena clear,a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated.The simulated DC arc plasma was presented with the temperature distribution and the current density distribution.Furthermore,the calculated arc flow vclocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress.The combined action of volume force and contact surface was the main reason of the arc jet flow.

  19. Nonlinear phenomena in RF wave propagation in magnetized plasma: A review

    Energy Technology Data Exchange (ETDEWEB)

    Porkolab, Miklos

    2015-12-10

    Nonlinear phenomena in RF wave propagation has been observed from the earliest days in basic laboratory experiments going back to the 1960s [1], followed by observations of parametric instability (PDI) phenomena in large scale RF heating experiments in magnetized fusion plasmas in the 1970s and beyond [2]. Although not discussed here, the importance of PDI phenomena has also been central to understanding anomalous absorption in laser-fusion experiments (ICF) [3]. In this review I shall discuss the fundamentals of nonlinear interactions among waves and particles, and in particular, their role in PDIs. This phenomenon is distinct from quasi-linear phenomena that are often invoked in calculating absorption of RF power in wave heating experiments in the core of magnetically confined plasmas [4]. Indeed, PDIs are most likely to occur in the edge of magnetized fusion plasmas where the electron temperature is modest and hence the oscillating quiver velocity of charged particles can be comparable to their thermal speeds. Specifically, I will review important aspects of PDI theory and give examples from past experiments in the ECH/EBW, lower hybrid (LHCD) and ICRF/IBW frequency regimes. Importantly, PDI is likely to play a fundamental role in determining the so-called “density limit” in lower hybrid experiments that has persisted over the decades and still central to understanding present day experiments [5-7].

  20. The effect of anode shape on neon soft x-ray emissions and current sheath configuration in plasma focus device

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadi, M A; Sobhanian, S [Faculty of Physics, University of Tabriz, Tabriz (Iran, Islamic Republic of); Wong, C S [Plasma Research Laboratory, Physics Department, University of Malaya, Kuala Lumpur (Malaysia); Lee, S; Lee, P; Rawat, R S, E-mail: rajdeep.rawat@nie.edu.s [Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University (Singapore)

    2009-02-21

    The effect of three different anode shapes, flat, tapered and hemispherical, on the x-ray emission characteristics of a neon filled UNU-ICTP plasma focus device is investigated. The current sheath dynamics, in the radial collapse phase, has been simultaneously interrogated using the laser shadowgraphy method to understand the variation in x-ray emission characteristics for anodes of different shapes used in the experiments. The maximum neon soft x-ray (SXR) yield for the flat anode is about 7.5 {+-} 0.4 J at 4 mbar, whereas for hemispherical and tapered anodes the neon SXR is almost halved with the optimum pressure shifting to a lower value of 3 mbar. The laser shadowgraphic images confirm that the reduction in the overall neon SXR yield is due to the reduced focused plasma column length for these anodes. The relative HXR yield was the highest for the hemispherical anode followed by the tapered and the flat anodes in that order. The shadowgraphic images and the voltage probe signals confirmed that for the hemispherical anode the multiple-pinch phenomenon was most commonly observed, which could be responsible for multiple HXR bursts for this anode with maximum HXR yields.

  1. Modeling of evaporation and oxidation phenomena in plasma spraying of metal powders

    Science.gov (United States)

    Zhang, Hanwei

    Plasma spraying of metals in air is usually accompanied by evaporation and oxidation of the sprayed material. Optimization of the spraying process must ensure that the particles are fully molten during their short residence time in the plasma jet and prior to hitting the substrate, but not overheated to minimize evaporation losses. In atmospheric plasma spraying (ASP), it is also clearly desirable to be able to control the extent of oxide formation. The objective of this work to develop an overall mathematical model of the oxidization and volatilization phenomena involved in the plasma-spraying of metallic particles in air atmosphere. Four models were developed to simulate the following aspects of the atmospheric plasma spraying (APS) process: (a) the particle trajectories and the velocity and temperature profiles in an Ar-H 2 plasma jet, (b) the heat and mass transfer between particles and plasma jet, (c) the interaction between the evaporation and oxidation phenomena, and (d) the oxidation of liquid metal droplets. The resulting overall model was generated by adapting the computational fluid dynamics code FIDAP and was validated by experimental measurements carried out at the collaborating plasma laboratory of the University of Limoges. The thesis also examined the environmental implications of the oxidization and volatilization phenomena in the plasma spraying of metals. The modeling results showed that the combination of the standard k-s model of turbulence and the Boussinesq eddy-viscosity model provided a more accurate prediction of plasma gas behavior. The estimated NOx generation levels from APS were lower than the U.S.E.P.A. emission standard. Either enhanced evaporation or oxidation can occur on the surface of the metal particles and the relative extent is determined by the process parameters. Comparatively, the particle size has the greatest impact on both evaporation and oxidation. The extent of particle oxidation depends principally on gas

  2. EDITORIAL: Interrelationship between plasma phenomena in the laboratory and in space

    Science.gov (United States)

    Koepke, Mark

    2008-07-01

    The premise of investigating basic plasma phenomena relevant to space is that an alliance exists between both basic plasma physicists, using theory, computer modelling and laboratory experiments, and space science experimenters, using different instruments, either flown on different spacecraft in various orbits or stationed on the ground. The intent of this special issue on interrelated phenomena in laboratory and space plasmas is to promote the interpretation of scientific results in a broader context by sharing data, methods, knowledge, perspectives, and reasoning within this alliance. The desired outcomes are practical theories, predictive models, and credible interpretations based on the findings and expertise available. Laboratory-experiment papers that explicitly address a specific space mission or a specific manifestation of a space-plasma phenomenon, space-observation papers that explicitly address a specific laboratory experiment or a specific laboratory result, and theory or modelling papers that explicitly address a connection between both laboratory and space investigations were encouraged. Attention was given to the utility of the references for readers who seek further background, examples, and details. With the advent of instrumented spacecraft, the observation of waves (fluctuations), wind (flows), and weather (dynamics) in space plasmas was approached within the framework provided by theory with intuition provided by the laboratory experiments. Ideas on parallel electric field, magnetic topology, inhomogeneity, and anisotropy have been refined substantially by laboratory experiments. Satellite and rocket observations, theory and simulations, and laboratory experiments have contributed to the revelation of a complex set of processes affecting the accelerations of electrons and ions in the geospace plasma. The processes range from meso-scale of several thousands of kilometers to micro-scale of a few meters to kilometers. Papers included in this

  3. Effect of driving frequency on the electron energy distribution function and electron-sheath interaction in a low pressure capacitively coupled plasma

    Science.gov (United States)

    Sharma, S.; Sirse, N.; Kaw, P. K.; Turner, M. M.; Ellingboe, A. R.

    2016-11-01

    By using a self-consistent particle-in-cell simulation, we investigated the effect of driving frequency (27.12-70 MHz) on the electron energy distribution function (EEDF) and electron-sheath interaction in a low pressure (5 mTorr) capacitively coupled Ar discharge for a fixed discharge voltage. We observed a mode transition with driving frequency, changing the shape of EEDF from a strongly bi-Maxwellian at a driving frequency of 27.12 MHz to a convex type distribution at an intermediate frequency, 50 MHz, and finally becomes a weak bi-Maxwellian at a higher driving frequency, i.e., above 50 MHz. The transition is caused by the electric field transients, which is of the order of electron plasma frequency caused by the energetic "beams" of electrons ejected from near the sheath edge. Below the transition frequency, 50 MHz, these high energy electrons redistribute their energy with low energy electrons, thereby increasing the effective electron temperature in the plasma, whereas the plasma density remains nearly constant. Above the transition frequency, high-energy electrons are confined between opposite sheaths, which increase the ionization probability and therefore the plasma density increases drastically.

  4. Complex plasma experimental device – A test bed for studying dust vortices and other collective phenomena

    Indian Academy of Sciences (India)

    MANJIT KAUR; SAYAK BOSE; P K CHATTOPADHYAY; J GHOSH; Y C SAXENA

    2016-12-01

    A typical device for carrying out sophisticated and complex dusty plasma experiments is designed, fabricated and made operational at the Institute for Plasma Research, India. The device is named as complex plasma experimental device (CPED). The main aim of this multipurpose machine is to study the formation and behaviour of dust vortices in the absence of external magnetic field under the effect of various plasma parameters. Further, the device is equipped with advanced imaging diagnostics for studying many other interesting phenomena such as dust oscillations, three-dimensional crystalline structures, dust rotation, etc. The device is quite flexible to accommodate many innovative experiments. Detailed design of the device, its diagnostics capabilities and theadvanced image analysis techniques are presented in this paper.

  5. Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

    Science.gov (United States)

    Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

    2017-09-13

    Surface phenomena during atomic layer etching (ALE) of SiO2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CFx) film deposition and Ar plasma activation of the CFx film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CFx deposition half-cycle from a C4F8/Ar plasma show that an atomically thin mixing layer is formed between the deposited CFx layer and the underlying SiO2 film. Etching during the Ar plasma cycle is activated by Ar(+) bombardment of the CFx layer, which results in the simultaneous removal of surface CFx and the underlying SiO2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CFx deposition, which combined with an ultrathin CFx layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CFx film, ∼3-4 Å of SiO2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CFx layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CFx on reactor walls leads to a gradual increase in the etch per cycle.

  6. Chaotic-to-ordered state transition of cathode-sheath instabilities in DC glow discharge plasmas

    Indian Academy of Sciences (India)

    Md Nurujjaman; A N Sekar Iyengar

    2006-08-01

    Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical DC glow discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of the discharge glow and shows a period subtraction of order 7 period → 5 period → 3 period → 1 period, i.e. the system goes to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period doubling, like 1 period → 2 period → 4 period. On further increasing the voltage, the system goes to stable state through two period subtraction, like 4 period → 2 period → stable.

  7. X-ray spectroscopic study of charge exchange phenomena in plasma-wall interaction

    Directory of Open Access Journals (Sweden)

    Renner O.

    2013-11-01

    Full Text Available Jets of energetic ions launched at laser-burnt-through foils represent an efficient tool for investigation of plasma interaction with solid surfaces (plasma-wall interaction, PWI and for description of transient phenomena occurring close to the walls. Highly charged ions approaching the secondary target interpenetrate the near surface layer, collide with the counter-propagating matter and capture a large number of electrons. This results in a creation of atoms in highly excited Rydberg states or hollow ions with multiple inner vacancies; plasma jet and target ions may also undergo charge exchange (CE processes. We report PWI experiments with Al/Si(PMMA and Al/C targets irradiated at normal or oblique laser incidence. The distinct dip structures observed in red wings of Al Lyγ self-emission is interpreted in terms of CE between C6+ and Al12+ in the near-wall zone. The spectroscopic identification of CE phenomena is supported by results of analytical and numerical calculations.

  8. HIDENEK: An implicit particle simulation of kinetic-MHD phenomena in three-dimensional plasmas

    Science.gov (United States)

    Tanaka, Motohiko

    1993-05-01

    An advanced 'kinetic-MHD' simulation method and its applications to plasma physics are given in this lecture. This method is quite stable for studying strong nonlinear, kinetic processes associated with large space-scale, low-frequency electromagnetic phenomena of plasmas. A full set of the Maxwell equations, and the Newton-Lorentz equations of motion for particle ions and guiding-center electrons are adopted. In order to retain only the low-frquency waves and instabilities, implicit particle-field equations are derived. The present implicit-particle method is proved to reproduce the MHD eigenmodes such as Alfven, magnetosonic and kinetic Alfven waves in a thermally near-equilibrium plasma. In the second part of the lecture, several physics applications are shown. These include not only the growth of the instabilities of beam ions against the background plasmas and helical link of the current, but they also demonstrate nonlinear results such as pitch-angle scattering of the ions. Recent progress in the simulation of the Kelvin-Helmholtz instability is also presented with a special emphasis on the mixing of the plasma particles.

  9. 10.1142/9781911299660_fmatter years Laser Interaction and Related Plasma Phenomena (lirpp Vol. 13)

    Science.gov (United States)

    Hora, Heinrich

    2016-10-01

    When these proceedings of 13th international conference LASER INTERACTION AND RELATED PLASMA PHENOMENA (LIRPP) will be circulated in 1998, it is just 30 years that this conference series began. Professor Miley asked me to present some thoughts at this occasion since I am involved from the beginning to 1991 a director and then as emeritus director. The conferences were in the following years 1969, 1971, 1973, 1976, 1979, 1982, 1985, 1987, 1989, 1991, 1993, 1995 and 1997 and reference to each of the conferences is simply given by the year in brackets...

  10. From gluon topology to chiral anomaly: Emergent phenomena in quark-gluon plasma

    CERN Document Server

    Liao, Jinfeng

    2016-01-01

    Heavy-ion collision experiments at RHIC and the LHC have found a new emergent phase of QCD, a strongly coupled quark-gluon plasma (sQGP) that is distinctively different from either the low temperature hadron phase or the very high temperature weakly coupled plasma phase. Highly nontrivial emergent phenomena occur in such sQGP and two examples will be discussed in this contribution: the magnetic component of sQGP that stems from topologically nontrivial configurations in the gluon sector; and the anomalous chiral transport that arises as macroscopic manifestation of microscopic chiral anomaly in the quark sector. For both examples, their important roles in explaining pertinent heavy-ion data will be emphasized.

  11. From gluon topology to chiral anomaly: Emergent phenomena in quark-gluon plasma

    Science.gov (United States)

    Liao, Jinfeng

    2017-01-01

    Heavy-ion collision experiments at RHIC and the LHC have found a new emergent phase of QCD, a strongly coupled quark-gluon plasma (sQGP) that is distinctively different from either the low temperature hadron phase or the very high temperature weakly coupled plasma phase. Highly nontrivial emergent phenomena occur in such sQGP and two examples will be discussed in this contribution: the magnetic component of sQGP that stems from topologically nontrivial configurations in the gluon sector; and the anomalous chiral transport that arises as macroscopic manifestation of microscopic chiral anomaly in the quark sector. For both examples, their important roles in explaining pertinent heavy-ion data will be emphasized.

  12. Plasma Wall Interaction Phenomena on Tungsten Armour Materials for Fusion Applications

    Energy Technology Data Exchange (ETDEWEB)

    Uytdenhouwen, I. [SCK.CEN - The Belgian Nuclear Research Centre, Institute for Nuclear Materials Science, Boeretang 200, 2400 Mol (Belgium); Forschungszentrum Juelich GmbH, EURATOM-association, D-52425 Juelich (Germany); Department of Applied Physics, Ghent University, Rozier 44, 9000 Ghent (Belgium); Massaut, V. [Department of Applied Physics, Ghent University, Rozier 44, 9000 Ghent (Belgium); Linke, J. [Forschungszentrum Juelich GmbH, EURATOM-association, D-52425 Juelich (Germany); Van Oost, G. [Department of Applied Physics, Ghent University, Rozier 44, 9000 Ghent (Belgium)

    2008-07-01

    One of the most attractive future complements to present energy sources is nuclear fusion. A large progress was made throughout the last decade from both the physical as the technological area leading to the construction of the ITER machine. One of the key issues that recently received a large interest at international level is focused on the Plasma Wall Interaction (PWI). One of the promising Plasma Facing Materials (PFM) are Tungsten (W) and Tungsten alloys. However, despite the worldwide use and industrial availability of W, the database of physical and mechanical properties is very limited. Especially after fusion relevant neutron irradiation and PWI phenomena, most of the properties are still unknown. The plasma fuel consists out of deuterium (D) and tritium (T). Tritium is radio-active and therefore an issue from the safety point of view. During steady-state plasma operation of future fusion power plants, the PFM need to extract a power density of {approx}10-20 MW/m{sup 2}. On top of this heat, transient events will deposit an additional non-negligible amount of energy (Disruptions, Vertical Displacement Events, Edge Localized Modes) during short durations. These severe heat loads cause cracking and even melting of the surface resulting in a reduced lifetime and the creation of dust. A contribution to the understanding of cracking phenomena under the severe thermal loads is described as well as the properties degradation under neutron irradiation. Several W grades were irradiated in the BR2 reactor (SCK.CEN) and the thermal loads were simulated with the electron-beam facility JUDITH (FZJ). Since knowledge should be gained about the Tritium retention in the PFM for safety and licensing reasons, a unique test facility at SCK.CEN is being set-up. The plasmatron VISION-I will simulate steady state plasmas for Tritium retention studies. The formation of surface cracks and dust, the initial porosity, neutron induced traps, re-deposited material - change the Tritium

  13. Using the cold plasma dispersion relation and whistler mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument

    Science.gov (United States)

    Hartley, D. P.; Kletzing, C. A.; Kurth, W. S.; Bounds, S. R.; Averkamp, T. F.; Hospodarsky, G. B.; Wygant, J. R.; Bonnell, J. W.; Santolík, O.; Watt, C. E. J.

    2016-05-01

    Cold plasma theory and parallel wave propagation are often assumed when approximating the whistler mode magnetic field wave power from electric field observations. The current study is the first to include the wave normal angle from the Electric and Magnetic Field Instrument Suite and Integrated Science package on board the Van Allen Probes in the conversion factor, thus allowing for the accuracy of these assumptions to be quantified. Results indicate that removing the assumption of parallel propagation does not significantly affect calculated plasmaspheric hiss wave powers. Hence, the assumption of parallel propagation is valid. For chorus waves, inclusion of the wave normal angle in the conversion factor leads to significant alterations in the distribution of wave power ratios (observed/ calculated); the percentage of overestimates decreases, the percentage of underestimates increases, and the spread of values is significantly reduced. Calculated plasmaspheric hiss wave powers are, on average, a good estimate of those observed, whereas calculated chorus wave powers are persistently and systematically underestimated. Investigation of wave power ratios (observed/calculated), as a function of frequency and plasma density, reveals a structure consistent with signal attenuation via the formation of a plasma sheath around the Electric Field and Waves spherical double probes instrument. A simple, density-dependent model is developed in order to quantify this effect of variable impedance between the electric field antenna and the plasma interface. This sheath impedance model is then demonstrated to be successful in significantly improving agreement between calculated and observed power spectra and wave powers.

  14. Polarization force-induced changes in the dust sheath formation

    Energy Technology Data Exchange (ETDEWEB)

    Mayout, Saliha; Bentabet, Karima; Tribeche, Mouloud [Plasma Physics Group (PPG), Theoretical Physics Laboratory (TPL), Faculty of Physics, University of Bab-Ezzouar, USTHB, BP 32, El Alia, Algiers 16111 (Algeria)

    2015-09-15

    The modifications arising in the dusty plasma sheath structure due to the presence of polarization forces acting on the dust grains are investigated. The corresponding appropriate Bohm criterion for sheath formation is obtained. It is found that the critical Mach number, beyond which the dusty plasma electrostatic sheath sets in, decreases whenever the polarization effects become important. In addition, when the polarization force dominates over the electrical one, the dust plasma sheath cannot set in. This happens whenever the dust grain size exceeds a critical threshold. Moreover, the sheath electrostatic potential-gradient becomes abruptly steep, and the sheath thickness becomes broader as the polarization force effects strengthen.

  15. Effect of driving frequency on the electron-sheath interaction and electron energy distribution function in a low pressure capacitively coupled plasmas

    Science.gov (United States)

    Sharma, Sarveshwar; Sirse, Nishant; Kaw, Predhiman; Turner, Miles; Ellingboe, Albert R.; InstitutePlasma Research, Gandhinagar, Gujarat Team; School Of Physical Sciences; Ncpst, Dublin City University, Dublin 9, Ireland Collaboration

    2016-09-01

    The effect of driving frequency (27.12-70 MHz) on the electron-sheath interaction and electron energy distribution function (EEDF) is investigated in a low pressure capacitive discharges using a self-consistent particle-in-cell simulation. At a fixed discharge voltage the EEDF evolves from a strongly bi-Maxwellian at low frequency, 27.12 MHz, to a convex type distribution at an intermediate frequency, 50 MHz, and finally becomes a weak biMaxwellian above 50 MHz. The EEDF evolution leads to a two-fold increase in the effective electron temperature up to 50 MHz, whereas the electron density remains constant in this range. After 50MHz, the electron density increases rapidly and the electron temperature decreases. The transition is caused by the transient electric field excited by bursts of high energy electrons interacting strongly with the sheath edge. Above the transition frequency, high energy electrons are confined between two sheaths which increase the ionization probability and thus the plasma density increases.

  16. Acoustic measurement method in investigation of optical phenomena in a modulated CO II laser plasma

    Science.gov (United States)

    Wojaczek, Dorota A.; Plinski, Edward F.; Rosinski, Lukasz; Trawinski, Robert

    2007-02-01

    The paper describes the results of investigations of optical phenomena on an RF excited slab-waveguide CO II laser. The experiments are performed in two optical arrangements: two-mirror resonator and three-mirror one. The main purpose of the experiments is to check possibilities to observe the optical phenomena using a microphone. The laser plasma is modulated with a self-mixing signal in the three-mirror resonator. The response of the microphone is observed and analyzed. Detection of the laser signature phenomenon with the microphone is experimentally considered. The experiments are done at cw regime of the laser. The investigations are performed at pulse operation of the laser, as well. The response of the microphone is analyzed. It is checked how the laser pulse is reconstructed at a profile of the microphone signal. The output laser pulse with a mapped laser signature in the laser pulse profile is compared to the microphone signal shape. The presence of the laser signature at the acoustic signal is investigated.

  17. Enhancing Micro-Cathode Arc Thruster (muCAT) Plasma Generation to Analyze Magnetic Field Angle Effects on Sheath Formation in Hall Thrusters

    Science.gov (United States)

    Lukas, Joseph Nicholas

    Using a Delta IV or Atlas V launch vehicle to send a payload into Low Earth Orbit can cost between 13,000 and 14,000 per kilogram. With payloads that utilize a propulsion system, maximizing the efficiency of that propulsion system would not only be financially beneficial, but could also increase the range of possible missions and allow for a longer mission lifetime. This dissertation looks into efficiency increases in the Micro-Cathode Arc Thruster (muCAT) and Hall Thruster. The muCAT is an electric propulsion device that ablates solid cathode material, through an electrical arc discharge, to create plasma and ultimately produce thrust. About 90% of the arc discharge current is conducted by electrons, which go toward heating the anode and contribute very little to thrust, with only the remaining 10% going toward thrust in the form of ion current. I will discuss the results of an experiment in which electron heating on a low melting point anode was shown to increase ion current, which theoretically should increase thrust levels at low frequencies. Another feature of the muCAT is the use of an external magnetic solenoid which increases thrust, ion current, and causes uniform cathode erosion. An experiment has shown that efficiency can also be increased by removing the external magnetic field power supply and, instead, utilizing the residual arc current to power the magnetic solenoid. A Hall Thruster is a type of electric propulsion device that accelerates ions across an electric potential between an anode and magnetically trapped electrons. The limiting factor in Hall Thruster operation is the lifetime of the wall material. During operation, a positively charged layer forms over the surface of the walls, known as a plasma sheath, which contributes to wall erosion. Therefore, by reducing or eliminating the sheath layer, Hall Thruster operational lifetime can increase. Computational modeling has shown that large magnetic field angles and large perpendicular electric

  18. Collisional effects in weakly collisional plasmas: nonlinear electrostatic waves and recurrence phenomena

    Science.gov (United States)

    Camporeale, E.; Pezzi, O.; Valentini, F.

    2015-12-01

    The longstanding problem of collisions in plasmas is a very fascinating and huge topic in plasma physics. The 'natural' operator that describes the Coulombian interactions between charged particles is the Landau (LAN) integral operator. The LAN operator is a nonlinear, integro-differential and Fokker-Planck type operator which satisfies the H theorem for the entropy growth. Due to its nonlinear nature and multi-dimensionality, any approach to the solution of the Landau integral is almost prohibitive. Therefore collisions are usually modeled by simplified collisional operators. Here collisional effects are modeled by i) the one-dimensional Lenard-Bernstein (LB) operator and ii) the three-dimensional Dougherty (DG) operator. In the first case i), by focusing on a 1D-1V phase space, we study recurrence effects in a weakly collisional plasma, being collisions modeled by the LB operator. By decomposing the linear Vlasov-Poisson system in the Fourier-Hermite space, the recurrence problem is investigated in the linear regime of the damping of a Langmuir wave and of the onset of the bump-on-tail instability. The analysis is then confirmed and extended to the nonlinear regime through a Eulerian collisional Vlasov-Poisson code. Despite being routinely used, an artificial collisionality is not in general a viable way of preventing recurrence in numerical simulations. Moreover, recursive phenomena affect both the linear exponential growth and the nonlinear saturation of a linear instability by producing a fake growth in the electric field, thus showing that, although the filamentation is usually associated with low amplitude fluctuations contexts, it can occur also in nonlinear phenomena. On the other hand ii), the effects of electron-electron collisions on the propagation of nonlinear electrostatic waves are shown by means of Eulerian simulations in a 1D-3V (one dimension in physical space, three dimensions in velocity space) phase space. The nonlinear regime of the symmetric

  19. Kinetic and spectral descriptions of autoionization phenomena associated with atomic processes in plasmas

    Science.gov (United States)

    Jacobs, Verne L.

    2017-06-01

    This investigation has been devoted to the theoretical description and computer modeling of atomic processes giving rise to radiative emission in energetic electron and ion beam interactions and in laboratory plasmas. We are also interested in the effects of directed electron and ion collisions and of anisotropic electric and magnetic fields. In the kinetic-theory description, we treat excitation, de-excitation, ionization, and recombination in electron and ion encounters with partially ionized atomic systems, including the indirect contributions from processes involving autoionizing resonances. These fundamental collisional and electromagnetic interactions also provide particle and photon transport mechanisms. From the spectral perspective, the analysis of atomic radiative emission can reveal detailed information on the physical properties in the plasma environment, such as non-equilibrium electron and charge-state distributions as well as electric and magnetic field distributions. In this investigation, a reduced-density-matrix formulation is developed for the microscopic description of atomic electromagnetic interactions in the presence of environmental (collisional and radiative) relaxation and decoherence processes. Our central objective is a fundamental microscopic description of atomic electromagnetic processes, in which both bound-state and autoionization-resonance phenomena can be treated in a unified and self-consistent manner. The time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations of the reduced-density-matrix approach are developed in a unified and self-consistent manner. This is necessary for our ultimate goal of a systematic and self-consistent treatment of non-equilibrium (possibly coherent) atomic-state kinetics and high-resolution (possibly overlapping) spectral-line shapes. We thereby propose the introduction of a generalized collisional-radiative atomic-state kinetics model based on a reduced

  20. Analysis of non-equilibrium phenomena in inductively coupled plasma generators

    Science.gov (United States)

    Zhang, W.; Lani, A.; Panesi, M.

    2016-07-01

    This work addresses the modeling of non-equilibrium phenomena in inductively coupled plasma discharges. In the proposed computational model, the electromagnetic induction equation is solved together with the set of Navier-Stokes equations in order to compute the electromagnetic and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while transport properties are obtained from kinetic principles, with the method of Chapman and Enskog. Particle ambipolar diffusive fluxes are found by solving the Stefan-Maxwell equations with a simple iterative method. Two physico-mathematical formulations are used to model the chemical reaction processes: (1) A Local Thermodynamics Equilibrium (LTE) formulation and (2) a thermo-chemical non-equilibrium (TCNEQ) formulation. In the TCNEQ model, thermal non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules is accounted for. The electronic states of the chemical species are assumed in equilibrium with the vibrational temperature, whereas the rotational energy mode is assumed to be equilibrated with translation. Three different physical models are used to account for the coupling of chemistry and energy transfer processes. Numerical simulations obtained with the LTE and TCNEQ formulations are used to characterize the extent of non-equilibrium of the flow inside the Plasmatron facility at the von Karman Institute. Each model was tested using different kinetic mechanisms to assess the sensitivity of the results to variations in the reaction parameters. A comparison of temperatures and composition profiles at the outlet of the torch demonstrates that the flow is in non-equilibrium for operating conditions characterized by pressures below 30 000 Pa, frequency 0.37 MHz, input power 80 kW, and mass flow 8 g/s.

  1. Effects of electron emission on sheath potential

    Science.gov (United States)

    Dow, Ansel; Khrabrov, Alexander; Kaganovich, Igor; Schamis, Hanna

    2015-11-01

    We investigate the potential profile of a sheath under the influence of surface electron emission. The plasma and sheath profiles are simulated using the Large Scale Plasma (LSP) particle-in-cell code. Using one dimensional models we corroborate the analytical relationship between sheath potential and plasma electron and emitted electron temperatures derived earlier. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.

  2. Localized Overheating Phenomena and Optimization of Spark-Plasma Sintering Tooling Design

    Directory of Open Access Journals (Sweden)

    Darold G. Martin

    2013-06-01

    Full Text Available The present paper shows the application of a three-dimensional coupled electrical, thermal, mechanical finite element macro-scale modeling framework of Spark Plasma Sintering (SPS to an actual problem of SPS tooling overheating, encountered during SPS experimentation. The overheating phenomenon is analyzed by varying the geometry of the tooling that exhibits the problem, namely by modeling various tooling configurations involving sequences of disk-shape spacers with step-wise increasing radii. The analysis is conducted by means of finite element simulations, intended to obtain temperature spatial distributions in the graphite press-forms, including punches, dies, and spacers; to identify the temperature peaks and their respective timing, and to propose a more suitable SPS tooling configuration with the avoidance of the overheating as a final aim. Electric currents-based Joule heating, heat transfer, mechanical conditions, and densification are imbedded in the model, utilizing the finite-element software COMSOL™, which possesses a distinguishing ability of coupling multiple physics. Thereby the implementation of a finite element method applicable to a broad range of SPS procedures is carried out, together with the more specific optimization of the SPS tooling design when dealing with excessive heating phenomena.

  3. Collisionless and Kinetic Phenomena of Interpenetrating Plasma Streams via Neutron Self-Emission

    Science.gov (United States)

    Ross, J. S.; Higginson, D. P.; Hatarik, R.; Link, A.; Park, H.-S.; Ryutov, D. D.; Weber, S. V.; Wilks, S. C.; Fiuza, F.; Li, C. K.; Sio, H.; Zylstra, A. B.

    2016-10-01

    Recent NIF experiments focus on the generation and diagnosis of collisionless shocks relevant to astrophysical phenomena such as supernova remnants and gamma ray bursts. In the experiments, two opposing CD laser-generated plasmas flow into each other at high velocity ( 1000 km/s). As the ion-ion collisional mean-free-path is near to or greater than the system size, the flows interpenetrate and neutrons are generated via beam-beam deuteron interactions. We model this system using the hybrid particle-in-cell code LSP with electric and magnetic fields suppressed to capture the full temporal and spatial size of the experiment. These simulations show good agreement with the yield, spectrum and spatial/temporal profiles of the neutrons observed in the experiment. When one CD foil is replaced with CH an asymmetry develops in the neutron spectrum that is caused by the Doppler shift related to the flow velocity. Additionally, in this case the neutron yield is found to be lower in the simulations than is observed experimentally, which indicates that the deuterons thermalize more efficiently in the experiment. This suggests that another mechanism is responsible for this yield enhancement other than small angle scattering since it is included in the simulations. Possible mechanisms such as scattering across Weibel-mediated magnetic filaments and large-angle Coulomb scattering will be evaluated and discussed. Prepared by LLNL under Contract DE-AC52-07NA27344.

  4. Study of a dual frequency capacitively coupled rf discharge in the background of multi-component plasma and its validation by a simple analytical sheath model

    Science.gov (United States)

    Bhuyan, Heman; Saikia, Partha; Favre, Mario; Wyndham, Edmundo; Veloso, Felipe

    2016-10-01

    The behavior of a phase-locked dual frequency capacitively coupled rf discharges (2f-CCRF) in the background of multi-component plasma is experimentally studied by rf current-voltage measurements and optical emission spectroscopy (OES). The multi-component plasma is produced by adding hydrogen to the argon CCRF discharge. Variation of experimental parameters, like working pressure, low frequency (LF) and high frequency (HF) rf power indicate significant changes in the electron density and temperature as well as the DC self-bias developed on the power electrode. It is observed that the electron density decreases as the percentage of hydrogen increases in the argon plasma while the electron temperature follows opposite trend. An analytical sheath model for the 2f-CCRF discharge in the background of multi-component plasma is developed and its prediction on the observed variation of DC self-bias is well agreed with the experimental observations. Authors acknowledge Proyecto Puente No P1611 and FONDECYT 3160179.

  5. Axial magnetic field and toroidally streaming fast ions in the dense plasma focus are natural consequences of conservation laws in the curved axisymmetric geometry of the current sheath

    CERN Document Server

    Auluck, S K H

    2014-01-01

    Direct measurement of axial magnetic field in the PF-1000 dense plasma focus (DPF), and its reported correlation with neutron emission, call for a fresh look at previous reports of existence of axial magnetic field component in the DPF from other laboratories, and associated data suggesting toroidal directionality of fast ions participating in fusion reactions, with a view to understand the underlying physics. In this context, recent work dealing with application of the hyperbolic conservation law formalism to the DPF is extended in this paper to a curvilinear coordinate system, which reflects the shape of the DPF current sheath. Locally-unidirectional shock propagation in this coordinate system enables construction of a system of 7 one-dimensional hyperbolic conservation law equations with geometric source terms, taking into account all the components of magnetic field and flow velocity. Rankine-Hugoniot jump conditions for this system lead to expressions for the axial magnetic field and three components of ...

  6. The Bohm criterion and sheath formation

    Energy Technology Data Exchange (ETDEWEB)

    Riemann, K.U. (Bochum Univ. (Germany). Inst. fuer Theoretische Physik 1)

    1990-11-01

    In the limit of a small Debye length ({lambda}{sub D}{yields}0) the analysis of the plasma boundary layer leads to a two scale problem of a collision free sheath and of a quasineutral presheath. Bohm's criterion expresses a necessary condition for the formation of a stationary sheath in front of a negative absorbing wall. The basic features of the plasma-sheath transition and their relation to the Bohm criterion are discussed and illustrated from a simple cold-ion fluid model. A rigorous kinetic analysis of the vicinity of the sheath edge allows to generalize Bohm's criterion acounting not only for arbitrary ion- and electron distributions, but also for general boundary conditions at the wall. It is shown that the generalized sheath condition is (apart from special exceptions) fulfilled marginally and related to a sheath edge field singularity. Due to this singularity a smooth matching of the presheath and sheath solutions requires an additional transition layer. Previous investigations concerning special problems of the plasma-sheath transition are reviewed in the light of the general relations. (orig.).

  7. Analysis of Electromagnetic Wave Propagation in a Magnetized Re-Entry Plasma Sheath Via the Kinetic Equation

    Science.gov (United States)

    Manning, Robert M.

    2009-01-01

    Based on a theoretical model of the propagation of electromagnetic waves through a hypersonically induced plasma, it has been demonstrated that the classical radiofrequency communications blackout that is experienced during atmospheric reentry can be mitigated through the appropriate control of an external magnetic field of nominal magnitude. The model is based on the kinetic equation treatment of Vlasov and involves an analytical solution for the electric and magnetic fields within the plasma allowing for a description of the attendant transmission, reflection and absorption coefficients. The ability to transmit through the magnetized plasma is due to the magnetic windows that are created within the plasma via the well-known whistler modes of propagation. The case of 2 GHz transmission through a re-entry plasma is considered. The coefficients are found to be highly sensitive to the prevailing electron density and will thus require a dynamic control mechanism to vary the magnetic field as the plasma evolves through the re-entry phase.

  8. A Coupled MHD and Thermal Model Including Electrostatic Sheath for Magnetoplasmadynamic Thruster Simulation

    Science.gov (United States)

    Kawasaki, Akira; Kubota, Kenichi; Funaki, Ikkoh; Okuno, Yoshihiro

    2016-09-01

    Steady-state and self-field magnetoplasmadynamic (MPD) thruster, which utilizes high-intensity direct-current (DC) discharge, is one of the prospective candidates of future high-power electric propulsion devices. In order to accurately assess the thrust performance and the electrode temperature, input electric power and wall heat flux must correctly be evaluated where electrostatic sheaths formed in close proximity of the electrodes affect these quantities. Conventional model simulates only plasma flows occurring in MPD thrusters with the absence of electrostatic sheath consideration. Therefore, this study extends the conventional model to a coupled magnetohydrodynamic (MHD) and thermal model by incorporating the phenomena relevant to the electrostatic sheaths. The sheaths are implemented as boundary condition of the MHD model on the walls. This model simulated the operation of the 100-kW-class thruster at discharge current ranging from 6 to 10 kA with argon propellant. The extended model reproduced the discharge voltages and wall heat load which are consistent with past experimental results. In addition, the simulation results indicated that cathode sheath voltages account for approximately 5-7 V subject to approximately 20 V of discharge voltages applied between the electrodes. This work was supported by JSPS KAKENHI Grant Numbers 26289328 and 15J10821.

  9. SCREENING OF HIGH-Z GRAINS AND RELATED PHENOMENA IN COLLOIDAL PLASMAS

    Directory of Open Access Journals (Sweden)

    O.Bystrenko

    2003-01-01

    Full Text Available Recent important results are briefly presented concerning the screening of high-Z impurities in colloidal plasmas. The review focuses on the phenomenon of nonlinear screening and its effects on the structure of colloidal plasmas, the role of trapped ions in grain screening, and the effects of strong collisions in the plasma background. It is shown that the above effects may strongly modify the properties of the grain screening giving rise to considerable deviations from the conventional Debye-Huckel theory as dependent on the physical processes in the plasma background.

  10. Nonlinear phenomena of generation of longitudinal electric current by transversal electromagnetic field in plasmas

    CERN Document Server

    Latyshev, A V

    2015-01-01

    The analysis of nonlinear interaction of transversal electromagnetic field with collisionless plasma is carried out. Formulas for calculation electric current in collisionless plasma with arbitrary degree of degeneration of electronic gas are deduced. It has appeared, that the nonlinearity account leads to occurrence of the longitudinal electric current directed along a wave vector. This second current is orthogonal to the known transversal current, received at the classical linear analysis.

  11. Terahertz Josephson plasma waves in layered superconductors: spectrum, generation, nonlinear and quantum phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Savel' ev, Sergey; Yampol' skii, V A; Rakhmanov, A L; Nori, Franco [Advanced Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198 (Japan)

    2010-02-15

    The recent growing interest in terahertz (THz) and sub-THz science and technology is due to its many important applications in physics, astronomy, chemistry, biology and medicine, including THz imaging, spectroscopy, tomography, medical diagnosis, health monitoring, environmental control, as well as chemical and biological identification. We review the problem of linear and nonlinear THz and sub-THz Josephson plasma waves in layered superconductors and their excitations produced by moving Josephson vortices. We start by discussing the coupled sine-Gordon equations for the gauge-invariant phase difference of the order parameter in the junctions, taking into account the effect of breaking the charge neutrality, and deriving the spectrum of Josephson plasma waves. We also review surface and waveguide Josephson plasma waves. The spectrum of these waves is presented, and their excitation is discussed. We review the propagation of weakly nonlinear Josephson plasma waves below the plasma frequency, {omega}{sub J}, which is very unusual for plasma-like excitations. In close analogy to nonlinear optics, these waves exhibit numerous remarkable features, including a self-focusing effect and the pumping of weaker waves by a stronger one. In addition, an unusual stop-light phenomenon, when {partial_derivative}{omega}/{partial_derivative}k {approx} 0, caused by both nonlinearity and dissipation, can be observed in the Josephson plasma waves. At frequencies above {omega}{sub J}, the current-phase nonlinearity can be used for transforming continuous sub-THz radiation into short, strongly amplified, pulses. We also present quantum effects in layered superconductors, specifically, the problem of quantum tunneling of fluxons through stacks of Josephson junctions. Moreover, the nonlocal sine-Gordon equation for Josephson vortices is reviewed. We discuss the Cherenkov and transition radiations of the Josephson plasma waves produced by moving Josephson vortices, either in a single

  12. Fast transient transport phenomena measured by soft X-ray emission in TCV tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Furno, I. [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

    2001-08-01

    Energy and particle transport during sawtooth activity in TCV plasmas has been studied in this thesis with high temporal resolution many chord diagnostics. We indicated the influence of sawteeth on plasma profiles in ohmic conditions and in the presence of auxiliary electron cyclotron resonance heating and current drive. A 2-dimensional model for heat transport, including localised heat source and a magnetic island, has been used to interpret the experimental observations. These results provided a new interpretation of a coupled heat and transport phenomenon which is potentially important for plasma confinement. The observations validate the applicability and show the possibility of improvement of a 2-dimensional theoretic a1 model for the study of heat transport in the presence of localised heat source and a magnetic island. Furthermore, the TCV results showed a new possibility for the interpretation of a coupled heat and particle transport phenomenon previously understood only in stellarators. (author)

  13. Observation of Periodic Multiplication and Chaotic Phenomena in Atmospheric Cold Plasma Jets

    Institute of Scientific and Technical Information of China (English)

    QI Bing; HUANG Jian-Jun; ZHANG Zhe-Huang; WANG De-Zhen

    2008-01-01

    We investigate the temporal evolution of the current pulses from an ac He cold plasma jet at atmospheric pressure and with driving frequency in the range 14.76-15.30 kHz. The driving frequency is used as the plasma system's bifurcation parameter in analogy with the evolution in which the current pulses undergoes multiplication and chaos. Such time-domain nonlinearity is important for controlling instabilities in atmospheric glow discharges.In addition, the observation can provide some data to support the simulation results reported previously [Appl.Phys. Lett. 90 (2007) 071501].

  14. 正离子初速度对电负性等离子体磁鞘结构的影响%Effects of Positive Ion Initial Velocity on Electronegative Plasma Sheath Structure in a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    刘惠平; 邹秀; 邱明辉; 张志华; 何明

    2011-01-01

    Using a fluid model, the Bohm criterion is obtained for the electronegative plasma sheath in a magnetic field by theoretical deduction, and the effects of positive ion initial velocity into the sheath on the charged particle density and electric potential distributions in electronegative plasma sheath in the presence of a magnetic field are numerically investigated. The results reveal that the initial velocity of positive ion in the y axis direction has greater effects on the charged particle density and electric potential distributions , while the influence of positive ion initial velocity in z axis on the charged particle density distributions is unconspicuous.%采用流体模型经过理论推导得到了电负性等离子体磁鞘的玻姆判据,并数值研究了正离子进入鞘层时的初速度对电负性等离子体磁鞘中带电粒子密度及电势分布的影响.研究结果表明:正离子进入鞘层时y方向的初速度对磁鞘中带电粒子的密度和电势分布有较大的影响,而其z方向的初速度对磁鞘中带电粒子密度分布的影响很小.

  15. Recent results from studies of electron beam phenomena in space plasmas

    Science.gov (United States)

    Neubert, Torsten; Banks, Peter M.

    1992-01-01

    The paper examines selected results from experiments, performed in 1980s, involving the ejection of beams of electrons from spacecraft. Special attention is given to the basic processes associated with the spacecraft charging, passive current collection, beam-atmosphere interactions, beam-plasma interactions, and neutral gas emission. Consideration is also given to future experiments on active electron beam ejections in space.

  16. Theoretical and computational studies of magnetic insulation and other plasma-opening-switch phenomena

    Science.gov (United States)

    Lindeman, Erick L., Jr.

    1989-11-01

    The following topics are discussed: electron trajectories and magnetic insulation; blade-load simulation studies; azimuthal asymmetries; MAGIC simulation studies of a segmented plasma opening switch; PBFA II calculations with different spatial resolution; and analytic solution of the electron current layer in the magnetic front.

  17. Characteristics of a Sheath with Secondary Electron Emission in the Double Walls of a Hall Thruster

    Institute of Scientific and Technical Information of China (English)

    段萍; 李肸; 沈鸿娟; 陈龙; 鄂鹏

    2012-01-01

    In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission (SEE) coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions.

  18. Plasma and wave phenomena induced by neutral gas releases in the solar wind

    Directory of Open Access Journals (Sweden)

    H. Laakso

    Full Text Available We investigate plasma and wave disturbances generated by nitrogen (N2 gas releases from the cooling system of an IR-camera on board the Vega 1 and Vega 2 spacecraft, during their flybys of comet Halley in March 1986. N2 molecules are ionized by solar UV radiation at a rate of ~ 7 · 10-7 s-1 and give rise to a plasma cloud expanding around the spacecraft. Strong disturbances due to the interaction of the solar wind with the N+2 ion cloud are observed with a plasma and wave experiment (APV-V instrument. Three gas releases are accompanied by increases in cold electron density and simultaneous decreases of the spacecraft potential; this study shows that the spacecraft potential can be monitored with a reference sensor mounted on a short boom. The comparison between the model and observations suggests that the gas expands as an exhaust plume, and approximately only 1% of the ions can escape the beam within the first meters. The releases are also associated with significant increases in wave electric field emission (8 Hz–300 kHz; this phenomenon lasts for more than one hour after the end of the release, which is most likely due to the temporary contamination of the spacecraft surface by nitrogen gas. DC electric fields associated with the events are complex but interesting. No magnetic field perturbations are detected, suggesting that no significant diamagnetic effect (i.e. magnetic cavity is associated with these events.

    Key words. Ionosphere (planetary ionosphere – Space plasma physics (active perturbation experiments; instruments and techniques

  19. Collective phenomena in the non-equilibrium quark-gluon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Schenke, Bjoern Peter

    2008-07-03

    In this work we study the non-equilibrium dynamics of a quark-gluon plasma, as created in heavy-ion collisions. We investigate how big of a role plasma instabilities can play in the isotropization and equilibration of a quark-gluon plasma. In particular, we determine, among other things, how much collisions between the particles can reduce the growth rate of unstable modes. This is done both in a model calculation using the hard-loop approximation, as well as in a real-time lattice simulation combining both classical Yang-Mills-fields as well as inter-particle collisions. The new extended version of the simulation is also used to investigate jet transport in isotropic media, leading to a cutoff-independent result for the transport coefficient q. The precise determination of such transport coefficients is essential, since they can provide important information about the medium created in heavy ion collisions. In anisotropic media, the effect of instabilities on jet transport is studied, leading to a possible explanation for the experimental observation that high-energy jets traversing the plasma perpendicular to the beam axis experience much stronger broadening in rapidity than in azimuth. The investigation of collective modes in the hard-loop limit is extended to fermionic modes, which are shown to be all stable. Finally, we study the possibility of using high energy photon production as a tool to experimentally determine the anisotropy of the created system. Knowledge of the degree of local momentum-space anisotropy reached in a heavy-ion collision is essential for the study of instabilities and their role for isotropization and thermalization, because their growth rate depends strongly on the anisotropy. (orig.)

  20. Investigating high speed phenomena in laser plasma interactions using dilation x-ray imager (invited).

    Science.gov (United States)

    Nagel, S R; Hilsabeck, T J; Bell, P M; Bradley, D K; Ayers, M J; Piston, K; Felker, B; Kilkenny, J D; Chung, T; Sammuli, B; Hares, J D; Dymoke-Bradshaw, A K L

    2014-11-01

    The DIlation X-ray Imager (DIXI) is a new, high-speed x-ray framing camera at the National Ignition Facility (NIF) sensitive to x-rays in the range of ≈2-17 keV. DIXI uses the pulse-dilation technique to achieve a temporal resolution of less than 10 ps, a ≈10× improvement over conventional framing cameras currently employed on the NIF (≈100 ps resolution), and otherwise only attainable with 1D streaked imaging. The pulse-dilation technique utilizes a voltage ramp to impart a velocity gradient on the signal-bearing electrons. The temporal response, spatial resolution, and x-ray sensitivity of DIXI are characterized with a short x-ray impulse generated using the COMET laser facility at Lawrence Livermore National Laboratory. At the NIF a pinhole array at 10 cm from target chamber center (tcc) projects images onto the photocathode situated outside the NIF chamber wall with a magnification of ≈64×. DIXI will provide important capabilities for warm-dense-matter physics, high-energy-density science, and inertial confinement fusion, adding important capabilities to temporally resolve hot-spot formation, x-ray emission, fuel motion, and mix levels in the hot-spot at neutron yields of up to 10(17). We present characterization data as well as first results on electron-transport phenomena in buried-layer foil experiments.

  1. Investigating high speed phenomena in laser plasma interactions using dilation x-ray imager (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Nagel, S. R., E-mail: nagel7@llnl.gov; Bell, P. M.; Bradley, D. K.; Ayers, M. J.; Piston, K.; Felker, B. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Hilsabeck, T. J.; Kilkenny, J. D.; Chung, T.; Sammuli, B. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Hares, J. D.; Dymoke-Bradshaw, A. K. L. [Kentech Instruments Ltd., Wallingford, Oxfordshire OX10 (United Kingdom)

    2014-11-15

    The DIlation X-ray Imager (DIXI) is a new, high-speed x-ray framing camera at the National Ignition Facility (NIF) sensitive to x-rays in the range of ≈2–17 keV. DIXI uses the pulse-dilation technique to achieve a temporal resolution of less than 10 ps, a ≈10× improvement over conventional framing cameras currently employed on the NIF (≈100 ps resolution), and otherwise only attainable with 1D streaked imaging. The pulse-dilation technique utilizes a voltage ramp to impart a velocity gradient on the signal-bearing electrons. The temporal response, spatial resolution, and x-ray sensitivity of DIXI are characterized with a short x-ray impulse generated using the COMET laser facility at Lawrence Livermore National Laboratory. At the NIF a pinhole array at 10 cm from target chamber center (tcc) projects images onto the photocathode situated outside the NIF chamber wall with a magnification of ≈64×. DIXI will provide important capabilities for warm-dense-matter physics, high-energy-density science, and inertial confinement fusion, adding important capabilities to temporally resolve hot-spot formation, x-ray emission, fuel motion, and mix levels in the hot-spot at neutron yields of up to 10{sup 17}. We present characterization data as well as first results on electron-transport phenomena in buried-layer foil experiments.

  2. Overrelaxation phenomena during the formation of reversed-field pinch plasmas

    Science.gov (United States)

    Mazur, S.; Nordlund, P.

    1995-10-01

    Experiments on the Extrap T1 reversed-field pinch (RFP) [Phys. Scr. 49, 224 (1994)] have shown that the formation of the RFP configuration is quite sensitive to the relative programming of the toroidal field and Ohmic heating circuits. In this paper, new measurements of the evolution of the current density profile and of the spectral structure of the fluctuations during the setup phase of RFP plasmas in the T1 experiment are presented. These measurements improve the understanding of the role of different spectral components in the dynamics of RFP formation. Under unfavorable (slow) setup conditions, comparatively high energy is accumulated in m=1 internal kinks prior to reversal of the edge toroidal field. At reversal, nonlinearly driven m=0 modes trigger a rapid broadening of the m=1 spectrum. This behavior is associated with a violent suppression of the current density in the core, leading to an overrelaxation of the discharge involving a hollowing of the parallel current density profile. The setup conditions are found to affect the volt-second consumption and plasma/wall interaction during RFP formation, as well as the flat-top discharge performance.

  3. Two Types of Magnetohydrodynamic Sheath Jets

    CERN Document Server

    Kaburaki, Osamu

    2009-01-01

    Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma is balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature...

  4. Report of the Plasma Physics and Environmental Perturbation Laboratory (PPEPL) working groups. Volume 1: Plasma probes, wakes, and sheaths working group

    Science.gov (United States)

    1974-01-01

    It is shown in this report that comprehensive in-situ study of all aspects of the entire zone disturbance caused by a body in a flowing plasma resulted in a large number if requirements on the shuttle-PPEPL facility. A large amount of necessary in-situ observation can be obtained by adopting appropriate modes of performing the experiments. Requirements are indicated for worthwhile studies, of some aspects of the problems, which can be carried out effectively while imposing relatively few constraints on the early missions. Considerations for the desired growth and improvement of the PPEPL to facilitate more complete studies in later missions are also discussed. For Vol. 2, see N74-28170; for Vol# 3, see N74-28171.

  5. Efficient particle-in-cell simulation of auroral plasma phenomena using a CUDA enabled graphics processing unit

    Science.gov (United States)

    Sewell, Stephen

    This thesis introduces a software framework that effectively utilizes low-cost commercially available Graphic Processing Units (GPUs) to simulate complex scientific plasma phenomena that are modeled using the Particle-In-Cell (PIC) paradigm. The software framework that was developed conforms to the Compute Unified Device Architecture (CUDA), a standard for general purpose graphic processing that was introduced by NVIDIA Corporation. This framework has been verified for correctness and applied to advance the state of understanding of the electromagnetic aspects of the development of the Aurora Borealis and Aurora Australis. For each phase of the PIC methodology, this research has identified one or more methods to exploit the problem's natural parallelism and effectively map it for execution on the graphic processing unit and its host processor. The sources of overhead that can reduce the effectiveness of parallelization for each of these methods have also been identified. One of the novel aspects of this research was the utilization of particle sorting during the grid interpolation phase. The final representation resulted in simulations that executed about 38 times faster than simulations that were run on a single-core general-purpose processing system. The scalability of this framework to larger problem sizes and future generation systems has also been investigated.

  6. Characteristics of Collision, Capacitive Radio Frequency Sheath

    Institute of Scientific and Technical Information of China (English)

    Zhang Yu; DingWanYu; Wang Wenchun; Liu JinYuan; Wang Xiaogang; Liu Yue

    2005-01-01

    A simple collisional radio frequency (rf) sheath fluid model, which is not restricted by the ratio of rf frequency to ion plasma frequency (β=ωrf/ωpi), was established and solved numerically. In the ion balance equation, the effect of the collision on the ion and the ion velocity is assumed to be a direct ratio to ion velocity. The ion energy distributions (IEDs) calculated in the model in comparison with the experimental data [M. A. Sobolewski, J. K. Olthoff, and Y.C. Wang, J. Appl. Phys. 85, 3966 (1999)], proved the validity of the model. And the effect of the collision on the sheath characteristic was obtained and discussed. This paper demonstrates that the collision frequency is another crucial parameter as well as the ratio β to determine the rf sheath characteristics and the shape of IE Ds.

  7. Theory of the Electron Sheath and Presheath

    CERN Document Server

    Scheiner, Brett; Yee, Benjamin T; Hopkins, Matthew M; Barnat, Edward V

    2015-01-01

    Electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in Particle-In-Cell (PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperature plasma conditions ($T_e\\gg T_i$), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under co...

  8. Autolysis of Bacterial Cells Leads to Formation of Empty Sheaths by Leptothrix spp.

    Directory of Open Access Journals (Sweden)

    Jun Takada

    2013-06-01

    Full Text Available The aquatic, Fe-oxidizing bacteria Leptothrix spp. produce uniquely shaped extracellular sheaths composed of organic bacterial polymers encrusted with inorganic elements from its aquatic environments. At the initial stage of sheath formation, bacterial cells were aligned in the sheath, but later most sheaths became empty. Here, we studied the mechanism of sheath hollowing by examining an isolate of Leptothrix sp. strain OUMS1 cultured in either artificial medium or natural groundwater. After 3 days in the medium, most sheaths at the initial stage surrounded a line of live cells, while some cells in the line were dead regardless of their position in a sheath. In sheaths where cells and/or their remnants were barely distinguishable by differential interference contrast microscopy (DIC, a vital stain and a stain specific for nucleic acids occasionally revealed dead cells and/or nucleic acid remnants, while sheaths that lacked a positive response to these reagents looked transparent when viewed with DIC. In specimens cultured in the medium for 7 days, dead cells increased in number regardless of their position in the sheath. Almost the same phenomena occurred in specimens cultured in natural groundwater until day 7. Transmission electron microscopy (TEM showed that cells degenerated, leading to autolysis of bacterial cells in the sheath. These observations led us to conclude that autolysis of bacterial cells could be a major cause of sheath hollowing.

  9. Measurement of effective sheath width around the cutoff probe based on electromagnetic simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Oh, W. Y., E-mail: sjyou@cnu.ac.kr, E-mail: woh1@kaist.ac.kr [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, S. J., E-mail: sjyou@cnu.ac.kr, E-mail: woh1@kaist.ac.kr [Department of Physics, Chungnam National University, Daejeon 305-701 (Korea, Republic of); Kim, J. H. [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Chang, H. Y. [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); Yoon, J.-S. [Plasma Technology Research Center, National Fusion Research Institute, Gunsan 573-540 (Korea, Republic of)

    2016-05-15

    We inferred the effective sheath width using the cutoff probe and incorporating a full-wave three-dimensional electromagnetic (EM) simulation. The EM simulation reproduced the experimentally obtained plasma-sheath resonance (PSR) on the microwave transmission (S{sub 21}) spectrum well. The PSR frequency has a one-to-one correspondence with the width of the vacuum layer assumed to be the effective sheath in the EM simulation model. The sheath width was estimated by matching the S{sub 21} spectra of the experiment and the EM simulation for different widths of the sheath. We found that the inferred sheath widths quantitatively and qualitatively agree with the sheath width measured by incorporating an equivalent circuit model. These results demonstrate the excellent potential of the cutoff probe for inferring the effective sheath width from its experimental spectrum data.

  10. Self-similarity of skeletal structures in laboratory high current electric discharges (plasmas and fractal dust deposits), severe weather phenomena and space

    Science.gov (United States)

    Kukushkin, A. B.; Rantsev-Kartinov, V. A.

    2003-10-01

    The phenomenon of skeletal structures (tubules, cartwheels, and their simple combinations) formerly found in laboratory plasmas, is extended to atmospheric and cosmic phenomena (Phys. Lett. A 306, 175, Dec. 2002). The long-lived filaments in plasmas have been suggested (1998) to possess a skeleton self-assembled during electric breakdown from wildly produced nanodust. The proof-of-concept studies revealed the skeletal structures in (1) plasmas in tokamaks, Z-pinches, plasma focus (in the range 0.01-10 cm), including the electric breakdown stage of discharge, (2) dust deposits in tokamak (10 nm - 10 microns), (3) hailstones (1-10 cm), tornado (10 m -1 km), (4) a wide class of objects in space (10^11-10^23 cm). The similarity of, and the trend toward self-similarity in, skeletal structures suggest all them to possess a fractal condensed matter of particular topology of the fractal. Here we discuss probable role of skeletal structures in the fast nonlocal transport of energy in strongly localized severe weather phenomena (tornado) and laboratory plasmas.

  11. Experimental Study of Convective Cells and RF Sheaths Excited by a Fast Wave Antenna in the LAPD

    Science.gov (United States)

    Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy; van Eester, Dirk; Crombé, Kristel

    2016-10-01

    Ion cyclotron resonance heating (ICRH) will be essential for ITER where it is planned to couple 20 MW to the plasma. During ICRH, radio frequency (RF) sheaths may form on the antenna or farther away, and convective cells are suspected to form adjacent to ICRH antennas, negatively affecting both machine and plasma performance. The LAPD (ne 10 12 - 13cm-3 , Te 1-10 eV, B0 0.4 to 2 kG, diameter 60 cm, length 17m) is an ideal device for performing detailed experiments to fully diagnose these phenomena. A 200 kW RF system capable of pulsing at the 1 Hz. rep. rate of the LAPD and operating from 2 to 2.5 MHz has been constructed to perform such studies. B0 can be adjusted so that this encompasses the 1st to 7th harmonic of fci in H plasmas. Emissive, Mach, Langmuir, and B-field probes measured plasma potential, bulk plasma flows, wave patterns, ne, and Te in 2D planes at various axial locations from the antenna. Plasma potential enhancements of up to 90 V along magnetic field lines connected to the antenna and induced ExB flows consistent in structure with convective cells were observed. Details of these observations along with power scaling of RF sheath voltage and convective cell flows will be presented.

  12. Measurement of sheath thickness at a floating potential

    Energy Technology Data Exchange (ETDEWEB)

    Han, Hyung-Sik; Lee, Hyo-Chang; Oh, Se-Jin; Chung, Chin-Wook, E-mail: joykang@hanyang.ac.kr [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2014-02-15

    In a cylindrical Langmuir probe measurement, ion current is collected from the surface of the sheath surrounded at probe tip, not at the surface of the probe tip. By using this, the sheath thickness can be obtained, if we know some unknown parameters, such as ion current, plasma density, and electron temperature. In this paper, we present a method to measure sheath thickness by using a wave cutoff method and a floating harmonic method. The measured result is in a good agreement with Allen-Boyd-Reynolds theory.

  13. Continuum Kinetic and Multi-Fluid Simulations of Classical Sheaths

    CERN Document Server

    Cagas, Petr; Juno, James; Srinivasan, Bhuvana

    2016-01-01

    The kinetic study of plasma sheaths is critical, among other things, to understand the deposition of heat on walls, the effect of sputtering, and contamination of the plasma with detrimental impurities. The plasma sheath also provides a boundary condition and can often have a significant global impact on the bulk plasma. In this paper, kinetic studies of classical sheaths are performed with the continuum code, Gkeyll, that directly solves the Vlasov-Poisson/Maxwell equations. The code uses a novel version of the finite-element discontinuous Galerkin (DG) scheme that conserves energy in the continuous-time limit. The electrostatic field is computed using the Poisson equation. Ionization and scattering collisions are included, however, surface effects are neglected. The aim of this work is to introduce the continuum-kinetic method and compare its results to those obtained from an already established finite-volume multi-fluid model also implemented in Gkeyll. Novel boundary conditions on the fluids allow the she...

  14. Paranormal phenomena

    Science.gov (United States)

    Gaina, Alex

    1996-08-01

    Critical analysis is given of some paranormal phenomena events (UFO, healers, psychokinesis (telekinesis))reported in Moldova. It is argued that correct analysis of paranormal phenomena should be made in the framework of electromagnetism.

  15. Fibroma of tendon sheath.

    Science.gov (United States)

    Smith, P S; Pieterse, A S; McClure, J

    1982-01-01

    A series of nine cases of fibroma of tendon sheath is described including details of the ultrastructural features of two cases. The series was composed of lesions from six males and three females with a mean age of 38 yr. The most common site of involvement was the hand (including fingers) and the mean greater diameter was 19 mm. Typically the tumours were lobulated and microscopically there was a collagenous stroma with spindle and stellate cells in a moderate degree of cellularity. One recurrence was noted in the series. The lesion was distinguished from circumscribed fibromatosis, nodular fasciitis, neurofibroma, leiomyoma, scar tissue, giant cell tumour of tendon sheath (localised nodular tenosynovitis) and fibrous histiocytoma. Ultrastructural studies revealed that the large majority of cells present in the two cases studied were myofibroblasts and fibroma of tendon sheath is therefore the third instance of a benign tumour containing these cells (the other two being dermatofibroma and giant cell fibroma of the oral mucosa). Images PMID:7107956

  16. Bending and turbulent enhancement phenomena of neutral gas flow containing an atmospheric pressure plasma by applying external electric fields measured by schlieren optical method

    Science.gov (United States)

    Yamada, Hiromasa; Yamagishi, Yusuke; Sakakita, Hajime; Tsunoda, Syuichiro; Kasahara, Jiro; Fujiwara, Masanori; Kato, Susumu; Itagaki, Hirotomo; Kim, Jaeho; Kiyama, Satoru; Fujiwara, Yutaka; Ikehara, Yuzuru; Ikehara, Sanae; Nakanishi, Hayao; Shimizu, Nobuyuki

    2016-01-01

    To understand the mechanism of turbulent enhancement phenomena of a neutral gas flow containing plasma ejected from the nozzle of plasma equipment, the schlieren optical method was performed to visualize the neutral gas behavior. It was confirmed that the turbulent starting point became closer to the nozzle exit, as the amplitude of discharge voltage (electric field) increased. To study the effect of electric field on turbulent enhancement, two sets of external electrodes were arranged in parallel, and the gas from the nozzle was allowed to flow between the upper and lower electrodes. It was found that the neutral gas flow was bent, and the bending angle increased as the amplitude of the external electric field increased. The results obtained using a simple model analysis roughly coincide with experimental data. These results indicate that momentum transport from drifted ions induced by the electric field to neutral particles is an important factor that enhances turbulence.

  17. Radio-frequency sheath voltages and slow wave electric field spatial structure

    Energy Technology Data Exchange (ETDEWEB)

    Colas, Laurent, E-mail: laurent.colas@cea.fr; Lu, Ling-Feng [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Křivská, Alena [LPP-ERM-KMS, TEC partner, Brussels (Belgium); Jacquot, Jonathan [Max-Planck-Institut für Plasmaphysik, Garching (Germany)

    2015-12-10

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a “wide sheaths” asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  18. Investigation of Sheath Phenomena in Electronegative Glow Discharges.

    Science.gov (United States)

    1987-04-01

    al. 7 and Segur 3 similarly assumed a linearly decreasing electric field, but used the Monte Carlo model. These calculations are not considered self...fall region, was not examined. Since then Segur et al. 6 have coupled a Boltzmann solution for electrons with an analytical approximation to the...electrode distance (D) wee limited by the memory storage capability of a Cyber 74 computer. For 100% He, D was 2.2 cm and for the remaining He/HCI

  19. Investigation of Sheath Phenomena in Electronegative Glow Discharges.

    Science.gov (United States)

    1985-04-01

    EEEEEEEEEEEEEE EEEEEmmhhhhEEEE EEEEEEEEEEEEEIs EhEEEmhohEEEEE 322 _ . I I I- 11111 n : \\ Z w . ° Z 1.25 LA11 ’ 1 1.6 fIu,! MICROCOPY RESOLUTJON TESI CHART...84-2899 F/, 28/3 UL EEIIEIIEEEEEElll lilEl LL I- . ~III b:- II1I . 1gII1 8 11111.25 1 111. 111 .6 ’*. MILIROCOPY R[SOLUTION TESI CHART -33 A.. C...Fnercics" Journaf uf Physics F: ’ tur iic d~id Niiectflar Physics 14: L4b.*-(, , 2A 96. Woolsey, G. A. Kttdies of F 1cc-LYunegai vve Pl asmas I FhI bi

  20. Experimental study of gliding arc plasma channel motion: buoyancy and gas flow phenomena under normal and hypergravity conditions

    Science.gov (United States)

    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.

  1. Continuum kinetic and multi-fluid simulations of classical sheaths

    Science.gov (United States)

    Cagas, P.; Hakim, A.; Juno, J.; Srinivasan, B.

    2017-02-01

    The kinetic study of plasma sheaths is critical, among other things, to understand the deposition of heat on walls, the effect of sputtering, and contamination of the plasma with detrimental impurities. The plasma sheath also provides a boundary condition and can often have a significant global impact on the bulk plasma. In this paper, kinetic studies of classical sheaths are performed with the continuum kinetic code, Gkeyll, which directly solves the Vlasov-Maxwell equations. The code uses a novel version of the finite-element discontinuous Galerkin scheme that conserves energy in the continuous-time limit. The fields are computed using Maxwell equations. Ionization and scattering collisions are included; however, surface effects are neglected. The aim of this work is to introduce the continuum kinetic method and compare its results with those obtained from an already established finite-volume multi-fluid model also implemented in Gkeyll. Novel boundary conditions on the fluids allow the sheath to form without specifying wall fluxes, so the fluids and fields adjust self-consistently at the wall. The work presented here demonstrates that the kinetic and fluid results are in agreement for the momentum flux, showing that in certain regimes, a multi-fluid model can be a useful approximation for simulating the plasma boundary. There are differences in the electrostatic potential between the fluid and kinetic results. Further, the direct solutions of the distribution function presented here highlight the non-Maxwellian distribution of electrons in the sheath, emphasizing the need for a kinetic model. The densities, velocities, and the potential show a good agreement between the kinetic and fluid results. However, kinetic physics is highlighted through higher moments such as parallel and perpendicular temperatures which provide significant differences from the fluid results in which the temperature is assumed to be isotropic. Besides decompression cooling, the heat flux

  2. Physics-based parametrization of the surface impedance for radio frequency sheaths

    Science.gov (United States)

    Myra, J. R.

    2017-07-01

    The properties of sheaths near conducting surfaces are studied for the case where both magnetized plasma and intense radio frequency (rf) waves coexist. The work is motivated primarily by the need to understand, predict, and control ion cyclotron range of frequency (ICRF) interactions with tokamak scrape-off layer plasmas and is expected to be useful in modeling rf sheath interactions in global ICRF codes. Employing a previously developed model for oblique angle magnetized rf sheaths [J. R. Myra and D. A. D'Ippolito, Phys. Plasmas 22, 062507 (2015)], an investigation of the four-dimensional parameter space governing these sheath is carried out. By combining numerical and analytical results, a parametrization of the surface impedance and voltage rectification for rf sheaths in the entire four-dimensional space is obtained.

  3. On the biogenesis of the myelin sheath : Cognate polarized trafficking pathways in oligodendrocytes

    NARCIS (Netherlands)

    de Vries, H; Hoekstra, D

    2000-01-01

    Oligodendrocytes, the myelinating cells of the central nervous system, are capable of transporting vast quantities of proteins and of lipids, In particular galactosphingolipids, to the myelin sheath. The sheath is continuous with the plasma membrane of the oligodendrocyte, but the composition of bot

  4. Analytical expression for the sheath edge around wedge-shaped cathodes

    Science.gov (United States)

    Sheridan, T. E.

    2008-03-01

    The sheath is the boundary layer separating a quasi-neutral plasma from a material electrode. Understanding the sheath is important for numerous applications, including plasma-based ion implantation, plasma etching of semiconductors, plasma assisted electrostatic cleaning, and Langmuir probes. In a 1D planar geometry, the Child-Langmuir (CL) law describes the sheath when the bias on a negative electrode, i.e., a cathode, is much greater than the electron temperature. In this case, the sheath width s is an eigenvalue of the problem. In 2D, the sheath edge is an unknown line (an ``eigen-boundary") which is determined by a set of coupled, nonlinear, partial differential equations. I have found an expression for the sheath edge around a 2D wedge-shaped cathode with included angle θw. In polar coordinates (r,θ), the sheath edge is a solution of r(aθ)=as where s is the planar sheath width far from the corner and θw=2π- π/a, so that a=1/2 gives a knife edge, while a=2/3 gives a square corner. This result is verified by comparison with the numerical solutions of Watterson [P. A. Watterson, J. Phys. D 22, 1300 (1989)].

  5. Modelling of the dual frequency capacitive sheath in the intermediate pressure range

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, P C [Plasma Research Laboratory, National Centre for Plasma Science and Technology and School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Robiche, J [Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, Palaiseau 91 128 Cedex (France); Turner, M M [Plasma Research Laboratory, National Centre for Plasma Science and Technology and School of Physical Sciences, Dublin City University, Dublin 9 (Ireland)

    2004-05-21

    The nonlinearity of the plasma sheath in dual frequency capacitively coupled reactors is investigated for frequencies well above the ion plasma frequency. This work focuses on the behaviour of the voltage and the sheath width with respect to the driving current source and the collisionality regime. For typical plasma processing applications, the gas pressure ranges from a few milliTorrs to hundreds of milliTorrs, and the ion dynamics span different collisional regimes. To describe these different ion dynamics, we have used a collisionless model and a variable mobility model. The sheath widths and the voltages obtained from these two models have then been compared.

  6. The sheath effect on the floating harmonic method

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jaewon; Kim, Kyung-Hyun; Chung, Chin-Wook, E-mail: joykang@hanyang.ac.kr [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2015-12-15

    The floating harmonic method biases sinusoidal voltage to a probe sheath, and as its response, harmonic currents can be obtained. These currents can be used to determine the plasma parameters. However, different shapes of probes have different shapes of sheaths that can affect the diagnostic results. However, no research has been done on the sheath effect on the floating harmonic method. Therefore, we investigate the effect of the sheath during floating harmonic diagnostics by comparing cylindrical and planar probes. While the sinusoidal voltages were applied to a probe, because the sheath oscillated, the time variant ion current and their harmonic currents were added to the electron harmonic currents. In the floating harmonic method, the harmonic currents are composed of only the electron harmonic currents. Therefore, the ion harmonic currents affect the diagnostic results. In particular, the electron temperature obtained by the small probe tip was higher than that of the large probe tip. This effect was exacerbated when the ratio of the probe tip radius to the sheath length was smaller.

  7. Transport Phenomena.

    Science.gov (United States)

    Shah, D. B.

    1984-01-01

    Describes a course designed to achieve a balance between exposing students to (1) advanced topics in transport phenomena, pointing out similarities and differences between three transfer processes and (2) common methods of solving differential equations. (JN)

  8. Magnetic Field Generation in Core-Sheath Jets via the Kinetic Kelvin-Helmholtz Instability

    CERN Document Server

    Nishikawa, K -I; Dutan, I; Niemiec, J; Medvedev, M; Mizuno, Y; Meli, A; Sol, H; Zhang, B; Pohl, M; Hartmann, D H

    2014-01-01

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas we find generation of strong large-scale DC currents and magnetic fields which extend over the entire shear-surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates transverse structure similar to that produced by the Weibel instability.

  9. Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, K.-I. [Department of Physics, University of Alabama in Huntsville, ZP12, Huntsville, AL 35899 (United States); Hardee, P. E. [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, AL 35487 (United States); Duţan, I. [Institute of Space Science, Atomistilor 409, Bucharest-Magurele RO-077125 (Romania); Niemiec, J. [Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland); Medvedev, M. [Department of Physics and Astronomy, University of Kansas, KS 66045 (United States); Mizuno, Y. [Institute of Astronomy, National Tsing-Hua University, Hsinchu, Taiwan 30013 (China); Meli, A. [Department of Physics and Astronomy, University of Gent, Proeftuinstraat 86 B-9000, Gent (Belgium); Sol, H. [LUTH, Observatore de Paris-Meudon, 5 place Jules Jansen, F-92195 Meudon Cedex (France); Zhang, B. [Department of Physics, University of Nevada, Las Vegas, NV 89154 (United States); Pohl, M. [Institut fur Physik und Astronomie, Universität Potsdam, D-14476 Potsdam-Golm (Germany); Hartmann, D. H., E-mail: ken-ichi.nishikawa@nasa.gov [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States)

    2014-09-20

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

  10. Studies of RF sheaths and diagnostics on IShTAR

    Energy Technology Data Exchange (ETDEWEB)

    Crombé, K., E-mail: Kristel.Crombe@UGent.be [Department of Applied Physics, Ghent University, Ghent (Belgium); LPP-ERM/KMS, Royal Military Academy, Brussels (Belgium); Devaux, S.; Faudot, E.; Heuraux, S.; Moritz, J. [YIJL, UMR7198 CNRS-Université de Lorraine, Nancy (France); D’Inca, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Ochoukov, R. [Max-Planck-Institut für Plasmaphysik, Garching (Germany); Louche, F.; Tripsky, M.; Van Eester, D.; Wauters, T. [LPP-ERM/KMS, Royal Military Academy, Brussels (Belgium); Noterdaeme, J.-M. [Department of Applied Physics, Ghent University, Ghent (Belgium); Max-Planck-Institut für Plasmaphysik, Garching (Germany)

    2015-12-10

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  11. Magnetized sheath near positively biased wall between two permanent magnetic plates

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan; Wei, Zi-an; Ma, J. X., E-mail: jxma@ustc.edu.cn; Jiang, Zheng-qi; Wu, Fei [Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); CAS Key Laboratory of Geospace Environment, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-06-15

    The characteristics of magnetized electron sheath near a positively biased conducting wall parallel to magnetic field formed between two permanent magnetic plates were experimentally investigated in a double plasma device. The magnetic field strength between the magnetic plates is about 1200 G which is sufficient to magnetize the plasma such that the ion gyroradius is comparable to the electron Debye length. A virtual cathode (or potential dip) structure was found between the electron-rich sheath and bulk plasma. For a given neutral gas pressure, the potential minimum (dip position) remains almost the same for different positive biases on the wall. For a given bias on the wall, however, the electron sheath thickness and the potential drop from the bulk plasma to the dip decrease with the increase of the neutral gas pressure. In addition, the electron sheath and potential dip appear to be wider and deeper in the downstream side of the wall.

  12. Transport Phenomena.

    Science.gov (United States)

    McCready, Mark J.; Leighton, David T.

    1987-01-01

    Discusses the problems created in graduate chemical engineering programs when students enter with a wide diversity of understandings of transport phenomena. Describes a two-semester graduate transport course sequence at the University of Notre Dame which focuses on fluid mechanics and heat and mass transfer. (TW)

  13. Recent sheath physics studies on DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, J.G., E-mail: watkins@fusion.gat.com [Sandia National Laboratories, PO Box 969, Livermore, CA 94551 (United States); Labombard, B. [MIT Plasma Science and Fusion Center, 175 Albany St, Cambridge, MA 02139 (United States); Stangeby, P.C. [University of Toronto Institute for Aerospace Studies, Toronto M3H 5T6 (Canada); Lasnier, C.J.; McLean, A.G. [Lawrence Livermore National Laboratory, 700 East Ave, Livermore, CA 94550 (United States); Nygren, R.E. [Sandia National Laboratories, PO Box 969, Livermore, CA 94551 (United States); Boedo, J.A. [University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0417 (United States); Leonard, A.W. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Rudakov, D.L. [University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0417 (United States)

    2015-08-15

    A study to examine some current issues in the physics of the plasma sheath has been recently carried out in DIII-D low power Ohmic plasmas using both flush and domed Langmuir probes, divertor Thomson scattering (DTS), an infrared camera (IRTV), and a new calorimeter triple probe assembly mounted on the Divertor Materials Evaluation System (DIMES). The sheath power transmission factor was found to be consistent with the theoretically predicted value of 7 (±2) for low power plasmas. Using this factor, the three heat flux profiles derived from the LP, DTS, and calorimeter diagnostic measurements agree. Comparison of flush and domed Langmuir probes and divertor Thomson scattering indicates that proper interpretation of flush probe data to get target plate density and temperature is feasible and could potentially yield accurate measurements of target plate conditions where the probes are located.

  14. Intraoral myxoid nerve sheath tumour

    NARCIS (Netherlands)

    Schortinghuis, J; Hille, JJ; Singh, S

    2001-01-01

    A case of an intraoral myxoid nerve sheath tumour of the dorsum of the tongue in a 73-year-old Caucasian male is reported. This case describes the oldest patient with this pathology to date. Immunoperoxidase staining for neuronspecific enolase (NSE) and epithelial membrane antigen (EMA) expression d

  15. Intraoral myxoid nerve sheath tumour

    NARCIS (Netherlands)

    Schortinghuis, J; Hille, JJ; Singh, S

    2001-01-01

    A case of an intraoral myxoid nerve sheath tumour of the dorsum of the tongue in a 73-year-old Caucasian male is reported. This case describes the oldest patient with this pathology to date. Immunoperoxidase staining for neuronspecific enolase (NSE) and epithelial membrane antigen (EMA) expression d

  16. Dust charging and charge fluctuations in a weakly collisional radio-frequency sheath at low pressure

    Energy Technology Data Exchange (ETDEWEB)

    Piel, Alexander, E-mail: piel@physik.uni-kiel.de; Schmidt, Christian [IEAP, Christian-Albrechts-Universität, Kiel (Germany)

    2015-05-15

    Models for the charging of dust particles in the bulk plasma and in the sheath region are discussed. A new model is proposed that describes collision-enhanced ion currents in the sheath. The collisions result in a substantial reduction of the negative charge of the dust. Experimental data for the dust charge in the sheath can be described by this model when a Bi-Maxwellian electron distribution is taken into account. Expressions for the dust charging rate for all considered models are presented and their influence on the rise of the kinetic dust temperature is discussed.

  17. Fully kinetic model of breakdown during sheath expansion after interruption of vacuum arcs

    Science.gov (United States)

    Wang, Zhenxing; Wang, Haoran; Zhou, Zhipeng; Tian, Yunbo; Geng, Yingsan; Wang, Jianhua; Liu, Zhiyuan

    2016-08-01

    Research on sheath expansion is critical to the understanding of the dielectric recovery process in a vacuum interrupter after interruption of vacuum arcs. In this paper, we investigated how residual plasma affects breakdown in the sheath expansion period after the current zero. To simulate sheath expansion and breakdown, we developed a fully kinetic particle-in-cell Monte Carlo collision model with one spatial dimension and three velocity dimensions. The model accounted for various collisions, including ionization, excitation, elastic collisions, charge exchange, and momentum exchange, and we added an external circuit to the model to make the calculations self-consistent. The existence of metal vapor slowed the sheath expansion in the gap and caused high electric field formation in front of the cathode surface. The initial residual plasma, which was at sufficiently low density, seemed to have a limited impact on breakdown, and the metal vapor dominated the breakdown in this case. Additionally, the breakdown probability was sensitive to the initial plasma density if the value exceeded a specific threshold, and plasma at sufficiently high density could mean that breakdown would occur more easily. We found that if the simulation does not take the residual plasma into account, it could overestimate the critical value of the metal vapor density, which is always used to describe the boundary of breakdown after interruption of vacuum arcs. We discussed the breakdown mechanism in sheath expansion, and the breakdown is determined by a combination of metal vapor, residual plasma, and the electric field in front of the cathode surface.

  18. Dynamics of large-scale solar-wind streams obtained by the double superposed epoch analysis. 2. CIR.vs.Sheath and MC.vs.Ejecta comparisons

    CERN Document Server

    Yermolaev, Yu I; Nikolaeva, N S; Yermolaev, M Yu

    2016-01-01

    This work is a continuation of our previous paper [Yermolaevetal2015] which describes the average temporal profiles of interplanetary plasma and field parameters in large-scale solar-wind (SW) streams: CIR, ICME (both MC and Ejecta) and Sheath as well as the interplanetary shock (IS). Like in the previous work we use data of OMNI database, our catalog of large-scale solar-wind phenomena during 1976--2000 [Yermolaevetal2009] and the double superposed epoch analysis (DSEA) method [Yermolaevetal2010]: re-scaling the duration of interval for all types in such a manner that, respectively, beginning and end for all intervals of selected type coincide. We present new detailed results of comparison of two pair phenomena: (1) both types of compression regions (CIR.vs.Sheath) and (2) both types of ICMEs (MC.vs.Ejecta). Obtained data allows us to suggest that the formation of all types of compression regions has the same physical mechanism irrespective of piston (High-Speed Stream (HSS) or ICME) type and differences are...

  19. Using Dust as Probes to Determine Sheath Extent and Structure

    CERN Document Server

    Douglass, Angela; Qiao, Ke; Matthews, Lorin; Hyde, Truell

    2016-01-01

    Two in-situ experimental methods are presented in which dust particles are used to determine the extent of the sheath and gain information about the time-averaged electric force profile within a RF plasma sheath. These methods are advantageous because they are not only simple and quick to carry out, but they also can be performed using standard dusty plasma experimental equipment. In the first method, dust particles are tracked as they fall through the plasma toward the lower electrode. These trajectories are then used to determine the electric force on the particle as a function of height as well as the extent of the sheath. In the second method, dust particle levitation height is measured across a wide range of RF voltages. Similarities were observed between the two experiments, but in order to understand the underlying physics behind these observations, the same conditions were replicated using a self-consistent fluid model. Through comparison of the fluid model and experimental results, it is shown that t...

  20. On radiative acceleration in spine-sheath structured blazar jets

    CERN Document Server

    Chhotray, Atul; Ghisellini, Gabriele; Salafia, Om Sharan; Tavecchio, Fabrizio; Lazzati, Davide

    2016-01-01

    It has been proposed that blazar jets are structured, with a fast spine surrounded by a slower sheath or layer. This structured jet model explains some properties of their emission and morphology. Because of their relative motion, the radiation produced by one component is seen amplified by the other, thus enhancing the inverse Compton emission of both. Radiation is emitted anisotropically in the comoving frames, and causes the emitting plasma to recoil. As seen in the observer frame, this corresponds to a deceleration of the fastest component (the spine) and an acceleration of the slower one (the layer). While the deceleration of the spine has already been investigated, here we study for the first time the acceleration of the sheath and find self-consistent velocity profile solutions for both the spine and the sheath while accounting for radiative cooling. We find that the sheath can be accelerated to the velocities required by the observations if its leptons remain energetic in the acceleration region, assu...

  1. Excitation and Ionisation dynamics in high-frequency plasmas

    Science.gov (United States)

    O'Connell, D.

    2008-07-01

    excitation and sustainment of the discharge. As the pressure decreases the discharge operates in so-called 'alpha-mode' where the sheath expansion is responsible for discharge sustainment. Decreasing the pressure towards the limit of operation (below 1 Pa) the discharge operates in a regime where kinetic effects dominate plasma sustainment. Wave particle interactions resulting from the flux of highly energetic electrons interacting with thermal bulk electrons give rise to a series of oscillations in the electron excitation phase space at the sheath edge. This instability is responsible for a significant energy deposit in the plasma when so-called 'ohmic heating' is no longer efficient. In addition to this an interesting electron acceleration mechanism occurs during the sheath collapse. The large sheath width, due to low plasma densities at the lower pressure, and electron inertia allows the build up of a local electric field accelerating electrons towards the electrode. Multi-frequency plasmas, provide additional process control for technological applications, and through investigating the excitation dynamics in such discharges the limitations of functional separation is observed. Non-linear frequency coupling is observed in plasma boundary sheaths governed by two frequencies simultaneously. In an alpha-operated discharge the sheath edge velocity governs the excitation and ionisation within the plasma, and it will be shown that this is determined by the time varying sheath width. The nature of the coupling effects strongly depends on the ratio of the applied voltages. Under technologically relevant conditions (low frequency voltage >> high frequency voltage) interesting phenomena depending on the phase relation of the voltages are also observed and will be discussed.

  2. New technique for withdrawing broken sheath

    Directory of Open Access Journals (Sweden)

    Süleyman Cagan Efe

    2016-03-01

    Full Text Available A sheath that is broken inside vessel is a rare complication, and intravascular fragments from broken sheaths are retrieving transcutaneously by techniques including the loop snare catheter, basket catheter, and grasping/biopsy forceps. We reported a less common type of broken central venous sheath in location and a successful unique technique for retrieving it from subclavian vein by using noncompliant balloon from 40 year old female patient.

  3. Tendon sheath fibroma in the thigh.

    Science.gov (United States)

    Moretti, Vincent M; Ashana, Adedayo O; de la Cruz, Michael; Lackman, Richard D

    2012-04-01

    Tendon sheath fibromas are rare, benign soft tissue tumors that are predominantly found in the fingers, hands, and wrists of young adult men. This article describes a tendon sheath fibroma that developed in the thigh of a 70-year-old man, the only known tendon sheath fibroma to form in this location. Similar to tendon sheath fibromas that develop elsewhere, our patient's lesion presented as a painless, slow-growing soft tissue nodule. Physical examination revealed a firm, nontender mass with no other associated signs or symptoms. Although the imaging appearance of tendon sheath fibromas varies, our patient's lesion appeared dark on T1- and bright on T2-weighted magnetic resonance imaging. It was well marginated and enhanced with contrast.Histologically, tendon sheath fibromas are composed of dense fibrocollagenous stromas with scattered spindle-shaped fibroblasts and narrow slit-like vascular spaces. Most tendon sheath fibromas can be successfully removed by marginal excision, although 24% of lesions recur. No lesions have metastasized. Our patient's tendon sheath fibroma was removed by marginal excision, and the patient remained disease free 35 months postoperatively. Despite its rarity, tendon sheath fibroma should be included in the differential diagnosis of a thigh mass on physical examination or imaging, especially if it is painless, nontender, benign appearing, and present in men.

  4. Plasma and oscillations with contributions in memoriam including a complete bibliography of his works

    CERN Document Server

    Suits, C Guy

    1961-01-01

    The Collected Works of Irving Langmuir, Volume 5: Plasma and Oscillations is an 11-chapter text covers the extensive research study of Langmuir in the field of gas discharges. This book specifically tackles oscillations in ionized gases. The opening chapters describe the plasma-boundary phenomena and the use of a probe to separate the primary electron beam from the scattered electrons. The succeeding chapters deal with the collisions between electrons and gas molecules, oscillations in ionized gases, and the interaction of electron and positive ion space charges in cathode sheaths. These t

  5. Arrangement of burner with sheath tube

    Energy Technology Data Exchange (ETDEWEB)

    Graat, J.W.; Remie, H.T.; Verhagen, A.M.

    1980-10-02

    This is concerned with an addition to the burner described in patent 28 28 319 in which fluid pulverised fuel and air is burnt in a chamber. The additional patent concerns a sheath tube, which surrounds the chamber and conducts the burnt gases on. The sheath tube has openings for better guidance of the thermal flow.

  6. Ion flow and sheath structure near positively biased electrodes

    Science.gov (United States)

    Hood, R.; Scheiner, B.; Baalrud, S. D.; Hopkins, M. M.; Barnat, E. V.; Yee, B. T.; Merlino, R. L.; Skiff, F.

    2016-11-01

    What effect does a dielectric material surrounding a small positively biased electrode have on the ion flow and sheath structure near the electrode? Measurements of the ion velocity distribution function and plasma potential near positively biased electrodes were made using laser-induced fluorescence and an emissive probe. The results were compared with 2D particle-in-cell simulations. Both measurements and simulations showed that when the positive electrode was surrounded by the dielectric material, ions were accelerated toward the electrode to approximately 0.5 times the ion sound speed before being deflected radially by the electron sheath potential barrier of the electrode. The axial potential profile in this case contained a virtual cathode. In comparison, when the dielectric material was removed from around the electrode, both the ion flow and virtual cathode depth near the electrode were dramatically reduced. These measurements suggest that the ion presheath from the dielectric material surrounding the electrode may enclose the electron sheath of the electrode, resulting in a virtual cathode that substantially influences the ion flow profile in the region.

  7. Observation of Self-Sustaining Relativistic Ionization Wave Launched by a Sheath Field

    Science.gov (United States)

    McCormick, M.; Arefiev, A. V.; Quevedo, H. J.; Bengtson, R. D.; Ditmire, T.

    2014-01-01

    We present experimental evidence supported by simulations of a relativistic ionization wave launched into a surrounding gas by the sheath field of a plasma filament with high energy electrons. Such a filament is created by irradiating a clustering gas jet with a short pulse laser (115 fs) at a peak intensity of 5×1017 W/cm2. We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 c after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma.

  8. Observation of Self-Sustaining Relativistic Ionization Wave Launched by Sheath Field

    CERN Document Server

    McCormick, M W; Quevedo, H J; Bengtson, R D; Ditmire, T

    2013-01-01

    We present experimental evidence supported by simulations of a relativistic ionization wave launched into surrounding gas by the sheath field of a plasma filament with high energy electrons. Such filament is created by irradiating a clustering gas jet with a short pulse laser ($\\sim$115 fs) at a peak intensity of $5 \\times 10^{17}$ W/cm$^2$. We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 $c$ after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma.

  9. Primary optic nerve sheath meningioma

    Energy Technology Data Exchange (ETDEWEB)

    Jeremic, Branislav [International Atomic Energy Agency, Vienna (Austria); Pitz, Susanne (eds.) [University Eye Hospital, Mainz (Germany)

    2008-07-01

    Optic nerve sheath meningioma (ONSM) is a rare tumour. Cases are usually separated into primary ONSM, which arises either intraorbitally or, less commonly, intracanalicularly, and secondary ONSM, which arises intracranially and subsequently invades the optic canal and orbit. This is the first book to cover all important aspects of the diagnosis and treatment of primary ONSM. After a general introduction, individual chapters discuss the clinical presentation, clinical examination and diagnosis, imaging, and histology. Treatment options are then addressed in detail, with special emphasis on external beam radiation therapy, and in particular stereotactic fractionated radiation therapy. The latter has recently produced consistently good results and is now considered the emerging treatment of choice for the vast majority of patients with primary ONSM. This well-illustrated book will prove invaluable to all practitioners who encounter primary ONSM in their clinical work. (orig.)

  10. Planar magnetic structures in coronal mass ejection-driven sheath regions

    Energy Technology Data Exchange (ETDEWEB)

    Palmerio, Erika; Kilpua, Emilia K.J. [Helsinki Univ. (Finland). Dept. of Physics; Savani, Neel P. [Maryland Univ., Baltimore County, MD (United States). Goddard Planetary Heliophysics Inst. (GPHI); NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2016-05-01

    Planar magnetic structures (PMSs) are periods in the solar wind during which interplanetary magnetic field vectors are nearly parallel to a single plane. One of the specific regions where PMSs have been reported are coronal mass ejection (CME)-driven sheaths. We use here an automated method to identify PMSs in 95 CME sheath regions observed in situ by the Wind and ACE spacecraft between 1997 and 2015. The occurrence and location of the PMSs are related to various shock, sheath, and CME properties. We find that PMSs are ubiquitous in CME sheaths; 85% of the studied sheath regions had PMSs with the mean duration of 6 h. In about one-third of the cases the magnetic field vectors followed a single PMS plane that covered a significant part (at least 67 %) of the sheath region. Our analysis gives strong support for two suggested PMS formation mechanisms: the amplification and alignment of solar wind discontinuities near the CME-driven shock and the draping of the magnetic field lines around the CME ejecta. For example, we found that the shock and PMS plane normals generally coincided for the events where the PMSs occurred near the shock (68% of the PMS plane normals near the shock were separated by less than 20 from the shock normal), while deviations were clearly larger when PMSs occurred close to the ejecta leading edge. In addition, PMSs near the shock were generally associated with lower upstream plasma beta than the cases where PMSs occurred near the leading edge of the CME. We also demonstrate that the planar parts of the sheath contain a higher amount of strong southward magnetic field than the non-planar parts, suggesting that planar sheaths are more likely to drive magnetospheric activity.

  11. 3-D FDTD Maxwell's-Equations Modeling of Sub-30 kHz Electromagnetic Wave Propagation in the Earth-Ionosphere Waveguide including Ionospheric Plasma Phenomena as Influenced by the Geomagnetic Field

    Science.gov (United States)

    Simpson, J. J.; Taflove, A.

    2006-12-01

    We report a finite-difference time-domain (FDTD) computational solution of Maxwell's equations for sub-30 kHz electromagnetic (EM) propagation in the Earth-ionosphere waveguide. The FDTD technique used in this study enables a direct, full-vector, three-dimensional (3-D) time-domain calculation of EM propagation accounting for arbitrary horizontal as well as vertical geometrical and electrical inhomogeneities and anisotropies of the excitation, ionosphere, lithosphere, and oceans. This is unlike previous FDTD models which assumed azimuthal symmetry about a vertical current source excitation representing a lightning channel. Our model is therefore unique in that it includes fully 3-D anisotropic plasma phenomena in the ionosphere as influenced by the full-vector geomagnetic field. In this study, we show results for EM propagation from lightning strikes using a spherical-coordinate (latitude- longitude) grid having a 1 x 1 x 1 km resolution. Our new model provides additional capabilities to simulate EM wave phenomena arising from whistlers and other lightning-related events, as well as for better understanding anomalous ionospheric phenomena reported to have occurred prior to and during major earthquakes.

  12. Particle-in-cell study of the ion-to-electron sheath transition

    CERN Document Server

    Scheiner, Brett; Hopkins, Matthew M; Yee, Benjamin T; Barnat, Edward V

    2016-01-01

    The form of a sheath near a small electrode, with bias changing from below to above the plasma potential is studied using 2D particle-in-cell (PIC) simulations. Five cases are studied: (A) an electrode biased more than the electron temperature ($T_e/e$) below the plasma potential, (B) an electrode biased less than $T_e/2e$ below the plasma potential, (C) an electrode biased nearly at the plasma potential, (D) an electrode biased more than $T_i/2e$ but less than $T_e/2e$ above the plasma potential, and (E) an electrode biased much greater than $T_e/2e$ above the plasma potential. In case (A), the electron velocity distribution function (EVDF) is observed to be Maxwellian with a Boltzmann-type exponential density decay through the ion sheath and presheath. In cases (B) and (C), the EVDFs exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode....

  13. Structural properties of proteins specific to the myelin sheath.

    Science.gov (United States)

    Kursula, P

    2008-02-01

    The myelin sheath is an insulating membrane layer surrounding myelinated axons in vertebrates, which is formed when the plasma membrane of an oligodendrocyte or a Schwann cell wraps itself around the axon. A large fraction of the total protein in this membrane layer is comprised of only a small number of individual proteins, which have certain intriguing structural properties. The myelin proteins are implicated in a number of neurological diseases, including, for example, autoimmune diseases and peripheral neuropathies. In this review, the structural properties of a number of myelin-specific proteins are described.

  14. Rectus sheath abscess after laparoscopic appendicectomy

    Directory of Open Access Journals (Sweden)

    Golash Vishwanath

    2007-01-01

    Full Text Available Port site wound infection, abdominal wall hematoma and intraabdominal abscess formation has been reported after laparoscopic appendicectomy. We describe here a rectus sheath abscess which occurred three weeks after the laparoscopic appendicectomy. It was most likely the result of secondary infection of the rectus sheath hematoma due to bleeding into the rectus sheath from damage to the inferior epigastric arteries or a direct tear of the rectus muscle. As far as we are aware this complication has not been reported after laparoscopic appendicectomy.

  15. Side-welded fast response sheathed thermocouple

    Science.gov (United States)

    Carr, K.R.

    A method of fabricating the measuring junction of a grounded-junction sheathed thermocouple to obtain fast time response and good thermal cycling performance is provided. Slots are tooled or machined into the sheath wall at the measuring junction, the thermocouple wires are laser-welded into the slots. A thin metal closure cap is then laser-welded over the end of the sheath. Compared to a conventional grounded-junction thermocouple, the response time is 4 to 5 times faster and the thermal shock and cycling capabilities are substantially improved.

  16. Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

    Science.gov (United States)

    Pfaff, R. F.

    2009-01-01

    On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

  17. Intrasellar malignant peripheral nerve sheath tumor (MPNST).

    Science.gov (United States)

    Krayenbühl, N; Heppner, F; Yonekawa, Y; Bernays, R L

    2007-02-01

    Intracranial malignant peripheral nerve sheath tumors (MPNST) and intrasellar schwannomas are rare tumors. We describe a case of an intrasellar schwannoma with progression to a MPNST, a finding that, although very rare, extends the differential diagnosis of intrasellar lesions.

  18. Rectus sheath hematoma: three case reports

    Directory of Open Access Journals (Sweden)

    Kapan Selin

    2008-01-01

    Full Text Available Abstract Introduction Rectus sheath hematoma is an uncommon cause of acute abdominal pain. It is an accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear. It could occur spontaneously or after trauma. They are usually located infraumblically and often misdiagnosed as acute abdomen, inflammatory diseases or tumours of the abdomen. Case presentation We reported three cases of rectus sheath hematoma presenting with a mass in the abdomen and diagnosed by computerized tomography. The patients recovered uneventfully after bed rest, intravenous fluid replacement, blood transfusion and analgesic treatment. Conclusion Rectus sheath hematoma is a rarely seen pathology often misdiagnosed as acute abdomen that may lead to unnecessary laparotomies. Computerized tomography must be chosen for definitive diagnosis since ultrasonography is subject to error due to misinterpretation of the images. Main therapy is conservative management.

  19. Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

    Directory of Open Access Journals (Sweden)

    A. Keiling

    2006-10-01

    Full Text Available Recent Cluster studies reported properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL that showed substructure with several well separated ion beamlets, covering energies from 3 keV up to 100 keV (Keiling et al., 2004a, b. Here we report observations from two PSBL crossings, which show a number of identified one-to-one correlations between this beamlet substructure and several plasma-field characteristics: (a bimodal ion conics (<1 keV, (b field-aligned electron flow (<1 keV, (c perpendicular electric field spikes (~20 mV/m, (d broadband electrostatic ELF wave packets (<12.5 Hz, and (e enhanced broadband electromagnetic waves (<4 kHz. The one-to-one correlations strongly suggest that these phenomena were energetically driven by the ion beamlets, also noting that the energy flux of the ion beamlets was 1–2 orders of magnitude larger than, for example, the energy flux of the ion outflow. In addition, several more loosely associated correspondences were observed within the extended region containing the beamlets: (f electrostatic waves (BEN (up to 4 kHz, (g traveling and standing ULF Alfvén waves, (h field-aligned currents (FAC, and (i auroral emissions on conjugate magnetic field lines. Possible generation scenarios for these phenomena are discussed. In conclusion, it is argued that the free energy of magnetotail ion beamlets drove a variety of phenomena and that the spatial fine structure of the beamlets dictated the locations of where some of these phenomena occurred. This emphasizes the notion that PSBL ion beams are important for magnetosphere-ionosphere coupling. However, it is also shown that the dissipation of electromagnetic energy flux (at altitudes below Cluster of the simultaneously occurring Alfvén waves and FAC was larger (FAC being the largest than the dissipation of beam kinetic energy flux, and thus these two energy carriers contributed more to the energy transport on PSBL field lines

  20. The possibility of a Hall thruster operation in the absence of the anode sheath

    CERN Document Server

    Dorf, L; Raitses, Y; Fisch, N J

    2002-01-01

    A method of determining boundary conditions for quasi 1-D modeling of steady-state operation of a Hall Thruster with ceramic channel is presented. For a given mass flow rate and magnetic field profile the imposed condition of a smooth sonic transition uniquely determines plasma density at the anode. The discharge voltage determines the structure of the anode sheath and thus determines electron and ion velocities at the anode. These parameters appear to be sufficient for constructing a solution with given temperature profile. It is shown that a good correlation between simulated and experimental results can be achieved by selecting an appropriate electron mobility and temperature profile. The structure of the electrode sheath was studied theoretically over a wide range of input parameters, such as discharge voltage, incoming neutral velocity and channel length, and the possibility of realization of the no-sheath operating regime is discussed here.

  1. Heights integrated model as instrument for simulation of hydrodynamic, radiation transport, and heat conduction phenomena of laser-produced plasma in EUV applications.

    Energy Technology Data Exchange (ETDEWEB)

    Sizyuk, V.; Hassanein, A.; Morozov, V.; Sizyuk, T.; Mathematics and Computer Science

    2007-01-16

    The HEIGHTS integrated model has been developed as an instrument for simulation and optimization of laser-produced plasma (LPP) sources relevant to extreme ultraviolet (EUV) lithography. The model combines three general parts: hydrodynamics, radiation transport, and heat conduction. The first part employs a total variation diminishing scheme in the Lax-Friedrich formulation (TVD-LF); the second part, a Monte Carlo model; and the third part, implicit schemes with sparse matrix technology. All model parts consider physical processes in three-dimensional geometry. The influence of a generated magnetic field on laser plasma behavior was estimated, and it was found that this effect could be neglected for laser intensities relevant to EUV (up to {approx}10{sup 12} W/cm{sup 2}). All applied schemes were tested on analytical problems separately. Benchmark modeling of the full EUV source problem with a planar tin target showed good correspondence with experimental and theoretical data. Preliminary results are presented for tin droplet- and planar-target LPP devices. The influence of three-dimensional effects on EUV properties of source is discussed.

  2. Anode sheath transition in an anodic arc for synthesis of nanomaterials

    Science.gov (United States)

    Nemchinsky, V. A.; Raitses, Y.

    2016-06-01

    The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

  3. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    Science.gov (United States)

    Křivská, A.; Bobkov, V.; Colas, L.; Jacquot, J.; Milanesio, D.; Ochoukov, R.

    2015-12-01

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  4. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    Energy Technology Data Exchange (ETDEWEB)

    Křivská, A., E-mail: alena.krivska@rma.ac.be [LPP-ERM/KMS, Royal Military Academy, 30 Avenue de la Renaissance B-1000, Brussels (Belgium); Bobkov, V.; Jacquot, J.; Ochoukov, R. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany); Colas, L. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Milanesio, D. [Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy)

    2015-12-10

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  5. Plasma Processing of Materials

    Science.gov (United States)

    1985-02-22

    used in France. In this case, three ’ movable electrodes arranged about the central axis with a coaxial sheath gas are employed. Initially the...Demiocratic Republic plasma furnace. chrome -magnesite; the bottom section is lined with rammed chrome -magnesite refractory. Due to the high heat loads... sheath injector design, cathode tip shape, and degree of water cooling are important parameters in providing a stable, uncontaminating, long-lifetime

  6. Fluid model of the sheath in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field: Some comments on ion source terms and ion temperature effects

    Energy Technology Data Exchange (ETDEWEB)

    Gyergyek, T. [University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana (Slovenia); Jožef Stefan Institute, Jamova 39, POB 100, 1000 Ljubljana (Slovenia); Kovačič, J. [Jožef Stefan Institute, Jamova 39, POB 100, 1000 Ljubljana (Slovenia)

    2015-04-15

    A one-dimensional fluid model of the magnetized plasma-wall transition region in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field is presented. The Boltzmann relation is assumed for the electrons, while the positive ions obey the ion continuity and momentum exchange equation. The ions are assumed to be isothermal. By comparison with a two-fluid model, it is shown that assuming the Boltzmann relation for the electrons implies that there is no creation or annihilation of the electrons. Consequently, there should not be any creation and annihilation of the positive ions either. The models that assume the Boltzmann relation for the electrons and a non-zero ion source term at the same time are therefore inconsistent, but such models have nevertheless been used extensively by many authors. So, in this work, an extensive comparison of the results obtained using the zero source term on one hand and three different non-zero source terms on the other hand is made. Four different ion source terms are considered in total: the zero source term and three different non-zero ion source terms. When the zero source term is used, the model becomes very sensitive to the boundary conditions, and in some cases, the solutions exhibit large amplitude oscillations. If any of the three non-zero ion source terms is used, those problems are eliminated, but also the consistency of the model is broken. The model equations are solved numerically in the entire magnetized plasma-wall transition region. For zero ion temperature, the model can be solved even if a very small ion velocity is selected as a boundary condition. For finite ion temperature, the system of equations becomes stiff, unless the ion velocity at the boundary is increased slightly above the ion thermal velocity. A simple method how to find a solution with a very small ion velocity at the boundary also for finite ion temperature in the entire magnetized plasma-wall transition region is

  7. Attenuation of low-frequency electromagnetic wave in the thin sheath enveloping a high-speed vehicle upon re-entry

    Science.gov (United States)

    Liu, DongLin; Li, XiaoPing; Liu, YanMing; Xie, Kai; Bai, BoWen

    2017-02-01

    Low-frequency (LF) electromagnetic (EM) waves are suggested as potentially solving "radio blackout" caused by a plasma sheath enveloping a high-speed vehicle on re-entry. However, the traditional plasma absorption theory neglects the fact that the plasma sheath is electrically small compared to LF EM wavelengths. To understand clearly the attenuation of such waves through the plasma sheath, different attenuation mechanisms for the electric field (SE) and magnetic field (SH) were studied using the equivalent circuit approach. Analytical expressions were derived by modeling the plasma sheath as a spherical shell, and numerical simulations were performed to validate the effectiveness of the expressions. SE and SH are calculated for various plasma parameter settings; the EM wave attenuations obtained from plasma absorption theory are used for comparison. Results show that, instead of SE and SH being equal in the plasma absorption theory, SE and SH are no longer the same for electrically small sizes. Whereas |SH| is close to that from plasma absorption theory, |SE| is much higher. Further analysis shows that |SH| is a function of the ratio of electron density (ne) and collision frequency (ve) and increases with increasing ne/ve. Numerical simulations with radio-attenuation-measurement-C-like vehicle's plasma sheath parameters are performed and the results show that the magnetic field attenuation in the front part of the vehicle is much lower than in the rear. So it is suggested to place the magnetic loop antenna in the very front part of the vehicle. Finally, SH at different frequencies are calculated using plasma sheath parameter values simulating the re-entry phase of a radio-attenuation measurement-C vehicle and results show that such a vehicle might overcome radio blackout during the entire re-entry phase if systems operating below 3 MHz and above the L-band are combined with a lower-frequency system working below Earth's ionosphere and a higher-frequency system

  8. Frequency-dependent effects of gravitational lensing within plasma

    Science.gov (United States)

    Rogers, Adam

    2015-07-01

    The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions N ∝ 1/rh with h ≥ 0 in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii and angular momentum for general h. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density h = 0. We study the behaviour for general h and show that when h = 2 the plasma term acts like an additional contribution to the angular momentum of the passing ray. When h = 3 the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star.

  9. Use of miniature, single-wire, sheathed thermocouples

    Science.gov (United States)

    Glawe, G. E.; Holanda, R.; Krause, L. N.

    1977-01-01

    Temperature measurement with small thermocouples is improved by device. Each wire is sheathed separately which increases the interelement insulation by factor of 2 1/2. Each wire in its separate sheath can be brought to junction by independent paths.

  10. Macroscopic motion of sheath-connected blobs in magnetic fields with arbitrary topology

    Science.gov (United States)

    Stepanenko, A. A.; Lee, W.; Krasheninnikov, S. I.

    2017-01-01

    In this study, macroscopic motion of sheath-connected blobs in magnetic fields, having arbitrary topology of the field lines and unfrozen in plasma, is analyzed within the electrostatic limit. Two distinct cases of magnetic configurations, with small and large curvature of the field lines, are considered and the criterion to discern them is deduced. For magnetic configurations with small curvature of the field lines, it is demonstrated that asymmetry of plasma distribution at the blob ends can drive macroscopic motion of a filament due to formation of unequal sheath potentials and establishing the effective Boltzmann potential. For a specific case of magnetic fields with small curvature of the field lines and identical metrics at the sheaths, we show that macroscopic motion of a plasma filament is determined by an effective electrostatic potential, which remains constant in time. For magnetic configurations with large curvature of the field lines, it is shown that motion of sufficiently large blobs is governed by integral distribution of plasma and magnetic field parameters along the field lines leading to blob adjusting its shape and position to the lead of the magnetic field lines in the course of its motion, whereas propagation of small and medium sized blobs can be represented as mutually independent motion of filament transverse cross-sections across the magnetic field lines. The qualitative conclusions on regularities of filament motion are supplied with numerical simulations of blob dynamics in two cases of tokamak-like magnetic fields with sheared and non-sheared field lines.

  11. Injection inside the paraneural sheath of the sciatic nerve

    DEFF Research Database (Denmark)

    Andersen, Henning Lykke; Andersen, Sofie L; Tranum-Jensen, Jørgen

    2012-01-01

    There exists little anatomic knowledge regarding the structure and sonographic features of the sheath enveloping the sciatic nerve in the popliteal fossa. We investigated the spread of an injection inside the sheath to (1) determine whether the sheath is a structure distinct from the nerve or part...

  12. Negative plasma potential relative to electron-emitting surfaces.

    Science.gov (United States)

    Campanell, M D

    2013-09-01

    Most works on plasma-wall interaction predict that with strong electron emission, a nonmonotonic "space-charge-limited" (SCL) sheath forms where the plasma potential is positive relative to the wall. We show that a fundamentally different sheath structure is possible where the potential monotonically increases toward a positively charged wall that is shielded by a single layer of negative charge. No ion-accelerating presheath exists in the plasma and the ion wall flux is zero. An analytical solution of the "inverse sheath" regime is demonstrated for a general plasma-wall system where the plasma electrons and emitted electrons are Maxwellian with different temperatures. Implications of the inverse sheath effect are that (a) the plasma potential is negative, (b) ion sputtering vanishes, (c) no charge is lost at the wall, and (d) the electron energy flux is thermal. To test empirically what type of sheath structure forms under strong emission, a full plasma bounded by strongly emitting walls is simulated. It is found that inverse sheaths form at the walls and ions are confined in the plasma. This result differs from past particle-in-cell simulation studies of emission which contain an artificial "source sheath" that accelerates ions to the wall, leading to a SCL sheath at high emission intensity.

  13. Spatial proximity effects on the excitation of sheath RF voltages by evanescent slow waves in the ion cyclotron range of frequencies

    Science.gov (United States)

    Colas, Laurent; Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan; Hillairet, Julien; Helou, Walid; Goniche, Marc; Heuraux, Stéphane; Faudot, Eric

    2017-02-01

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the near RF parallel electric field E ∥ emitted by ion cyclotron (IC) wave launchers. We use a simple model of slow wave (SW) evanescence coupled with direct current (DC) plasma biasing via sheath boundary conditions in a 3D parallelepiped filled with homogeneous cold magnetized plasma. Within a ‘wide-sheath’ asymptotic regime, valid for large-amplitude near RF fields, the RF part of this simple RF  +  DC model becomes linear: the sheath oscillating voltage V RF at open field line boundaries can be re-expressed as a linear combination of individual contributions by every emitting point in the input field map. SW evanescence makes individual contributions all the larger as the wave emission point is located closer to the sheath walls. The decay of |V RF| with the emission point/sheath poloidal distance involves the transverse SW evanescence length and the radial protrusion depth of lateral boundaries. The decay of |V RF| with the emitter/sheath parallel distance is quantified as a function of the parallel SW evanescence length and the parallel connection length of open magnetic field lines. For realistic geometries and target SOL plasmas, poloidal decay occurs over a few centimeters. Typical parallel decay lengths for |V RF| are found to be smaller than IC antenna parallel extension. Oscillating sheath voltages at IC antenna side limiters are therefore mainly sensitive to E ∥ emission by active or passive conducting elements near these limiters, as suggested by recent experimental observations. Parallel proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel antisymmetry of the radiated field map. They could finally justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  14. Space charge saturated sheath regime and electron temperature saturation in Hall thrusters

    Science.gov (United States)

    Raitses, Y.; Staack, D.; Smirnov, A.; Fisch, N. J.

    2005-07-01

    Existing electron-wall interaction models predict that secondary electron emission in Hall thrusters is significant and that the near-wall sheaths are space charge saturated. The experimental electron-wall collision frequency is computed using plasma parameters measured in a laboratory Hall thruster. In spite of qualitative similarities between the measured and predicted dependencies of the maximum electron temperature on the discharge voltage, the deduced electron-wall collision frequency for high discharge voltages is much lower than the theoretical value obtained for space charge saturated sheath regime, but larger than the wall recombination frequency. The observed electron temperature saturation appears to be directly associated with a decrease of the Joule heating rather than with the enhancement of the electron energy loss at the walls due to a strong secondary electron emission. Another interesting experimental result is related to the near-field plasma plume, where electron energy balance appears to be independent on the magnetic field.

  15. Science and Paranormal Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Noyes, H. Pierre

    1999-06-03

    In order to ground my approach to the study of paranormal phenomena, I first explain my operational approach to physics, and to the ''historical'' sciences of cosmic, biological, human, social and political evolution. I then indicate why I believe that ''paranormal phenomena'' might-but need not- fit into this framework. I endorse the need for a new theoretical framework for the investigation of this field presented by Etter and Shoup at this meeting. I close with a short discussion of Ted Bastin's contention that paranormal phenomena should be defined as contradicting physics.

  16. Nonlinear surface electromagnetic phenomena

    CERN Document Server

    Ponath, H-E

    1991-01-01

    In recent years the physics of electromagnetic surface phenomena has developed rapidly, evolving into technologies for communications and industry, such as fiber and integrated optics. The variety of phenomena based on electromagnetism at surfaces is rich and this book was written with the aim of summarizing the available knowledge in selected areas of the field. The book contains reviews written by solid state and optical physicists on the nonlinear interaction of electromagnetic waves at and with surfaces and films. Both the physical phenomena and some potential applications are

  17. Science and Paranormal Phenomena

    CERN Document Server

    Noyes, H P

    1999-01-01

    In order to ground my approach to the study of paranormal phenomena, I first explain my operational approach to physics, and to the ``historical'' sciences of cosmic, biological, human, social and political evolution. I then indicate why I believe that ``paranormal phenomena'' might --- but need not --- fit into this framework. I endorse the need for a new theoretical framework for the investigation of this field presented by Etter and Shoup at this meeting. I close with a short discussion of Ted Bastin's contention that paranormal phenomena should be {\\it defined} as contradicting physics.

  18. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  19. Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data

    Science.gov (United States)

    Fisher, L. E.; Lynch, K. A.; Fernandes, P. A.; Bekkeng, T. A.; Moen, J.; Zettergren, M.; Miceli, R. J.; Powell, S.; Lessard, M. R.; Horak, P.

    2016-04-01

    The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry.

  20. Measurements of plasma density fluctuations and electric wave fields using spherical electrostatic probes

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, A.I.; Bostroem, R.

    1995-04-01

    Spherical electrostatic probes are in wide use for the measurements of electric fields and plasma density. This report concentrates on the measurements of fluctuations of these quantities rather than background values. Potential problems with the technique include the influence of density fluctuations on electric field measurements and vice versa, effects of varying satellite potential, and non-linear rectification in the probe and satellite sheaths. To study the actual importance of these and other possible effects, we simulate the response of the probe-satellite system to various wave phenomena in the plasma by applying approximate analytical as well as numerical methods. We use a set of non-linear probe equations, based on probe characteristics experimentally obtained in space, and therefore essentially independent of any specific probe theory. This approach is very useful since the probe theory for magnetized plasmas is incomplete. 47 refs.

  1. High Temperature Phenomena in Shock Waves

    CERN Document Server

    2012-01-01

    The high temperatures generated in gases by shock waves give rise to physical and chemical phenomena such as molecular vibrational excitation, dissociation, ionization, chemical reactions and inherently related radiation. In continuum regime, these processes start from the wave front, so that generally the gaseous media behind shock waves may be in a thermodynamic and chemical non-equilibrium state. This book presents the state of knowledge of these phenomena. Thus, the thermodynamic properties of high temperature gases, including the plasma state are described, as well as the kinetics of the various chemical phenomena cited above. Numerous results of measurement and computation of vibrational relaxation times, dissociation and reaction rate constants are given, and various ionization and radiative mechanisms and processes are presented. The coupling between these different phenomena is taken into account as well as their interaction with the flow-field. Particular points such as the case of rarefied flows an...

  2. Complex fission phenomena

    CERN Document Server

    Poenaru, D N; Greiner, W

    2005-01-01

    Complex fission phenomena can be studied in a unified way. Very general reflection asymmetrical equilibrium (saddle-point) nuclear shapes, may be obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in cold fission phenomena can be explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined. Predictions of two alpha accompanied fission are experimentally confirmed.

  3. On the biogenesis of the myelin sheath: cognate polarized trafficking pathways in oligodendrocytes.

    Science.gov (United States)

    de Vries, H; Hoekstra, D

    2000-01-01

    Oligodendrocytes, the myelinating cells of the central nervous system, are capable of transporting vast quantities of proteins and of lipids, in particular galactosphingolipids, to the myelin sheath. The sheath is continuous with the plasma membrane of the oligodendrocyte, but the composition of both membrane domains differs substantially. Given its high glycosphingolipid and cholesterol content the myelin sheath bears similarity to the lipid composition of the apical domain of a polarized cell. The question thus arises whether myelin components, like typical apical membrane proteins are transported by an apical-like trafficking mechanism to the sheath, involving a 'raft'-mediated mechanism. Indeed, the evidence indicates the presence of cognate apical and basolateral pathways in oligodendrocytes. However, all major myelin proteins do not participate in this pathway, and remarkably apical-like trafficking seems to be restricted to the oligodendrocyte cell body. In this review, we summarize the evidence on the existence of different trafficking pathways in the oligodendrocyte, and discuss possible mechanisms separating the oligodendrocyte's membrane domains.

  4. Structure Formation in Complex Plasma - Quantum Effects in Cryogenic Complex Plasmas

    Science.gov (United States)

    2014-09-26

    Plasma Physics , Magneto-optical imaging , Space Plasma Physics , Multiscale Phenomena 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT... plasma is rich research field to understand basic physics of various phenomena through the observation of dust particles by naked eyes with the help of...TERMS Plasma Physics , Magneto-optical imaging , Space Plasma Physics , Multiscale Phenomena 16. SECURITY CLASSIFICATION OF: 17.

  5. Continuum-kinetic approach to sheath simulations

    Science.gov (United States)

    Cagas, Petr; Hakim, Ammar; Srinivasan, Bhuvana

    2016-10-01

    Simulations of sheaths are performed using a novel continuum-kinetic model with collisions including ionization/recombination. A discontinuous Galerkin method is used to directly solve the Boltzmann-Poisson system to obtain a particle distribution function. Direct discretization of the distribution function has advantages of being noise-free compared to particle-in-cell methods. The distribution function, which is available at each node of the configuration space, can be readily used to calculate the collision integrals in order to get ionization and recombination operators. Analytical models are used to obtain the cross-sections as a function of energy. Results will be presented incorporating surface physics with a classical sheath in Hall thruster-relevant geometry. This work was sponsored by the Air Force Office of Scientific Research under Grant Number FA9550-15-1-0193.

  6. Transport phenomena in a plasma quasilinear theory

    Directory of Open Access Journals (Sweden)

    Enos D'Ambrogio

    1991-05-01

    Full Text Available Making use of a recently developed quasi-linear formulation of 1D Vlasov equation, we derive the balance relations for the space-averaged distribution function and spectral power density. The validity-range in the short-time behaviour as well as in the time asymptotic limit is discussed. The formalism is perturbative but non-markovian in character, as it formally generalizes, and in the appropriate limit reproduces, Pocobelli's kinetic theory.

  7. Ion exchange phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Bourg, I.C.; Sposito, G.

    2011-05-01

    Ion exchange phenomena involve the population of readily exchangeable ions, the subset of adsorbed solutes that balance the intrinsic surface charge and can be readily replaced by major background electrolyte ions (Sposito, 2008). These phenomena have occupied a central place in soil chemistry research since Way (1850) first showed that potassium uptake by soils resulted in the release of an equal quantity of moles of charge of calcium and magnesium. Ion exchange phenomena are now routinely modeled in studies of soil formation (White et al., 2005), soil reclamation (Kopittke et al., 2006), soil fertilitization (Agbenin and Yakubu, 2006), colloidal dispersion/flocculation (Charlet and Tournassat, 2005), the mechanics of argillaceous media (Gajo and Loret, 2007), aquitard pore water chemistry (Tournassat et al., 2008), and groundwater (Timms and Hendry, 2007; McNab et al., 2009) and contaminant hydrology (Chatterjee et al., 2008; van Oploo et al., 2008; Serrano et al., 2009).

  8. What can we learn about HiPIMS process from the multidimensional plasma modeling?

    Science.gov (United States)

    Minea, Tiberiu

    2016-09-01

    The modeling of PVD process and especially magnetron plasma is widely reported. The novel way to excite the plasma applying to the cathode very high power pulses brings the temporal dimension to the system together with new phenomena. From the kinetic model of the dense plasma region, so called Ionization Region - IR, one can quantify the global behavior of the plasma parameters during the pulse. The most significant are the plasma composition, especially in the case of reactive gases, the fraction of back-attracted sputtered ions, the rarefaction due to wind effect, but also the discharge heating mechanisms and contribution to the discharge current. From the 2D particle modeling of the plasma new insights are revealed concerning the shape of the dense plasma region, the time evolution of the sheath, the electron energy distribution function, but also the characteristics of the diffusion plasma facing the substrate. Adding the third dimension to the model, the results reveal the complex transport of electrons especially in the azimuthal direction (instabilities and drifts), the formation of spokes and flares, and the strong relation between the secondary emission of electrons from the target and the plasma structuring. Warm thanks to Peter Awakowicz and Ante Hecimovic for inviting me to this GEC edition.

  9. Optic Nerve Sheath Mechanics in VIIP Syndrome

    Science.gov (United States)

    Raykin, Julia; Forte, Taylor E.; Wang, Roy; Feola, Andrew; Samuels, Brian; Myers, Jerry; Nelson, Emily; Gleason, Rudy; Ethier, C. Ross

    2016-01-01

    Visual Impairment Intracranial Pressure (VIIP) syndrome is a major concern in current space medicine research. While the exact pathology of VIIP is not yet known, it is hypothesized that the microgravity-induced cephalad fluid shift increases intracranial pressure (ICP) and drives remodeling of the optic nerve sheath. To investigate this possibility, we are culturing optic nerve sheath dura mater samples under different pressures and investigating changes in tissue composition. To interpret results from this work, it is essential to first understand the biomechanical response of the optic nerve sheath dura mater to loading. Here, we investigated the effects of mechanical loading on the porcine optic nerve sheath.Porcine optic nerves (number: 6) were obtained immediately after death from a local abattoir. The optic nerve sheath (dura mater) was isolated from the optic nerve proper, leaving a hollow cylinder of connective tissue that was used for biomechanical characterization. We developed a custom mechanical testing system that allowed for unconfined lengthening, twisting, and circumferential distension of the dura mater during inflation and under fixed axial loading. To determine the effects of variations in ICP, the sample was inflated (0-60 millimeters Hg) and circumferential distension was simultaneously recorded. These tests were performed under variable axial loads (0.6 grams - 5.6 grams at increments of 1 gram) by attaching different weights to one end of the dura mater. Results and Conclusions: The samples demonstrated nonlinear behavior, similar to other soft connective tissue (Figure 1). Large increases in diameter were observed at lower transmural pressures (approximately 0 to 5 millimeters Hg), whereas only small diameter changes were observed at higher pressures. Particularly interesting was the existence of a cross-over point at a pressure of approximately 11 millimeters Hg. At this pressure, the same diameter is obtained for all axial loads applied

  10. Plasma waves

    CERN Document Server

    Swanson, DG

    1989-01-01

    Plasma Waves discusses the basic development and equations for the many aspects of plasma waves. The book is organized into two major parts, examining both linear and nonlinear plasma waves in the eight chapters it encompasses. After briefly discussing the properties and applications of plasma wave, the book goes on examining the wave types in a cold, magnetized plasma and the general forms of the dispersion relation that characterize the waves and label the various types of solutions. Chapters 3 and 4 analyze the acoustic phenomena through the fluid model of plasma and the kinetic effects. Th

  11. Plasma astrophysics

    CERN Document Server

    Kaplan, S A; ter Haar, D

    2013-01-01

    Plasma Astrophysics is a translation from the Russian language; the topics discussed are based on lectures given by V.N. Tsytovich at several universities. The book describes the physics of the various phenomena and their mathematical formulation connected with plasma astrophysics. This book also explains the theory of the interaction of fast particles plasma, their radiation activities, as well as the plasma behavior when exposed to a very strong magnetic field. The text describes the nature of collective plasma processes and of plasma turbulence. One author explains the method of elementary

  12. Rheological phenomena in focus

    CERN Document Server

    Boger, DV

    1993-01-01

    More than possibly any other scientific discipline, rheology is easily visualized and the relevant literature contains many excellent photographs of unusual and often bizarre phenomena. The present book brings together these photographs for the first time. They are supported by a full explanatory text. Rheological Phenomena in Focus will be an indispensable support manual to all those who teach rheology or have to convince colleagues of the practical relevance of the subject within an industrial setting. For those who teach fluid mechanics, the book clearly illustrates the difference be

  13. Wave phenomena in sunspots

    Science.gov (United States)

    Löhner-Böttcher, Johannes

    2016-03-01

    Context: The dynamic atmosphere of the Sun exhibits a wealth of magnetohydrodynamic (MHD) waves. In the presence of strong magnetic fields, most spectacular and powerful waves evolve in the sunspot atmosphere. Allover the sunspot area, continuously propagating waves generate strong oscillations in spectral intensity and velocity. The most prominent and fascinating phenomena are the 'umbral flashes' and 'running penumbral waves' as seen in the sunspot chromosphere. Their nature and relation have been under intense discussion in the last decades. Aims: Waves are suggested to propagate upward along the magnetic field lines of sunspots. An observational study is performed to prove or disprove the field-guided nature and coupling of the prevalent umbral and penumbral waves. Comprehensive spectroscopic observations at high resolution shall provide new insights into the wave characteristics and distribution across the sunspot atmosphere. Methods: Two prime sunspot observations were carried out with the Dunn Solar Telescope at the National Solar Observatory in New Mexico and with the Vacuum Tower Telescope at the Teide Observatory on Tenerife. The two-dimensional spectroscopic observations were performed with the interferometric spectrometers IBIS and TESOS. Multiple spectral lines are scanned co-temporally to sample the dynamics at the photospheric and chromospheric layers. The time series (1 - 2.5 h) taken at high spatial and temporal resolution are analyzed according to their evolution in spectral intensities and Doppler velocities. A wavelet analysis was used to obtain the wave power and dominating wave periods. A reconstruction of the magnetic field inclination based on sunspot oscillations was developed. Results and conclusions: Sunspot oscillations occur continuously in spectral intensity and velocity. The obtained wave characteristics of umbral flashes and running penumbral waves strongly support the scenario of slow-mode magnetoacoustic wave propagation along the

  14. Arcing phenomena in fusion devices workshop

    Energy Technology Data Exchange (ETDEWEB)

    Clausing, R.E.

    1979-01-01

    The workshop on arcing phenomena in fusion devices was organized (1) to review the pesent status of our understanding of arcing as it relates to confinement devices, (2) to determine what informaion is needed to suppress arcing and (3) to define both laboratory and in-situ experiments which can ultimately lead to reduction of impurities in the plasma caused by arcing. The workshop was attended by experts in the area of vacuum arc electrode phenomena and ion source technology, materials scientists, and both theoreticians and experimentalists engaged in assessing the importance of unipolar arcing in today's tokamaks. Abstracts for papers presented at the workshop are included.

  15. Bioelectrochemistry II membrane phenomena

    CERN Document Server

    Blank, M

    1987-01-01

    This book contains the lectures of the second course devoted to bioelectro­ chemistry, held within the framework of the International School of Biophysics. In this course another very large field of bioelectrochemistry, i. e. the field of Membrane Phenomena, was considered, which itself consists of several different, but yet related subfields. Here again, it can be easily stated that it is impossible to give a complete and detailed picture of all membrane phenomena of biological interest in a short course of about one and half week. Therefore the same philosophy, as the one of the first course, was followed, to select a series of lectures at postgraduate level, giving a synthesis of several membrane phenomena chosen among the most'important ones. These lectures should show the large variety of membrane-regulated events occurring in living bodies, and serve as sound interdisciplinary basis to start a special­ ized study of biological phenomena, for which the investigation using the dual approach, physico-che...

  16. Currents between tethered electrodes in a magnetized laboratory plasma

    Science.gov (United States)

    Stenzel, R. L.; Urrutia, J. M.

    1989-01-01

    Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

  17. Steerable sheath technology in the ablation of atrial fibrillation.

    Science.gov (United States)

    Joseph, Jubin; Wong, Kelvin C K; Ginks, Matthew R; Bashir, Yaver; Betts, Timothy R; Rajappan, Kim

    2013-12-01

    Steerable sheaths have been shown to reduce procedure time in the catheter ablation of atrial fibrillation (AF), where catheter positioning and stability is typically challenging. This review critically addresses and highlights the recent developments in design of sheaths used to manipulate the ablation catheter and how these developments may impact on the ablation procedure itself, in particular the likelihood of first-time success. Patents relating to steerable sheaths are reviewed and discussed to gauge potential future developments in this area.

  18. The double sheath on cathodes of discharges burning in cathode vapour

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M S; Benilova, L G [Departamento de Fisica, Universidade da Madeira, Largo do MunicIpio, 9000 Funchal (Portugal)

    2010-09-01

    The model of a collisionless near-cathode space-charge sheath with ionization of atoms emitted by the cathode surface is considered. Numerical calculations showed that the mathematical problem is solvable and its solution is unique. In the framework of this model, the sheath represents a double layer with a potential maximum, with the ions which are produced before the maximum returning to the cathode surface and those produced after the maximum escaping into the plasma. Numerical results are given in a form to be readily applicable in analysis of discharges burning in cathode vapour, such as vacuum arcs. In particular, the results indicate that the ion backflow coefficient in such discharges exceeds 0.5, in agreement with values extracted from the experiment.

  19. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    Science.gov (United States)

    Sydorenko, Dmytro; Kaganovich, Igor D.; Ventzek, Peter L. G.

    2016-10-01

    Electrons emitted from electrodes are accelerated by the sheath electric field and become the electron beams penetrating the plasma. The electron beam can interact with the plasma in collisionless manner via two-stream instability and produce suprathermal electrons. In order to understand the mechanism of suprathermal electrons acceleration, a beam-plasma system was simulated using a 1D3V particle-in-cell code EDIPIC. These simulation results show that the acceleration may be caused by the effects related to the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The short waves near the anode accelerate plasma bulk electrons to suprathermal energies. Rich complexity of beam- plasma interaction phenomena was also observed: intermittency and multiple regimes of two-stream instability in a dc discharge, band structure of the growth rate of the two-stream instability of an electron beam propagating in a bounded plasma, multi-stage acceleration of electrons in a finite system.

  20. Shock wave reflection phenomena

    CERN Document Server

    Ben-dor, Gabi

    2007-01-01

    This book provides a comprehensive state-of-the-knowledge description of the shock wave reflection phenomena from a phenomenological point of view. The first part is a thorough introduction to oblique shock wave reflections, presenting the two major well-known reflection wave configurations, namely, regular (RR) and Mach (MR) reflections, the corresponding two- and three-shock theories, their analytical and graphical solution and the proposed transition boundaries between these two reflection-wave configurations. The second, third and fourth parts describe the reflection phenomena in steady, pseudo-steady and unsteady flows, respectively. Here, the possible specific types of reflection wave configurations are described, criteria for their formation and termination are presented and their governing equations are solved analytically and graphically and compared with experimental results. The resolution of the well-known von Neumann paradox and a detailed description of two new reflection-wave configurations - t...

  1. Fundamentals of Fire Phenomena

    DEFF Research Database (Denmark)

    Quintiere, James

    discipline. It covers thermo chemistry including mixtures and chemical reactions; Introduces combustion to the fire protection student; Discusses premixed flames and spontaneous ignition; Presents conservation laws for control volumes, including the effects of fire; Describes the theoretical bases...... analyses. Fire phenomena encompass everything about the scientific principles behind fire behaviour. Combining the principles of chemistry, physics, heat and mass transfer, and fluid dynamics necessary to understand the fundamentals of fire phenomena, this book integrates the subject into a clear...... for empirical aspects of the subject of fire; Analyses ignition of liquids and the importance of evaporation including heat and mass transfer; Features the stages of fire in compartments, and the role of scale modelling in fire. The book is written by Prof. James G. Quintiere from University of Maryland...

  2. Fundamentals of Fire Phenomena

    DEFF Research Database (Denmark)

    Quintiere, James

    Understanding fire dynamics and combustion is essential in fire safety engineering and in fire science curricula. Engineers and students involved in fire protection, safety and investigation need to know and predict how fire behaves to be able to implement adequate safety measures and hazard...... analyses. Fire phenomena encompass everything about the scientific principles behind fire behaviour. Combining the principles of chemistry, physics, heat and mass transfer, and fluid dynamics necessary to understand the fundamentals of fire phenomena, this book integrates the subject into a clear...... discipline. It covers thermo chemistry including mixtures and chemical reactions; Introduces combustion to the fire protection student; Discusses premixed flames and spontaneous ignition; Presents conservation laws for control volumes, including the effects of fire; Describes the theoretical bases...

  3. Complex fission phenomena

    Science.gov (United States)

    Poenaru, D. N.; Gherghescu, R. A.; Greiner, W.

    2005-01-01

    Complex fission phenomena are studied in a unified way. Very general reflection asymmetrical equilibrium (saddle point) nuclear shapes are obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in binary cold fission of Th and U isotopes is explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined.

  4. Transport phenomena II essentials

    CERN Document Server

    REA, The Editors of

    2012-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Transport Phenomena II covers forced convention, temperature distribution, free convection, diffusitivity and the mechanism of mass transfer, convective mass transfer, concentration

  5. Membrane Transport Phenomena (MTP)

    Science.gov (United States)

    Mason, Larry W.

    1997-01-01

    The third semi-annual period of the MTP project has been involved with performing experiments using the Membrane Transport Apparatus (MTA), development of analysis techniques for the experiment results, analytical modeling of the osmotic transport phenomena, and completion of a DC-9 microgravity flight to test candidate fluid cell geometries. Preparations were also made for the MTP Science Concept Review (SCR), held on 13 June 1997 at Lockheed Martin Astronautics in Denver. These activities are detailed in the report.

  6. Paramutation phenomena in plants.

    Science.gov (United States)

    Pilu, Roberto

    2015-08-01

    Paramutation is a particular epigenetic phenomenon discovered in Zea mays by Alexander Brink in the 1950s, and then also found in other plants and animals. Brink coined the term paramutation (from the Greek syllable "para" meaning beside, near, beyond, aside) in 1958, with the aim to differentiate paramutation from mutation. The peculiarity of paramutation with respect to other gene silencing phenomena consists in the ability of the silenced allele (named paramutagenic) to silence the other allele (paramutable) present in trans. The newly silenced (paramutated) allele remains stable in the next generations even after segregation from the paramutagenic allele and acquires paramutagenic ability itself. The inheritance behaviour of these epialleles permits a fast diffusion of a particular gene expression level/phenotype in a population even in the absence of other evolutionary influences, thus breaking the Hardy-Weinberg law. As with other gene silencing phenomena such as quelling in the fungus Neurospora crassa, transvection in Drosophila, co-suppression and virus-induced gene silencing (VIGS) described in transgenic plants and RNA interference (RNAi) in the nematode Caenorhabditis elegans, paramutation occurs without changes in the DNA sequence. So far the molecular basis of paramutation remains not fully understood, although many studies point to the involvement of RNA causing changes in DNA methylation and chromatin structure of the silenced genes. In this review I summarize all paramutation phenomena described in plants, focusing on the similarities and differences between them.

  7. Prediction of etching-shape anomaly due to distortion of ion sheath around a large-scale three-dimensional structure by means of on-wafer monitoring technique and computer simulation

    Science.gov (United States)

    Kubota, Tomohiro; Ohtake, Hiroto; Araki, Ryosuke; Yanagisawa, Yuuki; Iwasaki, Takuya; Ono, Kohei; Miwa, Kazuhiro; Samukawa, Seiji

    2013-10-01

    A system for predicting distortion of a profile during plasma etching was developed. The system consists of a combination of measurement and simulation. An ‘on-wafer sheath-shape sensor’ for measuring the plasma-sheath parameters (sheath potential and thickness) on the stage of the plasma etcher was developed. The sensor has numerous small electrodes for measuring sheath potential and saturation ion-current density, from which sheath thickness can be calculated. The results of the measurement show reasonable dependence on source power, bias power and pressure. Based on self-consistent calculation of potential distribution and ion- and electron-density distributions, simulation of the sheath potential distribution around an arbitrary 3D structure and the trajectory of incident ions from the plasma to the structure was developed. To confirm the validity of the distortion prediction by comparing it with experimentally measured distortion, silicon trench etching under chlorine inductively coupled plasma (ICP) was performed using a sample with a vertical step. It was found that the etched trench was distorted when the distance from the step was several millimetres or less. The distortion angle was about 20° at maximum. Measurement was performed using the on-wafer sheath-shape sensor in the same plasma condition as the etching. The ion incident angle, calculated as a function of distance from the step, successfully reproduced the experimentally measured angle, indicating that the combination of measurement by the on-wafer sheath-shape sensor and simulation can predict distortion of an etched structure. This prediction system will be useful for designing devices with large-scale 3D structures (such as those in MEMS) and determining the optimum etching conditions to obtain the desired profiles.

  8. Anomalous Light Phenomena vs. Bioelectric Brain Activity

    Science.gov (United States)

    Teodorani, M.; Nobili, G.

    We present a research proposal concerning the instrumented investigation of anomalous light phenomena that are apparently correlated with particular mind states, such as prayer, meditation or psi. Previous research by these authors demonstrate that such light phenomena can be monitored and measured quite efficiently in areas of the world where they are reported in a recurrent way. Instruments such as optical equipment for photography and spectroscopy, VLF spectrometers, magnetometers, radar and IR viewers were deployed and used massively in several areas of the world. Results allowed us to develop physical models concerning the structural and time-variable behaviour of light phenomena, and their kinematics. Recent insights and witnesses have suggested to us that a sort of "synchronous connection" seems to exist between plasma-like phenomena and particular mind states of experiencers who seem to trigger a light manifestation which is very similar to the one previously investigated. The main goal of these authors is now aimed at the search for a concrete "entanglement-like effect" between the experiencer's mind and the light phenomena, in such a way that both aspects are intended to be monitored and measured simultaneously using appropriate instrumentation. The goal of this research project is twofold: a) to verify quantitatively the existence of one very particular kind of mind-matter interaction and to study in real time its physical and biophysical manifestations; b) to repeat the same kind of experiment using the same test-subject in different locations and under various conditions of geomagnetic activity.

  9. Arrangement of burner without pump with subsequent sheath tube

    Energy Technology Data Exchange (ETDEWEB)

    Graat, J.W.; Remie, H.T.; Verhagen, A.M.

    1980-10-02

    The burner described in main patent 2828319 is operated with fluid pulverised fuel and air. The additional patent concerns a sheath tube, which surrounds the combustion chamber and conducts the hot gases on. Flow guide elements, e.g. a cylindrical guide sleeve, are installed in the sheath tube to improve the guidance of the thermal flow.

  10. Electrospinning jet behaviors under the constraints of a sheath gas

    Directory of Open Access Journals (Sweden)

    Yang Zhao

    2016-11-01

    Full Text Available Increasing the ejection efficiency and uniformity of nanofibers is the key to applications of electrospinning technology. In this work, a novel electrospinning spinneret with a sheath gas passageway is designed. The frictional resistance that stems from the sheath gas provides additional stretching and restriction forces on the jet. The sheath gas also reduces interference and enhances the stability of the charged jet. A bead-on-strain simulation model is built up to determine the constraint effects of the sheath gas. Simulation results show that the sheath gas decreases the motion area and increases the stretching ratio of the liquid jet. The stretching force from the sheath gas decreases the diameter and increases the uniformity of the nanofiber. As the gas pressure increases from 0 kPa to 50 kPa, the critical voltage of the jet ejection decreases from 8.4 kV to 2.5 kV, the diameter of the nanofiber deposition zone decreases from 40 cm to 10 cm, and the diameter of the nanofibers decreases from 557.97 nm to 277.73 nm. The uniformity of nanofibers can be improved significantly using a sheath gas. The sheath gas contributes to the rapid deposition of a uniform nanofibrous membrane and the industrial applications of electrospinning.

  11. Retrospective analysis of oral peripheral nerve sheath tumors in Brazilians

    Directory of Open Access Journals (Sweden)

    Juliana Tito Salla

    2009-03-01

    Full Text Available Traumatic neuroma, neurofibroma, neurilemmoma, palisaded encapsulated neuroma and malignant peripheral nerve sheath tumor (MPNST are peripheral nerve sheath tumors and present neural origin. The goal of this study was to describe the epidemiological data of oral peripheral nerve sheath tumors in a sample of the Brazilian population. Biopsies requested from the Oral Pathology Service, School of Dentistry, Federal University of Minas Gerais (MG, Brazil, between 1966 and 2006 were evaluated. Lesions diagnosed as peripheral nerve sheath tumors were submitted to morphologic and to immunohistochemical analyses. All cases were immunopositive to the S-100 protein. Thirty-five oral peripheral nerve sheath tumors were found, representing 0.16% of all lesions archived in the Oral Pathology Service. Traumatic neuroma (15 cases most frequently affected the mental foramen. Solitary neurofibroma (10 cases was more frequently observed in the palate. Neurofibroma associated with neurofibromatosis type I (2 cases was observed in the gingival and alveolar mucosa. Neurilemmoma (4 cases was more commonly observed in the buccal mucosa. Malignant peripheral nerve sheath tumors (3 cases occurred in the mandible, palate, and tongue. Palisaded encapsulated neuroma (1 case occurred in the buccal mucosa. The data confirmed that oral peripheral nerve sheath tumors are uncommon in the oral region, with some lesions presenting a predilection for a specific gender or site. This study may be useful in clinical dentistry and oral pathology practice and may be used as baseline data regarding oral peripheral nerve sheath tumors in other populations.

  12. A rare case of malignant peripheral nerve sheath tumour

    Directory of Open Access Journals (Sweden)

    Anita Harry, Nirankumar Samuel, Vigil TD

    2014-04-01

    Full Text Available Malignant Peripheral Nerve Sheath Tumours are tumours of ectomesenchymal origin often originating from major nerves or their nerve sheaths, they are commonly found in patients with neurofibromatosis-1 though sporadic cases have been reported. We report a rare sporadic case of MPNST in a 20 year old patient arising from the spinal accessory nerve.

  13. Electrohydrodynamic direct-writing orderly pattern with sheath gas focusing

    Science.gov (United States)

    Zheng, Jianyi; Zhang, Kai; Jiang, Jiaxin; He, Guangqi; Xu, Lei; Liu, Yifang; Liu, Juan; Wu, Dezhi; Zheng, Gaofeng

    2016-11-01

    Laminar sheath gas is introduced to increase the stability of Electrohydrodynamic Direct-Writing (EDW). The external stretching force from sheath gas promotes the ejection threshold, the diameter of jet and printed fibers as well. The critical voltage decreases with the increase of sheath gas pressure. The stretching force from sheath gas decreases the diameter of printed fiber as well as that of charged jet. As sheath gas pressure increases from 0 to 25 kPa, the average diameter of micro/nano structure reduces from 4.46 μ m to 845.25 nm. The laminar field flow of sheath gas shelters the charged jet free from the surrounding interferences, and helps charged jet to move in a straight line. With the help of sheath gas, the stability of charged jet can be improved to direct-write precise complex micro-pattern. The position precision of direct-written pattern is less than 5 μ m . As a novel method, EDW with laminar sheath gas would promote the deposition precision of printed micro/nano structure and its application.

  14. Electrospinning jet behaviors under the constraints of a sheath gas

    Science.gov (United States)

    Zhao, Yang; Jiang, Jiaxin; Li, Wenwang; Wang, Xiang; Zhang, Kai; Zhu, Ping; Zheng, Gaofeng

    2016-11-01

    Increasing the ejection efficiency and uniformity of nanofibers is the key to applications of electrospinning technology. In this work, a novel electrospinning spinneret with a sheath gas passageway is designed. The frictional resistance that stems from the sheath gas provides additional stretching and restriction forces on the jet. The sheath gas also reduces interference and enhances the stability of the charged jet. A bead-on-strain simulation model is built up to determine the constraint effects of the sheath gas. Simulation results show that the sheath gas decreases the motion area and increases the stretching ratio of the liquid jet. The stretching force from the sheath gas decreases the diameter and increases the uniformity of the nanofiber. As the gas pressure increases from 0 kPa to 50 kPa, the critical voltage of the jet ejection decreases from 8.4 kV to 2.5 kV, the diameter of the nanofiber deposition zone decreases from 40 cm to 10 cm, and the diameter of the nanofibers decreases from 557.97 nm to 277.73 nm. The uniformity of nanofibers can be improved significantly using a sheath gas. The sheath gas contributes to the rapid deposition of a uniform nanofibrous membrane and the industrial applications of electrospinning.

  15. Electrohydrodynamic direct-writing orderly pattern with sheath gas focusing

    Directory of Open Access Journals (Sweden)

    Jianyi Zheng

    2016-11-01

    Full Text Available Laminar sheath gas is introduced to increase the stability of Electrohydrodynamic Direct-Writing (EDW. The external stretching force from sheath gas promotes the ejection threshold, the diameter of jet and printed fibers as well. The critical voltage decreases with the increase of sheath gas pressure. The stretching force from sheath gas decreases the diameter of printed fiber as well as that of charged jet. As sheath gas pressure increases from 0 to 25 kPa, the average diameter of micro/nano structure reduces from 4.46μm to 845.25 nm. The laminar field flow of sheath gas shelters the charged jet free from the surrounding interferences, and helps charged jet to move in a straight line. With the help of sheath gas, the stability of charged jet can be improved to direct-write precise complex micro-pattern. The position precision of direct-written pattern is less than 5μm. As a novel method, EDW with laminar sheath gas would promote the deposition precision of printed micro/nano structure and its application.

  16. Tendon sheath fibroma of the medial canthal tendon.

    Science.gov (United States)

    Andrew, Nicholas; Dodd, Tom; Selva, Dinesh; Davis, Garry

    2013-01-01

    Fibromas of the tendon sheath are slow-growing, benign tumors most commonly found on the hands and wrist. A fibroma of the tendon sheath arising from the medial canthal tendon presented as an enlarging nodule that had been present for 40 years. The fibroma was identified by microscopy and immunohistochemistry, and surgical resection appears to have been curative.

  17. Introduction to plasma dynamics

    CERN Document Server

    Morozov, A I

    2013-01-01

    As the twenty-first century progresses, plasma technology will play an increasing role in our lives, providing new sources of energy, ion-plasma processing of materials, wave electromagnetic radiation sources, space plasma thrusters, and more. Studies of the plasma state of matter not only accelerate technological developments but also improve the understanding of natural phenomena. Beginning with an introduction to the characteristics and types of plasmas, Introduction to Plasma Dynamics covers the basic models of classical diffuse plasmas used to describe such phenomena as linear and shock w

  18. Gas insulated transmission line having low inductance intercalated sheath

    Science.gov (United States)

    Cookson, Alan H.

    1978-01-01

    A gas insulated transmission line including an outer sheath, an inner conductor disposed within the outer sheath, and an insulating gas between the inner conductor and the outer sheath. The outer sheath comprises an insulating tube having first and second ends, and having interior and exterior surfaces. A first electrically conducting foil is secured to the interior surface of the insulating tube, is spirally wound from one tube end to the second tube end, and has a plurality of overlapping turns. A second electrically conducting foil is secured to the exterior surface of the insulating tube, and is spirally wound in the opposite direction from the first electrically conducting foil. By winding the foils in opposite directions, the inductances within the intercalated sheath will cancel each other out.

  19. Double spinal dural sheath: a cadaveric case report

    Directory of Open Access Journals (Sweden)

    Loughenbury P

    2010-03-01

    Full Text Available A previously unreported variation in the anatomy of the spinal dural sheath was observed during routine cadaveric dissection, consisting of a duplication of the dural layer, with layers adherent throughout their length. The double dural sheath completely enveloped the spinal cord and nerve roots, and extended from C2 to L5: both layers were of similar thickness to a single dural sheath. Duplication of the dura mater in the form of two complete dural sheaths has not been previously observed and/or reported in a cadaveric study. However, areas of localised duplication of the ventral aspect of the dural sheath have been observed during intra-operative dissection, particularly in association with idiopathic herniation of the spinal cord. Complete duplication of the spinal dura mater is of clinical interest in spinal surgery, particularly in relation to idiopathic spinal cord herniation.

  20. Solid state phenomena

    CERN Document Server

    Lawrance, R

    1972-01-01

    Solid State Phenomena explores the fundamentals of the structure and their influence on the properties of solids. This book is composed of five chapters that focus on the electrical and thermal conductivities of crystalline solids. Chapter 1 describes the nature of solids, particularly metals and crystalline materials. This chapter also presents a model to evaluate crystal structure, the forces between atom pairs, and the mechanism of plastic and elastic deformation. Chapter 2 demonstrates random vibrations of atoms in a solid using a one-dimensional array, while Chapter 3 examines the resista

  1. Transport phenomena I essentials

    CERN Document Server

    REA, The Editors of

    2012-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Transport Phenomena I includes viscosity, flow of Newtonian fluids, velocity distribution in laminar flow, velocity distributions with more than one independent variable, thermal con

  2. Birefringence phenomena revisited

    CERN Document Server

    Pereira, Dante D; Gonçalves, Bruno

    2016-01-01

    The propagation of electromagnetic waves is investigated in the context of the isotropic and nonlinear dielectric media at rest in the eikonal limit of the geometrical optics. Taking into account the functional dependence $\\varepsilon=\\varepsilon(E,B)$ and $\\mu=\\mu(E,B)$ for the dielectric coefficients, a set of phenomena related to the birefringence of the electromagnetic waves induced by external fields are derived and discussed. Our results contemplate the known cases already reported in the literature: Kerr, Cotton-Mouton, Jones and magnetoelectric effects. Moreover, new effects are presented here as well as the perspectives of its experimental confirmations.

  3. Onset of normal and inverse homoclinic bifurcation in a double plasma system near a plasma fireball

    Energy Technology Data Exchange (ETDEWEB)

    Mitra, Vramori; Sarma, Bornali; Sarma, Arun [VIT University Chennai Campus, Vandalur-Kelambakkam Road, Chennai-600127, Tamil Nadu (India); Janaki, M. S.; Sekar Iyengar, A. N. [Plasma Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)

    2016-03-15

    Plasma fireballs are generated due to a localized discharge and appear as a luminous glow with a sharp boundary, which suggests the presence of a localized electric field such as electrical sheath or double layer structure. The present work reports the observation of normal and inverse homoclinic bifurcation phenomena in plasma oscillations that are excited in the presence of fireball in a double plasma device. The controlling parameters for these observations are the ratio of target to source chamber (n{sub T}/n{sub S}) densities and applied electrode voltage. Homoclinic bifurcation is noticed in the plasma potential fluctuations as the system evolves from narrow to long time period oscillations and vice versa with the change of control parameter. The dynamical transition in plasma fireball is demonstrated by spectral analysis, recurrence quantification analysis (RQA), and statistical measures, viz., skewness and kurtosis. The increasing trend of normalized variance reflects that enhancing n{sub T}/n{sub S} induces irregularity in plasma dynamics. The exponential growth of the time period is strongly indicative of homoclinic bifurcation in the system. The gradual decrease of skewness and increase of kurtosis with the increase of n{sub T}/n{sub S} also reflect growing complexity in the system. The visual change of recurrence plot and gradual enhancement of RQA variables DET, L{sub max}, and ENT reflects the bifurcation behavior in the dynamics. The combination of RQA and spectral analysis is a clear evidence that homoclinic bifurcation occurs due to the presence of plasma fireball with different density ratios. However, inverse bifurcation takes place due to the change of fireball voltage. Some of the features observed in the experiment are consistent with a model that describes the dynamics of ionization instabilities.

  4. Onset of normal and inverse homoclinic bifurcation in a double plasma system near a plasma fireball

    Science.gov (United States)

    Mitra, Vramori; Sarma, Bornali; Sarma, Arun; Janaki, M. S.; Sekar Iyengar, A. N.

    2016-03-01

    Plasma fireballs are generated due to a localized discharge and appear as a luminous glow with a sharp boundary, which suggests the presence of a localized electric field such as electrical sheath or double layer structure. The present work reports the observation of normal and inverse homoclinic bifurcation phenomena in plasma oscillations that are excited in the presence of fireball in a double plasma device. The controlling parameters for these observations are the ratio of target to source chamber (nT/nS) densities and applied electrode voltage. Homoclinic bifurcation is noticed in the plasma potential fluctuations as the system evolves from narrow to long time period oscillations and vice versa with the change of control parameter. The dynamical transition in plasma fireball is demonstrated by spectral analysis, recurrence quantification analysis (RQA), and statistical measures, viz., skewness and kurtosis. The increasing trend of normalized variance reflects that enhancing nT/nS induces irregularity in plasma dynamics. The exponential growth of the time period is strongly indicative of homoclinic bifurcation in the system. The gradual decrease of skewness and increase of kurtosis with the increase of nT/nS also reflect growing complexity in the system. The visual change of recurrence plot and gradual enhancement of RQA variables DET, Lmax, and ENT reflects the bifurcation behavior in the dynamics. The combination of RQA and spectral analysis is a clear evidence that homoclinic bifurcation occurs due to the presence of plasma fireball with different density ratios. However, inverse bifurcation takes place due to the change of fireball voltage. Some of the features observed in the experiment are consistent with a model that describes the dynamics of ionization instabilities.

  5. Linear electromagnetic excitation of an asymmetric low pressure capacitive discharge with unequal sheath widths

    Energy Technology Data Exchange (ETDEWEB)

    Lieberman, M. A., E-mail: lieber@eecs.berkeley.edu; Lichtenberg, A. J.; Kawamura, E. [Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720-1770 (United States); Chabert, P. [Laboratoire de Physique des Plasmas, CNRS, Ecole Polytechnique, UPMC, Paris XI, Observatoire de Paris, 91128 Palaiseau (France)

    2016-01-15

    It is well-known that standing waves having radially center-high radio frequency (rf) voltage profiles exist in high frequency capacitive discharges. In this work, we determine the symmetric and antisymmetric radially propagating waves in a cylindrical capacitive discharge that is asymmetrically driven at the lower electrode by an rf voltage source. The discharge is modeled as a uniform bulk plasma which at lower frequencies has a thicker sheath at the smaller area powered electrode and a thinner sheath at the larger area grounded electrode. These are self-consistently determined at a specified density using the Child law to calculate sheath widths and the electron power balance to calculate the rf voltage. The fields and the system resonant frequencies are determined. The center-to-edge voltage ratio on the powered electrode is calculated versus frequency, and central highs are found near the resonances. The results are compared with simulations in a similar geometry using a two-dimensional hybrid fluid-analytical code, giving mainly a reasonable agreement. The analytic model may be useful for finding good operating frequencies for a given discharge geometry and power.

  6. Plasma density enhancement in atmospheric-pressure dielectric-barrier discharges by high-voltage nanosecond pulse in the pulse-on period: a PIC simulation

    Science.gov (United States)

    Sang, Chaofeng; Sun, Jizhong; Wang, Dezhen

    2010-02-01

    A particle-in-cell (PIC) plus Monte Carlo collision simulation is employed to investigate how a sustainable atmospheric pressure single dielectric-barrier discharge responds to a high-voltage nanosecond pulse (HVNP) further applied to the metal electrode. The results show that the HVNP can significantly increase the plasma density in the pulse-on period. The ion-induced secondary electrons can give rise to avalanche ionization in the positive sheath, which widens the discharge region and enhances the plasma density drastically. However, the plasma density stops increasing as the applied pulse lasts over certain time; therefore, lengthening the pulse duration alone cannot improve the discharge efficiency further. Physical reasons for these phenomena are then discussed.

  7. MULTISCALE PHENOMENA IN MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    A. BISHOP

    2000-09-01

    This project developed and supported a technology base in nonequilibrium phenomena underpinning fundamental issues in condensed matter and materials science, and applied this technology to selected problems. In this way the increasingly sophisticated synthesis and characterization available for classes of complex electronic and structural materials provided a testbed for nonlinear science, while nonlinear and nonequilibrium techniques helped advance our understanding of the scientific principles underlying the control of material microstructure, their evolution, fundamental to macroscopic functionalities. The project focused on overlapping areas of emerging thrusts and programs in the Los Alamos materials community for which nonlinear and nonequilibrium approaches will have decisive roles and where productive teamwork among elements of modeling, simulations, synthesis, characterization and applications could be anticipated--particularly multiscale and nonequilibrium phenomena, and complex matter in and between fields of soft, hard and biomimetic materials. Principal topics were: (i) Complex organic and inorganic electronic materials, including hard, soft and biomimetic materials, self-assembly processes and photophysics; (ii) Microstructure and evolution in multiscale and hierarchical materials, including dynamic fracture and friction, dislocation and large-scale deformation, metastability, and inhomogeneity; and (iii) Equilibrium and nonequilibrium phases and phase transformations, emphasizing competing interactions, frustration, landscapes, glassy and stochastic dynamics, and energy focusing.

  8. Malignant peripheral nerve sheath tumour of penis.

    Science.gov (United States)

    Kaur, J; Madan, R; Singh, L; Sharma, D N; Julka, P K; Rath, G K; Roy, S

    2015-04-01

    Malignant peripheral nerve sheath tumour (MPNST) is a rare variety of soft tissue sarcoma that originates from Schwann cells or pluripotent cells of neural crest origin. They have historically been difficult tumours to diagnose and treat. Surgery is the mainstay of treatment with a goal to achieve negative margins. Despite aggressive surgery and adjuvant therapy, the prognosis of patients with MPNST remains poor. MPNST arising from penis is a very rare entity; thus, it presents a diagnostic and therapeutic challenge. We present a case of penile MPNST in a 38-year-old man in the absence of neurofibromatosis treated with surgery followed by post-operative radiotherapy to a dose of 60 Gray in 30 fractions and adjuvant chemotherapy with ifosfamide and adriamycin.

  9. Plasma Physics An Introduction to Laboratory, Space, and Fusion Plasmas

    CERN Document Server

    Piel, Alexander

    2010-01-01

    Plasma Physics gives a comprehensive introduction to the basic processes in plasmas and demonstrates that the same fundamental concepts describe cold gas-discharge plasmas, space plasmas, and hot fusion plasmas. Starting from particle drifts in magnetic fields, the principles of magnetic confinement fusion are explained and compared with laser fusion. Collective processes are discussed in terms of plasma waves and instabilities. The concepts of plasma description by magnetohydrodynamics, kinetic theory, and particle simulation are stepwise introduced. Space charge effects in sheath regions, double layers and plasma diodes are given the necessary attention. The new fundamental mechanisms of dusty plasmas are explored and integrated into the framework of conventional plasmas. The book concludes with a brief introduction to plasma discharges. Written by an internationally renowned researcher in experimental plasma physics, the text keeps the mathematical apparatus simple and emphasizes the underlying concepts. T...

  10. Workshop on Interface Phenomena

    CERN Document Server

    Kreuzer, Hans

    1987-01-01

    This book contains the proceedings of the first Workshop on Interface Phenomena, organized jointly by the surface science groups at Dalhousie University and the University of Maine. It was our intention to concentrate on just three topics related to the kinetics of interface reactions which, in our opinion, were frequently obscured unnecessarily in the literature and whose fundamental nature warranted an extensive discussion to help clarify the issues, very much in the spirit of the Discussions of the Faraday Society. Each session (day) saw two principal speakers expounding the different views; the session chairmen were asked to summarize the ensuing discussions. To understand the complexity of interface reactions, paradigms must be formulated to provide a framework for the interpretation of experimen­ tal data and for the construction of theoretical models. Phenomenological approaches have been based on a small number of rate equations for the concentrations or mole numbers of the various species involved i...

  11. Some aspects of geomagnetically conjugate phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Rycroft, M.J.

    1987-12-01

    Both charged particles and waves convey information about the thermosphere, ionosphere and magnetosphere from the Northern to the Southern Hemisphere and vice versa, along geomagnetic flux tubes.The interhemispheric travel time of electrons or ions, being dependent upon L-value , pitch angle and energy (which may lie between less than or equal to 1 eV and greater than or equal to 1 MeV) may be many hours, ranging down to less than or equal to 1 s. However, the one-hop propagation time for magnetohydrodynamic or whistler mode waves generally lies between 10/sup 2/s and 1 s. Such times, therefore, give the time scales of transient phenomena that are geomagnetically conjugate and of changes in steady-state plasma processes occurring in geomagnetically conjugate regions. Contrasting examples are presented of conjugate physical phenomena, obtained using satellite, rocket, aircraft and ground-based observations; the latter capitalise upon the rather rare disposition of land - rather than ocean - at each end of a geophysically interesting flux tube. Particular attention is paid to the interactions between whistler mode waves and energetic electrons. Geomagnetic, radio, optical and plasma observations, taken together with model computations, provide a wealth of knowledge on conjugate phenomena and their dependence on conditions in the solar wind, substorms, L-value, etc... Finally, some suggestions are made for future lines of research.

  12. Supported plasma-made 1D heterostructures: perspectives and applications

    Energy Technology Data Exchange (ETDEWEB)

    Borras, Ana; Macias-Montero, Manuel; Romero-Gomez, Pablo; Gonzalez-Elipe, Agustin R, E-mail: anaisabel.borras@icmse.csic.es [Materials Science Institute of Seville (CSIC-Universidad Sevilla), C/Americo Vespucio 49 41092, Sevilla (Spain)

    2011-05-04

    Plasma-related methods have been widely used in the fabrication of carbon nanotubes and nanofibres (NFs) and semiconducting inorganic nanowires (NWs). A natural progression of the research in the field of 1D nanostructures is the synthesis of multicomponent NWs and NFs. In this paper we review the state of the art of the fabrication by plasma methods of 1D heterostructures including applications and perspectives. Furthermore, recent developments on the use of metal seeds (Ag, Au, Pt) to obtain metal-oxide nanostructures are also extensively described. Results are shown for various metal substrates, either metal foils or supported nanoparticles/thin films of the metal where the effects of the size, surface coverage, percolation degree and thickness of the metal seeds have been systematically evaluated. The possibilities of the process are illustrated by the preparation of nanostructured films and supported NFs of different metal-oxides (Ag, Au and SiO{sub 2}, TiO{sub 2}, ZnO). Particularly, in the case of silver, the application of an oxygen plasma treatment prior to the deposition of the oxide was critical for efficiently controlling the growth of the 1D heterostructures. A phenomenological model is proposed to account for the thin-film nanostructuring and fibre formation by considering basic phenomena such as stress relaxation, inhomogeneities in the plasma sheath electrical field and the local disturbance of the oxide growth.

  13. On the interpretation of Langmuir probe data inside a spacecraft sheath

    Energy Technology Data Exchange (ETDEWEB)

    Olson, J.; Brenning, N. [Space and Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, SE-10044 Stockholm (Sweden); Wahlund, J.-E. [Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala (Sweden); Gunell, H. [Belgian Institute for Space Aeronomy, Avenue Circulaire 3, B-1180 Brussels (Belgium)

    2010-10-15

    If a Langmuir probe is located inside the sheath of a negatively charged spacecraft, there is a risk that the probe characteristic is modified compared to that of a free probe in the ambient plasma. We have studied this probe-in-spacecraft-sheath problem in the parameter range of a small Langmuir probe (with radius r{sub LP}<<{lambda}{sub D}) using a modified version of the orbit motion limited (OML) probe theory. We find that the ambient electron contribution I{sub e}(U{sub LP}) to the probe characteristic is suitably analyzed in terms of three regions of applied probe potential U{sub LP}. In region I, where the probe is negatively charged (i.e., U{sub LP}sheath at the probe position), the probe characteristic I{sub e}(U{sub LP}) is close to that of OML theory for a free probe in the ambient plasma. In the probe potential range U{sub LP}>U{sub 1}, there is first a transition region II in applied potential, U{sub 1}plasma. This minimum gives the depth U{sub pl}-U{sub M} of a potential barrier that prevents the lowest energy ambient electrons from reaching the probe. For a high enough positive probe potential, in region III, the barrier becomes small. Here, I{sub e}(U{sub LP}) again approaches OML theory for a free probe. The boundary U{sub 2} between regions II and III is somewhat arbitrary; we propose a condition on the barrier, U{sub pl}-U{sub M}<plasma parameters from measured I(U{sub LP}) as the probe characteristic is likely to depart from usual OML in crucial respects: (1) the ambient plasma potential U{sub pl} falls into the transition

  14. Plasma physics an introduction to laboratory, space, and fusion plasmas

    CERN Document Server

    Piel, Alexander

    2017-01-01

    The enlarged new edition of this textbook provides a comprehensive introduction to the basic processes in plasmas and demonstrates that the same fundamental concepts describe cold gas-discharge plasmas, space plasmas, and hot fusion plasmas. Starting from particle drifts in magnetic fields, the principles of magnetic confinement fusion are explained and compared with laser fusion. Collective processes are discussed in terms of plasma waves and instabilities. The concepts of plasma description by magnetohydrodynamics, kinetic theory, and particle simulation are stepwise introduced. Space charge effects in sheath regions, double layers and plasma diodes are given the necessary attention. The novel fundamental mechanisms of dusty plasmas are explored and integrated into the framework of conventional plasmas. The book concludes with a concise description of modern plasma discharges. Written by an internationally renowned researcher in experimental plasma physics, the text keeps the mathematical apparatus simple a...

  15. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    Energy Technology Data Exchange (ETDEWEB)

    Grin, A. [Building Science Corporation, Somerville, MA (United States); Lstiburek, J. [Building Science Corporation, Somerville, MA (United States)

    2014-09-01

    The goal of this research is to provide durable and long-term water management solutions using exterior insulating sheathing as part of the water management system. It is possible to tape or seal the joints in insulating sheathing to create a drainage plane and even an air control layer. There exists the material durability component of the tape as well as the system durability component being the taped insulating sheathing as the drainage plane. This measure guideline provides best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant issues were discussed with the group, which are required to make taped insulating sheathing a simple, long-term, and durable drainage plane: horizontal joints should be limited or eliminated wherever possible; where a horizontal joint exists use superior materials; and frequent installation inspection and regular trade training are required to maintain proper installation.

  16. Flexor Tendon Sheath Engineering Using Decellularized Porcine Pericardium.

    Science.gov (United States)

    Megerle, Kai; Woon, Colin; Kraus, Armin; Raghavan, Shyam; Pham, Hung; Chang, James

    2016-10-01

    The flexor tendon sheath is an ideal target for tissue engineering because it is difficult to reconstruct by conventional surgical methods. The authors hypothesized that decellularized porcine pericardium can be used as a scaffold for engineering a biologically active tendon sheath. The authors' protocol removed cellular material from the pericardium and preserved the structural architecture in addition to the collagen and glycosaminoglycan content. The scaffold was successfully reseeded with human sheath synoviocytes and human adipose-derived stem cells. Cells were evaluated for 8 weeks after reseeding. The reseeded construct demonstrated continuous production of hyaluronic acid, the main component of synovial fluid. After being seeded on the membrane, adipose-derived stem cells demonstrated down-regulation of collagen I and III and up-regulation of hyaluronan synthase 2. The results indicate that decellularized porcine pericardium may be a potential scaffold for engineering a biologically active human tendon sheath.

  17. Malignant Peripheral Nerve Sheath Tumour of the Maxilla

    Directory of Open Access Journals (Sweden)

    Puja Sahai

    2014-01-01

    Full Text Available A 38-year-old man was diagnosed with malignant peripheral nerve sheath tumour of the maxilla. He was treated with total maxillectomy. Histopathological examination of the resected specimen revealed a close resection margin. The tumour was of high grade with an MIB-1 labelling index of almost 60%. At six weeks following the surgery, he developed local tumour relapse. The patient succumbed to the disease at five months from the time of diagnosis. The present report underlines the locally aggressive nature of malignant peripheral nerve sheath tumour of the maxilla which necessitates an early therapeutic intervention. A complete resection with clear margins is the most important prognostic factor for malignant peripheral nerve sheath tumour in the head and neck region. Adjuvant radiotherapy may be considered to improve the local control. Future research may demarcate the role of targeted therapy for patients with malignant peripheral nerve sheath tumour.

  18. A comparative study of sheath potential profile measurements with laser-heated and current-heated emissive probes

    Science.gov (United States)

    Kella, Vara Prasad; Mehta, Payal; Sarma, A.; Ghosh, J.; Chattopadhyay, P. K.

    2016-04-01

    Emissive Langmuir probe is one of the most efficient diagnostic tools available for plasma potential measurements. Extensive studies have been carried out in designing different kinds of conventional (electrically heated) emissive probes (CEPs) to estimate the plasma potential. Laser heated emissive probe (LHEP) has been developed with certain advantages over the conventional probes such as low evaporation rate of the probe material, high lifetime, and high emission levels. Most importantly, the LHEP uses laser to heat the probe-tip and does not require electric current to heat the probe-tip like in CEP. The heating current in CEP substantially affects the plasma potential measurements, especially in the regions of plasma where high electric and magnetic field gradients are present. In this paper, we studied the plasma potential structures in sheath-presheath region using both LHEP and CEP in an unmagnetized dc-filament discharge plasma. Measurements of sheath spatial potential profile using laser heated emissive probe are compared with those obtained using conventional emissive probe.

  19. An unusual radiological presentation of optic nerve sheath meningiom

    Directory of Open Access Journals (Sweden)

    Chameen Samarawickrama

    2016-04-01

    Full Text Available Our report describes an unusual radiological presentation of optic nerve sheath meningioma. The classic radiological appearance of optic nerve thickening with enhancement and calcification within the tumor was not seen; instead, an elongating gadolinium enhancing band-like area adjacent to the superomedial aspect of the left optic nerve sheath was identified. The diagnosis was confirmed on histopathology. Our report adds to the spectrum of presentations of this relatively common clinical entity.

  20. Use of an introducer sheath for colonic stent placement

    Energy Technology Data Exchange (ETDEWEB)

    De Gregorio, Miguel A.; Mainar, Antonio; Alfonso, Eduardo; Gimeno, Maria Jose [Department of Interventional Radiology, University Hospital of Zaragoza, C/ San Juan Bosco, 15, 50009 Zaragoza (Spain); Tejero, Eloy [Department of Surgery, University Hospital of Zaragoza, C/ San Juan Bosco, 15, 50009 Zaragoza (Spain); Herrera, Marcos [Department of Radiology, Hennepin County Medical Center, Minneapolis, MN 55408 (United States)

    2002-09-01

    We describe a technical modification of Wallstent implantation for the treatment of malignant rectosigmoid and descending colonic obstructions. The modification is the routine placement of an introducer sheath via the rectum before stent implantation in order to straighten the rectosigmoid region. This device facilitates catheter and guide wire manipulations and obtaining specimen biopsies for histopathological studies. The introducer sheath has been used without complications in 21 consecutive patients. (orig.)

  1. Giant Cell Tumor of Tendon Sheath

    Directory of Open Access Journals (Sweden)

    Jan Paul Briët

    2015-01-01

    Full Text Available Background:  Giant cell tumor of tendon sheath (GCTTS is often thought of as a volar finger mass. We hypothesized that GCTTS are equally common on the dorsal and volar aspects of the hand. In addition, we hypothesized that there are no factors associated with the location (volar versus dorsal and largest measured dimension of a GCTTS.  Methods:  A total of 126 patients with a pathological diagnosis of a GCTTS of the hand or finger were reviewed. Basic emographic and GCTTS specific information was obtained. Bivariable analyses were used to assess predicting factors for location (volar or dorsal side and largest measured diameter of a GCTTS.  Results:  Seventy-two tumors (57% were on the volar side of the hand, 47 (37% were dorsal, 6 (4.8% were both dorsal and volar, and one was midaxial (0.79%. The most common site of a GCTTS was the index finger (30%. There were no factors significantly associated with the location (volar or dorsal, n=119 of the GCTTS. There were also no factors significantly associated with a larger diameter of a GCTTS.  Conclusions:  A GCTTS was more frequently seen on the volar aspect of the hand. No significant factors associated with the location or an increased size of a GCTTS were found in this study.

  2. Solitary fibrous tumor surrounding the carotid sheath.

    Science.gov (United States)

    Gómez-Oliveira, Guillermo; Alvarez-Flores, Modesto; Arribas-García, Ignacio; Martínez-Gimeno, Carlos

    2010-03-01

    Solitary fibrous tumors (SFTs) are rare spindle cell neoplasms that are mostly found arising from the pleura. Although SFTs recently have been reported in other regions, they are rare in the head and neck and have often been misdiagnosed due to their rarity. SFTs are benign in most cases. Clinically, SFTs usually manifest as well-circumscribed, slow-growing, smooth and painless masses. Symptoms are often minimal, although they may include sore throat, difficulty in swallowing, change of voice or trismus. CT-Scan and MRI are the most sensitive imaging procedures used. The treatment of choice is complete surgical excision of the lesion. Because recurrences have been noted up to 30 years after surgery, long-term follow up is mandatory. In this article, we present a case of a Solitary Fibrous Tumor arising in the parapharyngeal space in a 20-year-old man, involving the carotid sheath, treated by surgical excision with no recurrence after 1 year. The clinical presentation, surgical management and pathological findings are described.

  3. Miniature sheathed thermocouples for turbine blade temperature measurement

    Science.gov (United States)

    Holanda, R.; Glawe, G. E.; Krause, L. N.

    1974-01-01

    An investigation was made of sheathed thermocouples for turbine blade temperature measurements. Tests were performed on the Chromel-Alumel sheathed thermocouples with both two-wire and single-wire configurations. Sheath diameters ranged from 0.25 to 0.76 mm, and temperatures ranged from 1080 to 1250 K. Both steady-state and thermal cycling tests were performed for times up to 450 hr. Special-order and commercial-grade thermocouples were tested. The tests showed that special-order single-wire sheathed thermocouples can be obtained that are reliable and accurate with diameters as small as 0.25 mm. However, all samples of 0.25-mm-diameter sheathed commercial-grade two-wire and single-wire thermocouples that were tested showed unacceptable drift rates for long-duration engine testing programs. The drift rates were about 1 percent in 10 hr. A thermocouple drift test is recommended in addition to the normal acceptance tests in order to select reliable miniature sheathed thermocouples for turbine blade applications.

  4. The Sheath Transport Observer for the Redistribution of Mass (STORM) Image

    Science.gov (United States)

    Kuntz, Kip; Collier, Michael; Sibeck, David G.; Porter, F. Scott; Carter, J. A.; Cravens, Thomas; Omidi, N.; Robertson, Ina; Sembay, S.; Snowden, Steven L.

    2008-01-01

    All of the solar wind energy that powers magnetospheric processes passes through the magnetosheath and magnetopause. Global images of the magnetosheath and magnetopause boundary layers will resolve longstanding controversy surrounding fundamental phenomena that occur at the magnetopause and provide information needed to improve operational space weather models. Recent developments showing that soft X-rays (0.15-1 keV) result from high charge state solar wind ions undergoing charge exchange recombination through collisions with exospheric neutral atoms has led to the realization that soft X-ray imaging can provide global maps of the high-density shocked solar wind within the magnetosheath and cusps, regions lying between the lower density solar wind and magnetosphere. We discuss an instrument concept called the Sheath Transport Observer for the Redistribution of Mass (STORM), an X-ray imager suitable for simultaneously imaging the dayside magnetosheath, the magnetopause boundary layers, and the cusps.

  5. The Sheath Transport Observer for the Redistribution of Mass (STORM) Imager

    Science.gov (United States)

    Collier, Michael R.; Sibeck, David G.; Porter, F. Scott; Burch, J.; Carter, J. A.; Cravens, Thomas; Kuntz, Kip; Omidi, N.; Read, A.; Robertson, Ina; hide

    2010-01-01

    All of the solar wind energy that powers magnetospheric processes passes through the magnetosheath and magnetopause. Global images of the magnetosheath and magnetopause boundary layers will resolve longstanding controversies surrounding fundamental phenomena that occur at the magnetopause and provide information needed to improve operational space weather models. Recent developments showing that soft X-rays (0.15-1 keV) result from high charge state solar wind ions undergoing charge exchange recombination through collisions with exospheric neutral atoms has led to the realization that soft X-ray imaging can provide global maps of the high-density shocked solar wind within the magnetosheath and cusps, regions lying between the lower density solar wind and magnetosphere. We discuss an instrument concept called the Sheath Transport Observer for the Redistribution of Mass (STORM), an X-ray imager suitable for simultaneously imaging the dayside magnetosheath, the magnetopause boundary layers, and the cusps.

  6. The Sheath Transport Observer for the Redistribution of Mass (STORM) Image

    Science.gov (United States)

    Kuntz, Kip; Collier, Michael; Sibeck, David G.; Porter, F. Scott; Carter, J. A.; Cravens, Thomas; Omidi, N.; Robertson, Ina; Sembay, S.; Snowden, Steven L.

    2008-01-01

    All of the solar wind energy that powers magnetospheric processes passes through the magnetosheath and magnetopause. Global images of the magnetosheath and magnetopause boundary layers will resolve longstanding controversy surrounding fundamental phenomena that occur at the magnetopause and provide information needed to improve operational space weather models. Recent developments showing that soft X-rays (0.15-1 keV) result from high charge state solar wind ions undergoing charge exchange recombination through collisions with exospheric neutral atoms has led to the realization that soft X-ray imaging can provide global maps of the high-density shocked solar wind within the magnetosheath and cusps, regions lying between the lower density solar wind and magnetosphere. We discuss an instrument concept called the Sheath Transport Observer for the Redistribution of Mass (STORM), an X-ray imager suitable for simultaneously imaging the dayside magnetosheath, the magnetopause boundary layers, and the cusps.

  7. On Plasma Theory and Simulation.

    Science.gov (United States)

    2014-09-26

    SHEATH REGION INCLUDING ION REFLECTION Lou Ann Schwager (Prof. C. K. Birdsall, Dr. I. Roth ) A low temperature plasma interacts with a collector plate...Hitchcock. Katz. Lankford. Nelson. Barnes. Borovsky. Forslund. Kwan. Sadowski Lindemuth. Mason . Mostrom. Nielson, Oliphant. Sgro. Thode Department of

  8. Particle-in-cell and Monte Carlo collision simulations of the cathode sheath in an atmospheric direct-current arc discharge

    Science.gov (United States)

    Zhou, Wen; Guo, Heng; Jiang, Wei; Li, He-Ping; Li, Zeng-Yao; Lapenta, Giovanni

    2016-10-01

    A sheath is the transition region from plasma to a solid surface, which also plays a critical role in determining the behaviors of many lab and industrial plasmas. However, the cathode sheath properties in arc discharges are not well understood yet due to its multi-scale and kinetic features. In this letter, we have adopted an implicit particle-in-cell Monte Carlo collision (PIC-MCC) method to study the cathode sheath in an atmospheric arc discharge plasma. The cathode sheath thickness, number densities and averaged energies of electrons and ions, the electric field distribution, as well as the spatially averaged electron energy probability function (EEPF), are predicted self-consistently by using this newly developed kinetic model. It is also shown that the thermionic emission at the hot cathode surface is the dominant electron emission process to sustain the arc discharges, while the effects from secondary and field electron emissions are negligible. The present results verify the previous conjectures and experimental observations.

  9. Collisionless plasmas in astrophysics

    CERN Document Server

    Belmont, Gerard; Mottez, Fabrice; Pantellini, Filippo; Pelletier, Guy

    2013-01-01

    Collisionless Plasmas in Astrophysics examines the unique properties of media without collisions in plasma physics. Experts in this field, the authors present the first book to concentrate on collisionless conditions in plasmas, whether close or not to thermal equilibrium. Filling a void in scientific literature, Collisionless Plasmas in Astrophysics explains the possibilities of modeling such plasmas, using a fluid or a kinetic framework. It also addresses common misconceptions that even professionals may possess, on phenomena such as "collisionless (Landau) damping". Abundant illustrations

  10. Application of Nonlocal Electron Kinetics to Plasma Technologies

    Science.gov (United States)

    Kaganovich, Igor D.

    2011-10-01

    Partially ionized plasmas are typically in a highly non-equilibrium thermodynamic state: the electrons are not in equilibrium with the neutral particle species or the ions, and the electrons are also not in equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function (EVDF) from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas-discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Significant progress in understanding the formation of non-Maxwellian EVDF in the self-consistent electric fields has been one of the major achievements in the low-temperature plasmas during the last decade. This progress was made possible by a synergy between full-scale particle-in-cell simulations, analytical models, and experiments. Specific examples include rf discharges, dc discharges with auxiliary electrodes, Hall thruster discharges. In each example, nonlocal kinetic effects are identified as the main mechanisms responsible for the surprising degree of discharge self-organization. These phenomena include: explosive generation of cold electrons with rf power increase in low-pressure rf discharges; abrupt changes in discharge structure with increased bias voltage on a third electrode in a dc discharge with hot cathode; absence of a steady-state regime in Hall thruster discharges with intense secondary electron emission due to coupling of the sheath properties and the EVDF. In collaboration with Y. Raitses, A.V. Khrabrov, M. Campanell, V. I. Demidov, D. Sydorenko, I. Schweigert, and A. S. Mustafaev. Research supported by the U.S. Department of Energy.

  11. Plasma diagnostics and plasma-surface interactions in inductively coupled plasmas

    Science.gov (United States)

    Titus, Monica Joy

    The semiconductor industry's continued trend of manufacturing device features on the nanometer scale requires increased plasma processing control and improved understanding of plasma characteristics and plasma-surface interactions. This dissertation presents a series of experimental results for focus studies conducted in an inductively coupled plasma (ICP) system. First novel "on-wafer" diagnostic tools are characterized and related to plasma characteristics. Second, plasma-polymer interactions are characterized as a function of plasma species and processing parameters. Complementary simulations accompany each focus study to supplement experimental findings. Wafer heating mechanisms in inductively coupled molecular gas plasmas are explored with PlasmaTemp(TM), a novel "on-wafer" diagnostic tool. Experimental wafer measurements are obtained with the PlasmaTemp(TM) wafer processed in argon (Ar) and argon-oxygen (Ar/O2) mixed plasmas. Wafer heating mechanisms were determined by combining the experimental measurements with a 3-dimensional heat transfer model of the wafer. Comparisons between pure Ar and Ar/O2 plasmas demonstrate that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. Thermal heat conduction from the neutral gas and O-atom recombination on wafer surface can contribute as much as 60% to wafer heating under conditions of low-energy ion bombardment in molecular plasmas. Measurements of a second novel "on-wafer" diagnostic sensor, the PlasmaVolt(TM), were tested and validated in the ICP system for Ar plasmas varying in power and pressure. Sensor measurements were interpreted with a numerical sheath simulation and comparison to scaling laws derived from the inhomogeneous sheath model. The study demonstrates sensor measurements are proportional to the RF-current through the sheath and the scaling is a function of sheath impedance. PlasmaVolt(TM) sensor measurements are proportional to the

  12. Electron Acceleration by Transient Ion Foreshock Phenomena

    Science.gov (United States)

    Wilson, L. B., III; Turner, D. L.

    2015-12-01

    Particle acceleration is a topic of considerable interest in space, laboratory, and astrophysical plasmas as it is a fundamental physical process to all areas of physics. Recent THEMIS [e.g., Turner et al., 2014] and Wind [e.g., Wilson et al., 2013] observations have found evidence for strong particle acceleration at macro- and meso-scale structures and/or pulsations called transient ion foreshock phenomena (TIFP). Ion acceleration has been extensively studied, but electron acceleration has received less attention. Electron acceleration can arise from fundamentally different processes than those affecting ions due to differences in their gyroradii. Electron acceleration is ubiquitous, occurring in the solar corona (e.g., solar flares), magnetic reconnection, at shocks, astrophysical plasmas, etc. We present new results analyzing the dependencies of electron acceleration on the properties of TIFP observed by the THEMIS spacecraft.

  13. Sorghum [Sorghum bicolor (L.) Moench] leaf sheath dye protects against cisplatin-induced hepatotoxicity and oxidative stress in rats.

    Science.gov (United States)

    Ademiluyi, Adedayo O; Oboh, Ganiyu; Agbebi, Oluwaseun J; Boligon, Aline A; Athayde, Margareth L

    2014-12-01

    This study sought to determine the protective effect of dietary inclusion of sorghum leaf sheath dye on cisplatin-induced hepatotoxicity and oxidative stress in rats. Adult male rats were randomly divided into four groups with six animals in each group. Groups I and II were fed a basal diet, while groups III and IV were fed diets containing 0.5% and 1% sorghum leaf sheath dye, respectively, for 20 days before cisplatin administration. Hepatotoxicity was induced by a single dose of cisplatin (7 mg/kg body weight, i.p.), and the experiment was terminated at 3 days after cisplatin injection. The liver and plasma were studied for hepatotoxicity and antioxidant capacity. Cisplatin caused a significant (Pinduced alteration of both plasma and liver antioxidant indices suggests an antioxidant mechanism of action. Hence, this protective effect of Sorghum bicolor leaf sheath dye against cisplatin-induced hepatotoxicity in rats reflects its potential and beneficial role in the prevention of liver damage associated with cisplatin administration.

  14. Optical and electrostatic potential investigations of electrical breakdown phenomena in a low-pressure gas discharge lamp

    Science.gov (United States)

    Gendre, M. F.; Haverlag, M.; Kroesen, G. M. W.

    2010-06-01

    The ignition phase is a critical stage in the operation of gas discharge lamps where the neutral gas enclosed between the electrodes undergoes a transformation from the dielectric state to a conducting phase, eventually enabling the production of light. The phenomena occurring during this phase transition are not fully understood and the related experimental studies are often limited to local optical measurements in environments prone to influencing these transient phenomena. In this work unipolar ignition phenomena at sub-kilovolt levels are investigated in a 3 Torr argon discharge tube. The lamp is placed in a highly controlled environment so as to prevent any bias on the measurements. A fast intensified CCD camera and a specially designed novel electrostatic probe are used simultaneously so as to provide a broad array of measured and computed parameters which are displayed in space-time diagrams for cross comparisons. Experiments show that three distinct phases exist during successful ignitions: upon the application of voltage a first ionization wave starts from the active electrode and propagates in the neutral gas towards the opposite electrode. A local front of high axial E field strength is associated with this process and causes a local ionization to occur, leading to the electrostatic charging of the lamp. Next, a second wave propagates from the ground electrode back towards the active electrode with a higher velocity, and in this process leads to a partial discharging of the lamp. This return stroke draws a homogeneous plasma column which eventually bridges both electrodes at the end of the wave propagation. At this point both electrode sheaths are formed and the common features of a glow discharge are observed. The third phase is an increase in the light intensity of the plasma column until the lamp reaches a steady-state operation. Failed ignitions present only the first phase where the first wave starts its propagation but extinguishes in the lamp

  15. The optic nerve sheath on MRI in acute optic neuritis

    Energy Technology Data Exchange (ETDEWEB)

    Hickman, S.J. [University College London, NMR Research Unit, Department of Neuroinflammation, Institute of Neurology, London (United Kingdom); Moorfields Eye Hospital, Department of Neuro-Ophthalmology, London (United Kingdom); Miszkiel, K.A. [National Hospital for Neurology and Neurosurgery, Lysholm Department of Neuroradiology, London (United Kingdom); Plant, G.T. [Moorfields Eye Hospital, Department of Neuro-Ophthalmology, London (United Kingdom); Miller, D.H. [University College London, NMR Research Unit, Department of Neuroinflammation, Institute of Neurology, London (United Kingdom)

    2005-01-01

    Optic nerve sheath dilatation or gadolinium-enhancement on magnetic resonance imaging in acute optic neuritis have been previously reported but have been thought to be rare occurrences. This study recruited 33 patients with acute unilateral optic neuritis. All had their optic nerves imaged with fat-saturated fast spin-echo (FSE) imaging, and 28 had imaging before and after triple-dose gadolinium-enhanced fat-saturated T{sub 1}-weighted imaging. Follow-up imaging was performed on 20 patients (15 following gadolinium). A dilated subarachnoid space at the anterior end of the symptomatic optic nerve on FSE imaging was seen in 15/33 cases. In three of these cases, dilatation was visible on short-term follow-up. Optic nerve sheath enhancement was seen in 21/28 cases acutely: seven at the anterior end of the lesion only, five at the posterior end only and nine at both ends. Optic sheath enhancement was seen in 13 patients on follow-up. This study suggests that optic nerve sheath dilatation on FSE images and optic nerve sheath enhancement on triple-dose gadolinium-enhanced images are common findings in acute optic neuritis. Optic nerve sheath dilatation may be due to inflammation of the optic nerve, with its associated swelling, interrupting the communication between the subarachnoid space of the diseased optic nerve and the chiasmal cistern. Optic nerve sheath enhancement suggests that meningeal inflammation occurs in optic neuritis, in agreement with pathological studies of both optic neuritis and multiple sclerosis. (orig.)

  16. An Uncommon Presentation of Spontaneous Rectus Sheath Hematoma with Acute Kidney Injury due to Obstructive Uropathy and Prerenal Azotemia

    Directory of Open Access Journals (Sweden)

    Eleni Paschou

    2014-01-01

    Full Text Available Rectus Sheath Hematoma (RSH represents an unusual entity which is characterized by acute abdominal pain and tender palpable abdominal mass usually, among elderly patients receiving anticoagulant therapy. We report the case of an 81-year-old woman admitted to our department due to acute abdominal pain and oligoanuria. The patient had recently been hospitalized due to acute myocardial infarction (AMI and atrial fibrillation (AF and received both anticoagulant and antiplatelet therapies. The radiological assessments revealed an extended Rectus Sheath Hematoma and bilateral hydronephrosis. Treatment of the hematoma required cessation of anticoagulants and antiplatelet agents, immobilization, blood and fresh frozen plasma transfusion, and administration of vasopressors. The patient recovered gradually and was discharged home fifteen (15 days later.

  17. On the usefulness of sheath folds as kinematic indicators

    Science.gov (United States)

    Reber, J. E.; Galland, O.; Dabrowski, M.; Schmid, D. W.; Cobbold, P. R.

    2012-04-01

    Sheath folds are cone-shaped structures that can be found in different rock types. They are mostly associated with shear zones. Even though they are three-dimensional structures they are most commonly recognized in nature in cross sections perpendicular to their stretching direction. These cross-sections exhibit so called eye-structures. The geometry of sheath folds has been used to deduce kinematic information such as strain, shear sense, and bulk strain type. However, how sheath folds form and how they evolve with increasing strain is still a matter of debate. We studied the development of sheath folds at the tip of a slip surface (weak inclusion) embedded in a layered matrix subjected to simple shear by means of analytical and experimental modeling. With this combined approach we tested the usefulness of sheath folds as indicators of strain, shear direction and bulk strain type. The analytical model is three-dimensional and based on an adapted external Eshelby solution. The slip surface is embedded in a homogeneous matrix, which is subjected to simple shear. Layers are introduced as passive markers for the visualization. With this method we tested the influence of the initial slip surface orientation (0°, 90°, or 135° with respect to the shear direction) and the number of layers on the evolving eye-structure. To study the effect of mechanical layering (viscosity contrast, layer thickness) on the geometry of the eye-structures we designed an experimental model using silicones as rock analogues. Although sheath folds are commonly considered as high strain markers, the analytical model shows that very little strain is needed to produce a sheath fold and the corresponding eye-pattern, and that the minimum strain is mainly dependent on the orientation of the slip surface and the number of layers. Our analytical as well as the experimental models revealed a sheath fold at both tips of the deformed slip surface. The two sheath folds show opposing closing direction

  18. An investigation of tendon sheathing filler migration into concrete

    Energy Technology Data Exchange (ETDEWEB)

    Naus, D.J.; Oland, C.B. [Oak Ridge National Lab., TN (United States)

    1998-03-01

    During some of the inspections at nuclear power plants with prestressed concrete containments, it was observed that the containments has experienced leakage of the tendon sheathing filler (i.e., streaks). The objective of this activity was to provide an indication of the extent of tendon sheathing filler leakage into the concrete and its affects on concrete properties. Literature was reviewed and concrete core samples were obtained from the Trojan Nuclear Plant and tested. The literature primarily addressed effects of crude or lubricating oils that are known to cause concrete damage. However, these materials have significantly different characteristics relative to the materials used as tendon sheathing fillers. Examination and testing of the concrete cores indicated that the appearance of tendon sheathing filler on the concrete surface was due to leakage from the conduits and its subsequent migration through cracks that were present. Migration of the tendon sheathing filler was confined to the cracks and there was no perceptible movement into the concrete. Results of compressive strength testing indicated that the concrete quality was consistent in the containment and that the strength had increased over 40% in 25.4 years relative to the average compressive strength at 28-days age.

  19. Structural Conservation of the Myoviridae Phage Tail Sheath Protein Fold

    Energy Technology Data Exchange (ETDEWEB)

    Aksyuk, Anastasia A.; Kurochkina, Lidia P.; Fokine, Andrei; Forouhar, Farhad; Mesyanzhinov, Vadim V.; Tong, Liang; Rossmann, Michael G. (SOIBC); (Purdue); (Columbia)

    2012-02-21

    Bacteriophage phiKZ is a giant phage that infects Pseudomonas aeruginosa, a human pathogen. The phiKZ virion consists of a 1450 {angstrom} diameter icosahedral head and a 2000 {angstrom}-long contractile tail. The structure of the whole virus was previously reported, showing that its tail organization in the extended state is similar to the well-studied Myovirus bacteriophage T4 tail. The crystal structure of a tail sheath protein fragment of phiKZ was determined to 2.4 {angstrom} resolution. Furthermore, crystal structures of two prophage tail sheath proteins were determined to 1.9 and 3.3 {angstrom} resolution. Despite low sequence identity between these proteins, all of these structures have a similar fold. The crystal structure of the phiKZ tail sheath protein has been fitted into cryo-electron-microscopy reconstructions of the extended tail sheath and of a polysheath. The structural rearrangement of the phiKZ tail sheath contraction was found to be similar to that of phage T4.

  20. Fibroma of tendon sheath with 11q rearrangements.

    Science.gov (United States)

    Nishio, Jun; Iwasaki, Hiroshi; Nagatomo, Masaya; Naito, Masatoshi

    2014-09-01

    Fibroma of tendon sheath is an uncommon, benign fibroblastic tumor that usually occurs in the upper extremities of young and middle-aged adults. A clonal chromosomal aberration, t(2;11)(q31-32;q12), has been described in one case. We herein present a unique cytogenetic finding of fibroma of tendon sheath arising in the first web space of the right hand of a 38-year-old woman. Physical examination showed a 3.5-cm, firm, mobile, non-tender mass. Magnetic resonance imaging showed a well-defined soft tissue mass with iso- to slightly-low signal intensity relative to skeletal muscle on both T1- and T2-weighted sequences. Contrast-enhanced T1-weighted sequences demonstrated moderate patchy enhancement of the mass. A fibroma or giant cell tumor of tendon sheath was suggested, and the lesion was marginally excised. Histological examination confirmed the diagnosis of fibroma of tendon sheath. Cytogenetic analysis revealed a novel t(9;11)(p24;q13-14) translocation among other karyotypic abnormalities. The postoperative course was uneventful, and the patient is doing well without local recurrence two months after surgery. To the best of our knowledge, this is only the second report of fibroma of tendon sheath with clonal chromosomal abnormalities.

  1. Ontogeny of the sheathing leaf base in maize (Zea mays).

    Science.gov (United States)

    Johnston, Robyn; Leiboff, Samuel; Scanlon, Michael J

    2015-01-01

    Leaves develop from the shoot apical meristem (SAM) via recruitment of leaf founder cells. Unlike eudicots, most monocot leaves display parallel venation and sheathing bases wherein the margins overlap the stem. Here we utilized computed tomography (CT) imaging, localization of PIN-FORMED1 (PIN1) auxin transport proteins, and in situ hybridization of leaf developmental transcripts to analyze the ontogeny of monocot leaf morphology in maize (Zea mays). CT imaging of whole-mounted shoot apices illustrates the plastochron-specific stages during initiation of the basal sheath margins from the tubular disc of insertion (DOI). PIN1 localizations identify basipetal auxin transport in the SAM L1 layer at the site of leaf initiation, a process that continues reiteratively during later recruitment of lateral leaf domains. Refinement of these auxin transport domains results in multiple, parallel provascular strands within the initiating primordium. By contrast, auxin is transported from the L2 toward the L1 at the developing margins of the leaf sheath. Transcripts involved in organ boundary formation and dorsiventral patterning accumulate within the DOI, preceding the outgrowth of the overlapping margins of the sheathing leaf base. We suggest a model wherein sheathing bases and parallel veins are both patterned via the extended recruitment of lateral maize leaf domains from the SAM.

  2. Account of near-cathode sheath in numerical models of high-pressure arc discharges

    Science.gov (United States)

    Benilov, M. S.; Almeida, N. A.; Baeva, M.; Cunha, M. D.; Benilova, L. G.; Uhrlandt, D.

    2016-06-01

    Three approaches to describing the separation of charges in near-cathode regions of high-pressure arc discharges are compared. The first approach employs a single set of equations, including the Poisson equation, in the whole interelectrode gap. The second approach employs a fully non-equilibrium description of the quasi-neutral bulk plasma, complemented with a newly developed description of the space-charge sheaths. The third, and the simplest, approach exploits the fact that significant power is deposited by the arc power supply into the near-cathode plasma layer, which allows one to simulate the plasma-cathode interaction to the first approximation independently of processes in the bulk plasma. It is found that results given by the different models are generally in good agreement, and in some cases the agreement is even surprisingly good. It follows that the predicted integral characteristics of the plasma-cathode interaction are not strongly affected by details of the model provided that the basic physics is right.

  3. [The history of the contraceptive sheath].

    Science.gov (United States)

    Guyotjeannin, C

    1984-06-01

    The condom, effective in preventing both pregnancy and venereal disease, had a limited role until the 19th century, when its use spread through all social strata. The 1st condoms may have been linen sheaths designed to protect against syphilis. A 16th century Neapolitan doctor provided a recipe for an antiseptic preparation to be applied for 4-5 hourrs, but after intercourse had occurred. A physician to Louis XV mentioned the condom in a book published in 1736, and in 1770 the condom was again described without being named. 4 yeears later it was again described and called the condom or English redingote. Later it was mentioned by the Marques de Sade, who alluded to its contraceptive effect. In the early 19th century, condoms made of sheep entrails were mentioned. Descriptions of the preparation of 3 grades of condom, regular, fine, and superfine, were later found. The discovery of the process of vulcanization of rubber in 1839 made possible more solid, marketable, and usable latex condoms. The condom apparently began to be used in the late 17th or early 18th century. Some authors state that it was invented by a Dr. Condom or Conton, a physician or knight in the court of Charls II of England. Othrs suggested that it was named after the city of Condom in Gascony or derived from a foreign word. The antivenereal disease qualities of condoms were described by Casanova and Gustave Flaubert, and other references to them may be found in the literature. Later the contraceptive use of the condom became progressively more common, beginning in the wealthier classes and spreading to the rural and lower classes perhaps by the later 18th century. The diffusion of contraception during the 19th century was cited as the cause of th slow decline in illegitimacy rates starting at the end of the century. The Church condemned the use of condoms for contraception, but the medical profession took a less hostile view due to their health function. At the present time, condoms are widely

  4. Advanced diffusion processes and phenomena

    CERN Document Server

    Öchsner, Andreas; Belova, Irina

    2014-01-01

    This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the

  5. A spine-sheath model for strong-line blazars

    Science.gov (United States)

    Sikora, Marek; Rutkowski, Mieszko; Begelman, Mitchell C.

    2016-04-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of `the blazar zone'. We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why γ-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme γ-ray events.

  6. A spine-sheath model for strong-line blazars

    CERN Document Server

    Sikora, Marek; Begelman, Mitchell

    2015-01-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of "the blazar zone". We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why gamma-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme gamma-ray events.

  7. Photovoltaic sheathing element with a flexible connector assembly

    Energy Technology Data Exchange (ETDEWEB)

    Langmaid, Joseph A; Keenihan, James R; Mills, Michael E; Lopez, Leonardo C

    2016-07-12

    The present invention is premised upon an assembly including at least a photovoltaic sheathing element capable of being affixed on a building structure, the sheathing element including at least: a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; at least a first and a second connector assembly disposed on opposing sides of the sheathing element and capable of directly or indirectly electrically connecting the photovoltaic cell assembly to at least two adjoining devices that are affixed to the building structure and wherein at least one of the connector assemblies includes a flexible portion; one or more connector pockets disposed in the body portion the pockets capable of receiving at least a portion of the connector assembly.

  8. In vitro morphogenic response of leaf sheath of Phyllostachys bambusoides

    Institute of Scientific and Technical Information of China (English)

    Yurika H. Komatsu; Katherine Derlene Batagin-Piotto; Gilvano Ebling Brondani; Ant(o)nio Natal Goncalves; Marcilio de Almeida

    2011-01-01

    Nodal segments from secondary branches of saplings of Phyllostachys bambusoides were inoculated in MS medium to assess the in vitro morphogenic response of leaf sheath through the induction to callogenesis by Picloram (4-amino-3,5,6-trichloropicolinic acid) at different concentrations of carbohydrate under the same conditions with presence or absence of luminosity. In our experiment, secondary explants were kept in MS medium containing 8.0 mg·L-1 of Picloram for the callus formation. Calluses were transferred in MS medium supplemented with sucrose, fructose and glucose (control, 2%, 4% and 6%). Results show that Picloram induced the callogenesis in leaf sheath. The secondary embryogenesis was formed in yellow-globular callus. The sucrose as carbohydrate source in the absence of light was more efficient to induce rhizogenesis. Glucose was more efficiency in the presence of light. Callogenic induction and further embryogenesis evidenced the competence and determination of leaf sheath cells.

  9. Fibroma of tendon sheath located within Kager's triangle.

    Science.gov (United States)

    Jacobs, Eva; Witlox, Marianne A; Hermus, Joris P S

    2014-01-01

    The formation of a fibroma of the tendon sheath, a rare, slow-growing, benign tumor, usually occurs in the upper extremities of young adult males. We present an extremely rare case of a fibroma of the tendon sheath arising adjacent to the Achilles tendon within Kager's triangle in a 41-year-old female. The patient presented with progressive pain localized to the posterior aspect of the left ankle. Complete excision and histopathologic analysis of the fibroma were performed. The patient experienced an uneventful recovery after the intervention and had no evidence of recurrence after 3 months of follow-up. Fibroma of the tendon sheath should be included in the differential diagnosis when a patient presents with a painful soft tissue mass in Kager's triangle.

  10. Autoregressive description of biological phenomena

    CERN Document Server

    Morariu, Vasile V; Pop, Alexadru; Soltuz, Stefan M; Buimaga-Iarinca, Luiza; Zainea, Oana

    2008-01-01

    Many natural phenomena can be described by power-laws. A closer look at various experimental data reveals more or less significant deviations from a 1/f spectrum. We exemplify such cases with phenomena offered by molecular biology, cell biophysics, and cognitive psychology. Some of these cases can be described by first order autoregressive (AR) models or by higher order AR models which are short range correlation models. The calculations are checked against astrophysical data which were fitted to a an AR model by a different method. We found that our fitting method of the data give similar results for the astrhophysical data and therefore applied the method for examples mentioned above. Our results show that such phenomena can be described by first or higher order of AR models. Therefore such examples are described by short range correlation properties while they can be easily confounded with long range correlation phenomena.

  11. Mathematical Model for Hit Phenomena

    CERN Document Server

    Ishii, Akira; Hayashi, Takefumi; Matsuda, Naoya; Nakagawa, Takeshi; Arakaki, Hisashi; Yoshida, Narihiko

    2010-01-01

    The mathematical model for hit phenomena in entertainments is presented as a nonlinear, dynamical and non-equilibrium phenomena. The purchase intention for each person is introduced and direct and indirect communications are expressed as two-body and three-body interaction in our model. The mathematical model is expressed as coupled nonlinear differential equations. The important factor in the model is the decay time of rumor for the hit. The calculated results agree very well with revenues of recent 25 movies.

  12. Dengue Fever with rectus sheath hematoma: a case report.

    Science.gov (United States)

    Sharma, Anurag; Bhatia, Sonia; Singh, Rajendra Pratap; Malik, Gaurav

    2014-04-01

    Dengue fever, also known as breakbone fever, is an infectious tropical disease caused by the Dengue virus. It is associated with a number of complications, which are well documented. However, Dengue fever associated with rectus sheath hematoma (RSH) is a very rare complication. Only one case report has been published prior supporting the association of Dengue fever with RSH. We report a case of Dengue fever who presented with RSH and was successfully treated conservatively. RSH is also an uncommon cause of acute abdominal pain. It is accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear.

  13. Dengue fever with rectus sheath hematoma: A case report

    Directory of Open Access Journals (Sweden)

    Anurag Sharma

    2014-01-01

    Full Text Available Dengue fever, also known as breakbone fever, is an infectious tropical disease caused by the Dengue virus. It is associated with a number of complications, which are well documented. However, Dengue fever associated with rectus sheath hematoma (RSH is a very rare complication. Only one case report has been published prior supporting the association of Dengue fever with RSH. We report a case of Dengue fever who presented with RSH and was successfully treated conservatively. RSH is also an uncommon cause of acute abdominal pain. It is accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear.

  14. A spine-sheath model for strong-line blazars

    OpenAIRE

    2015-01-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of "the blazar zone". We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation me...

  15. Wakes in inhomogeneous plasmas

    CERN Document Server

    Kompaneets, Roman; Nosenko, Vladimir; Morfill, Gregor E

    2014-01-01

    The Debye shielding of a charge immersed in a flowing plasma is an old classic problem in plasma physics. It has been given renewed attention in the last two decades in view of experiments with complex plasmas, where charged dust particles are often levitated in a region with strong ion flow. Efforts to describe the shielding of the dust particles in such conditions have been focused on the homogeneous plasma approximation, which ignores the substantial inhomogeneity of the levitation region. We address the role of the plasma inhomogeneity by rigorously calculating the point charge potential in the collisionless Bohm sheath. We demonstrate that the inhomogeneity can dramatically modify the wake, making it non-oscillatory and weaker.

  16. Dimension effects in plasma immersion ion implantation of cylindrical bore

    CERN Document Server

    Tian Xiu Bo; Tong Hong Hui; Chu, P K

    2002-01-01

    Plasma immersion ion implantation is a new technique pertaining to ion implantation. Different from the case of exterior surface treatment, plasma immersion ion implantation of interior surface possesses dimension effects. Consequently it is a challenge to implant the inner wall of a cylindrical bore due to this finite dimension.The ion energy cannot be linearly changed with applied voltage and there exists a saturation value due to overlap effect of plasma sheath. The plasma in the bore may rapidly be depleted, which is attributed to finite plasma volume and plasma-sheath con-flowing effect. For instance the plasma depletion time is about 0.55 mu s when a bore with a diameter of 20 cm is treated under conditions of applied voltage of 30 kV and plasma density of 2 x 10 sup 1 sup 5 ions/cm sup 3. Interior plasma-source hardware may be an effective solution

  17. EDITORIAL: 80 Years of Plasma 80 Years of Plasma

    Science.gov (United States)

    Franklin, R. N.; Braithwaite, N. St J.

    2009-02-01

    papers published in the early 1930s Langmuir stated in words what was needed for a sheath to develop surrounding a plasma, and did so more generally than Bohm did in his subsequent 1949 paper. Langmuir's life and work, described by Sir Hugh Taylor in the Biographical Memoirs of Fellows of the Royal Society, was criticised by Dennis Gabor because it ignored his contribution to plasma physics. Gabor was aware of the Langmuir paradox arising from the knowledge that electron energy distributions when measured by a Langmuir probe are shown to contain high-energy tails. Some of the reason for the Biographical Memoir being deficient is undoubtedly the fact that in 1932 Langmuir was awarded the Nobel Prize in chemistry. The period of Langmuir's life from 1923 to 1932, as evidenced by his published papers, was largely given over to considerations of electrical discharges in gases with thermionic and liquid mercury cathodes, and in 1928 he introduced the term 'plasma' essentially to describe the positive column of a low-pressure gas discharge. These papers, though fewer than 50 in number (which we list in Appendix II), created a whole new area of physics, although we know that there was parallel work going on in Europe as evidenced by the two volumes of Electrische Gasentladungen by von Engel and Steenbeck, who adopted the term. The period before 1923 was concerned largely with atomic structure, molecules and crystalline structure, whereas from 1937 onwards attention was directed to proteins leading to the study of Langmuir-Blodgett films, and even later after World War II to atmospheric and oceanic phenomena. His scientific legacy, named to commemorate his contributions, can be found in (i) the Child-Langmuir Law, (ii) Langmuir probes, (iii) the Langmuir paradox, (iv) Langmuir waves, (v) Langmuir turbulence, (vi) the Langmuir isotherm, (vii) Langmuir-Blodgett films, together with the associated unit of monolayer coverage 'the Langmuir', and (viii) Langmuir circulation of oceanic

  18. Electron density and plasma dynamics of a colliding plasma experiment

    Energy Technology Data Exchange (ETDEWEB)

    Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J. [Plasma Physics Group, Institute of Applied Physics, Goethe University, 60438 Frankfurt am Main (Germany)

    2016-07-15

    We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

  19. Permeability of the Suberized Mestome Sheath in Winter Rye 1

    Science.gov (United States)

    Peterson, Carol A.; Griffith, Marilyn; Huner, Norman P. A.

    1985-01-01

    Mestome sheath cells of winter rye (Secale cereale L. cv Puma) deposit suberized lamellae in their secondary cell walls. Histochemical tests including acid digestion and staining with Sudan IV and Chelidonium majus root extract were used to detect the presence of suberin in the primary cell wall. There was no evidence of a Casparian band between adjacent mestome sheath cells. Fluorescent dye techniques were used to trace solute movement through the rye leaf apoplast. Calcofluor white M2R, a fluorescent dye which binds to cell walls as it moves apoplastically, proved to be too limited in its mobility in leaves to test mestome sheath permeability. Trisodium 3-hydroxy-5,8,10 pyrene trisulfonate, a fluorescent dye which is mobile in the apoplast, moved easily up the vascular bundles in the transpiration stream, and diffused outward from the veins to the epidermal cell walls within minutes of reaching a particular level in the leaf. We conclude that the suberized mestome sheath of rye leaves is freely permeable to solutes moving apoplastically through radial primary cell walls. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:16663999

  20. Leaf sheaths and obturators in Rutaceae – Pilocarpinae

    NARCIS (Netherlands)

    Kaastra, Roel C.

    1977-01-01

    From morphological and anatomical study it is clear that the dilated leaf bases of Metrodorea can be regarded as sheaths. They are not homologous with the spines of Raulinoa, as suggested by Cowan. The outgrowths on the ovules and immature seeds of Pilocarpinae have to be regarded as obturators.

  1. Malignant Peripheral Nerve Sheath Tumor: MRI and CT Findings

    Directory of Open Access Journals (Sweden)

    K. O. Kragha

    2015-01-01

    important in its diagnosis. A rare case of MPNST that produced urinary retention and bowel incontinence is presented that may aid clinicians in the diagnosis of this rare clinical entity. Motor weakness, central enhancement, and immunohistochemistry may assist in the diagnosis of MPNST and differentiation between benign peripheral nerve sheath tumor (BPNST and MPNST.

  2. Rice Sheath Rot: An Emerging Ubiquitous Destructive Disease Complex.

    Science.gov (United States)

    Bigirimana, Vincent de P; Hua, Gia K H; Nyamangyoku, Obedi I; Höfte, Monica

    2015-01-01

    Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium sp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness, and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: S. oryzae, the Fusarium fujikuroi complex, and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution, and control options will be discussed.

  3. Extraction of antioxidant pigments from dye sorghum leaf sheaths

    NARCIS (Netherlands)

    Kayode, A.P.P.; Bara, C.A.; Dalode-Vieira, G.; Linnemann, A.R.; Nout, M.J.R.

    2012-01-01

    Extraction of antioxidant biocolorant pigments from leaf sheaths of dye sorghum was optimized. Effects of temperature and ethanol concentration of the extraction solvent on the concentrations of the 3-deoxyanthocyanidins, total phenolics and total anthocyanins, and the colour parameters of the bioco

  4. Fibroma of tendon sheath of the infrapatellar fat pad

    Energy Technology Data Exchange (ETDEWEB)

    Hur, J. [College of Medicine, State University of New York Health Science Center at Syracuse, Syracuse, NY (United States); Damron, T.A. [Department of Orthopedic Surgery, 550 Harrison Center, Syracuse, NY (United States); Vermont, A.I. [Department of Radiology, State University of New York Health Science Center at Syracuse, Syracuse, NY (United States); Mathur, S.C. [Department of Pathology, State University of New York Health Science Center at Syracuse, Syracuse, NY (United States)

    1999-07-01

    We report on a 13-year-old boy who was found to have a fibroma of the tendon sheath associated with the patellar tendon and within Hoffa`s fat pad of the knee. This benign tumor has never been described in this location previously. The MRI characteristics are correlated with the histologic findings. (orig.) With 2 figs., 18 refs.

  5. Maize development: Cell wall changes in leaves and sheaths

    Science.gov (United States)

    Developmental changes occur in maize (Zea mays L.) as it transitions from juvenile stages to the mature plant. Changes also occur as newly formed cells mature into adult cells. Maize leaf blades, including the midribs and sheaths, undergo cell wall changes as cells transition to fully mature cell ty...

  6. Separation system with a sheath-flow supported electrochemical detector

    Science.gov (United States)

    Mathies, Richard A.; Emrich, Charles A.; Singhal, Pankaj; Ertl, Peter

    2008-10-21

    An electrochemical detector including side channels associated with a separation channel of a sample component separation apparatus is provided. The side channels of the detector, in one configuration, provide a sheath-flow for an analyte exiting the separation channel which directs the analyte to the electrically developed electrochemical detector.

  7. Temperature response of bundle-sheath conductance in maize leaves

    NARCIS (Netherlands)

    Yin, Xinyou; Putten, Van Der Peter E.L.; Struik, Paul C.; Driever, Steven M.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g

  8. Mineralized fibroma of the tendon sheath presenting as a bursitis

    Energy Technology Data Exchange (ETDEWEB)

    Le Corroller, Thomas; Champsaur, Pierre [Hopital Sainte-Marguerite, Service de Radiologie, Marseille (France); Faculte de Medecine de Marseille, Departement d' Anatomie, Marseille (France); Bouvier-Labit, Corinne [Hopital La Timone, Service d' Anatomopathologie, Marseille (France); Sbihi, Abderrahmane [Clinique Juge, Service de Chirurgie orthopedique, Marseille (France)

    2008-12-15

    We report on the clinical, imaging - including ultrasound, computed tomography, and magnetic resonance imaging - and histological features of a fibroma of the tendon sheath with mineralized chondroid and osseous metaplasia, presenting as a semimembranosus bursitis. The anatomical characteristics of the semimembranosus bursa are demonstrated by dissection in a cadaveric specimen and correlated with the imaging findings in our patient. (orig.)

  9. Modelling of Complex Plasmas

    Science.gov (United States)

    Akdim, Mohamed Reda

    2003-09-01

    Nowadays plasmas are used for various applications such as the fabrication of silicon solar cells, integrated circuits, coatings and dental cleaning. In the case of a processing plasma, e.g. for the fabrication of amorphous silicon solar cells, a mixture of silane and hydrogen gas is injected in a reactor. These gases are decomposed by making a plasma. A plasma with a low degree of ionization (typically 10_5) is usually made in a reactor containing two electrodes driven by a radio-frequency (RF) power source in the megahertz range. Under the right circumstances the radicals, neutrals and ions can react further to produce nanometer sized dust particles. The particles can stick to the surface and thereby contribute to a higher deposition rate. Another possibility is that the nanometer sized particles coagulate and form larger micron sized particles. These particles obtain a high negative charge, due to their large radius and are usually trapped in a radiofrequency plasma. The electric field present in the discharge sheaths causes the entrapment. Such plasmas are called dusty or complex plasmas. In this thesis numerical models are presented which describe dusty plasmas in reactive and nonreactive plasmas. We started first with the development of a simple one-dimensional silane fluid model where a dusty radio-frequency silane/hydrogen discharge is simulated. In the model, discharge quantities like the fluxes, densities and electric field are calculated self-consistently. A radius and an initial density profile for the spherical dust particles are given and the charge and the density of the dust are calculated with an iterative method. During the transport of the dust, its charge is kept constant in time. The dust influences the electric field distribution through its charge and the density of the plasma through recombination of positive ions and electrons at its surface. In the model this process gives an extra production of silane radicals, since the growth of dust is

  10. Fusion plasma physics

    CERN Document Server

    Stacey, Weston M

    2012-01-01

    This revised and enlarged second edition of the popular textbook and reference contains comprehensive treatments of both the established foundations of magnetic fusion plasma physics and of the newly developing areas of active research. It concludes with a look ahead to fusion power reactors of the future. The well-established topics of fusion plasma physics -- basic plasma phenomena, Coulomb scattering, drifts of charged particles in magnetic and electric fields, plasma confinement by magnetic fields, kinetic and fluid collective plasma theories, plasma equilibria and flux surface geometry, plasma waves and instabilities, classical and neoclassical transport, plasma-materials interactions, radiation, etc. -- are fully developed from first principles through to the computational models employed in modern plasma physics. The new and emerging topics of fusion plasma physics research -- fluctuation-driven plasma transport and gyrokinetic/gyrofluid computational methodology, the physics of the divertor, neutral ...

  11. Chondroma within the flexor hallucis longus tendon sheath. A case report and literature review.

    Science.gov (United States)

    Brahms, M A; Fumich, R M

    1978-01-01

    Chondromas in tendon sheaths are a rare entity proviously reported in the flexor sheaths on the hand and possibly the foot. This is the first reported case of condroma of the flexor hallucis longus tendon sheath at the ankle region. A literature review with regard to pathogenesis, classification, and recurrence has been presented.

  12. Malignant peripheral nerve sheath tumour of the bladder associated with neurofibromatosis I.

    LENUS (Irish Health Repository)

    O'Brien, Julie

    2008-12-01

    Neurofibromatosis is a hamartomatous disorder of autonomic peripheral nerve sheaths associated with peripheral nerve sheath tumours. Most tumours are neurofibromas; however, the genitourinary system is rarely involved. We present a rare case of a nerve sheath tumour of the bladder in a young patient, which was discovered to be malignant.

  13. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Science.gov (United States)

    2010-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that specified...

  14. File list: DNS.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 DNase-seq Neural Nerve Sheath Neoplasms... http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  15. File list: Oth.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 TFs and others Neural Nerve Sheath Neop...lasms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  16. File list: ALL.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available ALL.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 All antigens Neural Nerve Sheath Neopla...sms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/ALL.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  17. File list: Pol.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 RNA polymerase Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  18. File list: ALL.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available ALL.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 All antigens Neural Nerve Sheath Neopla...sms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/ALL.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  19. File list: DNS.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 DNase-seq Neural Nerve Sheath Neoplasms... http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  20. File list: DNS.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 DNase-seq Neural Nerve Sheath Neoplasms... http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  1. File list: Unc.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 Unclassified Neural Nerve Sheath Neopla...sms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  2. File list: Unc.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 Unclassified Neural Nerve Sheath Neopla...sms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  3. File list: ALL.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available ALL.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 All antigens Neural Nerve Sheath Neopla...sms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/ALL.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  4. File list: Oth.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 TFs and others Neural Nerve Sheath Neop...lasms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  5. File list: Pol.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 RNA polymerase Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  6. File list: Pol.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 RNA polymerase Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  7. File list: Unc.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 Unclassified Neural Nerve Sheath Neopla...sms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  8. File list: Pol.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 RNA polymerase Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  9. File list: His.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 Histone Neural Nerve Sheath Neoplasms h...ttp://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  10. File list: ALL.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available ALL.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 All antigens Neural Nerve Sheath Neopla...sms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/ALL.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  11. File list: His.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 Histone Neural Nerve Sheath Neoplasms h...ttp://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  12. File list: His.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 Histone Neural Nerve Sheath Neoplasms h...ttp://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  13. File list: Oth.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 TFs and others Neural Nerve Sheath Neop...lasms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  14. File list: His.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 Histone Neural Nerve Sheath Neoplasms h...ttp://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  15. File list: Oth.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 TFs and others Neural Nerve Sheath Neop...lasms SRX337965 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  16. File list: DNS.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 DNase-seq Neural Nerve Sheath Neoplasms... http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...

  17. File list: Unc.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 Unclassified Neural Nerve Sheath Neopla...sms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  18. Do counts of salivary sheath flanges predict food consumption in herbivorous stink bugs [Hemiptera: Pentatomidae]?

    Science.gov (United States)

    For Pentatomid stink bug agricultural pests, the number of salivary sheaths and sheath flanges—the portion of the sheath visible on the exterior surface of a food item—are good predictors of the loss of crop yield or quality from stink bug feeding. As the often assumed relationship between salivary ...

  19. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Science.gov (United States)

    2010-10-01

    ... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the installation requirements of Section 25 of IEEE 45-2002 (incorporated by reference; see 46 CFR 110.10-1). ... 46 Shipping 4 2010-10-01 2010-10-01 false Armored and metallic sheathed cable. 111.05-7...

  20. Critical Phenomena in Gravitational Collapse

    Directory of Open Access Journals (Sweden)

    Gundlach Carsten

    1999-01-01

    Full Text Available As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term 'critical phenomena'. They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. This review gives an introduction to the phenomena, tries to summarize the essential features of what is happening, and then presents extensions and applications of this basic scenario. Critical phenomena are of interest particularly for creating surprising structure from simple equations, and for the light they throw on cosmic censorship and the generic dynamics of general relativity.

  1. Critical Phenomena in Gravitational Collapse.

    Science.gov (United States)

    Gundlach, Carsten

    1999-01-01

    As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term "critical phenomena". They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. This review gives an introduction to the phenomena, tries to summarize the essential features of what is happening, and then presents extensions and applications of this basic scenario. Critical phenomena are of interest particularly for creating surprising structure from simple equations, and for the light they throw on cosmic censorship and the generic dynamics of general relativity.

  2. Transport Phenomena and Materials Processing

    Science.gov (United States)

    Kou, Sindo

    1996-10-01

    An extremely useful guide to the theory and applications of transport phenomena in materials processing This book defines the unique role that transport phenomena play in materials processing and offers a graphic, comprehensive treatment unlike any other book on the subject. The two parts of the text are, in fact, two useful books. Part I is a very readable introduction to fluid flow, heat transfer, and mass transfer for materials engineers and anyone not yet thoroughly familiar with the subject. It includes governing equations and boundary conditions particularly useful for studying materials processing. For mechanical and chemical engineers, and anyone already familiar with transport phenomena, Part II covers the many specific applications to materials processing, including a brief description of various materials processing technologies. Readable and unencumbered by mathematical manipulations (most of which are allocated to the appendixes), this book is also a useful text for upper-level undergraduate and graduate-level courses in materials, mechanical, and chemical engineering. It includes hundreds of photographs of materials processing in action, single and composite figures of computer simulation, handy charts for problem solving, and more. Transport Phenomena and Materials Processing: * Describes eight key materials processing technologies, including crystal growth, casting, welding, powder and fiber processing, bulk and surface heat treating, and semiconductor device fabrication * Covers the latest advances in the field, including recent results of computer simulation and flow visualization * Presents special boundary conditions for transport phenomena in materials processing * Includes charts that summarize commonly encountered boundary conditions and step-by-step procedures for problem solving * Offers a unique derivation of governing equations that leads to both overall and differential balance equations * Provides a list of publicly available computer

  3. Charged dust phenomena in the near-Earth space environment

    Science.gov (United States)

    Scales, W. A.; Mahmoudian, A.

    2016-10-01

    Dusty (or complex) plasmas in the Earth’s middle and upper atmosphere ultimately result in exotic phenomena that are currently forefront research issues in the space science community. This paper presents some of the basic criteria and fundamental physical processes associated with the creation, evolution and dynamics of dusty plasmas in the near-Earth space environment. Recent remote sensing techniques to probe naturally created dusty plasma regions are also discussed. These include ground-based experiments employing high-power radio wave interaction. Some characteristics of the dusty plasmas that are actively produced by space-borne aerosol release experiments are discussed. Basic models that may be used to investigate the characteristics of such dusty plasma regions are presented.

  4. Whistlers and related ionospheric phenomena

    CERN Document Server

    Helliwell, Robert A

    2006-01-01

    The investigation of whistlers and related phenomena is a key element in studies of very-low-frequency propagation, satellite communication, the outer ionosphere, and solar-terrestrial relationships. This comprehensive text presents a history of the study of the phenomena and includes all the elements necessary for the calculation of the characteristics of whistlers and whistler-mode signals.An introduction and brief history are followed by a summary of the theory of whistlers and a detailed explanation of the calculation of their characteristics. Succeeding chapters offer a complete atlas of

  5. Undergraduates' understanding of cardiovascular phenomena.

    Science.gov (United States)

    Michael, Joel A; Wenderoth, Mary Pat; Modell, Harold I; Cliff, William; Horwitz, Barbara; McHale, Philip; Richardson, Daniel; Silverthorn, Dee; Williams, Stephen; Whitescarver, Shirley

    2002-12-01

    Undergraduates students in 12 courses at 8 different institutions were surveyed to determine the prevalence of 13 different misconceptions (conceptual difficulties) about cardiovascular function. The prevalence of these misconceptions ranged from 20 to 81% and, for each misconception, was consistent across the different student populations. We also obtained explanations for the students' answers either as free responses or with follow-up multiple-choice questions. These results suggest that students have a number of underlying conceptual difficulties about cardiovascular phenomena. One possible source of some misconceptions is the students' inability to apply simple general models to specific cardiovascular phenomena. Some implications of these results for teachers of physiology are discussed.

  6. Complex Phenomena in Nanoscale Systems

    CERN Document Server

    Casati, Giulio

    2009-01-01

    Nanoscale physics has become one of the rapidly developing areas of contemporary physics because of its direct relevance to newly emerging area, nanotechnologies. Nanoscale devices and quantum functional materials are usually constructed based on the results of fundamental studies on nanoscale physics. Therefore studying physical phenomena in nanosized systems is of importance for progressive development of nanotechnologies. In this context study of complex phenomena in such systems and using them for controlling purposes is of great practical importance. Namely, such studies are brought together in this book, which contains 27 papers on various aspects of nanoscale physics and nonlinear dynamics.

  7. Abnormal pressures as hydrodynamic phenomena

    Science.gov (United States)

    Neuzil, C.E.

    1995-01-01

    So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author

  8. Structure of the velocity distribution of sheath-accelerated secondary electrons in an asymmetric RF-dc discharge

    Science.gov (United States)

    Khrabrov, Alexander V.; Kaganovich, Igor D.; Ventzek, Peter L. G.; Ranjan, Alok; Chen, Lee

    2015-10-01

    Low-pressure capacitively-coupled discharges with additional dc bias applied to a separate electrode are utilized in plasma-assisted etching for semiconductor device manufacturing. Measurements of the electron velocity distribution function (EVDF) of the flux impinging on the wafer, as well as in the plasma bulk, show a thermal population and additional peaks within a broad range of energies. That range extends from the thermal level up to the value for the ‘ballistic’ peak, corresponding to the bias potential. The non-thermal electron flux has been correlated to alleviating the electron shading effect and providing etch-resistance properties to masking photoresist layers. ‘Middle-energy peak electrons’ at energies of several hundred eV may provide an additional sustaining mechanism for the discharge. These features in the electron velocity (or energy) distribution functions are possibly caused by secondary electrons emitted from the electrodes and interacting with two high-voltage sheaths: a stationary sheath at the dc electrode and an oscillating self-biased sheath at the powered electrode. Since at those energies the mean free path for large-angle scattering (momentum relaxation length) is comparable to, or exceeds the size of the discharge gap, these ‘ballistic’ electrons will not be fully scattered by the background gas as they traverse the inter-electrode space. We have performed test-particle simulations in which the features in the EVDF of electrons impacting the RF electrode are fully resolved at all energies. An analytical model has been developed to predict existence of peaked and step-like structures in the EVDF. Those features can be explained by analyzing the kinematics of electron trajectories in the discharge gap. Step-like structures in the EVDF near the powered electrode appear due to accumulation of electrons emitted from the dc electrode within a portion of the RF cycle, and their subsequent release. Trapping occurs when the RF

  9. Magneto-photonic phenomena at terahertz frequencies

    CERN Document Server

    Shalaby, Mostafa

    2014-01-01

    Magneto-terahertz phenomena are the main focus of the thesis. This work started as supporting research for the science of an X-ray laser (SwissFEL). X-ray lasers have recently drawn great attention as an unprecedented tool for scientific research on the ultrafast scale..... To answer this fundamental question, we performed original numerical simulations using a coupled Landau- Lifshitz-Gilbert Maxwell model. ... Those requirements were the motivations for the experiments performed in the second part of the thesis. To shape the terahertz pulses, .... Regarding the field intensities, we followed two approaches. The first deals with field enhancement in nanoslits arrays. We designed a subwavelength structure characterized by simultaneous high field enhancement and high transmission at terahertz frequencies to suit nonlinear sources. The second approach depended on up-scaling the generation from laser-induced plasma by increasing the pump wavelengths. Numerical calculations have also brought to our attention the ...

  10. Magnetohydrodynamic (MHD) modelling of solar active phenomena via numerical methods

    Science.gov (United States)

    Wu, S. T.

    1988-01-01

    Numerical ideal MHD models for the study of solar active phenomena are summarized. Particular attention is given to the following physical phenomena: (1) local heating of a coronal loop in an isothermal and stratified atmosphere, and (2) the coronal dynamic responses due to magnetic field movement. The results suggest that local heating of a magnetic loop will lead to the enhancement of the density of the neighboring loops through MHD wave compression. It is noted that field lines can be pinched off and may form a self-contained magnetized plasma blob that may move outward into interplanetary space.

  11. Multiscale phenomena in the Earth's Magnetosphere

    Science.gov (United States)

    Surjalal Sharma, A.

    The multiscale phenomena in the Earth's magnetosphere have been studied using data from ground-based and space-borne measurements. The ground-based observations provide data over decades and are suitable for characterizing the inherent nature of the multiscale behavior and for studying the dynamical and statistical features. On the other hand, the spacecraft data provide in-situ observations of the processes. The multipoint measurements by Cluster have provided a new understanding of the plasma processes at microand meso-scales and the cross-scale coupling among them. The role of cross-scale coupling is evident in phenomena such as bursty bulk flows, flux ropes, and reconnection. The characteristic scales of the processes range from electron skin depth to MHD scales and the modeling of these processes need different physical models, such as kinetic, EMHD, Hall MHD, and MHD. The ground-based data have been used to develop models based on techniques of nonlinear science and yield predictive models which can be used for forecasting. These models characterize the magnetospheric dynaics and yield its global and multiscale aspects. The distribution of scales in the magnetosphere is studied using an extensive database of the solar wind and the magnetosphere. The distributions of the waiting times deviate significantly from a power law as well as stretched exponential distributions, and show a scaling with respect to the mean, indicating a limited role of long-term correlations in the magnetospheric dynamics.

  12. A Sheath Collision Model with Thermionic Electron Emission and the Schottky Correction Factor for Work Function of Wall Material

    CERN Document Server

    Pekker, Leonid

    2015-01-01

    This paper proposes a model that expands Godyak's collisional sheath model to the case of hot electrodes (anode or cathode) with thermionic electron emission. In the model, the electrodes are assumed to be made from refractory metals and, consequently, the erosion of the electrodes is small and can be neglected. In the frame of two temperature thermal plasma modeling, this model allows self-consistent calculation of the sheath potential drop, the Schottky correction factor for the work function of the wall material, the thermionic electron current density, and the heat fluxes of the charged particles from the plasma to the wall. The model is applied to the cathode spot at the tungsten cathode in argon. It is shown that the Shottky correction factor plays a crucial role in modeling high-intensity arcs. It is demonstrated that a virtual cathode can be formed in the atmospheric pressure argon plasma at the cathode surface temperature of 4785 K if the cathode current density is sufficiently small. The heat flux t...

  13. Kinetic simulation study of one dimensional collisional bounded plasma

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A self-consistent kinetic simulation study ofone dimensional collisional bounded plasma is presented.The formation of stable sheath potential is investigated.It is found that mass ratio of electron and ion not onlyaffects the level of sheath potential, but also affectsthe ion temperature of system. It is clarified that the effects of secondaryemission electron on both the total potential dropand the temperature are not important.

  14. Performance of sheath electric field measurement by saturation spectroscopy in Balmer-α line of atomic hydrogen

    Science.gov (United States)

    Nishiyama, Shusuke; Katayama, Kento; Nakano, Haruhisa; Goto, Motoshi; Sasaki, Koichi

    2017-03-01

    We developed a diode laser-based system for measuring the sheath electric fields in low-temperature plasmas. The Stark spectrum of the Balmer-α line of atomic hydrogen was measured by saturation spectroscopy with a fine spectral resolution. The spectrum observed experimentally was consistent with the theoretical Stark spectrum, and we succeeded in evaluating the electric field strength on the basis of the experimental Stark spectrum. A sensitive detection limit of 10 V/cm was achieved by the developed system.

  15. Hydrophilic coating aids radial sheath withdrawal and reduces patient discomfort following transradial coronary intervention: a randomized double-blind comparison of coated and uncoated sheaths.

    Science.gov (United States)

    Kiemeneij, Ferdinand; Fraser, Douglas; Slagboom, Ton; Laarman, GertJan; van der Wieken, Ron

    2003-06-01

    Radial artery spasm may cause severe discomfort during radial artery sheath removal. A hydrophilic-coated sheath may reduce the force required to remove a radial sheath. This force may be quantified using an automatic pullback device (APD). The objective of this study was to assess if a hydrophilic coating reduces the required force and discomfort associated with removal of a radial sheath following transradial coronary intervention. Ninety patients undergoing percutaneous coronary intervention via the radial artery were randomly assigned to two groups receiving either coated or uncoated introducer sheaths. Radifocus Introducer II (Terumo) 25 cm, 6 Fr radial sheaths and sheaths that were identical apart from the presence of the coating were used in all patients. The APD was used for sheath removal at the end of the procedure. Three patients (7%) in the coated group experienced discomfort during automatic sheath removal, compared to 12 patients (27%) in the uncoated group (P = 0.02). The maximum pullback force (MPF) was significantly lower in the coated compared to the uncoated group (0.24 +/- 0.31 vs. 0.44 +/- 0.33 kg; P = 0.003). Similarly, the mean pullback force was significantly lower in the coated group (0.14 +/- 0.23 vs. 0.32 +/- 0.24 kg; P < 0.001). Only one patient (2%) in each group had an MPF greater than 1.0 kg together with clinical evidence of radial artery spasm. Removal of the coated Terumo Radifocus sheath requires less force than an identical uncoated sheath. The coated sheath was also associated with less discomfort for the patient.

  16. USING COORDINATED OBSERVATIONS IN POLARIZED WHITE LIGHT AND FARADAY ROTATION TO PROBE THE SPATIAL POSITION AND MAGNETIC FIELD OF AN INTERPLANETARY SHEATH

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Ming; Feng, Xueshang; Liu, Ying D. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing (China); Davies, Jackie A.; Harrison, Richard A. [Rutherford-Appleton Laboratory (RAL) Space, Harwell Oxford (United Kingdom); Owens, Mathew J.; Davis, Chris J., E-mail: mxiong@spacweather.ac.cn [Reading University, Reading (United Kingdom)

    2013-11-01

    Coronal mass ejections (CMEs) can be continuously tracked through a large portion of the inner heliosphere by direct imaging in visible and radio wavebands. White light (WL) signatures of solar wind transients, such as CMEs, result from Thomson scattering of sunlight by free electrons and therefore depend on both viewing geometry and electron density. The Faraday rotation (FR) of radio waves from extragalactic pulsars and quasars, which arises due to the presence of such solar wind features, depends on the line-of-sight magnetic field component B{sub ∥} and the electron density. To understand coordinated WL and FR observations of CMEs, we perform forward magnetohydrodynamic modeling of an Earth-directed shock and synthesize the signatures that would be remotely sensed at a number of widely distributed vantage points in the inner heliosphere. Removal of the background solar wind contribution reveals the shock-associated enhancements in WL and FR. While the efficiency of Thomson scattering depends on scattering angle, WL radiance I decreases with heliocentric distance r roughly according to the expression I∝r {sup –3}. The sheath region downstream of the Earth-directed shock is well viewed from the L4 and L5 Lagrangian points, demonstrating the benefits of these points in terms of space weather forecasting. The spatial position of the main scattering site r{sub sheath} and the mass of plasma at that position M{sub sheath} can be inferred from the polarization of the shock-associated enhancement in WL radiance. From the FR measurements, the local B{sub ∥sheath} at r{sub sheath} can then be estimated. Simultaneous observations in polarized WL and FR can not only be used to detect CMEs, but also to diagnose their plasma and magnetic field properties.

  17. Experiments with an rf dusty plasma and an external plasma jet

    Science.gov (United States)

    Ticoş, C. M.

    2010-12-01

    A plasma jet produced in a coaxial plasma gun was aimed at a cloud of dust particles levitated in the sheath of a radio-frequency (rf) plasma produced between two parallel-plate electrodes. A high-speed camera with a side-view on the dust cloud was used to track the dust particles. Several cases of dust motion could be observed. When the jet was parallel with the horizontal electrodes of the rf plasma the dust particles were either pushed out of the trapping region by the plasma jet or were only perturbed from their equilibrium position, oscillating with a frequency of the order of a few kHz. In the first case the trajectory of the dust particles followed the curvature of the sheath. In the second case, when the jet was fired at a small angle with the horizontal electrodes the dust particles hit the bottom electrode and ricocheted back into the sheath. Finally, another situation was observed when the jet perturbed the rf plasma and its sheath and the whole dust crystal fell to the electrode.

  18. A hybrid model of radio frequency biased inductively coupled plasma discharges: description of model and experimental validation in argon

    Science.gov (United States)

    Wen, De-Qi; Liu, Wei; Gao, Fei; Lieberman, M. A.; Wang, You-Nian

    2016-08-01

    A hybrid model, i.e. a global model coupled bidirectionally with a parallel Monte-Carlo collision (MCC) sheath model, is developed to investigate an inductively coupled discharge with a bias source. This hybrid model can self-consistently reveal the interaction between the bulk plasma and the radio frequency (rf) bias sheath. More specifically, the plasma parameters affecting characteristics of rf bias sheath (sheath length and self-bias) are calculated by a global model and the effect of the rf bias sheath on the bulk plasma is determined by the voltage drop of the rf bias sheath. Moreover, specific numbers of ions are tracked in the rf bias sheath and ultimately the ion energy distribution function (IEDF) incident on the bias electrode is obtained. To validate this model, both bulk plasma density and IEDF on the bias electrode in an argon discharge are compared with experimental measurements, and a good agreement is obtained. The advantage of this model is that it can quickly calculate the bulk plasma density and IEDF on the bias electrode, which are of practical interest in industrial plasma processing, and the model could be easily extended to serve for industrial gases.

  19. Plasmas for environmental issues: from hydrogen production to 2D materials assembly

    Science.gov (United States)

    Tatarova, E.; Bundaleska, N.; Sarrette, J. Ph; Ferreira, C. M.

    2014-12-01

    It is well recognized at present that the unique, high energy density plasma environment provides suitable conditions to dissociate/atomize molecules in remediation systems, to convert waste and biomass into sustainable energy sources, to purify water, to assemble nanostructures, etc. The remarkable plasma potential is based on its ability to supply simultaneously high fluxes of charged particles, chemically active molecules, radicals (e.g. O, H, OH), heat, highly energetic photons (UV and extreme UV radiation), and strong electric fields in intrinsic sheath domains. Due to this complexity, low-temperature plasma science and engineering is a huge, highly interdisciplinary field that spans many research disciplines and applications across many areas of our daily life and industrial activities. For this reason, this review deals only with some selected aspects of low-temperature plasma applications for a clean and sustainable environment. It is not intended to be a comprehensive survey, but just to highlight some important works and achievements in specific areas. The selected issues demonstrate the diversity of plasma-based applications associated with clean and sustainable ambiance and also show the unity of the underlying science. Fundamental plasma phenomena/processes/features are the common fibers that pass across all these areas and unify all these applications. Browsing through different topics, we try to emphasize these phenomena/processes/features and their uniqueness in an attempt to build a general overview. The presented survey of recently published works demonstrates that plasma processes show a significant potential as a solution for waste/biomass-to-energy recovery problems. The reforming technologies based on non-thermal plasma treatment of hydrocarbons show promising prospects for the production of hydrogen as a future clean energy carrier. It is also shown that plasmas can provide numerous agents that influence biological activity. The simultaneous

  20. Transport phenomena in particulate systems

    CERN Document Server

    Freire, José Teixeira; Ferreira, Maria do Carmo

    2012-01-01

    This volume spans 10 chapters covering different aspects of transport phenomena including fixed and fluidized systems, spouted beds, electrochemical and wastewater treatment reactors. This e-book will be valuable for students, engineers and researchers aiming to keep updated on the latest developments on particulate systems.

  1. Generalized polarization force acting on dust grains in a dusty plasma

    Science.gov (United States)

    Bentabet, Karima; Mayout, Saliha; Tribeche, Mouloud

    2017-01-01

    The polarization force acting on dust particles in a dusty plasma is revisited within the theoretical framework of the Tsallis statistical mechanics. The generalized nonextensive polarization force expression is derived. As application, the modifications arising in the propagation of dust-acoustic solitary waves, and dust sheath formation are analyzed. Our results should be of wide relevance to explain and interpret the sheath formation and its structure in nonequilibrium plasmas related process such as surface treatments and ion implantation.

  2. Microwave power coupling in a surface wave excited plasma

    CERN Document Server

    Kar, Satyananda; Kousaka, Hiroyuki

    2014-01-01

    In recent decades, different types of plasma sources have been used for various types of plasma processing, such as, etching and thin film deposition. The critical parameter for effective plasma processing is high plasma density. One type of high density plasma source is Microwave sheath-Voltage combination Plasma (MVP). In the present investigation, a better design of MVP source is reported, in which over-dense plasma is generated for low input microwave powers. The results indicate that the length of plasma column increases significantly with increase in input microwave power.

  3. JET: Recent results and edge phenomena

    Energy Technology Data Exchange (ETDEWEB)

    De Kock, L.; Behringer, K.; Bickerton, R.J.; Boschi, A.; Brinkschulte, H.; Bures, M.; Campbell, D.J.; Christiansen, J.; Cordey, J.G.; Coad, J.P.

    1987-02-01

    Ohmic heating studies in hydrogen and deuterium up to currents of I/sub p/ = 5 MA have been completed and additional heating experiments by means of ICRH and NBI are now in process. With ICRH powers up to 7 MW, the global energy confinement time tau/sub E/ is observed to deteriorate with increasing heating power. NBI experiments are at a more preliminary stage, but also show deterioration in tau/sub E/. Detailed studies of confinement time scaling in ohmically heated discharges show a strong dependence of plasma size, tau/sub E/ proportional to R/sup 1.7/a/sup 1.3/, but a much weaker dependence on q and n/sub e/ than seen in smaller experiments. Boundary phenomena have been studied from early 1984. Data on the impurity coverage of limiters and wall have been collected during three successive experimental campaigns. Substantial amounts of wall material have consistently been found on the limiters and a large inventory of hydrogen isotopes concentrated on the colder edges. The wall in the shadow of protective elements shows non-uniform erosion. Langmuir probe measurements of edge plasma parameters have been taken in OH, RF and NB discharges. Additional heating leads generally to a temperature increase of the scrape-off layer. Model calculations using data from these diagnostics seem to produce a consistent picture of impurity production in the scrape-off layer which agrees reasonably well with spectroscopic observations.

  4. An optical tweezer for complex plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Schablinski, Jan; Wieben, Frank; Block, Dietmar [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 17-19, 24098 Kiel (Germany)

    2015-04-15

    This paper describes the experimental realization of an optical trap for microparticles levitating in the plasma sheath. Single particles can be trapped in a laser beam comparable to optical tweezers known from colloidal suspensions. The trapping mechanism is discussed and two applications of the system are shown.

  5. Leptomeningeal metastasis of an intradural malignant peripheral nerve sheath tumor.

    Science.gov (United States)

    Stark, Andreas M; Mehdorn, H Maximilian

    2013-08-01

    Malignant peripheral nerve sheath tumors (MPNST) are defined as any malignant tumor arising from or differentiating towards the peripheral nerve sheath. Intradural MPNST metastases are very rare. We report, to our knowledge, the first case of leptomeningeal metastasis of a MPNST to the spine and intracranial space. A 56-year-old woman with primary intradural MPNST of the S1 nerve root developed leptomeningeal metastases as well as brain metastases 19 months after diagnosis. The patient had a history of non-Hodgkins lymphoma for which she had received irradiation to the spine 15 years prior to this presentation. She had no stigmata of neurofibromatosis type 1. Patients with MPNST may also develop leptomeningeal metastases as demonstrated in this patient with intradural post-radiation MPNST.

  6. Ewing sarcoma mimicking a peripheral nerve sheath tumor.

    Science.gov (United States)

    Mitchell, B D; Fox, B D; Viswanathan, A; Mitchell, A H; Powell, S Z; Cech, D A

    2010-10-01

    We describe the first patient with an extradural, extramedullary Ewing's sarcoma tumor mimicking a nerve sheath tumor with no overt evidence of metastasis. A 28-year-old woman with no past medical history presented with a progressive 3-year history of low back pain and right-sided lower extremity radiculopathy after having failed conservative therapies. MRI of the lumbar spine revealed a right-sided enhancing, dumbbell-shaped lesion at the right neural foramen appearing to originate from the L4 nerve root, suspicious for a peripheral nerve sheath tumor or schwannoma. The patient and findings are discussed in the context of the literature, including an update on the relatively recent diagnostic redesignation of the Ewing's sarcoma family tumors.

  7. Moisture Durability with Vapor-Permeable Insulating Sheathing

    Energy Technology Data Exchange (ETDEWEB)

    Lepage, R. [Building Science Corporation, Somerville, MA (United States); Lstiburek, J. [Building Science Corporation, Somerville, MA (United States)

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However,uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and theprocedures utilized to analyse the problems.

  8. Moisture Durability with Vapor-Permeable Insulating Sheathing

    Energy Technology Data Exchange (ETDEWEB)

    Lepage, R. [Building Science Corporation, Somerville, MA (United States); Lstiburek, J. [Building Science Corporation, Somerville, MA (United States)

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However, uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and the procedures utilized to analyse the problems.

  9. Thermodynamic constraints on fluctuation phenomena

    Science.gov (United States)

    Maroney, O. J. E.

    2009-12-01

    The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.

  10. Molecular model for chirality phenomena.

    Science.gov (United States)

    Latinwo, Folarin; Stillinger, Frank H; Debenedetti, Pablo G

    2016-10-21

    Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations. Using this model, we explore a range of chirality-specific phenomena, including the kinetics of chiral inversion, the mechanism of spontaneous chiral symmetry breaking in the liquid, chirally driven liquid-liquid phase separation, and chiral crystal structures.

  11. Transport phenomena in multiphase flows

    CERN Document Server

    Mauri, Roberto

    2015-01-01

    This textbook provides a thorough presentation of the phenomena related to the transport of mass, momentum and energy.  It lays all the basic physical principles, then for the more advanced readers, it offers an in-depth treatment with advanced mathematical derivations and ends with some useful applications of the models and equations in specific settings. The important idea behind the book is to unify all types of transport phenomena, describing them within a common framework in terms of cause and effect, respectively represented by the driving force and the flux of the transported quantity. The approach and presentation are original in that the book starts with a general description of transport processes, providing the macroscopic balance relations of fluid dynamics and heat and mass transfer, before diving into the mathematical realm of continuum mechanics to derive the microscopic governing equations at the microscopic level. The book is a modular teaching tool and can be used either for an introductory...

  12. Thermodynamic constraints on fluctuation phenomena.

    Science.gov (United States)

    Maroney, O J E

    2009-12-01

    The relationships among reversible Carnot cycles, the absence of perpetual motion machines, and the existence of a nondecreasing globally unique entropy function form the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending rather than restricting the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.

  13. Charged dust and shock phenomena in the Solar System

    Directory of Open Access Journals (Sweden)

    S. I. Popel

    2006-01-01

    Full Text Available The results on shock phenomena in dusty plasmas of the Solar System are reviewed. The problems of dust ion acoustic bow shock in interaction of the solar wind with dusty cometary coma and formation of transient atmospheres of atmosphereless cosmic bodies such as Moon, Mercury, asteroids and comets are considered. The latter assumes the evolution of meteoroid impact plumes and production of charged dust grains due to the condensation of both the plume substance and the vapor thrown from the crater and the surrounding regolith layer. Physical phenomena occurring during large meteoroid impacts can be modeled with the aid of active rocket experiments, which involve the release of some gaseous substance in near-Earth space. New vistas in investigation of shock processes in natural dusty plasmas are determined.

  14. Monographella nivalis on the leof sheath of winter Triticale

    Directory of Open Access Journals (Sweden)

    Barbara Łacicowa

    2014-08-01

    Full Text Available Monographella nivatis (Schaffnit Mülier was found in 1983. Punctiform perithecia were scattered irregularly on the bleached tissues of the sheaths at the beginning of July. The ascospores were mostly mono- or bicellular. The cultures from the ascospores were producing typical conidia of the fungus Fusarium nivale (Fr. Ces. in exposure to light were successfuly cultivated on leafs of the wheat agar.

  15. A rare case of bilateral optic nerve sheath meningioma

    Directory of Open Access Journals (Sweden)

    Somen Misra

    2014-01-01

    Full Text Available A 60-year-old female presented with gradual, painless, progressive diminution of vision, and progressive proptosis of left eye since 7 years. Ophthalmological examination revealed mild proptosis and total optic atrophy in the left eye. Magnetic resonance imaging (MRI and computed tomography (CT brain with orbit showed bilateral optic nerve sheath meningioma (ONSM involving the intracranial, intracanalicular, intraorbital part of the optic nerve extending up to optic chiasma and left cavernous sinus.

  16. Giant cell tumor of tendon sheath: Spectrum of radiologic findings

    Energy Technology Data Exchange (ETDEWEB)

    Karasick, D.; Karasick, S. (Jefferson Medical Coll., Philadelphia, PA (United States) Thomas Jefferson Univ. Hospital, Philadelphia, PA (United States))

    1992-05-01

    Giant cell tumor of tendon sheath is the second most common tumor of the hand. It can also occur in larger joints. Radiologic features include a soft-tissue mass with or without osseous erosion. Less commonly, it can cause periostitis or permeative osseous invasion; it may rarely calcify. The entire imaging spectrum of this lesion is presented, with emphasis on atypical appearances which can mimic other lesions. (orig.).

  17. Photovoltaic sheathing element with one or more tabs

    Energy Technology Data Exchange (ETDEWEB)

    Keenihan, James R; Langmaid, Joseph A; Lopez, Leonardo C.

    2017-02-07

    The present invention is premised upon an assembly that includes at least a photovoltaic sheathing element capable of being affixed on a building structure. The shingle including at least a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly. Wherein the body portion includes one or more top peripheral tabs each capable of fitting under one or more vertically adjoining devices.

  18. Rice Sheath Rot: An Emerging Ubiquitous Destructive Disease Complex

    OpenAIRE

    Vincent de Paul Bigirimana; Khuong Hoang Gia Hua; Obedi Ishibwela Nyamangyoku; Monica eHöfte

    2015-01-01

    Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium spp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discolorati...

  19. The phenomena of social reality

    OpenAIRE

    Tina Kumelj; Barbara Turk

    2000-01-01

    Social reality originates from social interaction in a social group. It is consolidated with social consensus. It is transcendent and relatively stable. Social reality is maintained in relatively isolated, balanced social environment. Majority of members in a social group spontaneously reacts to deviations. These are characteristics which many authors contribute to social reality. If social reality is to be understood as a collection of social-psychological phenomena, of which the important f...

  20. New phenomena searches at CDF

    Energy Technology Data Exchange (ETDEWEB)

    Soha, Aron; /UC, Davis

    2006-04-01

    The authors report on recent results from the Collider Detector at Fermilab (CDF) experiment, which is accumulating data from proton-antiproton collisions with {radical}s = 1.96 TeV at Run II of the Fermilab Tevatron. The new phenomena being explored include Higgs, Supersymmetry, and large extra dimensions. They also present the latest results of searches for heavy objects, which would indicate physics beyond the Standard Model.

  1. Particle-in-cell simulation of an electronegative plasma under direct current bias studied in a large range of electronegativity

    Energy Technology Data Exchange (ETDEWEB)

    Oudini, N. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Laboratoire des plasmas de Decharges, Centre de Developement des Technologies Avancees, Cite du 20 Aout BP 17 Baba Hassen, 16081 Algiers (Algeria); Raimbault, J.-L.; Chabert, P.; Aanesland, A. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Meige, A. [PRESANS / X-Technologies/Ecole Polytechnique, 91128 Palaiseau Cedex (France)

    2013-04-15

    A one-dimensional electronegative plasma situated between two symmetrical parallel electrodes under DC bias is studied by Particle-In-Cell simulation with Monte Carlo Collisions. By varying the electronegativity {alpha}{identical_to}n{sub -}/n{sub e} from the limit of electron-ion plasmas (negative ion free) to ion-ion plasmas (electron free), the sheaths formation, the negative ion flux flowing towards the electrodes, and the particle velocities at the sheath edges are investigated. Depending on {alpha}, it is shown that the electronegative plasma behavior can be described by four regimes. In the lowest regime of {alpha}, i.e., {alpha} < 50, negative ions are confined by two positive sheaths within the plasma, while in the higher regimes of {alpha}, a negative sheath is formed and the negative ion flux can be extracted from the bulk plasma. In the two intermediate regimes of {alpha}, i.e., 50 < {alpha} < 10{sup 5}, both the electron and the negative ion fluxes are involved in the neutralization of the positive ions flux that leaves the plasma. In particular, we show that the velocity of the negative ions entering the negative sheath is affected by the presence of the electrons, and is not given by the modified Bohm velocity generally accepted for electronegative plasmas. For extremely high electronegativity, i.e., {alpha} > 10{sup 5}, the presence of electrons in the plasma is marginal and the electronegative plasma can be considered as an ion-ion plasma (electron free).

  2. Differential expression of angiogenic factors in peripheral nerve sheath tumors.

    Science.gov (United States)

    Wasa, Junji; Nishida, Yoshihiro; Suzuki, Yoshitaka; Tsukushi, Satoshi; Shido, Yoji; Hosono, Kozo; Shimoyama, Yoshie; Nakamura, Shigeo; Ishiguro, Naoki

    2008-01-01

    It is difficult to differentiate some malignant peripheral nerve sheath tumors (MPNST) from benign peripheral nerve sheath tumors (BPNST) histologically, and to predict the clinical outcome of patients with MPNST. In this study, the expression of VEGF and MVD were evaluated immunohistochemically in 22 cases of MPNST, 14 of neurofibroma and 19 of schwannoma and correlation of the staining grade of VEGF or MVD and the various clinical factors were analyzed, and statistically evaluated. Levels of VEGF mRNA expression were also determined with real-time RT-PCR. Statistically higher positive staining for VEGF was observed in MPNST compared to neurofibroma (P=0.004) and schwannoma (PMPNST showed higher VEGF positive staining than neurofibroma. Moreover, high VEGF expression statistically correlated with the poor prognosis of the patients with MPNST (P=0.015). Although MVD in MPNST was significantly higher than that in neurofibroma (P=0.038) and schwannoma (PMPNST. Although VEGF mRNA expression tended to be higher in MPNST compared to neurofibroma, the difference was not significant. Levels of VEGF protein expression serve as a novel diagnostic and prognostic tools for peripheral nerve sheath tumors.

  3. Luminous Phenomena - A Scientific Investigation of Anomalous Luminous Atmospheric Phenomena

    Science.gov (United States)

    Teodorani, M.

    2003-12-01

    Anomalous atmospheric luminous phenomena reoccur in several locations of Earth, in the form of multi-color light balls characterized by large dimensions, erratic motion, long duration and a correlated electromagnetic field. The author (an astrophysicist) of this book, which is organized as a selection of some of his technical and popularizing papers and seminars, describes and discusses all the efforts that have been done in 10 years, through several missions and a massive data analysis, in order to obtain some scientific explanation of this kind of anomalies, in particular the Hessdalen anomaly in Norway. The following topics are treated in the book: a) geographic archive of the areas of Earth where such phenomena are known to reoccur most often; b) observational techniques of astrophysical kind that have been used to acquire the data; c) main scientific results obtained so far; d) physical interpretation and natural hypothesis vs. ETV hypothesis; e) historical and chronological issues; f) the importance to brindle new energy sources; g) the importance to keep distance from any kind of "ufology". An unpublished chapter is entirely devoted to a detailed scientific investigation project of light phenomena reoccurring on the Ontario lake; the chosen new-generation multi-wavelength sensing instrumentation that is planned to be used in future missions in that specific area, is described together with scientific rationale and planned procedures. The main results, which were obtained in other areas of the world, such as the Arizona desert, USA and the Sibillini Mountains, Italy, are also briefly mentioned. One chapter is entirely dedicated to the presentation of extensive abstracts of technical papers by the author concerning this specific subject. The book is accompanied with a rich source of bibliographic references.

  4. PREFACE Integrability and nonlinear phenomena Integrability and nonlinear phenomena

    Science.gov (United States)

    Gómez-Ullate, David; Lombardo, Sara; Mañas, Manuel; Mazzocco, Marta; Nijhoff, Frank; Sommacal, Matteo

    2010-10-01

    Back in 1967, Clifford Gardner, John Greene, Martin Kruskal and Robert Miura published a seminal paper in Physical Review Letters which was to become a cornerstone in the theory of integrable systems. In 2006, the authors of this paper received the AMS Steele Prize. In this award the AMS pointed out that `In applications of mathematics, solitons and their descendants (kinks, anti-kinks, instantons, and breathers) have entered and changed such diverse fields as nonlinear optics, plasma physics, and ocean, atmospheric, and planetary sciences. Nonlinearity has undergone a revolution: from a nuisance to be eliminated, to a new tool to be exploited.' From this discovery the modern theory of integrability bloomed, leading scientists to a deep understanding of many nonlinear phenomena which is by no means reachable by perturbation methods or other previous tools from linear theories. Nonlinear phenomena appear everywhere in nature, their description and understanding is therefore of great interest both from the theoretical and applicative point of view. If a nonlinear phenomenon can be represented by an integrable system then we have at our disposal a variety of tools to achieve a better mathematical description of the phenomenon. This special issue is largely dedicated to investigations of nonlinear phenomena which are related to the concept of integrability, either involving integrable systems themselves or because they use techniques from the theory of integrability. The idea of this special issue originated during the 18th edition of the Nonlinear Evolution Equations and Dynamical Systems (NEEDS) workshop, held at Isola Rossa, Sardinia, Italy, 16-23 May 2009 (http://needs-conferences.net/2009/). The issue benefits from the occasion offered by the meeting, in particular by its mini-workshops programme, and contains invited review papers and contributed papers. It is worth pointing out that there was an open call for papers and all contributions were peer reviewed

  5. Separation phenomena in Liquids and Gases

    Energy Technology Data Exchange (ETDEWEB)

    Louvet, P.; Dr Soubbaramayer [CEA Saclay, Dept. des Lasers et de la Physico-Chimie, DESICP/DLPC/SPP, 91 - Gif-sur-Yvette (France); Noe, P

    1989-07-01

    technology was up to the task but the programme was shelved mainly because of lack of demand. Finally, seven papers deal with laser processes. Two of them review the AVLIS program in the UK and one paper gives the status of the MLIS project in West Germany. One communication from China and three papers by French authors deal with specific problems currently met in AVLIS studies, on the vapour beam and the ion extraction. A number of phenomena observed in AVLIS needs satisfactory explanations: the high value of the vapour velocity, the low value of metastables in the vapour beam, the extraction of ions at high density, etc. Session 1: plasma separation (review of isotopic plasma separation processes; production of depleted zirconium using a plasma centrifuge; measurements of isotope separation in a vacuum arc centrifuge). Session 2: plasma separation and centrifugation (recent developments in stable isotope separation by ionic cyclotron resonance; some aspects of the separation of multi-isotope mixtures with gas centrifuges; review paper on centrifuge technology and status of the URENCO centrifuge project; solution of the two-fluid equations for flow in a centrifuge; influence of stationary poles in the central region of gas centrifuges; extension of the analytic sixth order theory; applications of different analytic solutions for the centrifuge flow). Sessions 4 and 5: rotating flows (convection flows driven by centrifugal buoyancy in rapidly rotating systems; experimental investigation of the flow in a rotating pie-shaped cylinder; temperature distribution on rotating spherical shells; centrifugal separation of a suspension in a rotating vessel; spin-up from rest of a suspension - preliminary insight). Session 6: particle fluid mixture (modelling, simulation and comprehension of the flow field of a particles-fluid mixture; the effect of shear and lift on particle-gas separation; on the hydrodynamics of electrolytic refining of metals). Session 7 (calculation of condensation

  6. Interpretation of cell culture phenomena.

    Science.gov (United States)

    Vierck, J L; Dodson, M V

    2000-03-01

    This paper discusses the dilemma of interpreting unusual or abnormal phenomena seen in cell cultures and is not intended to address the statistical design of experiments. Problems that can be encountered when growing cells in experimental situations include low or decreasing cell numbers, abnormal cell morphology, microbial contamination, and detachment of the cell monolayer. If any of these situations occur, it is not realistic to proceed with data analysis until the problem is corrected. The best policy is to attempt to standardize all types of cultures used for analysis and to avoid using any cultures that display atypical characteristics.

  7. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2001-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in

  8. Violent phenomena in the Universe

    CERN Document Server

    Narlikar, Jayant V

    2007-01-01

    The serenity of a clear night sky belies the evidence-gathered by balloons, rockets, satellites, and telescopes-that the universe contains centers of furious activity that pour out vast amounts of energy, some in regular cycles and some in gigantic bursts. This reader-friendly book, acclaimed by Nature as ""excellent and uncompromising,"" traces the development of modern astrophysics and its explanations of these startling celestial fireworks.This lively narrative ranges from the gravitational theories of Newton and Einstein to recent exciting discoveries of such violent phenomena as supernova

  9. Nonlinear Dynamic Phenomena in Mechanics

    CERN Document Server

    Warminski, Jerzy; Cartmell, Matthew P

    2012-01-01

    Nonlinear phenomena should play a crucial role in the design and control of engineering systems and structures as they can drastically change the prevailing dynamical responses. This book covers theoretical and applications-based problems of nonlinear dynamics concerned with both discrete and continuous systems of interest in civil and mechanical engineering. They include pendulum-like systems, slender footbridges, shape memory alloys, sagged elastic cables and non-smooth problems. Pendulums can be used as a dynamic absorber mounted in high buildings, bridges or chimneys. Geometrical nonlinear

  10. Quantum theory of collective phenomena

    CERN Document Server

    Sewell, G L

    2014-01-01

    ""An excellent and competent introduction to the field … [and] … a source of information for the expert."" - Physics Today""This a book of major importance…. I trust that this book will be used as a basis for the teaching of a balanced, modern and rigorous course on statistical mechanics in all universities."" - Bulletin of the London Mathematical Society""This is one of the best introductions to the subject, and it is strongly recommended to anyone interested in collective phenomena."" - Physics Bulletin ""The book may be recommended for students as a well-balanced introduction to this rich s

  11. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2000-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m

  12. "Orphan" $\\gamma$-ray Flares and Stationary Sheaths of Blazar Jets

    CERN Document Server

    MacDonald, Nicholas R; Marscher, Alan P

    2016-01-01

    Blazars exhibit flares across the entire electromagnetic spectrum. Many $\\gamma$-ray flares are highly correlated with flares detected at longer wavelengths; however, a small subset appears to occur in isolation, with little or no correlated variability at longer wavelengths. These "orphan" $\\gamma$-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. Macdonald et al. have developed the Ring of Fire model to explain the origin of orphan $\\gamma$-ray flares from within blazar jets. In this model, electrons contained within a blob of plasma moving relativistically along the spine of the jet inverse-Compton scatter synchrotron photons emanating off of a ring of shocked sheath plasma that enshrouds the jet spine. As the blob propagates through the ring, the scattering of the ring photons by the blob electrons creates an orphan $\\gamma$-ray flare. This model was successfully applied to modeling a prominent orphan $\\gamma$-ray flare observed in the ...

  13. Ultrasound-induced encapsulated microbubble phenomena

    NARCIS (Netherlands)

    Postema, Michiel; Wamel, van Annemieke; Lancée, Charles T.; Jong, de Nico

    2004-01-01

    When encapsulated microbubbles are subjected to high-amplitude ultrasound, the following phenomena have been reported: oscillation, translation, coalescence, fragmentation, sonic cracking and jetting. In this paper, we explain these phenomena, based on theories that were validated for relatively big

  14. Functional theories of thermoelectric phenomena

    Science.gov (United States)

    Eich, F. G.; Di Ventra, M.; Vignale, G.

    2017-02-01

    We review the progress that has been recently made in the application of time-dependent density functional theory to thermoelectric phenomena. As the field is very young, we emphasize open problems and fundamental issues. We begin by introducing the formal structure of thermal density functional theory, a density functional theory with two basic variables—the density and the energy density—and two conjugate fields—the ordinary scalar potential and Luttinger’s thermomechanical potential. The static version of this theory is contrasted with the familiar finite-temperature density functional theory, in which only the density is a variable. We then proceed to constructing the full time-dependent non equilibrium theory, including the practically important Kohn-Sham equations that go with it. The theory is shown to recover standard results of the Landauer theory for thermal transport in the steady state, while showing greater flexibility by allowing a description of fast thermal response, temperature oscillations and related phenomena. Several results are presented here for the first time, i.e. the proof of invertibility of the thermal response function in the linear regime, the full expression of the thermal currents in the presence of Luttinger’s thermomechanical potential, an explicit prescription for the evaluation of the Kohn-Sham potentials in the adiabatic local density approximation, a detailed discussion of the leading dissipative corrections to the adiabatic local density approximation and the thermal corrections to the resistivity that follow from it.

  15. Design of Cold-Formed Steel Screw Connections with Gypsum Sheathing at Ambient and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2016-09-01

    Full Text Available Load-bearing cold-formed steel (CFS walls sheathed with double layers of gypsum plasterboard on both sides have demonstrated good fire resistance and attracted increasing interest for use in mid-rise CFS structures. As the main connection method, screw connections between CFS and gypsum sheathing play an important role in both the structural design and fire resistance of this wall system. However, studies on the mechanical behavior of screw connections with double-layer gypsum sheathing are still limited. In this study, 200 monotonic tests of screw connections with single- or double-layer gypsum sheathing at both ambient and elevated temperatures were conducted. The failure of screw connections with double-layer gypsum sheathing in shear was different from that of single-layer gypsum sheathing connections at ambient temperature, and it could be described as the breaking of the loaded sheathing edge combined with significant screw tilting and the loaded sheathing edge flexing fracture. However, the screw tilting and flexing fracture of the loaded sheathing edge gradually disappear at elevated temperatures. In addition, the influence of the loaded edge distance, double-layer sheathing and elevated temperatures is discussed in detail with clear conclusions. A unified design formula for the shear strength of screw connections with gypsum sheathing is proposed for ambient and elevated temperatures with adequate accuracy. A simplified load–displacement model with the post-peak branch is developed to evaluate the load–displacement response of screw connections with gypsum sheathing at ambient and elevated temperatures.

  16. Novel Therapeutic Development of NF1-Associated Malignant Peripheral Nerve Sheath Tumor (MPNST)

    Science.gov (United States)

    2016-08-01

    AWARD NUMBER: W81XWH-15-1-0124 TITLE: Novel Therapeutic Development of NF1-Associated Malignant Peripheral Nerve Sheath Tumor (MPNST...Nerve Sheath Tumor (MPNST) 5b. GRANT NUMBER W81XWH-15-1-0124 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Ping Chi, MD, PhD 5e. TASK...that affects approximately 1 in 3000 people. Although multiple defects can arise, malignant peripheral nerve sheath tumor (MPNST) represents the most

  17. Solar system plasma waves

    Science.gov (United States)

    Gurnett, Donald A.

    1995-01-01

    An overview is given of spacecraft observations of plasma waves in the solar system. In situ measurements of plasma phenomena have now been obtained at all of the planets except Mercury and Pluto, and in the interplanetary medium at heliocentric radial distances ranging from 0.29 to 58 AU. To illustrate the range of phenomena involved, we discuss plasma waves in three regions of physical interest: (1) planetary radiation belts, (2) planetary auroral acceleration regions and (3) the solar wind. In each region we describe examples of plasma waves that are of some importance, either due to the role they play in determining the physical properties of the plasma, or to the unique mechanism involved in their generation.

  18. Dynacore Final Report , Plasma Physics prototype

    NARCIS (Netherlands)

    Lourens, W.

    2001-01-01

    The generation and behaviour of plasma in a fusion device and its interaction with sur-rounding materials is studied by observing several phenomena that will accompany a plasma discharge. These phenomena are recorded by means of so called Diagnostics. These are instruments that comprise complex elec

  19. Black Hole Critical Phenomena Without Black Holes

    CERN Document Server

    Liebling, S L

    2000-01-01

    Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.

  20. Near-wall conductivity effect under a space-charge-saturated sheath in the Hall thruster

    Institute of Scientific and Technical Information of China (English)

    Zhang Feng-Kui; Ding Yong-Jie; Qing Shao-Wei; Wu Xian-De

    2011-01-01

    In this paper,we adopt the modified Morozov secondary electron emission model to investigate the influence of the characteristic of a space-charge-saturated sheath near the insulated wall of the Hall thruster on the near-wall conductivity,by the method of two-dimensional (2D) particle simulation (2D+3V).The results show that due to the sharp increase of collision frequency between the electrons and the wall under the space-charge-saturated sheath,the near-wall transport current under this sheath is remarkably higher than that under a classical sheath,and equals the near-wall transport current under a spatially oscillating sheath in order of magnitude.However,the transport currents under a space-charge-saturated sheath and a spatially oscillating sheath are different in mechanism,causing different current density distributions under the above two sheaths,and a great influence of channel width on the near-wall transport current under a space-charge-saturated sheath.

  1. Theoretical Study of a Spherical Plasma Focus

    Science.gov (United States)

    Ay, Yasar

    A theoretical model is developed for two concentric electrodes spherical plasma focus device in order to investigate the plasma sheath dynamics, radiative emission, and the ion properties. The work focuses on the model development of the plasma sheath dynamics and its validation, followed by studying of the radiation effects and the beam-ion properties in such unique geometry as a pulsed source for neutrons, soft and hard x-rays, and electron and ion beams. Chapter 1 is an introduction on fusion systems including plasma focus. Chapter 2 is an extensive literature survey on plasma focus modeling and experiments including the various radiations and their mechanism. Chapter 3 details modeling and validation of the plasma sheath dynamics model with comparison between hydrogen, deuterium, tritium and deuterium-tritium mixture for the production of pulsed neutrons. Chapter 4 is a study of the radiative phase, in which neutron yield is investigated, as well as the predicted beam-ion properties. Chapter 5 summarizes and discusses the results. Chapter 6 provides concluding remarks and proposed future works. The phases of the developed model are the rundown phase I, rundown phase II, the reflected phase and a radiative phase. The rundown phase I starts immediately after the completion of the gas breakdown and ends when the current sheath reaches the equator point of the spherical shape. Then immediately followed by rundown phase II to start and it ends when the shock front hits the axis, which is the beginning of the reflected shock phase. Reflected shock front moves towards the incoming current sheath and meets it which is both the end of the reflected shock phase and the beginning of the radiative phase. After the reflected shock front and the current sheath meet, the current sheath continues to move radially inward by compressing the produced plasma column until it reaches the axis. Since the discharge current contains important information about the plasma dynamic

  2. Oscillating plasma bubbles. III. Internal electron sources and sinks

    Energy Technology Data Exchange (ETDEWEB)

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    An internal electron source has been used to neutralize ions injected from an ambient plasma into a spherical grid. The resultant plasma is termed a plasma 'bubble.' When the electron supply from the filament is reduced, the sheath inside the bubble becomes unstable. The plasma potential of the bubble oscillates near but below the ion plasma frequency. Different modes of oscillations have been observed as well as a subharmonic and multiple harmonics. The frequency increases with ion density and decreases with electron density. The peak amplitude occurs for an optimum current and the instability is quenched at large electron densities. The frequency also increases if Langmuir probes inside the bubble draw electrons. Allowing electrons from the ambient plasma to enter, the bubble changes the frequency dependence on grid voltage. It is concluded that the net space charge density in the sheath determines the oscillation frequency. It is suggested that the sheath instability is caused by ion inertia in an oscillating sheath electric field which is created by ion bunching.

  3. Comparative Oncogenomics for Peripheral Nerve Sheath Cancer Gene Discovery

    Science.gov (United States)

    2015-06-01

    pathway is often dysregulated (7-15). This can occur via multiple mechanisms including CDK4 overexpression, a loss of Rb expression or inappropriate...Malignant transformation of neurofibromas in neurofibromatosis 1 is associated with CDKN2A/ p16 inactivation. Am J Pathol. 1999;155:1879-84. 10. Birindelli S...nerve sheath tumors. Lab Invest. 2001;81:833-44. 11. Perry A, Kunz SN, Fuller CE, Banerjee R, Marley EF, Liapis H, et al. Differential NF1, p16 , and

  4. Retracted: Spontaneous rectus sheath haematoma associated with rivaroxaban treatment.

    Science.gov (United States)

    Tas Tuna, A; Palabiyik, O; Beyaz, S G

    2015-08-01

    http://onlinelibrary.wiley.com/doi/10.1111/jcpt.12228/pdf The above article, published online on 10 November 2014 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, A. Li Wan Po, and John Wiley & Sons Ltd. The retraction has been agreed because, unknown to the authors, another group published a similar study based on the same material in the Indian Journal of Pharmacology: Kocayigit I, Can Y, Sahinkus S, et al. Spontaneous rectus sheath haematoma during rivaroxaban therapy. Indian Journal of Pharmacology. 2014;46(3):339-340. doi:10.4103/0253-7613.132193.

  5. Malignant Peripheral Nerve Sheath Tumor - A Case Report

    Directory of Open Access Journals (Sweden)

    Anju N Duttargi

    2007-01-01

    Full Text Available Malignant Peripheral Nerve Sheath Tumor [MPNST] is an extremely rare tumor affecting the oral cavity. It refers to sarcomas that arise from nerve or display features of neural differentiation. Here we present a case of 30-year old male patient with MPNST of right side of the mandible. There was a family history of neurotibromatosis in this case. Histologically, pleomorphic spindle cells with wavy nuclei, light stained cytoplasm, and mitotic activity were observed. The clinical presentation, radiological findings, and light microscopic findings are described in detail. The criteria for diagnosing these tumors and recent advances for diagnosis have also been highlighted.

  6. Malignant peripheral nerve sheath tumor with divergent differentiation

    Directory of Open Access Journals (Sweden)

    Suresh T

    2009-01-01

    Full Text Available A malignant peripheral nerve sheath tumor (MPNST is an uncommon spindle cell sarcoma accounting for approximately 5% of all soft tissue sarcomas. A 55-year-old female with a right suprarenal tumor showed MPNST with additional foci of epithelioid, rhabdomyoblastic, osteogenic and lipogenic differentiation. Although the capacity of MPNST to undergo epithelioid, rhabdomyoblastic, osteogenic and very rarely lipogenic differentiation is reported in literature, the occurrence of all these differentiation in one case has not been described in literature before. To the best of our knowledge, this is only the second MPNST case with lipomatous differentiation

  7. Malignant Peripheral Nerve Sheath Tumour: CT and MRI Findings

    Directory of Open Access Journals (Sweden)

    Massimiliano Sperandio

    2013-01-01

    Full Text Available Malignant peripheral nerve sheath tumour (MPNST is extremely rare malignancy in the general population, occurring more frequently in patients with Neurofibromatosis type 1 (NF1. In the literature five cases of MPNST arising from the parapharyngeal space (PPS in patients without neurofibromatosis have been reported. We report imaging techniques in a patient with MPNST in the PPS, who had neither a family history nor sign of NF1. Computed tomography (CT scan and magnetic resonance imaging (MRI were performed for a correct therapeutic planning. CT and MRI findings were correlated with hystopathological diagnosis.

  8. Balloon angioplasty for disruption of tunneled dialysis catheter fibrin sheath.

    Science.gov (United States)

    Watorek, Ewa; Golebiowski, Tomasz; Letachowicz, Krzysztof; Garcarek, Jerzy; Kurcz, Jacek; Bartosik, Hanna Augustyniak; Letachowicz, Waldemar; Weyde, Waclaw; Klinger, Marian

    2012-01-01

    Management of failing tunneled hemodialysis catheters, sometimes the only vascular access for hemodialysis, presents a difficult problem. In spite of various techniques having been developed, no consensus has been reached about the preferred technique, associated with the longest catheter patency. We report disruption of the fibrin sheath covering dysfunctional tunneled hemodialysis catheter by means of angioplasty, followed by over guidewire catheter exchange. Following the procedure, the catheter placed in the recovered lumen of the vessel presented correct function. The described procedure allowed maintenance of vascular access in our patient. Additionally, dilatation of the concomitant central vein stenosis opens an option for another attempt for arteriovenous fistula creation.

  9. The new concept of ureteral access sheath with guidewire disengagement

    DEFF Research Database (Denmark)

    Breda, Alberto; Emiliani, Esteban; Millán, Felix

    2016-01-01

    was the only independent factor for a successful access sheath insertion: 98.5 % of the pre-stented patients had a successful UAS placement vs. 82 % of non-pre-stented (p = 0.001, C.I. 95 %: 1.2). Evaluation of the material and radiopacity was considered very good in over 90 % of cases. Release...... guidewire in a prospective multicentric scenario was clinically applicable in the majority of cases. Pre-stenting increased the chance of a successful insertion from 82 to 98.5 %....

  10. Cystic change in primary paediatric optic nerve sheath meningioma.

    Science.gov (United States)

    Narayan, Daniel; Rajak, Saul; Patel, Sandy; Selva, Dinesh

    2016-08-01

    Primary optic nerve sheath meningiomas (PONSM) are rare in children. Cystic meningiomas are an uncommon subgroup of meningiomas. We report a case of paediatric PONSM managed using observation alone that underwent cystic change and radiological regression. A 5-year-old girl presented with visual impairment and proptosis. Magnetic resonance (MR) imaging demonstrated a PONSM. The patient was left untreated and followed up with regular MR imaging. Repeat imaging at 16 years of age showed the tumour had started to develop cystic change. Repeat imaging at 21 years of age showed the tumour had decreased in size.

  11. Fundamental studies of fusion plasmas. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Aamodt, R.E.

    1998-01-30

    Lodestar has carried out a vigorous research program in the areas of rf, edge plasma and divertor physics, with emphasis largely geared towards improving the understanding and performance of ion-cyclotron heating and current drive (ICRF) systems. Additionally, a research program in the field of edge plasma and divertor modeling was initiated. Theoretical work on high power rf sheath formation for multi-strap rf arrays was developed and benchmarked against recent experimental data from the new JET A2 antennas. Sophisticated modeling tools were employed to understand the sheath formation taking into account realistic three-dimensional antenna geometry. A novel physics explanation of an observed anomaly in the low power loading of antennas was applied to qualitatively interpret data on DIII-D in terms of rf sheaths, and potential applications of the idea to develop a near-field sheath diagnostic were explored. Other rf-wave related topics were also investigated. Full wave ICRF modeling studies were carried out in support of ongoing and planned tokamaks experiments, including the investigation of low frequency plasma heating and current drive regimes for IGNITOR. In a cross-disciplinary study involving both MHD and ICRF physics, ponderomotive feedback stabilization by rf was investigated as a potential means of controlling external kink mode disruptions. In another study, the instability of the ion hybrid wave (IHW) in the presence of fusion alpha particles was studied. In the field of edge plasma and divertor modeling studies, Lodestar began the development of a theory of generalized ballooning and sheath instabilities in the scrape off layer (SOL) of divertor tokamaks. A detailed summary of the technical progress in these areas during the contract period is included, as well as where references to published work can be found. A separate listing of publications, meeting abstracts, and other presentations is also given at the end of this final report.

  12. Multiple Time and Spatial Scale Plasma Simulation -Prospect Based on Current Status- 5.Prospect for Multiple Time and Spatial Scale Simulation Research in Astrophysical Plasma Phenomena 5.2Grand Challenge for Studying the History of Universe from the Dark Ages to the Solar System

    Science.gov (United States)

    Takabe, Hideaki; Computational Observatory Project, Hideaki

    We intend to reveal the physics of the evolution of the Universe from the pre-formation stage of the first stars to the structure and phenomena of the present solar system through the use of large-scale supercomputing. This project is named ”Computational Observatory” and sixteen research groups from throughout Japanare attempting simulations of four subjects in the different phases of the evolution of the Universe after the dark ages. This project involves finding numerical methods to very hierarchical problems regarding space and time. At the same time, a variety of complex physics should be modeled in the codes that are to be developed. A so-called integrated code for each subject should be developed. The integrated codes, of course, should be checked and improved through comparisons with observational and experimental data. Throughout this project, we would like to analyze not only observational data but also to predict, for example, what new findings we could obtain if we increase the resolution of observation instruments in the future. This project consists a great challenge in computer science in regard to developing a highly integrated system with very hierarchical phenomena..

  13. Space plasma physics results from Spacelab 1

    Science.gov (United States)

    Burch, J. L.

    1985-01-01

    The Spacelab 1 payload carried several instrument systems which together investigated a number of space plasma phenomena. These experiments used the Space Shuttle Orbiter as a platform for making controlled particle-beam, plasma and neutral gas inputs to the ionosphere and magnetosphere and for observing the outputs produced. Spacelab 1 space-plasma investigations included the Space Experiments with Particle Accelerators (SEPAC), Phenomena Induced by Charged Particle Beams (PICPAB), Atmospheric Emissions Photometric Imaging (AEPI) and the Low Energy Electron Spectrometer and Magnetometer. Among the major phenomena investigated both singly and jointly by these experiments are vehicle charging and neutralization, beam-plasma and wave-particle interactions, anomalous ionization phenomena produced by neutral-gas and plasma injections and several phenomena induced by modulated particle beam injections.

  14. Superfluid analogies of cosmological phenomena

    CERN Document Server

    Volovik, G E

    2001-01-01

    Superfluid 3He-A gives example of how chirality, Weyl fermions, gauge fields and gravity appear in low emergy corner together with corresponding symmetries, including Lorentz symmetry and local SU(N). This supports idea that quantum field theory (Standard Model or GUT) is effective theory describing low-energy phenomena. * Momentum space topology of fermionic vacuum provides topological stability of universality class of systems, where above properties appear. * BCS scheme for 3He-A incorporates both ``relativistic'' infrared regime and ultraviolet ``transplanckian'' range: subtle issues of cut-off in quantum field theory and anomalies can be resolved on physical grounds. This allows to separate ``renormalizable'' terms in action, treated by effective theory, from those obtained only in ``transPlanckian'' physics. * Energy density of superfluid vacuum within effective theory is ~ E_{Planck}^4. Stability analysis of ground state beyond effective theory leads to exact nullification of vacuum energy: equilibrium...

  15. Interpolating function and Stokes Phenomena

    CERN Document Server

    Honda, Masazumi

    2015-01-01

    When we have two expansions of physical quantity around two different points in parameter space, we can usually construct a family of functions, which interpolates the both expansions. In this paper we study analytic structures of such interpolating functions and discuss their physical implications. We propose that the analytic structures of the interpolating functions provide information on analytic property and Stokes phenomena of the physical quantity, which we approximate by the interpolating functions. We explicitly check our proposal for partition functions of zero-dimensional $\\varphi^4$ theory and Sine-Gordon model. In the zero dimensional Sine-Gordon model, we compare our result with a recent result from resurgence analysis. We also comment on construction of interpolating function in Borel plane.

  16. Earthquake prediction with electromagnetic phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Hayakawa, Masashi, E-mail: hayakawa@hi-seismo-em.jp [Hayakawa Institute of Seismo Electomagnetics, Co. Ltd., University of Electro-Communications (UEC) Incubation Center, 1-5-1 Chofugaoka, Chofu Tokyo, 182-8585 (Japan); Advanced Wireless & Communications Research Center, UEC, Chofu Tokyo (Japan); Earthquake Analysis Laboratory, Information Systems Inc., 4-8-15, Minami-aoyama, Minato-ku, Tokyo, 107-0062 (Japan); Fuji Security Systems. Co. Ltd., Iwato-cho 1, Shinjyuku-ku, Tokyo (Japan)

    2016-02-01

    Short-term earthquake (EQ) prediction is defined as prospective prediction with the time scale of about one week, which is considered to be one of the most important and urgent topics for the human beings. If this short-term prediction is realized, casualty will be drastically reduced. Unlike the conventional seismic measurement, we proposed the use of electromagnetic phenomena as precursors to EQs in the prediction, and an extensive amount of progress has been achieved in the field of seismo-electromagnetics during the last two decades. This paper deals with the review on this short-term EQ prediction, including the impossibility myth of EQs prediction by seismometers, the reason why we are interested in electromagnetics, the history of seismo-electromagnetics, the ionospheric perturbation as the most promising candidate of EQ prediction, then the future of EQ predictology from two standpoints of a practical science and a pure science, and finally a brief summary.

  17. Induced-charge Electrokinetic Phenomena

    CERN Document Server

    Bazant, M Z; Bazant, Martin Z.; Squires, Todd M.

    2003-01-01

    Motivated by the recent discovery of AC electro-osmosis near micro-electrodes, we predict a broad class of nonlinear electrokinetic phenomena involving induced interfacial charge. By considering various polarizable objects (metals or dielectrics) in DC and AC applied fields, we develop a simple physical picture of `induced-charge electro-osmosis' (ICEO), the fluid slip at a surface due to an electric field acting on the diffuse charge it induces. We also discuss `induced-charge electrophoresis' (ICEP), the analogous motion of a freely-suspended polarizable particle. Both differ significantly from their classical linear counterparts. We present a mathematical theory of ICEO flows in the weakly nonlinear limit of thin double layers. As an example, we calculate the time-dependent ICEO slip around a metallic sphere with a thin dielectric coating in a suddenly-applied DC field. We briefly discuss possible applications of ICEO to microfluidics and of ICEP to colloidal manipulation.

  18. Interference Phenomena in Quantum Information

    CERN Document Server

    Stefanak, Martin

    2010-01-01

    One of the key features of quantum mechanics is the interference of probability amplitudes. The reason for the appearance of interference is mathematically very simple. It is the linear structure of the Hilbert space which is used for the description of quantum systems. In terms of physics we usually talk about the superposition principle valid for individual and composed quantum objects. So, while the source of interference is understandable it leads in fact to many counter-intuitive physical phenomena which puzzle physicists for almost hundred years. The present thesis studies interference in two seemingly disjoint fields of physics. However, both have strong links to quantum information processing and hence are related. In the first part we study the intriguing properties of quantum walks. In the second part we analyze a sophisticated application of wave packet dynamics in atoms and molecules for factorization of integers. The main body of the thesis is based on the original contributions listed separately...

  19. Transport phenomena in porous media

    CERN Document Server

    Ingham, Derek B

    1998-01-01

    Research into thermal convection in porous media has substantially increased during recent years due to its numerous practical applications. These problems have attracted the attention of industrialists, engineers and scientists from many very diversified disciplines, such as applied mathematics, chemical, civil, environmental, mechanical and nuclear engineering, geothermal physics and food science. Thus, there is a wealth of information now available on convective processes in porous media and it is therefore appropriate and timely to undertake a new critical evaluation of this contemporary information. Transport Phenomena in Porous Media contains 17 chapters and represents the collective work of 27 of the world's leading experts, from 12 countries, in heat transfer in porous media. The recent intensive research in this area has substantially raised the expectations for numerous new practical applications and this makes the book a most timely addition to the existing literature. It includes recent major deve...

  20. Critical Phenomena in Gravitational Collapse

    Directory of Open Access Journals (Sweden)

    Martín-García José M.

    2007-12-01

    Full Text Available As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term “critical phenomena”. They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. Critical phenomena give a natural route from smooth initial data to arbitrarily large curvatures visible from infinity, and are therefore likely to be relevant for cosmic censorship, quantum gravity, astrophysics, and our general understanding of the dynamics of general relativity.

  1. Emergent Phenomena at Oxide Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, H.Y.

    2012-02-16

    Transition metal oxides (TMOs) are an ideal arena for the study of electronic correlations because the s-electrons of the transition metal ions are removed and transferred to oxygen ions, and hence the strongly correlated d-electrons determine their physical properties such as electrical transport, magnetism, optical response, thermal conductivity, and superconductivity. These electron correlations prohibit the double occupancy of metal sites and induce a local entanglement of charge, spin, and orbital degrees of freedom. This gives rise to a variety of phenomena, e.g., Mott insulators, various charge/spin/orbital orderings, metal-insulator transitions, multiferroics, and superconductivity. In recent years, there has been a burst of activity to manipulate these phenomena, as well as create new ones, using oxide heterostructures. Most fundamental to understanding the physical properties of TMOs is the concept of symmetry of the order parameter. As Landau recognized, the essence of phase transitions is the change of the symmetry. For example, ferromagnetic ordering breaks the rotational symmetry in spin space, i.e., the ordered phase has lower symmetry than the Hamiltonian of the system. There are three most important symmetries to be considered here. (i) Spatial inversion (I), defined as r {yields} -r. In the case of an insulator, breaking this symmetry can lead to spontaneous electric polarization, i.e. ferroelectricity, or pyroelectricity once the point group belongs to polar group symmetry. (ii) Time-reversal symmetry (T) defined as t {yields} -t. In quantum mechanics, the time-evolution of the wave-function {Psi} is given by the phase factor e{sup -iEt/{h_bar}} with E being the energy, and hence time-reversal basically corresponds to taking the complex conjugate of the wave-function. Also the spin, which is induced by the 'spinning' of the particle, is reversed by time-reversal. Broken T-symmetry is most naturally associated with magnetism, since the

  2. Autistic phenomena in neurotic patients.

    Science.gov (United States)

    Klien, S

    1980-01-01

    I have described a group of patients who are seemingly successful in their professional and social lives, and who seek analysis ostensibly for professional reasons or for minor difficulties in their relationship. However, sooner or later they reveal phenomena which are strikingly similar to those observed in so-called autistic children. These autistic phenomena are characterized by an almost impenetrable encapsulation of part of the personality, mute and implacable resistance to change, and a lack of real emotional contact either with themselves or the analyst. Progress of the analysis reveals an underlying intense fear of pain, and of death, disintegration or breakdown. These anxieties occur as a reaction to real or feared separation, especially when commitment to analysis deepens. In the case I have described in detail the patient used various projective processes to deflect painful emotions either into other people, including the analyst, or into their own bodies. As a consequence the various objects or organs of the body swell up and became suffused with rage as a result of having to contain the unwanted feelings. This process leads in turn to intense persecutory fears and a heightened sensitivity to the analyst's tone of voice and facial expression. It would seem that the initial hypersensitivity of part of the personality is such as to lead it to anticipate danger to such an extent that it expels feelings even before they reach awareness. The sooner the analyst realizes the existence of this hidden part of the patient the less the danger of the analysis becoming an endless and meaningless intellectual dialogue and the greater the possibilities of the patient achieving a relatively stable equilibrium. Although the analyst has to live through a great deal of anxiety with the patient I feel that ultimately the results make it worth while.

  3. Solar wind plasma interaction with solar probe plus spacecraft

    Energy Technology Data Exchange (ETDEWEB)

    Guillemant, S. [Univ. Paul Sabatier de Toulouse et CNRS, Toulouse (FR). IRAP (Inst. der Recherche en Astrophysique et Planetologie); ONERA (Office National d' Etudes et Recherches Aerospatiales), Toulouse (France); Genot, V.; Louarn, P. [Univ. Paul Sabatier de Toulouse et CNRS, Toulouse (FR). IRAP (Inst. der Recherche en Astrophysique et Planetologie); Mateo-Velez, J.C. [ONERA (Office National d' Etudes et Recherches Aerospatiales), Toulouse (France); Ergun, R. [Colorado Univ., Boulder, CO (United States). Lab. for Atmospheric and Space Physics

    2012-07-01

    3-D PIC (Particle In Cell) simulations of spacecraft-plasma interactions in the solar wind context of the Solar Probe Plus mission are presented. The SPIS software is used to simulate a simplified probe in the near-Sun environment (at a distance of 0.044AU or 9.5 R{sub S} from the Sun surface).We begin this study with a cross comparison of SPIS with another PIC code, aiming at providing the static potential structure surrounding a spacecraft in a high photoelectron environment. This paper presents then a sensitivity study using generic SPIS capabilities, investigating the role of some physical phenomena and numerical models. It confirms that in the near- sun environment, the Solar Probe Plus spacecraft would rather be negatively charged, despite the high yield of photoemission. This negative potential is explained through the dense sheath of photoelectrons and secondary electrons both emitted with low energies (2-3 eV). Due to this low energy of emission, these particles are not ejected at an infinite distance of the spacecraft and would rather surround it. As involved densities of photoelectrons can reach 10{sup 6} cm{sup -3} (compared to ambient ions and electrons densities of about 7 x 10{sup 3} cm{sup -3}), those populations affect the surrounding plasma potential generating potential barriers for low energy electrons, leading to high recollection. This charging could interfere with the low energy (up to a few tens of eV) plasma sensors and particle detectors, by biasing the particle distribution functions measured by the instruments. Moreover, if the spacecraft charges to large negative potentials, the problem will be more severe as low energy electrons will not be seen at all. The importance of the modelling requirements in terms of precise prediction of spacecraft potential is also discussed. (orig.)

  4. Remote sensing of natural phenomena

    Directory of Open Access Journals (Sweden)

    Miodrag D. Regodić

    2014-06-01

    Full Text Available There has always been a need to directly perceive and study the events whose extent is beyond people's possibilities. In order to get new data and to make observations and studying much more objective in comparison with past syntheses - a new method of examination called remote sensing has been adopted. The paper deals with the principles and elements of remote sensing, as well as with the basic aspects of using remote research in examining meteorological (weather parameters and the conditions of the atmosphere. The usage of satellite images is possible in all phases of the global and systematic research of different natural phenomena when airplane and satellite images of different characteristics are used and their analysis and interpretation is carried out by viewing and computer added procedures. Introduction Remote sensing of the Earth enables observing and studying global and local events that occur on it. Satellite images are nowadays used in geology, agriculture, forestry, geodesy, meteorology, spatial and urbanism planning, designing of infrastructure and other objects, protection from natural and technological catastrophes, etc. It it possible to use satellite images in all phases of global and systematic research of different natural phenomena. Basics of remote sensing Remote sensing is a method of the acquisition and interpretation of information about remote objects without making a physical contact with them. The term Daljinska detekcija is a literal translation of the English term Remote Sensing. In French it isTeledetection, in German - Fernerkundung, in Russian - дистанционие иследования. We also use terms such as: remote survailance, remote research, teledetection, remote methods, and distance research. The basic elements included in Remote Sensing are: object, electromagnetic energy, sensor, platform, image, analysis, interpretation and the information (data, fact. Usage of satellite remote research in

  5. Kinetic theory and transport phenomena

    CERN Document Server

    Soto, Rodrigo

    2016-01-01

    This textbook presents kinetic theory, which is a systematic approach to describing nonequilibrium systems. The text is balanced between the fundamental concepts of kinetic theory (irreversibility, transport processes, separation of time scales, conservations, coarse graining, distribution functions, etc.) and the results and predictions of the theory, where the relevant properties of different systems are computed. The book is organised in thematic chapters where different paradigmatic systems are studied. The specific features of these systems are described, building and analysing the appropriate kinetic equations. Specifically, the book considers the classical transport of charges, the dynamics of classical gases, Brownian motion, plasmas, and self-gravitating systems, quantum gases, the electronic transport in solids and, finally, semiconductors. Besides these systems that are studied in detail, concepts are applied to some modern examples including the quark–gluon plasma, the motion of bacterial suspen...

  6. Radial interchange motions of plasma filaments

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Fundamenski, W.

    2006-01-01

    Radial convection of isolated filamentary structures due to interchange motions in magnetized plasmas is investigated. Following a basic discussion of vorticity generation, ballooning, and the role of sheaths, a two-field interchange model is studied by means of numerical simulations...... on a biperiodic domain perpendicular to the magnetic field. It is demonstrated that a blob-like plasma structure develops dipolar vorticity and electrostatic potential fields, resulting in rapid radial acceleration and formation of a steep front and a trailing wake. While the dynamical evolution strongly depends...... as the acoustic speed times the square root of the structure size relative to the length scale of the magnetic field. The plasma filament eventually decelerates due to mixing and collisional dissipation. Finally, the role of sheath dissipation is investigated. When included in the simulations, it significantly...

  7. Which ureteral access sheath is compatible with your flexible ureteroscope?

    Science.gov (United States)

    Al-Qahtani, Saeed M; Letendre, Julien; Thomas, Alexandre; Natalin, Ricardo; Saussez, Thibaud; Traxer, Olivier

    2014-03-01

    Our aim is to evaluate different ureteral access sheaths (UASs), which are available in the international market and their compatibility with different available flexible ureteroscopes (F-URSs) to help the urologist choose the proper ureteral access sheath for his or her endoscope before commencing the procedure. A total of 21 UASs and 12 F-URSs were evaluated. Measurements were obtained in French (F) units considering different characteristics for each UAS and each F-URS. Insertion test without friction between F-URS and UAS was considered as a successful test and was referred as (YES). All UASs and F-URSs were successfully submitted to the insertion test. All F-URSs that were inserted into UASs without friction had an internal diameter of at least 12F. Different lengths of UAS did not influence the test outcome. This study was able to establish a correlation table between different UASs and different flexible ureteroscopes. As of now, the 12/14F UAS is considered the universal UAS that accepts all F-URSs that are available in the endourology field. Nevertheless, we are expecting a significant change with the new standard size 10/12F UAS as well as huge advances in minimizing the size of different endoscopes.

  8. Resistance Evaluation to Sheath Blight in Transgenic Rice Lines

    Institute of Scientific and Technical Information of China (English)

    LI Ai-hong; XU Xin-ping; DAI Zheng-yuan; CHEN Zong-xiang; LI Bao-jian; ZHANG Hong-xi; PAN Xue-biao

    2004-01-01

    Resistance of forty-one homozygous rice lines transformed with chitinase gene (RC24) and β-1,3 -glucanse gene (β-1,3-Glu) to sheath blight was analyzed by inoculation. Among different lines, the resistance had significant differences according to the result by cluster analysis. The lines could be categorized into resistant, moderately resistant, moderately susceptible and susceptible types, while 92.1% of which belonging to moderately resistant or moderately susceptible type. For different resistant or susceptible lines, the resistance to rice sheath blight was remarkable correlated with the chitinase activity of transgenic lines except resistant type lines, in which enzyme activity coded by target gene was lower than moderately resistant type. The chitinase activity of transgenic lines tested at different time after inoculation or different organs of the same plant was uniform, which suggested that the expression of chitinase gene was constitutive in nature. Check varieties' chitinase activity would change at different time after inoculation and reach a peak at sometime, but it had no difference at various parts of the same plant.

  9. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    Energy Technology Data Exchange (ETDEWEB)

    Grin, A.; Lstiburek, J.

    2014-09-01

    This guide provides information and recommendations to the following groups: insulation contractors; general contractors; builders; home remodelers; mechanical contractors; and homeowners, as a guide to the work that needs to be done. The order of work completed during home construction and retrofit improvements is important. Health and safety issues must be addressed first and are more important than durability issues. And durability issues are more important than saving energy. Not all techniques can apply to all houses. Special conditions will require special action. Some builders or homeowners will wish to do more than the important but basic retrofit strategies outlined by this guide. The following are best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant items were discussed with the group which are required to make taped insulating sheathing a simple, long term, and durable drainage plane: 1. Horizontal joints should be limited or eliminated wherever possible; 2. Where a horizontal joint exists use superior materials; 3. Frequent installation inspection and regular trade training are required to maintain proper installation. Section 5 of this measure guideline contains the detailed construction procedure for the three recommended methods to effectively seal the joints in exterior insulating sheathing to create a simple, long term, and durable drainage plane.

  10. Resistance Evaluation to Sheath Blight in Transgenic Rice Lines

    Institute of Scientific and Technical Information of China (English)

    LIAi-hong; XuXin-ping; DAIZheng-yuan; CHENZong-xiang; LIBao-jian; ZHANGHong-xi; PANXue-biao

    2004-01-01

    Resistance of forty one homozygous rice lines transformed with chitinase gene (RC24) and β-1,3-glucanse gene (β-1,3-Glu) to sheath blight was analyzed by inoculation. Among different lines, the resistance had significant differences according to the result by cluster analysis. The lines could be categorized into resistant, moderately resistant, moderately susceptible and susceptible typcs, while 92.1% of which belonging to moderately resistant or moderately susceptible type. For different resistant or susceptible lines, the resistance to rice sheath blight was remarkable correlated with the chitinase activity of transgenic lines except resistant type lines, in which enzyme activity coded by target gene was lower than moderately resistant type. The chitinase activity of transgenic lines tested at different time after inoculation or different organs of the same plant was uniform, which suggested that the expression of chitinase gene was constitutive in nature. Check varieties' chitinase acdvity would change at different time after inoculation and reach a peak at sometime, but it had no difference at various parts of the same plant.

  11. 30 CFR 75.700 - Grounding metallic sheaths, armors, and conduits enclosing power conductors.

    Science.gov (United States)

    2010-07-01

    ... conduits enclosing power conductors. 75.700 Section 75.700 Mineral Resources MINE SAFETY AND HEALTH... Grounding § 75.700 Grounding metallic sheaths, armors, and conduits enclosing power conductors. All metallic sheaths, armors, and conduits enclosing power conductors shall be electrically continuous throughout...

  12. Malignant peripheral nerve cell sheath tumour of the upper lip: a rare case

    Directory of Open Access Journals (Sweden)

    Joseph Ward

    2010-07-01

    Full Text Available We present the case of a malignant peripheral nerve sheath tumour (MPNST that developed on the upper lip of an 86 year old woman. MPNSTs are highly aggressive sarcomas that very rarely occur in the face. We know of no other reported cases of a malignant peripheral nerve sheath tumour arising from the upper lip.

  13. Biceps tendon sheath effusion as a diagnostic clue to rotator cuff pathology.

    Science.gov (United States)

    Yadav, Pankaj K; Shah, Bhavin; Shende, Amol; Rajesh, S

    2014-02-01

    The objective of this study was to evaluate the role of biceps tendon sheath effusion detected on ultrasound as a diagnostic clue to rotator cuff pathology. Despite being the most common cause of shoulder pain in adults early sonographic changes of rotator cuff tendinopathy are easy to miss. A total of 31 patients out of whom 27 had unilateral shoulder pain and 4 had bilateral complaints under- went ultrasonographic examination of shoulder joint using high frequency linear array transducer. Any fluid surrounding the long head of biceps tendon was noted followed by a careful search for any associated sonographic abnormality involving the rotator cuff. Eighteen out of the 35 had presence of fluid in their biceps tendon sheath. Twelve had presence of both biceps tendon sheath effusion and rotator cuff pathologies. Among 17 patients, who had no fluid in their biceps tendon sheath, only 2 had rotator cuff involvement whereas rest 15 had neither biceps tendon sheath fluid nor rotator cuff pathologies. A significant association was found between presence of fluid in long head of biceps tendon sheath and rotator cuff pathologies. Thus the most common finding observed in association with the presence of fluid around the long head of biceps tendon sheath in this study was tendinosis of rotator cuff. On ultrasonography simple presence of fluid around the long head of biceps tendon sheath demands careful examination of rotator cuff.

  14. Biology of a Pine Needle Sheath Midge, Contarinia Acuta Gagne (Diptera: Cecidomyiidae), on Loblolly Pine

    Science.gov (United States)

    Julie C. Weatherby; John C. Moser; Raymond J. Gagné; Huey N. Wallace

    1989-01-01

    The biology of a pine needle sheath midge, Contarinia acuta Gagné is described for a new host in Louisiana. This midge was found feeding within the needle sheath on elongating needles of loblolly pine, P. taeda L. Needle droop and partial defoliation were evident on heavily infested trees. Overwintering C. acuta...

  15. Arc Plasma Torch Modeling

    CERN Document Server

    Trelles, J P; Vardelle, A; Heberlein, J V R

    2013-01-01

    Arc plasma torches are the primary components of various industrial thermal plasma processes involving plasma spraying, metal cutting and welding, thermal plasma CVD, metal melting and remelting, waste treatment and gas production. They are relatively simple devices whose operation implies intricate thermal, chemical, electrical, and fluid dynamics phenomena. Modeling may be used as a means to better understand the physical processes involved in their operation. This paper presents an overview of the main aspects involved in the modeling of DC arc plasma torches: the mathematical models including thermodynamic and chemical non-equilibrium models, turbulent and radiative transport, thermodynamic and transport property calculation, boundary conditions and arc reattachment models. It focuses on the conventional plasma torches used for plasma spraying that include a hot-cathode and a nozzle anode.

  16. EDITORIAL: Quantum phenomena in Nanotechnology Quantum phenomena in Nanotechnology

    Science.gov (United States)

    Loss, Daniel

    2009-10-01

    Twenty years ago the Institute of Physics launched the journal Nanotechnology from its publishing house based in the home town of Paul Dirac, a legendary figure in the development of quantum mechanics at the turn of the last century. At the beginning of the 20th century, the adoption of quantum mechanical descriptions of events transformed the existing deterministic world view. But in many ways it also revolutionised the progress of research itself. For the first time since the 17th century when Francis Bacon established inductive reasoning as the means of advancing science from fact to axiom to law, theory was progressing ahead of experiments instead of providing explanations for observations that had already been made. Dirac's postulation of antimatter through purely theoretical investigation before its observation is the archetypal example of theory leading the way for experiment. The progress of nanotechnology and the development of tools and techniques that enabled the investigation of systems at the nanoscale brought with them many fascinating observations of phenomena that could only be explained through quantum mechanics, first theoretically deduced decades previously. At the nanoscale, quantum confinement effects dominate the electrical and optical properties of systems. They also render new opportunities for manipulating the response of systems. For example, a better understanding of these systems has enabled the rapid development of quantum dots with precisely determined properties, which can be exploited in a range of applications from medical imaging and photovoltaic solar cells to quantum computation, a radically new information technology being currently developed in many labs worldwide. As the first ever academic journal in nanotechnology, {\\it Nanotechnology} has been the forum for papers detailing progress of the science through extremely exciting times. In the early years of the journal, the investigation of electron spin led to the formulation

  17. Modelling of impurity transport and plasma-wall interaction in fusion devices with the ERO code: basics of the code and examples of application

    Energy Technology Data Exchange (ETDEWEB)

    Kirschner, A.; Borodin, D.; Brezinsek, S.; Linsmeier, C.; Romazanov, J. [Forschungszentrum Juelich GmbH, Institut fuer Energie- und Klimaforschung - Plasmaphysik, Juelich (Germany); Tskhakaya, D. [Fusion rate at OeAW, Institute of Applied Physics, TU Wien (Austria); Institute of Theoretical Physics, University of Innsbruck (Austria); Kawamura, G. [National Institute for Fusion Science, Gifu (Japan); Ding, R. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui (China)

    2016-08-15

    The 3D ERO code, which simulates plasma-wall interaction and impurity transport in magnetically confined fusion-relevant devices is described. As application, prompt deposition of eroded tungsten has been simulated at surfaces with shallow magnetic field of 3 T. Dedicated PIC simulations have been performed to calculate the characteristics of the sheath in front of plasma-exposed surfaces to use as input for these ERO simulations. Prompt deposition of tungsten reaches 100% at the highest electron temperature and density. In comparison to more simplified assumptions for the sheath the amount of prompt deposition is in general smaller if the PIC-calculated sheath is used. Due to friction with the background plasma the impact energy of deposited tungsten can be significantly larger than the energy gained in the sheath potential. (copyright 2016 The Authors. Contributions to Plasma Physics published by Wiley-VCH Verlag GmbH and Co. KGaA Weinheim. This)

  18. Plasma Nanoscience: from Nano-Solids in Plasmas to Nano-Plasmas in Solids

    CERN Document Server

    Ostrikov, K; Meyyappan, M

    2013-01-01

    The unique plasma-specific features and physical phenomena in the organization of nanoscale solid-state systems in a broad range of elemental composition, structure, and dimensionality are critically reviewed. These effects lead to the possibility to localize and control energy and matter at nanoscales and to produce self-organized nano-solids with highly unusual and superior properties. A unifying conceptual framework based on the control of production, transport, and self-organization of precursor species is introduced and a variety of plasma-specific non-equilibrium and kinetics-driven phenomena across the many temporal and spatial scales is explained. When the plasma is localized to micrometer and nanometer dimensions, new emergent phenomena arise. The examples range from semiconducting quantum dots and nanowires, chirality control of single-walled carbon nanotubes, ultra-fine manipulation of graphenes, nano-diamond, and organic matter, to nano-plasma effects and nano-plasmas of different states of matter...

  19. Bleed Hole Flow Phenomena Studied

    Science.gov (United States)

    1997-01-01

    Boundary-layer bleed is an invaluable tool for controlling the airflow in supersonic aircraft engine inlets. Incoming air is decelerated to subsonic speeds prior to entering the compressor via a series of oblique shocks. The low momentum flow in the boundary layer interacts with these shocks, growing in thickness and, under some conditions, leading to flow separation. To remedy this, bleed holes are strategically located to remove mass from the boundary layer, reducing its thickness and helping to maintain uniform flow to the compressor. The bleed requirements for any inlet design are unique and must be validated by extensive wind tunnel testing to optimize performance and efficiency. To accelerate this process and reduce cost, researchers at the NASA Lewis Research Center initiated an experimental program to study the flow phenomena associated with bleed holes. Knowledge of these flow properties will be incorporated into computational fluid dynamics (CFD) models that will aid engine inlet designers in optimizing bleed configurations before any hardware is fabricated. This ongoing investigation is currently examining two hole geometries, 90 and 20 (both with 5-mm diameters), and various flow features.

  20. Mixed Fluid Conditions: Capillary Phenomena

    KAUST Repository

    Santamarina, Carlos

    2017-07-06

    Mixed fluid phenomena in porous media have profound implications on soil-atmosphere interaction, energy geotechnology, environmental engineering and infrastructure design. Surface tension varies with pressure, temperature, solute concentration, and surfactant concentration; on the other hand, the contact angle responds to interfacial tensions, surface topography, invasion velocity, and chemical interactions. Interfaces are not isolated but interact through the fluid pressure and respond to external fields. Jumps, snap-offs and percolating wetting liquids along edges and crevices are ubiquitous in real, non-cylindrical porous networks. Pore- and macroscale instabilities together with pore structure variability-and-correlation favor fluid trapping and hinder recovery efficiency. The saturation-pressure characteristic curve is affected by the saturation-history, flow-rate, the mechanical response of the porous medium, and time-dependent reactive and diffusive processes; in addition, there are salient differences between unsaturation by internal gas nucleation and gas invasion. Capillary forces add to other skeletal forces in the porous medium and can generate open-mode discontinuities when the capillary entry pressure is high relative to the effective stress. Time emerges as an important variable in mixed-fluid conditions and common quasi-static analyses may fail to capture the system response.

  1. Understanding empathy and related phenomena.

    Science.gov (United States)

    Shamasundar, C

    1999-01-01

    Over a period of time, the author arrived at a few tentative postulates concerning empathy and related processes based on some of his experiences and observations. The central theme of these postulates is, firstly, that interpersonal interaction is an interaction of the personal-space fields. Secondly, empathy, therapeutic benefit, and the professional stress are all related to the same process of interpersonal interaction. This interaction takes place as an enmeshment of personal spaces of the interacting individuals, and involves transfer of a wide range of information in the affective, cognitive, and other areas. This is because the personal spaces have fieldlike qualities analogous to what Kurt Lewin described. Thus, such phenomena as empathy, therapeutic benefit, professional stress are all consequences of the same process. It is possible to substantiate these postulates by diverse evidences in the published literature. The natural consequences of such an interpersonal interaction are empathic understanding, transfer of mood states (like hope, distress or expectancy), affective states (like anxiety, sadness, anger or hostility), ideas, images and even attitudes and values, etc. This phenomenon of transfer can explain such processes as therapeutic benefit in individual and group settings, professional stress, shared delusions, and even experimenter bias. Whether one becomes aware of such transferred information or not depends upon the intent and sensitivity of the participants.

  2. Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Matthew T. Cole

    2013-05-01

    Full Text Available A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices.

  3. Comparative analysis of CT and pathological findings of peripheral nerve sheath tumors

    Institute of Scientific and Technical Information of China (English)

    张雪林; 王晓琪; 邱士军

    2003-01-01

    Objective: To improve the qualitative diagnosis of peripheral nerve sheath tumors by computed tomography (CT). Methods: CT findings of 64 cases of pathologically confirmed nerve sheath tumors were compared with the pathological findings of the tumors. Results: Low density of the tumors shown in plain CT images was related to dominating reticular structure in the tumor as found pathologically. Tumors with intact capsule found by pathological findings were shown with smooth margin in CT images. Inhomogeneous density and enhancement of the tumors in CT images was related to tumor necrosis, liquefaction and cystic degeneration, and inhomogeneous enhancement also involved the reticular structure. Conclusion: Nerve sheath tumors are characterized by distribution along the nerves, lower density than that of muscles in plain CT images, and inhomogeneous enhancement in enhanced CT, which can help differentiate nerve sheath tumors from other soft tissue tumors. When nerve sheath tumors lack distinctive CT features, the diagnoses have to depend on their pathological findings.

  4. An investigation of friction-based tendon sheath model appropriate for control purposes

    Science.gov (United States)

    Do, T. N.; Tjahjowidodo, T.; Lau, M. W. S.; Phee, S. J.

    2014-01-01

    The tendon sheath mechanism plays an important role in many robotic systems from surgical devices to robot hands. However, many unexpected properties such as nonlinear hysteresis and backlash, which appear in the tendon sheath system, cause major losses in force transmission. This report deals with the characterization of hysteresis phenomenon, which is attributed to the presence of frictional effects on its elements, in a tendon-sheath driven surgical robot. Unlike various approaches presented in the literature that utilized multiple lumped mass elements, this proposed approach models the tendon sheath as one element. A new dynamic friction model that allows accurate description of friction lag and hysteresis behavior in two regimes, i.e. presliding and sliding regimes, for a sheath in arbitrary configuration such as helical and spatial shape has been developed.

  5. Fibroma of the tendon sheath of the long head of the biceps tendon.

    Science.gov (United States)

    De Maeseneer, Michel; Van Isacker, Tom; Lenchik, Leon; Van Caillie, Marie-Astrid; Shahabpour, Maryam

    2014-03-01

    Fibroma of the tendon sheath is a benign tumor that is less common than giant cell tumor of the tendon sheath. Both tumors may present as a painless, slowly enlarging mass. Radiological findings may be similar for both tumors. Histologically, fibroma of the tendon sheath lacks the hemosiderin-laden macrophages that are typical for giant cell tumor of the tendon sheath. We report on a 49-year-old woman with fibroma of the tendon sheath of the long head of the biceps tendon. In our case, on MR images, we observed band-like hypointense areas centrally in the tumor, mild patchy contrast enhancement, and most importantly, no decrease of signal intensity on gradient echo images. These characteristics reflected histological findings.

  6. Fibroma of the tendon sheath of the long head of the biceps tendon

    Energy Technology Data Exchange (ETDEWEB)

    Maeseneer, Michel de; Shahabpour, Maryam [Universitair Ziekenhuis Brussel, Department of Radiology, Brussels (Belgium); Isacker, Tom van [Sint-Lucas Hospital, Department of Orthopedic Surgery, Brugge (Belgium); Lenchik, Leon [Wake Forest School of Medicine, Department of Radiology, Winston Salem, NC (United States); Caillie, Marie-Astrid van [Sint-Lucas Hospital, Department of Pathology, Brugge (Belgium)

    2014-03-15

    Fibroma of the tendon sheath is a benign tumor that is less common than giant cell tumor of the tendon sheath. Both tumors may present as a painless, slowly enlarging mass. Radiological findings may be similar for both tumors. Histologically, fibroma of the tendon sheath lacks the hemosiderin-laden macrophages that are typical for giant cell tumor of the tendon sheath. We report on a 49-year-old woman with fibroma of the tendon sheath of the long head of the biceps tendon. In our case, on MR images, we observed band-like hypointense areas centrally in the tumor, mild patchy contrast enhancement, and most importantly, no decrease of signal intensity on gradient echo images. These characteristics reflected histological findings. (orig.)

  7. Composite pheochromocytoma with a malignant peripheral nerve sheath tumor: Case report and review of the literature.

    Science.gov (United States)

    Namekawa, Takeshi; Utsumi, Takanobu; Imamoto, Takashi; Kawamura, Koji; Oide, Takashi; Tanaka, Tomoaki; Nihei, Naoki; Suzuki, Hiroyoshi; Nakatani, Yukio; Ichikawa, Tomohiko

    2016-07-01

    Adrenal tumors with more than one cellular component are uncommon. Furthermore, an adrenal tumor composed of a pheochromocytoma and a malignant peripheral nerve sheath tumor is extremely rare. A composite pheochromocytoma with malignant peripheral nerve sheath tumor in a 42-year-old man is reported here. After adequate preoperative control, left adrenalectomy was performed simultaneously with resection of the ipsilateral kidney for spontaneous rupture of the left adrenal tumor. Pathological findings demonstrated pheochromocytoma and malignant peripheral nerve sheath tumor in a ruptured adrenal tumor. To date, there have been only four reported cases of composite pheochromocytoma with malignant peripheral nerve sheath tumor, so the present case is only the fifth case in the world. Despite the very poor prognosis of patients with pheochromocytoma and malignant peripheral nerve sheath tumors reported in the literature, the patient remains well without evidence of recurrence or new metastatic lesions at 36 months postoperatively. Copyright © 2012. Published by Elsevier Taiwan.

  8. Feline cutaneous nerve sheath tumours: histological features and immunohistochemical evaluations.

    Science.gov (United States)

    Mandara, M T; Fabriani, E; Pavone, S; Pumarola, M

    2013-10-01

    Feline cutaneous nerve sheath tumours (CNSTs) are uncommonly reported in the skin, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In this study, 26 nerve sheath tumours selected from 337 skin neoplasms of cats were examined. Histologically, they were classified into malignant (MPNSTs) and benign tumours (BPNSTs) based on degree of cellular atypia and polymorphism as well as mitotic rate and diffuse necrosis. CPNSTs were tipically characterised by Antoni A pattern, in some cases associated with Antoni B pattern. In the malignant peripheral nerve sheath tumours (MPNSTs) the polymorphism was marked, while it was mild to moderate in the benign forms (BPNSTs). In the MPNSTs the mitotic activity was generally higher than in the BPNSTs. In five cases, including three MPNSTs and two BPNSTs, there were multinucleated giant cells. Necrotic foci occurred in a BPNST and in two MPNSTs, while osseous/chondroid metaplasia was found in two cases. Immunohistochemically, all the tumours showed a marked diffuse vimentin expression. S-100 protein was expressed in 17 cases, including 81.8% of BPNSTs and 57.14% of MPNSTs. Twenty-five tumours expressed NSE and twenty-four cases showed immunoreaction for laminin. Thirteen tumours were positive for GFAP, while five tumours were positive for SMA. PGP 9.5 expression was detected in all cases, except for two MPNSTs. NGFR was expressed in eleven cases, including four MPNSTs and seven BPNSTs. Ki67 was expressed in twenty tumours without any relationship with morphologic malignancy of the neoplasm. In this case series we confirmed neoplastic spindloid cells with wavy cytoplasm arranged in compact areas, with occasional nuclear palisading or whirls, and interchanged with loosely arranged areas, as the morphological features supporting a diagnosis of CPNST. A constant concurrent expression of vimentin, NSE, and laminin might confirm the diagnosis of PNST in the absence of clear S-100 protein

  9. Benign and malignant neurogenic tumors of nerve sheath origin on FDG PET

    Energy Technology Data Exchange (ETDEWEB)

    Yun, M. J.; Go, D. H.; Yoo, Y. H.; Shin, K. H.; Lee, J. D [College of Medicine, Yonsei University, Seoul (Korea, Republic of)

    2004-07-01

    The differentiation between benign and malignant nerve sheath tumors is difficult based on conventional radiological imaging. This study was undertaken to investigate the value of FDG PET in distinguishing benign from malignant neurogenic tumors of nerve sheath origin. We performed a retrospective review of the medical record to select patients with nerve sheath tumors who had underdone FDG PET imaging. Fifteen patients (7F: 8M) with benign or malignant nerve sheath tumors were included in this study. Of the 15 patients, 9 were diagnosed with the known neurofibromatosis type I. A total of 19 nerve sheath tumors were included from the 15 patients. All patients had undergone FDG PET to evaluate for malignant potential of the known lesions. Images of FDG PET were semi-quantitatively analyzed and a region of interest (ROI) was placed over the area of the maximum FDG uptake and an average standardized uptake value was taken for final analysis. There were 5 malignant peripheral nerve sheath tumors, 5 schwannomas, and 9 neurofibromas. The mean SUV was 2 (ranged from 1.6 to 3.3) for schwannomas, 1.3 (0.7 to 2.5) for neurofibromas, and 8.4 (4.6 to 12.2) for malignant peripheral nerve sheath tumors. Of 14 benign tumors, all except one schwannoma showed a SUV less than 3. When a cutoff SUV of 4 was used to differentiate the nerve sheath tumors, all tumors were correctly classified as benign or malignant, respectively. Among the 9 patients diagnosed with neurofibromatosis type I. 4 had malignant peripheral nerve sheath tumors and FDG PET accurately detected all the 4 lesions with malignant transformation. According to our results, FDG PET seems to have a great potential for accurately characterizing benign versus malignant nerve sheath tumors. It appears to be extremely useful for patients with neurofibromatosis to localize the lesion with malignant transformation.

  10. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    Steven L Liebling

    2000-10-01

    Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.

  11. Understanding the physics of changing mass phenomena

    OpenAIRE

    2008-01-01

    Changing mass phenomena, like a falling chain or a bungee jumper, might give surprising results, even for experienced physicists. They have resulted in hot discussions in journals, in which for instance Physics professors claim the impossibility of an acceleration larger then g in case of a bungee jumper. These phenomena are also interesting as topics for challenging student projects, and used as such by Dutch high school students. I will take these phenomena as the context in which I like to...

  12. Chodura and Debye sheaths for magnetic fields with grazing incidence -- kinetic simulations

    CERN Document Server

    Coulette, David

    2016-01-01

    When an unmagnetized plasma comes in contact with a material surface, the difference in mobility between the electrons and the ions creates a nonneutral layer known as the Debye sheath (DS). However, in magnetic fusion devices, the open magnetic field lines intersect the structural elements of the device with near grazing incidence angles. The magnetic field tends to align the particle flow along its own field lines, thus counteracting the mechanism that leads to the formation of the DS. Recent work using a fluid model [P. Stangeby, Nucl. Fusion {\\bf 52}, 083012 (2012)] showed that the DS disappears when the incidence angle is smaller than a critical value (around $5^\\circ$ for ITER-like parameters). Here, we study this transition by means of numerical simulations of a kinetic model both in the collisionless and weakly collisional regimes. We show that the main features observed in the fluid model are preserved: for grazing incidence, the space charge density near the wall is reduced, the ion flow is subsonic...

  13. Modified gravito-electrostatic sheath in the presence of turbu-magnetic pressure effects

    Science.gov (United States)

    Prasad Goutam, Hari; Karmakar, Pralay Kumar

    2016-07-01

    The gravito-electrostatic sheath (GES) model, previously formulated to investigate the equilibrium properties of the Sun and its unbounded atmosphere coupled via the interfacial solar surface boundary (SSB) under the gravito-electrostatic interplay, is re-examined. It is modified, for the first time, with the self-consistent inclusion of turbu-magnetic pressure effects originating from intrinsic continuous instability processes. The role of the new effects is interestingly realized through considerable changes in the dynamic properties of the solar plasma system on both the bounded and unbounded scales. The SSB, as a result of the outward turbu-magnetic action relative to the inward self-gravitating one, is found to shift radially outwards by 5.71% relative to the sheer GES model, and by 7.50% inwards relative to the pure uniformly magnetized counterpart. The sonic point moves inwards by 30% in the former, and by 24% in the latter; respectively. It is further found that the floating surface and floating potential increase by 47% each relative to the GES; and by 27% and 160% relative to the pure magnetic case; respectively. The implications and applications are discussed in the panoptical light of real astronomical observations alongside the facts, faults and future refinements.

  14. Observation of Celestial Phenomena in Ancient China

    Science.gov (United States)

    Sun, Xiaochun

    Because of the need for calendar-making and portent astrology, the Chinese were diligent and meticulous observers of celestial phenomena. China has maintained the longest continuous historical records of celestial phenomena in the world. Extraordinary or abnormal celestial events were particularly noted because of their astrological significance. The historical records cover various types of celestial phenomena, which include solar and lunar eclipses, sunspots, "guest stars" (novae or supernovae as we understand today), comets and meteors, and all kinds of planetary phenomena. These records provide valuable historical data for astronomical studies today.

  15. File list: InP.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available InP.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 Input control Neural Nerve Sheath Neopl...asms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/InP.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  16. File list: InP.Neu.05.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available InP.Neu.05.AllAg.Nerve_Sheath_Neoplasms mm9 Input control Neural Nerve Sheath Neopl...asms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/InP.Neu.05.AllAg.Nerve_Sheath_Neoplasms.bed ...

  17. File list: NoD.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available NoD.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 No description Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/NoD.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  18. File list: InP.Neu.50.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available InP.Neu.50.AllAg.Nerve_Sheath_Neoplasms mm9 Input control Neural Nerve Sheath Neopl...asms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/InP.Neu.50.AllAg.Nerve_Sheath_Neoplasms.bed ...

  19. File list: NoD.Neu.20.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available NoD.Neu.20.AllAg.Nerve_Sheath_Neoplasms mm9 No description Neural Nerve Sheath Neop...lasms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/NoD.Neu.20.AllAg.Nerve_Sheath_Neoplasms.bed ...

  20. File list: InP.Neu.10.AllAg.Nerve_Sheath_Neoplasms [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available InP.Neu.10.AllAg.Nerve_Sheath_Neoplasms mm9 Input control Neural Nerve Sheath Neopl...asms http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/InP.Neu.10.AllAg.Nerve_Sheath_Neoplasms.bed ...