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Sample records for ii ionization equilibrium

  1. NON-EQUILIBRIUM CHEMISTRY OF DYNAMICALLY EVOLVING PRESTELLAR CORES. II. IONIZATION AND MAGNETIC FIELD

    SciTech Connect

    Tassis, Konstantinos; Willacy, Karen; Yorke, Harold W.; Turner, Neal J.

    2012-07-20

    We study the effect that non-equilibrium chemistry in dynamical models of collapsing molecular cloud cores has on measurements of the magnetic field in these cores, the degree of ionization, and the mean molecular weight of ions. We find that OH and CN, usually used in Zeeman observations of the line-of-sight magnetic field, have an abundance that decreases toward the center of the core much faster than the density increases. As a result, Zeeman observations tend to sample the outer layers of the core and consistently underestimate the core magnetic field. The degree of ionization follows a complicated dependence on the number density at central densities up to 10{sup 5} cm{sup -3} for magnetic models and 10{sup 6} cm{sup -3} in non-magnetic models. At higher central densities, the scaling approaches a power law with a slope of -0.6 and a normalization which depends on the cosmic-ray ionization rate {zeta} and the temperature T as ({zeta}T){sup 1/2}. The mean molecular weight of ions is systematically lower than the usually assumed value of 20-30, and, at high densities, approaches a value of 3 due to the asymptotic dominance of the H{sup +}{sub 3} ion. This significantly lower value implies that ambipolar diffusion operates faster.

  2. IEHI: Ionization Equilibrium for Heavy Ions

    NASA Astrophysics Data System (ADS)

    Cranmer, Steven R.

    2015-07-01

    IEHI, written in Fortran, outputs a simple "coronal" ionization equilibrium (i.e., collisional ionization and auto-ionization balanced by radiative and dielectronic recombination) for a plasma at a given electron temperature.

  3. IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS

    SciTech Connect

    Smith, Randall K.; Hughes, John P. E-mail: jph@physics.rutgers.ed

    2010-07-20

    Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai and Hughes and Helfand. In general, the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z + 1 first-order differential equations. However, they can be recast as Z uncoupled first-order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of the slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombining plasma, or even a plasma with random initial conditions, and will allow users of these diagnostics to determine directly if their best-fit result significantly limits the timescale since a disturbance or is so close to equilibrium as to include an arbitrarily long time.

  4. Iron ionization and recombination rates and ionization equilibrium

    NASA Technical Reports Server (NTRS)

    Arnaud, M.; Raymond, J.

    1992-01-01

    In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.

  5. Collisional Ionization Equilibrium for Optically Thin Plasmas

    NASA Technical Reports Server (NTRS)

    Bryans, P.; Mitthumsiri, W.; Savin, D. W.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.

    2006-01-01

    Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have utilized state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn. We have also utilized state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of Mazzotta et al. (1998), we have calculated improved collisional ionization equilibrium calculations. We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. (1998) for all elements from H to Ni, and with the fractional abundances derived from the modern DR and RR calculations of Gu (2003a,b, 2004) for Mg, Si, S, Ar, Ca, Fe, and Ni.

  6. Non-LTE effects on the ionization equilibrium of Fe I/Fe II: Application to the red giants of Carina dSph Galaxy

    NASA Astrophysics Data System (ADS)

    Merle, T.; Fabrizio, M.; Thévenin, F.; Nonino, M.; Bono, G.

    2012-12-01

    In the context of the Carina Project, we re-analyze the iron abundances of 44 red giants of the Carina dSph galaxy to derive its metallicity distribution function. The abundance analyses were performed with the LTE spectrum synthesis fitting method using ESO/VLT high resolution spectra. Using {Fe I} lines, we obtained stellar metallicities of ˜0.1 dex lower than using {Fe II} lines. This discrepancy is classically interpreted as an error on the surface gravity (based on photometry and evolutionary tracks) which is removed by changing gravity until {Fe I} abundances match {Fe II} ones. However, the NLTE mechanism of over-ionization regarding LTE can also explain this discrepancy in giant stars. To support this idea, we performed NLTE computations with a {Fe I}/II model atom and show that this discrepancy is well reproduced. NLTE computations also highlight large discrepancies in individual lines of {Fe I} and {Fe II}.

  7. Non-equilibrium ionized blast wave

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1974-01-01

    The structure of a cylindrical blast wave with ionization at non-LTE conditions was calculated using equations previously developed by Wu and Fu (1970). The degree of ionization was predicted by a modified Saha equation. Temperature profiles show that the temperature at non-LTE conditions is lower than at LTE near the shock front. This corresponds to a higher degree of ionization for the non-LTE limit, which indicates that the neutral gas absorption is much more efficient at non-LTE than at the LTE limit. The decaying velocity under non-LTE is approximately 15% less than under LTE.

  8. NON-EQUILIBRIUM IONIZATION IN THE BIFROST STELLAR ATMOSPHERE CODE

    SciTech Connect

    Olluri, K.; Gudiksen, B. V.; Hansteen, V. H.

    2013-03-15

    The chromosphere and transition region have for the last 20 years been known to be quite dynamic layers of the solar atmosphere, characterized by timescales shorter than the ionization equilibrium timescales of many of the ions dominating emission in these regions. Due to the fast changes in the properties of the atmosphere, long ionization and recombination times can lead these ions to being found far from their equilibrium temperatures. A number of the spectral lines that we observe can therefore not be expected a priori to reflect information about local quantities such as the density or temperature, and interpreting observations requires numerical modeling. Modeling the ionization balance is computationally expensive and has earlier only been done in one dimension. However, one-dimensional models can primarily be used to investigate the possible importance of a physical effect, but cannot verify or disprove the importance of that effect in the fully three-dimensional solar atmosphere. Here, using the atomic database package DIPER, we extend one-dimensional methods and implement a solver for the rate equations of the full three-dimensional problem, using the numerical code Bifrost. We present our implementation and report on a few test cases. We also report on studies of the important C IV and Fe XII ions in a semi-realistic two-dimensional solar atmosphere model, focusing on differences between statistical equilibrium and non-equilibrium ionization results.

  9. Equilibrium structures in partially ionized rotating plasmas within Hall magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Krishan, V.; Yoshida, Z.

    2006-09-01

    The formation of equilibrium structures in partially ionized rotating plasmas, consisting of electrons, ions, and neutral molecules, including the Hall effect, is studied in order to diagnose the possible velocity and the magnetic field configurations in a self-consistent manner. A few simple examples show that the linear and the nonlinear force-free magnetic configurations along with essentially nonlinear Beltrami flow field seem to be the general features of plasmas in the special case of the Keplerian rotation relevant for astrophysical plasmas. Thus rotation along with axial bipolar flows emerges as a natural pattern in gravitationally controlled magnetohydrodynamic systems. However, the equilibrium conditions permit more general flow and the magnetic field profiles that can perhaps be fully explored numerically. A special class of equilibria with unit magnetic Prandtl number and equal values of the fractional ion mass density α =ρi/ρn and the Hall parameter ɛ =λi/L exists where ρ's are the uniform mass densities, λi is the ion inertial scale, and L is the scale of the equilibrium structure. An approximate scaling law between the ionization fraction and the scale of the structure is found. Further by expressing the not so well known ionization fraction in terms of the temperature of the system, assuming thermal equilibrium, relationships among the extensive parameters such as the scale, the neutral particle density, the flow velocity, the temperature, and the magnetic field of the equilibrium structure can be determined. There seems to be a good overlap between the Hall and the thermal equilibria. The validity of the neglect of the ion dynamics is discussed.

  10. Non-equilibrium Helium Ionization in an MHD Simulation of the Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Golding, Thomas Peter; Leenaarts, Jorrit; Carlsson, Mats

    2016-02-01

    The ionization state of the gas in the dynamic solar chromosphere can depart strongly from the instantaneous statistical equilibrium commonly assumed in numerical modeling. We improve on earlier simulations of the solar atmosphere that only included non-equilibrium hydrogen ionization by performing a 2D radiation-magnetohydrodynamics simulation featuring non-equilibrium ionization of both hydrogen and helium. The simulation includes the effect of hydrogen Lyα and the EUV radiation from the corona on the ionization and heating of the atmosphere. Details on code implementation are given. We obtain helium ion fractions that are far from their equilibrium values. Comparison with models with local thermodynamic equilibrium (LTE) ionization shows that non-equilibrium helium ionization leads to higher temperatures in wavefronts and lower temperatures in the gas between shocks. Assuming LTE ionization results in a thermostat-like behavior with matter accumulating around the temperatures where the LTE ionization fractions change rapidly. Comparison of DEM curves computed from our models shows that non-equilibrium ionization leads to more radiating material in the temperature range 11-18 kK, compared to models with LTE helium ionization. We conclude that non-equilibrium helium ionization is important for the dynamics and thermal structure of the upper chromosphere and transition region. It might also help resolve the problem that intensities of chromospheric lines computed from current models are smaller than those observed.

  11. NEBULAR: Spectrum synthesis for mixed hydrogen-helium gas in ionization equilibrium

    NASA Astrophysics Data System (ADS)

    Schirmer, Mischa

    2016-08-01

    NEBULAR synthesizes the spectrum of a mixed hydrogen helium gas in collisional ionization equilibrium. It is not a spectral fitting code, but it can be used to resample a model spectrum onto the wavelength grid of a real observation. It supports a wide range of temperatures and densities. NEBULAR includes free-free, free-bound, two-photon and line emission from HI, HeI and HeII. The code will either return the composite model spectrum, or, if desired, the unrescaled atomic emission coefficients. It is written in C++ and depends on the GNU Scientific Library (GSL).

  12. On local ionization equilibrium and disk winds in QSOs

    SciTech Connect

    Pereyra, Nicolas A.

    2014-11-01

    We present theoretical C IV λλ1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5-dimensional time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura-Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90° ({sup e}dge on{sup )}. In the shielded region, we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region, we assume that both the line-force and the C IV populations are nonexistent. The model can account for P-Cygni absorption troughs (produced at edge on viewing angles), multiple absorption troughs (produced at viewing angles close to the angle that separates the shielded region and the non-shielded region), and for detached absorption troughs (produced at an angle in between the first two absorption line types); that is, the model can account for the general types of broad absorption lines seen in QSOs as a viewing angle effect. The steady nature of ADWs, in turn, may account for the steady nature of the absorption structure observed in multiple-trough broad absorption line QSOs. The model parameters are M {sub bh} = 10{sup 9} M {sub ☉} and L {sub disk} = 10{sup 47} erg s{sup –1}.

  13. On Local Ionization Equilibrium and Disk Winds in QSOs

    NASA Astrophysics Data System (ADS)

    Pereyra, Nicolas A.

    2014-11-01

    We present theoretical C IV λλ1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5-dimensional time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura-Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90° ("edge on"). In the shielded region, we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region, we assume that both the line-force and the C IV populations are nonexistent. The model can account for P-Cygni absorption troughs (produced at edge on viewing angles), multiple absorption troughs (produced at viewing angles close to the angle that separates the shielded region and the non-shielded region), and for detached absorption troughs (produced at an angle in between the first two absorption line types); that is, the model can account for the general types of broad absorption lines seen in QSOs as a viewing angle effect. The steady nature of ADWs, in turn, may account for the steady nature of the absorption structure observed in multiple-trough broad absorption line QSOs. The model parameters are M bh = 109 M ⊙ and L disk = 1047 erg s-1.

  14. Non-equilibrium Ionization Modeling of Simulated Pseudostreamers in a Solar Corona Model

    NASA Astrophysics Data System (ADS)

    Shen, Chengcai; Raymond, John C.; Mikić, Zoran; Linker, Jon; Reeves, Katharine K.; Murphy, Nicholas A.

    2015-04-01

    Time-dependent ionization is important for diagnostics of coronal streamers, where the thermodynamic time scale could be shorter than the ionization or recombination time scales, and ions are therefor in non-equilibrium ionization states. In this work, we perform post-processing time-dependent ionization calculations for a three dimensional solar corona and inner heliosphere model from Predictive Sciences Inc. (Mikić & Linker 1999) to analyze the influence of non-equilibrium ionization on emission from coronal streamers. Using the plasma temperature, density, velocity and magnetic field distributions provided by the 3D MHD simulation covering the Whole Sun Month (Carrington rotation CR1913, 1996 August 22 to September 18), we calculate non-equilibrium ionization states in the region around a pseudostreamer. We then obtain the synthetic emissivities with the non-equilibrium ion populations. Under the assumption that the corona is optically thin, we also obtain intensity profiles of several emission lines. We compare our calculations with intensities of Lyman-alpha lines and OVI lines from SOHO/Ultraviolet Coronagraph Spectrometer (UVCS) observations at 14 different heights. The results show that intensity profiles of both Lyman-alpha and OVI lines match well UVCS observations at low heights. At large heights, OVI intensites are higher for non-equilibrium ionization than equilibrium ionization inside this pseudostreamer. The assumption of ionization equilibrium would lead to a underestimate of the OVI intensity by about ten percent at a height of 2 solar radii, and the difference between these two ionization cases increases with height. The intensity ratio of OVI 1032 line to OVI 1037 lines is also obtained for non-equilibrium ionization modeling.

  15. Ionization equilibrium in a cluster plasma with strong interparticle interaction

    SciTech Connect

    Likal'ter, A.A.

    1987-07-01

    An expansion, accurate up to the Madelung term, is derived for the drop in the ionization potential (and pressure) due to the strong Coulomb interaction. The ionization limit, separating the free and bound electron states, is determined with the help of the percolation theory. The principle of no explicit dependence of the total thermodynamic functions of the plasma on the ionization limit is employed. This has the consequence that the region of thermodynamic stability is greatly expanded compared with other models.

  16. Spontaneity and Equilibrium II: Multireaction Systems

    ERIC Educational Resources Information Center

    Raff, Lionel M.

    2014-01-01

    The thermodynamic criteria for spontaneity and equilibrium in multireaction systems are developed and discussed. When N reactions are occurring simultaneously, it is shown that G and A will depend upon N independent reaction coordinates, ?a (a = 1,2, ..., N), in addition to T and p for G or T and V for A. The general criteria for spontaneity and…

  17. The ionization structure of helium in H II region complexes

    NASA Astrophysics Data System (ADS)

    Pena, Miriam

    1986-10-01

    Ionization structure models of H II regions are constructed to analyze the behavior of the helium ionization correction factor, icf, for combinations of different stellar radiation fields as well as for mixtures of individual H II regions of different degrees of ionization. It is found that the amount of neutral He is less than 3 percent and that icf is between 0.98 and 1.00, for H II region coomplexes ionized by OB associations where the hottest stars are earlier than O6, if the ionizing stars are distributed according to a normal IMF. This result applies for a single H II region or for a mixture of unconnected H II regions. This result implies that the He(+)/H(+) ratio observed in extragalactic H II regions of high degree of ionization corresponds to the true He/H abundance ratios.

  18. The equation of state and ionization equilibrium of dense aluminum plasma with conductivity verification

    SciTech Connect

    Wang, Kun; Shi, Zongqian; Shi, Yuanjie; Bai, Jun; Wu, Jian; Jia, Shenli

    2015-06-15

    The equation of state, ionization equilibrium, and conductivity are the most important parameters for investigation of dense plasma. The equation of state is calculated with the non-ideal effects taken into consideration. The electron chemical potential and pressure, which are commonly used thermodynamic quantities, are calculated by the non-ideal free energy and compared with results of a semi-empirical equation of state based on Thomas-Fermi-Kirzhnits model. The lowering of ionization potential, which is a crucial factor in the calculation of non-ideal Saha equation, is settled according to the non-ideal free energy. The full coupled non-ideal Saha equation is applied to describe the ionization equilibrium of dense plasma. The conductivity calculated by the Lee-More-Desjarlais model combined with non-ideal Saha equation is compared with experimental data. It provides a possible approach to verify the accuracy of the equation of state and ionization equilibrium.

  19. Characterizing the non-equilibrium ionization state of the intergalactic medium

    NASA Astrophysics Data System (ADS)

    Silvia, Devin W.; O'Shea, Brian W.; Smith, Britton D.; Shull, J. Michael; Turk, Matthew; Reynolds, Daniel

    2015-01-01

    One of the most common ions used to track metals in the intergalactic medium (IGM) is OVI. Ion species in the IGM are typically assumed to be in ionization equilibrium, but owing to the low density of the plasma they may be significantly out of equilibrium. Divergences from equilibrium would make estimates of the amount and evolution of metals in the IGM incorrect. Using a new software package for building and solving complex chemical networks coupled to cosmological hydrodynamic + N-body simulations, we investigate the non-equilibrium properties of the IGM. In particular, we explore how significantly the ionization structure of the IGM diverges from the equilibrium state as a function of time and physical environment. Motivated by the abundant observational data that probes the intergalactic medium via OVI absorption lines in quasar spectra, we track all ionization states of atomic oxygen alongside those of hydrogen and helium. We use the results of these non-equilibrium simulations to characterize the mass content and ionization properties of the IGM and help interpret current observations made by the Cosmic Origins Spectrograph.

  20. AQUEOUS AMMONIA EQUILIBRIUM - TABULATION OF PERCENT UN-IONIZED AMMONIA

    EPA Science Inventory

    The percent of un-ionized ammonia as a function of pH and temperature in aqueous ammonia solutions of zero salinity is presented in tabular form over the following ranges: temperature 0.0 to 40.0 C in increments of 0.2 degree, and pH 5.00 to 12.00 in increments of 0.01 pH unit.

  1. Approximate analytic solutions for the ionization structure of a pressure equilibrium Strömgren sphere

    NASA Astrophysics Data System (ADS)

    Tinoco Arenas, A.; González Bolívar, M.; Medina Covarrubias, R.; Raga, A. C.

    2015-10-01

    We present analytic models for a photoionized region in pressure equilibrium with the surrounding, neutral material. The models are based on the assumption of a linear relation between the H ionization fraction and the square of the sound speed of the gas. We show that under these assumptions the "grey" radiative transfer equation has analytic solutions that provide the ionization structure and the density of the nebula as a function of radius.

  2. H to Zn Ionization Equilibrium for the Non-Maxwellian Electron κ-distributions: Updated Calculations

    NASA Astrophysics Data System (ADS)

    Dzifčáková, E.; Dudík, J.

    2013-05-01

    New data for the calculation of ionization and recombination rates have been published in the past few years, most of which are included in the CHIANTI database. We used these data to calculate collisional ionization and recombination rates for the non-Maxwellian κ-distributions with an enhanced number of particles in the high-energy tail, which have been detected in the solar transition region and the solar wind. Ionization equilibria for elements H to Zn are derived. The κ-distributions significantly influence both the ionization and recombination rates and widen the ion abundance peaks. In comparison with the Maxwellian distribution, the ion abundance peaks can also be shifted to lower or higher temperatures. The updated ionization equilibrium calculations result in large changes for several ions, notably Fe VIII-Fe XIV. The results are supplied in electronic form compatible with the CHIANTI database.

  3. Hydrodynamic Models of Line-Driven Accretion Disk Winds III: Local Ionization Equilibrium

    NASA Technical Reports Server (NTRS)

    Pereyra, Nicolas Antonio; Kallman, Timothy R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We present time-dependent numerical hydrodynamic models of line-driven accretion disk winds in cataclysmic variable systems and calculate wind mass-loss rates and terminal velocities. The models are 2.5-dimensional, include an energy balance condition with radiative heating and cooling processes, and includes local ionization equilibrium introducing time dependence and spatial dependence on the line radiation force parameters. The radiation field is assumed to originate in an optically thick accretion disk. Wind ion populations are calculated under the assumption that local ionization equilibrium is determined by photoionization and radiative recombination, similar to a photoionized nebula. We find a steady wind flowing from the accretion disk. Radiative heating tends to maintain the temperature in the higher density wind regions near the disk surface, rather than cooling adiabatically. For a disk luminosity L (sub disk) = solar luminosity, white dwarf mass M(sub wd) = 0.6 solar mass, and white dwarf radii R(sub wd) = 0.01 solar radius, we obtain a wind mass-loss rate of M(sub wind) = 4 x 10(exp -12) solar mass yr(exp -1) and a terminal velocity of approximately 3000 km per second. These results confirm the general velocity and density structures found in our earlier constant ionization equilibrium adiabatic CV wind models. Further we establish here 2.5D numerical models that can be extended to QSO/AGN winds where the local ionization equilibrium will play a crucial role in the overall dynamics.

  4. Ionization balance of impurities in turbulent scrape-off layer plasmas I: local ionization-recombination equilibrium

    NASA Astrophysics Data System (ADS)

    Guzman, F.; Marandet, Y.; Tamain, P.; Bufferand, H.; Ciraolo, G.; Ghendrih, Ph; Guirlet, R.; Rosato, J.; Valentinuzzi, M.

    2015-12-01

    In magnetized fusion devices, cross field impurity transport is often dominated by turbulence, in particular in the scrape-off layer. In these outer regions of the plasma, fluctuations of plasma parameters can be comparable to mean values, and the way ionization and recombination sources are treated in transport codes becomes questionnable. In fact, sources are calculated using the mean density and temperature values, with no account of fluctuations. In this work we investigate the modeling uncertainties introduced by this approximation, both qualitatively and quantitatively for the local ionization equilibrium. As a first step transport effects are neglected, and their role will be discussed in a companion paper. We show that temperature fluctuations shift the ionization balance towards lower temperatures, essentially because of the very steep temperature dependence of the ionization rate coefficients near the threshold. To reach this conclusion, a thorough analysis of the time scales involved is carried out, in order to devise a proper way of averaging over fluctuations. The effects are found to be substantial only for fairly large relative fluctuation levels for temperature, that is of the order of a few tens of percents.

  5. NON-EQUILIBRIUM IONIZATION EFFECTS ON THE DENSITY LINE RATIO DIAGNOSTICS OF O IV

    SciTech Connect

    Olluri, K.; Gudiksen, B. V.; Hansteen, V. H.

    2013-04-10

    The dynamic timescales in the solar atmosphere are shorter than the ionization and recombination times of many ions used for line ratio diagnostics of the transition region and corona. The long ionization and recombination times for these ions imply that they can be found far from their equilibrium temperatures, and spectroscopic investigations require more care before being trusted in giving correct information on local quantities, such as density and temperature. By solving the full time-dependent rate equations for an oxygen model atom in the three-dimensional numerical model of the solar atmosphere generated by the Bifrost code, we are able to construct synthetic intensity maps and study the emergent emission. We investigate the method of electron density diagnostics through line ratio analysis of the O IV 140.1 nm to the 140.4 nm ratio, the assumptions made in carrying out the diagnostics, and the different interpretations of the electron density. The results show big discrepancies between emission in statistical equilibrium and emission where non-equilibrium (NEQ) ionization is treated. Deduced electron densities are up to an order of magnitude higher when NEQ effects are accounted for. The inferred electron density is found to be a weighted mean average electron density along the line of sight and has no relation to the temperature of emission. This study shows that numerical modeling is essential for electron density diagnostics and is a valuable tool when the ions used for such studies are expected to be out of ionization equilibrium. Though this study has been performed on the O IV ion, similar results are also expected for other transition region ions.

  6. Ionization equilibrium of hydrogen in strong magnetic field with allowance for pressure effects

    SciTech Connect

    Bulik, P.; Pavlov, G. ); Potekhin, A.

    1992-01-01

    The ionization equilibrium in highly magnetized (B = 10[sup 10] to 10[sup 12]G) hydrogen is investigated at temperatures from 5 eV to 50 keV and densities in the range 10[sup [minus]3] to 10[sup 3] g/cm[sup 3]. We have used the occupation probability formalism in order to take into account the pressure and density effects. The occupation probabilities used are slightly modified as compared to those derived by Hummer and Mihalas. We find that pressure ionization degree varies with the form of microfield distribution function. The non-ionized fraction is increased by the magnetic field in most of the parameter space. It is large enough so that the bound-free absorption must be taken into account in realistic models of neutron star atmospheres.

  7. [C II] and [N II] from dense ionized regions in the Galaxy

    NASA Astrophysics Data System (ADS)

    Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

    2016-05-01

    Context. The interstellar medium (ISM) consists of highly ionized and neutral atomic, as well as molecular, components. Knowledge of their distribution is important for tracing the structure and lifecycle of the ISM. Aims: To determine the properties of the highly ionized gas and neutral weakly ionized gas in the Galaxy traced by the fine-structure lines of ionized nitrogen, [N ii], and ionized carbon, [C ii]. Methods: We utilize observations of the [C ii] 158 μm and [N ii] 205 μm fine-structure lines taken with the high spectral resolution Heterodyne Instrument in the Far-Infrared (HIFI) on the Herschel Space Observatory along ten lines of sight towards the inner Galaxy to analyze the ionized ISM. The [N ii] emission can be used to estimate the contribution of the highly ionized gas to the [C ii] emission and separate the contributions from highly ionized and weakly ionized neutral gas. Results: We find that [N ii] has strong emission in distinct spectral features along all lines of sight associated with strong [C ii] emission. The [N ii] arises from moderate density extended H ii regions or ionized boundary layers of clouds. Comparison of the [N ii] and [C ii] spectra in 31 separate kinematic features shows that many of the [C ii] spectra are affected by absorption from low excitation gas associated with molecular clouds, sometimes strongly so. The apparent fraction of the [C ii] associated with the [N ii] gas is unrealistically large in many cases, most likely due to the reduction of [C ii] by absorption. In a few cases the foreground absorption can be modeled to determine the true source intensity. In these sources we find that the foreground absorbing gas layer has C+ column densities of order 1018 cm-2. Conclusions: [C ii] emission arising from strong sources of [N ii] emission is frequently absorbed by low excitation foreground gas complicating the interpretation of the properties of the ionized and neutral gas components that give rise to [C ii] emission.

  8. Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

    NASA Astrophysics Data System (ADS)

    Hahn, M.; Savin, D. W.

    2015-02-01

    We describe the influence of electron-impact multiple ionization (EIMI) on the ionization balance of collisionally ionized plasmas. Previous ionization balance calculations have largely neglected EIMI. Here, EIMI cross-section data are incorporated into calculations of both equilibrium and non-equilibrium charge-state distributions (CSDs). For equilibrium CSDs, we find that EIMI has only a small effect and can usually be ignored. However, for non-equilibrium plasmas the influence of EIMI can be important. In particular, we find that for plasmas in which the temperature oscillates there are significant differences in the CSD when including versus neglecting EIMI. These results have implications for modeling and spectroscopy of impulsively heated plasmas, such as nanoflare heating of the solar corona.

  9. INFLUENCE OF ELECTRON-IMPACT MULTIPLE IONIZATION ON EQUILIBRIUM AND DYNAMIC CHARGE STATE DISTRIBUTIONS: A CASE STUDY USING IRON

    SciTech Connect

    Hahn, M.; Savin, D. W.

    2015-02-10

    We describe the influence of electron-impact multiple ionization (EIMI) on the ionization balance of collisionally ionized plasmas. Previous ionization balance calculations have largely neglected EIMI. Here, EIMI cross-section data are incorporated into calculations of both equilibrium and non-equilibrium charge-state distributions (CSDs). For equilibrium CSDs, we find that EIMI has only a small effect and can usually be ignored. However, for non-equilibrium plasmas the influence of EIMI can be important. In particular, we find that for plasmas in which the temperature oscillates there are significant differences in the CSD when including versus neglecting EIMI. These results have implications for modeling and spectroscopy of impulsively heated plasmas, such as nanoflare heating of the solar corona.

  10. Analyses on the Ionization Instability of Non-Equilibrium Seeded Plasma in an MHD Generator

    NASA Astrophysics Data System (ADS)

    Le, Chi Kien

    2016-06-01

    Recently, closed cycle magnetohydrodynamic power generation system research has been focused on improving the isentropic efficiency and the enthalpy extraction ratio. By reducing the cross-section area ratio of the disk magnetohydrodynamic generator, it is believed that a high isentropic efficiency can be achieved with the same enthalpy extraction. In this study, the result relating to a plasma state which takes into account the ionization instability of non-equilibrium seeded plasma is added to the theoretical prediction of the relationship between enthalpy extraction and isentropic efficiency. As a result, the electron temperature which reaches the seed complete ionization state without the growth of ionization instability can be realized at a relatively high seed fraction condition. However, the upper limit of the power generation performance is suggested to remain lower than the value expected in the low seed fraction condition. It is also suggested that a higher power generation performance may be obtained by implementing the electron temperature range which reaches the seed complete ionization state at a low seed fraction.

  11. The Role of Diffusive Shock Acceleration on Non-Equilibrium Ionization in Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Patnaude, Daniel; Ellison, D.; Slane, P.

    2009-01-01

    We present new model simulations which show clear evidence for changes in the non-equilibrium ionization behind a supernova remnant forward shock undergoing efficient diffusive shock acceleration. The efficient acceleration of particles (i.e., cosmic rays) lowers the shock temperature and raises the density of the shocked gas, thus altering the ionization state of the plasma in comparison to the test-particle approximation where cosmic rays gain an insignificant fraction of the shock energy. The differences between the test-particle and efficient acceleration cases are substantial: in cases of higher efficiency, particular ion states are more populated at lower electron temperatures. We also present results which show that in the efficient shock acceleration case, higher ionization fractions are reached immediately behind the shock front, relative to those in the test particle case. We attribute this to the higher postshock densities which lead to higher ionization rates. We show that these spatial differences are resolvable with current and future X-ray missions, and can be used as diagnostics in estimating the acceleration efficiency in cosmic--ray modified shocks in Galactic supernova remnants such as Tycho and Cassiopeia A.

  12. Effect of neutrino rest mass on ionization equilibrium freeze-out

    NASA Astrophysics Data System (ADS)

    Grohs, E.; Fuller, G. M.; Kishimoto, C. T.; Paris, M. W.

    2015-12-01

    We show how small neutrino rest masses can increase the expansion rate near the photon decoupling epoch in the early Universe, causing an earlier, higher temperature freeze-out for ionization equilibrium compared to the massless neutrino case. This yields a larger free-electron fraction, thereby affecting the photon diffusion length differently than the sound horizon at photon decoupling. This neutrino-mass and recombination effect depends strongly on the neutrino rest masses. Though below current sensitivity, this effect could be probed by next-generation cosmic microwave background experiments, giving another observational handle on neutrino rest mass.

  13. Effect of neutrino rest mass on ionization equilibrium freeze-out

    DOE PAGESBeta

    Grohs, Evan Bradley; Fuller, George M.; Kishimoto, Chad T.; Paris, Mark W.

    2015-12-23

    We show how small neutrino rest masses can increase the expansion rate near the photon decoupling epoch in the early Universe, causing an earlier, higher temperature freeze-out for ionization equilibrium compared to the massless neutrino case. This yields a larger free-electron fraction, thereby affecting the photon diffusion length differently than the sound horizon at photon decoupling. This neutrino-mass and recombination effect depends strongly on the neutrino rest masses. Ultimately, though below current sensitivity, this effect could be probed by next-generation cosmic microwave background experiments, giving another observational handle on neutrino rest mass.

  14. Equilibrium composition in II?VI telluride MOCVD systems

    NASA Astrophysics Data System (ADS)

    Ben-Dor, L.; Greenberg, J. H.

    1999-03-01

    Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P- T- X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II-VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P- T- X regions of existence were outlined for each of the five materials.

  15. Relaxation from Steady States Far from Equilibrium and the Persistence of Anomalous Shock Behavior in Weakly Ionized Gases

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Auslender, Aaron H.

    1999-01-01

    The decay of anomalous effects on shock waves in weakly ionized gases following plasma generator extinction has been measured in the anticipation that the decay time must correlate well with the relaxation time of the mechanism responsible for the anomalous effects. When the relaxation times cannot be measured directly, they are inferred theoretically, usually assuming that the initial state is nearly in thermal equilibrium. In this paper, it is demonstrated that relaxation from any steady state far from equilibrium, including the state of a weakly ionized gas, can proceed much more slowly than arguments based on relaxation from near equilibrium states might suggest. This result justifies a more careful analysis of the relaxation times in weakly ionized gases and suggests that although the experimental measurements of relaxation times did not lead to an unambiguous conclusion, this approach to understanding the anomalous effects may warrant further investigation.

  16. Benchmark Measurements of the Ionization Balance of Non-Local-Thermodynamic-Equilibrium Gold Plasmas

    SciTech Connect

    Heeter, R. F.; Hansen, S. B.; Fournier, K. B.; Foord, M. E.; Froula, D. H.; Mackinnon, A. J.; May, M. J.; Schneider, M. B.; Young, B. K. F.

    2007-11-09

    We present a series of benchmark measurements of the ionization balance of well-characterized gold plasmas with and without external radiation fields at electron densities near 10{sup 21} cm{sup -3} and electron temperatures spanning the range 0.8 to 2.4 keV. We have analyzed time- and space-resolved M-shell gold emission spectra using a sophisticated collisional-radiative model with hybrid level structure, finding average ion charges ranging from 42 to 50. At the lower temperatures, the spectra exhibit significant sensitivity to external radiation fields and include emission features from complex N-shell ions. The measured spectra and inferred provide a stringent test for non-local-thermodynamic-equilibrium models of complex high-Z ions.

  17. Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations

    NASA Astrophysics Data System (ADS)

    Dzifčáková, E.; Dudík, J.; Mackovjak, Š.

    2016-05-01

    Context. Coronal heating is currently thought to proceed via the mechanism of nanoflares, small-scale and possibly recurring heating events that release magnetic energy. Aims: We investigate the effects of a periodic high-energy electron beam on the synthetic spectra of coronal Fe ions. Methods: Initially, the coronal plasma is assumed to be Maxwellian with a temperature of 1 MK. The high-energy beam, described by a κ-distribution, is then switched on every period P for the duration of P/ 2. The periods are on the order of several tens of seconds, similar to exposure times or cadences of space-borne spectrometers. Ionization, recombination, and excitation rates for the respective distributions are used to calculate the resulting non-equilibrium ionization state of Fe and the instantaneous and period-averaged synthetic spectra. Results: Under the presence of the periodic electron beam, the plasma is out of ionization equilibrium at all times. The resulting spectra averaged over one period are almost always multithermal if interpreted in terms of ionization equilibrium for either a Maxwellian or a κ-distribution. Exceptions occur, however; the EM-loci curves appear to have a nearly isothermal crossing-point for some values of κs. The instantaneous spectra show fast changes in intensities of some lines, especially those formed outside of the peak of the respective EM(T) distributions if the ionization equilibrium is assumed. Movies 1-5 are available in electronic form at http://www.aanda.org

  18. Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations

    NASA Astrophysics Data System (ADS)

    Dzifčáková, E.; Dudík, J.; Mackovjak, Š.

    2016-04-01

    Context. Coronal heating is currently thought to proceed via the mechanism of nanoflares, small-scale and possibly recurring heating events that release magnetic energy. Aims: We investigate the effects of a periodic high-energy electron beam on the synthetic spectra of coronal Fe ions. Methods: Initially, the coronal plasma is assumed to be Maxwellian with a temperature of 1 MK. The high-energy beam, described by a κ-distribution, is then switched on every period P for the duration of P/ 2. The periods are on the order of several tens of seconds, similar to exposure times or cadences of space-borne spectrometers. Ionization, recombination, and excitation rates for the respective distributions are used to calculate the resulting non-equilibrium ionization state of Fe and the instantaneous and period-averaged synthetic spectra. Results: Under the presence of the periodic electron beam, the plasma is out of ionization equilibrium at all times. The resulting spectra averaged over one period are almost always multithermal if interpreted in terms of ionization equilibrium for either a Maxwellian or a κ-distribution. Exceptions occur, however; the EM-loci curves appear to have a nearly isothermal crossing-point for some values of κs. The instantaneous spectra show fast changes in intensities of some lines, especially those formed outside of the peak of the respective EM(T) distributions if the ionization equilibrium is assumed. Movies 1-5 are available in electronic form at http://www.aanda.org

  19. Theoretical basal Ca II and Mg II fluxes for late-type stars: results from acoustic wave spectra with time-dependent ionization and multilevel radiation treatments

    NASA Astrophysics Data System (ADS)

    Fawzy, Diaa E.

    2015-08-01

    Computations of chromospheric models and the resulting spectral line emission fluxes are presented for late-type stars exhibiting very low level of chromospheric activity, referred to as a basal flux stars or low activity stars. The computations are self-consistent, and consider the entire acoustic wave energy spectra generated in the stellar convection zones. We consider multilevel atomic models, take into account departures from local thermodynamic equilibrium and also consider the time-dependent ionization processes of hydrogen. We employ the new finding of the mixing-length parameter α = 1.8. The Ca II H+K and Mg II h+k line fluxes are computed assuming pseudo-partial redistribution. The results show the importance of time-dependent ionization in modelling the middle and high chromospheres. Models without considering time-dependent ionization overestimate the emitted Ca II fluxes by factors between 1.1 and 5.6 for F8V and M0V stars, respectively, while factors between 1.8 for G0V and 17.4 for M0V stars have been obtained for the Mg II fluxes. The theoretically computed basal fluxes in Ca II and Mg II, respectively, follow simple linear formulae depending on the effective temperature log Teff. The obtained results for Ca II fluxes show reasonable agreement with observations.

  20. Equilibrium K-, L-, and M-shell ionizations and charge-state distribution of sulfur projectiles passing through solid targets

    NASA Astrophysics Data System (ADS)

    Braziewicz, J.; Polasik, M.; Słabkowska, K.; Majewska, U.; Banaś, D.; Jaskóła, M.; Korman, A.; Kozioł, K.; Kretschmer, W.; Choinski, J.

    2010-08-01

    In the present work, an alternative approach for the evaluation of the equilibrium K-, L-, and M-shell ionizations and the mean charge state q¯ for projectiles passing through various targets has been proposed. The approach is based on measured K x-ray energy shifts and line intensity ratios and utilizes the theoretical analysis of projectile spectra using multiconfiguration Dirac-Fock calculations. It was applied for the satellite and hypersatellite K lines in the x-ray spectra emitted by sulfur projectiles passing with energies of 9.6-122 MeV through carbon, aluminium, titanium, and iron targets, recorded by a Si(Li) detector. It was found that only in the high projectile energy region there was significant dependence of mean equilibrium K-shell ionization on the target atomic number. The equilibrium L-shell ionization rises with the increase of sulfur energy until 32 MeV, but for higher energies the changes are very weak. The equilibrium M-shell ionization changes very weakly for low projectile energy while for higher energies this ionization is practically constant. For each target, the estimated value of q¯ rises with the increase of the sulfur energy value. The dependence of the sulfur charge state on the target atomic number was discussed by taking into account the cross sections for ionization, decay, and electron capture processes. The data were compared with the experimental data measured by other authors and with the predictions of Shima’s and Schiwietz and Grande’s semiempirical formulas. The presented good agreement points out that this alternative approach delivers quantitative results.

  1. Equilibrium K-, L-, and M-shell ionizations and charge-state distribution of sulfur projectiles passing through solid targets

    SciTech Connect

    Braziewicz, J.; Majewska, U.; Banas, D.; Polasik, M.; Slabkowska, K.; Koziol, K.; Jaskola, M.; Korman, A.; Kretschmer, W.; Choinski, J.

    2010-08-15

    In the present work, an alternative approach for the evaluation of the equilibrium K-, L-, and M-shell ionizations and the mean charge state q for projectiles passing through various targets has been proposed. The approach is based on measured K x-ray energy shifts and line intensity ratios and utilizes the theoretical analysis of projectile spectra using multiconfiguration Dirac-Fock calculations. It was applied for the satellite and hypersatellite K lines in the x-ray spectra emitted by sulfur projectiles passing with energies of 9.6-122 MeV through carbon, aluminium, titanium, and iron targets, recorded by a Si(Li) detector. It was found that only in the high projectile energy region there was significant dependence of mean equilibrium K-shell ionization on the target atomic number. The equilibrium L-shell ionization rises with the increase of sulfur energy until 32 MeV, but for higher energies the changes are very weak. The equilibrium M-shell ionization changes very weakly for low projectile energy while for higher energies this ionization is practically constant. For each target, the estimated value of q rises with the increase of the sulfur energy value. The dependence of the sulfur charge state on the target atomic number was discussed by taking into account the cross sections for ionization, decay, and electron capture processes. The data were compared with the experimental data measured by other authors and with the predictions of Shima's and Schiwietz and Grande's semiempirical formulas. The presented good agreement points out that this alternative approach delivers quantitative results.

  2. Soft x-ray spectra and collisional ionization equilibrium of iron ions with data upgrade of electron–ion collisions

    NASA Astrophysics Data System (ADS)

    Liang, G. Y.; Wei, H. G.; Zhao, G.; Zhong, J. Y.

    2016-06-01

    Line emissivities and ionic fraction in (non-)equilibrium are crucial for understanding the x-ray and extreme ultraviolet (EUV) spectra. These emission originate from electron-impact excitations for a level population of highly charged ions in coronal-like plasma. Recently, a large amount of excitation data was generated within the R-matrix framework by the computational atomic physics community, especially the UK APAP network. These data take resonances in electron–ion collisions into account appropriately, which enhances the effective excitation rates and also the line emissivities in x-ray and EUV regions. For ionization equilibrium data, the earlier compilation by Mazzotta et al (1998 Astron. Astrophys. Supp. Ser. 133 403) was used extensively by the astronomical community until the update by Bryans et al (2006 Astrophys. J. Supp. Ser. 167 343), as well as the compilation of Dere (2007 Astron. Astrophys. 466 771) for electron-impact ionization rates. In past years, many experimental measurements have been performed of highly charged iron ions in heavy-ion storage ring facilities. In this work, we will investigate the line emissivities and ionization equilibrium of highly charged iron ions by using recent theoretical or experimental data of electron-impact excitations and ionizations.

  3. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  4. INSTABILITY OF MAGNETIZED IONIZATION FRONTS SURROUNDING H II REGIONS

    SciTech Connect

    Kim, Jeong-Gyu; Kim, Woong-Tae E-mail: wkim@astro.snu.ac.kr

    2014-12-20

    An ionization front (IF) surrounding an H II region is a sharp interface where a cold neutral gas makes the transition to a warm ionized phase by absorbing UV photons from central stars. We investigate the instability of a plane-parallel D-type IF threaded by parallel magnetic fields, by neglecting the effects of recombination within the ionized gas. We find that weak D-type IFs always have the post-IF magnetosonic Mach number M{sub M2}≤1. For such fronts, magnetic fields increase the maximum propagation speed of the IFs, while reducing the expansion factor α by a factor of 1 + 1/(2β{sub 1}) compared to the unmagnetized case, with β{sub 1} denoting the plasma beta in the pre-IF region. IFs become unstable to distortional perturbations owing to gas expansion across the fronts, exactly analogous to the Darrieus-Landau instability of ablation fronts in terrestrial flames. The growth rate of the IF instability is proportional linearly to the perturbation wavenumber, as well as the upstream flow speed, and approximately to α{sup 1/2}. The IF instability is stabilized by gas compressibility and becomes completely quenched when the front is D-critical. The instability is also stabilized by magnetic pressure when the perturbations propagate in the direction perpendicular to the fields. When the perturbations propagate in the direction parallel to the fields, on the other hand, it is magnetic tension that reduces the growth rate, completely suppressing the instability when M{sub M2}{sup 2}<2/(2β{sub 1}−1). When the front experiences an acceleration, the IF instability cooperates with the Rayleigh-Taylor instability to make the front more unstable.

  5. Collisionless Shocks in a Partially Ionized Medium. II. Balmer Emission

    NASA Astrophysics Data System (ADS)

    Morlino, G.; Bandiera, R.; Blasi, P.; Amato, E.

    2012-12-01

    Strong shocks propagating into a partially ionized medium are often associated with optical Balmer lines. This emission is due to impact excitation of neutral hydrogen by hot protons and electrons in the shocked gas. The structure of such Balmer-dominated shocks has been computed in a previous paper, where the distribution function of neutral particles was derived from the appropriate Boltzmann equation including coupling with ions and electrons through charge exchange and ionization. This calculation showed how the presence of neutrals can significantly modify the shock structure through the formation of a neutral-induced precursor ahead of the shock. Here we follow up on our previous work and investigate the properties of the resulting Balmer emission, with the aim of using the observed radiation as a diagnostic tool for shock parameters. Our main focus is on supernova remnant shocks, and we find that, for typical parameters, the Hα emission typically has a three-component spectral profile, where (1) a narrow component originates from upstream cold hydrogen atoms, (2) a broad component comes from hydrogen atoms that have undergone charge exchange with shocked protons downstream of the shock, and (3) an intermediate component is due to hydrogen atoms that have undergone charge exchange with warm protons in the neutral-induced precursor. The relative importance of these three components depends on the shock velocity, on the original degree of ionization, and on the electron-ion temperature equilibration level. The intermediate component, which is the main signature of the presence of a neutral-induced precursor, becomes negligible for shock velocities <~ 1500 km s-1. The width of the intermediate line reflects the temperature in the precursor, while the width of the narrow one is left unaltered by the precursor. In addition, we show that the profiles of both the intermediate and broad components generally depart from a thermal distribution, as a consequence of the

  6. Statistical equilibrium in simple exchange games II. The redistribution game

    NASA Astrophysics Data System (ADS)

    Garibaldi, U.; Scalas, E.; Viarengo, P.

    2007-11-01

    We propose a simple stochastic exchange game mimicking taxation and redistribution. There are g agents and n coins; taxation is modeled by randomly extracting some coins; then, these coins are redistributed to agents following Polya's scheme. The individual wealth equilibrium distribution for the resulting Markov chain is the multivariate symmetric Polya distribution. In the continuum limit, the wealth distribution converges to a Gamma distribution, whose form factor is just the initial redistribution weight. The relationship between this taxation-and-redistribution scheme and other simple conservative stochastic exchange games (such as the BDY game) is discussed.

  7. CALIBRATION OF EQUILIBRIUM TIDE THEORY FOR EXTRASOLAR PLANET SYSTEMS. II

    SciTech Connect

    Hansen, Brad M. S.

    2012-09-20

    We present a new empirical calibration of equilibrium tidal theory for extrasolar planet systems, extending a prior study by incorporating detailed physical models for the internal structure of planets and host stars. The resulting strength of the stellar tide produces a coupling that is strong enough to reorient the spins of some host stars without causing catastrophic orbital evolution, thereby potentially explaining the observed trend in alignment between stellar spin and planetary orbital angular momentum. By isolating the sample whose spins should not have been altered in this model, we also show evidence for two different processes that contribute to the population of planets with short orbital periods. We apply our results to estimate the remaining lifetimes for short-period planets, examine the survival of planets around evolving stars, and determine the limits for circularization of planets with highly eccentric orbits. Our analysis suggests that the survival of circularized planets is strongly affected by the amount of heat dissipated, which is often large enough to lead to runaway orbital inflation and Roche lobe overflow.

  8. Dielectronic recombination rates, ionization equilibrium, and radiative emission rates for Mn ions in low-density high-temperature plasmas

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.; Davis, J.

    1983-01-01

    The analysis of optically-thin far-ultraviolet and X-ray emission lines of multiply-charged ions is one of the basic methods for determining the temperatures and densities of laboratory and astrophysical plasmas. In addition, the energy balance in these plasmas can be significantly influenced by the emission of radiation from relatively low concentrations of multiple-charged atomic ions. Because the populations of the excited levels are expected to depart substantially from their local thermodynamic equilibrium values a detailed treatment of the elementary collisional and radiative processes must be employed in order to predict the emission line intensities. In this investigation the authors present the results of calculations based on a corona equilibrium model in which a detailed evaluation is made of the dielectronic recombination rate coefficients. The ionization and autoionization following inner-shell electron excitation from each ground state are balanced by direct radiative and dielectronic recombination. The spectral line intensities emitted by the low-lying excited states, which are assumed to undergo spontaneous radiative decay in times that are short compared with the collision time, are evaluated in terms of the corona ionization equilibrium distributions of the ground states and their electron-impact excitation states.

  9. Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria.

    PubMed

    Kappler, A; Johnson, C M; Crosby, H A; Beard, B L; Newman, D K

    2010-05-10

    Iron isotope fractionations produced during chemical and biological Fe(II) oxidation are sensitive to the proportions and nature of dissolved and solid-phase Fe species present, as well as the extent of isotopic exchange between precipitates and aqueous Fe. Iron isotopes therefore potentially constrain the mechanisms and pathways of Fe redox transformations in modern and ancient environments. In the present study, we followed in batch experiments Fe isotope fractionations between Fe(II)(aq) and Fe(III) oxide/hydroxide precipitates produced by the Fe(III) mineral encrusting, nitrate-reducing, Fe(II)-oxidizing Acidovorax sp. strain BoFeN1. Isotopic fractionation in (56)Fe/(54)Fe approached that expected for equilibrium conditions, assuming an equilibrium Δ(56)Fe(Fe(OH)3 - Fe(II)aq) fractionation factor of +3.0 ‰. Previous studies have shown that Fe(II) oxidation by this Acidovorax strain occurs in the periplasm, and we propose that Fe isotope equilibrium is maintained through redox cycling via coupled electron and atom exchange between Fe(II)(aq) and Fe(III) precipitates in the contained environment of the periplasm. In addition to the apparent equilibrium isotopic fractionation, these experiments also record the kinetic effects of initial rapid oxidation, and possible phase transformations of the Fe(III) precipitates. Attainment of Fe isotope equilibrium between Fe(III) oxide/hydroxide precipitates and Fe(II)(aq) by neutrophilic, Fe(II)-oxidizing bacteria or through abiologic Fe(II)(aq) oxidation is generally not expected or observed, because the poor solubility of their metabolic product, i.e. Fe(III), usually leads to rapid precipitation of Fe(III) minerals, and hence expression of a kinetic fractionation upon precipitation; in the absence of redox cycling between Fe(II)(aq) and precipitate, kinetic isotope fractionations are likely to be retained. These results highlight the distinct Fe isotope fractionations that are produced by different pathways of

  10. Optimization of Electrospray Ionization by Statistical Design of Experiments and Response Surface Methodology: Protein-Ligand Equilibrium Dissociation Constant Determinations

    NASA Astrophysics Data System (ADS)

    Pedro, Liliana; Van Voorhis, Wesley C.; Quinn, Ronald J.

    2016-09-01

    Electrospray ionization mass spectrometry (ESI-MS) binding studies between proteins and ligands under native conditions require that instrumental ESI source conditions are optimized if relative solution-phase equilibrium concentrations between the protein-ligand complex and free protein are to be retained. Instrumental ESI source conditions that simultaneously maximize the relative ionization efficiency of the protein-ligand complex over free protein and minimize the protein-ligand complex dissociation during the ESI process and the transfer from atmospheric pressure to vacuum are generally specific for each protein-ligand system and should be established when an accurate equilibrium dissociation constant (KD) is to be determined via titration. In this paper, a straightforward and systematic approach for ESI source optimization is presented. The method uses statistical design of experiments (DOE) in conjunction with response surface methodology (RSM) and is demonstrated for the complexes between Plasmodium vivax guanylate kinase ( PvGK) and two ligands: 5'-guanosine monophosphate (GMP) and 5'-guanosine diphosphate (GDP). It was verified that even though the ligands are structurally similar, the most appropriate ESI conditions for KD determination by titration are different for each.

  11. Optimization of Electrospray Ionization by Statistical Design of Experiments and Response Surface Methodology: Protein-Ligand Equilibrium Dissociation Constant Determinations.

    PubMed

    Pedro, Liliana; Van Voorhis, Wesley C; Quinn, Ronald J

    2016-09-01

    Electrospray ionization mass spectrometry (ESI-MS) binding studies between proteins and ligands under native conditions require that instrumental ESI source conditions are optimized if relative solution-phase equilibrium concentrations between the protein-ligand complex and free protein are to be retained. Instrumental ESI source conditions that simultaneously maximize the relative ionization efficiency of the protein-ligand complex over free protein and minimize the protein-ligand complex dissociation during the ESI process and the transfer from atmospheric pressure to vacuum are generally specific for each protein-ligand system and should be established when an accurate equilibrium dissociation constant (KD) is to be determined via titration. In this paper, a straightforward and systematic approach for ESI source optimization is presented. The method uses statistical design of experiments (DOE) in conjunction with response surface methodology (RSM) and is demonstrated for the complexes between Plasmodium vivax guanylate kinase (PvGK) and two ligands: 5'-guanosine monophosphate (GMP) and 5'-guanosine diphosphate (GDP). It was verified that even though the ligands are structurally similar, the most appropriate ESI conditions for KD determination by titration are different for each. Graphical Abstract ᅟ. PMID:27225419

  12. Optimization of Electrospray Ionization by Statistical Design of Experiments and Response Surface Methodology: Protein-Ligand Equilibrium Dissociation Constant Determinations

    NASA Astrophysics Data System (ADS)

    Pedro, Liliana; Van Voorhis, Wesley C.; Quinn, Ronald J.

    2016-05-01

    Electrospray ionization mass spectrometry (ESI-MS) binding studies between proteins and ligands under native conditions require that instrumental ESI source conditions are optimized if relative solution-phase equilibrium concentrations between the protein-ligand complex and free protein are to be retained. Instrumental ESI source conditions that simultaneously maximize the relative ionization efficiency of the protein-ligand complex over free protein and minimize the protein-ligand complex dissociation during the ESI process and the transfer from atmospheric pressure to vacuum are generally specific for each protein-ligand system and should be established when an accurate equilibrium dissociation constant (KD) is to be determined via titration. In this paper, a straightforward and systematic approach for ESI source optimization is presented. The method uses statistical design of experiments (DOE) in conjunction with response surface methodology (RSM) and is demonstrated for the complexes between Plasmodium vivax guanylate kinase (PvGK) and two ligands: 5'-guanosine monophosphate (GMP) and 5'-guanosine diphosphate (GDP). It was verified that even though the ligands are structurally similar, the most appropriate ESI conditions for KD determination by titration are different for each.

  13. THE DIAGNOSTIC O VI ABSORPTION LINE IN DIFFUSE PLASMAS: COMPARISON OF NON-EQUILIBRIUM IONIZATION STRUCTURE SIMULATIONS TO FUSE DATA

    SciTech Connect

    De Avillez, Miguel A.; Breitschwerdt, Dieter

    2012-12-20

    The nature of the interstellar O VI in the Galactic disk is studied by means of a multi-fluid hydrodynamical approximation, tracing the detailed time-dependent evolution of the ionization structure of the plasma. Our focus is to explore the signature of any non-equilibrium ionization condition present in the interstellar medium using the diagnostic O VI ion. A detailed comparison between the simulations and FUSE data is carried out by taking lines of sight (LOS) measurements through the simulated Galactic disk, covering an extent of 4 kpc from different vantage points. The simulation results bear a striking resemblance with the observations: (1) the N(O VI) distribution with distance and angle fall within the minimum and maximum values of the FUSE data; (2) the column density dispersion with distance is constant for all the LOS, showing a mild decrease at large distances; (3) O VI has a clumpy distribution along the LOS; and (4) the time-averaged midplane density for distances >400 pc has a value of (1.3-1.4) Multiplication-Sign 10{sup -8} cm{sup -3}. The highest concentration of O VI by mass occurs in the thermally stable (10{sup 3.9} K < T {<=} 10{sup 4.2} K; 20%) and unstable (10{sup 4.2} K < T < 10{sup 5} K; 50%) regimes, both well below its peak temperature in collisional ionization equilibrium, with the corresponding volume filling factors oscillating with time between 8%-20% and 4%-5%, respectively. These results may also be relevant for intergalactic metal absorption systems at high redshifts.

  14. Ionization and thermal equilibrium models for O star winds based on time-independent radiation-driven wind theory

    NASA Technical Reports Server (NTRS)

    Drew, J. E.

    1989-01-01

    Ab initio ionization and thermal equilibrium models are calculated for the winds of O stars using the results of steady state radiation-driven wind theory to determine the input parameters. Self-consistent methods are used for the roles of H, He, and the most abundant heavy elements in both the statistical and the thermal equilibrium. The model grid was chosen to encompass all O spectral subtypes and the full range of luminosity classes. Results of earlier modeling of O star winds by Klein and Castor (1978) are reproduced and used to motivate improvements in the treatment of the hydrogen equilibrium. The wind temperature profile is revealed to be sensitive to gross changes in the heavy element abundances, but insensitive to other factors considered such as the mass-loss rate and velocity law. The reduced wind temperatures obtained in observing the luminosity dependence of the Si IV lambda 1397 wind absorption profile are shown to eliminate any prospect of explaining the observed O VI lambda 1036 line profiles in terms of time-independent radiation-driven wind theory.

  15. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. II. DUST-INDUCED COLLISIONAL IONIZATION

    SciTech Connect

    Helling, Ch.; Jardine, M.; Mokler, F.

    2011-08-10

    Observations have shown that continuous radio emission and also sporadic H{alpha} and X-ray emission are prominent in singular, low-mass objects later than spectral class M. These activity signatures are interpreted as being caused by coupling of an ionized atmosphere to the stellar magnetic field. What remains a puzzle, however, is the mechanism by which such a cool atmosphere can produce the necessary level of ionization. At these low temperatures, thermal gas processes are insufficient, but the formation of clouds sets in. Cloud particles can act as seeds for electron avalanches in streamers that ionize the ambient gas, and can lead to lightning and indirectly to magnetic field coupling, a combination of processes also expected for protoplanetary disks. However, the precondition is that the cloud particles are charged. We use results from DRIFT-PHOENIX model atmospheres to investigate collisional processes that can lead to the ionization of dust grains inside clouds. We show that ionization by turbulence-induced dust-dust collisions is the most efficient kinetic process. The efficiency is highest in the inner cloud where particles grow quickly and, hence, the dust-to-gas ratio is high. Dust-dust collisions alone are not sufficient to improve the magnetic coupling of the atmosphere inside the cloud layers, but the charges supplied either on grains or within the gas phase as separated electrons can trigger secondary nonlinear processes. Cosmic rays are likely to increase the global level of ionization, but their influence decreases if a strong, large-scale magnetic field is present as on brown dwarfs. We suggest that although thermal gas ionization declines in objects across the fully convective boundary, dust charging by collisional processes can play an important role in the lowest mass objects. The onset of atmospheric dust may therefore correlate with the anomalous X-ray and radio emission in atmospheres that are cool, but charged more than expected by pure

  16. Investigating the Chemical Evolution of the Universe via Numerical Simulations: Supernova Dust Destruction and Non-Equilibrium Ionization Chemistry

    NASA Astrophysics Data System (ADS)

    Silvia, Devin W.

    2013-12-01

    The chemical evolution of the Universe is a complicated process with countless facets that define its properties over the course of time. In the early Universe, the metal-free first stars were responsible for originally introducing metals into the pristine gas left over from the Big Bang. Once these metals became prevalent, they forever altered the thermodynamics of the Universe. Understanding precisely where these metals originated, where they end up, and the conditions they experience along the way is of great interest in the astrophysical community. In this work, I have used numerical simulations as a means of understanding two separate phenomena related to the chemical evolution the Universe. The first topic focuses on the question as to whether or not core-collapse supernovae in the high-redshift universe are capable of being "dust factories" for the production of galactic dust. To achieve this, I carried out idealized simulations of supernova ejecta clouds being impacted by reverse-shock blast waves. By post-processing the results of these simulations, I was able to estimate the amount of dust destruction that would occur due to thermal sputtering. In the most extreme scenarios, simulated with high relative velocities between the shock and the ejecta cloud and high gas metallicities, I find complete destruction for some grains species and only 44% dust mass survival for even the most robust species. This raises the question as to whether or not high-redshift supernova can produce dust masses in sufficient excess of the ˜1 Msun per event required to match observations of high-z galaxies. The second investigation was driven by the desire to find an answer to the missing baryon problem and a curiosity as to the impact that including a full non-equilibrium treatment of ionization chemistry has on simulations of the intergalactic medium. To address these questions, I have helped to develop Dengo, a new software package for solving complex chemical networks. Once

  17. Age, size, and position of H ii regions in the Galaxy. Expansion of ionized gas in turbulent molecular clouds

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Anderson, L. D.; Didelon, P.; Raga, A. C.; Minier, V.; Ntormousi, E.; Pettitt, A.; Pinto, C.; Samal, M. R.; Schneider, N.; Zavagno, A.

    2014-08-01

    Aims: This work aims to improve the current understanding of the interaction between H ii regions and turbulent molecular clouds. We propose a new method to determine the age of a large sample of OB associations by investigating the development of their associated H ii regions in the surrounding turbulent medium. Methods: Using analytical solutions, one-dimensional (1D), and three-dimensional (3D) simulations, we constrained the expansion of the ionized bubble depending on the turbulence level of the parent molecular cloud. A grid of 1D simulations was then computed in order to build isochrone curves for H ii regions in a pressure-size diagram. This grid of models allowed us to date a large sample of OB associations that we obtained from the H ii Region Discovery Survey (HRDS). Results: Analytical solutions and numerical simulations showed that the expansion of H ii regions is slowed down by the turbulence up to the point where the pressure of the ionized gas is in a quasi-equilibrium with the turbulent ram pressure. Based on this result, we built a grid of 1D models of the expansion of H ii regions in a profile based on Larson's laws. We take the 3D turbulence into account with an effective 1D temperature profile. The ages estimated by the isochrones of this grid agree well with literature values of well known regions such as Rosette, RCW 36, RCW 79, and M 16. We thus propose that this method can be used to find ages of young OB associations through the Galaxy and also in nearby extra-galactic sources.

  18. Prompt ionization in the CRIT II barium releases

    NASA Astrophysics Data System (ADS)

    Torbert, R. B.; Kletzing, C. A.; Liou, K.; Rau, D.

    1992-05-01

    Observations of electron and ion distributions inside a fast neutral barium jet in the ionosphere show significant fluxes within 4 km of release, presumably related to beam plasma instability processes involved in the Critical Ionization Velocity (CIV) effect. Electron fluxes exceeding 5 x 10 exp 12/sq cm-str-sec-keV were responsible for ionizing both the streaming barium and ambient oxygen. Resulting ion fluxes seem to be consistent with 1-2 percent ionization of the fast barium, as reported by optical observations, although the extended spatial distribution of the optically observed ions is difficult to reconcile with the in situ observations. When the perpendicular velocity of the neutrals falls below critical values, these processes shut off. Although these observations resemble the earlier Porcupine experimental results (Haerendel, 1982), theoretical understanding of the differences between these data and that of earlier negative experiments is still lacking.

  19. Single-photon double ionization of H2 away from equilibrium: A showcase of two-center electron interference

    NASA Astrophysics Data System (ADS)

    Serov, Vladislav V.; Ivanov, I. A.; Kheifets, A. S.

    2012-08-01

    We demonstrate the effect of two-center interference on single-photon double ionization [double photoionization (DPI)] of the aligned H2 molecule when it shrinks or expands from the equilibrium internuclear distance. This interference affects the first stage of the DPI process in which the primary photoelectron is ejected predominantly along the polarization axis of light and its geometrical interference factor is most sensitive to the internuclear distance in the parallel (Σ) orientation of the internuclear and polarization axes. This effect is responsible for strong modification of the DPI amplitude in the parallel orientation while the corresponding amplitude for the perpendicular (Π) orientation is rather insensitive to the internuclear distance. The combination of these two factors explains the profound kinetic energy release effect on the fully differential cross sections of DPI of H2.

  20. Prompt ionization in the CRIT II barium releases. [Critical Ionization Tests

    NASA Technical Reports Server (NTRS)

    Torbert, R. B.; Kletzing, C. A.; Liou, K.; Rau, D.

    1992-01-01

    Observations of electron and ion distributions inside a fast neutral barium jet in the ionosphere show significant fluxes within 4 km of release, presumably related to beam plasma instability processes involved in the Critical Ionization Velocity (CIV) effect. Electron fluxes exceeding 5 x 10 exp 12/sq cm-str-sec-keV were responsible for ionizing both the streaming barium and ambient oxygen. Resulting ion fluxes seem to be consistent with 1-2 percent ionization of the fast barium, as reported by optical observations, although the extended spatial distribution of the optically observed ions is difficult to reconcile with the in situ observations. When the perpendicular velocity of the neutrals falls below critical values, these processes shut off. Although these observations resemble the earlier Porcupine experimental results (Haerendel, 1982), theoretical understanding of the differences between these data and that of earlier negative experiments is still lacking.

  1. Equilibrium studies on the binding of cadmium(II) to human serum transferrin

    SciTech Connect

    Harris, W.R.; Madsen, L.J.

    1988-01-12

    The binding of cadmium(II) to human serum transferrin in 0.01 M N-(2-hydroxyethyl)-piperazine-N'-2-ethanesulfonic acid with 5 mM bicarbonate at 25/sup 0/C has been evaluated by difference ultraviolet spectroscopy. Equilibrium constants were determined by competition versus three different low molecular weight chelating agents: nitrilotriacetic acid, ethylenediamine-N,N'-diacetic acid, and triethylenetetramine. Conditional equilibrium constants for the sequential binding of two cadmium ions to transferrin under the stated experimental conditions are log K/sub 1/ = 5.95 +/- 0.10 and log K/sub 2/ = 4.86 +/- 0.13. A linear free energy relationship for the complexation of cadmium and zinc has been prepared by using equilibrium data on 243 complexes of these metal ions with low molecular weight ligands. The transferrin binding constants for cadmium and zinc are in good agreement with this linear free energy relationship. This indicates that the larger size of the cadmium(II) ion does not significantly hinder its binding to the protein.

  2. Adsorption of Pb(II) ions onto biomass from Trifolium resupinatum: equilibrium and kinetic studies

    NASA Astrophysics Data System (ADS)

    Athar, Makshoof; Farooq, Umar; Aslam, Muhammad; Salman, M.

    2013-09-01

    The present study provides information about the binding of Pb(II) ions on an eco-friendly and easily available biodegradable biomass Trifolium resupinatum. The powdered biomass was characterized by FTIR, potentiometric titration and surface area analyses. The FTIR spectrum showed the presence of hydroxyl, carbonyl and amino functional groups and Pb(II) ions bound with the oxygen- and nitrogen-containing sites (hydroxyl and amino groups). The acidic groups were also confirmed by titrations. Effects of various environmental parameters (time, pH and concentration) have been studied. The biosorption process achieved equilibrium in a very short period of time (25 min). Non-linear approach for Langmuir and Freundlich models was used to study equilibrium process and root mean-square error was used as an indicator to decide the fitness of the mathematical model. The biosorption process was found to follow pseudo-second-order kinetics and was very fast. Thus, the biomass can be cost-effectively used for the binding of Pb(II) ions from aqueous solutions.

  3. Accurate energy levels for singly ionized platinum (Pt II)

    NASA Technical Reports Server (NTRS)

    Reader, Joseph; Acquista, Nicolo; Sansonetti, Craig J.; Engleman, Rolf, Jr.

    1988-01-01

    New observations of the spectrum of Pt II have been made with hollow-cathode lamps. The region from 1032 to 4101 A was observed photographically with a 10.7-m normal-incidence spectrograph. The region from 2245 to 5223 A was observed with a Fourier-transform spectrometer. Wavelength measurements were made for 558 lines. The uncertainties vary from 0.0005 to 0.004 A. From these measurements and three parity-forbidden transitions in the infrared, accurate values were determined for 28 even and 72 odd energy levels of Pt II.

  4. Pb(II) binding to humic substances: an equilibrium and spectroscopic study.

    PubMed

    Orsetti, Silvia; Marco-Brown, Jose L; Andrade, Estela M; Molina, Fernando V

    2013-08-01

    The binding of Pb(II) to humic acids is studied through an approach combining equilibrium and spectroscopic measurements. The methods employed are potentiometric and fluorometric titrations, fluorescence excitation-emission matrices (EEM) and IR spectroscopy. Potentiometric titration curves are analyzed using the NICA equations and an electrostatic model treating the humic particles as an elastic polyelectrolyte network. EEMs are analyzed using parallel factor analysis, decomposing the signal in its independent components and finding their dependence on Pb(II) activity. Potentiometric results are consistent with bimodal affinity distributions for Pb(II) binding, whereas fluorometric titrations are explained by monomodal distributions. EEM analysis is consistent with three independent components in the humic fluorescence response, which are assigned to moieties with different degree of aromaticity. All three components show a similar quenching behavior upon Pb(II) binding, saturating at relatively low Pb(II) concentrations. This is attributed to metal ion induced aggregation of humic molecules, resulting in the interaction between the aromatic groups responsible for fluorescence; this is also consistent with IR spectroscopy results. The observed behavior is interpreted considering that initial metal binding (observed as strongly binding sites), correspond to bi- or multidentate complexation to carboxylate groups, including binding between groups of different humic molecules, promoting aggregation; further metal ions (observed as weakly binding sites) bind to single ligand groups. PMID:23805795

  5. Flux line non-equilibrium relaxation kinetics following current quenches in disordered type-II superconductors

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Harshwardhan; Assi, Hiba; Dobramysl, Ulrich; Pleimling, Michel; Täuber, Uwe

    We investigate the relaxation dynamics of magnetic vortex lines in disordered type-II superconductors following rapid changes in the external driving current by means of Langevin molecular dynamics simulations for an elastic line model. A system of driven interacting flux lines in a sample with randomly distributed point pinning centers is initially relaxed to a moving non-equilibrium steady state. The current is then instantaneously decreased, such that the final stationary state resides either still in the moving regime, or in the pinned Bragg glass phase. The ensuing non-equilibrium relaxation kinetics of the vortices is studied in detail by measuring the mean flux line gyration radius and the two-time transverse height autocorrelation function. The latter allows us to investigate the physical aging properties for quenches from the moving into the glassy phase, and to compare with non-equilibrium relaxation features obtained with different initial configurations. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.

  6. Dielectronic recombination rates, ionization equilibrium, and radiative energy-loss rates for neon, magnesium, and sulfur ions in low-density plasmas. [in solar corona

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.; Davis, J.; Rogerson, J. E.; Blaha, M.

    1979-01-01

    Results of detailed and systematic calculations are presented for the total dielectronic recombination rate coefficients for the ions of Ne, Mg, and S in a low-density predominantly hydrogen plasma. The new recombination rates are used to calculate solar corona ionization-equilibrium distributions of the ions. The most important effect of dielectronic recombination for ions in corona equilibrium is found to be a shift in the maximum-abundance temperatures toward higher temperatures, which are in some cases reduced from those predicted on the basis of the simple Burgess formula.

  7. Biosorption of Cu(II) by immobilized microalgae using silica: kinetic, equilibrium, and thermodynamic study.

    PubMed

    Lee, Hongkyun; Shim, Eunjung; Yun, Hyun-Shik; Park, Young-Tae; Kim, Dohyeong; Ji, Min-Kyu; Kim, Chi-Kyung; Shin, Won-Sik; Choi, Jaeyoung

    2016-01-01

    Immobilized microalgae using silica (IMS) from Micractinium reisseri KGE33 was synthesized through a sol-gel reaction. Green algal waste biomass, the residue of M. reisseri KGE33 after oil extraction, was used as the biomaterial. The adsorption of Cu(II) on IMS was tested in batch experiments with varying algal doses, pH, contact times, initial Cu(II) concentrations, and temperatures. Three types of IMSs (IMS 14, 70, and 100) were synthesized according to different algal doses. The removal efficiency of Cu(II) in the aqueous phase was in the following order: IMS 14 (77.0%) < IMS 70 (83.3%) < IMS 100 (87.1%) at pH 5. The point of zero charge (PZC) value of IMS100 was 4.5, and the optimum pH for Cu(II) adsorption was 5. Equilibrium data were described using a Langmuir isotherm model. The Langmuir model maximum Cu(II) adsorption capacity (q m) increased with the algal dose in the following order: IMS 100 (1.710 mg g(-1)) > IMS 70 (1.548 mg g(-1)) > IMS 14 (1.282 mg g(-1)). The pseudo-second-order equation fitted the kinetics data well, and the value of the second-order rate constant increased with increasing algal dose. Gibbs free energies (ΔG°) were negative within the temperature range studied, which indicates that the adsorption process was spontaneous. The negative value of enthalpy (ΔH°) again indicates the exothermic nature of the adsorption process. In addition, SEM-energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses of the IMS surface reveal that the algal biomass on IMS is the main site for Cu(II) binding. This study shows that immobilized microalgae using silica, a synthesized biosorbent, can be used as a cost-effective sorbent for Cu(II) removal from the aqueous phase. PMID:25953610

  8. Equilibrium between radiation and matter for classical relativistic multiperiodic systems. II. Study of radiative equilibrium with Rayleigh-Jeans radiation

    NASA Astrophysics Data System (ADS)

    Blanco, R.; Pesquera, L.; Santos, E.

    1984-05-01

    We continue the study of the problem of equilibrium between radiation and classical relativistic systems begun previously

    [Phys. Rev. D 27, 1254 (1983)]
    . We consider the emission and absorption of energy by a relativistic pointlike particle immersed in a Rayleigh-Jeans radiation field. The particle is acted upon by a force which, if alone, would produce a multiply periodic motion. It is shown that radiative balance at each frequency holds. A discussion is given of the results reported in both papers.

  9. [Ne III]/[O II] as an ionization parameter diagnostic in star-forming galaxies

    SciTech Connect

    Levesque, Emily M.; Richardson, Mark L. A.

    2014-01-01

    We present our parameterizations of the log([Ne III]λ3869/[O II]λ3727) (Ne3O2) and log([O III]λ5007/[O II]λ3727) (O3O2) ratios as diagnostics of ionization parameter in star-forming galaxies. Our calibrations are based on the Starburst99/Mappings III photoionization models, which extend up to the extremely high values of ionization parameter found in high-redshift galaxies. While similar calibrations have been presented previously for O3O2, this is the first such calibration of Ne3O2. We illustrate the tight correlation between these two ratios for star-forming galaxies and discuss the underlying physics that dictates their very similar evolution. Based on this work, we propose the Ne3O2 ratio as a new and useful diagnostic of ionization parameter for star-forming galaxies. Given the Ne3O2 ratio's relative insensitivity to reddening, this ratio is particularly valuable for use with galaxies that have uncertain amounts of extinction. The short wavelengths of the Ne3O2 ratio can also be applied out to very high redshifts, extending studies of galaxies' ionization parameters out to z ∼ 1.6 with optical spectroscopy and z ∼ 5.2 with ground-based near-infrared spectra.

  10. EXTENDED ANALYSIS OF THE SPECTRUM OF SINGLY IONIZED CHROMIUM (Cr II)

    SciTech Connect

    Sansonetti, Craig J.; Nave, Gillian

    2014-08-01

    We have made new observations of the spectrum of singly ionized chromium (Cr II) in the region 2850-37900 Å with the National Institute of Standards and Technology 2 m Fourier transform spectrometer. These data extend our previously reported observations in the near-ultra-violet region. We present a comprehensive list of more than 5300 Cr II lines classified as transitions among 456 even and 457 odd levels, 179 of which are newly located in this work. Using highly excited levels of the 3d {sup 4}({sup 5} D)5g, 3d {sup 4}({sup 5} D)6g, and 3d {sup 4}({sup 5}D)6h configurations, we derive an improved ionization energy of 132971.02 ± 0.12 cm{sup –1} (16.486305 ± 0.000015 eV)

  11. Extended Analysis of the Spectrum of Singly Ionized Chromium (Cr II)

    NASA Astrophysics Data System (ADS)

    Sansonetti, Craig J.; Nave, Gillian

    2014-08-01

    We have made new observations of the spectrum of singly ionized chromium (Cr II) in the region 2850-37900 Å with the National Institute of Standards and Technology 2 m Fourier transform spectrometer. These data extend our previously reported observations in the near-ultra-violet region. We present a comprehensive list of more than 5300 Cr II lines classified as transitions among 456 even and 457 odd levels, 179 of which are newly located in this work. Using highly excited levels of the 3d 4(5 D)5g, 3d 4(5 D)6g, and 3d 4(5D)6h configurations, we derive an improved ionization energy of 132971.02 ± 0.12 cm-1 (16.486305 ± 0.000015 eV).

  12. Prediction of equilibrium parameters of adsorption of lead (II) ions onto diatomite

    NASA Astrophysics Data System (ADS)

    Salman, Taylan; Ardalı, Yüksel; Gamze Turan, N.

    2013-04-01

    Heavy metals from industrial wastewaters are one of the most important environmental issues to be solved today. Due to their toxicity and nonbiodegradable nature, heavy metals cause environmental and public health problems. Various techniques have been developed to remove heavy metals from aqueous solutions. These include chemical precipitation, reverse osmosis, ion Exchange and adsorption. Among them, adsorption is considered to be a particularly competitive and effective process for the removal of heavy metals from aqueous solutions. There is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. Diatomite is a siliceous sedimentary rock having an amorphous form of silica (SiO2. nH2O) containing a small amount of microcrystalline material. It has unique combination of physical and chemical properties such as high porosity, high permeability, small particle size, large surface area, and low thermal conductivity. In addition, it is available in Turkey and in various locations around the world. Therefore, diatomite has been successfully used as adsorbent for the removal of heavy metals. The aim of the study is to investigate the adsorption properties of diatomite. The equilibrium adsorption data were applied to the Langmuir, Freundlich and Dubinin-Radushkevic (D-R) isotherm models. Adsorption experiments were performed under batch process, using Pb (II) initial concentration, pH of solution and contact time as variables. The results demonstrated that the adsorption of Pb (II) was strongly dependent on pH of solution. The effect of pH on adsorption of Pb(II) on diatomite was conducted by varying pH from 2 to 12 at 20 oC. In the pH range of 2.0-4.0, the adsorption percentage increases slightly as the pH increasing. At pH>4, the adsorption percentage decreases with increasing pH because hydrolysis product and the precipitation begin to play an important role in the sorption of Pb (II). At pH4, the maximum adsorption

  13. ENERGY LEVELS AND SPECTRAL LINES OF SINGLY IONIZED MANGANESE (Mn II)

    SciTech Connect

    Kramida, Alexander; Sansonetti, Jean E.

    2013-04-01

    This compilation revises the previously recommended list of energy levels of singly ionized manganese (Mn II) and provides a comprehensive list of observed spectral lines and transition probabilities in this spectrum. The new level optimization takes into account critically assessed uncertainties of measured wavelengths and includes about a hundred high-precision wavelengths determined by laser spectroscopy and Fourier transform techniques. Uncertainties of 63% of energy levels and 74% of Ritz wavelengths are reduced by a factor of three on average.

  14. Anomalously slow cyanide binding to Glycera dibranchiata monomer methemoglobin component II: Implication for the equilibrium constant

    SciTech Connect

    Mintorovitch, J.; Satterlee, J.D. )

    1988-10-18

    In comparison to sperm whale metmyoglobin, metleghemoglobin {alpha}, methemoglobins, and heme peroxidases, the purified Glycera dibranchiata monomer methemoglobin component II exhibits anomalously slow cyanide ligation kinetics. For the component II monomer methemoglobin this reaction has been studied under pseudo-first-order conditions at pH 6.0, 7.0, 8.0, and 9.0, employing 100-250-fold mole excesses of potassium cyanide at each pH. The analysis shows that the concentration-independent bimolecular rate constant is small in comparison to those of the other heme proteins. Furthermore, the results show that the dissociation rate is extremely slow. Separation of the bimolecular rate constant into contributions from k{sub CN{sup {minus}}} (the rate constant for CN{sup {minus}} binding) and from k{sub HCN} (the rate constant for HCN binding) shows that the former is approximately 90 times greater. These results indicate that cyanide ligation reactions are not instantaneous for this protein, which is important for those attempting to study the ligand-binding equilibria. From the results presented here the authors estimate that the actual equilibrium dissociation constant (K{sub D}) for cyanide binding to this G. dibranchiata monomer methemoglobin has a numerical upper limit that is at least 2 orders of magnitude smaller than the value reported before the kinetic results were known.

  15. Biosorption of lead (II) from water using heartwood charcoal of Areca catechu: equilibrium and kinetics studies

    NASA Astrophysics Data System (ADS)

    Haloi, Nabanita; Sarma, H. P.; Chakravarty, P.

    2013-09-01

    Present study was conducted to investigate the removal of Pb(II) from water by using heartwood charcoal of Areca catechu (HCAC). Batch experiments were conducted to determine the adsorption properties at different contact times (5-30 min), concentrations (0.1-10 mg/L), amounts of adsorbents (0.1-0.6 g), and in a range of pH 2-7. Most favorable biosorption condition was found at pH 5.0, 0.5 g biomass dosage and at 25 min equilibrium time. The experimental results were fitted to the Langmuir and Freundlich isotherm models; the Freundlich isotherm was found to well represent the measured sorption data implying HCAC has heterogeneous surface. Lagergren first-order and pseudo-second-order kinetic model were used to analyze the biosorption data; it was observed that the pseudo-second-order model best represented the relationship. Scanning electron microscopy image and energy dispersive X-ray analysis were also incorporated in support of the study. The result shows that HCAC has the potentiality to remove Pb(II) from water.

  16. Numerical Analysis on Non-Equilibrium Mechanism of Laser-Supported Detonation Wave Using Multiply-Charged Ionization

    SciTech Connect

    Shiraishi, Hiroyuki

    2006-05-02

    Laser-Supported Detonation (LSD), one type of Laser-Supported Plasma (LSP), is considered as the most important phenomena because it can generate high pressure and high temperature for laser absorption. In this study, I have numerically simulated the 1-D LSD waves propagating through a helium gas, in which Multiply-charged ionization model is considered for describing an accurate ionization process.

  17. The N (II) 205 micron line in M82: The warm ionized medium

    NASA Technical Reports Server (NTRS)

    Petuchowski, S. J.; Bennett, C. L.; Haas, Michael R.; Erickson, Edwin F.; Lord, Steven D.; Rubin, Robert H.; Colgan, Sean W. J.; Hollenbach, D. J.

    1994-01-01

    Detection of the 205 micrometer fine structure line of N II in the nearby starburst galaxy M82 is reported. The intensity wihin a 54 sec Full width at Half Maximum (FWHM) beam is (7.1 +/- 1.2) x 10(exp -19) W cm(exp -2). The ratio of the intensity of the recently detected 122 micrometer line to that of the 2.5 micrometer lines is = (4.2) (sup =1.6) (sub -1.2), significantly larger than the corresponding Galactic value of 1.6 +/- 0.3, reflecting higher electron densities within the central 850 pc of M82 in comparison to the Cosmic Background Explorer (COBE) Galactic average. The 2.5 micrometer line profile is consistent with other far-infrared fine-structure line profiles observed in M82. The observations are interpreted in the context of a two-component model of the ionized medium in M82. We find that a component of density as low as approximately 50 cm(exp -3) can comprise up to 70% of the total mass of warm ionized gas within the beam. The balance of the ionized mass is comprised of a component of density approximately greater than 100 cm(exp -3). A model is explored in which the dneser ionized medium constitute the boundaries of neutral surfaces which border the expanding hot plasma from the nuclear region.

  18. Critically Evaluated Energy Levels and Spectral Lines of Singly Ionized Indium (In II)

    PubMed Central

    Kramida, A

    2013-01-01

    A comprehensive list of the best measured wavelengths in the In II spectrum has been compiled. Uncertainties of the wavelength measurements have been analyzed, and existing inconsistencies have been resolved. An optimized set of fine-structure energy levels that fits all observed wavelengths has been derived. Uncertainties of the energy level values have been reduced by an order of magnitude. An improved value of the ionization limit of In II has been determined by fitting quantum-defect and polarization formulas for several series of levels. Intensities of lines observed by different authors have been analyzed and converted to a uniform scale. A set of recommended values of radiative transition rates has been critically compiled, and uncertainties of these rates have been estimated. The hyperfine structure interval in the 5s 2S ground state of In III has been determined from the measurements of the 5sng and 5snh series in In II. PMID:26401424

  19. Spatial ionization effects of a shock layer in the RAM-C-II flight experiment

    NASA Astrophysics Data System (ADS)

    Surzhikov, S. T.

    2015-02-01

    A three-dimensional computer model of the nonequilibrium ionization aerophysics of descent moduli entering dense atmospheric layers with orbital velocity in the height range of 60-90 km is developed. A three-dimensional numerical analysis of the experimental data on the ionization of the shock layer near the surface of a hypersonic flying module having the form of a blunt-sphere cone with the flight velocity higher than 7.5 km/s at heights of 61-81 km is fulfilled. The data of the flight experiment are obtained in the framework of the RAM-C-II investigatory program. The use of a three-dimensional computer model made it possible to find the calculated data in good agreement with the flight experiment data, as well as to explain some spatial effects not considered before.

  20. Charge exchange contamination of CRIT-II barium CIV experiment. [critical ionization velocity in ionosphere

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.; Mende, S. B.; Meyerott, R. E.; Rairden, R. L.

    1991-01-01

    Experiments have been recently performed which attempted to confirm critical ionization velocity (CIV) ionization by deploying chemicals at high velocity in the ionosphere. Specifically, the CRIT-II rocket performed a barium release in the ionosphere, where observations of Ba(+) resonant emissions following the release are believed to have resulted from the CIV process. Calculations are presented which suggest a significant fraction (if not all) of the Ba(+) observed likely resulted from charge exchange with the thermosphere ions and not through CIV processes. The results presented here are pertinent to other CIV experiments performed in the ionosphere. It is recommended that laboratory measurements should be made of the charge exchange cross section between O(+) and Ba as well as other metal vapors used in CIV experiments.

  1. Can the Lyman Continuum Leaked Out of H II Regions Explain Diffuse Ionized Gas?

    NASA Astrophysics Data System (ADS)

    Seon, Kwang-Il

    2009-09-01

    We present an attempt to explain the diffuse Hα emission of a face-on galaxy M 51 with the "standard" photoionization model, in which the Lyman continuum (Lyc) escaping from H II regions propagates large distances into the diffuse interstellar medium (ISM). The diffuse Hα emission of M 51 is analyzed using thin slab models and exponential disk models in the context of the "on-the-spot" approximation. The scale height of the ionized gas needed to explain the diffuse Hα emission with the scenario is found to be of the order of ~1-2 kpc, consistent with those of our Galaxy and edge-on galaxies. The model also provides a vertical profile, when the galaxy is viewed edge-on, consisting of two-exponential components. However, it is found that an incredibly low absorption coefficient of κ0 ≈ 0.4-0.8 kpc-1 at the galactic plane, or, equivalently, an effective cross section as low as σeff ~ 10-5 of the photoionization cross section at 912 Å is required to allow the stellar Lyc photons to travel through the H I disk. Such a low absorption coefficient is out of accord with the properties of the ISM. Furthermore, we found that even the model that has the diffuse ionized gas (DIG) phase only and no H I gas phase shows highly concentrated Hα emissions around H II regions, and can account for only lsim26% of the Hα luminosity of the DIG. This result places a strong constraint on the ionizing source of the DIG. We also report that the Hα intensity distribution functions not only of the DIG, but also of H II regions in M 51, appear to be lognormal.

  2. COMPREHENSIVE OBSERVATIONS OF THE ULTRAVIOLET SPECTRUM AND IMPROVED ENERGY LEVELS FOR SINGLY IONIZED CHROMIUM (Cr II)

    SciTech Connect

    Sansonetti, Craig J.; Nave, Gillian; Reader, Joseph; Kerber, Florian

    2012-10-15

    We report new observations of the spectrum of singly ionized chromium (Cr II) in the region 1142-3954 A. The spectra were recorded with the National Institute of Standards and Technology 10.7 m normal-incidence vacuum spectrograph and FT700 vacuum ultraviolet Fourier transform spectrometer. More than 3600 lines are classified as transitions among 283 even and 368 odd levels. The new spectral data are used to re-optimize the energy levels, reducing their uncertainties by a typical factor of 20.

  3. Equilibrium II: Acids and Bases. Independent Learning Project for Advanced Chemistry (ILPAC). Unit P3.

    ERIC Educational Resources Information Center

    Inner London Education Authority (England).

    This unit on equilibrium is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, focuses on the application of equilibrium principles to equilibria involving weak acids and bases, including buffer solutions and indicators. Level one uses Le Chatelier's…

  4. Temperature lapse rates at restricted thermodynamic equilibrium. Part II: Saturated air and further discussions

    NASA Astrophysics Data System (ADS)

    Björnbom, Pehr

    2016-03-01

    In the first part of this work equilibrium temperature profiles in fluid columns with ideal gas or ideal liquid were obtained by numerically minimizing the column energy at constant entropy, equivalent to maximizing column entropy at constant energy. A minimum in internal plus potential energy for an isothermal temperature profile was obtained in line with Gibbs' classical equilibrium criterion. However, a minimum in internal energy alone for adiabatic temperature profiles was also obtained. This led to a hypothesis that the adiabatic lapse rate corresponds to a restricted equilibrium state, a type of state in fact discussed already by Gibbs. In this paper similar numerical results for a fluid column with saturated air suggest that also the saturated adiabatic lapse rate corresponds to a restricted equilibrium state. The proposed hypothesis is further discussed and amended based on the previous and the present numerical results and a theoretical analysis based on Gibbs' equilibrium theory.

  5. Adsorption/desorption of Cd(II), Cu(II) and Pb(II) using chemically modified orange peel: Equilibrium and kinetic studies

    NASA Astrophysics Data System (ADS)

    Lasheen, Mohamed R.; Ammar, Nabila S.; Ibrahim, Hanan S.

    2012-02-01

    Waste materials from industries such as food processing may act as cost effective and efficient biosorbents to remove toxic contaminants from wastewater. This study aimed to establish an optimized condition and closed loop application of processed orange peel for metals removal. A comparative study of the adsorption capacity of the chemically modified orange peel was performed against environmentally problematic metal ions, namely, Cd 2+, Cu 2+ and Pb 2+, from aqueous solutions. Chemically modified orange peel (MOP) showed a significantly higher metal uptake capacity compared to original orange peel (OP). Fourier Transform Infrared (FTIR) Spectra of peel showed that the carboxylic group peak shifted from 1637 to 1644 cm -1 after Pb (II) ions binding, indicated the involvement of carboxyl groups in Pb(II) ions binding. The metals uptake by MOP was rapid and the equilibrium time was 30 min at constant temperature and pH. Sorption kinetics followed a second-order model. The mechanism of metal sorption by MOP gave good fits for Freundlich and Langmuir models. Desorption of metals and regeneration of the biosorbent was attained simultaneously by acid elution. Even after four cycles of adsorption-elution, the adsorption capacity was regained completely and adsorption efficiency of metal was maintained at around 90%.

  6. Kinetics, equilibrium, and thermodynamics investigation on the adsorption of lead(II) by coal-based activated carbon.

    PubMed

    Yi, Zhengji; Yao, Jun; Zhu, Mijia; Chen, Huilun; Wang, Fei; Liu, Xing

    2016-01-01

    The goal of this research is to investigate the feasibility of using activated coal-based activated carbon (CBAC) to adsorb Pb(II) from aqueous solutions through batch tests. Effects of contact time, pH, temperature and initial Pb(II) concentration on the Pb(II) adsorption were examined. The Pb(II) adsorption is strongly dependent on pH, but insensitive to temperature. The best pH for Pb(II) removal is in the range of 5.0-5.5 with more than 90 % of Pb(II) removed. The equilibrium time was found to be 60 min and the adsorption data followed the pseudo-second-order kinetics. Isotherm data followed Langmuir isotherm model with a maximum adsorption capacity of 162.33 mg/g. The adsorption was exothermic and spontaneous in nature. The Fourier transform infrared spectroscopy and scanning electron microscopy analysis suggested that CBAC possessed a porous structure and was rich in carboxyl and hydroxyl groups on its surface, which might play a major role in Pb(II) adsorption. These findings indicated that CBAC has great potential as an alternative adsorbent for Pb(II) removal. PMID:27504258

  7. A non-local thermodynamical equilibrium line formation for neutral and singly ionized titanium in model atmospheres of reference A-K stars

    NASA Astrophysics Data System (ADS)

    Sitnova, T. M.; Mashonkina, L. I.; Ryabchikova, T. A.

    2016-09-01

    We construct a model atom for Ti I-II using more than 3600 measured and predicted energy levels of Ti I and 1800 energy levels of Ti II, and quantum mechanical photoionization cross-sections. Non-local thermodynamical equilibrium (NLTE) line formation for Ti I and Ti II is treated through a wide range of spectral types from A to K, including metal-poor stars with [Fe/H] down to -2.6 dex. NLTE leads to weakened Ti I lines and positive abundance corrections. The magnitude of NLTE corrections is smaller compared to the literature data for FGK atmospheres. NLTE leads to strengthened Ti II lines and negative NLTE abundance corrections. For the first time, we have performed NLTE calculations for Ti I-II in the 6500 ≤ Teff ≤ 13 000 K range. For four A-type stars, we derived in LTE an abundance discrepancy of up to 0.22 dex between Ti I and Ti II, which vanishes in NLTE. For four other A-B stars, with only Ti II lines observed, NLTE leads to a decrease of line-to-line scatter. An efficiency of inelastic Ti I + H I collisions was estimated from an analysis of Ti I and Ti II lines in 17 cool stars with -2.6 ≤ [Fe/H] ≤ 0.0. Consistent NLTE abundances from Ti I and Ti II were obtained by applying classical Drawinian rates for the stars with log g ≥ 4.1, and neglecting inelastic collisions with H I for the very metal-poor (VMP) giant HD 122563. For the VMP turn-off stars ([Fe/H] ≤ -2 and log g ≤ 4.1), we obtained the positive abundance difference Ti I-II already in LTE, which increases in NLTE. Accurate collisional data for Ti I and Ti II are necessary to help solve this problem.

  8. Statistical equilibrium in cometary C2. II - Swan/Phillips band ratios

    NASA Technical Reports Server (NTRS)

    Swamy, K. S. K.; Odell, C. R.

    1979-01-01

    Statistical equilibrium calculations have been made for both the triplet and ground state singlets for C2 in comets, using the exchange rate as a free parameter. The predictions of the results are consistent with optical observations and may be tested definitively by accurate observations of the Phillips and Swan band ratios. Comparison with the one reported observation indicates compatibility with a low exchange rate and resonance fluorescence statistical equilibrium.

  9. Dense clumps of ionized gas near Pi Scorpii, as revealed by the fine-structure excitation of N II

    NASA Technical Reports Server (NTRS)

    Bertoldi, Frank; Jenkins, Edward B.

    1992-01-01

    The column density and the emission of the ionized gas along the line of sight toward the B1 V + B2 V binary star Pi Sco are measured on the basis of the fine-structure absorption lines of the ground state N II. It is found that the bulk of this ionized gas must be clumped on a length scale of 0.025 pc, which is far smaller than the observed size of the diffuse H II region surrounding Pi Sco of about 6 pc. The observed column density of S III toward Pi Sco yields an upper limit on the distance of the absorbing, clumped gas from the star of less than about 0.02 pc, assuming that both the N II and S III absorption arise from the same gas. The possibility that the ionized gas originates from a photoevaporating circumstellar disk directly surrounding Pi Sco is excluded, since such a disk would have an unusual size of order 0.025 pc and would have had to survive for the estimated age of Pi Sco of 5-8 Myr. The derived mean density of the clumped gas is of order 40/cu cm, so that the gas is at a pressure that far exceeds the mean pressure in the H II region. It is concluded that the ionized gas could originate from evaporation flows off a cluster of compact neutral objects that evaporate due to the ionizing radiation of Pi Sco.

  10. Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization, Equilibrium Isotherms, and Adsorption Kinetics Study

    PubMed Central

    Khandanlou, Roshanak; Ahmad, Mansor B.; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

    2015-01-01

    Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles. PMID:25815470

  11. Equilibrium and kinetic studies on biosorption of Pb(II) by common edible macrofungi: a comparative study.

    PubMed

    Jiang, Yuan; Hao, Ruixia; Yang, Shiqin

    2016-04-01

    In this work, we studied the natural bioaccumulation and biosorption of Pb(II) in several common edible macrofungi. The macrofungi include the following species: Lentinus edodes, Pleurotus eryngii, Flammulina velutipes, Hypsizygus marmoreus, and Agrocybe cylindracea. The present analysis of Pb(II) revealed distinct capabilities of metal accumulation among individual species. Moreover, the natural concentrations of lead did not reach a health risk level when cultivated in uncontaminated soil. In the biosorption experiment by edible macrofungi, we found that the equilibrium data of living sporocarp (P. eryngii and H. marmoreus) and the homogenate of L. edodes and F. velutipes fit the Freundlich model well. Other data samples exhibited a better fit to the Langmuir model. The edible macrofungi showed a higher lead removal capacity than did other biosorbents. Furthermore, the pseudo-second-order kinetics model exhibited the best fit to the biosorption processes. The effectiveness of edible macrofungi as biosorbents for Pb(II) was confirmed. PMID:26928439

  12. [C II] 158 μm and [N II] 205 μm emission from IC 342. Disentangling the emission from ionized and photo-dissociated regions

    NASA Astrophysics Data System (ADS)

    Röllig, M.; Simon, R.; Güsten, R.; Stutzki, J.; Israel, F. P.; Jacobs, K.

    2016-06-01

    Context. Atomic fine-structure line emission is a major cooling process in the interstellar medium (ISM). In particular the [C II] 158 μm line is one of the dominant cooling lines in photon-dominated regions (PDRs). However, it is not confined to PDRs but can also originate from the ionized gas closely surrounding young massive stars. The proportion of the [C II] emission from H II regions relative to that from PDRs can vary significantly. Aims: We investigate the question of how much of the [C II] emission in the nucleus of the nearby spiral galaxy IC 342 is contributed by PDRs and by the ionized gas. We examine the spatial variations of starburst/PDR activity and study the correlation of the [C II] line with the [N II] 205 μm emission line coming exclusively from the H II regions. Methods: We present small maps of [C II] 158 μm and [N II] 205 μm lines recently observed with the GREAT receiver on board SOFIA. We present different methods to utilize the superior spatial and spectral resolution of our new data to infer information on how the gas kinematics in the nuclear region influence the observed line profiles. In particular we present a super-resolution method to derive how unresolved, kinematically correlated structures in the beam contribute to the observed line shapes. Results: We find that the emission coming from the ionized gas shows a kinematic component in addition to the general Doppler signature of the molecular gas. We interpret this as the signature of two bi-polar lobes of ionized gas expanding out of the galactic plane. We then show how this requires an adaptation of our understanding of the geometrical structure of the nucleus of IC 342. Examining the starburst activity we find ratios I( [C II] ) /I(12CO(1-0)) between 400 and 1800 in energy units. Applying predictions from numerical models of H II and PDR regions to derive the contribution from the ionized phase to the total [C II] emission we find that 35-90% of the observed [C II] intensity

  13. Radiation fields of intermediate-age stellar populations with binaries as ionizing sources of H II regions

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Li, L.; Cheng, L.; Wang, L.; Kang, X.; Zhuang, Y.; Han, Z.

    2015-02-01

    Radiation fields emitted by O- and B-type stars or young stellar populations (SPs) are generally considered as significant central ionizing sources (CISs) of classic H II regions. In our previous studies, we showed that the inclusion of binary interactions in stellar population synthesis models can significantly increase the ultraviolet spectrum hardness and the number of ionizing photons of intermediate-age (IA) SPs (7 ≲ log(t/yr) ≲ 8). In this work, we present photoionization models of H II regions ionized by radiation fields emitted by IA SPs, including binary systems, and show that these fields are in theory possible candidates for significant CISs of classic H II regions. When radiation fields of IA SPs comprising binary systems are used as the CISs of classic H II regions, the theoretical strengths of a number of lines (such as [O III] λ4959', [S II] λ6716', etc.), which are weaker than observations, are increased; the border or selection-criterion lines between star-forming galaxies and active galactic nuclei (AGNs) in the diagnostic diagrams (for example, [N II] λ6583/Hα versus [O III] λ5007/Hβ), move into the region occupied originally by AGNs; and the He II λ1640 line, observed in Lyman break and high-redshift gravitationally lensed galaxies, also can be produced.

  14. A numerical model of non-equilibrium thermal plasmas. II. Governing equations

    SciTech Connect

    Li HePing; Zhang XiaoNing; Xia Weidong

    2013-03-15

    Governing equations and the corresponding physical properties of the plasmas are both prerequisites for studying the fundamental processes in a non-equilibrium thermal plasma system numerically. In this paper, a kinetic derivation of the governing equations used for describing the complicated thermo-electro-magneto-hydrodynamic-chemical coupling effects in non-equilibrium thermal plasmas is presented. This derivation, which is achieved using the Chapman-Enskog method, is completely consistent with the theory of the transport properties reported in the previous paper by the same authors. It is shown, based on this self-consistent theory, that the definitions of the specific heat at constant pressure and the reactive thermal conductivity of two-temperature plasmas are not necessary. The governing equations can be reduced to their counterparts under local thermodynamic equilibrium (LTE) and local chemical equilibrium (LCE) conditions. The general method for the determination of the boundary conditions of the solved variables is also discussed briefly. The two papers establish a self-consistent physical-mathematical model that describes the complicated physical and chemical processes in a thermal plasma system for the cases both in LTE or LCE conditions and under non-equilibrium conditions.

  15. Excitation in the ionized diffuse interstellar medium

    NASA Astrophysics Data System (ADS)

    Sivan, J.-P.; Stasińska, G.; Lequeux, J.

    1986-04-01

    Large-scale spectra have been obtained in the diffuse, ionized background of the Sagittarius-Carina arm and in the large complex of loops and filaments located in Orion and Eridanus. The intensity ratios of the emission lines of O III forbidden line, H-beta, H-alpha, N II forbidden line and S II forbidden line have been derived from these spectra, and are analyzed using models of H II regions in ionization equilibrium at very low densities, down to 0.01/cu cm. The confrontation of the observed ratios with the predictions of the models, which have been calibrated against observations of classical H II regions, shows that the S II forbidden line (6717 + 6731)/H-alpha ratio is too large to arise in a gas submitted only to a stellar flux with which it comes into ionization equilibrium, whatever the dilution of the matter. Contribution of shock excitation seems a natural explanation, as shocks are likely to occur considering the chaotic morphology of the studied regions. Some alternative explanations are also suggested. However, this medium is principally ionized by radiation, and it is shown that the forbidden line O III/H-beta ratios are well accounted for by the known population of O stars within the expected uncertainties, while ionization by white dwarfs or by B stars suggested by previous authors are excluded. The mean effective temperature for ionizing stars (less than 35,000 K) is lower than that of stars exciting classical H II regions.

  16. H II Region Ionization of the Interstellar Medium: A Case Study of NGC 7538

    NASA Astrophysics Data System (ADS)

    Luisi, Matteo; Anderson, L. D.; Balser, Dana S.; Bania, T. M.; Wenger, Trey V.

    2016-06-01

    Using data from the Green Bank Telescope, we analyze the radio continuum (free–free) and radio recombination line (RRL) emission of the compact H ii region NGC 7538 (Sharpless 158). We detect extended radio continuum and hydrogen RRL emission beyond the photodissociation region (PDR) toward the north and east, but a sharp decrease in emission toward the south and west. This indicates that a non-uniform PDR morphology is affecting the amount of radiation “leaking” through the PDR. The strongest carbon RRL emission is found in the western PDR that appears to be dense. We compute a leaking fraction f R = 15 ± 5% of the radio continuum emission measured in the plane of the sky which represents a lower limit when accounting for the three-dimensional geometry of the region. We detect an average {}4{{{He}}}+/{{{H}}}+ abundance ratio by number of 0.088 ± 0.003 inside the H ii region and a decrease in this ratio with increasing distance from the region beyond the PDR. Using Herschel Space Observatory data, we show that small dust temperature enhancements to the north and east of NGC 7538 coincide with extended radio emission, but that the dust temperature enhancements are mostly contained within a second PDR to the east. Unlike the giant H ii region W43, the radiation leaking from NGC 7538 seems to only affect the local ambient medium. This suggests that giant H ii regions may have a large effect in maintaining the ionization of the interstellar medium.

  17. Equilibrium gas flow computations. II - An analysis of numerical formulations of conservation laws

    NASA Technical Reports Server (NTRS)

    Vinokur, Marcel; Liu, Yen

    1988-01-01

    Modern numerical techniques employing properties of flux Jacobian matrices are extended to general, equilibrium gas laws. Generalizations of the Beam-Warming scheme, Steger-Warming and van Leer flux-vector splittings, and Roe's approximate Riemann solver are presented for three-dimensional, time-varying grids. The approximations inherent in previous generalizations are discussed.

  18. Equilibrium analysis of aggregation behavior in the solvent extraction of Cu(II) from sulfuric acid by didodecylnaphthalene sulfonic acid

    SciTech Connect

    Moyer, B.A.; Baes, C.F. Jr.; Case, G.N.; Lumetta, G.J.; Wilson, N.M.

    1993-01-01

    By use of the principles of equilibrium analysis, the liquid-liquid cation exchange of Cu(II) from aqueous sulfuric acid at 25{degrees}C by didodecylnaphthalenesulfonic acid (HDDNS) in toluene may be understood in terms of small hydrated aggregated species in the organic phase. Extraction data were measured as a function of organic-phase HDDNS molarity (1.0 {times} 10{sup {minus}4} to 1.0 {times} 10{sup {minus}1}), aqueous copper(II) sulfate molarity (1.2 {times} 10{sup {minus}8} to 1.3 {times} 10{sup {minus}2}), and aqueous sulfuric acid molarity (0.03 to 6.0). Graphical analysis of linear regions of the data support a model in which organic-phase aggregates of HDDNS function by cation exchange to incorporate Cu(II) ions with no apparent change in aggregation number at low loading. Supporting FTIR spectra and water-content measurements of HDDNS solutions in toluene show that the HDDNS aggregates are highly hydrated. By use of the computer program SXLSQA, a comprehensive equilibrium model was developed with inclusion of activity effects. Aqueous-phase activity coefficients and degree of aqueous bisulfate formation were estimated by use of the Pitzer treatment. Organic-phase nonideality was estimated by the Hildebrand-Scott treatment and was shown to be a negligible effect under the conditions tested. Excluding aqueous sulfuric acid molarities greater than 1, it was possible to model the data to within experimental error by assuming only the equilibrium extraction of Cu{sup 2+} ion by the aggregate (HDDNS){sub 4}(H{sub 2}O){sub 22} and the equilibrium dissociation of (HDDNS){sub 4}(H{sub 2}O){sub 22} to the monomer. The dependence of Cu(II) distribution on aqueous sulfuric acid molarity was shown to be quantitatively consistent with a cation-exchange process. In comparison with the graphical approach, the computer analysis allows comprehensive model testing over large, nonlinear data sets and eliminates the need to make limiting assumptions.

  19. The Ionization Structure of Sharpless 2-264: Multiwavelength Observations of the λ Ori H II Region

    NASA Astrophysics Data System (ADS)

    Sahan, M.; Haffner, L. M.

    2016-06-01

    We present velocity-resolved maps taken with the Wisconsin H-Alpha Mapper (WHAM) in Hα, [S ii] λ 6716, and [N ii] λ 6583 around the well-known O8 III star λ Ori A (HD 36861) ({\\ell }=185^\\circ to 205^\\circ ,b=-24^\\circ to -1^\\circ ). The integrated intensity ({v}{{LSR}}=-80 to +80 km s‑1), {I}{{H}α }, within WHAM’s one-degree beams varies from ∼190 R near the center to ∼10 R on the periphery of the nebula where it becomes comparable to foreground and/or background emission in this complex region. Intensity ratios for [N ii]/Hα and [S ii]/Hα average 0.28 and 0.35, respectively. In both ratios, higher values are found preferentially at larger radii from λ Ori, although the behavior of [N ii]/Hα is complicated near the edges of the nebula. The [S ii]/[N ii] intensity ratio ranges from ∼0.5 to ∼1.0, with the value increasing toward larger radii (and lower Hα intensities). Variations of the [S ii]/Hα, [N ii]/Hα, and [S ii]/[N ii] line ratios in this diffuse region show some similar trends to those seen in the warm ionized medium (WIM) but with generally lower metal-line ratios. As with the WIM, the trends are driven by changes in the underlying physical parameters, most notably the ionization states and gas temperature. To investigate which cause might be dominant in this region, we use these extremely high signal-to-noise observations to construct a map of temperature and non-thermal velocity throughout the nebula. Using the line widths of Hα and [S ii], we separate thermal and non-thermal components and find spatial trends of these parameters within the nebula. Ion temperatures range between 4000 and 8000 K throughout the nebula. The non-thermal velocity map reveals a decrease in velocity from about 10 to 5 km s‑1 from the center to the edge of the lower half of the H ii region. In addition to using the widths as a measure of temperature, we also use the variation in [N ii]/Hα to estimate electron temperature. The results obtained from

  20. Comparative equilibrium studies of sorption of Pb(II) ions by sodium and calcium alginate.

    PubMed

    Khotimchenko, Maxim; Kovalev, Valeri; Khotimchenko, Yuri

    2008-01-01

    The absorption of Pb(II) ions from aqueous solution by different alginate compounds was studied in a batch sorption system. Water soluble sodium alginate and insoluble calcium alginate beads were investigated. The lead-binding capacity of both alginate compounds was highest within the pH range 6-8. The binding capacities and rates of Pb(II) ions by alginate compounds were evaluated. The Langmuir, Freundlich, and Bruneaur, Emmet and Teller (BET) sorption models were applied to describe the isotherms and isotherm constants. Sorption isothermal data could be well interpreted by the Langmuir model. The results obtained through the study suggest that alginate compounds are favorable sorbents. The largest amount of Pb(II) ions were bound by sodium alginate although the difference between two compounds was slight. Therefore, alginate substances may be considered as an alternative for sorption and removal of Pb(II) ions from wastewaters. PMID:18814578

  1. A fitting formula for radiative cooling based on non-local thermodynamic equilibrium population from weakly-ionized air plasma

    NASA Astrophysics Data System (ADS)

    Ogino, Yousuke; Nagano, Atsushi; Ishihara, Tomoaki; Ohnishi, Naofumi

    2013-08-01

    A fitting formula for radiative cooling with collisional-radiative population for air plasma flowfield has been developed. Population number densities are calculated from rate equations in order to evaluate the effects of nonequilibrium atomic and molecular processes. Many elementary processes are integrated to be applied to optically-thin plasmas in the number density range of 1012/cm3 <= N <= 1019/cm3 and the temperature range of 300 K <= T <= 40,000 K. Our results of the total radiative emissivity calculated from the collisional-radiative population are fitted in terms of temperature and total number density. To validate the analytic fitting formula, numerical simulation of a laser-induced blast wave propagation with the nonequilibrium radiative cooling is conducted and successfully reproduces the shock and plasma wave front time history observed by experiments. In addition, from the comparison between numerical simulations with the radiation cooling effect based on the fitting formula and those with a gray gas radiation model that assumes local thermodynamic equilibrium, we find that the displacement of the plasma front is slightly different due to the deviation of population probabilities. By using the fitting formula, we can easily and more accurately evaluate the radiative cooling effect without solving detailed collisional-radiative rate equations.

  2. Magnetohydrostatic equilibrium. II. Three-dimensional multiple open magnetic flux tubes in the stratified solar atmosphere

    SciTech Connect

    Gent, F. A.; Erdélyi, R.; Fedun, V.

    2014-07-01

    A system of multiple open magnetic flux tubes spanning the solar photosphere and lower corona is modeled analytically, within a realistic stratified atmosphere subject to solar gravity. This extends results for a single magnetic flux tube in magnetohydrostatic equilibrium, described in Gent et al. Self-similar magnetic flux tubes are combined to form magnetic structures, which are consistent with high-resolution observations. The observational evidence supports the existence of strands of open flux tubes and loops persisting in a relatively steady state. Self-similar magnetic flux tubes, for which an analytic solution to the plasma density and pressure distribution is possible, are combined. We calculate the appropriate balancing forces, applying to the equations of momentum and energy conservation to preserve equilibrium. Multiplex flux tube configurations are observed to remain relatively stable for up to a day or more, and it is our aim to apply our model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona. We apply magnetic field strength, plasma density, pressure, and temperature distributions consistent with observational and theoretical estimates for the lower solar atmosphere. Although each flux tube is identical in construction apart from the location of the radial axis, combinations can be applied to generate a non-axisymmetric magnetic field with multiple non-uniform flux tubes. This is a considerable step forward in modeling the realistic magnetized three-dimensional equilibria of the solar atmosphere.

  3. Batch sorption dynamics, kinetics and equilibrium studies of Cr(VI), Ni(II) and Cu(II) from aqueous phase using agricultural residues

    NASA Astrophysics Data System (ADS)

    Kaur, Rajvinder; Singh, Joginder; Khare, Rajshree; Cameotra, Swaranjit Singh; Ali, Amjad

    2013-03-01

    In the present study, the agricultural residues viz., Syzygium cumini and Populus deltoides leaves powder have been used for the biosorption of Cu(II), Ni(II), and Cr(VI) from aqueous solutions. FTIR and SEM analysis of the biosorbents were performed to explore the type of functional groups available for metal binding and to study the surface morphology. Various physico-chemical parameters such as pH, adsorbent dosage, initial metal ion concentration, and equilibrium contact time were studied. Thermodynamic studies were carried out and the results demonstrated the spontaneous and endothermic nature of the biosorption process. The equilibrium data were tested using four isotherm models—Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the maximum biosorption capacities were evaluated. The Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were applied to study the reaction kinetics with pseudo-second order model giving the best fit ( R 2 = 0.99) to the experimental data.

  4. The Ionized Gas in Nearby Galaxies as Traced by the [N II] 122 and 205 μm Transitions

    NASA Astrophysics Data System (ADS)

    Herrera-Camus, R.; Bolatto, A.; Smith, J. D.; Draine, B.; Pellegrini, E.; Wolfire, M.; Croxall, K.; de Looze, I.; Calzetti, D.; Kennicutt, R.; Crocker, A.; Armus, L.; van der Werf, P.; Sandstrom, K.; Galametz, M.; Brandl, B.; Groves, B.; Rigopoulou, D.; Walter, F.; Leroy, A.; Boquien, M.; Tabatabaei, F. S.; Beirao, P.

    2016-08-01

    The [N ii] 122 and 205 μm transitions are powerful tracers of the ionized gas in the interstellar medium. By combining data from 21 galaxies selected from the Herschel KINGFISH and Beyond the Peak surveys, we have compiled 141 spatially resolved regions with a typical size of ˜1 kpc, with observations of both [N ii] far-infrared lines. We measure [N ii] 122/205 line ratios in the ˜0.6–6 range, which corresponds to electron gas densities of n e ˜ 1–300 cm‑3, with a median value of n e = 30 cm‑3. Variations in the electron density within individual galaxies can be as high as a factor of ˜50, frequently with strong radial gradients. We find that n e increases as a function of infrared color, dust-weighted mean starlight intensity, and star-formation rate (SFR) surface density (ΣSFR). As the intensity of the [N ii] transitions is related to the ionizing photon flux, we investigate their reliability as tracers of the SFR. We derive relations between the [N ii] emission and SFR in the low-density limit and in the case of a log-normal distribution of densities. The scatter in the correlation between [N ii] surface brightness and ΣSFR can be understood as a property of the n e distribution. For regions with n e close to or higher than the [N ii] line critical densities, the low-density limit [N ii]-based SFR calibration systematically underestimates the SFR because the [N ii] emission is collisionally quenched. Finally, we investigate the relation between [N ii] emission, SFR, and n e by comparing our observations to predictions from the MAPPINGS-III code.

  5. Physics of Partially Ionized Plasmas

    NASA Astrophysics Data System (ADS)

    Krishan, Vinod

    2016-05-01

    Figures; Preface; 1. Partially ionized plasmas here and everywhere; 2. Multifluid description of partially ionized plasmas; 3. Equilibrium of partially ionized plasmas; 4. Waves in partially ionized plasmas; 5. Advanced topics in partially ionized plasmas; 6. Research problems in partially ionized plasmas; Supplementary matter; Index.

  6. A 2D multiwavelength study of the ionized gas and stellar population in the giant H II region NGC 588

    NASA Astrophysics Data System (ADS)

    Monreal-Ibero, A.; Relaño, M.; Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M.; Kelz, A.; Roth, M. M.; Streicher, O.

    2011-05-01

    Giant H II regions (GHIIRs) in nearby galaxies are a local sample in which we can study in detail processes in the interaction of gas, dust and newly formed stars which are analogous to those which occurred in episodes of higher intensity in which much of the current stellar population was born. Here, we present an analysis of NGC 588, a GHIIR in M33, based on optical Integral Field Spectroscopy data obtained with the Potsdam Multi-Aperture Spectrophotometer at the 3.5-m telescope of the Calar Alto Observatory, CAHA, together with Spitzer infrared images at 8 and 24 μm. The extinction distribution measured in the optical shows complex structure, with three maxima which correlate in position with those of the emission at 24 and 8 μm. Furthermore, the Hα luminosity absorbed by the dust within the H II region reproduces the structure observed in the 24-μm image, supporting the use of the 24-μm band as a valid tracer of recent star formation. A velocity difference of ˜50 km s-1 was measured between the areas of high and low surface brightness, which would be expected if NGC 588 were an evolved GHIIR. We have carefully identified the areas which contribute most to the line ratios measured in the integrated spectrum. Those line ratios which are used in diagnostic diagrams proposed by Baldwin, Phillips & Terlevich (i.e. the BPT diagrams) show a larger range of variation in the low surface brightness areas. The ranges are ˜0.5-1.2 dex for [N II]λ6584/Hα, 0.7-1.7 dex for [S II]λλ6717,6731/Hα and 0.3-0.5 dex for [O III]λ5007/Hβ, with higher values of [N II]λ6584/Hα and [S II]λλ6717,6731/Hα, and lower values of [O III]λ5007/Hβ in the areas of lower surface brightness. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in Hβ and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ˜0.8 dex, notably when

  7. [Equilibrium surface charge distribution in phospholipid vesicles. II. Results of calculations].

    PubMed

    Tenchov, B G; Raĭchev, B D

    1977-01-01

    The results of the calculations of the equilibrium potential and surface charge distribution in a vesicle with radii r1=55 A and r2=100 A are presented. The calculations were carried out for the electrolyte concentrations 100 mM, 10mM, 1mM and 0.1 mM. The digitally obtained solutions of the Poisson-Boltzman equation for the case of spherical symmetry were utilized in the exact solution of the problem. The predictions of the exact solution differ significantly from these of the linear approximation in the range of low electrolyte concentrations. The influence of the membrane dielectric permeability on the charge distribution is negligible. PMID:588605

  8. Ionization equilibrium at the transition from valence-band to acceptor-band migration of holes in boron-doped diamond

    NASA Astrophysics Data System (ADS)

    Poklonski, N. A.; Vyrko, S. A.; Poklonskaya, O. N.; Kovalev, A. I.; Zabrodskii, A. G.

    2016-06-01

    A quasi-classical model of ionization equilibrium in the p-type diamond between hydrogen-like acceptors (boron atoms which substitute carbon atoms in the crystal lattice) and holes in the valence band (v-band) is proposed. The model is applicable on the insulator side of the insulator-metal concentration phase transition (Mott transition) in p-Dia:B crystals. The densities of the spatial distributions of impurity atoms (acceptors and donors) and of holes in the crystal are considered to be Poissonian, and the fluctuations of their electrostatic potential energy are considered to be Gaussian. The model accounts for the decrease in thermal ionization energy of boron atoms with increasing concentration, as well as for electrostatic fluctuations due to the Coulomb interaction limited to two nearest point charges (impurity ions and holes). The mobility edge of holes in the v-band is assumed to be equal to the sum of the threshold energy for diffusion percolation and the exchange energy of the holes. On the basis of the virial theorem, the temperature Tj is determined, in the vicinity of which the dc band-like conductivity of holes in the v-band is approximately equal to the hopping conductivity of holes via the boron atoms. For compensation ratio (hydrogen-like donor to acceptor concentration ratio) K ≈ 0.15 and temperature Tj, the concentration of "free" holes in the v-band and their jumping (turbulent) drift mobility are calculated. Dependence of the differential energy of thermal ionization of boron atoms (at the temperature 3Tj/2) as a function of their concentration N is calculated. The estimates of the extrapolated into the temperature region close to Tj hopping drift mobility of holes hopping from the boron atoms in the charge states (0) to the boron atoms in the charge states (-1) are given. Calculations based on the model show good agreement with electrical conductivity and Hall effect measurements for p-type diamond with boron atom concentrations in the

  9. Equilibrium and thermodynamic studies of Cd (II) biosorption by chemically modified orange peel.

    PubMed

    Kumar, Arbind; Kumar, Vipin

    2016-03-01

    Agricultural wastes have great potential of removing heavy metal ions from aqueous solution. Removal of Cd (II) from aqueous solutions onto chemically modified orange peel was studied at different pH, contact time, initial metal concentrations, adsorbent doses and temperature. Batch experiments were carried out under optimized conditions to evaluate the adsorption capacity of orange peel chemically modified with NaOH. The results showed that maximum adsorption capacity of modified orange peel, approximately 97.0%, was observed 3 mg 1⁻¹ of initial Cd(II) concentration pH 6 for 4 g 1⁻¹ adsorbent dosage, 200 min contact time and 298 K temperature. Adsorption efficiency of modified orange peel decreased with increase in temperature indicated exothermic nature of adsorption. A negative value of ΔG⁰(-8.59 kJ mol⁻¹) confirmed the feasibility of adsorption process and spontaneous nature of adsorption. A negative value of ΔH⁰ (-28.08 kJ mol⁻¹) indicated exothermic nature while a negative ΔS⁰ (-66.86 J K⁻¹ mol⁻¹) value suggested decrease in degree of freedom of the adsorbed species. The results showed that biosorption process of Cd(II) ions by chemically modified orange peel is feasible, spontaneous and exothermic under studied conditions. Chemically by modified orange peel investigated in the present study showed good potential for the removal of cadmium from aqueous solutions. PMID:27097438

  10. Microscopic Conductivity of Lattice Fermions at Equilibrium. Part II: Interacting Particles

    NASA Astrophysics Data System (ADS)

    Bru, Jean-Bernard; de Siqueira Pedra, Walter

    2016-01-01

    We apply Lieb-Robinson bounds for multi-commutators we recently derived (Bru and de Siqueira Pedra, Lieb-Robinson bounds for multi-commutators and applications to response theory, 2015) to study the (possibly non-linear) response of interacting fermions at thermal equilibrium to perturbations of the external electromagnetic field. This analysis leads to an extension of the results for quasi-free fermions of (Bru et al. Commun Pure Appl Math 68(6):964-1013, 2015; Bru et al. J Math Phys 56:051901-1-051901-51, 2015) to fermion systems on the lattice with short-range interactions. More precisely, we investigate entropy production and charge transport properties of non-autonomous C*-dynamical systems associated with interacting lattice fermions within bounded static potentials and in presence of an electric field that is time and space dependent. We verify the 1st law of thermodynamics for the heat production of the system under consideration. In linear response theory, the latter is related with Ohm and Joule's laws. These laws are proven here to hold at the microscopic scale, uniformly with respect to the size of the (microscopic) region where the electric field is applied. An important outcome is the extension of the notion of conductivity measures to interacting fermions.

  11. Fluids with competing interactions. II. Validating a free energy model for equilibrium cluster size

    NASA Astrophysics Data System (ADS)

    Bollinger, Jonathan A.; Truskett, Thomas M.

    2016-08-01

    Using computer simulations, we validate a simple free energy model that can be analytically solved to predict the equilibrium size of self-limiting clusters of particles in the fluid state governed by a combination of short-range attractive and long-range repulsive pair potentials. The model is a semi-empirical adaptation and extension of the canonical free energy-based result due to Groenewold and Kegel [J. Phys. Chem. B 105, 11702-11709 (2001)], where we use new computer simulation data to systematically improve the cluster-size scalings with respect to the strengths of the competing interactions driving aggregation. We find that one can adapt a classical nucleation like theory for small energetically frustrated aggregates provided one appropriately accounts for a size-dependent, microscopic energy penalty of interface formation, which requires new scaling arguments. This framework is verified in part by considering the extensive scaling of intracluster bonding, where we uncover a superlinear scaling regime distinct from (and located between) the known regimes for small and large aggregates. We validate our model based on comparisons against approximately 100 different simulated systems comprising compact spherical aggregates with characteristic (terminal) sizes between six and sixty monomers, which correspond to wide ranges in experimentally controllable parameters.

  12. Metastable and equilibrium defect structure of II VI/GaAs interfaces

    NASA Astrophysics Data System (ADS)

    Schwartzman, A. F.; Sinclair, R.

    1991-07-01

    Defect characterization by high-resolution electron microscopy is presented for (001) epitaxy of the CdTe/GaAs and ZnTe/GaAs heterojunctions, before and after a long vacuum anneal. The annealed interface structure consists of a periodic array of perfect edge Lomer misfit dislocations, with spacing corresponding to a strain-free thin film. Since this is the most efficient manner to obtain complete relaxation, it represents the equilibrium microstructure. The as-deposited films are very thick, three to four orders of magnitude greater than the critical thicknesses, which are both less than a monolayer for these large lattice mismatch systems. Their microstructure corresponds to a metastable distribution of defects in that the thin film residual strain is nearly zero and neighboring defects can react to form Lomer misfits. A variety of defects exist both in the form of perfect misfit dislocations at the interface and extended defects into the thin film. The extended defects result from formation of stacking faults bounded by either Shockley or Frank partials, and more complicated defect structures due to interacting perfect and partial dislocations on intersecting slip planes. The purpose of this paper is to investigate the means by which complete stress relaxation can occur through dislocation reactions during annealing of very thick as-deposited films.

  13. Constraining the escape fraction of ionizing photons from H ii regions within NGC 300: A concept paper

    NASA Astrophysics Data System (ADS)

    Niederhofer, F.; Hilker, M.; Bastian, N.; Ercolano, B.

    2016-07-01

    Using broadband photometry from the Hubble Space Telescope in combination with Very Large Telescope narrowband Hα observations of the nearby spiral galaxy NGC 300, we explore a method for estimating the escape fractions of hydrogen-ionizing photons from H ii regions within this galaxy. Our goal in this concept study is to evaluate the spectral types of the most massive stars using the broadband data and estimating their ionizing photon output with the help of stellar atmosphere models. A comparison with the Hα flux that gives the amount of ionized gas in the H ii region provides a measure of the escape fraction of ionizing photons from that region. We performed some tests with a number of synthetic young clusters with varying parameters to assess the reliability of the method. However, we found that the derived stellar spectral types and consequently the expected ionizing photon luminosity of a region is highly uncertain. The tests also show that on one hand we tended to overestimate the integrated photon output of a region for young ages and low numbers of stars, and on the other hand we mostly underestimated the combined ionizing luminosity for a large stellar number and older cluster ages. We conclude that the proposed method of using stellar broadband photometry to infer the leakage of ionizing photons from H ii regions is highly uncertain and dominated by the errors of the resulting stellar spectral types. Therefore this method is not suitable. Stellar spectra are needed to reliably determine the stellar types and escape fractions. Studies to this end have been carried out for the Magellanic Clouds. Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).Based on observations made with ESO telescopes

  14. Age and hormonal status as determinants of cataractogenesis induced by ionizing radiation. II. Sparsely ionizing (low-LET) radiation.

    PubMed

    Dynlacht, Joseph R; Valluri, Shailaja; Garrett, Joy; Nees, Jessica; Caperell-Grant, Andrea; DesRosiers, Colleen; Bigsby, Robert M

    2012-10-01

    Age at the time of exposure to sparsely ionizing radiation has been established as a key determinant of radiation cataractogenesis. However, while some reports suggest that the lenses of the young are hypersensitive, data from older studies are often conflicting and somewhat difficult to interpret when the radioresponse of young lenses is compared to that of adult lenses. Moreover, the mechanism of the age-response function for radiation cataractogenesis has yet to be identified. Since steroid sex hormones, notably estradiol, appear to play a role in age-related cataractogenesis, we hypothesized that the age response for radiation cataractogenesis could be dictated by estradiol status. We recently showed that exposure to high-linear energy transfer (LET) radiation resulted in a reduced latent period for, and enhanced progression of cataracts in rats that were 1 year old at the time of exposure compared to those that were 56 days old. However, the enhanced sensitivity of older lenses compared to younger lenses was independent of estradiol status. In the current study, we found that for 1-year-old rats exposed to 10 Gy of low-LET (60)Co γ rays, the rate of increase in the development of posterior and anterior subcapsular cataracts was higher in older ovary-intact rats compared to young rats. However, cataracts were detected much earlier in ovary-intact 56-day-old rats compared to 1-year-old rats, regardless of their treatment groups (ovary-intact, ovariectomized, or ovariectomized and implanted with capsules containing estradiol). Thus, despite a consistent estradiol response (potentiating effect of estrogen) within a given age group, the differences between the radiation response of old and young lenses cannot be accounted for solely by estradiol status. PMID:22880623

  15. CHEMICAL PROCESSES IN PROTOPLANETARY DISKS. II. ON THE IMPORTANCE OF PHOTOCHEMISTRY AND X-RAY IONIZATION

    SciTech Connect

    Walsh, Catherine; Millar, T. J.; Nomura, Hideko; Aikawa, Yuri

    2012-03-10

    We investigate the impact of photochemistry and X-ray ionization on the molecular composition of, and ionization fraction in, a protoplanetary disk surrounding a typical T Tauri star. We use a sophisticated physical model, which includes a robust treatment of the radiative transfer of UV and X-ray radiation, and calculate the time-dependent chemical structure using a comprehensive chemical network. In previous work, we approximated the photochemistry and X-ray ionization; here, we recalculate the photoreaction rates using the explicit UV wavelength spectrum and wavelength-dependent reaction cross sections. We recalculate the X-ray ionization rate using our explicit elemental composition and X-ray energy spectrum. We find that photochemistry has a larger influence on the molecular composition than X-ray ionization. Observable molecules sensitive to the photorates include OH, HCO{sup +}, N{sub 2}H{sup +}, H{sub 2}O, CO{sub 2}, and CH{sub 3}OH. The only molecule significantly affected by the X-ray ionization is N{sub 2}H{sup +}, indicating that it is safe to adopt existing approximations of the X-ray ionization rate in typical T Tauri star-disk systems. The recalculation of the photorates increases the abundances of neutral molecules in the outer disk, highlighting the importance of taking into account the shape of the UV spectrum in protoplanetary disks. A recalculation of the photoreaction rates also affects the gas-phase chemistry due to the adjustment of the H/H{sub 2} and C{sup +}/C ratios. The disk ionization fraction is not significantly affected by the methods adopted to calculate the photochemistry and X-ray ionization. We determine that there is a probable 'dead zone' where accretion is suppressed, present in a layer, Z/R {approx}< 0.1-0.2, in the disk midplane, within R Almost-Equal-To 200 AU.

  16. BAT AGN spectroscopic survey-II. X-ray emission and high-ionization optical emission lines

    NASA Astrophysics Data System (ADS)

    Berney, Simon; Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Schawinski, Kevin; Baloković, Mislav; Crenshaw, D. Michael; Fischer, Travis; Gehrels, Neil; Harrison, Fiona; Hashimoto, Yasuhiro; Ichikawa, Kohei; Mushotzky, Richard; Oh, Kyuseok; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain; Winter, Lisa

    2015-12-01

    We investigate the relationship between X-ray and optical line emission in 340 nearby (z ≃ 0.04) AGN selected above 10 keV using Swift BAT. We find a weak correlation between the extinction corrected [O III] and hard X-ray luminosity (L_[O III]^{int} ∝ L_{14-195}) with a large scatter (RPear = 0.64, σ = 0.62 dex) and a similarly large scatter with the intrinsic 2-10 keV to [O III] luminosities (RPear = 0.63, σ = 0.63 dex). Correlations of the hard X-ray fluxes with the fluxes of high-ionization narrow lines ([O III], He II, [Ne III] and [Ne V]) are not significantly better than with the low-ionization lines (H α, [S II]). Factors like obscuration or physical slit size are not found to be a significant part of the large scatter. In contrast, the optical emission lines show much better correlations with each other (σ = 0.3 dex) than with the X-ray flux. The inherent large scatter questions the common usage of narrow emission lines as AGN bolometric luminosity indicators and suggests that other issues such as geometrical differences in the scattering of the ionized gas or long-term AGN variability are important.

  17. Synthesis, characterization, equilibrium study and biological activity of Cu(II), Ni(II) and Co(II) complexes of polydentate Schiff base ligand.

    PubMed

    El-Sherif, Ahmed A; Shehata, Mohamed R; Shoukry, Mohamed M; Barakat, Mohammad H

    2012-10-01

    Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV-vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH(2)O, where M=Co(II), Ni(II) and Cu(II), L=BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogen's, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu(2+), Co(2+) and Ni(2+) complexes were determined by potentiometric titration method in 50% DMSO-water solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu(2+), Ni(2+) and Co(2+) form 1:1 complexes. PMID:22935596

  18. Synthesis, characterization, equilibrium study and biological activity of Cu(II), Ni(II) and Co(II) complexes of polydentate Schiff base ligand

    NASA Astrophysics Data System (ADS)

    El-Sherif, Ahmed A.; Shehata, Mohamed R.; Shoukry, Mohamed M.; Barakat, Mohammad H.

    2012-10-01

    Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV-vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH2O, where M = Co(II), Ni(II) and Cu(II), L = BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogen's, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu2+, Co2+ and Ni2+ complexes were determined by potentiometric titration method in 50% DMSO-water solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu2+, Ni2+ and Co2+ form 1:1 complexes.

  19. How do type II topoisomerases use ATP hydrolysis to simplify DNA topology beyond equilibrium? Investigating the relaxation reaction of nonsupercoiling type II topoisomerases.

    PubMed

    Stuchinskaya, Tanya; Mitchenall, Lesley A; Schoeffler, Allyn J; Corbett, Kevin D; Berger, James M; Bates, Andrew D; Maxwell, Anthony

    2009-02-01

    DNA topoisomerases control the topology of DNA (e.g., the level of supercoiling) in all cells. Type IIA topoisomerases are ATP-dependent enzymes that have been shown to simplify the topology of their DNA substrates to a level beyond that expected at equilibrium (i.e., more relaxed than the product of relaxation by ATP-independent enzymes, such as type I topoisomerases, or a lower-than-equilibrium level of catenation). The mechanism of this effect is currently unknown, although several models have been suggested. We have analyzed the DNA relaxation reactions of type II topoisomerases to further explore this phenomenon. We find that all type IIA topoisomerases tested exhibit the effect to a similar degree and that it is not dependent on the supercoil-sensing C-terminal domains of the enzymes. As recently reported, the type IIB topoisomerase, topoisomerase VI (which is only distantly related to type IIA enzymes), does not exhibit topology simplification. We find that topology simplification is not significantly dependent on circle size in the range approximately 2-9 kbp and is not altered by reducing the free energy available from ATP hydrolysis by varying the ADP:ATP ratio. A direct test of one model (DNA tracking; i.e., sliding of a protein clamp along DNA to trap supercoils) suggests that this is unlikely to be the explanation for the effect. We conclude that geometric selection of DNA segments by the enzymes is likely to be a primary source of the effect, but that it is possible that other kinetic factors contribute. We also speculate whether topology simplification might simply be an evolutionary relic, with no adaptive significance. PMID:19094994

  20. The merging/AGN connection. II. Ionization of the circumnuclear regions

    NASA Astrophysics Data System (ADS)

    Sánchez, S. F.; Becker, T.; Garcia-Lorenzo, B.; Benn, C. R.; Christensen, L.; Kelz, A.; Jahnke, K.; Roth, M. M.

    2005-01-01

    We report the first results of a study of a sample of 20 galaxy mergers/interacting systems, using the VIMOS and PMAS integral field spectrographs. For each object, we extracted the integrated spectrum of the central regions and analyzed the ionization state using classical diagnostic diagrams \\citep{veil87}. There is evidence of AGN ionization in 4 of the objects, i.e. 20% of the sample, a considerably higher fraction than found in previous studies (˜4%). An increase of the nuclear activity with the far infrared temperature may account for the difference.

  1. Iron isotope fractionation between aqueous Fe(II) and goethite revisited: New insights based on a multi-direction approach to equilibrium and isotopic exchange rate modification

    NASA Astrophysics Data System (ADS)

    Frierdich, Andrew J.; Beard, Brian L.; Reddy, Thiruchelvi R.; Scherer, Michelle M.; Johnson, Clark M.

    2014-08-01

    The Fe isotope compositions of naturally occurring Fe oxide minerals provide insights into biogeochemical processes that occur in modern and ancient environments. Key to understanding isotopic variations in such minerals is knowledge of the equilibrium Fe isotope fractionation factors between common minerals and aqueous Fe species. Because experimental measurements of isotopic fractionation may reflect a combination of kinetic and equilibrium fractionations during rapid dissolution and precipitation, even in experiments that employ the three-isotope method, assessment of the attainment of equilibrium is often difficult. Here, we re-examine Fe isotope exchange, via a 57Fe tracer, and natural mass-dependent fractionation, through changes in initial 56Fe/54Fe ratios, between aqueous Fe(II) (Fe(II)aq) and goethite. This approach uses the three-isotope method, but is distinct in its evaluation of kinetic isotope fractionation and the attainment of equilibrium by: (i) employing a multi-direction approach to equilibrium at 22 °C via reaction of three Fe(II)aq solutions that had different initial 56Fe/54Fe ratios, (ii) conducting isotopic exchange experiments at elevated temperature (50 °C), and (iii) modifying the rate of isotopic exchange through a combination of trace-element substitutions and particle coarsening to evaluate corresponding temporal changes in fractionation trajectories that may reflect changing instantaneous fractionation factors. We find that rapid isotopic exchange produces kinetic isotope effects between Fe(II)aq and goethite, which shifts the 56Fe/54Fe ratios of Fe(II)aq early in reactions toward that of goethite, indicating that the instantaneous Fe(II)aq-goethite fractionation factor under kinetic conditions is small. Importantly, however, this kinetic fractionation is “erased” with continued reaction, and this is evident by the congruence for multiple-exchange trajectories of distinct initial Fe(II)aq solutions toward the same final value

  2. THE ROLE OF DIFFUSIVE SHOCK ACCELERATION ON NONEQUILIBRIUM IONIZATION IN SUPERNOVA REMNANT SHOCKS. II. EMITTED SPECTRA

    SciTech Connect

    Patnaude, Daniel J.; Slane, Patrick; Raymond, John C.; Ellison, Donald C.

    2010-12-20

    We present a grid of nonequilibrium ionization models for the X-ray spectra from supernova remnants undergoing efficient diffusive shock acceleration. The calculation follows the hydrodynamics of the blast wave as well as the time-dependent ionization of the plasma behind the shock. The ionization state is passed to a plasma emissivity code to compute the thermal X-ray emission, which is combined with the emission from nonthermal synchrotron emission to produce a self-consistent model for the thermal and nonthermal emission from cosmic-ray dominated shocks. We show how plasma diagnostics such as the G'-ratio of He-like ions, defined as the ratio of the sum of the intercombination, forbidden, and satellite lines to the resonance line, can vary with acceleration efficiency, and discuss how the thermal X-ray emission, when the time-dependent ionization is not calculated self-consistently with the hydrodynamics, can differ from the thermal X-ray emission from models which do account for the hydrodynamics. Finally, we compare the thermal X-ray emission from models which show moderate acceleration ({approx}35%) to the thermal X-ray emission from test-particle models.

  3. Optical observations on the CRIT-II Critical Ionization Velocity Experiment

    NASA Technical Reports Server (NTRS)

    Stenbaek-Nielsen, H. C.; Wescott, E. M.; Haerendel, G.; Valenzuela, A.

    1990-01-01

    A rocket borne Critical Ionization Velocity (CIV0 experiment was carried out from Wallops Island at dusk on May 4, 1989. Two barium shaped charges were released below the solar terminator (to prevent photoionization) at altitudes near 400 km. The ambient ionospheric electron density was 50,000/cu cm. The neutral barium jet was directed upward and at an angle of nominally 45 degrees to B which gives approximately 3 x 10 to the 23rd neutrals with super critical velocity. Ions created by a CIV process in the region of the neutral jet would travel up along B into sunlight where they can be detected optically. Well defined ion clouds (max. brightness 750 R) were observed in both releases. An ionization rate of 0.8 percent/sec (125 sec ionization time constant) can account for the observed ion cloud near the release field line, but the ionization rate falls off with increasing distance from the release. It is concluded that a CIV process was present in the neutral jet out to about 50 km from the release, which is significantly further than allowed by current theories.

  4. Dynamics of Coronal Rain and Descending Plasma Blobs in Solar Prominences. II. Partially Ionized Case

    NASA Astrophysics Data System (ADS)

    Oliver, R.; Soler, R.; Terradas, J.; Zaqarashvili, T. V.

    2016-02-01

    Coronal rain clumps and prominence knots are dense condensations with chromospheric to transition region temperatures that fall down in the much hotter corona. Their typical speeds are in the range 30-150 km s-1 and of the order of 10-30 km s-1, respectively, i.e., they are considerably smaller than free-fall velocities. These cold blobs contain a mixture of ionized and neutral material that must be dynamically coupled in order to fall together, as observed. We investigate this coupling by means of hydrodynamic simulations in which the coupling arises from the friction between ions and neutrals. The numerical simulations presented here are an extension of those of Oliver et al. to the partially ionized case. We find that, although the relative drift speed between the two species is smaller than 1 m s-1 at the blob center, it is sufficient to produce the forces required to strongly couple charged particles and neutrals. The ionization degree has no discernible effect on the main results of our previous work for a fully ionized plasma: the condensation has an initial acceleration phase followed by a period with roughly constant velocity, and, in addition, the maximum descending speed is clearly correlated with the ratio of initial blob to environment density.

  5. IONIZATION PARAMETER AS A DIAGNOSTIC OF RADIATION AND WIND PRESSURES IN H II REGIONS AND STARBURST GALAXIES

    SciTech Connect

    Yeh, Sherry C. C.; Matzner, Christopher D.

    2012-10-01

    The ionization parameter U is potentially useful as a tool to measure radiation pressure feedback from massive star clusters, as it directly reflects the ratio of radiation to gas pressure and is readily derived from mid-infrared line ratios. We consider a number of physical effects which combine to determine the apparent value of U in observations encompassing one or many H II regions. An upper limit is set by the compression of gas by radiation pressure, when this is important. The pressure of shocked stellar winds and the presence of neutral clumps both tend to reduce U for a given intensity of irradiation. The most intensely irradiated regions are selectively dimmed by internal dust absorption of ionizing photons, leading to a bias for observations on galactic scales. We explore these effects in analytical and numerical models for dusty H II regions and use them to interpret previous observational results. We find that radiation pressure confinement sets the upper limit log{sub 10}U{approx_equal}-1 seen in individual regions. Unresolved starbursts are known to display a maximum value of {approx_equal} - 2.3. While lower, this is also consistent with a large portion of their H II regions being radiation pressure dominated, given the different technique used to interpret unresolved regions, and given the bias caused by dust absorption. We infer that many individual, strongly illuminated regions cannot be significantly overpressured by stellar winds, and that even when averaged on galactic scales, the shocked wind pressure cannot be large compared to radiation pressure. Therefore, most H II regions cannot be adiabatic wind bubbles. Our models imply a metallicity dependence in the physical structure and dust attenuation of radiation-dominated regions, both of which should vary strongly across a critical metallicity of about one-twentieth solar.

  6. Ionization Parameter as a Diagnostic of Radiation and Wind Pressures in H II Regions and Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Yeh, Sherry C. C.; Matzner, Christopher D.

    2012-10-01

    The ionization parameter {\\cal U} is potentially useful as a tool to measure radiation pressure feedback from massive star clusters, as it directly reflects the ratio of radiation to gas pressure and is readily derived from mid-infrared line ratios. We consider a number of physical effects which combine to determine the apparent value of {\\cal U} in observations encompassing one or many H II regions. An upper limit is set by the compression of gas by radiation pressure, when this is important. The pressure of shocked stellar winds and the presence of neutral clumps both tend to reduce {\\cal U} for a given intensity of irradiation. The most intensely irradiated regions are selectively dimmed by internal dust absorption of ionizing photons, leading to a bias for observations on galactic scales. We explore these effects in analytical and numerical models for dusty H II regions and use them to interpret previous observational results. We find that radiation pressure confinement sets the upper limit log _{10} {\\cal U}\\simeq -1 seen in individual regions. Unresolved starbursts are known to display a maximum value of ~= - 2.3. While lower, this is also consistent with a large portion of their H II regions being radiation pressure dominated, given the different technique used to interpret unresolved regions, and given the bias caused by dust absorption. We infer that many individual, strongly illuminated regions cannot be significantly overpressured by stellar winds, and that even when averaged on galactic scales, the shocked wind pressure cannot be large compared to radiation pressure. Therefore, most H II regions cannot be adiabatic wind bubbles. Our models imply a metallicity dependence in the physical structure and dust attenuation of radiation-dominated regions, both of which should vary strongly across a critical metallicity of about one-twentieth solar.

  7. High-Resolution Emission-Line Imaging of Seyfert Galaxies. II. Evidence for Anisotropic Ionizing Radiation

    NASA Astrophysics Data System (ADS)

    Wilson, Andrew S.; Ward, Martin J.; Haniff, Christopher A.

    1988-11-01

    In the preceding paper, we describe a direct imaging survey of Seyfert galaxies with "linear" radio structures and find that the major axes and spatial scales of the circumnuclear emission-line gas are very similar to those of the radio continuum sources. In the present paper, the nature of this close connection between thermal and relativistic gases is assessed in detail. Models in which the kinetic energy of the radio jets or plasmoids powers shock waves, which ionize the gas, seem energetically feasible but disagree with the off-nuclear line intensity ratios. Ionization by relativistic electrons is negligible, but they may contribute to the heating of the gas. We favor a scenario in which the radio jets and plasmoids shock, accelerate, and compress ambient and entrained gas, but the dominant source of ionization is the nonstellar nuclear ultraviolet continuum. This ultraviolet source appears to be partially beamed along the axis of the radio jet. Photoionization by ultraviolet synchrotron radiation generated via shocks in the ejecta may also contribute, especially in Seyfert 2 galaxies. A comparison between the number of ionizing photons, N_i_, inferred by extrapolation of the directly observed continuum, and the number of ionizing photons, N_Hβ_, required to generate the Hβ emission has been made for six galaxies in our sample. In at least two galaxies, we find N_i_ << N_Hβ_, suggesting that the gas is exposed to a higher ionizing flux than inferred from direct observations of the nucleus, and supporting the idea of partial beaming. Similarly, the energy in the continuum between 100 A and 1 micron, if emitted isotropically, is inadequate to fuel the thermal nuclear infrared sources, implying that the radiating dust is heated by a more luminous optical-ultraviolet source. We speculate that the nuclear infrared emission of Seyfert 2 galaxies arises from dust in molecular clouds exposed to the partially beamed radiation, and we predict that the 10 micron

  8. Internal structure of spiral arms traced with [C II]: Unraveling the warm ionized medium, H I, and molecular emission lanes

    NASA Astrophysics Data System (ADS)

    Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

    2015-06-01

    Context. The spiral arm tangencies are ideal lines of sight in which to determine the distribution of interstellar gas components in the spiral arms and study the influence of spiral density waves on the interarm gas in the Milky Way. [C II] emission in the tangencies delineates the warm ionized component and the photon-dominated regions and is thus an important probe of spiral arm structure and dynamics. Aims: We aim to use [C II], H I, and 12CO spectral line maps of the Crux, Norma, and Perseus tangencies to analyze the internal structure of the spiral arms in different gas layers. Methods: We used [C II] l-V maps along with those for H I and 12CO to derive the average spectral line intensity profiles over the longitudinal range of each tangency. Using the VLSR of the emission features, we located the [C II], H I, and 12CO emissions along a cross cut of the spiral arm. We used the [C II] velocity profile to identify the compressed warm ionized medium (WIM) in the spiral arm. Results: We present a large-scale (~15°) position-velocity map of the Galactic plane in [C II] from l = 326.6° to 341.4° observed with Herschel HIFI. In the spectral line profiles at the tangencies, [C II] has two emission peaks, one associated with the compressed WIM and the other the molecular gas photon-dominated regions. When represented as a cut across the inner to outer edge of the spiral arm, the [C II]-WIM peak appears closest to the inner edge while 12CO and [C II] associated with molecular gas are at the outermost edge. H I has broader emission with an intermediate peak located nearer to that of 12CO. Conclusions: The velocity-resolved spectral line data of the spiral arm tangencies unravel the internal structure in the arms locating the emission lanes within them. We interpret the excess [C II] near the tangent velocities as shock compression of the WIM induced by the spiral density waves and as the innermost edge of spiral arms. For the Norma and Perseus arms, we estimate

  9. H II Region G46.5-0.2: The Interplay between Ionizing Radiation, Molecular Gas, and Star Formation

    NASA Astrophysics Data System (ADS)

    Paron, S.; Ortega, M. E.; Dubner, G.; Yuan, Jing-Hua; Petriella, A.; Giacani, E.; Li, Jin Zeng; Wu, Yuefang; Liu, Hongli; Huang, Ya Fang; Zhang, Si-Ju

    2015-06-01

    H ii regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing toward the ionizing sources, and cometary globules of dense gas where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic H ii region located at about 4 kpc, is an excellent target for performing this kind of study. Using public molecular data extracted from the Galactic Ring Survey (13CO J = 1-0) and from the James Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J = 3-2, HCO+, and HCN J = 4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment, and the young stellar objects (YSOs) placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in the direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission toward its open border. We found that about 10‧ to the southwest of G46 there are some pillar-like features, shining at 8 μm and pointing toward the H ii region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several YSOs likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and another mostly composed of Class I type YSOs located just ahead of the pillar-like features, strongly suggesting an age gradient in the YSO distribution.

  10. Evidence for Fluorescent Fe II Emission from Extended Low Ionization Outflows in Obscured Quasars

    NASA Astrophysics Data System (ADS)

    Wang, Tinggui; Ferland, Gary J.; Yang, Chenwei; Wang, Huiyuan; Zhang, Shaohua

    2016-06-01

    Recent studies have shown that outflows in at least some broad absorption line (BAL) quasars are extended well beyond the putative dusty torus. Such outflows should be detectable in obscured quasars. We present four WISE selected infrared red quasars with very strong and peculiar ultraviolet Fe ii emission lines: strong UV Fe ii UV arising from transitions to ground/low excitation levels, and very weak Fe ii at wavelengths longer than 2800 Å. The spectra of these quasars display strong resonant emission lines, such as C iv, Al iii and Mg ii but sometimes, a lack of non-resonant lines such as C iii], S iii and He ii. We interpret the Fe ii lines as resonantly scattered light from the extended outflows that are viewed nearly edge-on, so that the accretion disk and broad line region are obscured by the dusty torus, while the extended outflows are not. We show that dust free gas exposed to strong radiation longward of 912 Å produces Fe ii emission very similar to that observed. The gas is too cool to collisionally excite Fe ii lines, accounting for the lack of optical emission. The spectral energy distribution from the UV to the mid-infrared can be modeled as emission from a clumpy dusty torus, with UV emission being reflected/scattered light either by the dusty torus or the outflow. Within this scenario, we estimate a minimum covering factor of the outflows from a few to 20% for the Fe ii scattering region, suggesting that Fe ii BAL quasars are at a special stage of quasar evolution.

  11. Flash Spectroscopy: Emission Lines from the Ionized Circumstellar Material around <10-day-old Type II Supernovae

    NASA Astrophysics Data System (ADS)

    Khazov, D.; Yaron, O.; Gal-Yam, A.; Manulis, I.; Rubin, A.; Kulkarni, S. R.; Arcavi, I.; Kasliwal, M. M.; Ofek, E. O.; Cao, Y.; Perley, D.; Sollerman, J.; Horesh, A.; Sullivan, M.; Filippenko, A. V.; Nugent, P. E.; Howell, D. A.; Cenko, S. B.; Silverman, J. M.; Ebeling, H.; Taddia, F.; Johansson, J.; Laher, R. R.; Surace, J.; Rebbapragada, U. D.; Wozniak, P. R.; Matheson, T.

    2016-02-01

    Supernovae (SNe) embedded in dense circumstellar material (CSM) may show prominent emission lines in their early-time spectra (≤10 days after the explosion), owing to recombination of the CSM ionized by the shock-breakout flash. From such spectra (“flash spectroscopy”), we can measure various physical properties of the CSM, as well as the mass-loss rate of the progenitor during the year prior to its explosion. Searching through the Palomar Transient Factory (PTF and iPTF) SN spectroscopy databases from 2009 through 2014, we found 12 SNe II showing flash-ionized (FI) signatures in their first spectra. All are younger than 10 days. These events constitute 14% of all 84 SNe in our sample having a spectrum within 10 days from explosion, and 18% of SNe II observed at ages <5 days, thereby setting lower limits on the fraction of FI events. We classified as “blue/featureless” (BF) those events having a first spectrum that is similar to that of a blackbody, without any emission or absorption signatures. It is possible that some BF events had FI signatures at an earlier phase than observed, or that they lack dense CSM around the progenitor. Within 2 days after explosion, 8 out of 11 SNe in our sample are either BF events or show FI signatures. Interestingly, we found that 19 out of 21 SNe brighter than an absolute magnitude MR = -18.2 belong to the FI or BF groups, and that all FI events peaked above MR = -17.6 mag, significantly brighter than average SNe II.

  12. CRIT II electric, magnetic, and density measurements within an ionizing neutral stream

    NASA Technical Reports Server (NTRS)

    Swenson, C. M.; Kelley, M. C.; Primdahl, F.; Baker, K. D.

    1990-01-01

    Measurements from rocket-borne sensors inside a high-velocity neutral barium beam show a-factor-of-six increase in plasma density in a moving ionizing front. This region was colocated with intense fluctuating electric fields at frequencies well under the lower hybrid frequency for a barium plasma. Large quasi-dc electric and magnetic field fluctuations were also detected with a large component of the current and the electric field parallel to B(0). An Alfven wave with a finite electric field component parallel to the geomagnetic field was observed to propagate along B(0), where it was detected by an instrumented subpayload.

  13. Ionization and excitation in cool giant stars. I - Hydrogen and helium

    NASA Technical Reports Server (NTRS)

    Luttermoser, Donald G.; Johnson, Hollis R.

    1992-01-01

    The influence that non-LTE radiative transfer has on the electron density, ionization equilibrium, and excitation equilibrium in model atmospheres representative of both oxygen-rich and carbon-rich red giant stars is demonstrated. The radiative transfer and statistical equilibrium equations are solved self-consistently for H, H(-), H2, He I, C I, C II, Na I, Mg I, Mg II, Ca I, and Ca II in a plane-parallel static medium. Calculations are made for both radiative-equilibrium model photospheres alone and model photospheres with attached chromospheric models as determined semiempirically with IUE spectra of g Her (M6 III) and TX Psc (C6, 2). The excitation and ionization results for hydrogen and helium are reported.

  14. Screening derivatized peptide libraries for tight binding inhibitors to carbonic anhydrase II by electrospray ionization-mass spectrometry.

    PubMed

    Gao, J; Cheng, X; Chen, R; Sigal, G B; Bruce, J E; Schwartz, B L; Hofstadler, S A; Anderson, G A; Smith, R D; Whitesides, G M

    1996-05-10

    This paper describes the use of electrospray ionization-mass spectrometry (ESI-MS) to screen two libraries of soluble compounds to search for tight binding inhibitors for carbonic anhydrase II (EC 4.2.1.1). The two libraries, H2NO2SC6H4C(O)NH-AA1-AA2-C(O)NHCH2CH2CO2H where AA1 and AA2 are L-amino acids (library size: 289 compounds) or D-amino acids (256 compounds), were constructed by attaching tripeptides to the carboxyl group of 4-carboxybenzenesulfonamide. Screening of both libraries yielded, as the tightest binding inhibitor, compound 1 (AA1 = AA2 = L-Leu; binding constant Kb = 1.4 x 10(8) M-1). The ability of ESI-MS to estimate simultaneously the relative binding affinities of a protein to soluble ligands in a library, if general, should be useful in drug development. PMID:8642553

  15. Potential and flux field landscape theory. II. Non-equilibrium thermodynamics of spatially inhomogeneous stochastic dynamical systems

    SciTech Connect

    Wu, Wei; Wang, Jin

    2014-09-14

    We have established a general non-equilibrium thermodynamic formalism consistently applicable to both spatially homogeneous and, more importantly, spatially inhomogeneous systems, governed by the Langevin and Fokker-Planck stochastic dynamics with multiple state transition mechanisms, using the potential-flux landscape framework as a bridge connecting stochastic dynamics with non-equilibrium thermodynamics. A set of non-equilibrium thermodynamic equations, quantifying the relations of the non-equilibrium entropy, entropy flow, entropy production, and other thermodynamic quantities, together with their specific expressions, is constructed from a set of dynamical decomposition equations associated with the potential-flux landscape framework. The flux velocity plays a pivotal role on both the dynamic and thermodynamic levels. On the dynamic level, it represents a dynamic force breaking detailed balance, entailing the dynamical decomposition equations. On the thermodynamic level, it represents a thermodynamic force generating entropy production, manifested in the non-equilibrium thermodynamic equations. The Ornstein-Uhlenbeck process and more specific examples, the spatial stochastic neuronal model, in particular, are studied to test and illustrate the general theory. This theoretical framework is particularly suitable to study the non-equilibrium (thermo)dynamics of spatially inhomogeneous systems abundant in nature. This paper is the second of a series.

  16. Ionizing shocks in argon. Part II: Transient and multi-dimensional effects

    SciTech Connect

    Kapper, M. G.; Cambier, J.-L.

    2011-06-01

    We extend the computations of ionizing shocks in argon to the unsteady and multi-dimensional, using a collisional-radiative model and a single-fluid, two-temperature formulation of the conservation equations. It is shown that the fluctuations of the shock structure observed in shock-tube experiments can be reproduced by the numerical simulations and explained on the basis of the coupling of the nonlinear kinetics of the collisional-radiative model with wave propagation within the induction zone. The mechanism is analogous to instabilities of detonation waves and also produces a cellular structure commonly observed in gaseous detonations. We suggest that detailed simulations of such unsteady phenomena can yield further information for the validation of nonequilibrium kinetics.

  17. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. II

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    The consistent kinetic approach developed in Paper I [Ya. S. Dimant and R. N. Sudan, Phys. Plasmas {bold 2}, 1157 (1995)] is applied to obtain the general dispersion relation of the two-stream {bold E}{times}{bold B} instability in collisionally dominated weakly ionized plasmas for wave frequencies small compared to the ion--neutral collision frequency. This dispersion relation covers the whole low-frequency band from the asymptotic short-wave limit studied in Paper I to the long-wave limit. Previous theories employing simplified kinetic theory or fluid equations for electron behavior are only correct in the long-wave limit. The principal new results are that the threshold conditions for this instability and the growth rates are altered from those predicted by earlier simplified theories. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  18. Observations of feedback from radio-quiet quasars - II. Kinematics of ionized gas nebulae

    NASA Astrophysics Data System (ADS)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.; Nesvadba, Nicole P. H.; Liu, Xin

    2013-12-01

    The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around 11 luminous, obscured, radio-quiet quasars at z ˜ 0.5 out to ˜15 kpc from the quasar; specifically, we measure the kinematics and morphology of [O III] λ5007 Å emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80 per cent of the emission as high as 103 km s-1) combined with relatively small velocity difference across them (from 90 to 520 km s-1) point towards wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km s-1, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly towards outer parts of the nebulae (by 3 per cent kpc-1 on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, signifying gas outflows. For the median outflow velocity, we find dot{E}_kin between 4 × 1044 and 3 × 1045 erg s-1 and dot{M} between 2 × 103 and 2 × 104 M⊙ yr-1. These values are large enough for the observed quasar winds to have a significant impact on their host galaxies. The median rate of converting bolometric luminosity to kinetic energy of ionized gas clouds is ˜2 per cent. We report four new candidates for `superbubbles' - outflows that may have broken out of the denser regions of the host galaxy.

  19. The Ionizing Star Clusters of Giant H II Regions in NGC 2403

    NASA Astrophysics Data System (ADS)

    Drissen, Laurent; Roy, Jean-René; Moffat, Anthony F. J.; Shara, Michael M.

    1999-03-01

    We present the results of a study on the massive star population down to about M_V~-3.1, or 12-15 M_solar, of the most luminous giant H II regions in the nearby spiral galaxy NGC 2403, based on Hubble Space Telescope images and ground-based spectrograms. Particular emphasis is placed on the distribution of the Wolf-Rayet and red supergiant stars and the information they provide about the recent star-forming history of these large complexes. We find direct evidence for the presence of Wolf-Rayet (WR) stars in five of the six giant H II regions investigated; 25-40 WR stars are inferred for the sole NGC 2403-I giant H II region. Red supergiant (RSG) stars are mainly distributed over a more extended halo, while the young blue stars and most WR stars are in or close to a compact core. One appears to be seeing young cores of O and WR stars surrounded by older halos containing red supergiants. We propose a scenario in which RSG stars belonging to an early phase of star formation were followed by a more recent burst corresponding to a very blue mean sequence. Delayed trigger with preheating over several 100 pc by the first generation of massive stars allowed the build-up of the required confinement for the production of parsec-scale cluster cores with luminosity up to a few times 10^6 L_solar. Finally, we present some interesting objects found in the field of NGC 2403 outside the giant H II regions, such as field WR stars, globular clusters and background galaxies.

  20. Search for lightly ionizing particles using CDMS-II data and fabrication of CDMS detectors with improved homogeneity in properties

    SciTech Connect

    Prasad, Kunj Bihari

    2013-12-01

    Fundamental particles are always observed to carry charges which are integral multiples of one-third charge of electron, e/3. While this is a well established experimental fact, the theoretical understanding for the charge quantization phenomenon is lacking. On the other hand, there exist numerous theoretical models that naturally allow for existence of particles with fractional electromagnetic charge. These particles, if existing, hint towards existence of physics beyond the standard model. Multiple high energy, optical, cosmological and astrophysical considerations restrict the allowable mass-charge parameter space for these fractional charges. Still, a huge unexplored region remains. The Cryogenic Dark Matter Search (CDMS-II), located at Soudan mines in northern Minnesota, employs germanium and silicon crystals to perform direct searches for a leading candidate to dark matter called Weakly Interacting Massive Particles (WIMPs). Alternately, the low detection threshold allows search for fractional electromagnetic-charged particles, or Lightly Ionizing Particles (LIPs), moving at relativistic speed. Background rejection is obtained by requiring that the magnitude and location of energy deposited in each detector be consistent with corresponding \\signatures" resulting from the passage of a fractionally charged particle. In this dissertation, the CDMS-II data is analyzed to search for LIPs, with an expected background of 0.078 0.078 events. No candidate events are observed, allowing exclusion of new parameter space for charges between e/6 and e/200.

  1. Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. II. Global analysis

    NASA Astrophysics Data System (ADS)

    Escobar, D.; Ahedo, E.

    2015-10-01

    The linear stability of the Hall thruster discharge is analysed against axial-azimuthal perturbations in the low frequency range using a time-dependent 2D code of the discharge. This azimuthal stability analysis is spatially global, as opposed to the more common local stability analyses, already afforded previously (D. Escobar and E. Ahedo, Phys. Plasmas 21(4), 043505 (2014)). The study covers both axial and axial-azimuthal oscillations, known as breathing mode and spoke, respectively. The influence on the spoke instability of different operation parameters such as discharge voltage, mass flow, and thruster size is assessed by means of different parametric variations and compared against experimental results. Additionally, simplified models are used to unveil and characterize the mechanisms driving the spoke. The results indicate that the spoke is linked to azimuthal oscillations of the ionization process and to the Bohm condition in the transition to the anode sheath. Finally, results obtained from local and global stability analyses are compared in order to explain the discrepancies between both methods.

  2. A model of comet comae. II - Effects of solar photodissociative ionization

    NASA Astrophysics Data System (ADS)

    Huebner, W. F.; Giguere, P. T.

    1980-06-01

    Improvements to a computer model of coma photochemistry are described. These include an expansion of the chemical reactions network and new rate constants that have been measured only recently. Photolytic reactions of additional molecules are incorporated, and photolytic branching ratios are treated in far greater detail than previously. A total of 25 photodissociative ionization (PDI) reactions are now considered (as compared to only 3 PDI reactions previously). Solar PDI of the mother molecule CO2 is shown to compete effectively with photoionization of CO in the production of observed CO(+). The CO(+) density peak predicted by the improved model, for CO2 or CO mother molecules, is deep in the inner coma, in better agreement with observation than the old CO2 model. However, neither CO2 nor CO mother molecule calculations reproduce the CO(+)/H2O(+) ratio observed in comet Kohoutek. PDI products of CO2, CO, CH4, and NH3 mother molecules fuel a complex chemistry scheme, producing inner coma abundances of CN, C2, and C3 much greater than previously calculated.

  3. Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. II. Global analysis

    SciTech Connect

    Escobar, D.; Ahedo, E.

    2015-10-15

    The linear stability of the Hall thruster discharge is analysed against axial-azimuthal perturbations in the low frequency range using a time-dependent 2D code of the discharge. This azimuthal stability analysis is spatially global, as opposed to the more common local stability analyses, already afforded previously (D. Escobar and E. Ahedo, Phys. Plasmas 21(4), 043505 (2014)). The study covers both axial and axial-azimuthal oscillations, known as breathing mode and spoke, respectively. The influence on the spoke instability of different operation parameters such as discharge voltage, mass flow, and thruster size is assessed by means of different parametric variations and compared against experimental results. Additionally, simplified models are used to unveil and characterize the mechanisms driving the spoke. The results indicate that the spoke is linked to azimuthal oscillations of the ionization process and to the Bohm condition in the transition to the anode sheath. Finally, results obtained from local and global stability analyses are compared in order to explain the discrepancies between both methods.

  4. The effect of recombination radiation on the temperature and ionization state of partially ionized gas

    NASA Astrophysics Data System (ADS)

    Raičević, Milan; Pawlik, Andreas H.; Schaye, Joop; Rahmati, Alireza

    2014-01-01

    A substantial fraction of all ionizing photons originate from radiative recombinations. However, in radiative transfer calculations this recombination radiation is often assumed to be absorbed `on-the-spot' because for most methods the computational cost associated with the inclusion of gas elements as sources is prohibitive. We present a new, CPU and memory efficient implementation for the transport of ionizing recombination radiation in the TRAPHIC radiative transfer scheme. TRAPHIC solves the radiative transfer equation by tracing photon packets at the speed of light and in a photon-conserving manner in spatially adaptive smoothed particle hydrodynamics simulations. Our new implementation uses existing features of the TRAPHIC scheme to add recombination radiation at no additional cost in the limit in which the fraction of the simulation box filled with radiation approaches 1. We test the implementation by simulating an H II region in photoionization equilibrium and comparing to reference solutions presented in the literature, finding excellent agreement. We apply our implementation to discuss the evolution of the H II region to equilibrium. We show that the widely used case A and B approximations yield accurate ionization profiles only near the source and near the ionization front, respectively. We also discuss the impact of recombination radiation on the geometry of shadows behind optically thick absorbers. We demonstrate that the shadow region may be completely ionized by the diffuse recombination radiation field and discuss the important role of heating by recombination radiation in the shadow region.

  5. Hyperfine structure constants for singly ionized manganese (Mn II) using Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Townley-Smith, Keeley; Nave, Gillian; Pickering, Juliet C.; Blackwell-Whitehead, Richard J.

    2016-09-01

    We expand on the comprehensive study of hyperfine structure (HFS) in Mn II conducted by Holt et al. (1999) by verifying hyperfine magnetic dipole constants (A) for 20 levels previously measured by Holt et al. (1999) and deriving A constants for 47 previously unstudied levels. The HFS patterns were measured in archival spectra from Fourier transform (FT) spectrometers at Imperial College London and the National Institute of Standards and Technology. Analysis of the FT spectra was carried out in XGREMLIN. Our A constant for the ground level has a lower uncertainty by a factor of 6 than that of Blackwell-Whitehead et al.

  6. Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: equilibrium, kinetic and thermodynamic study.

    PubMed

    Ozdes, Duygu; Gundogdu, Ali; Kemer, Baris; Duran, Celal; Senturk, Hasan Basri; Soylak, Mustafa

    2009-07-30

    The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud (a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4 mg g(-1) for 10 g L(-1) of a-WM concentration. Thermodynamic parameters including the Gibbs free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (DeltaS degrees) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0-40 degrees C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions. PMID:19167162

  7. Clusters of DNA damage induced by ionizing radiation: formation of short DNA fragments. II. Experimental detection

    NASA Technical Reports Server (NTRS)

    Rydberg, B.; Chatterjee, A. (Principal Investigator)

    1996-01-01

    The basic 30-nm chromatin fiber in the mammalian cell consists of an unknown (possibly helical) arrangement of nucleosomes, with about 1.2 kb of DNA per 10-nm length of fiber. Track-structure considerations suggest that interactions of single delta rays or high-LET particles with the chromatin fiber might result in the formation of multiple lesions spread over a few kilobases of DNA (see the accompanying paper: W.R. Holley and A. Chatterjee, Radiat. Res. 145, 188-199, 1996). In particular, multiple DNA double-strand breaks and single-strand breaks may form. To test this experimentally, primary human fibroblasts were labeled with [3H]thymidine and exposed at 0 degrees C to X rays or accelerated nitrogen or iron ions in the LET range of 97-440 keV/microns. DNA was isolated inside agarose plugs and subjected to agarose gel electrophoresis under conditions that allowed good separation of 0.1-2 kb size DNA. The bulk of DNA remained in the well or migrated only a small distance into the gel. It was found that DNA fragments in the expected size range were formed linearly with dose with an efficiency that increased with LET. A comparison of the yield of such fragments with the yield of total DNA double-strand breaks suggests that for the high-LET ions a substantial proportion (20-90%) of DNA double-strand breaks are accompanied within 0.1-2 kb by at least one additional DNA double-strand break. It is shown that these results are in good agreement with theoretical calculations based on treating the 30-nm chromatin fiber as the target for ionizing particles. Theoretical considerations also predict that the clusters will contain numerous single-strand breaks and base damages. It is proposed that such clusters be designated "regionally multiply damaged sites." Postirradiation incubation at 37 degrees C resulted in a decline in the number of short DNA fragments, suggesting a repair activity. The biological significance of regionally multiply damaged sites is presently unknown.

  8. Kinetic, Equilibrium and thermodynamic studies on the biosorption of Cd(II) from aqueous solutions by the leaf biomass of Calotropis procera - 'Sodom apple'

    NASA Astrophysics Data System (ADS)

    Chukwudumebi Overah, Loretta; Babalola, Oyebamiji.; Babarinde, Adesola; Oninla, Vincent; Olatunde, Abimbola

    2013-04-01

    The kinetics, equilibrium and thermodynamics of the biosorption of Cd (II) from aqueous solution by the leaf biomass of Calotropis procera popularly known in western Nigeria as 'bom bom' and generally known as Sodom apple were investigated at different experimental conditions. Optimum conditions of pH,contact time, biomass dosage, initial metal ion concentration and temperature were determined to be 5, 60 minutes, 110 mg, 0.3 mM and 27°C respectively. The maximum biosorption capacity was found to be 8.91 mg/g. The kinetic studies indicated that the biosorption process of the metal ion followed the pseudo-second-order and intra-particle diffusion models with an R-square value of 0.998 and 0.985 respectively. Equilibrium studies showed that the biosorption of Cd (II) is well represented by both Freundlich and Langmuir isotherms but the Langmuir model gave a better fit with an R-square value of 0.979,Langmuir constant, bm of 0.0080 and monolayer adsorption capacity, μm of 123.46. The calculated thermodynamic parameters (ΔG° -4.846 kJmol-1, ΔH° 10.60 kJmol-1 and ΔS° 0.052 kJK-1mol-1) showed that the biosorption of Cd (II)is feasible, spontaneous, endothermic and highly disordered in nature under the experimental conditions. Thesefindings indicate that the leaf of Calotropis procera could be employed in the removal of Cd (II) from industrial effluents. Key words: Calotropis procera, Cadmium, Adsorption isotherm.

  9. Theory of fluorescence induction in photosystem II: derivation of analytical expressions in a model including exciton-radical-pair equilibrium and restricted energy transfer between photosynthetic units.

    PubMed Central

    Lavergne, J; Trissl, H W

    1995-01-01

    The theoretical relationships between the fluorescence and photochemical yields of PS II and the fraction of open reaction centers are examined in a general model endowed with the following features: i) a homogeneous, infinite PS II domain; ii) exciton-radical-pair equilibrium; and iii) different rates of exciton transfer between core and peripheral antenna beds. Simple analytical relations are derived for the yields and their time courses in induction experiments. The introduction of the exciton-radical-pair equilibrium, for both the open and closed states of the trap, is shown to be equivalent to an irreversible trapping scheme with modified parameters. Variation of the interunit transfer rate allows continuous modulation from the case of separated units to the pure lake model. Broadly used relations for estimating the relative amount of reaction centers from the complementary area of the fluorescence kinetics or the photochemical yield from fluorescence levels are examined in this framework. Their dependence on parameters controlling exciton decay is discussed, allowing assessment of their range of applicability. An experimental induction curve is analyzed, with a discussion of its decomposition into alpha and beta contributions. The sigmoidicity of the induction kinetics is characterized by a single parameter J related to Joliot's p, which is shown to depend on both the connectivity of the photosynthetic units and reaction center parameters. On the other hand, the relation between J and the extreme fluorescence levels (or the deviation from the linear Stern-Volmer dependence of 1/phi f on the fraction of open traps) is controlled only by antenna connectivity. Experimental data are consistent with a model of connected units for PS II alpha, intermediate between the pure lake model of unrestricted exciton transfer and the isolated units model. PMID:7647250

  10. A simple simulation of adsorption equilibrium of Pb(II) on Andosols in the presence of dissolved humic substances for monitoring soil contamination.

    PubMed

    Liu, Yuyu; Kobayashi, Takeshi; Takahashi, Yukari; Kameya, Takashi; Urano, Kohei

    2013-01-01

    The adsorption equilibrium of Pb(II) on Andosols was investigated and described quantitatively in order to develop a simple method for the rapid monitoring of heavy metals in soils. The effect of solution pH on adsorption isotherms was investigated experimentally and in simulations. At pH 7, the considerable desorption of Pb(II) due to the extensive dissolution of humic substances (HS) from soils into aqueous phases is known to be an obstacle to carrying out simulations. In batch experiments, the total organic carbon (TOC) of the aqueous phases was shown to be enhanced by the addition of pre-extracted HS to soil suspensions. By combining the ion-exchange and Freundlich models, the adsorption equilibriums of free Pb(2+) ions and Pb(2+)-HS were simulated and were shown to be in good agreement with the experimental results. By estimating the concentrations and adsorption amounts of Pb(2+) and Pb(2+)-HS from measured CPb and TOC, it is possible to accurately simulate the soil contamination status even in in the presence of dissolved HS in the water in the solid-liquid extraction samples. PMID:23947708

  11. Ionizing stellar population in the disc of NGC 3310 - II. The Wolf-Rayet population

    NASA Astrophysics Data System (ADS)

    Miralles-Caballero, D.; Rosales-Ortega, F. F.; Díaz, A. I.; Otí-Floranes, H.; Pérez-Montero, E.; Sánchez, S. F.

    2014-12-01

    We use integral field spectroscopy to study in detail the Wolf-Rayet (WR) population in NGC 3310, spatially resolving 18 star-forming knots with typical sizes of 200-300 pc in the disc of the galaxy hosting a substantial population of WRs. The detected emission in the so-called blue bump is attributed mainly to late-type nitrogen WRs (WNL), ranging from a few dozens to several hundreds of stars per region. Our estimated WNL/(WNL+O) ratio is comparable to reported empirical relations once the extinction-corrected emission is further corrected by the presence of dust grains inside the nebula that absorb a non-negligible fraction of UV photons. Comparisons of observables with stellar population models show disagreement by factors larger than 2-3. However, if the effects of interacting binaries and/or photon leakage are taken into account, observations and predictions tend to converge. We estimate the binary fraction of the H II regions hosting WRs to be significant in order to recover the observed X-ray flux, hence proving that the binary channel can be critical when predicting observables. We also explore the connection of the environment with the current hypothesis that WRs can be progenitors to long-duration gamma-ray bursts (GRBs). Galaxy interactions, which can trigger strong episodes of star formation in the central regions, may be a plausible environment where WRs may act as progenitors of GRBs. Finally, even though the chemical abundance is generally homogeneous, we also find weak evidence for rapid N pollution by WR stellar winds at scales of ˜200 pc.

  12. Equilibrium 2H/ 1H fractionations in organic molecules. II: Linear alkanes, alkenes, ketones, carboxylic acids, esters, alcohols and ethers

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Sessions, Alex L.; Nielsen, Robert J.; Goddard, William A., III

    2009-12-01

    Equilibrium 2H/ 1H fractionation factors (α eq) for various H positions in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, and ethers were calculated between 0 and 100 °C using vibrational frequencies from ab initio QM calculations (B3LYP/6-311G**). Results were then corrected using a temperature-dependent linear calibration curve based on experimental data for H α in ketones ( Wang et al., 2009). The total uncertainty in reported α eq values is estimated at 10-20‰. The effects of functional groups were found to increase the value of α eq for H next to electron-donating groups, e.g. sbnd OR, sbnd OH or sbnd O(C dbnd O)R, and to decrease the value of α eq for H next to electron-withdrawing groups, e.g. sbnd (C dbnd O)R or sbnd (C dbnd O)OR. Smaller but significant functional group effects are also observed for H β and sometimes H γ. By summing over individual H positions, we estimate the equilibrium fractionation relative to water to be -90‰ to -70‰ for n-alkanes and around -100‰ for pristane and phytane. The temperature dependence of these fractionations is very weak between 0 and 100 °C. Our estimates of α eq agree well with field data for thermally mature hydrocarbons (δ 2H values between -80‰ and -110‰ relative to water). Therefore the observed δ 2H increase of individual hydrocarbons and the disappearance of the biosynthetic δ 2H offset between n-alkyl and linear isoprenoid lipids during maturation of organic matter can be confidently attributed to H exchange towards an equilibrium state. Our results also indicate that many n-alkyl lipids are biosynthesized with δ 2H values that are close to equilibrium with water. In these cases, constant down-core δ 2H values for n-alkyl lipids cannot be reliably used to infer a lack of isotopic exchange.

  13. A nonlinear analysis of an equilibrium craze. I - Problem formulation and solution. II - Simulations of craze and crack growth

    NASA Technical Reports Server (NTRS)

    Ungsuwarungsri, T.; Knauss, W. G.

    1988-01-01

    A numerical method is developed for the determinations of the equilibrium shape of a craze in an infinite elastic plane whose fibrils exhibit very general nonlinear force-displacement behavior. The problem formulation is based on the superposition of the relevant elasticity Green's function; the solution of the resulting nonlinear problem is obtained by using Picard's successive approximation scheme. The model is used to investigate the effect of nonlinear fibril behavior on the mechanics of craze and crack growth, and the results are compared with the Dugdale model.

  14. Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: Analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Kelly, H.

    2013-12-15

    This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.

  15. Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe.

    PubMed

    Prevosto, L; Kelly, H; Mancinelli, B

    2013-12-01

    This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core. PMID:24387432

  16. Equilibrium properties of the fluxoid lattice in single-crystal niobium. II. Small-angle neutron-diffraction measurements

    SciTech Connect

    Christen, D.K.; Kerchner, H.R.; Sekula, S.T.; Thorel, P.

    1980-01-01

    A small-angle neutron-diffraction technique has been used to measure several properties of the flux-line lattice (FLL) in a single-crystal sphere of pure niobium. For applied fields parallel to several crystallographic directions in the (100) and (110) planes, the low-field mixed state and intermediate mixed state were investigated. From these results, the orientation dependence of the low-field critical parameters H/sub c/1 and B/sub 0/ are deduced. The consistency of these results is verified by comparison with direct measurements of the equilibrium misalignment angle between the applied-field direction and the fluxoid axes. In addition, results are reported which extend the available information concerning correlations between the FLL and crystal lattice (CL) symmetry properties.

  17. Characterization of picroside II metabolites in rats by ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

    PubMed

    Gao, Tingting; Sheng, Tingting; Zhang, Tong; Han, Han

    2016-09-01

    Picroside II, a bioactive compound isolated from Picrorhiza scrophulariiflora Pennell, has been reported to have hepatoprotective, neuroprotective, and antioxidant effects. However, the detailed in vivo biotransformation of this compound has been rarely reported. This study aimed to investigate the metabolic profiles of picroside II in rats by using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Metabolite structures were elucidated based on accurate mass measurements of deprotonated molecules and their fragmentation patterns. Thirteen metabolites were structurally identified, and the detailed metabolic pathways were proposed. The findings revealed that after oral administration, picroside II mainly undergoes four metabolic pathways. In the first pathway, picroside II is deglycosylated to generate aglycone, which is isomerized to a dialdehyde-type intermediate. A series of metabolic reactions, including glucuronidation, subsequently occurs. In the second pathway, picroside II is subjected to ester bond hydrolysis to form vanillic acid, which is further subjected to sulfate conjugation, glycine conjugation, glucuronidation, and demethylation. In the third pathway, picroside II is directly conjugated with glucuronic acid to yield a predominant metabolite (M01) in plasma. In the fourth pathway, picroside II is directly conjugated with sulfate. These findings provide insights into the in vivo disposition of picroside II and are useful to understand the mechanism of effectiveness and toxicity of this compound as well as P. scrophulariiflora-related preparations. PMID:27328362

  18. Structure and evolution of irradiated accretion disks. I - Static thermal equilibrium structure. II - Dynamical evolution of a thermally unstable torus

    NASA Technical Reports Server (NTRS)

    Tuchman, Y.; Mineshige, S.; Wheeler, J. C.

    1990-01-01

    The thermal equilibrum structure and dynamical behavior of externally irradiated accretion disks are investigated. For radiative disks only the surface layer is heated, while for convective disks the heat penetrates deeply into the disk. For sufficiently strong radiation and given irradiation flux F(irr), the disk is completely stabilized against thermal instabilities of the sort invoked to explain dwarf novae. For moderately strong irradiation there is still an unstable branch in the thermal equilibrium curve. In typical soft X-ray transients, the disk is unstable against the dwarf-nova type instability. Fixed F(irr) on accretion disk annuli reduces the amplitude and the quiescent times and increases the outburst duration of the resultant light curves. Varying F(irr) in proportion to the mass accretion rate at the disks's inner edge results in light curves with a plateau in the decay from outbursts. In the case when irradiation is suddenly switched on, a temperature inversion results which leads to the formation of an accretion corona.

  19. Comprehensive equilibrium analysis of the complexation of Cu(II) by tetrathia-14-crown-4 in a synergistic extraction system employing didodecylnaphthalene sulfonic acid

    SciTech Connect

    Moyer, B.A.; Delmau, L.H.; Case, G.N.

    1995-04-01

    Liquid-liquid extraction experiments, UV/vis spectra, and equilibrium modeling by use of the program SXLSQA have been employed to reveal the origin of synergism in the extraction of Cu(II) from sulfuric acid by the tetradentate macrocycle tetrathia-14-crown-4 (TT14C4) combined with the cation exchanger didodecylnaphthalene sulfonic acid (HDDNS) in toluene. The key feature of the system is the 1:1 complexation of Cu(II) by TT14C4. HDDNS functions both as a source of exchangeable protons and as a solvating agent that promotes the formation of small, hydrated aggregates. In the absence of the cation-exchange vehicle provided by HDDNS, the macrocycle does not extract Cu(II) detectably. Combined with HDDNS, however, TT14C4 significantly enhances the extraction of the metal by HDDNS. Comparative UV/vis spectrophotometry indicates the formation of the deep-blue chromophore attributed to the complex ion Cu(TT14C4){sup 2+}, wherein the planar set of four endo sulfur donor atoms of TT14C4 circumscribes the metal cation. Modeling of the extraction and spectral absorbance data by use of the program SXLSQA supports the conclusion that this 1:1 complex accounts for essentially all of the extracted Cu(II) in excess of that extracted by HDDNS alone. The best model includes HDDNS aggregates incorporating Cu(TT14C4){sup 2+} or Cu{sup 2+} ions. In the analysis, activity effects in both aqueous and organic phases have been taken into account by the Pitzer and Hildebrand-Scott treatments, respectively, with explicit inclusion of the formation of aqueous hydrogen sulfate ion. The model accounts for the effect of variation of the solute components CuSO{sub 4}, H{sub 2}SO{sub 4}, HDDNS, and TT14C4.

  20. Improved log(gf) Values Of Selected Lines In Mn I And Mn II For Studies Of Non-equilibrium Effects In Stellar Photospheres

    NASA Astrophysics Data System (ADS)

    Den Hartog, Elizabeth; Lawler, J. E.; Sobeck, J.; Sneden, C.; Cowan, J. J.; Asplund, M.

    2010-01-01

    The work presents transition probabilities with very low uncertainties for a selected set of multiplets of Mn I and Mn II. Multiplets are chosen which are accessible to ground-based observation, are relatively unblended and unsaturated in stellar spectra and which are amenable to accurate branching fraction determination. These lab measurements provide a foundation for studies of non-LTE and 3-dimensional effects in stellar photospheres. We report on new radiative lifetime measurements for 22 levels of Mn I from the e8D, z6P, z6D, z4F, e8S and e6S multiplets and 3 levels of Mn II from the z5P multiplet using time-resolved laser-induced fluorescence on a slow atomic beam. New branching fractions for transitions from these levels, measured using a Fourier-transform spectrometer, are also reported. When combined, these measurements yield transition probabilities for 47 transitions of Mn I and 12 transitions of Mn II. Comparisons are made to data from the literature and to simple Russell-Saunders or LS theory. Final recommended values, which are weighted averages of all available modern measurements and in some cases LS theory, are given for the transition probabilities. These recommended log(gf) values are accurate to +/- 0.02 dex with high ( 2 sigma) confidence. The companion paper applies these new lab results to studies of departures from both LTE in Mn I and Saha equilibrium between Mn I and Mn II on a variety of stellar photospheres. This research is supported in part by NASA Grant NNX08AQ09G and NSF Grant AST-0907732.

  1. Interaction of Triapine and related thiosemicarbazones with iron(III)/(II) and gallium(III): a comparative solution equilibrium study†

    PubMed Central

    Enyedy, Éva A.; Primik, Michael F.; Kowol, Christian R.; Arion, Vladimir B.; Kiss, Tamás; Keppler, Bernhard K.

    2012-01-01

    Stoichiometry and stability of GaIII, FeIII, FeII complexes of Triapine and five related α-N heterocyclic thiosemicarbazones with potential antitumor activity have been determined by pH-potentiometry, UV-vis spectrophotometry, 1H NMR spectroscopy, and spectrofluorimetry in aqueous solution (with 30% DMSO), together with the characterization of the proton dissociation processes. Additionally, the redox properties of the iron complexes were studied by cyclic voltammetry at various pH values. Formation of high stability bis-ligand complexes was found in all cases, which are predominant at physiological pH with FeIII/FeII, whilst only at the acidic pH range with GaIII. The results show that among the thiosemicarbazones with various substituents the N-terminal dimethylation does not exert a measurable effect on the redox potential, but has the highest impact on the stability of the complexes as well as the cytotoxicity, especially in the absence of a pyridine-NH2 group in the molecule. In addition the fluorescence properties of the ligands in aqueous solution and their changes caused by GaIII were studied. PMID:21523301

  2. Detailed and Simplified Nonequilibrium Helium Ionization in the Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit

    2014-03-01

    Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional radiation-hydrodynamics simulations of the solar atmosphere and find that the helium ionization is set mostly by photoionization and direct collisional ionization, counteracted by radiative recombination cascades. By introducing an additional recombination rate mimicking the recombination cascades, we construct a simplified three-level helium model atom consisting of only the ground states. This model atom is suitable for modeling nonequilibrium helium ionization in three-dimensional numerical models. We perform a brief investigation of the formation of the He I 10830 and He II 304 spectral lines. Both lines show nonequilibrium features that are not recovered with statistical equilibrium models, and caution should therefore be exercised when such models are used as a basis for interpretating observations.

  3. Detailed and simplified nonequilibrium helium ionization in the solar atmosphere

    SciTech Connect

    Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit E-mail: mats.carlsson@astro.uio.no

    2014-03-20

    Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional radiation-hydrodynamics simulations of the solar atmosphere and find that the helium ionization is set mostly by photoionization and direct collisional ionization, counteracted by radiative recombination cascades. By introducing an additional recombination rate mimicking the recombination cascades, we construct a simplified three-level helium model atom consisting of only the ground states. This model atom is suitable for modeling nonequilibrium helium ionization in three-dimensional numerical models. We perform a brief investigation of the formation of the He I 10830 and He II 304 spectral lines. Both lines show nonequilibrium features that are not recovered with statistical equilibrium models, and caution should therefore be exercised when such models are used as a basis for interpretating observations.

  4. Synthesis, characterization and equilibrium studies of some potential antimicrobial and antitumor complexes of Cu(II), Ni(II), Zn(II) and Cd(II) ions involving 2-aminomethylbenzimidazole and glycine

    NASA Astrophysics Data System (ADS)

    Aljahdali, M.

    2013-08-01

    The ternary complexes of Cu(II), Zn(II), Ni(II) and Cd(II) with 2-aminomethylbenzimidazole (AMBI) and glycine as a representative example of amino acids have been isolated and characterized by elemental analyses, IR, ESR, UV-vis, magnetic moment, molar conductance and 1H NMR spectra. AMBI behaves as neutral bidentate ligands with coordination through imidazole and amino group nitrogens while the glycine amino acid behaves as a monodenate anion with coordination involving the amino group and carboxylate oxygen after deprotonation. The magnetic and spectral data indicates a square planar geometry for both Cu2+ and Ni2+ complexes and a tetrahedral geometry for both Zn2+ and Cd2+ complexes. The isolated chelates have been screened for their antifungal and antibacterial activities using the disc diffusion method. A cytotoxicity of the compounds against colon (HCT116) and larynx (HEP2) cancer cells have been studied. The stability constants of ternary M-AMBI-Gly complexes were determined potentiometrically in aqueous solution at I = 0.1 mol dm-3 NaCl.

  5. Removal of cadmium(II) ions from aqueous solution using Ni (15 wt.%)-doped α-Fe2O3 nanocrystals: equilibrium, thermodynamic, and kinetic studies.

    PubMed

    OuldM'hamed, Mohamed; Khezami, L; Alshammari, Abdulrahman G; Ould-Mame, S M; Ghiloufi, I; Lemine, O M

    2015-01-01

    The present publication investigates the performance of nanocrystalline Ni (15 wt.%)-doped α-Fe2O3 as an effective nanomaterial for the removal of Cd(II) ions from aqueous solutions. The nanocrystalline Ni-doped α-Fe2O3 powders were prepared by mechanical alloying, and characterized by X-ray diffraction and a vibrating sample magnetometer. Batch-mode experiments were realized to determine the adsorption equilibrium, kinetics, and thermodynamic parameters of toxic heavy metal ions by Ni (15 wt.%)-doped α-Fe2O3. The adsorption isotherms data were found to be in good agreement with the Langmuir model. The adsorption capacity of Cd(II) ion reached a maximum value of about 90.91 mg g(-1) at 328 K and pH 7. The adsorption process kinetics was found to comply with pseudo-second-order rate law. Thermodynamic parameters related to the adsorption reaction, free energy change, enthalpy change and entropy change, were evaluated. The found values of free energy and enthalpy revealed a spontaneous endothermic adsorption-process. Moreover, the positive entropy suggests an increase of randomness during the process of heavy metal removal at the adsorbent-solution interface. PMID:26247760

  6. Strong-field approximation for ionization of a diatomic molecule by a strong laser field. II. The role of electron rescattering off the molecular centers

    NASA Astrophysics Data System (ADS)

    Busuladžić, M.; Gazibegović-Busuladžić, A.; Milošević, D. B.; Becker, W.

    2008-09-01

    The strong-field approximation for ionization of diatomic molecules by a strong laser field [D. B. Milošević, Phys. Rev. A 74, 063404 (2006)] is generalized to include rescattering of the ionized electron wave packet off the molecular centers (the electron’s parent ion or the second atom). There are four rescattering contributions to the ionization rate, which are responsible for the high-energy plateau in the electron spectra and which interfere in a complicated manner. The spectra are even more complicated due to the different symmetry properties of the atomic orbitals of which a particular molecular orbital consists. Nevertheless, a comparatively simple condition emerges for the destructive interference of all these contributions, which yields a curve in the (Epf,θ) plane. Here θ is the electron emission angle and Epf is the electron kinetic energy. The resulting suppression of the rescattering plateau can be strong and affect a large area of the (Epf,θ) plane, depending on the orientation of the molecule. We illustrate this using the examples of the 3σg molecular orbital of N2 and the 1πg molecular orbital of O2 for various orientations of these molecules with respect to the laser polarization axis. For N2 , for perpendicular orientation and the equilibrium internuclear distance R0 , we find that the minima of the ionization rate form the curve Epfcos2θ=π2/(2R02) in the (Epf,θ) plane. For O2 the rescattering plateau is absent for perpendicular orientation.

  7. A Spitzer Survey of Mid-infrared Molecular Emission from Protoplanetary Disks. II. Correlations and Local Thermal Equilibrium Models

    NASA Astrophysics Data System (ADS)

    Salyk, C.; Pontoppidan, K. M.; Blake, G. A.; Najita, J. R.; Carr, J. S.

    2011-04-01

    We present an analysis of Spitzer Infrared Spectrograph observations of H2O, OH, HCN, C2H2, and CO2 emission, and Keck-NIRSPEC observations of CO emission, from a diverse sample of T Tauri and Herbig Ae/Be circumstellar disks. We find that detections and strengths of most mid-IR molecular emission features are correlated with each other, suggesting a common origin and similar excitation conditions for this mid-infrared line forest. Aside from the remarkable differences in molecular line strengths between T Tauri, Herbig Ae/Be, and transitional disks discussed in Pontoppidan et al., we note that the line detection efficiency is anti-correlated with the 13/30 μm spectral slope, which is a measure of the degree of grain settling in the disk atmosphere. We also note a correlation between detection efficiency and Hα equivalent width, and tentatively with accretion rate, suggesting that accretional heating contributes to line excitation. If detected, H2O line fluxes are correlated with the mid-IR continuum flux, and other co-varying system parameters, such as L sstarf. However, significant sample variation, especially in molecular line ratios, remains, and its origin has yet to be explained. Local thermal equilibrium (LTE) models of the H2O emission show that line strength is primarily related to the best-fit emitting area, and this accounts for most source-to-source variation in H2O emitted flux. Best-fit temperatures and column densities cover only a small range of parameter space, near ~1018 cm-2 and 450 K for all sources, suggesting a high abundance of H2O in many planet-forming regions. Other molecules have a range of excitation temperatures from ~500to1500 K, also consistent with an origin in planet-forming regions. We find molecular ratios relative to water of ~10-3 for all molecules, with the exception of CO, for which n(CO)/n(H2O) ~ 1. However, LTE fitting caveats and differences in the way thermo-chemical modeling results are reported make comparisons with

  8. A SPITZER SURVEY OF MID-INFRARED MOLECULAR EMISSION FROM PROTOPLANETARY DISKS. II. CORRELATIONS AND LOCAL THERMAL EQUILIBRIUM MODELS

    SciTech Connect

    Salyk, C.; Pontoppidan, K. M.; Blake, G. A.; Najita, J. R.; Carr, J. S.

    2011-04-20

    We present an analysis of Spitzer Infrared Spectrograph observations of H{sub 2}O, OH, HCN, C{sub 2}H{sub 2}, and CO{sub 2} emission, and Keck-NIRSPEC observations of CO emission, from a diverse sample of T Tauri and Herbig Ae/Be circumstellar disks. We find that detections and strengths of most mid-IR molecular emission features are correlated with each other, suggesting a common origin and similar excitation conditions for this mid-infrared line forest. Aside from the remarkable differences in molecular line strengths between T Tauri, Herbig Ae/Be, and transitional disks discussed in Pontoppidan et al., we note that the line detection efficiency is anti-correlated with the 13/30 {mu}m spectral slope, which is a measure of the degree of grain settling in the disk atmosphere. We also note a correlation between detection efficiency and H{alpha} equivalent width, and tentatively with accretion rate, suggesting that accretional heating contributes to line excitation. If detected, H{sub 2}O line fluxes are correlated with the mid-IR continuum flux, and other co-varying system parameters, such as L{sub *}. However, significant sample variation, especially in molecular line ratios, remains, and its origin has yet to be explained. Local thermal equilibrium (LTE) models of the H{sub 2}O emission show that line strength is primarily related to the best-fit emitting area, and this accounts for most source-to-source variation in H{sub 2}O emitted flux. Best-fit temperatures and column densities cover only a small range of parameter space, near {approx}10{sup 18} cm{sup -2} and 450 K for all sources, suggesting a high abundance of H{sub 2}O in many planet-forming regions. Other molecules have a range of excitation temperatures from {approx}500to1500 K, also consistent with an origin in planet-forming regions. We find molecular ratios relative to water of {approx}10{sup -3} for all molecules, with the exception of CO, for which n(CO)/n(H{sub 2}O) {approx} 1. However, LTE

  9. On the modeling of equilibrium twin interfaces in a single-crystalline magnetic shape memory alloy sample. II: numerical algorithm

    NASA Astrophysics Data System (ADS)

    Wang, Jiong; Steinmann, Paul

    2016-05-01

    This is part II of this series of papers. The aim of the current paper was to solve the governing PDE system derived in part I numerically, such that the procedure of variant reorientation in a magnetic shape memory alloy (MSMA) sample can be simulated. The sample to be considered in this paper has a 3D cuboid shape and is subject to typical magnetic and mechanical loading conditions. To investigate the demagnetization effect on the sample's response, the surrounding space of the sample is taken into account. By considering the different properties of the independent variables, an iterative numerical algorithm is proposed to solve the governing system. The related mathematical formulas and some techniques facilitating the numerical calculations are introduced. Based on the results of numerical simulations, the distributions of some important physical quantities (e.g., magnetization, demagnetization field, and mechanical stress) in the sample can be determined. Furthermore, the properties of configurational force on the twin interfaces are investigated. By virtue of the twin interface movement criteria derived in part I, the whole procedure of magnetic field- or stress-induced variant reorientations in the MSMA sample can be properly simulated.

  10. Chemical Equilibrium Models for the S3 State of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Isobe, Hiroshi; Shoji, Mitsuo; Shen, Jian-Ren; Yamaguchi, Kizashi

    2016-01-19

    We have performed hybrid density functional theory (DFT) calculations to investigate how chemical equilibria can be described in the S3 state of the oxygen-evolving complex in photosystem II. For a chosen 340-atom model, 1 stable and 11 metastable intermediates have been identified within the range of 13 kcal mol(-1) that differ in protonation, charge, spin, and conformational states. The results imply that reversible interconversion of these intermediates gives rise to dynamic equilibria that involve processes with relocations of protons and electrons residing in the Mn4CaO5 cluster, as well as bound water ligands, with concomitant large changes in the cluster geometry. Such proton tautomerism and redox isomerism are responsible for reversible activation/deactivation processes of substrate oxygen species, through which Mn-O and O-O bonds are transiently ruptured and formed. These results may allow for a tentative interpretation of kinetic data on substrate water exchange on the order of seconds at room temperature, as measured by time-resolved mass spectrometry. The reliability of the hybrid DFT method for the multielectron redox reaction in such an intricate system is also addressed. PMID:26717045

  11. Theory of the Protein Equilibrium Population Snapshot by H/D Exchange Electrospray Ionization Mass Spectrometry (PEPS-HDX-ESI-MS) Method used to obtain Protein Folding Energies/Rates and Selected Supporting Experimental Evidence

    PubMed Central

    Liyanage, Rohana; Devarapalli, Nagarjuna; Pyland, Derek B.; Puckett, Latisha M.; Phan, N. H.; Starch, Joel A.; Okimoto, Mark R.; Gidden, Jennifer; Stites, Wesley E.; Lay, Jackson O.

    2012-01-01

    Protein equilibrium snapshot by hydrogen/deuterium exchange electrospray ionization mass spectrometry (PEPS-HDX-ESI-MS or PEPS) is a method recently introduced for estimating protein folding energies and rates. Herein we describe the basis for this method using both theory and new experiments. Benchmark experiments were conducted using ubiquitin because of the availability of reference data for folding and unfolding rates from NMR studies. A second set of experiments was also conducted to illustrate the surprising resilience of the PEPS to changes in HDX time, using staphylococcal nuclease and time frames ranging from a few seconds to several minutes. Theory suggests that PEPS experiments should be conducted at relatively high denaturant concentrations, where the protein folding/unfolding rates are slow with respect to HDX and the life times of both the closed and open states are long enough to be sampled experimentally. Upon deliberate denaturation, changes in folding/unfolding are correlated with associated changes in the ESI-MS signal upon fast HDX. When experiments are done quickly, typically within a few seconds, ESI-MS signals, corresponding to the equilibrium population of the native (closed) and denatured (open) states can both be detected. The interior of folded proteins remains largely un-exchanged. Amongst MS methods, the simultaneous detection of both states in the spectrum is unique to PEPS and provides a “snapshot” of these populations. The associated ion intensities are used to estimate the protein folding equilibrium constant (or the free energy change, ΔG). Linear extrapolation method (LEM) plots of derived ΔG values for each denaturant concentration can then be used to calculate ΔG in the absence of denaturant, ΔGH2O. In accordance with the requirement for detection of signals for both the folded and unfolded states, this theoretical framework predicts that PEPS experiments work best at the middle of the denaturation curve where natured

  12. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  13. Roles of ROS and PKC-βII in ionizing radiation-induced eNOS activation in human vascular endothelial cells.

    PubMed

    Sakata, Kimimasa; Kondo, Takashi; Mizuno, Natsumi; Shoji, Miki; Yasui, Hironobu; Yamamori, Tohru; Inanami, Osamu; Yokoo, Hiroki; Yoshimura, Naoki; Hattori, Yuichi

    2015-07-01

    Vascular endothelial cells can absorb higher radiation doses than any other tissue in the body, and post-radiation impaired endothelial nitric oxide synthase (eNOS) function may be developed as a potential contributor to the pathogenesis of vascular injury. In this study, we investigated early alterations of eNOS signaling in human umbilical venous endothelial cells (HUVECs) exposed to X-ray radiation. We found that ionizing radiation increased eNOS phosphorylation at Ser-1177 and dephosphorylation at Thr-495 in HUVECs in a dose-dependent (≤ 20 Gy) and time-dependent (6-72 h) manner. The total expression levels of eNOS were unchanged by radiation. Although a transient but significant increase in extracellular signal-regulated protein kinase 1/2 (ERK1/2) phosphorylation and a biphasic decline in Akt phosphorylation were observed after irradiation, these inhibitors were without effect on the radiation-induced changes in eNOS phosphorylation. There was an increase in protein kinase C-βII (PKC-βII) expression and the ablation of PKC-βII by small interfering RNA (siRNA) negated the radiation effect on the two eNOS phosphorylation events. Furthermore, when the radiation-induced increase in reactive oxygen species (ROS) generation was prevented by the anti-oxidant N-acetyl-L-cysteine, eNOS Ser-1177 phosphorylation and Thr-495 dephosphorylation in irradiated HUVECs were significantly reduced. However, transfection of PKC-β siRNA did not alter ROS production after irradiation, and NAC failed to block the radiation-induced increase in PKC-βII expression. Taken together, our results suggest that ionizing radiation-induced eNOS activation in human vascular endothelial cells is attributed to both the up-regulation of PKC-βII and the increase in ROS generation which were independent of each other. PMID:25869503

  14. Uncovering multiple Wolf-Rayet star clusters and the ionized ISM in Mrk 178: the closest metal-poor Wolf-Rayet H II galaxy

    NASA Astrophysics Data System (ADS)

    Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M.; Brinchmann, J.; Kunth, D.; García-Benito, R.; Crowther, P. A.; Hernández-Fernández, J.; Durret, F.; Contini, T.; Fernández-Martín, A.; James, B. L.

    2013-07-01

    New integral field spectroscopy (IFS) has been obtained for the nearby metal-poor Wolf-Rayet (WR) galaxy Mrk 178 to examine the spatial correlation between its WR stars and the neighbouring ionized interstellar medium (ISM). The strength of the broad WR features and its low metallicity make Mrk 178 an intriguing object. We have detected the blue and red WR bumps in different locations across the field of view (˜300 pc × 230 pc) in Mrk 178. The study of the WR content has been extended, for the first time, beyond its brightest star-forming knot uncovering new WR star clusters. Using Large/Small Magellanic Cloud-template WR stars, we empirically estimate a minimum of ˜20 WR stars within the region sampled. Maps of the spatial distribution of the emission lines and of the physical-chemical properties of the ionized ISM have been created and analysed. Here, we refine the statistical methodology by Pérez-Montero et al. (2011) to probe the presence of variations in the ISM properties. An error-weighted mean of 12+log(O/H) = 7.72 ± 0.01 is taken as the representative oxygen abundance for Mrk 178. A localized N and He enrichment, spatially correlated with WR stars, is suggested by this analysis. Nebular He II λ4686 emission is shown to be spatially extended reaching well beyond the location of the WR stars. This spatial offset between WRs and He II emission can be explained based on the mechanical energy input into the ISM by the WR star winds, and does not rule out WR stars as the He II ionization source. We study systematic aperture effects on the detection and measurement of the WR features, using Sloan Digital Sky Survey spectra combined with the power of IFS. In this regard, the importance of targeting low metallicity nearby systems is discussed.

  15. The primordial abundance of deuterium: ionization correction

    NASA Astrophysics Data System (ADS)

    Cooke, Ryan; Pettini, Max

    2016-01-01

    We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman α (DLA) and sub-DLA systems using a detailed suite of photoionization simulations. We model metal-poor DLAs as clouds of gas in pressure equilibrium with a host dark matter halo, exposed to the Haardt & Madau background radiation of galaxies and quasars at redshift z ≃ 3. Our results indicate that the deuterium ionization correction correlates with the H I column density and the ratio of successive ion stages of the most commonly observed metals. The N(N II)/N(N I) column density ratio provides the most reliable correction factor, being essentially independent of the gas geometry, H I column density, and the radiation field. We provide a series of convenient fitting formulae to calculate the deuterium ionization correction based on observable quantities. The ionization correction typically does not exceed 0.1 per cent for metal-poor DLAs, which is comfortably below the current measurement precision (2 per cent). However, the deuterium ionization correction may need to be applied when a larger sample of D/H measurements becomes available.

  16. The energy of waves in the photosphere and lower chromosphere. III. Inversion setup for Ca II H spectra in local thermal equilibrium

    NASA Astrophysics Data System (ADS)

    Beck, C.; Rezaei, R.; Puschmann, K. G.

    2013-01-01

    Context. The Ca II H line is one of the strongest lines in the solar spectrum, and it provides continuous information on the solar atmosphere from the photosphere to the lower chromosphere. Aims: We describe an inversion approach that reproduces observed Ca II H spectra by assuming local thermal equilibrium (LTE). Methods: We developed an inversion strategy based on the SIR code that reproduces Ca II H spectra in the LTE approximation. The approach uses a two-step procedure with an archive of pre-calculated spectra to fit the line core and a subsequent iterative modification to improve the fit mainly in the line wing. Simultaneous spectra in the 630 nm range can optionally be used to fix the continuum temperature. The method retrieves one-dimensional (1D) temperature stratifications while neglecting lateral radiative transport. Line-of-sight velocities are included post facto with an empirical approach. Results: An archive of about 300 000 pre-calculated spectra is more than sufficient to reproduce the line core of observed Ca II H spectra both in the quiet Sun and in active regions. The subsequent iterative adjustment of the thermodynamical stratification matches observed and best-fit spectra to a level of about 0.5% of Ic in the line wing and about 1% of Ic in the line core. Conclusions: The successful application of the LTE inversion strategy suggests that inversion schemes based on pre-calculated spectra allow a reliable and relatively fast retrieval of solar properties from observed chromospheric spectra. The approach can be easily extended to a 1D non-LTE (NLTE) case by a simple exchange of the pre-calculated archive spectra. Using synthetic NLTE spectra from numerical three-dimensional (3D) simulations instead will finally allow one to extend the approach from the static 1D-case to dynamical atmosphere models, including the complete 3D radiative transport. The animation is available in electronic form at http://www.aanda.org

  17. Rapid assessment of human amylin aggregation and its inhibition by copper(II) ions by laser ablation electrospray ionization mass spectrometry with ion mobility separation.

    PubMed

    Li, Hang; Ha, Emmeline; Donaldson, Robert P; Jeremic, Aleksandar M; Vertes, Akos

    2015-10-01

    Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. Here, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin-copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the -HSSNN- residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin-copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin

  18. Rapid Assessment of Human Amylin Aggregation and Its Inhibition by Copper(II) Ions by Laser Ablation Electrospray Ionization Mass Spectrometry with Ion Mobility Separation

    PubMed Central

    Donaldson, Robert P.; Jeremic, Aleksandar M.; Vertes, Akos

    2015-01-01

    Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. Here, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the –HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of

  19. Helical equilibrium

    SciTech Connect

    Yoshikawa, S.

    1981-08-01

    A straight, helical plasma equilibrium equation is solved numerically for a plasma with a helical magnetic axis. As is expected, by a suitable choice of the plasma boundary, the vacuum configuration is made line ..integral.. dl/B stable. As the plasma pressure increases, the line ..integral.. dl/B criterion will improve (again as expected). There is apparently no limit on the plasma ..beta.. from the equilibrium consideration. Thus helical-axis stellarator ..beta.. will presumably be limited by MHD stability ..beta.., and not by equilibrium ..beta...

  20. Picosecond spectroscopic studies of equilibrium structural fluctuations of native and partially unfolded states of Zinc II-substituted and metal-free cytochromes C

    NASA Astrophysics Data System (ADS)

    Tripathy, Jagnyaseni

    Picosecond time-resolved fluorescence spectroscopy was employed to characterize the equilibrium and non-equilibrium protein structural fluctuations in Zn II-substituted (ZnCytc) and metal-free (fbCytc) cytochromes c using dynamic fluorescence Stokes shift (FSS) and fluorescence anisotropy (FA) measurements. The intrinsic porphyrin chromophore is used as the probe for the structural fluctuations of the surrounding protein and solvent. The FSS experiments examine how the time scales detected from the dynamic solvation of a chromoprotein report changes in the character of motion. ZnCytc and fbCytc serve as limited, single-chromophore models for photosynthetic reaction center and light-harvesting proteins. The dynamic solvation of redox and light-harvesting chromophores in photosynthesis plays an important role in the quantum efficiency of electron transfer and energy transfer performed by these systems, respectively. The FSS response function of fbCytc in water is biexponential over the 100-ps--50-ns regime and the two time constants are 1.4 ns and 9.1 ns. ZnCytc under similar solution conditions shows a biexponential FSS response but with time constants of 0.2 ns and 1.5 ns. The two correlation times from the FSS response function correspond to motions of the hydrophobic core and the solvent-contact layer, respectively. Both FSS correlation times were lengthened and the solvation reorganization energy was reduced from 43 cm-1 to 33 cm-1 in the presence of 50% (v/v) glycerol. A Brownian diffusion model with thermally activated barrier crossings on the protein-folding energy landscape is used to interpret these results. The conclusion is that the mean-squared deviations of the fluctuations exhibited by fbCytc are perhaps a factor of ten larger than those in ZnCytc, which is consistent with the suggestion that fbCytc assumes a dynamic, partially unfolded structure with some of the characteristics of a molten globule. The nature of the motion associated with the

  1. Ionization in nearby interstellar gas

    NASA Technical Reports Server (NTRS)

    Frisch, P. C.; Welty, D. E.; York, D. G.; Fowler, J. R.

    1990-01-01

    Due to dielectric recombination, neutral magnesium represents an important tracer for the warm low-density gas around the solar system. New Mg I 2852 absorption-line data from IUE are presented, including detections in a few stars within 40 pc of the sun. The absence of detectable Mg I in Alpha CMa and other stars sets limits on the combined size and electron density of the interstellar cloud which gives rise to the local interstellar wind. For a cloud radius greater than 1 pc and density of 0.1/cu cm, the local cloud has a low fractional ionization, n(e)/n(tot) less than 0.05, if magnesium is undepleted, equilibrium conditions prevail, the cloud temperature is 11,750 K, and 80 percent of the magnesium in the sightline is Mg II.

  2. Excitation properties of galaxies with the highest [O iii]/[O ii] ratios. No evidence for massive escape of ionizing photons

    NASA Astrophysics Data System (ADS)

    Stasińska, G.; Izotov, Yu.; Morisset, C.; Guseva, N.

    2015-04-01

    The possibility that star-forming galaxies may leak ionizing photons is at the heart of many present-day studies that investigate the reionization of the Universe. We test this hypothesis on local blue compact dwarf galaxies of very high excitation. We assembled a sample of such galaxies by examining the spectra from data releases 7 and 10 of the Sloan Digital Sky Survey. We argue that reliable conclusions cannot be based on strong lines alone, and adopt a strategy that includes important weak lines such as [O i] and the high-excitation He ii and [Ar iv] lines. Our analysis is based on purely observational diagrams and on a comparison of photoionization models with well-chosen emission-line ratio diagrams. We show that spectral energy distributions from current stellar population synthesis models cannot account for all the observational constraints, which led us to mimick several scenarios that could explain the data. These include the additional presence of hard X-rays or of shocks. We find that only ionization-bounded models (or models with an escape fraction of ionizing photons lower than 10%) are able to simultaneously explain all the observational constraints. Appendices are available in electronic form at http://www.aanda.org

  3. Nonequilibrium ionization phenomena behind shock waves

    SciTech Connect

    Panesi, Marco; Magin, Thierry; Huo, Winifred

    2011-05-20

    An accurate investigation of the behavior of electronically excited states of atoms and molecules in the post shock relaxation zone of a trajectory point of the FIRE II flight experiment is carried out by means of a one-dimensional flow solver coupled to a collisional-radiative model. In the rapidly ionizing regime behind a strong shock wave, the high lying bound electronic states of atoms are depleted. This leads the electronic energy level populations of atoms to depart from Boltzmann distributions which strongly affects the non-equilibrium ionization process as well as the radiative signature. The importance of correct modeling of the interaction of radiation and matter is discussed showing a strong influence on the physico-chemical properties of the gas. The paper clearly puts forward the shortcomings of the simplified approach often used in literature which strongly relies on the escape factors to characterize the optical thickness of the gas.

  4. FATE OF TRACE METALS IN A ROTARY KILN INCINERATOR WITH A SINGLE-STAGE IONIZING WET SCRUBBER - VOLUME II: APPENDICES

    EPA Science Inventory

    A series of pilot-scale incineration tests was performed at EPA's Incineration Research Facility (IRF) in Jefferson, Arkansas, to evaluate the fate of trace metals fed to a rotary kiln incinerator equipped with an ionizing wet scrubber (IWS) for particulate and acid gas control. ...

  5. Ionization of gases by a pulsed electron beam as studied by self-focusing. II. Polyatomic gases

    SciTech Connect

    Arai, H.; Hotta, H.

    1981-09-15

    In order to analyze data on the self-focusing of a pulsed electron beam in polyatomic gases, the net current I/sub net/ in H/sub 2/, N/sub 2/, and CH/sub 4/ was computed self-consistently as functions of time in the pressure range between 5 and 300 Torr of these gases by using swarm parameters. The computational result indicates that the larger dose D/sub obs/, observed by a piled dosimeter on the beam axis, is attributed to the larger I/sub net/, which is mainly determined by a mean ionization time t/sub 1/ for secondary ionization by the electric field induced by the pulsed beam. When values of D/sub obs/ for different gases are compared at the same pressure, the larger D/sub obs/ is given by the larger t/sub i/. This relationship is demonstrated for several polyatomic gases by estimating t/sub i/ from various parameters in a function of secondary electron energy or E/p such as the electron drift velocity, the first Townsend ionization coefficient, the ionization cross section, and so on. For the short pulse duration of a Febetron 706, electron--ion recombination processes scarcely affect I/sub net/ except at high pressures of some polyatomic gases, while the effect of electron-attachment processes is appreciable in SF/sub 6/, CCl/sub 2/F/sub 2/, and N/sub 2/O.

  6. Indirect dark matter signatures in the cosmic dark ages. II. Ionization, heating, and photon production from arbitrary energy injections

    NASA Astrophysics Data System (ADS)

    Slatyer, Tracy R.

    2016-01-01

    Any injection of electromagnetically interacting particles during the cosmic dark ages will lead to increased ionization, heating, production of Lyman-α photons and distortions to the energy spectrum of the cosmic microwave background, with potentially observable consequences. In this paper we describe numerical results for the low-energy electrons and photons produced by the cooling of particles injected at energies from keV to multi-TeV scales, at arbitrary injection redshifts (but focusing on the post-recombination epoch). We use these data, combined with existing calculations modeling the cooling of these low-energy particles, to estimate the resulting contributions to ionization, excitation and heating of the gas, and production of low-energy photons below the threshold for excitation and ionization. We compute corrected deposition-efficiency curves for annihilating dark matter, and demonstrate how to compute equivalent curves for arbitrary energy-injection histories. These calculations provide the necessary inputs for the limits on dark matter annihilation presented in the accompanying paper I, but also have potential applications in the context of dark matter decay or deexcitation, decay of other metastable species, or similar energy injections from new physics. We make our full results publicly available at http://nebel.rc.fas.harvard.edu/epsilon, to facilitate further independent studies. In particular, we provide the full low-energy electron and photon spectra, to allow matching onto more detailed codes that describe the cooling of such particles at low energies.

  7. A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

    USGS Publications Warehouse

    Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

    2008-01-01

    Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

  8. Theoretical fluorescence induction curves derived from coupled differential equations describing the primary photochemistry of photosystem II by an exciton-radical pair equilibrium

    PubMed Central

    Trissl, H.-W.; Gao, Y.; Wulf, K.

    1993-01-01

    Fluorescence induction curves were calculated from a molecular model for the primary photophysical and photochemical processes of photosystem II that includes reversible exciton trapping by open (PHQA) and closed (PHQ-A) reaction centers (RCs), charge stabilization as well as quenching by oxidized (P+HQ(-)A) RCs. For the limiting case of perfectly connected photosynthetic units (“lake model”) and thermal equilibrium between the primary radical pair (P+H-) and the excited singlet state, the primary reactions can be mathematically formulated by a set of coupled ordinary differential equations (ODE). These were numerically solved for weak flashes in a recursive way to simulate experiments with continuous illumination. Using recently published values for the molecular rate constants, this procedure yielded the time dependence of closed RCs as well as of the fluorescence yield (= fluorescence induction curves). The theoretical curves displayed the same sigmoidal shapes as experimental fluorescence induction curves. From the time development of closed RCs and the fluorescence yield, it was possible to check currently assumed proportionalities between the fraction of closed RCs and either (a) the variable fluorescence, (b) the complementary area above the fluorescence induction curve, or (c) the complementary area normalized to the variable fluorescence. By changing selected molecular rate constants, it is shown that, in contrast to current beliefs, none of these correlations obeys simple laws. The time dependence of these quantities is strongly nonexponential. In the presence of substances that quench the excited state, the model predicts straight lines in Stern-Volmer plots. We further conclude that it is impossible to estimate the degree of physical interunit energy transfer from the sigmoidicity of the fluorescence induction curve or from the curvature of the variable fluorescence plotted versus the fraction of closed RCs. PMID:19431889

  9. 3D radiative transfer simulations of Eta Carinae's inner colliding winds - II. Ionization structure of helium at periastron

    NASA Astrophysics Data System (ADS)

    Clementel, N.; Madura, T. I.; Kruip, C. J. H.; Paardekooper, J.-P.

    2015-06-01

    Spectral observations of the massive colliding wind binary Eta Carinae show phase-dependent variations, in intensity and velocity, of numerous helium emission and absorption lines throughout the entire 5.54-yr orbit. Approaching periastron, the 3D structure of the wind-wind interaction region (WWIR) gets highly distorted due to the eccentric (e ˜ 0.9) binary orbit. The secondary star (ηB) at these phases is located deep within the primary's dense wind photosphere. The combination of these effects is thought to be the cause of the particularly interesting features observed in the helium lines at periastron. We perform 3D radiative transfer simulations of η Car's interacting winds at periastron. Using the SIMPLEX radiative transfer algorithm, we post-process output from 3D smoothed particle hydrodynamic simulations of the inner 150 au of the η Car system for two different primary star mass-loss rates (dot{M}_{η A}). Using previous results from simulations at apastron as a guide for the initial conditions, we compute 3D helium ionization maps. We find that, for higher dot{M}_{η A}, ηB He0+-ionizing photons are not able to penetrate into the pre-shock primary wind. He+ due to ηB is only present in a thin layer along the leading arm of the WWIR and in a small region close to the stars. Lowering dot{M}_{η A} allows ηB's ionizing photons to reach the expanding unshocked secondary wind on the apastron side of the system, and create a low fraction of He+ in the pre-shock primary wind. With apastron on our side of the system, our results are qualitatively consistent with the observed variations in strength and radial velocity of η Car's helium emission and absorption lines, which helps better constrain the regions where these lines arise.

  10. Single photon simultaneous K-shell ionization and K-shell excitation. II. Specificities of hollow nitrogen molecular ions

    SciTech Connect

    Carniato, S. Selles, P.; Andric, L.; Palaudoux, J.; Penent, F.; Lablanquie, P.; Žitnik, M.; Bučar, K.; Nakano, M.; Hikosaka, Y.; Ito, K.

    2015-01-07

    The formalism developed in the companion Paper I is used here for the interpretation of spectra obtained recently on the nitrogen molecule. Double core-hole ionization K{sup −2} and core ionization-core excitation K{sup −2}V processes have been observed by coincidence electron spectroscopy after ionization by synchrotron radiation at different photon energies. Theoretical and experimental cross sections reported on an absolute scale are in satisfactory agreement. The evolution with photon energy of the relative contribution of shake-up and conjugate shake-up processes is discussed. The first main resonance in the K{sup −2}V spectrum is assigned to a K{sup −2}π{sup ∗} state mainly populated by the 1s→ lowest unoccupied molecular orbital dipolar excitation, as it is in the K{sup −1}V NEXAFS (Near-Edge X-ray Absorption Fine Structure) signals. Closer to the K{sup −2} threshold Rydberg resonances have been also identified, and among them a K{sup −2}σ{sup ∗} resonance characterized by a large amount of 2s/2p hybridization, and double K{sup −2}(2σ{sup ∗}/1π/3σ){sup −1}1π{sup ∗2} shake-up states. These resonances correspond in NEXAFS spectra to, respectively, the well-known σ{sup ∗} shape resonance and double excitation K{sup −1}(2σ{sup ∗}/1π/3σ){sup −1}1π{sup ∗2} resonances, all being positioned above the threshold.

  11. A Critical Compilation of Energy Levels, Spectral Lines, and Transition Probabilities of Singly Ionized Silver, Ag II

    PubMed Central

    Kramida, Alexander

    2013-01-01

    All available experimental measurements of the spectrum of the Ag+ ion are critically reviewed. Systematic shifts are removed from the measured wavelengths. The compiled list of critically evaluated wavelengths is used to derive a comprehensive list of energy levels with well-defined uncertainties. Eigenvector compositions and level designations are found in two alternate coupling schemes. Some of the older work is found to be incorrect. A revised value of the ionization energy, 173283(7) cm−1, equivalent to 21.4844(8) eV, is derived from the new energy levels. A set of critically evaluated transition probabilities is given. PMID:26401429

  12. Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules II: Non-Empirically Tuned Long-Range Corrected Hybrid Functionals.

    PubMed

    Gallandi, Lukas; Marom, Noa; Rinke, Patrick; Körzdörfer, Thomas

    2016-02-01

    The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set-extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations. PMID:26731340

  13. Dynamical Expansion of Ionization and Dissociation Front around a Massive Star. II. On the Generality of Triggered Star Formation

    NASA Astrophysics Data System (ADS)

    Hosokawa, Takashi; Inutsuka, Shu-ichiro

    2006-07-01

    We analyze the dynamical expansion of the H II region, photodissociation region, and the swept-up shell, solving the UV and far-UV radiative transfer and the thermal and chemical processes in the time-dependent hydrodynamics code. Following our previous paper, we investigate the time evolutions with various ambient number densities and central stars. Our calculations show that basic evolution is qualitatively similar among our models with different parameters. The molecular gas is finally accumulated in the shell, and the gravitational fragmentation of the shell is generally expected. The quantitative differences among models are well understood with analytic scaling relations. The detailed physical and chemical structure of the shell is mainly determined by the incident far-UV flux and the column density of the shell, which also follow the scaling relations. The time of shell fragmentation and the mass of the gathered molecular gas are sensitive to the ambient number density. In the case of a low density, the shell fragmentation occurs over a longer timescale, and the accumulated molecular gas is more massive than in the case of a high density. The variations with different central stars are more moderate. The time of the shell fragmentation differs by a factor of several with the various stars of M*=12-101 Msolar. According to our numerical results, we conclude that the expanding H II region should be an efficient trigger for star formation in molecular clouds if the mass of the ambient molecular material is large enough.

  14. Proteomics of light-harvesting proteins in different plant species. Analysis and comparison by liquid chromatography-electrospray ionization mass spectrometry. Photosystem II.

    PubMed

    Zolla, Lello; Timperio, Anna-Maria; Walcher, Wolfgang; Huber, Christian G

    2003-01-01

    An overview of the intact molecular masses and the hydrophobic properties of the photosystem II (PSII) light-harvesting proteins in 14 different plant species is presented. The protein separation and identification was achieved by means of reversed-phase high-performance liquid chromatography-electrospray ionization-mass spectrometry. The good correspondence of the molecular masses measured by reversed-phase high-performance liquid chromatography-electrospray ionization-mass spectrometry with those deduced from the DNA sequence (0.008%-0.016% relative deviation in Arabidopsis) enabled the identification of the different protein types. Utilizing this correlation, it was possible in several cases to spot a gene product for the previously cloned genes. In PSII, all antenna proteins show hydrophobic properties considerably different within the same as well as among various species, in contrast to observations made previously with PSI. These differences might reflect a tuning of protein-protein interactions that play a role in inducing different supramolecular organizations of PSII: within the same species as a consequence of short-term adaptations, and among species for seasonal species adaptation. The relative antenna stoichiometry was readily established on the basis of relative peak areas of the separated proteins in the ultraviolet chromatograms. The correspondence found between the high copy number of genes with the gene products reveals that the genes are not silent in their protein expression. Moreover, the high copy number of gene products as well as protein heterogeneity observed in PSII suggest a possible plant strategy to realize the high degree of organization and interconnection of the light-harvesting systems under any environmental conditions. PMID:12529528

  15. Equilibrium Shaping

    NASA Astrophysics Data System (ADS)

    Izzo, Dario; Petazzi, Lorenzo

    2006-08-01

    We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.

  16. The Suzaku view of highly ionized outflows in AGN - II. Location, energetics and scalings with bolometric luminosity

    NASA Astrophysics Data System (ADS)

    Gofford, J.; Reeves, J. N.; McLaughlin, D. E.; Braito, V.; Turner, T. J.; Tombesi, F.; Cappi, M.

    2015-08-01

    Ongoing studies with XMM-Newton have shown that powerful accretion disc winds, as revealed through highly ionized Fe K-shell absorption at E ≥ 6.7 keV, are present in a significant fraction of active galactic nuclei (AGNs) in the local Universe (Tombesi et al. 2010a). In Gofford et al., we analysed a sample of 51 Suzaku-observed AGNs and independently detected Fe K absorption in ˜40 per cent of the sample, and we measured the properties of the absorbing gas. In this work, we build upon these results to consider the properties of the associated wind. On average, the fast winds (vw > 0.01c) are located ˜ 1015-18 cm (typically ˜102-4 rs) from their black hole, their mass outflow rates are of the order of < dot{M}_w > ˜ 0.01-1 M⊙ yr-1 or {˜ }(0.01-1)dot{M}_Edd and kinetic power is constrained to ˜ 1043-45 erg s-1, equivalent to ˜(0.1-10 per cent)LEdd. We find a fundamental correlation between the source bolometric luminosity and the wind velocity, with v_w ∝ L_bol^{α } and α =0.4^{+0.3}_{-0.2} (90 per cent confidence), which indicates that more luminous AGN tend to harbour faster Fe K winds. The mass outflow rate dot{M}_w, kinetic power Lw and momentum flux dot{p}_w of the winds are also consequently correlated with Lbol, such that more massive and more energetic winds are present in more luminous AGN. We investigate these properties in the framework of a continuum-driven wind, showing that the observed relationships are broadly consistent with a wind being accelerated by continuum-scattering. We find that, globally, a significant fraction (˜85 per cent) of the sample can plausibly exceed the Lw/Lbol ˜ 0.5 per cent threshold thought necessary for feedback, while 45 per cent may also exceed the less conservative ˜5 per cent of Lbol threshold as well. This suggests that the winds may be energetically significant for AGN-host-galaxy feedback processes.

  17. Definitions and Basic Concepts of Supply and Demand Analysis Used to Determine Market Equilibrium. Principles of Economics II (Microeconomics), Lesson Plan No. 6.

    ERIC Educational Resources Information Center

    Chiu-Irion, Vicky

    Developed as part of a 37.5-hour microeconomics course, this lesson plan focuses on the concepts of supply and demand analysis used to determine market equilibrium. The objectives of the 50-minute lesson are to enable the student to: (1) explain how a demand schedule is derived from raw data; (2) graph a demand curve from the demand schedule; (3)…

  18. Calcium - ionized

    MedlinePlus

    ... at both ionized calcium and calcium attached to proteins. You may need to have a separate ionized calcium test if you have factors that increase or decrease total calcium levels. These may include abnormal blood levels ...

  19. Measurements of miniature ionization chamber currents in the JSI TRIGA Mark II reactor demonstrate the importance of the delayed contribution to the photon field in nuclear reactors

    NASA Astrophysics Data System (ADS)

    Radulović, Vladimir; Fourmentel, Damien; Barbot, Loïc; Villard, Jean-François; Kaiba, Tanja; Gašper, Žerovnik; Snoj, Luka

    2015-12-01

    The characterization of experimental locations of a research nuclear reactor implies the determination of neutron and photon flux levels within, with the best achievable accuracy. In nuclear reactors, photon fluxes are commonly calculated by Monte Carlo simulations but rarely measured on-line. In this context, experiments were conducted with a miniature gas ionization chamber (MIC) based on miniature fission chamber mechanical parts, recently developed by the CEA (French Atomic Energy and Alternative Energies Commission) irradiated in the core of the Jožef Stefan Institute TRIGA Mark II reactor in Ljubljana, Slovenia. The aim of the study was to compare the measured MIC currents with calculated currents based on simulations with the MCNP6 code. A discrepancy of around 50% was observed between the measured and the calculated currents; in the latter taking into consideration only the prompt photon field. Further experimental measurements of MIC currents following reactor SCRAMs (reactor shutdown with rapid insertions of control rods) provide evidence that over 30% of the total measured signal is due to the delayed photon field, originating from fission and activation products, which are untreated in the calculations. In the comparison between the measured and calculated values, these findings imply an overall discrepancy of less than 20% of the total signal which is still unexplained.

  20. Computer Program for Calculation of Complex Chemical Equilibrium Compositions and Applications II. Users Manual and Program Description. 2; Users Manual and Program Description

    NASA Technical Reports Server (NTRS)

    McBride, Bonnie J.; Gordon, Sanford

    1996-01-01

    This users manual is the second part of a two-part report describing the NASA Lewis CEA (Chemical Equilibrium with Applications) program. The program obtains chemical equilibrium compositions of complex mixtures with applications to several types of problems. The topics presented in this manual are: (1) details for preparing input data sets; (2) a description of output tables for various types of problems; (3) the overall modular organization of the program with information on how to make modifications; (4) a description of the function of each subroutine; (5) error messages and their significance; and (6) a number of examples that illustrate various types of problems handled by CEA and that cover many of the options available in both input and output. Seven appendixes give information on the thermodynamic and thermal transport data used in CEA; some information on common variables used in or generated by the equilibrium module; and output tables for 14 example problems. The CEA program was written in ANSI standard FORTRAN 77. CEA should work on any system with sufficient storage. There are about 6300 lines in the source code, which uses about 225 kilobytes of memory. The compiled program takes about 975 kilobytes.

  1. On Radiation Pressure in Static, Dusty H II Regions

    NASA Astrophysics Data System (ADS)

    Draine, B. T.

    2011-05-01

    Radiation pressure acting on gas and dust causes H II regions to have central densities that are lower than the density near the ionized boundary. H II regions in static equilibrium comprise a family of similarity solutions with three parameters: β, γ, and the product Q 0 n rms; β characterizes the stellar spectrum, γ characterizes the dust/gas ratio, Q 0 is the stellar ionizing output (photons/s), and n rms is the rms density within the ionized region. Adopting standard values for β and γ, varying Q 0 n rms generates a one-parameter family of density profiles, ranging from nearly uniform density (small Q 0 n rms) to shell-like (large Q 0 n rms). When Q 0 n rms >~ 1052 cm-3 s-1, dusty H II regions have conspicuous central cavities, even if no stellar wind is present. For given β, γ, and Q 0 n rms, a fourth quantity, which can be Q 0, determines the overall size and density of the H II region. Examples of density and emissivity profiles are given. We show how quantities of interest—such as the peak-to-central emission measure ratio, the rms-to-mean density ratio, the edge-to-rms density ratio, and the fraction of the ionizing photons absorbed by the gas—depend on β, γ, and Q 0 n rms. For dusty H II regions, compression of the gas and dust into an ionized shell results in a substantial increase in the fraction of the stellar photons that actually ionize H (relative to a uniform-density H II region with the same dust/gas ratio and density n = n rms). We discuss the extent to which radial drift of dust grains in H II regions can alter the dust-to-gas ratio. The applicability of these solutions to real H II regions is discussed.

  2. Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

    NASA Technical Reports Server (NTRS)

    Davy, W. C.; Green, M. J.; Lombard, C. K.

    1981-01-01

    The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

  3. Evidence for an essential role of intradimer interaction in catalytic function of carnosine dipeptidase II using electrospray-ionization mass spectrometry.

    PubMed

    Okumura, Nobuaki; Tamura, Jun; Takao, Toshifumi

    2016-02-01

    Carnosine dipeptidase II (CN2/CNDP2) is an M20 family metallopeptidase that hydrolyses various dipeptides including β-alanyl-L-histidine (carnosine). Crystallographic analysis showed that CN2 monomer is composed of one catalytic and one dimerization domains, and likely to form homodimer. In this crystal, H228 residue of the dimerization domain interacts with the substrate analogue bestatin on the active site of the dimer counterpart, indicating that H228 is involved in enzymatic reaction. In the present study, the role of intradimer interaction of CN2 in its catalytic activity was investigated using electrospray-ionization time-of-flight mass spectrometry (ESI-TOF MS). First, a dimer interface mutant I319K was prepared and shown to be present as a folded monomer in solution as examined by using ESI-TOF MS. Since the mutant was inactive, it was suggested that dimer formation is essential to its enzymatic activity. Next, we prepared H228A and D132A mutant proteins with different N-terminal extended sequences, which enabled us to monitor dimer exchange reaction by ESI-TOF MS. The D132A mutant is a metal ligand mutant and also inactive. But the activity was partially recovered time-dependently when H228A and D132A mutant proteins were incubated together. In parallel, H228A/D132A heterodimer was formed as detected by ESI-TOF MS, indicating that interaction of a catalytic center with H228 residue of the other subunit is essential to the enzymatic reaction. These results provide evidence showing that intradimer interaction of H228 with the reaction center of the dimer counterpart is essential to the enzymatic activity of CN2. PMID:26549037

  4. Equilibrium and kinetic studies for the biosorption system of copper(II) ion from aqueous solution using Tectona grandis L.f. leaves powder.

    PubMed

    Prasanna Kumar, Y; King, P; Prasad, V S R K

    2006-09-21

    The biosorption of copper(II) ions from aqueous solution by Tectona grandis L.f. was studied in a batch adsorption system as a function of pH, metal ion concentration, adsorbent concentration and adsorbent size. The biosorption capacities and rates of copper(II) ions onto T. grandis L.f. were evaluated. The Langmuir, Freundlich, Redlich-Peterson and Temkin adsorption models were applied to describe the isotherms and isotherm constants. Biosorption isothermal data could be well interpreted by the Langmuir model with maximum adsorption capacity of 15.43 mg/g of copper(II) ion on T. grandis L.f. leaves powder. The kinetic experimental data properly correlated with the second-order kinetic model. Various thermodynamic parameters such as deltaG(o), deltaH(o), and deltaS(o) were calculated indicating that this system was a spontaneous and exothermic process. PMID:16704905

  5. Optimization, equilibrium, kinetic, thermodynamic and desorption studies on the sorption of Cu(II) from an aqueous solution using marine green algae: Halimeda gracilis.

    PubMed

    Jayakumar, R; Rajasimman, M; Karthikeyan, C

    2015-11-01

    The aptitude of marine green algae Helimeda gracilis for sorption of Cu(II) ions from an aqueous solution was studied in batch experiments. The effect of relevant parameters such as function of pH, sorbent dosage, agitation speed and contact time was evaluated by using Response surface methodology (RSM). A maximum percentage removal of Cu (II) by Halimeda gracilis occurs at pH-4.49, sorbent dosage-1.98g/L, agitation speed-119.43rpm and contact time-60.21min. Further, the sorbent was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron microscope (SEM) analysis. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order, intraparticle diffusion, power function and elovich kinetic models. The results showed that the sorption process of Cu(II) ions followed well pseudo-second order kinetics. The sorption data of Cu(II) ions at 308.15K are fitted to Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Sips and Toth isotherms. Sorption of Cu(II) onto marine green algae Helimeda gracilis followed the Langmuir and Toth isotherm models (R(2)=0.998 and R(2)=0.999) with the maximum sorption capacity of 38.46 and 38.07mg/g. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the sorption of Cu(II) ions onto Helimeda gracilis biomass was feasible, spontaneous and endothermic. Desorption study shows that the sorbent could be regenerated using 0.2M HCl solution, with up to 89% recovery. PMID:25866206

  6. Neutral zinc(II) O,O-di-alkyldithiopho- sphates-variable temperature 31P NMR and quantum chemical study of the ZDDP monomer-dimer equilibrium.

    PubMed

    Harrison, J J; Chan, C Y; Onopchenko, A; Pradhan, A R; Petersen, M

    2008-02-01

    A full line-shape analysis of the VT 31P NMR spectra was carried out for the monomer-dimer equilibrium of neutral ZDDP. The energy surface and the energetics of the monomer-dimer equilibrium (DeltaH degrees , DeltaG degrees , Ea, DeltaH(not equal), and DeltaG(not equal)) are reported for three variants wherein the alkyl groups in the ZDDP are 2-ethylhexyl, isopropyl, and isobutyl. We explored a reaction pathway between the monomer and dimer form by means of density functional theory (DFT). The linear combination of atomic orbitals (LCAO) code DMol3 was used together with a synchronous transient method to effectively locate transition states. Vibrational eigenmodes of all intermediates were computed to capture finite temperature effects. Methyl and ethyl were considered as alkyl groups. Two novel intermediates were located-a four-membered ring and a six-membered ring intermediate along the reaction coordinate. Comparison of the experimentally derived and computed energy surfaces was carried out. PMID:18098153

  7. Thermo-chemical dynamics and chemical quasi-equilibrium of plasmas in thermal non-equilibrium

    SciTech Connect

    Massot, Marc; Graille, Benjamin; Magin, Thierry E.

    2011-05-20

    We examine both processes of ionization by electron and heavy-particle impact in spatially uniform plasmas at rest in the absence of external forces. A singular perturbation analysis is used to study the following physical scenario, in which thermal relaxation becomes much slower than chemical reactions. First, electron-impact ionization is investigated. The dynamics of the system rapidly becomes close to a slow dynamics manifold that allows for defining a unique chemical quasi-equilibrium for two-temperature plasmas and proving that the second law of thermodynamics is satisfied. Then, all ionization reactions are taken into account simultaneously, leading to a surprising conclusion: the inner layer for short time scale (or time boundary layer) directly leads to thermal equilibrium. Global thermo-chemical equilibrium is reached within a short time scale, involving only chemical reactions, even if thermal relaxation through elastic collisions is assumed to be slow.

  8. Ionizing radiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter gives a comprehensive review on ionizing irradiation of fresh fruits and vegetables. Topics include principles of ionizing radiation, its effects on pathogenic and spoilage microorganisms, shelf-life, sensory quality, nutritional and phytochemical composition, as well as physiologic and...

  9. Grid-based methods for diatomic quantum scattering problems II: Time-dependent treatment of single- and two-photon ionization of H2+

    SciTech Connect

    Rescigno, Thomas N.; Tao, L.; McCurdy, C.W.

    2009-04-20

    The time-dependent Schr\\"odinger equation for H2+ in a time-varying electromagnetic field is solved in the fixed-nuclei approximation using a previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates. Amplitudes for single- and two-photon ionization are obtained using the method of exterior complex scaling to effectively propagate the field-free solutions from the end of the radiation pulse to infinite times. Cross sections are presented for one-and two-photon ionization for both parallel and perpendicular polarization of the photon field, as well as photoelectron angular distributions for two-photon ionization.

  10. The effects of metallicity, UV radiation and non-equilibrium chemistry in high-resolution simulations of galaxies

    NASA Astrophysics Data System (ADS)

    Richings, A. J.; Schaye, Joop

    2016-05-01

    We present a series of hydrodynamic simulations of isolated galaxies with stellar mass of 109 M⊙. The models use a resolution of 750 M⊙ per particle and include a treatment for the full non-equilibrium chemical evolution of ions and molecules (157 species in total), along with gas cooling rates computed self-consistently using the non-equilibrium abundances. We compare these to simulations evolved using cooling rates calculated assuming chemical (including ionization) equilibrium, and we consider a wide range of metallicities and UV radiation fields, including a local prescription for self-shielding by gas and dust. We find higher star formation rates and stronger outflows at higher metallicity and for weaker radiation fields, as gas can more easily cool to a cold (few hundred Kelvin) star-forming phase under such conditions. Contrary to variations in the metallicity and the radiation field, non-equilibrium chemistry generally has no strong effect on the total star formation rates or outflow properties. However, it is important for modelling molecular outflows. For example, the mass of H2 outflowing with velocities {>}50 {km} {s}^{-1} is enhanced by a factor ˜20 in non-equilibrium. We also compute the observable line emission from C II and CO. Both are stronger at higher metallicity, while C II and CO emission are higher for stronger and weaker radiation fields, respectively. We find that C II is generally unaffected by non-equilibrium chemistry. However, emission from CO varies by a factor of ˜2-4. This has implications for the mean XCO conversion factor between CO emission and H2 column density, which we find is lowered by up to a factor ˜2.3 in non-equilibrium, and for the fraction of CO-dark molecular gas.

  11. Experimental approaches for studying non-equilibrium atmospheric plasma jets

    SciTech Connect

    Shashurin, A.; Keidar, M.

    2015-12-15

    This work reviews recent research efforts undertaken in the area non-equilibrium atmospheric plasma jets with special focus on experimental approaches. Physics of small non-equilibrium atmospheric plasma jets operating in kHz frequency range at powers around few Watts will be analyzed, including mechanism of breakdown, process of ionization front propagation, electrical coupling of the ionization front with the discharge electrodes, distributions of excited and ionized species, discharge current spreading, transient dynamics of various plasma parameters, etc. Experimental diagnostic approaches utilized in the field will be considered, including Rayleigh microwave scattering, Thomson laser scattering, electrostatic streamer scatterers, optical emission spectroscopy, fast photographing, etc.

  12. Experimental approaches for studying non-equilibrium atmospheric plasma jets

    NASA Astrophysics Data System (ADS)

    Shashurin, A.; Keidar, M.

    2015-12-01

    This work reviews recent research efforts undertaken in the area non-equilibrium atmospheric plasma jets with special focus on experimental approaches. Physics of small non-equilibrium atmospheric plasma jets operating in kHz frequency range at powers around few Watts will be analyzed, including mechanism of breakdown, process of ionization front propagation, electrical coupling of the ionization front with the discharge electrodes, distributions of excited and ionized species, discharge current spreading, transient dynamics of various plasma parameters, etc. Experimental diagnostic approaches utilized in the field will be considered, including Rayleigh microwave scattering, Thomson laser scattering, electrostatic streamer scatterers, optical emission spectroscopy, fast photographing, etc.

  13. Calculation of equilibrium constants from multiwavelength spectroscopic data--II: SPECFIT: two user-friendly programs in basic and standard FORTRAN 77.

    PubMed

    Gampp, H; Maeder, M; Meyer, C J; Zuberbühler, A D

    1985-04-01

    A new program (SPECFIT), written in HP BASIC or FORTRAN 77, for the calculation of stability constants from spectroscopic data, is presented. Stability constants have been successfully calculated from multiwavelength spectrophotometric and EPR data, but the program can be equally well applied to the numerical treatment of other spectroscopic measurements. The special features included in SPECFIT to improve convergence, increase numerical reliability, and minimize memory as well as computing time requirements, include (i) elimination of the linear parameters (i.e., molar absorptivities), (ii) the use of analytical instead of numerical derivatives and (iii) factor analysis. Calculation of stability constants from spectroscopic data is then as straightforward as from potentiometric titration curves and gives results of analogous reproducibility. The spectroscopic method has proved, however, to be superior in discrimination between chemical models. PMID:18963840

  14. Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire. II. Electron energy loss spectroscopic study

    SciTech Connect

    Lee, Sung Bo Han, Heung Nam; Kim, Young-Min

    2015-07-15

    In Part I, we have shown that the addition of Si into sapphire by ion implantationmakes the sapphire substrate elastically softer than for the undoped sapphire. The more compliant layer of the Si-implanted sapphire substrate can absorb the misfit stress at the GaN/sapphire interface, which produces a lower threading-dislocation density in the GaN overlayer. Here in Part II, based on experimental results by electron energy loss spectroscopy and a first-principle molecular orbital calculation in the literature, we suggest that the softening effect of Si results from a reduction of ionic bonding strength in sapphire (α-Al{sub 2}O{sub 3}) with the substitution of Si for Al.

  15. Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire. II. Electron energy loss spectroscopic study

    NASA Astrophysics Data System (ADS)

    Lee, Sung Bo; Kim, Young-Min; Han, Heung Nam

    2015-07-01

    In Part I, we have shown that the addition of Si into sapphire by ion implantationmakes the sapphire substrate elastically softer than for the undoped sapphire. The more compliant layer of the Si-implanted sapphire substrate can absorb the misfit stress at the GaN/sapphire interface, which produces a lower threading-dislocation density in the GaN overlayer. Here in Part II, based on experimental results by electron energy loss spectroscopy and a first-principle molecular orbital calculation in the literature, we suggest that the softening effect of Si results from a reduction of ionic bonding strength in sapphire (α-Al2O3) with the substitution of Si for Al.

  16. Removal of mercury(II) ions in aqueous solution using the peel biomass of Pachira aquatica Aubl: kinetics and adsorption equilibrium studies.

    PubMed

    Santana, Andrea J; Dos Santos, Walter N L; Silva, Laiana O B; das Virgens, Cesário F

    2016-05-01

    Mercury is a highly toxic substance that is a health hazard to humans. This study aims to investigate powders obtained from the peel of the fruit of Pachira aquatica Aubl, in its in natura and/or acidified form, as an adsorbent for the removal of mercury ions in aqueous solution. The materials were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The infrared spectra showed bands corresponding to the axial deformation of carbonyls from carboxylic acids, the most important functional group responsible for fixing the metal species to the adsorbent material. The thermograms displayed mass losses related to the decomposition of three major components, i.e., hemicellulose, cellulose, and lignin. The adsorption process was evaluated using cold-vapor atomic fluorescence spectrometry (CV AFS) and cold-vapor atomic absorption spectrometry (CV AAS). Three isotherm models were employed. The adsorption isotherm model, Langmuir-Freundlich, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 0.71 and 0.58 mg g(-1) at 25 °C in nature and acidified, respectively. Adsorption efficiencies were further tested on real aqueous wastewater samples, and removal of Hg(II) was recorded as 69.6 % for biomass acidified and 76.3 % for biomass in nature. Results obtained from sorption experiments on real aqueous wastewater samples revealed that recovery of the target metal ions was very satisfactory. The pseudo-second-order model showed the best correlation to the experimental data. The current findings showed that the investigated materials are potential adsorbents for mercury(II) ion removal in aqueous solution, with acidified P. aquatica Aubl being the most efficient adsorbent. PMID:27084802

  17. VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies. II. Evidence for shock ionization caused by tidal forces in the extra-nuclear regions of interacting and merging LIRGs

    NASA Astrophysics Data System (ADS)

    Monreal-Ibero, A.; Arribas, S.; Colina, L.; Rodríguez-Zaurín, J.; Alonso-Herrero, A.; García-Marín, M.

    2010-07-01

    Context. Luminous infrared galaxies (LIRGs) are an important class of objects in the low-z universe bridging the gap between normal spirals and the strongly interacting and starbursting ultraluminous infrared galaxies (ULIRGs). Since a large fraction of the stars in the Universe have been formed in these objects, LIRGs are also relevant in a high-z context. Studies of the two-dimensional physical properties of LIRGs are still lacking. Aims: We aim to understand the nature and origin of the ionization mechanisms operating in the extra-nuclear regions of LIRGs as a function of the interaction phase and infrared luminosity. Methods: This study uses optical integral field spectroscopy (IFS) data obtained with VIMOS. Our analysis is based on over 25 300 spectra of 32 LIRGs covering all types of morphologies (isolated galaxies, interacting pairs, and advanced mergers), and the entire 1011-1012 L⊙ infrared luminosity range. Results: We found strong evidence for shock ionization, with a clear trend with the dynamical status of the system. Specifically, we quantified the variation with interaction phase of several line ratios indicative of the excitation degree. While the [N ii]λ6584/Hα ratio does not show any significant change, the [S ii]λλ6717,6731/Hα and [O i]λ6300/Hα ratios are higher for more advanced interaction stages. Velocity dispersions are higher than in normal spirals and increase with the interaction class (medians of 37, 46, and 51 km s-1 for class 0-2, respectively). We constrained the main mechanisms causing the ionization in the extra-nuclear regions (typically for distances ranging from ~0.2-2.1 kpc to ~0.9-13.2 kpc) using diagnostic diagrams. Isolated systems are mainly consistent with ionization caused by young stars. Large fractions of the extra-nuclear regions in interacting pairs and more advanced mergers are consistent with ionization caused by shocks of vs ⪉ 200 km s-1. This is supported by the relation between the excitation degree and

  18. Reinvestigation of the copper(II)-carcinine equilibrium system: "two-dimensional" EPR simulation and NMR relaxation studies for determining the formation constants and coordination modes.

    PubMed

    Arkosi, Zsuzsanna; Paksi, Zoltán; Korecz, László; Gajda, Tamás; Henry, Bernard; Rockenbauer, Antal

    2004-12-01

    The equilibria and solution structure of complexes formed between copper(II) and carcinine (beta-alanyl-histamine) at 2< or = pH< or =11.2 have been studied by EPR and NMR relaxation methods. Beside the species that have already been described in the literature from pH-potentiometric measurements, several new complexes have been identified and/or structurally characterized. The singlet on the EPR spectrum detected in equimolar solutions at pH 7, indicates the formation of an oligomerized (CuL)n(2n+) complex, with [NH2,Nim] coordination. The oligomerization is probably associated with the low stability of the ten-membered macrochelate ring, which would form in the mononuclear complex CuL2+. In presence of moderate excess of ligand the formation of four new bis-complexes (CuL2Hn(2+n), n=2,1 and 0/-1) was detected with [Nim][Nim], [NH2,Nim][Nim] and [NH2,N-,Nim][Nim] type co-ordination modes, respectively. At higher excess of ligand ([L]/[Cu2+]>10) and at pH approximately 7, the predominant species is CuL4H2(4+). The 1H and 13C relaxation measurements of carcinine solutions (0.6 M) in presence of 0 mM< or = [Cu2+](tot)< or = 5 mM at pH=6.8, allowed us to extract the carbon-to-metal distances, the electronic relaxation and tumbling correlation times, as well as the ligand exchange rate for the species CuL4H2(4+). According to these results, the metal ion is [4Nim] co-ordinated in the equatorial plane, while the neutral amino groups are unbounded. Since naturally occurring carcinine shows in vivo antioxidant property, the SOD-like activity of the copper(II)-carcinine system has also been investigated and the complex CuLH(-1) was found to be highly active. PMID:15541487

  19. Ionization chamber

    DOEpatents

    Walenta, Albert H.

    1981-01-01

    An ionization chamber has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionize the gas.

  20. Ionization chamber

    DOEpatents

    Walenta, A.H.

    An ionization chamber is described which has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionizes the gas.

  1. Fine- and hyperfine-structure effects in molecular photoionization. II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations

    NASA Astrophysics Data System (ADS)

    Germann, Matthias; Willitsch, Stefan

    2016-07-01

    Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine-structure effects in one-photon ionization of molecules presented in Paper I [M. Germann and S. Willitsch, J. Chem. Phys. 145, 044314 (2016)]. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including the hyperfine structure that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ionization experiments.

  2. THE FATE OF TRACE METALS IN A ROTARY KILN INCINERATOR WITH A SINGLE-STAGE IONIZING WET SCRUBBER - VOLUME II: APPENDICES

    EPA Science Inventory

    A series of pilot-scale incineration tests was performed at EPA's Incineration Research Facility (IRF) in Jefferson, Arkansas, to evaluate the fate of trace metals fed to a rotary kiln incinerator equipped with an ionizing wet scrubber (IWS) for particulate and acid gas control. ...

  3. Fine- and hyperfine-structure effects in molecular photoionization. II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations.

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine-structure effects in one-photon ionization of molecules presented in Paper I [M. Germann and S. Willitsch, J. Chem. Phys. 145, 044314 (2016)]. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including the hyperfine structure that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ionization experiments. PMID:27475369

  4. IONIZATION CHAMBER

    DOEpatents

    Redman, W.C.; Shonka, F.R.

    1958-02-18

    This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

  5. Fluid hydrogen at high density - Pressure ionization

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1992-01-01

    The Helmholtz-free-energy model for nonideal mixtures of hydrogen atoms and molecules by Saumon and Chabrier (1991) is extended to describe dissociation and ionization in similar mixtures in chemical equilibrium. A free-energy model is given that describes partial ionization in the pressure and temperature ionization region. The plasma-phase transition predicted by the model is described for hydrogen mixtures including such components as H2, H, H(+), and e(-). The plasma-phase transition has a critical point at Tc = 15,300 K and Pc = 0.614 Mbar, and thermodynamic instability is noted in the pressure-ionization regime. The pressure dissociation and ionization of fluid hydrogen are described well with the model yielding information on the nature of the plasma-phase transition. The model is shown to be valuable for studying dissociation and ionization in astrophysical objects and in high-pressure studies where pressure and temperature effects are significant.

  6. NON-LOCAL THERMODYNAMICAL EQUILIBRIUM EFFECTS ON THE IRON ABUNDANCE OF ASYMPTOTIC GIANT BRANCH STARS IN 47 TUCANAE

    SciTech Connect

    Lapenna, E.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Massari, D.

    2014-12-20

    We present the iron abundance of 24 asymptotic giant branch (AGB) stars, members of the globular cluster 47 Tucanae, obtained with high-resolution spectra collected with the FEROS spectrograph at the MPG/ESO 2.2 m Telescope. We find that the iron abundances derived from neutral lines (with a mean value [Fe I/H] =–0.94 ± 0.01, σ = 0.08 dex) are systematically lower than those derived from single ionized lines ([Fe II/H] =–0.83 ± 0.01, σ = 0.05 dex). Only the latter are in agreement with those obtained for a sample of red giant branch (RGB) cluster stars, for which the Fe I and Fe II lines provide the same iron abundance. This finding suggests that non-local thermodynamical equilibrium (NLTE) effects driven by overionization mechanisms are present in the atmosphere of AGB stars and significantly affect the Fe I lines while leaving Fe II features unaltered. On the other hand, the very good ionization equilibrium found for RGB stars indicates that these NLTE effects may depend on the evolutionary stage. We discuss the impact of this finding on both the chemical analysis of AGB stars and on the search for evolved blue stragglers.

  7. Line emission from H II blister models

    NASA Technical Reports Server (NTRS)

    Rubin, R. H.

    1984-01-01

    Numerical techniques to calculate the thermal and geometric properties of line emission from H II 'blister' regions are presented. It is assumed that the density distributions of the H II regions are a function of two dimensions, with rotational symmetry specifying the shape in three-dimensions. The thermal and ionization equilibrium equations of the problem are solved by spherical modeling, and a spherical sector approximation is used to simplify the three-dimensional treatment of diffuse ionizing radiation. The global properties of H II 'blister' regions near the edges of a molecular cloud are simulated by means of the geometry/density distribution, and the results are compared with observational data. It is shown that there is a monotonic increase of peak surface brightness from the i = 0 deg (pole-on) observational position to the i = 90 deg (edge-on) position. The enhancement of the line peak intensity from the edge-on to the pole-on positions is found to depend on the density, stratification, ionization, and electron temperature weighting. It is found that as i increases, the position of peak line brightness of the lower excitation species is displaced to the high-density side of the high excitation species.

  8. On the Dynamical Evolution of H II Regions: An Investigation of the Ionized Component of W4, a Galactic Chimney Candidate. I. Kinematics and Dynamics in the Latitude Range 0° <= b <= 3°

    NASA Astrophysics Data System (ADS)

    Lagrois, Dominic; Joncas, Gilles

    2009-02-01

    Fabry-Perot interferometry was used to obtain an Hα survey of the most emissive part of W4, a giant superbubble/H II region located in the Perseus arm. Presented by Normandeau and colleagues as an H I cavity aiming away from the Galactic plane, the void has been morphologically interpreted as a Galactic chimney candidate in interaction with the Galactic corona. We present the kinematical results of nearly five million Hα spectra obtained in the southern portion of the nebula (0° <= b <= 3°). Many small-scale radial velocity gradients are detected in the embedded ionized component and are attributed to the photoionization of dense, mostly molecular, fragments found either in or at the periphery of the expanding supershell. The mean local standard of rest radial velocity associated with our Hα survey is found at -42.565 ± 5.204 (1σ) km s-1, redshifted by roughly 5 km s-1 from the molecular material found in the vicinity of the large superbubble. Investigation of the Hα line-width measurements has shown W4-south to fall in a transient regime between low velocity dispersions characteristic of small-size Galactic H II regions and supersonic line widths associated with supergiant extragalactic structures. The overall kinematics of W4-south is best explained with the Champagne model for the dynamical evolution of H II regions where at least 10 independent gas flows crisscross the nebula. For the first time, a Champagne flow is seen coming to an end within a nebula, mingling with the surrounding ionized gas. The nature (molecular versus atomic) of the neutral material, prone to erosion, is critical as it leads to much different kinematical interpretations. W4-south appears as a text book example of the last stage in the life of a giant molecular cloud complex.

  9. The He II Proximity Effect and The Lifetime of Quasars

    NASA Astrophysics Data System (ADS)

    Khrykin, I. S.; Hennawi, J. F.; McQuinn, M.; Worseck, G.

    2016-06-01

    The lifetime of quasars is fundamental for understanding the growth of supermassive black holes, and is an important ingredient in models of the reionization of the intergalactic medium (IGM). However, despite various attempts to determine quasar lifetimes, current estimates from a variety of methods are uncertain by orders of magnitude. This work combines cosmological hydrodynamical simulations and 1D radiative transfer to investigate the structure and evolution of the He ii Lyα proximity zones around quasars at z ≃ 3–4. We show that the time evolution in the proximity zone can be described by a simple analytical model for the approach of the He ii fraction {x}{He{{II}}}(t) to ionization equilibrium, and use this picture to illustrate how the transmission profile depends on the quasar lifetime, quasar UV luminosity, and the ionization state of Helium in the ambient IGM (i.e., the average He ii fraction, or equivalently the metagalactic He ii ionizing background). A significant degeneracy exists between the lifetime and the average He ii fraction, however the latter can be determined from measurements of the He ii Lyα optical depth far from quasars, allowing the lifetime to be measured. We advocate stacking existing He ii quasar spectra at z ∼ 3, and show that the shape of this average proximity zone profile is sensitive to lifetimes as long as ∼30 Myr. At higher redshift z ∼ 4 where the He ii fraction is poorly constrained, degeneracies will make it challenging to determine these parameters independently. Our analytical model for He ii proximity zones should also provide a useful description of the properties of H i proximity zones around quasars at z ≃ 6–7.

  10. Princeton spectral equilibrium code: PSEC

    SciTech Connect

    Ling, K.M.; Jardin, S.C.

    1984-03-01

    A fast computer code has been developed to calculate free-boundary solutions to the plasma equilibrium equation that are consistent with the currents in external coils and conductors. The free-boundary formulation is based on the minimization of a mean-square error epsilon while the fixed-boundary solution is based on a variational principle and spectral representation of the coordinates x(psi,theta) and z(psi,theta). Specific calculations using the Columbia University Torus II, the Poloidal Divertor Experiment (PDX), and the Tokamak Fusion Test Reactor (TFTR) geometries are performed.

  11. Atmospheric and ionospheric response to trace gas perturbations through the ice age to the next century in the middle atmosphere. Part II-ionization

    NASA Astrophysics Data System (ADS)

    Beig, G.; Mitra, A. P.

    1997-07-01

    A global two-dimensional meridional ion composition model of the middle atmosphere is used to examine the effect of changing concentrations of several greenhouse gases on the overall distribution of ionization for this region, along with a steady state calculation for the upper heights. Changes in the neutral parameters for this study are taken from the companion article (Beig and Mitra, 1997). It has been predicted that there are several sensitive signals of man-made perturbations in the middle atmospheric ionization. In the mesospheric region, for a doubled CO2 scenario, we find that the total ionization density does not change appreciably and the maximum variation is found to be around 15% at about 70 km. However, the distribution of individual ions shows a considerable variation (up to about 100%) throughout the middle atmosphere. The fall-off height of the fractional abundance of water cluster ions is higher for 2050 A.D., suggesting domination of these ions up to greater heights. The concentration of water cluster ions increases below about 85 km; above this height it starts to decrease sharply with height. When a scenario with doubled CO2, with CH4 and business-as-usual (BAU) (for CFCs and N2O) is considered in the stratospheric region, it is found that only one family of negative ions, called NO3-core ions, is dominant instead of two in the normal case. Simulations are also made through the ages since the last ice age. Results indicate a reverse trend as compared to the above.

  12. Getting Freshman in Equilibrium.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 1983

    1983-01-01

    Various aspects of chemical equilibrium were discussed in six papers presented at the Seventh Biennial Conference on Chemical Education (Stillwater, Oklahoma 1982). These include student problems in understanding hydrolysis, helping students discover/uncover topics, equilibrium demonstrations, instructional strategies, and flaws to kinetic…

  13. The Diffuse Ionized Gas in the large telescopes era

    NASA Astrophysics Data System (ADS)

    Hidalgo-Gámez, A. M.

    2005-12-01

    In this workshop we summarize the ``state of the art'' of the Diffuse Ionized Gas. We present all the possible situations which can produce ionization outside an H II region, as well as some of the observations that can be performed with the GTC instrumentation and how relevant they can be in the undestanding of the ionization mechanisms of the DIG.

  14. Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z~6 Quasars II: A Sample of 19 Quasars

    SciTech Connect

    Fan, X; Strauss, M A; Becker, R H; White, R L; Gunn, J E; Knapp, G R; Richards, G T; Schneider, D P; Brinkmann, J; Fukugita, M

    2006-01-05

    We study the evolution of the ionization state of the intergalactic medium (IGM) at the end of the reionization epoch using moderate resolution spectra of a sample of nineteen quasars at 5.74 < z{sub em} < 6.42 discovered in the Sloan Digital Sky Survey. Three methods are used to trace IGM properties: (a) the evolution of the Gunn-Peterson (GP) optical depth in the Ly{alpha}, {beta}, and {gamma} transitions; (b) the distribution of lengths of dark absorption gaps, and (c) the size of HII regions around luminous quasars. Using this large sample, we find that the evolution of the ionization state of the IGM accelerated at z > 5.7: the GP optical depth evolution changes from {tau}{sub GP}{sup eff} {approx} (1 + z){sup 4.3} to (1 + z){sup {approx}> 11}, and the average length of dark gaps with {tau} > 3.5 increases from < 10 to > 80 comoving Mpc. The dispersion of IGM properties along different lines of sight also increases rapidly, implying fluctuations by a factor of {approx}> 4 in the UV background at z > 6, when the mean free path of UV photons is comparable to the correlation length of the star forming galaxies that are thought to have caused reionization. The mean length of dark gaps shows the most dramatic increase at z {approx} 6, as well as the largest line-of-sight variations. We suggest using dark gap statistics as a powerful probe of the ionization state of the IGM at yet higher redshift. The sizes of HII regions around luminous quasars decrease rapidly towards higher redshift, suggesting that the neutral fraction of the IGM has increased by a factor of {approx}> 10 from z = 5.7 to 6.4, consistent with the value derived from the GP optical depth. The mass-averaged neutral fraction is 1-4% at z {approx} 6.2 based on the GP optical depth and HII region size measurements. The observations suggest that z {approx} 6 is the end of the overlapping stage of reionization, and are inconsistent with a mostly neutral IGM at z {approx} 6, as indicated by the finite

  15. Non-targeted and delayed effects of exposure to ionizing radiation: II. Radiation-induced genomic instability and bystander effects in vivo, clastogenic factors and transgenerational effects

    NASA Technical Reports Server (NTRS)

    Morgan, William F.

    2003-01-01

    The goal of this review is to summarize the evidence for non-targeted and delayed effects of exposure to ionizing radiation in vivo. Currently, human health risks associated with radiation exposures are based primarily on the assumption that the detrimental effects of radiation occur in irradiated cells. Over the years a number of non-targeted effects of radiation exposure in vivo have been described that challenge this concept. These include radiation-induced genomic instability, bystander effects, clastogenic factors produced in plasma from irradiated individuals that can cause chromosomal damage when cultured with nonirradiated cells, and transgenerational effects of parental irradiation that can manifest in the progeny. These effects pose new challenges to evaluating the risk(s) associated with radiation exposure and understanding radiation-induced carcinogenesis.

  16. Ionization transition in low-density plasma

    SciTech Connect

    Triger, S. A.; Khomkin, A. L.; Shumikhin, A. S.

    2011-09-15

    Ionization equilibrium in low-density low-temperature plasma is considered. It is demonstrated using hydrogen and cesium as examples that the Saha equation predicts an almost jump-like change in the electron density on isochors in a narrow temperature range. Thus, in contrast to a smooth rise in the degree of ionization with increasing temperature at high plasma densities, an increase in the temperature in low-density plasma should result in a sharp transition from a neutral state to a fully ionized plasma. This transition is accompanied by a jump-like increase in the electric conductivity. The relation of these effects to the recombination transition in the model of the early Universe is discussed. The possibility of observing such a transition experimentally and the problems concerning the time of plasma relaxation into an equilibrium state at long free path lengths of plasma particles are considered.

  17. Chemical Principles Revisited: Chemical Equilibrium.

    ERIC Educational Resources Information Center

    Mickey, Charles D.

    1980-01-01

    Describes: (1) Law of Mass Action; (2) equilibrium constant and ideal behavior; (3) general form of the equilibrium constant; (4) forward and reverse reactions; (5) factors influencing equilibrium; (6) Le Chatelier's principle; (7) effects of temperature, changing concentration, and pressure on equilibrium; and (8) catalysts and equilibrium. (JN)

  18. Wave propagation in a quasi-chemical equilibrium plasma

    NASA Technical Reports Server (NTRS)

    Fang, T.-M.; Baum, H. R.

    1975-01-01

    Wave propagation in a quasi-chemical equilibrium plasma is studied. The plasma is infinite and without external fields. The chemical reactions are assumed to result from the ionization and recombination processes. When the gas is near equilibrium, the dominant role describing the evolution of a reacting plasma is played by the global conservation equations. These equations are first derived and then used to study the small amplitude wave motion for a near-equilibrium situation. Nontrivial damping effects have been obtained by including the conduction current terms.

  19. Epsilon Canis Majoris and the ionization of the local cloud

    NASA Technical Reports Server (NTRS)

    Vallerga, J. V.; Welsh, B. Y.

    1995-01-01

    The Lyman continuum radiation from the brightest extreme ultraviolet (EUV) source, the B2 II star epsilon Canis Majoris (Adara), is so intense that it dominates the local stellar EUV radiation field at wavelengths longer than 450 A and therefore sets a lower limit to the ionization of hydrogen in the Local Cloud. Using the EUV (70-730 A) spectrum of epsilon CMa taken with the Extreme Ultraviolet Explorer Satellite (EUVE) and simple models that extrapolate this spectrum to the Lyman edge at 912 A, we have determined the local interstellar hydrogen photionizatin parameter Gamma solely from epsilon CMa to be 1.1 x 10(exp -15)/s. This fiugre is a factor of 7 greater than previous estimates of Gamma calculated for all nearby stars combined (Bruhweiler & Cheng 1988). Using measured values of the density and temperature of neutral interstellar hydrogen gas in the Local Cloud, we derive a particle density of ionized hydrogen n(H(+)) and electrons n(sub e) of 0.015-0.019/cu cm assuming ionization equilibrium and a helium ionization fraction of less than 20%. These values correspond to a hydrogen ionizatin fraction, chi(sub H) from 19% to 15%, respectively. The range of these derived quantities is due to the uncertainties in the local values of the neutral hydrogen and helium interstellar densities derived from both (1) solar backscatter measurements of Ly alpha lines of hydrogen and helium (1216 and 584 A), and (2) the average neutral densities along the line of sight to nearby stars. The local proton density produced by epsilon CMa is enough to allow the ionization mechanism of Ripken & Fahr (1983) to work at the heliopause and explain the discrepancy between the neutral hydrogen density derived from solar backscatter measurements and line-of-sight averages to nearby stars. A large value of electron density in the Local Cloud of n(sub e) is approximately 0.3-0.7/cu cm (T = 7000 K) has recently been reported by Lallement et al. (1994) using observations of Mg II and Mg I

  20. An analytical theory of a scattering of radio-waves on meteoric ionization. II. Solution of the integro-differential equation in case of backscatter

    NASA Astrophysics Data System (ADS)

    Pecina, P.

    2016-08-01

    The integro-differential equation for the polarization vector P inside the meteor trail, representing the analytical solution of the set of Maxwell equations, is solved for the case of backscattering of radio waves on meteoric ionization. The transversal and longitudinal dimensions of a typical meteor trail are small in comparison to the distances to both transmitter and receiver and so the phase factor appearing in the kernel of the integral equation is large and rapidly changing. This allows us to use the method of stationary phase to obtain an approximate solution of the integral equation for the scattered field and for the corresponding generalized radar equation. The final solution is obtained by expanding it into the complete set of Bessel functions, which results in solving a system of linear algebraic equations for the coefficients of the expansion. The time behaviour of the meteor echoes is then obtained using the generalized radar equation. Examples are given for values of the electron density spanning a range from underdense meteor echoes to overdense meteor echoes. We show that the time behaviour of overdense meteor echoes using this method is very different from the one obtained using purely numerical solutions of the Maxwell equations. Our results are in much better agreement with the observations performed e. g. by the Ondřejov radar.

  1. Computing Equilibrium Chemical Compositions

    NASA Technical Reports Server (NTRS)

    Mcbride, Bonnie J.; Gordon, Sanford

    1995-01-01

    Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

  2. Universality in equilibrium and away from it: A personal perspective

    SciTech Connect

    Munoz, Miguel A.

    2011-03-24

    In this talk/paper I discuss the concept of universality in phase transitions and the question of whether universality classes are more robust in equilibrium than away from it. In both of these situations, the main ingredients determining universality are symmetries, conservation laws, the dimension of the space and of the order-parameter and the presence of long-range interactions or quenched disorder. The existence of detailed-balance and fluctuation-dissipation theorems imposes severe constraints on equilibrium systems, allowing to define universality classes in a very robust way; instead, non-equilibrium allows for more variability. Still, quite robust non-equilibrium universality classes have been identified in the last decades. Here, I discuss some examples in which (i) non-equilibrium phase transitions are simply controlled by equilibrium critical points, i.e. non-equilibrium ingredients turn out to be irrelevant in the renormalization group sense and (ii) non-equilibrium situations in which equilibrium seems to come out of the blue, generating an adequate effective description of intrinsically non-equilibrium problems. Afterwards, I shall describe different genuinely non-equilibrium phase transitions in which introducing small, apparently innocuous changes (namely: presence or absence of an underlying lattice, parity conservation in the overall number of particles, existence of an un-accessible vacuum state, deterministic versus stochastic microscopic rules, presence or absence of a Fermionic constraint), the critical behavior is altered, making the case for lack of robustness. However, it will be argued that in all these examples, there is an underlying good reason (in terms of general principles) for universality to be altered. The final conclusions are that: (i) robust universality classes exist both in equilibrium and non-equilibrium; (ii) symmetry and conservation principles are crucial in both, (iii) non-equilibrium allows for more variability (i

  3. Poly [1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] solutions used as low dose ionizing radiation dosimeter

    SciTech Connect

    Bronze-Uhle, E. S.; Graeff, C. F. O.; Batagin-Neto, A.; Fernandes, D. M.; Fratoddi, I.; Russo, M. V.

    2013-06-17

    In this work, the effect of gamma radiation on the optical properties of polymetallayne poly[1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] (Pt-DEBP) in chloroform solution is studied. The samples were irradiated at room temperature with doses from 0.01 Gy to 1 Gy using a {sup 60}Co gamma ray source. A new band at 420 nm is observed in the emission spectra, in superposition to the emission maximum at 398 nm, linearly dependent on dose. We propose to use the ratio of the emission amplitude bands as the dosimetric parameter. This method proved to be robust, accurate, and can be used as a dosimeter in medical applications.

  4. Equilibrium games in networks

    NASA Astrophysics Data System (ADS)

    Li, Angsheng; Zhang, Xiaohui; Pan, Yicheng; Peng, Pan

    2014-12-01

    It seems a universal phenomenon of networks that the attacks on a small number of nodes by an adversary player Alice may generate a global cascading failure of the networks. It has been shown (Li et al., 2013) that classic scale-free networks (Barabási and Albert, 1999, Barabási, 2009) are insecure against attacks of as small as O(logn) many nodes. This poses a natural and fundamental question: Can we introduce a second player Bob to prevent Alice from global cascading failure of the networks? We proposed a game in networks. We say that a network has an equilibrium game if the second player Bob has a strategy to balance the cascading influence of attacks by the adversary player Alice. It was shown that networks of the preferential attachment model (Barabási and Albert, 1999) fail to have equilibrium games, that random graphs of the Erdös-Rényi model (Erdös and Rényi, 1959, Erdös and Rényi, 1960) have, for which randomness is the mechanism, and that homophyly networks (Li et al., 2013) have equilibrium games, for which homophyly and preferential attachment are the underlying mechanisms. We found that some real networks have equilibrium games, but most real networks fail to have. We anticipate that our results lead to an interesting new direction of network theory, that is, equilibrium games in networks.

  5. Weakly ionized cosmic gas: Ionization and characterization

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.; Mendis, D. A.; Chow, V. W.

    1994-01-01

    Since collective plasma behavior may determine important transport processes (e.g., plasma diffusion across a magnetic field) in certain cosmic environments, it is important to delineate the parameter space in which weakly ionized cosmic gases may be characterized as plasmas. In this short note, we do so. First, we use values for the ionization fraction given in the literature, wherein the ionization is generally assumed to be due primarily to ionization by cosmic rays. We also discuss an additional mechanism for ionization in such environments, namely, the photoelectric emission of electrons from cosmic dust grains in an interstellar Far Ultra Violet (FUV) radiation field. Simple estimates suggest that under certain conditions this mechanism may dominate cosmic ray ionization, and possibly also the photoionization of metal atoms by the interstellar FUV field, and thereby lead to an enhanced ionization level.

  6. An Updated Equilibrium Machine

    ERIC Educational Resources Information Center

    Schultz, Emeric

    2008-01-01

    A device that can demonstrate equilibrium, kinetic, and thermodynamic concepts is described. The device consists of a leaf blower attached to a plastic container divided into two chambers by a barrier of variable size and form. Styrofoam balls can be exchanged across the barrier when the leaf blower is turned on and various air pressures are…

  7. Microwave Mapping Demonstration Using the Thermochromic Cobalt Chloride Equilibrium

    ERIC Educational Resources Information Center

    Nguyen, Vu D.; Birdwhistell, Kurt R.

    2014-01-01

    An update to the thermochromic cobalt(II) chloride equilibrium demonstration is described. Filter paper that has been saturated with aqueous cobalt(II) chloride is heated for seconds in a microwave oven, producing a color change. The resulting pink and blue map is used to colorfully demonstrate Le Châtelier's principle and to illuminate the…

  8. Thermal low spin-high spin equilibrium of Fe(II) in thiospinels CuFe{sub 0.5}(Sn{sub (1-x)}Ti{sub x}){sub 1.5}S{sub 4} (0{<=}x{<=}1)

    SciTech Connect

    Womes, M.; Reibel, C.; Mari, A.; Zitoun, D.

    2011-04-15

    A series of spinel compounds with composition CuFe{sub 0.5}(Sn{sub (1-x)}Ti{sub x}){sub 1.5}S{sub 4} (0{<=}x{<=}1) is analysed by X-ray diffraction, measurements of magnetic susceptibilities and {sup 57}Fe Moessbauer spectroscopy. All samples show a temperature-dependent equilibrium between an electronic low spin 3d(t{sub 2g}){sup 6}(e{sub g}){sup 0} and a high spin 3d(t{sub 2g}){sup 4}(e{sub g}){sup 2} state of the Fe(II) ions. The spin crossover is of the continuous type and extends over several hundred degrees in all samples. The Sn/Ti ratio influences the thermal equilibrium between the two spin states. Substitution of Sn(IV) by the smaller Ti(IV) ions leads to a more compact crystal lattice, which, in contrast to many metal-organic Fe(II) complexes, does not stabilise the low spin state, but increases the residual high spin fraction for T{yields}0 K. The role played by antiferromagnetic spin coupling in the stabilisation of the high spin state is discussed. The results are compared with model calculations treating the effect of magnetic interactions on spin state equilibria. -- Graphical Abstract: Comparison of fractions of high spin Fe(II) from Moessbauer spectra (circles) with plots of {chi}{sub m}T (dots) versus T. Discrepancies between both methods indicate anti-ferromagnetic spin coupling. Display Omitted Research highlights: {yields} Many Fe(II) complexes show thermally induced high spin-low spin crossover. {yields} Spin crossover in spinel compounds is extremely scarce. {yields} Usually, lattice contraction favours the low spin state in Fe(II) complexes. {yields} In these spinels, lattice contraction favours the high spin state. {yields} The stabilisation of the high spin state is explained by spin-spin interactions.

  9. Tuning of the copper-thioether bond in tetradentate N₃S(thioether) ligands; O-O bond reductive cleavage via a [Cu(II)₂(μ-1,2-peroxo)]²⁺/[Cu(III)₂(μ-oxo)₂]²⁺ equilibrium.

    PubMed

    Kim, Sunghee; Ginsbach, Jake W; Billah, A Imtiaz; Siegler, Maxime A; Moore, Cathy D; Solomon, Edward I; Karlin, Kenneth D

    2014-06-01

    Current interest in copper/dioxygen reactivity includes the influence of thioether sulfur ligation, as it concerns the formation, structures, and properties of derived copper-dioxygen complexes. Here, we report on the chemistry of {L-Cu(I)}2-(O2) species L = (DMM)ESE, (DMM)ESP, and (DMM)ESDP, which are N3S(thioether)-based ligands varied in the nature of a substituent on the S atom, along with a related N3O(ether) (EOE) ligand. Cu(I) and Cu(II) complexes have been synthesized and crystallographically characterized. Copper(I) complexes are dimeric in the solid state, [{L-Cu(I)}2](B(C6F5)4)2, however are shown by diffusion-ordered NMR spectroscopy to be mononuclear in solution. Copper(II) complexes with a general formulation [L-Cu(II)(X)](n+) {X = ClO4(-), n = 1, or X = H2O, n = 2} exhibit distorted square pyramidal coordination geometries and progressively weaker axial thioether ligation across the series. Oxygenation (-130 °C) of {((DMM)ESE)Cu(I)}(+) results in the formation of a trans-μ-1,2-peroxodicopper(II) species [{((DMM)ESE)Cu(II)}2(μ-1,2-O2(2-))](2+) (1(P)). Weakening the Cu-S bond via a change to the thioether donor found in (DMM)ESP leads to the initial formation of [{((DMM)ESP)Cu(II)}2(μ-1,2-O2(2-))](2+) (2(P)) that subsequently isomerizes to a bis-μ-oxodicopper(III) complex, [{((DMM)ESP)Cu(III)}2(μ-O(2-))2](2+) (2(O)), with 2(P) and 2(O) in equilibrium (K(eq) = [2(O)]/[2(P)] = 2.6 at -130 °C). Formulations for these Cu/O2 adducts were confirmed by resonance Raman (rR) spectroscopy. This solution mixture is sensitive to the addition of methylsulfonate, which shifts the equilibrium toward the bis-μ-oxo isomer. Further weakening of the Cu-S bond in (DMM)ESDP or substitution with an ether donor in (DMM)EOE leads to only a bis-μ-oxo species (3(O) and 4(O), respectively). Reactivity studies indicate that the bis-μ-oxodicopper(III) species (2(O), 3(O)) and not the trans-peroxo isomers (1(P) and 2(P)) are responsible for the observed ligand

  10. Local interstellar cloud electron density from magnesium and sodium ionization: a comparison.

    NASA Astrophysics Data System (ADS)

    Lallement, R.; Ferlet, R.

    1997-08-01

    The ambient interstellar plasma density (i.e. the plasma density of the interstellar medium surrounding the Sun) directly governs the structure and the size of our heliosphere. Information on this density can be derived from the ionization states of the interstellar species which can be detected in absorption along the paths to the nearby stars, and which can be shown to belong to the Local Interstellar Cloud (LIC). Echelle spectra around the resonance lines of neutral and singly ionized magnesium have been obtained for the nearby star δ Cas with the Goddard High-Resolution Spectrograph (GHRS) on board the Hubble Space Telescope. While apparently a unique velocity component (a unique cloudlet) is detected in both lines of the MgII λλ2800 resonance doublet, at the expected Doppler shift for the LIC, an extremely small λλ2853 Mg line is also detected at a Doppler shift compatible with the LIC motion, allowing a measurement of the LIC MgII/MgI ratio, here found to be 400 (-130,+190). This ratio implies a mean electron density of about 0.28 (-0.14, +0.34)cm^-3^ along this line-of-sight, if equilibrium conditions prevail, and if T=7000K, when using the most recent recombination and charge-exchange rates. This MgII/MgI ratio is larger than for Sirius (R=~220), which lies at 110^o^ from δ Cas, providing some evidence for an ionization gradient in the local cloud. Such an electron density implies a surprisingly large ionization degree, and the upper range of the interval is incompatible with the minimum size of our heliosphere. A second and independent way to derive the electron density along the path to δ Cas uses the simplicity of the LIC geometry in the sky region surrounding the star, which allows an estimate of the H column-density to the star, as well as previous ground-based CaII data, and the measured NaI/CaII ratio and calcium depletion in the LIC. The resulting most probable electron density at 7000K, 0.05cm^-3^, provides a new evidence for a significant