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Sample records for ion flux activity

  1. Role of a mitogen-activated protein kinase cascade in ion flux-mediated turgor regulation in fungi.

    PubMed

    Lew, Roger R; Levina, Natalia N; Shabala, Lana; Anderca, Marinela I; Shabala, Sergey N

    2006-03-01

    Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca(2+) influx and the sustained hyperpolarization is due to H(+) efflux by activation of the plasma membrane H(+)-ATPase. Protein synthesis is not required for H(+)-ATPase activation. Net K(+) and Cl(-) uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2, homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl(-) uptake increases, but net K(+) flux barely changes and net H(+) efflux declines) (os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H(+)-ATPase, and net K(+) and Cl(-) uptake during turgor regulation. Other pathways regulating turgor must also exist.

  2. Monitoring charge flux to quantify unusual ligand-induced ion channel activity for use in biological nanopore-based sensors.

    PubMed

    Macazo, Florika C; White, Ryan J

    2014-06-01

    The utility of biological nanopores for the development of sensors has become a growing area of interest in analytical chemistry. Their emerging use in chemical analysis is a result of several ideal characteristics. First, they provide reproducible control over nanoscale pore sizes with an atomic level of precision. Second, they are amenable to resistive-pulse type measurement systems when embedded into an artificial lipid bilayer. A single binding event causes a change in the flow of millions of ions across the membrane per second that is readily measured as a change in current with excellent signal-to-noise ratio. To date, ion channel-based biosensors have been limited to well-behaved proteins. Most demonstrations of using ion channels as sensors have been limited to proteins that remain in the open, conducting state, unless occupied by an analyte of interest. Furthermore, these proteins are nonspecific, requiring chemical, biochemical, or genetic manipulations to impart chemical specificity. Here, we report on the use of the pore-forming abilities of heat shock cognate 70 (Hsc70) to quantify a specific analyte. Hsc70 reconstitutes into phospholipid membranes and opens to form multiple conductance states specifically in the presence of ATP. We introduce the measurement of "charge flux" to characterize the ATP-regulated multiconductance nature of Hsc70, which enables sensitive quantification of ATP (100 μM-4 mM). We believe that monitoring protein-induced charge flux across a bilayer membrane represents a universal method for quantitatively monitoring ion-channel activity. This measurement has the potential to broaden the library of usable proteins in the development of nanopore-based biosensors.

  3. Autonomic control of neuronal-astrocytic interactions, regulating metabolic activities, and ion fluxes in the CNS.

    PubMed

    Hertz, L

    1992-01-01

    It is generally assumed that the brain, in contrast to all other organs, is not equipped with an autonomic nervous system, regulating blood supply, and cellular activities. This may be because systemic administration of most drugs acting on monoaminergic or cholinergic receptors have little or no effect on cerebral blood flow and metabolism. However, intrathecal administration of noradrenaline does, indeed, influence both blood flow and energy metabolism in the brain. The present review focuses on effects of noradrenaline or serotonin on energy metabolism, turnover of amino acid transmitters and ion homeostasis, with special emphasis on the cellular localization. Noradrenergic agonists stimulate brain metabolism in vivo as well as many aspects of energy metabolism, Na+,K(+)-ATPase activity and uptake of transmitter amino acids in astrocytes in primary cultures, with little or no effect on corresponding preparations of neurons. Serotonin acts differently, decreasing potassium-induced release of glutamate from both neurons and astrocytes. Little is known about the effects of acetylcholine. The functional significance of these effects is discussed. PMID:1393603

  4. Sperm-activating peptides in the regulation of ion fluxes, signal transduction and motility.

    PubMed

    Darszon, Alberto; Guerrero, Adán; Galindo, Blanca E; Nishigaki, Takuya; Wood, Christopher D

    2008-01-01

    Echinoderm sperm use cyclic nucleotides (CNs) as essential second messengers to locate and swim towards the egg. Sea urchin sperm constitute a rich source of membrane-bound guanylyl cyclase (mGC), which was first cloned from sea urchin testis by the group of David Garbers. His group also identified speract, the first sperm-activating peptide (SAP) to be isolated from the egg investment (or egg jelly). This decapeptide stimulates sperm mGC causing a fast transient increase in cGMP that triggers an orchestrated set of physiological responses including: changes in: membrane potential, intracellular pH (pHi), intracellular Ca2+ concentration ([Ca2+]i) and cAMP levels. Evidence from several groups indicated that cGMP activation of a K+ selective channel was the first ion permeability change in the signaling cascade induced by SAPs, and recently the candidate gene was finally identified. Each of the 4 repeated, 6 trans-membrane segments of this channel contains a cyclic nucleotide binding domain. Together they comprise a single polypeptide chain like voltage-gated Na+ or Ca2+ channels. This new type of channel, named tetraKCNG, appears to belong to the exclusive club of novel protein families expressed only in sperm and its progenitors. SAPs also induce fluctuations in flagellar [Ca2+]i that correlate with changes in flagellar form and regulate sperm trajectory. The motility changes depend on [Ca2+]i influx through specific Ca2+ channels and not on the overall [Ca2+]i in the sperm flagellum. All cilia and flagella have a conserved axonemal structure and thus understanding how Ca2+ regulates cilia and flagella beating is a fundamental question. PMID:18649273

  5. Monitoring Charge Flux to Quantify Unusual Ligand-Induced Ion Channel Activity for Use in Biological Nanopore-Based Sensors

    PubMed Central

    2015-01-01

    The utility of biological nanopores for the development of sensors has become a growing area of interest in analytical chemistry. Their emerging use in chemical analysis is a result of several ideal characteristics. First, they provide reproducible control over nanoscale pore sizes with an atomic level of precision. Second, they are amenable to resistive-pulse type measurement systems when embedded into an artificial lipid bilayer. A single binding event causes a change in the flow of millions of ions across the membrane per second that is readily measured as a change in current with excellent signal-to-noise ratio. To date, ion channel-based biosensors have been limited to well-behaved proteins. Most demonstrations of using ion channels as sensors have been limited to proteins that remain in the open, conducting state, unless occupied by an analyte of interest. Furthermore, these proteins are nonspecific, requiring chemical, biochemical, or genetic manipulations to impart chemical specificity. Here, we report on the use of the pore-forming abilities of heat shock cognate 70 (Hsc70) to quantify a specific analyte. Hsc70 reconstitutes into phospholipid membranes and opens to form multiple conductance states specifically in the presence of ATP. We introduce the measurement of “charge flux” to characterize the ATP-regulated multiconductance nature of Hsc70, which enables sensitive quantification of ATP (100 μM–4 mM). We believe that monitoring protein-induced charge flux across a bilayer membrane represents a universal method for quantitatively monitoring ion-channel activity. This measurement has the potential to broaden the library of usable proteins in the development of nanopore-based biosensors. PMID:24794413

  6. The effects of alkaline earth metal ions and halogen ions on the chromium oxide activities in alkaline earth metal oxide-halide-Cr2O3 system fluxes

    NASA Astrophysics Data System (ADS)

    Li, Lian-Fu; Jiang, Mao-Fa; Wang, Wen-Zhong; Chen, Zhao-Ping

    2000-06-01

    The solid electrolyte cell — Mo|Cr + Cr2O3‖ZrO2(MgO)‖{Cu-Cr}alloy + (Cr2O3)fluxes|Mo+ is used at 1673 K to determine Cr2O3 activities in MO-MX 2-Cr2O3 (M = Ca2+, Ba2-, X = F- or Cl-) ternary fluxes, which are in equilibrium with the copper-chromium binary alloy. The ternary isothermal phase diagrams of CaO-CaF2-Cr2O3 and BaO-BaCl2-Cr2O3 system fluxes are inferred on the basis of the experimental results and binary phase diagrams. The results indicate that Cr2O3 activities in all fluxes always decrease with the increase of the X MO /X MX2 ratio. Partial replacement of BaO in BaO-BaF2-Cr2O3 fluxes by CaO is acceptable for economy and efficiency considerations. At the same time, partial substitution of BaO for CaO in CaO-CaF2-Cr2O3 fluxes is advantageous for phosphorus removal and chromium retention as a result of the increased Cr2O3 activities, increased basicities, and widening of the liquid zones. Compared to those in BaO-BaF2-Cr2O3 fluxes, Cr2O3 activities in CaO-CaF2-Cr2O3 fluxes approximately follow the same curve as the former, although the position and the width of the liquid zones are considerably different, and activities in BaO-BaCl2-Cr2O3 fluxes are higher at the lower Cr2O3 content, or vice versa. The activity coefficients of Cr2O3 in the fluxes decrease with the increase of the X MO /X MX 2 ratios.

  7. Turgor and net ion flux responses to activation of the osmotic MAP kinase cascade by fludioxonil in the filamentous fungus Neurospora crassa.

    PubMed

    Lew, Roger R

    2010-08-01

    The internal hydrostatic pressure (turgor) of the filamentous fungus Neurospora crassa is regulated at about 400-500 kiloPascals, primarily by an osmotic MAP kinase cascade which activates ion uptake from the extracellular medium and glycerol synthesis. In the absence of hyperosmotic stress, the phenylpyrrole fungicide fludioxonil activates the osmotic MAP kinase cascade, resulting in cell death. Turgor, the electrical potential and net ion fluxes were measured after treatment with fludioxonil. In wildtype, fludioxonil causes a hyperpolarization of the plasma membrane and net H(+) efflux from the cell, consistent with activation of the H(+)-ATPase. At the same time, net K(+) uptake occurs, and turgor increases (about 2-fold above normal levels). None of these changes are observed in the os-2 mutant (which lacks a functional MAP kinase, the last of the three kinases in the osmotic MAP kinase cascade). Tip growth ceases as hyperpolarization, net ion flux changes, and turgor increases begin. The inappropriate turgor increase is the probable cause of eventual lysis and death. The results corroborate a multi-pathway response to hyperosmotic stress that includes activation of plasma membrane transport. The relation to cell expansion (tip growth) is not direct. Increases in turgor due to ion transport might be expected to increase growth rate, but this does not occur. Instead, there must be a complex regulatory interplay between the growth and the turgor driving force, possibly mediated by regulation of cell wall extensibility.

  8. Ion flux profiles observed at Mars

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.; Lundin, R. N.; Frahm, R. A.

    2012-12-01

    How Mars lost it's water and atmosphere is still an important question. Many studies have investigated high-energy ion fluxes (>10 eV) surrounding the planet and derived ion outflow rates in order to determine atmospheric loss. These rates suggest that the outflow from high-energy ions is not the dominant escape path for atmospheric loss. Over the years increasing evidence has indicated that the loss of low-energy ions are more important than the high-energy ion loss. In this presentation ion observations (down to the spacecraft potential) from the Mars Express (MEX) mission (2010/11), are used to describe the ion altitude distribution at Mars. The focus of this study is below the altitude of ~1000 km. Within the Mars environment, using the MEX electron observations different plasma regions was identified. Supported by electron identification, different altitude profiles of ion fluxes have been analyzed from the different plasma regions. One of the results from this study is that the altitude profile of the ion flux observed below the photoelectron boundary is different when comparing the northern and the southern hemispheres. The ion distributions, resulting altitude profile, the influence of the crustal magnetic field at Mars, and the implications relating to plasma outflow will be discussed in this presentation.

  9. Fast Ion Transport by Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Preiwisch, Adam; Heidbrink, William; Boehmer, Heinrich; McWilliams, Roger; Carter, Troy; Gekelman, Walter; Tripathi, Shreekrishna; Compernolle, Bart; Vincena, Steven

    2014-10-01

    Energetic Lithium test ions (500 <= Efast/Ti <= 1000) are launched in a Helium plasma in the presence of current-produced magnetic flux ropes at the upgraded Large Plasma Device (LAPD) at UCLA. Perturbing flux ropes are introduced via a hot, biased LaB6 cathode in the main chamber. Ion beam broadening up to fifty percent above background levels is observed in the radial direction after passing through the flux rope region (Te,max = 7 eV, Bperp = 7G, ΔV = 160 V). Density, temperature, and magnetic fluctuation profiles are also obtained. A noise model has been developed to assess the quality of ion signals during the flux rope discharge period. The enhancement to transport may be a result of increased Coulomb scattering, magnetic fluctuations, or electric fields. Further analysis to determine the primary mechanism is ongoing.

  10. Measurement of extracellular ion fluxes using the ion-selective self-referencing microelectrode technique.

    PubMed

    Luxardi, Guillaume; Reid, Brian; Ferreira, Fernando; Maillard, Pauline; Zhao, Min

    2015-05-03

    Cells from animals, plants and single cells are enclosed by a barrier called the cell membrane that separates the cytoplasm from the outside. Cell layers such as epithelia also form a barrier that separates the inside from the outside or different compartments of multicellular organisms. A key feature of these barriers is the differential distribution of ions across cell membranes or cell layers. Two properties allow this distribution: 1) membranes and epithelia display selective permeability to specific ions; 2) ions are transported through pumps across cell membranes and cell layers. These properties play crucial roles in maintaining tissue physiology and act as signaling cues after damage, during repair, or under pathological condition. The ion-selective self-referencing microelectrode allows measurements of specific fluxes of ions such as calcium, potassium or sodium at single cell and tissue levels. The microelectrode contains an ionophore cocktail which is selectively permeable to a specific ion. The internal filling solution contains a set concentration of the ion of interest. The electric potential of the microelectrode is determined by the outside concentration of the ion. As the ion concentration varies, the potential of the microelectrode changes as a function of the log of the ion activity. When moved back and forth near a source or sink of the ion (i.e. in a concentration gradient due to ion flux) the microelectrode potential fluctuates at an amplitude proportional to the ion flux/gradient. The amplifier amplifies the microelectrode signal and the output is recorded on computer. The ion flux can then be calculated by Fick's law of diffusion using the electrode potential fluctuation, the excursion of microelectrode, and other parameters such as the specific ion mobility. In this paper, we describe in detail the methodology to measure extracellular ion fluxes using the ion-selective self-referencing microelectrode and present some representative results.

  11. The Empirical Low Energy Ion Flux Model for the Terrestrial Magnetosphere

    NASA Technical Reports Server (NTRS)

    Blackwell, William C.; Minow, Joseph I.; Diekmann, Anne M.

    2007-01-01

    This document includes a viewgraph presentation plus the full paper presented at the conference. The Living With a Star Ion Flux Model (IFM) is a radiation environment risk mitigation tool that provides magnetospheric ion flux values for varying geomagnetic disturbance levels in the geospace environment. IFM incorporates flux observations from the Polar and Geotail spacecraft in a single statistical flux model. IFM is an engineering environment model which predicts the proton flux not only in the magnetosphere, but also in the solar wind and magnetosheath phenomenological regions. This paper describes the ion flux databases that allows for IFM output to be correlated with the geomagnetic activity level, as represented by the Kp index.

  12. Planetary Ion fluxes in the Venus Wake

    NASA Astrophysics Data System (ADS)

    Pérez-de-Tejada, H.; Lundin, R.; Durand-Manterola, H.; Barabash, S.; Zhang, T. L.; Sauvaud, J. A.; Reyes-Ruiz, M.

    2012-09-01

    Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the kinetic pressure of planetary O+ ions measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. Peak values of the kinetic pressure of the O+ ions are sufficient to produce superalfvenic flow conditions. It is suggested that such O+ ion beams are eroded from the magnetic polar regions of the Venus ionosphere where the solar wind carves out plasma channels that extend downstream from those regions. Issues related to the acceleration of planetary ions as the solar wind interacts with the Venus ionosphere are related to the energetics of the plasma. When the kinetic pressure of the particle populations involved in the interaction is smaller than the local magnetic pressure the latter will be dominant and hence the particles will follow trajectories dictated by the magnetic field. Such conditions should occur by the magnetic barrier that is formed over the dayside Venus ionosphere where the interplanetary magnetic fluxes pile up thus leading to enhanced values of the magnetic field intensity. Different conditions are expected when the kinetic pressure of the plasma is larger than the local magnetic pressure. In this case the latter will be convected by the particle fluxes as it occurs in the superalfvenic solar wind. Plasma conditions applicable to the planetary ions that stream in the Venus wake and that have been removed from the Venus ionosphere can be examined using the plasma and magnetic field data obtained from the Venus Express (VEX) measurements. A suitable example is provided by the plasma and

  13. Flux Estimates of Ions from the Lunar Exosphere

    NASA Technical Reports Server (NTRS)

    Sarantos, M.; Hartle, R. E.; Killen, R. M.; Saito, Y.; Slavin, J. A.; Glocer, A.

    2012-01-01

    We compare estimates for the ion fluxes of twelve expected constituents of the lunar exosphere with estimates for the ion fluxes ejected from the lunar surface by solar wind ions and electrons. Our estimates demonstrate that measurements of lunar ions will help constrain the abundances of many undetected species in the lunar exosphere, particularly AI and Si, because the expected ion flux levels from the exosphere exceed those from the surface. To correctly infer the relative abundances of exospheric ions and neutrals from Kaguya Ion Mass Analyzer (IMA) measurements, we must take into account the velocity distributions of local ions. The predicted spectrum underestimates the measured levels of 0+ relative to other lunar ion species, a result that may suggest contributions by molecular ions to the measured 0+ rates.

  14. Ion fluxes in Acetabularia: vesicular shuttle.

    PubMed

    Mummert, H; Gradmann, D

    1991-12-01

    Ion flux relations in the unicellular marine alga Acetabularia have been investigated by uptake and washout kinetics of radioactive tracers (22Na+, 42K+, 36Cl- and 86Rb+) in normal cells and in cell segments with altered compartmentation (depleted of vacuole or of cytoplasm). Some flux experiments were supplemented by simultaneous electrophysiological recordings. The main results and conclusions about the steady-state relations are: the plasmalemma is the dominating barrier for translocation of K+ with influx and efflux of about 100 nmol.m-2.sec-1. K+ passes three- to sevenfold more easily than Rb+ does. Under normal conditions, Cl- (the substrate of the electrogenic pump, which dominates the electrical properties of the plasmalemma in the resting state) shows two efflux components of about 17 and 2 mumol.m-2.sec-1, and a cytoplasmic as well as vacuolar [Cl-] of about 420 mM ([Cl-]o = 529 mM). At 4 degrees C, when the pump is inhibited, both influx and efflux, as well as the cellular [Cl-], are significantly reduced. Na+ ([Na+]i: about 70 mM, [Na+]o: 461 mM), which is of minor electrophysiological relevance compared to K+, exhibits rapid and virtually temperature-insensitive (electroneutral) exchange (two components with about 2 and 0.2 mumol.m-2.sec-1 for influx and efflux). Some results with Na+ and Cl- are inconsistent with conventional (noncyclic) compartmentation models: (i) equilibration of the vacuole (with the external medium) can be faster than equilibration of the cytoplasm, (ii) absurd concentration values result when calculated by conventional compartmental analysis, and (iii) large amounts of ions can be released from the cell without changes in the electrical potential of the cytoplasm. These observations can be explained by the particular compartmentation of normal Acetabularia cells (as known by electron micrographs) with about 1 part cytoplasm, 5 parts central vacuole, and 5 parts vacuolar vesicles. These vesicles communicate directly with the

  15. Implications of Saito's coronal density model on the polar solar wind flow and heavy ion abundances. [mathematical models of proton flux density and solar activity

    NASA Technical Reports Server (NTRS)

    Feldman, W. C.

    1976-01-01

    A comparison of polar solar wind proton flux upper limits derived using a coronal density model, with Lyman alpha measurements of the length of the neutral H tail of comet Bennet at high latitudes, shows that either extended heating beyond 2 solar radii is necessary some of the time or that the model's polar densities are too low. Whichever possibility is the case, the fact that the solar wind particle flux does not appear to decrease with increasing latitude indicates that the heavy element content of the high latitude wind may be similar to that observed in the ecliptic. It was then shown that solar wind heavy ion observations at high latitudes allow a determination of the electron temperature at heights which bracket the nominal location of the coronal temperature maximum thus providing information concerning the magnitude and extent of mechanical dissipation in the intermediate corona.

  16. Microvillar ion channels: cytoskeletal modulation of ion fluxes.

    PubMed

    Lange, K

    2000-10-21

    movement of the system (electro-mechanical coupling). Because ionic transmission through linear polyelectrolytes is very slow compared with electronic conduction, only low-frequency electromagnetic fields can interact with the condensed counterion systems of linear polyelectrolytes. The delineated characteristics of microvillar ion conduction are strongly supported by the phenomenon of electro-mechanical coupling (reverse transduction) in microvilli of the audioreceptor (hair) cells and the recently reported dynamics of Ca(2+)signaling in microvilli of audio- and photoreceptor cells. Due to the cell-specific expression of different types and combinations of ion channels and transporters in the microvillar tip membrane of differentiated cells, the functional properties of this cell surface organelle are highly variable serving a multitude of different cellular functions including receptor-mediated effects such as Ca(2+)signaling, regulation of glucose and amino acid transport, as well as modulation of membrane potential. Even mechanical channel activation involved in cell volume regulation can be deduced from the systematic properties of the microvillar channel concept. In addition, the specific ion conduction properties of microfilaments combined with their proposed role in Ca(2+)signaling make microvilli the most likely cellular site for the interaction with external electric and magnetic fields.

  17. Ion fluxes through nanopores and transmembrane channels

    NASA Astrophysics Data System (ADS)

    Bordin, J. R.; Diehl, A.; Barbosa, M. C.; Levin, Y.

    2012-03-01

    We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through narrow nanopores and transmembrane channels. The method relies on a dual-control-volume grand-canonical molecular dynamics (DCV-GCMD) simulation and the analytical solution for the electrostatic potential inside a cylindrical nanopore recently obtained by Levin [Europhys. Lett.EULEEJ0295-507510.1209/epl/i2006-10240-4 76, 163 (2006)]. The theory is used to calculate the ionic fluxes through an artificial transmembrane channel which mimics the antibacterial gramicidin A channel. Both current-voltage and current-concentration relations are calculated under various experimental conditions. We show that our results are comparable to the characteristics associated to the gramicidin A pore, especially the existence of two binding sites inside the pore and the observed saturation in the current-concentration profiles.

  18. Ion Flux Environments for Exposed Spacecraft Surfaces in Interplanetary Space

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Altstatt, Richard; NeergaardParker, Linda; Skipworth, William

    2004-01-01

    Spacecraft surfaces in interplanetary space are exposed to solar wind ions. The bulk of the ions exhibit energies of a few kilovolts and are important only to surface interactions while a fraction of the solar wind extends to greater energies and may penetrate below the material surface. The importance of including solar wind ions in analysis of space environment effects on spacecraft is becoming more important as new spacecraft designs are considered which include systems such as sunshades, solar sail propulsion systems, and other mission critical features based on very thin materials. This paper provides a status report on development of solar wind ion environments to support engineering analysis of materials exposed to the space environment including techniques for reconstructing ion environments from solar wind plasma moments and energetic flux measurements and comparison of statistical flux environments to integrated mission fluence.

  19. 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

  20. Ion flux and ion distribution function measurements in synchronously pulsed inductively coupled plasmas

    SciTech Connect

    Brihoum, Melisa; Cunge, Gilles; Darnon, Maxime; Joubert, Olivier; Gahan, David; Braithwaite, Nicholas St. J.

    2013-03-15

    Changes in the ion flux and the time-averaged ion distribution functions are reported for pulsed, inductively coupled RF plasmas (ICPs) operated over a range of duty cycles. For helium and argon plasmas, the ion flux increases rapidly after the start of the RF pulse and after about 50 {mu}s reaches the same steady state value as that in continuous ICPs. Therefore, when the plasma is pulsed at 1 kHz, the ion flux during the pulse has a value that is almost independent of the duty cycle. By contrast, in molecular electronegative chlorine/chlorosilane plasmas, the ion flux during the pulse reaches a steady state value that depends strongly on the duty cycle. This is because both the plasma chemistry and the electronegativity depend on the duty cycle. As a result, the ion flux is 15 times smaller in a pulsed 10% duty cycle plasma than in the continuous wave (CW) plasma. The consequence is that for a given synchronous RF biasing of a wafer-chuck, the ion energy is much higher in the pulsed plasma than it is in the CW plasma of chlorine/chlorosilane. Under these conditions, the wafer is bombarded by a low flux of very energetic ions, very much as it would in a low density, capacitively coupled plasma. Therefore, one can extend the operating range of ICPs through synchronous pulsing of the inductive excitation and capacitive chuck-bias, offering new means by which to control plasma etching.

  1. AmeriFlux US-Var Vaira Ranch- Ione

    SciTech Connect

    Baldocchi, Dennis

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Var Vaira Ranch- Ione. Site Description - Located in the lower foothills of the Sierra Nevada Mountains on privately owned land, the Vaira Ranch site is classified as a grassland dominated by C3 annual grasses. Managed by local rancher, Fran Vaira, brush has been periodically removed for cattle grazing. Species include a variety of grasses and herbs, including purple false brome, smooth cat's ear, and rose clover. Growing season is confined to the wet season only, typically from October to early May.

  2. 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.

  3. Dual Active Surface Heat Flux Gage Probe

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Kolodziej, Paul

    1995-01-01

    A unique plug-type heat flux gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat flux gage body to the end of a hollow metal cylindrical bolt containing a metal inner tube. Cooling air flows through the inner tube, impinges onto the back of the gage body and then flows out through the annulus formed between the inner tube and the hollow bolt wall. Heat flux was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat flux, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat fluxes measured with the probe were compared with absorbed heat fluxes measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat fluxes measured with the reference calorimeters and heat flux gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat flux measurement. A current application for dual active surface heat flux gages is for transient and steady absorbed heat flux, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.

  4. Mars heavy ion precipitating flux as measured by MAVEN

    NASA Astrophysics Data System (ADS)

    Leblanc, F.

    2015-12-01

    Mars' atmospheric escape induced by heavy planetary ions accelerated by the solar wind and reimpacting Mars' atmosphere has been suggested to occur. The sputtering of Mars' atmosphere has been even suggested to lead to a significant cumulated loss along Mars' history. Up to now, only a limited number of observations have been possible. ASPERA-3/Mars Express observed such precipitation only during extreme solar conditions events suggesting that sputtering might be not as intense as theoretically predicted. Based on MAVEN first six months of observations, we here show that precipitation of heavy ions also occur during quiet solar conditions and that the average precipitating flux during this period is significant and globally in good agreement with predictions. From these measured precipitating flux, we propose a first estimate of the atmospheric escape induced by sputtering. Up to 8.8×105 O/cm2/s was lost by Mars' atmosphere between November 2014 and April 2015.

  5. Changes in Ion Fluxes During Phototropic Bending of Etiolated Oat Coleoptiles

    PubMed Central

    BABOURINA, OLGA; GODFREY, LEITH; VOLTCHANSKII, KONSTANTIN

    2004-01-01

    • Background and Aims This work has been conducted to assist theoretical modelling of the different stages of the blue light (BL)‐induced phototropic signalling pathway and ion transport activity across plant membranes. Ion fluxes (Ca2+, H+, K+ and Cl–) in etiolated oat coleoptiles have been measured continuously before and during unilateral BL exposure. • Methods Changes in ion fluxes at the illuminated (light) and shadowed (dark) sides of etiolated oat coleoptiles (Avena sativa) were studied using a non‐invasive ion‐selective microelectrode technique (MIFE). The bending response was also measured continuously, and correlations between the changes in various ion fluxes and bending response have been investigated. For each ion the difference (Δ) between the magnitudes of flux at the light and dark sides of the coleoptile was calculated. • Key results Plants that demonstrated a phototropic bending response also demonstrated Ca2+ influx into the light side approximately 20 min after the start of BL exposure. This is regarded as part of the perception and transduction stages of the BL‐induced signal cascade. The first 10 min of bending were associated with substantial influx of H+, K+ and Cl– into the light (concave) side of the coleoptiles. • Conclusions The data suggest that Ca2+ participates in the signalling stage of the BL‐induced phototropism, whereas the phototropic bending response is linked to changes in the transport of H+, K+ and Cl–. PMID:15155378

  6. Ion Flows Associated with Two Flux Ropes in a Magnetoplasma

    NASA Astrophysics Data System (ADS)

    DeHaas, T.; Gekelman, W. N.; Van Compernolle, B.

    2013-12-01

    Magnetic flux ropes are ubiquitous as they are located on and near the sun, presumably other stars, and near the earth and other planets. They consist of helical field lines which vary in pitch due to the electric current flowing along a background magnetic field. Multiple braided flux ropes have been observed in the solar corona, and their unraveling is theorized to be the signature of magnetic reconnection. In this laboratory experiment, two flux ropes (L=10 m, A=7 cm2, J=10 amp/cm2) were created in the Large Plasma Device (LAPD) at UCLA (Bo=330 G, no = 1012 cm-3, Te=4eV, Ar). These kink unstable ropes violently twist and oscillate about a central axis. To diagnose the plasma, a six-faced Mach probe and a three-axis magnetic field probe was used to create volumetric datasets of the plasma flow and magnetic fluctuations. The three-dimensional data is conditionally averaged to construct the average flux rope dynamic. The flux ropes are shown to collide, creating a quasi-separatrix layer (QSL) between them as the magnetic field lines reconnect. This induces a strong antiparallel electric field and creates a localized reversal in ion flow around the reconnection region. The cross helicity does not show small eddy structures in the ropes of around them. The ropes do exhibit chaotic behavior, however. It is likely that MHD theory cannot explain their behavior. The flux ropes are shown to twist, interact, then merge; while the plasma flows are shown to spiral around the two flux ropes in a singular O-point with a Gaussian distribution of parallel plasma flows centered around one fifth of the sound speed.

  7. Ion-acoustic cnoidal wave and associated non-linear ion flux in dusty plasma

    SciTech Connect

    Jain, S. L.; Tiwari, R. S.; Mishra, M. K.

    2012-10-15

    Using reductive perturbation method with appropriate boundary conditions, coupled evolution equations for first and second order potentials are derived for ion-acoustic waves in a collisionless, un-magnetized plasma consisting of hot isothermal electrons, cold ions, and massive mobile charged dust grains. The boundary conditions give rise to renormalization term, which enable us to eliminate secular contribution in higher order terms. Determining the non secular solution of these coupled equations, expressions for wave phase velocity and averaged non-linear ion flux associated with ion-acoustic cnoidal wave are obtained. Variation of the wave phase velocity and averaged non-linear ion flux as a function of modulus (k{sup 2}) dependent wave amplitude are numerically examined for different values of dust concentration, charge on dust grains, and mass ratio of dust grains with plasma ions. It is found that for a given amplitude, the presence of positively (negatively) charged dust grains in plasma decreases (increases) the wave phase velocity. This behavior is more pronounced with increase in dust concentrations or increase in charge on dust grains or decrease in mass ratio of dust grains. The averaged non-linear ion flux associated with wave is positive (negative) for negatively (positively) charged dust grains in the plasma and increases (decreases) with modulus (k{sup 2}) dependent wave amplitude. For given amplitude, it increases (decreases) as dust concentration or charge of negatively (positively) charged dust grains increases in the plasma.

  8. The distribution of ion orbit loss fluxes of ions and energy from the plasma edge across the last closed flux surface into the scrape-off layer

    SciTech Connect

    Stacey, Weston M.; Schumann, Matthew T.

    2015-04-15

    A more detailed calculation strategy for the evaluation of ion orbit loss of thermalized plasma ions in the edge of tokamaks is presented. In both this and previous papers, the direct loss of particles from internal flux surfaces is calculated from the conservation of canonical angular momentum, energy, and magnetic moment. The previous result that almost all of the ion energy and particle fluxes crossing the last closed flux surface are in the form of ion orbit fluxes is confirmed, and the new result that the distributions of these fluxes crossing the last closed flux surface into the scrape-off layer are very strongly peaked about the outboard midplane is demonstrated. Previous results of a preferential loss of counter current particles leading to a co-current intrinsic rotation peaking just inside of the last closed flux surface are confirmed. Various physical details are discussed.

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

    SciTech Connect

    Denton, M. H.; Thomsen, M. F.; Jordanova, V. K.; Henderson, M. G.; Borovsky, J. E.; Denton, J. S.; Pitchford, D.; Hartley, D. P.

    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 ion 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.

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

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Jordanova, V. K.; Henderson, M. G.; Borovsky, J. E.; Denton, J. S.; Pitchford, D.; Hartley, D. P.

    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. Bilinear interpolation is used between grid points to provide the ion flux and the electron flux values at any energy and local time, and for given values of geomagnetic activity (proxied by the 3 h 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, also located at geosynchronous orbit, indicates 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.

  11. Ion-selective self-referencing probes for measuring specific ion flux

    PubMed Central

    Reid, Brian

    2011-01-01

    The metal vibrating probe developed in the 1970s to measure electric current is sensitive down to the micro-Amp range, but detects only net current due to flow of multiple ions and is too large to measure from single cells. Electrophysiological techniques which use glass microelectrodes such as voltage clamping can be used on single cells but are also non-specific. Ion-selective probes are glass microelectrodes containing at their tip a small amount of ionophore permeable to a particular ion. The electrode is therefore sensitive to changes in concentration of this ion. If the probe tip is moved at low frequency between two points in a concentration gradient of this ion then the electrochemical potential of the solution inside the electrode fluctuates in proportion to the size of the ion gradient. This fluctuation is amplified and recorded and is used to calculate the actual ion flux using Fick's law of diffusion. In this mini-review we describe the technique of ion-selective self-referencing microelectrodes to measure specific ion fluxes. We discuss the development of the technique and describe in detail the methodology and present some representative results. PMID:22046453

  12. Temperature measurements during high flux ion beam irradiations

    DOE PAGES

    Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    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 Au3+ ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 1012 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. Comparison with numerical calculations suggestsmore » 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

  13. Temperature measurements during high flux ion beam irradiations

    NASA Astrophysics Data System (ADS)

    Crespillo, M. L.; Graham, J. T.; Zhang, Y.; Weber, W. J.

    2016-02-01

    A systematic study of the ion beam heating effect was performed in a temperature range of -170 to 900 °C using a 10 MeV Au3+ ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 1012 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. Comparison with numerical calculations suggests that the observed heating effect is, in reality, a predominantly electronic effect and the true temperature rise is small. 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 beam analysis apparatus, as the operation of temperature feedback systems can be significantly distorted by this effect.

  14. Decoupling ion flux and mechanical strength in polymer battery membranes

    NASA Astrophysics Data System (ADS)

    Smith, Derrick; Cheng, Shan; Bunning, Timothy; Li, Christopher

    2013-03-01

    While much research has demonstrated repeatable characteristics of electrolyte membranes, the fundamentals behind the interactions during ionic diffusion in solid polymer electrolyte membranes for battery applications are not well understood, specifically the role of nanostructures, which hold the key to improving performance of energy storage devices such as fuel cells and Lithium ion batteries. The challenges in fabricating highly controlled model systems are largely responsible for the interdependent ambiguities between nanostructures and the corresponding ion transport behavior. In this work, Holographic Polymer Electrolyte Membrane (hPEM) volume gratings comprised of alternating layers of cross-linked polymer resin and ionic liquid were fabricated using holographic polymerization with an average d-spacing of 180 nm. These one-dimensional confinement structures were used to quantitatively study the anisotropic ionic conductivity properties, and correlate this behavior to nano-confinement and phase mixing. These membranes provide a platform in decoupling ion flux and bulk mechanical properties for future blend systems for battery applications. These volume gratings also offer an exciting route to fabricate multifunctional gratings for optic and sensing applications.

  15. 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.; Henderson, M. G.; Borovsky, J. E.; Denton, J. S.; Pitchford, D.; Hartley, D. P.

    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

  16. 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.

  17. In vivo ion fluxes across the eggs of Armadillidium vulgare (Oniscidea: Isopoda): the role of the dorsal organ.

    PubMed

    Wright, Jonathan C; O'Donnell, Michael J

    2010-01-01

    The thin-walled, lecithotrophic eggs of land isopods (suborder Oniscidea) are brooded in a fluid-filled maternal marsupium until a few days following the second embryonic molt. Eggs of Armadillidium vulgare possess a well-developed dorsal organ underlying a broad silver-staining saddle on the vitelline membrane. Based on its chloride permeability and known transport functions in planktotrophic crustaceans, we hypothesized that the dorsal organ functions in passive or active ion movements. To study this, we employed the automated scanning electrode technique with self-referencing ion-selective microelectrodes to measure ion fluxes across the dorsal organ and adjacent egg poles. Stage 1 (chorionated) eggs revealed only small ion fluxes, indicating low permeability. Early stage 2 eggs--between the first embryonic molt and blastokinesis--showed evidence for active uptake of Ca(2+) and Cl(-) and possibly Na(+) against low bathing concentrations, and uptake fluxes were predominantly localized over the dorsal organ. Late stage 2 eggs revealed no capacity for ion uptake, consistent with the atrophy of the dorsal organ at blastokinesis, but high ion permeability. In all stages, the silver-staining saddle showed a sustained outward proton flux indicating that it is the primary site for metabolic acid/CO(2) excretion. The emerging picture is that the embryo dorsal organ in A. vulgare serves important functions in ion regulation, calcium provisioning, and acid excretion. PMID:20465420

  18. Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC.

    PubMed

    Gupta, D; Bolte, N; Gota, H; Hayashi, R; Kiyashko, V; Marsili, P; Morehouse, M; Primavera, S; Roche, T; Wessel, F

    2010-10-01

    One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.

  19. Sensitivity of the interpretation of the experimental ion thermal diffusivity to the determination of the ion conductive heat flux

    SciTech Connect

    Stacey, W. M.

    2014-04-15

    A moments equation formalism for the interpretation of the experimental ion thermal diffusivity from experimental data is used to determine the radial ion thermal conduction flux that must be used to interpret the measured data. It is shown that the total ion energy flux must be corrected for thermal and rotational energy convection, for the work done by the flowing plasma against the pressure and viscosity, and for ion orbit loss of particles and energy, and expressions are presented for these corrections. Each of these factors is shown to have a significant effect on the interpreted ion thermal diffusivity in a representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharge.

  20. The spatial distribution of planetary ion fluxes near Mars observed by MAVEN

    NASA Astrophysics Data System (ADS)

    Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E. P.; Bougher, S. W.; Curry, S.; Dong, C. F.; Dong, Y.; Eparvier, F.; Fang, X.; Fortier, K.; Hara, T.; Harada, Y.; Jakosky, B. M.; Lillis, R. J.; Livi, R.; Luhmann, J. G.; Ma, Y.; Modolo, R.; Seki, K.

    2015-11-01

    We present the results of an initial effort to statistically map the fluxes of planetary ions on a closed surface around Mars. Choosing a spherical shell ~1000 km above the planet, we map both outgoing and incoming ion fluxes (with energies >25 eV) over a 4 month period. The results show net escape of planetary ions behind Mars and strong fluxes of escaping ions from the northern hemisphere with respect to the solar wind convection electric field. Planetary ions also travel toward the planet, and return fluxes are particularly strong in the southern electric field hemisphere. We obtain a lower bound estimate for planetary ion escape of ~3 × 1024 s-1, accounting for the ~10% of ions that return toward the planet and assuming that the ~70% of the surface covered so far is representative of the regions not yet visited by Mars Atmosphere and Volatile EvolutioN (MAVEN).

  1. A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitating Fluxes

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.

    2002-01-01

    Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.

  2. Dust-ion acoustic cnoidal waves and associated nonlinear ion flux in a nonthermal dusty plasma

    NASA Astrophysics Data System (ADS)

    Ur-Rehman, Hafeez; Mahmood, S.

    2016-09-01

    The dust-ion acoustic nonlinear periodic (cnoidal) waves and solitons are investigated in a dusty plasma containing dynamic cold ions, superthermal kappa distributed electrons and static charged dust particles. The massive dust particles can have positive or negative charge depending on the plasma environment. Using reductive perturbation method (RPM) with appropriate periodic boundary conditions, the evolution equations for the first and second order nonlinear potentials are derived. The first order potential is determined through Korteweg-de Vries (KdV) equation which gives dust-ion acoustic cnoidal waves and solitons structures. The solution of second order nonlinear potential is obtained through an inhomogeneous differential equation derived from collecting higher order terms of dynamic equations, which is linear for second order electrostatic potential. The nonlinear ion flux associated with the cnoidal waves is also found out numerically. The numerical plots of the dust-ion acoustic cnoidal wave and soliton structures for both positively and negatively charged dust particles cases and nonthermal electrons are also presented for illustration. It is found that only compressive nonlinear electrostatic structures are formed in case of positively dust charged particles while both compressive and rarefactive nonlinear structures are obtained in case of negatively charged particles depending on the negatively charged dust density in a nonthermal dusty plasma. The numerical results are obtained using data of the ionospheric region containing dusty plasma exist in the literature.

  3. Testing and optimizing active rotary flux compressors

    SciTech Connect

    Carder, B.M.; Eimerl, D.; Goodwin, E.J.; Trenholme, J.; Foley, R.J.; Bird, W.L.

    1981-06-01

    The test program for an Active Rotary Flux Compressor (ARFC) has demonstrated conclusively that large compression factors can be obtained with a laminated-iron, wave-wound, rotary flux compressor. Peak-current to startup-current ratios of 17 have been produced with a rotor tip speed of 60 meters per second. Sub-millisecond pulse widths were also measured: the minimum, 590 ..mu..sec (FWHM), was obtained at 5607 rpm with an 8-inch diameter, 4-pole rotor. The machine was operated without a high current output switch, proving the feasibility of a novel commutation scheme described. A computational code has been developed that will calculate the output waveshape of the model ARFC with reasonable accuracy. The code is being refined to better account for saturation in the iron laminations. A second optimization code selects the best design for a given application. This code shows favorable cost effectiveness of large ARFC's over the conventional capacitors to drive flashlamps for large lasers.

  4. Role of plasma enhanced atomic layer deposition reactor wall conditions on radical and ion substrate fluxes

    SciTech Connect

    Sowa, Mark J.

    2014-01-15

    Chamber wall conditions, such as wall temperature and film deposits, have long been known to influence plasma source performance on thin film processing equipment. Plasma physical characteristics depend on conductive/insulating properties of chamber walls. Radical fluxes depend on plasma characteristics as well as wall recombination rates, which can be wall material and temperature dependent. Variations in substrate delivery of plasma generated species (radicals, ions, etc.) impact the resulting etch or deposition process resulting in process drift. Plasma enhanced atomic layer deposition is known to depend strongly on substrate radical flux, but film properties can be influenced by other plasma generated phenomena, such as ion bombardment. In this paper, the chamber wall conditions on a plasma enhanced atomic layer deposition process are investigated. The downstream oxygen radical and ion fluxes from an inductively coupled plasma source are indirectly monitored in temperature controlled (25–190 °C) stainless steel and quartz reactors over a range of oxygen flow rates. Etch rates of a photoresist coated quartz crystal microbalance are used to study the oxygen radical flux dependence on reactor characteristics. Plasma density estimates from Langmuir probe ion saturation current measurements are used to study the ion flux dependence on reactor characteristics. Reactor temperature was not found to impact radical and ion fluxes substantially. Radical and ion fluxes were higher for quartz walls compared to stainless steel walls over all oxygen flow rates considered. The radical flux to ion flux ratio is likely to be a critical parameter for the deposition of consistent film properties. Reactor wall material, gas flow rate/pressure, and distance from the plasma source all impact the radical to ion flux ratio. These results indicate maintaining chamber wall conditions will be important for delivering consistent results from plasma enhanced atomic layer deposition

  5. Calcium ion-gated proton fluxes in choroplast thylakoid membranes

    SciTech Connect

    Chiang, G.G.

    1989-01-01

    Replacement of sucrose by 100 mM KCl in the choroplast thylakoid storage media, shifts proton gradients in thylakoids from a localized to a delocalized mode of energy coupling. This conversion appears to be regulated by Ca{sup 2+} ions. Addition of divalent cations to the KCl containing medium maintained thylakoids in a localized coupling response. Inclusion of lipid soluble Ca{sup 2+} chelators to sucrose stored thylakoids normally displaying localized coupling behavior, resulted in a conversion to a delocalized pattern typical of KCl stored thylakoids. The Ca{sup 2+} antagonists directed towards calmodulin, chorpromazine and trifluoperazine, perturb the H{sup +} gating function in a way consistent with the Ca{sup 2+} gating action, involving a membrane protein analogous to a calmodulin-Ca{sup 2+} complex functioning as the closed gate structure. Chlorpromazine bound at the Ca{sup 2+} occupied sites causes partial blockage of the proton flux between the membrane domains and the lumen. ({sup 3}H)Chlorpromazine used as a photoaffinity probe, identified four membrane proteins of Mr 7-14 kDa, as possibly being part of the gating function. One of the proteins was identified as the 8 kDa CF{sub 0} subunit by its N-terminus amino acid sequence analysis of co-labeling with ({sup 14}C)DCCD. A 6 kDa protein also bound ({sup 3}H)CPZ similarly, from which a 10 amino acid peptide sequence was determined. This polypeptide may be part of a yet unidentified protein involved in the gating mechanism.

  6. Amyloid-β-Induced Ion Flux in Artificial Lipid Bilayers and Neuronal Cells: Resolving a Controversy

    PubMed Central

    Capone, Ricardo; Quiroz, Felipe Garcia; Prangkio, Panchika; Saluja, Inderjeet; Sauer, Anna M.; Bautista, Mahealani R.; Turner, Raymond S.

    2010-01-01

    Understanding the pathogenicity of amyloid-beta (Aβ) peptides constitutes a major goal in research on Alzheimer’s disease (AD). One hypothesis entails that Aβ peptides induce uncontrolled, neurotoxic ion flux through cellular membranes. The exact biophysical mechanism of this ion flux is, however, a subject of an ongoing controversy which has attenuated progress toward understanding the importance of Aβ-induced ion flux in AD. The work presented here addresses two prevalent controversies regarding the nature of transmembrane ion flux induced by Aβ peptides. First, the results clarify that Aβ can induce stepwise ion flux across planar lipid bilayers as opposed to a gradual increase in transmembrane current; they show that the previously reported gradual thinning of membranes with concomitant increase in transmembrane current arises from residues of the solvent hexafluoroisopropanol, which is commonly used for the preparation of amyloid samples. Second, the results provide additional evidence suggesting that Aβ peptides can induce ion channel-like ion flux in cellular membranes that is independent from the postulated ability of Aβ to modulate intrinsic cellular ion channels or transporter proteins. PMID:19526294

  7. Noninvasive microelectrode ion flux estimation technique (MIFE) for the study of the regulation of root membrane transport by cyclic nucleotides.

    PubMed

    Ordoñez, Natalia Maria; Shabala, Lana; Gehring, Chris; Shabala, Sergey

    2013-01-01

    Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular.

  8. Mass analysis addition to the Differential Ion Flux Probe (DIFP) study

    NASA Technical Reports Server (NTRS)

    Wright, K. H., Jr.; Jolley, Richard

    1994-01-01

    The objective of this study is to develop a technique to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The approach, conducted in conjunction with current MSFC activities, is to extend the capabilities of the Differential Ion Flux Probe (DIFP) to include a high throughput mass measurement that does not require either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This will significantly reduce the complexity and expense of instrument fabrication, testing, and integration of flight hardware compared to classical mass analyzers. The feasibility of the enhanced DIFP has been verified by using breadboard test models in a controlled plasma environment. The ability to manipulate particles through the instrument regardless of incident angle, energy, or ionic component has been amply demonstrated. The energy analysis mode is differential and leads directly to a time-of-flight mass measurement. With the new design, the DIFP will separate multiple ion streams and analyze each stream independently for ion flux intensity, velocity (including direction of motion), mass, and temperature (or energy distribution). In particular, such an instrument will be invaluable on follow-on electrodynamic TSS missions and, possibly, for environmental monitoring on the space station.

  9. Spatial profiles of potential, ion concentration and flux in short unipolar and bipolar nanopores.

    PubMed

    Tajparast, Mohammad; Virdi, Gautam; Glavinović, Mladen I

    2015-10-01

    During release of vesicular content the resistance of the fusion pore sometimes changes rapidly and repeatedly. However, it is not clear why the pore 'flickers'. Engineered nanopores often rectify, but how different factors influence the rectification requires clarification. To better understand the ionic 'causes' of pore conductivity and its changes we simulated ion transport through a short nanopore using Poisson-Nernst-Planck equations, coupling it to the transport of water using Navier-Stokes equations. We extracted the potential, concentration, and ion flux profiles. In uniformly charged nanopores the voltage bias determines which counter-ion flux dominates, and it is carried by the counter-ions of the highest concentration. In unipolar nanopores this simple rule breaks down. The dominant counter-ion in the charged half is from the adjacent compartment, but the bias determines what counter-ion flux is dominant--the same ion (regular bias), or a different and smaller (reverse bias), and this difference determines the level of rectification. In bipolar nanopores the dominant counter-ions in each half are from the adjacent compartments, and the total ion concentration dips in the middle near the wall. With regular bias the total ion concentration peaks in the pore center; the ions that carry the current through the nanopore start as counter-ions and their fluxes are large. With reverse bias the total concentration dips near the wall and in the center, both dominant ion fluxes through the nanopore start as co-ions and are very small, whereas those starting as counter-ions do not go through.

  10. Ion fluxes across the pitcher walls of three Bornean Nepenthes pitcher plant species: flux rates and gland distribution patterns reflect nitrogen sequestration strategies

    PubMed Central

    Moran, Jonathan A.; Hawkins, Barbara J.; Gowen, Brent E.; Robbins, Samantha L.

    2010-01-01

    Nepenthes pitcher plant species differ in their prey capture strategies, prey capture rates, and pitcher longevity. In this study, it is investigated whether or not interspecific differences in nutrient sequestration strategy are reflected in the physiology and microstructure of the pitchers themselves. Using a non-invasive technique (MIFE), ion fluxes in pitchers of Nepenthes ampullaria Jack, Nepenthes bicalcarata Hook.f., and Nepenthes rafflesiana Jack were measured. Scanning electron microscopy was also used to characterize the distribution of glandular and other structures on the inner pitcher walls. The results demonstrate that nutrient sequestration strategy is indeed mirrored in pitcher physiology and microstructure. Species producing long-lived pitchers with low prey capture rates (N. ampullaria, N. bicalcarata) showed lower rates of NH4+ uptake than N. rafflesiana, a species producing short-lived pitchers with high capture rates. Crucially, species dependent upon aquatic commensals (N. ampullaria, N. bicalcarata) actively manipulated H+ fluxes to maintain less acid pitcher fluid than found in ‘typical’ species; in addition, these species lacked the lunate cells and epicuticular waxes characteristic of ‘typical’ insectivorous congeners. An unexpected finding was that ion fluxes occurred in the wax-covered, non-glandular zones in N. rafflesiana. The only candidates for active transport of aqueous ions in these zones appear to be the epidermal cells lying beneath the lunate cells, as these are the only sites not visibly coated with epicuticular waxes. PMID:20150519

  11. 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.

  12. 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.

  13. Abundances and charge states in quiet-time low-energy ion fluxes at 1 AU

    NASA Astrophysics Data System (ADS)

    Kecskemety, Karoly; Zeldovich, Mariya; Klecker, Berndt; Logachev, Yurii

    Abundances of C and Fe ions with energies 0.04-1.28 MeV/nuc in the 23rd solar activity cycle are examined in the quiet-time fluxes using ACE, SOHO and STEREO data. They are com-bined with charge state measurement data from SEPICA (ACE, 0.18-0.43 MeV/nuc). Quiet periods of solar activity were selected using the criteria a) Jp < 2x10-4 protons/(cm2 s sr MeV) for 4-8 MeV protons (from EPHIN/SOHO) and b) the ratio H/He < 10 at these energies. The values of C/O and Fe/O were determined over the solar cycle and the following was found. In about 50% of the time intervals during high activity they both were near the average values observed in the solar corona, whereas at solar minimum in more than 90% of the periods the ratios were around the solar wind values. Most of the quiet time periods around maximum, which have sufficient statistics show high average Fe charge states (>15), consistent with im-pulsive solar event origin. During the SC minima the abundances in almost all cases correspond to solar wind values. The results obtained suggest that the active structures on the Sun arising at low solar activity are mostly responsible for background particle fluxes at these energies. There may be microflares, disappearing of ribbons, soft X-ray bright points etc.

  14. The Flux Control of Cyclotron Ions Incident upon the Substrate by Employing the Ponderomotive Potential

    NASA Astrophysics Data System (ADS)

    Sato, Naoyuki; Nakamori, Hidetaka; Ikehata, Takashi; Mase, Hiroshi

    2000-10-01

    The plasma-assisted deposition is desirable processing technique to grow the epitaxial film such as oxide-metal compound semiconductor on the lower temperature substrate. To control its stoichiometry ratio and orientation more precisely, handling the flux of oxygen and metallic ions incident upon the substrate is required. Here, we propose to employ the ponderomotive potential acting independently on each species of cyclotron ions in order to govern a new method for the flux control of ions selected before the substrate. Our idea is to form the potential structure decelerating the ions before the substrate, resulting in the enhancement of the ponderomotive force on their ions. The preliminary experiment is carried out using the magnetized plasma column terminated by the floating substrate where the localized rotating electrostatic field yielding the ponderomotive potential is impressed. It is found that the ion flux decreases when rf frequency approaches to the cyclotron frequency of helium ion. However, Q-value is small because the ions would not make the cyclotron motion many times until arriving at the substrate. In order to decelerate ions, we try to form the potential hump and/or to reconstruct the ion sheath to the effective electron sheath by the ponderomotive potential.

  15. Controlling ion fluxes during reactive sputter-deposition of SnO{sub 2}:F

    SciTech Connect

    Jäger, Timo Romanyuk, Yaroslav E.; Tiwari, Ayodhya N.; Anders, André

    2014-07-21

    Magnetron sputtering of fluorine-doped tin oxide (FTO) is a scalable deposition method for large-area transparent conducting films used in fenestration, photovoltaics, and other applications. The electrical conductivity of sputtered FTO is, however, lower than that of spray-pyrolized FTO because of the ion damage induced by high energy ions leading to a reduction of the crystal quality in sputtered FTO films. In this study, various ion species present during the reactive sputtering of a metallic tin target in a mixed Ar/O{sub 2}/CF{sub 4} atmosphere are systematically characterized by energy and mass spectrometry, and possible ways of controlling the ion fluxes are explored. Ion energy distribution functions (IEDFs) of the negative ions F{sup −} and O{sup −} exhibit large peaks at an energy corresponding to the full target voltage. Although the applied partial pressure of CF{sub 4} is about 1/30 than that of O{sub 2}, the obtained IEDFs of F{sup −} and O{sup −} have comparable peak height, which can be attributed to a higher electronegativity of F. The IEDFs of positively charged O{sup +}, O{sub 2}{sup +}, Ar{sup +}, and Sn{sup +} species have their peaks around 2–8 eV. To control ion fluxes a solenoid or permanent magnets were placed between the target and the mass spectrometer. The flux of positive ions could be varied by several orders of magnitude as a function of the applied current through the solenoid, whereas the high-energy (>100 eV) negative F{sup −} and O{sup −} ions were not notably deflected. By using permanent magnets with the B-field orthogonal to the ion trajectory, the flux of O{sup −} ions could be decreased by two orders and the exposure to the high-energy F{sup −} ions was completely suppressed.

  16. The experiment MONICA for the investigation of solar cosmic ray ion fluxes

    NASA Astrophysics Data System (ADS)

    Bakaldin, Alexey; Karelin, Alexander; Stozhkov, Yuri; Koldashov, Sergey; Sergey, Voronov; Galper, Arkady; Khabarov, Sergey; Kvashnin, Alexander; Zamyatin, Nikolay

    The current status of onboard experiment MONICA for study of the fluxes of cosmic ray energetic ions from He to Ni in the energy range 10-300 MeV/n in vicinity of the Earth is presented. MONICA main scientific objective is the measurement of ion charge states, as well as elemental, isotope composition and energy spectra of Solar Energetic Particle (SEP) fluxes for separate SEP events (including impulsive events), and study the evolution of these characteristics in time. The experiment MONICA will be able to study the ion and isotopic composition as Anomalous Cosmic Rays (ACR) and Galactic Cosmic Rays (GCR), as well as the nuclear fluxes in Earth radiation belt. The observation of the ion fluxes will be carried out with the large acceptance multilayer silicon telescope-spectrometer MONICA onboard the polar-orbiting satellite. The satellite orbit parameters (LEO, circular with altitude about 600 km, polar) were chosen for the realization of the ion charge state measurement method at energies more 10 MeV/n based on using of Earth magnetic field as a separator of ion charge. This technique is unique possible for this ion energy range.

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

    SciTech Connect

    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 created 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.

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

    PubMed

    Rafalskyi, Dmytro; Dudin, Stanislav; Aanesland, Ane

    2015-05-01

    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 created 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. PMID:26026517

  19. Geodesic mode instability driven by electron and ion fluxes in tokamaks

    SciTech Connect

    Elfimov, A. G. Camilo de Souza, F.; Galvão, R. M. O.

    2015-11-15

    The effect of the parallel electron current and plasma flux on Geodesic Acoustic Modes (GAM) in a tokamak is analyzed by kinetic theory taking into the account the ion Landau damping and diamagnetic drifts. It is shown that the electron current and plasma flow, modeled by shifted Maxwell distributions of electrons and ions, may overcome the ion Landau damping generating the GAM instability when the parallel electron current velocity is larger than the effective parallel GAM phase velocity of sidebands, Rqω. The instability is driven by the electron current and the parallel ion flux cross term. Possible applications to tokamak experiments are discussed. The existence of the geodesic ion sound mode due to plasma flow is shown.

  20. IIB soliton spectra with all fluxes activated

    NASA Astrophysics Data System (ADS)

    Evslin, Jarah

    2003-05-01

    Building upon an earlier proposal for the classification of fluxes, a sequence is proposed which generalizes the AHSS by computing type IIB string theory's group of conserved RR and also NS charges, which is conjectured to be a K-theory of dual pairs. As a test of this proposal, the formalism of Maldacena, Moore and Seiberg ( arxiv:hep-th/0108100) is applied to classify D-branes, NS5-branes, F-strings and their dielectric counterparts in IIB compactified on a 3-sphere with both NS and RR background fluxes. The soliton spectra on the 3-sphere are then compared with the output of the sequence, as is the baryon spectrum in Witten's non- spinc example, AdS 5× RP5. The group of conserved charges is seen to change during Brown-Teitelboim-like phase transitions which change the effective cosmological constant.

  1. Ion flux interaction with cytoplasmic streaming in branchlets of Chara australis.

    PubMed

    Babourina, Olga; Voltchanskii, Konstantin; Newman, Ian

    2004-12-01

    Both parts of the actin-myosin complex involved in cytoplasmic streaming could be regulated by mineral ions. The main goal of this study was to find a relationship between cyclosis and ion transport across the cell wall and plasma membrane. The transport of K(+) and Ca(2+) along pH bands in Chara branchlet internodal cells was characterized by using the MIFE system for non-invasive microelectrode measurement of ion fluxes. Branchlets formed acidic and alkaline bands with the pH ranging from 5 to 8. Different pH patterns were observed for different sides of the branchlets. Sides with cyclosis streaming acropetally generally showed greater variation in the profiles of pH and H(+) fluxes. Although a high correlation was not found between pH bands and Ca(2+) or K(+) fluxes, there was a positive correlation between Ca(2+) and K(+) fluxes themselves for both sides of the branchlets. Application of cytochalasin D, an inhibitor of cyclosis, had no immediate effect on pH and ion fluxes, however, the time of cyclosis cessation corresponded with a dramatic change in Ca(2+) and K(+) fluxes; pH profiles and H(+) fluxes were affected within 2 h. The evidence suggests that, in Chara branchlets, pH band formation and Gd(3+)-insensitive Ca(2+) transport systems are linked to the cyclosis machinery: (i) the pH band amplitude for the acropetally streaming side was larger than that for the basipetally streaming side; (ii) cessation of cytoplasmic streaming after cytochalasin D application resulted in changed pH banding profiles and H(+), Ca(2+) and K(+) fluxes; and (iii) the application of GdCl(3) or incubation in GdCl(3) solutions did not lead to the cessation of cytoplasmic streaming, although external Ca(2+) fluxes changed.

  2. 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.

  3. Heat flux and viscosity of ions in the collisionless solar wind

    NASA Technical Reports Server (NTRS)

    Williams, L. L.

    1995-01-01

    Between 1 and 2 solar radii, the Coulomb-collision mean free path for thermal ions exceeds the scale height of the solar atmosphere. The expanding solar plasma becomes collisionless and the kinetics of the solar wind are no longer dominated by thermalizing collisions. The usual Braginskii-type expressions for solar wind ion heat flux and viscosity are no longer valid. However, another microscale still exists in the solar wind, dictated by the gyro-radius of ions in the turbulent embedded solar wind magnetic field. Wave-particle interactions will act to isotropize (but not thermalize) particle distributions, and the relevant microscale for this process is the ion gyro-radius. The ion distribution can be modelled as undergoing isotropizing 'collisions,' with the relevant mean free path scaling with gyro-radius. Here, the author presents the heat flux and viscosity expected for solar wind protons which are relaxing to isotropy on a microscale that scales with gyro-radius. The collisionless viscosity and heat flux have a functional dependence different than their collisional analogs. The collisional expressions for ion viscosity and heat flux drastically overestimate the efficiency of diffusive energy and momentum transport actually operative in the solar wind.

  4. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  5. Ion-scale secondary flux ropes generated by magnetopause reconnection as resolved by MMS

    NASA Astrophysics Data System (ADS)

    Eastwood, J. P.; Phan, T. D.; Cassak, P. A.; Gershman, D. J.; Haggerty, C.; Malakit, K.; Shay, M. A.; Mistry, R.; Øieroset, M.; Russell, C. T.; Slavin, J. A.; Argall, M. R.; Avanov, L. A.; Burch, J. L.; Chen, L. J.; Dorelli, J. C.; Ergun, R. E.; Giles, B. L.; Khotyaintsev, Y.; Lavraud, B.; Lindqvist, P. A.; Moore, T. E.; Nakamura, R.; Paterson, W.; Pollock, C.; Strangeway, R. J.; Torbert, R. B.; Wang, S.

    2016-05-01

    New Magnetospheric Multiscale (MMS) observations of small-scale (~7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non-frozen-in ion behavior. The data are further compared with a particle-in-cell simulation. It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.

  6. Energetic ion diagnostics using neutron flux measurements during pellet injection

    SciTech Connect

    Heidbrink, W.W.

    1986-01-01

    Neutron measurements during injection of deuterium pellets into deuterium plasmas on the Tokamak Fusion Test Reactor (TFTR) indicate that the fractional increase in neutron emission about 0.5 msec after pellet injection is proportional to the fraction of beam-plasma reactions to total fusion reactions in the unperturbed plasma. These observations suggest three diagnostic applications of neutron measurements during pellet injection: (1) measurement of the beam-plasma reaction rate in deuterium plasmas for use in determining the fusion Q in an equivalent deuterium-tritium plasma, (2) measurement of the radial profile of energetic beam ions by varying the pellet size and velocity, and (3) measurement of the ''temperature'' of ions accelerated during wave heating. 18 refs., 3 figs.

  7. Ion chemistry of N2/+/ and the solar ultraviolet flux in the thermosphere

    NASA Technical Reports Server (NTRS)

    Oppenheimer, M.; Dalgarno, A.; Brinton, H. C.

    1976-01-01

    We have analyzed daytime composition measurements in the thermosphere from Atmosphere Explorer-C by use of a theory of the ion chemistry. Predicted and measured N2(+) densities are compared to infer global variation of the solar ionizing flux. Results indicate that the solar flux of Hinteregger measured on Atmosphere Explorer-C provides an adequate basis for the calculation of solar ultraviolet photoionization rates. The role of metastable species is examined, and theoretical O+(2D) densities are presented.

  8. Cycle Flux Algebra for Ion and Water Flux through the KcsA Channel Single-File Pore Links Microscopic Trajectories and Macroscopic Observables

    PubMed Central

    Oiki, Shigetoshi; Iwamoto, Masayuki; Sumikama, Takashi

    2011-01-01

    In narrow pore ion channels, ions and water molecules diffuse in a single-file manner and cannot pass each other. Under such constraints, ion and water fluxes are coupled, leading to experimentally observable phenomena such as the streaming potential. Analysis of this coupled flux would provide unprecedented insights into the mechanism of permeation. In this study, ion and water permeation through the KcsA potassium channel was the focus, for which an eight-state discrete-state Markov model has been proposed based on the crystal structure, exhibiting four ion-binding sites. Random transitions on the model lead to the generation of the net flux. Here we introduced the concept of cycle flux to derive exact solutions of experimental observables from the permeation model. There are multiple cyclic paths on the model, and random transitions complete the cycles. The rate of cycle completion is called the cycle flux. The net flux is generated by a combination of cyclic paths with their own cycle flux. T.L. Hill developed a graphical method of exact solutions for the cycle flux. This method was extended to calculate one-way cycle fluxes of the KcsA channel. By assigning the stoichiometric numbers for ion and water transfer to each cycle, we established a method to calculate the water-ion coupling ratio (CRw-i) through cycle flux algebra. These calculations predicted that CRw-i would increase at low potassium concentrations. One envisions an intuitive picture of permeation as random transitions among cyclic paths, and the relative contributions of the cycle fluxes afford experimental observables. PMID:21304994

  9. Cycle flux algebra for ion and water flux through the KcsA channel single-file pore links microscopic trajectories and macroscopic observables.

    PubMed

    Oiki, Shigetoshi; Iwamoto, Masayuki; Sumikama, Takashi

    2011-01-31

    In narrow pore ion channels, ions and water molecules diffuse in a single-file manner and cannot pass each other. Under such constraints, ion and water fluxes are coupled, leading to experimentally observable phenomena such as the streaming potential. Analysis of this coupled flux would provide unprecedented insights into the mechanism of permeation. In this study, ion and water permeation through the KcsA potassium channel was the focus, for which an eight-state discrete-state Markov model has been proposed based on the crystal structure, exhibiting four ion-binding sites. Random transitions on the model lead to the generation of the net flux. Here we introduced the concept of cycle flux to derive exact solutions of experimental observables from the permeation model. There are multiple cyclic paths on the model, and random transitions complete the cycles. The rate of cycle completion is called the cycle flux. The net flux is generated by a combination of cyclic paths with their own cycle flux. T.L. Hill developed a graphical method of exact solutions for the cycle flux. This method was extended to calculate one-way cycle fluxes of the KcsA channel. By assigning the stoichiometric numbers for ion and water transfer to each cycle, we established a method to calculate the water-ion coupling ratio (CR(w-i)) through cycle flux algebra. These calculations predicted that CR(w-i) would increase at low potassium concentrations. One envisions an intuitive picture of permeation as random transitions among cyclic paths, and the relative contributions of the cycle fluxes afford experimental observables.

  10. Comparisons of Earthward Poynting flux and the kinetic energy flux of up-flowing transversely heated ions from the Polar spacecraft on cusp magnetic field lines

    NASA Astrophysics Data System (ADS)

    Tian, S.; Wygant, J. R.; Cattell, C. A.; Scudder, J. D.; Mozer, F.; Russell, C. T.

    2013-12-01

    This paper presents estimates of the Poynting flux flowing along magnetic field lines in the Earth's cusp region over altitudes from 0.8 Re to 7 Re using measurements during several passes from the Polar spacecraft. The Poynting flux is calculated from measurements of electric fields from the University of California, Berkeley double probe electric field instrument, and from magnetic field measurements from the U.C.L.A. fluxgate magnetometer. The estimates of Poynting flux are of special interest because the high altitude mapping of the cusp magnetic flux tubes may connect to newly reconnected field lines and the low altitude mapping of these field lines is the scene of powerful acceleration processes, most notably transverse heating and outflow of ions. The data show that the Poynting flux is predominantly downward over the frequency range from 1 mHz to 1 Hz . This frequency range includes the Poynting flux due to steady state convection and field-aligned current systems, Alfven waves, and kinetic Alfven waves. Measurement of transversely heated ions over the energy ranges from 10 eV to several keV and their associated ion kinetic energy flux are presented from the University of Iowa Hydra instrument and compared to the values of the downward Poynting flux. Generally the downward Poynting flux exceeds the upward kinetic energy flux of the ions.

  11. Uniformity of postprocessing of dense nanotube arrays by neutral and ion fluxes

    SciTech Connect

    Levchenko, I.; Ostrikov, K.; Tam, E.

    2006-11-27

    The advantages of using low-temperature plasma environments for postprocessing of dense nanotube arrays are shown by means of multiscale hybrid numerical simulations. By controlling plasma-extracted ion fluxes and varying the plasma and sheath parameters, one can selectively coat, dope, or functionalize different areas on nanotube surfaces. Conditions of uniform deposition of ion fluxes over the entire nanotube surfaces are obtained for different array densities. The plasma route enables a uniform processing of lateral nanotube surfaces in very dense (with a step-to-height ratio of 1:4) arrays, impossible via the neutral gas process wherein radical penetration into the internanotube gaps is poor.

  12. Explosive Flux Compression: 50 Years of Los Alamos Activities

    SciTech Connect

    Fowler, C.M.; Thomson, D.B.; Garn, W.B.

    1998-10-18

    Los Alamos flux compression activities are surveyed, mainly through references in view of space limitations. However, two plasma physics programs done with Sandia National Laboratory are discussed in more detail.

  13. Effect of pulse frequency on the ion fluxes during pulsed dc magnetron sputtering

    SciTech Connect

    Rahamathunnisa, M.; Cameron, D. C.

    2009-03-15

    The ion fluxes and energies which impinge on the substrate during the deposition of chromium nitride by asymmetric bipolar pulsed dc reactive magnetron sputtering have been analyzed using energy resolved mass spectrometry. It has been found that there is a remarkable increase in ion flux at higher pulse frequencies and that the peak ion energy is directly related to the positive voltage overshoot of the target voltage. The magnitude of the metal flux depositing on the substrate is consistent with a 'dead time' of {approx}0.7 {mu}s at the start of the on period. The variation of the ion flux with pulse frequency has been explained by a simple model in which the ion density during the on period has a large peak which is slightly delayed from the large negative voltage overshoot which occurs at the start of the on pulse due to increased ionization at that time. This is consistent with the previously observed phenomena in pulsed sputtering.

  14. Interstellar helium pickup ion flux variations observed with SOHO/CELIAS

    NASA Astrophysics Data System (ADS)

    Saul, Lukas A.

    Interstellar pickup ions are formed when neutral atoms freely enter the heliosphere and are subsequently ionized. Once these particles are charged they become a component of the interplanetary plasma and are transported outward with the solar wind (SW). Measurements of these particles give information about the local interstellar gas in which our sun resides. However, fluxes of pickup ions in the solar wind are observed to vary substantially in both magnitude and energy spectrum. Hypothesized is that the main causes of these variations are transport phenomenon in the solar wind, determined by the solar wind and the interplanetary magnetic field. If so, solar wind conditions can be used to predict pickup ion fluxes, and pickup ion fluxes can be used to indicate solar wind transport conditions. To prove the feasibility of this hypothesis, in situ measurements of helium pickup ions from the CTOF instrument on the SOHO spacecraft are used to characterize transport parameters. Results are presented which show the effect of solar wind structures on pickup ions. Compression regions are shown to strongly affect measured fluxes of pickup ions. Observations show that compression regions can also cause an adiabatic heating or a shift in the pickup ion velocity distribution. Also investigated is the effect of interplanetary magnetic field fluctuations and waves on pickup ions. These fluctuations can scatter pickup ions, in both pitch angle and energy. Comparison with WIND/MFI magnetic field measurements show that the pitch angle scattering rate is correlated with the wave-power hemispheric model for the pickup ion distribution is used to determine pitch angle diffusion coefficients from observed spectra. We find that the observed scattering rate differs from the predictions of simple diffusion models, especially in low wave-powers. Energy diffusion or particle acceleration is also observed in the pickup ion velocity distribution, most notably in the passage of solar wind

  15. 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.

  16. Ion-scale secondary island flux-ropes in magnetopause reconnection as resolved by MMS

    NASA Astrophysics Data System (ADS)

    Eastwood, Jonathan

    2016-04-01

    Magnetic reconnection on the dayside magnetopause of the Earth's magnetosphere leads to the formation of flux transfer events (FTEs), whose primary signature is a bipolar variation in the component of the magnetic field perpendicular to the magnetopause plane. Many FTEs exhibit a flux rope type structure, and several different formation mechanisms have been proposed, including: as a consequence of patchy reconnection; bursty reconnection at a single X-line; or multiple X-line reconnection. Here we present new observations from the four-spacecraft Magnetospheric MultiScale mission of FTE-type structure observed at the dayside magnetopause. These FTE structures last only a few seconds, and are embedded in a reconnection jet that is close to a reconnection X-line. They are identified as flux rope type islands produced by secondary reconnection processes. We examine the structure and properties of the flux ropes using multispacecraft techniques applied to the MMS data where the spacecraft were separated by only 10 km. Measurements of the ion and electron from the Fast Plasma Instrument are used to calculate the flux rope current density and this is compared with current densities calculated from the four-point magnetic field measurements. The velocity moments together with measurements of the electric and magnetic field are also used to examine the sub-structure of the flux rope and assess differences in the ion and electron behaviour inside the flux rope on ion-scales and below. This reveals flux-rope sub-structure in new detail which is compared with the output of particle-in-cell simulation.

  17. Transendothelial albumin flux: evidence against active transport of albumin

    SciTech Connect

    Siflinger-Birnboim, A.; Del Vecchio, P.J.; Cooper, J.A.; Malik, A.B.

    1986-03-01

    The authors studied whether albumin is actively transported across cultured pulmonary endothelium by comparing the transendothelial flux of /sup 125/I-albumin from the luminal-to-abluminal side to the flux from the abluminal-to-luminal side. Bovine pulmonary artery endothelial cells were grown to confluence on gelatinized polycarbonated filters separating abluminal from luminal compartments. Each compartment had an albumin concentration of 1 g/100 ml to equalize oncotic pressure gradients. The effect of hydrostatic pressure was eliminated by maintaining an equal level of fluid in both compartments. The transendothelial flux of albumin across the monolayer was measured by placing /sup 125/I-albumin tracer either on the luminal or the abluminal side. Equal fluxes of /sup 125/I-albumin from luminal-to-abluminal side and from abluminal-to-luminal side were observed. The results indicate that the pulmonary endothelium behaves symmetrically for albumin, indicating the absence of active transport of albumin.

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

    SciTech Connect

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

    2014-09-15

    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.

  19. 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.

  20. Dissection of heat-induced systemic signals: superiority of ion fluxes to voltage changes in substomatal cavities.

    PubMed

    Zimmermann, Mathias R; Felle, Hubert H

    2009-02-01

    Using non-invasive ion-selective microprobes, that were placed in substomatal cavities, long-distance signalling has been investigated in intact Hordeum vulgare and Vicia faba seedlings. Heat (flame), applied to one leaf (S-leaf), triggers apoplastic ion activity (pH, pCa, pCl) transients in a distant leaf (T-leaf), all largely independent of simultaneously occurring action potential-like voltage changes. While apoplastic pCa and pH increase (Ca(2+)-, H(+)-activities decrease), pCl decreases (Cl(-)-activity increases). As the signal transfer from the S- to the T-leaf is too fast to account for mass flow, the heat-induced pressure change is primarily responsible for changes in voltage (H(+) pump deactivation) as well as for the ion fluxes. The pCa transient precedes the pCl- and pH responses, but not the voltage change. Since the apoplastic pCl decrease (Cl(-) increase) occurs after the pCa increase (Ca(2+) decrease) and after the depolarization, we argue that the Cl(-) efflux is a consequence of the Ca(2+) response, but has no part in the depolarization. Kinetic analysis reveals that pH- and pCl changes are interrelated, indicated by the action of the anion channel antagonist NPPB, which inhibits both pCl- and pH changes. It is suggested that efflux of organic anions into the apoplast causes the pH increase rather than the deactivation of the plasma membrane H(+) pump. Since there is considerably more information in ion activity changes than in a single action- or variation potential and heat-induced ion fluxes occur more reliably than voltage changes, released by milder stimuli, they are considered systemic signalling components superior to voltage. PMID:19011895

  1. On the flux and the energy spectrum of interstellar ions in the solar system

    NASA Technical Reports Server (NTRS)

    Vasyliunas, V. M.; Siscoe, G. L.

    1976-01-01

    The flux density of ions created by ionization of interstellar neutral particles in the solar system and picked up by the solar wind is calculated as a function of the neutral particles. For atomic hydrogen the flux density is estimated to exceed 10,000/sq cm/sec over the distance range from a few to nearly 100 AU. The velocity space distribution of the interstellar ions is calculated under the assumption of no significant energy diffusion but with inclusion of adiabatic effects as well as a possible strong pitch angle diffusion. The energy spectrum is highly nonthermal and much broader than that of the solar wind ions; interstellar protons are easily distinguishable from solar wind protons by their location in velocity space. If charge exchange is an important contributor to the ionization of hydrogen, the observed local intensity of interstellar protons should exhibit time variations correlated with the density changes of the solar wind stream structure.

  2. Surface Modifications Induced by High Fluxes of Low Energy Helium Ions

    PubMed Central

    Tanyeli, İrem; Marot, Laurent; Mathys, Daniel; van de Sanden, Mauritius C. M.; De Temmerman, Gregory

    2015-01-01

    Several metal surfaces, such as titanium, aluminum and copper, were exposed to high fluxes (in the range of 1023 m−2s−1) of low energy (<100 eV) Helium (He) ions. The surfaces were analyzed by scanning electron microscopy and to get a better understanding on morphology changes both top view and cross sectional images were taken. Different surface modifications, such as voids and nano pillars, are observed on these metals. The differences and similarities in the development of surface morphologies are discussed in terms of the material properties and compared with the results of similar experimental studies. The results show that He ions induced void growth and physical sputtering play a significant role in surface modification using high fluxes of low energy He ions. PMID:25919912

  3. Finite ballooning angle effects on ion temperature gradient driven mode in gyrokinetic flux tube simulations

    SciTech Connect

    Singh, Rameswar; Brunner, S.; Ganesh, R.; Jenko, F.

    2014-03-15

    This paper presents effects of finite ballooning angles on linear ion temperature gradient (ITG) driven mode and associated heat and momentum flux in Gyrokinetic flux tube simulation GENE. It is found that zero ballooning angle is not always the one at which the linear growth rate is maximum. The ITG mode acquires a short wavelength (SW) branch (k{sub ⊥}ρ{sub i} > 1) when growth rates maximized over all ballooning angles are considered. However, the SW branch disappears on reducing temperature gradient showing characteristics of zero ballooning angle SWITG in case of extremely high temperature gradient. Associated heat flux is even with respect to ballooning angle and maximizes at nonzero ballooning angle while the parallel momentum flux is odd with respect to the ballooning angle.

  4. The non-active stellar chromosphere: Ca II basal flux

    NASA Astrophysics Data System (ADS)

    Pérez Martínez, M. I.; Schröder, K.-P.; Hauschildt, P.

    2014-11-01

    We analyse high-resolution, high-s/n European Southern Observatories (ESO)-archive spectra (from UVES, the UV echelle spectrograph) of 76 inactive or modestly active stars of spectral type G to M, main sequence and giants. Using PHOENIX model photospheres with Ca II K lines that match the observed line profiles, we (i) revise the effective temperatures, (ii) obtain a precise surface flux scale for each star and (iii) directly determine the exact surface fluxes of each Ca II K chromospheric emission with respect to the photospheric line profile. We find that our stellar sample exhibits a lower boundary to its chromospheric surface flux distribution with an unprecedented definition. From a subsample of the 25 least active stars, we obtain a simple empirical formula for the basal Ca II flux as a function of effective temperature: log {F^basal_{Ca II(H+K)}} = 7.05(± 0.31) log {T_eff} - 20.86(± 1.15). This is in good agreement with the Mg II basal flux. In a direct comparison with the large body of Mt Wilson S-measurements of the chromospheric Ca II emission and its well-defined cut-off, excellent agreement is achieved as well. A new result, however, is the small scatter of the least active star's fluxes about the basal flux. It is about 25 per cent and equals the residual uncertainties of our approach. At the same time, we do not find any evidence for a gravity dependence within these limits. This strongly confirms the basal flux as a well-defined and universal phenomenon, which characterizes every inactive chromosphere.

  5. Ion Flux Measurements in Electron Beam Produced Plasmas in Atomic and Molecular Gases

    NASA Astrophysics Data System (ADS)

    Walton, S. G.; Leonhardt, D.; Blackwell, D. D.; Murphy, D. P.; Fernsler, R. F.; Meger, R. A.

    2001-10-01

    In this presentation, mass- and time-resolved measurements of ion fluxes sampled from pulsed, electron beam-generated plasmas will be discussed. Previous works have shown that energetic electron beams are efficient at producing high-density plasmas (10^10-10^12 cm-3) with low electron temperatures (Te < 1.0 eV) over the volume of the beam. Outside the beam, the plasma density and electron temperature vary due, in part, to ion-neutral and electron-ion interactions. In molecular gases, electron-ion recombination plays a significant role while in atomic gases, ion-neutral interactions are important. These interactions also determine the temporal variations in the electron temperature and plasma density when the electron beam is pulsed. Temporally resolved ion flux and energy distributions at a grounded electrode surface located adjacent to pulsed plasmas in pure Ar, N_2, O_2, and their mixtures are discussed. Measurements are presented as a function of operating pressure, mixture ratio, and electron beam-electrode separation. The differences in the results for atomic and molecular gases will also be discussed and related to their respective gas-phase kinetics.

  6. Electrogenic and nonelectrogenic ion fluxes across lipid and mitochondrial membranes mediated by monensin and monensin ethyl ester.

    PubMed

    Antonenko, Yuri N; Rokitskaya, Tatyana I; Huczyński, Adam

    2015-04-01

    Monensin is a carrier of cations through lipid membranes capable of exchanging sodium (potassium) cations for protons by an electroneutral mechanism, whereas its ethyl ester derivative ethyl-monensin is supposed to transport sodium (potassium) cations in an electrogenic manner. To elucidate mechanistic details of the ionophoric activity, ion fluxes mediated by monensin and ethyl-monensin were measured on planar bilayer lipid membranes, liposomes, and mitochondria. In particular, generation of membrane potential on liposomes was studied via the measurements of rhodamine 6G uptake by fluorescence correlation spectroscopy. In mitochondria, swelling experiments were expounded by the additional measurements of respiration, membrane potential, and matrix pH. It can be concluded that both monensin and ethyl-monensin can perform nonelectrogenic exchange of potassium (sodium) ions for protons and serve as electrogenic potassium ion carriers similar to valinomycin. The results obtained are in line with the predictions based on the crystal structures of the monensin complexes with sodium ions and protons (Huczyński et al., Biochim. Biophys. Acta, 1818 (2012) pp. 2108-2119). The functional activity observed for artificial membranes and mitochondria can be applied to explain the activity of ionophores in living systems. It can also be important for studying the antitumor activity of monensin.

  7. 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.

  8. Enhanced ion particle flux and momentum outward of a plasma ball

    NASA Astrophysics Data System (ADS)

    Makrinich, Gennady; Fruchtman, Amnon

    2013-09-01

    A plasma ball has been produced near the anode in a configuration that, when magnetized, operates as a radial plasma source (RPS). Plasma balls have been studied recently in different configurations. We find that the plasma particle flux outward of the plasma ball is larger than that expected by the Langmuir relation in double layers. The frequency of oscillations of a pendulum is larger than due to gravity only, reflecting the force by the plasma ball. The force by the plasma ball is larger than expected by the model. We address these two questions: the increased ion flux and the increased force relative to the model. We suggest that the Langmuir relation underestimates the ratio of ion to electron flux. We also suggest that the ions gain most of the momentum in the quasi-neutral plasma rather than in the double layer; the impulse enhancement is suggested to result from ion-neutral collisions in the plasma. Partially supported by the Israel Science Foundation, Grant 765/11.

  9. SNS Sample Activation Calculator Flux Recommendations and Validation

    SciTech Connect

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

    2015-02-01

    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. 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.

  10. Simulation of Active-Region-Scale Flux Emergence

    NASA Astrophysics Data System (ADS)

    Manchester, W.; van der Holst, B.

    2015-12-01

    Shear flows long observed in solar active regions are now understood to be a consequence of the Lorentz force that develops from a complex interaction between magnetic fields and the thermal pressure of the Sun's gravitationally stratified atmosphere. The shearing motions transport magnetic flux and energy from the submerged portion of the field to the corona providing the necessary energy for flares, filament eruptions and CMEs. To further examine this shearing process, we simulate flux emergence on the scale of active regions with a large-scale model of the near surface convection zone constructed on an adaptive spherical grid. This model is designed to simulate flux emerging on the scale of active regions from a depth of 30 Mm. Here, we show results of a twisted flux rope emerging through the hierarchy of granular convection, and examine the flow patterns that arise as the flux approaches the photosphere. We show how these organized flows driven by the Lorentz force cause the coronal field evolve to a highly non-potential configuration capable of driving solar eruptions such as CMEs and flares.

  11. A unifying mechanism for cancer cell death through ion channel activation by HAMLET.

    PubMed

    Storm, Petter; Klausen, Thomas Kjaer; Trulsson, Maria; Ho C S, James; Dosnon, Marion; Westergren, Tomas; Chao, Yinxia; Rydström, Anna; Yang, Henry; Pedersen, Stine Falsig; Svanborg, Catharina

    2013-01-01

    Ion channels and ion fluxes control many aspects of tissue homeostasis. During oncogenic transformation, critical ion channel functions may be perturbed but conserved tumor specific ion fluxes remain to be defined. Here we used the tumoricidal protein-lipid complex HAMLET as a probe to identify ion fluxes involved in tumor cell death. We show that HAMLET activates a non-selective cation current, which reached a magnitude of 2.74±0.88 nA within 1.43±0.13 min from HAMLET application. Rapid ion fluxes were essential for HAMLET-induced carcinoma cell death as inhibitors (amiloride, BaCl2), preventing the changes in free cellular Na(+) and K(+) concentrations also prevented essential steps accompanying carcinoma cell death, including changes in morphology, uptake, global transcription, and MAP kinase activation. Through global transcriptional analysis and phosphorylation arrays, a strong ion flux dependent p38 MAPK response was detected and inhibition of p38 signaling delayed HAMLET-induced death. Healthy, differentiated cells were resistant to HAMLET challenge, which was accompanied by innate immunity rather than p38-activation. The results suggest, for the first time, a unifying mechanism for the initiation of HAMLET's broad and rapid lethal effect on tumor cells. These findings are particularly significant in view of HAMLET's documented therapeutic efficacy in human studies and animal models. The results also suggest that HAMLET offers a two-tiered therapeutic approach, killing cancer cells while stimulating an innate immune response in surrounding healthy tissues.

  12. Low flux and low energy helium ion implantation into tungsten using a dedicated plasma source

    NASA Astrophysics Data System (ADS)

    Pentecoste, Lucile; Thomann, Anne-Lise; Melhem, Amer; Caillard, Amael; Cuynet, Stéphane; Lecas, Thomas; Brault, Pascal; Desgardin, Pierre; Barthe, Marie-France

    2016-09-01

    The aim of this work is to investigate the first stages of defect formation in tungsten (W) due to the accumulation of helium (He) atoms inside the crystal lattice. To reach the required implantation conditions, i.e. low He ion fluxes (1011-1014 ions.cm2.s-1) and kinetic energies below the W atom displacement threshold (about 500 eV for He+), an ICP source has been designed and connected to a diffusion chamber. Implantation conditions have been characterized by means of complementary diagnostics modified for measurements in this very low density helium plasma. It was shown that lowest ion fluxes could only be reached for the discharge working in capacitive mode either in α or γ regime. Special attention was paid to control the energy gained by the ions by acceleration through the sheath at the direct current biased substrate. At very low helium pressure, in α regime, a broad ion energy distribution function was evidenced, whereas a peak centered on the potential difference between the plasma and the biased substrate was found at higher pressures in the γ mode. Polycrystalline tungsten samples were exposed to the helium plasma in both regimes of the discharge and characterized by positron annihilation spectroscopy in order to detect the formed vacancy defects. It was found that W vacancies are able to be formed just by helium accumulation and that the same final implanted state is reached, whatever the operating mode of the capacitive discharge.

  13. 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.

  14. 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.

  15. Study of Flux Ratio of C60 to Ar Cluster Ion for Hard DLC Film deposition

    SciTech Connect

    Miyauchi, K.; Toyoda, N.; Kanda, K.; Matsui, S.; Kitagawa, T.; Yamada, I.

    2003-08-26

    To study the influence of the flux ratio of C60 molecule to Ar cluster ion on (diamond like carbon) DLC film characteristics, DLC films deposited under various flux ratios were characterized with Raman spectrometry and Near Edge X-ray Absorption Fine Structure (NEXAFS). From results of these measurements, hard DLC films were deposited when the flux ratio of C60 to Ar cluster ion was between 0.7 and 4. Furthermore the DLC film with constant sp2 content was obtained in the range of the ratio from 0.7 to 4, which contents are lower values than that of conventional films such as RF plasma. DLC films deposited under the ratio from 1 to 4 had hardness from 40 to 45GPa. It was shown that DLC films with stable properties of low sp2 content and high hardness were formed even when the fluxes were varied from 1 to 4 during deposition. It was indicated that this process was useful in the view of industrial application.

  16. Ion Flux Characterization of H2 and D2 Plasmas Produced by an ECR Plasma Source

    NASA Astrophysics Data System (ADS)

    Kaiser, Eric; Capece, Angela; Roszell, John; Skinner, Charles; Koel, Bruce

    2013-10-01

    The use of lithium-conditioned plasma facing components in tokamaks has been shown to improve plasma confinement through a reduction in hydrogen recycling. Surface science techniques are being applied to probe the interactions between lithiated PFC's and H/D plasmas. A TectraTM Gen 2 plasma source has been commissioned that utilizes electron cyclotron resonance to produce a plasma discharge inside a vacuum test chamber and can produce ion fluxes similar to those typically seen in tokamaks. This source will be utilized to study H/D uptake by lithium films on Mo substrates as a precursor to NSTX-U experiments. In this work we report on the characterization of this source as a first step in its use in surface analysis studies. The source is operated in H2 and D2 gases and the subsequent ion flux of the plasma is measured by a Faraday Cup. Ion flux measurements are presented in a range of gas pressures and grid voltages up to 2 kV. Science Undergraduate Laboratory Internship funded by Department of Energy.

  17. Observations of plasma waves in the colliding jet region of a magnetic flux rope flanked by two active X lines at the subsolar magnetopause

    NASA Astrophysics Data System (ADS)

    Øieroset, M.; Sundkvist, D.; Chaston, C. C.; Phan, T. D.; Mozer, F. S.; McFadden, J. P.; Angelopoulos, V.; Andersson, L.; Eastwood, J. P.

    2014-08-01

    We have performed a detailed analysis of plasma and wave observations in a magnetic flux rope encountered by the THEMIS-D spacecraft at the subsolar magnetopause. The extent of the flux rope was ˜270 ion skin depths in the outflow direction, and it was flanked by two active X lines producing colliding plasma jets in the flux rope core where ion heating and suprathermal electrons were observed. The colliding jet region was highly dynamic and characterized by enhanced wave power in a broad frequency range. High-frequency waves, including ion acoustic-like waves, electron holes, and whistler mode waves, were observed in a limited spatial region near the flux rope center and did not appear to be associated with the observed large-scale heating and energization. Low-frequency kinetic Alfvén waves, on the other hand, were enhanced in the entire flux rope core, suggesting a possible link with the observed ion heating.

  18. 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

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

    PubMed

    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

  20. Mechanisms of focused ion beam (FIB) material removal and rearrangement at high beam flux

    NASA Astrophysics Data System (ADS)

    Das, Kallol

    Focused ion beam (FIB) is widely used as a material removal tool for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing. Despite the wide spread use of FIB, the basic material removal mechanisms are not well understood and may depend upon FIB operations. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms as described by large-scale MD simulations of FIB and describe the role of explosive boiling and Marangoni effect as a material removal and rearrangement mechanism and the mixing and transport that occur at the atomic scale. Nanopore fabrication using FIB is typically understood to occur via sputter erosion. While this theory may describe low-flux systems, where individual ion impacts are sufficiently separated in time to consider them as independent events, it cannot explain the thermal events observed during high flux simulations. A dimensionless number is introduced, which is constructed from the key variables including material properties and FIB parameters. This number suggests strong thermal effects when it is greater than unity. Similarly, our detailed MD simulations suggest that for ion beam fluxes above a threshold level, the dominant mechanism of material removal changes to a significantly accelerated, thermally dominated process, consistent with our dimensional analysis. During this time, the target is heated faster than it cools, leading to melting, with local temperatures approaching the critical temperature. This leads to an explosive boiling of the target material with spontaneous bubble formation. Atomic mass is rapidly rearranged via bubble growth and coalescence and material removal is orders of magnitude faster than would occur by simple sputtering. For a range of ion intensities in a realistic configuration, a recirculating melt

  1. Noninvasive measurement of hydrogen and potassium ion flux from single cells and epithelial structures.

    PubMed

    Smith, P J; Trimarchi, J

    2001-01-01

    This review introduces new developments in a technique for measuring the movement of ions across the plasma membrane. With the use of a self-referencing ion-selective (Seris) probe, transport mechanisms can be studied on a variety of preparations ranging from tissues to single cells. In this paper we illustrate this versatility with examples from the vas deferens and inner ear epithelium to large and small single cells represented by mouse single-cell embryos and rat microglia. Potassium and hydrogen ion fluxes are studied and pharmacological manipulation of the signals are reported. The strengths of the self-referencing technique are reviewed with regard to biological applications, and the expansion of self-referencing probes to include electrochemical and enzyme-based sensors is discussed.

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

    SciTech Connect

    Kurapov, Denis; Reiss, Jennifer; Trinh, David H.; Hultman, Lars; Schneider, Jochen M.

    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. These changes in structure, composition, and properties induced by normalized ion flux may be understood by considering mechanisms related to surface and bulk diffusion.

  3. Ion heat flux and energy transport near the magnetotail neutral sheet

    NASA Astrophysics Data System (ADS)

    Kaufmann, Richard L.; Paterson, William R.

    2008-05-01

    Ten-year averages of energy transport rates near the neutral sheet showed that the enthalpy flux density or thermal energy term QT = (5/2)PV was the largest, where P is the isotropic pressure and V is the bulk flow velocity. The ion heat flux, qi, was the next largest term. Sorting data using a magnetic flux transport parameter showed that qi could become dominant during periods of slow flow. Both qi and the ion bulk velocity Vi were duskward on the dusk side of the neutral sheet. This relationship is characteristic of cross-tail drift and a heat flux that can be attributed to the energy dependent gradient and curvature drifts. The qi and Vi vectors often pointed in different directions on the dawn side. The x component of qi on the dawn side pointed tailward, suggesting entry through the magnetopause of a suprathermal ion component. On the dusk side the qix plots that were sorted using a magnetic flux transport parameter showed evidence of plasma sheet reconnection. The long-term averaged x component of QT pointed earthward almost everywhere in the neutral sheet, and was attributed to periods of very fast plasma flow. The cross-tail component of QT was separated into two contributions. One part of QTy involved a common drift away from midnight during both earthward and tailward fast flows. This feature suggests that thermal energy and plasma flow from the outer plasma sheet toward the neutral sheet near midnight, and then toward the flanks. The other part of QTy involved a differential duskward drift during fast earthward flows and a dawnward drift during fast tailward flows. The incremental E fields that would produce such convection point tailward during the fastest earthward flows and earthward during the fastest tailward flows. The dependencies of Vi, qi and QT on the interplanetary magnetic field (IMF) clock angle also were studied. Both Vi and QT were reduced when the IMF was northward and the neutral sheet plasma became cold and dense. However, no

  4. Activation of large ions in FT-ICR mass spectrometry.

    PubMed

    Laskin, Julia; Futrell, Jean H

    2005-01-01

    can be effected using IR or UV/vis lasers and generally requires tuning lasers to specific wavelengths and/or utilizing high flux, multiphoton excitation to match energy levels in the ion. Photodissociation of complex ions is much easier to accomplish from the basic physics perspective. The quasi-continuum of vibrational states at room temperature makes it very easy to pump relatively large amounts of energy into complex ions and infrared multiphoton dissociation (IRMPD) is a powerful technique for characterizing large ions, particularly biologically relevant molecules. Since both SORI-CID and IRMPD are slow activation methods they have many common characteristics. They are also distinctly different because SORI-CID is intrinsically selective (only ions that have a cyclotron frequency close to the frequency of the excitation field are excited), whereas IRMPD is not (all ions that reside on the optical path of the laser are excited). There are advantages and disadvantages to each technique and in many applications they complement each other. In contrast with these slow activation methods, the less widely appreciated activation method of surface induced dissociation (SID) appears to offer unique advantages because excitation in SID occurs on a sub-picosecond time scale, instantaneously relative to the observation time of any mass spectrometer. Internal energy deposition is quite efficient and readily adjusted by altering the kinetic energy of the impacting ion. The shattering transition--instantaneous decomposition of the ion on the surface--observed at high collision energies enables access to dissociation channels that are not accessible using SORI-CID or IRMPD. Finally, we discuss some approaches for tailoring the surface to achieve particular aims in SID. PMID:15389858

  5. 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.…

  6. CA II Emission surface fluxes in active chromosphere stars

    NASA Technical Reports Server (NTRS)

    Bopp, B. W.

    1984-01-01

    Ca II emission-line surface fluxes are derived for 14 stars from 17 A/mm photographic spectra. Most of the stars observed are active chromosphere binaries; a few are known X-ray sources or have been observed by the IUE. The status of optical information on each of the objects is reviewed, and new information on v sin i and duplicity is presented.

  7. Investigation of the LAPPS Ion Flux to a Surface Biased with an Arbitrary High Frequency Waveform

    NASA Astrophysics Data System (ADS)

    Blackwell, David; Walton, Scott; Leonhardt, Darrin; Murphy, Donald; Fernsler, Richard; Meger, Robert

    2001-10-01

    Materials etching using accelerated ions has become a widely used procedure in the semiconductor industry. Typically the substrate is biased with high frequency voltage waveforms, which cause the substrate to acquire a negative DC voltage to accelerate the ions. However, the ions do not reach the substrate as a monoenergetic beam. The ion energy distribution function (IEDF) is profoundly influenced by the frequency and shape of the applied waveform. At NRL, we have been experimenting with electron-beam produced plasmas as an alternative to radiofrequency (RF) driven discharges. The most promising of these sources is the hollow cathode driven \\underlineLarge \\underlineArea \\underlinePlasma \\underlineProcessing \\underlineSystem. This source is designed to produce large area (> 1 m^2), high density, uniform sheets of plasma. In this presentation we will show measurements of the ion energy distribution function (IEDF) from continuous and pulsed electron beam plasmas produced in 20-30 cm wide × 1 cm thick sheets by a 2 kV hollow cathode. The IEDF is obtained using a gridded energy analyzer incorporated into a biasable stage. The surface flux and IEDF as a function of the waveform input to the stage will be investigated by using various types of pulse functions and variable frequency RF voltages. Typical operating conditions are 15-20 millitorr of argon, oxygen, or nitrogen, and 150-200 Gauss magnetic field.

  8. Cardiac BIN1 folds T-tubule membrane, controlling ion flux and limiting arrhythmia.

    PubMed

    Hong, TingTing; Yang, Huanghe; Zhang, Shan-Shan; Cho, Hee Cheol; Kalashnikova, Mariya; Sun, Baiming; Zhang, Hao; Bhargava, Anamika; Grabe, Michael; Olgin, Jeffrey; Gorelik, Julia; Marbán, Eduardo; Jan, Lily Y; Shaw, Robin M

    2014-06-01

    Cardiomyocyte T tubules are important for regulating ion flux. Bridging integrator 1 (BIN1) is a T-tubule protein associated with calcium channel trafficking that is downregulated in failing hearts. Here we find that cardiac T tubules normally contain dense protective inner membrane folds that are formed by a cardiac isoform of BIN1. In mice with cardiac Bin1 deletion, T-tubule folding is decreased, which does not change overall cardiomyocyte morphology but leads to free diffusion of local extracellular calcium and potassium ions, prolonging action-potential duration and increasing susceptibility to ventricular arrhythmias. We also found that T-tubule inner folds are rescued by expression of the BIN1 isoform BIN1+13+17, which promotes N-WASP-dependent actin polymerization to stabilize the T-tubule membrane at cardiac Z discs. BIN1+13+17 recruits actin to fold the T-tubule membrane, creating a 'fuzzy space' that protectively restricts ion flux. When the amount of the BIN1+13+17 isoform is decreased, as occurs in acquired cardiomyopathy, T-tubule morphology is altered, and arrhythmia can result. PMID:24836577

  9. Mars heavy ion precipitating flux as measured by Mars Atmosphere and Volatile EvolutioN

    NASA Astrophysics Data System (ADS)

    Leblanc, F.; Modolo, R.; Curry, S.; Luhmann, J.; Lillis, R.; Chaufray, J. Y.; Hara, T.; McFadden, J.; Halekas, J.; Eparvier, F.; Larson, D.; Connerney, J.; Jakosky, B.

    2015-11-01

    In the absence of an intrinsic dipole magnetic field, Mars' O+ planetary ions are accelerated by the solar wind. Because of their large gyroradius, a population of these planetary ions can precipitate back into Mars' upper atmosphere with enough energy to eject neutrals into space via collision. This process, referred to as sputtering, may have been a dominant atmospheric loss process during earlier stages of our Sun. Yet until now, a limited number of observations have been possible; Analyzer of Space Plasmas and Energetic Atoms-3/Mars Express observed such a precipitation only during extreme conditions, suggesting that sputtering might be not as intense as theoretically predicted. Here we describe one example of precipitation of heavy ions during quiet solar conditions. Between November 2014 and April 2015, the average precipitating flux is significant and in agreement with predictions. From these measured precipitating fluxes, we estimate that a maximum of 1.0 × 1024 O/s could have been lost due to sputtering.

  10. Antibacterial activity of nanosilver ions and particles.

    PubMed

    Sotiriou, Georgios A; Pratsinis, Sotiris E

    2010-07-15

    The antibacterial activity of nanosilver against Gram negative Escherichia coli bacteria is investigated by immobilizing nanosilver on nanostructured silica particles and closely controlling Ag content and size. These Ag/SiO(2) nanoparticles were characterized by S/TEM, EDX spectroscopy, X-ray diffraction the exposed Ag surface area was measured qualitatively by O(2) chemisorption. Furthermore, the fraction of dissolved nanosilver was determined by measuring the released (leached) Ag(+) ion concentration in aqueous suspensions of such Ag/SiO(2) particles. The antibacterial effect of Ag(+) ions was distinguished from that of nanosilver particles by monitoring the growth of E. coli populations in the presence and absence of Ag/SiO(2) particles. The antibacterial activity of nanosilver was dominated by Ag(+) ions when fine Ag nanoparticles (less than about 10 nm in average diameter) were employed that release high concentrations of Ag(+) ions. In contrast, when relatively larger Ag nanoparticles were used, the concentration of the released Ag(+) ions was lower. Then the antibacterial activity of the released Ag(+) ions and nanosilver particles was comparable.

  11. Experimental evidence of the effect of heat flux on thomson scattering off ion acoustic waves

    PubMed

    Amiranoff; Baton; Huller; Malka; Modena; Mounaix; Galloudec; Rousseaux; Salvati

    2000-02-01

    Thomson self-scattering measurements are performed in a preionized helium gas jet plasma at different locations along the laser propagation direction. A systematic and important variation of the intensity ratio between the blue and the red ion spectral components is observed, depending on whether the location of the probed region is in front of or behind the focal plane. A simple theoretical calculation of Thomson scattering shows that this behavior can be qualitatively understood in terms of a deformation of the electron distribution function due to the return current correlated with the classical thermal heat flux. PMID:11046481

  12. Determination of Ion Content and Ion Fluxes in the Halotolerant Alga Dunaliella salina

    PubMed Central

    Pick, Uri; Karni, Leah; Avron, Mordhay

    1986-01-01

    A method to determine intracellular cation contents in Dunaliella by separation on cation-exchange minicolumns is described. The separation efficiency of cells from extracellular cations is over 99.9%; the procedure causes no apparent perturbation to the cells and can be applied to measure both fluxes and internal content of any desired cation. Using this technique it is demonstrated that the intracellular averaged Na+, K+, and Ca2+ concentrations in Dunaliella salina cultured at 1 to 4 molar NaCl, 5 millimolar K+, and 0.3 millimolar Ca2+ are 20 to 100 millimolar, 150 to 250 millimolar, and 1 to 3 millimolar, respectively. The intracellular K+ concentration is maintained constant over a wide range of media K+ concentrations (0.5-10 millimolar), leading to a ratio of K+ in the cells to K+ in the medium of 10 to 1,000. Severe limitation of external K+, induces loss of K+ and increase in Na+ inside the cells. The results suggest that Dunaliella cells possess efficient mechanisms to eliminate Na+ and accumulate K+ and that intracellular Na+ and K+ concentrations are carefully regulated. The contribution of the intracellular Na+ and K+ salts to the total osmotic pressure of cells grown at 1 to 4 molar NaCl, is 5 to 20%. PMID:16664814

  13. Role of Ion Kinetic Physics in the Interaction of Magnetic Flux Ropes.

    PubMed

    Stanier, A; Daughton, W; Chacón, L; Karimabadi, H; Ng, J; Huang, Y-M; Hakim, A; Bhattacharjee, A

    2015-10-23

    To explain many natural magnetized plasma phenomena, it is crucial to understand how rates of collisionless magnetic reconnection scale in large magnetohydrodynamic (MHD) scale systems. Simulations of isolated current sheets conclude such rates are independent of system size and can be reproduced by the Hall-MHD model, but neglect sheet formation and coupling to MHD scales. Here, it is shown for the problem of flux-rope merging, which includes this formation and coupling, that the Hall-MHD model fails to reproduce the kinetic results. The minimum sufficient model must retain ion kinetic effects, which set the ion diffusion region geometry and give time-averaged rates that reduce significantly with system size, leading to different global evolution in large systems. PMID:26551121

  14. Carbon nanotube/carbon nanotube composite AFM probes prepared using ion flux molding

    NASA Astrophysics Data System (ADS)

    Chesmore, Grace; Roque, Carrollyn; Barber, Richard

    The performance of carbon nanotube-carbon nanotube composite (CNT/CNT composite) atomic force microscopy (AFM) probes is compared to that of conventional Si probes in AFM tapping mode. The ion flux molding (IFM) process, aiming an ion beam at the CNT probe, aligns the tip to a desired angle. The result is a relatively rigid tip that is oriented to offset the cantilever angle. Scans using these probes reveal an improvement in image accuracy over conventional tips, while allowing higher aspect ratio imaging of 3D surface features. Furthermore, the lifetimes of CNT-CNT composite tips are observed to be longer than both conventional tips and those claimed for other CNT technologies. Novel applications include the imaging of embiid silk. Supported by the Clare Boothe Luce Research Scholars Award and Carbon Design Innovations.

  15. Ion Flows Associated with Two Flux Ropes in a Background Plasma

    NASA Astrophysics Data System (ADS)

    Dehaas, Timothy; Gekelman, Walter; van Compernolle, Bart

    2013-10-01

    Magnetic flux ropes are ubiquitous as they are located on and near the sun, presumably other stars, and near the earth and other planets. They consist of helical field lines which vary in pitch due to the electric current flowing along a background magnetic field. Multiple braided flux ropes have been observed in the solar corona, and their unraveling is theorized to be the signature of magnetic reconnection. Two flux ropes (L = 10 m, A = 7 cm2, J = 10 amp/cm2) were created in the Large Plasma Device (LAPD) at UCLA (Bo = 330 G, no = 1012 cm-3, T e = 4eV, Ar). These kink unstable ropes violently twist and oscillate about a central axis. A quasi-separatrix layer (QSL) forms as the ropes collide and the magnetic field lines reconnect. Through the use of a six-faced Mach probe, volumetric data was taken to determine the three-dimensional plasma flow. Volumetric magnetic fields were obtained through use of a three-axis magnetic probe. The three-dimensional data is conditionally averaged to construct the average flux rope dynamic. In this experiment, the ropes are shown to twist, interact, then merge; while the plasma flows are shown to spiral around the two flux ropes in a singular O-point. As they collide and a QSL is formed and an induced electric field is generated, slowing parallel ion flows. This work is supported by LANL-UC research grant and done at the Basic Plasma Science Facility, which is funded by DOE and NSF.

  16. Low Temperature Nitriding of 304 Austenitic Stainless Steel Using RF-ICP Method: the Role of Ion Beam Flux Density

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Ba, Dechun; Ming, Yue; Xu, Lin; Guo, Deyu

    2014-10-01

    The significant role of ion beam flux during nitriding 304 austenitic stainless steel has been investigated by using a radio frequency inductively-coupled plasma reactor into which a sample with negative bias voltage was inserted. A milliammeter is used to detect the current of ions which collide with the sample and optical emission spectroscopy is used to discern the reactive species included in the nitrogen plasma. The nitriding efficiency is indicated by X-ray diffraction and the microhardness test. The reported data reveal that the ion beam flux density as well as the deposition pressure, bias voltage and time can strongly affect the nitriding of stainless steel via the expanded multiphase microstructure inside the nitrided layer. The increase in the density of ion flux results in an ascent in the intensity of the expanded peak and a simultaneous decline in the intensity of the γ austenite peak. The evolution trend of ion beam flux density is described as a function of the operating pressure and the bias voltage. The maximum ion flux density has been achieved at 10 Pa pressure and -500 V bias voltage. A reasonable nitriding region has been, consequently, suggested after comparing this work with previously reported results.

  17. Active ion tracer experiments attempted in conjunction with the ion composition experiment on GEOS-2

    NASA Astrophysics Data System (ADS)

    Young, D. T.

    It is pointed out that to date six ion injection/tracer experiments have been attempted in conjunction with the GEOS-2 Ion Composition Experiment: three rocket borne Ba shaped-charge releases (Porcupine 3 and 4 and Ba-GEOS), one Li release, and two periods of operation of the Xe(+) accelerator on the SCATHA satellite. The characteristics of each of these six releases are outlined, and upper limits are placed on possible ion fluxes reaching GEOS-2. The order of magnitude of ion fluxes to be expected from each release is estimated, and it is shown that three of the experiments had no real chance of succeeding in the first place.

  18. Angular Distribution of Tungsten Material and Ion Flux during Nanosecond Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Hussain, M. S.; Dogar, A. H.; Qayyum, A.; Abbasi, S. A.

    2016-01-01

    Tungsten thin films were prepared by pulsed laser deposition (PLD) technique on glass substrates placed at the angles of 0∘ to 70∘ with respect to the target surface normal. Rutherford backscattering Spectrometry (RBS) analysis of the films indicated that about 90% of tungsten material flux is distributed in a cone of 40∘ solid angle while about 54% of it lies even in a narrower cone of 10∘ solid angle. Significant diffusion of tungsten in glass substrate has been observed in the films deposited at smaller angles with respect to target surface normal. Time-of-flight (TOF) measurements performed using Langmuir probe indicated that the most probable ion energy decreases from about 600 to 91eV for variation of θ from 0∘ to 70∘. In general ion energy spread is quite large at all angles investigated here. The enhanced tungsten diffusion in glass substrate observed at smaller angles is most probably due to the higher ion energy and ion assisted recoil implantation of already deposited tungsten.

  19. Flux effect on the ion-beam nitriding of austenitic stainless-steel AISI 304L

    SciTech Connect

    Abrasonis, G.; Riviere, J.P.; Templier, C.; Pranevicius, L.; Barradas, N.P.

    2005-06-15

    The effect of flux and Ar pretreatment during ion-beam nitriding of austenitic stainless steel is investigated. The ion energy and temperature were 1.2 keV and 400 deg. C, respectively, the ion current densities were 0.5, 0.67, and 0.83 mA cm{sup -2}. The nitrogen distribution profiles were measured using nuclear reaction analysis. The obtained nitrogen distribution profiles were analyzed by the means of the nitrided layer thickness evolution due to sputtering and diffusion and the model of trapping-detrapping. Both approaches could fit well the experimental results, however, different diffusion coefficients have to be assumed for each current density. In addition, the diffusion coefficients are higher for higher current densities. On the other hand, it is shown that the pretreatment with Ar-ion beam at nitriding temperatures produces only a thermal effect without any other influence on the following nitrogen diffusion. The results are discussed in relation with surface and temperature effects and atomic transport mechanisms.

  20. 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.

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

    SciTech Connect

    Wingen, A.; Schmitz, O.; Evans, T. E.; Spatschek, K. H.

    2014-01-15

    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. This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show different 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 q{sub 95}. This analysis provides evidence for the dominate effect 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.

  2. Ion fluxes, transmembrane potential, and osmotic stabilization: a new dynamic electrophysiological model for eukaryotic cells.

    PubMed

    Poignard, Clair; Silve, Aude; Campion, Frederic; Mir, Lluis M; Saut, Olivier; Schwartz, Laurent

    2011-03-01

    Survival of mammalian cells is achieved by tight control of cell volume, while transmembrane potential has been known to control many cellular functions since the seminal work of Hodgkin and Huxley. Regulation of cell volume and transmembrane potential have a wide range of implications in physiology, from neurological and cardiac disorders to cancer and muscle fatigue. Therefore, understanding the relationship between transmembrane potential, ion fluxes, and cell volume regulation has become of great interest. In this paper we derive a system of differential equations that links transmembrane potential, ionic concentrations, and cell volume. In particular, we describe the dynamics of the cell within a few seconds after an osmotic stress, which cannot be done by the previous models in which either cell volume was constant or osmotic regulation instantaneous. This new model demonstrates that both membrane potential and cell volume stabilization occur within tens of seconds of changes in extracellular osmotic pressure. When the extracellular osmotic pressure is constant, the cell volume varies as a function of transmembrane potential and ion fluxes, thus providing an implicit link between transmembrane potential and cell volume. Experimental data provide results that corroborate the numerical simulations of the model in terms of time-related changes in cell volume and dynamics of the phenomena. This paper can be seen as a generalization of previous electrophysiological results, since under restrictive conditions they can be derived from our model. PMID:21079946

  3. A Planar Probe for Ion Flux and Electron Temperature in the Electrode of a GEC Cell

    NASA Astrophysics Data System (ADS)

    Goodyear, A.; Lubeigt, W.; Verdonck, P. B.; Barroy, P. R. J.; Braithwaite, N. St. J.

    2000-10-01

    A radio frequency (rf) self-biased planar probe technique(J P Booth, N St J Braithwaite, A Goodyear, and P Barroy, Rev. Sci. Instrum., in press (July 2000)) for the measurement of positive ion flux and electron energy distribution functions has been implemented into the Gaseous Electronics Conference (GEC) standard reference cell. Results are presented across a wide range of power-pressure parameter space. Insertion of electrostatic probes into plasmas can lead to perturbation of the plasma and this is particularly problematic in the GEC cell where the inter-electrode distance is small. Planar probes are inherently large, requiring a guard ring (at least as large as typical sheath thicknesses) to ensure that the sheath in front of the probe is truly planar. Once this criterion is satisfied, analysis of current-voltage (IV) characteristics obtained in this planar geometry is relatively straight forward. A planar probe has been engineered into the surface of the showerhead electrode of the GEC cell, aimed at minimal perturbation to the GEC standard, in terms of both physical presence and electrical influence. The probe is self-biased by a burst of rf voltage. It is then allowed to return to its original floating condition under the arrival of charged particles from the plasma. An IV characteristic is recorded during this time, giving positive ion flux and the high energy tail (a few eV and above) of the electron energy distribution function.

  4. Optogenetics in Developmental Biology: using light to control ion flux-dependent signals in Xenopus embryos.

    PubMed

    Spencer Adams, Dany; Lemire, Joan M; Kramer, Richard H; Levin, Michael

    2014-01-01

    Developmental bioelectricity, electrical signaling among non-excitable cells, is now known to regulate proliferation, apoptosis, gene expression, and patterning during development. The extraordinary temporal and spatial resolution offered by optogenetics could revolutionize the study of bioelectricity the same way it has revolutionized neuroscience. There is, however, no guide to adapting optogenetics to patterning systems. To fill this gap, we used optogenetic reagents, both proteins and photochemical switches, to vary steady-state bioelectrical properties of non-spiking embryonic cells in Xenopus laevis. We injected mRNA for various proteins, including Channelrhodopsins and Archaerhodopsin, into 1-8 cell embryos, or soaked embryos in media containing photochemical switches, then examined the effect of light and dark on membrane voltage (Vmem) using both electrodes and fluorescent membrane voltage reporters. We also scored tadpoles for known effects of varying Vmem, including left-right asymmetry disruption, hyperpigmentation, and craniofacial phenotypes. The majority of reagents we tested caused a significant increase in the percentage of light-exposed tadpoles showing relevant phenotypes; however, the majority of reagents also induced phenotypes in controls kept in the dark. Experiments on this "dark phenotype" yielded evidence that the direction of ion flux via common optogenetic reagents may be reversed, or unpredictable in non-neural cells. When used in combination with rigorous controls, optogenetics can be a powerful tool for investigating ion-flux based signaling in non-excitable systems. Nonetheless, it is crucial that new reagents be designed with these non-neural cell types in mind.

  5. 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.

  6. Radon-222 activity flux measurement using activated charcoal canisters: revisiting the methodology.

    PubMed

    Alharbi, Sami H; Akber, Riaz A

    2014-03-01

    The measurement of radon ((222)Rn) activity flux using activated charcoal canisters was examined to investigate the distribution of the adsorbed (222)Rn in the charcoal bed and the relationship between (222)Rn activity flux and exposure time. The activity flux of (222)Rn from five sources of varying strengths was measured for exposure times of one, two, three, five, seven, 10, and 14 days. The distribution of the adsorbed (222)Rn in the charcoal bed was obtained by dividing the bed into six layers and counting each layer separately after the exposure. (222)Rn activity decreased in the layers that were away from the exposed surface. Nevertheless, the results demonstrated that only a small correction might be required in the actual application of charcoal canisters for activity flux measurement, where calibration standards were often prepared by the uniform mixing of radium ((226)Ra) in the matrix. This was because the diffusion of (222)Rn in the charcoal bed and the detection efficiency as a function of the charcoal depth tended to counterbalance each other. The influence of exposure time on the measured (222)Rn activity flux was observed in two situations of the canister exposure layout: (a) canister sealed to an open bed of the material and (b) canister sealed over a jar containing the material. The measured (222)Rn activity flux decreased as the exposure time increased. The change in the former situation was significant with an exponential decrease as the exposure time increased. In the latter case, lesser reduction was noticed in the observed activity flux with respect to exposure time. This reduction might have been related to certain factors, such as absorption site saturation or the back diffusion of (222)Rn gas occurring at the canister-soil interface.

  7. Effects of Implantation Temperature and Ion Flux on Damage Accumulation in Al-Implanted 4H-SiC

    SciTech Connect

    Zhang, Yanwen; Weber, William J.; Jiang, Weilin; Wang, Chong M.; Hallen, Anders; Possnert, Goran

    2003-02-15

    The effects of implantation temperature and ion flux on damage accumulation on both the Si and C sublattices in 4H-SiC are investigated under 1.1 MeV Al irradiation at temperatures from 150 to 450 K. The rate of damage accumulation decreases dramatically and the damage profile sharpens due to significant dynamic recovery at temperatures close to the critical temperature for amorphization. At 450 K, the relative disorder and the density of planar defects increase rapidly with the increasing ion flux, exhibiting saturation at high ion fluxes. Planar defects are generated through the agglomeration of excess Si and C interstitials during irradiation and post-irradiation annealing at 450 K. Termination of (0001) planes is attributed to the accumulation of vacancies. A volume expansion of {approx}8% is observed for the peak damage region.

  8. 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. PMID:27249799

  9. 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

  10. Activation Mechanisms in Ion-Implanted Gallium -

    NASA Astrophysics Data System (ADS)

    Morris, Neil

    Available from UMI in association with The British Library. Rapid Thermal Annealing has been used to study the electrical activation of a range of donor and acceptor species in ion-implanted GaAs. By varying the time and temperature of the post implant anneal, it was found that the activation processes for most implants can be characterised in terms of two distinct regions. The first of these occurs at short annealing times, where the electrical activity is seen to follow a time-dependent behaviour. At longer annealing times, however, a time-independent saturation value is reached, this value being dependent on the annealing temperature. By analysing the data from Be, Mg, S and Se implants in GaAs, a comprehensive model has been evolved for the time and temperature dependence of the sheet electrical properties. Application of this model to each of the ions studied suggests that the activation processes may be dominated by the extent to which ions form impurity-vacancy complexes. An analysis of the time-dependent regime also shows that, at short annealing times, the mobile species is more likely to be the substrate atoms (or vacancies) rather than the implanted impurities. In the time-dependent region, the values of diffusion energy were found to be between 2.3 to 3.0 eV for all ions, these values corresponding to a diffusion of Ga or As vacancies (or atoms). In the saturation region, activation energies of 0.3 to 0.4 eV and 1.0 to 1.2 eV were obtained for the activation processes of interstitial or complexed impurities respectively.

  11. 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

  12. Copper ion fluxes through the floating water bridge under strong electric potential.

    PubMed

    Giuliani, Livio; D'Emilia, Enrico; Lisi, Antonella; Grimaldi, Settimio; Brizhik, Larissa; Del Giudice, Emilio

    2015-01-01

    We have performed a series of experiments applying high voltage between two electrodes, immersed in two beakers containing bidistilled water in a way similar to experiments conducted by Fuchs and collaborators, which showed that a water bridge can be formed between the two containers. We also observed the formation of water bridge. Moreover, choosing different pairs of electrodes depending on the material they are made up of, we observed that copper ions flow can pass along the bridge if the negative electrode is made up of copper. We show that the direction of the flux not only depends on the applied electrostatic field but on the relative electronegativity of the electrodes too. These results open new perspectives in understanding the properties of water. We suggest a possible explanation of the obtained results.

  13. Optogenetics in Developmental Biology: using light to control ion flux-dependent signals in Xenopus embryos.

    PubMed

    Spencer Adams, Dany; Lemire, Joan M; Kramer, Richard H; Levin, Michael

    2014-01-01

    Developmental bioelectricity, electrical signaling among non-excitable cells, is now known to regulate proliferation, apoptosis, gene expression, and patterning during development. The extraordinary temporal and spatial resolution offered by optogenetics could revolutionize the study of bioelectricity the same way it has revolutionized neuroscience. There is, however, no guide to adapting optogenetics to patterning systems. To fill this gap, we used optogenetic reagents, both proteins and photochemical switches, to vary steady-state bioelectrical properties of non-spiking embryonic cells in Xenopus laevis. We injected mRNA for various proteins, including Channelrhodopsins and Archaerhodopsin, into 1-8 cell embryos, or soaked embryos in media containing photochemical switches, then examined the effect of light and dark on membrane voltage (Vmem) using both electrodes and fluorescent membrane voltage reporters. We also scored tadpoles for known effects of varying Vmem, including left-right asymmetry disruption, hyperpigmentation, and craniofacial phenotypes. The majority of reagents we tested caused a significant increase in the percentage of light-exposed tadpoles showing relevant phenotypes; however, the majority of reagents also induced phenotypes in controls kept in the dark. Experiments on this "dark phenotype" yielded evidence that the direction of ion flux via common optogenetic reagents may be reversed, or unpredictable in non-neural cells. When used in combination with rigorous controls, optogenetics can be a powerful tool for investigating ion-flux based signaling in non-excitable systems. Nonetheless, it is crucial that new reagents be designed with these non-neural cell types in mind. PMID:25896279

  14. Observations of Plasma Waves in the Colliding Jet Region of a 3D Magnetic Flux Rope Flanked by Two Active Reconnection X Lines at the Subsolar Magnetopause

    NASA Astrophysics Data System (ADS)

    Oieroset, M.; Sundkvist, D. J.; Chaston, C. C.; Phan, T. D.; Mozer, F.; McFadden, J. P.; Angelopoulos, V.; Andersson, L.; Eastwood, J. P.

    2014-12-01

    We have performed a detailed analysis of plasma and wave observations in a 3D magnetic flux rope encountered by the THEMIS spacecraft at the subsolar magnetopause. The extent of the flux rope was ˜270 ion skin depths in the outflow direction, and it was flanked by two active reconnection X lines producing colliding plasma jets in the flux rope core where ion heating and suprathermal electrons were observed. The colliding jet region was highly dynamic and characterized by the presence of high-frequency waves such as ion acoustic-like waves, electron holes, and whistler mode waves near the flux rope center and low-frequency kinetic Alfvén waves over a larger region. We will discuss possible links between these waves and particle heating.

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

    SciTech Connect

    McSkimming, Brian M. 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, 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.

  16. DyFK Simulation of Field-Aligned Ion Flows Observed by POLAR within Convecting Flux Over the Polar Ionosphere

    NASA Technical Reports Server (NTRS)

    Tu, J.-N.; Wu, X. Y.; Horwitz, J. L.; Stevenson, B. A.; Moore, T. E.; Coffey, V. N.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Ion (O+ and H+) parallel flows along antisunward convecting flux tubes across the polar ionosphere from day to night side are simulated by an extended Dynamic Fluid semiKinetic (DyFK) model. The collision dominated portion of the flux tubes is treated with a moment-based fluid model for altitudes from 120 ?1100 km, while the generalized semikinetic model is used for the topside through 3 RE region. The effects of cleft/auroral soft electron precipitation and wave-driven transverse ion heating are incorporated into the generalized semi-kinetic treatment of topside ionosphere. The simulated evolution of field-aligned ion flow parameters is compared with observations made by the Thermal Ion Dynamics Experiment (TIDE) on board the POLAR satellite near 5000 km altitude over the southern hemisphere polar ionosphere.

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

    SciTech Connect

    Girka, O.; Bizyukov, I.; Sereda, K.; Bizyukov, A.; Gutkin, M.; Sleptsov, V.

    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}- 3 Multiplication-Sign 10{sup 23} m{sup -2}s{sup -1}), which approaches the upper limit for the flux range expected in ITER.

  18. Generation of large-amplitude electric field and subsequent enhancement of O+ ion flux in the inner magnetosphere during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2015-06-01

    Energetic O+ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O+ ions and the spatial and temporal evolution of the differential flux of the O+ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13 mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O+ ions coming from the lobe are accelerated from ~eV to >100 keV in ~10 min. The reconstructed flux of the O+ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10 keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.

  19. 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

    2016-04-01

    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.

  20. 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

    2016-04-01

    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. PMID:26960551

  1. Triggering an Eruptive Flare by Emerging Flux in a Solar Active-Region Complex

    NASA Astrophysics Data System (ADS)

    Louis, Rohan E.; Kliem, Bernhard; Ravindra, B.; Chintzoglou, Georgios

    2015-12-01

    A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on 2012 July 1 (SOL2012-07-01) in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade ({≈} 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions.

  2. 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

  3. 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

  4. 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

  5. Temperature-dependent surface modification of Ta due to high-flux, low-energy He+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Novakowski, T. J.; Tripathi, J. K.; Hassanein, A.

    2015-12-01

    This work examines the response of Tantalum (Ta) as a potential candidate for plasma-facing components (PFCs) in future nuclear fusion reactors. Tantalum samples were exposed to high-flux, low-energy He+ ion irradiation at different temperatures in the range of 823-1223 K. The samples were irradiated at normal incidence with 100 eV He+ ions at constant flux of 1.2 × 1021 ions m-2 s-1 to a total fluence of 4.3 × 1024 ions m-2. An additional Ta sample was also irradiated at 1023 K using a higher ion fluence of 1.7 × 1025 ions m-2 (at the same flux of 1.2 × 1021 ions m-2 s-1), to confirm the possibility of fuzz formation at higher fluence. This higher fluence was chosen to roughly correspond to the lower fluence threshold of fuzz formation in Tungsten (W). Surface morphology was characterized with a combination of field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). These results demonstrate that the main mode of surface damage is pinholes with an average size of ∼70 nm2 for all temperatures. However, significantly larger pinholes are observed at elevated temperatures (1123 and 1223 K) resulting from the agglomeration of smaller pinholes. Ex situ X-ray photoelectron spectroscopy (XPS) provides information about the oxidation characteristics of irradiated surfaces, showing minimal exfoliation of the irradiated Ta surface. Additionally, optical reflectivity measurements are performed to further characterize radiation damage on Ta samples, showing gradual reductions in the optical reflectivity as a function of temperature.

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

    NASA Astrophysics Data System (ADS)

    Bruneau, B.; Diomede, P.; Economou, D. J.; Longo, S.; Gans, T.; O'Connell, D.; Greb, A.; Johnson, E.; Booth, J.-P.

    2016-08-01

    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 the \\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.

  7. 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.

  8. Magnetic flux cancellation and Doppler shifts in flaring active regions

    NASA Astrophysics Data System (ADS)

    Burtseva, Olga; Petrie, Gordon

    2016-05-01

    Flux cancellation plays an important role in some theories of solar eruptions. The mechanism of flux cancellation is suggested by many models to be a necessary condition of flare initiation as a part of slow reconnection processes in the lower atmosphere. In our earlier work we analyzed flux cancellation events during major flares using GONG line-of-sight magnetograms. In this work we use vector magnetic field data from SDO/HMI for better interpretation of the longitudinal field changes. We also compute Doppler velocity shifts at the cancellation sites in attempt to distinguish between the three physical processes that could stand behind flux removal from the photosphere: submergence of U-shaped loops, emergence of Ω-shaped loops and magnetic reconnection.

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

    NASA Astrophysics Data System (ADS)

    Peeters, A. G.; Rath, F.; Buchholz, R.; Camenen, Y.; Candy, J.; Casson, F. J.; Grosshauser, S. R.; Hornsby, W. A.; Strintzi, D.; Weikl, A.

    2016-08-01

    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 does 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.

  10. Determination of the entropy change profile of a cylindrical lithium-ion battery by heat flux measurements

    NASA Astrophysics Data System (ADS)

    Murashko, K. A.; Mityakov, A. V.; Mityakov, V. Y.; Sapozhnikov, S. Z.; Jokiniemi, J.; Pyrhönen, J.

    2016-10-01

    The popularity of lithium-ion (Li-ion) batteries has increased over the recent years. Because of the strong dependence of the Li-ion battery operation characteristics on temperature, heat generation in the battery has to be taken into account. The entropy change of a Li-ion battery has a significant influence on heat generation, especially at a low C-rate current. Therefore, it is necessary to consider the entropy change profile in the estimation of heat generation. In the paper, a method to determine the entropy change (ΔS) profile by heat flux measurements of a cylindrical Li-ion cell is proposed. The method allows simultaneous measurements of the thermal diffusivity and ΔS of the cylindrical cell. The thermal diffusivity and ΔS measurements are carried out by a gradient heat flux sensor (GHFS). The comparison between the ΔS profile determined by the GHFS method with that obtained using a standard potentiometric method clearly shows that the entropy change measurements could be made by using a GHFS. Even though the uncertainty of the reported method is higher than that of the potentiometric method, a significant decrease in the experiment time compared with the potentiometric method is a major advantage of this method.

  11. Structural, morphological and electrical studies of lithium ion irradiated sodium potassium niobate single crystal grown by flux method

    SciTech Connect

    Saravanan, R.; Rajesh, D.; Rajasekaran, S. V.; Perumal, R.; Chitra, M.; Jayavel, R.

    2013-02-05

    Single crystals of sodium potassium niobate (K{sub 0.5}Na{sub 0.5})NbO{sub 3} (KNN) were grown by flux method and crystals were irradiated with 45 MeV Li ions to modify the electrical properties. Energy of the irradiated heavy ion was lower than the threshold energy to produce columnar defect and only clusters of defect was observed. The surface morphology of the irradiated single crystals was studied using scanning electron microscope (SEM) and atomic force microscope (AFM). The results show that the surface roughness value was found to increase with increasing fluence.

  12. A 5D gyrokinetic full- f global semi-Lagrangian code for flux-driven ion turbulence simulations

    NASA Astrophysics Data System (ADS)

    Grandgirard, V.; Abiteboul, J.; Bigot, J.; Cartier-Michaud, T.; Crouseilles, N.; Dif-Pradalier, G.; Ehrlacher, Ch.; Esteve, D.; Garbet, X.; Ghendrih, Ph.; Latu, G.; Mehrenberger, M.; Norscini, C.; Passeron, Ch.; Rozar, F.; Sarazin, Y.; Sonnendrücker, E.; Strugarek, A.; Zarzoso, D.

    2016-10-01

    This paper addresses non-linear gyrokinetic simulations of ion temperature gradient (ITG) turbulence in tokamak plasmas. The electrostatic GYSELA code is one of the few international 5D gyrokinetic codes able to perform global, full- f and flux-driven simulations. Its has also the numerical originality of being based on a semi-Lagrangian (SL) method. This reference paper for the GYSELA code presents a complete description of its multi-ion species version including: (i) numerical scheme, (ii) high level of parallelism up to 500k cores and (iii) conservation law properties.

  13. Pickup Ion Production in the Global Heliosphere and Heliosheath and Their Diagnostics by Fluxes of Energetic Neutral Atoms

    NASA Astrophysics Data System (ADS)

    Wu, Y.

    2015-12-01

    An anisotropic particle transport model, based on an expansion of a focused transport equation in Legendre polynomials, is used here as a tool to analyze the distributions of pickup ions (PUIs) in the heliosphere and heliosheath. A three-dimensional, MHD-kinetic model for flows of a thermal plasma, neutral atoms and PUIs has been developed. The preliminary results from our model are in qualitative agreement with observations made by New Horizons, Ulysses, Voyager 1 and 2. All-sky maps of energetic neutral atoms (ENA) fluxes with energies of about 0.2-6 keV based on our current PUI model are qualitatively similar to IBEX-Hi distributed ENA maps. Also, simulated spectra of ENA fluxes nearly match IBEX-Hi spectra of distributed ENA fluxes. It is demonstrated that preserving some pitch-angle information of the PUI distribution is important for correctly interpreting the data.

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

    PubMed Central

    Henriksen, Gordon H.; Bloom, Arnold J.; Spanswick, Roger M.

    1990-01-01

    Neutral carrier-based liquid membrane ion-selective microelectrodes for NH4+ and NO3− were developed and used to investigate inorganic nitrogen acquisition in two varieties of barley, Hordeum vulgare L. cv Olli and H. vulgare L. cv Prato, originating in cold and warm climates, respectively. In the present paper, the methods used in the fabrication of ammonium- and nitrate-selective microelectrodes are described, and their application in the study of inorganic nitrogen uptake is demonstrated. Net ionic fluxes of NH4+ and NO3− were measured in the unstirred layer of solution immediately external to the root surface. The preference for the uptake of a particular ionic form was examined by measuring the net flux of the predominant form of inorganic nitrogen, with and without the alternative ion in solution. Net flux of NH4+ into the cold-adapted variety remained unchanged when equimolar concentrations (200 micromolar) of NH4+ and NO3− were present. Similarly, net flux of NO3− into the warm-adapted variety was not affected when NH4+ was also present in solution. The high temporal and spatial resolution afforded by ammonium- and nitrate-selective microelectrodes permits a detailed examination of inorganic nitrogen acquisition and its component ionic interactions. PMID:16667447

  15. Superthermal Ion Transport and Acceleration in Multiple Contracting and Reconnecting Inertial-scale Flux Ropes in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Le Roux, Jakobus; Zank, Gary; Webb, Gary

    2014-10-01

    MHD turbulence simulations with a strong large-scale magnetic field show that the turbulence is filled with quasi-2D inertial-scale flux ropes that intermittently reconnect. Solar wind observations indicate that the statistical properties of the turbulence agree well with the MHD turbulence simulations, while particle simulations stress how ions can be efficiently accelerated to produce power law spectra when traversing multiple flux ropes. Recent observations show the presence of different size inertial-scale magnetic islands in the slow solar wind near the heliospheric current sheet, evidence of island merging, and of heating of ions and electrons in the vicinity. We will present a new statistical transport theory designed to model the acceleration and transport of superthermal ions traversing multiple contracting and reconnecting inertial-scale quasi-2D flux ropes in the supersonic slow solar wind. A steady-state solution for the accelerated particle spectrum in a radially expanding solar wind will discussed, showing that the theory potentially can explain naturally the existence of superthermal power-law spectra observed during quiet solar wind conditions.

  16. Suprathermal Ion Acceleration in Multiple Contracting and Reconnecting Inertial-scale Flux Ropes in the Supersonic Solar Wind.

    NASA Astrophysics Data System (ADS)

    le Roux, J. A.; Zank, G. P.; Webb, G. M.

    2014-12-01

    3D and 2D MHD turbulence simulations with a strong large-scale magnetic field show that the turbulence is filled with quasi-2D inertial-scale flux ropes that intermittently reconnect, while test particle simulations stress how suprathermal particles can be efficiently accelerated to produce power law spectra (kappa distributions) when traversing multiple flux ropes. Solar wind observations indicate that the statistical properties of the turbulence agree well with the MHD turbulence simulation. In addition, recent observations show the presence of different size inertial-scale magnetic islands in the slow solar wind near the heliospheric current sheet, evidence of island merging, and of heating of ions and electrons in their vicinity. At the same time, observations in the supersonic solar wind suggest the existence of suprathermal ion spectra in the solar wind frame where the distribution function is a power law in momentum with a -5 exponent. We present a new statistical transport theory to model the acceleration of superthermal ions traversing multiple contracting and reconnecting inertial-scale quasi-2D flux ropes in the supersonic solar wind. Steady-state analytical solutions for the accelerated suprathermal particle spectrum in a radially expanding solar wind will be explored to show under what conditions one can reproduce the observed superthermal power-law slope.

  17. Temperature-dependent surface porosity of Nb2O5 under high-flux, low-energy He+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Novakowski, T. J.; Tripathi, J. K.; Hosinski, G. M.; Joseph, G.; Hassanein, A.

    2016-01-01

    The present study reports on high-flux, low-energy He+ ion irradiation as a novel method of enhancing the surface porosity and surface area of naturally oxidized niobium (Nb). Our study shows that ion-irradiation-induced Nb surface micro- and nano-structures are highly tunable by varying the target temperature during ion bombardment. Mirror-polished Nb samples were irradiated with 100 eV He+ ions at a flux of 1.2 × 1021 ions m-2 s-1 to a total fluence of 4.3 × 1024 ions m-2 with simultaneous sample annealing in the temperature range of 773-1223 K to demonstrate the influence of sample temperature on the resulting Nb surface morphology. This surface morphology was primarily characterized using field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Below 923 K, Nb surfaces form nano-scale tendrils and exhibit significant increases in surface porosity. Above 923 K, homogeneously populated nano-pores with an average diameter of ∼60 nm are observed in addition to a smaller population of sub-micron sized pores (up to ∼230 nm in diameter). Our analysis shows a significant reduction in surface pore number density and surface porosity with increasing sample temperature. High-resolution ex situ X-ray photoelectron spectroscopy (XPS) shows Nb2O5 phase in all of the ion-irradiated samples. To further demonstrate the length scales in which radiation-induced surface roughening occurs, optical reflectivity was performed over a spectrum of light between 200 and 1100 nm, showing a recovery of nano-scale surface damage at high sample temperatures.

  18. L-H transition physics in hydrogen and deuterium: key role of the edge radial electric field and ion heat flux

    NASA Astrophysics Data System (ADS)

    Ryter, F.; Cavedon, M.; Happel, T.; McDermott, R. M.; Viezzer, E.; Conway, G. D.; Fischer, R.; Kurzan, B.; Pütterich, T.; Tardini, G.; Willensdorfer, M.; the ASDEX Upgrade Team

    2016-01-01

    Previous work carried out in the ASDEX Upgrade tokamak on the role of the edge radial electric field and ion heat flux in the L-H transition physics in deuterium plasmas has been extended in hydrogen plasmas. Similar discharges were performed in the two gases providing a detailed comparison of the edge kinetic profiles and heat fluxes in L-mode up to the L-H transition, as the heating power is increased. At the L-H transition, the edge ion heat flux just inside the separatrix is about two times higher in hydrogen than in deuterium. However, the ion plasma parameters at the plasma edge, T i and \

  19. 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.

  20. Flux dependent MeV self-ion-induced effects on Au nanostructures: dramatic mass transport and nanosilicide formation.

    PubMed

    Ghatak, J; Umananda Bhatta, M; Sundaravel, B; Nair, K G M; Liou, Sz-Chian; Chen, Cheng-Hsuan; Wang, Yuh-Lin; Satyam, P V

    2008-08-13

    We report a direct observation of dramatic mass transport due to 1.5 MeV Au(2+) ion impact on isolated Au nanostructures of average size ≈7.6 nm and height ≈6.9 nm that are deposited on Si(111) substrate under high flux (3.2 × 10(10)-6.3 × 10(12) ions cm(-2) s(-1)) conditions. The mass transport from nanostructures was found to extend up to a distance of about 60 nm into the substrate, much beyond their size. This forward mass transport is compared with the recoil implantation profiles using SRIM simulation. The observed anomalies with theory and simulations are discussed. At a given energy, the incident flux plays a major role in mass transport and its redistribution. The mass transport is explained on the basis of thermal effects and the creation of rapid diffusion paths in the nanoscale regime during the course of ion irradiation. The unusual mass transport is found to be associated with the formation of gold silicide nano-alloys at subsurfaces. The complexity of the ion-nanostructure interaction process is discussed with a direct observation of melting (in the form of spherical fragments on the surface) phenomena. Transmission electron microscopy, scanning transmission electron microscopy, and Rutherford backscattering spectroscopy methods have been used.

  1. Intraneuronal ion distribution during experimental oxygen/glucose deprivation. Routes of ion flux as targets of neuroprotective strategies.

    PubMed

    Lopachin, R M

    1999-01-01

    Ischemic neuronal injury appears to be mediated by disruption of subcellular ion distribution and, therefore, prevention of ion relocation might be neuroprotective. X-ray microanalysis was used to measure concentrations of Na, K, Ca and other elements in subcellular compartments (e.g., mitochondria) of CA1 neurons from oxygen/glucose-deprived (OGD) hippocampal slices. Results showed that OGD produced progressive loss of ion regulation in CA1 cells. Post-OGD reperfusion with normal media exacerbated the initial ion deregulation. To study neuroprotective mechanisms, we determined the ability of hypothermia (31 degrees C) or ion channel blockade to retard intraneuronal ion disruption induced by OGD/reperfusion. Whereas Ca2+ channel blockade (omega-conotoxin MVIIC, 3 microM) was ineffective, hypothermia and Na+ channel blockers (tetrodotoxin, TTX, 1 microM; lidocaine, 200 microM) reduced ion deregulation in subneuronal compartments. Blockade of glutamate receptors (AMPA, 10 microM; the non-NMDA receptor antagonist CNQX, 10 microM/100 microM glycine; the NMDA receptor antagonist CCP, 100 microM) during OGD/reperfusion provided nearly complete protection. These findings provide a foundation for identifying potential pharmacotherapeutic approaches and for discerning corresponding mechanisms of neuroprotection. PMID:10668426

  2. Self-referencing, non-invasive, ion selective electrode for single cell detection of trans-plasma membrane calcium flux.

    PubMed

    Smith, P J; Hammar, K; Porterfield, D M; Sanger, R H; Trimarchi, J R

    1999-09-15

    Biological systems have very different internal ion compositions in comparison with their surrounding media. The difference is maintained by transport mechanisms across the plasma membrane and by internal stores. On the plasma membrane, we can classify these mechanisms into three types, pumps, porters, and channels. Channels have been extensively studied, particularly since the advent of the patch clamp technique, which opened new windows into ion channel selectivity and dynamics. Pumps, particularly the plasma membrane Ca(2+)-ATPase, and porters are more illusive. The technique described in this paper, the self-referencing, ion-selective (or Seris) probe, has the ability to monitor the behavior of membrane transport mechanisms, such as the pumps and porters, in near to real-time by non-invasively measuring local extracellular ion gradients with high sensitivity and square micron spatial resolution. The principles behind the self-referencing technique are described with an overview of systems utilizing ion, electrochemical and voltage sensors. Each of these sensors employs the simple expedient of increasing the system resolution by self-referencing and, thereby, removing the drift component inherent to all electrodes. The approach is described in detail, as is the manner in which differential voltage measurements can be converted into a flux value. For the calcium selective probes, we can resolve flux values in the low to sub pmol.cm(-2)s(-1) range. Complications in the use of the liquid ion exchange cocktail are discussed. Applications of the calcium selective probe are given, drawing on examples from the plant sciences, developmental biology, muscle physiology, and the neurosciences.

  3. Measurements of Ion Energy and Ion Flux Distributions in Inductively Coupled Plasmas in CF4/O2/Ar Mixtures

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Kim, J. S.; Cappelli, M. A.; Sharma, Surendra; Partridge, Harry (Technical Monitor)

    1999-01-01

    We report mass spectrometric studies of energy distributions and absolute concentrations of ions generated in CF4/O2/Ar inductively coupled rf plasmas. The ions were collected through a 100 mm orifice in the grounded and water cooled lower electrode in a GEC cell configuration. The measurements were made at gas pressures in the 10-50 mTorr range and rf coil power in the 100-300 W range. The observed ions are CF3(+), CF2(+), CF(+), C(+), F(+), COF(+), CO(+), O2(+), and O(+). The relative abundance of these ions varies with pressure and rf power. The energy distribution and absolute concentrations are correlated with electron number density and floating plasma potential measured by a compensated Langmuir probe.

  4. Neutron Unfolding Code System for Calculating Neutron Flux Spectra from Activation Data of Dosimeter Foils.

    1982-04-30

    Version 00 As a part of the measurement and analysis plan for the Dosimetry Experiment at the "JOYO" experimental fast reactor, neutron flux spectral analysis is performed using the NEUPAC (Neutron Unfolding Code Package) code system. NEUPAC calculates the neutron flux spectra and other integral quantities from the activation data of the dosimeter foils.

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

    SciTech Connect

    Vemareddy, P.

    2015-06-20

    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 flux 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.

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

    PubMed

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

    2016-03-01

    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

  7. 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

  8. Passive and active ion transport by the urinary bladder of a euryhaline flounder.

    PubMed

    Demarest, J R; Machen, T E

    1984-04-01

    The effects of voltage clamping on the flux ratios and unidirectional and net fluxes of Na and Cl were used to gain insight into the mechanisms of active and passive ion transport across urinary bladders isolated from seawater-(SW) and freshwater-acclimated (FW) flounder, Platichthys stellatus. Although the transepithelial conductance (Gt = 2.77 mS X cm-2) of FW bladders was much greater than that of SW bladders (Gt = 0.40 mS X cm-2), the current-voltage relationships of both SW and FW bladders were markedly nonlinear. Under short-circuit conditions there was a large difference in the serosal-to-mucosal Na flux (JNasm) between SW (0.10 mueq X cm-2 X h-1) and FW (1.71 mueq X cm-2 X h-1) bladders, but their mannitol permeabilities were identical. The results indicate that 1) the paracellular pathway of both SW and FW bladders is Cl selective and Cl movements through the shunt account for a maximum of 90% of Gt in SW bladders and 19% in FW bladders; 2) the larger Gt of FW bladders is due to greater conductance of the apical cell membrane; 3) the majority of the passive ion movement across these epithelia proceeds through nonconductive, presumably transcellular, pathways; and 4) active transport of Na and Cl occurs by neutral coupling to each other and to other unidentified ions.

  9. Microbial Activity and Volatile Fluxes in Seafloor Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Corrigan, R. S.; Lowell, R. P.

    2013-12-01

    Understanding geographically and biologically the production or utilization of volatile chemical species such as CO2, CH4, and H2 is crucial not only for understanding hydrothermal processes but also for understanding life processes in the oceanic crust. To estimate the microbial effect on the transport of these volatiles, we consider a double-loop single pass model as shown in Figure 1 to estimate the mass fluxes shown. We then use a simple mixing formulation: C4Q4 = C3 (Q1 -Q3)+ C2Q2, where C2 is the concentration of the chemical in seawater, C3 is the average concentration of the chemical in high temperature focused flow, C4 is the expected concentration of the chemical as a result of mixing, and the relevant mass flows are as shown in Figure 1. Finally, we compare the calculated values of CO2, CH4, and H2 in diffuse flow fluids to those observed. The required data are available for both the Main Endeavour Field on the Juan de Fuca Ridge and the East Pacific Rise 9°50' N systems. In both cases we find that, although individual diffuse flow sites have observed concentrations of some elements that are greater than average, the average concentration of these volatiles is smaller in all cases than the concentration that would be expected from simple mixing. This indicates that subsurface microbes are net utilizers of these chemical constituents at the Main Endeavour Field and at EPR 9°50' N on the vent field scale. Figure 1. Schematic of a 'double-loop' single-pass model above a convecting, crystallizing, replenished AMC (not to scale). Heat transfer from the vigorously convecting, cooling, and replenished AMC across the conductive boundary layer δ drives the overlying hydrothermal system. The deep circulation represented by mass flux Q1 and black smoker temperature T3 induces shallow circulation noted by Q2. Some black smoker fluid mixes with seawater resulting in diffuse discharge Q4, T4, while the direct black smoker mass flux with temperature T3 is reduced

  10. Enzymatically active high-flux selectively gas-permeable membranes

    DOEpatents

    Jiang, Ying-Bing; Cecchi, Joseph L.; Rempe, Susan; FU, Yaqin; Brinker, C. Jeffrey

    2016-01-26

    An ultra-thin, catalyzed liquid transport medium-based membrane structure fabricated with a porous supporting substrate may be used for separating an object species such as a carbon dioxide object species. Carbon dioxide flux through this membrane structures may be several orders of magnitude higher than traditional polymer membranes with a high selectivity to carbon dioxide. Other gases such as molecular oxygen, molecular hydrogen, and other species including non-gaseous species, for example ionic materials, may be separated using variations to the membrane discussed.

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

    SciTech Connect

    Yang, Shuhong; Zhang, Jun; Liu, Zhong; Xiang, Yongyuan E-mail: zjun@nao.cas.cn

    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, 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.

  12. Design and Performance of a High-Flux Electrospray Ionization Source for Ion Soft-Landing

    SciTech Connect

    Gunaratne, Kalupathirannehelage Don D.; Prabhakaran, Venkateshkumar; Ibrahim, Yehia M.; Norheim, Randolph V.; Johnson, Grant E.; Laskin, Julia

    2015-01-01

    We report the design and evaluation of a new high-intensity electrospray ionization source for ion soft-landing experiments. The source incorporates a dual ion funnel, which enables operation with a higher gas load through an expanded heated inlet into the additional first region of differential pumping. This capability allowed us to examine the effect of the inner diameter (ID) of the heated stainless steel inlet on the total ion current transmitted through the dual funnel interface and, more importantly, the mass-selected ion current delivered to the deposition target. The ion transmission of the dual funnel is similar to the transmission of the single funnel used in our previous soft landing studies. However, substantially higher ion currents were obtained using larger ID heated inlets and an orthogonal inlet geometry, in which the heated inlet is positioned perpendicular to the direction of ion propagation through the instrument. The highest ion currents were obtained using the orthogonal geometry and a 1.4 mm ID heated inlet. The corresponding stable deposition rate of ~1 μg of mass-selected ions per day will facilitate future studies focused on the controlled deposition of biological molecules on substrates and preparation of materials for studies in catalysis, energy storage, and self-assembly

  13. Design and performance of a high-flux electrospray ionization source for ion soft landing.

    PubMed

    Gunaratne, K Don D; Prabhakaran, Venkateshkumar; Ibrahim, Yehia M; Norheim, Randolph V; Johnson, Grant E; Laskin, Julia

    2015-05-01

    We report the design and evaluation of a new high-intensity electrospray ionization source for ion soft-landing experiments. The source incorporates a dual ion funnel, which enables operation with a higher gas load through an expanded diameter heated inlet into the additional first region of differential pumping. This capability allowed us to examine the effect of the inner diameter (ID) of the heated stainless steel inlet on the total ion current transmitted through the dual funnel interface and, more importantly, the mass-selected ion current delivered to the deposition target. The ion transmission of the dual funnel is similar to the transmission of the single funnel used in our previous soft landing studies. However, substantially higher ion currents were obtained using larger ID heated inlets and an orthogonal inlet geometry, in which the heated inlet was positioned perpendicular to the direction of ion propagation through the instrument. The highest ion currents were obtained using the orthogonal geometry and a 1.4 mm ID heated inlet. The corresponding stable deposition rate of ∼1 μg of mass-selected ions per day will facilitate future studies focused on the controlled deposition of complex molecules on substrates for studies in catalysis, energy storage, and self-assembly.

  14. Dynamic volume changes in astrocytes are an intrinsic phenomenon mediated by bicarbonate ion flux.

    PubMed

    Florence, Clare M; Baillie, Landon D; Mulligan, Sean J

    2012-01-01

    Astrocytes, the major type of non-neuronal cells in the brain, play an important functional role in extracellular potassium ([K(+)](o)) and pH homeostasis. Pathological brain states that result in [K(+)](o) and pH dysregulation have been shown to cause astrocyte swelling. However, whether astrocyte volume changes occur under physiological conditions is not known. In this study we used two-photon imaging to visualize real-time astrocyte volume changes in the stratum radiatum of the hippocampus CA1 region. Astrocytes were observed to swell by 19.0±0.9% in response to a small physiological increase in the concentration of [K(+)](o) (3 mM). Astrocyte swelling was mediated by the influx of bicarbonate (HCO(3-)) ions as swelling was significantly decreased when the influx of HCO(3-) was reduced. We found: 1) in HCO(3-) free extracellular solution astrocytes swelled by 5.4±0.7%, 2) when the activity of the sodium-bicarbonate cotransporter (NBC) was blocked the astrocytes swelled by 8.3±0.7%, and 3) in the presence of an extracellular carbonic anhydrase (CA) inhibitor astrocytes swelled by 11.4±0.6%. Because a significant HCO(3-) efflux is known to occur through the γ-amino-butyric acid (GABA) channel, we performed a series of experiments to determine if astrocytes were capable of HCO(3-) mediated volume shrinkage with GABA channel activation. Astrocytes were found to shrink -7.7±0.5% of control in response to the GABA(A) channel agonist muscimol. Astrocyte shrinkage from GABA(A) channel activation was significantly decreased to -5.0±0.6% of control in the presence of the membrane-permeant CA inhibitor acetazolamide (ACTZ). These dynamic astrocyte volume changes may represent a previously unappreciated yet fundamental mechanism by which astrocytes regulate physiological brain functioning. PMID:23226475

  15. Collisional activation with random noise in ion trap mass spectrometry

    SciTech Connect

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

    1992-07-01

    Random noise applied to the end caps of a quadrupole ion trap is shown to be an effective means for the collisional activation of trapped ions independent of mass/charge ratio and number of ions. This technique is compared and contrasted with conventional single-frequency collisional activation for the molecular ion of N,N-dimethylaniline, protonated cocaine, the molecular anion of 2,4,6-trinitrotoluene, and doubly protonated neuromedin U-8. Collisional activation with noise tends to produce more extensive fragmentation than the conventional approach due to the fact that product ions are also kinetically excited in the noise experiment. The efficiency of the noise experiment in producing detectable product ions relative to the conventional approach ranges from being equivalent to being a factor of 3 less efficient. Furthermore, discrimination against low mass/charge product ions is apparent in the data from multiply charged biomolecules. Nevertheless, collisional activation with random noise provides a very simple means for overcoming problems associated with the dependence of single-frequency collisional activation on mass/charge ratio and the number of ions in the ion trap. 45 refs., 7 figs.

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

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Henderson, M. G.; Jordanova, V. K.; Thomsen, M. F.; Borovsky, J. E.; Woodroffe, J.; Hartley, D. P.; Pitchford, D.

    2016-07-01

    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 predictions 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.

  17. 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.; Thomsen, M. F.; Borovsky, J. E.; Woodroffe, J.; Hartley, D. P.; Pitchford, D.

    2016-07-27

    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

  18. Seasonal fluxes of some ions through the overstory, underbrush, and organic soil horizons of an aspen-birch forest

    NASA Astrophysics Data System (ADS)

    Price, Anthony G.; Watters, Robert J.

    1988-03-01

    A study was made of the water and chemical fluxes in a predominantly deciduous forest at Chalk River, Ontario. The chemistry of water moving to the soil through trembling aspen, large-tooth aspen and paper birch is strongly modified by interaction with all major components in the system: the overstory leaves and trunks, the underbrush stems and leaves, and the organic plus upper mineral soil horizon. The dominant controls on the chemistry of water reaching the forest floor are those exerted by the overstory. Hydrochemical changes through the underbrush are, generally, of the same type as those through the overstory, but of a smaller size. A significant, positive relationship was found between the hydrogen ion flux imposed on the overstory, and the net loss of calcium, magnesium, and potassium from the canopy, showing that acid deposition is having an effect on the export of these nutrients from the canopy.

  19. Variational calculation of neoclassical ion heat flux and poloidal flow in the banana regime for axisymmetric magnetic geometry

    NASA Astrophysics Data System (ADS)

    Parker, Jeffrey B.; Catto, Peter J.

    2012-08-01

    We present a numerical solution of the drift-kinetic equation retaining the linearized Fokker-Planck collision operator which is valid for general axisymmetric magnetic geometry in the low collisionality limit. We use the well-known variational principle based on entropy production and expand in basis functions. Uniquely, we expand in pitch-angle basis functions which are eigenfunctions of the transit-averaged test particle collision operator. These eigenfunctions, which depend on the geometry, are extremely well suited to this problem, with only one or two basis functions required to obtain an accurate solution. As a simple example of the technique, the neoclassical ion heat flux and poloidal flow are calculated for circular flux surfaces and compared with analytic approximations for arbitrary aspect ratio.

  20. Ion exchange defines the biological activity of titanate nanotubes.

    PubMed

    Rónavári, Andrea; Kovács, Dávid; Vágvölgyi, Csaba; Kónya, Zoltán; Kiricsi, Mónika; Pfeiffer, Ilona

    2016-05-01

    One-dimensional titanate nanotubes (TiONTs) were subjected to systematic ion exchange to determine the impact of these modifications on biological activities. Ion exchanged TiONTs (with Ag, Mg, Bi, Sb, Ca, K, Sr, Fe, and Cu ions) were successfully synthesized and the presence of the substituted ions was verified by energy dispersive X-ray spectroscopy (EDS). A complex screening was carried out to reveal differences in toxicity to human cells, as well as in antibacterial, antifungal, and antiviral activities between the various modified nanotubes. Our results demonstrated that Ag ion exchanged TiONTs exerted potent antibacterial and antifungal effects against all examined microbial species but were ineffective on viruses. Surprisingly, the antibacterial activity of Cu/TiONTs was restricted to Micrococcus luteus. Most ion exchanged TiONTs did not show antimicrobial activity against the tested bacterial and fungal species. Incorporation of various ions into nanotube architectures lead to mild, moderate, or even to a massive loss of human cell viability; therefore, this type of biological effect exerted by TiONTs can be greatly modulated by ion exchange. These findings further emphasize the contribution of ion exchange in determining not only the physical and chemical characteristics but also the bioactivity of TiONT against different types of living cells.

  1. 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.

  2. Pathway confirmation and flux analysis of central metabolicpathways in Desulfovibrio vulgaris Hildenborough using GasChromatography-Mass Spectrometry and Fourier Transform-Ion CyclotronResonance Mass Spectrometry

    SciTech Connect

    Tang, Yinjie; Pingitore, Francesco; Mukhopadhyay, Aindrila; Phan,Richard; Hazen, Terry C.; Keasling, Jay D.

    2007-03-15

    Flux distribution in central metabolic pathways ofDesulfovibrio vulgaris Hildenborough was examined using 13C tracerexperiments. Consistent with the current genome annotation andindependent evidence from enzyme activity assays, the isotopomer resultsfrom both GC-MS and Fourier Transform-Ion Cyclotron Resonance massspectrometry (FT-ICR MS) indicate the lack of oxidatively functional TCAcycle and an incomplete pentose phosphate pathway. Results from thisstudy suggest that fluxes through both pathways are limited tobiosynthesis. The data also indicate that>80 percent of the lactatewas converted to acetate and the reactions involved are the primary routeof energy production (NAD(P)H and ATP production). Independent of the TCAcycle, direct cleavage of acetyl-CoA to CO and 5,10-methyl-THF also leadsto production of NADH and ATP. Although the genome annotation implicatesa ferredoxin-dependentoxoglutarate synthase, isotopic evidence does notsupport flux through this reaction in either the oxidative or reductivemode; therefore, the TCA cycle is incomplete. FT-ICR MS was used tolocate the labeled carbon distribution in aspartate and glutamate andconfirmed the presence of an atypical enzyme for citrate formationsuggested in previous reports (the citrate synthesized by this enzyme isthe isotopic antipode of the citrate synthesized by the (S)-citratesynthase). These findings enable a better understanding of the relationbetween genome annotation and actual metabolic pathways in D. vulgaris,and also demonstrate FT-ICR MS as a powerful tool for isotopomeranalysis, overcoming problems in both GC-MS and NMRspectroscopy.

  3. Strong ambipolar-driven ion upflow within the cleft ion fountain during low geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Shen, Yangyang; Knudsen, David J.; Burchill, Johnathan K.; Howarth, Andrew; Yau, Andrew; Redmon, Robert J.; Miles, David M.; Varney, Roger H.; Nicolls, Michael J.

    2016-07-01

    We investigate low-energy (<10 eV) ion upflows (mainly O+) within the cleft ion fountain (CIF) using conjunctions of the Enhanced Polar Outflow Probe (e-POP) satellite, the DMSP F16 satellite, the SuperDARN radar, and the Resolute Bay Incoherent Scatter Radar North (RISR-N). The SEI instrument on board e-POP enables us to derive ion upflow velocities from the 2-D images of ion distribution functions with a frame rate of 100 images per second, and with a velocity resolution of the order of 25 m/s. We identify three cleft ion fountain events with very intense (>1.6 km/s) ion upflow velocities near 1000 km altitude during quiet geomagnetic activity (Kp < 3). Such large ion upflow velocities have been reported previously at or below 1000 km, but only during active periods. Analysis of the core ion distribution images allows us to demonstrate that the ion temperature within the CIF does not rise by more than 0.3 eV relative to background values, which is consistent with RISR-N observations in the F region. The presence of soft electron precipitation seen by DMSP and lack of significant ion heating indicate that the ion upflows we observe near 1000 km altitude are primarily driven by ambipolar electric fields. DC field-aligned currents (FACs) and convection velocity gradients accompany these events. The strongest ion upflows are associated with downward current regions, which is consistent with some (although not all) previously published results. The moderate correlation coefficient (0.51) between upflow velocities and currents implies that FACs serve as indirect energy inputs to the ion upflow process.

  4. Magnetic Flux Transport and the Long-term Evolution of Solar Active Regions

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 infer 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.

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

    SciTech Connect

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

    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 infer 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.

  6. Imaging intracellular elemental distribution and ion fluxes in cultured cells using ion microscopy: a freeze-fracture methodology.

    PubMed

    Chandra, S; Morrison, G H; Wolcott, C C

    1986-10-01

    A freeze-fracture methodology was standardized for tissue culture cells to study intracellular distribution of diffusible elements with ion microscopy. Chinese hamster ovary (CHO) and normal rat kidney (NRK) cells grown on a silicon substrate were sandwiched using another smooth surface (silicon, glass, mica) in the presence of spacers and fast frozen in liquid nitrogen slush. The sandwich was fractured by prying the two halves apart under liquid nitrogen. This procedure produced large areas on the silicon substrate containing hundreds of cells grouped together and fractured at the apical cell surface. After freeze-drying, these cells revealed a subcellular distribution of Na, K, Ca, Mg, P, Cl and S with the approximately 0.5 micron lateral resolution of the ion microscope. Between the nuclei and the cytoplasm of cells, no major differences were observed for Na, K, Mg, P, Cl and S intensities. Calcium alone, however, exhibited a remarkable distribution. Calcium accumulated more in the cytoplasm than in the nuclei of cells. Even within the cytoplasm its distribution was heterogeneous, suggesting Ca binding sites. The fractured cells consistently exhibited high K-low Na intensities. The injured or dead cells were easily recognized among the healthy ones due to their abnormal ion composition. This simple freeze-fracture methodology allowed fracturing of cells without removing the cells from the substrate. In addition, it eliminated the need for washing the nutrient media away and cryo-sectioning before ion microanalysis. The methodology was successfully extended to 3T3 mouse fibroblast, PtK2 rat kangaroo and L5 rat myoblast cultures. PMID:3795262

  7. Active and passive Na+ fluxes across the basolateral membrane of rabbit urinary bladder.

    PubMed

    Eaton, D C; Frace, A M; Silverthorn, S U

    1982-01-01

    The apical membrane of rabbit urinary bladder can be functionally removed by application of nystatin at high concentration if the mucosal surface of the tissue is bathed in a saline which mimics intracellular ion concentrations. Under these conditions, the tissue is as far as the movement of univalent ions no more than a sheet of basolateral membrane with some tight junctional membrane in parallel. In this manner the Na+ concentration at the inner surface of the basolateral membrane can be varied by altering the concentration in the mucosal bulk solution. When this was done both mucosal-to-serosal 22Na flux and net change in basolateral current were measured. The flux and the current could be further divided into the components of each that were either blocked by ouabain or insensitive to ouabain. Ouabain-insensitive mucosal-to-serosal Na+ flux was a linear function of mucosal Na+ concentration. Ouabain-sensitive Na+ flux and ouabain-sensitive, Na+-induced current both display a saturating relationship which cannot be accounted for by the presence of unstirred layers. If the interaction of Na+ with the basolateral transport process is assumed to involve the interaction of some number of Na+ ions, n, with a maximal flux, MMAX, then the data can be fit by assuming 3.2 equivalent sites for interaction and a value for MMAX of 287.8 pM cm-2 sec-1 with an intracellular Na concentration of 2.0 mM Na+ at half-maximal saturation. By comparing these values with the ouabain-sensitive, Na+-induced current, we calculate a Na+ to K+ coupling ratio of 1.40 +/- 0.07 for the transport process.

  8. Enhanced momentum delivery by electric force to an ion flux due to collisions of ions with neutrals

    NASA Astrophysics Data System (ADS)

    Fruchtman, Amnon

    2014-10-01

    A major figure of merit in propulsion in general and in electric propulsion in particular is the thrust per unit of deposited power, the ratio of thrust over power. We have recently demonstrated experimentally and theoretically [1--4] that for a fixed deposited power in the ions, the momentum delivered by the electric force is larger if the accelerated ions collide with neutrals during the acceleration. The higher thrust for given power is achieved for a collisional plasma at the expense of a lower thrust per unit mass flow rate, reflecting what is true in general, that the lower the flow velocity is, the higher the thrust for a given power. This is the usual trade-off between having a large specific impulse and a large thrust. Broadening the range of jet velocities and thrust levels is desirable since there are different propulsion requirements for different space missions. The mechanism of thrust enhancement by ion-neutral collisions has been investigated in the past in the case of electric pressure, what is called ionic wind. I will describe in the talk experimental results for an enhanced thrust due to ion-neutral collisions in a configuration where the thrust is a result of magnetic pressure [1,3]. The plasma is accelerated by J × B force, in a configuration similar to that of Hall thrusters. Our measurements for three different gases and for various gas flow rates and magnetic field intensities, confirmed that the thrust increase is proportional to the square-root of the number of ion-neutral collisions. Additional measurements of local discharge parameters will be shown to be consistent with the force measurements. Issues that are crucial for the use of this mechanism in an electric thruster will also be discussed. These are the possible increase of the electron transport across magnetic field lines by electron-neutral collisions, and the possible effect on various sources of inefficiency. Supported by Grant No. 765/11 from the Israel Science Foundation.

  9. 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

  10. 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.

  11. Flux rope proxies and fan-spine structures in active region NOAA 11897

    NASA Astrophysics Data System (ADS)

    Hou, Y. J.; Li, T.; Zhang, J.

    2016-08-01

    Context. Flux ropes are composed of twisted magnetic fields and are closely connected with coronal mass ejections. The fan-spine magnetic topology is another type of complex magnetic fields. It has been reported by several authors, and is believed to be associated with null-point-type magnetic reconnection. Aims: We try to determine the number of flux rope proxies and reveal fan-spine structures in the complex active region (AR) NOAA 11897. Methods: Employing the high-resolution observations from the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS), we statistically investigated flux rope proxies in NOAA AR 11897 from 14 November 2013 to 19 November 2013 and display two fan-spine structures in this AR. Results: For the first time, we detect flux rope proxies of NOAA 11897 for a total of 30 times in four different locations during this AR's transference from solar east to west on the disk. Moreover, we notice that these flux rope proxies were tracked by active or eruptive material of filaments 12 times, while for the remaining 18 times they appeared as brightenings in the corona. These flux rope proxies were either tracked in both lower and higher temperature wavelengths or only detected in hot channels. None of these flux rope proxies was observed to erupt; they faded away gradually. In addition to these flux rope proxies, we detect for the first time a secondary fan-spine structure. It was covered by dome-shaped magnetic fields that belong to a larger fan-spine topology. Conclusions: These new observations imply that many flux ropes can exist in an AR and that the complexity of AR magnetic configurations is far beyond our imagination. Movies 1-8 are available in electronic form at http://www.aanda.org

  12. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    NASA Astrophysics Data System (ADS)

    Li, Ting; Zhang, Jun; Ji, Haisheng

    2015-06-01

    We conducted a comparative analysis of two filaments that showed a quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) were made to analyze the two filaments on 2013 August 17 - 20 (SOL2013-08-17) and September 29 (SOL2013-09-29). The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4×1021 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest a similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed three days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2×1020 Mx, about one order of magnitude lower than that of the first event. Two patches of parasitic polarity in the vicinity of the barb merged, then cancelled with nearby network fields. About 20 hours after the onset of the emergence, the filament erupted. Our findings imply that the location of emerging flux within the filament channel is probably crucial to filament evolution. If the flux emergence appears nearby the barbs, it is highly likely that the emerging flux and the filament magnetic fields will cancel, which may lead to the eruption of the filament. The comparison of the two events shows that the emergence of a small AR may still not be enough to disrupt the stability of a filament system, and the actual eruption only occurs after the flux cancellation sets in.

  13. Mechanosensitive ion channel MscL controls ionic fluxes during cold and heat stress in Synechocystis.

    PubMed

    Bachin, Dmitry; Nazarenko, Lyudmila V; Mironov, Kirill S; Pisareva, Tatiana; Allakhverdiev, Suleyman I; Los, Dmitry A

    2015-06-01

    Calcium plays an essential role in a variety of stress responses of eukaryotic cells; however, its function in prokaryotes is obscure. Bacterial ion channels that transport Ca(2+) are barely known. We investigated temperature-induced changes in intracellular concentration of Ca(2+), Na(+) and K(+) in the cyanobacterium Synechocystis sp. strain PCC 6803 and its mutant that is defective in mechanosensitive ion channel MscL. Concentration of cations rapidly and transiently increased in wild-type cells in response to cold and heat treatments. These changes in ionic concentrations correlated with the changes in cytoplasmic volume that transiently decreased in response to temperature treatments. However, no increase in ionic concentrations was observed in the MscL-mutant cells. It implies that MscL functions as a non-specific ion channel, and it participates in regulation of cell volume under temperature-stress conditions.

  14. Diurnal variations on a plasmaspheric flux tube - Light ion flows and F region temperature enhancements

    NASA Technical Reports Server (NTRS)

    Guiter, S. M.; Gombosi, T. I.; Rasmussen, C. E.

    1991-01-01

    The paper concentrates on the diurnal variations on a plasmaspheric flux tube modeled using a time-dependent multispecies one-stream interhemispheric model for plasma flows. The model takes into account the effects of ionization, charge exchange, recombination, collisions, heat conduction, and allows for external heat sources. The simulation is done for June solstice conditions during solar minimum. Focus is placed on the presence of large downward H(+) velocities at about 320-km altitude in the winter (southern) hemisphere, in early morning when the summer hemisphere is sunlit but the winter hemisphere is dark. In addition, an upward H(+) flux is seen in the Southern Hemisphere at altitudes above 2000 km when the sun rises in the northern end.

  15. Dynamics of Double Layers, Ion Acceleration, and Heat Flux Suppression during Solar Flares

    NASA Astrophysics Data System (ADS)

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2014-09-01

    Observations of flare-heated electrons in the corona typically suggest confinement of electrons. The confinement mechanism, however, remains unclear. The transport of coronal hot electrons into ambient plasma was recently investigated by particle-in-cell (PIC) simulations. Electron transport was significantly suppressed by the formation of a highly localized, nonlinear electrostatic potential in the form of a double layer (DL). In this work large-scale PIC simulations are performed to explore the dynamics of DLs in larger systems where, instead of a single DL, multiple DLs are generated. The primary DL accelerates return current electrons, resulting in high velocity electron beams that interact with ambient ions. This forms a Buneman unstable system that spawns more DLs. Trapping of heated return current electrons between multiple DLs strongly suppresses electron transport. DLs also accelerate ambient ions and produce strong ion flows over an extended region. This clarifies the mechanism by which hot electrons in the corona couple to and accelerate ions to form the solar wind. These new dynamics in larger systems reveal a more likely picture of DL development and their impact on the ambient plasma in the solar corona. They are applicable to the preparation for in situ coronal space missions like the Solar Probe Plus.

  16. Ion flux onto conducting and isolated surfaces in the beam-plasma discharge: Computer simulation

    SciTech Connect

    Klykov, I. L.; Shustin, E. G.; Tarakanov, V. P.

    2010-12-15

    A physical model which allows the use of the program code KARAT for simulating the quasisteady state of the beam-plasma discharge with plasma regeneration from a neutral gas is developed. The results of simulation of the modes of discharge at different potentials at the discharge collector are reported. The results obtained for isolated and grounded ion collectors are compared.

  17. Dynamics of double layers, ion acceleration, and heat flux suppression during solar flares

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2014-09-20

    Observations of flare-heated electrons in the corona typically suggest confinement of electrons. The confinement mechanism, however, remains unclear. The transport of coronal hot electrons into ambient plasma was recently investigated by particle-in-cell (PIC) simulations. Electron transport was significantly suppressed by the formation of a highly localized, nonlinear electrostatic potential in the form of a double layer (DL). In this work large-scale PIC simulations are performed to explore the dynamics of DLs in larger systems where, instead of a single DL, multiple DLs are generated. The primary DL accelerates return current electrons, resulting in high velocity electron beams that interact with ambient ions. This forms a Buneman unstable system that spawns more DLs. Trapping of heated return current electrons between multiple DLs strongly suppresses electron transport. DLs also accelerate ambient ions and produce strong ion flows over an extended region. This clarifies the mechanism by which hot electrons in the corona couple to and accelerate ions to form the solar wind. These new dynamics in larger systems reveal a more likely picture of DL development and their impact on the ambient plasma in the solar corona. They are applicable to the preparation for in situ coronal space missions like the Solar Probe Plus.

  18. The change in the surface topography of magnesium under high-flux C ion irradiation

    NASA Astrophysics Data System (ADS)

    Potyomkin, G. V.; Ligachev, A. E.; Zhidkov, M. V.; Kolobov, Y. R.; Remnev, G. E.; Y Gazizova, M.; Bozhko, S. A.; Pavlov, S. K.

    2015-11-01

    The topography of the surface of the magnesium sample after irradiation by the high-intensity pulsed ion beam of a TEMP-4M accelerator was studied. The irradiation causes the formation of a regular comb structure and the creation of craters, their depth reaches 1-1.5 μm.

  19. Neutron Flux Spectra Determination by Multiple Foil Activation - Iterative Method.

    1994-07-08

    Version 00 Neutron energy spectra are determined by an analysis of experimental activation detector data. As with the original CCC-112/SAND-II program, which was developed at Air Force Weapons Laboratory, this code system consists of four modules, CSTAPE, SLACTS, SLATPE, and SANDII. The first three modules pre-process the dosimetry cross sections and the trial function spectrum library. The last module, SANDII, actually performs the iterative spectrum characterization.

  20. ACTIVE: a program to calculate and plot reaction rates from ANISN calculated fluxes

    SciTech Connect

    Judd, J.L.

    1981-12-01

    The ACTIVE code calculates spatial heating rates, tritium production rates, neutron reaction rates, and energy spectra from particle fluxes calculated by ANISN. ACTIVE has a variety of input options including the capability to plot all calculated spatial distributions. The code was primarily designed for use with fusion first wall/blanket systems, but could be applied to any one-dimensional problem.

  1. Decrease in T Cell Activation and Calcium Flux during Clinorotation

    NASA Technical Reports Server (NTRS)

    Sams, Clarence; Holtzclaw, J. David

    2006-01-01

    We investigated the effect of altered gravitational environments on T cell activation. We isolated human, naive T cells (CD3+CD14-CD19-CD16-CD56-CD25-CD69-CD45RA-) following IRB approved protocols. These purified T cells were then incubated with 6 mm polystyrene beads coated with OKT3 (Ortho Biotech, Raritan, NJ) and antiCD28 (Becton Dickinson (BD), San Jose, CA) at 37 C for 24 hours. Antibodies were at a 1:1 ratio and the bead-to-cell ratio was 2:1. Four incubation conditions existed: 1) static or "1g"; 2) centrifugation at 10 relative centrifugal force (RCF) or "10g"; 3) clinorotation at 25 RPM (functional weightlessness or "0g"); and 4) clinorotation at 80 RPM ("1g" plus net shear force approx.30 dynes/sq cm). Following incubation, T cells were stained for CD25 expression (BD) and intracellular calcium (ratio of Fluo4 to Fura Red, Molecular Probes, Eugene, OR) and analyzed by flow cytometry (Coulter EPICS XL, Miami, FL). Results: Static or "1g" T cells had the highest level of CD25 expression and intracellular calcium. T cells centrifuged at 10 RCF ("10g") had lower CD25 expression and calcium levels compared to the static control. However, cells centrifuged at 10 RCF had higher CD25 expression and calcium levels than those exposed to 24 RPM clinorotation ("0g"). T cells exposed to 24 RPM clinorotation had lower CD25 expression, but the approximately the same calcium levels than T cells exposed to 80 RPM clinorotation. These data suggest that stress-activated calcium channel exist in T cells and may play a role during T cell activation.

  2. 10.7-cm solar radio flux and the magnetic complexity of active regions

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Moore, Ronald L.; Rabin, Douglas

    1987-01-01

    During sunspot cycles 20 and 21, the maximum in smoothed 10.7-cm solar radio flux occurred about 1.5 yr after the maximum smoothed sunspot number, whereas during cycles 18 and 19 no lag was observed. Thus, although 10.7-cm radio flux and Zurich sunspot number are highly correlated, they are not interchangeable, especially near solar maximum. The 10.7-cm flux more closely follows the number of sunspots visible on the solar disk, while the Zurich sunspot number more closely follows the number of sunspot groups. The number of sunspots in an active region is one measure of the complexity of the magnetic structure of the region, and the coincidence in the maxima of radio flux and number of sunspots apparently reflects higher radio emission from active regions of greater magnetic complexity. The presence of a lag between sunspot-number maximum and radio-flux maximum in some cycles but not in others argues that some aspect of the average magnetic complexity near solar maximum must vary from cycle to cycle. A speculative possibility is that the radio-flux lag discriminates between long-period and short-period cycles, being another indicator that the solar cycle switches between long-period and short-period modes.

  3. Overview of LANL short-pulse ion acceleration activities

    SciTech Connect

    Flippo, Kirk A.; Schmitt, Mark J.; Offermann, Dustin; Cobble, James A.; Gautier, Donald; Kline, John; Workman, Jonathan; Archuleta, Fred; Gonzales, Raymond; Hurry, Thomas; Johnson, Randall; Letzring, Samuel; Montgomery, David; Reid, Sha-Marie; Shimada, Tsutomu; Gaillard, Sandrine A.; Sentoku, Yasuhiko; Bussman, Michael; Kluge, Thomas; Cowan, Thomas E.; Rassuchine, Jenny M.; Lowenstern, Mario E.; Mucino, J. Eduardo; Gall, Brady; Korgan, Grant; Malekos, Steven; Adams, Jesse; Bartal, Teresa; Chawla, Surgreev; Higginson, Drew; Beg, Farhat; Nilson, Phil; Mac Phee, Andrew; Le Pape, Sebastien; Hey, Daniel; Mac Kinnon, Andy; Geissel, Mattias; Schollmeier, Marius; Stephens, Rich

    2009-12-02

    An overview of Los Alamos National Laboratory's activities related to short-pulse ion acceleration is presented. LANL is involved is several projects related to Inertial Confinement Fusion (Fast Ignition) and Laser-Ion Acceleration. LANL has an active high energy X-ray backlighter program for radiographing ICF implosions and other High Energy Density Laboratory Physics experiments. Using the Trident 200TW laser we are currently developing high energy photon (>10 keV) phase contrast imaging techniques to be applied on Omega and the NIF. In addition we are engaged in multiple programs in laser ion acceleration to boost the ion energies and efficiencies for various potential applications including Fast Ignition, active material interrogation, and medical applications. Two basic avenues to increase ion performance are currently under study: one involves ultra-thin targets and the other involves changing the target geometry. We have recently had success in boosting proton energies above 65 MeV into the medical application range. Highlights covered in the presentation include: The Trident Laser System; X-ray Phase Contrast Imaging for ICF and HEDLP; Improving TNSA Ion Acceleration; Scaling Laws; Flat Targets; Thin Targets; Cone Targets; Ion Focusing;Trident; Omega EP; Scaling Comparisons; and, Conclusions.

  4. Argon-Hydrogen Shielding Gas Mixtures for Activating Flux-Assisted Gas Tungsten Arc Welding

    NASA Astrophysics Data System (ADS)

    Huang, Her-Yueh

    2010-11-01

    Using activating flux for gas tungsten arc welding (GTAW) to improve penetration capability is a well-established technique. Argon is an inert gas and the one most widely used as a shielding gas for GTAW. For the most austenitic stainless steels, pure argon does not provide adequate weld penetration. Argon-hydrogen mixtures give a more even heat input to the workpiece, increasing the arc voltage, which tends to increase the volume of molten material in the weld pool as well as the weld depth-to-width ratio. Great interest has been shown in the interaction between activating flux and the hydrogen concentration in an argon-based shielding gas. In this study, the weld morphology, the arc profile, the retained delta ferrite content, the angular distortion, and the microstructures were examined. The application of an activating flux combining argon and hydrogen for GTAW is important in the industry. The results of this study are presented here.

  5. Influence of Activating Flux and Helium Shielding Gas on an Austenitic Stainless Steel Weldment

    NASA Astrophysics Data System (ADS)

    Huang, Her-Yueh; Yang, Chung-Wei

    2013-06-01

    Activating flux-assisted gas tungsten arc welding (GTAW) is a well-established method for enhancing weld penetration. In GTAW, steel is usually welded with a shielding gas that contains mostly argon. However, pure argon does not provide enough weld penetration. Argon-helium mixtures are inert and a greater concentration of helium would increase the arc voltage and the weld depth-to-width (D/W) ratio. There is a significant level of interest in the interaction between activating flux and shielding gas composition. Weld morphology, arc profile, retained δ ferrite content, angular distortion, and microstructure are extremely important in applying the activating flux combination argon-helium in GTAW; therefore, in this work, all these were studied.

  6. 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.

  7. Magnetic flux density environment of several electron-bombardment ion thrusters

    NASA Technical Reports Server (NTRS)

    Danilowicz, R. L.

    1973-01-01

    Measurements of the external magnetic field of several electron-bombardment mercury ion thrusters were made using a single axis fluxgate magnetometer. The axial dipole moment accounted for most of the external field. In addition, residual fields from an electromagnet thruster were approximately 20 percent of the initial field. Simple degaussing of the axial magnets reduced the residual fields to 1 to 2 percent of the initial field.

  8. RADIAL DEPENDENCE OF PEAK PROTON AND IRON ION FLUXES IN SOLAR ENERGETIC PARTICLE EVENTS: APPLICATION OF THE PATH CODE

    SciTech Connect

    Verkhoglyadova, O. P.; Li, G.; Ao, X.; Zank, G. P.

    2012-09-20

    The radial dependence of particle peak fluxes in large solar energetic particle (SEP) events is important in determining the potential impact of space weather hazards on space missions. Using the Particle Acceleration and Transport in the Heliosphere code, we model the acceleration and transport of protons and iron ions at evolving coronal mass ejection shocks propagating throughout the inner heliosphere from about 0.1 to 2.5 AU. An example shock with a compression ratio of 3.9 and a speed of 1000 km s{sup -1} close to the Sun is modeled using a two-dimensional MHD ZEUS code. The compression ratio and shock speed weakened to 2.3 and 630 km s{sup -1}, correspondingly, at 2 AU. Shocks with 15 Degree-Sign , 45 Degree-Sign , and 75 Degree-Sign angles between the upstream magnetic field and the shock normal were studied. The shock angle was kept constant throughout the simulation. Both gradual and impulsive events are studied. Diffusive shock acceleration is assumed at the shock and we use a total diffusion coefficient that includes a parallel diffusion coefficient which takes into account the upstream wave amplification, and a perpendicular diffusion coefficient which is based on the NonLinear Guiding Center theory. The transport of particles escaping from the shock is modeled using a Monte Carlo approach. Time-intensity profiles for protons and iron ions are obtained. We analyzed the radial dependence of peak fluxes (J) for both protons and iron ions from 0.5 to 2 AU. We find that the functional dependence is softer than R {sup -3} and is about R {sup -2.9} to R {sup -1.8} in the energy range of 0.3-5 MeV nuc{sup -1}. Quasi-perpendicular shock showed a steeper radial dependence than a quasi-parallel shock. Mixed events show a softer radial dependence at energies above 500 keV nuc{sup -1} for iron ions and above 1 MeV for protons. The values of J(R) depend on seed particle composition, particle energy, shock obliquity, and the interplanetary turbulence level

  9. The distribution of reconnection geometry in flux transfer events using energetic ion, plasma and magnetic data. [on dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Daly, P. W.; Rijnbeek, R. P.; Sckopke, N.; Russell, C. T.; Saunders, M. A.

    1984-01-01

    The distribution of energetic ion anisotropies in flux transfer events (FTEs) about the dayside magnetopause has been determined for ISEE 2 crossings of the boundary in 1977 and 1978. When the events are sorted according to the sign of the east-west component of the magnetic field in the magnetosphere, a clear correlation is observed on the northern morningside. When the field is eastward, particles flow antiparallel to the field, implying field line connection to the Northern Hemisphere; when the field is westward, the opposite is true. On the afternoonside, the particle anisotropies are correlated with latitude. Explanations for this pattern are discussed which involve FTE formation at low latitudes with subsequent motion at a velocity given by the vector superposition of the Alfven velocity from the release of magnetic tension and the magnetosheath bulk flow velocity. Evidence that the geomagnetic and not the geocentric solar magnetospheric equator is the source of FTEs is considered.

  10. Effect of magnesium ion on human osteoblast activity

    PubMed Central

    He, L.Y.; Zhang, X.M.; Liu, B.; Tian, Y.; Ma, W.H.

    2016-01-01

    Magnesium, a promising biodegradable metal, has been reported in several studies to increase bone formation. Although there is some information regarding the concentrations of magnesium ions that affect bone remodeling at a cellular level, little is known about the effect of magnesium ions on cell gap junctions. Therefore, this study aimed to systematically investigate the effects of different concentrations of magnesium on bone cells, and further evaluate its effect on gap junctions of osteoblasts. Cultures of normal human osteoblasts were treated with magnesium ions at concentrations of 1, 2 and 3 mM, for 24, 48 and 72 h. The effects of magnesium ions on viability and function of normal human osteoblasts and on gap junction intercellular communication (GJIC) in osteoblasts were investigated. Magnesium ions induced significant (P<0.05) increases in cell viability, alkaline phosphate activity and osteocalcin levels of human osteoblasts. These stimulatory actions were positively associated with the concentration of magnesium and the time of exposure. Furthermore, the GJIC of osteoblasts was significantly promoted by magnesium ions. In conclusion, this study demonstrated that magnesium ions induced the activity of osteoblasts by enhancing GJIC between cells, and influenced bone formation. These findings may contribute to a better understanding of the influence of magnesium on bone remodeling and to the advance of its application in clinical practice. PMID:27383121

  11. Lipid-induced NOX2 activation inhibits autophagic flux by impairing lysosomal enzyme activity[S

    PubMed Central

    Jaishy, Bharat; Zhang, Quanjiang; Chung, Heaseung S.; Riehle, Christian; Soto, Jamie; Jenkins, Stephen; Abel, Patrick; Cowart, L. Ashley; Van Eyk, Jennifer E.; Abel, E. Dale

    2015-01-01

    Autophagy is a catabolic process involved in maintaining energy and organelle homeostasis. The relationship between obesity and the regulation of autophagy is cell type specific. Despite adverse consequences of obesity on cardiac structure and function, the contribution of altered cardiac autophagy in response to fatty acid overload is incompletely understood. Here, we report the suppression of autophagosome clearance and the activation of NADPH oxidase (Nox)2 in both high fat-fed murine hearts and palmitate-treated H9C2 cardiomyocytes (CMs). Defective autophagosome clearance is secondary to superoxide-dependent impairment of lysosomal acidification and enzyme activity in palmitate-treated CMs. Inhibition of Nox2 prevented superoxide overproduction, restored lysosome acidification and enzyme activity, and reduced autophagosome accumulation in palmitate-treated CMs. Palmitate-induced Nox2 activation was dependent on the activation of classical protein kinase Cs (PKCs), specifically PKCβII. These findings reveal a novel mechanism linking lipotoxicity with a PKCβ-Nox2-mediated impairment in pH-dependent lysosomal enzyme activity that diminishes autophagic turnover in CMs. PMID:25529920

  12. Banana Regime Neoclassical Ion Heat Flux with Retention of the Field Term in the Linearized Collision Operator

    NASA Astrophysics Data System (ADS)

    Parker, J. B.; Catto, P. J.

    2011-10-01

    The standard calculation of neoclassical ion heat flux in the large aspect ratio, circular flux surface, banana regime limit uses a model collision operator where only pitch angle scattering is retained and an ad hoc term is introduced to preserve conservation of momentum. The full linearized collision operator contains also an energy diffusion term and a complicated field term which involves an integral over the perturbed distribution, both of which are dropped in the standard calculation. We reexamine the standard treatment by considering the field as well as the test particle portions of the linearized collision operator and by using an expansion in the eigenfunctions associated with the transit-averaged pitch angle scattering collision operator. We focus on modifications due to the field term to attempt to determine if corrections are needed to the standard result in the large aspect ratio limit. Work supported by a U.S. DOE FES Fellowship and by U.S. DOE Contract No. DE-FG02-91ER-54109.

  13. Limited impact of escaping photoelectrons on the terrestrial polar wind flux in the polar cap

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Seki, K.; Nishimura, Y.; McFadden, J. P.

    2015-05-01

    A statistical analysis using a long-term (over one solar cycle) photoelectron data set obtained by the Fast Auroral SnapshoT satellite demonstrates that photoelectron outflows has little impact on the polar wind ion flux. This result implies that it is the source region of H+ ions in the topside ionosphere and not the photoelectron flux that controls the terrestrial polar wind flux. The polar wind ion flux, estimated from electron outflow does not change with increasing net photoelectron production due to increasing solar activity. The magnitude of a self-created field-aligned potential drop is likely determined so as to equilibrate electron fluxes with ion fluxes regulated by a net production rate of H+ ions. The result suggests that the polar wind H+ ion flux from magnetized terrestrial planets, including Earth-like exoplanets, can be estimated once the composition and temperature of its atmosphere, which determine the net ion production rate, are known.

  14. A novel heat flux study of a geothermally active lake - Lake Rotomahana, New Zealand

    NASA Astrophysics Data System (ADS)

    Tivey, Maurice A.; de Ronde, Cornel E. J.; Tontini, Fabio Caratori; Walker, Sharon L.; Fornari, Daniel J.

    2016-03-01

    A new technique for measuring conductive heat flux in a lake was adapted from the marine environment to allow for multiple measurements to be made in areas where bottom sediment cover is sparse, or even absent. This thermal blanket technique, pioneered in the deep ocean for use in volcanic mid-ocean rift environments, was recently used in the geothermally active Lake Rotomahana, New Zealand. Heat flow from the lake floor propagates into the 0.5 m diameter blanket and establishes a thermal gradient across the known blanket thickness and thereby provides an estimate of the conductive heat flux of the underlying terrain. This approach allows conductive heat flux to be measured over a spatially dense set of stations in a relatively short period of time. We used 10 blankets and deployed them for 1 day each to complete 110 stations over an 11-day program in the 6 × 3 km lake. Results show that Lake Rotomahana has a total conductive heat flux of about 47 MW averaging 6 W/m2 over the geothermally active lake. The western half of the lake has two main areas of high heat flux; 1) a high heat flux area averaging 21.3 W/m2 along the western shoreline, which is likely the location of the pre-existing geothermal system that fed the famous Pink Terraces, mostly destroyed during the 1886 eruption 2) a region southwest of Patiti Island with a heat flux averaging 13.1 W/m2 that appears to be related to the explosive rift that formed the lake in the 1886 Tarawera eruption. A small rise in bottom water temperature over the survey period of 0.01 °C/day suggests the total thermal output of the lake is ~ 112-132 MW and when compared to the conductive heat output suggests that 18-42% of the total thermal energy is by conductive heat transfer.

  15. Fluxes of ions in precipitation, throughfall and stemflow in an urban forest in Kuala Lumpur, Malaysia.

    PubMed

    Radzi Abas, M; Ahmad-Shah, A; Nor Awang, M

    1992-01-01

    A study was carried out to determine the chemical composition of bulk precipitation, throughfall and stemflow in an urban forest in Kuala Lumpur, Malaysia. The mean weekly rainfall recorded during the period of study was 63.2 mm. Throughfall, stemflow and canopy interception of incident precipitation were 77.1%, 1.2% and 21.7% respectively. Bulk precipitation, througfall and stemflow were acidic, the pH recorded being 4.37, 4.71 and 4.15 respectively. In all cases the dominant ions were NO3, SO4, Cl, NH4, K, Ca and Na. Of the ions studied Ca, K, Cl, SO4, Mg and Mn showed net increases in passing through the forest canopy, while NH4, Na, NO3, Zn, H and Fe showed net retention. This study shows that the urban environment of Kuala Lumpur contributes considerable amounts of materials to the atmosphere, as reflected by the high ionic contents in bulk precipitation, throughfall and stemflow.

  16. Ion Flux in Roots of Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook) under Aluminum Stress

    PubMed Central

    Ma, Zhihui; Huang, Binlong; Xu, Shanshan; Chen, Yu; Cao, Guangqiu; Ding, Guochang; Lin, Sizu

    2016-01-01

    Chinese fir is a tall, fast-growing species that is unique to southern China. In Chinese fir plantations, successive plantings have led to a decline in soil fertility, and aluminum toxicity is thought to be one of the main reasons for this decline. In this study, Non-invasive Micro-test Technology was used to study the effect of aluminum stress on the absorption of 4 different ions in the roots of the Chinese fir clone FS01. The results are as follows: with increased aluminum concentration and longer periods of aluminum stress, the H+ ion flow gradually changed from influx into efflux; there was a large variation in the K+ efflux, which gradually decreased with increasing duration of aluminum stress; and 1 h of aluminum stress uniformly resulted in Ca2+ influx, but it changed from influx to efflux after a longer period of aluminum stress. Changes in the different concentrations of aluminum had the largest influence on Mg2+. PMID:27270726

  17. Ion Flux in Roots of Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook) under Aluminum Stress.

    PubMed

    Ma, Zhihui; Huang, Binlong; Xu, Shanshan; Chen, Yu; Cao, Guangqiu; Ding, Guochang; Lin, Sizu

    2016-01-01

    Chinese fir is a tall, fast-growing species that is unique to southern China. In Chinese fir plantations, successive plantings have led to a decline in soil fertility, and aluminum toxicity is thought to be one of the main reasons for this decline. In this study, Non-invasive Micro-test Technology was used to study the effect of aluminum stress on the absorption of 4 different ions in the roots of the Chinese fir clone FS01. The results are as follows: with increased aluminum concentration and longer periods of aluminum stress, the H+ ion flow gradually changed from influx into efflux; there was a large variation in the K+ efflux, which gradually decreased with increasing duration of aluminum stress; and 1 h of aluminum stress uniformly resulted in Ca2+ influx, but it changed from influx to efflux after a longer period of aluminum stress. Changes in the different concentrations of aluminum had the largest influence on Mg2+. PMID:27270726

  18. An active role of extratropical sea surface temperature anomalies in determining anomalous turbulent heat flux

    NASA Astrophysics Data System (ADS)

    Tanimoto, Youichi; Nakamura, Hisashi; Kagimoto, Takashi; Yamane, Shozo

    2003-10-01

    Temporal and spatial structures of turbulent latent and sensible heat flux anomalies are examined in relation to dominant patterns of sea surface temperature anomalies (SSTA) observed over the North Pacific. Relative importance among observed anomalies in SST, surface air temperature, and wind speed in determining the anomalous turbulent heat fluxes is assessed through linearizing the observed flux anomalies. Over the central basin of the North Pacific, changes in the atmospheric variables, including air temperature and wind speed, are primarily responsible for the generation of local SST variations by changing turbulent heat flux, which supports a conventional view of extratropical air-sea interaction. In the region where ocean dynamics is very important in forming SSTAs, in contrast, SSTAs that have been formed in early winter play the primary role in determining mid- and late-winter turbulent heat flux anomalies, indicative of the SST forcing upon the overlying atmosphere. Specifically, both decadal scale SSTAs in the western Pacific subarctic frontal zone and El Niño related SSTAs south of Japan are found to be engaged actively in such forcing on the atmosphere. The atmospheric response to this forcing appears to include the anomalous storm track activity. The observed atmospheric anomalies, which may be, in part, forced by the preexisting SSTAs in those two regions, act to force SSTAs in other portions of the basin, leading to the time evolution of SSTAs as observed in the course of the winter season.

  19. 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.

  20. 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.

  1. Description of light ion production cross sections and fluxes on the Mars surface using the QMSFRG model.

    PubMed

    Cucinotta, Francis A; Kim, Myung-Hee; Schneider, Susana I; Hassler, Donald M

    2007-06-01

    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 near 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 the RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface. PMID:17342547

  2. The relevance of particle flux monitors in accelerator-based activation analysis

    SciTech Connect

    Segebade, Chr.; Maimaitimin, M.; Sun Zaijing

    2013-04-19

    One of the most critical parameters in activation analysis is the flux density of the activating radiation, its spatial distribution in particular. The validity of the basic equation for calculating the activity induced to the exposed item depends upon the fulfilment of several conditions, the most relevant of them being equal doses of incident activating radiation received by the unknown sample, the calibration material and the reference material, respectively. This requirement is most problematic if accelerator-produced radiation is used for activation. Whilst nuclear research reactors usually are equipped with exposure positions that provide fairly homogenous activation fields for thermal neutron activation analysis accelerator-generated particle beams (neutrons, photons, charged particles) usually exhibit axial and, in particular, sharp radial flux gradients. Different experimental procedures have been developed to fulfil the condition mentioned above. In this paper, three variants of the application of flux monitors in photon activation analysis are discussed (external monitor, additive and inherent internal monitor). Experiments have indicated that the latter technique yields highest quality of the analytical results.

  3. 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.

  4. 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

  5. Detection of single ion channel activity with carbon nanotubes

    PubMed Central

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

    2015-01-01

    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. PMID:25778101

  6. Detection of single ion channel activity with carbon nanotubes.

    PubMed

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

    2015-01-01

    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.

  7. 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.

  8. Gamma-ray-spectroscopy following high-flux 14-MeV neutron activation

    SciTech Connect

    Williams, R.E.

    1981-10-12

    The Rotating Target Neutron Source (RTNS-I), a high-intensity source of 14-MeV neutrons at the Lawrence Livermore National Laboratory (LLNL), has been used for applications in activation analysis, inertial-confinement-fusion diagnostic development, and fission decay-heat studies. The fast-neutron flux from the RTNS-I is at least 50 times the maximum fluxes available from typical neutron generators, making these applications possible. Facilities and procedures necessary for gamma-ray spectroscopy of samples irradiated at the RTNS-I were developed.

  9. Applications of scanned pipettes to the localized characterization of actuating conducting polymers: an SICM design for simultaneous ion flux and topography measurements

    NASA Astrophysics Data System (ADS)

    Kannappan, Karthik; Laslau, Cosmin; Williams, David E.; Travas-Sejdic, Jadranka

    2012-04-01

    Recent applications of the scanned pipette to materials science problems have included its quantification of the ion flux resulting from conducting polymer actuation. However, in order to correlate this flux with the precise height changes arising from actuation, a separate experiment must be carried out. Herein we propose a new design that may be capable of simultaneously determining both ion flux and topography, on the basis of subtle current density magnitude shifts and precisely chosen experimental positioning parameters. A simulation of the geometrical model - consisting of the pipette, conducting polymer film and electrodes - was setup and solved in 2D axi-symmetrical domain. The ion concentrations, voltage potentials and current densities were determined as a function of time, with three key parameters varied: the maximum ion flux value Jmax, conducting polymer swelling Tp and overall separation distance d between pipette and polymer. It was found that the separation Tp - d should be around 50 to 150 nm, roughly the same as the actuation itself. Furthermore, the current density component arising from geometrical changes due to actuation was on the order of a few percent, and was highly sensitive to Jmax levels.

  10. Basic properties of magnetic flux tubes and restrictions on theories of solar activity

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1976-01-01

    It is shown that the mean longitudinal field in a magnetic flux tube is reduced, rather than enhanced, by twisting the tube to form a rope. It is shown that there is no magnetohydrostatic equilibrium when one twisted rope is wound around another. Instead there is rapid line cutting (neutral point annihilation). It is shown that the twisting increases, and the field strength decreases, along a flux tube extending upward through a stratified atmosphere. These facts are at variance with Piddington's (1975) recent suggestion that solar activity is to be understood as the result of flux tubes which are enormously concentrated by twisting, which consist of several twisted ropes wound around each other, and which came untwisted where they emerge through the photosphere.

  11. Niacin alleviates TRAIL-mediated colon cancer cell death via autophagy flux activation

    PubMed Central

    Kim, Sung-Wook; Lee, Ju-Hee; Moon, Ji-Hong; Nazim, Uddin M.D.; Lee, You-Jin; Seol, Jae-Won; Hur, Jin; Eo, Seong-Kug; Lee, John-Hwa; Park, Sang-Youel

    2016-01-01

    Niacin, also known as vitamin B3 or nicotinamide is a water-soluble vitamin that is present in black beans and rice among other foods. Niacin is well known as an inhibitor of metastasis in human breast carcinoma cells but the effect of niacin treatment on TRAIL-mediated apoptosis is unknown. Here, we show that niacin plays an important role in the regulation of autophagic flux and protects tumor cells against TRAIL-mediated apoptosis. Our results indicated that niacin activated autophagic flux in human colon cancer cells and the autophagic flux activation protected tumor cells from TRAIL-induced dysfunction of mitochondrial membrane potential and tumor cell death. We also demonstrated that ATG5 siRNA and autophagy inhibitor blocked the niacin-mediated inhibition of TRAIL-induced apoptosis. Taken together, our study is the first report demonstrating that niacin inhibits TRAIL-induced apoptosis through activation of autophagic flux in human colon cancer cells. And our results also suggest that autophagy inhibitors including genetic and pharmacological tools may be a successful therapeutics during anticancer therapy using TRAIL. PMID:26517672

  12. 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. PMID:25084579

  13. High Resolution Simulations of Tearing and Flux-Rope Formation in Active Region Jets

    NASA Astrophysics Data System (ADS)

    Wyper, P. F.; DeVore, C. R.; Karpen, J. T.

    2015-12-01

    Observations of coronal jets increasingly suggest that local fragmentation and the generation of small-scale structure plays an important role in the dynamics of these events. In the magnetically closed corona, jets most often occur near active regions and are associated with an embedded-bipole topology consisting of a 3D magnetic null point atop a domed fan separatrix surface at the base of a coronal loop. Impulsive reconnection in the vicinity of the null point between the magnetic fluxes inside and outside the dome launches the jet along the loop. Wyper & Pontin 2014 showed that the 3D current layers that facilitate such reconnection are explosively unstable to tearing, generating complex flux-rope structures. Utilizing the adaptive mesh capabilities of the Adaptively Refined Magnetohydrodynamics Solver, we investigate the generation of such fine-scale structure in high-resolution simulations of active-region jets. We observe the formation of multiple flux-rope structures forming across the fan separatrix surface and discuss the photospheric signatures of these flux ropes and the associated local topology change. We also introduce a new way of identifying such flux ropes in the magnetic field, based on structures observed in the magnetic squashing factor calculated on the photosphere. By tracking the position and number of new null points produced by the fragmentation, we also show that the formation of flux ropes can occur away from the main null region on the flanks of the separatrix dome and that the jet curtain has a highly complex magnetic structure. This work was funded through an appointment to the NASA Postdoctoral Program and by NASA's Living With a Star TR&T program.

  14. Investigation on the electron flux to the wall in the VENUS ion source

    NASA Astrophysics Data System (ADS)

    Thuillier, T.; Angot, J.; Benitez, J. Y.; Hodgkinson, A.; Lyneis, C. M.; Todd, D. S.; Xie, D. Z.

    2016-02-01

    The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. A burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines are presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.

  15. Investigation on the electron flux to the wall in the VENUS ion source.

    PubMed

    Thuillier, T; Angot, J; Benitez, J Y; Hodgkinson, A; Lyneis, C M; Todd, D S; Xie, D Z

    2016-02-01

    The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. A burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines are presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall. PMID:26931954

  16. Investigation on the electron flux to the wall in the VENUS ion source.

    PubMed

    Thuillier, T; Angot, J; Benitez, J Y; Hodgkinson, A; Lyneis, C M; Todd, D S; Xie, D Z

    2016-02-01

    The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. A burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines are presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.

  17. Tailored-waveform collisional activation of peptide ion electron transfer survivor ions in cation transmission mode ion/ion reaction experiments.

    PubMed

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

    2009-04-01

    Broadband 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 V(p-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.

  18. Charge-exchange coupling between pickup ions across the heliopause and its effect on energetic neutral hydrogen flux

    SciTech Connect

    Zirnstein, E. J.; Heerikhuisen, J.; Zank, G. P.; Pogorelov, N. V.; McComas, D. J.; Desai, M. I.

    2014-03-10

    Pickup ions (PUIs) appear to play an integral role in the multi-component nature of the plasma in the interaction between the solar wind (SW) and local interstellar medium (LISM). Three-dimensional (3D) MHD simulations with a kinetic treatment for neutrals and PUIs are currently still not viable. In light of recent energetic neutral atom (ENA) observations by the Interstellar Boundary EXplorer, the purpose of this paper is to illustrate the complex coupling between PUIs across the heliopause (HP) as facilitated by ENAs using estimates of PUI properties extracted from a 3D MHD simulation of the SW-LISM interaction with kinetic neutrals. First, we improve upon the multi-component treatment of the inner heliosheath (IHS) plasma from Zank et al. by including the extinction of PUIs through charge-exchange. We find a significant amount of energy is transferred away from hot, termination shock-processed PUIs into a colder, 'freshly injected' PUI population. Second, we extend the multi-component approach to estimate ENA flux from the outer heliosheath (OHS), formed from charge-exchange between interstellar hydrogen atoms and energetic PUIs. These PUIs are formed from ENAs in the IHS that crossed the HP and experienced charge-exchange. Our estimates, based on plasma-neutral simulations of the SW-LISM interaction and a post-processing analysis of ENAs and PUIs, suggest the majority of flux visible at 1 AU from the front of the heliosphere, between ∼0.02 and 10 keV, originates from OHS PUIs, indicating strong coupling between the IHS and OHS plasmas through charge-exchange.

  19. Charge-exchange Coupling between Pickup Ions across the Heliopause and its Effect on Energetic Neutral Hydrogen Flux

    NASA Astrophysics Data System (ADS)

    Zirnstein, E. J.; Heerikhuisen, J.; Zank, G. P.; Pogorelov, N. V.; McComas, D. J.; Desai, M. I.

    2014-03-01

    Pickup ions (PUIs) appear to play an integral role in the multi-component nature of the plasma in the interaction between the solar wind (SW) and local interstellar medium (LISM). Three-dimensional (3D) MHD simulations with a kinetic treatment for neutrals and PUIs are currently still not viable. In light of recent energetic neutral atom (ENA) observations by the Interstellar Boundary EXplorer, the purpose of this paper is to illustrate the complex coupling between PUIs across the heliopause (HP) as facilitated by ENAs using estimates of PUI properties extracted from a 3D MHD simulation of the SW-LISM interaction with kinetic neutrals. First, we improve upon the multi-component treatment of the inner heliosheath (IHS) plasma from Zank et al. by including the extinction of PUIs through charge-exchange. We find a significant amount of energy is transferred away from hot, termination shock-processed PUIs into a colder, "freshly injected" PUI population. Second, we extend the multi-component approach to estimate ENA flux from the outer heliosheath (OHS), formed from charge-exchange between interstellar hydrogen atoms and energetic PUIs. These PUIs are formed from ENAs in the IHS that crossed the HP and experienced charge-exchange. Our estimates, based on plasma-neutral simulations of the SW-LISM interaction and a post-processing analysis of ENAs and PUIs, suggest the majority of flux visible at 1 AU from the front of the heliosphere, between ~0.02 and 10 keV, originates from OHS PUIs, indicating strong coupling between the IHS and OHS plasmas through charge-exchange.

  20. Selective activation of mechanosensitive ion channels using magnetic particles.

    PubMed

    Hughes, Steven; McBain, Stuart; Dobson, Jon; El Haj, Alicia J

    2008-08-01

    This study reports the preliminary development of a novel magnetic particle-based technique that permits the application of highly localized mechanical forces directly to specific regions of an ion-channel structure. We demonstrate that this approach can be used to directly and selectively activate a mechanosensitive ion channel of interest, namely TREK-1. It is shown that manipulation of particles targeted against the extended extracellular loop region of TREK-1 leads to changes in whole-cell currents consistent with changes in TREK-1 activity. Responses were absent when particles were coated with RGD (Arg-Gly-Asp) peptide or when magnetic fields were applied in the absence of magnetic particles. It is concluded that changes in whole-cell current are the result of direct force application to the extracellular loop region of TREK-1 and thus these results implicate this region of the channel structure in mechano-gating. It is hypothesized that the extended loop region of TREK-1 may act as a tension spring that acts to regulate sensitivity to mechanical forces, in a nature similar to that described for MscL. The development of a technique that permits the direct manipulation of mechanosensitive ion channels in real time without the need for pharmacological drugs has huge potential benefits not only for basic biological research of ion-channel gating mechanisms, but also potentially as a tool for the treatment of human diseases caused by ion-channel dysfunction.

  1. Major ion chemistry of the Ganga-Brahmaputra river system: Weathering processes and fluxes to the Bay of Bengal

    SciTech Connect

    Sarin, M.M.; Krishnaswami, S.; Dilli, K.; Somayajulu, B.L.K. ); Moore, W.S. )

    1989-05-01

    The Ganga-Brahmaputra, one of the worlds's largest river systems, is first in terms of sediment transport and fourth in terms of water discharge. A detailed and systematic study of the major ion chemistry of these rivers and their tributaries, as well as the clay mineral composition of the bed sediments has been conducted. The chemistry of the highland rivers are all dominated by carbonate weathering; (Ca + Mg) and HCO{sub 3} account for about 80% of the cations and anions. In the lowland rivers, HCO{sub 3} excess over (Ca + Mg) and a relatively high contribution of (Na + K) to the total cations indicate that silicate weathering and/or contributions from alkaline/saline soils and ground waters could be important sources of major ions to these waters. The chemistry of the Ganga and the Yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions. The highland rivers weather acidic rocks, whereas the others flow initially through basic effusives. The Ganga-Brahmaputra river system transports about 130 million tons of dissolved salts to the Bay of Bengal, which is nearly 3% of the global river flux to the oceans. The chemical denudation rates for the Ganga and the Brahmaputra basins are about 72 and 105 tons{center dot}km{sup {minus}2}{center dot}yr{sup {minus}1}, respectively, which are factors of 2 to 3 higher than the global average. The high denudation rate, particularly in the Brahmaputra, is attributable to high relief and heavy rainfall.

  2. Numerical simulations of active region scale flux emergence: From spot formation to decay

    SciTech Connect

    Rempel, M.; Cheung, M. C. M.

    2014-04-20

    We present numerical simulations of active region scale flux emergence covering a time span of up to 6 days. Flux emergence is driven by a bottom boundary condition that advects a semi-torus of magnetic field with 1.7 × 10{sup 22} Mx flux into the computational domain. The simulations show that, even in the absence of twist, the magnetic flux is able the rise through the upper 15.5 Mm of the convection zone and emerge into the photosphere to form spots. We find that spot formation is sensitive to the persistence of upflows at the bottom boundary footpoints, i.e., a continuing upflow would prevent spot formation. In addition, the presence of a torus-aligned flow (such flow into the retrograde direction is expected from angular momentum conservation during the rise of flux ropes through the convection zone) leads to a significant asymmetry between the pair of spots, with the spot corresponding to the leading spot on the Sun being more axisymmetric and coherent, but also forming with a delay relative to the following spot. The spot formation phase transitions directly into a decay phase. Subsurface flows fragment the magnetic field and lead to intrusions of almost field free plasma underneath the photosphere. When such intrusions reach photospheric layers, the spot fragments. The timescale for spot decay is comparable to the longest convective timescales present in the simulation domain. We find that the dispersal of flux from a simulated spot in the first two days of the decay phase is consistent with self-similar decay by turbulent diffusion.

  3. Numerical Simulations of Active Region Scale Flux Emergence: From Spot Formation to Decay

    NASA Astrophysics Data System (ADS)

    Rempel, M.; Cheung, M. C. M.

    2014-04-01

    We present numerical simulations of active region scale flux emergence covering a time span of up to 6 days. Flux emergence is driven by a bottom boundary condition that advects a semi-torus of magnetic field with 1.7 × 1022 Mx flux into the computational domain. The simulations show that, even in the absence of twist, the magnetic flux is able the rise through the upper 15.5 Mm of the convection zone and emerge into the photosphere to form spots. We find that spot formation is sensitive to the persistence of upflows at the bottom boundary footpoints, i.e., a continuing upflow would prevent spot formation. In addition, the presence of a torus-aligned flow (such flow into the retrograde direction is expected from angular momentum conservation during the rise of flux ropes through the convection zone) leads to a significant asymmetry between the pair of spots, with the spot corresponding to the leading spot on the Sun being more axisymmetric and coherent, but also forming with a delay relative to the following spot. The spot formation phase transitions directly into a decay phase. Subsurface flows fragment the magnetic field and lead to intrusions of almost field free plasma underneath the photosphere. When such intrusions reach photospheric layers, the spot fragments. The timescale for spot decay is comparable to the longest convective timescales present in the simulation domain. We find that the dispersal of flux from a simulated spot in the first two days of the decay phase is consistent with self-similar decay by turbulent diffusion.

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

    SciTech Connect

    Ravindra, B.; Yoshimura, Keiji; Dasso, Sergio E-mail: yosimura@solar.physics.montana.edu

    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 the 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

  5. THE RISE OF ACTIVE REGION FLUX TUBES IN THE TURBULENT SOLAR CONVECTIVE ENVELOPE

    SciTech Connect

    Weber, Maria A.; Fan Yuhong; Miesch, Mark S.

    2011-11-01

    We use a thin flux tube model in a rotating spherical shell of turbulent convective flows to study how active region scale flux tubes rise buoyantly from the bottom of the convection zone to near the solar surface. We investigate toroidal flux tubes at the base of the convection zone with field strengths ranging from 15 kG to 100 kG at initial latitudes ranging from 1{sup 0} to 40{sup 0} with a total flux of 10{sup 22} Mx. We find that the dynamic evolution of the flux tube changes from convection dominated to magnetic buoyancy dominated as the initial field strength increases from 15 kG to 100 kG. At 100 kG, the development of {Omega}-shaped rising loops is mainly controlled by the growth of the magnetic buoyancy instability. However, at low field strengths of 15 kG, the development of rising {Omega}-shaped loops is largely controlled by convective flows, and properties of the emerging loops are significantly changed compared to previous results in the absence of convection. With convection, rise times are drastically reduced (from years to a few months), loops are able to emerge at low latitudes, and tilt angles of emerging loops are consistent with Joy's law for initial field strengths of {approx}>40 kG. We also examine other asymmetries that develop between the leading and following legs of the emerging loops. Taking all the results together, we find that mid-range field strengths of {approx}40-50 kG produce emerging loops that best match the observed properties of solar active regions.

  6. 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.

  7. Effect of ferrous ions on the monophenolase activity of tyrosinase.

    PubMed

    Ros, J R; Rodríguez-López, J N; García-Cánovas, F

    1993-06-01

    The effect of ferrous ions on the monophenolase activity of tyrosinase has been studied. Although a shortening of the lag period which characterizes this hydroxylation reaction was observed, no direct effect on the enzyme was found. The reaction between ferrous ions and molecular oxygen in the presence of chelating agents, such as phosphate or EDTA, produces hydroxyl radicals. These radicals can hydroxylate tyrosine to generate L-3,4-dihydroxyphenylalanine (dopa). Catalase and scavengers of hydroxyl radicals inhibited both the shortening of the lag period and dopa formation. On the basis of these results, it is proposed that the influence of ferrous ions on tyrosinase is due to the formation of dopa in the chemical hydroxylation of tyrosine. Dopa transforms the Emet form of the enzyme (Cu2+Cu2+) into the Edeoxy form (Cu1+Cu1+) and, thus, shortens the lag period. PMID:8507669

  8. 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.

  9. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Brun, A. S.; Rouillard, A. P.

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  10. 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.

  11. HDAC6 activity is not required for basal autophagic flux in metastatic prostate cancer cells.

    PubMed

    Watson, Gregory W; Wickramasekara, Samanthi; Fang, Yufeng; Maier, Claudia S; Williams, David E; Dashwood, Roderick H; Perez, Viviana I; Ho, Emily

    2016-06-01

    Histone deacetylase 6 is a multifunctional lysine deacetylase that is recently emerging as a central facilitator of response to stress and may play an important role in cancer cell proliferation. The histone deacetylase 6-inhibitor tubacin has been shown to slow the growth of metastatic prostate cancer cells and sensitize cancer cells to chemotherapeutic agents. However, the proteins histone deacetylase 6 interacts with, and thus its role in cancer cells, remains poorly characterized. Histone deacetylase 6 deacetylase activity has recently been shown to be required for efficient basal autophagic flux. Autophagy is often dysregulated in cancer cells and may confer stress resistance and allow for cell maintenance and a high proliferation rate. Tubacin may therefore slow cancer cell proliferation by decreasing autophagic flux. We characterized the histone deacetylase 6-interacting proteins in LNCaP metastatic prostate cancer cells and found that histone deacetylase 6 interacts with proteins involved in several cellular processes, including autophagy. Based on our interaction screen, we assessed the impact of the histone deacetylase 6-inhibitor tubacin on autophagic flux in two metastatic prostate cancer cell lines and found that tubacin does not influence autophagic flux. Histone deacetylase 6 therefore influences cell proliferation through an autophagy-independent mechanism. PMID:26643866

  12. Finger heat flux/temperature as an indicator of thermal imbalance with application for extravehicular activity

    NASA Astrophysics Data System (ADS)

    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.

  13. Effects of high-flux low-energy ion bombardment on the low-temperature growth morphology of TiN(001) epitaxial layers

    SciTech Connect

    Karr, Brian W.; Cahill, David G.; Petrov, I.; Greene, J. E.

    2000-06-15

    Ultrahigh vacuum scanning tunneling microscopy (STM) is used to characterize the surface morphology of TiN(001) epitaxial layers grown by dc reactive magnetron sputtering at growth temperatures of T{sub s}=650 and T{sub s}=750 degree sign C. An auxiliary anode is used to bias the N{sub 2} plasma and produce a large flux of low-energy N{sub 2}{sup +} ions that bombard the film surface during growth: the ratio of the N{sub 2}{sup +} flux to the Ti growth flux is {approx_equal}25. At ion energies E{sub i} near the threshold for the production of bulk defects (E{sub i}=43 eV and T{sub s}=650 degree sign C), ion bombardment decreases the amplitude of the roughness, decreases the average distance between growth mounds, and reduces the sharpness of grooves between growth mounds. The critical island radius for second layer nucleation R{sub c} is approximately 12 and 17 nm at growth temperatures of 650 and 750 degree sign C respectively; at 650 degree sign C, R{sub c} is reduced to (approx =)10 nm by ion bombardment. (c) 2000 The American Physical Society.

  14. 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

    2016-08-01

    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.

  15. 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.

  16. A hyperpolarization-activated ion current of amphibian oocytes.

    PubMed

    Ochoa-de la Paz, L D; Salazar-Soto, D B; Reyes, J P; Miledi, R; Martinez-Torres, A

    2013-08-01

    A comparative analysis of a hyperpolarization-activated ion current present in amphibian oocytes was performed using the two-electrode voltage-clamp technique in Xenopus laevis, Xenopus tropicalis, and Ambystoma mexicanum. This current appears to be driven mainly by Cl(-) ions, is independent of Ca(2+), and is made evident by applying extremely negative voltage pulses; it shows a slow activating phase and little or no desensitization. The pharmacological profile of the current is complex. The different channel blocker used for Cl(-), K(+), Na(+) and Ca(2+) conductances, exhibited various degrees of inhibition depending of the species. The profiles illustrate the intricacy of the components that give rise to this current. During X. laevis oogenesis, the hyperpolarization-activated current is present at all stages of oocytes tested (II-VI), and the amplitude of the current increases from about 50 nA in stage I to more than 1 μA in stage VI; nevertheless, there was no apparent modification of the kinetics. Our results suggest that the hyperpolarization-activated current is present both in order Anura and Urodela oocytes. However, the electrophysiological and pharmacological characteristics are quite perplexing and seem to suggest a mixture of ionic conductances that includes the activation of both anionic and cationic channels, most probably transiently opened due to the extreme hyperpolarizion of the plasma membrane. As a possible mechanism for the generation of the current, a kinetic model which fits the data suggests the opening of pores in the plasma membrane whose ion selectivity is dependent on the extracellular Cl(-) concentration. The extreme voltage conditions could induce the opening of otherwise latent pores in plasma membrane proteins (i.e., carriers), resembling the ´slippage´ events already described for some carriers. These observations should be valuable for other groups trying to express cloned, voltage-dependent ion channels in oocytes of

  17. 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

  18. The dependence of solar energetic particle fluxes in the Earth-Mars-Earth route on solar activity period.

    PubMed

    Kuznetsov, N V; Nymmik, R A

    2002-01-01

    This report presents the results of analyzing the relative importance of particle fluxes of different origin in the Earth-Mars-Earth route during different solar activity periods. The analysis has been made in terms of the galactic cosmic ray and solar energetic particle flux models developed at Moscow State University. The results demonstrate the extreme importance of the high-energy solar particle fluxes in interplanetary space even during the years of "quiet" Sun.

  19. 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

  20. 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

  1. Effect of PO2 and metabolic inhibitors on ionic fluxes across the isolated rabbit corneal endothelium.

    PubMed

    Green, K; Cheeks, L; Armstrong, E; Berdecia, R; Kramer, K; Hull, D S

    1990-01-01

    Bicarbonate and sodium fluxes were measured across the isolated rabbit corneal endothelium under the influence of several inhibitors. Depression of PO2 in the bathing medium decreased net sodium movement but increased bicarbonate movement. Furosemide did not alter bicarbonate fluxes at either 10(-4) or 10(-5) M, but increased passive sodium flux leading to a decrease in net flux. Thiocyanate, at 5 x 10(-3) or 5 x 10(-2) M, decreased active bicarbonate flux and hence net flux, but had no effect on sodium fluxes. Dinitrophenol increased only the passive bicarbonate flux while decreasing both active and passive sodium fluxes, albeit unequally, leading to a decreased net flux. Ethacrynic acid affected only passive bicarbonate flux, while decreasing net sodium flux. The stilbene derivatives, SITS and DIDS caused opposite effects on both sodium and bicarbonate fluxes. SITS decreased net bicarbonate flux by decreasing active and increasing passive flux, yet increased net sodium flux. DIDS, however, increased net bicarbonate flux but decreased net sodium flux. The results may be explained by current models for endothelial ion transport that include a Na+/H+ antiport and a HCO3-/Na+ symport system in parallel with an independent pathway for HCO3- exit from the endothelial cells. When compared with prior corneal swelling data using these same inhibitors, the maintenance of corneal thickness appears to be dependent on the variation of ion fluxes from normal values, and the dissociation of the two active ion fluxes. In addition, there appears to be a significant ability of ion transport systems to compensate for disturbances to other ion exchange or transport mechanisms. PMID:2275927

  2. Effect of divalent ions on the activity of cancer procoagulant.

    PubMed

    Mielicki, W P; Kozwich, D L; Kramer, L C; Gordon, S G

    1994-10-01

    The effect of calcium (Ca2+), magnesium (Mg2+), manganese (Mn2+), iron (Fe2+), and zinc (Zn2+) on the factor X-activating activity of cancer procoagulant (CP) was studied. Activity of CP was evaluated with a three-stage chromogenic assay (liquid-phase assay, "native" CP) and with an immunocapture enzyme (ICE) assay (solid-phase assay, immobilized CP). In the liquid-phase assay, CP activity was Ca(2+)-dependent, and Mg2+ (5 mM) or Mn2+ (0.01-0.1 mM) could substitute for Ca2+. There was no additive effect of Mg2+ and Ca2+ on the activity of CP. Activity of CP in the liquid-phase assay, in the presence of 7 mM Ca2+, was enhanced by 0.1 mM Mn2+ to about 240% of the activity observed when only Ca2+ was present in the reaction. Zn2+ and Fe2+ did not activate CP in the absence of Ca2+; they inhibited CP activity in a concentration-dependent mode when administered in the presence of Ca2+. The activity of CP evaluated by the solid-phase assay (ICE assay) was neither Ca(2+)-dependent nor was it susceptible to potentiation by Mn2+ administered after CP was bound to IgM. CP exposed to 5 mM Mn2+ before binding to IgM expressed about 85% higher activity than without the presence of Mn2+. When CP was first preincubated with divalent ion and then immunocaptured, the signal generated in the enzyme-linked immunoadsorbent assay by Mn(2+)-containing CP was significantly different (30% greater) than signals generated by CP without Mn2+ or containing different ion. These data suggest that: (1) there is a significant conformational change of the CP molecule that takes place after capturing CP by the monoclonal IgM antibody on the solid surface; (2) the divalent ions are not directly involved in enzyme-substrate interactions in the CP moiety; and (3) the interaction of Mn2+ with CP seems to be different from that of the other divalent ions.

  3. A two-dimensional ion kinetic model of the scrape-off layer of a diverted plasma with a private flux region

    SciTech Connect

    Catto, P.J. ); Connor, J.W. , Culham, Abingdon, Oxfordshire, OX143DB )

    1995-01-01

    Earlier two-dimensional (radial and poloidal angle), analytically tractable ion kinetic models of the scrape-off layer (SOL) in which a steady state is achieved by balancing the streaming loss of ions to the divertor target plates with the radial diffusion of ions from the core are unable to distinguish between limited and diverted plasmas. The model presented here removes this limitation while still remaining amenable to a similar Wiener--Hopf solution procedure. To phenomenologically model ion recycling, the boundary conditions employed at the divertor plates allow for partial reflection. The diffusion into the private flux region and the extended divertor channels (all of normalized length [ital d] along the magnetic field), as well as the rest of the SOL, is evaluated. The SOL is shown to be asymmetric about the separatrix because ions from the core must stream by the X point be- fore diffusing into the private flux region. The channel or leg SOL width is of order [[ital LD](1+2[ital d])/[ital v][sub [ital i

  4. 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).

  5. Major ion chemistry of the Ganga-Brahmaputra river system: Weathering processes and fluxes to the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Sarin, M. M.; Krishnaswami, S.; Dilli, K.; Somayajulu, B. L. K.; Moore, W. S.

    1989-05-01

    The Ganga-Brahmaputra, one of the world's largest river systems, is first in terms of sediment transport and fourth in terms of water discharge. A detailed and systematic study of the major ion chemistry of these rivers and their tributaries, as well as the clay mineral composition of the bed sediments has been conducted. The chemistry of the highland rivers (upper reaches of the Ganga, the Yamuna, the Brahmaputra, the Gandak and the Ghaghra) are all dominated by carbonate weathering; (Ca + Mg) and HCO 3 account for about 80% of the cations and anions. In the lowland rivers (the Chambal, the Betwa and the Ken), HCO 3 excess over (Ca + Mg) and a relatively high contribution of (Na + K) to the total cations indicate that silicate weathering and/or contributions from alkaline/saline soils and groundwaters could be important sources of major ions to these waters. The chemistry of the Ganga and the Yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions. Illite is the dominant clay mineral (about 80%) in the bedload sediments of the highland rivers. Kaolinite and chlorite together constitute the remaining 20% of the clays. In the Chambal, Betwa and Ken, smectite accounts for about 80% of the clays. This difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins. The highland rivers weather acidic rocks, whereas the others flow initially through basic effusives. The Ganga-Brahmaputra river system transports about 130 million tons of dissolved salts to the Bay of Bengal, which is nearly 3% of the global river flux to the oceans. The chemical denudation rates for the Ganga and the Brahmaputra basins are about 72 and 105 tons· km -· yr -1, respectively, which are factors of 2 to 3 higher than the global average. The high denudation rate, particularly in the Brahmaputra, is attributable to high relief and heavy rainfall.

  6. Ion Heating Anisotropy during Dynamo Activity in the MST RFP

    NASA Astrophysics Data System (ADS)

    den Hartog, D. J.; Chapman, J. T.; Craig, D.; Fiksel, G.; Fontana, P. W.

    1999-11-01

    MHD dynamo activity is large in the MST Reversed-Field Pinch during sawtooth crashes, and small otherwise. During a sawtooth crash, ion temperature increases rapidly to a level several times as high as the temperature between sawteeth, which itself can be larger than the electron temperature. Several theories have been developed to explain this ion heating, some indicating a possible asymmetry in perpendicular to parallel heating [C. G. Gimblett, Europhys. Lett. 11, 541 (1990); Z. Yoshida, Nucl. Fusion 31, 386 (1991); N. Mattor, P. W. Terry, and S. C. Prager, Comments Plasma Phys. Controlled Fusion 15, 65 (1992)]. In standard MST discharges, impurity ion temperature measured perpendicular to the magnetic field (T_⊥) is higher than impurity ion temperature parallel to the magnetic field (T_allel) during a sawtooth crash. Throughout the rest of the sawtooth cycle, T_⊥ <= T_allel. This is in contrast to results obtained on the EXTRAP-T2 RFP which showed T_⊥ < T_allel throughout the discharge [K. Sasaki et al., Plasma Phys. Control. Fusion 39, 333 (1997)

  7. Erosional flux from tectonically active landscapes: Case studies from Southern Italy

    NASA Astrophysics Data System (ADS)

    Roda-Boluda, Duna; D'Arcy, Mitch; Whittaker, Alex; Allen, Philip; Gheorghiu, Delia; Rodes, Angel

    2016-04-01

    Erosion and sediment supply are fundamentally important controls on landscape evolution, governing the denudation of relief, the stratigraphy deposited in basins, and the ultimate destruction of orogens. However, quantifying the rates, timescales, and predominant processes of erosion remains a major challenge in many tectonically active areas. Here, we use Southern Italy as a case study to demonstrate how these challenges can be overcome. We present 15 new 10Be catchment-averaged erosion rates, for systems distributed along 5 active normal faults for which we have excellent constraints on throw rates along strike and uplift history. These footwall catchments have a total relief of up to 1800 m and throw rates up to 1.4 mm/yr. We show that sediment supply estimates based on the 10Be erosion rates agree well with sediment supply predictions based on the fault throw profiles. Our results suggest that about 80% of the material uplifted by the faults is being eroded at a similar magnitude to the fault throw rates, offering new insights into the topographic balance of uplift and erosion in this area. These findings imply that active normal faulting is the primary control on sediment supply in Southern Italy. Our field observations suggest that landslides are an important source of sediment in our study area, and are largely driven by incision in response to fault activity. Using a field-calibrated landslide inventory, we estimate landslide-derived sediment flux for our sampled catchments. These estimates correlate well with total sediment flux estimates, demonstrating quantitatively that landslides must be a major source of sediment. Their erosional signal is adequately captured by the 10Be analyses most likely because of the high frequency of small landslides and their high spatial density in these catchments (typically >10% of the total area), which ensures sufficient sediment mixing. Finally, we use our results to calibrate the BQART model of sediment supply, enabling

  8. Comprehensive measurement of respiratory activity in permeabilized cells using extracellular flux analysis

    PubMed Central

    Salabei, Joshua K.; Gibb, Andrew A.; Hill, Bradford G.

    2014-01-01

    Extracellular flux (XF) analysis has become a mainstream method to measure bioenergetic function in cells and tissues. While this technique is commonly used to measure energetics in intact cells, we outline here a detailed XF protocol for measuring respiration in permeabilized cells. Cells are permeabilized using saponin, digitonin, or recombinant perfringolysin O (XF PMP reagent) and provided with specific substrates to measure complex I- or II-mediated respiratory activity, Complex III+IV respiratory activity, or Complex IV activity. Medium- and long-chain acylcarnitines or glutamine may also be provided for measuring fatty acid oxidation or glutamine oxidation, respectively. This protocol allows for such measurements using a minimal number of cells compared with other protocols, without the need for mitochondrial isolation. The results are highly reproducible, and mitochondria remain well coupled. Collectively, this protocol provides comprehensive and detailed information regarding mitochondrial activity and efficiency, and, following preparative steps, takes approximately 6 hours to complete. PMID:24457333

  9. EMIC-wave-moderated flux limitations of ring current energetic ion intensities in the multi-species plasmas of Earth's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Mauk, B.

    2013-12-01

    One of the early sophisticated integrations of theory and observations of the space age was the development in 1966 of the integral Kennel-Petschek flux limit for trapped energetic electrons and ions within Earth's inner magnetosphere. Specifically, it was proposed that: 1) trapped particle distributions in the magnetic bottle configuration of the inner magnetosphere are intrinsically unstable to the generation various plasma waves and 2) ionospheric reflection of some waves back into the trapped populations leads to runaway growth of the waves and dramatic loss of particles for particle integral intensities that rise above a fairly rigidly specified upper limit. While there has been a long hiatus in utilization of the KP limit in inner magnetospheric research, there have been recent highly successful reconsiderations of more general forms of the KP limit for understanding radiation belt electron intensities and spectral shapes, resulting from improvements in theoretical tools. Such a reconsideration has not happened for energetic trapped ions, perhaps due to the perceived immense complexity of the generation of the Electromagnetic Ion Cyclotron (EMIC) waves, that scatter the energetic ions, for plasmas containing multiple ionic species (H, He, O). Here, a differential Kennel-Petschek (KP) flux limit for magnetospheric energetic ions is devised taking into account multiple ion species effects on the EMIC waves. This new theoretical approach is applied to measured Earth magnetosphere energetic ion spectra (~ keV to ~ 1 MeV) for radial positions (L) 3 to 6.7 RE. The flatness of the most intense spectral shapes for <100 keV indicate sculpting by just such a mechanism, but modifications of traditional KP parameters are needed to account for maximum intensities up to 5 times greater than expected. Future work using the Van Allen Probes mission will likely resolve outstanding uncertainties.

  10. The effect of carbon impurities on molybdenum surface morphology evolution under high-flux low-energy helium ion irradiation

    NASA Astrophysics Data System (ADS)

    Tripathi, J. K.; Novakowski, T. J.; Gonderman, S.; Bharadwaj, N.; Hassanein, A.

    2016-09-01

    We report on the role of carbon (C) impurities, in molybdenum (Mo) fuzz evolutions on Mo surface during 100 eV He+ ion irradiations. In this study we considered 0.01, 0.05, and 0.5% C+ ion impurities in He+ ion irradiations. For introducing such tiny C+ ion impurities, gas mixtures of He and CH4 have been chosen in following ratios; 99.95: 0.05, 99.75: 0.25, and 97.5: 2.5. Apart from these three cases, two additional cases, 100% He+ ion (for Mo fuzz growth due to only He+ ions) and 100% H+ ion (for confirming the significance of tiny 0.04-2.0% H+ ions in terms of Mo fuzz evolutions on Mo surface, if any), have also been considered. Ion energy (100 eV), ion fluence (2.6 × 1024 ions m-2), and target temperature (923 K) were kept constant for each experiment and their selections were based on our previous studies [1,2]. Our study shows homogeneously populated and highly dense Mo fuzz evolutions on entire Mo surface for 100% He+ ion irradiation case. Enhancement of C+ ion impurities in He+ ions causes a sequential reduction in Mo fuzz evolutions, leading to almost complete prevention of Mo fuzz evolutions for 0.5% C+ ion impurity concentrations. Additionally, no fuzz formation for 100% H+ ion irradiation at all, were seen (apart from some tiny nano-structuring, in very limited regions). This indicates that there is no significant role of H+ ions in Mo fuzz evolutions (at least for such tiny amount, 0.04-2.0% H+ ions). The study is significant to understand the behavior of potential high-Z plasma facing components (PFCs), in the, presence of tiny amount of C impurities, for nuclear fusion relevant applications.

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

    SciTech Connect

    Schroth, M.H.; Eugster, W.; Gomez, K.E.; Gonzalez-Gil, G.; Niklaus, P.A.; Oester, P.

    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 microorganisms 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 was a

  12. INCLINATION-DEPENDENT ACTIVE GALACTIC NUCLEUS FLUX PROFILES FROM STRONG LENSING OF THE KERR SPACETIME

    SciTech Connect

    Chen, Bin; Dai, Xinyu; Baron, E.

    2013-01-10

    Recent quasar microlensing observations have constrained the X-ray emission sizes of quasars to be about 10 gravitational radii, one order of magnitude smaller than the optical emission sizes. Using a new ray-tracing code for the Kerr spacetime, we find that the observed X-ray flux is strongly influenced by the gravity field of the central black hole, even for observers at moderate inclination angles. We calculate inclination-dependent flux profiles of active galactic nuclei in the optical and X-ray bands by combining the Kerr lensing and projection effects for future reference. We further study the dependence of the X-ray-to-optical flux ratio on the inclination angle caused by differential lensing distortion of the X-ray and optical emission, assuming several corona geometries. The strong lensing X-ray-to-optical magnification ratio can change by a factor of {approx}10 for normal quasars in some cases, and a further factor of {approx}10 for broad absorption line (BAL) quasars and obscured quasars. Comparing our results with the observed distributions in normal and BAL quasars, we find that the inclination angle dependence of the magnification ratios can significantly change the X-ray-to-optical flux ratio distributions. In particular, the mean value of the spectrum slope parameter {alpha}{sub ox}, 0.3838log F {sub 2keV}/F {sub 2500A}, can differ by {approx}0.1-0.2 between normal and BAL quasars, depending on corona geometries, suggesting larger intrinsic absorptions in BAL quasars.

  13. 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.; Nishimura, Yukitoshi; Zong, Qiugang; Ma, Qianli; Bortnik, Jacob; Thorne, Richard M.; Spence, Harlan E.; Kletzing, Craig A.; et al

    2016-07-15

    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. During the 2more » 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

  14. 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

    NASA Astrophysics Data System (ADS)

    Yue, Chao; Li, Wen; Nishimura, Yukitoshi; Zong, Qiugang; Ma, Qianli; Bortnik, Jacob; Thorne, Richard M.; Reeves, Geoffrey D.; Spence, Harlan E.; Kletzing, Craig A.; Wygant, John R.; Nicolls, Michael J.

    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. 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. However, 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.

  15. On the area expansion of magnetic flux tubes in solar active regions

    SciTech Connect

    Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W. E-mail: elena@asu.cas.cz

    2014-11-20

    We calculated the three-dimensional (3D) distribution of the area expansion factors in a potential magnetic field, extrapolated from the high-resolution Hinode/SOT magnetogram of the quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the distribution of area expansion factors show significant structure. Loop-like structures characterized by locally lower values of the expansion factor are embedded in a smooth background. These loop-like flux tubes have squashed cross-sections and expand with height. The distribution of the expansion factors show an overall increase with height, allowing an active region core characterized by low values of the expansion factor to be distinguished. The area expansion factors obtained from extrapolation of the Solar Optical Telescope magnetogram are compared to those obtained from an approximation of the observed magnetogram by a series of 134 submerged charges. This approximation retains the general flux distribution in the observed magnetogram, but removes the small-scale structure in both the approximated magnetogram and the 3D distribution of the area expansion factors. We argue that the structuring of the expansion factor can be a significant ingredient in producing the observed structuring of the solar corona. However, due to the potential approximation used, these results may not be applicable to loops exhibiting twist or to active regions producing significant flares.

  16. Ethanol effects on active and passive Na+ flux in toad bladder.

    PubMed

    Amaranath, L; Anton, A H

    1977-11-01

    Ethanol, like other anesthetics, has been reported to interfere with active Na+ transport in living membranes. In an attempt to elucidate the mechanism by which ethanol exerts this action, we tested in the toad bladder membrane: 1) the effect of ethanol on active Na+ transport, 2) the interaction of ethanol with vasopressin on Na+ transport, and 3) the effect of ethanol on passive Na+ flux. We found that, a) 1-500 microgram/ml of ethanol stimulated, and 10,000 microgram/ml depressed active Na+ transport; b) the combined effect of stimulating concentrations of ethanol and vasopressin, although suggestive of a positive interaction, might have arisen by chance (p = 0.08); c) depressant concentrations of ethanol failed to suppress the stimulation by vasopressin; and d) passive Na+ flux in bladders treated with ouabain and ethacrynic acid was not affected by ethanol (1-100 microgram/ml). These results indicate that ethanol in concentrations ranging from 1 to 10,000 microgram/ml does not block ATP/ATPase Na+ pump but apparently exerts a dose-dependent, stimulant-depressant effect on Na+ channels in the membrane.

  17. Exogenous hydrogen peroxide, nitric oxide and calcium mediate root ion fluxes in two non-secretor mangrove species subjected to NaCl stress.

    PubMed

    Lu, Yanjun; Li, Niya; Sun, Jian; Hou, Peichen; Jing, Xiaoshu; Zhu, Huipeng; Deng, Shurong; Han, Yansha; Huang, Xuxin; Ma, Xujun; Zhao, Nan; Zhang, Yuhong; Shen, Xin; Chen, Shaoliang

    2013-01-01

    Using 3-month-old seedlings of Bruguiera gymnorrhiza (L.) Savigny and Kandelia candel (L.) Druce, we compared species differences in ionic homeostasis control between the two non-secretor mangrove species. A high salinity (400 mM NaCl, 4 weeks) resulted in a decline of the K(+)/Na(+) ratio in root and leaf tissues, and the reduction was more pronounced in K. candel (41-66%) as compared with B. gymnorrhiza (5-36%). Salt-altered flux profiles of Na(+), K(+), H(+) and Ca(2+) in roots and effects of exogenous hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and Ca(2+) on root ion fluxes were examined in seedlings that were hydroponically treated short term with 100 mM NaCl (ST, 24 h) and long term with 200 mM NaCl (LT, 7 days). Short term and LT salinity resulted in Na(+) efflux and a correspondingly increased H(+) influx in roots of both species, although a more pronounced effect was observed in B. gymnorrhiza. The salt-enhanced exchange of Na(+) with H(+) was obviously inhibited by amiloride (a Na(+)/H(+) antiporter inhibitor) or sodium orthovanadate (a plasma membrane H(+)-ATPase inhibitor), indicating that the Na(+) efflux resulted from active Na(+) exclusion across the plasma membrane. Short term and LT salinity accelerated K(+) efflux in the two species, but K. candel exhibited a higher flux rate. The salt-induced K(+) efflux was markedly restricted by the K(+) channel blocker, tetraethylammonium chloride, indicating that the K(+) efflux is mediated by depolarization-activated channels, e.g., KORCs (outward rectifying K(+) channels) and NSCCs (non-selective cation channels). Exogenous H(2)O(2) application (10 mM) markedly increased the apparent Na(+) efflux and limited K(+) efflux in ST-treated roots, although H(2)O(2) caused a higher Na(+) efflux in B. gymnorrhiza roots. CaCl(2) (10 mM) reduced the efflux of K(+) in salinized roots of the two mangroves, but its enhancement of Na(+) efflux was found only in B. gymnorrhiza. Under ST treatment, sodium nitroprusside

  18. Characteristics of upstream energetic (E>=50keV) ion events during intense geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Anagnostopoulos, G. C.; Rigas, A. G.; Sarris, E. T.; Krimigis, S. M.

    1998-05-01

    In this work we examine the statistical presence of some important features of upstream energetic (>=50 keV) ion events under some special conditions in the upstream region and the magnetosphere. The 125 ion events considered in the statistic were observed by the IMP 7 and IMP 8 spacecraft, at ~35RE from the Earth, during nine long time intervals of a total of 153 hours. The time intervals analyzed were selected under the following restrictions: existence of high proton flux (i.e., >=900 pcm-2s-1sr-1) and of a great number of events (an occurrence frequency of ~10 events per 12 hours in the whole statistics) in the energy range 50-220 keV. The most striking findings are the following: (1) The upstream events were observed during times with high values of the geomagnetic activity index Kp(>=3-) (2) all of the upstream events (100%) have energy spectra extending up to energies E>=290keV (3) 86% of these events are accompanied by relativistic (E>=220keV) electrons; and (4) the majority of the upstream ion events (82%) showed noninverse velocity dispersion during their onset phase (22% of the events showed forward velocity dispersion, and 60% showed no velocity dispersion at all when 5.5-min averaged observations were analyzed). Further statistical analysis of this sample of upstream particle events shows that the 50- to 220-keV proton flux shows a positive correlation with the following parameters: the Kp index of geomagnetic activity and the flux of the high-energy (290-500 keV) protons and (>=220 keV) electrons. More specific findings are the following: (1) The spectral index γ for a power law distribution of ions detected by the National Oceanic and Atmospheric Administration Energetic Particle Experiment (EPE) instrument (50<=E<=220keV) and The Johns Hopkins University Applied Physics Laboratory Charged Particle Measurement Experiment (CPME) instrument (290<=E<=500keV) ranges between 2 and 6, with maximum probability between 4 and 5 and (2) the peak

  19. Molecular candidates for cardiac stretch-activated ion channels

    PubMed Central

    Reed, Alistair; Kohl, Peter; Peyronnet, Rémi

    2014-01-01

    The heart is a mechanically-active organ that dynamically senses its own mechanical environment. This environment is constantly changing, on a beat-by-beat basis, with additional modulation by respiratory activity and changes in posture or physical activity, and further overlaid with more slowly occurring physiological (e.g. pregnancy, endurance training) or pathological challenges (e.g. pressure or volume overload). Far from being a simple pump, the heart detects changes in mechanical demand and adjusts its performance accordingly, both via heart rate and stroke volume alteration. Many of the underlying regulatory processes are encoded intracardially, and are thus maintained even in heart transplant recipients. Over the last three decades, molecular substrates of cardiac mechanosensitivity have gained increasing recognition in the scientific and clinical communities. Nonetheless, the processes underlying this phenomenon are still poorly understood. Stretch-activated ion channels (SAC) have been identified as one contributor to mechanosensitive autoregulation of the heartbeat. They also appear to play important roles in the development of cardiac pathologies – most notably stretch-induced arrhythmias. As recently discovered, some established cardiac drugs act, in part at least, via mechanotransduction pathways suggesting SAC as potential therapeutic targets. Clearly, identification of the molecular substrate of cardiac SAC is of clinical importance and a number of candidate proteins have been identified. At the same time, experimental studies have revealed variable–and at times contrasting–results regarding their function. Further complication arises from the fact that many ion channels that are not classically defined as SAC, including voltage and ligand-gated ion channels, can respond to mechanical stimulation. Here, we summarise what is known about the molecular substrate of the main candidates for cardiac SAC, before identifying potential further

  20. The Dynamic Evolution of Active-Region-Scale Magnetic Flux Tubes in the Turbulent Solar Convective Envelope

    NASA Astrophysics Data System (ADS)

    Weber, Maria A.; Fan, Yuhong; Miesch, Mark S.

    2014-06-01

    The manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective upflows help tilt the apex of rising flux tubes toward the equator in accordance with Joy’s Law. Additionally, rotationally aligned, columnar convective structures called giant cells present in the ASH simulation organizes flux emergence into a large-scale longitudinal pattern similar to the active longitude trend on the Sun and other solar-like stars. The effect of radiative diffusion across the radiation zone-convection zone interface on the buoyant rise of magnetic flux tubes is also studied, as well as the possibility of an induced twist of flux tube magnetic fields lines due to the Coriolis force induced tilting of the flux tube apex, presence of turbulent convection, and the conservation of helicity. Flux emergence simulations through the convection zone of a Sun rotating at 5 times

  1. Pollen tube growth is coupled to the extracellular calcium ion flux and the intracellular calcium gradient: effect of BAPTA-type buffers and hypertonic media.

    PubMed Central

    Pierson, E S; Miller, D D; Callaham, D A; Shipley, A M; Rivers, B A; Cresti, M; Hepler, P K

    1994-01-01

    Lily pollen tubes possess a steep, tip-focused intracellular Ca2+ gradient and a tip-directed extracellular Ca2+ influx. Ratiometric ion imaging revealed that the gradient extends from above 3.0 microM at the apex to approximately 0.2 microM within 20 microns from the tip, while application of the Ca(2+)-specific vibrating electrode indicated that the extracellular influx measured between 1.4 and 14 pmol cm-2 sec-1. We examined the relationship between these phenomena and their role in tube growth by using different 1,2-bis(o-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA)-type buffers and hypertonic media. Injection of active BAPTA-type buffers or application of elevated levels of sucrose reversibly inhibited growth, destroyed tip zonation of organelles, and modified normal patterns of cytoplasmic streaming. Simultaneously, these treatments dissipated both the intracellular tip-focused gradient and the extracellular Ca2+ flux. Of the BAPTA-type buffers, 5,5'-dibromo-BAPTA (dissociation constant [Kd] is 1.5 microM) and 4,4'-difluoro-BAPTA (Kd of 1.7 microM) exhibited greater activity than those buffers with either a higher affinity (5,5'-dimethyl-BAPTA, Kd of 0.15 microM; BAPTA, Kd of 0.21 microM; 5,5'-difluoro-BAPTA, Kd of 0.25 microM) or lower affinity (5-methyl, 5'-nitro-BAPTA, Kd of 22 microM) for Ca2+. Our findings provide evidence that growing pollen tubes have open Ca2+ channels in their tip and that these channels become inactivated in nongrowing tubes. The studies with elevated sucrose support the view that stretching of the apical plasma membrane contributes to the maintenance of the Ca2+ signal. PMID:7866026

  2. Physiological mechanisms for high salt tolerance in wild soybean (Glycine soja) from Yellow River Delta, China: photosynthesis, osmotic regulation, ion flux and antioxidant capacity.

    PubMed

    Chen, Peng; Yan, Kun; Shao, Hongbo; Zhao, Shijie

    2013-01-01

    Glycine soja (BB52) is a wild soybean cultivar grown in coastal saline land in Yellow River Delta, China. In order to reveal the physiological mechanisms adapting to salinity, we examined photosynthesis, ion flux, antioxidant system and water status in Glycine soja under NaCl treatments, taking a cultivated soybean, ZH13, as control. Upon NaCl exposure, higher relative water content and water potential were maintained in the leaf of BB52 than ZH13, which might depend on the more accumulation of osmotic substances such as glycinebetaine and proline. Compared with ZH13, activities of antioxidant enzymes including superoxide dismutase, catalase, ascorbate peroxidase and contents of ascorbate, glutathione and phenolics were enhanced to a higher level in BB52 leaf under NaCl stress, which could mitigate the salt-induced oxidative damage in BB52. Consistently, lipid peroxidation indicated by malondialdehyde content was lower in BB52 leaf. Photosynthetic rate (Pn) was decreased by NaCl stress in BB52 and ZH13, and the decrease was greater in ZH13. The decreased Pn in BB52 was mainly due to stomatal limitation. The inhibited activation of rubisco enzyme in ZH13 due to the decrease of rubisco activase content became an important limiting factor of Pn, when NaCl concentration increased to 200 mM. Rubisco activase in BB52 was not affected by NaCl stress. Less negative impact in BB52 derived from lower contents of Na(+) and Cl(-) in the tissues, and non-invasive micro-test technique revealed that BB52 roots had higher ability to extrude Na(+) and Cl(-). Wild soybean is a valuable genetic resource, and our study may provide a reference for molecular biologist to improve the salt tolerance of cultivated soybean in face of farmland salinity.

  3. Characterization of cathodoluminescence activated by Mn ions in dolomite

    NASA Astrophysics Data System (ADS)

    Kusano, N.; Nishido, H.; Makio, M.; Ninagawa, K.

    2011-12-01

    Cathodoluminescence (CL), the light emission induced by electron irradiation, has been widely applied in mineralogical and petrological investigations, especially for carbonates. Dolomite usually emits a red CL emission related to an impurity center of divalent Mn, but of which each occupancy in Ca and/or Mg site has not been quantitatively estimated. In this study, we have characterized an emission center of CL and developed a method to evaluate site occupancy of Mn ions in dolomite lattice. Three dolomite samples from Hase, Japan (D-06), Binntal, Swiss (D-17) and Blackrock, USA (D-26) were selected for CL measurements after carbon-coating on their polished surfaces. These samples contain Mn ions as an activator, but too low for divalent Fe as a quencher. SEM-CL analysis was conducted using an SEM (JEOL: JSM-5410) combined with a grating monochromator (Oxford: Mono CL2) to measure CL spectra ranging from 300 to 800 nm in 1 nm steps with a temperature controlled stage from -190 to 45 degree C. The dispersed CL was collected by a photoncounting method using a photomultiplier tube (Hamamatsu: R2228) and converted to digital data. All CL spectra were corrected for the total instrumental response. All samples exhibit a broad band in red region between 580 and 640 nm at room temperature, but having a complicated shape overlapped with several bands. It suggests that Mn ions as an activator can be located at deferent sites with deferent occupancies in dolomite lattice. Therefore, a Gaussian fit was conducted to quantitatively deconvolute the emission band in an energy unit. CL of D-06 and D-26 consists of two emission components at around 1.84 and 2.15 eV. The former corresponds to an emission center of impurity Mn ions substituted for Mg site, and the latter to an emission center of divalent Mn for Ca site, resulting in deferent crystal fields. If the concentration of Mn in dolomite is not so high (above 10000 ppm) to cause quenching effect, the intensity might be

  4. Immunologically active metallic ion-containing polysaccharides of Achyrocline satureioides.

    PubMed

    Puhlmann, J; Knaus, U; Tubaro, L; Schaefer, W; Wagner, H

    1992-08-01

    Two homogeneous, metallic ion-containing pectic polysaccharides with mean M(r)s of 7600 and 15,000 were isolated from dried aerial parts of Achyrocline satureioides by anion exchange column chromatography on DEAE-Sepharose CL-6B and gel filtration column chromatography on Fractogel TSK HW-50 (S). The structures, as determined by methylation analysis, carboxyl reduction, and partial acid hydrolysis, were shown to be rhamnogalacturonans. Both pectins show a pronounced anticomplementary effect in vitro. The larger carbohydrate AS 4 of higher M(r) exerts anti-inflammatory activity and a strong enhancement of phagocytosis in vivo.

  5. Stretch-Activated Ion Channels: What Are They?

    PubMed Central

    Sachs, Frederick

    2010-01-01

    Mechanosensitive ion channels (MSCs) exist in all cells, but mechanosensitivity is a phenotype not a genotype. Specialized mechanoreceptors such as the hair cells of the cochlea require elaborate mechanical impedance matching to couple the channels to the external stress. In contrast, MSCs in nonspecialized cells appear activated by stress in the bilayer local to the channel—within about three lipids. Local mechanical stress can be produced by far-field tension, amphipaths, phase separations, the cytoskeleton, the extracellular matrix, and the adhesion energy between the membrane and a patch pipette. Understanding MSC function requires understanding the stimulus. PMID:20134028

  6. Lipid bilayer array for simultaneous recording of ion channel activities

    NASA Astrophysics Data System (ADS)

    Hirano-Iwata, Ayumi; Nasu, Tomohiro; Oshima, Azusa; Kimura, Yasuo; Niwano, Michio

    2012-07-01

    This paper describes an array of stable and reduced-solvent bilayer lipid membranes (BLMs) formed in microfabricated silicon chips. BLMs were first vertically formed simultaneously and then turned 90° in order to realize a horizontal BLM array. Since the present BLMs are mechanically stable and robust, the BLMs survive this relatively tough process. Typically, a ˜60% yield in simultaneous BLM formation over 9 sites was obtained. Parallel recordings of gramicidin channel activities from different BLMs were demonstrated. The present system has great potential as a platform of BLM-based high throughput drug screening for ion channel proteins.

  7. The dynamic evolution of active-region-scale magnetic flux tubes in the turbulent solar convective envelope

    NASA Astrophysics Data System (ADS)

    Weber, Maria Ann

    2014-12-01

    The Sun exhibits cyclic properties of its large-scale magnetic field on the order of sigma22 years, with a ˜11 year frequency of sunspot occurrence. These sunspots, or active regions, are the centers of magnetically driven phenomena such as flares and coronal mass ejections. Volatile solar magnetic events directed toward the Earth pose a threat to human activities and our increasingly technological society. As such, the origin and nature of solar magnetic flux emergence is a topic of global concern. Sunspots are observable manifestations of solar magnetic fields, thus providing a photospheric link to the deep-seated dynamo mechanism. However, the manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. The convective velocity field interacts with the flux tube through the drag force it experiences as it traverses through the convecting medium. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective

  8. How Phosphorylation and ATPase Activity Regulate Anion Flux though the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR).

    PubMed

    Zwick, Matthias; Esposito, Cinzia; Hellstern, Manuel; Seelig, Anna

    2016-07-01

    The cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), mutations of which cause cystic fibrosis, belongs to the ATP-binding cassette (ABC) transporter family and works as a channel for small anions, such as chloride and bicarbonate. Anion channel activity is known to depend on phosphorylation by cAMP-dependent protein kinase A (PKA) and CFTR-ATPase activity. Whereas anion channel activity has been extensively investigated, phosphorylation and CFTR-ATPase activity are still poorly understood. Here, we show that the two processes can be measured in a label-free and non-invasive manner in real time in live cells, stably transfected with CFTR. This study reveals three key findings. (i) The major contribution (≥90%) to the total CFTR-related ATP hydrolysis rate is due to phosphorylation by PKA and the minor contribution (≤10%) to CFTR-ATPase activity. (ii) The mutant CFTR-E1371S that is still conductive, but defective in ATP hydrolysis, is not phosphorylated, suggesting that phosphorylation requires a functional nucleotide binding domain and occurs in the post-hydrolysis transition state. (iii) CFTR-ATPase activity is inversely related to CFTR anion flux. The present data are consistent with a model in which CFTR is in a closed conformation with two ATPs bound. The open conformation is induced by ATP hydrolysis and corresponds to the post-hydrolysis transition state that is stabilized by phosphorylation and binding of chloride channel potentiators. PMID:27226582

  9. EMERGENCE OF HELICAL FLUX AND THE FORMATION OF AN ACTIVE REGION FILAMENT CHANNEL

    SciTech Connect

    Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.

    2010-07-20

    We present comprehensive observations of the formation and evolution of a filament channel within NOAA Active Region (AR) 10978 from Hinode/Solar Optical Telescope and TRACE. We employ sequences of Hinode spectro-polarimeter maps of the AR, accompanying Hinode Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode Broadband Filter Instrument filtergrams in the Ca II H line and G-band, Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 A image sequences. The development of the channel resembles qualitatively that presented by Okamoto et al. in that many indicators point to the emergence of a pre-existing sub-surface magnetic flux rope. The consolidation of the filament channel into a coherent structure takes place rapidly during the course of a few hours, and the filament form then gradually shrinks in width over the following two days. Particular to this filament channel is the observation of a segment along its length of horizontal, weak (500 G) flux that, unlike the rest of the filament channel, is not immediately flanked by strong vertical plage fields of opposite polarity on each side of the filament. Because this isolated horizontal field is observed in photospheric lines, we infer that it is unlikely that the channel formed as a result of reconnection in the corona, but the low values of inferred magnetic fill fraction along the entire length of the filament channel suggest that the bulk of the field resides somewhat above the low photosphere. Correlation tracking of granulation in the G band presents no evidence for either systematic flows toward the channel or systematic shear flows along it. The absence of these flows, along with other indications of these data from multiple sources, reinforces (but does not conclusively demonstrate) the picture of an emerging flux rope as the origin of this AR filament channel.

  10. Distribution of the Effect of Solar Proton Flux And Geomagnetic Activity on the Stratospheric Ozone Profile

    NASA Astrophysics Data System (ADS)

    Velinov, P. I. Y.; Tassev, Y.; Yanev, T.; Tomova, D.

    Two-way MANOVA was used to examine the impact of two factors: 1) the proton flux intensity and 2) the geomagnetic activity on the dependant variable "ozone mixing ratio" which characterizes the stratospheric ozone profiles. The examination was carried out with fixed levels of two other factors: a) the heights at which the "ozone mixing ratio" was recorded, i,e, 35 km, 30.2 km, 24.5 km, 18.4 km, 15.6 km and b) the energetic intervals within which the proton flux was measured, i.e. =0,6-4,2 MeV; 4,2-8,7 MeV; 8,7-14,5 MeV; 15-44 MeV; 39-82 MeV; 84-200 MeV; 110-500 MeV. The analysis was performed for all combinations of levels of the factors a) and b) for which data was available. It was aimed at revealing which of the factors 1) and 2) were dominating with different combinations of the factors a) and b) with fixed levels. For this purpose a post hoc analysis was performed as well. The main results are as follows: factors 1) and 2) exert statistically significant impact on the dependant variable at all of the heights examined, but not for all of energetic intervals; increase of the ozone mixing ratio was observed as a main effect of the proton flux intensity at heights 24.5 km, 18.4 km, 15.6 km, but the analysis of the simultaneous acting of factors 1) and 2) revealed a decrease of the dependant variable at these heights; these effects possibly indicate the existence of two different mechanisms of impact on the ozone mixing ratio; the afore- discussed effects decrease with the height and therefore their graphical image was named "Christmas tree".

  11. 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...

  12. Using poly(3-aminophenylboronic acid) thin film with binding-induced ion flux blocking for amperometric detection of hemoglobin A1c.

    PubMed

    Wang, Jen-Yuan; Chou, Tse-Chuan; Chen, Lin-Chi; Ho, Kuo-Chuan

    2015-01-15

    This study reports a novel enzyme-free, label-free amperometric method for direct detection of hemoglobin A1c (Hb(A1c)), a potent biomarker for diabetes diagnosis and prognosis. The method relies on an electrode modified with poly(3-aminophenylboronic acid) (PAPBA) nanoparticles (20-50 nm) and a sensing scheme named "binding-induced ion flux blocking." The PAPBA nanoparticles were characterized by FT-IR, XPS, TEM, and SEM. Being a polyaniline derivative, PAPBA showed an ion-dependent redox behavior, in which insertion or extraction of ions into or out of PABPA occurred for charge balance during the electron transfer process. The polymer allowed Hb(A1c) selectively bound to its surface via forming the cis-diol linkage between the boronic acid and sugar moieties. Voltammetric analyses showed that Hb(A1c) binding decreased the redox current of PAPBA; however, the binding did not alter the redox potentials and the apparent diffusivities of ions. This suggests that the redox current of PAPBA decreased due to an Hb(A1c) binding-induced ion flux blocking mechanism, which was then verified and characterized through an in situ electrochemical quartz crystal microbalance (EQCM) study. Assay with Hb(A1c) by differential pulse voltammetry (DPV) indicates that the peak current of a PAPBA electrode has a linear dependence on the logarithm of Hb(A1c) concentration ranging from 0.975 to 156 μM. The Hb(A1c) assay also showed high selectivity against ascorbic acid, dopamine, uric acid, glucose and bovine serum albumin. This study has demonstrated a new method for developing an electrochemical Hb(A1c) biosensor and can be extended to other label-free, indicator-free protein biosensors based on a similar redox polymer electrode. PMID:25113050

  13. Comparison of Simulated and Observed Ring Current Magnetic Field and Ion Fluxes and ENA Intensity during the 5 April 2010 Storm

    NASA Astrophysics Data System (ADS)

    Chen, M. W.; Lemon, C.; Guild, T. B.; Schulz, M.; Lui, A.; Keesee, A. M.; Goldstein, J.; Rodriguez, J. V.

    2011-12-01

    In this study we compare simulated and observed stormtime magnetic intensities, proton flux spectra and ENA intensity for the 5 April 2010 storm (minimum Dst ≈ -73 nT) to test how well self-consistent simulations can simultaneously reproduce these quantities. We simulate the ring current and plasma sheet using the magnetically and electrostatically self-consistent Rice Convection Model-Equilibrium (RCM-E) [Lemon et al., JGR, 2004] with a time-varying magnetopause driven by upstream solar wind and interplanetary magnetic field (IMF) conditions. We use ion temperatures inferred from TWINS energetic neutral atom (ENA) images and THEMIS/ESA and SST ion data, and proton densities from the empirical IMF-dependent model of Tsyganenko and Mukai [JGR, 2003] to guide our specification of the plasma sheet at 10 RE, our plasma boundary location in the RCM-E. The oxygen to proton density ratio at the plasma boundary is specified from the empirical Young et al. [JGR, 1982] study. We compare the simulated magnetic intensity with the magnetic intensity measured by magnetometers on the GOES satellites at geosynchronous (GEO) altitude (6.6 Earth radii) and on THEMIS satellites. The simulated and observed proton spectra (GOES-14/MAGPD) at GEO and global ENA intensity (TWINS 1 and 2) are compared. We discuss the response of the ring current magnetic field and ion flux distribution to expansions and compressions of the magnetosphere associated with the dynamic solar wind pressure for this storm event.

  14. Flux Tensor Constrained Geodesic Active Contours with Sensor Fusion for Persistent Object Tracking

    PubMed Central

    Bunyak, Filiz; Palaniappan, Kannappan; Nath, Sumit Kumar; Seetharaman, Gunasekaran

    2007-01-01

    This paper makes new contributions in motion detection, object segmentation and trajectory estimation to create a successful object tracking system. A new efficient motion detection algorithm referred to as the flux tensor is used to detect moving objects in infrared video without requiring background modeling or contour extraction. The flux tensor-based motion detector when applied to infrared video is more accurate than thresholding ”hot-spots”, and is insensitive to shadows as well as illumination changes in the visible channel. In real world monitoring tasks fusing scene information from multiple sensors and sources is a useful core mechanism to deal with complex scenes, lighting conditions and environmental variables. The object segmentation algorithm uses level set-based geodesic active contour evolution that incorporates the fusion of visible color and infrared edge informations in a novel manner. Touching or overlapping objects are further refined during the segmentation process using an appropriate shape-based model. Multiple object tracking using correspondence graphs is extended to handle groups of objects and occlusion events by Kalman filter-based cluster trajectory analysis and watershed segmentation. The proposed object tracking algorithm was successfully tested on several difficult outdoor multispectral videos from stationary sensors and is not confounded by shadows or illumination variations. PMID:19096530

  15. MAGNETIC HELICITY TRANSPORTED BY FLUX EMERGENCE AND SHUFFLING MOTIONS IN SOLAR ACTIVE REGION NOAA 10930

    SciTech Connect

    Zhang, Y.; Kitai, R.; Takizawa, K. E-mail: zhangyin@bao.ac.cn

    2012-06-01

    We present a new methodology which can determine magnetic helicity transport by the passage of helical magnetic field lines from the sub-photosphere and the shuffling motions of footpoints of preexisting coronal field lines separately. It is well known that only the velocity component, which is perpendicular to the magnetic field ({upsilon}{sub B}), has contributed to the helicity accumulation. Here, we demonstrate that {upsilon}{sub B} can be deduced from a horizontal motion and vector magnetograms under a simple relation of {upsilon}{sub t} = {mu}{sub t} + ({upsilon}{sub n}/B{sub n} ) B{sub t}, as suggested by Demoulin and Berger. Then after dividing {upsilon}{sub B} into two components, as one is tangential and the other is normal to the solar surface, we can determine both terms of helicity transport. Active region (AR) NOAA 10930 is analyzed as an example during its solar disk center passage by using data obtained by the Spectropolarimeter and the Narrowband Filter Imager of Solar Optical Telescope on board Hinode. We find that in our calculation the helicity injection by flux emergence and shuffling motions have the same sign. During the period we studied, the main contribution of helicity accumulation comes from the flux emergence effect, while the dynamic transient evolution comes from the shuffling motions effect. Our observational results further indicate that for this AR the apparent rotational motion in the following sunspot is the real shuffling motions on the solar surface.

  16. δ-SUNSPOT FORMATION IN SIMULATION OF ACTIVE-REGION-SCALE FLUX EMERGENCE

    SciTech Connect

    Fang, Fang; Fan, Yuhong

    2015-06-10

    δ-sunspots, with highly complex magnetic structures, are very productive in energetic eruptive events, such as X-class flares and homologous eruptions. We here study the formation of such complex magnetic structures by numerical simulations of magnetic flux emergence from the convection zone into the corona in an active-region-scale domain. In our simulation, two pairs of bipolar sunspots form on the surface, originating from two buoyant segments of a single subsurface twisted flux rope, following the approach of Toriumi et al. Expansion and rotation of the emerging fields in the two bipoles drive the two opposite polarities into each other with apparent rotating motion, producing a compact δ-sunspot with a sharp polarity inversion line. The formation of the δ-sunspot in such a realistic-scale domain produces emerging patterns similar to those formed in observations, e.g., the inverted polarity against Hale's law, the curvilinear motion of the spot, and strong transverse field with highly sheared magnetic and velocity fields at the polarity inversion line (PIL). Strong current builds up at the PIL, giving rise to reconnection, which produces a complex coronal magnetic connectivity with non-potential fields in the δ-spot overlaid by more relaxed fields connecting the two polarities at the two ends.

  17. Control of Pitching Airfoil Aerodynamics by Vorticity Flux Modification using Active Bleed

    NASA Astrophysics Data System (ADS)

    Kearney, John; Glezer, Ari

    2014-11-01

    Distributed active bleed driven by pressure differences across a pitching airfoil is used to regulate the vorticity flux over the airfoil's surface and thereby to control aerodynamic loads in wind tunnel experiments. The range of pitch angles is varied beyond the static stall margin of the 2-D VR-7 airfoil at reduced pitching rates up to k = 0.42. Bleed is regulated dynamically using piezoelectric louvers between the model's pressure side near the trailing edge and the suction surface near the leading edge. The time-dependent evolution of vorticity concentrations over the airfoil and in the wake during the pitch cycle is investigated using high-speed PIV and the aerodynamic forces and moments are measured using integrated load cells. The timing of the dynamic stall vorticity flux into the near wake and its effect on the flow field are analyzed in the presence and absence of bleed using proper orthogonal decomposition (POD). It is shown that bleed actuation alters the production, accumulation, and advection of vorticity concentrations near the surface with significant effects on the evolution, and, in particular, the timing of dynamic stall vortices. These changes are manifested by alteration of the lift hysteresis and improvement of pitch stability during the cycle, while maintaining cycle-averaged lift to within 5% of the base flow level with significant implications for improvement of the stability of flexible wings and rotor blades. This work is supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  18. Trend of photospheric helicity flux in active regions generating halo CMEs

    NASA Astrophysics Data System (ADS)

    Smyrli, Aimilia; Zuccarello, Francesco; Zuccarello, Francesca; Romano, Paolo; Guglielmino, Salvatore Luigi; Spadaro, Daniele; Hood, Alan; Mackay, Duncan

    Coronal Mass Ejections (CMEs) are very energetic events initiated in the solar atmosphere, re-sulting in the expulsion of magnetized plasma clouds that propagate into interplanetary space. It has been proposed that CMEs can play an important role in shedding magnetic helicity, avoiding its endless accumulation in the corona. We therefore investigated the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred, in order to de-termine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence. After identifying the active regions (AR) where the CMEs were ini-tiated by means of a double cross-check based on the flaring-eruptive activity and the use of SOHO/EIT difference images, we used MDI magnetograms to calculate magnetic flux evolu-tion, magnetic helicity injection rate and magnetic helicity injection in 10 active regions that gave rise to 12 halo CMEs observed during the period February 2000 -June 2003. No unique behavior in magnetic helicity injection accompanying halo CME occurrence is found. In fact, in some cases there is an abrupt change in helicity injection timely correlated with the CME event, while in some others no significant variation is recorded. However, our analysis show that the most significant changes in magnetic flux and magnetic helicity injection are associated with impulsive CMEs rather than gradual CMEs. Moreover, the most significant changes in mag-netic helicity are observed when X-class flares or eruptive filaments occur, while the occurrence of flares of class C or M seems not to affect significantly the magnetic helicity accumulation.

  19. A model for the formation of the active region corona driven by magnetic flux emergence

    NASA Astrophysics Data System (ADS)

    Chen, F.; Peter, H.; Bingert, S.; Cheung, M. C. M.

    2014-04-01

    Aims: We present the first model that couples the formation of the corona of a solar active region to a model of the emergence of a sunspot pair. This allows us to study when, where, and why active region loops form, and how they evolve. Methods: We use a 3D radiation magnetohydrodynamics (MHD) simulation of the emergence of an active region through the upper convection zone and the photosphere as a lower boundary for a 3D MHD coronal model. The coronal model accounts for the braiding of the magnetic fieldlines, which induces currents in the corona to heat up the plasma. We synthesize the coronal emission for a direct comparison to observations. Starting with a basically field-free atmosphere we follow the filling of the corona with magnetic field and plasma. Results: Numerous individually identifiable hot coronal loops form, and reach temperatures well above 1 MK with densities comparable to observations. The footpoints of these loops are found where small patches of magnetic flux concentrations move into the sunspots. The loop formation is triggered by an increase in upward-directed Poynting flux at their footpoints in the photosphere. In the synthesized extreme ultraviolet (EUV) emission these loops develop within a few minutes. The first EUV loop appears as a thin tube, then rises and expands significantly in the horizontal direction. Later, the spatially inhomogeneous heat input leads to a fragmented system of multiple loops or strands in a growing envelope. Animation associated with Fig. 2 is available in electronic form at http://www.aanda.org

  20. 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.

  1. Polar observations of ion/electron bursts at the pre-dawn polar cap boundary: evidence for internal reconnection of overdraped lobe flux

    NASA Astrophysics Data System (ADS)

    Sandholt, P. E.; Farrugia, C. J.

    2008-08-01

    Observations made by Polar of ion-electron bursts on the dawn side of the polar cap are presented. They occurred when conditions external to the magnetosphere corresponded to that of the sheath region of a magnetic cloud, which was characterized by very high densities/dynamic pressure and a magnetic field which was strong in all components and which was tilted antisunward (Bx<0) and northward (Bz>0) with its clock angle lying between 20 and 90° (By: 8 15 nT). A clear temporal development in the energy range spanned by the individual ion bursts (from 0.2 2 keV to 1 10 keV) was present. We relate this to a corresponding temporal evolution in the cloud sheath field and plasma. We analyze the solar wind-magnetosphere aspects of the observations using the concepts of (i) (i) overdraped lobe flux, (ii) Bx- and By-regulated sequential reconnections in opposite hemispheres (magnetopause and internal modes), and (iii) newly-closed magnetic flux. In particular, we find that the most energetic ion bursts (accompanied by bi-directionally streaming electrons at 1 10 keV and intense magnetosheath-origin fluxes) are located on newly closed field lines generated by internal reconnection occurring between overdraped lobe field lines and the closed geomagnetic field. This result corroborates a topology of lobe reconnection under conditions of dipole tilt and/or nonzero IMF Bx component advanced by Watanabe et al. (2006), which in our case is adapted to nonzero IMF By conditions.

  2. Surface flux transport simulations. Inflows towards active regions and the modulation of the solar cycle.

    NASA Astrophysics Data System (ADS)

    Martin-Belda, David; Cameron, Robert

    2016-07-01

    Aims. We investigate the way near-surface converging flows towards active regions affect the build-up of magnetic field at the Sun's polar caps. In the Babcock-Leighton dynamo framework, this modulation of the polar fields could explain the variability of the solar cycle. Methods. We develop a surface flux transport code incorporating a parametrized model of the inflows and run simulations spanning several cycles. We carry out a parameter study to test how the strength and extension of the inflows affect the amplitude of the polar fields. Results. Inflows are seen to play an important role in the build-up of the polar fields, and can act as the non-linearity feedback mechanism required to limit the strength of the solar cycles in the Babcock-Leighton dynamo framework.

  3. Neutron flux measurements at the TRIGA reactor in Vienna for the prediction of the activation of the biological shield.

    PubMed

    Merz, Stefan; Djuricic, Mile; Villa, Mario; Böck, Helmuth; Steinhauser, Georg

    2011-11-01

    The activation of the biological shield is an important process for waste management considerations of nuclear facilities. The final activity can be estimated by modeling using the neutron flux density rather than the radiometric approach of activity measurements. Measurement series at the TRIGA reactor Vienna reveal that the flux density next to the biological shield is in the order of 10(9)cm(-2)s(-1) at maximum power; but it is strongly influenced by reactor installations. The data allow the estimation of the final waste categorization of the concrete according to the Austrian legislation. PMID:21646026

  4. Energetics of Ion Permeation in an Open-Activated TRPV1 Channel.

    PubMed

    Jorgensen, Christian; Furini, Simone; Domene, Carmen

    2016-09-20

    Ion channels enable diffusion of ions down physiological electrochemical gradients. Modulation of ion permeation is crucial for the physiological functioning of cells, and misregulation of ion channels is linked to a myriad of channelopathies. The ion permeation mechanism in the transient receptor potential (TRP) ion channel family is currently not understood at an atomistic level. In this work, we employed a simulation strategy for ion permeation (molecular-dynamics simulations with bias-exchange metadynamics) to study and compare monovalent (Na(+), K(+)) ion permeation in the open-activated TRP vanniloid-1 (TRPV1) ion channel. Using ∼3.6 μs of simulation trajectories, we obtained atomistic evidence for the nonselective nature of TRPV1. Our analysis shows that solvated monovalent ions permeate through the selectivity filter with comparable energetic barriers via a two-site mechanism. Finally, we confirmed that an intracellular binding site is located between the intracellular gate residues I679 and E684. PMID:27653480

  5. Energetics of Ion Permeation in an Open-Activated TRPV1 Channel.

    PubMed

    Jorgensen, Christian; Furini, Simone; Domene, Carmen

    2016-09-20

    Ion channels enable diffusion of ions down physiological electrochemical gradients. Modulation of ion permeation is crucial for the physiological functioning of cells, and misregulation of ion channels is linked to a myriad of channelopathies. The ion permeation mechanism in the transient receptor potential (TRP) ion channel family is currently not understood at an atomistic level. In this work, we employed a simulation strategy for ion permeation (molecular-dynamics simulations with bias-exchange metadynamics) to study and compare monovalent (Na(+), K(+)) ion permeation in the open-activated TRP vanniloid-1 (TRPV1) ion channel. Using ∼3.6 μs of simulation trajectories, we obtained atomistic evidence for the nonselective nature of TRPV1. Our analysis shows that solvated monovalent ions permeate through the selectivity filter with comparable energetic barriers via a two-site mechanism. Finally, we confirmed that an intracellular binding site is located between the intracellular gate residues I679 and E684.

  6. Formation of a Double-decker Magnetic Flux Rope in the Sigmoidal Solar Active Region 11520

    NASA Astrophysics Data System (ADS)

    Cheng, X.; Ding, M. D.; Zhang, J.; Sun, X. D.; Guo, Y.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-01

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s-1. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  7. Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520

    SciTech Connect

    Cheng, X.; Ding, M. D.; Zhang, J.; Guo, Y.; Sun, X. D.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-10

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s{sup –1}. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  8. Nuclear pore ion channel activity in live syncytial nuclei.

    PubMed

    Bustamante, Jose Omar

    2002-05-01

    Nuclear pore complexes (NPCs) are important nanochannels for the control of gene activity and expression. Most of our knowledge of NPC function has been derived from isolated nuclei and permeabilized cells in cell lysates/extracts. Since recent patch-clamp work has challenged the dogma that NPCs are freely permeable to small particles, a preparation of isolated living nuclei in their native liquid environment was sought and found: the syncytial nuclei in the water of the coconut Cocos nucifera. These nuclei have all properties of NPC-mediated macromolecular transport (MMT) and express foreign green fluorescent protein (GFP) plasmids. They display chromatin movement, are created by particle aggregation or by division, can grow by throwing filaments to catch material, etc. This study shows, for the first time, that living NPCs engaged in MMT do not transport physiological ions - a phenomenon that explains observations of nucleocytoplasmic ion gradients. Since coconuts are inexpensive (less than US$1/nut per litre), this robust preparation may contribute to our understanding of NPCs and cell nucleus and to the development of biotechnologies for the production of DNA, RNA and proteins.

  9. Modulation Effects of Curcumin on Erythrocyte Ion-Transporter Activity

    PubMed Central

    Singh, Prabhakar; Rizvi, Syed Ibrahim

    2015-01-01

    Curcumin ((1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), the yellow biphenolic pigment isolated from turmeric (Curcuma longa), has various medicinal benefits through antioxidation, anti-inflammation, cardiovascular protection, immunomodulation, enhancing of the apoptotic process, and antiangiogenic property. We explored the effects of curcumin in vitro (10−5 M to 10−8 M) and in vivo (340 and 170 mg/kg b.w., oral) on Na+/K+ ATPase (NKA), Na+/H+ exchanger (NHE) activity, and membrane lipid hydroperoxides (ROOH) in control and experimental oxidative stress erythrocytes of Wistar rats. As a result, we found that curcumin potently modulated the membrane transporters activity with protecting membrane lipids against hydro-peroxidation in control as well as oxidatively challenged erythrocytes evidenced by stimulation of NKA, downregulation of NHE, and reduction of ROOH in the membrane. The observed results corroborate membrane transporters activity with susceptibility of erythrocyte membrane towards oxidative damage. Results explain the protective mechanism of curcumin against oxidative stress mediated impairment in ions-transporters activity and health beneficial effects. PMID:26421014

  10. On a novel rate theory for transport in narrow ion channels and its application to the study of flux optimization via geometric effects

    NASA Astrophysics Data System (ADS)

    Abad, E.; Reingruber, J.; Sansom, M. S. P.

    2009-02-01

    We present a novel rate theory based on the notions of splitting probability and mean first passage time to describe single-ion conduction in narrow, effectively one-dimensional membrane channels. In contrast to traditional approaches such as transition state theory or Kramers theory, transitions between different conduction states in our model are governed by rates which depend on the full geometry of the potential of mean force (PMF) resulting from the superposition of an equilibrium free energy profile and a transmembrane potential induced by a nonequilibrium constraint. If a detailed theoretical PMF is available (e.g., from atomistic molecular dynamics simulations), it can be used to compute characteristic conductance curves in the framework of our model, thereby bridging the gap between the atomistic and the mesoscopic level of description. Explicit analytic solutions for the rates, the ion flux, and the associated electric current can be obtained by approximating the actual PMF by a piecewise linear potential. As illustrative examples, we consider both a theoretical and an experimental application of the model. The theoretical example is based on a hypothetical channel with a fully symmetric sawtooth equilibrium PMF. For this system, we explore how changes in the spatial extent of the binding sites affect the rate of transport when a linear voltage ramp is applied. Already for the case of a single binding site, we find that there is an optimum size of the site which maximizes the current through the channel provided that the applied voltage exceeds a threshold value given by the binding energy of the site. The above optimization effect is shown to arise from the complex interplay between the channel structure and the applied electric field, expressed by a nonlinear dependence of the rates with respect to the linear size of the binding site. In studying the properties of current-voltage curves, we find a double crossover between sublinear and superlinear

  11. 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.

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1993-12-01

    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.

  15. Quantifying the Topology and Evolution of a Magnetic Flux Rope Associated with Multi-flare Activities

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Guo, Yang; Ding, M. D.

    2016-06-01

    Magnetic flux ropes (MFRs) play an important role in solar activities. The quantitative assessment of the topology of an MFR and its evolution is crucial for a better understanding of the relationship between the MFR and associated activities. In this paper, we investigate the magnetic field of active region (AR) 12017 from 2014 March 28-29, during which time 12 flares were triggered by intermittent eruptions of a filament (either successful or confined). Using vector magnetic field data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we calculate the magnetic energy and helicity injection in the AR, and extrapolate the 3D magnetic field with a nonlinear force-free field model. From the extrapolations, we find an MFR that is cospatial with the filament. We further determine the configuration of this MFR from the closed quasi-separatrix layer (QSL) around it. Then, we calculate the twist number and the magnetic helicity for the field lines composing the MFR. The results show that the closed QSL structure surrounding the MFR becomes smaller as a consequence of flare occurrence. We also find that the flares in our sample are mainly triggered by kink instability. Moreover, the twist number varies more sensitively than other parameters with the occurrence of flares.

  16. Determination of traces of hetero-charged ions in nonionogenic surface-active substances by ion chromatography

    SciTech Connect

    Klyuchnikova, N.V.; Denisova, L.V.; Balyatinskaya, L.N.

    1995-07-01

    An ion-chromatographic method for the separation and determination of K, Na, Mg, and Al ions, the sum of heavy-metal ions (Fe, Cu, Pb, Cr, Sn), and chloride, sulfate, and orthophosphate ions present in amounts of 10{sup {minus}6} - 10{sup {minus}5}% in 1% solutions of nonionogenic surface-active substances (NSAS) is proposed. We use 10{sup {minus}3} M HCl and 3 x 10{sup {minus}3}M HNO{sub 3} solutions and a 2 x 10{sup {minus}3}M solution as eluents to determine K{sup +}, Na{sup +}, Mg{sup 2+}, Al{sup 3+} cations and ions of heavy and transition metals, respectively. The method proposed is shown to enable reliable evaluation of the purity of NSAS.

  17. Temperature Activated Diffusion of Radicals through Ion Implanted Polymers.

    PubMed

    Wakelin, Edgar A; Davies, Michael J; Bilek, Marcela M M; McKenzie, David R

    2015-12-01

    Plasma immersion ion implantation (PIII) is a promising technique for immobilizing biomolecules on the surface of polymers. Radicals generated in a subsurface layer by PIII treatment diffuse throughout the substrate, forming covalent bonds to molecules when they reach the surface. Understanding and controlling the diffusion of radicals through this layer will enable efficient optimization of this technique. We develop a model based on site to site diffusion according to Fick's second law with temperature activation according to the Arrhenius relation. Using our model, the Arrhenius exponential prefactor (for barrierless diffusion), D0, and activation energy, EA, for a radical to diffuse from one position to another are found to be 3.11 × 10(-17) m(2) s(-1) and 0.31 eV, respectively. The model fits experimental data with a high degree of accuracy and allows for accurate prediction of radical diffusion to the surface. The model makes useful predictions for the lifetime over which the surface is sufficiently active to covalently immobilize biomolecules and it can be used to determine radical fluence during biomolecule incubation for a range of storage and incubation temperatures so facilitating selection of the most appropriate parameters.

  18. INVESTIGATING TWO SUCCESSIVE FLUX ROPE ERUPTIONS IN A SOLAR ACTIVE REGION

    SciTech Connect

    Cheng, X.; Zhang, J.; Ding, M. D.; Guo, Y.; Olmedo, O.; Sun, X. D.; Liu, Y.

    2013-06-01

    We investigate two successive flux rope (FR1 and FR2) eruptions resulting in two coronal mass ejections (CMEs) on 2012 January 23. Both flux ropes (FRs) appeared as an EUV channel structure in the images of high temperature passbands of the Atmospheric Imaging Assembly prior to the CME eruption. Through fitting their height evolution with a function consisting of linear and exponential components, we determine the onset time of the FR impulsive acceleration with high temporal accuracy for the first time. Using this onset time, we divide the evolution of the FRs in the low corona into two phases: a slow rise phase and an impulsive acceleration phase. In the slow rise phase of FR1, the appearance of sporadic EUV and UV brightening and the strong shearing along the polarity inverse line indicates that the quasi-separatrix-layer reconnection likely initiates the slow rise. On the other hand, for FR2, we mainly contribute its slow rise to the FR1 eruption, which partially opened the overlying field and thus decreased the magnetic restriction. At the onset of the impulsive acceleration phase, FR1 (FR2) reaches the critical height of 84.4 ± 11.2 Mm (86.2 ± 13.0 Mm) where the decline of the overlying field with height is fast enough to trigger the torus instability. After a very short interval (∼2 minutes), the flare emission began to enhance. These results reveal the compound activity involving multiple magnetic FRs and further suggest that the ideal torus instability probably plays the essential role of initiating the impulsive acceleration of CMEs.

  19. 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

    2014-01-01

    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

  20. 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

  1. 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.

  2. Evaluation of CETP activity in vivo under non-steady-state conditions: influence of anacetrapib on HDL-TG flux.

    PubMed

    McLaren, David G; Previs, Stephen F; Phair, Robert D; Stout, Steven J; Xie, Dan; Chen, Ying; Salituro, Gino M; Xu, Suoyu S; Castro-Perez, Jose M; Opiteck, Gregory J; Akinsanya, Karen O; Cleary, Michele A; Dansky, Hayes M; Johns, Douglas G; Roddy, Thomas P

    2016-03-01

    Studies in lipoprotein kinetics almost exclusively rely on steady-state approaches to modeling. Herein, we have used a non-steady-state experimental design to examine the role of cholesteryl ester transfer protein (CETP) in mediating HDL-TG flux in vivo in rhesus macaques, and therefore, we developed an alternative strategy to model the data. Two isotopomers ([(2)H11] and [(13)C18]) of oleic acid were administered (orally and intravenously, respectively) to serve as precursors for labeling TGs in apoB-containing lipoproteins. The flux of a specific TG (52:2) from these donor lipoproteins to HDL was used as the measure of CETP activity; calculations are also presented to estimate total HDL-TG flux. Based on our data, we estimate that the peak total postprandial TG flux to HDL via CETP is ∼ 13 mg · h(-1) · kg(-1) and show that this transfer was inhibited by 97% following anacetrapib treatment. Collectively, these data demonstrate that HDL TG flux can be used as a measure of CETP activity in vivo. The fact that the donor lipoproteins can be labeled in situ using well-established stable isotope tracer techniques suggests ways to measure this activity for native lipoproteins in free-living subjects under any physiological conditions.

  3. Enhancement of Ion Activation and Collision-Induced Dissociation by Simultaneous Dipolar Excitation of Ions in x- and y-Directions in a Linear Ion Trap.

    PubMed

    Dang, Qiankun; Xu, Fuxing; Xie, Xiaodong; Xu, Chongsheng; Dai, Xinhua; Fang, Xiang; Ding, Li; Ding, Chuan-Fan

    2015-06-01

    Collision-induced dissociation (CID) in linear ion traps is usually performed by applying a dipolar alternating current (AC) signal to one pair of electrodes, which results in ion excitation mainly in one direction. In this paper, we report simulation and experimental studies of the ion excitation in two coordinate directions by applying identical dipolar AC signals to two pairs of electrodes simultaneously. Theoretical analysis and simulation results demonstrate that the ion kinetic energy is higher than that using the conventional CID method. Experimental results show that more activation energy (as determined by the intensity ratio of the a4/b4 fragments from the CID of protonated leucine enkephalin) can be deposited into parent ions in this method. The dissociation rate constant in this method was about 3.8 times higher than that in the conventional method under the same experimental condition, at the Mathieu parameter qu (where u = x, y) value of 0.25. The ion fragmentation efficiency is also significantly improved. Compared with the conventional method, the smaller qu value can be used in this method to obtain the same internal energy deposited into ions. Consequently, the "low mass cut-off" is redeemed and more fragment ions can be detected. This excitation method can be implemented easily without changing any experimental parameters.

  4. Characteristics of Ion Activation and Collision Induced Dissociation Using Digital Ion Trap Technology.

    PubMed

    Xu, Fuxing; Dang, Qiankun; Dai, Xinhua; Fang, Xiang; Wang, Yuanyuan; Ding, Li; Ding, Chuan-Fan

    2016-08-01

    Collision induced dissociation (CID) is one of the most established techniques for tandem mass spectrometry analysis. The CID of mass selected ion could be realized by ion resonance excitation with a digital rectangular waveform. The method is simple, and highly efficient CID result could be obtained by optimizing the experimental parameters, such as digital waveform voltage, frequency, and q value. In this work, the relationship between ion trapping waveform voltage and frequency at preselected q value, the relationship between waveform frequency and the q value at certain ion trapping voltage for optimum CID efficiency were investigated. Experiment results showed that the max CID efficiency of precursor reserpine ions can be obtained at different trapping waveform voltage and frequency when q and β are different. Based on systematic experimental analysis, the optimum experimental conditions for high CID efficiency can be calculated at any selected β or q. By using digital ion trap technology, the CID process and efficient fragmentation of parent ions can be realized by simply changing the trapping waveform amplitude, frequency, and the β values in the digital ion trap mass spectrometry. The technology and method are simple. It has potential use in ion trap mass spectrometry. Graphical Abstract ᅟ. PMID:27150507

  5. Characteristics of Ion Activation and Collision Induced Dissociation Using Digital Ion Trap Technology

    NASA Astrophysics Data System (ADS)

    Xu, Fuxing; Dang, Qiankun; Dai, Xinhua; Fang, Xiang; Wang, Yuanyuan; Ding, Li; Ding, Chuan-Fan

    2016-08-01

    Collision induced dissociation (CID) is one of the most established techniques for tandem mass spectrometry analysis. The CID of mass selected ion could be realized by ion resonance excitation with a digital rectangular waveform. The method is simple, and highly efficient CID result could be obtained by optimizing the experimental parameters, such as digital waveform voltage, frequency, and q value. In this work, the relationship between ion trapping waveform voltage and frequency at preselected q value, the relationship between waveform frequency and the q value at certain ion trapping voltage for optimum CID efficiency were investigated. Experiment results showed that the max CID efficiency of precursor reserpine ions can be obtained at different trapping waveform voltage and frequency when q and β are different. Based on systematic experimental analysis, the optimum experimental conditions for high CID efficiency can be calculated at any selected β or q. By using digital ion trap technology, the CID process and efficient fragmentation of parent ions can be realized by simply changing the trapping waveform amplitude, frequency, and the β values in the digital ion trap mass spectrometry. The technology and method are simple. It has potential use in ion trap mass spectrometry.

  6. Initiation and Eruption Process of Magnetic Flux Rope from Solar Active Region NOAA 11719 to Earth-directed CME

    NASA Astrophysics Data System (ADS)

    Vemareddy, P.; Zhang, J.

    2014-12-01

    An eruption event launched from the solar active region (AR) NOAA 11719 is investigated based on coronal EUV observations and photospheric magnetic field measurements obtained from the Solar Dynamic Observatory. The AR consists of a filament channel originating from a major sunspot and its south section is associated with an inverse-S sigmoidal system as observed in Atmospheric Imaging Assembly passbands. We regard the sigmoid as the main body of the flux rope (FR). There also exists a twisted flux bundle crossing over this FR. This overlying flux bundle transforms in shape similar to kink-rise evolution, which corresponds with the rise motion of the FR. The emission measure and temperature along the FR exhibits an increasing trend with its rising motion, indicating reconnection in the thinning current sheet underneath the FR. Net magnetic flux of the AR, evaluated at north and south polarities, showed decreasing behavior whereas the net current in these fluxes exhibits an increasing trend. Because the negative (positive) flux has a dominant positive (negative) current, the chirality of AR flux system is likely negative (left handed) in order to be consistent with the chirality of inverse S-sigmoidal FR. This analysis of magnetic fields of the source AR suggests that the cancelling fluxes are prime factors of the monotonous twisting of the FR system, reaching to a critical state to trigger kink instability and rise motion. This rise motion may have led to the onset of the torus instability, resulting in an Earth-directed coronal mass ejection, and the progressive reconnection in the thinning current sheet beneath the rising FR led to the M6.5 flare.

  7. INITIATION AND ERUPTION PROCESS OF MAGNETIC FLUX ROPE FROM SOLAR ACTIVE REGION NOAA 11719 TO EARTH-DIRECTED CME

    SciTech Connect

    Vemareddy, P.; Zhang, J.

    2014-12-20

    An eruption event launched from the solar active region (AR) NOAA 11719 is investigated based on coronal EUV observations and photospheric magnetic field measurements obtained from the Solar Dynamic Observatory. The AR consists of a filament channel originating from a major sunspot and its south section is associated with an inverse-S sigmoidal system as observed in Atmospheric Imaging Assembly passbands. We regard the sigmoid as the main body of the flux rope (FR). There also exists a twisted flux bundle crossing over this FR. This overlying flux bundle transforms in shape similar to kink-rise evolution, which corresponds with the rise motion of the FR. The emission measure and temperature along the FR exhibits an increasing trend with its rising motion, indicating reconnection in the thinning current sheet underneath the FR. Net magnetic flux of the AR, evaluated at north and south polarities, showed decreasing behavior whereas the net current in these fluxes exhibits an increasing trend. Because the negative (positive) flux has a dominant positive (negative) current, the chirality of AR flux system is likely negative (left handed) in order to be consistent with the chirality of inverse S-sigmoidal FR. This analysis of magnetic fields of the source AR suggests that the cancelling fluxes are prime factors of the monotonous twisting of the FR system, reaching to a critical state to trigger kink instability and rise motion. This rise motion may have led to the onset of the torus instability, resulting in an Earth-directed coronal mass ejection, and the progressive reconnection in the thinning current sheet beneath the rising FR led to the M6.5 flare.

  8. Comparative Study of Solar Wind Control on Ion and Electron Fluxes at Geo from Low to Relativistic Energies

    NASA Astrophysics Data System (ADS)

    Boynton, R. J.; Balikhin, M. A.; Billings, S. A.; Amariutei, O. A.

    2012-12-01

    A system identification approach is applied to find the relationship between solar wind parameters and particle measurements at geostationary orbit. The magnetosphere is treated as a black box input-output system, where ACE measurements are used as the inputs and GOES particle data are considered as the outputs. The Error Reduction Ratio is used to assess the significance of various solar wind parameters with respect to the evolution of plasma populations. In the case of electron fluxes, it is shown that the solar wind influence is in accordance with previously obtained results: a major influence of the bulk velocity for lower energies and substantial influence of the solar wind density on the electrons with higher energies. An online real time forecasting tool has been developed as the result to this approach. This tool provides more accurate and reliable forecasts of particle fluxes in various energy ranges.

  9. 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.

  10. Comparisons of Simulated and Observed Stormtime Magnetic Intensities, Ion Plasma Parameters, and ENA Proton Flux in the Ring Current During Storms

    NASA Astrophysics Data System (ADS)

    Chen, M. W.; Lemon, C.; Guild, T. B.; Schulz, M.; Roeder, J. L.; Le, G.; Lui, T.; Goldstein, J.

    2010-12-01

    In this study we compare simulated and observed stormtime magnetic intensities, proton flux spectra and/or ENA fluxes for two storm events to test how well self-consistent simulations can simultaneously reproduce these quantities. We simulate the ring current and plasma sheet using the magnetically and electrostatically self-consistent Rice Convection Model-Equilibrium (RCM-E) [Lemon et al., JGR, 2004] with a time-varying magnetopause driven by upstream solar wind and interplanetary magnetic field (IMF) conditions. Using either in-situ data (e.g., LANL/MPA and SOPA) or the empirical IMF-dependent model of Tsyganenko and Mukai [JGR, 2003], we specify the plasma sheet pressure and density at 10 Earth radii as the plasma boundary location in the RCM-E. We compare the simulated magnetic intensity with the magnetic intensity measured by magnetometers on the GOES satellites at geosynchronous altitude (6.6 Earth radii) and any other available satellite. We simulate a larger (11 August 2000; minimum Dst = -106 nT) and a smaller (6 April 2010; minimum Dst = 73 nT) storm. For the 11 August 2000 storm, we compare simulated and observed proton spectra (LANL/MPA and SOPA and Polar/CAMMICE). For the more recent 6 April 2010 storm we compare simulated and observed proton spectra (THEMIS) and energetic neutral atom (ENA) flux (TWINS). We discuss the response of the ring current magnetic field and ion flux distribution to expansions and compressions of the magnetosphere associated with the dynamic solar wind pressure for these storm events.

  11. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: application to the hydrogen molecule ion.

    PubMed

    Diestler, D J; Kenfack, A; Manz, J; Paulus, B

    2012-03-22

    This article presents the results of the first quantum simulations of the electronic flux density (j(e)) by the "coupled-channels" (CC) theory, the fundamentals of which are presented in the previous article [Diestler, D. J. J. Phys. Chem. A 2012, DOI: 10.1021/jp207843z]. The principal advantage of the CC scheme is that it employs exclusively standard methods of quantum chemistry and quantum dynamics within the framework of the Born-Oppenheimer approximation (BOA). The CC theory goes beyond the BOA in that it yields a nonzero j(e) for electronically adiabatic processes, in contradistinction to the BOA itself, which always gives j(e) = 0. The CC is applied to oriented H(2)(+) vibrating in the electronic ground state ((2)Σ(g)(+)), for which the nuclear and electronic flux densities evolve on a common time scale of about 22 fs per vibrational period. The system is chosen as a touchstone for the CC theory, because it is the only one for which highly accurate flux densities have been calculated numerically without invoking the BOA [Barth et al, Chem. Phys. Lett. 2009, 481, 118]. Good agreement between CC and accurate results supports the CC approach, another advantage of which is that it allows a transparent interpretation of the temporal and spatial properties of j(e).

  12. Zooplankton diel vertical migration and contribution to deep active carbon flux in the NW Mediterranean

    NASA Astrophysics Data System (ADS)

    Isla, Alejandro; Scharek, Renate; Latasa, Mikel

    2015-03-01

    The diel vertical migration (DVM) of zooplankton contributes to the biological pump transporting material from surface to deep waters. We examined the DVM of the zooplankton community in different size fractions (53-200 μm, 200-500 μm, 500-1000 μm, 1000-2000 μm and > 2000 μm) during three cruises carried out in the open NW Mediterranean Sea. We assessed their metabolic rates from empirical published relationships and estimated the active fluxes of dissolved carbon to the mesopelagic zone driven by migrant zooplankton. Within the predominantly oligotrophic Mediterranean Sea, the NW region is one of the most productive ones, with a seasonal cycle characterized by a prominent spring bloom. The study area was visited at three different phases of the seasonal cycle: during the spring bloom, the post-bloom, and strongly stratified oligotrophic conditions. We found seasonal differences in DVM, less evident during the bloom. Changes in DVM intensity were related to the composition of the zooplanktonic assemblage, which also varied between cruises. Euphausiids appeared as the most active migrants in all seasons, and their life cycle conditioned the observed pattern. Immature stages, which are unable to perform large diel vertical movements, dominated during the bloom, in contrast to the higher relative importance of migrating adults in the other two sampling periods. The amount of dissolved carbon exported was determined by the migrant zooplankton biomass, being highest during the post-bloom (2.2 mmol C respired m- 2 d- 1, and up to 3.1 mmol C exported m- 2 d- 1 when DOC release estimations are added). The active transport by diel migrants represented a substantial contribution to total carbon export to deep waters, especially under stratified oligotrophic conditions, revealing the importance of zooplankton in the biological pump operating in the study area.

  13. Significance of active ion transport in transalveolar water absorption: a study on isolated rat lung.

    PubMed

    Basset, G; Crone, C; Saumon, G

    1987-03-01

    1. Experiments were performed on isolated rat lungs perfused with Ringer solutions containing red cells. The goal was to clarify the role of active transport of Na+ for the absorption of fluid across the alveolar membrane, and to characterize active and passive pathways. 2. Partially degassed lungs were filled with 5 ml of an isotonic Ringer solution containing 125I-labelled albumin in order to calculate the fluid movement, and 22Na+ or 36Cl- for measurement of ion fluxes. Passive non-electrolyte permeability was determined in all experiments using [3H]mannitol. 3. The average rate of fluid absorption in phosphate-buffered instillates was 134 nl/s (S.E., 18.5; n = 14). With ouabain (10(-4) M) in the perfusate the fluid absorption rate fell to 57 nl/s (S.E., 8.2; n = 18). Amiloride (10(-3)-10(-4) M) in the instillate reduced the absorption to 75 nl/s (S.E., 8.6; n = 16). These results show that fluid absorption depends on transcellular transport of Na+ and that alveolar epithelial cells have a Na+ entry system in the luminal membrane and a Na+-K+ pump in the abluminal membrane. 4. The transcellular ion transport operates in parallel with a paracellular, passive leak that allows mannitol to pass with a permeability surface area product of 1.2 X 10(-4) ml/s, corresponding to a permeability coefficient of 2.4 X 10(-8) cm/s, assuming an alveolar surface area of 5000 cm2. 5. The passive fluxes of Na+ were 9.4 pmol/(cm2s) (S.E., 1.3; n = 25) in the direction from alveoli to perfusate and 8.0 pmol/(cm2s) (S.E., 0.86; n = 6) from perfusate to plasma. The passive fluxes of Cl- in the two directions were not significantly different either. Thus the transalveolar electrical potential difference is too small to affect ion movements measurably. 6. The passive permeability to Na+ was 6.7 X 10(-8) cm/s and to Cl- was 10.2 X 10(-8) cm/s (alveolar surface area assumed to be 5000 cm2). The ratio of the permeabilities is close to the ratio of the diffusion coefficients in free

  14. Development of a transparent, non-cytotoxic, silver ion-exchanged glass with antimicrobial activity and low ion elution.

    PubMed

    Shim, Gyu-In; Kim, Seong-Hwan; Eom, Hyung-Woo; Kim, Kwang-Mahn; Choi, Se-Young

    2015-05-01

    We investigated the antimicrobial, cytotoxicity, skin irritation, and ion elution behaviors of glass doped with silver ions with respect to its application to electronic equipment such as phones and tablet screens. The microbes tested were Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum. AgNO3 powder was spread on both sides of aluminosilicate glass, and it was heated to 250-280°C for 10min. Under optimized heating conditions (260°C, 10min), the antimicrobial activity of ion-exchanged glass against bacteria and fungi was over 99.9% after 24 weeks. The glass failed to irritate the skin of experimental animals and was considered non-cytotoxic. The maximum amount of Ag ions that were eluted from the ion-exchanged glass into drinking water was measured at 0.037±0.003μgL(-1), an amount which is several orders of magnitude below the standard limit of 0.1mgL(-1) in drinking water. Ag ion-exchanged glass had characteristics suitable for use as a display screen, such as a light transmittance of 90% and a surface roughness of 0.704nm. Our findings suggest that glass doped with silver ions is more hygienic than non-doped glass is, and should be applied to display screens and glassware.

  15. Platelet activating factor raises intracellular calcium ion concentration in macrophages

    PubMed Central

    1986-01-01

    Peritoneal cells from thioglycollate-stimulated mice were allowed to adhere to coverglasses for 2 h to give a dense monolayer of adherent cells greater than 95% of which were macrophages. After incubation with the tetra-acetoxymethyl ester of quin2, coverglasses were rinsed with Ca2+-free saline, oriented at a 45 degree angle in square cuvettes containing a magnetically driven stir bar, and analyzed for changes in quin2 fluorescence in a spectrofluorimeter. Such fluorescence, taken as an indication of intracellular calcium ion concentration ([Ca2+]i), increased as exogenous calcium ion concentration ([Ca2+]o) was raised to 1 mM. At [Ca2+]o approximately equal to 10 microM, [Ca2+]i = 72 +/- 14 nM (n = 26); at [Ca2+]o = 1 mM, [Ca2+]i = 140-220 nM, levels not increased by N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine, a membrane-permeant chelator of heavy metals than can quench quin2. Addition of mouse alpha + beta fibroblast interferon, lipopolysaccharide, thrombin, collagen, vasopressin, ADP, compound 48/80, or U46619 did not change [Ca2+]i. However, addition of platelet activating factor (PAF) (2-20 ng/ml) raised [Ca2+]i by 480 nM within 1 min if [Ca2+]o = 1 mM. In the presence of 5 mM EGTA, PAF raised [Ca2+]i by 25 nM. This suggests that PAF causes influx of exogenous Ca2+, as well as releasing some Ca2+ from intracellular stores. Consistent with these results, when PAF was added to 1 mM Ca2+ in the presence of 100 microM Cd2+ or Mn2+ to block Ca2+ influx, [Ca2+]i increased by only intermediate amounts; at the times of such dampened peak response, [Ca2+]i could be raised within 1 min to normal PAF-stimulated levels by chelation of the exogenous heavy metals with diethylenetriaminepentaacetic acid. Normal PAF responses were observed in the presence of indomethacin. The lowest dose of PAF observed to raise [Ca2+]i was 0.1 ng/ml. Response of [Ca2+]i to 2-20 ng/ml PAF was transient, and second applications had no effect. The PAF response also was seen in

  16. Flux enhancement with powdered activated carbon addition in the membrane anaerobic bioreactor

    SciTech Connect

    Park, H.; Choo, K.H.; Lee, C.H.

    1999-10-01

    The effect of powdered activated carbon (PAC) addition on the performance of a membrane-coupled anaerobic bioreactor (MCAB) was investigated in terms of membrane filterability and treatability through a series of batch and continuous microfiltration (MF) experiments. In both batch and continuous MF of the digestion broth, a flux improvement with PAC addition was achieved, especially when a higher shear rate and/or a higher PAC dose were applied. Both the fouling and cake layer resistances decreased continuously with increasing the PAC dose up to 5 g/L. PAC played an important role in substantially reducing the biomass cake resistance due to its incompressible nature and higher backtransport velocities. PAC might have a scouring effect for removing the deposited biomass cake from the membrane surface while sorbing and/or coagulating dissolved organics and colloidal particles in the broth. The chemical oxygen demand and color in the effluent were much removed with PAC addition, and the system was also more stable against shock loading.

  17. Eruption of the magnetic flux rope in a fast decayed active region

    NASA Astrophysics Data System (ADS)

    Yang, Shangbin

    2012-07-01

    An isolated and fast decayed active region was observed when passing through solar disk. There is only one CME related with it that give us a good opportunity to investigate the whole process of the CME. Filament in this active region rises up rapidly and then hesitates and disintegrates into flare loops. The rising filament from EIT images separates into two parts just before eruption. It is interesting that this filament rises up with positive kink which is opposite to the negative helicity according to the inverse S-shaped X-ray sigmoid and accumulated magnetic helicity. A new filament reforms several hours later after CME and the axis of this new one rotates clockwise about 22° comparing with that of the former one. We also observed a bright transient J-shaped X-ray sigmoid immediately appears after filament eruption. It quickly develops into a soft X-ray cusp and rises up firstly then drops down. We propose that field lines underneath bald-patch sparatrix surface (BPSS) where for the formation of a magnetic tangential discontinuity are locally rooted to the photosphere near the bald-patch (BP) inversion line. Field lines above the surface are detached from the photosphere to form this CME and partially open the field which make the filament loses equilibrium to rise quickly and then be drawn back by the tension force of magnetic field after eruption to form a new filament. Two magnetic cancelation regions have been observed clearly just before filament eruption that reflect the existence of BPs. On the other hand, the values of total magnetic helicity to the corona taken by emergence and differential rotation normalized by the square total magnetic flux implies the possibility of upper bound on the total magnetic helicity that a force-free field can contain.

  18. Flux emergence in the solar active region NOAA 11158: the evolution of net current

    NASA Astrophysics Data System (ADS)

    Vemareddy, Panditi; Venkatakrishnan, Parameswaran; Karthikreddy, Solipuram

    2015-09-01

    We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region (AR) NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality: one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evolution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere.

  19. Anti-biofilm activity of Fe heavy ion irradiated polycarbonate

    NASA Astrophysics Data System (ADS)

    Joshi, R. P.; Hareesh, K.; Bankar, A.; Sanjeev, Ganesh; Asokan, K.; Kanjilal, D.; Dahiwale, S. S.; Bhoraskar, V. N.; Dhole, S. D.

    2016-10-01

    Polycarbonate (PC) polymers were investigated before and after high energy heavy ion irradiation for anti-bacterial properties. These PC films were irradiated by Fe heavy ions with two energies, viz, 60 and 120 MeV, at different fluences in the range from 1 × 1011 ions/cm2 to 1 × 1013 ions/cm2. UV-Visible spectroscopic results showed optical band gap decreased with increase in ion fluences due to chain scission mainly at carbonyl group of PC which is also corroborated by Fourier transform infrared spectroscopic results. X-ray diffractogram results showed decrease in crystallinity of PC after irradiation which leads to decrease in molecular weight. This is confirmed by rheological studies and also by differential scanning calorimetric results. The irradiated PC samples showed modification in their surfaces prevents biofilm formation of human pathogen, Salmonella typhi.

  20. 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

  1. An Ion Chamber Dedicated to Carbon NEXAFS: Removal of High-Order X-Rays and Reliable Flux Measurement

    SciTech Connect

    Fan, L.-J.; Yang, Y.-W.; Lee, Kaidee

    2007-02-02

    The difficulty of performing a reliable carbon NEXAFS measurement for thin films and adsorbate systems has long been recognized. The difficulty is typically related to lower S/B, carbon buildup in beamline optics, dirty mesh, presence of the high-order x-rays, etc. To alleviate the experimental difficulty, we have constructed an intensity-monitoring ion chamber situated between the beamline and sample chamber. The ion chamber is filled with argon up to a working pressure of 10-3 Torr and terminated with 0.1 {mu}m thick Ti foils at both ends. Titanium foils and the filled argon gas effectively remove the high-order x-rays. Consequently, the data are acquired with predominant 1st-order x-rays and thus free of the aforementioned interference, leading to a more reliable data analysis.

  2. Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

    PubMed Central

    Pflieger, Rachel; Chave, Tony; Virot, Matthieu; Nikitenko, Sergey I.

    2014-01-01

    The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects. PMID:24747272

  3. Changing nanoslot ion flux with a dynamic nanocolloid ion-selective filter: Secondary overlimiting currents due to nanocolloid-nanoslot interaction

    NASA Astrophysics Data System (ADS)

    Yossifon, Gilad; Chang, Hsueh-Chia

    2010-06-01

    Nanocolloids trapped at the depleted side (anodic) of a fluidic nanoslot entrance are shown to sensitively regulate dc ion transport through the nanoslot, such that a second limiting-overlimiting transition occurs in its nonlinear current-voltage characteristics. The nanocolloids, brought to the entrance by electro-osmosis, are not stationary but are confined to closed circular and toroidal streamlines, driven by a back-pressure corner vortex and an orthogonal electroconvection vortex instability. The transition from the corner vortex to a complex torus with both vortical motions coincides with the first overlimiting transition, while electrostatic interaction of nanocolloids in these vortices with the nanoslot entrance drives the second limiting transition.

  4. Kinetics of Ion Transport in Perovskite Active Layers and Its Implications for Active Layer Stability.

    PubMed

    Bag, Monojit; Renna, Lawrence A; Adhikari, Ramesh Y; Karak, Supravat; Liu, Feng; Lahti, Paul M; Russell, Thomas P; Tuominen, Mark T; Venkataraman, D

    2015-10-14

    Solar cells fabricated using alkyl ammonium metal halides as light absorbers have the right combination of high power conversion efficiency and ease of fabrication to realize inexpensive but efficient thin film solar cells. However, they degrade under prolonged exposure to sunlight. Herein, we show that this degradation is quasi-reversible, and that it can be greatly lessened by simple modifications of the solar cell operating conditions. We studied perovskite devices using electrochemical impedance spectroscopy (EIS) with methylammonium (MA)-, formamidinium (FA)-, and MA(x)FA(1-x) lead triiodide as active layers. From variable temperature EIS studies, we found that the diffusion coefficient using MA ions was greater than when using FA ions. Structural studies using powder X-ray diffraction (PXRD) show that for MAPbI3 a structural change and lattice expansion occurs at device operating temperatures. On the basis of EIS and PXRD studies, we postulate that in MAPbI3 the predominant mechanism of accelerated device degradation under sunlight involves thermally activated fast ion transport coupled with a lattice-expanding phase transition, both of which are facilitated by absorption of the infrared component of the solar spectrum. Using these findings, we show that the devices show greatly improved operation lifetimes and stability under white-light emitting diodes, or under a solar simulator with an infrared cutoff filter or with cooling. PMID:26414066

  5. Formation of sunspots and active regions through the emergence of magnetic flux generated in a solar convective dynamo

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Rempel, Matthias D.; Fan, Yuhong

    2016-05-01

    We present a realistic numerical model of sunspot and active region formation through the emergence of flux tubes generated in a solar convective dynamo. The magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation are used as a time-dependent bottom boundary to drive the near surface layer radiation MHD simulations of magneto-convection and flux emergence with the MURaM code. The latter code simulates the emergence of the flux tubes through the upper most layer of the convection zone to the photosphere.The emerging flux tubes interact with the convection and break into small scale magnetic elements that further rise to the photosphere. At the photosphere, several bipolar pairs of sunspots are formed through the coalescence of the small scale magnetic elements. The sunspot pairs in the simulation successfully reproduce the fundamental observed properties of solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of the bipolar pairs. These asymmetries come most probably from the intrinsic asymmetries in the emerging fields imposed at the bottom boundary, where the horizontal fields are already tilted and the leading sides of the emerging flux tubes are usually up against the downdraft lanes of the giant cells. It is also found that penumbrae with numerous filamentary structures form in regions of strong horizontal magnetic fields that naturally comes from the ongoing flux emergence. In contrast to previous models, the penumbrae and umbrae are divided by very sharp boarders, which is highly consistent with observations.

  6. Design of an actively cooled plate calorimeter for the investigation of pool fire heat fluxes

    SciTech Connect

    Koski, J. A.; Keltner, N. R.; Nicolette, V. F.; Wix, S. D.

    1992-01-01

    For final qualification of shipping containers for transport of hazardous materials, thermal testing in accordance with regulations such as 10CFR71 must be completed. Such tests typically consist of 30 minute exposures with the container fully engulfed in flames from a large, open pool of JP4 jet engine fuel. Despite careful engineering analyses of the container, testing often reveals design problems that must be solved by modification and expensive retesting of the container. One source of this problem is the wide variation in surface heat flux to the container that occurs in pool fires. Average heat fluxes of 50 to 60 kW/m{sup 2} are typical and close the values implied by the radiation model in 10CFR71, but peak fluxes up to 150 kW/m{sup 2} are routinely observed in fires. Heat fluxes in pool fires have been shown to be a function of surface temperature of the container, height above the pool, surface orientation, wind, and other variables. If local variations in the surface heat flux to the container could be better predicted, design analyses would become more accurate, and fewer problems will be uncovered during testing. The objective of the calorimeter design described in this paper is to measure accurately pool fire heat fluxes under controlled conditions, and to provide data for calibration of improved analytical models of local flame-surface interactions.

  7. Gravity wave activity in the thermosphere inferred from GOCE data, and its dependence on solar flux conditions.

    NASA Astrophysics Data System (ADS)

    Garcia, Raphael F.; Bruinsma, Sean; Doornbos, Eelco; Massarweh, Lotfi

    2016-04-01

    This study is focused on the effect of solar flux conditions on the dynamics of Gravity Waves (GW) in thermosphere. Air density and cross-wind in situ estimates from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometers are analyzed for the whole mission duration. The analysis was performed in the Fourier spectral domain averaging spectral results over periods of 2 months close to solstices. First the Amplitude Spectral Density (ASD) and the Magnitude Squared Coherence (MSC) of physical parameters are linked to local gravity waves. Then, a new GW marker (called Cf3) was introduced here to constrain GWs activity under Low, Medium and High solar flux conditions, showing a clear solar dumping effect on GW activity. Most of GW signal has been found in a spectral range above 8 mHz in GOCE data, meaning a maximum horizontal wavelength around 1000 km. The level GW activity at GOCE altitude is strongly decreasing with increasing solar flux. Furthermore, a shift in the dominant frequency with solar flux conditions has been noted, leading to a larger horizontal wavelengths (from 200 to 500 km) during high solar flux conditions. The influence of correlated error sources, between air density and cross-winds, is discussed. Consistency of the spectral domain results has been verified in time-domain with a global mapping of high frequency perturbations along GOCE orbit. This analysis shows a clear dependence with geomagnetic latitude with strong perturbations at magnetic poles, and an extension to lower latitudes favoured by low solar activity conditions. Various possible causes of this spatial trend are discussed.

  8. Gas flux measurements of episodic bimodal eruptive activity at Karymsky volcano (Kamchatka, Russia)

    NASA Astrophysics Data System (ADS)

    Arellano, S.; Galle, B.; Melnikov, D.

    2012-04-01

    Volcanoes of intermediate magmatic composition commonly exhibit episodes of intermittent gas and ash emission of variable duration. Due to the multiple conditions present at each system, different mechanisms have been proposed to account for the observed activity, and without key measurements at hand, a definite understanding of the situation might not be singled out. Karymsky, the most active volcano of Central Kamchatka, has presented a remarkably stable pattern of bimodal eruption since a few weeks after its violent reactivation in 1996. Periods of quasi-periodic explosive emissions with typical recurrence intervals of 3-10 min are alternated with episodes of semi-continuous discharge which intensity has a typical modulation at a frequency of 1 Hz. Geophysical studies at Karymsky have identified the main visual, seismic and acoustic features of these two eruption modalities. From these observations, the time scales of the processes have been defined and relevant models have been formulated, according to which the two modes are controlled by the rheological properties of an intruding gas-saturated magma batch and a shallow gas-depleted magma plug. Explosions are explained as the consequence of the formation of temporary sealing, overpressure buildup and vent clearance. Clearly, direct measurements of the gas emission rate are the key parameter to test such models. In this work, we report on the results of a field campaign for SO2 gas measurements carried out at Karymsky during 10-14 September 2011. We deployed 2 NOVAC-type, scanning DOAS systems as well as 1 rapid wide-Field of View mini-DOAS plume tracker. With this setup, we derived time-resolved SO2 flux, plume height, direction and speed, and detected pulses of increasing emission with high temporal resolution. We observed phases of explosive and quiescent degassing with variable amounts of ash emission and detected intensity changes of the associated acoustic signals. The repose time intervals between these

  9. How high do ion fluxes go? A re-evaluation of the two-mechanism model of K(+) transport in plant roots.

    PubMed

    Coskun, Devrim; Britto, Dev T; Kochian, Leon V; Kronzucker, Herbert J

    2016-02-01

    Potassium (K(+)) acquisition in roots is generally described by a two-mechanism model, consisting of a saturable, high-affinity transport system (HATS) operating via H(+)/K(+) symport at low (<1mM) external [K(+)] ([K(+)]ext), and a linear, low-affinity system (LATS) operating via ion channels at high (>1mM) [K(+)]ext. Radiotracer measurements in the LATS range indicate that the linear rise in influx continues well beyond nutritionally relevant concentrations (>10mM), suggesting K(+) transport may be pushed to extraordinary, and seemingly limitless, capacity. Here, we assess this rise, asking whether LATS measurements faithfully report transmembrane fluxes. Using (42)K(+)-isotope and electrophysiological methods in barley, we show that this flux is part of a K(+)-transport cycle through the apoplast, and masks a genuine plasma-membrane influx that displays Michaelis-Menten kinetics. Rapid apoplastic cycling of K(+) is corroborated by an absence of transmembrane (42)K(+) efflux above 1mM, and by the efflux kinetics of PTS, an apoplastic tracer. A linear apoplastic influx, masking a saturating transmembrane influx, was also found in Arabidopsis mutants lacking the K(+) transporters AtHAK5 and AtAKT1. Our work significantly revises the model of K(+) transport by demonstrating a surprisingly modest upper limit for plasma-membrane influx, and offers insight into sodium transport under salt stress. PMID:26795154

  10. Identification of active elementary flux modes in mitochondria using selectively permeabilized CHO cells.

    PubMed

    Nicolae, Averina; Wahrheit, Judith; Nonnenmacher, Yannic; Weyler, Christian; Heinzle, Elmar

    2015-11-01

    Metabolic compartmentation is a key feature of mammalian cells. Mitochondria are the powerhouse of eukaryotic cells, responsible for respiration and the TCA cycle. We accessed the mitochondrial metabolism of the economically important Chinese hamster ovary (CHO) cells using selective permeabilization. We tested key substrates without and with addition of ADP. Based on quantified uptake and production rates, we could determine the contribution of different elementary flux modes to the metabolism of a substrate or substrate combination. ADP stimulated the uptake of most metabolites, directly by serving as substrate for the respiratory chain, thus removing the inhibitory effect of NADH, or as allosteric effector. Addition of ADP favored substrate metabolization to CO2 and did not enhance the production of other metabolites. The controlling effect of ADP was more pronounced when we supplied metabolites to the first part of the TCA cycle: pyruvate, citrate, α-ketoglutarate and glutamine. In the second part of the TCA cycle, the rates were primarily controlled by the concentrations of C4-dicarboxylates. Without ADP addition, the activity of the pyruvate carboxylase-malate dehydrogenase-malic enzyme cycle consumed the ATP produced by oxidative phosphorylation, preventing its accumulation and maintaining metabolic steady state conditions. Aspartate was taken up only in combination with pyruvate, whose uptake also increased, a fact explained by complex regulatory effects. Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase were identified as the key regulators of the TCA cycle, confirming existent knowledge from other cells. We have shown that selectively permeabilized cells combined with elementary mode analysis allow in-depth studying of the mitochondrial metabolism and regulation. PMID:26417715

  11. Identification of active elementary flux modes in mitochondria using selectively permeabilized CHO cells.

    PubMed

    Nicolae, Averina; Wahrheit, Judith; Nonnenmacher, Yannic; Weyler, Christian; Heinzle, Elmar

    2015-11-01

    Metabolic compartmentation is a key feature of mammalian cells. Mitochondria are the powerhouse of eukaryotic cells, responsible for respiration and the TCA cycle. We accessed the mitochondrial metabolism of the economically important Chinese hamster ovary (CHO) cells using selective permeabilization. We tested key substrates without and with addition of ADP. Based on quantified uptake and production rates, we could determine the contribution of different elementary flux modes to the metabolism of a substrate or substrate combination. ADP stimulated the uptake of most metabolites, directly by serving as substrate for the respiratory chain, thus removing the inhibitory effect of NADH, or as allosteric effector. Addition of ADP favored substrate metabolization to CO2 and did not enhance the production of other metabolites. The controlling effect of ADP was more pronounced when we supplied metabolites to the first part of the TCA cycle: pyruvate, citrate, α-ketoglutarate and glutamine. In the second part of the TCA cycle, the rates were primarily controlled by the concentrations of C4-dicarboxylates. Without ADP addition, the activity of the pyruvate carboxylase-malate dehydrogenase-malic enzyme cycle consumed the ATP produced by oxidative phosphorylation, preventing its accumulation and maintaining metabolic steady state conditions. Aspartate was taken up only in combination with pyruvate, whose uptake also increased, a fact explained by complex regulatory effects. Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase were identified as the key regulators of the TCA cycle, confirming existent knowledge from other cells. We have shown that selectively permeabilized cells combined with elementary mode analysis allow in-depth studying of the mitochondrial metabolism and regulation.

  12. The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study

    NASA Astrophysics Data System (ADS)

    Jones, Morgan T.; Hembury, Deborah J.; Palmer, Martin R.; Tonge, Bill; Darling, W. George; Loughlin, Susan C.

    2011-04-01

    The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO2 emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO2 due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO2 is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island's inhabitants.

  13. Laser ion source activities at Brookhaven National Laboratory

    DOE PAGES

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010more » of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.« less

  14. Laser ion source activities at Brookhaven National Laboratory

    SciTech Connect

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010 of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.

  15. Vacuum ARC ion sources - activities & developments at LBL

    SciTech Connect

    Brown, I.

    1996-08-01

    The author describes work at LBL on the development and application of vacuum arc ion sources. Work has been done on vacuum spark sources - to produce very high charge states, studies of high charge states in magnetic field, hybrid ion source operation on metal/gas plasma, multipole operation, work on MEVVA V for implantation applications, development of broad beam sources, and removal of particles from the output of the source.

  16. 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. PMID:23590290

  17. Pathway Confirmation and Flux Analysis of Central Metabolic Pathways in Desulfovibrio vulgaris Hildenborough using Gas Chromatography-Mass Spectrometry and Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry▿ †

    PubMed Central

    Tang, Yinjie; Pingitore, Francesco; Mukhopadhyay, Aindrila; Phan, Richard; Hazen, Terry C.; Keasling, Jay D.

    2007-01-01

    Flux distribution in central metabolic pathways of Desulfovibrio vulgaris Hildenborough was examined using 13C tracer experiments. Consistent with the current genome annotation and independent evidence from enzyme activity assays, the isotopomer results from both gas chromatography-mass spectrometry (GC-MS) and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) indicate the lack of an oxidatively functional tricarboxylic acid (TCA) cycle and an incomplete pentose phosphate pathway. Results from this study suggest that fluxes through both pathways are limited to biosynthesis. The data also indicate that >80% of the lactate was converted to acetate and that the reactions involved are the primary route of energy production [NAD(P)H and ATP production]. Independently of the TCA cycle, direct cleavage of acetyl coenzyme A to CO and 5,10-methyl tetrahydrofuran also leads to production of NADH and ATP. Although the genome annotation implicates a ferredoxin-dependent oxoglutarate synthase, isotopic evidence does not support flux through this reaction in either the oxidative or the reductive mode; therefore, the TCA cycle is incomplete. FT-ICR MS was used to locate the labeled carbon distribution in aspartate and glutamate and confirmed the presence of an atypical enzyme for citrate formation suggested in previous reports [the citrate synthesized by this enzyme is the isotopic antipode of the citrate synthesized by the (S)-citrate synthase]. These findings enable a better understanding of the relation between genome annotation and actual metabolic pathways in D. vulgaris and also demonstrate that FT-ICR MS is a powerful tool for isotopomer analysis, overcoming the problems with both GC-MS and nuclear magnetic resonance spectroscopy. PMID:17114264

  18. River solute fluxes reflecting active hydrothermal chemical weathering of the Yellowstone Plateau Volcanic Field, USA

    USGS Publications Warehouse

    Hurwitz, S.; Evans, William C.; Lowenstern, J. B.

    2010-01-01

    In the past few decades numerous studies have quantified the load of dissolved solids in large rivers to determine chemical weathering rates in orogenic belts and volcanic areas, mainly motivated by the notion that over timescales greater than ~100kyr, silicate hydrolysis may be the dominant sink for atmospheric CO2, thus creating a feedback between climate and weathering. Here, we report the results of a detailed study during water year 2007 (October 1, 2006 to September 30, 2007) in the major rivers of the Yellowstone Plateau Volcanic Field (YPVF) which hosts Earth's largest "restless" caldera and over 10,000 thermal features. The chemical compositions of rivers that drain thermal areas in the YPVF differ significantly from the compositions of rivers that drain non-thermal areas. There are large seasonal variations in river chemistry and solute flux, which increases with increasing water discharge. The river chemistry and discharge data collected periodically over an entire year allow us to constrain the annual solute fluxes and to distinguish between low-temperature weathering and hydrothermal flux components. The TDS flux from Yellowstone Caldera in water year 2007 was 93t/km2/year. Extensive magma degassing and hydrothermal interaction with rocks accounts for at least 82% of this TDS flux, 83% of the cation flux and 72% of the HCO3- flux. The low-temperature chemical weathering rate (17t/km2/year), calculated on the assumption that all the Cl- is of thermal origin, could include a component from low-temperature hydrolysis reactions induced by CO2 ascending from depth rather than by atmospheric CO2. Although this uncertainty remains, the calculated low-temperature weathering rate of the young rhyolitic rocks in the Yellowstone Caldera is comparable to the world average of large watersheds that drain also more soluble carbonates and evaporates but is slightly lower than calculated rates in other, less-silicic volcanic regions. Long-term average fluxes at

  19. Evidence of flux rope and sigmoid in Active Regions prior eruptions

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho; Bommier, Veronique; Dudik, Jaroslav; Gilchrist, Stuart; Zhao, Jie

    2016-07-01

    In the solar corona, the magnetic field is dominant, and the current density vector is nearly aligned with the magnetic field lines for strong and stressed field regions. Stressed and highly twisted flux ropes are at the origin of eruptive events such as flares and coronal mass ejections, which inject material into the interplanetary medium. The standard three dimensional (3D) flare model predicts the complex evolution of flare loops and the flux rope before the eruption. Flux ropes are not directly observed in the corona, however it has started to be possible to detect their footprints in the photosphere. Recent high spatial and temporal resolution spectro-polarimeters have allowed us to compute the photospheric electric currents and follow their evolution. Characteristics pattern like J-shaped ribbons indicate the presence of a flux rope before the flare. The results confirm the predictions of the 3D MHD standard model of eruptive flares. It is interesting to compare the magnetic helicity of the ejected flux rope with the in situ measurements of the corresponding ICME at L1. We will show some examples (February 15 2011, July 12 2012, Sept 10 2014).

  20. Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes.

    PubMed

    Castaldi, S; Riondino, M; Baronti, S; Esposito, F R; Marzaioli, R; Rutigliano, F A; Vaccari, F P; Miglietta, F

    2011-11-01

    Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6 kg m(-2)) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3 months and 14 months after char addition. N(2)O, CH(4) and CO(2) fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3 months, but after 14 months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N(2)O fluxes were from 26% to 79% lower than N(2)O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N(2)O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH(4) fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14 months after biochar incorporation.

  1. 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.

  2. 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

  3. A minimum mechanism for Na+-Ca++ exchange: net and unidirectional Ca++ fluxes as functions of ion composition and membrane potential.

    PubMed

    Johnson, E A; Kootsey, J M

    1985-01-01

    Both simultaneous and consecutive mechanisms for Na+-Ca++ exchange are formulated and the associated systems of steady-state equations are solved numerically, and the net and unidirectional Ca++ fluxes computed for a variety of ionic and electrical boundary conditions. A simultaneous mechanism is shown to be consistent with a broad range of experimental data from the squid giant axon, cardiac muscle and isolated sarcolemmal vesicles. In this mechanism, random binding of three Na+ ions and one Ca++ on apposing sides of a membrane are required before a conformational change can occur, translocating the binding sites to the opposite sides of the membranes. A similar (return) translocation step is also permitted if all the sites are empty. None of the other states of binding can undergo such translocating conformational changes. The resulting reaction scheme has 22 reaction steps involving 16 ion-binding intermediates. The voltage dependence of the equilibrium constant for the overall reaction, required by the 3:1 Na+: Ca++ stoichiometry was obtained by multiplying and dividing, respectively, the forward and reverse rate constants of one of the translocational steps by exp(-FV/2RT). With reasonable values for the membrane density of the enzyme (approximately 120 sites micron 2) and an upper limit for the rate constants of both translocational steps of 10(5) . sec-1, satisfactory behavior was obtainable with identical binding constants for Ca++ on the two sides of the membrane (10(6) M-1), similar symmetry also being assumed for the Na+ binding constant (12 to 60 M-1). Introduction of order into the ion-binding process eliminates behavior that is consistent with experimental findings.

  4. Gas flux dynamics in high arctic permafrost polygon and ice wedge active layer soil; microbial feedback implications

    NASA Astrophysics Data System (ADS)

    Mykytczuk, N. C.; Stackhouse, B. T.; Bennett, P.; Lamarche-Gagnon, G.; Hettich, R. L.; Phelps, T. J.; Layton, A.; Pfiffner, S. M.; Allan, J.; Vishnivetskaya, T. A.; Chourey, K.; Whyte, L.; Onstott, T. C.

    2011-12-01

    Temperatures in the Arctic may increase 4-8°C over the next 100 years, thereby increasing the depth of the active layer (AL) and thawing the underlying permafrost, with ice wedges in particular acting as an early indicator, a bellwether, for changing permafrost. Although data on CO2 and CH4 fluxes have been studied along with microbial diversity of AL and permafrost environments, the relationship between methanogenic, methanotrophic and heterotrophic in situ activities within the AL and CO2 and CH4 fluxes as a function of temperature has not been delineated. Defining these relationships is critical for accurately modeling the extent and rate of + / - feedback in global climate models. Initial field investigations of diurnal CO2 and CH4 flux from permafrost and ice-wedge AL soils were conducted during July on Axel Heiberg Island in the Canadian high arctic. The AL soils (68-69 cm depth) were completely thawed while ambient air temperatures were between 9 and 27°C. The AL soils above the ice wedges had a higher water content and finer texture than the polygon AL soils. Diurnal patterns using in situ flux chambers and a Picarro C-13 CO2 cavity ring-down spectrometer recorded net outward flux of CO2 (3.2 to 8.8 g/m2/day) and consumption of atmospheric CH4 (-2.2 mg/m2/day) from the AL surfaces. Gas flux from the ice wedge soil surface were in a similar range as the polygon soil surface, having slightly higher maximal flux of CO2 (10.4 g/m2/day) and net efflux of CH4 (-2.2 to 14 mg/m2/day). Using a vertical probe, gas flux below the surface measured higher amounts of CO2 with increasing depth ranging from 10.4 to 21.4 g/m2/day in the polygon soils vs. 10 to 28.5 g/m2/day in the ice wedge soils. Through the same profile, the CH4 concentration decreased from 0.59 ppmv to < 0.1 ppmv within 30 cm of the surface in the ice wedge and from 1.1 to 0.54 ppmv at the base of the polygon AL. The δ13C of the CO2 efflux from the surface were consistent with microbial activity

  5. Ion Channels in Regulation of Neuronal Regenerative Activities

    PubMed Central

    Chen, Dongdong; Yu, Shan Ping; Wei, Ling

    2014-01-01

    The regeneration of the nervous system is achieved by the regrowth of damaged neuronal axons, the restoration of damaged nerve cells, and the generation of new neurons to replace those that have been lost. In the central nervous system the regenerative ability is limited by various factors including damaged oligodendrocytes that are essential for neuronal axon myelination, an emerging glial scar, and secondary injury in the surrounding areas. Stem cell transplantation therapy has been shown to be a promising approach to treating neurodegenerative diseases because of the regenerative capability of stem cells that secrete neurotrophic factors and give rise to differentiated progeny. However, some issues of stem cell transplantation, such as survival, homing, and efficiency of neural differentiation after transplantation, still need to be improved. Ion channels allow for the exchange of ions between the intra- and extracellular spaces or between the cytoplasm and organelles. These ion channels maintain the ion homeostasis in the brain and play a key role in regulating the physiological function of the nervous system and allowing the processing of neuronal signals. In seeking a potential strategy to enhance the efficacy of stem cell therapy in neurological and neurodegenerative diseases, this review briefly summarizes the roles of ion channels in cell proliferation, differentiation, migration, chemotropic axon guidance of growth cones and axon outgrowth after injury. PMID:24399572

  6. 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.

  7. Thermally Activated Energy and Flux-flow Hall Effect of Fe1+y(Te1+xSx)z

    SciTech Connect

    Petrovic, C.; Lei, H.; Hu, R.; Choi, E.S.

    2010-10-19

    Thermally activated flux flow (TAFF) and flux-flow Hall effect (FFHE) of Fe(Te,S) single crystal in the mixed state are studied in magnetic fields up to 35 T. Thermally activated energy (TAE) is analyzed using conventional Arrhenius relation and modified TAFF theory which is closer to experimental results. The results indicate that there is a crossover from single-vortex pinning region to collective creep pinning region with increasing magnetic field. The temperature dependence of TAE is different for H {parallel} ab and H {parallel} c. On the other hand, the analysis of FFHE in the mixed state indicates that there is no Hall sign reversal. We also observe scaling behavior |{rho}{sub xy}(H)|=A{rho}{sub xx}(H){sup {beta}}.

  8. Ferroelectric active models of ion channels in biomembranes.

    PubMed

    Bystrov, V S; Lakhno, V D; Molchanov, M

    1994-06-21

    Ferroactive models of ion channels in the theory of biological membranes are presented. The main equations are derived and their possible solutions are shown. The estimates of some experimentally measured parameters are given. Possible physical consequences of the suggested models are listed and the possibility of their experimental finding is discussed. The functioning of the biomembrane's ion channel is qualitatively described on the basis of the suggested ferroactive models. The main directions and prospects for development of the ferroactive approach to the theory of biological membranes and their structures are indicated.

  9. Nasal Potential Difference Measurements to Assess CFTR Ion Channel Activity

    PubMed Central

    Clancy, Jean-Paul; Wilschanski, Michael

    2013-01-01

    Nasal potential difference is used to measure the voltage across the nasal epithelium, which results from transepithelial ion transport and reflects in part CFTR function. The electrophysiologic abnormality in cystic fibrosis was first described 30 years ago and correlates with features of the CF phenotype. NPD is an important in vivo research and diagnostic tool, and is used to assess the efficacy of new treatments such as gene therapy and ion transport modulators. This chapter will elaborate on the electrophysiological principles behind the test, the equipment required, the methods, and the analysis of the data. PMID:21594779

  10. Fluxes of low-energy particles in quiet periods of solar activity and the MgII index

    NASA Astrophysics Data System (ADS)

    Zeldovich, M. A.; Logachev, Yu. I.; Kecskemety, K.; Surova, G. M.

    2009-10-01

    Low fluxes of protons with energies 0.3-10 MeV were studied during 21-23 solar cycles as a function of the MgII index using the data of the instruments CPME, EIS ( IMP8), and EPHIN ( SOHO). It has been shown that a) during quiet time of solar activity the fluxes of protons (background protons) have a positive correlation with the MgII index value throughout the solar cycle, b) specific features of variations of the MgII index during the solar minima of 1986-1987 and 1996-1997 can be considered, as well as variations of background fluxes of low energy charged particles, to be manifestations of the 22-year magnetic cycle of the Sun, and c) periods of the lowest value of the MgII index are also characterized by the smaller values of the ratio of intensities of protons and helium nuclei than in other quiet periods. A hypothesis is put forward that acceleration in a multitude of weak solar flares is one of the sources of background fluxes of low energy particles in the interplanetary space.

  11. Fitting Transporter Activities to Cellular Drug Concentrations and Fluxes: Why the Bumblebee Can Fly.

    PubMed

    Mendes, Pedro; Oliver, Stephen G; Kell, Douglas B

    2015-11-01

    A recent paper in this journal argued that reported expression levels, kcat and Km for drug transporters could be used to estimate the likelihood that drug fluxes through Caco-2 cells could be accounted for solely by protein transporters. It was in fact concluded that if five such transporters contributed 'randomly' they could account for the flux of the most permeable drug tested (verapamil) 35% of the time. However, the values of permeability cited for verapamil were unusually high; this and other drugs have much lower permeabilities. Even for the claimed permeabilities, we found that a single 'random' transporter could account for the flux 42% of the time, and that two transporters can achieve 10·10(-6)cm·s(-1) 90% of the time. Parameter optimisation methods show that even a single transporter can account for Caco-2 drug uptake of the most permeable drug. Overall, the proposal that 'phospholipid bilayer diffusion (of drugs) is negligible' is not disproved by the calculations of 'likely' transporter-based fluxes.

  12. Fitting Transporter Activities to Cellular Drug Concentrations and Fluxes: Why the Bumblebee Can Fly

    PubMed Central

    Mendes, Pedro; Oliver, Stephen G.; Kell, Douglas B.

    2015-01-01

    A recent paper in this journal argued that reported expression levels, kcat and Km for drug transporters could be used to estimate the likelihood that drug fluxes through Caco-2 cells could be accounted for solely by protein transporters. It was in fact concluded that if five such transporters contributed ‘randomly’ they could account for the flux of the most permeable drug tested (verapamil) 35% of the time. However, the values of permeability cited for verapamil were unusually high; this and other drugs have much lower permeabilities. Even for the claimed permeabilities, we found that a single ‘random’ transporter could account for the flux 42% of the time, and that two transporters can achieve 10 · 10−6 cm·s−1 90% of the time. Parameter optimisation methods show that even a single transporter can account for Caco-2 drug uptake of the most permeable drug. Overall, the proposal that ‘phospholipid bilayer diffusion (of drugs) is negligible’ is not disproved by the calculations of ‘likely’ transporter-based fluxes. PMID:26538313

  13. Activation of autophagy flux by metformin downregulates cellular FLICE–like inhibitory protein and enhances TRAIL- induced apoptosis

    PubMed Central

    Nazim, Uddin MD; Moon, Ji-Hong; Lee, Ju-Hee; Lee, You-Jin; Seol, Jae-Won; Eo, Seong-Kug; Lee, John-Hwa; Park, Sang-Youel

    2016-01-01

    Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily. TRAIL is regarded as one of the most promising anticancer agents, because it can destruct cancer cells without showing any toxicity to normal cells. Metformin is an anti-diabetic drug with anticancer activity by inhibiting tumor cell proliferation. In this study, we demonstrated that metformin could induce TRAIL-mediated apoptotic cell death in TRAIL-resistant human lung adenocarcinoma A549 cells. Pretreatment of metformindownregulation of c-FLIP and markedly enhanced TRAIL-induced tumor cell death by dose-dependent manner. Treatment with metformin resulted in slight increase in the accumulation of microtubule-associated protein light chain LC3-II and significantly decreased the p62 protein levels by dose-dependent manner indicated that metformin induced autophagy flux activation in the lung cancer cells. Inhibition of autophagy flux using a specific inhibitor and genetically modified ATG5 siRNA blocked the metformin-mediated enhancing effect of TRAIL. These data demonstrated that downregulation of c-FLIP by metformin enhanced TRAIL-induced tumor cell death via activating autophagy flux in TRAIL-resistant lung cancer cells and also suggest that metformin may be a successful combination therapeutic strategy with TRAIL in TRAIL-resistant cancer cells including lung adenocarcinoma cells. PMID:26992204

  14. Effect of active-ion concentration on holmium fibre laser efficiency

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-08-03

    We have measured the fraction of holmium ions that relax nonradiatively to the ground level as a result of interaction at a metastable level in optical fibres with a silica-based core doped with holmium ions to 2 x 10{sup 19} - 2 x 10{sup 20} cm{sup -3}. The percentage of such ions has been shown to depend on the absolute active-ion concentration. The fibres have been used to make a number of 2.05-{mu}m lasers, and their slope efficiency has been measured. The laser efficiency decreases with increasing holmium concentration in the fibres (lasers)

  15. Resonance activation and collision-induced-dissociation of ions using rectangular wave dipolar potentials in a digital ion trap mass spectrometer.

    PubMed

    Xu, Fuxing; Wang, Liang; Dai, Xinhua; Fang, Xiang; Ding, Chuan-Fan

    2014-04-01

    Collision-induced dissociation (CID) of ions by resonance activation in a quadrupole ion trap is usually accomplished by resonance exciting the ions to higher kinetic energy, whereby the high kinetic energy ions collide with a bath gas, such as helium or argon, inside the trap and dissociate to fragments. A new ion activation method using a well-defined rectangular wave dipolar potential formed by dividing down the trapping rectangular waveform is developed and examined herein. The mass-selected parent ions are resonance excited to high kinetic energies by simply changing the frequency of the rectangular wave dipolar potential and dissociation proceeds. A relationship between the ion mass and the activation waveform frequency is also identified and described. This highly efficient (CID) procedure can be realized by simply changing the waveform frequency of the dipolar potential, which could certainly simplify tandem mass spectrometry analysis methods.

  16. Azamacrocycle activated quantum dot for zinc ion detection.

    PubMed

    Ruedas-Rama, Maria Jose; Hall, Elizabeth A H

    2008-11-01

    A new fluorescent nanosensor family for Zn (2+) determination is reported based on azamacrocycle derivatization of CdSe/ZnS core/shell quantum dot nanoparticles. They are the first zinc ion sensors using QD nanoparticles in a host-guest and receptor-fluorophore system. Three azamacrocycles are demonstrated as receptors: TACN (1,4,7-triazacyclononane), cyclen (1,4,7,10-tetraazacyclododecane), and cyclam (1,4,8,11-tetraazacyclotetradecane). Azamacrocycles conjugated to QDs via an amide link interact directly with one of the photoinduced QD charge carriers, probably transferring the hole in the QD to the azamacrocycle, thereby disrupting the radiative recombination process. When zinc ion enters the aza-crown, the lone pair electrons of the nitrogen atom become involved in the coordination and the energy level is no longer available for the hole-transfer mechanism, switching on the QD emission and a dramatic increase of the fluorescence intensity results, allowing the detection of low concentrations of zinc ions. Using this operating principle, three zinc ion sensors based on CdSe-ZnS core-shell QD nanoparticles showed a very good linearity in the range 5-500 microM, with detection limits lower than 2.4 microM and RSDs approximately 3% ( n = 10). In addition, the versatility of the sensors was demonstrated, since different sizes (and colors) of QDs can be employed and will respond to zinc in a similar way. In a study of interferences, the zinc-sensitive QDs showed good selectivity in comparison with other physiologically important cations and other transition metals tested. The results from fetal calf serum and samples mimicking physiological conditions suggested very good applicability in the determination of zinc ion in physiological samples.

  17. Plasma effects of active ion beam injections in the ionosphere at rocket altitudes

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Cahill, L. J., Jr.; Kintner, P. M.; Moore, T. E.; Pollock, C. J.

    1992-01-01

    Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.

  18. 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

  19. Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and major and trace ions in the Fraser River, Canada

    NASA Astrophysics Data System (ADS)

    Voss, B. M.; Peucker-Ehrenbrink, B.; Eglinton, T. I.; Spencer, R. G. M.; Bulygina, E.; Galy, V.; Lamborg, C. H.; Ganguli, P. M.; Montluçon, D. B.; Marsh, S.; Gillies, S. L.; Fanslau, J.; Epp, A.; Luymes, R.

    2015-10-01

    Rapid changes in the volume and sources of discharge during the spring freshet lead to pronounced variations in biogeochemical properties in snowmelt-dominated river basins. We used daily sampling during the onset of the freshet in the Fraser River (southwestern Canada) in 2013 to identify rapid changes in the flux and composition of dissolved material, with a focus on dissolved organic matter (DOM). Previous time series sampling (at twice monthly frequency) of dissolved inorganic species in the Fraser River has revealed smooth seasonal transitions in concentrations of major ions and tracers of water and dissolved load sources between freshet and base flow periods. In contrast, daily sampling reveals a significant increase in dissolved organic carbon (DOC) concentration (200 to 550 μmol L-1) occurring over a matter of days, accompanied by a shift in DOM optical properties, indicating a transition towards higher molecular weight, more aromatic DOM composition. Comparable changes in DOM composition, but not concentration, occur at other times of year, underscoring the role of seasonal climatology in DOM cycling. A smaller data set of total and dissolved Hg concentrations also showed variability during the spring freshet period, although dissolved Hg dynamics appear to be driven by factors beyond DOM as characterized here. The time series records of DOC and particulate organic carbon (POC) concentrations indicate that the Fraser River exports 0.25-0.35 % of its annual basin net primary productivity. The snowmelt-dominated hydrology, forested land cover, and minimal reservoir impoundment of the Fraser River may influence the DOC yield of the basin, which is high relative to the nearby Columbia River and of similar magnitude to that of the Yukon River to the north. Anticipated warming and decreased snowfall due to climate changes in the region may cause an overall decrease in DOM flux from the Fraser River to the coastal ocean in coming decades

  20. Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength

    NASA Astrophysics Data System (ADS)

    Weber, M. A.; Fan, Y.; Miesch, M. S.

    2013-10-01

    We study how active-region-scale flux tubes rise buoyantly from the base of the convection zone to near the solar surface by embedding a thin flux tube model in a rotating spherical shell of solar-like turbulent convection. These toroidal flux tubes that we simulate range in magnetic field strength from 15 kG to 100 kG at initial latitudes of 1∘ to 40∘ in both hemispheres. This article expands upon Weber, Fan, and Miesch ( Astrophys. J. 741, 11, 2011) (Article 1) with the inclusion of tubes with magnetic flux of 1020 Mx and 1021 Mx, and more simulations of the previously investigated case of 1022 Mx, sampling more convective flows than the previous article, greatly improving statistics. Observed properties of active regions are compared to properties of the simulated emerging flux tubes, including: the tilt of active regions in accordance with Joy's Law as in Article 1, and in addition the scatter of tilt angles about the Joy's Law trend, the most commonly occurring tilt angle, the rotation rate of the emerging loops with respect to the surrounding plasma, and the nature of the magnetic field at the flux tube apex. We discuss how these diagnostic properties constrain the initial field strength of the active-region flux tubes at the bottom of the solar convection zone, and suggest that flux tubes of initial magnetic field strengths of ≥ 40 kG are good candidates for the progenitors of large (1021 Mx to 1022 Mx) solar active regions, which agrees with the results from Article 1 for flux tubes of 1022 Mx. With the addition of more magnetic flux values and more simulations, we find that for all magnetic field strengths, the emerging tubes show a positive Joy's Law trend, and that this trend does not show a statistically significant dependence on the magnetic flux.

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

    SciTech Connect

    Kojima, A.; Hanada, M.; Yoshida, M.; Umeda, N.; Hiratsuka, J.; Kashiwagi, M.; Tobari, H.; Watanabe, K.; Grisham, L. R.

    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 the 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.

  2. Impurities analysis of polycrystalline silicon substrates: Neutronic Activation Analysis (NAA) and Secondary Ion Mass Spectrometry (SIMS)

    NASA Astrophysics Data System (ADS)

    Lounis, A.; Lenouar, K.; Gritly, Y.; Abbad, B.; Azzaz, M.; Taïbi, K.

    2010-01-01

    In this study we have determined the concentration of some impurities such as carbon, iron, copper, titanium, nickel of the flat product (polycrystalline silicon). These impurities generate a yield decrease in the photovoltaic components. The material (polycrystalline silicon) used in this work is manufactured by the Unit of Silicon Technology Development (UDTS Algiers, Algeria). The 80 kg ingot has been cutted into 16 briquettes in order to have plates (flat product) of 100 mm×100 mm dimensions. Each briquette is divided into three parts top (T), middle (M) and bottom (B). For this purpose, the following instrumental analysis techniques have been employed: neutronic analysis (neutronic activation analysis) and secondary ion mass spectrometry (SIMS). Masses of 80 mg are sampled and form of discs 18 mm in diameter, then exposed to a flux of neutron of 2.1012neutron cm-2 s-1 during 15 min. The energetic profile of incidental flux is constituted of fast neutrons (ΦR = 3.1012n.cm-2 s-1; E = 2 Mev), thermal neutrons (ΦTH = 1013n.cm-2 s-1; E = 0.025 ev) and epithermal neutrons (Φepi = 7.1011 n cm-2 s-1; E>4.9 ev), irradiation time 15 mn, after 20 mn of decrement, acquisitions of 300 s are carried out. The results are expressed by disintegration per second which does not exceed the 9000 Bq, 500 Bq and 2600 Bq, respectively for copper, titanium and nickel. It is observed that the impurities concentrations in the medium are higher. The impurities in the bottom of the ingots originate from the crucible. The impurities in the top originate from impurities dissolved in the liquid silicon, which have segregated to the top layer of the ingot and after solidification diffuse. Silicon corresponds to a mixture of three isotopes 28Si, 29Si and 30Si. These elements clearly appear on the mass spectrum (SIMS). The presence of iron and the one of nickel has been noticed.

  3. Measurement of the total active 8B solar neutrino flux at the Sudbury Neutrino Observatory with enhanced neutral current sensitivity.

    PubMed

    Ahmed, S N; Anthony, A E; Beier, E W; Bellerive, A; Biller, S D; Boger, J; Boulay, M G; Bowler, M G; Bowles, T J; Brice, S J; Bullard, T V; Chan, Y D; Chen, M; Chen, X; Cleveland, B T; Cox, G A; Dai, X; Dalnoki-Veress, F; Doe, P J; Dosanjh, R S; Doucas, G; Dragowsky, M R; Duba, C A; Duncan, F A; Dunford, M; Dunmore, J A; Earle, E D; Elliott, S R; Evans, H C; Ewan, G T; Farine, J; Fergani, H; Fleurot, F; Formaggio, J A; Fowler, M M; Frame, K; Fulsom, B G; Gagnon, N; Graham, K; Grant, D R; Hahn, R L; Hall, J C; Hallin, A L; Hallman, E D; Hamer, A S; Handler, W B; Hargrove, C K; Harvey, P J; Hazama, R; Heeger, K M; Heintzelman, W J; Heise, J; Helmer, R L; Hemingway, R J; Hime, A; Howe, M A; Jagam, P; Jelley, N A; Klein, J R; Kos, M S; Krumins, A V; Kutter, T; Kyba, C C M; Labranche, H; Lange, R; Law, J; Lawson, I T; Lesko, K T; Leslie, J R; Levine, I; Luoma, S; MacLellan, R; Majerus, S; Mak, H B; Maneira, J; Marino, A D; McCauley, N; McDonald, A B; McGee, S; McGregor, G; Mifflin, C; Miknaitis, K K S; Miller, G G; Moffat, B A; Nally, C W; Nickel, B G; Noble, A J; Norman, E B; Oblath, N S; Okada, C E; Ollerhead, R W; Orrell, J L; Oser, S M; Ouellet, C; Peeters, S J M; Poon, A W P; Robertson, B C; Robertson, R G H; Rollin, E; Rosendahl, S S E; Rusu, V L; Schwendener, M H; Simard, O; Simpson, J J; Sims, C J; Sinclair, D; Skensved, P; Smith, M W E; Starinsky, N; Stokstad, R G; Stonehill, L C; Tafirout, R; Takeuchi, Y; Tesić, G; Thomson, M; Thorman, M; Van Berg, R; Van de Water, R G; Virtue, C J; Wall, B L; Waller, D; Waltham, C E; Tseung, H Wan Chan; Wark, D L; West, N; Wilhelmy, J B; Wilkerson, J F; Wilson, J R; Wouters, J M; Yeh, M; Zuber, K

    2004-05-01

    The Sudbury Neutrino Observatory has precisely determined the total active (nu(x)) 8B solar neutrino flux without assumptions about the energy dependence of the nu(e) survival probability. The measurements were made with dissolved NaCl in heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 +/- 0.27(stat)+/-0.38(syst) x 10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Deltam(2)=7.1(+1.2)(-0.6) x 10(-5) eV(2) and theta=32.5(+2.4)(-2.3) degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations.

  4. Effect of the active-ion concentration on the lasing dynamics of holmium fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-12-09

    The lasing dynamics of fibre lasers with a core based on quartz glass doped with holmium ions to concentrations in the range of 10{sup 19}-10{sup 20} cm{sup -3} is investigated. It is shown that fibre lasers with a high concentration of active holmium ions generate pulses, but a decrease in the holmium concentration changes the lasing from pulsed to cw regime. At the same time, a decrease in the active-ion concentration and the corresponding increase in the fibre length in the cavity reduce the lasing efficiency. (lasers)

  5. Effects of Al(3+) Ions on Formation of Silica Framework and Surface Active Sites for SO4(2-) Ions.

    PubMed

    Sasahara, Shigeo; Ozeki, Sumio

    2016-07-19

    Al(3+) ions were introduced into silica framework at 318 K in order to make active Al sites for SO4(2-) by the addition of aqueous sodium silicate solution to aqueous sulfuric acid solution of Al2(SO4)3. The (27)Al and (29)Si NMR spectra of aluminosilicates were measured at 278 K with reaction time. (29)Si NMR spectra were analyzed by the multivariate curve resolution. The addition of Al(3+) ions to aqueous silicate solution promoted gel formation. Small amounts of Al(3+) ions were incorporated as a four-coordinated complex at early stage of polymerization reaction of silicates and during subsequent reaction six-coordinated Al complex increased, suggesting reversible conversion between 4- and 6-coordinated complexes. SO4(2-) ions interact with positive surfaces of aluminosilicates and are specifically adsorbed on the surface sites of 6-coordinated Al(3+) species, which may be stabilized on silicate surfaces as [Al(H2O)5SO4](+). PMID:27352046

  6. Effects of Al(3+) Ions on Formation of Silica Framework and Surface Active Sites for SO4(2-) Ions.

    PubMed

    Sasahara, Shigeo; Ozeki, Sumio

    2016-07-19

    Al(3+) ions were introduced into silica framework at 318 K in order to make active Al sites for SO4(2-) by the addition of aqueous sodium silicate solution to aqueous sulfuric acid solution of Al2(SO4)3. The (27)Al and (29)Si NMR spectra of aluminosilicates were measured at 278 K with reaction time. (29)Si NMR spectra were analyzed by the multivariate curve resolution. The addition of Al(3+) ions to aqueous silicate solution promoted gel formation. Small amounts of Al(3+) ions were incorporated as a four-coordinated complex at early stage of polymerization reaction of silicates and during subsequent reaction six-coordinated Al complex increased, suggesting reversible conversion between 4- and 6-coordinated complexes. SO4(2-) ions interact with positive surfaces of aluminosilicates and are specifically adsorbed on the surface sites of 6-coordinated Al(3+) species, which may be stabilized on silicate surfaces as [Al(H2O)5SO4](+).

  7. Ion dynamics during seizures

    PubMed Central

    Raimondo, Joseph V.; Burman, Richard J.; Katz, Arieh A.; Akerman, Colin J.

    2015-01-01

    Changes in membrane voltage brought about by ion fluxes through voltage and transmitter-gated channels represent the basis of neural activity. As such, electrochemical gradients across the membrane determine the direction and driving force for the flow of ions and are therefore crucial in setting the properties of synaptic transmission and signal propagation. Ion concentration gradients are established by a variety of mechanisms, including specialized transporter proteins. However, transmembrane gradients can be affected by ionic fluxes through channels during periods of elevated neural activity, which in turn are predicted to influence the properties of on-going synaptic transmission. Such activity-induced changes to ion concentration gradients are a feature of both physiological and pathological neural processes. An epileptic seizure is an example of severely perturbed neural activity, which is accompanied by pronounced changes in intracellular and extracellular ion concentrations. Appreciating the factors that contribute to these ion dynamics is critical if we are to understand how a seizure event evolves and is sustained and terminated by neural tissue. Indeed, this issue is of significant clinical importance as status epilepticus—a type of seizure that does not stop of its own accord—is a life-threatening medical emergency. In this review we explore how the transmembrane concentration gradient of the six major ions (K+, Na+, Cl−, Ca2+, H+and HCO3−) is altered during an epileptic seizure. We will first examine each ion individually, before describing how multiple interacting mechanisms between ions might contribute to concentration changes and whether these act to prolong or terminate epileptic activity. In doing so, we will consider how the availability of experimental techniques has both advanced and restricted our ability to study these phenomena. PMID:26539081

  8. Mass Spectrometric Collisional Activation and Product Ion Mobility of Human Serum Neutral Lipid Extracts

    PubMed Central

    Hankin, Joseph A.; Barkley, Robert M.; Zemski-Berry, Karin; Deng, Yiming; Murphy, Robert C.

    2016-01-01

    A novel method for lipid analysis called CTS (collisional activation and traveling wave mass spectrometry) involving tandem mass spectrometry of all precursor ions with ion mobility determinations of all product ions was applied to a sample of human serum. The resulting four dimensional data set (precursor ion, product ion, ion mobility values, and intensity) was found to be useful for characterization of lipids as classes as well as identification of specific species. Utilization of ion mobility measurements of the product ions is a novel approach for lipid analysis. The trends and patterns of product mobility values when visually displayed yield information on lipid classes and specific species independent of mass determination. The collection of a comprehensive set of data that incorporates all precursor-product relationships combined with ion mobility measurements of all products enables data analysis where different molecular properties can be juxtaposed and analyzed to assist with class and species identification. Overall, CTS is powerful, specific, and comprehensive method for lipid analysis. PMID:27213895

  9. Use of Temperature and Surface Gas Flux as Novel Measures of Microbial Activity at a Crude Oil Spill Site

    NASA Astrophysics Data System (ADS)

    Bekins, B. A.; Warren, E.; Sihota, N. J.; Hostettler, F. D.

    2012-12-01

    Degradation of crude oil in the subsurface has been studied for over 30 years at a spill site located near Bemidji, Minnesota, USA. The well-characterized site is being used to experiment with the use of surface gas flux and temperature measurements as novel methods for quantifying microbial activity. In the largest subsurface oil body, a 2-m-thick smear zone spans the water table 6-8 m below the surface. Methane produced from degradation of the oil diffuses upward and mixes with oxygen from the surface supporting aerobic methanotrophy at 2-4 m depth. The methane oxidation produces CO2 and heat at rates which are hypothetically proportional to other measures of subsurface microbial activity. To test this hypothesis, vertical profiles of temperature and microbial populations, surface CO2 flux, and oil degradation state were measured at three sites in the oil body and one background site. Temperature increases in the oil zone near the water table were 1-4°C above the background site. The site with the highest temperature increase at the water table also had the highest concentrations of gene copy numbers for methanogens (mcrA) and methanotrophs (pmoA) along with the most degraded oil. Surface CO2 flux over the oil sites averaged more than twice that at the background site but was not consistently highest over the site with the highest activity by other measures. One possible explanation for this discrepancy is variation in the effective diffusion coefficient of the vadose zone between the methanotrophic zone and the surface. At the level of the methanotrophic zone, temperatures were elevated 2-6°C over the background values but again the site with greatest average annual temperature increase was not at the most active site. This may be due to enhanced recharge at the most active site, which lies at the center of a local topographic depression where focused recharge occurs. Overall, the temperature and flux data showed significant increases at the oil sites compared

  10. Chemical weathering in the plain and peninsular sub-basins of the Ganga: Impact on major ion chemistry and elemental fluxes

    NASA Astrophysics Data System (ADS)

    Rai, Santosh K.; Singh, Sunil K.; Krishnaswami, S.

    2010-04-01

    Concentrations of major ions, Sr and 87Sr/ 86Sr have been measured in the Gomti, the Son and the Yamuna, tributaries of the Ganga draining its peninsular and plain sub-basins to determine their contribution to the water chemistry of the Ganga and silicate and carbonate erosion of the Ganga basin. The results show high concentrations of Na and Sr in the Gomti, the Yamuna and the Ganga (at Varanasi) with much of the Na in excess of Cl. The use of this 'excess Na' (Na∗ = Na riv - Cl riv) a common index of silicate weathering yield values of ˜18 tons km -2 yr -1 for silicate erosion rate (SER) in the Gomti and the Yamuna basins. There are however, indications that part of this Na∗ can be from saline/alkaline soils abundant in their basins, raising questions about its use as a proxy to determine SER of the Ganga plain. Independent estimation of SER based on dissolved Si as a proxy give an average value of ˜5 tons km -2 yr -1 for the peninsular and the plain drainages, several times lower than that derived using Na∗. The major source of uncertainty in this estimate is the potential removal of Si from rivers by biological and chemical processes. The Si based SER and CER (carbonate erosion rate) are also much lower than that in the Himalayan sub-basin of the Ganga. The lower relief, runoff and physical erosion in the peninsular and the plain basins relative to the Himalayan sub-basin and calcite precipitation in them all could be contributing to their lower erosion rates. Budget calculations show that the Yamuna, the Son and Gomti together account for ˜75% Na, 41% Mg and ˜53% Sr and 87Sr of their supply to the Ganga from its major tributaries, with the Yamuna dominating the contribution. The results highlight the important role of the plain and peninsular sub-basins in determining the solute and Sr isotope budgets of the Ganga. The study also shows that the anthropogenic contribution accounts for ⩽10% of the major ion fluxes of the Ganga at Rajmahal during high

  11. Effect of metal ions on structure and activity of papain from Carica papaya.

    PubMed

    Kaul, P; Sathish, H A; Prakash, V

    2002-02-01

    Papain, a powerful proteolytic enzyme, is an endoprotease belonging to cysteine endopeptidase family. It is used extensively in food processing especially in tenderization of meat. In this study, we have made an attempt to show the structure activity relationship of this enzyme and the role of calcium and magnesium ions in the activity and stability of the enzyme. Results of activation and stabilization of the enzyme by these cations showed concentration dependent effect. The enzymatic activity of papain increases to a maximum of 18% and 24% in presence of calcium and magnesium ions at 1 x 10(-3) M concentration, respectively. Thermal denaturation studies showed that the binding of calcium and magnesium ions bring about change in the thermal stability of papain at various concentrations of these metal ions. Far ultraviolet circular dichroic studies showed no significant change in the alpha-helix and beta-sheet structure of the papain upon binding of these metal ions. The mechanism underlying the structure activity relationship of papain in presence of these metal ions have been discussed here with reference to the ionic radii, ligand binding preference, coordination numbers and the electrostatic forces between the protein molecule and cations present in the microenvironment of the enzyme. PMID:11890048

  12. Effect of ions on antibacterial activity of human beta defensin 2.

    PubMed

    Tomita, T; Hitomi, S; Nagase, T; Matsui, H; Matsuse, T; Kimura, S; Ouchi, Y

    2000-01-01

    Human beta defensin 2 (HBD-2), the most recently discovered human defensin, has been considered to work as a host defense substance against microbial infection. Using Escherichia coli ATCC 25922, we investigated how some cations and anions influenced the antimicrobial activity of HBD-2. This activity, measured in 10 mM phosphate buffer at a concentration of 20 microg/ml, reduced significantly in the presence of 100 and 150 mM sodium or potassium chloride. The reduction was not significantly different when the total amounts of sodium and potassium ions were equal. The kind and the valence of anions (chlorine and sulfate ions) did not affect the bactericidal activity as long as the concentrations of sodium ions were equal. Divalent ions (calcium and magnesium ions) added to 10 mM of Tris buffer significantly inactivated HBD-2 at much lower concentrations (more than or equal to 0.01 mM and 0.05 mM, respectively) than the monovalent ions did. These findings suggest that HBD-2 kills the bacteria through at least two phases, which are affected independently by either monovalent or divalent ions and unaffected by anions.

  13. Solar energetic particle flux enhancement as a predictor of geomagnetic activity in a neural network-based model

    NASA Astrophysics Data System (ADS)

    Valach, F.; Revallo, M.; Bochníček, J.; Hejda, P.

    2009-04-01

    Coronal mass ejections (CMEs) are believed to be the principal cause of increased geomagnetic activity. They are regarded as being in context of a series of related solar energetic events, such as X-ray flares (XRAs) accompanied by solar radio bursts (RSPs) and also by solar energetic particle (SEP) flux. Two types of the RSP events are known to be geoeffective, namely, the RSP of type II, interpreted as the signature of shock initiation in the solar corona, and type IV, representing material moving upward in the corona. The SEP events causing geomagnetic response are known to be produced by CME-driven shocks. In this paper, we use the method of the artificial neural network in order to quantify the geomagnetic response of particular solar events. The data concerning XRAs and RSPs II and/or IV together with their heliographic positions are taken as the input for the neural network. There is a key question posed in our study: can the successfulness of the neural network prediction scheme based solely on the solar disc observations (XRA and RSP) be improved by additional information concerning the SEP flux? To resolve this problem, we chose the SEP events possessing significant enhancement in the 10-h window, commencing 12 h after the generation of XRAs. In particular, we consider the flux of high-energy protons with energies over 10 MeV. We have used a chi-square test to demonstrate that supplying such extra input data improves the neural network prediction scheme.

  14. Severe acute respiratory syndrome coronavirus envelope protein ion channel activity promotes virus fitness and pathogenesis.

    PubMed

    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

    2014-05-01

    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

  15. Validation of the MCNP computational model for neutron flux distribution with the neutron activation analysis measurement

    NASA Astrophysics Data System (ADS)

    Tiyapun, K.; Chimtin, M.; Munsorn, S.; Somchit, S.

    2015-05-01

    The objective of this work is to demonstrate the method for validating the predication of the calculation methods for neutron flux distribution in the irradiation tubes of TRIGA research reactor (TRR-1/M1) using the MCNP computer code model. The reaction rate using in the experiment includes 27Al(n, α)24Na and 197Au(n, γ)198Au reactions. Aluminium (99.9 wt%) and gold (0.1 wt%) foils and the gold foils covered with cadmium were irradiated in 9 locations in the core referred to as CT, C8, C12, F3, F12, F22, F29, G5, and G33. The experimental results were compared to the calculations performed using MCNP which consisted of the detailed geometrical model of the reactor core. The results from the experimental and calculated normalized reaction rates in the reactor core are in good agreement for both reactions showing that the material and geometrical properties of the reactor core are modelled very well. The results indicated that the difference between the experimental measurements and the calculation of the reactor core using the MCNP geometrical model was below 10%. In conclusion the MCNP computational model which was used to calculate the neutron flux and reaction rate distribution in the reactor core can be used for others reactor core parameters including neutron spectra calculation, dose rate calculation, power peaking factors calculation and optimization of research reactor utilization in the future with the confidence in the accuracy and reliability of the calculation.

  16. Metal-ion spin-on glasses: Novel materials for active waveguides

    SciTech Connect

    Ashby, C.I.H.; Sullivan, C.T.; Vawter, G.A.; Hohimer, J.P.; Hadley, G.R.; Neal, D.R.

    1993-12-31

    Monolithic integration of a rare-earth-ion-based active waveguide on the same wafer as its diode pump laser would permit compact packaging of the technology demonstrated in fiber lasers and amplifiers. This new monolithic technology would offer the potential for developing compact infrared and visible (up-conversion) lasers, amplifiers, and other photonic integrated circuit components. One approach that we are investigating for such monolithic integration uses a high concentration of one or more rare-earth ions incorporated into polysiloxane spin-on glasses that are solvent-cast onto III-V semiconductor wafers. This ``fiber on a chip`` technology substitute a relatively high-ion-concentration, short-length metal-ion spin-on glass (MISOG) waveguide for the low-ion-concentration, long-length fiber. Progress to data on developing MISOG waveguide materials and technology is discussed.

  17. Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells.

    PubMed

    Wang, Yizhou; Blatt, Michael R

    2011-10-01

    Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (I(Cl)) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect I(Cl), but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with I(Cl) through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes.

  18. Dual mode antibacterial activity of ion substituted calcium phosphate nanocarriers for bone infections.

    PubMed

    Sampath Kumar, T S; Madhumathi, K; Rubaiya, Y; Doble, Mukesh

    2015-01-01

    Nanotechnology has tremendous potential for the management of infectious diseases caused by multi-drug resistant bacteria, through the development of newer antibacterial materials and efficient modes of antibiotic delivery. Calcium phosphate (CaP) bioceramics are commonly used as bone substitutes due to their similarity to bone mineral and are widely researched upon for the treatment of bone infections associated with bone loss. CaPs can be used as local antibiotic delivery agents for bone infections and can be substituted with antibacterial ions in their crystal structure to have a wide spectrum, sustained antibacterial activity even against drug resistant bacteria. In the present work, a dual mode antibiotic delivery system with antibacterial ion substituted calcium deficient hydroxyapatite (CDHA) nanoparticles has been developed. Antibacterial ions such as zinc, silver, and strontium have been incorporated into CDHA at concentrations of 6, 0.25-0.75, and 2.5-7.5 at. %, respectively. The samples were found to be phase pure, acicular nanoparticles of length 40-50 nm and width 5-6 nm approximately. The loading and release profile of doxycycline, a commonly used antibiotic, was studied from the nanocarriers. The drug release was studied for 5 days and the release profile was influenced by the ion concentrations. The release of antibacterial ions was studied over a period of 21 days. The ion substituted CDHA samples were tested for antibacterial efficacy on Staphylococcus aureus and Escherichia coli by MIC/MBC studies and time-kill assay. AgCDHA and ZnCDHA showed high antibacterial activity against both bacteria, while SrCDHA was weakly active against S. aureus. Present study shows that the antibiotic release can provide the initial high antibacterial activity, and the sustained ion release can provide a long-term antibacterial activity. Such dual mode antibiotic and antibacterial ion release offers an efficient and potent way to treat an incumbent drug

  19. [Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

    PubMed

    Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

    2015-09-01

    Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter

  20. [Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

    PubMed

    Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

    2015-09-01

    Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter

  1. Meaning and Measurability of Single-Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials

    PubMed Central

    Rockwood, Alan L

    2015-01-01

    Considering the relationship between concentration and vapor pressure (or the relationship between concentration and fugacity) single-ion activity coefficients are definable in purely thermodynamic terms. The measurement process involves measuring a contact potential between a solution and an external electrode. Contact potentials are measurable by using thermodynamically reversible processes. Extrapolation of an equation to zero concentration and ionic strength enables determination of single-ion activity coefficients. Single-ion activities can be defined and measured without using any extra-thermodynamic assumptions, concepts, or measurements. This method could serve as a gold standard for the validation of extra-thermodynamic methods for determining single-ion activities. Furthermore, it places the concept of pH on a thermodynamically solid foundation. Contact potential measurements can also be used to determine the Gibbs free energy for the transfer of ions between dissimilar materials. PMID:25919971

  2. Meaning and Measurability of Single-Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials.

    PubMed

    Rockwood, Alan L

    2015-06-22

    Considering the relationship between concentration and vapor pressure (or the relationship between concentration and fugacity) single-ion activity coefficients are definable in purely thermodynamic terms. The measurement process involves measuring a contact potential between a solution and an external electrode. Contact potentials are measurable by using thermodynamically reversible processes. Extrapolation of an equation to zero concentration and ionic strength enables determination of single-ion activity coefficients. Single-ion activities can be defined and measured without using any extra-thermodynamic assumptions, concepts, or measurements. This method could serve as a gold standard for the validation of extra-thermodynamic methods for determining single-ion activities. Furthermore, it places the concept of pH on a thermodynamically solid foundation. Contact potential measurements can also be used to determine the Gibbs free energy for the transfer of ions between dissimilar materials. PMID:25919971

  3. Diamondlike Carbon Thin Films From Ion Activated Techniques

    NASA Astrophysics Data System (ADS)

    Moravec, T. J.

    1982-04-01

    Diamondlike carbon thin films can be made by several different processes. We discuss two methods we have used to produce these films: deposition by low energy carbon ion beam and rf decomposition of hydrocarbon gases. In many ways, the films made by the two methods are similar, but there are some slight differences. The films have been characterized by electron spectroscopy, optical spectroscopy and transmission electron microscopy, and these measurements will be discussed. The films are mechanically hard, resist abrasion, transparent in the infrared and less so in the visible with a refractive index that can be varied between 1.8 and 2.3. Very efficient single layer quarterwave AR coatings have been produced on silicon solar cells. Other applications will be discussed.

  4. 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

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

    PubMed

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

    2015-07-20

    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.

  6. Metal ion specificities for folding and cleavage activity in the Schistosoma hammerhead ribozyme

    PubMed Central

    Boots, Jennifer L.; Canny, Marella D.; Azimi, Ehsan; Pardi, Arthur

    2008-01-01

    The effects of various metal ions on cleavage activity and global folding have been studied in the extended Schistosoma hammerhead ribozyme. Fluorescence resonance energy transfer was used to probe global folding as a function of various monovalent and divalent metal ions in this ribozyme. The divalent metals ions Ca2+, Mg2+, Mn2+, and Sr2+ have a relatively small variation (less than sixfold) in their ability to globally fold the hammerhead ribozyme, which contrasts with the very large difference (>10,000-fold) in apparent rate constants for cleavage for these divalent metal ions in single-turnover kinetic experiments. There is still a very large range (>4600-fold) in the apparent rate constants for cleavage for these divalent metal ions measured in high salt (2 M NaCl) conditions where the ribozyme is globally folded. These results demonstrate that the identity of the divalent metal ion has little effect on global folding of the Schistosoma hammerhead ribozyme, whereas it has a very large effect on the cleavage kinetics. Mechanisms by which the identity of the divalent metal ion can have such a large effect on cleavage activity in the Schistosoma hammerhead ribozyme are discussed. PMID:18755844

  7. Effect of pH and metal ions on DPPH radical scavenging activity of tea.

    PubMed

    Pękal, Anna; Pyrzynska, Krystyna

    2015-02-01

    The 2,2'-diphenyl-1-picrylhydrazyl (DPPH) assay is commonly applied for the estimation of antioxidant activity of plant extracts. This article discusses the effect of a sample pH and the presence of metal ions on the results obtained using DPPH method for several tea infusions. Higher radical quenching was observed in less acidic media. The impact of metal ions depends of the types of metal ion and its concentration. Quercetin and epigallocatechin gallate were less efficient in the reaction with DPPH in the presence of Al(III). Desalting process using cation-exchange resin Dowex 50Wx8 decreased the content of metal ions in all studied tea infusions. The DPPH scavenging activity of the effluents after this process were higher than those of the primary extracts and this may be related to the actual antioxidant capacity of these samples.

  8. Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption.

    PubMed

    Jiang, Chaowei; Wu, S T; Feng, Xuesheng; Hu, Qiang

    2016-05-16

    Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling.

  9. Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption

    PubMed Central

    Jiang, Chaowei; Wu, S. T.; Feng, Xuesheng; Hu, Qiang

    2016-01-01

    Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling. PMID:27181846

  10. Modulation of gill Na+,K+-ATPase activity by ammonium ions: Putative coupling of nitrogen excretion and ion uptake in the freshwater shrimp Macrobrachium olfersii.

    PubMed

    Furriel, Rosa Prazeres Melo; Masui, Douglas Chodi; McNamara, John Campbell; Leone, Francisco Assis

    2004-01-01

    The effect of NH4+ ions on (Na+,K+)-ATPase hydrolytic activity was examined in a gill microsomal fraction from M. olfersii. In the absence of NH4+ ions, K+ ions stimulated ATP hydrolysis, exhibiting cooperative kinetics (nH=0.8), to a maximal specific activity of V=556.1+/-22.2 nmol.min(-1).mg(-1) with K(0.5)=2.4+/-0.1 mmol.L(-1). No further stimulation by K+ ions was observed in the presence of 50 mmol.L(-1) NH4+ ions. ATP hydrolysis was also stimulated by NH4+ ions obeying Michaelian kinetics to a maximal specific activity of V=744.8+/-22.3 nmol.min(-1).mg(-1) and KM=8.4+/-0.2 mmol.L(-1). In the presence of 10 mmol.L(-1) K+ ions, ATP hydrolysis was synergistically stimulated by NH4+ ions to V=689.8+/-13.8 nmol.min(-1).mg(-1) and K(0.5)=6.6+/-0.1 mmol.L(-1), suggesting that NH4+ ions bind to different sites than K+ ions. PNPP hydrolysis was also stimulated cooperatively by K+ or NH4+ ions to maximal values of V= 235.5+/-11.8 nmol.min(-1).mg(-1) and V=234.8+/-7.0 nmol.min(-1).mg(-1), respectively. In contrast to ATP hydrolysis, K(+)-phosphatase activity was not synergistically stimulated by NH4+ and K+ ions. These data suggest that at high NH4+ ion concentrations, the (Na+, K+)-ATPase exposes a new site; the subsequent binding of NH4+ ions stimulates ATP hydrolysis to rates higher than those for K+ ions alone. This is the first demonstration that (Na+, K+)-ATPase activity in a freshwater shrimp gill is modulated by ammonium ions, independently of K+ ions, an effect that may constitute a fine-tuning mechanism of physiological relevance to osmoregulatory and excretory processes in palaemonid shrimps.

  11. Neutron activation analysis for reference determination of the implantation dose of cobalt ions

    SciTech Connect

    Garten, R.P.H.; Bubert, H.; Palmetshofer, L.

    1992-05-15

    The authors prepared depth profilling reference materials by cobalt ion implantation at an ion energy of 300 keV into n-type silicon. The implanted Co dose was then determined by instrumental neutron activation analysis (INAA) giving an analytical dynamic range of almost 5 decades and uncertainty of 1.5%. This form of analysis allows sources of error (beam spreading, misalignment) to be corrected. 70 refs., 3 tabs.

  12. The inhibitory effect of metals and other ions on acid phosphatase activity from Vigna aconitifolia seeds.

    PubMed

    Srivastava, Pramod Kumar; Anand, Asha

    2015-01-01

    Sensitivity of acid phosphatase from Vigna aconitifolia seeds to metal ions, fluoride, and phosphate was examined. All the effectors had different degree of inhibitory effect on the enzyme. Among metal ions, molybdate and ferric ion were observed to be most potent inhibitors and both exhibited mixed type of inhibition. Acid phosphatase activity was inhibited by Cu2+ in a noncompetitive manner. Zn and Mn showed mild inhibition on the enzyme activity. Inhibition kinetics analysis explored molybdate as a potent inhibitor for acid phosphatase in comparison with other effectors used in this study. Fluoride was the next most strong inhibitor for the enzyme activity, and caused a mixed type of inhibition. Phosphate inhibited the enzyme competitively, which demonstrates that inhibition due to phosphate is one of the regulatory factors for enzyme activity.

  13. Mutagenicity of the nuclease activity of 1,10-phenanthroline-copper ion

    SciTech Connect

    Feig, A.L.; Thederahn, T.; Sigman, D.S.

    1988-08-30

    The nuclease activity of 1,10-phenanthroline-copper functions intracellularly. This was shown by its mutagenicity in the Ames Test using the tester strain TA 102 and the in vivo nicking of plasmids derived from this strain. In vivo DNA strand scission requires all the components essential for the in vitro activity: 1,10-phenanthroline, cupric ion, thiol and hydrogen peroxide. Although /sup 60/Co gamma radiation potentiates the nuclease activity of 1,10-phenanthroline-copper ion in vitro via a superoxide dependent pathway, it does not promote significant mutagenesis in vivo at exposure levels below cytotoxicity.

  14. Superfine powdered activated carbon (S-PAC) coatings on microfiltration membranes: Effects of milling time on contaminant removal and flux.

    PubMed

    Amaral, Pauline; Partlan, Erin; Li, Mengfei; Lapolli, Flavio; Mefford, O Thompson; Karanfil, Tanju; Ladner, David A

    2016-09-01

    In microfiltration processes for drinking water treatment, one method of removing trace contaminants is to add powdered activated carbon (PAC). Recently, a version of PAC called superfine PAC (S-PAC) has been under development. S-PAC has a smaller particle size and thus faster adsorption kinetics than conventionally sized PAC. Membrane coating performance of various S-PAC samples was evaluated by measuring adsorption of atrazine, a model micropollutant. S-PACs were created in-house from PACs of three different materials: coal, wood, and coconut shell. Milling time was varied to produce S-PACs pulverized with different amounts of energy. These had different particles sizes, but other properties (e.g. oxygen content), also differed. In pure water the coal based S-PACs showed superior atrazine adsorption; all milled carbons had over 90% removal while the PAC had only 45% removal. With addition of calcium and/or NOM, removal rates decreased, but milled carbons still removed more atrazine than PAC. Oxygen content and specific external surface area (both of which increased with longer milling times) were the most significant predictors of atrazine removal. S-PAC coatings resulted in loss of filtration flux compared to an uncoated membrane and smaller particles caused more flux decline than larger particles; however, the data suggest that NOM fouling is still more of a concern than S-PAC fouling. The addition of calcium improved the flux, especially for the longer-milled carbons. Overall the data show that when milling S-PAC with different levels of energy there is a tradeoff: smaller particles adsorb contaminants better, but cause greater flux decline. Fortunately, an acceptable balance may be possible; for example, in these experiments the coal-based S-PAC after 30 min of milling achieved a fairly high atrazine removal (overall 80%) with a fairly low flux reduction (under 30%) even in the presence of NOM. This suggests that relatively short duration (low energy

  15. The effects of high-voltage pulse electric discharges on ion adsorption on activated carbons

    NASA Astrophysics Data System (ADS)

    Gafurov, M. M.; Sveshnikova, D. A.; Larin, S. V.; Rabadanov, K. Sh.; Shabanova, Z. E.; Yusupova, A. A.; Ramazanov, A. Sh.

    2008-07-01

    The effects of high-voltage pulse electric discharges (HPED) on sorption of boron and sulfate ions on activated carbons of different kinds (KM-2, BAU, DAK) were investigated. The effect of HPED activation on the sorption characteristics of the systems was found to be similar to the temperature effect.

  16. Fragmentation of positively-charged biological ions activated with a beam of high-energy cations.

    PubMed

    Chingin, Konstantin; Makarov, Alexander; Denisov, Eduard; Rebrov, Oleksii; Zubarev, Roman A

    2014-01-01

    First results are reported on the fragmentation of multiply protonated polypeptide ions produced in electrospray ionization mass spectrometry (ESI-MS) with a beam of high-energy cations as a source of activation. The ion beam is generated with a microwave plasma gun installed on a benchtop Q Exactive mass spectrometer. Precursor polypeptide ions are activated when trapped inside the collision cell of the instrument (HCD cell), and product species are detected in the Orbitrap analyzer. Upon exposure to the beam of air plasma cations (∼100 μA, 5 s), model precursor species such as multiply protonated angiotensin I and ubiquitin dissociated across a variety of pathways. Those pathways include the cleavages of C-CO, C-N as well as N-Cα backbone bonds, accordingly manifested as b/y, a, and c/z fragment ion series in tandem mass spectra. The fragmentation pattern observed includes characteristic fragments of collision-induced dissociation (CID) (b/y/a fragments) as well as electron capture/transfer dissociation (ECD, ETD) (c/z fragments), suggesting substantial contribution of both vibrational and electronic excitation in our experiments. Besides backbone cleavages, notable amounts of nondissociated precursor species were observed with reduced net charge, formed via electron or proton transfer between the colliding partners. Peaks corresponding to increased charge states of the precursor ions were also detected, which is the major distinctive feature of ion beam activation.

  17. Activity-dependent branching ratios in stocks, solar x-ray flux, and the Bak-Tang-Wiesenfeld sandpile model

    NASA Astrophysics Data System (ADS)

    Martin, Elliot; Shreim, Amer; Paczuski, Maya

    2010-01-01

    We define an activity-dependent branching ratio that allows comparison of different time series Xt . The branching ratio bx is defined as bx=E[ξx/x] . The random variable ξx is the value of the next signal given that the previous one is equal to x , so ξx={Xt+1∣Xt=x} . If bx>1 , the process is on average supercritical when the signal is equal to x , while if bx<1 , it is subcritical. For stock prices we find bx=1 within statistical uncertainty, for all x , consistent with an “efficient market hypothesis.” For stock volumes, solar x-ray flux intensities, and the Bak-Tang-Wiesenfeld (BTW) sandpile model, bx is supercritical for small values of activity and subcritical for the largest ones, indicating a tendency to return to a typical value. For stock volumes this tendency has an approximate power-law behavior. For solar x-ray flux and the BTW model, there is a broad regime of activity where bx≃1 , which we interpret as an indicator of critical behavior. This is true despite different underlying probability distributions for Xt and for ξx . For the BTW model the distribution of ξx is Gaussian, for x sufficiently larger than 1, and its variance grows linearly with x . Hence, the activity in the BTW model obeys a central limit theorem when sampling over past histories. The broad region of activity where bx is close to one disappears once bulk dissipation is introduced in the BTW model—supporting our hypothesis that it is an indicator of criticality.

  18. The active ion transport properties of canine lingual epithelia in vitro. Implications for gustatory transduction.

    PubMed

    Desimone, J A; Heck, G L; Mierson, S; Desimone, S K

    1984-05-01

    The electrophysiological properties of the dorsal and ventral canine lingual epithelium are studied in vitro. The dorsal epithelium contains a special ion transport system activated by mucosal solutions hyperosmotic in NaCl or LiCl. Hyperosmotic KCl is significantly less effective as an activator of this system. The lingual frenulum does not contain the transport system. In the dorsal surface it is characterized by a rapid increase in inward current and can be quantitated as a second component in the time course of either the open-circuit potential or short-circuit current when the mucosal solution is hyperosmotic in NaCl or LiCl. The increased inward current (hyperosmotic response) can be eliminated by amiloride (10(-4) M). The specific location of this transport system in the dorsal surface and the fact that it operates over the concentration range characteristic of mammalian salt taste suggests a possible link to gustatory transduction. This possibility is tested by recording neural responses in the rat to NaCl and KCl over a concentration range including the hyperosmotic. We demonstrate that amiloride specifically blocks the response to NaCl over the hyperosmotic range while affecting the KCl response significantly less. The results suggest that gustatory transduction for NaCl is mediated by Na entry into the taste cells via the same amiloride-sensitive pathway responsible for the hyperosmotic response in vitro. Further studies of the in vitro system give evidence for paracellular as well as transcellular current paths. The transmural current-voltage relations are linear under both symmetrical and asymmetrical conditions. After ouabain treatment under symmetrical conditions, the short-circuit current decays to zero. The increase in resistance, though significant, is small, which suggests a sizeable shunt pathway for current. Flux measurements show that sodium is absorbed under symmetrical conditions. Mucosal solutions hyperosmotic in various sugars also induce

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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+, Bi3+, Pb2+, Pt4+, and Hg2+), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag+, Bi3+, or Pb2+ 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+/Hg2+ and Hg2+/Bi3+ 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 Hg2+ and/or Bi3+ 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 Hg2+/Bi3+ as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt4+ and Hg2+ 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 Pb2+ and Hg2+ ions for the Au NPs allowed us to develop an INHIBIT logic gate--using Pb2+ and Hg2+ 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 Bi3+ enabled us to construct an XOR logic gate.In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs

  20. Removing Fluoride Ions with Continously Fed Activated Alumina.

    ERIC Educational Resources Information Center

    Wu, Yeun C.; Itemaking, Isara Cholapranee

    1979-01-01

    Discussed is the mathematical basis for determining fluoride removal during water treatment with activated alumina. The study indicates that decreasing particle size decreases the pore diffusion effect and increases fluoride removal. (AS)

  1. Neuroprotective effect of cellular prion protein (PrPC) is related with activation of alpha7 nicotinic acetylcholine receptor (α7nAchR)-mediated autophagy flux.

    PubMed

    Jeong, Jae-Kyo; Park, Sang-Youel

    2015-09-22

    Activation of the alpha7 nicotinic acetylcholine receptor (α7nAchR) is regulated by prion protein (PrPC) expression and has a neuroprotective effect by modulating autophagic flux. In this study, we hypothesized that PrPC may regulate α7nAchR activation and that may prevent prion-related neurodegenerative diseases by regulating autophagic flux. PrP(106-126) treatment decreased α7nAchR expression and activation of autophagic flux. In addition, the α7nAchR activator PNU-282987 enhanced autophagic flux and protected neuron cells against PrP(106-126)-induced apoptosis. However, activation of autophagy and the protective effects of PNU-282987 were inhibited in PrPC knockout hippocampal neuron cells. In addition, PrPC knockout hippocampal neuron cells showed decreased α7nAchR expression levels. Adenoviral overexpression of PrPC in PrPC knockout hippocampal neuron cells resulted in activation of autophagic flux and inhibition of prion peptide-mediated cell death via α7nAchR activation. This is the first report demonstrating that activation of α7nAchR-mediated autophagic flux is regulated by PrPC, and that activation of α7nAchR regulated by PrPC expression may play a pivotal role in protection of neuron cells against prion peptide-induced neuron cell death by autophagy. These results suggest that α7nAchR-mediated autophagic flux may be involved in the pathogenesis of prion-related diseases and may be a therapeutic target for prion-related neurodegenerative diseases.

  2. Neuroprotective effect of cellular prion protein (PrPC) is related with activation of alpha7 nicotinic acetylcholine receptor (α7nAchR)-mediated autophagy flux.

    PubMed

    Jeong, Jae-Kyo; Park, Sang-Youel

    2015-09-22

    Activation of the alpha7 nicotinic acetylcholine receptor (α7nAchR) is regulated by prion protein (PrPC) expression and has a neuroprotective effect by modulating autophagic flux. In this study, we hypothesized that PrPC may regulate α7nAchR activation and that may prevent prion-related neurodegenerative diseases by regulating autophagic flux. PrP(106-126) treatment decreased α7nAchR expression and activation of autophagic flux. In addition, the α7nAchR activator PNU-282987 enhanced autophagic flux and protected neuron cells against PrP(106-126)-induced apoptosis. However, activation of autophagy and the protective effects of PNU-282987 were inhibited in PrPC knockout hippocampal neuron cells. In addition, PrPC knockout hippocampal neuron cells showed decreased α7nAchR expression levels. Adenoviral overexpression of PrPC in PrPC knockout hippocampal neuron cells resulted in activation of autophagic flux and inhibition of prion peptide-mediated cell death via α7nAchR activation. This is the first report demonstrating that activation of α7nAchR-mediated autophagic flux is regulated by PrPC, and that activation of α7nAchR regulated by PrPC expression may play a pivotal role in protection of neuron cells against prion peptide-induced neuron cell death by autophagy. These results suggest that α7nAchR-mediated autophagic flux may be involved in the pathogenesis of prion-related diseases and may be a therapeutic target for prion-related neurodegenerative diseases. PMID:26295309

  3. [Concurrence of multiple and integrated mechanisms in the modulation of enzyme activities: significance for the regulation of metabolic fluxes].

    PubMed

    Niemeyer, H; Cárdenas, M L

    1985-12-01

    The activity of some enzymes in a given metabolic pathway is modulated through multiple mechanisms, which operate in a simultaneous and coherent way to produce either stimulation or inhibition. The operation of these mechanisms is illustrated with several enzymes involved in glucose metabolism, by choosing examples from the presentations at the Symposium. Thus the reciprocal interactions of the regulatory mechanisms acting upon hexokinase D ('glucokinase'), phosphofructokinase, fructose 1,6-bisphosphatase and pyruvate kinase were discussed, as well as their relationships with the induction of enzyme conformational changes. In addition, the effects of covalent interconversions on glutamine synthetase activity were briefly analyzed. An outstanding feature exhibited by all these enzymes is the display of a great number of elasticity coefficients, which are differential quotients measuring the dependence of enzymatic activity on each variable that modulates it. A general assumption is that these enzymes make an important contribution to the control of the metabolic flux in which they participate. The flux control, however, appears to be shared in different degrees by all the components of the system, and may be quantified through the differential quotient denominated control coefficient. Some of the problems that emerge in any attempt to estimate these coefficients in the living cells are discussed. The problems derive partly from the complex subcellular structure, the formation of functional compartments resulting from reversible association of the enzymes, one to another and to different cellular components, and the actual state of cell water. These problems make that the results obtained with purified and highly diluted enzymes in most enzymological studies should not be extrapolated directly to what happens in vivo, without a careful evaluation of each particular case. The regulatory role of enzyme activity of fructose 2,6-bisphosphate and its eventual

  4. Giant suppression of flux-flow resistivity in heavy-ion irradiated Tl2Ba2Ca2Cu3O10 films - Influence of linear defects on vortex transport

    NASA Technical Reports Server (NTRS)

    Budhani, R. C.; Suenaga, M.; Liou, S. H.

    1992-01-01

    A large shift of the onset of flux-flow resistivity and the irreversibility line H(irr)(T) to higher temperatures is observed in Tl2Ba2Ca2Cu3O10 films containing linear defects created by Ag(+21) ion irradiation. The H(irr)(T), which has a characteristic L shape in highly anisotropic Tl and Bi based cuprates, becomes more like that of YBa2Cu3O7 in the presence of these defects. The Jc at 77 K also shows a large increase as a result of flux localization at the defects. The transport data indicate that in the H-T plane above H(irr)(T) of the unirradiated material, an ensemble of unoccupied defects is required for effective pinning of each flux line in the system.

  5. The Variation of Solar Fe 14 and Fe 10 Flux over 1.5 Solar Activity Cycles

    NASA Technical Reports Server (NTRS)

    Altrock, Richard C.

    1990-01-01

    A new source of data on the solar output, namely limb flux from the one- and two-million degree corona is presented. This parameter is derived from data obtained at the National Solar Observatory at Sacramento Peak with the 40 cm coronagraph of the John W. Evans Solar Facility and the Emission Line Coronal Photometer. The limb flux is defined to be the latitude-averaged intensity in millionths of the brightness of disk center from an annulus of width 1.1 minutes centered at a height of 0.15 solar constant above the limb of emission from lines at 6374A (Fe X) or 5303A (Fe XIV). Fe XIV data have been obtained since 1973 and Fe X since 1984. Examination of the Fe XIV data shows that there is ambiguity in the definition of the last two solar activity minima, which can affect the determination of cycle rise times and lengths. There is an indication that a constant minimum or basal corona may exist at solar minimum. Cycle 22 has had a much faster onset than Cycle 21 and has now overtaken Cycle 21. The rise characteristics of the two cycles were very similar up until Jul. to Aug. 1989, at which time a long-term maximum occurred in Fe X and Fe XIV, which could possibly be the solar maximum. Another maximum is developing at the current time. Cycle 21 was characterized in Fe XIV by at least 4 major thrusts or bursts of activity, each lasting on the order of a year and all having similar maximum limb fluxes which indicates that coronal energy output is sustained over periods in which the sunspot number declines significantly. Dramatic increases in the limb fluxes occur from minimum to maximum, ranging from factors of 14 to 21 in the two lines. Two different techniques to predict the epoch of solar maximum have been applied to the Fe XIV data, resulting in estimates of April 1989 (plus or minus 1 mo) and May 1990 (plus or minus 2 mos).

  6. Inhibitory role of monovalent ions on rat brain cortex adenylyl cyclase activity.

    PubMed

    Nikolic, Ivana; Mitrovic, Marina; Zelen, Ivanka; Zaric, Milan; Kastratovic, Tatjana; Stanojevic, Marijana; Nenadovic, Milutin; Stojanovic, Tomislav

    2013-10-01

    Adenylyl cyclases, comprise of a large family of enzymes that catalyze synthesis of the cyclic AMP from ATP. The aim of our study was to determine the effect of monovalent ions on both basal, stimulated adenylate cyclase EC 4.6.1.1 (AC) activity and C unit of AC and on GTPase active G-protein in the synaptic membranes of rat brain cortex. The effect of ion concentration from 30 to 200 mM (1 mM MgCl2) showed dose-dependent and significant inhibition of the basal AC activity, stimulated and unstimulated C unit activity. Stimulation of AC with 5 μM GTPγS in the presence of 50-200 mM of tested salts showed inhibitory effect on the AC activity. From our results it could be postulated that the investigated monovalent ions exert inhibitory effect on the AC complex activity by affecting the intermolecular interaction of the activated α subunit of G/F protein and the C unit of AC complex an inhibitory influence of tested monovalent ions on these molecular interaction.

  7. Direct and indirect effects of ammonia, ammonium and nitrate on phosphatase activity and carbon fluxes from decomposing litter in peatland.

    PubMed

    Johnson, David; Moore, Lucy; Green, Samuel; Leith, Ian D; Sheppard, Lucy J

    2010-10-01

    Here we investigate the response of soils and litter to 5 years of experimental additions of ammonium (NH4), nitrate (NO3), and ammonia (NH3) to an ombrotrophic peatland. We test the importance of direct (via soil) and indirect (via litter) effects on phosphatase activity and efflux of CO2. We also determined how species representing different functional types responded to the nitrogen treatments. Our results demonstrate that additions of NO3, NH4 and NH3 all stimulated phosphatase activity but the effects were dependent on species of litter and mechanism (direct or indirect). Deposition of NH3 had no effect on efflux of CO2 from Calluna vulgaris litter, despite it showing signs of stress in the field, whereas both NO3 and NH4 reduced CO2 fluxes. Our results show that the collective impacts on peatlands of the three principal forms of nitrogen in atmospheric deposition are a result of differential effects and mechanisms on individual components.

  8. Ion channels activated by light in Limulus ventral photoreceptors

    PubMed Central

    1986-01-01

    The light-activated conductance of Limulus ventral photoreceptors was studied using the patch-clamp technique. Channels (40 pS) were observed whose probability of opening was greatly increased by light. In some cells the latency of channel activation was nearly the same as that of the macroscopic response, while in other cells the channel latency was much greater. Like the macroscopic conductance, channel activity was reduced by light adaptation but enhanced by the intracellular injection of the calcium chelator EGTA. The latter observation indicates that channel activation was not a secondary result of the light-induced rise in intracellular calcium. A two-microelectrode voltage-clamp method was used to measure the voltage dependence of the light-activated macroscopic conductance. It was found that this conductance is constant over a wide voltage range more negative than zero, but it increases markedly at positive voltages. The single channel currents measured over this same voltage range show that the single channel conductance is independent of voltage, but that channel gating properties are dependent on voltage. Both the mean channel open time and the opening rate increase at positive voltages. These properties change in a manner consistent with the voltage dependence of the macroscopic conductance. The broad range of similarities between the macroscopic and single channel currents supports the conclusion that the 40-pS channel that we have observed is the principal channel underlying the response to light in these photoreceptors. PMID:2419481

  9. The downward flux of O(+) over the nightside of Venus

    NASA Technical Reports Server (NTRS)

    Brannon, J. J.; Fox, J. L.

    1994-01-01

    We have constructed a map of the downward flux of O(+) over the nightside of Venus at high and low solar activities through a combination of modeling and analysis of Pioneer Venus ion mass spectrometer data. O(+) density profiles were obtained for almost 40 inbound or outbound segments of orbits from the first 2 years of the mission and about 40 more in the recent reentry phase of the mission. We have determined the nearly linear relationship between the 0(+) maximum density and the downward O(+) flux for several solar zenith angles and local times by constructing models of the nightside ionosphere of Venus for a range of downward ion fluxes at the upper boundaries. We find that the largest downward fluxes occur near the terminators, and the fluxes fall off sharply toward the antisolar point. Although the standard deviations in the data are large, there is a suggestion of a local maximum near 155 deg, and the location of this maximum correlates fairly well with structure in the peak electron density as a function of solar zenith angle reported for the Pioneer Venus radio occulation experiment. The average downward ion flux is inferred to be about 1.7 x 10(exp 8)/sq cm/sec over the nightside hemisphere at solar maximum and a factor of 7 less at moderately low solar activity.

  10. Bacterial persistence is an active σS stress response to metabolic flux limitation.

    PubMed

    Radzikowski, Jakub Leszek; Vedelaar, Silke; Siegel, David; Ortega, Álvaro Dario; Schmidt, Alexander; Heinemann, Matthias

    2016-09-21

    While persisters are a health threat due to their transient antibiotic tolerance, little is known about their phenotype and what actually causes persistence. Using a new method for persister generation and high-throughput methods, we comprehensively mapped the molecular phenotype of Escherichia coli during the entry and in the state of persistence in nutrient-rich conditions. The persister proteome is characterized by σ(S)-mediated stress response and a shift to catabolism, a proteome that starved cells tried to but could not reach due to absence of a carbon and energy source. Metabolism of persisters is geared toward energy production, with depleted metabolite pools. We developed and experimentally verified a model, in which persistence is established through a system-level feedback: Strong perturbations of metabolic homeostasis cause metabolic fluxes to collapse, prohibiting adjustments toward restoring homeostasis. This vicious cycle is stabilized and modulated by high ppGpp levels, toxin/anti-toxin systems, and the σ(S)-mediated stress response. Our system-level model consistently integrates past findings with our new data, thereby providing an important basis for future research on persisters.

  11. Multiple measurement of the coupling between benthic carbon fluxes and bioturbation activity during the spring bloom''

    SciTech Connect

    Aller, R.C.; Aller, J.J.; Cochran, J.K.; Lee, C.

    1992-01-01

    In accordance with the research plan outlined in our original proposal, we began monitoring indicators of plankton production (Chl-a, cell counts) in surface waters of Long Island Sound from the Port Jefferson / Bridgeport Ferry on Dec. 3, 1992. In contrast to past years no dramatic bloom has occurred to date although a significant pattern of increasing chl-a began during the first week of April. We anticipate that the bloom wig be complete by mid to late April. This has been a particularly cold year based on comparison of 1993 bottom water temperatures and previously reported patterns from LIS, possibly reflecting climatic conditions which delayed the bloom. Typical sampling includes: surface and bottom water sampling for suspended matter, cell counts, chlorophyll-a, nutrients; triplicate box cores for macro-, meio-, and microfauna analysis; subcores for O[sub 2] microelectrode profiles; box core for radiochemical analyses ([sup 234]Th, [sup 7]Be); box core subcores for benthic fluxes under aerated and nonaerated conditions (O[sub 2], [Sigma]N, Mn[sup ++], [Sigma]CO[sub 2]); Br[sup [minus

  12. Manufacturing and thermomechanical testing of actively cooled all beryllium high heat flux test pieces

    SciTech Connect

    Vasiliev, N.N.; Sokolov, Yu.A.; Shatalov, G.E.

    1995-09-01

    One of the problems affiliated to ITER high heat flux elements development is a problem of interface of beryllium protection with heat sink routinely made of copper alloys. To get rid of this problem all beryllium elements could be used as heat receivers in places of enhanced thermal loads. In accordance with this objectives four beryllium test pieces of two types have been manufactured in {open_quotes}Institute of Beryllium{close_quotes} for succeeding thermomechanical testing. Two of them were manufactured in accordance with JET team design; they are round {open_quotes}hypervapotron type{close_quotes} test pieces. Another two ones are rectangular test sections with a twisted tape installed inside of the circular channel. Preliminary stress-strain analysis have been performed for both type of the test pieces. Hypervapotrons have been shipped to JET where they were tested on JET test bed. Thermomechanical testing of pieces of the type of {open_quotes}swirl tape inside of tube{close_quotes} have been performed on Kurchatov Institute test bed. Chosen beryllium grade properties, some details of manufacturing, results of preliminary stress-strain analysis and thermomechanical testing of the test pieces {open_quotes}swirl tape inside of tube{close_quotes} type are given in this report.

  13. Bacterial persistence is an active σS stress response to metabolic flux limitation.

    PubMed

    Radzikowski, Jakub Leszek; Vedelaar, Silke; Siegel, David; Ortega, Álvaro Dario; Schmidt, Alexander; Heinemann, Matthias

    2016-01-01

    While persisters are a health threat due to their transient antibiotic tolerance, little is known about their phenotype and what actually causes persistence. Using a new method for persister generation and high-throughput methods, we comprehensively mapped the molecular phenotype of Escherichia coli during the entry and in the state of persistence in nutrient-rich conditions. The persister proteome is characterized by σ(S)-mediated stress response and a shift to catabolism, a proteome that starved cells tried to but could not reach due to absence of a carbon and energy source. Metabolism of persisters is geared toward energy production, with depleted metabolite pools. We developed and experimentally verified a model, in which persistence is established through a system-level feedback: Strong perturbations of metabolic homeostasis cause metabolic fluxes to collapse, prohibiting adjustments toward restoring homeostasis. This vicious cycle is stabilized and modulated by high ppGpp levels, toxin/anti-toxin systems, and the σ(S)-mediated stress response. Our system-level model consistently integrates past findings with our new data, thereby providing an important basis for future research on persisters. PMID:27655400

  14. THE ROLE OF THE ACTIVITY COEFFICIENT OF THE HYDROGEN ION IN THE HYDROLYSIS OF GELATIN.

    PubMed

    Northrop, J H

    1921-07-20

    1. The hydrolysis of gelatin at a constant hydrogen ion concentration follows the course of a monomolecular reaction for about one-third of the reaction. 2. If the hydrogen ion concentration is not kept constant the amount of hydrolysis in certain ranges of acidity is proportional to the square root of the time (Schütz's rule). 3. The velocity of hydrolysis in strongly acid solution (pH less than 2.0) is directly proportional to the hydrogen ion concentration as determined by the hydrogen electrode i.e., the "activity;" it is not proportional to the hydrogen ion concentration as determined by the conductivity ratio. 4. The addition of neutral salts increases the velocity of hydrolysis and the hydrogen ion concentration (as determined by the hydrogen electrode) to approximately the same extent. 5. The velocity in strongly alkaline solutions (pH greater than 10) is directly proportional to the hydroxyl ion concentration. 6. Between pH 2.0 and pH 10.0 the rate of hydrolysis is approximately constant and very much greater than would be calculated from the hydrogen and hydroxyl ion concentration. This may be roughly accounted for by the assumption that the uncombined gelatin hydrolyzes much more rapidly than the gelatin salt.

  15. Effect of surface property of activated carbon on adsorption of nitrate ion.

    PubMed

    Iida, Tatsuya; Amano, Yoshimasa; Machida, Motoi; Imazeki, Fumio

    2013-01-01

    In this study, the removal of acidic functional groups and introduction of basic groups/sites on activated carbons (ACs) by outgassing and ammonia gas treatment were respectively carried out to enhance the nitrate ion adsorption in aqueous solution. Then, the relationships between nitrate ion adsorption and solution pH as well as surface charge of AC were investigated to understand the basic mechanisms of nitrate ion adsorption by AC. The result showed that the nitrate ion adsorption depended on the equilibrium solution pH (pHe) and the adsorption amount was promoted with decreasing pHe. The ACs treated by outgassing and ammonia gas treatment showed larger amount of nitrate ion adsorption than that by untreated AC. These results indicated that, since basic groups/sites could adsorb protons in the solution, the AC surface would be charged positively, and that the nitrate ion would be electrically interacted with positively charged carbon surface. Accordingly, it was concluded that basic groups/sites on the surface of AC could promote nitrate ion adsorption.

  16. Molecular mechanism of ATP binding and ion channel activation in P2X receptors

    SciTech Connect

    Hattori, Motoyuki; Gouaux, Eric

    2012-10-24

    P2X receptors are trimeric ATP-activated ion channels permeable to Na{sup +}, K{sup +} and Ca{sup 2+}. The seven P2X receptor subtypes are implicated in physiological processes that include modulation of synaptic transmission, contraction of smooth muscle, secretion of chemical transmitters and regulation of immune responses. Despite the importance of P2X receptors in cellular physiology, the three-dimensional composition of the ATP-binding site, the structural mechanism of ATP-dependent ion channel gating and the architecture of the open ion channel pore are unknown. Here we report the crystal structure of the zebrafish P2X4 receptor in complex with ATP and a new structure of the apo receptor. The agonist-bound structure reveals a previously unseen ATP-binding motif and an open ion channel pore. ATP binding induces cleft closure of the nucleotide-binding pocket, flexing of the lower body {beta}-sheet and a radial expansion of the extracellular vestibule. The structural widening of the extracellular vestibule is directly coupled to the opening of the ion channel pore by way of an iris-like expansion of the transmembrane helices. The structural delineation of the ATP-binding site and the ion channel pore, together with the conformational changes associated with ion channel gating, will stimulate development of new pharmacological agents.

  17. Zinc activates damage-sensing TRPA1 ion channels

    PubMed Central

    Hu, Hongzhen; Bandell, Michael; Petrus, Matt J.; Zhu, Michael X.; Patapoutian, Ardem

    2009-01-01

    Zinc is an essential biological trace element. It is required for the structure or function of over 300 proteins, and is increasingly recognized for its role in cell signaling. However, high concentrations of zinc have cytotoxic effects, and overexposure to zinc can cause pain and inflammation through unknown mechanisms. Here we show that zinc excites nociceptive somatosensory neurons and causes nociception in mice through TRPA1, a cation channel previously shown to mediate the pungency of wasabi and cinnamon through cysteine-modification. Zinc activates TRPA1 through a novel mechanism that requires zinc influx through TRPA1 channels and subsequent activation via specific intracellular cysteine and histidine residues. TRPA1 is highly sensitive to intracellular zinc, as low nanomolar concentrations activate TRPA1 and modulate its sensitivity. These findings identify TRPA1 as a major target for the sensory effects of zinc, and support an emerging role for zinc as a signaling molecule that can modulate sensory transmission. PMID:19202543

  18. Surface diffusion activation energy determination using ion beam microtexturing

    NASA Technical Reports Server (NTRS)

    Rossnagel, S. M.; Robinson, R. S.

    1982-01-01

    The activation energy for impurity atom (adatom) surface diffusion can be determined from the temperature dependence of the spacing of sputter cones. These cones are formed on the surface during sputtering while simultaneously adding impurities. The impurities form clusters by means of surface diffusion, and these clusters in turn initiate cone formation. Values are given for the surface diffusion activation energies for various materials on polycrystalline Cu, Al, Pb, Au, and Ni. The values for different impurity species on each of these substrates are approximately independent of impurity species within the experimental uncertainty, suggesting the absence of strong chemical bonding effects on the diffusion.

  19. Self-diffusion and activity coefficients of ions in charged disordered media

    NASA Astrophysics Data System (ADS)

    Jardat, Marie; Hribar-Lee, Barbara; Dahirel, Vincent; Vlachy, Vojko

    2012-09-01

    Self-diffusion and single ion activity coefficients of ions of size symmetric electrolytes were studied in the presence of a collection of charged obstacles (called matrix) within a "soft" version of the primitive model of electrolyte solutions. The matrix subsystem possesses a net charge, depending on the concentration and charge of obstacles. The Brownian dynamics method was used to calculate the self-diffusion coefficients of mobile species. The replica Ornstein-Zernike theory for the partly quenched systems was used to calculate the individual activity coefficients of mobile ionic species. The results reflect the competition between attractive (obstacle-counterion, co-ion-counterion), and repulsive (obstacle-co-ion) interactions in these model systems. For the simplest possible system of symmetric monovalent ions the latter effect wins: Co-ions are excluded from the area around obstacles, and this slows down their diffusion compared to that of counterions. Introduction of divalent charges into the system changes this result when the concentration of obstacles is low. We compare these results to those obtained for the corresponding fully annealed systems, i.e., where all the species are mobile. In most cases the self-diffusion and activity coefficients of counterions and co-ions in the presence of charged obstacles follow the trends of the fully annealed solution, which are dictated by the composition of the mixture. In few situations, however, the presence of charged obstacles modifies these trends. Our study allows us to clearly identify the effects due to obstacles, and to separate them from those arising from the composition of the solution. In the case of charge and size symmetric systems, the results for the individual activity coefficients fully support the hypothesis of the "electrostatic excluded volume". Thermodynamic and dynamic results are consistent in explaining the behavior of the systems studied.

  20. The superthermal ion environment near comet 67P/Churyumov-Gerasimenko at low activity

    NASA Astrophysics Data System (ADS)

    Nilsson, Hans; Stenberg Wieser, Gabriella; Behar, Etienne; Yamauchi, Masatoshi; Wedlund, Cyril Simon; Kallio, Esa; Burch, Jim; Carr, Chris; Eriksson, Anders; Glassmeier, Karl-Heinz; Lebreton, Jean-Pierre; Henri, Pierre; Gunell, Herbert

    2015-04-01

    The Rosetta mission has been designed to rendezvous with and escort comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, when the comet still has a low activity level, until perihelion passage at 1.25 AU where the comet reaches the maximum of its activity. Initially, the solar wind permeates the thin comet atmosphere that has just begun to form from sublimation. Eventually the size and plasma pressure of the ionized atmosphere leads to the formation of plasma boundaries: a magnetosphere is born. Using the Rosetta Plasma Consortium Ion Composition Analyzer, we study the gradual evolution from the first detectable traces of water ions to the stage where the comet atmosphere starts to repel the solar wind at a distance from the sun of about 3.3 AU. Gradually the mass loading caused by picked-up comet ions starts to deflect the solar wind. Charge exchange between the solar wind and comet atmosphere gradually increases with comet activity, leading to a situation where a significant fraction of the solar wind has charge-exchanged close to the comet nucleus. Pick up ions created upstream of the comet nucleus are accelerated by the solar wind electric field and are seen with energies up to about 1 keV as they move back towards the nucleus. Locally produced water ions are seen moving with velocities similar to the neutral outgassing velocity of the order of 1 km/s ( 10 eV), but with their direction and speed influenced by the solar wind electric field. High charge state solar wind ions (O6+, O5+) are also seen at times. We quantify the super thermal ion environment near a low activity comet and show how it depends on the solar wind intensity and the distance to the sun.

  1. Patterns of Flux Emergence

    NASA Astrophysics Data System (ADS)

    Title, A.; Cheung, M.

    2008-05-01

    The high spatial resolution and high cadence of the Solar Optical Telescope on the JAXA Hinode spacecraft have allowed capturing many examples of magnetic flux emergence from the scale of granulation to active regions. The observed patterns of emergence are quite similar. Flux emerges as a array of small bipoles on scales from 1 to 5 arc seconds throughout the region that the flux eventually condenses. Because the fields emerging from the underlying flux rope my appear many in small segments and the total flux (absolute sum) is not a conserved quantity the amount of total flux on the surface may vary significantly during the emergence process. Numerical simulations of flux emergence exhibit patterns similar to observations. Movies of both observations and numerical simulations will be presented.

  2. Activity of metazoa governs biofilm structure formation and enhances permeate flux during Gravity-Driven Membrane (GDM) filtration.

    PubMed

    Derlon, Nicolas; Koch, Nicolas; Eugster, Bettina; Posch, Thomas; Pernthaler, Jakob; Pronk, Wouter; Morgenroth, Eberhard

    2013-04-15

    The impact of different feed waters in terms of eukaryotic populations and organic carbon content on the biofilm structure formation and permeate flux during Gravity-Driven Membrane (GDM) filtration was investigated in this study. GDM filtration was performed at ultra-low pressure (65 mbar) in dead-end mode without control of the biofilm formation. Different feed waters were tested (River water, pre-treated river water, lake water, and tap water) and varied with regard to their organic substrate content and their predator community. River water was manipulated either by chemically inhibiting all eukaryotes or by filtering out macrozoobenthos (metazoan organisms). The structure of the biofilm was characterized at the meso- and micro-scale using Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM), respectively. Based on Total Organic Carbon (TOC) measurements, the river waters provided the highest potential for bacterial growth whereas tap water had the lowest. An increasing content in soluble and particulate organic substrate resulted in increasing biofilm accumulation on membrane surface. However, enhanced biofilm accumulation did not result in lower flux values and permeate flux was mainly influenced by the structure of the biofilm. Metazoan organisms (in particular nematodes and oligochaetes) built-up protective habitats, which resulted in the formation of open and spatially heterogeneous biofilms composed of biomass patches. In the absence of predation by metazoan organisms, a flat and compact biofilm developed. It is concluded that the activity of metazoan organisms in natural river water and its impact on biofilm structure balances the detrimental effect of a high biofilm accumulation, thus allowing for a broader application of GDM filtration. Finally, our results suggest that for surface waters with high particulate organic carbon (POC) content, the use of worms is suitable to enhance POC removal before ultrafiltration units.

  3. Calibration of a direct nuclear activation diagnostic which uses boron nitride to measure energetic deuterium ions

    SciTech Connect

    Cooper, G.W.; Chambers, G.D.; Savage, M.E.; Ruiz, C.L.; Schmidlapp, F.A.

    1998-07-01

    A direct nuclear activation diagnostic for the measurement of the kinetic energy of deuterium ions in the energy range of 1 to 3 MeV has been successfully developed. This diagnostic is based on the fact that the ratio of two different thick target yields which are generated by the same incident ion species can be a sensitive function of incident ion energy. Targets for this diagnostic are made of {alpha}-boron nitride (BN) and use the two reactions: {sup 10}B(d,n){sup 11}C({beta}+) and {sup 14}N(d,n){sup 15}O({beta}+). As long as the BN material matrix remains constant, the ratio of thick target yields depends only on the deuterium ion energy and is independent of ion fluence and detector efficiency. Calibration of the diagnostic was accomplished by irradiating BN targets with deuterium beams of known ion kinetic energy and fluence. The calibrated diagnostic was then fielded to measure the voltage in a Plasma Opening Switch (POS). Electrical measurements of the POS voltage and the voltage inferred from the BN nuclear activation diagnostic were in good agreement.

  4. Metal Ion Activation of Clostridium sordellii Lethal Toxin and Clostridium difficile Toxin B.

    PubMed

    Genth, Harald; Schelle, Ilona; Just, Ingo

    2016-04-01

    Lethal Toxin from Clostridium sordellii (TcsL) and Toxin B from Clostridium difficile (TcdB) belong to the family of the "Large clostridial glycosylating toxins." These toxins mono-O-glucosylate low molecular weight GTPases of the Rho and Ras families by exploiting UDP-glucose as a hexose donor. TcsL is casually involved in the toxic shock syndrome and the gas gangrene. TcdB-together with Toxin A (TcdA)-is causative for the pseudomembranous colitis (PMC). Here, we present evidence for the in vitro metal ion activation of the glucosyltransferase and the UDP-glucose hydrolysis activity of TcsL and TcdB. The following rating is found for activation by divalent metal ions: Mn(2+) > Co(2+) > Mg(2+) > Ca(2+), Cu(2+), Zn(2+). TcsL and TcdB thus require divalent metal ions providing an octahedral coordination sphere. The EC50 values for TcsL were estimated at about 28 µM for Mn(2+) and 180 µM for Mg(2+). TcsL and TcdB further require co-stimulation by monovalent K⁺ (not by Na⁺). Finally, prebound divalent metal ions were dispensible for the cytopathic effects of TcsL and TcdB, leading to the conclusion that TcsL and TcdB recruit intracellular metal ions for activation of the glucosyltransferase activity. With regard to the intracellular metal ion concentrations, TcsL and TcdB are most likely activated by K⁺ and Mg(2+) (rather than Mn(2+)) in mammalian target cells. PMID:27089365

  5. Gas-phase activation and reaction dynamics of chiral ion-dipole complexes.

    PubMed

    Filippi, Antonello; Speranza, Maurizio

    2003-11-01

    A family of enantiomerically pure oxonium ions, that is O-protonated 1-aryl-1-methoxyethanes, has been generated in the gas phase by the (CH(3))(2)Cl(+) methylation of the corresponding 1-arylethanols. Some information on their reaction dynamics was obtained from a detailed kinetic study of their inversion of configuration and dissociation. The activation parameters of the inversion reaction are found to obey two different isokinetic relationships depending upon the nature and the position of the substituents in the oxonium ions. In contrast, the activation parameters of the dissociation reaction obey a single isokinetic relationship. The inversion and dissociation rate constants do not follow simple linear free-energy relationships. This complicated kinetic picture has been rationalized in terms of different activation dynamics in gaseous CH(3)Cl, which, in turn, determine the reaction dynamics of the oxonium ion. When the predominant activation of the oxonium ion involves resonant energy exchange from the 1015 cm(-1) CH(3) rocking mode of unperturbed CH(3)Cl, the inversion reaction proceeds through the dynamically most favored TS, characterized by the unassisted C(alpha)bond;O bond elongation. When, instead, the activation of the oxonium ions requires the formation of an intimate encounter complex with CH(3)Cl, the inversion reaction takes place via the energetically most favored TS, characterized by multiple coordination of the CH(3)OH moiety with the H(alpha) and H(ortho) atoms of the benzylic residue. The activation dynamics operating in the intimate encounter complex with CH(3)Cl is also responsible for the dissociation of most selected oxonium ions.

  6. Coordination number of zinc ions in the phosphotriesterase active site by molecular dynamics and quantum mechanics.

    PubMed

    Koca, Jaroslav; Zhan, Chang-Guo; Rittenhouse, Robert C; Ornstein, Rick L

    2003-02-01

    We have run several molecular dynamics (MD) simulations on zinc-containing phosphotriesterase (PTE) with two bound substrates, sarin and paraoxon, and with the substrate analog diethyl 4-methylbenzylphosphonate. A standard nonbonded model was employed to treat the zinc ions with the commonly used charge of +2. In all the trajectories, we observed a tightly bound water (TBW) molecule in the active site that was coordinated to the less buried zinc ion. The phosphoryl oxygen of the substrate/inhibitor was found to be coordinated to the same zinc ion so that, considering all ligands, the less buried zinc was hexa-coordinated. The hexa-coordination of this zinc ion was not seen in the deposited X-ray pdb files for PTE. Several additional MD simulations were then performed using different charges (+1, +1.5) on the zinc ions, along with ab initio and density functional theory (DFT) calculations, to evaluate the following possibilities: the crystal diffraction data were not correctly interpreted; the hexa-coordinated zinc ion in PTE is only present in solution and not in the crystal; and the hexa-coordinated zinc ion in PTE is an artifact of the force field used. A charge of +1.5 leads to a coordination number (CN) of 5 on both zinc ions, which is consistent with the results from ab initio and DFT calculations and with the latest high resolution X-ray crystal structure. The commonly used charge of +2 produces a CN of 6 on the less buried zinc. The CN on the more buried zinc ion is 5 when the substrate/inhibitor is present in the simulation, and increases to 6 when the substrate/inhibitor is removed prior to the simulation. The results of both of the MD and quantum mechanical calculations lead to the conclusion that the zinc ions in the PTE active site are both penta-coordinated, and that the MD simulations performed with the charge of +2 overestimate the CN of the zinc ions in the PTE active site. The overall protein structures in the simulations remain unaffected by the

  7. Suprathermal Charged Particle Acceleration by Small-scale Flux Ropes.

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; le Roux, J. A.; Webb, G. M.

    2015-12-01

    We consider different limits of our recently developed kinetic transport theory to investigate the potential of super-Alvenic solar wind regions containing several small-scale flux ropes to explain the acceleration of suprathermal ions to power-law spectra as observations show. Particle acceleration is modeled in response to flux-rope activity involving contraction, merging (reconnection), and collisions in the limit where the particle gyoradius is smaller than the characteristic flux-rope scale length. The emphasis is mainly on the statistical variance in the electric fields induced by flux-rope dynamics rather than on the mean electric field induced by multiple flux ropes whose acceleration effects are discussed elsewhere. Our steady-state analytical solutions suggest that particle drift acceleration by flux ropes, irrespective of whether displaying incompressible or compressible behavior, can yield power laws asymptotically at higher energies whereas an exponential spectral rollover results asymptotically when field-aligned guiding center motion acceleration occur by reconnection electric fields from merging flux ropes. This implies that at sufficiently high particle energies, drift acceleration might dominate. We also expect compressive flux ropes to yield harder power-law spectra than incompressible flux ropes. Preliminary results will be discussed to illustrate how particle acceleration might be affected when both diffusive shock and small-scale flux acceleration occur simultaneously at interplanetary shocks.

  8. Poisson-Fermi model of single ion activities in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Liu, Jinn-Liang; Eisenberg, Bob

    2015-09-01

    A Poisson-Fermi model is proposed for calculating activity coefficients of single ions in strong electrolyte solutions based on the experimental Born radii and hydration shells of ions in aqueous solutions. The steric effect of water molecules and interstitial voids in the first and second hydration shells play an important role in our model. The screening and polarization effects of water are also included in the model that can thus describe spatial variations of dielectric permittivity, water density, void volume, and ionic concentration. The activity coefficients obtained by the Poisson-Fermi model with only one adjustable parameter are shown to agree with experimental data, which vary nonmonotonically with salt concentrations.

  9. Modulation of bone remodeling via mechanically activated ion channels

    NASA Technical Reports Server (NTRS)

    Duncan, Randall L. (Principal Investigator)

    1996-01-01

    A critical factor in the maintenance of bone mass is the physical forces imposed upon the skeleton. Removal of these forces, such as in a weightless environment, results in a rapid loss of bone, whereas application of exogenous mechanical strain has been shown to increase bone formation. Numerous flight and ground-based experiments indicate that the osteoblast is the key bone cell influenced by mechanical stimulation. Aside from early transient fluctuations in response to unloading, osteoclast number and activity seem unaffected by removal of strain. However, bone formation is drastically reduced in weightlessness and osteoblasts respond to mechanical strain with an increase in the activity of a number of second messenger pathways resulting in increased anabolic activity. Unfortunately, the mechanism by which the osteoblast converts physical stimuli into a biochemical message, a process we have termed biochemical coupling, remains elusive. Prior to the application of this grant, we had characterized a mechanosensitive, cation nonselective channel (SA-cat) in osteoblast-like osteosarcoma cells that we proposed is the initial signalling mechanism for mechanotransduction. During the execution of this grant, we have made considerable progress to further characterize this channel as well as to determine its role in the osteoblastic response to mechanical strain. To achieve these goals, we combined electrophysiologic techniques with cellular and molecular biology methods to examine the role of these channels in the normal function of the osteoblast in vitro.

  10. Impact of Human Activities on the Flux of Terrestrial Sediments to the Coastal Ocean Offshore Northeastern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Tzu-Ting; Su, Chih-Chieh; Liu, Char-Shine; Huang, Chen-fen; Hsu, Ho-Han

    2016-04-01

    Land to ocean material fluxes play an important role in global biogeochemical cycles. Changes in sediment supply not only greatly influence the benthic environment of coastal estuaries but also might threaten human lives and properties. Artificial constructions, such as roads and reservoirs, could affect natural environments and change sediment discharges. Due to its high precipitation, steep slopes, small basin areas, and frequent flood events, Taiwan is characterized with rapid erosion rates and extremely high sediment yields. In northeastern Taiwan, the high mean annual precipitation lead to large amounts of sediments being delivered into the ocean through the Lanyang River. Since 1957, the road constructions along the Lanyang River greatly increased terrestrial sediment flux to the coastal ocean. However, its influence on offshore area is not yet clear. In this study, we combine geochemical and geophysical data to evaluate the modern sedimentation history and discuss the impact of human activities on the Ilan Shelf. The preliminary results of grain size and 210Pb analyses from five sediment cores taken from the upper South Guishan Channel indicate the existence of local differences on hydrodynamic conditions. In addition, we also applied similarity index which based on a quantitative analysis algorithm to the chirp sonar data on echo character classification and calculated continuous grain size variations of the seafloor surface sediments. By combining all geochemical and geophysical data, we may reconstruct the holistic picture of human impacts on offshore environment from sedimentology records.

  11. A New Way of Sensing: Need-Based Activation of Antibiotic Resistance by a Flux-Sensing Mechanism

    PubMed Central

    Fritz, Georg; Dintner, Sebastian; Treichel, Nicole Simone; Radeck, Jara; Gerland, Ulrich; Gebhard, Susanne

    2015-01-01

    ABSTRACT Sensing of and responding to environmental changes are of vital importance for microbial cells. Consequently, bacteria have evolved a plethora of signaling systems that usually sense biochemical cues either via direct ligand binding acting as “concentration sensors” or by responding to downstream effects on bacterial physiology, such as structural damage to the cell. Here, we describe a novel, alternative signaling mechanism that effectively implements a “flux sensor” to regulate antibiotic resistance. It relies on a sensory complex consisting of a histidine kinase and an ABC transporter, in which the transporter fulfills the dual role of both the sensor of the antibiotic and the mediator of resistance against it. Combining systems biological modeling with in vivo experimentation, we show that these systems in fact respond to changes in activity of individual resistance transporters rather than to changes in the antibiotic concentration. Our model shows that the cell thereby adjusts the rate of de novo transporter synthesis to precisely the level needed for protection. Such a flux-sensing mechanism may serve as a cost-efficient produce-to-demand strategy, controlling a widely conserved class of antibiotic resistance systems. PMID:26199330

  12. Continuous monitoring of soil CO2 flux in tectonic active area of Sicily: relationship between gas emissions and crustal stress

    NASA Astrophysics Data System (ADS)

    Camarda, Marco; De Gregorio, Sofia; Favara, Rocco; Di Martino, Roberto M. R.

    2015-04-01

    Tectonic active areas are subjected to continue modification of the stress fields as result of the relative movement of portions of the crust. In these areas the stress generated the seismogenetic processes and at same time produces detectable modifications in the shallower portion of the crust such as superficial deformation, increase or decrease of pore pressure and change in fluids circulation. As results a wide variety of changes can be recorded in several parameters due to stress field modifications. The aim of this study was to monitor in continuous soil gas emissions of selected tectonic active area of the Sicily in order to investigate the relation between changes on this parameter and stress field modifications linked to seismogenetic processes. For this reason, in cooperation with DPC Sicilia a network of 20 stations for continuous monitoring of soil CO2 flux in the main seismic area of Sicily was deployed. The selection of the monitoring sites was based on a detailed geological structural study aimed to recognize active tectonic structures and on geochemical survey for identifying areas of anomalous degassing along the structures. Time series of soil CO2 flux long from 1 to 3 years were obtained. The acquired series were filtered for removing atmospheric parameters induced variations by applying the fast Fourier transform (FFT) and regression analysis.The results of comparison of filtered signals showed as almost all the stations have a low coefficient correlation, indicating that the recorded variations are likely due to minor stress modification having small spatial scale. A discrete correlation was founded between the signals of three stations placed in the same tectonic context in northeastern sector of Sicily. Interesting these stations showed a contemporary steep increase few days before the onset of seismic sequence, with events of magnitude up to 4.4, occurred in August 2013 in the northeastern Sicily. The concomitance of change in soil CO2 flux

  13. Influence of several metal ions on the gelation activation energy of silicon tetraethoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1990-01-01

    The effects of nine metal cations Li(+), Na(+), Mg(2+), Ca(2+), Sr(2+), Cu(2+), Al(3+), La(3+), and Y(3+) on silica gel formation has been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of water:TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for -Si-O-Si- network formation is found to be 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increase in the presence of Cu(2+), Al(3+), La(3+) and Y(3+). In contrast, the presence of Li(+), Na(+), Mg(2+), Ca(2+), or Sr(2+) lowers the gelation time, but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during the polycondensation step. The concentration of metal ion Mg(2+), Ca(2+), Y(3+) or the water:TEOS mole ratio had no appreaciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.

  14. Influence of several metal ions on the gelation activation energy of silicon tetraethoxide

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1988-01-01

    The effects of nine metal cations (Li(+), Na(+), Mg(2+), Ca(2+), Sr(2+), Cu(2+), Al(3+), La(3+), and Y(3+) on silica gel formation has been investigated by studying the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) in the presence of metal nitrates. The influence of water: TEOS mole ratio, metal ion concentration, and the reaction temperature has been investigated. The overall activation energy for gel formation has been determined from the temperature dependence of the time of gelation for each system. The activation energy for -Si-O-Si- network formation is found to be 54.5 kJ/mol. The gel formation time as well as the activation energy sharply increase in the presence of Cu(2+), Al(3+), La(3+) and Y(3+). In contrast, the presence of Li(+), Na(+), Mg(2+), Ca(2+), or, Sr(2+) lowers the gelation time, but has no appreciable effect on the activation energy. This difference may be attributed to the participation or nonparticipation of the metal ions in the formation of the three-dimensional polymeric network during the polycondensation step. The concentration of metal ion (Mg(2+), Ca(2+), Y(3+) or the water: TEOS mole ratio had no appreciable effect on the gelation activation energy. A simple test has been proposed to determine whether a metal ion would act as a network intermediate or modifier in silica and other glassy networks.

  15. Unidirectional ion movements in the hindgut of larval Sarcophaga bullata (Diptera: Sarcophagidae).

    PubMed

    Prusch, R D

    1976-02-01

    1. Unidirectional Na+, K+, and Cl- fluxes were measured across the isolated hindgut of larval Sarcophaga bullata. 2. Both K+ and Cl- are actively secreted into the hindgut lumen, whereas Na+ is distributed passively. 3. The movements of K+ and Cl- are not entirely independent of each other, and the movement of one ion influences the flux of the co-ion. 4. The NH4+ ion is secreted into the hindgut by a mechanism separate from K+ secretion.

  16. Allosteric activation of brain hexokinase by magnesium ions and by magnesium ion--adenosine triphosphate complex.

    PubMed

    Bachelard, H S

    1971-11-01

    1. Substrate-saturation curves of brain hexokinase for MgATP(2-) were sigmoidal at sub-saturating concentrations of glucose when the Mg(2+)/ATP ratio was maintained at 1:1. Under identical conditions, except that Mg(2+) was present in excess, hyperbolic curves were observed. 2. The number of binding sites (calculated from Hill plots) is 1.8 at a Mg(2+)/ATP ratio 1:1, and 1.0 with excess of Mg(2+). The apparent K(m) for MgATP(2-) is 6.5x10(-4)m at a Mg(2+)/ATP ratio 1:1, and 3.5x10(-4)m with excess of Mg(2+). 3. Interdependence between substrate-binding sites was indicated by the effects of varying the concentration of glucose. The sigmoidality and deviation from Michaelis-Menten kinetics at a Mg(2+)/ATP ratio 1:1 became less pronounced with increasing glucose concentration. Also, although substrate-saturation curves for glucose were hyperbolic when the Mg(2+)/ATP ratio was 1:1, reciprocal plots were non-linear. These were linear with excess of Mg(2+). 4. High concentrations of Mg(2+) (Mg(2+)/ATP ratios above 5:1) were inhibitory. 5. The results are taken to indicate homotropic co-operative binding of MgATP(2-) and that Mg(2+) is an allosteric activator. Possible implications in regulation are discussed.

  17. An activated microporous carbon prepared from phenol-melamine-formaldehyde resin for lithium ion battery anode

    SciTech Connect

    Zhu, Yinhai; Xiang, Xiaoxia; Liu, Enhui; Wu, Yuhu; Xie, Hui; Wu, Zhilian; Tian, Yingying

    2012-08-15

    Highlights: ► Microporous carbon was prepared by chemical activation of phenol-melamine-formaldehyde resin. ► Activation leads to high surface area, well-developed micropores. ► Micropores lead to strong intercalation between carbon and lithium ion. ► Large surface area promotes to improve the lithium storage capacity. -- Abstract: Microporous carbon anode materials were prepared from phenol-melamine-formaldehyde resin by ZnCl{sub 2} and KOH activation. The physicochemical properties of the obtained carbon materials were characterized by scanning electron microscope, X-ray diffraction, Brunauer–Emmett–Teller, and elemental analysis. The electrochemical properties of the microporous carbon as anode materials in lithium ion secondary batteries were evaluated. At a current density of 100 mA g{sup −1}, the carbon without activation shows a first discharge capacity of 515 mAh g{sup −1}. After activation, the capacity improved obviously. The first discharge capacity of the carbon prepared by ZnCl{sub 2} and KOH activation was 1010 and 2085 mAh g{sup −1}, respectively. The reversible capacity of the carbon prepared by KOH activation was still as high as 717 mAh g{sup −1} after 20 cycles, which was much better than that activated by ZnCl{sub 2}. These results demonstrated that it may be a promising candidate as an anode material for lithium ion secondary batteries.

  18. Effect of multi-ions on active flow regulation in plants

    NASA Astrophysics Data System (ADS)

    Ryu, Jeongeun; Ahn, Sungsook; Kim, Seung-Gon; Oh, Hwasuk; Kim, Taejoo; Lee, Sang Joon

    2012-11-01

    Plants have been known to regulate ion-mediated flows actively in xylem vessels. Pits, the porous structures in xylem vessels, are presumed to play a key role in the ion-mediated flow regulation based on dynamic swelling and shrinking of their pectic matrix. However, the autonomous flow regulation in plants has not been elucidated yet and the pectin-swelling hypothesis seems to be simply applied to account for dynamic modulation of xylem conductance. In this study, the effects of multiple ions and their concentration on the water transport in plants were experimentally investigated. In addition, the active regulation mechanism of xylem water flow was also examined with considering the ionic effect.

  19. Influence of air ions on brain activity induced by electrical stimulation in the rat

    NASA Astrophysics Data System (ADS)

    Olivereau, J. M.; Lambert, J. F.; Truong-Ngoc, A.

    1981-03-01

    The brain induced activity was studied in 18 rats wearing chronically skull implanted electrodes. The stimulating factor was various electrical stimulations of the mesencephalic reticular activating formation, given during the slow wave state of sleep. The results of 300 stimulations were measured by amplitude and frequency changes in the EEG simultaneously recorded. Animals previously exposed to positive air ions (3 weeks 80,000 ions/ml) exhibited lowered excitability of the reticulocortical system. Significantly higher stimulations were necessary to induce arousal. Negative air ions induced more intricate effects: brain excitability was lowered when tested with weak stimulations, but normal when evaluated with medium high level stimilations. Sleep seems first more stable but as stimulation increases, arousal is soon as effective as in controls. These results are in agreement with others findings in behavioral fields and partly explains them.

  20. Two distinct modes of metal ion binding in the nuclease active site of a viral DNA-packaging terminase: insight into the two-metal-ion catalytic mechanism.

    PubMed

    Zhao, Haiyan; Lin, Zihan; Lynn, Anna Y; Varnado, Brittany; Beutler, John A; Murelli, Ryan P; Le Grice, Stuart F J; Tang, Liang

    2015-12-15

    Many dsDNA viruses encode DNA-packaging terminases, each containing a nuclease domain that resolves concatemeric DNA into genome-length units. Terminase nucleases resemble the RNase H-superfamily nucleotidyltransferases in folds, and share a two-metal-ion catalytic mechanism. Here we show that residue K428 of a bacteriophage terminase gp2 nuclease domain mediates binding of the metal cofactor Mg(2+). A K428A mutation allows visualization, at high resolution, of a metal ion binding mode with a coupled-octahedral configuration at the active site, exhibiting an unusually short metal-metal distance of 2.42 Å. Such proximity of the two metal ions may play an essential role in catalysis by generating a highly positive electrostatic niche to enable formation of the negatively charged pentacovalent phosphate transition state, and provides the structural basis for distinguishing Mg(2+) from Ca(2+). Using a metal ion chelator β-thujaplicinol as a molecular probe, we observed a second mode of metal ion binding at the active site, mimicking the DNA binding state. Arrangement of the active site residues differs drastically from those in RNase H-like nucleases, suggesting a drifting of the active site configuration during evolution. The two distinct metal ion binding modes unveiled mechanistic details of the two-metal-ion catalysis at atomic resolution.

  1. MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

    SciTech Connect

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay E-mail: sgosain@prl.res.i

    2010-09-20

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  2. Magnetic Non-potentiality of Solar Active Regions and Peak X-ray Flux of the Associated Flares

    NASA Astrophysics Data System (ADS)

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay

    2010-09-01

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  3. Combined effects of water temperature and copper ion concentration on catalase activity in Crassostrea ariakensis

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Yang, Hongshuai; Liu, Jiahui; Li, Yanhong; Liu, Zhigang

    2015-07-01

    A central composite experimental design and response surface method were used to investigate the combined effects of water temperature (18-34°C) and copper ion concentration (0.1-1.5 mg/L) on the catalase (CAT) activity in the digestive gland of Crassostrea ariakensis. The results showed that the linear effects of temperature were significant ( P<0.01), the quadratic effects of temperature were significant ( P<0.05), the linear effects of copper ion concentration were not significant ( P>0.05), and the quadratic effects of copper ion concentration were significant ( P<0.05). Additionally, the synergistic effects of temperature and copper ion concentration were not significant ( P>0.05), and the effect of temperature was greater than that of copper ion concentration. A model equation of CAT enzyme activity in the digestive gland of C. ariakensis toward the two factors of interest was established, with R 2, Adj. R 2 and Pred. R 2 values as high as 0.943 7, 0.887 3 and 0.838 5, respectively. These findings suggested that the goodness of fit to experimental data and predictive capability of the model were satisfactory, and could be practically applied for prediction under the conditions of the study. Overall, the results suggest that the simultaneous variation of temperature and copper ion concentration alters the activity of the antioxidant enzyme CAT by modulating active oxygen species metabolism, which may be utilized as a biomarker to detect the effects of copper pollution.

  4. A Two-Metal-Ion-Mediated Conformational Switching Pathway for HDV Ribozyme Activation

    PubMed Central

    Lee, Tai-Sung; Radak, Brian K.; Harris, Michael E.; York, Darrin M.

    2016-01-01

    RNA enzymes serve as a potentially powerful platform from which to design catalysts and engineer new biotechnology. A fundamental understanding of these systems provides insight to guide design. The hepatitis delta virus ribozyme (HDVr) is a small, self-cleaving RNA motif widely distributed in nature, that has served as a paradigm for understanding basic principles of RNA catalysis. Nevertheless, questions remain regarding the precise roles of divalent metal ions and key nucleotides in catalysis. In an effort to establish a reaction mechanism model consistent with available experimental data, we utilize molecular dynamics simulations to explore different conformations and metal ion binding modes along the HDVr reaction path. Building upon recent crystallographic data, our results provide a dynamic model of the HDVr reaction mechanism involving a conformational switch between multiple non-canonical G25:U20 base pair conformations in the active site. These local nucleobase dynamics play an important role in catalysis by modulating the metal binding environments of two Mg2+ ions that support catalysis at different steps of the reaction pathway. The first ion plays a structural role by inducing a base pair flip necessary to obtain the catalytic fold in which C75 moves towards to the scissile phosphate in the active site. Ejection of this ion then permits a second ion to bind elsewhere in the active site and facilitate nucleophile activation. The simulations collectively describe a mechanistic scenario that is consistent with currently available experimental data from crystallography, phosphorothioate substitutions, and chemical probing studies. Avenues for further experimental verification are suggested. PMID:27774349

  5. Impact of Ion Implantation on Licorice (Glycyrrhiza uralensis Fisch) Growth and Antioxidant Activity Under Drought Stress

    NASA Astrophysics Data System (ADS)

    Liu, Jingnan; Tong, Liping; Shen, Tongwei; Li, Jie; Wu, Lijun; Yu, Zengliang

    2007-06-01

    Low energy ion beams are known to have stimulation effects on plant generation and to improve plants' intrinsic quality. In the present study, the growth and physiological index of licorice implanted with 0, 8, 10, 12 and 14× (2.6×1015) ions/cm2 were investigated under well-watered and drought-stress conditions. The results showed that a proper dose of ion implantation was particularly efficient in stimulating the licorice growth and improving the plant biomass significantly in both the well-watered and drought-stress conditions. The physiological results of licorice measured by leaf water potential, lipid oxidation, soluble protein and antioxidant system showed a significant correlation between ion implantation and water regime except for leaf water potential. Therefore, the study indicated that ion implantation can enhance licorice's drought tolerance by increasing the activity of superoxide dismutase (SOD), catalase (CAT) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability to lower oxidative damage to lipids in plants. Ion beam implantation, therefore, provides an alternative method to enhance licorice drought tolerance.

  6. Activity, size, and flux of resuspended particles from Rocky Flats soil

    SciTech Connect

    Langer, G.

    1982-01-01

    Wind erosion processes that resuspend soil from Rocky Flats (rf) sites known as the pad field and the east field were studied. The soil in these sites contains above background amounts of Pu and Am. The following five major areas of concern were studied: Pu levels in source area soil; total Pu activity and activity-particle size relationship in the wind resuspended dust; culpability of suspected source areas for Pu activity reported by the RF surveillance samplers; Pu activity in the respirable and coarse fraction of wind resuspended dust; Pu activity in resuspended dust from wind tunnel simulations of wind erosion. Results indicate that Pu attached to wind blown dust from the pad field and the east field at rf does not present a health hazard. The Pu carrying dust particles are too large (> 3 ..mu..m) to be respirable and most are above the inhalable size (> 10 ..mu..m). For the July 1981 to March 1982 period, 90% of the Pu collected by the surveillance samplers east of the pad field originated from this field. For those months 90% of the winds over 14 m/s originated from the two western quadrants. Winds over 14 m/s resuspend most of the dust. From April to June 1982 there were no winds over 14 m/s and Pu originated about equally from the pad and east field. Wind tunnel resuspension of dust varied as the 2.8 to 4.2 power of wind speed for a soil moisture range of 14 to 1% respectively. Above 14% moisture little dust was resuspended. No measurable respirable particles (< 3 ..mu..m) were resuspended.

  7. Gypenoside XVII Enhances Lysosome Biogenesis and Autophagy Flux and Accelerates Autophagic Clearance of Amyloid-β through TFEB Activation.

    PubMed

    Meng, Xiangbao; Luo, Yun; Liang, Tian; Wang, Mengxia; Zhao, Jingyu; Sun, Guibo; Sun, Xiaobo

    2016-04-01

    A strategy for activating transcription factor EB (TFEB) to restore autophagy flux may provide neuroprotection against Alzheimer's disease. Our previous study reported that gypenoside XVII (GP-17), which is a major saponin abundant in ginseng and Panax notoginseng, ameliorated amyloid-β (Aβ)25-35-induced apoptosis in PC12 cells by regulating autophagy. In the present study, we aimed to determine whether GP-17 has neuroprotective effects on PC12 cells expressing the Swedish mutant of APP695 (APP695swe) and APP/PS1 mice. We also investigated the underlying mechanism. We found that GP-17 could significantly increase Atg5 expression and the conversion of LC3-I to LC3-II in APP695 cells, which was associated with a reduction in p62 expression. GP-17 also elevated the number of LC3 puncta in APP695 cells transduced with pCMV-GFP-LC3. GP-17 promoted the autophagy-based elimination of AβPP, Aβ40, and Aβ42 in APP695swe cells and prevented the formation of Aβ plaques in the hippocampus and cortex of APP/PS1 mice. Furthermore, spatial learning and memory deficits were cured. Atg5 knockdown could abrogate the GP-17-mediated removal of AβPP, Aβ40, and Aβ42 in APP695swe cells. GP-17 upregulated LAMP-1, increased LysoTracker staining, and augmented LAMP-1/LC3-II co-localization. GP-17 could release TFEB from TFEB/14-3-3 complexes, which led to TFEB nuclear translocation and the induction of autophagy and lysosome biogenesis and resulted in the amelioration of autophagy flux. The knockdown of TFEB could abolish these effects of GP-17. In summary, these results demonstrated that GP-17 conferred protective effects to the cellular and rodent models of Alzheimer's disease by activating TFEB. PMID:27060963

  8. Characterization of flux-grown Trace-element-doped titanite using the high-mass-resolution ion microprobe (SHRIMP-RG)

    USGS Publications Warehouse

    Mazdab, F.K.

    2009-01-01

    Crystals of titanite can be readily grown under ambient pressure from a mixture of CaO, TiO2 and SiO2 in the presence of molten sodium tetraborate. The crystals produced are euhedral and prismatic, lustrous and transparent, and up to 5 mm in length. Titanite obtained by this method contains approximately 4300 ppm Na and 220 ppm B contributed from the flux. In addition to dopant-free material, titanite containing trace alkali and alkaline earth metals (K, Sr, Ba), transition metals (Sc, Cr, Ni, Y, Zr, Nb, Hf and Ta), rare-earth elements (REE), actinides (Th, U) and p-block elements (F, S, Cl, Ge, Sn and Pb) have been prepared using the same procedure. Back-scattered electron (BSE) imaging accompanied by ion-microprobe (SHRIMP-RG) analysis confirms significant incorporation of selected trace-elements at structural sites. Regardless of some zonation, the large size of the crystals and broad regions of chemical homogeneity make these crystals useful as experimental starting material, and as matrix-matched trace-element standards for a variety of microbeam analytical techniques where amorphous titanite glass, heterogeneous natural titanite or a non-titanite standard may be less than satisfactory. Trace-element-doped synthetic crystals can also provide a convenient proxy for a better understanding of trace-element incorporation in natural titanite. Comparisons with igneous, authigenic and high-temperature metasomatic titanite are examined. The use of high-mass-resolution SIMS also demonstrates the analytical challenges inherent to any in situ mass-spectrometry-based analysis of titanite, owing to the production of difficult-to-resolve molecular interferences. These interferences are dominated by Ca-Ca, Ca-Ti and Ti-Ti dimers that are significant in the mass range of 80-100, affecting all isotopes of Sr and Zr, as well as 89Y and 93Nb. Methods do exist for the evaluation of interferences by these dimers and of polyatomic interferences on the LREE.

  9. Persulfate oxidation for in situ remediation of TCE. II. Activated by chelated ferrous ion.

    PubMed

    Liang, Chenju; Bruell, Clifford J; Marley, Michael C; Sperry, Kenneth L

    2004-06-01

    In situ chemical oxidation (ISCO) is a technique used to remediate contaminated soil and groundwater systems. It has been postulated that sodium persulfate (Na2S2O8) can be activated by transition metal ions such as ferrous ion (Fe2+) to produce a powerful oxidant known as the sulfate free radical (SO4-*) with a redox potential of 2.6 V, which can potentially destroy organic contaminants. In this laboratory study persulfate oxidation of dissolved trichloroethylene (TCE) was investigated in aqueous and soil slurry systems under a variety of experimental conditions. A chelating agent (i.e., citric acid) was used in attempt to manipulate the quantity of ferrous ion in solution by providing an appropriate chelate/Fe2+ molar ratio. In an aqueous system a chelate/Fe2+ molar ratio of 1/5 (e.g., S2O8(2)-/chelate/Fe2+/TCE ratio of 20/2/10/1) was found to be the lowest acceptable ratio to maintain sufficient quantities of Fe2+ activator in solution resulting in nearly complete TCE destruction after only 20 min. The availability of Fe2+ appeared to be controlled by adjusting the molar ratio of chelate/Fe2+. In general, high levels of chelated ferrous ion concentrations resulted in faster TCE degradation and more persulfate decomposition. However, if initial ferrous ion contents are relatively low, sufficient quantities of chelate must be provided to ensure the chelation of a greater percentage of the limited ferrous ion present. Citric acid chelated ferrous ion appeared effective for TCE degradation within soil slurries but required longer reaction times. Additionally