Sample records for accurate ionization balance

  1. Derivation of ionization balance for calcium XVIII/XIX using XRP solar X-ray data

    NASA Astrophysics Data System (ADS)

    Antonucci, E.; Gabriel, A. H.; Doyle, J. G.; Dubau, J.; Faucher, P.; Jordan, C.; Veck, N.

    1984-04-01

    Spectra of calcium from solar flares are used in an attempt to derive an ionization balance for Ca XVIII/Ca XIX. The isothermal assumption inherent in this derivation is shown not to introduce errors, by modelling a number of hypothetical nonisothermal plasmas. The unresolved blend of calcium and argon lines prevents a definitive determination of the results, owing to uncertainties in the ratio of abundances of these elements. The resulting ionization balance curves are presented as a function of the solar argon/calcium abundance ratio. The theoretical ionization balance of Doyle and Raymond is consistent with the data. To within the expected accuracy of the atomic theories, there is no reason to assume that the flare plasma is other than close to steady-state ionization balance.

  2. Remote balance weighs accurately amid high radiation

    NASA Technical Reports Server (NTRS)

    Eggenberger, D. N.; Shuck, A. B.

    1969-01-01

    Commercial beam-type balance, modified and outfitted with electronic controls and digital readout, can be remotely controlled for use in high radiation environments. This allows accurate weighing of breeder-reactor fuel pieces when they are radioactively hot.

  3. Calcium ionization balance and argon/calcium abundance in solar flares

    NASA Astrophysics Data System (ADS)

    Antonucci, E.; Marocchi, D.; Gabriel, A. H.; Doschek, G. A.

    1987-12-01

    An earlier analysis of solar flare calcium spectra from XRP and P78-1 aimed at measuring the calcium ionization balance resulted in an ambiguity due to a line blend between the calcium q line and an Ar XVII line. In the present work the calcium line 'r' is included in the analysis in order to resolve this problem. It is shown that the correct calcium ionization balance is that indicated in the earlier paper as corresponding to an argon/calcium abundance ratio of 0.2. The argon/calcium abundance ratio in the group of solar flares studied is shown to be 0.2 + or - 0.2. It is further argued that while the abundance of heavy elements may be enhanced in energetic flare events, this enhancement is less for argon than for calcium, leading to an argon/calcium ratio smaller than that present in the quiet sun.

  4. Accurate Valence Ionization Energies from Kohn-Sham Eigenvalues with the Help of Potential Adjustors.

    PubMed

    Thierbach, Adrian; Neiss, Christian; Gallandi, Lukas; Marom, Noa; Körzdörfer, Thomas; Görling, Andreas

    2017-10-10

    An accurate yet computationally very efficient and formally well justified approach to calculate molecular ionization potentials is presented and tested. The first as well as higher ionization potentials are obtained as the negatives of the Kohn-Sham eigenvalues of the neutral molecule after adjusting the eigenvalues by a recently [ Görling Phys. Rev. B 2015 , 91 , 245120 ] introduced potential adjustor for exchange-correlation potentials. Technically the method is very simple. Besides a Kohn-Sham calculation of the neutral molecule, only a second Kohn-Sham calculation of the cation is required. The eigenvalue spectrum of the neutral molecule is shifted such that the negative of the eigenvalue of the highest occupied molecular orbital equals the energy difference of the total electronic energies of the cation minus the neutral molecule. For the first ionization potential this simply amounts to a ΔSCF calculation. Then, the higher ionization potentials are obtained as the negatives of the correspondingly shifted Kohn-Sham eigenvalues. Importantly, this shift of the Kohn-Sham eigenvalue spectrum is not just ad hoc. In fact, it is formally necessary for the physically correct energetic adjustment of the eigenvalue spectrum as it results from ensemble density-functional theory. An analogous approach for electron affinities is equally well obtained and justified. To illustrate the practical benefits of the approach, we calculate the valence ionization energies of test sets of small- and medium-sized molecules and photoelectron spectra of medium-sized electron acceptor molecules using a typical semilocal (PBE) and two typical global hybrid functionals (B3LYP and PBE0). The potential adjusted B3LYP and PBE0 eigenvalues yield valence ionization potentials that are in very good agreement with experimental values, reaching an accuracy that is as good as the best G 0 W 0 methods, however, at much lower computational costs. The potential adjusted PBE eigenvalues result in

  5. 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.

  6. Ionization balance for iron XXV, XXIV and XXIII derived from solar flare X-ray spectra

    NASA Astrophysics Data System (ADS)

    Antonucci, E.; Dodero, M. A.; Gabriel, A. H.; Tanaka, K.; Dubau, J.

    1987-06-01

    An analysis has been carried out using over 300 spectra of solar flares from both the XRP instrument on SMM and the SOX instrument on Hinotori. The helium-like iron and associated dielectronic satellite spectra were used in order to derive a revised ionization balance for Fe XXIV/Fe XXV. This is found to lie between the theoretical curves based upon ECIP ionization rates, and those using Lotz formalism, with a tendency to be closer to the former. An extension of the analysis to include Fe XXIII is subject to a somewhat larger uncertainty in the interpretation. However it indicates a similar effect for this ion. Using all three ions, a revised ionization balance for iron is presented.

  7. Ionization balance in Titan's nightside ionosphere

    NASA Astrophysics Data System (ADS)

    Vigren, E.; Galand, M.; Yelle, R. V.; Wellbrock, A.; Coates, A. J.; Snowden, D.; Cui, J.; Lavvas, P.; Edberg, N. J. T.; Shebanits, O.; Wahlund, J.-E.; Vuitton, V.; Mandt, K.

    2015-03-01

    Based on a multi-instrumental Cassini dataset we make model versus observation comparisons of plasma number densities, nP = (nenI)1/2 (ne and nI being the electron number density and total positive ion number density, respectively) and short-lived ion number densities (N+, CH2+, CH3+, CH4+) in the southern hemisphere of Titan's nightside ionosphere over altitudes ranging from 1100 and 1200 km and from 1100 to 1350 km, respectively. The nP model assumes photochemical equilibrium, ion-electron pair production driven by magnetospheric electron precipitation and dissociative recombination as the principal plasma neutralization process. The model to derive short-lived-ion number densities assumes photochemical equilibrium for the short-lived ions, primary ion production by electron-impact ionization of N2 and CH4 and removal of the short-lived ions through reactions with CH4. It is shown that the models reasonably reproduce the observations, both with regards to nP and the number densities of the short-lived ions. This is contrasted by the difficulties in accurately reproducing ion and electron number densities in Titan's sunlit ionosphere.

  8. 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.

  9. Accurate quantification of creatinine in serum by coupling a measurement standard to extractive electrospray ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Huang, Keke; Li, Ming; Li, Hongmei; Li, Mengwan; Jiang, You; Fang, Xiang

    2016-01-01

    Ambient ionization (AI) techniques have been widely used in chemistry, medicine, material science, environmental science, forensic science. AI takes advantage of direct desorption/ionization of chemicals in raw samples under ambient environmental conditions with minimal or no sample preparation. However, its quantitative accuracy is restricted by matrix effects during the ionization process. To improve the quantitative accuracy of AI, a matrix reference material, which is a particular form of measurement standard, was coupled to an AI technique in this study. Consequently the analyte concentration in a complex matrix can be easily quantified with high accuracy. As a demonstration, this novel method was applied for the accurate quantification of creatinine in serum by using extractive electrospray ionization (EESI) mass spectrometry. Over the concentration range investigated (0.166 ~ 1.617 μg/mL), a calibration curve was obtained with a satisfactory linearity (R2 = 0.994), and acceptable relative standard deviations (RSD) of 4.6 ~ 8.0% (n = 6). Finally, the creatinine concentration value of a serum sample was determined to be 36.18 ± 1.08 μg/mL, which is in excellent agreement with the certified value of 35.16 ± 0.39 μg/mL.

  10. Toward the accurate first-principles prediction of ionization equilibria in proteins.

    PubMed

    Khandogin, Jana; Brooks, Charles L

    2006-08-08

    The calculation of pK(a) values for ionizable sites in proteins has been traditionally based on numerical solutions of the Poisson-Boltzmann equation carried out using a high-resolution protein structure. In this paper, we present a method based on continuous constant pH molecular dynamics (CPHMD) simulations, which allows the first-principles description of protein ionization equilibria. Our method utilizes an improved generalized Born implicit solvent model with an approximate Debye-Hückel screening function to account for salt effects and the replica-exchange (REX) protocol for enhanced conformational and protonation state sampling. The accuracy and robustness of the present method are demonstrated by 1 ns REX-CPHMD titration simulations of 10 proteins, which exhibit anomalously large pK(a) shifts for the carboxylate and histidine side chains. The experimental pK(a) values of these proteins are reliably reproduced with a root-mean-square error ranging from 0.6 unit for proteins containing few buried ionizable side chains to 1.0 unit or slightly higher for proteins containing ionizable side chains deeply buried in the core and experiencing strong charge-charge interactions. This unprecedented level of agreement with experimental benchmarks for the de novo calculation of pK(a) values suggests that the CPHMD method is maturing into a practical tool for the quantitative prediction of protein ionization equilibria, and this, in turn, opens a door to atomistic simulations of a wide variety of pH-coupled conformational phenomena in biological macromolecules such as protein folding or misfolding, aggregation, ligand binding, membrane interaction, and catalysis.

  11. Heating the warm ionized medium

    NASA Technical Reports Server (NTRS)

    Reynolds, R. J.; Cox, D. P.

    1992-01-01

    If photoelectric heating by grains within the diffuse ionized component of the interstellar medium is 10 exp -25 ergs/s per H atom, the average value within diffuse H I regions, then grain heating equals or exceeds photoionization heating of the ionized gas. This supplemental heat source would obviate the need for energetic ionizing photons to balance the observed forbidden-line cooling and could be responsible in part for enhanced intensities of some of the forbidden lines.

  12. Accurate optical vector network analyzer based on optical single-sideband modulation and balanced photodetection.

    PubMed

    Xue, Min; Pan, Shilong; Zhao, Yongjiu

    2015-02-15

    A novel optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation and balanced photodetection is proposed and experimentally demonstrated, which can eliminate the measurement error induced by the high-order sidebands in the OSSB signal. According to the analytical model of the conventional OSSB-based OVNA, if the optical carrier in the OSSB signal is fully suppressed, the measurement result is exactly the high-order-sideband-induced measurement error. By splitting the OSSB signal after the optical device-under-test (ODUT) into two paths, removing the optical carrier in one path, and then detecting the two signals in the two paths using a balanced photodetector (BPD), high-order-sideband-induced measurement error can be ideally eliminated. As a result, accurate responses of the ODUT can be achieved without complex post-signal processing. A proof-of-concept experiment is carried out. The magnitude and phase responses of a fiber Bragg grating (FBG) measured by the proposed OVNA with different modulation indices are superimposed, showing that the high-order-sideband-induced measurement error is effectively removed.

  13. Accurate potentiometric determination of lipid membrane-water partition coefficients and apparent dissociation constants of ionizable drugs: electrostatic corrections.

    PubMed

    Elsayed, Mustafa M A; Vierl, Ulrich; Cevc, Gregor

    2009-06-01

    Potentiometric lipid membrane-water partition coefficient studies neglect electrostatic interactions to date; this leads to incorrect results. We herein show how to account properly for such interactions in potentiometric data analysis. We conducted potentiometric titration experiments to determine lipid membrane-water partition coefficients of four illustrative drugs, bupivacaine, diclofenac, ketoprofen and terbinafine. We then analyzed the results conventionally and with an improved analytical approach that considers Coulombic electrostatic interactions. The new analytical approach delivers robust partition coefficient values. In contrast, the conventional data analysis yields apparent partition coefficients of the ionized drug forms that depend on experimental conditions (mainly the lipid-drug ratio and the bulk ionic strength). This is due to changing electrostatic effects originating either from bound drug and/or lipid charges. A membrane comprising 10 mol-% mono-charged molecules in a 150 mM (monovalent) electrolyte solution yields results that differ by a factor of 4 from uncharged membranes results. Allowance for the Coulombic electrostatic interactions is a prerequisite for accurate and reliable determination of lipid membrane-water partition coefficients of ionizable drugs from potentiometric titration data. The same conclusion applies to all analytical methods involving drug binding to a surface.

  14. Iron oxide nanomatrix facilitating metal ionization in matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Obena, Rofeamor P; Lin, Po-Chiao; Lu, Ying-Wei; Li, I-Che; del Mundo, Florian; Arco, Susan dR; Nuesca, Guillermo M; Lin, Chung-Chen; Chen, Yu-Ju

    2011-12-15

    The significance and epidemiological effects of metals to life necessitate the development of direct, efficient, and rapid method of analysis. Taking advantage of its simple, fast, and high-throughput features, we present a novel approach to metal ion detection by matrix-functionalized magnetic nanoparticle (matrix@MNP)-assisted MALDI-MS. Utilizing 21 biologically and environmentally relevant metal ion solutions, the performance of core and matrix@MNP against conventional matrixes in MALDI-MS and laser desorption ionization (LDI) MS were systemically tested to evaluate the versatility of matrix@MNP as ionization element. The matrix@MNPs provided 20- to >100-fold enhancement on detection sensitivity of metal ions and unambiguous identification through characteristic isotope patterns and accurate mass (<5 ppm), which may be attributed to its multifunctional role as metal chelator, preconcentrator, absorber, and reservoir of energy. Together with the comparison on the ionization behaviors of various metals having different ionization potentials (IP), we formulated a metal ionization mechanism model, alluding to the role of exciton pooling in matrix@MNP-assisted MALDI-MS. Moreover, the detection of Cu in spiked tap water demonstrated the practicability of this new approach as an efficient and direct alternative tool for fast, sensitive, and accurate determination of trace metal ions in real samples.

  15. Apparatus for accurate density measurements of fluids based on a magnetic suspension balance

    NASA Astrophysics Data System (ADS)

    Gong, Maoqiong; Li, Huiya; Guo, Hao; Dong, Xueqiang; Wu, J. F.

    2012-06-01

    A new apparatus for accurate pressure, density and temperature (p, ρ, T) measurements over wide ranges of (p, ρ, T) (90 K to 290 K; 0 MPa to 3 MPa; 0 kg/m3 to 2000 kg/m3) is described. This apparatus is based on a magnetic suspension balance which applies the Archimedes' buoyancy principle. In order to verify the new apparatus, comprehensive (p, ρ, T) measurements on pure nitrogen were carried out. The maximum relative standard uncertainty is 0.09% in density. The maximum standard uncertainty in temperature is 5 mK, and that in pressure is 250 Pa for 1.5 MPa and 390 Pa for 3MPa full scale range respectively. The experimental data were compared with selected literature data and good agreements were found.

  16. Neutral Atom Diffusion in a Partially Ionized Prominence Plasma

    NASA Technical Reports Server (NTRS)

    Gilbert, Holly

    2010-01-01

    The support of solar prominences is normally described in terms of a magnetic force on the prominence plasma that balances the solar gravitational force. Because the prominence plasma is only partially ionized. it is necessary to consider in addition the support of the neutral component of the prominence plasma. This support is accomplished through a frictional interaction between the neutral and ionized components of the plasma, and its efficacy depends strongly on the degree of ionization of the plasma. More specifically, the frictional force is proportional to the relative flow of neutral and ion species, and for a sufficiently weakly ionized plasma, this flow must be relatively large to produce a frictional force that balances gravity. A large relative flow, of course, implies significant draining of neutral particles from the prominence. We evaluate the importance of this draining effect for a hydrogen-helium plasma, and consider the observational evidence for cross-field diffusion of neutral prominence material,

  17. Atmospheric Ionization Measurements

    NASA Astrophysics Data System (ADS)

    Slack, Thomas; Mayes, Riley

    2015-04-01

    The measurement of atmospheric ionization is a largely unexplored science that potentially holds the key to better understanding many different geophysical phenomena through this new and valuable source of data. Through the LaACES program, which is funded by NASA through the Louisiana Space Consortium, students at Loyola University New Orleans have pursued the goal of measuring high altitude ionization for nearly three years, and were the first to successfully collect ionization data at altitudes over 30,000 feet using a scientific weather balloon flown from the NASA Columbia Scientific Ballooning Facility in Palestine, TX. In order to measure atmospheric ionization, the science team uses a lightweight and highly customized sensor known as a Gerdien condenser. Among other branches of science the data is already being used for, such as the study of aerosol pollution levels in the atmosphere, the data may also be useful in meteorology and seismology. Ionization data might provide another variable with which to predict weather or seismic activity more accurately and further in advance. Thomas Slack and Riley Mayes have served as project managers for the experiment, and have extensive knowledge of the experiment from the ground up. LaSPACE Louisiana Space Consortium.

  18. Laser-Induced Ionization Efficiency Enhancement On A Filament For Thermal Ionization Mass Spectrometry

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

    Siegfried, M.

    2015-10-14

    The evaluation of trace Uranium and Plutonium isotope ratios for nanogram to femtogram material quantities is a vital tool for nuclear counter-proliferation and safeguard activities. Thermal Ionization Mass Spectrometry (TIMS) is generally accepted as the state of the art technology for highly accurate and ultra-trace measurements of these actinide ratios. However, the very low TIMS ionization yield (typically less than 1%) leaves much room for improvement. Enhanced ionization of Nd and Sm from a TIMS filament was demonstrated using wavelength resonance with a nanosecond (pulse width) laser operating at 10 Hz when light was directed toward the filament.1 For thismore » study, femtosecond and picosecond laser capabilities were to be employed to study the dissociation and ionization mechanisms of actinides/lanthanides and measure the enhanced ionization of the metal of interest. Since the underlying chemistry of the actinide/lanthanide carbides produced and dissociated on a TIMS filament is not well understood, the experimental parameters affecting the photodissociation and photoionization with one and two laser beams were to be investigated.« less

  19. Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

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

    Liu, Yuan; Gottwald, T.; Mattolat, C.

    We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 74s5s h 4F 9/2, 3d 74s4d f 4G 11/2, and 3d 74s4d f 4H 13/2 and converge to the first four excited states of singly ionized Co. Our analyses of the Rydberg series yield 63564.689 0.036 cm -1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonancemore » ionization scheme that employs an autoinizing Rydberg state in the last transition, we obtained an overall ionization efficiency of about 18% for Co.« less

  20. Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

    DOE PAGES

    Liu, Yuan; Gottwald, T.; Mattolat, C.; ...

    2017-03-20

    We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 74s5s h 4F 9/2, 3d 74s4d f 4G 11/2, and 3d 74s4d f 4H 13/2 and converge to the first four excited states of singly ionized Co. Our analyses of the Rydberg series yield 63564.689 0.036 cm -1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonancemore » ionization scheme that employs an autoinizing Rydberg state in the last transition, we obtained an overall ionization efficiency of about 18% for Co.« less

  1. Investigation into accurate mass capability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, with respect to radical ion species.

    PubMed

    Wyatt, Mark F; Stein, Bridget K; Brenton, A Gareth

    2006-05-01

    Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been shown to be an effective technique for the characterization of organometallic, coordination, and highly conjugated compounds. The preferred matrix is 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), with radical ions observed. However, MALDI-TOFMS is generally not favored for accurate mass measurement. A specific method had to be developed for such compounds to assure the quality of our accurate mass results. Therefore, in this preliminary study, two methods of data acquisition, and both even-electron (EE+) ion and odd-electron (OE+.) radical ion mass calibration standards, have been investigated to establish the basic measurement technique. The benefit of this technique is demonstrated for a copper compound for which ions were observed by MALDI, but not by electrospray (ESI) or liquid secondary ion mass spectrometry (LSIMS); a mean mass accuracy error of -1.2 ppm was obtained.

  2. Calculation of multiphoton ionization processes

    NASA Technical Reports Server (NTRS)

    Chang, T. N.; Poe, R. T.

    1976-01-01

    We propose an accurate and efficient procedure in the calculation of multiphoton ionization processes. In addition to the calculational advantage, this procedure also enables us to study the relative contributions of the resonant and nonresonant intermediate states.

  3. Energy Balance for a Sonoluminescence Bubble Yields a Measure of Ionization Potential Lowering

    NASA Astrophysics Data System (ADS)

    Kappus, B.; Bataller, A.; Putterman, S. J.

    2013-12-01

    Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization >36%. Analysis reveals only 2.1±0.6eV/atom of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

  4. Energy balance for a sonoluminescence bubble yields a measure of ionization potential lowering.

    PubMed

    Kappus, B; Bataller, A; Putterman, S J

    2013-12-06

    Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization >36%. Analysis reveals only 2.1±0.6  eV/atom of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

  5. Accurate Ionization Energies for Mononuclear Copper Complexes Remain a Challenge for Density Functional Theory.

    PubMed

    Dereli, Büsra; Ortuño, Manuel A; Cramer, Christopher J

    2018-04-17

    Copper is ubiquitous and its one-electron redox chemistry is central to many catalytic processes. Modeling such chemistry requires electronic structure methods capable of the accurate prediction of ionization energies (IEs) for compounds including copper in different oxidation states and supported by various ligands. Herein, we estimate IEs for 12 mononuclear Cu species previously reported in the literature by using 21 modern density functionals and the DLPNO-CCSD(T) wave function theory model; we consider extrapolated values of the latter to provide reference values of acceptable accuracy. Our results reveal a considerable diversity in functional performance. Although there is nearly always at least one functional that performs well for any given species, there are none that do so for every member of the test set, and certain cases are particularly pathological. Over the entire test set, the SOGGA11-X functional performs best with a mean unsigned error (MUE) of 0.22 eV. PBE0, ωB97X-D, CAM-B3LYP, M11-L, B3LYP, and M11 exhibit MUEs ranging between 0.23 and 0.34 eV. When including relativistic effects with the zero-order regular approximation, ωB97X-D, CAM-B3LYP, and PBE0 are found to provide the best accuracy. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Laser stripping of hydrogen atoms by direct ionization

    DOE PAGES

    Brunetti, E.; Becker, W.; Bryant, H. C.; ...

    2015-05-08

    Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

  7. Laser stripping of hydrogen atoms by direct ionization

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

    Brunetti, E.; Becker, W.; Bryant, H. C.

    Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

  8. Acceptor Ionization Energies in GaN*

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Ban Chen, An

    2001-03-01

    The k.p Hamiltonian and a model potential are used to deduce the acceptor ionization energies in GaN from a systematic study of the chemical trend in GaAs, GaP, and InP. The acceptors studied include Be, Mg, Ca, Zn, and Cd on the cation sites and C, Si, and Ge on the anion sites. Our calculated acceptor ionization energies are estimated to be accurate to better than ten percent across the board. The ionization energies of C and Be (152 and 187 meV respectively) in wurtzite GaN are found to be lower than that of Mg (224 meV). The C was found to behave like the hydrogenic acceptor in all systems and it has the smallest ionization energy among all the acceptors studied.

  9. Electron-Atom Ionization Calculations using Propagating Exterior Complex Scaling

    NASA Astrophysics Data System (ADS)

    Bartlett, Philip

    2007-10-01

    The exterior complex scaling method (Science 286 (1999) 2474), pioneered by Rescigno, McCurdy and coworkers, provided highly accurate ab initio solutions for electron-hydrogen collisions by directly solving the time-independent Schr"odinger equation in coordinate space. An extension of this method, propagating exterior complex scaling (PECS), was developed by Bartlett and Stelbovics (J. Phys. B 37 (2004) L69, J. Phys. B 39 (2006) R379) and has been demonstrated to provide computationally efficient and accurate calculations of ionization and scattering cross sections over a large range of energies below, above and near the ionization threshold. An overview of the PECS method for three-body collisions and the computational advantages of its propagation and iterative coupling techniques will be presented along with results of: (1) near-threshold ionization of electron-hydrogen collisions and the Wannier threshold laws, (2) scattering cross section resonances below the ionization threshold, and (3) total and differential cross sections for electron collisions with excited targets and hydrogenic ions from low through to high energies. Recently, the PECS method has been extended to solve four-body collisions using time-independent methods in coordinate space and has initially been applied to the s-wave model for electron-helium collisions. A description of the extensions made to the PECS method to facilitate these significantly more computationally demanding calculations will be given, and results will be presented for elastic, single-excitation, double-excitation, single-ionization and double-ionization collisions.

  10. Calculations of acceptor ionization energies in GaN

    NASA Astrophysics Data System (ADS)

    Wang, H.; Chen, A.-B.

    2001-03-01

    The k.p Hamiltonian and a model potential are used to deduce the acceptor ionization energies in GaN from a systematic study of the chemical trend in GaAs, GaP, and InP. The acceptors studied include Be, Mg, Ca, Zn, and Cd on the cation sites and C, Si, and Ge on the anion sites. Our calculated acceptor ionization energies are estimated to be accurate to better than 10% across the board. The ionization energies of C and Be (152 and 187 meV, respectively) in wurtzite GaN are found to be lower than that of Mg (224 meV). The C was found to behave like the hydrogenic acceptor in all systems and it has the smallest ionization energy among all the acceptors studied.

  11. Ionized hypercalcemia in dogs: a retrospective study of 109 cases (1998-2003).

    PubMed

    Messinger, J S; Windham, W R; Ward, C R

    2009-01-01

    Serum hypercalcemia in dogs has been reported in association with a variety of diseases. Serum-ionized calcium (iCa) concentration is a more accurate measure of hypercalcemia than total serum calcium or corrected serum calcium concentrations. The severity of hypercalcemia has been utilized to suggest the most likely differential diagnosis for the hypercalcemia. Diseases causing ionized hypercalcemia may be different than those that cause increases in total or corrected serum calcium concentrations. The severity of ionized hypercalcemia in specific diseases cannot be used to determine the most likely differential diagnosis for ionized hypercalcemia. One-hundred and nine client-owned dogs with a definitive cause for their ionized hypercalcemia evaluated between 1998 and 2003 were included in this study. Retrospective, medical records review. Neoplasia, specifically lymphosarcoma, followed by renal failure, hyperparathyroidism, and hypoadrenocorticism were the most common causes of ionized hypercalcemia. Dogs with lymphoma and anal sac adenocarcinoma have higher serum iCa concentrations than those with renal failure, hypoadrenocorticism, and other types of neoplasia. The magnitude of serum-ionized hypercalcemia did not predict specific disease states. Serum-ionized hypercalcemia was most commonly associated with neoplasia, specifically lymphosarcoma. Although dogs with lymphosarcoma and anal sac adenocarcinoma had higher serum iCa concentrations than dogs with other diseases, the magnitude of the serum iCa concentration could not be used to predict the cause of hypercalcemia. Total serum calcium and corrected calcium concentrations did not accurately reflect the calcium status of the dogs in this study.

  12. Variational description of the positive column with two-stem ionization

    NASA Technical Reports Server (NTRS)

    Crawford, F. W.

    1979-01-01

    The ionization balance in diffusion dominated discharges which depends on both one and two step ionization processes is considered. The Spenke diffusion equation (D sq delta n + neutrino n + sq kn =0) describing such conditions is solved by the Rayleigh-Ritz variational method. Simple analytic approximations to the density profile, and the similarity relation between neutrino,k,D and the discharge dimensions, are derived for planar and cylindrical geometry, and compared with exact computations for certain limiting cases.

  13. Attenuation characteristics of electromagnetic waves in a weak collisional and fully ionized dusty plasma

    NASA Astrophysics Data System (ADS)

    Dan, Li; Guo, Li-Xin; Li, Jiang-Ting; Chen, Wei; Yan, Xu; Huang, Qing-Qing

    2017-09-01

    The expression of complex dielectric permittivity for non-magnetized fully ionized dusty plasma is obtained based on the kinetic equation in the Fokker-Planck-Landau collision model and the charging equation of the statistical theory. The influences of density, average size of dust grains, and balanced charging of the charge number of dust particles on the attenuation properties of electromagnetic waves in fully ionized dusty plasma are investigated by calculating the attenuation constant. In addition, the attenuation characteristics of weakly ionized and fully ionized dusty plasmas are compared. Results enriched the physical mechanisms of microwave attenuation for fully ionized dusty plasma and provide a theoretical basis for future studies.

  14. Advanced Kr Atomic Structure and Ionization Kinetics for Pinches on ZR

    NASA Astrophysics Data System (ADS)

    Dasgupta, Arati; Clark, Robert; Giuliani, John; Ouart, Nick; Davis, Jack; Jones, Brent; Ampleford, Dave; Hansen, Stephanie

    2011-10-01

    High fluence photon sources above 10 keV are a challenge for HED plasmas. This motivates Kr atomic modeling as its K-shell radiation starts at 13 keV. We have developed atomic structure and collisional-radiatve data for the full K-and L-shell and much of the M-shell using the the state-of-the-art Flexible Atomic Code. All relevant atomic collisional and radiative processes that affect ionization balance and are necessary to accurately model the pinch dynamics and the spectroscopic details of the emitted radiation are included in constructing the model. This non-LTE CRE model will be used to generate synthetic spectra for fixed densities and temperatures relevant for Kr gas-puff simulations in ZR. Work supported by DOE/NNSA. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. BALANCE: Towards a Usable Pervasive Wellness Application with Accurate Activity Inference

    PubMed Central

    Denning, Tamara; Andrew, Adrienne; Chaudhri, Rohit; Hartung, Carl; Lester, Jonathan; Borriello, Gaetano; Duncan, Glen

    2010-01-01

    Technology offers the potential to objectively monitor people’s eating and activity behaviors and encourage healthier lifestyles. BALANCE is a mobile phone-based system for long term wellness management. The BALANCE system automatically detects the user’s caloric expenditure via sensor data from a Mobile Sensing Platform unit worn on the hip. Users manually enter information on foods eaten via an interface on an N95 mobile phone. Initial validation experiments measuring oxygen consumption during treadmill walking and jogging show that the system’s estimate of caloric output is within 87% of the actual value. Future work will refine and continue to evaluate the system’s efficacy and develop more robust data input and activity inference methods. PMID:20445819

  16. 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.

  17. Propagation direction reversal of ionization zones in the transition between high and low current magnetron sputtering

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

    School of Materials Science and Engineering, State Key Lab for Materials Processing and Die & Mold Technology, Huazhong University of Science and Technology, Wuhan 430074, China; Department of Physics, University of California Berkeley, Berkeley, California 94720, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA

    2014-12-11

    Past research has revealed the propagation of dense, asymmetric ionization zones in both high and low current magnetron discharges. Here we report about the direction reversal of ionization zone propagation as observed with fast cameras. At high currents, zones move in the E B direction with velocities of 103 to 104 m/s. However at lower currents, ionization zones are observed to move in the opposite, the -E B direction, with velocities ~;; 103 m/s. It is proposed that the direction reversal is associated with the local balance of ionization and supply of neutrals in the ionization zone.

  18. Experimental investigation of the ionization mechanisms of uranium in thermal ionization mass spectrometry in the presence of carbon

    NASA Astrophysics Data System (ADS)

    Kraiem, M.; Mayer, K.; Gouder, T.; Seibert, A.; Wiss, T.; Thiele, H.; Hiernaut, J.-P.

    2010-01-01

    Thermal ionization mass spectrometry (TIMS) is a well established instrumental technique for providing accurate and precise isotope ratio measurements of elements with reasonably low first ionization potential. In nuclear safeguards and in environmental research, it is often required to measure the isotope ratios in small samples of uranium. Empirical studies had shown that the ionization yield of uranium and plutonium in a TIMS ion source can be significantly increased in the presence of a carbon source. But, even though carbon appeared crucial in providing high ionization yields, processes taking place on the ionization surface were still not well understood. This paper describes the experimental results obtained from an extended study on the evaporation and ionization mechanisms of uranium occurring on a rhenium mass spectrometry filament in the presence of carbon. Solid state reactions were investigated using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Additionally, vaporization measurements were performed with a modified-Knudsen cell mass spectrometer for providing information on the neutral uranium species in the vapor phase. Upon heating, under vacuum, the uranyl nitrate sample was found to turn into a uranium carbide compound, independent of the type of carbon used as ionization enhancer. With further heating, uranium carbide leads to formation of single charged uranium metal ions and a small amount of uranium carbide ions. The results are relevant for a thorough understanding of the ion source chemistry of a uranyl nitrate sample under reducing conditions. The significant increase in ionization yield described by many authors on the basis of empirical results can be now fully explained and understood.

  19. Surface Mass Balance of the Columbia Glacier, Alaska, 1978 and 2010 Balance Years

    USGS Publications Warehouse

    O'Neel, Shad

    2012-01-01

    Although Columbia Glacier is one of the largest sources of glacier mass loss in Alaska, surface mass balance measurements are sparse, with only a single data set available from 1978. The dearth of surface mass-balance data prohibits partitioning of the total mass losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total mass balance. During 2010, the U.S. Geological Survey collected surface balance data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual balance for balance year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface balance, and uses these observations to constrain the 2010 values, particularly the shape of the balance profile. Both years exhibit balances indicative of near-equilibrium surface mass-balance conditions, and demonstrate the importance of dynamic processes during the rapid retreat.

  20. Theory of dissociative tunneling ionization

    NASA Astrophysics Data System (ADS)

    Svensmark, Jens; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2016-05-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees of freedom. In the regime where the BO approximation is applicable, imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally, the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.

  1. Increased upstream ionization due to formation of a double layer.

    PubMed

    Thakur, S Chakraborty; Harvey, Z; Biloiu, I A; Hansen, A; Hardin, R A; Przybysz, W S; Scime, E E

    2009-01-23

    We report observations that confirm a theoretical prediction that formation of a current-free double layer in a plasma expanding into a chamber of larger diameter is accompanied by an increase in ionization upstream of the double layer. The theoretical model argues that the increased ionization is needed to balance the difference in diffusive losses upstream and downstream of the expansion region. In our expanding helicon source experiments, we find that the upstream plasma density increases sharply at the same antenna frequency at which the double layer appears.

  2. Partially ionized hydrogen plasma in strong magnetic fields.

    PubMed

    Potekhin, A Y; Chabrier, G; Shibanov, Y A

    1999-08-01

    We study the thermodynamic properties of a partially ionized hydrogen plasma in strong magnetic fields, B approximately 10(12)-10(13) G, typical of neutron stars. The properties of the plasma depend significantly on the quantum-mechanical sizes and binding energies of the atoms, which are strongly modified by thermal motion across the field. We use new fitting formulas for the atomic binding energies and sizes, based on accurate numerical calculations and valid for any state of motion of the atom. In particular, we take into account decentered atomic states, neglected in previous studies of thermodynamics of magnetized plasmas. We also employ analytic fits for the thermodynamic functions of nonideal fully ionized electron-ion Coulomb plasmas. This enables us to construct an analytic model of the free energy. An ionization equilibrium equation is derived, taking into account the strong magnetic field effects and the nonideality effects. This equation is solved by an iteration technique. Ionization degrees, occupancies, and the equation of state are calculated.

  3. RICO: A NEW APPROACH FOR FAST AND ACCURATE REPRESENTATION OF THE COSMOLOGICAL RECOMBINATION HISTORY

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

    Fendt, W. A.; Wandelt, B. D.; Chluba, J.

    2009-04-15

    We present RICO, a code designed to compute the ionization fraction of the universe during the epoch of hydrogen and helium recombination with an unprecedented combination of speed and accuracy. This is accomplished by training the machine learning code PICO on the calculations of a multilevel cosmological recombination code which self-consistently includes several physical processes that were neglected previously. After training, RICO is used to fit the free electron fraction as a function of the cosmological parameters. While, for example, at low redshifts (z {approx}< 900), much of the net change in the ionization fraction can be captured by loweringmore » the hydrogen fudge factor in RECFAST by about 3%, RICO provides a means of effectively using the accurate ionization history of the full recombination code in the standard cosmological parameter estimation framework without the need to add new or refined fudge factors or functions to a simple recombination model. Within the new approach presented here, it is easy to update RICO whenever a more accurate full recombination code becomes available. Once trained, RICO computes the cosmological ionization history with negligible fitting error in {approx}10 ms, a speedup of at least 10{sup 6} over the full recombination code that was used here. Also RICO is able to reproduce the ionization history of the full code to a level well below 0.1%, thereby ensuring that the theoretical power spectra of cosmic microwave background (CMB) fluctuations can be computed to sufficient accuracy and speed for analysis from upcoming CMB experiments like Planck. Furthermore, it will enable cross-checking different recombination codes across cosmological parameter space, a comparison that will be very important in order to assure the accurate interpretation of future CMB data.« less

  4. The Six-Component Wind Balance

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1923-01-01

    Dr. Zahm's report is a description of the six-component wind-tunnel balance in use at the Aerodynamic Laboratory, Washington Navy Yard. The description of the balance gives the mechanical details and the method of operation, and is accompanied by line drawings showing the construction of the balance. The balance is of particular interest, as it allows the model to be set up quickly and accurately in roll, pitch, and yaw, without stopping the wind. It is possible to measure automatically, directly, and independently the drag, cross-wind force, and lift; also the rolling, pitching, and yawing moments. It is also possible to make the balance self-recording.

  5. Fatty acids composition of Caenorhabditis elegans using accurate mass GCMS-QTOF

    PubMed Central

    Henry, Parise; Owopetu, Olufunmilayo; Adisa, Demilade; Nguyen, Thao; Anthony, Kevin; Ijoni-Animadu, David; Jamadar, Sakha; Abdel-Rahman, Fawzia; Saleh, Mahmoud A.

    2016-01-01

    The free living nematode Caenorhabditis elegans is a proven model organism for lipid metabolism research. Total lipids of C. elegans were extracted using chloroform, methanol 2:1(v/v). Fatty acids composition of the extracted total lipids were converted to their corresponding methyl esters (FAMEs) and analyzed by gas chromatography/accurate mass quadrupole time of flight mass spectrometry (GCMS-QTOF) using both electron ionization (EI) and chemical ionization (CI) techniques. 28 fatty acids consisting of 12 to 22 carbon atoms were identified, 65% of them were unsaturated. Fatty acids containing 12 to 17 carbons were mostly saturated with stearic acid (18:0) as the major constituent. Several branched-chain fatty acids were identified. Methyl-14-methylhexadecanoate (iso-17:0) was the major identified branched fatty acid. This is the first report to detect the intact molecular parent ions of the identified fatty acids using chemical ionization compared to electron ionization which produced fragmentations of the fatty acids methyl esters (FAMEs). PMID:27166662

  6. A Dynamic/Anisotropic Low Earth Orbit (LEO) Ionizing Radiation Model

    NASA Technical Reports Server (NTRS)

    Badavi, Francis F.; West, Katie J.; Nealy, John E.; Wilson, John W.; Abrahms, Briana L.; Luetke, Nathan J.

    2006-01-01

    The International Space Station (ISS) provides the proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the experimental validation of ionizing radiation environmental models, nuclear transport code algorithms, and nuclear reaction cross sections. Indeed, prior measurements on the Space Transportation System (STS; Shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the Low Earth Orbit (LEO) environment. Previous studies using Computer Aided Design (CAD) models of the evolving ISS configurations with Thermo Luminescent Detector (TLD) area monitors, demonstrated that computational dosimetry requires environmental models with accurate non-isotropic as well as dynamic behavior, detailed information on rack loading, and an accurate 6 degree of freedom (DOF) description of ISS trajectory and orientation.

  7. Quantum statistical mechanics of dense partially ionized hydrogen

    NASA Technical Reports Server (NTRS)

    Dewitt, H. E.; Rogers, F. J.

    1972-01-01

    The theory of dense hydrogen plasmas beginning with the two component quantum grand partition function is reviewed. It is shown that ionization equilibrium and molecular dissociation equilibrium can be treated in the same manner with proper consideration of all two-body states. A quantum perturbation expansion is used to give an accurate calculation of the equation of state of the gas for any degree of dissociation and ionization. The statistical mechanical calculation of the plasma equation of state is intended for stellar interiors. The general approach is extended to the calculation of the equation of state of the outer layers of large planets.

  8. Microprocessor-Controlled Laser Balancing System

    NASA Technical Reports Server (NTRS)

    Demuth, R. S.

    1985-01-01

    Material removed by laser action as part tested for balance. Directed by microprocessor, laser fires appropriate amount of pulses in correct locations to remove necessary amount of material. Operator and microprocessor software interact through video screen and keypad; no programing skills or unprompted system-control decisions required. System provides complete and accurate balancing in single load-and-spinup cycle.

  9. Developing hybrid approaches to predict pKa values of ionizable groups

    PubMed Central

    Witham, Shawn; Talley, Kemper; Wang, Lin; Zhang, Zhe; Sarkar, Subhra; Gao, Daquan; Yang, Wei

    2011-01-01

    Accurate predictions of pKa values of titratable groups require taking into account all relevant processes associated with the ionization/deionization. Frequently, however, the ionization does not involve significant structural changes and the dominating effects are purely electrostatic in origin allowing accurate predictions to be made based on the electrostatic energy difference between ionized and neutral forms alone using a static structure. On another hand, if the change of the charge state is accompanied by a structural reorganization of the target protein, then the relevant conformational changes have to be taken into account in the pKa calculations. Here we report a hybrid approach that first predicts the titratable groups, which ionization is expected to cause conformational changes, termed “problematic” residues, then applies a special protocol on them, while the rest of the pKa’s are predicted with rigid backbone approach as implemented in multi-conformation continuum electrostatics (MCCE) method. The backbone representative conformations for “problematic” groups are generated with either molecular dynamics simulations with charged and uncharged amino acid or with ab-initio local segment modeling. The corresponding ensembles are then used to calculate the pKa of the “problematic” residues and then the results are averaged. PMID:21744395

  10. Decision peptide-driven: a free software tool for accurate protein quantification using gel electrophoresis and matrix assisted laser desorption ionization time of flight mass spectrometry.

    PubMed

    Santos, Hugo M; Reboiro-Jato, Miguel; Glez-Peña, Daniel; Nunes-Miranda, J D; Fdez-Riverola, Florentino; Carvallo, R; Capelo, J L

    2010-09-15

    The decision peptide-driven tool implements a software application for assisting the user in a protocol for accurate protein quantification based on the following steps: (1) protein separation through gel electrophoresis; (2) in-gel protein digestion; (3) direct and inverse (18)O-labeling and (4) matrix assisted laser desorption ionization time of flight mass spectrometry, MALDI analysis. The DPD software compares the MALDI results of the direct and inverse (18)O-labeling experiments and quickly identifies those peptides with paralleled loses in different sets of a typical proteomic workflow. Those peptides are used for subsequent accurate protein quantification. The interpretation of the MALDI data from direct and inverse labeling experiments is time-consuming requiring a significant amount of time to do all comparisons manually. The DPD software shortens and simplifies the searching of the peptides that must be used for quantification from a week to just some minutes. To do so, it takes as input several MALDI spectra and aids the researcher in an automatic mode (i) to compare data from direct and inverse (18)O-labeling experiments, calculating the corresponding ratios to determine those peptides with paralleled losses throughout different sets of experiments; and (ii) allow to use those peptides as internal standards for subsequent accurate protein quantification using (18)O-labeling. In this work the DPD software is presented and explained with the quantification of protein carbonic anhydrase. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  11. Accurate Mass Fragment Library for Rapid Analysis of Pesticides on Produce Using Ambient Pressure Desorption Ionization with High-Resolution Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Kern, Sara E.; Lin, Lora A.; Fricke, Frederick L.

    2014-08-01

    U.S. food imports have been increasing steadily for decades, intensifying the need for a rapid and sensitive screening technique. A method has been developed that uses foam disks to sample the surface of incoming produce. This work provides complimentary information to the extensive amount of published pesticide fragmentation data collected using LCMS systems (Sack et al. Journal of Agricultural and Food Chemistry, 59, 6383-6411, 2011; Mol et al. Analytical and Bioanalytical Chemistry, 403, 2891-2908, 2012). The disks are directly analyzed using transmission-mode direct analysis in real time (DART) ambient pressure desorption ionization coupled to a high resolution accurate mass-mass spectrometer (HRAM-MS). In order to provide more certainty in the identification of the pesticides detected, a library of accurate mass fragments and isotopes of the protonated parent molecular ion (the [M+H]+) has been developed. The HRAM-MS is equipped with a quadrupole mass filter, providing the capability of "data-dependent" fragmentation, as opposed to "all -ion" fragmentation (where all of the ions enter a collision chamber and are fragmented at once). A temperature gradient for the DART helium stream and multiple collision energies were employed to detect and fragment 164 pesticides of varying chemical classes, sizes, and polarities. The accurate mass information of precursor ([M+H]+ ion) and fragment ions is essential in correctly identifying chemical contaminants on the surface of imported produce. Additionally, the inclusion of isotopes of the [M+H]+ in the database adds another metric to the confirmation process. The fragmentation data were collected using a Q-Exactive mass spectrometer and were added to a database used to process data collected with an Exactive mass spectrometer, an instrument that is more readily available for this screening application. The commodities investigated range from smooth-skinned produce such as apples to rougher surfaces like broccoli. The

  12. Cardiac imaging modalities with ionizing radiation: the role of informed consent.

    PubMed

    Paterick, Timothy E; Jan, M Fuad; Paterick, Zachary R; Tajik, A Jamil; Gerber, Thomas C

    2012-06-01

    Informed consent ideally results in patient autonomy and rational health care decisions. Frequently, patients face complex medical decisions that require a delicate balancing of anticipated benefits and potential risks, which is the concept of informed consent. This balancing process requires an understanding of available medical evidence and alternative medical options, and input from experienced physicians. The informed consent doctrine places a positive obligation on physicians to partner with patients as they try to make the best decision for their specific medical situation. The high prevalence and mortality related to heart disease in our society has led to increased cardiac imaging with modalities that use ionizing radiation. This paper reviews how physicians can meet the ideals of informed consent when considering cardiac imaging with ionizing radiation, given the limited evidence for risks and benefits. The goal is an informed patient making rational choices based on available medical information. Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  13. CMacIonize: Monte Carlo photoionisation and moving-mesh radiation hydrodynamics

    NASA Astrophysics Data System (ADS)

    Vandenbroucke, Bert; Wood, Kenneth

    2018-02-01

    CMacIonize simulates the self-consistent evolution of HII regions surrounding young O and B stars, or other sources of ionizing radiation. The code combines a Monte Carlo photoionization algorithm that uses a complex mix of hydrogen, helium and several coolants in order to self-consistently solve for the ionization and temperature balance at any given time, with a standard first order hydrodynamics scheme. The code can be run as a post-processing tool to get the line emission from an existing simulation snapshot, but can also be used to run full radiation hydrodynamical simulations. Both the radiation transfer and the hydrodynamics are implemented in a general way that is independent of the grid structure that is used to discretize the system, allowing it to be run both as a standard fixed grid code and also as a moving-mesh code.

  14. Ionization Injection of Electrons into a Plasma Wakefield Accelerator at FACET

    NASA Astrophysics Data System (ADS)

    Clayton, Chris; E-200 At Facet Collaboration

    2013-10-01

    In the PWFA experiments at FACET, a low ionization-potential (IP) metal vapor gas (Li) is confined within a heat-pipe oven by a higher IP buffer gas (typically He). The Li is easily field-ionized by the FACET beam. A non-linear wake is formed in the blowout regime when the 20.3 GeV bunch containing 2e10 electrons in a σz ~ 30 μm is focused to a (vacuum) σr < 25 near the ~ 10cm-long boundary region. There the Li density rises from zero up to the oven's 30cm-long flat-topped density of 2.5e17 cm-3. To obtain a mono-energetic beam from accelerated ionization-injected electrons at the far end of the oven--the goal of this experiment--it is necessary for the FACET beam to have a betatron pinch just where the flat-topped region begins; i.e., where the wake wavelength is no longer changing. If the buffer gas contains a mixture of He and a moderate IP gas, the ``impurity'' gases will also be field ionized and potentially contribute more charge to the injected bunch than with He alone. Moderate IP gases were added to the He buffer gas: 10%, 20%, and 50% Ar (balance He) and 30% Ne (balance He) have been used. Evidence for ionization injection and acceleration appears through the observation of distinct features, characterized by their very narrow size and thus angular spread, at the image plane of a magnetic imaging spectrometer. Analysis aimed at characterizing these features with respect to energy, charge, and angular spread is underway and will be presented. This work was supported by the DOE and the NSF.

  15. HEATING OF THE WARM IONIZED MEDIUM BY LOW-ENERGY COSMIC RAYS

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

    Walker, Mark A., E-mail: Mark.Walker@manlyastrophysics.org

    2016-02-10

    In light of evidence for a high ionization rate due to low-energy cosmic rays (LECR) in diffuse molecular gas in the solar neighborhood, we evaluate their heat input to the warm ionized medium (WIM). LECR are much more effective at heating plasma than they are at heating neutrals. We show that the upper end of the measured ionization rates corresponds to a local LECR heating rate sufficient to maintain the WIM against radiative cooling, independent of the nature of the ionizing particles or the detailed shape of their spectrum. Elsewhere in the Galaxy the LECR heating rates may be highermore » than those measured locally. In particular, higher fluxes of LECR have been suggested for the inner Galactic disk, based on the observed hard X-ray emission, with correspondingly larger heating rates implied for the WIM. We conclude that LECR play an important and perhaps dominant role in the thermal balance of the WIM.« less

  16. Measuring Ionization in Highly Compressed, Near-Degenerate Plasmas

    NASA Astrophysics Data System (ADS)

    Doeppner, Tilo; Kraus, D.; Neumayer, P.; Bachmann, B.; Collins, G. W.; Divol, L.; Kritcher, A.; Landen, O. L.; Pak, A.; Weber, C.; Fletcher, L.; Glenzer, S. H.; Falcone, R. W.; Saunders, A.; Chapman, D.; Baggott, R.; Gericke, D. O.; Yi, A.

    2016-10-01

    A precise knowledge of ionization at given temperature and density is required to accurately model compressibility and heat capacity of materials at extreme conditions. We use x-ray Thomson scattering to characterize the plasma conditions in plastic and beryllium capsules near stagnation in implosion experiments at the National Ignition Facility. We expect the capsules to be compressed to more than 20x and electron densities approaching 1025 cm-3, corresponding to a Fermi energy of 170 eV. Zinc Heα x-rays (9 keV) scattering at 120° off the plasma yields high sensitivity to K-shell ionization, while at the same time constraining density and temperature. We will discuss recent results in the context of ionization potential depression at these extreme conditions. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  17. 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.

  18. Determination of structure parameters in strong-field tunneling ionization theory of molecules

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

    Zhao Songfeng; Jin Cheng; College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou, Gansu 730070

    2010-03-15

    In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wave function of the molecular orbital from which the electron is removed. The orbital wave functions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory. We show that the asymptotic wave function can be improved with an iteration method and after one iteration accurate asymptotic wave functions and structure parameters are determined. Withmore » the new parameters we examine the alignment-dependent tunneling ionization probabilities for several molecules and compare with other calculations and with recent measurements, including ionization from inner molecular orbitals.« less

  19. A Multistep Algorithm for the Radiation Hydrodynamical Transport of Cosmological Ionization Fronts and Ionized Flows

    NASA Astrophysics Data System (ADS)

    Whalen, Daniel; Norman, Michael L.

    2006-02-01

    Radiation hydrodynamical transport of ionization fronts (I-fronts) in the next generation of cosmological reionization simulations holds the promise of predicting UV escape fractions from first principles as well as investigating the role of photoionization in feedback processes and structure formation. We present a multistep integration scheme for radiative transfer and hydrodynamics for accurate propagation of I-fronts and ionized flows from a point source in cosmological simulations. The algorithm is a photon-conserving method that correctly tracks the position of I-fronts at much lower resolutions than nonconservative techniques. The method applies direct hierarchical updates to the ionic species, bypassing the need for the costly matrix solutions required by implicit methods while retaining sufficient accuracy to capture the true evolution of the fronts. We review the physics of ionization fronts in power-law density gradients, whose analytical solutions provide excellent validation tests for radiation coupling schemes. The advantages and potential drawbacks of direct and implicit schemes are also considered, with particular focus on problem time-stepping, which if not properly implemented can lead to morphologically plausible I-front behavior that nonetheless departs from theory. We also examine the effect of radiation pressure from very luminous central sources on the evolution of I-fronts and flows.

  20. Ionization chamber-based reference dosimetry of intensity modulated radiation beams.

    PubMed

    Bouchard, Hugo; Seuntjens, Jan

    2004-09-01

    The present paper addresses reference dose measurements using thimble ionization chambers for quality assurance in IMRT fields. In these radiation fields, detector fluence perturbation effects invalidate the application of open-field dosimetry protocol data for the derivation of absorbed dose to water from ionization chamber measurements. We define a correction factor C(Q)IMRT to correct the absorbed dose to water calibration coefficient N(D, w)Q for fluence perturbation effects in individual segments of an IMRT delivery and developed a calculation method to evaluate the factor. The method consists of precalculating, using accurate Monte Carlo techniques, ionization chamber, type-dependent cavity air dose, and in-phantom dose to water at the reference point for zero-width pencil beams as a function of position of the pencil beams impinging on the phantom surface. These precalculated kernels are convolved with the IMRT fluence distribution to arrive at the dose-to-water-dose-to-cavity air ratio [D(a)w (IMRT)] for IMRT fields and with a 10x10 cm2 open-field fluence to arrive at the same ratio D(a)w (Q) for the 10x10 cm2 reference field. The correction factor C(Q)IMRT is then calculated as the ratio of D(a)w (IMRT) and D(a)w (Q). The calculation method was experimentally validated and the magnitude of chamber correction factors in reference dose measurements in single static and dynamic IMRT fields was studied. The results show that, for thimble-type ionization chambers the correction factor in a single, realistic dynamic IMRT field can be of the order of 10% or more. We therefore propose that for accurate reference dosimetry of complete n-beam IMRT deliveries, ionization chamber fluence perturbation correction factors must explicitly be taken into account.

  1. Validation of a robotic balance system for investigations in the control of human standing balance.

    PubMed

    Luu, Billy L; Huryn, Thomas P; Van der Loos, H F Machiel; Croft, Elizabeth A; Blouin, Jean-Sébastien

    2011-08-01

    Previous studies have shown that human body sway during standing approximates the mechanics of an inverted pendulum pivoted at the ankle joints. In this study, a robotic balance system incorporating a Stewart platform base was developed to provide a new technique to investigate the neural mechanisms involved in standing balance. The robotic system, programmed with the mechanics of an inverted pendulum, controlled the motion of the body in response to a change in applied ankle torque. The ability of the robotic system to replicate the load properties of standing was validated by comparing the load stiffness generated when subjects balanced their own body to the robot's mechanical load programmed with a low (concentrated-mass model) or high (distributed-mass model) inertia. The results show that static load stiffness was not significantly (p > 0.05) different for standing and the robotic system. Dynamic load stiffness for the robotic system increased with the frequency of sway, as predicted by the mechanics of an inverted pendulum, with the higher inertia being accurately matched to the load properties of the human body. This robotic balance system accurately replicated the physical model of standing and represents a useful tool to simulate the dynamics of a standing person. © 2011 IEEE

  2. Electron energy balance and ionization in the channel of a stationary plasma thruster

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

    Veselovzorov, A. N., E-mail: Veselovzorov-AN@nrcki.ru; Pogorelov, A. A.; Svirskiy, E. B.

    2016-03-15

    The paper presents results of numerical simulations of the electron dynamics in the field of the azimuthal and longitudinal waves excited in the channel of a stationary plasma thruster (SPT). The simulations are based on the experimentally determined wave characteristics. The simulation results show that the azimuthal wave displayed as ionization instability enhances electron transport along the thruster channel. It is established that the electron transport rate in the azimuthal wave increases as compared to the rate of diffusion caused by electron scattering from neutral atoms in proportion to the ratio between the times of electron− neutral collisions responsible formore » ionization and elastic electron scattering, respectively. An expression governing the plasma conductivity is derived with allowance for electron interaction with the azimuthal wave. The Hall parameter, the electron component of the discharge current, and the electron heating power in the thruster channel are calculated for two model SPTs operating with krypton and xenon. The simulation results agree well with the results of experimental studies of these two SPTs.« less

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

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

    Shiraishi, Hiroyuki

    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.

  4. Impact of ionization equilibrium on electrokinetic flow of weak electrolytes in nanochannels

    NASA Astrophysics Data System (ADS)

    Ji, Ziwei; Huang, Zhuo; Chen, Bowei; He, Yuhui; Tsutsui, Makusu; Miao, Xiangshui

    2018-07-01

    Weak electrolyte transport in nanochannels or nanopores has been actively explored in recent experiments. In this paper, we establish a new electrokinetic model where the ionization balance effect of weak electrolytes is outlined, and performed numerical calculations for H3PO4 concentration-biased nanochannel systems. By considering the roles of local chemical equilibrium in phosphorous acid ionization, the simulation results show quantitative agreement with experimental observations. Based on the model, we predict that enhanced energy harvesting capacity could be accomplished by utilizing weak electrolytes compared to the conventional strong electrolyte approaches in a concentration gradient-based power-generating system.

  5. Tunnel ionization of atoms and molecules: How accurate are the weak-field asymptotic formulas?

    NASA Astrophysics Data System (ADS)

    Labeye, Marie; Risoud, François; Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard

    2018-05-01

    Weak-field asymptotic formulas for the tunnel ionization rate of atoms and molecules in strong laser fields are often used for the analysis of strong field recollision experiments. We investigate their accuracy and domain of validity for different model systems by confronting them to exact numerical results, obtained by solving the time dependent Schrödinger equation. We find that corrections that take the dc-Stark shift into account are a simple and efficient way to improve the formula. Furthermore, analyzing the different approximations used, we show that error compensation plays a crucial role in the fair agreement between exact and analytical results.

  6. Accurate and precise determination of isotopic ratios by MC-ICP-MS: a review.

    PubMed

    Yang, Lu

    2009-01-01

    For many decades the accurate and precise determination of isotope ratios has remained a very strong interest to many researchers due to its important applications in earth, environmental, biological, archeological, and medical sciences. Traditionally, thermal ionization mass spectrometry (TIMS) has been the technique of choice for achieving the highest accuracy and precision. However, recent developments in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) have brought a new dimension to this field. In addition to its simple and robust sample introduction, high sample throughput, and high mass resolution, the flat-topped peaks generated by this technique provide for accurate and precise determination of isotope ratios with precision reaching 0.001%, comparable to that achieved with TIMS. These features, in combination with the ability of the ICP source to ionize nearly all elements in the periodic table, have resulted in an increased use of MC-ICP-MS for such measurements in various sample matrices. To determine accurate and precise isotope ratios with MC-ICP-MS, utmost care must be exercised during sample preparation, optimization of the instrument, and mass bias corrections. Unfortunately, there are inconsistencies and errors evident in many MC-ICP-MS publications, including errors in mass bias correction models. This review examines "state-of-the-art" methodologies presented in the literature for achievement of precise and accurate determinations of isotope ratios by MC-ICP-MS. Some general rules for such accurate and precise measurements are suggested, and calculations of combined uncertainty of the data using a few common mass bias correction models are outlined.

  7. Ambient Ionization Mass Spectrometry for Cancer Diagnosis and Surgical Margin Evaluation

    PubMed Central

    Ifa, Demian R.; Eberlin, Livia S.

    2017-01-01

    Background There is a clinical need for new technologies that would enable rapid disease diagnosis based on diagnostic molecular signatures. Ambient ionization mass spectrometry has revolutionized the means by which molecular information can be obtained from tissue samples in real time and with minimal sample pretreatment. New developments in ambient ionization techniques applied to clinical research suggest that ambient ionization mass spectrometry will soon become a routine medical tool for tissue diagnosis. Content This review summarizes the main developments in ambient ionization techniques applied to tissue analysis, with focus on desorption electrospray ionization mass spectrometry, probe electrospray ionization, touch spray, and rapid evaporative ionization mass spectrometry. We describe their applications to human cancer research and surgical margin evaluation, highlighting integrated approaches tested for ex vivo and in vivo human cancer tissue analysis. We also discuss the challenges for clinical implementation of these tools and offer perspectives on the future of the field. Summary A variety of studies have showcased the value of ambient ionization mass spectrometry for rapid and accurate cancer diagnosis. Small molecules have been identified as potential diagnostic biomarkers, including metabolites, fatty acids, and glycerophospholipids. Statistical analysis allows tissue discrimination with high accuracy rates (>95%) being common. This young field has challenges to overcome before it is ready to be broadly accepted as a medical tool for cancer diagnosis. Growing research in new, integrated ambient ionization mass spectrometry technologies and the ongoing improvements in the existing tools make this field very promising for future translation into the clinic. PMID:26555455

  8. Balance Velocities of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced flow associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning.

  9. Footprints of electron correlation in strong-field double ionization of Kr close to the sequential-ionization regime

    NASA Astrophysics Data System (ADS)

    Li, Xiaokai; Wang, Chuncheng; Yuan, Zongqiang; Ye, Difa; Ma, Pan; Hu, Wenhui; Luo, Sizuo; Fu, Libin; Ding, Dajun

    2017-09-01

    By combining kinematically complete measurements and a semiclassical Monte Carlo simulation we study the correlated-electron dynamics in the strong-field double ionization of Kr. Interestingly, we find that, as we step into the sequential-ionization regime, there are still signatures of correlation in the two-electron joint momentum spectrum and, more intriguingly, the scaling law of the high-energy tail is completely different from early predictions on the low-Z atom (He). These experimental observations are well reproduced by our generalized semiclassical model adapting a Green-Sellin-Zachor potential. It is revealed that the competition between the screening effect of inner-shell electrons and the Coulomb focusing of nuclei leads to a non-inverse-square central force, which twists the returned electron trajectory at the vicinity of the parent core and thus significantly increases the probability of hard recollisions between two electrons. Our results might have promising applications ranging from accurately retrieving atomic structures to simulating celestial phenomena in the laboratory.

  10. Absolute cross sections for the ionization-excitation of helium by electron impact

    NASA Astrophysics Data System (ADS)

    Bellm, S.; Lower, J.; Weigold, E.; Bray, I.; Fursa, D. V.; Bartschat, K.; Harris, A. L.; Madison, D. H.

    2008-09-01

    In a recent publication we presented detailed experimental and theoretical results for the electron-impact-induced ionization of ground-state helium atoms. The purpose of that work was to refine theoretical approaches and provide further insight into the Coulomb four-body problem. Cross section ratios were presented for transitions leading to excited states, relative to those leading to the ground state, of the helium ion. We now build on that study by presenting individual relative triple-differential ionization cross sections (TDCSs) for an additional body of experimental data measured at lower values of scattered-electron energies. This has been facilitated through the development of new electron-gun optics which enables us to accurately characterize the spectrometer transmission at low energies. The experimental results are compared to calculations resulting from a number of different approaches. For ionization leading to He+(1s2)1S , cross sections are calculated by the highly accurate convergent close-coupling (CCC) method. The CCC data are used to place the relative experimental data on to an absolute scale. TDCSs describing transitions to the excited states are calculated through three different approaches, namely, through a hybrid distorted- wave+R -matrix (close-coupling) model, through the recently developed four-body distorted-wave model, and by a first Born approximation calculation. Comparison of the first- and second-order theories with experiment allows for the accuracy of the different theoretical approaches to be assessed and gives insight into which physical aspects of the problem are most important to accurately model.

  11. Quantum statistical mechanics of dense partially ionized hydrogen.

    NASA Technical Reports Server (NTRS)

    Dewitt, H. E.; Rogers, F. J.

    1972-01-01

    The theory of dense hydrogenic plasmas beginning with the two component quantum grand partition function is reviewed. It is shown that ionization equilibrium and molecular dissociation equilibrium can be treated in the same manner with proper consideration of all two-body states. A quantum perturbation expansion is used to give an accurate calculation of the equation of state of the gas for any degree of dissociation and ionization. In this theory, the effective interaction between any two charges is the dynamic screened potential obtained from the plasma dielectric function. We make the static approximation; and we carry out detailed numerical calculations with the bound and scattering states of the Debye potential, using the Beth-Uhlenbeck form of the quantum second virial coefficient. We compare our results with calculations from the Saha equation.

  12. Ionospheric chemistry. [minor neutrals and ionized constituents of thermosphere

    NASA Technical Reports Server (NTRS)

    Torr, D. G.

    1979-01-01

    This report deals primarily with progress in the chemistry of minor neutrals and ionized constituents of the thermosphere. Significant progress was made over the last few years in quantitative studies of many chemical processes. This success was primarily due to the advent of multiparameter multisatellite programs which permitted accurate simultaneous measurements to be made of many important parameters. In many cases studies of chemical reactions were made with laboratory-like precision. Rate coefficients have been derived as functions of temperature for a number of important reactions. New information has been acquired on nearly every major process which occurs in the thermosphere, including the recombination rates of all major molecular ions, charge transfer reactions, ion atom interchange reactions, and reactions of neutral and ionized metastable atoms and molecules.

  13. Low-energy electron-impact ionization of helium

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

    Schow, E.; Hazlett, K.; Childers, J. G.

    2005-12-15

    Normalized doubly differential cross sections for the electron-impact ionization of helium at low energies are presented. The data are taken at the incident electron energies of 26.3, 28.3, 30.3, 32.5, 34.3, 36.5, and 40.7 eV and for scattering angles of 10 deg. -130 deg. The measurements involve the use of the moveable target method developed at California State University Fullerton to accurately determine the continuum background in the energy-loss spectra. Normalization of experimental data is made on a relative scale to well-established experimental differential cross sections for excitation of the n=2 manifold of helium and then on an absolute scalemore » to the well-established total ionization cross sections of Shah et al. [J. Phys. B 21, 2751 (1988)]. Comparisons are made with available experimental data and the results of the convergent close-coupling theory.« less

  14. [Ionizing and non-ionizing radiation (comparative risk estimations)].

    PubMed

    Grigor'ev, Iu G

    2012-01-01

    The population has widely used mobile communication for already more than 15 years. It is important to note that the use of mobile communication has sharply changed the conditions of daily exposure of the population to EME We expose our brain daily for the first time in the entire civilization. The mobile phone is an open and uncontrollable source of electromagnetic radiation. The comparative risk estimation for the population of ionizing and non-ionizing radiation was carried out taking into account the real conditions of influence. Comparison of risks for the population of ionizing and non-ionizing radiation leads us to a conclusion that EMF RF exposure in conditions of wide use of mobile communication is potentially more harmful than ionizing radiation influence.

  15. Numerical models for the diffuse ionized gas in galaxies. I. Synthetic spectra of thermally excited gas with turbulent magnetic reconnection as energy source

    NASA Astrophysics Data System (ADS)

    Hoffmann, T. L.; Lieb, S.; Pauldrach, A. W. A.; Lesch, H.; Hultzsch, P. J. N.; Birk, G. T.

    2012-08-01

    Aims: The aim of this work is to verify whether turbulent magnetic reconnection can provide the additional energy input required to explain the up to now only poorly understood ionization mechanism of the diffuse ionized gas (DIG) in galaxies and its observed emission line spectra. Methods: We use a detailed non-LTE radiative transfer code that does not make use of the usual restrictive gaseous nebula approximations to compute synthetic spectra for gas at low densities. Excitation of the gas is via an additional heating term in the energy balance as well as by photoionization. Numerical values for this heating term are derived from three-dimensional resistive magnetohydrodynamic two-fluid plasma-neutral-gas simulations to compute energy dissipation rates for the DIG under typical conditions. Results: Our simulations show that magnetic reconnection can liberate enough energy to by itself fully or partially ionize the gas. However, synthetic spectra from purely thermally excited gas are incompatible with the observed spectra; a photoionization source must additionally be present to establish the correct (observed) ionization balance in the gas.

  16. Cavendish Balance Automation

    NASA Technical Reports Server (NTRS)

    Thompson, Bryan

    2000-01-01

    This is the final report for a project carried out to modify a manual commercial Cavendish Balance for automated use in cryostat. The scope of this project was to modify an off-the-shelf manually operated Cavendish Balance to allow for automated operation for periods of hours or days in cryostat. The purpose of this modification was to allow the balance to be used in the study of effects of superconducting materials on the local gravitational field strength to determine if the strength of gravitational fields can be reduced. A Cavendish Balance was chosen because it is a fairly simple piece of equipment for measuring gravity, one the least accurately known and least understood physical constants. The principle activities that occurred under this purchase order were: (1) All the components necessary to hold and automate the Cavendish Balance in a cryostat were designed. Engineering drawings were made of custom parts to be fabricated, other off-the-shelf parts were procured; (2) Software was written in LabView to control the automation process via a stepper motor controller and stepper motor, and to collect data from the balance during testing; (3)Software was written to take the data collected from the Cavendish Balance and reduce it to give a value for the gravitational constant; (4) The components of the system were assembled and fitted to a cryostat. Also the LabView hardware including the control computer, stepper motor driver, data collection boards, and necessary cabling were assembled; and (5) The system was operated for a number of periods, data collected, and reduced to give an average value for the gravitational constant.

  17. Treatment of Electronic Energy Level Transition and Ionization Following the Particle-Based Chemistry Model

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark

    2010-01-01

    A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.

  18. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

    PubMed Central

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

    2016-01-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 – 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models. PMID:27212712

  19. VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes.

    PubMed

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M

    2016-05-10

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 - 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

  20. Analytical instruments, ionization sources, and ionization methods

    DOEpatents

    Atkinson, David A.; Mottishaw, Paul

    2006-04-11

    Methods and apparatus for simultaneous vaporization and ionization of a sample in a spectrometer prior to introducing the sample into the drift tube of the analyzer are disclosed. The apparatus includes a vaporization/ionization source having an electrically conductive conduit configured to receive sample particulate which is conveyed to a discharge end of the conduit. Positioned proximate to the discharge end of the conduit is an electrically conductive reference device. The conduit and the reference device act as electrodes and have an electrical potential maintained between them sufficient to cause a corona effect, which will cause at least partial simultaneous ionization and vaporization of the sample particulate. The electrical potential can be maintained to establish a continuous corona, or can be held slightly below the breakdown potential such that arrival of particulate at the point of proximity of the electrodes disrupts the potential, causing arcing and the corona effect. The electrical potential can also be varied to cause periodic arcing between the electrodes such that particulate passing through the arc is simultaneously vaporized and ionized. The invention further includes a spectrometer containing the source. The invention is particularly useful for ion mobility spectrometers and atmospheric pressure ionization mass spectrometers.

  1. Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.

    PubMed

    Capolupo, A; Giampaolo, S M; Illuminati, F

    2013-10-01

    Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.

  2. Radiation protection and dosimetry issues in the medical applications of ionizing radiation

    NASA Astrophysics Data System (ADS)

    Vaz, Pedro

    2014-11-01

    The technological advances that occurred during the last few decades paved the way to the dissemination of CT-based procedures in radiology, to an increasing number of procedures in interventional radiology and cardiology as well as to new techniques and hybrid modalities in nuclear medicine and in radiotherapy. These technological advances encompass the exposure of patients and medical staff to unprecedentedly high dose values that are a cause for concern due to the potential detrimental effects of ionizing radiation to the human health. As a consequence, new issues and challenges in radiological protection and dosimetry in the medical applications of ionizing radiation have emerged. The scientific knowledge of the radiosensitivity of individuals as a function of age, gender and other factors has also contributed to raising the awareness of scientists, medical staff, regulators, decision makers and other stakeholders (including the patients and the public) for the need to correctly and accurately assess the radiation induced long-term health effects after medical exposure. Pediatric exposures and their late effects became a cause of great concern. The scientific communities of experts involved in the study of the biological effects of ionizing radiation have made a strong case about the need to undertake low dose radiation research and the International System of Radiological Protection is being challenged to address and incorporate issues such as the individual sensitivities, the shape of dose-response relationship and tissue sensitivity for cancer and non-cancer effects. Some of the answers to the radiation protection and dosimetry issues and challenges in the medical applications of ionizing radiation lie in computational studies using Monte Carlo or hybrid methods to model and simulate particle transport in the organs and tissues of the human body. The development of sophisticated Monte Carlo computer programs and voxel phantoms paves the way to an accurate

  3. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry for fast and accurate identification of clinically relevant Aspergillus species.

    PubMed

    Alanio, A; Beretti, J-L; Dauphin, B; Mellado, E; Quesne, G; Lacroix, C; Amara, A; Berche, P; Nassif, X; Bougnoux, M-E

    2011-05-01

    New Aspergillus species have recently been described with the use of multilocus sequencing in refractory cases of invasive aspergillosis. The classical phenotypic identification methods routinely used in clinical laboratories failed to identify them adequately. Some of these Aspergillus species have specific patterns of susceptibility to antifungal agents, and misidentification may lead to inappropriate therapy. We developed a matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS)-based strategy to adequately identify Aspergillus species to the species level. A database including the reference spectra of 28 clinically relevant species from seven Aspergillus sections (five common and 23 unusual species) was engineered. The profiles of young and mature colonies were analysed for each reference strain, and species-specific spectral fingerprints were identified. The performance of the database was then tested on 124 clinical and 16 environmental isolates previously characterized by partial sequencing of the β-tubulin and calmodulin genes. One hundred and thirty-eight isolates of 140 (98.6%) were correctly identified. Two atypical isolates could not be identified, but no isolate was misidentified (specificity: 100%). The database, including species-specific spectral fingerprints of young and mature colonies of the reference strains, allowed identification regardless of the maturity of the clinical isolate. These results indicate that MALDI-TOF MS is a powerful tool for rapid and accurate identification of both common and unusual species of Aspergillus. It can give better results than morphological identification in clinical laboratories. © 2010 The Authors. Clinical Microbiology and Infection © 2010 European Society of Clinical Microbiology and Infectious Diseases.

  4. Fourier Transform Mass Spectrometry and Nuclear Magnetic Resonance Analysis for the Rapid and Accurate Characterization of Hexacosanoylceramide.

    PubMed

    Ross, Charles W; Simonsick, William J; Bogusky, Michael J; Celikay, Recep W; Guare, James P; Newton, Randall C

    2016-06-28

    Ceramides are a central unit of all sphingolipids which have been identified as sites of biological recognition on cellular membranes mediating cell growth and differentiation. Several glycosphingolipids have been isolated, displaying immunomodulatory and anti-tumor activities. These molecules have generated considerable interest as potential vaccine adjuvants in humans. Accurate analyses of these and related sphingosine analogues are important for the characterization of structure, biological function, and metabolism. We report the complementary use of direct laser desorption ionization (DLDI), sheath flow electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and high-field nuclear magnetic resonance (NMR) analysis for the rapid, accurate identification of hexacosanoylceramide and starting materials. DLDI does not require stringent sample preparation and yields representative ions. Sheath-flow ESI yields ions of the product and byproducts and was significantly better than monospray ESI due to improved compound solubility. Negative ion sheath flow ESI provided data of starting materials and products all in one acquisition as hexacosanoic acid does not ionize efficiently when ceramides are present. NMR provided characterization of these lipid molecules complementing the results obtained from MS analyses. NMR data was able to differentiate straight chain versus branched chain alkyl groups not easily obtained from mass spectrometry.

  5. Quantum mechanical calculations related to ionization and charge transfer in DNA

    NASA Astrophysics Data System (ADS)

    Cauët, E.; Valiev, M.; Weare, J. H.; Liévin, J.

    2012-07-01

    Ionization and charge migration in DNA play crucial roles in mechanisms of DNA damage caused by ionizing radiation, oxidizing agents and photo-irradiation. Therefore, an evaluation of the ionization properties of the DNA bases is central to the full interpretation and understanding of the elementary reactive processes that occur at the molecular level during the initial exposure and afterwards. Ab initio quantum mechanical (QM) methods have been successful in providing highly accurate evaluations of key parameters, such as ionization energies (IE) of DNA bases. Hence, in this study, we performed high-level QM calculations to characterize the molecular energy levels and potential energy surfaces, which shed light on ionization and charge migration between DNA bases. In particular, we examined the IEs of guanine, the most easily oxidized base, isolated and embedded in base clusters, and investigated the mechanism of charge migration over two and three stacked guanines. The IE of guanine in the human telomere sequence has also been evaluated. We report a simple molecular orbital analysis to explain how modifications in the base sequence are expected to change the efficiency of the sequence as a hole trap. Finally, the application of a hybrid approach combining quantum mechanics with molecular mechanics brings an interesting discussion as to how the native aqueous DNA environment affects the IE threshold of nucleobases.

  6. FAMBE-pH: A Fast and Accurate Method to Compute the Total Solvation Free Energies of Proteins

    PubMed Central

    Vorobjev, Yury N.; Vila, Jorge A.

    2009-01-01

    A fast and accurate method to compute the total solvation free energies of proteins as a function of pH is presented. The method makes use of a combination of approaches, some of which have already appeared in the literature; (i) the Poisson equation is solved with an optimized fast adaptive multigrid boundary element (FAMBE) method; (ii) the electrostatic free energies of the ionizable sites are calculated for their neutral and charged states by using a detailed model of atomic charges; (iii) a set of optimal atomic radii is used to define a precise dielectric surface interface; (iv) a multilevel adaptive tessellation of this dielectric surface interface is achieved by using multisized boundary elements; and (v) 1:1 salt effects are included. The equilibrium proton binding/release is calculated with the Tanford–Schellman integral if the proteins contain more than ∼20–25 ionizable groups; for a smaller number of ionizable groups, the ionization partition function is calculated directly. The FAMBE method is tested as a function of pH (FAMBE-pH) with three proteins, namely, bovine pancreatic trypsin inhibitor (BPTI), hen egg white lysozyme (HEWL), and bovine pancreatic ribonuclease A (RNaseA). The results are (a) the FAMBE-pH method reproduces the observed pKa's of the ionizable groups of these proteins within an average absolute value of 0.4 pK units and a maximum error of 1.2 pK units and (b) comparison of the calculated total pH-dependent solvation free energy for BPTI, between the exact calculation of the ionization partition function and the Tanford–Schellman integral method, shows agreement within 1.2 kcal/mol. These results indicate that calculation of total solvation free energies with the FAMBE-pH method can provide an accurate prediction of protein conformational stability at a given fixed pH and, if coupled with molecular mechanics or molecular dynamics methods, can also be used for more realistic studies of protein folding, unfolding, and dynamics

  7. Electron Impact Multiple Ionization Cross Sections for Solar Physics

    NASA Astrophysics Data System (ADS)

    Hahn, M.; Savin, D. W.; Mueller, A.

    2017-12-01

    We have compiled a set of electron-impact multiple ionization (EIMI) cross sections for astrophysically relevant ions. EIMI can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature, as in solar flares or in nanoflare coronal heating. EIMI is also likely to be significant when the electron energy distribution is non-thermal, such as if the electrons follow a kappa distribution. Cross sections for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation. Here, we describe our comparison of proposed semiempirical formulae to the available experimental EIMI cross section data. Based on this comparison, we have interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for thousands of EIMI cross sections. We also highlight some outstanding issues that remain to be resolved.

  8. Liquid-circulating garment controls thermal balance

    NASA Technical Reports Server (NTRS)

    Kuznetz, L. H.

    1977-01-01

    Experimental data and mathematical model of human thermoregulatory system have been used to investigate use of liquid-circulatory garment (LCG) to control thermal balance. Model proved useful as accurate simulator of such variables as sweat rate, skin temperature, core temperature, and radiative, evaporative, and LCG heat loss.

  9. Accurate and rapid modeling of iron-bleomycin-induced DNA damage using tethered duplex oligonucleotides and electrospray ionization ion trap mass spectrometric analysis.

    PubMed

    Harsch, A; Marzilli, L A; Bunt, R C; Stubbe, J; Vouros, P

    2000-05-01

    Bleomycin B(2)(BLM) in the presence of iron [Fe(II)] and O(2)catalyzes single-stranded (ss) and double-stranded (ds) cleavage of DNA. Electrospray ionization ion trap mass spectrometry was used to monitor these cleavage processes. Two duplex oligonucleotides containing an ethylene oxide tether between both strands were used in this investigation, allowing facile monitoring of all ss and ds cleavage events. A sequence for site-specific binding and cleavage by Fe-BLM was incorporated into each analyte. One of these core sequences, GTAC, is a known hot-spot for ds cleavage, while the other sequence, GGCC, is a hot-spot for ss cleavage. Incubation of each oligo-nucleotide under anaerobic conditions with Fe(II)-BLM allowed detection of the non-covalent ternary Fe-BLM/oligonucleotide complex in the gas phase. Cleavage studies were then performed utilizing O(2)-activated Fe(II)-BLM. No work-up or separation steps were required and direct MS and MS/MS analyses of the crude reaction mixtures confirmed sequence-specific Fe-BLM-induced cleavage. Comparison of the cleavage patterns for both oligonucleotides revealed sequence-dependent preferences for ss and ds cleavages in accordance with previously established gel electrophoresis analysis of hairpin oligonucleotides. This novel methodology allowed direct, rapid and accurate determination of cleavage profiles of model duplex oligonucleotides after exposure to activated Fe-BLM.

  10. Ionization energies of aqueous nucleic acids: photoelectron spectroscopy of pyrimidine nucleosides and ab initio calculations.

    PubMed

    Slavícek, Petr; Winter, Bernd; Faubel, Manfred; Bradforth, Stephen E; Jungwirth, Pavel

    2009-05-13

    Vertical ionization energies of the nucleosides cytidine and deoxythymidine in water, the lowest ones amounting in both cases to 8.3 eV, are obtained from photoelectron spectroscopy measurements in aqueous microjets. Ab initio calculations employing a nonequilibrium polarizable continuum model quantitatively reproduce the experimental spectra and provide molecular interpretation of the individual peaks of the photoelectron spectrum, showing also that lowest ionization originates from the base. Comparison of calculated vertical ionization potentials of pyrimidine bases, nucleosides, and nucleotides in water and in the gas phase underlines the dramatic effect of bulk hydration on the electronic structure. In the gas phase, the presence of sugar and, in particular, of phosphate has a strong effect on the energetics of ionization of the base. Upon bulk hydration, the ionization potential of the base in contrast becomes rather insensitive to the presence of the sugar and phosphate, which indicates a remarkable screening ability of the aqueous solvent. Accurate aqueous-phase vertical ionization potentials provide a significant improvement to the corrected gas-phase values used in the literature and represent important information in assessing the threshold energies for photooxidation and oxidation free energies of solvent-exposed DNA components. Likewise, such energetic data should allow improved assessment of delocalization and charge-hopping mechanisms in DNA ionized by radiation.

  11. Self-reported balance status is not a reliable indicator of balance performance in adolescents at one-month post-concussion.

    PubMed

    Rochefort, Coralie; Walters-Stewart, Coren; Aglipay, Mary; Barrowman, Nick; Zemek, Roger; Sveistrup, Heidi

    2017-11-01

    To determine if self-reported balance symptoms can be used as a proxy for measures of the center of pressure (COP) to identify balance deficits in a group of concussed adolescents. Case-control. Thirteen adolescents 1-month post-concussion who reported ongoing balance problems (Balance+), 20 adolescent 1-month post-concussion who reported no balance problems (Balance-), and 30 non-injured adolescents (control) completed a series of balance tests. Participants completed two 2-min trials standing on a Nintendo Wii Balance Board™ during which the COP under their feet was recorded: i) double-leg stance, eyes open; ii) double-leg stance, eyes closed. Participants also completed a dual-task condition combining a double-leg stance and a Stroop Colour-word test. Participants in both the Balance+ and Balance- group swayed over a larger ellipse area compared to the control group while completing the Eyes Closed (Balance+, p=0.002; Balance-, p=0.002) and Dual-Task (Balance+, p=0.001; Balance-, p=0.004) conditions and performed the Dual-Task condition with faster medio-lateral velocity (Balance+, p=0.003; Balance-, p=0.009). The participants in the Balance- group also swayed over a larger ellipse area compared to the control group while completing the Eyes Open condition (p=0.005). No significant differences were identified between the Balance+ and Balance- groups. At 1-month post-concussion, adolescents demonstrated balance deficits compared to non-injured adolescents regardless of whether they reported balance problems. These results suggest that self-reported balance status might not be an accurate reflection of balance performance following a concussion in adolescents. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  12. Well-ionization chamber response relative to NIST air-kerma strength standard for prostate brachytherapy seeds.

    PubMed

    Mitch, M G; Zimmerman, B E; Lamperti, P J; Seltzer, S M; Coursey, B M

    2000-10-01

    The response of well-ionization chambers to the emissions of 103Pd and 125I radioactive seed sources used in prostate cancer brachytherapy has been measured. Calibration factors relating chamber response (current or dial setting) to measured air-kerma strength have been determined for seeds from nine manufacturers, each with different designs. Variations in well-ionization chamber response relative to measured air-kerma strength have been observed because of differences in the emitted energy spectrum due to both the radionuclide support material (125I seeds) and the mass ratio of 103Pd to 102Pd (103Pd seeds). Obtaining accurate results from quality assurance measurements using well-ionization chambers at a therapy clinic requires knowledge of such differences in chamber response as a function of seed design.

  13. Achieving perceptually-accurate aural telepresence

    NASA Astrophysics Data System (ADS)

    Henderson, Paul D.

    Immersive multimedia requires not only realistic visual imagery but also a perceptually-accurate aural experience. A sound field may be presented simultaneously to a listener via a loudspeaker rendering system using the direct sound from acoustic sources as well as a simulation or "auralization" of room acoustics. Beginning with classical Wave-Field Synthesis (WFS), improvements are made to correct for asymmetries in loudspeaker array geometry. Presented is a new Spatially-Equalized WFS (SE-WFS) technique to maintain the energy-time balance of a simulated room by equalizing the reproduced spectrum at the listener for a distribution of possible source angles. Each reproduced source or reflection is filtered according to its incidence angle to the listener. An SE-WFS loudspeaker array of arbitrary geometry reproduces the sound field of a room with correct spectral and temporal balance, compared with classically-processed WFS systems. Localization accuracy of human listeners in SE-WFS sound fields is quantified by psychoacoustical testing. At a loudspeaker spacing of 0.17 m (equivalent to an aliasing cutoff frequency of 1 kHz), SE-WFS exhibits a localization blur of 3 degrees, nearly equal to real point sources. Increasing the loudspeaker spacing to 0.68 m (for a cutoff frequency of 170 Hz) results in a blur of less than 5 degrees. In contrast, stereophonic reproduction is less accurate with a blur of 7 degrees. The ventriloquist effect is psychometrically investigated to determine the effect of an intentional directional incongruence between audio and video stimuli. Subjects were presented with prerecorded full-spectrum speech and motion video of a talker's head as well as broadband noise bursts with a static image. The video image was displaced from the audio stimulus in azimuth by varying amounts, and the perceived auditory location measured. A strong bias was detectable for small angular discrepancies between audio and video stimuli for separations of less than 8

  14. VUV PHOTO-PROCESSING OF PAH CATIONS: QUANTITATIVE STUDY ON THE IONIZATION VERSUS FRAGMENTATION PROCESSES

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

    Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine

    2016-05-10

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7–20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation andmore » photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ∼13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ∼18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.« less

  15. Equation of motion coupled cluster methods for electron attachment and ionization potential in polyacenes

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

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark

    2015-11-05

    Polyacenes have attracted considerable attention due to their use in organic based optoelectronic materials. Polyacenes are polycyclic aromatic hydrocarbons composed of fused benzene rings. Key to understanding and design of new functional materials is an understanding of their excited state properties starting with their electron affinity (EA) and ionization potential (IP). We have developed a highly accurate and com- putationally e*fficient EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) method that is capable of treating large systems and large basis set. In this study we employ the EA/IP-EOMCCSD method to calculate the electron affinity and ionization potential ofmore » naphthalene, anthracene, tetracene, pentacene, hex- acene and heptacene. We have compared our results with other previous theoretical studies and experimental data. Our EA/IP results are in very good agreement with experiment and when compared with the other theoretical investigations our results represent the most accurate calculations as compared to experiment.« less

  16. Balance in non-hydrostatic rotating stratified turbulence

    NASA Astrophysics Data System (ADS)

    McKiver, William J.; Dritschel, David G.

    It is now well established that two distinct types of motion occur in geophysical turbulence: slow motions associated with potential vorticity advection and fast oscillations due to inertiamaster variable this is known as balance. In real geophysical flows, deviations from balance in the form of inertiaimbalance|N/f) where optimal potential vorticity balancenonlinear quasi-geostrophic balance’ procedure expands the equations of motion to second order in Rossby number but retains the exact (unexpanded) definition of potential vorticity. This proves crucial for obtaining an accurate estimate of balanced motions. In the analysis of rotating stratified turbulence at Ro1 and N/f1, this procedure captures a significantly greater fraction of the underlying balance than standard (linear) quasi-geostrophic balance (which is based on the linearized equations about a state of rest). Nonlinear quasi-geostrophic balance also compares well with optimal potential vorticity balance, which captures the greatest fraction of the underlying balance overall.More fundamentally, the results of these analyses indicate that balance dominates in carefully initialized simulations of freely decaying rotating stratified turbulence up to O(1) Rossby numbers when N/f1. The fluid motion exhibits important quasi-geostrophic features with, in particular, typical height-to-width scale ratios remaining comparable to f/N.

  17. Unveiling the Ionization Energy of the CN Radical.

    PubMed

    Gans, Bérenger; Boyé-Péronne, Séverine; Garcia, Gustavo A; Röder, Anja; Schleier, Domenik; Halvick, Philippe; Loison, Jean-Christophe

    2017-09-07

    The cyano radical is a ubiquitous molecule and was, for instance, one of the first species detected in astrophysical media such as comets or diffuse clouds. In photodissociation regions, the reaction rate of CN + + CO → CN + CO + is one of the critical parameters defining nitrile chemistry. The enthalpy of this charge transfer reaction is defined as the difference of ionization energies (E I ) between CN and CO. Although E I (CO) is known accurately, the E I (CN) values are more dispersed and deduced indirectly from thermodynamic thresholds only, all above E I (CO), leading to the assumption that the reaction is fast even at low temperature. Using a combination of synchrotron radiation, electron/ion imaging coincidence techniques, and supporting ab initio calculations, we directly determine the first adiabatic ionization energy of CN at 13.956(7) eV, and we demonstrate that E I (CN) < E I (CO). The findings suggest a very slow reaction in the cold regions of interstellar media.

  18. Ionization ratios and elemental abundances in the atmosphere of 68 Tauri

    NASA Astrophysics Data System (ADS)

    Aouina, A.; Monier, R.

    2017-12-01

    We have derived the ionization ratios of twelve elements in the atmosphere of the star 68 Tauri (HD 27962) using an ATLAS9 model atmosphere with 72 layers computed for the effective temperature and surface gravity of the star. We then computed a grid of synthetic spectra generated by SYNSPEC49 based on an ATLAS9 model atmosphere in order to model one high resolution spectrum secured by one of us (RM) with the échelle spectrograph SOPHIE at Observatoire de Haute Provence. We could determine the abundances of several elements in their dominant ionization stage, including those defining the Am phenomenon. We thus provide new abundance determinations for 68 Tauri using updated accurate atomic data retrieved from the NIST database which extend previous abundance works.

  19. Low-sample flow secondary electrospray ionization: improving vapor ionization efficiency.

    PubMed

    Vidal-de-Miguel, G; Macía, M; Pinacho, P; Blanco, J

    2012-10-16

    In secondary electrospray ionization (SESI) systems, gaseous analytes exposed to an elecrospray plume become ionized after charge is transferred from the charging electrosprayed particles to the sample species. Current SESI systems have shown a certain potential. However, their ionization efficiency is limited by space charge repulsion and by the high sample flows required to prevent vapor dilution. As a result, they have a poor conversion ratio of vapor into ions. We have developed and tested a new SESI configuration, termed low-flow SESI, that permits the reduction of the required sample flows. Although the ion to vapor concentration ratio is limited, the ionic flow to sample vapor flow ratio theoretically is not. The new ionizer is coupled to a planar differential mobility analyzer (DMA) and requires only 0.2 lpm of vapor sample flow to produce 3.5 lpm of ionic flow. The achieved ionization efficiency is 1/700 (one ion for every 700 molecules) for TNT and, thus, compared with previous SESI ionizers coupled with atmospheric pressure ionization-mass spectrometry (API-MS) (Mesonero, E.; Sillero, J. A.; Hernández, M.; Fernandez de la Mora, J. Philadelphia PA, 2009) has been improved by a large factor of at least 50-100 (our measurements indicate 70). The new ionizer coupled with the planar DMA and a triple quadrupole mass spectrometer (ABSciex API5000) requires only 20 fg (50 million molecules) to produce a discernible signal after mobility and MS(2) analysis.

  20. Electron-impact total ionization cross sections of DNA sugar-phosphate backbone and an additivity principle

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Dateo, Christopher E.

    2005-01-01

    The improved binary-encounter dipole (iBED) model [W.M. Huo, Phys. Rev. A64, 042719-1 (2001)l is used to study the total ionization cross sections of the DNA sugar-phosphate backbone by electron impact. Calculations using neutral fragments found that the total ionization cross sections of C3' - and C5', -deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3' - and C5" -deoxyribose-phospate cross sections, differing by less than 10%. The result implies that certain properties of the-DNA, like the total singly ionization cross section, are localized properties and a building-up or additivity principle may apply. This allows us to obtain accurate properties of larger molecular systems built up from the results of smaller subsystem fragments. Calculations are underway using a negatively charged sugar-phosphate backbone with a metal counter-ion.

  1. Enhancement of ionization efficiency of mass spectrometric analysis from non-electrospray ionization friendly solvents with conventional and novel ionization techniques.

    PubMed

    Jiang, Ping; Lucy, Charles A

    2015-10-15

    Electrospray ionization mass spectrometry (ESI-MS) has significantly impacted the analysis of complex biological and petroleum samples. However ESI-MS has limited ionization efficiency for samples in low dielectric and low polarity solvents. Addition of a make-up solvent through a T union or electrospray solvent through continuous flow extractive desorption electrospray ionization (CF-EDESI) enable ionization of analytes in non-ESI friendly solvents. A conventional make-up solvent addition setup was used and a CF-EDESI source was built for ionization of nitrogen-containing standards in hexane or hexane/isopropanol. Factors affecting the performance of both sources have been investigated and optimized. Both the make-up solvent addition and CF-EDESI improve the ionization efficiency for heteroatom compounds in non-ESI friendly solvents. Make-up solvent addition provides higher ionization efficiency than CF-EDESI. Neither the make-up solvent addition nor the CF-EDESI eliminates ionization suppression of nitrogen-containing compounds caused by compounds of the same chemical class. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Assessing and training standing balance in older adults: a novel approach using the 'Nintendo Wii' Balance Board.

    PubMed

    Young, William; Ferguson, Stuart; Brault, Sébastien; Craig, Cathy

    2011-02-01

    Older adults, deemed to be at a high risk of falling, are often unable to participate in dynamic exercises due to physical constraints and/or a fear of falling. Using the Nintendo 'Wii Balance Board' (WBB) (Nintendo, Kyoto, Japan), we have developed an interface that allows a user to accurately calculate a participant's centre of pressure (COP) and incorporate it into a virtual environment to create bespoke diagnostic or training programmes that exploit real-time visual feedback of current COP position. This platform allows researchers to design, control and validate tasks that both train and test balance function. This technology provides a safe, adaptable and low-cost balance training/testing solution for older adults, particularly those at high-risk of falling. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Computations of Torque-Balanced Coaxial Rotor Flows

    NASA Technical Reports Server (NTRS)

    Yoon, Seokkwan; Chan, William M.; Pulliam, Thomas H.

    2017-01-01

    Interactional aerodynamics has been studied for counter-rotating coaxial rotors in hover. The effects of torque balancing on the performance of coaxial-rotor systems have been investigated. The three-dimensional unsteady Navier-Stokes equations are solved on overset grids using high-order accurate schemes, dual-time stepping, and a hybrid turbulence model. Computational results for an experimental model are compared to available data. The results for a coaxial quadcopter vehicle with and without torque balancing are discussed. Understanding interactions in coaxial-rotor flows would help improve the design of next-generation autonomous drones.

  4. Mass balance assessment using GPS

    NASA Technical Reports Server (NTRS)

    Hulbe, Christina L.

    1993-01-01

    Mass balance is an integral part of any comprehensive glaciological investigation. Unfortunately, it is hard to determine at remote locations where there is no fixed reference. The Global Positioning System (GPS) offers a solution. Simultaneous GPS observations at a known location and the remote field site, processed differentially, will accurately position the camp site. From there, a monument planted in the firn atop the ice can also be accurately positioned. Change in the monument's vertical position is a direct indicator of ice thickness change. Because the monument is not connected to the ice, its motion is due to both mass balance change and to the settling of firn as it densifies into ice. Observations of relative position change between the monument and anchors at various depths within the firn are used to remove the settling effect. An experiment to test this method has begun at Byrd Station on the West Antarctic Ice Sheet and the first epoch of observations was made. Analysis indicates that positioning errors will be very small. It appears likely that the largest errors involved with this technique will arise from ancillary data needed to determine firn settling.

  5. Accurate Emission Line Diagnostics at High Redshift

    NASA Astrophysics Data System (ADS)

    Jones, Tucker

    2017-08-01

    How do the physical conditions of high redshift galaxies differ from those seen locally? Spectroscopic surveys have invested hundreds of nights of 8- and 10-meter telescope time as well as hundreds of Hubble orbits to study evolution in the galaxy population at redshifts z 0.5-4 using rest-frame optical strong emission line diagnostics. These surveys reveal evolution in the gas excitation with redshift but the physical cause is not yet understood. Consequently there are large systematic errors in derived quantities such as metallicity.We have used direct measurements of gas density, temperature, and metallicity in a unique sample at z=0.8 to determine reliable diagnostics for high redshift galaxies. Our measurements suggest that offsets in emission line ratios at high redshift are primarily caused by high N/O abundance ratios. However, our ground-based data cannot rule out other interpretations. Spatially resolved Hubble grism spectra are needed to distinguish between the remaining plausible causes such as active nuclei, shocks, diffuse ionized gas emission, and HII regions with escaping ionizing flux. Identifying the physical origin of evolving excitation will allow us to build the necessary foundation for accurate measurements of metallicity and other properties of high redshift galaxies. Only then can we expoit the wealth of data from current surveys and near-future JWST spectroscopy to understand how galaxies evolve over time.

  6. Proton dissociation properties of arylphosphonates: Determination of accurate Hammett equation parameters.

    PubMed

    Dargó, Gergő; Bölcskei, Adrienn; Grün, Alajos; Béni, Szabolcs; Szántó, Zoltán; Lopata, Antal; Keglevich, György; Balogh, György T

    2017-09-05

    Determination of the proton dissociation constants of several arylphosphonic acid derivatives was carried out to investigate the accuracy of the Hammett equations available for this family of compounds. For the measurement of the pK a values modern, accurate methods, such as the differential potentiometric titration and NMR-pH titration were used. We found our results significantly different from the pK a values reported before (pK a1 : MAE = 0.16 pK a2 : MAE=0.59). Based on our recently measured pK a values, refined Hammett equations were determined that might be used for predicting highly accurate ionization constants of newly synthesized compounds (pK a1 =1.70-0.894σ, pK a2 =6.92-0.934σ). Copyright © 2017 Elsevier B.V. All rights reserved.

  7. [Morphology determination of ionization region in multi-needle-to-plate negative corona discharge].

    PubMed

    Su, Peng-Hao; Zhu, Yi-Min; Chen, Hai-Feng

    2007-11-01

    Based on the former work on the current-voltage characteristics of a multi-needle-to-plate negative corona discharge at atmospheric pressure, the present work uses the method of OES (optical emission spectrum) for measuring N2 emission spectrum, and the morphology determination of the ionization region has been investigated. According to the distribution of N2 second positive band's intensity I(SPB), the highest of all bands, the outline of the ionization region was drawn fairly accurately. The relationship between I(SPB) and discharge current I can be obtained through the volume integral of the I(SPB). The experimental results show that the size of the ionization region enhances with the rise of the applied voltage U, and the electron avalanche begins at about 1 mm off the tips of needle electrode and multiplies only in the range of several millimeters, indicating that, the range of the ionization region is at the magnitude of mm. The electron avalanche along the axis of the needle develops farther than that along the radial direction of needle, and the shape of the ionization region looks like a bullet. The integral of I(SPB) is second-order linear to I, with a very second order coefficient, meaning that the main excited substance is N2. Energetic electrons mainly exist in ionization region while ions are the main charged particles to form discharge current in the transfer region.

  8. The Automated Assessment of Postural Stability: Balance Detection Algorithm.

    PubMed

    Napoli, Alessandro; Glass, Stephen M; Tucker, Carole; Obeid, Iyad

    2017-12-01

    Impaired balance is a common indicator of mild traumatic brain injury, concussion and musculoskeletal injury. Given the clinical relevance of such injuries, especially in military settings, it is paramount to develop more accurate and reliable on-field evaluation tools. This work presents the design and implementation of the automated assessment of postural stability (AAPS) system, for on-field evaluations following concussion. The AAPS is a computer system, based on inexpensive off-the-shelf components and custom software, that aims to automatically and reliably evaluate balance deficits, by replicating a known on-field clinical test, namely, the Balance Error Scoring System (BESS). The AAPS main innovation is its balance error detection algorithm that has been designed to acquire data from a Microsoft Kinect ® sensor and convert them into clinically-relevant BESS scores, using the same detection criteria defined by the original BESS test. In order to assess the AAPS balance evaluation capability, a total of 15 healthy subjects (7 male, 8 female) were required to perform the BESS test, while simultaneously being tracked by a Kinect 2.0 sensor and a professional-grade motion capture system (Qualisys AB, Gothenburg, Sweden). High definition videos with BESS trials were scored off-line by three experienced observers for reference scores. AAPS performance was assessed by comparing the AAPS automated scores to those derived by three experienced observers. Our results show that the AAPS error detection algorithm presented here can accurately and precisely detect balance deficits with performance levels that are comparable to those of experienced medical personnel. Specifically, agreement levels between the AAPS algorithm and the human average BESS scores ranging between 87.9% (single-leg on foam) and 99.8% (double-leg on firm ground) were detected. Moreover, statistically significant differences in balance scores were not detected by an ANOVA test with alpha equal to 0

  9. Characterization of anti-theft devices directly from the surface of banknotes via easy ambient sonic spray ionization mass spectrometry.

    PubMed

    Schmidt, Eduardo Morgado; Franco, Marcos Fernando; Cuelbas, Claudio José; Zacca, Jorge Jardim; de Carvalho Rocha, Werickson Fortunato; Borges, Rodrigo; de Souza, Wanderley; Sawaya, Alexandra Christine Helena Frankland; Eberlin, Marcos Nogueira; Correa, Deleon Nascimento

    2015-09-01

    Using Brazilian banknotes as a test case, forensic examination and identification of Rhodamine B dye anti-theft device (ATD) staining on banknotes were performed. Easy ambient sonic spray ionization mass spectrometry (EASI-MS) was used since it allows fast and simple analysis with no sample preparation providing molecular screening of the surface with direct desorption and ionization of the security dye. For a more accurate molecular characterization of the ATD dye, Q Exactive Orbitrap™ Fourier transform (tandem) mass spectrometry using eletrospray ionization (ESI-HRMS/MS) was also applied. Copyright © 2015 The Chartered Society of Forensic Sciences. Published by Elsevier Ireland Ltd. All rights reserved.

  10. Evaluating analytical ionization quenching correction models for 3D liquid organic scintillator detector

    NASA Astrophysics Data System (ADS)

    Alsanea, F.; Beddar, S.

    2017-05-01

    Proton therapy offers dosimetric advantage over conventional photon therapy due to the finite range of the proton beam, which improves dose conformity. However, one of the main challenges of proton beam therapy is verification of the complex treatment plans delivered to a patient. Thus, 3D measurements are needed to verify the complex dose distribution. A 3D organic scintillator detector is capable of such measurements. However, organic scintillators exhibit a non-linear relation to the ionization density called ionization quenching. The ionization quenching phenomenon in organic scintillators must be accounted for to obtain accurate dose measurements. We investigated the energy deposition by secondary electrons (EDSE) model to explain ionization quenching in 3D liquid organic scintillator when exposed to proton beams. The EDSE model was applied to volumetric scintillation measurement of proton pencil beam with energies of 85.6, 100.9, 144.9 and 161.9 MeV. The quenching parameter in EDSE model ρq was determined by plotting the total light output vs the initial energy of the ion. The results were compared to the Birks semi-empirical formula of scintillation light emission.

  11. Quantitative ionization chamber alignment to a water surface: Theory and simulation.

    PubMed

    Siebers, Jeffrey V; Ververs, James D; Tessier, Frédéric

    2017-07-01

    and/or be applied retrospectively to scan data to quantify absolute IC depth. Utilization of the gCAP should yield accurate and reproducible depth calibration for clinical depth-ionization measurements between setups and between users. © 2017 American Association of Physicists in Medicine.

  12. Directed Field Ionization

    NASA Astrophysics Data System (ADS)

    Gregoric, Vincent C.; Kang, Xinyue; Liu, Zhimin Cheryl; Rowley, Zoe A.; Carroll, Thomas J.; Noel, Michael W.

    2017-04-01

    Selective field ionization is an important experimental technique used to study the state distribution of Rydberg atoms. This is achieved by applying a steadily increasing electric field, which successively ionizes more tightly bound states. An atom prepared in an energy eigenstate encounters many avoided Stark level crossings on the way to ionization. As it traverses these avoided crossings, its amplitude is split among multiple different states, spreading out the time resolved electron ionization signal. By perturbing the electric field ramp, we can change how the atoms traverse the avoided crossings, and thus alter the shape of the ionization signal. We have used a genetic algorithm to evolve these perturbations in real time in order to arrive at a target ionization signal shape. This process is robust to large fluctuations in experimental conditions. This work was supported by the National Science Foundation under Grants No. 1607335 and No. 1607377 and used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant Number OCI-1053575.

  13. Electron Impact Ionization of Heavier Ions including relativistic effects

    NASA Astrophysics Data System (ADS)

    Saha, B. C.; Haque, A. K. F.; Uddin, M. A.; Basak, A. K.

    2006-11-01

    The demands of the electron impact ionization cross sections in diverse fields are enormous. And this is hard to fulfill either by experimental or ab initio calculations. So various analytical and semi-classical models are applied for a rapid generation of ionization cross sections accurately. We have applied a modified version [1] of the Bell et. al. equations [2] including both the ionic and relativistic corrections. In this report we show how to generalize the MBELL parameters for treating the orbital quantum numbers nl dependency; the accuracy of the procedure is tested by evaluating cross sections for various species and energies. Detail results will be presented at the meeting. [1] A. K. F. Haque, M. A. Uddin, A. K. Basak, K. R. Karim and B. C. Saha, Phys. Rev. A73, 052703 (2006). [2] K. L. Bell, H. B. Gilbody, J. G. Hughes, A. E. Kingston, and F. J. Smith, J. Phys. Chem. Ref. Data 12, 891 (1983).

  14. Energy balance and mass conservation in reduced order models of fluid flows

    NASA Astrophysics Data System (ADS)

    Mohebujjaman, Muhammad; Rebholz, Leo G.; Xie, Xuping; Iliescu, Traian

    2017-10-01

    In this paper, we investigate theoretically and computationally the conservation properties of reduced order models (ROMs) for fluid flows. Specifically, we investigate whether the ROMs satisfy the same (or similar) energy balance and mass conservation as those satisfied by the Navier-Stokes equations. All of our theoretical findings are illustrated and tested in numerical simulations of a 2D flow past a circular cylinder at a Reynolds number Re = 100. First, we investigate the ROM energy balance. We show that using the snapshot average for the centering trajectory (which is a popular treatment of nonhomogeneous boundary conditions in ROMs) yields an incorrect energy balance. Then, we propose a new approach, in which we replace the snapshot average with the Stokes extension. Theoretically, the Stokes extension produces an accurate energy balance. Numerically, the Stokes extension yields more accurate results than the standard snapshot average, especially for longer time intervals. Our second contribution centers around ROM mass conservation. We consider ROMs created using two types of finite elements: the standard Taylor-Hood (TH) element, which satisfies the mass conservation weakly, and the Scott-Vogelius (SV) element, which satisfies the mass conservation pointwise. Theoretically, the error estimates for the SV-ROM are sharper than those for the TH-ROM. Numerically, the SV-ROM yields significantly more accurate results, especially for coarser meshes and longer time intervals.

  15. Electron Impact K-shell Ionization of Atomic Targets

    NASA Astrophysics Data System (ADS)

    Saha, Bidhan; Basak, Arun K.; Alfaz Uddin, M.; Patoary, A. A. R.

    2008-05-01

    In spite of considerable progress -both theoretically and experimentally- recently in evaluating accurate K-shell ionization cross sections that play a decisive role for quantitative analyses using (i) electron probe microanalysis, (ii) Auger electron spectroscopy and (iii) electron energy loss spectra, attempts are still continuing to search for a model that can easily generate reliable cross sections for a wide range of energies and for various targets needed for plasma modeling code We report few modifications of the widely used binary encounter approximation (BEA) [1,2] and have tested by evaluating the electron impact K-shell ionization of few neutral targets at various projectile energies. Details will be presented at the meeting. [1] M. Gryziniski, Phys. Rev. A 138, 336 (1965); [2] L. Vriens, Proc. Phys. Soc. (London) 89, 13, (1966). [3M. A. Uddin , A. K. F. Haque, M. M. Billah, A. K. Basak, K, R, Karim and B. C. Saha, ,Phys. Rev. A 71,032715 (2005); [4] M. A. Uddin, A. K. Basak, and B. C. Saha, Int. J. Quan. Chem 100, 184 (2004).

  16. Biological Effects of Ionizing Radiation

    DOE R&D Accomplishments Database

    Ingram, M.; Mason, W. B.; Whipple, G. H.; Howland, J. W.

    1952-04-07

    This report presents a review of present knowledge and concepts of the biological effects of ionizing radiations. Among the topics discussed are the physical and chemical effects of ionizing radiation on biological systems, morphological and physiological changes observed in biological systems subjected to ionizing radiations, physiological changes in the intact animal, latent changes following exposure of biological systems to ionizing radiations, factors influencing the biological response to ionizing radiation, relative effects of various ionizing radiations, and biological dosimetry.

  17. Ionization Waves of Arbitrary Velocity

    NASA Astrophysics Data System (ADS)

    Turnbull, D.; Franke, P.; Katz, J.; Palastro, J. P.; Begishev, I. A.; Boni, R.; Bromage, J.; Milder, A. L.; Shaw, J. L.; Froula, D. H.

    2018-06-01

    Flying focus is a technique that uses a chirped laser beam focused by a highly chromatic lens to produce an extended focal region within which the peak laser intensity can propagate at any velocity. When that intensity is high enough to ionize a background gas, an ionization wave will track the intensity isosurface corresponding to the ionization threshold. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced that propagated both forward and backward relative to the ionizing laser. All backward and all superluminal cases mitigated the issue of ionization-induced refraction that typically inhibits the formation of long, contiguous plasma channels.

  18. Balancing the Assessment "of" Learning and "for" Learning in Support of Student Literacy Achievement

    ERIC Educational Resources Information Center

    Edwards, Patricia A.; Turner, Jennifer D.; Mokhtari, Kouider

    2008-01-01

    There is a delicate balance between the assessment of learning and assessment for learning. The recommendations included in this Assessment department may be useful for teachers working to achieve this balance and find a more accurate and complete understandings of students' literacy strengths and needs.

  19. MULTI-FLUID APPROACH TO HIGH-FREQUENCY WAVES IN PLASMAS. I. SMALL-AMPLITUDE REGIME IN FULLY IONIZED MEDIUM

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

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume, E-mail: david.martinez@uib.es

    Ideal magnetohydrodynamics (MHD) provides an accurate description of low-frequency Alfvén waves in fully ionized plasmas. However, higher-frequency waves in many plasmas of the solar atmosphere cannot be correctly described by ideal MHD and a more accurate model is required. Here, we study the properties of small-amplitude incompressible perturbations in both the low- and the high-frequency ranges in plasmas composed of several ionized species. We use a multi-fluid approach and take into account the effects of collisions between ions and the inclusion of Hall’s term in the induction equation. Through the analysis of the corresponding dispersion relations and numerical simulations, wemore » check that at high frequencies ions of different species are not as strongly coupled as in the low-frequency limit. Hence, they cannot be treated as a single fluid. In addition, elastic collisions between the distinct ionized species are not negligible for high-frequency waves, since an appreciable damping is obtained. Furthermore, Coulomb collisions between ions remove the cyclotron resonances and the strict cutoff regions, which are present when collisions are not taken into account. The implications of these results for the modeling of high-frequency waves in solar plasmas are discussed.« less

  20. Regional citrate anticoagulation in hemodialysis: an observational study of safety, efficacy, and effect on calcium balance during routine care.

    PubMed

    Singer, Richard F; Williams, Oliver; Mercado, Chari; Chen, Bonny; Talaulikar, Girish; Walters, Giles; Roberts, Darren M

    2016-01-01

    Regional citrate hemodialysis anticoagulation is used when heparin is contraindicated, but most protocols require large infusions of calcium and frequent intradialytic plasma ionized calcium measurements. The objective of this study was to determine the safety, efficacy, and effect on calcium balance of regional citrate anticoagulation using sparse plasma ionized calcium sampling. The design of this study was observational. The setting of this study was the hospital hemodialysis center. The subjects of this study were the hospital hemodialysis patients. Dialysate calcium concentration by atomic absorption spectroscopy and total dialysate weight were used as measurements. Regional citrate anticoagulation was introduced using zero calcium dialysate, pre-dialyzer citrate infusion, and post-dialyzer calcium infusion. Infusions were adjusted based on pre- and post-dialyzer calcium measurements obtained at least twice during a 4-h dialysis. The protocol was simplified after the first 357 sessions to dispense with post-dialyzer calcium measurements. Heparin-anticoagulated sessions were performed using acetate-acidified 1.25 mmol/L calcium or citrate-acidified 1.5 mmol/L calcium dialysate. Calcium balance assessment was by complete dialysate recovery. Safety and efficacy were assessed prospectively using a point-of-care database to record ionized calcium and clinical events. Groups were compared using t test, ANOVA, Wilcoxon rank sum, or Kruskal-Wallis as appropriate. Seventy-five patients received regional citrate-anticoagulated dialysis over 1051 dialysis sessions. Of these, 357 dialysis sessions were performed using the original citrate anticoagulation protocol and 694 using the simplified protocol. Dialysis was effective and safe. Only 3 dialyzers clotted; 1 patient suffered symptomatic hypercalcemia and none suffered symptomatic hypocalcemia. Calcium balance was assessed in 15 regional citrate-anticoagulated dialysis sessions and 30 heparin-anticoagulated sessions

  1. 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.

  2. Ultrasound ionization of biomolecules.

    PubMed

    Wu, Chen-I; Wang, Yi-Sheng; Chen, Nelson G; Wu, Chung-Yi; Chen, Chung-Hsuan

    2010-09-15

    To date, mass spectrometric analysis of biomolecules has been primarily performed with either matrix-assisted laser desorption/ionization (MALDI) or electrospray ionization (ESI). In this work, ultrasound produced by a simple piezoelectric device is shown as an alternative method for soft ionization of biomolecules. Precursor ions of proteins, saccharides and fatty acids showed little fragmentation. Cavitation is considered as a primary mechanism for the ionization of biomolecules. Copyright 2010 John Wiley & Sons, Ltd.

  3. Detection of compensatory balance responses using wearable electromyography sensors for fall-risk assessment.

    PubMed

    Nouredanesh, Mina; Kukreja, Sunil L; Tung, James

    2016-08-01

    Loss of balance is prevalent in older adults and populations with gait and balance impairments. The present paper aims to develop a method to automatically distinguish compensatory balance responses (CBRs) from normal gait, based on activity patterns of muscles involved in maintaining balance. In this study, subjects were perturbed by lateral pushes while walking and surface electromyography (sEMG) signals were recorded from four muscles in their right leg. To extract sEMG time domain features, several filtering characteristics and segmentation approaches are examined. The performance of three classification methods, i.e., k-nearest neighbor, support vector machines, and random forests, were investigated for accurate detection of CBRs. Our results show that features extracted in the 50-200Hz band, segmented using peak sEMG amplitudes, and a random forest classifier detected CBRs with an accuracy of 92.35%. Moreover, our results support the important role of biceps femoris and rectus femoris muscles in stabilization and consequently discerning CBRs. This study contributes towards the development of wearable sensor systems to accurately and reliably monitor gait and balance control behavior in at-home settings (unsupervised conditions), over long periods of time, towards personalized fall risk assessment tools.

  4. Ionization Waves of Arbitrary Velocity

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

    Turnbull, D.; Franke, P.; Katz, J.

    The flying focus is a technique in which a chirped laser beam is focused by a chromatic lens to produce an extended focal spot within which laser intensity can propagate at any velocity. If the intensity is above the ionization threshold of a background gas, an ionization wave will track the ionization threshold intensity isosurface as it propagates. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced, both forward- and backward-propagating relative to the ionizing laser. In conclusion, all backward and all superluminal cases mitigated the issue of ionization-induced refractionmore » that typically challenges the formation of long, contiguous plasma channels.« less

  5. Ionization Waves of Arbitrary Velocity

    DOE PAGES

    Turnbull, D.; Franke, P.; Katz, J.; ...

    2018-05-31

    The flying focus is a technique in which a chirped laser beam is focused by a chromatic lens to produce an extended focal spot within which laser intensity can propagate at any velocity. If the intensity is above the ionization threshold of a background gas, an ionization wave will track the ionization threshold intensity isosurface as it propagates. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced, both forward- and backward-propagating relative to the ionizing laser. In conclusion, all backward and all superluminal cases mitigated the issue of ionization-induced refractionmore » that typically challenges the formation of long, contiguous plasma channels.« less

  6. Tunable Ionization Modes of a Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source.

    PubMed

    Badal, Sunil P; Michalak, Shawn D; Chan, George C-Y; You, Yi; Shelley, Jacob T

    2016-04-05

    Plasma-based ambient desorption/ionization sources are versatile in that they enable direct ionization of gaseous samples as well as desorption/ionization of analytes from liquid and solid samples. However, ionization matrix effects, caused by competitive ionization processes, can worsen sensitivity or even inhibit detection all together. The present study is focused on expanding the analytical capabilities of the flowing atmospheric-pressure afterglow (FAPA) source by exploring additional types of ionization chemistry. Specifically, it was found that the abundance and type of reagent ions produced by the FAPA source and, thus, the corresponding ionization pathways of analytes, can be altered by changing the source working conditions. High abundance of proton-transfer reagent ions was observed with relatively high gas flow rates and low discharge currents. Conversely, charge-transfer reagent species were most abundant at low gas flows and high discharge currents. A rather nonpolar model analyte, biphenyl, was found to significantly change ionization pathway based on source operating parameters. Different analyte ions (e.g., MH(+) via proton-transfer and M(+.) via charge-transfer) were formed under unique operating parameters demonstrating two different operating regimes. These tunable ionization modes of the FAPA were used to enable or enhance detection of analytes which traditionally exhibit low-sensitivity in plasma-based ADI-MS analyses. In one example, 2,2'-dichloroquaterphenyl was detected under charge-transfer FAPA conditions, which were difficult or impossible to detect with proton-transfer FAPA or direct analysis in real-time (DART). Overall, this unique mode of operation increases the number and range of detectable analytes and has the potential to lessen ionization matrix effects in ADI-MS analyses.

  7. Remote Sensing Estimates of Glacier Mass Balance Changes in the Himalayas of Nepal

    NASA Astrophysics Data System (ADS)

    Ambinakudige, S.; Joshi, K.

    2011-12-01

    Mass balance changes of glaciers are important indicators of climate change. There are only 30 'reference' glaciers in the world that have continuous mass balance data with world glacier monitoring service since 1976. Especially, Himalayan glaciers are conspicuously absent from global mass balance records. This shows the urgent need for mass balance data for glaciers throughout the world. In this study, we estimated mass balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. The SNP is one of the densest glaciated regions in the Himalayan range consisting approximately 296 glacial lakes. The region has experienced several glacial lake outburst floods (GLOFs) in recent years, causing extensive damage to local infrastructure and loss of human life. In general, mass balance is determined at seasonal or yearly intervals. Because of the rugged and difficult terrain of the Himalayan region, there are only a few field based measurements of mass balance available. Moreover, there are only few cases where the applications of remote sensing methods were used to calculate mass balance of the Himalayan glaciers due to the lack of accurate elevation data. Studies have shown that estimations of mass balance using remote sensing applications were within the range of field-based mass balance measurements from the same period. This study used ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area. 3N and 3B bands generate an along track stereo pair with a base-to-height (B/H) ratio of about 0.6. Accurate measurement of ground control points (GCPs), their numbers and distribution are important inputs in creating accurate DEMs. Because of the availability of topographic maps for this area, we were able to provide very accurate GCPs, in sufficient numbers and distribution. We created DEMs for the years 2002, 2003, 2004 and 2005 using ENVI DEM extraction tool. Bands

  8. Constrained Allocation Flux Balance Analysis

    PubMed Central

    Mori, Matteo; Hwa, Terence; Martin, Olivier C.

    2016-01-01

    New experimental results on bacterial growth inspire a novel top-down approach to study cell metabolism, combining mass balance and proteomic constraints to extend and complement Flux Balance Analysis. We introduce here Constrained Allocation Flux Balance Analysis, CAFBA, in which the biosynthetic costs associated to growth are accounted for in an effective way through a single additional genome-wide constraint. Its roots lie in the experimentally observed pattern of proteome allocation for metabolic functions, allowing to bridge regulation and metabolism in a transparent way under the principle of growth-rate maximization. We provide a simple method to solve CAFBA efficiently and propose an “ensemble averaging” procedure to account for unknown protein costs. Applying this approach to modeling E. coli metabolism, we find that, as the growth rate increases, CAFBA solutions cross over from respiratory, growth-yield maximizing states (preferred at slow growth) to fermentative states with carbon overflow (preferred at fast growth). In addition, CAFBA allows for quantitatively accurate predictions on the rate of acetate excretion and growth yield based on only 3 parameters determined by empirical growth laws. PMID:27355325

  9. Mammalian Tissue Response to Low Dose Ionizing Radiation: The Role of Oxidative Metabolism and Intercellular Communication

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

    Azzam, Edouard I

    2013-01-16

    The objective of the project was to elucidate the mechanisms underlying the biological effects of low dose/low dose rate ionizing radiation in organs/tissues of irradiated mice that differ in their susceptibility to ionizing radiation, and in human cells grown under conditions that mimic the natural in vivo environment. The focus was on the effects of sparsely ionizing cesium-137 gamma rays and the role of oxidative metabolism and intercellular communication in these effects. Four Specific Aims were proposed. The integrated outcome of the experiments performed to investigate these aims has been significant towards developing a scientific basis to more accurately estimatemore » human health risks from exposures to low doses ionizing radiation. By understanding the biochemical and molecular changes induced by low dose radiation, several novel markers associated with mitochondrial functions were identified, which has opened new avenues to investigate metabolic processes that may be affected by such exposure. In particular, a sensitive biomarker that is differentially modulated by low and high dose gamma rays was discovered.« less

  10. Fuel cell with ionization membrane

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2007-01-01

    A fuel cell is disclosed comprising an ionization membrane having at least one area through which gas is passed, and which ionizes the gas passing therethrough, and a cathode for receiving the ions generated by the ionization membrane. The ionization membrane may include one or more openings in the membrane with electrodes that are located closer than a mean free path of molecules within the gas to be ionized. Methods of manufacture are also provided.

  11. Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

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

    Song, Mi-Young; Yoon, Jung-Sik; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

    2015-04-15

    The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it ismore » found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.« less

  12. Low-dimensional, morphologically accurate models of subthreshold membrane potential

    PubMed Central

    Kellems, Anthony R.; Roos, Derrick; Xiao, Nan; Cox, Steven J.

    2009-01-01

    The accurate simulation of a neuron’s ability to integrate distributed synaptic input typically requires the simultaneous solution of tens of thousands of ordinary differential equations. For, in order to understand how a cell distinguishes between input patterns we apparently need a model that is biophysically accurate down to the space scale of a single spine, i.e., 1 μm. We argue here that one can retain this highly detailed input structure while dramatically reducing the overall system dimension if one is content to accurately reproduce the associated membrane potential at a small number of places, e.g., at the site of action potential initiation, under subthreshold stimulation. The latter hypothesis permits us to approximate the active cell model with an associated quasi-active model, which in turn we reduce by both time-domain (Balanced Truncation) and frequency-domain (ℋ2 approximation of the transfer function) methods. We apply and contrast these methods on a suite of typical cells, achieving up to four orders of magnitude in dimension reduction and an associated speed-up in the simulation of dendritic democratization and resonance. We also append a threshold mechanism and indicate that this reduction has the potential to deliver an accurate quasi-integrate and fire model. PMID:19172386

  13. Energy balance in the solar transition region. I - Hydrostatic thermal models with ambipolar diffusion

    NASA Technical Reports Server (NTRS)

    Fontenla, J. M.; Avrett, E. H.; Loeser, R.

    1990-01-01

    The energy balance in the lower transition region is analyzed by constructing theoretical models which satisfy the energy balance constraint. The energy balance is achieved by balancing the radiative losses and the energy flowing downward from the corona. This energy flow is mainly in two forms: conductive heat flow and hydrogen ionization energy flow due to ambipolar diffusion. Hydrostatic equilibrium is assumed, and, in a first calculation, local mechanical heating and Joule heating are ignored. In a second model, some mechanical heating compatible with chromospheric energy-balance calculations is introduced. The models are computed for a partial non-LTE approach in which radiation departs strongly from LTE but particles depart from Maxwellian distributions only to first order. The results, which apply to cases where the magnetic field is either absent, or uniform and vertical, are compared with the observed Lyman lines and continuum from the average quiet sun. The approximate agreement suggests that this type of model can roughly explain the observed intensities in a physically meaningful way, assuming only a few free parameters specified as chromospheric boundary conditions.

  14. An Integrated Fuselage-Sting Balance for a Sonic-Boom Wind-Tunnel Model

    NASA Technical Reports Server (NTRS)

    Mack, Robert J.

    2004-01-01

    Measured and predicted pressure signatures from a lifting wind-tunnel model can be compared when the lift on the model is accurately known. The model's lift can be set by bending the support sting to a desired angle of attack. This method is simple in practice, but difficult to accurately apply. A second method is to build a normal force/pitching moment balance into the aft end of the sting, and use an angle-of-attack mechanism to set model attitude. In this report, a method for designing a sting/balance into the aft fuselage/sting of a sonic-boom model is described. A computer code is given, and a sample sting design is outlined to demonstrate the method.

  15. Ionization equilibrium and radiative energy loss rates for C, N, and O ions in low-density plasmas

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    The results of calculations of the ionization equilibrium and radiative energy loss rates for C, N and O ions in low-density plasmas are presented for electron temperatures in the range 10,000-10,000,000 K. The ionization structure is determined by using the steady-state corona model, in which electron impact ionization from the ground states is balanced by direct radiative and dielectronic recombination. With an improved theory, detailed calculations are carried out for the dielectronic recombination rates in which account is taken of all radiative and autoionization processes involving a single-electron electric-dipole transition of the recombining ion. The radiative energy loss processes considered are electron-impact excitation of resonance line emission, direct radiative recombination, dielectronic recombination, and electron-ion bremsstrahlung. For all three elements, resonance line emission resulting from 2s-2p transitions produces a broad maximum in the energy loss rate near 100,000 K.

  16. Simple and universal model for electron-impact ionization of complex biomolecules

    NASA Astrophysics Data System (ADS)

    Tan, Hong Qi; Mi, Zhaohong; Bettiol, Andrew A.

    2018-03-01

    We present a simple and universal approach to calculate the total ionization cross section (TICS) for electron impact ionization in DNA bases and other biomaterials in the condensed phase. Evaluating the electron impact TICS plays a vital role in ion-beam radiobiology simulation at the cellular level, as secondary electrons are the main cause of DNA damage in particle cancer therapy. Our method is based on extending the dielectric formalism. The calculated results agree well with experimental data and show a good comparison with other theoretical calculations. This method only requires information of the chemical composition and density and an estimate of the mean binding energy to produce reasonably accurate TICS of complex biomolecules. Because of its simplicity and great predictive effectiveness, this method could be helpful in situations where the experimental TICS data are absent or scarce, such as in particle cancer therapy.

  17. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  18. Accurate Cross Sections for Microanalysis.

    PubMed

    Rez, Peter

    2002-01-01

    To calculate the intensity of x-ray emission in electron beam microanalysis requires a knowledge of the energy distribution of the electrons in the solid, the energy variation of the ionization cross section of the relevant subshell, the fraction of ionizations events producing x rays of interest and the absorption coefficient of the x rays on the path to the detector. The theoretical predictions and experimental data available for ionization cross sections are limited mainly to K shells of a few elements. Results of systematic plane wave Born approximation calculations with exchange for K, L, and M shell ionization cross sections over the range of electron energies used in microanalysis are presented. Comparisons are made with experimental measurement for selected K shells and it is shown that the plane wave theory is not appropriate for overvoltages less than 2.5 V.

  19. Reproducing impact ionization mass spectra of E and F ring ice grains at different impact speeds

    NASA Astrophysics Data System (ADS)

    Klenner, F.; Reviol, R.; Postberg, F.

    2017-09-01

    As impact speeds of E and F ring ice grains impinging onto the target of impact ionization mass spectrometers in space can vary greatly, the resulting cationic or anionic mass spectra can have very different appearances. The mass spectra can be accurately reproduced with an analog experimental setup IR-FL-MALDI-ToF-MS (Infrared Free Liquid Matrix Assisted Laser Desorption and Ionization Time of Flight Mass Spectrometry). We compare mass spectra of E and F ring ice grains taken by the Cosmic Dust Analyzer (CDA) onboard Cassini recorded at different impact speeds with our analog spectra and prove the capability of the analog experiment.

  20. Atmospheric Pressure Ionization Using a High Voltage Target Compared to Electrospray Ionization.

    PubMed

    Lubin, Arnaud; Bajic, Steve; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip

    2017-02-01

    A new atmospheric pressure ionization (API) source, viz. UniSpray, was evaluated for mass spectrometry (MS) analysis of pharmaceutical compounds by head-to-head comparison with electrospray ionization (ESI) on the same high-resolution MS system. The atmospheric pressure ionization source is composed of a grounded nebulizer spraying onto a high voltage, cylindrical stainless steel target. Molecules are ionized in a similar fashion to electrospray ionization, predominantly producing protonated or deprotonated species. Adduct formation (e.g., proton and sodium adducts) and in-source fragmentation is shown to be almost identical between the two sources. The performance of the new API source was compared with electrospray by infusion of a mix of 22 pharmaceutical compounds with a wide variety of functional groups and physico-chemical properties (molecular weight, logP, and pKa) in more than 100 different conditions (mobile phase strength, solvents, pH, and flow rate). The new API source shows an intensity gain of a factor 2.2 compared with ESI considering all conditions on all compounds tested. Finally, some hypotheses on the ionization mechanism, similarities, and differences with ESI, are discussed. Graphical Abstract ᅟ.

  1. Atmospheric Pressure Ionization Using a High Voltage Target Compared to Electrospray Ionization

    NASA Astrophysics Data System (ADS)

    Lubin, Arnaud; Bajic, Steve; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip

    2017-02-01

    A new atmospheric pressure ionization (API) source, viz. UniSpray, was evaluated for mass spectrometry (MS) analysis of pharmaceutical compounds by head-to-head comparison with electrospray ionization (ESI) on the same high-resolution MS system. The atmospheric pressure ionization source is composed of a grounded nebulizer spraying onto a high voltage, cylindrical stainless steel target. Molecules are ionized in a similar fashion to electrospray ionization, predominantly producing protonated or deprotonated species. Adduct formation (e.g., proton and sodium adducts) and in-source fragmentation is shown to be almost identical between the two sources. The performance of the new API source was compared with electrospray by infusion of a mix of 22 pharmaceutical compounds with a wide variety of functional groups and physico-chemical properties (molecular weight, logP, and pKa) in more than 100 different conditions (mobile phase strength, solvents, pH, and flow rate). The new API source shows an intensity gain of a factor 2.2 compared with ESI considering all conditions on all compounds tested. Finally, some hypotheses on the ionization mechanism, similarities, and differences with ESI, are discussed.

  2. Power balance and loss mechanism analysis in RF transmit coil arrays.

    PubMed

    Kuehne, Andre; Goluch, Sigrun; Waxmann, Patrick; Seifert, Frank; Ittermann, Bernd; Moser, Ewald; Laistler, Elmar

    2015-10-01

    To establish a framework for transmit array power balance calculations based on power correlation matrices to accurately quantify the loss contributions from different mechanisms such as coupling, lumped components, and radiation. Starting from Poynting's theorem, power correlation matrices are derived for all terms in the power balance, which is formulated as a matrix equation. Finite-difference time-domain simulations of two 7 T eight-channel head array coils at 297.2 MHz are used to verify the theoretical considerations and demonstrate their application. Care is taken to accurately incorporate all loss mechanisms. The power balance for static B1 phase shims as well as two-dimensional spatially selective transmit SENSE pulses is shown. The simulated power balance shows an excellent agreement with theory, with a maximum power imbalance of less than 0.11%. Power loss contributions from the different loss mechanisms vary significantly between the investigated setups, and depending on the excitation mode imposed on the coil. The presented approach enables a straightforward loss evaluation for an arbitrary excitation of transmit coil arrays. Worst-case power imbalance and losses are calculated in a straightforward manner. This allows for deeper insight into transmit array loss mechanisms, incorporation of radiated power components in specific absorption rate calculations and verification of electromagnetic simulations. © 2014 Wiley Periodicals, Inc.

  3. Advances in the two-source energy balance model:Partioning of evaporation and transpiration for row crops

    USDA-ARS?s Scientific Manuscript database

    Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. The two-source energy balance (TSEB) model solves the energy balance of the soil-plant...

  4. Roles of Tunneling, Multiphoton Ionization, and Cascade Ionization for Femtosecond Optical Breakdown in Aqueous Media

    DTIC Science & Technology

    2009-09-01

    observed in the wavelength dependence of femtosecond breakdown would indicate a significant role of multiphoton ionization compared to tunneling ...relevant for femtosecond breakdown, and tunnel ionization featuring no Ith() dependence becomes ever more with decreasing pulse duration. However, it...c) Figure 4.22 Wavelength dependence of ionization probabilities by a) avalanche, b) multiphoton, and c) tunneling ionization. 1

  5. Balanced Flow Meters without Moving Parts

    NASA Technical Reports Server (NTRS)

    Kelley, Anthony R.; VanBuskirk, Paul

    2008-01-01

    Balanced flow meters are recent additions to an established class of simple, rugged flow meters that contain no moving parts in contact with flow and are based on measurement of pressure drops across objects placed in flow paths. These flow meters are highly accurate, minimally intrusive, easily manufacturable, and reliable. A balanced flow meter can be easily mounted in a flow path by bolting it between conventional pipe flanges. A balanced flow meter can be used to measure the flow of any of a variety of liquids or gases, provided that it has been properly calibrated. Relative to the standard orifice-plate flow meter, the balanced flow meter introduces less turbulence and two times less permanent pressure loss and is therefore capable of offering 10 times greater accuracy and repeatability with less dissipation of energy. A secondary benefit of the reduction of turbulence is the reduction of vibration and up to 15 times less acoustic noise generation. Both the balanced flow meter and the standard orifice-plate flow meter are basically disks that contain holes and are instrumented with pressure transducers on their upstream and downstream faces. The most obvious difference between them is that the standard orifice plate contains a single, central hole while the balanced flow meter contains multiple holes. The term 'balanced' signifies that in designing the meter, the sizes and locations of the holes are determined in an optimization procedure that involves balancing of numerous factors, including volumetric flow, mass flow, dynamic pressure, kinetic energy, all in an effort to minimize such undesired effects as turbulence, pressure loss, dissipation of kinetic energy, and non-repeatability and nonlinearity of response over the anticipated range of flow conditions. Due to proper balancing of these factors, recent testing demonstrated that the balanced flow-meter performance was similar to a Venturi tube in both accuracy and pressure recovery, but featured reduced

  6. CHAMBER - IONIZATION - EXPERIMENT - GEMINI-TITAN (GT)-6 EQUIPMENT - CAPE

    NASA Image and Video Library

    1965-12-10

    S65-61788 (For release: 11 Dec. 1965) --- Close-up view of equipment which will be used in the D-8 (Radiation in Spacecraft) experiment on the National Aeronautics and Space Administration's Gemini-6 spaceflight. This experiment is designed to make highly accurate measurements of the absorbed dose rate of radiation which penetrates the Gemini spacecraft, and determine the spatial distribution of dose levels inside the spacecraft particularly in the crew area. This is experimentation of the U.S. Air Force Weapons Laboratory, Kirtland AFB, N.M. LOWER LEFT: The second ionization chamber, this one is unshielded. This chamber can be removed from its bracket by the astronaut who will periodically take measurements at various locations in the spacecraft. Nearby is Passive Dosimeter Unit which is one of five small packets each containing a standard pocket ionization chamber, gamma electron sensitive film, glass needles and thermo luminescent dosimeters which are mounted at various locations in the cabin. UPPER LEFT: Photo illustrates how ionization chamber can be removed from bracket for measurements. LOWER RIGHT: Shield of bulb-shaped chamber will be removed (shown in photo) as the spacecraft passes through the South Atlantic anomaly, the area where the radiation belt dips closest to Earth's surface. UPPER RIGHT: Dome-shaped object is shield covering one of two Tissue Equivalent Ionization Chambers (sensors) which will read out continuously the instantaneous rate at which dose is delivered during the flight. This chamber is mounted permanently. The information will be recorded aboard the spacecraft, and will also be received directly by ground stations. This chamber is shielded to simulate the amount of radiation the crew members are receiving beneath their skin. Photo credit: NASA or National Aeronautics and Space Administration

  7. Stable isotope dilution HILIC-MS/MS method for accurate quantification of glutamic acid, glutamine, pyroglutamic acid, GABA and theanine in mouse brain tissues.

    PubMed

    Inoue, Koichi; Miyazaki, Yasuto; Unno, Keiko; Min, Jun Zhe; Todoroki, Kenichiro; Toyo'oka, Toshimasa

    2016-01-01

    In this study, we developed the stable isotope dilution hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS) technique for the accurate, reasonable and simultaneous quantification of glutamic acid (Glu), glutamine (Gln), pyroglutamic acid (pGlu), γ-aminobutyric acid (GABA) and theanine in mouse brain tissues. The quantification of these analytes was accomplished using stable isotope internal standards and the HILIC separating mode to fully correct the intramolecular cyclization during the electrospray ionization. It was shown that linear calibrations were available with high coefficients of correlation (r(2)  > 0.999, range from 10 pmol/mL to 50 mol/mL). For application of the theanine intake, the determination of Glu, Gln, pGlu, GABA and theanine in the hippocampus and central cortex tissues was performed based on our developed method. In the region of the hippocampus, the concentration levels of Glu and pGlu were significantly reduced during reality-based theanine intake. Conversely, the concentration level of GABA increased. This result showed that transited theanine has an effect on the metabolic balance of Glu analogs in the hippocampus. Copyright © 2015 John Wiley & Sons, Ltd.

  8. Direct Standard-Free Quantitation of Tamiflu® and Other Pharmaceutical Tablets using Clustering Agents with Electrospray Ionization Mass Spectrometry

    PubMed Central

    Flick, Tawnya G.; Leib, Ryan D.; Williams, Evan R.

    2010-01-01

    Accurate and rapid quantitation is advantageous to identify counterfeit and substandard pharmaceutical drugs. A standard-free electrospray ionization mass spectrometry method is used to directly determine the dosage in the prescription and over-the-counter drugs, Tamiflu®, Sudafed®, and Dramamine®. A tablet of each drug was dissolved in aqueous solution, filtered, and introduced into solutions containing a known concentration of either L-tryptophan, L-phenylalanine or prednisone as clustering agents. The active ingredient(s) incorporates statistically into large clusters of the clustering agent where effects of differential ionization/detection are substantially reduced. From the abundances of large clusters, the dosages of the active ingredients in each of the tablets were determined to typically better than 20% accuracy even when the ionization/detection efficiency of the individual components differed by over 100×. Although this unorthodox method for quantitation is not as accurate as using conventional standards, it has the advantages that it is fast, it can be applied to mixtures where the identities of the analytes are unknown, and it can be used when suitable standards may not be readily available, such as schedule I or II controlled substances or new designer drugs that have not previously been identified. PMID:20092258

  9. Dissociative Ionization and Product Distributions of Benzene and Pyridine by Electron Impact

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher E.; Huo, Winifred M.; Fletcher, Graham D.

    2003-01-01

    We report a theoretical study of the dissociative ionization (DI) and product distributions of benzene (C6H6) and pyridine (C5H5N) from their low-lying ionization channels. Our approach makes use of the fact that electronic motion is much faster than nuclear motion allowing DI to be treated as a two-step process. The first step is the electron-impact ionization resulting in an ion with the same nuclear geometry as the neutral molecule. In the second step, the nuclei relax from the initial geometry and undergo unimolecular dissociation. For the ionization process we use the improved binary-encounter dipole (iBED) model [W.M. Huo, Phys. Rev. A64,042719-I (2001)]. For the unimolecular dissociation, we use multiconfigurational self-consistent field (MCSCF) methods to determine the steepest descent pathways to the possible product channels. More accurate methods are then used to obtain better energetics of the paths which are used to determine unimolecular dissociation probabilities and product distributions. Our analysis of the dissociation products and the thresholds of their productions for benzene are compared with the recent dissociative photoionization meausurements of benzene by Feng et al. [R. Feng, G. Cooper, C.E. Brion, J. Electron Spectrosc. Relat. Phenom. 123,211 (2002)] and the dissociative photoionization measurements of pyridine by Tixier et al. [S. Tixier, G. Cooper, R. Feng, C.E. Brion, J. Electron Spectrosc. Relat. Phenom. 123,185 (2002)] using dipole (e,e+ion) coincidence spectroscopy.

  10. Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

    NASA Astrophysics Data System (ADS)

    Kauppila, Tiina J.; Kersten, Hendrik; Benter, Thorsten

    2015-06-01

    Seventy-seven EPA priority environmental pollutants were analyzed using gas chromatography-mass spectrometry (GC-MS) equipped with an optimized atmospheric pressure photoionization (APPI) and an atmospheric pressure laser ionization (APLI) interface with and without dopants. The analyzed compounds included e.g., polycyclic aromatic hydrocarbons (PAHs), nitro compounds, halogenated compounds, aromatic compounds with phenolic, acidic, alcohol, and amino groups, phthalate and adipatic esters, and aliphatic ethers. Toluene, anisole, chlorobenzene, and acetone were tested as dopants. The widest range of analytes was ionized using direct APPI (66/77 compounds). The introduction of dopants decreased the amount of compounds ionized in APPI (e.g., 54/77 with toluene), but in many cases the ionization efficiency increased. While in direct APPI the formation of molecular ions via photoionization was the main ionization reaction, dopant-assisted (DA) APPI promoted ionization reactions, such as charge exchange and proton transfer. Direct APLI ionized a much smaller amount of compounds than APPI (41/77 compounds), showing selectivity towards compounds with low ionization energies (IEs) and long-lived resonantly excited intermediate states. DA-APLI, however, was able to ionize a higher amount of compounds (e.g. 51/77 with toluene), as the ionization took place entirely through dopant-assisted ion/molecule reactions similar to those in DA-APPI. Best ionization efficiency in APPI and APLI (both direct and DA) was obtained for PAHs and aromatics with O- and N-functionalities, whereas nitro compounds and aliphatic ethers were the most difficult to ionize. Halogenated aromatics and esters were (mainly) ionized in APPI, but not in APLI.

  11. Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies.

    PubMed

    Beste, A; Harrison, R J; Yanai, T

    2006-08-21

    Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (cf. thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a nongeometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as the constraint on the orbitals to be orthogonal.

  12. An Analysis of Mass Balance of Chilean Glaciers

    NASA Astrophysics Data System (ADS)

    Ambinakudige, S.; Tetteh, L.

    2013-12-01

    Glaciers in Chile range from very small glacierets found on the isolated volcanoes of northern Chile to the 13,000 sq.km Southern Patagonian Ice Field. Regular monitoring of these glaciers is very important as they are considered as sensitive indicators of climate change. Millions of people's lives are dependent on these glaciers for fresh water and irrigation purpose. In this study, mass balances of several Chilean glaciers were estimated using Aster satellite images between 2007 and 2012. Highly accurate DEMs were created with supplementary information from IceSat data. The result indicated a negative mass balance for many glaciers indicating the need for further monitoring of glaciers in the Andes.

  13. Electron-impact Multiple-ionization Cross Sections for Atoms and Ions of Helium through Zinc

    NASA Astrophysics Data System (ADS)

    Hahn, M.; Müller, A.; Savin, D. W.

    2017-12-01

    We compiled a set of electron-impact multiple-ionization (EIMI) cross section for astrophysically relevant ions. EIMIs can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature or if there is a non-thermal electron energy distribution, such as a kappa distribution. Cross section for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation. Here, we describe our comparison of proposed semiempirical formulae to available experimental EIMI cross-section data. Based on this comparison, we interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for 3466 EIMI cross sections and the associated Maxwellian plasma rate coefficients. We also highlight some outstanding issues that remain to be resolved.

  14. Negative chemical ionization gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry and automated accurate mass data processing for determination of pesticides in fruit and vegetables.

    PubMed

    Besil, Natalia; Uclés, Samanta; Mezcúa, Milagros; Heinzen, Horacio; Fernández-Alba, Amadeo R

    2015-08-01

    Gas chromatography coupled to high resolution hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS), operating in negative chemical ionization (NCI) mode and combining full scan with MSMS experiments using accurate mass analysis, has been explored for the automated determination of pesticide residues in fruit and vegetables. Seventy compounds were included in this approach where 50 % of them are not approved by the EU legislation. A global 76 % of the analytes could be identified at 1 μg kg(-1). Recovery studies were developed at three concentration levels (1, 5, and 10 μg kg(-1)). Seventy-seven percent of the detected pesticides at the lowest level yielded recoveries within the 70 %-120 % range, whereas 94 % could be quantified at 5 μg kg(-1), and the 100 % were determined at 10 μg kg(-1). Good repeatability, expressed as relative standard deviation (RSD <20 %), was obtained for all compounds. The main drawback of the method was the limited dynamic range that was observed for some analytes that can be overcome either diluting the sample or lowering the injection volume. A home-made database was developed and applied to an automatic accurate mass data processing. Measured mass accuracies of the generated ions were mainly less than 5 ppm for at least one diagnostic ion. When only one ion was obtained in the single-stage NCI-MS, a representative product ion from MSMS experiments was used as identification criterion. A total of 30 real samples were analyzed and 67 % of the samples were positive for 12 different pesticides in the range 1.0-1321.3 μg kg(-1).

  15. Performance and cost analysis of matrix-assisted laser desorption ionization-time of flight mass spectrometry for routine identification of yeast.

    PubMed

    Dhiman, Neelam; Hall, Leslie; Wohlfiel, Sherri L; Buckwalter, Seanne P; Wengenack, Nancy L

    2011-04-01

    Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry was compared to phenotypic testing for yeast identification. MALDI-TOF mass spectrometry yielded 96.3% and 84.5% accurate species level identifications (spectral scores, ≥ 1.8) for 138 common and 103 archived strains of yeast. MALDI-TOF mass spectrometry is accurate, rapid (5.1 min of hands-on time/identification), and cost-effective ($0.50/sample) for yeast identification in the clinical laboratory.

  16. An investigation of energy balances in palladium cathode electrolysis experiments

    NASA Astrophysics Data System (ADS)

    Longhurst, G. R.; Dolan, T. J.; Henriksen, G. L.

    1990-09-01

    A series of experiments was performed at the Idaho National Engineering Laboratory (INEL) to investigate mechanisms that may contribute to energy flows in electrolysis cells like those of Fleischmann and Pons. Ordinary water (H2O), heavy water (D2O), and a mixture of the two were used in the INEL experiments. Cathodes used include a 51-μm Pd foil and 1-mm diameter extruded wire Pd rods in straight and coiled configurations. Energy balances in these experiments revealed no significant net gain or net loss of energy. Cell overpotential curves were fit well with a Tafel equation, with parameters dependent on electrode configuration, electrolyte composition, and temperature. Water evaporation and interactions of hydrogen isotopes with the Pd cathode were evaluated and found not to be significant to energy balances. No ionizing radiation, tritium production, or other evidence of fusion reactions was observed in the INEL experiments.

  17. Nitric oxide coordinates development of genomic instability in realization of combined effect with ionizing radiation.

    PubMed

    Mikhailenko, V M; Diomina, E A; Muzalov, I I; Gerashchenko, B I

    2013-03-01

    The aim of this study was to investigate the ability of environmental nitrogen oxides or natural nitric oxide (NO) donors to modify free radicals ba-lance and development of genomic instability alone or in combination with ionizing radiation. Genotoxicity and cytogenetic abnormalities were assessed in vitro in peripheral blood lymphocytes (PBL) isolated from healthy humans or in vivo in rats PBL. Human PBL were treated with physiologically relevant NO donor - S-Nitrosoglutathione and X-ray irradiation. The inhalation treatment of animals with NO was carried out in chamber with purified gaseous NO mixed inside with air. Levels of S-Nitrosohemoglobin and methemoglobin in the blood were assessed with electron paramagnetic resonance. The total level of reactive oxygen and nitrogen species in PBL was determined fluorometrically, and serum levels of reactive oxygen species was determined by spectrophotometric assay. DNA damages were assessed by alkaline single-cell gel electrophoresis. The frequency of chromosomal aberrations in human PBL measured with the conventional cytogenetic assay in metaphase cells on short-term (52 h) and long-term (72 h) cultures. Environmental nitrogen oxides or release of NO from stable complexes with biomolecules (such as S-Nitrosothiols) intensified generation of free radicals, DNA damage and development of genomic instability alone or in combination with ionizing radiation. Treatment of PBL by S-Nitrosoglutathione caused prevalent induction of chromatid type but irradiation - chromosome aberrations. The dose dependence of chromatid-type aberrations observed in human PBL after combined influence of S-Nitrosoglutathione and ionizing radiation indicates a crucial role of NO in the formation of chromosomal instability. NO can deregulate free radicals balance resulted in genotoxic effect, posttranslational modification of repair enzymes and thus coordinated development of genomic instability and increase of cancer risk.

  18. How effective are traditional methods of compositional analysis in providing an accurate material balance for a range of softwood derived residues?

    PubMed Central

    2013-01-01

    Background Forest residues represent an abundant and sustainable source of biomass which could be used as a biorefinery feedstock. Due to the heterogeneity of forest residues, such as hog fuel and bark, one of the expected challenges is to obtain an accurate material balance of these feedstocks. Current compositional analytical methods have been standardised for more homogenous feedstocks such as white wood and agricultural residues. The described work assessed the accuracy of existing and modified methods on a variety of forest residues both before and after a typical pretreatment process. Results When “traditional” pulp and paper methods were used, the total amount of material that could be quantified in each of the six softwood-derived residues ranged from 88% to 96%. It was apparent that the extractives present in the substrate were most influential in limiting the accuracy of a more representative material balance. This was particularly evident when trying to determine the lignin content, due to the incomplete removal of the extractives, even after a two stage water-ethanol extraction. Residual extractives likely precipitated with the acid insoluble lignin during analysis, contributing to an overestimation of the lignin content. Despite the minor dissolution of hemicellulosic sugars, extraction with mild alkali removed most of the extractives from the bark and improved the raw material mass closure to 95% in comparison to the 88% value obtained after water-ethanol extraction. After pretreatment, the extent of extractive removal and their reaction/precipitation with lignin was heavily dependent on the pretreatment conditions used. The selective removal of extractives and their quantification after a pretreatment proved to be even more challenging. Regardless of the amount of extractives that were originally present, the analytical methods could be refined to provide reproducible quantification of the carbohydrates present in both the starting material and

  19. High pressure xenon ionization detector

    DOEpatents

    Markey, J.K.

    1989-11-14

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

  20. High pressure xenon ionization detector

    DOEpatents

    Markey, John K.

    1989-01-01

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

  1. Ab initio approaches for the determination of heavy element energetics: Ionization energies of trivalent lanthanides (Ln = La-Eu)

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

    Peterson, Charles; Penchoff, Deborah A.; Wilson, Angela K., E-mail: wilson@chemistry.msu.edu

    2015-11-21

    An effective approach for the determination of lanthanide energetics, as demonstrated by application to the third ionization energy (in the gas phase) for the first half of the lanthanide series, has been developed. This approach uses a combination of highly correlated and fully relativistic ab initio methods to accurately describe the electronic structure of heavy elements. Both scalar and fully relativistic methods are used to achieve an approach that is both computationally feasible and accurate. The impact of basis set choice and the number of electrons included in the correlation space has also been examined.

  2. Gap-Balancing versus Measured Resection Technique in Total Knee Arthroplasty: A Comparison Study.

    PubMed

    Churchill, Jessica L; Khlopas, Anton; Sultan, Assem A; Harwin, Steven F; Mont, Michael A

    2018-01-01

    Proper femoral component alignment in the axial plane during total knee arthroplasty (TKA) depends on accurate bone cuts and soft tissue balancing. Two methods that are used to achieve this are "measured resection" and "gap balancing." However, a controversy exists as to which method is more accurate and leads to better outcomes. Therefore, the purpose of this study was to evaluate: (1) implant survivorship, (2) patient outcomes, (3) complications, and (4) radiographic analysis comparing patients who underwent TKA with either gap-balancing or measured resection techniques. A total of 214 consecutive patients (221 knees) underwent primary TKA by a single surgeon between 2011 and 2012. Component alignment was achieved by using measured resection in 116 knees and gap balancing was used in 105 knees. The patients had a mean age of 66 years (range, 44-86 years) and a mean body mass index of 32 kg/m 2 (range, 22-52 kg/m 2 ). Patient range-of-motion (ROM) and Knee Society (KS) function and pain scores, and radiographic assessment, were assessed preoperatively and postoperatively at ∼6 weeks, 3 months, 1 year, and then annually. The mean follow-up time was 3 years. A Kaplan-Meier's analysis was performed to calculate the survivorship. The aseptic survivorship was 98% in both the measured resection and gap-balancing groups. The mean ROM was not significantly different between the measured resection and gap-balancing groups (123 vs. 123 degrees, p  = 0.990). There were no significant differences between the two groups in terms of the KS function scores (86 vs. 85 points, p  = 0.829) or the KS pain scores (93 vs. 92 points, p  = 0.425). Otherwise, the radiographic evaluation at latest follow-up did not demonstrate any evidence of progressive radiolucencies or loosening, of any prosthesis. The results of this study found that at a mean follow-up of 3 years, both the measured resection and gap-balancing techniques achieved excellent survivorship and

  3. How accurately are climatological characteristics and surface water and energy balances represented for the Colombian Caribbean Catchment Basin?

    NASA Astrophysics Data System (ADS)

    Hoyos, Isabel; Baquero-Bernal, Astrid; Hagemann, Stefan

    2013-09-01

    In Colombia, the access to climate related observational data is restricted and their quantity is limited. But information about the current climate is fundamental for studies on present and future climate changes and their impacts. In this respect, this information is especially important over the Colombian Caribbean Catchment Basin (CCCB) that comprises over 80 % of the population of Colombia and produces about 85 % of its GDP. Consequently, an ensemble of several datasets has been evaluated and compared with respect to their capability to represent the climate over the CCCB. The comparison includes observations, reconstructed data (CPC, Delaware), reanalyses (ERA-40, NCEP/NCAR), and simulated data produced with the regional climate model REMO. The capabilities to represent the average annual state, the seasonal cycle, and the interannual variability are investigated. The analyses focus on surface air temperature and precipitation as well as on surface water and energy balances. On one hand the CCCB characteristics poses some difficulties to the datasets as the CCCB includes a mountainous region with three mountain ranges, where the dynamical core of models and model parameterizations can fail. On the other hand, it has the most dense network of stations, with the longest records, in the country. The results can be summarised as follows: all of the datasets demonstrate a cold bias in the average temperature of CCCB. However, the variability of the average temperature of CCCB is most poorly represented by the NCEP/NCAR dataset. The average precipitation in CCCB is overestimated by all datasets. For the ERA-40, NCEP/NCAR, and REMO datasets, the amplitude of the annual cycle is extremely high. The variability of the average precipitation in CCCB is better represented by the reconstructed data of CPC and Delaware, as well as by NCEP/NCAR. Regarding the capability to represent the spatial behaviour of CCCB, temperature is better represented by Delaware and REMO, while

  4. Tunneling Time and Weak Measurement in Strong Field Ionization.

    PubMed

    Zimmermann, Tomáš; Mishra, Siddhartha; Doran, Brent R; Gordon, Daniel F; Landsman, Alexandra S

    2016-06-10

    Tunneling delays represent a hotly debated topic, with many conflicting definitions and little consensus on when and if such definitions accurately describe the physical observables. Here, we relate these different definitions to distinct experimental observables in strong field ionization, finding that two definitions, Larmor time and Bohmian time, are compatible with the attoclock observable and the resonance lifetime of a bound state, respectively. Both of these definitions are closely connected to the theory of weak measurement, with Larmor time being the weak measurement value of tunneling time and Bohmian trajectory corresponding to the average particle trajectory, which has been recently reconstructed using weak measurement in a two-slit experiment [S. Kocsis, B. Braverman, S. Ravets, M. J. Stevens, R. P. Mirin, L. K. Shalm, and A. M. Steinberg, Science 332, 1170 (2011)]. We demonstrate a big discrepancy in strong field ionization between the Bohmian and weak measurement values of tunneling time, and we suggest this arises because the tunneling time is calculated for a small probability postselected ensemble of electrons. Our results have important implications for the interpretation of experiments in attosecond science, suggesting that tunneling is unlikely to be an instantaneous process.

  5. Electron-Impact Ionization and Dissociative Ionization of Biomolecules

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Chaban, Galina M.; Dateo, Christopher E.

    2006-01-01

    It is well recognized that secondary electrons play an important role in radiation damage to humans. Particularly important is the damage of DNA by electrons, potentially leading to mutagenesis. Molecular-level study of electron interaction with DNA provides information on the damage pathways and dominant mechanisms. Our study of electron-impact ionization of DNA fragments uses the improved binary-encounter dipole model and covers DNA bases, sugar phosphate backbone, and nucleotides. An additivity principle is observed. For example, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3(sup prime)- and C5 (sup prime)-deoxyribose-phospate cross sections, differing by less than 5%. Investigation of tandem double lesion initiated by electron-impact dissociative ionization of guanine, followed by proton reaction with the cytosine in the Watson-Crick pair, is currently being studied to see if tandem double lesion can be initiated by electron impact. Up to now only OH-induced tandem double lesion has been studied.

  6. LiF TLD-100 as a dosimeter in high energy proton beam therapy--can it yield accurate results?

    PubMed

    Zullo, John R; Kudchadker, Rajat J; Zhu, X Ronald; Sahoo, Narayan; Gillin, Michael T

    2010-01-01

    In the region of high-dose gradients at the end of the proton range, the stopping power ratio of the protons undergoes significant changes, allowing for a broad spectrum of proton energies to be deposited within a relatively small volume. Because of the potential linear energy transfer dependence of LiF TLD-100 (thermolumescent dosimeter), dose measurements made in the distal fall-off region of a proton beam may be less accurate than those made in regions of low-dose gradients. The purpose of this study is to determine the accuracy and precision of dose measured using TLD-100 for a pristine Bragg peak, particularly in the distal fall-off region. All measurements were made along the central axis of an unmodulated 200-MeV proton beam from a Probeat passive beam-scattering proton accelerator (Hitachi, Ltd., Tokyo, Japan) at varying depths along the Bragg peak. Measurements were made using TLD-100 powder flat packs, placed in a virtual water slab phantom. The measurements were repeated using a parallel plate ionization chamber. The dose measurements using TLD-100 in a proton beam were accurate to within +/-5.0% of the expected dose, previously seen in our past photon and electron measurements. The ionization chamber and the TLD relative dose measurements agreed well with each other. Absolute dose measurements using TLD agreed with ionization chamber measurements to within +/- 3.0 cGy, for an exposure of 100 cGy. In our study, the differences in the dose measured by the ionization chamber and those measured by TLD-100 were minimal, indicating that the accuracy and precision of measurements made in the distal fall-off region of a pristine Bragg peak is within the expected range. Thus, the rapid change in stopping power ratios at the end of the range should not affect such measurements, and TLD-100 may be used with confidence as an in vivo dosimeter for proton beam therapy. Copyright 2010 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights

  7. LiF TLD-100 as a Dosimeter in High Energy Proton Beam Therapy-Can It Yield Accurate Results?

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

    Zullo, John R.; Kudchadker, Rajat J.; Zhu, X. Ronald

    In the region of high-dose gradients at the end of the proton range, the stopping power ratio of the protons undergoes significant changes, allowing for a broad spectrum of proton energies to be deposited within a relatively small volume. Because of the potential linear energy transfer dependence of LiF TLD-100 (thermolumescent dosimeter), dose measurements made in the distal fall-off region of a proton beam may be less accurate than those made in regions of low-dose gradients. The purpose of this study is to determine the accuracy and precision of dose measured using TLD-100 for a pristine Bragg peak, particularly inmore » the distal fall-off region. All measurements were made along the central axis of an unmodulated 200-MeV proton beam from a Probeat passive beam-scattering proton accelerator (Hitachi, Ltd., Tokyo, Japan) at varying depths along the Bragg peak. Measurements were made using TLD-100 powder flat packs, placed in a virtual water slab phantom. The measurements were repeated using a parallel plate ionization chamber. The dose measurements using TLD-100 in a proton beam were accurate to within {+-}5.0% of the expected dose, previously seen in our past photon and electron measurements. The ionization chamber and the TLD relative dose measurements agreed well with each other. Absolute dose measurements using TLD agreed with ionization chamber measurements to within {+-} 3.0 cGy, for an exposure of 100 cGy. In our study, the differences in the dose measured by the ionization chamber and those measured by TLD-100 were minimal, indicating that the accuracy and precision of measurements made in the distal fall-off region of a pristine Bragg peak is within the expected range. Thus, the rapid change in stopping power ratios at the end of the range should not affect such measurements, and TLD-100 may be used with confidence as an in vivo dosimeter for proton beam therapy.« less

  8. Electron Impact Ionization: A New Parameterization for 100 eV to 1 MeV Electrons

    NASA Technical Reports Server (NTRS)

    Fang, Xiaohua; Randall, Cora E.; Lummerzheim, Dirk; Solomon, Stanley C.; Mills, Michael J.; Marsh, Daniel; Jackman, Charles H.; Wang, Wenbin; Lu, Gang

    2008-01-01

    Low, medium and high energy electrons can penetrate to the thermosphere (90-400 km; 55-240 miles) and mesosphere (50-90 km; 30-55 miles). These precipitating electrons ionize that region of the atmosphere, creating positively charged atoms and molecules and knocking off other negatively charged electrons. The precipitating electrons also create nitrogen-containing compounds along with other constituents. Since the electron precipitation amounts change within minutes, it is necessary to have a rapid method of computing the ionization and production of nitrogen-containing compounds for inclusion in computationally-demanding global models. A new methodology has been developed, which has parameterized a more detailed model computation of the ionizing impact of precipitating electrons over the very large range of 100 eV up to 1,000,000 eV. This new parameterization method is more accurate than a previous parameterization scheme, when compared with the more detailed model computation. Global models at the National Center for Atmospheric Research will use this new parameterization method in the near future.

  9. Alkali metal ionization detector

    DOEpatents

    Bauerle, James E.; Reed, William H.; Berkey, Edgar

    1978-01-01

    Variations in the conventional filament and collector electrodes of an alkali metal ionization detector, including the substitution of helical electrode configurations for either the conventional wire filament or flat plate collector; or, the substitution of a plurality of discrete filament electrodes providing an in situ capability for transferring from an operationally defective filament electrode to a previously unused filament electrode without removing the alkali metal ionization detector from the monitored environment. In particular, the helical collector arrangement which is coaxially disposed about the filament electrode, i.e. the thermal ionizer, provides an improved collection of positive ions developed by the filament electrode. The helical filament design, on the other hand, provides the advantage of an increased surface area for ionization of alkali metal-bearing species in a monitored gas environment as well as providing a relatively strong electric field for collecting the ions at the collector electrode about which the helical filament electrode is coaxially positioned. Alternatively, both the filament and collector electrodes can be helical. Furthermore, the operation of the conventional alkali metal ionization detector as a leak detector can be simplified as to cost and complexity, by operating the detector at a reduced collector potential while maintaining the sensitivity of the alkali metal ionization detector adequate for the relatively low concentration of alkali vapor and aerosol typically encountered in leak detection applications.

  10. Partially Ionized Plasmas in Astrophysics

    NASA Astrophysics Data System (ADS)

    Ballester, José Luis; Alexeev, Igor; Collados, Manuel; Downes, Turlough; Pfaff, Robert F.; Gilbert, Holly; Khodachenko, Maxim; Khomenko, Elena; Shaikhislamov, Ildar F.; Soler, Roberto; Vázquez-Semadeni, Enrique; Zaqarashvili, Teimuraz

    2018-03-01

    Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.

  11. Advances in the two-source energy balance model: Partioning of evaporation and transpiration for row crops for cotton

    USDA-ARS?s Scientific Manuscript database

    Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. The two-source energy balance (TSEB) model solves the energy balance of the soil-plant...

  12. Measurement of the first ionization potential of astatine by laser ionization spectroscopy

    PubMed Central

    Rothe, S.; Andreyev, A. N.; Antalic, S.; Borschevsky, A.; Capponi, L.; Cocolios, T. E.; De Witte, H.; Eliav, E.; Fedorov, D. V.; Fedosseev, V. N.; Fink, D. A.; Fritzsche, S.; Ghys, L.; Huyse, M.; Imai, N.; Kaldor, U.; Kudryavtsev, Yuri; Köster, U.; Lane, J. F. W.; Lassen, J.; Liberati, V.; Lynch, K. M.; Marsh, B. A.; Nishio, K.; Pauwels, D.; Pershina, V.; Popescu, L.; Procter, T. J.; Radulov, D.; Raeder, S.; Rajabali, M. M.; Rapisarda, E.; Rossel, R. E.; Sandhu, K.; Seliverstov, M. D.; Sjödin, A. M.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Wakabayashi, Y.; Wendt, K. D. A.

    2013-01-01

    The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine. PMID:23673620

  13. Analysis of Data on the Cross Sections for Electron-Impact Ionization and Excitation of Electronic States of Atomic Hydrogen (Review)

    NASA Astrophysics Data System (ADS)

    Shakhatov, V. A.; Lebedev, Yu. A.

    2018-01-01

    A review is given of experimental and theoretical data on the cross sections for ionization, excitation, and deexcitation of atomic hydrogen. The set of the cross sections required to calculate the electron energy distribution function and find the level-to-level rate coefficients needed to solve balance equations for the densities of neutral and charged particles in hydrogen plasma is determined.

  14. Comments on ionization cooling channels

    DOE PAGES

    Neuffer, David

    2017-09-25

    Ionization cooling channels with a wide variety of characteristics and cooling properties are being developed. These channels can produce cooling performances that are largely consistent with the linear ionization cooling theory developed previously. In this study, we review ionization cooling theory, discuss its application to presently developing cooling channels, and discuss criteria for optimizing cooling.

  15. Comments on ionization cooling channels

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

    Neuffer, David

    Ionization cooling channels with a wide variety of characteristics and cooling properties are being developed. These channels can produce cooling performances that are largely consistent with the linear ionization cooling theory developed previously. In this study, we review ionization cooling theory, discuss its application to presently developing cooling channels, and discuss criteria for optimizing cooling.

  16. Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry*

    PubMed Central

    Inutan, Ellen D.; Trimpin, Sarah

    2013-01-01

    The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry. PMID:23242551

  17. "Magic" Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The "magic" that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers.

  18. A tripolar-electrode ionization gas sensor using a carbon nanotube cathode for NO detection

    NASA Astrophysics Data System (ADS)

    Song, Hui; Li, Kun; Li, Quanfu

    2018-06-01

    Nitric oxide accounts for more than 95% of the total NO X emission from power plants, which is a major air pollutant. Therefore, it is imperative to accurately detect NO for environmental protection. A tripolar-electrode ionization sensor with a carbon nanotube (CNT) cathode is proposed for NO detection. The non-self-sustaining discharge state and the tripolar-electrode configuration ensures a long nanotube life, which ensures a good stability and fast response of the sensor. Experimental results demonstrate that the tripolar-electrode ionization sensor with 120 µm separations has an intrinsic monotonously decreasing response to NO and exhibits a fast response time of 7 s and recovery time of 8 s. More consumption of the two metastable states N2(A3  ∑  u +) and N2(aʹ1  ∑  u +) of N2 with the increasing of NO concentration is responsible for this. The tripolar-electrode ionization sensor also shows excellent long-term stability of at least one month due to the long CNT life. In addition, the weak effect of SO2 introduction on NO response indicates a good selectivity of the sensor to NO.

  19. Application of the accurate mass and time tag approach in studies of the human blood lipidome

    PubMed Central

    Ding, Jie; Sorensen, Christina M.; Jaitly, Navdeep; Jiang, Hongliang; Orton, Daniel J.; Monroe, Matthew E.; Moore, Ronald J.; Smith, Richard D.; Metz, Thomas O.

    2008-01-01

    We report a preliminary demonstration of the accurate mass and time (AMT) tag approach for lipidomics. Initial data-dependent LC-MS/MS analyses of human plasma, erythrocyte, and lymphocyte lipids were performed in order to identify lipid molecular species in conjunction with complementary accurate mass and isotopic distribution information. Identified lipids were used to populate initial lipid AMT tag databases containing 250 and 45 entries for those species detected in positive and negative electrospray ionization (ESI) modes, respectively. The positive ESI database was then utilized to identify human plasma, erythrocyte, and lymphocyte lipids in high-throughput LC-MS analyses based on the AMT tag approach. We were able to define the lipid profiles of human plasma, erythrocytes, and lymphocytes based on qualitative and quantitative differences in lipid abundance. PMID:18502191

  20. Conformational responses to changes in the state of ionization of titrable groups in proteins

    NASA Astrophysics Data System (ADS)

    Richman, Daniel Eric

    Electrostatic energy links the structural properties of proteins with some of their important biological functions, including catalysis, energy transduction, and binding and recognition. Accurate calculation of electrostatic energy is essential for predicting and for analyzing function from structure. All proteins have many ionizable residues at the protein-water interface. These groups tend to have ionization equilibria (pK a values) shifted slightly relative to their values in water. In contrast, groups buried in the hydrophobic interior usually have highly anomalous p Ka values. These shifts are what structure-based calculations have to reproduce to allow examination of contributions from electrostatics to stability, solubility and interactions of proteins. Electrostatic energies are challenging to calculate accurately because proteins are heterogeneous dielectric materials. Any individual ionizable group can experience very different local environments with different dielectric properties. The studies in this thesis examine the hypothesis that proteins reorganize concomitant with changes in their state of ionization. It appears that the pKa value measured experimentally reflects the average of pKa values experienced in the different electrostatic environments corresponding to different conformational microstates. Current computational models fail to sample conformational reorganization of the backbone correctly. Staphyloccocal nuclease (SNase) was used as a model protein in nuclear magnetic resonance (NMR) spectroscopy studies to characterize the conformational rearrangements of the protein coupled to changes in the ionization state of titrable groups. One set of experiments tests the hypothesis that proton binding to surface Asp and Glu side chains drives local unfolding by stabilizing less-native, more water-solvated conformations in which the side chains have normalized pKa values. Increased backbone flexibility in the ps-ns timescale, hydrogen bond (H

  1. Spectroscopy of neutral and ionized PAHs. From laboratory studies to astronomical observations

    NASA Technical Reports Server (NTRS)

    Salama, Farid

    2005-01-01

    Polycyclic Aromatic Hydrocarbons (PAHs) are an important and ubiquitous component of carbon-bearing materials in space. PAHs are the best-known candidates to account for the IR emission bands (UIR bands) and PAH spectral features are now being used as new probes of the ISM. PAHs are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). In the model dealing with the interstellar spectral features, PAHs are present as a mixture of radicals, ions and neutral species. PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge for laboratory astrochemistry is to reproduce (in a realistic way) the physical conditions that are associated with the emission and absorption interstellar zones. An extensive laboratory program has been developed at NASA Ames to assess the physical and chemical properties of PAHs in such environments and to describe how they influence the radiation and energy balance in space and the interstellar chemistry. PAHs, neutrals and ions, are expanded through a pulsed discharge nozzle (PDN) and probed with high-sensitivity cavity ringdown spectroscopy (CRDS). These laboratory experiments provide unique information on the spectra of free, cold large carbon molecules and ions in the gas phase from the ultraviolet and visible range to the near-infrared range. Intrinsic band profiles and band positions of cold gas-phase PAHs can now be measured with high-sensitivity spectroscopy and directly compared to the astronomical data. Preliminary conclusions from the comparison of the laboratory data with astronomical observations of interstellar and circumstellar environments will also be discussed.

  2. Ionization Processes in the Atmosphere of Titan (Research Note). III. Ionization by High-Z Nuclei Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Gronoff, G.; Mertens, C.; Lilensten, J.; Desorgher, L.; Fluckiger, E.; Velinov, P.

    2011-01-01

    Context. The Cassini-Huygens mission has revealed the importance of particle precipitation in the atmosphere of Titan thanks to in-situ measurements. These ionizing particles (electrons, protons, and cosmic rays) have a strong impact on the chemistry, hence must be modeled. Aims. We revisit our computation of ionization in the atmosphere of Titan by cosmic rays. The high-energy high-mass ions are taken into account to improve the precision of the calculation of the ion production profile. Methods. The Badhwahr and O Neill model for cosmic ray spectrum was adapted for the Titan model. We used the TransTitan model coupled with the Planetocosmics model to compute the ion production by cosmic rays. We compared the results with the NAIRAS/HZETRN ionization model used for the first time for a body that differs from the Earth. Results. The cosmic ray ionization is computed for five groups of cosmic rays, depending on their charge and mass: protons, alpha, Z = 8 (oxygen), Z = 14 (silicon), and Z = 26 (iron) nucleus. Protons and alpha particles ionize mainly at 65 km altitude, while the higher mass nucleons ionize at higher altitudes. Nevertheless, the ionization at higher altitude is insufficient to obscure the impact of Saturn s magnetosphere protons at a 500 km altitude. The ionization rate at the peak (altitude: 65 km, for all the different conditions) lies between 30 and 40/cu cm/s. Conclusions. These new computations show for the first time the importance of high Z cosmic rays on the ionization of the Titan atmosphere. The updated full ionization profile shape does not differ significantly from that found in our previous calculations (Paper I: Gronoff et al. 2009, 506, 955) but undergoes a strong increase in intensity below an altitude of 400 km, especially between 200 and 400 km altitude where alpha and heavier particles (in the cosmic ray spectrum) are responsible for 40% of the ionization. The comparison of several models of ionization and cosmic ray spectra (in

  3. Laser resonance ionization spectroscopy of antimony

    NASA Astrophysics Data System (ADS)

    Li, R.; Lassen, J.; Ruczkowski, J.; Teigelhöfer, A.; Bricault, P.

    2017-02-01

    The resonant ionization laser ion source is an element selective, efficient and versatile ion source to generate radioactive ion beams at on-line mass separator facilities. For some elements with complex atomic structures and incomplete spectroscopic data, laser spectroscopic investigations are required for ionization scheme development. Laser resonance ionization spectroscopy using Ti:Sa lasers has been performed on antimony (Sb) at TRIUMF's off-line laser ion source test stand. Laser light of 230.217 nm (vacuum wavelength) as the first excitation step and light from a frequency-doubled Nd:YVO4 laser (532 nm) as the nonresonant ionization step allowed to search for suitable second excitation steps by continuous wavelength scans from 720 nm to 920 nm across the wavelength tuning range of a grating-tuned Ti:Sa laser. Upon the identification of efficient SES, the third excitation steps for resonance ionization were investigated by laser scans across Rydberg states, the ionization potential and autoionizing states. One Rydberg state and six AI states were found to be well suitable for efficient resonance ionization.

  4. Technical note: A new wedge-shaped ionization chamber component module for BEAMnrc to model the integral quality monitoring system®

    NASA Astrophysics Data System (ADS)

    Oderinde, Oluwaseyi Michael; du Plessis, FCP

    2017-12-01

    The purpose of this study was to develop a new component module (CM) namely IQM to accurately model the integral quality monitoring (IQM) system® to be used in the BEAMnrc Monte Carlo (MC) code. The IQM is essentially a double wedge ionization chamber with the central electrode plate bisecting the wedge. The IQM CM allows the user to characterize the double wedge of this ionization chamber and BEAMnrc can then accurately calculate the dose in this CM including its enclosed air regions. This has been verified against measured data. The newly created CM was added into the standard BEAMnrc CMs, and it will be made available through the NRCC website. The BEAMnrc graphical user interface (GUI) and particle ray-tracing techniques were used to validate the IQM geometry. In subsequent MC simulations, the dose scored in the IQM was verified against measured data over a range of square fields ranging from 1 × 1-30 × 30 cm2. The IQM system is designed for the present day need for a device that could verify beam output in real-time during treatment. This CM is authentic, and it can serve as a basis for researchers that have an interest in real-time beam delivery checking using wedge-shaped ionization chamber based instruments like the IQM.

  5. Increasing the applicability of density functional theory. V. X-ray absorption spectra with ionization potential corrected exchange and correlation potentials.

    PubMed

    Verma, Prakash; Bartlett, Rodney J

    2016-07-21

    Core excitation energies are computed with time-dependent density functional theory (TD-DFT) using the ionization energy corrected exchange and correlation potential QTP(0,0). QTP(0,0) provides C, N, and O K-edge spectra to about an electron volt. A mean absolute error (MAE) of 0.77 and a maximum error of 2.6 eV is observed for QTP(0,0) for many small molecules. TD-DFT based on QTP (0,0) is then used to describe the core-excitation spectra of the 22 amino acids. TD-DFT with conventional functionals greatly underestimates core excitation energies, largely due to the significant error in the Kohn-Sham occupied eigenvalues. To the contrary, the ionization energy corrected potential, QTP(0,0), provides excellent approximations (MAE of 0.53 eV) for core ionization energies as eigenvalues of the Kohn-Sham equations. As a consequence, core excitation energies are accurately described with QTP(0,0), as are the core ionization energies important in X-ray photoionization spectra or electron spectroscopy for chemical analysis.

  6. 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.

  7. Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

    NASA Astrophysics Data System (ADS)

    Madsen, Lars Bojer; Jensen, Frank; Dnestryan, Andrey I.; Tolstikhin, Oleg I.

    2017-07-01

    In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO2 and for NH3 in the pyramidal and planar geometries.

  8. Ionization detection system for aerosols

    DOEpatents

    Jacobs, Martin E.

    1977-01-01

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber.

  9. Effects of activity and energy budget balancing algorithm on laboratory performance of a fish bioenergetics model

    USGS Publications Warehouse

    Madenjian, Charles P.; David, Solomon R.; Pothoven, Steven A.

    2012-01-01

    We evaluated the performance of the Wisconsin bioenergetics model for lake trout Salvelinus namaycush that were fed ad libitum in laboratory tanks under regimes of low activity and high activity. In addition, we compared model performance under two different model algorithms: (1) balancing the lake trout energy budget on day t based on lake trout energy density on day t and (2) balancing the lake trout energy budget on day t based on lake trout energy density on day t + 1. Results indicated that the model significantly underestimated consumption for both inactive and active lake trout when algorithm 1 was used and that the degree of underestimation was similar for the two activity levels. In contrast, model performance substantially improved when using algorithm 2, as no detectable bias was found in model predictions of consumption for inactive fish and only a slight degree of overestimation was detected for active fish. The energy budget was accurately balanced by using algorithm 2 but not by using algorithm 1. Based on the results of this study, we recommend the use of algorithm 2 to estimate food consumption by fish in the field. Our study results highlight the importance of accurately accounting for changes in fish energy density when balancing the energy budget; furthermore, these results have implications for the science of evaluating fish bioenergetics model performance and for more accurate estimation of food consumption by fish in the field when fish energy density undergoes relatively rapid changes.

  10. Application of an energy balance method for estimating evapotranspiration in cropping systems

    USDA-ARS?s Scientific Manuscript database

    Accurate quantification of evapotranspiration (ET, consumptive water use) from planting through harvest is critical for managing the limited water resources for crop irrigation. Our objective was to develop and apply an improved land-crop surface residual energy balance (EB) method for quantifying E...

  11. Experimental optimization of directed field ionization

    NASA Astrophysics Data System (ADS)

    Liu, Zhimin Cheryl; Gregoric, Vincent C.; Carroll, Thomas J.; Noel, Michael W.

    2017-04-01

    The state distribution of an ensemble of Rydberg atoms is commonly measured using selective field ionization. The resulting time resolved ionization signal from a single energy eigenstate tends to spread out due to the multiple avoided Stark level crossings atoms must traverse on the way to ionization. The shape of the ionization signal can be modified by adding a perturbation field to the main field ramp. Here, we present experimental results of the manipulation of the ionization signal using a genetic algorithm. We address how both the genetic algorithm and the experimental parameters were adjusted to achieve an optimized result. This work was supported by the National Science Foundation under Grants No. 1607335 and No. 1607377.

  12. Radiative Rates for Forbidden Transitions in Doubly-Ionized Fe-Peak Elements

    NASA Astrophysics Data System (ADS)

    Fivet, Vanessa; Quinet, P.; Bautista, M.

    2012-05-01

    Accurate and reliable atomic data for lowly-ionized Fe-peak species (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) are of paramount importance for the analysis of the high resolution astrophysical spectra currently available. The third spectra of several iron group elements have been observed in different galactic sources like Herbig-Haro objects in the Orion Nebula [1] and stars like Eta Carinae [2]. However, forbidden transitions between low-lying metastable levels of doubly-ionized iron-peak ions have been very little investigated so far and radiative rates for those lines remain sparse or inexistent. We are carrying out a systematic study of the electronic structure of doubly-ionized iron-peak elements. The magnetic dipole (M1) and electric quadrupole (E2) transition probabilities are computed using the pseudo-relativistic Hartree-Fock (HFR) code of Cowan [3] and the central Thomas-Fermi-Dirac potential approximation implemented in AUTOSTRUCTURE [4]. This multi-platform approach allows for consistency checks and intercomparison and has proven very successful in the study of the complex Fe-peak species where many different effects contribute [5]. References [1] A. Mesa-Delgado et al., MNRAS 395 (2009) 855 [2] S. Johansson et al., A&A 361 (2000) 977 [3] R.D. Cowan, The Theory of Atomic Structure and Spectra, Berkeley: Univ. California Press (1981) [4] N.R. Badnell, J. Phys. B: At. Mol. Opt. Phys. 30 (1997) 1 [5] M. Bautista et al., ApJ 718 (2010) L189

  13. A practical theoretical formalism for atomic multielectron processes: direct multiple ionization by a single auger decay or by impact of a single electron or photon

    NASA Astrophysics Data System (ADS)

    Liu, Pengfei; Zeng, Jiaolong; Yuan, Jianmin

    2018-04-01

    Multiple electron processes occur widely in atoms, molecules, clusters, and condensed matters when they are interacting with energetic particles or intense laser fields. Direct multielectron processes (DMEP) are the most complicated among the general multiple electron processes and are the most difficult to describe theoretically. In this work, a unified and accurate theoretical formalism is proposed on the DMEP of atoms including the multiple auger decay and multiple ionization by an impact of a single electron or a single photon based on the atomic collision theory described by a correlated many-body Green's function. Such a practical treatment is made possible by taking consideration of the different coherence features of the atoms (matter waves) in the initial and final states. We first explain how the coherence characteristics of the ejected continuum electrons is largely destructed, by taking the electron impact direct double ionization process as an example. The direct double ionization process is completely different from the single ionization where the complete interference can be maintained. The detailed expressions are obtained for the energy correlations among the continuum electrons and energy resolved differential and integral cross sections according to the separation of knock-out (KO) and shake-off (SO) mechanisms for the electron impact direct double ionization, direct double and triple auger decay, and double and triple photoionization (TPI) processes. Extension to higher order DMEP than triple ionization is straight forward by adding contributions of the following KO and SO processes. The approach is applied to investigate the electron impact double ionization processes of C+, N+, and O+, the direct double and triple auger decay of the K-shell excited states of C+ 1s2{s}22{p}2{}2D and {}2P, and the double and TPI of lithium. Comparisons with the experimental and other theoretical investigations wherever available in the literature show that our

  14. Selectivity of Electronic Coherence and Attosecond Ionization Delays in Strong-Field Double Ionization

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yuki; Reduzzi, Maurizio; Chang, Kristina F.; Timmers, Henry; Neumark, Daniel M.; Leone, Stephen R.

    2018-06-01

    Experiments are presented on real-time probing of coherent electron dynamics in xenon initiated by strong-field double ionization. Attosecond transient absorption measurements allow for characterization of electronic coherences as well as relative ionization timings in multiple electronic states of Xe+ and Xe2 + . A high degree of coherence g =0.4 is observed between P3 2 0-P3 0 0 of Xe2 + , whereas for other possible pairs of states the coherences are below the detection limits of the experiments. A comparison of the experimental results with numerical simulations based on an uncorrelated electron-emission model shows that the coherences produced by strong-field double ionization are more selective than predicted. Surprisingly short ionization time delays, 0.85 fs, 0.64 fs, and 0.75 fs relative to Xe+ formation, are also measured for the P2 3 , P0 3 , and P1 3 states of Xe2 + , respectively. Both the unpredicted selectivity in the formation of coherence and the subfemtosecond time delays of specific states provide new insight into correlated electron dynamics in strong-field double ionization.

  15. Electron Impact Ionization and Dissociative Ionization of C2H2

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K.

    1995-01-01

    By utilizing a crossed electron beam collision geometry, a combination of time-of-flight (TOF) and quadrupole mass spectrometers, and the relative flow technique1 normalized values of cross sections and appearance energies (AP) were obtained for the formation of singly and multiply ionized species resulting from the ionization and dissociation of C2H2. Details ont he apparatus and technique have been published previously.2,3.

  16. Double-frequency microwave ionization of Na

    NASA Astrophysics Data System (ADS)

    Ruff, G. A.; Dietrick, K. M.; Gallagher, T. F.

    1990-11-01

    We report the ionization of Na atoms by the simultaneous application of microwave fields of two different frequencies. We conclude that the salient features of double-frequency ionization can be readily understood. Both the hydrogenlike ||m||=2 states and the nonhydrogenic ||m||=0 and 1 states ionize when the sum of the field amplitudes, the peak field, reaches the field required for ionization by a single microwave frequency, E=1/9n4 and E=1/3n5, respectively.

  17. Classical vs. evolved quenching parameters and procedures in scintillation measurements: The importance of ionization quenching

    NASA Astrophysics Data System (ADS)

    Bagán, H.; Tarancón, A.; Rauret, G.; García, J. F.

    2008-07-01

    The quenching parameters used to model detection efficiency variations in scintillation measurements have not evolved since the decade of 1970s. Meanwhile, computer capabilities have increased enormously and ionization quenching has appeared in practical measurements using plastic scintillation. This study compares the results obtained in activity quantification by plastic scintillation of 14C samples that contain colour and ionization quenchers, using classical (SIS, SCR-limited, SCR-non-limited, SIS(ext), SQP(E)) and evolved (MWA-SCR and WDW) parameters and following three calibration approaches: single step, which does not take into account the quenching mechanism; two steps, which takes into account the quenching phenomena; and multivariate calibration. Two-step calibration (ionization followed by colour) yielded the lowest relative errors, which means that each quenching phenomenon must be specifically modelled. In addition, the sample activity was quantified more accurately when the evolved parameters were used. Multivariate calibration-PLS also yielded better results than those obtained using classical parameters, which confirms that the quenching phenomena must be taken into account. The detection limits for each calibration method and each parameter were close to those obtained theoretically using the Currie approach.

  18. 29 CFR 1926.53 - Ionizing radiation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Ionizing radiation. 1926.53 Section 1926.53 Labor... § 1926.53 Ionizing radiation. (a) In construction and related activities involving the use of sources of ionizing radiation, the pertinent provisions of the Nuclear Regulatory Commission's Standards for...

  19. 29 CFR 1926.53 - Ionizing radiation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 8 2012-07-01 2012-07-01 false Ionizing radiation. 1926.53 Section 1926.53 Labor... § 1926.53 Ionizing radiation. (a) In construction and related activities involving the use of sources of ionizing radiation, the pertinent provisions of the Nuclear Regulatory Commission's Standards for...

  20. 29 CFR 1926.53 - Ionizing radiation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 8 2014-07-01 2014-07-01 false Ionizing radiation. 1926.53 Section 1926.53 Labor... § 1926.53 Ionizing radiation. (a) In construction and related activities involving the use of sources of ionizing radiation, the pertinent provisions of the Nuclear Regulatory Commission's Standards for...

  1. Mobility Lab to Assess Balance and Gait with Synchronized Body-worn Sensors

    PubMed Central

    Mancini, Martina; King, Laurie; Salarian, Arash; Holmstrom, Lars; McNames, James; Horak, Fay B

    2014-01-01

    This paper is a commentary to introduce how rehabilitation professionals can use a new, body-worn sensor system to obtain objective measures of balance and gait. Current assessments of balance and gait in clinical rehabilitation are largely limited to subjective scales, simple stop-watch measures, or complex, expensive machines not practical or largely available. Although accelerometers and gyroscopes have been shown to accurately quantify many aspects of gait and balance kinematics, only recently a comprehensive, portable system has become available for clinicians. By measuring body motion during tests that clinicians are already performing, such as the Timed Up and Go test (TUG) and the Clinical Test of Sensory Integration for Balance (CITSIB), the additional time for assessment is minimal. By providing instant analysis of balance and gait and comparing a patient’s performance to age-matched control values, therapists receive an objective, sensitive screening profile of balance and gait strategies. This motion screening profile can be used to identify mild abnormalities not obvious with traditional clinical testing, measure small changes due to rehabilitation, and design customized rehabilitation programs for each individual’s specific balance and gait deficits. PMID:24955286

  2. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, Scott A.; Glish, Gary L.

    1989-01-01

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

  3. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, S.A.; Glish, G.L.

    1989-07-18

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

  4. Resonant two-photon ionization and mass-analyzed threshold ionization spectroscopy of p-vinylaniline

    NASA Astrophysics Data System (ADS)

    Tzeng, Sheng Yuan; Dong, Changwu; Tzeng, Wen Bih

    2012-10-01

    We report the vibronic and cation spectra of p-vinylaniline, which are recorded by using the resonant two-photon ionization and the mass-analyzed threshold ionization spectroscopic techniques. The band origin of the S1 ← S0 electronic transition appears at 31,490 ± 2 cm-1 and the adiabatic ionization energy is determined to be 59,203 ± 5 cm-1. Due to the nature of the substituent, the amino and vinyl groups lead to lower electronic excitation and ionization energies by a few thousand wave numbers. Most of the observed active modes result from the in-plane ring deformation and substituent-sensitive vibrations of this molecule in the electronically excited S1 and cationic ground D0 states. By comparing the frequencies of the observed active vibrations, one may conclude that the molecular geometry and the vibrational coordinates of these modes of the p-vinylaniline cation in the D0 state resemble those of the neutral species in the S1 state.

  5. On the accuracy of density functional theory and wave function methods for calculating vertical ionization energies

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

    McKechnie, Scott; Booth, George H.; Cohen, Aron J.

    The best practice in computational methods for determining vertical ionization energies (VIEs) is assessed, via reference to experimentally determined VIEs that are corroborated by highly accurate coupled-cluster calculations. These reference values are used to benchmark the performance of density-functional theory (DFT) and wave function methods: Hartree-Fock theory (HF), second-order Møller-Plesset perturbation theory (MP2) and Electron Propagator Theory (EPT). The core test set consists of 147 small molecules. An extended set of six larger molecules, from benzene to hexacene, is also considered to investigate the dependence of the results on molecule size. The closest agreement with experiment is found for ionizationmore » energies obtained from total energy diff calculations. In particular, DFT calculations using exchange-correlation functionals with either a large amount of exact exchange or long-range correction perform best. The results from these functionals are also the least sensitive to an increase in molecule size. In general, ionization energies calculated directly from the orbital energies of the neutral species are less accurate and more sensitive to an increase in molecule size. For the single-calculation approach, the EPT calculations are in closest agreement for both sets of molecules. For the orbital energies from DFT functionals, only those with long-range correction give quantitative agreement with dramatic failing for all other functionals considered. The results offer a practical hierarchy of approximations for the calculation of vertical ionization energies. In addition, the experimental and computational reference values can be used as a standardized set of benchmarks, against which other approximate methods can be compared.« less

  6. Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics

    DOE PAGES

    Clementson, Joel; Lennartsson, Thomas; Beiersdorfer, Peter

    2015-09-09

    The extreme ultraviolet (EUV) emission from few-times ionized tungsten atoms has been experimentally studied at the Livermore electron beam ion trap facility. The ions were produced and confined during low-energy operations of the EBIT-I electron beam ion trap. By varying the electron-beam energy from around 30–300 eV, tungsten ions in charge states expected to be abundant in tokamak divertor plasmas were excited, and the resulting EUV emission was studied using a survey spectrometer covering 120–320 Å. It is found that the emission strongly depends on the excitation energy; below 150 eV, it is relatively simple, consisting of strong isolated linesmore » from a few charge states, whereas at higher energies, it becomes very complex. For divertor plasmas with tungsten impurity ions, this emission should prove useful for diagnostics of tungsten flux rates and charge balance, as well as for radiative cooling of the divertor volume. Several lines in the 194–223 Å interval belonging to the spectra of five- and seven-times ionized tungsten (Tm-like W VI and Ho-like W VIII) were also measured using a high-resolution spectrometer.« less

  7. A comprehensive high-resolution mass spectrometry approach for characterization of metabolites by combination of ambient ionization, chromatography and imaging methods.

    PubMed

    Berisha, Arton; Dold, Sebastian; Guenther, Sabine; Desbenoit, Nicolas; Takats, Zoltan; Spengler, Bernhard; Römpp, Andreas

    2014-08-30

    An ideal method for bioanalytical applications would deliver spatially resolved quantitative information in real time and without sample preparation. In reality these requirements can typically not be met by a single analytical technique. Therefore, we combine different mass spectrometry approaches: chromatographic separation, ambient ionization and imaging techniques, in order to obtain comprehensive information about metabolites in complex biological samples. Samples were analyzed by laser desorption followed by electrospray ionization (LD-ESI) as an ambient ionization technique, by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging for spatial distribution analysis and by high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) for quantitation and validation of compound identification. All MS data were acquired with high mass resolution and accurate mass (using orbital trapping and ion cyclotron resonance mass spectrometers). Grape berries were analyzed and evaluated in detail, whereas wheat seeds and mouse brain tissue were analyzed in proof-of-concept experiments. In situ measurements by LD-ESI without any sample preparation allowed for fast screening of plant metabolites on the grape surface. MALDI imaging of grape cross sections at 20 µm pixel size revealed the detailed distribution of metabolites which were in accordance with their biological function. HPLC/ESI-MS was used to quantify 13 anthocyanin species as well as to separate and identify isomeric compounds. A total of 41 metabolites (amino acids, carbohydrates, anthocyanins) were identified with all three approaches. Mass accuracy for all MS measurements was better than 2 ppm (root mean square error). The combined approach provides fast screening capabilities, spatial distribution information and the possibility to quantify metabolites. Accurate mass measurements proved to be critical in order to reliably combine data from different MS

  8. Simultaneous resonant enhanced multiphoton ionization and electron avalanche ionization in gas mixtures

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

    Shneider, Mikhail N.; Zhang Zhili; Miles, Richard B.

    2008-07-15

    Resonant enhanced multiphoton ionization (REMPI) and electron avalanche ionization (EAI) are measured simultaneously in Ar:Xe mixtures at different partial pressures of mixture components. A simple theory for combined REMPI+EAI in gas mixture is developed. It is shown that the REMPI electrons seed the avalanche process, and thus the avalanche process amplifies the REMPI signal. Possible applications are discussed.

  9. Geometry and mass model of ionizing radiation experiments on the LDEF satellite

    NASA Technical Reports Server (NTRS)

    Colborn, B. L.; Armstrong, T. W.

    1992-01-01

    Extensive measurements related to ionizing radiation environments and effects were made on the LDEF satellite during its mission lifetime of almost 6 years. These data, together with the opportunity they provide for evaluating predictive models and analysis methods, should allow more accurate assessments of the space radiation environment and related effects for future missions in low Earth orbit. The LDEF radiation dosimetry data is influenced to varying degrees by material shielding effects due to the dosimeter itself, nearby components and experiments, and the spacecraft structure. A geometry and mass model is generated of LDEF, incorporating sufficient detail that it can be applied in determining the influence of material shielding on ionizing radiation measurements and predictions. This model can be used as an aid in data interpretation by unfolding shielding effects from the LDEF radiation dosimeter responses. Use of the LDEF geometry/mass model, in conjunction with predictions and comparisons with LDEF dosimetry data currently underway, will also allow more definitive evaluations of current radiation models for future mission applications.

  10. 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.

  11. Ionization in MHD-Gas interactions

    NASA Astrophysics Data System (ADS)

    Wilson, A.; Diver, D. A.

    2013-09-01

    The study of partially ionized plasmas is important in a number of astrophysical situations and is vital for the study of laboratory plasmas. The interactions between a neutral gas and a plasma define a hybrid medium that has aspects of each, but does not only sustain the pure modes of the individual species. Previously we have shown that momentum coupling between the gas and the magnetized plasma alters the behaviour of both; as an extension of that simulation, we present results for the extension to the coupling in which the relative motion between the species provides enough kinetic energy in the flow to allow a measure of species exchange Alfvén ionization (AI) (also known as critical velocity ionization), allowing the ionization fraction to evolve as the dynamics evolve.

  12. Miniature Oxidizer Ionizer for a Fuel Cell

    NASA Technical Reports Server (NTRS)

    Hartley, Frank

    2006-01-01

    A proposed miniature device for ionizing the oxygen (or other oxidizing gas) in a fuel cell would consist mostly of a membrane ionizer using the same principles as those of the device described in the earlier article, Miniature Bipolar Electrostatic Ion Thruster (NPO-21057). The oxidizing gas would be completely ionized upon passage through the holes in the membrane ionizer. The resulting positively charged atoms or molecules of oxidizing gas could then, under the influence of the fringe fields of the ionizer, move toward the fuel-cell cathode that would be part of a membrane/electrode assembly comprising the cathode, a solid-electrolyte membrane, and an anode. The electro-oxidized state of the oxidizer atoms and molecules would enhance transfer of them through the cathode, thereby reducing the partial pressure of the oxidizer gas between the ionizer and the fuel-cell cathode, thereby, in turn, causing further inflow of oxidizer gas through the holes in the membrane ionizer. Optionally the ionizer could be maintained at a positive electric potential with respect to the cathode, in which case the resulting electric field would accelerate the ions toward the cathode.

  13. Spontaneous-Desorption Ionizer for a TOF-MS

    NASA Technical Reports Server (NTRS)

    Schultz, J. Albert

    2006-01-01

    A time-of-flight mass spectrometer (TOF-MS) like the one mentioned in the immediately preceding article has been retrofitted with an ionizer based on a surface spontaneous-desorption process. This ionizer includes an electron multiplier in the form of a microchannel plate (MCP). Relative to an ionizer based on a hot-filament electron source, this ionizer offers advantages of less power consumption and greater mechanical ruggedness. The current density and stability characteristics of the electron emission of this ionizer are similar to those of a filament-based ionizer. In tests of various versions of this ionizer in the TOF-MS, electron currents up to 100 nA were registered. Currents of microamperes or more - great enough to satisfy requirements in most TOFMS applications - could be obtained by use of MCPs different from those used in the tests, albeit at the cost of greater bulk. One drawback of this ionizer is that the gain of the MCP decreases as a function of the charge extracted thus far; the total charge that can be extracted over the operational lifetime is about 1 coulomb. An MCP in the ion-detector portion of the TOF-MS is subject to the same limitation.

  14. Forensic applications of ambient ionization mass spectrometry.

    PubMed

    Ifa, Demian R; Jackson, Ayanna U; Paglia, Giuseppe; Cooks, R Graham

    2009-08-01

    This review highlights and critically assesses forensic applications in the developing field of ambient ionization mass spectrometry. Ambient ionization methods permit the ionization of samples outside the mass spectrometer in the ordinary atmosphere, with minimal sample preparation. Several ambient ionization methods have been created since 2004 and they utilize different mechanisms to create ions for mass-spectrometric analysis. Forensic applications of these techniques--to the analysis of toxic industrial compounds, chemical warfare agents, illicit drugs and formulations, explosives, foodstuff, inks, fingerprints, and skin--are reviewed. The minimal sample pretreatment needed is illustrated with examples of analysis from complex matrices (e.g., food) on various substrates (e.g., paper). The low limits of detection achieved by most of the ambient ionization methods for compounds of forensic interest readily offer qualitative confirmation of chemical identity; in some cases quantitative data are also available. The forensic applications of ambient ionization methods are a growing research field and there are still many types of applications which remain to be explored, particularly those involving on-site analysis. Aspects of ambient ionization currently undergoing rapid development include molecular imaging and increased detection specificity through simultaneous chemical reaction and ionization by addition of appropriate chemical reagents.

  15. Diode laser based resonance ionization mass spectrometric measurement of strontium-90

    NASA Astrophysics Data System (ADS)

    Bushaw, B. A.; Cannon, B. D.

    1997-10-01

    A diode laser based scheme for the isotopically selective excitation and ionization of strontium is presented. The double-resonance excitation 5s 21S 0→5s5p 3P 1→5s6s 3S 1 is followed by photoionization at 488 nm. The isotope shifts and hyperfine structure in the resonance transitions have been accurately measured for the stable isotopes and 90Sr, with the measurement of the 90Sr shifts using sub-pg samples. Analytical tests, using graphite crucible atomization, demonstrated 90Sr detection limits of 0.8 fg and overall (optical+mass spectrometer) isotopic selectivity of >10 10 against stable strontium.

  16. Fundamental Studies of Molecular Secondary Ion Mass Spectrometry Ionization Probability Measured With Femtosecond, Infrared Laser Post-Ionization

    NASA Astrophysics Data System (ADS)

    Popczun, Nicholas James

    The work presented in this dissertation is focused on increasing the fundamental understanding of molecular secondary ion mass spectrometry (SIMS) ionization probability by measuring neutral molecule behavior with femtosecond, mid-infrared laser post-ionization (LPI). To accomplish this, a model system was designed with a homogeneous organic film comprised of coronene, a polycyclic hydrocarbon which provides substantial LPI signal. Careful consideration was given to signal lost to photofragmentation and undersampling of the sputtered plume that is contained within the extraction volume of the mass spectrometer. This study provided the first ionization probability for an organic compound measured directly by the relative secondary ions and sputtered neutral molecules using a strong-field ionization (SFI) ionization method. The measured value of ˜10-3 is near the upper limit of previous estimations of ionization probability for organic molecules. The measurement method was refined, and then applied to a homogeneous guanine film, which produces protonated secondary ions. This measurement found the probability of protonation to occur to be on the order of 10-3, although with less uncertainty than that of the coronene. Finally, molecular depth profiles were obtained for SIMS and LPI signals as a function of primary ion fluence to determine the effect of ionization probability on the depth resolution of chemical interfaces. The interfaces chosen were organic/inorganic interfaces to limit chemical mixing. It is shown that approaching the inorganic chemical interface can enhance or suppress the ionization probability for the organic molecule, which can lead to artificially sharpened or broadened depths, respectively. Overall, the research described in this dissertation provides new methods for measuring ionization efficiency in SIMS in both absolute and relative terms, and will inform both innovation in the technique, as well as increase understanding of depth

  17. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, R.S.; Todd, R.A.

    1985-04-09

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  18. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  19. Multireference configuration interaction calculations of the first six ionization potentials of the uranium atom

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

    Bross, David H.; Parmar, Payal; Peterson, Kirk A.

    The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set (CBS) limit using new all-electron correlation consistent basis sets. The latter were carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons have been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. As amore » result, the final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV), and thus more reliable than the current experimental values of IP 3 through IP 6.« less

  20. A review of quantitative structure-property relationships for the fate of ionizable organic chemicals in water matrices and identification of knowledge gaps.

    PubMed

    Nolte, Tom M; Ragas, Ad M J

    2017-03-22

    Many organic chemicals are ionizable by nature. After use and release into the environment, various fate processes determine their concentrations, and hence exposure to aquatic organisms. In the absence of suitable data, such fate processes can be estimated using Quantitative Structure-Property Relationships (QSPRs). In this review we compiled available QSPRs from the open literature and assessed their applicability towards ionizable organic chemicals. Using quantitative and qualitative criteria we selected the 'best' QSPRs for sorption, (a)biotic degradation, and bioconcentration. The results indicate that many suitable QSPRs exist, but some critical knowledge gaps remain. Specifically, future focus should be directed towards the development of QSPR models for biodegradation in wastewater and sediment systems, direct photolysis and reaction with singlet oxygen, as well as additional reactive intermediates. Adequate QSPRs for bioconcentration in fish exist, but more accurate assessments can be achieved using pharmacologically based toxicokinetic (PBTK) models. No adequate QSPRs exist for bioconcentration in non-fish species. Due to the high variability of chemical and biological species as well as environmental conditions in QSPR datasets, accurate predictions for specific systems and inter-dataset conversions are problematic, for which standardization is needed. For all QSPR endpoints, additional data requirements involve supplementing the current chemical space covered and accurately characterizing the test systems used.

  1. Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

    NASA Astrophysics Data System (ADS)

    McNiven, Andrea L.

    The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the

  2. BALANCE

    DOEpatents

    Carmichael, H.

    1953-01-01

    A torsional-type analytical balance designed to arrive at its equilibrium point more quickly than previous balances is described. In order to prevent external heat sources creating air currents inside the balance casing that would reiard the attainment of equilibrium conditions, a relatively thick casing shaped as an inverted U is placed over the load support arms and the balance beam. This casing is of a metal of good thernnal conductivity characteristics, such as copper or aluminum, in order that heat applied to one portion of the balance is quickly conducted to all other sensitive areas, thus effectively preventing the fornnation of air currents caused by unequal heating of the balance.

  3. Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry

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

    Waltman, Melanie J.

    2010-05-01

    Explosives detection is a necessary and wide spread field of research. From large shipping containers to airline luggage, numerous items are tested for explosives every day. In the area of trace explosives detection, ion mobility spectrometry (IMS) is the technique employed most often because it is a quick, simple, and accurate way to test many items in a short amount of time. Detection by IMS is based on the difference in drift times of product ions through the drift region of an IMS instrument. The product ions are created when the explosive compounds, introduced to the instrument, are chemically ionizedmore » through interactions with the reactant ions. The identity of the reactant ions determines the outcomes of the ionization process. This research investigated the reactant ions created by various ionization sources and looked into ways to manipulate the chemistry occurring in the sources.« less

  4. Modeling of Plutonium Ionization Probabilities for Use in Nuclear Forensic Analysis by Resonance Ionization Mass Spectrometry

    DTIC Science & Technology

    2016-12-01

    masses collide, they form a supercritical mass . Criticality refers to the neutron population within the system. A critical system is one that can...Spectrometry, no. 242, pp. 161–168, 2005. [9] S. Raeder, “Trace analysis of actinides in the environment by means of resonance ionization mass ...first ionization potential of actinide elements by resonance ionization mass spectrometry.” Spectrochimica Acta part B: Atomic Spectroscopy. vol. 52

  5. Ionization enhancement in atmospheric pressure chemical ionization and suppression in electrospray ionization between target drugs and stable-isotope-labeled internal standards in quantitative liquid chromatography/tandem mass spectrometry.

    PubMed

    Liang, H R; Foltz, R L; Meng, M; Bennett, P

    2003-01-01

    The phenomena of ionization suppression in electrospray ionization (ESI) and enhancement in atmospheric pressure chemical ionization (APCI) were investigated in selected-ion monitoring and selected-reaction monitoring modes for nine drugs and their corresponding stable-isotope-labeled internal standards (IS). The results showed that all investigated target drugs and their co-eluting isotope-labeled IS suppress each other's ionization responses in ESI. The factors affecting the extent of suppression in ESI were investigated, including structures and concentrations of drugs, matrix effects, and flow rate. In contrast to the ESI results, APCI caused seven of the nine investigated target drugs and their co-eluting isotope-labeled IS to enhance each other's ionization responses. The mutual ionization suppression or enhancement between drugs and their isotope-labeled IS could possibly influence assay sensitivity, reproducibility, accuracy and linearity in quantitative liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). However, calibration curves were linear if an appropriate IS concentration was selected for a desired calibration range to keep the response factors constant. Copyright 2003 John Wiley & Sons, Ltd.

  6. Accurate ab initio binding energies of the benzene dimer.

    PubMed

    Park, Young Choon; Lee, Jae Shin

    2006-04-20

    Accurate binding energies of the benzene dimer at the T and parallel displaced (PD) configurations were determined using the single- and double-coupled cluster method with perturbative triple correction (CCSD(T)) with correlation-consistent basis sets and an effective basis set extrapolation scheme recently devised. The difference between the estimated CCSD(T) basis set limit electronic binding energies for the T and PD shapes appears to amount to more than 0.3 kcal/mol, indicating the PD shape is a more stable configuration than the T shape for this dimer in the gas phase. This conclusion is further strengthened when a vibrational zero-point correction to the electronic binding energies of this dimer is made, which increases the difference between the two configurations to 0.4-0.5 kcal/mol. The binding energies of 2.4 and 2.8 kcal/mol for the T and PD configurations are in good accord with the previous experimental result from ionization potential measurement.

  7. Watt and joule balances

    NASA Astrophysics Data System (ADS)

    Robinson, Ian A.

    2014-04-01

    The time is fast approaching when the SI unit of mass will cease to be based on a single material artefact and will instead be based upon the defined value of a fundamental constant—the Planck constant—h . This change requires that techniques exist both to determine the appropriate value to be assigned to the constant, and to measure mass in terms of the redefined unit. It is important to ensure that these techniques are accurate and reliable to allow full advantage to be taken of the stability and universality provided by the new definition and to guarantee the continuity of the world's mass measurements, which can affect the measurement of many other quantities such as energy and force. Up to now, efforts to provide the basis for such a redefinition of the kilogram were mainly concerned with resolving the discrepancies between individual implementations of the two principal techniques: the x-ray crystal density (XRCD) method [1] and the watt and joule balance methods which are the subject of this special issue. The first three papers report results from the NRC and NIST watt balance groups and the NIM joule balance group. The result from the NRC (formerly the NPL Mk II) watt balance is the first to be reported with a relative standard uncertainty below 2 × 10-8 and the NIST result has a relative standard uncertainty below 5 × 10-8. Both results are shown in figure 1 along with some previous results; the result from the NIM group is not shown on the plot but has a relative uncertainty of 8.9 × 10-6 and is consistent with all the results shown. The Consultative Committee for Mass and Related Quantities (CCM) in its meeting in 2013 produced a resolution [2] which set out the requirements for the number, type and quality of results intended to support the redefinition of the kilogram and required that there should be agreement between them. These results from NRC, NIST and the IAC may be considered to meet these requirements and are likely to be widely debated

  8. Dynamic load balancing for petascale quantum Monte Carlo applications: The Alias method

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

    Sudheer, C. D.; Krishnan, S.; Srinivasan, A.

    Diffusion Monte Carlo is the most accurate widely used Quantum Monte Carlo method for the electronic structure of materials, but it requires frequent load balancing or population redistribution steps to maintain efficiency and avoid accumulation of systematic errors on parallel machines. The load balancing step can be a significant factor affecting performance, and will become more important as the number of processing elements increases. We propose a new dynamic load balancing algorithm, the Alias Method, and evaluate it theoretically and empirically. An important feature of the new algorithm is that the load can be perfectly balanced with each process receivingmore » at most one message. It is also optimal in the maximum size of messages received by any process. We also optimize its implementation to reduce network contention, a process facilitated by the low messaging requirement of the algorithm. Empirical results on the petaflop Cray XT Jaguar supercomputer at ORNL showing up to 30% improvement in performance on 120,000 cores. The load balancing algorithm may be straightforwardly implemented in existing codes. The algorithm may also be employed by any method with many near identical computational tasks that requires load balancing.« less

  9. Exploration of the Dissociative Recombination following DNA ionization to DNA+ due to ionizing radiation

    NASA Astrophysics Data System (ADS)

    Strom, Richard A.; Zimmerly, Andrew T.; Andrianarijaona, Vola M.

    2014-05-01

    It is known that ionizing radiation generates low-energy secondary electrons, which may interact with the surrounding area, including biomolecules, such as triggering DNA single strand and double strand breaks as demonstrated by Sanche and coworkers (Radiat. Res. 157, 227(2002)). The bio-effects of low-energy electrons are currently a topic of high interest. Most of the studies are dedicated to dissociative electron attachments; however, the area is still mostly unexplored and still not well understood. We are computationally investigating the effect of ionizing radiation on DNA, such as its ionization to DNA+. More specifically, we are exploring the possibility of the dissociative recombination of the temporary DNA+ with one of the low-energy secondary electrons, produced by the ionizing radiation, to be another process of DNA strand breaks. Our preliminary results, which are performed with the binaries of ORCA, will be presented. Authors wish to give special thanks to Pacific Union College Student Senate in Angwin, California, for their financial support.

  10. A Versatile Integrated Ambient Ionization Source Platform.

    PubMed

    Ai, Wanpeng; Nie, Honggang; Song, Shiyao; Liu, Xiaoyun; Bai, Yu; Liu, Huwei

    2018-04-30

    The pursuit of high-throughput sample analysis from complex matrix demands development of multiple ionization techniques with complementary specialties. A versatile integrated ambient ionization source (iAmIS) platform is proposed in this work, based on the idea of integrating multiple functions, enhancing the efficiency of current ionization techniques, extending the applications, and decreasing the cost of the instrument. The design of the iAmIS platform combines flowing atmospheric pressure afterglow (FAPA) source/direct analysis in real time (DART), dielectric barrier discharge ionization (DBDI)/low-temperature plasma (LTP), desorption electrospray ionization (DESI), and laser desorption (LD) technique. All individual and combined ionization modes can be easily attained by modulating parameters. In particular, the FAPA/DART&DESI mode can realize the detection of polar and nonpolar compounds at the same time with two different ionization mechanisms: proton transfer and charge transfer. The introduction of LD contributes to the mass spectrometry imaging and the surface-assisted laser desorption (SALDI) under ambient condition. Compared with other individual or multi-mode ion source, the iAmIS platform provides the flexibility of choosing different ionization modes, broadens the scope of the analyte detection, and facilitates the analysis of complex samples. Graphical abstract ᅟ.

  11. A Versatile Integrated Ambient Ionization Source Platform

    NASA Astrophysics Data System (ADS)

    Ai, Wanpeng; Nie, Honggang; Song, Shiyao; Liu, Xiaoyun; Bai, Yu; Liu, Huwei

    2018-04-01

    The pursuit of high-throughput sample analysis from complex matrix demands development of multiple ionization techniques with complementary specialties. A versatile integrated ambient ionization source (iAmIS) platform is proposed in this work, based on the idea of integrating multiple functions, enhancing the efficiency of current ionization techniques, extending the applications, and decreasing the cost of the instrument. The design of the iAmIS platform combines flowing atmospheric pressure afterglow (FAPA) source/direct analysis in real time (DART), dielectric barrier discharge ionization (DBDI)/low-temperature plasma (LTP), desorption electrospray ionization (DESI), and laser desorption (LD) technique. All individual and combined ionization modes can be easily attained by modulating parameters. In particular, the FAPA/DART&DESI mode can realize the detection of polar and nonpolar compounds at the same time with two different ionization mechanisms: proton transfer and charge transfer. The introduction of LD contributes to the mass spectrometry imaging and the surface-assisted laser desorption (SALDI) under ambient condition. Compared with other individual or multi-mode ion source, the iAmIS platform provides the flexibility of choosing different ionization modes, broadens the scope of the analyte detection, and facilitates the analysis of complex samples. [Figure not available: see fulltext.

  12. Accurate physical laws can permit new standard units: The two laws F→=ma→ and the proportionality of weight to mass

    NASA Astrophysics Data System (ADS)

    Saslow, Wayne M.

    2014-04-01

    Three common approaches to F→=ma→ are: (1) as an exactly true definition of force F→ in terms of measured inertial mass m and measured acceleration a→; (2) as an exactly true axiom relating measured values of a→, F→ and m; and (3) as an imperfect but accurately true physical law relating measured a→ to measured F→, with m an experimentally determined, matter-dependent constant, in the spirit of the resistance R in Ohm's law. In the third case, the natural units are those of a→ and F→, where a→ is normally specified using distance and time as standard units, and F→ from a spring scale as a standard unit; thus mass units are derived from force, distance, and time units such as newtons, meters, and seconds. The present work develops the third approach when one includes a second physical law (again, imperfect but accurate)—that balance-scale weight W is proportional to m—and the fact that balance-scale measurements of relative weight are more accurate than those of absolute force. When distance and time also are more accurately measurable than absolute force, this second physical law permits a shift to standards of mass, distance, and time units, such as kilograms, meters, and seconds, with the unit of force—the newton—a derived unit. However, were force and distance more accurately measurable than time (e.g., time measured with an hourglass), this second physical law would permit a shift to standards of force, mass, and distance units such as newtons, kilograms, and meters, with the unit of time—the second—a derived unit. Therefore, the choice of the most accurate standard units depends both on what is most accurately measurable and on the accuracy of physical law.

  13. Employment of Both Mn I and II Transitions to Determine the Abundance Trend and Ionization Balance in Three Stellar Evolutionary Classes

    NASA Astrophysics Data System (ADS)

    Sobeck, Jennifer; Den Hartog, B.; Lawler, J.; Sneden, C.

    2010-01-01

    Several prior investigations have repeatedly found that Manganese is under-abundant with respect to solar in metal-deficient stars. However a recent study, which employed a non-LTE approach/methodology, found that the [Mn/Fe] abundance ratio remains solar in the range -2.5 < [Fe/H] < 0 (results which stand in direct contrast to previous data). We will re-determine the [Mn/Fe] ratio over a large range of metallicity in a statistically significant sample consisting of stars from three evolutionary classes (dwarf, turnoff, and giant). We will employ new laboratory work (reported also at this meeting) to analyze the transitions of *both* the neutral (Mn I) and the first-ionized species (Mn II) in stellar spectra. We intend to determine the ionization equilibrium within each star and identify departures from LTE in each stellar group. We will explore the Mn abundance trend with metallicity and provide insight into its astrophysical origin (with special emphasis on the explosive nucleosynthetic contribution).

  14. GMI Instrument Spin Balance Method, Optimization, Calibration, and Test

    NASA Technical Reports Server (NTRS)

    Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

    2014-01-01

    The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3 year mission life. Therefore, GMI must be very precisely balanced about the spin axis and CG to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

  15. GMI Instrument Spin Balance Method, Optimization, Calibration and Test

    NASA Technical Reports Server (NTRS)

    Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

    2014-01-01

    The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3-year mission life. Therefore, GMI must be very precisely balanced about the spin axis and center of gravity (CG) to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

  16. Projection-free approximate balanced truncation of large unstable systems

    NASA Astrophysics Data System (ADS)

    Flinois, Thibault L. B.; Morgans, Aimee S.; Schmid, Peter J.

    2015-08-01

    In this article, we show that the projection-free, snapshot-based, balanced truncation method can be applied directly to unstable systems. We prove that even for unstable systems, the unmodified balanced proper orthogonal decomposition algorithm theoretically yields a converged transformation that balances the Gramians (including the unstable subspace). We then apply the method to a spatially developing unstable system and show that it results in reduced-order models of similar quality to the ones obtained with existing methods. Due to the unbounded growth of unstable modes, a practical restriction on the final impulse response simulation time appears, which can be adjusted depending on the desired order of the reduced-order model. Recommendations are given to further reduce the cost of the method if the system is large and to improve the performance of the method if it does not yield acceptable results in its unmodified form. Finally, the method is applied to the linearized flow around a cylinder at Re = 100 to show that it actually is able to accurately reproduce impulse responses for more realistic unstable large-scale systems in practice. The well-established approximate balanced truncation numerical framework therefore can be safely applied to unstable systems without any modifications. Additionally, balanced reduced-order models can readily be obtained even for large systems, where the computational cost of existing methods is prohibitive.

  17. PROCEDURES FOR ACCURATE PRODUCTION OF COLOR IMAGES FROM SATELLITE OR AIRCRAFT MULTISPECTRAL DIGITAL DATA.

    USGS Publications Warehouse

    Duval, Joseph S.

    1985-01-01

    Because the display and interpretation of satellite and aircraft remote-sensing data make extensive use of color film products, accurate reproduction of the color images is important. To achieve accurate color reproduction, the exposure and chemical processing of the film must be monitored and controlled. By using a combination of sensitometry, densitometry, and transfer functions that control film response curves, all of the different steps in the making of film images can be monitored and controlled. Because a sensitometer produces a calibrated exposure, the resulting step wedge can be used to monitor the chemical processing of the film. Step wedges put on film by image recording machines provide a means of monitoring the film exposure and color balance of the machines.

  18. Ionizing radiation and life.

    PubMed

    Dartnell, Lewis R

    2011-01-01

    Ionizing radiation is a ubiquitous feature of the Cosmos, from exogenous cosmic rays (CR) to the intrinsic mineral radioactivity of a habitable world, and its influences on the emergence and persistence of life are wide-ranging and profound. Much attention has already been focused on the deleterious effects of ionizing radiation on organisms and the complex molecules of life, but ionizing radiation also performs many crucial functions in the generation of habitable planetary environments and the origins of life. This review surveys the role of CR and mineral radioactivity in star formation, generation of biogenic elements, and the synthesis of organic molecules and driving of prebiotic chemistry. Another major theme is the multiple layers of shielding of planetary surfaces from the flux of cosmic radiation and the various effects on a biosphere of violent but rare astrophysical events such as supernovae and gamma-ray bursts. The influences of CR can also be duplicitous, such as limiting the survival of surface life on Mars while potentially supporting a subsurface biosphere in the ocean of Europa. This review highlights the common thread that ionizing radiation forms between the disparate component disciplines of astrobiology. © Mary Ann Liebert, Inc.

  19. Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

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

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume, E-mail: david.martinez@uib.es

    2017-03-01

    The presence of neutral species in a plasma has been shown to greatly affect the properties of magnetohydrodynamic waves. For instance, the interaction between ions and neutrals through momentum transfer collisions causes the damping of Alfvén waves and alters their oscillation frequency and phase speed. When the collision frequencies are larger than the frequency of the waves, single-fluid magnetohydrodynamic approximations can accurately describe the effects of partial ionization, since there is a strong coupling between the various species. However, at higher frequencies, the single-fluid models are not applicable and more complex approaches are required. Here, we use a five-fluid modelmore » with three ionized and two neutral components, which takes into consideration Hall’s current and Ohm’s diffusion in addition to the friction due to collisions between different species. We apply our model to plasmas composed of hydrogen and helium, and allow the ionization degree to be arbitrary. By analyzing the corresponding dispersion relation and numerical simulations, we study the properties of small-amplitude perturbations. We discuss the effect of momentum transfer collisions on the ion-cyclotron resonances and compare the importance of magnetic resistivity, and ion–neutral and ion–ion collisions on the wave damping at various frequency ranges. Applications to partially ionized plasmas of the solar atmosphere are performed.« less

  20. High-Sensitivity Ionization Trace-Species Detector

    NASA Technical Reports Server (NTRS)

    Bernius, Mark T.; Chutjian, Ara

    1990-01-01

    Features include high ion-extraction efficiency, compactness, and light weight. Improved version of previous ionization detector features in-line geometry that enables extraction of almost every ion from region of formation. Focusing electrodes arranged and shaped into compact system of space-charge-limited reversal electron optics and ion-extraction optics. Provides controllability of ionizing electron energies, greater efficiency of ionization, and nearly 100 percent ion-collection efficiency.

  1. Single electron impact ionization of the methane molecule

    NASA Astrophysics Data System (ADS)

    Bouamoud, Mammar; Sahlaoui, Mohammed; Benmansour, Nour El Houda; Atomic and Molecular Collisions Team

    2014-10-01

    Triply differential cross sections (TDCS) results of electron-impact ionization of the inner 2a1 molecular orbital of CH4 are presented in the framework of the Second Born Approximation and compared with the experimental data performed in coplanar asymmetric geometry. The cross sections are averaged on the random orientations of the molecular target for accurate comparison with experiments and are compared also with the theoretical calculations of the Three Coulomb wave (3CW) model. Our results are in good agreement with experiments and 3CW results in the binary peak. In contrast the Second Born Approximation yields a significant higher values compared to the 3CW results for the recoil peak and seems to describe suitably the recoil region where higher order effects can occur with the participation of the recoiling ion in the collision process.

  2. Tunneling ionization and Wigner transform diagnostics in OSIRIS

    NASA Astrophysics Data System (ADS)

    Martins, S.; Fonseca, R. A.; Silva, L. O.; Deng, S.; Katsouleas, T.; Tsung, F.; Mori, W. B.

    2004-11-01

    We describe the ionization module implemented in the PIC code OSIRIS [1]. Benchmarks with previously published tunnel ionization results were made. Our ionization module works in 1D, 2D and 3D simulations with barrier suppression ionization or the ADK ionization model, and allows for moving ions. Several illustrative 3D numerical simulations were performed, namely of the propagation of a SLAC beam in a Li gas cell, for the parameters of [2]. We compare the performance of OSIRIS with/without the ionization module, concluding that much less simulation time is usually required when using the ionization module. A novel diagnostic over the electric field is implemented, the Wigner transform, that provides information on the local spectral content of the field. This diagnostic is applied to the analysis of the chirp induced in an ionizing laser pulse. [1] R. A. Fonseca et al., LNCS 2331, 342-351, (Springer, Heidelberg, 2002). [2] S. Deng et al., Phys. Rev. E 68, 047401 (2003).

  3. Ionization of Interstellar Hydrogen

    NASA Astrophysics Data System (ADS)

    Whang, Y. C.

    1996-09-01

    Interstellar hydrogen can penetrate through the heliopause, enter the heliosphere, and may become ionized by photoionization and by charge exchange with solar wind protons. A fluid model is introduced to study the flow of interstellar hydrogen in the heliosphere. The flow is governed by moment equations obtained from integration of the Boltzmann equation over the velocity space. Under the assumption that the flow is steady axisymmetric and the pressure is isotropic, we develop a method of solution for this fluid model. This model and the method of solution can be used to study the flow of neutral hydrogen with various forms of ionization rate β and boundary conditions for the flow on the upwind side. We study the solution of a special case in which the ionization rate β is inversely proportional to R2 and the interstellar hydrogen flow is uniform at infinity on the upwind side. We solve the moment equations directly for the normalized density NH/NN∞, bulk velocity VH/VN∞, and temperature TH/TN∞ of interstellar hydrogen as functions of r/λ and z/λ, where λ is the ionization scale length. The solution is compared with the kinetic theory solution of Lallement et al. The fluid solution is much less time-consuming than the kinetic theory solutions. Since the ionization rate for production of pickup protons is directly proportional to the local density of neutral hydrogen, the high-resolution solution of interstellar neutral hydrogen obtained here will be used to study the global distribution of pickup protons.

  4. Ion-recombination correction for different ionization chambers in high dose rate flattening-filter-free photon beams

    NASA Astrophysics Data System (ADS)

    Lang, Stephanie; Hrbacek, Jan; Leong, Aidan; Klöck, Stephan

    2012-05-01

    Recently, there has been an increased interest in flattening-filter-free (FFF) linear accelerators. Removal of the filter results in available dose rates up to 24 Gy min-1 (for nominal energy 10 MV in depth of maximum dose, a source-surface distance of 100 cm and a field size of 10×10 cm2). To guarantee accurate relative and reference dosimetry for the FFF beams, we investigated the charge collection efficiency of multiple air-vented and one liquid ionization chamber for dose rates up to 31.9 Gy min-1. For flattened beams, the ion-collection efficiency of all air-vented ionization chambers (except for the PinPoint chamber) was above 0.995. By removing the flattening filter, we found a reduction in collection efficiency of approximately 0.5-0.9% for a 10 MV beam. For FFF beams, the Markus chamber showed the largest collection efficiency of 0.994. The observed collection efficiencies were dependent on dose per pulse, but independent of the pulse repetition frequency. Using the liquid ionization chamber, the ion-collection efficiency for flattened beams was above 0.990 for all dose rates. However, this chamber showed a low collection efficiency of 0.940 for the FFF 10 MV beam at a dose rate of 31.9 Gy min-1. All investigated air-vented ionization chambers can be reliably used for relative dosimetry of FFF beams. The order of correction for reference dosimetry is given in the manuscript. Due to their increased saturation in high dose rate FFF beams, liquid ionization chambers appear to be unsuitable for dosimetry within these contexts.

  5. Clinical Application of Ambient Ionization Mass Spectrometry

    PubMed Central

    Li, Li-Hua; Hsieh, Hua-Yi; Hsu, Cheng-Chih

    2017-01-01

    Ambient ionization allows mass spectrometry analysis directly on the sample surface under atmospheric pressure with almost zero sample pretreatment. Since the development of desorption electrospray ionization (DESI) in 2004, many other ambient ionization techniques were developed. Due to their simplicity and low operation cost, rapid and on-site clinical mass spectrometry analysis becomes real. In this review, we will highlight some of the most widely used ambient ionization mass spectrometry approaches and their applications in clinical study. PMID:28337399

  6. Force instrumentation for cryogenic wind tunnels using one-piece strain-gage balances

    NASA Technical Reports Server (NTRS)

    Ferris, A. T.; Moore, T. C.

    1981-01-01

    Materials and techniques for a transducer capable of obtaining accurate force measurements at cryogenic temperatures (down to 77 K) and high pressures (up to 9 atm) have been determined. Areas of high stress concentration are minimized by balance design, and model and sting attachment methods able to withstand cryogenic temperatures are used. Maraging 200 is the material used for the balances, due to its high impact strength and simple heat treatment procedure. Test results verify that the balances produce reliable, repeatable, and predictable data from 300 K to 110 K under steady state conditions. Techniques have been developed to reduce the temperature-induced bridge output, such as the use of bridges with two gages mounted transverse to the principal stress direction. Under these conditions, the results given by the balances should be equally good during transient temperatures on five of the six components. The work will be used at the National Transonic Facility (NTF) at NASA Langley.

  7. Mining balance disorders' data for the development of diagnostic decision support systems.

    PubMed

    Exarchos, T P; Rigas, G; Bibas, A; Kikidis, D; Nikitas, C; Wuyts, F L; Ihtijarevic, B; Maes, L; Cenciarini, M; Maurer, C; Macdonald, N; Bamiou, D-E; Luxon, L; Prasinos, M; Spanoudakis, G; Koutsouris, D D; Fotiadis, D I

    2016-10-01

    In this work we present the methodology for the development of the EMBalance diagnostic Decision Support System (DSS) for balance disorders. Medical data from patients with balance disorders have been analysed using data mining techniques for the development of the diagnostic DSS. The proposed methodology uses various data, ranging from demographic characteristics to clinical examination, auditory and vestibular tests, in order to provide an accurate diagnosis. The system aims to provide decision support for general practitioners (GPs) and experts in the diagnosis of balance disorders as well as to provide recommendations for the appropriate information and data to be requested at each step of the diagnostic process. Detailed results are provided for the diagnosis of 12 balance disorders, both for GPs and experts. Overall, the reported accuracy ranges from 59.3 to 89.8% for GPs and from 74.3 to 92.1% for experts. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Laser Pulse Width Dependence and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization

    NASA Astrophysics Data System (ADS)

    Liang, Sheng-Ping; Lu, I.-Chung; Tsai, Shang-Ting; Chen, Jien-Lian; Lee, Yuan Tseh; Ni, Chi-Kung

    2017-10-01

    Ultraviolet laser pulses at 355 nm with variable pulse widths in the region from 170 ps to 1.5 ns were used to investigate the ionization mechanism of matrix-assisted laser desorption/ionization (MALDI) for matrices 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapinic acid (SA). The mass spectra of desorbed ions and the intensity and velocity distribution of desorbed neutrals were measured simultaneously for each laser shot. These quantities were found to be independent of the laser pulse width. A comparison of the experimental measurements and numerical simulations according to the multiphoton ionization, coupled photophysical and chemical dynamics (CPCD), and thermally induced proton transfer models showed that the predictions of thermally induced proton transfer model were in agreement with the experimental data, but those of the multiphoton ionization model were not. Moreover, the predictions of the CPCD model based on singlet-singlet energy pooling were inconsistent with the experimental data of CHCA and SA, but were consistent with the experimental data of DHB only when some parameters used in the model were adjusted to extreme values. [Figure not available: see fulltext.

  9. Matrix-assisted laser desorption ionization-time of flight mass spectrometry for direct bacterial identification from positive blood culture pellets.

    PubMed

    Prod'hom, Guy; Bizzini, Alain; Durussel, Christian; Bille, Jacques; Greub, Gilbert

    2010-04-01

    An ammonium chloride erythrocyte-lysing procedure was used to prepare a bacterial pellet from positive blood cultures for direct matrix-assisted laser desorption-ionization time of flight (MALDI-TOF) mass spectrometry analysis. Identification was obtained for 78.7% of the pellets tested. Moreover, 99% of the MALDI-TOF identifications were congruent at the species level when considering valid scores. This fast and accurate method is promising.

  10. Relativistic runaway ionization fronts.

    PubMed

    Luque, A

    2014-01-31

    We investigate the first example of self-consistent impact ionization fronts propagating at relativistic speeds and involving interacting, high-energy electrons. These fronts, which we name relativistic runaway ionization fronts, show remarkable features such as a bulk speed within less than one percent of the speed of light and the stochastic selection of high-energy electrons for further acceleration, which leads to a power-law distribution of particle energies. A simplified model explains this selection in terms of the overrun of Coulomb-scattered electrons. Appearing as the electromagnetic interaction between electrons saturates the exponential growth of a relativistic runaway electron avalanche, relativistic runaway ionization fronts may occur in conjunction with terrestrial gamma-ray flashes and thus explain recent observations of long, power-law tails in the terrestrial gamma-ray flash energy spectrum.

  11. Electron ionization of SiCl4

    NASA Astrophysics Data System (ADS)

    King, Simon J.; Price, Stephen D.

    2011-02-01

    Relative partial ionization cross sections (PICS) for the formation of fragment ions following electron ionization of SiCl4, in the electron energy range 30-200 eV, have been determined using time-of-flight mass spectrometry coupled with an ion coincidence technique. By this method, the contributions to the yield of each fragment ion from dissociative single, double, and triple ionization, are distinguished. These yields are quantified in the form of relative precursor-specific PICS, which are reported here for the first time for SiCl4. For the formation of singly charged ionic fragments, the low-energy maxima appearing in the PICS curves are due to contributions from single ionization involving predominantly indirect ionization processes, while contributions to the yields of these ions at higher electron energies are often dominated by dissociative double ionization. Our data, in the reduced form of relative PICS, are shown to be in good agreement with a previous determination of the PICS of SiCl4. Only for the formation of doubly charged fragment ions are the current relative PICS values lower than those measured in a previous study, although both datasets agree within combined error limits. The relative PICS data presented here include the first quantitative measurements of the formation of Cl2+ fragment ions and of the formation of ion pairs via dissociative double ionization. The peaks appearing in the 2D ion coincidence data are analyzed to provide further information concerning the mechanism and energetics of the charge-separating dissociations of SiCl42+. The lowest energy dicationic precursor state, leading to SiCl3+ + Cl+ formation, lies 27.4 ± 0.3 eV above the ground state of SiCl4 and is in close agreement with a calculated value of the adiabatic double ionization energy (27.3 eV).

  12. Electron ionization of SiCl4.

    PubMed

    King, Simon J; Price, Stephen D

    2011-02-21

    Relative partial ionization cross sections (PICS) for the formation of fragment ions following electron ionization of SiCl(4), in the electron energy range 30-200 eV, have been determined using time-of-flight mass spectrometry coupled with an ion coincidence technique. By this method, the contributions to the yield of each fragment ion from dissociative single, double, and triple ionization, are distinguished. These yields are quantified in the form of relative precursor-specific PICS, which are reported here for the first time for SiCl(4). For the formation of singly charged ionic fragments, the low-energy maxima appearing in the PICS curves are due to contributions from single ionization involving predominantly indirect ionization processes, while contributions to the yields of these ions at higher electron energies are often dominated by dissociative double ionization. Our data, in the reduced form of relative PICS, are shown to be in good agreement with a previous determination of the PICS of SiCl(4). Only for the formation of doubly charged fragment ions are the current relative PICS values lower than those measured in a previous study, although both datasets agree within combined error limits. The relative PICS data presented here include the first quantitative measurements of the formation of Cl(2) (+) fragment ions and of the formation of ion pairs via dissociative double ionization. The peaks appearing in the 2D ion coincidence data are analyzed to provide further information concerning the mechanism and energetics of the charge-separating dissociations of SiCl(4) (2+). The lowest energy dicationic precursor state, leading to SiCl(3) (+) + Cl(+) formation, lies 27.4 ± 0.3 eV above the ground state of SiCl(4) and is in close agreement with a calculated value of the adiabatic double ionization energy (27.3 eV).

  13. A new approach to enforce element-wise mass/species balance using the augmented Lagrangian method

    NASA Astrophysics Data System (ADS)

    Chang, J.; Nakshatrala, K.

    2015-12-01

    The least-squares finite element method (LSFEM) is one of many ways in which one can discretize and express a set of first ordered partial differential equations as a mixed formulation. However, the standard LSFEM is not locally conservative by design. The absence of this physical property can have serious implications in the numerical simulation of subsurface flow and transport. Two commonly employed ways to circumvent this issue is through the Lagrange multiplier method, which explicitly satisfies the element-wise divergence by introducing new unknowns, or through appending a penalty factor to the continuity constraint, which reduces the violation in the mass balance. However, these methodologies have some well-known drawbacks. Herein, we propose a new approach to improve the local balance of species/mass balance. The approach augments constraints to a least-square function by a novel mathematical construction of the local species/mass balance, which is different from the conventional ways. The resulting constrained optimization problem is solved using the augmented Lagrangian, which corrects the balance errors in an iterative fashion. The advantages of this methodology are that the problem size is not increased (thus preserving the symmetry and positive definite-ness) and that one need not provide an accurate guess for the initial penalty to reach a prescribed mass balance tolerance. We derive the least-squares weighting needed to ensure accurate solutions. We also demonstrate the robustness of the weighted LSFEM coupled with the augmented Lagrangian by solving large-scale heterogenous and variably saturated flow through porous media problems. The performance of the iterative solvers with respect to various user-defined augmented Lagrangian parameters will be documented.

  14. Capillary atmospheric pressure electron capture ionization (cAPECI): a highly efficient ionization method for nitroaromatic compounds.

    PubMed

    Derpmann, Valerie; Mueller, David; Bejan, Iustinian; Sonderfeld, Hannah; Wilberscheid, Sonja; Koppmann, Ralf; Brockmann, Klaus J; Benter, Thorsten

    2014-03-01

    We report on a novel method for atmospheric pressure ionization of compounds with elevated electron affinity (e.g., nitroaromatic compounds) or gas phase acidity (e.g., phenols), respectively. The method is based on the generation of thermal electrons by the photo-electric effect, followed by electron capture of oxygen when air is the gas matrix yielding O2(-) or of the analyte directly with nitrogen as matrix. Charge transfer or proton abstraction by O2(-) leads to the ionization of the analytes. The interaction of UV-light with metals is a clean method for the generation of thermal electrons at atmospheric pressure. Furthermore, only negative ions are generated and neutral radical formation is minimized, in contrast to discharge- or dopant assisted methods. Ionization takes place inside the transfer capillary of the mass spectrometer leading to comparably short transfer times of ions to the high vacuum region of the mass spectrometer. This strongly reduces ion transformation processes, resulting in mass spectra that more closely relate to the neutral analyte distribution. cAPECI is thus a soft and selective ionization method with detection limits in the pptV range. In comparison to standard ionization methods (e.g., PTR), cAPECI is superior with respect to both selectivity and achievable detection limits. cAPECI demonstrates to be a promising ionization method for applications in relevant fields as, for example, explosives detection and atmospheric chemistry.

  15. Comparison of geodetic and glaciological mass-balance techniques, Gulkana Glacier, Alaska, U.S.A

    USGS Publications Warehouse

    Cox, L.H.; March, R.S.

    2004-01-01

    The net mass balance on Gulkana Glacier, Alaska, U.S.A., has been measured since 1966 by the glaciological method, in which seasonal balances are measured at three index sites and extrapolated over large areas of the glacier. Systematic errors can accumulate linearly with time in this method. Therefore, the geodetic balance, in which errors are less time-dependent, was calculated for comparison with the glaciological method. Digital elevation models of the glacier in 1974, 1993 and 1999 were prepared using aerial photographs, and geodetic balances were computed, giving - 6.0??0.7 m w.e. from 1974 to 1993 and - 11.8??0.7 m w.e. from 1974 to 1999. These balances are compared with the glaciological balances over the same intervals, which were - 5.8??0.9 and -11.2??1.0 m w.e. respectively; both balances show that the thinning rate tripled in the 1990s. These cumulative balances differ by <6%. For this close agreement, the glaciologically measured mass balance of Gulkana Glacier must be largely free of systematic errors and be based on a time-variable area-altitude distribution, and the photography used in the geodetic method must have enough contrast to enable accurate photogrammetry.

  16. High-Resolution Photoionization, Photoelectron and Photodissociation Studies. Determination of Accurate Energetic and Spectroscopic Database for Combustion Radicals and Molecules

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

    Ng, Cheuk-Yiu

    2016-04-25

    The main goal of this research program was to obtain accurate thermochemical and spectroscopic data, such as ionization energies (IEs), 0 K bond dissociation energies, 0 K heats of formation, and spectroscopic constants for radicals and molecules and their ions of relevance to combustion chemistry. Two unique, generally applicable vacuum ultraviolet (VUV) laser photoion-photoelectron apparatuses have been developed in our group, which have used for high-resolution photoionization, photoelectron, and photodissociation studies for many small molecules of combustion relevance.

  17. The study of the effects of ionizing and non-ionizing radiations on birth weight of newborns to exposed mothers.

    PubMed

    Mortazavi, S M J; Shirazi, K R; Mortazavi, G

    2013-01-01

    Life evolved in an environment filled with a wide variety of ionizing and non-ionizing radiation. It was previously reported that medical exposures to pregnant women increases the risk of low birth weight. This study intends to investigate the relationship between exposure to ionizing and non-ionizing radiation and the risk of low birth weight. One thousand two hundred mothers with their first-term labor (vaginal or cesarean) whose newborns' history had been registered in neonates' screening program in Shiraz were interviewed and surveyed. Data collection was performed by the assessment of mother's history of radiography before and during pregnancy, physical examination of the mother for height and weight and weighing and examining the newborn for any diagnosis of disease and anomalies. There were no statistical significant differences between the mean weight of newborns whose mothers had been exposed to some common sources of ionizing and non-ionizing radiations such as dental or non dental radiographies, mobile phone, cordless phone and cathode ray tube (CRT) and those of non-exposed mothers. The findings of this study cast doubt on previous reports, which indicated that exposure to ionizing radiation during pregnancy increased the risk of low birth weight.

  18. Characterization of nonpolar lipids and selected steroids by using laser-induced acoustic desorption/chemical ionization, atmospheric pressure chemical ionization, and electrospray ionization mass spectrometry

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

    Jin, Zhicheng; Daiya, Shivani; Kenttämaa, Hilkka I.

    2011-03-01

    Laser-induced acoustic desorption (LIAD) combined with ClMn(H2O)+ chemical ionization (CI) was tested for the analysis of nonpolar lipids and selected steroids in a Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR). The nonpolar lipids studied, cholesterol, 5α-cholestane, cholesta-3,5-diene, squalene, and β-carotene, were found to solely form the desired water replacement product (adduct-H2O) upon reaction with the ClMn(H2O)+ ions. The steroids, androsterone, dehydroepiandrosterone (DHEA), estrone, estradiol, and estriol, also form abundant adduct-H2O ions, but less abundant adduct-2H2O ions were also observed. Neither (+)APCI nor (+)ESI can ionize the saturated hydrocarbon lipid, cholestane. APCI successfully ionizes the unsaturated hydrocarbon lipids to form exclusivelymore » the intact protonated analytes. However, it causes extensive fragmentation for cholesterol and the steroids. The worst case is cholesterol that does not produce any stable protonated molecules. On the other hand, ESI cannot ionize any of the hydrocarbon analytes, saturated or unsaturated. However, ESI can be used to protonate the oxygen-containing analytes with substantially less fragmentation than for APCI in all cases except for cholesterol and estrone. In conclusion, LIAD/ClMn(H2O)+ chemical ionization is superior over APCI and ESI for the mass spectrometric characterization of underivatized nonpolar lipids and steroids.« less

  19. Factorization of laser-pulse ionization probabilities in the multiphotonic regime

    NASA Astrophysics Data System (ADS)

    Della Picca, R.; Fiol, J.; Fainstein, P. D.

    2013-09-01

    We present a detailed study of the ionization probability of H and H_{2}^{+} induced by a short intense laser pulse. Starting from a Coulomb-Volkov description of the process we derive a multipole-like expansion where each term is factored into two contributions: one that accounts for the effect of the electromagnetic field on the free-electron final state and a second factor that depends only on the target structure. Such a separation may be valuable to solve complex atomic or molecular systems as well as to interpret the dynamics of the process in simpler terms. We show that the series expansion converges rapidly, and thus the inclusion of the first few terms is sufficient to produce accurate results.

  20. Impact ionization study

    NASA Technical Reports Server (NTRS)

    Whipple, E. C., Jr.

    1982-01-01

    The impact ionization phenomenon which was observed on certain spacecraft was studied. The phenomenon occurs when a neutral atom, molecule, or ion strikes a surface with sufficient kinetic energy that either the incident neutral or atoms on the surface are ionized, with subsequent escape of ions and/or electrons. The released ions and electrons can interfere with measurements on the spacecraft by confusing interpretation of the data. On the other hand, there is the possibility that the effect could be developed into a diagnostic tool for investigating neutral atmospheric species or for studying physical processes on spacecraft surfaces.

  1. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  2. Accurate structural and spectroscopic characterization of prebiotic molecules: The neutral and cationic acetyl cyanide and their related species.

    PubMed

    Bellili, A; Linguerri, R; Hochlaf, M; Puzzarini, C

    2015-11-14

    In an effort to provide an accurate structural and spectroscopic characterization of acetyl cyanide, its two enolic isomers and the corresponding cationic species, state-of-the-art computational methods, and approaches have been employed. The coupled-cluster theory including single and double excitations together with a perturbative treatment of triples has been used as starting point in composite schemes accounting for extrapolation to the complete basis-set limit as well as core-valence correlation effects to determine highly accurate molecular structures, fundamental vibrational frequencies, and rotational parameters. The available experimental data for acetyl cyanide allowed us to assess the reliability of our computations: structural, energetic, and spectroscopic properties have been obtained with an overall accuracy of about, or better than, 0.001 Å, 2 kcal/mol, 1-10 MHz, and 11 cm(-1) for bond distances, adiabatic ionization potentials, rotational constants, and fundamental vibrational frequencies, respectively. We are therefore confident that the highly accurate spectroscopic data provided herein can be useful for guiding future experimental investigations and/or astronomical observations.

  3. Fan Flutter Computations Using the Harmonic Balance Method

    NASA Technical Reports Server (NTRS)

    Bakhle, Milind A.; Thomas, Jeffrey P.; Reddy, T.S.R.

    2009-01-01

    An experimental forward-swept fan encountered flutter at part-speed conditions during wind tunnel testing. A new propulsion aeroelasticity code, based on a computational fluid dynamics (CFD) approach, was used to model the aeroelastic behavior of this fan. This threedimensional code models the unsteady flowfield due to blade vibrations using a harmonic balance method to solve the Navier-Stokes equations. This paper describes the flutter calculations and compares the results to experimental measurements and previous results from a time-accurate propulsion aeroelasticity code.

  4. Low-Pressure, Field-Ionizing Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Hartley, Frank; Smith, Steven

    2009-01-01

    A small mass spectrometer utilizing a miniature field ionization source is now undergoing development. It is designed for use in a variety of applications in which there are requirements for a lightweight, low-power-consumption instrument that can analyze the masses of a wide variety of molecules and ions. The device can operate without need for a high-vacuum, carrier-gas feed radioactive ionizing source, or thermal ionizer. This mass spectrometer can operate either in the natural vacuum of outer space or on Earth at any ambient pressure below 50 torr (below about 6.7 kPa) - a partial vacuum that can easily be reached by use of a small sampling pump. This mass spectrometer also has a large dynamic range - from singly charged small gas ions to deoxyribonucleic acid (DNA) fragments larger than 104 atomic mass units - with sensitivity adequate for detecting some molecules and ions at relative abundances of less than one part per billion. This instrument (see figure) includes a field ionizer integrated with a rotating-field mass spectrometer (RFMS). The field ionizer effects ionization of a type characterized as "soft" in the art because it does not fragment molecules or initiate avalanche arcing. What makes the "soft" ionization mode possible is that the distance between the ionizing electrodes is less than mean free path for ions at the maximum anticipated operating pressure, so that the ionizer always operates on the non-breakdown side of the applicable Paschen curve (a standard plot of breakdown potential on the ordinate and pressure electrode separation on the abscissa). The field ionizer in this instrument is fabricated by micromachining a submicron-thick membrane out of an electrically nonconductive substrate, coating the membrane on both sides to form electrodes, then micromachining small holes through the electrodes and membrane. Because of the submicron electrode separation, even a potential of only 1 V applied between the electrodes gives rise to an electric

  5. The balance sheet technique. Volume I. The balance sheet analysis technique for preconstruction review of airports and highways

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

    LaBelle, S.J.; Smith, A.E.; Seymour, D.A.

    1977-02-01

    The technique applies equally well to new or existing airports. The importance of accurate accounting of emissions, cannot be overstated. The regional oxidant modelling technique used in conjunction with a balance sheet review must be a proportional reduction technique. This type of emission balancing presumes equality of all sources in the analysis region. The technique can be applied successfully in the highway context, either in planning at the system level or looking only at projects individually. The project-by-project reviews could be used to examine each project in the same way as the airport projects are examined for their impact onmore » regional desired emission levels. The primary limitation of this technique is that it should not be used when simulation models have been used for regional oxidant air quality. In the case of highway projects, the balance sheet technique might appear to be limited; the real limitations are in the transportation planning process. That planning process is not well-suited to the needs of air quality forecasting. If the transportation forecasting techniques are insensitive to change in the variables that affect HC emissions, then no internal emission trade-offs can be identified, and the initial highway emission forecasts are themselves suspect. In general, the balance sheet technique is limited by the quality of the data used in the review. Additionally, the technique does not point out effective trade-off strategies, nor does it indicate when it might be worthwhile to ignore small amounts of excess emissions. Used in the context of regional air quality plans based on proportional reduction models, the balance sheet analysis technique shows promise as a useful method by state or regional reviewing agencies.« less

  6. Lattice design and expected performance of the Muon Ionization Cooling Experiment demonstration of ionization cooling

    NASA Astrophysics Data System (ADS)

    Bogomilov, M.; Tsenov, R.; Vankova-Kirilova, G.; Song, Y.; Tang, J.; Li, Z.; Bertoni, R.; Bonesini, M.; Chignoli, F.; Mazza, R.; Palladino, V.; de Bari, A.; Cecchet, G.; Orestano, D.; Tortora, L.; Kuno, Y.; Ishimoto, S.; Filthaut, F.; Jokovic, D.; Maletic, D.; Savic, M.; Hansen, O. M.; Ramberger, S.; Vretenar, M.; Asfandiyarov, R.; Blondel, A.; Drielsma, F.; Karadzhov, Y.; Charnley, G.; Collomb, N.; Dumbell, K.; Gallagher, A.; Grant, A.; Griffiths, S.; Hartnett, T.; Martlew, B.; Moss, A.; Muir, A.; Mullacrane, I.; Oates, A.; Owens, P.; Stokes, G.; Warburton, P.; White, C.; Adams, D.; Anderson, R. J.; Barclay, P.; Bayliss, V.; Boehm, J.; Bradshaw, T. W.; Courthold, M.; Francis, V.; Fry, L.; Hayler, T.; Hills, M.; Lintern, A.; Macwaters, C.; Nichols, A.; Preece, R.; Ricciardi, S.; Rogers, C.; Stanley, T.; Tarrant, J.; Tucker, M.; Wilson, A.; Watson, S.; Bayes, R.; Nugent, J. C.; Soler, F. J. P.; Gamet, R.; Barber, G.; Blackmore, V. J.; Colling, D.; Dobbs, A.; Dornan, P.; Hunt, C.; Kurup, A.; Lagrange, J.-B.; Long, K.; Martyniak, J.; Middleton, S.; Pasternak, J.; Uchida, M. A.; Cobb, J. H.; Lau, W.; Booth, C. N.; Hodgson, P.; Langlands, J.; Overton, E.; Robinson, M.; Smith, P. J.; Wilbur, S.; Dick, A. J.; Ronald, K.; Whyte, C. G.; Young, A. R.; Boyd, S.; Franchini, P.; Greis, J. R.; Pidcott, C.; Taylor, I.; Gardener, R. B. S.; Kyberd, P.; Nebrensky, J. J.; Palmer, M.; Witte, H.; Bross, A. D.; Bowring, D.; Liu, A.; Neuffer, D.; Popovic, M.; Rubinov, P.; DeMello, A.; Gourlay, S.; Li, D.; Prestemon, S.; Virostek, S.; Freemire, B.; Hanlet, P.; Kaplan, D. M.; Mohayai, T. A.; Rajaram, D.; Snopok, P.; Suezaki, V.; Torun, Y.; Onel, Y.; Cremaldi, L. M.; Sanders, D. A.; Summers, D. J.; Hanson, G. G.; Heidt, C.; MICE Collaboration

    2017-06-01

    Muon beams of low emittance provide the basis for the intense, well-characterized neutrino beams necessary to elucidate the physics of flavor at a neutrino factory and to provide lepton-antilepton collisions at energies of up to several TeV at a muon collider. The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam passes through a material in which it loses energy. The energy lost is then replaced using rf cavities. The combined effect of energy loss and reacceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised experiment can deliver a demonstration of ionization cooling. The design of the cooling demonstration experiment will be described together with its predicted cooling performance.

  7. [Ionization energies and infrared spectra studies of histidine using density functional theory].

    PubMed

    Hu, Qiong; Wang, Guo-Ying; Liu, Gang; Ou, Jia-Ming; Wang, Rui-Li

    2010-05-01

    Histidines provide axial ligands to the primary electron donors in photosynthetic reaction centers (RCs) and play an important role in the protein environments of these donors. In this paper the authors present a systematic study of ionization energies and vibrational properties of histidine using hybrid density functional theory (DFT). All calculations were undertaken by using B3LYP method in combination with four basis sets: 6-31G(d), 6-31G(df, p), 6-31+G(d) and 6-311+G(2d, 2p) with the aim to investigate how the basis sets influence the calculation results. To investigate solvent effects and gain a detailed understanding of marker bands of histidine, the ionization energies of histidine and the vibrational frequencies of histidine which are unlabeled and 13C, 15N, and 2H labeled in the gas phase, CCl4, protein environment, THF and water solution, which span a wide range of dielectric constant, were also calculated. Our results showed that: (1) The main geometry parameters of histidine were impacted by basis sets and mediums, and C2-N3 and N3-C4 bond of imidazole ring of histidine side chain display the maximum bond lengths in the gas phase; (2) single point energies and frequencies calculated were decreased while ionization energies increased with the increasing level of basis sets and diffuse function applied in the same solvent; (3) with the same computational method, the higher the dielectric constant of the solvent used, the lower the ionization energy and vibrational frequency and the higher the intensity obtained. In addition, calculated ionization energy in the gas phase and marker bands of histidine as well as frequency shift upon 13C and 15N labeling at the computationally more expensive 6-311+G(2d, 2p) level are in good agreement with experimental observations available in literatures. All calculations indicated that the results calculated by using higher level basis set with diffuse function were more accurate and closer to the experimental value. In

  8. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  9. Purification of pharmaceutical preparations using thin-layer chromatography to obtain mass spectra with Direct Analysis in Real Time and accurate mass spectrometry.

    PubMed

    Wood, Jessica L; Steiner, Robert R

    2011-06-01

    Forensic analysis of pharmaceutical preparations requires a comparative analysis with a standard of the suspected drug in order to identify the active ingredient. Purchasing analytical standards can be expensive or unattainable from the drug manufacturers. Direct Analysis in Real Time (DART™) is a novel, ambient ionization technique, typically coupled with a JEOL AccuTOF™ (accurate mass) mass spectrometer. While a fast and easy technique to perform, a drawback of using DART™ is the lack of component separation of mixtures prior to ionization. Various in-house pharmaceutical preparations were purified using thin-layer chromatography (TLC) and mass spectra were subsequently obtained using the AccuTOF™- DART™ technique. Utilizing TLC prior to sample introduction provides a simple, low-cost solution to acquiring mass spectra of the purified preparation. Each spectrum was compared against an in-house molecular formula list to confirm the accurate mass elemental compositions. Spectra of purified ingredients of known pharmaceuticals were added to an in-house library for use as comparators for casework samples. Resolving isomers from one another can be accomplished using collision-induced dissociation after ionization. Challenges arose when the pharmaceutical preparation required an optimized TLC solvent to achieve proper separation and purity of the standard. Purified spectra were obtained for 91 preparations and included in an in-house drug standard library. Primary standards would only need to be purchased when pharmaceutical preparations not previously encountered are submitted for comparative analysis. TLC prior to DART™ analysis demonstrates a time efficient and cost saving technique for the forensic drug analysis community. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.

  10. Calcium - ionized

    MedlinePlus

    ... diuretics Thrombocytosis (high platelet count) Tumors Vitamin A excess Vitamin D excess Lower-than-normal levels may be due to: Hypoparathyroidism Malabsorption Osteomalacia Pancreatitis Renal failure Rickets Vitamin D deficiency Alternative Names Free calcium; Ionized calcium ...

  11. Dynamic basis for dG•dT misincorporation via tautomerization and ionization

    NASA Astrophysics Data System (ADS)

    Kimsey, Isaac J.; Szymanski, Eric S.; Zahurancik, Walter J.; Shakya, Anisha; Xue, Yi; Chu, Chia-Chieh; Sathyamoorthy, Bharathwaj; Suo, Zucai; Al-Hashimi, Hashim M.

    2018-02-01

    Tautomeric and anionic Watson-Crick-like mismatches have important roles in replication and translation errors through mechanisms that are not fully understood. Here, using NMR relaxation dispersion, we resolve a sequence-dependent kinetic network connecting G•T/U wobbles with three distinct Watson-Crick mismatches: two rapidly exchanging tautomeric species (Genol•T/UG•Tenol/Uenol population less than 0.4%) and one anionic species (G•T-/U- population around 0.001% at neutral pH). The sequence-dependent tautomerization or ionization step was inserted into a minimal kinetic mechanism for correct incorporation during replication after the initial binding of the nucleotide, leading to accurate predictions of the probability of dG•dT misincorporation across different polymerases and pH conditions and for a chemically modified nucleotide, and providing mechanisms for sequence-dependent misincorporation. Our results indicate that the energetic penalty for tautomerization and/or ionization accounts for an approximately 10-2 to 10-3-fold discrimination against misincorporation, which proceeds primarily via tautomeric dGenol•dT and dG•dTenol, with contributions from anionic dG•dT- dominant at pH 8.4 and above or for some mutagenic nucleotides.

  12. Deep-down ionization of protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Glassgold, A. E.; Lizano, S.; Galli, D.

    2017-12-01

    The possible occurrence of dead zones in protoplanetary discs subject to the magneto-rotational instability highlights the importance of disc ionization. We present a closed-form theory for the deep-down ionization by X-rays at depths below the disc surface dominated by far-ultraviolet radiation. Simple analytic solutions are given for the major ion classes, electrons, atomic ions, molecular ions and negatively charged grains. In addition to the formation of molecular ions by X-ray ionization of H2 and their destruction by dissociative recombination, several key processes that operate in this region are included, e.g. charge exchange of molecular ions and neutral atoms and destruction of ions by grains. Over much of the inner disc, the vertical decrease in ionization with depth into the disc is described by simple power laws, which can easily be included in more detailed modelling of magnetized discs. The new ionization theory is used to illustrate the non-ideal magnetohydrodynamic effects of Ohmic, Hall and Ambipolar diffusion for a magnetic model of a T Tauri star disc using the appropriate Elsasser numbers.

  13. Low latitude middle atmosphere ionization studies

    NASA Technical Reports Server (NTRS)

    Bassi, J. P.

    1976-01-01

    Low latitude middle atmosphere ionization was studied with data obtained from three blunt conductivity probes and one Gerdien condenser. An investigation was conducted into the effects of various ionization sources in the 40 to 65 Km altitude range. An observed enhancement of positive ion conductivity taking place during the night can be explained by an atmsopheric effect, with cosmic rays being the only source of ionization only if the ion-ion recombination coefficient (alpha sub i) is small(10 to the -7 power cu cm/s) and varies greatly with altitude. More generally accepted values of alpha sub i ( approximately equal to 3x10 to the -7 power cu cm/s) require an additional source of ionization peaking at about 65 Km, and corresponding approximately to the integrated effect of an X-ray flux measured on a rocket flown in conjunction with the ionization measurements. The reasonable assumption of an alpha sub i which does not vary with altitude in the 50-70 Km range implies an even greater value alpha sub i and a more intense and harder X-ray spectrum.

  14. Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source.

    PubMed

    Orejas, Jaime; Pfeuffer, Kevin P; Ray, Steven J; Pisonero, Jorge; Sanz-Medel, Alfredo; Hieftje, Gary M

    2014-11-01

    Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected.

  15. Down syndrome and ionizing radiation.

    PubMed

    Verger, P

    1997-12-01

    This review examines the epidemiologic and experimental studies into the possible role ionizing radiation might play in Down Syndrome (trisomy 21). It is prompted by a report of a temporal cluster of cases of this chromosomal disorder observed in West Berlin exactly 9 mo after the radioactive cloud from Chernobyl passed. In approximately 90% of cases, Down Syndrome is due to the nondisjunction of chromosome 21, most often in the oocyte, which may be exposed to ionizing radiation during two separate periods: before the completion of the first meiosis or around the time of ovulation. Most epidemiologic studies into trisomies and exposure to ionizing radiation examine only the first period; the Chernobyl cluster is related to the second. Analysis of these epidemiologic results indicates that the possibility that ionizing radiation might be a risk factor in Down Syndrome cannot be excluded. The experimental results, although sometimes contradictory, demonstrate that irradiation may induce nondisjunction in oogenesis and spermatogenesis; they cannot, however, be easily extrapolated to humans. The weaknesses of epidemiologic studies into the risk factors for Down Syndrome at birth (especially the failure to take into account the trisomy cases leading to spontaneous abortion) are discussed. We envisage the utility and feasibility of new studies, in particular among women exposed to prolonged or repeated artificially-produced ionizing radiation.

  16. Simulation study of the ionizing front in the critical ionization velocity phenomenon

    NASA Technical Reports Server (NTRS)

    Machida, S.; Goertz, C. K.; Lu, G.

    1988-01-01

    The simulation of the critical ionization velocity for a neutral gas cloud moving across the static magnetic field is presented. A low-beta plasma is studied, using a two and a half-dimensional electrostatic code linked with the Plasma and Neutral Interaction Code (Goertz and Machida, 1987). The physics of the ionizing front and the instabilities which occur there are discussed. Results are presented from four numerical runs designed so that the effects of the charge separation field can be distinguished from the wave heating.

  17. A Miniaturized Linear Wire Ion Trap with Electron Ionization and Single Photon Ionization Sources

    NASA Astrophysics Data System (ADS)

    Wu, Qinghao; Tian, Yuan; Li, Ailin; Andrews, Derek; Hawkins, Aaron R.; Austin, Daniel E.

    2017-05-01

    A linear wire ion trap (LWIT) with both electron ionization (EI) and single photon ionization (SPI) sources was built. The SPI was provided by a vacuum ultraviolet (VUV) lamp with the ability to softly ionize organic compounds. The VUV lamp was driven by a pulse amplifier, which was controlled by a pulse generator, to avoid the detection of photons during ion detection. Sample gas was introduced through a leak valve, and the pressure in the system is shown to affect the signal-to-noise ratio and resolving power. Under optimized conditions, the limit of detection (LOD) for benzene was 80 ppbv using SPI, better than the LOD using EI (137 ppbv). System performance was demonstrated by distinguishing compounds in different classes from gasoline.

  18. The study of the effects of ionizing and non-ionizing radiations on birth weight of newborns to exposed mothers

    PubMed Central

    Mortazavi, S. M. J.; Shirazi, K. R.; Mortazavi, G.

    2013-01-01

    Objectives: Life evolved in an environment filled with a wide variety of ionizing and non-ionizing radiation. It was previously reported that medical exposures to pregnant women increases the risk of low birth weight. This study intends to investigate the relationship between exposure to ionizing and non-ionizing radiation and the risk of low birth weight. Materials and Methods: One thousand two hundred mothers with their first-term labor (vaginal or cesarean) whose newborns’ history had been registered in neonates’ screening program in Shiraz were interviewed and surveyed. Data collection was performed by the assessment of mother's history of radiography before and during pregnancy, physical examination of the mother for height and weight and weighing and examining the newborn for any diagnosis of disease and anomalies. Results: There were no statistical significant differences between the mean weight of newborns whose mothers had been exposed to some common sources of ionizing and non-ionizing radiations such as dental or non dental radiographies, mobile phone, cordless phone and cathode ray tube (CRT) and those of non-exposed mothers. Conclusions: The findings of this study cast doubt on previous reports, which indicated that exposure to ionizing radiation during pregnancy increased the risk of low birth weight. PMID:23633865

  19. The Evolution of Electrospray Generated Droplets is Not Affected by Ionization Mode

    NASA Astrophysics Data System (ADS)

    Liigand, Piia; Heering (Suu), Agnes; Kaupmees, Karl; Leito, Ivo; Girod, Marion; Antoine, Rodolphe; Kruve, Anneli

    2017-10-01

    Ionization efficiency and mechanism in ESI is strongly affected by the properties of mobile phase. The use of mobile-phase properties to accurately describe droplets in ESI source is convenient but may be inadequate as the composition of the droplets is changing in the plume due to electrochemical reactions occurring in the needle tip as well as continuous drying and fission of droplets. Presently, there is paucity of research on the effect of the polarity of the ESI mode on mobile phase composition in the droplets. In this paper, the change in the organic solvent content, pH, and droplet size are studied in the ESI plume in both ESI+ and ESI- ionization mode. We introduce a rigorous way - the absolute pH (pHabs H 2 O) - to describe pH change in the plume that takes into account organic solvent content in the mobile phase. pHabs H 2 O enables comparing acidities of ESI droplets with different organic solvent contents. The results are surprisingly similar for both ionization modes, indicating that the dynamics of the change of mobile-phase properties is independent from the ESI mode used. This allows us to conclude that the evolution of ESI droplets first of all proceeds via the evaporation of the organic modifier and to a lesser extent via fission of smaller droplets from parent droplets. Secondly, our study shows that qualitative findings related to the ESI process obtained on the ESI+ mode can almost directly be applied also in the ESI- mode. [Figure not available: see fulltext.

  20. Applications of High-Resolution Electrospray Ionization Mass Spectrometry to Measurements of Average Oxygen to Carbon Ratios in Secondary Organic Aerosols

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

    Bateman, Adam P.; Laskin, Julia; Laskin, Alexander

    2012-07-02

    The applicability of high resolution electrospray ionization mass spectrometry (HR ESI-MS) to measurements of the average oxygen to carbon ratio (O/C) in organic aerosols was investigated. Solutions with known average O/C containing up to 10 standard compounds representative of secondary organic aerosol (SOA) were analyzed and corresponding electrospray ionization efficiencies were quantified. The assumption of equal ionization efficiency commonly used in estimating O/C ratios of organic aerosols was found to be reasonably accurate. We found that the accuracy of the measured O/C ratios increases by averaging the values obtained from both (+) and (-) modes. A correlation was found betweenmore » the ratio of the ionization efficiencies in the positive and negative ESI modes with the octanol-water partition constant, and more importantly, with the compound's O/C. To demonstrate the utility of this correlation for estimating average O/C values of unknown mixtures, we analyzed the ESI (+) and ESI (-) data for SOA produced by oxidation of limonene and isoprene and compared to online O/C measurements using an aerosol mass spectrometer (AMS). This work demonstrates that the accuracy of the HR ESI-MS methods is comparable to that of the AMS, with the added benefit of molecular identification of the aerosol constituents.« less

  1. Microfluidic nitrogen-assisted nanoelectrospray emitter: A monolithic interface for accurate mass measurements based on a single nozzle.

    PubMed

    Wang, Lingling; Wang, Yujiao; Jiang, Shichang; Ye, Mingyue; Su, Ping; Xiong, Bo

    2016-10-28

    Nitrogen-assisted nanoelectrospray emitter (NANE) was developed to achieve accurate mass-to-charge ratio (m/z) measurements with a single monolithic nozzle. Deposition patterns of generated electrosprays from NANE confirmed their wrapped configurations. Additionally, the intensity of the sample ion and its ratio relative to a reference ion was inclined to focus on the central region of the spray; this trend further supported the existence of wrapped configurations. Further, the proposed NANE was fabricated from poly-(dimethylsiloxane) (PDMS) with octadecyltrichlorosilane modification to restrain the dissolution of PDMS monomers. Assist nitrogen flows were introduced to improve the ionization of reference ions. Moreover, the NANE could regulate the distribution of reference ions by microfluidic three dimensional hydrodynamic focusing. By regulating the distribution of reference ions, the ionization depression was reduced to some degree, and an improved sensitivity was accomplished compared with the mixing of sample and reference solutions. Achieved relative errors of m/z were between 0.2-4.5ppm and 5.2-9.2ppm for ten organic molecules and four biological macromolecules, respectively. Acceptable linear ranges were obtained in quantifications for rhodamine B and emamectin benzoate. Finally, the NANE was compatible with broad infusion rates (from 50nLmin -1 to 15μLmin -1 ) and solutions of different compositions (from 100% methanol to 100% water). Considering the comprehensive application of PDMS in microfluidics, the proposed NANE could be used as a compact and monolithic interface to achieve accurate m/z measurements. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Electron impact ionization in the vicinity of comets

    NASA Astrophysics Data System (ADS)

    Cravens, T. E.; Kozyra, J. U.; Nagy, A. F.; Gombosi, T. I.; Kurtz, M.

    1987-07-01

    The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation.Electron distributions measured in the vicinity of comets Halley and Giacobini-Zinner by instruments on the VEGA and ICE spacecraft, respectively, are used to calculate electron impact ionization frequencies. Ionization by electrons is of comparable importance to photoionization in the magnetosheaths of Comets Halley and Giacobini-Zinner. The ionization frequency in the inner part of the cometary plasma region of comet Halley is several times greater than the photoionization value. Tables of ionization frequencies as functions of electron temperature are presented for H2O, CO2, CO, O, N2, and H.

  3. Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques

    NASA Technical Reports Server (NTRS)

    Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

    2002-01-01

    The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization. c. 2002 American Society for Mass Spectrometry.

  4. Ionization of NO at high temperature

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1991-01-01

    Space vehicles flying through the atmosphere at high speed are known to excite a complex set of chemical reactions in the atmospheric gases, ranging from simple vibrational excitation to dissociation, atom exchange, electronic excitation, ionization, and charge exchange. Simple arguments are developed for the temperature dependence of the reactions leading to ionization of NO, including the effect of vibrational electronic thermal nonequilibrium. NO ionization is the most important source of electrons at intermediate temperatures and at higher temperatures provides the trigger electrons that ionize atoms. Based on these arguments, recommendations are made for formulae which fit observed experimental results, and which include a dependence on both a heavy particle temperature and different vibration electron temperatures. In addition, these expressions will presumably provide the most reliable extrapolation of experimental results to much higher temperatures.

  5. Ionizing Collisions of Electrons with Radical Species OH, H2 O2 and HO2; Theoretical Calculations

    NASA Astrophysics Data System (ADS)

    Joshipura, K. N.; Pandya, S. H.; Vaishnav, B. G.; Patel, U. R.

    2016-05-01

    In this paper we present our calculated total ionization cross sections (TICS) of electron impact on radical targets OH, H2 O2 and HO2 at energies from threshold to 2000 eV. Reactive species such as these pose difficulties in measurements of electron scattering cross sections. No measured data have been reported in this regard except an isolated TICS measurement on OH radical, and hence the present work on the title radicals hold significance. These radical species are present in an environment in which water molecules undergo dissociation (neutral or ionic) in interactions with photons or electrons. The embedding environments could be quite diverse, ranging from our atmosphere to membranes of living cells. Ionization of OH, H2 O2 or HO2 can give rise to further chemistry in the relevant bulk medium. Therefore, it is appropriate and meaningful to examine electron impact ionization of these radicals in comparison with that of water molecules, for which accurate da are available. For the OH target single-centre scattering calculations are performed by starting with a 4-term complex potential, that describes simultaneous elastic plus inelastic scattering. TICS are obtained from the total inelastic cross sections in the complex scattering potential - ionization contribution formalism , a well established method. For H2 O2 and HO2 targets, we employ the additivity rule with overlap or screening corrections. Detailed results will be presented in the Conference.

  6. Ionization Efficiency in the Dayside Martian Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Cui, J.; Wu, X.-S.; Xu, S.-S.; Wang, X.-D.; Wellbrock, A.; Nordheim, T. A.; Cao, Y.-T.; Wang, W.-R.; Sun, W.-Q.; Wu, S.-Q.; Wei, Y.

    2018-04-01

    Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO2 and O ionization efficiencies tend to be constant from 160 km up to 250 km, with respective median values of 0.19 ± 0.03 and 0.27 ± 0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.

  7. Development of a 5-Component Balance for Water Tunnel Applications

    NASA Technical Reports Server (NTRS)

    Suarez, Carlos J.; Kramer, Brian R.; Smith, Brooke C.

    1999-01-01

    The principal objective of this research/development effort was to develop a multi-component strain gage balance to measure both static and dynamic forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 90 grams or 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models. The five-component balance was calibrated and demonstrated linearity in the responses of the primary components to applied loads, very low interactions between the sections and no hysteresis. Static experiments were conducted in the Eidetics water tunnel with delta wings and F/A-18 models. The data were compared to forces and moments from wind tunnel tests of the same or similar configurations. The comparison showed very good agreement, providing confidence that loads can be measured accurately in the water tunnel with a relatively simple multi-component internal balance. The success of the static experiments encouraged the use of the balance for dynamic experiments. Among the advantages of conducting dynamic tests in a water tunnel are less demanding motion and data acquisition rates than in a wind tunnel test (because of the low-speed flow) and the capability of performing flow visualization and force/moment (F/M) measurements simultaneously with relative simplicity. This capability of simultaneous flow visualization and for F/M measurements proved extremely useful to explain the results obtained during these dynamic tests. In general, the development of this balance should encourage the use of water tunnels for a

  8. Typical balance exercises or exergames for balance improvement?

    PubMed

    Gioftsidou, Asimenia; Vernadakis, Nikolaos; Malliou, Paraskevi; Batzios, Stavros; Sofokleous, Polina; Antoniou, Panagiotis; Kouli, Olga; Tsapralis, Kyriakos; Godolias, George

    2013-01-01

    Balance training is an effective intervention to improve static postural sway and balance. The purpose of the present study was to investigate the effectiveness of the Nintendo Wii Fit Plus exercises for improving balance ability in healthy collegiate students in comparison with a typical balance training program. Forty students were randomly divided into two groups, a traditional (T group) and a Nintendo Wii group (W group) performed an 8 week balance program. The "W group" used the interactive games as a training method, while the "T group" used an exercise program with mini trampoline and inflatable discs (BOSU). Pre and Post-training participants completed balance assessments. Two-way repeated measures analyses of variance (ANOVAs) were conducted to determine the effect of training program. Analysis of the data illustrated that both training program groups demonstrated an improvement in Total, Anterior-posterior and Medial Lateral Stability Index scores for both limbs. Only at the test performed in the balance board with anterior-posterior motion, the improvement in balance ability was greater in the "T group" than the "W group", when the assessment was performed post-training (p=0.023). Findings support the effectiveness of using the Nintendo Wii gaming console as a balance training intervention tool.

  9. The energy balance within a bubble column evaporator

    NASA Astrophysics Data System (ADS)

    Fan, Chao; Shahid, Muhammad; Pashley, Richard M.

    2018-05-01

    Bubble column evaporator (BCE) systems have been studied and developed for many applications, such as thermal desalination, sterilization, evaporative cooling and controlled precipitation. The heat supplied from warm/hot dry bubbles is to vaporize the water in various salt solutions until the solution temperature reaches steady state, which was derived into the energy balance of the BCE. The energy balance and utilization involved in each BCE process form the fundamental theory of these applications. More importantly, it opened a new field for the thermodynamics study in the form of heat and vapor transfer in the bubbles. In this paper, the originally derived energy balance was reviewed on the basis of its physics in the BCE process and compared with new proposed energy balance equations in terms of obtained the enthalpy of vaporization (Δ H vap) values of salt solutions from BCE experiments. Based on the analysis of derivation and Δ H vap values comparison, it is demonstrated that the original balance equation has high accuracy and precision, within 2% over 19-55 °C using improved systems. Also, the experimental and theoretical techniques used for determining Δ H vap values of salt solutions were reviewed for the operation conditions and their accuracies compared to the literature data. The BCE method, as one of the most simple and accurate techniques, offers a novel way to determine Δ H vap values of salt solutions based on its energy balance equation, which had error less than 3%. The thermal energy required to heat the inlet gas, the energy used for water evaporation in the BCE and the energy conserved from water vapor condensation were estimated in an overall energy balance analysis. The good agreement observed between input and potential vapor condensation energy illustrates the efficiency of the BCE system. Typical energy consumption levels for thermal desalination for producing pure water using the BCE process was also analyzed for different inlet air

  10. Lattice design and expected performance of the Muon Ionization Cooling Experiment demonstration of ionization cooling

    DOE PAGES

    Bogomilov, M.; Tsenov, R.; Vankova-Kirilova, G.; ...

    2017-06-19

    Muon beams of low emittance provide the basis for the intense, well-characterized neutrino beams necessary to elucidate the physics of flavor at a neutrino factory and to provide lepton-antilepton collisions at energies of up to several TeV at a muon collider. The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam passes through a material in which it loses energy. The energy lost is then replaced using rf cavities. The combinedmore » effect of energy loss and reacceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised experiment can deliver a demonstration of ionization cooling. The design of the cooling demonstration experiment will be described together with its predicted cooling performance.« less

  11. Low-energy electron scattering from atomic hydrogen. I. Ionization

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

    Childers, J.G.; James, K.E. Jr.; Bray, Igor

    2004-02-01

    Absolute doubly differential cross sections for the ionization of atomic hydrogen by electron impact have been measured at energies ranging from near threshold to intermediate values. The measurements are normalized to the accurate differential cross section for the electron-impact excitation of the H 1 {sup 2}S{yields}2 {sup 2}S+2 {sup 2}P transition. These measurements were made possible through the use of a moveable target source which enables the collection of hydrogen energy loss spectra free of all backgrounds. The measurements cover the incident electron energy range of 14.6-40 eV and scattering angles from 12 deg. to 127 deg., and are inmore » very good agreement with the results of the latest theoretical models--the convergent close-coupling model and the exterior complex scaling model.« less

  12. Electron impact ionization of atomic targets at relativistic energies

    NASA Astrophysics Data System (ADS)

    Uddin, M. A.; Basak, A. K.; Saha, B. C.

    2009-05-01

    The huge demand and scarcity of electron impact ionization cross sections (EIICS) that are essential not only in modeling but also in basic researches can be best filled in by simple to use analytical models [1] that are sufficiently accurate and provide fast generation of EIICS data over wide domain. We report few such models and compare their productive powers in terms of few adjustable parameters. Details of our results will be presented in the conference. [1] A. K. F. Haque, M. A. Uddin, A. K. Basak, K. R. Karim, B. C. Saha, and F. B. Malik, Phys. Scr. 74, 377 (2006); Phys. Rev A 73, 052703; M. A. R. Patoary, M. A. Uddin, A. K. F. Haque, M. Shahjahan, A. K. Basak, M. R. Talukdar and B. C. Saha, Int. J. Quan. Chem (in press). Supported by NSF CREST.

  13. Spectrally resolved opacities and Rosseland and Planck mean opacities of lowly ionized gold plasmas: a detailed level-accounting investigation.

    PubMed

    Zeng, Jiaolong; Yuan, Jianmin

    2007-08-01

    Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fully relativistic detailed level-accounting approach are presented to show the importance of accurate atomic data for a quantitative reproduction of the experimental observations. Even though a huge number of transition lines are involved in the radiative absorption of high- Z plasmas so that one believes that statistical models can often give a reasonable description of their opacities, we first show in detail that an adequate treatment of physical effects, in particular the configuration interaction (including the core-valence electron correlation), is essential to produce atomic data of bound-bound and bound-free processes for gold plasmas, which are accurate enough to correctly explain the relative intensity of two strong absorption peaks experimentally observed located near photon energy of 70 and 80 eV. A detailed study is also carried out for gold plasmas of an average ionization degree sequence of 10, for both spectrally resolved opacities and Rosseland and Planck means. For comparison, results obtained by using an average atom model are also given to show that even for a relatively higher density of matter, correlation effects are also important to predict the correct positions of absorption peaks of transition arrays.

  14. Two competing ionization processes in ESI-MS analysis of N-(1,3-diphenylallyl)benzenamines: formation of the unusual [M-H]+ ion versus the regular [M+H]+ ion.

    PubMed

    Fang, Liwen; Dong, Cheng; Guo, Cheng; Xu, Jianxing; Liu, Qiaoling; Qu, Zhirong; Jiang, Kezhi

    2018-06-01

    A series of N-(1,3-diphenylallyl)benzenamine derivatives (M) were investigated by electrospray ionization mass spectrometry in the positive-ion mode. Both the anomalous [M-H] + and the regular [M+H] + were observed in the ESI mass spectra. The occurrence of [M-H] + has been supported by accurate mass spectrometry, liquid chromatography mass spectrometry, and tandem mass spectrometry analysis. Calculation results indicated that formation of [M-H] + is attributed to the ion-molecule reaction of M with the protonated ESI solvent molecule (e.g. CH 3 OH 2 + ) via hydride abstraction from a tertiary C sp3 -H. The competing ionization processes leading to [M-H] + or [M+H] + were significantly affected by the concentration of formic acid in the electrospray ionization solvent and the proton affinity of the N atom.

  15. Advanced liquid chromatography-mass spectrometry interface based on electron ionization.

    PubMed

    Cappiello, A; Famiglini, G; Pierini, E; Palma, P; Trufelli, H

    2007-07-15

    Major progress in interfacing liquid chromatography and electron ionization mass spectrometry is presented. The minimalism of the first prototype, called the Direct-EI interface, has been widely refined, improved, and applied to modern instrumentation. The simple interfacing principle is based on the straight connection between a nanoHPLC system and a mass spectrometer equipped with an EI source forming a solid and reliable unicum resembling the immediacy and straightforwardness of GC/MS. The interface shows a superior performance in the analysis of small-medium molecular weight compounds, especially when compared to its predecessors, and a unique trait that excels particularly in the following aspects: (1) It delivers high-quality, fully library matchable mass spectra of most sub-1 kDa molecules amenable by HPLC. (2) It is a chemical ionization free interface (unless operated intentionally) with accurate reproduction of the expected isotope ion abundances. (3) Response is never influenced by matrix components in the sample or in the mobile phase (nonvolatile salts are also well accepted). A deep evaluation of these aspects is presented and discussed in detail. Other characteristics of the interface performance such as limits of detections, range of linear response, and intra- and interday signal stability were also considered. The usefulness of the interface has been tested in a few real-world applications where matrix components played a detrimental role with other LC/MS techniques.

  16. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

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

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

  17. Ionizing radiation

    NASA Technical Reports Server (NTRS)

    Tobias, C. A.; Grigoryev, Y. G.

    1975-01-01

    The biological effects of ionizing radiation encountered in space are considered. Biological experiments conducted in space and some experiences of astronauts during space flight are described. The effects of various levels of radiation exposure and the determination of permissible dosages are discussed.

  18. Aerodynamic measurements and thermal tests of a strain-gage balance in a cryogenic wind tunnel

    NASA Technical Reports Server (NTRS)

    Boyden, Richmond P.; Ferris, Alice T.; Johnson, William G., Jr.; Dress, David A.; Hill, Acquilla S.

    1987-01-01

    An internal strain-gage balance designed and constructed in Europe for use in cryogenic wind tunnels has been tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. Part of the evaluation was made at equilibrium balance temperatures and it consisted of comparing the data taken at a tunnel stagnation temperature of 300 K with the data taken at 200 K and 110 K while maintaining either the Reynolds number or the stagnation pressure. A sharp-leading-edge delta-wing model was used to provide the aerodynamic loading for these tests. Results obtained with the balance during the force tests were found to be accurate and repeatable both with and without the use of a convection shield on the balance. An additional part of this investigation involved obtaining data on the transient temperature response of the balance during both normal and rapid changes in the tunnel stagnation temperature. The variation of the temperature with time was measured at three locations on the balance near the physical locations of the strain gages. The use of a convection shield significantly increased the time required for the balance to stabilize at a new temperature during the temperature response tests.

  19. Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial mass balance from surface mass balance

    NASA Astrophysics Data System (ADS)

    Bonin, J. A.; Chambers, D. P.

    2015-09-01

    Mass change over Greenland can be caused by either changes in the glacial dynamic mass balance (DMB) or the surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate cumulative SMB from DMB with GRACE, using a least squares inversion technique with knowledge of the location of the glaciers. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from DMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 10 at a resolution of 90 × 90 would provide the accuracy needed for the interannual cumulative SMB and DMB to be accurately separated.

  20. Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial mass balance from surface mass balance

    NASA Astrophysics Data System (ADS)

    Bonin, J. A.; Chambers, D. P.

    2015-02-01

    Mass change over Greenland can be caused by either changes in the glacial mass balance (GMB) or the precipitation-based surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate SMB from GMB with GRACE, using a least squares inversion technique with knowledge of the location of the glacier. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from GMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 9 at a resolution of 90 × 90 would provide the accuracy needed for the interannual SMB and GMB to be accurately separated.

  1. Multidimensional gas chromatography in combination with accurate mass, tandem mass spectrometry, and element-specific detection for identification of sulfur compounds in tobacco smoke.

    PubMed

    Ochiai, Nobuo; Mitsui, Kazuhisa; Sasamoto, Kikuo; Yoshimura, Yuta; David, Frank; Sandra, Pat

    2014-09-05

    A method is developed for identification of sulfur compounds in tobacco smoke extract. The method is based on large volume injection (LVI) of 10μL of tobacco smoke extract followed by selectable one-dimensional ((1)D) or two-dimensional ((2)D) gas chromatography (GC) coupled to a hybrid quadrupole time-of-flight mass spectrometer (Q-TOF-MS) using electron ionization (EI) and positive chemical ionization (PCI), with parallel sulfur chemiluminescence detection (SCD). In order to identify each individual sulfur compound, sequential heart-cuts of 28 sulfur fractions from (1)D GC to (2)D GC were performed with the three MS detection modes (SCD/EI-TOF-MS, SCD/PCI-TOF-MS, and SCD/PCI-Q-TOF-MS). Thirty sulfur compounds were positively identified by MS library search, linear retention indices (LRI), molecular mass determination using PCI accurate mass spectra, formula calculation using EI and PCI accurate mass spectra, and structure elucidation using collision activated dissociation (CAD) of the protonated molecule. Additionally, 11 molecular formulas were obtained for unknown sulfur compounds. The determined values of the identified and unknown sulfur compounds were in the range of 10-740ngmg total particulate matter (TPM) (RSD: 1.2-12%, n=3). Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  2. The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties

    PubMed Central

    Xu, Xin; Goddard, William A.

    2004-01-01

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee–Yang–Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energies [over the most popular and accurate method, B3LYP (Becke three-parameter hybrid functional combined with Lee–Yang–Parr correlation functional)]. X3LYP also leads to a good description of dipole moments, polarizabilities, and accurate excitation energies from s to d orbitals for transition metal atoms and ions. We suggest that X3LYP will be useful for predicting ligand binding in proteins and DNA. PMID:14981235

  3. Ionization nebulae surrounding supersoft X-ray sources

    NASA Technical Reports Server (NTRS)

    Rappaport, S.; Chiang, E.; Kallman, T.; Malina, R.

    1994-01-01

    In this work we carry out a theoretical investigation of a new type of astrophysical gaseous nebula, viz., ionized regions surrounding supersoft X-ray sources. Supersoft X-ray sources, many of which have characteristic luminosities of approximately 10(exp 37)-(10(exp 38) ergs/s and effective temperatures of approximately 4 x 10(exp 5) K, were first discovered with the Einstein Observatory. These sources have now been shown to constitute a distinct class of X-ray source and are being found in substantial numbers with ROSAT. We predict that these sources should be surrounded by regions of ionized hydrogen and helium with properties that are distinct from other astrophysical gaseous nebulae. We present caluations of the ionization and temperature structure of these ionization nebulae, as well as the expected optical line fluxes. The ionization profiles for both hydrogen and helium exhibit substantially more gradual transitions from the ionized to the unionized state than is the case for conventional H II regions. The calculated optical line intensitites are presented as absolute fluxes from sources in the Large Magellanic Cloud and as fractions of the central source luminosity. We find, in particular, that (O III) lambda 5008 and He II lambda 4686 are especially prominent in these ionization nebulae as compared to other astrophysical nebulae. We propose that searches for supersoft X-rays via their characteristic optical lines may reveal sources in regions where the soft X-rays are nearly completely absorbed by the interstellar medium.

  4. A water balance based, spatiotemporal evaluation of terrestrial evapotranspiration products across the contiguous United States

    USDA-ARS?s Scientific Manuscript database

    Accurate gridded estimates of evapotranspiration (ET) are essential to the analysis of terrestrial water budgets. In this study, ET estimates from three gridded energy-balance based products (ETEB) with independent model formations and data forcings are evaluated for their ability to capture long te...

  5. Sensitive Quantitative Assessment of Balance Disorders

    NASA Technical Reports Server (NTRS)

    Paloski, Willilam H.

    2007-01-01

    Computerized dynamic posturography (CDP) has become a standard technique for objectively quantifying balance control performance, diagnosing the nature of functional impairments underlying balance disorders, and monitoring clinical treatment outcomes. We have long used CDP protocols to assess recovery of sensory-motor function in astronauts following space flight. The most reliable indicators of post-flight crew performance are the sensory organization tests (SOTs), particularly SOTs 5 and 6, which are sensitive to changes in availability and/or utilization of vestibular cues. We have noted, however, that some astronauts exhibiting obvious signs of balance impairment after flight are able to score within clinical norms on these tests, perhaps as a result of adopting competitive strategies or by their natural skills at substituting alternate sensory information sources. This insensitivity of the CDP protocol could underestimate of the degree of impairment and, perhaps, lead to premature release of those crewmembers to normal duties. To improve the sensitivity of the CDP protocol we have introduced static and dynamic head tilt SOT trials into our protocol. The pattern of postflight recovery quantified by the enhanced CDP protocol appears to more aptly track the re-integration of sensory-motor function, with recovery time increasing as the complexity of sensory-motor/biomechanical task increases. The new CDP protocol therefore seems more suitable for monitoring post-flight sensory-motor recovery and for indicating to crewmembers and flight surgeons fitness for return to duty and/or activities of daily living. There may be classes of patients (e.g., athletes, pilots) having motivation and/or performance characteristics similar to astronauts whose sensory-motor treatment outcomes would also be more accurately monitored using the enhanced CDP protocol. Furthermore, the enhanced protocol may be useful in early detection of age-related balance disorders.

  6. Development of a Portable Single Photon Ionization-Photoelectron Ionization Time-of-Flight Mass Spectrometer

    PubMed Central

    Huang, Yunguang; Li, Jinxu; Tang, Bin; Zhu, Liping; Hou, Keyong; Li, Haiyang

    2015-01-01

    A vacuum ultraviolet lamp based single photon ionization- (SPI-) photoelectron ionization (PEI) portable reflecting time-of-flight mass spectrometer (TOFMS) was designed for online monitoring gas samples. It has a dual mode ionization source: SPI for analyte with ionization energy (IE) below 10.6 eV and PEI for IE higher than 10.6 eV. Two kinds of sampling inlets, a capillary inlet and a membrane inlet, are utilized for high concentration and trace volatile organic compounds, respectively. A mass resolution of 1100 at m/z 64 has been obtained with a total size of 40 × 31 × 29 cm, the weight is 27 kg, and the power consumption is only 70 W. A mixture of benzene, toluene, and xylene (BTX), SO2, and discharging products of SF6 were used to test its performance, and the result showed that the limit of quantitation for BTX is as low as 5 ppbv (S/N = 10 : 1) with linear dynamic ranges greater than four orders of magnitude. The portable TOFMS was also evaluated by analyzing volatile organic compounds from wine and decomposition products of SF6 inside of a gas-insulated switchgear. PMID:26587023

  7. Modeling carbon dioxide, pH, and un-ionized ammonia relationships in serial reuse systems

    USGS Publications Warehouse

    Colt, J.; Watten, B.; Rust, M.

    2009-01-01

    In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity-pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air-water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air-water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

  8. Modeling Carbon Dioxide, pH and Un-Ionized Ammonia Relationships in Serial Reuse Systems

    USGS Publications Warehouse

    Watten, Barnaby J.; Rust, Michael; Colt, John

    2009-01-01

    In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity–pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air–water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air–water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.

  9. Ionization of Interstellar Hydrogen Beyond the Termination Shock

    NASA Astrophysics Data System (ADS)

    Gruntman, Mike

    2016-11-01

    Models of solar wind interaction with the surrounding interstellar medium usually disregard ionization of interstellar hydrogen atoms beyond the solar wind termination shock. If and when included, the effects of ionization in the heliospheric interface region are often obscured by complexities of the interaction. This work assesses the importance of interstellar hydrogen ionization in the heliosheath. Photoionization could be accounted for in a straightforward way. In contrast, electron impact ionization is largely unknown because of poorly understood energy transfer to electrons at the termination shock and beyond. We first estimate the effect of photoionization and then use it as a yardstick to assess the role of electron impact ionization. The physical estimates show that ionization of interstellar hydrogen may lead to significant mass loading in the inner heliosheath which would slow down plasma flowing toward the heliotail and deplete populations of nonthermal protons, with the corresponding effect on heliospheric fluxes of energetic neutral atoms.

  10. Interchangeability of the Wii Balance Board for Bipedal Balance Assessment.

    PubMed

    Bonnechère, Bruno; Jansen, Bart; Omelina, Lubos; Rooze, Marcel; Van Sint Jan, Serge

    2015-08-27

    Since 2010, an increasing interest in more portable and flexible hardware for balance and posture assessment led to previously published studies determining whether or not the Wii Balance Board could be used to assess balance and posture, both scientifically and clinically. However, no previous studies aimed at comparing results from different Wii Balance Boards for clinical balance evaluation exist. The objective of this crossover study is to assess the interchangeability of the Wii Balance Board. A total of 6 subjects participated in the study and their balance was assessed using 4 different Wii Balance Boards. Trials were recorded simultaneously with Wii Balance Boards and with a laboratory force plate. Nine relevant clinical parameters were derived from center of pressure displacement data obtained from Wii Balance Board and force plate systems. Intraclass correlation coefficients (ICC), F tests, and Friedman tests were computed to assess the agreement between trials and to compare the Wii Balance Board and force plate results. Excellent correlations were found between the Wii Balance Board and force plate (mean ρ =.83). With the exception of 2 parameters, strong to excellent agreements were found for the 7 remaining parameters (ICC=.96). No significant differences were found between trials recorded with different Wii Balance Boards. Our results indicate that for most of the parameters analyzed, balance and posture assessed with one Wii Balance Board were statistically similar to results obtained from another. Furthermore, the good correlation between the Wii Balance Board and force plate results shows that Wii Balance Boards can be reliably used for scientific assessment using most of the parameters analyzed in this study. These results also suggest that the Wii Balance Board could be used in multicenter studies and therefore, would allow for the creation of larger populations for clinical studies. Ethical Committee of the Erasme Hospital (CCB B406201215142

  11. Interchangeability of the Wii Balance Board for Bipedal Balance Assessment

    PubMed Central

    Jansen, Bart; Omelina, Lubos; Rooze, Marcel; Van Sint Jan, Serge

    2015-01-01

    Background Since 2010, an increasing interest in more portable and flexible hardware for balance and posture assessment led to previously published studies determining whether or not the Wii Balance Board could be used to assess balance and posture, both scientifically and clinically. However, no previous studies aimed at comparing results from different Wii Balance Boards for clinical balance evaluation exist. Objective The objective of this crossover study is to assess the interchangeability of the Wii Balance Board. Methods A total of 6 subjects participated in the study and their balance was assessed using 4 different Wii Balance Boards. Trials were recorded simultaneously with Wii Balance Boards and with a laboratory force plate. Nine relevant clinical parameters were derived from center of pressure displacement data obtained from Wii Balance Board and force plate systems. Intraclass correlation coefficients (ICC), F tests, and Friedman tests were computed to assess the agreement between trials and to compare the Wii Balance Board and force plate results. Results Excellent correlations were found between the Wii Balance Board and force plate (mean ρ =.83). With the exception of 2 parameters, strong to excellent agreements were found for the 7 remaining parameters (ICC=.96). No significant differences were found between trials recorded with different Wii Balance Boards. Conclusions Our results indicate that for most of the parameters analyzed, balance and posture assessed with one Wii Balance Board were statistically similar to results obtained from another. Furthermore, the good correlation between the Wii Balance Board and force plate results shows that Wii Balance Boards can be reliably used for scientific assessment using most of the parameters analyzed in this study. These results also suggest that the Wii Balance Board could be used in multicenter studies and therefore, would allow for the creation of larger populations for clinical studies. Trial

  12. Dielectric barrier discharge ionization for liquid chromatography/mass spectrometry.

    PubMed

    Hayen, Heiko; Michels, Antje; Franzke, Joachim

    2009-12-15

    An atmospheric pressure microplasma ionization source based on a dielectric barrier discharge with a helium plasma cone outside the electrode region has been developed for liquid chromatography/mass spectrometry (LC/MS). For this purpose, the plasma was realized in a commercial atmospheric pressure ionization source. Dielectric barrier discharge ionization (DBDI) was compared to conventional electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) in the positive ionization mode. Therefore, a heterogeneous compound library was investigated that covered polar compounds such as amino acids, water-soluble vitamins, and nonpolar compounds like polycyclic aromatic hydrocarbons and functionalized hydrocarbons. It turned out that DBDI can be regarded as a soft ionization technique characterized by only minor fragmentation similar to APCI. Mainly protonated molecules were detected. Additionally, molecular ions were observed for polycyclic aromatic hydrocarbons and derivatives thereof. During DBDI, adduct formation with acetonitrile occurred. For aromatic compounds, addition of one to four oxygen atoms and to a smaller extend one nitrogen and oxygen was observed which delivered insight into the complexity of the ionization processes. In general, compounds covering a wider range of polarities can be ionized by DBDI than by ESI. Furthermore, limits of detection compared to APCI are in most cases equal or even better.

  13. A systematic review of balance and fall risk assessments with mobile phone technology.

    PubMed

    Roeing, Kathleen L; Hsieh, Katherine L; Sosnoff, Jacob J

    2017-11-01

    Falls are a major health concern for older adults. Preventative measures can help reduce the incidence and severity of falls. Methods for assessing balance and fall risk factors are necessary to effectively implement preventative measures. Research groups are currently developing mobile applications to enable seniors, caregivers, and clinicians to monitor balance and fall risk. The following systematic review assesses the current state of mobile health apps for testing balance as a fall risk factor. Thirteen studies were identified and included in the review and analyzed based on study design, population, sample size, measures of balance, main outcome measures, and evaluation of validity and reliability. All studies successfully tested their applications, but only 38% evaluated the validity, and 23% evaluated the reliability of their applications. Of those, all applications were found to accurately and reliably measure balance on select variables. Four of the 13 studies included special populations groups. Out of the 13 studies, 12 reported clinicians as their intended user and seven reported seniors as their intended user. Further research should examine the validity of mobile health applications as well as report on the application's usability. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Highly Accurate Analytical Approximate Solution to a Nonlinear Pseudo-Oscillator

    NASA Astrophysics Data System (ADS)

    Wu, Baisheng; Liu, Weijia; Lim, C. W.

    2017-07-01

    A second-order Newton method is presented to construct analytical approximate solutions to a nonlinear pseudo-oscillator in which the restoring force is inversely proportional to the dependent variable. The nonlinear equation is first expressed in a specific form, and it is then solved in two steps, a predictor and a corrector step. In each step, the harmonic balance method is used in an appropriate manner to obtain a set of linear algebraic equations. With only one simple second-order Newton iteration step, a short, explicit, and highly accurate analytical approximate solution can be derived. The approximate solutions are valid for all amplitudes of the pseudo-oscillator. Furthermore, the method incorporates second-order Taylor expansion in a natural way, and it is of significant faster convergence rate.

  15. Ionization Electron Signal Processing in Single Phase LArTPCs II. Data/Simulation Comparison and Performance in MicroBooNE

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

    Adams, C.; et al.

    The single-phase liquid argon time projection chamber (LArTPC) provides a large amount of detailed information in the form of fine-grained drifted ionization charge from particle traces. To fully utilize this information, the deposited charge must be accurately extracted from the raw digitized waveforms via a robust signal processing chain. Enabled by the ultra-low noise levels associated with cryogenic electronics in the MicroBooNE detector, the precise extraction of ionization charge from the induction wire planes in a single-phase LArTPC is qualitatively demonstrated on MicroBooNE data with event display images, and quantitatively demonstrated via waveform-level and track-level metrics. Improved performance of inductionmore » plane calorimetry is demonstrated through the agreement of extracted ionization charge measurements across different wire planes for various event topologies. In addition to the comprehensive waveform-level comparison of data and simulation, a calibration of the cryogenic electronics response is presented and solutions to various MicroBooNE-specific TPC issues are discussed. This work presents an important improvement in LArTPC signal processing, the foundation of reconstruction and therefore physics analyses in MicroBooNE.« less

  16. Reconceptualizing Balance: Attributes associated with balance performance

    PubMed Central

    Thomas, Julia C.; Odonkor, Charles; Griffith, Laura; Holt, Nicole; Percac-Lima, Sanja; Leveille, Suzanne; Ni, Pensheng; Latham, Nancy K.; Jette, Alan M.; Bean, Jonathan F.

    2014-01-01

    Balance tests are commonly used to screen for impairments that put older adults at risk for falls. The purpose of this study was to determine the attributes that were associated with balance performance as measured by the The Frailty and Injuries: Cooperative Studies of Intervention Techniques (FICSIT) balance test. This study was a cross-sectional secondary analysis of baseline data from a longitudinal cohort study, the Boston Rehabilitative Impairment Study of the Elderly (Boston RISE). Boston RISE was performed in an outpatient rehabilitation research center and evaluated Boston area primary care patients aged 65 to 96 (N=364) with self-reported difficulty or task-modification climbing a flight of stairs or walking ½ of a mile. The outcome measure was standing balance as measured by the FICSIT-4 balance assessment. Other measures included: self-efficacy, pain, depression, executive function, vision, sensory loss, reaction time, kyphosis, leg range of motion, trunk extensor muscle endurance, leg strength and leg velocity at peak power. Participants were 67% female, had an average age of 76.5 (± 7.0) years, an average of 4.1 (± 2.0) chronic conditions, and an average FICSIT-4 score of 6.7 (± 2.2) out of 9. After adjusting for age and gender, attributes significantly associated with balance performance were falls self-efficacy, trunk extensor muscle endurance, sensory loss, and leg velocity at peak power. FICSIT-4 balance performance is associated with a number of behavioral and physiologic attributes, many of which are amenable to rehabilitative treatment. Our findings support a consideration of balance as multidimensional activity as proposed by the current International Classification of Functioning, Disability, and Health (ICF) model. PMID:24952097

  17. Choosing between atmospheric pressure chemical ionization and electrospray ionization interfaces for the HPLC/MS analysis of pesticides

    USGS Publications Warehouse

    Thurman, E.M.; Ferrer, I.; Barcelo, D.

    2001-01-01

    An evaluation of over 75 pesticides by high-performance liquid chromatography/mass spectrometry (HPLC/MS) clearly shows that different classes of pesticides are more sensitive using either atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI). For example, neutral and basic pesticides (phenylureas, triazines) are more sensitive using APCI (especially positive ion). While cationic and anionic herbicides (bipyridylium ions, sulfonic acids) are more sensitive using ESI (especially negative ion). These data are expressed graphically in a figure called an ionization-continuum diagram, which shows that protonation in the gas phase (proton affinity) and polarity in solution, expressed as proton addition or subtraction (pKa), is useful in selecting APCI or ESI. Furthermore, sodium adduct formation commonly occurs using positive ion ESI but not using positive ion APCI, which reflects the different mechanisms of ionization and strengthens the usefulness of the ionization-continuum diagram. The data also show that the concept of "wrong-way around" ESI (the sensitivity of acidic pesticides in an acidic mobile phase) is a useful modification of simple pKa theory for mobile-phase selection. Finally, this finding is used to enhance the chromatographic separation of oxanilic and sulfonic acid herbicides while maintaining good sensitivity in LC/MS using ESI negative.

  18. Electron impact ionization of the gas-phase sorbitol

    NASA Astrophysics Data System (ADS)

    Chernyshova, Irina; Markush, Pavlo; Zavilopulo, Anatoly; Shpenik, Otto

    2015-03-01

    Ionization and dissociative ionization of the sorbitol molecule by electron impact have been studied using two different experimental methods. In the mass range of m/ z = 10-190, the mass spectra of sorbitol were recorded at the ionizing electron energies of 70 and 30 eV. The ion yield curves for the fragment ions have been analyzed and the appearance energies of these ions have been determined. The relative total ionization cross section of the sorbitol molecule was measured using monoenergetic electron beam. Possible fragmentation pathways for the sorbitol molecule were proposed.

  19. Invited article: Time accurate mass flow measurements of solid-fueled systems.

    PubMed

    Olliges, Jordan D; Lilly, Taylor C; Joslyn, Thomas B; Ketsdever, Andrew D

    2008-10-01

    A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.

  20. Invited Article: Time accurate mass flow measurements of solid-fueled systems

    NASA Astrophysics Data System (ADS)

    Olliges, Jordan D.; Lilly, Taylor C.; Joslyn, Thomas B.; Ketsdever, Andrew D.

    2008-10-01

    A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.

  1. Resonance ionization for analytical spectroscopy

    DOEpatents

    Hurst, George S.; Payne, Marvin G.; Wagner, Edward B.

    1976-01-01

    This invention relates to a method for the sensitive and selective analysis of an atomic or molecular component of a gas. According to this method, the desired neutral component is ionized by one or more resonance photon absorptions, and the resultant ions are measured in a sensitive counter. Numerous energy pathways are described for accomplishing the ionization including the use of one or two tunable pulsed dye lasers.

  2. Ionization oscillations in Hall accelerators

    NASA Astrophysics Data System (ADS)

    Barral, S.; Peradzyński, Z.

    2010-01-01

    The underlying mechanism of low-frequency oscillations in Hall accelerators is investigated theoretically. It is shown that relaxation oscillations arise from a competition between avalanche ionization and the advective transport of the working gas. The model derived recovers the slow progression and fast recession of the ionization front. Analytical approximations of the shape of current pulses and of the oscillation frequency are provided for the case of large amplitude oscillations.

  3. CIFOG: Cosmological Ionization Fields frOm Galaxies

    NASA Astrophysics Data System (ADS)

    Hutter, Anne

    2018-03-01

    CIFOG is a versatile MPI-parallelised semi-numerical tool to perform simulations of the Epoch of Reionization. From a set of evolving cosmological gas density and ionizing emissivity fields, it computes the time and spatially dependent ionization of neutral hydrogen (HI), neutral (HeI) and singly ionized helium (HeII) in the intergalactic medium (IGM). The code accounts for HII, HeII, HeIII recombinations, and provides different descriptions for the photoionization rate that are used to calculate the residual HI fraction in ionized regions. This tool has been designed to be coupled to semi-analytic galaxy formation models or hydrodynamical simulations. The modular fashion of the code allows the user to easily introduce new descriptions for recombinations and the photoionization rate.

  4. Quantum entanglement in strong-field ionization

    NASA Astrophysics Data System (ADS)

    Majorosi, Szilárd; Benedict, Mihály G.; Czirják, Attila

    2017-10-01

    We investigate the time evolution of quantum entanglement between an electron, liberated by a strong few-cycle laser pulse, and its parent ion core. Since the standard procedure is numerically prohibitive in this case, we propose a method to quantify the quantum correlation in such a system: we use the reduced density matrices of the directional subspaces along the polarization of the laser pulse and along the transverse directions as building blocks for an approximate entanglement entropy. We present our results, based on accurate numerical simulations, in terms of several of these entropies, for selected values of the peak electric-field strength and the carrier-envelope phase difference of the laser pulse. The time evolution of the mutual entropy of the electron and the ion-core motion along the direction of the laser polarization is similar to our earlier results based on a simple one-dimensional model. However, taking into account also the dynamics perpendicular to the laser polarization reveals a surprisingly different entanglement dynamics above the laser intensity range corresponding to pure tunneling: the quantum entanglement decreases with time in the over-the-barrier ionization regime.

  5. Use of matrix-assisted laser desorption ionization-time of flight mass spectrometry for caspofungin susceptibility testing of Candida and Aspergillus species.

    PubMed

    De Carolis, Elena; Vella, Antonietta; Florio, Ada R; Posteraro, Patrizia; Perlin, David S; Sanguinetti, Maurizio; Posteraro, Brunella

    2012-07-01

    Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was evaluated for testing susceptibility to caspofungin of wild-type and fks mutant isolates of Candida and Aspergillus. Complete essential agreement was observed with the CLSI reference method, with categorical agreement for 94.1% of the Candida isolates tested. Thus, MALDI-TOF MS is a reliable and accurate method to detect fungal isolates with reduced caspofungin susceptibility.

  6. Short-term Power Load Forecasting Based on Balanced KNN

    NASA Astrophysics Data System (ADS)

    Lv, Xianlong; Cheng, Xingong; YanShuang; Tang, Yan-mei

    2018-03-01

    To improve the accuracy of load forecasting, a short-term load forecasting model based on balanced KNN algorithm is proposed; According to the load characteristics, the historical data of massive power load are divided into scenes by the K-means algorithm; In view of unbalanced load scenes, the balanced KNN algorithm is proposed to classify the scene accurately; The local weighted linear regression algorithm is used to fitting and predict the load; Adopting the Apache Hadoop programming framework of cloud computing, the proposed algorithm model is parallelized and improved to enhance its ability of dealing with massive and high-dimension data. The analysis of the household electricity consumption data for a residential district is done by 23-nodes cloud computing cluster, and experimental results show that the load forecasting accuracy and execution time by the proposed model are the better than those of traditional forecasting algorithm.

  7. Identification of Aeromonas isolates by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

    PubMed

    Lamy, Brigitte; Kodjo, Angeli; Laurent, Frédéric

    2011-09-01

    We evaluated the accuracy of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for identifying aeromonads with an extraction procedure. Genus-level accuracy was 100%. Compared to rpoB gene sequencing, species-level accuracy was 90.6% (29/32) for type and reference strains and 91.4% for a collection of 139 clinical and environmental isolates, making this system one of the most accurate and rapid methods for phenotypic identification. The reliability of this technique was very promising, although some improvements in database composition, taxonomy, and discriminatory power are needed. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Theoretical study on the dissociation energies, ionization potentials and electron affinities of three perfluoroalkyl iodides

    NASA Astrophysics Data System (ADS)

    Cheng, Li; Shen, Zuochun; Lu, Jianye; Gao, Huide; Lü, Zhiwei

    2005-11-01

    Dissociation energies, ionization potentials and electron affinities of three perfluoroalkyl iodides, CF 3I, C 2F 5I, and i-C 3F 7I are calculated accurately with B3LYP, MP n ( n = 2-4), QCISD, QCISD(T), CCSD, and CCSD(T) methods. Calculations are performed by using large-core correlation-consistent pseudopotential basis set (SDB-aug-cc-pVTZ) for iodine atom. In all energy calculations, the zero point vibration energy is corrected. And the basis set superposition error is corrected by counterpoise method in the calculation of dissociation energy. Theoretical results are compared with the experimental values.

  9. Extreme ionization of Xe clusters driven by ultraintense laser fields

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

    Heidenreich, Andreas; Last, Isidore; Jortner, Joshua

    We applied theoretical models and molecular dynamics simulations to explore extreme multielectron ionization in Xe{sub n} clusters (n=2-2171, initial cluster radius R{sub 0}=2.16-31.0 A ring ) driven by ultraintense infrared Gaussian laser fields (peak intensity I{sub M}=10{sup 15}-10{sup 20} W cm{sup -2}, temporal pulse length {tau}=10-100 fs, and frequency {nu}=0.35 fs{sup -1}). Cluster compound ionization was described by three processes of inner ionization, nanoplasma formation, and outer ionization. Inner ionization gives rise to high ionization levels (with the formation of (Xe{sup q+}){sub n} with q=2-36), which are amenable to experimental observation. The cluster size and laser intensity dependence of themore » inner ionization levels are induced by a superposition of barrier suppression ionization (BSI) and electron impact ionization (EII). The BSI was induced by a composite field involving the laser field and an inner field of the ions and electrons, which manifests ignition enhancement and screening retardation effects. EII was treated using experimental cross sections, with a proper account of sequential impact ionization. At the highest intensities (I{sub M}=10{sup 18}-10{sup 20} W cm{sup -2}) inner ionization is dominated by BSI. At lower intensities (I{sub M}=10{sup 15}-10{sup 16} W cm{sup -2}), where the nanoplasma is persistent, the EII contribution to the inner ionization yield is substantial. It increases with increasing the cluster size, exerts a marked effect on the increase of the (Xe{sup q+}){sub n} ionization level, is most pronounced in the cluster center, and manifests a marked increase with increasing the pulse length (i.e., becoming the dominant ionization channel (56%) for Xe{sub 2171} at {tau}=100 fs). The EII yield and the ionization level enhancement decrease with increasing the laser intensity. The pulse length dependence of the EII yield at I{sub M}=10{sup 15}-10{sup 16} W cm{sup -2} establishes an ultraintense laser pulse

  10. A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique

    PubMed Central

    Lloyd, John R.; Hess, Sonja

    2009-01-01

    We report here the development of a corona discharge (CD) initiated electrochemical (EC) electrospray ionization (ESI) technique using a standard electrospray ion source. This is a new ionization technique distinct from ESI, electrochemistry inherent to ESI, APCI, and techniques using hydroxyl radicals produced under atmospheric pressure conditions. By maximizing the observable CD at the tip of a stainless steel ESI capillary, efficient electrochemical oxidation of electrochemically active compounds is observed. For electrochemical oxidation to be observed, the ionization potential of the analyte must be lower than Fe. Ferrocene labeled compounds were chosen as the electrochemically active moiety. The electrochemical cell in the ESI source was robust and generated ions with selectivity according to the ionization potential of the analytes and up to zeptomolar sensitivity. Our results indicate that CD initiated electrochemical ionization has the potential to become a powerful technique to increase the dynamic range, sensitivity and selectivity of ESI experiments. Synopsis Using a standard ESI source a corona discharge initiated electrochemical ionization technique was established resulting from the electrochemistry occurring at the CD electrode surface. PMID:19747843

  11. Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons.

    PubMed

    Jin, Chunfen; Viidanoja, Jyrki; Li, Mingzhe; Zhang, Yuyang; Ikonen, Elias; Root, Andrew; Romanczyk, Mark; Manheim, Jeremy; Dziekonski, Eric; Kenttämaa, Hilkka I

    2016-11-01

    Direct infusion atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was compared to field ionization mass spectrometry (FI-MS) for the determination of hydrocarbon class distributions in lubricant base oils. When positive ion mode APCI with oxygen as the ion source gas was employed to ionize saturated hydrocarbon model compounds (M) in hexane, only stable [M - H] + ions were produced. Ion-molecule reaction studies performed in a linear quadrupole ion trap suggested that fragment ions of ionized hexane can ionize saturated hydrocarbons via hydride abstraction with minimal fragmentation. Hence, APCI-MS shows potential as an alternative of FI-MS in lubricant base oil analysis. Indeed, the APCI-MS method gave similar average molecular weights and hydrocarbon class distributions as FI-MS for three lubricant base oils. However, the reproducibility of APCI-MS method was found to be substantially better than for FI-MS. The paraffinic content determined using the APCI-MS and FI-MS methods for the base oils was similar. The average number of carbons in paraffinic chains followed the same increasing trend from low viscosity to high viscosity base oils for the two methods.

  12. Re-ionization and decaying dark matter

    NASA Technical Reports Server (NTRS)

    Dodelson, Scott; Jubas, Jay M.

    1991-01-01

    Gunn-Peterson tests suggest that the Universe was reionized after the standard recombination epoch. A systematic treatment is presented of the ionization process by deriving the Boltzmann equations appropriate to this regime. A compact solution for the photon spectrum is found in terms of the ionization ratio. These equations are then solved numerically for the Decaying Dark Matter scenario, wherein neutrinos with mass of order 30 eV radiatively decay producing photons which ionize the intergalactic medium. It was found that the neutrino mass and lifetime are severely constrained by Gunn-Peterson tests, observations of the diffuse photon spectrum in the ultraviolet regime, and the Hubble parameter.

  13. Critical assessment of ionization patterns and applications of ambient desorption/ionization mass spectrometry using FAPA-MS.

    PubMed

    Brüggemann, Martin; Karu, Einar; Hoffmann, Thorsten

    2016-02-01

    Ambient desorption/ionization mass spectrometry (MS) has gained growing interest during the last decade due to its high analytical performance and yet simplicity. Here, one of the recently developed ambient desorption/ionization MS sources, the flowing atmospheric-pressure afterglow (FAPA) source, was investigated in detail regarding background ions and typical ionization patterns in the positive as well as the negative ion mode for a variety of compound classes, comprising alkanes, alcohols, aldehydes, ketones, carboxylic acids, organic peroxides and alkaloids. A broad range of signals for adducts and losses was found, besides the usually emphasized detection of quasimolecular ions, i.e. [M + H](+) and [M - H](-) in the positive and the negative mode, respectively. It was found that FAPA-MS is best suited for polar analytes containing nitrogen and/or oxygen functionalities, e.g. carboxylic acids, with low molecular weights and relatively high vapor pressures. In addition, the source was used in proof-of-principle studies, illustrating the capabilities and limitations of the technique: Firstly, traces of cocaine were detected and unambiguously identified on euro banknotes using FAPA ionization in combination with tandem MS, suggesting a correlation between cocaine abundance and age of the banknote. Secondly, FAPA-MS was used for the identification of acidic marker compounds in organic aerosol samples, indicating yet-undiscovered matrix and sample surface effects of ionization pathways in the afterglow region. Copyright © 2016 John Wiley & Sons, Ltd.

  14. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields.

    PubMed

    Zhu, Wuming; Trickey, S B

    2017-12-28

    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li + , Be + , and B + , in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B

  15. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Zhu, Wuming; Trickey, S. B.

    2017-12-01

    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li+, Be+, and B+, in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B field.

  16. Ionization-chamber smoke detector system

    DOEpatents

    Roe, Robert F.

    1976-10-19

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system is designed to reduce false alarms caused by fluctuations in ambient temperature. Means are provided for periodically firing the gas discharge triode and each time recording the triggering voltage required. A computer compares each triggering voltage with its predecessor. The computer is programmed to energize an alarm if the difference between the two compared voltages is a relatively large value indicative of particulates in the measuring chamber and to disregard smaller differences typically resulting from changes in ambient temperature.

  17. The SPES surface ionization source

    NASA Astrophysics Data System (ADS)

    Manzolaro, M.; D'Agostini, F.; Monetti, A.; Andrighetto, A.

    2017-09-01

    Ion sources and target systems play a crucial role in isotope separation on line facilities, determining the main characteristics of the radioactive ion beams available for experiments. In the context of the selective production of exotic species (SPES) facility, a 40 MeV, 200 μA proton beam directly impinges a uranium carbide target, generating approximately 1013 fissions per second. The radioactive isotopes produced by the 238U fissions are delivered to the 1+ ion source by means of a tubular transfer line. Here they can be ionized and subsequently accelerated toward the experimental areas. In this work, the characterization of the surface ionization source currently adopted for the SPES facility is presented, taking as a reference ionization efficiency and transversal emittance measurements. The effects of long term operation at high temperature are also illustrated and discussed.

  18. Development of anatomically and dielectrically accurate breast phantoms for microwave imaging applications

    NASA Astrophysics Data System (ADS)

    O'Halloran, M.; Lohfeld, S.; Ruvio, G.; Browne, J.; Krewer, F.; Ribeiro, C. O.; Inacio Pita, V. C.; Conceicao, R. C.; Jones, E.; Glavin, M.

    2014-05-01

    Breast cancer is one of the most common cancers in women. In the United States alone, it accounts for 31% of new cancer cases, and is second only to lung cancer as the leading cause of deaths in American women. More than 184,000 new cases of breast cancer are diagnosed each year resulting in approximately 41,000 deaths. Early detection and intervention is one of the most significant factors in improving the survival rates and quality of life experienced by breast cancer sufferers, since this is the time when treatment is most effective. One of the most promising breast imaging modalities is microwave imaging. The physical basis of active microwave imaging is the dielectric contrast between normal and malignant breast tissue that exists at microwave frequencies. The dielectric contrast is mainly due to the increased water content present in the cancerous tissue. Microwave imaging is non-ionizing, does not require breast compression, is less invasive than X-ray mammography, and is potentially low cost. While several prototype microwave breast imaging systems are currently in various stages of development, the design and fabrication of anatomically and dielectrically representative breast phantoms to evaluate these systems is often problematic. While some existing phantoms are composed of dielectrically representative materials, they rarely accurately represent the shape and size of a typical breast. Conversely, several phantoms have been developed to accurately model the shape of the human breast, but have inappropriate dielectric properties. This study will brie y review existing phantoms before describing the development of a more accurate and practical breast phantom for the evaluation of microwave breast imaging systems.

  19. Polarizabilities of highly ionized atoms

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Wolf, M. L.

    1979-01-01

    An extrapolation method based on a screening approximation, applied to available initial values of polarizability for low stages of ionization, is used to obtain dipole and quadrupole polarizabilities for more highly ionized members of many isoelectronic sequences. It is suggested that the derived screening constants x sub L and limiting ratios F sub L may have significant physical meaning, especially the latter which may have an interpretation in terms of hydrogenic polarizabilities.

  20. Optical Imaging of Ionizing Radiation from Clinical Sources

    PubMed Central

    Shaffer, Travis M.; Drain, Charles Michael

    2016-01-01

    Nuclear medicine uses ionizing radiation for both in vivo diagnosis and therapy. Ionizing radiation comes from a variety of sources, including x-rays, beam therapy, brachytherapy, and various injected radionuclides. Although PET and SPECT remain clinical mainstays, optical readouts of ionizing radiation offer numerous benefits and complement these standard techniques. Furthermore, for ionizing radiation sources that cannot be imaged using these standard techniques, optical imaging offers a unique imaging alternative. This article reviews optical imaging of both radionuclide- and beam-based ionizing radiation from high-energy photons and charged particles through mechanisms including radioluminescence, Cerenkov luminescence, and scintillation. Therapeutically, these visible photons have been combined with photodynamic therapeutic agents preclinically for increasing therapeutic response at depths difficult to reach with external light sources. Last, new microscopy methods that allow single-cell optical imaging of radionuclides are reviewed. PMID:27688469

  1. Neutron-Impact Ionization of H and He

    NASA Astrophysics Data System (ADS)

    Lee, T.-G.; Ciappina, M. F.; Robicheaux, F.; Pindzola, M. S.

    2014-05-01

    Perturbative distorted-wave and non-perturbative close-coupling methods are used to study neutron-impact ionization of H and He. For single ionization of H, we find excellent agreement between the distorted-wave and close-coupling results at all incident energies. For double ionization of He, we find poor agreement between the distorted-wave and close-coupling results, except at the highest incident energies. We present the ratio of double to single ionization for He as a guide to experimental checks of theory at low energies and experimental confirmation of the rapid rise of the ratio at high energies. This work was supported in part by grants from NSF and US DoE. Computational work was carried out at NERSC in Oakland, California, NICS in Knoxville, Tennessee, and OLCF in Oak Ridge, Tennessee.

  2. Probing electron delays in above-threshold ionization

    DOE PAGES

    Zipp, Lucas J.; Natan, Adi; Bucksbaum, Philip H.

    2014-11-21

    Recent experiments have revealed attosecond delays in the emission of electrons from atoms ionized by extreme UV light, offering a glimpse into the ultrafast nature of light-induced electron dynamics. In this work, we extend these measurements to the strong-field above-threshold ionization (ATI) regime, by measuring delays in the photoemission of electrons from argon in the presence of an intense laser field. We probe the ATI process with a weak coherent reference, at half the laser frequency. The interfering ionization signal reveals the relative spectral phase of adjacent ATI channels, with an equivalent resolution of a few attoseconds. These relative delaysmore » depend on the strong field, and approach zero at higher intensity. Our phase measurements of ATI electrons show how strong fields alter ionization dynamics in atoms.« less

  3. Simplified energy-balance model for pragmatic multi-dimensional device simulation

    NASA Astrophysics Data System (ADS)

    Chang, Duckhyun; Fossum, Jerry G.

    1997-11-01

    To pragmatically account for non-local carrier heating and hot-carrier effects such as velocity overshoot and impact ionization in multi-dimensional numerical device simulation, a new simplified energy-balance (SEB) model is developed and implemented in FLOODS[16] as a pragmatic option. In the SEB model, the energy-relaxation length is estimated from a pre-process drift-diffusion simulation using the carrier-velocity distribution predicted throughout the device domain, and is used without change in a subsequent simpler hydrodynamic (SHD) simulation. The new SEB model was verified by comparison of two-dimensional SHD and full HD DC simulations of a submicron MOSFET. The SHD simulations yield detailed distributions of carrier temperature, carrier velocity, and impact-ionization rate, which agree well with the full HD simulation results obtained with FLOODS. The most noteworthy feature of the new SEB/SHD model is its computational efficiency, which results from reduced Newton iteration counts caused by the enhanced linearity. Relative to full HD, SHD simulation times can be shorter by as much as an order of magnitude since larger voltage steps for DC sweeps and larger time steps for transient simulations can be used. The improved computational efficiency can enable pragmatic three-dimensional SHD device simulation as well, for which the SEB implementation would be straightforward as it is in FLOODS or any robust HD simulator.

  4. An Engineering Model of Human Balance Control-Part I: Biomechanical Model.

    PubMed

    Barton, Joseph E; Roy, Anindo; Sorkin, John D; Rogers, Mark W; Macko, Richard

    2016-01-01

    We developed a balance measurement tool (the balanced reach test (BRT)) to assess standing balance while reaching and pointing to a target moving in three-dimensional space according to a sum-of-sines function. We also developed a three-dimensional, 13-segment biomechanical model to analyze performance in this task. Using kinematic and ground reaction force (GRF) data from the BRT, we performed an inverse dynamics analysis to compute the forces and torques applied at each of the joints during the course of a 90 s test. We also performed spectral analyses of each joint's force activations. We found that the joints act in a different but highly coordinated manner to accomplish the tracking task-with individual joints responding congruently to different portions of the target disk's frequency spectrum. The test and the model also identified clear differences between a young healthy subject (YHS), an older high fall risk (HFR) subject before participating in a balance training intervention; and in the older subject's performance after training (which improved to the point that his performance approached that of the young subject). This is the first phase of an effort to model the balance control system with sufficient physiological detail and complexity to accurately simulate the multisegmental control of balance during functional reach across the spectra of aging, medical, and neurological conditions that affect performance. Such a model would provide insight into the function and interaction of the biomechanical and neurophysiological elements making up this system; and system adaptations to changes in these elements' performance and capabilities.

  5. An Engineering Model of Human Balance Control—Part I: Biomechanical Model

    PubMed Central

    Barton, Joseph E.; Roy, Anindo; Sorkin, John D.; Rogers, Mark W.; Macko, Richard

    2016-01-01

    We developed a balance measurement tool (the balanced reach test (BRT)) to assess standing balance while reaching and pointing to a target moving in three-dimensional space according to a sum-of-sines function. We also developed a three-dimensional, 13-segment biomechanical model to analyze performance in this task. Using kinematic and ground reaction force (GRF) data from the BRT, we performed an inverse dynamics analysis to compute the forces and torques applied at each of the joints during the course of a 90 s test. We also performed spectral analyses of each joint's force activations. We found that the joints act in a different but highly coordinated manner to accomplish the tracking task—with individual joints responding congruently to different portions of the target disk's frequency spectrum. The test and the model also identified clear differences between a young healthy subject (YHS), an older high fall risk (HFR) subject before participating in a balance training intervention; and in the older subject's performance after training (which improved to the point that his performance approached that of the young subject). This is the first phase of an effort to model the balance control system with sufficient physiological detail and complexity to accurately simulate the multisegmental control of balance during functional reach across the spectra of aging, medical, and neurological conditions that affect performance. Such a model would provide insight into the function and interaction of the biomechanical and neurophysiological elements making up this system; and system adaptations to changes in these elements' performance and capabilities. PMID:26328608

  6. Intense laser pulse propagation in ionizing gases

    NASA Astrophysics Data System (ADS)

    Bian, Zhigang

    2003-10-01

    There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The

  7. One-leg balance is an important predictor of injurious falls in older persons.

    PubMed

    Vellas, B J; Wayne, S J; Romero, L; Baumgartner, R N; Rubenstein, L Z; Garry, P J

    1997-06-01

    To test the hypothesis that one-leg balance is a significant predictor of falls and injurious falls. Analysis of data from a longitudinal cohort study. Healthy, community-living volunteers older than age 60 enrolled in the Albuquerque Falls Study and followed for 3 years (N = 316; mean age 73 years). Falls and injurious falls detected via reports every other month. Baseline measures of demographics, history, physical examination, Iowa Self Assessment Inventory, balance and gait assessment, and one-leg balance (ability to stand unassisted for 5 seconds on one leg). At baseline, 84.5% of subjects could perform one-leg balance. (Impairment was associated with older age and gait abnormalities.) Over the 3-year follow-up, 71% experienced a fall and 22% an injurious fall. The only independent significant predictor of all falls using logistic regression was age greater than 73. However, impaired one-leg balance was the only significant independent predictor of injurious falls (relative risk: 2.13; 95% CI: 1.04, 4.34; P = .03). One-leg balance appears to be a significant and easy-to-administer predictor of injurious falls, but not of all falls. In our study, it was the strongest individual predictor. However, no single factor seems to be accurate enough to be relied on as a sole predictor of fall risk or fall injury risk because so many diverse factors are involved in falling.

  8. Isomer and Fluorination Effects among Fluorine Substituted Hydrocarbon C3/C4 Molecules in Electron Impact Ionization

    NASA Astrophysics Data System (ADS)

    Patel, U. R.; Joshipura, K. N.

    2015-05-01

    Electron collision processes are very important in both man-made and natural plasmas, for determining the energy balances and transport properties of electrons. Electron -molecule scattering leading to ionization represents one of the most fundamental processes in collision physics. In the gas phase, the total efficiency of the process is described by the absolute total electron impact ionization cross section. Carbon based materials are some of the widely used materials for a divertor plate and magnetically confined fusion devices. In the ``ITER,'' it is very important for steady state operation to have an estimate of the lifetime of carbon plasma facing components. Apart from fusion plasma relevance, the present theoretical study is very important in modeling and controlling other electron assisted processes in many areas. Hydrocarbons play an important role for plasma diagnostics as impurities in the Tokamak fusion divertor, as seed gases for the production of radicals and ions in low temperature plasma processing. Fluorine substituted hydrocarbons (perfluorocarbons) are important as reactants in plasma assisted fabrication processes. In the present work, we have calculated total ionization cross sections Qion for C3/C4 Hydrocarbon isomers by electron impact, and comparisons are made mutually to observe isomer effect. Comparisons are also made by substituting H atom by F atom and revealing fluorination effect. The present calculations are quite significant owing to the lack of experimental data, with just an isolated previous theoretical work in some cases.

  9. The role of Upper Hybrid Turbulence on HF Artificial Ionization

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Konstantinos Dennis; Najmi, Amir; Eliasson, Bengt; Milikh, Gennady

    2016-07-01

    One of the most fascinating and scientifically interesting phenomena of active space experiments is the discovery of artificial ionization by Todd Pedersen when the HAARP ERP reached the GW level. The phenomenon has been well documented experimentally. A theoretical model based on ionization by energetic electrons accelerated by 50-100 V/m localized electric fields due to Strong Langmuir Turbulence (SLT) near the reflection surface of the HF pump wave, reproduced the observed dynamics of the descending plasma layer quite accurately. A major defect of the model was that the electron temperature in the SLT region was a free parameter. When taken as the 2000 K representing the ambient electron temperature the SLT driven electron flux was insufficient to produce ionization. An equivalent electron temperature of 5000 K or higher was necessary to reproduce the observations. The needed electron heating was attributed to the interaction of the HF at the Upper Hybrid (UH) resonant layer, approximately 5 Km below the reflection region where the HF electric field is perpendicular to the ambient magnetic field. The heated electrons expanded upwards along the magnetic field line and interacted with SLT fields near the resonance region. A consequence of this defect was that the theory could not explain the puzzling double resonance effect. Namely the observation that the ionization level was much stronger when the HF frequency and the UH resonance were a multiple of the electron cyclotron frequency. To remedy this we used a series of Vlasov simulations to explore the HF-plasma interaction in the vicinity of the UH resonance. The simulations followed the evolution of the spectral density of the electric field over a 7.5 MHz frequency band and cm scale lengths and of the electron distribution function over one millisecond for both double resonant and non-resonant cases. Many new features were revealed by the analysis of the simulations such as: 1. Broadening of the wave

  10. Electrospray Post-Ionization Mass Spectrometry of Electrosurgical Aerosols

    NASA Astrophysics Data System (ADS)

    Guenther, Sabine; Schäfer, Karl-Christian; Balog, Júlia; Dénes, Júlia; Majoros, Tamás; Albrecht, Katalin; Tóth, Miklós; Spengler, Bernhard; Takáts, Zoltán

    2011-11-01

    The feasibility of electrospray (ES) ionization of aerosols generated by electrosurgical disintegration methods was investigated. Although electrosurgery itself was demonstrated to produce gaseous ions, post-ionization methods were implemented to enhance the ion yield, especially in those cases when the ion current produced by the applied electrosurgical method is not sufficient for MS analysis. Post-ionization was implemented by mounting an ES emitter onto a Venturi pump, which is used for ion transfer. The effect of various parameters including geometry, high voltage setting, flow parameters, and solvent composition was investigated in detail. Experimental setups were optimized accordingly. ES post-ionization was found to yield spectra similar to those obtained by the REIMS technique, featuring predominantly lipid-type species. Signal enhancement was 20- to 50-fold compared with electrosurgical disintegration in positive mode, while no improvement was observed in negative mode. ES post-ionization was also demonstrated to allow the detection of non-lipid type species in the electrosurgical aerosol, including drug molecules. Since the tissue specificity of the MS data was preserved in the ES post-ionization setup, feasibility of tissue identification was demonstrated using different electrosurgical methods.

  11. Optical Imaging of Ionizing Radiation from Clinical Sources.

    PubMed

    Shaffer, Travis M; Drain, Charles Michael; Grimm, Jan

    2016-11-01

    Nuclear medicine uses ionizing radiation for both in vivo diagnosis and therapy. Ionizing radiation comes from a variety of sources, including x-rays, beam therapy, brachytherapy, and various injected radionuclides. Although PET and SPECT remain clinical mainstays, optical readouts of ionizing radiation offer numerous benefits and complement these standard techniques. Furthermore, for ionizing radiation sources that cannot be imaged using these standard techniques, optical imaging offers a unique imaging alternative. This article reviews optical imaging of both radionuclide- and beam-based ionizing radiation from high-energy photons and charged particles through mechanisms including radioluminescence, Cerenkov luminescence, and scintillation. Therapeutically, these visible photons have been combined with photodynamic therapeutic agents preclinically for increasing therapeutic response at depths difficult to reach with external light sources. Last, new microscopy methods that allow single-cell optical imaging of radionuclides are reviewed. © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

  12. Impact Ionization: Beyond the Golden Rule

    DTIC Science & Technology

    1992-01-01

    3]. Hence, the use electronic kinetic energy, H. is the phonon bath Hamil- of Monte Carlo methods combined with density matrix tonian, HA, is the...0 o5 () Wace i.a (bN w...,,,ae (W ( Ib) k- Figure 2. (a) Ionization rate in the 1 11 > direction. Figure 3. (a) Equal ionization rate curves in the k

  13. Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability

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

    Isselhardt, Brett H.

    2011-09-01

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of 235U/ 238U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser inmore » a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios.« less

  14. Development and evaluation of low cost game-based balance rehabilitation tool using the Microsoft Kinect sensor.

    PubMed

    Lange, Belinda; Chang, Chien-Yen; Suma, Evan; Newman, Bradley; Rizzo, Albert Skip; Bolas, Mark

    2011-01-01

    The use of the commercial video games as rehabilitation tools, such as the Nintendo WiiFit, has recently gained much interest in the physical therapy arena. Motion tracking controllers such as the Nintendo Wiimote are not sensitive enough to accurately measure performance in all components of balance. Additionally, users can figure out how to "cheat" inaccurate trackers by performing minimal movement (e.g. wrist twisting a Wiimote instead of a full arm swing). Physical rehabilitation requires accurate and appropriate tracking and feedback of performance. To this end, we are developing applications that leverage recent advances in commercial video game technology to provide full-body control of animated virtual characters. A key component of our approach is the use of newly available low cost depth sensing camera technology that provides markerless full-body tracking on a conventional PC. The aim of this research was to develop and assess an interactive game-based rehabilitation tool for balance training of adults with neurological injury.

  15. Delayed Ionization in Transition Metal Carbon Clusters

    NASA Astrophysics Data System (ADS)

    Kooi, S. E.; Castleman, A. W., Jr.

    1997-03-01

    Mass spectrometric studies of several single and binary transition metal carbon cluster systems, produced in a laser vaporization source, reveal several species that undergo delayed ionization. Pulsed extraction and blocking electric fields, in a time-of-flight mass spectrometer, allow the study of delayed ionization over a time window after excitation with a pulsed laser. In systems where metallocarbohedrenes (Met-Cars) are produced, the Met-Cars are the dominate delayed species. Delayed ionization of binary metal Met-Cars Ti_xM_yC_12 (M=Zr,Nb,Y; x+y=8) is dependent on the ratio of the two metals. Delayed behavior is investigated over a range of photoionization wavelengths and fluences. In order to determine the degree to which the delayed ionization is thermionic in character, the experimental data have been compared to Klots's model for thermionic emission from small particles.

  16. Radar detection of radiation-induced ionization in air

    DOEpatents

    Gopalsami, Nachappa; Heifetz, Alexander; Chien, Hual-Te; Liao, Shaolin; Koehl, Eugene R.; Raptis, Apostolos C.

    2015-07-21

    A millimeter wave measurement system has been developed for remote detection of airborne nuclear radiation, based on electromagnetic scattering from radiation-induced ionization in air. Specifically, methods of monitoring radiation-induced ionization of air have been investigated, and the ionized air has been identified as a source of millimeter wave radar reflection, which can be utilized to determine the size and strength of a radiation source.

  17. Is ionizing radiation regulated more stringently than chemical carcinogens

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

    Travis, C.C.; Pack, S.R.; Hattemer-Frey, H.A.

    1989-04-01

    It is widely believed that United States government agencies regulate exposure to ionizing radiation more stringently than exposure to chemical carcinogens. It is difficult to verify this perception, however, because chemical carcinogens and ionizing radiation are regulated using vastly different strategies. Chemical carcinogens are generally regulated individually. Regulators consider the risk of exposure to one chemical rather than the cumulative radiation exposure from all sources. Moreover, standards for chemical carcinogens are generally set in terms of quantities released or resultant environmental concentrations, while standards for ionizing radiation are set in terms of dose to the human body. Since chemicals andmore » ionizing radiation cannot be compared on the basis of equal dose to the exposed individual, standards regulating chemicals and ionizing radiation cannot be compared directly. It is feasible, however, to compare the two sets of standards on the basis of equal risk to the exposed individual, assuming that standards for chemicals and ionizing radiation are equivalent if estimated risk levels are equitable. This paper compares risk levels associated with current standards for ionizing radiation and chemical carcinogens. The authors do not attempt to determine whether either type of risk is regulated too stringently or not stringently enough but endeavor only to ascertain if ionizing radiation is actually regulated more strictly than chemical carcinogens.« less

  18. From The Cover: The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties.

    PubMed

    Xu, Xin; Goddard, William A

    2004-03-02

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee-Yang-Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energies [over the most popular and accurate method, B3LYP (Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional)]. X3LYP also leads to a good description of dipole moments, polarizabilities, and accurate excitation energies from s to d orbitals for transition metal atoms and ions. We suggest that X3LYP will be useful for predicting ligand binding in proteins and DNA.

  19. From The Cover: The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties

    NASA Astrophysics Data System (ADS)

    Xu, Xin; Goddard, William A., III

    2004-03-01

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee-Yang-Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energies [over the most popular and accurate method, B3LYP (Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional)]. X3LYP also leads to a good description of dipole moments, polarizabilities, and accurate excitation energies from s to d orbitals for transition metal atoms and ions. We suggest that X3LYP will be useful for predicting ligand binding in proteins and DNA.

  20. New Atomic Data for Doubly Ionized Iron Group Atoms by High Resolution UV Fourier Transform Spectroscopy

    NASA Technical Reports Server (NTRS)

    Smith, Peter L.; Pickering, Juliet C.; Thorne, A. P.

    2002-01-01

    Currently available laboratory spectroscopic data of doubly ionized iron-group element were obtained about 50 years ago using spectrographs of modest dispersion, photographic plates, and eye estimates of intensities. The accuracy of the older wavelength data is about 10 mAngstroms at best, whereas wavelengths are now needed to an accuracy of 1 part in 10(exp 6) to 10(exp 7) (0.2 to 2 mAngstroms at 2000 Angstroms). The Fourier transform (FT) spectroscopy group at Imperial College, London, and collaborators at the Harvard College Observatory have used a unique VUV FT spectrometer in a program focussed on improving knowledge of spectra of many neutral and singly and doubly ionized, astrophysically important, iron group elements. Spectra of Fe II and Fe III have been recorded at UV and VUV wavelengths with signal-to-noise ratios of several hundred for the stronger lines. Wavelengths and energy levels for Fe III are an order of magnitude more accurate than previous work; analysis is close to completion. f-values for Fe II have been published.

  1. Increasing the applicability of density functional theory. IV. Consequences of ionization-potential improved exchange-correlation potentials.

    PubMed

    Verma, Prakash; Bartlett, Rodney J

    2014-05-14

    This paper's objective is to create a "consistent" mean-field based Kohn-Sham (KS) density functional theory (DFT) meaning the functional should not only provide good total energy properties, but also the corresponding KS eigenvalues should be accurate approximations to the vertical ionization potentials (VIPs) of the molecule, as the latter condition attests to the viability of the exchange-correlation potential (VXC). None of the prominently used DFT approaches show these properties: the optimized effective potential VXC based ab initio dft does. A local, range-separated hybrid potential cam-QTP-00 is introduced as the basis for a "consistent" KS DFT approach. The computed VIPs as the negative of KS eigenvalue have a mean absolute error of 0.8 eV for an extensive set of molecule's electron ionizations, including the core. Barrier heights, equilibrium geometries, and magnetic properties obtained from the potential are in good agreement with experiment. A similar accuracy with less computational efforts can be achieved by using a non-variational global hybrid variant of the QTP-00 approach.

  2. Efficacy of virtual reality-based balance training versus the Biodex balance system training on the body balance of adults

    PubMed Central

    Ibrahim, Manal S.; Mattar, Ayman G.; Elhafez, Salam M.

    2016-01-01

    [Purpose] This study investigated efficacy of virtual reality (VR)-based balance training on enhancing balance and postural reactions of adults as a low-cost new modality compared to the established Biodex Balance System (BBS). [Subjects] Thirty normal adults of both genders were divided randomly into two equal-sized experimental groups of 15: BBS balance training and VR balance training. [Methods] The training programmes were conducted in 12 sessions, three 15-min sessions per week. The Nintendo® Wii Fit Plus (NWFP) and its balance board were used to train of the VR group. Each participant answered a questionnaire concerning usability, enjoyment, balance improvement, and fatigue at the end of the training programs. [Results] The study found a significant increase the measure of mean overall balance (OLB) in both groups. No significant difference was found between the groups, but a significant decrease in the mean balance-test time was found for both groups, with no significant difference between the two training methods. The VR programme was rated highly enjoyable by 81.8% of the group. [Conclusion] The Wii Fit Plus system with the balance board as a new VR balance-training technique, can be considered an effective and enjoyable tool for the training of adults’ body balance. PMID:26957722

  3. Life Balancing -- A Better Way to Balance Large Batteries

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

    Anderson, R. Dyche; Zane, Regan; Plett, Gregory

    2017-03-28

    A new cell balancing technology was developed under a Department of Energy contract which merges the DC/DC converter function into cell balancing. Instead of conventional passive cell balancing technology which bypasses current through a resistor, or active cell balancing which moves current from one cell to another, with significant cost and additional inefficiencies, this concept takes variable amount of current from each cell or small group of cells and converts it to current for the low voltage system.

  4. Molecular Data for a Biochemical Model of DNA Radiation Damage: Electron Impact Ionization and Dissociative Ionization of DNA Bases and Sugar-Phosphate Backbone

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher E.; Fletcher, Graham D.

    2004-01-01

    As part of the database for building up a biochemical model of DNA radiation damage, electron impact ionization cross sections of sugar-phosphate backbone and DNA bases have been calculated using the improved binary-encounter dipole (iBED) model. It is found that the total ionization cross sections of C3'- and C5'-deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3'- and C5'-deoxyribose-phospate cross sections, differing by less than 10%. Of the four DNA bases, the ionization cross section of guanine is the largest, then in decreasing order, adenine, thymine, and cytosine. The order is in accordance with the known propensity of oxidation of the bases by ionizing radiation. Dissociative ionization (DI), a process that both ionizes and dissociates a molecule, is investigated for cytosine. The DI cross section for the formation of H and (cytosine-Hl)(+), with the cytosine ion losing H at the 1 position, is also reported. The threshold of this process is calculated to be 17.1 eV. Detailed analysis of ionization products such as in DI is important to trace the sequential steps in the biochemical process of DNA damage.

  5. LABORATORY PHOTO-CHEMISTRY OF PAHS: IONIZATION VERSUS FRAGMENTATION

    PubMed Central

    Zhen, Junfeng; Castellanos, Pablo; Paardekooper, Daniel M.; Ligterink, Niels; Linnartz, Harold; Nahon, Laurent; Joblin, Christine; Tielens, Alexander G. G. M.

    2015-01-01

    Interstellar Polycyclic Aromatic Hydrocarbons (PAH) are expected to be strongly processed by Vacuum Ultra-Violet (VUV) photons. Here, we report experimental studies on the ionization and fragmentation of coronene (C24H12), ovalene (C32H14) and hexa-peri-hexabenzocoronene (HBC; C42H18) cations by exposure to synchrotron radiation in the range of 8–40 eV. The results show that for small PAH cations such as coronene, fragmentation (H-loss) is more important than ionization. However, as the size increases, ionization becomes more and more important and for the HBC cation, ionization dominates. These results are discussed and it is concluded that, for large PAHs, fragmentation only becomes important when the photon energy has reached the highest ionization potential accessible. This implies that PAHs are even more photo-stable than previously thought. The implications of this experimental study for the photo-chemical evolution of PAHs in the interstellar medium (ISM) are briefly discussed. PMID:26688710

  6. Ion Yields in the Coupled Chemical and Physical Dynamics Model of Matrix-Assisted Laser Desorption/Ionization

    NASA Astrophysics Data System (ADS)

    Knochenmuss, Richard

    2015-08-01

    The Coupled Chemical and Physical Dynamics (CPCD) model of matrix assisted laser desorption ionization has been restricted to relative rather than absolute yield comparisons because the rate constant for one step in the model was not accurately known. Recent measurements are used to constrain this constant, leading to good agreement with experimental yield versus fluence data for 2,5-dihydroxybenzoic acid. Parameters for alpha-cyano-4-hydroxycinnamic acid are also estimated, including contributions from a possible triplet state. The results are compared with the polar fluid model, the CPCD is found to give better agreement with the data.

  7. Numerical evaluation of a sensible heat balance method to determine rates of soil freezing and thawing

    USDA-ARS?s Scientific Manuscript database

    In-situ determination of ice formation and thawing in soils is difficult despite its importance for many environmental processes. A sensible heat balance (SHB) method using a sequence of heat pulse probes has been shown to accurately measure water evaporation in subsurface soil, and it has the poten...

  8. Density functional theory calculations of continuum lowering in strongly coupled plasmas.

    PubMed

    Vinko, S M; Ciricosta, O; Wark, J S

    2014-03-24

    An accurate description of the ionization potential depression of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here we present a method to study the structure and position of the continuum of highly ionized dense plasmas using finite-temperature density functional theory in combination with excited-state projector augmented-wave potentials. The method is applied to aluminium plasmas created by intense X-ray irradiation, and shows excellent agreement with recently obtained experimental results. We find that the continuum lowering for ions in dense plasmas at intermediate temperatures is larger than predicted by standard plasma models and explain this effect through the electronic structure of the valence states in these strong-coupling conditions.

  9. Development of a multicomponent force and moment balance for water tunnel applications, volume 1

    NASA Technical Reports Server (NTRS)

    Suarez, Carlos J.; Malcolm, Gerald N.; Kramer, Brian R.; Smith, Brooke C.; Ayers, Bert F.

    1994-01-01

    The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. An internal balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The five-components to applied loads, low interactions between the sections and no hysteresis. Static experiments (which are discussed in this Volume) were conducted in the Eidetics water tunnel with delta wings and a model of the F/A-18. Experiments with the F/A-18 model included a thorough baseline study and investigations of the effect of control surface deflections and of several Forebody Vortex Control (FVC) techniques. Results were compared to wind tunnel data and, in general, the agreement is very satisfactory. The results of the static tests provide confidence that loads can be measured accurately in the water tunnel with a relatively simple multicomponent internal balance. Dynamic experiments were also performed using the balance, and the results are discussed in detail in Volume 2 of this report.

  10. Ionization techniques in capillary electrophoresis-mass spectrometry: principles, design, and application.

    PubMed

    Hommerson, Paul; Khan, Amjad M; de Jong, Gerhardus J; Somsen, Govert W

    2011-01-01

    A major step forward in the development and application of capillary electrophoresis (CE) was its coupling to ESI-MS, first reported in 1987. More than two decades later, ESI has remained the principal ionization technique in CE-MS, but a number of other ionization techniques have also been implemented. In this review the state-of-the-art in the employment of soft ionization techniques for CE-MS is presented. First the fundamentals and general challenges of hyphenating conventional CE and microchip electrophoresis with MS are outlined. After elaborating on the characteristics and role of ESI, emphasis is put on alternative ionization techniques including sonic spray ionization (SSI), thermospray ionization (TSI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), matrix-assisted laser desorption ionization (MALDI) and continuous-flow fast atom bombardment (CF-FAB). The principle of each ionization technique is outlined and the experimental set-ups of the CE-MS couplings are described. The strengths and limitations of each ionization technique with respect to CE-MS are discussed and the applicability of the various systems is illustrated by a number of typical examples. Copyright © 2011 Wiley Periodicals, Inc.

  11. Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a mass-to-structure (MTS) Search Engine with integral isotope pattern ranking.

    PubMed

    Liao, Wenta; Draper, William M

    2013-02-21

    The mass-to-structure or MTS Search Engine is an Access 2010 database containing theoretical molecular mass information for 19,438 compounds assembled from common sources such as the Merck Index, pesticide and pharmaceutical compilations, and chemical catalogues. This database, which contains no experimental mass spectral data, was developed as an aid to identification of compounds in atmospheric pressure ionization (API)-LC-MS. This paper describes a powerful upgrade to this database, a fully integrated utility for filtering or ranking candidates based on isotope ratios and patterns. The new MTS Search Engine is applied here to the identification of volatile and semivolatile compounds including pesticides, nitrosoamines and other pollutants. Methane and isobutane chemical ionization (CI) GC-MS spectra were obtained from unit mass resolution mass spectrometers to determine MH(+) masses and isotope ratios. Isotopes were measured accurately with errors of <4% and <6%, respectively, for A + 1 and A + 2 peaks. Deconvolution of interfering isotope clusters (e.g., M(+) and [M - H](+)) was required for accurate determination of the A + 1 isotope in halogenated compounds. Integrating the isotope data greatly improved the speed and accuracy of the database identifications. The database accurately identified unknowns from isobutane CI spectra in 100% of cases where as many as 40 candidates satisfied the mass tolerance. The paper describes the development and basic operation of the new MTS Search Engine and details performance testing with over 50 model compounds.

  12. Biomechanical assessment of dynamic balance: Specificity of different balance tests.

    PubMed

    Ringhof, Steffen; Stein, Thorsten

    2018-04-01

    Dynamic balance is vitally important for most sports and activities of daily living, so the assessment of dynamic stability has become an important issue. In consequence, a large number of balance tests have been developed. However, it is not yet known whether these tests (i) measure the same construct and (ii) can differentiate between athletes with different balance expertise. We therefore studied three common dynamic balance tests: one-leg jump landings, Posturomed perturbations and simulated forward falls. Participants were 24 healthy young females in regular training in either gymnastics (n = 12) or swimming (n = 12). In each of the tests, the participants were instructed to recover balance as quickly as possible. Dynamic stability was computed by time to stabilization and margin of stability, deduced from force plates and motion capture respectively. Pearson's correlations between the dynamic balance tests found no significant associations between the respective dynamic stability measures. Furthermore, independent t-tests indicated that only jump landings could properly distinguish between both groups of athletes. In essence, the different dynamic balance tests applied did not measure the same construct but rather task-specific skills, each of which depends on multifactorial internal and external constraints. Our study therefore contradicts the traditional view of considering balance as a general ability, and reinforces that dynamic balance measures are not interchangeable. This highlights the importance of selecting appropriate balance tests. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Electron ionization and dissociation of aliphatic amino acids

    NASA Astrophysics Data System (ADS)

    Papp, P.; Shchukin, P.; Kočíšek, J.; Matejčík, Š.

    2012-09-01

    We present experimental and theoretical study of electron ionization and dissociative ionization to the gas phase amino acids valine, leucine, and isoleucine. A crossed electron/molecular beams technique equipped with quadrupole mass analyzer has been applied to measure mass spectra and ion efficiency curves for formation of particular ions. From experimental data the ionization energies of the molecules and the appearance energies of the fragment ions were determined. Ab initio calculations (Density Functional Theory and G3MP2 methods) were performed in order to calculate the fragmentation paths and interpret the experimental data. The experimental ionization energies of parent molecules [P]+ 8.91 ± 0.05, 8.85 ± 0.05, and 8.79 ± 0.05 eV and G3MP2 ionization energies (adiabatic) of 8.89, 8.88, and 8.81 eV were determined for valine, leucine, and isoleucine, respectively, as well as the experimental and theoretical threshold energies for dissociative ionization channels. The comparison of experimental data with calculations resulted in identification of the ions as well as the neutral fragments formed in the dissociative reactions. Around 15 mass/charge ratio fragments were identified from the mass spectra by comparison of experimental appearance energies with calculated reaction enthalpies for particular dissociative reactions.

  14. On the SIMS Ionization Probability of Organic Molecules.

    PubMed

    Popczun, Nicholas J; Breuer, Lars; Wucher, Andreas; Winograd, Nicholas

    2017-06-01

    The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α + ) of sputtered material, a value rarely measured directly, but estimated to be in some cases as low as 10 -5 . Our lab has developed a method for the direct determination of α + in a SIMS experiment using laser post-ionization (LPI) to detect neutral molecular species in the sputtered plume for an organic compound. Here, we apply this method to coronene (C 24 H 12 ), a polyaromatic hydrocarbon that exhibits strong molecular signal during gas-phase photoionization. A two-dimensional spatial distribution of sputtered neutral molecules is measured and presented. It is shown that the ionization probability of molecular coronene desorbed from a clean film under bombardment with 40 keV C 60 cluster projectiles is of the order of 10 -3 , with some remaining uncertainty arising from laser-induced fragmentation and possible differences in the emission velocity distributions of neutral and ionized molecules. In general, this work establishes a method to estimate the ionization efficiency of molecular species sputtered during a single bombardment event. Graphical Abstract .

  15. Electron-impact-ionization dynamics of S F6

    NASA Astrophysics Data System (ADS)

    Bull, James N.; Lee, Jason W. L.; Vallance, Claire

    2017-10-01

    A detailed understanding of the dissociative electron ionization dynamics of S F6 is important in the modeling and tuning of dry-etching plasmas used in the semiconductor manufacture industry. This paper reports a crossed-beam electron ionization velocity-map imaging study on the dissociative ionization of cold S F6 molecules, providing complete, unbiased kinetic energy distributions for all significant product ions. Analysis of these distributions suggests that fragmentation following single ionization proceeds via formation of S F5 + or S F3 + ions that then dissociate in a statistical manner through loss of F atoms or F2, until most internal energy has been liberated. Similarly, formation of stable dications is consistent with initial formation of S F4 2 + ions, which then dissociate on a longer time scale. These data allow a comparison between electron ionization and photoionization dynamics, revealing similar dynamical behavior. In parallel with the ion kinetic energy distributions, the velocity-map imaging approach provides a set of partial ionization cross sections for all detected ionic fragments over an electron energy range of 50-100 eV, providing partial cross sections for S2 +, and enables the cross sections for S F4 2 + from S F+ to be resolved.

  16. Effect of the corrected ionization potential and spatial distribution on the angular and energy distribution in tunnel ionization

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

    Petrović, V. M.; Miladinović, T. B., E-mail: tanja.miladinovic@gmail.com

    2016-05-15

    Within the framework of the Ammosov–Delone–Krainov theory, we consider the angular and energy distribution of outgoing electrons due to ionization by a circularly polarized electromagnetic field. A correction of the ground ionization potential by the ponderomotive and Stark shift is incorporated in both distributions. Spatial dependence is analyzed.

  17. Alkali ionization detector

    DOEpatents

    Hrizo, John; Bauerle, James E.; Witkowski, Robert E.

    1982-01-01

    A calibration filament containing a sodium-bearing compound is included in combination with the sensing filament and ion collector plate of a sodium ionization detector to permit periodic generation of sodium atoms for the in-situ calibration of the detector.

  18. Balancing Vanguard Satellites

    NASA Technical Reports Server (NTRS)

    Simkovich, A.; Baumann, Robert C.

    1961-01-01

    The Vanguard satellites and component parts were balanced within the specified limits by using a Gisholt Type-S balancer in combination with a portable International Research and Development vibration analyzer and filter, with low-frequency pickups. Equipment and procedures used for balancing are described; and the determination of residual imbalance is accomplished by two methods: calculation, and graphical interpretation. Between-the-bearings balancing is recommended for future balancing of payloads.

  19. Testing experience with unheated stain-gage balances in the NTF. [National Transonic Facility

    NASA Technical Reports Server (NTRS)

    Jacobs, Peter F.; Ferris, Alice T.

    1986-01-01

    A series of cryogenic (cryo) cycles was conducted in the cryo chamber at the National Transonic Facility (NTF) in order to identify the cause of apparent strain shifts in axial force with temperature for the Pathfinder I model and to minimize their effects. The results of the investigation indicated that the major cause of axial force end point shifts and thermal hysteresis loops was the thickness of the Teflon insulation on the instrumentation wires crossing the balance. By reducing the thickness of the insulation and the total number and size of the wires, apparent strain values were achieved for the model with instrumentation wires which were nearly identical to those for the model without wires. Because of the special design features used, the balance output was very accurate and repeatable over the entire NTF temperature range, even with balance thermal gradients as large as 64 F and transient conditions as large as 3 F/minute.

  20. [Balance trainability using the Nintendo Wii balance board in sportive people].

    PubMed

    Paukowits, S; Stöggl, T

    2014-03-01

    A multivariable training has a positive impact on balance skills and risk of injury. To date the effect of this training using the Nintendo Wii balance board in sportive people has not yet been investigated. The aim of this study was to investigate whether training with the Nintendo Wii balance board can improve balance skills. 20 people were randomized into a control and an intervention group each with 10 people who performed a unilateral stance test with eyes open and closed as well as the star excursion balance test before and after the intervention. The control group completed their usual sports and the intervention group an adjunct training with the Nintendo Wii balance board for 4 weeks. Adjunct Training using the Nintendo Wii Balance Board did not improve sportive people's balance skills significantly. The intervention group, however, attained better results in the star excursion balance test, whereas the control group did not show any changes. The unilateral stance tests did not provide significant differences before and after training within both groups. The use of the Nintendo Wii balance board should be further investigated by employing individual difficulty levels. © Georg Thieme Verlag KG Stuttgart · New York.

  1. Laser-induced volatilization and ionization of microparticles

    NASA Technical Reports Server (NTRS)

    Sinha, M. P.

    1984-01-01

    A method for the laser vaporization and ionization of individual micron-size particles is presented whereby a particle is ionized by a laser pulse while in flight in the beam. Ionization in the beam offers a real-time analytical capability and eliminates any possible substrate-sample interferences during an analysis. An experimental arrangement using a high-energy Nd-YAG laser is described, and results are presented for ions generated from potassium biphthalate particles (1.96 micron in diameter). The method proposed here is useful for the chemical analysis of aerosol particles by mass spectrometry and for other spectroscopic and chemical kinetic studies.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Vorgul, I.; Helling, Ch.

    2016-05-01

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

  4. Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)

    2002-01-01

    The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.

  5. Accurate Mass Determination of Organotrifluoroborates

    PubMed Central

    Petrillo, Daniel E.; Kohli, Rakesh K.; Molander, Gary A.

    2007-01-01

    Exact mass measurements were obtained for a variety of potassium- and tetra-n-butylammonium organotrifluoroborates using commercially available organic sulfate salts as internal reference standards. Accuracies were determined within 5 ppm using a sector ESI mass spectrometer operating in the negative ionization mode. PMID:17112738

  6. Multiphoton Ionization Mass and Photoelectron Spectroscopy.

    DTIC Science & Technology

    1984-07-01

    tracted information about ion vibrational energy levels. Molecules studted include benzene, toluene, aniline, paradifluorobenzene, nitric oxide ...molecules or subgroups and not to others. Ion specific electrodes play an analogous role in electro - chemistry. The prospect of selectively ionizing a... acetaldehyde and butyraldehyde have been studied at the KrF and ArF laser wavelengths. Their ionization potentials are 10.2 and 9.8 eV, respectively

  7. Energy balance in the core of the Saturn plasma sheet: H2O chemistry

    NASA Astrophysics Data System (ADS)

    Shemansky, D. E.; Yoshii, J.; Liu, X.

    2011-10-01

    A model of the weakly ionized plasma at Saturn has been developed to investigate the properties of the system. Energy balance is a critical consideration. The present model is based on two sources of mass, H2O, and HI. H2O is a variable. HI is a significant volume of gas flowing through the plasma imposed by the source at Saturn [1,2,3]. The energy sources are solar radiation and heterogeneous magnetosphere electrons. The model calculations produce energy rates, species partitioning, and relaxation lifetimes. For the first time the state of the ambient plasma sheet electrons is directly connected to the energy forcing functions. Within limits of knowledge, the predicted state of the core region of the plasma sheet in neutral and ionized gas corresponds satisfactorily to observation. The dominant ions in these calculations are H2O+ and H3O+ with lifetimes of several days. The lifetime of H2O is roughly 60 days. In calculations carried out so far the predicted source rate for H2O is lower than the rates quoted from the Enceladus encounters.

  8. A Chemogenomic Analysis of Ionization Constants - Implications for Drug Discovery

    PubMed Central

    Manallack, David T.; Prankerd, Richard J.; Nassta, Gemma C.; Ursu, Oleg; Oprea, Tudor I.; Chalmers, David K.

    2013-01-01

    Chemogenomics methods seek to characterize the interaction between drugs and biological systems and are an important guide for the selection of screening compounds. The acid/base character of drugs has a profound influence on their affinity for the receptor, on their absorption, distribution, metabolism, excretion and toxicity (ADMET) profile and the way the drug can be formulated. In particular, the charge state of a molecule greatly influences its lipophilicity and biopharmaceutical characteristics. This study investigates the acid/base profile of human small molecule drugs, chemogenomics datasets and screening compounds including a natural products set. We estimate the ionization constants (pKa values) of these compounds and determine the identity of the ionizable functional groups in each set. We find substantial differences in acid/base profiles of the chemogenomic classes. In many cases, these differences can be linked to the nature of the target binding site and the corresponding functional groups needed for recognition of the ligand. Clear differences are also observed between the acid/base characteristics of drugs and screening compounds. For example, the proportion of drugs containing a carboxylic acid was 20%, in stark contrast to a value of 2.4% for the screening set sample. The proportion of aliphatic amines was 27% for drugs and only 3.4% for screening compounds. This suggests that there is a mismatch between commercially available screening compounds and the compounds that are likely to interact with a given chemogenomic target family. Our analysis provides a guide for the selection of screening compounds to better target specific chemogenomic families with regard to the overall balance of acids, bases and pKa distributions. PMID:23303535

  9. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    DOE PAGES

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; ...

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated.more » Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.« less

  10. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

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

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated.more » Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.« less

  11. False Balance in Climate Change Reporting Among TV Meteorologists

    NASA Astrophysics Data System (ADS)

    Timm, K.; Maibach, E.; Boykoff, M.; Broeckelman-Post, M.; Myers, T.; Perkins, D. R., IV

    2017-12-01

    False balance is the journalistic practice of giving equal weight to both sides of a story, regardless of an established truth and validity on one side. Despite widespread scientific agreement about the anthropogenic causes of climate change, false balance on the subject of climate change remains common in television despite a documented decline in other media. In this exploratory study, 452 American TV meteorologists were surveyed about their climate change beliefs and asked how often and why they present an opposing viewpoint when they present about human contributions to climate change. The results indicate that this practice is fairly common, with nearly 30% of TV meteorologists presenting an opposing viewpoint at least half the time or more frequently when they present about climate change. Weathercasters described including an opposing viewpoint in their stories for many different reasons, including that it is essential to objective and balanced reporting, that it is used to acknowledge different audience viewpoints, and because the science is perceived to be uncertain. The results also suggest that being more certain that climate change is happening, that it is primarily caused by humans, and perceiving the full extent of the scientific consensus about human-caused climate change, are associated with decreased frequency of presenting an opposing viewpoint. This is the first time the issue of false balance has been studied in the context of TV weathercasters, and while more research is needed, these results provide some preliminary evidence to suggest that increasing weathercasters' understanding of the scientific consensus of human caused climate change may help reduce false balance reporting. Furthermore, as meteorologists and weathercasters become more prominent reporters of local climate news, it will be important for them to have techniques to accurately report the science, while maintaining their sense of objectivity.

  12. Gas chromatography/chemical ionization triple quadrupole mass spectrometry analysis of anabolic steroids: ionization and collision-induced dissociation behavior.

    PubMed

    Polet, Michael; Van Gansbeke, Wim; Van Eenoo, Peter; Deventer, Koen

    2016-02-28

    The detection of new anabolic steroid metabolites and new designer steroids is a challenging task in doping analysis. Switching from electron ionization gas chromatography triple quadrupole mass spectrometry (GC/EI-MS/MS) to chemical ionization (CI) has proven to be an efficient way to increase the sensitivity of GC/MS/MS analyses and facilitate the detection of anabolic steroids. CI also extends the possibilities of GC/MS/MS analyses as the molecular ion is retained in its protonated form due to the softer ionization. In EI it can be difficult to find previously unknown but expected metabolites due to the low abundance or absence of the molecular ion and the extensive (and to a large extent unpredictable) fragmentation. The main aim of this work was to study the CI and collision-induced dissociation (CID) behavior of a large number of anabolic androgenic steroids (AAS) as their trimethylsilyl derivatives in order to determine correlations between structures and CID fragmentation. Clarification of these correlations is needed for the elucidation of structures of unknown steroids and new metabolites. The ionization and CID behavior of 65 AAS have been studied using GC/CI-MS/MS with ammonia as the reagent gas. Glucuronidated AAS reference standards were first hydrolyzed to obtain their free forms. Afterwards, all the standards were derivatized to their trimethylsilyl forms. Full scan and product ion scan analyses were used to examine the ionization and CID behavior. Full scan and product ion scan analyses revealed clear correlations between AAS structure and the obtained mass spectra. These correlations were confirmed by analysis of multiple hydroxylated, methylated, chlorinated and deuterated analogs. AAS have been divided into three groups according to their ionization behavior and into seven groups according to their CID behavior. Correlations between fragmentation and structure were revealed and fragmentation pathways were postulated. Copyright © 2016 John Wiley

  13. Balance in Assessment

    ERIC Educational Resources Information Center

    White, Richard

    2007-01-01

    The review by Black and Wiliam of national systems makes clear the complexity of assessment, and identifies important issues. One of these is "balance": balance between local and central responsibilities, balance between the weights given to various purposes of schooling, balance between weights for various functions of assessment, and balance…

  14. Electron Impact Ionization of Heavier Ions

    NASA Astrophysics Data System (ADS)

    Saha, B. C.

    2006-10-01

    The electron impact ionization (EII) is a dominant ion creation process in various kinds of plasmas. Hydrogenic atoms occurs not only in plasmas but may also be formed due to radiation effects in many organic and inorganic materials. Apart from its fundamental importance in collisional physics the knowledge of the EII cross sections finds its wide applications in modeling astrophysical and fusion plasmas. So the demand of the EIICS is enormous. It is hard to fulfill such a demand either by experimental or ab initio calculations. Thus various analytical and semi-classical models are employed to generate accurate EII cross sections. We report here a modified version [1] of the Bell et. al. equations [2] including both the ionic and relativistic corrections (MBELL). We generalize the MBELL parameters for treating the dependency of the orbital quantum numbers nl; evaluating cross sections for various species at different energies tests the accuracy of the procedure. Detail will be presented at the meeting. [1] A. K. F. Haque, M. A. Uddin, A. K. Basak, K. R. Karim and B. C. Saha, Phys. Rev. A73, 052703 (2006). [2] K. L. Bell, H. B. Gilbody, J. G. Hughes, A. E. Kingston, and F. J. Smith, J. Phys. Chem. Ref. Data 12, 891 (1983).

  15. LABORATORY PHOTO-CHEMISTRY OF PAHs: IONIZATION VERSUS FRAGMENTATION

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

    Zhen, Junfeng; Castellanos, Pablo; Ligterink, Niels

    2015-05-01

    Interstellar polycyclic aromatic hydrocarbons (PAHs) are expected to be strongly processed by vacuum ultraviolet photons. Here, we report experimental studies on the ionization and fragmentation of coronene (C{sub 24}H{sub 12}), ovalene (C{sub 32}H{sub 14}) and hexa-peri-hexabenzocoronene (HBC; C{sub 42}H{sub 18}) cations by exposure to synchrotron radiation in the range of 8–40 eV. The results show that for small PAH cations such as coronene, fragmentation (H-loss) is more important than ionization. However, as the size increases, ionization becomes more and more important and for the HBC cation, ionization dominates. These results are discussed and it is concluded that, for large PAHs,more » fragmentation only becomes important when the photon energy has reached the highest ionization potential accessible. This implies that PAHs are even more photo-stable than previously thought. The implications of this experimental study for the photo-chemical evolution of PAHs in the interstellar medium are briefly discussed.« less

  16. Relativistic Ionization with Intense Linearly Polarized Light

    NASA Astrophysics Data System (ADS)

    Crawford, Douglas Plummer

    The Strong Field Approximation (SFA) method is used to derive relativistic ionization rate expressions for ground state hydrogen-like atoms in the presence of an intense electromagnetic field. The emitted particle, which is initially bound to a hydrogen nucleus, is either an electron described by the Dirac equation, with spin effects fully included, or a spinless "electron" described by the Klein-Gordon equation. The derivations and subsequent calculations for both particles are made assuming a linearly polarized electromagnetic field which is monochromatic and which exhibits neither diffraction nor temporal dependence. From each of the relativistic ionization rate expressions, the corresponding expression in the nonrelativistic limit is derived. The resultant expressions are found to be equivalent to those derived using the SFA with the nonrelativistic formalism. This comparison provides the first check of the validity for the core results of this dissertation. Intensity-dependent ionization rates are then calculated for two ultraviolet frequencies using a numerical implementation of the derived expressions. Calculations of ionization rates and related phenomena demonstrate that there are negligible differences between relativistic and nonrelativistic predictions for low intensities. In addition, the differences in behavior between linearly and circularly polarized ionizing fields and between particles with and without spin are explored. The spin comparisons provide additional confidence in the derivations by showing negligible differences between ionization rates for Dirac and Klein -Gordon particles in strong linearly-polarized fields. Also of interest are the differential transition rates which exhibit dynamic profiles as the intensity is increased. This behavior is interpreted as an indication of more atomic influence for linearly polarized electromagnetic (em) fields than for circularly polarized em fields.

  17. Rotor balance system

    NASA Technical Reports Server (NTRS)

    Novotny, Rudolph J. (Inventor)

    1989-01-01

    A balance ring (18) which is shrunk fit within each disk (12) of a rotor is selectively ground for detail balance. A plurality of openings (20) through the outer edge of the balance ring receive weights during the asssembly balance of the rotor. A snap ring (42) retains the weights within the openings.

  18. Hot interstellar gas and ionization of embedded clouds

    NASA Technical Reports Server (NTRS)

    Cheng, K.-P.; Bruhweiler, F.

    1990-01-01

    Researchers present detailed photoionization calculations for the instellar cloud in which the Sun is embedded. They consider the EUV radiation field with contribution from discrete stellar sources and from a thermal bremsstrahlung-radiative recombination spectrum emitted from the surrounding 10 to the 6th power k coronal substrate. They establish lower limits to the fractional ionization of hydrogen and helium of 0.17 and 0.29 respectively. The high He ionization fraction results primarily from very strong line emission below 500 A originating in the surrounding coronal substrate while the H ionization is dominated by the EUV radiation from the discrete stellar sources. The dual effects of thermal conduction and the EUV spectrum of the 10 to the 6th k plasma on ionization in the cloud skin are explored. The EUV radiation field and Auger ionization have insignificant effects on the resulting ionic column densities of Si IV, C IV, N V and O VI through the cloud skin. Calculations show that the abundances of these species are dominated by collisional ionization in the thermal conduction front. Because of a low charge exchange rate with hydrogen, the ionic column density ratios of N (CIII)/N (CII) and N (NII)/N (NI) are dominated by the EUV radiation field in the local interstellar medium. These ratios should be important diagnostics for the EUV radiation field and serve as surrogate indicators of the interstellar He and H ionization fraction respectively. Spacecraft such as Lyman which is designed to obtain high resolution spectral data down to the Lyman limit at 912 A could sample interstellar lines of these ions.

  19. Onset of space charge effects in liquid argon ionization chambers

    NASA Astrophysics Data System (ADS)

    Toggerson, B.; Newcomer, A.; Rutherfoord, J.; Walker, R. B.

    2009-09-01

    Using a thin-gap liquid argon ionization chamber and Strontium-90 beta sources we have measured ionization currents over a wide range of gap potentials. These precision "HV plateau curves" advance the understanding of liquid argon sampling calorimeter signals, particularly at high ionization rates. The order of magnitude differences in the activities of the beta sources allow us to estimate where the ionization chamber is driven into the space-charge dominated regime.

  20. Ultrafast Electron Plasma Index: An Ionization Perspective

    DTIC Science & Technology

    2014-05-29

    picture in mind, the derivation of the index was a combination of the principle of least action and Fermat’s principle. In the current textbook ...multiphoton ionization. Phys Rev Lett 71: 1994-1997. 27. Ivanov MY, Spanner M, Smirnova O (2005) Anatomy of strong field ionization. J. Mod.Phys 52

  1. Oxygen ionization rates at Mars and Venus - Relative contributions of impact ionization and charge exchange

    NASA Astrophysics Data System (ADS)

    Zhang, M. H. G.; Luhmann, J. G.; Nagy, A. F.; Spreiter, J. R.; Stahara, S. S.

    1993-02-01

    Oxygen ion production rates above the ionopauses of Venus and Mars are calculated for photoionization, charge exchange, and solar wind electron impact ionization processes. The latter two require the use of the Spreiter and Stahara (1980) gas dynamic model to estimate magnetosheath velocities, densities, and temperatures. The results indicate that impact ionization is the dominant mechanism for the production of O(+) ions at both Venus and Mars. This finding might explain both the high ion escape rates measured by Phobos 2 and the greater mass loading rate inferred for Venus from the bow shock positions.

  2. Assessing the role of Hartree-Fock exchange, correlation energy and long range corrections in evaluating ionization potential, and electron affinity in density functional theory.

    PubMed

    Vikramaditya, Talapunur; Lin, Shiang-Tai

    2017-06-05

    Accurate determination of ionization potentials (IPs), electron affinities (EAs), fundamental gaps (FGs), and HOMO, LUMO energy levels of organic molecules play an important role in modeling and predicting the efficiencies of organic photovoltaics, OLEDs etc. In this work, we investigate the effects of Hartree Fock (HF) Exchange, correlation energy, and long range corrections in predicting IP and EA in Hybrid Functionals. We observe increase in percentage of HF exchange results in increase of IPs and decrease in EAs. Contrary to the general expectations inclusion of both HF exchange and correlation energy (from the second order perturbation theory MP2) leads to poor prediction. Range separated Hybrid Functionals are found to be more reliable among various DFT Functionals investigated. DFT Functionals predict accurate IPs whereas post HF methods predict accurate EAs. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  3. A Well-Balanced Path-Integral f-Wave Method for Hyperbolic Problems with Source Terms

    PubMed Central

    2014-01-01

    Systems of hyperbolic partial differential equations with source terms (balance laws) arise in many applications where it is important to compute accurate time-dependent solutions modeling small perturbations of equilibrium solutions in which the source terms balance the hyperbolic part. The f-wave version of the wave-propagation algorithm is one approach, but requires the use of a particular averaged value of the source terms at each cell interface in order to be “well balanced” and exactly maintain steady states. A general approach to choosing this average is developed using the theory of path conservative methods. A scalar advection equation with a decay or growth term is introduced as a model problem for numerical experiments. PMID:24563581

  4. Electron impact ionization of cycloalkanes, aldehydes, and ketones

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

    Gupta, Dhanoj; Antony, Bobby, E-mail: bka.ism@gmail.com

    The theoretical calculations of electron impact total ionization cross section for cycloalkane, aldehyde, and ketone group molecules are undertaken from ionization threshold to 2 keV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionization contribution method. The results of most of the targets studied compare fairly well with the recent measurements, wherever available and the cross sections for many targets are predicted for the first time. The correlation between the peak of ionization cross sections with number of target electrons and target parameters is also reported. It was found that the crossmore » sections at their maximum depend linearly with the number of target electrons and with other target parameters, confirming the consistency of the values reported here.« less

  5. Soft Argon-Propane Dielectric Barrier Discharge Ionization.

    PubMed

    Schütz, Alexander; Lara-Ortega, Felipe J; Klute, Felix David; Brandt, Sebastian; Schilling, Michael; Michels, Antje; Veza, Damir; Horvatic, Vlasta; García-Reyes, Juan F; Franzke, Joachim

    2018-03-06

    Dielectric barrier discharges (DBDs) have been used as soft ionization sources (DBDI) for organic mass spectrometry (DBDI-MS) for approximately ten years. Helium-based DBDI is often used because of its good ionization efficiency, low ignition voltage, and homogeneous plasma conditions. Argon needs much higher ignition voltages than helium when the same discharge geometry is used. A filamentary plasma, which is not suitable for soft ionization, may be produced instead of a homogeneous plasma. This difference results in N 2 , present in helium and argon as an impurity, being Penning-ionized by helium but not by metastable argon atoms. In this study, a mixture of argon and propane (C 3 H 8 ) was used as an ignition aid to decrease the ignition and working voltages, because propane can be Penning-ionized by argon metastables. This approach leads to homogeneous argon-based DBDI. Furthermore, operating DBDI in an open environment assumes that many uncharged analyte molecules do not interact with the reactant ions. To overcome this disadvantage, we present a novel approach, where the analyte is introduced in an enclosed system through the discharge capillary itself. This nonambient DBDI-MS arrangement is presented and characterized and could advance the novel connection of DBDI with analytical separation techniques such as gas chromatography (GC) and high-pressure liquid chromatography (HPLC) in the near future.

  6. Fast Ionized X-ray Absorbers in AGNs

    NASA Astrophysics Data System (ADS)

    Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

    2015-07-01

    We present a study of X-ray ionization of MHD accretion-disk wind models in an effort to explain the highly-ionized ultra-fast outflows (UFOs) identified as X-ray absorbers recently detected in various sub-classes of Seyfert AGNs. Our primary focus is to show that magnetically-driven outflows are physically plausible candidates to account for the AGN X-ray spectroscopic observations. We calculate its X-ray ionization and the ensuing X-ray absorption line spectra in comparison with an XXM-Newton/EPIC spectrum of the narrow-line Seyfert AGN, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log(xi[erg cm/s]) = 5-6 and a hydrogen-equivalent column density on the order of 1e23 cm-2, outflowing at a sub-relativistic velocity of v/c = 0.1-0.2. The best-fit model favors its radial location at R = 200 Rs (Rs is the Schwarzschild radius), with a disk inner truncation radius at Rt = 30Rs. The overall K-shell feature in data is suggested to be dominated by Fe XXV with very little contribution from Fe XXVI and weakly-ionized iron, which is in a good agreement with a series of earlier analysis of the UFOs in various AGNs including PG 1211+143.

  7. Electron Impact Excitation-Ionization of Molecules

    NASA Astrophysics Data System (ADS)

    Ali, Esam Abobakr A.

    In the last few decades, the study of atomic collisions by electron-impact has made significant advances. The most difficult case to study is electron impact ionization of molecules for which many approximations have to be made and the validity of these approximations can only be checked by comparing with experiment. In this thesis, I have examined the Molecular three-body distorted wave (M3DW) or Molecular four-body distorted wave (M4DW) approximations for electron-impact ionization. These models use a fully quantum mechanical approach where all particles are treated quantum mechanically and the post collision interaction (PCI) is treated to all orders of perturbation. These electron impact ionization collisions play central roles in the physics and chemistry of upper atmosphere, biofuel, the operation of discharges and lasers, radiation induced damage in biological material like damage to DNA by secondary electrons, and plasma etching processes. For the M3DW model, I will present results for electron impact single ionization of small molecules such as Water, Ethane, and Carbon Dioxide and the much larger molecules Tetrahydrofuran, phenol, furfural, 1-4 Benzoquinone. I will also present results for the four-body problem in which there are two target electrons involved in the collision. M4DW results will be presented for dissociative excitation-ionization of orientated D2. I will show that M4DW calculations using a variational wave function for the ground state that included s- and p- orbital states give better agreement to the experimental measurements than a ground state approximated as a product of two 1s-type Dyson orbitals.

  8. Ionization cross section, pressure shift and isotope shift measurements of osmium

    NASA Astrophysics Data System (ADS)

    Hirayama, Yoshikazu; Mukai, Momo; Watanabe, Yutaka; Oyaizu, Michihiro; Ahmed, Murad; Kakiguchi, Yutaka; Kimura, Sota; Miyatake, Hiroari; Schury, Peter; Wada, Michiharu; Jeong, Sun-Chan

    2017-11-01

    In-gas-cell laser resonance ionization spectroscopy of neutral osmium atoms was performed with the use of a two-color two-step laser resonance ionization technique. Saturation curves for the ionization scheme were measured, and the ionization cross section was experimentally determined by solving the rate equations for the ground, intermediate and ionization continuum populations. The pressure shift and pressure broadening in the resonance spectra of the excitation transition were measured. The electronic factor {F}247 for the transition {λ }1=247.7583 nm to the intermediate state was deduced from the measured isotope shifts of stable {}{188,189,{190,192}}Os isotopes. The efficient ionization scheme, pressure shift, nuclear isotope shift and {F}247 are expected to be useful for applications of laser ion sources to unstable nuclei and for nuclear spectroscopy based on laser ionization techniques.

  9. Ambient mass spectrometry: Direct analysis of dimethoate, tebuconazole, and trifloxystrobin on olive and vine leaves by desorption electrospray ionization interface.

    PubMed

    Mainero Rocca, Lucia; Cecca, Juri; L'Episcopo, Nunziata; Fabrizi, Giovanni

    2017-11-01

    A new field of application for a relatively new mass-spectrometric interface such as desorption electrospray ionization was evaluated. For this purpose, its behavior was tested versus quantitative analysis of dimethoate, trifloxystrobin, and tebuconazole directly on olive and vine leaves surface. The goal was workers exposure assessment during field re-entry operations since evidence suggests an association between chronic occupational exposure to some agrochemicals and severe adverse effects. Desorption electrospray ionization gave good response working in positive ionization mode, while numerous test were necessary for the choice of a unique blend of spray solvents suitable for all 3 substances. The best compromise, in terms of signal to noise ratios, was obtained with the CH 3 OH/H 2 O (80:20) mixture. The obvious difficulties related to the impossibility to use the internal standard were overcome through an accurate validation. Limits of detection and quantitation, dynamic ranges, matrix effects, and intraday precisions were calculated, and a small monitoring campaign was arranged to test method applicability and to evaluate potential dermal exposure. This protocol was developed in work safety field, but after a brief investigation, it was find to be suitable also for food residue evaluation. Copyright © 2017 John Wiley & Sons, Ltd.

  10. The interaction of an ionizing ligand with enzymes having a single ionizing group. Implications for the reaction of folate analogues with dihydrofolate reductase.

    PubMed

    Stone, S R; Morrison, J F

    1983-06-29

    Binding theory has been developed for the reaction of an ionizing enzyme with an ionizing ligand. Consideration has been given to the most general scheme in which all possible reactions and interconversions occur as well as to schemes in which certain interactions do not take place. Equations have been derived in terms of the variation of the apparent dissociation constant (Kiapp) as a function of pH. These equations indicate that plots of pKiapp against pH can be wave-, half-bell- or bell-shaped according to the reactions involved. A wave is obtained whenever there is formation of the enzyme-ligand complexes, ionized enzyme . ionized ligand and protonated enzyme . protonated ligand. The additional formation of singly protonated enzyme-ligand complexes does not affect the wave form of the plot, but can influence the shape of the overall curve. The formation of either ionized enzyme . ionized ligand or protonated enzyme . protonated ligand, with or without singly protonated enzyme-ligand species, gives rise to a half-bell-shaped plot. If only singly protonated enzyme-ligand complexes are formed the plots are bell-shaped, but it is not possible to deduce the ionic forms of the reactants that participate in complex formation. Depending on the reaction pathways, true values for the ionization and dissociation constants may or may not be determined.

  11. Influence of ionization on ultrafast gas-based nonlinear fiber optics.

    PubMed

    Chang, W; Nazarkin, A; Travers, J C; Nold, J; Hölzer, P; Joly, N Y; Russell, P St J

    2011-10-10

    We numerically investigate the effect of ionization on ultrashort high-energy pulses propagating in gas-filled kagomé-lattice hollow-core photonic crystal fibers by solving an established uni-directional field equation. We consider the dynamics of two distinct regimes: ionization induced blue-shift and resonant dispersive wave emission in the deep-UV. We illustrate how the system evolves between these regimes and the changing influence of ionization. Finally, we consider the effect of higher ionization stages.

  12. Alfvén ionization in an MHD-gas interactions code

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

    Wilson, A. D.; Diver, D. A.

    A numerical model of partially ionized plasmas is developed in order to capture their evolving ionization fractions as a result of Alfvén ionization (AI). The mechanism of, and the parameter regime necessary for, AI is discussed and an expression for the AI rate based on fluid parameters, from a gas-MHD model, is derived. This AI term is added to an existing MHD-gas interactions' code, and the result is a linear, 2D, two-fluid model that includes momentum transfer between charged and neutral species as well as an ionization rate that depends on the velocity fields of both fluids. The dynamics ofmore » waves propagating through such a partially ionized plasma are investigated, and it is found that AI has a significant influence on the fluid dynamics as well as both the local and global ionization fraction.« less

  13. Load Balancing Using Time Series Analysis for Soft Real Time Systems with Statistically Periodic Loads

    NASA Technical Reports Server (NTRS)

    Hailperin, M.

    1993-01-01

    This thesis provides design and analysis of techniques for global load balancing on ensemble architectures running soft-real-time object-oriented applications with statistically periodic loads. It focuses on estimating the instantaneous average load over all the processing elements. The major contribution is the use of explicit stochastic process models for both the loading and the averaging itself. These models are exploited via statistical time-series analysis and Bayesian inference to provide improved average load estimates, and thus to facilitate global load balancing. This thesis explains the distributed algorithms used and provides some optimality results. It also describes the algorithms' implementation and gives performance results from simulation. These results show that the authors' techniques allow more accurate estimation of the global system loading, resulting in fewer object migrations than local methods. The authors' method is shown to provide superior performance, relative not only to static load-balancing schemes but also to many adaptive load-balancing methods. Results from a preliminary analysis of another system and from simulation with a synthetic load provide some evidence of more general applicability.

  14. Energy balance in the solar transition region. III - Helium emission in hydrostatic, constant-abundance models with diffusion

    NASA Technical Reports Server (NTRS)

    Fontenla, J. M.; Avrett, E. H.; Loeser, R.

    1993-01-01

    In our previous papers we described the mathematical formalism and the computed results for energy-balance hydrostatic models of the solar transition region. In this paper we discuss in some detail the limitations of the hydrostatic and one-dimensional assumptions used. Then we analyze the determination of helium emission when diffusion is included. We use transport coefficients estimated from kinetic theory to determine the helium departures from local ionization balance. We calculate the helium spectra for each of our models and evaluate the role of helium in the energy transport. Also, we investigate the effects of coronal illumination on the structure of the transition region and upper chromosphere, and show how coronal illumination affects various EUV lines and the He I 10830 A line. Comparing with both absolute intensities and detailed line profiles, we show that our models are consistent not only with the observed hydrogen spectra but also with the available helium spectra.

  15. Method and apparatus to monitor a beam of ionizing radiation

    DOEpatents

    Blackburn, Brandon W.; Chichester, David L.; Watson, Scott M.; Johnson, James T.; Kinlaw, Mathew T.

    2015-06-02

    Methods and apparatus to capture images of fluorescence generated by ionizing radiation and determine a position of a beam of ionizing radiation generating the fluorescence from the captured images. In one embodiment, the fluorescence is the result of ionization and recombination of nitrogen in air.

  16. HF Accelerated Electron Fluxes, Spectra, and Ionization

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert C.; Jensen, Joseph B.

    2015-10-01

    Wave particle interactions, an essential aspect of laboratory, terrestrial, and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth's weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich in Usp Fizicheskikh Nauk 177(11):1145-1177, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al. in J Atmos Terr Phys 44:1089-1100, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~eV, but instead to -100 times thermal energy (10 s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich et al (J Atmos Terr Phys 47:1057-1070, 1985) quantified the theory of this transport effect. Merging experiment with theory in plasma physics and aeronomy, enabled prediction (Carlson in Adv Space Res 13:1015-1024, 1993) of creating artificial ionospheres once ~GW HF effective radiated power could be achieved. Eventual confirmation of this prediction (Pedersen et al. in Geophys Res Lett 36:L18107, 2009; Pedersen et al. in Geophys Res Lett 37:L02106, 2010; Blagoveshchenskaya et al. in Ann Geophys 27:131-145, 2009) sparked renewed interest in optical inversion to estimate electron spectra in terrestrial (Hysell et al. in J Geophys Res Space Phys 119:2038-2045, 2014) and planetary (Simon et al. in Ann Geophys 29:187-195, 2011) atmospheres. Here we present our unpublished optical data, which combined with our modeling, lead to conclusions that should meaningfully improve future estimates of the spectrum of HF accelerated electron fluxes. Photometric imaging data can significantly improve detection of emissions near ionization threshold, and confirm depth of penetration of accelerated electrons many km below the excitation altitude. Comparing observed to modeled emission altitude shows future experiments need electron density profiles

  17. Calcium Balance in Mature Rats Exposed to a Space Flight Model

    NASA Technical Reports Server (NTRS)

    Wolinsky, Ira

    1996-01-01

    metabolic cage developed in our laboratory it is now possible to accurately measure urinary and fecal calcium excretions in this space flight model. The purpose of this study, then, was to extend and enlarge our previous findings viz: to measure calcium balances in mature rats exposed to a space flight model.

  18. Assessment of a flow-through balance for hypersonic wind tunnel models with scramjet exhaust flow simulation

    NASA Technical Reports Server (NTRS)

    Huebner, Lawrence D.; Kniskern, Marc W.; Monta, William J.

    1993-01-01

    The purpose of this investigation were twofold: first, to determine whether accurate force and moment data could be obtained during hypersonic wind tunnel tests of a model with a scramjet exhaust flow simulation that uses a representative nonwatercooled, flow-through balance; second, to analyze temperature time histories on various parts of the balance to address thermal effects on force and moment data. The tests were conducted in the NASA Langley Research Center 20-Inch Mach 6 Wind Tunnel at free-stream Reynolds numbers ranging from 0.5 to 7.4 x 10(exp 6)/ft and nominal angles of attack of -3.5 deg, 0 deg, and 5 deg. The simulant exhaust gases were cold air, hot air, and a mixture of 50 percent Argon and 50 percent Freon by volume, which reached stagnation temperatures within the balance of 111, 214, and 283 F, respectively. All force and moment values were unaffected by the balance thermal response from exhaust gas simulation and external aerodynamic heating except for axial-force measurements, which were significantly affected by balance heating. This investigation showed that for this model at the conditions tested, a nonwatercooled, flow-through balance is not suitable for axial-force measurements during scramjet exhaust flow simulation tests at hypersonic speeds. In general, heated exhaust gas may produce unacceptable force and moment uncertainties when used with thermally sensitive balances.

  19. Dynamics of tunneling ionization using Bohmian mechanics

    NASA Astrophysics Data System (ADS)

    Douguet, Nicolas; Bartschat, Klaus

    2018-01-01

    Recent attoclock experiments and theoretical studies regarding the strong-field ionization of atoms by few-cycle infrared pulses revealed features that have attracted much attention. Here we investigate tunneling ionization and the dynamics of the electron probability using Bohmian mechanics. We consider a one-dimensional problem to illustrate the underlying mechanisms of the ionization process. It is revealed that in the major part of the below-the-barrier ionization regime, in an intense and short infrared pulse, the electron does not tunnel through the entire barrier, but rather starts already from the classically forbidden region. Moreover, we highlight the correspondence between the probability of locating the electron at a particular initial position and its asymptotic momentum. Bohmian mechanics also provides a natural definition of mean tunneling time and exit position, taking account of the time dependence of the barrier. Finally, we find that the electron can exit the barrier with significant kinetic energy, thereby corroborating the results of a recent study [N. Camus et al., Phys. Rev. Lett. 119, 023201 (2017), 10.1103/PhysRevLett.119.023201].

  20. Dissociative Ionization of Benzene by Electron Impact

    NASA Technical Reports Server (NTRS)

    Huo, Winifred; Dateo, Christopher; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We report a theoretical study of the dissociative ionization (DI) of benzene from the low-lying ionization channels. Our approach makes use of the fact that electron motion is much faster than nuclear motion and DI is treated as a two-step process. The first step is electron-impact ionization resulting in an ion with the same nuclear geometry as the neutral molecule. In the second step the nuclei relax from the initial geometry and undergo unimolecular dissociation. For the ionization process we use the improved binary-encounter dipole (iBED) model. For the unimolecular dissociation step, we study the steepest descent reaction path to the minimum of the ion potential energy surface. The path is used to analyze the probability of unimolecular dissociation and to determine the product distributions. Our analysis of the dissociation products and the thresholds of the productions are compared with the result dissociative photoionization measurements of Feng et al. The partial oscillator strengths from Feng et al. are then used in the iBED cross section calculations.

  1. Hydraulic effects in a radiative atmosphere with ionization

    NASA Astrophysics Data System (ADS)

    Bhat, P.; Brandenburg, A.

    2016-03-01

    Context. In his 1978 paper, Eugene Parker postulated the need for hydraulic downward motion to explain magnetic flux concentrations at the solar surface. A similar process has also recently been seen in simplified (e.g., isothermal) models of flux concentrations from the negative effective magnetic pressure instability (NEMPI). Aims: We study the effects of partial ionization near the radiative surface on the formation of these magnetic flux concentrations. Methods: We first obtain one-dimensional (1D) equilibrium solutions using either a Kramers-like opacity or the H- opacity. The resulting atmospheres are then used as initial conditions in two-dimensional (2D) models where flows are driven by an imposed gradient force that resembles a localized negative pressure in the form of a blob. To isolate the effects of partial ionization and radiation, we ignore turbulence and convection. Results: Because of partial ionization, an unstable stratification always forms near the surface. We show that the extrema in the specific entropy profiles correspond to the extrema in the degree of ionization. In the 2D models without partial ionization, strong flux concentrations form just above the height where the blob is placed. Interestingly, in models with partial ionization, such flux concentrations always form at the surface well above the blob. This is due to the corresponding negative gradient in specific entropy. Owing to the absence of turbulence, the downflows reach transonic speeds. Conclusions: We demonstrate that, together with density stratification, the imposed source of negative pressure drives the formation of flux concentrations. We find that the inclusion of partial ionization affects the entropy profile dramatically, causing strong flux concentrations to form closer to the surface. We speculate that turbulence effects are needed to limit the strength of flux concentrations and homogenize the specific entropy to a stratification that is close to marginal.

  2. Ionization in the local interstellar and intergalactic media

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

    Cheng, K.

    1990-01-01

    Detailed photoionization calculations for the local interstellar medium (LISM) and the intergalactic medium (IGM) are presented. Constraints in the LISM are imposed by H I column density derived from IUE and Copernicus data toward nearby B stars and hot white dwarfs. The EUV radiation field is modeled including contributions from discrete stellar sources and from a thermal bremsstrahlung-radiative recombination spectrum emitted from the surrounding 10(exp 6) K coronal substrate. Lower limits to the fractional ionization of hydrogen and helium of 0.17 and 0.30 respectively are established. The derived limits have important implications for the interpretation of the H I andmore » He I backscattering results. The high He ionization fraction results primarily from very strong line emission below 500 A originating in the surrounding coronal substrate while the H ionization is dominated by the EUV radiation from the discrete stellar sources. The dual effects of thermal conduction and the EUV spectrum of the 10(exp 6) K plasma on ionization in the cloud skin are explored. The EUV radiation field and Auger ionization have insignificant effects on the resulting ionic column densities of Si IV, C IV, N V and O VI through the cloud skin. Calculations show that the abundances of these species are dominated by collisional ionization in the thermal conduction front. Because of a low charge exchange rate with hydrogen, the ionic column density ratios of N(C III)/N(C II) and N(N II)/N(N I) are dominated by the EUV radiation field in the local interstellar medium. These ratios should be important diagnostics for the EUV radiation field and serve as surrogate indicators of the interstellar He and H ionization fraction respectively. The same photoionization model is applied to the intergalactic medium.« less

  3. Recent advances in bacteria identification by matrix-assisted laser desorption/ionization mass spectrometry using nanomaterials as affinity probes.

    PubMed

    Chiu, Tai-Chia

    2014-04-28

    Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided.

  4. Observation of increased space-charge limited thermionic electron emission current by neutral gas ionization in a weakly-ionized deuterium plasma

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

    Hollmann, E. M.; Yu, J. H.; Doerner, R. P.

    2015-09-14

    The thermionic electron emission current emitted from a laser-produced hot spot on a tungsten target in weakly-ionized deuterium plasma is measured. It is found to be one to two orders of magnitude larger than expected for bipolar space charge limited thermionic emission current assuming an unperturbed background plasma. This difference is attributed to the plasma being modified by ionization of background neutrals by the emitted electrons. This result indicates that the allowable level of emitted thermionic electron current can be significantly enhanced in weakly-ionized plasmas due to the presence of large neutral densities.

  5. Heating of the solar chromosphere by ionization pumping

    NASA Technical Reports Server (NTRS)

    Lindsey, C. A.

    1981-01-01

    A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the dissipative mechanism, here referred to as ionization pumping, is hysteresis caused by irreversible relaxation of the chromospheric medium to ionization equilibrium following pressure perturbations. In the middle chromosphere, where hydrogen is partially ionized, it is shown that ionization pumping will cause strong dissipation of waves whose periods are 200s or less. This could cause heating of the chromosphere sufficient to compensate for the radiative losses. The mechanism retains a high efficiency for waves of arbitrarily small amplitude and, thus, can be more efficient than shock dissipation for small perturbations in pressure. The formation of shocks therefore is not required for the dissipation of waves whose periods are several minutes or less.

  6. The Effects of Ionizing Radiation on the Oral Cavity.

    PubMed

    de Barros da Cunha, Sandra Ribeiro; Ramos, Pedro Augusto Mendes; Nesrallah, Ana Cristina Aló; Parahyba, Cláudia Joffily; Fregnani, Eduardo Rodrigues; Aranha, Ana Cecília Corrêa

    2015-08-01

    The aim of this study is to present a literature review on the effects of the ionizing radiation from radiotherapy treatment on dental tissues. Among the effects of increasing global life expectancy and longevity of the teeth in the oral cavity, increasing rates of neoplastic diseases have been observed. One of the important treatment modalities for head and neck neoplastic diseases is radiotherapy, which uses ionizing radiation as the main mechanism of action. Therefore, it is essential for dentists to be aware of the changes in oral and dental tissues caused by ionizing radiation, and to develop treatment and prevention strategies. In general, there is still controversy about the effects of ionizing radiation on dental structures. However, qualitative and quantitative changes in saliva and oral microbiota, presence of oral mucositis and radiation-related caries are expected, as they represent the well-known side effects of treatment with ionizing radiation. Points that still remain unclear are the effects of radiotherapy on enamel and dentin, and on their mechanisms of bonding to contemporary adhesive materials. Ionizing radiation has shown important interaction with organic tissues, since more deleterious effects have been shown on the oral mucosa, salivary glands and dentin, than on enamel. With the increasing number of patients with cancer seeking dental treatment before and after head and neck radiotherapy, it is important for dentists to be aware of the effects of ionizing radiation on the oral cavity.

  7. Electrodynamic balance-mass spectrometry of single particles as a new platform for atmospheric chemistry research

    NASA Astrophysics Data System (ADS)

    Birdsall, Adam W.; Krieger, Ulrich K.; Keutsch, Frank N.

    2018-01-01

    New analytical techniques are needed to improve our understanding of the intertwined physical and chemical processes that affect the composition of aerosol particles in the Earth's atmosphere, such as gas-particle partitioning and homogenous or heterogeneous chemistry, and their ultimate relation to air quality and climate. We describe a new laboratory setup that couples an electrodynamic balance (EDB) to a mass spectrometer (MS). The EDB stores a single laboratory-generated particle in an electric field under atmospheric conditions for an arbitrarily long length of time. The particle is then transferred via gas flow to an ionization region that vaporizes and ionizes the analyte molecules before MS measurement. We demonstrate the feasibility of the technique by tracking evaporation of polyethylene glycol molecules and finding agreement with a kinetic model. Fitting data to the kinetic model also allows determination of vapor pressures to within a factor of 2. This EDB-MS system can be used to study fundamental chemical and physical processes involving particles that are difficult to isolate and study with other techniques. The results of such measurements can be used to improve our understanding of atmospheric particles.

  8. Lattice Boltzmann method for weakly ionized isothermal plasmas

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

    Li Huayu; Ki, Hyungson

    2007-12-15

    In this paper, a lattice Boltzmann method (LBM) for weakly ionized isothermal plasmas is presented by introducing a rescaling scheme for the Boltzmann transport equation. Without using this rescaling, we found that the nondimensional relaxation time used in the LBM is too large and the LBM does not produce physically realistic results. The developed model was applied to the electrostatic wave problem and the diffusion process of singly ionized helium plasmas with a 1-3% degree of ionization under an electric field. The obtained results agree well with theoretical values.

  9. Field ionizing elements and applications thereof

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2003-01-01

    A field ionizing element formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. The membrane includes a supporting portion, and a non supporting portion where the ions are formed. The membrane may be used as the front end for a number of different applications including a mass spectrometer, a thruster, an ion mobility element, or an electrochemical device such as a fuel cell.

  10. Polycyclic Aromatic Hydrocarbon Ionization Energy Lowering in Water Ices

    NASA Technical Reports Server (NTRS)

    Gudipati, Murthy S.; Allamandola, Louis J.

    2004-01-01

    In studying various interstellar and solar system ice analogs, we have recently found that upon vacuum ultraviolet photolysis, polycyclic aromatic hydrocarbons (PAHs) frozen in water ice at low temperatures are easily ionized and indefinitely stabilized as trapped ions (Gudipati; Gudipati & Allamandola). Here we report the first experimental study that shows that PAH ionization energy is significantly lowered in PAH/H2O ices, in agreement with recent theoretical work (Woon & Park). The ionization energy (IE) of the PAH studied here, quaterrylene (C40H20, IE = 6.11 eV), is lowered by up to 2.11 eV in water ice. PAH ionization energy reduction in low-temperature water ice substantially expands the astronomical regions in which trapped ions and electrons may be important. This reduction in ionization energy should also hold for other types of trapped species in waterrich interstellar, circumstellar, and solar system ices. Subject headings: ISM: clouds - methods: laboratory - molecular processes - radiation mechanisms: nonthermal -ultraviolet: ISM - ultraviolet: solar system

  11. Two-color ionization injection using a plasma beatwave accelerator

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

    Schroeder, C. B.; Benedetti, C.; Esarey, E.

    Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

  12. Renormalization group method based on the ionization energy theory

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

    Arulsamy, Andrew Das, E-mail: sadwerdna@gmail.com; School of Physics, University of Sydney, Sydney, New South Wales 2006

    2011-03-15

    Proofs are developed to explicitly show that the ionization energy theory is a renormalized theory, which mathematically exactly satisfies the renormalization group formalisms developed by Gell-Mann-Low, Shankar and Zinn-Justin. However, the cutoff parameter for the ionization energy theory relies on the energy-level spacing, instead of lattice point spacing in k-space. Subsequently, we apply the earlier proofs to prove that the mathematical structure of the ionization-energy dressed electron-electron screened Coulomb potential is exactly the same as the ionization-energy dressed electron-phonon interaction potential. The latter proof is proven by means of the second-order time-independent perturbation theory with the heavier effective mass condition,more » as required by the electron-electron screened Coulomb potential. The outcome of this proof is that we can derive the heat capacity and the Debye frequency as a function of ionization energy, which can be applied in strongly correlated matter and nanostructures.« less

  13. Two-color ionization injection using a plasma beatwave accelerator

    DOE PAGES

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; ...

    2018-01-10

    Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

  14. Soft ionization device with characterization systems and methods of manufacture

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2004-01-01

    Various configurations of characterization systems such as ion mobility spectrometers and mass spectrometers are disclosed that are coupled to an ionization device. The ionization device is formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. Small voltages across the electrodes generate large electric fields which act to ionize substantially all molecules passing therethrough without fracture. Methods to manufacture the mass spectrometer and ion mobility spectrometer systems are also described.

  15. Quantitative Method to Investigate the Balance between Metabolism and Proteome Biomass: Starting from Glycine.

    PubMed

    Gu, Haiwei; Carroll, Patrick A; Du, Jianhai; Zhu, Jiangjiang; Neto, Fausto Carnevale; Eisenman, Robert N; Raftery, Daniel

    2016-12-12

    The balance between metabolism and biomass is very important in biological systems; however, to date there has been no quantitative method to characterize the balance. In this methodological study, we propose to use the distribution of amino acids in different domains to investigate this balance. It is well known that endogenous or exogenous amino acids in a biological system are either metabolized or incorporated into free amino acids (FAAs) or proteome amino acids (PAAs). Using glycine (Gly) as an example, we demonstrate a novel method to accurately determine the amounts of amino acids in various domains using serum, urine, and cell samples. As expected, serum and urine had very different distributions of FAA- and PAA-Gly. Using Tet21N human neuroblastoma cells, we also found that Myc(oncogene)-induced metabolic reprogramming included a higher rate of metabolizing Gly, which provides additional evidence that the metabolism of proliferating cells is adapted to facilitate producing new cells. It is therefore anticipated that our method will be very valuable for further studies of the metabolism and biomass balance that will lead to a better understanding of human cancers. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Covalent organic framework as efficient desorption/ionization matrix for direct detection of small molecules by laser desorption/ionization mass spectrometry.

    PubMed

    Feng, Dan; Xia, Yan

    2018-07-19

    Covalent organic framework (COF) was explored as a novel matrix with a high desorption/ionization efficiency for direct detection of small molecules by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS). By using COF as an LDI MS matrix, we could detect not only biological micro molecules such as amino acids and fatty acids, but also emerging environmental pollutants like bisphenol S (BPS) and pyrene. With COF as the matrix, higher desorption/ionization efficiency, and less background interference were achieved than the conventional organic matrices. Good salt tolerance (as high as 500 mM NaCl) and repeatability allowed the detection limit of amino acids was 90 fmol. In addition, COF matrix performed well for amino acids analysis in the honey sample. The ionization mechanism was also discussed. These results demonstrate that COF is a powerful matrix for small molecules analysis in real samples by MS. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. High-resolution liquid chromatography/electrospray ionization time-of-flight mass spectrometry combined with liquid chromatography/electrospray ionization tandem mass spectrometry to identify polyphenols from grape antioxidant dietary fiber.

    PubMed

    Touriño, Sonia; Fuguet, Elisabet; Jáuregui, Olga; Saura-Calixto, Fulgencio; Cascante, Marta; Torres, Josep Lluís

    2008-11-01

    Grape antioxidant dietary fiber (GADF) is a dietary supplement that combines the benefits of both fiber and antioxidants that help prevent cancer and cardiovascular diseases. The antioxidant polyphenolic components in GADF probably help prevent cancer in the digestive tract, where they are bioavailable. Mass spectrometry coupled to liquid chromatography is a powerful tool for the analysis of complex plant derivatives such as GADF. We use a combination of MS techniques, namely liquid chromatography/electrospray ionization time-of-flight mass spectrometry (LC/ESI-TOF-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) on a triple quadrupole, for the identification of the polyphenolic constituents of the soluble fraction of GADF. First, we separated the mixture into four fractions which were tested for phenolic constituents using the TOF system in the full scan mode. The high sensitivity and resolution of the TOF detector over the triple quadrupole facilitate the preliminary characterization of the fractions. Then we used LC/ESI-MS/MS to identify the individual phenols through MS/MS experiments (product ion scan, neutral loss scan, precursor ion scan). Finally, most of the identities were unequivocally confirmed by accurate mass measurements on the TOF spectrometer. LC/ESI-TOF-MS combined with MS/MS correctly identifies the bioactive polyphenolic components from the soluble fraction of GADF. High-resolution TOF-MS is particularly useful for identifying the structure of compounds with the same LC/ESI-MS/MS fragmentation patterns.

  18. Role of body-worn movement monitor technology for balance and gait rehabilitation.

    PubMed

    Horak, Fay; King, Laurie; Mancini, Martina

    2015-03-01

    This perspective article will discuss the potential role of body-worn movement monitors for balance and gait assessment and treatment in rehabilitation. Recent advances in inexpensive, wireless sensor technology and smart devices are resulting in an explosion of miniature, portable sensors that can quickly and accurately quantify body motion. Practical and useful movement monitoring systems are now becoming available. It is critical that therapists understand the potential advantages and limitations of such emerging technology. One important advantage of obtaining objective measures of balance and gait from body-worn sensors is impairment-level metrics characterizing how and why functional performance of balance and gait activities are impaired. Therapy can then be focused on the specific physiological reasons for difficulty in walking or balancing during specific tasks. A second advantage of using technology to measure balance and gait behavior is the increased sensitivity of the balance and gait measures to document mild disability and change with rehabilitation. A third advantage of measuring movement, such as postural sway and gait characteristics, with body-worn sensors is the opportunity for immediate biofeedback provided to patients that can focus attention and enhance performance. In the future, body-worn sensors may allow therapists to perform telerehabilitation to monitor compliance with home exercise programs and the quality of their natural mobility in the community. Therapists need technological systems that are quick to use and provide actionable information and useful reports for their patients and referring physicians. Therapists should look for systems that provide measures that have been validated with respect to gold standard accuracy and to clinically relevant outcomes such as fall risk and severity of disability. © 2015 American Physical Therapy Association.

  19. Role of Body-Worn Movement Monitor Technology for Balance and Gait Rehabilitation

    PubMed Central

    King, Laurie; Mancini, Martina

    2015-01-01

    This perspective article will discuss the potential role of body-worn movement monitors for balance and gait assessment and treatment in rehabilitation. Recent advances in inexpensive, wireless sensor technology and smart devices are resulting in an explosion of miniature, portable sensors that can quickly and accurately quantify body motion. Practical and useful movement monitoring systems are now becoming available. It is critical that therapists understand the potential advantages and limitations of such emerging technology. One important advantage of obtaining objective measures of balance and gait from body-worn sensors is impairment-level metrics characterizing how and why functional performance of balance and gait activities are impaired. Therapy can then be focused on the specific physiological reasons for difficulty in walking or balancing during specific tasks. A second advantage of using technology to measure balance and gait behavior is the increased sensitivity of the balance and gait measures to document mild disability and change with rehabilitation. A third advantage of measuring movement, such as postural sway and gait characteristics, with body-worn sensors is the opportunity for immediate biofeedback provided to patients that can focus attention and enhance performance. In the future, body-worn sensors may allow therapists to perform telerehabilitation to monitor compliance with home exercise programs and the quality of their natural mobility in the community. Therapists need technological systems that are quick to use and provide actionable information and useful reports for their patients and referring physicians. Therapists should look for systems that provide measures that have been validated with respect to gold standard accuracy and to clinically relevant outcomes such as fall risk and severity of disability. PMID:25504484

  20. Photoelectron circular dichroism in the multiphoton ionization by short laser pulses. II. Three- and four-photon ionization of fenchone and camphor.

    PubMed

    Müller, Anne D; Artemyev, Anton N; Demekhin, Philipp V

    2018-06-07

    Angle-resolved multiphoton ionization of fenchone and camphor by short intense laser pulses is computed by the time-dependent single center method. Thereby, the photoelectron circular dichroism (PECD) in the three-photon resonance enhanced ionization and four-photon above-threshold ionization of these molecules is investigated in detail. The computational results are in satisfactory agreement with the available experimental data, measured for randomly oriented fenchone and camphor molecules at different wavelengths of the exciting pulses. We predict a significant enhancement of the multiphoton PECD for uniaxially oriented fenchone and camphor.

  1. Photoelectron circular dichroism in the multiphoton ionization by short laser pulses. II. Three- and four-photon ionization of fenchone and camphor

    NASA Astrophysics Data System (ADS)

    Müller, Anne D.; Artemyev, Anton N.; Demekhin, Philipp V.

    2018-06-01

    Angle-resolved multiphoton ionization of fenchone and camphor by short intense laser pulses is computed by the time-dependent single center method. Thereby, the photoelectron circular dichroism (PECD) in the three-photon resonance enhanced ionization and four-photon above-threshold ionization of these molecules is investigated in detail. The computational results are in satisfactory agreement with the available experimental data, measured for randomly oriented fenchone and camphor molecules at different wavelengths of the exciting pulses. We predict a significant enhancement of the multiphoton PECD for uniaxially oriented fenchone and camphor.

  2. Skylab water balance analysis

    NASA Technical Reports Server (NTRS)

    Leonard, J. I.

    1977-01-01

    The water balance of the Skylab crew was analyzed. Evaporative water loss using a whole body input/output balance equation, water, body tissue, and energy balance was analyzed. The approach utilizes the results of several major Skylab medical experiments. Subsystems were designed for the use of the software necessary for the analysis. A partitional water balance that graphically depicts the changes due to water intake is presented. The energy balance analysis determines the net available energy to the individual crewman during any period. The balances produce a visual description of the total change of a particular body component during the course of the mission. The information is salvaged from metabolic balance data if certain techniques are used to reduce errors inherent in the balance method.

  3. Amount of balance necessary for the independence of transfer and stair-climbing in stroke inpatients.

    PubMed

    Fujita, Takaaki; Sato, Atsushi; Ohashi, Yuji; Nishiyama, Kazutaka; Ohashi, Takuro; Yamane, Kazuhiro; Yamamoto, Yuichi; Tsuchiya, Kenji; Otsuki, Koji; Tozato, Fusae

    2018-05-01

    The purpose of this study was to clarify the amount of balance necessary for the independence of transfer and stair-climbing in stroke patients. This study included 111 stroke inpatients. Simple and multiple regression analyses were conducted to establish the association between the FIM ® instrument scores for transfer or stair-climbing and Berg Balance Scale. Furthermore, receiver operating characteristic curves were used to elucidate the amount of balance necessary for the independence of transfer and stair-climbing. Simple and multiple regression analyses showed that the FIM ® instrument scores for transfer and stair-climbing were strongly associated with Berg Balance Scale. On comparison of the independent and supervision-dependent groups, Berg Balance Scale cut-off values for transfer and stair-climbing were 41/40 and 54/53 points, respectively. On comparison of the independent-supervision and dependent groups, the cut-off values for transfer and stair-climbing were 30/29 and 41/40 points, respectively. The calculated cut-off values indicated the amount of balance necessary for the independence of transfer and stair-climbing, with and without supervision, in stroke patients. Berg Balance Scale has a good discriminatory ability and cut-off values are clinically useful to determine the appropriate independence levels of transfer and stair-climbing in hospital wards. Implications for rehabilitation The Berg Balance Scale's (BBS) strong association with transfer and stair-climbing independence and performance indicates that establishing cut-off values is vitally important for the established use of the BBS clinically. The cut-off values calculated herein accurately demonstrate the level of balance necessary for transfer and stair-climbing independence, with and without supervision, in stroke patients. These criteria should be employed clinically for determining the level of independence for transfer and stair-climbing as well as for setting balance training

  4. A balancing act: physical balance, through arousal, influences size perception.

    PubMed

    Geuss, Michael N; Stefanucci, Jeanine K; de Benedictis-Kessner, Justin; Stevens, Nicholas R

    2010-10-01

    Previous research has demonstrated that manipulating vision influences balance. Here, we question whether manipulating balance can influence vision and how it may influence vision--specifically, the perception of width. In Experiment 1, participants estimated the width of beams while balanced and unbalanced. When unbalanced, participants judged the widths to be smaller. One possible explanation is that unbalanced participants did not view the stimulus as long as when balanced because they were focused on remaining balanced. In Experiment 2, we tested this notion by limiting viewing time. Experiment 2 replicated the findings of Experiment 1, but viewing time had no effect on width judgments. In Experiment 3, participants' level of arousal was manipulated, because the balancing task likely produced arousal. While jogging, participants judged the beams to be smaller. In Experiment 4, participants completed another arousing task (counting backward by sevens) that did not involve movement. Again, participants judged the beams to be smaller when aroused. Experiment 5A raised participants' level of arousal before estimating the board widths (to control for potential dual-task effects) and showed that heightened arousal still influenced perceived width of the boards. Collectively, heightened levels of arousal, caused by multiple manipulations (including balance), influenced perceived width.

  5. An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability.

    PubMed

    Cruise, Denise R; Chagdes, James R; Liddy, Joshua J; Rietdyk, Shirley; Haddad, Jeffrey M; Zelaznik, Howard N; Raman, Arvind

    2017-07-26

    Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Wii Fit Balance Board Playing Improves Balance and Gait in Parkinson Disease

    PubMed Central

    Mhatre, Priya V.; Vilares, Iris; Stibb, Stacy M.; Albert, Mark V.; Pickering, Laura; Marciniak, Christina M.; Kording, Konrad; Toledo, Santiago

    2014-01-01

    Objective To assess the effect of exercise training by using the Nintendo Wii Fit video game and balance board system on balance and gait in adults with Parkinson disease (PD). Design A prospective interventional cohort study. Setting An outpatient group exercise class. Participants Ten subjects with PD, Hoehn and Yahr stages 2.5 or 3, with a mean age of 67.1 years; 4 men, 6 women. Interventions The subjects participated in supervised group exercise sessions 3 times per week for 8 weeks by practicing 3 different Wii balance board games (marble tracking, skiing, and bubble rafting) adjusted for their individualized function level. The subjects trained for 10 minutes per game, a total of 30 minutes training per session. Main Outcome Measurements Pre-and postexercise training, a physical therapist evaluated subjects’ function by using the Berg Balance Scale, Dynamic Gait Index, and Sharpened Romberg with eyes open and closed. Postural sway was assessed at rest and with tracking tasks by using the Wii balance board. The subjects rated their confidence in balance by using the Activities-specific Balance Confidence scale and depression on the Geriatric Depression Scale. Results Balance as measured by the Berg Balance Scale improved significantly, with an increase of 3.3 points (P = .016). The Dynamic Gait Index improved as well (mean increase, 2.8; P = .004), as did postural sway measured with the balance board (decreased variance in stance with eyes open by 31%; P = .049). Although the Sharpened Romberg with eyes closed increased by 6.85 points and with eyes opened by 3.3 points, improvements neared significance only for eyes closed (P = .07 versus P = .188). There were no significant changes on patient ratings for the Activities-specific Balance Confidence (mean decrease, −1%; P = .922) or the Geriatric Depression Scale (mean increase, 2.2; P = .188). Conclusions An 8-week exercise training class by using the Wii Fit balance board improved selective measures of

  7. Basic poly(propylene glycols) as reference compounds for internal mass calibration in positive-ion matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Gross, Jürgen H

    2017-12-01

    Basic poly(propylene glycols), commercially available under the trade name Jeffamine, are evaluated for their potential use as internal mass calibrants in matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry. Due to their basic amino endgroups Jeffamines are expected to deliver [M+H] + ions in higher yields than neutral poly(propylene glycols) or poly(ethylene glycols). Aiming at accurate mass measurements and molecular formula determinations by matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry, four Jeffamines (M-600, M-2005, D-400, D-230) were thus compared. As a result, Jeffamine M-2005 is introduced as a new mass calibrant for positive-ion matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry in the range of m/z 200-1200 and the reference mass list is provided. While Jeffamine M-2005 is compatible with α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid, and 2-[(2 E)-3-(4- tert-butylphenyl)-2-methylprop-2-enylidene]malonitrile matrix, its use in combination with 2-[(2 E)-3-(4- tert-butylphenyl)-2-methylprop-2-enylidene]malonitrile provides best results due to low laser fluence requirements. Applications to PEG 300, PEG 600, the ionic liquid trihexyl(tetradecyl)-phosphonium tris(pentafluoroethyl)-trifluorophosphate, and [60]fullerene demonstrate mass accuracies of 2-5 ppm.

  8. Systems and methods for cylindrical hall thrusters with independently controllable ionization and acceleration stages

    DOEpatents

    Diamant, Kevin David; Raitses, Yevgeny; Fisch, Nathaniel Joseph

    2014-05-13

    Systems and methods may be provided for cylindrical Hall thrusters with independently controllable ionization and acceleration stages. The systems and methods may include a cylindrical channel having a center axial direction, a gas inlet for directing ionizable gas to an ionization section of the cylindrical channel, an ionization device that ionizes at least a portion of the ionizable gas within the ionization section to generate ionized gas, and an acceleration device distinct from the ionization device. The acceleration device may provide an axial electric field for an acceleration section of the cylindrical channel to accelerate the ionized gas through the acceleration section, where the axial electric field has an axial direction in relation to the center axial direction. The ionization section and the acceleration section of the cylindrical channel may be substantially non-overlapping.

  9. Experimental Evaluation of Balance Prediction Models for Sit-to-Stand Movement in the Sagittal Plane

    PubMed Central

    Pena Cabra, Oscar David; Watanabe, Takashi

    2013-01-01

    Evaluation of balance control ability would become important in the rehabilitation training. In this paper, in order to make clear usefulness and limitation of a traditional simple inverted pendulum model in balance prediction in sit-to-stand movements, the traditional simple model was compared to an inertia (rotational radius) variable inverted pendulum model including multiple-joint influence in the balance predictions. The predictions were tested upon experimentation with six healthy subjects. The evaluation showed that the multiple-joint influence model is more accurate in predicting balance under demanding sit-to-stand conditions. On the other hand, the evaluation also showed that the traditionally used simple inverted pendulum model is still reliable in predicting balance during sit-to-stand movement under non-demanding (normal) condition. Especially, the simple model was shown to be effective for sit-to-stand movements with low center of mass velocity at the seat-off. Moreover, almost all trajectories under the normal condition seemed to follow the same control strategy, in which the subjects used extra energy than the minimum one necessary for standing up. This suggests that the safety considerations come first than the energy efficiency considerations during a sit to stand, since the most energy efficient trajectory is close to the backward fall boundary. PMID:24187580

  10. Polarization-balanced beamsplitter

    DOEpatents

    Decker, D.E.

    1998-02-17

    A beamsplitter assembly is disclosed that includes several beamsplitter cubes arranged to define a plurality of polarization-balanced light paths. Each polarization-balanced light path contains one or more balanced pairs of light paths, where each balanced pair of light paths includes either two transmission light paths with orthogonal polarization effects or two reflection light paths with orthogonal polarization effects. The orthogonal pairing of said transmission and reflection light paths cancels polarization effects otherwise caused by beamsplitting. 10 figs.

  11. NON-EQUILIBRIUM HELIUM IONIZATION IN AN MHD SIMULATION OF THE SOLAR ATMOSPHERE

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

    Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit, E-mail: thomas.golding@astro.uio.no, E-mail: mats.carlsson@astro.uio.no, E-mail: jorrit.leenaarts@astro.su.se

    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 thermodynamicmore » 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.« less

  12. Near-Threshold Ionization of Argon by Positron Impact

    NASA Astrophysics Data System (ADS)

    Babij, T. J.; Machacek, J. R.; Murtagh, D. J.; Buckman, S. J.; Sullivan, J. P.

    2018-03-01

    The direct single-ionization cross section for Ar by positron impact has been measured in the region above the first ionization threshold. These measurements are compared to semiclassical calculations which give rise to a power law variation of the cross section in the threshold region. The experimental results appear to be in disagreement with extensions to the Wannier theory applied to positron impact ionization, with a smaller exponent than that calculated by most previous works. In fact, in this work, we see no difference in threshold behavior between the positron and electron cases. Possible reasons for this discrepancy are discussed.

  13. Coupled-cluster treatment of molecular strong-field ionization

    NASA Astrophysics Data System (ADS)

    Jagau, Thomas-C.

    2018-05-01

    Ionization rates and Stark shifts of H2, CO, O2, H2O, and CH4 in static electric fields have been computed with coupled-cluster methods in a basis set of atom-centered Gaussian functions with a complex-scaled exponent. Consideration of electron correlation is found to be of great importance even for a qualitatively correct description of the dependence of ionization rates and Stark shifts on the strength and orientation of the external field. The analysis of the second moments of the molecular charge distribution suggests a simple criterion for distinguishing tunnel and barrier suppression ionization in polyatomic molecules.

  14. Metal-cluster ionization energy: A profile-insensitive exact expression for the size effect

    NASA Astrophysics Data System (ADS)

    Seidl, Michael; Perdew, John P.; Brajczewska, Marta; Fiolhais, Carlos

    1997-05-01

    The ionization energy of a large spherical metal cluster of radius R is I(R)=W+(+c)/R, where W is the bulk work function and c~-0.1 is a material-dependent quantum correction to the electrostatic size effect. We present 'Koopmans' and 'displaced-profile change-in-self-consistent-field' expressions for W and c within the ordinary and stabilized-jellium models. These expressions are shown to be exact and equivalent when the exact density profile of a large neutral cluster is employed; these equivalences generalize the Budd-Vannimenus theorem. With an approximate profile obtained from a restricted variational calculation, the 'displaced-profile' expressions are the more accurate ones. This profile insensitivity is important, because it is not practical to extract c from solutions of the Kohn-Sham equations for small metal clusters.

  15. Gait and Balance Measures Can Identify Change From a Cerebrospinal Fluid Tap Test in Idiopathic Normal Pressure Hydrocephalus.

    PubMed

    Gallagher, Ryan; Marquez, Jodie; Osmotherly, Peter

    2018-04-25

    To identify in patients with idiopathic normal pressure hydrocephalus (iNPH) undergoing a cerebrospinal fluid (CSF) tap test (TT) for consideration of a ventricular peritoneal (VP) shunt: (1) gait and balance measures, which identify symptom change; (2) differences present between pre- and post-CSF TT scores between patients classified as responders and nonresponder; (3) ability of patients with iNPH to accurately quantify change in their gait and balance symptoms from a CSF TT. Prospective observational study. Post-CSF TT assessment was completed 2-4 hours post. Tertiary referral neurological and neurosurgical hospital. Patients (N=74) with iNPH receiving a 30 mL CSF TT for consideration of a VP shunt. Patients underwent a battery of gait and balance measures pre- and post-CSF TT and indicated their perceived change on a global rating of change (GRC). Patients deemed to improve and offered VP shunt insertion by a neurologist or neurosurgeon were labeled responders. Performance oriented mobility assessment (Tinetti), Berg Balance Scale (BBS), timed Up and Go (TUG), 10-meter walk test (10MWT), GRC. Forty patients were classified responders, 34 nonresponders. Significant differences were identified for responders: Tinetti (3.88 points), TUG (3.98 seconds), 10MWT (0.08 m/sec), and BBS (5.29 points). Significant differences were found for nonresponders for the Tinetti (0.91 points) and BBS (2.06 points). Change scores for responders and nonresponders were significantly different for all tests between responders and nonresponders. GRC scores for gait (+2 for responders, 0 for nonresponders) and balance (+2.5 for responders, 0 for nonresponders) were both significantly different. The Tinetti, BBS, and TUG can identify change in patients undergoing a CSF TT for iNPH. Patients appear to be able to accurately identify if change has occurred. Copyright © 2018 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  16. Ionization pattern obtained in electrospray ionization or atmospheric pressure chemical ionization interfaces for authorized antidepressants in Romania

    NASA Astrophysics Data System (ADS)

    Grecu, Iulia; Ionicǎ, Mihai; Vlǎdescu, Marian; Truţǎ, Elena; Sultan, Carmen; Viscol, Oana; Horhotǎ, Luminiţa; Radu, Simona

    2016-12-01

    Antidepressants were found in 1950. In the 1990s there was a new generation of antidepressants. They act on the level of certain neurotransmitters extrasinpatic by its growth. After their mode of action antidepressants may be: SSRIs (Selective Serotonin Reuptake Inhibitors); (Serotonin-Norepinephrine Reuptake Inhibitors); SARIs (Serotonin Antagonist Reuptake Inhibitors); NRIs (Norepinephrine Reuptake Inhibitors); NDRIs (Norepinephrine-Dopamine Reuptake Inhibitors) NDRAs (Norepinephrine-Dopamine Releasing Agents); TCAs (Tricyclic Antidepressants); TeCAs (Tetracyclic Antidepressants); MAOIs (Monoamine Oxidase Inhibitors); agonist receptor 5-HT1A (5- hydroxytryptamine); antagonist receptor 5-HT2; SSREs (Selective Serotonin Reuptake Enhancers) and Sigma agonist receptor. To determine the presence of antidepressants in biological products, it has been used a system HPLC-MS (High Performance Liquid Chromatography - Mass Spectrometry) Varian 12001. The system is equipped with APCI (Atmospheric Pressure Chemical Ionization) or ESI (ElectroSpray Ionization) interface. To find antidepressants in unknown samples is necessary to recognize them after mass spectrum. Because the mass spectrum it is dependent on obtaining private parameters work of HPLC-MS system, and control interfaces, the mass spectra library was filled with the mass spectra of all approved antidepressants in Romania. The paper shows the mass spectra obtained in the HPLCMS system.

  17. Air density correction in ionization dosimetry.

    PubMed

    Christ, G; Dohm, O S; Schüle, E; Gaupp, S; Martin, M

    2004-05-21

    Air density must be taken into account when ionization dosimetry is performed with unsealed ionization chambers. The German dosimetry protocol DIN 6800-2 states an air density correction factor for which current barometric pressure and temperature and their reference values must be known. It also states that differences between air density and the attendant reference value, as well as changes in ionization chamber sensitivity, can be determined using a radioactive check source. Both methods have advantages and drawbacks which the paper discusses in detail. Barometric pressure at a given height above sea level can be determined by using a suitable barometer, or data downloaded from airport or weather service internet sites. The main focus of the paper is to show how barometric data from measurement or from the internet are correctly processed. Therefore the paper also provides all the requisite equations and terminological explanations. Computed and measured barometric pressure readings are compared, and long-term experience with air density correction factors obtained using both methods is described.

  18. Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance.

    PubMed

    Yang, Hong; Xing, Yangping; Xie, Ping; Ni, Leyi; Rong, Kewen

    2008-02-01

    Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO(2) and CH(4) causing a net release of CO(2) and CH(4) to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic lake, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 t, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO(2) and CH(4)) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange.

  19. Autoionizing resonances in electron-impact ionization of O5+ ions

    NASA Astrophysics Data System (ADS)

    Müller, A.; Teng, H.; Hofmann, G.; Phaneuf, R. A.; Salzborn, E.

    2000-12-01

    We report on a detailed experimental and theoretical study of electron-impact ionization of O5+ ions. A high-resolution scan measurement of the K-shell excitation threshold region has been performed with statistical uncertainties as low as 0.03%. At this level of precision a wealth of features in the cross section arising from indirect ionization processes becomes visible, and even interference of direct ionization with resonant-excitation/auto-double-ionization (READI) is clearly observed. The experimental results are compared with R-matrix calculations that include both direct and indirect processes in a unified way. Radiative damping of autoionizing Li-like states is found to be about 10-15 %. The calculations almost perfectly reproduce most of the experimental resonance features found in the present measurement including READI. They also agree with the direct-ionization converged close-coupling results of I. Bray [J. Phys. B 28, L247 (1995)] and the absolute total ionization cross section measurement of K. Rinn et al. [Phys. Rev. A 36, 595 (1987)].

  20. Coaching for Balance.

    ERIC Educational Resources Information Center

    Larson, Bonnie

    2001-01-01

    Discusses coaching for balance the integration of the whole self: physical (body), intellectual (mind), spiritual (soul), and emotional (heart). Offers four ways to identify problems and tell whether someone is out of balance and four coaching techniques for creating balance. (Contains 11 references.) (JOW)

  1. The Activity-Related Ionization in Carbonic Anhydrase

    PubMed Central

    Appleton, David W.; Sarkar, Bibudhendra

    1974-01-01

    The catalytic activity of carbonic anhydrase (EC 4.2.1.1) is linked to the ionization of a group in close proximity to the essential zinc ion. Studies have been undertaken to delineate the ionizations germane to the active-site chelate system. Several imidazole ligand systems were studied in order to approach a representative chelate. The simplest involved the complexation of Zn(II) by imidazole and by N-methylimidazole. As well, two bidentate systems, Zn(II)-4,4′-bis-imidazoylmethane and Co(II)-cyclic-L-histidyl-L-histidine were investigated. It was found that in a species containing metal-bound water and imidazole coordinated by means of the pyridinium nitrogen, the most acidic group was the pyrrole N-H in the imidazole ring. By the use of N-methylimidazole, the pKa of a metal-bound water molecule in a tri-imidazole ligand field was found to be 9.1. Noting the preference for labilization of the pyrrole hydrogen, the catalytic features of carbonic anhydrase are reexamined assuming that the pKenz is associated with the N-H ionization, and not with the ionization of metal-bound water. PMID:4209558

  2. Theory of electron-impact ionization of atoms

    NASA Astrophysics Data System (ADS)

    Kadyrov, A. S.; Mukhamedzhanov, A. M.; Stelbovics, A. T.; Bray, I.

    2004-12-01

    The existing formulations of electron-impact ionization of a hydrogenic target suffer from a number of formal problems including an ambiguous and phase-divergent definition of the ionization amplitude. An alternative formulation of the theory is given. An integral representation for the ionization amplitude which is free of ambiguity and divergence problems is derived and is shown to have four alternative, but equivalent, forms well suited for practical calculations. The extension to amplitudes of all possible scattering processes taking place in an arbitrary three-body system follows. A well-defined conventional post form of the breakup amplitude valid for arbitrary potentials including the long-range Coulomb interaction is given. Practical approaches are based on partial-wave expansions, so the formulation is also recast in terms of partial waves and partial-wave expansions of the asymptotic wave functions are presented. In particular, expansions of the asymptotic forms of the total scattering wave function, developed from both the initial and the final state, for electron-impact ionization of hydrogen are given. Finally, the utility of the present formulation is demonstrated on some well-known model problems.

  3. Fast Atom Ionization in Strong Electromagnetic Radiation

    NASA Astrophysics Data System (ADS)

    Apostol, M.

    2018-05-01

    The Goeppert-Mayer and Kramers-Henneberger transformations are examined for bound charges placed in electromagnetic radiation in the non-relativistic approximation. The consistent inclusion of the interaction with the radiation field provides the time evolution of the wavefunction with both structural interaction (which ensures the bound state) and electromagnetic interaction. It is shown that in a short time after switching on the high-intensity radiation the bound charges are set free. In these conditions, a statistical criterion is used to estimate the rate of atom ionization. The results correspond to a sudden application of the electromagnetic interaction, in contrast with the well-known ionization probability obtained by quasi-classical tunneling through classically unavailable non-stationary states, or other equivalent methods, where the interaction is introduced adiabatically. For low-intensity radiation the charges oscillate and emit higher-order harmonics, the charge configuration is re-arranged and the process is resumed. Tunneling ionization may appear in these circumstances. Extension of the approach to other applications involving radiation-induced charge emission from bound states is discussed, like ionization of molecules, atomic clusters or proton emission from atomic nuclei. Also, results for a static electric field are included.

  4. Chemical protection against ionizing radiation. Final report

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

    Livesey, J.C.; Reed, D.J.; Adamson, L.F.

    1984-08-01

    The scientific literature on radiation-protective drugs is reviewed. Emphasis is placed on the mechanisms involved in determining the sensitivity of biological material to ionizing radiation and mechanisms of chemical radioprotection. In Section I, the types of radiation are described and the effects of ionizing radiation on biological systems are reviewed. The effects of ionizing radiation are briefly contrasted with the effects of non-ionizing radiation. Section II reviews the contributions of various natural factors which influence the inherent radiosensitivity of biological systems. Inlcuded in the list of these factors are water, oxygen, thiols, vitamins and antioxidants. Brief attention is given tomore » the model describing competition between oxygen and natural radioprotective substances (principally, thiols) in determining the net cellular radiosensitivity. Several theories of the mechanism(s) of action of radioprotective drugs are described in Section III. These mechanisms include the production of hypoxia, detoxication of radiochemical reactive species, stabilization of the radiobiological target and the enhancement of damage repair processes. Section IV describes the current strategies for the treatment of radiation injury. Likely areas in which fruitful research might be performed are described in Section V. 495 references.« less

  5. Ionization Mechanism of Positive-Ion Nitrogen Direct Analysis in Real Time.

    PubMed

    Song, Liguo; Chuah, Wei Chean; Lu, Xinyi; Remsen, Edward; Bartmess, John E

    2018-04-01

    Nitrogen can be an inexpensive alternative to helium used by direct analysis in real time (DART), especially in consideration of the looming helium shortage. Therefore, the ionization mechanism of positive-ion N 2 DART has been systematically investigated. Our experiments suggest that a range of metastable nitrogen species with a variety of internal energies existed and all of them were less energetic than metastable helium atoms. However, compounds with ionization energies (IE) equal to or lower than 10.2 eV (all organic compounds except the extremely small ones) can be efficiently ionized. Because N 2 DART was unable to efficiently ionize ambient moisture and common organic solvents such as methanol and acetonitrile, the most important ionization mechanism was direct Penning ionization followed by self-protonation of polar compounds generating [M+H] + ions. On the other hand, N 2 DART was able to efficiently ionize ammonia, which was beneficial in the ionization of hydrogen-bonding compounds with proton affinities (PA) weaker than ammonia generating [M+NH 4 ] + ions and large PAHs generating [M+H] + ions through proton transfer. N 2 DART was also able to efficiently ionize NO, which led to the ionization of nonpolar compounds such as alkanes and small aromatics generating [M-(2m+1)H] + (m=0,1…) ions. Lastly, metastable nitrogen species was also able to produce oxygen atoms, which resulted in increased oxygen adducts as the polarity of organic compounds decreased. In comparison with He DART, N 2 DART was approximately one order of magnitude less sensitive in generating [M+H] + ions, but could be more sensitive in generating [M+NH 4 ] + ions. Graphical Abstract ᅟ.

  6. Ionization Mechanism of Positive-Ion Nitrogen Direct Analysis in Real Time

    NASA Astrophysics Data System (ADS)

    Song, Liguo; Chuah, Wei Chean; Lu, Xinyi; Remsen, Edward; Bartmess, John E.

    2018-02-01

    Nitrogen can be an inexpensive alternative to helium used by direct analysis in real time (DART), especially in consideration of the looming helium shortage. Therefore, the ionization mechanism of positive-ion N2 DART has been systematically investigated. Our experiments suggest that a range of metastable nitrogen species with a variety of internal energies existed and all of them were less energetic than metastable helium atoms. However, compounds with ionization energies (IE) equal to or lower than 10.2 eV (all organic compounds except the extremely small ones) can be efficiently ionized. Because N2 DART was unable to efficiently ionize ambient moisture and common organic solvents such as methanol and acetonitrile, the most important ionization mechanism was direct Penning ionization followed by self-protonation of polar compounds generating [M+H]+ ions. On the other hand, N2 DART was able to efficiently ionize ammonia, which was beneficial in the ionization of hydrogen-bonding compounds with proton affinities (PA) weaker than ammonia generating [M+NH4]+ ions and large PAHs generating [M+H]+ ions through proton transfer. N2 DART was also able to efficiently ionize NO, which led to the ionization of nonpolar compounds such as alkanes and small aromatics generating [M-(2m+1)H]+ (m=0,1…) ions. Lastly, metastable nitrogen species was also able to produce oxygen atoms, which resulted in increased oxygen adducts as the polarity of organic compounds decreased. In comparison with He DART, N2 DART was approximately one order of magnitude less sensitive in generating [M+H]+ ions, but could be more sensitive in generating [M+NH4]+ ions. [Figure not available: see fulltext.

  7. Chapter 6 Quantum Mechanical Methods for Loss-Excitation and Loss-Ionization in Fast Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Belkic, Dzevad

    quantum mechanical perturbation theories applied to electron loss collisions involving two hydrogen-like atoms. Both the one- and two-electron transitions (target unaffected by collision, as well as loss-ionization) are thoroughly examined in various intervals of impact energies varying from the threshold via the Massey peak to the Bethe asymptotic region. Systematics are established for the fast, simple, and accurate computations of cross sections for loss-excitation and loss-ionization accounting for the entire spectra of all four particles, including two free electrons and two free protons. The expounded algorithmic strategy of quantum mechanical methodologies is of great importance for wide applications to particle transport physics, especially in fusion research and hadron radiotherapy. This should advantageously replace the current overwhelming tendency in these fields for using phenomenological modeling with artificial functions extracted from fitting the existing experimental/theoretical data bases for cross sections.

  8. Increasing Polyaromatic Hydrocarbon (PAH) Molecular Coverage during Fossil Oil Analysis by Combining Gas Chromatography and Atmospheric-Pressure Laser Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

    PubMed Central

    Benigni, Paolo; DeBord, J. Daniel; Thompson, Christopher J.; Gardinali, Piero; Fernandez-Lima, Francisco

    2016-01-01

    Thousands of chemically distinct compounds are encountered in fossil oil samples that require rapid screening and accurate identification. In the present paper, we show for the first time, the advantages of gas chromatography (GC) separation in combination with atmospheric-pressure laser ionization (APLI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the screening of polyaromatic hydrocarbons (PAHs) in fossil oils. In particular, reference standards of organics in shale oil, petroleum crude oil, and heavy sweet crude oil were characterized by GC-APLI-FT-ICR MS and APLI-FT-ICR MS. Results showed that, while APLI increases the ionization efficiency of PAHs, when compared to other ionization sources, the complexity of the fossil oils reduces the probability of ionizing lower-concentration compounds during direct infusion. When gas chromatography precedes APLI-FT-ICR MS, an increase (more than 2-fold) in the ionization efficiency and an increase in the signal-to-noise ratio of lower-concentration fractions are observed, giving better molecular coverage in the m/z 100–450 range. That is, the use of GC prior to APLI-FT-ICR MS resulted in higher molecular coverage, higher sensitivity, and the ability to separate and characterize molecular isomers, while maintaining the ultrahigh resolution and mass accuracy of the FT-ICR MS separation. PMID:27212790

  9. How does ionizing radiation escape from galaxies?

    NASA Astrophysics Data System (ADS)

    Orlitova, Ivana

    2016-10-01

    Search for sources that reionized the Universe from z 15 to z 6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift 0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping: from the strongest starburst, from the galaxy edge, through a hole along our line-of-sight, through clumpy medium, or directly from all the production sites due to highly ionized medium in the entire galaxy. In parallel, we will test the predictive power of two highly debated indirect indicators of LyC leakage: the [OIII]5007/[OII]3727 ratio, and Lyman-alpha. We predict that their spatial distribution should closely follow that of the ionizing continuum if column densities of the neutral gas are low. This combined study, which relies on the HST unique capabilities, will bring crucial information on the structure of the leaking galaxies, provide constraints for hydrodynamic simulations, and will lead to efficient future searches for LyC leakers across a large range of redshifts.

  10. A new ring-shaped graphite monitor ionization chamber

    NASA Astrophysics Data System (ADS)

    Yoshizumi, M. T.; Caldas, L. V. E.

    2010-07-01

    A ring-shaped monitor ionization chamber was developed at the Instituto de Pesquisas Energéticas e Nucleares. This ionization chamber presents an entrance window of aluminized polyester foil. The guard ring and collecting electrode are made of graphite coated Lucite plates. The main difference between this new ionization chamber and commercial monitor chambers is its ring-shaped design. The new monitor chamber has a central hole, allowing the passage of the direct radiation beam without attenuation; only the penumbra radiation is measured by the sensitive volume. This kind of ionization chamber design has already been tested, but using aluminium electrodes. By changing the electrode material from aluminium to a graphite coating, an improvement in the chamber response stability was expected. The pre-operational tests, as saturation curve, recombination loss and polarity effect showed satisfactory results. The repeatability and the long-term stability tests were also evaluated, showing good agreement with international recommendations.

  11. Epicyclic helical channels for parametric resonance ionization cooling

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

    Johson, Rolland Paul; Derbenev, Yaroslav

    Proposed next-generation muon colliders will require major technical advances to achieve rapid muon beam cooling requirements. Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. In PIC, a half-integer parametric resonance causes strong focusing of a muon beam at appropriately placed energy absorbers while ionization cooling limits the beam’s angular spread. Combining muon ionization cooling with parametric resonant dynamics in this way should then allow much smaller final transverse muon beam sizes than conventional ionization cooling alone. One of the PIC challenges is compensation of beam aberrations over a sufficiently wide parametermore » range while maintaining the dynamical stability with correlated behavior of the horizontal and vertical betatron motion and dispersion. We explore use of a coupling resonance to reduce the dimensionality of the problem and to shift the dynamics away from non-linear resonances. PIC simulations are presented.« less

  12. Electron-Impact Ionization Cross Section Database

    National Institute of Standards and Technology Data Gateway

    SRD 107 Electron-Impact Ionization Cross Section Database (Web, free access)   This is a database primarily of total ionization cross sections of molecules by electron impact. The database also includes cross sections for a small number of atoms and energy distributions of ejected electrons for H, He, and H2. The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section. Selected experimental data are included.

  13. Ionization of Rydberg atoms colliding with a metal surface

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

    Sjakste, J.; Borisov, A. G.; Gauyacq, J. P.

    2006-04-15

    We report on a theoretical study of the ionization process of Xe* Rydberg atoms colliding with a metal surface, in the presence of an external electric field. The evolution of the Xe* outer electron is studied by a wave packet propagation approach, allowing to include all dynamical aspects of the collision, in particular nonadiabatic inter-Rydberg transitions. We investigate how the different Xe* Stark states formed in the external field couple together and ionize on the surface and how the different polarizations of the electronic cloud in the Xe* states are reflected in their ionization properties. We show that the presencemore » of the external electric field can significantly perturb the dynamics of the ionization process. Our results account for recent results from Dunning et al. [Nucl. Inst. Meth. B 203, 69 (2003)]. In particular, it is explained how the external electric field present in the experimental procedure of Dunning et al. leads to the apparent absence of a polarization effect in the ionization process.« less

  14. Phosphorus ionization in silicon doped by self-assembled macromolecular monolayers

    NASA Astrophysics Data System (ADS)

    Wu, Haigang; Li, Ke; Gao, Xuejiao; Dan, Yaping

    2017-10-01

    Individual dopant atoms can be potentially controlled at large scale by the self-assembly of macromolecular dopant carriers. However, low concentration phosphorus dopants often suffer from a low ionization rate due to defects and impurities introduced by the carrier molecules. In this work, we demonstrated a nitrogen-free macromolecule doping technique and investigated the phosphorus ionization process by low temperature Hall effect measurements. It was found that the phosphorus dopants diffused into the silicon bulk are in nearly full ionization. However, the electrons ionized from the phosphorus dopants are mostly trapped by deep level defects that are likely carbon interstitials.

  15. Cartesian Off-Body Grid Adaption for Viscous Time- Accurate Flow Simulation

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.; Pulliam, Thomas H.

    2011-01-01

    An improved solution adaption capability has been implemented in the OVERFLOW overset grid CFD code. Building on the Cartesian off-body approach inherent in OVERFLOW and the original adaptive refinement method developed by Meakin, the new scheme provides for automated creation of multiple levels of finer Cartesian grids. Refinement can be based on the undivided second-difference of the flow solution variables, or on a specific flow quantity such as vorticity. Coupled with load-balancing and an inmemory solution interpolation procedure, the adaption process provides very good performance for time-accurate simulations on parallel compute platforms. A method of using refined, thin body-fitted grids combined with adaption in the off-body grids is presented, which maximizes the part of the domain subject to adaption. Two- and three-dimensional examples are used to illustrate the effectiveness and performance of the adaption scheme.

  16. Work-life balance: history, costs, and budgeting for balance.

    PubMed

    Raja, Siva; Stein, Sharon L

    2014-06-01

    The concept and difficulties of work-life balance are not unique to surgeons, but professional responsibilities make maintaining a work-life balance difficult. Consequences of being exclusively career focused include burn out, physical, and mental ailments. In addition, physician burn out may hinder optimal patient care and incur significant costs on health care in general. Assessing current uses of time, allocating goals catered to an individual surgeon, and continual self-assessment may help balance time, and ideally will help prevent burn out.

  17. Wii Fit balance board playing improves balance and gait in Parkinson disease.

    PubMed

    Mhatre, Priya V; Vilares, Iris; Stibb, Stacy M; Albert, Mark V; Pickering, Laura; Marciniak, Christina M; Kording, Konrad; Toledo, Santiago

    2013-09-01

    To assess the effect of exercise training by using the Nintendo Wii Fit video game and balance board system on balance and gait in adults with Parkinson disease (PD). A prospective interventional cohort study. An outpatient group exercise class. Ten subjects with PD, Hoehn and Yahr stages 2.5 or 3, with a mean age of 67.1 years; 4 men, 6 women. The subjects participated in supervised group exercise sessions 3 times per week for 8 weeks by practicing 3 different Wii balance board games (marble tracking, skiing, and bubble rafting) adjusted for their individualized function level. The subjects trained for 10 minutes per game, a total of 30 minutes training per session. Pre-and postexercise training, a physical therapist evaluated subjects' function by using the Berg Balance Scale, Dynamic Gait Index, and Sharpened Romberg with eyes open and closed. Postural sway was assessed at rest and with tracking tasks by using the Wii balance board. The subjects rated their confidence in balance by using the Activities-specific Balance Confidence scale and depression on the Geriatric Depression Scale. Balance as measured by the Berg Balance Scale improved significantly, with an increase of 3.3 points (P = .016). The Dynamic Gait Index improved as well (mean increase, 2.8; P = .004), as did postural sway measured with the balance board (decreased variance in stance with eyes open by 31%; P = .049). Although the Sharpened Romberg with eyes closed increased by 6.85 points and with eyes opened by 3.3 points, improvements neared significance only for eyes closed (P = .07 versus P = .188). There were no significant changes on patient ratings for the Activities-specific Balance Confidence (mean decrease, -1%; P = .922) or the Geriatric Depression Scale (mean increase, 2.2; P = .188). An 8-week exercise training class by using the Wii Fit balance board improved selective measures of balance and gait in adults with PD. However, no significant changes were seen in mood or

  18. Differential Sensitivity Between a Virtual Reality Balance Module and Clinically Used Concussion Balance Modalities.

    PubMed

    Teel, Elizabeth F; Gay, Michael R; Arnett, Peter A; Slobounov, Semyon M

    2016-03-01

    Balance assessments are part of the recommended clinical concussion evaluation, along with computerized neuropsychological testing and self-reported symptoms checklists. New technology has allowed for the creation of virtual reality (VR) balance assessments to be used in concussion care, but there is little information on the sensitivity and specificity of these evaluations. The purpose of this study is to establish the sensitivity and specificity of a VR balance module for detecting lingering balance deficits clinical concussion care. Retrospective case-control study. Institutional research laboratory. Normal controls (n = 94) and concussed participants (n = 27). All participants completed a VR balance assessment paradigm. Concussed participants were diagnosed by a Certified Athletic Trainer or physician (with 48 hours postinjury) and tested in the laboratory between 7 and 10 days postinjury. Receiver operating characteristic curves were performed to establish the VR module's sensitivity and specificity for detecting lingering balance deficits. Final balance score. For the VR balance module, a cutoff score of 8.25 was established to maximize sensitivity at 85.7% and specificity at 87.8%. The VR balance module has high sensitivity and specificity for detecting subacute balance deficits after concussive injury. The VR balance has a high subacute sensitivity and specificity as a stand-alone balance assessment tool and may detect ongoing balance deficits not readily detectable by the Balance Error Scoring System or Sensory Organization Test. Virtual reality balance modules may be a beneficial addition to the current clinical concussion diagnostic battery.

  19. Ionization processes in combined high-voltage nanosecond - laser discharges in inert gas

    NASA Astrophysics Data System (ADS)

    Starikovskiy, Andrey; Shneider, Mikhail; PU Team

    2016-09-01

    Remote control of plasmas induced by laser radiation in the atmosphere is one of the challenging issues of free space communication, long-distance energy transmission, remote sensing of the atmosphere, and standoff detection of trace gases and bio-threat species. Sequences of laser pulses, as demonstrated by an extensive earlier work, offer an advantageous tool providing access to the control of air-plasma dynamics and optical interactions. The avalanche ionization induced in a pre-ionized region by infrared laser pulses where investigated. Pre-ionization was created by an ionization wave, initiated by high-voltage nanosecond pulse. Then, behind the front of ionization wave extra avalanche ionization was initiated by the focused infrared laser pulse. The experiment was carried out in argon. It is shown that the gas pre-ionization inhibits the laser spark generation under low pressure conditions.

  20. Real Time Monitoring of Containerless Microreactions in Acoustically Levitated Droplets via Ambient Ionization Mass Spectrometry.

    PubMed

    Crawford, Elizabeth A; Esen, Cemal; Volmer, Dietrich A

    2016-09-06

    Direct in-droplet (in stillo) microreaction monitoring using acoustically levitated micro droplets has been achieved by combining acoustic (ultrasonic) levitation for the first time with real time ambient tandem mass spectrometry (MS/MS). The acoustic levitation and inherent mixing of microliter volumes of reactants (3 μL droplets), yielding total reaction volumes of 6 μL, supported monitoring the acid-catalyzed degradation reaction of erythromycin A. This reaction was chosen to demonstrate the proof-of-principle of directly monitoring in stillo microreactions via hyphenated acoustic levitation and ambient ionization mass spectrometry. The microreactions took place completely in stillo over 30, 60, and 120 s within the containerless stable central pressure node of an acoustic levitator, thus readily promoting reaction miniaturization. For the evaluation of the miniaturized in stillo reactions, the degradation reactions were also carried out in vials (in vitro) with a total reaction volume of 400 μL. The reacted in vitro mixtures (6 μL total) were similarly introduced into the acoustic levitator prior to ambient ionization MS/MS analysis. The in stillo miniaturized reactions provided immediate real-time snap-shots of the degradation process for more accurate reaction monitoring and used a fraction of the reactants, while the larger scale in vitro reactions only yielded general reaction information.

  1. Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface mass balance of Saint-Sorlin Glacier (French Alps)

    NASA Astrophysics Data System (ADS)

    Réveillet, Marion; Six, Delphine; Vincent, Christian; Rabatel, Antoine; Dumont, Marie; Lafaysse, Matthieu; Morin, Samuel; Vionnet, Vincent; Litt, Maxime

    2018-04-01

    This study focuses on simulations of the seasonal and annual surface mass balance (SMB) of Saint-Sorlin Glacier (French Alps) for the period 1996-2015 using the detailed SURFEX/ISBA-Crocus snowpack model. The model is forced by SAFRAN meteorological reanalysis data, adjusted with automatic weather station (AWS) measurements to ensure that simulations of all the energy balance components, in particular turbulent fluxes, are accurately represented with respect to the measured energy balance. Results indicate good model performance for the simulation of summer SMB when using meteorological forcing adjusted with in situ measurements. Model performance however strongly decreases without in situ meteorological measurements. The sensitivity of the model to meteorological forcing indicates a strong sensitivity to wind speed, higher than the sensitivity to ice albedo. Compared to an empirical approach, the model exhibited better performance for simulations of snow and firn melting in the accumulation area and similar performance in the ablation area when forced with meteorological data adjusted with nearby AWS measurements. When such measurements were not available close to the glacier, the empirical model performed better. Our results suggest that simulations of the evolution of future mass balance using an energy balance model require very accurate meteorological data. Given the uncertainties in the temporal evolution of the relevant meteorological variables and glacier surface properties in the future, empirical approaches based on temperature and precipitation could be more appropriate for simulations of glaciers in the future.

  2. Load Balancing Using Time Series Analysis for Soft Real Time Systems with Statistically Periodic Loads

    NASA Technical Reports Server (NTRS)

    Hailperin, Max

    1993-01-01

    This thesis provides design and analysis of techniques for global load balancing on ensemble architectures running soft-real-time object-oriented applications with statistically periodic loads. It focuses on estimating the instantaneous average load over all the processing elements. The major contribution is the use of explicit stochastic process models for both the loading and the averaging itself. These models are exploited via statistical time-series analysis and Bayesian inference to provide improved average load estimates, and thus to facilitate global load balancing. This thesis explains the distributed algorithms used and provides some optimality results. It also describes the algorithms' implementation and gives performance results from simulation. These results show that our techniques allow more accurate estimation of the global system load ing, resulting in fewer object migration than local methods. Our method is shown to provide superior performance, relative not only to static load-balancing schemes but also to many adaptive methods.

  3. AN INITIAL EVALUATION OF THE BTRACKS BALANCE PLATE AND SPORTS BALANCE SOFTWARE FOR CONCUSSION DIAGNOSIS

    PubMed Central

    Manyak, Kristin A.; Abdenour, Thomas E.; Rauh, Mitchell J.; Baweja, Harsimran S.

    2016-01-01

    Background As recently dictated by the American Medical Society, balance testing is an important component in the clinical evaluation of concussion. Despite this, previous research on the efficacy of balance testing for concussion diagnosis suggests low sensitivity (∼30%), based primarily on the popular Balance Error Scoring System (BESS). The Balance Tracking System (BTrackS, Balance Tracking Systems Inc., San Diego, CA, USA) consists of a force plate (BTrackS Balance Plate) and software (BTrackS Sport Balance) which can quickly (<2 min) perform concussion balance testing with gold standard accuracy. Purpose The present study aimed to determine the sensitivity of the BTrackS Balance Plate and Sports Balance Software for concussion diagnosis. Study Design Cross-Sectional Study Methods Preseason baseline balance testing of 519 healthy Division I college athletes playing sports with a relatively high risk for concussions was performed with the BTrackS Balance Test. Testing was administered by certified athletic training staff using the BTrackS Balance Plate and Sport Balance software. Of the baselined athletes, 25 later experienced a concussion during the ensuing sport season. Post-injury balance testing was performed on these concussed athletes within 48 of injury and the sensitivity of the BTrackS Balance Plate and Sport Balance software was estimated based on the number of athletes showing a balance decline according to the criteria specified in the Sport Balance software. This criteria is based on the minimal detectable change statistic with a 90% confidence level (i.e. 90% specificity). Results Of 25 athletes who experienced concussions, 16 had balance declines relative to baseline testing results according to the BTrackS Sport Balance software criteria. This corresponds to an estimated concussion sensitivity of 64%, which is twice as great as that reported previously for the BESS. Conclusions The BTrackS Balance Plate and Sport Balance software has the

  4. Coupled molecular dynamics and continuum electrostatic method to compute the ionization pKa's of proteins as a function of pH. Test on a large set of proteins.

    PubMed

    Vorobjev, Yury N; Scheraga, Harold A; Vila, Jorge A

    2018-02-01

    A computational method, to predict the pKa values of the ionizable residues Asp, Glu, His, Tyr, and Lys of proteins, is presented here. Calculation of the electrostatic free-energy of the proteins is based on an efficient version of a continuum dielectric electrostatic model. The conformational flexibility of the protein is taken into account by carrying out molecular dynamics simulations of 10 ns in implicit water. The accuracy of the proposed method of calculation of pKa values is estimated from a test set of experimental pKa data for 297 ionizable residues from 34 proteins. The pKa-prediction test shows that, on average, 57, 86, and 95% of all predictions have an error lower than 0.5, 1.0, and 1.5 pKa units, respectively. This work contributes to our general understanding of the importance of protein flexibility for an accurate computation of pKa, providing critical insight about the significance of the multiple neutral states of acid and histidine residues for pKa-prediction, and may spur significant progress in our effort to develop a fast and accurate electrostatic-based method for pKa-predictions of proteins as a function of pH.

  5. Exergaming for balance training of elderly: state of the art and future developments

    PubMed Central

    2013-01-01

    Fall injuries are responsible for physical dysfunction, significant disability, and loss of independence among elderly. Poor postural control is one of the major risk factors for falling but can be trained in fall prevention programs. These however suffer from low therapy adherence, particularly if prevention is the goal. To provide a fun and motivating training environment for elderly, exercise games, or exergames, have been studied as balance training tools in the past years. The present paper reviews the effects of exergame training programs on postural control of elderly reported so far. Additionally we aim to provide an in-depth discussion of technologies and outcome measures utilized in exergame studies. Thirteen papers were included in the analysis. Most of the reviewed studies reported positive results with respect to improvements in balance ability after a training period, yet few reached significant levels. Outcome measures for quantification of postural control are under continuous dispute and no gold standard is present. Clinical measures used in the studies reviewed are well validated yet only give a global indication of balance ability. Instrumented measures were unable to detect small changes in balance ability as they are mainly based on calculating summary statistics, thereby ignoring the time-varying structure of the signals. Both methods only allow for measuring balance after the exergame intervention program. Current developments in sensor technology allow for accurate registration of movements and rapid analysis of signals. We propose to quantify the time-varying structure of postural control during gameplay using low-cost sensor systems. Continuous monitoring of balance ability leaves the user unaware of the measurements and allows for generating user-specific exergame training programs and feedback, both during one game and in timeframes of weeks or months. This approach is unique and unlocks the as of yet untapped potential of exergames as

  6. Exergaming for balance training of elderly: state of the art and future developments.

    PubMed

    van Diest, Mike; Lamoth, Claudine J C; Stegenga, Jan; Verkerke, Gijsbertus J; Postema, Klaas

    2013-09-25

    Fall injuries are responsible for physical dysfunction, significant disability, and loss of independence among elderly. Poor postural control is one of the major risk factors for falling but can be trained in fall prevention programs. These however suffer from low therapy adherence, particularly if prevention is the goal. To provide a fun and motivating training environment for elderly, exercise games, or exergames, have been studied as balance training tools in the past years. The present paper reviews the effects of exergame training programs on postural control of elderly reported so far. Additionally we aim to provide an in-depth discussion of technologies and outcome measures utilized in exergame studies. Thirteen papers were included in the analysis. Most of the reviewed studies reported positive results with respect to improvements in balance ability after a training period, yet few reached significant levels. Outcome measures for quantification of postural control are under continuous dispute and no gold standard is present. Clinical measures used in the studies reviewed are well validated yet only give a global indication of balance ability. Instrumented measures were unable to detect small changes in balance ability as they are mainly based on calculating summary statistics, thereby ignoring the time-varying structure of the signals. Both methods only allow for measuring balance after the exergame intervention program. Current developments in sensor technology allow for accurate registration of movements and rapid analysis of signals. We propose to quantify the time-varying structure of postural control during gameplay using low-cost sensor systems. Continuous monitoring of balance ability leaves the user unaware of the measurements and allows for generating user-specific exergame training programs and feedback, both during one game and in timeframes of weeks or months. This approach is unique and unlocks the as of yet untapped potential of exergames as

  7. Recent Advances in Bacteria Identification by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Using Nanomaterials as Affinity Probes

    PubMed Central

    Chiu, Tai-Chia

    2014-01-01

    Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided. PMID:24786089

  8. Capillary electrophoresis electrospray ionization mass spectrometry interface

    DOEpatents

    Smith, Richard D.; Severs, Joanne C.

    1999-01-01

    The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

  9. Oxidative Ionization Under Certain Negative-Ion Mass Spectrometric Conditions

    NASA Astrophysics Data System (ADS)

    Hassan, Isra; Pavlov, Julius; Errabelli, Ramu; Attygalle, Athula B.

    2017-02-01

    1,4-Hydroquinone and several other phenolic compounds generate (M - 2) -• radical-anions, rather than deprotonated molecules, under certain negative-ion mass spectrometric conditions. In fact, spectra generated under helium-plasma ionization (HePI) conditions from 1,4-hydroquinone and 1,4-benzoquinone (by electron capture) were practically indistinguishable. Because this process involves a net loss of H• and H+, it can be termed oxidative ionization. The superoxide radical-anion (O2 -•), known to be present in many atmospheric-pressure plasma ion sources operated in the negative mode, plays a critical role in the oxidative ionization process. The presence of a small peak at m/z 142 in the spectrum of 1,4-hydroquinone, but not in that of 1,4-benzoquinone, indicated that the initial step in the oxidative ionization process is the formation of an O2 -• adduct. On the other hand, under bona fide electrospray ionization (ESI) conditions, 1,4-hydroquinone generates predominantly an (M - 1) - ion. It is known that at sufficiently high capillary voltages, corona discharges begin to occur even in an ESI source. At lower ESI capillary voltages, deprotonation predominates; as the capillary voltage is raised, the abundance of O2 -• present in the plasma increases, and the source in turn increasingly behaves as a composite ESI/APCI source. While maintaining post-ionization ion activation to a minimum (to prevent fragmentation), and monitoring the relative intensities of the m/z 109 (due to deprotonation) and 108 (oxidative ionization) peaks recorded from 1,4-hydroquinone, a semiquantitative estimation of the APCI contribution to the overall ion-generation process can be obtained.

  10. Opportunities and Challenges in Enhancing Value of Annual Glacier Mass Balance Monitoring Examples from Western North America

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.

    2017-12-01

    Alpine glacier mass balance is the most accurate indicator of glacier response to climate and with retreat of alpine glaciers is one of the clearest signals of global climate change. Completion of long term, representative and homogenous mass balance field measurement of mass balance, compiled by WGMS, is a key climate data record. To ensure a monitoring program remains vital and funded local collaboration and connecting the research to local societal impacts is crucial. Working with local partners in collecting and providing the right data is critical whether their interest is in hydropower, irrigation, municipal supply, hazard reduction and/or aquatic ecosystems. The expansion of remote sensing and modeling capability provides both a challenge to continued relevance and an opportunity for field mass balance programs to expand relevance. In modelling studies of both glacier mass balance and glacier runoff transient balance data has equivalent value with annual balance data, for both calibration runs and as an input variable. This increases the utility of mid-season field observations. Remote sensing provides repeat imagery that often identifies the AAR and transient snowline of a glacier. For runoff assessment understanding the specific percent of glacier surface area that is glacier ice, older firn, and retained snowpack from the previous winter at frequent intervals during the melt season is vital since each region has a different melt factor. A denser field observation network combined with this imagery can provide additional point balance values of ablation that complement the mass balance record. Periodic measurement of mass balance at a denser network using GPR, LIDAR, TLS or probing is required to better understand long term point balance locations and is important at end of the melt season not just beginning, and has value mid-season for modelling. Applications of each of utility of field mass balance observations will be illustrated.

  11. Analysis of chirality by femtosecond laser ionization mass spectrometry.

    PubMed

    Horsch, Philipp; Urbasch, Gunter; Weitzel, Karl-Michael

    2012-09-01

    Recent progress in the field of chirality analysis employing laser ionization mass spectrometry is reviewed. Emphasis is given to femtosecond (fs) laser ionization work from the author's group. We begin by reviewing fundamental aspects of determining circular dichroism (CD) in fs-laser ionization mass spectrometry (fs-LIMS) discussing an example from the literature (resonant fs-LIMS of 3-methylcyclopentanone). Second, we present new data indicating CD in non-resonant fs-LIMS of propylene oxide. Copyright © 2012 Wiley Periodicals, Inc., A Wiley Company.

  12. Revised energy levels of singly ionized lanthanum

    NASA Astrophysics Data System (ADS)

    Güzelçimen, Feyza; Tonka, Mehdi; Uddin, Zaheer; Bhatti, Naveed Anjum; Windholz, Laurentius; Kröger, Sophie; Başar, Gönül

    2018-05-01

    Based on the experimental wavenumbers of 344 spectral lines from calibrated Fourier transform (FT) spectra as well as wavenumbers of 81 lines from the wavelength tables from literature, the energy of 115 fine structure levels of singly ionized lanthanum has been revised by weighted global fits. The classifications of the lines are provided by numerous previous investigations of lanthanum by different spectroscopic methods and authors. For the high accurate determination of the center of gravity wavenumbers from the experimental spectrum, the hyperfine constants of the involved levels have been taken into account, if possible. For the 94 levels with known hyperfine constants the accuracy of energy values is better than 0.01 cm-1. For 34 levels the magnetic dipole hyperfine constants A have been determined from FT spectra as part of this work. For four of these 34 levels even electric quadrupole hyperfine constants B could be estimated. For levels, which have experimentally unknown hyperfine constants and which are connected only by lines not found in the FT spectra but taken from literature, the uncertainties of energy values are about a factor of 10 higher. A list of all revised level energies together with a compilation of hyperfine structure data is given as well as a list of all lines used.

  13. Sensitivity of hot-cathode ionization vacuum gages in several gases

    NASA Technical Reports Server (NTRS)

    Holanda, R.

    1972-01-01

    Four hot-cathode ionization vacuum gages were calibrated in 12 gases. The relative sensitivities of these gages were compared to several gas properties. Ionization cross section was the physical property which correlated best with gage sensitivity. The effects of gage accelerating voltage and ionization-cross-section energy level were analyzed. Recommendations for predicting gage sensitivity according to gage type were made.

  14. Ground Levels and Ionization Energies for the Neutral Atoms

    National Institute of Standards and Technology Data Gateway

    SRD 111 Ground Levels and Ionization Energies for the Neutral Atoms (Web, free access)   Data for ground state electron configurations and ionization energies for the neutral atoms (Z = 1-104) including references.

  15. Reduced-order modeling for hyperthermia: an extended balanced-realization-based approach.

    PubMed

    Mattingly, M; Bailey, E A; Dutton, A W; Roemer, R B; Devasia, S

    1998-09-01

    Accurate thermal models are needed in hyperthermia cancer treatments for such tasks as actuator and sensor placement design, parameter estimation, and feedback temperature control. The complexity of the human body produces full-order models which are too large for effective execution of these tasks, making use of reduced-order models necessary. However, standard balanced-realization (SBR)-based model reduction techniques require a priori knowledge of the particular placement of actuators and sensors for model reduction. Since placement design is intractable (computationally) on the full-order models, SBR techniques must use ad hoc placements. To alleviate this problem, an extended balanced-realization (EBR)-based model-order reduction approach is presented. The new technique allows model order reduction to be performed over all possible placement designs and does not require ad hoc placement designs. It is shown that models obtained using the EBR method are more robust to intratreatment changes in the placement of the applied power field than those models obtained using the SBR method.

  16. Ionization studies in laser-excited alkaline-earth vapors.

    PubMed

    Hermann, J P; Wynne, J J

    1980-06-01

    We report on the time behavior of ionization signals produced by laser excitation of Ca and Ba atomic vapor to high-Rydberg states. A space-charge-limited thermionic diode detector shows a long-lived (>I-msec) ionization signal. However, optical detection of atomic ions (Ca+, Ba+) shows that these species live for much shorter times (<100 microsec). These results, in conjunction with published results on mass-spectrometric studies of high-density atomic beams, suggest that our ionization signal is primarily due to molecular species (Ca2+, Ba2+). We also observed optically pumped amplified spontaneous emission and stimulated electronic Raman scattering in Ca+ and Ba+.

  17. Work–Life Balance: History, Costs, and Budgeting for Balance

    PubMed Central

    Raja, Siva; Stein, Sharon L.

    2014-01-01

    The concept and difficulties of work–life balance are not unique to surgeons, but professional responsibilities make maintaining a work–life balance difficult. Consequences of being exclusively career focused include burn out, physical, and mental ailments. In addition, physician burn out may hinder optimal patient care and incur significant costs on health care in general. Assessing current uses of time, allocating goals catered to an individual surgeon, and continual self-assessment may help balance time, and ideally will help prevent burn out. PMID:25067921

  18. Ionizing radiation, ion transports, and radioresistance of cancer cells

    PubMed Central

    Huber, Stephan M.; Butz, Lena; Stegen, Benjamin; Klumpp, Dominik; Braun, Norbert; Ruth, Peter; Eckert, Franziska

    2013-01-01

    The standard treatment of many tumor entities comprises fractionated radiation therapy which applies ionizing radiation to the tumor-bearing target volume. Ionizing radiation causes double-strand breaks in the DNA backbone that result in cell death if the number of DNA double-strand breaks exceeds the DNA repair capacity of the tumor cell. Ionizing radiation reportedly does not only act on the DNA in the nucleus but also on the plasma membrane. In particular, ionizing radiation-induced modifications of ion channels and transporters have been reported. Importantly, these altered transports seem to contribute to the survival of the irradiated tumor cells. The present review article summarizes our current knowledge on the underlying mechanisms and introduces strategies to radiosensitize tumor cells by targeting plasma membrane ion transports. PMID:23966948

  19. Appearance of ionization instability in a low-voltage arc

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

    Kobelevskii, A.V.; Nastoyashchii, A.F.

    1986-09-01

    The conditions for the appearance of the ionization instability in a low-voltage arc are examined. On the basis of the model of a Knudsen arc a criterion is obtained for the appearance of the instability and the possible types of dispersion relations are analyzed. The possibility of ionization instability in a short arc in cesium vapor is discussed. The results of a numerical investigation of the appearance of ionization instability, including the nonlinear stage, in a two-dimensional formulation of the problem are presented. When the fluctuations in the elec tron temperature are in antiphase with the density fluctuations, stable (long-lived)more » two-dimensional structures, which are characterized by a high degree of modulation of the degree of ionization of the gas, can form.« less

  20. Laser Balancing

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Mechanical Technology, Incorporated developed a fully automatic laser machining process that allows more precise balancing removes metal faster, eliminates excess metal removal and other operator induced inaccuracies, and provides significant reduction in balancing time. Manufacturing costs are reduced as a result.