Ion Acceleration by Flux Transfer Events in the Terrestrial Magnetosheath

NASA Astrophysics Data System (ADS)

Jarvinen, R.; Vainio, R.; Palmroth, M.; Juusola, L.; Hoilijoki, S.; Pfau-Kempf, Y.; Ganse, U.; Turc, L.; von Alfthan, S.

2018-02-01

We report ion acceleration by flux transfer events in the terrestrial magnetosheath in a global two-dimensional hybrid-Vlasov polar plane simulation of Earth's solar wind interaction. In the model we find that propagating flux transfer events created in magnetic reconnection at the dayside magnetopause drive fast-mode bow waves in the magnetosheath, which accelerate ions in the shocked solar wind flow. The acceleration at the bow waves is caused by a shock drift-like acceleration process under stationary solar wind and interplanetary magnetic field upstream conditions. Thus, the energization is not externally driven but results from plasma dynamics within the magnetosheath. Energetic proton populations reach the energy of 30 keV, and their velocity distributions resemble time-energy dispersive ion injections observed by the Cluster spacecraft in the magnetosheath.

MMS Observations of the Evolution of Ion-Scale Flux Transfer Events

NASA Astrophysics Data System (ADS)

Zhao, C.; Russell, C. T.; Strangeway, R. J.; Paterson, W.; Petrinec, S.; Zhou, M.; Anderson, B. J.; Baumjohann, W.; Bromund, K. R.; Chutter, M.; Fischer, D.; Gershman, D. J.; Giles, B. L.; Le, G.; Nakamura, R.; Plaschke, F.; Slavin, J. A.; Torbert, R. B.

2017-12-01

Flux transfer events are key processes in the solar wind-magnetosphere interaction. Previously, the observed flux transfer events have had scale sizes of 10,000 km radius in the cross-section and connect about 2 MWb magnetic flux from solar wind to the terrestrial magnetosphere. Recently, from the high-temporal resolution MMS magnetic field data, many ion-scale FTEs have been found. These FTEs contains only about 2 kWb magnetic flux and are believed to be in an early stage of FTE evolution. With the help of the well-calibrated MMS data, we are also able to determine the velocity profile and forces within the FTE events. We find that some ion-scale FTEs are expanding as we expect, but there are also contracting FTEs. We examine the differences between the two classes of FTEs and their differences with the larger previously studied class of FTE.

An empirical model of electron and ion fluxes derived from observations at geosynchronous orbit

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

Denton, M. H.; Thomsen, M. F.; Jordanova, V. K.

Knowledge of the plasma fluxes at geosynchronous orbit is important to both scientific and operational investigations. We present a new empirical model of the ion flux and the electron flux at geosynchronous orbit (GEO) in the energy range ~1 eV to ~40 keV. The model is based on a total of 82 satellite-years of observations from the Magnetospheric Plasma Analyzer instruments on Los Alamos National Laboratory satellites at GEO. These data are assigned to a fixed grid of 24 local-times and 40 energies, at all possible values of Kp. Bi-linear interpolation is used between grid points to provide the ionmore » flux and the electron flux values at any energy and local-time, and for given values of geomagnetic activity (proxied by the 3-hour Kp index), and also for given values of solar activity (proxied by the daily F10.7 index). Initial comparison of the electron flux from the model with data from a Compact Environmental Anomaly Sensor II (CEASE-II), also located at geosynchronous orbit, indicate a good match during both quiet and disturbed periods. The model is available for distribution as a FORTRAN code that can be modified to suit user-requirements.« less

An empirical model of electron and ion fluxes derived from observations at geosynchronous orbit

DOE PAGES

Denton, M. H.; Thomsen, M. F.; Jordanova, V. K.; ...

2015-04-01

Knowledge of the plasma fluxes at geosynchronous orbit is important to both scientific and operational investigations. We present a new empirical model of the ion flux and the electron flux at geosynchronous orbit (GEO) in the energy range ~1 eV to ~40 keV. The model is based on a total of 82 satellite-years of observations from the Magnetospheric Plasma Analyzer instruments on Los Alamos National Laboratory satellites at GEO. These data are assigned to a fixed grid of 24 local-times and 40 energies, at all possible values of Kp. Bi-linear interpolation is used between grid points to provide the ionmore » flux and the electron flux values at any energy and local-time, and for given values of geomagnetic activity (proxied by the 3-hour Kp index), and also for given values of solar activity (proxied by the daily F10.7 index). Initial comparison of the electron flux from the model with data from a Compact Environmental Anomaly Sensor II (CEASE-II), also located at geosynchronous orbit, indicate a good match during both quiet and disturbed periods. The model is available for distribution as a FORTRAN code that can be modified to suit user-requirements.« less

Ion flux oscillations and ULF waves observed by ARASE satellite and their origin

NASA Astrophysics Data System (ADS)

Yamamoto, K.; Masahito, N.; Kasahara, S.; Yokota, S.; Keika, K.; Matsuoka, A.; Teramoto, M.; Nomura, R.; Fujimoto, A.; Tanaka, Y.; Shinohara, M.; Shinohara, I.; Yoshizumi, M.

2017-12-01

The ARASE satellite, which was launched on December 20, 2016, is now observing thenightside inner magnetosphere. The inclination of the orbit is larger than those of otherrecent spacecraft flying in the inner magnetosphere such as THMEIS and Van Allen Probes.This unique orbit provides us new information on ULF waves since ULF waves havelatitudinal structure and the antinode of magnetic fluctuations of fundamental mode is athigh magnetic latitudes.Although Pc pulsations are predominantly observed on the dayside, ARASE satellitesometimes observes Pc4-5 pulsations on the nightside. Some of these waves are accompaniedwith energetic particle flux modulations. We found 6 events of the particle flux modulationsaccompanying Pc pulsations on the dawnside and nightside. Theoretical studies suggest thatULF waves detected at afternoon are generated by plasma instabilities like drift-mirror instability [Hasegawa, 1969] and drift-bounce resonance [Southwood et al, 1969].These instabilities cause plasma pressure disturbances or flux modulation of ions. Nonresonant ion clouds injected on the duskside are also considered to be one of the candidates ofULF wave driver [Zolotukhina, 1974]. We therefore discuss whether the ULF waves observedby ARASE satellite are generated internally or externally, and the flux modulations arecreated by plasma instabilities or the other non-resonant effects.On March 31, 2017, Medium-Energy Particle Experiments - Ion Mass Analyzer (MEPi)onboard ARASE detected ion flux oscillations at 12-70 keV with a period of 120 seconds inthe normal (NML) mode observation. NML mode observation provides details of the directionof particle movements. The pitch angle distribution of proton flux showed isotropic fluxoscillations. At the same time, Pc4 pulsations with the same oscillation period were observed.These flux and field perturbations were seen on the dawnside (4.3-5.9 MLT).ARASE found oscillations of ion count with a period of 130 seconds in the time

Study of the storm time fluxes of heavy ions

NASA Technical Reports Server (NTRS)

1978-01-01

The characteristics of the storm time ring current ions in the energy range of 0.5 to 16 keV were investigated. Data were processed and analyzed from the energetic ion mass spectrometer aboard the S3-3 satellite. Results are used for planning and operating the ion mass spectrometer experiment on the ISEE spacecraft, for selecting and processing the ISEE ion data, and for planning and conducting coordinated satellite experiments in support of the International Magnetospheric Study (IMS). It is established from the S3-3 ion data that relatively large fluxes of energetic (keV) 0(+) and H(+) ions are frequently flowing upward from the ionosphere along magnetic field lines in the polar auroral regions. Also, from investigations with the same instrument during the main phase of three moderate (D sub ST approximately 100) magnetic storms, it is found that the number density of 0(+) ions in the ring current was comparable to H(+) ion density the range 0.5 to 15 keV.

Heat flux modeling using ion drift effects in DIII-D H-mode plasmas with resonant magnetic perturbations

DOE PAGES

Wingen, Andreas; Schmitz, Oliver; Evans, Todd E.; ...

2014-01-01

The heat flux patterns measured in low-collisionality DIII-D H-mode plasmas strongly deviate from simultaneously measured CII emission patterns, used as indicator of particle flux, during applied resonant magnetic perturbations. While the CII emission clearly shows typical striations, which are similar to magnetic footprint patterns obtained from vacuum field line tracing, the heat flux is usually dominated by one large peak at the strike point position. The vacuum approximation, which only considers applied magnetic fields and neglects plasma response and plasma effects, cannot explain the shape of the observed heat flux pattern. One possible explanation is the effect of particle drifts.more » This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show di fferent drift motions at thermal energy levels in a guiding center approximation. While electrons hardly deviate from the field lines, ions can drift several centimetres away from field line flux surfaces. A model is presented in which an ion heat flux, based on the ion drift motion from various kinetic energies as they contribute to a thermal Maxwellian distribution, is calculated. The simulated heat flux is directly compared to measurements with a varying edge safety factor q95. This analysis provides evidence for the dominate e ect of high-energy ions in carrying heat from the plasma inside the separatrix to the target. High-energy ions are deposited close to the unperturbed strike line while low-energy ions can travel into the striated magnetic topology.« less

Flux threshold determination for tungsten nano-fuzz formation using an 80 eV He-ion beam

NASA Astrophysics Data System (ADS)

Meyer, Fred W.; Bannister, Mark E.; Parish, Chad M.

2017-10-01

At the ORNL Multicharged Ion Research Facility (MIRF), we have extended our investigation of flux thresholds for He-ion induced nano-fuzz formation on hot tungsten surfaces down to plasma-edge-relevant energies of 80 eV. We measured the size of the incident ion beam by accurate flux-profile measurements, and the size of the region where tungsten nano-fuzz was formed by post-exposure SEM surface analysis and real-time monitoring of the hot W surface-emissivity change throughout the beam exposure. If tungsten nano-fuzz formation had a fluence threshold, the size of the observed nano-fuzz region would be expected to increase with exposure time, eventually filling the entire ion beam spot. Instead, we found that the region of nano-fuzz formation (1) was always smaller than the beam spot itself and (2) did not increase in size with time, i.e. with accumulated He ion fluence. By comparison of the flux profile and the spatial extent of the fuzz region we determined a flux threshold of 9.5 +-3×1019/m2s at 80 eV He ion impact energy. We show that the observed flux-threshold energy dependence for nano-fuzz formation, which we have now mapped out from 80 eV to 8.5 keV, is well reproduced by the combined energy dependences of He-ion reflection, He-ion range and target-damage creation, determined using SRIM. Research sponsored by the LDRD program at ORNL, managed by UT-Battelle for the USDOE, and by the DOE OFES.

Surface modification and deuterium retention in reduced-activation steels under low-energy deuterium plasma exposure. Part II: steels pre-damaged with 20 MeV W ions and high heat flux

NASA Astrophysics Data System (ADS)

Ogorodnikova, O. V.; Zhou, Z.; Sugiyama, K.; Balden, M.; Pintsuk, G.; Gasparyan, Yu.; Efimov, V.

2017-03-01

The reduced-activation ferritic/martensitic (RAFM) steels including Eurofer (9Cr) and oxide dispersion strengthened (ODS) steels by the addition of Y2O3 particles investigated in Part I were pre-damaged either with 20 MeV W ions at room temperature at IPP (Garching) or with high heat flux at FZJ (Juelich) and subsequently exposed to low energy (~20-200 eV per D) deuterium (D) plasma up to a fluence of 2.9  ×  1025 D m-2 in the temperature range from 290 K to 700 K. The pre-irradiation with 20 MeV W ions at room temperature up to 1 displacement per atom (dpa) has no noticeable influence on the steel surface morphology before and after the D plasma exposure. The pre-irradiation with W ions leads to the same concentration of deuterium in all kinds of investigated steels, regardless of the presence of nanoparticles and Cr content. It was found that (i) both kinds of irradiation with W ions and high heat flux increase the D retention in steels compared to undamaged steels and (ii) the D retention in both pre-damaged and undamaged steels decreases with a formation of surface roughness under the irradiation of steels with deuterium ions with incident energy which exceeds the threshold of sputtering. The increase in the D retention in RAFM steels pre-damaged either with W ions (damage up to ~3 µm) or high heat flux (damage up to ~10 µm) diminishes with increasing the temperature. It is important to mention that the near surface modifications caused by either implantation of high energy ions or a high heat flux load, significantly affect the total D retention at low temperatures or low fluences but have a negligible impact on the total D retention at elevated temperatures and high fluences because, in these cases, the D retention is mainly determined by bulk diffusion.

BRIEF COMMUNICATION: The negative ion flux across a double sheath at the formation of a virtual cathode

NASA Astrophysics Data System (ADS)

McAdams, R.; Bacal, M.

2010-08-01

For the case of negative ions from a cathode entering a plasma, the maximum negative ion flux and the positive ion flux before the formation of a virtual cathode have been calculated for particular plasma conditions. The calculation is based on a simple modification of an analysis of electron emission into a plasma containing negative ions. The results are in good agreement with a 1d3v PIC code model.

Modulation of terrestrial ion escape flux composition /by low-altitude acceleration and charge exchange chemistry/

NASA Technical Reports Server (NTRS)

Moore, T. E.

1980-01-01

Motivated by recent observations of highly variable hot plasma composition in the magnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e(-), H(+), O(+) ionosphere. It is found that the fraction of the steady state escape flux which is O(+) can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O(+) tends to be rapidly converted by charge exchange to H(+). The acceleration is required both to overcome the gravitational confinement of O(+) and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O(+). Constraints are placed on the acceleration processes, and it is shown that O(+) escape is facilitated by observed ionospheric responses to magnetic activity.

Temperature measurements during high flux ion beam irradiations

DOE PAGES

Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; ...

2016-02-16

A systematic study of the ion beam heating effect was performed in a temperature range of –170 to 900 °C using a 10 MeV Au 3+ ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 10 12 cm –2 s –1. Different geometric configurations of beam, sample, thermocouple positioning, and sample holder were compared to understand the heat/charge transport mechanisms responsible for the observed temperature increase. The beam heating exhibited a strong dependence on the background (initial) sample temperature with the largest temperature increases occurring at cryogenic temperatures and decreasing with increasing temperature. Comparisonmore » with numerical calculations suggests that the observed heating effect is, in reality, a predominantly electronic effect and the true temperature rise is small. Furthermore, a simple model was developed to explain this electronic effect in terms of an electrostatic potential that forms during ion irradiation. Such an artificial beam heating effect is potentially problematic in thermostated ion irradiation and ion beamanalysis apparatus, as the operation of temperature feedback systems can be significantly distorted by this effect.« less

Development of high flux thermal neutron generator for neutron activation analysis

NASA Astrophysics Data System (ADS)

Vainionpaa, Jaakko H.; Chen, Allan X.; Piestrup, Melvin A.; Gary, Charles K.; Jones, Glenn; Pantell, Richard H.

2015-05-01

The new model DD110MB neutron generator from Adelphi Technology produces thermal (<0.5 eV) neutron flux that is normally achieved in a nuclear reactor or larger accelerator based systems. Thermal neutron fluxes of 3-5 · 107 n/cm2/s are measured. This flux is achieved using four ion beams arranged concentrically around a target chamber containing a compact moderator with a central sample cylinder. Fast neutron yield of ∼2 · 1010 n/s is created at the titanium surface of the target chamber. The thickness and material of the moderator is selected to maximize the thermal neutron flux at the center. The 2.5 MeV neutrons are quickly thermalized to energies below 0.5 eV and concentrated at the sample cylinder. The maximum flux of thermal neutrons at the target is achieved when approximately half of the neutrons at the sample area are thermalized. In this paper we present simulation results used to characterize performance of the neutron generator. The neutron flux can be used for neutron activation analysis (NAA) prompt gamma neutron activation analysis (PGNAA) for determining the concentrations of elements in many materials. Another envisioned use of the generator is production of radioactive isotopes. DD110MB is small enough for modest-sized laboratories and universities. Compared to nuclear reactors the DD110MB produces comparable thermal flux but provides reduced administrative and safety requirements and it can be run in pulsed mode, which is beneficial in many neutron activation techniques.

Energetic ion losses caused by magnetohydrodynamic activity resonant and non-resonant with energetic ions in Large Helical Device

NASA Astrophysics Data System (ADS)

Ogawa, Kunihiro; Isobe, Mitsutaka; Toi, Kazuo; Shimizu, Akihiro; Spong, Donald A.; Osakabe, Masaki; Yamamoto, Satoshi; the LHD Experiment Group

2014-09-01

Experiments to reveal energetic ion dynamics associated with magnetohydrodynamic activity are ongoing in the Large Helical Device (LHD). Interactions between beam-driven toroidal Alfvén eigenmodes (TAEs) and energetic ions have been investigated. Energetic ion losses induced by beam-driven burst TAEs have been observed using a scintillator-based lost fast-ion probe (SLIP) in neutral beam-heated high β plasmas. The loss flux of co-going beam ions increases as the TAE amplitude increases. In addition to this, the expulsion of beam ions associated with edge-localized modes (ELMs) has been also recognized in LHD. The SLIP has indicated that beam ions having co-going and barely co-going orbits are affected by ELMs. The relation between ELM amplitude and ELM-induced loss has a dispersed structure. To understand the energetic ion loss process, a numerical simulation based on an orbit-following model, DELTA5D, that incorporates magnetic fluctuations is performed. The calculation result shows that energetic ions confined in the interior region are lost due to TAE instability, with a diffusive process characterizing their loss. For the ELM, energetic ions existing near the confinement/loss boundary are lost through a convective process. We found that the ELM-induced loss flux measured by SLIP changes with the ELM phase. This relation between the ELM amplitude and measured ELM-induced loss results in a more dispersed loss structure.

Effects of different drivers on ion fluxes at Mars. MARS EXPRESS and MAVEN observations

NASA Astrophysics Data System (ADS)

Dubinin, Eduard; Fraenz, Markus; McFadden, James; Halekas, Jasper; Epavier, Frank; Connerney, Jack; Brain, David; Jakosky, Bruce; Andrews, David; Barabash, Stas

2017-04-01

Recent observations by Mars Express and MAVEN spacecraft have shown that the Martian atmosphere/ionosphere is exposed to the impact of solar wind which results in losses of volatiles from Mars. This erosion is an important factor for the evolution of the Martian atmosphere and its water inventory. To estimate the escape forced by the solar wind during the early Solar System conditions we need to know how the ionosphere of Mars and escape fluxes depend on variations in the strength of the external drivers, in particularly, of solar wind and solar EUV flux. We present multi-instrument observations of the influence of the solar wind and solar irradiance on the Martian ionosphere and escape fluxes. We use data obtained by the ASPERA-3 and MARSIS experiments on Mars Express and by the STATIC, SWIA, MAG and EUV monitor on MAVEN. Observations by Mars Express supplemented by the EUV monitoring at Earth orbit and translated to Mars orbit provide us information about this dependence over more than 10 years whereas the measurements made by MAVEN provide us for the first time the opportunity to study these processes with simultaneous monitoring of the solar wind and ionospheric variations, planetary ion fluxes and solar irradiance. It will be shown that that fluxes of planetary ions through different escape channels (trans-terminator fluxes, ion plume, plasma sheet) respond differently on the variations of the different drivers.

Ion Energy and Ion Flux Distributions of CF4/Ar/O2 Inductively Coupled Plasmas in a GEC Cell

NASA Technical Reports Server (NTRS)

Rao, M. V. V. S.; Cruden, Brett; Sharma, Surendra; Meyyappan, Meyya

2001-01-01

Knowledge of ion kinetics in plasma processing gas mixtures, such as CF4:Ar:O2, is important for understanding plasma assisted etching and deposition of materials. Ion energies and ion fluxes were measured in this mixture for 80:10:10, 60:20:20, and 40:30:30 mixture ratios in the pressure range of 10-50 mTorr, and at 200 and 300 W of RF power. Ions from plasma, sampled through a 10 micron orifice in the center of the lower plane electrode, were energy and mass analyzed by a combination of electrostatic energy and quadrupole mass filters. CFx(+) (x = 1 - 3), F2(+), F(+), C(+) from CF4, Ar(+) from Ar, and O2(+) and O(+) from O2, and by-product ions SiFx(+)(x = 1 - 3) from etching of quartz coupling window, COFx(+)(x = 1 - 3), CO(+), CO2(+), and OF(+) were detected. In all conditions ion flux decreases with increase of pressure but increase with increase of RF power. Ar(+) signal decreases with increase of pressure while CF3(+), which is the dominant ion at all conditions, increases with increase in pressure. The loss mechanism for Ar(+) and increase of CF3(+) is due to large cross section for Ar(+) + CF4 yields Ar + CF3(+) + F. Ion energies, which range from 15-25 eV depending on plasma operating conditions, are nearly Gaussian. By-product ion signals are higher at lower pressures indicating stronger plasma interaction with quartz window.

A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic ICWs. Initial Results: Waves and Precipitation Fluxes

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Initial results from the new developed model of the interacting ring current ions and ion cyclotron waves are presented. The model described by the system of two bound kinetic equations: one equation describes the ring current ion dynamics, and another one gives wave evolution. Such system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. Calculating ion-wave relationships, on a global scale under non steady-state conditions during May 2-5, 1998 storm, we presented the data at three time cuts around initial, main, and late recovery phases of May 4, 1998 storm phase. The structure and dynamics of the ring current proton precipitating flux regions and the wave active ones are discussed in detail.

High-flux source of low-energy neutral beams using reflection of ions from metals

NASA Technical Reports Server (NTRS)

Cuthbertson, John W.; Motley, Robert W.; Langer, William D.

1992-01-01

Reflection of low-energy ions from surfaces can be applied as a method of producing high-flux beams of low-energy neutral particles, and is an important effect in several areas of plasma technology, such as in the edge region of fusion devices. We have developed a beam source based on acceleration and reflection of ions from a magnetically confined coaxial RF plasma source. The beam provides a large enough flux to allow the energy distribution of the reflected neutrals to be measured despite the inefficiency of detection, by means of an electrostatic cylindrical mirror analyzer coupled with a quadrupole mass spectrometer. Energy distributions have been measured for oxygen, nitrogen, and inert gas ions incident with from 15 to 70 eV reflected from amorphous metal surfaces of several compositions. For ions of lighter atomic mass than the reflecting metal, reflected beams have peaked energy distributions; beams with the peak at 4-32 eV have been measured. The energy and mass dependences of the energy distributions as well as measurements of absolute flux, and angular distribution and divergence are reported. Applications of the neutral beams produced are described.

Quantitative evaluation of high-energy O- ion particle flux in a DC magnetron sputter plasma with an indium-tin-oxide target

NASA Astrophysics Data System (ADS)

Suyama, Taku; Bae, Hansin; Setaka, Kenta; Ogawa, Hayato; Fukuoka, Yushi; Suzuki, Haruka; Toyoda, Hirotaka

2017-11-01

O- ion flux from the indium tin oxide (ITO) sputter target under Ar ion bombardment is quantitatively evaluated using a calorimetry method. Using a mass spectrometer with an energy analyzer, O- energy distribution is measured with spatial dependence. Directional high-energy O- ion ejected from the target surface is observed. Using a calorimetry method, localized heat flux originated from high-energy O- ion is measured. From absolute evaluation of the heat flux from O- ion, O- particle flux in order of 1018 m-2 s-1 is evaluated at a distance of 10 cm from the target. Production yield of O- ion on the ITO target by one Ar+ ion impingement at a kinetic energy of 244 eV is estimated to be 3.3  ×  10-3 as the minimum value.

Unidirectional Flux Balance of Monovalent Ions in Cells with Na/Na and Li/Na Exchange: Experimental and Computational Studies on Lymphoid U937 Cells

PubMed Central

Vereninov, Igor A.; Yurinskaya, Valentina E.; Model, Michael A.; Vereninov, Alexey A.

2016-01-01

Monovalent ion traffic across the cell membrane occurs via various pathways. Evaluation of individual fluxes in whole cell is hampered by their strong interdependence. This difficulty can be overcome by computational analysis of the whole cell flux balance. However, the previous computational studies disregarded ion movement of the self-exchange type. We have taken this exchange into account. The developed software allows determination of unidirectional fluxes of all monovalent ions via the major pathways both under the balanced state and during transient processes. We show how the problem of finding the rate coefficients can be solved by measurement of monovalent ion concentrations and some of the fluxes. Interdependence of fluxes due to the mandatory conditions of electroneutrality and osmotic balance and due to specific effects can be discriminated, enabling one to identify specific changes in ion transfer machinery under varied conditions. To test the effectiveness of the developed approach we made use of the fact that Li/Na exchange is known to be an analogue of the coupled Na/Na exchange. Thus, we compared the predicted and experimental data obtained on U937 cells under varied Li+ concentrations and following inhibition of the sodium pump with ouabain. We found that the coupled Na/Na exchange in U937 cells comprises a significant portion of the entire Na+ turnover. The data showed that the loading of the sodium pump by Li/Na exchange involved in the secondary active Li+ transport at 1–10 mM external Li+ is small. This result may be extrapolated to similar Li+ and Na+ flux relationships in erythrocytes and other cells in patients treated with Li+ in therapeutic doses. The developed computational approach is applicable for studying various cells and can be useful in education for demonstrating the effects of individual transporters and channels on ion gradients, cell water content and membrane potential. PMID:27159324

Influence of the normalized ion flux on the constitution of alumina films deposited by plasma-assisted chemical vapor deposition

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

Kurapov, Denis; Reiss, Jennifer; Trinh, David H.

2007-07-15

Alumina thin films were deposited onto tempered hot working steel substrates from an AlCl{sub 3}-O{sub 2}-Ar-H{sub 2} gas mixture by plasma-assisted chemical vapor deposition. The normalized ion flux was varied during deposition through changes in precursor content while keeping the cathode voltage and the total pressure constant. As the precursor content in the total gas mixture was increased from 0.8% to 5.8%, the deposition rate increased 12-fold, while the normalized ion flux decreased by approximately 90%. The constitution, morphology, impurity incorporation, and the elastic properties of the alumina thin films were found to depend on the normalized ion flux. Thesemore » changes in structure, composition, and properties induced by normalized ion flux may be understood by considering mechanisms related to surface and bulk diffusion.« less

Compact steady-state and high-flux Falcon ion source for tests of plasma-facing materials

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

Girka, O.; Bizyukov, I.; Sereda, K.

2012-08-15

This paper describes the design and operation of the Falcon ion source. It is based on conventional design of anode layer thrusters. This ion source is a versatile, compact, affordable, and highly functional in the research field of the fusion materials. The reversed magnetic field configuration of the source allows precise focusing of the ion beam into small spot of Almost-Equal-To 3 mm and also provides the limited capabilities for impurity mass-separation. As the result, the source generates steady-state ion beam, which irradiates surface with high heat (0.3 - 21 MW m{sup -2}) and particle fluxes (4 Multiplication-Sign 10{sup 21}-more » 3 Multiplication-Sign 10{sup 23} m{sup -2}s{sup -1}), which approaches the upper limit for the flux range expected in ITER.« less

Oxygen Ion Upflow/Outflow Fluxes of Ionospheric Origin in the Stormtime Plasmasphere Boundary Layer

NASA Astrophysics Data System (ADS)

Erickson, P. J.; Zhang, S.; Foster, J. C.; Coster, A. J.

2017-12-01

During geomagnetic storm intervals, Earth's ionosphere is a source of heavy, cold O+ rich plasma to the inner magnetosphere, providing mass flux enhancement with strong dynamic geospace influence. Advancing understanding of the relative strength of ionospheric O+ sources is important for refining modeling of global ionosphere-thermosphere-plasmasphere response, and ultimately for quantitative understanding of the dynamics of energy inputs from solar wind to the magnetosphere. An important but often overlooked source of inner magnetospheric O+ can occur within the plasmasphere boundary layer, well equatorward of higher latitude processes. In particular, at the outer edge of the plasmasphere, O+ dynamics capable of accelerating heavy ions most probably occurs in two steps: (1) ion upflow with thermal velocities above the F2 electron density peak, and (2) ion outflow with suprathermal velocities at higher altitudes. Below approximately 500 km altitude in the near topside ionosphere, ion and electron precipitation in the 10s of eV to 10s of keV range can cause `backsplash' effects, providing sources of upwelling ions. Alternately, strong frictional ion heating from intense horizontal cross-field sub auroral polarization stream (SAPS) flows also provide significant ion temperature enhancements that lead to upwards velocities. Although these vertical flows are challenging to observe due to their short temporal nature and confined spatial extent, direct quantification of the upwelling O+ ion flux is available during several historical storm events using the Millstone Hill incoherent scatter radar, including the recent March 2015 storm interval. DMSP overflights and GPS based large scale TEC maps place these ionospheric radar measurements in correct geophysical context. Results show heavy ion upwelling fluxes lasting for at least 30 minutes to 1 hour (upper bound limited by observational restrictions), at rates exceeding 1E13 ions/m2/sec. We will present a summary of these

MMS observations of magnetic reconnection signatures of dissipating ion inertial-scale flux ropes associated with dipolarization events

NASA Astrophysics Data System (ADS)

Poh, G.; Slavin, J. A.; Lu, S.; Le, G.; Cassak, P.; Eastwood, J. P.; Ozturk, D. S.; Zou, S.; Nakamura, R.; Baumjohann, W.; Russell, C. T.; Gershman, D. J.; Giles, B. L.; Pollock, C.; Moore, T. E.; Torbert, R. B.; Burch, J. L.

2017-12-01

The formation of flux ropes is thought to be an integral part of the process that may have important consequences for the onset and subsequent rate of reconnection in the tail. Earthward flows, i.e. bursty bulk flows (BBFs), generate dipolarization fronts (DFs) as they interact with the closed magnetic flux in their path. Global hybrid simulations and THEMIS observations have shown that earthward-moving flux ropes can undergo magnetic reconnection with the near-Earth dipole field in the downtail region between the Near Earth Neutral Line and the near-Earth dipole field to create DFs-like signatures. In this study, we analyzed sequential "chains" of earthward-moving, ion-scale flux ropes embedded within DFs observed during MMS first tail season. MMS high-resolution plasma measurements indicate that these earthward flux ropes embedded in DFs have a mean bulk flow velocity and diameter of 250 km/s and 1000 km ( 2‒3 ion inertial length λi), respectively. Magnetic reconnection signatures preceding the flux rope/DF encounter were also observed. As the southward-pointing magnetic field in the leading edge of the flux rope reconnects with the northward-pointing geomagnetic field, the characteristic quadrupolar Hall magnetic field in the ion diffusion region and electron outflow jets in the north-south direction are observed. Our results strongly suggest that the earthward moving flux ropes brake and gradually dissipate due to magnetic reconnection with the near Earth magnetic field. We have also examined the occurrence rate of these dissipating flux ropes/DF events as a function of downtail distances.

Effects of ion exchange on stream solute fluxes in a basin receiving highway deicing salts

USGS Publications Warehouse

Shanley, J.B.

1994-01-01

At Fever Brook, a 1260-ha forested basin in central Massachusetts, highway deicing salt application increased the solute flux in streamflow by 120% above background flux (equivalent basis) during a 2-yr period. Attempts to isolate the nonsalt component of stream solute fluxes have commonly subtracted salt contributions based on the net Cl flux (Cl output in streamflow minus Cl input in precipitation). In these studies, any net Na flux in excess of the amount needed to balance the net Cl flux has been attributed to weathering. At Fever Brook, however, the net output of Na was less than the net output of Cl, suggesting a loss of Na within the basin. The Na sink was inferred to be cation exchange of Na for Ca and Mg in the soil. A method was developed to quantify the exchange based on a Na budget, which included an independent estimate of the Na flux from weathering. The amount of exchange was apportioned to Ca and Mg based on their relative concentrations in the stream. The background fluxes of Ca and Mg (i.e., those that would occur in the absence of deicing salts) were calculated by subtracting the amounts from ion exchange plus the much smaller direct contributions in deicing salts from the observed fluxes. Ion exchange and direct salt contributions increased the net output fluxes of Ca and Mg, each by 44% above background. In basins that receive deicing salts, failure to account for cation exchange thus may result in an underestimate of the flux of Na from weathering and overestimates of the fluxes of Ca and Mg from weathering.

Particle tracing modeling of ion fluxes at geosynchronous orbit during substorms

NASA Astrophysics Data System (ADS)

Brito, T. V.; Jordanova, V.; Woodroffe, J. R.; Henderson, M. G.; Morley, S.; Birn, J.

2016-12-01

The SHIELDS project aims to couple a host of different models for different regions of the magnetosphere using different numerical methods such as MHD, PIC and particle tracing, with the ultimate goal of having a more realistic model of the whole magnetospheric environment capturing, as much as possible, the different physics of the various plasma populations. In that context, we present a modeling framework that can be coupled with a global MHD model to calculate particle fluxes in the inner magnetosphere, which can in turn be used to constantly update the input for a ring current model. In that regard, one advantage of that approach over using spacecraft data is that it produces a much better spatial and temporal coverage of the nightside geosynchronous region and thus a possibly more complete input for the ring current model, which will likely produce more accurate global results for the ring current population. In this presentation, we will describe the particle tracing method in more detail, describe the method used to couple it to the BATS-R-US 3D global MHD code, and the method used to update the flux results to the RAM-SCB ring current model. We will also present the simulation results for the July 18, 2013 period, which showed significant substorm activity. We will compare simulated ion fluxes on the nightside magnetosphere with spacecraft observations to gauge how well our simulations are capturing substorm dynamics.

Investigation of the critical edge ion heat flux for L-H transitions in Alcator C-Mod and its dependence on B T

NASA Astrophysics Data System (ADS)

Schmidtmayr, M.; Hughes, J. W.; Ryter, F.; Wolfrum, E.; Cao, N.; Creely, A. J.; Howard, N.; Hubbard, A. E.; Lin, Y.; Reinke, M. L.; Rice, J. E.; Tolman, E. A.; Wukitch, S.; Ma, Y.; ASDEX Upgrade Team; Alcator C-Mod Team

2018-05-01

This paper presents investigations on the role of the edge ion heat flux for transitions from L-mode to H-mode in Alcator C-Mod. Previous results from the ASDEX Upgrade tokamak indicated that a critical value of edge ion heat flux per particle is needed for the transition. Analysis of C-Mod data confirms this result. The edge ion heat flux is indeed found to increase linearly with density at given magnetic field and plasma current. Furthermore, the Alcator C-Mod data indicate that the edge ion heat flux at the L-H transition also increases with magnetic field. Combining the data from Alcator C-Mod and ASDEX Upgrade yields a general expression for the edge ion heat flux at the L-H transition. These results are discussed from the point of view of the possible physics mechanism of the L-H transition. They are also compared to the L-H power threshold scaling and an extrapolation for ITER is given.

Active ion transport in dog tongue: a possible role in taste.

PubMed

DeSimone, J A; Heck, G L; DeSimone, S K

1981-11-27

An in vitro preparation of the dorsal epithelium of the dog tongue actively transports ions, producing a transepithelial potential difference characteristic of the ions and their concentration. Hypertonic sodium chloride solutions generally cause increased potentials and short-circuit currents and reduced resistances when placed on the mucosal surface. This hypertonic flux is eliminated by ouabain and is not found in ventral lingual epithelia. When either sodium acetate or tetramethylammonium chloride is substituted for sodium chloride in the mucosal medium, the currents are diminished but their sum at a given concentration approximates that for sodium chloride at the same concentration. This result suggests a current composed of inward sodium ion movement and outward chloride ion movement. Actively regulated potentials and currents, whether generated in the taste buds or in supporting cells, may be important in both normal chemotransduction and in taste responses evoked by currents passing through the tongue.

Optical study of active ion transport in lipid vesicles containing reconstituted Na,K-ATPase.

PubMed

Apell, H J; Marcus, M M; Anner, B M; Oetliker, H; Läuger, P

1985-01-01

A fluorescence method is described for the measurement of ATP-driven ion fluxes in lipid vesicles containing purified Na,K-ATPase. The membrane voltage of enzyme containing vesicles was measured by using a voltage-sensitive indocyanine dye. By addition of valinomycin the vesicle membrane is made selectively permeable to K+ so that the membrane voltage approaches the Nernst potential for K+. With constant external K+ concentration, the time course of internal K+ concentration can be continuously measured as change of the fluorescence signal after activation of the pump. The optical method has a higher time resolution than tracer-flux experiments and allows an accurate determination of initial flux rates. From the temperature dependence of active K+ transport its activation energy was determined to be 115 kJ/mol. ATP-stimulated electrogenic pumping can be measured as fast fluorescence change when the membrane conductance is low (i.e., at low or zero valinomycin concentration). In accordance with expectation, the amplitude of the fast signal change increases with decreasing passive ion permeability of the vesicle membrane. The resolution of the charge movement is so high that a few pump turnovers can be easily detected.

Vacuolar Chloride Fluxes Impact Ion Content and Distribution during Early Salinity Stress1

PubMed Central

Baetz, Ulrike; Tohge, Takayuki; Martinoia, Enrico; De Angeli, Alexis

2016-01-01

The ability to control the cytoplasmic environment is a prerequisite for plants to cope with changing environmental conditions. During salt stress, for instance, Na+ and Cl− are sequestered into the vacuole to help maintain cytosolic ion homeostasis and avoid cellular damage. It has been observed that vacuolar ion uptake is tied to fluxes across the plasma membrane. The coordination of both transport processes and relative contribution to plant adaptation, however, is still poorly understood. To investigate the link between vacuolar anion uptake and whole-plant ion distribution during salinity, we used mutants of the only vacuolar Cl− channel described to date: the Arabidopsis (Arabidopsis thaliana) ALMT9. After 24-h NaCl treatment, almt9 knock-out mutants had reduced shoot accumulation of both Cl− and Na+. In contrast, almt9 plants complemented with a mutant variant of ALMT9 that exhibits enhanced channel activity showed higher Cl− and Na+ accumulation. The altered shoot ion contents were not based on differences in transpiration, pointing to a vacuolar function in regulating xylem loading during salinity. In line with this finding, GUS staining demonstrated that ALMT9 is highly expressed in the vasculature of shoots and roots. RNA-seq analysis of almt9 mutants under salinity revealed specific expression profiles of transporters involved in long-distance ion translocation. Taken together, our study uncovers that the capacity of vacuolar Cl− loading in vascular cells plays a crucial role in controlling whole-plant ion movement rapidly after onset of salinity. PMID:27503602

Fog chemical composition and its feedback to fog water fluxes, water vapor fluxes, and microphysical evolution of two events near Paris

NASA Astrophysics Data System (ADS)

Degefie, D. T.; El-Madany, T.-S.; Held, M.; Hejkal, J.; Hammer, E.; Dupont, J.-C.; Haeffelin, M.; Fleischer, E.; Klemm, O.

2015-10-01

The chemical composition of collected fog water and its temporal evolution was studied during the PARISFOG campaign in winter 2012/2013 at the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphéric) atmospheric observatory outside Paris, France. A further development of the caltech active fog collector was applied, in which the collected fog water gets into contact with Teflon and polyether ether ketone (PEEK) material exclusively. The collector was operational whenever the visibility was below 1000 m. In addition, the turbulent and gravitational fluxes of fog water and water vapor flux were used to examine in detail the temporal evolution the chemical composition of two fogs. The technique was applied to two fog events, one representing a radiation fog and the other one representing a stratus lowering fog. The result revealed that the dominant inorganic species in the fog water were NH4+, NO3-, Ca2 + and SO42 -, which accounted for more than 85% of the ion balance. The pH ranged from 3.7 to 6.2. In the evolution the two fog events, the interaction among the turbulent fog water flux, gravitational fog water flux and water vapor flux controlled the major ion loads (amount of ions, dissolved in fog droplets per volume of air) and ion concentrations (amount dissolved per volume of liquid water) of the fog water. In the radiation fog event, an increase of ion loads and ion concentrations occurred when the direction of water vapor flux towards to the place where the condensation process occurred. A decrease of ion loads and ion concentrations mainly happened by gravitational fog water flux with a minor contribution from turbulent fog water flux. However, when the turbulent water vapor flux was oriented downward, it turned the turbulent fog water flux upward and offset the removal of ions in the fog. In the stratus lowering fog event, the turbulent fog water flux and the gravitational water flux together mainly contributed to the fog water deposition and

Ion flux enhancements and oscillations in spatially confined laser produced aluminum plasmas

NASA Astrophysics Data System (ADS)

Singh, S. C.; Fallon, C.; Hayden, P.; Mujawar, M.; Yeates, P.; Costello, J. T.

2014-09-01

Ion signals from laser produced plasmas (LPPs) generated inside aluminum rectangular cavities at a fixed depth d = 2 mm and varying width, x = 1.0, 1.6, and 2.75 mm were obtained by spatially varying the position of a negatively biased Langmuir probe. Damped oscillatory features superimposed on Maxwellian distributed ion signals were observed. Depending on the distance of the probe from the target surface, three to twelve fold enhancements in peak ion density were observed via confinement of the LPP, generated within rectangular cavities of varying width which constrained the plasma plume to near one dimensional expansion in the vertical plane. The effects of lateral spatial confinement on the expansion velocity of the LPP plume front, the temperature, density and expansion velocity of ions, enhancement of ion flux, and ion energy distribution were recorded. The periodic behavior of ion signals was analyzed and found to be related to the electron plasma frequency and electron-ion collision frequency. The effects of confinement and enhancement of various ion parameters and expansion velocities of the LPP ion plume are explained on the basis of shock wave theory.

The Cystic Fibrosis Transmembrane Conductance Regulator and Chloride-Dependent Ion Fluxes of Ovine Vocal Fold Epithelium

ERIC Educational Resources Information Center

Leydon, Ciara; Fisher, Kimberly V.; Lodewyck-Falciglia, Danielle

2009-01-01

Purpose: Ion-driven transepithelial water fluxes participate in maintaining superficial vocal fold hydration, which is necessary for normal voice production. The authors hypothesized that Cl[superscript -] channels are present in vocal fold epithelial cells and that transepithelial Cl[superscript -] fluxes can be manipulated pharmacologically.…

Picomolar detection limits with current-polarized Pb2+ ion-selective membranes.

PubMed

Pergel, E; Gyurcsányi, R E; Tóth, K; Lindner, E

2001-09-01

Minor ion fluxes across ion-selective membranes bias submicromolar activity measurements with conventional ion-selective electrodes. When ion fluxes are balanced, the lower limit of detection is expected to be dramatically improved. As proof of principle, the flux of lead ions across an ETH 5435 ionophore-based lead-selective membrane was gradually compensated by applying a few nanoamperes of galvanostatic current. When the opposite ion fluxes were matched, and the undesirable leaching of primary ions was eliminated, Nernstian response down to 3 x 10(-12) M was achieved.

Localized spiraling plasma ejection contributing the ion-flux broadening in the detached linear plasma

NASA Astrophysics Data System (ADS)

Tanaka, H.; Takeyama, K.; Yoshikawa, M.; Kajita, S.; Ohno, N.; Hayashi, Y.

2018-07-01

We have performed multipoint measurements with segmented electrodes and a microwave interferometer in the linear plasma device NAGDIS-II, in order to reveal cross-field motion and axial localization of the enhanced radial transport in the detached plasma. By changing the neutral pressure successively and applying several statistical analysis techniques, it was clarified that there is axially localized ion flux broadening accompanying an enhanced plasma ejection from the center with radially elongated spiraling structure. The spiraling plasma ejection accompanies the m = 0 mode drop near the center with the similar time scale. Further, such behavior composed of f > 1 kHz fluctuations is modulated by several-hundred-hertz fluctuation with m = 0. This cross-field transport causes non-negligible effect for the reduction of the ion flux peak in the detached plasma.

The importance of ion fluxes for cancer proliferation and metastasis: A thermodynamic analysis.

PubMed

Lucia, Umberto; Deisboeck, Thomas S

2018-05-14

Following a thermodynamic approach, we develop a new theoretical analysis of ion transfer across cell membranes. Supported also by experimental data from the literature, we highlight that ion channels determine the typical features of cancer cells, i.e. independence from growth-regulatory signals, avoidance of apoptosis, indefinite proliferative potential, and the capability of inducing angiogenesis. Specifically, we analyse how ion transport, with particular regards to Ca 2+ fluxes, modulates cancer cell proliferation, and regulates cell cycle checkpoints. Finally, our analysis also suggests that in malignant tumours aerobic glycolysis is the more efficient metabolic process when taking the required solvent capacity into account. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measurements of fast ion spatial dynamics during magnetic activity in the RFP

NASA Astrophysics Data System (ADS)

Goetz, J. A.; Anderson, J. K.; Bonofiglo, P.; Kim, J.; McConnell, R.; Magee, R. M.

2017-10-01

Fast ions in the RFP are only weakly affected by a stochastic magnetic field and behave nearly classically in concentration too low to excite Alfvenic activity. At high fast ion concentration sourced by H-NBI in 300kA RFP discharges, a substantial drop in core-localized high pitch fast ions is observed during bursts of coupled EPM and IAE (magnetic island-induced Alfven eigenmode) activity (100-200kHz) through neutral particle analysis. Sourcing instead fast deuterium with NBI, the DD fusion products can measure the dynamics of the fast ion density profile. Both a collimated neutron detector and a new 3MeV fusion proton detector loaned by TriAlpha Energy measure the fast ion density profile with 5cm spatial resolution and 100 μs temporal resolution. In D-NBI, the bursting EPM is excited at slightly lower frequency and the IAE activity is nearly absent, likely due to an isotope effect and loss of wave-particle interaction. In these cases, neutral particle analysis shows little change in the core-localized high pitch fast ion content, and the fusion product profile indicates little change in the fast ion density profile, leaving unexplained the mechanism removing EPM drive. We measure a substantial redistribution of the fast ion profile due to strong lower-frequency ( 30kHz) MHD activity that accompanies the current profile relaxation in the RFP. Profile flattening is strongest in low bulk density discharges, which often occur with a total increase in global neutron flux from acceleration of the beam ions. Work supported by US DoE.

Solar proton fluxes since 1956. [sunspot activity correlation

NASA Technical Reports Server (NTRS)

Reedy, R. C.

1977-01-01

The fluxes of protons emitted during solar flares since 1956 were evaluated. The depth-versus-activity profiles of Co-56 in several lunar rocks are consistent with the solar proton fluxes detected by experiments on several satellites. Only about 20% of the solar-proton-induced activities of Na-22 and Fe-55 in lunar rocks from early Apollo missions were produced by protons emitted from the sun during solar cycle 20 (1965-1975). The depth-versus-activity data for these radionuclides in several lunar rocks were used to determine the fluxes of protons during solar cycle 19 (1954-1964). The average proton fluxes for cycle 19 are about five times those for both the last million years and for cycle 20 and are about five times the previous estimate for cycle 19 based on neutron-monitor and radio ionospheric measurements. These solar-proton flux variations correlate with changes in sunspot activity.

Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes.

PubMed

Volkov, Vadim

2015-01-01

Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na(+) and K(+) concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and

Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes

PubMed Central

Volkov, Vadim

2015-01-01

Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na+ and K+ concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and

Transdermal penetration of vasoconstrictors--present understanding and assessment of the human epidermal flux and retention of free bases and ion-pairs.

PubMed

Cross, Sheree E; Thompson, Melanie J; Roberts, Michael S

2003-02-01

As reductions in dermal clearance increase the residence time of solutes in the skin and underlying tissues we compared the topical penetration of potentially useful vasoconstrictors (VCs) through human epidermis as both free bases and ion-pairs with salicylic acid (SA). We determined the in vitro epidermal flux of ephedrine, naphazoline, oxymetazoline, phenylephrine, and xylometazoline applied as saturated solutions in propylene glycol:water (1:1) and of ephedrine, naphazoline and tetrahydrozoline as 10% solutions of 1:1 molar ratio ion-pairs with SA in liquid paraffin. As free bases, ephedrine had the highest maximal flux, Jmax = 77.4 +/- 11.7 microg/cm2/h, being 4-fold higher than tetrahydrozoline and xylometazoline, 6-fold higher than phenylephrine, 10-fold higher than naphazoline and 100-fold higher than oxymetazoline. Stepwise regression of solute physicochemical properties identified melting point as the most significant predictor of flux. As ion-pairs with SA, ephedrine and naphazoline had similar fluxes (11.5 +/- 2.3 and 12.0 +/- 1.6 microg/cm2/h respectively), whereas tetrahydrozoline was approximately 3-fold slower. Corresponding fluxes of SA from the ion-pairs were 18.6 +/- 0.6, 7.8+/- 0.8 and 1.1 +/- 0.1 respectively. Transdermal transport of VC's is discussed. Epidermal retention of VCs and SA did not correspond to their molar ratio on application and confirmed that following partitioning into the stratum corneum, ion-pairs separate and further penetration is governed by individual solute characteristics.

Conical pitch angle distributions of very low-energy ion fluxes observed by ISEE 1

NASA Technical Reports Server (NTRS)

Horwitz, J. L.; Baugher, C. R.; Chappell, C. R.; Shelley, E. G.; Young, D. T.

1982-01-01

Observations are presented of conical distributions of low-energy ion fluxes from throughout the magnetosphere. The data were provided by the plasma composition experiment (PCE) on ISEE 1. ISEE 1 was launched in October 1977 into a highly elliptical orbit with a 30 deg inclination to the equator and 22.5 earth radii apogee. Particular attention is given to data taken when the instrument was in its thermal plasma mode, sampling ions in the energy per charge range 0-100 eV/e. Attention is given to examples of conical distributions in 0- to 100-eV/e ions, the occurrence of conical distributions of 0- to 100-eV ions in local time-geocentric distance and latitude-geocentric distance coordinates, the cone angles in 0- to 100-eV ion conics, Kp distributions of 0- to 100-eV ion conics, and some compositional aspects of 0- to 100-eV ion conics.

Scaling of ion expansion energy with laser flux in moderate-Z plasmas produced by lasers

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

Gupta, P.D.; Goel, S.K.; Uppal, J.S.

1982-09-01

Ion expansion energy measurements in plasmas created by focusing 1-GW, 5-nsec Nd:glass laser on plane solid targets of polythene, carbon, and aluminum are reported. It is observed that the scaling of ion expansion energy with laser flux Phi varies between Phi/sup 0.28/ and Phi/sup 0.66/ for polythene, Phi/sup 0.28/ and Phi/sup 0.70/ for carbon, and Phi/sup 0.51/ and Phi/sup 0.44/ for aluminum in the flux range 5 x 10/sup 10/--5 x 10/sup 12/ W/cm/sup 2/ of our experiment. The scaling is either much slower or faster than a scaling of Phi/sup 4/9/ expected from a self-regulating model for plasmas createdmore » in the low flux range. It is shown that this behavior, as well as results of experiments on similar plasmas reported by other authors, can be explained when radiation losses and the energy spent in ionization are also considered in the self-regulating model.« less

Characteristics of ion distribution functions in dipolarizing flux bundles: Event studies

NASA Astrophysics Data System (ADS)

Runov, A.; Angelopoulos, V.; Artemyev, A.; Birn, J.; Pritchett, P. L.; Zhou, X.-Z.

2017-06-01

Taking advantage of multipoint observations from a repeating configuration of the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes separated by 1 to 2 Earth radii (RE) along X, Y, and Z in the geocentric solar magnetospheric system (GSM), we study ion distribution functions collected by the probes during three dipolarizing flux bundle (DFB) events observed at geocentric distances 9 < R < 14 RE. By comparing these probes' observations, we characterize changes in the ion distribution functions with respect to probe separation along the X and Y GSM directions and |Bx| levels, which characterize the distance from the neutral sheet. We found that the characteristics of the ion distribution functions strongly depended on the |Bx| level, whereas changes with respect to X and Y were minor. In all three events, ion distribution functions f(v) observed inside DFBs were organized by magnetic and electric fields. The probes near the magnetic equator observed perpendicular anisotropy of the phase space density in the range between thermal energy and twice the thermal energy, although the distribution in the ambient plasma sheet was isotropic. The anisotropic ion distribution in DFBs injected toward the inner magnetosphere may provide the free energy for waves and instabilities, which are important elements of particle energization.

Single surface barrier detectors for neutron dosimetry and associated light-ion fluxes

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

Treado, P.A.; Allas, R.G.; Eman, B.

1981-04-01

In this paper the authors have attempted to perfect a simple, compact and inexpensive single surface barrier detection system to measure both the intensities and approximate spectral shape of continuous neutron and light ion fluxes. They have measured such fluxes for three known collimated and uncollimated neutron beams with two geometrical configurations and with at least two different thicknesses of CH/sub 2/ and CD/sub 2/ radiators. All neutron flux data were obtained with a Au shield in front of the detector; this was removed for LIF measurements. The known shapes of the impinging neutron beams were used to calculate themore » expected recoil-particle spectra and such predictions have been compared with the experimental data. Also, data have been obtained with telescopes, with carbon foil and thin detector-grade silicon foil radiators. These data allow the authors to estimate contributions to the higher-energy portion of the recoil-particle spectra from reactions due to the carbon in the CH/sub 2/ and CD/sub 2/ radiators and due to the silicon in the detector. Corrections for rim effects in the detector and multiple scattering in the radiator are calculable. The precipitous decrease in the number of observed events, expected at the maximum energy that can be deposited by a recoil particle from the radiator, was observed for each of the radiator/detector combinations studied. The data agree reasonably well with both the intensity and spectral shape predictions for recoil-particle energies above about 300 keV. The telescope data confirm the single-detector data and add significant information about the LIFs created by the collimation of the neutron beams. In fact, both the single-detector and telescope data indicate that (n,p) reactions in collimation and target-backing materials contribute significant proton components to the light-ion fluxes.« less

On the Acceleration and Anisotropy of Ions Within Magnetotail Dipolarizing Flux Bundles

NASA Astrophysics Data System (ADS)

Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Artemyev, Anton V.; Birn, Joachim

2018-01-01

Dipolarizing flux bundles (DFBs), earthward propagating structures with enhanced northward magnetic field Bz, are usually believed to carry a distinctly different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, have been recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFB. According to these observations, the ambient κ values of 2-3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFB, whereas for lower κ values the DFB ions become more isotropic. Here we utilize a simple, test particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the anisotropy originates from successive ion reflections and reentries to the DFB, during which the ions are consecutively accelerated in the perpendicular direction by the DFB-associated electric field. This consecutive acceleration may be interrupted, however, when magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories become stochastic outside the DFB, which makes the reflected ions less likely to return to the DFB for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected toward Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between magnetotail and inner magnetosphere.

The Role of Kinetic Alfven Waves in Plasma Transport in an Ion-scale Flux Rope

NASA Astrophysics Data System (ADS)

Tang, B.; Li, W.; Wang, C.; Dai, L.

2017-12-01

Magnetic flux ropes, if generated by multiply X-line reconnections, would be born as a crater type one, meaning the plasma density within is relatively high. They will then evolve into typical flux ropes as plasma are transported away along the magnetic field lines [Zhang et al., 2010]. In this study, we report an ion-scale flux rope observed by MMS on November 28, 2016, which is accompanied by strong kinetic Alfven waves (KAW). The related wave parallel electric field can effectively accelerate electrons inside the flux rope by Landau resonance, resulting into a significant decrease of the electron at 90° pitch angle. The change of electron pitch angle distribution would cause the rapid plasma transport along the magnetic field lines, and help the flux rope evolve into a strong magnetic core in a short time. This wave-particle interaction would be a candidate mechanism to explain the rareness of crater flux ropes in reality.

Localization of Hydrogen Ion and Chloride Ion Fluxes in Nitella

PubMed Central

Spear, Donald G.; Barr, June K.; Barr, C. E.

1969-01-01

Alternating bands of acid and base formation have been detected along the length of the internodal cell of Nitella clavata when it is illuminated, while in the dark this phenomenon is minimal. Chloride influx occurs only or largely in the acid-extruding regions, and this is also a light-dependent ion movement. Chloride efflux is slightly dependent on illumination and is not localized as are H+ efflux and Cl- influx. The results obtained support Kitasato's (1968) proposal that a large passive H+ influx is balanced by an active efflux of this ion. Transport mechanisms suggested by the correlations of Cl- and HCO3 - influxes with H+ extrusion are discussed. PMID:5806597

Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

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

Rafalskyi, Dmytro; Aanesland, Ane; Dudin, Stanislav

2015-05-15

This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier createdmore » in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.« less

Characteristics of Ion Distribution Functions in Dipolarizing FluxBundles: THEMIS Event Studies

NASA Astrophysics Data System (ADS)

Runov, A.; Artemyev, A.; Birn, J.; Pritchett, P. L.; Zhou, X.

2016-12-01

Taking advantage of multi-point observations from repeating configuration of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) fleet with probe separation of 1 to 2 Earth radii (RE) along X, Y, and Z in the geocentric solar magnetospheric system (GSM), we study ion distribution functions observed by the probes during three transient dipolarization events. Comparing observations by the multiple probes, we characterize changes in the ion distribution functions with respect to geocentric distance (X), cross-tail probe separation (Y), and levels of |Bx|, which characterize the distance from the neutral sheet. We examined 2-D and 1-D cuts of the 3-D velocity distribution functions by the {Vb,Vbxv} plane. The results indicate that the velocity distribution functions observed inside the dipolarizing flux bundles (DFB) close to the magnetic equator are often perpendicularly anisotropic for velocities Vth≤v≤2Vth, where Vth is the ion thermal velocity. Ions of higher energies (v>2Vth) are isotropic. Hence, interaction of DFBs and ambient ions may result in the perpendicular anisotropy of the injecting energetic ions, which is an important factor for plasma waves and instabilities excitation and further particle acceleration in the inner magnetosphere. We also compare the observations with the results of test-particles and PIC simulations.

Dynamic ion-ion and water-ion interactions in ion channels.

PubMed Central

Wu, J V

1992-01-01

The dynamic interactions among ions and water molecules in ion channels are treated based on an assumption that ions at binding sites can be knocked off by both transient entering ions and local water molecules. The theory, when applied to a single-site model K+ channel, provides solutions for super- and subsaturations, flux-ratio exponent (n') greater than 1, osmotic streaming current, activity-dependent reversal potentials, and anomalous mole-fraction behavior. The analysis predicts that: (a) the saturation may but, in general, does not follow the Michaelis-Menten relation; (b) streaming current results from imbalanced water-ion knock-off interactions; (c) n' greater than 1 even for single-site channels, but it is unlikely to exceed 1.4 unless the pore is occupied by one or more ion(s); (d) in the calculation involving two permeant ion species with similar radii, the heavier ions show higher affinity; the ion-ion knock-off dissociation from the site is more effective when two interacting ions are identical. Therefore, the "multi-ion behaviors" found in most ion channels are the consequences of dynamic ion-ion and water-ion interactions. The presence of these interactions does not require two or more binding sites in channels. PMID:1376158

Rapid enhancement of low energy (<100 eV) ion flux in response to interplanetary shocks based on two Van Allen Probes case studies: Implications for source regions and heating mechanisms

DOE PAGES

Yue, Chao; Li, Wen; Reeves, Geoffrey D.; ...

2016-07-01

Interactions between interplanetary (IP) shocks and the Earth's magnetosphere manifest many important space physics phenomena including low-energy ion flux enhancements and particle acceleration. In order to investigate the mechanisms driving shock-induced enhancement of low-energy ion flux, we have examined two IP shock events that occurred when the Van Allen Probes were located near the equator while ionospheric and ground observations were available around the spacecraft footprints. We have found that, associated with the shock arrival, electromagnetic fields intensified, and low-energy ion fluxes, including H +, He +, and O +, were enhanced dramatically in both the parallel and perpendicular directions.more » During the 2 October 2013 shock event, both parallel and perpendicular flux enhancements lasted more than 20 min with larger fluxes observed in the perpendicular direction. In contrast, for the 15 March 2013 shock event, the low-energy perpendicular ion fluxes increased only in the first 5 min during an impulse of electric field, while the parallel flux enhancement lasted more than 30 min. In addition, ionospheric outflows were observed after shock arrivals. From a simple particle motion calculation, we found that the rapid response of low-energy ions is due to drifts of plasmaspheric population by the enhanced electric field. Furthermore, the fast acceleration in the perpendicular direction cannot solely be explained by E × B drift but betatron acceleration also plays a role. Adiabatic acceleration may also explain the fast response of the enhanced parallel ion fluxes, while ion outflows may contribute to the enhanced parallel fluxes that last longer than the perpendicular fluxes.« less

Rapid enhancement of low energy (<100 eV) ion flux in response to interplanetary shocks based on two Van Allen Probes case studies: Implications for source regions and heating mechanisms

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

Yue, Chao; Li, Wen; Reeves, Geoffrey D.

Interactions between interplanetary (IP) shocks and the Earth's magnetosphere manifest many important space physics phenomena including low-energy ion flux enhancements and particle acceleration. In order to investigate the mechanisms driving shock-induced enhancement of low-energy ion flux, we have examined two IP shock events that occurred when the Van Allen Probes were located near the equator while ionospheric and ground observations were available around the spacecraft footprints. We have found that, associated with the shock arrival, electromagnetic fields intensified, and low-energy ion fluxes, including H +, He +, and O +, were enhanced dramatically in both the parallel and perpendicular directions.more » During the 2 October 2013 shock event, both parallel and perpendicular flux enhancements lasted more than 20 min with larger fluxes observed in the perpendicular direction. In contrast, for the 15 March 2013 shock event, the low-energy perpendicular ion fluxes increased only in the first 5 min during an impulse of electric field, while the parallel flux enhancement lasted more than 30 min. In addition, ionospheric outflows were observed after shock arrivals. From a simple particle motion calculation, we found that the rapid response of low-energy ions is due to drifts of plasmaspheric population by the enhanced electric field. Furthermore, the fast acceleration in the perpendicular direction cannot solely be explained by E × B drift but betatron acceleration also plays a role. Adiabatic acceleration may also explain the fast response of the enhanced parallel ion fluxes, while ion outflows may contribute to the enhanced parallel fluxes that last longer than the perpendicular fluxes.« less

Electron-less negative ion extraction from ion-ion plasmas

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

Rafalskyi, Dmytro; Aanesland, Ane

2015-03-09

This paper presents experimental results showing that continuous negative ion extraction, without co-extracted electrons, is possible from highly electronegative SF{sub 6} ion-ion plasma at low gas pressure (1 mTorr). The ratio between the negative ion and electron densities is more than 3000 in the vicinity of the two-grid extraction and acceleration system. The measurements are conducted by both magnetized and non-magnetized energy analyzers attached to the external grid. With these two analyzers, we show that the extracted negative ion flux is almost electron-free and has the same magnitude as the positive ion flux extracted and accelerated when the grids aremore » biased oppositely. The results presented here can be used for validation of numerical and analytical models of ion extraction from ion-ion plasma.« less

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbO x film growth

DOE PAGES

Franz, Robert; Clavero, César; Kolbeck, Jonathan; ...

2016-01-21

Here, the ion energies and fluxes in the high power impulse magnetron sputtering plasma from a Nb target were analysed angularly resolved along the tangential direction of the racetrack. A reactive oxygen-containing atmosphere was used as such discharge conditions are typically employed for the synthesis of thin films. Asymmetries in the flux distribution of the recorded ions as well as their energies and charge states were noticed when varying the angle between mass-energy analyser and target surface. More positively charged ions with higher count rates in the medium energy range of their distributions were detected in +E x B thanmore » in -E x B direction, thus confirming the notion that ionisation zones (also known as spokes or plasma bunches) are associated with moving potential humps. The motion of the recorded negatively charged high-energy oxygen ions was unaffected. NbO x thin films at different angles and positions were synthesised and analysed as to their structure and properties in order to correlate the observed plasma properties to the film growth conditions. The chemical composition and the film thickness varied with changing deposition angle, where the latter, similar to the ion fluxes, was higher in +E x B than in -E x B direction.« less

High active nitrogen flux growth of GaN by plasma assisted molecular beam epitaxy

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

McSkimming, Brian M., E-mail: mcskimming@engineering.ucsb.edu; Speck, James S.; Chaix, Catherine

2015-09-15

In the present study, the authors report on a modified Riber radio frequency (RF) nitrogen plasma source that provides active nitrogen fluxes more than 30 times higher than those commonly used for plasma assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N{sub 2} gas flow rates between 5 and 25 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux, achieved was ∼7.6 μm/h. For optimized growth conditions,more » the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 × 3 μm) on the order of 1 nm. Secondary ion mass spectroscopy impurity analysis demonstrates oxygen and hydrogen incorporation of 1 × 10{sup 16} and ∼5 × 10{sup 17}, respectively. In addition, the authors have achieved PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ∼100 °C greater than any previously reported PAMBE growth of GaN. This growth temperature corresponds to GaN decomposition in vacuum of more than 20 nm/min; a regime previously unattainable with conventional nitrogen plasma sources. Arrhenius analysis of the decomposition rate shows that samples with a flux ratio below stoichiometry have an activation energy greater than decomposition of GaN in vacuum while samples grown at or above stoichiometry have decreased activation energy. The activation energy of decomposition for GaN in vacuum was previously determined to be ∼3.1 eV. For a Ga/N flux ratio of ∼1.5, this activation energy was found to be ∼2.8 eV, while for a Ga/N flux ratio of ∼0.5, it was found to be ∼7.9 eV.« less

Fog deposition fluxes of water and ions to a mountainous site in Central Europe

NASA Astrophysics Data System (ADS)

Klemm, Otto; Wrzesinsky, Thomas

2007-09-01

Fog and precipitation composition and deposition were measured over a 1-yr period. Ion concentrations were higher in fog than in precipitation by factors of between 6 and 18. The causes of these differences were less dilution of fog water due to non-availability of condensable water vapour, and more efficient transfer of surface emissions to fog water as compared to rain water or snow. Fogwater and dissolved ions depositions were measured with eddy covariance in combination with a bulk fogwater collector. Annual fogwater deposition was 9.4% that of precipitation. The annual deposition of ions through fog was of the same order as that for precipitation. Ammonium, representing local emission sources, had 46% more annual deposition through fog than through precipitation. The fog droplet number and mass size distributions are reported. Fog droplets of 15 μm diameter contribute most to the deposition flux. The variability of processes and parameters contributing to deposition of ions through fog (ion concentrations in fog water, liquid water content in air, fog duration and turbulence) is high.

On singlet metastable states, ion flux and ion energy in single and dual frequency capacitively coupled oxygen discharges

NASA Astrophysics Data System (ADS)

Hannesdottir, H.; Gudmundsson, J. T.

2017-05-01

We apply particle-in-cell simulations with Monte Carlo collisions to study the influence of the singlet metastable states on the ion energy distribution in single and dual frequency capacitively coupled oxygen discharges. For this purpose, the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used, in which the discharge model includes the following nine species: electrons, the neutrals O(3P) and O{{}2}≤ft({{\\text{X}}3} Σ g-\\right. ), the negative ions O-, the positive ions O+ and O2+ , and the metastables O(1D), O{{}2}≤ft({{\\text{a}}1}{{ Δ }g}\\right) and O2(b{{}1} Σ g+ ). Earlier, we have explored the effects of adding the species O{{}2}≤ft({{\\text{a}}1}{{ Δ }g}\\right. ) and O2(b{{}1} Σ g+ ), and an energy-dependent secondary electron emission yield for oxygen ions and neutrals, to the discharge model. We found that including the two molecular singlet metastable states decreases the ohmic heating and the effective electron temperature in the bulk region (the electronegative core). Here we explore how these metastable states influence dual frequency discharges consisting of a fundamental frequency and the lowest even harmonics. Including or excluding the detachment reactions of the metastables O{{}2}≤ft({{\\text{a}}1}{{ Δ }g}\\right. ) and O2(b{{}1} Σ g+ ) can shift the peak electron temperature from the grounded to the powered electrode or vice versa, depending on the phase difference of the two applied frequencies. These metastable states can furthermore significantly influence the peak of the ion energy distribution for O2+ -ions bombarding the powered electrode, and hence the average ion energy upon bombardment of the electrode, and lower the ion flux.

Increased abscisic acid levels in transgenic maize overexpressing AtLOS5 mediated root ion fluxes and leaf water status under salt stress

PubMed Central

Zhang, Juan; Yu, Haiyue; Zhang, Yushi; Wang, Yubing; Li, Maoying; Zhang, Jiachang; Duan, Liusheng; Zhang, Mingcai; Li, Zhaohu

2016-01-01

Abscisic acid (ABA) is a vital cellular signal in plants, and effective ABA signalling is pivotal for stress tolerance. AtLOS5 encoding molybdenum cofactor sulphurase is a key regulator of ABA biosynthesis. Here, transgenic AtLOS5 plants were generated to explore the role of AtLOS5 in salt tolerance in maize. AtLOS5 overexpression significantly up-regulated the expression of ZmVp14-2, ZmAO, and ZmMOCO, and increased aldehyde oxidase activities, which enhanced ABA accumulation in transgenic plants under salt stress. Concurrently, AtLOS5 overexpression induced the expression of ZmNHX1, ZmCBL4, and ZmCIPK16, and enhanced the root net Na+ efflux and H+ influx, but decreased net K+ efflux, which maintained a high cytosolic K+/Na+ ratio in transgenic plants under salt stress. However, amiloride or sodium orthovanadate could significantly elevate K+ effluxes and decrease Na+ efflux and H+ influx in salt-treated transgenic roots, but the K+ effluxes were inhibited by TEA, suggesting that ion fluxes regulated by AtLOS5 overexpression were possibly due to activation of Na+/H+ antiport and K+ channels across the plasma membrane. Moreover, AtLOS5 overexpression could up-regulate the transcripts of ZmPIP1:1, ZmPIP1:5, and ZmPIP2:4, and enhance root hydraulic conductivity. Thus transgenic plants had higher leaf water potential and turgor, which was correlated with greater biomass accumulation under salt stress. Thus AtLOS5 overexpression induced the expression of ABA biosynthetic genes to promote ABA accumulation, which activated ion transporter and PIP aquaporin gene expression to regulate root ion fluxes and water uptake, thus maintaining high cytosolic K+ and Na+ homeostasis and better water status in maize exposed to salt stress. PMID:26743432

SNS Sample Activation Calculator Flux Recommendations and Validation

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

McClanahan, Tucker C.; Gallmeier, Franz X.; Iverson, Erik B.

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) uses the Sample Activation Calculator (SAC) to calculate the activation of a sample after the sample has been exposed to the neutron beam in one of the SNS beamlines. The SAC webpage takes user inputs (choice of beamline, the mass, composition and area of the sample, irradiation time, decay time, etc.) and calculates the activation for the sample. In recent years, the SAC has been incorporated into the user proposal and sample handling process, and instrument teams and users have noticed discrepancies in the predicted activation of their samples.more » The Neutronics Analysis Team validated SAC by performing measurements on select beamlines and confirmed the discrepancies seen by the instrument teams and users. The conclusions were that the discrepancies were a result of a combination of faulty neutron flux spectra for the instruments, improper inputs supplied by SAC (1.12), and a mishandling of cross section data in the Sample Activation Program for Easy Use (SAPEU) (1.1.2). This report focuses on the conclusion that the SAPEU (1.1.2) beamline neutron flux spectra have errors and are a significant contributor to the activation discrepancies. The results of the analysis of the SAPEU (1.1.2) flux spectra for all beamlines will be discussed in detail. The recommendations for the implementation of improved neutron flux spectra in SAPEU (1.1.3) are also discussed.« less

Structural Changes in the Vanadium Sample Surface Induced by Pulsed High-Temperature Deuterium Plasma and Deuterium Ion Fluxes

NASA Astrophysics Data System (ADS)

Borovitskaya, I. V.; Pimenov, V. N.; Gribkov, V. A.; Padukh, M.; Bondarenko, G. G.; Gaidar, A. I.; Paramonova, V. V.; Morozov, E. V.

2017-11-01

The structural changes in the vanadium sample surface are studied as functions of the conditions of irradiation by pulsed high-temperature deuterium plasma and deuterium ion fluxes in the Plasma Focus installation. It is found that processes of partial evaporation, melting, and crystallization of the surface layer of vanadium samples take place in the plasma flux power density range q = 108-1010 W/cm2 and the ion flux density range q = 1010-1012 W/cm2. The surface relief is wavelike. There are microcracks, gas-filled bubbles (blisters), and traces of fracture on the surface. The blisters are failed in the solid state. The character of blister fracture is similar to that observed during usual ion irradiation in accelerators. The samples irradiated at relatively low power density ( q = 107-108 W/cm2) demonstrate the ejection of microparticles (surface fragments) on the side facing plasma. This process is assumed to be due to the fact that the unloading wave formed in the sample-target volume reaches its irradiated surface. Under certain irradiation conditions (sample-anode distance, the number of plasma pulses), a block microstructure with block sizes of several tens of microns forms on the sample surfaces. This structure is likely to form via directional crack propagation upon cooling of a thin melted surface layer.

Measurement of Net Fluxes of Ammonium and Nitrate at the Surface of Barley Roots Using Ion-Selective Microelectrodes 1

PubMed Central

Henriksen, Gordon H.; Raman, D. Raj; Walker, Larry P.; Spanswick, Roger M.

1992-01-01

Net fluxes of NH4+ and NO3− into roots of 7-day-old barley (Hordeum vulgare L. cv Prato) seedlings varied both with position along the root axis and with time. These variations were not consistent between replicate plants; different roots showed unique temporal and spatial patterns of uptake. Axial scans of NH4+ and NO3− net fluxes were conducted along the apical 7 centimeters of seminal roots of intact barley seedlings in solution culture using ion-selective microelectrodes in the unstirred layer immediately external to the root surface. Theoretically derived relationships between uptake and concentration gradients, combined with experimental observations of the conditions existing in our experimental system, permitted evaluation of the contribution of bulk water flow to ion movement in the unstirred layer, as well as a measure of the spatial resolution of the microelectrode flux estimation technique. Finally, a method was adopted to assess the accuracy of this technique. PMID:16668947

Universal collisional activation ion trap mass spectrometry

DOEpatents

McLuckey, S.A.; Goeringer, D.E.; Glish, G.L.

1993-04-27

A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.

Universal collisional activation ion trap mass spectrometry

DOEpatents

McLuckey, Scott A.; Goeringer, Douglas E.; Glish, Gary L.

1993-01-01

A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.

In situ investigation of helium fuzz growth on tungsten in relation to ion flux, fluence, surface temperature and ion energy using infrared imaging in PSI-2

NASA Astrophysics Data System (ADS)

Möller, S.; Kachko, O.; Rasinski, M.; Kreter, A.; Linsmeier, Ch

2017-12-01

Tungsten is a candidate material for plasma-facing components in nuclear fusion reactors. In operation it will face temperatures >800 K together with an influx of helium ions. Previously, the evolution of special surface nanostructures called fuzz was found under these conditions in a limited window of surface temperature, ion flux and ion energy. Fuzz potentially leads to lower heat load tolerances, enhanced erosion and dust formation, hence should be avoided in a fusion reactor. Here the fuzz growth is reinvestigated in situ during its growth by considering its impact on the surfaces infrared emissivity at 4 μm wavelength with an infrared camera in the linear plasma device PSI-2. A hole in the surface serves as an emissivity reference to calibrate fuzz thickness versus infrared emissivity. Among new data on the above mentioned relations, a lower fuzz growth threshold of 815 ± 24 K is found. Fuzz is seen to grow on rough and polished surfaces and even on the hole’s side walls alike. Literature scalings for thickness, flux and time relations of the fuzz growth rate could not be reproduced, but for the temperature scaling a good agreement to the Arrhenius equation was found.

An observational study of the relationship between precipitating ions and ENAs emerging from the ion/atmosphere interaction region

NASA Astrophysics Data System (ADS)

Mackler, David A.

Plasmasheet particles transported Earthward during times of active magnetospheric convection can interact with thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low altitude (300--800 km) ion precipitation in the high latitude atmosphere/ionosphere are termed Low Altitude Emissions (LAEs). Remotely observed LAEs are highly non-isotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90 degrees. The Geomagnetic Emission Cone (GEC) of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity as well as comparisons of LAE signatures with in situ ion precipitation. The LAE data is from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000--2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The in situ data is from the Defense Meteorological Satellite Program (DMSP). The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest non-linearity. The MLT distribution of LAEs are centered about midnight and spread with increasing activity. The Invariant Latitude for all indices has a slightly negative correlation. The combined results indicate that both LAE and DMSP data behave similarly to geomagnetic activity. LAEs are more spread out in latitude, possibly due to multiple charge exchange interactions, while the in situ data changes to lower latitudes dramatically with increasing flux. The bulk of the data indicates that the

Ga flux dependence of Er-doped GaN luminescent thin films

NASA Astrophysics Data System (ADS)

Lee, D. S.; Steckl, A. J.

2002-02-01

Er-doped GaN thin films have been grown on (111) Si substrates with various Ga fluxes in a radio frequency plasma molecular beam epitaxy system. Visible photoluminescence (PL) and electroluminescence (EL) emission at 537/558 nm and infrared (IR) PL emission at 1.5 μm from GaN:Er films exhibited strong dependence on the Ga flux. Both visible and IR PL and visible EL increase with the Ga flux up to the stoichiometric growth condition, as determined by growth rate saturation. Beyond this condition, all luminescence levels abruptly dropped to the detection limit with increasing Ga flux. The Er concentration, measured by secondary ion mass spectroscopy and Rutherford backscattering, decreases with increasing Ga flux under N-rich growth conditions and remains constant above the stoichiometric growth condition. X-ray diffraction indicated that the crystalline quality of the GaN:Er film was improved with increasing Ga flux up to stoichiometric growth condition and then saturated. Er ions in the films grown under N-rich conditions appear much more optically active than those in the films grown under Ga-rich conditions.

Ion transfer through solvent polymeric membranes driven by an exponential current flux.

PubMed

Molina, A; Torralba, E; González, J; Serna, C; Ortuño, J A

2011-03-21

General analytical equations which govern ion transfer through liquid membranes with one and two polarized interfaces driven by an exponential current flux are derived. Expressions for the transient and stationary E-t, dt/dE-E and dI/dE-E curves are obtained, and the evolution from transient to steady behaviour has been analyzed in depth. We have also shown mathematically that the voltammetric and stationary chronopotentiometric I(N)-E curves are identical (with E being the applied potential for voltammetric techniques and the measured potential for chronopotentiometric techniques), and hence, their derivatives provide identical information.

THE TOPOLOGY OF CANONICAL FLUX TUBES IN FLARED JET GEOMETRY

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

Lavine, Eric Sander; You, Setthivoine, E-mail: Slavine2@uw.edu, E-mail: syou@aa.washington.edu

2017-01-20

Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). We outline here a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of the species’ canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. A flared, current-carrying magnetic flux tube in an ion-electron plasma with finite ion momentum is thus equivalent to either a pair of electron andmore » ion flow flux tubes, a pair of electron and ion canonical momentum flux tubes, or a pair of electron and ion canonical vorticity flux tubes. We examine the morphology of all these flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, axisymmetric magnetic geometry. Calculations of gauge-invariant relative canonical helicities track the evolution of magnetic, cross, and kinetic helicities in the system, and show that ion flow fields can unwind to compensate for an increasing magnetic twist. The results demonstrate that including a species’ finite momentum can result in a very long collimated canonical vorticity flux tube even if the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities, not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes.« less

Characterization of active ion transport across primary rabbit corneal epithelial cell layers (RCrECL) cultured at an air-interface.

PubMed

Chang-Lin, Joan-En; Kim, Kwang-Jin; Lee, Vincent H L

2005-06-01

Previously, we reported the development of a primary culture model of tight rabbit corneal epithelial cell layers (RCrECL) characterizing bioelectric parameters, morphology, cytokeratin, and passive permeability. In the present study, we specifically evaluated the active ion transport processes of RCrECL cultured from either pigmented or albino rabbits. Primary cultured RCrECL were grown at an air-interface on Clear-Snapwells precoated with collagen/fibronectin/laminin and mounted in a modified Ussing-type chamber for the evaluation of their active ion transport processes under short-circuited conditions. Contribution of active Na(+) and Cl(-) transport to overall short-circuit current (I(sc)) was evaluated by removing Na(+) and Cl(-), respectively, from bathing fluids of RCrECL and measurements of net fluxes of Na(+) and Cl(-) using (22)Na and (36)Cl, respectively. Amiloride and benzamil were used to determine the role of apical Na(+)-channel activities to net Na(+) fluxes. N-phenylanthranilic acid (NPAA), ouabain, BaCl(2) and bumetanide were used to determine the role of basolateral Na,K-ATPase, apical Cl(-)-channel, and basolateral K(+)-channel and Na(+)(K(+))2Cl(-)-cotransporter activities, respectively, in active ion transport across RCrECL. I(sc) of RCrECL derived from pigmented rabbits was comprised of 64+/-2% and 44+/-5% for active Na(+) and Cl(-) transport, respectively, consistent with net Na(+) absorption and Cl(-) secretion of 0.062+/-0.006 and 0.046+/-0.008 muEq/cm(2)/hr estimated from radionuclide fluxes. Apical amiloride and benzamil inhibited I(sc) by up to approximately 50% with an IC(50) of 1 and 0.1 microm, respectively, consistent with participation of apical epithelial Na(+)-channels to net Na(+) absorption across RCrECL cultured from pigmented rabbits. Addition of ouabain to the basolateral, NPAA to the apical, BaCl(2) to the basolateral and bumetanide to basolateral fluid decreased I(sc) by 86+/-1.5%, 53+/-3%, 18+/-1.8% and 13+/-1.9% in RCr

Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

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

Peeters, A. G.; Rath, F.; Buchholz, R.

2016-08-15

It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then doesmore » not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.« less

Multispacecraft study of shock-flux rope interaction

NASA Astrophysics Data System (ADS)

Blanco-Cano, X.; Burgess, D.; Sundberg, T.; Kajdic, P.

2016-12-01

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections. These shocks play an active role in particle acceleration near the Sun and through the heliosphere, being associated to solar energetic particle (SEP) and energetic storm particle (ESP) events. IP shocks can interact with structures in the solar wind, and with planetary magnetospheres. In this work we study how the properties of an IP shock change when it interacts with a medium scale flux rope (FR). We use measurements from CLUSTER, WIND and ACE. These three spacecraft observed the shock-FR interaction at different stages of its evolution. We find that the shock-FR interaction locally changes the shock geometry, affecting ion injection processes, and the upstream and downstream regions. While WIND and ACE observed a quasi-perpendicular shock, CLUSTER crossed a quasi-parallel shock and a foreshock with a variety of ion distributions. The complexity of the ion foreshock can be explained by the dynamics of the shock transitioning from quasi-perpendicular to quasi-parallel, and the geometry of the magnetic field around the flux rope.

The Evolution of the Plasma Sheet Ion Composition: Storms and Recoveries: Plasma Sheet Ion Composition

DOE PAGES

Denton, M. H.; Thomsen, M. F.; Reeves, G. D.; ...

2017-10-03

The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H + ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H +, O +, and He + ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux ofmore » each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O + and He +) become increasingly important during such periods as charge-exchange reactions result in faster loss for H + than for O + or He +. Results confirm previous investigations showing that the ion composition of the plasma sheet can be largely understood (and predicted) during calm intervals from knowledge of: (a) the composition of previously injected plasma at the onset of calm conditions, and (b) use of simple drift-physics models combined with calculations of charge-exchange losses.« less

The Evolution of the Plasma Sheet Ion Composition: Storms and Recoveries: Plasma Sheet Ion Composition

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

Denton, M. H.; Thomsen, M. F.; Reeves, G. D.

The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H + ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H +, O +, and He + ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux ofmore » each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O + and He +) become increasingly important during such periods as charge-exchange reactions result in faster loss for H + than for O + or He +. Results confirm previous investigations showing that the ion composition of the plasma sheet can be largely understood (and predicted) during calm intervals from knowledge of: (a) the composition of previously injected plasma at the onset of calm conditions, and (b) use of simple drift-physics models combined with calculations of charge-exchange losses.« less

An S-Type Anion Channel SLAC1 Is Involved in Cryptogein-Induced Ion Fluxes and Modulates Hypersensitive Responses in Tobacco BY-2 Cells

PubMed Central

Horikoshi, Sonoko; Hanamata, Shigeru; Negi, Juntaro; Yagi, Chikako; Kitahata, Nobutaka; Iba, Koh; Kuchitsu, Kazuyuki

2013-01-01

Pharmacological evidence suggests that anion channel-mediated plasma membrane anion effluxes are crucial in early defense signaling to induce immune responses and hypersensitive cell death in plants. However, their molecular bases and regulation remain largely unknown. We overexpressed Arabidopsis SLAC1, an S-type anion channel involved in stomatal closure, in cultured tobacco BY-2 cells and analyzed the effect on cryptogein-induced defense responses including fluxes of Cl− and other ions, production of reactive oxygen species (ROS), gene expression and hypersensitive responses. The SLAC1-GFP fusion protein was localized at the plasma membrane in BY-2 cells. Overexpression of SLAC1 enhanced cryptogein-induced Cl− efflux and extracellular alkalinization as well as rapid/transient and slow/prolonged phases of NADPH oxidase-mediated ROS production, which was suppressed by an anion channel inhibitor, DIDS. The overexpressor also showed enhanced sensitivity to cryptogein to induce downstream immune responses, including the induction of defense marker genes and the hypersensitive cell death. These results suggest that SLAC1 expressed in BY-2 cells mediates cryptogein-induced plasma membrane Cl− efflux to positively modulate the elicitor-triggered activation of other ion fluxes, ROS as well as a wide range of defense signaling pathways. These findings shed light on the possible involvement of the SLAC/SLAH family anion channels in cryptogein signaling to trigger the plasma membrane ion channel cascade in the plant defense signal transduction network. PMID:23950973

An S-type anion channel SLAC1 is involved in cryptogein-induced ion fluxes and modulates hypersensitive responses in tobacco BY-2 cells.

PubMed

Kurusu, Takamitsu; Saito, Katsunori; Horikoshi, Sonoko; Hanamata, Shigeru; Negi, Juntaro; Yagi, Chikako; Kitahata, Nobutaka; Iba, Koh; Kuchitsu, Kazuyuki

2013-01-01

Pharmacological evidence suggests that anion channel-mediated plasma membrane anion effluxes are crucial in early defense signaling to induce immune responses and hypersensitive cell death in plants. However, their molecular bases and regulation remain largely unknown. We overexpressed Arabidopsis SLAC1, an S-type anion channel involved in stomatal closure, in cultured tobacco BY-2 cells and analyzed the effect on cryptogein-induced defense responses including fluxes of Cl(-) and other ions, production of reactive oxygen species (ROS), gene expression and hypersensitive responses. The SLAC1-GFP fusion protein was localized at the plasma membrane in BY-2 cells. Overexpression of SLAC1 enhanced cryptogein-induced Cl(-) efflux and extracellular alkalinization as well as rapid/transient and slow/prolonged phases of NADPH oxidase-mediated ROS production, which was suppressed by an anion channel inhibitor, DIDS. The overexpressor also showed enhanced sensitivity to cryptogein to induce downstream immune responses, including the induction of defense marker genes and the hypersensitive cell death. These results suggest that SLAC1 expressed in BY-2 cells mediates cryptogein-induced plasma membrane Cl(-) efflux to positively modulate the elicitor-triggered activation of other ion fluxes, ROS as well as a wide range of defense signaling pathways. These findings shed light on the possible involvement of the SLAC/SLAH family anion channels in cryptogein signaling to trigger the plasma membrane ion channel cascade in the plant defense signal transduction network.

Monitoring Ion Activities In and Around Cells Using Ion-Selective Liquid-Membrane Microelectrodes

PubMed Central

Lee, Seong-Ki; Boron, Walter F.; Parker, Mark D.

2013-01-01

Determining the effective concentration (i.e., activity) of ions in and around living cells is important to our understanding of the contribution of those ions to cellular function. Moreover, monitoring changes in ion activities in and around cells is informative about the actions of the transporters and/or channels operating in the cell membrane. The activity of an ion can be measured using a glass microelectrode that includes in its tip a liquid-membrane doped with an ion-selective ionophore. Because these electrodes can be fabricated with tip diameters that are less than 1 μm, they can be used to impale single cells in order to monitor the activities of intracellular ions. This review summarizes the history, theory, and practice of ion-selective microelectrode use and brings together a number of classic and recent examples of their usefulness in the realm of physiological study. PMID:23322102

Evidence for day-to-night ion transport at low solar activity in the Venus pre-dawn ionosphere

NASA Technical Reports Server (NTRS)

Brannon, J. F.; Fox, J. L.; Porter, H. S.

1993-01-01

Periapsis of the Pioneer Venus (PV) spacecraft dropped below 180 km on August 28, 1992 near midnight, and 42 orbits of low altitude data at moderately low solar activity in the pre-dawn sector were obtained before contact was lost to the spacecraft in October, 1992. Through a combination of analysis of data from the PV orbiter ion mass spectrometer (OIMS) and modeling, we consider here what can be learned about the relative importance of plasma transport from the dayside and electron precipitation in maintaining the nightside ionosphere during the re-entry period. In particular, we examine here the atomic ion density profiles. We compute the average peak density of O(+) as a function of solar zenith angle and determine what fluxes of atomic ions or precipitating electrons would be necessary to produce those values. We then compare model calculations of the ion densities to those observed during the re-entry period. We find that the low solar activity nightside ionosphere shows evidence of significant day-to-night plasma transport.

Evidence for Day-to-Night Ion Transport at Low Solar Activity in the Venus Pre-Dawn Ionosphere

NASA Technical Reports Server (NTRS)

Brannon, J. F.; Fox, J. L.; Porter, H. S.

1993-01-01

Periapsis of the Pioneer Venus spacecraft dropped below 180 km on August 28, 1992 near midnight, and 42 orbits of low altitude data at moderately low solar activity in the pre-dawn sector were obtained before contact was lost to the spacecraft in October, 1992. Through a combination of analysis of data from the PV orbiter ion mass spectrometer (OIMS) and modeling, we consider here what can be learned about the relative importance of plasma transport from the dayside and electron precipitation in maintaining the nightside ionosphere during the re-entry period. In particular, we examine here the atomic ion density profiles. We compute the average peak density of O(+) as a function of solar zenith angle and determine what fluxes of atomic ions or precipitating electrons would be necessary to produce those values. We then compare model calculations of the ion densities to those observed during the re-entry period. We find that the low solar activity nightside ionosphere shows evidence of significant day-to-night plasma transport.

Evidence for Day-to-Night Ion Transport at Low Solar Activity in the Venus Pre-Dawn Ionosphere

NASA Technical Reports Server (NTRS)

Brannon, J. F.; Fox, J. L.; Porter, H. S.

1993-01-01

Periapsis of the Pioneer Venus spacecraft 2 dropped below 180 km on August 28, 1992 near midnight, and 42 orbits of low altitude data at moderately low solar activity in the pre-dawn sector were obtained before contact was lost to the spacecraft in October, 1992. Through a combination of analysis of data from the PV orbiter ion mass spectrometer (OIMS) and modeling, we consider here what can be learned about the relative importance of plasma transport from the dayside and electron precipitation in maintaining the nightside ionosphere during the re-entry period. In particular, we examine here the atomic ion density profiles. We compute the average peak density of O(+) as a function of solar zenith angle and determine what fluxes of atomic ions or precipitating electrons would he necessary to produce those values. We then compare model calculations of the ion densities to those observed during the re-entry period. We find that the low solar activity nightside ionosphere shows evidence of significant day-to-night plasma transport.

Molecular mechanism of acetylcholine receptor-controlled ion translocation across cell membranes

PubMed Central

Cash, Derek J.; Hess, George P.

1980-01-01

Two molecular processes, the binding of acetylcholine to the membrane-bound acetylcholine receptor protein and the receptor-controlled flux rates of specific inorganic ions, are essential in determining the electrical membrane potential of nerve and muscle cells. The measurements reported establish the relationship between the two processes: the acetylcholine receptor-controlled transmembrane ion flux of 86Rb+ and the concentration of carbamoylcholine, a stable analog of acetylcholine. A 200-fold concentration range of carbamoylcholine was used. The flux was measured in the millisecond-to-minute time region by using a quench flow technique with membrane vesicles prepared from the electric organ of Electrophorus electricus in eel Ringer's solution at pH 7.0 and 1°C. The technique makes possible the study of the transmembrane transport of specific ions, with variable known internal and external ion concentrations, in a system in which a determinable number of receptors is exposed to a known concentration of ligand. The response curve of ion flux to ligand was sigmoidal with an average maximum rate of 84 sec-1. Carbamoylcholine induced inactivation of the receptor with a maximum rate of 2.7 sec-1 and a different ligand dependence so that it was fast relative to ion flux at low ligand concentration but slow relative to ion flux at high ligand concentration. The simplest model that fits the data consists of receptor in the active and inactive states in ligand-controlled equilibria. Receptor inactivation occurs with one or two ligand molecules bound. For channel opening, two ligand molecules bound to the active state are required, and cooperativity results from the channel opening process itself. With carbamoylcholine, apparently, the equilibrium position for the channel opening step is only one-fourth open. The integrated rate equation, based on the model, predicts the time dependence of receptor-controlled ion flux over the concentration range of carbamoylcholine

Intermittency in flux driven kinetic simulations of trapped ion turbulence

NASA Astrophysics Data System (ADS)

Darmet, G.; Ghendrih, Ph.; Sarazin, Y.; Garbet, X.; Grandgirard, V.

2008-02-01

Flux driven kinetic transport is analysed for deeply trapped ion turbulence with the code GYSELA. The main observation is the existence of a steady state situation with respect to the statistics, in particular the balance between the injected energy and the time averaged energy flowing out through the outer edge boundary layer. The temperature is characterised by a very bursty behaviour with a skewed PDF. Superimposed to these short time scale fluctuations, one finds a regime with a strong increase of the zonal flows and a quenching of the turbulent energy. During this phase of such a predator-prey cycle, the core temperature rapidly increases while the edge temperature gradually decreases. The end of this reduced transport regime is governed by the onset of turbulence that governs large relaxation events, and a strong modification of the zonal flow pattern.

Ion Trap Collisional Activation of c and z• Ions Formed via Gas-Phase Ion/Ion Electron Transfer Dissociation

PubMed Central

Han, Hongling; Xia, Yu; McLuckey, Scott A.

2008-01-01

A series of c- and z•-type product ions formed via gas-phase electron transfer ion/ion reactions between protonated polypeptides with azobenzene radical anions are subjected to ion trap collision activation in a linear ion trap. Fragment ions including a-, b-, y-type and ammonia-loss ions are typically observed in collision induced dissociation (CID) of c ions, showing almost identical CID patterns as those of the C-terminal amidated peptides consisting of the same sequences. Collisional activation of z• species mainly gives rise to side-chain losses and peptide backbone cleavages resulting in a-, b-, c-, x-, y-and z-type ions. Most of the fragmentation pathways of z• species upon ion trap CID can be accounted for by radical driven processes. The side-chain losses from z• species are different from the small losses observed from the charge-reduced peptide molecular species in electron transfer dissociation (ETD), which indicates rearrangement of the radical species. Characteristic side-chain losses are observed for several amino acid residues, which are useful to predict their presence in peptide/protein ions. Furthermore, the unique side-chain losses from leucine and isoleucine residues allow facile distinction of these two isomeric residues. PMID:17608403

High-flux ionic diodes, ionic transistors and ionic amplifiers based on external ion concentration polarization by an ion exchange membrane: a new scalable ionic circuit platform.

PubMed

Sun, Gongchen; Senapati, Satyajyoti; Chang, Hsueh-Chia

2016-04-07

A microfluidic ion exchange membrane hybrid chip is fabricated using polymer-based, lithography-free methods to achieve ionic diode, transistor and amplifier functionalities with the same four-terminal design. The high ionic flux (>100 μA) feature of the chip can enable a scalable integrated ionic circuit platform for micro-total-analytical systems.

High-flux ionic diodes, ionic transistors and ionic amplifiers based on external ion concentration polarization by an ion exchange membrane: a new scalable ionic circuit platform†

PubMed Central

Sun, Gongchen; Senapati, Satyajyoti

2016-01-01

A microfluidic-ion exchange membrane hybrid chip is fabricated by polymer-based, lithography-free methods to achieve ionic diode, transistor and amplifier functionalities with the same four-terminal design. The high ionic flux (> 100 μA) feature of the chip can enable a scalable integrated ionic circuit platform for micro-total-analytical systems. PMID:26960551

Ion and Electron Transport in an Nstar-derivative Ion Thruster. Revised

NASA Technical Reports Server (NTRS)

Foster, John E.

2001-01-01

Diffusion of electrons and ions to anode surfaces between the magnetic cusps of a NASA Solar Electric Propulsion Technology Application Readiness ion thruster has been characterized. Ion flux measurements were made at the anode and at the screen grid electrode. The measurements indicated that the average ion current density at the anode and at the screen grid were approximately equal. Additionally, it was found that the electron flux to the anode between cusps is best described by the classical cross-field diffusion coefficient.

HADES RV Programme with HARPS-N at TNG . III. Flux-flux and activity-rotation relationships of early-M dwarfs

NASA Astrophysics Data System (ADS)

Maldonado, J.; Scandariato, G.; Stelzer, B.; Biazzo, K.; Lanza, A. F.; Maggio, A.; Micela, G.; González-Álvarez, E.; Affer, L.; Claudi, R. U.; Cosentino, R.; Damasso, M.; Desidera, S.; González Hernández, J. I.; Gratton, R.; Leto, G.; Messina, S.; Molinari, E.; Pagano, I.; Perger, M.; Piotto, G.; Rebolo, R.; Ribas, I.; Sozzetti, A.; Suárez Mascareño, A.; Zanmar Sanchez, R.

2017-02-01

Context. Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres and for ongoing radial velocity exoplanet programmes. Despite the increasing interest in M dwarfs, our knowledge of the chromospheres of these stars is far from being complete. Aims: We test whether the relations between activity, rotation, and stellar parameters and flux-flux relationships previously investigated for main-sequence FGK stars and for pre-main-sequence M stars also hold for early-M dwarfs on the main-sequence. Although several attempts have been made so far, here we analyse a large sample of stars undergoing relatively low activity. Methods: We analyse in a homogeneous and coherent way a well-defined sample of 71 late-K/early-M dwarfs that are currently being observed in the framework of the HArps-N red Dwarf Exoplanet Survey (HADES). Rotational velocities are derived using the cross-correlation technique, while emission flux excesses in the Ca II H & K and Balmer lines from Hα up to Hɛ are obtained by using the spectral subtraction technique. The relationships between the emission excesses and the stellar parameters (projected rotational velocity, effective temperature, kinematics, and age) are studied. Relations between pairs of fluxes of different chromospheric lines (flux-flux relationships) are also studied and compared with the literature results for other samples of stars. Results: We find that the strength of the chromospheric emission in the Ca II H & K and Balmer lines is roughly constant for stars in the M0-M3 spectral range. Although our sample is likely to be biased towards inactive stars, our data suggest that a moderate but significant correlation between activity and rotation might be present, as well as a hint of kinematically selected young stars showing higher levels of emission in the calcium line and in most of the Balmer lines. We find our sample of M dwarfs to be complementary in terms of chromospheric and X-ray fluxes with

MAGNETIC FLUX TRANSPORT AND THE LONG-TERM EVOLUTION OF SOLAR ACTIVE REGIONS

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

Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P.

2015-12-20

With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infermore » the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible.« less

Characterization of Membrane Patch-Ion Channel Probes for Scanning Ion Conductance Microscopy.

PubMed

Shi, Wenqing; Zeng, Yuhan; Zhu, Cheng; Xiao, Yucheng; Cummins, Theodore R; Hou, Jianghui; Baker, Lane A

2018-05-01

Integration of dual-barrel membrane patch-ion channel probes (MP-ICPs) to scanning ion conductance microscopy (SICM) holds promise of providing a revolutionized approach of spatially resolved chemical sensing. A series of experiments are performed to further the understanding of the system and to answer some fundamental questions, in preparation for future developments of this approach. First, MP-ICPs are constructed that contain different types of ion channels including transient receptor potential vanilloid 1 and large conductance Ca2 + -activated K + channels to establish the generalizability of the methods. Next, the capability of the MP-ICP platforms in single ion channel activity measurements is proved. In addition, the interplay between the SICM barrel and the ICP barrel is studied. For ion channels gated by uncharged ligands, channel activity at the ICP barrel is unaffected by the SICM barrel potential; whereas for ion channels that are gated by charged ligands, enhanced channel activity can be obtained by biasing the SICM barrel at potentials with opposite polarity to the charge of the ligand molecules. Finally, a proof-of-principle experiment is performed and site-specific molecular/ionic flux sensing is demonstrated at single-ion-channel level, which show that the MP-ICP platform can be used to quantify local molecular/ionic concentrations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Activity computer program for calculating ion irradiation activation

NASA Astrophysics Data System (ADS)

Palmer, Ben; Connolly, Brian; Read, Mark

2017-07-01

A computer program, Activity, was developed to predict the activity and gamma lines of materials irradiated with an ion beam. It uses the TENDL (Koning and Rochman, 2012) [1] proton reaction cross section database, the Stopping and Range of Ions in Matter (SRIM) (Biersack et al., 2010) code, a Nuclear Data Services (NDS) radioactive decay database (Sonzogni, 2006) [2] and an ENDF gamma decay database (Herman and Chadwick, 2006) [3]. An extended version of Bateman's equation is used to calculate the activity at time t, and this equation is solved analytically, with the option to also solve by numeric inverse Laplace Transform as a failsafe. The program outputs the expected activity and gamma lines of the activated material.

Mechanically Activated Ion Channels

PubMed Central

Ranade, Sanjeev S.; Syeda, Ruhma; Patapoutian, Ardem

2015-01-01

Mechanotransduction, the conversion of physical forces into biochemical signals, is an essential component of numerous physiological processes including not only conscious senses of touch and hearing, but also unconscious senses such as blood pressure regulation. Mechanically activated (MA) ion channels have been proposed as sensors of physical force, but the identity of these channels and an understanding of how mechanical force is transduced has remained elusive. A number of recent studies on previously known ion channels along with the identification of novel MA ion channels have greatly transformed our understanding of touch and hearing in both vertebrates and invertebrates. Here, we present an updated review of eukaryotic ion channel families that have been implicated in mechanotransduction processes and evaluate the qualifications of the candidate genes according to specified criteria. We then discuss the proposed gating models for MA ion channels and highlight recent structural studies of mechanosensitive potassium channels. PMID:26402601

Lithium nickel cobalt manganese oxide synthesized using alkali chloride flux: morphology and performance as a cathode material for lithium ion batteries.

PubMed

Kim, Yongseon

2012-05-01

Li(Ni(0.8)Co(0.1)Mn(0.1))O(2) (NCM811) was synthesized using alkali chlorides as a flux and the performance as a cathode material for lithium ion batteries was examined. Primary particles of the powder were segregated and grown separately in the presence of liquid state fluxes, which induced each particle to be composed of one primary particle with well-developed facet planes, not the shape of agglomerates as appears with commercial NCMs. The new NCM showed far less gas emission during high temperature storage at charged states, and higher volumetric capacity thanks to its high bulk density. The material is expected to provide optimal performances for pouch type lithium ion batteries, which require high volumetric capacity and are vulnerable to deformation caused by gas generation from the electrode materials.

Ion fluxes from fog and rain to an agricultural and a forest ecosystem in Europe

NASA Astrophysics Data System (ADS)

Thalmann, E.; Burkard, R.; Wrzesinsky, T.; Eugster, W.; Klemm, O.

The deposition fluxes of inorganic compounds dissolved in fog and rain were quantified for two different ecosystems in Europe. The fogwater deposition fluxes were measured by employing the eddy covariance method. The site in Switzerland that lies within an agricultural area surrounded by the Jura mountains and the Alps is often exposed to radiation fog. At the German mountain forest ecosystem, on the other hand, advection fog occurs most frequently. At the Swiss site, fogwater deposition fluxes of the dominant components SO 42- (0.027 mg S m -2 day -1), NO 3- (0.030 mg N m -2 day -1) and NH 4+ (0.060 mg N m -2 day -1) were estimated to be <5% of the measured wet deposition (0.85, 0.70 and 1.34 mg m -2 day -1, respectively). The corresponding fluxes at the forest site (0.62, 0.82 and 1.16 mg m -2 day -1, respectively) were of the same order of magnitude as wet deposition (1.04, 1.01 and 1.36 mg m -2 day -1), illustrating the importance of fog (or occult) deposition. Trajectory analyses at the forest site indicate significantly higher fogwater concentrations of all major ions if air originated from the east (i.e. the Czech Republic), which is in close agreement with earlier studies.

Mechanism of ion transport by avian salt gland primary cell cultures.

PubMed

Lowy, R J; Dawson, D C; Ernst, S A

1989-06-01

Confluent sheets formed from primary culture of avian salt gland secretory cells exhibit a short-circuit current (Isc) in response to cholinergic and beta-adrenergic stimulation [Lowy, R. J., D. C. Dawson, and S. A. Ernst. Am J. Physiol. 249 (Cell Physiol. 18): C41-C47, 1985]. To establish the ionic basis for the Isc, transmural fluxes of 22Na and 36Cl were measured. Under short-circuit conditions there was little net flux of either ion in the absence of agonists. Addition of carbachol elevated net serosal-to-mucosal Cl flux to 1.71 mu eq.h-1.cm-2, whereas a smaller increase to 0.85 mu eq.h-1.cm-2 occurred with isoproterenol. Neither agonist altered net Na flux. The stimulated Isc accounted for 70% of the net Cl flux induced by carbachol and nearly 100% of that induced by isoproterenol. Replacement of Cl by gluconate or Na by choline abolished (carbachol) or greatly reduced (isoproterenol) the Isc, which could be restored in a dose-dependent fashion by ion restitution. Active ion transport was preferentially inhibited by basal (vs. apical) addition of ouabain, furosemide, or barium. The results provide evidence that cholinergic and beta-adrenergic agonists elicit active transmural Cl secretion. They further suggest that transport is dependent on the Na+-K+-adenosine-triphosphatase, a Na-Cl cotransport process, and a basal K conductance, all features of a secondary active Cl secretory mechanism.

Inter-cusp Ion and Electron Transport in a Nstar-derivative Ion Thruster

NASA Technical Reports Server (NTRS)

Foster, John E.

2001-01-01

Diffusion of electrons and ions to anode surfaces between the magnetic cusps of a NASA Solar Electric Propulsion Technology Application Readiness ion thruster has been characterized. Ion flux measurements were made at the anode and at the screen grid electrode. The measurements indicated that the average ion current density at the anode and at the screen grid were approximately equal. Additionally, it was found that the electron flux to the anode between cusps is best described by the classical cross-field diffusion coefficient.

Do Ions Injected with the Dipolarizing Flux Bundles Provide the Free Energy for Waves in the Inner Magnetosphere?

NASA Astrophysics Data System (ADS)

Runov, A.; Angelopoulos, V.; Artemyev, A.; Lu, S.; Birn, J.; Pritchett, P. L.

2017-12-01

Electron interactions with Electromagnetic Ion Cyclotron (EMIC) amd Magnetosnic (MS) waves are considered as a mechanism of electron acceleration up to relativistic energies in the inner magnetosphere. The free energy for these waves is provided by ion populations with unstable energy distributions. It is established that the perpendicular anisotropy (T_perp > T_par) of energetic ions may provide the free energy for EMIC waves. The ring-type ion distributions are considered as the free energy source for the MS waves. Where and how do these distributions formed? To answer this question, we examined ion distribution functions within earthward-contracting dipolarizing flux bundles (DFBs) observed in the near-Earth plasma sheet at R 10 - 12 RE. It was found that ion distributions are often characterized by the perpendicular anisotropy at supra-thermal energies (at velocities V_thermal ≤ v ≤ 2*V_thermal). The effect was found to be stronger at largerbackground Bz (i.e., closer to the dipole). Similar characteristics wereobserved in particle-in-cell and test-particle simulations. Moreover, the simulations showed the ring-type ion distribution formation. These results suggest that ions, injected towards the inner magnetosphere with DFBs may indeed provide free energy for the EMIC and MS wave excitations.

Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate

PubMed Central

Molina, Anthony J A; Verzi, Michael P; Birnbaum, Andrea D; Yamoah, Ebenezer N; Hammar, Katherine; Smith, Peter J S; Malchow, Robert Paul

2004-01-01

Self-referencing H+-selective microelectrodes were used to measure extracellular H+ fluxes from horizontal cells isolated from the skate retina. A standing H+ flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H+ flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na+–H+ exchanger. Glutamate decreased H+ flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H+ flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H+ flux. Immunocytochemical localization of the plasmalemma Ca2+–H+-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H+ flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca2+–H+-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neurones. PMID:15272044

Sugar-activated ion transport in canine lingual epithelium. Implications for sugar taste transduction

PubMed Central

1988-01-01

There is good evidence indicating that ion-transport pathways in the apical regions of lingual epithelial cells, including taste bud cells, may play a role in salt taste reception. In this article, we present evidence that, in the case of the dog, there also exists a sugar- activated ion-transport pathway that is linked to sugar taste transduction. Evidence was drawn from two parallel lines of experiments: (a) ion-transport studies on the isolated canine lingual epithelium, and (b) recordings from the canine chorda tympani. The results in vitro showed that both mono- and disaccharides in the mucosal bath stimulate a dose-dependent increase in the short-circuit current over the concentration range coincident with mammalian sugar taste responses. Transepithelial current evoked by glucose, fructose, or sucrose in either 30 mM NaCl or in Krebs-Henseleit buffer (K-H) was partially blocked by amiloride. Among current carriers activated by saccharides, the current response was greater with Na than with K. Ion flux measurements in K-H during stimulation with 3-O-methylglucose showed that the sugar-evoked current was due to an increase in the Na influx. Ouabain or amiloride reduced the sugar-evoked Na influx without effect on sugar transport as measured with tritiated 3-O-methylglucose. Amiloride inhibited the canine chorda tympani response to 0.5 M NaCl by 70-80% and the response to 0.5 M KCl by approximately 40%. This agreed with the percent inhibition by amiloride of the short-circuit current supported in vitro by NaCl and KCl. Amiloride also partially inhibited the chorda tympani responses to sucrose and to fructose. The results indicate that in the dog: (a) the ion transporter subserving Na taste also subserves part of the response to K, and (b) a sugar-activated, Na- preferring ion-transport system is one mechanism mediating sugar taste transduction. Results in the literature indicate a similar sweet taste mechanism for humans. PMID:3171536

Shaking stack model of ion conduction through the Ca(2+)-activated K+ channel.

PubMed Central

Schumaker, M F

1992-01-01

Motivated by the results of Neyton and Miller (1988. J. Gen. Physiol. 92:549-586), suggesting that the Ca(2+)-activated K+ channel has four high affinity ion binding sites, we propose a physically attractive variant of the single-vacancy conduction mechanism for this channel. Simple analytical expressions for conductance, current, flux ratio exponent, and reversal potential under bi-ionic conditions are found. A set of conductance data are analyzed to determine a realistic range of parameter values. Using these, we find qualitative agreement with a variety of experimental results previously reported in the literature. The exquisite selectivity of the Ca(2+)-activated K+ channel may be explained as a consequence of the concerted motion of the "stack" in the proposed mechanism. PMID:1420923

On Membrane Motor Activity and Chloride Flux in the Outer Hair Cell: Lessons Learned from the Environmental Toxin Tributyltin

PubMed Central

Song, Lei; Seeger, Achim; Santos-Sacchi, Joseph

2005-01-01

The outer hair cell (OHC) underlies mammalian cochlea amplification, and its lateral membrane motor, prestin, which drives the cell's mechanical activity, is modulated by intracellular chloride ions. We have previously described a native nonselective conductance (GmetL) that influences OHC motor activity via Cl flux across the lateral membrane. Here we further investigate this conductance and use the environmental toxin tributyltin (TBT) to better understand Cl-prestin interactions. Capitalizing on measures of prestin-derived nonlinear capacitance to gauge Cl flux across the lateral membrane, we show that the Cl ionophore TBT, which affects neither the motor nor GmetL directly, is capable of augmenting the native flux of Cl in OHCs. These observations were confirmed using the chloride-sensitive dye MQAE. Furthermore, the compound's potent ability, at nanomolar concentrations, to equilibrate intra- and extracellular Cl concentrations is shown to surpass the effectiveness of GmetL in promoting Cl flux, and secure a quantitative analysis of Cl-prestin interactions in intact OHCs. Using malate as an anion replacement, we quantify chloride effects on the nonlinear charge density and operating voltage range of prestin. Our data additionally suggest that ototoxic effects of organotins can derive from their disruption of OHC Cl homeostasis, ultimately interfering with anionic modulation of the mammalian cochlear amplifier. Notably, this observation identifies a new environmental threat for marine mammals by TBT, which is known to accumulate in the food chain. PMID:15596517

[Spectra and thermal analysis of the arc in activating flux plasma arc welding].

PubMed

Chai, Guo-Ming; Zhu, Yi-Feng

2010-04-01

In activating flux plasma arc welding the welding arc was analyzed by spectra analysis technique, and the welding arc temperature field was measured by the infrared sensing and computer image technique. The distribution models of welding arc heat flow density of activating flux PAW welding were developed. The composition of welding arc affected by activated flux was studied, and the welding arc temperature field was studied. The results show that the spectral lines of argon atom and ionized argon atom of primary ionization are the main spectra lines of the conventional plasma welding arc. The spectra lines of weld metal are inappreciable in the spectra lines of the conventional plasma welding arc. The gas particle is the main in the conventional plasma welding arc. The conventional plasma welding arc is gas welding arc. The spectra lines of argon atom and ionized argon atom of primary ionization are intensified in the activating flux plasma welding arc, and the spectra lines of Ti, Cr and Fe elements are found in the activating flux plasma welding arc. The welding arc temperature distribution in activating flux plasma arc welding is compact, the outline of the welding arc temperature field is narrow, the range of the welding arc temperature distribution is concentrated, the welding arc radial temperature gradient is large, and the welding arc radial temperature gradient shows normal Gauss distribution.

Investigation of Ion Channel Activities of Gramicidin A in the Presence of Ionic Liquids Using Model Cell Membranes

PubMed Central

Ryu, Hyunil; Lee, Hwankyu; Iwata, Seigo; Choi, Sangbaek; Ki Kim, Moon; Kim, Young-Rok; Maruta, Shinsaku; Min Kim, Sun; Jeon, Tae-Joon

2015-01-01

Ionic liquids (ILs) are considered to be green solvents because of their non-volatility. Although ILs are relatively safe in the atmospheric environment, they may be toxic in other environments. Our previous research showed that the cytotoxicity of ILs to biological organisms is attributable to interference with cell membranes by IL insertion. However, the effects of ILs on ion channels, which play important roles in cell homeostasis, have not been comprehensively studied to date. In this work, we studied the interactions between ILs and lipid bilayer membranes with gramicidin A ion channels. We used two methods, namely electrical and fluorescence measurements of ions that permeate the membrane. The lifetimes of channels were increased by all the ILs tested in this work via stabilizing the compressed structure of the lipid bilayer and the rate of ion flux through gA channels was decreased by changing the membrane surface charge. The former effect, which increased the rate of ion flux, was dominant at high salt concentrations, whereas the latter, which decreased the rate of ion flux, was dominant at low salt concentrations. The effects of ILs increased with increasing concentration and alkyl chain length. The experimental results were further studied using molecular dynamics simulations. PMID:26189604

Substituted 2-benzothiazolamines as sodium flux inhibitors: quantitative structure-activity relationships and anticonvulsant activity.

PubMed

Hays, S J; Rice, M J; Ortwine, D F; Johnson, G; Schwarz, R D; Boyd, D K; Copeland, L F; Vartanian, M G; Boxer, P A

1994-10-01

Thirty-two aryl-substituted 2-benzothiazolamines have been tested for their ability to modulate sodium flux in rat cortical slices. A QSAR analysis, applied to these derivatives, showed a trend toward increasing potency as sodium flux inhibitors with increasing lipophilicity, decreasing size, and increasing electron withdrawal of the benzo ring substituents. Additionally, 4- or 5-substitution of the benzo ring was found to decrease potency. The combination of increased lipophilicity, small size, and electron withdrawal severely limited which groups were tolerated on the benzo ring, thus suggesting that the optimal substitution patterns have been prepared within this series. Nine of these compounds were potent inhibitors of veratridine-induced sodium flux (NaFl). These nine compounds also proved to be anticonvulsant in the maximal electroshock (MES) assay. Fourteen additional 2-benzothiazolamines demonstrated activity in the MES screen, yet exhibited no activity in the NaFl assay. These derivatives may be interacting at the sodium channel in a manner not discernible by the flux paradigm, or they may be acting by an alternative mechanism in vivo.

Absolute photon-flux measurements in the vacuum ultraviolet

NASA Technical Reports Server (NTRS)

Samson, J. A. R.; Haddad, G. N.

1974-01-01

Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

Chain Rule Approach for Calculating the Time-Derivative of Flux

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

Langenbrunner, James R.; Booker, Jane M.

The reaction history (gamma-flux observable) is mathematically studied by using the chain rule for taking the total-time derivatives. That is, the total time-derivative of flux is written as the product of the ion temperature derivative with respect to time and the derivative of the flux with respect to ion temperature. Some equations are derived using the further simplification that the fusion reactivity is a parametrized function of ion temperature, T. Deuterium-tritium (D-T) fusion is used as the application with reactivity calculations from three established reactivity parametrizations.

The Solar Connection of Enhanced Heavy Ion Charge States in the Interplanetary Medium: Implications for the Flux-Rope Structure of CMEs

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Makela, P.; Akiyama, S.; Xie, H.; Yashiro, S.; Reinard, A. A.

2013-01-01

We investigated a set of 54 interplanetary coronal mass ejection (ICME) events whose solar sources are very close to the disk center (within +/- 15deg from the central meridian). The ICMEs consisted of 23 magnetic-cloud (MC) events and 31 non-MC events. Our analyses suggest that the MC and non-MC ICMEs have more or less the same eruption characteristics at the Sun in terms of soft X-ray flares and CMEs. Both types have significant enhancements in ion charge states, although the non-MC structures have slightly lower levels of enhancement. The overall duration of charge-state enhancement is also considerably smaller than that in MCs as derived from solar wind plasma and magnetic signatures. We find very good correlation between the Fe and O charge-state measurements and the flare properties such as soft X-ray flare intensity and flare temperature for both MCs and non-MCs. These observations suggest that both MC and non-MC ICMEs are likely to have a flux-rope structure and the unfavorable observational geometry may be responsible for the appearance of non-MC structures at 1 AU. We do not find any evidence for an active region expansion resulting in ICMEs lacking a flux-rope structure because the mechanism of producing high charge states and the flux-rope structure at the Sun is the same for MC and non-MC events.

Long-pulse production of high current negative ion beam by using actively temperature controlled plasma grid for JT-60SA negative ion source

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

Kojima, A.; Hanada, M.; Yoshida, M.

2015-04-08

The temperature control system of the large-size plasma grid has been developed to realize the long pulse production of high-current negative ions for JT-60SA. By using this prototype system for the JT-60SA ion source, 15 A negative ions has been sustained for 100 s for the first time, which is three times longer than that obtained in JT-60U. In this system, a high-temperature fluorinated fluid with a high boiling point of 270 degree Celsius is circulated in the cooling channels of the plasma grids (PG) where a cesium (Cs) coverage is formed to enhance the negative ion production. Because themore » PG temperature control had been applied to only 10% of the extraction area previously, the prototype PG with the full extraction area (110 cm × 45 cm) was developed to increase the negative ion current in this time. In the preliminary results of long pulse productions of high-current negative ions at a Cs conditioning phase, the negative ion production was gradually degraded in the last half of 100 s pulse where the temperature of an arc chamber wall was not saturated. From the spectroscopic measurements, it was found that the Cs flux released from the wall might affect to the negative ion production, which implied the wall temperature should be kept low to control the Cs flux to the PG for the long-pulse high-current production. The obtained results of long-pulse production and the PG temperature control method contributes the design of the ITER ion source.« less

Measurements of the Canonical Helicity Evolution of a Gyrating Kinked Flux Rope

NASA Astrophysics Data System (ADS)

von der Linden, J.; Sears, J.; Intrator, T.; You, S.

2017-12-01

Magnetic structures in the solar corona and planetary magnetospheres are often modelled as magnetic flux ropes governed by magnetohydrodynamics (MHD); however, inside these structures, as exhibited in reconnection, conversions between magnetic and kinetic energies occur over a wide range of scales. Flux ropes based on the flux of canonical momentum circulation extend the flux rope concept to include effects of finite particle momentum and present the distinct advantage of reconciling all plasma regimes - e.g. kinetic, two-fluid, and MHD - with the topological concept of helicity: twists, writhes, and linkages. This presentation shows the first visualization and analysis of the 3D dynamics of canonical flux ropes and their relative helicity evolution from laboratory measurements. Ion and electron canonical flux ropes are visualized from a dataset of Mach, triple, and Ḃ probe measurements at over 10,000 spatial locations of a gyrating kinked flux rope. The flux ropes co-gyrate with the peak density and electron temperature in and out of a measurement volume. The electron and ion canonical flux ropes twist with opposite handedness and the ion flux ropes writhe around the electron flux ropes. The relative cross helicity between the magnetic and ion flow vorticity flux ropes dominates the relative ion canonical helicity and is anti-correlated with the relative magnetic helicity. The 3D nature of the kink and a reverse eddy current affect the helicity evolution. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-735426

Simulations of the Cleft Ion Fountain outflows resulting from the passage of Storm Enhanced Density (SED) plasma flux tubes through the dayside cleft auroral processes region

NASA Astrophysics Data System (ADS)

Horwitz, James; Zeng, Wen

2007-10-01

Foster et al. [2002] reported elevated ionospheric density regions convected from subauroral plasmaspheric regions toward noon, in association with convection of plasmaspheric tails. These Storm Enhanced Density (SED) regions could supply cleft ion fountain outflows. Here, we will utilize our Dynamic Fluid Kinetic (DyFK) model to simulate the entry of a high-density ``plasmasphere-like'' flux tube entering the cleft region and subjected to an episode of wave-driven transverse ion heating. It is found that the O^+ ion density at higher altitudes increases and the density at lower altitudes decreases, following this heating episode, indicating increased fluxes of O^+ ions from the ionospheric source gain sufficient energy to reach higher altitudes after the effects of transverse wave heating. Foster, J. C., P. J. Erickson, A. J. Coster, J. Goldstein, and F. J. Rich, Ionospheric signatures of plasmaspheric tails, Geophys. Res. Lett., 29(13), 1623, doi:10.1029/2002GL015067, 2002.

The cancellation of magnetic flux. II - In a decaying active region. [of sun

NASA Technical Reports Server (NTRS)

Martin, S. F.; Livi, S. H. B.; Wang, J.

1985-01-01

H-alpha filtergrams and videomagnetograms are used to study an active region during its period of decay on August 3-8, 1984; the decay had been initiated by a fragmentation process in which very small knots of magnetic flux separated from larger concentration of flux. The disappearance of magnetic flux was always observed when the small fragments of flux encountered other small fragments or concentrations of flux of opposite polarity. Such 'cancellations' are shared by both polarities of magnetic field, and it is deduced that the disappearance of flux occurred either at or within 5 arcsec of the apparent dividing line between the opposite polarities. All of the 22 flares observed during the decay of this region were initiated around sites where magnetic flux was cancelling or was deduced to be cancelling during the flares. It is hypothesized that cancellation was one of the necessary conditions for flaring in this active region.

High flux, beamed neutron sources employing deuteron-rich ion beams from D2O-ice layered targets

NASA Astrophysics Data System (ADS)

Alejo, A.; Krygier, A. G.; Ahmed, H.; Morrison, J. T.; Clarke, R. J.; Fuchs, J.; Green, A.; Green, J. S.; Jung, D.; Kleinschmidt, A.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Notley, M.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.; Freeman, R. R.; Kar, S.

2017-06-01

A forwardly-peaked bright neutron source was produced using a laser-driven, deuteron-rich ion beam in a pitcher-catcher scenario. A proton-free ion source was produced via target normal sheath acceleration from Au foils having a thin layer of D2O ice at the rear side, irradiated by sub-petawatt laser pulses (˜200 J, ˜750 fs) at peak intensity ˜ 2× {10}20 {{W}} {{cm}}-2. The neutrons were preferentially produced in a beam of ˜70° FWHM cone along the ion beam forward direction, with maximum energy up to ˜40 MeV and a peak flux along the axis ˜ 2× {10}9 {{n}} {{sr}}-1 for neutron energy above 2.5 MeV. The experimental data is in good agreement with the simulations carried out for the d(d,n)3He reaction using the deuteron beam produced by the ice-layered target.

INVESTIGATION OF HELICITY AND ENERGY FLUX TRANSPORT IN THREE EMERGING SOLAR ACTIVE REGIONS

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

Vemareddy, P., E-mail: vemareddy@iiap.res.in

We report the results of an investigation of helicity and energy flux transport from three emerging solar active regions (ARs). Using time sequence vector magnetic field observations obtained from the Helioseismic Magnetic Imager, the velocity field of plasma flows is derived by the differential affine velocity estimator for vector magnetograms. In three cases, the magnetic fluxes evolve to pump net positive, negative, and mixed-sign helicity flux into the corona. The coronal helicity flux is dominantly coming from the shear term that is related to horizontal flux motions, whereas energy flux is dominantly contributed by the emergence term. The shear helicity fluxmore » has a phase delay of 5–14 hr with respect to absolute magnetic flux. The nonlinear curve of coronal energy versus relative helicity identifies the configuration of coronal magnetic fields, which is approximated by a fit of linear force-free fields. The nature of coronal helicity related to the particular pattern of evolving magnetic fluxes at the photosphere has implications for the generation mechanism of two kinds of observed activity in the ARs.« less

Sorption studies of nickel ions onto activated carbon

NASA Astrophysics Data System (ADS)

Joshi, Parth; Vyas, Meet; Patel, Chirag

2018-05-01

Activated porous carbons are made through pyrolysis and activation of carbonaceous natural as well as synthetic precursors. The use of low-cost activated carbon derived from azadirachta indica, an agricultural waste material, has been investigated as a replacement for the current expensive methods of removing nickel ions from wastewater. The temperature variation study showed that the nickel ions adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the nickel ion solutions. Therefore, this study revealed that azadirachta indica can serve as a good source of activated carbon with multiple and simultaneous metal ions removing potentials and may serve as a better replacement for commercial activated carbons in applications that warrant their use.

An improved empirical model of electron and ion fluxes at geosynchronous orbit based on upstream solar wind conditions

DOE PAGES

Denton, M. H.; Henderson, M. G.; Jordanova, V. K.; ...

2016-07-01

In this study, a new empirical model of the electron fluxes and ion fluxes at geosynchronous orbit (GEO) is introduced, based on observations by Los Alamos National Laboratory (LANL) satellites. The model provides flux predictions in the energy range ~1 eV to ~40 keV, as a function of local time, energy, and the strength of the solar wind electric field (the negative product of the solar wind speed and the z component of the magnetic field). Given appropriate upstream solar wind measurements, the model provides a forecast of the fluxes at GEO with a ~1 h lead time. Model predictionsmore » are tested against in-sample observations from LANL satellites and also against out-of-sample observations from the Compact Environmental Anomaly Sensor II detector on the AMC-12 satellite. The model does not reproduce all structure seen in the observations. However, for the intervals studied here (quiet and storm times) the normalized root-mean-square deviation < ~0.3. It is intended that the model will improve forecasting of the spacecraft environment at GEO and also provide improved boundary/input conditions for physical models of the magnetosphere.« less

Response of thermal ions to electromagnetic ion cyclotron waves

NASA Technical Reports Server (NTRS)

Anderson, B. J.; Fuselier, S. A.

1994-01-01

Electromagnetic ion cyclotron waves generated by 10 - 50 keV protons in the Earth's equatorial magnetosphere will interact with the ambient low-energy ions also found in this region. We examine H(+) and He(+) distribution functions from approx. equals 1 to 160 eV using the Hot Plasma Composition Experiment instrument on AMPTE/CCE to investigate the thermal ion response to the waves. A total of 48 intervals were chosen on the basis of electromagnetic ion cyclotron (EMIC) wave activity: 24 with prevalent EMIC waves and 24 with no EMIC waves observed on the orbit. There is a close correlation between EMIC waves and perpendicular heated ion distributions. For protons the perpendicular temperature increase is modest, about 5 eV, and is always observed at 90 deg pitch angles. This is consistent with a nonresonant interaction near the equator. By contrast, He(+) temperatures during EMIC wave events averaged 35 eV and sometimes exceeded 100 eV, indicating stronger interaction with the waves. Furthermore, heated He(+) ions have X-type distributions with maximum fluxes occurring at pitch angles intermediate between field-aligned and perpendicular directions. The X-type He(+) distributions are consistent with a gyroresonant interaction off the equator. The concentration of He(+) relative to H(+) is found to correlate with EMIC wave activity, but it is suggested that the preferential heating of He(+) accounts for the apparent increase in relative He(+) concentration by increasing the proportion of He(+) detected by the ion instrument.

Impact of Ring Current Ions on Electromagnetic Ion Cyclotron Wave Dispersion Relation

NASA Technical Reports Server (NTRS)

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

2007-01-01

Effect of the ring current ions in the real part of electromagnetic ion Cyclotron wave dispersion relation is studied on global scale. Recent Cluster observations by Engebretson et al. showed that although the temperature anisotropy of is energetic (> 10 keV) ring current protons was high during the entire 22 November 2003 perigee pass, electromagnetic ion cyclotron waves were observed only in conjunction with intensification of the ion fluxes below 1 keV by over an order of magnitude. To study the effect of the ring current ions on the wave dispersive properties and the corresponding global wave redistribution, we use a self-consistent model of interacting ring current and electromagnetic ion cyclotron waves, and simulate the May 1998 storm. The main findings of our simulation can be summarized as follows: First, the plasma density enhancement in the night MLT sector during the main and recovery storm phases is mostly caused by injection of suprathermal plasma sheet H + (approximately < 1 keV), which dominate the thermal plasma density. Second, during the recovery storm phases, the ring current modification of the wave dispersion relation leads to a qualitative change of the wave patterns in the postmidnight-dawn sector for L > 4.75. This "new" wave activity is well organized by outward edges of dense suprathermal ring current spots, and the waves are not observed if the ring current ions are not included in the real part of dispersion relation. Third, the most intense wave-induced ring current precipitation is located in the night MLT sector and caused by modification of the wave dispersion relation. The strongest precipitating fluxes of about 8 X 10(exp 6)/ (cm(exp 2) - s X st) are found near L=5.75, MLT=2 during the early recovery phase on 4 May. Finally, the nightside precipitation is more intense than the dayside fluxes, even if there are less intense waves, because the convection field moves ring current ions into the loss cone on the nightside, but drives

Auxin effects on ion transport in Chara corallina.

PubMed

Zhang, Suyun; de Boer, Albertus H; van Duijn, Bert

2016-04-01

The plant hormone auxin has been widely studied with regard to synthesis, transport, signaling and functions among the land plants while there is still a lack of knowledge about the possible role for auxin regulation mechanisms in algae with "plant-like" structures. Here we use the alga Chara corallina as a model to study aspects of auxin signaling. In this respect we measured auxin on membrane potential changes and different ion fluxes (K(+), H(+)) through the plasma membrane. Results showed that auxin, mainly IAA, could hyperpolarize the membrane potential of C. corallina internodal cells. Ion flux measurements showed that the auxin-induced membrane potential change may be based on the change of K(+) permeability and/or channel activity rather than through the activation of proton pumps as known in land plants. Copyright © 2016 Elsevier GmbH. All rights reserved.

The impact of the fast ion fluxes and thermal plasma loads on the design of the ITER fast ion loss detector

NASA Astrophysics Data System (ADS)

Kocan, M.; Garcia-Munoz, M.; Ayllon-Guerola, J.; Bertalot, L.; Bonnet, Y.; Casal, N.; Galdon, J.; Garcia-Lopez, J.; Giacomin, T.; Gonzalez-Martin, J.; Gunn, J. P.; Rodriguez-Ramos, M.; Reichle, R.; Rivero-Rodriguez, J. F.; Sanchis-Sanchez, L.; Vayakis, G.; Veshchev, E.; Vorpahl, C.; Walsh, M.; Walton, R.

2017-12-01

Thermal plasma loads to the ITER Fast Ion Loss Detector are studied for QDT = 10 burning plasma equilibrium using the 3D field line tracing. The simulations are performed for a FILD insertion 9-13 cm past the port plasma facing surface, optimized for fast ion measurements, and include the worst-case perturbation of the plasma boundary and the error in the magnetic reconstruction. The FILD head is exposed to superimposed time-averaged ELM heat load, static inter-ELM heat flux and plasma radiation. The study includes the estimate of the instantaneous temperature rise due to individual 0.6 MJ controlled ELMs. The maximum time-averaged surface heat load is lesssim 12 MW/m2 and will lead to increase of the FILD surface temperature well below the melting temperature of the materials considered here, for the FILD insertion time of 0.2 s. The worst-case instantaneous temperature rise during controlled 0.6 MJ ELMs is also significantly smaller than the melting temperature of e.g. Tungsten or Molybdenum, foreseen for the FILD housing.

Zinc-ion-dependent acid phosphatase exhibits magnesium-ion-dependent myo-inositol-1-phosphatase activity.

PubMed

Fujimoto, S; Okano, I; Tanaka, Y; Sumida, Y; Tsuda, J; Kawakami, N; Shimohama, S

1996-06-01

We have purified bovine brain Zn(2+)-dependent acid phosphatase (Zn(2+)-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn(2+)-APase at a physiological pH was also studied. The enzyme exhibited hydrolytic activity on myo-inositol-1- and -2-monophosphates, 2'-adenosine monophosphate, 2'-guanosine monophosphate, and the alpha- and beta-glycerophosphates, glucose-1-phosphate, and fructose-6-phosphate in 50 mM Tris-HCl buffer (pH 7.4) in the presence of Mg2+ ions, but not on pNPP and phosphotyrosine. Zn2+, Mn2+ and Co2+ ions were less effective for activation. Among the above substrates, myo-inositol-1-phosphate was the most susceptible to hydrolysis by the enzyme in the presence of 3 mM Mg2+ ions. The enzyme exhibited an optimum pH at around 8 for myo-inositol-1-phosphate in the presence of 3 mM Mg2+ ions. The Mg(2+)-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn(2+)-dependent p-nitrophenyl phosphatase activity and Mg(2+)-dependent myo-inositol-1-phosphatase activity of the purified enzyme fraction exhibited similar behavior on Sephadex G-100 and Mono Q colomns. These findings suggest that Zn(2+)-APase also exhibits Mg(2+)-dependent myo-inositol-1-phosphatase activity under physiological conditions.

Predictions of ion energy distributions and radical fluxes in radio frequency biased inductively coupled plasma etching reactors

NASA Astrophysics Data System (ADS)

Hoekstra, Robert J.; Kushner, Mark J.

1996-03-01

Inductively coupled plasma (ICP) reactors are being developed for low gas pressure (<10s mTorr) and high plasma density ([e]≳1011 cm-3) microelectronics fabrication. In these reactors, the plasma is generated by the inductively coupled electric field while an additional radio frequency (rf) bias is applied to the substrate. One of the goals of these systems is to independently control the magnitude of the ion flux by the inductively coupled power deposition, and the acceleration of ions into the substrate by the rf bias. In high plasma density reactors the width of the sheath above the wafer may be sufficiently thin that ions are able to traverse it in approximately 1 rf cycle, even at 13.56 MHz. As a consequence, the ion energy distribution (IED) may have a shape typically associated with lower frequency operation in conventional reactive ion etching tools. In this paper, we present results from a computer model for the IED incident on the wafer in ICP etching reactors. We find that in the parameter space of interest, the shape of the IED depends both on the amplitude of the rf bias and on the ICP power. The former quantity determines the average energy of the IED. The latter quantity controls the width of the sheath, the transit time of ions across the sheath and hence the width of the IED. In general, high ICP powers (thinner sheaths) produce wider IEDs.

Multi-GEM Detectors in High Particle Fluxes

NASA Astrophysics Data System (ADS)

Thuiner, P.; Resnati, F.; Franchino, S.; Gonzalez Diaz, D.; Hall-Wilton, R.; Müller, H.; Oliveri, E.; Pfeiffer, D.; Ropelewski, L.; Van Stenis, M.; Streli, C.; Veenhof, R.

2018-02-01

Gaseous Electron Multipliers (GEM) are well known for stable operation at high particle fluxes. We present a study of the intrinsic limits of GEMdetectors when exposed to very high particle fluxes of the order of MHz/mm2. We give an interpretation to the variations of the effective gain, which, as a function of the particle flux, first increases and then decreases. We also discuss the reduction of the ion back-flow with increasing flux. We present measurements and simulations of a triple GEM detector, describing its behaviour in terms of accumulation of positive ions that results in changes of the transfer fields and the amplification fields. The behaviour is expected to be common to all multi-stage amplification devices where the efficiency of transferring the electrons from one stage to the next one is not 100%.

The ISEE-3 ULEWAT: Flux tape description and heavy ion fluxes 1978-1984. [plasma diagnostics

NASA Technical Reports Server (NTRS)

Mason, G. M.; Klecker, B.

1985-01-01

The ISEE ULEWAT FLUX tapes contain ULEWAT and ISEE pool tape data summarized over relatively long time intervals (1hr) in order to compact the data set into an easily usable size. (Roughly 3 years of data fit onto one 1600 BPI 9-track magnetic tape). In making the tapes, corrections were made to the ULEWAT basic data tapes in order to, remove rate spikes and account for changes in instrument response so that to a large extent instrument fluxes can be calculated easily from the FLUX tapes without further consideration of instrument performance.

NEW VACUUM SOLAR TELESCOPE OBSERVATIONS OF A FLUX ROPE TRACKED BY A FILAMENT ACTIVATION

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

Yang, Shuhong; Zhang, Jun; Liu, Zhong

2014-04-01

One main goal of the New Vacuum Solar Telescope (NVST) which is located at the Fuxian Solar Observatory is to image the Sun at high resolution. Based on the high spatial and temporal resolution NVST Hα data and combined with the simultaneous observations from the Solar Dynamics Observatory for the first time, we investigate a flux rope tracked by filament activation. The filament material is initially located at one end of the flux rope and fills in a section of the rope; the filament is then activated by magnetic field cancellation. The activated filament rises and flows along helical threads,more » tracking the twisted flux rope structure. The length of the flux rope is about 75 Mm, the average width of its individual threads is 1.11 Mm, and the estimated twist is 1π. The flux rope appears as a dark structure in Hα images, a partial dark and partial bright structure in 304 Å, and as a bright structure in 171 Å and 131 Å images. During this process, the overlying coronal loops are quite steady since the filament is confined within the flux rope and does not erupt successfully. It seems that, for the event in this study, the filament is located and confined within the flux rope threads, instead of being suspended in the dips of twisted magnetic flux.« less

Effects of muscarinic, alpha-adrenergic, and substance P agonists and ionomycin on ion transport mechanisms in the rat parotid acinar cell. The dependence of ion transport on intracellular calcium

PubMed Central

1989-01-01

The relationship between receptor-mediated increases in the intracellular free calcium concentration [( Ca]i) and the stimulation of ion fluxes involved in fluid secretion was examined in the rat parotid acinar cell. Agonist-induced increases in [Ca]i caused the rapid net loss of up to 50-60% of the total content of intracellular chloride (Cli) and potassium (Ki), which is consistent with the activation of calcium-sensitive chloride and potassium channels. These ion movements were accompanied by a 25% reduction in the intracellular volume. The relative magnitudes of the losses of Ki and the net potassium fluxes promoted by carbachol (a muscarinic agonist), phenylephrine (an alpha-adrenergic agonist), and substance P were very similar to their characteristic effects on elevating [Ca]i. Carbachol stimulated the loss of Ki through multiple efflux pathways, including the large-conductance Ca-activated K channel. Carbachol and substance P increased the levels of intracellular sodium (Nai) to more than 2.5 times the normal level by stimulating the net uptake of sodium through multiple pathways; Na-K-2Cl cotransport accounted for greater than 50% of the influx, and approximately 20% was via Na-H exchange, which led to a net alkalinization of the cells. Ionomycin stimulated similar fluxes through these two pathways, but also promoted sodium influx through an additional pathway which was nearly equivalent in magnitude to the combined uptake through the other two pathways. The carbachol- induced increase in Nai and decrease in Ki stimulated the activity of the sodium pump, measured by the ouabain-sensitive rate of oxygen consumption, to nearly maximal levels. In the absence of extracellular calcium or in cells loaded with the calcium chelator BAPTA (bis[o- aminophenoxy]ethane-N,N,N',N'-tetraacetic acid) the magnitudes of agonist- or ionomycin-stimulated ion fluxes were greatly reduced. The parotid cells displayed a marked desensitization to substance P; within 10 min the

Kinetic Monte Carlo simulations of ion-induced ripple formation: Dependence on flux, temperature, and defect concentration in the linear regime

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

Chason, E.; Chan, W. L.; Bharathi, M. S.

Low-energy ion bombardment produces spontaneous periodic structures (sputter ripples) on many surfaces. Continuum theories describe the pattern formation in terms of ion-surface interactions and surface relaxation kinetics, but many features of these models (such as defect concentration) are unknown or difficult to determine. In this work, we present results of kinetic Monte Carlo simulations that model surface evolution using discrete atomistic versions of the physical processes included in the continuum theories. From simulations over a range of parameters, we obtain the dependence of the ripple growth rate, wavelength, and velocity on the ion flux and temperature. The results are discussedmore » in terms of the thermally dependent concentration and diffusivity of ion-induced surface defects. We find that in the early stages of ripple formation the simulation results are surprisingly well described by the predictions of the continuum theory, in spite of simplifying approximations used in the continuum model.« less

Oxyanion flux characterization using passive flux meters: Development and field testing of surfactant-modified granular activated carbon

NASA Astrophysics Data System (ADS)

Lee, Jimi; Rao, P. S. C.; Poyer, Irene C.; Toole, Robyn M.; Annable, M. D.; Hatfield, K.

2007-07-01

We report here on the extension of Passive Flux Meter (PFM) applications for measuring fluxes of oxyanions in groundwater, and present results for laboratory and field studies. Granular activated carbon, with and without impregnated silver (GAC and SI-GAC, respectively), was modified with a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the anion exchange capacity (AEC). Langmuir isotherm sorption maxima for oxyanions measured in batch experiments were in the following order: perchlorate >> chromate > selenate, consistent with their selectivity. Linear sorption isotherms for several alcohols suggest that surfactant modification of GAC and SI-GAC reduced (˜ 30-45%) sorption of alcohols by GAC. Water and oxyanion fluxes (perchlorate and chromate) measured by deploying PFMs packed with surfactant-modified GAC (SM-GAC) or surfactant-modified, silver-impregnated GAC (SM-SI-GAC) in laboratory flow chambers were in close agreement with the imposed fluxes. The use of SM-SI-GAC as a PFM sorbent was evaluated at a field site with perchlorate contamination of a shallow unconfined aquifer. PFMs packed with SM-SI-GAC were deployed in three existing monitoring wells with a perchlorate concentration range of ˜ 2.5 to 190 mg/L. PFM-measured, depth-averaged, groundwater fluxes ranged from 1.8 to 7.6 cm/day, while depth-averaged perchlorate fluxes varied from 0.22 to 1.7 g/m 2/day. Groundwater and perchlorate flux distributions measured in two PFM deployments closely matched each other. Depth-averaged Darcy fluxes measured with PFMs were in line with an estimate from a borehole dilution test, but much smaller than those based on hydraulic conductivity and head gradients; this is likely due to flow divergence caused by well-screen clogging. Flux-averaged perchlorate concentrations measured with PFM deployments matched concentrations in groundwater samples taken from one well, but not in two other wells, pointing to the need for additional field testing. Use of

Oxyanion flux characterization using passive flux meters: development and field testing of surfactant-modified granular activated carbon.

PubMed

Lee, Jimi; Rao, P S C; Poyer, Irene C; Toole, Robyn M; Annable, M D; Hatfield, K

2007-07-17

We report here on the extension of Passive Flux Meter (PFM) applications for measuring fluxes of oxyanions in groundwater, and present results for laboratory and field studies. Granular activated carbon, with and without impregnated silver (GAC and SI-GAC, respectively), was modified with a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the anion exchange capacity (AEC). Langmuir isotherm sorption maxima for oxyanions measured in batch experiments were in the following order: perchlorate>chromate>selenate, consistent with their selectivity. Linear sorption isotherms for several alcohols suggest that surfactant modification of GAC and SI-GAC reduced (approximately 30-45%) sorption of alcohols by GAC. Water and oxyanion fluxes (perchlorate and chromate) measured by deploying PFMs packed with surfactant-modified GAC (SM-GAC) or surfactant-modified, silver-impregnated GAC (SM-SI-GAC) in laboratory flow chambers were in close agreement with the imposed fluxes. The use of SM-SI-GAC as a PFM sorbent was evaluated at a field site with perchlorate contamination of a shallow unconfined aquifer. PFMs packed with SM-SI-GAC were deployed in three existing monitoring wells with a perchlorate concentration range of approximately 2.5 to 190 mg/L. PFM-measured, depth-averaged, groundwater fluxes ranged from 1.8 to 7.6 cm/day, while depth-averaged perchlorate fluxes varied from 0.22 to 1.7 g/m2/day. Groundwater and perchlorate flux distributions measured in two PFM deployments closely matched each other. Depth-averaged Darcy fluxes measured with PFMs were in line with an estimate from a borehole dilution test, but much smaller than those based on hydraulic conductivity and head gradients; this is likely due to flow divergence caused by well-screen clogging. Flux-averaged perchlorate concentrations measured with PFM deployments matched concentrations in groundwater samples taken from one well, but not in two other wells, pointing to the need for additional field

Autophagic flux is highly active in early mitosis and differentially regulated throughout the cell cycle

PubMed Central

Li, Zhiyuan; Ji, Xinmiao; Wang, Dongmei; Liu, Juanjuan; Zhang, Xin

2016-01-01

Mitosis is a fast process that involves dramatic cellular remodeling and has a high energy demand. Whether autophagy is active or inactive during the early stages of mitosis in a naturally dividing cell is still debated. Here we aimed to use multiple assays to resolve this apparent discrepancy. Although the LC3 puncta number was reduced in mitosis, the four different cell lines we tested all have active autophagic flux in both interphase and mitosis. In addition, the autophagic flux was highly active in nocodazole-induced, double-thymidine synchronization released as well as naturally occurring mitosis in HeLa cells. Multiple autophagy proteins are upregulated in mitosis and the increased Beclin-1 level likely contributes to the active autophagic flux in early mitosis. It is interesting that although the autophagic flux is active throughout the cell cycle, early mitosis and S phase have relatively higher autophagic flux than G1 and late G2 phases, which might be helpful to degrade the damaged organelles and provide energy during S phase and mitosis. PMID:27213594

Autophagic flux is highly active in early mitosis and differentially regulated throughout the cell cycle.

PubMed

Li, Zhiyuan; Ji, Xinmiao; Wang, Dongmei; Liu, Juanjuan; Zhang, Xin

2016-06-28

Mitosis is a fast process that involves dramatic cellular remodeling and has a high energy demand. Whether autophagy is active or inactive during the early stages of mitosis in a naturally dividing cell is still debated. Here we aimed to use multiple assays to resolve this apparent discrepancy. Although the LC3 puncta number was reduced in mitosis, the four different cell lines we tested all have active autophagic flux in both interphase and mitosis. In addition, the autophagic flux was highly active in nocodazole-induced, double-thymidine synchronization released as well as naturally occurring mitosis in HeLa cells. Multiple autophagy proteins are upregulated in mitosis and the increased Beclin-1 level likely contributes to the active autophagic flux in early mitosis. It is interesting that although the autophagic flux is active throughout the cell cycle, early mitosis and S phase have relatively higher autophagic flux than G1 and late G2 phases, which might be helpful to degrade the damaged organelles and provide energy during S phase and mitosis.

Adsorption of metal ions by pecan shell-based granular activated carbons.

PubMed

Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

2003-09-01

The present investigation was undertaken to evaluate the adsorption effectiveness of pecan shell-based granular activated carbons (GACs) in removing metal ions (Cu(2+), Pb(2+), Zn(2+)) commonly found in municipal and industrial wastewater. Pecan shells were activated by phosphoric acid, steam or carbon dioxide activation methods. Metal ion adsorption of shell-based GACs was compared to the metal ion adsorption of a commercial carbon, namely, Calgon's Filtrasorb 200. Adsorption experiments were conducted using solutions containing all three metal ions in order to investigate the competitive effects of the metal ions as would occur in contaminated wastewater. The results obtained from this study showed that acid-activated pecan shell carbon adsorbed more lead ion and zinc ion than any of the other carbons, especially at carbon doses of 0.2-1.0%. However, steam-activated pecan shell carbon adsorbed more copper ion than the other carbons, particularly using carbon doses above 0.2%. In general, Filtrasorb 200 and carbon dioxide-activated pecan shell carbons were poor metal ion adsorbents. The results indicate that acid- and steam-activated pecan shell-based GACs are effective metal ion adsorbents and can potentially replace typical coal-based GACs in treatment of metal contaminated wastewater.

Ion and neutral energy flux distributions to the cathode in glow discharges in Ar/Ne and Xe/Ne mixtures

NASA Astrophysics Data System (ADS)

Capdeville, H.; Pédoussat, C.; Pitchford, L. C.

2002-02-01

The work presented in the article is a study of the heavy particle (ion and neutral) energy flux distributions to the cathode in conditions typical of discharges used for luminous signs for advertising ("neon" signs). The purpose of this work is to evaluate the effect of the gas mixture on the sputtering of the cathode. We have combined two models for this study: a hybrid model of the electrical properties of the cathode region of a glow discharge and a Monte Carlo simulation of the heavy particle trajectories. Using known sputtering yields for Ne, Ar, and Xe on iron cathodes, we estimate the sputtered atom flux for mixtures of Ar/Ne and Xe/Ne as a function of the percent neon in the mixture.

Transition region fluxes in A-F Dwarfs: Basal fluxes and dynamo activity

NASA Technical Reports Server (NTRS)

Walter, Frederick M.; Schrijver, Carolus J.; Boyd, William

1988-01-01

The transition region spectra of 87 late A and early F dwarfs and subgiants were analyzed. The emission line fluxes are uniformly strong in the early F stars, and drop off rapidly among the late A stars. The basal flux level in the F stars is consistent with an extrapolation of that observed among the G stars, while the magnetic component displays the same flux-flux relations seen among solar-like stars. Despite the steep decrease in transition region emission flux for B-V less than 0.28, C II emission is detected in alpha Aql (B-V = 0.22). The dropoff in emission is inconsistent with models of the mechanically generated acoustic flux available. It is concluded that, although the nonmagnetic basal heating is an increasingly important source of atmospheric heating among the early F stars, magnetic heating occurs in any star which has a sufficiently thick convective zone to generate acoustic heating.

Empirical Model of Precipitating Ion Oval

NASA Astrophysics Data System (ADS)

Goldstein, Jerry

2017-10-01

In this brief technical report published maps of ion integral flux are used to constrain an empirical model of the precipitating ion oval. The ion oval is modeled as a Gaussian function of ionospheric latitude that depends on local time and the Kp geomagnetic index. The three parameters defining this function are the centroid latitude, width, and amplitude. The local time dependences of these three parameters are approximated by Fourier series expansions whose coefficients are constrained by the published ion maps. The Kp dependence of each coefficient is modeled by a linear fit. Optimization of the number of terms in the expansion is achieved via minimization of the global standard deviation between the model and the published ion map at each Kp. The empirical model is valid near the peak flux of the auroral oval; inside its centroid region the model reproduces the published ion maps with standard deviations of less than 5% of the peak integral flux. On the subglobal scale, average local errors (measured as a fraction of the point-to-point integral flux) are below 30% in the centroid region. Outside its centroid region the model deviates significantly from the H89 integral flux maps. The model's performance is assessed by comparing it with both local and global data from a 17 April 2002 substorm event. The model can reproduce important features of the macroscale auroral region but none of its subglobal structure, and not immediately following a substorm.

Local time variations of high-energy plasmaspheric ion pitch angle distributions

DOE PAGES

Sarno-Smith, Lois K.; Liemohn, Michael W.; Skoug, Ruth M.; ...

2016-07-01

Recent observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument revealed a persistent depletion in the 1–10 eV ion population in the postmidnight sector during quiet times in the 2 < L < 3 region. This study explores the source of this ion depletion by developing an algorithm to classify 26 months of pitch angle distributions measured by the HOPE instrument. We correct the HOPE low energy fluxes for spacecraft potential using measurements from the Electric Field and Waves (EFW) instrument. A high percentage of low count pitch angle distributions is found in the postmidnight sector coupledmore » with a low percentage of ion distributions peaked perpendicular to the field line. A peak in loss cone distributions in the dusk sector is also observed. Here, these results characterize the nature of the dearth of the near 90° pitch angle 1–10 eV ion population in the near-Earth postmidnight sector. This study also shows, for the first time, low-energy HOPE differential number fluxes corrected for spacecraft potential and 1–10 eV H + fluxes at different levels of geomagnetic activity.« less

Antibacterial, Antifungal and Nematicidal Activities of Rare Earth Ions.

PubMed

Wakabayashi, Tokumitsu; Ymamoto, Ayumi; Kazaana, Akira; Nakano, Yuta; Nojiri, Yui; Kashiwazaki, Moeko

2016-12-01

Despite the name, rare earth elements are relatively abundant in soil. Therefore, these elements might interact with biosphere during the history of life. In this study, we have examined the effect of rare earth ions on the growth of bacteria, fungi and soil nematode. All rare earth ions, except radioactive promethium that we have not tested, showed antibacterial and antifungal activities comparable to that of copper ions, which is widely used as antibacterial metals in our daily life. Rare earth ions also have nematicidal activities as they strongly perturb the embryonic development of the nematode, Caenorhabditis elegans. Interestingly, the nematicidal activity increased with increasing atomic number of lanthanide ions. Since the rare earth ions did not show high toxicity to the human lymphoblastoid cell line or even stimulate the growth of the cultured cells at 1 mM, it raised the possibility that we can substitute rare earth elements for the antibacterial metals usually used because of their safety.

The activity of calcium in calcium-metal-fluoride fluxes

NASA Astrophysics Data System (ADS)

Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

1995-08-01

The standard Gibbs energy of reaction Ca (1) + O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: Δ G° = -64,300(±700) + 19.8(±3.5) T J/mol (1373 to 1623 K) The activities of calcium in the CaOsatd-Ca- MF2 ( M: Ca, Ba, Mg) and CaOsatd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF2, BaF2, and MgF2 at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

ASYMMETRY OF HELICITY INJECTION FLUX IN EMERGING ACTIVE REGIONS

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

Tian Lirong; Alexander, David

Observational and modeling results indicate that typically the leading magnetic field of bipolar active regions (ARs) is often spatially more compact, while more dispersed and fragmented in following polarity. In this paper, we address the origin of this morphological asymmetry, which is not well understood. Although it may be assumed that, in an emerging {omega}-shaped flux tube, those portions of the flux tube in which the magnetic field has a higher twist may maintain its coherence more readily, this has not been tested observationally. To assess this possibility, it is important to characterize the nature of the fragmentation and asymmetrymore » in solar ARs and this provides the motivation for this paper. We separately calculate the distribution of the helicity flux injected in the leading and following polarities of 15 emerging bipolar ARs, using the Michelson Doppler Image 96 minute line-of-sight magnetograms and a local correlation tracking technique. We find from this statistical study that the leading (compact) polarity injects several times more helicity flux than the following (fragmented) one (typically 3-10 times). This result suggests that the leading polarity of the {omega}-shaped flux tube possesses a much larger amount of twist than the following field prior to emergence. We argue that the helicity asymmetry between the leading and following magnetic field for the ARs studied here results in the observed magnetic field asymmetry of the two polarities due to an imbalance in the magnetic tension of the emerging flux tube. We suggest that the observed imbalance in the helicity distribution results from a difference in the speed of emergence between the leading and following legs of an inclined {omega}-shaped flux tube. In addition, there is also the effect of magnetic flux imbalance between the two polarities with the fragmented following polarity displaying spatial fluctuation in both the magnitude and sign of helicity measured.« less

Altered swelling and ion fluxes in articular cartilage as a biomarker in osteoarthritis and joint immobilization: a computational analysis

PubMed Central

Manzano, Sara; Manzano, Raquel; Doblaré, Manuel; Doweidar, Mohamed Hamdy

2015-01-01

In healthy cartilage, mechano-electrochemical phenomena act together to maintain tissue homeostasis. Osteoarthritis (OA) and degenerative diseases disrupt this biological equilibrium by causing structural deterioration and subsequent dysfunction of the tissue. Swelling and ion flux alteration as well as abnormal ion distribution are proposed as primary indicators of tissue degradation. In this paper, we present an extension of a previous three-dimensional computational model of the cartilage behaviour developed by the authors to simulate the contribution of the main tissue components in its behaviour. The model considers the mechano-electrochemical events as concurrent phenomena in a three-dimensional environment. This model has been extended here to include the effect of repulsion of negative charges attached to proteoglycans. Moreover, we have studied the fluctuation of these charges owning to proteoglycan variations in healthy and pathological articular cartilage. In this sense, standard patterns of healthy and degraded tissue behaviour can be obtained which could be a helpful diagnostic tool. By introducing measured properties of unhealthy cartilage into the computational model, the severity of tissue degeneration can be predicted avoiding complex tissue extraction and subsequent in vitro analysis. In this work, the model has been applied to monitor and analyse cartilage behaviour at different stages of OA and in both short (four, six and eight weeks) and long-term (11 weeks) fully immobilized joints. Simulation results showed marked differences in the corresponding swelling phenomena, in outgoing cation fluxes and in cation distributions. Furthermore, long-term immobilized patients display similar swelling as well as fluxes and distribution of cations to patients in the early stages of OA, thus, preventive treatments are highly recommended to avoid tissue deterioration. PMID:25392400

Modeling Coronal Response in Decaying Active Regions with Magnetic Flux Transport and Steady Heating

NASA Astrophysics Data System (ADS)

Ugarte-Urra, Ignacio; Warren, Harry P.; Upton, Lisa A.; Young, Peter R.

2017-09-01

We present new measurements of the dependence of the extreme ultraviolet (EUV) radiance on the total magnetic flux in active regions as obtained from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Using observations of nine active regions tracked along different stages of evolution, we extend the known radiance—magnetic flux power-law relationship (I\\propto {{{Φ }}}α ) to the AIA 335 Å passband, and the Fe xviii 93.93 Å spectral line in the 94 Å passband. We find that the total unsigned magnetic flux divided by the polarity separation ({{Φ }}/D) is a better indicator of radiance for the Fe xviii line with a slope of α =3.22+/- 0.03. We then use these results to test our current understanding of magnetic flux evolution and coronal heating. We use magnetograms from the simulated decay of these active regions produced by the Advective Flux Transport model as boundary conditions for potential extrapolations of the magnetic field in the corona. We then model the hydrodynamics of each individual field line with the Enthalpy-based Thermal Evolution of Loops model with steady heating scaled as the ratio of the average field strength and the length (\\bar{B}/L) and render the Fe xviii and 335 Å emission. We find that steady heating is able to partially reproduce the magnitudes and slopes of the EUV radiance—magnetic flux relationships and discuss how impulsive heating can help reconcile the discrepancies. This study demonstrates that combined models of magnetic flux transport, magnetic topology, and heating can yield realistic estimates for the decay of active region radiances with time.

United in Diversity: Mechanosensitive Ion Channels in Plants

PubMed Central

Hamilton, Eric S.; Schlegel, Angela M.; Haswell, Elizabeth S.

2015-01-01

Mechanosensitive (MS) ion channels are a common mechanism for perceiving and responding to mechanical force. This class of mechanoreceptors is capable of transducing membrane tension directly into ion flux. In plant systems, MS ion channels have been proposed to play a wide array of roles, from the perception of touch and gravity to the osmotic homeostasis of intracellular organelles. Three families of plant MS ion channels have been identified: the MscS-like (MSL), Mid1-complementing activity (MCA), and two-pore potassium (TPK) families. Channels from these families vary widely in structure and function, localize to multiple cellular compartments, and conduct chloride, calcium, and/or potassium ions. However, they are still likely to represent only a fraction of the MS ion channel diversity in plant systems. PMID:25494462

Effects of active flux on plasma behavior and weld shape in laser welding of X5CrNi189 stainless steel

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Peng, Jun

2016-11-01

In this paper, stainless steel was welded by active flux-aided laser welding method. The effects of single active flux (Cr2O3, SiO2 and TiO2) and composite active flux on laser welding were studied. In the welding process, laser plasma behavior was recorded by a high-speed imaging system. The results show that, with the addition of active flux, the absorption of laser energy and melting efficiency increase. In the laser power of 750 W, effects of active flux on weld depth to width ratio are given by the order: composite active flux > SiO2 > Cr2O3 > TiO2. The effect of composite active flux is the most significant and it can increase the weld depth to width ratio to 85%. Active flux can restrict the laser plasma. With the addition of composite active flux, the projected area of laser plasma obtained obviously reduced, and it can be reduced by 41.39%. Active flux cannot obviously change the main components in weld zone, but can change the grains of austenite and ferrite.

Activation of accelerator construction materials by heavy ions

NASA Astrophysics Data System (ADS)

Katrík, P.; Mustafin, E.; Hoffmann, D. H. H.; Pavlovič, M.; Strašík, I.

2015-12-01

Activation data for an aluminum target irradiated by 200 MeV/u 238U ion beam are presented in the paper. The target was irradiated in the stacked-foil geometry and analyzed using gamma-ray spectroscopy. The purpose of the experiment was to study the role of primary particles, projectile fragments, and target fragments in the activation process using the depth profiling of residual activity. The study brought information on which particles contribute dominantly to the target activation. The experimental data were compared with the Monte Carlo simulations by the FLUKA 2011.2c.0 code. This study is a part of a research program devoted to activation of accelerator construction materials by high-energy (⩾200 MeV/u) heavy ions at GSI Darmstadt. The experimental data are needed to validate the computer codes used for simulation of interaction of swift heavy ions with matter.

High time resolution characteristics of intermediate ion distributions upstream of the earth's bow shock

NASA Technical Reports Server (NTRS)

Potter, D. W.

1985-01-01

High time resolution particle data upstream of the bow shock during time intervals that have been identified as having intermediate ion distributions often show high amplitude oscillations in the ion fluxes of energy 2 and 6 keV. These ion oscillations, observed with the particle instruments of the University of California, Berkeley, on the ISEE 1 and 2 spacecraft, are at the same frequency (about 0.04 Hz) as the magnetic field oscillations. Typically, the 6-keV ion flux increases then the 2-keV flux increases followed by a decrease in the 2-keV flux and then the 6-keV flux decreases. This process repeats many times. Although there is no entirely satisfactory explanation, the presence of these ion flux oscillations suggests that distributions often are misidentified as intermediate ion distributions.

Characteristics of Ions Emission from Ultrashort Laser Produced Plasma

PubMed Central

Elsied, Ahmed M.; Termini, Nicholas C.; Diwakar, Prasoon K.; Hassanein, Ahmed

2016-01-01

The dynamic characteristics of the ions emitted from ultrashort laser interaction with materials were studied. A series of successive experiments were conducted for six different elements (C, Al, Cu, Mo, Gd, and W) using 40 fs, 800 nm Ti: Sapphire laser. Time-of-flight (TOF) ion profile was analyzed and charge emission dependencies were investigated. The effects of incident laser interaction with each element were studied over a wide range of laser fluences (0.8 J/cm2 to 24 J/cm2) corresponding to laser intensities (2.0 × 1013 W/cm2 to 6.0 × 1014 W/cm2). The dependencies of the angular resolved ion flux and energy were also investigated. The TOF ion profile exhibits two peaks corresponding to a fast and a slow ion regime. The slow ions emission was the result of thermal vaporization while fast ions emission was due to time dependent ambipolar electric field. A theoretical model is proposed to predict the total ion flux emitted during femtosecond laser interaction that depends on laser parameters, material properties, and plume hydrodynamics. Incident laser fluence directly impacts average charge state and in turn affects the ion flux. Slow ions velocity exhibited different behavior from fast ions velocity. The fast ions energy and flux were found to be more collimated. PMID:27905553

Vertical divergence of fogwater fluxes above a spruce forest

NASA Astrophysics Data System (ADS)

Burkard, R.; Eugster, W.; Wrzesinsky, T.; Klemm, O.

Two almost identical eddy covariance measurement setups were used to measure the fogwater fluxes to a forest ecosystem in the "Fichtelgebirge" mountains (Waldstein research site, 786 m a.s.l.) in Germany. During the first experiment, an intercomparison was carried out with both setups running simultaneously at the same measuring height on a meteorological tower, 12.5 m above the forest canopy. The results confirmed a close agreement of the turbulent fluxes between the two setups, and allowed to intercalibrate liquid water content (LWC) and gravitational fluxes. During the second experiment, the setups were mounted at a height of 12.5 and 3 m above the canopy, respectively. For the 22 fog events, a persistent negative flux divergence was observed with a greater downward flux at the upper level. To extrapolate the turbulent liquid water fluxes measured at height z to the canopy of height hc, a conversion factor 1/[1+0.116( z- hc)] was determined. For the fluxes of nonvolatile ions, no such correction is necessary since the net evaporation of the fog droplets appears to be the primary cause of the vertical flux divergence. Although the net evaporation reduces the liquid water flux reaching the canopy, it is not expected to change the absolute amount of ions dissolved in fogwater.

Cold Ion Escape from Mars

NASA Astrophysics Data System (ADS)

Fränz, M.; Dubinin, E.; Wei, Y.; Morgan, D.; Andrews, D.; Barabash, S.; Lundin, R.; Fedorov, A.

2013-09-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express in combination with the MARSIS radar experiment. We first compare calculations of the mean ion flux observed by ASPERA-3 alone with previously published results. We then combine observations of the cold ion velocity by ASPERA-3 with observations of the cold plasma density by MARSIS since ASPERA-3 misses the cold core of the ion distribution. We show that the mean density of the nightside plasma observed by MARSIS is about two orders higher than observed by ASPERA-3 (Fig.1). Combining both datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars (Fig. 2). At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 3) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Quiet-time 0.04 - 2 MeV/nucleon Ions at 1 AU in Solar Cycles 23 and 24

NASA Astrophysics Data System (ADS)

Zeldovich, M. A.; Logachev, Y. I.; Kecskeméty, K.

2018-01-01

The fluxes of 3He, 4He, C, O, and Fe ions at low energies (about 0.04 - 2 MeV/nucleon) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using data from the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section 2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysis of the ion energy spectra and their relative abundances shows that their behavior is governed by their first-ionization potential. Substantial differences in the ion energy spectra in two consecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxes are divided into three distinct types according to the {˜} 80 - 320 keV/nucleon Fe/O ratio. Our results confirm the earlier observation that these types of suprathermal particles have different origins, that is, they represent different seed populations that are accelerated by different processes. Except for the solar activity minimum, the Fe/O ratio during quiet-time periods correspond either to the abundances of ions in particle fluxes accelerated in impulsive solar flares or to the mean abundances of elements in the solar corona. At the activity minimum, this ratio takes on values that are characteristic for the solar wind. These results indicate that the background fluxes of low-energy particles in the ascending, maximum, and decay phases of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal energies and ions accelerated in small impulsive solar flares rich in Fe, while the contribution of remnants from earlier SEP events cannot be excluded. The comparison of suprathermal ion abundances during the first five years of SC 23 and SC 24 suggests that the quiet-time and non-quiet fluxes of Fe and 3He were lower in SC 24.

Mass flux measurements at active lava lakes: Implications for magma recycling

NASA Astrophysics Data System (ADS)

Harris, Andrew J. L.; Flynn, Luke P.; Rothery, David A.; Oppenheimer, Clive; Sherman, Sarah B.

1999-04-01

Remotely sensed and field data can be used to estimate heat and mass fluxes at active lava lakes. Here we use a three thermal component pixel model with three bands of Landsat thematic mapper (TM) data to constrain the thermal structure of, and flux from, active lava lakes. Our approach considers that a subpixel lake is surrounded by ground at ambient temperatures and that the surface of the lake is composed of crusted and/or molten material. We then use TM band 6 (10.42-12.42 μm) with bands 3 (0.63-0.69 μm) or 4 (0.76-0.90 μm) and 5 (1.55-1.75 μm) or 7 (2.08-2.35 μm), along with field data (e.g., lava lake area), to place limits on the size and temperature of each thermal component. Previous attempts to achieve this have used two bands of TM data with a two-component thermal model. Using our model results with further field data (e.g., petrological data) for lava lakes at Erebus, Erta 'Ale, and Pu'u 'O'o, we calculate combined radiative and convective fluxes of 11-20, 14-27 and 368-373 MW, respectively. These yield mass fluxes, of 30-76, 44-104 and 1553-2079 kg s-1, respectively. We also identify a hot volcanic feature at Nyiragongo during 1987 from which a combined radiative and convective flux of 0.2-0.6 MW implies a mass flux of 1-2 kg s-1. We use our mass flux estimates to constrain circulation rates in each reservoir-conduit-lake system and consider four models whereby circulation results in intrusion within or beneath the volcano (leading to endogenous or cryptic growth) and/or magma mixing in the reservoir (leading to recycling). We suggest that the presence of lava lakes does not necessarily imply endogenous or cryptic growth: lava lakes could be symptomatic of magma recycling in supraliquidus reservoirs.

Heat-Flux Measurements from Collective Thomson-Scattering Spectra

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Hu, S. X.; Katz, J.; Froula, D. H.; Rozmus, W.

2015-11-01

Collective Thomson scattering was used to measure heat flux in coronal plasmas. The relative amplitude of the Thomson-scattered power into the up- and downshifted electron plasma wave features was used to determine the flux of electrons moving along the temperature gradient at three to four times the electron thermal velocity. Simultaneously, the ion-acoustic wave features were measured. Their relative amplitude is used to measure the flux of the return-current electrons. The frequencies of these ion-acoustic and electron plasma wave features provide local measurements of the electron temperature and density. These spectra were obtained at five locations along the temperature gradient in a laser-produced blowoff plasma. These measurements of plasma parameters are used to infer the Spitzer -Härm flux qSH = - κ∇Te and are in good agreement with the values of the heat flux measured from the scattering-feature asymmetries. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Evidence of Twisted Flux-Tube Emergence in Active Regions

NASA Astrophysics Data System (ADS)

Poisson, M.; Mandrini, C. H.; Démoulin, P.; López Fuentes, M.

2015-03-01

Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ τ] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, τ is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs (41 ARs) that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of τ, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tubes.

Simulation of flux during electro-membrane extraction based on the Nernst-Planck equation.

PubMed

Gjelstad, Astrid; Rasmussen, Knut Einar; Pedersen-Bjergaard, Stig

2007-12-07

The present work has for the first time described and verified a theoretical model of the analytical extraction process electro-membrane extraction (EME), where target analytes are extracted from an aqueous sample, through a thin layer of 2-nitrophenyl octylether immobilized as a supported liquid membrane (SLM) in the pores in the wall of a porous hollow fibre, and into an acceptor solution present inside the lumen of the hollow fibre by the application of an electrical potential difference. The mathematical model was based on the Nernst-Planck equation, and described the flux over the SLM. The model demonstrated that the magnitude of the electrical potential difference, the ion balance of the system, and the absolute temperature influenced the flux of analyte across the SLM. These conclusions were verified by experimental data with five basic drugs. The flux was strongly dependent of the potential difference over the SLM, and increased potential difference resulted in an increase in the flux. The ion balance, defined as the sum of ions in the donor solution divided by the sum of ions in the acceptor solution, was shown to influence the flux, and high ionic concentration in the acceptor solution relative to the sample solution was advantageous for high flux. Different temperatures also led to changes in the flux in the EME system.

NADPH oxidases as electrochemical generators to produce ion fluxes and turgor in fungi, plants and humans

PubMed Central

2016-01-01

The NOXs are a family of flavocytochromes whose basic structure has been largely conserved from algae to man. This is a very simple system. NADPH is generally available, in plants it is a direct product of photosynthesis, and oxygen is a largely ubiquitous electron acceptor, and the electron-transporting core of an FAD and two haems is the minimal required to pass electrons across the plasma membrane. These NOXs have been shown to be essential for diverse functions throughout the biological world and, lacking a clear mechanism of action, their effects have generally been attributed to free radical reactions. Investigation into the function of neutrophil leucocytes has demonstrated that electron transport through the prototype NOX2 is accompanied by the generation of a charge across the membrane that provides the driving force propelling protons and other ions across the plasma membrane. The contention is that the primary function of the NOXs is to supply the driving force to transport ions, the nature of which will depend upon the composition and characteristics of the local ion channels, to undertake a host of diverse functions. These include the generation of turgor in fungi and plants for the growth of filaments and invasion by appressoria in the former, and extension of pollen tubes and root hairs, and stomatal closure, in the latter. In neutrophils, they elevate the pH in the phagocytic vacuole coupled to other ion fluxes. In endothelial cells of blood vessels, they could alter luminal volume to regulate blood pressure and tissue perfusion. PMID:27249799

NADPH oxidases as electrochemical generators to produce ion fluxes and turgor in fungi, plants and humans.

PubMed

Segal, Anthony W

2016-05-01

The NOXs are a family of flavocytochromes whose basic structure has been largely conserved from algae to man. This is a very simple system. NADPH is generally available, in plants it is a direct product of photosynthesis, and oxygen is a largely ubiquitous electron acceptor, and the electron-transporting core of an FAD and two haems is the minimal required to pass electrons across the plasma membrane. These NOXs have been shown to be essential for diverse functions throughout the biological world and, lacking a clear mechanism of action, their effects have generally been attributed to free radical reactions. Investigation into the function of neutrophil leucocytes has demonstrated that electron transport through the prototype NOX2 is accompanied by the generation of a charge across the membrane that provides the driving force propelling protons and other ions across the plasma membrane. The contention is that the primary function of the NOXs is to supply the driving force to transport ions, the nature of which will depend upon the composition and characteristics of the local ion channels, to undertake a host of diverse functions. These include the generation of turgor in fungi and plants for the growth of filaments and invasion by appressoria in the former, and extension of pollen tubes and root hairs, and stomatal closure, in the latter. In neutrophils, they elevate the pH in the phagocytic vacuole coupled to other ion fluxes. In endothelial cells of blood vessels, they could alter luminal volume to regulate blood pressure and tissue perfusion. © 2016 The Authors.

Interaction between neoclassical effects and ion temperature gradient turbulence in gradient- and flux-driven gyrokinetic simulations

NASA Astrophysics Data System (ADS)

Oberparleiter, M.; Jenko, F.; Told, D.; Doerk, H.; Görler, T.

2016-04-01

Neoclassical and turbulent transport in tokamaks has been studied extensively over the past decades, but their possible interaction remains largely an open question. The two are only truly independent if the length scales governing each of them are sufficiently separate, i.e., if the ratio ρ* between ion gyroradius and the pressure gradient scale length is small. This is not the case in particularly interesting regions such as transport barriers. Global simulations of a collisional ion-temperature-gradient-driven microturbulence performed with the nonlinear global gyrokinetic code Gene are presented. In particular, comparisons are made between systems with and without neoclassical effects. In fixed-gradient simulations, the modified radial electric field is shown to alter the zonal flow pattern such that a significant increase in turbulent transport is observed for ρ*≳1 /300 . Furthermore, the dependency of the flux on the collisionality changes. In simulations with fixed power input, we find that the presence of neoclassical effects decreases the frequency and amplitude of intermittent turbulent transport bursts (avalanches) and thus plays an important role for the self-organisation behaviour.

The effect of a radial electric field on ripple-trapped ions observed by neutral particle fluxes

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

Heikkinen, J.A.; Herrmann, W.; Kurki-Suonio, T.

1997-10-01

The effect of a radial electric field on nonthermal ripple-trapped ions is investigated using toroidal Monte Carlo simulations for edge tokamak plasmas. The increase in the neutral particle flux from the ions trapped in local magnetic wells observed by the charge exchange (CX) detector at a low confinement to high confinement transition at ASDEX (Axially Symmetric Divertor Experiment). Upgrade tokamak [{ital Proceedings of the 20th European Conference on Controlled Fusion and Plasma Physics}, Lisbon (European Physical Society, Petit-Lancy, Switzerland, 1993), Vol. 17C, Part I, p. 267] is reproduced in the simulations by turning on a radial electric field near themore » plasma periphery. The poloidal and toroidal angles at which the CX detector signal is most sensitive to the radial electric field are determined. A fast response time of the signal in the range of 50{endash}100 {mu}s to the appearance of the electric field can be found in the simulations with a relatively large half-width of the negative electric field region. {copyright} {ital 1997 American Institute of Physics.}« less

Cadmium alteration of root physiology and potassium ion fluxes.

PubMed

Keck, R W

1978-07-01

Segments of oat (Avena sativa L.) roots which had been exposed to 1 millimolar CdSO(4) in quarter-strength Hoagland No. 1 solution exhibited decreased respiratory rates, ATP levels, membrane-bound ATPase activity, and reduced K(+) fluxes. Respiration and ATP levels were decreased after a 2-hour treatment with 1 millimolar CdSO(4) to 65 and 75%, respectively, of control rates. A membrane-bound, Mg(2+)-dependent, K(+)-stimulated acid ATPase was rapidly inhibited to 12% of control activity in the presence of 1 millimolar CdSO(4). Potassium uptake into root segments was inhibited to 80% of control values after 30 minutes in the presence of CdSO(4). A 2-hour pretreatment of root segments with CdSO(4) inhibited K(+) uptake to 15% of control values. Cytoplasmic K(+) efflux was inhibited with 1 millimolar CdSO(4).The rates and the degree of Cd(2+) inhibition of the parameters listed above suggest that one of the first sites of Cd(2+) action is the plasmalemma K(+) carrier (ATPase) in oat roots.

Intracellular Chloride and Scaffold Protein Mo25 Cooperatively Regulate Transepithelial Ion Transport through WNK Signaling in the Malpighian Tubule.

PubMed

Sun, Qifei; Wu, Yipin; Jonusaite, Sima; Pleinis, John M; Humphreys, John M; He, Haixia; Schellinger, Jeffrey N; Akella, Radha; Stenesen, Drew; Krämer, Helmut; Goldsmith, Elizabeth J; Rodan, Aylin R

2018-05-01

Background With No Lysine kinase (WNK) signaling regulates mammalian renal epithelial ion transport to maintain electrolyte and BP homeostasis. Our previous studies showed a conserved role for WNK in the regulation of transepithelial ion transport in the Drosophila Malpighian tubule. Methods Using in vitro assays and transgenic Drosophila lines, we examined two potential WNK regulators, chloride ion and the scaffold protein mouse protein 25 (Mo25), in the stimulation of transepithelial ion flux. Results In vitro , autophosphorylation of purified Drosophila WNK decreased as chloride concentration increased. In conditions in which tubule intracellular chloride concentration decreased from 30 to 15 mM as measured using a transgenic sensor, Drosophila WNK activity acutely increased. Drosophila WNK activity in tubules also increased or decreased when bath potassium concentration decreased or increased, respectively. However, a mutation that reduces chloride sensitivity of Drosophila WNK failed to alter transepithelial ion transport in 30 mM chloride. We, therefore, examined a role for Mo25. In in vitro kinase assays, Drosophila Mo25 enhanced the activity of the Drosophila WNK downstream kinase Fray, the fly homolog of mammalian Ste20-related proline/alanine-rich kinase (SPAK), and oxidative stress-responsive 1 protein (OSR1). Knockdown of Drosophila Mo25 in the Malpighian tubule decreased transepithelial ion flux under stimulated but not basal conditions. Finally, whereas overexpression of wild-type Drosophila WNK , with or without Drosophila Mo25 , did not affect transepithelial ion transport, Drosophila Mo25 overexpressed with chloride-insensitive Drosophila WNK increased ion flux. Conclusions Cooperative interactions between chloride and Mo25 regulate WNK signaling in a transporting renal epithelium. Copyright © 2018 by the American Society of Nephrology.

Heating of ions to superthermal energies in the topside ionosphere by electrostatic ion cyclotron waves

NASA Technical Reports Server (NTRS)

Ungstrup, E.; Klumpar, D. M.; Heikkila, W. J.

1979-01-01

The soft particle spectrometer on the Isis 2 spacecraft occasionally observes fluxes of ions moving upward out of the ionosphere in the vicinity of the auroral oval. These ion fluxes are characterized by a sharp pitch angle distribution usually peaked at an angle somewhat greater than 90 deg, indicative of particles heated to a large transverse temperature in a narrow range below the spacecraft. The observations are interpreted in terms of electrostatic ion cyclotron waves, which heat the ions to superthermal energies transverse to the earth's magnetic field. When the transverse energy increases, the repulsive force of the earth's magnetic field, proportional to the particle magnetic moment, repels the particles away from the earth.

Ion-exchange and iontophoresis-controlled delivery of apomorphine.

PubMed

Malinovskaja, Kristina; Laaksonen, Timo; Kontturi, Kyösti; Hirvonen, Jouni

2013-04-01

The objective of this study was to test a drug delivery system that combines iontophoresis and cation-exchange fibers as drug matrices for the controlled transdermal delivery of antiparkinsonian drug apomorphine. Positively charged apomorphine was bound to the ion-exchange groups of the cation-exchange fibers until it was released by mobile counter-ions in the external solution. The release of the drug was controlled by modifying either the fiber type or the ionic composition of the external solution. Due to high affinity of apomorphine toward the ion-exchanger, a clear reduction in the in vitro transdermal fluxes from the fibers was observed compared to the respective fluxes from apomorphine solutions. Changes in the ionic composition of the donor formulations affected both the release and iontophoretic flux of the drug. Upon the application of higher co-ion concentrations or co-ions of higher valence in the donor formulation, the release from the fibers was enhanced, but the iontophoretic steady-state flux was decreased. Overall, the present study has demonstrated a promising approach using ion-exchange fibers for controlling the release and iontophoretic transdermal delivery of apomorphine. Copyright © 2012 Elsevier B.V. All rights reserved.

Case Study of Ion Beams Observed By Cluster At Perigee

NASA Astrophysics Data System (ADS)

Sergeev, V.; Sauvaud, J.-A.; Perigee Beam Team

During substorms the short beams of ions in the keV-to-tens keV energy range are injected into the auroral flux tubes from the magnetotail (sometimes extending up to >100 keV energy) carrying the information on the source distance, scale-size and temporal history of plasma acceleration. We present observations with the CLUSTER crossing inward the auroral zone flux tubes at ~4Re distance near its perigee during the substorm activity on February 14, 2001. The ion beams cover the same region (poleward half) of the auroral oval where the low-energy ions are extracted from the ionosphere, and where the small-scale transient transverse Alfven waves are observed which carry predominantly the downward parallel Poynting flux into the ionosphere. The multiple beams were basically confirmed to be the transient effects, although some effects including the (spatial) velocity filter and the parallel electric fields (im- posed by quasineutrality requirement) may complicate the interpretation. The gener- ation region of ion beams is not limited to most poleward, newly-reconnected flux tubes; the beam generation region could extend across magnetic field inward by as much as >100km (if mapped to the ionosphere). Surprising variety of injection dis- tances observed nearly simultaneously (ranging between >60 Re and ~10 Re) have been inferred when using the full available energy and time resolution, with shorter injection distances be possibly associated with the flow braking process. The beam multiplicity often displays the apparent ~3 min quasiperiodicity inherent to the basic dissipation process, it was not yet explained by any substorm theory.

Theoretical studies of the solar atmosphere and interstellar pickup ions

NASA Technical Reports Server (NTRS)

1994-01-01

Solar atmosphere research activities are summarized. Specific topics addressed include: (1) coronal mass ejections and related phenomena; (2) parametric instabilities of Alfven waves; (3) pickup ions in the solar wind; and (4) cosmic rays in the outer heliosphere. Also included is a list of publications covering the following topics: catastrophic evolution of a force-free flux rope; maximum energy release in flux-rope models of eruptive flares; sheet approximations in models of eruptive flares; material ejection, motions of loops and ribbons of two-ribbon flares; dispersion relations for parametric instabilities of parallel-propagating; parametric instabilities of parallel-propagating Alfven waves; beat, modulation, and decay instabilities of a circularly-polarized Alfven wave; effects of time-dependent photoionization on interstellar pickup helium; observation of waves generated by the solar wind pickup of interstellar hydrogen ions; ion thermalization and wave excitation downstream of the quasi-perpendicular bowshock; ion cyclotron instability and the inverse correlation between proton anisotrophy and proton beta; and effects of cosmic rays and interstellar gas on the dynamics of a wind.

Dynamics of low- and high-Z metal ions emitted during nanosecond laser-produced plasmas

NASA Astrophysics Data System (ADS)

Elsied, Ahmed M.; Diwakar, Prasoon K.; Polek, Mathew; Hassanein, Ahmed

2016-11-01

Dynamics of metal ions during laser-produced plasmas was studied. A 1064 nm, Nd: YAG laser pulse was used to ablate pure Al, Fe, Co, Mo, and Sn samples. Ion flux and velocity were measured using Faraday cup ion collector. Time-of-flight measurements showed decreasing ion flux and ion velocity with increasing atomic weight, and heavy metal ion flux profile exhibited multiple peaks that was not observed in lighter metals. Slow peak was found to follow shifted Maxwell Boltzmann distribution, while the fast peak was found to follow Gaussian distribution. Ion flux angular distribution that was carried out on Mo and Al using fixed laser intensity 2.5 × 1010 W/cm2 revealed that the slow ion flux peaks at small angles, that is, close to normal to the target ˜0° independent of target's atomic weight, and fast ion flux for Mo peaks at large angles ˜40° measured from the target normal, while it completely absents for Al. This difference in spatial and temporal distribution reveals that the emission mechanism of the fast and slow ions is different. From the slow ion flux angular distribution, the measured plume expansion ratio (plume forward peaking) was 1.90 and 2.10 for Al and Mo, respectively. Moreover, the effect of incident laser intensity on the ion flux emission as well as the emitted ion velocity were investigated using laser intensities varying from 2.5 × 1010 W/cm2 to 1.0 × 1011 W/cm2. Linear increase of fast ion flux and velocity, and quadratic increase of slow ion flux and velocity were observed. For further understanding of plume dynamics, laser optical emission spectroscopy was used to characterize Sn plasma by measuring the temporal and spatial evolution of plasma electron density Ne and electron temperature Te. At 3.5 mm away from the target, plasma density showed slow decrease with time, however electron temperature was observed to decrease dramatically. The maximum plasma density and temperature occurred at 0.5 mm away from target and were measured to

Robust ion current oscillations under a steady electric field: An ion channel analog.

PubMed

Yan, Yu; Wang, Yunshan; Senapati, Satyajyoti; Schiffbauer, Jarrod; Yossifon, Gilad; Chang, Hsueh-Chia

2016-08-01

We demonstrate a nonlinear, nonequilibrium field-driven ion flux phenomenon, which unlike Teorell's nonlinear multiple field theory, requires only the application of one field: robust autonomous current-mass flux oscillations across a porous monolith coupled to a capillary with a long air bubble, which mimics a hydrophobic protein in an ion channel. The oscillations are driven by the hysteretic wetting dynamics of the meniscus when electro-osmotic flow and pressure driven backflow, due to bubble expansion, compete to approach zero mass flux within the monolith. Delayed rupture of the film around the advancing bubble cuts off the electric field and switches the monolith mass flow from the former to the latter. The meniscus then recedes and repairs the rupture to sustain an oscillation for a range of applied fields. This generic mechanism shares many analogs with current oscillations in cell membrane ion channel. At sufficiently high voltage, the system undergoes a state transition characterized by appearance of the ubiquitous 1/f power spectrum.

Flux trap effect study in a sub-critical neutron assembly using activation methods

NASA Astrophysics Data System (ADS)

Routsonis, K.; Stoulos, S.; Clouvas, A.; Catsaros, N.; Varvayianni, M.; Manolopoulou, M.

2016-09-01

The neutron flux trap effect was experimentally studied in the subcritical assembly of the Atomic and Nuclear Physics Laboratory of the Aristotle University of Thessaloniki, using delayed gamma neutron activation analysis. Measurements were taken within the natural uranium fuel grid, in vertical levels symmetrical to the Am-Be neutron source, before and after the removal of fuel elements, permitting likewise a basic study of the vertical flux profile. Three identical flux traps of diamond shape were created by removing four fuel rods for each one. Two (n, γ) reactions and one (n, p) threshold reaction were selected for thermal, epithermal and fast flux study. Results of thermal and epithermal flux obtained through the 197Au (n, γ) 198Au and 186W (n, γ) 187W reactions, with and without Cd covers, to differentiate between the two flux regions. The 58Ni (n, p) 58Co reaction was used for the fast flux determination. An interpolation technique based on local procedures was applied to fit the cross sections data and the neutron flux spectrum. End results show a maximum thermal flux increase of 105% at the source level, pointing to a high potential to increase in the available thermal flux for future experiments. The increase in thermal flux is not accompanied by a comparable decrease in epithermal or fast flux, since thermal flux gain is higher than epithermal and fast neutron flux loss. So, the neutron reflection is mainly responsible for the thermal neutron increase, contributing to 89% at the central axial position.

The GOES-16 Energetic Heavy Ion Sensor (EHIS) Ion Composition and Flux Measurements

NASA Astrophysics Data System (ADS)

Connell, J. J.; Lopate, C.

2017-12-01

The Energetic Heavy Ion Sensor (EHIS) was built by the University of New Hampshire, subcontracted to Assurance Technology Corporation, as part of the Space Environmental In-Situ Suite (SEISS) on the new GOES-16 satellite (formerly GOES-R) in Geostationary orbit. EHIS measures energetic ions over the range 10-200 MeV for protons, and energy ranges for heavy ions corresponding to the same stopping range (e.g., 19-207 MeV/u for carbon and 38-488 MeV/u for iron). EHIS uses the Angle Detecting Inclined Sensors (ADIS) technique to provide single-element charge resolution. Though on an operational mission for Space Weather monitoring, EHIS can thus provide a new source of high quality Solar Particle Event (SPE) data for science studies. With a high rate of on-board processing ( 2000 events/s), EHIS will provide exceptional statistics for ion composition measurements in large SPEs. For the GOES Level 1-B and Level 2 data products, heavy ions are distinguished in EHIS using pulse-height analysis with on-board processing producing charge histograms for five energy bands. Fits to these data are normalized to priority rate data on the ground. The instrumental cadence for histograms is 1 minute and the primary Level 1-B heavy ion data products are 1-minute and 5-minute averages. We discuss the preliminary EHIS heavy ion data results which show elemental peaks from H to Fe, with peaks for the isotopes D and 3He. (GOES-16 was launched in 19 November, 2016 and data has, though July 2017, been dominated by Galactic Cosmic Rays.) The EHIS instrument development project was funded by NASA under contract NNG06HX01C.

The role of energetic ions from plasma in the creation of nanostructured materials and stable polymer surface treatments

NASA Astrophysics Data System (ADS)

Bilek, M. M. M.; Newton-McGee, K.; McKenzie, D. R.; McCulloch, D. G.

2006-01-01

Plasma processes for the synthesis of new materials as thin films have enabled the production of a wide variety of new materials. These include meta-stable phases, which are not readily found in nature, and more recently, materials with structure on the nanoscale. Study of plasma synthesis processes at the fundamental level has revealed that ion energy, depositing flux and growth surface temperature are the critical parameters affecting the microstructure and the properties of the thin film materials formed. In this paper, we focus on the role of ion flux and impact energy in the creation of thin films with nanoscale structure in the form of multilayers. We describe three synthesis strategies, based on the extraction of ions from plasma sources and involving modulation of ion flux and ion energy. The microstructure, intrinsic stress and physical properties of the multilayered samples synthesized are studied and related back to the conditions at the growth surface during deposition. When energetic ions of a non-condensing species are used, it is possible to place active groups on the surfaces of materials such as polymers. These active groups can then be used as bonding sites in subsequent chemical attachment of proteins or other macromolecules. If the energy of the non-condensing ions is increased to a few keV then modified layers buried under the surface can be produced. Here we describe a method by which the aging effect, which is often observed in plasma surface modifications on polymers, can be reduced and even eliminated using high energy ion bombardment.

Active stabilization of ion trap radiofrequency potentials

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

Johnson, K. G.; Wong-Campos, J. D.; Restelli, A.

2016-05-15

We actively stabilize the harmonic oscillation frequency of a laser-cooled atomic ion confined in a radiofrequency (rf) Paul trap by sampling and rectifying the high voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz atomic oscillation frequency to be better than 10 Hz or 10 ppm. This represents a suppression of ambient noise on the rf circuit by 34 dB. This technique could impact the sensitivity of ion trap mass spectrometry and the fidelity of quantum operations in ion trap quantum information applications.

ALTERATIONS IN CALCIUM ION ACTIVITY BY ELF AND RF ELECTROMAGNETIC FIELDS

EPA Science Inventory

Alterations in calcium ion activity by ELF and RF electromagnetic fields

Introduction

Calcium ions play many important roles in biological systems. For example, calcium ion activity can be used as an indicator of second-messenger signal-transduction processe...

Benchmarking gyrokinetic simulations in a toroidal flux-tube

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

Chen, Y.; Parker, S. E.; Wan, W.

2013-09-15

A flux-tube model is implemented in the global turbulence code GEM [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)] in order to facilitate benchmarking with Eulerian codes. The global GEM assumes the magnetic equilibrium to be completely given. The initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, etc.) to be equal to the values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. This implementationmore » shows disagreement with Eulerian codes in linear simulations. An alternative flux-tube model based on a complete local equilibrium solution of the Grad-Shafranov equation [J. Candy, Plasma Phys. Controlled Fusion 51, 105009 (2009)] is then implemented. This results in better agreement between Eulerian codes and the particle-in-cell (PIC) method. The PIC algorithm based on the v{sub ||}-formalism [J. Reynders, Ph.D. dissertation, Princeton University, 1992] and the gyrokinetic ion/fluid electron hybrid model with kinetic electron closure [Y. Chan and S. E. Parker, Phys. Plasmas 18, 055703 (2011)] are also implemented in the flux-tube geometry and compared with the direct method for both the ion temperature gradient driven modes and the kinetic ballooning modes.« less

Ion flux oscillations associated with a radially polarized transverse Pc 5 magnetic pulsation

NASA Technical Reports Server (NTRS)

Takahashi, K.; Mcentire, R. W.; Lui, A. T. Y.; Potemra, T. A.

1990-01-01

The AMPTE CCE spacecraft observed a transverse Pc 5 magnetic pulsation (period of about 200 s) at 2155-2310 UT on November 20, 1985, at a radial distance of 5.7 - 7.0 earth radii, at a magnetic latitude of 1.2 - 19 deg, and near 1300 magnetic local time. The magnetic pulsation exhibits properties consistent with a standing Alfven wave with a second-harmonic standing structure along the ambient magnetic field. The amplitude and the phase of the flux pulsation are found to be a function of the particle detector look direction and the particle energy. The observed energy dependence of the shift is interpreted as the result of a drift-bounce resonance of the ions with the wave. From this interpretation it follows that the wave propagated westward with an azimuthal wave number of approximately 100. Thus the study demonstrates that particle data can be useful for determining the spatial structure of some types of ULF waves.

Active membrane having uniform physico-chemically functionalized ion channels

DOEpatents

Gerald, II, Rex E; Ruscic, Katarina J; Sears, Devin N; Smith, Luis J; Klingler, Robert J; Rathke, Jerome W

2012-09-24

The present invention relates to a physicochemically-active porous membrane for electrochemical cells that purports dual functions: an electronic insulator (separator) and a unidirectional ion-transporter (electrolyte). The electrochemical cell membrane is activated for the transport of ions by contiguous ion coordination sites on the interior two-dimensional surfaces of the trans-membrane unidirectional pores. One dimension of the pore surface has a macroscopic length (1 nm-1000 .mu.m) and is directed parallel to the direction of an electric field, which is produced between the cathode and the anode electrodes of an electrochemical cell. The membrane material is designed to have physicochemical interaction with ions. Control of the extent of the interactions between the ions and the interior pore walls of the membrane and other materials, chemicals, or structures contained within the pores provides adjustability of the ionic conductivity of the membrane.

Tailored-waveform Collisional Activation of Peptide Ion Electron Transfer Survivor Ions in Cation Transmission Mode Ion/Ion Reaction Experiments

PubMed Central

Han, Hongling; Londry, Frank A.; Erickson, David E.; McLuckey, Scott A.

2010-01-01

SUMMARY Broad-band resonance excitation via a tailored waveform in a high pressure collision cell (Q2) on a hybrid quadrupole/time-of-flight (QqTOF) tandem mass spectrometer has been implemented for cation transmission mode electron transfer ion/ion reactions of tryptic polypeptides. The frequency components in the broadband waveform were defined to excite the first generation intact electron transfer products for relatively large tryptic peptides. The optimum amplitude of the arbitrary waveform applied has been determined empirically to be 3.0 Vp-p, which is effective for relatively high mass-to-charge (m/z) ratio precursor ions with little elimination of sequence information for low m/z ions. The application of broadband activation during the transmission mode ion/ion reaction obviates frequency and amplitude tuning normally associated with ion trap collision induced dissociation (CID). This approach has been demonstrated with triply and doubly charged tryptic peptides with and without post-translational modifications. Enhanced structural information was achieved by production of a larger number of informative c- and z-type fragments using the tailored waveform on unmodified and modified (phosphorylated and glycosylated) peptides when the first generation intact electron transfer products fell into the defined frequency range. This approach can be applied to a wide range of tryptic peptide ions, making it attractive as a rapid and general approach for ETD LC-MS/MS of tryptic peptides in a QqTOF instrument. PMID:19305916

Effects of activating fluxes on the weld penetration and corrosion resistant property of laser welded joint of ferritic stainless steel

NASA Astrophysics Data System (ADS)

Wang, Yonghui; Hu, Shengsun; Shen, Junqi

2015-10-01

This study was based on the ferritic stainless steel SUS430. Under the parallel welding conditions, the critical penetration power values (CPPV) of 3mm steel plates with different surface-coating activating fluxes were tested. Results showed that, after coating with activating fluxes, such as ZrO2, CaCO3, CaF2 and CaO, the CPPV could reduce 100~250 W, which indicating the increases of the weld penetrations (WP). Nevertheless, the variation range of WP with or without activating fluxes was less than 16.7%. Compared with single-component ones, a multi-component activating flux composed of 50% ZrO2, 12.09% CaCO3, 10.43% CaO, and 27.49% MgO was testified to be much more efficient, the WP of which was about 2.3-fold of that without any activating fluxes. Furthermore, a FeCl3 spot corrosion experiment was carried out with samples cut from weld zone to test the effects of different activating fluxes on the corrosion resistant (CR) property of the laser welded joints. It was found that all kinds of activating fluxes could improve the CR of the welded joints. And, it was interesting to find that the effect of the mixed activating fluxes was inferior to those single-component ones. Among all the activating fluxes, the single-component of CaCO3 seemed to be the best in resisting corrosion. By means of Energy Dispersive Spectrometer (EDS) testing, it was found that the use of activating fluxes could effectively restrain the loss of Cr element of weld zone in the process of laser welding, thus greatly improving the CR of welded joints.

Magnetic fields applied to collagen-coated ferric oxide beads induce stretch-activated Ca2+ flux in fibroblasts.

PubMed

Glogauer, M; Ferrier, J; McCulloch, C A

1995-11-01

The ability to apply controlled forces to the cell membrane may enable elucidation of the mechanisms and pathways involved in signal transduction in response to applied physical stimuli. We have developed a magnetic particle-electromagnet model that allows the application of controlled forces to the plasma membrane of substrate-attached fibroblasts. The system allows applied forces to be controlled by the magnitude of the magnetic field and by the surface area of cell membrane covered with collagen-coated ferric beads. Analysis by single-cell ratio fluorimetry of fura 2-loaded cells demonstrated large calcium transients (50-300 nM) in response to the magnetic force applications. Experiments using either the stretch-activated channel blocker gadolinium chloride or ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to eliminate external calcium ions, or addition of extracellular manganese ions, indicated that there was a calcium influx through putative stretch-activated channels. The probability of a calcium influx in single cells was increased by higher surface bead loading and the degree of cell spreading. Depolymerization of actin filaments by cytochalasin D increased the amplitude of calcium response twofold. The regulation of calcium flux by filamentous actin content and by cell spreading indicates a possible modulatory role for the cytoskeleton in channel sensitivity. Magnetic force application to beads on single cells provides a controlled model to study mechanisms and heterogeneity in physical force stimulation of cation-permeable channels.

An ion displacement membrame model.

PubMed

Hladky, S B; Harris, J D

1967-09-01

The usual assumption in treating the diffusion of ions in an electric field has been that the movement of each ion is independent of the movement of the others. The resulting equation for diffusion by a succession of spontaneous jumps has been well stated by Parlin and Eyring. This paper will consider one simple case in which a different assumption is reasonable. Diffusion of monovalent positive ions is considered as a series of jumps from one fixed negative site to another. The sites are assumed to be full (electrical neutrality). Interaction occurs by the displacement of one ion by another. An ion leaves a site if and only if another ion, not necessarily of the same species, attempts to occupy the same site. Flux ratios and net fluxes are given as functions of the electrical potential, concentration ratios, and number of sites encountered in crossing the membrane. Quantitative comparisons with observations of Hodgkin and Keynes are presented.

Transport of ions in presence of induced electric field and electrostatic turbulence - Source of ions injected into ring current

NASA Technical Reports Server (NTRS)

Cladis, J. B.; Francis, W. E.

1985-01-01

The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.

Magnetic Field Dipolarization and Its Associated Ion Flux Variations in the Inner Magnetosphere: Simultaneous Observations by Arase and Michibiki Satellites

NASA Astrophysics Data System (ADS)

Nose, M.; Matsuoka, A.; Kasahara, S.; Yokota, S.; Higashio, N.; Koshiishi, H.; Imajo, S.; Teramoto, M.; Nomura, R.; Fujimoto, A.; Keika, K.; Tanaka, Y.; Shinohara, M.; Shinohara, I.; Yoshizumi, M.

2017-12-01

Recent satellite observations by MDS-1 and Van Allen Probes statistically revealed that magnetic field dipolarization can be detected over a wide range of L in the deep inner magnetosphere (i.e., L = 3.5-6.5, which is far inside the geosynchronous altitude). It is accompanied by magnetic field fluctuations having a characteristic timescale of a few to 10 s, which is comparable to the local gyroperiod of O+ ions. These magnetic field fluctuations are considered to cause nonadiabatic local acceleration of ions. In this study, we intend to confirm the above-mentioned characteristics of magnetic field dipolarization in the inner magnetosphere, using the magnetic field data and the energetic ion flux data measured by the Exploration of energization and Radiation in Geospace (ERG) "Arase" satellite. The Arase satellite was launched on December 20, 2016 into an elliptical orbit having an apogee of 6.0 Re, a perigee of 440 km altitude, an orbital period of 9.5 h, and an orbital inclination of 32 degrees. During the first magnetic storm of March 27, 2017 after Arase started scientific operation, Arase observes clear dipolarization signatures around 1500 UT at L 4.6 and MLT 5.7 hr. Strong magnetic field fluctuations are embedded in the magnetic field dipolarization and their characteristic frequency is close to the local gyrofrequency of O+ ions. Both H+ and O+ flux enhancements are observed in accordance with the dipolarization. These results are consistent with the previous results. In this event, the Quasi-Zenith Satellite (QZS)-1 "Michibiki" satellite was located at L 7.0 and MLT 23.8 hr, and observes similar dipolarization signatures with a few minute time difference. Simultaneous observations by both Arase and Michibiki provides us a unique opportunity to investigate how fast and wide the dipolarization propagates in the inner magnetosphere. In the presentation, we will show detailed analysis results of the dipolarization event on March 27, 2017 as well as similar

Regeneration of spent powdered activated carbon saturated with inorganic ions by cavitation united with ion exchange method.

PubMed

Li, Gang; Gao, Hong; Li, Yansheng; Yang, Huixin

2011-06-01

Using ion exchange resin as transfer media, regenerate powdered activated carbon (PAC) adsorbed inorganic ions by cavitation to enhance the transfer; we studied how the regeneration time and the mass ratio of resin and PAC influence the regeneration rate respectively through re-adsorption. The result showed that the effective regeneration of PAC saturated with inorganic ions was above 90% using ion exchange resin as media and transfer carrier, the quantity of PAC did not reduced but activated in the process. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

GEM-CEDAR Challenge: Poynting Flux at DMSP and Modeled Joule Heat

NASA Technical Reports Server (NTRS)

Rastaetter, Lutz; Shim, Ja Soon; Kuznetsova, Maria M.; Kilcommons, Liam M.; Knipp, Delores J.; Codrescu, Mihail; Fuller-Rowell, Tim; Emery, Barbara; Weimer, Daniel R.; Cosgrove, Russell;

Correlation between core ion energization, suprathermal electron bursts, and broadband ELF plasma waves

NASA Astrophysics Data System (ADS)

Knudsen, David J.; Clemmons, James H.; Wahlund, Jan-Erik

1998-03-01

Observations of the lowest energy or core ions provide a particularly sensitive measure of the early stages of auroral ion energization. Freja satellite observations of 0-20 eV core ions in the topside auroral ionosphere and cusp/cleft show signs of heating within both regions of VLF hiss and broadband ELF plasma waves. However, heating to several eV or more is associated predominantly with the ELF waves. A correlation analysis of wave and core ion data formed from orbital segments shows that, on average, correlations are highest for wave frequencies below several hundred Hz, and less at VLF hiss frequencies. A similar analysis shows a higher correlation between electron precipitation and ion heating for electron energies below several hundred eV (i.e., the energies associated with suprathermal electron bursts) and a lower correlation above the 1 keV energies associated with auroral inverted-V's. Signs of core ion heating begin to appear when wave power at the O+ gyrofrequency exceeds about 10-3(mVm-1)2/Hz, and when the integrated field-aligned electron flux exceeds a few times 107cm-2s-1sr-1. This electron energy flux threshold is at least an order of magnitude lower than previously inferred from earlier studies comparing suprathermal electron fluxes and energetic ions. Almost all observed heating events occur during enhanced or active geomagnetic conditions; i.e., Kp>=4. While the most intense core ion heating is correlated with broadband ELF waves, we also present one example of weak ion heating of a few eV in a region of VLF auroral hiss.

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fraenz, M.; Dubinin, E.; Wei, Y.; Woch, J. G.; Morgan, D. D.; Barabash, S. V.; Lundin, R. N.; Fedorov, A.

2012-12-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first use support from the MARSIS radar experiment for some orbits with fortunate observation geometry. Here we have observed a transterminator flow of O+ and O2+ ions with a super-sonic velocity of around 5km/s and fluxes of 0.8x10^9/cm^2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1x10^25/s half of which is expected to escape from Mars (Fraenz et al, 2010). This escape flux is significantly higher than previously observed on the tailside of Mars, we discuss possible reasons for the difference. Since 2008 the MARSIS radar does nightside local plasma density measurement which often coincide with ASPERA-3 measurements. In a new analysis of the combined nightside datasets (Fig. 1) we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 2) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvenic regime.; Median oxygen ion flux reconstructed by combining ion velocity observations of the Mars Express ASPERA-3 IMA sensor and local plasma density observations by the MARSIS radar. Each bin value is the median from observations on about 3000 orbits between May 2007 and July 2011. Horizontal axis is MSO X-axis (Sun towards the left), vertical axis is vertical distance from MSO X-axis. ; Ring median flux of cylindrical ring regions of all bins shown in previous figure. The different colors show median fluxes

Tailoring nanoscopic confines to maximize catalytic activity of hydronium ions

NASA Astrophysics Data System (ADS)

Shi, Hui; Eckstein, Sebastian; Vjunov, Aleksei; Camaioni, Donald M.; Lercher, Johannes A.

2017-05-01

Acid catalysis by hydronium ions is ubiquitous in aqueous-phase organic reactions. Here we show that hydronium ion catalysis, exemplified by intramolecular dehydration of cyclohexanol, is markedly influenced by steric constraints, yielding turnover rates that increase by up to two orders of magnitude in tight confines relative to an aqueous solution of a Brønsted acid. The higher activities in zeolites BEA and FAU than in water are caused by more positive activation entropies that more than offset higher activation enthalpies. The higher activity in zeolite MFI with pores smaller than BEA and FAU is caused by a lower activation enthalpy in the tighter confines that more than offsets a less positive activation entropy. Molecularly sized pores significantly enhance the association between hydronium ions and alcohols in a steric environment resembling the constraints in pockets of enzymes stabilizing active sites.

Description of Light Ion Production Cross Sections and Fluxes on the Mars Surface using the QMSFRG Model

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Kim, Myung-Hee; Schneider, Irene; Hassler, Donald M.

2006-01-01

The atmosphere of Mars significantly attenuates the heavy ion component of the primary galactic cosmic rays (GCR), however increases the fluence of secondary light ions (neutrons, and hydrogen and helium isotopes) because of particle production processes. We describe results of the quantum multiple scattering fragmentation (QMSFRG) model for the production of light nuclei through the distinct mechanisms of nuclear abrasion and ablation, coalescence, and cluster knockout. The QMSFRG model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections. We use the QMSFRG model and the space radiation transport code, HZETRN to make predictions of the light particle environment on the Martian surface at solar minimum and maximum. The radiation assessment detector (RAD) experiment will be launched in 2009 as part of the Mars Science Laboratory (MSL). We make predictions of the expected results for time dependent count-rates to be observed by RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface.

Modeling of the solar cycle modulated interstellar He, Ne, and O pick-up ion flux along the Earth orbit

NASA Astrophysics Data System (ADS)

Bzowski, M.; Sokol, J. M.; Kubiak, M. A.; Moebius, E.

2015-12-01

Interstellar pick-up ions (PUIs) are used to study in-situ the interstellar flow through the heliosphere. The locations of the peaks of the downwind focusing cone and the upwind crescent as observed in the PUI flux have been used as signatures for the flow direction of neutral interstellar (ISN) gas into the heliosphere. We study the modulation of interstellar He, Ne, and O PUI along the Earth orbit over almost the entire solar activity cycle from 2002 to 2013. We present the expected density of ISN atoms and the resulting PUI fluxes with their modulation due to varying ionization over the solar cycle. Considering the important role of the finite injection speed of ISN atoms and of adiabatic PUI cooling, we show that Ne and O always form an upwind crescent in the PUI flux, but that the crescent formation for He PUIs strongly depends on the integration boundaries for the PUI distribution. Because the crescent has been observed for all three species, we find that the classical model of PUI evolution by Vasyliunas & Siscoe (1976) may not be sufficient to reproduce the upwind structure of He PUIs. We also find that ecliptic longitude of the PUI peak in the focusing cone is a good proxy for the inflow direction of ISN He and Ne during solar minimum, but not for ISN O, which exhibits a systematic shift in the model. On the other hand, the peak location derived from the crescent may not be a good proxy to determine the inflow longitude because it is highly modulated by short-time (few months) variations in the ionization losses. These lead to a corrugated crescent structure and may shift the fitted position of the crescent peak used to determine the inflow direction by up to 10°, with the strongest effects for the species that are heavily affected by ionization, i.e., O and Ne. These findings are in a qualitative agreement with results of in-situ PUI measurements, which showed that the location of PUI maximum varies.

Achieving Zero Current for Polar Wind Outflow on Open Flux Tubes Subjected to Large Photoelectron Fluxes

NASA Technical Reports Server (NTRS)

Wilson, G. R.; Khazanov, G.; Horwitz, J. L.

1997-01-01

In this study we investigate how the condition of zero current on open flux tubes with polar wind outflow, subjected to large photoelectron fluxes, can be achieved. We employ a steady state collisionless semikinetic model to determine the density profiles of O(+), H(+), thermal electrons and photoelectrons coming from the ionosphere along with H(+), ions and electrons coming from the magnetosphere. The model solution attains a potential distribution which both satisfies the condition of charge neutrality and zero current. For the range of parameters considered in this study we find that a 45-60 volt discontinuous potential drop may develop to reflect most of the photoelectrons back toward the ionosphere. This develops because the downward flux of electrons from the magnetosphere to the ionosphere on typical open flux tubes (e.g. the polar rain) appears to be insufficient to balance the photoelectron flux from the ionosphere.

Yeast enolase: mechanism of activation by metal ions.

PubMed

Brewer, J M

1981-01-01

Yeast enolase as prepared by current procedures is inherently chemically homogeneous, though deamidation and partial denaturation can produce electrophoretically distinct forms. A true isozyme of the enzyme exists but does not survive the purification procedure. The chemical sequence for both has been established. The enzyme behaves in solution like a compact, nearly spherical molecule of moderate hydration. Strong intramolecular forces maintain the structure of the individual subunits. The enzyme as isolated is dimeric. If dissociated in the presence of magnesium ions and substrate, then the subunits are active, but if the dissociation occurs in the absence of metal ions, they are inactive until they have reassociated and undergone a first order "annealing" process. Magnesium (II) enhances association. The interaction between the subunits is hydrophobic in character. The enzyme can bind up to 2 mol of most metal ions in "conformational" sites which then allows up to 2 mol of substrate or some substrate analogue to bind. This is not sufficient for catalysis, but conformational metal ions do more than just allow substrate binding. A change in the environment of the metal ions occurs on substrate or substrate analogue binding. There is an absolute correlation between the occurrence of a structural change undergone by the 3-amino analogue of phosphoenolpyruvate and whether the metal ions produce any level of enzymatic activity. For catalysis, two more moles of metal ions, called "catalytic", must bind. There is evidence that the enzymatic reaction involves a carbanion mechanism. It is likely that two more moles of metal ion can bind which inhibit the reaction. The requirement for 2 mol of metal ion per subunit which contribute in different ways to catalysis is exhibited by a number of other enzymes.

Observations of ULF oscillations in the ion fluxes at small pitch angles with ATS 6. [low energy particle detection

NASA Technical Reports Server (NTRS)

Su, S.-Y.; Mcpherron, R. L.; Konradi, A.; Fritz, T. A.

1980-01-01

The ultra-low-frequency modulation of ion flux densities at small pitch angles observed by ATS 6 is examined, with particular attention given to a detailed analysis of a representative event. ULF modulation events with maximum modulation at small pitch angles were identified 14 times during the first eight months of operation of the NOAA low-energy particle detector on ATS 6. For the event of October 23, 1974, maximum flux modulation, with a maximum/minimum intensity ratio of 3.7, was observed in the 100 to 150 keV detector at an angle of 32 deg to the ambient field. Spectral analysis of magnetic field data reveals a right elliptically polarized magnetic perturbation with a 96-sec period and a 5-gamma rms amplitude, propagating in the dipole meridian at an angle of about 15 deg to the ambient field and the dipole axis. Proton flux modulation is found to lag the field by up to 180 deg for the lowest-energy channel. Observations are compared with the drift wave, MHD slow wave, and bounce resonant interaction associated with transverse wave models, and it is found that none of the wave models can adequately account for all of the correlated particle and field oscillations.

Low methane flux from a constructed boreal wetland

NASA Astrophysics Data System (ADS)

Clark, M. G.; Humphreys, E.; Carey, S. K.

2016-12-01

The Sandhill Fen Watershed project in northern Alberta, Canada, is a pilot study in reconstructing a mixed upland and lowland boreal plain ecosystem. The physical construction of the 50 ha area was completed in 2012 and revegetation programs, through planting and seeding, began that same year and continued into 2013. Since then, the vegetation has developed a substantial cover over the reclaimed soil and peat substrates used to cap the engineered topography constructed from mine tailings. To monitor the dynamics of carbon cycling processes in this novel ecosystem, near weekly gas chamber measurements of methane fluxes were carried out over 3 growing seasons. Soil moisture, temperature and ion flux measurements, using Plant Root Simulator probes, were also collected alongside the gas flux plots. In the 3rd season, a transect was established in the lowlands along a moisture gradient to collect continuous reduction-oxidation potential measurements along with these other variables. Overall, methane effluxes remained low relative to what is expected for rewetted organic substrates. However, there is a trend over time towards increasing methane gas emissions that coincides with increasing fluxes of reduced metal ions and decreasing fluxes of sulphate in the fully saturated substrates. The suppressed levels of methane fluxes are possibly due to naturally occurring high levels of sulphate in the donor materials used to cap the ecosystem construction.

Greenhouse Gas Fluxes at the Tablelands, NL, Canada: A Site of Active Serpentinization

NASA Astrophysics Data System (ADS)

Morrill, P. L.; Morrissey, L. S.; Cumming, E.

2016-12-01

Active sites of serpentinization have been proposed as sites for carbon capture and storage (CCS) projects. However, in addition to their ability to convert carbon dioxide to carbonate rock, sites of serpentinization also have the potential release methane, which is a more power greenhouse gas than carbon dioxide. Very little is known about the natural flux of carbon dioxide sequestered and methane released into the atmosphere from active sites of serpentinization. In this study we measured carbon dioxide, methane, and nitrous oxide gas fluxes at a pool of ultra-basic water discharging from serpentinized rock in Winterhouse Canyon, Gros Morne, Newfoundland. We found that the flux of methane released was 4.6 x 10-7 mol/m2/min and the carbon dioxide sequestered was 1.9 x 10-5 mol/m2/min, while the concentrations of nitrous oxide showed little change. Based on these fluxes we calculated predictive climate change parameters such as net radiative forcing and global warming potential which predicted that despite the methane being released the site still had an overall long-term atmospheric cooling effect based on the natural rate of carbon dioxide sequestration.

Particle tracing modeling of ion fluxes at geosynchronous orbit

DOE PAGES

Brito, Thiago V.; Woodroffe, Jesse; Jordanova, Vania K.; ...

2017-10-31

The initial results of a coupled MHD/particle tracing method to evaluate particle fluxes in the inner magnetosphere are presented. This setup is capable of capturing the earthward particle acceleration process resulting from dipolarization events in the tail region of the magnetosphere. On the period of study, the MHD code was able to capture a dipolarization event and the particle tracing algorithm was able to capture our results of these disturbances and calculate proton fluxes in the night side geosynchronous orbit region. The simulation captured dispersionless injections as well as the energy dispersion signatures that are frequently observed by satellites atmore » geosynchronous orbit. Currently, ring current models rely on Maxwellian-type distributions based on either empirical flux values or sparse satellite data for their boundary conditions close to geosynchronous orbit. In spite of some differences in intensity and timing, the setup presented here is able to capture substorm injections, which represents an improvement regarding a reverse way of coupling these ring current models with MHD codes through the use of boundary conditions.« less

Particle tracing modeling of ion fluxes at geosynchronous orbit

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

Brito, Thiago V.; Woodroffe, Jesse; Jordanova, Vania K.

The initial results of a coupled MHD/particle tracing method to evaluate particle fluxes in the inner magnetosphere are presented. This setup is capable of capturing the earthward particle acceleration process resulting from dipolarization events in the tail region of the magnetosphere. On the period of study, the MHD code was able to capture a dipolarization event and the particle tracing algorithm was able to capture our results of these disturbances and calculate proton fluxes in the night side geosynchronous orbit region. The simulation captured dispersionless injections as well as the energy dispersion signatures that are frequently observed by satellites atmore » geosynchronous orbit. Currently, ring current models rely on Maxwellian-type distributions based on either empirical flux values or sparse satellite data for their boundary conditions close to geosynchronous orbit. In spite of some differences in intensity and timing, the setup presented here is able to capture substorm injections, which represents an improvement regarding a reverse way of coupling these ring current models with MHD codes through the use of boundary conditions.« less

Energetic Ion Interactions with the Galilean Satellites

NASA Technical Reports Server (NTRS)

Cooper, John F.

2000-01-01

The principal research tasks of this investigation are: (1) specification of the energetic (keV to MeV) ion environments upstream of the four Galilean satellites and (2) data analysis and numerical modeling of observed ion interactions with the satellites. Differential flux spectra are being compiled for the most abundant ions (protons, oxygen, and sulfur) from measurements at 20 keV to 100 MeV total energy by the Energetic Particle Detector (EPD) experiment and at higher ion energies by the Heavy Ion Counter (HIC) experiment. Runge-Kutta and other numerical techniques are used to propagate test particles sampled from the measured upstream spectra to the satellite surface or spacecraft through the local magnetic and corotational electric field environment of each satellite. Modeling of spatial variations in directional flux anisotropies measured during each close flyby provides limits on atomic charge states for heavy (O, S) magnetospheric ions and on internal or induced magnetic fields of the satellites. Validation of models for magnetic and electric field configurations then allows computation of rates for ion implantation, sputtering, and energy deposition into the satellite surfaces for further modeling of observable chemical changes induced by irradiation. Our ongoing work on production of oxidants and other secondary species by ice irradiation on Europa's surface has significant applications, already acknowledged in current literature, to astrobiological evolution. Finally, the work will improve understanding of energetic ion sources and sinks at the satellite orbits for improved modeling of magnetospheric transport processes. The scope of the research effort mainly includes data from the primary Galileo mission (1995-1997) but may also include some later data where directly relevant (e.g., comparison of J0 and I27 data for Io) to the primary mission objectives. Funding for this contract also includes partial support for our related education and public

Evidence for a hydroxide ion bridging two magnesium ions at the active site of the hammerhead ribozyme.

PubMed Central

Hermann, T; Auffinger, P; Scott, W G; Westhof, E

1997-01-01

In the presence of magnesium ions, cleavage by the hammerhead ribozyme RNA at a specific residue leads to 2'3'-cyclic phosphate and 5'-OH extremities. In the cleavage reaction an activated ribose 2'-hydroxyl group attacks its attached 3'-phosphate. Molecular dynamics simulations of the crystal structure of the hammerhead ribozyme, obtained after flash-freezing of crystals under conditions where the ribozyme is active, provide evidence that a mu-bridging OH-ion is located between two Mg2+ions close to the cleavable phosphate. Constrained simulations show further that a flip from the C3'- endo to the C2'- endo conformation of the ribose at the cleavable phosphate brings the 2'-hydroxyl in proximity to both the attacked phosphorous atom and the mu-bridging OH-ion. Thus, the simulations lead to a detailed new insight into the mechanism of hammerhead ribozyme cleavage where a mu-hydroxo bridged magnesium cluster, located on the deep groove side, provides an OH-ion that is able to activate the 2'-hydroxyl nucleophile after a minor and localized conformational change in the RNA. PMID:9254698

Scalable Loading of a Two-Dimensional Trapped-Ion Array

DTIC Science & Technology

2015-11-25

ion -trap array based on two crossed photo-ionization laser beams . With the use of a continuous flux of pre-cooled neutral...push laser Atomic beam Dierential pumping tube Push laser 2D-MOT 50 K Shield 4 K Shield 4 K stage Trap chip MOT laser Ion To ion pump 5s2 1S0 461...conducted a series of Ramsey experiments on a single trapped ion in the presence and absence of neu- tral atom flux as well as each of the PI laser

MARIE Dose and Flux Measurements in Mars Orbit

NASA Technical Reports Server (NTRS)

Zeitlin, C.; Cleghorn, T.; Cucinotta, F. A.; Saganti, P.; Andersen, V.; Lee, K. T.; Pinsky, L. S.; Turner, R.; Atwell, W.

2004-01-01

We present results from the Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft in orbit around Mars. MARIE operated successfully from March 2002 through October 2003. At the time of this writing, the instrument is off due to a loss of communications during an extremely intense Solar Particle Event. Efforts to revive MARIE are planned for Spring 2004, when Odyssey's role as a communications relay for the MER rovers is completed. During the period of successful operation, MARIE returned the first detailed energetic charged particle data from Mars. Due to limitations of the instrument, normalizing MARIE data to flux or dose is not straightforward - several large corrections are needed. Thus normalized results (like dose or flux) have large uncertainties and/or significant model-dependence. The problems in normalization are mainly due to inefficiency in detecting high-energy protons (signal-to-noise problems force the trigger threshold to be higher than optimal), to the excessively high gains employed in the signal processing electronics (many ions deposit energy sufficient to saturate the electronics, and dE/dx information is lost), and to artifacts associated with the two trigger detectors (incomplete registration of dE/dx). Despite these problems, MARIE is efficient for detecting helium ions with kinetic energies above about 30 MeV/nucleon, and for detecting high-energy ions (energies above about 400 MeV/nucleon) with charges from 5 to 10. Fluxes of these heavier ions can be compared to fluxes obtained from the ACE/CRIS instrument, providing at least one area of direct comparison between data obtained at Earth and at Mars; this analysis will be presented as a work in progress. We will also present dose-rate data, with a detailed explanation of the many sources of uncertainty in normalization. The results for both flux and dose will be compared to predictions of the HZETRN model of the GCR.

Multidirectional Cosmic Ray Ion Detector for Deep Space CubeSats

NASA Technical Reports Server (NTRS)

Wrbanek, John D.; Wrbanek, Susan Y.

2016-01-01

Understanding the nature of anisotropy of solar energetic protons (SEPs) and galactic cosmic ray (GCR) fluxes in the interplanetary medium is crucial in characterizing time-dependent radiation exposure in interplanetary space for future exploration missions. NASA Glenn Research Center has proposed a CubeSat-based instrument to study solar and cosmic ray ions in lunar orbit or deep space. The objective of Solar Proton Anisotropy and Galactic cosmic ray High Energy Transport Instrument (SPAGHETI) is to provide multi-directional ion data to further understand anisotropies in SEP and GCR flux. The instrument is to be developed using large area detectors fabricated from high density, high purity silicon carbide (SiC) to measure linear energy transfer (LET) of ions. Stacks of these LET detectors are arranged in a CubeSat at orthogonal directions to provide multidirectional measurements. The low-noise, thermally-stable nature of silicon carbide and its radiation tolerance allows the multidirectional array of detector stacks to be packed in a 6U CubeSat without active cooling. A concept involving additional coincidence/anticoincidence detectors and a high energy Cherenkov detector is possible to further expand ion energy range and sensitivity.

Protein kinase C alpha drives fibroblast activation and kidney fibrosis by stimulating autophagic flux.

PubMed

Xue, Xian; Ren, Jiafa; Sun, Xiaoli; Gui, Yuan; Feng, Ye; Shu, Bingyan; Wei, Wei; Lu, Qingmiao; Liang, Yan; He, Weichun; Yang, Junwei; Dai, Chunsun

2018-05-23

Kidney fibrosis is a histological hallmark of chronic kidney disease and arises in large part through excessive extracellular matrix (ECM) deposition by activated fibroblasts. The signaling protein complex mTOR complex 2 (mTORC2) plays a critical role in fibroblast activation and kidney fibrosis. Protein kinase C alpha (PKCα) is one of the major sub-pathways of mTORC2, but its role in fibroblast activation and kidney fibrosis remains to be determined. Here, we found that transforming growth factor beta 1 (TGFβ1) activates PKCα signaling in cultured NRK-49F cells in a time-dependent manner. Blocking PKCα signaling with the chemical inhibitor Go6976 or by transfection with PKCα siRNA largely reduced expression of the autophagy-associated protein lysosomal-associated membrane protein 2 (LAMP2) and also inhibited autophagosome-lysosome fusion and autophagic flux in the cells. Similarly to chloroquine, Go6976 treatment and PKCα siRNA transfection also markedly inhibited TGFβ1-induced fibroblast activation. In murine fibrotic kidneys with unilateral ureteral obstruction (UUO) nephropathy, PKCα signaling is activated in the interstitial myofibroblasts. Go6976 administration largely blocked autophagic flux in fibroblasts in the fibrotic kidneys and attenuated the UUO nephropathy. Together, our findings suggest that blocking PKCα activity may retard autophagic flux and thereby prevent fibroblast activation and kidney fibrosis. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

Influence of average ion energy and atomic oxygen flux per Si atom on the formation of silicon oxide permeation barrier coatings on PET

NASA Astrophysics Data System (ADS)

Mitschker, F.; Wißing, J.; Hoppe, Ch; de los Arcos, T.; Grundmeier, G.; Awakowicz, P.

2018-04-01

The respective effect of average incorporated ion energy and impinging atomic oxygen flux on the deposition of silicon oxide (SiO x ) barrier coatings for polymers is studied in a microwave driven low pressure discharge with additional variable RF bias. Under consideration of plasma parameters, bias voltage, film density, chemical composition and particle fluxes, both are determined relative to the effective flux of Si atoms contributing to film growth. Subsequently, a correlation with barrier performance and chemical structure is achieved by measuring the oxygen transmission rate (OTR) and by performing x-ray photoelectron spectroscopy. It is observed that an increase in incorporated energy to 160 eV per deposited Si atom result in an enhanced cross-linking of the SiO x network and, therefore, an improved barrier performance by almost two orders of magnitude. Furthermore, independently increasing the number of oxygen atoms to 10 500 per deposited Si atom also lead to a comparable barrier improvement by an enhanced cross-linking.

Model predictions and visualization of the particle flux on the surface of Mars.

PubMed

Cucinotta, Francis A; Saganti, Premkumar B; Wilson, John W; Simonsen, Lisa C

2002-12-01

Model calculations of the particle flux on the surface of Mars due to the Galactic Cosmic Rays (GCR) can provide guidance on radiobiological research and shielding design studies in support of Mars exploration science objectives. Particle flux calculations for protons, helium ions, and heavy ions are reported for solar minimum and solar maximum conditions. These flux calculations include a description of the altitude variations on the Martian surface using the data obtained by the Mars Global Surveyor (MGS) mission with its Mars Orbiter Laser Altimeter (MOLA) instrument. These particle flux calculations are then used to estimate the average particle hits per cell at various organ depths of a human body in a conceptual shelter vehicle. The estimated particle hits by protons for an average location at skin depth on the Martian surface are about 10 to 100 particle-hits/cell/year and the particle hits by heavy ions are estimated to be 0.001 to 0.01 particle-hits/cell/year.

Trends in the Northern-hemisphere Climatologies of Local Wave Activity and Fluxes in a Warming Climate

NASA Astrophysics Data System (ADS)

Huang, S. Y.; Nakamura, N.

2016-12-01

The finite-amplitude local wave activity (LWA) identifies both the locations and magnitudes of anomalous wave events (Huang and Nakamura 2016, JAS), which are often associated with extreme weather conditions such as heat waves and storms at the rim. Variance in LWA in synoptic timescale is well-explained by the wave activity flux variance (i.e. conservative dynamics), while beyond seasonal time scale, the convergence/divergence of wave activity flux is balanced by non-conservative processes (e.g. vertical fluxes of heat and momentum at the surface, mixing, radiative forcing etc.). Analysis of ERA-Interim data during 1979-2015 shows that there is generally an increasing trend in the vertically-integrated interior LWA in Northern Winter, except over Central Pacific and Southern Europe. There is, in contrast, a decreasing trend in LWA in Northern summer, except over the high-latitude oceanic regions and low-latitude continental regions. The trends in the wave activity flux convergence in both seasons are consistent with such observations in LWA except over the Atlantic sector. In this presentation, I will illustrate how the change in circulation in a warming climate is associated with change in spatial distribution and frequency of extreme weather events by comparing the change in wave activity flux vectors with the observed change in LWA climatology. I will also quantify the permanent effect of non-conservative processes in terms of decadal change in eddy-free reference states of zonal wind and temperature (Nakamura and Solomon 2011).

Empirical predictive models of daily relativistic electron flux at geostationary orbit: Multiple regression analysis

DOE PAGES

Simms, Laura E.; Engebretson, Mark J.; Pilipenko, Viacheslav; ...

2016-04-07

The daily maximum relativistic electron flux at geostationary orbit can be predicted well with a set of daily averaged predictor variables including previous day's flux, seed electron flux, solar wind velocity and number density, AE index, IMF Bz, Dst, and ULF and VLF wave power. As predictor variables are intercorrelated, we used multiple regression analyses to determine which are the most predictive of flux when other variables are controlled. Empirical models produced from regressions of flux on measured predictors from 1 day previous were reasonably effective at predicting novel observations. Adding previous flux to the parameter set improves the predictionmore » of the peak of the increases but delays its anticipation of an event. Previous day's solar wind number density and velocity, AE index, and ULF wave activity are the most significant explanatory variables; however, the AE index, measuring substorm processes, shows a negative correlation with flux when other parameters are controlled. This may be due to the triggering of electromagnetic ion cyclotron waves by substorms that cause electron precipitation. VLF waves show lower, but significant, influence. The combined effect of ULF and VLF waves shows a synergistic interaction, where each increases the influence of the other on flux enhancement. Correlations between observations and predictions for this 1 day lag model ranged from 0.71 to 0.89 (average: 0.78). Furthermore, a path analysis of correlations between predictors suggests that solar wind and IMF parameters affect flux through intermediate processes such as ring current ( Dst), AE, and wave activity.« less

Empirical predictive models of daily relativistic electron flux at geostationary orbit: Multiple regression analysis

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

Simms, Laura E.; Engebretson, Mark J.; Pilipenko, Viacheslav

The daily maximum relativistic electron flux at geostationary orbit can be predicted well with a set of daily averaged predictor variables including previous day's flux, seed electron flux, solar wind velocity and number density, AE index, IMF Bz, Dst, and ULF and VLF wave power. As predictor variables are intercorrelated, we used multiple regression analyses to determine which are the most predictive of flux when other variables are controlled. Empirical models produced from regressions of flux on measured predictors from 1 day previous were reasonably effective at predicting novel observations. Adding previous flux to the parameter set improves the predictionmore » of the peak of the increases but delays its anticipation of an event. Previous day's solar wind number density and velocity, AE index, and ULF wave activity are the most significant explanatory variables; however, the AE index, measuring substorm processes, shows a negative correlation with flux when other parameters are controlled. This may be due to the triggering of electromagnetic ion cyclotron waves by substorms that cause electron precipitation. VLF waves show lower, but significant, influence. The combined effect of ULF and VLF waves shows a synergistic interaction, where each increases the influence of the other on flux enhancement. Correlations between observations and predictions for this 1 day lag model ranged from 0.71 to 0.89 (average: 0.78). Furthermore, a path analysis of correlations between predictors suggests that solar wind and IMF parameters affect flux through intermediate processes such as ring current ( Dst), AE, and wave activity.« less

Active spacecraft potential control: An ion emitter experiment. [Cluster mission

NASA Technical Reports Server (NTRS)

Riedler, W.; Goldstein, R.; Hamelin, M.; Maehlum, B. N.; Troim, J.; Olsen, R. C.; Pedersen, A.; Grard, R. J. L.; Schmidt, R.; Rudenauer, F.

1988-01-01

The cluster spacecraft are instrumented with ion emitters for charge neutralization. The emitters produce indium ions at 6 keV. The ion current is adjusted in a feedback loop with instruments measuring the spacecraft potential. The system is based on the evaporation of indium in the apex field of a needle. The design of the active spacecraft potential control instruments, and the ion emitters is presented.

How Cells Can Control Their Size by Pumping Ions.

PubMed

Kay, Alan R

2017-01-01

The ability of all cells to set and regulate their size is a fundamental aspect of cellular physiology. It has been known for sometime but not widely so, that size stability in animal cells is dependent upon the operation of the sodium pump, through the so-called pump-leak mechanism (Tosteson and Hoffman, 1960). Impermeant molecules in cells establish an unstable osmotic condition, the Donnan effect, which is counteracted by the operation of the sodium pump, creating an asymmetry in the distribution of Na + and K + staving off water inundation. In this paper, which is in part a tutorial, I show how to model quantitatively the ion and water fluxes in a cell that determine the cell volume and membrane potential. The movement of water and ions is constrained by both osmotic and charge balance, and is driven by ion and voltage gradients and active ion transport. Transforming these constraints and forces into a set of coupled differential equations allows us to model how the ion distributions, volume and voltage change with time. I introduce an analytical solution to these equations that clarifies the influence of ion conductances, pump rates and water permeability in this multidimensional system. I show that the number of impermeant ions ( x ) and their average charge have a powerful influence on the distribution of ions and voltage in a cell. Moreover, I demonstrate that in a cell where the operation of active ion transport eliminates an osmotic gradient, the size of the cell is directly proportional to x . In addition, I use graphics to reveal how the physico-chemical constraints and chemical forces interact with one another in apportioning ions inside the cell. The form of model used here is applicable to all membrane systems, including mitochondria and bacteria, and I show how pumps other than the sodium pump can be used to stabilize cells. Cell biologists may think of electrophysiology as the exclusive domain of neuroscience, however the electrical effects of ion

Spectral characteristics of plasma sheet ion and electron populations during undisturbed geomagnetic conditions

NASA Technical Reports Server (NTRS)

Christon, S. P.; Williams, D. J.; Mitchell, D. G.; Frank, L. A.; Huang, C. Y.

1989-01-01

The spectral characteristics of plasma-sheet ion and electron populations during periods of low geomagnetic activity were determined from the analysis of 127 one-hour average samples of central plasma sheet ions and electrons. Particle data from the ISEE-1 low-energy proton and electron differential energy analyzer and medium-energy particle instrument were combined to obtain differential energy spectra in the plasma sheet at geocentric radial distances above 12 earth radii. The relationships between the ion and electron spectral shapes and between the spectral shapes and the geomagnetic activity index were statistically investigated. It was found that the presence of interplanetary particle fluxes does not affect the plasma sheet particle spectral shape.

A thermal extrapolation method for the effective temperatures and internal energies of activated ions

NASA Astrophysics Data System (ADS)

Meot-Ner (Mautner), Michael; Somogyi, Árpád

2007-11-01

The internal energies of dissociating ions, activated chemically or collisionally, can be estimated using the kinetics of thermal dissociation. The thermal Arrhenius parameters can be combined with the observed dissociation rate of the activated ions using kdiss = Athermalexp(-Ea,thermal/RTeff). This Arrhenius-type relation yields the effective temperature, Teff, at which the ions would dissociate thermally at the same rate, or yield the same product distributions, as the activated ions. In turn, Teff is used to calculate the internal energy of the ions and the energy deposited by the activation process. The method yields an energy deposition efficiency of 10% for a chemical ionization proton transfer reaction and 8-26% for the surface collisions of various peptide ions. Internal energies of ions activated by chemical ionization or by gas phase collisions, and of ions produced by desorption methods such as fast atom bombardment, can be also evaluated. Thermal extrapolation is especially useful for ion-molecule reaction products and for biological ions, where other methods to evaluate internal energies are laborious or unavailable.

The interaction of intracellular Mg2+ and pH on Cl- fluxes associated with intracellular pH regulation in barnacle muscle fibers

PubMed Central

1988-01-01

The intracellular dialysis technique was used to measure unidirectional Cl- fluxes and net acid extrusion by single muscle fibers from the giant barnacle. Decreasing pHi below normal levels of 7.35 stimulated both Cl- efflux and influx. These increases of Cl- fluxes were blocked by disulfonic acid stilbene derivatives such as SITS and DIDS. The SITS- sensitive Cl- efflux was sharply dependent upon pHi, increasing approximately 20-fold as pHi was decreased from 7.35 to 6.7. Under conditions of normal intracellular Mg2+ concentration, the apparent pKa for the activation of Cl- efflux was 7.0. We found that raising [Mg2+]i, but not [Mg2+]o, had a pronounced inhibitory effect on both SITS-sensitive unidirectional Cl- fluxes as well as on SITS-sensitive net acid extrusion. Increasing [Mg2+]i shifted the apparent pKa of Cl- efflux to a more acid value without affecting the maximal flux that could be attained. This relation between pHi and [Mg2+]i on SITS- sensitive Cl- efflux is consistent with a competition between H ions and Mg ions. We conclude that the SITS-inhibitable Cl- fluxes are mediated by the pHi-regulatory transport mechanism and that changes of intracellular Mg2+ levels can modify the activity of the pHi regulator/anion transporter. PMID:3392519

Anomalous high-frequency wave activity flux preceding anomalous changes in the Northern polar jet

NASA Astrophysics Data System (ADS)

Nakamura, Mototaka; Kadota, Minoru; Yamane, Shozo

2010-05-01

Anomalous forcing by quasi-geostrophic (QG) waves has been reported as an important forcing factor in the Northern Annular Mode (NAM) in recent literatures. In order to shed a light on the dynamics of the NAM from a different angle, we have examined anomalous behavior of the winter jets in the upper troposphere and stratosphere by focusing our diagnosis on not the anomalous geopotential height (Z) itself, but on the anomalous change in the Z (dZ) between two successive months and preceding transient QG wave activity flux during the cold season. We calculated EOFs of dZ between two successive months at 150hPa for a 46-year period, from 1958 to 2003, using the monthly mean NCEP reanalysis data. We then formed anomaly composites of changes in Z and the zonal velocity (U), as well as the preceding and following wave activity flux, Z, U, and temperature at various heights, for both positive and negative phases of the first EOF. For the wave forcing fields, we adopted the diagnostic system for the three-dimensional QG transient wave activity flux in the zonally-varying three-dimensional mean flow developed by Plumb (1986) with a slight modification in its application to the data. Our choice of the Plumb86 is based on the fact that the winter mean flow in the Northern Hemisphere is characterized by noticeable zonal asymmetry, and has a symbiotic relationship with waves in the extra-tropics. The Plumb86 flux was calculated for high-frequency (period of 2 to 7 days) and low-frequency (period of 10 to 20 days) waves with the ultra-low-frequency (period of 30 days or longer) flow as the reference state for each time frame of the 6 hourly NCEP reanalysis data from 1958 to 2003. By replacing the mean flow with the ultra-low-frequency flow in the application of the Plumb86 formula, the flux fields were calculated as time series at 6 hour intervals. The time series of the wave activity flux was then averaged for each month. The patterns of composited anomalous dZ and dU clearly

Effects of nitrogen seeding on core ion thermal transport in JET ILW L-mode plasmas

NASA Astrophysics Data System (ADS)

Bonanomi, N.; Mantica, P.; Citrin, J.; Giroud, C.; Lerche, E.; Sozzi, C.; Taylor, D.; Tsalas, M.; Van Eester, D.; contributors, JET

2018-02-01

A set of experiments was carried out in JET ILW (Joint European Torus with ITER-Like Wall) L-mode plasmas in order to study the effects of light impurities on core ion thermal transport. N was puffed into some discharges and its profile was measured by active Charge Exchange diagnostics, while ICRH power was deposited on- and off-axis in ({\\hspace{0pt}}3He)-D minority scheme in order to have a scan of local heat flux at constant total power with and without N injection. Experimentally, the ion temperature profiles are more peaked for similar heat fluxes when N is injected in the plasma. Gyro-kinetic simulations using the GENE code indicate that a stabilization of Ion Temperature Gradient driven turbulent transport due to main ion dilution and to changes in Te/Ti and s/q is responsible of the enhanced peaking. The quasi-linear models TGLF and QuaLiKiz are tested against the experimental and the gyro-kinetic results.

Quasi-biennial modulation of solar neutrino flux: connections with solar activity

NASA Astrophysics Data System (ADS)

Vecchio, A.; Laurenza, M.; D'alessi, L.; Carbone, V.; Storini, M.

2011-12-01

A quasi-biennial periodicity has been recently found (Vecchio et al., 2010) in the solar neutrino flux, as detected at the Homestake experiment, as well as in the flux of solar energetic protons, by means of the Empirical Modes Decomposition technique. Moreover, both fluxes have been found to be significantly correlated at the quasi-biennial timescale, thus supporting the hypothesis of a connection between solar neutrinos and solar activity. The origin of this connection is investigated, by modeling how the standard Mikheyev-Smirnov-Wolfenstein (MSW) effect (the process for which the well-known neutrino flavor oscillations are modified in passing through the material) could be influenced by matter fluctuations. As proposed by Burgess et al., 2004, by introducing a background magnetic field in the helioseismic model, density fluctuations can be excited in the radiative zone by the resonance between helioseismic g-modes and Alfvén waves. In particular, with reasonable values of the background magnetic field (10-100 kG), the distance between resonant layers could be of the same order of neutrino oscillation length. We study the effect over this distance of a background magnetic field which is variable with a ~2 yr period, in agreement with typical variations of solar activity. Our findings suggest that the quasi-biennial modulation of the neutrino flux is theoretically possible as a consequence of the magnetic field variations in the solar interior. A. Vecchio, M. Laurenza, V. Carbone, M. Storini, The Astrophysical Journal Letters, 709, L1-L5 (2010). C. Burgess, N. S. Dzhalilov, T. I. Rashba, V., B.Semikoz, J. W. F. Valle, Mon. Not. R. Astron. Soc., 348, 609-624 (2004).

Molecular dynamics analysis of silicon chloride ion incidence during Si etching in Cl-based plasmas: Effects of ion incident energy, angle, and neutral radical-to-ion flux ratio

NASA Astrophysics Data System (ADS)

Nakazaki, Nobuya; Eriguchi, Koji; Ono, Kouichi

2014-10-01

Profile anomalies and surface roughness are critical issues to be resolved in plasma etching of nanometer-scale microelectronic devices, which in turn requires a better understanding of the effects of ion incident energy and angle on surface reaction kinetics. This paper presents a classical molecular dynamics (MD) simulation of Si(100) etching by energetic Clx+ (x = 1-2) and SiClx+ (x = 0-4) ion beams with different incident energies Ei = 20-500 eV and angles θi = 0-85°, with and without low-energy neutral Cl radicals (neutral-to-ion flux ratios Γn/Γi = 0 and 100). An improved Stillinger-Weber interatomic potential was used for the Si/Cl system. Numerical results indicated that in Cl+, Cl2+, SiCl3+, and SiCl4+ incidences for θi = 0° and Γn/Γi = 0, the etching occurs in the whole Ei range investigated; on the other hand, in SiCl+ and SiCl2+ incidences, the deposition occurs at low Ei < 300 and 150 eV, respectively, while the etching occurs at further increased Ei. For SiCl+ and SiCl2+, the transition energies from deposition and etching become lowered for Γn/Γi = 100. Numerical results further indicated that in the SiCl+ incidence for Γn/Γi = 0, the etching occurs in the whole θi range investigated for Ei >= 300 eV; on the other hand, for Ei = 100 and 150 eV, the deposition occurs at low θi < 60° and 40°, respectively, while the etching occurs at further increased θi; in addition, for Ei <= 50 eV, the deposition occurs in the whole θi range investigated.

Magnetopause modeling - Flux transfer events and magnetosheath quasi-trapped distributions

NASA Technical Reports Server (NTRS)

Speiser, T. W.; Williams, D. J.

1982-01-01

Three-dimensional distribution functions for energetic ions are studied numerically in the magnetosphere, through the magnetopause, and in the magnetosheath using a simple one-dimensional quasi-static model and ISEE 1 magnetopause crossing data for November 10, 1977. Quasi-trapped populations in the magnetosheath observed near flux transfer events (FTEs) are investigated, and it is shown that the population in the sheath appears to sandwich the FTE distributions. These quasi-trapped distributions are due to slow, large pitch angle, outward moving particles left behind by the outward rush of the ions more field-aligned at the time the flux was opened. It is found that sheath convective flows can map along the connected flux tube without drastically changing the distribution function, and results suggest that localized tangential fields above the upper limit may exist.

Regional differences in rat conjunctival ion transport activities

PubMed Central

Yu, Dongfang; Thelin, William R.; Rogers, Troy D.; Stutts, M. Jackson; Randell, Scott H.; Grubb, Barbara R.

2012-01-01

Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na+ transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface. PMID:22814399

Regional differences in rat conjunctival ion transport activities.

PubMed

Yu, Dongfang; Thelin, William R; Rogers, Troy D; Stutts, M Jackson; Randell, Scott H; Grubb, Barbara R; Boucher, Richard C

2012-10-01

Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na(+) transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface.

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fränz, M.; Dubinin, E.; Wei, Y.; Woch, J.; Morgan, D.; Barabash, S.; Fedorov, A.

2012-09-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first use support from the MARSIS radar experiment for some orbits with fortunate observation geometry. Here we have observed a transterminator flow of O+ and O+ 2 ions with a super-sonic velocity of around 5km/s and fluxes of 0.8 · 109/cm2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1 ± 0.5 × 1025/s half of which is expected to escape from Mars (Fraenz et al, 2010). This escape flux is significantly higher than previously observed on the tailside of Mars, we discuss possible reasons for the difference. Since 2008 the MARSIS radar does nightside local plasma density measurement which often coincide with ASPERA-3 measurements. In a new analysis of the combined nightside datasets (Fig. 1) we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 2) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fränz, Markus; Dubinin, Eduard; Wei, Yong; Morgan, David; Barabash, Stas; Lundin, Rickard; Fedorov, Andrei

2013-04-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first use support from the MARSIS radar experiment for some orbits with fortunate observation geometry. Here we have observed a transterminator flow of O+ and O2+ ions with a super-sonic velocity of around 5km/s and fluxes of 0.8 ? 109/cm2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1 ± 0.5 × 1025-s half of which is expected to escape from Mars (Fraenz et al, Plan.Space Sci., 2010). This escape flux is significantly higher than previously observed on the tailside of Mars, we discuss possible reasons for the difference. Since 2008 the MARSIS radar does nightside local plasma density measurements which often coincide with ASPERA-3 measurements. In a new analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of half a Martian radius the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Cusp field-aligned currents and ion outflows

NASA Astrophysics Data System (ADS)

Strangeway, R. J.; Russell, C. T.; Carlson, C. W.; McFadden, J. P.; Ergun, R. E.; Temerin, M.; Klumpar, D. M.; Peterson, W. K.; Moore, T. E.

2000-09-01

On September 24 and 25, 1998, the Polar spacecraft observed intense outflows of terrestrial ions in association with the passage of an interplanetary shock and coronal mass ejection. The orbit of the Fast Auroral Snapshot (FAST) Explorer was in the noon-midnight meridian during this ion outflow event, and FAST passed through the day side cusp region at ˜4000 km altitude every 2.2 hours. FAST was therefore able to monitor the ion outflows subsequently observed by Polar. We show that while the outflows were more intense after the shock passage, the overall particle and field signatures within the cusp region were qualitatively similar both before and after the shock passage. FAST observations show that the cusp particle precipitation marks the lower latitude leg of a pair of field-aligned currents and further, that both field-aligned current sheets appear to be on open field lines. Moreover, the polarity of the cusp currents is controlled by the polarity of the interplanetary magnetic field (IMF) y-component, such that the magnetic field perturbation associated with the pair of cusp currents is in the same direction as the IMF By. This is a consequence of the reconnection of cusp-region field lines at the magnetopause, with the flux transport resulting in electromagnetic energy being transmitted along field lines to the ionosphere as Poynting flux. We show that this Poynting flux can be as high as 120 mW m-2 (120 ergs cm-2 s-1) at FAST altitudes (˜500 mW m-2 at ionospheric altitudes), presumably because of the strong IMF By (˜40 nT), and is the dominant energy input to the cusp-region ionosphere. Furthermore, we find that the peak ion outflow flux is correlated with the peak downward Poynting flux, although only a few passes through the cusp centered around the time of the shock passage were used to determine this correlation. The energy carried by Poynting flux is dissipated as heat within the ionosphere, through Joule dissipation. The heating will tend to

Fe(III) and Fe(II) ions different effects on Enterococcus hirae cell growth and membrane-associated ATPase activity

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

Vardanyan, Zaruhi; Trchounian, Armen, E-mail: trchounian@ysu.am

2012-01-06

Highlights: Black-Right-Pointing-Pointer Fe{sup 3+} stimulates but Fe{sup 2+} suppresses Enterococcus hirae wild-type and atpD mutant growth. Black-Right-Pointing-Pointer Fe ions change oxidation-reduction potential drop during cell growth. Black-Right-Pointing-Pointer Fe{sup 3+} and Fe{sup 2+} have opposite effects on a membrane-associated ATPase activity. Black-Right-Pointing-Pointer These effects are either in the presence of F{sub 0}F{sub 1} inhibitor or non-functional F{sub 0}F{sub 1}. Black-Right-Pointing-Pointer Fe ions decrease protons and coupled potassium ions fluxes across the membrane. -- Abstract: Enterococcus hirae is able to grow under anaerobic conditions during glucose fermentation (pH 8.0) which is accompanied by acidification of the medium and drop in its oxidation-reductionmore » potential (E{sub h}) from positive values to negative ones (down to {approx}-200 mV). In this study, iron (III) ions (Fe{sup 3+}) have been shown to affect bacterial growth in a concentration-dependent manner (within the range of 0.05-2 mM) by decreasing lag phase duration and increasing specific growth rate. While iron(II) ions (Fe{sup 2+}) had opposite effects which were reflected by suppressing bacterial growth. These ions also affected the changes in E{sub h} values during bacterial growth. It was revealed that ATPase activity with and without N,N Prime -dicyclohexylcarbodiimide (DCCD), an inhibitor of the F{sub 0}F{sub 1}-ATPase, increased in the presence of even low Fe{sup 3+} concentration (0.05 mM) but decreased in the presence of Fe{sup 2+}. It was established that Fe{sup 3+} and Fe{sup 2+} both significantly inhibited the proton-potassium exchange of bacteria, but stronger effects were in the case of Fe{sup 2+} with DCCD. Such results were observed with both wild-type ATCC9790 and atpD mutant (with defective F{sub 0}F{sub 1}) MS116 strains but they were different with Fe{sup 3+} and Fe{sup 2+}. It is suggested that the effects of Fe{sup 3+} might be due to

Activation mechanism of ammonium ions on sulfidation of malachite (-201) surface by DFT study

NASA Astrophysics Data System (ADS)

Wu, Dandan; Mao, Yingbo; Deng, Jiushuai; Wen, Shuming

2017-07-01

The activation mechanism of ammonium ions on the sulfidation of malachite (-201) was determined by density functional theory (DFT) calculations. Results of DFT calculations indicated that interlayer sulfidation occurs during the sulfidation process of malachite (-201). The absorption of both the ammonium ion and sulfide ion on the malachite (-201) surface is stronger than that of sulfur ion. After sulfidation was activated with ammonium ion, the Cu 3d orbital peak is closer to the Fermi level and characterized by a stronger peak value. Therefore, the addition of ammonium ions activated the sulfidation of malachite (-201), thereby improving the flotation performance.

Ion plating for the future

NASA Technical Reports Server (NTRS)

Spalvins, T.

1981-01-01

The ion plating techniques are classified relative to the instrumental set up, evaporation media and mode of transport. Distinction is drawn between the low vacuum (plasma) and high vacuum (ion beam) techniques. Ion plating technology is discussed at the fundamental and industrial level. At the fundamental level, the capabilities and limitations of the plasma (evaporant flux) and film characteristics are evaluated. On the industrial level, the performance and potential uses of ion plated films are discussed.

Ion plating for the future

NASA Technical Reports Server (NTRS)

Spalvins, T.

1981-01-01

The ion plating techniques are classified relative to the instrumental set up, evaporation media, and mode of transport. A distinction is drawn between the low vacuum (plasma) and high vacuum (ion beam) techniques. Ion plating technology is discussed at the fundamental and industrial level. At the fundamental level, the capabilities and limitations of the plasma (evaporant flux) and film characteristics are evaluated. And on the industrial level, the performance and potential uses of ion plated films are discussed.

Bumetanide-sensitive ion fluxes in vascular smooth muscle cells: lack of functional Na+, K+, 2 Cl- cotransport.

PubMed

Orlov, S N; Tremblay, J; Hamet, P

1996-09-01

To examine the involvement of Na+,K+,2Cl- cotransport in monovalent ion fluxes in vascular smooth muscle cells (VSMC), we compared the effect of bumetanide on 86Rb, 36Cl and 22Na uptake by quiescent cultures of VSMC from rat aorta. Under basal conditions, the values of bumetanide-sensitive (BS) inward and outward 86Rb fluxes were not different. Bumetanide decreased basal 86Rb uptake by 70-75% with a Ki of approximately 0.2-0.3 microM. At concentrations ranging up to 1 microM, bumetanide did not affect 36Cl influx and reduced it by 20-30% in the range from 3 to 100 microM. In contrast to 86Rb and 36Cl influx, bumetanide did not inhibit 22Na uptake by VSMC. BS 86Rb uptake was completely abolished in Na(+)- or Cl(-)-free media. In contrast to 86Rb, basal BS 36Cl influx was not affected by Nao+ and Ko+. Hyperosmotic and isosmotic shrinkage of VSMC increased 86Rb and 36Cl influx to the same extent. Shrinkage-induced increments of 86Rb and 36Cl uptake were completely abolished by bumetanide with a Ki or approximately 0.3 microM. Shrinkage did not induce BS 86Rb and 36Cl influx in (Na+ or Cl-)- and (Na+ or K+)-depleted media, respectively. In the presence of an inhibitor of Na+/H+ exchange (EIPA), neither hyperosmotic nor isosmotic shrinkage activated 22Na influx. Bumetanide (1 microM) did not modify basal VSMC volume and intracellular content of sodium, potassium and chloride but abolished the regulatory volume increase in isosmotically-shrunken VSMC. These data demonstrate the absence of the functional Na+,K+,2Cl- cotransporter in VSMC and suggest that in these cells basal and shrinkage-induced BS K+ influx is mediated by (Nao+ + Clo-)-dependent K+/K+ exchange and Nao(+)-dependent K+,Cl- cotransport, respectively.

Imaging elemental distribution and ion transport in cultured cells with ion microscopy.

PubMed

Chandra, S; Morrison, G H

1985-06-28

Both elemental distribution and ion transport in cultured cells have been imaged by ion microscopy. Morphological and chemical information was obtained with a spatial resolution of approximately 0.5 micron for sodium, potassium, calcium, and magnesium in freeze-fixed, cryofractured, and freeze-dried normal rat kidney cells and Chinese hamster ovary cells. Ion transport was successfully demonstrated by imaging Na+-K+ fluxes after the inhibition of Na+- and K+ -dependent adenosine triphosphatase with ouabain. This method allows measurements of elemental (isotopic) distribution to be related to cell morphology, thereby providing the means for studying ion distribution and ion transport under different physiological, pathological, and toxicological conditions in cell culture systems.

Detection of single ion channel activity with carbon nanotubes

NASA Astrophysics Data System (ADS)

Zhou, Weiwei; Wang, Yung Yu; Lim, Tae-Sun; Pham, Ted; Jain, Dheeraj; Burke, Peter J.

2015-03-01

Many processes in life are based on ion currents and membrane voltages controlled by a sophisticated and diverse family of membrane proteins (ion channels), which are comparable in size to the most advanced nanoelectronic components currently under development. Here we demonstrate an electrical assay of individual ion channel activity by measuring the dynamic opening and closing of the ion channel nanopores using single-walled carbon nanotubes (SWNTs). Two canonical dynamic ion channels (gramicidin A (gA) and alamethicin) and one static biological nanopore (α-hemolysin (α-HL)) were successfully incorporated into supported lipid bilayers (SLBs, an artificial cell membrane), which in turn were interfaced to the carbon nanotubes through a variety of polymer-cushion surface functionalization schemes. The ion channel current directly charges the quantum capacitance of a single nanotube in a network of purified semiconducting nanotubes. This work forms the foundation for a scalable, massively parallel architecture of 1d nanoelectronic devices interrogating electrophysiology at the single ion channel level.

Hydrodynamic description of an unmagnetized plasma with multiple ion species. II. Two and three ion species plasmas

DOE PAGES

Simakov, Andrei Nikolaevich; Molvig, Kim

2016-03-17

Paper I [A. N. Simakov and K. Molvig, Phys. Plasmas23, 032115 (2016)] obtained a fluid description for an unmagnetized collisional plasma with multiple ion species. To evaluate collisional plasmatransport fluxes, required for such a description, two linear systems of equations need to be solved to obtain corresponding transport coefficients. In general, this should be done numerically. Herein, the general formalism is used to obtain analytical expressions for such fluxes for several specific cases of interest: a deuterium-tritium plasma; a plasma containing two ion species with strongly disparate masses, which agrees with previously obtained results; and a three ion species plasmamore » made of deuterium, tritium, and gold. We find that these results can be used for understanding the behavior of the aforementioned plasmas, or for verifying a code implementation of the general multi-ion formalism.« less

Oxygen Pickup Ions Measured by MAVEN Outside the Martian Bow Shock

NASA Astrophysics Data System (ADS)

Rahmati, A.; Cravens, T.; Larson, D. E.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.; Jakosky, B. M.

2015-12-01

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft entered orbit around Mars on September 21, 2014 and has since been detecting energetic oxygen pickup ions by its SEP (Solar Energetic Particles) and SWIA (Solar Wind Ion Analyzer) instruments. The oxygen pickup ions detected outside the Martian bowshock and in the upstream solar wind are associated with the extended hot oxygen exosphere of Mars, which is created mainly by the dissociative recombination of molecular oxygen ions with electrons in the ionosphere. We use analytic solutions to the equations of motion of pickup ions moving in the undisturbed upstream solar wind magnetic and motional electric fields and calculate the flux of oxygen pickup ions at the location of MAVEN. Our model calculates the ionization rate of oxygen atoms in the exosphere based on the hot oxygen densities predicted by Rahmati et al. (2014), and the sources of ionization include photo-ionization, charge exchange, and electron impact ionization. The photo-ionization frequency is calculated using the FISM (Flare Irradiance Spectral Model) solar flux model, based on MAVEN EUVM (Extreme Ultra-Violet Monitor) measurements. The frequency of charge exchange between a solar wind proton and an oxygen atom is calculated using MAVEN SWIA solar wind proton flux measurements, and the electron impact ionization frequency is calculated based on MAVEN SWEA (Solar Wind Electron Analyzer) solar wind electron flux measurements. The solar wind magnetic field used in the model is from the measurements taken by MAVEN MAG (magnetometer) in the upstream solar wind. The good agreement between our predicted pickup oxygen fluxes and the MAVEN SEP and SWIA measured ones confirms detection of oxygen pickup ions and these model-data comparisons can be used to constrain models of hot oxygen densities and photochemical escape flux.

Intramolecular Nuclear Flux Densities

NASA Astrophysics Data System (ADS)

Barth, I.; Daniel, C.; Gindensperger, E.; Manz, J.; PéRez-Torres, J. F.; Schild, A.; Stemmle, C.; Sulzer, D.; Yang, Y.

The topic of this survey article has seen a renaissance during the past couple of years. Here we present and extend the results for various phenomena which we have published from 2012-2014, with gratitude to our coauthors. The new phenomena include (a) the first reduced nuclear flux densities in vibrating diatomic molecules or ions which have been deduced from experimental pump-probe spectra; these "experimental" nuclear flux densities reveal several quantum effects including (b) the "quantum accordion", i.e., during the turn from bond stretch to bond compression, the diatomic system never stands still — instead, various parts of it with different bond lengths flow into opposite directions. (c) Wavepacket interferometry has been extended from nuclear densities to flux densities, again revealing new phenomena: For example, (d) a vibrating nuclear wave function with compact initial shape may split into two partial waves which run into opposite directions, thus causing interfering flux densities. (e) Tunneling in symmetric 1-dimensional double-well systems yields maximum values of the associated nuclear flux density just below the potential barrier; this is in marked contrast with negligible values of the nuclear density just below the barrier. (f) Nuclear flux densities of pseudorotating nuclei may induce huge magnetic fields. A common methodologic theme of all topics is the continuity equation which connects the time derivative of the nuclear density to the divergence of the flux density, subject to the proper boundary conditions. (g) Nearly identical nuclear densities with different boundary conditions may be related to entirely different flux densities, e.g., during tunneling in cyclic versus non-cyclic systems. The original continuity equation, density and flux density of all nuclei, or of all nuclear degrees of freedom, may be reduced to the corresponding quantities for just a single nucleus, or just a single degree of freedom.

Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

NASA Astrophysics Data System (ADS)

Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

2015-12-01

The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

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

Bai, Xue-Ning; Stone, James M.

2017-02-10

The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can playmore » a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.« less

Monte Carlo simulation of thermal neutron flux of americium-beryllium source used in neutron activation analysis

NASA Astrophysics Data System (ADS)

Didi, Abdessamad; Dadouch, Ahmed; Bencheikh, Mohamed; Jai, Otman

2017-09-01

The neutron activation analysis is a method of exclusively elemental analysis. Its implementation of irradiates the sample which can be analyzed by a high neutron flux, this method is widely used in developed countries with nuclear reactors or accelerators of particle. The purpose of this study is to develop a prototype to increase the neutron flux such as americium-beryllium and have the opportunity to produce radioisotopes. Americium-beryllium is a mobile source of neutron activity of 20 curie, and gives a thermal neutron flux of (1.8 ± 0.0007) × 106 n/cm2 s when using water as moderator, when using the paraffin, the thermal neutron flux increases to (2.2 ± 0.0008) × 106 n/cm2 s, in the case of adding two solid beryllium barriers, the distance between them is 24 cm, parallel and symmetrical about the source, the thermal flux is increased to (2.5 ± 0.0008) × 106 n/cm2 s and in the case of multi-source (6 sources), with-out barriers, increases to (1.17 ± 0.0008) × 107 n/cm2 s with a rate of increase equal to 4.3 and with the both barriers flux increased to (1.37 ± 0.0008) × 107 n/cm2 s.

AMPTE/CCE CHEM observations of the energetic ion population at geosynchronous altitudes

NASA Technical Reports Server (NTRS)

Daglis, Ioannis A.; Sarris, Emmanuel T.; Wilken, Berend

1993-01-01

The paper presents results of a statistical study of average characteristics of the energetic ion population at geosynchronous altitudes, using energetic-ion (1-300 keV/e) measurements from the CHEM spectrometer aboard the AMPTE Charge Composition Explorer between January 1985 and June 1987. Data were sorted into four MLT groups and two extreme geomagnetic activity levels ('very quiet' for AE less than 30 nT and 'very active' for AE greater than 700 nT). A clear quiet-time dayside feature found in the measurements was a dip in H(+) and He(2+) spectra, at 6.6 keV/e in the prenoon sector and at 3.5 keV/e in the postnoon sector. During active times, the ion fluxes increased (except for He(+)), and the O(+) contribution to the total energy density increased dramatically. The pitch angle distributions were normal during quiet times and isotropic or field-aligned during active times.

Distinct regions that control ion selectivity and calcium-dependent activation in the bestrophin ion channel.

PubMed

Vaisey, George; Miller, Alexandria N; Long, Stephen B

2016-11-22

Cytoplasmic calcium (Ca 2+ ) activates the bestrophin anion channel, allowing chloride ions to flow down their electrochemical gradient. Mutations in bestrophin 1 (BEST1) cause macular degenerative disorders. Previously, we determined an X-ray structure of chicken BEST1 that revealed the architecture of the channel. Here, we present electrophysiological studies of purified wild-type and mutant BEST1 channels and an X-ray structure of a Ca 2+ -independent mutant. From these experiments, we identify regions of BEST1 responsible for Ca 2+ activation and ion selectivity. A "Ca 2+ clasp" within the channel's intracellular region acts as a sensor of cytoplasmic Ca 2+ . Alanine substitutions within a hydrophobic "neck" of the pore, which widen it, cause the channel to be constitutively active, irrespective of Ca 2+ . We conclude that the primary function of the neck is as a "gate" that controls chloride permeation in a Ca 2+ -dependent manner. In contrast to what others have proposed, we find that the neck is not a major contributor to the channel's ion selectivity. We find that mutation of a cytosolic "aperture" of the pore does not perturb the Ca 2+ dependence of the channel or its preference for anions over cations, but its mutation dramatically alters relative permeabilities among anions. The data suggest that the aperture functions as a size-selective filter that permits the passage of small entities such as partially dehydrated chloride ions while excluding larger molecules such as amino acids. Thus, unlike ion channels that have a single "selectivity filter," in bestrophin, distinct regions of the pore govern anion-vs.-cation selectivity and the relative permeabilities among anions.

Measuring Fast Calcium Fluxes in Cardiomyocytes

PubMed Central

Golebiewska, Urszula; Scarlata, Suzanne

2011-01-01

Cardiomyocytes have multiple Ca2+ fluxes of varying duration that work together to optimize function 1,2. Changes in Ca2+ activity in response to extracellular agents is predominantly regulated by the phospholipase Cβ- Gαq pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine 3,4. We have recently found that plasma membrane protein domains called caveolae5,6 can entrap activated Gαq7. This entrapment has the effect of stabilizing the activated state of Gαq and resulting in prolonged Ca2+ signals in cardiomyocytes and other cell types8. We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca2+ indicator. In our studies, we used Ca2+ Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca2+ responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca2+ waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca2+ waves show binned data with a broad

Measuring fast calcium fluxes in cardiomyocytes.

PubMed

Golebiewska, Urszula; Scarlata, Suzanne

2011-11-29

Cardiomyocytes have multiple Ca(2+) fluxes of varying duration that work together to optimize function (1,2). Changes in Ca(2+) activity in response to extracellular agents is predominantly regulated by the phospholipase Cβ- Gα(q;) pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine (3,4). We have recently found that plasma membrane protein domains called caveolae(5,6) can entrap activated Gα(q;)(7). This entrapment has the effect of stabilizing the activated state of Gα(q;) and resulting in prolonged Ca(2+) signals in cardiomyocytes and other cell types(8). We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca(2+) indicator. In our studies, we used Ca(2+) Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca(2+) responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca(2+) waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca(2+) waves

Above- and below-ground methane fluxes and methanotrophic activity in a landfill-cover soil

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

Schroth, M.H., E-mail: martin.schroth@env.ethz.ch; Eugster, W.; Gomez, K.E.

2012-05-15

Highlights: Black-Right-Pointing-Pointer We quantify above- and below-ground CH{sub 4} fluxes in a landfill-cover soil. Black-Right-Pointing-Pointer We link methanotrophic activity to estimates of CH{sub 4} loading from the waste body. Black-Right-Pointing-Pointer Methane loading and emissions are highly variable in space and time. Black-Right-Pointing-Pointer Eddy covariance measurements yield largest estimates of CH{sub 4} emissions. Black-Right-Pointing-Pointer Potential methanotrophic activity is high at a location with substantial CH{sub 4} loading. - Abstract: Landfills are a major anthropogenic source of the greenhouse gas methane (CH{sub 4}). However, much of the CH{sub 4} produced during the anaerobic degradation of organic waste is consumed by methanotrophic microorganismsmore » during passage through the landfill-cover soil. On a section of a closed landfill near Liestal, Switzerland, we performed experiments to compare CH{sub 4} fluxes obtained by different methods at or above the cover-soil surface with below-ground fluxes, and to link methanotrophic activity to estimates of CH{sub 4} ingress (loading) from the waste body at selected locations. Fluxes of CH{sub 4} into or out of the cover soil were quantified by eddy-covariance and static flux-chamber measurements. In addition, CH{sub 4} concentrations at the soil surface were monitored using a field-portable FID detector. Near-surface CH{sub 4} fluxes and CH{sub 4} loading were estimated from soil-gas concentration profiles in conjunction with radon measurements, and gas push-pull tests (GPPTs) were performed to quantify rates of microbial CH{sub 4} oxidation. Eddy-covariance measurements yielded by far the largest and probably most representative estimates of overall CH{sub 4} emissions from the test section (daily mean up to {approx}91,500 {mu}mol m{sup -2} d{sup -1}), whereas flux-chamber measurements and CH{sub 4} concentration profiles indicated that at the majority of locations the cover soil

EVOLUTION OF SPINNING AND BRAIDING HELICITY FLUXES IN SOLAR ACTIVE REGION NOAA 10930

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

Ravindra, B.; Yoshimura, Keiji; Dasso, Sergio, E-mail: ravindra@iiap.res.in, E-mail: yosimura@solar.physics.montana.edu, E-mail: dasso@df.uba.ar

2011-12-10

The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8 Degree-Sign hr{sup -1} on the third day of the observations. On themore » fourth and fifth days it remained at 4 Degree-Sign hr{sup -1} with small undulations in its magnitude. The sunspot rotated about 260 Degree-Sign in the last three days. The S-polarity sunspot did not complete more than 20 Degree-Sign in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of -7 Multiplication-Sign 10{sup 43} Mx{sup 2} over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than -6

Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere

NASA Technical Reports Server (NTRS)

Mathews, J. D.

1987-01-01

The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed.

Seasonal fluxes of major ions to a high altitude cold alpine glacier

NASA Astrophysics Data System (ADS)

Maupetit, F.; Wagenbach, D.; Weddeling, P.; Delmas, R. J.

A 13 m fimcore was recovered in April 1991 at Col du Dome (4250 m.a.s.l.), located below the Mont Blanc summit (Northern French Alps). The core spans a complete sequence of 3.5 years of high alpine precipitation, as indicated by the stratigraphic and the isotopic profiles. Subsamples were analysed for Na +, NH 4+, K +, Mg 2+, Ca 2+, Cl -, NO 3- and SO 42- using ion chromatography, and for H + or HCO 3- using a titration technique. In absence of alkaline Saharan dust, the snow is slightly acid (2-20 μ Eq l-1. All analysed ions show a sharply pronounced seasonal pattern, with concentrations, extremely low in winter, increasing in spring and reaching a maximum in summer. This picture supports the idea that in winter the high alpine sites are generally not affected by polluted air masses from lower altitudes, whereas during spring and summer, vertical convective transport significantly affects the highest sites located well above 4000 m a.s.l. The lowest impurity levels of alpine winter snow are comparable with central Greenland values, suggesting that at this time, and just in opposite to what occurs in the Arctic, the highest alpine regions are representative of the continental free troposphere. Annual and seasonal deposition fluxes are calculated. In order to assess the spatial representativeness of these results, a comparison is made with similar records obtained from a 10m firncore recovered in summer 1991, at the low accumulation site Colle Gnifetti (4450 m.a.s.l.) located in the Swiss Alps, 80 km east of Col du Dôme. An excellent agreement is found between the overall mean isotopic and chemical composition of the two firncores, suggesting that, since clean winter snow is well preserved at Col du Dome, this site is presumably more influenced by precipitation during summer. Finally, the attractive perspectives for deep drilling in the Mont Blanc area are assessed, and the merits of making use of both sites, where comparable and complementary information can be

Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: excitation dynamics and ion flux asymmetry

DOE PAGES

Bruneau, B.; Diomede, P.; Economou, D. J.; ...

2016-06-08

Parallel plate capacitively coupled plasmas in hydrogen at relatively high pressure (~1 Torr) are excited with tailored voltage waveforms containing up to five frequencies. Predictions of a hybrid model combining a particle-in-cell simulation with Monte Carlo collisions and a fluid model are compared to phase resolved optical emission spectroscopy measurements, yielding information on the dynamics of the excitation rate in these discharges. When the discharge is excited with amplitude asymmetric waveforms, the discharge becomes electrically asymmetric, with different ion energies at each of the two electrodes. Unexpectedly, large differences in themore » $$\\text{H}_{2}^{+}$$ fluxes to each of the two electrodes are caused by the different $$\\text{H}_{3}^{+}$$ energies. When the discharge is excited with slope asymmetric waveforms, only weak electrical asymmetry of the discharge is observed. In this case, electron power absorption due to fast sheath expansion at one electrode is balanced by electron power absorption at the opposite electrode due to a strong electric field reversal.« less

Conversion from solvent rinsable fluxes to aqueous rinsable fluxes for hot oil solder leveling

NASA Astrophysics Data System (ADS)

1992-03-01

A water rinsable flux was evaluated for hot oil solder leveling of printed wiring boards. The previously used rosin-activated flux required a solvent containing a chlorinated hydrocarbon for removing the flux residues after soldering. The water rinsable flux requires hot water or a solution of hot detergent for removing flux residues after smoldering. The water rinsable flux produced an acceptable soldered surface. Flux residues were removed by either hot water (120 F) or a solution of hot detergent (120 F).

Plasma flux-dependent lipid A deactivation

NASA Astrophysics Data System (ADS)

Chang, Hung-Wen; Hsu, Cheng-Che; Ahmed, Musahid; Liu, Suet Yi; Fang, Yigang; Seog, Joonil; Oehrlein, Gottlieb S.; Graves, David B.

2014-06-01

This paper reports the influence of gas plasma flux on endotoxin lipid A film deactivation. To study the effect of the flux magnitude of reactive species, a modified low-pressure inductively coupled plasma (ICP) with O radical flux ˜1016 cm-2 s-1 was used. After ICP exposures, it was observed that while the Fourier transform infrared absorbance of fatty chains responsible for the toxicity drops by 80% through the film, no obvious film endotoxin deactivation is seen. This is in contrast to that previously observed under low flux exposure conducted in a vacuum beam system: near-surface only loss of fatty chains led to significant film deactivation. Secondary ion mass spectrometry characterization of changes at the film surface did not appear to correlate with the degree of deactivation. Lipid A films need to be nearly completely removed in order to detect significant deactivation under high flux conditions. Additional high reactive species flux experiments were conducted using an atmospheric pressure helium plasma jet and a UV/ozone device. Exposure of lipid A films to reactive species with these devices showed similar deactivation behaviour. The causes for the difference between low and high flux exposures may be due to the nature of near-surface structural modifications as a function of the rate of film removal.

Electric force on plasma ions and the momentum of the ion-neutrals flow

NASA Astrophysics Data System (ADS)

Makrinich, G.; Fruchtman, A.; Zoler, D.; Boxman, R. L.

2018-05-01

The electric force on ions in plasma and the momentum flux carried by the mixed ion-neutral flow were measured and found to be equal. The experiment was performed in a direct-current gas discharge of cylindrical geometry with applied radial electric field and axial magnetic field. The unmagnetized plasma ions, neutralized by magnetized electrons, were accelerated radially outward transferring part of the gained momentum to neutrals. Measurements were taken for various argon gas flow rates between 13 and 100 Standard Cubic Centimeter per Minute, for a discharge current of 1.9 A and a magnetic field intensity of 136 G. The plasma density, electron temperature, and plasma potential were measured at various locations along the flow. These measurements were used to determine the local electric force on the ions. The total electric force on the plasma ions was then determined by integrating radially the local electric force. In parallel, the momentum flux of the mixed ion-neutral flow was determined by measuring the force exerted by the flow on a balance force meter (BFM). The maximal plasma density was between 6 × 1010 cm-3 and 5 × 1011 cm-3, the maximal electron temperature was between 8 eV and 25 eV, and the deduced maximal electric field was between 2200 V/m and 5800 V/m. The force exerted by the mixed ion-neutral flow on the BFM agreed with the total electric force on the plasma ions. This agreement showed that it is the electric force on the plasma ions that is the source of the momentum acquired by the mixed ion-neutral flow.

Plasma focus ion beam-scaling laws

NASA Astrophysics Data System (ADS)

Saw, S. H.

2014-08-01

Measurements on plasma focus ion beams include various advanced techniques producing a variety of data which has yet to produce benchmark numbers. Recent numerical experiments using an extended version of the Lee Code has produced reference numbers and scaling trends for number and energy fluence of deuteron beams as functions of stored energy E0. At the pinch exit the ion number fluence (ions m-2) and energy fluence (J m-2) computed as 2.4-7.8×1020 and 2.2-33×106 respectively were found to be independent of E0 from 0.4 - 486 kJ. This work was extended to the ion beams for various gases. The results show that, for a given plasma focus, the fluence, flux, ion number and ion current decrease from the lightest to the heaviest gas except for trend-breaking higher values for Ar fluence and flux. The energy fluence, energy flux, power flow and damage factors are relatively constant from H2 to N2 but increase for Ne, Ar, Kr and Xe due to radiative cooling and collapse effects. This paper reviews this work and in a concluding section attempts to put the accumulating large amounts of data into the form of a scaling law of beam energy Ebeam versus storage energy E0 taking the form for deuteron as: {Ebeam} = 18.2{E}01.23; where Ebeam is in J and E0 is in kJ. It is hoped that the establishment of such scaling laws places on a firm footing the reference quantitative ideas for plasma focus ion beams.

Anomalous fluxes in the plateau regime for a weakly turbulent, magnetically confined plasma

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

Balescu, R.

1990-09-01

The anomalous particle and heat fluxes, together with the parallel electric current, are determined for a confined plasma in the plateau regime in the presence of weak electrostatic drift-wave turbulence. Proper account is taken of nonstationarity and of the finite ion Larmor radius (FLR). The quasineutrality of the drift-wave fluctuations imposes a consistency condition, by which the evaluation of the anomalous fluxes is closely related to the drift-wave dispersion equation. On the other hand, these fluxes are related to the thermodynamic forces via the poloidal fluxes. For the weak turbulence approximation considered here, a unified formulation of the anomalous transportmore » problem has been obtained, including all aspects of neoclassical theory. The complete set of transport coefficients is calculated and various relations between them are exhibited. It clearly appears, for instance, that the anomalous ion heat flux is a pure FLR effect that vanishes as the Larmor radius goes to zero. The Onsager symmetry is broken for anomalous transport. The Appendix is devoted to a general discussion of the concept of heat flux in turbulent plasmas.« less

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

NASA Technical Reports Server (NTRS)

Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

2016-01-01

We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

Net ammonium and nitrate fluxes in wheat roots under different environmental conditions as assessed by scanning ion-selective electrode technique

PubMed Central

Zhong, Yangquanwei; Yan, Weiming; Chen, Juan; Shangguan, Zhouping

2014-01-01

Wheat is one of the most important food crops in the world, its availability affects global food security. In this study, we investigated variations in NH4+ and NO3- fluxes in the fine roots of wheat using a scanning ion-selective electrode technique in the presence of different nitrogen (N) forms, N concentrations, and pH levels as well as under water stress. Our results show that the fine roots of wheat demonstrated maximum NH4+ and NO3− influxes at 20 mm and 25 mm from the root tip, respectively. The maximal net NH4+ and NO3− influxes were observed at pH 6.2 in the presence of a 1/4 N solution. We observed N efflux in two different cultivars following the exposure of roots to a 10% PEG-6000 solution. Furthermore, the drought-tolerant cultivar generally performed better than the drought-intolerant cultivar. Net NH4+ and NO3− fluxes may be determined by plant growth status, but environmental conditions can also affect the magnitude and direction of N flux. Interestingly, we found that NO3− was more sensitive to environmental changes than NH4+. Our results may be used to guide future hydroponic experiments in wheat as well as to aid in the development of effective fertilisation protocols for this crop. PMID:25428199

Net ammonium and nitrate fluxes in wheat roots under different environmental conditions as assessed by scanning ion-selective electrode technique.

PubMed

Zhong, Yangquanwei; Yan, Weiming; Chen, Juan; Shangguan, Zhouping

2014-11-27

Wheat is one of the most important food crops in the world, its availability affects global food security. In this study, we investigated variations in NH4(+) and NO3(-) fluxes in the fine roots of wheat using a scanning ion-selective electrode technique in the presence of different nitrogen (N) forms, N concentrations, and pH levels as well as under water stress. Our results show that the fine roots of wheat demonstrated maximum NH4(+) and NO3(-) influxes at 20 mm and 25 mm from the root tip, respectively. The maximal net NH4(+) and NO3(-) influxes were observed at pH 6.2 in the presence of a 1/4 N solution. We observed N efflux in two different cultivars following the exposure of roots to a 10% PEG-6000 solution. Furthermore, the drought-tolerant cultivar generally performed better than the drought-intolerant cultivar. Net NH4(+) and NO3(-) fluxes may be determined by plant growth status, but environmental conditions can also affect the magnitude and direction of N flux. Interestingly, we found that NO3(-) was more sensitive to environmental changes than NH4(+). Our results may be used to guide future hydroponic experiments in wheat as well as to aid in the development of effective fertilisation protocols for this crop.

Properties of planetward ion flows in Venus' magnetotail

NASA Astrophysics Data System (ADS)

Kollmann, P.; Brandt, P. C.; Collinson, G.; Rong, Z. J.; Futaana, Y.; Zhang, T. L.

2016-08-01

Venus is gradually losing some of its atmosphere in the form of ions through its induced magnetotail. Some of these ions have been reported previously to flow back to the planet. Proposed drivers are magnetic reconnection and deflection of pickup ions in the magnetic field. We analyze protons and oxygen ions with eV to keV energies acquired by the ASPERA-4/IMA instrument throughout the entire Venus Express mission. We find that venusward flowing ions are important in the sense that their density and deposition rate into the atmosphere is of the same order of magnitude as the density and escape rate of downtail flowing ions. Our analysis shows that during strong EUV irradiance, which occurs during solar maximum, the flux of venusward flowing protons is weaker and of oxygen ions is stronger than during weak irradiance. Since such a behavior was observed when tracing oxygen ions through a MHD model, the ultimate driver of the venusward flowing ions may simply be the magnetic field configuration around Venus. Although the pure downtail oxygen flux stays mostly unchanged for all observed EUV conditions, the increase in venusward oxygen flux for high irradiance results in a lower net atmospheric escape rate. Venusward bulk flows are mostly found in locations where the magnetic field is weak relative to the interplanetary conditions. Although a weak field is generally an indicator of proximity to the magnetotail current sheet, these flows do not cluster around current sheet crossings, as one may expect if they would be driven by magnetic reconnection.

Frozen flux violation, electron demagnetization and magnetic reconnection

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

Scudder, J. D.; Karimabadi, H.; Roytershteyn, V.

2015-10-15

We argue that the analogue in collisionless plasma of the collisional diffusion region of magnetic reconnection is properly defined in terms of the demagnetization of the plasma electrons that enable “frozen flux” slippage to occur. This condition differs from the violation of the “frozen-in” condition, which only implies that two fluid effects are involved, rather than the necessary slippage of magnetic flux as viewed in the electron frame. Using 2D Particle In Cell (PIC) simulations, this approach properly finds the saddle point region of the flux function. Our demagnetization conditions are the dimensionless guiding center approximation expansion parameters for electronsmore » which we show are observable and determined locally by the ratio of non-ideal electric to magnetic field strengths. Proxies for frozen flux slippage are developed that (a) are measurable on a single spacecraft, (b) are dimensionless with theoretically justified threshold values of significance, and (c) are shown in 2D simulations to recover distinctions theoretically possible with the (unmeasurable) flux function. A new potentially observable dimensionless frozen flux rate, Λ{sub Φ}, differentiates significant from anecdotal frozen flux slippage. A single spacecraft observable, ϒ, is shown with PIC simulations to be essentially proportional to the unobservable local Maxwell frozen flux rate. This relationship theoretically establishes electron demagnetization in 3D as the general cause of frozen flux slippage. In simple 2D cases with an isolated central diffusion region surrounded by separatrices, these diagnostics uniquely identify the traditional diffusion region (without confusing it with the two fluid “ion-diffusion” region) and clarify the role of the separatrices where frozen flux violations do occur but are not substantial. In the more complicated guide and asymmetric 2D cases, substantial flux slippage regions extend out along, but inside of, the preferred

Classical Heat-Flux Measurements in Coronal Plasmas from Collective Thomson-Scattering Spectra

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Hu, S. X.; Katz, J.; Froula, D. H.; Rozmus, W.

2016-10-01

Collective Thomson scattering was used to measure heat flux in coronal plasmas. The relative amplitude of the Thomson-scattered power into the up- and downshifted electron plasma wave features was used to determine the flux of electrons moving along the temperature gradient at three to four times the electron thermal velocity. Simultaneously, the ion-acoustic wave features were measured. Their relative amplitude was used to measure the flux of the return-current electrons. The frequencies of these ion-acoustic and electron plasma wave features provide local measurements of the electron temperature and density. These spectra were obtained at five locations along the temperature gradient in a laser-produced blowoff plasma. These measurements of plasma parameters are used to infer the Spitzer-Härm flux (qSH = - κ∇Te ) and are in good agreement with the values of the heat flux measured from the scattering-feature asymmetries. Additional experiments probed plasma waves perpendicular to the temperature gradient. The data show small effects resulting from heat flux compared to probing waves along the temperature gradient. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Multiple-channel detection of cellular activities by ion-sensitive transistors

NASA Astrophysics Data System (ADS)

Machida, Satoru; Shimada, Hideto; Motoyama, Yumi

2018-04-01

An ion-sensitive field-effect transistor to record cellular activities was demonstrated. This field-effect transistor (bio transistor) includes cultured cells on the gate insulator instead of gate electrode. The bio transistor converts a change in potential underneath the cells into variation of the drain current when ion channels open. The bio transistor has high detection sensitivity to even minute variations in potential utilizing a subthreshold swing region. To open ion channels, a reagent solution (acetylcholine) was added to a human-originating cell cultured on the bio transistor. The drain current was successfully decreased with the addition of acetylcholine. Moreover, we attempted to detect the opening of ion channels using a multiple-channel measurement circuit containing several bio transistors. As a consequence, the drain current distinctly decreased only after the addition of acetylcholine. We confirmed that this measurement system including bio transistors enables to observation of cellular activities sensitively and simultaneously.

Characteristics of an Electron Cyclotron Resonance Plasma Source for the Production of Active Nitrogen Species in III-V Nitride Epitaxy

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

A simple analysis is provided to determine the characteristics of an electron cyclotron resonance (ECR) plasma source for the generation of active nitrogen species in the molecular beam epitaxy of III-V nitrides. The effects of reactor geometry, pressure, power, and flow rate on the dissociation efficiency and ion flux are presented. Pulsing the input power is proposed to reduce the ion flux.

Sources and cycling of major ions and nutrients in Devils Lake, North Dakota

USGS Publications Warehouse

Lent, R.M.

1994-01-01

Devils Lake is a saline lake in a large, closed drainage basin in northeastern North Dakota. Previous studies determined that major-ion and nutrient concentrations in Devils Lake are strongly affected by microbially mediated sulfate reduction and dissolution of sulfate and carbonate minerals in the bottom sediments. These studies documented substantial spatial variability in the magnitude of calculated benthic fluxes coincident with the horizontal salinity gradient in Devils Lake. The purpose of the present study is to evaluate seasonal variability in benthic-flux rates, and to understand the effect of these fluxes on the major-ion and nutrient chemistries in Devils Lake between May and October 1991. During the study period, the water column was well mixed, and specific conductance, pH, and temperature did not vary with depth. Dissolved oxygen was enriched near the lake surface due to photosynthesis. Major-ion concentrations and nutrient concentrations did not vary with depth. Because the water-quality data were obtained during open-water periods, the vertical profiles reflect well-mixed conditions. However, the first and last profiles for the study period did document near-bottom maxima of major cations. Secchi-disk depth varied from 0.82 meter on May 7,1991, to 2.13 meters on June 5, 1991. The mean Secchi-disk depth during the study period was 1.24 meters. Seasonal variations in Secchi-disk depths were attributed to variations in primary productivity and phytoplankton communities. Nutrient cycles in Devils Lake were evaluated using gross primary productivity rate data, sediment trap data, and major-ion and nutrient benthic-flux rate data. Gross primary productivity rate was smallest in May (0.076 gram of carbon per square meter per day) and largest in September (1.8 grams of carbon per square meter per day). Average gross primary productivity for the study period was 0.87 gram of carbon per square meter per day. Average gross primary productivity is consistent

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Technical Reports Server (NTRS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-01-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Astrophysics Data System (ADS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-11-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

Plasma expansion dynamics physics: An understanding on ion energy reduction process

NASA Astrophysics Data System (ADS)

Ruzic, David; Srivastava, Shailendra; Thompson, Keith; Spencer, Joshua; Sporre, John

2007-11-01

This paper studies the expanding plasma dynamics of ions produced from a 5J Z-pinch xenon light source used for EUV lithography. Ion energy reduction is essential for the successful implementation of this technology. To aid this investigation, ion energy from a z-pinch DPP plasma source is measured using an ion energy analyzer and effect of introducing a small percentage of low Z material on the ion energy and flux is investigated. Presence of low mass such as H2 or N2, shows a considerable reduction in total flux and in average energy. For example, Xe^+ ion flux at 5 keV are recorded as 425 ± 42 ions/cm^2.eV.pulse at 157 cm and reduced to 125 ± 12 ions/cm^2.eV.pulse when using the low mass into the system at same energy. It is also noticed that such a combination leads to decrease in sputtering without changing the EUV output. Study of the possible mechanism supporting the experimental results is numerically calculated. This computational work indicates that the observed high energies of ions are probably resulting from coulomb explosion initiated by pinch instability. It is postulated that the electrons leave first setting up an electrostatic potential which accelerates the ions. The addition of small mass actually screens the potential and decorates the ions.

Investigation of ionized metal flux in enhanced high power impulse magnetron sputtering discharges

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

Stranak, Vitezslav, E-mail: stranak@prf.jcu.cz; Hubicka, Zdenek; Cada, Martin

2014-04-21

The metal ionized flux fraction and production of double charged metal ions Me{sup 2+} of different materials (Al, Cu, Fe, Ti) by High Power Impulse Magnetron Sputtering (HiPIMS) operated with and without a pre-ionization assistance is compared in the paper. The Electron Cyclotron Wave Resonance (ECWR) discharge was employed as the pre-ionization agent providing a seed of charge in the idle time of HiPIMS pulses. A modified grid-free biased quartz crystal microbalance was used to estimate the metal ionized flux fraction ξ. The energy-resolved mass spectrometry served as a complementary method to distinguish particular ion contributions to the total ionizedmore » flux onto the substrate. The ratio between densities of doubly Me{sup 2+} and singly Me{sup +} charged metal ions was determined. It is shown that ECWR assistance enhances Me{sup 2+} production with respect of absorbed rf-power. The ECWR discharge also increases the metal ionized flux fraction of about 30% especially in the region of lower pressures. Further, the suppression of the gas rarefaction effect due to enhanced secondary electron emission of Me{sup 2+} was observed.« less

Ion energy distributions in silane-hydrogen plasmas

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

Hamers, E.A.G.; Sark, W.G.J.H.M. van; Bezemer, J.

1996-12-31

For the first time ion energy distributions (IED) of different ions from silane-hydrogen (SiH{sub 4}-H{sub 2}) RF plasmas are presented, i.e., the distributions of SiH{sub 3}{sup +}, SiH{sub 2}{sup +} and Si{sub 2}H{sub 4}{sup +}. The energy distributions of SiH{sub 3}{sup +} and SiH{sub 2}{sup +} ions show peaks, which are caused by a charge exchange process in the sheath. A method is presented by which the net charge density in the sheath is determined from the plasma potential and the energy positions of the charge exchange peaks. Knowing the net charge density in the sheath and the plasma potential,more » the sheath thickness can be determined and an estimation of the absolute ion fluxes can be made. The flux of ions can, at maximum, account for 10% of the observed deposition rate.« less

Induction of antioxidant enzyme activity and lipid peroxidation level in ion-beam-bombarded rice seeds

NASA Astrophysics Data System (ADS)

Semsang, Nuananong; Yu, LiangDeng

2013-07-01

Low-energy ion beam bombardment has been used to mutate a wide variety of plant species. To explore the indirect effects of low-energy ion beam on biological damage due to the free radical production in plant cells, the increase in antioxidant enzyme activities and lipid peroxidation level was investigated in ion-bombarded rice seeds. Local rice seeds were bombarded with nitrogen or argon ion beams at energies of 29-60 keV and ion fluences of 1 × 1016 ions cm-2. The activities of the antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione S-transferase (GST) and lipid peroxidation level were assayed in the germinated rice seeds after ion bombardment. The results showed most of the enzyme activities and lipid peroxidation levels in both the argon and nitrogen bombarded samples were higher than those in the natural control. N-ion bombardment could induce higher levels of antioxidant enzyme activities in the rice samples than the Ar-ion bombardment. Additional effects due to the vacuum condition were found to affect activities of some antioxidant enzymes and lipid peroxidation level. This study demonstrates that ion beam bombardment and vacuum condition could induce the antioxidant enzyme activity and lipid peroxidation level which might be due to free radical production in the bombarded rice seeds.

Activated graphene as a cathode material for Li-ion hybrid supercapacitors.

PubMed

Stoller, Meryl D; Murali, Shanthi; Quarles, Neil; Zhu, Yanwu; Potts, Jeffrey R; Zhu, Xianjun; Ha, Hyung-Wook; Ruoff, Rodney S

2012-03-14

Chemically activated graphene ('activated microwave expanded graphite oxide', a-MEGO) was used as a cathode material for Li-ion hybrid supercapacitors. The performance of a-MEGO was first verified with Li-ion electrolyte in a symmetrical supercapacitor cell. Hybrid supercapacitors were then constructed with a-MEGO as the cathode and with either graphite or Li(4)Ti(5)O(12) (LTO) for the anode materials. The results show that the activated graphene material works well in a symmetrical cell with the Li-ion electrolyte with specific capacitances as high as 182 F g(-1). In a full a-MEGO/graphite hybrid cell, specific capacitances as high as 266 F g(-1) for the active materials at operating potentials of 4 V yielded gravimetric energy densities for a packaged cell of 53.2 W h kg(-1).

Model for Cumulative Solar Heavy Ion Energy and LET Spectra

NASA Technical Reports Server (NTRS)

Xapsos, Mike; Barth, Janet; Stauffer, Craig; Jordan, Tom; Mewaldt, Richard

2007-01-01

A probabilistic model of cumulative solar heavy ion energy and lineary energy transfer (LET) spectra is developed for spacecraft design applications. Spectra are given as a function of confidence level, mission time period during solar maximum and shielding thickness. It is shown that long-term solar heavy ion fluxes exceed galactic cosmic ray fluxes during solar maximum for shielding levels of interest. Cumulative solar heavy ion fluences should therefore be accounted for in single event effects rate calculations and in the planning of space missions.

A high flux source of swift oxygen atoms

NASA Technical Reports Server (NTRS)

Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

1987-01-01

A source of swift oxygen atoms is described which has several unique features. A high current ion beam is produced by a microwave discharge, accelerated to 10 keV and the mass selected by a modified Du Pont 21-110 mass spectrometer. The O(+) beam exciting the mass spectrometer is focused into a rectangular shape with an energy spread of less than 1 eV. The next section of the machine decelerates the ion beam into a counterpropagating electron beam in order to minimize space charge effects. After deceleration, the ion beam intersects at 90 deg, a neutral oxygen atom beam, which via resonant charge exchange produces a mixture of O(+) and O. Any remaining O(+) are swept out of the beam by an electric field and differentially pumped away while the desired O beam, collimated by slits, impinges on the target. In situ monitoring of the target surface is done by X-ray photoelectron or Auger spectroscopy. Faraday cups provide flux measurements in the ion sections while the neutral flux is determined by a special torsion balance or by a quadrupole mass spectrometer specially adapted for swift atoms. While the vacuum from the source through the mass spectrometer is maintained by diffusion pumps, the rest of the machine is UHV.

Ring Current He Ion Control by Bounce Resonant ULF Waves

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Gerrard, Andrew J.; Lanzerotti, Louis J.; Soto-Chavez, Rualdo; Cohen, Ross J.; Manweiler, Jerry W.

2017-12-01

Ring current energy He ion (˜65 keV to ˜520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (˜9 h) of the spacecraft and is observed to be ˜50-100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of tens of seconds. These periods correspond to the bounce resonant timescales of the ring current He ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately 2 years) shows that the wave and He ion flux variations are generally anticorrelated, suggesting the bounce resonant pitch angle scattering process as a major component in the scattering of He ions.

Ion Selectivity in the KcsA Potassium Channel from the Perspective of the Ion Binding Site

PubMed Central

Dixit, Purushottam D.; Merchant, Safir; Asthagiri, D.

2009-01-01

To understand the thermodynamic exclusion of Na+ relative to K+ from the S2 site of the selectivity filter, the distribution PX(ɛ) (X = K+ or Na+) of the binding energy (ɛ) of the ion with the channel is analyzed using the potential distribution theorem. By expressing the excess chemical potential of the ion as a sum of mean-field 〈ɛ〉 and fluctuation μexflux,X contributions, we find that selectivity arises from a higher value of μflux,Na+ex relative to μflux,K+ex. To understand the role of site-site interactions on μexflux,X, we decompose PX(ɛ) into n-dependent distributions, where n is the number of ion-coordinating ligands within a distance λ from the ion. For λ comparable to typical ion-oxygen bond distances, investigations building on this multistate model reveal an inverse correlation between favorable ion-site and site-site interactions: the ion-coordination states that most influence the thermodynamics of the ion are also those for which the binding site is energetically less strained and vice versa. This correlation motivates understanding entropic effects in ion binding to the site and leads to the finding that μexflux,X is directly proportional to the average site-site interaction energy, a quantity that is sensitive to the chemical type of the ligand coordinating the ion. Increasing the coordination number around Na+ only partially accounts for the observed magnitude of selectivity; acknowledging the chemical type of the ion-coordinating ligand is essential. PMID:19289040

Production of High Energy Ions Near an Ion Thruster Discharge Hollow Cathode

NASA Technical Reports Server (NTRS)

Katz, Ira; Mikellides, I. G.; Goebel, D. M.; Jameson, K. K.; Wirz, R.; Polk, James E.

2006-01-01

Several researchers have measured ions leaving ion thruster discharge chambers with energies far greater than measured discharge chamber potentials. Presented in this paper is a new mechanism for the generation of high energy ions and a comparison with measured ion spectra. The source of high energy ions has been a puzzle because they not only have energies in excess of measured steady state potentials, but as reported by Goebel et. al. [1], their flux is independent of the amplitude of time dependent plasma fluctuations. The mechanism relies on the charge exchange neutralization of xenon ions accelerated radially into the potential trough in front of the discharge cathode. Previous researchers [2] have identified the importance of charge exchange in this region as a mechanism for protecting discharge cathode surfaces from ion bombardment. This paper is the first to identify how charge exchange in this region can lead to ion energy enhancement.

Novel KCNQ2 channel activators discovered using fluorescence-based and automated patch-clamp-based high-throughput screening techniques

PubMed Central

Yue, Jin-feng; Qiao, Guan-hua; Liu, Ni; Nan, Fa-jun; Gao, Zhao-bing

2016-01-01

Aim: To establish an improved, high-throughput screening techniques for identifying novel KCNQ2 channel activators. Methods: KCNQ2 channels were stably expressed in CHO cells (KCNQ2 cells). Thallium flux assay was used for primary screening, and 384-well automated patch-clamp IonWorks Barracuda was used for hit validation. Two validated activators were characterized using a conventional patch-clamp recording technique. Results: From a collection of 80 000 compounds, the primary screening revealed a total of 565 compounds that potentiated the fluorescence signals in thallium flux assay by more than 150%. When the 565 hits were examined in IonWorks Barracuda, 38 compounds significantly enhanced the outward currents recorded in KCNQ2 cells, and were confirmed as KCNQ2 activators. In the conventional patch-clamp recordings, two validated activators ZG1732 and ZG2083 enhanced KCNQ2 currents with EC50 values of 1.04±0.18 μmol/L and 1.37±0.06 μmol/L, respectively. Conclusion: The combination of thallium flux assay and IonWorks Barracuda assay is an efficient high-throughput screening (HTS) route for discovering KCNQ2 activators. PMID:26725738

Application of an online ion-chromatography-based instrument for gradient flux measurements of speciated nitrogen and sulfur

NASA Astrophysics Data System (ADS)

Rumsey, Ian C.; Walker, John T.

2016-06-01

The dry component of total nitrogen and sulfur atmospheric deposition remains uncertain. The lack of measurements of sufficient chemical speciation and temporal extent make it difficult to develop accurate mass budgets and sufficient process level detail is not available to improve current air-surface exchange models. Over the past decade, significant advances have been made in the development of continuous air sampling measurement techniques, resulting with instruments of sufficient sensitivity and temporal resolution to directly quantify air-surface exchange of nitrogen and sulfur compounds. However, their applicability is generally restricted to only one or a few of the compounds within the deposition budget. Here, the performance of the Monitor for AeRosols and GAses in ambient air (MARGA 2S), a commercially available online ion-chromatography-based analyzer is characterized for the first time as applied for air-surface exchange measurements of HNO3, NH3, NH4+, NO3-, SO2 and SO42-. Analytical accuracy and precision are assessed under field conditions. Chemical concentrations gradient precision are determined at the same sampling site. Flux uncertainty measured by the aerodynamic gradient method is determined for a representative 3-week period in fall 2012 over a grass field. Analytical precision and chemical concentration gradient precision were found to compare favorably in comparison to previous studies. During the 3-week period, percentages of hourly chemical concentration gradients greater than the corresponding chemical concentration gradient detection limit were 86, 42, 82, 73, 74 and 69 % for NH3, NH4+, HNO3, NO3-, SO2 and SO42-, respectively. As expected, percentages were lowest for aerosol species, owing to their relatively low deposition velocities and correspondingly smaller gradients relative to gas phase species. Relative hourly median flux uncertainties were 31, 121, 42, 43, 67 and 56 % for NH3, NH4+, HNO3, NO3-, SO2 and SO42-, respectively. Flux

Solution Dependence of the Collisional Activation of Ubiquitin [M+7H]7+ Ions

PubMed Central

Shi, Huilin; Atlasevich, Natalya; Merenbloom, Samuel I.; Clemmer, David E.

2014-01-01

The solution dependence of gas-phase unfolding for ubiquitin [M+7H]7+ ions has been studied by ion mobility spectrometry-mass spectrometry (IMS-MS). Different acidic water:methanol solutions are used to favor the native (N), more helical (A), or unfolded (U) solution states of ubiquitin. Unfolding of gas-phase ubiquitin ions is achieved by collisional heating and newly formed structures are examined by IMS. With an activation voltage of 100 V, a selected distribution of compact structures unfolds, forming three resolvable elongated states (E1-E3). The relative populations of these elongated structures depend strongly on the solution composition. Activation of compact ions from aqueous solutions known to favor N-state ubiquitin produces mostly the E1 type elongated state, whereas, activation of compact ions from methanol containing solutions that populate A-state ubiquitin favors the E3 elongated state. Presumably, this difference arises because of differences in precursor ion structures emerging from solution. Thus, it appears that information about solution populations can be retained after ionization, selection, and activation to produce the elongated states. These data as well as others are discussed. PMID:24658799

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.

Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δψ and ΔpH.

PubMed

Davis, Geoffry A; Rutherford, A William; Kramer, David M

2017-09-26

There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the 'energy-dependent' form of non-photochemical quenching ( q E ), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δ ψ ) induce photosystem II recombination reactions that produce damaging singlet oxygen ( 1 O 2 ). Both q E and FRIP are directly linked to the thylakoid proton motive force ( pmf ), and in particular, the slow kinetics of partitioning pmf into its ΔpH and Δ ψ components. Using a series of computational simulations, we explored the possibility of 'hacking' pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δ ψ and formation of ΔpH. This would result in increased rates for the formation and decay of q E while resulting in a more rapid decline in the amplitudes of Δ ψ -spikes and decreasing 1 O 2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP : NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo , while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the programme available, we hope to enable the community of photosynthesis

Magnetic flux transport of decaying active regions and enhanced magnetic network. [of solar supergranulation

NASA Technical Reports Server (NTRS)

Wang, Haimin; Zirin, Harold; Ai, Guoxiang

1991-01-01

Several series of coordinated observations on decaying active regions and enhanced magnetic network regions on the sun were carried out jointly at Big Bear Solar Observatory and at the Huairou Solar Observing Station of the Bejing Astronomical Observatory in China. The magnetic field evolution in several regions was followed closely for three to seven days. The magnetic flux transport from the remnants of decayed active regions was studied, along with the evolution and lifetime of the magnetic network which defines the boundaries of supergranules. The magnetic flux transport in an enhanced network region was studied in detail and found to be negative. Also briefly described are some properties of moving magnetic features around a sunspot. Results of all of the above studies are presented.

Trapping Mode Dipolar DC Collisional Activation in the RF-Only Ion Guide of a Linear Ion Trap/Time-of-Flight Instrument for Gaseous Bio-Ion Declustering

PubMed Central

Webb, Ian K.; Gao, Yang; Londry, Frank A.; McLuckey, Scott A.

2013-01-01

The application of dipolar DC (DDC) to the RF-only ion guide (Q0) of a hybrid quadrupole/time-of-flight (QqTOF) mass spectrometer for collision-induced declustering of large bio-ions is described. As a broadband technique, ion trap DDC collision activation (CA) is employed to decluster ions simultaneously over a relatively broad mass-to-charge range. Declustering DDC CA can yield significantly narrower peaks relative to those observed in the absence of declustering methods, depending upon the extent of non-covalent adduction associated with the ions, and can also be used in conjunction with other methods, such as nozzle-skimmer collisional activation. The key experimental variables in the DDC experiment are the dipolar DC voltage (VDDC), VRF, and the time over which VDDC is applied. The VDDC/VRF ratio is key to the extent to which ion temperatures are elevated and also influences the upper mass-to-charge limit for ion storage. The VDDC/VRF ratio affects ion temperatures and upper m/z limit in opposing directions. That is, as the ratio increases, ion temperature increases whereas the upper m/z storage limit decreases. However, for a given VDDC/VRF ratio, the upper m/z storage limit can be increased by increasing VRF, at the expense of the lower m/z limit for ion storage. The key value of the approach is that it affords a relatively precise degree of control over ion temperatures as well as the time over which they are elevated to the higher temperature. The utility of the method is illustrated by the application of ion trap DDC CA in Q0 to oligonucleotide, protein, and multimeric protein complex analyte ions. PMID:24078247

Ion beam activation for materials analysis: Methods and application

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

Conlon, T.W.

1981-04-01

A number of ion beam methods for materials analysis have been developed using Harwell's high voltage accelerators and these are currently being exploited for applications 'in house' and in industry. Ion beam activation is a relatively new area which has exhibited exceptional growth over the last few years. Activation by ion beams to produce a single dominant radioisotope as a surface label (thin layer activation or TLA) is becoming a mature technology offering ever increasing sensitivity for surface loss measurement (currently better than 0.1 ..mu..m or 10/sup -7/ cm/sup 3/ depending on the method of measurement) and remote monitoring ofmore » inaccessible components during studies of wear/erosion/ corrosion/sputtering and the like. With the increasingly established credibility of the method has come the realisation that: (i) more complex and even multiple activation profiles can be used to extract more information on the characteristics of the surface loss process, (ii) that an analogous method can be used even on radiation sensitive materials through the newly established indirect recoil implantation process. (iii) that there is scope for treatment of truly immovable objects through the implantation of fission fragments, (iv) there is vast potential in the area of activation analysis. The current state of development of these methods which greatly extend the scope of conventional TLA will be briefly reviewed. Current applications of these and TLA in industry are discussed.« less

Selective electrodiffusion of zinc ions in a Zrt-, Irt-like protein, ZIPB

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

Lin, W.; Fu, D.; Chai, J.

2010-12-10

All living cells need zinc ions to support cell growth. Zrt-, Irt-like proteins (ZIPs) represent a major route for entry of zinc ions into cells, but how ZIPs promote zinc uptake has been unclear. Here we report the molecular characterization of ZIPB from Bordetella bronchiseptica, the first ZIP homolog to be purified and functionally reconstituted into proteoliposomes. Zinc flux through ZIPB was found to be nonsaturable and electrogenic, yielding membrane potentials as predicted by the Nernst equation. Conversely, membrane potentials drove zinc fluxes with a linear voltage-flux relationship. Direct measurements of metal uptake by inductively coupled plasma mass spectroscopy demonstratedmore » that ZIPB is selective for two group 12 transition metal ions, Zn{sup 2+} and Cd{sup 2+}, whereas rejecting transition metal ions in groups 7 through 11. Our results provide the molecular basis for cellular zinc acquisition by a zinc-selective channel that exploits in vivo zinc concentration gradients to move zinc ions into the cytoplasm.« less

Logical regulation of the enzyme-like activity of gold nanoparticles by using heavy metal ions.

PubMed

Lien, Chia-Wen; Chen, Ying-Chieh; Chang, Huan-Tsung; Huang, Chih-Ching

2013-09-07

In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag(+), Bi(3+), Pb(2+), Pt(4+), and Hg(2+)), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag(+), Bi(3+), or Pb(2+) ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag(+)/Hg(2+) and Hg(2+)/Bi(3+) ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations-OR, AND, INHIBIT, and XOR logic gates-through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg(2+) and/or Bi(3+) ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg(2+)/Bi(3+) as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt(4+) and Hg(2+) as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb(2+) and Hg(2+) ions for the Au NPs allowed us to develop an INHIBIT logic gate-using Pb(2+) and Hg(2+) as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag(+) and Bi(3+) enabled us to construct an XOR logic gate.

Contact Activation of Blood Plasma and Factor XII by Ion-exchange Resins

PubMed Central

Yeh, Chyi-Huey Josh; Dimachkie, Ziad O.; Golas, Avantika; Cheng, Alice; Parhi, Purnendu; Vogler, Erwin A.

2011-01-01

Sepharose ion-exchange particles bearing strong Lewis acid/base functional groups (sulfopropyl, carboxymethyl, quarternary ammonium, dimethyl aminoethyl, and iminodiacetic acid) exhibiting high plasma protein adsorbent capacities are shown to be more efficient activators of blood factor XII in neat-buffer solution than either hydrophilic clean-glass particles or hydrophobic octyl sepharose particles ( FXII→surfaceactivatorFXIIa; a.k.a autoactivation, where FXII is the zymogen and FXIIa is a procoagulant protease). In sharp contrast to the clean-glass standard of comparison, ion-exchange activators are shown to be inefficient activators of blood plasma coagulation. These contrasting activation properties are proposed to be due to the moderating effect of plasma-protein adsorption on plasma coagulation. Efficient adsorption of blood plasma proteins unrelated to the coagulation cascade impedes FXII contacts with ion-exchange particles immersed in plasma, reducing autoactivation, and causing sluggish plasma coagulation. By contrast, plasma proteins do not adsorb to hydrophilic clean glass and efficient autoactivation leads directly to efficient activation of plasma coagulation. It is also shown that competitive-protein adsorption can displace FXIIa adsorbed to the surface of ion-exchange resins. As a consequence of highly-efficient autoactivation and FXIIa displacement by plasma proteins, ion-exchange particles are slightly more efficient activators of plasma coagulation than hydrophobic octyl sepharose particles that do not bear strong Lewis acid/base surface functionalities but to which plasma proteins adsorb efficiently. Plasma proteins thus play a dual role in moderating contact activation of the plasma coagulation cascade. The principal role is impeding FXII contact with activating surfaces but this same effect can displace FXIIa from an activating surface into solution where the protease can potentiate subsequent steps of the plasma coagulation cascade. PMID

Observations of Poynting fluxes, ion temperatures and neutral densities during the March 2015 magnetic storm

NASA Astrophysics Data System (ADS)

Huang, Y.; Su, Y. J.; Huang, C. Y.; Hairston, M. R.; Sutton, E. K.

2015-12-01

We will present various observations regarding the geomagnetic energy input and the response of Ionosphere-Thermosphere (IT) system during the March 17, 2015 storm, the largest one in solar cycle 24. The Poynting fluxes measured by Defense Meteorological Satellite Program (DMSP) satellites (F16, F17 and F18) show significant enhancements in the auroral oval and at high latitudes poleward of the auroral oval. Moreover, the ion temperatures observed by DMSP satellites (F16, F17 and F19) at magnetic latitudes greater than 80° are higher than those in the auroral oval, and the their averaged increases are 316K in the northern hemisphere and 248 K in the southern hemisphere, respectively. In addition, the neutral density residuals measured by the Gravity Recovery and Climate Experiment (GRACE) satellite indicate the largest values at the highest orbital latitudes. The wave-like perturbations originating at high latitudes move equatorward with decreasing amplitudes along GRACE orbits, implying a source region for Traveling Atmospheric Disturbances (TADs) at polar latitudes.

ION PRODUCING MECHANISM

DOEpatents

Lawrence, E.O.

1958-09-16

Improvements are presented in calutron devices and, more specifically, dealswith an improved mounting arrangement fer the ion source of the calutron. An important feature of the invention resides in a pluraiity of insulators so mounted as to be accessible from the exterior of the calutron tank and supporting at their inner ends the ion source. These insutators are arranged in mutually parallel relation and also parallel to the flux of the nmgnetic field, whereby the strain of the supporting elements is reduced to a minimum. In addition the support assembly is secured to a removable wall portion of the task to facilitate withdrawal and examination of the ion producing mechanism.

Poultry litter-based activated carbon for removing heavy metal ions in water.

PubMed

Guo, Mingxin; Qiu, Guannan; Song, Weiping

2010-02-01

Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu2+, 945 mmol of Pb2+, 236 mmol of Zn2+, and 250-300 mmol of Cd2+ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.

Effects of Cr2O3 Activating Flux on the Plasma Plume in Pulsed Laser Welding

NASA Astrophysics Data System (ADS)

Yi, Luo; Yunfei, Du; Xiaojian, Xie; Rui, Wan; Liang, Zhu; Jingtao, Han

2016-11-01

The effects of Cr2O3 activating flux on pulsed YAG laser welding of stainless steel and, particularly, on the behavior of the plasma plume in the welding process were investigated. According to the acoustic emission (AE) signals detected in the welding process, the possible mechanism for the improvement in penetration depth was discussed. The results indicated that the AE signals detected in the welding process reflected the behavior of the plasma plume as pulsed laser energy affecting the molten pool. The root-mean-square (RMS) waveform, AE count, and power spectrum of AE signals were three effective means to characterize the behavior of the plasma plume, which indicated the characteristics of energy released by the plasma plume. The activating flux affected by the laser beam helped to increase the duration and intensity of energy released by the plasma plume, which improved the recoil force and thermal effect transferred from the plasma plume to the molten pool. These results were the main mechanism for Cr2O3 activating flux addition improving the penetration depth in pulsed YAG laser welding.

Minimum activation martensitic alloys for surface disposal after exposure to neutron flux

DOEpatents

Lechtenberg, Thomas

1985-01-01

Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

Hydrodynamic description of an unmagnetized plasma with multiple ion species. II. Two and three ion species plasmas

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

Simakov, Andrei N., E-mail: simakov@lanl.gov; Molvig, Kim

2016-03-15

Paper I [A. N. Simakov and K. Molvig, Phys. Plasmas 23, 032115 (2016)] obtained a fluid description for an unmagnetized collisional plasma with multiple ion species. To evaluate collisional plasma transport fluxes, required for such a description, two linear systems of equations need to be solved to obtain corresponding transport coefficients. In general, this should be done numerically. Herein, the general formalism is used to obtain analytical expressions for such fluxes for several specific cases of interest: a deuterium-tritium plasma; a plasma containing two ion species with strongly disparate masses, which agrees with previously obtained results; and a three ionmore » species plasma made of deuterium, tritium, and gold. These results can be used for understanding the behavior of the aforementioned plasmas, or for verifying a code implementation of the general multi-ion formalism.« less

Multispacecraft study of shock-flux rope interaction

NASA Astrophysics Data System (ADS)

Blanco-Cano, Xochitl; Burgess, David; Sundberg, Torbjorn; Kajdic, Primoz

2017-04-01

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections. These shocks can accelerate particles near the Sun and through the heliosphere, being associated to solar energetic particle (SEP) and energetic storm particle (ESP) events. IP shocks can interact with structures in the solar wind, and with planetary magnetospheres. In this study we show how the properties of an IP shock change when it interacts with a medium scale flux rope (FR) like structure. We use data measurements from CLUSTER, WIND and ACE. These three spacecraft observed the shock-FR interaction at different stages of its evolution. We find that the shock-FR interaction locally changes the shock geometry, affecting ion injection processes, and the upstream and downstream regions. While WIND and ACE observed a quasi-perpendicular shock, CLUSTER crossed a quasi-parallel shock and a foreshock with a variety of ion distributions. The complexity of the ion foreshock can be explained by the dynamics of the shock transitioning from quasi-perpendicular to quasi-parallel, and the geometry of the magnetic field around the flux rope. Interactions such as the one we discuss can occur often along the extended IP shock fronts, and hence their importance towards a better understanding of shock acceleration.

Clustering of Emerging Flux

NASA Technical Reports Server (NTRS)

Ruzmaikin, A.

1997-01-01

Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

A Self-Consistent Model of the Interacting Ring Current Ions with Electromagnetic ICWs

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

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 bound kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of ring current ions and ion cyclotron waves in a quasilinear approach. These two equations were solved on a global scale under non steady-state conditions during the May 2-5, 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the wave active zones at three time cuts around initial, main, and late recovery phases of the May 4, 1998 storm phase are presented and discussed in detail. Comparisons of the model wave-ion data with the Polar/HYDRA and Polar/MFE instruments results are presented..

Parasitic momentum flux in the tokamak core

DOE PAGES

Stoltzfus-Dueck, T.

2017-03-06

A geometrical correction to the E × B drift causes an outward flux of co-current momentum whenever electrostatic potential energy is transferred to ion parallel flows. The robust, fully nonlinear symmetry breaking follows from the free-energy flow in phase space and does not depend on any assumed linear eigenmode structure. The resulting rotation peaking is counter-current and scales as temperature over plasma current. Lastly, this peaking mechanism can only act when fluctuations are low-frequency enough to excite ion parallel flows, which may explain some recent experimental observations related to rotation reversals.

Meteoric Magnesium Ions in the Martian Atmosphere

NASA Technical Reports Server (NTRS)

Pesnell, William Dean; Grebowsky, Joseph

1999-01-01

From a thorough modeling of the altitude profile of meteoritic ionization in the Martian atmosphere we deduce that a persistent layer of magnesium ions should exist around an altitude of 70 km. Based on current estimates of the meteoroid mass flux density, a peak ion density of about 10(exp 4) ions/cm is predicted. Allowing for the uncertainties in all of the model parameters, this value is probably within an order of magnitude of the correct density. Of these parameters, the peak density is most sensitive to the meteoroid mass flux density which directly determines the ablated line density into a source function for Mg. Unlike the terrestrial case, where the metallic ion production is dominated by charge-exchange of the deposited neutral Mg with the ambient ions, Mg+ in the Martian atmosphere is produced predominantly by photoionization. The low ultraviolet absorption of the Martian atmosphere makes Mars an excellent laboratory in which to study meteoric ablation. Resonance lines not seen in the spectra of terrestrial meteors may be visible to a surface observatory in the Martian highlands.

Effects of Stopping Ions and LET Fluctuations on Soft Error Rate Prediction.

DOE PAGES

Weeden-Wright, S. L.; King, Michael Patrick; Hooten, N. C.; ...

2015-02-01

Variability in energy deposition from stopping ions and LET fluctuations is quantified for specific radiation environments. When compared to predictions using average LET via CREME96, LET fluctuations lead to an order-of-magnitude difference in effective flux and a nearly 4x decrease in predicted soft error rate (SER) in an example calculation performed on a commercial 65 nm SRAM. The large LET fluctuations reported here will be even greater for the smaller sensitive volumes that are characteristic of highly scaled technologies. End-of-range effects of stopping ions do not lead to significant inaccuracies in radiation environments with low solar activity unless the sensitivevolumemore » thickness is 100 μm or greater. In contrast, end-of-range effects for stopping ions lead to significant inaccuracies for sensitive- volume thicknesses less than 10 μm in radiation environments with high solar activity.« less

Cold Ion Escape from the Martian Ionosphere - 2005-2014

NASA Astrophysics Data System (ADS)

Fränz, Markus; Dubinin, Eduard; Andrews, David; Nilsson, Hans; Fedorov, Andrei

2015-04-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. The ion sensor IMA of this experiment has in principle a low-energy cut-off at 10eV but in negative spacecraft charging cold ions are lifted into the range of measurement but the field of view is restricted to about 4x360 deg. In a recent paper Nilsson et al. (Earth Planets Space, 64, 135, 2012) tried to use the method of long-time averaged distribution functions to overcome these constraints. In this paper we first use the same method to show that we get results consistent with this when using ASPERA-3 observations only. But then we can show that these results are inconsistent with observations of the local plasma density by the MARSIS radar instrument on board Mars Express. We demonstrate that the method of averaged distribution function can deliver the mean flow speed of the plasma but the low-energy cut-off does usually not allow to reconstruct the density. We then combine measurements of the cold ion flow speed with the plasma density observations of MARSIS to derive the cold ion flux. In an analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 RM the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. To derive the mean escape flux we include all combined observations of ASPERA-3 and MARSIS from 2005 to 2014. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fränz, Markus; Dubinin, Eduard; Andrews, David; Nilsson, Hans; Fedorov, Andrei

2014-05-01

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. The ion sensor IMA of this experiment has in principle a low-energy cut-off at 10eV but in negative spacecraft charging cold ions are lifted into the range of measurement but the field of view is restricted to about 4x360 deg. In a recent paper Nilsson et al. (Earth Planets Space, 64, 135, 2012) tried to use the method of long-time averaged distribution functions to overcome these constraints. In this paper we first use the same method to show that we get results consistent with this when using ASPERA-3 observations only. But then we can show that these results are inconsistent with observations of the local plasma density by the MARSIS radar instrument on board Mars Express. We demonstrate that the method of averaged distribution function can deliver the mean flow speed of the plasma but the low-energy cut-off does usually not allow to reconstruct the density. We then combine measurements of the cold ion flow speed with the plasma density observations of MARSIS to derive the cold ion flux. In an analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 Martian radii the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones.

PubMed

Lammer, Helmut; Lichtenegger, Herbert I M; Kulikov, Yuri N; Griessmeier, Jean-Mathias; Terada, N; Erkaev, Nikolai V; Biernat, Helfried K; Khodachenko, Maxim L; Ribas, Ignasi; Penz, Thomas; Selsis, Franck

2007-02-01

Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances fluxes, atmospheres with CO2/N2 mixing ratios lower than 96% will show an increase in exospheric temperatures and expanded thermosphere-exosphere environments. Hence, they suffer stronger atmospheric erosion, which can result in the total loss of several hundred bars even if an exoplanet is protected by a "magnetic shield" with its boundary located at 1 Earth radius above the surface. Furthermore, our study indicates that magnetic moments of tidally locked Earth-like exoplanets are essential for protecting their expanded upper atmospheres because of intense XUV radiation against CME plasma erosion. Therefore, we suggest that larger and more massive terrestrial-type exoplanets may better protect their

Real-time diamagnetic flux measurements on ASDEX Upgrade.

PubMed

Giannone, L; Geiger, B; Bilato, R; Maraschek, M; Odstrčil, T; Fischer, R; Fuchs, J C; McCarthy, P J; Mertens, V; Schuhbeck, K H

2016-05-01

Real-time diamagnetic flux measurements are now available on ASDEX Upgrade. In contrast to the majority of diamagnetic flux measurements on other tokamaks, no analog summation of signals is necessary for measuring the change in toroidal flux or for removing contributions arising from unwanted coupling to the plasma and poloidal field coil currents. To achieve the highest possible sensitivity, the diamagnetic measurement and compensation coil integrators are triggered shortly before plasma initiation when the toroidal field coil current is close to its maximum. In this way, the integration time can be chosen to measure only the small changes in flux due to the presence of plasma. Two identical plasma discharges with positive and negative magnetic field have shown that the alignment error with respect to the plasma current is negligible. The measured diamagnetic flux is compared to that predicted by TRANSP simulations. The poloidal beta inferred from the diamagnetic flux measurement is compared to the values calculated from magnetic equilibrium reconstruction codes. The diamagnetic flux measurement and TRANSP simulation can be used together to estimate the coupled power in discharges with dominant ion cyclotron resonance heating.

Flux of high-LET cosmic-ray particles in manned space flight

NASA Technical Reports Server (NTRS)

Benton, E. V.; Henke, R. P.; Peterson, D. D.; Bailey, J. V.; Tobias, C. A.

1975-01-01

On the Apollo and Skylab missions the high-energy heavy ion (HZE) flux was measured by means of plastic nuclear track detectors. Measurements involved the fluxes of high linear energy transfer (LET), particles with Z between 6 and 26 incident on astronauts and on several biological experiments. Partial results of these measurements are presented; the effects of shielding and solar modulation are discussed.-

A Kinetic-MHD Theory for the Self-Consistent Energy Exchange Between Energetic Particles and Active Small-scale Flux Ropes

NASA Astrophysics Data System (ADS)

le Roux, J. A.

2017-12-01

We developed previously a focused transport kinetic theory formalism with Fokker-plank coefficients (and its Parker transport limit) to model large-scale energetic particle transport and acceleration in solar wind regions with multiple contracting and merging small-scale flux ropes on MHD (inertial) scales (Zank et al. 2014; le Roux et al. 2015). The theory unifies the main acceleration mechanisms identified in particle simulations for particles temporarily trapped in such active flux rope structures, such as acceleration by the parallel electric field in reconnection regions between merging flux ropes, curvature drift acceleration in incompressible/compressible contracting and merging flux ropes, and betatron acceleration (e.g., Dahlin et al 2016). Initial analytical solutions of the Parker transport equation in the test particle limit showed that the energetic particle pressure from efficient flux-rope energization can potentially be high in turbulent solar wind regions containing active flux-rope structures. This requires taking into account the back reaction of energetic particles on flux ropes to more accurately determine the efficiency of energetic particles acceleration by small-scale flux ropes. To accomplish this goal we developed recently an extension of the kinetic theory to a kinetic-MHD level. We will present the extended theory showing the focused transport equation to be coupled to a solar wind MHD transport equation for small-scale flux-rope energy density extracted from a recently published nearly incompressible theory for solar wind MHD turbulence with a plasma beta of 1 (Zank et al. 2017). In the flux-rope transport equation appears new expressions for the damping/growth rates of flux-rope energy derived from assuming energy conservation in the interaction between energetic particles and small-scale flux ropes for all the main flux-rope acceleration mechanisms, whereas previous expressions for average particle acceleration rates have been

YANA – a software tool for analyzing flux modes, gene-expression and enzyme activities

PubMed Central

Schwarz, Roland; Musch, Patrick; von Kamp, Axel; Engels, Bernd; Schirmer, Heiner; Schuster, Stefan; Dandekar, Thomas

2005-01-01

Background A number of algorithms for steady state analysis of metabolic networks have been developed over the years. Of these, Elementary Mode Analysis (EMA) has proven especially useful. Despite its low user-friendliness, METATOOL as a reliable high-performance implementation of the algorithm has been the instrument of choice up to now. As reported here, the analysis of metabolic networks has been improved by an editor and analyzer of metabolic flux modes. Analysis routines for expression levels and the most central, well connected metabolites and their metabolic connections are of particular interest. Results YANA features a platform-independent, dedicated toolbox for metabolic networks with a graphical user interface to calculate (integrating METATOOL), edit (including support for the SBML format), visualize, centralize, and compare elementary flux modes. Further, YANA calculates expected flux distributions for a given Elementary Mode (EM) activity pattern and vice versa. Moreover, a dissection algorithm, a centralization algorithm, and an average diameter routine can be used to simplify and analyze complex networks. Proteomics or gene expression data give a rough indication of some individual enzyme activities, whereas the complete flux distribution in the network is often not known. As such data are noisy, YANA features a fast evolutionary algorithm (EA) for the prediction of EM activities with minimum error, including alerts for inconsistent experimental data. We offer the possibility to include further known constraints (e.g. growth constraints) in the EA calculation process. The redox metabolism around glutathione reductase serves as an illustration example. All software and documentation are available for download at . Conclusion A graphical toolbox and an editor for METATOOL as well as a series of additional routines for metabolic network analyses constitute a new user-friendly software for such efforts. PMID:15929789

Void structure of O+ ions in the inner magnetosphere observed by the Van Allen Probes

NASA Astrophysics Data System (ADS)

Nakayama, Y.; Ebihara, Y.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Tanaka, T.

2016-12-01

The Van Allen Probes Helium Oxygen Proton Electron instrument observed a new type of enhancement of O+ ions in the inner magnetosphere during substorms. As the satellite moved outward in the premidnight sector, the flux of the O+ ions with energy 10 keV appeared first in the energy-time spectrograms. Then, the enhancement of the flux spread toward high and low energies. The enhanced flux of the O+ ions with the highest energy remained, whereas the flux of the ions with lower energy vanished near apogee, forming what we call the void structure. The structure cannot be found in the H+ spectrogram. We studied the generation mechanism of this structure by using numerical simulation. We traced the trajectories of O+ ions in the electric and magnetic fields from the global magnetohydrodynamics simulation and calculated the flux of O+ ions in the inner magnetosphere in accordance with the Liouville theorem. The simulated spectrograms are well consistent with the ones observed by Van Allen Probes. We suggest the following processes. (1) When magnetic reconnection starts, an intensive equatorward and tailward plasma flow appears in the plasma lobe. (2) The flow transports plasma from the lobe to the plasma sheet where the radius of curvature of the magnetic field line is small. (3) The intensive dawn-dusk electric field transports the O+ ions earthward and accelerates them nonadiabatically to an energy threshold; (4) the void structure appears at energies below the threshold.

Scalable loading of a two-dimensional trapped-ion array

PubMed Central

Bruzewicz, Colin D.; McConnell, Robert; Chiaverini, John; Sage, Jeremy M.

2016-01-01

Two-dimensional arrays of trapped-ion qubits are attractive platforms for scalable quantum information processing. Sufficiently rapid reloading capable of sustaining a large array, however, remains a significant challenge. Here with the use of a continuous flux of pre-cooled neutral atoms from a remotely located source, we achieve fast loading of a single ion per site while maintaining long trap lifetimes and without disturbing the coherence of an ion quantum bit in an adjacent site. This demonstration satisfies all major criteria necessary for loading and reloading extensive two-dimensional arrays, as will be required for large-scale quantum information processing. Moreover, the already high loading rate can be increased by loading ions in parallel with only a concomitant increase in photo-ionization laser power and no need for additional atomic flux. PMID:27677357

Electrochemical activation and inhibition of neuromuscular systems through modulation of ion concentrations with ion-selective membranes

NASA Astrophysics Data System (ADS)

Song, Yong-Ak; Melik, Rohat; Rabie, Amr N.; Ibrahim, Ahmed M. S.; Moses, David; Tan, Ara; Han, Jongyoon; Lin, Samuel J.

2011-12-01

Conventional functional electrical stimulation aims to restore functional motor activity of patients with disabilities resulting from spinal cord injury or neurological disorders. However, intervention with functional electrical stimulation in neurological diseases lacks an effective implantable method that suppresses unwanted nerve signals. We have developed an electrochemical method to activate and inhibit a nerve by electrically modulating ion concentrations in situ along the nerve. Using ion-selective membranes to achieve different excitability states of the nerve, we observe either a reduction of the electrical threshold for stimulation by up to approximately 40%, or voluntary, reversible inhibition of nerve signal propagation. This low-threshold electrochemical stimulation method is applicable in current implantable neuroprosthetic devices, whereas the on-demand nerve-blocking mechanism could offer effective clinical intervention in disease states caused by uncontrolled nerve activation, such as epilepsy and chronic pain syndromes.

Ion Mediated Nucleation: how is it Influenced by Changes in the Solar Activity?

NASA Astrophysics Data System (ADS)

D'Auria, R.; Turco, R. P.

2003-12-01

Recently it has been pointed out that tropospheric cloudiness can be correlated with the galactic cosmic rays (GCRs) intensity [Svensmark and Friis-Christensen, 1997]. A possible explanation for such a correlation relies on the fact that GCRs are the main ionization source in the upper troposphere, hence, throughout ionic mediated nucleation, they could possibly influence the global cloud condensation nuclei (CCN) formation [e.g., Yu, 2001; Dickinson, 1975]. Because the GCRs are modulated by the interaction between the solar wind and the Earth's magnetosphere and their intensity generally decreases with increasing solar activity, subtle changes in the solar activity could indirectly affect the Earth's climate. We have been studying the very first steps of ionic nucleation considering the molecular species of atmospheric interest (e.g.,water, nitric acid, sulfuric acid, ammonia etc.). In our approach the formation and evolution of ionic clusters is followed by resolving the time dependent kinetic aggregation process and considering the ions sources (ultimately the atmospheric ionization of neutral species) and sinks. We show how in typical atmospheric conditions stable populations of molecular ions forms. The novelty of our work consists in the determination of the kinetic parameters that govern the molecular ions growth (i.e., the forward and reverse clustering reaction constants for each cluster type and size) at a microscopic level. In fact a thermochemistry data base is built for the species of interest by integrating laboratory measurements, quantum mechanical calculations and, when appropriate, results from the macroscopic liquid droplet model [Thomson, 1928]. Such database is than used to retrieve the reverse clustering reaction coefficients for the molecular ion type and size and for the environmental conditions (pressure and temperature) of interest. The forward reaction is instead determined by calculating the ionic-neutral collisional rate or is assumed

Integration between Glycolysis and Glutamate-Glutamine Cycle Flux May Explain Preferential Glycolytic Increase during Brain Activation, Requiring Glutamate

PubMed Central

Hertz, Leif; Chen, Ye

2017-01-01

The 1988 observation by Fox et al. (1988) that brief intense brain activation increases glycolysis (pyruvate formation from glucose) much more than oxidative metabolism has been abundantly confirmed. Specifically glycolytic increase was unexpected because the amount of ATP it generates is much smaller than that formed by subsequent oxidative metabolism of pyruvate. The present article shows that preferential glycolysis can be explained by metabolic processes associated with activation of the glutamate-glutamine cycle. The flux in this cycle, which is essential for production of transmitter glutamate and GABA, equals 75% of brain glucose utilization and each turn is associated with utilization of ~1 glucose molecule. About one half of the association between cycle flux and glucose metabolism occurs during neuronal conversion of glutamine to glutamate in a process similar to the malate-aspartate shuttle (MAS) except that glutamate is supplied from glutamine, not formed from α-ketoglutarate (αKG) as during operation of conventional MAS. Regular MAS function is triggered by one oxidative process in the cytosol during glycolysis causing NAD+ reduction to NADH. Since NADH cannot cross the mitochondrial membrane (MEM) for oxidation NAD+ is re-generated by conversion of cytosolic oxaloacetate (OAA) to malate, which enters the mitochondria for oxidation and in a cyclic process regenerates cytosolic OAA. Therefore MAS as well as the “pseudo-MAS” necessary for neuronal glutamate formation can only operate together with cytosolic reduction of NAD+ to NADH. The major process causing NAD+ reduction is glycolysis which therefore also must occur during neuronal conversion of glutamine to glutamate and may energize vesicular glutamate uptake which preferentially uses glycolytically derived energy. Another major contributor to the association between glutamate-glutamine cycle and glucose utilization is the need for astrocytic pyruvate to generate glutamate. Although some

AMPK activation protects cells from oxidative stress-induced senescence via autophagic flux restoration and intracellular NAD(+) elevation.

PubMed

Han, Xiaojuan; Tai, Haoran; Wang, Xiaobo; Wang, Zhe; Zhou, Jiao; Wei, Xiawei; Ding, Yi; Gong, Hui; Mo, Chunfen; Zhang, Jie; Qin, Jianqiong; Ma, Yuanji; Huang, Ning; Xiang, Rong; Xiao, Hengyi

2016-06-01

AMPK activation is beneficial for cellular homeostasis and senescence prevention. However, the molecular events involved in AMPK activation are not well defined. In this study, we addressed the mechanism underlying the protective effect of AMPK on oxidative stress-induced senescence. The results showed that AMPK was inactivated in senescent cells. However, pharmacological activation of AMPK by metformin and berberine significantly prevented the development of senescence and, accordingly, inhibition of AMPK by Compound C was accelerated. Importantly, AMPK activation prevented hydrogen peroxide-induced impairment of the autophagic flux in senescent cells, evidenced by the decreased p62 degradation, GFP-RFP-LC3 cancellation, and activity of lysosomal hydrolases. We also found that AMPK activation restored the NAD(+) levels in the senescent cells via a mechanism involving mostly the salvage pathway for NAD(+) synthesis. In addition, the mechanistic relationship of autophagic flux and NAD(+) synthesis and the involvement of mTOR and Sirt1 activities were assessed. In summary, our results suggest that AMPK prevents oxidative stress-induced senescence by improving autophagic flux and NAD(+) homeostasis. This study provides a new insight for exploring the mechanisms of aging, autophagy and NAD(+) homeostasis, and it is also valuable in the development of innovative strategies to combat aging. © 2016 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

NADPH Oxidase Activation Contributes to Heavy Ion Irradiation–Induced Cell Death

PubMed Central

Wang, Yupei; Liu, Qing; Zhao, Weiping; Zhou, Xin; Miao, Guoying; Sun, Chao

2017-01-01

Increased oxidative stress plays an important role in heavy ion radiation–induced cell death. The mechanism involved in the generation of elevated reactive oxygen species (ROS) is not fully illustrated. Here we show that NADPH oxidase activation is closely related to heavy ion radiation–induced cell death via excessive ROS generation. Cell death and cellular ROS can be greatly reduced in irradiated cancer cells with the preincubation of diphenyleneiodium, an inhibitor of NADPH oxidase. Most of the NADPH oxidase (NOX) family proteins (NOX1, NOX2, NOX3, NOX4, and NOX5) showed increased expression after heavy ion irradiation. Meanwhile, the cytoplasmic subunit p47phox was translocated to the cell membrane and localized with NOX2 to form reactive NADPH oxidase. Our data suggest for the first time that ROS generation, as mediated by NADPH oxidase activation, could be an important contributor to heavy ion irradiation–induced cell death. PMID:28473742

Relevance of Viroporin Ion Channel Activity on Viral Replication and Pathogenesis

PubMed Central

Nieto-Torres, Jose L.; Verdiá-Báguena, Carmina; Castaño-Rodriguez, Carlos; Aguilella, Vicente M.; Enjuanes, Luis

2015-01-01

Modification of host-cell ionic content is a significant issue for viruses, as several viral proteins displaying ion channel activity, named viroporins, have been identified. Viroporins interact with different cellular membranes and self-assemble forming ion conductive pores. In general, these channels display mild ion selectivity, and, eventually, membrane lipids play key structural and functional roles in the pore. Viroporins stimulate virus production through different mechanisms, and ion channel conductivity has been proved particularly relevant in several cases. Key stages of the viral cycle such as virus uncoating, transport and maturation are ion-influenced processes in many viral species. Besides boosting virus propagation, viroporins have also been associated with pathogenesis. Linking pathogenesis either to the ion conductivity or to other functions of viroporins has been elusive for a long time. This article summarizes novel pathways leading to disease stimulated by viroporin ion conduction, such as inflammasome driven immunopathology. PMID:26151305

Momentum flux parasitic to free-energy transfer

DOE PAGES

Stoltzfus-Dueck, T.; Scott, B.

2017-05-11

An often-neglected portion of the radialmore » $$\\boldsymbol{E}\\times \\boldsymbol{B}$$ drift is shown to drive an outward flux of co-current momentum when free energy is transferred from the electrostatic potential to ion parallel flows. This symmetry breaking is fully nonlinear, not quasilinear, necessitated simply by free-energy balance in parameter regimes for which significant energy is dissipated via ion parallel flows. The resulting rotation peaking is counter-current and has a scaling and order of magnitude that are comparable with experimental observations. Finally, the residual stress becomes inactive when frequencies are much higher than the ion transit frequency, which may explain the observed relation of density peaking and counter-current rotation peaking in the core.« less

Characteristics of the spatial structure of Martian magnetic flux ropes recovered by the Grad-Shafranov reconstruction technique

NASA Astrophysics Data System (ADS)

Hara, T.; Seki, K.; Hasegawa, H.; Brain, D. A.; Matsunaga, K.; Saito, M. H.

2013-12-01

Mars is a unique planet because it locally possesses strong crustal magnetic fields mainly located in the southern hemisphere [e.g., Acuna et al., 1999]. The Martian electromagnetic environment can thus become highly complicated and variable, since the interplanetary magnetic field embedded in the solar wind interacts with the Martian crustal magnetic fields. Whereas it is known that the Martian upper atmosphere is escaping to interplanetary space due to the interaction with the solar wind [e.g., Lundin et al., 1989; Barabash et al., 2007], the contribution of crustal magnetic fields to atmospheric escape from Mars has not yet been well understood. Flux ropes are characteristic magnetic field structures seen throughout the solar system, e.g., at the Sun, in the interplanetary space, and at the terrestrial magnetosphere. Flux ropes are also observed at planets such as at Venus and Mars [e.g., Russell and Elphic, 1979; Vignes et al., 2004], which do not possess a global intrinsic magnetic field. Brain et al. [2010] found a large-scale isolated magnetic flux rope filled with Martian atmospheric plasma located downstream from the crustal magnetic fields with respect to the solar wind flow based on the Mars Global Surveyor (MGS) measurements. They suggested that the magnetic flux rope could be intermittently detached from Mars, and remove significant amounts of atmosphere away from Mars. They proposed that this process might occur frequently and account for as much as 10% of the total present-day ion escape from Mars. However, this estimation of the ion escape rate is somewhat ambiguous, because it is difficult to infer the spatial structure of them from the single spacecraft data. We here investigated characteristics of the Martian magnetic flux ropes based on the Grad-Shafranov (GS) reconstruction technique using the MGS magnetic field data. This technique is capable of recovering the two-dimensional spatial structure of the magnetic flux ropes from single spacecraft

A Long Decay of X-Ray Flux and Spectral Evolution in the Supersoft Active Galactic Nucleus GSN 069

NASA Astrophysics Data System (ADS)

Shu, X. W.; Wang, S. S.; Dou, L. M.; Jiang, N.; Wang, J. X.; Wang, T. G.

2018-04-01

GSN 069 is an optically identified very low-mass active galactic nuclei (AGN) that shows supersoft X-ray emission. The source is known to exhibit a huge X-ray outburst, with flux increased by more than a factor of ∼240 compared to the quiescence state. We report its long-term evolution in the X-ray flux and spectral variations over a timescale of ∼decade, using both new and archival X-ray observations from the XMM-Newton and Swift. The new Swift observations detected the source in its lowest level of X-ray activity since the outburst, a factor of ∼4 lower in the 0.2–2 keV flux than that obtained with the XMM-Newton observations nearly eight years ago. Combining with the historical X-ray measurements, we find that the X-ray flux is decreasing slowly. There seemed to be spectral softening associated with the drop of X-ray flux. In addition, we find evidence for the presence of a weak, variable, hard X-ray component, in addition to the dominant thermal blackbody emission reported before. The long decay of X-ray flux and spectral evolution, as well as the supersoft X-ray spectra, suggest that the source could be a tidal disruption event (TDE), though a highly variable AGN cannot be fully ruled out. Further continued X-ray monitoring would be required to test the TDE interpretation, by better determining the flux evolution in the decay phase.

Multi-species analysis of ion distributions at Mars

NASA Astrophysics Data System (ADS)

Curry, S.; Liemohn, M. W.; Fang, X.; Ma, Y.; Johnson, B.; Bougher, S. W.; Dong, C.

2012-12-01

This study focuses on using the Mars Test Particle simulation to compare observations with virtual detections of O+, O2+, CO2+, and H+ in an orbital configuration in the Mars space environment. These planetary pick-up ions are formed when the solar wind directly interacts with the neutral atmosphere, causing the ions to be accelerated by the background convective electric field. The subsequent mass loading and ion escape are still the subject of great interest, specifically with respect to which species dominates ion loss from Mars. Modeling efforts and observations have found different results; some conclude that O+ is the most dominant escaping ion while others conclude that O2+ has the larger total loss rate. Furthermore, mass loss might actually favor CO2+ because of its tri-atomic structure. To address this unresolved issue, this study will present velocity space distributions for different species and discuss fluxes and escape rates using different modeling parameters. The simulation will also illustrate individual particle traces, which reveal the origin and trajectories of the different ion species. Finally, results from different solar conditions will be presented with respect to ion fluxes and energies as well as overall escape in order to robustly describe the physical processes controlling planetary ion distributions and atmospheric escape.

Guanine-based amphiphiles: synthesis, ion transport properties and biological activity.

PubMed

Musumeci, Domenica; Irace, Carlo; Santamaria, Rita; Milano, Domenico; Tecilla, Paolo; Montesarchio, Daniela

2015-03-01

Novel amphiphilic guanine derivatives, here named Gua1 and Gua2, have been prepared through few, simple and efficient synthetic steps. In ion transport experiments through phospholipid bilayers, carried out to evaluate their ability to mediate H(+) transport, Gua2 showed high activity. When this compound was investigated for ion-selective transport activities, no major differences were observed in the behaviour with cations while, in the case of anions, selective activity was observed in the series I(-)>Br(-)>Cl(-)>F(-). The bioactivity of these guanine analogues has been evaluated on a panel of human tumour and non-tumour cell lines in preliminary in vitro cytotoxicity assays, showing a relevant antiproliferative profile for Gua2. Copyright © 2014 Elsevier Ltd. All rights reserved.

Flux of high-LET cosmic-ray particles in manned space flight.

PubMed

Benton, E V; Henke, R P; Peterson, D D; Bailey, J V; Tobias, C A

1975-01-01

On the Apollo and Skylab missions the high energy heavy ion (HZE) flux was measured by means of plastic nuclear track detectors. Measurements involve the fluxes of high linear energy transfer (LET), 6 < or approximately Z < or approximately 26 particles incident on astronauts and on several biological experiments. Partial results of these measurements are presented; the effects of shielding and solar modulation are discussed.

Analysis of the ion sources of the Martian dayside magnetosphere based on MAVEN measurements

NASA Astrophysics Data System (ADS)

Ermakov, V.; Zelenyi, L. M.; Vaisberg, O. L.; Shuvalov, S. D.; Znobishchev, A.; Dubinin, E.

2017-12-01

The dayside Martian magnetosphere formed from the solar wind magnetic flux tubes is a thin region between ionosheath and Martian ionosphere. The Martian magnetosphere is originated as solar wind magnetic flux tubes decelerate in front of Mars due to mass-loading and pile-up forming in most cases magnetic barrier. Then magnetic flux tubes, mass-loaded by atmospheric photoions, convect around Mars and form magnetotail. This region is predominantly filled with heavy atmospheric ions with energies intermediate between solar wind protons and ionospheric ions energies. There are several possibilities for filling this region with atmospheric heavy ions. We made an attempt to identify the most important sources of ions in Martian magnetosphere analyzing a number of crossings of Martian magnetosphere at terminator region by MAVEN spacecraft. Ion measurements during MAVEN passage of Martian magnetosphere at terminator region were used in order to calculate neutrals altitude profiles for different ion species, using assumption that these flux tubes accumulate photoions during the drift within magnetosphere. Some of calculated neutral profiles are in a satisfactory agreement with neutral profiles measured by NGIMS. This supports the mass-loading by photoions as the main process responsible for filling Martian magnetosphere with heavy ions. We wish to thank J.McFadden and J.Conerney for the opportunity to use ion and magnetic field measurements data from STATIC and MAG instruments, respectively. This work was supported by Russian Science Foundation (grant #16-42-01103).

V-ATPase proton pumping activity is required for adult zebrafish appendage regeneration.

PubMed

Monteiro, Joana; Aires, Rita; Becker, Jörg D; Jacinto, António; Certal, Ana C; Rodríguez-León, Joaquín

2014-01-01

The activity of ion channels and transporters generates ion-specific fluxes that encode electrical and/or chemical signals with biological significance. Even though it is long known that some of those signals are crucial for regeneration, only in recent years the corresponding molecular sources started to be identified using mainly invertebrate or larval vertebrate models. We used adult zebrafish caudal fin as a model to investigate which and how ion transporters affect regeneration in an adult vertebrate model. Through the combined use of biophysical and molecular approaches, we show that V-ATPase activity contributes to a regeneration-specific H+ ef`flux. The onset and intensity of both V-ATPase expression and H+ efflux correlate with the different regeneration rate along the proximal-distal axis. Moreover, we show that V-ATPase inhibition impairs regeneration in adult vertebrate. Notably, the activity of this H+ pump is necessary for aldh1a2 and mkp3 expression, blastema cell proliferation and fin innervation. To the best of our knowledge, this is the first report on the role of V-ATPase during adult vertebrate regeneration.

V-ATPase Proton Pumping Activity Is Required for Adult Zebrafish Appendage Regeneration

PubMed Central

Monteiro, Joana; Aires, Rita; Becker, Jörg D.; Jacinto, António; Certal, Ana C.; Rodríguez-León, Joaquín

2014-01-01

The activity of ion channels and transporters generates ion-specific fluxes that encode electrical and/or chemical signals with biological significance. Even though it is long known that some of those signals are crucial for regeneration, only in recent years the corresponding molecular sources started to be identified using mainly invertebrate or larval vertebrate models. We used adult zebrafish caudal fin as a model to investigate which and how ion transporters affect regeneration in an adult vertebrate model. Through the combined use of biophysical and molecular approaches, we show that V-ATPase activity contributes to a regeneration-specific H+ ef`flux. The onset and intensity of both V-ATPase expression and H+ efflux correlate with the different regeneration rate along the proximal-distal axis. Moreover, we show that V-ATPase inhibition impairs regeneration in adult vertebrate. Notably, the activity of this H+ pump is necessary for aldh1a2 and mkp3 expression, blastema cell proliferation and fin innervation. To the best of our knowledge, this is the first report on the role of V-ATPase during adult vertebrate regeneration. PMID:24671205

ARCS 3 ionospheric artificial argon ion beam injections - Waves near the heavy ion gyrofrequencies

NASA Technical Reports Server (NTRS)

Erlandson, R. E.; Cahill, L. J., Jr.; Kaufmann, R. L.; Arnoldy, R. L.; Pollock, C. J.

1989-01-01

Low-frequency electric field data below the proton gyrofrequency are presented for the duration of the argon ion beam experiment conducted as part of the Argon Release for Controlled Studies (ARCS) program. An argon ion beam was injected from the subpayload antiparallel or perpendicular to the magnetic field at altitudes from 250 to 405 km. During the injections, the wave spectra were broadband near the subpayload and narrow-band near heavy ion gyrofrequencies at perpendicular separation distances between 42 and 254 m. It is suggested that the narrow-band waves are associated with both the perpendicular argon ion beam and an unexpected flux of low-energy ions which peaked in energy near 15 eV and pitch angle near 90 deg with respect to the magnetic field.

Observations of low-energy ions with Arase/LEPi

NASA Astrophysics Data System (ADS)

Yoshizumi, M.; Asamura, K.; Kazama, Y.; Yokota, S.; Kasahara, S.

2017-12-01

LEPi is one of the instruments onboard Arase, which is an energy-mass spectrometer designed to measure ions with energies from 0.01keV/q up to 25keV/q. In order to discriminate species of incoming ions, LEPi uses a TOF (Time-Of-Flight) technique. TOF also works as a noise rejector, which is useful for rejection of background noise due to high energy particles in the inner magnetosphere. LEPi has passed the initial checkout phase after launch, and now under regular observations. Since the regular observation started (end of March, 2017), Arase encountered several magnetic storms driven by CIR and CMEs. LEPi observed sudden flux enhancement and subsequent gradual decay of low-energy ( 10eV/q) ions around L=4 associated with the magnetic storms. In some cases, these flux modulations coinside with eclipse (absent of Sun light on the spacecraft), but others do not. Spacecraft potential decreases when the spacecraft gets eclipse. Therefore, a part of ions whose enegies are lower than energy range of LEPi are accelerated and appeared in the range. These fluxes might reflect transportation / energization of cold component in the inner magnetosphere. We will present current LEPi operations and initial scientific results.

Adaptable and adaptive materials for light flux control

NASA Astrophysics Data System (ADS)

Sixou, Pierre; Magnaldo, A.; Nourry, J.; Laye, C.

1996-04-01

The purpose of this paper is to describe and examine properties of light flux control materials. Indeed, intelligent light flux control is necessary not only to improve everyday visual convenience but also in an economical point of view in order to reduce global home energetic cost. Several types of materials are good potential candidates for such functions: (1) The most well-known investigations concern inorganic materials such as tungsten or molybdenum oxides in which an electrochrom layer darkens when enriched in ions, and looses its color when impoverished. Unfortunately, at the moment, there is no convenient way to realize correct ions suppliers. Moreover, other drawbacks arise, such as poor reversibility, reactive interferences or a sensitivity of the material to its environment. These systems only need a low voltage level to work. But, their dynamic response, which is correlated to the component surface, is quite long. (2) At the present time, another attractive issue seems promising. More and more studies concern micro-composite liquid crystal films. For first, we shall remind their principles as well as their way of preparation. After having talked about their main advantages as intelligent materials, we shall discuss their control, their light flux adaptability, or their memory capabilities.

Measurements of plasma sheath heat flux in the Alcator C-Mod divertor

NASA Astrophysics Data System (ADS)

Brunner, Dan; Labombard, Brian; Terry, Jim; Reinke, Matt

2010-11-01

Heat flux is one of the most important parameters controlling the lifetime of first-wall components in fusion experiments and reactors. The sheath heat flux coefficient (γ) is a parameter relating heat flux (from a plasma to a material surface) to the electron temperature and ion saturation current. Being such a simple expression for a kinetic process, it is of great interest to plasma edge fluid modelers. Under the assumptions of equal ion and electron temperatures, no secondary electron emission, and no net current to the surface the value of γ is approximately 7 [1]. Alcator C-Mod provides a unique opportunity among today's experiments to measure reactor-relevant heat fluxes (100's of MW/m^2 parallel to the magnetic field) in reactor-like divertor geometry. Motivated by the DoE 2010 joint milestone to measure heat flux footprints, the lower outer divertor of Alcator has been instrumented with a suite of Langmuir probes, novel surface thermocouples, and calorimeters in tiles purposefully ramped to eliminate shadowing; all within view of an IR camera. Initial results indicate that the experimentally inferred values of γ are found to agree with simple theory in the sheath limited regime and diverges to lower values as the density increases.

LADEE/LDEX observations of lunar pickup ion distribution and variability

NASA Astrophysics Data System (ADS)

Poppe, A. R.; Halekas, J. S.; Szalay, J. R.; Horányi, M.; Levin, Z.; Kempf, S.

2016-04-01

We report fortuitous observations of low-energy lunar pickup ion fluxes near the Moon while in the solar wind by the Lunar Dust Experiment (LDEX) on board the Lunar Atmosphere and Dust Environment Explorer (LADEE). We describe the method of observation and the empirical calibration of the instrument for ion observations. LDEX observes several trends in the exospheric ion production rate, including a scale height of approximately 100 km, a positive, linear correlation with solar wind flux, and evidence of a slight enhancement near 7-8 h local time. We compare the LDEX observations to both LADEE Neutral Mass Spectrometer ion mode observations and theoretical models. The LDEX data are best fit by total exospheric ion production rates of ≈6 × 103 m-3 s-1 with dominant contributions from Al+, CO+, and Ar+, although the LDEX data suggest that the aluminum neutral density and corresponding ion production rate are lower than predicted by recent models.

Adaptation of a 3-D Quadrupole Ion Trap for Dipolar DC Collisional Activation

PubMed Central

Prentice, Boone M.; Santini, Robert E.; McLuckey, Scott A.

2011-01-01

Means to allow for the application of a dipolar DC pulse to the end-cap electrodes of a three-dimensional (3-D) quadrupole ion trap for as short as a millisecond to as long as hundreds of milliseconds are described. The implementation of dipolar DC does not compromise the ability to apply AC waveforms to the end-cap electrodes at other times in the experiment. Dipolar DC provides a nonresonant means for ion acceleration by displacing ions from the center of the ion trap where they experience stronger rf electric fields, which increases the extent of micro-motion. The evolution of the product ion spectrum to higher generation products with time, as shown using protonated leucine enkephalin as a model protonated peptide, illustrates the broad-band nature of the activation. Dipolar DC activation is also shown to be effective as an ion heating approach in mimicking high amplitude short time excitation (HASTE)/pulsed Q dissociation (PQD) resonance excitation experiments that are intended to enhance the likelihood for observing low m/z products in ion trap tandem mass spectrometry. PMID:21953251

Influence of spokes on the ionized metal flux fraction in chromium high power impulse magnetron sputtering

NASA Astrophysics Data System (ADS)

Biskup, B.; Maszl, C.; Breilmann, W.; Held, J.; Böke, M.; Benedikt, J.; von Keudell, A.

2018-03-01

High power impulse magnetron sputtering (HiPIMS) discharges are an excellent tool for deposition of thin films with superior properties. By adjusting the plasma parameters, an energetic metal and reactive species growth flux can be controlled. This control requires, however, a quantitative knowledge of the ion-to-neutral ratio in the growth flux and of the ion energy distribution function to optimize the deposited energy per incorporated atom in the film. This quantification is performed by combining two diagnostics, a quartz crystal microbalance (QCM) combined with an ion-repelling grid system (IReGS) to discriminate ions versus neutrals and a HIDEN EQP plasma monitor to measure the ion energy distribution function (IEDF). This approach yields the ionized metal flux fraction (IMFF) as the ionization degree in the growth flux. This is correlated to the plasma performance recorded by time resolved ICCD camera measurements, which allow to identify the formation of pronounced ionization zones, so called spokes, in the HiPIMS plasma. Thereby an automatic technique was developed to identify the spoke mode number. The data indicates two distinct regimes with respect to spoke formation that occur with increasing peak power, a stochastic regime with no spokes at low peak powers followed by a regime with distinct spokes at varying mode numbers at higher peak powers. The IMFF increases with increasing peak power reaching values of almost 80% at very high peak powers. The transition in between the two regimes coincides with a pronounced change in the IMFF. This change indicates that the formation of spokes apparently counteracts the return effect in HiPIMS. Based on the IMFF and the mean energy of the ions, the energy per deposited atom together with the overall energy flux onto the substrate is calculated. This allows us to determine an optimum for the peak power density around 0.5 kW cm-2 for chromium HiPIMS.

Fe(2+) substrate transport through ferritin protein cage ion channels influences enzyme activity and biomineralization.

PubMed

Behera, Rabindra K; Torres, Rodrigo; Tosha, Takehiko; Bradley, Justin M; Goulding, Celia W; Theil, Elizabeth C

2015-09-01

Ferritins, complex protein nanocages, form internal iron-oxy minerals (Fe2O3·H2O), by moving cytoplasmic Fe(2+) through intracage ion channels to cage-embedded enzyme (2Fe(2+)/O2 oxidoreductase) sites where ferritin biomineralization is initiated. The products of ferritin enzyme activity are diferric oxy complexes that are mineral precursors. Conserved, carboxylate amino acid side chains of D127 from each of three cage subunits project into ferritin ion channels near the interior ion channel exits and, thus, could direct Fe(2+) movement to the internal enzyme sites. Ferritin D127E was designed and analyzed to probe properties of ion channel size and carboxylate crowding near the internal ion channel opening. Glu side chains are chemically equivalent to, but longer by one -CH2 than Asp, side chains. Ferritin D127E assembled into normal protein cages, but diferric peroxo formation (enzyme activity) was not observed, when measured at 650 nm (DFP λ max). The caged biomineral formation, measured at 350 nm in the middle of the broad, nonspecific Fe(3+)-O absorption band, was slower. Structural differences (protein X-ray crystallography), between ion channels in wild type and ferritin D127E, which correlate with the inhibition of ferritin D127E enzyme activity include: (1) narrower interior ion channel openings/pores; (2) increased numbers of ion channel protein-metal binding sites, and (3) a change in ion channel electrostatics due to carboxylate crowding. The contributions of ion channel size and structure to ferritin activity reflect metal ion transport in ion channels are precisely regulated both in ferritin protein nanocages and membranes of living cells.

Fe2+ Substrate Transport through Ferritin Protein Cage Ion Channels Influences Enzyme Activity and Biomineralization

PubMed Central

Behera, Rabindra K.; Torres, Rodrigo; Tosha, Takehiko; Bradley, Justin M.; Goulding, Celia W.; Theil, Elizabeth C.

2015-01-01

Ferritins, complex protein nanocages, form internal iron-oxy minerals (Fe2O3.H2O), by moving cytoplasmic Fe2+ through intracage ion channels to cage-embedded enzyme (2Fe2+/O2 oxidoreductase) sites where ferritin biomineralization is initiated. The products of ferritin enzyme activity are diferric oxy complexes that are mineral precursors. Conserved, carboxylate amino acid side chains of D127 from each of three cage subunits project into ferritin ion channels near the interior ion channel exits and, thus, could direct Fe2+ movement to the internal enzyme sites. Ferritin D127E was designed and analyzed to probe properties of ion channel size and carboxylate crowding near the internal ion channel opening. Glu side chains are chemically equivalent to, but longer by one – CH2 than Asp, side chains. Ferritin D127E assembled into normal protein cages, but diferric peroxo formation (enzyme activity) was not observed, when measured at 650nm (DFP λmax). The caged biomineral formation, measured at 350 nm in the middle of the broad, nonspecific Fe3+-O absorption band, was slower. Structural differences (protein X-ray crystallography), between ion channels in wild type and ferritin D127E, which correlate with the inhibition of ferritin D127E enzyme activity include: 1. narrower interior ion channel openings/pores, 2. increased numbers of ion channel protein-metal binding sites, and 3. a change in ion channel electrostatics due to carboxylate crowding. The contributions of ion channel size and structure to ferritin activity reflect metal ion transport in ion channels are precisely regulated both in ferritin protein nanocages and membranes of living cells. PMID:26202907

Active control of spacecraft potentials at geosynchronous orbit

NASA Technical Reports Server (NTRS)

Goldstein, R.; Deforest, S. E.

1976-01-01

Tests have been conducted concerning the active control of the potentials of the geosynchronous satellites ATS-5 and ATS-6. The ATS-5 tests show that a simple electron emitter can be used to reduce the magnitude of the potential of a spacecraft which has been charged negatively by the environment. The ATS-6 ion thruster had also a pronounced effect on the potential barrier. In this case, the flux of high-energy primary ions and of low-charge exchange ions produces a space-charge neutralization effect which the electron gun alone cannot achieve.

Impairment of neutrophil Fc gamma receptor mediated transmembrane signalling in active rheumatoid arthritis.

PubMed Central

Goulding, N J; Guyre, P M

1992-01-01

Neutrophil Fc gamma receptor (Fc gamma R) signalling responses were compared in healthy subjects, patients with definite rheumatoid arthritis (RA), ankylosing spondylitis, and osteoarthritis. The patients with A were subdivided into those with active synovitis and those with quiescent disease. Basal intracellular calcium ion concentrations in patients with inactive RA were significantly higher than in control subjects, which in turn were greater than in patients with active RA. Transient cytosolic calcium ion fluxes were observed after binding Fc gamma RII or Fc gamma RIII with specific monoclonal antibodies and cross linking with the F(ab')2 fragment of antimouse IgG. Response times were significantly faster for Fc gamma RII than for Fc gamma RIII. Peak concentrations of intracellular calcium ions after neutrophil stimulation were comparable for Fc gamma RII and RIII in healthy subjects. Neutrophils in patients with ankylosing spondylitis and osteoarthritis responded to Fc gamma R triggering, but in the group with active RA fluxes of calcium ions were severely depressed. Neutrophils isolated from patients with RA with quiescent disease showed exaggerated responses when compared with controls. Expression of all three Fc gamma R types on neutrophils from patients with active RA, as measured by monoclonal antibody binding, was comparable with control cells. Impairment of neutrophil Fc gamma R cytosolic signalling in active RA could reflect a receptor signalling defect with potential effects on Fc mediated functions, or a fundamental defect in calcium ion homeostasis within these cells. PMID:1535494

Mechanism of Metal Ion Activation of the Diphtheria Toxin Repressor DtxR

NASA Astrophysics Data System (ADS)

D'Aquino, J. Alejandro; Ringe, Dagmar

2006-08-01

The diphtheria toxin repressor, DtxR, is a metal ion-activated transcriptional regulator that has been linked to the virulence of Corynebacterium diphtheriae. Structure determination has shown that there are two metal ion binding sites per repressor monomer, and site-directed mutagenesis has demonstrated that binding site 2 (primary) is essential for recognition of the target DNA repressor, leaving the role of binding site 1 (ancillary) unclear (1 - 3). Calorimetric techniques have demonstrated that while binding site 1 (ancillary) has high affinity for metal ion with a binding constant of 2 × 10-7, binding site 2 (primary) is a low affinity binding site with a binding constant of 6.3 × 10-4. These two binding sites act independently and their contribution can be easily dissected by traditional mutational analysis. Our results clearly demonstrate that binding site 1 (ancillary) is the first one to be occupied during metal ion activation, playing a critical role in stabilization of the repressor. In addition, structural data obtained for the mutants Ni-DtxR(H79A,C102D), reported here and the previously reported DtxR(H79A) (4) has allowed us to propose a mechanism of metal ion activation for DtxR.

Comparison of lighting activity and inner radiation belt particle fluxes perturbations

NASA Astrophysics Data System (ADS)

Martinez Calderon, C.; Bortnik, J.; Li, W.; Spence, H. E.; Rodger, C. J.

2016-12-01

Lightning discharges are known to inject whistlers into the inner magnetosphere over a wide range of latitudes around their source. When a discharge occurs, it radiates electromagnetic energy, some of which propagates in the whistler-mode wave through the ionospheric plasma travelling away from the Earth. Previous studies have discussed the effects of whistler-induced electron precipitation and radiation belt losses associated with lightning but there has been little research on the long term effects of these precipitation on the inner radiation belts [Rodger et al. (2004), Clilverd et al. (2004)].Here, we use data from the World Wide Lightning Location Network (WWLLN), which has continuously monitored global lightning since 2004, to examine one year of lightning data and locate the L-shells with high lighting activity. We use Van Allen Probes' Energetic Particle, Composition, and Thermal Plasma Suite (ECT) from both satellites (RBSP-A/B) to measure electron fluxes in the inner radiation belt at the L-shells of interest. We compare these fluxes to a globally-integrated count of lightning strikes and investigate the relationship between global lightning occurrence and RBSP electron fluxes. We examine several factors, such as different energy ranges, timescales ranging from a few weeks to the entire year and seasonal changes in order to quantify the loss process driven by lightning in the inner radiation belts.

Numerical simulation of filling a magnetic flux tube with a cold plasma: Anomalous plasma effects

NASA Technical Reports Server (NTRS)

Singh, Nagendra; Leung, W. C.

1995-01-01

Large-scale models of plasmaspheric refilling have revealed that during the early stage of the refilling counterstreaming ion beams are a common feature. However, the instability of such ion beams and its effect on refilling remain unexplored. In order to learn the basic effects of ion beam instabilities on refilling, we have performed numerical simulations of the refilling of an artificial magnetic flux tube. (The shape and size of the tube are assumed so that the essential features of the refilling problem are kept in the simulation and at the same time the small scale processes driven by the ion beams are sufficiently resolved.) We have also studied the effect of commonly found equatorially trapped warm and/or hot plasma on the filling of a flux tube with a cold plasma. Three types of simulation runs have been performed.

"Trunk-like" heavy ion structures observed by the Van Allen Probes

NASA Astrophysics Data System (ADS)

Zhang, J.-C.; Kistler, L. M.; Spence, H. E.; Wolf, R. A.; Reeves, G.; Skoug, R.; Funsten, H.; Larsen, B. A.; Niehof, J. T.; MacDonald, E. A.; Friedel, R.; Ferradas, C. P.; Luo, H.

2015-10-01

Dynamic ion spectral features in the inner magnetosphere are the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. We report "trunk-like" ion structures observed by the Van Allen Probes on 2 November 2012. This new type of ion structure looks like an elephant's trunk on an energy-time spectrogram, with the energy of the peak flux decreasing Earthward. The trunks are present in He+ and O+ ions but not in H+. During the event, ion energies in the He+ trunk, located at L = 3.6-2.6, magnetic local time (MLT) = 9.1-10.5, and magnetic latitude (MLAT) = -2.4-0.09°, vary monotonically from 3.5 to 0.04 keV. The values at the two end points of the O+ trunk are energy = 4.5-0.7 keV, L = 3.6-2.5, MLT = 9.1-10.7, and MLAT = -2.4-0.4°. Results from backward ion drift path tracings indicate that the trunks are likely due to (1) a gap in the nightside ion source or (2) greatly enhanced impulsive electric fields associated with elevated geomagnetic activity. Different ion loss lifetimes cause the trunks to differ among ion species.

Ion-beam-induced bending of semiconductor nanowires.

PubMed

Hanif, Imran; Camara, Osmane; Tunes, Matheus A; Harrison, Robert W; Greaves, Graeme; Donnelly, Stephen E; Hinks, Jonathan A

2018-08-17

The miniaturisation of technology increasingly requires the development of both new structures as well as novel techniques for their manufacture and modification. Semiconductor nanowires (NWs) are a prime example of this and as such have been the subject of intense scientific research for applications ranging from microelectronics to nano-electromechanical devices. Ion irradiation has long been a key processing step for semiconductors and the natural extension of this technique to the modification of semiconductor NWs has led to the discovery of ion beam-induced deformation effects. In this work, transmission electron microscopy with in situ ion bombardment has been used to directly observe the evolution of individual silicon and germanium NWs under irradiation. Silicon NWs were irradiated with either 6 keV neon ions or xenon ions at 5, 7 or 9.5 keV with a flux of 3 × 10 13 ions cm -2 s -1 . Germanium NWs were irradiated with 30 or 70 keV xenon ions with a flux of 10 13 ions cm -2 s -1 . These new results are combined with those reported in the literature in a systematic analysis using a custom implementation of the transport of ions in matter Monte Carlo computer code to facilitate a direct comparison with experimental results taking into account the wide range of experimental conditions. Across the various studies this has revealed underlying trends and forms the basis of a critical review of the various mechanisms which have been proposed to explain the deformation of semiconductor NWs under ion irradiation.

Does historical wildfire activity alter metal fluxes to northern lakes?

NASA Astrophysics Data System (ADS)

Pelletier, N.; Chetelat, J.; Vermaire, J. C.; Palmer, M.; Black, J.; Pellisey, J.; Tracz, B.; van der Wielen, S.

2017-12-01

Current drought conditions in northwestern Canada are conducive to more frequent and severe wildfires that may mobilize mercury and other metals accumulated in soil and biomass. There is evidence that wildfires can remobilize and transport mercury within and outside catchments by atmospheric volatilization, particulate emissions and catchment soil erosion. However, the effect of fires on mercury fluxes to nearby lake sediments remains unclear. In this study, we use a combination of 10 dated lake sediment cores and four nearby ombrotrophic peatland cores to investigate the effects of wildfires on mercury fluxes to lake sediments. Lakes varying in catchment size and distance from recent fire events were sampled. Mercury concentrations in the environmental archives were measured, and macroscopic charcoal particles (>100 um) were counted at high resolution in the sediments to observe the co-variation of the local fire history and mercury fluxes. Mercury flux recorded in ombrotrophic peat cores provided an estimate of the historical atmospheric mercury flux from local and regional atmospheric deposition. The mercury flux recorded in lake sediments corresponds to the sum of direct atmospheric deposition and catchment transport. In combination, these archives will allow for the partitioning of mercury loading attributable to catchment transport from direct atmospheric deposition. After correcting the fluxes for particle focusing and terragenic elements input, flux from different lakes will be compared based on their catchment size and their temporal and spatial proximity known fire events. Altogether, our preliminary results using these paleolimnological methods will provide new insights on mercury transport processes that are predicted to become more important under a changing climate.

Characterization of high flux magnetized helium plasma in SCU-PSI linear device

NASA Astrophysics Data System (ADS)

Xiaochun, MA; Xiaogang, CAO; Lei, HAN; Zhiyan, ZHANG; Jianjun, WEI; Fujun, GOU

2018-02-01

A high-flux linear plasma device in Sichuan University plasma-surface interaction (SCU-PSI) based on a cascaded arc source has been established to simulate the interactions between helium and hydrogen plasma with the plasma-facing components in fusion reactors. In this paper, the helium plasma has been characterized by a double-pin Langmuir probe. The results show that the stable helium plasma beam with a diameter of 26 mm was constrained very well at a magnetic field strength of 0.3 T. The core density and ion flux of helium plasma have a strong dependence on the applied current, magnetic field strength and gas flow rate. It could reach an electron density of 1.2 × 1019 m-3 and helium ion flux of 3.2 × 1022 m-2 s-1, with a gas flow rate of 4 standard liter per minute, magnetic field strength of 0.2 T and input power of 11 kW. With the addition of -80 V applied to the target to increase the helium ion energy and the exposure time of 2 h, the flat top temperature reached about 530 °C. The different sizes of nanostructured fuzz on irradiated tungsten and molybdenum samples surfaces under the bombardment of helium ions were observed by scanning electron microscopy. These results measured in the SCU-PSI linear device provide a reference for International Thermonuclear Experimental Reactor related PSI research.

The interaction of heavy ions from Comet P/Giacobini-Zinner with the solar wind

NASA Astrophysics Data System (ADS)

Sanderson, T. R.; Wenzel, K.-P.; Daly, P.; Cowley, S. W. H.; Hynds, R. J.; Smith, E. J.; Bame, S. J.; Zwickl, R. D.

1986-04-01

The encounter between the ICE spacecraft and Comet P/Giacobini-Zinner was characterized in the solar wind by intense fluxes of heavy ions, measurable over a region 6 x 10 to the 6th km in extent. The ions are observed with highly anisotropic angular distributions, steep energy spectra, and a change in the energy spectrum at around 80 keV, consistent with a composition predominantly of the water group. Flux versus time profiles follow a general fall off with increasing distance from the comet, but with a marked inbound/outbound asymmetry. This asymmetry is due to the higher solar wind velocity on the outbound pass, giving rise to an increased energy gain of the pick-up ions. The flux versus time profiles are strongly modulated by the rapid changes in the direction of interplanetary magnetic field. Correlated observations of energetic ions, the interplanetary magnetic field and the solar wind are presented, and these observations are compared with theoretical predictions of the ion pick-up process.

The effect of ion-pair formation combined with penetration enhancers on the skin permeation of loxoprofen.

PubMed

Hui, Mei; Quan, Peng; Yang, Yingying; Fang, Liang

2016-06-01

Loxoprofen (LOXO) is a non-steroidal anti-inflammatory drug. Repeated oral administrations induce gastrointestinal side effects. Patches are a promising alternative. The aim of this study was to investigate the effects of organic amines on the skin permeation of LOXO and finally design a patch with a comparable permeation profile and pharmacodynamic effects to the commercial LOXONA® plaster. The effects of organic amines were assessed by flux values of LOXO from isopropyl myristate (IPM), using horizontal diffusion cell and rabbit skin. FTIR spectroscopy was used to confirm ion-pair formation. Anti-inflammatory and analgesic activity assessments were performed in the adjuvant arthritis rat model and acetic acid-induced writhing syndrome in mouse, separately. Results showed that triethylamine (TEA) was the most potential candidate in IPM, with the highest flux of 499.75 ± 32.40 µg/cm(2)/h. In patch, the highest flux of 369.37 ± 34.32 µg/cm(2)/h was still obtained by LOXO-TEA. Combined with penetration enhancers, the cumulative amounts were further increased in presence of 5% IPM, which exhibited a flux of 840.04 ± 66.38 µg/cm(2)/h as two times of the commercial one. Ultimately, anti-inflammatory and analgesic activity assessment presented that a comparable pharmacodynamic activity with the commercial one could be obtained by the patch we designed. Additionally, we also found that LOXO patch applied topically exerted a systemic effect, and the effect was dose-dependent. It was feasible for LOXO patch design by combination of ion-pair technology and chemical enhancers.

AmeriFlux Network Data Activities: updates, progress and plans

NASA Astrophysics Data System (ADS)

Yang, B.; Boden, T.; Krassovski, M.; Song, X.

2013-12-01

The Carbon Dioxide Information Analysis Center (CDIAC) at the Oak Ridge National Laboratory serves as the long-term data repository for the AmeriFlux network. Datasets currently available include hourly or half-hourly meteorological and flux observations, biological measurement records, and synthesis data products. In this presentation, we provide an update of this network database including a comprehensive review and evaluation of the biological data from about 70 sites, development of a new product for flux uncertainty estimates, and re-formatting of Level-2 standard files. In 2013, we also provided data support to two synthesis studies --- 2012 drought synthesis and FACE synthesis. Issues related to data quality and solutions in compiling datasets for these synthesis studies will be discussed. We will also present our work plans in developing and producing other high-level products, such as derivation of phenology from the available measurements at flux sites.

Cool seafloor hydrothermal springs reveal global geochemical fluxes

NASA Astrophysics Data System (ADS)

Wheat, C. Geoffrey; Fisher, Andrew T.; McManus, James; Hulme, Samuel M.; Orcutt, Beth N.

2017-10-01

We present geochemical data from the first samples of spring fluids from Dorado Outcrop, a basaltic edifice on 23 M.y. old seafloor of the Cocos Plate, eastern Pacific Ocean. These samples were collected from the discharge of a cool hydrothermal system (CHS) on a ridge flank, where typical reaction temperatures in the volcanic crust are low (2-20 °C) and fluid residence times are short. Ridge-flank hydrothermal systems extract 25% of Earth's lithospheric heat, with a global discharge rate equivalent to that of Earth's river discharge to the ocean; CHSs comprise a significant fraction of this global flow. Upper crustal temperatures around Dorado Outcrop are ∼15 °C, the calculated residence time is <3 y, and the composition of discharging fluids is only slightly altered from bottom seawater. Many of the major ions concentrations in spring fluids are indistinguishable from those of bottom seawater; however, concentrations of Rb, Mo, V, U, Mg, phosphate, Si and Li are different. Applying these observed differences to calculated global CHS fluxes results in chemical fluxes for these ions that are ≥15% of riverine fluxes. Fluxes of K and B also may be significant, but better analytical resolution is required to confirm this result. Spring fluids also have ∼50% less dissolved oxygen (DO) than bottom seawater. Calculations of an analytical model suggest that the loss of DO occurs primarily (>80%) within the upper basaltic crust by biotic and/or abiotic consumption. This calculation demonstrates that permeable pathways within the upper crust can support oxic water-rock interactions for millions of years.

Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

PubMed

Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

2013-05-21

Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column.

Beam current controller for laser ion source

DOEpatents

Okamura, Masahiro

2014-10-28

The present invention relates to the design and use of an ion source with a rapid beam current controller for experimental and medicinal purposes. More particularly, the present invention relates to the design and use of a laser ion source with a magnetic field applied to confine a plasma flux caused by laser ablation.

A new use of high resolution magnetograms. [solar activity and magnetic flux

NASA Technical Reports Server (NTRS)

Baum, P. J.; Bratenahl, A.

1978-01-01

Ground-based solar magnetograms are frequently in error by as much as twenty percent and contribute to the poor correlation between magnetic changes and solar flares. High resolution measurement of the magnetic field component, which is normal to the photosphere and measured at photospheric height, can be used to construct a magnetic flux partition function F. Therefore, dF/dt is an EMF which drives atmospheric currents in reconnecting solar active regions. With a high quality magnetograph, the solar probe can be used to obtain good estimates of F and dF/dt and thereby the energy stored as induced solar atmospheric currents during quiescent interflare periods. Should a flare occur during a favorable observing period, the present method of analysis should show characteristic signatures in F, DF/dt, and especially, in the stored flux computed from dF/dt.

Tailoring molybdenum nanostructure evolution by low-energy He+ ion irradiation

NASA Astrophysics Data System (ADS)

Tripathi, J. K.; Novakowski, T. J.; Hassanein, A.

2015-10-01

Mirror-finished polished molybdenum (Mo) samples were irradiated with 100 eV He+ ions as a function of ion fluence (using a constant flux of 7.2 × 1020 ions m-2 s-1) at normal incidence and at 923 K. Mo surface deterioration and nanoscopic fiber-form filament ("Mo fuzz") growth evolution were monitored by using field emission (FE) scanning electron (SEM) and atomic force (AFM) microscopy studies. Those studies confirm a reasonably clean and flat surface, up to several micrometer scales along with a few mechanical-polishing-induced scratches. However, He+ ion irradiation deteriorates the surface significantly even at 2.1 × 1023 ions m-2 fluence (about 5 min. irradiation time) and leads to evolution of homogeneously populated ∼75-nm-long Mo nanograins having ∼8 nm intergrain width. The primary stages of Mo fuzz growth, i.e., elongated half-cylindrical ∼70 nm nanoplatelets, and encapsulated bubbles of 20-45 nm in diameter and preferably within the grain boundaries of sub-micron-sized grains, were observed after 1.3 × 1024 ions m-2 fluence irradiation. Additionally, a sequential enhancement in the sharpness, density, and protrusions of Mo fuzz at the surface with ion fluence was also observed. Fluence- and flux-dependent studies have also been performed at 1223 K target temperature (beyond the temperature window for Mo fuzz formation). At a constant fluence of 2.6 × 1024 ions m-2, 7.2 × 1020 ions m-2 s-1 flux generates a homogeneous layered and stacked nanodiscs of ∼70 nm diameter. On the other hand, 1.2 × 1021 ions m-2 s-1 flux generates a combination of randomly patched netlike nanomatrix networked structure, mostly with ∼105 nm nanostructure wall width, various-shaped pores, and self-organized nano arrays. While the observed netlike nanomatrix network structures for 8.6 × 1024 ions m-2 fluence (at a constant flux of 1.2 × 1021 ions m-2 s-1) is quite similar to those for 2.6 × 1024 ions m-2 fluence, the nanostructure wall width extends up to ∼45

Hydrogenated amorphous silicon formation by flux control and hydrogen effects on the growth mechanism

NASA Astrophysics Data System (ADS)

Toyoda, H.; Sugai, H.; Kato, K.; Yoshida, A.; Okuda, T.

1986-06-01

The composition of particle flux to deposit hydrogenated amorphous silicon films in a glow discharge is controlled by a combined electrostatic-magnetic deflection technique. As a result, the films are formed firstly without hydrogen ion flux, secondly by neutral flux only, and thirdly by all species fluxes. Comparison of these films reveals the significant role of hydrogen in the surface reactions. Hydrogen breaks the Si-Si bond, decreases the sticking probability of the Si atom, and replaces the SiH bond by a SiH2 bond to increase the hydrogen content of the films.

Impact of seabird activity on nitrous oxide and methane fluxes from High Arctic tundra in Svalbard, Norway

NASA Astrophysics Data System (ADS)

Zhu, Renbin; Chen, Qingqing; Ding, Wei; Xu, Hua

2012-12-01

In this study, tundra N2O and CH4 fluxes were measured from one seabird sanctuary (SBT) and two non-seabird colonies (NST-I and NST-II) in Ny-Ålesund (79°55'N, 11°56'E), Svalbard during the summers of 2008 and 2009. N2O and CH4 fluxes from SBT showed large temporal and spatial variations depending on the intensity of seabird activity. High seabird activity sites showed large N2O and CH4 emissions while low N2O and CH4 emissions, even CH4 uptake occurred at medium and low seabird activity sites. Overall the mean fluxes were 18.3 ± 3.6 μg N2O m-2 h-1 and 53.5 ± 20.3 μg CH4 m-2 h-1 from tundra SBT whereas tundra NST-I and NST-II represented a relatively weak N2O source (8.3 ± 13.2 μg N2O m-2 h-1) and strong CH4 sink (-82.8 ± 22.3 μg CH4 m-2 h-1). Seabird activity was the strongest control of N2O and CH4 fluxes compared with soil temperature and moisture, and high N2O and CH4 emissions were created by soil physical and chemical processes (the sufficient supply of nutrients NH4+-N, NO3--N, total nitrogen, total phosphorus and total carbon from seabird guano, seabird tramp and appropriate water content) related to the seabird activity. Our work suggests that tundra ecosystems impacted by seabird activity are the potential "hotspots" for N2O and CH4 emissions although these sources have been largely neglected at present. Furthermore the combination of seabird activity and warming climate will likely further enhance N2O and CH4 emissions from the High Arctic tundra.

Increasing dust fluxes on the northeastern Tibetan Plateau linked with the Little Ice Age and recent human activity since the 1950s

NASA Astrophysics Data System (ADS)

Wan, Dejun; Jin, Zhangdong; Zhang, Fei; Song, Lei; Yang, Jinsong

2016-12-01

Arid and semi-arid areas in inner Asia contribute lots of mineral dust in the northern hemisphere, but dust flux evolution in the past is poorly constrained. Based on particle sizes and elemental compositions of a sediment core from Lake Qinghai on the northeastern Tibetan Plateau, dust fluxes during ∼1518-2011 A.D. were reconstructed based on 18-100 μm fractions of the lake sediment. The dust fluxes during the past ∼500 years ranged between 100 and 300 g/m2/yr, averaging 202 g/m2/yr, experiencing four stages: Stage 1 (∼1518-1590s), the flux was averaged 165 g/m2/yr, much lower than that in the Stage 2 (1590s-1730s, 254 g/m2/yr); similarly, an average flux of 169 g/m2/yr in the Stage 3 (1730s-1950s) was followed by an increased flux of 259 g/m2/yr in the Stage 4 (1950s-2011). During the first three stages the fluxes were dominated by natural dust activities in arid inner Asia, having a positive relation with wind intensity but a poor correlation with effective moisture (or precipitation) and temperature. The high dust flux in Stage 2 was due to relatively strong wind during the maximum Little Ice Age, whereas the remarkably high flux in 1950s-2011 was resulted from recent increasing human activities in northwestern China. The dust record not only documents past dust fluxes on the northeastern Tibetan Plateau but also reflects evolutions and mechanisms of dust activity/emission in inner Asia during the past ∼500 years.

Energy Deposition and Escape Fluxes Induced by Energetic Solar Wind Ions and ENAs Precipitating into Mars Atmosphere: Accurate Consideration of Energy Transfer Collisions

NASA Astrophysics Data System (ADS)

Kharchenko, V. A.; Lewkow, N.; Gacesa, M.

2014-12-01

Formation and evolution of neutral fluxes of atoms and molecules escaping from the Mars atmosphere have been investigated for the sputtering and photo-chemical mechanisms. Energy and momentum transfer in collisions between the atmospheric gas and fast atoms and molecules have been considered using our recently obtained angular and energy dependent cross sections[1]. We have showed that accurate angular dependent collision cross sections are critical for the description of the energy relaxation of precipitating keV energetic ions/ENAs and for computations of altitude profiles of the fast atom and molecule production rates in recoil collisions. Upward and escape fluxes of the secondary energetic He and O atoms and H2, N2, CO and CO2 molecules, induced by precipitating ENAs, have been determined and their non-thermal energy distribution functions have been computed at different altitudes for different solar conditions. Precipitation and energy deposition of the energetic H2O molecules and products of their dissociations into the Mars atmosphere in the Comet C/2013 A1 (Siding Spring) - Mars interaction have been modeled using accurate cross sections. Reflection of precipitating ENAs by the Mars atmosphere has been analyzed in detail. [1] N. Lewkow and V. Kharchenko, "Precipitation of Energetic Neutral Atoms and Escape Fluxes induced from the Mars Atmosphere, ApJ, v.790, p.98 (2014).

Finger heat flux/temperature as an indicator of thermal imbalance with application for extravehicular activity.

PubMed

Koscheyev, Victor S; Leon, Gloria R; Coca, Aitor

2005-11-01

The designation of a simple, non-invasive, and highly precise method to monitor the thermal status of astronauts is important to enhance safety during extravehicular activities (EVA) and onboard emergencies. Finger temperature (Tfing), finger heat flux, and indices of core temperature (Tc) [rectal (Tre), ear canal (Tec)] were assessed in 3 studies involving different patterns of heat removal/insertion from/to the body by a multi-compartment liquid cooling/warming garment (LCWG). Under both uniform and nonuniform temperature conditions on the body surface, Tfing and finger heat flux were highly correlated with garment heat flux, and also highly correlated with each other. Tc responses did not adequately reflect changes in thermal balance during the ongoing process of heat insertion/removal from the body. Overall, Tfing/finger heat flux adequately reflected the initial destabilization of thermal balance, and therefore appears to have significant potential as a useful index for monitoring and maintaining thermal balance and comfort in extreme conditions in space as well as on Earth. c2005 Elsevier Ltd. All rights reserved.

Trimodal Control of Ion-Transport Activity on Cyclo-oligo-(1→6)-β-D-glucosamine-Based Artificial Ion-Transport Systems.

PubMed

Roy, Arundhati; Saha, Tanmoy; Gening, Marina L; Titov, Denis V; Gerbst, Alexey G; Tsvetkov, Yury E; Nifantiev, Nikolay E; Talukdar, Pinaki

2015-11-23

Cyclo-oligo-(1→6)-β-D-glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion-transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails. Hydrophobic tails of 3 different sizes were synthesized and coupled with each glucosamine scaffold through the amide linkage to obtain 18 derivatives. The ion-transport activity increased from di- to tetrameric glucosamine macrocycles, but decreased further when flexible pentameric glucosamine was introduced. The ion-transport activity also increased with increasing length of attached linkers. For a fixed length of linkers, the transport activity decreased when the number of such tails was reduced. All glycoconjugates displayed a uniform anion-selectivity sequence: Cl(-) >Br(-) >I(-) . From theoretical studies, hydrogen bonding between the macrocycle backbone and the anion bridged through water molecules was observed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The calcium feedback loop and T cell activation: how cytoskeleton networks control intracellular calcium flux.

PubMed

Joseph, Noah; Reicher, Barak; Barda-Saad, Mira

2014-02-01

During T cell activation, the engagement of a T cell with an antigen-presenting cell (APC) results in rapid cytoskeletal rearrangements and a dramatic increase of intracellular calcium (Ca(2+)) concentration, downstream to T cell antigen receptor (TCR) ligation. These events facilitate the organization of an immunological synapse (IS), which supports the redistribution of receptors, signaling molecules and organelles towards the T cell-APC interface to induce downstream signaling events, ultimately supporting T cell effector functions. Thus, Ca(2+) signaling and cytoskeleton rearrangements are essential for T cell activation and T cell-dependent immune response. Rapid release of Ca(2+) from intracellular stores, e.g. the endoplasmic reticulum (ER), triggers the opening of Ca(2+) release-activated Ca(2+) (CRAC) channels, residing in the plasma membrane. These channels facilitate a sustained influx of extracellular Ca(2+) across the plasma membrane in a process termed store-operated Ca(2+) entry (SOCE). Because CRAC channels are themselves inhibited by Ca(2+) ions, additional factors are suggested to enable the sustained Ca(2+) influx required for T cell function. Among these factors, we focus here on the contribution of the actin and microtubule cytoskeleton. The TCR-mediated increase in intracellular Ca(2+) evokes a rapid cytoskeleton-dependent polarization, which involves actin cytoskeleton rearrangements and microtubule-organizing center (MTOC) reorientation. Here, we review the molecular mechanisms of Ca(2+) flux and cytoskeletal rearrangements, and further describe the way by which the cytoskeletal networks feedback to Ca(2+) signaling by controlling the spatial and temporal distribution of Ca(2+) sources and sinks, modulating TCR-dependent Ca(2+) signals, which are required for an appropriate T cell response. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters

Phototransduction Influences Metabolic Flux and Nucleotide Metabolism in Mouse Retina.

PubMed

Du, Jianhai; Rountree, Austin; Cleghorn, Whitney M; Contreras, Laura; Lindsay, Ken J; Sadilek, Martin; Gu, Haiwei; Djukovic, Danijel; Raftery, Dan; Satrústegui, Jorgina; Kanow, Mark; Chan, Lawrence; Tsang, Stephen H; Sweet, Ian R; Hurley, James B

2016-02-26

Production of energy in a cell must keep pace with demand. Photoreceptors use ATP to maintain ion gradients in darkness, whereas in light they use it to support phototransduction. Matching production with consumption can be accomplished by coupling production directly to consumption. Alternatively, production can be set by a signal that anticipates demand. In this report we investigate the hypothesis that signaling through phototransduction controls production of energy in mouse retinas. We found that respiration in mouse retinas is not coupled tightly to ATP consumption. By analyzing metabolic flux in mouse retinas, we also found that phototransduction slows metabolic flux through glycolysis and through intermediates of the citric acid cycle. We also evaluated the relative contributions of regulation of the activities of α-ketoglutarate dehydrogenase and the aspartate-glutamate carrier 1. In addition, a comprehensive analysis of the retinal metabolome showed that phototransduction also influences steady-state concentrations of 5'-GMP, ribose-5-phosphate, ketone bodies, and purines. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

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

Martinavicius, A.; Abrasonis, G.; Moeller, W.

2011-10-01

The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm{sup -2}), ion energy (0.5-1.2 keV), and temperature (370-430 deg. C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasingmore » ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.« less

Benchmark solutions for the galactic heavy-ion transport equations with energy and spatial coupling

NASA Technical Reports Server (NTRS)

Ganapol, Barry D.; Townsend, Lawrence W.; Lamkin, Stanley L.; Wilson, John W.

1991-01-01

Nontrivial benchmark solutions are developed for the galactic heavy ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical LaPlace transform inversion to yield a closed form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield design studies.

Near equality of ion phase space densities at earth, Jupiter, and Saturn

NASA Technical Reports Server (NTRS)

Cheng, A. F.; Krimigis, S. M.; Armstrong, T. P.

1985-01-01

Energetic-ion phase-space density profiles are strikingly similar in the inner magnetospheres of earth, Jupiter, and Saturn for ions of first adiabatic invariant near 100 MeV/G and small mirror latitudes. Losses occur inside L approximately equal to 7 for Jupiter and Saturn and inside L approximately equal to 5 at earth. At these L values there exist steep plasma-density gradients at all three planets, associated with the Io plasma torus at Jupiter, the Rhea-Dione-Tethys torus at Saturn, and the plasmasphere at earth. Measurements of ion flux-tube contents at Jupiter and Saturn by the low-energy charged-particle experiment show that these are similar (for O ions at L = 5-9) to those at earth (for protons at L = 2-6). Furthermore, the thermal-ion flux-tube contents from Voyager plasma-science data at Jupiter and Saturn are also very nearly equal, and again similar to those at earth, differing by less than a factor of 3 at the respective L values. The near equality of energetic and thermal ion flux-tube contents at earth, Jupiter, and Saturn suggests the possibility of strong physical analogies in the interaction between plasma and energetic particles at the plasma tori/plasma sheets of Jupiter and Saturn and the plasmasphere of earth.

Severe Acute Respiratory Syndrome Coronavirus Envelope Protein Ion Channel Activity Promotes Virus Fitness and Pathogenesis

PubMed Central

Nieto-Torres, Jose L.; DeDiego, Marta L.; Verdiá-Báguena, Carmina; Jimenez-Guardeño, Jose M.; Regla-Nava, Jose A.; Fernandez-Delgado, Raul; Castaño-Rodriguez, Carlos; Alcaraz, Antonio; Torres, Jaume; Aguilella, Vicente M.; Enjuanes, Luis

2014-01-01

Deletion of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) envelope (E) gene attenuates the virus. E gene encodes a small multifunctional protein that possesses ion channel (IC) activity, an important function in virus-host interaction. To test the contribution of E protein IC activity in virus pathogenesis, two recombinant mouse-adapted SARS-CoVs, each containing one single amino acid mutation that suppressed ion conductivity, were engineered. After serial infections, mutant viruses, in general, incorporated compensatory mutations within E gene that rendered active ion channels. Furthermore, IC activity conferred better fitness in competition assays, suggesting that ion conductivity represents an advantage for the virus. Interestingly, mice infected with viruses displaying E protein IC activity, either with the wild-type E protein sequence or with the revertants that restored ion transport, rapidly lost weight and died. In contrast, mice infected with mutants lacking IC activity, which did not incorporate mutations within E gene during the experiment, recovered from disease and most survived. Knocking down E protein IC activity did not significantly affect virus growth in infected mice but decreased edema accumulation, the major determinant of acute respiratory distress syndrome (ARDS) leading to death. Reduced edema correlated with lung epithelia integrity and proper localization of Na+/K+ ATPase, which participates in edema resolution. Levels of inflammasome-activated IL-1β were reduced in the lung airways of the animals infected with viruses lacking E protein IC activity, indicating that E protein IC function is required for inflammasome activation. Reduction of IL-1β was accompanied by diminished amounts of TNF and IL-6 in the absence of E protein ion conductivity. All these key cytokines promote the progression of lung damage and ARDS pathology. In conclusion, E protein IC activity represents a new determinant for SARS-CoV virulence. PMID:24788150

Ion velocity analysis of rotating structures in a magnetic linear plasma device

NASA Astrophysics Data System (ADS)

Claire, N.; Escarguel, A.; Rebont, C.; Doveil, F.

2018-06-01

The MISTRAL device is designed to produce a linear magnetized plasma column. It has been used a few years ago to study a nonlinear low frequency instability exhibiting an azimuthal number m = 2. By changing the experimental configuration of MISTRAL, this work shows experimental results on an m = 1 rotating instability with strongly different behavior. The spatio-temporal evolution of the ion velocity distribution function given by a laser-induced fluorescence diagnostic is measured to infer the radial and azimuthal velocities, ion fluxes, and electric fields. The naive image of a plasma exhibiting a global rotation is again invalidated in this m = 1 mode but in a different way. Contrary to the m = 2 mode, the rotation frequency of the instability is lower than the ion cyclotron frequency and ions exhibit a complex behavior with a radial outward flux inside the unstable arm and azimuthal ion fluxes always directed toward the unstable arm. The azimuthal ion velocity is close to zero inside the ionization region, whereas the radial ion velocity grows linearly with radius. The radial electric field is oriented inward inside the unstable arm and outward outside. An axial velocity perturbation is also present, indicating that contrary to the m = 2 mode, the m = 1 mode is not a flute mode. These results cannot be easily interpreted with existing theories.

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.

Removal of zinc (II) ion from aqueous solution by adsorption onto activated palm midrib bio-sorbent

NASA Astrophysics Data System (ADS)

Mulana, F.; Mariana; Muslim, A.; Mohibah, M.; Halim, K. H. Ku

2018-03-01

In this paper, palm midrib that was activated with mixed citric acid and tartaric acid as biosorbent was used to remove Zn (II) ion from aqueous solution. The aim of this research is to activate palm midrib by using a mixed citric acid and tartaric acid and to determine adsorption capacity of activated palm midrib biosorbent on Zn (II) ion uptake from aqueous solution. The effect of several parameters such as contact time, initial Zn (II) ion concentration and activator concentration on the degree of Zn (II) ion removal was examined. Atomic Absorption Spectroscopy method was performed to determine adsorbed amount of Zn (II) ion into activated biosorbent. The result showed that the adsorption process was relatively not so fast and equilibrium was reached after contact time of 120 min. The adsorption capacity of biosorbent reached a maximum when the concentration of mixed citric acid and tartaric acid was 1.6 M. The optimum adsorption capacity was 5.72 mg/g. The result was obtained on initial Zn (II) ion concentration of 80 ppm for 120-min contact time. Langmuir isotherm was found as the best fit for the equilibrium data indicating homogeneous adsorption of metal ions onto the biosorbent surface.

Ion Traps at the Sun: Implications for Elemental Fractionation

NASA Astrophysics Data System (ADS)

Fleishman, Gregory D.; Musset, Sophie; Bommier, Véronique; Glesener, Lindsay

2018-04-01

Why the tenuous solar outer atmosphere, or corona, is much hotter than the underlying layers remains one of the greatest challenges for solar modeling. Detailed diagnostics of the coronal thermal structure come from extreme ultraviolet (EUV) emission. The EUV emission is produced by heavy ions in various ionization states and depends on the amount of these ions and on plasma temperature and density. Any nonuniformity of the elemental distribution in space or variability in time affects thermal diagnostics of the corona. Here we theoretically predict ionized chemical element concentrations in some areas of the solar atmosphere, where the electric current is directed upward. We then detect these areas observationally, by comparing the electric current density with the EUV brightness in an active region. We found a significant excess in EUV brightness in the areas with positive current density rather than negative. Therefore, we report the observational discovery of substantial concentrations of heavy ions in current-carrying magnetic flux tubes, which might have important implications for the elemental fractionation in the solar corona known as the first ionization potential effect. We call such areas of heavy ion concentration the “ion traps.” These traps hold enhanced ion levels until they are disrupted by a flare, whether large or small.

Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model

NASA Astrophysics Data System (ADS)

Nishioka, S.; Goto, I.; Miyamoto, K.; Hatayama, A.; Fukano, A.