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Sample records for cyclotron dynamics leading

  1. Cyclotron Resonances in Electron Cloud Dynamics

    SciTech Connect

    Celata, C M; Furman, M A; Vay, J L; Grote, D P; Ng, J T; Pivi, M F; Wang, L F

    2009-05-05

    A new set of resonances for electron cloud dynamics in the presence of a magnetic field has been found. For short beam bunch lengths and low magnetic fields where l{sub b} << 2{pi}{omega}{sub c}, (l{sub b} = bunch duration, {omega}{sub c} = non-relativistic cyclotron frequency) resonances between the bunch frequency and harmonics of the cyclotron frequency cause an increase in the electron cloud density in narrow ranges of magnetic field near the resonances. For ILC parameters the increase in the density is up to a factor {approx} 3, and the spatial distribution of the electrons is broader near resonances, lacking the well-defined density 'stripes' of multipactoring found for non-resonant cases. Simulations with the 2D computer code POSINST, as well as a single-particle tracking code, were used to elucidate the physics of the dynamics. The resonances are expected to affect the electron cloud dynamics in the fringe fields of conventional lattice magnets and in wigglers, where the magnetic fields are low. Results of the simulations, the reason for the bunch-length dependence, and details of the dynamics will be discussed.

  2. Cyclotron Resonances in Electron Cloud Dynamics

    SciTech Connect

    Celata, C. M.; Furman, Miguel A.; Vay, J.-L.; Ng, J. S.T.; Grote, D. P.; Pivi, M. T. F.; Wang, L. F.

    2009-04-29

    A new set of resonances for electron cloud dynamics in the presence of a magnetic field has been found. For short beam bunch lengths and low magnetic fields where lb<< 2pi c/omega c (with lb = bunch length, omega c = non-relativistic cyclotron frequency) resonances between the bunch frequency and harmonics of the electron cyclotron frequency cause an increase in the electron cloud density in narrow ranges of magnetic field near the resonances. For ILC parameters the increase in the density is up to a factor ~;;3, and the spatial distribution of the electrons is broader near resonances, lacking the well-defined vertical density"stripes" found for non-resonant cases. Simulations with the 2D computer code POSINST, as well as a single-particle tracking code, were used to elucidate the physics of the dynamics. The existence of the resonances has been confirmed in experiments at PEP-II. The resonances are expected to affect the electron cloud dynamics in the fringe fields of conventional lattice magnets and in wigglers, where the magnetic fields are low. Results of the simulations and experimental observations, the reason for the bunch-length dependence, and details of the dynamics are discussed here.

  3. Electron Cyclotron Resonances in Electron Cloud Dynamics

    SciTech Connect

    Celata, Christine; Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Yu, Jennifer W.

    2008-06-25

    We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"POSINST" was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. An electron equilibrium density enhancement of up to a factor of 3 was found at magnetic field values for which the bunch frequency is an integral multiple of the electron cyclotron frequency. At low magnetic fields the effects of the resonance are prominent, but when B exceeds ~;;(2 pi mec/(elb)), with lb = bunch length, effects of the resonance disappear. Thus short bunches and low B fields are required for observing the effect. The reason for the B field dependence, an explanation of the dynamics, and the results of the 2D simulations and of a single-particle tracking code used to elucidate details of the dynamics are discussed.

  4. Peculiarities of charged particle dynamics under cyclotron resonance conditions

    SciTech Connect

    Moiseev, S. S.; Buts, V. A.; Erokhin, N. S.

    2016-08-15

    Peculiarities of the dynamics of charged particles interacting with electromagnetic radiation under nearly autoresonance conditions are analyzed. In particular, analysis of nonlinear cyclotron resonances shows that their widths increase when the autoresonance conditions are approached. In this case, however, the distance between nonlinear resonances increases even faster, due to which nonlinear resonances do not overlap and, accordingly, regimes with dynamic chaos do not occur. According to calculations, the dynamics of charged particles under the autoresonance conditions is very sensitive to fluctuations, the effect of which can be anomalously large and lead to superdiffusion. It is shown that, under the autoresonance conditions, particle dynamics on small time intervals can differ significantly from that on large time intervals. This effect is most pronounced in the presence of fluctuations in the system.

  5. Dynamic regimes of cyclotron instability in the afterglow mode of minimum-B electron cyclotron resonance ion source plasma

    NASA Astrophysics Data System (ADS)

    Mansfeld, D.; Izotov, I.; Skalyga, V.; Tarvainen, O.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.

    2016-04-01

    The paper is concerned with the dynamic regimes of cyclotron instabilities in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source operated in pulsed mode. The instability appears in decaying ion source plasma shortly (1-10 ms) after switching off the microwave radiation of the klystron, and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high-energy electrons along the magnetic field lines. Recently it was shown that this plasma instability causes perturbations of the extracted ion current, which limits the performance of the ion source and generates strong bursts of bremsstrahlung emission. In this article we present time-resolved diagnostics of electromagnetic emission bursts related to cyclotron instability in the decaying plasma. The temporal resolution is sufficient to study the fine structure of the dynamic spectra of the electromagnetic emission at different operating regimes of the ion source. It was found that at different values of magnetic field and heating power the dynamic spectra demonstrate common features: Decreasing frequency from burst to burst and an always falling tone during a single burst of instability. The analysis has shown that the instability is driven by the resonant interaction of hot electrons, distributed between the electron cyclotron resonance (ECR) zone and the trap center, with slow extraordinary wave propagation quasi-parallel with respect to the external magnetic field.

  6. Nonlinear dynamical modelling of chaotic electrostatic ion cyclotron oscillations by jerk equations

    NASA Astrophysics Data System (ADS)

    Wharton, A. M.; Janaki, M. S.; Iyengar, A. N. S.

    2013-07-01

    Plasma being a nonlinear and complex system, is capable of sustaining a wide spectrum of waves, oscillations and instabilities. These fluctuations interact nonlinearly amongst themselves and also with particles: electrons/ions and thus lead to nonlinear wave-wave or wave-particle interaction. In the presence of coherent waves the particles are accelerated whereas irregular oscillations can give rise to particle heating which is also called stochastic heating. Particle orbits are known to be randomized by the wave fields such that their motion can also become stochastic. For fusion to be sustained one needs a very high temperature plasma for an extended duration. It quite common to deploy external waves like electron cyclotron waves or ion cyclotron waves for plasma heating and current drive. These external waves also work only in certain regimes. Conventional plasma techniques have been able to answer several of the observations of the above processes related to heating transport etc, but nonlinear dynamics as a tool has helped in comprehending the plasma oscillations better. We have for the first time obtained a Third Order nonlinear ordinary differential equation (TONLODE) also known as jerk equation to describe the electrostatic ion cyclotron plasma oscillations in a magnetic field. The interesting feature of this equation is that it does not require an external forcing term to obtain chaotic behaviour.

  7. Plasma ion dynamics and beam formation in electron cyclotron resonance ion sources

    SciTech Connect

    Mascali, D.; Neri, L.; Miracoli, R.; Gammino, S.; Celona, L.; Ciavola, G.; Gambino, N.; Chikin, S.

    2010-02-15

    In electron cyclotron resonance ion sources it has been demonstrated that plasma heating may be improved by means of different microwave to plasma coupling mechanisms, including the ''frequency tuning'' and the ''two frequency heating''. These techniques affect evidently the electron dynamics, but the relationship with the ion dynamics has not been investigated in details up to now. Here we will try to outline these relations: through the study of ion dynamics we may try to understand how to optimize the electron cyclotron resonance ion sources brightness. A simple model of the ion confinement and beam formation will be presented, based on particle-in-cell and single particle simulations.

  8. Some aspects of electron dynamics in electron cyclotron resonance ion sources

    NASA Astrophysics Data System (ADS)

    Mironov, V.; Bogomolov, S.; Bondarchenko, A.; Efremov, A.; Loginov, V.

    2017-07-01

    Electron dynamics in an electron cyclotron resonance ion source is numerically simulated by using a particle-in-cell code combined with simulations of the ion dynamics. Mean electron energies are found to be around 70 keV, close to values that are derived from spectra of x-ray emission out of the source. The electron lifetime is defined by losses of low-energy electrons created in ionizing collisions; the losses are regulated by electron heating rate, which depends on the magnitude of the microwave electric field. Changes in the ion confinement with variations in the microwave electric field and gas flow are simulated. The influence of electron dynamics on the afterglow and two-frequency heating effects is discussed.

  9. Cyclotron dynamics of a Kondo singlet in a spin-orbit-coupled alkaline-earth-metal atomic gas

    NASA Astrophysics Data System (ADS)

    Jiang, Bo-Nan; Lv, Hao; Wang, Wen-Li; Du, Juan; Qian, Jun; Wang, Yu-Zhu

    2014-11-01

    We propose a scheme to investigate the interplay between the Kondo-exchange interaction and the quantum spin Hall effect with ultracold fermionic alkaline-earth-metal atoms trapped in two-dimensional optical lattices using ultracold collision and laser-assisted tunneling. In the strong Kondo-coupling regime, although the loop trajectory of the mobile atom disappears, collective dynamics of an atom pair in two clock states can exhibit an unexpected spin-dependent cyclotron orbit in a plaquette, realizing the quantum spin Hall effect of the Kondo singlet. We demonstrate that the collective cyclotron dynamics of the spin-zero Kondo singlet is governed by an effective Harper-Hofstadter model in addition to second-order diagonal tunneling.

  10. Fourier Transform Ion Cyclotron Resonance Mass Resolution and Dynamic Range Limits Calculated by Computer Modeling of Ion Cloud Motion

    NASA Astrophysics Data System (ADS)

    Vladimirov, Gleb; Hendrickson, Christopher L.; Blakney, Greg T.; Marshall, Alan G.; Heeren, Ron M. A.; Nikolaev, Eugene N.

    2012-02-01

    Particle-in-Cell (PIC) ion trajectory calculations provide the most realistic simulation of Fourier transform ion cyclotron resonance (FT-ICR) experiments by efficient and accurate calculation of the forces acting on each ion in an ensemble (cloud), including Coulomb interactions (space charge), the electric field of the ICR trap electrodes, image charges on the trap electrodes, the magnetic field, and collisions with neutral gas molecules. It has been shown recently that ion cloud collective behavior is required to generate an FT-ICR signal and that two main phenomena influence mass resolution and dynamic range. The first is formation of an ellipsoidal ion cloud (termed "condensation") at a critical ion number (density), which facilitates signal generation in an FT-ICR cell of arbitrary geometry because the condensed cloud behaves as a quasi-ion. The second phenomenon is peak coalescence. Ion resonances that are closely spaced in m/z coalesce into one resonance if the ion number (density) exceeds a threshold that depends on magnetic field strength, ion cyclotron radius, ion masses and mass difference, and ion initial spatial distribution. These two phenomena decrease dynamic range by rapid cloud dephasing at small ion density and by cloud coalescence at high ion density. Here, we use PIC simulations to quantitate the dependence of coalescence on each critical parameter. Transitions between independent and coalesced motion were observed in a series of the experiments that systematically varied ion number, magnetic field strength, ion radius, ion m/z, ion m/z difference, and ion initial spatial distribution (the present simulations begin from elliptically-shaped ion clouds with constant ion density distribution). Our simulations show that mass resolution is constant at a given magnetic field strength with increasing ion number until a critical value (N) is reached. N dependence on magnetic field strength, cyclotron radius, ion mass, and difference between ion masses

  11. Electromagnetic Ion Cyclotron Wave Triggering by Solar Wind Dynamic Pressure Enhancements at Multiple Locations

    NASA Astrophysics Data System (ADS)

    Cho, J.; Lee, D. Y.; Kim, H.

    2016-12-01

    Electromagnetic Ion cyclotron (EMIC) waves are one of the key plasma waves which play a critical role in the magnetosphere by interacting with charged particles. One of the generation mechanisms of EMIC waves is magnetospheric compression due to impact of enhanced solar wind dynamic pressure Pdyn. With the multi-satellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere and ground-based magnetometers, we examine two EMIC wave events that are triggered by Pdyn enhancements under prolonged northward IMF quiet time preconditions. For both events, the impact of enhanced Pdyn causes EMIC waves at multiple points. However, we find a strong spatial dependence of EMIC wave triggering and the accompanied wave properties. For Event 1, a satellite near noon observes no dramatic EMIC waves. In contrast, three other satellites are situated at a nearly same dawn side zone but at slightly different L shells and see notable EMIC waves but in different frequencies relative to local ion gyrofrequencies. These waves are found inside or outer edge of the plasmasphere. For Event 2, the satellites are situated at three different MLT zones, late afternoon-dusk, early evening-pre-midnight, and post-midnight, when they see the triggered EMIC waves. They are again found at different frequencies relative to local ion gyrofrequencies, and all outside the plasmasphere. Furthermore, the triggered EMIC waves for both events are observed from high-latitude ground stations in Antarctica. The results in this work imply that triggering of EMIC waves by enhanced Pdyn can occur at multiple points but with different wave properties, which must be due to different local plasma and magnetic conditions.

  12. Van Allen Probes observations of electromagnetic ion cyclotron waves triggered by enhanced solar wind dynamic pressure

    NASA Astrophysics Data System (ADS)

    Cho, J.-H.; Lee, D.-Y.; Noh, S.-J.; Shin, D.-K.; Hwang, J.; Kim, K.-C.; Lee, J. J.; Choi, C. R.; Thaller, S.; Skoug, R.

    2016-10-01

    Magnetospheric compression due to impact of enhanced solar wind dynamic pressure Pdyn has long been considered as one of the generation mechanisms of electromagnetic ion cyclotron (EMIC) waves. With the Van Allen Probe-A observations, we identify three EMIC wave events that are triggered by Pdyn enhancements under prolonged northward interplanetary magnetic field (IMF) quiet time preconditions. They are in contrast to one another in a few aspects. Event 1 occurs in the middle of continuously increasing Pdyn while Van Allen Probe-A is located outside the plasmapause at postmidnight and near the equator (magnetic latitude (MLAT) -3°). Event 2 occurs by a sharp Pdyn pulse impact while Van Allen Probe-A is located inside the plasmapause in the dawn sector and rather away from the equator (MLAT 12°). Event 3 is characterized by amplification of a preexisting EMIC wave by a sharp Pdyn pulse impact while Van Allen Probe-A is located outside the plasmapause at noon and rather away from the equator (MLAT -15°). These three events represent various situations where EMIC waves can be triggered by Pdyn increases. Several common features are also found among the three events. (i) The strongest wave is found just above the He+ gyrofrequency. (ii) The waves are nearly linearly polarized with a rather oblique propagation direction ( 28° to 39° on average). (iii) The proton fluxes increase in immediate response to the Pdyn impact, most significantly in tens of keV energy, corresponding to the proton resonant energy. (iv) The temperature anisotropy with T⊥ > T|| is seen in the resonant energy for all the events, although its increase by the Pdyn impact is not necessarily always significant. The last two points (iii) and (iv) may imply that in addition to the temperature anisotropy, the increase of the resonant protons must have played a critical role in triggering the EMIC waves by the enhanced Pdyn impact.

  13. Leading edge gypsy moth population dynamics

    Treesearch

    M. R. Carter; F. W. Ravlin; M. L. McManus

    1991-01-01

    Leading edge gypsy moth populations have been the focus of several intervention programs (MDIPM, AIPM). Knowledge of gypsy moth population dynamics in leading edge area is crucial for effective management. Populations in these areas tend to reach outbreak levels (noticeable defoliation) within three to four years after egg masses are first detected. Pheromone traps...

  14. Design of a superconducting beam transport channel and beam dynamics for a strong-focusing cyclotron

    NASA Astrophysics Data System (ADS)

    Badgley, Karie Elizabeth

    There is an increasing interest in high power proton accelerators for use as neutron and muon sources, accelerator driven systems (ADS) for nuclear waste transmutation, high energy physics, medical physics, nuclear physics, and medical isotope production. Accelerating high current beams has a number of challenges; including avoiding harmful resonance crossing, space charge effects and, specific to cyclotrons, sufficient turn separation at injection and extraction. The Accelerator Research Laboratory at Texas A&M University is developing a high-power strong-focusing cyclotron with two main technologies to overcome these challenges. The first is a superconducting RF cavity to provide the energy gain required for fully separated turns. The second is the use of superconducting beam transport channels within the sectors of the cyclotron to provide strong-focusing with alternating focusing and defocusing quadrupoles. A method has been developed to find the equilibrium spiral orbit through the cyclotron which maintains isochronicity. The isochronous spiral orbit was then used to perform full linear optics calculations. The strengths of the quadrupoles were adjusted to hold the horizontal and vertical betatron tunes constant per turn to avoid resonance crossing. Particle tracking was performed with a modified MAD-X-PTC code and Synergia to provide a framework for future space charge studies. Magnetic modeling was performed on a 2D cross section of the beam transport channel. The wire locations were adjusted to reduce the higher order multipoles and a good field region was obtained at 70% of the beam pipe aperture with multipoles less than 10-4 . The 2D model was also used to determine the required current density needed to produce the quadrupole gradients. MgB2 superconducting wire was chosen as it meets all the field and current requirements and can operate at a reduced cryogenic cost. A winding mandrel was also designed and fabricated which minimized the bend radius for

  15. Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and Dynamics Explorer

    NASA Technical Reports Server (NTRS)

    Erlandson, Robert E.

    1993-01-01

    The principal activity during the past six months has involved the analysis of ion cyclotron waves recorded from DE-2 using the magnetic field experiment and electric field experiment. The results of this study have been published in the Geophysical Research Letters (GRL). The primary finding of this paper is that ion cyclotron waves were found to heat electrons, as observed in the DE-2 Langmuir probe data, through a Landau damping process. A second activity, which was started during the last six months, involves the study of large amplitude approximately one Hz electric and magnetic field oscillations recorded in the nightside auroral zone at substorm onset. Work is under way to determine the properties of these waves and investigate any association these waves may have with the substorm initiation process. A third activity under way involves a comprehensive study of ion cyclotron waves recorded at ionospheric altitudes by DE-2. This study will be an extension of the work reported in the GRL paper and will involve a larger sampling of wave events. This paper will focus on wave properties at ionospheric altitudes. A fourth activity involves a more in-depth analysis of the acceleration mechanisms and the resulting electron distributions based on the observations presented in the GRL paper.

  16. The power absorption and the penetration depth of electromagnetic radiation in lead telluride under cyclotron resonance conditions

    NASA Astrophysics Data System (ADS)

    Özalp, S.; Güngör, A.

    1999-10-01

    Cyclotron resonance absorption in n- and p-type PbTe was observed by Nii and was analysed under classical skin effect conditions. When the values of DC magnetic field corresponding to peaks are plotted against the field directions, a close fit is obtained between the calculated and observed results based on the assumption of a <1 1 1> ellipsoids of revolution model for the both conduction and valance band extrema. From the best fit mt=0.024 m0 and 0.03 m0 for the transverse effective masses and K= ml/ mt=9.8 and 12.2 for the anisotropic mass rations are obtained for the conduction and valance band, respectively. The observed absorption curve shows weak structures at low magnetic field. They are supposed to be due to second harmonics of Azbel'-Kaner cyclotron resonance. However, it turns out to be unnecessary to introduce other bands to explain the experimental results. The applicability of the classical magneto-optical theory is examined by calculating the power absorption coefficient and penetration depth as a function of DC magnetic field.

  17. Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements

    NASA Astrophysics Data System (ADS)

    Cho, J.-H.; Lee, D.-Y.; Noh, S.-J.; Kim, H.; Choi, C. R.; Lee, J.; Hwang, J.

    2017-05-01

    In this paper, using the multisatellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere, we examine two electromagnetic ion cyclotron (EMIC) wave events that are triggered by Pdyn enhancements under prolonged northward interplanetary magnetic field quiet time preconditions. For both events, the impact of enhanced Pdyn causes EMIC waves at multiple points. However, we find a strong spatial dependence that EMIC waves due to enhanced Pdyn impact can occur at multiple points (likely globally but not necessarily everywhere) but with different wave properties. For Event 1, three satellites situated at a nearly same dawnside zone but at slightly different L shells see occurrence of EMIC waves but in different frequencies relative to local ion gyrofrequencies and with different polarizations. These waves are found inside or at the outer edge of the plasmasphere. Another satellite near noon observes no dramatic EMIC wave despite the strongest magnetic compression there. For Event 2, the four satellites are situated at widely separated magnetic local time zones when they see occurrence of EMIC waves. They are again found at different frequencies relative to local ion gyrofrequencies with different polarizations and all outside the plasmasphere. We propose two possible explanations that (i) if triggered by enhanced Pdyn impact, details of ion cyclotron instability growth can be sensitive to local plasma conditions related to background proton distributions, and (ii) there can be preexisting waves with a specific spatial distribution, which determines occurrence and specific properties of EMIC waves depending on satellite's relative position after an enhanced Pdyn arrives.

  18. Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and dynamics explorer

    NASA Technical Reports Server (NTRS)

    Erlandson, Robert E.

    1994-01-01

    The overall objective of this research is to investigate the generation and propagation of electromagnetic ion cyclotron (EMIC) waves in the frequency range from 0.2 to 5 Hz (Pc 1 frequency band). Data used in this research were acquired by the AMPTE/CCE, DE-1, and DE-2 satellites. One of the primary questions addressed in this research is the role which EMIC waves have on the transfer of energy from the equatorial magnetosphere to the ionosphere. The primary result from this research is that some fraction of EMIC waves, generated in the equatorial magnetosphere, are Landau damped in the ionosphere and are therefore a heat source for ionospheric electrons. This result as well as other results are summarized below.

  19. Molecular-dynamics simulations of lead clusters

    NASA Astrophysics Data System (ADS)

    Hendy, S. C.; Hall, B. D.

    2001-08-01

    Molecular-dynamics simulations of nanometer-sized lead clusters have been performed using the Lim-Ong-Ercolessi glue potential [Surf. Sci. 269/270, 1109 (1992)]. The binding energies of clusters forming crystalline (fcc), decahedron and icosahedron structures are compared, showing that fcc cuboctahedra are the most energetically favored of these polyhedral model structures. However, simulations of the freezing of liquid droplets produced a characteristic form of surface-reconstructed ``shaved'' icosahedron, in which atoms are absent at the edges and apexes of the polyhedron. This arrangement is energetically favored for 600-4000 atom clusters. Larger clusters favor crystalline structures. Indeed, simulated freezing of a 6525-atom liquid droplet produced an imperfect fcc Wulff particle, containing a number of parallel stacking faults. The effects of temperature on the preferred structure of crystalline clusters below the melting point have been considered. The implications of these results for the interpretation of experimental data is discussed.

  20. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of metal-ion selected dynamic protein libraries.

    PubMed

    Cooper, Helen J; Case, Martin A; McLendon, George L; Marshall, Alan G

    2003-05-07

    The application of electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry to the investigation of the relative stabilities (and thus packing efficiencies) of Fe-bound trihelix peptide bundles is demonstrated. Small dynamic protein libraries are created by metal-ion assisted assembly of peptide subunits. Control of the trimeric aggregation state is coupled to stability selection by exploiting the coordination requirements of Fe(2+) in the presence of bidentate 2,2'-bipyridyl ligands covalently appended to the peptide monomers. At limiting metal-ion concentration, the most thermodynamically stable, optimally packed peptide trimers dominate the mass spectrum. The identities of optimally stable candidate trimers observed in the ESI FT-ICR mass spectra are confirmed by resynthesis of exchange-inert analogues and measurement of their folding free energies. The peptide composition of the trimers may be determined by infrared multiphoton dissociation (IRMPD) MS(3) experiments. Additional sequence information for the peptide subunits is obtained from electron capture dissociation (ECD) of peptides and metal-bound trimers. The experiments also suggest the presence of secondary structure in the gas phase, possibly due to partial retention of the solution-phase coiled coil structure.

  1. Terahertz Dynamics of a Topologically Protected State: Quantum Hall Effect Plateaus near the Cyclotron Resonance of a Two-Dimensional Electron Gas.

    PubMed

    Stier, A V; Ellis, C T; Kwon, J; Xing, H; Zhang, H; Eason, D; Strasser, G; Morimoto, T; Aoki, H; Zeng, H; McCombe, B D; Cerne, J

    2015-12-11

    We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency using highly sensitive Faraday rotation measurements. The sample is electrically gated, allowing the electron density to be changed continuously by more than a factor of 3. We observe clear plateaulike and steplike features in the Faraday rotation angle vs electron density and magnetic field (Landau-level filling factor) even at fields or frequencies very close to cyclotron resonance absorption. These features are the high frequency manifestation of quantum Hall plateaus-a signature of topologically protected edge states. We observe both odd and even filling factor plateaus and explore the temperature dependence of these plateaus. Although dynamical scaling theory begins to break down in the frequency region of our measurements, we find good agreement with theory.

  2. CLOVERLEAF CYCLOTRON

    DOEpatents

    McMillan, E.M.; Judd, D.L.

    1959-02-01

    A cyclotron is presented embodying a unique magnetic field configuration, which configuration increases in intensity with radius and therefore compensates for the reltivistic mass effect, the field having further convolutions productive of axial stability in the particle beam. By reconciling the seemingly opposed requirements of mass increase compensation on one hand and anial stability on the other, the production of extremely high current particle beams in the relativistie energy range is made feasible. Certain further advantages inhere in the invention, notably an increase in the usable magnet gap, simplified and more efficient extraction of the beam from the accelerator, and ready adaptation to the use of multiply phased excitation as contrasted with the single phased systems herstofore utilized. General

  3. Frazil ice dynamics in polynyas and leads

    NASA Astrophysics Data System (ADS)

    Wells, Andrew; Rees Jones, David

    2016-04-01

    The initial stage of sea ice formation in a turbulent ocean typically involves the growth of a suspension of frazil ice crystals in supercooled waters. In competition with turbulent mixing, these crystals rise buoyantly and eventually settle at the ocean surface. The resulting rapid growth of granular ice has been observed to make up a significant fraction of ice cover in certain locations. Our recent theoretical work suggests that the growth of individual frazil ice crystals may be significantly faster than had commonly been supposed. We here explore the consequences for the dynamics of a suspension of many frazil ice crystals in a well mixed layer. Frazil suspensions are affected by many processes, including the fluid dynamics of suspensions, nucleation, the collision and sintering of crystals, as well as crystal growth. These processes combine to control the evolving distribution of crystal sizes. We apply a model of the crystal size distribution in a well mixed layer to investigate the comparative importance of these mechanisms, quantify the controls on ice growth, and compare to available laboratory data. We complement our theoretical model with two-dimensional direct numerical simulations of turbulent convection with a suspension of resolved crystals, in order to elucidate the fluid dynamical coupling between ocean convection with crystal rise, and its impact on ice precipitation rates.

  4. Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and Dynamics Explorer. Semiannual report, 1 June-1 December 1993

    SciTech Connect

    Erlandson, R. E.

    1993-12-31

    The principal activity during the past six months has involved the analysis of ion cyclotron waves recorded from DE-2 using the magnetic field experiment and electric field experiment. The results of this study have been published in the Geophysical Research Letters (GRL). The primary finding of this paper is that ion cyclotron waves were found to heat electrons, as observed in the DE-2 Langmuir probe data, through a Landau damping process. A second activity, which was started during the last six months, involves the study of large amplitude approximately one Hz electric and magnetic field oscillations recorded in the nightside auroral zone at substorm onset. Work is under way to determine the properties of these waves and investigate any association these waves may have with the substorm initiation process. A third activity under way involves a comprehensive study of ion cyclotron waves recorded at ionospheric altitudes by DE-2. This study will be an extension of the work reported in the GRL paper and will involve a larger sampling of wave events. This paper will focus on wave properties at ionospheric altitudes. A fourth activity involves a more in-depth analysis of the acceleration mechanisms and the resulting electron distributions based on the observations presented in the GRL paper.

  5. Molecular dynamics of liquid lead near its melting point

    SciTech Connect

    Khusnutdinov, R. M.; Mokshin, A. V. Yul'met'ev, R. M.

    2009-03-15

    The molecular dynamics of liquid lead is simulated at T = 613 K using the following three models of an interparticle interaction potential: the Dzugutov pair potential and two multiparticle potentials (the 'glue' potential and the Gupta potential). One of the purposes of this work is to determine the optimal model potential of the interatomic interaction in liquid lead. The calculated structural static and dynamic characteristics are compared with the experimental data on X-ray and neutron scattering. On the whole, all three model potentials adequately reproduce the experimental data. The calculations using the Dzugutov pair potential are found to reproduce the structural properties and dynamics of liquid lead on the nanoscale best of all. The role of a multiparticle contribution to the glue and Gupta potentials is studied, and its effect on the dynamic properties of liquid lead in nanoregions is revealed. In particular, the neglect of this contribution is shown to noticeably decrease the acoustic-mode frequency.

  6. Dynamic Stall Characteristics of Drooped Leading Edge Airfoils

    NASA Technical Reports Server (NTRS)

    Sankar, Lakshmi N.; Sahin, Mehmet; Gopal, Naveen

    2000-01-01

    Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.

  7. The effects of leading edge roughness on dynamic stall

    NASA Astrophysics Data System (ADS)

    Hrynuk, John

    2016-11-01

    Dynamic stall is a fundamental flow phenomenon that is commonly observed for insect flight and rotorcraft. Under certain conditions a leading edge vortex forms generating large but temporary lift forces. Historically, computations studying dynamic stall on airfoil shapes have struggled to predict this vortex formation time and separation point. Reduced order models and CFD have performed well when experiments have been performed to develop separation models, but this has limited the development of robust design tools. The current study looks at the effect of leading edge surface roughness on the formation of the Dynamic Stall Vortex (DSV). Roughness elements were applied to the leading edge of a NACA 0012 airfoil and PIV data of the vortex formation process was recorded. Measurements were taken at a Reynolds number of Re = 12,000 and baseline smooth NACA 0012 data was also recorded for comparison. Surface roughness elements, below the typical scale modeled by CFD, are shown to change DSV formation angle and location.

  8. Cyclotron resonance in topological insulators: non-relativistic effects

    NASA Astrophysics Data System (ADS)

    Tabert, C. J.; Carbotte, J. P.

    2015-09-01

    The low-energy Hamiltonian used to describe the dynamics of the helical Dirac fermions on the surface of a topological insulator contains a subdominant non-relativistic (Schrödinger) contribution. This term can have an important effect on some properties while having no effect on others. The Hall plateaus retain the same relativistic quantization as the pure Dirac case. The height of the universal interband background conductivity is unaltered, but its onset is changed. However, the non-relativistic term leads directly to particle-hole asymmetry. It also splits the interband magneto-optical lines into doublets. Here, we find that, while the shape of the semiclassical cyclotron resonance line is unaltered, the cyclotron frequency and its optical spectral weight are changed. There are significant differences in both of these quantities for a fixed value of chemical potential or fixed doping away from charge neutrality depending on whether the Fermi energy lies in the valence or conduction band.

  9. Building 211 cyclotron characterization survey report

    SciTech Connect

    1998-03-30

    The Building 211 Cyclotron Characterization Survey includes an assessment of the radioactive and chemical inventory of materials stored within the facility; an evaluation of the relative distribution of accelerator-produced activation products within various cyclotron components and adjacent structures; measurement of the radiation fields throughout the facility; measurement and assessment of internal and external radioactive surface contamination on various equipment, facility structures, and air-handling systems; and an assessment of lead (Pb) paint and asbestos hazards within the facility.

  10. The effect of leading edge tubercles on dynamic stall

    NASA Astrophysics Data System (ADS)

    Hrynuk, John

    The effect of the leading edge tubercles of humpback whales has been heavily studied for their static benefits. These studies have shown that tubercles inhibit flow separation, limit spanwise flow, and extend the operating angle of a wing beyond the static stall point while maintaining lift, all while having a comparatively low negative impact on drag. The current study extends the prior work to investigating the effect of tubercles on dynamic stall, a fundamental flow phenomenon that occurs when wings undergo dynamic pitching motions. Flow fields around the wing models tested were studied using Laser Induced Fluorescence (LIF) and Molecular Tagging Velocimetry (MTV).Resulting velocity fields show that the dynamics of the formation and separation of the leading edge vortex were fundamentally different between the straight wing and the tubercled wing. Tracking of the Dynamic Stall Vortex (DSV) and Shear Layer Vortices (SLVs), which may have a significant impact on the overall flow behavior, was done along with calculations of vortex circulation. Proximity to the wing surface and total circulation were used to evaluate potential dynamic lift increases provided by the tubercles. The effects of pitch rate on the formation process and benefits of the tubercles were also studied and were generally consistent with prior dynamic stall studies. However, tubercles were shown to affect the SLV formation and the circulation differently at higher pitch rates.

  11. Defining the clonal dynamics leading to mouse skin tumour initiation

    PubMed Central

    Sánchez-Danés, Adriana; Hannezo, Edouard; Larsimont, Jean-Christophe; Liagre, Mélanie; Youssef, Khalil Kass; Simons, Benjamin D; Blanpain, Cédric

    2016-01-01

    The changes that occur in cell dynamics following oncogenic mutation that lead to the development of tumours are currently unknown. Here, using skin epidermis as a model, we assessed the impact of oncogenic hedgehog signalling in distinct cell populations and their capacity to induce basal cell carcinoma, the most frequent cancer in humans. We found that only stem cells, and not progenitors, were competent to initiate tumour formation upon oncogenic hedgehog signalling. Interestingly, this difference was due to the hierarchical organization of tumour growth in oncogene-targeted stem cells, characterized by an increase of symmetric self-renewing divisions and a higher p53-dependent resistance to apoptosis, leading to rapid clonal expansion and progression into invasive tumours. Our work reveals that the capacity of oncogene-targeted cells to induce tumour formation is not only dependent on their long-term survival and expansion, but also on the specific clonal dynamics of the cancer cell of origin. PMID:27459053

  12. Simulations of ion cyclotron anisotropy instabilities in the terrestrial magnetosheath

    NASA Technical Reports Server (NTRS)

    Gary, S. P.; Winske, Dan

    1993-01-01

    Enhanced transverse magnetic fluctuations observed below the proton cyclotron frequency in the terrestrial magnetosheath have been identified as due to the proton cyclotron and helium cyclotron instabilities driven by the T-perpendicular greater than T-parallel condition of the sheath ions. One-dimensional hybrid computer simulations are used here to examine the nonlinear properties of these two growing modes at relatively weak fluctuation energies and for wave vectors parallel to the background magnetic field. Second-order theory predicts fluctuating magnetic field energies at saturation of the proton cyclotron anisotropy instability in semiquantitative agreement with the simulation results. Introduction of the helium component enhances the wave-particle exchange rate for proton anisotropy reduction by that instability, thereby reducing the saturation energy of that mode. The simulations demonstrate that wave-particle interactions by the proton cyclotron and helium cyclotron instabilities lead to the anticorrelation observed by Anderson and Fuselier (1993).

  13. 88-Inch Cyclotron newsletter

    SciTech Connect

    Stokstad, R.

    1987-02-01

    Activities at the 88-Inch Cyclotron are discussed. Increased beam time demand and operation of the ECR source and cyclotron are reported. Experimental facility improvements are reported, including improvements to the High Energy Resolution Array and to the Recoil Atom Mass Analyzer, a new capture beamline, development of a low background counting facility. Other general improvements are reported that relate to the facility computer network and electronics pool. Approved heavy nuclei research is briefly highlighted. Also listed are the beams accelerated by the cyclotron. (LEW)

  14. Leading edge vortex dynamics on a pitching delta wing

    NASA Technical Reports Server (NTRS)

    Lemay, S. P.; Batill, S. M.; Nelson, R. C.

    1988-01-01

    A study of the dynamic behavior of the leading edge vortices on a delta wing undergoing oscillatory pitching motion is presented. A sharp edge, flat plate, delta wing having a sweep angle of 70 deg was used in this investigation. The wing was sinusoidally pitched about its 1/2 chord position at reduced frequencies ranging from k = 2(pi)fc/u = 0.05 to 0.30 at chord Reynolds numbers between 90,000 and 350,000, for angle of attack ranges of 29 to 39 deg and 0 to 45 deg. During these dynamic motions, visualization of the leading edge vortices was obtained by marking the vortices with TiCl4 introduced through ports located near the model apex. The location of vortex breakdown was recorded using high speed motion picture photography. The motion picture records were analyzed to determine vortex trajectory and breakdown position as a function of angle of attack. When the wing was sinusoidally pitched, a hysteresis was observed in the location of breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing, and the phase lag between model motion and breakdown location were also determined. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases.

  15. Structural defects lead to dynamic entrapment in cardiac electrophysiology.

    PubMed

    Bates, Oliver R J; Suki, Bela; Spector, Peter S; Bates, Jason H T

    2015-01-01

    Biological networks are typically comprised of many parts whose interactions are governed by nonlinear dynamics. This potentially imbues them with the ability to support multiple attractors, and therefore to exhibit correspondingly distinct patterns of behavior. In particular, multiple attractors have been demonstrated for the electrical activity of the diseased heart in situations where cardioversion is able to convert a reentrant arrhythmia to a stable normal rhythm. Healthy hearts, however, are typically resilient to abnormal rhythms. This raises the question as to how a healthy cardiac cell network must be altered so that it can support multiple distinct behaviors. Here we demonstrate how anatomic defects can give rise to multi-stability in the heart as a function of the electrophysiological properties of the cardiac tissue and the timing of activation of ectopic foci. This leads to a form of hysteretic behavior, which we call dynamic entrapment, whereby the heart can become trapped in aberrant attractor as a result of a transient change in tissue properties. We show that this can lead to a highly inconsistent relationship between clinical symptoms and underlying pathophysiology, which raises the possibility that dynamic entrapment may underlie other forms of chronic idiopathic illness.

  16. Structural Defects Lead to Dynamic Entrapment in Cardiac Electrophysiology

    PubMed Central

    Bates, Oliver R. J.; Suki, Bela; Spector, Peter S.; Bates, Jason H. T.

    2015-01-01

    Biological networks are typically comprised of many parts whose interactions are governed by nonlinear dynamics. This potentially imbues them with the ability to support multiple attractors, and therefore to exhibit correspondingly distinct patterns of behavior. In particular, multiple attractors have been demonstrated for the electrical activity of the diseased heart in situations where cardioversion is able to convert a reentrant arrhythmia to a stable normal rhythm. Healthy hearts, however, are typically resilient to abnormal rhythms. This raises the question as to how a healthy cardiac cell network must be altered so that it can support multiple distinct behaviors. Here we demonstrate how anatomic defects can give rise to multi-stability in the heart as a function of the electrophysiological properties of the cardiac tissue and the timing of activation of ectopic foci. This leads to a form of hysteretic behavior, which we call dynamic entrapment, whereby the heart can become trapped in aberrant attractor as a result of a transient change in tissue properties. We show that this can lead to a highly inconsistent relationship between clinical symptoms and underlying pathophysiology, which raises the possibility that dynamic entrapment may underlie other forms of chronic idiopathic illness. PMID:25756656

  17. Cyclotron Institute Upgrade Project

    SciTech Connect

    Clark, Henry; Yennello, Sherry; Tribble, Robert

    2014-08-26

    The Cyclotron Institute at Texas A&M University has upgraded its accelerator facilities to extend research capabilities with both stable and radioactive beams. The upgrade is divided into three major tasks: (1) re-commission the K-150 (88”) cyclotron, couple it to existing beam lines to provide intense stable beams into the K-500 experimental areas and use it as a driver to produce radioactive beams; (2) develop light ion and heavy ion guides for stopping radioactive ions created with the K-150 beams; and (3) transport 1+ ions from the ion guides into a charge-breeding electron-cyclotron-resonance ion source (CB-ECR) to produce highly-charged radioactive ions for acceleration in the K-500 cyclotron. When completed, the upgraded facility will provide high-quality re-accelerated secondary beams in a unique energy range in the world.

  18. Generalized Master Equations Leading to Completely Positive Dynamics

    NASA Astrophysics Data System (ADS)

    Vacchini, Bassano

    2016-12-01

    We provide a general construction of quantum generalized master equations with a memory kernel leading to well-defined, that is, completely positive and trace-preserving, time evolutions. The approach builds on an operator generalization of memory kernels appearing in the description of non-Markovian classical processes and puts into evidence the nonuniqueness of the relationship arising due to the typical quantum issue of operator ordering. The approach provides a physical interpretation of the structure of the kernels, and its connection with the classical viewpoint allows for a trajectory description of the dynamics. Previous apparently unrelated results are now connected in a unified framework, which further allows us to phenomenologically construct a large class of non-Markovian evolutions taking as the starting point collections of time-dependent maps and instantaneous transformations describing the microscopic interaction dynamics.

  19. Relaxation dynamics of lithium ions in lead bismuthate glasses

    NASA Astrophysics Data System (ADS)

    Pan, A.; Ghosh, A.

    2000-08-01

    We have investigated relaxation dynamics of lithium ions in lead bismuthate glasses in the frequency range from 10 Hz to 2 MHz and in the temperature range from 303-553 K. Using the Anderson-Stuart model, we have calculated the activation energy, which is observed to be lower than that of the dc conductivity. We have studied the relaxation mechanism of these glasses in the framework of the electric modulus and conductivity formalisms. The microscopic parameters obtained from these formalisms have been compared. We have also calculated the decoupling index and correlated them with the stretched exponential relaxation parameter and the dc conductivity.

  20. Stability of the Electron Cyclotron Resonance

    NASA Astrophysics Data System (ADS)

    Asch, Joachim; Bourget, Olivier; Meresse, Cédric

    2015-12-01

    We consider the magnetic AC Stark effect for the quantum dynamics of a single particle in the plane under the influence of an oscillating homogeneous electric and a constant perpendicular magnetic field. We prove that the electron cyclotron resonance is insensitive to impurity potentials.

  1. Spatial cyclotron damping

    NASA Technical Reports Server (NTRS)

    Olson, C. L.

    1970-01-01

    To examine spatial electron cyclotron damping in a uniform Vlasov plasma, it is noted that the plasma response to a steady-state transverse excitation consists of several terms (dielectric-pole, free-streaming, and branch-cut), but that the cyclotron-damped pole term is the dominant term for z l = c/w sub ce provided (w sub pe/w sub ce) squared (c/a) is much greater than 1. If the latter inequality does not hold, then the free-streaming and branch-cut terms persist well past z = c/w sub ce as w sub 1 approaches w sub ce, making experimental measurement of cyclotron damping essentially impossible. Considering only (w sub pe/w sub ce) squared (c/a) is much greater than 1, it is shown how collisional effects should be estimated and how a finite-width excitation usually has little effect on the cyclotron-damped part of the response. Criteria is established concerning collisional damping, measurable damping length sizes, and allowed uncertainty in the magnetic field Beta. Results of numerical calculations, showing the regions in the appropriate parameter spaces that meet these criteria, are presented. From these results, one can determine the feasibility of, or propose parameter values for, an experiment designed to measure spatial cyclotron damping. It is concluded that the electron temperature T sub e should be at least 1 ev., and preferably 10 ev. or higher, for a successful experiment.

  2. The electromagnetic ion cyclotron beam anisotropy instability

    NASA Technical Reports Server (NTRS)

    Peter Gary, S.; Schriver, David

    1987-01-01

    Electromagnetic instabilities driven by an anisotropic, relatively cool ion beam are studied for the case in which both the beam and the instabilities propagate parallel or antiparallel to a uniform magnetic field. At modest beam-core relative drift speeds, sufficiently large perpendicular-to-parallel beam temperature ratios and sufficiently large plasma beta, the mode of fastest growth rate is the ion cyclotron beam anisotropy instability. Because the right-hand polarized waves observed upstream of slow shocks in the earth's magnetotail can lead to the appropriate beam anisotropy, the ion cyclotron instability may be present and account for the left-hand polarized magnetic waves observed there. Also, because of its relatively low phase speed, the ion cyclotron beam anisotropy instability may provide the scattering necessary for ion Fermi acceleration at slow shocks of sufficiently high plasma beta.

  3. Solvent Exchange Leading to Nanobubble Nucleation: A Molecular Dynamics Study

    PubMed Central

    2017-01-01

    The solvent exchange procedure has become the most-used protocol to produce surface nanobubbles, while the molecular mechanisms behind the solvent exchange are far from being fully understood. In this paper, we build a simple model and use molecular dynamics simulations to investigate the dynamic characteristics of solvent exchange for producing nanobubbles. We find that at the first stage of solvent exchange, there exists an interface between interchanging solvents of different gas solubility. This interface moves toward the substrate gradually as the exchange process proceeds. Our simulations reveal directed diffusion of gas molecules against the gas concentration gradient, driven by the solubility gradient of the liquid composition across the moving solvent–solvent interface. It is this directed diffusion that causes gas retention and produces a local gas oversaturation much higher near the substrate than far from it. At the second stage of solvent exchange, the high local gas oversaturation leads to bubble nucleation either on the solid surface or in the bulk solution, which is found to depend on the substrate hydrophobicity and the degree of local gas oversaturation. Our findings suggest that solvent exchange could be developed into a standard procedure to produce oversaturation and used to a variety of nucleation applications other than generating nanobubbles. PMID:28742364

  4. Solvent Exchange Leading to Nanobubble Nucleation: A Molecular Dynamics Study.

    PubMed

    Xiao, Qianxiang; Liu, Yawei; Guo, Zhenjiang; Liu, Zhiping; Lohse, Detlef; Zhang, Xianren

    2017-08-15

    The solvent exchange procedure has become the most-used protocol to produce surface nanobubbles, while the molecular mechanisms behind the solvent exchange are far from being fully understood. In this paper, we build a simple model and use molecular dynamics simulations to investigate the dynamic characteristics of solvent exchange for producing nanobubbles. We find that at the first stage of solvent exchange, there exists an interface between interchanging solvents of different gas solubility. This interface moves toward the substrate gradually as the exchange process proceeds. Our simulations reveal directed diffusion of gas molecules against the gas concentration gradient, driven by the solubility gradient of the liquid composition across the moving solvent-solvent interface. It is this directed diffusion that causes gas retention and produces a local gas oversaturation much higher near the substrate than far from it. At the second stage of solvent exchange, the high local gas oversaturation leads to bubble nucleation either on the solid surface or in the bulk solution, which is found to depend on the substrate hydrophobicity and the degree of local gas oversaturation. Our findings suggest that solvent exchange could be developed into a standard procedure to produce oversaturation and used to a variety of nucleation applications other than generating nanobubbles.

  5. Quantifying the Determinants of Evolutionary Dynamics Leading to Drug Resistance

    PubMed Central

    Chevereau, Guillaume; Dravecká, Marta; Batur, Tugce; Guvenek, Aysegul; Ayhan, Dilay Hazal; Toprak, Erdal; Bollenbach, Tobias

    2015-01-01

    The emergence of drug resistant pathogens is a serious public health problem. It is a long-standing goal to predict rates of resistance evolution and design optimal treatment strategies accordingly. To this end, it is crucial to reveal the underlying causes of drug-specific differences in the evolutionary dynamics leading to resistance. However, it remains largely unknown why the rates of resistance evolution via spontaneous mutations and the diversity of mutational paths vary substantially between drugs. Here we comprehensively quantify the distribution of fitness effects (DFE) of mutations, a key determinant of evolutionary dynamics, in the presence of eight antibiotics representing the main modes of action. Using precise high-throughput fitness measurements for genome-wide Escherichia coli gene deletion strains, we find that the width of the DFE varies dramatically between antibiotics and, contrary to conventional wisdom, for some drugs the DFE width is lower than in the absence of stress. We show that this previously underappreciated divergence in DFE width among antibiotics is largely caused by their distinct drug-specific dose-response characteristics. Unlike the DFE, the magnitude of the changes in tolerated drug concentration resulting from genome-wide mutations is similar for most drugs but exceptionally small for the antibiotic nitrofurantoin, i.e., mutations generally have considerably smaller resistance effects for nitrofurantoin than for other drugs. A population genetics model predicts that resistance evolution for drugs with this property is severely limited and confined to reproducible mutational paths. We tested this prediction in laboratory evolution experiments using the “morbidostat”, a device for evolving bacteria in well-controlled drug environments. Nitrofurantoin resistance indeed evolved extremely slowly via reproducible mutations—an almost paradoxical behavior since this drug causes DNA damage and increases the mutation rate. Overall

  6. A dynamic simulation of a lead blast furnace

    NASA Astrophysics Data System (ADS)

    Chao, John T.

    1981-06-01

    A dynamic model has been developed to simulate the operation of the stack zone of a lead blast furnace. The mathematical formulation of the governing equations of change leads to a system of 2nd order partial differential equations, which is solved by finite difference methods. A reduction model of ash-layer diffusion controlled mechanism, which allows the stepwise reduction to the lowest oxide or metal thermodynamically possible for the local gas composition within the sinter, is employed in this model. The surface reaction and the internal diffusion in the porous solid particles are taken into account in the coke gasification reaction. The profiles of the temperatures of gases and solids, solid compositions, and gas compositions and pressure in both radial and axial directions are predicted by the model. The results provide a good representation of the experimental data obtained for the blast furnace at Brunswick Mining and Smelting Corp., Ltd., New Brunswick, Canada and also of the less extensive data available for the Cominco blast furnace at Trail, British Columbia, Canada. In addition to the modelling of the stack, a mass and energy balance for the bosh zone is also included in the present calculation. The improvement of coke efficiency due to oxygen enrichment in the blast air for the Brunswick Furnace were interpreted semiquantitatively. The effect of sinter size distribution on the furnace performance has also been studied.

  7. Inflation and cyclotron motion

    NASA Astrophysics Data System (ADS)

    Greensite, Jeff

    2017-01-01

    We consider, in the context of a braneworld cosmology, the motion of the Universe coupled to a four-form gauge field, with constant field strength, defined in higher dimensions. It is found, under rather general initial conditions, that in this situation there is a period of exponential inflation combined with cyclotron motion in the inflaton field space. The main effect of the cyclotron motion is that slow roll conditions on the inflaton potential, which are typically necessary for exponential inflation, can be evaded. There are Landau levels associated with the four-form gauge field, and these correspond to quantum excitations of the inflaton field satisfying unconventional dispersion relations.

  8. Lawrence's Legacy : Seaborg's Cyclotron - The 88-Inch Cyclotron turns 40

    NASA Astrophysics Data System (ADS)

    McMahan, Margaret; Clark, David

    2003-04-01

    In 1958, Sputnik had recently been launched by the Russians, leading to worry in Congress and increased funding for science and technology. Ernest Lawrence was director of the "Rad Lab" at Berkeley. Another Nobel Prize winner, Glenn Seaborg, was Associate Laboratory Director and Director of the Nuclear Chemistry Division. In this atmosphere, Lawrence was phoned by commissioners of the Atomic Energy Commission and asked what they could do for Seaborg, "because he did such a fine job of setting up the chemistry for extracting plutonium from spent reactor fuel" [1]. In this informal way, the 90-Inch (eventually 88-Inch) Cyclotron became a line item in the federal budget at a cost of 3M (later increased to 5M). The 88-Inch Cyclotron achieved first internal beam on Dec. 12, 1961 and first external beam in May 1962. Forty years later it is still going strong. Pieced together from interviews with the retirees who built it, Rad Lab reports and archives from the Seaborg and Lawrence collections, the story of its design and construction - on-time and under-budget - provides a glimpse into the early days of big science. [1] remarks made by Elmer Kelly, "Physicist-in-charge' of the project on the occasion of the 40th anniversary celebration.

  9. Lead

    MedlinePlus

    ... EPA United States Environmental Protection Agency Search Search Lead Contact Us Share Lead Poisoning is Preventable If your home was built ... to protect people from harmful lead exposures. Less Lead in Drinking Water = Better Health Learn about the ...

  10. Cyclotron Research and Applications

    SciTech Connect

    Mach, Rostislav

    2010-01-05

    The twenty years old cyclotron U-120M was upgraded for R and D and Production of Radiopharmaceuticals. R and D on short-lived Radiopharmaceuticals production is done at this accelerator. These Radiopharmaceuticals are eventually delivered to nearby hospitals. Development of new diagnostic radiopharmaceuticals is also pursued at the facility. your paper.

  11. The Warsaw K=160 cyclotron

    NASA Astrophysics Data System (ADS)

    Choinski, J.; Miszczak, J.; Sura, J.

    2001-12-01

    The overview of the Warsaw cyclotron facility is presented. The facility consists of K=160 cyclotron, 10 GHz ECR ion source, and several experimental stations. The cyclotron is of compact design with 2 straight dees. A yearly operation time is about 2900 hours on an average for the past few years. The cyclotron can deliver beams up to Ar with energy up to 10 MeV/amu to the experimental area. Experimental stations are: 1) The multidetector OSIRIS II, allows the study of exotic nuclei in the double magic 100Sn region. The experimental set-up consists of 8 HPGe detectors equipped with charged particle 4π multiplicity filter SiBall, 50 elements BGO γ-rays multiplicity filter, 4 sector polarimeter and electron conversion detector system. 2) CUDAC-Coulomb Universal Detector Scattering Chamber-an array of PIN-diodes in connection with HPGe detectors and the computer data analysis package GOSIA, maintained by the Laboratory allows investigation the Coulomb Excitation (COULEX) reactions. 3) IGISOL or Helium-jet transport system opened investigation of the reaction products by means of the online mass separator with ion-guide system. The system uses the Scandinavian-type mass separator built in INR Świerk, Poland. 4) Giant Dipole Resonance studies using experimental set-up JANOSIK developed for the detection of high-energy photons emitted in heavy-ion collisions. The set-up consists of a large NaI(Tl) detector (25 cm×29 cm) surrounded by shields: passive lead shield, active anticoincidence plastic shield and LiH shield to absorb neutrons, and a multiplicity filter of 32 small scintillator detectors (BaF2 and NaI(Tl)). 5) Laser spectroscopy stand now in test phase. The laser spectroscopy group at HIL has completed an equipment consisting of Argon ion Laser Innova 400-25W in all lines and coherent Ring Laser 669-21 as well as atomic beam apparatus.

  12. Shielding design of the Mayo Clinic Scottsdale cyclotron vault

    NASA Astrophysics Data System (ADS)

    Riper, Kenneth A. Van; Metzger, Robert L.; Nelson, Kevin

    2017-09-01

    Mayo Clinic Scottsdale (Scottsdale, Arizona) is building a cyclotron vault containing a cyclotron with adjacent targets and a beam line leading to an external target. The targets are irradiated by high energy (15 to 16.5 MeV) protons for the production of radioisotopes. We performed Monte Carlo radiation transport simulations to calculate the radiation dose outside of the vault during irradiation of the cyclotron and external targets. We present the Monte Carlo model including the geometry, sources, and variance reduction methods. Mesh tallies surrounding the vault show the external dose rate is within acceptable limits.

  13. Influence of static electron beam`s self-fields on the cyclotron-undulator resonance

    SciTech Connect

    Rozanov, N.E.; Golub, Yu.Ya. |

    1995-12-31

    When undulators with a leading magnetic field B are used, the regime of double resonance is possible in which an undulator period is equal to an electron cyclotron wavelength. In the vicinity of this resonance an amplitude of particle oscillations in the undulator strongly depends on a difference between B and a resonant value of the leading magnetic field. Consequently, it is important to investigate a role of self-fields of the electron beam, in particular, due to its influence on the electron cyclotron wavelength. At the paper analytically and by numerical simulation the influence of the static fields of the annular electron beam on its dynamics in the axisymmetrical magnetic undulator with the leading magnetic field in the vicinity of the cyclotron-undulator resonance is investigated. It is shown that the value of the resonant magnetic field is changed with the rise of beam`s current. A shift of the resonant magnetic field may be both to larger values of B and to smaller ones, when different values of beam and waveguide radii, beam energy and undulator period are considered. A width of the resonance (on B - scale) is increased with the beam current.

  14. Cyclotron-based neutron source for BNCT

    SciTech Connect

    Mitsumoto, T.; Yajima, S.; Tsutsui, H.; Ogasawara, T.; Fujita, K.; Tanaka, H.; Sakurai, Y.; Maruhashi, A.

    2013-04-19

    Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation and treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutron collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8 Multiplication-Sign 109 neutrons/cm{sup 2}/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with {sup 10}B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.

  15. Leading Dynamic Schools: How to Create and Implement Ethical Policies

    ERIC Educational Resources Information Center

    Rallis, Sharon F.; Rossman, Gretchen B.; Cobb, Casey D.; Reagan, Timothy G.; Kuntz, Aaron

    2007-01-01

    This companion book to "Principals of Dynamic Schools" and "Dynamic Teachers" brings to life the process of making and enacting educational policy and helps decision makers evaluate, interpret, and analyze the policies that govern their schools. In accessible language, this book presents educational leaders with a conceptual framework for…

  16. Leading Dynamic Schools: How to Create and Implement Ethical Policies

    ERIC Educational Resources Information Center

    Rallis, Sharon F.; Rossman, Gretchen B.; Cobb, Casey D.; Reagan, Timothy G.; Kuntz, Aaron

    2007-01-01

    This companion book to "Principals of Dynamic Schools" and "Dynamic Teachers" brings to life the process of making and enacting educational policy and helps decision makers evaluate, interpret, and analyze the policies that govern their schools. In accessible language, this book presents educational leaders with a conceptual framework for…

  17. Design Study Of Cyclotron Magnet With Permanent Magnet

    SciTech Connect

    Kim, Hyun Wook; Chai, Jong Seo

    2011-06-01

    Low energy cyclotrons for Positron emission tomography (PET) have been wanted for the production of radio-isotopes after 2002. In the low energy cyclotron magnet design, increase of magnetic field between the poles is needed to make a smaller size of magnet and decrease power consumption. The Permanent magnet can support this work without additional electric power consumption in the cyclotron. In this paper the study of cyclotron magnet design using permanent magnet is shown and also the comparison between normal magnet and the magnet which is designed with permanent magnet is shown. Maximum energy of proton is 8 MeV and RF frequency is 79.3 MHz. 3D CAD design was done by CATIA P3 V5 R18 and the All field calculations had been performed by OPERA-3D TOSCA. The self-made beam dynamics program OPTICY is used for making isochronous field and other calculations.

  18. Design Study Of Cyclotron Magnet With Permanent Magnet

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Wook; Chai, Jong Seo

    2011-06-01

    Low energy cyclotrons for Positron emission tomography (PET) have been wanted for the production of radio-isotopes after 2002. In the low energy cyclotron magnet design, increase of magnetic field between the poles is needed to make a smaller size of magnet and decrease power consumption. The Permanent magnet can support this work without additional electric power consumption in the cyclotron. In this paper the study of cyclotron magnet design using permanent magnet is shown and also the comparison between normal magnet and the magnet which is designed with permanent magnet is shown. Maximum energy of proton is 8 MeV and RF frequency is 79.3 MHz. 3D CAD design was done by CATIA P3 V5 R18 [1] and the All field calculations had been performed by OPERA-3D TOSCA [2]. The self-made beam dynamics program OPTICY [3] is used for making isochronous field and other calculations.

  19. Balanced excitation and inhibition lead to statistical and dynamical criticality

    NASA Astrophysics Data System (ADS)

    Cecchi, Guillermo

    2010-03-01

    We present a simple abstract model, an anti-Hebbian network which spontaneously poises itself, by balancing excitation and inhibition, at a dynamically critical state: an extensive number of degrees of freedom approach Hopf bifurcations, becoming arbitrarily sensitive to external perturbations (PRL 102, 258102 - 2009). As the dynamics controlling this state has itself a marginal fixed point, the eigenvalues fluctuate close to the imaginary axis; when they become slightly unstable, the corresponding mode ``breaks out'' and becomes more prominent, and as they become slightly stable the mode slowly damps out. This breakout dynamics displays avalanche-like activity bursts whose sizes may be power-law distributed, i.e. statistically critical. Within these epochs the neurons of our model are slightly correlated; yet, as the number of small but significant correlations is high, the model has strongly correlated network states. This system is, on the short time-scale, sensitive in bulk to any outside input, even if applied only to a small subset of the neurons. We also present preliminary results showing that human brain electro-physiological recordings display both statistical and dynamical criticality.

  20. Lead

    MedlinePlus

    ... are approximately half a million U.S. children ages 1-5 with blood lead levels above 5 micrograms per deciliter (µg/dL), the reference level at which CDC recommends public health actions be initiated. No safe blood lead level in children has been ...

  1. Cyclotrons and positron emitting radiopharmaceuticals

    SciTech Connect

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs. (ACR)

  2. Dynamics of Leading-strand Lesion Skipping by the Replisome

    PubMed Central

    Yeeles, Joseph T.P.; Marians, Kenneth J.

    2013-01-01

    SUMMARY The E. coli replisome stalls transiently when it encounters a lesion in the leading-strand template, skipping over the damage by reinitiating replication at a new primer synthesized downstream by the primase. We report here that template unwinding and lagging-strand synthesis continue downstream of the lesion at a reduced rate after replisome stalling, that one replisome is capable of skipping multiple lesions, and that the rate limiting steps of replication restart involve the synthesis and activation of the new primer downstream. We also find little support for the concept that polymerase uncoupling, where extensive lagging-strand synthesis proceeds downstream in the absence of leading-strand synthesis, involves physical separation of the leading-strand polymerase from the replisome. Instead, our data indicate that extensive uncoupled replication likely results from a failure of the leading-strand polymerase still associated with the DNA helicase and the lagging-strand polymerase that are proceeding downstream to reinitiate synthesis. PMID:24268579

  3. Dynamic Instability Leading to Increased Interchange Reconnection Rates

    NASA Astrophysics Data System (ADS)

    Edmondson, J. K.; Antiochos, S. K.; Zurbuchen, T. H.

    2008-12-01

    Interchange reconnection is widely believed to play an important role in coronal magnetic field dynamics. In this investigation we investigate the 3D dynamics of interchange reconnection by extending the concept of a magnetic null-point to a null-volume, the so-called "acute-cusp field" configuration. The acute-cusp field geometry is characterized by high-beta plasma confined with favorable curvature, surrounded by a low-beta environment. First, we construct an initial translationally-symmetric potential field configuration. This configuration contains the required topological characteristics of four separate flux systems in the perpendicular plane. We then drive the system by a slow, incompressible, uniform flow at the boundary. The resulting evolution is calculated by solving numerically the MHD equations in full 3D Cartesian coordinates using the Adaptively Refined MHD Solver developed at the U.S. Naval Research Laboratory. Field shearing along the topological boundaries changes the shape of the acute-cusp field surface separating the high and low plasma beta regions. An extended, 2D current sheet is generated by the photospheric driving. We discuss the effect of 3D perturbations on the current sheet dynamics and on the rate of the resulting interchange reconnection. Finally, we discuss the implications of our simulations for coronal observations. This work has been supported, in part, by the NASA HTP and SR&T programs.

  4. Leading at the Front: How EB Proteins Regulate Microtubule Dynamics

    NASA Astrophysics Data System (ADS)

    Hawkins, Taviare

    2012-02-01

    Microtubules are the most rigid of the cytoskeletal filaments, they provide the cell's scaffolding, form the byways on which motor proteins transport intracellular cargo and reorganize to form the mitotic spindle when the cell needs to divide. These biopolymers are composed of alpha and beta tubulin monomers that create hollow cylindrical nanotubes with an outer diameter of 25 nm and an inner diameter of 17 nm. At steady state concentrations, microtubules undergo a process known as dynamic instability. During dynamic instability the length of individual microtubules is changing as the filament alternates between periods of growth to shrinkage (catastrophe) and shrinkage to growth (rescue). This process can be enhanced or diminished with the addition of microtubule associated proteins (MAPs). MAPs are microtubule binding proteins that stabilize, destabilize, or nucleate microtubules. We will discuss the effects of the stabilizing end-binding proteins (EB1, EB2 and EB3), on microtubule dynamics observed in vitro. The EBs are a unique family of MAPs known to tip track and enhance microtubule growth by stabilizing the ends. This is a different mechanism than those employed by structural MAPs such as tau or MAP4.

  5. Female juvenile murderers: Biological and psychological dynamics leading to homicide.

    PubMed

    Heide, Kathleen M; Solomon, Eldra P

    2009-01-01

    The increasing involvement of girls under 18 in violent crime has been a matter of growing concern in the United States in recent years. This article reviews the arrests of female juveniles for violent crime and then focuses specifically on their involvement in homicide. Arrests of girls for murder, unlike arrests for assault, have not risen over the last 30 years, suggesting that the dynamics that propel female juveniles to engage in lethal violence differ from those contributing to assaultive behavior by this same group. A review of the literature indicates that theories as to why female adolescents kill do not take into account recent scientific findings on brain development and the biological effects of early trauma in explaining serious violent behavior by girls. Three cases, evaluated by the authors, involving female adolescents charged with murder or attempted murder, are presented. The authors focus on the biological and psychological dynamics that help explain their violent behavior. They discuss the effects of insecure attachment and child maltreatment, and trace a critical pathway between these early experiences and future risk of violent behavior. The dynamics of child maltreatment in fostering rage and violence are discussed thereafter in terms of offender accountability. The article concludes with a discussion of treatment and recommendations for future research.

  6. Ion cyclotron resonance cell

    DOEpatents

    Weller, R.R.

    1995-02-14

    An ion cyclotron resonance cell is disclosed having two adjacent sections separated by a center trapping plate. The first section is defined by the center trapping plate, a first end trapping plate, and excitation and detector electrodes. The second section includes a second end trapping plate spaced apart from the center plate, a mirror, and an analyzer. The analyzer includes a wavelength-selective light detector, such as a detector incorporating an acousto-optical device (AOD) and a photodetector. One or more ion guides, grounded plates with holes for the ion beam, are positioned within the vacuum chamber of the mass spectrometer between the ion source and the cell. After ions are trapped and analyzed by ion cyclotron resonance techniques in the first section, the ions of interest are selected according to their mass and passed into the second section for optical spectroscopic studies. The trapped ions are excited by light from a laser and caused thereby to fluoresce. The fluorescent light emitted by the excited ions is reflected by the mirror and directed onto the detector. The AOD is scanned, and the photodetector output is recorded and analyzed. The ions remain in the second section for an extended period, enabling multiple studies to be carried out on the same ensemble of ions. 5 figs.

  7. Ion cyclotron resonance cell

    DOEpatents

    Weller, Robert R.

    1995-01-01

    An ion cyclotron resonance cell having two adjacent sections separated by a center trapping plate. The first section is defined by the center trapping plate, a first end trapping plate, and excitation and detector electrodes. The second section includes a second end trapping plate spaced apart from the center plate, a mirror, and an analyzer. The analyzer includes a wavelength-selective light detector, such as a detector incorporating an acousto-optical device (AOD) and a photodetector. One or more ion guides, grounded plates with holes for the ion beam, are positioned within the vacuum chamber of the mass spectrometer between the ion source and the cell. After ions are trapped and analyzed by ion cyclotron resonance techniques in the first section, the ions of interest are selected according to their mass and passed into the second section for optical spectroscopic studies. The trapped ions are excited by light from a laser and caused thereby to fluoresce. The fluorescent light emitted by the excited ions is reflected by the mirror and directed onto the detector. The AOD is scanned, and the photodetector output is recorded and analyzed. The ions remain in the second section for an extended period, enabling multiple studies to be carried out on the same ensemble of ions.

  8. Generation of multi-charged high current ion beams using the SMIS 37 gas-dynamic electron cyclotron resonance (ECR) ion source

    SciTech Connect

    Dorf, M. A.; Zorin, V. G.; Sidorov, A. V.; Bokhanov, A. F.; Izotov, I. V.; Razin, S. V.; Skalyga, V. A.

    2013-06-02

    A gas-dynamic ECR ion source (GaDIS) is distinguished by its ability to produce high current and high brightness beams of moderately charged ions. Contrary to a classical ECR ion source where the plasma confinement is determined by the slow electron scattering into an empty loss-cone, the higher density and lower electron temperature in a GaDIS plasma lead to an isotropic electron distribution with the confinement time determined by the prompt gas-dynamic flow losses. As a result, much higher ion fluxes are available, however a decrease in the confinement time of the GaDIS plasma lowers the ion charge state. The gas-dynamic ECR ion source concept has been successfully realized in the SMIS 37 experimental facility operated at the Institute of Applied Physics, Russia. The use of high-power (~100 kW) microwave (37.5 GHz) radiation provides a dense plasma (~1013 cm-3) with a relatively low electron temperature (~50- 100 eV) and allows for the generation of high current (~1 A/cm2) beams of multi-charged ions. In this work we report on the present status of the SMIS 37 ion source and discuss the advanced numerical modeling of ion beam extraction using the particle-in-cell code WARP

  9. Exploring the cation dynamics in lead-bromide hybrid perovskites

    NASA Astrophysics Data System (ADS)

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2016-06-01

    Density functional theory including a many-body treatment of dispersive forces is used to describe the interplay between structure and electronic properties of two prototypical Br-based hybrid perovskites, namely, CH3NH3PbBr3 and HC (NH2)2PbBr3 . We find that, like for some of their iodine-based counterparts, the molecules' orientation plays a crucial role in determining the shape of both the conduction and valence bands around the band edges. This is mostly evident in the case of CH3NH3PbBr3 , which is a direct band-gap semiconductor when the CH3NH3 group is oriented along the (111) direction but turns indirect when the orientation is (100). We have constructed a simple dipole model, with parameters all evaluated from ab initio calculations, to describe the molecules' depolarization dynamics. We find that, once the molecules are initially orientated along a given high-symmetry direction, their room-temperature depolarization depends on the specific material investigated. In particular we find that the ratio between the polarization decay constant of CH3NH3PbBr3 and that of HC (NH2)2PbBr3 is about 2 at room temperature. With these results at hand we suggest a simple luminescence decay experiment to prove our findings and establish a correlation between optical activity and the molecules' dynamics in these materials.

  10. Ultrafast exciton fine structure relaxation dynamics in lead chalcogenide nanocrystals.

    PubMed

    Johnson, Justin C; Gerth, Kathrine A; Song, Qing; Murphy, James E; Nozik, Arthur J; Scholes, Gregory D

    2008-05-01

    The rates of fine structure relaxation in PbS, PbSe, and PbTe nanocrystals were measured on a femtosecond time scale as a function of temperature with no applied magnetic field by cross-polarized transient grating spectroscopy (CPTG) and circularly polarized pump-probe spectroscopy. The relaxation rates among exciton fine structure states follow trends with nanocrystal composition and size that are consistent with the expected influence of material dependent spin-orbit coupling, confinement enhanced electron-hole exchange interaction, and splitting between L valleys that are degenerate in the bulk. The size dependence of the fine structure relaxation rate is considerably different from what is observed for small CdSe nanocrystals, which appears to result from the unique material properties of the highly confined lead chalcogenide quantum dots. Modeling and qualitative considerations lead to conclusions about the fine structure of the lowest exciton absorption band, which has a potentially significant bearing on photophysical processes that make these materials attractive for practical purposes.

  11. Lead from the center. How to manage divisions dynamically.

    PubMed

    Raynor, M E; Bower, J L

    2001-05-01

    Conventional wisdom holds that a company's divisions should be given almost total autonomy--especially under conditions of uncertainty--because they are closer to emerging technologies, customers, and competitors than corporate headquarters could ever be. But research from Michael Raynor and Joseph Bower suggests that the corporate office should be more, not less, directive in turbulent markets. Rapid changes in an industry make it difficult to predict where and when synergies among divisions might emerge. With so many possibilities and such uncertainty, companies can't afford to sacrifice their ability to flexibly execute business strategy. Corporate headquarters must play an active role in defining the scope of division-level strategy, the authors say, so that divisions do not act in ways that undermine opportunities to collaborate in the future. But neither can companies afford to sacrifice the competitiveness of their divisions as stand-alone businesses. In creating corporate-level strategic flexibility, a corporate office must balance the need for divisional autonomy now with the potential need for cooperation in the future. Through an examination of four corporations--Sprint, WPP, Teradyne, and Viacom--the authors challenge traditional approaches to diversification in which a company's divisions are either related (they share resources and collaborate) or unrelated (they compete for resources and operate as stand-alone businesses). They argue that companies should adopt a dynamic approach to cooperation among divisions, enabling varying degrees of relatedness between divisions depending on strategic circumstances. The authors offer four tactics to help executives manage divisions dynamically.

  12. Membrane and actin dynamics interplay at lamellipodia leading edge.

    PubMed

    Bisi, Sara; Disanza, Andrea; Malinverno, Chiara; Frittoli, Emanuela; Palamidessi, Andrea; Scita, Giorgio

    2013-10-01

    The multimolecular WAVE regulatory (WRC) and Arp2/3 complexes are primarily responsible to generate pushing forces at migratory leading edges by promoting branch elongation of actin filaments. The architectural complexity of these units betrays the necessity to impose a tight control on their activity. This is exerted through temporally coordinated and coincident signals which limit the intensity and duration of this activity. In addition, interactions of the WRC and Arp2/3 complexes with membrane binding and surprisingly membrane trafficking proteins is also emerging, revealing the existence of an 'endocytic wiring system' that spatially restrict branched actin elongation for the execution of polarized functions during cell migration. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and dynamics explorer. Final report, 1 June 1991-31 August 1994

    SciTech Connect

    Erlandson, R.E.

    1994-08-01

    The overall objective of this research is to investigate the generation and propagation of electromagnetic ion cyclotron (EMIC) waves in the frequency range from 0.2 to 5 Hz (Pc 1 frequency band). Data used in this research were acquired by the AMPTE/CCE, DE-1, and DE-2 satellites. One of the primary questions addressed in this research is the role which EMIC waves have on the transfer of energy from the equatorial magnetosphere to the ionosphere. The primary result from this research is that some fraction of EMIC waves, generated in the equatorial magnetosphere, are Landau damped in the ionosphere and are therefore a heat source for ionospheric electrons. This result as well as other results are summarized below.

  14. Transparency of Magnetized Plasma at Cyclotron Frequency

    SciTech Connect

    G. Shvets; J.S. Wurtele

    2002-03-14

    Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration.

  15. Dynamic behavior and applicability of lead alloy absorber

    NASA Astrophysics Data System (ADS)

    Li, Ya-Qi; Li, Xiao-Jun; Liu, Xi-Hui

    2005-01-01

    The paper describes the damping effect of lead alloy absorber (LAA) by shake table test and finite element method of a kind of high-voltage electrical equipment, LW11-252/Q SF6 Circuit Breaker (LSCB). The strain reduction of the porcelain bushing of LSCB is defined as the damping effect of LAA in the paper based on the damage pattern of test equipment under earthquake. The test results show that LAA has reduced the acceleration response and strain response of the LSCB, at the same time, it does not increase the displacement response of the LSCB. There is a reduction of 30% in the strain of porcelain pipe. Moreover, the stronger the input ground motion is, the larger the reduction will be. The finite element method also indicates the damping effect of LAA, especially under ground motions with significant long period contents and ground motions with velocity pulse. Combined with the test results and calculation results, the paper gives the applicability of LAA finally.

  16. Helium cyclotron resonance within the earth's magnetosphere

    SciTech Connect

    Mauk, B.H.; McIlwain, C.E.; McPherron, R.L.

    1981-01-01

    A histogram of electromagnetic Alfven/ion cyclotron wave frequencies, sampled within the geostationary enviroment and normalized by the equatorial proton cyclotron frequency, shows a dramatic gap centered near the helium (He/sup +/) cyclotron frequency. Also, strongly cyclotron phase bunched helium ions (20--200 eV) have been observed directly within the vicinity of wave environments. These observations are interpreted as resulting from the absorption of the waves through cyclotron resonance by cool ambient populations of helium ions.

  17. ECR (Electron Cyclotron Resonance) ion sources for cyclotrons

    SciTech Connect

    Lyneis, C.M.

    1986-10-01

    In the last decade ECR (Electron Cyclotron Resonance) ion sources have evolved from a single large, power consuming, complex prototype into a variety of compact, simple, reliable, efficient, high performance sources of high charge state ions for accelerators and atomic physics. The coupling of ECR sources to cyclotrons has resulted in significant performance gains in energy, intensity, reliability, and variety of ion species. Seven ECR sources are in regular operation with cyclotrons and numerous other projects are under development or in the planning stag. At least four laboratories have ECR sources dedicated for atomic physics research and other atomic physics programs share ECR sources with cyclotrons. An ECR source is now installed on the injector for the CERN SPS synchrotron to accelerate O/sup 8 +/ to relativistic energies. A project is underway at Argonne to couple an ECR source to a superconducting heavy-ion linac. Although tremendous progress has been made, the field of ECR sources is still a relatively young technology and there is still the potential for further advances both in source development and understanding of the plasma physics. The development of ECR sources is reviewed. The important physics mechanisms which come into play in the operation of ECR Sources are discussed, along with various models for charge state distributions (CSD). The design and performance of several ECR sources are compared. The 88-Inch Cyclotron and the LBL ECR is used as an example of cyclotron+ECR operation. The future of ECR sources is considered.

  18. EC-5 fifth international workshop on electron cyclotron emission and electron cyclotron heating

    SciTech Connect

    Prater, R.; Lohr, J.

    1985-12-31

    This report contains papers on the following topics: electron cyclotron emission measurements; electron cyclotron emission theory; electron cyclotron heating; gyrotron development; and ECH systems and waveguide development. These paper have been indexed separately elsewhere. (LSP).

  19. BEST medical radioisotope production cyclotrons

    SciTech Connect

    Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan; Johnson, Richard R.; Gelbart, W. Z.

    2013-04-19

    Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beam intensity ranges from 400 {mu}A to 1000 {mu}A, depending on the cyclotron energy and application.

  20. BEST medical radioisotope production cyclotrons

    NASA Astrophysics Data System (ADS)

    Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan; Gelbart, W. Z.; Johnson, Richard R.

    2013-04-01

    Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beam intensity ranges from 400 μA to 1000 μA, depending on the cyclotron energy and application [1].

  1. FEL on slow cyclotron wave

    SciTech Connect

    Silivra, A.

    1995-12-31

    A physical mechanism of interaction of fast electromagnetic wave with slow cyclotron wave of relativistic electron beam in a FEL with helical wiggler field is described. It is shown that: (1) interaction is possible for both group of steady state electron trajectories (2) positive gain is achieved within certain interval of guide field strength (3) operation wavelength for group 1 trajectories ({Omega}{sub 0}/{gamma} < k{omega}{upsilon}{parallel}) is shorter than for the conventional FEL synchronism. A nonlinear analysis shows that efficiency of slow cyclotron FEL is restricted mainly by a breakdown of a single electron synchronism due to dependence of (modified) electron cyclotron frequency on an energy of electron. Nevertheless, as numerical simulation shows, typical efficiency of 15 % order is achieved in millimeter wavelength band for the midrelativistic ({gamma}= 3 {divided_by} 4) slow cyclotron wave FEL. Tapering of magnetic field results in a substantial increase of efficiency.

  2. Cyclotron Production of Medical Radioisotopes

    SciTech Connect

    Avila-Rodriguez, M. A.; Zarate-Morales, A.; Flores-Moreno, A.

    2010-08-04

    The cyclotron production of radioisotopes for medical applications is gaining increased significance in diagnostic molecular imaging techniques such as PET and SPECT. In this regard, radioisotope production has never been easier or more convenient until de introduction of compact medical cyclotrons in the last few decades, which allowed the use of short-lived radioisotopes in in vivo nuclear medicine studies on a routine basis. This review outlines some general considerations about the production of radioisotopes using charged particle accelerators.

  3. Calculation of cyclotron rf systems

    NASA Astrophysics Data System (ADS)

    Van Genderen, W.; Van Der Heide, J. A.; Bräutigam, W.

    1987-08-01

    An approximate calculation of the characteristic properties of resonators for cyclotron rf systems is described. Formulas for the characteristic impedence of line segments are evaluated and an approximation for a dee-dummy dee system is given. A computer program has been written which also takes into account the capacity due to line discontinuities. The computed resonance frequency for cyclotrons in Eindhoven and Jülich agrees within 5% with experimental data. The power consumption is also computed and analyzed.

  4. Higher-order spin and charge dynamics in a quantum dot-lead hybrid system.

    PubMed

    Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Stano, Peter; Noiri, Akito; Ito, Takumi; Loss, Daniel; Ludwig, Arne; Wieck, Andreas D; Tarucha, Seigo

    2017-09-22

    Understanding the dynamics of open quantum systems is important and challenging in basic physics and applications for quantum devices and quantum computing. Semiconductor quantum dots offer a good platform to explore the physics of open quantum systems because we can tune parameters including the coupling to the environment or leads. Here, we apply the fast single-shot measurement techniques from spin qubit experiments to explore the spin and charge dynamics due to tunnel coupling to a lead in a quantum dot-lead hybrid system. We experimentally observe both spin and charge time evolution via first- and second-order tunneling processes, and reveal the dynamics of the spin-flip through the intermediate state. These results enable and stimulate the exploration of spin dynamics in dot-lead hybrid systems, and may offer useful resources for spin manipulation and simulation of open quantum systems.

  5. Proton Cyclotron Waves Occurrence Rate Upstream From the Martian Bow Shock: Related Properties of the Planetary Proton Population and Dynamics of the Upper Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Romanelli, N. J.; Mazelle, C. X.; Chaufray, J. Y.; Meziane, K.; Shan, L.; Ruhunusiri, S.; Connerney, J. E. P.; Espley, J. R.; Eparvier, F. G.; Thiemann, E.; Halekas, J. S.; Mitchell, D. L.; McFadden, J. P.; Brain, D. A.; Jakosky, B. M.

    2016-12-01

    Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) observations provided by the Magnetometer (MAG) and the Extreme Ultraviolet Monitor (EUVM) during the time period from October 2014 up to the end of March 2016 are analyzed along with atomic H exospheric densities derived from numerical simulations. We calculate the proton cyclotron waves (PCWs) occurrence rate observed upstream from the Martian bow shock at different times. Additionally, we study the connection with temporal variabilities of the high altitude hydrogen exosphere of Mars and the solar EUV flux reaching the Martian environment. We determine that the occurrence of PCWs is higher when Mars is close to perihelion, and decreases to lower and approximately constant values after the Martian Northern Spring Equinox. We further conclude that these variabilities are not the result of biases in MAVEN's spatial coverage or changes in the interplanetary magnetic field cone angle distribution. Our simulations predict higher H exospheric densities on the Martian day side when Mars is closer to perihelion, a consequence of changes in the thermospheric response to variability in the ultraviolet flux reaching the planet at different orbital positions. Analyses of daily irradiances measured by the MAVEN EUVM show a consistent behavior. In addition, complementary studies on the properties of the planetary proton population observed by MAVEN ion spectrometers SWIA and STATIC are also performed. These results suggest a method to indirectly monitor the variability of the upper Martian H exosphere over large temporal scales, based on the occurrence of PCWs.

  6. Dynamics of multiple flux tubes in sawtoothing KSTAR plasmas heated by electron cyclotron waves: I. Experimental analysis of the tube structure

    NASA Astrophysics Data System (ADS)

    Choe, G. H.; Yun, G. S.; Nam, Y.; Lee, W.; Park, H. K.; Bierwage, A.; Domier, C. W.; Luhmann, N. C., Jr.; Jeong, J. H.; Bae, Y. S.; the KSTAR Team

    2015-01-01

    Multiple (two or more) flux tubes are commonly observed inside and/or near the q = 1 flux surface in KSTAR tokamak plasmas with localized electron cyclotron resonance heating and current drive (ECH/CD). Detailed 2D and quasi-3D images of the flux tubes obtained by an advanced imaging diagnostic system showed that the flux tubes are m/n = 1/1 field-aligned structures co-rotating around the magnetic axis. The flux tubes typically merge together and become like the internal kink mode of the usual sawtooth, which then collapses like a usual sawtooth crash. A systematic scan of ECH/CD beam position showed a strong correlation with the number of flux tubes. In the presence of multiple flux tubes close to the q = 1 surface, the radially outward heat transport was enhanced, which explains naturally temporal changes of electron temperature. We emphasize that the multiple flux tubes are a universal feature distinct from the internal kink instability and play a critical role in the control of sawteeth using ECH/CD.

  7. Fluid equations in the presence of electron cyclotron current drive

    NASA Astrophysics Data System (ADS)

    Jenkins, Thomas G.; Kruger, Scott E.

    2012-12-01

    Two-fluid equations, which include the physics imparted by an externally applied radiofrequency source near electron cyclotron resonance, are derived in their extended magnetohydrodynamic forms using the formalism of Hegna and Callen [Phys. Plasmas 16, 112501 (2009)]. The equations are compatible with the closed fluid/drift-kinetic model developed by Ramos [Phys. Plasmas 17, 082502 (2010); 18, 102506 (2011)] for fusion-relevant regimes with low collisionality and slow dynamics, and they facilitate the development of advanced computational models for electron cyclotron current drive-induced suppression of neoclassical tearing modes.

  8. Fluid equations in the presence of electron cyclotron current drive

    SciTech Connect

    Jenkins, Thomas G.; Kruger, Scott E.

    2012-12-15

    Two-fluid equations, which include the physics imparted by an externally applied radiofrequency source near electron cyclotron resonance, are derived in their extended magnetohydrodynamic forms using the formalism of Hegna and Callen [Phys. Plasmas 16, 112501 (2009)]. The equations are compatible with the closed fluid/drift-kinetic model developed by Ramos [Phys. Plasmas 17, 082502 (2010); 18, 102506 (2011)] for fusion-relevant regimes with low collisionality and slow dynamics, and they facilitate the development of advanced computational models for electron cyclotron current drive-induced suppression of neoclassical tearing modes.

  9. Electron cyclotron current drive efficiency in general tokamak geometry

    SciTech Connect

    Lin-Liu, Y. R.; Chan, V. S.; Prater, R.

    2003-01-01

    Green's-function techniques are used to calculate electron cyclotron current drive (ECCD) efficiency in general tokamak geometry in the low-collisionality regime. Fully relativistic electron dynamics is employed in the theoretical formulation. The high-velocity collision model is used to model Coulomb collisions and a simplified quasi-linear rf diffusion operator describes wave-particle interactions. The approximate analytic solutions which are benchmarked with a widely used ECCD model, facilitate time-dependent simulations of tokamak operational scenarios using the non-inductive current drive of electron cyclotron waves.

  10. Maryland University sectored isochronous cyclotron (MUSIC): Progress report No. 35

    SciTech Connect

    Not Available

    1986-10-29

    Efforts are reported on the installation and checkout of cyclotron components which had been previously fabricated. Final integration of subsystems and major systems leading to internal beam tests is reported near completion. Progress is reported in relation to control system components, focus and steering magnet design, and rf system testing. (LEW)

  11. Potential of cyclotron based accelerators for energy production and transmutation

    SciTech Connect

    Stammbach, T.; Adam, S.; Fitze, H.R.

    1995-10-01

    PSI operates a 590 MeV-cyclotron facility for high intensity proton beams for the production of intense beams of pions and muons. The facility, commissioned in 1974, has been partially upgraded and is now operated routinely at a beam current of 1 mA, which corresponds to a beam power of 0.6 MW. At this current, the beam losses in the cyclotron are about 0.02%. By the end of 1995 the authors expect to have 1.5 mA of protons. Extensive theoretical investigations on beam current limitations in isochronous cyclotrons were undertaken. They show that the longitudinal space charge effects dominate. Based on their experience the authors present a preliminary design of a cyclotron scheme that could produce a 10 MW beam as a driver for an {open_quotes}energy amplifier{close_quotes} as proposed by C. Rubbia and his collaborators. The expected efficiency for the conversion of AC into beam power would be about 50% (for the RF-systems only). The beam losses in the cyclotron are expected to be a few {mu}A, leading to a tolerable activation level.

  12. Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata

    SciTech Connect

    Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash

    2013-11-15

    Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A and M university cyclotrons. The radio frequency (RF) system of SCC has been commissioned with the stringent requirement of various RF parameters. The three-phase RF system of Superconducting cyclotron has been developed in the frequency range 9–27 MHz with amplitude and phase stability of 100 ppm and ±0.1°, respectively. The phase control system has the option to change the relative phase difference between any two RF cavities and maintain the phase stability within ±0.1° during round-the-clock cyclotron operation. The said precision phase loop consists of both analogue In-phase/Quadrature modulator to achieve faster response and also Direct Digital Synthesis based phase shifter to achieve wide dynamic range as well. This paper discusses detail insights into the various issues of phase control for the K500 SCC at VECC, Kolkata.

  13. Evolution of the axial electron cyclotron maser instability, with applications to solar microwave spikes

    NASA Technical Reports Server (NTRS)

    Vlahos, Loukas; Sprangle, Phillip

    1987-01-01

    The nonlinear evolution of cyclotron radiation from streaming and gyrating electrons in an external magnetic field is analyzed. The nonlinear dynamics of both the fields and the particles are treated fully relativistically and self-consistently. The model includes a background plasma and electrostatic effects. The analytical and numerical results show that a substantial portion of the beam particle energy can be converted to electromagnetic wave energy at frequencies far above the electron cyclotron frequency. In general, the excited radiation can propagate parallel to the magnetic field and, hence, escape gyrothermal absorption at higher cyclotron harmonics. The high-frequency Doppler-shifted cyclotron instability can have saturation efficiencies far higher than those associated with well-known instabilities of the electron cyclotron maser type. Although the analysis is general, the possibility of using this model to explain the intense radio emission observed from the sun is explored in detail.

  14. Electron cyclotron harmonic wave acceleration

    NASA Technical Reports Server (NTRS)

    Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

    1987-01-01

    A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

  15. Electron cyclotron harmonic wave acceleration

    NASA Technical Reports Server (NTRS)

    Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

    1987-01-01

    A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

  16. Use of cyclotrons in medicine

    NASA Astrophysics Data System (ADS)

    Qaim, S. M.

    2004-10-01

    Cyclotrons are versatile ion-accelerating machines which find many applications in medicine. In this short review their use in hadron therapy is briefly discussed. Proton therapy is gaining significance because of its capability to treat deep-lying tumours. A strong area of application of cyclotrons involves the production of short-lived neutron deficient radiotracers for use in emission tomography, especially positron emission tomography. This fast and quantitative in vivo diagnostic technique is being increasingly used in neurology, cardiology and oncology. Besides routine patient care, considerable interdisciplinary work on development of new positron emitters is under way. A short account of those efforts is given. The use of cyclotrons in the production of radionuclides for internal radiotherapy is also briefly described.

  17. Leading Order Response of Statistical Averages of a Dynamical System to Small Stochastic Perturbations

    NASA Astrophysics Data System (ADS)

    Abramov, Rafail V.

    2017-03-01

    The classical fluctuation-dissipation theorem predicts the average response of a dynamical system to an external deterministic perturbation via time-lagged statistical correlation functions of the corresponding unperturbed system. In this work we develop a fluctuation-response theory and test a computational framework for the leading order response of statistical averages of a deterministic or stochastic dynamical system to an external stochastic perturbation. In the case of a stochastic unperturbed dynamical system, we compute the leading order fluctuation-response formulas for two different cases: when the existing stochastic term is perturbed, and when a new, statistically independent, stochastic perturbation is introduced. We numerically investigate the effectiveness of the new response formulas for an appropriately rescaled Lorenz 96 system, in both the deterministic and stochastic unperturbed dynamical regimes.

  18. NACA Researcher Examines the Cyclotron

    NASA Image and Video Library

    1951-02-21

    Researcher James Blue examines the new cyclotron at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. Researchers at NACA Lewis began postulating about the use of atomic power for propulsion immediately after World War II. The NACA concentrated its efforts on the study of high temperature materials and heat transfer since it did not have access to the top secret fission information. The military studied the plausibility of nuclear propulsion for aircraft in the late 1940s. The military program was cancelled after four years without any breakthroughs, but the Atomic Energy Commission took on the effort in 1951. The NACA Lewis laboratory was expanding its nuclear-related research during this period. In 1948, Lewis engineers were assigned to the Oak Ridge National Laboratory to obtain expertise in high temperature heat transfer and advanced materials technology. The following year a new 80-person Nuclear Reactor Division was created, and an in-house nuclear school was established to train these researchers. The cyclotron was built behind the Materials and Structures Laboratory to support thermodynamic and materials research for both nuclear aircraft and nuclear rockets. The original NACA Lewis cyclotron was used to accelerate two kinds of particles. To better match the space radiation environment, the cyclotron was later modified to accelerate particles of the newly-discovered Van Allen radiation belts.

  19. Molecular-Dynamic Calculation of Effects Appearing in Removing a Lead Film from Graphene

    NASA Astrophysics Data System (ADS)

    Galashev, A. E.; Rakhmanova, O. R.

    2017-07-01

    By the molecular-dynamics technique, the authors have investigated the bombardment of a thin lead film on graphene by a beam of Xe clusters in the range of energies 5-30 eV at an angle of incidence of 45o. Visual observation and the density profile of the Pb film point to a complete separation of the film from graphene followed by the formation of a lead cluster during the bombardment with a cluster energy of 20 eV. Such bombardment leads to maximum horizontal and minimum vertical mobilities of C atoms in graphene and also generates a minimum stress in the film's plane due to vertical forces.

  20. The nature of dynamic disorder in lead halide perovskite crystals (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yaffe, Omer; Guo, Yinsheng; Hull, Trevor; Stoumpos, Costas; Tan, Liang Z.; Egger, David A.; Zheng, Fan; Szpak, Guilherme; Semonin, Octavi E.; Beecher, Alexander N.; Heinz, Tony F.; Kronik, Leeor; Rappe, Andrew M.; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Pimenta, Marcos A.; Brus, Louis E.

    2016-09-01

    We combine low frequency Raman scattering measurements with first-principles molecular dynamics (MD) to study the nature of dynamic disorder in hybrid lead-halide perovskite crystals. We conduct a comparative study between a hybrid (CH3NH3PbBr3) and an all-inorganic lead-halide perovskite (CsPbBr3). Both are of the general ABX3 perovskite formula, and have a similar band gap and structural phase sequence, orthorhombic at low temperature, changing first to tetragonal and then to cubic symmetry as temperature increases. In the high temperature phases, we find that both compounds show a pronounced Raman quasi-elastic central peak, indicating that both are dynamically disordered.

  1. Dynamic Stall Measurements and Computations for a VR-12 Airfoil with a Variable Droop Leading Edge

    NASA Technical Reports Server (NTRS)

    Martin, P. B.; McAlister, K. W.; Chandrasekhara, M. S.; Geissler, W.

    2003-01-01

    High density-altitude operations of helicopters with advanced performance and maneuver capabilities have lead to fundamental research on active high-lift system concepts for rotor blades. The requirement for this type of system was to improve the sectional lift-to-drag ratio by alleviating dynamic stall on the retreating blade while simultaneously reducing the transonic drag rise of the advancing blade. Both measured and computational results showed that a Variable Droop Leading Edge (VDLE) airfoil is a viable concept for application to a rotor high-lift system. Results are presented for a series of 2D compressible dynamic stall wind tunnel tests with supporting CFD results for selected test cases. These measurements and computations show a dramatic decrease in the drag and pitching moment associated with severe dynamic stall when the VDLE concept is applied to the Boeing VR-12 airfoil. Test results also show an elimination of the negative pitch damping observed in the baseline moment hysteresis curves.

  2. The electron-cyclotron maser for astrophysical application

    NASA Astrophysics Data System (ADS)

    Treumann, Rudolf A.

    2006-08-01

    The electron-cyclotron maser is a process that generates coherent radiation from plasma. In the last two decades, it has gained increasing attention as a dominant mechanism of producing high-power radiation in natural high-temperature magnetized plasmas. Originally proposed as a somewhat exotic idea and subsequently applied to include non-relativistic plasmas, the electron-cyclotron maser was considered as an alternative to turbulent though coherent wave-wave interaction which results in radio emission. However, when it was recognized that weak relativistic corrections had to be taken into account in the radiation process, the importance of the electron-cyclotron maser rose to the recognition it deserves. Here we review the theory and application of the electron-cyclotron maser to the directly accessible plasmas in our immediate terrestrial and planetary environments. In situ access to the radiating plasmas has turned out to be crucial in identifying the conditions under which the electron-cyclotron maser mechanism is working. Under extreme astrophysical conditions, radiation from plasmas may provide a major energy loss; however, for generating the powerful radiation in which the electron-cyclotron maser mechanism is capable, the plasma must be in a state where release of susceptible amounts of energy in the form of radiation is favorable. Such conditions are realized when the plasma is unable to digest the available free energy that is imposed from outside and stored in its particle distribution. The lack of dissipative processes is a common property of collisionless plasmas. When, in addition, the plasma density becomes so low that the amount of free energy per particle is large, direct emission becomes favorable. This can be expressed as negative absorption of the plasma which, like in conventional masers, leads to coherent emission even though no quantum correlations are involved. The physical basis of this formal analogy between a quantum maser and the

  3. Design Features Of K = 100 Cyclotron Magnet For ISOL RIB Production

    SciTech Connect

    Park, Jin Ah; Gad, Kh. M. M.; Chai, Jong-Seo

    2011-06-01

    K = 100 Separated Sector Cyclotron was designed in conceptual for the ISOL driver. It has 4 separated sector magnets. Two SF cyclotrons will be used as the injectors for separated sector cyclotron. RF frequency is 70 MHz, 4th harmonics. We have designed sector magnet without trim and harmonic coils. Minimum radius of the magnet is 55 cm and maximum radius is 1.8 m. Designed magnets were calculated and simulated by OPERA 3D (TOSCA) code. Ion beam dynamics calculations have been done using particle studio code to prove the focusing properties of the designed magnets.

  4. Competition between drift and spatial defects leads to oscillatory and excitable dynamics of dissipative solitons.

    PubMed

    Parra-Rivas, P; Gomila, D; Matías, M A; Colet, P; Gelens, L

    2016-01-01

    We have reported in Phys. Rev. Lett. 110, 064103 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.064103 that in systems which otherwise do not show oscillatory dynamics, the interplay between pinning to a defect and pulling by drift allows the system to exhibit excitability and oscillations. Here we build on this work and present a detailed bifurcation analysis of the various dynamical instabilities that result from the competition between a pulling force generated by the drift and a pinning of the solitons to spatial defects. We show that oscillatory and excitable dynamics of dissipative solitons find their origin in multiple codimension-2 bifurcation points. Moreover, we demonstrate that the mechanisms leading to these dynamical regimes are generic for any system admitting dissipative solitons.

  5. Real-time estimation of lead-acid battery parameters: A dynamic data-driven approach

    NASA Astrophysics Data System (ADS)

    Li, Yue; Shen, Zheng; Ray, Asok; Rahn, Christopher D.

    2014-12-01

    This short paper presents a recently reported dynamic data-driven method, Symbolic Dynamic Filtering (SDF), for real-time estimation of the state-of-health (SOH) and state-of-charge (SOC) in lead-acid batteries, as an alternative to model-based analysis techniques. In particular, SOC estimation relies on a k-NN regression algorithm while SOH estimation is obtained from the divergence between extracted features. The results show that the proposed data-driven method successfully distinguishes battery voltage responses under different SOC and SOH situations.

  6. Electron Cyclotron Maser Emissions from Evolving Fast Electron Beams

    NASA Astrophysics Data System (ADS)

    Tang, J. F.; Wu, D. J.; Chen, L.; Zhao, G. Q.; Tan, C. M.

    2016-05-01

    Fast electron beams (FEBs) are common products of solar active phenomena. Solar radio bursts are an important diagnostic tool for understanding FEBs and the solar plasma environment in which they propagate along solar magnetic fields. In particular, the evolution of the energy spectrum and velocity distribution of FEBs due to the interaction with the ambient plasma and field during propagation can significantly influence the efficiency and properties of their emissions. In this paper, we discuss the possible evolution of the energy spectrum and velocity distribution of FEBs due to energy loss processes and the pitch-angle effect caused by magnetic field inhomogeneity, and we analyze the effects of the evolution on electron-cyclotron maser (ECM) emission, which is one of the most important mechanisms for producing solar radio bursts by FEBs. Our results show that the growth rates all decrease with the energy loss factor Q, but increase with the magnetic mirror ratio σ as well as with the steepness index δ. Moreover, the evolution of FEBs can also significantly influence the fastest growing mode and the fastest growing phase angle. This leads to the change of the polarization sense of the ECM emission. In particular, our results also reveal that an FEB that undergoes different evolution processes will generate different types of ECM emission. We believe the present results to be very helpful for a more comprehensive understanding of the dynamic spectra of solar radio bursts.

  7. TRIUMF cyclotron vacuum system refurbishing

    NASA Astrophysics Data System (ADS)

    Sekachev, I.

    2008-03-01

    The cyclotron at TRIUMF was commissioned to full energy in 1974. The volume of the cyclotron vacuum tank is about 100 m3 and it operates at 5×10-8 Torr pressure during beam production. The pumping is mainly based on a Phillips B-20 cryogenerator (Stirling cycle 4-cylinder engine). The cryogenerator supplies helium gas at 16 K and 70 K to cryopanels in the tank. The decreasing reliability of the B-20 and demanding maintenance requirements triggered the decision to completely overhaul or replace the cryogenerator. Replacement with the LINDE-1630 helium refrigerator was found to be the most attractive (technically and economically) option. The details of the proposal with installation of the helium refrigerator and with a continuous flow liquid nitrogen shield cooling system are presented.

  8. Global Simulation of Electromagnetic Ion Cyclotron Waves

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K.; Gallagher, D. L.; Kozyra, J. U.

    2007-01-01

    It is well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. [2002 - 2007]. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis

  9. Global Simulation of Electromagnetic Ion Cyclotron Waves

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Gallagher, D. L.; Kozyra, J. U.

    2007-01-01

    It is very well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis of modern

  10. Global Simulation of Electromagnetic Ion Cyclotron Waves

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K.; Gallagher, D. L.; Kozyra, J. U.

    2007-01-01

    It is well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. [2002 - 2007]. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis

  11. Global Simulation of Electromagnetic Ion Cyclotron Waves

    NASA Astrophysics Data System (ADS)

    Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.

    2007-12-01

    It is well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. [2002 - 2007]. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis

  12. Image analysis tools to quantify cell shape and protein dynamics near the leading edge.

    PubMed

    Ryan, Gillian L; Watanabe, Naoki; Vavylonis, Dimitrios

    2013-01-01

    We present a set of flexible image analysis tools to analyze dynamics of cell shape and protein concentrations near the leading edge of cells adhered to glass coverslips. Plugins for ImageJ streamline common analyses of microscopic images of cells, including the calculation of leading edge speeds, total and average intensities of fluorescent markers, and retrograde flow rate measurements of fluorescent single-molecule speckles. We also provide automated calculations of auto- and cross-correlation functions between velocity and intensity measurements. The application of the methods is illustrated on images of XTC cells.

  13. Numerical study: Iron corrosion-resistance in lead-bismuth eutectic coolant by molecular dynamics method

    SciTech Connect

    Arkundato, Artoto; Su'ud, Zaki; Abdullah, Mikrajuddin; Widayani,; Celino, Massimo

    2012-06-06

    In this present work, we report numerical results of iron (cladding) corrosion study in interaction with lead-bismuth eutectic coolant of advanced nuclear reactors. The goal of this work is to study how the oxygen can be used to reduce the corrosion rate of cladding. The molecular dynamics method was applied to simulate corrosion process. By evaluating the diffusion coefficients, RDF functions, MSD curves of the iron and also observed the crystal structure of iron before and after oxygen injection to the coolant then we concluded that a significant and effective reduction can be achieved by issuing about 2% number of oxygen atoms to lead-bismuth eutectic coolant.

  14. Chronophin coordinates cell leading edge dynamics by controlling active cofilin levels.

    PubMed

    Delorme-Walker, Violaine; Seo, Ji-Yeon; Gohla, Antje; Fowler, Bruce; Bohl, Ben; DerMardirossian, Céline

    2015-09-15

    Cofilin, a critical player of actin dynamics, is spatially and temporally regulated to control the direction and force of membrane extension required for cell locomotion. In carcinoma cells, although the signaling pathways regulating cofilin activity to control cell direction have been established, the molecular machinery required to generate the force of the protrusion remains unclear. We show that the cofilin phosphatase chronophin (CIN) spatiotemporally regulates cofilin activity at the cell edge to generate persistent membrane extension. We show that CIN translocates to the leading edge in a PI3-kinase-, Rac1-, and cofilin-dependent manner after EGF stimulation to activate cofilin, promotes actin free barbed end formation, accelerates actin turnover, and enhances membrane protrusion. In addition, we establish that CIN is crucial for the balance of protrusion/retraction events during cell migration. Thus, CIN coordinates the leading edge dynamics by controlling active cofilin levels to promote MTLn3 cell protrusion.

  15. Chronophin coordinates cell leading edge dynamics by controlling active cofilin levels

    PubMed Central

    Delorme-Walker, Violaine; Seo, Ji-Yeon; Gohla, Antje; Fowler, Bruce; Bohl, Ben; DerMardirossian, Céline

    2015-01-01

    Cofilin, a critical player of actin dynamics, is spatially and temporally regulated to control the direction and force of membrane extension required for cell locomotion. In carcinoma cells, although the signaling pathways regulating cofilin activity to control cell direction have been established, the molecular machinery required to generate the force of the protrusion remains unclear. We show that the cofilin phosphatase chronophin (CIN) spatiotemporally regulates cofilin activity at the cell edge to generate persistent membrane extension. We show that CIN translocates to the leading edge in a PI3-kinase–, Rac1-, and cofilin-dependent manner after EGF stimulation to activate cofilin, promotes actin free barbed end formation, accelerates actin turnover, and enhances membrane protrusion. In addition, we establish that CIN is crucial for the balance of protrusion/retraction events during cell migration. Thus, CIN coordinates the leading edge dynamics by controlling active cofilin levels to promote MTLn3 cell protrusion. PMID:26324884

  16. Method and apparatus for ion cyclotron spectrometry

    DOEpatents

    Dahl, David A [Idaho Falls, ID; Scott, Jill R [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

    2010-08-17

    An ion cyclotron spectrometer may include a vacuum chamber that extends at least along a z-axis and means for producing a magnetic field within the vacuum chamber so that a magnetic field vector is generally parallel to the z-axis. The ion cyclotron spectrometer may also include means for producing a trapping electric field within the vacuum chamber that includes at least a first section that induces a first magnetron effect that increases a cyclotron frequency of an ion and at least a second section that induces a second magnetron effect that decreases the cyclotron frequency of an ion. The cyclotron frequency changes induced by the first and second magnetron effects substantially cancel one another so that an ion traversing the at least first and second sections will experience no net change in cyclotron frequency.

  17. Future cyclotron systems: An industrial perspective

    SciTech Connect

    Stevenson, N.R.; Dickie, W.J.

    1995-09-01

    The use of commercial cyclotron systems for the production of radioisotopes continues to grow on a world-wide scale. Improvements in technology have significantly increased the production capabilities of modern cyclotron-based isotope production facilities. In particular, the change to negative ion acceleration and new high power systems have resulted in dramatic improvements in reliability, increases in capacity, and decreases in personnel radiation dose. As more and more older machines are retired, decisions regarding their replacement are made based on several factors including the market`s potential and the cyclotron system`s abilities. Taking the case of the recently upgraded TR30 cyclotron at TRIUMF/Nordion, the authors investigate the requirements industrial/medical users are likely to impose on future commercial cyclotron systems and the impact this will have on cyclotron technology by the end of the century.

  18. Commercial compact cyclotrons in the 90`s

    SciTech Connect

    Milton, B.F.

    1995-09-01

    Cyclotrons continue to be efficient accelerators for radio-isotope production. In recent years, developments in the accelerator technology have greatly increased the practical beam current in these machines while also improving the overall system reliability. These developments combined with the development of new isotopes for medicine and industry, and a retiring of older machines indicate a strong future for commercial cyclotrons. In this paper the authors will survey recent developments in the areas of cyclotron technology, as they relate to the new generation of commercial cyclotrons. Design criteria for the different types of commercial cyclotrons will be presented, with reference to those demands that differ from those in a research oriented cyclotron project. The authors also discuss the possibility of systems designed for higher energies and capable of extracted beam currents of up to 2.0 mA.

  19. Infra red active modes due to coupling of cyclotron excitation and LO phonons in polar semiconductor

    NASA Astrophysics Data System (ADS)

    Agrawal, Ratna; Dubey, Swati; Ghosh, S.

    2013-06-01

    Effects of free carrier concentration, external magnetic field and Callen effective charge on infra red active modes in a polar semiconductor have been analytically investigated using simple harmonic oscillator model. Callen effective charge considerably enhances reflectivity and shifts minima towards lower values of energy. Presence of magnetic field leads towards the coupling of collective cyclotron excitations with LO phonon giving rise to maximum reflectivity whereas cyclotron resonance absorption results into minimum reflectivity.

  20. Technical Note: Building a combined cyclotron and MRI facility: Implications for interference

    SciTech Connect

    Hofman, Mark B. M.; Kuijer, Joost P. A.; Ridder, Jan Willem de; Perk, Lars R.; Verdaasdonk, Rudolf M.

    2013-01-15

    Purpose: With the introduction of hybrid PET/MRI systems, it has become more likely that the cyclotron and MRI systems will be located close to each other. This study considered the interference between a cyclotron and a superconducting MRI system. Methods: Interactions between cyclotrons and MRIs are theoretically considered. The main interference is expected to be the perturbation of the magnetic field in the MRI due to switching on or off the magnetic field of the cyclotron. MR imaging is distorted by a dynamic spatial gradient of an external inplane magnetic field larger than 0.5-0.04 {mu}T/m, depending on the specific MR application. From the design of a cyclotron, it is expected that the magnetic fringe field at large distances behaves as a magnetic dipolar field. This allows estimation of the full dipolar field and its spatial gradients from a single measurement. Around an 18 MeV cyclotron (Cyclone, IBA), magnetic field measurements were performed on 5 locations and compared with calculations based upon a dipolar field model. Results: At the measurement locations the estimated and measured values of the magnetic field component and its spatial gradients of the inplane component were compared, and found to agree within a factor 1.1 for the magnetic field and within a factor of 1.5 for the spatial gradients of the field. In the specific case of the 18 MeV cyclotron with a vertical magnetic field and a 3T superconducting whole body MR system, a minimum distance of 20 m has to be considered to prevent interference. Conclusions: This study showed that a dipole model is sufficiently accurate to predict the interference of a cyclotron on a MRI scanner, for site planning purposes. The cyclotron and a whole body MRI system considered in this study need to be placed more than 20 m apart, or magnetic shielding should be utilized.

  1. Room-temperature dynamic correlation between methylammonium molecules in lead-iodine based perovskites: An ab initio molecular dynamics perspective

    NASA Astrophysics Data System (ADS)

    Lahnsteiner, Jonathan; Kresse, Georg; Kumar, Abhinav; Sarma, D. D.; Franchini, Cesare; Bokdam, Menno

    2016-12-01

    The high efficiency of lead organo-metal-halide perovskite solar cells has raised many questions about the role of the methylammonium (MA) molecules in the Pb-I framework. Experiments indicate that the MA molecules are able to "freely" spin around at room temperature even though they carry an intrinsic dipole moment. We have performed large supercell (2592 atoms) finite-temperature ab initio molecular dynamics calculations to study the correlation between the molecules in the framework. An underlying long-range antiferroelectric ordering of the molecular dipoles is observed. The dynamical correlation between neighboring molecules shows a maximum around room temperature in the mid-temperature phase. In this phase, the rotations are slow enough to (partially) couple to neighbors via the Pb-I cage. This results in a collective motion of neighboring molecules in which the cage acts as the mediator. At lower and higher temperatures, the motions are less correlated.

  2. Use of cyclotrons in medical research: Past, present, future

    NASA Astrophysics Data System (ADS)

    Smathers, James B.; Myers, Lee T.

    1985-05-01

    The use of cyclotrons in medical research started in the late 1930s with the most prominent use being neutron irradiation in cancer therapy. Due to a lack of understanding of the biological effect of neutrons, the results were less than encouraging. In the 1940s and 1950s, small cyclotrons were used for isotope production and in the mid 60s, the biological effect of neutrons was more thoroughly studied, with the result that a second trial of neutron therapy was initiated at Hammersmith Hospital, England. Concurrent with this, work on the use of high energy charged particles, initially protons and alphas, was initiated in Sweden and Russia and at Harvard and Berkeley. The English success in neutron therapy led to some pilot studies in the USA using physics cyclotrons of various energies and targets. These results in turn lead to the present series of machines presently being installed at M.D. Anderson Hospital (42 MeV), Seattle (50 MeV) and UCLA (46 MeV). The future probably bodes well for cyclotrons at the two extremes of the energy range. For nuclear medicine the shift is away from the use of multiple isotopes, which requires a large range of particles and energies to 11C, 13N, 15O, and 18F, which can be incorporated in metabolic specific compounds and be made with small 8-10 MeV p+ "table top" cyclotrons. For tumor therapy machines of 60 MeV or so will probably be the choice for the future, as they allow the treatment of deep seated tumors with neutrons and the charged particles have sufficient range to allow the treatment of ocular tumors.

  3. EURAC: A liquid target neutron spallation source using cyclotron technology

    NASA Astrophysics Data System (ADS)

    Perlado, J. M.; Mínguez, E.; Sanz, J.; Piera, M.

    1995-09-01

    Euratom/JRC Ispra led some years ago the design of an accelerator based neutron spallation source EURAC, with special emphasis as a fusion material testing device. DENIM was involved in the development of the last version of this source. EURAC proposes to use a beam of 600 MeV or 1.5 GeV protons, produced by an effective and low cost ring cyclotron with a current of 6 mA impinging in a liquid lead, or lead-bismuth, target. It will use an advanced cyclotron technology which can be implemented in the next future, in the line of the actual technology of the upgraded SIN-type cyclotron. The adjacent rows to the target correspond to the lead, or Li17Pb83, cooled channels where the samples will be located. The available volumes there were shown enough for material testing purposes. Here, proposal of using those experimental areas to introduce small masses of radioactive wastes for testing of transmutation in spallation source is made. In addition, extrapolation of present conceptual design to make available larger volumes under flexible conditions seems to be possible. Neutrons leaking from the test zone drive a subcritical booster (< 10 MW) which could provide a thermal neutron flux trap with a liquid hidrogen moderator in the center.

  4. Simulations of peeling-ballooning modes with electron cyclotron resonance heating

    SciTech Connect

    Huang, J.; Tang, C. J.; Chen, S. Y.

    2016-05-15

    The effects of the deposited power and deposited position of Electron Cyclotron Resonance Heating (ECRH) on Peeling-Ballooning (P-B) modes are simulated using BOUT++ code in this paper. The simulation results show that as the deposited position moves from the top to the bottom of the pedestal, the edge localized mode (ELM) size decreases first and then increases, finally decreases again. For ECRH with different deposited power, the effects on P-B modes are similar if they have the same peak value of the power deposition profile. These results show that the effects of ECRH on P-B modes are primarily determined by the change in pressure profile caused by ECRH. As long as ECRH can lead to large enough change in pressure profile, ECRH can efficiently affect the dynamics of P-B modes.

  5. Cyclotron Maser Emission - Stars, Planets and Laboratory

    NASA Astrophysics Data System (ADS)

    Vorgul, Irena

    2010-11-01

    X-ray and radio observations of active stars over many years have shown that they frequently generate X-ray bursts that are quickly followed by radio bursts. In many cases the radio bursts are highly polarised. More recently, the star CU Virginis has been found to exhibit pulsar-like behaviour. In both these situations we believe that the radio emission can be best explained by a cyclotron maser type instability initiated by electron beams funnelling down converging magnetic field configurations typical of a dipole magnetic topology. Just such a geometry also exists in the Earth's auroral zone and so our model can explain the Earth's auroral kilometric radiation (AKR). Via a similar process, all the gas giant/magnetised planets in the solar system also emit radio emission. We have established a laboratory-based facility that has verified many of the details of our original theoretical description. The experiment has demonstrated, for example, that an electron beam entering a strongly converging magnetic field geometry does indeed produce a ``horse-shoe'' (or crescent-shaped) distribution in velocity space. It is the generation of this horse-shoe distribution, also observed in the Earth's auroral zone, which is vital for our theoretical model. It leads to a population inversion in the perpendicular velocity distribution and generation of electromagnetic waves close to the cyclotron frequency. We will discuss recent developments in the theory and simulation of the instability and relate these to the laboratory, space and astrophysical observations. The research was supported by UK Engineering and Physical Sciences Research Council. The input of R.A. Cairns, R. Bingham, B.J. Kellett and the experimental and computer modelling team at Strathclyde University, Glasgow is gratefully acknowledged.

  6. Formation and Development of the Dynamic Stall Vortex on a Wing with Leading Edge Tubercles

    NASA Astrophysics Data System (ADS)

    Hrynuk, John; Bohl, Douglas

    2015-11-01

    Humpback whales are unique in that their flippers have leading edge ``bumps'' or tubercles. Past work on airfoils inspired by whale flippers has centered on the static aerodynamic characteristics of these airfoils. The current study uses Molecular Tagging Velocimetry (MTV) to investigate the effects of tubercles on dynamically pitching NACA 0012 airfoils. A baseline (i.e. straight leading edge) wing and one modified with leading edge tubercles are investigated. Tracking of the Dynamic Stall Vortex (DSV) is performed to quantitatively compare the DSV formation location, path, and convective velocity for tubercled and baseline wings. The results show that there is a spanwise variation in the initial formation location and motion of the DSV on the modified wing. Once formed, the DSV aligns into a more uniform spanwise structure. As the pitching motion progresses, the DSV on the modified wing convects away from the airfoil surface later and slower than is observed for the baseline airfoil. The results indicate that the tubercles may delay stall when compared to the baseline airfoil. This work was supported by NSF Grant # 0845882.

  7. Cyclotron Line Measurements with INTEGRAL

    NASA Technical Reports Server (NTRS)

    Pottschmidt, K.; Kreykenbohm, I.; Caballero, I.; Fritz, S.; Schoenherr, G.; Kretschmar, P.; Wilms, J.; McBride, V. A.; Suchy, S.; Rothschild, R. E.

    2008-01-01

    Due to its broadband energy coverage, INTEGRAL has made important contributions to observing and interpreting cyclotron lines, which are present in the 10-100 keV range of a sample of accreting pulsars. In these systems photons with energies fulfilling the resonance condition inelastically Compton scatter off electrons quantized in the accretion column above the neutron star's magnetic pole(s). This process gives rise to the broad, absorption-like lines or 'cyclotron resonant scattering features' (CRSF). The observed lines allow to directly measure the B-fields of these sources, resulting in values of a few times 1E12G. In this overview I will present recent highlights regarding CRSF observations as well as discuss current ideas and models for the physical conditions in the accretion column. Among the former are the stability of the spectrum of Vela X-1 during giant flares in 2003, the observation of three cyclotron lines during the 2004 outburst of V0332+53, the confirmation of the fundamental line at approximately 45 keV during a 2005 normal outburst of A0535-26, and the simultaneous detection of the two lines in the dipping source 4U 1907+09 (for which also a torque reversal was detected for the first time). Through these and other observations it has become increasingly apparent that two types of observations can potentially be used to constrain the accretion column geometry: the determination of energy ratios for multiple harmonic lines (only two sources with greater than 2 lines are known), was well as the evolution of the fundamental line centroid, which, for different sources, may or may not be correlated with flux. Furthermore, first steps have been taken away from the usual phenomenological description of the lines, towards a physical approach based on self-consistent CRSF modeling. Initial applications are presented.

  8. Cyclotron Line Measurements with INTEGRAL

    NASA Technical Reports Server (NTRS)

    Pottschmidt, K.; Kreykenbohm, I.; Caballero, I.; Fritz, S.; Schoenherr, G.; Kretschmar, P.; Wilms, J.; McBride, V. A.; Suchy, S.; Rothschild, R. E.

    2008-01-01

    Due to its broadband energy coverage, INTEGRAL has made important contributions to observing and interpreting cyclotron lines, which are present in the 10-100 keV range of a sample of accreting pulsars. In these systems photons with energies fulfilling the resonance condition inelastically Compton scatter off electrons quantized in the accretion column above the neutron star's magnetic pole(s). This process gives rise to the broad, absorption-like lines or 'cyclotron resonant scattering features' (CRSF). The observed lines allow to directly measure the B-fields of these sources, resulting in values of a few times 1E12G. In this overview I will present recent highlights regarding CRSF observations as well as discuss current ideas and models for the physical conditions in the accretion column. Among the former are the stability of the spectrum of Vela X-1 during giant flares in 2003, the observation of three cyclotron lines during the 2004 outburst of V0332+53, the confirmation of the fundamental line at approximately 45 keV during a 2005 normal outburst of A0535-26, and the simultaneous detection of the two lines in the dipping source 4U 1907+09 (for which also a torque reversal was detected for the first time). Through these and other observations it has become increasingly apparent that two types of observations can potentially be used to constrain the accretion column geometry: the determination of energy ratios for multiple harmonic lines (only two sources with greater than 2 lines are known), was well as the evolution of the fundamental line centroid, which, for different sources, may or may not be correlated with flux. Furthermore, first steps have been taken away from the usual phenomenological description of the lines, towards a physical approach based on self-consistent CRSF modeling. Initial applications are presented.

  9. High Power Cyclotrons for Accelerator Driven System (ADS)

    NASA Astrophysics Data System (ADS)

    Calabretta, Luciano

    2012-03-01

    We present an accelerator module based on a injector cyclotron and a Superconducting Ring Cyclotron (SRC) able to accelerate H2+ molecules. H2+ molecules are extracted from the SRC stripping the binding electron by a thin carbon foil. The SRC will be able to deliver proton beam with maximum energy of 800 MeV and a maximum power of 8 MW. This module is forecasted for the DAEdALUS (Decay At rest Experiment for δcp At Laboratory for Underground Science) experiment, which is a neutrino experiment proposed by groups of MIT and Columbia University. Extensive beam dynamics studies have been carrying out in the last two years and proved the feasibility of the design. The use of H2+ molecules beam has three main advantages: 1) it reduces the space charge effects, 2) because of stripping extraction, it simplifies the extraction process w.r.t. single turn extraction and 3) we can extract more than one beam out of one SRC. A suitable upgraded version of the cyclotron module able to deliver up to 10MW beam is proposed to drive ADS. The accelerator system which is presented, consists of having three accelerators modules. Each SRC is equipped with two extraction systems delivering two beams each one with a power up to 5 MW. Each accelerator module, feeds both the two reactors at the same time. The three accelerators modules assure to maintain continuity in functioning of the two reactors. In normal operation, all the three accelerators module will deliver 6.6 MW each one, just in case one of the three accelerator module will be off, due to a fault or maintenance, the other two modules are pushed at maximum power of 10 MW. The superconducting magnetic sector of the SRC, as well as the normal conducting sector of the injector cyclotron, is calculated with the TOSCA module of OPERA3D. Here the main features of the injector cyclotron, of the SRC and the beam dynamic along the cyclotrons are presented.

  10. GMF promotes leading-edge dynamics and collective cell migration in vivo.

    PubMed

    Poukkula, Minna; Hakala, Markku; Pentinmikko, Nalle; Sweeney, Meredith O; Jansen, Silvia; Mattila, Jaakko; Hietakangas, Ville; Goode, Bruce L; Lappalainen, Pekka

    2014-11-03

    Lamellipodia are dynamic actin-rich cellular extensions that drive advancement of the leading edge during cell migration. Lamellipodia undergo periodic extension and retraction cycles, but the molecular mechanisms underlying these dynamics and their role in cell migration have remained obscure. We show that glia-maturation factor (GMF), which is an Arp2/3 complex inhibitor and actin filament debranching factor, regulates lamellipodial protrusion dynamics in living cells. In cultured S2R(+) cells, GMF silencing resulted in an increase in the width of lamellipodial actin filament arrays. Importantly, live-cell imaging of mutant Drosophila egg chambers revealed that the dynamics of actin-rich protrusions in migrating border cells is diminished in the absence of GMF. Consequently, velocity of border cell clusters undergoing guided migration was reduced in GMF mutant flies. Furthermore, genetic studies demonstrated that GMF cooperates with the Drosophila homolog of Aip1 (flare) in promoting disassembly of Arp2/3-nucleated actin filament networks and driving border cell migration. These data suggest that GMF functions in vivo to promote the disassembly of Arp2/3-nucleated actin filament arrays, making an important contribution to cell migration within a 3D tissue environment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, D. J; Slaughter, D. S; Osipov, T.; Weber, T.; Rescigno, T. N; Belkacem, A.; Adaniya, H.; Rudek, B.; McCurdy, C. W

    2011-09-15

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ({sup 2}{Pi}) and OH ({sup 2}{Sigma}), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear configurations.

  12. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, Dan; Adaniya, Hidihito; Slaughter, Dan; Rudek, B.; Osipov, Timur; Weber, Thorsten; Rescigno, Tom; McCurdy, Bill; Belkacem, Ali

    2011-06-08

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ((sup 2}{Pi} ) and OH ({sup 2}{Sigma} ), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear con gurations.

  13. Cyclotron in the Materials and Stresses Building

    NASA Image and Video Library

    1976-11-21

    Researchers check the cyclotron in the Materials and Stresses Building at the National Aeronautics and Space Administration (NASA) Lewis Research Center. The Materials and Stresses Building, built in 1949, contained a number of laboratories to test the strength, diffusion, and other facets of materials. The materials could be subjected to high temperatures, high stresses, corrosion, irradiation, and hot gasses. The Physics of Solids Laboratory included a cyclotron, cloud chamber, helium cryostat, and metallurgy cave. The cyclotron was built in the early 1950s to test the effects of radiation on different materials so that the proper materials could be used to construct a nuclear aircraft engine and other components. By the late 1950s, the focus had shifted to similar studies for rockets. NASA cancelled its entire nuclear program in January 1973, and the cyclotron was mothballed. In 1975 the Cleveland Clinic Foundation partnered with NASA Lewis to use the cyclotron to treat cancer patients with a new type of radiation therapy. The cyclotron split beryllium atoms which caused neutrons to be released. The neutrons were streamed directly at the patient’s tumor. Over the course of five years, the cyclotron was used to treat 1200 patients. The program was terminated in 1980 as the Clinic shifted its efforts to concentrate on non-radiation treatments. The Lewis cyclotron was mothballed for a number of years before being demolished.

  14. A Dynamical Origin Of The Leading/trailing Asymmetry In Jupiter's Trojan Swarms?

    NASA Astrophysics Data System (ADS)

    O'Brien, David P.

    2012-10-01

    The cataloged population of Jupiter Trojans has long shown a puzzling asymmetry between the leading (L4) and trailing (L5) swarms down to the smallest observable sizes. Estimates from the Sloan Digital Sky Survey (SDSS) place the leading/trailing ratio at 1.6 ± 0.1 [1], survey observations with the Subaru telescope give a leading/trailing ratio of around 1.8 [2], and most recently, estimates from the WISE mission give a leading/trailing ratio of 1.4 ± 0.2 [3]. Current models for Trojan capture [eg. 4] predict that the two swarms should begin with roughly equal numbers of bodies, and there is no inherent difference in stability between the leading and trailing swarms in the three-body problem. However, several researchers have proposed that when Saturn is included in the dynamics, the trailing swarm might be less stable than the leading swarm [5-8], and this difference may be able to explain the asymmetry. Here we test that hypothesis with long-term orbital integrations using a wider range of initial conditions than explored by those authors. References: [1] Szabo, G. M. et al., MNRAS 377, 1393-1406 (2007). [2] Nakamura, T. and Yoshida, F., PASJ 60, 293-296 (2008). [3] Grav, T. et al., ApJ 742, 40-49 (2011). [4] Morbidelli, A. et al., Nature 435, 462-465 (2005). [5] Pal, A. and Suli, A., Publications of the Astronomy Department of the Eotvos University (PADEU) 14, 285-292 (2004). [6] Schwarz, R. et al., CMDA 90, 139-148 (2004). [7] Dvorak, R. and Schwarz, R., CMDA 92, 19-28 (2005). [8] Freistetter, F., A&A 453, 353-361 (2006).

  15. Dynamic tricuspid valve stenosis induced with a pacemaker lead: a case report.

    PubMed

    Skoric, Bosko; Baricevic, Zeljko; Brida, Margarita; Samardzic, Jure; Jurin, Hrvoje; Milicic, Davor

    2014-01-01

    Isolated severe tricuspid valve stenosis due to an endocardial pacemaker lead is extremely rare, and is usually caused by either fibrosis of a perforated or lacerated leaflet, or fibrotic adherence between the lead and the valvular apparatus. Reported cases typically include clinical manifestations of both systemic venous stasis and low cardiac output. The case is presented of a 20-year-old female with a surgically repaired congenital heart disease who developed severe tricuspid stenosis at six years after the implantation of a DDD pacemaker. Unexpectedly, the patient had no signs of venous stasis and suffered only from exercise intolerance. Right heart catheterization under fluoroscopic guidance revealed an atrial lead forming a loop at the level of the tricuspid valve. A paradoxical inspiratory decrease in the transvalvular diastolic gradient, caused by the caudal heart motion and straightening of the loop during inspiration, was noted. Such a dynamic nature with a temporary inspiratory relief of the obstruction may explain the partial clinical presentation of tricuspid stenosis in this case. The lead was removed and the tricuspid valve repaired surgically, after which the patient's recovery was uneventful with normalization of exercise tolerance.

  16. Impaired dynamics and function of mitochondria caused by mtDNA toxicity leads to heart failure.

    PubMed

    Lauritzen, Knut H; Kleppa, Liv; Aronsen, Jan Magnus; Eide, Lars; Carlsen, Harald; Haugen, Øyvind P; Sjaastad, Ivar; Klungland, Arne; Rasmussen, Lene Juel; Attramadal, Håvard; Storm-Mathisen, Jon; Bergersen, Linda H

    2015-08-01

    Cardiac mitochondrial dysfunction has been implicated in heart failure of diverse etiologies. Generalized mitochondrial disease also leads to cardiomyopathy with various clinical manifestations. Impaired mitochondrial homeostasis may over time, such as in the aging heart, lead to cardiac dysfunction. Mitochondrial DNA (mtDNA), close to the electron transport chain and unprotected by histones, may be a primary pathogenetic site, but this is not known. Here, we test the hypothesis that cumulative damage of cardiomyocyte mtDNA leads to cardiomyopathy and heart failure. Transgenic mice with Tet-on inducible, cardiomyocyte-specific expression of a mutant uracil-DNA glycosylase 1 (mutUNG1) were generated. The mutUNG1 is known to remove thymine in addition to uracil from the mitochondrial genome, generating apyrimidinic sites, which obstruct mtDNA function. Following induction of mutUNG1 in cardiac myocytes by administering doxycycline, the mice developed hypertrophic cardiomyopathy, leading to congestive heart failure and premature death after ∼2 mo. The heart showed reduced mtDNA replication, severely diminished mtDNA transcription, and suppressed mitochondrial respiration with increased Pgc-1α, mitochondrial mass, and antioxidative defense enzymes, and finally failing mitochondrial fission/fusion dynamics and deteriorating myocardial contractility as the mechanism of heart failure. The approach provides a model with induced cardiac-restricted mtDNA damage for investigation of mtDNA-based heart disease.

  17. PGC-1α controls mitochondrial biogenesis and dynamics in lead-induced neurotoxicity

    PubMed Central

    Dabrowska, Aleksandra; Venero, Jose Luis; Iwasawa, Ryota; Hankir, Mohammed-khair; Rahman, Sunniyat; Boobis, Alan; Hajji, Nabil

    2015-01-01

    Due to its role in regulation of mitochondrial function, PGC1α is emerging as an important player in ageing and neurodegenerative disorders. PGC1α exerts its neuroprotective effects by promoting mitochondrial biogenesis (MB) and functioning. However, the precise regulatory role of PGC1α in the control of mitochondrial dynamics (MD) and neurotoxicity is still unknown. Here we elucidate the role of PGC1α in vitro and in vivo in the regulatory context of MB and MD in response to lead (II) acetate as a relevant model of neurotoxicity. We show that there is an adaptive response (AR) to lead, orchestrated by the BAP31-calcium signalling system operating between the ER and mitochondria. We find that this hormetic response is controlled by a cell-tolerated increase of PGC1α expression, which in turn induces a balanced expression of fusion/fission genes by binding to their promoters and implying its direct role in regulation of MD. However, dysregulation of PGC1α expression through either stable downregulation or overexpression, renders cells more susceptible to lead insult leading to mitochondrial fragmentation and cell death. Our data provide novel evidence that PGC1α expression is a key regulator of MD and the maintenance of tolerated PGC1α expression may offer a promising strategy for neuroprotective therapies. PMID:26363853

  18. PGC-1α controls mitochondrial biogenesis and dynamics in lead-induced neurotoxicity.

    PubMed

    Dabrowska, Aleksandra; Venero, Jose Luis; Iwasawa, Ryota; Hankir, Mohammed-Khair; Rahman, Sunniyat; Boobis, Alan; Hajji, Nabil

    2015-09-01

    Due to its role in regulation of mitochondrial function, PGC1α is emerging as an important player in ageing and neurodegenerative disorders. PGC1α exerts its neuroprotective effects by promoting mitochondrial biogenesis (MB) and functioning. However, the precise regulatory role of PGC1α in the control of mitochondrial dynamics (MD) and neurotoxicity is still unknown. Here we elucidate the role of PGC1αin vitro and in vivo in the regulatory context of MB and MD in response to lead (II) acetate as a relevant model of neurotoxicity. We show that there is an adaptive response (AR) to lead, orchestrated by the BAP31-calcium signalling system operating between the ER and mitochondria. We find that this hormetic response is controlled by a cell-tolerated increase of PGC1α expression, which in turn induces a balanced expression of fusion/fission genes by binding to their promoters and implying its direct role in regulation of MD. However, dysregulation of PGC1α expression through either stable downregulation or overexpression, renders cells more susceptible to lead insult leading to mitochondrial fragmentation and cell death. Our data provide novel evidence that PGC1α expression is a key regulator of MD and the maintenance of tolerated PGC1α expression may offer a promising strategy for neuroprotective therapies.

  19. Recent development and progress of IBA cyclotrons

    NASA Astrophysics Data System (ADS)

    Kleeven, W.; Abs, M.; Delvaux, J. L.; Forton, E.; Jongen, Y.; Medeiros Romao, L.; Nactergal, B.; Nuttens, V.; Servais, T.; Vanderlinden, T.; Zaremba, S.

    2011-12-01

    Several cyclotron development projects were recently realized by Ion Beam Applications S.A. (IBA). This contribution presents three of them: (i) the intensity enhancement of the Cyclone 30 cyclotron, a machine mainly used for the production of SPECT isotopes. This project is related with the increased demand for 201Tl because of the shortage of Mo/Tc generators from nuclear reactors, (ii) development of a new versatile multiple-particle K = 30 isotope-production cyclotron (the Cyclone 30XP) being able to accelerate H -, D - and also α-particles. The α-beam of this cyclotron will allow the production of new therapeutic isotopes (e.g. 211At) and (iii) commissioning of the Cyclone 70 cyclotron installed for Arronax in France. This machine is similar to the C30XP but provides higher energy ( K = 70) and allows research on new types of medical isotopes.

  20. K-130 Cyclotron vacuum system

    NASA Astrophysics Data System (ADS)

    Yadav, R. C.; Bhattacharya, S.; Bhole, R. B.; Roy, Anindya; Pal, Sarbajit; Mallik, C.; Bhandari, R. K.

    2012-11-01

    The vacuum system for K-130 cyclotron has been operational since 1977. It consists of two sub-systems, main vacuum system and beam line vacuum system. The main vacuum system is designed to achieve and maintain vacuum of about 1 × 10-6 mbar inside the 23 m3 volume of acceleration chamber comprising the Resonator tank and the Dee tank. The beam line vacuum system is required for transporting the extracted beam with minimum loss. These vacuum systems consist of diffusion pumps backed by mechanical pumps like roots and rotary pumps. The large vacuum pumps and valves of the cyclotron vacuum system were operational for more than twenty five years. In recent times, problems of frequent failures and maintenance were occurring due to aging and lack of appropriate spares. Hence, modernisation of the vacuum systems was taken up in order to ensure a stable high voltage for radio frequency system and the extraction system. This is required for efficient acceleration and transportation of high intensity ion beam. The vacuum systems have been upgraded by replacing several pumps, valves, gauges and freon units. The relay based control system for main vacuum system has also been replaced by PLC based state of the art control system. The upgraded control system enables inclusion of additional operational logics and safety interlocks into the system. The paper presents the details of the vacuum system and describes the modifications carried out for improving the performance and reliability of the vacuum system.

  1. Electrostatic ion-cyclotron waves in magnetospheric plasmas Nonlocal aspects

    NASA Technical Reports Server (NTRS)

    Ganguli, G.; Bakshi, P.; Palmadesso, P.

    1984-01-01

    The importance of the effect of the magnetic shear and the finite size of current channel on the electrostatic ion-cyclotron instability for the space plasmas is illustrated. A non-local treatment is used. When the channel width Lc, is larger than the shear length Ls, there is a large reduction in the growth rate along with a noteworthy reduction of the band of the unstable perpendicular wavelengths. For Lc less than or = Ls/10 the growth rate is not much altered from its local value, however for Lc/pi i less than or = 10 to the second power the growth rate starts falling below the local value and vanishes for Lc pi i. The non-local effects lead to enhanced coherence in the ion cyclotron waves. Previously announced in STAR as N84-14917

  2. Electrostatic ion-cyclotron waves in magnetospheric plasmas Nonlocal aspects

    NASA Technical Reports Server (NTRS)

    Ganguli, G.; Bakshi, P.; Palmadesso, P.

    1984-01-01

    The importance of the effect of the magnetic shear and the finite size of current channel on the electrostatic ion-cyclotron instability for the space plasmas is illustrated. A non-local treatment is used. When the channel width Lc, is larger than the shear length Ls, there is a large reduction in the growth rate along with a noteworthy reduction of the band of the unstable perpendicular wavelengths. For Lc less than or = Ls/10 the growth rate is not much altered from its local value, however for Lc/pi i less than or = 10 to the second power the growth rate starts falling below the local value and vanishes for Lc pi i. The non-local effects lead to enhanced coherence in the ion cyclotron waves. Previously announced in STAR as N84-14917

  3. Leading edge vortex dynamics on a pitching delta wing. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Lemay, Scott P.

    1988-01-01

    The leading edge flow structure was investigated on a 70 deg flat plate delta wing which was pitched about its 1/2 chord position, to increase understanding of the high angle of attack aerodynamics on an unsteady delta wing. The wing was sinusoidally pitched at reduced frequencies ranging from k being identical with 2pi fc/u = 0.05 to 0.30 at chord Reynolds numbers between 90,000 and 350,000, for angle of attack ranges of alpha = 29 to 39 deg and alpha = 0 to 45 deg. The wing was also impulsively pitched at an approximate rate of 0.7 rad/s. During these dynamic motions, visualization of the leading edge vorticies was obtained by entraining titanium tetrachloride into the flow at the model apex. The location of vortex breakdown was recorded using 16mm high speed motion picture photography. When the wing was sinusoidally pitched, a hysteresis was observed in the location of breakdown position. This hysteresis increased with reduced frequency. The velocity of breakdown propagation along the wing, and the phase lag between model motion and breakdown location were also determined. When the wing was impulsively pitched, several convective times were required for the vortex flow to reach a steady state. Detailed information was also obtained on the oscillation of breakdown position in both static and dynamic cases.

  4. A dynamic model for the assessment of the replacement of lead in solders

    NASA Astrophysics Data System (ADS)

    Reuter, Markus A.; Verhoef, Ewoud V.

    2004-12-01

    A dynamic, interactive map has been developed of the life cycle of a number of metals, from mining through to minerals processing, metal production, product manufacturing, recovery, and waste management. While the existing metal process network and waste management infrastructure provide substantial scope for (product) design, these also limit change because of the strong path dependency of industry and infrastructure development. Therefore, models for dynamic simulation were constructed that allow the specification and evaluation of the metal process network and waste management infrastructure “products” over a longer time span. The model has been constructed using a bottom-up approach, to enable assessment of the environmental aspects of metallurgy, and to simulate changes in the system structure and technology, i.e., from the reactor or individual process step up to integrated material cycles. This dynamic interconnected model is used to investigate the impact of the removal of lead from solders on the coupled flows of the metals Ag, Au, Bi, Cu, Fe, Ni, Pb, Sn, Zn, and PGMs.

  5. Coupling of electrostatic ion cyclotron and ion acoustic waves in the solar wind

    SciTech Connect

    Sreeraj, T.; Singh, S. V. Lakhina, G. S.

    2016-08-15

    The coupling of electrostatic ion cyclotron and ion acoustic waves is examined in three component magnetized plasma consisting of electrons, protons, and alpha particles. In the theoretical model relevant to solar wind plasma, electrons are assumed to be superthermal with kappa distribution and protons as well as alpha particles follow the fluid dynamical equations. A general linear dispersion relation is derived for such a plasma system which is analyzed both analytically and numerically. For parallel propagation, electrostatic ion cyclotron (proton and helium cyclotron) and ion acoustic (slow and fast) modes are decoupled. For oblique propagation, coupling between the cyclotron and acoustic modes occurs. Furthermore, when the angle of propagation is increased, the separation between acoustic and cyclotron modes increases which is an indication of weaker coupling at large angle of propagation. For perpendicular propagation, only cyclotron modes are observed. The effect of various parameters such as number density and temperature of alpha particles and superthermality on dispersion characteristics is examined in details. The coupling between various modes occurs for small values of wavenumber.

  6. Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

    NASA Technical Reports Server (NTRS)

    Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

    1997-01-01

    Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low- frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

  7. Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

    NASA Technical Reports Server (NTRS)

    Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

    1997-01-01

    Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low-frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

  8. Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals.

    PubMed

    De Roo, Jonathan; Ibáñez, Maria; Geiregat, Pieter; Nedelcu, Georgian; Walravens, Willem; Maes, Jorick; Martins, Jose C; Van Driessche, Isabel; Kovalenko, Maksym V; Hens, Zeger

    2016-02-23

    Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. (1)H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We find that ligand binding to the NC surface is highly dynamic, and therefore, ligands are easily lost during the isolation and purification procedures. However, when a small amount of both oleic acid and oleylamine is added, the NCs can be purified, maintaining optical, colloidal, and material integrity. In addition, we find that a high amine content in the ligand shell increases the quantum yield due to the improved binding of the carboxylic acid.

  9. A numerical and experimental study of the effects of dynamic roughness on laminar leading edge separation

    NASA Astrophysics Data System (ADS)

    Gall, Peter D.

    The aircraft industry, as a whole, has been deeply concerned with improving the aerodynamic efficiency of current and future flight vehicles, particularly in the commercial and military markets. However, of particular interest to the field of aerodynamics is the elusive concept of a workable flow control mechanism. Effective flow control is a concept which if properly applied can increase aerodynamic efficiency. Various concepts and ideas to obtain successful flow control have been studied in an attempt to reap these rewards. Some examples include boundary layer blowing (steady and periodic), suction, and compliant walls for laminar flow control. The overall goal of flow control is to increase performance by increasing lift, reducing drag, and delaying or eliminating leading edge separation. The specific objectives of flow control are to (1) delay or eliminate flow separation, (2) delay boundary layer transition, and (3) and reduce skin friction drag. The purpose of this research is to investigate dynamic roughness as a novel method of flow control technology for external boundary layer flows. As opposed to standard surface roughness, dynamic roughness incorporates small time dependent perturbations to the surface of the airfoil. These surface perturbations are actual humps and/or ridges on the surface of the airfoil that are on the scale of the laminar boundary, and oscillate with an unsteady motion. Research has shown that this can provide a means to modify the instantaneous and mean velocity profile near the wall and favorably control the existing state of the boundary layer. Several flow control parameters were studied including dynamic roughness frequency, amplitude, and geometry. The results of this study have shown, both numerically and experimentally, that dynamic roughness can provide an effective means for eliminating both a short and long laminar separation bubble and possibly prove a viable alternative in effective flow control, hence reaping some of

  10. Cyclotrons: From Science to Human Health

    NASA Astrophysics Data System (ADS)

    Craddock, Michael

    2011-04-01

    Lawrence's invention of the cyclotron, whose 80th anniversary we have just celebrated, not only revolutionized nuclear physics, but proved the starting point for a whole variety of recirculating accelerators, from the smallest microtron to the largest synchrotron, that have had an enormous impact in almost every branch of science and in several areas of medicine and industry. Cyclotrons themselves have proved remarkably adaptable, incorporating a variety of new ideas and technologies over the years: frequency modulation, edge focusing, AG focusing, separate magnet sectors, axial and azimuthal injection, ring geometries, stripping extraction, superconducting magnets and rf...... Even FFAGs, those most complex members of the cyclotron (fixed-magnetic-field) family, are making a comeback. Currently there are more than 50 medium or large cyclotrons around the world devoted to research. These provide intense primary beams of protons or stable ions, and correspondingly intense secondary beams of neutrons, pions, muons and radioactive ions, for experiments in nuclear, particle and condensed-matter physics, and in the materials and life sciences. Far outnumbering these, however, are the 800 or so small and medium cyclotrons used to produce radioisotopes for medical and other purposes. In addition, a rapidly growing number of 230-MeV proton cyclotrons are being built for cancer therapy -12 brought into operation since 1998 and as many more in the works. Altogether, cyclotrons are flourishing!

  11. Electron cyclotron resonance plasma photosa)

    NASA Astrophysics Data System (ADS)

    Rácz, R.; Biri, S.; Pálinkás, J.

    2010-02-01

    In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

  12. Electron cyclotron resonance plasma photos.

    PubMed

    Rácz, R; Biri, S; Pálinkás, J

    2010-02-01

    In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

  13. Electron cyclotron resonance plasma photos

    SciTech Connect

    Racz, R.; Palinkas, J.; Biri, S.

    2010-02-15

    In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

  14. Cyclotron resonance absorption in ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Villalon, Elena

    1991-04-01

    The mode conversion of ordinary polarized electromagnetic waves into electrostatic cyclotron waves in the inhomogeneous ionospheric plasma is investigated. Near resonance the warm plasma dispersion relation is a function of the angle theta between the geomagnetic field and the density gradient and of the wave frequency omega, which lies between the electron cyclotron frequency and its doubling. The differential equations describing the electric field amplitudes near the plasma resonance are studied, including damping at the second gyroharmonic. The energy transmission coefficients and power absorbed by the cyclotron waves are calculated. The vertical penetration of the plasma wave amplitudes is estimated using a WKB analysis of the wave equation.

  15. Nonlinear heating of ions by electron cyclotron frequency waves

    NASA Astrophysics Data System (ADS)

    Zestanakis, P. A.; Hizanidis, K.; Ram, A. K.; Kominis, Y.

    2010-11-01

    We study the nonlinear interaction of ions with electron cyclotron (EC) wave packets in a magnetized plasma. Previous studies have shown that such interactions with high frequency electrostatic lower hybrid waves can lead to coherent energization of ions. It requires the frequency bandwidth of the wave packet to be broader than the ion cyclotron frequency [1,2]. For the electromagnetic high frequency EC waves we have developed a more general theory, based on the Lie transform canonical perturbation method [3,4]. We apply the theory to the case of two overlapping EC beams. The wave frequency of each beam is assumed to be frequency modulated with a modulation bandwidth comparable to the ion cyclotron frequency. We present results for both X-mode and O-mode and illustrate the conditions for ion energization. [4pt] [1] D. Benisti, A. K. Ram, and A. Bers, Phys. Plasmas 5, 3224 (1998). [0pt] [2] A. K. Ram, A. Bers, and D. Benisti , J. Geophys. Res. 103, 9431 (1998). [0pt] [3] J.R. Cary and A.N. Kaufman, Phys. Fluids 24, 1238 (1981). [0pt] [4] R.L. Dewar, J. Phys A-Math. Gen 9, 2043 (1976).

  16. Signalling crosstalk at the leading edge controls tissue closure dynamics in the Drosophila embryo.

    PubMed

    Rousset, Raphaël; Carballès, Fabrice; Parassol, Nadège; Schaub, Sébastien; Cérézo, Delphine; Noselli, Stéphane

    2017-02-01

    Tissue morphogenesis relies on proper differentiation of morphogenetic domains, adopting specific cell behaviours. Yet, how signalling pathways interact to determine and coordinate these domains remains poorly understood. Dorsal closure (DC) of the Drosophila embryo represents a powerful model to study epithelial cell sheet sealing. In this process, JNK (JUN N-terminal Kinase) signalling controls leading edge (LE) differentiation generating local forces and cell shape changes essential for DC. The LE represents a key morphogenetic domain in which, in addition to JNK, a number of signalling pathways converges and interacts (anterior/posterior -AP- determination; segmentation genes, such as Wnt/Wingless; TGFβ/Decapentaplegic). To better characterize properties of the LE morphogenetic domain, we sought out new JNK target genes through a genomic approach: 25 were identified of which 8 are specifically expressed in the LE, similarly to decapentaplegic or puckered. Quantitative in situ gene profiling of this new set of LE genes reveals complex patterning of the LE along the AP axis, involving a three-way interplay between the JNK pathway, segmentation and HOX genes. Patterning of the LE into discrete domains appears essential for coordination of tissue sealing dynamics. Loss of anterior or posterior HOX gene function leads to strongly delayed and asymmetric DC, due to incorrect zipping in their respective functional domain. Therefore, in addition to significantly increasing the number of JNK target genes identified so far, our results reveal that the LE is a highly heterogeneous morphogenetic organizer, sculpted through crosstalk between JNK, segmental and AP signalling. This fine-tuning regulatory mechanism is essential to coordinate morphogenesis and dynamics of tissue sealing.

  17. Signalling crosstalk at the leading edge controls tissue closure dynamics in the Drosophila embryo

    PubMed Central

    Carballès, Fabrice; Parassol, Nadège; Schaub, Sébastien; Cérézo, Delphine; Noselli, Stéphane

    2017-01-01

    Tissue morphogenesis relies on proper differentiation of morphogenetic domains, adopting specific cell behaviours. Yet, how signalling pathways interact to determine and coordinate these domains remains poorly understood. Dorsal closure (DC) of the Drosophila embryo represents a powerful model to study epithelial cell sheet sealing. In this process, JNK (JUN N-terminal Kinase) signalling controls leading edge (LE) differentiation generating local forces and cell shape changes essential for DC. The LE represents a key morphogenetic domain in which, in addition to JNK, a number of signalling pathways converges and interacts (anterior/posterior -AP- determination; segmentation genes, such as Wnt/Wingless; TGFβ/Decapentaplegic). To better characterize properties of the LE morphogenetic domain, we sought out new JNK target genes through a genomic approach: 25 were identified of which 8 are specifically expressed in the LE, similarly to decapentaplegic or puckered. Quantitative in situ gene profiling of this new set of LE genes reveals complex patterning of the LE along the AP axis, involving a three-way interplay between the JNK pathway, segmentation and HOX genes. Patterning of the LE into discrete domains appears essential for coordination of tissue sealing dynamics. Loss of anterior or posterior HOX gene function leads to strongly delayed and asymmetric DC, due to incorrect zipping in their respective functional domain. Therefore, in addition to significantly increasing the number of JNK target genes identified so far, our results reveal that the LE is a highly heterogeneous morphogenetic organizer, sculpted through crosstalk between JNK, segmental and AP signalling. This fine-tuning regulatory mechanism is essential to coordinate morphogenesis and dynamics of tissue sealing. PMID:28231245

  18. All-magnetic extraction for cyclotron beam reacceleration

    DOEpatents

    Hudson, E.D.; Mallory, M.L.

    1975-07-22

    An isochronous cyclotron can be modified to provide an initial electron stripping stage, a complete acceleration of the stripped ions through the cyclotron to a first energy state, means for returning the ions to an intermediate cyclotron orbit through a second stripping stage, further acceleration of the now higher energy stripped ions through the cyclotron to their final energy, and final extraction of the ions from the cyclotron. (auth)

  19. Local interactions lead to pathogen-driven change to host population dynamics.

    PubMed

    Boots, Michael; Childs, Dylan; Reuman, Daniel C; Mealor, Michael

    2009-10-13

    Individuals tend to interact more strongly with nearby individuals or within particular social groups. Recent theoretical advances have demonstrated that these within-population relationships can have fundamental implications for ecological and evolutionary dynamics. In particular, contact networks are crucial to the spread and evolution of disease. However, the theory remains largely untested experimentally. Here, we manipulate habitat viscosity and thereby the frequency of local interactions in an insect-pathogen model system in which the virus had previously been shown to have little effect on host population dynamics. At high viscosity, the pathogen caused the collapse of dominant and otherwise stable host generation cycles. Modeling shows that this collapse can be explained by an increase in the frequency of intracohort interactions relative to intercohort interactions, leading to more disease transmission. Our work emphasizes that spatial structure can subtly mediate intraspecific competition and the effects of natural enemies. A decrease in dispersal in a population may actually (sometimes rather counterintuitively) intensify the effects of parasites. Broadly, because anthropological and environmental change often cause changes in population mixing, our work highlights the potential for dramatic changes in the effects of parasites on host populations.

  20. Leading edge velocity field of an oscillating airfoil in compressible dynamic stall

    NASA Technical Reports Server (NTRS)

    Vandyken, R. D.; Chandrasekhara, M. S.

    1992-01-01

    Phase-averaged mean-velocity and turbulence data are obtained and analyzed for the leading-edge region of an oscillating airfoil under compressibility conditions. A two-component laser-Doppler velocimetry system was used to make the measurements. Results are compared for the two Mach numbers 0.3 and 0.4 at a reduced frequency of 0.05 with varying airfoil angles of attack. For a Mach number of 0.3, a separation bubble is present on the airfoil throughout the oscillation cycle and no dynamic stall occurs as the peak angle of attack is below the static stall angle. However, a slight imprint of vortical structures is seen in the shear layer enveloping the bubble at the top of the cycle, a result confirmed also by the vorticity contours and in agreement with the earlier stroboscopic schlieren studies. When the Mach number is 0.4, dynamic stall occurs with its origin in the break-up of the separation bubble. Turbulence intensities in the bubble were found to be very large.

  1. Polarization switching dynamics in BZT-0.5BCT lead free ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Bhaumik, Anagh; Kolekar, Y.; Shaikh, P.; Ramana, C.; Ghosh, K.

    2014-03-01

    We report polarization switching dynamics in lead (Pb) free BaTi0.8Zr0.2O3-0.5Ba0.7Ca0.3TiO3, (BZT- 0.5 BCT) ferroelectric thin films. High quality thin films of Pb free BZT- 0.5 BCT were grown on Pt/Ti/SiO2/Si and SRO/LAO single crystal substrates using pulsed laser deposition (PLD). Polarization versus electric field data shows a hysteresis loop with a large remnant (35 micro C/cm2) and saturation polarization (40 micro C/cm2) and a small coercive field (1.5 kV/cm) which is essential for practical device applications. The polarization switching dynamics are well correlated with the structural distortion and phonon vibration observed in XRD and Raman spectroscopy. These results may stimulate to develop new Pb free ferroelectric thin films for future non-volatile random access memory and many other high-tech applications.

  2. Leading role of internal dynamics in the 2009 Indian summer monsoon drought

    NASA Astrophysics Data System (ADS)

    Neena, J. M.; Suhas, E.; Goswami, B. N.

    2011-07-01

    Understanding the underlying dynamics of the Indian summer monsoon (ISM) extremes such as severe droughts is key to improving seasonal prediction of the ISM rainfall. A large number of ISM droughts over the past century occurred unrelated to external forcing like the El Niño-Southern Oscillation (ENSO). In this study, we challenge the perception that the 2009 ISM drought was driven by ENSO and show that it was caused by internally driven processes. The 2009 drought of ISM was the result of two very long breaks, one in the month of June and the other in July-August (JA). While some studies provide strong evidence that the June break was caused by dry air intrusion associated with extratropical waves, a mechanism for the equally important JA break has not been elucidated so far. In this study, we unravel a new process in which westward propagating convectively coupled planetary-scale equatorial Rossby (PSER) waves emanating from the eastern Pacific as a remnant of Madden-Julian Oscillation (MJO), interact with the monsoon intraseasonal oscillation (MISO), modulate the active/break spells, and thereby influence the seasonal mean. It was found that during JA 2009 the arrival of the divergent phase of this PSER mode over the ISM domain reinforced and extended the break condition initiated by the northward propagating MISO, thereby creating a long break. Nonlinear kinetic energy exchanges between the PSER mode and the northward propagating MISO were found to be at the heart of such interactions. Evidence of such interactions can be seen during different active/break events in other monsoon seasons as well. As both long breaks were primarily driven by internal dynamical processes of the atmosphere, the study underscores the major role played by internal dynamics in causing the 2009 ISM drought. Our discovery that interactions between PSER waves and MISO can lead to significant modulations of the active/break spells opens up a new unexplored mechanism for understanding

  3. Dynamics Impact Tolerance of Shuttle RCC Leading Edge Panels Using LS-DYNA

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

    2005-01-01

    This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using physics-based codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which is used because of its thermal properties to protect the shuttle during reentry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of foam cylinders impacting 6- in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

  4. Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels using LS-DYNA

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

    2008-01-01

    This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using 'physics-based- codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which issued because of its thermal properties to protect the shuttle during re-entry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of individual foam cylinders impacting 6-in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

  5. Study on Dynamic Failure Model of Lead-Free Solders Using Shpb Techniques

    NASA Astrophysics Data System (ADS)

    Niu, Xiaoyan; Yuan, Guozheng; Li, Zhigang; Shu, Xuefeng

    The dynamic compressive properties of 96.3Sn3Ag0.7Cu and 99.3Sn0.7Cu solders were studied by means of a split Hopkinson pressure bar at strain rates ranging from 500 to 2000 s-1. Tests were conducted at room temperature and under uniaxial compressive conditions. Eutectic SnPb solders were used as the reference. From the data of tests, it was found that yield strength and flow stress increased remarkably with the increase of strain rate. On logarithmic scales, the yield strength increased linearly with strain rate. These lead-free solders revealed certain visco-plastic behavior and strain rate sensitivity, which predicted using Johnson-Cook material model. Related parameters in the model were determined from the experiment. Compared with the typical Pb-containing solder Sn63Pb37, these lead-free solders showed some fine properties and could substitute some Pb-containing solder alloys in microelectronic components packaging and interconnects.

  6. How do tree competition and stand dynamics lead to spatial patterns in monospecific mangroves?

    NASA Astrophysics Data System (ADS)

    Khan, M. N. I.; Sharma, S.; Berger, U.; Koedam, N.; Dahdouh-Guebas, F.; Hagihara, A.

    2013-04-01

    Information on mangrove stand development is rare because long-term monitoring data is often lacking. Such information is important in order to plan management measures effectively. Novel approaches based on existing datasets are required to bridge this gap of knowledge. This study uses a unique combination of field data analyses with simulation experiments in order to demonstrate how information on mangrove dynamics can be extracted if data are sparse. The paper provides a baseline characterization of stand development in a monospecific pioneer mangrove stand of Kandelia obovata. Point pattern analyses revealed that in the young stage, self-thinning has started but has not yet lead to a regularity of spatial tree distribution in the entire stand, and trees located in smaller clumps hinder each other in growth but do not lead to a significant size class differentiation. However, after ca. 2 decades the self-thinning and the size class differentiation start to become more visible. A mutual inhibition of growth was observed within 2 m circular distance (r) in the young stage and within 3 m distance after two decades of stand development as confirmed by the negative values of mark correlation function. As a stand grows older the spatial pattern of individuals become more regular from a clustered pattern. In order to understand and predict the future stand development, simulation experiments were carried out by means of the individual-based model KiWi.

  7. How do tree competition and stand dynamics lead to spatial patterns in monospecific mangroves?

    NASA Astrophysics Data System (ADS)

    Khan, M. N. I.; Sharma, S.; Berger, U.; Koedam, N.; Dahdouh-Guebas, F.; Hagihara, A.

    2013-01-01

    Information on mangrove stand development is rare because long-term monitoring data is often lacking. Such information is important in order to plan management measures effectively. Novel approaches are required to bridge this gap of knowledge based on existing data sets. This study uses a unique combination of field data analyses with simulation experiments in order to demonstrate how information on mangrove dynamics can be extracted if data are sparse. The paper provides a~baseline characterization of stand development in a monospecific pioneer mangrove stand of Kandelia obovata. Point pattern analyses revealed that in the young stage, self-thinning has started but has not yet lead to a regularity of spatial tree distribution in the entire stand, and trees located in smaller clumps hinder each other in growth but do not lead to a significant size class differentiation. However, after ca. 2 decades the self-thinning and the size class differentiation start to become more visible. A mutual inhibition of growth was observed within 2 m circular distance (r) in the young stage and within 3 m distance after two decades of stand development as confirmed by the negative values of mark correlation function. As a stand grows older the spatial pattern of individuals become more regular from a clustered pattern. In order to understand and predict the future stand development, simulation experiments were carried out by means of the individual-based model KiWi.

  8. Microwave emission related to cyclotron instabilities in a minimum-B electron cyclotron resonance ion source plasma

    NASA Astrophysics Data System (ADS)

    Izotov, I.; Tarvainen, O.; Mansfeld, D.; Skalyga, V.; Koivisto, H.; Kalvas, T.; Komppula, J.; Kronholm, R.; Laulainen, J.

    2015-08-01

    Electron cyclotron resonance ion sources (ECRIS) have been essential in the research and applications of nuclear physics over the past 40 years. They are extensively used in a wide range of large-scale accelerator facilities for the production of highly charged heavy ion beams of stable and radioactive elements. ECRISs are susceptible to kinetic instabilities due to resonance heating mechanism leading to anisotropic electron velocity distribution function. Instabilities of cyclotron type are a proven cause of frequently observed periodic bursts of ‘hot’ electrons and bremsstrahlung, accompanied with emission of microwave radiation and followed by considerable drop of multiply charged ions current. Detailed studies of the microwave radiation associated with the instabilities have been performed with a minimum-B 14 GHz ECRIS operating on helium, oxygen and argon plasmas. It is demonstrated that during the development of cyclotron instability ‘hot’ electrons emit microwaves in sub-microsecond scale bursts at temporally descending frequencies in the 8-15 GHz range with two dominant frequencies of 11.09 and 12.59 GHz regardless of ECRIS settings i.e. magnetic field strength, neutral gas pressure or species and microwave power. The experimental data suggest that the most probable excited plasma wave is a slow extraordinary Z-mode propagating quasi-longitudinally with respect to the external magnetic field.

  9. Method and apparatuses for ion cyclotron spectrometry

    DOEpatents

    Dahl, David A [Idaho Falls, ID; Scott, Jill R [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

    2012-03-06

    An ion cyclotron spectrometer may include a vacuum chamber that extends at least along a z-axis and means for producing a magnetic field within the vacuum chamber so that a magnetic field vector is generally parallel to the z-axis. The ion cyclotron spectrometer may also include means for producing a trapping electric field within the vacuum chamber. The trapping electric field may comprise a field potential that, when taken in cross-section along the z-axis, includes at least one section that is concave down and at least one section that is concave up so that ions traversing the field potential experience a net magnetron effect on a cyclotron frequency of the ions that is substantially equal to zero. Other apparatuses and a method for performing ion cyclotron spectrometry are also disclosed herein.

  10. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1985-01-01

    The author built and tested a low energy cyclotron for radiocarbon dating similar to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. The author found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. The author shows how a conventional carbon negative ion source located outside the cyclotron magnet, would produce sufficient beam and provide for quick sample changing to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  11. Development of a Medical Cyclotron Production Facility

    SciTech Connect

    Allen, Danny R.

    2003-08-26

    Development of a Cyclotron manufacturing facility begins with a business plan. Geographics, the size and activity of the medical community, the growth potential of the modality being served, and other business connections are all considered. This business used the customer base established by NuTech, Inc., an independent centralized nuclear pharmacy founded by Danny Allen. With two pharmacies in operation in Tyler and College Station and a customer base of 47 hospitals and clinics the existing delivery system and pharmacist staff is used for the cyclotron facility. We then added cyclotron products to contracts with these customers to guarantee a supply. We partnered with a company in the process of developing PET imaging centers. We then built an independent imaging center attached to the cyclotron facility to allow for the use of short-lived isotopes.

  12. Development of a Medical Cyclotron Production Facility

    NASA Astrophysics Data System (ADS)

    Allen, Danny R.

    2003-08-01

    Development of a Cyclotron manufacturing facility begins with a business plan. Geographics, the size and activity of the medical community, the growth potential of the modality being served, and other business connections are all considered. This business used the customer base established by NuTech, Inc., an independent centralized nuclear pharmacy founded by Danny Allen. With two pharmacies in operation in Tyler and College Station and a customer base of 47 hospitals and clinics the existing delivery system and pharmacist staff is used for the cyclotron facility. We then added cyclotron products to contracts with these customers to guarantee a supply. We partnered with a company in the process of developing PET imaging centers. We then built an independent imaging center attached to the cyclotron facility to allow for the use of short-lived isotopes.

  13. The superconducting separated orbit cyclotron tritron

    SciTech Connect

    Trinks, U.; Assmann, W.; Dietl, L.; Hinderer, H.J.; Korner, A; Platzer, A.; Rehm, B.; Rieger, K.; Riess, C.; Savoy, R.

    1985-10-01

    At the Munich Accelerator Laboratory a booster for the existing MP-tandem-the Tritron - is under construction for acceleration of heavy ions to specific energies up to 21 MeV/u. The Tritron/sup +/ is a separated orbit cyclotron similar to the SOC but with the magnets and cavities both superconducting. The Tritron fits well into the existing laboratory. It is projected to be a prototype to demonstrate the feasibility of this type of cyclotron, which may be suited to overcome the limits of the conventional cyclotron concept. First, there are no axial focusing problems. Secondly, there is no crossing of resonances in the betatron frequency diagram, and thirdly, there are no injection and extraction problems. Thus continuous ion beams of high intensity and high quality with energies up to about 1 GeV/u seem within reach by connecting several separated orbit cyclotrons with increasing radii in series.

  14. Rotatable superconducting cyclotron adapted for medical use

    DOEpatents

    Blosser, Henry G.; Johnson, David A.; Riedel, Jack; Burleigh, Richard J.

    1985-01-01

    A superconducting cyclotron (10) rotatable on a support structure (11) in an arc of about 180.degree. around a pivot axis (A--A) and particularly adapted for medical use is described. The rotatable support structure (13, 15) is balanced by being counterweighted (14) so as to allow rotation of the cyclotron and a beam (12), such as a subparticle (neutron) or atomic particle beam, from the cyclotron in the arc around a patient. Flexible hose (25) is moveably attached to the support structure for providing a liquified gas which is supercooled to near 0.degree. K. to an inlet means (122) to a chamber (105) around superconducting coils (101, 102). The liquid (34) level in the cyclotron is maintained approximately half full so that rotation of the support structure and cyclotron through the 180.degree. can be accomplished without spilling the liquid from the cyclotron. With the coils vertically oriented, each turn of the winding is approximately half immersed in liquid (34) and half exposed to cold gas and adequate cooling to maintain superconducting temperatures in the section of coil above the liquid level is provided by the combination of cold gas/vapor and by the conductive flow of heat along each turn of the winding from the half above the liquid to the half below.

  15. Spectral Features and Charge Dynamics of Lead Halide Perovskites: Origins and Interpretations.

    PubMed

    Sum, Tze Chien; Mathews, Nripan; Xing, Guichuan; Lim, Swee Sien; Chong, Wee Kiang; Giovanni, David; Dewi, Herlina Arianita

    2016-02-16

    Lead halide perovskite solar cells are presently the forerunner among the third generation solution-processed photovoltaic technologies. With efficiencies exceeding 20% and low production costs, they are prime candidates for commercialization. Critical insights into their light harvesting, charge transport, and loss mechanisms have been gained through time-resolved optical probes such as femtosecond transient absorption spectroscopy (fs-TAS), transient photoluminescence spectroscopy, and time-resolved terahertz spectroscopy. Specifically, the discoveries of long balanced electron-hole diffusion lengths and gain properties in halide perovskites underpin their significant roles in uncovering structure-function relations and providing essential feedback for materials development and device optimization. In particular, fs-TAS is becoming increasingly popular in perovskite characterization studies, with commercial one-box pump-probe systems readily available as part of a researcher's toolkit. Although TAS is a powerful probe in the study of charge dynamics and recombination mechanisms, its instrumentation and data interpretation can be daunting even for experienced researchers. This issue is exacerbated by the sensitive nature of halide perovskites where the kinetics are especially susceptible to pump fluence, sample preparation and handling and even degradation effects that could lead to disparate conclusions. Nonetheless, with end-users having a clear understanding of TAS's capabilities, subtleties, and limitations, cutting-edge work with deep insights can still be performed using commercial setups as has been the trend for ubiquitous spectroscopy instruments like absorption, fluorescence, and transient photoluminescence spectrometers. Herein, we will first briefly examine the photophysical processes in lead halide perovskites, highlighting their novel properties. Next, we proceed to give a succinct overview of the fundamentals of pump-probe spectroscopy in relation

  16. Ion cyclotron resonance heated conics - Theory and observations

    NASA Technical Reports Server (NTRS)

    Crew, G. B.; Chang, Tom; Retterer, J. M.; Peterson, W. K.; Gurnett, D. A.

    1990-01-01

    A general theoretical treatment of energetic oxygen ion conic formation through cyclotron resonance with magnetospheric electromagnetic plasma turbulence is presented. With suitable assumptions, there exists a similarity regime in which the process may be profitably characterized by two parameters corresponding roughly to the velocity scale and pitch angle of the ion distribution. These may be independently determined from the wave and particle observations of a conic event, as is illustrated here using typical auroral passes of the Dynamics Explorer 1 satellite. The predictions of the theory are found to be in excellent agreement with the observations.

  17. Superthermal electron distribution measurements from polarized electron cyclotron emission

    SciTech Connect

    Luce, T.C.; Efthimion, P.C.; Fisch, N.J.

    1988-06-01

    Measurements of the superthermal electron distribution can be made by observing the polarized electron cyclotron emission. The emission is viewed along a constant magnetic field surface. This simplifies the resonance condition and gives a direct correlation between emission frequency and kinetic energy of the emitting electron. A transformation technique is formulated which determines the anisotropy of the distribution and number density of superthermals at each energy measured. The steady-state distribution during lower hybrid current drive and examples of the superthermal dynamics as the runaway conditions is varied are presented for discharges in the PLT tokamak. 15 refs., 8 figs.

  18. Laboratory study of pulsed regimes of electron cyclotron instabilities in a mirror-confined plasma for astrophysical applications

    NASA Astrophysics Data System (ADS)

    Viktorov, Mikhail; Golubev, Sergey; Mansfeld, Dmitry; Izotov, Ivan; Gospodchikov, Egor; Shalashov, Alexander; Demekhov, Andrei

    2014-05-01

    We discuss the use of a mirror-confined plasma of the electron cyclotron resonance discharge for modeling of burst processes in the inner magnetosphere of the Earth associated with the implementation of the plasma cyclotron maser. Heating under the electron cyclotron resonance conditions allows to create two component plasma which is typical for the inner magnetosphere of the Earth. One of the most interesting electron cyclotron resonance manifestations is the generation of bursts of electromagnetic radiation that are related to the explosive growth of cyclotron instabilities of the magnetoactive plasma confined in magnetic traps of various kinds and that are accompanied by particle precipitations from the trap. We investigate several regimes of cyclotron maser which are realized in dense and rarefied plasma, in the presence and absence of a permanent powerful gyrotron microwave radiation as a source of nonequilibrium particles in the plasma. Using the new technique for detection of microwave radiation we studied the dynamical spectrum and the intensity of stimulated electromagnetic radiation from the plasma in a wide frequency band covering all types of cyclotron instabilities. Also possible applications for astrophysical plasma are discussed.

  19. Nonlinearities Lead to Qualitative Differences in Population Dynamics of Predator-Prey Systems

    PubMed Central

    Ameixa, Olga M. C. C.; Messelink, Gerben J.; Kindlmann, Pavel

    2013-01-01

    Since typically there are many predators feeding on most herbivores in natural communities, understanding multiple predator effects is critical for both community and applied ecology. Experiments of multiple predator effects on prey populations are extremely demanding, as the number of treatments and the amount of labour associated with these experiments increases exponentially with the number of species in question. Therefore, researchers tend to vary only presence/absence of the species and use only one (supposedly realistic) combination of their numbers in experiments. However, nonlinearities in density dependence, functional responses, interactions between natural enemies etc. are typical for such systems, and nonlinear models of population dynamics generally predict qualitatively different results, if initial absolute densities of the species studied differ, even if their relative densities are maintained. Therefore, testing combinations of natural enemies without varying their densities may not be sufficient. Here we test this prediction experimentally. We show that the population dynamics of a system consisting of 2 natural enemies (aphid predator Adalia bipunctata (L.), and aphid parasitoid, Aphidius colemani Viereck) and their shared prey (peach aphid, Myzus persicae Sulzer) are strongly affected by the absolute initial densities of the species in question. Even if their relative densities are kept constant, the natural enemy species or combination thereof that most effectively suppresses the prey may depend on the absolute initial densities used in the experiment. Future empirical studies of multiple predator – one prey interactions should therefore use a two-dimensional array of initial densities of the studied species. Varying only combinations of natural enemies without varying their densities is not sufficient and can lead to misleading results. PMID:23638107

  20. Order-disorder transition in conflicting dynamics leading to rank-frequency generalized beta distributions

    NASA Astrophysics Data System (ADS)

    Alvarez-Martinez, R.; Martinez-Mekler, G.; Cocho, G.

    2011-01-01

    The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes.

  1. Observation of Ion Cyclotron Heating in a Fast-flowing Plasma for an Advanced Plasma Thruster

    NASA Astrophysics Data System (ADS)

    Ando, Akira; Hatanaka, Motoi; Shibata, Masaki; Tobari, Hiroyuki; Hattori, Kunihiko; Inutake, Masaaki

    2004-11-01

    In the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) project in NASA, the combined system of the ion cyclotron heating and the magnetic nozzle is proposed to control a ratio of specific impulse to thrust at constant power. In order to establish the advanced plasma thruster, experiments of an ion heating and plasma acceleration by a magnetic nozzle are performed in a fast-flowing plasma in the HITOP device. A fast-flowing He plasma is produced by Magneto-Plasma-Dynamic Arcjet (MPDA) operated with an externally-applied magnetic field up to 1kG. RF waves with an ion cyclotron range of frequency (f=20-300kHz) is excited by a helically-wound antenna located downstream of the MPDA. Increases of an ion temperature and plasma stored energy measured by a diamagnetic coil clearly observed during the RF pulse. The heating efficiency is compared for various magnetic field configurations and strengths. There appears no indication of cyclotron resonance in a high density plasma where the ratio of ion cyclotron frequency to ion-ion collision one is below unity, because an ion-ion collisional effect is dominant. When the density becomes low and the ratio of ion cyclotron frequency to ion-ion collision one becomes high, features of ion cyclotron resonance are clearly appeared. The optimum magnetic field strength for the ion heating is slightly lower than that of the cyclotron resonance, which is caused by the Doppler effect due to the fast-flowing plasma. An ion energy distribution function is measured at a magnetic nozzle region by an electrostatic analyzer and increase of the parallel velocity is also observed.

  2. Linear coupling of acoustic and cyclotron waves in plasma flows

    SciTech Connect

    Rogava, Andria; Gogoberidze, Grigol

    2005-05-15

    It is found that in magnetized electrostatic plasma flows the velocity shear couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable conditions, to their efficient reciprocal transformations. It is shown that in a two-dimensional setup this coupling has a remarkable feature: it is governed by equations that are mathematically equal to the ones describing coupling of sound waves with internal gravity waves [Rogava and Mahajan, Phys. Rev. E 55, 1185 (1997)] in neutral fluids. For flows with low shearing rates a fully analytic, quantitative description of the coupling efficiency, based on a noteworthy quantum-mechanical analogy, is given and transformation coefficients are calculated.

  3. Effect of the minority concentration on ion cyclotron resonance heating in presence of the ITER-like wall in JET

    SciTech Connect

    Van Eester, D.; Lerche, E.; Crombé, K.; Jachmich, S.; Bobkov, V.; Maggi, C.; Neu, R.; Pütterich, T.; Czarnecka, A.; Coenen, J. W.; and others

    2014-02-12

    The most recent JET campaign has focused on characterizing operation with the 'ITER-like' wall. One of the questions that needed to be answered is whether the auxiliary heating methods do not lead to unacceptably high levels of impurity influx, preventing fusion-relevant operation. In view of its high single pass absorption, hydrogen minority fundamental cyclotron heating in a deuterium plasma was chosen as the reference wave heating scheme in the ion cyclotron domain of frequencies. The present paper discusses the plasma behavior as a function of the minority concentration X[H] in L-mode with up to 4MW of RF power. It was found that the tungsten concentration decreases by a factor of 4 when the minority concentration is increased from X[H] ≈ 5% to X[H] % 20% and that it remains at a similar level when X[H] is further increased to 30%; a monotonic decrease in Beryllium emission is simultaneously observed. The radiated power drops by a factor of 2 and reaches a minimum at X[H] ≈ 20%. It is discussed that poor single pass absorption at too high minority concentrations ultimately tailors the avoidance of the RF induced impurity influx. The edge density being different for different minority concentrations, it is argued that the impact ICRH has on the fate of heavy ions is not only a result of core (wave and transport) physics but also of edge dynamics and fueling.

  4. Effect of the minority concentration on ion cyclotron resonance heating in presence of the ITER-like wall in JET

    NASA Astrophysics Data System (ADS)

    Van Eester, D.; Lerche, E.; Jacquet, P.; Bobkov, V.; Czarnecka, A.; Coenen, J. W.; Colas, L.; Crombé, K.; Graham, M.; Jachmich, S.; Joffrin, E.; Klepper, C. C.; Kiptily, V.; Lehnen, M.; Maggi, C.; Marcotte, F.; Matthews, G.; Mayoral, M.-L.; Mc Cormick, K.; Monakhov, I.; Nave, M. F. F.; Neu, R.; Noble, C.; Ongena, J.; Pütterich, T.; Rimini, F.; Solano, E. R.; van Rooij, G.; JET-EFDA contributors

    2014-02-01

    The most recent JET campaign has focused on characterizing operation with the "ITER-like" wall. One of the questions that needed to be answered is whether the auxiliary heating methods do not lead to unacceptably high levels of impurity influx, preventing fusion-relevant operation. In view of its high single pass absorption, hydrogen minority fundamental cyclotron heating in a deuterium plasma was chosen as the reference wave heating scheme in the ion cyclotron domain of frequencies. The present paper discusses the plasma behavior as a function of the minority concentration X[H] in L-mode with up to 4MW of RF power. It was found that the tungsten concentration decreases by a factor of 4 when the minority concentration is increased from X[H] ≈ 5% to X[H] % 20% and that it remains at a similar level when X[H] is further increased to 30%; a monotonic decrease in Beryllium emission is simultaneously observed. The radiated power drops by a factor of 2 and reaches a minimum at X[H] ≈ 20%. It is discussed that poor single pass absorption at too high minority concentrations ultimately tailors the avoidance of the RF induced impurity influx. The edge density being different for different minority concentrations, it is argued that the impact ICRH has on the fate of heavy ions is not only a result of core (wave and transport) physics but also of edge dynamics and fueling.

  5. Self-Consistent Model of Magnetospheric Ring Current and Electromagnetic Ion Cyclotron Waves: The 2-7 May 1998 Storm

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.

    2003-01-01

    A complete description of a self-consistent model of magnetospheric ring current interacting with electromagnetic ion cyclotron waves is presented. The model is based on the system of two kinetic equations; one equation describes the ring current ion dynamics, and another equation describes the wave evolution. The effects on ring current ions interacting with electromagnetic ion cyclotron waves and back on waves are considered self-consistently by solving both equations on a global magnetospheric scale under nonsteady state conditions. The developed model is employed to simulate the entire 2-7 May 1998 storm period. First, the trapped number fluxes of the ring current protons are calculated and presented along with comparison with the data measured by the three- dimensional hot plasma instrument Polar/HYDRA. Incorporating in the model the wave-particle interaction leads to much better agreement between the experimental data and the model results. Second, examining of the wave (MLT, L shell) distributions produced by the model during the storm progress reveals an essential intensification of the wave emission about 2 days after the main phase of the storm. This result is well consistent with the earlier ground-based observations. Finally, the theoretical shapes and the occurrence rates of the wave power spectral densities are studied. It is found that about 2 days after the storm s main phase on 4 May, mainly non-Gaussian shapes of power spectral densities are produced.

  6. Self-Consistent Model of Magnetospheric Ring Current and Electromagnetic Ion Cyclotron Waves: The 2-7 May 1998 Storm

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.

    2003-01-01

    A complete description of a self-consistent model of magnetospheric ring current interacting with electromagnetic ion cyclotron waves is presented. The model is based on the system of two kinetic equations; one equation describes the ring current ion dynamics, and another equation describes the wave evolution. The effects on ring current ions interacting with electromagnetic ion cyclotron waves and back on waves are considered self-consistently by solving both equations on a global magnetospheric scale under nonsteady state conditions. The developed model is employed to simulate the entire 2-7 May 1998 storm period. First, the trapped number fluxes of the ring current protons are calculated and presented along with comparison with the data measured by the three- dimensional hot plasma instrument Polar/HYDRA. Incorporating in the model the wave-particle interaction leads to much better agreement between the experimental data and the model results. Second, examining of the wave (MLT, L shell) distributions produced by the model during the storm progress reveals an essential intensification of the wave emission about 2 days after the main phase of the storm. This result is well consistent with the earlier ground-based observations. Finally, the theoretical shapes and the occurrence rates of the wave power spectral densities are studied. It is found that about 2 days after the storm s main phase on 4 May, mainly non-Gaussian shapes of power spectral densities are produced.

  7. Effects of Lead Exposure, Environmental Conditions, and Metapopulation Processes on Population Dynamics of Spectacled Eiders.

    USGS Publications Warehouse

    Flint, Paul L.; Grand, James B.; Petersen, Margaret; Rockwell, Robert F.

    2016-01-01

    Spectacled eider Somateria fischeri numbers have declined and they are considered threatened in accordance with the US Endangered Species Act throughout their range. We synthesized the available information for spectacled eiders to construct deterministic, stochastic, and metapopulation models for this species that incorporated current estimates of vital rates such as nest success, adult survival, and the impact of lead poisoning on survival. Elasticities of our deterministic models suggested that the populations would respond most dramatically to changes in adult female survival and that the reductions in adult female survival related to lead poisoning were locally important. We also examined the sensitivity of the population to changes in lead exposure rates. With the knowledge that some vital rates vary with environmental conditions, we cast stochastic models that mimicked observed variation in productivity. We also used the stochastic model to examine the probability that a specific population will persist for periods of up to 50 y. Elasticity analysis of these models was consistent with that for the deterministic models, with perturbations to adult female survival having the greatest effect on population projections. When used in single population models, demographic data for some localities predicted rapid declines that were inconsistent with our observations in the field. Thus, we constructed a metapopulation model and examined the predictions for local subpopulations and the metapopulation over a wide range of dispersal rates. Using the metapopulation model, we were able to simulate the observed stability of local subpopulations as well as that of the metapopulation. Finally, we developed a global metapopulation model that simulates periodic winter habitat limitation, similar to that which might be experienced in years of heavy sea ice in the core wintering area of spectacled eiders in the central Bering Sea. Our metapopulation analyses suggested that no

  8. Simulation of Median Plane Effects in the Extraction Region of the C235 Cyclotron

    SciTech Connect

    Jongen, Y.; Karamysheva, G.; Shirkov, S.

    2010-01-05

    The Study of beam dynamics in the C235 cyclotron dedicated for proton therapy is presented. Results of computer simulations of the particle motion in the measured magnetic field are given. This of the median plane effects in the extraction region was carried out. The tolerance on the radial component of the magnetic field was defined using these simulations.

  9. Ultrafast carrier dynamics in bimetallic nanostructure-enhanced methylammonium lead bromide perovskites.

    PubMed

    Zarick, Holly F; Boulesbaa, Abdelaziz; Puretzky, Alexander A; Talbert, Eric M; DeBra, Zachary R; Soetan, Naiya; Geohegan, David B; Bardhan, Rizia

    2017-01-26

    In this work, we examine the impact of hybrid bimetallic Au/Ag core/shell nanostructures on the carrier dynamics of methylammonium lead tribromide (MAPbBr3) mesoporous perovskite solar cells (PSCs). Plasmon-enhanced PSCs incorporated with Au/Ag nanostructures demonstrated improved light harvesting and increased power conversion efficiency by 26% relative to reference devices. Two complementary spectral techniques, transient absorption spectroscopy (TAS) and time-resolved photoluminescence (trPL), were employed to gain a mechanistic understanding of plasmonic enhancement processes. TAS revealed a decrease in the photobleach formation time, which suggests that the nanostructures improve hot carrier thermalization to an equilibrium distribution, relieving hot phonon bottleneck in MAPbBr3 perovskites. TAS also showed a decrease in carrier decay lifetimes, indicating that nanostructures enhance photoinduced carrier generation and promote efficient electron injection into TiO2 prior to bulk recombination. Furthermore, nanostructure-incorporated perovskite films demonstrated quenching in steady-state PL and decreases in trPL carrier lifetimes, providing further evidence of improved carrier injection in plasmon-enhanced mesoporous PSCs.

  10. Stochastic dynamics of resistive switching: fluctuations lead to optimal particle number

    NASA Astrophysics Data System (ADS)

    Radtke, Paul K.; Hazel, Andrew L.; Straube, Arthur V.; Schimansky-Geier, Lutz

    2017-09-01

    Resistive switching (RS) is one of the foremost candidates for building novel types of non-volatile random access memories. Any practical implementation of such a memory cell calls for a strong miniaturization, at which point fluctuations start playing a role that cannot be neglected. A detailed understanding of switching mechanisms and reliability is essential. For this reason, we formulate a particle model based on the stochastic motion of oxygen vacancies. It allows us to investigate fluctuations in the resistance states of a switch with two active zones. The vacancies’ dynamics are governed by a master equation. Upon the application of a voltage pulse, the vacancies travel collectively through the switch. By deriving a generalized Burgers equation we can interpret this collective motion as nonlinear traveling waves, and numerically verify this result. Further, we define binary logical states by means of the underlying vacancy distributions, and establish a framework of writing and reading such memory element with voltage pulses. Considerations about the discriminability of these operations under fluctuations together with the markedness of the RS effect itself lead to the conclusion, that an intermediate vacancy number is optimal for performance.

  11. Photocatalytic hydrogen generation from hydriodic acid using methylammonium lead iodide in dynamic equilibrium with aqueous solution

    NASA Astrophysics Data System (ADS)

    Park, Sunghak; Chang, Woo Je; Lee, Chan Woo; Park, Sangbaek; Ahn, Hyo-Yong; Nam, Ki Tae

    2017-01-01

    The solar-driven splitting of hydrohalic acids (HX) is an important and fast growing research direction for H2 production. In addition to the hydrogen, the resulting chemicals (X2/X3-) can be used to propagate a continuous process in a closed cycle and are themselves useful products. Here we present a strategy for photocatalytic hydrogen iodide (HI) splitting using methylammonium lead iodide (MAPbI3) in an effort to develop a cost-effective and easily scalable process. Considering that MAPbI3 is a water-soluble ionic compound, we exploit the dynamic equilibrium of the dissolution and precipitation of MAPbI3 in saturated aqueous solutions. The I- and H+ concentrations of the aqueous solution are determined to be the critical parameters for the stabilization of the tetragonal MAPbI3 phase. Stable and efficient H2 production under visible light irradiation was demonstrated. The solar HI splitting efficiency of MAPbI3 was 0.81% when using Pt as a cocatalyst.

  12. Ultrafast charge generation and relaxation dynamics in methylammonium lead bromide perovskites

    NASA Astrophysics Data System (ADS)

    Deng, Xiaofan; Wen, Xiaoming; Sheng, Rui; Huang, Shujuan; Harada, Takaaki; Kee, Tak W.; Green, Martin A.; Ho-Baillie, Anita

    2015-12-01

    Methylammonium Lead Bromide (CH3NH3PbBr3) is a promising material for tandem solar cell due to its high band gap. Ultrafast optical techniques on a time scale of femto- and picosecond are used to investigate the carrier dynamics in CH3NH3PbBr3. An ultrafast cooling of hot carriers occurs in sub-picoseconds in CH3NH3PbBr3 by phonon scattering. Two ultrafast relaxation processes are attributed to optical phonon scattering and acoustic phonon scattering. The relaxation processes are evidently slower when CH3NH3PbBr3 is in contact with compact TiO2 (c-TiO2) layer, suggesting better quality CH3NH3PbBr3. when deposited on c-TiO2. The nanosecond decay in CH3NH3PbBr3 film is ascribed to electron-hole recombination. With the presence of c-TiO2 layer, this process is accelerated due to electron transport across the CH3NH3PbBr3/ c-TiO2 interface.

  13. Ultrafast carrier dynamics in bimetallic nanostructure-enhanced methylammonium lead bromide perovskites

    SciTech Connect

    Zarick, Holly; Boulesbaa, Abdelaziz; Puretzky, Alexander A; Talbert, Eric; Soetan, Naiya; Geohegan, David B; Bardhan, Rizia

    2016-12-14

    In this paper, we examine the impact of hybrid bimetallic Au/Ag core/shell nanostructures on the carrier dynamics of methylammonium lead tribromide (MAPbBr3) mesoporous perovskite solar cells (PSCs). Plasmon-enhanced PSCs incorporated with Au/Ag nanostructures demonstrated improved light harvesting and increased power conversion efficiency by 26% relative to reference devices. Two complementary spectral techniques, transient absorption spectroscopy (TAS) and time-resolved photoluminescence (trPL), were employed to gain a mechanistic understanding of plasmonic enhancement processes. TAS revealed a decrease in the photobleach formation time, which suggests that the nanostructures improve hot carrier thermalization to an equilibrium distribution, relieving hot phonon bottleneck in MAPbBr3 perovskites. TAS also showed a decrease in carrier decay lifetimes, indicating that nanostructures enhance photoinduced carrier generation and promote efficient electron injection into TiO2 prior to bulk recombination. Furthermore, nanostructure-incorporated perovskite films demonstrated quenching in steady-state PL and decreases in trPL carrier lifetimes, providing further evidence of improved carrier injection in plasmon-enhanced mesoporous PSCs.

  14. Suppression of dynamic stall with a leading-edge slat on a VR-7 airfoil

    NASA Technical Reports Server (NTRS)

    Mcalister, K. W.; Tung, C.

    1993-01-01

    The VR-7 airfoil was experimentally studied with and without a leading-edge slat at fixed angles of attack from 0 deg to 30 deg at Re = 200,000 and for unsteady pitching motions described by alpha equals alpha(sub m) + 10 deg(sin(wt)). The models were two dimensional, and the test was performed in a water tunnel at Ames Research Center. The unsteady conditions ranged over Re equals 100,000 to 250,000, k equals 0.001 to 0.2, and alpha(sub m) = 10 deg to 20 deg. Unsteady lift, drag, and pitching-moment measurements were obtained along with fluorescent-dye flow visualizations. The addition of the slat was found to delay the static-drag and static-moment stall by about 5 degrees and to eliminate completely the development of a dynamic-stall vortex during unsteady motions that reached angles as high as 25 degrees. In all of the unsteady cases studied, the slat caused a significant reduction in the force and moment hysteresis amplitudes. The reduced frequency was found to have the greatest effect on the results, whereas the Reynolds number had little effect on the behavior of either the basic or the slatted airfoil. The slat caused a slight drag penalty at low angles of attack, but generally increased the lift/drag ratio when averaged over the full cycle of oscillation.

  15. Entrance Channel Dynamics of Hot and Cold Fusion Reactions Leading to Superheavy Elements

    NASA Astrophysics Data System (ADS)

    Umar, Sait; Oberacker, Volker

    2010-11-01

    One of the most fascinating research areas involving low-energy nuclear reactions is the search for superheavy elements. Experimentally, two approaches have been used for the synthesis of these elements, one utilizing closed shell nuclei with lead-based targets (cold-fusion), the other utilizing deformed actinide targets with ^48Ca projectiles (hot-fusion). In this talk we investigate the entrance channel dynamics for the reactions ^70Zn+^208Pb and ^48Ca+^238U using the fully microscopic time-dependent Hartree-Fock (TDHF) theory coupled with a density constraint [1-3]. We calculate excitation energies and capture cross-sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the ^48Ca+^238U system and perform an alignment angle averaging for the calculation of the capture cross-section. The results show that this approach can generate results in good agreement with experiment and other theories.[4pt] [1] Umar, Oberacker, PRC 74, 061601(R) (2006).[0pt] [2] Umar, Oberacker, EPJA 39, 243 (2009).[0pt] [3] Umar, Maruhn, Itagaki, and Oberacker, PRL 104, 212503.

  16. Ultrafast carrier dynamics in bimetallic nanostructure-enhanced methylammonium lead bromide perovskites

    DOE PAGES

    Zarick, Holly; Boulesbaa, Abdelaziz; Puretzky, Alexander A; ...

    2016-12-14

    In this paper, we examine the impact of hybrid bimetallic Au/Ag core/shell nanostructures on the carrier dynamics of methylammonium lead tribromide (MAPbBr3) mesoporous perovskite solar cells (PSCs). Plasmon-enhanced PSCs incorporated with Au/Ag nanostructures demonstrated improved light harvesting and increased power conversion efficiency by 26% relative to reference devices. Two complementary spectral techniques, transient absorption spectroscopy (TAS) and time-resolved photoluminescence (trPL), were employed to gain a mechanistic understanding of plasmonic enhancement processes. TAS revealed a decrease in the photobleach formation time, which suggests that the nanostructures improve hot carrier thermalization to an equilibrium distribution, relieving hot phonon bottleneck in MAPbBr3 perovskites.more » TAS also showed a decrease in carrier decay lifetimes, indicating that nanostructures enhance photoinduced carrier generation and promote efficient electron injection into TiO2 prior to bulk recombination. Furthermore, nanostructure-incorporated perovskite films demonstrated quenching in steady-state PL and decreases in trPL carrier lifetimes, providing further evidence of improved carrier injection in plasmon-enhanced mesoporous PSCs.« less

  17. Cyclotron resonance of figure-of-eight orbits in a type-II Weyl semimetal

    NASA Astrophysics Data System (ADS)

    Koshino, Mikito

    2016-07-01

    We study the cyclotron resonance in the electron-hole joint Fermi surface of a type-II Weyl semimetal. In magnetic field, the electron and hole pockets touching at the Weyl node are hybridized to form quantized Landau levels corresponding to semiclassical 8-shaped orbits. We calculate the dynamical conductivities for the electric fields oscillating in x and y directions and find that the resonant frequencies in x and y differ by a factor of two, reflecting the figure-of-eight electron motion in real space. The peculiar anisotropy in the cyclotron resonance serves as a unique characteristic of the dumbbell-like Fermi surface.

  18. A study of density in electron-cyclotron-resonance plasma

    SciTech Connect

    Uhm, H.S.; Lee, P.H.; Kim, Y.I.; Kim, J.H.; Chang, H.Y.

    1995-08-01

    A theory is developed for the density profile of low-temperature plasmas confined by applied magnetic field and an experiment of the electron-cyclotron-resonance (ECR) plasma is conducted to compare the theoretical prediction and experimental measurements. Due to a large electron mobility along the magnetic field, electrons move quickly out of the system, leaving ions behind and building a space charge potential, which leads to the ambipolar diffusion of ions. In a steady-state condition, the plasma generation by ionization of neutral molecules is in balance with plasma loss due to the diffusion, leading to the electron temperature equation, which is expressed in terms of the plasma size, chamber pressure, and the ionization energy and cross section of neutrals. The power balance condition leads to the plasma density equation, which is also expressed in terms of the electron temperature, the input microwave power and the chamber pressure. It is shown that the plasma density increases, reaches its peak and decreases, as the chamber pressure increases from a small value (0.1 mTorr). These simple expressions of electron temperature and density provide a scaling law of ECR plasma in terms of system parameters. After carrying out an experimental observation, it is concluded that the theoretical predictions of the electron temperature and plasma density agree remarkably well with experimental data. A large-volume plasma generated by the electron-cyclotron-resonance (ECR) mechanism plays a pivotal role in the plasma processing, including thin-film depositions and plasma etching technologies.

  19. Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

    NASA Technical Reports Server (NTRS)

    Singh, N.; Conrad, J. R.; Schunk, R. W.

    1985-01-01

    It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves.

  20. Design study of an ultra-compact superconducting cyclotron for isotope production

    NASA Astrophysics Data System (ADS)

    Smirnov, V.; Vorozhtsov, S.; Vincent, J.

    2014-11-01

    A 12.5 MeV, 25 μA, proton compact superconducting cyclotron for medical isotope production has been designed and is currently in fabrication. The machine is initially aimed at producing 13N ammonia for Positron Emission Tomography (PET) cardiology applications. With an ultra-compact size and cost-effective price point, this system will offer clinicians unprecedented access to the preferred radiopharmaceutical isotope for cardiac PET imaging. A systems approach that carefully balanced the subsystem requirements coupled to precise beam dynamics calculations was followed. The system is designed to irradiate a liquid target internal to the cyclotron and to minimize the need for radiation shielding. The main parameters of the cyclotron, its design, and principal steps of the development work are presented here.

  1. Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

    SciTech Connect

    Singh, N.; Conrad, J.R.; Schunk, R.W.

    1985-06-01

    It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves. 39 references.

  2. Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

    NASA Technical Reports Server (NTRS)

    Singh, N.; Conrad, J. R.; Schunk, R. W.

    1985-01-01

    It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves.

  3. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1984-12-01

    The measurement of naturally occurring radioisotopes whose half lives are less than a few hundred million years but more than a few years provides information about the temporal behavior of geologic and climatic processes, the temporal history of meteoritic bodies as well as the production mechanisms of these radioisotopes. A new extremely sensitive technique for measuring these radioisotopes at tandem Van de Graaff and cyclotron facilities has been very successful though the high cost and limited availability have been discouraging. We have built and tested a low energy cyclotron for radiocarbon dating similar in size to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. We found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. We show how a conventional carbon negative ion source, located outside the cyclotron magnet, would produce sufficient beam and provide for quick sampling to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  4. Recycling and recommissioning a used biomedical cyclotron

    NASA Astrophysics Data System (ADS)

    Carroll, L. R.; Ramsey, F.; Armbruster, J.; Montenero, M.

    2001-07-01

    Biomedical Cyclotrons have a very long life, but there eventually comes a time when any piece of equipment has to be retired from service. From time to time, we have the opportunity to help find new homes for used cyclotrons which, with relatively modest overhaul and refurbishment, can have many additional years of productive service, and thus represent a very valuable asset. The reasons for retiring a cyclotron vary, of course, but in our experience it is often due to an institution's changing priorities or changing needs, rather than the due to any fundamental age-related deficiency in the cyclotron itself. In this paper we will report on the relocation and successful restoration of a used TCC CP-42 cyclotron, which was moved from M.D. Anderson Hospital in Houston to Denton, Texas in early 1998, where it is presently being used for R&D and commercial production of biomedical isotopes. Ownership of the machine has been transferred to the University of North Texas; facility, manpower, and operational resources are provided by International Isotopes, Inc.

  5. Cyclotron Provides Neutron Therapy for Cancer Patients

    NASA Image and Video Library

    1978-01-21

    A cancer patient undergoes treatment in the Neutron Therapy Treatment Facility, or Cylotron, at the National Aeronautics and Space Administration (NASA) Lewis Research Center. After World War II Lewis researchers became interested in nuclear energy for propulsion. The focused their efforts on thermodynamics and strength of materials after radiation. In 1950 an 80-person Nuclear Reactor Division was created, and a cyclotron was built behind the Materials and Structures Laboratory. An in-house nuclear school was established to train these researchers in their new field. NASA cancelled its entire nuclear program in January 1973, just as the cyclotron was about to resume operations after a major upgrade. In 1975 the Cleveland Clinic Foundation partnered with NASA Lewis to use the cyclotron for a new type of radiation treatment for cancer patients. The cyclotron split beryllium atoms which caused neutrons to be released. The neutrons were streamed directly at the patient’s tumor. The facility had a dual-beam system that could target the tumor both vertically and horizontally. Over the course of five years, the cyclotron was used to treat 1200 patients. It was found to be particularly effective on salivary gland, prostrate, and other tumors. It was not as successful with tumors of the central nervous system. The program was terminated in 1980 as the Clinic began concentrating on non-radiation treatments.

  6. Nonlinear sub-cyclotron resonance as a formation mechanism for gaps in banded chorus

    DOE PAGES

    Fu, Xiangrong; Guo, Zehua; Dong, Chuanfei; ...

    2015-05-14

    An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at ω ≃ 0.5Ωe, where Ωe is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near 0.3Ωe and 0.6Ωe. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency can resonate with electrons, leading to effective energy exchange between the wave and particles.

  7. Optimization of beam dump shielding for K-130 cyclotron at VECC.

    PubMed

    Chatterjee, S; Banerjee, K; Pandit, Deepak; Roy, Pratap; Bandyopadhyay, T; Ravishankar, R; Bhattacharya, C; Bhattacharya, S; Datta, D; Banerjee, S R

    2017-10-01

    A compact and efficient beam dump shield has been designed using Monte Carlo simulation code FLUKA to facilitate low background measurement of neutron and gamma rays using K130 cyclotron at Variable Energy Cyclotron Centre, Kolkata (VECC). Iron, lead and high density Polyethylene (HDPE) were considered in the design of the beam dump shield. Representative FLUKA simulation results have been validated using in-beam experiment performed on the same beam dump constituents. Experimental neutron and gamma-rays energy spectra have been found to be in fair agreement with the simulation results. Activation of various beam dump shield components were also carried out. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Ratchet transport of a two-dimensional electron gas at cyclotron resonance

    NASA Astrophysics Data System (ADS)

    Budkin, G. V.; Tarasenko, S. A.

    2016-02-01

    The driving of charge carriers confined in a quantum well lacking the center of space inversion by an alternating electric field leads to the formation of a direct electric current. We develop a microscopic theory of such a quantum ratchet effect for quantum wells subjected to a static magnetic field. We show that the ratchet current emerges for a linearly polarized alternating electric field as well as a rotating electric field and drastically increases at the cyclotron resonance conditions. For the magnetic field tilted with respect to the quantum well normal, the ratchet current contains an additional resonance at the first subharmonic of the cyclotron resonance.

  9. Making Sense Out of Chaos: Leading and Living in Dynamic Systems.

    ERIC Educational Resources Information Center

    Allen, Kathleen E.

    1990-01-01

    As the world is changing, higher education program administrators must give up a linear way of thinking and search for another that fits a nonlinear, dynamic system. Leaders can learn much from the science of chaos studies about how dynamic human organizations function and the underlying principles of complex dynamic systems. (MSE)

  10. A SCENARIO FOR THE FINE STRUCTURES OF SOLAR TYPE IIIb RADIO BURSTS BASED ON ELECTRON CYCLOTRON MASER EMISSION

    SciTech Connect

    Wang, C. B.

    2015-06-10

    A scenario based on electron cyclotron maser (ECM) emission is proposed for the fine structures of solar radio emission. It is suggested that under certain conditions modulation of the ratio between the plasma frequency and electron gyro frequency by ultra-low-frequency waves, which is a key parameter for excitation of ECM instability, may lead to the intermittent emission of radio waves. As an example, the explanation for the observed fine-structure components in the solar Type IIIb bursts is discussed in detail. Three primary issues of Type IIIb bursts are addressed: (1) the physical mechanism that results in intermittent emission elements that form a chain in the dynamic spectrum of Type IIIb bursts, (2) the cause of split pairs (or double stria) and triple stria, and (3) why only IIIb–III bursts are observed in the events of fundamental harmonic pair emission whereas IIIb–IIIb or III–IIIb bursts are very rarely observed.

  11. A Scenario for the Fine Structures of Solar Type IIIb Radio Bursts Based on Electron Cyclotron Maser Emission

    NASA Astrophysics Data System (ADS)

    Wang, C. B.

    2015-06-01

    A scenario based on electron cyclotron maser (ECM) emission is proposed for the fine structures of solar radio emission. It is suggested that under certain conditions modulation of the ratio between the plasma frequency and electron gyro frequency by ultra-low-frequency waves, which is a key parameter for excitation of ECM instability, may lead to the intermittent emission of radio waves. As an example, the explanation for the observed fine-structure components in the solar Type IIIb bursts is discussed in detail. Three primary issues of Type IIIb bursts are addressed: (1) the physical mechanism that results in intermittent emission elements that form a chain in the dynamic spectrum of Type IIIb bursts, (2) the cause of split pairs (or double stria) and triple stria, and (3) why only IIIb-III bursts are observed in the events of fundamental harmonic pair emission whereas IIIb-IIIb or III-IIIb bursts are very rarely observed.

  12. Alternative packing modes leading to amyloid polymorphism in five fragments studied with molecular dynamics.

    PubMed

    Berhanu, Workalemahu M; Masunov, Artëm E

    2012-01-01

    Amyloid aggregates have been implicated in the pathogenesis of diseases such as type 2 diabetes, Alzheimer's, Parkinson's, and prion disease. Recently determined microcrystal structures of several short peptide segments derived from fibril-forming proteins revealed coexistence of alternative aggregation modes (amyloid polymorphism) formed by the same segment. This polymorphism may help in understanding the influence of the side chain packing on the amyloid stability. Here we use molecular dynamics (MD) simulation to analyze the stability of five pairs of polar and nonpolar polymorphic oligomers. MD simulation shows polymorphs with steric zipper interface containing large polar and/or aromatic side chains (GNNQQNY, and NNQNTF) are more stable than steric zipper interfaces made of small or hydrophobic residues (SSTNGVG, VQIVYK, and MVGGVV). Several geometric analyses revealed that larger sheet to sheet interface of the dry steric zipper through polar Q/N rich side chains holds the sheets together. Mutant simulations (Q/N→G) show substitutions with glycine disrupt the steric zipper, leading to unstable oligomers. Stability of Q/N rich oligomers was found to result from the large average number of hydrogen bonds. The molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) method reports the nonpolar component of free energy to be favorable, while electrostatic solvation is unfavorable for β-sheet association. Knowledge of structural properties of these fibrils might be useful for developing therapeutic agents against amyloidoses as well as for developing biomaterials. © 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 98: 131-144, 2012. Copyright © 2011 Wiley Periodicals, Inc.

  13. Improving cancer treatment with cyclotron produced radionuclides

    SciTech Connect

    Larson, S.M. Finn, R.D.

    1992-08-04

    This report describes the author's continuing long term goal of promoting nuclear medicine applications by improving the scientific basis for tumor diagnosis treatment and treatment follow-up based on the use of cyclotron produced radiotracers in oncology. The program has 3 interactive components: Radiochemistry /Cyclotron; Pharmacology; and Immunology. An essential strategy is as follows: novel radionuclides and radiotracers developed in the Radiochemistry/Cyclotron section under the DOE grant during the 1989--1992 grant period, will be employed in the Pharmacology and Immunology sections of the DOE grant during the 1992--1995 grant period. The development of novel radionuclides and tracers is of course useful in and of itself, but their utility is greatly enhanced by the interaction with the immunology and pharmacology components of the program.

  14. A room temperature electron cyclotron resonance ion source for the DC-110 cyclotron

    SciTech Connect

    Efremov, A. Bogomolov, S.; Lebedev, A.; Loginov, V.; Yazvitsky, N.

    2014-02-15

    The project of the DC-110 cyclotron facility to provide applied research in the nanotechnologies (track pore membranes, surface modification of materials, etc.) has been designed by the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research (Dubna). The facility includes the isochronous cyclotron DC-110 for accelerating the intensive Ar, Kr, Xe ion beams with 2.5 MeV/nucleon fixed energy. The cyclotron is equipped with system of axial injection and ECR ion source DECRIS-5, operating at the frequency of 18 GHz. This article reviews the design and construction of DECRIS-5 ion source along with some initial commissioning results.

  15. Electromagnetic waves near the proton cyclotron frequency: Stereo observations

    SciTech Connect

    Jian, L. K.; Wei, H. Y.; Russell, C. T.; Luhmann, J. G.; Klecker, B.; Omidi, N.; Isenberg, P. A.; Goldstein, M. L.; Figueroa-Viñas, A.; Blanco-Cano, X.

    2014-05-10

    Transverse, near-circularly polarized, parallel-propagating electromagnetic waves around the proton cyclotron frequency were found sporadically in the solar wind throughout the inner heliosphere. They could play an important role in heating and accelerating the solar wind. These low-frequency waves (LFWs) are intermittent but often occur in prolonged bursts lasting over 10 minutes, named 'LFW storms'. Through a comprehensive survey of them from Solar Terrestrial Relations Observatory A using dynamic spectral wave analysis, we have identified 241 LFW storms in 2008, present 0.9% of the time. They are left-hand (LH) or right-hand (RH) polarized in the spacecraft frame with similar characteristics, probably due to Doppler shift of the same type of waves or waves of intrinsically different polarities. In rare cases, the opposite polarities are observed closely in time or even simultaneously. Having ruled out interplanetary coronal mass ejections, shocks, energetic particles, comets, planets, and interstellar ions as LFW sources, we discuss the remaining generation scenarios: LH ion cyclotron instability driven by greater perpendicular temperature than parallel temperature or by ring-beam distribution, and RH ion fire hose instability driven by inverse temperature anisotropy or by cool ion beams. The investigation of solar wind conditions is compromised by the bias of the one-dimensional Maxwellian fit used for plasma data calibration. However, the LFW storms are preferentially detected in rarefaction regions following fast winds and when the magnetic field is radial. This preference may be related to the ion cyclotron anisotropy instability in fast wind and the minimum in damping along the radial field.

  16. Cyclotron Lines in Accreting Neutron Star Spectra

    NASA Astrophysics Data System (ADS)

    Wilms, Jörn; Schönherr, Gabriele; Schmid, Julia; Dauser, Thomas; Kreykenbohm, Ingo

    2009-05-01

    Cyclotron lines are formed through transitions of electrons between discrete Landau levels in the accretion columns of accreting neutron stars with strong (1012 G) magnetic fields. We summarize recent results on the formation of the spectral continuum of such systems, describe recent advances in the modeling of the lines based on a modification of the commonly used Monte Carlo approach, and discuss new results on the dependence of the measured cyclotron line energy from the luminosity of transient neutron star systems. Finally, we show that Simbol-X will be ideally suited to build and improve the observational database of accreting and strongly magnetized neutron stars.

  17. Leading-process actomyosin coordinates organelle positioning and adhesion receptor dynamics in radially migrating cerebellar granule neurons

    SciTech Connect

    Trivedi, Niraj; Ramahi, Joseph S.; Karakaya, Mahmut; Howell, Danielle; Kerekes, Ryan A.; Solecki, David J.

    2014-12-02

    During brain development, neurons migrate from germinal zones to their final positions to assemble neural circuits. A unique saltatory cadence involving cyclical organelle movement (e.g., centrosome motility) and leading-process actomyosin enrichment prior to nucleokinesis organizes neuronal migration. While functional evidence suggests that leading-process actomyosin is essential for centrosome motility, the role of the actin-enriched leading process in globally organizing organelle transport or traction forces remains unexplored. Our results show that myosin ii motors and F-actin dynamics are required for Golgi apparatus positioning before nucleokinesis in cerebellar granule neurons (CGNs) migrating along glial fibers. Moreover, we show that primary cilia are motile organelles, localized to the leading-process F-actin-rich domain and immobilized by pharmacological inhibition of myosin ii and F-actin dynamics. Finally, leading process adhesion dynamics are dependent on myosin ii and F-actin. In conclusion, we propose that actomyosin coordinates the overall polarity of migrating CGNs by controlling asymmetric organelle positioning and cell-cell contacts as these cells move along their glial guides.

  18. Leading-process actomyosin coordinates organelle positioning and adhesion receptor dynamics in radially migrating cerebellar granule neurons

    DOE PAGES

    Trivedi, Niraj; Ramahi, Joseph S.; Karakaya, Mahmut; ...

    2014-12-02

    During brain development, neurons migrate from germinal zones to their final positions to assemble neural circuits. A unique saltatory cadence involving cyclical organelle movement (e.g., centrosome motility) and leading-process actomyosin enrichment prior to nucleokinesis organizes neuronal migration. While functional evidence suggests that leading-process actomyosin is essential for centrosome motility, the role of the actin-enriched leading process in globally organizing organelle transport or traction forces remains unexplored. Our results show that myosin ii motors and F-actin dynamics are required for Golgi apparatus positioning before nucleokinesis in cerebellar granule neurons (CGNs) migrating along glial fibers. Moreover, we show that primary cilia aremore » motile organelles, localized to the leading-process F-actin-rich domain and immobilized by pharmacological inhibition of myosin ii and F-actin dynamics. Finally, leading process adhesion dynamics are dependent on myosin ii and F-actin. In conclusion, we propose that actomyosin coordinates the overall polarity of migrating CGNs by controlling asymmetric organelle positioning and cell-cell contacts as these cells move along their glial guides.« less

  19. Leading-process actomyosin coordinates organelle positioning and adhesion receptor dynamics in radially migrating cerebellar granule neurons.

    PubMed

    Trivedi, Niraj; Ramahi, Joseph S; Karakaya, Mahmut; Howell, Danielle; Kerekes, Ryan A; Solecki, David J

    2014-12-02

    During brain development, neurons migrate from germinal zones to their final positions to assemble neural circuits. A unique saltatory cadence involving cyclical organelle movement (e.g., centrosome motility) and leading-process actomyosin enrichment prior to nucleokinesis organizes neuronal migration. While functional evidence suggests that leading-process actomyosin is essential for centrosome motility, the role of the actin-enriched leading process in globally organizing organelle transport or traction forces remains unexplored. We show that myosin ii motors and F-actin dynamics are required for Golgi apparatus positioning before nucleokinesis in cerebellar granule neurons (CGNs) migrating along glial fibers. Moreover, we show that primary cilia are motile organelles, localized to the leading-process F-actin-rich domain and immobilized by pharmacological inhibition of myosin ii and F-actin dynamics. Finally, leading process adhesion dynamics are dependent on myosin ii and F-actin. We propose that actomyosin coordinates the overall polarity of migrating CGNs by controlling asymmetric organelle positioning and cell-cell contacts as these cells move along their glial guides.

  20. Glow plasma trigger for electron cyclotron resonance ion sources.

    PubMed

    Vodopianov, A V; Golubev, S V; Izotov, I V; Nikolaev, A G; Oks, E M; Savkin, K P; Yushkov, G Yu

    2010-02-01

    Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 micros and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10(12) cm(-3), required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T(e) approximately = 20 eV.

  1. Ring Current Ion Coupling with Electromagnetic Ion Cyclotron Waves

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.

    2002-01-01

    A new ring current global model has been developed for the first time that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes wave evolution of electromagnetic ion cyclotron waves (EMIC). The coupled model is able to simulate, for the first time self-consistently calculated RC ion kinetic and evolution of EMIC waves that propagate along geomagnetic field lines and reflect from the ionosphere. Ionospheric properties affect the reflection index through the integral Pedersen and Hall coductivities. The structure and dynamics of the ring current proton precipitating flux regions, intensities of EMIC, global RC energy balance, and some other parameters will be studied in detail for the selected geomagnetic storms. The space whether aspects of RC modelling and comparison with the data will also be discussed.

  2. Ring Current Ion Coupling with Electromagnetic Ion Cyclotron Waves

    NASA Technical Reports Server (NTRS)

    Khazanov. G. V.; Gamayunov, K. V.; Jordanova, V. K.; Six, N. Frank (Technical Monitor)

    2002-01-01

    A new ring current global model has been developed that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes wave evolution of electromagnetic ion cyclotron waves (EMIC). The coupled model is able to simulate, for the first time self-consistently calculated RC ion kinetic and evolution of EMIC waves that propagate along geomagnetic field lines and reflect from the ionosphere. Ionospheric properties affect the reflection index through the integral Pedersen and Hall conductivities. The structure and dynamics of the ring current proton precipitating flux regions, intensities of EMIC global RC energy balance, and some other parameters will be studied in detail for the selected geomagnetic storms.

  3. Dynamics of contamination of urban soils with lead in the eastern district of Moscow

    NASA Astrophysics Data System (ADS)

    Nikiforova, E. M.; Kosheleva, N. E.

    2007-08-01

    Spatial-temporal trends were revealed in the contamination of Moscow soils with lead as a priority pollutant emitted with automobile exhaust. From the data of 1989 and 2005, maps of technogenic lead aureoles in soils of the eastern district were compiled, the average annual rate of increase in the element content was estimated, and its doubling time was predicted. Ecological-indication properties controlling the accumulation of lead in soils were determined.

  4. A Hybrid Model for the Spectra of Neutron Star Accretion Columns Including Comptonization and Cyclotron Lines

    NASA Astrophysics Data System (ADS)

    Schwarm, Fritz-Walter; Schönherr, G.; Becker, P. A.; Wolff, M. T.; Wilms, J.; Ferrigno, C.; West, B.

    2013-04-01

    A physical model for the radiation emitted from accretion columns of neutron stars with magnetic fields on the order of 1012 G has to reflect the large-scale dynamical structure of the inflowing matter as well as the quantum mechanical scattering processes leading to the formation of cyclotron resonant scattering features (CRSFs). Becker & Wolff (B&W) developed an analytic model for the broadband continuum while the CRSFs have been investigated by Schönherr & Schwarm (S&S). While both models describe the separate trends seen in observational data very well, a fully self-consistent fitting approach to determine the physical parameters (e.g., accretion rate, magnetic field strength) of the accretion column in accreting X-ray pulsars requires accounting for both processes in one unified model. We present our first approach towards such an unified hybrid model covering both the macro- and the microphysics of the accreting plasma. We assume a cylinder symmetrical dual layer structure of the accretion column. The inner layer reflects the dynamical structure described by the B&W model while the optical thin outer layer acts as a CRSF forming region similar to a photosphere. We adopt the parameters from a fit of the B&W model to Her X-1 and calculate the emergent radiation as well as the dynamical properties such as bulk velocity within the core of the accretion column. Radiation escaping the optical thick core region is further altered by the outer shell, a thin layer with an optical depth on the order of 10-4-10-2 Thomson optical depth, adding cyclotron lines by processing it through the S&S model. This hybrid model is only a first step towards an unified model for accreting neutron stars with strong magnetic fields. In the future we will investigate the insertion of a third layer in the middle as a transition region, parameter boundaries, and also incorporate general relativity with the ultimate goal to use this new tool to model phase-resolved spectroscopy of

  5. Physics of Cyclotron Resonance Scattering Features

    NASA Astrophysics Data System (ADS)

    Sschoenherr, Gabriele; Schwarm, Fritz-Walter; Falkner, Sebastian; Dauser, Thomas; Pottschmidt, Katja; Kretschmar, Peter; Klochkov, Dmitry; Ferrigno, Carlo; Britton Hemphill, Paul; Wilms, Joern

    2016-04-01

    Cyclotron resonant scattering features (short: cyclotron lines) are sensitive tracers of the physics of the accretion columns and mounds of X-ray pulsars. They form by interaction of X-ray photons with magnetically quantized electrons in the accreted plasma close to the neutron star. Such lines have been observed as absorption-like features for about 20 X-ray pulsars. Their energies provide a direct measure of the magnetic field strength in the line-forming region. By detailed modelling of the lines and of their parameter dependencies we can further decipher the physical conditions in the accretion column. For instance the fact that the complex scattering cross sections have a strong angle-dependence relates the phase-resolved cyclotron line shapes to parameters that constrain the systems’ still poorly understood geometry. Modelling the physics of cyclotron lines to a degree that allows for detailed and solid comparison to data therefore provides a unique access also to a better understanding of the overall picture of magnetically accreting neutron star systems.

  6. Electron-cyclotron-resonance ion sources (review)

    SciTech Connect

    Golovanivskii, K.S.; Dougar-Jabon, V.D.

    1992-01-01

    The physical principles are described and a brief survey of the present state is given of ion sources based on electron-cyclotron heating of plasma in a mirror trap. The characteristics of ECR sources of positive and negative ions used chiefly in accelerator technology are presented. 20 refs., 10 figs., 3 tabs.

  7. Tokamak startup with electron cyclotron heating

    SciTech Connect

    Holly, D J; Prager, S C; Shepard, D A; Sprott, J C

    1980-04-01

    Experiments are described in which the startup voltage in a tokamak is reduced by approx. 60% by the use of a modest amount of electron cyclotron resonance heating power for preionization. A 50% reduction in volt-second requirement and impurity reflux are also observed.

  8. Ion-cyclotron instability in magnetic mirrors

    SciTech Connect

    Pearlstein, L.D.

    1987-02-02

    This report reviews the role of ion-cyclotron frequency instability in magnetic mirrors. The modes discussed here are loss-cone or anisotropy driven. The discussion includes quasilinear theory, explosive instabilities of 3-wave interaction and non-linear Landau damping, and saturation due to non-linear orbits. (JDH)

  9. Currents driven by electron cyclotron waves

    SciTech Connect

    Karney, C.F.F.; Fisch, N.J.

    1981-07-01

    Certain aspects of the generation of steady-state currents by electron cyclotron waves are explored. A numerical solution of the Fokker-Planck equation is used to verify the theory of Fisch and Boozer and to extend their results into the nonlinear regime. Relativistic effects on the current generated are discussed. Applications to steady-state tokamak reactors are considered.

  10. Dynamically triggered slip leading to sustained fault gouge weakening under laboratory shear conditions

    SciTech Connect

    Johnson, Paul Allan

    2016-02-28

    We investigate dynamic wave-triggered slip under laboratory shear conditions. The experiment is composed of a three-block system containing two gouge layers composed of glass beads and held in place by a fixed load in a biaxial configuration. When the system is sheared under steady state conditions at a normal load of 4 MPa, we find that shear failure may be instantaneously triggered by a dynamic wave, corresponding to material weakening and softening if the system is in a critical shear stress state (near failure). Following triggering, the gouge material remains in a perturbed state over multiple slip cycles as evidenced by the recovery of the material strength, shear modulus, and slip recurrence time. This work suggests that faults must be critically stressed to trigger under dynamic conditions and that the recovery process following a dynamically triggered event differs from the recovery following a spontaneous event.

  11. Dynamically triggered slip leading to sustained fault gouge weakening under laboratory shear conditions

    DOE PAGES

    Johnson, Paul Allan

    2016-02-28

    We investigate dynamic wave-triggered slip under laboratory shear conditions. The experiment is composed of a three-block system containing two gouge layers composed of glass beads and held in place by a fixed load in a biaxial configuration. When the system is sheared under steady state conditions at a normal load of 4 MPa, we find that shear failure may be instantaneously triggered by a dynamic wave, corresponding to material weakening and softening if the system is in a critical shear stress state (near failure). Following triggering, the gouge material remains in a perturbed state over multiple slip cycles as evidencedmore » by the recovery of the material strength, shear modulus, and slip recurrence time. This work suggests that faults must be critically stressed to trigger under dynamic conditions and that the recovery process following a dynamically triggered event differs from the recovery following a spontaneous event.« less

  12. Cyclotron resonance cooling by strong laser field

    SciTech Connect

    Tagcuhi, Toshihiro; Mima, Kunioka

    1995-12-31

    Reduction of energy spread of electron beam is very important to increase a total output radiation power in free electron lasers. Although several cooling systems of particle beams such as a stochastic cooling are successfully operated in the accelerator physics, these cooling mechanisms are very slow and they are only applicable to high energy charged particle beams of ring accelerators. We propose here a new concept of laser cooling system by means of cyclotron resonance. Electrons being in cyclotron motion under a strong magnetic field can resonate with circular polarized electromagnetic field, and the resonance take place selectively depending on the velocity of the electrons. If cyclotron frequency of electrons is equal to the frequency of the electromagnetic field, they absorb the electromagnetic field energy strongly, but the other electrons remain unchanged. The absorbed energy will be converted to transverse kinetic energy, and the energy will be dumped into the radiation energy through bremastrahlung. To build a cooling system, we must use two laser beams, where one of them is counter-propagating and the other is co-propagating with electron beam. When the frequency of the counter-propagating laser is tuned with the cyclotron frequency of fast electrons and the co-propagating laser is tuned with the cyclotron frequency of slow electrons, the energy of two groups will approach and the cooling will be achieved. We solve relativistic motions of electrons with relativistic radiation dumping force, and estimate the cooling rate of this mechanism. We will report optimum parameters for the electron beam cooling system for free electron lasers.

  13. Single-molecule visualization of Saccharomyces cerevisiae leading-strand synthesis reveals dynamic interaction between MTC and the replisome.

    PubMed

    Lewis, Jacob S; Spenkelink, Lisanne M; Schauer, Grant D; Hill, Flynn R; Georgescu, Roxanna E; O'Donnell, Michael E; van Oijen, Antoine M

    2017-09-18

    The replisome, the multiprotein system responsible for genome duplication, is a highly dynamic complex displaying a large number of different enzyme activities. Recently, the Saccharomyces cerevisiae minimal replication reaction has been successfully reconstituted in vitro. This provided an opportunity to uncover the enzymatic activities of many of the components in a eukaryotic system. Their dynamic behavior and interactions in the context of the replisome, however, remain unclear. We use a tethered-bead assay to provide real-time visualization of leading-strand synthesis by the S. cerevisiae replisome at the single-molecule level. The minimal reconstituted leading-strand replisome requires 24 proteins, forming the CMG helicase, the Pol ε DNA polymerase, the RFC clamp loader, the PCNA sliding clamp, and the RPA single-stranded DNA binding protein. We observe rates and product lengths similar to those obtained from ensemble biochemical experiments. At the single-molecule level, we probe the behavior of two components of the replication progression complex and characterize their interaction with active leading-strand replisomes. The Minichromosome maintenance protein 10 (Mcm10), an important player in CMG activation, increases the number of productive replication events in our assay. Furthermore, we show that the fork protection complex Mrc1-Tof1-Csm3 (MTC) enhances the rate of the leading-strand replisome threefold. The introduction of periods of fast replication by MTC leads to an average rate enhancement of a factor of 2, similar to observations in cellular studies. We observe that the MTC complex acts in a dynamic fashion with the moving replisome, leading to alternating phases of slow and fast replication.

  14. Nonlinear decay of electromagnetic ion cyclotron waves in the magnetosphere

    SciTech Connect

    Gomberoff, L.; Gratton, F.T.; Gnavi, G.

    1995-02-01

    The authors study the parametric decays of left-hand polarized electromagnetic ion cyclotron waves, propagating parallel to the external magnetic field, in the magnetosphere. They show that the presence of He{sup +} ions and a mixed population of thermal and hot protons give rise to new wave couplings. These couplings lead to a number of new instabilities. Some of the instabilities involve sound waves carried mainly by the He{sup +} ions, which can be very efficient in heating up the bulk of the He{sup +} ions via Landau damping. Other instabilities involve the branch of the left-hand polarized electromagnetic ion cyclotron waves which has a resonance at the He{sup +} ion gyrofrequency. These instabilities can also play a role in the energy transfer from the pump wave to the He{sup +} ions through resonance absorption, preferably in the direction perpendicular to the external magnetic field. The new couplings give rise to several types of parametric instabilities such as ordinary decay instabilities, beat wave instabilities, and modulational instabilities. There are also couplings where the pump wave decays into the two electromagnetic sideband waves. 42 refs., 10 figs.

  15. Study of iron structure stability in high temperature molten lead-bismuth eutectic with oxygen injection using molecular dynamics simulation

    SciTech Connect

    Arkundato, Artoto; Su'ud, Zaki; Sudarko; Shafii, Mohammad Ali; Celino, Massimo

    2014-09-30

    Corrosion of structural materials in high temperature molten lead-bismuth eutectic is a major problem for design of PbBi cooled reactor. One technique to inhibit corrosion process is to inject oxygen into coolant. In this paper we study and focus on a way of inhibiting the corrosion of iron using molecular dynamics method. For the simulation results we concluded that effective corrosion inhibition of iron may be achieved by injection 0.0532 wt% to 0.1156 wt% oxygen into liquid lead-bismuth. At this oxygen concentration the structure of iron material will be maintained at about 70% in bcc crystal structure during interaction with liquid metal.

  16. Study of iron structure stability in high temperature molten lead-bismuth eutectic with oxygen injection using molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Arkundato, Artoto; Su'ud, Zaki; Sudarko, Shafii, Mohammad Ali; Celino, Massimo

    2014-09-01

    Corrosion of structural materials in high temperature molten lead-bismuth eutectic is a major problem for design of PbBi cooled reactor. One technique to inhibit corrosion process is to inject oxygen into coolant. In this paper we study and focus on a way of inhibiting the corrosion of iron using molecular dynamics method. For the simulation results we concluded that effective corrosion inhibition of iron may be achieved by injection 0.0532 wt% to 0.1156 wt% oxygen into liquid lead-bismuth. At this oxygen concentration the structure of iron material will be maintained at about 70% in bcc crystal structure during interaction with liquid metal.

  17. Cycling State that Can Lead to Glassy Dynamics in Intracellular Transport

    NASA Astrophysics Data System (ADS)

    Scholz, Monika; Burov, Stanislav; Weirich, Kimberly L.; Scholz, Björn J.; Tabei, S. M. Ali; Gardel, Margaret L.; Dinner, Aaron R.

    2016-01-01

    Power-law dwell times have been observed for molecular motors in living cells, but the origins of these trapped states are not known. We introduce a minimal model of motors moving on a two-dimensional network of filaments, and simulations of its dynamics exhibit statistics comparable to those observed experimentally. Analysis of the model trajectories, as well as experimental particle tracking data, reveals a state in which motors cycle unproductively at junctions of three or more filaments. We formulate a master equation for these junction dynamics and show that the time required to escape from this vortexlike state can account for the power-law dwell times. We identify trends in the dynamics with the motor valency for further experimental validation. We demonstrate that these trends exist in individual trajectories of myosin II on an actin network. We discuss how cells could regulate intracellular transport and, in turn, biological function by controlling their cytoskeletal network structures locally.

  18. A cycling state that can lead to glassy dynamics in intracellular transport

    NASA Astrophysics Data System (ADS)

    Scholz, Monika; Burov, Stanislav; Weirich, Kimberly L.; Scholz, Bjorn J.; Tabei, S. M. Ali; Gardel, Margaret L.; Dinner, Aaron

    Power-law dwell times have been observed for molecular motors in living cells, but the origins of these trapped states are not known. We introduce a minimal model of motors moving on a two- dimensional network of filaments, and simulations of its dynamics exhibit statistics comparable to those observed experimentally. Analysis of the model trajectories, as well as experimental particle tracking data, reveals a state in which motors cycle unproductively at junctions of three or more filaments. We formulate a master equation for these junction dynamics and show that the time required to escape from this vortex-like state can account for the power-law dwell times. We identify trends in the dynamics with the motor valency for further experimental validation. We demonstrate that these trends exist in individual trajectories of myosin II on an actin network. We discuss how cells could regulate intracellular transport and, in turn, biological function, by controlling their cytoskeletal network structures locally.

  19. Screening of Potential Lead Molecule as Novel MurE Inhibitor: Virtual Screening, Molecular Dynamics and In Vitro Studies.

    PubMed

    Zaveri, Kunal; Kiranmayi, Patnala

    2017-01-01

    The prevalence of multi-drug resistance S. aureus is one of the most challenging tasks for the treatment of nosocomial infections. Proteins and enzymes of peptidoglycan biosynthesis pathway are one among the well-studied targets, but many of the enzymes are unexplored as targets. MurE is one such enzyme featured to be a promising target. As MurE plays an important role in ligating the L-lys to stem peptide at third position that is crucial for peptidoglycan synthesis. To screen the potential MurE inhibitor by in silico approach and evaluate the best potential lead molecule by in vitro methods. In the current study, we have employed structure based virtual screening targeting the active site of MurE, followed by Molecular dynamics and in vitro studies. Virtual screening resulted in successful screening of potential lead molecule ((2R)-2-[[1-[(2R)- 2-(benzyloxycarbonylamino) propanoyl] piperidine-4-carbonyl]amino]-5-guanidino-pentan). The molecular dynamics of the MurE and Lead molecule complex emphasizes that lead molecule has shown stable interactions with active site residues Asp 406 and with Glu 460. In vitro studies demonstrate that the lead molecule shows antibacterial activity close to standard antibiotic Vancomycin and higher than that of Ampicillin, Streptomycin and Rifampicin. The MIC of lead molecule at 50μg/mL was observed to be 3.75 μg/mL, MBC being bactericidal with value of 6.25 μg/mL, cytotoxicity showing 34.44% and IC50 of 40.06μg/mL. These results suggest ((2R)-2-[[1-[(2R)-2-(benzyloxycarbonylamino) propanoyl] piperidine-4-carbonyl]amino]-5-guanidino-pentan) as a promising lead molecule for developing a MurE inhibitor against treatment of S. aureus infections. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  20. Infinite swapping replica exchange molecular dynamics leads to a simple simulation patch using mixture potentials.

    PubMed

    Lu, Jianfeng; Vanden-Eijnden, Eric

    2013-02-28

    Replica exchange molecular dynamics (REMD) becomes more efficient as the frequency of swap between the temperatures is increased. Recently Plattner et al. [J. Chem. Phys. 135, 134111 (2011)] proposed a method to implement infinite swapping REMD in practice. Here we introduce a natural modification of this method that involves molecular dynamics simulations over a mixture potential. This modification is both simple to implement in practice and provides a better, energy based understanding of how to choose the temperatures in REMD to optimize efficiency. It also has implications for generalizations of REMD in which the swaps involve other parameters than the temperature.

  1. Vibrational lifetimes of hydrogen on lead films: An ab initio molecular dynamics with electronic friction (AIMDEF) study

    SciTech Connect

    Saalfrank, Peter; Juaristi, J. I.

    2014-12-21

    Using density functional theory and Ab Initio Molecular Dynamics with Electronic Friction (AIMDEF), we study the adsorption and dissipative vibrational dynamics of hydrogen atoms chemisorbed on free-standing lead films of increasing thickness. Lead films are known for their oscillatory behaviour of certain properties with increasing thickness, e.g., energy and electron spillout change in discontinuous manner, due to quantum size effects [G. Materzanini, P. Saalfrank, and P. J. D. Lindan, Phys. Rev. B 63, 235405 (2001)]. Here, we demonstrate that oscillatory features arise also for hydrogen when chemisorbed on lead films. Besides stationary properties of the adsorbate, we concentrate on finite vibrational lifetimes of H-surface vibrations. As shown by AIMDEF, the damping via vibration-electron hole pair coupling dominates clearly over the vibration-phonon channel, in particular for high-frequency modes. Vibrational relaxation times are a characteristic function of layer thickness due to the oscillating behaviour of the embedding surface electronic density. Implications derived from AIMDEF for frictional many-atom dynamics, and physisorbed species will also be given.

  2. Loss of ACL function leads to alterations in tibial plateau common dynamic contact stress profiles.

    PubMed

    Chen, Tony; Wang, Hongsheng; Warren, Russell; Maher, Suzanne

    2017-08-16

    It has been suggested that the repetitive nature of altered joint tissue loading which occurs after anterior cruciate ligament (ACL) rupture can contribute to the development of osteoarthritis (OA). However, changes in dynamic knee joint contact stresses after ACL rupture have not been quantified for activities of daily living. Our objective was to characterize changes in dynamic contact stress profiles that occur across the tibial plateau immediately after ACL transection. By subjecting sensor-augmented cadaveric knees to simulated gait, and analyzing the resulting contact stress profiles using a normalized cross-correlation algorithm, we tested the hypothesis that common changes in dynamic contact stress profiles exist after ACL injury. Three common profiles were identified in intact knees, occurring on the: (I) posterior lateral plateau, (II) posterior medial plateau, and (III) central region of the medial plateau. In ACL-transected knees, the magnitude and shape of the common dynamic stress profiles did not change, but their locations on the tibial plateau and the number of knees identified for each profile changed. Furthermore, in the ACL transected knees, a unique common contact stress profile was identified in the posterior region of the lateral plateau near the tibial spine. This framework can be used to understand the regional and temporal changes in joint mechanics after injury. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Next-to-leading order gravitational spin(1)-spin(2) dynamics in Hamiltonian form

    SciTech Connect

    Steinhoff, Jan; Hergt, Steven; Schaefer, Gerhard

    2008-04-15

    Based on recent developments by the authors a next-to-leading order spin(1)-spin(2) Hamiltonian is derived for the first time. The result is obtained within the canonical formalism of Arnowitt, Deser, and Misner (ADM) utilizing their generalized isotropic coordinates. A comparison with other methods is given.

  4. Learning from Accident Analysis: The Dynamics Leading Up to a Rafting Accident.

    ERIC Educational Resources Information Center

    Hovelynck, Johan

    1998-01-01

    Analysis of a case study of a whitewater rafting accident reveals that such accidents tend to result from multiple actions. Many events leading up to such accidents include procedural and process factors, suggesting that hard-skills technical training is an insufficient approach to accident prevention. Contains 26 references. (SAS)

  5. Learning from Accident Analysis: The Dynamics Leading Up to a Rafting Accident.

    ERIC Educational Resources Information Center

    Hovelynck, Johan

    1998-01-01

    Analysis of a case study of a whitewater rafting accident reveals that such accidents tend to result from multiple actions. Many events leading up to such accidents include procedural and process factors, suggesting that hard-skills technical training is an insufficient approach to accident prevention. Contains 26 references. (SAS)

  6. Numerical and experimental study on the ability of dynamic roughness to alter the development of a leading edge vortex

    NASA Astrophysics Data System (ADS)

    Griffin, Christopher D.

    Dynamic stall is an unsteady aerodynamic phenomenon garnering much research interest because it occurs in a variety of applications. For example, dynamic stall is known to occur on helicopter rotor blades, wind turbines, high maneuvering military aircraft, and flapping wings. Dynamic stall occurs when an aerodynamic lifting device, such as an airfoil, wing, or turbomachine blade, undergoes a rapid pitching motion. It also occurs on lifting devices that are impulsively started at high angles of attack. Dynamic stall can "delay" aerodynamic stall to angles of attack that are significantly beyond the static stall angle of attack. During dynamic stall a large leading edge vortex (LEV) is formed, which creates greater fluid acceleration over the wing or airfoil, thus sustaining lift. As this vortex is shed downstream stall eventually occurs and there is an abrupt increase in drag and a large shift in pitching moment. Research has been performed to better understand the mechanisms occurring during dynamic stall in an effort to find ways to best take advantage of the increased lift associated with dynamic stall, but avoid the downfalls that occur once stall is initiated. Few attempts have been made to alter the LEV, and these attempts have used methods associated with laminar boundary layer separation control. Although these methods have shown promise, they suffer from the drawback that they exhaust more energy than is gained by flow control, while also only being effective at certain flight regimes. The research described herein documents the first study on the ability of dynamic roughness to alter the LEV encountered on a rapidly pitching airfoil. Both numerical and experimental studies were performed, including two-dimensional and three-dimensional computational fluid dynamics (CFD) simulations as well as stereo and planar particle image velocimetry (PIV) experiments. Evidence for the ability of small scale dynamic roughness to alter the development of the LEV was

  7. Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

    NASA Technical Reports Server (NTRS)

    Anderson, B. J.; Hamilton, D. C.

    1993-01-01

    AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

  8. Nonresonant interactions of electromagnetic ion cyclotron waves with relativistic electrons

    NASA Astrophysics Data System (ADS)

    Chen, Lunjin; Thorne, Richard M.; Bortnik, Jacob; Zhang, Xiao-Jia

    2016-10-01

    The dynamics of relativistic electrons traveling through a parallel-propagating, monochromatic electromagnetic ion cyclotron (EMIC) wave in the Earth's dipole field are investigated via test particle simulations. Both resonant and nonresonant responses in electron pitch angle are considered, and the differences between the two are highlighted. Nonresonant electrons, with energies below the minimum resonant energy down to hundreds of keV, are scattered stochastically in pitch angle and can be scattered into the atmospheric loss cone. The nonresonant effect is attributed to the spatial edge associated with EMIC wave packets. A condition for effective nonresonant response is also provided. This effect is excluded from current quasi-linear theory and can be a potentially important loss mechanism of relativistic and subrelativistic electrons in the radiation belts.

  9. The effect of a leading-edge slat on the dynamic stall of an oscillating airfoil

    NASA Technical Reports Server (NTRS)

    Carr, L. W.; Mcalister, K. W.

    1983-01-01

    The dynamic stall characteristics of a slatted airfoil were investigated experimentally on a 2-ft-chord airfoil oscillating in pitch at M = 0.2 for a range of reduced frequency and mean angle of oscillation. The slat produced a flow that remained attached to the airfoil for angles well above those normally attained by the retreating blade of a helicopter during high speed flight. The dynamic stall vortex usually associated with these flight conditions was completely eliminated for all angles under 30 deg. Instantaneous surface pressure, lift, and pitching moment data are presented as a function of incidence throughout the oscillation cycle; a detailed analysis of instantaneous boundary-layer flow behavior for the various test conditions is included.

  10. Interplay between stochasticity and negative feedback leads to pulsed dynamics and distinct gene activity patterns.

    PubMed

    Zambrano, Samuel; Bianchi, Marco E; Agresti, Alessandra; Molina, Nacho

    2015-08-01

    Gene expression is an inherently stochastic process that depends on the structure of the biochemical regulatory network in which the gene is embedded. Here we study the dynamical consequences of the interplay between stochastic gene switching and the widespread negative feedback regulatory loop in a simple model of a biochemical regulatory network. Using a simplified hybrid simulation approach, in which only the gene activation is modeled stochastically, we find that stochasticity in gene switching by itself can induce pulses in the system, providing also analytical insights into their origin. Furthermore, we find that this simple network is able to reproduce both exponential and peaked distributions of gene active and inactive times similar to those that have been observed experimentally. This simplified hybrid simulation approach also allows us to link these patterns to the dynamics of the system for each gene state.

  11. Effect of Cation Rotation on Charge Dynamics in Hybrid Lead Halide Perovskites

    SciTech Connect

    Gélvez-Rueda, María C.; Cao, Duyen H.; Patwardhan, Sameer; Renaud, Nicolas; Stoumpos, Constantinos C.; Schatz, George C.; Hupp, Joseph T.; Farha, Omar K.; Savenije, Tom J.; Kanatzidis, Mercouri G.; Grozema, Ferdinand C.

    2016-08-04

    Organic-inorganic hybrid halide perovskites are a promising class of materials for photovoltaic application with reported power efficiencies over similar to 22%. However, not much is known about the influence of the organic dipole rotation and phase transitions on charge carrier dynamics. Here, we report substantial changes in mobility and lifetime of charge carriers in CH3NH3PbI3 after the low-temperature tetragonal (beta) to orthorhombic (gamma) phase transition. By using microwave conductivity measurements, we observed that the mobility and lifetime of ionized charge carriers increase as the temperature decreases and a sudden increment is seen after the beta-gamma phase transition. For CH3NH3PbI3, the mobility and the half-lifetime increase by a factor of 36 compared with the values before the beta-gamma phase transition. We attribute the considerable change in the dynamics at low temperature to the decrease of the inherent dynamic disorder of the organic cation (CH3NH3+) inside the perovskite crystal structure.

  12. Control of Synchronization of Brain Dynamics Leads to Control of Epileptic Seizures in Rodents

    PubMed Central

    Good, Levi B.; Sabesan, Shivkumar; Marsh, Steven T.; Tsakalis, Kostas; Treiman, David

    2010-01-01

    We have designed and implemented an automated, just-in-time stimulation, seizure control method using a seizure prediction method from nonlinear dynamics coupled with deep brain stimulation in the centromedial thalamic nuclei in epileptic rats. A comparison to periodic stimulation, with identical stimulation parameters, was also performed. The two schemes were compared in terms of their efficacy in control of seizures, as well as their effect on synchronization of brain dynamics. The automated just-in-time (JIT) stimulation showed reduction of seizure frequency and duration in 5 of the 6 rats, with significant reduction of seizure frequency (>50%) in 33% of the rats. This constituted a significant improvement over the efficacy of the periodic control scheme in the same animals. Actually, periodic stimulation showed an increase of seizure frequency in 50% of the rats, reduction of seizure frequency in 3 rats and significant reduction in 1 rat. Importantly, successful seizure control was highly correlated with desynchronization of brain dynamics. This study provides initial evidence for the use of closed-loop feedback control systems in epileptic seizures combining methods from seizure prediction and deep brain stimulation. PMID:19575507

  13. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at the Cyclotron Frequency

    NASA Astrophysics Data System (ADS)

    Nagornov, Konstantin O.; Kozhinov, Anton N.; Tsybin, Yury O.

    2017-02-01

    The phenomenon of ion cyclotron resonance allows for determining mass-to-charge ratio, m/z, of an ensemble of ions by means of measurements of their cyclotron frequency, ω c . In Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the ω c quantity is usually unavailable for direct measurements: the resonant state is located close to the reduced cyclotron frequency (ω+), whereas the ω c and the corresponding m/z values may be calculated via theoretical derivation from an experimental estimate of the ω+ quantity. Here, we describe an experimental observation of a new resonant state, which is located close to the ω c frequency and is established because of azimuthally-dependent trapping electric fields of the recently developed ICR cells with narrow aperture detection electrodes. We show that in mass spectra, peaks close to ω+ frequencies can be reduced to negligible levels relative to peaks close to ω c frequencies. Due to reduced errors with which the ω c quantity is obtained, the new resonance provides a means of cyclotron frequency measurements with precision greater than that achieved when ω+ frequency peaks are employed. The described phenomenon may be considered for a development into an FT-ICR MS technology with increased mass accuracy for applications in basic research, life, and environmental sciences.

  14. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at the Cyclotron Frequency.

    PubMed

    Nagornov, Konstantin O; Kozhinov, Anton N; Tsybin, Yury O

    2017-04-01

    The phenomenon of ion cyclotron resonance allows for determining mass-to-charge ratio, m/z, of an ensemble of ions by means of measurements of their cyclotron frequency, ω c . In Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the ω c quantity is usually unavailable for direct measurements: the resonant state is located close to the reduced cyclotron frequency (ω+), whereas the ω c and the corresponding m/z values may be calculated via theoretical derivation from an experimental estimate of the ω+ quantity. Here, we describe an experimental observation of a new resonant state, which is located close to the ω c frequency and is established because of azimuthally-dependent trapping electric fields of the recently developed ICR cells with narrow aperture detection electrodes. We show that in mass spectra, peaks close to ω+ frequencies can be reduced to negligible levels relative to peaks close to ω c frequencies. Due to reduced errors with which the ω c quantity is obtained, the new resonance provides a means of cyclotron frequency measurements with precision greater than that achieved when ω+ frequency peaks are employed. The described phenomenon may be considered for a development into an FT-ICR MS technology with increased mass accuracy for applications in basic research, life, and environmental sciences. Graphical Abstract ᅟ.

  15. The mirror and ion cyclotron anisotropy instabilities

    NASA Technical Reports Server (NTRS)

    Gary, S. P.

    1992-01-01

    The linear dispersion equation for fully electromagnetic waves and instabilities at arbitrary directions of propagation relative to a background magnetic field B(0) in a homogeneous Vlasov plasma is solved numerically for bi-Maxwellian particle distributions. For isotropic plasmas the dispersion and damping of the three modes below the proton cyclotron frequency are studied as functions of Beta(i) and T(e)/T(i). The transport ratios of helicity, cross-helicity, Alfven ratio, compressibility, and parallel compressibility are defined. Under the condition that the proton temperature perpendicular to B(0) is greater than the parallel temperature, the growth rates and transport ratios of the mirror instability and the ion cyclotron anisotropy instability are examined and compared. Both the proton parallel compressibility and the proton Alfven ratio are significantly different for the two growing modes.

  16. New magnet pole shape for isochronous cyclotrons

    SciTech Connect

    Thorn, C.E.; Chasman, C.; Baltz, A.J.

    1981-06-01

    A new design has been developed for shaping pole tips to produce the radially increasing fields required for isochronous cyclotrons. The conventional solid hillpoles are replaced by poles mounted over a small secondary gap which tapers radially from maximum at the magnet edge to zero near the center. Field measurements with a model magnet and calculations with the code TRIM show an increase in field at the edge of the magnet without the usual corresponding large increase in fringing, and a radial field shape more nearly field independent than for conventional hills. The flying hills have several advantages for variable energy multiparticle cyclotrons: (1) a large reduction in the power dissipated by isochronizing trim coils; (2) a more constant shape and magnitude flutter factor, eliminating flutter coils and increasing the operating range; and (3) a sharper fall-off of the fringe field, simplifying beam extraction. 6 figures.

  17. New magnet pole shape for isochronous cyclotrons

    SciTech Connect

    Thorn, C.E.; Chasman, C.; Baltz, A.J.

    1981-01-01

    A new design has been developed for shaping pole tips to produce the radially increasing fields required for isochronous cyclotrons. The conventional solid hill poles are replaced by poles mounted over a small secondary gap which tapers radially from maximum at the magnet edge to zero near the center. Field measurements with a model magnet and calculations with the code TRIM show an increase in field at the edge of the magnet without the usual corresponding large increase in fringing, and a radial field shape more nearly field independent than for conventional hills. The flying hills have several advantages for variable energy multiparticle cyclotrons: (1) a large reduction in the power dissipated by isochronizing trim coils; (2) a more constant shape and magnitude flutter factor, eliminating flutter coils and increasing the operating range; and (3) a sharper fall-off of the fringe field, simplifying beam extraction.

  18. Electrostatic ion cyclotron velocity shear instability

    NASA Technical Reports Server (NTRS)

    Lemons, D. S.; Winske, D.; Gary, S. P.

    1992-01-01

    A local electrostatic dispersion equation is derived for a shear flow perpendicular to an ambient magnetic field, which includes all kinetic effects and involves only one important parameter. The dispersion equation is cast in the form of Gordeyev integrals and is solved numerically. Numerical solutions indicate that an ion cyclotron instability is excited. The instability occurs roughly at multiples of the ion cyclotron frequency (modified by the shear), with the growth rate or the individual harmonics overlapping in the wavenumber. At large values of the shear parameter, the instability is confined to long wavelengths, but at smaller shear, a second distinct branch at shorter wavelengths also appears. The properties of the instability obtained are compared with those obtained in the nonlocal limit by Ganguli et al. (1985, 1988).

  19. Ion cyclotron waves observed near the plasmapause

    NASA Technical Reports Server (NTRS)

    Fraser, B. J.; Samson, J. C.; Mcpherron, R. L.; Russell, C. T.

    1986-01-01

    Pc2 electromagnetic ion cyclotron waves at 0.1 Hz, near the oxygen cyclotron frequency, have been observed by ISEE-1 and -2 between L = 7.6 - 5.8 on an inbound near equatorial pass in the dusk sector. The waves occurred in a thick plasmapause of width about 1 earth radius and penetrated about 1 earth radius into the plasmasphere. Wave onset was accompanied by significant increases in the thermal (0-100 eV) He(+) and the warm (0.1-16 keV/e) O(+) and He(+) heavy ion populations. Wave polarization is predominantly left-handed with propagation almost parallel to the ambient magnetic field, and the spectral slot and polarization reversal predicted by multicomponent cold plasma propagation theory are identified in the wave data. The results are considered as an example of wave-particle interactions occurring during the outer plasmasphere refilling process at the time of the substorm recovery phase.

  20. Xe/+/ -induced ion-cyclotron harmonic waves

    NASA Astrophysics Data System (ADS)

    Jones, D.

    Xenon ion sources on an ejectable package separated from the main payload during the flights of Porcupine rockets F3 and F4 which were launched from Kiruna, Sweden on March 19 and 31, 1979, respectively. The effects of the xenon ion beam, detected by the LF (f less than 16 kHz) wideband electric field experiment and analyzed by using a sonograph, are discussed. Particular attention is given to the stimulation of the ion-cyclotron harmonic waves which are usually linked to the local proton gyro-frequency, but are sometimes related to half that frequency. It was found that in a plasma dominated by O(+) ions, a small amount (1-10%) of protons could cause an effect such that the O(+) cyclotron harmonic waves are set up by the hydrogen ions, the net result being the observation of harmonic emissions separated by the hydrogen ion gyro frequency.

  1. Cyclotron production of (44)Sc: From bench to bedside.

    PubMed

    van der Meulen, Nicholas P; Bunka, Maruta; Domnanich, Katharina A; Müller, Cristina; Haller, Stephanie; Vermeulen, Christiaan; Türler, Andreas; Schibli, Roger

    2015-09-01

    (44)Sc, a PET radionuclide, has promising decay characteristics (T1/2 = 3.97 h, Eβ(+)av = 632 keV) for nuclear imaging and is an attractive alternative to the short-lived (68)Ga (T1/2 = 68 min, Eβ(+)av = 830 keV). The aim of this study was the optimization of the (44)Sc production process at an accelerator, allowing its use for preclinical and clinical PET imaging. (44)CaCO3 targets were prepared and irradiated with protons (~11 MeV) at a beam current of 50 μA for 90 min. (44)Sc was separated from its target material using DGA extraction resin and concentrated using SCX cation exchange resin. Radiolabeling experiments at activities up to 500 MBq and stability tests were performed with DOTANOC by investigating different scavengers, including gentisic acid. Dynamic PET of an AR42J tumor-bearing mouse was performed after injection of (44)Sc-DOTANOC. The optimized chemical separation method yielded up to 2 GBq (44)Sc of high radionuclidic purity. In the presence of gentisic acid, radiolabeling of (44)Sc with DOTANOC was achieved with a radiochemical yield of ~99% at high specific activity (10 MBq/nmol) and quantities which would allow clinical application. The dynamic PET images visualized increasing uptake of (44)Sc-DOTANOC into AR42J tumors and excretion of radioactivity through the kidneys of the investigated mouse. The concept "from-bench-to-bedside" was clearly demonstrated in this extended study using cyclotron-produced (44)Sc. Sufficiently high activities of (44)Sc of excellent radionuclidic purity are obtainable for clinical application, by irradiation of enriched calcium at a cyclotron. This work demonstrates a promising basis for introducing (44)Sc to clinical routine of nuclear imaging using PET. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Radiation Sources at Electron Cyclotron Harmonic Frequencies.

    DTIC Science & Technology

    1983-01-28

    KEY WORDS (Continue on reverse side it necesear and Identify by block number) Radiation source, electron cyclotron frequency, gyrotron, travelling ...investigation of gyrotron devices operating in cylindrical geometry. Specific topics include an analysis of oscillations in a gyrotron travelling wave...amplifier, the study of the effects of velocity spread and wall resistivity on gain and bandwidth in a gyrotron travell - ing wave amplifier, an

  3. Cyclotron Wave Electrostatic and Parametric Amplifiers.

    DTIC Science & Technology

    2008-02-15

    Plasma Physics Division GEORGE EwEI.• Georgia Tech Research Institute Atlanta, Georgia, 30332 February 28, 1997 Approved for public release...and transmitted to the external circuit load. Thus, as far as the input resonator is concerned, noises of the electron gun on the fast cyclotron wave...characteristics of CWESA. Engineering the permanent magnet system is often the most challenging part CWESA design at ISTOK. The plane cathode electron gun

  4. Cyclotron instability in the afterglow mode of minimum-B ECRIS

    SciTech Connect

    Izotov, I. Mansfeld, D.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Tarvainen, O.; Skalyga, V.

    2016-02-15

    It was shown recently that cyclotron instability in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source (ECRIS) causes perturbation of the extracted ion current and generation of strong bursts of bremsstrahlung emission, which limit the performance of the ion source. The present work is devoted to the dynamic regimes of plasma instability in ECRIS operated in pulsed mode. Instability develops in decaying plasma shortly after heating microwaves are switched off and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high energy electrons. Time-resolved measurements of microwave emission bursts are presented. It was found that even in various gases (helium and oxygen were studied) and at different values of magnetic field and heating power, the dynamic spectra demonstrate common features: decreasing frequency within a single burst as well as from one burst to another.

  5. Cyclotron instability in the afterglow mode of minimum-B ECRIS

    NASA Astrophysics Data System (ADS)

    Izotov, I.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Mansfeld, D.; Skalyga, V.; Tarvainen, O.

    2016-02-01

    It was shown recently that cyclotron instability in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source (ECRIS) causes perturbation of the extracted ion current and generation of strong bursts of bremsstrahlung emission, which limit the performance of the ion source. The present work is devoted to the dynamic regimes of plasma instability in ECRIS operated in pulsed mode. Instability develops in decaying plasma shortly after heating microwaves are switched off and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high energy electrons. Time-resolved measurements of microwave emission bursts are presented. It was found that even in various gases (helium and oxygen were studied) and at different values of magnetic field and heating power, the dynamic spectra demonstrate common features: decreasing frequency within a single burst as well as from one burst to another.

  6. Causality Analysis: Identifying the Leading Element in a Coupled Dynamical System.

    PubMed

    BozorgMagham, Amir E; Motesharrei, Safa; Penny, Stephen G; Kalnay, Eugenia

    2015-01-01

    Physical systems with time-varying internal couplings are abundant in nature. While the full governing equations of these systems are typically unknown due to insufficient understanding of their internal mechanisms, there is often interest in determining the leading element. Here, the leading element is defined as the sub-system with the largest coupling coefficient averaged over a selected time span. Previously, the Convergent Cross Mapping (CCM) method has been employed to determine causality and dominant component in weakly coupled systems with constant coupling coefficients. In this study, CCM is applied to a pair of coupled Lorenz systems with time-varying coupling coefficients, exhibiting switching between dominant sub-systems in different periods. Four sets of numerical experiments are carried out. The first three cases consist of different coupling coefficient schemes: I) Periodic-constant, II) Normal, and III) Mixed Normal/Non-normal. In case IV, numerical experiment of cases II and III are repeated with imposed temporal uncertainties as well as additive normal noise. Our results show that, through detecting directional interactions, CCM identifies the leading sub-system in all cases except when the average coupling coefficients are approximately equal, i.e., when the dominant sub-system is not well defined.

  7. Causality Analysis: Identifying the Leading Element in a Coupled Dynamical System

    PubMed Central

    BozorgMagham, Amir E.; Motesharrei, Safa; Penny, Stephen G.; Kalnay, Eugenia

    2015-01-01

    Physical systems with time-varying internal couplings are abundant in nature. While the full governing equations of these systems are typically unknown due to insufficient understanding of their internal mechanisms, there is often interest in determining the leading element. Here, the leading element is defined as the sub-system with the largest coupling coefficient averaged over a selected time span. Previously, the Convergent Cross Mapping (CCM) method has been employed to determine causality and dominant component in weakly coupled systems with constant coupling coefficients. In this study, CCM is applied to a pair of coupled Lorenz systems with time-varying coupling coefficients, exhibiting switching between dominant sub-systems in different periods. Four sets of numerical experiments are carried out. The first three cases consist of different coupling coefficient schemes: I) Periodic–constant, II) Normal, and III) Mixed Normal/Non-normal. In case IV, numerical experiment of cases II and III are repeated with imposed temporal uncertainties as well as additive normal noise. Our results show that, through detecting directional interactions, CCM identifies the leading sub-system in all cases except when the average coupling coefficients are approximately equal, i.e., when the dominant sub-system is not well defined. PMID:26125157

  8. Regional lead dynamics in the Northeastern United States - Local versus regional industrial influences

    NASA Astrophysics Data System (ADS)

    Wreschnig, A. J.; Bain, D. J.; Green, M. B.; Ruffing, C. M.; Adams, L. E.

    2009-12-01

    Elevated concentrations of lead in sediments are a phenomenon that has been primarily examined in the context of leaded gasoline usage and prehistoric smelting. However, regional trends in the Northeastern United States have not been well explained, particularly between the years of 1800 and 1920. Sediment core data from throughout the region were synthesized to characterize regional Pb deposition. There is a consistent increase in sediment Pb concentrations independent of geographic location that begins to occur around 1870. This increase occurs before the advent of leaded gasoline, requiring apportionment to other sources. Previous studies have used smaller scale distributions of Pb sediment concentrations to estimate the contribution of various anthropogenic sources including coal combustion, Pb smelting, and industrial waste. However, the robustness of these estimates when scaled up to an entire region is questionable. To improve understanding at larger scales, local, regional, and national metal production and coal combustion records are compared to sediment core data across the region. It is expected that both Midwestern smelting, undergoing great intensification during this time period, and local production of Pb intensive goods will be strongly correlated with Pb concentrations in sediments. Further, it is expected the large regional increase in coal combustion should influence regional Pb flux less than local metal production.

  9. Resonance of relativistic electrons with electromagnetic ion cyclotron waves

    DOE PAGES

    Denton, R. E.; Jordanova, V. K.; Bortnik, J.

    2015-06-29

    Relativistic electrons have been thought to more easily resonate with electromagnetic ion cyclotron EMIC waves if the total density is large. We show that, for a particular EMIC mode, this dependence is weak due to the dependence of the wave frequency and wave vector on the density. A significant increase in relativistic electron minimum resonant energy might occur for the H band EMIC mode only for small density, but no changes in parameters significantly decrease the minimum resonant energy from a nominal value. The minimum resonant energy depends most strongly on the thermal velocity associated with the field line motionmore » of the hot ring current protons that drive the instability. High density due to a plasmasphere or plasmaspheric plume could possibly lead to lower minimum resonance energy by causing the He band EMIC mode to be dominant. We demonstrate these points using parameters from a ring current simulation.« less

  10. Resonance of relativistic electrons with electromagnetic ion cyclotron waves

    SciTech Connect

    Denton, R. E.; Jordanova, V. K.; Bortnik, J.

    2015-06-29

    Relativistic electrons have been thought to more easily resonate with electromagnetic ion cyclotron EMIC waves if the total density is large. We show that, for a particular EMIC mode, this dependence is weak due to the dependence of the wave frequency and wave vector on the density. A significant increase in relativistic electron minimum resonant energy might occur for the H band EMIC mode only for small density, but no changes in parameters significantly decrease the minimum resonant energy from a nominal value. The minimum resonant energy depends most strongly on the thermal velocity associated with the field line motion of the hot ring current protons that drive the instability. High density due to a plasmasphere or plasmaspheric plume could possibly lead to lower minimum resonance energy by causing the He band EMIC mode to be dominant. We demonstrate these points using parameters from a ring current simulation.

  11. Alternative optical concept for electron cyclotron emission imaging

    SciTech Connect

    Liu, J. X.; Milbourne, T.; Bitter, M.; Delgado-Aparicio, L.; Dominguez, A.; Efthimion, P. C.; Hill, K. W.; Kramer, G. J.; Kung, C.; Pablant, N. A.; Tobias, B.; Kubota, S.; Kasparek, W.; Lu, J.; Park, H.

    2014-11-15

    The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.

  12. Characteristics of microinstabilities in electron cyclotron and ohmic heated discharges

    SciTech Connect

    Pusztai, I.; Moradi, S.; Fueloep, T.; Timchenko, N.

    2011-08-15

    Characteristics of microinstabilities in electron cyclotron (EC) and ohmic heated (OH) discharges in the T10 tokamak have been analyzed by linear electrostatic gyrokinetic simulations with gyro[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] aiming to find insights into the effect of auxiliary heating on the transport. Trapped electron modes are found to be unstable in both OH and the EC heated scenarios. In the OH case the main drive is from the density gradient and in the EC case from the electron temperature gradient. The growth rates and particle fluxes exhibit qualitatively different scaling with the electron-to-ion temperature ratios in the two cases. This is mainly due to the fact that the dominant drives and the collisionalities are different. The inward flow velocity of impurities and the impurity diffusion coefficient decreases when applying EC heating, which leads to lower impurity peaking, consistently with experimental observations.

  13. Characteristics of microinstabilities in electron cyclotron and ohmic heated discharges

    NASA Astrophysics Data System (ADS)

    Pusztai, I.; Moradi, S.; Fülöp, T.; Timchenko, N.

    2011-08-01

    Characteristics of microinstabilities in electron cyclotron (EC) and ohmic heated (OH) discharges in the T10 tokamak have been analyzed by linear electrostatic gyrokinetic simulations with gyro [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] aiming to find insights into the effect of auxiliary heating on the transport. Trapped electron modes are found to be unstable in both OH and the EC heated scenarios. In the OH case the main drive is from the density gradient and in the EC case from the electron temperature gradient. The growth rates and particle fluxes exhibit qualitatively different scaling with the electron-to-ion temperature ratios in the two cases. This is mainly due to the fact that the dominant drives and the collisionalities are different. The inward flow velocity of impurities and the impurity diffusion coefficient decreases when applying EC heating, which leads to lower impurity peaking, consistently with experimental observations.

  14. Improving cancer treatment with cyclotron produced radionuclides

    SciTech Connect

    Larson, S.M.; Finn, R.D.

    1992-08-04

    Our goal is to improve the scientific basis for tumor diagnosis, treatment and treatment follow-up based on the use of cyclotron produced radiotracers in oncology. The grant includes 3 interactive components: Radiochemistry/Cyclotron; Pharmacology; and Immunology. The radiochemistry group seeks to develop innovative cyclotron targetry, radiopharmaceuticals, and radiolabeled antibodies, which are then used to assess important unanswered questions in tumor pharmacology and immunology. Examples include selected positron emitting radionuclides, such as Iodine-124, and Ga-66; I-124, I-123, I-131 labeled iododeoxyuridine, C-11 colchicine, and antimetabolites, like C-11 methotrexate; and radiolabeled antibodies, 3F8, M195, A33, and MRK16 for application in the pharmacology and immunology projects. The pharmacology program studies tumor resistance to chemotherapy, particularly the phenomenon of multidrug resistance and the relationship between tumor uptake and retention and the tumor response for anti-metabolite drugs. The immunology program studies the physiology of antibody localization at the tissue level as the basis for novel approaches to improving tumor localization such as through the use of an artificial lymphatic system which mechanically reduces intratumoral pressures in tumors in vivo. Quantitative imaging approaches based on PET and SPECT in radioimmunotherapy are studied to give greater insight into the physiology of tumor localization and dosimetry.

  15. Cyclotron Requirements for Multi-disciplinary Programs

    NASA Astrophysics Data System (ADS)

    Armbruster, John M.

    2009-03-01

    As time has passed, the various Cyclotron programs have changed over the years. In the "early" times of Cyclotron operations, the emphasis was on a more single sided approach such as Clinical or Research or Production. However, as time passed, the disciplines became more interconnected until today, it is unusual to have a Cyclotron and only have a single program unless it is pure production. More and more, especially in public areas such as Universities or Health Centers, you are seeing programs that do all three types of disciplines: Production; Clinical or Patient Diagnostics and/or Treatment; and Research, either in the development and manufacture of new Radio-Isotopes, new Diagnostic or Therapeutic Compound Development, or Clinical Research involving subject testing. While all three of these disciplines have some common requirements, they also have some very different requirements that may be completely counterproductive to other requirements. For a program where all three disciplines are required to be successful, it is necessary come up with some sort of compromise that meets all the various requirements. During this talk, we will try to identify some of these different requirements for the various disciplines and how these could impact the other disciplines. We will also discuss ideas for some possible compromises that might reduce the conflict between the various disciplines.

  16. Ion Cyclotron Heating on Proto-MPEX

    NASA Astrophysics Data System (ADS)

    Goulding, R. H.; Caughman, J. B. O.; Rapp, J.; Biewer, T. M.; Campbell, I. H.; Caneses, J. F.; Kafle, N.; Ray, H. B.; Showers, M. A.; Piotrowicz, P. A.

    2016-10-01

    Ion cyclotron heating will be used on Proto-MPEX (Prototype Material Plasma Exposure eXperiment) to increase heat flux to the target, to produce varying ion energies without substrate biasing, and to vary the extent of the magnetic pre-sheath for the case of a tilted target. A 25 cm long, 9 cm diameter dual half-turn helical ion cyclotron antenna has been installed in the device located at the magnetic field maximum. It couples power to ions via single pass damping of the slow wave at the fundamental resonance, and operates with ω 0.8ωci at the antenna location. It is designed to operate at power levels up to 30 kW, with a later 200 kW upgrade planned. Near term experiments include measuring RF loading at low power as a function of frequency and antenna gap. The plasma is generated by a helicon plasma source that has achieved ne > 5 ×1019m-3 operating with deuterium, as measured downstream from the ion cyclotron antenna location. Measurements will be compared with 1-D and 2-D models of RF coupling. The latest results will be presented. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.

  17. Ensemble MD simulations restrained via crystallographic data: Accurate structure leads to accurate dynamics

    PubMed Central

    Xue, Yi; Skrynnikov, Nikolai R

    2014-01-01

    Currently, the best existing molecular dynamics (MD) force fields cannot accurately reproduce the global free-energy minimum which realizes the experimental protein structure. As a result, long MD trajectories tend to drift away from the starting coordinates (e.g., crystallographic structures). To address this problem, we have devised a new simulation strategy aimed at protein crystals. An MD simulation of protein crystal is essentially an ensemble simulation involving multiple protein molecules in a crystal unit cell (or a block of unit cells). To ensure that average protein coordinates remain correct during the simulation, we introduced crystallography-based restraints into the MD protocol. Because these restraints are aimed at the ensemble-average structure, they have only minimal impact on conformational dynamics of the individual protein molecules. So long as the average structure remains reasonable, the proteins move in a native-like fashion as dictated by the original force field. To validate this approach, we have used the data from solid-state NMR spectroscopy, which is the orthogonal experimental technique uniquely sensitive to protein local dynamics. The new method has been tested on the well-established model protein, ubiquitin. The ensemble-restrained MD simulations produced lower crystallographic R factors than conventional simulations; they also led to more accurate predictions for crystallographic temperature factors, solid-state chemical shifts, and backbone order parameters. The predictions for 15N R1 relaxation rates are at least as accurate as those obtained from conventional simulations. Taken together, these results suggest that the presented trajectories may be among the most realistic protein MD simulations ever reported. In this context, the ensemble restraints based on high-resolution crystallographic data can be viewed as protein-specific empirical corrections to the standard force fields. PMID:24452989

  18. Ultrafast lattice dynamics in lead selenide quantum dot induced by laser excitation

    SciTech Connect

    Wang, Xuan; Rahmani, Hamidreza; Zhou, Jun; Gorfien, Matthew; Mendez Plaskus, Joshua; Li, Dong; Voss, Ryan; Nelson, Cory A.; Wai Lei, Kin; Wolcott, Abraham; Zhu, Xiaoyang; Li, Junjie; Cao, Jianming

    2016-10-10

    We directly monitored the lattice dynamics in PbSe quantum dots induced by laser excitation using ultrafast electron di raction. The energy relaxation between the carriers and the lattice took place within 10 ps, showing no evidence of any signi cant phonon bottleneck e ect. Meanwhile, the lattice dilation exhibited some unusual features that could not be explained by the available mechanisms of photon- induced acoustic vibrations in semiconductors alone. The heat transport between the QDs and the substrate deviates signi cantly from Fourier's Law, which opens questions about the heat transfer under nonequilibrium conditions in nanoscale materials.

  19. Ultrafast lattice dynamics in lead selenide quantum dot induced by laser excitation

    DOE PAGES

    Wang, Xuan; Rahmani, Hamidreza; Zhou, Jun; ...

    2016-10-10

    We directly monitored the lattice dynamics in PbSe quantum dots induced by laser excitation using ultrafast electron di raction. The energy relaxation between the carriers and the lattice took place within 10 ps, showing no evidence of any signi cant phonon bottleneck e ect. Meanwhile, the lattice dilation exhibited some unusual features that could not be explained by the available mechanisms of photon- induced acoustic vibrations in semiconductors alone. The heat transport between the QDs and the substrate deviates signi cantly from Fourier's Law, which opens questions about the heat transfer under nonequilibrium conditions in nanoscale materials.

  20. Entrance channel dynamics of hot and cold fusion reactions leading to superheavy elements

    NASA Astrophysics Data System (ADS)

    Umar, A. S.; Oberacker, V. E.; Maruhn, J. A.; Reinhard, P.-G.

    2010-06-01

    We investigate the entrance channel dynamics for the reactions Zn70+Pb208 and Ca48+U238 by using the fully microscopic time-dependent Hartree-Fock theory coupled with a density constraint. We calculate excitation energies and capture cross sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the Ca48+U238 system and perform an alignment angle averaging for the calculation of the capture cross section. The results show that this approach can generate results in good agreement with experiments and other theories.

  1. Entrance channel dynamics of hot and cold fusion reactions leading to superheavy elements

    SciTech Connect

    Umar, A. S.; Oberacker, V. E.; Maruhn, J. A.; Reinhard, P.-G.

    2010-06-15

    We investigate the entrance channel dynamics for the reactions {sup 70}Zn+{sup 208}Pb and {sup 48}Ca+{sup 238}U by using the fully microscopic time-dependent Hartree-Fock theory coupled with a density constraint. We calculate excitation energies and capture cross sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the {sup 48}Ca+{sup 238}U system and perform an alignment angle averaging for the calculation of the capture cross section. The results show that this approach can generate results in good agreement with experiments and other theories.

  2. Ultrafast lattice dynamics in lead selenide quantum dot induced by laser excitation

    NASA Astrophysics Data System (ADS)

    Wang, Xuan; Rahmani, Hamidreza; Zhou, Jun; Gorfien, Matthew; Mendez Plaskus, Joshua; Li, Dong; Voss, Ryan; Nelson, Cory A.; Wai Lei, Kin; Wolcott, Abraham; Zhu, Xiaoyang; Li, Junjie; Cao, Jianming

    2016-10-01

    We directly monitored the lattice dynamics in PbSe quantum dots (QD) induced by laser excitation using ultrafast electron diffraction. The energy relaxation between the carriers and the lattice took place within 10 ps, showing no evidence of any significant phonon bottleneck effect. Meanwhile, the lattice dilation exhibited some unusual features that could not be explained by the available mechanisms of photon-induced acoustic vibrations in semiconductors alone. The heat transport between the QDs and the substrate deviates significantly from Fourier's Law, which opens questions about the heat transfer under nonequilibrium conditions in nanoscale materials.

  3. Molecular dynamics simulation of the ice nucleation and growth process leading to water freezing.

    PubMed

    Matsumoto, Masakazu; Saito, Shinji; Ohmine, Iwao

    2002-03-28

    Upon cooling, water freezes to ice. This familiar phase transition occurs widely in nature, yet unlike the freezing of simple liquids, it has never been successfully simulated on a computer. The difficulty lies with the fact that hydrogen bonding between individual water molecules yields a disordered three-dimensional hydrogen-bond network whose rugged and complex global potential energy surface permits a large number of possible network configurations. As a result, it is very challenging to reproduce the freezing of 'real' water into a solid with a unique crystalline structure. For systems with a limited number of possible disordered hydrogen-bond network structures, such as confined water, it is relatively easy to locate a pathway from a liquid state to a crystalline structure. For pure and spatially unconfined water, however, molecular dynamics simulations of freezing are severely hampered by the large number of possible network configurations that exist. Here we present a molecular dynamics trajectory that captures the molecular processes involved in the freezing of pure water. We find that ice nucleation occurs once a sufficient number of relatively long-lived hydrogen bonds develop spontaneously at the same location to form a fairly compact initial nucleus. The initial nucleus then slowly changes shape and size until it reaches a stage that allows rapid expansion, resulting in crystallization of the entire system.

  4. Positive feedback can lead to dynamic nanometer-scale clustering on cell membranes

    SciTech Connect

    Wehrens, Martijn; Rein ten Wolde, Pieter; Mugler, Andrew

    2014-11-28

    Clustering of molecules on biological membranes is a widely observed phenomenon. A key example is the clustering of the oncoprotein Ras, which is known to be important for signal transduction in mammalian cells. Yet, the mechanism by which Ras clusters form and are maintained remains unclear. Recently, it has been discovered that activated Ras promotes further Ras activation. Here we show using particle-based simulation that this positive feedback is sufficient to produce persistent clusters of active Ras molecules at the nanometer scale via a dynamic nucleation mechanism. Furthermore, we find that our cluster statistics are consistent with experimental observations of the Ras system. Interestingly, we show that our model does not support a Turing regime of macroscopic reaction-diffusion patterning, and therefore that the clustering we observe is a purely stochastic effect, arising from the coupling of positive feedback with the discrete nature of individual molecules. These results underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

  5. Volunteering leads to rock-paper-scissors dynamics in a public goods game

    NASA Astrophysics Data System (ADS)

    Semmann, Dirk; Krambeck, Hans-Jürgen; Milinski, Manfred

    2003-09-01

    Collective efforts are a trademark of both insect and human societies. They are achieved through relatedness in the former and unknown mechanisms in the latter. The problem of achieving cooperation among non-kin has been described as the `tragedy of the commons', prophesying the inescapable collapse of many human enterprises. In public goods experiments, initial cooperation usually drops quickly to almost zero. It can be maintained by the opportunity to punish defectors or the need to maintain good reputation. Both schemes require that defectors are identified. Theorists propose that a simple but effective mechanism operates under full anonymity. With optional participation in the public goods game, `loners' (players who do not join the group), defectors and cooperators will coexist through rock-paper-scissors dynamics. Here we show experimentally that volunteering generates these dynamics in public goods games and that manipulating initial conditions can produce each predicted direction. If, by manipulating displayed decisions, it is pretended that defectors have the highest frequency, loners soon become most frequent, as do cooperators after loners and defectors after cooperators. On average, cooperation is perpetuated at a substantial level.

  6. Parametric Instabilities of Electron Cyclotron Waves in Plasmas.

    DTIC Science & Technology

    1980-03-01

    tokamaks eg. PLT. In the EBT, the electron cyclotron pump of finite wavenumber 1% decays into two Bernstein modes at the second harmonic cyclotron...convective threshold with finite k, is -200 W/ . For large tokamaks , the convective threshold for various decay channels turns out to be >200 KW/cu 2...efforts on the electron cyclotron heating of large devices, eg., Elmo bumpy torus, tokamak and mirrors. In the Elmo 1bumpy torus (EBT) the microwaves

  7. Removal of lead ions by keramzite sand coated with electroplating sludge under dynamic conditions.

    PubMed

    Stefanova, R Y

    2001-01-01

    Column studies were performed to determine the effect of bed height, linear flow rate, adsorbent particle size and initial metal ion concentration on lead removal by keramzite sand coated with electroplating sludge. The Bed depth service time (BDST) model applied to the data at 2% breakthrough gave the best approximation to the experimental results compared with other investigated breakthrough points. The adsorption performance of the thermally modified coated keramzite columns could be well described by the Wolborska model up to 50% breakthrough point. The application of this model allowed determination of the kinetic coefficients of external mass transfer in the fixed bed and the time for protective action of the sorbent layers. The experimental results support the assumption that the external mass transfer of the solute through the hydrodynamic boundary layer is the rate-limiting step. It has been established that the keramzite sand coated with electroplating sludge (particle size 0.5-0.8 mm) can be successfully used for lead removal from dilute metal ion solutions at linear flow rate 4-6 cm/min and empty bed contact time > or = 3 min.

  8. Photoinduced Single- and Multiple- Electron Dynamics Processes Enhanced by Quantum Confinement in Lead Halide Perovskite Quantum Dots.

    PubMed

    Vogel, Dayton Jon; Kryjevski, Andrei; Inerbaev, Talgat M; Kilin, Dmitri S

    2017-03-21

    Methyl-ammonium lead iodide perovskite (MAPbI3) is a promising material for photovoltaic devices. A modification of the MAPbI3 into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photo-excited dynamic processes in a MAPbI3 quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or non-radiative recombination (NRR), or multi-exciton generation (MEG) processes. Computed times of these processes fall in the order of MEG < EC < RR < NRR, where MEG is in the order of a few femtoseconds, EC at the picosecond range while RR and NRR are in the order of nanoseconds. Computed timescales indicate which electronic transition pathways can contribute to increase in charge collection efficiency. Simulated mechanism relaxation rates show that quantum confinement promotes MEG in MAPbI3 QDs.

  9. Photoinduced Single- and Multiple-Electron Dynamics Processes Enhanced by Quantum Confinement in Lead Halide Perovskite Quantum Dots

    DOE PAGES

    Vogel, Dayton J.; Kryjevski, Andrei; Inerbaev, Talgat; ...

    2017-03-21

    Methylammonium lead iodide perovskite (MAPbI3) is a promising material for photovoltaic devices. A modification of MAPbI3 into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photoexcited dynamic processes in a MAPbI3 quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or nonradiative recombination (NRR), or multiexciton generation (MEG) processes. Computed times of these processes fall in the order of MEG < EC < RR < NRR, where MEG is on the order of a few femtoseconds, EC is in themore » picosecond range, while RR and NRR are on the order of nanoseconds. Computed time scales indicate which electronic transition pathways can contribute to increase in charge collection efficiency. Simulated mechanisms of relaxation and their rates show that quantum confinement promotes MEG in MAPbI3 QDs.« less

  10. Tunneling Microscopy of Dynamical Processes on the LEAD/GERMANIUM(111) Surface

    NASA Astrophysics Data System (ADS)

    Hwang, Ing-Shouh

    Knowledge about atomic scale motions is essential for understanding dynamical phenomena on surfaces, such as diffusion, phase transitions, and epitaxial growth. This report describes the results of a study of dynamical processes on the Pb/Ge(111) surface using a scanning tunneling microscope (STM). Individual Pb atom diffUsion and concerted atomic motions on the Ge(111) surface are observed in real time. We also study a structural surface phase transformation at elevated temperatures. At very low Pb coverage, migration of individual Pb atoms is observed in the Ge(111)-c(2 x 8) surface near room temperature. The activation energy of this migration can be measured by analyzing a large number of individual atomic motions from room temperature to 80^ circC. The Pb diffusion is found to occur mainly along the (011) adatom row direction of the c(2 x 8) reconstruction. About half of the adatom migrations are "long jumps". We also observe the formation and annihilation of metastable structural surface excitations, which occur much less often than Pb diffusion. They involve a number of adatoms in the same row moving in concert along the row direction like beads on an abacus. This "adatom row shift" may be responsible for the anisotropy of the Pb atom diffusion. It also provides a new mechanism for atomic transport on crystal surfaces and can explain several structural phenomena associated with the Ge(111) surface. At high coverage, a one monolayer Pb/Ge(111) undergoes a reversible phase transformation from sqrt{3} x sqrt{3 }R30^circ to 1 x 1 at about 180 ^circC. Atomic structures of both high and low temperature phases are resolved, which reveals an order-order transition. Spatial and temporal fluctuations are exposed just above the transition temperature. In addition, the influence of surface strain, phase boundaries, and finite size domains are found to play an important role in the phase transformation.

  11. MW-class 800 MeV/n H2+ SC-cyclotron for ADS application, design and study goals

    SciTech Connect

    Meot F.; Calabretta, L.; Calanna, A.; Roser, T.; Weng, B.

    2012-05-20

    This paper addresses an attempt to start investigating the use of the Superconducting Ring Cyclotron (SRC) developed for DAE{delta}ALUS experiment for ADS application [1], focusing on the magnet design and its implication for lattice parameters and dynamic aperture performance.

  12. The Michigan State University Cyclotron Laboratory: Its Early Years

    NASA Astrophysics Data System (ADS)

    Austin, Sam M.

    2016-01-01

    The Michigan State University Cyclotron Laboratory was founded in 1958 and over the years grew in stature, becoming the highest-ranked university-based program in nuclear science. Its K50 cyclotron had unmatched capability as a light-ion accelerator and helped to define what a modern cyclotron could do to advance our understanding of nuclei. This paper describes the first twenty years of the Cyclotron Laboratory's evolution and gives some insight into the cultural characteristics of the laboratory, and of its early members, that led it to thrive.

  13. Observations of multiharmonic ion cyclotron waves due to inverse ion cyclotron damping in the northern magnetospheric cusp

    NASA Astrophysics Data System (ADS)

    Slapak, R.; Gunell, H.; Hamrin, M.

    2017-01-01

    We present a case study of inverse ion cyclotron damping taking place in the northern terrestrial magnetospheric cusp, exciting waves at the ion cyclotron frequency and its harmonics. The ion cyclotron waves are primarily seen as peaks in the magnetic-field spectral densities. The corresponding peaks in the electric-field spectral densities are not as profound, suggesting a background electric field noise or other processes of wave generation causing the electric spectral densities to smoothen out more compared to the magnetic counterpart. The required condition for inverse ion cyclotron damping is a velocity shear in the magnetic field-aligned ion bulk flow, and this condition is often naturally met for magnetosheath influx in the northern magnetospheric cusp, just as in the presented case. We note that some ion cyclotron wave activity is present in a few similar shear events in the southern cusp, which indicates that other mechanisms generating ion cyclotron waves may also be present during such conditions.

  14. Porewater dynamics of silver, lead and copper in coastal sediments and implications for benthic metal fluxes

    USGS Publications Warehouse

    Kalnejais, Linda H.; Martin, W. R.; Bothner, Michael H.

    2015-01-01

    To determine the conditions that lead to a diffusive release of dissolved metals from coastal sediments, porewater profiles of Ag, Cu, and Pb have been collected over seven years at two contrasting coastal sites in Massachusetts, USA. The Hingham Bay (HB) site is a contaminated location in Boston Harbor, while the Massachusetts Bay (MB) site is 11 km offshore and less impacted. At both sites, the biogeochemical cycles include scavenging by Fe-oxyhydroxides and release of dissolved metals when Fe-oxyhydroxides are reduced. Important differences in the metal cycles at the two sites, however, result from different redox conditions. Porewater sulfide and seasonal variation in redox zone depth is observed at HB, but not at MB. In summer, as the conditions become more reducing at HB, trace metals are precipitated as sulfides and are no longer associated with Fe-oxyhydroxides. Sulfide precipitation close to the sediment–water interface limits the trace metal flux in summer and autumn at HB, while in winter, oxidation of the sulfide phases drives high benthic fluxes of Cu and Ag, as oxic conditions return. The annual diffusive flux of Cu at HB is found to be significant and contributes to the higher than expected water column Cu concentrations observed in Boston Harbor. At MB, due to the lower sulfide concentrations, the association of trace metals with Fe-oxyhydroxides occurs throughout the year, leading to more stable fluxes. A surface enrichment of solid phase trace metals was found at MB and is attributed to the persistent scavenging by Fe-oxyhydroxides. This process is important, particularly at sites that are less reducing, because it maintains elevated metal concentrations at the surface despite the effects of bioturbation and sediment accumulation, and because it may increase the persistence of metal contamination in surface sediments.

  15. Porewater dynamics of silver, lead and copper in coastal sediments and implications for benthic metal fluxes.

    PubMed

    Kalnejais, Linda H; Martin, W R; Bothner, Michael H

    2015-06-01

    To determine the conditions that lead to a diffusive release of dissolved metals from coastal sediments, porewater profiles of Ag, Cu, and Pb have been collected over seven years at two contrasting coastal sites in Massachusetts, USA. The Hingham Bay (HB) site is a contaminated location in Boston Harbor, while the Massachusetts Bay (MB) site is 11 km offshore and less impacted. At both sites, the biogeochemical cycles include scavenging by Fe-oxyhydroxides and release of dissolved metals when Fe-oxyhydroxides are reduced. Important differences in the metal cycles at the two sites, however, result from different redox conditions. Porewater sulfide and seasonal variation in redox zone depth is observed at HB, but not at MB. In summer, as the conditions become more reducing at HB, trace metals are precipitated as sulfides and are no longer associated with Fe-oxyhydroxides. Sulfide precipitation close to the sediment-water interface limits the trace metal flux in summer and autumn at HB, while in winter, oxidation of the sulfide phases drives high benthic fluxes of Cu and Ag, as oxic conditions return. The annual diffusive flux of Cu at HB is found to be significant and contributes to the higher than expected water column Cu concentrations observed in Boston Harbor. At MB, due to the lower sulfide concentrations, the association of trace metals with Fe-oxyhydroxides occurs throughout the year, leading to more stable fluxes. A surface enrichment of solid phase trace metals was found at MB and is attributed to the persistent scavenging by Fe-oxyhydroxides. This process is important, particularly at sites that are less reducing, because it maintains elevated metal concentrations at the surface despite the effects of bioturbation and sediment accumulation, and because it may increase the persistence of metal contamination in surface sediments.

  16. Discovery of Cyclotron Resonance Features in the Soft Gamma Repeater SGR 1806-20

    NASA Technical Reports Server (NTRS)

    Ibrahim, Alaa I.; Safi-Harb, Samar; Swank, Jean H.; Parke, William; Zane, Silvia; Turolla, Roberto

    2002-01-01

    We report evidence of cyclotron resonance features from the Soft Gamma Repeater SGR 1806-20 in outburst, detected with the Rossi X-ray Timing Explorer in the spectrum of a long, complex precursor that preceded a strong burst. The features consist of a narrow 5.0 keV absorption line with modulation near its second and third harmonics (at 11.2 keV and 17.5 keV respectively). The line features are transient and are detected in the harder part of the precursor. The 5.0 keV feature is strong, with an equivalent width of approx. 500 eV and a narrow width of less than 0.4 keV. Interpreting the features as electron cyclotron lines in the context of accretion models leads to a large mass-radius ratio (M/R greater than 0.3 solar mass/km) that is inconsistent with neutron stars or that requires a low (5-7) x 10(exp 11) G magnetic field that is unlikely for SGRs. The line widths are also narrow compared with those of electron cyclotron resonances observed so far in X-ray pulsars. In the magnetar picture, the features are plausibly explained as ion cyclotron resonances in an ultra-strong magnetic field that have recently been predicted from magnetar candidates. In this view, the 5.0 keV feature is consistent with a proton cyclotron fundamental whose energy and width are close to model predictions. The line energy would correspond to a surface magnetic field of 1.0 x 10(exp 15) G for SGR 1806-20, in good agreement with that inferred from the spin-down measure in the source.

  17. Discovery of Cyclotron Resonance Features in the Soft Gamma Repeater SGR 1806-20

    NASA Technical Reports Server (NTRS)

    Ibrahim, A. I.; Safi-Harb, Samar; Swank, Jean H.; Parke, William; Zane, Silvia; Turolla, Roberto; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report evidence for cyclotron resonance features from the Soft Gamma Repeater SCR 1806-20 in outburst, detected with the Rossi X-ray Timing Explorer in the spectrum of a long, complex precursor that preceded a strong burst. The features consist of a narrow 5.0 keV absorption line with modulation near its second and third harmonics (at 11.2 keV and 17.5 keV respectively). The line features are transient and are detected in the harder part of the precursor. The 5.0 keV feature is strong, with an equivalent width of approx. 500 eV, and a narrow width of < 0.4 keV. Interpreting the features as electron cyclotron lines in the context of accretion models leads to a large mass-radius ratio (M/R > 0.3 Solar Mass/km) that is inconsistent with neutron stars, or requires a low (5 - 7) x 10(exp 11) G magnetic field that is unlikely for SGRs. The line widths are also narrow compared to those of electron cyclotron resonances observed so far in X-ray pulsars. In the magnetar picture, the features are plausibly explained as ion cyclotron resonances in an ultra-strong magnetic field, which have recently been predicted from magnetar candidates. In this view, the 5.0 keV feature is consistent with a proton cyclotron fundamental whose energy and width are close to model predictions. The line energy would correspond to a surface magnetic field of 1.0 x 10(exp 15) G for SGR 1806-20, in good agreement with that inferred from the spin-down measure in the source.

  18. T-wave alternans in LQTS: repolarization-rate dynamics from digital 12-lead Holter data.

    PubMed

    Brockmeier, K; Aslan, I; Hilbel, T; Eberle, T; Ulmer, H E; Lux, R L

    2001-01-01

    T-wave alternans (TWA) is a harbinger of ventricular vulnerability and an important prognostic indicator for torsade de pointes and likely sudden death in patients with LQTS. We analyzed the occurrence of TWA in 18 patients with LQTS (7 males, 11 females, ages ranging from 6 months to 32 years--median 8.4 years). Analysis was performed with software to investigate dynamics of cycle length mediated repolarization changes. Digital Holter ECG analysis revealed macroscopic, true TWA in 3 of 18 patients. TWA showed a variable morphological expression. One patient had continuous changes of T wave polarity, but not on a periodic beat-to-beat basis. Onsets of macroscopic TWA were preceded by long/short cycle length sequences and tachycardic rates above 130 to 140 bpm. Impact of ventricular premature beats on TWA onset was insignificant. Two of the identified patients with TWA had sudden cardiac death during follow-up (one refused PM therapy). At present, TWA cannot be detected automatically from Holter ECGs and therefore may be missed, despite the potential danger for the individuals. The observation that predominantly high beat rates and not beat rate changes, per se, triggered episodes of TWA renders difficult general therapeutic recommendations for the identified patients at risk.

  19. Dynamic processes in the lithosphere leading to extension, rifting and basin formation

    NASA Astrophysics Data System (ADS)

    Anderson, Thomas

    2014-05-01

    The similarity of ages of extensional core complexes, co-genetic basin formation, and kinematically compatible movements along large strike-slip faults in western North America to ages of comparable events within the Himalayas-Alps orogenic belt leads to the speculation that strain related to changes in Pacific (PAC)-North America(NA) plate motions may be recorded on a global scale affecting the coupled plates and extending eastward across Eurasia. The contemporaneous global deformation reflects abrupt changes in PAC-NA plate motions in response to coupling following convergence of buoyant oceanic lithosphere, commonly part of a spreading center, which impedes subduction and leads to collision followed by coupling when the buoyant lithosphere binds against the base of the overriding continental plate. Critical coupling of a sufficiently long ridge segment leads to "capture", after which the former movements of the newly coupled plates are integrated abruptly and changed from previous directions. In western North America, episodes of capture of the NA plate by the (PAC) plate are recorded by break-up unconformities (ca. 55, 35, and 17 Ma) and basins commonly within extensional domains distinguished by age and direction of tectonic transport (Eocene [~55-42 Ma], ca. 285o, Oligocene [~35-20 Ma], 240o, Miocene [17-0 Ma], ca. 280o). The transport directions record the integration of the southwesterly motion of NA , related to mantle convection, and the northwesterly motion of PAC, driven by slab pull. Following each coupling event, PAC moves westward dragging: 1) the formerly subducting Farallon slab, 2) the coupled, formerly overriding, NA plate, and 3) Eurasia (EA), with it. In response to the strong extension that is imposed upon rocks within domains encompassed by the PAC-NA coupled region, and along the southern margin of Eurasia, brittle deformation, accommodated by normal and strike-slip faults, and formation of contemporaneous basins, takes place. Core

  20. Actin dynamics is rapidly regulated by the PTEN and PIP2 signaling pathways leading to myocyte hypertrophy.

    PubMed

    Li, Jieli; Tanhehco, Elaine J; Russell, Brenda

    2014-12-01

    Mature cardiac myocytes are terminally differentiated, and the heart has limited capacity to replace lost myocytes. Thus adaptation of myocyte size plays an important role in the determination of cardiac function. The hypothesis tested is that regulation of the dynamic exchange of actin leads to cardiac hypertrophy. ANG II was used as a hypertrophic stimulant in mouse heart and neonatal rat ventricular myocytes (NRVMs) in culture for assessment of a mechanism for regulation of actin dynamics by phosphatidylinositol 4,5-bisphosphate (PIP2). Actin dynamics in NRVMs rapidly increased in a PIP2-dependent manner, measured by imaging and fluorescence recovery after photobleaching (FRAP). A significant increase in PIP2 levels was found by immunoblotting in both adult mouse heart tissue and cultured NRVMs. Inhibition of phosphatase and tensin homolog (PTEN) in NRVMs markedly blunted ANG II-induced increases in actin dynamics, the PIP2 level, and cell size. Furthermore, PTEN activity was dramatically upregulated in ANG II-treated NRVMs but downregulated when PTEN inhibitors were used. The time course of the rise in the PIP2 level was inversely related to the fall in the PIP3 level, which was significant by 30 min in ANG II-treated NRVMs. However, significant translocation of PTEN to the plasma membrane occurred by 10 min, suggesting a crucial initial step for PTEN for the cellular responses to ANG II. In conclusion, PTEN and PIP2 signaling may play an important role in myocyte hypertrophy by the regulation of actin filament dynamics, which is induced by ANG II stimulation. Copyright © 2014 the American Physiological Society.

  1. Actin dynamics is rapidly regulated by the PTEN and PIP2 signaling pathways leading to myocyte hypertrophy

    PubMed Central

    Li, Jieli; Tanhehco, Elaine J.

    2014-01-01

    Mature cardiac myocytes are terminally differentiated, and the heart has limited capacity to replace lost myocytes. Thus adaptation of myocyte size plays an important role in the determination of cardiac function. The hypothesis tested is that regulation of the dynamic exchange of actin leads to cardiac hypertrophy. ANG II was used as a hypertrophic stimulant in mouse heart and neonatal rat ventricular myocytes (NRVMs) in culture for assessment of a mechanism for regulation of actin dynamics by phosphatidylinositol 4,5-bisphosphate (PIP2). Actin dynamics in NRVMs rapidly increased in a PIP2-dependent manner, measured by imaging and fluorescence recovery after photobleaching (FRAP). A significant increase in PIP2 levels was found by immunoblotting in both adult mouse heart tissue and cultured NRVMs. Inhibition of phosphatase and tensin homolog (PTEN) in NRVMs markedly blunted ANG II-induced increases in actin dynamics, the PIP2 level, and cell size. Furthermore, PTEN activity was dramatically upregulated in ANG II-treated NRVMs but downregulated when PTEN inhibitors were used. The time course of the rise in the PIP2 level was inversely related to the fall in the PIP3 level, which was significant by 30 min in ANG II-treated NRVMs. However, significant translocation of PTEN to the plasma membrane occurred by 10 min, suggesting a crucial initial step for PTEN for the cellular responses to ANG II. In conclusion, PTEN and PIP2 signaling may play an important role in myocyte hypertrophy by the regulation of actin filament dynamics, which is induced by ANG II stimulation. PMID:25260617

  2. The dynamic association processes leading from a silica precursor to a mesoporous SBA-15 material.

    PubMed

    Alfredsson, Viveka; Wennerström, Håkan

    2015-07-21

    During the last two decades, the synthesis of silica with an ordered mesoporous structure has been thoroughly explored. The basis of the synthesis is to let silica monomers polymerize in the presence of an amphiphilic template component. In the first studies, cationic surfactants were used as structure inducer. Later it was shown that pluronic copolymers also could have the role. One advantage with the pluronics copolymers is that they allow for a wider variation in the radius of pores in the resulting silica material. Another advantage lies in the higher stability resulting from the thicker walls between the pores. Mesoporous silica has a very high area to volume ratio, and the ordered structure ensures surface homogeneity. There are a number of applications of this type of material. It can be used as support for catalysts, as templates to produces other mesoporous inorganic materials, or in controlled release applications. The synthesis of mesoporous silica is, from a practical point of view, simple, but there are significant possibilities to vary synthesis conditions with a concomitant effect on the properties of the resulting material. It is clear that the structural properties on the nanometer scale are determined by the self-assembly properties of the amphiphile, and this knowledge has been used to optimize pore geometry and pore size. To have a practical functional material it is desirable to also control the structure on a micrometer scale and larger. In practice, one has largely taken an empirical approach in optimizing reaction conditions, paying less attention to underlying chemical and physicochemical mechanisms that lead from starting conditions to the final product. In this Account, we present our systematic studies of the processes involved not only in the formation of the mesoporous structure as such, but also of the formation of structures on the micrometer scale. The main point is to show how the ongoing silica polymerization triggers a sequence

  3. Amplitudes of electron cyclotron waves transmitted in the ionosphere

    NASA Astrophysics Data System (ADS)

    James, H. G.

    2011-07-01

    During the two-point sounding rocket experiment Observations of Electric-field Distributions in the Ionospheric Plasma-A Unique Strategy-C (OEDIPUS-C, hereinafter OC), Bernstein or electron cyclotron waves (ECWs) were transmitted over magnetic field-aligned emitter-receiver separations of hundreds of meters. Signals were observed at harmonic frequencies mfc of the electron cyclotron frequency fc, where m was 2, 3, and 4, fc ≈ 1.3 MHz, and the electron plasma frequency was less than half of fc. The electric fields at 2fc radiated by the emitting dipoles have been computed from the inhomogeneous Helmholtz wave equation. Using the full hot plasma theory to evaluate the dielectric tensor, a Green's function has been derived, based partly on numerical inversion and facilitated by some simplifications made possible by the given frequency and plasma parameters. Under the assumption of straight-line rays, it is found that the computed absolute voltage levels induced on the receiving dipoles are of the same order of magnitude as the observed levels. The electric field E radiation patterns at 2fc are found to be highly elongated along the direction of the Earth's magnetic induction field B. The component of E perpendicular to B, the radial or ρ component, is much stronger than the other two components in a cylindrical coordinate system. The prediction of strong radial E magnitudes along ray directions very close to B is consistent with the OC observations. These results enlarge our appreciation of distinct characteristics of ECW radiation and propagation that may improve understanding of the role of these electrostatic waves in ionospheric dynamics.

  4. Flash ionization signature in coherent cyclotron emission from brown dwarfs

    NASA Astrophysics Data System (ADS)

    Vorgul, I.; Helling, Ch.

    2016-05-01

    Brown dwarfs (BDs) form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in the form of lightning resulting in substantial sudden increase of local ionization. BDs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionization events (flash ionization) can be imprinted on a pre-existing radiation. Detection of such flash ionization events will open investigations into the ionization state and atmospheric dynamics. Such events can also result from explosion shock waves, material outbursts or (volcanic) eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionization events like lightning. Our conductivity model reproduces the conductivity function derived from observations of terrestrial gamma-ray flashes, and is applicable to astrophysical objects with strong temporal variations in the local ionization, as in planetary atmospheres and protoplanetary discs. We show that the field responds with a characteristic flash-shaped pulse to a conductivity flash of intermediate intensity. More powerful ionization events result in smaller variations of the initial radiation, or in its damping. We show that the characteristic damping of the response field for high-power initial radiation carries information about the ionization flash magnitude and duration. The duration of the pulse amplification or the damping is consistently shorter for larger conductivity variations and can be used to evaluate the intensity of the flash ionization. Our work suggests that cyclotron emission could be probe signals for electrification processes inside BD atmosphere.

  5. 4D imaging of the seism-geochemical dynamics leading to recent Campi Flegrei unrest

    NASA Astrophysics Data System (ADS)

    De Siena, Luca; Chiodini, Giovanni; Vilardo, Giuseppe; Del Pezzo, Edoardo; Castellano, Mario; Colombelli, Simona; Tisato, Nicola; Ventura, Guido

    2017-04-01

    Understanding what produced historical unrests at Campi Flegrei super volcanic caldera is key to forecasting eruptions at the volcano in the near future. Here, we present a novel seismic attenuation and 4D lapse-time source model spanning the years 1983-84 and working in parallel with geochemical data and physical simulations. Results reveal a 4-5 km deep, NNW-SSE striking hot zone, either a magma sill or fluid reservoir, offshore the city of Pozzuoli, feeding a reservoir of supercritical fluids/foams topping at a depth of about 3 km. Repeated injections of hot materials from depth in September-October 1983 into the reservoir produce a second fluid phase accumulating under a rock-physics derived caprock, enhancing subsidence. The release of this additional stress after the breaking of the reservoir, on April 1st 1984, leads to the opening of a western, morphologically-defined path, connecting the centre of the caldera with the site of its last eruption (1538 AD). The hot zone offshore Pozzuoli is the deepest source of seismic activity, ground deformation, and vertical/lateral fluid migration inducing subsidence detected at the volcano during its major monitored unrest (1983-84). Still active today and related to its last historical eruption, it thus controls unrest and eruptive behaviour of the area of highest volcanic hazard in continental Europe.

  6. Dynamic thermal testing of lead-acid batteries for the PREPA battery energy storage system

    SciTech Connect

    Jungst, R.G.; Freese, J.M.; Rodriguez, G.P.; Dykhuizen, R.C.; Braithwaite, J.W.; Woods, C.

    1993-08-01

    A test is being carried out to determine the thermal load that will be present in a 20 MW battery energy storage system (BESS) facility being built by the Puerto Rico Electric Power Authority (PREPA). Efforts were made to duplicate, on a smaller scale, the arrangement of the flooded lead-acid cells in the BESS and to generate ambient temperatures typical of Puerto Rico through use of an environmental chamber. A utility energy storage (UES) test cycle for the 12-cell series string was set up based on projected operating parameters scaled from the BESS for frequency regulation and spinning reserve operating modes. Battery temperatures were measured during UES cycling and fit to a thermal model for the system. Cell temperatures increased slowly over a week-long utility cycle and eventually were elevated by 13{degrees}C (23{degrees}F) in the most extreme case observed to date. Temperature increases are expected to be lower in the BESS facility due to a much higher air flow rate than in the test chamber.

  7. Population dynamics, synchrony, and environmental quality of Hokkaido voles lead to temporal and spatial Taylor's laws.

    PubMed

    Cohen, Joel E; Saitoh, Takashi

    2016-12-01

    Taylor's law (TL) asserts that the variance in a species' population density is a power-law function of its mean population density: log(variance) = a + b × log(mean). TL is widely verified. We show here that empirical time series of density of the Hokkaido gray-sided vole, Myodes rufocanus, sampled 1962-1992 at 85 locations, satisfied temporal and spatial forms of TL. The slopes (b ± standard error) of the temporal and spatial TL were estimated to be 1.613 ± 0.141 and 1.430 ± 0.132, respectively. A previously verified autoregressive Gompertz model of the dynamics of these populations generated time series of density which reproduced the form of temporal and spatial TLs, but with slopes that were significantly steeper than the slopes estimated from data. The density-dependent components of the Gompertz model were essential for the temporal TL. Adding to the Gompertz model assumptions that populations with higher mean density have reduced variance of density-independent perturbations and that density-independent perturbations are spatially correlated among populations yielded simulated time series that satisfactorily reproduced the slopes from data. The slopes (b ± standard error) of the enhanced simulations were 1.619 ± 0.199 for temporal TL and 1.575 ± 0.204 for spatial TL. © 2016 by the Ecological Society of America.

  8. Dexamethasone Treatment Leads to Enhanced Fear Extinction and Dynamic Fkbp5 Regulation in Amygdala.

    PubMed

    Sawamura, Takehito; Klengel, Torsten; Armario, Antonio; Jovanovic, Tanja; Norrholm, Seth D; Ressler, Kerry J; Andero, Raül

    2016-02-01

    Posttraumatic stress disorder (PTSD) is both a prevalent and debilitating trauma-related disorder associated with dysregulated fear learning at the core of many of its signs and symptoms. Improvements in the currently available psychological and pharmacological treatments are needed in order to improve PTSD treatment outcomes and to prevent symptom relapse. In the present study, we used a putative animal model of PTSD that included presentation of immobilization stress (IMO) followed by fear conditioning (FC) a week later. We then investigated the acute effects of GR receptor activation on the extinction (EXT) of conditioned freezing, using dexamethasone administered systemically which is known to result in suppression of the HPA axis. In our previous work, IMO followed by tone-shock-mediated FC was associated with impaired fear EXT. In this study, we administered dexamethasone 4 h before EXT training and then examined EXT retention (RET) 24 h later to determine whether dexamethasone suppression rescued EXT deficits. Dexamethasone treatment produced dose-dependent enhancement of both EXT and RET. Dexamethasone was also associated with reduced amygdala Fkbp5 mRNA expression following EXT and after RET. Moreover, DNA methylation of the Fkbp5 gene occurred in a dose-dependent and time course-dependent manner within the amygdala. Additionally, we found dynamic changes in epigenetic regulation, including Dnmt and Tet gene pathways, as a function of both fear EXT and dexamethasone suppression of the HPA axis. Together, these data suggest that dexamethasone may serve to enhance EXT by altering Fkbp5-mediated glucocorticoid sensitivity via epigenetic regulation of Fkbp5 expression.

  9. Poverty alleviation strategies in eastern China lead to critical ecological dynamics.

    PubMed

    Zhang, Ke; Dearing, John A; Dawson, Terence P; Dong, Xuhui; Yang, Xiangdong; Zhang, Weiguo

    2015-02-15

    Poverty alleviation linked to agricultural intensification has been achieved in many regions but there is often only limited understanding of the impacts on ecological dynamics. A central need is to observe long term changes in regulating and supporting services as the basis for assessing the likelihood of sustainable agriculture or ecological collapse. We show how the analyses of 55 time-series of social, economic and ecological conditions can provide an evolutionary perspective for the modern Lower Yangtze River Basin region since the 1950s with powerful insights about the sustainability of modern ecosystem services. Increasing trends in provisioning ecosystem services within the region over the past 60 years reflect economic growth and successful poverty alleviation but are paralleled by steep losses in a range of regulating ecosystem services mainly since the 1980s. Increasing connectedness across the social and ecological domains after 1985 points to a greater uniformity in the drivers of the rural economy. Regime shifts and heightened levels of variability since the 1970s in local ecosystem services indicate progressive loss of resilience across the region. Of special concern are water quality services that have already passed critical transitions in several areas. Viewed collectively, our results suggest that the regional social-ecological system passed a tipping point in the late 1970s and is now in a transient phase heading towards a new steady state. However, the long-term relationship between economic growth and ecological degradation shows no sign of decoupling as demanded by the need to reverse an unsustainable trajectory. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Dexamethasone Treatment Leads to Enhanced Fear Extinction and Dynamic Fkbp5 Regulation in Amygdala

    PubMed Central

    Sawamura, Takehito; Klengel, Torsten; Armario, Antonio; Jovanovic, Tanja; Norrholm, Seth D; Ressler, Kerry J; Andero, Raül

    2016-01-01

    Posttraumatic stress disorder (PTSD) is both a prevalent and debilitating trauma-related disorder associated with dysregulated fear learning at the core of many of its signs and symptoms. Improvements in the currently available psychological and pharmacological treatments are needed in order to improve PTSD treatment outcomes and to prevent symptom relapse. In the present study, we used a putative animal model of PTSD that included presentation of immobilization stress (IMO) followed by fear conditioning (FC) a week later. We then investigated the acute effects of GR receptor activation on the extinction (EXT) of conditioned freezing, using dexamethasone administered systemically which is known to result in suppression of the HPA axis. In our previous work, IMO followed by tone-shock-mediated FC was associated with impaired fear EXT. In this study, we administered dexamethasone 4 h before EXT training and then examined EXT retention (RET) 24 h later to determine whether dexamethasone suppression rescued EXT deficits. Dexamethasone treatment produced dose-dependent enhancement of both EXT and RET. Dexamethasone was also associated with reduced amygdala Fkbp5 mRNA expression following EXT and after RET. Moreover, DNA methylation of the Fkbp5 gene occurred in a dose-dependent and time course-dependent manner within the amygdala. Additionally, we found dynamic changes in epigenetic regulation, including Dnmt and Tet gene pathways, as a function of both fear EXT and dexamethasone suppression of the HPA axis. Together, these data suggest that dexamethasone may serve to enhance EXT by altering Fkbp5-mediated glucocorticoid sensitivity via epigenetic regulation of Fkbp5 expression. PMID:26174596

  11. Study of ion beam transport from the SECRAL electron cyclotron resonance ion source at the Institute of Modern Physics.

    PubMed

    Cao, Y; Lu, W; Zhang, W H; Sha, S; Yang, Y; Ma, B H; Wang, H; Zhu, Y H; Guo, J W; Fang, X; Lin, S H; Li, X X; Feng, Y C; Li, J Y; Zhao, H Y; Ma, H Y; Zhang, X Z; Guo, X H; Wu, Q; Sun, L T; Zhao, H W; Xie, D Z

    2012-02-01

    Ion beam transport from the Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou (SECRAL) electron cyclotron resonance ion source was studied at the Institute of Modern Physics during 2010. Particle-in-cell simulations and experimental results have shown that both space charge and magnetic aberrations lead to a larger beam envelope and emittance growth. In the existing SECRAL extraction beam line, it has been shown that raising the solenoid lens magnetic field reduces aberrations in the subsequent dipole and results in lower emittance. Detailed beam emittance measurements are presented in this paper.

  12. cAMP-induced Epac-Rap activation inhibits epithelial cell migration by modulating focal adhesion and leading edge dynamics.

    PubMed

    Lyle, Karen S; Raaijmakers, Judith H; Bruinsma, Wytse; Bos, Johannes L; de Rooij, Johan

    2008-06-01

    Epithelial cell migration is a complex process crucial for embryonic development, wound healing and tumor metastasis. It depends on alterations in cell-cell adhesion and integrin-extracellular matrix interactions and on actomyosin-driven, polarized leading edge protrusion. The small GTPase Rap is a known regulator of integrins and cadherins that has also been implicated in the regulation of actin and myosin, but a direct role in cell migration has not been investigated. Here, we report that activation of endogenous Rap by cAMP results in an inhibition of HGF- and TGFbeta-induced epithelial cell migration in several model systems, irrespective of the presence of E-cadherin adhesion. We show that Rap activation slows the dynamics of focal adhesions and inhibits polarized membrane protrusion. Importantly, forced integrin activation by antibodies does not mimic these effects of Rap on cell motility, even though it does mimic Rap effects in short-term cell adhesion assays. From these results, we conclude that Rap inhibits epithelial cell migration, by modulating focal adhesion dynamics and leading edge activity. This extends beyond the effect of integrin affinity modulation and argues for an additional function of Rap in controlling the migration machinery of epithelial cells.

  13. Detecting early-warning signals of type 1 diabetes and its leading biomolecular networks by dynamical network biomarkers

    PubMed Central

    2013-01-01

    Background Type 1 diabetes (T1D) is a complex disease and harmful to human health, and most of the existing biomarkers are mainly to measure the disease phenotype after the disease onset (or drastic deterioration). Until now, there is no effective biomarker which can predict the upcoming disease (or pre-disease state) before disease onset or disease deterioration. Further, the detail molecular mechanism for such deterioration of the disease, e.g., driver genes or causal network of the disease, is still unclear. Methods In this study, we detected early-warning signals of T1D and its leading biomolecular networks based on serial gene expression profiles of NOD (non-obese diabetic) mice by identifying a new type of biomarker, i.e., dynamical network biomarker (DNB) which forms a specific module for marking the time period just before the drastic deterioration of T1D. Results Two dynamical network biomarkers were obtained to signal the emergence of two critical deteriorations for the disease, and could be used to predict the upcoming sudden changes during the disease progression. We found that the two critical transitions led to peri-insulitis and hyperglycemia in NOD mices, which are consistent with other independent experimental results from literature. Conclusions The identified dynamical network biomarkers can be used to detect the early-warning signals of T1D and predict upcoming disease onset before the drastic deterioration. In addition, we also demonstrated that the leading biomolecular networks are causally related to the initiation and progression of T1D, and provided the biological insight into the molecular mechanism of T1D. Experimental data from literature and functional analysis on DNBs validated the computational results. PMID:23819540

  14. Status of the Cyclotron Institute Upgrade Project

    NASA Astrophysics Data System (ADS)

    Melconian, Dan

    2016-09-01

    The Texas A&M University Re-accelerated EXotics (T-REX) project, an upgrade to the Cyclotron Institute, will provide high-quality re-accelerated secondary beams of a unique energy range and the ability to provide primary beams to two experiments concurrently. The upgrade is nearing completion of its three major tasks: re-commissioning of the existing K150 cyclotron; construction of light- and heavy-ion guide transport systems; and charge-boosting the K150 RIB for re-acceleration using the K500 cyclotron. The light-ion guide transport system will utilize the high intensity (>= 10 μ A) proton beam from the K150 to produce rare ions via fusion-evapouration reactions or proton-induced fission fragments. These ions will be transported to an ECR charge breeder prior to injection in the K500. The heavy-ion guide will use deep inelastic, transfer and fragmentation reactions using the up to 25 MeV/u primary beams from the K150. The products will be separated by a superconducting solenoid and collected in a large gas-catcher, after which a multi-RFQ system will transport the RIB to any of: the charge-breeder and K500; the TAMU Penning Trap beamline; or an MR-TOF for beam analysis. The status of the T-REX upgrade and an overview of its capabilities will be presented Supported by DOE Grant Number DE-FG03-93ER40773 and the Robert A. Welch Foundation Grant Number H-A-0098.

  15. Phase field simulation of domain switching dynamics in multiaxial lead zirconate titanate thin films

    NASA Astrophysics Data System (ADS)

    Britson, Jason

    The defining characteristic of ferroelectric materials is their ability to be switched between energetically equivalent polarization states. This behavior has led to an interest in ferroelectrics for a wide range of bulk and thin film applications such as mechanical actuators and ferroelectric random access memory devices. Ferroelectric switching depends on domain wall motion, however, and is critically influenced by the existence of defects such as dislocations and preexisting domains. Domain wall motion in thin film applications can be controlled by individual local defects due to the reduced length scale of the system. This dissertation describes the impact of preexisting ferroelastic domains and misfits dislocations in coherent (001)-oriented Pb(Zr0.2,Ti0.8)O3 (PZT) thin films on the switching response and domain structure. A phase field model based on the Landau-Ginzburg-Devonshire theory that accounts for the electrostatic and mechanical interactions is used to describe domain structures in ferroelectric PZT thin films. To solve the governing equations a semi-implicit Fourier-Spectral scheme is developed that accommodates boundary conditions appropriate to the thin film geometry. Errors are reduced in the solutions at the film edges through extensions to the model developed to correct the Fourier transform around stationary discontinuities at the thin film edges. This correction is shown to result in increased accuracy of the phase field model needed to appropriately describe dynamic switching responses in the thin film. Investigation of switching around preexisting ferroelastic domains showed these defects are strong obstacles to switching in PZT thin films. Directly above the ferroelastic domain the magnitude of the required nucleation bias underneath a tip-like electrode was found to be elevated compared to the required bias far from the domain. Locally both the piezoelectric and dielectric responses of the thin film were found to be suppressed, which is

  16. The Mechanisms of Particle Kinetics and Dynamics Leading to Seismic Emission and Sunquakes

    NASA Astrophysics Data System (ADS)

    Zharkova, V. V.

    2008-09-01

    In this paper the mechanisms responsible for observational features associated with sunquakes induced by different classes of solar flares are compared. The role of high-energy particle beams via Coulomb and Ohmic heating of the ambient plasma and nonthermal excitation and ionization is explored for different beam parameters at various atmospheric depths. On the one hand, only hard electron beams with high-energy fluxes are found producing extensive nonthermal hydrogen ionization, four orders of magnitude higher than in the quiet atmosphere. This excess ionization leads to the white-light flares associated with the seismic emission appearing simultaneously with hard X-ray emission and, consequently, to a strong increase of Ni-line emission observed as the seismic emission measured with the holographic technique. On the other hand, the ambient plasma hydrodynamic response to heating by such beam electrons forms hydrodynamic shocks just below the transition region, in the upper chromosphere, and they travel with supersonic velocity for up to five minutes before reaching the photosphere. These hydrodynamic responses caused by the beam electrons are maximized in the lower chromosphere for moderate electron beams because of their smaller Ohmic losses in the upper atmosphere compared to those for higher-energy electron beams whose bulk energy is deposited in the transition region. These shocks caused by electron beams can explain the observations of seismic emission by time distance (TD) diagrams and the holographic method in M- and C-class flares, whereas to account for the quakes in X-class flares, high-energy quasi-thermal protons or power-law proton beams either by themselves or blended with electron beams are the most likely agents. Nonthermal ionization and excitation of lower atmospheric levels during the beam injection followed by thermo-conductive heating after the beam is stopped can contribute to the seismic signatures observed with the holographic technique

  17. Electron cyclotron emission diagnostics on KSTAR tokamak

    SciTech Connect

    Jeong, S. H.; Lee, K. D.; Kwon, M.; Kogi, Y.; Kawahata, K.; Nagayama, Y.; Mase, A.

    2010-10-15

    A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110-162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.

  18. Initial Operation of CIAE medically used cyclotron

    NASA Astrophysics Data System (ADS)

    Fan, Mingwu; Zhang, Tainjue

    1997-05-01

    CIAE medically used cyclotron is a 30 MeV fixed, isochronous field and fixed RF frequency machine with high -H beam intensity. -H beams with energy variable were obtained in December 1994 up to 0.4 mA. Two years operation has proved the design and manufacture successfully. The mapping results of magnetic field has shown the magnet perfect that would ensure the high intensity beam accelerated to the final energy. Now 7 medically useful isotopes were produced, e. g. thallium-201, cobalt-57, gallium-67, iodine-123 have been supplied for hospitals.

  19. Electron Cyclotron Heating on DIII-D

    SciTech Connect

    Prater, R.; Petty, C.C.

    2005-10-15

    Electron cyclotron heating (ECH) has proved to be a very flexible system for heating applications in DIII-D. The outstanding characteristics of ECH - controllable heating location, a high degree of localization of the power, ability to heat without introducing particles, and ability to heat only the electron fluid - have been used in a wide variety of experiments to study wave physics and transport, to control magnetohydrodynamic activity, and to improve discharges. These characteristics along with relatively easy coupling to the plasma make ECH a valuable resource for both heating and instability control in burning plasmas.

  20. [Electron cyclotron resonance (ECR) plasma film deposition

    SciTech Connect

    1999-04-01

    During the third quarter of 1995, an electron cyclotron resonance (ECR) plasma film deposition facility was constructed at the University of New Mexico. This work was conducted in support of the Los Alamos/Tycom CRADA agreement to pursue methods of improving drill bit lifetime. Work in the fourth quarter will center on the coating of drill bits and the treating and testing of various test samples. New material systems as well as treatment techniques will be attempted during this period. The following is a brief description of the various subsystems of the film deposition facility. Particular emphasis is placed on the slotted waveguide system as requested.

  1. Electron cyclotron heating in TMX-Upgrade

    SciTech Connect

    Stallard, B.W.; Hooper, E.B. Jr.

    1981-01-01

    TMX-Upgrade, an improved tandem mirror experiment under construction at LLNL, will use electron cyclotron resonance heating (ECRH) to create thermal barriers and to increase the center cell ion confining potential. Gyrotron oscillators (200 kW, 28 GHz) supply the heating power for the potential confined electron (fundamental heating) and the mirror-confined electrons (harmonic heating) in the thermal barriers. Important issues are temperature limitation and microstability for the hot electrons. Off-midplane heating can control anisotropy-driven microstability. Spacially restricting heating offers the possibility of temperature control by limiting the energy for resonant interaction.

  2. Method of enhancing cyclotron beam intensity

    DOEpatents

    Hudson, Ed D.; Mallory, Merrit L.

    1977-01-01

    When an easily ionized support gas such as xenon is added to the cold cathode in sources of the Oak Ridge Isochronous Cyclotron, large beam enhancements are produced. For example, .sup.20 Ne.sup.7+ is increased from 0.05 enA to 27 enA, and .sup.16 O.sup.5+ intensities in excess of 35 e.mu.A have been extracted for periods up to 30 minutes. Approximately 0.15 cc/min of the easily ionized support gas is supplied to the ion source through a separate gas feed line and the primary gas flow is reduced by about 30%.

  3. Cavity QED of the graphene cyclotron transition.

    PubMed

    Hagenmüller, David; Ciuti, Cristiano

    2012-12-28

    We investigate theoretically the cavity quantum electrodynamics of the cyclotron transition for Dirac fermions in graphene. We show that the ultrastrong coupling regime characterized by a vacuum Rabi frequency comparable or even larger than the transition frequency can be obtained for high enough filling factors of the graphene Landau levels. Important qualitative differences occur with respect to the corresponding physics of massive electrons in a semiconductor quantum well. In particular, an instability for the ground state analogous to the one occurring in the Dicke model is predicted for an increasing value of the electron density.

  4. Van Allen Probes observations of oxygen cyclotron harmonic waves in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Usanova, M.; Malaspina, D.; Jaynes, A. N.; Bruder, R.; Mann, I. R.; Wygant, J. R.; Ergun, R.

    2016-12-01

    Waves with frequencies in the vicinity of the oxygen cyclotron frequency and its harmonics have been regularly observed on the Van Allen Probes satellites during geomagnetic storms. We focus on properties of these waves and present events from the main phase of two storms on November 1, 2012 and March 17, 2013 and associated dropouts of few MeV electron fluxes. They are electromagnetic, in the frequency range 0.5 - several Hz, and amplitude 0.1- a few nT in magnetic and 0.1- a few mV/m in electric field, with both the wave velocity and the Poynting vector directed almost parallel to the background magnetic field. These properties are very similar to those of electromagnetic ion cyclotron (EMIC) waves, which are believed to contribute to loss of ring current ions and radiation belt electrons and therefore can be also important for inner magnetosphere dynamics.

  5. Van Allen Probes observations of oxygen cyclotron harmonic waves in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Usanova, M. E.; Malaspina, D. M.; Jaynes, A. N.; Bruder, R. J.; Mann, I. R.; Wygant, J. R.; Ergun, R. E.

    2016-09-01

    Waves with frequencies in the vicinity of the oxygen cyclotron frequency and its harmonics have been regularly observed on the Van Allen Probes satellites during geomagnetic storms. We focus on properties of these waves and present events from the main phase of two storms on 1 November 2012 and 17 March 2013 and associated dropouts of a few MeV electron fluxes. They are electromagnetic, in the frequency range ~0.5 to several Hz, and amplitude ~0.1 to a few nT in magnetic and ~0.1 to a few mV/m in electric field, with both the wave velocity and the Poynting vector directed almost parallel to the background magnetic field. These properties are very similar to those of electromagnetic ion cyclotron waves, which are believed to contribute to loss of ring current ions and radiation belt electrons and therefore can be also important for inner magnetosphere dynamics.

  6. Cyclotrons and FFAG Accelerators as Drivers for ADS

    DOE PAGES

    Calabretta, Luciano; Méot, François

    2015-01-01

    Our review summarizes projects and studies on circular accelerators proposed for driving subcritical reactors. The early isochronous cyclotron cascades, proposed about 20 years ago, and the evolution of these layouts up to the most recent solutions or designs based on cyclotrons and fixed field alternating gradient accelerators, are reported. Additionally, the newest ideas and their prospects for development are discussed.

  7. Cyclotrons and FFAG Accelerators as Drivers for ADS

    SciTech Connect

    Calabretta, Luciano; Méot, François

    2015-01-01

    Our review summarizes projects and studies on circular accelerators proposed for driving subcritical reactors. The early isochronous cyclotron cascades, proposed about 20 years ago, and the evolution of these layouts up to the most recent solutions or designs based on cyclotrons and fixed field alternating gradient accelerators, are reported. Additionally, the newest ideas and their prospects for development are discussed.

  8. New superconducting cyclotron driven scanning proton therapy systems

    NASA Astrophysics Data System (ADS)

    Klein, Hans-Udo; Baumgarten, Christian; Geisler, Andreas; Heese, Jürgen; Hobl, Achim; Krischel, Detlef; Schillo, Michael; Schmidt, Stefan; Timmer, Jan

    2005-12-01

    Since one and a half decades ACCEL is investing in development and engineering of state of the art particle-therapy systems. A new medical superconducting 250 MeV proton cyclotron with special focus on the present and future beam requirements of fast scanning treatment systems has been designed. The first new ACCEL medical proton cyclotron is under commissioning at PSI for their PROSCAN proton therapy facility having undergone successful factory tests especially of the closed loop cryomagnetic system. The second cyclotron is part of ACCEL's integrated proton therapy system for Europe's first clinical center, RPTC in Munich. The cyclotron, the energy selection system, the beamline as well as the four gantries and patient positioners have been installed. The scanning system and major parts of the control software have already been tested. We will report on the concept of ACCEL's superconducting cyclotron driven scanning proton therapy systems and the current status of the commissioning work at PSI and RPTC.

  9. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Technical Reports Server (NTRS)

    Singh, N.; Schunk, R. W.; Sojka, J. J.

    1982-01-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  10. Ion cyclotron emission studies: Retrospects and prospects

    NASA Astrophysics Data System (ADS)

    Gorelenkov, N. N.

    2016-05-01

    Ion cyclotron emission (ICE) studies emerged in part from the papers by A.B. Mikhailovskii published in the 1970s. Among the discussed subjects were electromagnetic compressional Alfvénic cyclotron instabilities with the linear growth rate √ {n_α /n_e } driven by fusion products, -particles which draw a lot of attention to energetic particle physics. The theory of ICE excited by energetic particles was significantly advanced at the end of the 20th century motivated by first DT experiments on TFTR and subsequent JET experimental studies which we highlight. More recently ICE theory was advanced by detailed theoretical and experimental studies on spherical torus (ST) fusion devices where the instability signals previously indistinguishable in high aspect ratio tokamaks due to high toroidal magnetic field became the subjects of experiments. We discuss further prospects of ICE theory applications for future burning plasma (BP) experiments such as those to be conducted in ITER device in France, where neutron and gamma rays escaping the plasma create extremely challenging conditions fusion alpha particle diagnostics.

  11. Ion cyclotron emission studies: Retrospects and prospects

    SciTech Connect

    Gorelenkov, N. N.

    2016-06-05

    Ion cyclotron emission (ICE) studies emerged in part from the papers by A.B. Mikhailovskii published in the 1970s. Among the discussed subjects were electromagnetic compressional Alfv,nic cyclotron instabilities with the linear growth rate similar ~ √(nα/ne) driven by fusion products, -particles which draw a lot of attention to energetic particle physics. The theory of ICE excited by energetic particles was significantly advanced at the end of the 20th century motivated by first DT experiments on TFTR and subsequent JET experimental studies which we highlight. Recently ICE theory was advanced by detailed theoretical and experimental studies on spherical torus (ST) fusion devices where the instability signals previously indistinguishable in high aspect ratio tokamaks due to high toroidal magnetic field became the subjects of experiments. Finally, we discuss prospects of ICE theory applications for future burning plasma (BP) experiments such as those to be conducted in ITER device in France, where neutron and gamma rays escaping the plasma create extremely challenging conditions fusion alpha particle diagnostics.

  12. Ion cyclotron emission studies: Retrospects and prospects

    SciTech Connect

    Gorelenkov, N. N.

    2016-06-05

    Ion cyclotron emission (ICE) studies emerged in part from the papers by A.B. Mikhailovskii published in the 1970s. Among the discussed subjects were electromagnetic compressional Alfv,nic cyclotron instabilities with the linear growth rate similar ~ √(nα/ne) driven by fusion products, -particles which draw a lot of attention to energetic particle physics. The theory of ICE excited by energetic particles was significantly advanced at the end of the 20th century motivated by first DT experiments on TFTR and subsequent JET experimental studies which we highlight. Recently ICE theory was advanced by detailed theoretical and experimental studies on spherical torus (ST) fusion devices where the instability signals previously indistinguishable in high aspect ratio tokamaks due to high toroidal magnetic field became the subjects of experiments. Finally, we discuss prospects of ICE theory applications for future burning plasma (BP) experiments such as those to be conducted in ITER device in France, where neutron and gamma rays escaping the plasma create extremely challenging conditions fusion alpha particle diagnostics.

  13. Ion cyclotron emission studies: Retrospects and prospects

    DOE PAGES

    Gorelenkov, N. N.

    2016-06-05

    Ion cyclotron emission (ICE) studies emerged in part from the papers by A.B. Mikhailovskii published in the 1970s. Among the discussed subjects were electromagnetic compressional Alfv,nic cyclotron instabilities with the linear growth rate similar ~ √(nα/ne) driven by fusion products, -particles which draw a lot of attention to energetic particle physics. The theory of ICE excited by energetic particles was significantly advanced at the end of the 20th century motivated by first DT experiments on TFTR and subsequent JET experimental studies which we highlight. Recently ICE theory was advanced by detailed theoretical and experimental studies on spherical torus (ST) fusionmore » devices where the instability signals previously indistinguishable in high aspect ratio tokamaks due to high toroidal magnetic field became the subjects of experiments. Finally, we discuss prospects of ICE theory applications for future burning plasma (BP) experiments such as those to be conducted in ITER device in France, where neutron and gamma rays escaping the plasma create extremely challenging conditions fusion alpha particle diagnostics.« less

  14. Ion Cyclotron Waves in the VASIMR

    NASA Astrophysics Data System (ADS)

    Brukardt, M. S.; Bering, E. A.; Chang-Diaz, F. R.; Squire, J. P.; Longmier, B.

    2008-12-01

    The Variable Specific Impulse Magnetoplasma Rocket is an electric propulsion system under development at Ad Astra Rocket Company that utilizes several processes of ion acceleration and heating that occur in the Birkeland currents of an auroral arc system. Among these processes are parallel electric field acceleration, lower hybrid resonance heating, and ion cyclotron resonance heating. The VASIMR is capable of laboratory simulation of electromagnetic ion cyclotron wave heating during a single pass of the plasma through the resonance region. The plasma is generated by a helicon discharge of about 25 kW then passes through an RF booster stage that shoots left hand polarized slow mode waves from the high field side of the resonance. This paper will focus on the upgrades to the VX-200 test model over the last year. After summarizing the VX- 50 and VX-100 results, the new data from the VX-200 model will be presented. Lastly, the changes to the VASIMR experiment due to Ad Astra Rocket Company's new facility in Webster, Texas will also be discussed, including the possibility of collaborative experiments at the new facility.

  15. Loss cone-driven cyclotron maser instability

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Yi, Sibaek; Lim, Dayeh; Kim, Hee-Eun; Seough, Jungjoon; Yoon, Peter H.

    2013-11-01

    The weakly (or mildly) relativistic cyclotron maser instability has been successfully applied to explain the Earth's auroral kilometric radiation and other radio sources in nature and laboratory. Among the most important physical parameters that determine the instability criteria is the ratio of plasma-to-electron cyclotron frequencies, ωp/Ω. It is therefore instructive to consider how the normalized maximum growth rate, γmax/Ω, varies as a function of ωp/Ω. Although many authors have already discussed this problem, in order to complete the analysis, one must also understand how the radiation emission angle corresponding to the maximum growth, θmax, scales with ωp/Ω, since the propagation angle determines the radiation beaming pattern. Also, the behavior of the frequency corresponding to the maximum growth rate at each harmonic, (ωmax-sΩ)/Ω, where s=1,2,3,ċ , as a function of ωp/Ωis of importance for a complete understanding of the maser excitation. The present paper computes these additional quantities for the first time, making use of a model loss cone electron distribution function.

  16. Electrostatic ion cyclotron velocity shear instability

    SciTech Connect

    Lemons, D.S.; Winske, D.; Gary, S.P. )

    1992-12-01

    An electrostatic ion cyclotron instability driven by sheared velocity flow perpendicular to a uniform magnetic field is investigated in the local approximation. The dispersion equation, which includes all kinetic effects and involves only one important parameter, is cast in the form of Gordeyev integrals and solved numerically. The instability occurs roughly at multiples of the ion cyclotron frequency (but modified by the shear) with the growth rate of the individual harmonics overlapping in wavenumber. At small values of the shear parameter, the instability exists in two branches, one at long wavelength, [kappa][rho][sub i] [approximately] 0.5, and one at short wavelength, [kappa][rho][sub i] > 1.5 ([kappa][rho][sub i] is the wavenumber normalized to the ion gyroradius). At larger values of the shear parameter only the longer wavelength branch persists. The growth rate of the long wavelength mode, maximized over wavenumber and frequency, increases monotonically with the shear parameter. Properties of the instability are compared to those of Ganguli et al. obtained in the nonlocal limit.

  17. Nonlinear sub-cyclotron resonance as a formation mechanism for gaps in banded chorus

    SciTech Connect

    Fu, Xiangrong; Guo, Zehua; Dong, Chuanfei; Gary, S. Peter

    2015-05-14

    An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at ω ≃ 0.5Ωe, where Ωe is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near 0.3Ωe and 0.6Ωe. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency can resonate with electrons, leading to effective energy exchange between the wave and particles.

  18. Stability of drift-cyclotron loss-cone waves in H-mode plasmas

    SciTech Connect

    Farmer, W. A.; Morales, G. J.

    2016-05-24

    The drift-cyclotron loss-cone mode was first studied in mirror machines. In such devices, particles with small pitch angles are not confined, creating a hole in the velocity distribution function that is a source of free energy and leads to micro-instabilities in the cyclotron-range of frequencies. In the edge region of tokamak devices operating under H-mode conditions, ion loss also occurs. In this case, gradient drift carries ions moving opposite to the plasma current preferentially into the divertor, creating a one-sided loss cone. A simple analysis shows that for the quiescent H-mode plasmas in DIII-D the critical gradient for instability is exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3×107 s-1.

  19. The surface-state of the topological insulator Bi2Se3 revealed by cyclotron resonance

    SciTech Connect

    Mcdonald, Ross D; Ayala - Valenzuela, Oscar E; Altarawneh, Moaz M; Analytis, James G

    2011-01-14

    Transport measurements of topological insulators are dominated by the conductivity of the bulk, leading to substantial difficulties in resolving the properties of the surface. To this end, we use high magnetic field, rf- and microwave-spectroscopy to selectively couple to the surface conductivity of Bi2Se3 at high frequency. In the frequency range of a few GHz we observe a crossover from quantum oscillations indicative of a small 3D Fermi surface, to cyclotron resonance indicative of a 2D surface state. By probing the conductivity at reduced skin depths, we have observed a 2D cyclotron resonance from a material whose bulk Fermi-surface is 3D. The frequency-magnetic field scaling of this resonance is inconsistent with the bulk effective mass, but more consistent with the dispersion and band filling of a Dirac-like surface state as observed by ARPES, with substantial manybody renormalization.

  20. Electrostatic ion-cyclotron waves in magnetospheric plasmas: non-local aspects. Memorandum report

    SciTech Connect

    Ganguli, G.; Bakshi, P.; Palmadesso, P.

    1983-10-14

    The importance of the effect of the magnetic shear and the finite size of current channel on the electrostatic ion-cyclotron instability for the space plasmas is illustrated. A non-local treatment is used. When the channel width Lc, is larger than the shear length Ls, there is a large reduction in the growth rate along with a noteworthy reduction of the band of the unstable perpendicular wavelengths. For Lc < or = Ls/10 the growth rate is not much altered from its local value, however for Lc/pi i < or = 10 to the second power the growth rate starts falling below the local value and vanishes for Lc pi i. The non-local effects lead to enhanced coherence in the ion cyclotron waves.

  1. Cyclotron production of Ga-68 for human use from liquid targets: From theory to practice

    NASA Astrophysics Data System (ADS)

    Alves, F.; Alves, V. H.; Neves, A. C. B.; do Carmo, S. J. C.; Nactergal, B.; Hellas, V.; Kral, E.; Gonçalves-Gameiro, C.; Abrunhosa, A. J.

    2017-05-01

    A fully automated system for the production of 68Ga based on commercially available cyclotron liquid target and synthesis modules is described. A solution containing enriched 68Zn dissolved in a nitric solution is irradiated in a Cyclone 18/9 IBA cyclotron leading to the production of up to about 25 GBq of 68Ga. The irradiated solution is transferred to a Synthera synthesis module in which 68Ga is separated and purified with a yield superior to 85 % and where further labelling is achieved with yields no inferior to 70 %. The developed and implemented method presents an improved approach for the production of 68Ga-radiopharmaceuticals suitable for human use, in a process that takes less than 2 hours. This technique represents an economically viable alternative to 68Ge/68Ga generators with improved characteristics.

  2. Electron-cyclotron wave scattering by edge density fluctuations in ITER

    SciTech Connect

    Tsironis, Christos; Peeters, Arthur G.; Isliker, Heinz; Chatziantonaki, Ioanna; Vlahos, Loukas; Strintzi, Dafni

    2009-11-15

    The effect of edge turbulence on the electron-cyclotron wave propagation in ITER is investigated with emphasis on wave scattering, beam broadening, and its influence on localized heating and current drive. A wave used for electron-cyclotron current drive (ECCD) must cross the edge of the plasma, where density fluctuations can be large enough to bring on wave scattering. The scattering angle due to the density fluctuations is small, but the beam propagates over a distance of several meters up to the resonance layer and even small angle scattering leads to a deviation of several centimeters at the deposition location. Since the localization of ECCD is crucial for the control of neoclassical tearing modes, this issue is of great importance to the ITER design. The wave scattering process is described on the basis of a Fokker-Planck equation, where the diffusion coefficient is calculated analytically as well as computed numerically using a ray tracing code.

  3. Stability of drift-cyclotron loss-cone waves in H-mode plasmas

    SciTech Connect

    Farmer, W. A.; Morales, G. J.

    2016-05-24

    The drift-cyclotron loss-cone mode was first studied in mirror machines. In such devices, particles with small pitch angles are not confined, creating a hole in the velocity distribution function that is a source of free energy and leads to micro-instabilities in the cyclotron-range of frequencies. In the edge region of tokamak devices operating under H-mode conditions, ion loss also occurs. In this case, gradient drift carries ions moving opposite to the plasma current preferentially into the divertor, creating a one-sided loss cone. A simple analysis shows that for the quiescent H-mode plasmas in DIII-D the critical gradient for instability is exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3×107 s-1.

  4. Stability of drift-cyclotron loss-cone waves in H-mode plasmas

    DOE PAGES

    Farmer, W. A.; Morales, G. J.

    2016-05-24

    The drift-cyclotron loss-cone mode was first studied in mirror machines. In such devices, particles with small pitch angles are not confined, creating a hole in the velocity distribution function that is a source of free energy and leads to micro-instabilities in the cyclotron-range of frequencies. In the edge region of tokamak devices operating under H-mode conditions, ion loss also occurs. In this case, gradient drift carries ions moving opposite to the plasma current preferentially into the divertor, creating a one-sided loss cone. A simple analysis shows that for the quiescent H-mode plasmas in DIII-D the critical gradient for instability ismore » exceeded within 2 cm of the separatrix, and the maximum growth rate at the separatrix is 3×107 s-1.« less

  5. Cyclotron Production of Technetium-99m

    NASA Astrophysics Data System (ADS)

    Gagnon, Katherine M.

    Technetium-99m (99mTc) has emerged as the most widely used radionuclide in medicine and is currently obtained from a 99Mo/ 99mTc generator system. At present, there are only a handful of ageing reactors worldwide capable of producing large quantities of the parent isotope, 99Mo, and owing to the ever growing shutdown periods for maintenance and repair of these ageing reactors, the reliable supply 99mTc has been compromised in recent years. With an interest in alternative strategies for producing this key medical isotope, this thesis focuses on several technical challenges related to the direct cyclotron production of 99mTc via the 100Mo(p,2n)99mTc reaction. In addition to evaluating the 100Mo(p,2n)99mTc and 100Mo(p,x)99Mo reactions, this work presented the first experimental evaluation of the 100Mo(p,2n) 99gTc excitation function in the range of 8-18 MeV. Thick target calculations suggested that large quantities of cyclotron-produced 99mTc may be possible. For example, a 6 hr irradiation at 500 μA with an energy window of 18→10 MeV is expected to yield 1.15 TBq of 99mTc. The level of coproduced 99gTc contaminant was found to be on par with the current 99Mo/99mTc generator standard eluted with a 24 hr frequency. Highly enriched 100Mo was required as the target material for 99mTc production and a process for recycling of this expensive material is presented. An 87% recovery yield is reported, including metallic target preparation, irradiation, 99mTc extraction, molybdate isolation, and finally hydrogen reduction to the metal. Further improvements are expected with additional optimization experiments. A method for forming structurally stable metallic molybdenum targets has also been developed. These targets are capable of withstanding more than a kilowatt of beam power and the reliable production and extraction of Curie quantities of 99mTc has been demonstrated. With the end-goal of using the cyclotron-produced 99mTc clinically, the quality of the cyclotron

  6. Social dynamics within decomposer communities lead to nitrogen retention and organic matter build-up in soils.

    PubMed

    Kaiser, Christina; Franklin, Oskar; Richter, Andreas; Dieckmann, Ulf

    2015-12-01

    The chemical structure of organic matter has been shown to be only marginally important for its decomposability by microorganisms. The question of why organic matter does accumulate in the face of powerful microbial degraders is thus key for understanding terrestrial carbon and nitrogen cycling. Here we demonstrate, based on an individual-based microbial community model, that social dynamics among microbes producing extracellular enzymes ('decomposers') and microbes exploiting the catalytic activities of others ('cheaters') regulate organic matter turnover. We show that the presence of cheaters increases nitrogen retention and organic matter build-up by downregulating the ratio of extracellular enzymes to total microbial biomass, allowing nitrogen-rich microbial necromass to accumulate. Moreover, increasing catalytic efficiencies of enzymes are outbalanced by a strong negative feedback on enzyme producers, leading to less enzymes being produced at the community level. Our results thus reveal a possible control mechanism that may buffer soil CO2 emissions in a future climate.

  7. CMG–Pol epsilon dynamics suggests a mechanism for the establishment of leading-strand synthesis in the eukaryotic replisome

    PubMed Central

    Janska, Agnieszka; Goswami, Panchali; Renault, Ludovic; Abid Ali, Ferdos; Kotecha, Abhay; Costa, Alessandro

    2017-01-01

    The replisome unwinds and synthesizes DNA for genome duplication. In eukaryotes, the Cdc45–MCM–GINS (CMG) helicase and the leading-strand polymerase, Pol epsilon, form a stable assembly. The mechanism for coupling DNA unwinding with synthesis is starting to be elucidated, however the architecture and dynamics of the replication fork remain only partially understood, preventing a molecular understanding of chromosome replication. To address this issue, we conducted a systematic single-particle EM study on multiple permutations of the reconstituted CMG–Pol epsilon assembly. Pol epsilon contains two flexibly tethered lobes. The noncatalytic lobe is anchored to the motor of the helicase, whereas the polymerization domain extends toward the side of the helicase. We observe two alternate configurations of the DNA synthesis domain in the CMG-bound Pol epsilon. We propose that this conformational switch might control DNA template engagement and release, modulating replisome progression. PMID:28373564

  8. Ultrafast Transient Absorption Spectroscopy Investigation of Excited-State Dynamics of Methyl Ammonium Lead Bromide Perovskite Nanostructures

    NASA Astrophysics Data System (ADS)

    Jamhawi, Abdelqader; Telfah, Hamzeh; Teunis, Meghan B.; Sardar, Rajesh; Liu, Jinjun

    2017-06-01

    Metal halide perovskites are promising materials for light harvesting. Power conversion efficiency (PCE) of such materials can be improved by tuning the band gap energy and suppressing the trap states. In particular, quantum confinement and shape control of nanostructures are two effective approaches to enhance the photovoltaic properties. Here we report femtosecond transient absorption (TA) spectroscopy studies on the photo-induced dynamics of a series of different nanostructures of methyl ammonium lead bromide (MALB) CH_3NH_3PbBr_3: nanoplatelets (2D), nanowires (1D), nonoparticles (0D), and nanocubes (0D). Experimentally obtained TA spectra are simulated using a global model in both the time and wavelength domains. The fit values of center wavelengths and time constants for various processes demonstrate that dimensional and structural confinement affects not only band structure but also exciton dynamics: Sub-picosecond electron and hole relaxation (in the conduction and valence band, respectively) have been observed, while the exciton recombination process is on the timescale of hundreds of picoseconds. Comparison between TA spectra of different nanostructures suggest that the confinement effect plays a significant role in tuning band gaps and minimizing trap states, which can be utilized to improve the PCE of photovoltaic devices.

  9. How a Small Change in Retinal Leads to G-Protein Activation: Initial Events Suggested by Molecular Dynamics Calculations

    PubMed Central

    Crozier, Paul S.; Stevens, Mark J.; Woolf, Thomas B.

    2010-01-01

    Rhodopsin is the prototypical G-protein coupled receptor, coupling light activation with high efficiency to signaling molecules. The dark-state X-ray structures of the protein provide a starting point for consideration of the relaxation from initial light activation to conformational changes that may lead to signaling. In this study we create an energetically unstable retinal in the light activated state and then use molecular dynamics simulations to examine the types of compensation, relaxation, and conformational changes that occur following the cis–trans light activation. The results suggest that changes occur throughout the protein, with changes in the orientation of Helices 5 and 6, a closer interaction between Ala 169 on Helix 4 and retinal, and a shift in the Schiff base counterion that also reflects changes in sidechain interactions with the retinal. Taken together, the simulation is suggestive of the types of changes that lead from local conformational change to light-activated signaling in this prototypical system. PMID:17109408

  10. Electromagnetic ion cyclotron waves observed near the oxygen cyclotron frequency by ISEE 1 and 2

    NASA Technical Reports Server (NTRS)

    Fraser, B. J.; Samson, J. C.; Hu, Y. D.; Mcpherron, R. L.; Russell, C. T.

    1992-01-01

    The first results of observations of ion cyclotron waves by the elliptically orbiting ISEE 1 and 2 pair of spacecraft are reported. The most intense waves (8 nT) were observed in the outer plasmasphere where convection drift velocities were largest and the Alfven velocity was a minimum. Wave polarization is predominantly left-handed with propagation almost parallel to the ambient magnetic field, and the spectral slot and polarization reversal predicted by cold plasma propagation theory are identified in the wave data. Computations of the experimental wave spectra during the passage through the plasmapause show that the spectral slots relate to the local plasma parameters, possibly suggesting an ion cyclotron wave growth source near the spacecraft. A regular wave packet structure seen over the first 30 min of the event is attributed to the modulation of this energy source by the Pc 5 waves seen at the same time.

  11. Performance of Variable Energy Cyclotron Centre superconducting cyclotron liquid nitrogen distribution system

    NASA Astrophysics Data System (ADS)

    Pal, Gautam; Nandi, Chinmay; Bhattacharyya, Tamal Kumar; Chakrabarti, Alok

    2014-01-01

    The liquid nitrogen distribution at Variable Energy Cyclotron Centre, Kolkata, India K500 superconducting cyclotron uses parallel branches to cool the thermal shield of helium vessel housing the superconducting coil and the cryopanels. Liquid nitrogen is supplied to the thermal shields from a pressurised liquid nitrogen dewar. Direct measurement of flow is quite difficult and seldom used in an operational cryogenic system. The total flow and heat load of the liquid nitrogen system was estimated indirectly by continuous measurement of level in the liquid nitrogen tanks. A mathematical model was developed to evaluate liquid nitrogen flow in the parallel branches. The model was used to generate flow distribution for different settings and the total flow was compared with measured data.

  12. Cyclotrons and positron emission tomography radiopharmaceuticals for clinical imaging.

    PubMed

    Saha, G B; MacIntyre, W J; Go, R T

    1992-07-01

    Positron emission tomography (PET) requires positron-emitting radionuclides that emit 511-keV photons detectable by PET imagers. Positron-emitting radionuclides are commonly produced in charged particle accelerators, eg, linear accelerators or cyclotrons. The most widely available radiopharmaceuticals for PET imaging are carbon-11-, nitrogen-13-, and oxygen-15-labeled compounds, many of which, either in their normal state or incorporated in other compounds, serve as physiological tracers. Other useful PET radiopharmaceuticals include fluorine-18-, bromine-75-, gallium-68 (68Ga)-, rubidium-82 (82Rb)-, and copper-62 (62Cu)-labeled compounds. Many positron emitters have short half-lives and thus require on-site cyclotrons for application, and others (68Ga, 82Rb, and 62Cu) are available from radionuclides generators using relatively long-lived parent radionuclides. This review is divided into two sections: cyclotrons and PET radiopharmaceuticals for clinical imaging. In the cyclotron section, the principle of operation of the cyclotron, types of cyclotrons, medical cyclotrons, and production of radionuclides are discussed. In the section on PET radiopharmaceuticals, the synthesis and clinical use of PET radiopharmaceuticals are described.

  13. Electron Cloud Cyclotron Resonances in the Presence of a Short-bunch-length Relativistic Beam

    SciTech Connect

    Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Yu, Jennifer W.

    2008-09-02

    Computer simulations using the 2D code"POSINST" were used to study the formation of the electron cloud in the wiggler section of the positron damping ring of the International Linear Collider. In order to simulate an x-y slice of the wiggler (i.e., a slice perpendicular to the beam velocity), each simulation assumed a constant vertical magnetic field. At values of the magnetic field where the cyclotron frequency was an integral multiple of the bunch frequency, and where the field strength was less than approximately 0.6 T, equilibrium average electron densities were up to three times the density found at other neighboring field values. Effects of this resonance between the bunch and cyclotron frequency are expected to be non-negligible when the beam bunch length is much less than the product of the electron cyclotron period and the beam velocity, for a beam moving at v~;;c. Details of the dynamics of the resonance are described.

  14. Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations

    NASA Astrophysics Data System (ADS)

    Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr

    2016-08-01

    We present analysis of global three-dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single-species model with simplified neutral-plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self-consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate.

  15. Numerical simulation of ions acceleration and extraction in cyclotron DC-110

    NASA Astrophysics Data System (ADS)

    Samsonov, E. V.; Gikal, B. N.; Borisov, O. N.; Ivanenko, I. A.

    2014-03-01

    In Flerov's Laboratory of Nuclear Reactions of JINR in the framework of project "Beta" a cyclotron complex for a wide range of applied research in nanotechnology (track membranes, surface modification, etc.) is created. The complex includes a dedicated heavy-ion cyclotron DC-110, which yields intense beams of accelerated ions Ar, Kr and Xe with a fixed energy of 2.5 MeV/A. The cyclotron is equipped with external injection on the base of ECR ion source, a spiral inflector and the system of ions extraction consisting of an electrostatic deflector and a passive magnetic channel. The results of calculations of the beam dynamics in measured magnetic field from the exit of spiral inflector to correcting magnet located outside the accelerator vacuum chamber are presented. It is shown that the design parameters of ion beams at the entrance of correcting magnet will be obtained using false channel, which is a copy of the passive channel, located on the opposite side of the magnetic system. Extraction efficiency of ions will reach 75%.

  16. Progress in theory and simulation of ion cyclotron emission from magnetic confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Dendy, Richard; Chapman, Ben; Chapman, Sandra; Cook, James; Reman, Bernard; McClements, Ken; Carbajal, Leopoldo

    2016-10-01

    Suprathermal ion cyclotron emission (ICE) is detected from all large tokamak and stellarator plasmas. Its frequency spectrum has narrow peaks at sequential cyclotron harmonics of the energetic ion population (fusion-born or neutral beam-injected) at the outer edge of the plasma. ICE was the first collective radiative instability driven by confined fusion-born ions observed in deuterium-tritium plasmas in JET and TFTR, and the magnetoacoustic cyclotron instability is the most likely emission mechanism. Contemporary ICE measurements are taken at very high sampling rates from the LHD stellarator and from the conventional aspect ratio KSTAR tokamak. A correspondingly advanced modelling capability for the ICE emission mechanism has been developed using 1D3V PIC and hybrid-PIC codes, supplemented by analytical theory. These kinetic codes simulate the self-consistent full orbit dynamics of energetic and thermal ions, together with the electric and magnetic fields and the electrons. We report recent progress in theory and simulation that addresses: the scaling of ICE intensity with energetic particle density; the transition between super-Alfvénic and sub-Alfvénic regimes for the collectively radiating particles; and the rapid time evolution that is seen for some ICE measurements. This work was supported in part by the RCUK Energy Programme [Grant Number EP/I501045] and by Euratom.

  17. Study of the new return yoke for the upgraded Superconducting Cyclotron of INFN-LNS

    NASA Astrophysics Data System (ADS)

    Calanna, A.; Calabretta, L.; Rifuggiato, D.; Gallo, G.; Costa, G.; Allegra, L.; Russo, A. D.; D'Agostino, G.

    2017-07-01

    The LNS Superconducting Cyclotron (CS) has been working for 20 years making a wide range of ions and energies available. Many experiments are performed each year. In the near future a major upgrade is planned. This will allow to overcome the major limitation of the CS, which is the beam power delivered to the users, that at present does not exceed 100 W. In the new version of the CS, the extracted beam power will be increased up to a factor 100. This improvement will be reached extracting by stripping a specific set of light ions and energies extracted by stripping. Nevertheless, the extraction through the two electrostatic deflectors, providing a beam power limited to 100 W, will be also maintained to fulfil the users requests. The new design could strongly affect the beam dynamics. The iron yoke penetrations do not respect the three folds symmetry of our cyclotron and have a complex shape, due to the double extraction methods and all services entrances. This inhomogeneity produces unwanted field harmonics, which have to be reduced as much as possible to avoid beam precession or second order effects. Here the study accomplished to minimize the perturbation of the non- three fold field symmetry using the current sheet approximation (CSA) is presented, along with the state-of-art configuration of the updated cyclotron.

  18. EVIDENCE OF LANDAU AND CYCLOTRON RESONANCE BETWEEN PROTONS AND KINETIC WAVES IN SOLAR WIND TURBULENCE

    SciTech Connect

    He, Jiansen; Wang, Linghua; Tu, Chuanyi; Zong, Qiugang; Marsch, Eckart

    2015-02-20

    The wave–particle interaction processes occurring in the solar wind provide crucial information to understand the wave dissipation and simultaneous particle heating in plasma turbulence. One requires observations of both wave fluctuations and particle kinetics near the dissipation range, which have, however, not yet been analyzed simultaneously. Here we show new evidence of wave–particle interactions by combining the diagnosis of wave modes with the analysis of particle kinetics on the basis of measurements from the WIND spacecraft with a high cadence of about 3 s. Solar wind protons appear to be highly dynamic in their velocity distribution consisting of varying anisotropic core and beam components. The basic scenario of solar wind proton heating through wave–particle interaction is suggested to be the following. Left-handed cyclotron resonance occurs continuously, and is evident from the observed proton core velocity distribution and the concurrent quasi-parallel left-handed Alfvén cyclotron waves. Landau and right-handed cyclotron resonances are persistent and indicated by the observed drifting anisotropic beam and the simultaneous quasi-perpendicular right-handed kinetic Alfvén waves in a general sense. The persistence of non-gyrotropic proton distributions may cast new light on the nature of the interaction between particles and waves near and beyond the proton gyro-frequency.

  19. Electron Cyclotron Emission Diagnostics on ITER

    NASA Astrophysics Data System (ADS)

    Ellis, Richard; Austin, Max; Phillips, Perry; Rowan, William; Beno, Joseph; Auroua, Abelhamid; Feder, Russell; Patel, Ashish; Hubbard, Amanda; Pandya, Hitesh

    2010-11-01

    Electron cyclotron emission (ECE) will be employed on ITER to measure the radial profile of electron temperature and non thermal features of the electron distribution as well as measurements of ELMs, magnetic islands, high frequency instabilities, and turbulence. There are two quasioptical systems, designed with Gaussian beam analysis. One view is radial, primarily for temperature profile measurement, the other views at a small angle to radial for measuring non-thermal emission. Radiation is conducted to by a long corrugated waveguide to a multichannel Michelson interferometer which provides wide wavelength coverage but limited time response as well as two microwave radiometers which cover the fundamental and second harmonic ECE and provide excellent time response. Measurements will be made in both X and O mode. In-situ calibration is provided by a novel hot calibration source. We discuss spatial resolution and the implications for physics studies.

  20. Cyclotron maser using the anomalous Doppler effect

    NASA Astrophysics Data System (ADS)

    Didenko, A. N.; Borisov, A. R.; Fomenko, G. P.; Shlapakovskii, A. S.; Shtein, Iu. G.

    1983-11-01

    The operation of an anomalous-Doppler-effect cyclotron-resonance maser using a waveguide partially filled with dielectric as the slow-wave system is reported. The device investigated is similar to that of Didenko et al. (1983) and comprises a 300-mm-long 50-mm-o.d. 30-mm-i.d. waveguide with fabric-laminate dielectric, located 150 mm from the cathode in a 500-mm-long region of uniform 0-20-kG magnetic field, and a coaxial magnetic-insulation gun producing a 13-mm-i.d. 25-mm-o.d. hollow electron beam. Radiation at 12 + or - 1 mm wavelength and optimum power 20 MW is observed using hot-carrier detectors, with a clear peak in the power-versus-magnetic-field curve at about 6.4 kG.

  1. A simple electron cyclotron resonance ion sourcea)

    NASA Astrophysics Data System (ADS)

    Welton, R. F.; Moran, T. F.; Feeney, R. K.; Thomas, E. W.

    1996-04-01

    A simple, all permanent magnet, 2.45 GHz electron cyclotron resonance ion source has been developed for the production of stable beams of low charge state ions from gaseous feed materials. The source can produce ˜1 mA of low energy (3 kV) singly charged ion current in the 10-4 Torr pressure range. The source can also be operated in a more efficient low-pressure mode at an order of magnitude lower pressure. In this latter range, for example, the ionization efficiency of Ar is estimated to be 1% with charge states up to Ar8+ present. Operation in the low-pressure mode requires low power input (˜20 W). These features make the source especially suited for use with small accelerator systems for a number of applications including ion implantation, mass spectrometry, and atomic collision experiments where multiply charged ions are desirable. Design details and performance characteristics of the source are presented.

  2. Folded waveguide coupler for ion cyclotron heating

    SciTech Connect

    Owens, T.L.; Chen, G.L.

    1986-01-01

    A new type of waveguide coupler for plasma heating in the ion cyclotron range of frequencies is described. The coupler consists of a series of interleaved metallic vanes within a rectangular enclosure analogous to a wide rectangular waveguide that has been ''folded'' several times. At the mouth of the coupler, a plate is attached which contains coupling apertures in each fold or every other fold of the waveguide, depending upon the wavenumber spectrum desired. This plate serves primarily as a wave field polarizer that converts coupler fields to the polarization of the fast magnetosonic wave within the plasma. Theoretical estimates indicate that the folded waveguide is capable of high-efficiency, multimegawatt operation into a plasma. Bench tests have verified the predicted field structure within the waveguide in preparation for high-power tests on the Radio Frequency Test Facility at the Oak Ridge National Laboratory.

  3. Electron cyclotron resonance (ECR) ion sources

    SciTech Connect

    Jongen, Y.

    1984-05-01

    Starting with the pioneering work of R. Geller and his group in Grenoble (France), at least 14 ECR sources have been built and tested during the last five years. Most of those sources have been extremely successful, providing intense, stable and reliable beams of highly charged ions for cyclotron injection or atomic physics research. However, some of the operational features of those sources disagreed with commonly accepted theories on ECR source operation. To explain the observed behavior of actual sources, it was found necessary to refine some of the crude ideas we had about ECR sources. Some of those new propositions are explained, and used to make some extrapolations on the possible future developments in ECR sources.

  4. Ionospheric modification at twice the electron cyclotron frequency.

    PubMed

    Djuth, F T; Pedersen, T R; Gerken, E A; Bernhardt, P A; Selcher, C A; Bristow, W A; Kosch, M J

    2005-04-01

    In 2004, a new transmission band was added to the HAARP high-frequency ionospheric modification facility that encompasses the second electron cyclotron harmonic at altitudes between approximately 220 and 330 km. Initial observations indicate that greatly enhanced airglow occurs whenever the transmission frequency approximately matches the second electron cyclotron harmonic at the height of the upper hybrid resonance. This is the reverse of what happens at higher electron cyclotron harmonics. The measured optical emissions confirm the presence of accelerated electrons in the plasma.

  5. Accelerators for hadrontherapy: From Lawrence cyclotrons to linacs

    NASA Astrophysics Data System (ADS)

    Amaldi, U.; Bonomi, R.; Braccini, S.; Crescenti, M.; Degiovanni, A.; Garlasché, M.; Garonna, A.; Magrin, G.; Mellace, C.; Pearce, P.; Pittà, G.; Puggioni, P.; Rosso, E.; Verdú Andrés, S.; Wegner, R.; Weiss, M.; Zennaro, R.

    2010-08-01

    Hadrontherapy with protons and carbon ions is a fast developing methodology in radiation oncology. The accelerators used and planned for this purpose are reviewed starting from the cyclotrons used in the thirties. As discussed in the first part of this paper, normal and superconducting cyclotrons are still employed, together with synchrotrons, for proton therapy while for carbon ion therapy synchrotrons have been till now the only option. The latest developments concern a superconducting cyclotron for carbon ion therapy, fast-cycling high frequency linacs and 'single room' proton therapy facilities. These issues are discussed in the second part of the paper by underlining the present challenges, in particular the treatment of moving organs.

  6. ECR Ion Source for a High-Brightness Cyclotron

    NASA Astrophysics Data System (ADS)

    Comeaux, Justin; McIntyre, Peter; Assadi, Saeed

    2011-10-01

    New technology is being developed for high-brightness, high-current cyclotrons with performance benefits for accelerator-driven subcritical fission power, medical isotope production, and proton beam cancer therapy. This paper describes the design for a 65 kV electron cyclotron resonance (ECR) ion source that will provide high-brightness beam for injection into the cyclotron. The ion source is modeled closely upon the one that is used at the Paul Scherrer Institute. Modifications are being made to provide enhanced brightness and compatibility for higher-current operation.

  7. Improving cancer treatment with cyclotron produced radionuclides. Progress report

    SciTech Connect

    Larson, S.M.; Finn, R.D.

    1993-11-01

    This report describes our continuing long term goal of promoting nuclear medicine applications by improving the scientific basis for tumor diagnosis, treatment and treatment follow-up based on the use of cyclotron produced radiotracers in oncology. The program includes 3 interactive components: Radiochemistry/Cyclotron; Pharmacology; and Immunology. An essential strategy is as follows: novel radionuclides and radiotracers developed in the Radiochemistry/Cyclotron section will be employed in the Pharmacology and Immunology sections during the next year. The development of novel radionuclides and tracers is of course useful in and of itself, but their utility is greatly enhanced by the interaction with the immunology and pharmacology components of the program.

  8. Radiation Monitoring System of 30 MeV Cyclotron

    NASA Astrophysics Data System (ADS)

    Lee, Jin-Woo; Hur, Min-Goo; Jeong, Gyosung; Kim, Jongil

    2017-09-01

    A state-of-the-art radiation monitoring system was implemented at KAERI for a 30-MeV cyclotron. This system consists of several types of radiation measuring systems for ambient dose equivalent rate measurements of outside photon and neutron areas as well as inside the cyclotron, and monitors the alpha and beta particulates released from a stack, as well as the results of worker contamination at the portal of the cyclotron. In addition, an automatic alarm system is also mounted if there are alarms in the measuring systems.

  9. The NSCL cyclotron gas stopper - Entering commissioning

    NASA Astrophysics Data System (ADS)

    Schwarz, S.; Bollen, G.; Chouhan, S.; Das, J. J.; Green, M.; Magsig, C.; Morrissey, D. J.; Ottarson, J.; Sumithrarachchi, C.; Villari, A. C. C.; Zeller, A.

    2016-06-01

    Linear gas stopping cells have been used successfully at NSCL to slow down ions produced by projectile fragmentation from the 100 MeV/u to the keV energy range. These 'stopped beams' have first been used for low-energy high precision experiments and more recently for NSCLs re-accelerator ReA. A gas-filled reverse cyclotron is currently under construction by the NSCL to complement the existing stopping cells: Due to its extended stopping length, efficient stopping and fast extraction is expected even for light and medium-mass ions, which are difficult to thermalize in linear gas cells. The device is based on a 2.6 T maximum-field cyclotron-type magnet to confine the injected beam while it is slowed down in ≈100 mbar of LN2-temperature helium gas. Once thermalized, the beam will be transported to the center of the device by a traveling-wave RF-carpet system, extracted along the symmetry axis with an ion conveyor and miniature RF-carpets, and accelerated to a few tens of keV of energy for delivery to the users. The superconducting magnet has been constructed on a 60 kV platform and energized to its nominal field strength. The magnet's two cryostats use 3 cryo-refrigerators each and liquid-nitrogen cooled thermal shields to cool the coil pair to superconductivity. This concept, chosen not to have to rely on external liquid helium, has been working well. Measurements of axial and radial field profiles confirm the field calculations. The individual RF-ion guiding components for low-energy ion transport through the device have been tested successfully. The beam stopping chamber with its 0.9 m-diameter RF carpet system and the ion extraction system are being prepared for installation inside the magnet for low-energy ion transport tests.

  10. Overview of the future upgrade of the INFN-LNS superconducting cyclotron

    NASA Astrophysics Data System (ADS)

    Calabretta, Luciano; Calanna, Alessandra; Cuttone, Giacomo; D'Agostino, Grazia; Rifuggiato, Danilo; Domenico Russo, Antonio

    2017-06-01

    The LNS Superconducting Cyclotron, named “Ciclotrone Superconduttore” (CS), has been in operation for more than 20 years. A wide range of ion species from hydrogen to lead, with energy in the range 10 to 80 AMeV, have been delivered to users. The maximum beam power is limited to 100 W due to the beam dissipation on the electrostatic deflectors. To fulfil the demand of users aiming at studying rare processes in nuclear physics, an upgrade of the cyclotron is necessarily intended to increase the intensity of ion beams with mass lower than 40 a.m.u. up to a power 10 kW. This will be achieved by means of extraction by stripping. This solution needs to replace the cryostat including the superconducting coils. The present capability of the cyclotron will be maintained, i.e. all the ion species allowed by the operating diagram will be available, being extracted by electrostatic extraction. In addition to the high power beams for nuclear physics, it will be possible to produce medical radioisotopes like 211At using an internal target.

  11. Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Horne, Richard B.

    1994-01-01

    Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.

  12. Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Horne, Richard B.

    1994-01-01

    Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.

  13. Ion-cyclotron instability in plasmas described by product-bi-kappa distributions

    SciTech Connect

    Santos, M. S. dos; Ziebell, L. F. Gaelzer, R.

    2015-12-15

    The dispersion relation for parallel propagating waves in the ion-cyclotron branch is investigated numerically by considering that the velocity distribution of the ion population is a function of type product-bi-kappa. We investigate the effects of the non-thermal features and of the anisotropy associated with this type of distribution on the ion-cyclotron instability, as well as the influence of different forms of the electron distribution, by considering Maxwellian distributions, bi-kappa distributions, and product-bi-kappa distributions. The cases of ions described by either Maxwellian or bi-kappa distributions are also considered, for comparison. The results of the numerical analysis show that the increase in the non-thermal character associated with the anisotropic kappa distributions for ions contributes to enhance the instability as compared to that obtained in the Maxwellian case, in magnitude and in wave number range, with more significant enhancement for the case of ion product-bi-kappa distributions than for the case of ion bi-kappa distributions. It is also shown that the ion-cyclotron instability is decreased if the electrons are described by product-bi-kappa distributions, while electrons described by bi-kappa distributions lead to growth rates which are very similar to those obtained considering a Maxwellian distribution for the electron population.

  14. Linked Environment for Atmospheric Discovery (LEAD): Transforming the Sensing and Numerical Prediction of High Impact Local Weather Through Dynamic Adaptation

    NASA Astrophysics Data System (ADS)

    Ramamurthy, M.; Droegemeier, K.

    2006-12-01

    Those who have experienced the devastation of a tornado, the raging waters of a flash flood, or the paralyzing impacts of lake-effect snows understand that mesoscale weather develops rapidly, often with considerable uncertainty with regard to location. Such weather is also locally intense and frequently influenced by processes on both larger and smaller scales. Ironically, few of the technologies used to observe the atmosphere, predict its evolution, and compute, transmit, or store information about it operate in a manner that accommodates the dynamic behavior of mesoscale weather. Radars do not adaptively scan specific regions of thunderstorms; numerical models are run largely on fixed time schedules in fixed configurations; and cyberinfrastructure does not allow meteorological tools to run on-demand, change configurations in response to the weather, or provide the fault tolerance needed for rapid reconfiguration. As a result, today's weather technology is highly constrained and far from optimal when applied to any particular situation. This presentation describes a major paradigm shift now underway in the field of meteorology -- away from today's environment in which remote sensing systems, atmospheric prediction models, and hazardous weather detection systems operate in fixed configurations, and on fixed schedules largely independent of weather -- to one in which they can change their configuration dynamically in response to the evolving weather. A major driver of this change is a project known as Linked Environments for Atmospheric Discovery (LEAD) -- a 5-year NSF Large Information Technology Research (ITR) grant that is developing cyberinfrastructure to allow scientists, students, tools and sensors to interact with weather. This presentation will describe the research and technology development being performed to establish this capability

  15. Gas phase ion - molecule reactions studied by Fourier transform ion cyclotron resonance mass spectrometry

    SciTech Connect

    Ross, C.W. III.

    1993-01-01

    Intrinsic thermodynamic information of molecules can easily be determined in the low pressure FT/ICR mass spectrometer. The gas phase basicity of two carbenes were measured by isolating the protonated carbene ion and reacting it with neutral reference compounds by the bracketing method. A fundamentally new-dimensional FT/ICR/MS experiment, SWIM (stored waveform ion modulation) 2D-FT/ICR MS/MS, is described. Prior encodement of the second dimension by use of two identical excitation waveforms separated by a variable delay period is replaced by a new encodement in which each row of the two-dimensional data array is obtained by use of a single stored excitation waveform whose frequency-domain magnitude spectrum is a sinusoid whose frequency increases from one row to the next. In the two-dimensional mass spectrum, the conventional one-dimensional FT/ICR mass spectrum appears along the diagonal, and each off-diagonal peak corresponds to an ion-neutral reaction whose ionic components may be identified by horizontal and vertical projections to the diagonal spectrum. All ion-molecule reactions in a gaseous mixture may be identified from a single 2D-FT/ICR MS/MS experiment, without any prior knowledge of the system. In some endoergic reactions there is a minimum energy threshold that must overcome for a reaction to occur. Hence, a simple sinusoidal modulation of parent ion cyclotron radius leads to a clipped sinusoidal signal of the product ion abundance in the second dimension, which upon Fourier transformation produces signals with harmonic and combination ion cyclotron resonance frequencies. Moreover, ion-molecule reaction rates may vary directly within kinetic energy rather than cyclotron radius. With SWIM, it is possible to tailor the excitation profile so as to produce a sinusoidal modulation of ion kinetic energy as a function of cyclotron frequency.

  16. Dynamic modelling of the long term behaviour of cadmium, lead and mercury in Swiss forest soils using CHUM-AM.

    PubMed

    Rieder, Stephan R; Tipping, Edward; Zimmermann, Stefan; Graf-Pannatier, Elisabeth; Waldner, Peter; Meili, Markus; Frey, Beat

    2014-01-15

    The applicability of the dynamic soil model CHUM-AM was tested to simulate concentrations of Cd, Pb and Hg in five Swiss forest soils. Soil cores of up to 50 cm depth were sampled and separated into two defined soil layers. Soil leachates were collected below the litter by zero-tension lysimeters and at 15 and 50 cm soil depths by tension lysimeters over two years. The concentrations of Cd, Pb and Hg in the solid phase and soil solution were measured by ICP-MS (Cd, Pb) or CV-AFS (Hg). Measured metal concentrations were compared with modelled concentrations using CHUM-AM. Additionally we ran the model with three different deposition scenarios (current deposition; maximum acceptable deposition according to the Swiss ordinance on Air Pollution Control; critical loads according to CLRTAP) to predict metal concentrations in the soils for the next 1000 years. Assuming current loads concentrations of Cd and Pb showed varying trends (increasing/decreasing) between the soils. Soils rich in organic carbon or with a high pH value showed increasing trends in Cd and Pb concentrations whereas the concentrations in the other soils decreased. In contrast Hg concentrations are predicted to further increase in all soils. Critical limits for Pb and Hg will partly be exceeded by current loads or by the critical loads proposed by the CLRTAP but the critical limits for Cd will rarely be reached within the next 1000 years. In contrast, maximal acceptable deposition will partly lead to concentrations above the critical limits for Pb in soils within the next 400 years, whereas the acceptable deposition of Cd will not lead to concentrations above the proposed critical limits. In conclusion the CHUM-AM model is able to accurately simulate heavy metal (Cd, Pb and Hg) concentrations in Swiss forest soils of various soil properties.

  17. A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitating Fluxes

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.

    2002-01-01

    Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.

  18. A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes

    SciTech Connect

    Oosterbeek, J. W.; Buerger, A.; Westerhof, E.; Baar, M. R. de; Berg, M. A. van den; Bongers, W. A.; Graswinckel, M. F.; Hennen, B. A.; Kruijt, O. G.; Thoen, J.; Heidinger, R.; Korsholm, S. B.; Leipold, F.; Nielsen, S. K.

    2008-09-15

    An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry-Perot interferometer under an angle inside the electron cyclotron wave (ECW) beam. ECE measurements are obtained during high power ECRH operation. This demonstrates the successful operation of the diagnostic and, in particular, a sufficient suppression of the gyrotron component preventing it from interfering with ECE measurements. When integrated into a feedback system for the control of plasma instabilities this line-of-sight ECE diagnostic removes the need to localize the instabilities in absolute coordinates.

  19. Precipitation of Relativistic Electrons by Electromagnetic Ion Cyclotron (EMIC) Waves

    NASA Astrophysics Data System (ADS)

    Denton, R. E.

    2015-12-01

    We use the electromagnetic ion cyclotron (EMIC) wave fields produced in a two dimensional hybrid code simulation (full dynamics particle ions, but inertialess fluid electrons) in dipole geometry in order to investigate the effect of magnetospheric EMIC waves on relativistic electrons. The plane of the simulation includes variation in the L shell direction and along magnetic field lines. Relativistic test particle electrons are inserted into the simulation when the wave fields are near their maximum amplitude. These electrons can be scattered into the loss cone so that they precipitate into the ionosphere. We find the effective pitch angle diffusion coefficient and probability of precipitation using these test particles. The pitch angle diffusion coefficients are largest for relativistic energies greater than 2 MeV, though they may be substantial for lower energies. The probability of precipitation is highest for low energy particles at small initial equatorial pitch angle. For high initial equatorial pitch angles, the probability of precipitation increases greatly with respect to particle energy. Starting from an isotropic pitch angle distribution of relativistic electrons with a Gaussian spread in the relativistic momentum, we find only a small drop in the probability of precipitation during 13 s time as the particle energy decreases. But that result depends on the initial pitch angle distribution. Starting with a distribution of particles steeply peaked at 90° initial equatorial pitch angle, the probability of precipitation would be greater for high-energy particles. We will discuss the mechanism of pitch angle scattering.

  20. Electron cyclotron plasma startup in the GDT experiment

    NASA Astrophysics Data System (ADS)

    Yakovlev, D. V.; Shalashov, A. G.; Gospodchikov, E. D.; Solomakhin, A. L.; Savkin, V. Ya.; Bagryansky, P. A.

    2017-01-01

    We report on a new plasma startup scenario in the gas dynamic trap (GDT) magnetic mirror device. The primary 5 MW neutral beam injection (NBI) plasma heating system fires into a sufficiently dense plasma target (‘seed plasma’), which is commonly supplied by an arc plasma generator. In the reported experiments, a different approach to seed plasma generation is explored. One of the channels of the electron cyclotron resonance (ECR) heating system is used to ionize the neutral gas and build up the density of plasma to a level suitable for NBI capture. After a short transition of approximately 1 ms the discharge becomes essentially similar to a standard one initiated by the plasma gun. This paper presents the discharge scenario and experimental data on the seed plasma evolution during ECRH, along with the dependencies on incident microwave power, magnetic configuration and pressure of a neutral gas. The characteristics of the consequent high-power NBI discharge are studied and differences from the conventional scenario are discussed. A theoretical model describing the ECR breakdown and the seed plasma accumulation in a large-scale mirror trap is developed on the basis of the GDT experiment.

  1. Single-electron detection and spectroscopy via relativistic cyclotron radiation

    SciTech Connect

    Asner, D. M.; Bradley, R. F.; de Viveiros, L.; Doe, P. J.; Fernandes, J. L.; Fertl, M.; Finn, E. C.; Formaggio, J. A.; Furse, D.; Jones, A. M.; Kofron, J. N.; LaRoque, B. H.; Leber, M.; McBride, E. L.; Miller, M. L.; Mohanmurthy, P.; Monreal, B.; Oblath, N. S.; Robertson, R. G. H.; Rosenberg, L. J.; Rybka, G.; Rysewyk, D.; Sternberg, M. G.; Tedeschi, J. R.; Thummler, T.; VanDevender, B. A.; Woods, N. L.

    2015-04-20

    Since 1897, we've understood that accelerating charges must emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. We demonstrate single-electron detection in a novel radiofrequency spec- trometer. Here, we observe the cyclotron radiation emitted by individual magnetically-trapped electrons that are produced with mildly-relativistic energies by a gaseous radioactive source. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.

  2. Single-electron detection and spectroscopy via relativistic cyclotron radiation

    SciTech Connect

    Asner, David M.; Bradley, Rich; De Viveiros Souza Filho, Luiz A.; Doe, Peter J.; Fernandes, Justin L.; Fertl, M.; Finn, Erin C.; Formaggio, Joseph; Furse, Daniel L.; Jones, Anthony M.; Kofron, Jared N.; LaRoque, Benjamin; Leber, Michelle; MCBride, Lisa; Miller, M. L.; Mohanmurthy, Prajwal T.; Monreal, Ben; Oblath, Noah S.; Robertson, R. G. H.; Rosenberg, Leslie; Rybka, Gray; Rysewyk, Devyn M.; Sternberg, Michael G.; Tedeschi, Jonathan R.; Thummler, Thomas; VanDevender, Brent A.; Woods, N. L.

    2015-04-01

    It has been understood since 1897 that accelerating charges should emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. Here we demonstrate single-electron detection in a novel radiofrequency spectrometer. We observe the cyclotron radiation emitted by individual electrons that are produced with mildly-relativistic energies by a gaseous radioactive source and are magnetically trapped. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work is a proof-of-concept for future neutrino mass experiments using this technique.

  3. Single-electron detection and spectroscopy via relativistic cyclotron radiation

    DOE PAGES

    Asner, D. M.; Bradley, R. F.; de Viveiros, L.; ...

    2015-04-20

    Since 1897, we've understood that accelerating charges must emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. We demonstrate single-electron detection in a novel radiofrequency spec- trometer. Here, we observe the cyclotron radiation emitted by individual magnetically-trapped electrons that are produced with mildly-relativistic energies by a gaseous radioactive source. The relativistic shift in the cyclotron frequency permits a precisemore » electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.« less

  4. Intensity limitations in compact H{sup minus} cyclotrons

    SciTech Connect

    Baartman, R.A.

    1995-12-31

    At TRIUMF, we have demonstrated 2.5 mA in a compact H{sup -} cyclotron. It is worthwhile to explore possibility of going to even higher intensity. In small cyclotrons, vertical focusing vanishes at the center. The space charge tune shift further reduces vertical focusing, thus determining an upper limit on instantaneous current. Limit on average current is of course also dependent upon phase acceptance, but this can be made quite large in an H{sup -} cyclotron. Longitudinal space charge on the first turn can reduce the phase acceptance as well. For finite ion source brightness, another limit comes from bunching efficiency in presence of space charge forces. We present methods of calculating and optimizing these limits. In particular, we show that it is possible to achieve 10mA in a 50 MeV compact H{sup -} cyclotron.

  5. Undergraduate Education with the Rutgers 12-Inch Cyclotron

    NASA Astrophysics Data System (ADS)

    Koeth, Timothy W.

    The Rutgers 12-Inch Cyclotron is a research grade accelerator dedicated to undergraduate education. From its inception, it has been intended for instruction and has been designed to demonstrate classic beam physics phenomena and provides students hands on experience with accelerator technology. The cyclotron is easily reconfigured, allowing experiments to be designed and performed within one academic semester. Our cyclotron offers students the opportunity to operate an accelerator and directly observe many fundamental beam physics concepts, including axial and radial betatron motion, destructive resonances, weak and azimuthally varying field (AVF) focusing schemes, RF and DEE voltage effects, diagnostic techniques, and perform low energy nuclear reactions. This paper emphasizes the unique beam physics measurements and beam manipulations capable at the Rutgers 12-Inch Cyclotron.

  6. Some calculations of the resonator in INR cyclotron

    SciTech Connect

    Zhang, J.; Liu, X.L.

    1985-10-01

    Some calculation methods of the resonator parameters with single dee and two coaxial transmission lines in INR variable-energy cyclotron were described. Also calculated and experimental results have been compared with the original one (two dee system).

  7. Cyclotrons for clinical and biomedical research with PET

    SciTech Connect

    Wolf, A.P.

    1987-01-01

    The purpose of this commentary is to present some background material on cyclotrons and other particle accelerators particularly with a view toward the considerations behind acquiring and installing such a machine for purely clinical and/or biomedical research use.

  8. Vacuum Control Systems of the Cyclotrons in VECC, Kolkata

    NASA Astrophysics Data System (ADS)

    Roy, Anindya; Akhtar, Javed; Yadav, R. C.; Bhole, R. B.; Pal, Sarbajit; Sarkar, D.; Bhandari, R. K.

    2012-11-01

    VECC has undertaken the modernization of the K-130 Room Temperature Cyclotron (RTC) (operational since 1978) and commissioning of K-500 Superconducting Cyclotron (SCC) at present. The control system of RTC vacuum system has been upgraded to Programmable Logic Controller (PLC) based automated system from relay based manual system. A distributed PLC based system is under installation for SCC vacuum system. The requirement of high vacuum in both the cyclotrons (1×10-6 mbar for RTC and 5 × 10-8 mbar SCC) imposes the reliable local and remote operation of all vacuum components and instrumentation. The design and development of the vacuum control system of two cyclotrons using the Experimental Physics and Industrial Control System (EPICS) distributed real-time software tools are presented.

  9. Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites.

    PubMed

    Leguy, Aurélien M A; Goñi, Alejandro R; Frost, Jarvist M; Skelton, Jonathan; Brivio, Federico; Rodríguez-Martínez, Xabier; Weber, Oliver J; Pallipurath, Anuradha; Alonso, M Isabel; Campoy-Quiles, Mariano; Weller, Mark T; Nelson, Jenny; Walsh, Aron; Barnes, Piers R F

    2016-10-21

    We present Raman and terahertz absorbance spectra of methylammonium lead halide single crystals (MAPbX3, X = I, Br, Cl) at temperatures between 80 and 370 K. These results show good agreement with density-functional-theory phonon calculations. Comparison of experimental spectra and calculated vibrational modes enables confident assignment of most of the vibrational features between 50 and 3500 cm(-1). Reorientation of the methylammonium cations, unlocked in their cavities at the orthorhombic-to-tetragonal phase transition, plays a key role in shaping the vibrational spectra of the different compounds. Calculations show that these dynamic effects split Raman peaks and create more structure than predicted from the independent harmonic modes. This explains the presence of extra peaks in the experimental spectra that have been a source of confusion in earlier studies. We discuss singular features, in particular the torsional vibration of the C-N axis, which is the only molecular mode that is strongly influenced by the size of the lattice. From analysis of the spectral linewidths, we find that MAPbI3 shows exceptionally short phonon lifetimes, which can be linked to low lattice thermal conductivity. We show that optical rather than acoustic phonon scattering is likely to prevail at room temperature in these materials.

  10. Molecular dynamics simulation of corrosion mitigation of iron in lead-bismuth eutectic using nitrogen as corrosion inhibitor

    NASA Astrophysics Data System (ADS)

    Arkundato, Artoto; Su'ud, Zaki; Sudarko; Hasan, Mohammad; Celino, Massimo

    2015-06-01

    The corrosion of structural materials used in fast nuclear reactor design is a current major problem. It is due to the use of liquid metal as a coolant candidate in the heat transfer system. The liquid metal as lead-bismuth eutectic was found to make high corrosion to structural material as steel. One of the solutions of this problem is to inject some inhibitor into liquid metal. In this current work we simulate the effect of nitrogen injection as inhibitor candidate. The simulation will predict the proper concentration of injected nitrogen and also observe the microscopic structure of the material before and after injection to know the ability of nitrogen as an inhibitor. The simulation follows the molecular dynamics method and for preliminary study we use iron material rather than steel. We also use lennard-jones potential for simplification of the study. It is from our simulation we see nitrogen shows better corrosion mitigation compare with oxygen as in our previous study. The effective inhibition can be achieved by injecting at least 0.056wt.% nitrogen. This amount seems to be able to reduce the corrosion level of iron till about 99.5% for high corrosion at temperature 750 °C.

  11. Social dynamics within decomposer communities lead to nitrogen retention and organic matter build-up in soils

    PubMed Central

    Kaiser, Christina; Franklin, Oskar; Richter, Andreas; Dieckmann, Ulf

    2015-01-01

    The chemical structure of organic matter has been shown to be only marginally important for its decomposability by microorganisms. The question of why organic matter does accumulate in the face of powerful microbial degraders is thus key for understanding terrestrial carbon and nitrogen cycling. Here we demonstrate, based on an individual-based microbial community model, that social dynamics among microbes producing extracellular enzymes (‘decomposers') and microbes exploiting the catalytic activities of others (‘cheaters') regulate organic matter turnover. We show that the presence of cheaters increases nitrogen retention and organic matter build-up by downregulating the ratio of extracellular enzymes to total microbial biomass, allowing nitrogen-rich microbial necromass to accumulate. Moreover, increasing catalytic efficiencies of enzymes are outbalanced by a strong negative feedback on enzyme producers, leading to less enzymes being produced at the community level. Our results thus reveal a possible control mechanism that may buffer soil CO2 emissions in a future climate. PMID:26621582

  12. PET computer programs for use with the 88-inch cyclotron

    SciTech Connect

    Gough, R.A.; Chlosta, L.

    1981-06-01

    This report describes in detail several offline programs written for the PET computer which provide an efficient data management system to assist with the operation of the 88-Inch Cyclotron. This function includes the capability to predict settings for all cyclotron and beam line parameters for all beams within the present operating domain of the facility. The establishment of a data base for operational records is also described from which various aspects of the operating history can be projected.

  13. Theoretical determination of electron temperature in electron-cyclotron plasmas

    SciTech Connect

    Uhm, H.S.; Lee, P.H.; Kim, Y.I.; Kim, J.H.; Chang, H.Y.

    1995-12-31

    A basic theory of the plasma electron temperature in ECR plasmas has been reported in recent studies in connection with application to the plasma etching technologies. However, the previous theoretical study of the ECR plasmas is primitive and ad hoc. The authors therefore develop a theory for plasmas generated by the electron-cyclotron-resonance (ECR) mechanism and an experiment is conducted to compare the theoretical prediction and experimental measurements. Due to a large electron mobility along the magnetic field, electrons move quickly out of the system, leaving ions behind and building a space charge potential, which leads to the ambipolar diffusion of ions. In a steady-state condition, the plasma generation by ionization of neutral molecules is in balance with plasma loss due to the diffusion, leading to the electron temperature equation, which is expressed in terms of the plasma size, chamber pressure, and the ionization energy and cross section of neutrals. The electron temperature decreases as the chamber pressure increases. Based on the ambipolar diffusion of ions, a self-consistent theory of the plasma density profile is developed. The power balance condition leads to the plasma density equation, which is also expressed in terms of the electron temperature, the input microwave power and the chamber pressure. It is shown that the plasma density increases, reaches its peak and decreases, as the chamber pressure increases from a small value (0.1 mTorr). After carrying out an experimental observation, it is concluded that the theoretical predictions of the electron temperature and plasma density agree remarkably well with experimental data.

  14. Interpretation of the effects of electron cyclotron power absorption in pre-disruptive tokamak discharges in ASDEX Upgrade

    SciTech Connect

    Nowak, S.; Lazzaro, E.; Granucci, G.; Esposito, B.; Maraschek, M.; Zohm, H.; Sauter, O.; Brunetti, D.; Collaboration: ASDEX Upgrade Team

    2012-09-15

    Tokamak disruptions are events of fatal collapse of the magnetohydrodynamic (MHD) confinement configuration, which cause a rapid loss of the plasma thermal energy and the impulsive release of magnetic energy and heat on the tokamak first wall components. The physics of the disruptions is very complex and non-linear, strictly associated with the dynamics of magnetic tearing perturbations. The crucial problem of the response to the effects of localized heat deposition and current driven by external (rf) sources to avoid or quench the MHD tearing instabilities has been investigated both experimentally and theoretically on the ASDEX Upgrade tokamak. The analysis of the conditions under which a disruption can be prevented by injection of electron cyclotron (EC) rf power, or, alternatively, may be caused by it, shows that the local EC heating can be more significant than EC current drive in ensuring neoclassical tearing modes (NTMs) stability, due to two main reasons: first, the drop of temperature associated with the island thermal short circuit tends to reduce the neoclassical character of the instability and to limit the EC current drive generation; second, the different effects on the mode evolution of both the location of the power deposition relative to the island separatrix and the island shape deformation lead to less strict requirements of precise power deposition focussing. A contribution to the validation of theoretical models of the events associated with NTM is given and can be used to develop concepts for their control, relevant also for ITER-like scenarios.

  15. On the application of electron cyclotron emission imaging to the validation of theoretical models of magnetohydrodynamic activitya)

    NASA Astrophysics Data System (ADS)

    Tobias, B. J.; Boivin, R. L.; Boom, J. E.; Classen, I. G. J.; Domier, C. W.; Donné, A. J. H.; Heidbrink, W. W.; Luhmann, N. C.; Munsat, T.; Muscatello, C. M.; Nazikian, R.; Park, H. K.; Spong, D. A.; Turnbull, A. D.; Van Zeeland, M. A.; Yun, G. S.

    2011-05-01

    Two-dimensional (2D) imaging of electron temperature perturbations provides a powerful constraint for validating theoretical models describing magnetohydrodynamic plasma behavior. In observation of Alfvén wave induced temperature fluctuations, electron cyclotron emission imaging provides unambiguous determination of the 2D eigenmode structure. This has provided support for nonperturbative eigenmode solvers which predict symmetry breaking due to poloidal flows in the fast ion population. It is shown that for Alfvén eigenmodes, and in cases where convective flows or saturated perturbations lead to nonaxisymmetric equilibria, electron plasma displacements oriented parallel to a gradient in mean temperature are well defined. Furthermore, during highly dynamic behavior, such as the sawtooth crash, highly resolved 2D temperature behaviors yield valuable insight. In particular, addressing the role of adiabatic heating on time scales much shorter than the resistive diffusion time through the additional diagnosis of local electron density allows progress to be made toward a comprehensive understanding of fast reconnection in tokamak plasmas.

  16. A mechanism for the Fine Structures of Solar Radio Bursts Based on the Electron Cyclotron Maser Emission

    NASA Astrophysics Data System (ADS)

    Wang, C.; Tong, Z.; Liu, J.

    2015-12-01

    A scenario based on the electron cyclotron maser emission is proposed for the fine structures of solar radio emission in the present discussion. It is suggested that under certain conditions modulation of the ratio between the plasma frequency and electron gyro-frequency by ultra low frequency waves, which is a key parameter for excitation of the maser instability, may lead to the intermittent emission of radio waves. As an example, the explanation of the observed fine-structure components in the solar type IIIb burst is discussed in detail. Three primary issues of the type IIIb bursts are addressed: 1) what is the physical mechanism that results in the intermittent emission elements that form a chain in the dynamic spectrum of type IIIb bursts, 2) what causes the split pair (or double stria) and the triple stria, 3) why in the events of fundamental-harmonic pair emission there is only IIIb-III, but IIIb-IIIb or III-IIIb cases are very rarely observed. The application of the scenario to some other type of solar radio bursts and their fine structures are also discussed.

  17. Ion source and injection line for high intensity medical cyclotron

    SciTech Connect

    Jia, XianLu Guan, Fengping; Yao, Hongjuan; Zhang, TianJue; Yang, Jianjun; Song, Guofang; Ge, Tao; Qin, Jiuchang

    2014-02-15

    A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). An injection system based on the external H− ion source was used on CYCIAE-14 so as to provide high intensity beam, while most positron emission tomography cyclotrons adopt internal ion source. A beam intensity of 100 μA/14 MeV was extracted from the cyclotron with a small multi-cusp H− ion source (CIAE-CH-I type) and a short injection line, which the H− ion source of 3 mA/25 keV H− beam with emittance of 0.3π mm mrad and the injection line of with only 1.2 m from the extraction of ion source to the medial plane of the cyclotron. To increase the extracted beam intensity of the cyclotron, a new ion source (CIAE-CH-II type) of 9.1 mA was used, with maximum of 500 μA was achieved from the cyclotron. The design and test results of the ion source and injection line optimized for high intensity acceleration will be given in this paper.

  18. A 16-channel heterodyne electron cyclotron emission radiometer on J-TEXT.

    PubMed

    Yang, Z J; Phillips, P E; Zhuang, G; Xiao, J S; Huang, H; Rowan, W L; Wang, Z J

    2012-10-01

    To study equilibrium temporal dynamics and the mechanisms of magnetohydrodynamic instabilities, a 16-channel heterodyne electron cyclotron emission (ECE) radiometer has been developed to view the J-TEXT tokamak from the low field side. The ECE radiometer detects second-harmonic extraordinary mode in the frequency band of 94-125 GHz which corresponds to resonances from 1.8 T to 2.2 T. This ECE system consists of an ECE transmission line, a radio frequency unit, and two 8-channel intermediate frequency units. An in situ blackbody calibration source is applied for system calibration by comparison of hot and cold sources in order to provide an absolute temperature measurement.

  19. A 16-channel heterodyne electron cyclotron emission radiometer on J-TEXT

    SciTech Connect

    Yang, Z. J.; Zhuang, G.; Xiao, J. S.; Wang, Z. J.; Phillips, P. E.; Huang, H.; Rowan, W. L.

    2012-10-15

    To study equilibrium temporal dynamics and the mechanisms of magnetohydrodynamic instabilities, a 16-channel heterodyne electron cyclotron emission (ECE) radiometer has been developed to view the J-TEXT tokamak from the low field side. The ECE radiometer detects second-harmonic extraordinary mode in the frequency band of 94-125 GHz which corresponds to resonances from 1.8 T to 2.2 T. This ECE system consists of an ECE transmission line, a radio frequency unit, and two 8-channel intermediate frequency units. An in situ blackbody calibration source is applied for system calibration by comparison of hot and cold sources in order to provide an absolute temperature measurement.

  20. Monte Carlo modeling of ionospheric oxygen acceleration by cyclotron resonance with broad-band electromagnetic turbulence

    NASA Technical Reports Server (NTRS)

    Retterer, John M.; Chang, Tom; Crew, G. B.; Jasperse, J. R.; Winningham, J. D.

    1987-01-01

    It is demonstrated that cyclotron resonance with observed electric field fluctuations is responsible for production of the oxygen-ion conics that are observed by the Dynamics Explorer 1 satellite in the central plasma-sheet region of the earth's magnetosphere. The ion-velocity distribution is described by a quasi-linear diffusion equation which is solved by the Monte Carlo technique. The acceleration produced by the observed wave spectrum agrees well with the ion observations, in both form and magnitude. This is believed to represent the first successful comparison of an observed conic with any theoretical model.

  1. Spectra of KeV Protons Related to Ion-Cyclotron Wave Packets

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Sibeck, D. G.; Tel'Nikhin, A. A.; Kronberg, T. K.

    2017-01-01

    We use the Fokker-Planck-Kolmogorov equation to study the statistical aspects of stochastic dynamics of the radiation belt (RB) protons driven by nonlinear electromagnetic ion-cyclotron (EMIC) wave packets. We obtain the spectra of keV protons scattered by these waves that showsteeping near the gyroresonance, the signature of resonant wave-particle interaction that cannot be described by a simple power law. The most likely mechanism for proton precipitation events in RBs is shown to be nonlinear wave-particle interaction, namely, the scattering of RB protons into the loss cone by EMIC waves.

  2. First results of an auxiliary electron cyclotron resonance heating experiment in the GDT magnetic mirror

    NASA Astrophysics Data System (ADS)

    Bagryansky, P. A.; Kovalenko, Yu. V.; Savkin, V. Ya.; Solomakhin, A. L.; Yakovlev, D. V.

    2014-08-01

    The axially symmetric magnetic mirror device gas-dynamic trap (GDT, Budker Institute, Novosibirsk) has recently demonstrated a tangible increase in plasma electron temperature. According to laser scattering, a value of 0.4 keV has been achieved (a twofold increase). In addition to standard machine operation, utilizing a 5 MW neutral beam injection, a newly installed electron cyclotron resonance heating (ECRH) system was employed (54.5 GHz, 0.4 MW). The reported progress in electron temperature, along with previous experiments, which demonstrated plasma confinement at beta as high as 60%, is a significant advancement towards an energy efficient fusion neutron source based on GDT physics.

  3. Drude weight, cyclotron resonance, and the Dicke model of graphene cavity QED.

    PubMed

    Chirolli, Luca; Polini, Marco; Giovannetti, Vittorio; MacDonald, Allan H

    2012-12-28

    The unique optoelectronic properties of graphene make this two-dimensional material an ideal platform for fundamental studies of cavity quantum electrodynamics in the strong-coupling regime. The celebrated Dicke model of cavity quantum electrodynamics can be approximately realized in this material when the cyclotron transition of its 2D massless Dirac fermion carriers is nearly resonant with a cavity photon mode. We develop the theory of strong matter-photon coupling in this circumstance, emphasizing the essential role of a dynamically generated matter energy term that is quadratic in the photon field and absent in graphene's low-energy Dirac model.

  4. Pharmacoinformatics exploration of polyphenol oxidases leading to novel inhibitors by virtual screening and molecular dynamic simulation study.

    PubMed

    Hassan, Mubashir; Abbas, Qamar; Ashraf, Zaman; Moustafa, Ahmed A; Seo, Sung-Yum

    2017-03-15

    Polyphenol oxidases (PPOs)/tyrosinases are metal-dependent enzymes and known as important targets for melanogenesis. Although considerable attempts have been conducted to control the melanin-associated diseases by using various inhibitors. However, the exploration of the best anti-melanin inhibitor without side effect still remains a challenge in drug discovery. In present study, protein structure prediction, ligand-based pharmacophore modeling, virtual screening, molecular docking and dynamic simulation study were used to screen the strong novel inhibitor to cure melanogenesis. The 3D structures of PPO1 and PPO2 were built through homology modeling, while the 3D crystal structures of PPO3 and PPO4 were retrieved from PDB. Pharmacophore modeling was performed using LigandScout 3.1 software and top five models were selected to screen the libraries (2601 of Aurora and 727, 842 of ZINC). Top 10 hit compounds (C1-10) were short-listed having strong binding affinities for PPO1-4. Drug and synthetic accessibility (SA) scores along with absorption, distribution, metabolism, excretion and toxicity (ADMET) assessment were employed to scrutinize the best lead hit. C4 (name) hit showed the best predicted SA score (5.75), ADMET properties and drug-likeness behavior among the short-listed compounds. Furthermore, docking simulations were performed to check the binding affinity of C1-C10 compounds against target proteins (PPOs). The binding affinity values of complex between C4 and PPOs were higher than those of other complexes (-11.70, -12.1, -9.90 and -11.20kcal/mol with PPO1, PPO2, PPO3, or PPO4, respectively). From comparative docking energy and binding analyses, PPO2 may be considered as better target for melanogenesis than others. The potential binding modes of C4, C8 and C10 against PPO2 were explored using molecular dynamics simulations. The root mean square deviation and fluctuation (RMSD/RMSF) graphs results depict the significance of C4 over the other compounds

  5. Terahertz Imaging of cyclotron emission from quantum Hall conductors

    NASA Astrophysics Data System (ADS)

    Komiyama, Susumu

    2006-03-01

    Microscopy of extremely weak terahertz (THz) waves via photon-counting method is reported. A quantum-dot photon detector [1] is incorporated into a scanning terahertz microscope [2]. By using a quantum Hall detector [3] as well, measurements cover the intensity dynamic range more than five orders of magnitude. The minimum intensity reaches as lo as 10̂-21^ watt (one photon per one second). Applying the measurement system to the study of semiconductor quantum Hall (QH) devices, we image cyclotron radiation emitted by non-equilibrium electrons generated in QH electron systems. Owing to the unprecedented sensitivity, a variety of new features of electron kinetics are unveiled [4]. It is stressed that the present approach is in marked contrast to the THz- wave applications recently discussed extensively in a wide variety of fields including clinic, security, and environment. In the vast majority of those applications, room-temperature operation is implicit. The intensity of treated THz radiation is hence well beyond the level of 300K black body radiation (roughly 10̂-7 watts or 10̂14 photons/s per square centimeter in a 1/10 relative band width). From the scientific viewpoint, however, detecting extremely weak THz waves from an object without external illumination such as applied in the present work is of strong importance, because the microscopic kinetics of an object can be probed only in such a passive method. Besides semiconductor electric devices studied here, we will also discuss possible applications of the present method for molecular dynamics, micro thermography, and cell activities.. [1] S. Komiyama et al., Nature 403, 405 (2000). [2] K. Ikushima et al.,. Rev. Sci. Instrum. 74, 4209 (2003). [3] Y.Kawano et al., J. Appl. Phys. 89, 4037 (2001). [4] K.Ikushima et al., Phys. Rev. Lett. 93, 146804 (2004).

  6. Spectral and dynamical properties of single excitons, biexcitons, and trions in cesium-lead-halide perovskite quantum dots

    SciTech Connect

    Makarov, Nikolay Sergeevich; Guo, Shaojun; Isaienko, Oleksandr; Liu, Wenyong; Robel, Istvan; Klimov, Victor Ivanovich

    2016-02-16

    Organic–inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs–Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate-temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time-resolved spectroscopic techniques to conduct a comprehensive study of spectral and dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton–exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs–Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the “universal volume scaling” previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. Furthermore, this points toward the need for the development of approaches for effective

  7. Spectral and Dynamical Properties of Single Excitons, Biexcitons, and Trions in Cesium-Lead-Halide Perovskite Quantum Dots.

    PubMed

    Makarov, Nikolay S; Guo, Shaojun; Isaienko, Oleksandr; Liu, Wenyong; Robel, István; Klimov, Victor I

    2016-04-13

    Organic-inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs-Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate-temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time-resolved spectroscopic techniques to conduct a comprehensive study of spectral and dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton-exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs-Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the "universal volume scaling" previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. This points toward the need for the development of approaches for effective suppression of Auger

  8. Correlation electron cyclotron emission diagnostic in TCV

    NASA Astrophysics Data System (ADS)

    Fontana, M.; Porte, L.; Molina Cabrera, P.

    2017-08-01

    The correlation electron cyclotron emission diagnostic of tokamak à configuration variable has recently been upgraded. It now has the choice of three lines of sight: two horizontal lines placed on the low field side of the vessel, perpendicular to the magnetic field, and a dual-axis steerable antenna. The polarization of the radiation collected by the latter can be rotated using a universal polarizer situated in the transmission line. This line is also shared with a reflectometry system, allowing simultaneous measurements of temperature and density fluctuations in the same plasma volumes. When using this line, it is possible to choose between two dedicated front ends characterized by different local oscillator frequencies, adding flexibility in the choice of the plasma region to be studied. The intermediate frequency section is now equipped with six frequency tunable YIG filters allowing the study of turbulence properties in a wide range of radial positions. When studying fluctuations over the whole video bandwidth, the minimum detectable fluctuation level is δ Te/Te˜0.5 % . The new system has been used to measure electron temperature fluctuations over a large fraction of the plasma profiles in a series of plasmas with triangularity varying from 0.6 to -0.6 but comparable collisionality profiles.

  9. A storage ring for the JULIC cyclotron

    NASA Astrophysics Data System (ADS)

    Martin, S. A.; Prasuhn, D.; Schott, W.; Wiedner, C. A.

    1985-05-01

    The storage ring COSY is planned to provide higher intensity and resolution for nuclear structure experiments using the light heavy ion beams (p, d, τ, α) of the JULIC cyclotron and the magnet spectrograph BIG KARL. The ring contains the measuring target of BIG KARL as an internal target, two rf cavities for compensating the mean energy loss in the target and providing additional acceleration of the stored beam and an e --cooling section. In the recirculator mode, i.e., without e --cooling, a luminosity of L = 3.64 × 10 30 particles/(cm 2 s) is obtained for an experiment with 41 MeV protons and a 50 μg/cm 212C target at a spectrograph resolution p/d p = 10 4 and 100% duty factor. This corresponds to a gain in L of 546.5 in comparison with the same experiment without a storage ring. In the recirculator mode with acceleration L = 1.17 × 10 32 p/(cm 2 s) and 98.8% duty factor results for 1500 MeV protons on the same target at the same resolution. Using e --cooling L and the feasible p/d p can be enhanced, however, at a reduced duty factor.

  10. 30-cm electron cyclotron plasma generator

    NASA Technical Reports Server (NTRS)

    Goede, Hank

    1987-01-01

    Experimental results on the development of a 30-cm-diam electron cyclotron resonance plasma generator are presented. This plasma source utilizes samarium-cobalt magnets and microwave power at a frequency of 4.9 GHz to produce a uniform plasma with densities of up to 3 x 10 to the 11th/cu cm in a continuous fashion. The plasma generator contains no internal structures, and is thus inherently simple in construction and operation and inherently durable. The generator was operated with two different magnetic geometries. One used the rare-earth magnets arranged in an axial line cusp configuration, which directly showed plasma production taking place near the walls of the generator where the electron temperature was highest but with the plasma density peaking in the central low B-field regions. The second configuration had magnets arranged to form azimuthal line cusps with approximately closed electron drift surfaces; this configuration showed an improved electrical efficiency of about 135 eV/ion.

  11. Fourier transform ion cyclotron resonance mass spectrometry

    NASA Astrophysics Data System (ADS)

    Marshall, Alan G.

    1998-06-01

    As for Fourier transform infrared (FT-IR) interferometry and nuclear magnetic resonance (NMR) spectroscopy, the introduction of pulsed Fourier transform techniques revolutionized ion cyclotron resonance mass spectrometry: increased speed (factor of 10,000), increased sensitivity (factor of 100), increased mass resolution (factor of 10,000-an improvement not shared by the introduction of FT techniques to IR or NMR spectroscopy), increased mass range (factor of 500), and automated operation. FT-ICR mass spectrometry is the most versatile technique for unscrambling and quantifying ion-molecule reaction kinetics and equilibria in the absence of solvent (i.e., the gas phase). In addition, FT-ICR MS has the following analytically important features: speed (~1 second per spectrum); ultrahigh mass resolution and ultrahigh mass accuracy for analysis of mixtures and polymers; attomole sensitivity; MSn with one spectrometer, including two-dimensional FT/FT-ICR/MS; positive and/or negative ions; multiple ion sources (especially MALDI and electrospray); biomolecular molecular weight and sequencing; LC/MS; and single-molecule detection up to 108 Dalton. Here, some basic features and recent developments of FT-ICR mass spectrometry are reviewed, with applications ranging from crude oil to molecular biology.

  12. Two Dimensional Synthetic Electron Cyclotron Emission Imaging

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Valeo, Ernest J.; Tobias, Benjamin J.; Kramer, Gerrit J.; Liu, Chang; Tang, William M.

    2016-10-01

    Electron Cyclotron Emission (ECE) has been widely used as a measurement of the electron temperature profile in magnetically confined plasmas. The ECE Imaging (ECEI) system provides additional vertical resolutions, and is used to measure the electron temperature fluctuations. The vertical resolution is typically a few centi-meters which is sometimes comparable to the vertical wave length of the underlying fluctuations. The ray-tracing technique used in most synthetic ECE codes to determine the origin and spatial extent of the ECE radiations is not accurate when the refraction and diffraction due to the fluctuations are important. In this presentation, we introduce a new synthetic ECEI code which solves the wave propagation up to the 2nd order of the WKB approximation, and provides full 2D information of the ECE source. We'll show that when the ECE frequency is near the cutoff, the refraction due to the fluctuations is important. A ``trapping'' of the ECE source by the density fluctuations is identified, and is potentially useful for determining the cross phase between electron temperature and density fluctuations. The new formalism is also used to study the Runaway Electrons contribution to the ECE signal, and provides insights to the measured ECE spectrum on DIII-D. This work has been funded by the US Department of Energy under Contract Number DE-AC02-09CH11466.

  13. Fourth generation electron cyclotron resonance ion sources.

    PubMed

    Lyneis, Claude M; Leitner, D; Todd, D S; Sabbi, G; Prestemon, S; Caspi, S; Ferracin, P

    2008-02-01

    The concepts and technical challenges related to developing a fourth generation electron cyclotron resonance (ECR) ion source with a rf frequency greater than 40 GHz and magnetic confinement fields greater than twice B(ECR) will be explored in this article. Based on the semiempirical frequency scaling of ECR plasma density with the square of operating frequency, there should be significant gains in performance over current third generation ECR ion sources, which operate at rf frequencies between 20 and 30 GHz. While the third generation ECR ion sources use NbTi superconducting solenoid and sextupole coils, the new sources will need to use different superconducting materials, such as Nb(3)Sn, to reach the required magnetic confinement, which scales linearly with rf frequency. Additional technical challenges include increased bremsstrahlung production, which may increase faster than the plasma density, bremsstrahlung heating of the cold mass, and the availability of high power continuous wave microwave sources at these frequencies. With each generation of ECR ion sources, there are new challenges to be mastered, but the potential for higher performance and reduced cost of the associated accelerator continues to make this a promising avenue for development.

  14. Cyclotron-based effects on plant gravitropism

    NASA Astrophysics Data System (ADS)

    Kordyum, E.; Sobol, M.; Kalinina, Ia.; Bogatina, N.; Kondrachuk, A.

    Primary roots exhibit positive gravitropism and grow in the direction of the gravitational vector, while shoots respond negatively and grow opposite to the gravitational vector. We first demonstrated that the use of a weak combined magnetic field (CMF), which is comprised of a permanent magnetic field and an alternating magnetic field with the frequency resonance of the cyclotron frequency of calcium ions, can change root gravitropism from a positive direction to negative direction. Two-day-old cress seedlings were gravistimulated in a chamber that was placed into a μ-metal shield where this CMF was created. Using this "new model" of a root gravitropic response, we have studied some of its components including the movement of amyloplasts-statoliths in root cap statocytes and the distribution of Ca 2+ ions in the distal elongation zone during gravistimulation. Unlike results from the control, amyloplasts did not sediment in the distal part of a statocyte, and more Ca 2+ accumulation was observed in the upper side of a gravistimulated root for seedlings treated with the CMF. For plants treated with the CMF, it appears that a root gravitropic reaction occurs by a normal physiological process resulting in root bending although in the opposite direction. These results support the hypothesis that both the amyloplasts in the root cap statocytes and calcium are important signaling components in plant gravitropism.

  15. Fullerenes in electron cyclotron resonance ion sources

    SciTech Connect

    Biri, S.; Fekete, E.; Kitagawa, A.; Muramatsu, M.; Janossy, A.; Palinkas, J.

    2006-03-15

    Fullerene plasmas and beams have been produced in our electron cyclotron resonance ion sources (ECRIS) originally designed for other purposes. The ATOMKI-ECRIS is a traditional ion source with solenoid mirror coils to generate highly charged ions. The variable frequencies NIRS-KEI-1 and NIRS-KEI-2 are ECR ion sources built from permanent magnets and specialized for the production of carbon beams. The paper summarizes the experiments and results obtained by these facilities with fullerenes. Continuous effort has been made to get the highest C{sub 60} beam intensities. Surprisingly, the best result was obtained by moving the C{sub 60} oven deep inside the plasma chamber, very close to the resonance zone. Record intensity singly and doubly charged fullerene beams were obtained (600 and 1600 nA, respectively) at lower C{sub 60} material consumption. Fullerene derivatives were also produced. We mixed fullerenes with other plasmas (N, Fe) with the aim of making new materials. Nitrogen encapsulated fullerenes (mass: 720+14=734) were successfully produced. In the case of iron, two methods (ferrocene, oven) were tested. Molecules with mass of 720+56=776 were detected in the extracted beam spectra.

  16. Characterization of electron cyclotron resonance hydrogen plasmas

    SciTech Connect

    Outten, C.A. . Dept. of Nuclear Engineering); Barbour, J.C.; Wampler, W.R. )

    1990-01-01

    Electron cyclotron resonance (ECR) plasmas yield low energy and high ion density plasmas. The characteristics downstream of an ECR hydrogen plasma were investigated as a function of microwave power and magnetic field. A fast-injection Langmuir probe and a carbon resistance probe were used to determine plasma potential (V{sub p}), electron density (N{sub e}), electron temperature (T{sub e}), ion energy (T{sub i}), and ion fluence. Langmuir probe results showed that at 17 cm downstream from the ECR chamber the plasma characteristics are approximately constant across the center 7 cm of the plasma for 50 Watts of absorbed power. These results gave V{sub p} = 30 {plus minus} 5 eV, N{sub e} = 1 {times} 10{sup 8} cm{sup {minus}3}, and T{sub e} = 10--13 eV. In good agreement with the Langmuir probe results, carbon resistance probes have shown that T{sub i} {le} 50 eV. Also, based on hydrogen chemical sputtering of carbon, the hydrogen (ion and energetic neutrals) fluence rate was determined to be 1 {times} 10{sup 16}/cm{sup 2}-sec. at a pressure of 1 {times} 10{sup {minus}4} Torr and for 50 Watts of absorbed power. 19 refs.

  17. Cyclotron autoresonance maser in the millimeter region

    NASA Astrophysics Data System (ADS)

    Nikolov, N. A.; Spasovski, I. P.; Kostov, K. G.; Velichkov, J. N.; Spasov, V. A.

    1990-06-01

    This paper investigates the optimal experimental conditions for a cyclotron autoresonance maser (CARM) regime realized by a nonadiabatic magnetic beam pumping in the millimeter wavelength region. In the experiment, a Blumline-type accelerator with a voltage up to 650 kV and maximal current up to 10 kA is used to generate a hollow beam with a pulse duration of 30 ns. The electron beam, emitted from a graphite cathode with a 10-mm diameter, propagates in a cylindrical drift tube of 56 mm diam and a length of 500 mm. The external magnetic field B, provided by a solenoidal magnet, is homogeneous along the drift tube up to a distance of 300 mm from the cathode. The experiment demonstrated the generation of microwave radiation in the time interval from 0.0016 to 0.0023 sec after the switch-on of the external magnetic field. Two maxima of the output microwave power (8 and 10 MW) at a wavelength of 5 and 5.5 mm, respectively, were observed.

  18. The Oak Ridge Isochronous Cyclotron Refurbishment Project

    SciTech Connect

    Mendez, II, Anthony J; Ball, James B; Dowling, Darryl T; Mosko, Sigmund W; Tatum, B Alan

    2011-01-01

    The Oak Ridge Isochronous Cyclotron (ORIC) has been in operation for nearly fifty years at the Oak Ridge National Laboratory (ORNL). Presently, it serves as the driver accelerator for the ORNL Holifield Radioactive Ion Beam Facility (HRIBF), where radioactive ion beams are produced using the Isotope Separation Online (ISOL) technique for post-acceleration by the 25URC tandem electrostatic accelerator. Operability and reliability of ORIC are critical issues for the success of HRIBF and have presented increasingly difficult operational challenges for the facility in recent years. In February 2010, a trim coil failure rendered ORIC inoperable for several months. This presented HRIBF with the opportunity to undertake various repairs and maintenance upgrades aimed at restoring the full functionality of ORIC and improving the reliability to a level better than what had been typical over the previous decade. In this paper, we present details of these efforts, including the replacement of the entire trim coil set and measurements of their radial field profile. Comparison of measurements and operating tune parameters with setup code predictions will also be presented.

  19. Multiple Cyclotron Method to Search for CP Violation in the Neutrino Sector

    NASA Astrophysics Data System (ADS)

    Conrad, J. M.; Shaevitz, M. H.

    2010-04-01

    New low-cost, high-power proton cyclotrons open the opportunity for a novel precision search for CP violation in the light neutrino sector. The accelerators can produce decay-at-rest neutrino beams located at multiple distances from a Gd-doped ultralarge water Cherenkov detector in order to search for CP violation in ν¯μ→ν¯e oscillations at short baselines. This new type of search complements presently proposed experiments, providing measurements that could lead to a substantially better exploration of CP violation in the neutrino sector.

  20. Multiple cyclotron method to search for CP violation in the neutrino sector.

    PubMed

    Conrad, J M; Shaevitz, M H

    2010-04-09

    New low-cost, high-power proton cyclotrons open the opportunity for a novel precision search for CP violation in the light neutrino sector. The accelerators can produce decay-at-rest neutrino beams located at multiple distances from a Gd-doped ultralarge water Cherenkov detector in order to search for CP violation in nu(mu)-->nu(e) oscillations at short baselines. This new type of search complements presently proposed experiments, providing measurements that could lead to a substantially better exploration of CP violation in the neutrino sector.

  1. Cyclotron resonant scattering in gamma-ray bursts - Further analysis of GB880205

    NASA Technical Reports Server (NTRS)

    Freeman, P. E.; Lamb, D. Q.; Wang, J. C. L.; Loredo, T. J.; Fenimore, E. E.; Murakami, T.; Yoshida, A.

    1992-01-01

    We have extended our previous work by exploring several plane-parallel slab geometries to model the formation of cyclotron line features. We calculated the Compton temperature T(C) as a function of column density Ne for each of the new geometries. We then fit the resulting spectra to GB880205 exactly as described in Wang et al. (1989). The results show that the addition of column depth below the photon source plane leads to a modest improvement in chi-squared which, although not statistically significant, is pleasing because these geometries are more physically realistic.

  2. X-ray-spectroscopy analysis of electron-cyclotron-resonance ion-source plasmas

    SciTech Connect

    Santos, J. P.; Martins, M. C.; Parente, F.; Costa, A. M.; Marques, J. P.; Indelicato, P.

    2010-12-15

    Analysis of x-ray spectra emitted by highly charged ions in an electron-cyclotron-resonance ion source (ECRIS) may be used as a tool to estimate the charge-state distribution (CSD) in the source plasma. For that purpose, knowledge of the electron energy distribution in the plasma, as well as the most important processes leading to the creation and de-excitation of ionic excited states are needed. In this work we present a method to estimate the ion CSD in an ECRIS through the analysis of the x-ray spectra emitted by the plasma. The method is applied to the analysis of a sulfur ECRIS plasma.

  3. Cyclotron resonant scattering in gamma-ray bursts - Further analysis of GB880205

    NASA Technical Reports Server (NTRS)

    Freeman, P. E.; Lamb, D. Q.; Wang, J. C. L.; Loredo, T. J.; Fenimore, E. E.; Murakami, T.; Yoshida, A.

    1992-01-01

    We have extended our previous work by exploring several plane-parallel slab geometries to model the formation of cyclotron line features. We calculated the Compton temperature T(C) as a function of column density Ne for each of the new geometries. We then fit the resulting spectra to GB880205 exactly as described in Wang et al. (1989). The results show that the addition of column depth below the photon source plane leads to a modest improvement in chi-squared which, although not statistically significant, is pleasing because these geometries are more physically realistic.

  4. A small low energy cyclotron for radioisotope measurements

    SciTech Connect

    Bertsche, K.J.

    1989-11-01

    Direct detection of {sup 14}C by accelerator mass spectrometry has proved to be a much more sensitive method for radiocarbon dating than the decay counting method invented earlier by Libby. A small cyclotron (the cyclotrino'') was proposed for direct detection of radiocarbon in 1980. This combined the suppression of background through the use of negative ions, which had been used effectively in tandem accelerators, with the high intrinsic mass resolution of a cyclotron. Development of a small electrostatically-focused cyclotron for use as a mass spectrometer was previously reported but the sensitivity needed for detection of {sup 14}C at natural abundance was not achieved. The major contributions of this work are the integration of a high current external ion source with a small flat-field, electrostatically-focused cyclotron to comprise a system capable of measuring {sup 14}C at natural levels, and the analysis of ion motion in such a cyclotron, including a detailed analysis of phase bunching and its effect on mass resolution. A high current cesium sputter negative ion source generates a beam of carbon ions which is pre-separated with a Wien filter and is transported to the cyclotron via a series of electrostatic lenses. Beam is injected radially into the cyclotron using electrostatic deflectors and an electrostatic mirror. Axial focusing is entirely electrostatic. A microchannel plate detector is used with a phase-grated output. In its present form the system is capable of improving the sensitivity of detecting {sup 14}C in some biomedical experiments by a factor of 10{sup 4}. Modifications are discussed which could bring about an additional factor of 100 in sensitivity, which is important for archaeological and geological applications. Possibilities for measurements of other isotopes, such as {sup 3}H, and {sup 10}Be, and {sup 26}Al, are discussed. 70 refs.

  5. Electron cyclotron emissions from an electron cyclotron heated discharge in ISX-B

    SciTech Connect

    Elder, G.B.

    1983-01-01

    Observation of the electron cyclotron emissions (ECE) is especially effective when studying the effects of electron cyclotron heating (ECH). Two detectors were built to observe the optically thin third harmonic radiation from ISX B during the recent 28 GHz ECH experiments carried on at Oak Ridge National Laboratory. These detectors supplemented existing detectors at the fundamental frequency and at the second harmonic frequency. Observations of the three frequencies during and after the ECH was pulsed into the plasma showed an unexpected rise in their intensity, occurring after the ECH pulse was over. This rise lasted for many tens of milliseconds, well beyond estimates of the electron energy confinement time. The rise in the third harmonic intensity was frequently to an intensity 100 times greater than the pre-ECH intensity. The fundamental frequency and the second harmonic had a much milder change in their intensities. The rises were seen to depend critically on the density of the plasma and the length of the ECH pulse but only weakly on the pre-ECH temperature. A computer code that predicts the ECE from an electron distribution in ISX-B, taking into a account the effect of the plasma's dielectric response to the emissions from a single electron, was developed.

  6. Decommissioning procedures for an 11 MeV self-shielded medical cyclotron after 16 years of working time.

    PubMed

    Calandrino, R; del Vecchio, A; Savi, A; Todde, S; Griffoni, V; Brambilla, S; Parisi, R; Simone, G; Fazio, F

    2006-06-01

    The present article describes the decommissioning of a compact, self-shielded, 11 MeV medical cyclotron. A Monte Carlo simulation of the possible nuclear reactions was performed in order to plan the decommissioning activities. In the course of the cyclotron dismantling, cyclotron components, shields, and floor concrete samples were measured. Residual activities were analyzed with a Ge(Li) detector and compared with simulation data. Doses to staff involved in the decommissioning procedure were monitored by individual TL dosimeters. The simulations identified five radioactive nuclides in shields and floor concrete: 55Fe and 45Ca (beta emitters, total specific activity: 2.29 x 10(4) Bq kg) and 152Eu, 154Eu, 60Co (gamma emitters, total specific activity: 1.62 x 10(3) Bq kg-1). Gamma-ray spectrometry confirmed the presence of gamma emitters, corresponding to a total specific activity of 3.40 x 10(2) Bq kg-1. The presence of the radioisotope 124Sb in the lead contained in the shield structure, corresponding to a simulated specific activity of 9.38 x 10(3) Bq kg-1, was experimentally confirmed. The measured dose from external exposure of the involved staff was <20 muSv, in accordance with the expected range of values between 10 and 20 muSv. The measured dose from intake was negligible. Finally, the decommissioning of the 11 MeV cyclotron does not represent a risk for the involved staff, but due to the presence of long-lived radioisotopes, the cyclotron components are to be treated as low level radioactive waste and stored in an authorized storage area.

  7. C235-V3 cyclotron for a proton therapy center to be installed in the hospital complex of radiation medicine (Dimitrovgrad)

    NASA Astrophysics Data System (ADS)

    Galkin, R. V.; Gurskii, S. V.; Jongen, Y.; Karamysheva, G. A.; Kazarinov, M. Yu.; Korovkin, S. A.; Kostromin, S. A.; Calderan, J.-M.; Cahay, P.; Mokrenko, S. P.; Morozov, N. A.; Nkongolo, H.; Ol'shevskii, A. G.; Paradis, Y.; Petrov, D. S.; Romanov, V. M.; Samsonov, E. V.; Syresin, E. M.; Shakun, A. N.; Shakun, N. G.; Shirkov, G. D.; Shirkov, S. G.

    2014-06-01

    Proton therapy is an effective method of treating oncologic diseases. In Russia, construction of several centers for proton and ion therapy is slated for the years to come. A proton therapy center in Dimitrovgrad will be the first. The Joint Institute for Nuclear Research (Russia) in collaboration with Ion Beam Application (IBA) (Belgium) has designed an C235-V3 medical proton cyclotron for this center. It outperforms previous versions of commercial IBA cyclotrons, which have already been installed in 11 oncologic hospital centers in different countries. Experimental and calculation data for the beam dynamics in the C235-V3 medical cyclotron are presented. Reasons for beam losses during acceleration are considered, the influence of the magnetic field radial component in the midplane of the accelerator and main resonances is studied, and a beam extraction system is designed. In 2011-2012 in Dubna, the cyclotron was mounted, its magnetic field was properly configured, acceleration conditions were optimized, and beam extraction tests were carried out after which it was supplied to Dimitrovgrad. In the C235-V3 cyclotron, an acceleration efficiency of 72% and an extraction efficiency of 62% have been achieved without diaphragming to form a vertical profile of the beam.

  8. Spectral and dynamical properties of single excitons, biexcitons, and trions in cesium-lead-halide perovskite quantum dots

    DOE PAGES

    Makarov, Nikolay Sergeevich; Guo, Shaojun; Isaienko, Oleksandr; ...

    2016-02-16

    Organic–inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs–Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate-temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time-resolved spectroscopic techniques to conduct a comprehensive study of spectral andmore » dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton–exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs–Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the “universal volume scaling” previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. Furthermore, this points toward the need for the development of approaches for effective

  9. Inverse ion-cyclotron damping and excitation of multiharmonic ion-cyclotron waves in the northern magnetospheric cusp

    NASA Astrophysics Data System (ADS)

    Slapak, Rikard; Gunell, Herbert; Hamrin, Maria

    2017-04-01

    We have investigated a case of inverse ion-cyclotron damping taking place in the northern terrestrial magnetospheric cusp, exciting waves at the ion-cyclotron frequency and its harmonics. Magnetosheath influx in the cusps and the effect of convection and magnetic mirroring give rise to parallel velocity shears, dvallel/dx\\perp, often associated with instabilities in the plasma and corresponding ion-cyclotron waves, whose evolution is described by a damping factor. This damping factor depends on, for example, the wave numbers and the velocity shear itself and can under certain conditions be negative, hence describing inverse damping (or wave growth). However, an additional required condition for inverse ion-cyclotron damping is a velocity shear in the magnetic field-aligned ion-bulk flow, and this condition is only met for magnetosheath influx in the northern cusp, as oppose to the southern cusp. The ion-cyclotron waves are primarily seen as peaks in the magnetic-field spectral densities, as presented by Slapak et al., [GRL (2016), doi:10.1002/2016GL071680]. The corresponding peaks in the electric-field spectral densities are not as profound, suggesting a background electric field noise or other processes of wave generation causing the electric spectral densities to smoothen out more compared to the magnetic counterpart. We note that some ion-cyclotron wave activity is present in a few similar shear events in the southern cusp, which indicates that other mechanisms generating ion-cyclotron waves may also be present during such conditions.

  10. Design of RF system for CYCIAE-230 superconducting cyclotron

    NASA Astrophysics Data System (ADS)

    Yin, Zhiguo; Ji, Bin; Fu, Xiaoliang; Cao, Xuelong; Zhao, Zhenlu; Zhang, Tinajue

    2017-05-01

    The CYCIAE230 is a low-current, compact superconducting cyclotron designed for proton therapy. The Radio Frequency system consists of four RF cavities and applies second harmonic to accelerate beams. The driving power for the cavity system is estimated to be approximately 150 kW. The LLRF controller is a self-made device developed and tested at low power using a small-scale cavity model. In this paper, the resonator systems of an S.C. cyclotron in history are reviewed. Contrary to those RF systems, the cavities of the CYCIAE230 cyclotron connect two opposite dees. Two high-power RF windows are included in the system. Each window carries approximately 75 kW RF power from the driver to the cavities. Thus, the RF system for the CY-CIAE230 cyclotron is operated in driven push-pull mode. The two-way amplifier-coupler-cavity systems are operated with approximately the same amount of RF power but 180° out of phase compared with each other. The design, as well as the technical advantage and limitations of this operating mode, of the CYCIAE230 cyclotron RF system is analyzed.

  11. Heavy ion cocktail beams at the 88 inch Cyclotron

    SciTech Connect

    Leitner, Daniela; McMahan, Margaret A.; Argento, David; Gimpel, Thomas; Guy, Aran; Morel, James; Siero, Christine; Thatcher, Ray; Lyneis, Claude M.

    2002-09-03

    Cyclotrons in combination with ECR ion sources provide the ability to accelerate ''cocktails'' of ions. A cocktail is a mixture of ions of near-identical mass-to-charge (m/q) ratio. The different ions cannot be separated by the injector mass-analyzing magnet and are tuned out of the ion source together. The cyclotron then is utilized as a mass analyzer by shifting the accelerating frequency. This concept was developed soon after the first ECR ion source became operational at the 88-Inch Cyclotron and has since become a powerful tool in the field of heavy ion radiation effects testing. Several different ''cocktails'' at various energies are available at the 88-Inch cyclotron for radiation effect testing, covering a broad range of linear energy transfer and penetration depth. Two standard heavy ion cocktails at 4.5 MeV/nucleon and 10 MeV/nucleon have been developed over the years containing ions from boron to bismuth. Recently, following requests for higher penetration depths, a 15MeV/nucleon heavy ion cocktail has been developed. Up to nine different metal and gaseous ion beams at low to very high charge states are tuned out of the ion source simultaneously and injected together into the cyclotron. It is therefore crucial to balance the ion source very carefully to provide sufficient intensities throughout the cocktail. The paper describes the set-up and tuning of the ion source for the various heavy ion cocktails.

  12. Cyclotron targets and production technologies used for radiopharmaceuticals in NPI

    NASA Astrophysics Data System (ADS)

    Fišer, M.; Kopička, K.; Hradilek, P.; Hanč, P.; Lebeda, O.; Pánek, J.; Vognar, M.

    2003-01-01

    This paper deals with some technical aspects of the development and production of cyclotronmade radiopharmaceuticals (excluding PET). In this field, nuclear chemistry and pharmacy are in a close contact; therefore, requirements of the both should be taken into account. The principles of cyclotron targetry, separation/recovery of materials and synthesis of active substances are given, as well as issues connected with formulation of pharmaceutical forms. As the radiopharmaceuticals should fulfil the requirements on in vivo preparations, there exist a variety of demands pertaining to Good Manufacturing Practice (GMP) concept, which is also briefly discussed. A typical production chain is presented and practical examples of real technologies based on cyclotron-made radionuclides are given as they have been used in Nuclear Physics Institute of CAS (NPI). Special attention is devoted to the technology of enriched cyclotron targets. Frequently used medicinal products employing cyclotron-produced active substances are characterised (Rb/Kr generators, 123I-labelled MIBG, OIH and MAB's). The cyclotron produced radioactive implants for transluminal coronary angioplasty (radioactive stents) are introduced as an example of a medical device developed for therapeutic application.

  13. Electron and ion Bernstein waves excited in the ionosphere by high power EM waves at the second harmonic of the electron cyclotron frequency

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Selcher, C. A.; Kowtha, S.

    2011-10-01

    The transmission of a high power electromagnetic (EM) waves from the HAARP facility in Alaska can excite stimulated electromagnetic emissions offset from the transmitter frequency near harmonics of ion cyclotron frequency. Stimulated ion Bernstein (SIB) occurs when the pump frequency is tuned to an electron Bernstein (EB) frequency near twice the electron gyro frequency. The SIB process is thought to involve mode conversion from EM to EB waves followed by parametric decay of the EB wave to multiple EB and IB waves. The production of SIB waves may be an indicator of strong cyclotron acceleration of electrons by the EB waves that lead to artificial aurora and impact ionization of neutrals.

  14. Cyclotron-based of plant gravisensing

    NASA Astrophysics Data System (ADS)

    Kordyum, E.; Kalinina, Ia.; Bogatina, N.; Kondrachuk, A.

    Roots exhibit positive gravitropism they grow in the direction of a gravitational vector while shoots respond negatively and grow opposite to a gravitational vector We first demonstrated the inversion of roots gravitropism from positive to negative one under gravistimulation in the weak combined magnetic field WCMF consisted of permanent magnetic field PMF with the magnitude of order of 50 mu T and altering magnetic field AMF with the 6 mu T magnitude and a frequency of 32 Hz It was found that the effect of inversion has a resonance nature It means that in the interval of frequencies 1-45 Hz inversion of root gravitropism occurs only at frequency 32 Hz 2-3-day old cress seedlings were gravistimulated in moist chambers which are placed in mu -metal shields Inside mu -metal shields combined magnetic fields have been created The magnitude of magnetic fields was measured by a flux-gate magnetometer Experiments were performed in darkness at temperature 20 pm 1 0 C We measured the divergence angle of a growing root from its horizontal position After 1 h of gravistimulation in the WCMF we observed negative gravitropism of cress roots i e they grow in the opposite direction to a gravitational vector Frequency of 32 Hz for the magnitude of the PMF applied formally corresponds to cyclotron frequency of Ca 2 ions This indicates possible participation of calcium ions in root gravitropism There are many evidences of resonance effects of the WCMF on the biological processes that involve Ca 2 but the nature of

  15. Electrostatic electron cyclotron harmonic instability near Ganymede

    NASA Astrophysics Data System (ADS)

    Tripathi, A. K.; Singhal, R. P.; Singh, K. P.; Singh, O. N.

    2014-08-01

    Jupiter's moon—Ganymede—is the largest satellite in our solar system. Galileo spacecraft made six close flybys to explore Ganymede. More information was acquired about particle population, magnetic field and plasma waves during these encounters. In this paper, our aim is to study the generation of electrostatic electron cyclotron harmonic (ECH) emissions in the vicinity of Ganymede using the observed particle data. The calculated ECH wave's growth rates are analyzed in the light of observations of plasma waves along the path of Galileo near Ganymede. Dispersion relation for electrostatic mode is solved to obtain the temporal growth rates. A new electron distribution function, fitted to distribution observed near Ganymede, is used in the calculations. A parametric study is performed to evaluate the effect of loss-cone angle and the ratio of plasma to gyro-frequency on growth rates. It is found that ECH waves growth rates generally decrease as the loss-cone angle is increased. However, the ratio plasma to gyro-frequency has almost no effect on the growth rates. These parameters vary considerably along the Galileo trajectory near Ganymede. This is the first study which relates the occurrence of ECH waves with the particle and magnetic field data in the vicinity of Ganymede. The study of ECH wave growth rate near Ganymede is important for the calculation of pitch angle scattering rates of low-energy electrons and their subsequent precipitation into the thin atmosphere of Ganymede producing ultraviolet emissions. Results of the present study may also be relevant for the upcoming JUNO and JUICE missions to Jupiter.

  16. Solar cycle dependence of ion cyclotron wave frequencies

    NASA Astrophysics Data System (ADS)

    Lessard, Marc R.; Lindgren, Erik A.; Engebretson, Mark J.; Weaver, Carol

    2015-06-01

    Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earth's radiation belts is one of many topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approximately 60% from a minimum in 2009 to the end of 2012. Assuming that these waves are excited in the vicinity of the plasmapause, the change in Kp in going from solar minimum to near solar maximum would drive increased plasmapause erosion, potentially shifting the generation region of the EMIC to lower L and resulting in the higher frequencies. A numerical estimate of the change in plasmapause location, however, implies that it is not enough to account for the shift in EMIC frequencies that are observed at Halley Station. Another possible explanation for the frequency shift, however, is that the relative density of heavier ions in the magnetosphere (that would be associated with increased solar activity) could account for the change in frequencies. In terms of effects on radiation belt dynamics, the shift to higher frequencies tends to mean that these waves will interact with less energetic electrons, although the details involved in this process are complex and depend on the specific plasma and gyrofrequencies of all populations, including electrons. In addition, the change in location of the generation region to lower L shells means that the waves will have access to higher number fluxes of resonant electrons. Finally, we show that a sunlit ionosphere can inhibit ground observations of EMIC waves with frequencies higher than ˜0.5 Hz and note that the effect likely has resulted in an underestimate of the solar-cycle-driven frequency changes described here.

  17. Automated screening of microtubule growth dynamics identifies MARK2 as a regulator of leading edge microtubules downstream of Rac1 in migrating cells.

    PubMed

    Nishimura, Yukako; Applegate, Kathryn; Davidson, Michael W; Danuser, Gaudenz; Waterman, Clare M

    2012-01-01

    Polarized microtubule (MT) growth in the leading edge is critical to directed cell migration, and is mediated by Rac1 GTPase. To find downstream targets of Rac1 that affect MT assembly dynamics, we performed an RNAi screen of 23 MT binding and regulatory factors and identified RNAi treatments that suppressed changes in MT dynamics induced by constitutively activated Rac1. By analyzing fluorescent EB3 dynamics with automated tracking, we found that RNAi treatments targeting p150(glued), APC2, spastin, EB1, Op18, or MARK2 blocked Rac1-mediated MT growth in lamellipodia. MARK2 was the only protein whose RNAi targeting additionally suppressed Rac1 effects on MT orientation in lamellipodia, and thus became the focus of further study. We show that GFP-MARK2 rescued effects of MARK2 depletion on MT growth lifetime and orientation, and GFP-MARK2 localized in lamellipodia in a Rac1-activity-dependent manner. In a wound-edge motility assay, MARK2-depleted cells failed to polarize their centrosomes or exhibit oriented MT growth in the leading edge, and displayed defects in directional cell migration. Thus, automated image analysis of MT assembly dynamics identified MARK2 as a target regulated downstream of Rac1 that promotes oriented MT growth in the leading edge to mediate directed cell migration.

  18. Automated Screening of Microtubule Growth Dynamics Identifies MARK2 as a Regulator of Leading Edge Microtubules Downstream of Rac1 in Migrating Cells

    PubMed Central

    Nishimura, Yukako; Applegate, Kathryn; Davidson, Michael W.; Danuser, Gaudenz; Waterman, Clare M.

    2012-01-01

    Polarized microtubule (MT) growth in the leading edge is critical to directed cell migration, and is mediated by Rac1 GTPase. To find downstream targets of Rac1 that affect MT assembly dynamics, we performed an RNAi screen of 23 MT binding and regulatory factors and identified RNAi treatments that suppressed changes in MT dynamics induced by constitutively activated Rac1. By analyzing fluorescent EB3 dynamics with automated tracking, we found that RNAi treatments targeting p150glued, APC2, spastin, EB1, Op18, or MARK2 blocked Rac1-mediated MT growth in lamellipodia. MARK2 was the only protein whose RNAi targeting additionally suppressed Rac1 effects on MT orientation in lamellipodia, and thus became the focus of further study. We show that GFP-MARK2 rescued effects of MARK2 depletion on MT growth lifetime and orientation, and GFP-MARK2 localized in lamellipodia in a Rac1-activity-dependent manner. In a wound-edge motility assay, MARK2-depleted cells failed to polarize their centrosomes or exhibit oriented MT growth in the leading edge, and displayed defects in directional cell migration. Thus, automated image analysis of MT assembly dynamics identified MARK2 as a target regulated downstream of Rac1 that promotes oriented MT growth in the leading edge to mediate directed cell migration. PMID:22848487

  19. RNA-Seq of Human Neural Progenitor Cells Exposed to Lead (Pb) Reveals Transcriptome Dynamics, Splicing Alterations and Disease Risk Associations.

    PubMed

    Jiang, Peng; Hou, Zhonggang; Bolin, Jennifer M; Thomson, James A; Stewart, Ron

    2017-09-01

    Lead (Pb) is a well-known toxicant, especially for the developing nervous system, albeit the mechanism is largely unknown. In this study, we use time series RNA-seq to conduct a genome-wide survey of the transcriptome response of human embryonic stem cell-derived neural progenitor cells to lead treatment. Using a dynamic time warping algorithm coupled with statistical tests, we find that lead can either accelerate or decelerate the expression of specific genes during the time series. We further show that lead disrupts a neuron- and brain-specific splicing factor NOVA1 regulated splicing network. Using lead induced transcriptome change signatures, we predict several known and novel disease risks under lead exposure. The findings in this study will allow a better understanding of the mechanism of lead toxicity, facilitate the development of diagnostic biomarkers and treatment for lead exposure, and comprise a highly valuable resource for environmental toxicology. Our study also demonstrates that a human (embryonic stem) cell-derived system can be used for studying the mechanism of toxicants, which can be useful for drug or compound toxicity screens and safety assessment. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  20. Issues in the analysis and interpretation of cyclotron lines in gamma ray bursts

    NASA Technical Reports Server (NTRS)

    Lamb, D. Q.

    1992-01-01

    The Bayesian approach is discussed to establishing the existence of lines, the importance of observing multiple cyclotron harmonics in determining physical parameters from the lines, and evidence from cyclotron lines of neutron star rotation.

  1. 75 FR 48939 - National Superconducting Cyclotron Laboratory of Michigan State University; Notice of Decision on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-12

    ... International Trade Administration National Superconducting Cyclotron Laboratory of Michigan State University... pursuant to Section 6(c) of the Educational, Scientific, and Cultural Materials Importation Act of 1966...., NW., Washington, DC. Docket Number: 10-043. Applicant: National Superconducting Cyclotron Laboratory...

  2. Simultaneous observations of electrostatic oxygen cyclotron waves and ion conics

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.; Scales, W.; Vago, J.; Arnoldy, R.; Garbe, G.; Moore, T.

    1989-01-01

    A sounding rocket launched to 927 km apogee during an auroral substorm encountered regions of large quasi-static electric fields (not greater than 400 mV/m), ion conics (up to 700 eV maximum observed energy), and fluctuating electric fields near the oxygen cyclotron frequency. Since the fluctuating electric fields frequently exhibited spectral peaks just above the local oxygen cyclotron frequency, and since the fluctuating electric fields were linearly polarized, they are positively identified as electrostatic oxygen cyclotron waves (EOCW). The maximum amplitude of the EOCW was about 5 mV/m rms. The EOCW closely correlated with the presence of ion conics. Because of the relatively low amplitude of the EOCW and their relatively low coherence, it cannot be concluded that they are solely responsible for the production of the ion conics.

  3. Spectra and Neutron Dosimetry Inside a PET Cyclotron Vault Room

    SciTech Connect

    Vega-Carrillo, Hector Rene; Mendez, Roberto; Iniguez, Maria Pilar; Marti-Climent, Joseph; Penuelas, Ivan; Barquero, Raquel

    2006-09-08

    The neutron field around a PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Pairs of thermoluminescent dosemeters, TLD600 and TLD700, were used as thermal neutron detector inside a Bonner Spheres Spectrometer to measure the neutron spectra at three different positions inside the cyclotron's vault room. Neutron spectra were also determined by Monte Carlo calculations. The hardest spectrum was observed in front of cyclotron target and the softest was noticed at the antipode of target. Neutron doses derived from the measured spectra vary between 11 and 377 mSv/{mu}A-h of proton integrated current, Doses were also measured with a single-moderator remmeter, with an active thermal neutron detector, whose response in affected by the radiation field in the vault room.

  4. Radiation effects testing at the 88-inch cyclotron at LBNL

    SciTech Connect

    McMahan, Margaret A.; Koga, Rokotura

    2001-10-09

    The effects of ionizing particles on sensitive microelectronics is an important component of the design of systems as diverse as satellites and space probes, detectors for high energy physics experiments and even internet server farms. Understanding the effects of radiation on human cells is an equally important endeavor directed towards future manned missions in space and towards cancer therapy. At the 88-Inch Cyclotron at the Berkeley Laboratory, facilities are available for radiation effects testing (RET) with heavy ions and with protons. The techniques for doing these measurements and the advantages of using a cyclotron will be discussed, and the Cyclotron facilities will be compared with other facilities worldwide. RET of the same part at several facilities of varying beam energy can provide tests of the simple models used in this field and elucidate the relative importance of atomic and nuclear effects. The results and implications of such measurements will be discussed.

  5. Design study of the KIRAMS-430 superconducting cyclotron magnet

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Wook; Kang, Joonsun; Hong, Bong Hwan; Jung, In Su

    2016-07-01

    Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the 12C6+ ions up to 430 MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

  6. Alfven ion-cyclotron heating of ionospheric O(+) ions

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Sydora, R. D.; Ashour-Abdalla, M.

    1988-01-01

    Transversely heated ionospheric ions, in particular O(+) ions, are often observed flowing upward along auroral field lines. Currents observed in association with the transversely heated ions can drive shear Alfven waves and electrostatic ion-cyclotron waves unstable which can, in turn, be resonantly absorbed by the ions to produce the heating. Particle simulations are used to examine self-consistently the excitation of these waves and the associated heating. It is shown that the growth of the electrostatic ion-cyclotron waves quickly becomes suppressed as the ions become heated and the dominant wave fields are those of the shear Alfven wave. The resultant transverse ion heating is larger and faster than that produced by solely electrostatic ion-cyclotron wave heating. Due to trapping of ions by the shear Alfven wave, the temperature of the O(+) ions remains comparable to that of the H(+) ions.

  7. Cyclotron motion of a charged particle with anisotropic mass

    NASA Astrophysics Data System (ADS)

    Ciftja, Orion; Livingston, Victoria; Thomas, Elsa

    2017-05-01

    The cyclotron motion of a charged particle subject to a uniform magnetic field is thoroughly described in many classical physics textbooks. Although the assumption of a particle with isotropic mass is taken for granted in classical physics, a key concept in condensed matter physics is that of particles with an effective anisotropic mass, such as electrons in the context of band structure studies of solids. Since some exposure to the concept of anisotropic mass is important within the framework of classical physics, here we consider the cyclotron motion of a charged particle with anisotropic mass in the presence of a uniform magnetic field. The exact solution of this problem exposes a broad audience of readers to concepts in condensed matter physics that are rarely mentioned within the framework of classical physics. Key ideas on the topic are illustrated in a pedagogical way by considering specific examples that show how an anisotropic mass modifies the cyclotron motion of a charged particle.

  8. The next generation of electron cyclotron emission imaging diagnostics (invited).

    PubMed

    Zhang, P; Domier, C W; Liang, T; Kong, X; Tobias, B; Shen, Z; Luhmann, N C; Park, H; Classen, I G J; van de Pol, M J; Donné, A J H; Jaspers, R

    2008-10-01

    A 128 channel two-dimensional electron cyclotron emission imaging system collects time-resolved 16x8 images of T(e) profiles and fluctuations on the TEXTOR tokamak. Electron cyclotron emission imaging (ECEI) is undergoing significant changes which promise to revolutionize and extend its capabilities far beyond what has been achieved to date. These include the development of a minilens array configuration with increased sensitivity antennas, a new local oscillator pumping scheme, enhanced electron cyclotron resonance heating shielding, and a highly flexible optical design with vertical zoom capability. Horizontal zoom and spot size (rf bandwidth) capabilities are also being developed with new ECEI electronics. An interface module is under development to remotely control all key features of the new ECEI instrument, many of which can be changed during a plasma discharge for maximum flexibility.

  9. The next generation of electron cyclotron emission imaging diagnostics (invited)

    SciTech Connect

    Zhang, P.; Domier, C. W.; Liang, T.; Kong, X.; Tobias, B.; Shen, Z.; Luhmann, N. C. Jr.; Park, H.; Classen, I. G. J.; Pol, M. J. van de; Donne, A. J. H.; Jaspers, R.

    2008-10-15

    A 128 channel two-dimensional electron cyclotron emission imaging system collects time-resolved 16x8 images of T{sub e} profiles and fluctuations on the TEXTOR tokamak. Electron cyclotron emission imaging (ECEI) is undergoing significant changes which promise to revolutionize and extend its capabilities far beyond what has been achieved to date. These include the development of a minilens array configuration with increased sensitivity antennas, a new local oscillator pumping scheme, enhanced electron cyclotron resonance heating shielding, and a highly flexible optical design with vertical zoom capability. Horizontal zoom and spot size (rf bandwidth) capabilities are also being developed with new ECEI electronics. An interface module is under development to remotely control all key features of the new ECEI instrument, many of which can be changed during a plasma discharge for maximum flexibility.

  10. Proton and helium cyclotron anisotropy instability thresholds in the magnetosheath

    NASA Technical Reports Server (NTRS)

    Gary, S. Peter; Convery, Patrick D.; Denton, Richard E.; Fuselier, Stephen A.; Anderson, Brian J.

    1994-01-01

    Both the protons and the helium ions of the terrestrial magnetosheath typically display T (sub perpendicular) greater than T (sub parallel), where perpendicular to and parallel to denote directions perpendicular and parallel to the background magnetic field. Observations of the highly compressed magnetosheath show an inverse correlation between these ion temperature anisotropies and the parallel proton beta. Computer simulations have demonstrated that these correlations are due to wave-particle scattering by electromagnetic ion cyclotron anisotropy instabilities. These correlations correspond to linear theory thresholds of the proton cyclotron and the helium cyclotron instabilities. This paper uses linear Vlasov theory and the assumption of a constant maximum growth rate to obtain closed-form expressions for these thresholds as a function of the relative helium density and the parallel proton beta in a parameter model of the magnetosheath.

  11. DIII-D Electron Cyclotron Heating System Status and Upgrades

    DOE PAGES

    Cengher, Mirela; Lohr, John; Gorelov, Yuri; ...

    2016-06-23

    The DIII-D Electron Cyclotron Heating (ECH) system consists of six 110 GHz gyrotrons with corrugated coaxial 31.75 mm waveguide transmission lines and steerable launching mirrors. The system has been gradually updated, leading to increased experimental flexibility and a high system reliability of 91% in the past year. Operationally, the gyrotrons can generate up to a total of 4.8 MW of rf power for pulses up to 5 seconds. The maximum ECH energy injected into the DIII-D is 16.6 MJ. The HE1,1 mode content is over 85% for all the lines, and the transmission coefficient is better than -1.1 dB formore » all the transmission lines, close to the theoretical value. A new depressed collector gyrotron was recently installed and was injecting up to 640 kW of power into the plasma during 2014-2015 tokamak operations. Four dual waveguide launchers, which can steer the RF beams ±20 degrees poloidally and toroidally, are used for real-time neoclassical tearing mode control and suppression. The launchers now have increased poloidal scanning speed and beam positioning accuracy of ~±2 mm at the plasma center. Two more gyrotrons are expected to be installed and operational in 2015- 2016. The first is a repaired 110 GHz, 1 MW gyrotron that had a gun failure after more than 11 years of operation at DIII-D. The second is a newly designed depressed collector tube in the 1.5 MW class, operating at 117.5 GHz, manufactured by Communications and Power Industries (CPI).« less

  12. DIII-D Electron Cyclotron Heating System Status and Upgrades

    SciTech Connect

    Cengher, Mirela; Lohr, John; Gorelov, Yuri; Torrezan, Antonio; Ponce, Dan; Chen, Xi; Moeller, Charles

    2016-06-23

    The DIII-D Electron Cyclotron Heating (ECH) system consists of six 110 GHz gyrotrons with corrugated coaxial 31.75 mm waveguide transmission lines and steerable launching mirrors. The system has been gradually updated, leading to increased experimental flexibility and a high system reliability of 91% in the past year. Operationally, the gyrotrons can generate up to a total of 4.8 MW of rf power for pulses up to 5 seconds. The maximum ECH energy injected into the DIII-D is 16.6 MJ. The HE1,1 mode content is over 85% for all the lines, and the transmission coefficient is better than -1.1 dB for all the transmission lines, close to the theoretical value. A new depressed collector gyrotron was recently installed and was injecting up to 640 kW of power into the plasma during 2014-2015 tokamak operations. Four dual waveguide launchers, which can steer the RF beams ±20 degrees poloidally and toroidally, are used for real-time neoclassical tearing mode control and suppression. The launchers now have increased poloidal scanning speed and beam positioning accuracy of ~±2 mm at the plasma center. Two more gyrotrons are expected to be installed and operational in 2015- 2016. The first is a repaired 110 GHz, 1 MW gyrotron that had a gun failure after more than 11 years of operation at DIII-D. The second is a newly designed depressed collector tube in the 1.5 MW class, operating at 117.5 GHz, manufactured by Communications and Power Industries (CPI).

  13. Heating and Current Drive by Electron Cyclotron Waves

    NASA Astrophysics Data System (ADS)

    Prater, R.

    2003-10-01

    The physics model of electron cyclotron heating (ECH) and current drive (ECCD) is becoming well validated through systematic comparisons of theory and experiment. Work has shown that ECCD can be highly localized and robustly controlled, leading to applications including stabilization of MHD instabilities like neoclassical tearing modes, control and sustainment of desired profiles of current density and plasma pressure, and studies of localized transport. These physics applications and the study of the basic physics of ECH and ECCD were enabled by the advent of the gyrotron in the 1980s and of the diamond window for megawatt gyrotrons in the 1990s. The experimental work stimulated a broad base of theory based on first principles which is encapsulated in linear ray tracing codes and fully relativistic quasilinear Fokker-Planck codes. Recent experiments use measurements of the local poloidal magnetic field through the motional Stark effect to determine the magnitude and profile of the locally driven current. The subtle balance between wave-induced diffusion and Coulomb relaxation in velocity space provides an understanding of the effects of trapping of current-carrying electrons in the magnetic well, an effect which can be used to advantage. Strong quasilinear effects and radial transport of electrons which may broaden the driven current profile have also been observed under some conditions and appear to be consistent with theory, but in large devices these are usually insignificant. Additional advantages of ECH compared with other rf heating methods are that the antenna can be far removed from the plasma and the power density can be very high. The agreement of theory and experiment, the broad base of established applications, and the technical advantages of ECH support the application of ECH in next-step tokamaks and stellarators.

  14. Distribution of thermal neutron flux around a PET cyclotron.

    PubMed

    Ogata, Yoshimune; Ishigure, Nobuhito; Mochizuki, Shingo; Ito, Kengo; Hatano, Kentaro; Abe, Junichiro; Miyahara, Hiroshi; Masumoto, Kazuyoshi; Nakamura, Hajime

    2011-05-01

    The number of positron emission tomography (PET) examinations has greatly increased world-wide. Since positron emission nuclides for the PET examinations have short half-lives, they are mainly produced using on-site cyclotrons. During the production of the nuclides, significant quantities of neutrons are generated from the cyclotrons. Neutrons have potential to activate the materials around the cyclotrons and cause exposure to the staff. To investigate quantities and distribution of the thermal neutrons, thermal neutron fluxes were measured around a PET cyclotron in a laboratory associating with a hospital. The cyclotron accelerates protons up to 18 MeV, and the mean particle current is 20 μA. The neutron fluxes were measured during both 18F production and C production. Gold foils and thermoluminescent dosimeter (TLD) badges were used to measure the neutron fluxes. The neutron fluxes in the target box averaged 9.3 × 10(6) cm(-2) s(-1) and 1.7 × 10(6) cm(-2) s(-1) during 18F and 11C production, respectively. Those in the cyclotron room averaged 4.1 × 10(5) cm(-2) s(-1) and 1.2 × 10(5) cm(-2) s(-1), respectively. Those outside the concrete wall shielding were estimated as being equal to or less than ∼3 cm s, which corresponded to 0.1 μSv h(-1) in effective dose. The neutron fluxes outside the concrete shielding were confirmed to be quite low compared to the legal limit.

  15. The Origin of Narrow Band Cyclotron Wave Emissions Called Chorus

    NASA Astrophysics Data System (ADS)

    Skoug, Ruth Marie

    1995-01-01

    On May 6, 1993, a sounding rocket experiment designed to study microburst electron precipitation was launched from Poker Flat, Alaska, into a morningside auroral event. This was the first sounding rocket to simultaneously detect microburst electrons and associated very low frequency (VLF) waves. Both microbursts and narrow band VLF chorus (risers) were observed throughout the flight. Waves and electron bursts were observed in association with each other, but no one-to-one correlations were seen between the two phenomena. The association between waves and particles suggests that both phenomena may be produced by a wave -particle interaction. This dissertation discusses the design of the VLF wave antenna, a magnetic search coil, and the analysis of data from this instrument. The data are compared to chorus production theories to determine the source location and mechanism of the observed waves. In this work, the observed chorus emissions are interpreted in terms of a cyclotron resonance interaction. This is the first comprehensive test of the cyclotron resonance theory applied to chorus associated with microburst precipitation. The frequency range of the risers and the observed electron energy range agree with those required to satisfy the cyclotron resonance condition. Using a criterion derived from the conservation of energy during an interaction, it is determined that a cold plasma cyclotron resonance interaction could have produced only the lower frequency portions of the observed chorus risers. We present an extension of the cyclotron resonance theory which uses a warm plasma model of the wave-particle interaction. This model assumes a two-component plasma, with an isotropic cold component and a bi-Maxwellian warm component. The addition of the warm component produces sufficient changes in the wave dispersion relation that the interaction can produce the highest frequencies observed in our data set. As predicted by theory, an anisotropic plasma is required to

  16. Electron Cyclotron Emissions from AN Electron Cyclotron Heated Discharge in Isx-B

    NASA Astrophysics Data System (ADS)

    Elder, Gerald Blaine

    1983-09-01

    Observation of the electron cyclotron emissions (ECE) at both optically thick and optically thin frequencies can be a very useful tool in studying the behavior of the electron distribution. It is especially effective when studying the effects of electron cyclotron heating (ECH). Two detectors were built to observe the optically thin third harmonic radiation from ISX-B during the recent 28 GHz ECH experiments carried on at Oak Ridge National Laboratory. These detectors supplemented existing detectors at the fundamental frequency and at the second harmonic frequency. Observations of the three frequencies during and after the ECH was pulsed into the plasma showed an unexpected rise in their intensity, occurring after the ECH pulse was over. This rise lasted for many tens of milliseconds, well beyond estimates of the electron energy confinement time. The rise in the third harmonic intensity was frequently to an intensity 100 times greater than the pre-ECH intensity. The fundamental frequency and the second harmonic had a much milder change in their intensities. The rises were seen to depend critically on the density of the plasma and the length of the ECH pulse but only weakly on the pre-ECH temperature. A computer code which predicts the ECE from an electron distribution in ISX-B, taking into account the effect of the plasma's dielectric response to the emissions from a single electron, is developed. This code is the result of combining a ray tracing technique with the emissions from a single dressed test particle and summing over the electron distribution. The code confirms the sensitivity of the third harmonic emissions to small changes in the electron distribution. A Fokker-Planck code is combined with the emission code to predict the evolution of the ECE from a perturbed electron distribution. The codes clearly show that the rises in the emissions observed by the three detectors can be reasonably explained by consideration of the effect of pitch angle scattering

  17. Backward wave cyclotron-maser emission in the auroral magnetosphere.

    PubMed

    Speirs, D C; Bingham, R; Cairns, R A; Vorgul, I; Kellett, B J; Phelps, A D R; Ronald, K

    2014-10-10

    In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations.

  18. A 600 MeV cyclotron for radioactive beam production

    SciTech Connect

    Clark, D.J.

    1993-05-17

    The magnetic field design for a 600 MeV proton cyclotron is described. The cyclotron has a single stage, a normal conducting magnet coil and a 9.8 m outside yoke diameter. It has 8 sectors, with a transition to 4 sectors in the center region. The magnetic field design was done using 1958 Harwell rectangular ridge system measurements and was compared with recent 3-dimensional field calculations with the program TOSCA at NSCL. The center region 4--8 sector transition focussing was also checked with TOSCA.

  19. N-bursty emission from Uranus: A cyclotron maser source?

    NASA Technical Reports Server (NTRS)

    Curran, D. B.; Menietti, J. D.

    1993-01-01

    Ray tracing studies of RX-mode emission from the north polar regions of Uranus indicate that the n-bursty radio emission may have a source along field lines with footprints near the northern magnetic pole (perhaps in the cusp), but not necessarily associated with regions of strong UV emission. This is in contrast with similar studies for the Uranus nightside smooth radio emission, which are believed to be due to the cyclotron maser instability. Source regions can be found for both hollow and filled emission cones and for frequencies well above the local gyrofreuquency implying that mechanisms other than the cyclotron maser mechanism may be operating.

  20. RF cavity design for KIRAMS-430 superconducting cyclotron

    NASA Astrophysics Data System (ADS)

    Jung, In Su; Hong, Bong Hwan; Kang, Joonsun; Kim, Hyun Wook; Kim, Chang Hyeuk; Kwon, Key Ho

    2015-03-01

    The Korea Heavy Ion Medical Accelerator (KHIMA) has developed a superconducting cyclotron for the carbon therapy, which is called KIRAMS-430. The cyclotron is designed to accelerate only 12C6+ ions up to the energy of 430 MeV/u. It uses two normal conducting RF cavities. The RF frequency is about 70.76 MHz. The nominal dee voltage is 70 kV at the center and 160 kV at the extraction. The RF cavity was designed with 4 stems by using CST microwave studio (MWS). In this paper, we represent the simulation results and the optimized design of the RF cavity for the KIRAMS-430.

  1. Electron cyclotron emission diagnostics on the large helical device

    NASA Astrophysics Data System (ADS)

    Nagayama, Y.; Kawahata, K.; England, A.; Ito, Y.; Bretz, N.; McCarthy, M.; Taylor, G.; Doane, J.; Ikezi, H.; Edlington, T.; Tomas, J.

    1999-01-01

    The electron cyclotron emission (ECE) diagnostic system is installed on the large helical device (LHD). The system includes the following instruments: a heterodyne radiometer, a Michelson spectrometer, and a grating polychromator. A 63.5 mm corrugated waveguide system is fully utilized. Large collection optics and notch filters at the frequency of the LHD electron cyclotron heating (ECH) were developed for this system. In addition to these filters, the rectangular waveguide notch filters, the ECE measurement with the radiometer has been successfully performed during the ECH.

  2. Single-Electron Detection and Spectroscopy via Relativistic Cyclotron Radiation.

    PubMed

    Asner, D M; Bradley, R F; de Viveiros, L; Doe, P J; Fernandes, J L; Fertl, M; Finn, E C; Formaggio, J A; Furse, D; Jones, A M; Kofron, J N; LaRoque, B H; Leber, M; McBride, E L; Miller, M L; Mohanmurthy, P; Monreal, B; Oblath, N S; Robertson, R G H; Rosenberg, L J; Rybka, G; Rysewyk, D; Sternberg, M G; Tedeschi, J R; Thümmler, T; VanDevender, B A; Woods, N L

    2015-04-24

    It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.

  3. Analysis of gamma-ray burst spectra with cyclotron lines

    NASA Technical Reports Server (NTRS)

    Kargatis, Vincent; Liang, Edison P.

    1992-01-01

    Motivated by the recent developments in the cyclotron resonance upscattering of soft photons or CUSP model of Gamma Ray Burst (GBR) continuum spectra, we revisit a select database of GRBs with credible cyclotron absorption features. We measure the break energy of the continuum, the slope below the break and deduce the soft photon energy or the electron beam Lorentz factor cutoff. We study the correlation (or lack of) between various parameters in the context of the CUSP model. One surprise result is that there appears to be marginal correlation between the break energy and the spectral index below the break.

  4. Cyclotron modes of a multi-species ion plasma

    SciTech Connect

    Sarid, E.; Anderegg, F.; Driscoll, C. F.

    1995-04-15

    Cyclotron modes varying as exp(il{theta}), with l=1, 2 and 3, have been observed in an unneutralized Mg ion plasma. The l=1 mode is observed to be down-shifted from the corresponding cyclotron frequency, while the l{>=}2 modes are found to be up-shifted. Good agreement is found between the observed down-shifts of the l=1 modes of Mg{sup +} and Mg{sup ++} and the predictions of a multi-species cold plasma theory. The down-shifts depend on the composition and size of the plasma, and the relative abundance of each ion can thus be determined.

  5. Electron cyclotron heating experiments on the DIII-D tokamak

    SciTech Connect

    Prater, R.; Austin, M.E.; Bernabei, S.

    1998-01-01

    Initial experiments on heating and current drive using second harmonic electron cyclotron heating (ECH) are being performed on the DIII-D tokamak using the new 110 GHz ECH system. Modulation of the ECH power in the frequency range 50 to 300 Hz and detection of the temperature perturbation by ECE diagnostics is used to validate the location of the heating. This technique also determines an upper bound on the width of the deposition profile. Analysis of electron cyclotron current drive indicates that up to 0.17 MA of central current is driven, resulting in a negative loop voltage near the axis.

  6. Spatiotemporal exposome dynamics of soil lead and children's blood lead pre- and ten years post-Hurricane Katrina: Lead and other metals on public and private properties in the city of New Orleans, Louisiana, U.S.A.

    PubMed

    Mielke, Howard W; Gonzales, Christopher R; Powell, Eric T; Mielke, Paul W

    2017-05-01

    Anthropogenic re-distribution of lead (Pb) principally through its use in gasoline additives and lead-based paints have transformed the urban exposome. This unique study tracks urban-scale soil Pb (SPb) and blood Pb (BPb) responses of children living in public and private communities in New Orleans before and ten years after Hurricane Katrina (29 August 2005). To compare and evaluate associations of pre- and ten years post-Katrina SPb and children's BPb on public and private residential census tracts in the core and outer areas of New Orleans, and to examine correlations between SPb and nine other soil metals. The Louisiana Healthy Housing and Childhood Lead Poisoning Prevention Program BPb (µg/dL) data from pre- (2000-2005) and post-Katrina (2010-2015) for ≤6-year-old children. Data from public and adjacent private residential census tracts within core and outer areas are stratified from a database that includes 916 and 922 SPb and 13,379 and 4830 BPb results, respectively, from pre- and post-Katrina New Orleans. Statistical analyses utilize Multi-Response Permutation Procedure and Spearman's Rho Correlation. Pre- to Post-Katrina median SPb decreases in public and private core census tracts were from 285 to 55mg/kg and 710-291mg/kg, respectively. In public and private outer census tracts the median SPb decreased from 109 to 56mg/kg and 88-55mg/kg. Children's BPb percent ≥5µg/dL on public and private core areas pre-Katrina was 63.2% and 67.5%, and declined post-Katrina to 7.6% and 20.2%, respectively. BPb decreases also occurred in outer areas. Soil Pb is strongly correlated with other metals. Post-Katrina re-building of public housing plus landscaping amends the exposome and reduces children's BPb. Most importantly, Hurricane Katrina revealed that decreasing the toxicants in the soil exposome is an effective intervention for decreasing children's BPb. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Effects of the condensation and scattering of radiation at the plasma-dynamic expansion of the detonation products of lead azide

    NASA Astrophysics Data System (ADS)

    Izmailov, I. A.; Naumov, V. V.; Kochelap, V. A.

    2013-11-01

    The kinetics of the superluminescence of lead atoms, Pb 3 P {1/0} → 1 D 2 (722.9 nm) and 3 P {1/0} → 3 P 2 (405.8 nm), at the fast adiabatic expansion and cooling of the detonation products of lead azide Pb(N3)2 in vacuum has been studied. The effects of the condensation and scattering of light from drop clusters in an optically active heterophase medium has been analyzed in order to interpret the experiments in laser detonation plasma-dynamic systems based on metal azides.

  8. Inferring electromagnetic ion cyclotron wave intensity from low altitude POES proton flux measurements: A detailed case study with conjugate Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Shi, Run; Ni, Binbin; Gu, Xudong; Zhang, Xianguo; Zuo, Pingbing; Fu, Song; Xiang, Zheng; Wang, Qi; Cao, Xing; Zou, Zhengyang

    2017-03-01

    Electromagnetic ion cyclotron (EMIC) waves play an important role in the magnetospheric particle dynamics and can lead to resonant pitch-angle scattering and ultimate precipitation of ring current protons. Commonly, the statistics of in situ EMIC wave measurements is adopted for quantitative investigation of wave-particle interaction processes, which however becomes questionable for detailed case studies especially during geomagnetic storms and substorms. Here we establish a novel technique to infer EMIC wave amplitudes from low-altitude proton measurements onboard the Polar Operational Environmental Satellites (POES). The detailed procedure is elaborated regarding how to infer the EMIC wave intensity for one specific time point. We then test the technique with a case study comparing the inferred root-mean-square (RMS) EMIC wave amplitude with the conjugate Van Allen Probes EMFISIS wave measurements. Our results suggest that the developed technique can reasonably estimate EMIC wave intensities from low-altitude POES proton flux data, thereby providing a useful tool to construct a data-based, near-real-time, dynamic model of the global distribution of EMIC waves once the proton flux measurements from multiple POES satellites are available for any specific time period.

  9. Effect of Alfvén waves on the growth rate of the electron-cyclotron maser emission

    SciTech Connect

    Wu, D. J.

    2014-06-15

    By using the non-relativistic approximation for the calculation of growth rates, but taking account of the weakly relativistic modification for the electron-cyclotron resonance condition, it is shown that the effect of Alfvén waves (AWs) on the electron-cyclotron maser emission leads to the significant increase of the O-mode growth rate, but has little effect on the X-mode growth rate. We propose that this is because the O-mode wave has the field-aligned polarization sense in the same as the field-aligned oscillatory current, which is created by the field-aligned oscillatory motion of the energetic electrons caused via the presence of AWs. It is this field-aligned oscillatory current that contributes a novel growth rate to the O-mode wave but has little effect on the X-mode wave.

  10. Short-term synaptic plasticity in the deterministic Tsodyks–Markram model leads to unpredictable network dynamics

    PubMed Central

    Cortes, Jesus M.; Desroches, Mathieu; Rodrigues, Serafim; Veltz, Romain; Muñoz, Miguel A.; Sejnowski, Terrence J.

    2013-01-01

    Short-term synaptic plasticity strongly affects the neural dynamics of cortical networks. The Tsodyks and Markram (TM) model for short-term synaptic plasticity accurately accounts for a wide range of physiological responses at different types of cortical synapses. Here, we report a route to chaotic behavior via a Shilnikov homoclinic bifurcation that dynamically organizes some of the responses in the TM model. In particular, the presence of such a homoclinic bifurcation strongly affects the shape of the trajectories in the phase space and induces highly irregular transient dynamics; indeed, in the vicinity of the Shilnikov homoclinic bifurcation, the number of population spikes and their precise timing are unpredictable and highly sensitive to the initial conditions. Such an irregular deterministic dynamics has its counterpart in stochastic/network versions of the TM model: The existence of the Shilnikov homoclinic bifurcation generates complex and irregular spiking patterns and—acting as a sort of springboard—facilitates transitions between the down-state and unstable periodic orbits. The interplay between the (deterministic) homoclinic bifurcation and stochastic effects may give rise to some of the complex dynamics observed in neural systems. PMID:24062464

  11. Investigation of the biosorption characteristics of lead(II) ions onto Symphoricarpus albus: Batch and dynamic flow studies.

    PubMed

    Akar, Sibel Tunali; Gorgulu, Asli; Anilan, Burcu; Kaynak, Zerrin; Akar, Tamer

    2009-06-15

    This work reports the results of the study for lead(II) binding by the natural and low cost biosorbent Symphoricarpus albus. Batch biosorption experiments demonstrated the high rate of lead(II) biosorption and the kinetic data were successfully described by a pseudo-second-order model. Biosorption of lead(II) onto S. albus biomass showed a pH-dependent profile and lead(II) biosorption was higher when pH or temperature was increased. As much as 88.5% removal of lead(II) is also possible in the multi-metal mixture. The Langmuir isotherm better fits the biosorption data and the monolayer biosorption capacity was 3.00 x 10(-4) mol g(-1) at 45 C. The biomass was characterized with FTIR and SEM analysis. Desorption studies revealed that the natural biomass could be regenerated using 10mM HNO(3) solution with about 99% recovery and reused in five biosorption-desorption cycles. Therefore, S. albus which is cheap, highly selective and easily regenerable seems to be a promising substrate to entrap lead(II) ions in aqueous solutions.

  12. Dynamical next-to-next-to-leading order parton distributions and the perturbative stability of F{sub L}(x,Q{sup 2})

    SciTech Connect

    Glueck, M.; Reya, E.; Pisano, C.

    2008-04-01

    Recent measurements for F{sub 2}(x,Q{sup 2}) have been analyzed in terms of the 'dynamical' and 'standard' parton model approach at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of perturbative QCD. Having fixed the relevant NLO and NNLO parton distributions, we present the implications and predictions for the longitudinal structure function F{sub L}(x,Q{sup 2}). It is shown that the previously noted extreme perturbative NNLO/NLO instability of F{sub L}(x,Q{sup 2}) is an artifact of the commonly utilized 'standard' gluon distributions. In particular it is demonstrated that using the appropriate--dynamically generated--parton distributions at NLO and NNLO, F{sub L}(x,Q{sup 2}) turns out to be perturbatively rather stable already for Q{sup 2}{>=}O(2-3 GeV{sup 2})

  13. Performance of the beam chamber vacuum system of K = 500 cyclotron at Variable Energy Cyclotron Centre Kolkata.

    PubMed

    Pal, Gautam; DuttaGupta, Anjan; Chakrabarti, Alok

    2014-07-01

    The beam chamber of Variable Energy Cyclotron Centre, Kolkata's K = 500 superconducting cyclotron is pumped by liquid helium cooled cryopanel with liquid nitrogen cooled radiation shield. Performance of the vacuum system was evaluated by cooling the cryopanel assembly with liquid nitrogen and liquid helium. Direct measurement of beam chamber pressure is quite difficult because of space restrictions and the presence of high magnetic field. Pressure gauges were placed away from the beam chamber. The beam chamber pressure was evaluated using a Monte Carlo simulation software for vacuum system and compared with measurements. The details of the vacuum system, measurements, and estimation of pressure of the beam chamber are described in this paper.

  14. Electron-cyclotron-heating experiments in tokamaks and stellarators

    SciTech Connect

    England, A.C.

    1983-01-01

    This paper reviews the application of high-frequency microwave radiation to plasma heating near the electron-cyclotron frequency in tokamaks and stellarators. Successful plasma heating by microwave power has been demonstrated in numerous experiments. Predicted future technological developments and current theoretical understanding suggest that a vigorous program in plasma heating will continue to yield promising results.

  15. Cyclotron Resonance of Electrons Trapped in a Microwave Cavity

    ERIC Educational Resources Information Center

    Elmore, W. C.

    1975-01-01

    Describes an experiment in which the free-electron cyclotron resonance of electrons trapped in a microwave cavity by a Penning trap is observed. The experiment constitutes an attractive alternative to one of the Gardner-Purcell variety. (Author/GS)

  16. Cyclotron maser emission of auroral Z mode radiation

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Hewitt, R. G.; Dulk, G. A.

    1983-01-01

    Results are presented suggesting that loss cone driven cyclotron maser emission by upgoing electrons, closely analogous to auroral kilometric radiation (AKR), may be the mechanism behind the observed Z mode radiation. With this hypothesis, the lack of a strong correlation between the Z mode radiation and AKR is not surprising; the ray paths for the X mode and the Z mode are markedly different, with the former directed upward and the latter downward. In addition, it is expected that the generation of the Z mode will be favored only in regions where the ratio of the plasma frequency to the electron cyclotron frequency is greater than or approximately equal to 0.3, that is, where the X mode radiation is suppressed. If the fraction of the radiation generated that crosses the cyclotron layer is large, then the argument in favor of the loss cone driven cyclotron maser as the source of the observed Z mode radiation is a strong one. The spatial growth rates are fairly large in comparison with those for the X mode, and there seems to be little doubt that Z mode radiation should be generated under conditions that differ only slightly from those for the generation of X mode radiation in AKR.

  17. Digital control in LLRF system for CYCIAE-100 cyclotron

    NASA Astrophysics Data System (ADS)

    Yin, Zhiguo; Fu, Xiaoliang; Ji, Bin; Zhang, Tianjue; Wang, Chuan

    2016-05-01

    As a driven accelerator, the CYCIAE-100 cyclotron is designed by China Institute of Atomic Energy for the Beijing Radio Ion-beam Facility project. The cyclotron RF system is designed to use two RF power sources of 100 kW to drive two half-wavelength cavities respectively. Two Dee accelerating electrodes are kept separately from each other inside the cyclotron, while their accelerating voltages are maintained in phase by the efforts of LLRF control. An analog-digital hybrid LLRF system has been developed to achieve cavity tuning control, dee voltage amplitude and phase stabilization etc. The analog subsystems designs are focused on RF signal up/down conversion, tuning control, and dee voltage regulation. The digital system provides an RF signal source, aligns the cavity phases and maintains a Finite State Machine. The digital parts combine with the analog functions to provide the LLRF control. A brief system hardware introduction will be given in this paper, followed by the review of several major characteristics of the digital control in the 100 MeV cyclotron LLRF system. The commissioning is also introduced, and most of the optimization during the process was done by changing the digital parts.

  18. Nonlinear analysis of a relativistic beam-plasma cyclotron instability

    NASA Technical Reports Server (NTRS)

    Sprangle, P.; Vlahos, L.

    1986-01-01

    A self-consistent set of nonlinear and relativistic wave-particle equations are derived for a magnetized beam-plasma system interacting with electromagnetic cyclotron waves. In particular, the high-frequency cyclotron mode interacting with a streaming and gyrating electron beam within a background plasma is considered in some detail. This interaction mode may possibly find application as a high-power source of coherent short-wavelength radiation for laboratory devices. The background plasma, although passive, plays a central role in this mechanism by modifying the dielectric properties in which the magnetized electron beam propagates. For a particular choice of the transverse beam velocity (i.e., the speed of light divided by the relativistic mass factor), the interaction frequency equals the nonrelativistic electron cyclotron frequency times the relativistic mass factor. For this choice of transverse beam velocity the detrimental effects of a longitudinal beam velocity spread is virtually removed. Power conversion efficiencies in excess of 18 percent are both analytically calculated and obtained through numerical simulations of the wave-particle equations. The quality of the electron beam, degree of energy and pitch angle spread, and its effect on the beam-plasma cyclotron instability is studied.

  19. Parametric decay of an electromagnetic wave near electron cyclotron harmonics

    SciTech Connect

    Istomin, Y.N.; Leyser, T.B.

    1995-06-01

    A system of equations describing the nonlinear coupling of high frequency electron Bernstein (EB) and upper hybrid (UH) waves near harmonics of the electron cyclotron frequency with low frequency lower hybrid (LH) waves in a homogeneous, weakly magnetized, and weakly collisional plasma is derived. The EB and UH modes are described by a single second order equation, taking into account the interaction with low frequency density fluctuations. The ponderomotive force of the high frequency oscillations increases near the cyclotron harmonics due to the resonance with the electron motion. The obtained equations are used to study the parametric decay of an infinite wavelength electromagnetic pump wave into EB or UH waves and LH waves. The threshold electric fields are sufficiently low to be exceeded in high frequency ionospheric modification experiments. However, the instability cannot be excited for pump frequencies near the cyclotron harmonics. For the decay into EB waves, the resulting forbidden frequency range depends on the harmonic number in a power law manner, consistent with observations of stimulated electromagnetic emissions in ionospheric modification experiments. Further, for sufficiently high pump electric fields the instability is also suppressed, when the frequency mismatch around the eigenfrequencies at which the interaction can occur is of the order of the frequency separation between the EB and UH modes near the cyclotron harmonics. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. Cyclotron targetry for production of short-lived positron emitters

    SciTech Connect

    Schlyer, D.J.

    1989-01-01

    The basic concepts of cyclotron target design are presented along with the relevant practical experience gained by workers in this field over the years. Results are presented from several recent studies on the temperature and density distribution inside gas and liquid targets. 5 refs., 3 figs.

  1. An intense alpha ion source for INRS cyclotron

    SciTech Connect

    Chen Ling,-xing; Chen Mao-bei

    1985-10-01

    An intense PIG alpha source for INRS has been developed with low arc power and low gas flow. Generally, the alpha yield of the new source is twice as much as the old one. The structure and character of the source and its experimental results both on the bench and cyclotron are described in this paper.

  2. Electron cyclotron thruster new modeling results preparation for initial experiments

    NASA Technical Reports Server (NTRS)

    Hooper, E. Bickford

    1993-01-01

    The following topics are discussed: a whistler-based electron cyclotron resonance heating (ECRH) thruster; cross-field coupling in the helicon approximation; wave propagation; wave structure; plasma density; wave absorption; the electron distribution function; isothermal and adiabatic plasma flow; ECRH thruster modeling; a PIC code model; electron temperature; electron energy; and initial experimental tests. The discussion is presented in vugraph form.

  3. Cyclotron waves in a non-neutral plasma column

    SciTech Connect

    Dubin, Daniel H. E.

    2013-04-15

    A kinetic theory of linear electrostatic plasma waves with frequencies near the cyclotron frequency {Omega}{sub c{sub s}} of a given plasma species s is developed for a multispecies non-neutral plasma column with general radial density and electric field profiles. Terms in the perturbed distribution function up to O(1/{Omega}{sub c{sub s}{sup 2}}) are kept, as are the effects of finite cyclotron radius r{sub c} up to O(r{sub c}{sup 2}). At this order, the equilibrium distribution is not Maxwellian if the plasma temperature or rotation frequency is not uniform. For r{sub c}{yields}0, the theory reproduces cold-fluid theory and predicts surface cyclotron waves propagating azimuthally. For finite r{sub c}, the wave equation predicts that the surface wave couples to radially and azimuthally propagating Bernstein waves, at locations where the wave frequency equals the local upper hybrid frequency. The equation also predicts a second set of Bernstein waves that do not couple to the surface wave, and therefore have no effect on the external potential. The wave equation is solved both numerically and analytically in the WKB approximation, and analytic dispersion relations for the waves are obtained. The theory predicts that both types of Bernstein wave are damped at resonances, which are locations where the Doppler-shifted wave frequency matches the local cyclotron frequency as seen in the rotating frame.

  4. Ion cyclotron waves below the proton gyrofrequency in the magnetosphere

    SciTech Connect

    Gomberoff, L.; Molina, M.

    1985-02-01

    A numerical comparison between the linear theory of ion-cyclotron waves below the proton gyrofrequency and the data recorded on board the GEOS satellites is made. It is shown that the experimental data are in good agreement with the theory.

  5. Status of ECR (Electron Cyclotron Resonance) source technology

    SciTech Connect

    Lyneis, C.M.

    1987-03-01

    ECR (Electron Cyclotron Resonance) ion sources are now in widespread use for the production of high quality multiply charged ion beams for accelerators and atomic physics experiments, and industrial applications are being explored. Several general characteristics of ECR sources explain their widespread acceptance. For use with cyclotrons which require CW multiply charged ion beams, the ECR source has many advantages over heavy-ion PIG sources. Most important is the ability to produce higher charge states at useful intensities for nuclear physics experiments. Since the maximum energy set by the bending limit of a cyclotron scales with the square of the charge state, the installation of ECR sources on cyclotrons has provided an economical path to raise the energy. Another characteristic of ECR sources is that the discharge is produced without cathodes, so that only the source material injected into an ECR source is consumed. As a result, ECR sources can be operated continuously for periods of weeks without interruption. Techniques have been developed in the last few years, which allow these sources to produce beams from solid materials. The beam emittance from ECR sources is in the range of 50 to 200 ..pi.. mm-mrad at 10 kV. The principles of ECR ion sources are discussed, and present and future ECR sources are reviewed.

  6. Silicon meets cyclotron: muon spin resonance of organosilicon radicals.

    PubMed

    West, Robert; Samedov, Kerim; Percival, Paul W

    2014-07-21

    Muons, generated at a high-powered cyclotron, can capture electrons to form muonium atoms. Muon spin resonance spectra can be recorded for organosilyl radicals obtained by addition of muonium atoms to silylenes and silenes. We present a brief summary of progress in this new area since the first such experiments were reported in 2008.

  7. Axial injection and phase selection studies of the MSU K1200 cyclotron

    SciTech Connect

    Bailey, J.D. |

    1995-12-31

    Axial injection into a cyclotron through its iron yoke, a spiral inflector, and the central region electrodes couples the transverse coordinates of motion together, as well as with the longitudinal coordinates. The phase slits in the K1200 cyclotron use the r - {phi} correlations inherent in acceleration of ions in a cyclotron. Computer simulations of injection into and acceleration within the K1200 cyclotron encompassing the four transverse dimensions together with time were used to determine beam matching requirements for injection and phase selection in the K1200 cyclotron. The simulations were compared with measurements using an external timing detector.

  8. Progress in research, April 1, 1992--March 31, 1993, Texas A and M University Cyclotron Institute

    SciTech Connect

    1993-07-01

    This Institute annual report for the period 1 April 1992--31 March 1993 covers a period which has seen the initial runs of three new spectrometers which constitute a major portion of the new detection capabilities developed for this facility. These devices are the Proton Spectrometer (PSP), the Mass Achromat Recoil Mass Spectrometer (MARS), and the Multipole dipole Multipole (MDM) Particle Spectrometer. These devices are now available to pursue the studies of Gamow Teller states, reactions of astrophysical interest, and giant resonance studies for which they were constructed, as well as for other experiments. A beam analysis system which will deliver high resolution beams to the MDM spectrometer is currently under construction. With the completion of these spectrometer projects, the facility emphasis is now focused on the development of the full capabilities of the K500 cyclotron and on the research program. During the report period, the ECR-K500 cyclotron combination operated 5,849 hours. Theoretical work reported in this document ranges from nuclear structure calculations using the IBM-2 model to calculations of kaon production and the in-medium properties of the rho and phi mesons, the latter as a probe of the QCD phase transition. Nuclear dynamics and exotic shapes and fragmentation modes of hot nuclei are also addressed. In atomic physics, new measurements of x-ray emission from highly ionized ions, of molecular dissociation and of surface interactions are reported.

  9. VASIMR Simulation Studies of Auroral Ion Cyclotron Heating

    NASA Astrophysics Data System (ADS)

    Brukardt, M.; Bering, E. A.; Chang-Diaz, F. R.; Squire, J. P.; Glover, T. W.; Jacobs0n, V. T.; McCaskill, G. E.; Cassady, L. D.; Bengtson, R. D.

    2006-12-01

    Plasma physics has found an increasing range of practical industrial applications, including the development of electric spacecraft propulsion systems. One of these systems, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine, both applies and can be used to simulate several important physical processes occurring in the magnetosphere. These processes include the mechanisms involved in the ion acceleration and heating that occur in the Birkeland currents of an auroral arc system. Auroral current region processes that are simulated in VASIMR include lower hybrid heating, parallel electric field acceleration and ion cyclotron acceleration. This paper will focus on using a physics demonstration model VASIMR to study ion cyclotron heating (ICRH) similar to auroral zone processes. The production of upward moving `ion conics' and ion heating are significant features in auroral processes. It is believed that ion cyclotron heating plays a role in these processes, but laboratory simulation of these auroral effects is difficult owing to the fact that the ions involved only pass through the acceleration region once. In the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) we have successfully simulated these effects. The current configuration of the VASIMR uses a helicon antenna with up to 20 kW of power to generate plasma then uses an RF booster stage that uses left hand polarized slow mode waves launched from the high field side of the resonance. The current setup for the booster uses 2 to 4 MHz waves with up to 20 kW of power. This is similar to the ion cyclotron heating in tokamaks, but in the VASIMR the ions only pass through the resonance region once. The rapid absorption of ion cyclotron waves has been predicted in recent theoretical studies. These theoretical predictions have been confirmed with several independent measurements. The ion cyclotron resonance heating (ICRH) shows a substantial increase in ion velocity. Pitch angle distribution studies

  10. Electron acceleration by Z-mode waves associated with cyclotron maser instability

    SciTech Connect

    Lee, K. H.; Lee, L. C.; Omura, Y.

    2012-12-15

    We demonstrate by a particle simulation that Z-mode waves generated by the cyclotron maser instability can lead to a significant acceleration of energetic electrons. In the particle simulation, the initial electron ring distribution leads to the growth of Z-mode waves, which then accelerate and decelerate the energetic ring electrons. The initial ring distribution evolves into an X-like pattern in momentum space, which can be related to the electron diffusion curves. The peak kinetic energy of accelerated electrons can reach 3 to 6 times the initial kinetic energy. We further show that the acceleration process is related to the 'nonlinear resonant trapping' in phase space, and the test-particle calculations indicate that the maximum electron energy gain {Delta}{epsilon}{sub max} is proportional to B{sub w}{sup 0.57}, where B{sub w} is the wave magnetic field.

  11. Dynamical Origin of the Rashba Effect in Organohalide Lead Perovskites: A Key to Suppressed Carrier Recombination in Perovskite Solar Cells?

    PubMed

    Etienne, Thibaud; Mosconi, Edoardo; De Angelis, Filippo

    2016-05-05

    The presence of a Rashba band-splitting mechanism mediated by spin-orbit coupling and breaking of inversion symmetry has been suggested as a possible cause for the reduced recombination rates observed in organohalide perovskites. Here, we investigate the interplay of electronic and nuclear degrees of freedom in defining the Rashba splitting in realistic MAPbI3 models. Our simulations disclose a "dynamical Rashba effect", allowing for a quantification of its magnitude under thermal conditions. We find that even in globally centrosymmetric structures the dynamics of the coupled inorganic-organic degrees of freedom give rise to a spatially local Rashba effect which fluctuates on the subpicosecond time scale typical of the methylammonium cation dynamics. This effect is progressively quenched in globally centrosymmetric structures, likely representing the MAPbI3 perovskite at room temperature, on increasing the probed spatial scale up to 32 MAPbI3 units (∼3 nm size) because of the incoherent nuclear thermal motion mediated by the disorder of the organic cations.

  12. Characteristics of heat flux and electromagnetic electron-cyclotron instabilities driven by solar wind electrons

    NASA Astrophysics Data System (ADS)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Qureshi, M. N. S.

    2017-01-01

    In-situ observations reveal the existence of electron velocity distribution function in the solar wind, where the net distribution can be modeled by a combination of core, halo and strahl. These components often possess a relative drift and with respective temperature anisotropies. The relative drift between the core and halo components leads to heat flux (HF) instability, while temperature anisotropies drive electromagnetic electron-cyclotron (EMEC) instability. These instabilities have been separately studied in the literature, but for the first time, the present study combines both unstable modes in the presence of two free energy sources, namely, excessive parallel pressure and excessive perpendicular temperature. Heat flux instability (which is a left-hand circularly polarized mode) is effectively similar to electron firehose instability, except that the free energy is provided by net relative drift among two component electrons in the background of protons. The heat flux instability is discussed here along with (the right-hand polarized) EMEC instability driven by temperature anisotropy. The unstable heat flux mode is conventionally termed the "whistler" heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. Electromagnetic electron-cyclotron mode, on the other hand, reduces to the proper whistler wave in the absence of free energy source. The present combined analysis clarifies the polarization characteristics of these two modes in an unambiguous manner.

  13. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    DOE PAGES

    Tobias, B.; Domier, C. W.; Luhmann, Jr., N. C.; ...

    2016-07-25

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads tomore » 10x improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). As a result, implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.« less

  14. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    SciTech Connect

    Tobias, B.; Domier, C. W.; Luhmann, Jr., N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A. -V.; Wang, Y.

    2016-07-25

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10x improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). As a result, implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  15. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    SciTech Connect

    Tobias, B.; Domier, C. W.; Luhmann, N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A.-V.; Wang, Y.

    2016-11-15

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50–150 GHz) to an intermediate frequency (IF) band (e.g. 0.1–18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  16. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    SciTech Connect

    Tobias, B.; Domier, C. W.; Luhmann, Jr., N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A. -V.; Wang, Y.

    2016-07-25

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10x improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). As a result, implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  17. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    NASA Astrophysics Data System (ADS)

    Tobias, B.; Domier, C. W.; Luhmann, N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A.-V.; Wang, Y.

    2016-11-01

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  18. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry.

    PubMed

    Tobias, B; Domier, C W; Luhmann, N C; Luo, C; Mamidanna, M; Phan, T; Pham, A-V; Wang, Y

    2016-11-01

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  19. Self-Consistent Model of Magnetospheric Ring Current and Electromagnetic Ion Cyclotron Waves: The May 2-7, 1998, Storm

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.

    2003-01-01

    Complete description of a self-consistent model for magnetospheric ring current interacting with electromagnetic ion cyclotron waves is presented. The model is based on the system of two kinetic equations; one equation describes the ring current ion dynamics, and another equation describes the wave evolution. The effects on ring current ions interacting with electromagnetic ion cyclotron waves, and back on waves, are considered self-consistently by solving both equations on a global magnetospheric scale under non steady-state conditions. In the paper by Khazanov et al. [2002] this self-consistent model has only been shortly outlined, and discussions of many the model related details have been omitted. For example, in present study for the first time a new algorithm for numerical finding of the resonant numbers for quasilinear wave-particle interaction is described, or it is demonstrated that in order to describe quasilinear interaction in a multi-ion thermal plasma correctly, both e and He(+) modes of electromagnetic ion cyclotron waves should be employed. The developed model is used to simulate the entire May 2-7, 1998 storm period. Trapped number fluxes of the ring current protons are calculated and presented along with their comparison with the data measured by the 3D hot plasma instrument Polar/HYDRA. Examining of the wave (MLT, L shell) distributions produced during the storm progress reveals an essential intensification of the wave emissions in about two days after main phase of storm. This result is well consistent with the earlier ground-based observations. Also the theoretical shapes and the occurrence rates for power spectral densities of electromagnetic ion cyclotron waves are studied. It is found that in about 2 days after the storm main phase on May 4, mainly non Gaussian shapes of power spectral densities are produced.

  20. Influence of constant, alternating and cyclotron low-intensity electromagnetic fields on fibroblast proliferative activity in vitro.

    PubMed

    Afinogenov, Gennadi; Afinogenova, Anna; Kalinin, Andrey

    2009-12-16

    Available data allow assuming the presence of stimulation of reparative processes under influence of low-intensity electromagnetic field, commensurable with a magnetic field of the Earth. Research of effects of low-intensity electromagnetic fields on fibroblast proliferative activity in human lungs in cell culture was performed.The influence of a constant electromagnetic field, an alternating electromagnetic field by frequency of 50 Hz and cyclotron electromagnetic field with identical intensity for all kinds of fields - 80 mcTl - on value of cellular mass and a correlation of live and dead cells in culture is investigated in three series of experiments. We used the universal electromagnetic radiator generating all three kinds of fields and supplied by a magnetometer which allows measuring the intensity of accurate within 0.1 mcTl including taking into account the Earth's magnetic field intensity.The peak value for stimulation cellular proliferation in the present experiences was two-hour influence by any of the specified kinds of electromagnetic fields. The irradiation by cyclotron electromagnetic field conducts positive dynamics in growth of live cells (up to 206+/-22%) and decreases the number of dead cells (down to 31+/-6%). Application of cyclotron magnetic fields promoted creation of optimum conditions for proliferation. As a result of researches we observed the reliable 30% increase of nitro-tetrazolium index (in nitro-tetrazolium blue test) after irradiation by cyclotron electromagnetic field in experience that testifies to strengthening of the cell breathing of living cells.In our opinion, it is necessary to pay attention not only to a pure gain of cells, but also to reduction of number dead cells that can be criterion of creation of optimum conditions for their specific development and valuable functioning.